everyday_practical_electronics-1995_06

JUNE 1995

INCORPORATING ELECTRONICS MONTHLY | FULLY S.O.R.

hifi at a
Yulee

AA To PP3 Battery

CONVERTER
Save money on
battery costs
Smart Carbs
Barry Fox investigates 7
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7 em Tre No. 1 [vverenvent i‘
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seem 6) i ClectRoNics TecHNoLocy LU

& Computer Projects

NEW BULL ELECTRONICS STORE IN

WOLVERHAMPTON
554 WORCESTER ST. - TEL: 01902 22039

A4 DTP MONITORS Brand new, 300 DPI. Complete
with diagram but no interface details.(so you will
have to work it out!) Bargain at just £12.99 each!!!!
OPD MONITORS 9° mono monitor, fully cased complete with
raster board, switched mode psu etc. CGA/TTL input (15way D), IEC
mains. £15.99 ref DEC23. Price including kit to convert to composite
monitor for CCTV use etc is £21.99 ref DEC24

PC CONTROLLED 4 CHANNEL TIMER Control (on/off
times etc) up to 4 items (8A 240v each) with this kit. Complete with
Software, relays, PCB etc. £25.99 Ref 95/26

COMPLETE PC 300 WATT UPS SYSTEM Top of the range
UPS system providing protection for your computer system and
valuable software against mains power fluctuations and cuts. New and
boxed, UK made Provides up to 5 mins running time in the event of
complete power failure to allow you to run your system down correctly.
SALE PRICE just £119.00.

RACAL MODEM BONANZA! 1 Racal MPS1223 1200/75
modem, telephone lead, mainslead, manual and comms software, the
cheapest way onto the net! all this for just £13 ref DEC13.

HOW LOW ARE YOUR FLOPPIES? 3.5" (1.44) unbranded.
We have sold 100,000+ so ok! Pack of 50 £24.99 ref DEC 16
BRITISH TELECOMM MULTIMETERS SA9083 These are
‘returns’ so they may have faults but look ok. Complete with new leads
and leather case. Price for two meters & 1 case is £10 ref DEC89.
Smw LASER POINTER. Supplied in kit form, complete with
power adjuster, 1-Smw, and beam divergence adjuster. Runson2 AAA
batteries. Produces thin red beam ideal forlevels, gun sights, expen-
ments etc. Cheapest in the UK! just £39.95 ref DEC49

SHOP WOBBLERS!Small assemblies designed to take D size
batteries and ‘wobble’ cardboard model signs aboutin shop windows!
£3.99 Ref SEP4P2.

RADIO PAGERSBrand new, UK made pocket pagers dearance
price is just £4.99 each 100x40x 15mm packed with bits! Ref SEP5.
BULL TENS UNTT Fully built and tested TENS (Transcutaneous
Electrical Nerve Stimulation) unit, complete with electrodes and full
instructions. TENS is used for the relief of pain etc in up to 70% of
sufferers. Drug free pain relief, safe and easy to use, can be used in
conjunction with analgesics etc. £49 Ref TEN/1

COMPUTER RS232 TERMINALS. (LIBERTY)Excelient
quality modem units, (like wyse 50,s) 2xRS232, 20 function keys, 50
thro to 38,400 baud, menu driven port, screen, cursor, and keyboard
setup menus (18 menu's). £29 REF NOV4.

OMRON TEMPERATURE CONTROLLERS (E6C2).Brand
new controllers, adjustable from -50 deg C to +1,200 deg C using
graduated dial, 2% accuracy, thermocouple input, longlife relay output
,3A 240v o/p contacts. Perfect for exactly controlling a temperature,
Nomai trade £50+, ours £15. Ref E5C2.

ELECTRIC MOTOR BONANZA! 110x60mm.Brand new
precision, cap start (or spin to start), virtually silent and features a
moving outer case that acts as a fly wheel. Because of their unusual
design we think that 2 of these in a tube with some homemade fan
blades could form the basis for a wind tunnel etc. Clearance priceisjust
£4.99 FORAPAIR! (note-these will have to be wired in senesfor 240v
operation Ref NOV1.

MOTOR NO 2 BARGAIN 110x90mm.Similar to the above
motor but more suitable for mounting vertically (ie tumtable etc). Again
you will have to wire 2in series for 240v use. Bargain priceisjust£4 99
FOR A PAIR!! Ref NOVS.

OMRON ELECTRONKE INTERVAL TIMERS.
Minature adjustable timers, 4 pole c/o output 3A 240v,
HY1230S, 12vDC adjustable from 0-30 secs. £9.99
HY1210M, 12vDC adjustable from 0-10 mins. £9.99
HY1260M, 12vDC adjustable from 0-60 mins. £9.99
4 HY2460M, 24vAC adjustable from 0-60 mins. £5.99
HY241S, 24vAC adjustable from O-1 secs. £5.99
HY2460S, 24vAC adjustable from 0-60 secs, £5.99
HY243H, 24vAC adjustable from O-3 hours. £8.99
HY2401S, 240v adjustable from 0-1 secs. £9.99
HY2405S, 240v adjustable from 0-5 secs. £9.99
HY24060m, 240v adjustable from 0-60 mins. £12.99
PC PAL VGA TO TV CONVERTER Converts a colour TV into
a basic VGA screen. Complete with built in psu, lead and s/ware.
£49.95. Ideal forlaptops or acheap upgrade. We also can supply this
in kit form for home assembly at £34.95 ref EF 54.

DRINKING BIRD Remember these? hook onto wine glass (sup-
plied) and they drink, standup,drink, standup ETC! £4 each Ref EF 1
EMERGENCY LIGHTING UNIT Complete unit with 2 double

bulb floodlights, built in charger and auto switch. Fully cased. 6v 8AH
lead acid req'd. (secondhand) £4 ref MAG4P 11.

GUIDED MISSILE WIRE. 4,200 metre reel of ultra thin 4 core
insulated cable, 28lbs breaking strain, less than 1mm thick! Ideal
alarms, intercoms, fishing, dolls house's etc. £14.99 ref MAG15P5
300v PANEL METER 70X60X50MMM, AC, 90 degree scale. Good
quality meter. £5.99 ref MAG 6P 14. Ideal for monitoring mains etc.
ASTEC SWITCHED MODE PSU BM41012 Gives +5 @ 3.75A,
+12@1.5A, -12@.4A. 230/110, cased, BM41012. £5.99 ref AUG6P3.
TORRODIAL TX 30-0-30 480VA, Perfect for Mosfet amplifiers
etc. 120mm dia 55mm thick. £18.99 ref APR19.

AUTO SUNCHARGER 155x300mm solar panel with diode and
3metrelead fitted with a cigar plug. 12v 2watt.£9.99 ea ref AUG10P3.
FLOPPY DISCS DSDD Top quality 5.25" discs, these have been
written to once and are unused. Pack of 20 is £4 ref AUG4P1.
ECLATRON FLASH TUBE Asused in police car flashing lights
etc, full spec supplied, 60-100 flashes a min. £9.99 ref APR10P5.
24v AC S6WATT Cased power supply. New. £13.99 ref APR14.
MILITARY SPEC GEIGER COUNTERS Unused
anstraightfrom Her majesty's forces. £50 ref MAG SOP3.
STETHOSCOPE Fully functioning stethoscope, ideal for listening
to hearts, pipes, motors etc. £6 ref MAR6P6.

OUTDOOR SOLAR PATH LIGHT Captures sunlight during

the day and automatically switches on a built inlamp at dusk. Complete
with sealed lead acid battery etc £19.99 ref MAR20P1.

ALARM VERSION Of above unit comes with built in alarm and pir
to deter intruders. Good value at just £24.99 ref MAR25P4.
CARETAKER VOLUMETREK Alam, will cover the whole of the
ground floor against forcred entry. Includes mains power supply and
integral battery backup. Powerful internal sounder, will take external bell
if req'd. Retail £150+, ours? £49.99 ref MARSOP 1.

TELEPHONE CABLE White 6 core 100m ree! complete with a
pack of 100 ciips. Ideal ‘phone extns etc. £7.99 ref MAR8P3.
MICRODRIVE STRIPPER Small cased tape drives ideal for
stripping, lots of useful goodies including a smart case, and lots of
components. £2 each ref JUN2P3.

SOLAR POWER LAB SPECIAL You get TWO 6"x& 6v 130mA
solar cells, 4 LED's, wire, buzzer, switch plus 1 relay or motor. Superb
value kit just €5.99 REF: MAG6P8

SOLID STATE RELAYS Will switch 25A mains. Input 3.5-26v DC
57x43x2 1mm with terminal screws £3.99 REF MAG4P 10
BUGGING TAPE RECORDER Small voice activated recorder,
uses microcassette complete with headphones. £28.99 ref MAR29P 1.
ULTRAMINI BUG ME 6mmx3.5mm made by AKG, .5-12velectret
condenser. Cost £12 ea, Ours? just four for £9.99 REF MAG10P2.
RGB/CGA/EGA/TTL COLOUR MONITORS 12" in good
condition. Back anodised metal case. £79 each REF JUN79
ANSWER PHONES Retums with 2 faults, we give you the bits for
1 fault, you have to find the other yourself. BT Response 200's £18 ea
REF MAG18P1. PSU £5 ref MAGS5P 12.

SWITCHED MODE PSU ex equip, 60w +5v @5A, -5v@.5A,
+12V@2A,-12V@.5A 120/220v cased 245x88x55mm |ECinput socket
£6.99 REF MAG7P1

PLUG IN PSU 9V 200mA DC £2.99 each REF MAG3P9
PLUG IN ACORN PSU 19v AC 14w , £2.99 REF MAG3P 10
POWER SUPPLY fully cased with mains and o/p leads 17v DC
900mA output. Bargain price £5.99 ref MAG6P9

ACORN ARCHIMEDES PSU +5v @ 4.4A. on/off sw uncased,
selectable mains input, 145x100x45mm £7 REF MAG7P2
GEIGER COUNTER KIT Low cost professional twin tube, com-
plete with PCB and components. Now only £19 REF AUG19.

Sv DC POWER SUPPLY Standard plugin type 150ma 9v DC with
lead and DC power plug. price for two is £2.99 ref AUG3P4.

AA NICAD PACK encapsulated pack of 8 AA nicad batteries
(tagged) ex equip, 55x32x32mm. £3 a pack. REF MAG3P 11

13.8V 1.9A psu cased with leads. Just £9.99 REF MAG10P3
PPCMODEM CARDS. These are high spec plugin cards made for
the Amstrad laptop computers. 2400 baud dial up unit complete with
leads. Clearance price is £5 REF: MAG5P1

INFRA RED REMOTE CONTROLLERS Ojiginally made for
hi spec satellite equipment but perfect for all sorts of remote control
projects. Our clearance price is just £2 REF: MAG2

200 WATT INVERTER Converts 10-15v DC into either 110v or
240v AC. Fully cased 115x36x156mm, complete with heavy duty power
lead, cigar plug, AC outlet socket.Auto overoad shutdown, auto short
circuit shut down, auto input over voltage shutdown, auto input under
voltage shut down (with audible alarm), auto temp control, unit shuts
down if overheated and sounds audible alarm. Fused reversed polarity
protected. output frequency within 2%, voltage within 10%. Aextremely
well built unit at an excellent price. Just £64.99 ref AUG65.
UNIVERSAL SPEED CONTROLLER KIT Designed by us for
the C5 motor but ok for any 12v motor up to 30A. Complete with PCB
etc. A heat sink may be required. £17.00 REF: MAG17
MAINSCABLEPrecut black 2 core 2metre lengths ideal for repairs,
projects etc. 50 metres for £1.99 ref AUG2P7.

COMPUTER COMMUNICATIONS PACK Kit contains 100m
of 6 core cable, 100 cable dips, 2 line divers with RS232 interfaces
and all connectors etc. Ideal low cost method of communicating be-
tween PC's over along distance. Complete kit £8.99.

MINI CYCLOPS PIR 52x62x40mm runs on PP3 battery complete
with shrill sounder. Cheap protection at only £5.99 ref MAR6P4.
ELECTRIC MOTOR KIT Comprehensive educational kitincludes
all you need to build an electric motor. £9.99 ref MAR10P4.
VIEWDATA SYSTEMS made by Phillips, complete with internal
1200/75 modem, keyboard, psu etc RGB and composite outputs, menu
driven, autodialler etc. £18 each Ref EF88.

BOOMERANG High tech, patented poly propylene, 34cm wing
span. Get out and get some exercise for £4.99 ref EF83

AIR RIFLES .22As used by the Chinese army for training puposes,
so there is a lot about! £39.95 Ref EF78. 500 pellets £4.50 ref EF80.
PEANUT TREE Complete kit to grow your own peanuts! full
instructions supplied. £3 Ref EF45.

PLUG IN POWER SUPPLYS Plugs in to 13A socket with output
lead. three types available, 9vdc 150mA £2 ref EF58, 9vdc 200mA
£2.50 ref EF59, 6. S5vdc 500mA £3 ref EF61.

VIDEO SENDER UNIT. Transmits both audio and video signals
from either a video camera, video recorder, TV or Computer etcto any
standard TV set in a 100' range! (tune TV toa spare channel) 12v DC
op. Priceis £15 REF: MAG15 12v psu is £5 extra REF: MAG5P2
“FM CORDLESS MICROPHONE Smaii hand held unit with a
500' range! 2 transmit powerlevels. Reqs PP3 Sv battery. Tuneabie to
any FM receiver. Piceis£15 REF: MAG15P1

LOW COST WALKIE TALKIES Pair of battery operated units
with a range of about 200’. Ideal for garden useor as an educational toy.
Price is£8 a pair REF: MAG 8P1 2.x PP3 req'd.

*MINATURE RADW TRANSCEIVERS A pair of walkie talkies

“SOME OF OUR shssedia aA RE MAY BE URC ICENSASLE IN THE las

TELEPHONE ORDERS WELCOME
- TEL: 01273 203500 ©

FAX: 01273 323077

with a range of up to 2km in open country. Units measure 22x52x 155mm.
Induding cases and earp'ces. 2xPP3 req'd. £30.00 pr.REF: MAG30
COMPOSITE VIDEO KIT. Converts composite video into sepa
rate H sync, V sync, and video. 12v DC. £8.00 REF: MAG8P2.
LQ3600 PRINTER ASSEMBLIES Made by Amstrad they are
entire mechanical printer assemblies including printhead, stepper mo-
tors etc etc In fact everything bar the case and electronics, a good
Stripper £5 REF: MAGSP3 cr 2 for£8 REF: MAG8P3

LED PACK of 100 standard red 5m leds £5 REF MAG5P4
UNIVERSAL PC POWER SUPPLY complete with flyleads,
switch, fan etc. Two types available 150w at £15 REF:MAG15P2
(23x23x23mm) and 200w at £20 REF: MAG20P3 (23x23x23mm)
GYROSCOPE About 3° high and an excellent educational toy for all
ages! Price with instruction booklet £6 Ref EF 15.

FUTURE PC POWER SUPPLIES These are 295x135x60mm,
4 drive connectors 1 mother board connector. 150watt, 12v fan, iec
inlet and on/off switch. £12 Ref EF6.

VENUS FLY TRAP KIT Grow your own carnivorous plant with this
simple kit £3 ref EF 34.

PC POWER SUPPLIES (returns) These are 140x150x90mm. o/
ps are +12,-12,+5 and -5v. Builtin 12v fan. These are retums so they
may well need repairing! £3.50 each ref EF 42.

“FM TRANSMITTER KIT housed in a standard working 13A
adapter!! the bug runs directly off the mains so lasts forever! why pay
£700? or priceis£15 REF: EF62 Transmits to any FM radio. (this isin
kit form with full instructions.)

*FM BUG KIT New design with PCB embedded coil for extra stability.
Works to any FM radio. 9v battery req'd. £5 REF: MAGS5P5

*FM BUG BUILT AND TESTED superior design to kit. Supplied
to detective agencies. 9v battery req'd. £14 REF: MAG14
TALKING COIN BOX STRIPPER orginally made to retail at£79
each, these units are designed to convert an ordinary phone into a
payphone. Theunits have the locks missing and sometimes broken
hinges. However they can be adapted for their original use or used for
something else?? Price is just £3 REF: MAG3P1

TOP QUALITY SPEAKERS Made for Hi Fi televisions these are
10 watt 4R Jap made 4° round with large shielded magnets. Good
quality. £2 each REF: MAG2P4 or 4 for £6 REF: MAG6P2
TWEETERS 2" diameter good quality tweeter 140R (ok with the
above speaker) 2 for £2 REF: MAG2P5 or 4 for€3 REF: MAG3P4
AT KEYBOARDS Made by Apricot these quality keyboards need
justa small modtorunon any AT, they work perfectly but you will have
to put up with 1 or 2 foreign keycaps! Price £6 REF: MAG6P3
HEADPHONES Ex Virgin Atlantic. 8pairsfor€2 REF: MAG2P8
DOS PACKS Microsoft version 3.3 or higher complete with all
manuals or price just £5 REF: MAG5P8 Worth it just for the very
comprehensive manual! §.25° only.

GAS HOBS Brand new made by Optimus, basic three bumer suitable
for small flat etc bargain price just £29.95 ref EF73.

GAT AIR PISTOL PACK Complete with pistol, darts and peliets
£12.95 Ref EF82 extra pellets (500) £4.50 ref EF80.
CHRISTMAS TREE KIT Start growing it now! £3 ref EF53.
DOS PACK Microsoft version 5 Original software but no manuals
hence only £5.99. 3.5* only.

PIR DETECTOR Made by famous UK alarm manufacturer these
are hi spec, long range internal units. 12v operation. Slight marks on |
case and unboxed (although brand new) £8 REF: MAG8P5
MOBILE CAR PHONEE6.99 Weil almost! complete in carphone
excluding the box of electronics normally hidden under seat. Can be
made toilluminate with 12v also has built in light sensor so display only
illuminates when dark. Totally convincing! REF: MAG6P6

ALARM BEACONS Zenon strobe made to mount on an extemal
bell box but could be used for caravans etc. 12v operation. Just connect §
up and it flashes reguiany) £5 REF: MAG5P 11

6"°X12" AMORPHOUS SOLAR PANEL 12v 155x310mm
130mA. Bargain price just £5.99 ea REF MAG6P 12.

FIBRE OPTIC CABLE BUMPER PACK 10 metres for £4.99
ref MAG5P 13 ideal for experimenters! 30 m for £12.99 ref MAG13P1 §
HEATSINKS (finned) T0220, designed tomount vertically on apeb |
50x40x25mm you can have a pack of 4 for £1 ref JUN1P11.
STROBE LIGHT KIT Adjustable from 1 hz right up to 60hz!
(electronic asssembly kit with full instructions) £16 ref EF28.

ROCK LIGHTS Unusual things these, two pieces of rock that glow f
when rubbed together belived to cause raini€3 a pair Ref EF29.

NEW HIGH POWER LASERS

15mW, Helium neon, 3 switchable wavelengths 63um, 1.15um,3.39um
(2 ofthem are infrared) 500: 1 polarizer built in so good for holography.
Supplied complete with mains power supply. 790x65mm. Use with
EXTREME CAUTION AND QUALIFIED GUIDANCE. £349+Vat.

WE BUY SURPLUS STOCK FOR CASH

FREE CATALOGUE

1995 100 PAGE CATALOGUE NOW
AVAILABLE, 45P STAMP OR FREE
WITH ORDER.

WITH NEW COMPUTER INTERFACE.
£59.00

4 Hand held personal Gamma and X Ray detector.

his unit contains two Geiger Tubes, has a 4 digit LCD
display with a Piezo speaker, giving an audio visual
ndication. The unit detects high energy electromag-
netic quanta with an energy from 30K eV to over 1.2M
eV and a measuring range of 5-9999 UR/h or 10-99990

INr/h. Supplied complete with handbook.Ref. NOV 18.

D ects THEORY NEWS EVERYDAY
PROJE —_ ae poe
COMMENT... POPULAR FEATURES. . S. With PRAE

ELECTRONICS

INCORPORATING ELECTRONICS MONTHLY

The No. 1 Independent Magazine for Electronics,
Technology and Computer Projects

VOL. 24 No.6 JUNE 1995

Projects

EPE HiFi VALVE AMPLIFIER -1 by Jake Rothman 434
A brand new hybrid design that retains that unique ‘‘valve sound”

NAME OF THE GAME —4 @¢ Star-Struck! ¢ Six-Shot Zapper

¢ Wander Wands by Roy Bebbington 446
Easy-build modules to enhance your quiz and party games
PIC-DATS-2 4-Channel Light Chaser by Mark Stuart 465
Take your PIC and create your very own light show. Demonstration project
to show how easy it is to program your PICs
AA TO PP3 CONVERTER by Robert Penfold 476
Step up the power of your AA's with this low-cost d.c. to d.c. converter
R.F. SIGNAL GENERATOR - 2 by Steve Knight 487

Final construction of this high performance piece of test gear

SCrles

CIRCUIT SURGERY by Alan Winstanley 472
Voxbox upgrade, diodes and current flow |
ELECTRONICS FROM THE GROUND UP-9 480
by Mike Tooley B.A.

Concluding article — Further reading extends the range of Electronics Workbench
INTERFACE by Robert Penfold 4f4
The page for computer enthusiasts — Model train control

AMATEUR RADIO by Tony Smith G4FAI 500

Hobby or Politics; No DXCC Status; Young Amateur of the Year;
Story of the Key

Features

EDITORIAL 433
INNOVATIONS 442
Everyday news from the world of electronics |
NEW TECHNOLOGY UPDATE by lan Poole Aaa
The latest developments in memory storage
OHM SWEET OHM by Max Fidling 453
Max investigates strange ‘goings on” in the attic
SMART CARDS by Barry Fox | | 454
What they are, how they work, are they secure?
BACK ISSUES Did you miss these? 460
SHOPTALK with David Barrington | 478
Component buying for EPE projects
ELECTRONICS VIDEOS | 492
“yy Our range of educational videos |
DIRECT BOOK SERVICE 495
A wide range of technical books available by mail order
PRINTED CIRCUIT BOARD SERVICE 499
PCBs for EPE projects
ADVERTISERS INDEX 504
Wimbo Publishing Ltd 1995. Copyright in all
a and articles published in F R E E

EVERYDAY with PRACTICAL ELECTRONICS is fully
protected, and reproduction or imitations in whole THE BUDGETCD & TAPE CO. CATALOGUE

or in part are expressly forbidden. Banded to UK copies
SRS PSS SSS SSS SC oS SSS SSS Ss ST SS SS ch
Our July ’95 Issue will be published on Friday, Readers Service @ Editorial and Advertisement Departments 433
2 June 1995. See page 423 for details. Cover photo: Alfred Pasieka/Science Photo Library

Everyday with Practical Electronics, June 1995 | 421

SPECIAL BUY

AT 286

40Mb HD + 3Mb Ram

LIMITED QUANTITY only of these 12Mhz HI GRADE 286 pee
Made in the USA to an industrial specification, the system was
designed for total reliability. The compact case houses the mother-
board, PSU and EGA video card with single 5%" 1.2 Mb floppy disk
drive & integral 40Mb hard disk drive to the front. Real time clock
with battery backup is provided as standard. Supplied in good used
condition complete with enhanced keyboard, 640k + 2Mb RAM,
DOS 4.01 and 90 DAY Full ONLY 14 to Run !

Order as HIGRADE 286 QAVZ $9.0 E)
CALL ¥_ = I O90

Optional Fitted extras: VGA graphics card

1.4Mb 3%" floppy disk drive (instead of 1.2 Mb)
NE2000 Ethernet (thick, thin or twisted) network card

FLOPPY DISK DRIVES 3/2"- 8"

5%" from £22.95 - 3%" from £24.95

Massive purchases of standard 5%" and 3%" drives enables us to

present prime product at industry beating low prices! All units (unless
stated) are BRAND NEW or removed from often brand new equip-
ment and are fully tested, aligned and shipped to you with a 90 day
guarantee and operate from standard voltages and are of standard
size. All are IBM-PC compatible (if 3%" supported on your PC).

3%" Panasonic JU363/4 720K or equivalent £24.95(B)
3%" Mitsubishi MF355C-L. 1.4 Meg. Laptops only * £36.95(B)
3%" Mitsubishi MF355C-D. 1.4 Meg. Non laptop £29.95(B)
5%" Teac FD-55GFR 1.2 Meg £29.95 By
5%" BRAND NEW Mitsubishi MF501B 360K £22.95(B
* Data cable included in price.

Shugart 800/801 8" SS refurbished & tested £195.00(E)
Shugart 851 8" double sided refurbished & tested £250.00(E
Mitsubishi M2894-63 8" double sided NEW £275.00(E
Mitsubishi M2896-63-02U 8" DS slimline NEW £285.00(E

Dual 8" drives with 2 mbyte capacity housed in a smart case with
built in power supply. Ideal as exterior drives! £499.00(F)

HARD DISK DRIVES

End of line purchase scoop! Brand new NEC D2246 8" 85 Mbyte
of hard disk storage! Full industry standard SMD interface. Ultra
hi speed data transfer and access time, replaces Fujitsu equivalent
model. complete with manual. Only £299.00(E)

3%" FUJI FK-309-26 20mb MFM I/F RFE £59.95(C

3%" CONNER CP3024 20 mb IDE I/F (or equiv )JRFE £69.95(C
3%" CONNER CP3044 40mb IDE I/F (or equiv.)RFE £89.00(C
3%" RODIME RO3057S 45mb SCSI I/F (Mac & Acorn) £99.00(C
5%" MINISCRIBE 3425 20mb MFM I/F (or equiv.) RFE £49.95(C
5%" SEAGATE ST-238R 30 mb RLL I/F Refurb £69.95 6}
5%" CDC 94205-51 40mb HH MFM I/F RFE tested £69.95(C
8" FUJITSU M2322K 160Mb SMD I/F RFE tested £195.00(E)

Hard disc controllers for MFM , IDE, SCSI, RLL etc. from £16.95

THE AMAZING TELEBOX

Converts your colour monitor into a QUALITY COLOUR TV!!

TV SOUND
& VIDEO

TUNER!

The TELEBOX consists of an attractive fully cased mains powered
unit, containing all electronics ready to plug into a host of video moni-
tors made by makers such as MICROVITEC, ATARI, SANYO,
SONY, COMMODORE, PHILIPS, TATUNG, AMSTRAD etc. The
composite video output will also plug directly into most video
recorders, allowing reception of TV channels not normally receivable
on most television receivers* (TELEBOX MB). Push button controls
on the front panel allow reception of 8 fully tuneable ‘off air' UHF
colour television channels. TELEBOX MB covers virtually all televi-
sion frequencies VHF and UHF including the HYPERBAND as
used by most cable TV operators. A composite video output is
located on the rear panel for direct connection to most makes of
monitor or desktop video s pt For complete compatibility - even
for monitors without sound - an integral 4 watt audio amplifier and
low level Hi Fi audio output are provided as standard.

TELEBOX ST for composite video input type monitors
TELEBOX STL as ST but with inte efi speaker
TELEBOX MB Multiband VHF-UHF-Cable- Hyperband tuner £69.95
For overseas PAL versions state 5.5 or 6mhz sound specification.
*For cable / hyperband reception Telebox MB should be connected
to cable type service. Shipping code on all Teleboxes is (B

FANS & BLOWERS

MITSUBISHI MMF-D6D12DL 60x 25mm 12vDC £4.95 10/£42
MITSUBISHI MMF-09B12DH 92 x 25mm 12vDC = £5.95 10 / £53
PANCAKE 12-3.5 92 x 18 mm 12v DC £7.95 10 / £69

EX-EQUIP 120 x 38mm AC fans - tested specify 110 or 240 v £6.95
EX-EQUIP 80 x 38mm AC fans - tested specify 110 or 240 v_ £5.95
VERO rack mount 1U x 19" fan tra ay specify 110 or 240v £45.95 (8)
IMHOF B26 1900 rack mnt 3U x 19° Blower 110/240v NEW £79.95
Shipping on all fans (A). Blowers (B). 50,000 Fans Ex Stock CALL

IC's -TRANSISTORS - DIODES

OBSOLETE - SHORT SUPPLY - BULK

5,000,000 items EX STOCK

For MAJOR SAVINGS - SAE or CALL FOR LATEST LIST

issue 13 Of Display

LECT RGNICS -
Se 8 [eur

422

News now available - send lar

e e e

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a eee e @ e ® Open Mon - Sat 9: : Open Mon-Fri 9.00-5:30

© @t ee” SG os 215 Whitehorse Lane Dept EE. 32 Biggin Way

Seco 8 ° Secce es 8 {On 68A Bus Route Upper Norwood
Selhurst Park SR Rail Stations LONDON SE19 3XF

and Local Authorities - minimum
eramumyeo] Grae Ons 550, (C)-EB50, ana (E}-£15 00, (asad (CALL Allow approx
unless stated guaranteed for 90 days. All
notice. sate es nf Pech rg mel an Top CASH prices

THE ORIGINAL SURPLUS WONDERLAND!

THIS MONTH'S SELECTION FROM OUR VAST EVER CHANGING STOCKS

LOW COST PC's - ALL EXPANDABLE - ALL PC COMPATIBLE

PC SCOOP

COMPLETE
COLOUR SYSTEM

ONLY £99.00

A massive bulk purchase enables us to bring you a COMPLETE
poacy to run colour PC system at an unheard of price!
The Display Electronics PC99 youn comprises of fully com-
patible and expandab le XT PC with 256k of RAM, 5%" 360k flop-
py disk drive, 12" CGA colour monitor, standard 84 key key-

oard, MS DOS and all connecting cables - just plug in and go
I! Ideal students, schools or anybody wishing to learn the world of
PC's on an ultra low budget. Don't miss this opportunity.

Fully guaranteed for 90 i es PCSOCOL £99.00 (E)

Optional Fitted extras: 640k RAM
2nd floppy drive, specify 5%" 360k or 3%" 720k
Above prices for PC99 offer ONLY.

VIDEO MONITOR SPECIALS

One of the highest specification
ate monitors you will ever see -

At this price - Don’t miss it!!

Mitsubishi di sede 14” SVGA Multisync monitor with fine
0.28 dot pitch tube and guaranteed resolution of 1024 x 768. A
. variety of inputs allows connection to a host of
: computers fen Be PC's in CGA, EGA, VGA &
: SVGA modes C, COMMODORE (including
Amiga 1200), ARCHIMEDES and APPLE. Man
features: Etched faceplate, text switching and LO
Suni ire HEN ME ee Full 90 day warranty.
u in ittle u ition

P Orderasmirs-svGa Only £1396
Tilt & Swivel Base £8.00 Leads for IBM PC £8.95 (A)
External Cables for other com £ CALL

PHILIPS HCS35 (same s ae as CM8833) attractively styled 14”
colour monitor with both RGB and standard composite 15.625
Khz video inputs via SCART socket and separate phono jacks.
Integral audio power amp and speaker for all audio visual uses.
Will connect direct to Amiga and Atari BBC computers. Ideal for
all monitoring / security applications with direct connection to
most colour cameras. High Sage with many features such as front
concealed flap controls, VCR correction button etc. Good used

condition - fully tested with a 90 day guarantee
14" x H1236° x 1544" B. Only £99

Dimensions:
Special Offer save £16.95 - Order TELEBOX ST &
HCS35 together - giving you a quality colour TV & AV

system for Only £122.50 (E)
KME 10" pel definition colour monitors. Nice tight 0.28" dot pitch

for superb clarity and modern styling. Operates from ;
any 15.625 khz sync RGB video source, with RGB:
analog and composite sync such as Atari
Commodore Amiga, Acorn Archimedes & BBC. 3
Measures only 13%" x 12" x 11". Only £125 (E)
Good used condition. 90 day guarantee.

KME 10" as above for PC EGA standard £145.00 (E)

PHILIPS HCS31 Ultra compact 9” colour video monitor with stan-
dard composite 15.625 Khz video input via SCART socket. Ideal
for all monitoring / security applications. High quality, ex-equipment
fully tested with a 90 day guarantee (possible minor screen burns).
In attractive square black plastic case Dh amg, W10" x H10" x
13%" D. Mains powered Limited Quantity - Only £79.00 (D)

20" 22" and 26" AV SPECIALS

Superbly made UK manufacture. PIL all solid state colour monitors,
complete with composite video & optional sound inputs. Attractive
teak style case. Perfect for Schools, Shops, Disco, Clubs, etc.In
EXCELLENT little used condition with full 90 day guarantee.

20"....£135 22"....£155 26"....£185 (F)

DC POWER SUPPLIES

Mlaed Mas d every type of power
ply you can imagine.Over
000 Power Supplies Ex Stock

Call for info / list.

SPECIAL INTEREST

Zeta 3220-05 AO 4 pen HPGL RS232 fast drum plotter

10,

£1950
3M VDA - Video Distribution Amps.1 in 32 out £375

Trio 0-18 vdc bench PSU. 30 amps. New £470
Fujitsu M3041 600 LPM band oe £1950
VG Electronics 1035 TELETEXT Decoding Margin Meter £3750
Andrews LARGE 3.1 m Satellite Dish + mount (For Voyager!) £950
RED TOP IR Heat seeking missile (not armed !!) POA
KNS EMC / Line interference tester NEW

Thuriby LA 160B logic analyser

INTEL SBC 486/133SE Multibus 486 system. 8Mb Ram

GEC 1.5kw 115v 60hz power source £950
Brush 2Kw 400 Hz 3 phase frequency converter £850
Anton Pillar 75 kW 400 Hz 3 a frequency converter POA

Newton Derby 70 KW 400 Hz 3 phase frequency converter
COMPONEDEX T1000 Portable TELEX tester NEW £250
Sekonic SD 150H 18 channel digital Hybrid chart recorder £1995
HP 7580A A1 8 pen HPGL high speed drum plotter £1850
Computar MCA1613APC 16mm auto iris lenses 'C' mount £125
Seaward PAT 2000 dual ke computerised PAT tester £585
Densel MUD 0185AH 1KVa UPS system with batts NEW £575

m account order £50.

V21,V22, V22 BIS
0181 679 1888

i usin for fis Mainland. UK eat add 17.5% VAT yA TOTAL order amount. Minimum order £10. Bona Fide account orders accept

Surplus always
wanted for cash!
19" RACK CABINETS

Superb quality 6 foot 40U
Virtually New, Ultra Smart

Less than Half Price!

Top qualit y 19" rack cabinets made in UK by
Optima Enclosures Ltd. Units feature
designer, smoked acrylic lockable front door,
full height lockable half louvered back door
and removable side panels. Fully adjustable
internal fixing struts, ready punched for any
configuration of equipment mounting plus
ready mounted integral 12 way 13 amp socket
switched mains distribution strip make these
racks some of the most versatile we have
ever sold. Racks may be stacked side by side and therefore require
only two side panels to stand singly or in bays
Overall dimensions are: 77%" H x 32%" D x 22" W. Order as:

OPT Rack 1 Complete with removable side panels. £335.00 (G)

OPT Rack 2 Rack, Less side panels £225.00 (G)

32U - High Quality - All steel cabinet

Made by Eurocraft Enclosures Ltd to the highest possible spec,
rack features all steel construction with removable
side, front and back doors. Front and back doors are <>.
hinged for easy access and all are lockable with
five secure 5 lever barrel locks. The front door Ess
is constructed of double walled steel with a ES
‘designer style’ smoked acrylic front panel to
enable status indicators to be seen through the
panel, yet remain unobtrusive. Internally the rack
features full slotted reinforced vertical fixing mem-
bers to take the heaviest of 19” rack equip-
ment. The two movable vertical fixing struts
(extras available) are pre punched for standard
‘cage nuts’. A mains distribution panel internal-
ly mounted to the bottom rear, provides 8 IEC 3
pin Euro sockets and 1 x 13 amp 3 pin switched <a
utility socket. Overall ventilation is provided by ~
fully louvered back door and double skinned top section
with top and side louvres. The top panel may be removed for fitting
of integral fans to the sub plate etc. Other features include: fitted
castors and floor levelers, prepunched utility panel at lower rear for
cable / connector access etc. Supplied in excellent, slightly used
condition with keys. Colour Royal blue. External dimensions 64” H x
25” D x 23%” W.

Sold at LESS than a third of makers price !!
A superb buy at only £195.00 (a)

Over 1000 racks in all sizes 19" 22" & 24"
3 to 44 U. Available from stock !!

OF TIM Wi dam celelamacrelelic-tiatsia)

TOUCH SCREEN SYSTEM

The ultimate in ‘Touch Screen Technology’ made by the experts -
MicroTouch - but sold at a price below cost !! System consists of
a flat translucent glass laminated panel measuring 29.5 x 23.5 cm
connected to a PCB with on board sophisticated electronics. From
the board comes a standard serial RS232 or TTL output. The out-
put continuously gives simple serial data containing positional X & Y
co-ordinates as to where a finger is touching the panel - as the fin-
ger moves, the data instantly changes. The X & Y information is
given at an incredible matrix resolution of 1024 x 1024 positions
over the screen size !!! So, no position, however small fails detec-
tion. A host of available translation software enables direct con-
nection to a PC for a myriad of applications including: control pan-
els, pointing devices, POS systems, controllers for the disabled or
computer un-trained etc etc Imagine using your finger in ‘Windows’
instead of a mouse !! (a driver is indeed available !) The applica-
tions for this amazing product are only limited by your imagina-
tion!! Supplied as a complete system including Controller, Power

Supply and Data at an incredible price of only:
RFE. Full Software Support Available - Fully Gunna 145.00 (B)

LOW COST RAM & CPU’S

INTEL 'ABOVE' Memory Expansion Board. Full length PC-XT
and PC-AT compatible card with 2 Mbytes of memory on board.
Card is fully selectable for Expanded or Extended (286 processor
and above) memory. Full data and driver disk supplied. In good
used condition fully tested and guaranteed.
Windows compatible. Order as: ABOVE CARD £59.95,a1)
Half length 8 bit memory upgrade cards for PC AT XT expands
memory either 256k or 512k in 64k steps. ae ng be used to fill
in RAM above 640k DOS limit. Complete with d

Order as: XT RAM UG. 256k. £32.95 or 51 ok £38.95 (A1)

SIMM
1 MB x9 SIMM 9 chip 120ns onl

Wy £19.50 (A1
1MBx9 SIMM3chip80ns £23.50 70ns £26.00 (A1
1MBx9 SIMMQchip80ns £22.50 70ns £28.00 (A1)
4 MB 70ns 72 pin SIMM module only £125.00 (A1)
SPECIAL INTEL 486-DX33 CPU £79.99 (A1)

NO BREAK UNINTERRUPTIBLE PSU'S

EMERSON ACCUCARD UPS, brand new 8 Bit half length PC
compatible card for all IBM XT/AT compatibles. Card provides DC
power to all internal system components in the event of power sup-
ply failure. The Accusaver software provided uses only 6k of base
RAM and automatically copies all system, expanded and video
memory to the hard disk in the event of loss of power. When power
is returned the machine is returned to the exact status when the
power failed !! The unit features full self diagnostics on boot and is
supplied brand new, with full, ea instructions and manual.

fittin
Normally £189.00 now! r€69 ‘00 or 2 for £120 «

e SGE - PACKED with bargains!

DISTEL © The Original
FREE On line Database
Info on 1000's of items

ALL ‘@ ENQUIRIES

0181 678 4414

FAX 0181 679 1927

ed from

Govemment, Schools,
. Cheques over £100 are subject to 10 working days clearance. Carriage “sh ag (A)=£3.00, (A1)=£4.00,
6 days for shipping -
on a retum to base basis. Oe ee ee ee eee
for surplus goods. All trademarks etc acknowledged. © Display

faster CALL Scotland surcharge CALL All goods supplied to our
tions without prior
ics 1995.E& OE. 4/5

Everyday with Practical Electronics, June 1995

-WINDICATOR

A reasonably accurate, inexpensive and easy
to build anemometer. This unit employs
an electric motor to dispense with
complicated bearings, shafts
and transducers. It will_
indicate windspeed

from 10 to 75 m.p.h.
onanl.e.d. bargraph |
or moving dot readout. *

Sy NSPA NSE

AUTOMATIC CURTAIN
WINDER —

Automatically opens and closes curtains at preset light levels. Can be used with almost
any corded system. An infra-red remote control transmitter and receiver will also be
described and the unit could be interfaced to a computer control system if so desired.

RAMP GENERATOR

| A professional quality ramp generator aimed at the intermediate to advanced
constructor. This high quality design has a multitude of uses including: oscilloscope
calibrator, plotter timebase, curve tracer, frequency response analyser and spectrum

analyser.
* Plus all the regular * Don’t miss out place
features. an order with your
: newsagent or take out a
| subscription NOW!

_ EVERYDAY
with PRACTICA

ELECTRONICS

JULY ISSUE ON SALE FRIDAY, JUNE 2

Everyday with Practical Electronics, June 1995

SURVEILLANCE

PROFESSIONAL QUALITY KITS

No. 1 for Kits

Whether your requirement for surveillance equipment is amateur, professional or you are just fascinated by this unique area of
electronics SUMA DESIGNS has a kit to fit the bill. We have been designing electronic surveillance equipment for over 12 years
and you can be sure that all our kits are very well tried, tested and proven and come complete with full instructions, circuit
diagrams, assembly details and all high quality components including fibreglass PCB. Unless otherwise stated all transmitters
are tuneable and can be received on an ordinary VHF FM radio.

Genuine SUMA kits available only direct from Suma Designs. Beware inferior imitations!

UTX Ultra-miniature Room Transmitter
Smallest room transmitter kit in the world! Incredible 10mm x 20mm including:
MIC. 3-12V Operation. 500M range............cccccsccessccsseesssecsssecssscsseecssersescsesens £16.45

MTX Micro-miniature Room Transmitter
Best-selling micro-miniature Room Transmitter
Just 17mm x 17mm including mic. 3-12V operation. 1000m range..................... £13.45

STX High-performance Room Transmitter
Hi performance transmitter with a buffered output stage for greater stability and range.

Measures 22mm x 22mm including mic. 6-12V operation, 1500m range............. £15.45
VT500 High-power Room Transmitter

Powerful 250mW output providing excellent range and performance. Size 20mm x
40mm. 9-12V operation. 3000M range.............cccccccsscssscssesssssssescsesssssesssseseesens £16.45
VXT Voice Activated Transmitter

Triggers only when sounds are detected. Very low standby current. Variable sensitivity
and delay with LED indicator. Size 20mm x 67mm. 9V operation. 1000m range...£19.45

HVX400 Mains Powered Room Transmitter

Connects directly to 240V AC supply for long-term monitoring. Size 30mm x 35mm.
STE FIM sccssadsscovuncectsyessoacnsg tind) Sood beasanbtevesiipsoss eohetis colach estdtdbidenbdesvvein cokeaghoaaeas £19.45
SCRX Subcarrier Scrambled Room Transmitter

Scrambled output from this transmitter cannot be monitored without the SCDM decoder
connected to the receiver. Size 20mm x 67mm. 9V operation. 1000m range............. £22.95

SCLX Subcarrier Telephone Transmitter

Connects to telephone line anywhere, requires no batteries. Output scrambled so
requires. SCDM connected to receiver. Size 32mm x 37mm. 1000m range........... £23.95
SCDM Subcarrier Decoder Unit for SCRX

Connects to receiver earphone socket and provides decoded audio output to
headphones. Size 32mm x 70MM. 9-12V Operation .............ccccccseccescseseseseesesees £22.95

ATR2 Micro Size Telephone Recording Interface

Connects between telephone line (anywhere) and cassette recorder. Switches tape
automatically as phone is used. All conversations recorded. Size 16mm x 32mm.
POWEIOG FONT TING vnssisnsessincascivscsssscsasasavdnsensbossassanscuadanccbecotetooukdsotteisdeedenienteniseatioter £13.45

beeeeeas

individual Transmitter DLTX.
Individual Receiver DURX earn

favuurite music palate around t h
-operstion 250 ts A

Dept. EE

UTLX Ultra-miniature Telephone Transmitter

Smallest telephone transmitter kit available. Incredible size of 10mm x 20mm!
Connects to line (anywhere) and switches on and off with phone use.

All conversation transmitted. Powered from line. 500m rangé..................... £15.95

TLX700 Micro-miniature Telephone Transmitter

Best-selling telephone transmitter. Being 20mm x 20mm it is easier to assemble than
UTLX. Connects to line (anywhere) and switches on and off with phone use. All
conversations transmitted. Powered from line. 1000m range .................0...cc £13.45

STLX High-performance Telephone Transmitter

High performance transmitter with buffered output stage providing excellent stability
and performance. Connects to line (anywhere) and switches on and off with phone use.
All conversations transmitted. Powered from line. Size 22mm x 22mm.

LOO FRING assay as csstetnwciosyyasesacsesosanssanantoprsinns ceosadmvata capsnslin shy jonanoahaASodvvaaeesyabannees £16.45

TKX900 Signalling/Tracking Transmitter

Transmits a continous stream of audio pulses with variable tone and rate. Ideal for
signalling or tracking purposes. High power output giving range up to 3000m. Size
25MM X GSMM. OV Operation ...............ccccscesccscsscsscscscsscsscessscsscscsscsssscssesceseaveseess £22.95

CD400 Pocket Bug Detector/Locator

LED and piezo bleeper pulse slowly, rate of pulse and pitch of tome increase as you
approach signal. Gain control allows pinpointing of source. Size 45mm x 54mm. 9V
RINE iaiiiseccceirdecks haiseagastecrevsapaded vclcdannadlseaviaeniasnnensdedeoutempanes £30.95

CD600 Professional Bug Detector/Locator

Multicolour readout of signal strength with variable rate bleeper and variable sensitivity
used to detect and locate hidden transmitters. Switch to AUDIO CONFORM mode to
distinguish between localised bug transmission and normal legitimate signals such as
pagers, Cellular, taxis etc. Size 70mm x 100mm. 9V operation ...............cc cee £50.95

QTX180 Crystal Controlled Room Transmitter

Narrow band FM transmitter for the ultimate in privacy. Operates on 180 MHz and
requires the use of a scanner receiver or our QRX180 kit (see catalogue). Size
20mm x 67mm. 9V operation. 1000M range............... cee ceeeeeeeeeeeeeseneeeeeeteeneeeeees £40.95

QLX180 Crystal Controlled Telephone Transmitter
As per QTX180 but connects to telephone line to monitor both sides of conversat-
tions. 20mm x 67mm. 9V operation. 1000M range.............eceeeeeeeeteeesteeeeeeees £40.95

QSX180 Line Powered Crystal Controlled Phone Transmitter

As per QLX180 but draws power requirements from line. No batteries required. Size
SZ2MM X S7MM. RANGE SOOM............cesccrscsscsrsrcsssrbecsseeracerssssssesersscssestsrsccseseveserace £35.95

QRX180 Crystal Controlled FM Receiver

For monitoring any of the ‘Q’ range transmitters. High sensitivity unit. All RF section
supplied as a pre-built and aligned module ready to connect on board so no difficulty
setting up. Outpt to headphones. 60mm x 75mm. 9V operation ...................00 £60.95

A build-up service is available on all our kits if required.

UK customers please send cheques, POs or registered cash. Please add
£1.50 per order for P&P. Goods despatched ASAP allowing for cheque
Clearance. Overseas customers send sterling bank draft and add £5.00 per
order for shipment. Credit card orders welcomed on 0827 714476.

OUR LATEST CATALOGUE CONTAINING MANY MORE NEW
SURVEILLANCE KITS NOW AVAILABLE. SEND TWO FIRST
CLASS STAMPS OR OVERSEAS SEND TWO IRCS.

THE WorkKsHopPs, 95 Main ROAD,

Dy BY [CTR

BAXTERLEY. NEAR ATHERSTONE,
WARWICKSHIRE

Tel/Fax:

CV9 2LE
01827 714476

VISITORS STRICTLY BY APPOINTMENT ONLY

424

Everyday with Practical Electronics, June 1995

_ EASY-PC, Schematic and PCB CAD
Over 18,000 Installations —
in 80 Countries World-wide!

) \| ¢ Runs on:- PC/XT/AT/

286/ 386/ 486 with
Hercules, CGA, EGA
or VGA display and
many DOS emulations.

e Design:- Single sided,
Double sided and
Multi-layer (8) boards.

e Provides full Surface
Mount support.

-e Standard output
includes Dot Matrix /
Laser / Ink-jet Printer,
Pen Plotter, Photo-
plotter and N.C. Drill.

e Tech Support - free.

e Superbly easy to use.

- Options:-500 piece Surface Mount Symbol Library £48,
1000 piece Symbol Library £38, Gerber Import facility £98.

Electronic Designs Right First Time?

Affordable Electronics CAD

LAYAN: NEW, Electro-magnetic Layout
Simulator. Includes the effects of the
PCB LAYOUT into your simulation.

Links to EASY-PC Professional XM and
ANALYSER Ill Professional.

STOCKIT: NEW, Comprehensive Stock £145.00
Control program for the small or medium
sized business

ELECTRO-MAGNETIC
Simulation ONLY £495

: t VEER DIS Prefess iana ingar Circuit Siwiater
; guration iprartes 00: —s ows

F 1ke3€X7,0N2 Gesin: 10.000 Mite nd:300.000 Wis stens K-Scale:les.

Bain (48) ex? Phase (*)

= (ol

EASY- PC Professional: From £195.00
me, lie Schematic Capture and PCB CAD.
Links to ANALYSER IIl and PULSAR.
2 (OEM PULSAR / PULSAR Professional: From £98.00

Digital Circuit Simulators

ANALYSER Ill / ANALYSER Ill Professional: From £98.00
Linear Analogue Circuit Simulators

Z-MATCH for Windows: | £245.00]
Smith Chart based problem solving program
for R.F. Engineers

FILTECH/ FILTECH Professional: From £145.00
Active and Passive Filter design programs.

EASY-PC: — £98.00
Entry level PCB and Schematic CAD

Prices exclude P&P and VAT.

0.06 9.6 ws a6 Lal
Plot:Gein Vector! Mee/fngle Grew fute fel.te:0 @

e TECHNICAL SUPPORT FREE FOR LIFE
e PROGRAMS NOT COPY PROTECTED.
e SPECIAL PRICES FOR EDUCATION.

For full information, please write, phone or fax:-

Number One Systems

UK/EEC: Ref. EVD, HARDING WAY, ST.IVES, CAMBS., ENGLAND, PE17 4WR.
Telephone UK: 01480 461778 (7 lines) Fax: 01480 494042 International +44 1480 461778

USA: Ref. EVD, 386 Foxborough Drive, Mountain View, CA 94041
, Telephone/Fax: (415) 968-9306

MASTERCARD, VISA, DELTA, SWITCH Welcome. —

Everyday with Practical Electronics, June 1995. | | 425

SUMMER 1995
CATALO

| FEATURE PROJECT:

ulti Function
EPROM Programmer

The Summer ’95 edition has 280 pages packed
with over 4000 products and now with news and
features including a full construction project.

» The computer section is greatly increased with new
ranges of equipment and accessories for PCs including:

-Mother boards, CPUs and SIMMs
CD ROM drives and hard drives
Sound cards, I/O cards, disc drive
cards and video cards
Mice, trackerballs and joysticks
Power supplies and cases

» Feature project for an EPROM programmer

» New 20MHz ‘scope from Leader, training systems from
Flight and an extended range of mobile phone batteries
and accessories from Uniross

» Latest addition from Velleman kits including a video
digitiser card

» 280 pages, 26 sections, over 4000 products from some
of the worlds finest manufactures and suppliers

» Available at most large newsagents, from 13th April, or
directly from Cirkit

» Send for your copy today!

Cirkit Distribution Ltd
Park Lane - Broxbourne - Hertfordshire - EN10 7NQ
Telephone: 01992 448899 - Fax: 01992 471314

426

OMNI ELECTRONICS

174 Dalkeith Road, Edinburgh EH16 5DX * 0131 667 2611

High quality stepping motor kits (all including
stepping motors) ‘Comstep’ independent control of
2 stepping motors by PC (Via the Parallel Port) with
2 motors and software.
Kit £67.00; ready built £99.00
Software support and 4-digital inputs kit: .00
Power interface 4A kit £36.00, power interface 8A
kit, £46.00
Stepper kit 4 (manual control) includes 200 step
stepping motor and control circuit £23.

We are now stocking a range of stepping motors and
kits to drive them — please ask for the stepping motor
data sheet for full information.

Inverter toroidal transformers 225VA 10-5-0-10-5V
primary 0-260-285V secondary £29.95
LEDs 3mm or 5mm red or green 7p each; yellow
11p each.
part vgs 1p each, £5.95 per 1000, £49.50 per

High quality photo resist copper
clad epoxy glass boards

Dimensions single-sided double-sided
3x4 inches £1.09 1.23
4x8 inches ; £2.99
6x12 inches : -
12x12 inches

RECHARGEABLE BATTERIES |
AA (HP7) 500mAH
AA 700mAH

D 4AH with solder tags
1/2AA with solder tags
AAA (HP16) 180mAH
AA 500mAH with solder tags.
C (HP11) 1:8AH

D (HP2) 1:2AH

PP3 8-4V 110mAH

Sub C with solder tags

1/3 AA with tags (Philips CTV)

Standard Charger, charges 4 AA cells in 5 hours
or 4Cs or Ds in 12 to 14 hours plus 1xPP3 y ry fe
or 4 cells may be charged at a time)

High power charger, as above but charges fee
Cs and Ds in 5 hours; AAs, Cs and Ds mustbe
charged in twos or fours £10.95

Nickel Metal Hydryde AA cells, high capacity

with no memory. If charged at 100mA and discharged

at 250mA or less 1200mAH capacity (lower capacity
for high discharge rates) £3.75

SPECIAL OFFERS - PLEASE CHECK
FOR AVAILABILITY
Stick of 4, 42mm x 16mm NiCad batteries, 171mm x
16mm dia., with red and black leads, 4-8V......£5.95
ag, hed grade Capacitors with screw terminals,
58000puF 60 £4.9
115V AC, 80V DC Motor, 4mm x 22mm shaft,
50mm dia. x 60mm long body (excluding shaft),
it has a replaceable thermal fuse and brushes
£4.95 each, £3.95 100+
7-segment common anode |.e.d. display, 12mm..45p
LM337K TO3 case variable peauiater 1.

+

GaAs F.E.T. low leakage current S8873 £12.95

each, £9.95 10+, £7.95 100+
BS250 p-channel MOSFET
BC559 transistor £3.95 per 100
74LS05 Hex inverter £10.00 per 100
Used 8748 Microcontroller £3.50
SL952 UHF Limiting amplifier, LC 16 surface

mounting package with data sheet 1

PRICES
Oa

x MAIL ORDER - generally by x
RETURN OF POST

* FRIENDLY SERVICE *

OPEN:
Monday-Thursday 9.15 - 6.00
Friday 9.15-5.00
Saturday 9.30-5.00

The supplier to use if you're looking
for:—

£1.25 each; 90p 100 +
10p 100+, 6p 1000 +
Sinclair light gun terminated with a jack plug and
PP3 clip gives a signal when pointed at 50Hz
flickering light, with output waveform chart ..£3.95
DC-DC converter, Reliability model, V12P5, 12V input
5V 200mA out, 300V input to output isolation, with
£4.95 each or pack of 10 - £39.50
Hour counter used 7-digit 240V a.c. 50Hz...£1.45
QWERTY keyboard, 58-key good quality
switches, new
Airpax A82903-C large stepping motor 14V
7-5° step, 27 ohm, 68mm dia. body, 6.3mm
£8.95 or £200.00 for a box of 30
Polyester capacitors, box type, 22.5mm lead pitch
O0-9unF 250V d.c. 18p each, 14p 100+ , 9p 1000 +
1pF 250V d.c. 20p each, 15p 100 +, 10p 1000 +
1uF 50V bipolar electrolytic axial leads, 15p each,
7:5p 1000+
0-22u.F 250V polyester axial leads, 15p each,
100+ 7-5p each
Polypropylene 1,f 400V d.c. (Wima MKP10)
27.5mm pitch, 32 x 29 x 17mm case, 75p each,
60p 100+
Philips 123 series solid aluminium axial leads,
33yF 10V and 2.2uF 40V 40p each, 25p 100 +
Philips 108 series long life 22u.F 63V axial
30p each, 15p 1000 +
Multilayer AVX ceramic capacitors, all 5mm
pitch, 100V 100pF, 150pF, 220pF, 10,000pF
(10n) 10p each, 5p 100+ , 3.5p 1000 +
500pF compression trimmer p
40uF 370V a.c. motor start capacitor (dialectrol type
containing no p.c.b.s)........... £5.95 or £49.50 for 10
Solid carbon resistors, very low inductance, ideal
for r.f. circuits, 270hm 2W, 68o0hm 2W 25p each,
15p each 100+
we have a range of 0:25W, 0:5W, 1W and 2W
solid carbon resistors — please send SAE for list
P.C. 400W PSU (intel part 201035-001) with
standard motherboard and 5 disk drive
connectors, fan and mains inlet/outlet
connectors on back and switch on the side (top
» for tower case) dims. 212 x 149 x 149mm
excluding switch, £26.00 each, £138.00 for 6
MX180 Digital Multimeter 17 ranges, 1000V
d.c. 750V a.c. 2Mohm 200mA transistor Hfe 9V
and 1.5V battery test £12.95
AMD 27256-3 EPROMS £2.00 each, £1.25 100 +
DIP switch, 3PCO 12-pin (ERG SDC-3-023)
60p each, 40p 100 +
Disk Drive Boxes for a 5:25 disk drive, with room
for a power supply, light-grey plastic 67mm x
268mm x 247mm £7.95 or £49.50 for 10
Handheld Ultrasonic remote contro! £3.95
CV2486 gas relay 30mm x 10mm dia. with
3 wire terminals, will also work as a neon
20p each, £7.50 per 100
All products advertised are new and unused unless
otherwise stated.

Wide range of CMOS TTL 74HC 74F Linear
Transistors kits, rechargeable batteries, capacitors,
tools etc. always in stock

Please add £1.95 towards P&P. VAT included in all pri

JPG ELECTRONICS

276-278 Chatsworth Road
Chesterfield S40 2BH
Access/Visa Orders:

Tel: (01246) 211202 Fax: (01246) 550959
Callers welcome

Everyday with Practical Electronics, June 1995

LOADS MORE SUPER SURPLUS OFFERS!

POWER SUPPLIES|"™ “a

xcellent condition (less than a year old!) the unit is
otally enclosed in a steel case 340x 152x 152mm...
has an IEC mains inlet with suppressor fitted and
on/off mains rocker switch, and all outputs are on
jeads with power connectors. Now for the spec:
Inputs: 100-120V @ 10A or 200-240V @
6A, Outputs +5V @ 40A; +12V @ 165A; -6V
@ 1A; -12V @ 1A switchable on front panel.
A 12Vde 120x120mm fan is fitted at the rear of
= the case. Current distributor price of a unit of this
“ilk would be around £400. Save 92%

Oe Our Price £29.95

Another fine selection of SMPSUs recently anived These are all ex: , but in
order. All are 115/230 Vac input. Do not exceed maximum wattage

X3216 33yF 250V size 25x16 6/£1.00
X3191 100uF 160V size 40x25 3/£1.00
X3189 100uF 400V size 31x25 DP 3.89. £2.00
X3221 150uyF 385V sie 48x36 DP 3.88. £2.00
X3190 470uF 350V size 51x30 DP 6.00. £3.00

AERIAL REEL

25820 The story behind these is that they were going to
be sent to Metal Box shareholders to try and stave off a
bid. However, before they could be posted, a takeover
was announced - so now we've got them. The metal box
measures 200x 135x45mm and is finished in an attractive
blue and gold pattern. Inside, the tie is English made
100% pure silk in royal blue (sample of material on re-
quest) with a ci discreet logo (ideal if BM or MB are
£3.95

X6098 6V Constant cur-
rent ni-cad charger for up
to 4 1.2V cells. Red LED
indicates charging at
100mA and after 14 hrs,
the green LED illuminates

= =: and charging stops.
T104BA 10m aerial reall
Wind-on reel. Reel contains a builtin TV/radio splitter |25962 Astec SA70A-3400 70W unit. +5V8A: +12V 26966 Famell NOS5P210 55Wunit. +5V2.5A; +12V Great Value
| Pere 1A £4.96
£595. NOW £3.60 3.5A; -12V 1A; 5VO.7A. £14.95
ee! LAB BIOTA, EAAOR. at £3.95

25963 Hitron HSG40-31 40W unit +5V 3A: +12V 25967 Astec SA40-1304 44W unit. +5V 5A; +12V
O5A; -12V0.5A. £14.96 2A; -12V0.2A £4.96

Some ex-equip axial flow fans, all in good working order
at substantial savings over new models.

23866 Smallest fan we've seen! 42x42 by just 10mm
thick! Made by Nitev, model TA150DC. Rated 12V DC
0.11A Only £3.00

X6016 Papst (mostly) 612L 60x60x25mm 12V de
(6-15V) 0.7W fans. List is 27.47.

Our price £3.00

BO47E A
specifically for car, truck and bus use with a coverage volume
of 14m3. Removes unpleasant smells, airbome dust,
bacteria, tobacco smoke, etc. Supplied with a double sided
self adhesive pad. Power 12Vde 1.8W Dims: 110x65mm
Price £2.95

X9007 Superb BRAND NEW 200W Farnell PSU - 25968 Astec SA30-1305 30W unit. +5V 2A; +12V
their list price over £200! +5V 285A; +24V 05a; 2A -12V0.3A £3.96
+12V 3A; -12V 1A. £19.96

Ring, wnte, fax or call in for our scintillating NEW 64 page Spring
Supplement, listing stacks of surplus stock at super prices!

Our 1995 Catalogue, 192 pages of regular stock is just £2 post paid.

NEW! - The Budget CD & Tape Catalogue - 48 pages of tapes (mostly £ 1.99) and CDs (mostly £2.99)
Much of our surplus stock is never included in these ads - the only way to be ‘in the know’ is to
become a Subscriber. This pnvleged group of customers receive The Greenweld Guardian every
month with details of all our new surplus stocks. Don’t miss the Bargains (and there are plenty) -
become a Subscriber today! There’s a free prize draw every month, the occasional free gift and
the odd competition, too. All for just £6 a year (E 10 o‘seas) - or become a GOLD Subscriber with
the additional benefit of 5% discount on all goods* + half price postage for £12 (£20 o’seas)

‘Not bulk or sale prices “not o’seas
GOTTFTED!

IBM PS2 PC

: XX9006 This PC is! The hard disk, floppy and all bnards have bee
: taken out, leaving only a 12V fan, speaker, 6V lithium battery and
' @ very nice totally enclosed 94 watt power supply with the fol
: lowing spec: -12V@410mA; +12V@2A; +5V@ 2A So all we're
: asking for this magnificent lump of machinery is just: £12.96

MULTIPLEXER

X9009 Two part instrument case 445x330x 105mm in
blue aluminium containing a multiplexer PCB 290x195mm
with Z80B + 7 support chips, 27C512 and 8x41256-
12DRAMs all in sockets; also 25+ LS chips, MHz xtal osc
etc. There are also 10x32 way DIN sockets, 6 with
matching plugs. Three cl have V24 visi: Lgl 2
each containing 4x 1489 ICs and terminating in a ay ee

socket. There’s a 5OW switch mode PSU, too - and a 1 2 os ORR Cee Mais Almanac. ;
60x60x25mm 12V fan. What a lot you get! - all for just. Key Clip Art (5000 TIFF images),

Phone Nos: SALES 01703 S56565. Technical 305000, Key Fonts,
Accounts 231003; Fax (All depts) 236307; FaxOnDemand 236315" |Key Gourmet,

*To obtain latest lists, info etc, just dial 01703 236315 from any fax machine and follow instructions. [MPC Vizard,

Single prices in this advert include VAT; Quanti don't.
P&P €4 per order (£9.50 next day). Min Credit Card Ba: Otfelel Sport Image - World Cup 1994,
UFO (spooky),

Orders welcome from Education - min
accepted by cheque, PO, cash, book {Slob Zone 3D,
: tokens,

We're always looking for new
parcels of surplus goods - send
details to the address below

YO10AC Cast steel miniature bench vice. 66mm i jaws
open to GOmm. Two bolt fixing to bench. Red enamel
finish. Dims 100x65x70mm. Only £4.95

CSL20 Great offer on SCART leads! These are 1.5m
long with all pins connected. Super Price! Just £2.00

CD-ROMs

Just taken delivery of a great new collec-
tion of software on CD-ROM. Prices start
from £6.95 for individual disks, but there’s
even a better deal on offer at present -
11 CD-ROMs for just £29.95.

This collection from Softkey includes the
- following titles:

CNN Newsroom,

25964 Audix HM230S/Tact UDM100 professional
dynamic mic with on/off switch and cardoid character-
istics. 5m lead with XLR skt fitted mic end. Impressive
spec! Supplied with clip and adaptor, individually boxed.
List price £44.06. Our Price £19.95

99P CLOCK

COA
2,

Reece ory,

Z3873 Super Offer! A complete clock in a Geen I
40x25mm module. IV operation with sleep &
snooze, 24hr alarm, PM, colon and alarm ELECTRONIC

indicators. Sim Slow setting contr
5 display theaigghas shes selectable, a COMrOMNT> ft) have enormous stocks. We are |Game Empire (over 250 games)

brightness control. Full info supplied. Alli this SWITCH Be pee fd Reda 6-5.30 Mon-Sat. Come | cond for our latest lists which gives full

for 99p! 27D Park Road Southampton $015 3UQ_ |cetails of everything available!

invoice charge £15. Payment
witch, » Access, Visa,
Connect. Our stores (over 10,000 sq _|“\te0 Cube and

Everyday with Practical Electronics, June 1995 427

BREADBOARDS — CAPACITORS — SOLAR CELLS -

ewes, RRR aa ee (oes pee) GED QemetStse Gey) GuaeA
eam Gar aay Genea® Gare PSE GE Qeaarecsrs? Gece Ge
a ae eS eS SS SSS SS eS Se SS HEATSHRINK - ETC
— = — = = scm ee oe = os SOLAR CELL 2 voit 150mA max, size 60 x 100mm £1.35 each 5 for £6
— ae 2a. 33 = a — 2 on == | BNC SOCKETS 50 ohm single hole fixing 50p each 10 for £4.00
oo oman: ments oe ome = ~~ os » oom = os
a oon oe com one — == - pay ow a bow 2 = MERCURY TILT SWITCH BREADBOARD
ama - sh =-s on — .« = = = = Standard on/off £1.00 each 173 X 65mm 840TP £5.25 each
a=. cn bo: ae \om oom cms Ge =. -——- om — = 4 Contact (Directional) £1.50 each TEXTOOL ZIF SOCKET
Sane Ls FEED SUENCS Gt SS SK. SA a CMS PIEZO VIBRATION SENSOR 28 pin zero insertion socket £5.95 each

with data sheet £1.00 each

ELECTRONIC COMPONENTS

PROJECT BOXES A range of high quality boxes moulded in black high impact ABS,
easily drilled or punched to produce a professional looking end product
L H

EPROMS 27C256 - 30. Once programmed but never used eprom. Mounted on a
plastic carrier, can easily be removed from the carrier or used with a low insertion
force socket. 27C256 £1.00 each 6 for £5.00
Suitable low insertion force socket 28 pin

40p each 3 for £1.00

Ly A ke at dap MULTITURN PRESETS 20mm RECT, 1K, 5K, 10K, 20K, 50K, 100K 1MO.
. 40p each, 3 for £1.00
Th cAI 57 «220.92 Gl aeubibionaiatons 100db PIEZO SOUNDER : :
MB1 79 61 40 £1.36 0-12 Ohm 5W 30p each _ 2KHz note, 3-12V d.c. 40Ma, 45mm dia. x 26mm £1.76 each
MB2 100 76 41 £1.47 0:10 Ohm 25W 80p each SOUND BOMB Two tone alarm sounder incorporating four piezo elements in white
MB3 118 98 45 £1.71 1-00 Ohm 50W £1.00 each plastic box. 100db 12V D.C. £5.99
MB4 216 130 85 £5.19 2:20 Ohm 50W £1.00 each MINIATURE HORN SIREN 100db two-tone Piezo siren 12V D.C. £5.17
MB5 150 100 60 £2.35 3-9 Ohm 50W £1.00 each - VIBRATION SENSITIVE ALARM BOARD WITH PIEZO SOUNDER
MB6 220 150 64 £3.95 10:00 Ohm 100W £2.00 each Originally a bike alarm. There is a short delay after activation then the piezo
MB7 177 120 83 £3.42 2:2 kOhm 50W £1.00 each sounder operates for a preset period. £3.76 each
MB8 150 80 50 £2.22 or the above alarm board with custom designed case, fixing clip and keyswitch £9.95
All sizes are in millimetres INFRA-RED BREAK BEAM Transmitter and receiver p.c.b. with 2 lens assemblies.
MICRO SWITCH roller arm operation spdt 40p each BULKLEDS | 12V d.c. supply. These are ex-installation units and are not guaranteed to be
MINIATURE TOGGLE SWITCHES OFFER working. £4.96 pair
sali 60 sis 500 5mm round | FLOURESCENT LIGHT INVERTOR. Drives an 8 watt tuve directly from 6V d.c. Data
p peach spdt3 position c/off 70p each lied £4.50 h
dpat 70peach _dpdt3 position c/off 80peach | REDLEDS | Suplie -50 eeac

spdt 3 position c/off biased both ways 70p each £25.85

dpat 3 position c/off biased one way 80p each

spdt biased 60p each

£1.00 BARGAIN PACKS

MINIATURE PUSH TO MAKE SWITCH 50p each

DIL RELAYS 5 volt dp/changeover 60p 10 for £5.00 SUB-MINIATURE TOGGLE SWITCHES
12 volt dp/changeover 80p 10 for £6.00 P.C.B. Mounting

RELAY 10 amp contacts sp/changeover 12 volt coil £1.20 each BO1 S.P. on 4 for £1.00

CAR HORN RELAY in metal can with fixing lug,
s/poleon10ampcontacts £1.00 each6 for £5.00
20 AMP RELAY dp on 12 voit coil
£1.50 each 4 for £5.00
REED RELAY 12 volt . 50p each 10 for £4.00
240 VOLT AC RELAY. 3-pole c/o 10 amp
contacts £1.50 each 4 for £5.00

SEMICONDUCTORS - TRANSISTORS - ICS - DIODES - REGULATORS - ETC

VOLTAGE REGULATORS
1 amp 7805/7812/7815 all 33p each. 7905/7912/7915 all 39p each SPECIAL OFFER
PROJECT BOX

2 amp 78S05/78S212 54p each
In white

‘D’ CONNECTORS
plug socket cover
9pin 30p 30p 35p
15pin 40p 40p 35p
25pin 50p 50p 40p

100mA 78L05/78412/78L15 all 26p each. 79L05/79L12/79L15 all 29p each
Adjustable LM317T 70p each. LM723 29p each, L200 £1.28 each
Transistors TIP2955 70p each, TIP 3055 70p each

2N3053 29p each, 2N3055 70p each, 2N4403 28p each, 2N3819 40p each

~MICRO IC’S - Z80A CPU £1.20; Z80A PIO £1.50; Z80B SIO-1 £4.00;
SAB80C535-N £11.75; PCB80C31BH-16P £2.35.

OPTO DEVICES -— LEDS - ETC
5mm rnd red/yellow/green/amber 10p each 12 for £1.00 any mix
5mm rnd high brightness red/green 20p each 6 for £1.00 any mix
5mm rnd flashing red 60p each, yellow/green 70p each
5mm rnd bi-colour 35p each, tri-colour 45p each
LED mounted in chrome bezel red, yellow or green 30p each, 4 for £1
LED mounted in a black bezel red only 25p each, 5 for £1.00
PLASTIC BEZEL for 5mm rnd leds 10 for 40p
High brightness bi-colour |.e.d., rectangular, red/green, two leads 40p each

TEMPERATURE PROBE ,
High quality probe precision temperature sensor. Mounted in a plastic covered probe
with a 1 meter coiled lead. Temp. range — 40 to 150°C. Resistance at: 150°C 188.3 ohms;
25°C 10.0 kohm and at — 40°C 336.5 kohm. The original price of these probes was over

high impact ABS
50 x 70 x 25mm
60p each 10 for £5.00

£24.00. OUR PRICE £3.76 with data
| UNIVERSAL BELL TIMER

10 or 20 minute bell cut off + ve or — ve trigger” timed relay contacts. £4.96
ALARM CONTROL UNIT

Single zone alarm control unit built into a domestic light switch box. Ideal for home,
caravan, boat, garage, shed etc.

Facilities: - Normally closed loop for pir sensors, door/window contacts etc. Normally
open loop for pressure mats. 24-hour loop for personal attack button Visual indication
that the system is operational. Automatic SIREN

bllletad rs rib op Ne _ 12 volt de for external use 115db

PRICE COMPLETE WITH FULL INSTRUCTIONS £8.95
SUB-MINIATURE PASSIVE INFRA-RED SENSOR ONLY £7.95

Brand new passive infra-red sensor, measures only

33mmMW x 24mmH x 29mmD. Logic level output. Full data

and application notes supplied.

EX INSTALLATION PASSIVE INFRA-RED SENSORS TESTED WORKING!
NEW LOWER PRICES !

Type 1. Measures 130 x 70 x 50mm with walk test led, relay i i

and tamper protection. 12 volt dc supply required £6.50 each
Type 2. As above but a smaller unit 90 x 75 x 50mm £8.50 each
Type 3. Ceiling mounting passive, infra red sensor 360° detection, 12V d.c. supply relay
output, tamper circuit and pulse count option. Data supplied. £11.75 each

Please note: There may be variations in the size :
of the above passive infra red sensors depend- oceans ane
ing on stock at the time of ordering. But the unit €1.10 each
will certainly be within the stated sizes. JUNCTION BOX

60

hite 6
DUAL TECH SENSOR Microwave and passive eowe
infra-red combined. Separate ied indication for each function. Measures 120 x 75 x
50mm. 12 volt d.c. supply, Relay output. Tamper protection. £21.15 each

£8.95

CCD CAMERA
PCB CCD CAMERA. Mounted in a plastic dome.
12V d.c. supply. Composite video output. Fitted
with a 2-9mm lens. Mono. 0:5 lux. £98.70

428

BO2 D.P. on 3 for £1.00

BO3 3x D.P. 3 pos, centre off

BOO4 DIL SWITCHES 4-way S.P. on 3 for £1.00

BOOS DIL SWITCHES 8-way S.P. on 2 for £1.00

BOO6 DIL SWITCHES 12-way 90° sp on 2 for £1.00

BOO7 12 x PP3 BATTERY SNAPS

BOO8 1 x CAPACITOR 1 FARAD 5.5 VOLT 20mm dia. x 7mm high

BOOS INSTRUMENT KNOBS (0.25” SHAFT) High quality grey plastic knob, collet
fixing 15mm dia, 5 for £1.00

BO10 as above but 29mm dia, 3 for £1.00

BO11 4x MAGNETIC EARPIECE 8 ohm with 3.5mm plug

BO12 4x 28-WAY TURNED PIN DIL SOCKET

BO13 15 x 12 VOLT WIRE-ENDED LAMPS

BO14 8x2 PIN DIN PLUGS screw terminal connection

BO15 2x LIGHT DEPENDENT RESISTOR Less than 200 ohms in daylight, greater
than 10 megohms in darkness

BO16 1x KEYPAD 20-key in 5 x 4 matrix bubble type switch contacts

BO17 2x PIEZO BUZZERS approx 3 to 20 volt d.c.

BO18 5 x 78M12 VOLTAGE REGULATORS positive 12V 500mA

BO19 4x TLO82CP bi-fet op-amps

BO20 20 x ASSORTED LEDS full spec. various shapes and sizes

BO21 3x INFRA-RED DIODE TX/RX PAIRS made by Honeywell(no info)

BO22 4 x CONSTANT CURRENT LED 5mm round, red 2-18V d.c. or a.c. nominal
14mA

BO23 50 x IN4148 diode

BO24 2x INFRA-RED TRANSISTOR FPTS1 33 |

BO25 5x DIACS

BO26 3 BDX33C 10 amp 100V npn transistor

BO27 12 x 2N3702 Transisto:

BO28 12 x 2N3904 Transistor

BO29 12 x BC337 Transistor

BO31 2x MAN6610 2 digit 0.6” 7 segment display Com anode, amber

BO32 3x PHONO TO PHONO LEAD 63cm long

BO33 15 x RECTANGULAR RED LEDs 6 x 6 x 2mm stackable

BO34 1x PHOTO SENSITIVE SCR mounted on a PCB, data sheet supplied

BO35 4x IEC Panel Mounting Mains Plug Snap fix

BO36 5 x ASSORTED PIEZO TRANSDUCERS

BO37 5 LENGTHS OF HEATSHRINK SLEEVING 8mm dia. 400mm long

BO38 25 x CERAMIC DISC CAPACITORS 0.1 mfd 63V

BO39 15 x MONOLITHIC CERAMIC CAPACITORS 0.1 mfd 63V, in a dil package

BO40 25 x ASSORTED ELECTROLYTIC CAPACITORS PCB mounting useful values

BO41 25 ASSORTED PRE-SET RESISTORS

BO42 6x 3-S5mm LINE JACK SOCKETS (mono)

BO43 6 x3-5mm JACK PLUG (mono)

BO44 8 x 35mm CHASSIS SOCKET (mono)

BO45 2x TRIACS 800 volt 8 amp

BO46 12 x BC213L Transistor

BO47 12x MIN SLIDE SWITCH dpdt

BO48 15 x MIN CERMET TRIMMER POTS (good range of values)

BO49 1x PCB WITH TWO LARGE LEDS 15mm square, one red and one green

BO50 1x 12V DC RELAY 4-pole c/o with plug in base

BO51 4x LM324 quad op-amps

BOS2 4x 555 Timer

BO53 5x741o0p-amp .

. BOS4 25 x IN4001 diode

BO55 20 x IN4007 diode

BOS56 1x SLOTTED OPTO

BO57 1x DACO8 Digital to analogue convertor with data
BO58 4x OPTO ISOLATOR

BO60 3x C106D Thyristor

BO61 5 x 78M05 VOLTAGE REGULATORS positive 5 volt 500mA
BO62 10 x TACTILE SWITCHES

BO63 25 x 0:01MFD 50V CERAMIC DISK CAPACITORS
BO64 7 CMOS 4001B IC’s

BO65 6 CMOS 4011B IC’s

BO66 15 x VARIOUS LOW PROFILE DIL SOCKETS
BO67 15 VARIOUS TANTALUM BEAD CAPACITORS

. BO68 30 VARIOUS POLYESTER CAPACITORS

Please use order code when ordering the bargain packs.
Please make cheques and postal orders payable to Mailtech.
All prices include VAT. Please add £1.00 postage to all orders.
Telephone enquiries between 10a.m. and 5 p.m.
Tuesday to Thursday.

Fax and answerphone at other times on 0158 474475.

Dept EE, Maiultech
| ad OM =lod am Bom Serel leh’
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LON Me celine Ati mile b mel el am C212) elalelalomy (Ulaalelzi maul meat: late [=m co

01584 831475

Everyday with Practical Electronics, June 1995

aw

HART KITS give you the opportunity to build the
very best engineered hifi equipment there is,
designed by the leaders in their field, using the best
components that are available.

Every HART KIT is not just a new equipment ac-
quisition but a valuable investment in knowledge,
giving you guided hands-on experience of modern
electronic techniques.

In short HART is your ‘friend in the trade’ giving
you, as a knowledgeable constructor, access to bet-
ter equipment at lower prices than the man in the
street.

You can buy the reprints and construction manual
for any kit to see how easy it is to build your own
equipment the HART way. The FULL cost can be
credited against your subsequent kit purchase.

Our list will give you full details of a// our Audio Kits,
components and special offers.

INTRODUCING

The Hart ““Chcara

Single-Ended Class “A” Headphone Amplifier.

Most modern high fidelity amplifiers either do not
have a headphone output facility, or this may not be
up to the highest standard.

The new Hart ‘‘Chiara’’ has been introduced as
an add-on unit to remedy this situation, and will
provide two ultra high quality headphone outlets.
This is the first unit in our 2000 Range of mod-
ules to be introduced through the year. Housed in
the neat, black finished, Hart Minibox it features
the wide frequency response, low-distortion and
“musicality” that one associates with designs from
the renowned John Linsley Hood. ;

Both outputs will drive any standard high quality
headphones with an impedance greater than 30
ohms and the unit is ideal for use with the Senn-
heiser range. A signal link-through makes it easy to
incorporate into your system and two extra out-
puts, one at output level and one adjusted by the
Volume control are available on the back panel. The
high level output also makes a very useful long-line
driver where remote mounted power amplifiers are
used. Power requirements are very simple and can
be provided by either of our new ‘‘Andante”’ power
supplies. Use the K3565 to drive the ‘‘Chiara”’ on its
own, K3550 if driving other modules as well.

Volume and Balance controls are provided and as
befits any unit with serious aspirations to quality
these are the ultra high quality Alps ‘“‘Blue Velvet”
components.

Very easily built, even by beginners, since all
components fit directly on the single printed circuit
board and there is no conventional wiring what-
soever. The kit has very detailed instructions, and
even comes with a roll of Hart audiograde silver
solder. It can also be supplied factory assembled
and tested.

Selling for less than the total cost of all the com-
ponents, if they were bought separately, this unit
’ represents incredible value for money and makes
an attractive and harmonious addition to any hifi
system.

K2100 The total cost of a complete set of all com-
ponents to build this unit is £126.37. Our special

Mi sctiphacaeiauiecs soiwirrcsdessiaienastesinias eeivesasuestiesaeanes £109.50
K2100SA Series Audiophile, with extra selected
COMPOMNENMS...............ccceceeeessssesssseseeeeeeeeeeeeeeaaees £112.46

HART TC1D Triple Purpose TEST CASSETTE
Now available again and even better than before!
Our famous triple purpose test cassette will help
you set up your recorder for peak performance after
fitting a new record/play head. This quality preci-
sion Test Cassette is digitally mastered in real time
to give you an accurate standard to set the head
azimuth, Dolby/VU level and tape speed, all easily
done without test equipment.

TC1D Triple Purpose Test Cassette.................... £9.99

NEW BOOK
And now, hot off the press, yet another classic
from the pen of John Linsley Hood. Following the
ongoing enormous success of his ‘‘Art of Linear
Electronics” the latest offering is the all-new
edition of ‘‘Audio Electronics’, now entirely
re-written by the master himself.
Underlying audio techniques and equipment is a
world of electronics that determines the quality of
sound. For anyone involved in designing, adapt-
ing or using digital or analogue audio equipment
understanding electronics leads to far greater
control over the reproduced sound.
The subjects covered include tape recording,
tuners, power output stages, digital audio, test
instruments and loudspeaker crossover systems.
John’s lifetime of experience and personal in-
novation in this field allow him to apply his gift of
being so familiar with his subject that he can write
clearly about it and make it both interesting and
comprehensible to the reader.

Containing 240 pages and over 250 line illustra-

tions this new book represents great value for
money at only £18.99 plus £2.50 postage. Send or
telephone for your personal copy now.

ALPS ‘GlucVeluet

Precision Audio Controls

To fulfil the need for ultra high quality controls we
import a special range of precision audio pots in
values to cover most quality amplifier applications.
All in 2-gang stereo format, with 20mm long 6mm
diam. steel shafts, except for the 50K Log which is
25mm x 6mm. Overall size of the manual pot is 27W
x 24H x 27Deep, motorised versions are 72:-4mm
Deep from the mounting face. Mounting bush for
both types is 8mm diameter.

Now you can throw out those noisy ill-matched
carbon pots and replace with the real hi-fi com-
ponents only used selectively in the very top flight of
World class amplifiers. The improvement in track
accuracy and matching really is incredible giving
better tonal balance between channels and rock
solid image stability.

The motorised versions use a 5V DC motor coupled
to the normal control shaft with a friction clutch so
that the control can be operated manually or electri-
cally. The idea of having electrically operated pots
may seem odd, archaic even, but it is in fact the only
way that remote control can be applied to any serious
Hi-Fi system without loss of quality. The values
chosen are the most suitable available for a low loss
passive volume and balance control system, allow-
ing armchair control of these two functions. _

Our prices represent such super value for pots of
this quality due to large purchases for our own kits.

MANUAL POTENTIOMETERS

OT IY cess savissiesssssoiscdcananamrnraningcoase £15.67
2-Gang 10K, 50K or 100K Log. ............ceeeeeeeees £16.40
2-Gang 10K Special Balance, zero crosstalk and
DTT CT NR essisccsiisiaseisccsemssuaseiiecctitanincees £17.48

MOTORISED POTENTIOMETERS
2-Gang 20K Log Volume Control £26.20
2-Gang 10K RD Special Balance, zero crosstalk and

less than 10% loss in centre position............... £26.98
. REEL TO REEL HEADS
BOOM 274 RIP TOOMI. .2.....00scecavenssvescoscevenssosssasees £16.84

We have a few erase heads to suit which can only
be supplied when 2 R/P heads are purchased £36.80

TAPE RECORDER CARE PRODUCTS
DEM1 Mains Powered Tape Head
Demagentizer, prevents noise on playback

due to residual head magentisation................... £4.08
DEM115 Electronic, Cassette Type,
CTT BE so iiccisins doscareneanesecnnteentninticaesnksgonnine £8.61

Send or ‘phone for your copy of our FREE List of these and many other Kits & Components. Enquiries from Overseas
customers are equally welcome, but PLEASE send 2 IRCs if you want a list sent surface post, or 5 for Airmail.

get your order on its way to you THAT DAY.

QUALITY
AUDIO KITS

Ordering is easy. Just write or telephone your requirements to sample the friendly and efficient HART
service. Payment by cheque, cash or credit card. A telephoned order with your credit card number will

Please add part cost of carriage and insurance as follows:-INLAND Orders up to £20 - £1.50,
Orders over £20 - £3.50. Express Courier, next working day £10.
OVERSEAS - Please see the ordering information with our lists.

Everyday with Practical Electronics, June 1995

24 hr. SALES LINE [ALL PRICES

HART AUDIO KITS — YOUR VALUE FOR
MONEY ROUTE TO ULTIMATE HI-FI

LINSLEY HOOD ‘SHUNT FEEDBACK’ RIAA
MOVING COIL & MOVING MAGNET
PICKUP PREAMPLIFIERS

The HART K1450 Magnetic pickup preamplifier kit
features a totally discrete component implementa-
tion with a specially designed low input impedance
front end and the superior sound of the Shunt Feed-
back circuitry. High quality components fitting to an
advanced double-sided printed circuit board make

this a product at the leading edge of technology that

you will be proud to own. Nevertheless with our step
by step instructions it is very easy and satisfying to
assemble. The higher current consumption of this
unit means that it is best powered by our new
Andante Audio Power Supply, itself an advanced
piece of technology in a matching case. This sup-
plies the superbly smoothed and stabilised supply
lines needed by any sensitive preamplifer and fea-
tures a fully potted Hi-grade toroidal transformer
along with a special limited shift earth system for
hum free operation. The K1450 is suitable for all
moving coil and moving magent transducers this
unit is especially recommended for, and will extract
the very best from the modern generation of low
output high quality moving coil transducers.

K1450 Kit, complete with all parts ready to
assemble inside the fully finished 228mm x 134mm x
63mm _ case. Kit includes full, easy to follow,
assembly instructions as well as the Hart Guide to
PCB Construction, we even throw in enough Hart
Audiograde Silver Solder to construct your kit!

Sa ce eh wena staan aaa Phased aaagia £111.58

K1450SA Series Audiophile version with selected

NIT iiss vosssiaseesctxinaeccsuecnciceinisorsonions £133.94
HIGH QUALITY REPLACEMENT

CASSETTE HEADS

LER Sitacrnr

Do your tapes lack treble? A worn head could be the
problem. For top performance cassette recorder
heads should be replaced every 1,500 hours. Fitting
one of our high quality replacement heads could
restore performance to better than new! Standard
inductances and mountings make fitting easy on
nearly all machines (Sony are special dimensions,
we do not stock) and our TC1 Test Cassette helps
you set the azimuth spot on. As we are the actual
importers you get prime parts at lower prices, com-
pare our prices with other suppliers and see! All our
heads are suitable for use with any Dolby system
and are normally available ex-stock. We also stock
a wide range of special heads for home construc-
tion and industrial users.

HC80 NEW RANGE High Beta Permalloy Stereo
head. Modern space saver design for easy fitting
and ‘lower cost. Suitable for chrome, metal and
ferric tapes, truly a universal replacement head for
everything from hi-fi decks to car players and at an

incredible price tOO!............. ce ceeeeeeeeeeeeeeeeeees £11.70
HRP373 Downstream monitor combi head...... £62.59
HQ551A 4-Track R/P............ccccceccccccesssseeeeeeeeeeeees £8.75
HQ551S Sony Mount 4-Tr. R/P............cceeeeeeeeeee £14.90
*HQR560 Rotary Base 12-5mm R/P/E................ £21.90
HQR570 Rotary Base 15mm R/P/E.................... £22.59
HQR580 Rotary Base 12:5mm R’P.................... £14.29
HART Classical CD’s.

Top quality, Full Digital (DDD), over 100 titles from
only £1.99! Ring or send for your list!

TECHNICAL BOOKSHELF

We stock a good range of books of interest to the
electronics and audio enthusiast, including many
reprinted classics from the valve era. Some were in
last months advertisement, but see our list for the
full range.

New this month is the GEC Valve designs book at
£18.95, and the VTL Book, a modern look at valve
designs, £17.95.

(01691) 652894) uKjecvar ed
wna

ELECTRONICS
SHOP OPEN 9-5 MON-FRI. CLOSED SAT --- OFFICIAL ORDERS WELCOME

a ees |

Man ae ety

EPE MICROCONTROLLER,
P.l. TREASURE HUNTER!

I The latest MAGENTA DESIGN - highly #
I stable & sensitive — with uC control
I of all timing functions and advanced I

LTD

135 Hunter Street
Burton-on-Trent
Staffs. DE14 2ST

Output, efficient circuit.

1000V & 500V INSULATION Fspacewriter
TESTER

Superb new design. Regulated

Dual- y UP to 16 digits long. Comes pre-loaded
scale meter, compact case. Reads

All Prices
include V.A.T.
Add £3.00 per

Tel 01283 565435 Fax 546932 EE156 order p &p

An innovative and exciting —
project. Wave the wand through “™ie
the air and your message appears. “™™
Programmable to hold any message

with “MERRY XMAS". Kit includes

I pulse separation techniques. up to 200 Megohms ee,
I @ New circuit design 1994 i Kit includes wound coil, cut-out PKIT ° ”
, Si ntalssiaierieees £16.99
@ High stability i case, meter scale, PCB & ALL on oe on on on on on on on a a
I drift cancelling i COMPORSITS. 12V EPROM ERASER
I @ Easy to build ! SUL. Ete EoD trips tan 20 sinines Oyeteies fem a2) ppl
& use i 400mA). Used extensively for mobile work - up-
I ®No ground i M OS FET M k| | VAR IAB LE B EN C H perl ae sia ‘he fleld a Ales adic:
tional situations where mains supplies are not al-
1 effect, works | POWE R S U P P LY Q- 25V _ DA. lowed. Safety interlock prevents coniact with UV.
1 in seawater y Based on caeoitige ge kt and KIT 790 £28.51
preserving all the features, «§-_ «sty, NE Mette ‘
; e oe but now with switching MOSFET 25V 2.5A
f pre-regulator for much POWER SUPPLY
i non-terrous I higher efficiency. Panel High performance design has made this one of our
i metals | meters indicate Volts and classic kits. Two panel meters indicate Volts and
| @ Efficient quartz controlled g Amps. Fully variable down to SoRelaan Lek Rugged power MOSFET ay
microcontroller pulse generation. y Zer0. Toroidal mains trans- put stage. Toroidal mains transformer.
j @ Fullkitwith headphones & all fone". Kt includes punched KIT 769...seccecsccecsseeeesees £56.82
hardware
I parts. As featured in April. INSULATION TESTER
LKiT 847. ol Oeigebgr aa ol ...£63. 954 1994 EPE. An essential piece A reliable and neat electronic tester which checks
of equipment. hgh ag able of oe and abl a
at olts. The unit is battery powered, simple
DIGITAL LCD TH ER MOSTAT KIT 845 jiiieieowwes £64.95 and safe to operate. Leakage Lh Si of up to

A versatile thermostat using a thermistor probe and

having an I.c.d. display. MIN/MAX memories, -10 ULTRASONIC PEsT SCARER

to 110 degrees celsius, or can be set to read in

Fahrenheit. Individually settable upper and lower Keep pets/pests away from newly
sown areas, fruit, vegetable and
can result in substantial energy savings when used flower beds, children’s play areas,
patios etc. This project produces
brewing, etc. Mains powered, 10A SPCO relay out- Intense pulses of ultrasound
which deter visiting animals.

@ KIT INCLUDES ALL | PEsT
COMPONENTS, PCB & CASE

@ EFFICIENT 100V
TRANSDUCER OUTPUT
pact hand-held case. MOSFET output drives a @ COMPLETELY INAUDIBLE

TO HUMANS |

output is designed to give maximum output with- KIT Ref. 812..........ccccccccccccccceceeeeeeeeeeeeseeeeseees

‘COMSTEP’ P.C. COMPUTER STEPPING
MOTOR INTERFACE

An exciting project supplied with two 200 step motors, interface board, and easy MOSFET coil drive.
to use P.C. software.
Allows independent control of both motors — speed, direction, number of steps, amplification.

A really professional looking project. Kit is sup- and half/full step mode. Connects to computer parallel port. Requires 12V 1A Full kit includes

switching temperatures allow close control, or alter-
natively allow a wide ‘dead band’ to be set which

with domestic hot water systems. Ideal for green-
house ventilation or heating control, aquaria, home

put. Punched and printed case.

RUT B41 jo cisstsrtiemtaidenath woo

PORTABLE ULTRASONIC
PEsT SCARER

A powerful 23kHz ultrasound generator in a com-

special sealed transducer with intense pulses via
a special tuned transformer. Sweeping frequency

Out any special setting up.

BET BE seicvscsnesternivees £22.56

DIGITAL CAPACITANCE
METER

nth,
ss
-

ox
ao

RANGE

DMEOV |

494%

lO-ZOMr xr}

_SCARER

@ UPTO 4 METRES

@ LOWCURRENTDRAIN MKI
£14.81 Magenta’s highly

100 Megohms can be read easily. A very popular
college project.

KIT 444... eaeieues £22.37
DIGITAL COMBINATION LOCK

Digital lock with 12 key keypad. Entering a
four digit code operates a 250V 16A relay.
A special anti-tamper circuit permits the relay
board to be mounted remotely. Ideal car immobi-
liser, operates from 12V. Drilled case, brushed
aluminium keypad.

KIT 840... eee £19.86

E.E. TREASURE HUNTER
P.l. METAL DETECTOR

developed &
acclaimed design.
Quartz crystal
controlled circuit

D.C. coupled
@ KIT INC.

plied with a punched and printed front panel, case, D.C. supply and printer lead. PCB handle
.c.b. and all components. Quartz controlled ac- , ' ' HEADPHONES
sielen of 1%. bares clear 5 digit display and high KIT 846 (with 2 motors) ....... £67.00 (Printerlead £5.00) case & :
speed operation. Ideal for beginners — as the pF, hF search coil. @ EFFICIENT
and pF ranges give clear unambiguous read out of ION ISER CMOS DESIGN

marked and unmarked capacitors from a few pF up_ A highly efficient mains powered Negative lon Generator that clears the air by
neutralising excess positive ions. Many claimed health benefits due to the ioniser

KIT 493 £39 95 removing dust and pollen from the air and clearing smoke particles. Costs virtually
EN A eee e estes eesessseeseesess sh UYU = nothing to run and is completely safe in operation. Uses five point emitters.

Abo GF 2 dixiasecuestisnieonasmei eels eee eee £17.75

to thousands of pF.

ACOUSTIC PROBE

A very popular project which picks up vibrations by
means of a contact probe and passes them on to a BAT D ETECTO R

pair of headphones or an amplifier. Sounds from An excellent circuit which reduces ultrasound frequencies between 20 and 100 kHz

@ POWERFUL COIL
DRIVE

@ DETECTS FERROUS AND
NON-FERROUS METAL -— GOLD,
SILVER, COPPER ETC.

engines, watches, and speech travelling through to the normal (human) audible range. Operating rather like a radio receiver the circuit
walls can be amplified and heard clearly. Useful allows the listner to tune-in to the ultrasonic frequencies of interest. Listening to Bats @ 190mm SEARCH COIL

for mechanics, instrument engineers, and nosey _ is fascinating, and it is possible to identify various different types using this project. @ NO ‘GROUND EFFECT’

parkers!.

Other uses have been found in industry for vibration monitoring etc.

BET 290) vrcsssvavnautdateenecy. CIO 96. AT Aitken nclnieemieievat £21.44 KIT 815

HAMEG HM303 30 MHz
DUAL TRACE OSCILLOSCOPE &
COMPONENT CHECKER

Western Europe's best selling oscilloscope - now improved.
It now features 30MHz bandwidth, triggering to 100MHz
and 2mV/div sensitivity.

Sharp bright display on 8 x 10cm screen with internal
graticule. Special component tester built in - allows
Capacitors, resistors, transistors, diode, and many other
components to be checked at a glance.

As with its predecessor, the QUALITY OF THIS INSTRU-
MENT IS OUTSTANDING. It is supported with a two year
warranty covering parts and labour. If you are buying an
oscilloscope, this is the one. It costs a fraction more than
some others, but it is far far superior. Supplied with test
probes, mains lead, and manual.

£392. OT £68. 60 VAT Includes FREE

Next-day delivery

430

EDUCATIONAL BOOKS & PACKS
ADVENTURES WITH ELECTRONICS |

The classic book by Tom Duncan used throughout
schools. Very well illustrated, ideal first book for age 10
on. No soldering. Uses an S.DEC breadboard.

Book &Components £28.95, Book only £7.25

FUN WITH ELECTRONICS

An Usborne book, wonderfully illustrated in colour. Com-
ponent pack allows 6 projects to be built and kept. Sol-
dering is necessary. Age 12 on, or younger with adult
help. Book & Components £20.88, Book only £2.95

30 SOLDERLESS BREADBOARD PROJECTS
A more advanced book to follow the others. No soldering.
Circuits cover a wide range of interests.

Book & Components £30.69, Book only £2.95

Ideal for robots, buggies,
and many other mechanical
projects. Min. plastic gearbox
with 1.5-4.5V DC motor. 6
ratios can be set up.

Small type MGS....£4.77

STEPPING MOTORS

For computer control via standard 4 pole unipolar
drivers.

MD38 - miniature 48 steps per rev
MD35'4 - standard 48 steps per rev

Everyday with Practical Electronics, June 1 995

YOUR KEY
TO ANOTHER
NEWAGEOF @&
ELECTRONICS

PICs are being used
more and more because

they allow complicated jobs
to be done with a single chip.
All the work is done by programming.
One PIC replaces a board full of ICs.

7 TET FE ETT Oe nr

DEVELOPMENT

PIC & TRAINING SYSTEM PI
£9

ye” * WITH OPERATING
4 PROGRAMMING, AND
CODE ASSEMBLER
PROGRAMS

Saving time, space, power, and MONEY. Wz

HOW DOISTART WITH PICs?

STEP 1 — Buy the PIC-DATS

Development & Training System

STEP 2 - Follow May & June ‘95 EPE
Series — showing how to program

for practical applications
STEP 3- Start writing and testing
your own programs

PIC PROJECT - LIGHT CONTROLLER
DEVELOPMENT SYSTEM

A real-world application for a PIC microchip. This project can be made

to do just what you chose if you write your own software. OR works as
a 4-Channel hard fired — zero volt switching — Light Chaser. Kit includes
programmed PIC, software disk and all components (less case).

AL ere

INCLUDING
VAT

RUNS WITH ANY PC

POWER SUPPLY
(12V at 200mA)

£8.99

PC LEADS
9-WAY £6.00
25-WAY £7. £7.00

Motors and Controllers

A range of kits and components for motion control and computer interfacing. Ideal for Design
and.Technical projects, and a whale range of up to the minute ‘Home Automation’ applications.

Comstep PC Computer
Interface and Driver board

Drives two motors from PC With 2-200
Step Motors

parallel port. Supplied with
comprehensive software.
Needs 12Volt 1A supply.

Power Booster for Comstep

Adds to Comstep and allows With MD24
Motors

motors up to 4 Amps to be
driven. Two boosters drive

two motors from a single Comstep. Uses standard
Comstep software.

MOE BO ss icicearssesiascs

PC Communications Protocol
for Comstep

An interface board adding four switched inputs to
the Comstep + All the code to develop your
applications. Files in C, BASIC, FORTRAN &
ASSEMBLER + demo.

Kit 851

Mini-Lab & Micro Lab
Electronics Teach-In 7

As featured in EPE and now published as Teach-In 7. All parts
are supplied by Magenta. Teach-/n 7 is £3.95 from us or EPE
Full Mini Lab Kit - £119.95 — Power supply extra — £22.55
Full Micro Lab Kit —- £155.95 Built Micro Lab - £189.95

PC Joystick Interface for
Comstep

Software for operating Comstep fess a standard
PC Joystick. Allows two Axis control, with
acceleration, speed, and X-Y position control.
Stores co-ordinates.

Kit 852

Stand-Alone Stepping motor
Driver/Interface

A Stand alone interface giving full control in
all modes. Pushbutton operation with adjustable
acceleration and speed. Ideal for demo and setting
up. Then connect to computer port for full control.

Versatile Stepping motor

Interface

A Magenta design, gives Half and Full-Wave drive.
Up to 1Amp and 24Volts. CMOS inputs — Drive
from logic or computer port. Needs power supply.

Tel: 01283 565435 Fax: 01283546932 —_Allprices include VAT. Add £3.00 p&p.

Everyday with Practical Electronics, June 1995

DC Motor/Gearboxes

Our Popular and Versatile DC motor/Gearbox
sets. Ideal for Models, Robots, Buggies

etc. 1-5 to 4:5V Multi ratio gearbox

gives wide range of speeds.

LARGE TYPE —-MGL £5.95
SMALL — MGS - £4.77

Stepping Motors

MD38...Mini 48 step...£8.65
MD35...Std 48 step...£12.98
MD200...200 step...£16.80
MD24...Large 200 step...£22.95

More Information:

All listed items come with data and instructions.
For more information, including reprints of the
appropriate magazine articles, send an SAE +

£1.00 per kit — or phone and use
Mastercard/Visa etc.

TER

431

432

64
74HC4002 £0.16
74HC4017 £0.64
74HC4020, £0.35
74HC4040 £0.45
74HC4049 £0.25.
74HC4050 £0.25
74HC4060 £0.39
74HC4075 £0.27
74HC4078 £0.16
74HC4511 £0.64
74HC45 14 £0.84
74HC4538 £0.41
74HC4543 £0.90

74LS Series
74LSO00 = £0.25
74LSO1 £0.14
74LS02 £0.29
74LS03 £0.29
74LS04 £0.14
74LS05 £0.14
74LS08 £0.23
74LS09 £0.14
74LS10 £0.14
74LS11 £0.17
74LS12 £0.14
74LS13 £0.14
74LS14 £0.25"
74LS15 £0.14
74LS20 £0.16
74LS21 £0.14
74LS22 £0.14
74LS26 £0.14
74LS27 ~—- £0.14
74LS30 £0.14
74LS32 £0.14
74LS37 = £0.14
74LS38 £0.19
74LS40 = £0.14
T4LS42 £0.25

ORDERING INFORMATION -
ESR Electronic Com

74LS670

AD847JN

Cs
£24.18
69

£7.
£7.19

AD9696KN £12.45
FSCS Be £4.54
ADM222AH _ £3.55
ADM232AAN £3.55
ADM485JN — £2.57
ADM690AN_ £4.59
ADM69IAN_ £5.91
ADM695AN _ £5.91
ADM699AN £3.19
AMPO4FP £21.02
BUFO4GP £10.02
CA741CE £0.28
CA747CE £0.39
CA3046 £0.37
CA3059 £1.16
CA3080E £0.72
CA3130E £0.98
CA3140E £0.56
CA3189E £1.22
CA3240E £1.12
DG211CJ £1.49
DG212CJ £1.55
DG411DJ £3.11,
DG412DJ £4.19
EL2020CN £4.99
EL2030CN £5.67
ICL7 106 £2.80
ICL7611 £1.16
ICL7621 £1.70
ICL8038 £5.25
ICM7555 £0.43
ICM7556 £0.98
LI65V £2.63
L272M £1.89
L293E £4.32
L297 £6.37
L298 £6.99
LF347N £0.86
LF351N £0.43
LF353N £0.42
LF356 £0.84
LM301A £0.25
LM308N £0.42
LM311N-8 £0.28

318 £1.28
LM319N-14 £0.96
M324 £0.35
LM335Z £1.52
LM339N £0.24
LM348N £0.31
LM358N £0.27
LM377 £2.57
LM380N-14 = £1.12
LM381N £2.70
LM382 £2.30
LM386 £0.79
LM387 £1.60
LM392N £0.79
LM393N £0.28
LM709T £0.79
LM733 £0.64
LM748CN-8 = £0.31
LMS579CP £3.38
LM 1458 £0.26
LM 1881 £4.00
LM2917N8 ~— £3.20
LM3900N £0.72
LM3909N £1.76
LM3911 £2.56
LM3914 £2.70
LM3915 £2.70
LM 13600 £1.82
LMC660CN = £2.16
LMC6032IN = £1.55
LMC6042IN £1.82
LP311N £0.74
LP324N £0.74
LP339N £0.73
MAX202CPE £2.97
MAX208CNG £6.99
MAX220CPE £5.06
MAX222CPE £5.06
MAX232CPE £3.71
MAX238CNG £6.88
MAX242CPE £5.51
MAX631ACP £4.99
MAX635ACP £4.99
C1488 £0.46
MC1489 £0.46
MC3302 £0.56
MC3340P £1.60
MC4558P £0.36
MVS00DP £2.63
MV60!1DP £2.97
NES531 £1.47
NESS55N £0.25
NES56N £0.36
NE565 £1.84
NES66N £1.12
NES67N £0.39
NES71N £2.47
NE592 £0.58
NE5532N £0.80
NE5534N £0.60
OP07CN £1.42
OP27CN £2.49
OP77GP £3.12
OP90GP £4.14
OP97FP £4.02
OP113GP £4.04
OP176GP £2.30
OP177GP £2.49
OP183GP £3.78
OP200GP £6.81
OP213FP £6.38
OP275GP £2.84
OP282GP £2.63
OP283GP £5.81
OP290GP £6.24
OP295GP £5.54
OP297GP £7.56
£13.56
OP467GP £15.90
OP495GP £10.44
PMIO12GP =e £6.38
RC4136 £0.90
SAA1027 £4.52
SG3524N £1.08
SG3543 £6.88
SL486 £2.63
SL490 £2.63
SSM2017P —s £3.38
SSM2131P £4.87
SSM2141P £5.94
SSM2142P £6.08

ponents. Credit Card Orders Acce

pted. NO Surchar

SSM2143P —- £4.99_ 1N5407 £0.14 2SB548 £0.30 BC328 £0.10 ;
TBA120S £0.90 1N5408 £0.15 2SD1730 £1.44 BC328-16 £0.10 BD ries
TBA800 £0.70 BAI57 £0.10 AC126 £0.44 BC337 £0.10 BDX33C £0.49
TBA810S £0.68 BAIS58 £0.10 ACI27 £0.50 BC337-25 £0.10 BDX34C £0.50
TBA820M —‘ £0.39 BAI59 £0.10 ACI28 £0.28 BC338 £0.10 BDX53C_ £0.47
TDA1024 £1.49 BY126 £0.13 ACI87 £0.48 BC338-25 £0.10 BDX54C _ £0.50
TDAII70S £1.83 BY127 £0.11 ACI88 £0.48 BC348B. £0.14 —BFI80 £0.31
TDA2002 £1.04 BY133 £0.10 ACYI7 £3.84 BC357 £0.25. — BF 182 £0.31
TDA3030.—«ET'18. OASO for; | ABIl. © S0ee: peahiC. Eh BRise Seat
TDA2050V £3.98 OA9I £0.10 ADI62 £0.92 BC441 £040 BFI94B £0.19
TEASII5 £3.11 OA200 £0.10 | BCIO7 £0.16 BC461 £0.40 BFI95 £0.19
TLO61CP £0.35 OA202 £0.29 BCIO7B £0.15 BC463 £0.29 BF244 £0.35
HOSEN £092 4m 008 «BCIEA | eatia bree oe BME BS
ae 4 m . s BA bo
TLO7ICP £0.48 1.3W £0.14 BCIO8C £0.16 BC490 £0.24 BF257 £0.33
TLO72CP £0.68 Bridge Rectifiers BC109 £0.17 BCS16 £0.22 BF259 £0.33
TLO74CN £0.58 W005 1.5A 50V £0.19 BCIO9C £0.17 BC517 £0.20. BF337 £0.36
TLO8! £0.33 WO02 1.5A 200V £0.20 BCII4 £0.41 BC527 £0.20 BF355 £0.3
TLO82CP £0.54 WO4 1.5A 400V £0.22 BCII5 £0.41 BC528 £0.20 BF423 £0.13
TLO84CN £0.63 W06 1.5A 600V £0.22 BCII6 £0.41 BCS537 £0.20 BF451 £0.19
TL494CN £1.49 WO08 1.5A 800V £0.27 BCII8 £0.41 BC5S46B £0.08 BF459 £0.33
TL7705ACP £1.62 WO101.5A IkV £0.24 BC132 £0.36 BC546C £0.08 BF469 £0.36
TLC271 £0.54 BR32 3A 200V £0.36 BC134 £0.36 BC547B £0.09 BFX29 £0.29
TLC272 £0.88 BR34 3A 400V £0.40 BC135 £0.36 BC547C £0.09 BFX84 £03!
TMPOIFP £7.25 BR36 3A 600V £0.44 BCI40 £0.25 BCS48C £0.08 BFX85 £0.32
U257B £1.28 BR62 6A 200V £0.70 BCI4I £0.27 BC549C £0.10 BFYS5O £0.29
U267B 1.28 BR68 6A 800V £0.74 BC142 £0.31 BCS550C £0.10 BFY51 £0.26
UA2240CN £2.30 1004 10A 400V £1.39 BCI43 £0.34 BC556A £0.08 BFY52 £0.28
ULN2003 £0.52 2502 25A 200V £1.68 BCI49 £0.21 BCS557B £0.08 BSI07 £0.21
ULNIOS «£120 Thyristora Belsy, = Seis. Beasge «feck BS 0
ULN2803 £0.60 PON2AA £0.30 BCI59 £0.12 BC559C £0.08 BUI26 "33
ZN409CE £1.89 TIC106D £0.40 BC160 £0.28 BCS60A £0.09 BU205 £1.41
ZN414Z £1.16 TICII6D £0.66 BCI70 £0.16 BCS560B £0.09 BU208A_ £1.24
Nite’ > aha eee” |B Bere =. a Bue Be
5 riac \ i ‘Zz Py :
EPROM’s ie ZDLOSDA £0.42 BCI71B £0.16 BC639 = £0.21 BUSO8A = £1.42
2732 £484 TIC26D £0.73 BCIT3B O13 Bev 70 £031 era tt 74
2764-25 £4.20 BTAO08-600B £0.99 BCI77 £0.18 BCY71 £0.20 BU806 £1.06
27C64-25 £3.44 TIC236D £0.96 BCI78 £0.18 BCY72 £0.20 BUTIIA £1.33
$3820 £408 DBS 32V. £0.20. Balto, © SRL? BDineP 686 BUTMAF £133
27C 128-20 £4.08 Transistors BC182 £0.08 BDI36 £0.21 IRF540 £1.60
27256-20 £4.85 2NI1613 £0.31 BC182A £0.11 BD137 £0.23 IRF740 £1.80
27€256-20 £3.95 2NI711 £0.26 BCI82B £0.08 BDI38 £0.22 MJ2501 £1.60
270512 £3.95 3N1893 £0 «BC I82L £0.08 BDI39 £0.23 + MJ3001_~—-£1.80
RAM ine amotio Pee BC182LB £0.08 BD140 £0.25 MJIIOIS £2.11
6116-10 £1.53 2N2222A = £0.18 BCISSL_ Ss EDOR Biles. fons | Mubue fod
6264-10 £3.06 2N2646 £0.86 BC1I83LB £0.08 BD166 £0.35 MJE350 £0.42
41256-10 £2.80 2N2904A £0.25 BCI84 £0.08 BDI87 £0.39 MPSAOS £0.14
62256-10 £5.35 eo ree BCI84L £0.08 BD201 £0.40 MPSA06 £0.12
3142568 £688 2N2007A £020 Besb§c 072 Bbse 040 apsawe Eee
A/D Converters 2N2926 £0.16 = BC206B £0.72 BD204. £0.40. + MRF475_— ‘£7.28
Data Acquisition 2N3053 £0.27 BC207B £0.74 BD222 £0.58 290C "2
AD430AN" £29.62, 2N3054 £0.90 C208 £0.72 BD225 fa) TIP30C 3
ADSS7JN £8.75. 2N3055 £0.62 BC209A £0.72 BD232 £038 TIP3IC £0.34
ADS74AJN £20.66 2N3439 £0.62 BC212 £0.08 BD237 £0.32 TIP32C £0.32
AD767JN £22.44 2N3440 £0.50 = BC212L £0.08 BD238 £0.32 TIP33C £0.72
AD775JN = £21.54. 2N3702 £0.09 BC?212LB £0.08 BD?: £0.37 TIP4IA £0.48
AD7226KN £25.69 2N3703 £0.10 BC213 £0.08 BD243B £050 TIP42C £0.38
AD7528JN_ £14.28 2N3704 £0.10 BC213 £0.08 BD244A £053 TIP47 £0.48
AD7545AKN £15.18 2N3705 £0.10 BC213LC ‘£0.08 BD244C £0.53 TIP48 £0.62
AD7581JN £26.99 2N3706 £0.10 BC214 £0.08 BD245C £1.18 TIPSO £0.53
AD7828KN £26.76 2N3771 £1.44 9 BC214L £0.08 BD246 £1.18 TIPI21 £0.35
AD7845JN £18.06 2N3772 £1.51 = BC225 £0.15 BD246C £1.18 TIPI22 £0.40
ICL7109CPL £7.75 2N3773 £1.79 BC237B £0.09 BD283 £0.61 TIPI25 £0.37
TLCS49IP = £3.51 =. 2N3819 £0.39 = BC238B £0.09 BD284 £0.61 TIPI27 £0.40
42 £5.94 2N3820 £0.66 BC238C £0.09 BD400 £0.79 TIPI32 £0.46
ZN426E £3.03 2N3904 £0.10 BC239C £0.10 BD441 £0.41 TIPI37 £0.46
ZN427E £8.78 2N3905 £0.10 BC250A £0.15 BD442 £041 TIPI42 £1.08
N428 £5.94 2N3906 £0.10 BC251 £0.13 BDS34. = £0.47.—s TIPI47.~—s £1.12
ZN439E8 £7.13 2N4036 £0.34 BC252 £0.13. BD535 £0.50 TIP2955 £063
245 £0.80 rel Ly. ‘ 305 63
- ve vi £7.02 areas 2 a BC261B £0.24 BD536 £0.65 TIP3055 ~—-£0.63
Regulators —-2N5321_—=— £0.57 BC267B «£030 BDS07 «£092 VNGOARD ETS
5322 £0.57 3 59 :
780; er ane He at BC307 £0.10 BD646 £0.52 ZTX300 £0.16
He BRM Bg moe Bee RED
7905 £0.31 2N6491 £1.58 BC327-16 £0.10 BD708 £1.04
7915 £0.38 Electrolytic Radial Capacitors Electrolytic Axial Capacitors
7924 £0.38 pF lov 25v 63v_ 100v 450v F l6v 25v 63v 100v 450v
781.05 £0.25 O47 -- £0.05 £0.07 bai oa eS es ee
78L08 £0.31 10 --- - £0.05 £0.06 £0.15 1.0 --- -- £0.10 £0.10 £0.19
781.12 £0.24 2.2 -- -- £0.05 £0.06 £0.18 2.2 -- -- £0.10 £0.10 £0.22
781.15 £0.24 4.7 -- -=- £0.05 £0.08 --- 47 -- £0.09 £0.10 £0.10 £0.34
78124 £0.26 10 £0.05 £0.05 £0.06 £0.08 £0.44 10 -- -- £0.12 £0.12 £0.48
7905 £0.28 22 £0.05 £0.05 £0.09 --- —--- 99 --- £0.09 £0.13 £0.17 £1.06
7908 £0.28 47 £0.06 £0.06 £0.11 --- — --- 47 £0.10 £0.11 £0.16 £0.20 ---
79L12 £0.28 100 £0.06 £0.09 £0.11 --- --- 100 £0.10 £0.13 £0.21 --- ---
59115 £0.28 220 £0.09 £0.12 £031 -- --- 220 £0.13 £0.18 £0.42 --- —---
79124 £0.30 470 £0.15 £0.19 £0.57 -- — --- 470 £0.21 £0.24 £0.69 --- —---
ADM666AN £399 1000 £0.22 £0.29 -- -- 9 = 1000 £0.33 £0.40 £1.05 --- —---
L200CV 124 2200 £0.37 £0.57 -- -- 9 -- 2200 £0.52 £0.64 --- --- ---
1296 e14 410 em ELL oe ee AION: S00) a. a ee
L387A £3.24 Resistors _ ; PCB Production Equipment
LM2904CT £2.30 ply I th pas 5% ie Series 1Q-10M sete pa sear Spray 100ml pe
.02 . £0. r ux Spray m ;
eee Ey ’2W Carbon Film 5% E12 Series 1Q-10M PCB Plastic Laquer Spray 200ml £4.32
ee ete £0.02 Each, £0.95 per | Developing / Etching Tray £1.35
eveetTg tee “WW Metal Film 1% E24 Series 10Q-1M Plastic Tweezers £0.55
LN 1723 £0.29 £0.04 Each. £1.72 Sl Transfer Spatular (Alfac) £0.70
950CZ £2.9 Sgr pet yonn orz / Vert. 100Q - IMO hohe iad coun ape ve rae
ach Sma nife wit spare age a
MAXGGGCPA 4 76 Skeleton Presets Hore / Ver. 1002-1MO PCB Polishing Block | | £1.84
q ear Draltin um er A- i oe
REFOSGP £6.14 BOTS 14° Shaft 25mm Dia 4702 -2M2 Opaque Draltin ans od ee
REFI95GP £5.50 Lin or Log £0.42 Each Ferric Chloride Pellets 250g (Yalt) £1.31
EF25Z £1.22 nit, PE ten State Value* i Paty a eee
. ets In atin owder
REDSOZ, «fh? 8 Pin £0.07 -14Pin ‘£0.11. UV Exposure Unit, details available £76.31
Ave, Hs pee Bie ERS BUREN RM aS
ZN4SgB_ £1.89 28 Pin ‘£0.22 40 Pin. £0.25 _also available Transfers. Developers, Tanks
IN914 £0.06
Photo Resist - Glass Fibre - Pape ”
pei ; pe Size (1.6mm) Single Double Single PNouble oe 0.1 BO a
IN4002 £0.07 4x6" £1.58 £1.79 £1.20 £1.47 64x 95mm £0.90
1N4003 £0.07 6x 12” £4.62 £5.15 £3.46 £4.20 95x 127mm £1.50
1N4004 £0.07 9x 12” £6.93 £7.77 £5.19 £6.36 95 x 431mm £4.80
07 10x 12” £8.87 £9.81 £6.78 £8.30 x 454mm 2
Hae toe Ieee £9.09" =) £1049. £683: ; £334 . Seo | = os,
IN4148 £0.05 Glass Fibre - Photo Resist -Copper Clad 173 x 42mm £3.90
IN4149 £006 160x 100mm £1.94 £2.20 £0.70 £0.74 175 x 67mm £5.96
1N5400 £0.09 203x 114mm £2.52 £2.78 --- --- 203 x 75mm _ with terminals
IN5401 £0.09 220x 100mm £2.58 £2.88 en = & mounting plate.
1N5402 £0.10 233x 220mm £5.67 £6.41 £2.38 £ fans
1N5404 £0.11 233x 160mm £3.99 £4.41 £1.75 £1.89 No Minimum
1N5406 £0.12 0.8mm Thick Photoresist Board Now Available Order Value

All Prices Exclude Vat, Add £1.25 carriage & Vat to all orders. Send Payment with Order. PO / Cheques payable to
e on credit card orders. Trade discount for Schools & Colle

es.

Everyday with Practical Electronics, June 1995

EVERYDAY ake
with PRACTICAL

ELECTRONICS

| INCORPORATING ELECTRONICS MONTHLY |

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EVERYDAY with PRACTICAL ELECTRONICS
ADVERTISEMENTS
HOLLAND WOOD HOUSE, CHURCH LANE

VOL. 24 No. 6 JUNE ’95

PRICE HIKE

Wandering around an Antiques Fair over the Easter weekend, my attention was
captured by a working Bakelite cased radio, an unusual, rather ugly, design with
pushbutton tuning — it was obviously from the early Fifties and turned out to be of
American origin (115V a.c.). The most interesting feature was the price — just over
£200! I am told that some early radios, those made by Marconi in the very early days of
radio, can cost thousands of pounds. |

I started to wonder if any item of modern equipment might command such interest in
forty years’ time. It seems doubtful that many of our present day products could
be refurbished to full working order as any custom chips, microcontrollers and pro-
grammed memory would be difficult to reproduce. However, if you look at some
mundane items which are now becoming collectable, it makes you wonder if we should
be hoarding personal cassette players, radios, etc. No doubt the most interesting work-
ing designs of such things will become collectors items, possibly made more valuable
because of the difficulty in repairing them in the future.

COLLECTABLE

Jake Rothman, who has designed our EPE HiFi Valve Amplifier admits to having a
weakness for old transistor radios, of the type that Bush put out in the Seventies. Jake
has bought and restored a number of these and is threatening us with an article on how
it’s done — anyone interested? I guess we should all start collecting and restoring now
SO we can retire on the proceeds in years to come! Incidentally we expect to publish a
High Voltage Capacitor Reformer project next month — very useful to anyone refur-
bishing valve equipment.

The specialist knowledge and ingenuity needed to refurbish items using “blown”
chips can, of course, be gained by the hobbyist and, providing a replacement “blank”’
chip is available, it is not beyond the ability of the enthusiast to write new software
froma knowledge of the operation and circuitry of the original product and thus blow
a new device.

Our PIC-DATS (last month) and follow up PIC Light Chaser articles will give you an
excellent start in this rewarding operation. So, perhaps we should also be hoarding
some of the most popular programmable chips for future use too!

-SUBSCRIPTIONS

Annual Subscriptions for delivery
direct to any address in the UK:
£24. Overseas: £30 (£47.50 airmail).
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Everyday with Practical Electronics, June 1995

GREAT HOLLAND, ESSEX C013 0JS
Phone/Fax: (01255) 850596

Editor: MIKE KENWARD
Secretary: PAM BROWN
Deputy Editor: DAVID BARRINGTON

Technical Editor: JOHN BECKER

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READERS’ ENQUIRIES

We are unable to offer any advice on the use,
purchase, repair or modification of commercial
equipment or the incorporation or modifica-
tion of designs published in the magazine.
We regret that we cannot provide data or
answer queries on articles or projects that
are more than five years old. Letters requir-
ing a personal reply must be accompanied by
a stamped self-addressed envelope or a
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reply coupons. Due to the cost we cannot
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All reasonable precautions are taken to en-
sure that the advice and data given to readers is
reliable. We cannot, however, guarantee it and
we cannot accept legal responsibility for it.

~COMPONENT SUPPLIES

We do not supply electronic components
or kits for building the projects featured, these
can be supplied by advertisers.

We advise readers to check that all parts are
still available before commencing any project
in a back-dated issue.

We regret that we cannot provide data or
answer queries on projects that are more
than five years old.

ADVERTISEMENTS |
Although the proprietors and staff of EVERY-
DAY with PRACTICAL ELECTRONICS take
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of readers by ensuring as far as practicable that
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and its Publishers cannot give any undertak-
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The Publishers regret that under no cir-
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TRANSMITTERS/BUGS/TELEPHONE
EQUIPMENT

We advise readers that certain items of radio
transmitting and telephone equipment which
may be advertised in our pages cannot be
legally used in the UK. Readers should check
the law before buying any transmitting or
telephone equipment as a fine, confiscation of
equipment and/or imprisonment can result
from illegal use or ownership. The laws vary
from country to country; overseas readers
should check local laws.

433

Constructional Project

FIFI VALVE
AMPLIFIER

JAKE ROTHMAN

accede

Riding on the wave of the “valve revival”,
Jake presents his own design so that
constructors can create the valve sound,
without suffering “antique CGealer” prices!

e39OW rms. into 8 ohms ¢ 20OHZ to 2OKHz, +O0:20dB

e /nput Sens. SO0OMYV for full output ¢ less than O:1%

t.h.d. at TSW into 8 ohms e¢ Hybrid design for minimum
valve count ¢ Monoblock design (two required for Sberao!
e Optimised for use withCDe

HiFi Valve Amplifier. Designed to

sound at least as good as the Quad II
power-amp described in the February 1994
issue.

The design is not a rehashed 1950s
circuit. It is based around a brand new
hybrid topology combining the positive
attributes of vacuum and solid-state tech-
nologies. This amp enables the valve sound
to be obtained without suffering ‘‘antique
dealer”’ prices.

IN COMPARISION

In terms of “pounds-per-watt” valve
amplifiers cost around five to twenty times
more than equivalent power solid-state
designs, so why use valves? The answer
lies in the type of distortion produced,
generally valve type distortion sounds sub-
jectively better, even if it is much higher on
the ‘‘spec sheet.”

Audio distortion is a complex subject, in-
evitably intertwined with psychoacoustics.
The human ear produces its own distortion
which tends to increase smoothly with level
and comprises mainly low-order harmonics.

It does not seem surprising therefore that
studies have shown distortions very dis-
similar to this are much more noticeable,
humans may prefer to hear distortions they
are familiar with! Unfortunately the dis-
tortions produced by standard Class-AB
solid-state designs are almost the opposite
to that of the human hearing, tending to

Hi at last, is the promised EPE

suffer increasing distortion at low-levels

and hard clipping at overload.
Often distortion is at a minimum
just before clipping and the harmonics

434

produced tend to be high and of an

odd-order such as 5th and 7th. This tends

to manifest itself as a lack of clarity in
the top end and low-level reverberation.
Characteristic distortion curves for the two
different technologies are shown in Fig. 1
and Fig. 2.

HARMONIC GENERATION EXTENDED HIGH HARMONICS

LEVEL

234567 9

LOG
%THD

100%

1%

0-05

HARMONIC N°

SYSTEM
SYNERGY

More astute readers may have realised
that the transistor amplifier distortion
curve in Fig. 1 is very similar to that
produced by digital recording media. CDs

THD AT 10W DISTORTION LOWEST AT L.F.

0:2%

20Hz 20k

HIGH DISTORTION AT LOW LEVELS
HARD CLIPPING

O/P POWER (LOG)

SOW 60W

| Fig. 1. Solid-state distortion — Class-AB

Everyday with Practical Electronics, June 1995

exhibit a distortion rise at low levels simply
because there are fewer bits to convey the
information.

One could be excused for thinking this
means there is no point in using a valve
amplifier with CDs. There is — because for

some unknown reason, the distortion curve

of the valve amplifier seems to hide that of
the CD player and make the system sound
better.

What matters is the overall distortion
pattern (with regard to harmonics and
level) and the frequency response of the
complete hi-fi system. This effect of hi-fi
components complementing each other is
known as synergy. This effect has also been
used in studios for many years, where valve

condenser microphones and guitar proces- |

sors are common place, complementing
digital recording and sampling. A few years
ago a CD player was introduced that had
valves following the DAC!

NEGATIVE
FEEDBACK

Another aspect to amplifier sound is the
use of negative feedback. Feedback is

necessary to reduce distortion and flatten

frequency response.

Where a lot of feedback is used clip-
ping tends to be much harder and sudden.
The distortion harmonics although much
reduced, are pushed up to higher orders.
Soft clipping or gradual overload is subjec-
tively less unpleasant and is akin to the
effect of hitting a string or soundboard
harder.

There is a school of thought in hi-fi that
believes that any feedback is bad. This aim
is very difficult to achieve in practice, since
the only amplifying devices linear enough

to not need feedback are a select few triode |

valves.

Generally speaking the less linear an
amplifying device is, the more feedback is
required. Phase shift limits the amount of
feedback that can be applied before oscil-
lation occurs. Valve amplifiers generally
employ coupling capacitors and output
transformers which limit the amount of
feedback to a maximum of around 20dB
(open-loop gain reduced by ~ 10).

LOWER ORDER HARMONICS PREDOMINATE

LEVEL
HARMONIC N°
23456
%THD
100%
1
0:05
1W

PERL Tie ith Wars tl aia

OUTPUT
IMIPEDANCE

The output impedance of valve
amplifiers is generally higher than
transistor amps because of the smaller
amount of negative feedback used, the high
output impedance of valves themselves and
the resistance in the transformer windings.
A high output impedance means that the
loudspeaker damping factor is lower, often
giving the impression of better bass.

This often makes small closed-box
speakers sound better. The BBC designed
LS3/5a is such a design and is often seen
partnered with Quads (synergy again).

Table 1 compares the linearity of various
output devices. It is interesting to note that
MOSFETs are the least linear, it even says
in the Hitachi data book that a MOSFET
output stage produces ten times more dis-
tortion than a comparable bipolar stage.

Fortunately, MOSFETs have such a
high bandwidth that massive amounts of
negative feedback can be used to give
acceptable distortion.

A BETTER CLASS
OF AMPLIFIER

Another reason for the good sound of
valve amplifiers is not that they use valves
per se, but that they are usually Class-A
designs. Class-A amplifiers run at full
power even with no signal, with the
output devices never out of conduc-
tion throughout the whole cycle. This
means there is no low-level or crossover
distortion.

Valves are very effective at dissipating
heat so it is simple to run them in Class-A.
With solid-state devices massive heatsinks
and thermal stabilisation are needed, so
Class-A is rarely used.

HOW IT WORKS

The block diagram of the EPE HiFi
Valve Amplifier, with an op.amp based
phase-splitter followed by a triode driver
stage feeding an ultra-linear EL34 output
stage, is shown in Fig. 3. The ultra-linear
output stage is based on the Mullard 5-20
design.

Table. 1: Linear comparison of output devices

Device

Triode

Beam Tetrode
(in ultra-linear mode)

Note

Most linear, least distortion, lowest efficiency. e.g.
2A3,300B

Slightly more distortion but almost as efficient as
pentodes. e.g. 6L6, KT66, EL34, 5881. Used in 5-20

and Williamson design.

Pentode
(in ultra-linear mode)

Pentode

Used in Leak Stereo 20. Distortion between triode
and pentode. e.g. EL84

Good for guitar amps. Third harmonic distortion

predominates. e.g. Vox AC30 using EL84s.

Bipolar Transistor

Cheapest. Difficult to use in Class-A due to thermal

runaway risk. Most efficient. e.g. 2N3055.

MOSFET

Most reliable, best h.f. response but least linear. e.g.

2SK135 and 2SJ50.

DISTORTION LOWEST IN MID BAND

THD 4 AT 10W
1%

20Hz 1k : 20k

LOW DISTORTION AT LOW LEVELS
GRADUAL CLIPPING

60W

Fig. 2. Typical valve distrotion — Class-A.

Everyday with Practical Electronics, June 1995

Phase-splitter

A phase-splitter is always necessary in
push-pull valve amplifiers because com-
plementary valves are not available. All
valves are like n.p.n. devices, so unless
someone can invent a positron emitting
electrode using some kind of anti-matter,
the p.n.p. valve is a long way off.

Single-ended vs
Push-pull operation
Single-ended valve amplifier designs do
not need a phase-splitter at all and have a
nicer sound because the second harmonic
distortion is not cancelled, which can leave
remaining third harmonics exposed, as
with push-pull amplifiers. The drawback

_ with the single-ended approach is that the

output transformer is a pig to design —
because there is a net d.c. current flow.

In push-pull, the d.c. current flows of
both output valves are in opposite direc-
tions cancelling any generated steady-state
flux in the transformer core. In single-
ended designs a gap is required in the core
to prevent saturation which makes good
inductance figures hard to achieve.

The end result is that single-ended output
transformers start at four times the price of
an equivalent push-pull type. If cost is no
object, single-ended triode designs give the

435

nicest sound, but a push-pull ultra-linear
amp gives most of the attributes of valve
sound for the lowest cost.

Op.amp
Phase-splitter

The op.amp phase-splitter was chosen
because it is more stable, avoiding the drift
that occurs with valve based designs. Since
it operates at low levels, it operates in
Class-A and clips long after the output
valves clip, avoiding any solid-state type
sonic signatures. It also provides a low
impedance balanced input of the type used
in top studio technology to avoid hum
pick-up (most valve amplifier inputs are
very high impedance and unbalanced).

Since the amplifier is intended to be used
with CD players, which almost invariably
use 5532 op.amp i.c.s in their output fil-
ters, it is felt from an engineering point of
view that one extra will not be perceived.
Incidentally, 80 per cent of top selling al-
bums are mixed on SSLs which use at least
thirty 5534s in the signal path.

A pair of differential op.amp. stages
with their inputs wired in parallel anti-
phase form the basis of the phase-splitter.
This configuration was popularised by Ted
Fletcher of the Alice mixer company to
obtain an equal impedance on both inputs,
since the standard single differential amp
has unequal impedances, which impairs the
common mode rejection ratio. The circuit
also gives additional anti-phase output
making it ideal for use as a phase-splitter.

CIRCUIT
DESCRIPTION

Looking at the phase-splitter circuit in

more detail, the full circuit diagram of the

EPE HiFi Valve Amplifier is shown in Fig.
4. The phase-splitter circuit has a gain of
four times, sufficient to fully drive the
valves, but not so high that it clips with full
CD level signals.

To ensure maximum headroom the rail
voltage is 33V to 36V. The differential
stages are band limited to 40kHz by
capacitors C3 and CS. These also serve to
prevent r.f. breakthrough.

Both op.amps are biased to half-rail

(16:5V) for single-rail operation. This

necessitates the use of blocking capacitors
Cl and C4 at the input and C7 and C8 at
the output.

DRIVER STAGE

An ECC83 triode valve (V1) is used to
amplify the outputs of the op.amps to over
25V r.m.s. to fully drive the output stage.
Using a 400V h.t., anode resistors R26
and R29 and cathode resistors R15/R16
and R11/R12, the ECC83 sections deliver
almost their maximum gain of around 50
times.

‘OP. AMP BASED
PHASE -SPLITER

o> PY Ta Pee ee Ke | ;
Bis /

Fig. 3. Block diagram of the EPE HiFi Valve Amp/ifier.

To prevent oscillation the grids (pins 2
and 7) are fed by stopper resistors R25 and
R28. The grids are held at OV potential by
pull-down resistors R24 and R27. Negative
feedback is applied in a balanced fashion
from the output transformer secondary to
cathode resistors R16 and R12.

To make up the total 2-2 kilohm cathode
resistance required for correct biasing at
2V, two kilohm resistors R15 and R11 are
included in series with R16 and R12. These
resistors are bypassed by capacitors Cll
and C9 to ensure maximum open-loop
gain.

Finally, the output of the driver valves
are fed via capacitors C15 and C17 to the
output stage. Since the ECC83 anodes
(pins 1 and 6) sit at 205V it is essential
that low-leakage 400V capacitors, such as
polycarbonate or polypropylene, be used
here.

The ECC83 valve was chosen for its high
gain and availability. More adventurous
constructors may wish to use a _ higher
power valve such as the 6SL7, or better still
the 12BH7, to get lower distortion.

OUTPUT STAGE

A pair of EL34 valves (V2, V3) in the
standard Mullard ultra-linear configura-
tion will give around 20W at 0-8 per cent
total harmonic distortion (t.h.d.) open-
loop. The valves operate in pure Class-A
up to around 15W and after that point the
system operates to some extent in Class-B
and this is given the classification AB1.

SAFETY WARNING |
This project is NOT for beginners

Not only is there mains voltage in this amplifier, there is.
also 450V h.t. which is even more dangerous because it

is d.c., which means that muscles may ‘‘freeze”

Always

use well insulated probes when testing and always check if

switched off.

It should be pointed out that the I.e.d.

436

is extinguished
when the h.t. fuse has blown, this means that the bleeding
function is also disabled and the capacitors could still be
holding a lethal charge. The same applies if the amplifier is
operated with the phase-splitter board removed.

The maximum output power just before
clipping into 8 ohms is 24W r.m.s. Only
when the amp is driven beyond clipping
are the valves pushed to full cut-off. This
point is visible on the ‘scope and it
looks like a crossover kink in the middle
of the waveform when the amp 1s clipped
hard.

When this occurs the output valves are
being driven into “grid current”. Grid cur-
rent flows when the grid is driven more
positive than the cathode, causing it to
act like an anode picking up some of the
electron stream. In the case of the EL34 the
cathode voltage is around 32V so the input
voltage would have to exceed this figure to
give rise to grid current.

Grid current can cause problems in that
it tends to charge up the coupling
capacitors which, because of their long
time constant in association with the
discharge paths, can cause slow shifts in the
d.c. bias. This can manifest itself as
“speaker pumping” when the amp is driven
hard with pulsed signals.

To prevent parasitic oscillations, resis-
tors R35 and R31 are used as grid stoppers
on the control grids of the output valves.
Resistors R34 and R30 hold V2 and V3
grids (pin 5) at ground potential. Their
value is the highest allowable to reduce
loading on the driver stage.

The ultra-linear taps on the output trans-
former are connected via resistors R37 and
R33 to the suppressor grids, pin 4. These
help maintain linearity at high levels and
are also wired close to the valve socket to
help act as grid stoppers.

BIASING

The cathode resistors R32 and R36 have
to dissipate high power and thus MUST be
a high power type. These resistors generate
the necessary bias for the output valves by
making the cathode positive with respect
to the grid, which has the same effect as
making the grid negative with respect to
the cathode.

Indeed, some amplifiers employ a
separate negative power supply for the grid
bias. This system of biasing is called “‘fixed
bias” as opposed to cathode bias and can
be used to obtain higher continuous power
ratings.

Everyday with Practical Electronics, June 1995

Specification...

30W r.m.s. into 4 ohms
24W r.m.s. into 8 ohms
I7W r.m.s. into 15 ohms

300mV r.m.s. for full output
20Hz to 20kHz, +0-2dB

less than 0-1% T.H.D. at IS5W into 8 ohms
in midband.

0-25% at 50Hz mostly
second and third
harmonic

Power Output:

Input Sensitivity:
Frequency Response:
Distortion:

Power Consumption: 95W
Signal-to-Noise/Hum Ratio: — |00dB

For pulsed type music signals found in
hi-fi applications however, the power ad-
vantage is insignificant and so only tends to
be found in guitar amps. It is also less reli-
able since if the bias power rail should go
down, the direct grounding of the cathodes
would allow a huge current to flow through
the output valves and transformer, possibly
resulting in expensive failures.

To prevent localised negative feed-
back stopping the output valves being
fully driven, the cathode resistors are
bypassed with electrolytic capacitors C16
and C18. Proponents of fixed bias would
no doubt argue that the elimination of
these electrolytics would be beneficial.
However, as with all electrolytics used in
audio signal positions, if the value is made
big enough (so no signal voltage appears

across
the capacitor)
and there is a
positive bias voltage
across it, no distortion will occur.

It is possible to use a single cathode resis-
tor and capacitor common to both valves,
as used in the Quad, but this is a false
economy since it means matched valves
then have to be used.

NEGATIVE
FEEDBACK

Around 20dB of negative feedback is
included around the amplifier, mainly to
extend the frequency response, lower dis-
tortion to below around 0-1 per cent and
help mitigate the effects of any valve mis-
matching. The feedback is taken from the
output transformer secondary and applied
in a balanced form to the driver stage

Fig. 4.. Circuit diagram for the Phase-spiltter and power output stages for the HiFi Valve Amplifier. Note that capacitor C22 and

resistor R43 are optional, see text.

Everyday with Practical Electronics, June 1995

437

where it is developed across R12 and
R16, the unbypassed cathode resistors in
_ the driver stage. It was not considered
desirable to include the op.amp in the
overall feedback loop, since this would
have made the open-loop gain too high,
resulting in hard clipping.

The level of feedback is set by resistors
R14 and R18, with optional low frequency
compensation provided by the RC net-
works comprising resistors R13 and R17
and capacitors C10 and C12. The total
feedback resistance must not be reduced
below one kilohm or there is a risk of low
frequency instability setting in.

High frequency compensation was not
found to be necessary, but it could easily be
included using the p.c.b. positions occupied
by R14, C10, R17 and C12. Another op-
tion is afforded by C22 and R43 which
allow a little high frequency boost to be
included if desired. Note that these com-
ponents are such a rare option that there
are no holes for them on the p.c.b., they
will have to be soldered across the ends of
resistors R14 and R18.

The open-loop frequency response of the
amplifier, which exhibits —1dB points at
30Hz and 15kHz, is shown in Fig. 5. With
negative feedback the response is flat from
20Hz to 20kHz as shown in Fig. 6.

The feedback network can be used to
provide a degree of frequency response
manipulation to compensate for speaker
deficiencies etc. Fig. 7 shows such a curve
where a little boost at 50Hz and 12kHz has

been applied to give a better balance with a

pair of small bookshelf speakers.

In this case capacitors C10 and C12 were
made 470n while C22 was 6n8 and R43 was
given a value of 1-6 kilohms. To avoid ex-

cessive lift at extreme I.f., the phase-splitter

input coupling capacitors Cl and C4 were
reduced to lpF.

POWER SUPPLY

It was mainly the power requirements of
valves compared to transistors that led to
their demise in the 1960s. The power con-
sumption of this amplifier is very high, with
21W (3-3A at 6:3V) being used for heater
power alone. The h.t. current is 140mA at

(277) eo} C3 extern

430V or 60W, giving a total of around 95W
including transformer losses! This is even
when the amplifier is just idling since it is
basically Class-A.

The complete power supply circuit
diagram, based around Maplin’s “High
Power Valve Mains Transformer’’, is given
in Fig. 8. This transformer was used in
Maplin’s valve amp design to power two
stereo channels. In the authors opinion it
ran much too hot for long-term reliability,
so in this design, an individual transformer
should be used for each channel. This
allows the amplifiers to be constructed as
monoblocks (two for stereo), simplifying
“earth loop” and crosstalk considerations.

Original power supplies for valve
amplifiers used valve rectifiers and
smoothing chokes. A valve rectifier was
abandoned in favour of silicon since they
are expensive, wear out like any valve and
consume extra heater power. Another
advantage of the silicon rectifier is that it is
easy to use as a bridge.

Most valve rectifiers are of the double
diode type which needs a centre-tapped

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Everyday with Practical Electronics, June 1995

secondary on the power transformer with
twice the voltage. A silicon bridge saves
money on the mains transformer and
makes it more reliable because the voltage
Stress is lower.

However, there is a problem with solid-
state rectifiers and that is their immediate
turn-on, whereas a valve rectifier slowly
warms up and applies the h.t. voltage to
the circuit gradually. The slow turn-on
characteristic of valve rectifiers protects
capacitors from destructive surges, but
more importantly, prevents cathode strip-
ping in the valves where the full h.t. is
present but the cathode has not yet warmed
up. The mechanism involved is fairly com-
plex but is basically due to the electrons
being pulled from the barium oxide coating
on the cathode, resulting in reduced emis-
sion in the long term.

To minimise the problem of cathode
stripping, a Brimistor (R42) is. used. This is
a special type of thermal resistor (thermis-
tor) formerly made by Brimar and later
STC, which has a high resistance when cold
which reduces to a low value when hot.

The type used in this design is the CZ6,
which has a resistance of four kilohms cold
and 300 ohms hot. This is not as good as
the valve rectifier which is an open circuit
when cold, but it certainly helps.

If the thermistor cannot be obtained, a
Standby switch is an alternative. It is even
possible to wire a valve rectifier, such as a
GZ37, in series with the bridge rectifier
with both sections connected in parallel.

This would then still obviate the need for a

centre-tapped secondary.

In the days when electrolytic smoothing
capacitors were only available up to 16yF,
additional smoothing was needed and this
was achieved by using a smoothing choke.
Unfortunately, with the passing of time,
Capacitance has become a much cheaper
commodity, while the cost of inductors has
increased in line with inflation,

Since it is now possible to buy standard
smoothing caps up to 220uF, we can dis-
pense with the choke and use resistance in
its place. In this case, the Brimistor forms
the resistive smoothing element and a surge
resistor R39 protects the first smoothing
capacitor and the rectifier from the switch-
on surge. Note that the first capacitor C21
must be a 500V type because the no load
voltage at turn-on is around 480V.

For safety the chassis is Earthed directly
to the mains earth, while the “signal earth”’
is only connected to the mains earth via
resistor R41 to prevent ground loops. The

Fig. 8. Circuit diagram for the amplifier Power Sup,

SRE IE yee PRPs)

‘ F
Pe eee ee Bee Pe ies

‘ P| rr ‘ * 7 a ® Vik a oe

4 A Rey a Phas on

“star” earth point for the amplifier is
formed from a thick piece of tinned copper
wire strapped between the two smoothing
capacitors C20 and C21. To avoid the
charging current pulses causing buzzing,

sis

ply section.

the output of the rectifier is wired directly —

to the terminals of C21.

Further smoothing and decoupling for
the driver stage is provided by R38 and
C19. Since the driver stage only consumes
around 1-8mA, this rail can be used to
power external pre-amps etc. if desired.
Resistor R38 will have to be reduced
accordingly to compensate for the extra
current drawn.

HEATER POWER

All the heaters are run on a.c. straight
off the mains transformer T2. D.C. heater
power is not needed since all the valves run
at relatively high signal levels.

The heater winding is centre-tapped to
ground (OV) which reduces hum, by

balancing any residual electron emission.

from the heaters.

OPL_AMP

POWER SUPPLY

The relatively low voltage of 33V to 36V
needed for the op.amps was a bit of a
headache, in that almost 400V needed to be
dropped. This meant that around five watts
needed to be dissipated in a “dropper
resistor”. This would normally be con-
sidered unacceptable in an efficient solid-
State design, but where the output valves
are dissipating around 75W, this seemed to
be only a minor problem.

In the end, the dropper resistor solved two”

additional problems: it provided a bleeder
resistor function for the h.t. rail, prevent-
ing shock risk from residual charge in the
smoothing caps. Secondly, by placing an
l.e.d. in series, a reliable power indicator was
provided, which also showed when the h.t.
rail had discharged (see Fig. 4). |

The dropper resistor is composed of
three 10 kilohm 2W resistors R21, R22
and R23. However, the board will accom-
modate a single wirewound type if this can
be obtained. A more reliable choice would
be a metal-clad type bolted to the chassis to
aid cooling. :

A simple Zener diode regulator (DS)
holds the rail voltage at 36V and capacitor
C14 filters out any ripple and Zener noise.
The half-rail bias for the op.amp is derived
by resistor R19 and R20 wired as a poten-
tial divider. Decoupling of the bias is
provided by capacitor C13. ,

Everyday with Practical Electronics, June 1 995

Bh

very reliable. .
The driver anode load resistors are un-

COMPONENT
SELECTION

Components are under much greater
temperature stress in valve equipment.
Electrolytic capacitors tend to dry out,
especially the small ones used for cathode
bypasses and coupling because they have a
large surface area-to-volume ratio.

Fortunately, the smaller cathode
electrolytics can easily be replaced by solid
electrolyte types, such as solid tantalum
and solid aluminium _ types.
aluminium types (made by Philips and

Rifa) are even more reliable than tantalum.

The high wattage resistors are under con-
siderable stress and metal-oxide types such
as Vishay FP] and FP2 are recommended
for the film types. For the wirewound resis-
tors, Welwyn W22 series vitreous types are

der high voltage stress and physically small
resistors, such as Maplin’s 0-6W commer-
cial rating (0-25W industrial rating) metal-
film types, will not be robust enough. Use a
full-size industrially rated type such as the
0-5W metal-film types. Resistors mounted
on tag strips are under greater lead-pull
stress than resistors mounted
with the support of a p.c.b.,
so full-sized types are recom-
mended here also.

439

Solid

Cheap valves from Eastern Europe usually work well, Chinese tubes
do not seem to last as long. Using original Mullard types is not cost
effective because of inflated collector’ prices. The EL34B is slightly
stronger than the EL34S.

CONSTRUCTION

Traditional chassis construction is used for the bulk of the amplifier
(many TV service engineers discovered that power output valves soon
burnt their way through printed circuit boards!) However, a p.c.b. is
used for the op.amp phase-splitter and feedback components in view of

COMPONENTS

R1, R4, R5, R6, RY, R10 100k (6 off) See
R2,R3,R7,R8,R19,R20 22k (6off) SOP

R11,R15 2k (2 off)
R12, R16 200 (20) LZALK
_ R13, R17 4k3 (2 off) Page
R14, R18 1k2 (2 off) ©
R43 . 1k2 optional
All 0:-25W 1% metal film (for p.c.b.)
R24,R27 — 1M (2 off)
R25, R28, R31, R35: 2k2 (4 off)
R26, R29 220k (2 off)
R30, R34 680k (2 off)
R40 12 (depends on lamp LP1 current)
All full-size 0-5W 1% metal film .
R33, R37, R41 1k (3 off)
R38 18k
All 1W 5% carbon film or 2% metal oxide FP1
R21, R22, R23 10k (3 off) (can be replaced with
single 33k 7W WW)
All 2W 5% carbon film or 2% metal oxide FP2
R32, R36 470 (2 off)
R39 68
All 7W 5% wirewound Welwyn W22
R42 CZ6 Brimistor (thermistor) — see text
Capacitors
C1, C4 47, axial tantalum, 20V (2 off)
C2, C3,C5,C6 10p polystyrene 2:5% (4 off)
C7,C8 . 470n 5mm polyester 10% (2 off)
C9, C11 33 tantalum or solid aluminium, 10V (2 off)
C10, C12 22 polyester 20%, 63V (2 off)
C13 4u7 tantalum bead, 25V ;
C14 1000p radial elect. 35V
C15, C17 470n 400V axial polycarbonate or
polypropylene, 10% Wima MKB3
(see text) (2 off)
C16, C18 68p axial solid aluminium (type 123), 40V (2 off)
C19 47, 450V axial
C20 68p to 220 450V
C21 68pu to 220 500V
C22 6n8 polyester (eq. option)
C23 330n polyester
Valves
V1 ECC83 triode
V2, V3 EL34 beam tetrode (2 off)
Semiconductors
D1 to D4 BYX84 or 1N4007 1000V p.i.v. 1A rec. diode (4 off)
D5 36V or 33V 400mW Zener diode
D6 5mm red diffused I.e.d. 20mA
IC1 NE5532N dual low noise op.amp
Miscellaneous
T1 Valve output transformer, primary anode-to-anode impedance 6k6
T2 240V a.c. mains transformer, with 350V 250mA secondary and 6:3V
7:5V centre-tapped valve heater winding
SK1 | filtered mains IEC socket
S1 d.p.d.t. mains toggle switch, with indicator lamp
FS1 3A cartridge fuse, with panel fuseholder
FS2 315mA quick-blow 20mm fuse, with panel fuseholder

Diecast box, size 273mm x 172mm x 51mm; printed circuit board (phase-splitter) avail-
able from EPE PCB Service, code 941; 8-pin d.i.I. socket; chassis-mounted B9A valve
holder; chassis-mount octal valve holder (2 off); 3-pin XLR chassis socket; loudspeaker
terminals; |.e.d. holder; 2-pin Molex assembley (4 off); 3-pin Molex assembly (2 off);
6-way tag strip, plus two “earth” mounting tags; 2-way tag strip, plus three “earth”
mounting tags; capacitor clips (2 off); small cable ties (3 off); stick-down plastic cable tie
mounts (3 off); p.c.b. mounting pillars plus bolts (4 off); multistrand connecting wire,
7/0:1 for Molex connectors; 3-core mains lead; mains wire 7/0-2 for valve heaters; ap-
prox. 250mm length twin-screened cable; 102mm length 16 s.w.g. tinned copper wire;
102mm 22 s.w.g. tinned copper wire; one metre silicone sleeving; M4 nuts, bolts and
washers (8 off); M3 nuts, bolts and washers (9 off); screw locking compound; solder etc.

Approx cost £ y | 7 | O
guidance only

Fig. 9. Phase-splitter printed circuit
board component layout and full size
underside copper foil master.

Before we undertake the traditional task
of “‘chassis bashing” associated with valve
work, we can first tackle the more familiar
operation of constructing the printed cir-
cuit board (p.c.b.). The top side component
layout and full size underside copper foil
master pattern are shown in Fig. 9. This
board is available from the EPE PCB Serv-
ice, code 941.

Commence construction of the Phase-
splitter p.c.b. by mounting components in
height order starting with resistors first, but
leave the semiconductors until last. Be
especially careful to get the polarities of the
electrolytic capacitors, Zener diode and the
op.amp i.c. the right way round on the
board.

The dropper resistors R21, R22 and
R23 should be soldered in a clamped
fashion onto the track by firmly bending
the lead over. This is because components
that “run” hot put additional thermal
stress on the soldered joints. The resistors
should also be spaced away from the p.c.b.
by ceramic beads, if possible, to prevent
scorching.

Make sure that the straight pin p.c.b.
connectors are soldered on the board with

440 Everyday with Practical Electronics, June 1995

g 25mm
FOR OCTAL 90

VALVE
HOLDERS

03mm

CATHODE
TAGSTRIP

MOUNTING HOLES
FOR PHASE-SPLITTER -
P.C.B. J 3m
DRIVER e , 75

TAGSTRIP' ”
SMOOTHING
MOUNTING HOLES CAPACITOR

CUT OUTS

Chassis layout dimensions and drilling
details, with the position of all the com-
ponents having been worked out to ease
the wiring, minimise hum and prevent un-
desirable coupling, are shown in Fig. 10.
One of the basic considerations to minimise
hum is that the two transformers have been
placed as far apart as possible with their

- cores at right angles to each other. Another
is that the low-level part of the circuit, the
phase-splitter, has been placed as far away
as possible from the power transformer.

The smoothing electrolytics are away
from the drying heat of the output valves
and the output wiring is kept separate from
the input wiring by running each on op-
posite sides of the case. Since it is desirable
for aesthetic reasons to have all the con-
necting leads coming out of the rear of the
chassis the main input lead has to be a
screened cable, since it runs near the power
supply electrolytics.

SWITCH 016mm

16

LOUDSPEAKER
SOCKETS 08mm

Next Month: We conclude with all
the interwiring and final testing.

Fig. 10. Chassis top, front and rear component layout,
details and dimensions.

their locating “friction lock’? headers cor-

rectly positioned, see Fig. 9. The make up
of the interconnecting plugs is shown next

month.
Once the Phase-spilitter board has been
constructed it should be put to one side un-
til the diecast box chassis drilling has been pales hasan
completed. board showing the
component layout.
CHASSIS Note the high
CONSTRUCTION wattage resistors
A diecast box is used for the chassis be- are stood on-end

cause they have nice looking rounded edges and have ceramic
and are easy to drill. Do not use steel for beads keeping the
the chassis since this will spread the mag- resistor bodies
netic field of the mains transformer around. clear of the p.c.b.

Everyday with Practical Electronics, June 1995 . | 44]

A roundup of the latest
Everyday News from the

Innovations

VIRTUAL SURGERY

Virtual reality and I.c.d. holography combine to meet the need for

RGENT need for a method of

training “keyhole surgeons” in
conducting laser operations has
opened up a world of medi-
cal opportunity to Professor Bob
Stone’s Virtual Reality (VR) team at
Salford. He has recently taken on
the role of Director of Virtual Reality
Studies for the North of England
Wolfson Centre for Minimally
Invasive Therapy, and heads the VR
Division of Intelligent Systems
Solutions (formerly known as
Advanced Robotics Research).

In recent months the media has
drawn attention to public anxiety
about key-hole surgery, leading to a
call for action in improving the
training of surgeons graduating
from conventional open surgery to
the more remote techniques of laser
telesurgery.

OPERATIONAL
RESEARCH

Because live animal-based training
is prohibited by UK _ regulations,
primary key-hole surgical experience
is presently fostered through the
remote handling of ‘‘dolly mixtures”,
grapes, raw chicken tissue, plastic
tubing and foam-mounted balloons.
It is now realised that provision
of even a basic virtual human
simulator will help to develop speci-
fic surgical skills.

VR has the potential to reproduce
the natural and fluidic characteris-
tics of human anatomy, requiring
only a_ re-setting of the host
computer, once a training session
has been completed. Professor Stone
says the use of their techniques
will provide the “flight simulator”
qualities surgeons are demanding
- the ability to generate cost-
effective what-if scenarios, such
as insufflation failures, anatomical
ambiguities, patient distress and
instrument failure.

With support from the Department
of Health and the Wolfson Founda-
tion, a project was initiated at
Salford University integrating the
skills and talents of a number of
academic and small company teams
from throughout the UK, backed by
know-how from the VR team. In the
early part of the project the team
observed and recorded the work of
the surgeon by visiting operating
theatres and using video and digital
endoscopy.

442

training keyhole surgeons

— by Hazel Cavendish

Laparoscopic Cholecystectomy opera-
tion in progress. Courtesy of University
of Manchester.

During extensive discussions with
practising and trainee surgeons they
learned that medics would not accept
any form of head-mounted displays.
These were deemed unacceptable for
image quality, in-theatre communica-
tion, ergonomic and hygiene reasons.
There was a 50-50 split in opinions
as to the need for stereoscopic view-
ing and the importance of tactile and
force feedback.

Some surgeons claimed that vision
was the overriding sense; others in-
sisted that a simulator would have
to include a reasonable representa-
tion of such features as elasticity,
instrument constraints within the
body cavity, and varying degrees of
movement ‘‘viscosity’”’.

HOLOGRAPHIC
EVALUATION

It was necessary to adopt a dis-
play technology which did not re-
quire any form of head or face-
mounted peripheral to achieve the
necessary stereoscopic effect. A solu-
tion was offered by the Richmond
Holographics autostereoscopic dis-
play system which uses conventional
le.d.s combined with Holographic
Optical Elements (HOEs).

HOEs are devices made _ using
similar techniques to those used

for making holograms, and are
recordings of the interference pat-
tern which results when two or more
laser beams intersect. Unlike ordi-
nary holograms, they do not contain
an image: instead they are used to
bend, focus and otherwise mod-
ulate light in unusual and _ fre-
quently complex ways, with optical
properties that cannot be achieved
with conventional optics.

The use of special HOEs make it
easy to fabricate a display which
directs light from one image into one
of the viewer's eyes and light from a
second image into the other eye.
Both images can be displayed on one
l.c.d. The HOE permits the display to
compensate for viewer movement;
binocular fusion occurs to produce a
three-dimensional whole image. The
Richmond Holographics system will
allow Wolfson Centre researchers to
evaluate the necessity for three-
dimensional endoscopy.

In due course the VR system means
that a practice operation will be able
to be carried out in the same way as
a real one, but instead of a living
patient on the operating table, the
surgeon will have an electronic box
in which to insert his instruments.
Then, as in a conventional keyhole
operation, surgery will be performed
by looking at a TV monitor.

OVERCOMING
SCEPTICISM

Yet Professor Stone declares there
is still an uphill battle: “Surgeons
and the medical fraternity in the UK
generally look upon VR and related
technologies with sceptical eyes,” he
says. “Also, for some reason (and
with one notable exception), the
larger VR hardware and software
companies in Britain seem to have
written-off the medical area as being
a non-lucrative market.

At present, the cost of VR tech-
nologies is totally unjustifiable for
medical training; up to £150,000
for the computing platform alone.
Nevertheless, rapid advances are
being made in the development
of much cheaper, high-performance
graphics processors for PC _ plat-
forms. It is highly likely that com-
puters delivering the performance
required by the medical fraternity
will become available at a more
realistic in-hospital price within two
to four years.

Everyday with Practical Electronics, June 1995

emai iy an Ser Rae ae et <eampaacin —-
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4 * hte ah dat Nie tia,
Warne a2 RATES

WINDOWS P.C.B. PACKAGES

CADPAK and PROPAK for Windows have recently been
introduced into the Labcentre range of software products.
CADPAK for Windows includes both schematic drawing and
p.c.b. drafting tools but as an entry level product, there is no
netlist link between them. CADPAK is especially suited to
hobby, educational and small scale schematic and p.c.b. design.
PROPAK for Windows adds netlist based integration, auto-
matic power plan generation and a powerful auto-router.

Both of these packages for Windows are based on well proven
existing Labcenter products (which run from DOS). At the same
time, the new products make full use of Windows features such
as on-line help. PROPAK autorouting runs as a true 32-bit
application — making it faster than 16-bit products.

CADPAK and PROPAK for Windows are priced at £149 and
£495 respectively. Contact Labcenter Electronics, 53-55 Main
St., Grassington, N. Yorks BD23 SAA. Tel: 01756 753440, Fax:
01756 752857 for more details of these products and upgrades

from existing Labcenter products.

EVENTS

ON AIR

The Amateur Radio, Electronics and
Computer Club (AREC Club) of Malta
are organising an ‘‘on the air’ activity to
mark Victory in Europe Day. The call
sign is QH50VE and operation, on a 24
hour basis, will continue during May
6th, 7th and 8th. Frequencies, subject
to interference and propagation, will
be 3:775MHz, 7:044MHz, 14:225MHz,
21-25MHz and 28:55MHz SSB.

AREC Club, PO Box 114, Valletta
CMROI Malta.

CLACTON

CLPK have joined forces again with
Sharward Promotions (the Shows and
Exhibitions Division of Sharward Serv-
ices) to undertake the organisation of The
East Coast Amateur Radio and Com-
puter Rally, which this year will be
held on August Bank Holiday Sunday,
27th August. The venue is the Clacton
Leisure Centre, Vista Road, Clacton-on-
Sea, Essex.

Major suppliers and manufacturers of
radio equipment, computers and com-
puter software, accessories, antennas and
secondhand gear will be at the Rally.
There will also be a “Bring and Buy” sale.

The show runs from 10.30 a.m. to 4.00
p.m., with the bar and cafeteria available
from 11.00 a.m. There is a Free car park.

For further details please contact the
organisers: Sharward Promotions, Upland
Centre, 2 Upland Rd., Ipswich IP4 SBT.
Tel: 01473 272002, Fax: 01473 272008.

Also organised by the same company is
the Ipswich Computer Show, Saturday
May 20, 10 am. to 4 p.m. At Willis

VIRTUAL PA

A digital answerphone which can also store faxes,
operate as a high speed modem and automatically Ole Bae
forward messages is now available from Andest Ltd. er ei

The Virtual PA (V.PA) can be accessed from
anywhere in the world to retrieve voice messages
or redirect faxes to any fax machine. The
standard unit contains |Mbyte of memory,
enough to store 20 minutes of voice or |

approximately 50 fax pages, but this can be
expanded to 8Mbytes if needed.
The unit can be easily programmed using

the built in five button key pad and lLce.d. _
screen or it can be linked to a PC. The stan-
dard version operates at 2400bps for data and >

19200bps for fax and costs £399.

Contact Andest Ltd., Chancery Court, Lincoln
01494 429309, Fax:
Bulletin Board — Fax Back Service:

Rd., High Wycombe. Tel:
01494 538598,
01494 510560.

Carroon Sports and Social Club, The
Street, Rushmere St. Andrew, Ipswich.

LONGLEAT

The 38th Longleat Amateur Radio Rally
is at Longleat House (not the Safari Park)
on Sunday 25th June from 9.30 a.m. to 5
p.m. Further information from Gordon
Lindsay GOKGL, 66 Jubilee Crescent,
Mangotsfield, Bristol. Tel/Fax: 0117 940

2950.
VINTAGE

The fourth National Vintage Com-
munications Fair will take place in the
Pavilions Hall of the NEC in Birmin-
gham on Sunday, May 14 and _ will
feature thousands of rare and _ collec-
table vintage technology items with spe-
cial emphasis on early radios, television
receivers, gramophones, telephones and
classic 1950s hi-fi. In attendance will be
over 300 specialist dealers from the UK, the
Continent and the USA. For the seasoned
collector, it’s the event of the year.

The fair is presented annually by the
Sound and Vision Yearbook which is a
comprehensive reference guidebook to over
one hundred sound and vision collect-
ing hobbies from Amateur Radio through
Classic Audio, Theatre, Cinema and other
Organs/TV and Radio Related Collectables
etc., to Vintage Wireless. For early arrivals
at this year’s Fair, the £5 admission price
includes — while stocks last — a free copy of
the latest edition of the Yearbook.

More information and copies of. this
fascinating little Yearbook (£3.50 post free)
are available from Sunrise Press, 2-4 Brook
St., Bampton, Devon EX16 9LY. Tel:
01398 331532.

Everyday with Practical Electronics, June 1995

SCHOOLS ONLINE

A pilot scheme to help more secon-

dary schools get on-line to Internet

was recently launched by Tim Eggar,
Minister for Industry and Energy with
£250,000 of DTI backing.

“We are working with the
information technology and com-
munications industries who are
going to ‘adopt’ local schools,
providing equipment, line connec-
tion and training. Industry will be
contributing about £350,000, over
half the total cost. DTI will provide a
help desk and project management,
and will ensure that suitable
educational material is available,”
said Mr. Eggar.

“The companies are close to iden-
tifying the 50 schools who will
participate in the project. These are
either near the companies’ own
plants or are amongst those who
have been ringing asking to be
involved.

“If the pilot stage is a success,
and if enough schools sign up to
the initiative, then the scheme will
be extended with DTI committing
another £750,000 for a full pro-
gramme in 1996.”

The companies involved have
come together to form a ‘National
Information Infrastructure (NII) Task
Force’. Based on the Federation of
the Electronics Industry, these
companies include GPT, IBM, and
Lucas Systems as well as a number
of smaller companies such as
Softwright Systems, the independent .
software company.

lan Taylor, the DTI Technology
Minister responsible for coordinating
multimedia matters, has recently
established a Multimedia Industry
Advisory Group. “The Group will
monitor progress of the Online
project’, said Mr Taylor, ‘‘and assess
its contributions to education.

“We are aware of concerns about
information on the Internet. It will
obviously be important to provide
adequate protection against un-
desirable material, and this issue is
under consideration by members of
the Schools Online Project.”

443

New Technology

lan Poole investigates the intense development of flash and
ferro-electric memories which promises enhanced |
endurance, speed and density, while cavities replace gutters
in research to improve silicon purity.

EMORIES are one of the most impor-
Mien areas for development at the
moment. There has been phenomenal
growth in the sales of computers over the
last ten years. This has resulted in a greater
need for smaller and more _ portable
systems, which in turn has meant that the
requirements being placed on memories are

becoming even greater.

One development to hit the market in
recent years has been the flash memory.
This provides many improvements over
other memories which are available at the
moment because the technology consumes
less power and has a very high density.

Some manufacturers are even using these
memories to make replacements for disk
drives. Although they are more expensive
than a standard disk drive they offer the
advantage of being far more robust, and
much smaller.

There are many other uses for these
devices and as a result a large number of
manufacturers are entering the market.
This increased competition has forced the
development of these devices ahead. Intel
now manufacture a 16Mbit device and no
doubt other companies will follow suit in
due time.

Another area of development of flash
memories is in increasing their life time.
The memories have a limited number of
write/erase cycles and some of the first
devices to hit the market only had a lifetime
of about a thousand cycles or so. Now
development has improved their perfor-
mance quite considerably and most devices
will offer an endurance of 100,000 cycles,
and there is a growing trend for figures of
1,000,000 cycles to be quoted.

Obviously cost is an important factor.
Current flash devices are roughly three
times the cost of an equivalent EPROM.
This reduces sales and Intel are currently
working towards making flash the cheapest
form of memory on the market. This will
ensure that it is in a commanding position
for the next few years.

Ferro-Electric |
Memory

Despite the enormous interest in flash
technology and the great amount of
coverage it is receiving in the electronics
press it is not the only new memory
technology about. Over ten years ago a
company called Ramtron put forwards the
idea for a ferro-electric memory. Now they
have over forty patents granted for the idea
and a number of others pending.

Supporters of this type of memory des-
cribe it as the ideal solution for portable

444

equipment. It combines many of the fea-
tures required by today’s designers. It is
very low power, high density, high speed,
and offers an almost unlimited number of
write/erase cycles.

The technology uses the property of
certain crystals in which magnetic dipoles
align in different directions according to
the electric field which is applied. When the
electric field is removed the dipoles stay in
place and the data is stored almost per-
manently. The other advantage of ferro-
electric memories 1s that the life of the cells
is measured in hundreds of millions of
write/erase cycles instead of around a mil-
lion for flash memories.

Another advantage is that their power
requirement is around ten times less than
an equivalent flash memory. This is a dis-
tinct advantage for portable applications
where many of these memories are likely to
be used. |

== WORD LINE

FERRO -
ELECTRIC ]

“CAPACITOR™
l BIT LINE

Fig. 1. A cell in a “ferro-electric’
memory.

’

Despite these advantages, ferro-electrics
still have a way to go before they catch up
with flash. One of the main areas where
they are behind is in their density. It is
expected that the first 256K devices will be
made this year and there are rumoured to
be plans for |!Mbit memories sometime in
the future, although no dates are known.
This is a far cry from the 16Mbit flash
devices which are currently being manufac-
tured by Intel. Nevertheless ferro-electric
development is forging ahead.

For the long term, ferro-electrics ap-
pear to provide many exciting possibilities.
However, the technology is still very much
in its infancy and we will have to wait a few
more years to see if they come up with the
goods.

One of the key features which has
enabled today’s semiconductor technology
to progress as far as it has is the purity of
the semiconductors. The main reason why

f.e.t.s were not introduced any earlier was
simply the fact that it was not possible to
produce silicon which was pure enough to
enable them to work reliably.

Now with feature sizes many orders of
magnitude smaller and much more strin-
gent demands being placed on the device
performances, semiconductor material of
the highest grade has to be used. Often
when yields fall and devices do not come
up to their specification the reason 1s
that the base semiconductor was not pure
enough. Even very low levels of impurity
can have a marked effect.

In preparation of the basic silicon for
semiconductor crystals a technique known
as zone refining is used. This removes most
of the impurities, but even though this
method has been improved it is still not
always capable of reducing impurity levels
by the degrees necessary. |

Impurities can be wide ranging, and a
scheme called “guttering” is commonly
used to reduce their levels. To perform this
an unused portion of the wafer, normally
the back or underside is roughened using a
coarse etch. This breaks up the crystal
lattice creating many sites for the im-
purities to lodge as metal silicides. As the
chosen portion of the wafer is unused they
can remain here without any ill effects on
the remainder of the chip.

The process works reasonably well but as
demands on the purity of silicon increase,
it is not sufficient for many of the latest
processes. It does not remove all the im-
purities and the silicides sometimes form
in areas where they are not wanted. Cop-
per, one of the most troublesome impurities
can be reduced to much lower levels by a
process in which some microscopic cavities
are created just below the surface of the
wafer.

The cavities are formed by implanting
helium atoms into the wafer. The wafer is
then heated forcing out the helium atoms
but leaving microscopic cavities or voids
which have nanometre dimensions. These
serve to trap the copper by forming areas
where the copper atoms can migrate. Once
the copper atoms have migrated into the
voids they become bonded to the silicon.
As in the guttering process the voids are
formed in areas of the silicon not used for
the active circuitry.

The use of these voids has a number of
advantages. Once within the voids the cop-
per is held more firmly than if guttering
had been used. In fact the voids are stable
to temperatures over 1100°C; sufficiently
far above most of the temperatures which
would be needed in any of the subsequent
processes. In addition to this the voids are
capable of holding a relatively large num-
ber of copper atoms, making the process
useful when impurity levels are high.

Everyday with Practical Electronics, June 1995

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Constructional Project

THE NAME OF
THE GAME
STAR-STRUCK!
ROY BEBBINGTON

Ter Name of the Game is a series of electronics

PART 4 =

displays, new games employing electronic word-making,
and games of skill.

In the final part this month, we aim for the stars with both
Star-Struck! and Six-Shot Light Zapper, and find hidden at-
traction with a touch of wander-lust. |

projects based on party games or TV quiz games.
Featuring something old, something new, there are
electronic versions of popular, well-established TV games
such as Countdown and Catchword with alphanumeric

bows, 4

tri-colour light emitting diodes (l.e.d.s)

at its points is mounted on a board. To
its sides are two smaller stars, one painted
red and: one painted green. The smaller
stars are the targets and their six points are
fitted with pushbutton switches.

Initially, the central star displays three red
l.e.d.s.and three green ones. During play, the
red and green contestants stand in front of
the board and simultaneously throw soft
rubber balls at the pushbuttons of their star.
As each switch is hit, the l.e.d. at the same
point on the large star changes colour ac-
cording.to which star has been struck. The

N this game, a large star displaying six

aim is to make all six l.e.d.s change to the

same colour: a red team contestant aims to
get an all-red star, and his green opponent
aims to get an all-green one.

BATTLE STABLES

The tri-colour l.e.d.s are activated by six
bistable (flip-flop) circuits, which can be
reset by a central pushbutton switch on

- each.of the target stars to display three red

l.e.d.s.and three green ones. This switch
also offers a bonus target during play to
enable a player to pee a three l.e.d.s at
once. }

In the heat of battle, it may not be ob-
vious when ‘one player has succeeded in
turningzyall six l.e.d.s on to the same colour,
especially if one (or more) of the l.e.d.s
is almost immediately. reversed by the op-
ponent. A. useful addition is an optional

“‘six-light indicator” buzzer circuit, which
sounds.immediately l.e.d.s are displayed as
either-all red or all green. The buzzer sig-
nals the end of the round, or the end of the
game if there are only two contestants.

As seen in Fig. 1, the Star-Struck! circuit
mainly consists of the six identical bistable

- multivibrators, or flip-flops as they are

Estes

commonly called. As the name implies, a
eee has.two stable but opposite output
: states:’ when. one output is high, the other is
~ low and vice versa. Each time a bistable is
suitably triggered, its outputs change to
their opposite states.

446

For the purposes of this game, two
switches are used to trigger each bis-
table, and a tri-colour l.e.d. indicates its
output states. Although bi-colour l.e.d.s
are available, in this circuit the author
found that tri-colour |.e.d.s were easier to
use because of their common cathodes.
The author also preferred to use flip-flops
designed around transistors rather than
using integrated circuit flip-flops. (Desig-
ner’s “spares” boxes often have discrete
components which can be used in place of
more sophisticated devices!)

FLIPPING FLOPS

Taking the circuit formed around tran-
sistors TRI, TR2, and their associated
components as an example, the operation
of a transistorised flip-flop is as follows:
At power switch-on, depending on cir-
cuit parameters, component tolerances etc.,
one of the transistors will switch on in
preference to the other. If TRI is on,

current from resistor R1 flows from its

collector (c) to its emitter (e) and then
through the “red” anode (a) to the cathode
(k) of l.e.d. D1, so turning it on.

The collector of TRI is connected via
resistor R2 to the base (b) of TR2. Thus,
when the collector of TR1 is low so too is the
base of TR2, consequently the latter transis-
tor is held off, and its associated l.e.d. D1

“green” is inactive. In this stable state of the
flip-flop, pressing switch S8, which takes the
base of TR2 to the OV line, will have no
effect as the base is already low.

Pressing switch S1, however, will now.
take the base of TR1 low, so switching off
this transistor. As a result, l.e.d. D1 (red) is
turned off. The collector of transistor TR1
is now held high and current passes via
resistors Rl and R2 to the base of TR2, so
turning on both it and its associated l.e.d.
D1 (green).

The operation of the other five flip-
flops (TR3/TR4, TR5/TR6, TR7/TR8,
TR9/TRIO and TR11/TR12) is basically
identical to that of flip-flop TR1/TR2. The
three flip-flops around TR1 to TR6 are
considered as “Green’s”’ flip-flops, whilst
‘“‘Red’s”’ are those around TR7 to TRI12.
Both groups of flip-flops can be reset to
their “home” colours by switches S7 and
S14 respectively.

Everyday with Practical Electronics, June 1995

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© ' © TRANSISTOR ‘
~ Pe vote ye at ees ee ete PIN VIEW OF BC109
3S ON STRIPBOARD ON STRIPBOARD
BS
S Fig. 2. Topside component layout and underside stripboard
“ __ track cuts and solder joints for the Star-Struck! game.
2

Saas, 3
ee
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2
««€
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Assembled stripboard modules for Star-Struck! and its opp-
tional buzzer circuit mounted on the back of the target board.

Everyday with Practical Electronics, June 1995 447

Fig. 3. Wiring details for the components mounted directly on the Star- Struck! target board.

Pressing the “Reset Green” switch S7
takes to ground the bases of TR1, TR3 and
TRS, via diodes D7, D8 and D9. This
action bypasses switches S1, S2 and S3 but
has a similar effect to pressing all three
together, causing the three flip-flops to
switch to the state in which the green l.e.d.s
of D1, D2 and D3 are turned on. Pressing
the “Reset Red’ switch S14 has a similar
effect on the other three flip-flops, turning
on the red l.e.d.s of D4, DS and D6.

STARRING
CONSTRUCTION

The Star-Struck! game was built on a
sheet of 3-ply plywood measuring 1Sin. x
24in. (381mm xX 610mm), but the base
material and its size can be varied ac-
cording to individual requirements. For
stability, and to protect the components

COMPONENTS

STAR STRUCK! See
Resistors SOP

R1, R4, R5, R8, TALK

R9, R12, R13,

R16, R17, R20, ro

R21. R24 1k (12 off)
R2, R3, R6, R7,

R10, R11, R14,

R15, R18, R19.

R22. R23 10k (12 off)
All 0.25W 5% carbon film.

Semiconductors
Dito D6 _l.e.d., tri-colour (6 off)
D7toD12 1N4148 signal diode
(6 off)
TR1 to
TR12

1IC1,1C2

BC109 or similar npn
transistor (12 off)

4068B 8-input NAND
gate (2 off) (see text)

Miscellaneous

S1 to

$14 s.p. push-to-make switches
(14 off — see text)

$15 S.p.s.t. min. toggle switch

WD1 piezo buzzer (see text)

Stripboard O-1lin. pitch (see text);
plywood panel (see text); wood battens
for frame (see text); R6 size 1-5V cells
(6 off) and battery box; single-core and
stranded connecting wire; solder, etc.

LIS

excl. wood

Approx cost
guidance only

448

Rear view of the Star-Struck/ target board showing all the components and wiring

In their relative positions.

behind it, the board was edged by 5/8in.
(16mm) square battens. Holes should be
drilled in the board to suit the switches,
l.e.d.s and the buzzer. The l.e.d.s can be
mounted via a row of three small holes
drilled for their lead-out wires.

The author constructed his game elec-
tronics on two pieces of stripboard, one for
the circuit of the six flip-flops and one
for the buzzer circuit. The flip-flops were
constructed on a piece of 0-lin. pitch
stripboard (24 strips x 24 holes), com-
ponent layout assembly details for which
are shown in Fig. 2. Note that the transis-
tors need their pins to be re-orientated so
that they correspond with the notations on
the stripboard layout.

INTER-
STELLAR

Connections _ be-
tween the _l.e.d.s
and the pushbutton
switches of the stars
are best made using
rigid wire which,
providing care in
positioning it is
observed, need not be
insulated.. Connections
back to the stripboard
should then be made
using stranded and

insulated flexible wires. Details of the
interwiring are shown in Fig. 3.

Be sure to thoroughly check the com-
pleted assemblies, looking out for missed
track cuts, badly soldered joints and
wrongly orientated components.

When choosing the rubber balls, make
sure that they are sufficiently firm to coun-
teract the contact pressure of the pushbut-
ton switches. Avoid balls which may be so
hard as to damage the switches and 1.e.d.s.

SIX=-LIGHT
BUZZER

The circuit diagram for the optional
“‘six-light’’ buzzer is shown in Fig. 4. The
circuit is used to announce that all lights

Fig. 4. Buzzer circuit for Star- Struck!

Everyday with Practical Electronics, June 1995

of one colour have been switched on. The
circuit consists of two 8-input NAND
gates, IC1 and IC2, one for each colour,
both feeding to the same non-polarised
piezo sounder, WD1. Six inputs of gate
IC1 are connected to each of the collectors
of the odd-numbered transistors, and six
inputs of gate IC2 are connected to each
of the collectors of the even-numbered
transistors. The two spare inputs of each
gate (pins 11 and 12) are connected to the
+ 9V line.

During the game, when neither contest-
ant has gained all six l.e.d.s on, the out-
put pins 13 of both NAND gates will be
high and no current will flow through the
buzzer WD1. As soon as one contestant
gains all six l.e.d.s on, all eight inputs of the
relevant gate will be high and current will
flow through the buzzer into the still-low
output of the other gate. Consequently, the
buzzer will buzz! :

Usually, when the buzzer sounds the
display will immediately show which
contestant’s colour dominates. In a fast
moving game, though, it is possible that
balls may continue to hit the switches
immediately after the buzzer has sounded
and it may be unclear as who really is the
winner. To avoid potential aggravation
between players, the circuit could be
modified so that each gate is fitted with its
own buzzer, each possibly having a
different tone, or being mounted far

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Fig. 5. Stripboard assembly details for the Star-Struck! buzzer circuit.

enough apart so that direction will verify
the winner’s identity. In this case one lead
of each buzzer is connected to pin 13 of its
relevant gate, and the other lead is taken
to the +9V line. This technique may also
be used if readers have difficulty locating
non-polarised buzzers.

Construction of the buzzer circuit was
made on a piece of 0-linch pitch stripboard
measuring 20 strips <x 15 holes. The as-
sembly layout details for this board are

shown in Fig. 5. Both circuits may, of
course, be assembled on a single piece of
stripboard. Be sure, though, to cut the
tracks between the two circuits.

It is preferable that sockets should be
used for the two CMOS NAND gates,
IC1 and IC2. The current consumption of
the piezo sounder WD1 should not exceed
10mA, the maximum output current
available from the CMOS 4068 NAND
gates.

SIX-SHOT —
LIGHT ZAPPER

Throwing light on the war-games count-down.

HIS project is basically a_ light

gun that can be used for games

either having light-dependent resis-
tors (I.d.r.s) as targets or that can be
adapted for them. For instance, the
Star-Struck! project previously described
could be easily modified to use l.d.r.s
instead of the pushbutton targets; 1.e. the
targets would be “beamed” instead of
“struck”. In this case, because of the
spread of the light beam, it would be better
to space out the |.d.r.s to make the game
more skilful by having to re-aim.

Other ideas for using this zapper are
referred to later. The idea of aiming a light
beam to fire at a target is particularly
appealing as light rays travel in straight
lines. However, there are a few fundamen-
tal technical points to take into considera-
tion to make the project worthwhile.

FOCUS

The better the focus of the light beam, the
greater the skill required to strike the target.
If a diffused light beam is used to direct on to
the target I.d.r. then the intensity may not
be sufficient to activate whatever sensor is

Everyday with Practical Electronics, June 1995

449

used, e.g. to trigger the bistable in the Star-
Struck! project. Also, as less skill is required
the game will lose its appeal. A suitable lens
is therefore essential to narrow the beam of
light. The easiest way is probably to press
into service an old spotlight torch, just using
its bulb and lens holder.

TRIGGERED
LOADING

In the interests of skill, it is important
that the trigger action is controlled. Using
an ordinary torch as a light gun has other
drawbacks as well as its diffused area of
light. After switching on, it is all too easy
to locate the target by using the beam to
correct the angle — what might be called
“spraying the target’.

For this reason, when triggered the light
gun should ideally give one flash for a
fixed period independent of the length of
time for which the trigger is pressed. The
light gun described here gives a fixed
flash of about 0-5 seconds, but the circuit
parameters can be changed to suit in-
dividual requirements. If you’re a John
Wayne and quick on the trigger, then
split-second timing is a must! |

To make the game competitive all

marksmen and markswomen need to have

the same number of “shots in their
lockers”, and to hold with tradition, this
light gun has been designed as a six-
shooter. It gives a visual indication of the
number of shots fired and will not fire any
more shots after the sixth, unless the
Reload switch is pressed.

CIRCUIT DIAGRAM

Circuit diagram details for the Six-shot
Light Zapper are shown in Fig.1. To obtain
six, and only six pulses all of the same
length when the light gun is fired, the
circuit employs a 555 timer (IC1) in monos-
table mode and a 4017 decade counter
(IC2) limited to seven outputs.

Referring to timer ICI, output pin 3,
discharge pin 7 and threshold pin 6 are
normally pulled low internally and timing
capacitor Cl is held discharged. When the
Fire pushbutton switch S2 is pressed, logic
0 is applied from IC2 output pin 5 to IC]
input pin 2, and as a result IC] output

450

Fig. 1. Circuit diagram details for the Six-Shot Light Zapper.

pin 3 is triggered high. The monostable is
now in its unstable state.

Capacitor C1 now starts to charge up via
resistor Rl. When Cl has charged to ap-
proximately two-thirds of the supply volt-
age, IC] pin 6 and pin 7 are triggered
low. This discharges C1 again and also sets
IC1 output pin 3 to its low state. IC1 has
now been returned to its stable state and is
ready to receive the next trigger pulse.

The stated values for capacitor Cl and
resistor R1 give an output pulse length

PIN VIEW
BC 109

>MQ2OMnNDOT- RK

COMPONENTS

LIGHT ZAPPER - MAIN UNIT

Resistors
R1 100k
R2 ~5k6

R3,R6 10k (2 off)

R4 120k TALK
R5,R7 1k (2 off) age

All 0.25W 5% carbon film.

Capacitors
C1 4u7 axial elect. 10V
C2 10n disc ceramic

Semiconductors
TR1 BC109 n.p.n. transistor
D1 l.e.d. yellow

3mm or 5mm

D2 to D7 |.e.d. red 3mm or 5mm
(6 off)

IC1 555 timer

IC2 4017BE decade
counter/divider

Miscellaneous

$1,S2 s.p. push-make switch (2 off)

S3 s.p.s.t. min. toggle switch

Plastic box to suit torch used (see
text), 6V torch assembly (see text);
stripboard 0.1 inch pitch (11 strips x
25 holes); 6V battery; connecting wire,
solder, etc.

Approx cost
(COLUM el

ot £6,

excl torch and case

of about 0.5 seconds. To reduce the pulse
length, reduce the value of either, or both,
of these components.

Between them, capacitor C2 and resistors
R2 and R4 shape the short initial trigger

$3. BATTERY

BATTERY
-VE

Fig. 2. Stripboard component layout, wiring and track cutting details for the Six-

Shot Light Zapper.

Everyday with Practical Electronics, June 1995

/nterior detail of the assembled and cased Six-Shot Light Zapper.

pulse required by IC2 when the Fire switch
S2 is pressed. In this way, the flash has the
same duration no matter how long S2 is
held down. (The trigger pulse to IC] must
be shorter than the output pulse timing.)
Resistor R4 in parallel with C2 provides a
discharge path across it, allowing S2 to be
rapidly re-fired.

This fixed-length output pulse from IC]
pin 3 serves two purposes: via resistor RS it
provides a “‘one-shot”’ base current to tran-
sistor TR1, turning it on and so lighting
lamp LP! for the duration of the pulse.
Secondly, it triggers decade counter IC2 via
its clock input pin 14. Each of the first
seven outputs of IC2 is connected to a light
emitting diode (l.e.d.), D1 to D7.

Each time the Fire switch S2 is pressed,
the resulting output pulse from ICI se-
quentially triggers high the outputs of IC2
in turn, causing the respective l.e.d. to be
switched on. As each output goes high,
the preceding one goes low. The display
thus advances from D1 (Loaded position)
through to D7 (Reload position). Resistor
R7 limits the current through the l.e.d.s.

The Reload |.e.d. D7 is turned on by the
logic 1 on IC2 output pin 5 when trig-
gered after the sixth shot. Simultaneously,
switch S2 pin 1 is held at logic 1 by IC2
pin 5 and so the switch cannot generate a
negative-going pulse with which to trigger
timer IC1. A further connection is taken
from IC2 pin 5 to IC2 clock enable pin 13.
The high logic on this pin now holds the
counter inhibited and |.e.d. D7 stays on.

Counter IC2 remains inhibited until the
Reload switch S1 is pressed, an action
which connects the +9V rail to IC2 reset
pin.15, so resetting the counter to zero. The
now-active ‘“‘zero” output on [C2 pin 3
lights the “Loaded” |.e.d. D1 making the

circuit ready for the next six shots.

CONSTRUCTION

The circuit is built on a piece of 0-1 inch
pitch stripboard which carries IC], [C2
and their associated components. The
layout of the two sides of the stripboard
showing components, connections, track
cuts and solder points. are shown in Fig.2.
Normal precautions to protect the 1.c.s
from static’ should be observed and d.i.l.
sockets for them are recommended. The
i.c.s themselves should’ be fitted last
after the wiring and soldering has been
thoroughly checked.

With a little ingenuity, the light zapper
could look like a futuristic space-gun com-
plete with sights. In the prototype, as
shown in the photograph, the bulb-holder
and lens of a 6V torch were fitted to one
end of. a small plastic case. The seven
l.e.d.s were mounted in line on the front
panel, together with the On/off and Reload
switches, $3 and S1. The Fire switch S2 was
mounted below the lens at the end of the
box, in a convenient position for the trigger
finger.

Although the photo shows the case to
have a sloped front, in reality, any case
shape or size will do provided it can have
the torch assembly and small stripboard
mounted in it. The layout of the front panel
is not critical. The panel can be labelled
with rub-down lettering and protected un-
der a clear plastic cover.

The quiescent current is only about
10mA, but the bulb used will dictate the
current consumed during the flash period.
Suitable 6V mz.e.s. bulbs are readily
available with a current consumption of
only 40mA. The use of a lower voltage bulb
is not recommended. The unit should be
powered by a 6V battery, preferably a
long-life type. It may be powered by a 9V
battery if the bulb voltage rating is
increased accordingly.

ZAPPING IDEAS

As a suggestion for a game with the
Six-Shot Light Zapper, a very simple target
could be made by wiring-up just one of the
“Star-Struck!”’ project’s bistable circuits
(see its Fig.l), e.g. TRI, TR2 and as-
sociated components. Each of the pushbut-
ton switches S1 and S8 should be re-
placed by a light dependent resistor (I.d.r.).
The l.d.r.s can then be used as targets.
To encourage re-aiming, these should be
widely spaced either side of a tri-colour
l.e.d.

An interesting variation on this idea is to
make individual ‘“‘zapper targets” that can
be attached to a gaming participant like
a badge. The Aim of the Game, so to
speak, is for people in a team to get zapped!
For instance, in subdued lighting the Light
Zapper can be aimed by a member of one
team at the red glows of six opponents,
each wearing an l.e.d. and an 1.d.r., aiming
to change the glows to green (or vice versa).
There are endless possibilities, but a sug-
gested circuit for another zapper target is
given in Fig.3.

This circuit is a further variation on the
Star-Struck! bistable. Here switch SI] is
replaced by an I.d.r. (R5), switch S2 is the
same as S8 in the original circuit. Tri-
colour l.e.d. D1 has its twin anodes (a)

Fig. 3. Suggested circuit for a “Target
Badge”.

Close-up details of the stripboard assembly of the Six-Shot Light Zapper.

Everyday with Practical Electronics, June 1995

451

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COMPONENTS

TARGET BADGE

BATTERY
+VE

BATTERY —VE

b

PIN VIEW

BC 109

Fig. 4. Stripboard layout details for the “Target Badge” circuit. The inset shows a

possible “Badge” layout.

connected respectively to the collectors of
transistors TR1 and TR2. As before, the
common cathode (k) is grounded.

To start the game, switch S2 is pressed to
bring on the red l.e.d. within D1. When
I.d.r. RS is “‘zapped” by a correctly aimed
Light Zapper, the bistable changes output
states, so switching off the red l.e.d. and

switching on the green one. The starting
and “‘zapping” colours can be changed by
swapping over the two anode connections
of D1.

The suggested stripboard layout for the
small circuit is shown in Fig.4. There are
no track cuts required on this board. Be
sure to observe the correct polarities of

Resistors
R1,R4 = 1k (2 off)
-R2,R3 = 3k3 (2 off)
R5 ORP12
(or similar)
d.r.

See

SHOP

TALK
age

Semiconductors

D1 l.e.d. tri-colour
TR1,
TR2 BC109 (2 off)

Miscellaneous
S.p.s.t. min. slide switch
s.p. push-make switch
Stripboard O-1in. pitch (7 strips x 16
holes), rigid badge material (see text).

L’4

led. D1 and transistors TRI and TR2.
A suggested ‘Target Badge” layout and
its wiring detail is shown in Fig. 4. The
badge can be made from any rigid material
sized to your choice. This sub-circuit can be
powered by a 9V battery.

Approx cost
guidance only

WANDER WANDS

A simply wanderful way to keep the party colourful.

ANDER WANDS can be used to
“break the ice” at children’s
parties. No, they are not pick-axes:
they look like small white batons which
arriving guests will be curious to find out
what they are. They serve as a talking point
and are something to hold in the hand, but

in fact they are much more than that!

WANDERING
INSIDE

Each Wander Wand comprises a length
of plastic tubing which contains a bi-colour
light emitting diode (l.e.d.) at one end, two
small batteries, a reed switch, a current
limiting resistor, and a permanent mag-

net. The circuit diagram of the Wander |

Wand tube is shown in Fig.1. Its equiv-
alent schematic physical layout is shown in
Fig.2.

In Fig. 1, resistor R1 limits the current
through the bi-colour l.e.d. D1. The stated
value for Rl, 150 ohms, gives an l.e.d.
current of about 20mA. When the magnet

of another Wander Wand is held near reed
switch S1, the switch contacts close and
one of the two l.e.d.s within D1 is turned
on. With the battery polarity connected as

452

shown, current will flow through the red
led:

Turning the battery polarity round the
other way will cause the current to flow
through the green l.e.d. Alternatively, the
l.e.d. polarity can be changed at the con-
structional stage. When the l.e.d. is not
energised, it is impossible to tell whether it
is connected for a red or a green display.

CONSTRUCTION

The plastic case for the Wander Wand

Fig. 1. Circuit diagram for the Wander
Wand.

can vary in shape or size, largely depending
on the type of batteries used. The author’s
prototype, which was powered by two
AAA-size batteries, was cut from a length
of white, half-inch diameter plastic tubing
of a type obtainable at most d.i.y. stores.

As shown in Fig. 2, the batteries were
held under tension from their negative end
by a small spring soldered: to the point of a
drawing pin pushed through a small slice of
dowel. Similarly, dowelling and a drawing
pin were also used for the positive battery
contact.

The AAA-size batteries were a fairly
tight fit in the tube, but there was sufficient
space for a single length of enamelled
copper wire to link the far end of the two
batteries via resistor R1 to one side of the
l.e.d. The point of the drawing pin, from
the positive end of the batteries, was sol-
dered to one terminal of the reed switch.
The other reed. switch terminal was sol-
dered to the other side of the l.e.d.

The two legs of the l.e.d. were fed
through two small holes drilled in another
piece of dowel, which was a push-fit in the
end of the tube. Finally, a small bar magnet
was located in the other end and secured by
a fourth piece of dowel.

Everyday with Practical Electronics, June 1995

COMPONENTS

WANDER WAND cee

i gaat

1 ‘

carbon film TALK
Page

Semiconductor

D1 __i.e.d. bi-colour (red/green)

Miscellaneous
S1 reed switch
Battery, AAA-size (2 off); plastic tube
(see text); dowelling; small spring;
drawing pin (2 off); small bar magnet;

connecting wire; solder etc.

excl. batteries

WAYS WITH
WANDS

There are countless ways in which the
Wander Wands can be used. Here are some
of the more obvious ones:

On arrival, guests can be armed with a
wand and first of all establish to which

Approx cost

guidance only

Max Fidling

Plumb Crazy

Being a bit of a do-it-yourselfer, there’s
not much in the Fidling household which
has escaped the attention of my handyman
activities. Not content with my multi-pur-
pose screwdriver set which has seen me

through many a scrape, I recently added -

a set of pliers and wire cutters which I
spotted on a market stall.

I think it was possibly the colour of the
hot-dipped plastic handles which most
attracted me to them, since I like to colour
co-ordinate everything like the profes-
sionals do, and generally impress my
friends. If they do actually “‘ply” or cut
wire, then that’s a bit of a bonus as far as
I’m concerned! As I was to discover, much
to my dismay, they neither plied nor cut...
I’d hoped for much better at £1.49 the pair.

One spring morning I happened to be
ferreting around in the attic, in the general
vicinity of the cold water tank. Strange
rusty-looking ring-like patterns had started
to appear in the freshly applied white emul-
sion of the ceiling down below, and I had
been summoned to investigate. If I hadn’t
recently painted the ceiling, I pondered, it
would probably not have happened, and
obviously my five litres of vinyl silk had
tempted fate too far.

The attic is the one place I know where
Piddles won’t enter (pity, because we have
a mouse or two and so the moggie could do
some good for a change) so he was sat
at the bottom of the step ladder peering
up into the loft entrance and waiting for
events to unfurl.

Staring through the gloom using my
faltering plastic torch, I soon saw the
problem — the water tank’s level had risen
too far and so it had started to drain
through the overflow pipe. This pipe had

Ohm Sweet Ohm

GAR Siti ate SAO A 8
dy cod tae Vener.

ae re Ae
~i Shei Rhy

team colour they belong: touch the l.e.d.
(reed switch) end of one wand against the
magnet end of another wand and it will
glow either red or green, as appropriate.

Wands can also be used as batons in team >

games and relay races, e.g. a baton must
first be made to glow before the next team
member can proceed.

Charts or lists of questions placed
around the room are useful as party
starters, e.g. magazine clippings of famous
personalities to identify, adverts to recog-
nise, etc. These can have a magnet secreted
somewhere behind them: point to the right
answer and the wand will glow to score a
point for that team colour.

A quiz board could even have its own

recently been refitted by yours truly after I
thought I would try my hand at plumbing.
No problem except that sadly, the overflow
itself had, er, a slight gap where I’d joined it
-to another pipe, and so water was dribbling
out and ruining the ceiling below!

Back at the workshop, I started thumb-
ing through my comprehensive library of
ancient electronics magazines, looking for
inspiration. I had in mind a water level
alarm or moisture detector which could
warn me when the water tank level was
getting too high.

Not the most earth-shattering applica-
tion of electronics, but one which even
I should be able to implement without
doing too much damage! Anyway, having
repaired the paintwork I was still in “hot
water” with the Boss so I needed to make a
few smart moves, so eventually I designed a
simple unit which was a conglomeration of
several published designs.

A foot too far

I'd pressed a 555 timer chip into service,
since I always had these littered around the
place. Using an old telephone earpiece as a
loudspeaker, an audio oscillator was soon
soldered together on some stripboard, run-
ning from some old pen-cell batteries. Add
a transistor switch and two old wire coat
hangers with a terminal block, and voila!

When the two coat hangers were dipped
into water, a mechanical hum emanated
from the earpiece, not dissimilar to a
G.P.O. dialling tone, actually. It wasn’t
quite loud enough, so I adopted plan B
which was to jack up the supply voltage
until either something blew up or threshold
of pain sound level was reached, whichever
came first...

Everyday with Practical Electronics, June 1995

Fig. 2. How the Wander Wand components are assembled inside the tube.

_ Wands will come to mind once several have

MLL)

indicator display, using the same circuit as
shown in Fig. 1. In this case, the magnet
end of the wand would be used to activate
the reed switch, or switches if several cir-
cuits are used.

A firm favourite at parties is searching
for treasure on a large map. Small mag-
nets can be secreted behind the map at
strategic places. Copies of the treasure map
can be distributed with clues to help players
search out and sense these hidden magnets.
An adult can keep a tally of the number
of green or red wands activated when the
treasure is located.

No doubt other games with Wander

O

been built.

Piddles accompanied me back to the step
ladder and I clambered up into the at-
tic, carrying my latest brainchild, with its
battery hanging loosely on the end of a
PP3 clip. I perched precariously astride two
rafters, and started to beaver away happily,
humming a tune. Unfortunately, the wire
coat hanger “‘probes”’ proved too long and
so I needed to bend them to shape and
shorten them to just-above-water level.

Looking in my toolbox, my eyes lighted
on my new chromium-plated Pliers & Wire
Cutter Set (Qty. # 2 pcs.”’, as it said on the
pack) so now would be the acid test. Grab-
bing the wire cutters, I set about the wire
coat hangers gleefully, with all the skill of
an electronics hobbyist who’s also not very
good at plumbing.

Much to my dismay, the quality of
the old wire coat hangers seemed to ex-
cel that of the wire cutters, as one jaw
pinged off, ricocheted off the wooden roof
beams and plopped into the water tank!
This rather caught me by surprise and I
pirouetted deftly before temporarily losing
my balance — worse was yet to come as I
accidentally raised one foot and shoved it
straight through the newly re-painted ceil-
ing below! Now I really was in deep water!
Typically, through the gaping hole I could
see a certain cat peering up at me, tail
swishing and looking not at all surprised.

453

re ae aged

Special Report

SMART
CARDS

BARRY FOX

What they are, how they work, where they are going, are they
secure? Before long most of us will be using Smart Cards of one type
or another, in this feature Barry looks at the present and future
Smart Card scene paying particular attention to security.

HE Smart Card or cashless society is coming. Westminster

Bank is testing Mondex, a system that replaces traditional
magnetic stripe credit cards with an electronic purse that looks
like a stripe card but incorporates a microprocessor chip and
memory to store and process cash data.

Shell petrol stations have stopped giving drivers paper
tokens for Air Miles (without telling us how to convert them
into travel) and are..now giving us smart cards which store
electronic Air Miles (unfortunately still without telling us what
exactly to do with them). The government’s plans for health
and idendity cards all rely on smart card technology.

Smart Move

British Telecom will soon start converting all its payphones
from optical to smart card working. This is a massive com-
mitment. BT introduced the optical phonecard in 1981 and
now has a network of 35,000 card phones. “We have taken
the technology as far as we can go’, says Les King of BT.
‘Moving to smart card technology gives us freedom for future
development”’.

All existing optical card phones will be replaced with smart
card readers and new payphones will be designed to read
smart cards as well as credit cards. The cards will not be
rechargeable and BT has “no plans yet” to collect old cards
and recycle them.

The new phone cards will cost customers the same as ex-
isting cards even though it is far more expensive to produce
smart cards than optical cards. But the volume in which BT
will buy smart cards (from Gemplus and GPT) to sell through
50,000 retail outlets across the UK, will drive the manufactur-
ing costs down to similar levels.

Magnetic cards will not disappear overnight, but they are
likely to be used only where the data is secured by a mag-
netic watermark or vetted by online checking every time the
card is used. For added security the two technologies may be
combined.

All this paves the way for a cashless society, where electronic
credits are transferred instead of cash. Because smart cards
have a far greater memory capacity than magnetic cards, an
“electronic purse” can double as an identity card. Inevitably
there will be objections from those who see it as an intrusion
into personal liberty and privacy. Criminals will see it as an
opportunity to earn even more from fraud. For hackers the
smart card society represents a new challenge.

To, get a handle on the debate, it pays to understand the
technologies involved.

The use of plastic cards as a replacement for cash dates back
to the early 50s when the Diners’ Club and American Express
Company in the US started to issue members with cards which
vouched for their creditworthiness. European banks started

454

issuing cards in the 60s, with Barclaycard and Visa from
Barclays, and Access from Lloyds, National Westminster and
the Midland banks.

The banks then started installing ATMs (automatic teller
machines), popularly known as “‘hole-in-the-wall” cash dis-
pensers. This followed a technical specification set by ISO the
International Organisation for Standardisation (this is correct
full name, not International Standards Organisation). The
ISO 7810 series of standards ensure that any card with a
magnetic stripe can physically be read by any check-out till or
ATM, anywhere in the world.

Security

The banks have traditionally refused to discuss any aspect
of security, on the grounds that it helps criminals. But with
even the bankers’ own trade body, the Association for Pay-
ment Clearing Services (APACS), generating publicity for the
wildfire spread of card fraud, it is clear that criminals already
know all they need to know about card technology. Prisoners
in jail pass on the secrets, and at least one DIY manual on card
fraud has been circulated. The banks are now reluctant to dis-
cuss security because they do not want to trigger a rush of
claims from customers who say they have lost money through
technology loopholes.

The stripe on a magnetic card is divided into three parallel
tracks, like a three channel stereo sound recording. Tracks one
and two contain data, written or pre-recorded on the card
prior to issue. The data on track one is more tightly packed (at
210 bits/inch) than the data on track two (at 75 bits/inch).
Track three stores data at the same density as track 1, but

At the Mondex Centre in S windon s shopping centre,
cardholders can transfer funds from their bank account
directly “into” their Mondex card using special BT phones.

Everyday with Practical Electronics, June 1995

allows the card reader to record data on the card as well as
read it.

The banks use mainly track two, which is in the centre of the
stripe. Track three is used to carry a number which checks
against the personal identification number or PIN, which only
the legitimate owner of the card should know. Critics of bank
security argue that up until two years ago, it was possible
for anyone with expert knowledge, for instance an ex-bank
employee, to decode the PIN from a stolen card (much as it is
possible to decode a driver’s sex and birth date from the
innocent-looking number a the top of their driving licence)
and then use the PIN IT to draw cash from an ATM.

The banks’ formal line is that this is, and always has been,
impossible, and that there has never been sufficient code on a
card to allow extraction of the full PIN. The banks claim that
the PIN can only be derived from data which is securely stored
by the bank.

Although some members of staff will have access to PIN
data, the banks’ policy is to restrict the number of staff with
access to a carefully selected few. The source of any breach of
security can immediately be narrowed to a very small group of
employees. The theory then is that this group will work to-
gether to identify any one of their members who has stolen
data.

But critics say that service engineers working with ATMs,
and system progammers working on the bank’s computers,
may have access to PIN data.

Skirn KHlead

Because all magnetic cards follow the ISO standard, anyone
can easily obtain blanks. They are given away by Super-
markets and Petrol Stations, for customer loyalty schemes.
Any data on the card is just wiped off with an ordinary
magnet. Criminals can then buy the card readers and writers
which are sold for legitimate business use.

It is not even necessary to know how to decode a PIN from
supposedly secret data. An expert witness in a recent card
fraud case told a Court in Suffolk how he had personally
manufactured a card, using data obtained from a discarded
ATM transaction slip and a PIN observed over the card
owner’s shoulders.

Although many ATMs have now stopped printing out card
details, fraudsters have in the past used binoculars to col-
lect PINs, and then matched them by time of transaction to
discarded slips. More recently criminals have stolen PINs
at mock auctions, by persuading cardholders to swipe them
through a reader, and enter their PINs into a keypad with
hidden memory.

There are also several ways to transfer owner identification
data from a borrowed or stolen card to a blank. If two mag-
netic tapes are sandwiched together and pressed with a hot
iron, the magnetic pattern on one will transfer to the other. But
the more elegant solution is to use a device called a “skimmer”
which any electronics enthusiast can build from standard com-
ponents, costing only a few pounds.

A skimmer has two magnetic heads, like those in a tape
recorder. One head can read the magnetic field from a card
and the other can generate a magnetic field and so write to a
card. The two heads are connected together by an amplifier.

Two cards, one original and one blank, are laid side-by-side
on the surface of the skimmer and then by hand moved as a
pair over the two heads. As the read head picks up data from
the original card, the record head writes it to the blank card.
Skimming a card takes literally seconds, and produces a per-
fect copy of the original.

Audit Trail

There is no need for today’s cards to be so insecure. The ISO
standard allows for the reader to write to the third track and
_ So record a code which identifies the last ATM at which the
card was used. When the card is next used, this code is read by
the ATM before a new code is written. This gives the bank
the chance to build an audit trail of where a card has been
used and should thus let the bank know immediately whether
disputed transactions have been made by a customer’s own

Everyday with Practical Electronics, June 1995

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card, or a skimmed copy.

The banks have been cagey about discussing this valuable
security check. One explanation could be that the audit trail
will in some cases prove that the bank’s security has been

- breached; another is that some banks have been slow to invest

in the system modifications needed to exploit the track three
write option.

Although Mercury uses magnetic cards for its payphones, a
clever system of on-line checking stops people playing the ob-
vious trick and using a skimmer to add new units to an expired
card. When the caller puts a card in a Mercury payphone,
the system checks its previous usage with an on-line database,
and rejects any card that has mysteriously increased in value
instead of decreasing. A similar system could, if the banks
wished to implement it, sound an alarm as soon as anyone
tried to use a stolen card inan ATM. :

Hot Nurnber |

Although the banks have now tried to make cards more
secure by embossing a hologram patch in the surface, en-
terprising criminals have now found a way round this trick
too. They collect stolen cards and use- heat or solvents to
flatten out the embossed details of the legitimate owner. Then
they use an embossing tool to imprint details of a new owner.
These details are readily available from credit card transaction
slip copies and carbons which owners discard or which res-
taurants,and shops throw in their dustbins.

Criminals without their own embossing tools can now
simply telephone orders to the new wave of copy shops in the
Far East which make cards to order. The legitimate card
owner only finds out that their card has been copied when they
get their next bill. |

These cards need not even have valid magnetic data in their
stripes. The magnetic stripe on legitimate cards often wears, or
becomes de-magnetized, so staff in shops and restaurants are
not surprised to find that some customers’ cards refuse to work
in a reader. Even if they phone for approval, the embossed
details on the card will be correct so the transaction will be
authorised.

In the early 90s APACS had found that 75 per cent of all
card fraud was taking place at the point of sale. Criminals do
not waste time buying groceries, or cinema tickets, with stolen
cards, they use them to buy VCRs, camcorders and computers
which can quickly be re-sold for cash.

One trick is to swipe a stolen card through a credit card
payphone and see if it is accepted. If it is, then the card is not
yet registered as “hot” and can safely be used in a shop. A new
variation on this trick is for people who run shady premium
service phone lines (like sex lines) to run up bills on stolen
cards by dialing the service and leave the phone off the hook.
BT then has to pay the service a percentage of the charged
amount.

The pocket size Mondex card reader.

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Cardowners are often their own worst enemies. When
choosing a PIN, people take a simple number, like a birthdate,
to make it easier to remember. The first thing a thief with a
stolen wallet does is look for a note of the owners’s birthday
and try it with any credit cards. Some cardholders choose a
long number but then, because they cannot remember it, write
it on a piece of paper in the same wallet, or even the back of
the card.

Two years ago, at a conference organised by trade body the
Radio, Electrical and Television Retailers Association, John
Carnegie-Brown, of Barclays Merchant Services, told dealers
‘The cost of putting photographs on cards is greater than the
fraud it eliminates. We do not feel we can cope with it at this
time”. But TSB and The Royal Bank of Scotland think it is
worthwhile and have now been using photo-cards.

Biometric Technique
The major banks are more interested in biometric tech-

niques. The card stores a template which it checks against the

carrier. In its simplest form this template can be a passport
photograph, which is checked against a video image shot at
the checkpoint.

Every human eye has a characteristic pattern of blood ves-
sels in the retina. The card can store a map of this pattern
which is checked by asking the cardholder to peer into the
lens on a video camera at the check point. Although suitable
for the military, eye checks at the Supermarket would not be
popular.

The card can also store a voice print, which logs the fre-
quency content of the holder’s speech. But this is unreliable. A
common cold changes the human voice drastically.

Electronically sensing signatures is more attractive, and the.

new generation of Personal Digital Assitants, like Apple’s
Newton, are already designed to convert handwriting into
electronic signals. But signatures vary, not just from day to
day but from hour to hour. Rolls Royce and the British
Technology Group have separately worked out their own
ways of tracking these changes, but even the cleverest technol-
ogy cannot cope when shoppers have to sign on a crowded
counter at an awkward angle.

Surprisingly the best bet may prove to be the most secure
identification system of all, finger printing. At the point of sale,
cardholders put their fingers on a pad, which optically scans
the tips of the fingers with a laser, similar to the scanners now
widely used to read bar codes on Supermarket goods.

Low key market research by the banks suggests that only
around two per cent of cardholders have strong objections,
preferring finger printing to loss of money through fraud. But
the few people who do object, do so vehemently. They also
object to the idea of being photographed, or having their sig-
natures electronically recorded. So no bank will dare make
biometric identification mandatory. Also, manual workers of-
ten have unreadable fingerprints.

Two airports in New York, Newark and JFK, are now test-
ing a hand geometry system. The card stores a map of the
holder’s hand size and shape, and compares this with a reading
taken at the check point.

Optics

Magnetic cards cannot store enough data to encode a signa-

ture, or fingerprint, or any other biometric data. Standard
memory capacity is only around 200 characters, spread over
the three tracks. There are two solutions, Smart Cards with
built-in computer chip memories and Optical Cards which
store data like a stationary compact disc.

The Drexler Corporation of California leads in optical card

technology. The card writer houses a laser which burns lines of
five micrometre pits into a thin metal coating on the card.
These pits are then read by a lower powered laser which scans
the surface, sensing the changes in reflection caused by the pits.

Precision mechanics move the card backwards and forwards
under the laser optics. The optics must step sideways across
the card in increments of around 10 micrometres to create a
horizontal grid of several thousand parallel tracks across the
card width. Together these tracks can hold up to six megabytes

456

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of data in digital code, equivalent to four high density com-
puter floppy discs.

The optical card is relative cheap (under $5 in bulk). It is
secure in that data cannot be altered or copied or read. But if
the card surface is scuffed it may become unreadable. And the
reader must be expensive, costing several hundred dollars.

British Telecom has been testing Drexler cards as a means of
storing medical records for expectant mothers attending the
West London and Chelsea and Westminster Hospitals in Lon-
don. US Government agencies are now using optical megabyte
cards for storing sensitive information.

French Innovatron

The favourite technology for the future, however, remains
the Smart or IC (integrated circuit) card which was invented
and patented by French journalist Roland Moreno and his
company Innovatron, in the early 70s. Innovatron then
licensed Bull, Schlumberger and Philips to develop working
cards. The difficulty of building a microprocessor and solid
state memory into a credit card which is only 0-76mm thick
and is sufficiently flexible to be sat on, should not be
underestimated.

The French government has backed smart card technology,
seeing it as a national asset and means of modernising the
country’s telephone and banking systems. Since 1992 all bank
cards in France have been smart. The ISO 7816 series of stan-
dards ensures compatibility between cards and readers.

The very latest card reader terminal from the in ventors of
Smart Cards, Innovatron of Paris, France.

Cost is kept down because not all cards are stats smart.
The standard card contains an 8-bit microprocessor, and then
a wide range of memory options. This has let designers launch
new systems with cards which use the bare essentials of
memory and intelligence, then use more intelligence and
memory as the system demands it.

This is what has happened with satellite broadcaster BSkyB.
The scrambling system for the movie channels. uses a smart
card to authorise decoding, Each new issue of cards has been
progressively smarter, and more expensive, as hackers have
discovered new ways of breaching the security of the entry
level system.

Memory capacity ranges from 1 to 64 kilobytes, in a mix of
ROM (Read Only Memory) and EPROM (Electrically Pro-
grammable Read Only Memory) which is pre-programmed to
store the control codes for the microprocessor, RAM (Ran-
dom Access Memory) which acts as a temporary buffer when
the card is powered by a reader and EEPROM (Electrically
Erasable Programmable Read Only Memory) which stores
data written into the card by the reader, without the need for
battery back-up.

Smart IC cards fall into two broad types: thiode with a
cluster of electrical contacts which make direct connection
with mating contacts in the reader, and contactless cards
which rely on wireless communication.

Contact cards are cheap, now costing a dollar or so each in
bulk, with the reader hardware costing only a few dollars

Everyday with Practical Electronics, June 1995

more. Contact cards are only suitable for use where the card
remains in the reader most of the time e.g. in a satellite
decoder, and there is no risk of the contacts getting too dirty
for the contacts in the reader to wipe clean.

Where cards are intended to be carried by the owner,
dropped in the mud, and used in a variety of readers to pay for
goods or services, they must work without contacts. The
connection is then made by radio link. The reader emits a
signal which the card converts into power and uses to transmit
data back tothe reader.

Travel Cards

The power and frequency of the reader’s signal determine
the range of operation. For some applications, short range
connection is essential, for instance to prevent one passenger’s
travel card paying for another passenger’s journey. British
company GEC is making the contactless cards which London
Transport is now trialling on buses working in Harrow, North
London. The same technology is used in Manchester.

The Harrow test involves contactless cards on nineteen bus
routes. London Transport has equipped 200 vehicles with
smart card readers and around 25,000 passengers are now
regularly using cards to pay for journeys. The cards work like
ordinary travel cards, but store time information to give free
travel for a week or a month. When passengers get on a bus
they wipe the card over a reader. If the time has expired, a light
warns the driver. |

If the trials are successful LT plans to extend the system
throughout London’s bus network, and use the same cards to
pay for station car parking and buy from vending machines.

Although middle-aged passengers still fumble, school- |

children no longer bother even to take the cards out of their
pockets. They just brush their jacket pocket against the reader.

LT has had to delay the second phase of its trial, which
expands the scheme to stored-value fare cards. These will work
like an electronic purse, storing £10 worth of travel units which
the reader sucks out in return for a ticket. Around 200 shops in
Harrow already have the equipment needed to re-charge cards
in return for cash. |

LT blames “mundane” reasons for the delay. The first cards
were not strong enough. Whereas people treat their credit
cards carefully, they put travel tickets in a back pocket and sit
on them. Also bus gearboxes often vibrate when waiting at a
bus stop. This has been fooling the reader. When this happens
the travel cards can be be checked visually, like ordinary cards.
But the purse cards only work electronically.

Similar trials are underway in Bolton. If successful the
Greater Manchester Transport Executive will extend the
scheme county-wide to buses, trains and trams, with pas-
sengers able to use the same cards to buy goods.

Some 2500 people are now using smart cards on 120 of

Bolton’s buses. The Greater Manchester Passenger Transport

Authority plans to extend the scheme across the whole county,
over the next three years. The GMPTA cards already work as
electronic purses, storing a number of flat rate concessionary
fare payments. Each time a passenger uses a card the reader
sucks out another 30p. Cardholders can then go to re-chargers
installed at Supermarkets, Schools and Bolton Town Hall to
pay cash for an electronic top-up.

“The main complaint’, say the organisers “is from people
who get on buses which do not yet have a card reader”’.

The long-term plan is to encourage local shopkeepers, and
sandwich bars, to install readers and so let cardholders pay for
goods with their travel cards.

Call for SIM

The new digital cellphones now available for Mercury’s
One-to-One and Hutchison’s Orange networks (and on
Cellnet and Vodafone’s new GSM services) rely on similar (but
sometimes cut-down) cards called Subscriber Identification
Modules. Without a SIM, the cellphone cannot be used to
make or receive calls. Once the SIM is plugged in, the phone
springs to life, making calls which are billed to the
SIM-owner’s account.

The card also stores a library list of the telephone numbers
which the subscriber most frequently calls. If an Orange sub-

Everyday with Practical Electronics, June 1995

PFET

On entering the bus, passengers wipe their “contactless”
card across the reader and the driver verifies a valid card.
scriber gives Hutchison a written list of numbers, an operator
will key them into a transmitter which sends them to the phone
where they are stored in the SIM. When the SIM is plugged
into another cellphone it can immediately read the library list
of numbers, make calls on the SIM-owner’s account and
receive calls dialled to the SIM-owner’s number. If a cellphone
goes wrong, the owner just slots the SIM in a replacement,
which behaves just as if it were the original.

SmartCard

French payphones use smartcards, 70 million of them a year,
even though telephone services in most other countries cut
overheads by using cheap magnetic or holographic cards from
which credits are erased or burned away by the payphone
reader. .

Most French salaries are paid by the month into a bank. So
virtually everyone has a bank account. In France all cards are
debit cards, and the Groupe Cartes Banqueres (comparable to
the Association for Payment Clearing Services in the UK) rep-
resents all the banks which issue the cards, and runs a scheme
whereby each bank honours: every other banks cards for all
transactions. Any French national using a bank card must
now use a smart card. This has cut fraud inside France to
almost non-existent levels.

The GCB estimates are that at least half this fraud occurred
because the electronic point of sale, EPOS, equipment worked
“off line”. It collected information on all transactions during
the day and sent it to the bank for processing at night.

All 21 million bank cards in France are now smart. Direct
‘on line” connections with the banks let the EPOS terminals ©
check a smartcard’s validity, against a personal identification
number or PIN entered by the customer, in under two seconds.
If the PIN does not match the card, the reader displays a mes-
sage to the shop staff, telling them to pick up and keep the |
card. Soon the readers will be able to send a signal into a
suspect card to make it useless.

The only fraud on French cards now is abroad, where
people travel to other countries where there are no smart card
readers, and use the cards like conventional credit cards. This

is possible because French smart cards also have magnetic

stripes like ordinary credit cards.

Smart World

AT and T, Bull, Hitachi, Mitsubishi, Motorola, Philips,
Schlumberger, Siemens and Thomson now all make smartcard
chips and cards. Most countries are running tests to find out
what else the technology can do, and how reliable they are. |

A test in Helsinki lets travellers use the same smart card to
pay for bus or taxi travel. Dublin Bus is testing contact cards
as part of a research project funded by the European Com-
mission. The same card can be used in Irish car parks and
payphones.

The Japanese Government is storing the medical records of
300 mothers and young children on smart cards, in Awaji Is-
land, Hyogo Prefecture. The British Department of Health is
compare different card types for storing patients’ medical

etails. :

In the US President Clinton’s plans for health care and the
electronic delivery of benefits to replace food stamp coupons
has excited companies which smell the market potential. The

457

State of Wyoming looks likely to be the first to experiment
with smart card health records. Hughes Aircraft will soon
start transmitting digitally coded TV entertainment, direct into
North American homes by satellite. Viewers will need a smart
card to decode the signal.

In the UK, Wessex Water has been testing smart cards in the
city of Bath. The householder has a Water Card and charges
it with cash credits at a local shop or water company office.
When the card is slotted into a household meter, it opens the
valve to pass water to the value of the credits. The intelligence
of the card lets it run up a small debt if the credits run out over
a Bank Holiday weekend. When the householder next pays to
top up the card the debt is settled at the same time.

British Gas has developed a similar system, called Quan-
tum, for charging its customers for gas. The householder slots
a card into the Quantum meter to load it with credits and
pass gas. At the same time the meter loads information about
the householder’s gas use into the card. When the cardholder
takes it to a retailer, a card reader displays an estimate of how
much it will cost to charge up the card for another month
of similar use. At the same time the reader can relay a mes-

sage from the meter which warns the retailer if the meter has.

been tampered with. The meter also sucks enough extra credits
from the card to pay the quarterly standing charge.

At least fifteen countries around the world, including
Denmark, Switzerland and Taiwan are planning or testing
electronic purse systems which rely on the extra storage
capacity and intelligence of a smart card to control cash
debits and credits. Britain’s National Westminster Bank has
proposed the most ambitious scheme of all, Mondex.

Ambitious Mondex

‘Mondex will allow two cardholders to exchange cash units
directly, without clearance through a central control system,
just as if they were five pound notes. As one purse at a shop
check-out gains credits, another, from a customer’s wallet,
loses them. The cardholder can then fill up the card again by
slotting it into an automatic teller machine which delivers
electronic credits instead of cash, while debiting the holder’s
bank account. The credits can also be sucked into the card
down a telephone line by calling the bank. Or the credits can
be sent down the line into someone else’s card.

Because the Mondex card stores cash credits, anyone can
use it to make a purchase from any shop which has a Mondex
reader. So losing the card is the same as losing cash. Security
comes with an electronic wallet, like a pocket organiser, which
locks the card’s memory with a PIN.

The Mondex ecard will be loaded with credits at an ATM or
by connection to a phone line. So Mondex immediately be-
comes a target for criminals who will want to get money out of
a card without it losing value, or get money into a card with-
out debiting an account, or make copies of cards to spend the
same money several times over. Westminster’s security experts
are confident that Mondex will resist these attacks.

Liberty

Liberty, formerly the National Council for Civil Liberties,
has so far lobbied successfully against the Government’s plans
to use smart cards as a weapon against football hooliganism.
The idea, which came from Margaret Thatcher while she was
Prime Minister, was for football grounds to install turnstiles
that opened only when a spectator waved a valid smart card.
The card would store identity details along with any black
mark for bad behaviour.
_ The organisation was particularly worried because the
cards would have to be contactless, to work reliably in all
weathers, and after dropping into the mud. So a powerful
reader could have secretly interrogated a card while still in
the owner’s pocket. Although Liberty’s policies and position
come across as rather muddled, the organisation does have a
loud voice. 1

Says Atiya Lockwood, of Liberty, ““We don’t mind cards for
specific uses. But we don’t want to see too much information
stored on one card, because then it becomes an identity card.
You may be quite happy for a doctor to get details of your
medication or allergies from a card, but you would not want
your doctor to be able to read about your criminal record from
the same card.”

Watermark |
Thorn EMI’s Central Research Laboratories has been
watching the collapse of confidence in magnetic card
technology, and the trend to smart cards, with special
interest. It is now 25 years since CRL developed a method of
watermarking magnetic tape. The original intention was to
distinguish between original and pirate music recordings, but
the record industry was not interested. In 1978 Swedish
banks started using the system to distinguish between
genuine and copy magnetic bank cards. Since 1980, every
banking transaction in Sweden has been unambigiously tied
to the card used for that transaction. But outside Sweden

no-one was interested.

‘The idea was too early for its time’, says Hugh Tarrant,
Managing Director of Thorn Secure Science International, a
new company formed in Swindon to make watermarked tape
which card makers bond to ISO cards.

Tarrant has watched the explosion of fraud on all types
of magnetic card change attitudes. In 1986 South Korea
adopted watermarking to stop an explosion of fraud when
people found out how to clone telephone cards. The same
system is used in Australia to control poker gaming by phone
line and by the House of Commons, Windsor Castle and the
Ministry of Defence to control access to secure areas. The

- door locks are triggered by magnetic cards that look for the

watermark and reject any counterfeit copy. TSSI now sells
enough tape for a thousand million bank, phone and identity
cards each year.

In addition to the standard three ISO tracks. watermarked
magnetic cards have an extra track, numbered zero, nearest
the edge of the card. So a watermarked card is recognisable by
its wider than usual magnetic stripe.

TSSI reveals that at least one major bank tried and rejected
the system ten years ago, even though the price of watermark-
ing is only around 10 US cents per card. Card fraud was then
still a rarity.

The National Westminster and Barclays banks have since
last October been quietly running consumer tests in Nor-
thampton, with Visa International, now the largest consumer
payment system. The two banks have each issued 15,000
watermarked cards and a Safeway store and 12 ATMs have
been equipped with readers which can trap anyone attempting
to use a copy card.

Hugh Tarrant has an interesting view of the future. He
acknowledges that magnetic cards can never have enough
memory capacity to serve as electronic purses. But he also
believes that smart card technology will prove a lot less secure
than some of its proponents promise.

“But a system that combines both watermarked magnetic
stripe and an embedded chip, would give a mix of analogue,
chemical and digital technology.” says Tarrant. ““Now that
would be the most secure system of all’’. L

Everyday with Practical Electronics, June 1995

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fe) colex-to [Ul a-t-mmmOlalil(-mer-(elltcelar-l mm elielemlammel-it-M-(exelUll-Jidlelamer-|ael-p Pico mye “|
daT=SVAe-}ian) ed ava eo) (Ole Malcom (al-M oa Om-m of-1e-11(-]Meolm-t-)at-]melelammat-Ldiare Advanced data Mt
them ideal for use with portable PC's. logging software.

Call for your Guide on ‘Virtual Instrumentation’.

New from Pico TC-08 Thermocouple to PC Converter
8 channel Thermocouple Amplifier

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@ Supplied with PicoLog datalogging software
for advanced temperature processing, min/max detection and alarm.

@ 8 Thermocouple inputs (B,E,J,K,R,S and T types)

@ Resolution and accuracy dependant on thermocouple type. 3 ier
For type K the resolution is better than 0.1°C and accurate to : et - ~ 3) ae
+0.1°C over -270°C to +1300°C. *<S neta ee

TC-O8 £199

complete with PicoLog, software drivers and connecting cable. Riese
A range of thermocouple probes is available.

S.L-4-76 Logic Analyser x#OC- 7100 Virtual Instrument

Pocket sized 16 channel Logic Analyser Dual Channel 12 bit resolution

Digital Storage Scope
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Frequency Meter
Chart Recorder

Data Logger
Voltmeter

The ADC-100 offers both a high
sampling rate (100kHz) and a high
resolution. It is ideal as a general
purpose test instrument either in the
: Ja lab or in the field. Flexible input ranges
" or Y lo (+200mV to +20V) allows the unit to
- 2 connect directly to a wide variety of signals.

2#DEC-100 with PicoScope £199
with PicoScope & PicoLog £209

Connects to PC serial port.
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Internal and external
clock modes.

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_ = ff with software, power
ar = : ig supply and cables £ 219

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@ Lowest cost in the Pico range The ADC-10 gives your computer a single channel of
@ Up to 22kHz sampling analog input. Simply plug into the parallel port.
@ 0 -5V input range 2#OC-710 with PicoScope £49

Carriage UK free, Overseas £9 Oscilloscope Probes (x1,x10) £10 PicoScope & PicoLog £59

View Pico Technology Ltd. Broadway House, 149-151 St Neots Rd, Hardwick, Cambridge. CB3 7QJ

Tel: 01954 - 211716 Fax: 01954 - 211880

Everyday with Practical Electronics, June 1995

aa ale) ale) mu -V@(e) me-t-1(-\-Mmeolae(-1alalemlalcelgnit-1eie)ammer-1¢- Mo) al-1-] (mm (lel alal (er: | M10] ¢) ele) a emmy \) Me) glet-\-m-) Cel (UTTIV Moms UE

Releases PC

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Sh pe | Virtual
instrument
software.

Pond temperature

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}PICO TECHNOLOGY

,

|
|

459

EVERYDAY _

With PRACTICAL

ELECTRONICS

SE

BACK ISSUES

We can supply back issues of EPE by post, most issues from the past five years are available. An index for each year
is also available — see order form. Alternatively, indexes are published in the December issue for that year. Where we
are unable to provide a back issue a photostat of any one article (or one part of a series) can be purchased for the

same price.

DID YOU MISS THESE?

PROJECTS e
nightlight) e@ Timer and NiCad Capacity

Autolight cnuronnatec
Checker @ 250W/600W Inverter and
Uninterruptable Power Supply, Part 2 e
Multi-Purpose Audio System, Part 4 e Pond
Heater Thermostat.

FEATURES e Safety First, Part 2 e Calcula-
tion Corner, Part 1 @ Electronics Testing and
Fault Diagnosis, Course Review.

PROJECTS e Whistle Controlled Light

Switch e Reviving the Valve Sound
(rebuilding the Quad II power amp) e
Introduction to Microcontrollers — Timeout e

Battery To Mains Inverter and Uninterruptable

Power Supply, Part 3 e Multi-Purpose Audio
System, Part 5.

FEATURES e Calculation Corner, Part 2 e
Safety First, Part 3 @ European International
Audio & Video Fair.

Immobiliser e

PROJ ECTS e Smart-Key
Audio/R.F. Monitor e CCD TV Camera, Part 1
e Visual Doorbell e Three- Phase Generator.
FEATURES e Safety First, Part 4 e Calcula-
tion Corner, Part 3 e Free Wall Chart — Elec-
tronics Formulae 1.

PROJECTS e MOSFET Variable Bench
Power Supply e EPE Soundac PC sound
Output board e CCD TV Camera, Part 2/Frame
Grab e Impulse Clock Master Unit e Telephone
Ring Detector.

FEATURES e Best of British, Part 1 e

Calculation Corner, Part 4 e Electronics

Workbench Review e Free Wall Chart —
Electronics Formulae 2.

PROJECTS @ ‘Simple TENS nis
(transcutaneous pain relief) Py
Capacitance/Inductance Meter e L.E.D. Matrix
Message Display, Part 1 e Stereo Noise Gate @
Dual Stepping Motor Driver for PCs.
FEATURES e Calculation Corner, Part 5 e
Best of British, Part 2.

PROJECTS e Microcontroller P.!. Treasure
Hunter e Digital Water Meter e Microproces-
sor Smart Switch e Advanced TENS Unit
(transcutaneous pain relief) e L.E.D. Matrix
Message Display, Part 2.

FEATURES e Best of British, Part 3 @ Cal-
culation Corner, Part 6.

PROJECTS « e Voxbox Voice Recording Board
e Simple NiCad Charger e Watering Wizard
(automatic garden watering)e Pocket Print
Timer e Stereo HiFi Controller, Part 1.
FEATURES e Best of British, Part 4 e Cal-
culation Corner, Part 7.

460

eerie e Experimental Noise Cancelling
Unit e Dancing Fountains, Part 1 e Charged-
Up (PC battery tip) e 6802 Development
Board e TV Camera Update e Stereo HiFi
Controller, Part 2.

FEATURES e Calculation Corner, Part 8 e
Best of British, Part 5 e I'll Be Seeing You
Shik elle COMIN URES CE,

PROJECTS e Protector Plus Car Alarm e
Greenhouse Watering System e Experimental
Seismograph, Part 1 @ Three-Channel Lamp
Controller e Dancing Fountains, Part 2.

FEATURES e Calculation Corner, Part 9 e |
The Invisible Force (magnetic force).

PROJECTS e Digilogue Clock e
Visual/Audio Guitar Tuner e Hobby Power
Supply e Audio Auxiplexer e Experimental
Seismograph, Part 2.

FEATURES e Electronics from the Ground
Up, Part 1 with Free PC Software e Calculation
Corner, Part 10.

nsulation Tester

PROJECTS ® 1000V/500
e Video Modules, Part 1 (Simple Fader, Im-
proved Fader, Video Enhancer) e Active Guitar
Tone Control e Power Controller e TV Off-er.

FEATURES e Electronics from the Ground

wa Part 2 e ) Consumer Electronics Show

PROJECTS e Spacewriter Wand e EPE Fruit
Machine e Universal Digital Code Lock .e Video
Modules, Part 2 (Horizontal Wiper, Vertical
Wiper, Audio Mixer) e Rodent Repeller.
FEATURES e Electronics from the Ground
Up, Part 3 e Embedded Controllers e Index for
Volume 23.

PROJECTS e Magnetic Field Detector e
Moving Display Metronome e Model Railway
Track Cleaner e Beating the Christmas Lights e
EPE Fruit Machine, Part 2 eVideo Modules,
Part 3 (Dynamic Noise Limiter, System Mains
Power Supply).

FEATURES e Electronics from the Ground
Up, Part 4 e Electromagnetic Compatibility e
Gheeking Usa

PROJECTS e 12V 35W PA Amplifier e
Foot-Operated Drill Controller e The Ultimate
Screen Saver e MIDI Pedal Board e Model
Railway Signals.

FEATURES e Electronics from the Ground
Up, Part 5 e Transformerless Power Supplies e
Quickroute 3.0 peau

PROJECTS e Multi-Purpose Thermostat e
Name of the Game-1 Counterspell e Sound
Activated Switch e Audio Amplifier e Light
Beam Communicator.

FEATURES e Electronics from the Ground
Up, Part 6 e Understanding PIC Micro-
controllers e Visio Graphics Software Review.

FREE Multi- Project PCB with this issue

Lottery Predictor

PROJECTS e National
e Auto-Battery Charger e Light-Activated
Switch e Switch On/Off Timer e Continuity
Tester e Name of the Game-2 Counterspin.
FEATURES e Electronics from the Ground
Up, Part 7 e Circuit Surgery e The Hard Cell
Sea Telephones).

PROJECTS e PIC-DATS-1 (PIC Develop-
ment and Training System) e R.F. Signal
Generator e MIDI Pedal e Club Vote Totaliser
e Name of the Game-3, On Your Marks and
Games Timer.

FEATURES e Electronics from the Ground
Up, Part 8 e Las Vegas Show Report.

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Everyday with Practical Electronics, June 1995

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EVERYTHING YOU NEED TO
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The revised edition of the Modern Electronics Base REPAIRS AND MAINTENANCE: Basic circuit operation
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on the following subjects:

. ESSENTIAL DATA: Extensive tables on diodes,
BASIC PRINCIPLES: Symbols, components and their transistors, thyristors and triacs, digital and linear
characteristics, active and passive component circuits, i.c.S, microprocessors.
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CIRCUITS TO BUILD: There’s nothing to beat the is Manual and you ll find a comprehensive definition

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UNDERPINNING KNOWLEDGE: Specific sections enable you to Understand @ Easy-to-use format

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Diagrams, Circuit Measurements, Radio, Logic Gates, Computers, Microprocessors,

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Hazards, Assemble a Toolkit, Set Up a Workshop, Carry Out Soldering and Wiring, e Vital safety precautions

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Constructional Project =

PIC-DATS

4-CHANNEL
LIGHT CHASER

MARK STUART

——

Part 2

Highlighting the PIC microcontroller, Mark Stuart
channels your attention onto how its elegant
development system can be used CO good effect.

N Part One of the PIC-DATS article last

month, the PIC microcontroller was in-

troduced and the principles of its use
and programming described. This second
part follows on, introducing the practical
operation of the PIC-DATS system and
demonstrating its use in the development of
a typical hardware project.

The project chosen is a 4-Channel Light
Chaser controller. The main reason for the
choice is that such a project demonstrates
how to read switch (digital) and poten-
tiometer (analogue) inputs, and how to
control low voltage and mains power
devices. The programming described in-
volves timing loops and demonstrates
timed control of the outputs, which is
necessary for “Zero Volt Switching” of the
mains power devices.

OTHER
APPLICATIONS

Although the originally intended use of
the project is as a Light Chaser, it can
also be used for many other general pur-
pose applications where computer con-
trol of mains powered devices is needed.
For example, random switching of house
lights and appliances for security purposes,
central heating control and greenhouse
watering systems.

It can also be modified to provide low
voltage control outputs for operating
model motors, solenoids, and_ other
motion control devices. Inputs from other
types of sensor may also be applied
instead of switches, allowing a wide range
of “stand alone” applications to be
developed.

The design is such that program develop-
ment and simulation can be done without
any mains voltage being applied. There
is also total mains isolation so that the
system may also be operated and fur-
ther developed with mains power applied,
provided due care is taken.

As the main purpose of this article
is to cover PIC programming and the
PIC-DATS system, the description of the
hardware and construction of the project
will be kept to a minimum. The circuitry is
all on a single printed circuit board (p.c.b.),
but any mechanical construction, casing,
etc. is left to the user.

MAINS POWER
SECTION

The circuit diagram for the complete
4-Channel Light Chaser is shown in Fig. 1.
The circuit is divided into two parts: the
Mains Power section, and the low voltage
Control section. Between the two circuits
there is complete electrical isolation.

Mains power is controlled by four triacs,
CSRI to CSR4. These devices can switch
up to 600 volts and five amps (provided
they are fitted with heatsinks and there
is adequate ventilation). Each channel is
provided with a fuse, which will protect
the circuit in the event of an overload or
“short”. It is unlikely that the fuse will
protect the triac, however, as the short time
it takes to blow a triac is a lot less than the
time needed to blow a fuse.

The triacs are switched on by applying a
voltage between their MT1 and Gate (g)
terminals. This voltage is supplied by trans-
former T2, rectified by REC2 and smoothed
by capacitor C6. Although it is a low volt-
age, one side must be connected to Mains
Live (so that current can flow between MTI1
and Gate) and so it MUST be treated as

Everyday with Practical Electronics, June | 995

Mains Voltage. Resistor R18 is used to link
the low voltage supply to the Mains.

Gate voltage is applied to the triacs via
opto-isolators IC2 to IC5. Each opto-
isolator has a phototransistor at its output
and an l.e.d. at its input. Light from the l.e.d.
makes the phototransistor conduct. Resistor
R14 limits the gate current to CSRI, and
R19 reduces the sensitivity of the triac to
spurious electrical pulses and interference
that may be carried on the incoming mains
supply. Resistors R15 to R17, and R20 to
R22 do the same for the other triacs.

A separate fuse, FS1, is provided in the
supply to the two mains transformers.

As the only path through the opto-
isolators is for light, there is no electrical
connection, and so the input l.e.d.s are free
of mains voltage.

CONTROL
SECTION

The Control section of the circuit is
powered by a second mains transformer,
T1. The low voltage output is rectified by
REC! and smoothed by Capacitor Cl.
Diode D1 is added so that an unsmoothed

465

-RB7 RAO RA1 RA2 RAZ RB6 RBS RBS

IC1

RBI fe

RB2h

Vb PIC 16C54

SEE TEXT
RBIS

OSC1 OSC2 RTCC MCLR RBO

Fig. 1. Circuit diagram for the complete PIC-DATS 4-Channel Light Chaser.

output 1s available from which mains zero
crossing points can be derived.

The smoothed output is taken via resis-
tor R4 to Zener diode D4. This provides a
reference voltage for the base of transis-
tor TRI, which acts as a voltage regulator
producing 6:25V on its emitter. Resistor
R3 provides current limiting and short cir-
cuit protection, providing a stable limited
power source and making it almost impos-
sible to damage ICI even if it is fitted
backwards. Capacitor C2 provides decou-
pling to maintain a clean supply when IC]
draws pulses of current. .

ICI is a PICI6C54 microcontroller. Its
4-bit Input/Output (I/O) Port RA is used to
drive the opto-isolator l.e.d.s via current
limiting resistors R6 to RY and monitor
l.e.d.s DS to D8.

The 8-bit I/O Port RB is used for the
remaining functions. Port RBO senses the
setting of potentiometer VRI, using it
along with resistor RIO and capacitor C5
as a simple analogue to digital converter
(ADC) circuit. Port RB7 picks up pulses
from the collector of TR2, which is turned

466

off briefly when the unsmoothed full wave
rectified supply from REC! falls to zero at
each mains “zero crossing” point.

Ports RBI to RB6 are used to read the
keypad which consists of 12 individual
switches arranged in a matrix of three
columns of four rows. This arrangement
allows 12 switches to be read individually by
only seven connections. Unfortunately, only
six are available in this circuit, and so it has
been necessary to use a trick and add diodes
D2 and D3. These diodes give the top row of
switches (g) pull-up lines from d and e
simultaneously. This allows them to be
distinguished from the other keys which pull
up only one line at a time. |

The drawback to this method is that it
can give false Row g outputs if keys are
pressed simultaneously in Row d and Row
e, but this is not a problem when only
single keys are expected to be pressed.
Resistors R11 to R13 pull down Ports RB1
to RB3 so that when the keypad is not
pressed all three read as logic zeros.

All of the microcontroller operation ts
carried out at a speed determined by the

on-chip clock oscillator. The frequency is
determined by resonator or crystal X1. C3
and C4 provide the correct capacitive load-
ing for the oscillator circuit.

CONSTRUCTION

The circuit is built on a single printed
circuit board, which is available from the
EPE PCB Service, code 942. This board
can be assembled to different levels. as
required. For basic program development
it 1S necessary only to fit the components
around ICI.

The opto-isolators can be omitted if their
pins | and 2 are shorted together to provide
a current path to light l.e.d.s DS to D8. The
power supply section T1, D4 etc. can also be
omitted, and instead of mains power, a 6V
battery (easily provided by four AA cells ina
holder) can be connected across C2.

Leave resistor R5 in position so that Port
RB7 is always pulled up to a logic | level.
This is the ideal set-up whilst first ex-
perimenting as it is completely safe and
allows simple programs to be checked with
ease. The battery may also be used if the

Everyday with Practical Electronics, June 1995

power supply section has been assembled,
provided the mains input is unplugged.

All of the components are fitted as shown
on the component layout drawing in Fig. 2.
DO NOT use sockets for opto-isolators
IC2 to ICS as the distance between the
socket pins is less than that between the

pins of the opto-isolators and would reduce |

the clearance distance below that required
for safe isolation. Opto-isolators are reli-
able anyway, and so there 1s no reason to
have them in sockets — but do make sure
before soldering that they are fitted the
right way round!

The socket for IC] can be a turned pin
type or an ordinary one. Turned’ pin sock-
ets are more durable.

Assembly of the mains side of the circuit
is conventional. Use a nut and bolt to hold
each triac tab down to the board, and take
care to keep all of the soldering tidy to
avoid accidental track bridges.

Insulated wire links are needed to join
the Mains Neutral connections across to
all of the output terminals. These should
be made with 16/0-2 wire insulated with
sleeving.

It helps alignment when fitting the

Everyday with Practical Electronics, June 1995

Fig. 2. Component layout and full size copper foil track master for the PIC- DATS 4- Channel Light Chaser.

fuseholders if a fuse is clipped into them
before soldering. 7

TESTING

It is essential to make checks for solder
bridges, dry joints, and incorrectly fitted
components before applying power to the
board. If battery power is being used, con-
nect a 6V supply across capacitor C2. This
is best done by soldering a pair of 7/0-2
connecting wires to the track side of the
board where the pins of C2 are fitted. Do
not yet insert IC].

Using a short length of connecting wire,

467

COMPONENTS

Resistors
R1 100k
R2 47k
R3 47
R4,R10_ 1k (2 off)
R5,R11-
toR13 10k (4 off)
R6 to RO 150 (4 off)
~R14to
R17 —- 820 (4 off)
R18 10
~R19to
R22 470 (4 off).

Potentiometer |
VR1.—_:. 470k rotary carbon lin.

Capacitors
~C1,C6 - 220y radial elect. 16V
(2 off)
~€2 > = 47 radial elect. 10V
C3,C4 33p 2.5mm ceramic (2 off)
C5 see text

. Semiconductors
- D1 ©» : 1N4001 rectifier diode
D2,,D3 1N4148 signal diode (2 off) |
D4 6V8 400mW Zener diode
D5 to D8 3mm red l.e.d., standard
diffused
REC1,

REC2 W005 bridge rectifier (2 off)
TR1, TR2 BC183 npn transistor

(2 off)
CSR1 to
CSR4 TAG M29 triac, isolated tab
1C1 ~P1IC16C54 microcontroller

: (see text)
IC2 to

“1C5 CNY17-3 opto-isolator
/ (4 off)

Miscellaneous

X1 _. 4MHz crystal or resonator

FS1 250mA fuse, 20mm

FS2 to

FS5 3A fuse, 20mm (4 off)

T1,T2 11V0-8VA transformer,

p.c.b. mounting, Magenta
TX0811 (2 off)

Printed Circuit board, available from
the EPE PCB Service, code 942; 20mm
fuse clips, p.c.b. mounting (5 off); 3-
way terminal. block, p.c.b. mounting,
mains rated (5 off); mains connectors,
to suit application (5 off); case, to
suit.application (see text); 18-way d.i.l.
socket; insulating pillars and screws (4
off); keypad, 4 x 3 matrix; connecting

cable; wire; solder, etc.

link pin 5 of the i.c. socket in turn to pins 1,
2, 17, and 18. This should light the cor-
responding l.e.d.s D5 to D8 and will be ac-
tivating the opto-isolators if they have been
fitted. If the l.e.d.s do not light, check their
polarity, and that of the opto-isolators.

If a fully built mains powered circuit 1s
being built, the above battery test can still
be used before applying the mains.

FOR TESTING UNDER MAINS
POWER, BE EXTREMELY CAREFUL.
MAINS CIRCUITS MUST ONLY
BE CONNECTED BY FULLY
COMPETENT USERS. IF IN ANY
DOUBT - DO NOT APPLY MAINS
POWER: TEST THE CIRCUIT UNDER
BATTERY POWER ONLY.

If you are competent to use the mains
powered version, it is strongly recommended
that the p.c.b. is screwed down to a substan-
tial piece of wood before testing. This holds

Approx cost
guidance only

468

BGAOC EF

keying logic.

it in place, and takes away the temptation
to pick it up with bare hands. Use an in-
sulated test bench, and plug in to a cir-
cuit powered via an RCCB (residual current
circuit breaker). An RCCB is essential for
this and other electronics work using mains
power and greatly reduces any hazard.

Once mains power is applied, check the
regulated supply from the emitter of TRI,
which should be close to 6:25V. Check the
operation of l.e.d.s DS to D8 as before, and

that the triacs are being triggered when the ~

l.e.d.s are lit. This is best done using a low
wattage lamp as a load on each output.

Once this has been done, and power has
been switched off, the circuit is ready for
the PIC chip to be inserted. First, though, it
has to be programmed! _

PIC OPERATION

_ The PIC program can range from simple
to very complicated. To make an easy in-
troduction, the PIC-DATS will first be used
with some very simple examples, starting
with a program to turn on just one of the
outputs in response to the pressing of one
key on the keypad.

The program will then be extended in
several small stages until a simple light
sequencing program is developed. This pro-

cedure will have supplied the basic tools -

further programming development is left to
the individual to exercise his or her mind.
Those new to PICs will be surprised at the
ease with which simple working programs
can be written, and how simple steps can be
combined into larger programs.

All of the programs shown, and some
more complicated ones, are supplied on the
disk referred to last month, and in this
month’s Shop Talk.

CONNECTING UP

The outputs from the PIC SIM system,
described last month, are connected to a
40-way IDC plug on the end of the board.
Most of the connections are not used, but it
is difficult to fit individual wires, and so a
300mm length of 40-way rainbow (colour
coded) ribbon cable should be used. The
pins required are:

DATS PIN FUNCTION — ICI PIN

39 Ground Target pin 5
40 | Ground Target pin 5
"15 PORT RBO Target pin 6
17 PORT RBI Target pin 7
19 PORT RB2 Target pin 8
21 PORT RB3 Target pin 9
22 PORT RB4 Target pin 10
20 PORT RB5

Target pin 11

Fig. 3. Ke eypad connections and

COL2
B

COL1
A

OUTPUT ARRANGEMENT
OUTPUT PIN No. | SYMBOL

—

COL 2
ROW 1
COL 1
ROW 4
COL3 _
ROW 3.
ROW 2

OLOINIOI OATH Iw] dh

18 PORT RB6 Target pin 12
16 PORT RB7 Target pin 13
p&e, PORT RCO Target pin 17
25 PORT RCI Target pin 18
Zt PORT RC2 Target pin |
29 PORT RC3 Target pin 2

Port RC is being used since Port RA is
not available on the PIC-DATS. It is, how-
ever, a simple matter to change over when
programming the final chip so that Port
RA is used.

The ends of the ribbon cable must now
be connected to the Light Chaser board. As
this board is the one for which the final’
code is being developed, it is referred to
as the “target system’. The lead connect-
ing the PIC-DATS to the target system is
known as the “‘probe connecting lead” and
the connector used to make contact with
the socket of IC1 is the “target probe’’.

The ideal means of connecting the rib-
bon cable to the socket of ICI is to use an
18-way d.i.l. (dual-in-line) header which is
an IDC connector whose pins plug directly
into an 18-way 1.c. socket. |

There is a difficulty with this, though: the
ribbon cable from the PIC-DATS is not in
the correct order: to fit directly. To overcome
this, either solder the wires individually to
the d.i.1. header pins, taking care not to melt
the plastic connector body, or fit a separate
ribbon cable into the d.i.l. header and make
individual soldered and sleeved joints be-
tween the appropriate wires.

Alternative probe arrangements are pos-
sible, including the simple but effective
method of soldering the ribbon cable di-
rectly to the track side of the p.c.b. under-
neath the socket for IC1. If this method is
used, take care to unplug the 40-way

Everyday with Practical Electronics, June 1995

connector from the PIC-DATS when the
time comes to fit a programmed PIC into
the socket.

For the PIC-DATS simulation control of
this target circuit, DO NOT connect the
PIC-DATS control cable to pins 3, 4, 14, 15
or 16 of the socket for IC1.

Once the target probe connections are
made, and have been double checked, plug
in the 40-way connector, connect the PIC-
DATS power supply and power up the
target system using a 6V battery.

PROGRAMMING

One of the best aspects of the PIC-
DATS software is the way it is able to
switch to and from the Text Editor and
Cross Assembler programs. To achieve
this it is necessary to edit a simple file
called PICSIM.INI which indicates the
directories and paths through which to
access the two programs.

The file can be changed easily if neces-
sary using a word-processor. If the PIC-
DATS program has been loaded in the
standard way, and assuming it is to be run
from a hard disk on drive C, the first line
will read:

C:\ PIC\ MPASM.EXE

The second line is the path to the Text
Editor. The prototype was developed using
a word-processor package called PCWrite
which uses the command ED.EXE to start.
It is located in a directory called PCW1.
The second line reads:

C:\PCW1\ ED.EXE

Users who only have floppy disk drives
will need to make alternative entries, but
provided the disk capacity is sufficient the
system can be run successfully. It is useful

to have a compact word-processor as the |

programs need to be written in very simple
ASCII code. |

Assuming the software has been cor-
rectly loaded and the serial lead is
connected between’ connector PL2 and
the computer, enter the PIC directory,
and run PICSIM5X. Remember to enter
PICSIMSX 2 if the serial lead has been
connected to the COM 2 port of the PC
instead of COM 1.

If all is well, the PIC-DATS will sign on
and the COMMAND prompt will appear.
If not, check the lead and power supply. If
necessary switch off the PIC-DATS power,
and then switch on again to reset.

Once in Command mode, experiment
with some commands to see their effect.
The manual supplied with the software
gives full details of each command, and
only the bare essentials are provided here:

‘PROCESSOR 16C55
RADIX HEX

TITLE "PICA1.ASM"

LIST

ORG
MOVLW
TRIS
MOVWF
MOVLW
MOVWF
GOTO

ORG
GOTO
END

indicates where the next line of code should be loaded

loads the value 00 to W, which is the working register

copies the value in W to the Port RC control register - which
determines whether the port bits are inputs or aes loading
00 sets all Port RC bits to output

0X07
OXFF
0X07
START

loads

loads
sends

1FF |
START

the value 00 into Port RC setting all lines LOW

loads the value FF into W

the value FF into Port RC setting all lines HIGH

the PIC back to the first line so that the program loops

indicates where the next line of code should go.

located at 1FF. This is the first thing the PIC reads and so it
immediately jumps to START which is at address 00 and begins
running the instructions from there

Listing 2. Explanation of the commands used in Listing 7.

Key B_ switches alternately between
decimal and hex numbering. Hex is the
more usual system for programming and
should be selected.

Key M switches through the range of
processors covered. Select 16C54.

Key P steps through the available reg-
ister file pages, this should be set for page 0.

Key W allows the watchdog timer to be
enabled - the watchdog timer is an inde-
pendent counter that automatically resets
the PIC if the program runs away due to an
unforeseen programming bug. Its use can
be complicated, and it is not necessary in

_the current application so set function W to
“disabled”.

The other commands are either obvious,
such as Q for Quit, or are better explained
by example as programming proceeds.

PROGRAM FILES

As with all types of programming, there
are rules that must be obeyed, and com-
mands that will only be recognised in the
correct places. The MPASM Cross As-
sembler that is being used is not unfriendly,
but cannot work if it does not understand
the programmer’s intentions. The easiest
way to start is to modify a known working
program - some simple examples of which
are supplied on the software disk.

The first lines in a PIC program are to
tell the MPASM Cross Assembler program
which type of PIC the program is for,
which numbering system is being used
(Hex, Decimal, Binary etc.) and where to
locate the code in memory.

A simple program which sets Port RC to
operate as an output port and then switch
the eight outputs alternately between logic
0 and logic 1 is shown in Listing 1.

This file, PICA1.ASM, is included on the

software disk, but should be typed in as
an exercise to show how the system works.

;LOAD W WITH 00 (BINARY 00000000)
;COPY W INTO TRIS C SET PORT C AS O/P
;COPY W INTO PORT C TO SET ALL Os
;LOAD W WITH FF (BINARY 11111111)
;COPY W INTO PORT C TO SET ALL 1s
;LOOP BACK TO BEGINNING.

;RESET ADDRESS
3GO TO START POINT

Listing 1. PICA1.ASM. simple program which sets Port RC to operate as an output

port.

Everyday with Practical Electronics, June 1995

The name of the file in which the re-typed
program is stored is not important, but it
must have the suffix **.ASM” (pronounced
“dot A-S-M’’) and be in pure ASCII code,
that is, it must not contain any printer con-
trol or other non-text codes. Most word-
processors are able to work in this mode
without difficulty.

Take note of the columns used for the
various statements in the .ASM file, in par-
ticular the way that the label “START”.
begins in column one. Note also the semi-
colons (;) which indicate that the following
words on that line are comments.

Line by line the program works as des- —
cribed in Listing 2.

The two ORG statements are very im-
portant as they determine the starting ad-
dress (ORiGin) for the code. The main
part of the code starts from 0000, but the
PIC16C54 always starts at 01FF following
switch on or Reset so a simple command is
written and inserted directing the PIC to
the label START for its next instruction.

The use of a label allows a particular
piece of code to be found by the program
no matter where it is in the memory.
START could be at location 0OOFC and the
program would still find it correctly. Note
also that the word BANANA or any other
word (apart from a few reserved words
such as LIST that would cause confusion)
made from up to six letters and numbers,
could be used instead of START.

The .ASM program cannot be run directly
as it is, but must first be “Assembled” into
the correct form to be loaded into the PIC
chip. This is done by the MPASM.EXE pro-
gram. It takes the .ASM file and produces
two other main files, one is a listing file (suf-
fix .LST) which contains all of the original
information and adds the addresses and PIC
instruction codes. a

The other is the code file for program-
ming into the PIC processor (suffix .HEX).
If there are errors in the original .ASM file
which cannot be converted into code, a
third file is produced with the suffix .ERR
containing details of each error and the
reason it cannot be interpreted.

The listing file generated from the ASM
file in Listing 1 is shown in Listing 3. It
contains in columns one and two details of
the location and contents of the code that
would be loaded into the PIC processor.
For example, memory location 0000 will
contain the code 0CO00, and so on.

These codes are the “‘machine code”
equivalents of the statements entered in the
.ASM file. The listing file also shows the
amount of memory used, the date and time
of assembly and a table of labels and their
addresses. If errors have been made in the
.ASM file, these will be shown in the

LST file with details that help with their
correction.

469

To write a .ASM file from the PIC-DATS
software environment, press E and then
The PICA1.LST file: | select the file from the list provided. If a
new file is to be written press ‘“‘Esc”’ and the
text editor program will start up as usual.
When the file is complete, save in the usual

MPASM 01.02 Released C:\PICA\PICA 4-16-1995 20:20:10

scene , way and exit. A single keypress will then
ADDRESS CODE LINE SOURCE TEXT return to the PIC-DATS system. ;
To run the cross assembler, press XA and
0001 PROCESSOR 16C55 select the .ASM file from the menu. The
shui sighncdaglpaengi 4 ws 3 ~MPASM program will run, and report any
pon BEDE ERA Ree errors. A single keypress will again return
wane to the PIC-DATS. If there are errors, press
0007 tes Bae ié E and enter the file name with suffix .ERR
0008 ;LOAD W WITH 00 (BINARY 00000000) to see the error report. Alternatively, enter
0009 ;COPY W INTO TRIS C SET PORT C AS O/P. a .LST suffix and find the errors in the
0010 ;COPY W INTO PORT C TO SET ALL Os listing file. The error explanations and their
0011 sLOAD W WITH FF (BINARY ATL41111) solutions are often simple, but the more
phe ee complicated ones will need some thought
0013 ;LOOP BACK TO BEGINNING
0014 and reference to the PIC data sheets (sup-
0015 | | plied with the PIC-DATS kit).
0016 F ;RESET ADDRESS Once the code is correct, return to the
0017 ;GO TO START POINT : PIC-DATS program and use the L com-
0018 | mand to load the assembled .HEX file from
0019 ) the menu.
0020 :
MPASM 01.02 Released C:\PICA\PICA 4-16-1995 20:20:10 STEPPED
MONITORING
eee Now the real fun begins! Assuming the
SYMBOL TABLE | target system is connected to the PIC-
| DATS and powered, the code can be
LABEL stepped through one instruction at a time
. using the S command. As the state of the
ereee | I/O ports is changed, the l.e.d.s on the

target system will turn on and off. Note
that in this circuit, the l.e.d.s are turned on
by a logic 0 and off by a logic 1.
0000 : Press Q to end the single stepping, and
| then press T. The program will now run on
, pe its own and the l.e.d.s will appear to be
0180 : constantly lit, although they are actually
vate s flashing on and off very quickly. The speed
at which the program is now running is
much slower than the final speed of the PIC
teres « | device. This is because the PC computer
Warnings : . has to operate the PIC-DATS via a serial
Messages : link, and update the screen after each in-
struction. For testing programs, however,
it is fast enough, provided there are no time

MEMORY USAGE MAP ("X" = Used, " = Unused)

All other memory blocks unused.

Listing 3. The Listing file generated for the program in Listing 7.
The .HEX file is much shorter, and

is practically unreadable except by the PROCESSOR 16C55
PIC programming software. Thus the
PICA1.HEX file would read: RADIX HEX

:08000000000C07002700F FOCB3 ‘TITLE “PICA_B.ASM"

:040008002700000AC3

0203 FEOOO00AF3 . LIST

:00000001 FF |

, , ORG

This file contains the code that will - |
be loaded into the PIC when it is pro- MOVLW ;LOAD W WITH 00 (BINARY 00000000)
grammed, and other information giving the TRIS ;COPY W INTO TRIS C SET PORT C AS O/P
memory locations to be used, and a check- MOVWF ;COPY W INTO PORT C TO SET ALL Os
Ee ee ee eee ae ae MOVLW) _B"11111110" ;LOAD CHASE PATTERN 1 INTO W
detected as it is downloaded. MOVWF 0X07 ;COPY W INTO PORT C TO SET OUTPUTS
PROGRANM FILES MOVLW) -B"11111101" ;LOAD CHASE PATTERN 2 INTO W

Program .ASM files can be written with MOVWF 0X07 ;COPY W INTO PORT C TO SET OUTPUTS
enceadn Many tea aces ty MOVLW B"11111011" LOAD CHASE PATTERN 3 INTO W

yare. MOVWF 0X07 ;COPY W INTO PORT C TO SET OUTPUTS

running MPASM.EXE to produce .LST : :
and .HEX files (and a .ERR file if there are MOVLW B"11110111" ;LOAD CHASE PATTERN 4 INTO W
errors). This arrangement can be used MOVWF 0X07 ;COPY W INTO PORT C TO SET OUTPUTS
without PIC-DATS itself and is useful for
checking program ideas and learning the GOTO CHASE ;LOOP BACK TO BEGINNING OF CHASE
basic rules for the .ASM files. ae a suxate auberes

The PIC-DATS system is much more ef- nine ee G6 Te. EELEE DORE
fective for code development, however, as it END

allows the code to be run and developed in
hardware as well as software. Provided the
PICSIM.INI file has been set up correctly,
the PIC-DATS program allows easy access Listing 4. Program listing for PICA. B.ASM, which generates a simple chase light-
to and from the text editor and assembler. ing sequence. .

470 Everyday with Practical Electronics, June 1995

PROCESSOR 16C55

RADIX HEX ,
TITLE "PICA_C.ASM"
LIST

ORG 0x00

MOVLW 0x00
TRIS 07

MOVLW BB" 10001111"
TRIS 06

SWCOL1 0X06,4

0xX06,3
TNOFF
0X07,0
SWCOL1
0X07,0
SWCOL 1

1FF
START

;LOAD W WITH 00 (BINARY 00000000)
;COPY W INTO TRIS C SET PORT C AS O/P

;LOAD W WITH BINARY 10001111
;COPY W INTO TRIS B TO SET PORT
;B6, BS, AND B4 AS O/P OTHERS AS I/P

;LOAD W WITH 00 |
;COPY W INTO PORT C TO SET ALL Os
;COPY W INTO PORT B TO SET ALL Os

;CHECK THE SWITCHES IN COLUMN A

;SET BIT 4 OF PORT B TO LOGIC 1
;TEST BIT 3 OF PORT B

;IF IT iS 0 GO TO TURN OFF CODE

;IF IT IS 1 PREVIOUS LINE IS SKIPPED
;AND SET CO TO 0 TO TURN ON LED

; LOOP

;BUTTON IS NOT PRESSED SET CO TO 1
;TO TURN OFF LED
; LOOP

*;RESET ADDRESS

3;GO TO START POINT

Listing 5. Program to read the hash key and operate Channel 7 L.e.d.

critical applications, or long delay loops
which will cause tedious boredom!

Modify the .ASM file so that OXFI is
loaded instead of OXFF, run the XA
program again, then press L to reload, and
again repeatedly press S to single step
through the new code. This time only one
of the four l.e.d.s will turn on and off. Try
other changes, possibly including some
deliberate errors and see the codes gener-

ated in the .ERR file.

PROGRAM
INSTRUCTIONS

The codes such as MOVLW are instruc-
tions that the PIC16CS54 carries out. There
are only 33 of these, but as almost one mil-
lion can be executed in one second (using a
4MHz clock speed), they can be made into
powerful combinations.

This article is intended only to illustrate
some of the basic options so that the
PIC-DATS system can be operated, and
code can be written, assembled, corrected
(debugged) and run. The real work of
learning the instructions, their limitations
and applications, is down to the user.

Having produced a program which turns
the outputs on and off, its development
into one which produces a simple chase
sequence is relatively simple, as is il-
lustrated by the program PICA_B.ASM,
shown in Listing 4.

The listing file .LST is not printed here to
save space, but it can be produced by run-
ning MPASM as before.

_A program which reads the # (hash) key
on the unit’s keypad and then switches the
Channel | l.e.d as necessary is illustrated
by PICA_C.ASM, shown in Listing 5.

This uses BSF and BCF instructions to
set (make logic 1) and clear (make logic 0),
respectively. It also uses the BTFSS in-
struction, which tests the state of an I/O
port line and skips one instruction if the
I/O line is set to logic 1.

By following these examples, and those
on the software disk, it will be possible to

increasingly understand the nature of the
programs and how they are built up. With
the PIC-DATS system it is possible to ex-
periment with the whole range of instruc-
tions and so build up a working knowledge
in anefficient and easy manner.

The other keys on the unit’s keypad are
read in a similar way, as is the Zero Volt
Crossing signal. The reading of the set-
ting of potentiometer VR1 is more compli-
cated, however. This is done by first setting
Port RBO as an output port and charging
capacitor CS to + 5V, the logic | level. RBO
is then programmed as an input port and
read by the software. At first it reads a logic
1 as CS is fully charged, but gradually CS
discharges at a rate determined by VRI
until RBO reads as logic 0. The time for this
to happen indicates the setting of VR1.

In the Chaser Lights application, the
time is used directly to set the chase speed,
but the setting of VRI1 could be used
for other purposes in different programs.
This process is only a simple and not

very accurate analogue to digital converter.

(ADC), but it’s cheap!

PROGRAMMING
CHOICES

The PIC-DATS system comes with a
built-in programmer. This allows the code
which has been developed, or any other
-HEX code files, to be programmed into
any of the chips in the PIC16CSx family of
microcontrollers.

The low-cost versions of the PIC16CSx:
chips are fully enclosed plastic devices and
although they contain EPROM, cannot be
erased. This makes them One Time Pro-
grammable devices (OTP). However, an
alternative UV-Erasable type is available,
and it is highly recommended that at least
one of these is obtained. Such devices are
not very expensive and are essential for
serious programming where the cost of
wasted OTPs. with out-of-date programs
could soon build up. (It should be noted
that the PIC-DATS system cannot pro-

Everyday with Practical Electronics, June 1995

gram the PIC16C84 electronically erasable
(EEPROM) devices.)

To operate the programming part of
PIC-DATS, first Quit the PICSIMSX pro-
gram, and run the PICPROG program. As
with PICSIMS5X if Com 2 port is being
used, it is necessary to type PICPROG 2.

Once running, the PICPROG program
produces a screen display which has a num-
ber of self explanatory functions which can
be selected by mouse or cursor keys. The
commands can be explored one by one to
see their effect (without using the “pro-
gram” option). |

There are several “CONFIGURATION”
settings to be made. These allow the type of
oscillator to be set up — normally select XT
for 4MHz crystal or resonator operation,
and the Watchdog timer to be Enabled or
Disabled — set this to Disable.

The Code Protection option, if selected,

‘makes it impossible for the code to be read

out of the chip once it. has been pro-
grammed. It is an important security fea-
ture, but when code is being developed it is
useful to Disable the protection so that the
code can be checked and identified. It is
possible to Enable just the Code Protection
later on, once a prototype has been tested.

Before using the PIC-DATS as a pro-
grammer it 1s essential to disconnect any
other hardware by removing the 40-way
IDC header connector. This must be done
before inserting any devices into the pro-
gramming sockets.

PROGAMMING
THE PIC

To program a PIC chip, first insert the
device into the appropriate socket - taking
care to put it the right way round. Then set
up the required configuration and select the
wanted file. The file is found in the same
way that PICSIMS5X finds its files and so is
dependant upon the correct setting of the
INI file.

The device being programmed is not
powered until the program or read com-
mands have been entered. Up until then the
socket is “cold” and the chip can be
inserted or removed without danger of

- damage (provided normal anti-static han-

dling precautions are observed).
Downloading the program into the chip

is fast and is indicated by an l.e.d. (D2)

next to the programming sockets. The
screen display shows the result of the
programming.

When program downloading has been
completed, make sure the target system is
switched off, and plug in the programmed
PIC device. Switch on, and if all is well the
hardware will come to life and operate as a
stand alone system.

After many years experience in the use of
microcontrollers, it still delights (and some-
times surprises!) the author when a Target
System suddenly takes on its own new per-
sonality and springs to life.

It is hoped that this same satisfaction will
be achieved by all readers who are prepared
to put in the necessary time and effort.

CORRECTION

In Fig. 4 last month the pin notations for
transistors TR! and TR3 should read in
order of b, c, e (top to bottom).

Resource
See Shop Talk page for details on how
to obtain a complete kit, the software
programs and pre-programmed PIC
-microcontroller for this project.

47]

Regular Clinic

CIRCUIT
SURGERY

ALAN WINSTANLEY

i
5
wy

Our two-way “Surgery” of readers’ questions and comments looks at a “‘mes-

sage reminder” function for the popular Voxbox project. We also take the lid

off diode terminals with some typical diode applications. Finally, the Surgery
gets wired and goes on the Internet! |

ELCOME to this month’s Circuit

Surgery, our two-way column full
of advice, hints and general info. to
share amongst the readership. Let’s dip
straight into the post-bag with this en-
quiry from Barry Timms of Vermillion,
South Dakota, USA who posed a couple
of questions to the Surgery.

Voxbox Upgrade

I have two technical questions and
would be grateful if you could supply a
response to both. Firstly, concerning the
Voxbox project of July 1994. It’s men-
tioned that the addition of an l.e.d. to the
circuit could indicate that a message is
stored. I’m building this project and
wondered if you could tell me where to
connect the l.e.d. to provide this function.

Secondly, could you clarify why you
designate the terminals of a standard
diode the way you do? I know that the
polarities of most diodes and small
rectifiers are indicated by a band marked
around the cathode (k). Current flows
through the diode from anode to cathode,
but most textbook definitions of the
cathode and anode electrodes seem to me
to imply that current actually flows in the
opposite direction!

Your Voxbox ‘Message Waiting”
Indicator query first. This highly
popular project was designed jointly
by GEC-Plessey Telecomms engineers
*Guy Dance and Jeremy Austin as their
excellent contribution to the Technology
in Action Day event, which aims to
encourage engineering disciplines in
British schools.

To recap, Voxbox is a fully solid-state
recording unit which stores up to 20
seconds’ worth of speech — a kind of
talking memo pad! It uses the ISD1016
(16 seconds) or the ISD1020 (20 seconds)
integrated circuit at its heart: the latter
has a lower frequency sampling rate, so
reproduction isn’t quite as good.

The idea of a “jogger” l.e.d. to warn
that a message is stored, might appeal to
those who’ve already built this project.
The authors’ initial idea for an l.e.d.
reminder was to simply use an on-

472

SR

Fig. 1. Voxbox “Message Waiting” indicator modification.

WAITING

ae eS

(Courtesy Guy Dance and Jeremy Austin).

off switch and an le.d., arranged to
illuminate when the switch was in the
“on” position.

What they had in mind was that the
user would record a message and switch
on the l.e.d. as a reminder to others to
play it back. The recipient switches it
off again after inwardly digesting the
Voxbox’s pithy comments!

A high-efficiency |.e.d. could be used
to reduce current consumption. Alterna-
tively, you could try building a separate
l.e.d. flasher circuit based on something
like the LM3909 custom.|.e.d. oscillator
chip, driven by a separate 1-5V cell for

economy.
Our project designers have sub-
sequently proposed an “automatic”

version which illuminates an l.e.d. when
you record a message, and extinguishing
it after it’s been listened to. They
suggested using a single D-type latch for
this idea, see Fig. 1. The logic state of the
record buttons is loaded into the latch
when the “End of Message” (EOM)
pulse is generated. In record mode, the
EOM signal is initiated by the release of
the Record button.

An RC network adds a short delay in
the signal to allow the latch to catch the
record signal. Thus, starting the record-
ing mode will clock a Logic 0 into

the latch and light the l.e.d., playback
clocks a Logic 1 and extinguishes it
again. The authors tried this idea and it
seems to work OK, they say, but it’s
only intended for single messages since
the l.e.d. indicator circuit obviously
resets itself as soon as the first message
is played back.

Looking at the mechanical side, the
constructor could use half of a 74HC74
dual D-type flip-flop to implement this
idea. The ‘“‘extra’”’ chip can be grafted
into the circuit by mounting it on, say, a
small piece of stripboard and simply sol-
dering the connections over to the main
p.c.b. using hook-up wire to connect to
the copper track side.

It’s best to link any unused inputs (e.g.
on the unused half of the logic chip) to
OV for safety, rather than leave them
floating. Again, try a_ high-efficiency
l.e.d. for improved performance. In-
cidentally, the Voxbox printed circuit
board is available from the EPE PCB
Service, Code 885 £6.90 — see our PCB
page elsewhere in this issue. My thanks
to Guy and Jeremy for helping out.

*Guy was recently presented with a special
award at the Young Engineers Awards to

‘Industry in recognition of the active support and

help he has given to the Young Engineers Club at
Poole Grammar School.

Everyday with Practical Electronics, June | 995

Conventional current
flows from positive to
neaative potentials

~ Electrons flow the
reverse direction, in real
life

Fig. 2. Conventional current and
electron flow.

Darned Diodes!

Turning to Barry’s second question
on diode markings, this highlights a
common dilemma facing those involved
with other science disciplines such as
physics or chemistry. Just which way
does electric current flow?

Consider a battery powered flashlight
bulb, see Fig. 2. You can be forgiven for
thinking that electric current flows from
positive to negative. You might, how-
ever, be aware that in real life, current
actually flows the other way, from the
negative to the positive terminal of the
battery.

Perhaps the pioneers seemed to as-
sume from “Day One” that current
flowed from the positive to negative
poles. This has left us with a problem —
the fact that what happens in our circuit
diagrams is exactly the reverse of what a
chemist or a physicist would expect!

Without delving too deeply into the
physics, we now know that electrons hold
a negative charge, and so they will flow
out of the negative terminal and through
the bulb towards the positive terminal (to
which negative electrons are attracted).
So, electric current flows towards the
most positively-charged electrode, in real
life. We call this “true life’ current
electron flow.

In our own context, though, it’s only
in such disciplines as atomic physics or
electrochemistry that we would start to
worry about real-time electron flow.
Everybody in electronics still talks
generally in what we call “conventional
current flow” terms, where old-fashioned
conventions have it that current is
deemed to flow from positive to negative
potentials. In other words, we’re all
fooling ourselves in electronics because
in reality, electrons flow in the opposite
direction, but this doesn’t affect our use
of components or our understanding of
electronics at all.

Stop Press! Mr. Timms subsequently
advised by Internet (see later) that he’d
succeeded with the Voxbox add-on as

illustrated. He replaced the l.e.d. with
a flashing type to achieve a noticeable
visual signal for the message recipient.

One interesting way of looking at this

is to compare the semiconductor diode »

and also its thermionic valve (vacuum
tube) predecessor, see Fig. 3. In the case
of an old-fashioned thermionic diode
valve — probably easier to understand
than a semiconductor one — what hap-
pens is that when heat is applied to the
cathode by the heater filament, negative
electrons “boil off’ the cathode. These
free electrons will be attracted towards
the anode if a suitable positive “bias
voltage”’ is applied to the anode: then, an

electron flow is carried from cathode to

anode. However, by tradition we would
deem the conventional current to be flow-
ing through the valve the other way,
from anode to cathode.

True life
electron flow in

a valve -
electrons travel
from cathode to

anode
Heaters

Cathode

On your marks...

Our standard markings for diodes and
rectifiers are summarised in Fig. 4.
Nearly always, the cathode is readily
identifiable by a band or stripe at the
cathode lead-out.

Occasionally, you see diodes marked
with a series of stripes — a real nuisance if
you're not familiar with them! A com-
mon striped component is the faithful
1N4148 diode, which may arrive colour-
coded Yellow/ Brown/ Yellow/ Grey.
This actually borrows from the resistor
colour code for “4148” and the first
yellow stripe indicates the cathode.

As an aside, when I was putting
the finishing touches to a _ construc-

Conventional
current flows
through a diode
from anode to
cathode

Cathode

Fig. 3. Current flow through a thermionic diode valve and a semiconductor diode.

Any semiconductor physics book will
tell you in more detail how current
is carried by “holes” and electrons
gathered within a semiconductor diode
device, and how to bias them into
operation correctly. As you probably
know, it’s necessary for the anode to be
about 0-6V more positive than the
cathode, before (conventional!) current
can flow through a silicon diode at all.

Which way, and how, to mark the
terminals of a diode, is perhaps a bit
subjective. At one time — years ago now —
we did mark the cathode terminal with a
+ symbol, but now we letter each pin-
out with “a” and “k’’, to help the novice
to remember which terminal is which.
Perhaps it was too confusing when the
cathode was marked as positive — since
the direction of conventional current
flow implies that this is the “negative”

electrode.

Typical diode

4q>—
1N4148

Yellow Brown Yellow Grey |

SVs
ip

K

Schematic symbol

kK a

Fig. 4. Diode identification diagram.

Everyday with Practical Electronics, June 1995

tional project — actually a prototype
‘“Windicator’’ Wind Speed Indicator (to
appear next month — Ed.) — one
light-emitting diode resolutely refused to
light. It turned out that the lLe.d. (a
standard 0-2in. type) had in fact been
moulded wrongly, and the cathode
identifying “notch” was actually next to
the anode! Has that ever happened to
any reader?

If you come across an unusual l.e.d. |
such as a special-shape type, you can
often identify the cathode by peering
through the body of the l.e.d. and ex-
amining the l.e.d. chip assembly (if its
body is transparent). You'll see that the
light-emitting chip is mounted onto a
tiny saucer-shaped reflector. The lead
connected to this is the cathode. Look
even closer, and you'll possibly just see a
very fine wire jumping from the anode
termination over to the l.e.d. chip in the
reflector.

Clip Joint

Yes, my sub-titles get worse. My
thanks to Mr. Charles Hill of Carmar-
then, Wales who dropped us a line with
the following question, again concerning
the application of diodes. Mr. Hill
sketched a typical demodulator circuit as
depicted in Fig. 5.

I often see a reverse-connected diode
used in a circuit but don’t quite understand
why it’s necessary. I assume that the diode
D1 is a form of rectifier, but why the
reverse-biased diode D2. Could you shed
some light on this, please?

Certainly — thanks for the letter.
Everyone will have seen a diode reverse-
connected across an inductive load such
as a relay. This acts against the reverse
voltage spike (“back e.m.f.”’) generated —
by the relay coil when it switches out of
circuit. |

The pulse can easily be several hundred
volts instantaneous peak, which will

473

AC Input

Fig. 5. Diode demodulator circuit.

destroy any sensitive semiconductors on
the same circuit, so the diode shunts this
away before any harm can arise.
Anyone who followed our Teach-In
series (featuring the Mini Lab and Micro
Lab) might recall the back e.m.f. graphs
we managed to capture on a storage
C.R.O. (oscilloscope) and print out
(Teach In ’93, December 1992 issue
showed a peak 300V reverse voltage
generated by a 12V relay!)

In your circuit, Mr. Hill, diode D1 will
rectify the signal and if the input sig-
nal then falls below OV the ‘“‘redundant’”’
diode D2 will swing into action. The
OV rail is then in effect more positive
than the signal voltage, so eventually the
diode will become forward biased and
clip the signal away.

Obviously this can only happen once a
sufficient forward voltage has _ been
reached. It might be included just

+V supply

Fig. 6. CMOS Input protection diodes.

as a Safety pre-
caution to prevent
any transistors or
i.c.s from receiving
a reversed input
voltage, or there
could be a par-
ticular need to clip
or detect the signal

Rectified
Output

this way.. |
Exactly the
same protection

utilised by CMOS
i.c. manufacturers.
Constructors will
be aware of
the well-known
dangers of excess
static electricity
accumulation, since this can damage
CMOS circuits, the electrostatic
discharge punching a hole straight into
the metal-oxide silicon chip and
permanently killing it (I recently killed a
small MOSFET this way, when I forget
to use the anti-static wrist strap!). CMOS
circuits mainly incorporate an input
protection diode circuit on the input
circuit which guards against excess
electrostatic voltages.

For example, two diodes may be used

in an arrangement which I simplified in

Fig. 6. D1 would conduct if the input
voltage exceeds the supply rail, whilst D2
will shunt away any input voltages which
fall below the OV rail. Under normal
circumstances, neither diode would con-
duct. They’re not foolproof “‘catch-alls’’,
though, and you still need the usual anti-
static precautions.

alan@ Internet

As I type this month’s column into
my PC, ready to download the
article to ““Headquarters’’, I’m pleased
to announce the introduction of a
new E-mail/Internet connection. This
will be especially welcomed by many
of our overseas readers. Now anyone
with an E-mail connection can post
queries to Circuit Surgery via the
Internet.

You need a PC (or Mac, Amiga,
Archimedes, etc.) which is fitted with a
suitably compatible modem (these are
dropping in price all the time: a decent
BABT-Approved 14:4K type is less

principle 18:

than £100 now) and a connection to an

ordinary phone line. Users need to sign

up with a service provider if they don’t
already have access via a workplace,
college or University. There are several
providers available in the UK and
many more across Europe and the
United States. Preferably choose one
having a dial-in hub in your “local”
phone area, so you only pay for cheap
local rate calls.

Circuit Surgery is playing its modest
part on the Internet, helping out with
queries posted into various electronics
UseNet newsgroups: these are open
discussion areas where anyone can chip
in with information, in answer to a query
or comment. It’s often a rewarding
experience — recently a simple query
brought forth replies and friendly help
and advice from folks at the USS.
Johnson Space Center (NASA), not to
mention Hewlett Packard, IBM and
several Universities around the world!
For our own part, for example, we
solved an electronics query in Canada
and received an enthusiastic “thank
you” from a highly delighted student
over there!

Here’s the bit you’ve maybe been
waiting for: you can now E-mail Circuit
Surgery on alan@epemag.demon.co.uk.
Whilst the speed of your message may
be instantaneous (almost), please don’t
expect an immediate reply from your
hard-pressed scribe, who does his best!
Watch this space for news of future
developments.

If you have any queries or questions

which you would like us to investigate,
or any advice, hints and tips which you
think other readers would appreciate,
you can now contact Circuit Surgery
by writing to: Alan Winstanley,
Circuit Surgery, Wimborne Publishing
Ltd., Allen House, East Borough,
Wimborne, Dorset, BH21 IPF; or by
E-mail/Internet, as above.
_ The usual conditions apply — as al-
ways, we cannot guarantee an individual
reply unless material is to be published in
this column though we'll always try our
best to help.

Next time: an investigation of a preci-
sion rectifier with no forward voltage
drop! Also, more news from our Internet
feed. See you soon!

474

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Everyday with Practical Electronics, June 1995 475

Constructional Project

CONVERTER

ROBERT PENFOLD

A low voltage d.c.-to-d.c. converter —

that provides a 9GV output from one

or two AA cells.
HE humble PP3 battery has for many

} years been a popular method of

powering electronic projects. It repre-
sents a safe means of powering small
electronic gadgets, and at one time it
also represented a very inexpensive way
of powering circuits that required only
modest amounts of current (up to about
8mA).

Whereas electronic gadgets have tended
to become more complex but relatively in-
expensive over the last twenty years or so,
the batteries to power them have become
ever more expensive. In “real terms’’ bat-
teries are probably no more expensive now
than they were in the past, but relative to
the devices they power, most batteries are
now much more expensive. |

This has led to circuit designers looking
for lower cost methods of providing bat-
tery power. This has resulted in the in-
creased use of AA (HP7) size cells in
electronic gadgets.

Many radio sets, personal stereos, etc.
now use low voltage circuits powered from
two or three AA size cells. AA batteries
provide a given amount of power much
more cheaply than PP3s, or any of the
other 9V layer type batteries.

In terms of amp/hour capacity an AA
size cell typically has about five times more
capacity than a PP3 battery, but at one
sixth of the output voltage. A single AA
cell therefore has slightly less capacity than
a PP3 size battery, but is generally about 75
per cent to 80 per cent cheaper than an
equivalent PP3 battery.

STEPPING UP

Where it is practical, simply designing
circuits to operate on low supply voltages is
the best method. This is not always pos-
sible though, and circuits must then be
powered from a 9V battery, or a 9V supply
derived from a 1-5V or 3V battery via a
step-up circuit. This second method incurs
the additional cost of the d.c. to d.c.
converter circuit which provides the boost
from 1:5V/3V to 9V, but due to the reduced
running costs this additional outlay should
be more than recouped in the medium
term.
There are a number of small switching
regulator integrated circuits which, on the
face of it, would be ideal for this ap-
plication. However, a careful look at the
specifications of some common switching

476

weep Ae. >

regulator chips reveals that few are capable
of operating with an input voltage as low
as 3V, and none can operate with an input
voltage of around 1V to 1-5V. Fortunately,
there are now a few switching regulator
devices that are specifically designed for
operation with an input provided by one or
two 1-5V batteries.

REGULATED
STEPS

The step-up regulator featured here is
based on the LT1073CN8 switch mode
regulator chip. It will operate with a 1:5V
supply provided by a single AA cell, or a
3V supply provided by two AA cells in
series.

The circuit is exactly the same in either
case, with the regulator action of the device
ensuring that the output voltage remains at
about 9V regardless of which input voltage
is used. The circuit will operate with output
currents of up to about 15mA or so, even if
the power source is only a single cell.

Bear in mind though, that the voltage
step-up is obtained at the expense of a
current step-down. Using a 1-:5V input

there is a voltage step-up by a factor of six.

When the input voltage falls somewhat

due to ageing of the battery, the output —

voltage is maintained at about 9V due to
the regulator action of the circuit. This
gives an actual voltage step-up by a fac-
tor of about seven. Due to losses through
the circuit the input current is likely to be
closer to ten times the output current.

An output current of 15mA could there-
fore result in an input current of around
150mA, which would not give a very long
operating life from even a “high power”
AA battery. For output currents of more
than about 7mA it is better to use two AA
cells in series to provide an input poten-
tial of 3V (and a current step-down of
only about five times), or to use a higher
capacity cell such as a C-type or D-type.

STEP-UP BASICS

A d.c. voltage step-up is effectively
achieved by converting the input signal to
an a.c. type, feeding it through a step-up
transformer, and then rectifying the output
of the transformer to obtain a boosted d.c.
output voltage. In most practical d.c. to
d.c. converters the input signal is converted

to what is really a “chopped’’ d.c. signal

rather than a true a.c. type, and the step-up

is often provided by a simple inductor
rather than some form of transformer.
There is no obvious way in which a
simple inductor can provide a voltage
step-up, but it is actually possible. The
point to bear in mind here is that a high
reverse voltage is generated across an in-
ductor if the current flowing through it is
suddenly removed. This is caused by the
rapidly decaying magnetic lines of force
moving through the turns of wire on the
inductor. It is the same effect that causes a
high voltage to be produced across a relay
coil when it is de-energised, necessitating
the use of a protection diode.

Fig. 1.

Basic step-up switch mode
circuit diagram. |

The reverse voltage generated can be
many times higher than the forward volt-
age used to energise the inductor, and
a tenfold step-up is easily produced. Of
course, you do not get something for
nothing, and like a voltage step-up through
a transformer, the boost in voltage is
gained at the expense of reduced output
current.

BACK TO BASICS

The basic configuration for a switch
mode power supply that provides a voltage
step-up is shown in-Fig. 1. Transistor TR1
is the electronic switch, and the control
signal is normally a squarewave signal, or
something not too far removed from a
squarewave signal.

The operating frequency of the circuit is
generally much higher than the 50Hz mains
frequency, and is typically about 20kHz.
This relatively high operating frequency
makes it easier to obtain high efficiency,
and also enables a small inductor to be
used.

However, the inductor must be a type in-
tended for operation at about 20kHz. An
r.f. choke will not give a worthwhile level of
performance, and neither will an inductor
intended for operation at the 50Hz mains
frequency.

Everyday with Practical Electronics, June 1995

When transistor TR1 is switched on,
inductor LI is effectively short circuited
across the input supply, and the current
flowing through LI rapidly rises. A high
reverse voltage is generated across L1] when
TRI switches off. The left hand terminal of
L1 is then negative, and the right hand
terminal is positive. The voltage across L1
is therefore in series with the input supply,
and is added to it.

With TR1 being repeatedly switched on
and off at high speed, a rapid succession of
high voltage pulses are generated at the
collector (c) of TR1. These are fed to Cl,
which is a smoothing capacitor at the out-
put of the circuit. Diode D1 couples the
voltage pulses to Cl, but it also ensures
that TR1 does not short circuit the output
during its “‘on”’ periods.

ICI

LT1073CN8

circuits that will work efficiently at such a
low voltage.

Despite this the LT1073CN8 will operate
with good efficiency at supply voltages as
low as one volt. Consequently, it will work
properly using a single 1:5V cell as the
power source.

Furthermore, it will continue to work
properly even when the battery is nearing
exhaustion, and its actual output voltage
is only about 1:2V. Cl is a decoupling
capacitor on the input supply to IC1.

The regulator (IC1) has: built-in current
limiting at the input, and there is provision
for a discrete current limiting resistor be-
tween pins | and 2. This facility is not used
in this circuit though.

Pins 3 and 4 connect to the electronic
switch, which is driven by an internal oscil-

Fig. 2. Complete diagram for the AA to PP3 Converter.

With this basic configuration the output
voltage is dependent on a number of
factors, such as the input voltage, the
switching frequency, and the precise
characteristics of inductor L1. Practical
switch mode power supplies are almost
invariably based on integrated circuits
which include a regulator circuit that
provides a more predictable output
voltage.

Regulator R1 is a load resistor, and it is
not an essential part of the basic step-up
circuit. It is required with many practical
switch mode power supplies in order to
ensure that there is always sufficient out-
put current to keep the series regulator
working properly. Often this resistance 1s
provided by a feedback circuit, which is
likely to be part of the internal circuit in the
case of a fixed voltage regulator.

CONVERTER

CIRCUIT

The full circuit diagram for the AA To
PP3 Converter is shown in Fig. 2. Bl
is shown as being a 1:5V battery but,
as explained previously, the circuit will
work just as well with a 3V supply. Sl
is the On/Off switch of the unit in which
the converter is used, and the addition of
the converter will obviously necessitate
rewiring of this switch.

The on/off switch could simply be left on
the output side of the unit, since the quies-
cent current consumption of the circuit is
under 200nA. However, this would result
in some reduction in battery life, and it is
safer to have the circuit switched off when
it is not in use.

The LT1073CN8 device used for IC1 is a
switch mode regulator which is specifically
designed for this application. It is difficult
to produce semiconductor circuits that will
work at all on supply voltages as low as
1:-5V, and even more difficult to produce

lator circuit at frequency of between 15kHz
and 23kHz. Inductor L1 and diode D1 are
the equivalents of L1 and D1 in Fig. f.

In order to obtain good efficiency it is
important that D1 is a high speed device,
and that it has a low forward voltage drop.
A Schottky rectifier diode is therefore used
for Dl.

The circuit will work using an ordinary
rectifier such as a 1N4002, but with greatly
reduced efficiency. On the face of it, a
Schottky signal diode would be adequate in
this circuit, as it is only operating with low
output currents. In practice though, a
Schottky rectifier such as the 1N5822 gives
significantly better efficiency.

COMPONENTS

Resistors
R1 390k
R2 10k * »
-0:25W 5% carbon film

Capacitors
C1 47, radial elect. 16V
GZ 100, axial elect. 10V

Semiconductors
D1 1N5822 Schottky rec. diode
11 LT1073CN8 switch.mode
d.c. to d.c. adj. regulator:

Miscellaneous
L1 100pH min. radial inductors:
S1 min. s.p.s.t. toggle-switch
(see text)
B1 1-5V or 3V battery (see text)
Stripboard 0-1in. matrix, size 22 -holes
X°14 copper strips; 8-pin d.i.f socket;
battery holder; single-sided solder pins;
multistrand connecting wire; case to
choice; solder etc. ps

Approx cost
guidance only

£10

OUTPUT

Smoothing of the output signal 18
provided by capacitor C2. A value of
100uF is more than adequate as the
maximum output current is quite low, and
the ripple frequency is relatively high.
Resistors Rl and R2 provide a:load:across
the output under quiescent conditions, and
they are also the feedback network for the
regulator circuit.

The output voltage is typically a little un-
der 9V with the specified values, but there
will obviously be some variation in the out-
put voltage from one unit to another due'to
the component tolerances. If necessary, the
output voltage can be boosted slightly: by
increasing the value of resistor R1 to 430
kilohms.

The built-in regulator is very efficient,
and variations in output loading have very

Layout of components on the stripboard. The extra board space at the top 1s so that
/t can easily be mounted, on spacers, in a small plastic box.

Everyday with Practical Electronics, June 1995

477

The complete
Converter circuit
board. Note the use of a
.c. socket for the d.c. to d.c.
adjustable regulator.

- zranimoaoonse >
SSE SESE: .

Bi-

Fig. 3. Stripboard component layout and interwiring. The only breaks
required in the underside copper tracks are between the i.c. pins at points J14
toM14.

little effect on the output voltage. In fact
the output voltage is more stable than that
from a real PP3 battery.

CONSTRUCTION

‘This simple circuit is easily built on a
small piece of stripboard, and a suitable
topside component layout and the four un-
derside breaks in the copper strips is shown
in Fig. 3. This layout is based on a board
which has 22 holes by 14 copper strips.

+9V

ee ee

OUTPUT

OV

Construction of the board is not difficult,
but there are a few points which must be
borne in mind. .

The 1N5822 rectifier diode used for D1
has exceptionally heavy gauge leadout wires.
These are presumably designed to aid a very
low voltage drop when the device is used
at high currents, but they simply make the
component a bit awkward to deal with in
this case. D1’s leadout wires are too thick to
go through the holes in the stripboard!

One possible solution would be to en-
large the appropriate two holes, but it was
found easier to fit these holes with single-
sided pins, and then connect D1 to the pins.
This does not give particularly neat results,
but it works well, and is risk-free.

The choice of component for IC] must
be a plain LT1073CN8, and not an
LT1073CN8-5 (which has a fixed output
potential of SV). IC1 is not a static sensitive
component, but it is not a particularly
cheap type either. Therefore, it is strongly
recommended that an i.c. holder be used
for this component.

It is also recommended that only the
specified inductor be used for L1 (see Shop
Talk). The circuit should operate well using
any 100uH inductor that is suitable for
operation at around 20kHz and has a
reasonably low resistance, but the circuit
has only been tested using the specified
component. Also, other types might not fit
well into this component layout. Do not
overlook the three short link-wires.

IN) USE

The AA battery or batteries fit into a
plastic holder. It is probably best to use
a holder that has solder tags rather than a
PP3 style connector. This is due to the fact
that the circuit seems to stall at switch-on
unless the resistance between the battery
and the circuit board is kept very low.

Soldered connections avoid the risk of
poor connections between the battery
holder and the battery clip. The terminals
which connect to the battery or batteries
must be kept reasonably clean and free
from corrosion.

This device should work well with most
projects that require a 9V supply at no
more than a few milliamps. It is less than
ideal for use with radio equipment though,
or any sensitive circuits that could be
adversely affected by the signal that is
inevitably radiated due to the switching
action of the step-up circuit. O

EPE Valve HiFi Amplifier

_It is most important that constructors
undertaking the EPE Valve HiFi Amplifier
adhere to the correct ratings of the resistors
listed in the components box. Brimistors are
now considered obsolete technology and
are not now generally available. However,
Brian J. Reed (4 0787 393 9055) can, we
understand, supply them at a surplus price.

Due to their weight, the mains
and valve output transformers are best
ordered/purchased from your _ nearest
Maplin shop to save on the postage costs.
These transformers were specially wound
by Danbury Electronics (DB424 and
DB425) for Maplin, codes DM54J (Valve
Mains) and DM35H (O/P Trans.).

The “chassis” diecast box and solid
aluminium capacitors were purchased from
Farnell Electronic Services (07279
626777). Solid aluminium capacitors are
also stocked by many of our component
advertisers. Electro Supplies (@P 0767
477 9272) can supply high voltage
Capacitors.

The purchase of the valves can be a bit
tricky as prices will depend on where you
make your purchase and it is probably wise
to ring round our advertisers, such as Green-
weld, Cirkit, Mauritron, ESR, Bull and M&B
Electrical. One of the cheapest appears to be
Colomor (4 0787 743 0899). Ham radio
rallies are also a good source, but don’t buy

478

with David Barrington

from specialist HiFi suppliers unless you
have a large trust fund.

The Phase- Splitter p.c.b. is available from
the EPE PCB Service, code 941.

PIC-DATS 4-Channel Light Chaser |

A full kit of parts for the 4-Channe/ Light
Chaser, PIC-DATS demonstration project,
is available from Magenta Electronics,
Dept. EPE, 135 Hunter Street, Burton-
on-Trent, Staffs., DE14 2ST.

The kit (code 855) includes the p.c.b.,
a “one time programmable” PIC chip and
a disk containing all necessary software.
The cost of the kit is £39.95 (less case),
plus £3 for post and carriage. Also available
separately is the disk containing the basic
software and development programs for the
sum of £3.99, including p&p.

The printed circuit board is available from
the EPE PCB Service, code 942.

R.F. Signal Generator

Several components needed for the A.F.
Signal Generator can be classed as special
items and may not be available locally.

The first and probably most expensive
of these is the Jackson type-O twin-
gang air-spaced tuning capacitor. This is
available from Maplin (code FF40T) or

‘Electrovalue, (4 07784 442253), code

5250/2. The epicyclic reduction drive unit
and pointer were purchased from Maplin,
codes RX42V and HB47B respectively.

The presets should be as specified or
they will not fit on the p.c.b. These were
obtained through Electromail, (4 07536.
204555), code 186-750. The neon LP1
was also ordered from the same source and
is the ‘‘slim-line” type, code 576-614.

The only listing we have found for the
high frequency f.e.t. type 2N5486 has also
been Electromail, code 641-910. The 3VA
mains transformer has twin 15V_ secon-
daries and came from the above source,
code 210-796.

Capacitor C19 MUST be a type rated for
continuous operation across the mains sup-
ply. These are usually classified as class-X
or class-Y types and are stocked by most
component suppliers.

The p.c.b.s are available from the FPE
PCB Service, code 936 (R.F./Mod.) and
937a/b (Coil and Power Supply — pair).

AA to PP3 Converter

For best results it is recommended that
only the specified components be used in
the AA to PP3 Converter project.

The switch mode adjustable voltage
regulator 1C1 must be a plain LT1073CN8,
and not one with a suffix-5 added to the
type number. This device was purchased
from Electromail (@® 07536 204555),
code 265-364.

It is important that the 1N5822 Schottky
rectifier diode be used in this circuit. This
was purchased from Maplin, code GX30H.
The circuit will work with an.ordinary rec-
tifier diode, such as the 1N4002, but with
greatly reduced efficiency.

The 100uH radial inductor is listed by
Maplin code AH32K and Electromail, code
240-624.

Everyday with Practical Electronics, June 1995

ELECTRONICS ale
SOFTWARE =| AY 1

If you are looking for a means of
improving your knowledge of the
basics of electronics then this
software is for you.
Applied Voltage = 130V

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* Insulators, Conductors, Resistance * D.C. Circuits
* Capacitance and Inductance * A.C. Series Circuits TestDate. VR= Ovals: VL» 1Z0vals

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* PLN. Junction Diode * Bi-polar and MOSFET Transistors Designed to complement the EPE Teach-In
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* Memory * Microcomputer operation A Level students, this software can also
Electronics Principles 2.0 is a major revision of the success- be used as a stand alone learning package
ful original version currently used by electronics hobbyists; for everyone interested in electronics. From
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and currents or logic states are shown, drawn to scale, in full tions, digital numbering systems and goes on
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steps, exactly as in a textbook, using your input values. dressing modes and instruction sets. “It-even® '
- An ‘on screen’ electronics package including circuit theory produces a program listing, which can be
to enable a learning through doing approach to encourage ex-__ saved or retrieved from hard disk, when any
perimentation. For the young student, mature hobbyist or the _ of the instructions from the listed instruction —
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enjoyable way. monitor the registers for each of the address-
Having reviewed a dozen, or more, educational software ing modes.
packages designed to “teach” electronics, I was more than a little The original version is now. widely used in-
sceptical when I first heard about Electronics Principles: there schools and colleges throughout the UK, |
seemed to be little that could be done that has not been done An interactive, user friendly medium Aehich 2
elsewhere. When | started to use the package my views changed. assists learning in an enjoyable and interesting _.
Indeed, I was so impressed with it that I quickly came to the way. Only £39.95
conclusion that readers should have an opportunity to try the | Nily 497.

package out for themselves! - MIKE TOOLEY B.A. Dean of
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Everyday with Practical Electronics, June 1995 479

ee

Mike Tooley, BA

Part 9

provide you with a comprehensive and up-to-date
introduction to the world of electronics. The series is
based on Electronics Workbench, a remarkable software
package that lets you use your PC to build and test a wide

E LECTRONICS from the Ground Up is designed to

range of circuits.

In this final instalment we round-off the series by taking a
brief look back at the earlier parts and suggesting some
further reading for those wishing to explore the full poten-
tial of Electronics Workbench.

Back issues of earlier parts of this series are available —

see Back Issues page.

A BRIEF RESUME

Part One of Electronics from the Ground
Up provided you with a brief introduction to
electricity and electronics. Its five practical
assignments aimed to familiarize you with
the techniques for constructing simple
circuits and making measurements with
the basic test instruments provided in
Electronics Workbench (EWB).

Part Two dealt with d.c. and a.c. circuits
and also described the use of the oscillo-
scope for measuring waveforms. This part
also introduced capacitors and inductors
and their use in a.c. and d.c. circuits.

Semiconductor diodes were introduced
in Part Three. We investigated the be-
haviour of half-wave and full-wave rectifiers
and developed these into complete power
supply circuits incorporating smoothing
and voltage regulation.

5 V/biv
3.00
loc] ©

GROUND (ee

TRIGGER
EDGE @
LEVEL

2. V/Div &

Fig. 9.1 Push-pull output stage from Electronics Workbench: 150 Circuits.

480

Transistors featured in Part Four where
we also introduced the concept of gain
and amplification. Understanding transistor
operation is crucial to understanding most
analogue circuits and it is worth revisiting
this part if you intend to work with transistor
circuits in the future (note that, to keep
things simple, we did not cover field effect
devices).

Integrated circuit operational amplifiers
were explained in Part Five. We looked at a
variety of circuit applications for opera-
tional amplifiers (op.amps) and showed
how it was possible to design circuits to
provide specific amounts of gain as well as
an accurately defined frequency response.

Oscillators were described in Part Six
where we investigated the behaviour of
a variety of oscillator circuits including
sinusoidal, pulse and square-wave types.
Part Seven was devoted to logic gates,
digital circuits, truth tables and Boolean
algebra. Finally, Part Eight featured bis-
table elements and we illustrated their use
in counters and shift registers. These last
two parts are essential for those intending
to work primarily with digital circuits. |

FURTHER READING

Readers wishing to explore electronics
further will be pleased to know that EWB
is well supported with three books that
provide information on extending the use
of the package. Each book is supported
with a disk containing circuit files for
loading into EWB.

Everyday with Practical Electronics, June 1995

oan | |e

FRequency [120 iL Hz By

puTy cycLe [50

AMPLITUDE [if AL vey
Cs

OFFSET

Fig. 9.2 Notch filter from Electronics
Workbench: 150 Circuits (note the Bode
Plotter display clearly shows the notch in
the frequency response characteristic).

GROUND
TRIGGER

ence _FJE] @

TIME BASE
1.68ms/div =

HORIZONTAL

VERTICAL

LOG LIN|

Electronics Workbench: 150 Circuits (pub-
lished by Interactive, ISBN 0-921862-24-5)
contains 150 of the most frequently-used
electronic circuits. The book contains a typi-
cal screen shot of each circuit as supplied on
the accompanying floppy disk. Test equip-
ment settings and displays also feature as
does a brief written explanation of each circuit
together with some further suggestions for
experimentation. In many respects, this book
begins where Electronics from the Ground
Up ends and provides enormous scope for
further experimentation.

If you are interested in servicing or fault-
finding, Troubleshooting with Electronics
_ Workbench by Don Browning (published

_by Interactive, ISBN 0-921862-27-X) is just
for you! This book contains more than
00 ready-to-use circuits and assignments.
However, unlike Electronics Workbench:
150 Circuits, the circuit files in this book
are not working! Instead, you are left to
determine the cause of the fault using the
test equipment exactly as you would on

Electronics Workbench: 150 Circuits.
ISBN 0-921862-24-5.

Everyday with Practical Electronics, June 1995

Troubleshooting with Electronics
Workbench. ISBN 0-921862-27-X.

a real circuit. Troubleshooting with Elec-
tronics Workbench introduces the learner
to troubleshooting techniques and, most
important, it develops the logical thinking
process that results in rapid and efficient
fault finding.

Finally, Electronics Workbench: Practi-
cal Teaching Ideas by Allan Souder (pub-
lished by Interactive, ISBN 0-921862-22-9)

contains a teacher’s perspective on the use

of EWB in the classroom. Allan Souder
shares his experiences with readers in the
form of exercises, exarhples and assign-
ments. Teachers will find this a particularly
useful book as it shows how several im-
portant principles and concepts can be
brought to life with the aid of EWB.

UPGRADING
If you intend to make further use of EWB
you should seriously consider upgrading to

the full package. The full package will
provide you with a full range of test

equipment (including Bode Plotter and
Logic Converter that were not included in
the cut-down version) and an unlimited
Parts Bin. The package also comes with
some additional support materials, “on-
line” help, and an excellent User’s Guide
which includes tutorials, a reference sec-
tion and troubleshooting information. A

Electronics Workbench: Practical Teach-
ing Ideas: ISBN 0-921862-22-9.

481

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Fig. 9.3 Fault-finding a two-stage common-emitter amplifier with Troubleshooting with Electronics Workbench.

“Quick Reference Card” is also supplied.
You can use this to get started, or simply
keep it by you for reference.

Interactive demonstrations are included
on the disk that comes with the package.
These examples give you a quick overview
of EWB and show you how to build and test
circuits. Sample circuits (also supplied on

pr 3.3 KOHM

256 OHM

3.262 VOLT
B

482

the disk) include approximately 20 typical
analogue and digital circuits. You can ex-
amine, test and modify them or use them
as building blocks for your own circuits.
Tutorials are included within the User’s
Guide. These are invaluable for those who
may be unfamiliar with a graphical user
interface or who may have had little or

no experience of building and testing
electronic circuits. For registered users,
there is the User Support “help-line”. A
Bulletin Board Service (BBS) is also avail-
able to provide the latest product informa-
tion. Users can leave questions for answer
via the BBS and circuits may be down or
up-loaded for sharing with other users.

| a, FOL

$608 OHM

478 OHM

256 9)

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Fig. 9.4 An example of Thevenin’s Theorem in Electronics Workbench: Practical Teaching Ideas. |

Everyday with Practical Electronics, June 1995

The full version of EWB offers a wide
choice of printing facilities. You can print
the current display (exactly as it appears on
your computer's screen) or print out circuit
descriptions, component lists, parameters
associated with the component models,
circuit diagrams, and test equipment dis-

plays. You can also convert your display |

into a PCX file for loading into one of
many popular paint, graphics, CAD ‘or DTP
packages.

Finally, it is important to note that the full
version of EWB is copy protected and must
be uninstalled if you wish to move the
software to a different platform. However, if
you want to use EWB at two different
locations (for example, at work and at
home), you need not delete all of the EWB
files when uninstalling, just the authoriza-
tion code.

CIRCUIT DESIGN

One of the questions asked by several
readers relates to what else you can do with
EWB once you have finished using it as a
learning aid. One ‘of the advantages of
the package as far as the hobbyist and

i te . ‘ ~ — =~

Fig. 9.5 Answer to last month’s Brain Teaser.

enthusiast is concerned is that it permits

breadboarding of circuits before laying

them out for final prototype construction.

There are several stages to this process:

1. Sketch the basic circuit design and
identify component values

2. Select the required components from
the Parts Bin and place them within the
breadboard area

3. Change the component values (from
their default values to those that you
require)

4. Select the appropriate models for the
active components used in the circuit

5. Connect the circuit

6. Select the instruments that you require
to test the circuit (often you will start
with the multi-range meter in order to
check supplies and bias voltages, etc.)

7. Place the test instruments on the
breadboard and select appropriate
ranges

8. Refine the circuit layout (i.e., move the
components and test instruments so
that the symbols, component legends,
and wiring all fit neatly and logically
within the breadboard area)

clear] |

TRIGGER
Ei] «
EXTERNAL
BURST

9. Test the circuit and, where neces-
sary modify component values as
appropriate

10. Evaluate the circuit and check against
specification

11. Print out the circuit diagram and com-
ponents list (don’t forget to save the
circuit for future reference!).

Answer to last month’s Brain Teaser

Last month’s Brain Teaser involved the
design of a logic circuit arrangement that
would generate a waveform with a ratio of
high to low period of 7:1. Fig. 9.5 shows the
solution arrived at using the full version of
EWB together with the logic analyser display
(the output waveform is the lowest trace).

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' Everyday with Practical Electronics, June 1995 483

Robert Penfold

‘ pear
A COMPUTER operated model train con-
troller of the pulsed variety can be
quite a complex set up. Such a system can
be based on a conventional pulse width
modulation (p.w.m.) controller, with the
control voltage being provided from an
output port of the computer via a digi-
tal to analogue converter. This involves
quite a lot of hardware, and is relatively
expensive, but it does have a significant
advantage.

The speed of the train is controlled by
simply outputting suitable values to the
output port. High values give fast speeds,
and low values give slow speeds or stop
the model train. This method of control is
not particularly taxing on the computer,

which can therefore be a slow machine |

running a slow programming language.

The demands on the computer are so low —

that there will still be plenty of computing
time left for other tasks, such as controll-
ing signals, or providing some sort of
graphics display.

On The Pulse

There is an alternative approach that re-
quires far less hardware, and this is to use a
software routine to generate a suitable pulse
signal on a digital output line. The signal is
then used to drive the train via an amplifier
and a buffer stage. This method is quite
simple to implement in theory, since the
pulsed output signal is an extremely simple

To drive the train at half power a
squarewave signal is used. With its one-to-
one mark-space ratio the. average output
voltage squarewave is half the supply
potential. Using a higher mark-space ratio
gives an output signal that is high for a
greater proportion of the time. This gives a
higher average output voltage, and more
power is fed to the motor in the train. Using
a lower mark-space ratio give a lower
average output voltage, and less power to
the motor in the engine.

Although one might reasonably expect
the pulsed signal to interfere with the

correct operation of the motor, this does not

actually happen. In fact a pulsed signal gives

better low speed performance, with less

likelihood of stalling. Pulsed control also
gives more realistic starting, with no jump-

starts. Very low pulse speeds must be.

avoided as they would result in the motor
operating intermittently.

High pulse rates are also unsuitable, as
they can result in strong radio frequency
interference being radiated from the tracks.
Also, the motor provides a highly inductive
load which-could have a high impedance at
high frequencies. This would give an in-
adequate current flow. In practice, any fre-
quency from around 50Hz to 500Hz or so is
usually satisfactory.

484

In days gone by, this software based
method was not possible using an ordinary
BASIC language due to the slow operating
speed of an interpreted BASIC. Producing
an output signal having a suitable range of
mark-space ratios was possible, but not at a
high enough frequency to give good results.

However, modern computers are much
faster than the 8-bit machines of about ten —

years ago. A few experiments using a
33MHz 80386 based PC running GW
BASIC and Q BASIC programs showed that

it is possible to obtain quite good results

using a software generated pulse signal.
Results should be at least as good using a
faster PC, but it might not be worthwhile
using anything less than an 80386SX based
PC running at about 20 or 25MHz.

DO

To R1 2 R3

Printer
Port 10k 1k5

Gnd

a pala PAT FO PR RAE MART RY. Tae

the reference level, and the output of ICI

goes low. Transistor TRI is an emitter

follower buffer stage at the output of IC1. :
This is a high gain power Darlington device,
and although the drive current from IC1 is"
only a few milliamps, TR1 can drive the
motor with output currents of up to two
amps. Resistor R4 provides TR1 with a load
resistance when the output of the controller
is left unconnected. Diodes D1 and D2
suppress any high voltage transients that
are generated across the inductive load
provided by a small d.c. motor.

Switch S1 is the forward/reverse switch,
and this can be a set of d.p.d.t. relay contacts
if direction control via the computer is re-
quired. Fig. 2 shows the circuit diagram for a

suitable relay driver. The relay can be any 12

Fig. 1. Circuit diagram for the pulsed controller interface.

Hardware

The circuit diagram for the pulsed con-
troller interface is shown in Fig. 1. IC1 is an
operational amplifier, but in this circuit it is

used as a voltage comparator. IC1 must be

a device that can operate properly with
low input voltages. The NE5534P (and
NE5534AN) are suitable, but most other

operational amplifiers will not work in this

circuit.

Resistors R2 and R3 provide a reference ;

potential of between 1:5 and two volts to
ICI’s non-inverting input. In other words, a
voltage that is between the valid logic 0 and
logic 1 levels. IC1’s non-inverting input is
fed from the digital output of the computer.
Obviously any latching output will do, but
it will be assumed here that the interface is
driven from D0 of printer port one (LPT 1).

When the digital output is high, ICI’s ©

non-inverting input is taken above the
reference level, and the output of IC1 goes
high. When the digital output is low, ICI’s

‘non-inverting input (pin 3) is taken below

volt type which has a coil resistance of
about 250 ohms or more, and d.p.d.t. con-
tacts of adequate rating. Again, this circuit
can be driven from any latching digital out-
put, but we will proceed on the assump-
tion that it is driven from the “Initialise”

To
Printer
Port

Gnd

Fig. 2. Direction control relay driver.

Everyday with Practical Electronics, June 1995

Fig. 3. Printer port connections for the pulsed train controller.

output of LPT1. Fig. 3 provides details of
the connections to the printer port for both

the pulse controller interface and the relay

driver.

Both circuits require a 15 volt supply
which must be reasonably stable and ripple-
free. The maximum output voltage from the
controller is about 12 volts due to the
voltage losses introduced by IC1 and TR1.
For small gauge trains a maximum supply
current of one amp is adequate, and the
mains power supply circuit of Fig. 4 can then
be used. Transformer T1 should have a
secondary rating of at least two amps, and
FS1 should be an “anti-surge” or “time-
delay” fuse.

The same circuit can be used for larger
gauge locomotives that require up to two
amps, but transformer T1 must then have a
secondary rating of at least four amps, and
fuse FSI should have a rating of two
amps. Also, diodes D1 to D4 should be
1N5402 rectifiers, and IC1 should be a
78S15 regulator (which is available from
RS/Electromail). The normal safety precau-
tions should be observed when building
and using the power supply. Beginners
‘should not undertake construction of a
mains powered circuit such as this.

Transistor TR1 and regulator IC1 in the
power supply must be fitted with heatsinks.
For a one amp controller a couple of bolt-on
heatsinks having a rating of about 10 or 12
degrees Centigrade per watt will suffice. For
a two amp version it would be advisable
to use larger heatsinks having a rating of
about six to seven degrees Centigrade per
watt. Note that the heat-tab of TR1 con-
nects internally to its collector terminal. The
heat-tab of the voltage regulator connects
internally to its common terminal.

Software
The GW BASIC/Q BASIC program
shown in the software listing provides speed

control, and direction control as well if the |

relay driver circuit is included in the
controller.

The first part of the program simply clears
the screen and provides on-screen instruc-
tions on how to control the program.
Lines from 90 to 160 produce the output
_ waveform on output Do of the printer port.
Two FOR... NEXT delay loops set the high
and low output times. The number of loops
performed in each of these, and hence the
mark and space times, are controlled by
variables “M” and “S”. They are each given
an initial value of 50, giving a one-to-one
mark-space ratio. Other values can be used
at lines 90 and 100, but the two values must
total 100.

The GOTO in-
struction at line 190
continuously loops
the relevant part
of the program.
However, lines 170
and 180 detect key
presses, and take the
program into the

at line 200. If the
“A’ key is pressed,
‘M” is increased by
one, and “S” is
decreased by one, giving increased output
power. Pressing the “B” key has the
opposite effect, with “M” being decre-
mented by one, and “S” being incremented
by one. This produces reduced output
powe:. . .

Operating the “E” key brings the pro-
gram to a halt at line 220. Lines 230 and
240 provide forward/reverse switching if
the relay driver circuit is included: These
lines detect presses of the “R” and “F” keys

respectively, and set the “Initialise” output —

high or low. The purpose of lines 250 to 280
is to keep the values of “M” and “S” within
acceptable limits.

Although the hardware and software are
both pretty basic, the system provides
excellent control, with smooth acceleration
and deceleration. Results would probably be
a bit slow and jerky using a slow PC. Using
a fast 80486 or Pentium based PC it might
be necessary to use higher values in the
FOR ... NEXT loops. Otherwise accelera-
tion and deceleration might be too rapid. At
minimum power the motor is not com-
pletely switched off, and it is still fed with
very brief pulses. The power fed. to the
motor should be far too low to be of any
practical significance though.

_ nfo

240V AC
MAINS

subroutine _ starting.

Software listing for generating pulses
for Model Train Controlling.

10 REM SOFTWARE GENERATED
PULSE TRAIN CONTROLLER
PROGRAM

20 OUT &H378, 0

30 CLS

40 PRINT “PRESS ‘A TO ACCELERATE”.

50 PRINT “PRESS ‘B’ TO BRAKE” :

60 PRINT “PRESS ‘E’ TO END”

70 PRINT “PRESS ‘F’ FOR FORWARDS”

80 PRINT “PRESS ‘R’ FOR REVERSE” |

90 M=50 |

100 S = 50

110 OUT &H378, 1

120 FOR HIGH = 1TOM

130 NEXT HIGH

140 OUT &H378, 0

150 FORLOW = 1TOS

160 NEXT LOW

170 A$ = INKEY$

180 IF LEN(A$) = 1 THEN GOSUB 200
190 GOTO 110

200 IF ASC(A$) = 97 THENM = M+ 1

205 IF ASC(A$) = 97 THENS = S — 1

210 IF ASC(A$) = 98 THENS = S + 1

215 IF ASC(A$) = 98 THENM = M — 1

220 IF ASC(A$) = 101 THEN END

230 IF ASC(A$) = 114 THEN OUT
&H37A,4

240 IF ASC(A$) = 102 THEN OUT
&H37A,0

250 IFM > 100 THENM = 100

260 IFM < 1THENM = 1

270 IFS > 100 THENS = 100

280 IFS < 1THENS = 1

290 RETURN |

Fig. 4 (below). Circuit diagram for the
15 V mains power supply unit.

ICt = vA7815
Di to D4 = 1N4002

a

FS1
1A

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Everyday with Practical Electronics, June 1995 7 | 485

-“s mini FM transmitter, very high gain preamp,
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Designed to cover 88-108 Mhz but it is easy to
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Electronic siren kit with an impressive 5 watt
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3-30v Power supply, variable, stabilized power
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24v 3A transformer is also needed to complete the
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Powerful 1 watt FM transmitter supplied com-
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FM/AM Scanast, well not quite you have to turn
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no 1013.

Mosquito repeller, modern way to keep midges at
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Motorbike/cycle Near cree sdiiotabis ini
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0-5 minute timer, adjustable from 0 to 5 mins, will
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486

4 watt FM transmitter, small but powerful trans-
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25 watt FM transmitter 4 RF stages, preamp
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Strobe light, adjustable frequency from 1- to 60 Hz
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Ultrasonic radar ideal as a movement detector

" with arange of about 10 metres, automate your cat

flap! 12v operation so ideal for cars, caravans etc.
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Liquid level detector useful for detecting fluid
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Combination lock 9 key, easily programmable,
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Phone bug detector, this device will warn you if
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function generator, produces sinusoidal, saw tooth
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3 Channel light chaser, 800 watts per channel,
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VOX switch, sound activated switch ideal for turn-
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Phone callrelay, useful dtenteatvaieeins arelay
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Lead acid charger, two automatic charging rates,
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Car alarm system, works on voltage drop and/or
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Kit no 1019,

Portable alarm sy stem, based on a mercury switch.
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Everyday with Practical Electronics, June 1995

Constructional Project =

R.F. SIGNAL
GENERATOR

STEVE KNIGHT

A high performance, relatively
low cost design that covers the
range T15MHz to SOMHz in three

switched bands.

O FAR we have described the Sig-
nal Generator circuits, fabrication of
the component mounting chassis and
construction of the three p.c.b.s. We have
also covered the drilling of the front panel
and the mounting of the completed rf.
board, together with the coil bracket, on
the large L-shaped mounting chassis.
Before we move on to mounting the
power supply board on the case rear panel
and conclude with the calibration, we should
like to refer back to the front panel drilling
details (Fig. 9) given last month. The dis-
tance measurement from the /eft-hand edge
to holes ““D”’, the chassis mounting holes,
should be 22mm and not 12:5mm as shown.

POWER BOARD

The power supply unit is fitted to the
back panel of the case. This panel, like the
front one, can be completely removed to
make life easier, and the positioning and
fixing of the board is a simple job. Provi-
sion is also made here for the entry of the
mains cable and the fuseholder FS1.

Holes for these should be drilled to
suit the components you have; the mains
lead can be brought directly through a
grommeted hole, but must be adequately
anchored down on the inner surface. If you
use an appropriate plug and socket system,
such anchoring is unnecessary.

Again, you have the choice here. Fig. 17
shows the board position, interwiring and
suitable places for the fuseholder and
mains lead entry points.

PANEL |
COMPONENTS

Some of the panel components, switches
S1, S2 and S3, and the output poten-
tiometer VR3 are mounted on the rear
mounting chassis. The remaining pieces,
two 4mm sockets, the BNC output connec-
tor and the neon indicator LP1 go onto the
front panel proper.

When the panels are finally brought
together, these front panel parts project
through the corresponding holes in the rear
mounting panel for internal connections to
be made later. This is where accurate
alignment of the holes is vital, but any
slight deviations can be corrected with a
round file.

What follows now applies to those con- -
structors who are using the printed scale

provided (see Fig. 15); this should be. ac-
curate enough for general purpose use as-

suming that the coils have been carefully.

wound to specification. For those purists
who would wish to do their own calibration,

suitable methods will be givenlateron. =.
Mount first of all those parts which goon
the rear back mounting panel: switches S1,

S2 and $3 and the output control VR3. The
rotary switches have small locating lugs
which when used will prevent the switch
bodies rotating in use.

It is wise (but not absolutely essential) to

use this facility by drilling 3mm (’s") holes
positioned about 10mm (*s”) from the cen-
tre of the main fixing hole as Fig. 13 il-

lustrates; when the switches are fitted, these

holes should accept the locating lug snugly.
Using these holes also prevents unneces-
sary over-tightening of the locking nuts.

Part 2 ==

LINK-LUP

Now, for the time being, wire up in-
ternally the coil outlets to switch Sl,
adjusting the wire lengths as necessary
(but not tight); bring two leads from the
poles of this switch down to the two
nearest solder pin points on the main
board (P6 and P7), and connect the ‘‘tag”’
common connection from the coil board
to the appropriate pin (P5) on the main
p.c.b. (see Fig. 17).

SWITCH MAIN FIXING HOLE.
LUG LOCATING HOLE IS 9¢Smm
FROM ITS CENTRE.

Fig. 13. To stop the rotary switches
rotating during use their locating lugs
are secured in small holes SOpICA
their main fixing holes.

The input and output sockets are mounted on the front panel and protrude through
holes in the L-shaped mounting chassis so that they can be wired to the Function
switch and the R.F. Level contro/ potentiometer. Note the capacitors wired directly
between the switch tags and the 4mm sockets.

Everyday with Practical Electronics, June 1995

487

en

AN

(a)

Fig. 14. Oscilloscope display of the output as unmodulated
and as modulated carrier. In the modulated case the high

500 Hz MODULATION

frequency signal Is not seen as individual waves.

Connect also two leads from the power
supply unit to the r.f. board input pins
P4 and P8, making sure of the correct
polarity. This then completes the tem-
porary wire-up needed for test and calibra-
tion purposes.

Keep the power unit in the background
by using longish connections; you cannot
then touch it accidentally when doing the
checks. In this condition, both testing and
calibration can be completed before the
front panel and its components are fitted to
the rear mounting chassis.

Due to the presence of mains voltages on
the power supply p.c.b., and also from
the mains input socket and fuseholder on
the back panel, extreme care MUST be
taken when testing and calibrating the sub-
assemblies. In fact, apart from “keeping the
power panel in the background”’, it might be
wise to also put it in a temporary box for
additional safety.

TESTING

For comprehensive testing of the R.F.
Signal Generator you will need, as men-
tioned earlier, a voltmeter (digital or
analogue), an oscilloscope and, if you are
doing your own calibration later on, a
frequency meter.

Set the preset potentiometers VR1 and
VR2 to mid-travel, close the tuning
capacitor gang, set the Frequency Range
switch S1 to the lowest frequency range,
(fully anticlockwise), and have a voltmeter
ready. Switch on the power supply unit and
check the following voltages at the main
board points indicated:

P4: About 18V (if below 16V reduce
R18 in value slightly)

Across diode D1: 15V+0-5V

Across diode D3: 7:5V +0-5V

P5; About 4V +0-5V

P10 (collector of TR2): 13V+1V

Interpret these measurements’ with
respect to the tolerances of the Zener

diodes for example; very small differences

outside of the ranges given can be ignored.

If the voltages seem satisfactory and
there is no sign of discontent from any of
the board components, connect the oscillo-
scope to the output point pin P9 and switch
to a fast timebase; there should be a
continuous sinewave output as shown in
Fig. 14. If necessary, adjust preset VR2
carefully to ensure that there is no visible
distortion of the output waveform.

Check now on all three positions of
Range switch S1 and all rotations of the
tuning capacitor. There will probably be
small variations in the amplitude of the
waveform throughout these checks but the
oscillation should not collapse.

488

The amplitude on the upper range par-
ticularly may well be seen to diminish as
the tuning is adjusted, but this is most
likely to be due to the falling response
of the oscilloscope to frequencies above
some 20MHz. If you can use the scope to
measure the wave amplitude, this should be
about 3V peak-to-peak (1:07V r.m.s.).

Now connect together, with a short piece
of wire, the points PJ and P2. This will
enable the 500Hz oscillator/modulator sec-
tion. Check with the scope switched to a
relatively slow timebase that there is a
sinusoidal output at the collector of TRS,
point P3. This wave should be about
4V amplitude peak-to-peak (1-4V r.m.s.)
and approximately 500Hz in frequency,
though the exact value is not important;
more important is that there should be no
distortion.

Transfer the scope to the output P9 again
and with the same timebase setting adjust
preset VR1 carefully to give you a mod-
ulated output signal rather as shown in
Fig. 14b. VR1 controls the depth of modul-

Lettering and layout of components on the front panel of the
completed R.F. Signal Generator.

ation and any “unbalance’ or distortion
in the modulation envelope. You should
finish up with about 30 per cent modula-
tion depth as the figure indicates but again,
within reason, this is not a critical point.

If all the above checks are satisfactory,
the tuning scale can now be fitted (if this is
your choice) before the final assembly con-
struction is undertaken.

FITTING THE
SCALE

There are three choices available here
regarding the calibration of the R.F. Signal
Generator: you can use the ready prepared
scale, shown in Fig. 15; you can prepare
your own scale in the same form; or you
can use a frequency meter connected to
the generator and forgo the central paper
scale altogether. In this last case, as men-
tioned earlier, the scale cutout will have
been omitted from the front panel.

If you use the ready prepared scale,
its actual accuracy will essentially depend

The positioning of the power supply p.c.b. fuseholder and mains input socket must
be located on the case rear panel such that they do not short out on the coil board
when they are finally brought together in the case. |

Everyday with Practical Electronics, June 1995

Fig. 16. How the scale is situated rela-
tive to the position of the ball-drive
flange and spindle.

upon the care taken over the winding of the
coils. The tuning capacitor may also con-
tribute some slight error to the tracking but
this will be small in the worst case, and the
accuracy obtained will almost certainly be

_ attributable to the inductances.

To check on this point, three sets of the
coils were constructed and the error against
the scale calibration done with the first set
did not amount to more than about one
millimetre of scale position with the other
two. Averaged out, this does not make
the calibration worse than +3 per cent
which is comparable with commercial in-
struments in the lower price ranges.

If you decide to use this scale (Fig. 15),
don’t cut the copy from the magazine as
there will be a tendency for the back print
to show through when it is. glued in posi-
tion. Get a photocopy made on to a piece
of good quality paper, and trim this to the
outline indicated in the diagram.

Glue the scale (or edge tape it carefully)
to the face of the rear, front panel mount-
ing chassis so that the circular cut-out is
positioned centrally to the projecting ball-
drive flange and the bottom scale line in
effect passes “‘through”’ the centre of the
drive spindle. Fig. 16 should make these
points clear.

Next, cut the Perspex pointer to 57mm
(2%") in overall length and screw it with
a couple of short 8BA screws to the
flange face. Unlock the rear gang spindle
grubscrews so that the ball-drive does not
rotate the gang (vanes), close the gang
fully, and turn the ball-drive until the
pointer cursor line is exactly in coin-
cidence with the bottom scale line on the
right-hand side.

Fig. 16.

Now retighten the gang spindle grub
screws and check that the pointer travels
over the scale without rubbing against it
and finishes up along the bottom scale line
of the left-hand side. There may be a slight
overshoot here but ignore this as there is a
“dead” patch over a few degrees when the
capacitor vanes are fully disengaged.

FRONT PANEL

The completion of the work is now in
sight (did I hear somebody somewhere
make a comment?) but first the front panel
has to be finished off with the appropriate
legends and the fixing of a piece of Perspex
or other transparent material over the scale
cutout.

Before lettering, the front panel may be
sprayed a light colour, say, white or very
pale blue, if black letters are used, and
black or a dark blue if white letters are
used. If the panel is not unduly marked
from the hole cutting earlier, it may be left
in its natural brushed aluminium finish. In
all cases, make quite sure that the surface is
free of grease.

The required front panel marking, using
rub-off lettering and assuming that the
specified control knob sizes are used, can

es

settee ate

p aheratet alee

The tuning scale 1s glued or taped to the face of the mounting
chassis centrally above the ball-drive spindle — see opposite and

be seen in the photographs. The size of the
letters should not be more than 8-point
(2mm) as room is at a premium on this
panel, but you can decide for yourself if
you feel that in some places a 10-point
(2-5mm) or larger style might be more
attractive or help legibility. When the let-
tering is completed a thin coat of protective
lacquer will make the legends resistant to
scratching.

It now remains to glue a piece of thin
Perspex, say, 2mm ('16") thickness (or any
other transparent sheet) over the scale
cutout; this, of course, goes behind the
front panel. This sheet will need a clearance
hole for the drive spindle and an overlap of
about 6mm ('’4") at the top and sides; it
should not overlap at the bottom edge by
more than 3mm ('’8”) or it might foul the
4mm socket located below it. These points
can best be judged when you are doing the
work rather than my pouring out long
sermons of explanation.

FINAL ASSEMBLY

The final assembly is quite straightfor-
ward. The remaining panel components,
neon indicator LPl, the BNC output
socket and the two 4mm sockets can now

The ball-drive links the tuning capacitor to the front panel tuning cursor and knob.
One of the two spindle grub-screws can be clearly seen.

Everyday with Practical Electronics, June 1995

489

be fitted to the front panel and this in turn
secured to the rear panel piece.

Trim off the switch spindles to a
projecting length to suit the knobs used
(about 10mm (*s”) is suitable), fit the knobs
with the correct orientation to match the
panel markings where necessary, and
finally check that everything turns or
switches without scraping against the panel
or the frequency scale.

There is one important point to mention
here which can save you spending more
than you have to. The Lorlin switches and
the output level potentiometer are avail-
able with ain. (6-35mm) or 6mm spindles
and if you use collet knobs as given in the
parts list, make certain that you order the
right size to suit the spindles you have.

Also, some switches have a flat on the
spindle to accommodate grub screw fixing,
but if such a method is used here, the orien-
tation of the switches must be such that the
knob pointer marks match up to those on
the front panel. If you use collet type knobs
this problem does not arise, hence it is ad-
visable to get the 6mm spindle types as well
as minus the flat.

WIRING-UP

The internal connections can now be
made from the main board to the various
panel sockets and switches; these are leads
from board points PJ, P2 and P3 to Mod.
Function switch S2 with returns by way of
capacitor C9, C10/R17 to the 4mm sock-
ets; a lead from point P9 to the output
R.F. Level potentiometer VR3 and a short
length of screened lead down to the BNC
output socket with a return to the main
board “‘earth’’ line at P//. The placing of
these wires is not critical but keep them as
neat as possible.

The front panel can now be slid into the
base part of the case; the back panel with
the power supply board can be similarly
placed in position and connections made
for the positive and negative rails to board
points P4 and P5 respectively. The mains
lead is taken by way of the fuse FS1 to the
On-Off switch $3 and returned to the trans-
former input pads on the power supply
board.

The box top can now be finally screwed
into position. A short appendix follows for
those who wish to do their own calibra-
tion or use a Frequency Meter directly for
readout.

APPENDIX:
Own Calibration

If you decide to do your own scale
calibration, this can be carried out in one
of two ways: either against a radio receiver

which has a.m. medium and shortwave
bands (a good communications receiver is
really best for this purpose), or against a
Frequency Counter which goes up as far as
30MHz as a minimum.

The first method, used with care, enables
the work to be done with a fair degree
of accuracy; the second methcd enables
the calibration over the whole three ranges
to be accomplished with a high degree of
accuracy.

If you prefer to do away with a scale
altogether, you can connect the Frequency
Counter (or a suitable module) as your
readout. As mentioned in the text, this
method provides complete accuracy and
saves the metal work needed for the front
panel scale cutout. We will briefly examine
these methods in turn.

490

SPRL LTT ey

CALIBRATION
POINTER

If you are to calibrate your own scale
you will need a blank copy of the scale
based on Fig. 15 and a “half” pointer. This
latter if fabricated from a second Perspex
pointer as given in the parts list and sawing
it (with great care!) to the shape shown in
Fig. 18.

The cursor line now forms a calibration
‘edge’ when the half pointer is fitted over
the scale blank. A well pointed pencil can

Fig. 18. Adapting a pointer for calibra-
tion purposes.

“MOUNTING CHASSIS —™

REAR PANEL

SK2 ©) SK1 @

BASE

MOUNTING ——>
CHASSIS

TUNING BOARD

Fig. 17. The front and rear panels lard flat to show the interwiring and main

circuit board connecting points. Positioning of the power supply board,
mains input socket and fuse are fairly critical as they could possibly foul the
coil board when the sections are brought together in the case.

Everyday with Practical Electronics, June 1995

The top cover removed from the completed R.F. Signal Generator to show the
compact arrangement of component boards inside the case.

then make the various scale frequency
positions by operating along this edge
which effectively indicates the true cursor
line when the full-size pointer is later fitted
as described in the text.

You will, of course, transfer the pencilled
scale on to a fresh piece of paper using ink
and rub-off numbering to complete your
final scale.

RECEIVER
CALIBRATION

You will need a receiver which covers the
frequency range 1-SMHz to 30MHz or
wavelengths from 200m to 10m. These
ranges will be found on the shortwave
bands and possibly the bottom end of the
medium wave band.

A few inches of unscreened wire on the
end of the r.f. output cable placed close to
the receiver’s ferrite rod or the aerial input

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point will radiate enough to be picked
up by the receiver; only sufficient output

should be used to hear the 500Hz modula- .

tion adequately on the receiver speaker or
phones. Too much will lead to confusing
harmonics or swamping of the true tuning
points.

Starting with the lowest frequency
range, which is about 1-4MHz to 2-4MHz
(215m to 125m), set the receiver to
1-S5MHz (200m) and tune the R.F. Signal
Generator through the band until its
output is detected by the receiver. This
point is now marked on the scale. The
1-6MHz point is then found in the same
way, and so on.

In this way all three bands can be
calibrated at the main frequency points and
marking between these added by eye. It has
to be admitted that this method is tedious
and the accuracy only fair, but for general

purposes is possibly.good enough.

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FREQUENCY
COUNTER
METHOD

The use of a Frequency Counter for
calibration purposes gives very good ac-
curacy when transferred to the scale using
the half-pointer method.

The counter can be fed from the r.f. out-
put socket or from point P/O on the main
board; if you use this point, disconnect
capacitor C14 or the signal level at the
higher frequencies may not be adequate
enough for the counter input. This point is
actually useful if you build in a counter
module in place of the scale.

Switch to UNMOD. on the Function
switch so that an unmodulated output is
obtained for the counter. Tune the Signal
Generator to give as exact readings as you

-can hold on the counter (it is difficult to be

absolutely precise); then at the frequencies ©
1-SMHz, 1-55MHz, 1:6MHz etc. calibrate
the scale for the lowest range and repeat
at convenient intervals for the other two
ranges.

This is the method that was used to
draw up the scale of Fig. 15. If you are not
using that scale as such but calibrating
you own, you will find it a convenient
guide to work to.

CONCLUSION

This project is one involving a lot of
careful workmanship, with quite a bit of
thought given to each stage of construc-
tion. Describing its construction has also
not been easy, but hopefully the article
has given enough information to make a
worthwhile instrument. O

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Order Ref: 5P240.

Mains Klaxon Type Alarm. Very loud output but adjustable.
Completely encased, shelf or wall mounting, £5, Order
Ref: 5P226.

Speed Controller for 12V DC Motors. Suitable for motors
with horse powers up to one third and drawing currents
up to 30A. Gives very good control of speed. Uses MOS-
FETS and is based on a well tried circuit which appeared in
the Mode! Engineer some time ago. The complete kit with
case and on/off switch, price £18. Order Ref: 18P8.

Figure-8 Flex. Figure-8 flat white pvc lead, flexible with
‘4sq.mm cores. Ideal for speaker extensions and bell
circuits. Also adequately insulated for mains lighting.
50m coil, £2. Order Ref: 2P345. 12m coil, £1. Order Ref: 1014.
Friedland Underdome Bell. Their ref: 792, a loud ringer but
very neat, 3” diameter, complete with wall fixing screws,
£5. Order Ref: 5P232.

Flashing Beacon. ideal as a warning light, the fire
alarm, etc. Zenon tube produces intense pulse of

light. Operates from 12V DC and is supplied complete
with mounting base. Price £7.50, Order Ref: 7.5P13.

12V 10A Switch Mode Power Supply. For only £9.50 and a
little bit of work because you have to convert our 135W
PSU. Modifications are relatively simple — we supply
instructions. Simply order PSU Ref: 9.5P2 and request
modification details, price still £9.50

Medicine Cupboard Alarm. Or it could be used to warn
when any cupboard door is opened. The light shining on
the unit makes the bell ring. Completely built and neatly
cased, requires only a battery, £3. Order Ref: 3P155.

Don’t Let it Overflow! Be it bath, sink, cellar, sump or any
other thing that could flood. This device will tell you when
the water has risen to the pre-set level. Adjustable over
quite a useful range. Neatly cased for wall mounting, ready
to work when battery fitted, £3. Order Ref: 3P156.

Very Powerful Mains Motor. With extra long (2%”) shafts
extending out each side. Makes it ideal for a reversing
arrangement for, as you know, shaded-pole motors are not
reversible, £3. Order Ref: 3P157.

45A Double-Pole Mains Switch. Mounted on a 6” x 3%”
aluminium plate, beautifully finished in gold, with pilot
light. Top quality, made by MEM, £2. Order Ref: 2P316.
Lamp Dimmer. Suitable for up to 250W, on standard plate
so fits directly in place of existing switch. Coloured red,
blue, yellow or green but will take emulsion paint, £2 each,
Order Ref: 2P380.

LCD 3‘ Digit Panel Meter
This is a multi-range voltmeter/ammeter using the

A-D converter chip 7106 to provide five ranges each of
volts and amps. Supplied with full data sheet. Special
snip price of £12. Order Ref: 12P 19.

12V/24V DC Solenoid. The construction of this is such that |

it will push or pull. With 24V this is terrifically powerful but
is still quite good at 12V, £1. Order Ref: 877.

Don’t Stand Out In The Cold. Our 12m telephone extension
lead has a flat BT socket one end and flat BT plug other
end, £2. Order Ref: 2P338.

20 W 5” 4 Ohm Speaker. Mounted on baffle with front grille,
£3, Order Ref: 3P145. Matching 4 ohm 20W tweeter on
separate baffle, £1.50. Order Ref: 1.5P9.

Telephone Extension Wire, 4-core correctly colour coded,
intended for permanent extensions, 25m coil, £2, Order
Ref: 2P339.

High Power Switch Mode PSU, Normal mains input, three
outputs: +12V at 4A, +5A at 16A and —12V at ‘RA.
Completely enclosed in plated steel case. Brand new. Our
special offer price of £9.50, Order Ref: 9.5P 1.

Philips 9”° High Resolution Monitor. Black and white in
metal frame for easy mounting. Brand new, still in maker’s
packing, offered at less than price of tube alone, only £15.
Order Ref: 15P1.

3%” Rubber Grommets for insulation through panel. Packet
of 100, £1, Order Ref: 181.

Mains Transformer 6V-0V-6V 6VA, £1, Order Ref: 330.
Ceramic Wave Change Switch, 12-pole, 3-way with %”

~ spindle, £1, Order Ref: 303.

Luminous Rocker Switches. Packet of 3, £1, Order Ref: 373.
Cased Mains Power Supply with leads, ideal to operate
doorbell, £1, Order Ref: 102.

High Current A.C. Mains Relay. This has a 230V coil and
changeover switch rated at 15A with PCB mounting with
clear plastic cover, £1, Order Ref: 965.

Ultra Thin Drills, actually 0.3mm. To buy these regular
costs a fortune. However, these are packed in half dozens
and the price to you is £1 per pack. Order Ref: 797B.

You Can Stand On It! Made to house GPO telephone equip-
ment,.this box is extremely tough and would be ideal for
keeping your small tools in. Internal size approx. 10%”
x 4%" x 6” high. Complete with carrying strap, price £2.
Order Ref: 2P283B.

Ultrasonic Transducers. Two metal cased units, one trans-
mits, one receives. Built to operate around 40kHz. Price
£1.50 the pair. Order Ref: 1.5P/4.

Power Supply with Extras. Mains input is fused and filtered
and the 12V DC output is voltage regulated. Intended for
high class equipment, this is mounted on a PCB and, also
mounted on the board, but easily removed, are two 12V
relays and Piezo sounder, £3. Order Ref: 3P80B.

Mains 230V Fan. Best make ‘“‘PAPST’’, 412” square, metal
blades, £8. Order Ref: 8P8.

Everyday with Practical Electronics, June 1995.

sy Naferui, bwey.Vie) sj =

2MW Laser. Helium neon by Philips, full spec. £30. Order Ref:
30P1. Power supply for this in kit form with case is £15, Order
Ref: 15P 16, or in larger case to house tube as well £18, Order
Ref: 18P2. The larger unit, made up, tested and ready to use,
complete with laser tube £69, Order Ref: 69P1.

12V 8ohm speaker, only £1.50 and waterproof.

Solar Charger. Holds 4AA NiCads and recharges these in
eight hours, in very neat plastic case £6. Order Ref: 6P3.
Ferrite Aerial Rod. 8” long %” diameter, made by Mullard.
Complete with two coils, 2 for £1, Order Ref: 832P.
Air-Spaced Trimmer Caps. 2-20pF, ideal for precision
tuning UHF circuits, 4 for £1, Order Ref: 818B.

Modem Amstrad FM240. As new condition but customer
return, So you may need to fault find, £6, Order Ref: 6P34.
Amstrad Power Unit. 13-5V at 1:9A or 12V at 2A encased
and with leads and output plug, normal mains input, £6.

-Order Ref: 6P23.

80W Mains Transformer. Two available, good quality, both
with normal primaries and upright mounting, one is 20V
4A, Order Ref: 3P106, the other 40V 2A, Order Ref: 3P107,
only £3 each.

Project Box. Size approx. 8” x 4” x 4%” metal, sprayed grey, |

louvred ends for ventilation otherwise undrilled. Made for

.GPO so best quality, only £3 each. Order Ref: 3P74.

Sintinel Component Board. Amongst hundreds of other
parts, this has 15 ICs, all plug-in so do not need desolder-
ing. Cost well over £100, yours for £4. Order Ref: 4P67.
Sinclair 9V 2-1A Power Supply. Made to operate the 138K
Spectrum Plus 2, cased with input and output leads.
Originally listed at around £15, are brand new, our price is
only £3. Order Ref: 3P 151.

15W 8 Ohm 8” Speaker & 3” Tweeter. Made for a discon-
tinued high quality music centre, gives real hi-fi and only
£4 per pair. Order Ref: 4P57.

Water Pump. Very powerful, mains operated, £10. Order
Ref: 10P74.

0-1mA Full Vision Panel Meter. 2%” square, scaled 0-100
but scale easily removed for re-writing, £1, each. Order
Ref: 756.

Amstrad Keyboard Model KB5. This is a most comprehen-
sive keyboard, having over 100 keys including, of course,
full numerical and qwerty. Brand new, still in maker's
packing, £5. Order Ref. 5P202.

Unusual Solenoid. Solenoids normally have to be ener-
gised to pull in and hold the core, this is a disadvantage
where the appliance is left on for most of the time. We now
have magnetic solenoids which hold the core until a volt-
age is applied to release it. £2. Order Ref: 2P327.

Mains Filter. Resin impregnated, nicely cased, p.c.b.
mounting, £2, Order Ref: 2P315.

0V-20V DC Panel Meter. This is a nice size 65mm sq. It is
ideal if you are making a voltage variable instrument or
battery charger. Price £3, Order Ref: 3P188.

Another 12V-0V-12V Transformer is a 50VA and is suitable
for dropping through the chassis or as it is fitted with four
pillars it can be mounted above the chassis. Also should
you want a 12V 4A transformer then this one should be

quite suitable, you use just one half of the secondary. Price

£3.50, Order Ref: 3.5P7.

15W 8” 8 Ohm Speaker and 3” Tweeter. Amstrad, made

for their high quality music centre, £4 per pair, Order

Ref: 4P57.

Insulation Tester with Multimter. Internally generates volt-

ages which enables you to read insulation directly in

megohms. The multimeter has four ranges, AC/DC volts, 3

ranges milliamps, 3 ranges resistance and 5 amp range.

These instruments are ex-British Telecom tut in very good

condition, tested and guaranteed OK, probably cost at

least £50, yours for only £7.50 with leads, carrying case £2

extra, Order Ref: 7.5P4.

We Have Some of the above testers but slightly faulty, not

working on all ranges, should be repairable, we supply

diagram, £3, Order Ref: 3P176.

Clock Module. 2” LCD display, requires 1.5V battery, goes

back to zero when switched off so ideal for timing opera-

tions, £2, Order Ref: 2P307.

Field Telephones. Ex-GPO, reconditioned, just join

together with almost any length twin wire, £15 each, Order

Ref: 15P62.

Heavy Duty Time Switch (Smiths). Will switch on up to

100A, ex-electricty board, reconditioned, £10, Order Ref:

10P 14.

Lead Lamp. Ideal for motorists, normal handgrip and

hainging hook, takes 60W bulb protected by glass cover.

£4. Order Ref: 4P31.

Ultrasonic Car or House Alarm. Operates from its own bat-

tery, nicely cased, is reasonably loud and can be coupled

to external horn, £10, Order Ref: 10P76.

Clock Module. 2” LCD display, requires 1-5V battery, goes

back to zero when switched off so ideal for timing opera-

tions, £2, Order Ref: 2P307.

Quartz Clock Mechanisms. Complete with 2 sets of hands,

—_ or period, made up ready to work, £3, Order Ref:
11

12V-6V Reducer. Plugs into car socket to work radio, etc.

£2, Order Ref: 2P318.

Prices include VAT. Send cheque/postal order
or ring and quote credit card number.
Add £3 post and packing.

Orders over £25 post free.

M & B ELECTRICAL
SUPPLIES LTD

Pilgrim Works (Dept. E.E.)
Stairbridge Lane, Bolney,

Sussex RH17 5PA

Telephone: 01444 881965
OE Xomr-baeleim@elalela(cmila-39)
oF: 1 (=) c- Cole Wa fol Ulalot-| arm a fer-lom
Hove, Sussex.

493

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computer

@ A powerful set of basic functions,
statements, and operators — over 230 in

set of basic instructions this complete.
@ Advanced statistics functions
enabling computations on up to 15
independent variables.

@ Recursive subprograms and user
defined functions.

@ A keyboard that can be easily
customised for your specific application.
@ HP-!L Interface pre-installed to

commands, Interface to HP-1L, HP-1B,

HEWLETT PACKARD HP71B

all — many larger computers don’t havea _

OTE SS a EI eT ETT

These are second users systems, ex NHS,
are fully tested and working but have no
programming (THAT IS UP TO YOU).

Bar-code Reader..................cccceeeeeees £12.95

A.C. Power Supply
(Works from batteries normally)

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Complete kit of HP71B, Bar-code Reader
and power supply..............::ccceseeee £39.50

Unit 41, InShops, Wellington Centre

lll

BARCODE =
As easy to use as a calculator ;
but as powerful as a READER
Smart wand

TRACP eS ey BPE pe ae

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+ A ° “« ,
s »

‘Unit 15, Craven Way feauaeags Est., Newosarket Suffolk. CB8 0AP

£11.30
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4

— Automatically Telephone: (01638) 662989 Facsimile: (01683) 660799
recognises and TOROIDAL TRANSFORMER MANUFACTURERS
decodes all major 220/240V ANY Two Secondaries
bar-code standards. Price Dimensions

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‘

Prices include VAT & Carriage
For further information and quantity discounts, contact Michael Dornan

200 Signal diodes 1N4148
75 Rectifier Diodes 1N4001

BC327 Transistors

@ An advanced internal file system for Keyboard Overlay.............ccccccseeees £1.00 Phone: 01638 662989 Fax: 01638 660799
storing programs and data — The HP71 (Limited quantities)

has continuous memory — when you (Unkown Program — Memory

turn the computer offit retains Modules (2 different types). iain £3.00

programs and data. (Limited quantities)

SMM red 1.€.0.8.........ccceeceeeeeeeeeeneeeees
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create a system that can print, plot, shee ese VAT — Rectifier Diodes 1N4007 Axial |.e.d.s (Diode package)
store, retrieve and display information. Delivery Next day £3.00) Rectifier Diodes 1N5401 Asstd. 7-segment displays
Control or read instruments or speak to (Currently selling in US for over £500!) bec Lael oe Lideneseieadseenaaet £1.00 tog il dependant resistors
other computers, 5000 bytes/sec. sstd. Zener Diodes sstd. IF transformers

Built in ROM includes 46 separate INTERCONNECTIONS LTD ts og St ee Asstd. coil formers

Asstd. RF chokes (inductors)

Asstd. connectors edge.,d.i.I., sil etc
Asstd. d.i.l. sockets up to 40-pin

RS232C, GPIO or series 80. Includes Aldershot, Hants, GU11 SDB

BC328 Transistors

| connection cables. Tel: (01252) 341900 Fax: (01293) 822786 BC337 Transistors Asstd. disc ceramic capacitors
. - BC478 Transistors Asstd. capacitors 1nF to 1pF
| Please rush me ‘Please debit credit card BC546 Transistors Asstd electrolytic capacitors
BC547 Transistors 4P3W MBB min. rotary switches
im HP71 B Powerful Calc/Computer @ £29.95 No. eee eer eeeeeeceeeeccssceveees Exp eee eeeeeeeenes BC548 Transistors Min. SP/CO slide switches..
| [_] Bar-code Reader (@ £12.95 ania BC549 Transistors 1” glass reed switches
| na eee eS eee BC550 Transistors 4N7 mini axial capacitors
O willed 4 2 eta PI OGS io cisstintsussicisisieinimvcuiataladectie BC557 Transistors 24-pin d.i.|. wire wrap i.c. Skts. ........
CJ Keyboard overlay @ £1.00 BC558 Transistors 12V motorised volume control 50k...£1.
M dul F311 | EE BC559 Transistors Grommets 6-3mm id, 9-5mm od
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[_]Complete kit of HP7IB, Bar-code Reader (vrrrrrcrtrrereererrseeeeeeeessseeeeeeessteneeeeetereeeees ; value, E24, range 1R to 10M
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Total payment £........... + £3 delivery =£........... TE sinicicdcisdimndnces oman ENG904 Transistors ye

288 Abbeydale Road. Sheffield $7 1FL
Phone (0114) 2552886 Fax (0114) 2500689

78M08 8V 500mA Pos Regulators...
79M08 8V 500mA Neg Regulators....£1.00
5MM red 1.€.0.8.............cccceeesseeee cece £1.00

We accept Mastercard, Visa, Cheques or money orders — please post the above form to us,
or Fax it, or Telephone with a verbal credit card order.

* Back annotation (linked to schematic), » . .
— * ower; memory and signal autorouter - £50

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AGES sc sa PSR Os DR 2
cial fad SOY TR SP oS,

ELECTRONIC PROJECTS - BOOK 1

Published by Everyday Electronics in association
with Magenta Electronics. /

Contains twenty of the best projects from previous
issues of EE each backed with a kit of components. The
projects are: Seashell Sea Synthesiser, EE Treasure
Hunter, Mini Strobe, Digital Capacitance Meter, Three
Channel Sound to Light, BBC 16K Sideways Ram,
Simple Short Wave Radio, Insulation Tester, Stepper

_ Motor Interface, Eprom Eraser, 200MHz Digital Fre-

quency Meter, Infra Red Alarm, EE Equaliser loniser, Bat
Detector, Acoustic Probe, Mains Tester and Fuse Finder,
Light Rider — (Lapel Badge, Disco Lights, Chaser Light),
Musical Doorbell, Function Generator, Tilt Alarm, 10W
Audio Amplifier, EE Buccaneer Induction Balance Metal
Detector, BBC Midi Interface, Variable Bench Power
Supply, Pet Scarer, Audio Signal Generator.

128 pages (A4 size) £2.45

ELECTRONICS TEACH-IN 88/89 —

INTRODUCING MICROPROCESSORS

Mike Tooley BA (published by Everyday
Electronics)

A complete course that can lead successful readers to
the award of a City and Guilds Certificate in Introductory
Microprocessors (726/303). The book contains every-
thing you need to know including full details on regist-
ering for assessment, etc. Starting with basic terminol-
ogy, integrated circuits, logic families and numbering
systems the text builds in stages, with revision and
assessments built in, up to programming, languages,
flow charts, etc. The course is ideal for the newcomer to

the subject.
Order code TI-88/89 £2.45

80 pages (A4 size)

Everyday with Practical Electronics Books

ELECTRONICS TEACH-IN No. 6

DESIGN YOUR OWN CIRCUITS
(Published by Everyday with Practical Electronics)
Mike Tooley BA f

This book is designed for the beginner and experienced
reader alike, and aims to dispel some of the mystique
associated with the design of electronic circuits. It
shows how even the relative newcomer to electronics
can, with the right approach, design and realise quite
complex circuits.

Fourteen individual p.c.b. modules are described
which, with various detailed modifications, should allow
anyone to design and construct a very wide range of
different projects. Nine ‘‘hands-on’’ complete DIY
projects have also been included so readers can follow
the thinking behind design, assembly, construction,
testing and evaluation, together with suggested ‘‘mods”
to meet individual needs. The practical projects have
each been designed to stand on their own as complete
items of equipment. P.C.B.s for all the modules and
projects are available by mail order.

The subjects covered in each chapter of the book
are: Introduction and Power Supplies: Small Signal
Amplifiers: Power Amplifiers: Oscillators: Logic Circuits;
Timers; Radio; Power Control; Optoelectronics.

The nine complete constructional projects are: Ver-
satile Bench Power Supply; Simple Intercom; Bench
Amplifier/Signal Tracer; Waveform Generator; Electronic
Die; Pulse Generator; Radio Receiver; Disco Lights Con-
troller; Optical Communications Link.

136 pages (A4 size) £3.45

TEACH-IN No. 7 plus FREE Software

ANALOGUE AND DIGITAL

ELECTRONIC COURSE

(Published by Everyday with Practical
Electronics)

Alan Winstanley and Keith Dye
B.Eng(Tech)AMIEE

The highly acclaimed Teach-/n series, which included
the construction and use of the Mini Lab and Micro
Lab test and development units, has been put together
in book form. Additionally EPT Educational Software —

. have developed a GCSE Electronics software program to

compliment the course and a FREE DISC covering the
first two parts of the course is included with the book.

An interesting and thorough tutorial series aimed
specifically at the novice or complete beginner in
electronics. The series is designed to support those
undertaking either GCSE Electronics or GCE Advanced
Levels, and starts with fundamental principles.

If you are taking electronics or technology at school
or college, this book is for you. If you just want to
learn the basics of electronics then this is for you.
If you are teaching electronics or technology you
must make sure you see it. Jeach-/n No. 7 will be
invaluable if you are considering a career in electronics
or even if you are already training in one. The Mini Lab
and software enable the construction and testing of both

‘demonstration and development circuits. These learning

aids bring electronics to life in an enjoyable and interest-
ing way: you will both see and hear the electron in
action! The Micro Lab microprocessor add-on system
will appeal to higher level students and those develop-
ing microprocessor projects.

152 pages (A4 size) £3.95

Computers and Computing

HOW TO CHOOSE A SMALL BUSINESS
COMPUTER SYSTEM
D. Weale
This book is for anyone intending to buy an IBM com-
patible computer system, whether it is their first system or
a replacement. There are sections on hardware, applica-
tion and systems programs and how to actually make your
choice as well as sections on the law, ergonomics and a
glossary of common terms.

The text contains many useful tips and some warnings
(which could save much effort and expense).

114 pages £4.95

MAKING MS-DOS WORK
FOR YOU (covers version 6.2)
N. Kantanis & P. R. M. Oliver
This book was written with the busy person in mind and,
as such, it has an underlying structure based on ‘‘what you
need to know first, appears first’’. Nonetheless, the book
has also been designed to be circular, which means that
you don't have to start at the beginning and go to the end.
The book explains: How to write customised batch
files which allow you to display what you want on your
screen, and in the form and order you want it, instead
of being forced to use the DOS prompt on a blank
screen. How to design and set up a fast interactive
and professional fooking menu system, so that you or
anyone else can run utility applications or commercial
software packages easily. How the ANSI.SYS display
and keyboard commands can be used to position the
cursor on any part of the screen, change the inten-
sity of the displayed characters or change their colour.
How the Edit screen editor or the Edlin line editor can
be used to enter ESCape (ANSI.SYS) commands into
simple ASCII files to allow control of both your screen
display and your printer. How to control the opera-
tion of the two main types of printers in use today,
Epson compatible dot matrix and HP compatible laser
printers. How to use several routines, such as moving
and finding files, protecting files from accidental erasure,

a simplified backup process, a screen saver, and a disc
cataloguing system.

The Debug program and how it can be used to create,
see and change the contents of any file, including those
of programs written in assembler code. This includes
how to find your way around the names and tasks of the
CPU registers and the meeting of some simple assembler

mnemonics.
(olmel-lanetele loa 1 sans) £4.95

182 pages

MULTIMEDIA ON THE PC

lan R. Sinclair

In this book, you'll find out what a CD ROM is, how it
works, and why it is such a perfect add-on for a PC,
allowing you to buy programmes, text, graphics and
sound on a CD. It also describes the installation of a CD
ROM drive and a sound card, pointing out the common
problems that arise, and then shows how to use them to
create a complete multimedia presentation that contains
text, photos, a soundtrack with your own voice re-
corded as a commentary, even animation and edited

video footage.
£11.95

184 pages

A CONCISE INTRODUCTION TO MS-DOS

N. Kantaris

This guide is written with the non-expert, busy person

-in mind and, as such, it has an underlying structure

based on ‘what you need to know first, appears first’’.
Nevertheless, the guide is also designed to be circular,
which means that you don't have to start at the begin-
ning and go to the end. The more experienced user can
start from any section.

The guide covers versions 3.0, 3.1 and 3.2 of both
PC-DOS and MS-DOS as implemented by IBM and
other manufacturers of ‘‘compatible’’ microcomputers.

64 pages Order code BP232 £2.95

Everyday with Practical Electronics, June 1995

UNDERSTANDING PC SPECIFICATIONS

R.A. Penfold

If you require a microcomputer for business applications,
or a high quality home computer, an IBM PC or com-
patible is often the obvious choice. They are competi-
tively priced, and are backed up by an enormous range
of applications programs, hardware add-ons, etc. The
main difficulty for the uninitiated is deciding on the
specification that will best suit his or her needs. PCs
range from simple systems of limited capabilities up to
complex systems that can happily run applications that
would have been considered beyond the abilities of
a microcomputer not so long ago. It would be very
easy to choose a PC system that is inadequate to run
your applications efficiently, or one which goes beyond
your needs and consequently represents poor value for
money.

This book explains PC specifications in detail, and the
subjects covered include the following: Differences
between types of PC (XT, AT, 80386, etc); Maths
co-processors; Input devices (keyboards, mice, and
digitisers); Memory, including both expanded (EMS)
and extended RAM; RAM disks and disk caches; Floppy
disk drive formats and compatibility; Hard disk drives
(including interleave factors and access times); Display
adaptors, including all standard PC types (CGA, Her-
cules, Super VGA, etc); Contains everything you need to
know if you can’t tell your EMS from your EGA!

104 pages - @ Order code BP282 £4.95

AN INTRODUCTION TO 6800 ASSEMBLY
LANGUAGE

R.A. & J. W. Penfold

Obtain a vast increase in running speed by writing pro-
grams for 6800 based micros such as the Commodore,
Amiga, Atari ST range or Apple Macintosh range etc., in
assembly language. It is not as difficult as one might
think and this book covers the fundamentals.

112 pages £2.95

495

Testing and

Test Gear .

cov Dick be RAR ak a uy Se
‘

Audio and Music

HOW TO USE OSCILLOSCOPES AND OTHER TEST
EQUIPMENT

R. A. Penfold |

This book explains the basic function of an oscilloscope,
gives a detailed explanation of all the standard controls,
and provides advice on buying. A separate chapter deals
with using an oscilloscope for fault finding on linear and
logic circuits, plenty of example waveforms help to il-
lustrate the control functions and the effects of various
fault conditions. The function and use of various other
pieces of test equipment are also covered, including sig-
nal generators, logic probes, logic pulsers, and crystal

calibrators.
Order code BP267 £3.50

104 pages

PRACTICAL MIDI HANDBOOK

R. A. Penfold

The Musical Instrument Digital Interface (MIDI) is sur-
rounded by a great deal of misunderstanding, and many of
the user manuals that accompany MIDI equipment are
quite incomprehensible to the reader.

The Practical MIDI Handbook is aimed primarily at
musicians, enthusiasts and technicians who want to
exploit the vast capabilities of MIDI, but who have no
previous knowledge of electronics or computing. The
majority of the book is devoted to an explanation of what
MIDI can do and how to exploit it to the full, with practical
advice on connecting up a MIDI system and getting it to
work, as well as deciphering the technical information in
those manuals.

128 pages £6.95

(olazel-taerelelon a On key

Theory and Reference

ELECTRONIC HOBBYISTS HANDBOOK

R.A. Penfold

Provides an inexpensive single source of easily located
information that the amateur electronics enthusiast is likely
to need for the day-to-day pursuance of this fascinat-
ing hobby. Covers common component colour codes.
Detai's the characteristics and pinouts of many popular
semiconductor devices, including various types of logic
i.c.s, Operational amplifiers, transistors, FETs, unijunc-
tions, diodes, rectifiers, SCRs, diacs, triacs, regulators and
SMDs, etc. Illustrates many useful types of circuits, such
as timers and oscillators, audio amplifiers and filters, as
well as including a separate section on power supplies.
Also contains a multitude of other useful data.

88 pages £4.95
FROM ATOMS TO AMPERES
F. A. Wilson

Explains in crystal clear terms the absolute fundamentals
behind electricity and electronics. Really helps you to dis-
cover and understand the subject, perhaps for the first time
ever.

Have you ever: Wondered about the true link between
electricity and magnetism? Felt you could never under-
stand the work of Einstein, Newton, Boltzmann, Planck
and other early scientists? Just accepted that an electron is
like a little black ball? Got mixed up with e.m.f. and p.d.?
Thought the idea of holes in semiconductors is a bit much?

Then help is at hand with this inexpensive book, in as
simple a way as possible and without too much, complex
mathematics and formulae.

244 pages Temporarily out of print
ELECTRONICS - A “MADE SIMPLE” BOOK
G. H. Olsen

Electronic devices surround us on all sides and their num-
bers are increasing without mercy. Ours is the problem
therefore in keeping up with this relentless expansion.
Unfortunately we cannot know it all and most of us do not
wish to afford the cost of large reference books which
explain many concepts in fair detail. Here is an answer, an
inexpensive reference guide which explains briefly (but
we hope, well) many of the underlying electronics features
of practical devices, most of which, to a certain extent,
control our lives.

This book is in effect more than just a dictionary of prac-
tical electronics terms, it goes a stage further in also getting

down to fundamentals. Accordingly the number of terms

may be limited but the explanations of the many which are
included are designed to leave the reader more competent
and satisfied — and this is without the use of complicated

‘mathematics which often on first reading can be confus-

ing.

For those who also wish to get right down to the root of
the matter, there is a second volume entitled A Reference
Guide to Basic Electronics Terms (BP286), each of the
books referring to its companion as necessary.

A reference guide for practically everybody concerned
with electronics.

£5.95

432 pages Order code BP287

ELECTRONIC MODULES AND SYSTEMS FOR
BEGINNERS

Owen Bishop

This book describes over 60 modular electronic circuits,
how they work, how to build them, and how to use them.
The modules may be wired together to make hundreds of
different electronic systems, both analogue and digital. To
show the reader how to begin building systems from mod-
ules, a selection of over 25 electronic systems are des-
cribed in detail, covering such widely differing applica-
tions as timing, home security, measurement, audio (in-
cusing a simple radio receiver), games and remote con-
trol.

200 pages Temporarily out of print

Project Building

HOW TO GET YOUR ELECTRONIC PROJECTS
WORKING

R.A. Penfold

We have all built projects only to find that they did not
work correctly, or at all, when first switched on. The aim
of this book is to help the reader overcome just these
problems by indicating how and where to start looking for
many of the common faults that can occur when building

up projects. '
Order code BP110 £2.95

96 pages |

HOW TO DESIGN AND MAKE YOUR OWN P.C.B.S
R.A. Penfold

Deals with the simple methods of copying printed cir-
cuit board designs from magazines and books and covers
all aspects of simple p.c.b. construction including photo-
graphic methods and designing your own p.c.b.s.

80 pages Order code BP121 £2.50

A BEGINNER’S GUIDE TO MODERN ELECTRONIC
COMPONENTS

R. A. Penfold

The purpose of this book is to provide practical information
to help the reader sort out the bewildering array of com-
ponents currently on offer. An advanced knowledge of the
theory of electronics is not needed, and this book is not
intended to be a course in electronic theory. The main aim

496

is to explain the differences between components of the
same basic type (e.g. carbon, carbon film, metal film, and
wire-wound resistors) so that the right component for a
given application can be selected. A wide range of com-
ponents are included, with the emphasis firmly on those
components that are used a great deal in projects for the
home constructor.

166 pages £3.95

(Ol ael-)mexele (sm si oasis)

ELECTRONICS SIMPLIFIED - CRYSTAL SET
CONSTRUCTION
ee pa C.G.1.A., C.Eng., F.1.E.E., F.1.E.R.E.,

Especially written for those who wish to participate in
the intricacies of electronics more through practical con-
struction than by theoretical study. It is designed for all
ages upwards from the day one can read intelligently and

handle simple tools.
Order code BP92 £1.75

80 pages

DESIGN YOUR OWN CIRCUITS

See the first page of books - ELECTRONICS TEACH-IN
No. 6 — for full details.

ELECTRONICS PROJECT BOOK

Published by Everyday Electronics in association
with Magenta Electronics.

See the first page of books for full details.

AN INTRODUCTION TO LOUDSPEAKERS AND

ENCLOSURE DESIGN
V. Capel
This book explores the various features, good points and
snags of speaker designs. It examines the whys and
wherefores so that the reader can understand the
principles involved and so make an informed choice of
design, or even design loudspeaker enclosures for him or
herself. Crossover units are also explained, the various
types, how they work, the distortions they produce and
how to avoid them. Finally there is a step-by-step
description of the construction of the Kapellmeister
loudspeaker enclosure.

£2.95

148 pages Order code BP256

ACOUSTIC FEEDBACK - HOW TO AVOID IT

V. Capel

Feedback is the bane of all public address systems.
While feedback cannot be completely eliminated, many
things can be done to reduce it to a level at which it is no
longer a problem.

Much of the trouble is often the hall itself, not
the equipment, but there is a simple and practical
way of greatly improving acoustics. Some microphones
are prone to feedback while others are not. Certain
loudspeaker systems are much better than others, and
the way the units are positioned can produce or reduce
feedback. All these matters are fully explored as well as
electronic aids such as equalizers, frequency-shifters
and notch filters.

The special requirements of live group concerts are
considered, and also the related problem of instability
that is sometimes encountered with large set-ups. We
even take a look at some unsuccessful attempts to cure
feedback so as to save readers wasted time and effort
duplicating them.

Also included is the circuit and layout of an inexpen-
sive but highly successful twin-notch filter, and how to

operate it.
(Olzel-larerelel=m ston ne) £3.95

92 pages

PREAMPLIFIER AND FILTER CIRCUITS

R.A. Penfold

This book provides circuits and background informa-
tion for a range of preamplifiers, p!us tone controls,
filters, mixers, etc. The use of modern low noise opera-
tional amplifiers and a specialist high performance audio
preamplifier i.c. results in circuits that have excellent
performance, but which are still quite simple. All the
Circuits featured can be built at quite low cost (just a few
pounds in most cases).

The preamplifier circuits featured include: Microphone
preamplifiers (low impendance, high impedance, and
crystal). Magnetic cartridge pick-up preamplifiers
with R.I.A.A. equalisation. Crystal/ceramic pick-up
preamplifier. Guitar pick-up preamplifier. Tape head
preamplifier (for use with compact cassette systems).

Other circuits include: Audio limiter to prevent over-
loading of power amplifiers. Passive tone controls. Ac-
tive tone controls. PA filters (highpass and lowpass).
Scratch and rumble filters. Loudness filter. Audio mixers.
Volume and balance controls.

£3.95

92 pages Order code BP309

COMPUTERS AND MUSIC - AN INTRODUCTION
R.A. Penfold

Computers are playing an increasingly important part in
the world of music, and the days when computerised
music was strictly for the fanatical few are long gone. |

If you are more used to the black and white keys of a
synth keyboard than the QWERTY keyboard of a com-
puter, you may be understandably confused by the jar-
gon and terminology bandied about by computer buffs.
But fear not, setting up and using a computer-based
acy making system is not as difficult as you might
think.

This book will help you learn the basics of computing,
running applications programs, wiring up a MIDI sys-
tem and using the system to good effect, in fact just
about everything you need to know about hardware and
the programs, with no previous knowledge of computing
needed or assumed. This book will help you to choose the
right components for a system to suit your personal needs,
and equip you to exploit that system fully.

174 pages (Oydelclmerolelen a OnkOy, £8.95

ELECTRONIC PROJECTS FOR GUITAR

R.A. Penfold

This book contains a collection of guitar effects and some
general purpose effects units, many of which are suitable
for beginners to project building. An introductory chapter
gives guidance on construction.

Each project has an introduction, an explanation of how
it works, a circuit diagram, complete instructions on strip-
board layout and assembly, as well as notes on setting
up and using the units. Contents include: Guitar tuner;
Guitar preamplifier; Guitar headphone amplifier; Soft dis-
tortion unit; Compressor; Envelope waa waa; Phaser; Dual
tracking effects unit; Noise gate/expander; Treble booster;
Dynamic treble booster; Envelope modifier; Tremelo unit;

box. ;
Order code PC110 £8.95

110 pages

HIGH POWER AUDIO AMPLIFIER CONSTRUCTION
R. A. Penfold

Practical constructional details of how to build a num-
ber of audio power amplifiers ranging from about 50 to
300/400 watts r.m.s. Includes MOSFET and bipolar tran-

sistor designs.
Order code BP277 £3.95

96 pages

Everyday with Practical Electronics, June 1995

PRACTICAL ELECTRONIC FILTERS

Owen Bishop

This book deals with the subject in a non-mathematical
way. It reviews the main types of filter, explaining in simple
terms how each type works and how it is used.

The book also presents a dozen filter-based projects with
applications in and around the home or in the constructor’s
workshop. These include a number of audio projects such
as a rythm sequencer and a multi-voiced electronic organ.

Concluding the book is a practical step-by-step guide to
designing simple filters for a wide range of purposes, with
Circuit diagrams and worked examples.

88 pages Order code BP299 £4.95

ELECTRONIC ALARM CIRCUITS MANUAL

R. M. Marston .

One hundred and forty useful alarm circuits, of a variety of

types, are shown in this volume. The operating principle of

each one is explained in concise but comprehensive terms,

and brief construction notes are given where necessary.
Aimed at the practical design engineer, technician and

experimenter, as well as the electronics student and

amateur.
Order code NE11 £13.95

124 pages

DIGITAL GATES AND FLIP-FLOPS

lan R. Sinclair

This book, intended for enthusiasts, students and tech-

nicians, seeks to establish a firm foundation in digital

electronics by treating the topics of gates and flip-flops
thoroughly and from the beginning.

Topics such as Boolean algebra and Karnaugh mapping
are explained, demonstrated and used extensively, and
more attention is paid to the subject of synchronous
counters than to the simple but less important ripple
counters.

No background other than a basic- knowledge of elec-
tronics is assumed, and the more theoretical topics are

explained from the beginning, as also are many working -

practices. The book concludes with an explanation of
microprocessor techniques as applied to digital logic.

200 pages £8.95
ELECTRONIC CIRCUITS FOR THE COMPUTER
CONTROL OF ROBOTS

Robert Penfold

Robots and robotics offer one of the most interesting areas
for the electronics hobbyist to experiment in. Today the
mechanical side of robots is not too difficult, as there are

PROJECTS FOR RADIO AMATEURS AND S.W.L.S.

R. A. Penfold

This book describes a number of electronic circuits, most of
which are quite simple, which can be used to enhance the
performance of most short wave radio systems.

The circuits covered include:— An aerial tuning unit; A
simple active aerial; An add-on b.f.o. for portable sets;
Awavetrap to combat signals on spurious responses; An
audio notch filter; A parametric equaliser; C.W. and S.S.B.
audio filters; Simple noise limiters; A speech processor; A
volume expander.

Other useful circuits include a crystal oscillator, and
RTTY/C.W. tone decoder, and a RTTY serial to parallel
converter. A full range of interesting and useful circuits for

short wave enthusiasts.
Order code BP304 £3.95

92 pages

AN INTRODUCTION TO AMATEUR RADIO

1. D. Poole

Amateur radio is a unique and fascinating hobby which has

attracted thousands of people since it began at the turn of the
century. \

’ This book gives the newcomer a comprehensive and easy

~ to understand guide through the subject so that the reader

can gain the most from the hobby. It then remains an essen-

tial reference volume to be used time and again. Topics

covered include the basic aspects of the hobby, such as

operating procedures, jargon and setting up a station. Tech-

nical topics covered include propagation, receivers, transmit-

ters and aerials etc.

150 pages «£3.50
AERIAL PROJECTS
R. A. Penfold

The subject of aerials is vast but in this book the author has
considered practical aerial designs, including active, loop
and ferrite aerials which give good performances and are
relatively simple and inexpensive to build. The complex
theory and mathematics of aerial design have been avoided.
Also included are constructional details of a number of
aerial accessories including a pre-selector, attenuator, filters
and a tuning unit.
96 pages £2.50

SIMPLE SHORT WAVE RECEIVER CONSTRUCTION
R. A. Penfold
Short wave radio is a fascinating hobby, but one that seems
to be regarded by many as an expensive pastime these days.
In fact it is possible to pursue this hobby for a minimal
monetary outlay if you are prepared to undertake a bit of
d.i.y., and the receivers described in this book can all be built
at low cost. All the sets are easy to construct, full wiring
diagrams etc. are provided, and they are suitable for complete
beginners. The receivers only require simple aerials, and do
not need any complex alignment or other difficult setting up
procedures.

The topics covered in this book include: The broadcast
bands and their characteristics; The amateur bands and their

(Orel) merele (sm ot a hele)

Se TT RR EPI

Circuits and Design —

robotics kit and a wide range of mechanical components
available. The microcontroller is not too much of a problem
either, since the software need not be terribly complex and
many inexpensive home computers are well suited to the
task.

The main stumbling block for most would-be robot
builders is the electronics to interface the computer to the

motors, and the sensors which provide feedback from the -

robot to the computer. The purpose of this book is to
explain and provide some relatively simple electronic
circuits which bridge this gap.

92 pages Order code BP1/9] £2.95

ELECTRONIC POWER SUPPLY HANDBOOK
lan R. Sinclair
This book covers the often neglected topic of electronic
power supplies. All types of supplies that are used for elec-
tronics purposes are covered in detail, starting with cells
and batteries and extending by way of rectified supplies
and linear stabilisers to modern switch-mode systems, i.c.
switch-mode regulators, DC-DC converters and inverters.
The devices, their operating principles and typical cir-
cuits are all dealt with in detail. The action of rectifiers
and the reservoir capacitor is emphasised, and the subject
of stabilisation is covered. The book includes some useful
formulae for assessing the likely hum level of a conven-
tional rectifier reservoir supply.

136 pages Order code PC108 £7.95
50 SIMPLE LED CIRCUITS
R. N. Soar .

Contains 50 interesting and useful circuits and applica-
tions, covering many different branches of electronics,
using one of the most inexpensive and freely available
components — the light-emitting diode (LED). Also in-
cludes circuits for the 707 common anode display.

64 pages Order code BP42 £1.95
BOOK 2 50 more |l.e.d. circuits.

50 pages £1.95
CIRCUIT SOURCE BOOK 1

A. Penfold

Written to help you create and experiment with your own
electronic designs by combining and using the various
standard “building block” circuits provided. Where ap-
plicable, advice on how to alter the circuit parameters is
given.

The circuits covered in this book are mainly concerned
with analogue signal processing and include: Audio

Radio, TV. Satellite

characteristics; The propagation of radio signals; Simple
aerials; Making an earth connection; Short wave crystal set;
Simple t.r.f. receivers; Single sideband reception; Direct
conversion receiver.

Contains everything you need to know in order to get
started in this absorbing hobby.

88 pages Order code BP275 £3.95

AN INTRODUCTION TO AMATEUR
COMMUNICATIONS SATELLITES

A. Pickford

Communications and broadcast satellites are normally inac-
cessible to individuals unless they are actively involved in
their technicalities by working for organisations such as
British Telecom, the various space agencies or military
bodies. Even those who possess a satellite television receiver
system do not participate in the technical aspects of these
highly technological systems.

There are a large number of amateur communicatians
satellites in orbit around the world, traversing the globe
continuously and they can be tracked and their signals
received with relatively inexpensive equipment. This equip-
ment can be connected to a home computer such as the BBC
ee or IBM compatible PCs, for the decoding of received
signals.

Everyday with Practical Electronics, June 1995

amplifiers (op.amp and bipolar transistors); audio power
amplifiers; d.c. amplifiers; highpass, lowpass, bandpass
and notch filters; tone controls; voltage controlled
amplifiers and filters; triggers and voltage comparators;
gates and electronic switching; bargraphs; mixers; phase
shifters, current mirrors, hold circuits, etc.

Over 150 circuits are provided, which it is hoped will be
useful to all those involved in circuit design and applica-
tion, be they professionals, students or hobbyists.

182 pages £4.95
CIRCUIT SOURCE BOOK 2
R.A. Penfold

This book will help you to create and experiment with
your own electronic designs by combining and using
the various standard ‘“‘building blocks” circuits provided.
Where applicable, advice on how to alter the circuit
parameters is provided.

The circuits covered are mainly concerned with signal

_ generation, power supplies, and digital electronics.

The topics covered in this book include: 555 oscillators;
sinewave oscillators; function generators; CMOS oscil-

,lators; voltage controlled oscillators; radio frequency oscil-

lators; 555 monostables; CMOS monostables; TTL monos-
tables; precision long timers; power supply and regulator
Circuits; negative supply generators and voltage boosters;
digital dividers; decoders, etc; counters and display drivers;
D/A and A/D converters; opto-isolators, flip/flops, noise
generators, tone decoders, etc. ;

Over 170 circuits are provided, which it is hoped will be
useful to all those involved in circuit design and applica-
tion, be they professionals, students or hobbyists.

192 pages Order code BP322 £4.95
HOW TO USE OP.AMPS
E.A. Parr

This book has been written as a designer's guide covering
many operational amplifiers, serving both as a source book
of circuits and a reference book for design calculations.
The approach has been made as non-mathematical as pos-

sible.
160 pages £2.95

A BEGINNER’S GUIDE TO TTL DIGITAL ICs
R.A. Penfold

‘This book first covers the basics of simple logic circuits

in general, and then progresses to specific TTL logic in-
tegrated circuits. The devices covered include gates, os-
cillators, timers, flip/flops, dividers, and decoder circuits.
Some practical circuits are used to illustrate the use of TTL
devices in the ‘real world”

142 pages £4.95

This book describes several currently available systems,
their connection to an appropriate computer and how they

can be operated with suitable software.

102 pages (Olmelelmeorelelen =) oss10) £3.95

INTERNATIONAL RADIO STATIONS GUIDE

P. Shore

Provides the casual listener, amateur radio DXer and the
professional radio monitor with an essential reference
work designed to guide him or her around the ever
more complex radio bands. This new edition has been
completely revised and rewritten and incorporates much
more information which is divided into the following
sections:

Listening to Short Wave Radio; Choosing a Short
Wave Radio Receiver; How to Use the IRSG; Abbrevia-
tions; County Codes; Worldwide Short Wave Radio Sta-
tions; European, Middle Eastern and African Long Wave
Radio Stations; European, Near and Middle Eastern and
African Medium Wave Radio Stations; Canadian Medium
Wave Radio Stations; USA Medium Wave Radio Stations;
Broadcasts in English; Programmes for DXers and Short
Wave Listeners; UK FM Radio Stations; Time Differences
From GMT; Wavelength/Frequency Conversion.

226 pages £5.95

497

: CRICKLEWOOD £ Ie ctronics
Very Interesting CATALOGUE

ASTRONOMICAL RANGE AT
DOWN TO EARTH PRICES

TRANSISTORS+ICs+SEMICONDUCTORS
RESISTORS+CAPACITORS+INDUCTORS
SURVEILLANCE+SECRECY+SECURITY
PLUGS+SOCKETS+LEADS+CONNECTS

TV & VIDEO SPARES (inc Video Heads)
HIFI+DISCO+HIFI GADGETS+SPEAKERS
AUDIOPHILE COMPONENTS (inc Capacitors)
IN CAR AUDIO+SPEAKERS (inc Bass tubes)
COMPUTER ACCESSORIES+BOARDS

¢ TOOLS+TEST EQUIPMENT+BENCHWARE

& much much much more (over 10,000 lines).

SEND TODAY FOR THE VERY INTERESTING CATALOGUE
Pay by PO, Cheque, Credit Card or tape Coins to Paper __
Please send me ......copies of the 1995 Cricklewood Catalogue.
I enclose £2.50 per copy (UK & Europe). £5.00 overseas

eoe@l.efmUCOlmUmCOUCOUCOC COCO

Cricklewood Electronics Ltd, 40- 42 Cricklewood Broadway
London NW2 SET Tel 0181 450 0995 Fax 0181 208 1441

PCB Designer

For Windows 3. 1

PCB Desit

File

Looking for the price?
It's just £49.00 all inclusive!

..no VAT...no postage...

..no additional charges for
overseas orders. :
Dealers and distributors
wanted.

components.

unrestricted.

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Internet

A working demo is available via anonymous SF TP from
ftp.demon.co.uk as /pub/i ibmpc/windows/pcbdemo/pcbdemo. Zip

10 BEGINNERS PROJECTS £19.95

Produce Single or Double sided PCBs.

Print out to amy Windows supported printer.
Toolbar for rapid access to commonly used

Helpful prompts on screen as you work.
Pad, track & IC sizes fully customisable.
No charges for technical support.

Snap-to grid sizes 0.1", 0.05" 0.025" and

SMT pads and other pad shapes.
Prints at the resolution of your printer - much
igher than the screen shot shown here.

HIGH QUALITY LOW COST
C.C.T.V. CAMERA

LOW LIGHT LEVEL 0.03 LUX @ F1.4
AUTO ELECTRONIC SHUTTER.
COMPOSITE VIDEO OUT VIA
BNC PLUG.

SMALL DISCRETE SIZE.

CAN BE USED WITH PC DIGITISER.

This super quality CCD camera
can be connected into your existing

TV or video using the AV channel

and can be used for discrete

surveillance or observing your property externally using a suitable weatherproof
housing. Can accommodate lighting levels ranging from daylight to street
lighting using its built in electronic shutter. Excellent when using with an infra
red source. Built in wide angle fixed focus lens the camera has a resolution of 380
TVL. Can be housed inside an empty floodlight case, (extra).

Special offer price of only: £79.95 Plus VAT (P&P £2.50)
For full range of CCTV products send SAE to:

Direct CCTV Ltd., Dept. PE27., Unit 6, Carrick Court, Forrest Grove
Business Park, Middlesbrough, TS2 10E.

TIMER KIT. Controls 4 outputs at preset times over a 7 day cycle.
LED display. Easily programmed via keyboard. £65
ELECTRONIC LOCK KIT. Over 38,000 possible combinations.
Alarm sounds after 3-9 failed guesses and locks out keyboard for
preset time. £25.50
SUPER SENSITIVE FM MICROBUG. Runs off a 9V battery, fits
in a match box, listen in on any FM radio. £10.25
STROBE KIT. Can be triggered by external voltage e.g. loudspeaker
or as a Slave flash for photographic purposes. £21.85

Plus many many more. Including all TK Kits.
For full details send your SAE now.

COMPONENTS

We have a full range of electrical components at competitive prices.

Send an SAE for price lists. .

149 The Vale, Acton W3 7HR
KEL ECTRONICS

Tel: 0181 932 0144
Fax: 0181 932 0145

Runs on any PC running Windows 3.1 in standard or
enhanced mode with 2MB RAM

Will work with any Windows supported printer and monitor

- [c:\pcb\samplel.pcb]
Eat aoe lest eh Window eee

aad

set

e-mail enquiries can be addressed to orders@niche.demon.co.uk Be"

Niche Software (UK) et

22 Tavistock Drive, Belmont, Hereford, HR2 7XN

498

Phone (01432) 355 414

Everyday with Practical Electronics, June 1995

Printed circuit boards for certain EPE constructional projects are available from the
PCB Service, see list. These are fabricated in glass fibre, and are fully drilled and
roller tinned. All prices include VAT and postage and packing. Add £1 per board
for airmail outside of Europe. Remitances should be sent to The PCB Serv-
ice, Everyday with Practical Electronics, Allen House, East Borough,
Wimborne, Dorset BH21 1PF. Cheques should be crossed and made payable to
Everyday with Practical Electronics (Payment in £ sterling only).
NOTE: While 95% of our boards are now held in stock and are dispatched
within seven days of receipt of order, please allow a maximum of 28 days
for delivery — overseas readers allow extra if ordered by surface mail.
Back numbers or photostats of articles are available if required — see the
Back Issues page for details.
Please check price and availability in the latest issue.

Boards can only be supplied on a payment with order basis.

PROJECT TITLE Order Code

Bike Odometer (pair of boards) mil
Amstrad PCW A to D Converter (double-sided
Experimental Electronic Pipe a

L.E.D. Sandglass
Main and Display boards
Kettle Alert
Linear Power Supply (double-sided)
Multi- Purpose Audio System
Six Channel Stereo Mixer

Multi- Purpose Audio System
Microphone Pre-Amp module
RIAA Pre-Amp module

20 Metre Receiver

Multi-Purpose Audio System
Tone Control and 1W Stereo Amplifier
Tone Control
1W Stereo Amplifier

Three-Way Christmas Tree Lights Flasher

Auto Alarm

250W/600W Battery to Mains Inverter

Multi-Purpose Audio System
10W + 10W Stereo Power Amplifier
Amplifier
Power Supply
Pond Heater Thermostat
Timer/NiCad Capacity Checker

Multi- Purpose Audio System )
Balanced Microphone Preamplifier

Balanced Microphone Power Supply
Whistle Controlled Light Switch
Battery to Mains Inverter — U.P.S. charger board

Three Phase Generator

Visual Doorbell

CCD TV Camera — Control Board
(double-sided, plated-through-hole)

Telephone Ring Detector
CCD TV Camera
Combined Video, Test & Ext Plug Boards 866a/e
Frame Grab Control — 867
(double-sided plated-through-hole) oe
EPE Sound DAC PC Sound Board 868
MOSFET Variable Bench Power Supply | 869

L.E.D. Matrix Message Display Unit
Display Board
CPU Board
Stereo Noise Gate
Simple TENS Unit
Capacitance/Inductance Meter

Advanced TENS Unit
Digital Water Meter — Scaler 3
Counter/Display
L.E.D. Matrix Message Display Unit
Keypad
PC Interface
Microprocessor Smartswitch
Microcontroller P.I. Treasure Hunter

Print Timer

Watering Wizard
Simple NiCad Charger
Voxbox

Stereo HiFi Controller — 1 Power Supply

Stereo HiFi Controller — 2
Main Board
Expansion/Display Boards (pair)
Dancing Fountains — 1
Pre.amp
Pump Controller
Filter
6802 Microprocessor Development Board

Everyday with Practical Electronics, June 1995

Dancing Fountains - 2 oa
PC-Compatible Interface (double-side

Automatic Greenhouse Watering System
Seismograph — 1 Sensor/Filter

Clock/Mixer
3-Channel Lamp Controller

Seismograph — 2 Boeaecal
PC-Compatible Interface (double-side
Visual/Audio Guitar Tuner :

Digilogue Clock —

Hobby Power Supply

Audio Auxiplexer
Control Board
Receiver

Power Controller

1000V/500V Insulation Tester

Active Guitar Tone Control

TV Off-er = (pair) 908/909

Video Modules—1 Simple Fader 910
Improved Fader 911
Video Enhancer 912

Rodent Repeller

EPE Fruit Machine

Video Modules -2 Horizontal Wiper
Vertical Wiper
4-Channel Audio Mixer

Spacewriter Wand

Universal Digital Code Lock

Video Modules — | JAN'95 |
3 Dynamic Noise Limiter

System Mains Power Supply
Magnetic Field Detector

Model Railway Track Cleaner

Moving Display Metronome

The Ultimate Screen Saver
Foot-Operated Drill Controller
Model Railway Signals

12V 35W PA Amplifier

Multi- Purpose Thermostat
Multi- Project PCB
Sound-Activated Switch
Audio Amplifier
Light Beam Communicator (2 boards required)
Multi- Project PCB
Light-Activated Switch
Switch On/Off Timer
Continuity Tester
Auto Battery Charger
National Lottery Predictor
R.F. Signal Generator
R.F./Mod.
Coil & Power Supply (pair)
MIDI Pedal
Club Vote Totaliser
PIC-DATS Development System
(double-sided p.t.h.)
EPE HiFi Valve Amplifier —
Phase splitter
PIC-DATS 4 -channel Light Chaser

EPE PRINTED CIRCUIT °
BOARD SERVICE |

Order Code _ Project Quantity Price

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499

REPORTING

AMAT IEUIR VAD

Tony Smith G4FAL__

HOBBY OR POLITICS?

In 1992, an amateur station with the
callsign 1B1NCC came on the air from
the Turkish Republic of Northern Cyprus
(TRNC) and worked several thousand
other amateur stations worldwide. En-
thusiasts in the TRNC had been promot-
ing amateur radio and some UK-licensed
amateurs. donated transmitting equip-
ment to help get the station established.

1B1NCC was subject to extensive and
deliberate interference from other sta-
tions, mostly in Cyprus and Greece, and
the Ministry of Communications of the
Republic of Cyprus issued a statement
asking that “under no_ circumstances
should contact be made with this station”.

Since that time, 1B1NCC has become
the club station of the TRNC Amateur
Radio Society and four more stations,
with suffixes AA, AB, AC and AD (Class
A) and one in Class B, 1B2AA, have
come on the air.

The situation described arises from the
division of Cyprus, following the Turkish
invasion of 1974, which has been the
subject of several United Nations resolu-
tions calling for a peaceful solution to the
problem and the re-creation of a united
country.

Northern Cyprus has been unable to
join the United Nations or its agencies,
including the International Telecom-
munications Union (ITU), and the only
country that recognises it is Turkey.
Because it is not recognised by the ITU
there is no legal callsign series for TRNC
to use so it has taken the 1B prefix from
the non-allocated list of ITU callsigns
beginning with 1 or 0.

Although their stations have no in-
ternational status, the TRNC ARS has
persuaded its own government to amend
its Radio & Telegraphy Act to cover
amateur radio operation. The regulations
are based on CEPT licensing require-
ments and IARU band plans, and
licences are issued to any TRNC national
who passes an amateur radio examina-
tion and a Morse test. Temporary licences
are also issued to foreign nationals
equivalent to their home licences.

The Cyprus Amateur Radio Society
protested to the Executive Committee of
the International Amateur Radio Union,
Region 1, about the operation of amateur
radio stations in Northern Cyprus. The EC
expressed the opinion that the ITU
regulations should be adhered to and
that IARU Societies should inform their
members that amateur radio stations
should not contact stations with prefixes
not issued by the ITU.

NO DXCC STATUS

In the USA, the DX Advisory Com-
mittee of the American Radio Relay
League (ARRL) rejected a proposal that
the TRNC be granted separate country
status for DXCC purposes. Such status, if

500

approved, would have enabled contacts
with stations in Northern Cyprus to count
for scoring in the prestigious DXCC
Award programme, and in most contests,
irrespective of the furore about them.

The TRNC ARS says that no stations
have refused to work them because of
the IARU recommendation, and that they
take particular care to keep all of their
contacts strictly non-political and relative
to amateur matters.

The fact remains, however, that at
present amateur stations in Northern
Cyprus do not conform with international
regulations, and the IARU has recom-
mended that other amateur stations
should not contact them.

The situation is complicated by the fact
that radio amateurs are proud of their
ability to communicate with each other on
non-controversial matters irrespective of
differences between their political masters.
Some countries occasionally forbid con-
tacts with specified other countries, but

even at the height of the cold war it was

possible to have friendly personal contacts
between East and West.

The controversy over the TRNC
amateur stations is clearly a symbol of the
deep differences between Greek and
Turkish Cypriots and there seems little
possibility of amateur radio contacts
between them. Amongst the rest of the
world’s amateur radio community there
are divided opinions.

Some do take note of the the views of
the IARU and will not work TRNC sta-
tions. Others, because there has been
no formal prohibition, feel they should
be free to talk to either party without
hindrance. Much as we would like to
think otherwise, amateur radio is not
immune to the stresses of international
politics after all!

YOUNG AMATEUR OF THE YEAR
Details of the Young Amateur of the
Year Award 1995 have been announced
by the Radiocommunications Agency. It
is offered by the Agency in conjunction

with the Radio Society of Great Britain

and is open to anyone under 18 who has
an interest in radio.

' Applicants need not be _ licensed
amateurs but the following areas of
activity will be taken into account
when assessing their applications. DIY
radio construction; operation of radio;
community service (e.g., assisting in
emergency communications); encourag-
ing others (e.g., through the amateur
radio novice licence scheme), and school
projects.

The prize for the most outstanding
achievement between 1st August 1994

and 31st July 1995 will be £300 cash

and the runner-up will receive £50. There
may well be additional prizes for both
winners provided by the radiocom-
munications industry. Both winners will

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also be invited to visit the Agency's
Radio Monitoring Station at Baldock in
Hertfordshire. |

Further details can be obtained from the
Radio Society of Great Britain, Lambda
House, Cranborne Road, Potters Bar, Herts
EN6 3JE, to whom applications should be
sent not later than 31st July 1995.

THE STORY OF THE KEY

Many radio amateurs, and others, col- :
lect Morse keys. It is a fascinating hobby
since the keys come in a variety of types,
ranging from simple hand keys to modern
complex electronic keyers. In some cases
they go back long before radio, to the
time when the electric telegraph, using a
single wire and an earth return, was the
“wonder of the age” spanning continents
with ease.

Of interest to established collectors, and
to those just thinking about starting,
Morsum Magnificat, the Morse Magazine
has just published “7he Story of the Key”.
a reprint from the magazine of an
authoritative six part series by Louise
Moreau W3WRE. This covers. the
development of the key, beginning with
Alfred Vail’s “Correspondent”, used on
Samuel F.B. Morse’s triumphant Baltimore
to Washington demonstration of 1844.

It outlines the first attempts to in-
crease sending speed (and at the same
time alleviate ‘‘telegrapher’s paralysis’’ or
“glass arm’) leading to the ‘Double
Speed Key”, or ‘’Sideswiper’’ of 1888. It
goes on to tell the amazing story of the
Vibroplex semi-automatic key, which first
appeared in 1904, involving legal battles
by the company with its many imitators
and the eventual “licensing” of the so-
called ‘‘bastard bugs” to permit their use
professionally.

Finally it tells how, with the advent
of wireless, the landline straight key was
adapted for “‘spark’’ use, and was later
modified again when the power of the
spark was no longer a problem.

The book also includes an alphabetical

list of American Telegraph Instrument
Makers from 1837 to 1900, with their
addresses, dates of operation and a broad
indication of the types of instruments
they produced.
- Originally intended for existing readers
of Morsum Magnificat, the final result is a
book which will have a much wider ap-
peal. With over 75 indexed photographs
of the keys described in the text, coupled
with the information available in the list
of makers, it will be an invaluable and en-
tertaining source of reference for both key
collectors and today’s key users.

“The Story of the Key” has 60 pages x
A5 soft-cover format. It is obtainable by
post direct from G. C. Arnold Partners,
9 Wetherby Close, Broadstone, Dorset
BH18 8JB, price £3.95 post free (UK), or
£4.25 overseas by surface mail. Please
mention EPEwhen ordering a copy.

- Everyday with Practical Electronics, June 1995

r- a AR Lil OM as ical READ

Nee ee

aT NT eat kT) Xcamelt Tel[e RO) RUTSTS19IME MARCONI 2440 Microwave Counter 20GHz
MTemMolsorel cei ATL GROOLT RAGA coco. Frequency Counter SOMHZ-1:5CH2 LE

| , MARCONI 2435 Digital Frequency Meter 2GHz
TEKTRONIX 7000 SERIES OSCILLOSCOPES

RACAL 1998 Freq, Counter 1:3GHz (options GPIB & High St
Available from £200 - PLUG-INS SOLD SEPERATELY RACAL/DANA 1991 Universal Counter/Timer 160MHz 9 dig
TEKTRONIX 2465 4 Channel 3

MARCONI 2437 Universal Counter /Timer DC -100MHz 8 dig
Delay Sweep Cursors.......€4750 } Racal 9916 Frequency Counter 10HZ-520MHZ

TEKTRONIX 2246A 4.Channel 100MHz Cursors } pied ete... pie RACAL 9906A Universal Counter Timer 10Hz-200MHZ.

TEKTRONIX 2245A.4 Channel 100MHz Cursors etc. ... £1000 BLACK STAR Meteor 100 Frequency Counter 100MHz

TEKTRONIX 485 Dual Trace 350MHz Delay Sweep... DATRON 1081 1081 7: "5 digit Autocal Multimeter/True RMS

HP BASEN Oat DVM DC/True RMS AC/Res. HPIB.

PHILIPS PM2534 Multi Function DMM 3'-6' digit GPIB/IEEE

SOLARTRON 7065 6 digit Microprocessor Voltmeter
AC/DC/Ohms/Auto.. ;

SOLARTRON 7150 67-37 digit OMM with IEEE

SOLARTRON 7045 4’ digit Multimeter Volts/Amps/Ohms....

THANDAR 1504 4°. digit True RMS Multimeter with Adapt

WILTRON 560 Scaler Networ' k Analyser with Detectors

H.P.5005A Signature Multimeter

RACAL /Dana 9104 RF Power Meter 1MHz-1GH2; 40mW-300W

AVO.CT160 Valve Tester:(Valve Data not included)

PHILIPS PM5565 Waveform Monitor

TRIO CS1566A Dual Trace 20MHZ... PHILIPS PM6307 Wow and Flutter Meter

CROTECH 3132 Dual Trace 20MHZ £150
TAC VES ual rae 00D toragelCusors As. £1900 MET SBA ae

PHILIPS PM3305 4 Trace 35MHz Digital Storage...
GOULD 0S4000 Dual Trace 10M Digital Storage sila Shpenronidel by beer
TEKTRONIX 464 Dual Trace 100MHz Ana Stora RADFORD LDMS2 Low Distortion Measuring Set...
H.P.1741A Dual Trace 100MHz Analogue Storage a KEMO Dual Variable Filter VBF/3 012-1
THIS IS JUST A SAMPLE - MANY OTHERS AVAILABLE RACAL Instrumentation Recorder type Store 40N
EATON/AILTECH 380k11 Synthesized Sig sallncatascancin RACAL Instrumentation Recorder type Store 7DS. £500
with PM3602 AM/FM Phase Mod... veaeeevel?.O H.P. 4275A Multi Freq LCR Component veter with Test Fixtures. £3500
HP. 8656A Synthesized AM/FM Sig. Gen. 100kHz-990MHZ.... H.P.4264A LCR Meter with Test Fixture 16061A.
- MARCONI 2019 Synthesized AM/FM Sig Gen 80kHz-1040M MARCONI TF2700 Universal Bridge, Battery Oa
MARCONI 2022 Am/FM Sig. Gen. 10kHz-1000MHz f WAYNE KERR B424 Digital Component Meter LCR
MARCONI 2018 Synthesized AM/FM Sig Gen BOkHz- 520MHZ. H.P. 1630D 43 Channels: ;
HP. 8013B Pulse Gen. 1Hz-5OMHz

AT LAST. A comprehensive; easy to follow

guide to building short range transmitters
and surveillance devices. Packed with

useful information and circuits. |

* Only £3.95 inc p&p.

(Some of the circuits iricluded cannot be used legally in the UK)

All kits come with pre-drilled PCBs and high spec. ICG
components.

MICRO FM TRANSMITTER (a). 1km range, 80-100MHz itt
preset inc. mic., very small (2x 3cm) | “~“Y €6.95 |
MICRO FM TRANSMITTER (b). Variable mic. sens., tunable 90-110MHz. |
1km range £7.95
FM TRACKER. Transmits an audio tone for direction finding, tracking etc.
80-110MHz £8.50
ULTRA MINIATURE FM TRANSMITTER. Runs off watch battery (inc), only
1x2cm, 200mtrs range. 80-100MHz £8.95
FM RECEIVER (a). Tiny high quality FM-radio. Will drive headphones
direct (not inc) £10.90
FM RECEIVER (b). As (a) but with 3 watt audio output and tuning LED £1 3.50
CRYSTAL RADIO. Includes tuner, earphone, ferrite aerial, etc. ‘£7.50. |):
AM RADIO. Single chip radio for headphones (not inc.) £8.90

AUDIO KITS.
15 WATT General purpose upgrade
40 WATT High quality, HD 0-:003%, switch
on mute ideal for compact disc
150 WATT Rugged and powerful MOSFET |
design. PA/sound systems

PREAMPS ETC |.
GENERAL PURPOSE PREAMP. Variable gain 9-25V:40mV max in
ULTRA LOW NOISE. For high quality mixers, mics etc 9-25V
ACTIVE TONE. 12dB c/b bass and treble with variable gain
7 BAND EQ. 150Hz-18kHz for EQ units and-tone control,
includes on-board preamp and pots. Variable gain
NOISE GATE. Dynamic noise reduction system. Variable input
and cut off level. Will accept instruments, tape decks etc £15.95
MUSIC KITS. Full range of on-board units for guitars and other instruments.
Tone boosters, active circuits, delay lines, transducers. Send for list.

Prices include P&P. Mail Order Only. Make cheques and postal orders payable to:

a Woodhouse Street.

BECKMAN 9020 Dual Trace 20MHz Delay Sweep
HAMEG 412 Dual Trace 20MHz Delay Sweep.
IWATSU SS5702 Dual Trace 20MHz

HP. 6268 0-40V: 0-30A....
FARNELL H30/100 0-30V; 0-100A. Metered...
THURLBY PL320QMD 0-30V; 0-2A Twice Digiita
£250 | THURLBY PL320 0-30V; 0-2A Digiital
| FARNELL E350 0-350V;0-200mA Metered...
BRANDENBURG Model 472R +/-2kV Metered
MANY OTHER POWER SUPPLIES AVAILABLE

NEW EQUIPMENT

300mS
ape es eres Sony Digital Delay Kit

£847
HAMEG OSCILLOSCOPE HMO Dual Trace 6OMiz Delay Sweep Only
HAMEG OSOLLOSCOPE HM303 Dual Trace 30MM Comp Tester.” £382 £24.95
IFRA7750 Synthesized 1GHz.... £4000 Allother models availabl gh pti rant £655
4 ; 0 m avaliable — all OSC! 5
HP 8565A O01SCHZ-22GHZ._ | Ee

APOLLO 10 100MHz Counter Timer Ratio/Period/Time int. etc.
APOLLO 100 100Mbz (as above re tao functions)

H.P. 8495B Attenuator DC- A8GHZ. 0dB-110B in 1dB Steps

HATFIELD 2105 Attenuator 50 on AUDIO POWER AMPS
DX TDR1 502 .occsorocnmne

£8.95
£15.50
€22.95

£4.00
£4.50
£8.95

HP. 141T with 8554B & 85528 SOOkHz-125
HP. 141T with 8553B & 85524 1kHz-110M
HP.141T Main Frames Only. Good Tubes
MARCONI T2370. 30H2-10MHZ

JUPITOR 500 FUNCTION GEN. 01H2-500kHz si
ORION COLOUR BAR GENERATOR Pal/TV/Video
All other Black Star equipment available.

OSCILLOSCOPE PROBES Switched X1 X10 (P&P £3)

= ot Gusrentced. Manuals supplied if possible.
This is a VERY SMALL SAMPLE OF STOCK. SAE or telephone for lists. Please check availability before
ordering. CARRIAGE all units £16. VAT to be added to Total of Goods and Carriage.
eee aes

STEWART OF READING
-110 WYKEHAM ROAD, READING, BERKS RG6 1PL a

= Ty ‘a
Tel: 01734 268041 Fax: 01734 351696 Callers welcome 9am to 5.30pm MON-FRI (UNTIL 8pm THURS) Leeds

“BOFFINS SPECIAL” -
UNIQUE OFFER |

Surplus Precision Medical Unit, internally in excel-

lent condition. Designed primarily. to eject a precise

INPUT 220V/240V AC 50/60 controllable amount of fluid from a medical syringe

OUTPUT 0V-260V (latter not supplied). Contains the following remov-

Price P&P | able BN plait ee ee Eee gees 4

: ; EPR scap Precision otor wit
O-5KVA 2 5 amp max £31.90 : £6.00 300:1 Gearbox and optical encoder coupled to a
(£44.53 inc VAT) precision threaded drive mechanism. Mains supply
1KVA 5 amp max

2KVA 10 amp max
3KVA 15 amp max

VARIABLE VOLTAGE
TRANSFORMERS

COMPAC ELECTRONICS

~ 3LWEYLOND ROAD, DAGENHAM, ESSEX RM8 3AB
Tel: 0181 984 0831

REMOTE CONTROLS SATELLITE
Amstrad, Toshiba, from £5. Satellite Finder Kit, Meter etc. £29.99.
Ferguson, Philips, ITT, Sony from £10. Marconi Blue Cap, ex-rental, £5 plus £2
Universal Remote Control, operates TV, Video, post & carr.

Satellite, with Teletext buttons, £16.99 or Amstrad Compact Black Cap. LNB, voltage
non-Text £10.99. switching, 1dB, special price £23.95 plus £2

£41.15 £7.00 | with 6 x 1.5V Ni-Cad AA cells back-up. L.C.D.
(£56.58 inc VAT) | Digital readout 17mm high with legends. Audible
warning.
£59. ch. 78 Say) ree These are sold for the dismantling of the exceptional
. c quality components. Regret NO cncure available.
£78.65 £8.50 Ridiculously low price: £20.00 + £4.00 p&p

5 (£102.40 inc VAT) (£28.20 inc VAT). : jae post &carr.
5KVA 25 amp max £139.15 . 5 KVA ISOLATION TRANSFORMER We repair Philips hand sets, £5.00. Satellite dishes, Black Mesh 60cm, £25.99 plus
(Plus Carriage) | As New Ex-Equipment, fully shrouded, Line Noise Pinch Rollers from £2.99. £5 post & carr.

Buy direct from the Importers. Keenest prices in the country | Suppression, Ultra Isolation Transformer with Video Fig.-8 Mains Lead, Feletinken type, £1., SPECIAL OFFER, satellite owners upgrade to

COMPREHENSIVE RANGE OF
TRANSFORMERS-LT-ISOLATION & AUTO |
110V-240V Auto transfer either cased with American socket and
mains lead or open frame type. Available for immediate delivery.

WIDE RANGE OF XENON FLASHTUBES

Write/Phone your enquiries
ULTRA VIOLET BLACK LIGHT

FLUORESCENT TUBES
4ft 40 watt £14.00 (callers only) (£16.45 inc VAT)
2ft 20 watt £9.00 (callers only) (£10.58 inc VAT)
12in 8 watt £4.80+ 75p p&p (£6.52 inc VAT)
Yin 6 watt £3.96 + 50p p&p (£5.24 inc VAT)
6in 4 watt £3.96 + 50p p&p (£5.24 inc VAT)

terminal covers and knock-out cable entries.
Primary 120V/240V, Secondary 120V/240V,
50/60Hz, 0-O05pF Capacitance. Size, L 37cm x W
19cm x.H 16cm, Weight 42 kilos. Price £120 +
VAT. Ex-warehouse. Carriage on request.

240V AC CENTRIFUGAL BLOWER
New Manuf. Surplus Skeleton Blower suitable for
mounting inside an enclosure to cool equipment.
Overall size 130 x 110 x 85mm. Outlet 80 x 35mm.
Impellor 60mm dia. x 60mm long. Price £14.10 inc
p&p & VAT.

SEWING MACHINE MOTOR |
Brand new 220V/240V AC/DC SEW-TRIC 2 lead Brush
Motor. Size L. 100mm x H. 70mm x W. 55mm. Spindle %

R.F. Video leads, 50p.
SCART to SCART leads, £1 75.

SCART to SCART leads, all pins connected,

£2.33.

Aerial R.F. cable, RG62, 30p per mtr.
Aerial R.F. male plugs, 30p each.

TV on/off switches, from £1.95, most types.
Halogen Lamps, 240V S500W, for outdoor

floodilamps, £1

Miniature Tool Kit, comprises: side-cutters knife,

.75.

screwdrivers, £7.00.

Varta, p.c.b. mounting rechargeable batteries,
oval type Ni-Cad. Suitable for CMOS and

Astra TD with our ADX frequency extender,
£25.99. Can be used with standard or
enhanced LNB.

Satellite cable, high quality copper screen, 30p
mtr., 100 mtr. roll £27 plus £5 post & carr.

F. Connectors, 40p each.

MASPRO LNB FSS, 1:3dB max., £13.33.

NOKIA LNB FSS 1:3, £11.99.

NOKIA Feed Horns, for offset antenna, £8.

NOKIA Electromagnetic, Polarizers, £10. While

stocks fast.
VIDEO
Head Cleaners, £2.99.

NMOS systems, 2:4V 100nAH, 99p.

Ferguson TX90 tube bases, £2.

Ferguson TX100 SCART panels, £2.

Indoor amplified antenna, wide band, UH F/VHF.
£11.99 plus £3, post & carr.

Philips K30 colour brightness controls, front
draw etc. £2.

TV Loudspeakers, 6”x4”, 16 ohms, £1.50 each.

Power Supply AC adapters, universal 300mA,
£4.99, 750mA, £7.99

Philips Krypton Torches, £1 50.

Philips Television G11 line output panel,
complete, £5 plus £2, post & carr.

Philips Soldering lron, 240V, 25W, £5.99.

Voltage Regulators, LM340T, 44p.

1.C.s: SAA3010P £3.40; TDA3651 SI £1.10;
TDA3654 £1.89; TDA3651A £2.85;
TDA3562A £2.85; TDA2600 £5.73;
TDA2578 £3.43; TDA2579 £2.86; TDA2030
£2.28; TDA3653 £3.43; TDA3651 £2.29;
TDA3562 £3.44; TDA 3564 £4.59; TDA4500
£3.43; TDA8180 £5.48; TDA8190 £3.43;
TDA8361, £19.99; STK4793 £9.00.

DIODES: Type RH1, £2.00.

TRANSISTORS: BU208A £1.20; BU508AF
£1.75; BU11AF 55p; BC327 10p; BC337
10p; BC338 10p; BC548 10p; BC549 10p.

CAPACITORS ELECTROLYTIC: 0:22, 50V
5p; 1 50V 5p; 2:2y SOV 6p; 4:7 25V 10p;
47 100V 20p; 470p 25V boyy ni 63V 60p;

2,200 40V 60p; 3,300 25V 80

Amstrad Universal remote controls, £6.00.

Periswitch SCART switching box,
automatically switches between VCR,
Satellite and TV. Expensive unit! Originally
priced at £99.95. OUR PRICE £9.99. These
units require an additional 12V d.c. adaptor
at £4.99 and 3 SCART leads at £6. Technical
details on request. £4 post &carr.

AUDIO
CONNECTORS: Phono to Phono couplers,
40p each; Phono plugs, red or black, 50p
each; Phono sockets, red or black, 50p each.
Philips Audio Cassette Head Cleaning
Splicing Kit, £2.
High quality loudspeaker cable, 50p per mtr.
Servicing Sprays £3.00 most types.
Ceramic Type Pulse Capacitors, 20 for £1.
Ferguson surround sound extension TV speakers,
with stand, £25 a pair, plus £5 post & carr. ;
SPECIAL OFFER THIS MONTH
PYE Stereo Cassette/Radio, FM/AM, New,
Boxed, £25.99 plus £5 post & carr. ’

L.O.P.T. TRANSFORMERS -
WIDE RANGE AVAILABLE.
PHILIPS, FERGUSON etc.

This is just a small sample of components
available, please phone with your requirements.
Please add £1.00 postage & packing,
except where stated otherwise.

No VAT charged.

230V AC BALLAST KIT
For either 6in, 9in or 12in tubes £6.05 + £1.40 p&p
(£8.75 inc VAT) | 71 RPM 20lb/inch torque reversable 115V AC input
The above Tubes are suitable for Forged Bank Note detec- including capacitor and transformer for 240V AC
tion, security marking etc. operation. Price inc VAT and p&p £27.73.
Other Wavelengths of U.V. TUBE available please. tele- “SOLID STATE EHT UNIT |

phone your enquiries. Input 230V/240V AC, Output approx 15KV.
400 WATT UV LAMP _— Producing 10mm spark. Built-in 10 sec timer. |
Only £38.00+ £4.00 p&p (£49.35 inc VAT) Easily modified for 20 sec, 30 sec to continuous.
160 WATT SELF-BALLASTED Designed for boiler ignition. Dozens of uses in the

BLACK LIGHT MERCURY BULB field of physics and electronics, e.g. supplying
Available with E.S. fitting. neon or argon tubes etc. Price less case

Price inc VAT & p&p £25.55 £8.50 + £2.40 p&p (£12.81 inc VAT) NMS.

12V D.C. BILGE PUMPS EPROM ERASURE KIT
500 GPH 15ft head 3 amp £19.98 Build your own EPROM ERASURE for a fraction of
1750 GPH 15ft head 9 amp £34.55 the price of a made-up unit. Kit of parts less case
Also now available: includes 12in 8 watt 2537 Angst Tube Ballast unit, pair
24V D.C. 1750 GPH 15ft head of bi-pin leads, neon indicator, on/off switch, safety
5 amp £35.55 microswitch and circuit £15.00 + £2.00 p&p
All designed to be used submerged. (£19.98 inc VAT)
PRICES INCLUDE P&P & VAT MICROSWITCH
IGHT STROBE KIT Pye 15 amp changeover lever microswitch, ‘ens $171.
Decne tox Discd Theeirical uadeee Brand new. Price 5 for £7.05 inc VAT & p&p.
Approx 16-joules. Adjustable speed £50.00+ £3.00 p&p WASHING MACHINE WATER PUMP
(£62.28 inc VAT) Brand new 240V AC fan cooled.. Can be used for a
Case and reflector £24.00+ £3.00 p&p (£31.73 inc. VAT). | variety of purposes. Inlet 1%in., outlet 1in. dia. Price
SAE for further details including Hy-Light and] includes p&p. & VAT. £11.20 each or 2 for £20. 50
inciustrat Strobe Kits. inclusive.

eERVICE TRAN CG CO
SERVICE TRADING CO VISA

57 BRIDGMAN ROAD, CHISWICK, LONDON W4 5BB
TEL: 0181-995 1560 FAX: 0181 -995 0549 Ample
__ ACCOUNT CUSTOMERS MIN. ORDER £10 Parking Space

in. dia. x Tin. long. Price £14.10 inc p&p & VAT.
GEARED MOTORS |

Showroom open
Monday/Frida

Everyday with Practical Electronics, June 1995 501

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THE BUG CONSTRUCTOR’S MANUAL

All you will ever need to know about Bugs. Over
40 Bug circuits for every application. Telephone,
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and many pages of useful information... Many
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For immediate despatch, send cheque or P.O.’s payable to:

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YUGA ENTERPRISE

BA,LA, LB, LC, UPA,
UPB, UPC, TA,
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IX, LM, MN, PA

TEL: (69) 741 0300
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705 Sims Drive #03-09
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‘ ha | Pe mt ‘4k @)
SURVEILLANCE KITS
MTX MICRO TRANSMITTER 18 x 45mm in-
cluding sensitive electret mic., tuneable 70-115MHz,

500m range. KIT £5.95. ASSEMBLED £9.95.

TTX TELEPHONE TRANSMITTER 15 x 45mm,
powered from line, transmits all conversations, 500m
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Supplied with all components & high quality PCB's. Prices
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~ NEW CATALOGUE/PRICE LIST
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3000 items at competitive prices!

_ Batteries e Buzzers e Cable e Displays
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RCS VARIABLE VOLTAGE D.C. BENCH POWER SUPPLY

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rent readings. Overload protection inc
Fully variable. f4 5 :
Operates from , » ees = VAT
cae a be + Post and

ree we Sin, ay insurance £4

N

Twin panel meters. Size 14% x 11 x 4%in. £96 inc VAT. Carr £6.

RADIO COMPONENT SPECIALISTS

337 WHITEHORSE ROAD, CROYDON
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Lots of transformers, high volt caps, values, speakers, in stock.
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PLDs AND EPROMS copied or pro-
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MIDI LIGHTING MODULE, eight 500W
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60 WATT AMPLIFIERS, £5.00, SOV module
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LASER POINTERS 5mW 670nM (RED).
German quality, £69.50 post paid. Also
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Telephone 01925 575848 for details. Cheques
or PO to, English Scientific, 12 Orford Avenue,
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PLASTIC INJECTION MOULDING at
prices you can afford. Very low cost (sometimes
free) tooling. Small quantities speciality. 01685
(Aberdare) 874763.

ELECTRONIC HOBBYIST giving up has
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SHERWOOD ELECTRONICS

TOO OO III IO IO OO IO IO AIO
SPECIAL OFFER = for limited period only

CHOOSE 8 x £1 packs FREE with every 15 purchased
SP1 15 x 5mm Red Leds SP42 200 x Mixed 0.25W C.F. resistors

SP2 15 x 5mm Green Leds SP47 5 x Min. push button switches
SP3 12 x 5mm Yellow Leds SP102 20 x 8pin DIL sockets

SP4 10 x 5mm Amber Leds SP103 15 x 14pin DIL sockets

SP6 15 x 3mm Red Leds SP104 15 x 16 pin DIL sockets

SP10 100 x 1N4148 diodes SP112 5 x Cmos 4093

SP11 30 x 1N4001 diodes SP118 2 x Cmos 4047

SP12 30 x 1N4002 diodes SP125 10 x 1000/16V radial elect caps
SP18 20 x BC182 transistors SP130 100 x Mixed 0.5W C.F. resistors
SP19 20 x BC183 transistors SP135 6x Min. slide switches

SP20 20 x BC184 transistors SP137. 4 x W005 bridge rectifiers
SP21 20 x BC212 transistors SP138 20 x 2-2/50V rad elect caps
SP22 20 x BC214 transistors SP142 2x Cmos 4017

SP23 20 x BC549 transistors SP147 = 5 x Stripboard 9 strips/25 holes
SP28 5 x Cmos 4011 SP151 4 x 8mm RedLeds

SP29 4 x Cmos 4013 SP156 3 x Stripboard 14 strips/27 holes
SP33 5 x Cmos 4081 SP165 2 x LF351 0p.amps

SP36 25 x 10/25V radial elect caps SP173 10 x 220/25V rad elect caps
SP37 15 x 100/35V radial elect caps SP175 20 x 1/63V rad elect caps

SP40 15 x BC237 transistors SP183 20 x BC547 transistors

Catalogue £1 or FREE with first order.
P&P £1.25 per order. NO VAT.
Orders to: Sherwood Electronics,

7 Williamson St., Mansfield, Notts. NG19 6TD.

RESISTOR PACKS -— 0.25W C.Film
RP3 5 each value — total 365 £2.60
RP7 10 each value — total 730 £3.95
1000 popular values £5.30

Everyday with Practical Electronics, June 1995

STE ee

¥ ae J

SERVICE MANUALS

We have what is probably the largest range of
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From the Earliest Valve Wireless to the
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DISTANCE LEARNING COURSES

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ready for you. Write or telephone for details to:
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NCT Ltd., PO Box 11
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Tel: (01296) 624270

503

Mixed metal/carbon film resistors “sW E12 series 10 ohms to 1 Megonm.............:ce
Carbon Film resistors %W 5% E24 series 0.51 R to 1OMO

PPPoE eee eee eR COOP CCCC Creer eee ees

100 off per value — 75p. even hundreds ag value totalling 1000 ............ cece £6.00p
Metal Film resistors %W 10R to 1 MO 5% E12 series — 1 4p. 1% E24 series ...........:ccceeees 2p
Mixed metal/carbon film resistors ZW E24 series 1RO to 10MO .........ccccccsseneeeeeeeeeees 1’Ap

1 watt mixed metal/Carbon Film 5% E12 series 4R7 to 10 MeQON Is ............ccseceeseesseeees 5p
Linear Carbon pre-sets 100mW and %W 100R to 2M2 EG Ser i@S .........seseceeeeteteeeeeeentees . 7p
Miniature polyster capacitors 250V working for vertical mounting

015, .022, .033, .047, .068-4p. 0.1 - 5p. 0.12, 0.15, 0.22 - 6p. 0.47 - 8p. 0.68 - 8p. 1.0 - 12p
Mylar (polyester) capacitors 100V working E12 series vertical mountin

1000p to 8200p - 3p. .01 to .068 - 4p. 0.1 - 5p. 0.12, 0.15, 0.22 - 6p. 0.47/50V - 8p

Submin ceramic plate capacitors 100V w

2 btn mountings. E12 series

2% 1.8pf to 47pf - 3p. 2% 56pf to 330pf - 4p. 10% 39OP-4700p ........ ec eeecsssseseereeteeeeeees 4p
Disc/plate ceramics 50V E12 series 1PO to 1000P, E6 Series 1500P to 47000P............... 2p
Polystyrene capacitors 63V working E12 series long axial wires

10pf to 820pf - 5p. 1000pf to 10,000pf - 6p. 12,000PF ....... eee eee eeeeeeeeteeteteeeeeeeeeees 7p
741 Op Amp - 20p. 555 Timer — 20p. LM3900 ....0... ce ccecessceeeseseeeessssesessecaseeeseeseeeseeeeees 80p
CMOS 4001 - 20p. 4011 - 22p. 4017 — 40p. 4069UB unbuffered «0.0.00... cc eeeeteeeeeees 20p

DIL holders, 8-pin 9p; 14-, 16-, 18-pin 12p; 24-pin 18p; 28-pin 20p; 40-pin 25p.
ALUMINIUM ELECTROLYTICS (Mfds/Volts)

1/50, 2.2/50, 4.7/50, 10/25, he ke abasiptasusaias

22/16, 22/25, 22/50, 33/16, 47/
100/16, 100/25 7p; 100/50

VOLTAGE REGULATORS
DIODES (piv/amps

POUUUEPUSECUOOCOPOOOOOOOOOOCOCO CIE

1A + or — 5V, 8V, 12V, 15V, 18V & 24V - 55p. 100mMA. 5.8, 12, 15, V + oes 30p

ps) ,
75/25mA 1N4148 2p. 800/1A 1N4006 4%p. 400/3A 1N5404 14p. 115/15mA OA91 .. 8p
100/1A 1N4002 3%p. 1000/1A 1N4007 5p. 60/1.5A S1M1 5p. 100/1A bridge.......... 25p
400/1A 1N4004 4p. 1250/1A BY 127 10p. 30/150mA OA47 gold bonded .................. 18p
Zener diodes E24 series 3V3 to 33V 40O0MW - 6p. 1 Walt... ee ceeceeeeeteeeteeeneeeeeneeees 10p

Battery snaps for PP3 - 7p for PP9..................

L.E.D.’s 3mm. & 5mm. Red, Green, Yellow - 10p. Grommets 3mm - 2p. 5mm..............645 2p
Red flashing L.E.D.’s require 9-12V supply Only, SMM .........ccceeeeeeeeteeteeteeteeeeeetteeeenenees 50p

Mains indicator neons with 220k reSiStOF .............:ccsecccseeeeneeeeeeeeeeeeees serararnncasbaictay ueaies 10p
20mm fuses 100mA to 5A. O. blow 6p.A/surge 10p. Holders, chassis, mounting ............ 6p
High speed pc drill 0.8, 1.0, 1.3, 1.5, 2.0mm - 40p. Machines 12V dC ...........:ccceee £15.00

HELPING HANDS 6 ball joints and 2 croc clips to hold awkward jODS ............:se £4.50
AA/HP7 Nicad rechargeable cells 90p each. Universal charger unit ...............:cseeees £6.50
AA/HP7 zinc/carbon batteries in packs of 4

Glass reed switches with single pole make contacts - 8p. Magnets ..............:cccseceereees

0.1” Stripboard 2%” x 1” 9 rows 25 holes - 25p. 34 x 2%” 24 rows 37 holes ............5 70p
Jack plugs 2.5 & 3.5m — 14p; Sockets Panel Mtg. 2.5 & 3.5... ccccceeteeesteeeeneeees 10p
Ear pieces 2.5 & 3.5mm, dynamic — 20p; 3.5mM CryStal..........cceccceeeseeteeteeeteeeeeeetaaes £1.50

Multi cored solder, 22G — 8p yard, 18G — 14p yard.

TRANSISTORS

BC107/8/9 - 12p. BC547/8/9 - 8p. BC557/8/9 - 8p. BC182, 182L, BC183, 183L,

BC184, 184L, BC212, 212L - 10p.

BC327, 337, 337L - 12p. BC727, 737 - 12p. BD135/6/7/8/9 - 25p. BCY70 - 18p.

BFY50/51/52 - 20p.

15 Amstrad Games. ...............+.
15 Spectrum Games ...............

£1 PAC
50 BC547A; 20 BS107; 20 BSS92;
10 2N2907A; 20 2N5086;
50 2N5551; 3 BD145; 10 BD237;
10 BD239A; 5 BFW43; 10 BFX30;
3 BSX59; 10 VN2010-L; 20 ZTX304;
20 ZTX311; 20 ZTX510; 20 ZTX551;
5 5V d.i.l. relays; 10 21-1OMHz
crystals; 10 811 MHZ filters; 50 6-way
i.c. skts.; 50 14-way d.i.p. hors;
20 TO18 heatsinks; 20 TO5 heatsinks;
200 TO5 mounting pads; 200 TO18
mountings pads; 2 10092 LOPT Tx;
5 12-way terminal blocks; 10 silver
control knobs; 10 95V V.D.R.;312V
counters; 25 3:5mm jack plugs;
10 PCB MT microswitch; 10 6-way
d.i.|. switch; 10-1 pole 3-way rotary
switch; 25 slide switches; 5 3A 250V
power toggle switch; 50 4-7uF 25V
caps; 15 2200uF 25V caps;
10 0-047uF suppresion caps;
25 neons; 10 1p,.F 250V polyesters.

5%” to 3%” floppy converter

lead £1.50 ea
STC p.s.u. 240V Input; 5V 6A

Output, (converts to 12V 3A,

details supplied).................. £5
Temperature probes, with

apes sae, crtraniretenaied £3.95"
Universal Timer (10 min. delay and_,

20 min. cut-off functions) ..£3.95 |
12V 400mW Zeners, ....... 100 off £1
3AMP mains filters............ .
40 Character x 1-line dot

matrix display..................
Car Dashboard Display (show

lights, indicators, doors,

on picture of car)................. ,
4-digit clock display............... £2.50
4-digit I.c.d. with 7211 driver..£3.50"
17-digit v.f. display.........0.00.... £2.95"
Giant 2-digit v.f. display.........
12V stepper motors, 48 steps

per rev., 7-3° step angle.......

*

Cee ee eeeseeseneseseeseseseeeeese

250 off mixed electrolytic

BG: cis vnteintcnitten ae ;
250 off polyester caps............£4.95 |
1000 off mixed resistors “W..£4.95 |
100 off phono plugs............... £2.95

BFX88 - 15p, 2N3055 - 55p, TIP31, 32 - 30p, TIP41, 42 - 40p. BU208A - £1.50, BF195, 197 - 12p
lonisers with seven year guarantee, 240V AC, list price £16.95 or more ............6.000 £12.50
Do not add VAT. Postage 30p (free over £5). Stamp for list.

THE CR SUPPLY CO

127 Chesterfield Rd., Sheffield S8ORN Tel: 01742 557771 Return posting

50 off mixed terminal blocks..£2.50
25 off buzzers & sounders......

25 off mixed relays.................

50 off mixed switches.............

250 off i.c. sockets..................

1000 off Ceramic cap.s............

5 off 3V Lithium memory

5V SPCO S.I.L. reed relay........
12V Piezoelectric Sounders......
DIL Switches 3/4/6 and
3:5mm jack plugs...............
100 off Zener diodes, mixed........
21 -piece mini screwdriver set. £3.95"
Universal test lead kit.............. £3.95"
10 crocodile clip leads............
20 off mixed R.F. Filters,
Crystals, etc. ...cccccceceeeeeee £4.95"
100m P.V.C. sleeving.............. .

VALVES
Q0V0310, £10*; QQV0320A, £10":
QQV0640A, £20*; ECC 82, £3";
ECH 81, £2*: PCL 805, £3":

ORP 11, £3; ORP 40, £3; CV 4004,
4005, 4006, 4007, 4014, 4020,
4024, 4043, 4055, 4064, 5042,
5080, ALL £5 each”.

QUANTITY DISCOUNTS
AVAILABLE PLEASE RING. |
We also buy all forms of electronic
components, p.s.u’s, disk drives etc.
Lists to below address.

ALL PRICES INCLUDE V.A.T.
PLEASE ADD £2.00 p&p EXCEPT
ITEMS MARKED+* WHICH ARE 50P.
SAE FOR BULK BUYING LIST
PAYMENT WITH ORDER TO
DY=) 0) an =e =n O0 OF \N/ 1 od ot a ok Om
sé Bl @reyar-s ec] olism averclem
St. lves, Huntingdon,
Cambs PE17 6EO
Tel/Fax: 01480 300819

Published on approximately the first Friday of each month by Wimborne Publishing Ltd., Allen House, East Borough, Wimborne, Dorset BH21 1PF. Printed in England by Benham & Co. Ltd,

Millions of quality components
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Plus Tools, Watches, Fancy Goods, Toys.
Mail order UK only.

All inclusive prices —
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Send 43p stamped self addressed label or

envelope for catalogue/clearance list.
At least 2,100 offers to amaze you.

Brian J Reed
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Tel: 0181-393 9055

ADVERTISERS INDEX

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COOKE INTERNATIONAL. ....ccccccssccccsssecsssecsssssesesseeee 503
CRICKLEWOOD ELECTRONICS. .......cccccccssecsseesseeee 498
CR SUPPLY COMPANY. .....cccsscccsssscsssesssseccssecssesssees 504
DIRECT CCTV. ..cccccscccssseccsssecsssecssuccsssccsssecsseessessnecsseen 498
DISPLAY ELECTRONICS. .....cccsccccsssscssseccsseesseesseessees 422
EPT EDUCATIONAL SOFTWARE ......cccssecccsssessssseeses 479
ESR ELECTRONIC COMPONENTS.......--ssescssseesssees 432
EXPRESS COMPONENTS. .....cccssccssseccsseccssssccsssecenseee 486
FRASER ELECTRONICS. .....ccccccsscccsssescssseccsssseesssseeees502
GATS ELECTRONICS .....cccccsseccssscccsssccssseccssssccssseccessee 498
GREENWELD ELECTRONICS ......cccseccsseccsecssecssecseeen 427

HART ELECTRONIC KITS... cececeeeseeteesteeeeees

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MAPLIN ELECTRONICS.......ccccssccsseecsseesseessees Cover (iv)
MAURITRON.......-cssccccssssccccssssccssssssccssssscssssecsssecssvecese 503
M&B ELECTRICAL SUPPLIES........ccccssesccssseecsseesssees 493
NATIONAL COLLEGE OF TECHNOLOGY .............. 503
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ADVERTISEMENT MANAGER:
PETER J. MEW
ADVERTISEMENT OFFICES:
EVERYDAY with PRACTICAL ELECTRONICS,
ADVERTISEMENTS,

HOLLAND WOOD HOUSE, CHURCH LANE,
GREAT HOLLAND, ESSEX CO13 OJS.

Phone/Fax: (01255) 850596

For Editorial address and phone numbers see page 433.

Colchester, Essex. Distributed by Seymour, Windsor House, 1270 London Road, Norbury, London SW16 4DH. Sole Agents for Australia and New Zealand—Gordon & Gotch (Asi

Africa—Central News Agency Ltd. Subscriptions INLAND £24 and OVERSEAS £30 (£47.50 airmail) payable to “Everyday with Practical Electronics” Subs Dept. Alba House San Boot,
Wimborne, Dorset BH21 1PF. EVERYDAY with PRACTICAL ELECTRONICS is sold subject to the following conditions, namely that it shall not, without the written consent of the Publishers first
having been given, be lent, resold, hired out or otherwise disposed of by way of Trade at more than the recommended selling price shown on the cover, and that it shall not be lent, resold, hired out or

otherwise disposed of in a mutilated condition or in any unauthorised cover by way of Trade or affixed to or as part o

any publication or advertising, literary or pictorial matter whatsoever.

THOUSANDS PURCHASED
BY PROFESSIONAL USERS

THE RENOWNED MXF SERIES OF POWER AMPLIFIERS
FOUR MODELS:- MXF200 (100W + 100W) MXF400 (200W + 200W)

MXF600 (300W + 300W) MXF900 (450W + 450W)
ALL POWER RATINGS R.M.S. INTO 4 OHMS, BOTH CHANNELS DRIVEN
FEATURES: xindependent power supplies with two toroidal transformers * Twin L.E.D. Vu meters *
Level controls * Illuminated on/off switch * XLR connectors * Standard 775mV inputs * Open and short circuit
proof * Latest Mos-Fets for stress free power delivery into virtually any load * High slew rate * Very low
distortion * Aluminium cases * MXF600 & MXF900 fan cooled with D.C. loudspeaker and thermal protection

USED THE WORLD OVER IN CLUBS, PUBS, CINEMAS, DISCOS ETC.
SIZES:- MXF200 W19"xH3"2" (2U)xD11”
MXF400 W19"xH5"4" (3U)xD12”
MXF600 W19"xH5"4" (3U)xD13”
MXF900 W19"xH5"4" (3U)xD14%4”
PRICES:-MXF200 £175.00 MXF400 £233.85
MXF600 £329.00 MXFS900 £449.15
SPECIALIST CARRIER DEL. £12.50 EACH

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Advanced 3-Way Stereo Active Cross-Over, housed in a 19” x 1U case. Each channel has three level controls:
bass, mid & top. The removable front fascia allows access to the programmable DIL switches to adjust the
cross-over frequency: Bass-Mid 250/500/800Hz, Mid-Top 1.8/3/5KHz, all at 24dB per octave. Bass invert switches
on each bass channel. Nominal 775mV input/output. Fully compatible with OMP rack amplifier and modules.

Price £117.44 + £5.00 P&P
* ECHO & SOUND EFFECTS*

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STEREO DISCO MIXER with 2 x 7 band
L & R graphic equalisers with bar graph
LED Vu meters. MANY OUTSTANDING
FEATURES:- including Echo with repeat &
speed control, DJ Mic with talk-over
switch, 6 Channels with individual faders
plus cross fade, Cue Headphone Monitor. 8
Sound Effects. Useful combination of the
following inputs:- 3 turntables (mag), 3 |
mics, 5 Line for CD, Tape, Video etc.

Price £144.99 + £5.00 P&P

SIZE: 482 x 240 x 120mm

Join the Piezo revolution! The low dynamic mass (no voice coil) of a Piezo tweeter produces an improved
transient response with a lower distortion level than ordinary dynamic tweeters. As a crossover is not required
these units can be added to existing speaker systems of up to 100 watts (more if two are put in series. FREE
EXPLANATORY LEAFLETS ARE SUPPLIED WITH EACH TWEETER.

_ TYPE ‘A’ (KSN1036A) 3” round with protective wire mesh. Ideal for
bookshelf and medium sized Hi-Fi apeakers. Price £4.90 + 50p P&P.
TYPE ‘B’ (KSN1005A) 3'.” super horn for general purpose speakers,
disco and P.A. systems etc. Price £5.99 + 50p P&P.

_ TYPE ‘C’ (KSN1016A) 2"x5" wide dispersion horn for quality Hi-Fi sys-
» tems and quality discos etc. Price £6.99 + 50p P&P.

TYPE ‘D’ (KSN1025A) 2"x6” wide dispersion horn. Upper frequency
response retained extending down to mid-range (2KHz). Suitable for high
quality Hi-Fi systems and quality discos. Price £9.99 + 50p P&P.

TYPE ‘E’ (KSN1038A) 3%.” horn tweeter with attractive silver finish trim.
Suitable for Hi-Fi monitor systems etc. Price £5.99 + 50p P&P.

LEVEL CONTROL Combines, on a recessed mounting plate, level control
and cabinet input jack socket. 85x85mm. Price £4.10 + 50p P&P.

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A new range of quality loudspeakers, designed to take advantage of the latest
speaker technology and enclosure designs. Both models utilize studio quality
12" cast aluminium loudspeakers with factory fitted grilles, wide dispersion
constant directivity horns, extruded aluminium corner protection and steel
ball corners, complimented with heavy duty black covering. The enclosures
are fitted as standard with top hats for optional loudspeaker stands.

POWER RATINGS QUOTED IN WATTS RMS FOR EACH CABINET
FREQUENCY RESPONSE FULL RANGE 45Hz - 20KHz

ibL FC 12-100WATTS (100dB) PRICE £159.00 PER PAIR
ibl FC 12-200WATTS (100dB) PRICE £175.00 PER PAIR

SPECIALIST CARRIER DEL. £12.50 PER PAIR

OPTIONAL STANDS PRICE PER PAIR £49.00
Delivery £6.00 per pair

THREE SUPERB HIGH POWER
CAR STEREO BOOSTER AMPLIFIERS
150 WATTS (75 + 75) Stereo, 150W
Bridged Mono
250 WATTS (125 +
Bridged Mono
400 WATTS (200 +
Bridged Mono
ALL POWERS INTO 4 OHMS
Features:

& * Stereo, bridgable mono * Choice of
high & low level inputs * L & R level
controls * Remote on-off * Speaker &
thermal protection.

125) Stereo, 250W

200) Stereo, 400W

PRICES: 150W £49.99 250W £99.99
400W £109.95 P&P £2.00 EACH

SUPPLIED READY BUILT AND TESTED.

These modules now enjoy a world-wide reputation for quality, reliability and performance at a realistic price. Four
models are available to suit the needs of the professional and hobby market i.e. Industry, Leisure, Instrumental and Hi-Fi
etc. When comparing prices, NOTE that all models include toroidal power supply, integral heat sink, glass fibre P.C.B. and
drive circuits to power a compatible Vu meter. All models are open and short circuit proof.

THOUSANDS OF MODULES PURCHASED BY PROFESSIONAL USERS

OMP/MF 100 Mos-Fet Output power 110 watts
R.M.S. into 4 ohms, frequency response 1Hz - 100KHz
-3dB, Damping Factor >300, Slew Rate 45V/uS,
T.H.D. typical 0.002%, Input Sensitivity 500mV, S.N.R.
-110 dB. Size 300 x 123 x 60mm.
PRICE £40.85 + £3.50 P&P

OMP/MF 200 Mos-Fet Output power 200 watts
R.M.S. into 4 ohms, frequency response 1Hz - 100KHz
-3dB, Damping Factor >300, Slew Rate 50V/uS,
T.H.D. typical 0.001%, Input Sensitivity 500mV, S.N.R.
-110 dB. Size 300 x 155 x 100mm.

PRICE £64.35 + £4.00 P&P

OMP/MF 300 Mos-Fet Output power 300 watts
R.M.S. into 4 ohms, frequency response 1Hz - 100KHz
-3dB, Damping Factor >300, Slew Rate 60V/uS,
’» T.H.D. typical 0.001%, Input Sensitivity 500mV, S.N.R.
-110 dB. Size 330 x 175 x 100mm.

PRICE £81.75 + £5.00 P&P

OMP/MF 450 Mos-Fet Output power 450 watts
R.M.S. into 4 ohms, frequency response 1Hz - 100KHz
,-3dB, Damping Factor >300, Slew Rate 75V/uS,

T.H.D. typical 0.001%, Input Sensitivity 5}00mV, S.N.R.
-110 dB, Fan Cooled, D.C. Loudspeaker Protection, 2
Second Anti-Thump Delay. Size 385 x 210 x 105mm.
PRICE £132.85 + £5.00 P&P

OMP/MF 1000 Mos-Fet Output power 1000 watts
R.M.S. into 2 ohms, 725 watts R.M.S. into 4 ohms,
frequency response 1Hz - 100KHz -3dB, Damping
Factor >300, Slew Rate 75V/uS, T.H.D. typical
0.002%, Input Sensitivity 5}00mV, S.N.R. -110 dB, Fan
Cooled, D.C. Loudspeaker Protection, 2 Second
Anti-Thump Delay. Size 422 x 300 x 125mm.

PRICE £259.00 + £12.00 P&P

NOTE: MOS-FET MODULES ARE AVAILABLE IN TWO VERSIONS:
STANDARD - INPUT SENS 500mV, BAND WIDTH 100KHz.

PEC (PROFESSIONAL EQUIPMENT COMPATIBLE) - INPUT SENS
775mV, BAND WIDTH 50KHz. ORDER STANDARD OR PEC.

LARGE SELECTION OF SPECIALIST LOUDSPEAKERS
AVAILABLE, INCLUDING CABINET FITTINGS, SPEAKER
GRILLES, CROSS-OVERS AND HIGH POWER, HIGH
FREQUENCY BULLETS AND HORNS, LARGE (A4) S.A.E.
(60p STAMPED) FOR COMPLETE LIST.

McKenzie and Fane Loudspeakers are also available.

ALL EMINENCE UNITS 8 OHMS IMPEDANCE

8” 100 WATT R.M.S. ME8-100 GEN. PURPOSE, LEAD GUITAR, EXCELLENT MID, DISCO.

RES. FREQ. 72Hz, FREQ. RESP. TO 4KHz, SENS 97dB. PRICE £32.71 + £2.00 P&P
10” 100 WATT R.M.S. ME10-100 GUITAR, VOCAL, KEYBOARD, DISCO, EXCELLENT MID.

RES. FREQ. 71Hz, FREQ. RESP. TO 7KHz, SENS97<dB. PRICE £33.74 + £2.50 P&P
10” 200 WATT R.M.S. ME10-200 GUITAR, KEYB’D, DISCO, VOCAL, EXCELLENT HIGH POWER MID.
RES. FREQ. 65Hz, FREQ. RESP. TO 3.5KHz, SENS 99dB. PRICE £43.47 + £2.50 P&P
12” 100 WATT R.M.S. ME12-100LE GEN. PURPOSE, LEAD GUITAR, DISCO, STAGE MONITOR.
RES.FREQ. 49Hz, FREQ. RESP. TO 6KHz, SENS 100dB. PRICE £35.64 + £3.50 P&P
12” 100 WATT R.M.S. ME12-100LT (TWIN CONE) WIDE RESPONSE, P.A., VOCAL, STAGE
MONITOR. RES. FREQ 42Hz, FREQ. RESP. TO 10KHz, SENS 98dB. PRICE £36.67 + £3.50 P&P
12” 200 WATT R.M.S. ME12-200 GEN. PURPOSE, GUITAR, DISCO, VOCAL, EXCELLENT MID.

RES. FREQ. 58Hz, FREQ. RESP. TO 6KHz, SENS 98dB. PRICE £46.71 + £3.50 P&P
12” 300 WATT R.M.S ME12-300GP HIGH POWER BASS, LEAD GUITAR, KEYBOARD, DISCO ETC.
RES. FREQ. 47Hz, FREQ. RESP. TO 5KHz, SENS 103dB. PRICE £70.19 + £3.50 P&P
15” 200 WATT R.M.S. ME15-200 GEN. PURPOSE BASS, INCLUDING BASS GUITAR.

RES. FREQ. 46Hz, FREQ. RESP. TO 5KHz, SENS 99dB. PRICE £50.72 + £4.00 P&P
15” 300 WATT R.M.S. ME15-300 HIGH POWER BASS, INCLUDING BASS GUITAR.

RES. FREQ. 39Hz, FREQ. RESP. TO 3KHz, SENS 103dB. PRICE £73.34 + £4.00 P&P

ALL EARBENDER UNITS 8 OHMS (Except EB8-50 & EB10-50 which are dual impedance tapped @ 4 & 8 ohm)
BASS, SINGLE CONE, HIGH COMPLIANCE, ROLLED SURROUND

8” 50watt EB8-50 DUAL IMPEDENCE, TAPPED 4/8 OHM BASS, HI-FI, IN-CAR.

RES. FREQ. 40Hz, FREQ. RESP. TO 7KHz SENS 97cdB. PRICE £8.90 + £2.00 P&P
10” 50WATT EB10-50 DUAL IMPEDENCE, TAPPED 4/8 OHM BASS, HI-FI, IN-CAR.

RES. FREQ. 40Hz, FREQ. RESP. TO 5KHz, SENS. 99dB. PRICE £13.65 + £2.50 P&P
10” 100WATT EB10-100 BASS, HI-FI, STUDIO.

RES. FREQ. 35Hz, FREQ. RESP. TO 3KHz, SENS 96dB.

12” 100WATT EB12-100 BASS, STUDIO, HI-FI, EXCELLENT DISCO.
RES. FREQ. 26Hz, FREQ. RESP. TO 3 KHz, SENS 93dB. PRICE £42.12 + £3.50 P&P
FULL RANGE TWIN CONE, HIGH COMPLIANCE, ROLLED SURROUND

54" GOWATT EB5-60TC (TWIN CONE) HI-FI, MULTI-ARRAY DISCO ETC.
RES. FREQ. 63Hz, FREQ. RESP. TO 20KHz, SENS 92dB.

62" GOWATT EB6-60TC (TWIN CONE) HI-FI, MULTI-ARRAY DISCO ETC.
RES. FREQ. 38Hz, FREQ. RESP. TO 20KHz, SENS 94dB.

8” 6OWATT EB8-60TC (TWIN CONE) HI-FI, MILTI-ARRAY DISCO ETC.
RES. FREQ. 40Hz, FREQ. RESP. TO 18KHz, SENS 89dB. PRICE £12.99 + £1.50 P&P
10” GOWATT EB10-60TC (TWIN CONE) HI-FI, MULTI ARRAY DISCO ETC.

RES. FREQ. 35Hz, FREQ. RESP. TO 12KHz, SENS 98dB. PRICE £16.49 + £2.00 P&P

PRICE £30.39 + £3.50 P&P

PRICE £9.99 + £1.50 P&P
PRICE £10.99 + 1.50 P&P

PROVEN TRANSMITTER DESIGNS INCLUDING GLASS FIBRE
PRINTED CIRCUIT BOARD AND HIGH QUALITY COMPONENTS
COMPLETE WITH CIRCUIT AND INSTRUCTIONS

3W TRANSMITTER 80-108MHz, VARICAP CONTROLLED PROFESSIONAL

PERFORMANCE, RANGE UP TO 3 MILES, SIZE 38 x 123mm, SUPPLY 12V @ 0.5AMP.
PRICE £14.85 + £1.00 P&P

FM MICRO TRANSMITTER 100-108MHz, VARICAP TUNED, COMPLETE WITH

VERY SENS FET MIC, RANGE 100-300m, SIZE 56 x 46mm, SUPPLY 9V BATTERY.
PRICE £8.80 + £1.00 P&P

PHOTO: 3W FM TRANSMITTER

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with hundreds of Brand New
Products at Super Low Prices.

Available from all branches of WH SMITH, John Menzies in Scot
ONLY, Eason & Son in N. Ireland ONLY, and Maplin stores nationv

The Maplin Electronics 1995 Catalogue — OUT OF THIS WO