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CB RADIO
For A Dot
NEWS AND VIEWS INSIDE
Special featureon preparationsfor first flight
April 731ISSN 0142-6192
60p
To Electronics
can be used with other andspecial kit offer no circuit wiring
modulates your musictwo other projects for
you to build -see inside
chunks rtlarket is rapidly expanding. Whether it'siirient,accessitfities or .w hat have OU,
gincreaNingiv difticpo Leep up with the latestts. Or to get. them. Ai! ; ,
where we cottieiti. We ilintiahl\ 114le just i%11.11 vyn'reid a lot more hrsieles. We stoO*011,1.1.he top makes...will just make emi love us. SiniON phoni, i; i re of telex
. ,Y t.td.,io:4 High Street, Shepperton, 11ese RV r: 9 131
r England, Tel. Walton-on;Thames (sip 09.11241)43 and find out.
TON AHLERSELEKTRONIKA B.V.Aalsmeerderdijk 349, 1436 BH Rijsenhout -Holland, tel. 010 31 2977-2 86 11 (4 lines),telex 15181 tone! nl. (near Schiphol Airport ).
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Editor: Hugh Davies Assistant Editor Keith BrindleyDrawing Office Manager: Paul Edwards Group Art Editor: Paul Wilson -Patterson BA
Managing Editor: Ron Harris BSc
APRIL 1981Vol. 3 No. 6
FEATURES
PROJECTS
PRE -AMPLIFIERFirst part of a high fidelity sound system 11SUPER SIRENNoises galore 25DOORBELL MONITORWho's been knocking at your door? 32GUITAR TREMOLOUp and down - automatically 39SHORT CIRCUIT - READER'S DESIGNDirect Reading Ohmmeter 45RUSSIAN ROULETTE GAMEClick, click, click, click, click, bang 46WINDSCREEN WASHER ALARMA project for the motorist 53PCB FOIL PATTERNSTrack layouts for those who make their own PCBs 65
ANATOMY OF A SPACE SHUTTLEInner secrets of an outer -space ship 16* PROJECT DESIGN COMPETITIONYour chance to help the handicapped 22BUILDING SITEFrom hand-held toos to capacitor colour code 29* FAMOUS NAMESNew series, starting with Michael Faraday 35O LEVEL Q Et AA close look at transducers 49CLEVER DICKMore of your letters, picked from the postbagBREAKER ONE FOURLegal CB imminent? Preparations in advance
57
61
NEWS Et INFO
Monitor 6HE Next Month 8The HOBBY ELECTRONICS Bristol Exhibition 21* Oscilloscope Offer 43Back Numbers 45* Ni-Cad Cell Et Charger Offer 59Books From HE 60Subscriptions 63Hobbyprints 64Classified Ads 65
Advertisement Manager: Stephen Rowe Advertisement Representative: Sally HolleyCreative Director: Diego Rinc6nManaging Director: T. J. Connell
Hobby Electronics is normally published on the second Friday of the month prior to the cover date.Hobby Electronics, 145 Charing Cross Road, London WC2H OEE, 01-437 1002. Telex No. 8811896. Published by Modmags Ltd.
Distributed by Argus Press Sales Et Distribution Ltd, 1 2-1 8 Paul St., London EC2A 4JS. Printed by QB Ltd., Colchester. Covers printed byAlabaster Passmore.
Copyright: All material in this publication is subject to world-wide copyright protection. Permission to reproduce printed circuit board patternscommercially or marketing of kits of the projects must be sought from the Publisher. All reasonable care is taken in the preparation of the
magazine to ensure accuracy but Modmags cannot be held responsible for it legally. - Copyright 1981 Modmags Ltd ABC Member of AuditBureau of Circulation.
Hobby Electronics, April 1981 3
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The
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New
Pro
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Am
plif
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MO
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TC
HO
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PO
WE
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whe
n it
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vant
ageo
us to
hav
e a
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e, lo
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dis
tort
ion
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gher
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enh
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d th
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tabi
lity,
the
abili
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s ha
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her
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spec
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our
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MO
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Sign
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e
MonitorMiniature FlatScreen TVClive Sinclair, managing directorof Sinclair Research, announced inFebruary that his flat screen TVtube was about to go into produc-tion.
This tube, which is only about4" by 2" by Y." deep, will be in-corporated in a miniaturemonochrome set, combining FMradio.
The prototype receiver is onlyabout 6" by 4" by 1" , so it's trulypocket -sized. The productionmodel is expected to be on saleearly next year, at a cost of about£50. It is estimated that the set'sbatteries should give more than
15 hours viewing time.Research and development, in
conjunction with the NationalResearch and Development Cor-poration, has taken five years.
A total investment of £5m is tobe spread over four years up to1985. Phase one (up to 1982) willrequire £1.25m investment. TheScottish Economic PlanningDepartment will supply £1.5m,while £1.1m will be madeavailable from a Regional Develop-ment Grant. Sinclair Research is tosupply the remainder.
Production of the tubes andthe sets will start in 1982 inDundee, providing employmentfor an estimated 250 people in thefirst year. This figure could rise to1000 by 1985.
Guide to CBLanguageSmall enough to tuck into yourpocket (105 by 150 by 8 mm), CBin GB gives you a comprehensiveguide to CB slang.
Of course, until CB becomeslegal, it is doubtful whether more
6
--N
A glossary of British and Am- erican CB slang.
- Compiled by
Steve Braithwaite.
than (what is the latest estimate?)say, 800 000 people would find ause for it! But a least you can getsome practice with the lingo - ata cost of £2.20.
CB in GB was compiled bySteve Braithwaite, and is publish-ed by The Cherwell Press, 2 Sta-tion Field Industrial Estate, Kidl-ington, Oxford OX5 1JD.
'Is THAT YOU H1OUNPOG- PAREPREG-NANT R01-1-RScAETE
WITH THE yad-ow wRa 7'
'10 4 (AJILDC_AT, I TOST LAO
AN EYEBALL-- ON YA, YOUR IN
THE CAB OVER HEEL WITH
THE REFC-g. ON) C -HON./
!!!!!!! !!! !!!!!!!
£2.20
British Toy EtHobbyFair
So many toys and kits were ondisplay at the British Toy & HobbyFair, held at Earls Court, Londonbetween 31 January and 4February, that we couldn'tpossibly give a fair coverage insuch limited space. The interestfor HE, as you can imagine, was inelectronic games rather than cud-dly toys, two examples of thesegames being Split Second fromPalitoy and Milton from MiltonBradley.
Split Second incorporates a
LED display screen and provides avariety of maze games of varyingdegrees of difficulty. (These areespecially difficult when theobstacles are made invisible!) Itcosts around £37.50.
Milton is what is claimed to bea 'talking computer'. It beginswith: 'You've turned me on. I'mMilton - who's out there? Heehee hee - pick your play'. Andyou can select one of three wordgames for one or more players.Price is around f48.
More electronic toys will be in-cluded in next month's Gadgets,Games & Kits supplement.
HE Electronic OrganOn DisplayStarting next month in HE will bean exciting new project for you tobuild: a five -octave electronicorgan for under 1'100
A special demonstration of thisorgan has been arranged by theElectronic Organ Constructors
Society. It will take place at2.30 pm on Saturday 16 May at:
St. David's Church Hall,Lough Road,London N7
The nearest Underground stationis Caledonian Road (Piccadillyline): so don't miss this opportuni-ty to see and hear a project beforeyou build it.
Hobby Electronics, April 1981
Electronics News
Selectavision ForUnited StatesSelectavision - RCA's video discsystem - is due for its launch inthe US on 22 March 1981.(Details of the system were givenin View Into Video Discs, HEDecember 1980, pp 18 to 22.)
RCA gave a special presenta-tion to 5000 dealers throughoutthe US during February this year -using satellite transmission fromNew York.
Initial price for the system isestimated as being 'just belowS500'.
The CED (capacitance elec-tronic disc) can store a two hourprogramme (that is, 60minutes/side), but it is expectedthat average programme lengthwill be 90 minutes. Discs will costinitially between S15 to $25depending on programmematerial. A total of 100 titles willbe launched initially.
As mentioned in View IntoVideo Discs, the Selectavisionmachines will be for mono sound.But a stereo version is to be laun-ched in Europe during 1982. (TheJapanese will probably havestereo versions by this time too.)
A mono launch has been madein the US because there are nostereo TVs, most films are in monoand it has helped to keep the costof the system down.
We plan to take another look atvideo discs later this year, to keepyou informed of developments.
We've Had EnoughThat's it! We can't take anymore.
Our technical department is sooverloaded that we have had tomake the decision to call a halt totelephoned technical enquiries.However, our written technicalenquiry service is still operating.
But please remember, if youhave a project enquiry we can onlyanswer it if you send a SAE with it.
We cannot answer any queriesregarding modifications to ourdesigns.
Note For OurOverseas ReadersPayments for backnumbers,subscriptions, specials etc arriveat Modmags in an interestingvariety of forms.
We'd like to make it clear thatwe can only accept paymentsfrom overseas in one form: Sterl-ing Banker's Orders, madepayable to Modmags Ltd.
Not quite Electronics News,but it will help speed up our serviceto outside the UK.
Hobby Electronics, April 1981
Keeping Things TidyThree products from EdwardRoland's recently -introducedrange should help you keep yourelectronic components and oddsand ends in order: a multi -drawerstorage cabinet and 10- and14 -compartment cases.
Overall size of the cabinet is113/4" by 51/2" by 51/2 " , and itcontains 10 see-through drawersmounted in a dark brown cabinet.Cost is £7.75.
The 14 -compartment case is1 3% " by 91/2" by 2" , finished inbeige and has a clear lid with aclasp. It has various -sized com-partments. Cost is £5.75.
The smaller case (10/" by51/2" by 11/4" ( has 10 equal -sizedcompartments, a hinged lid and itcosts £2.40.
All the above prices includeVAT and post and packing in theUK.
Edward Roland Ltd., 215Putney Bridge Road, LondonSW15 2NY.
Important NoticeReaders have recently confusedElectronics Today Limited as beingassociated with the ownership ofour Magazine, Electronics TodayInternational. Our Magazine isowned by Modmags Limited, partof the Argus Press HoldingsLimited Group of Companies.
Electronics Today Limitedadvertises in our Magazine as"Metac", but so as to prevent anyfurther confusion we wish tomake it clear that Electronics To-day Limited is not owned ormanaged by any member of theArgus Press Holdings LimitedGroup of Companies.
ErrataAnd now for a compilation of theerrors arising in January's pro-jects.
In the Ladder -of -Light sound -into -light module there should be alink joining pins 6 Er 7 of IC 1 andthere should also be a track breakunder C5.
The Bench Amplifier has twofaults - the battery clip is shownreversed loops) and transistor Q1should be moved down one com-plete strip, ie it should mount intostrips E,F and G not D,E and F.
Finally, the Chuffer project suf-fered wrong numbering - the left-hand capacitor C9 in Fig.3 shouldin fact, be C8.
Another ThandarDigital MultimeterThe last Thandar DVM that welooked at in Monitor was theTM352, in the November 1980issue. (We compared the TM352with the TS1000 from Eagle Inter-national.)
Latest from the Thandar stableis the TM354 which, at £39.95plus VAT, is seen by Sinclair Elec-tronics as one of the lowest -pricedhand-held multimeters on themarket.
Main features are a 2000 hourbattery life and protection on all14 ranges. It has a 31/2 -digit LCDdisplay (0.5" characters) and issupplied with test prods and anABS case 155 by 75 by 30 mm.Weight is 165 g without batteries.It uses a 9 V alkaline battery (notsupplied). Diode check facility isincluded.
A brief specification is givenbelow:
Input impedance 10M (DC),4.5M (AC)
DC voltage 0 V to 1000 Vin four ranges
AC voltage 0 V to 500 V intwo ranges
DC current 0 mA to2000 mA infour ranges
Resistance OR to 2000k infour ranges
Accuracy Example:±0.75% of
reading + 1digit' on 2 V and20 VDC ranges
Further details from: Sinclair Elec-tronics, London Road, St Ives,Huntingdon, Cambs PE17 4HJ(tel. 0480 64646)
thor dor
DC v ACV- 4
7
1. NEXT MONTH. NEXT MONTH. NEXT MONTH. NEXT MONTH. NEXT MONT
EXTRA EXTRA - READ ALL ABOUT IT!Judging by the telephone queries and the reader responsewe get every time we publish articles on new electronicgames or gadgets, you obviously reckon that we are theundisputed experts on the subject (we don't disagree!).Well, starting from next month you'll get an added bonuswhenever you buy HE in the form of an 8 -page pull-outsupplement on the latest in gadgets, games - and kits.And we're calling it just that - Gadgets, Games & Kits.
In this new monthly feature we'll be covering all thelatest devices on the scene - we'll keep you right up todate on this rapidly moving area in electronics, with reports,tests and news.
ELECTRONICS IN MUSICALINSTRUMENTSWe invited Tim Orr to write this special feature on howelectronic instruments have made dramatic changesover the last few decades. He describes, for instance,the functions of active devices (valves, transistorsand ICs) during this time, and the impact of special-lised large-scale ICs. (The circuit of a complete musicalinstrument now can be contained in a handful of theseICs.) He also gives a round -up of some of the latestinstruments to hit the music world.
INFRA -RED CONTROLLEROur IR Controller project consists of two parts: a trans -miner which emits invisible beams of infra -red light and areceiver to detect them. Connect the receiver to any mains -powered electrical equipment, up to 500 W leg your hi-fi,TV, bedside lamp, etc) and you can switch them on and offremotely.
ELECTRONIC ORGANAt last! A home -constructor's dream come true - a cheap -to -build (under £100) five -octave organ!
It features a 2 watt monitor amplifier with headphoneoutput for home and private use, and a pre -amp output toplay it through a higher powered amplifier for concert use.Five voices and a tremolo effect are also included.Interwiring is kept to an absolute minimum and the fourcircuit boards have easy layouts. Don't miss it!
THE MAY ISSUE IS ONSALE APRIL 10th
PLUS PROJECTS:Things to do, things to build, test equipment, musicaleffects, etc, etc.
PLUS FEATURES:What to do when a transistor stops working, your very ownletters, constructional hints Et tips and theory.
PLUS, PLUS, PLUSNews, views, circuits, CB, all in next month's information -packed issue of Hobby Electronics - the magazine that'swritten for the electronics enthusiast and hobbyist.
Items mentioned here are those planned, but unforeseen circumstances may affect the actual contents.
8 Hobby Electronics, April 1981
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New from Casio, world leaders in creative technologycombined with high quality and reliability
A CLASSIC IN IT'S TIMEYou don't have to be a highbrow to appreciate the beauty of this clock. Batterypowered, it is ideal for office, lounge, bedroom, caravan or boat.
MA -1ALARMCLOCK
ONLY £9.95
Large blue LCD display of full digital time. Symphonic alarm or buzzer, withsnooze facility. Hourly time signal. Integral loudspeaker and amplifier with 3 -position volume control. Built-in night time illumination. Alarm: "Symphonie Nr.40 G moll" (W. A. Mozart, K.550) for about 30 seconds, or buzzer for 60 seconds.Three AA size batteries last approx. 15 months. Quartz accuracy. Dims: 43 x 115 x76mm 113/4 x 41/2 x 3 inches).
JOIN THE KEYBOARD REVOLUTIONBy closely analysing the natural sound variations in the waves and pitches ofdifferent instruments, Casio have been able to trace the characteristics peculiar toeach traditional instrument. Pitch, timbre and harmonics have been measured,digitalised and stored in electronic chip memory for faithful and exciting repro-duction of the clarity and beauty of the originals.
CASIOTONE 401
ONLY £295Fully polyphonic. 8 -note playing of 14 instruments and sounds over 4 octaves.Rhythm accompaniment. 16 different rhythms with full -in auto -rhythm.Casio Auto Chord. Allows one finger accompaniment. Just press one, two orthree keys and play major, minor and seventh chords, with bass accompaniment,automatically. Combines with auto -rhythm for professional sounds.Vibrato, delayed vibrato, sustain and hold are incorporated in the at -a -glance,simple to use operational panel. Pitch control makes group tuning easy.Compact 4% x 31% x 12% inches with integral amplifier and speaker. Thelightweight (28.21b.) allows playing anywhere there is an A.C. socket. Stand £39.
CASIOTONE 301The same size and basic specification as the 401 above, the 301 does not haveCasio Auto Chord or built-in sustain and hold facilities. There are 8 rhythm voiceswith a variation on each. Weight 271bs.
CASIOTONE MT -30£245
RRP £115.
ONLY £95Fully polyphonic playing of 22 instruments and sounds over 3 octaves, 4 -positionsound memory lets you switch between pre -selected sounds without pause.Built-in vibrato and sustain functions greatly enhance the overall musical effect.Compact 2%x 223/4 x 61/2 inches, with built-in amplifier and loudspeaker.Battery/mains power source and lightweight (61b.) allows playing anywhere.
CASIOTONE 201 and M-10Please telephone for availability.201. Mains version of the MT -30, 29 instruments over 4 octaves. £245.M-10. Four instruments over 21/2 octaves. Battery/mains. £69.
CASIO CALCULATORSBQ-1100 Biolator calculator, with calendar, two alarms, countdown alarm,stopwatch, time memory, three date memories (£17.951. £14.95.MG -880 Digital space invader game and calculator. £10.95.
SEND 20p (postage) for our illustrated catalogue of Casio watches and calculatorsand selected Seiko watches,
KEEP A DATE. WITH CASIOYo always wanted a musical calculator with date memories and date/time alarms- HERE IT IS!
UC-365 Universal Calendar
Clock, universal calendar, date memories, daily alarm, two daily or date/timealarms, hourly chimes, stopwatch, countdown alarm, time memory, calculator.Clock display: Hours, minutes, seconds, am/pm, or hours, minutes, full calendar.Calendar: Pre-programmed from 1901 to 2099. Full month display.Date memories: Any day or days pre-setable within 12 month period. (Birthdays,etc.).Alarms: Alarm 1 - Daily alarm. Alarm 2 & 3 - Daily alarms or time alarms onpre-set dates. (Pre-programmed melodies or electronic buzzer).Stopwatch: 1/10 second to 24 hours; net; lap and first and second place. OrTime memory: 24 -hour system. The time of any other zone can be stored.Calculator: Optional musical keys, full memory and percentage. Two silver oxidebatteries last approx. one year. RRP £22.95. 1/4 x 41/2 x 21/2 inches. Leatherettewallet with window.
UC-360. Card -sized version of above. 7/32 x 3%x 2%", £19.95.UC-3000. Office desk version. Angled display, 13/4 x 4 x 61/4'. £27.95
CASIO'S AMAZING NEW
FX-3500PProgrammable. Non-volatile memories and stores.Statistical regression and integrals.38 functional (non-volatile) steps, 2 programmestorage capability. Unconditional and conditionaljumps, 7 (non-volatile) memories, one indepen-dent, 6 constant memories, 18 pairs ofparentheses, nestable in 6 levels.61 built-in functions, including: Integrals (Simp-son's rule). Linear regression, logarithmic regres-sion, exponential regression and power regression.Hyperbolics, sexagesimal and co-ordinates conver-sions. 10 digit mantissa or 10+2 exponent. Twosilver oxide batteries give approximately 1,000hours' continuous use with power -saving auto-matic cut-off, with data and memory protection.Dims: 9/32 x 21/s x 51/4 inches. Supplied withleatherette wallet.
ALL THIS FOR ONLY £22.95
£19.95
FX180P. Hand held version without hyperbolics 2 x AA batteries, 3/4x3x57/s. £19.95FX-2700P. As FX3500P but 8+2; without integrals, regression, 1 program £19.95FX-8100 scientific with clock, calendar, alarm, chimes, stopwatch, etc. £24.95
CASIO'S BEST SELLING WATCHES
AA81 M1200 W1508
LCD ANALOGUE/DIGITAL ALARM CHRONOGRAPH, with countdown alarm.AA -81 chrome, s/s bracelet £29.95. AA -81G Gold-plated £49.95.AA -82. All -stainless steel, £39.95.12 -MELODY CHRONOGRAPHS with countdown alarm. M-12 resin case/strapf24.95. M-1200 all stainless steel £29.95.100 -METRE WATER RESISTANT Alarm chronographs with countdown alarm. W-100. Resin case/strap £19.95. W -150C Stainless steel case/resin strap £25.95. W-1506 Stainless steel case/bracelet 02.50.
NEW! F-500 sports chronograph. Resin case/strap E9.95.
Price includes VAT, P&P. Send yourcompany order, cheque, P.O. or phoneyour ACCESS or BARCLAYCARD
number to: TEMPUS Dept. H.E., FREEPOST, 164-167East Road, Cambridge CB1 1DB.
Tel: 0223 312866
10 Hobby Electronics, April 1 981
HE Hi-fi Amplifier System -1
Pre -amplifierHE HIGH PRECISION PRE -AMPLIFIER
basson
treble balance
stereo source phono
mono tape tuner
volume
The first part of an exciting new stereo amplifier system, this high quality pre -amplifieradds a new meaning to the term 'wireless'. Its one -board construction means that it iseasy to build with none of the wiring problems usually associated with audio projects
IT HAS BEEN over a year since welast published a high -quality stereoamplifier (5080 System, March1980). But even that system, goodas it is, does not compare with ourlatest amplifier, the first part of which(the pre -amplifier) is given here. In acouple of months' time, after we'vedealt with the pre -amplifier, thepower amplifier will be described.Either of these two units can be usedwith an existing system, so if yousimply wish to upgrade your presenthi-fi system with a higher quality pre-amplifier or power amplifier then thisis your chance. The power amplifieris also ideally suited as a high powerdisco amplifier. However, if you buildthe complete HE Amplifier you will berewarded with a low -distortion, low -noise (yet high -power - up to 100W per channel) stereo hi-fi amplifier.
Board With LifeFrom the photographs you can seethat the pre -amplifier is built totallyon one board. All switches, pots,input and output connectors and thepower supply are on this board,which means that there are nointerconnections which might causeinterference or wiring errors. Theboard is available with thecomponent layout printed onto it soyou shouldn't go wrong. You simply
Hobby Electronics, April 1981
line up each component from thecircuit diagram and insert it in itsmarked place on the board.
The pre -amplifier accepts inputsfrom the magnetic (phono) cartridgeof a record deck, a tuner or a taperecorder (cassette or reel-to-reel).Switch SW2 selects the onerequired. Stereo (two physicallyseparate channels) or mono mode(two channels with a common signal)is also selected by SW2. Bass, treble,balance and volume controls cater forindividual tonal and volumerequirements.
You Pays Your Money . . .
Designed around standard 8 -pinoperational amplifier ICs (op amps)the pre -amplifier will run happily onthe good old 741s. But, if you wantreally top -class performance then weadvise that you use the higher -qualityop amps with the numeric coding5534. These are, inevitably, moreexpensive but worth the difference ifyou can afford them. A suitablecompromise is to use 5534s for thephono input stage (IC1 and IC101)with 741 s as all other op amps. Thisis because the phono stage is a high -gain amplifier and any noiseintroduced by the op amp itself isthus amplified and made moreapparent.
ConstructionThe pre -amplifier board fromCapricorn Electronics is shown inFig. 1 and you can see that allcomponent positions are printed inwhite. So using either the board'scomponent markings or our ownoverlay shown in Fig. 6 . the PCB canbe built up. The following procedureapplies to our overlay.
Insert and solder the componentsof the power supply first (ie, R20, 21and 24, C25 to C30, IC4 and 5,SW1, the 100 mA fuse plus holder,BR1, and the link underneath thebody of C29). If you have atransformer which supplies ± 12VAC you should now connect it tothe input of the power supply and
Figure 1.The screened printed circuit board fromCapricorn Electronics
check, using a multimeter, that youhave ± 1 5 VDC at the output (ie,between the - 1 5 V rail and 0 Vthere should be a potential differenceof 1 5 V, and between 0 V and the+ 1 5 V rail also should be 1 5 V). Theboard at this stage is shown inFig. 2 .
L
Figure 2.
First constructional stage
FUSE 100mA
0I SW3IMAINS ON/OFF
120
120
Next, insert and solder all links, ICsockets and the input/output phonoconnectors, followed by the resistorsand capacitors for the rest of thecircuit. All tantalum capacitors mustbe polarised as shown in the overlay.
The bank of three push-buttonsignal switches (SW2) should besoldered into place, making sure thatit is flush to the surface of the board.Now, with a small file (a needle file isideal) carefully clean up the left-hand,outside edge of the switch bank sothat it can be soldered. Just to theleft of the switches is a solder pointand you should now insert and solder
DIN POWERSOCKETS
Figure 4. Circuit diagram of one channel+15V
PHONOI
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a short link between this point andthe switch body. This earthing of theswitch body will help shield againstinterference.
Put the four pots in next, but makesure they are squarely lined -up beforeyou solder them. Then, using yourfile, scrape a small notch in thecentre -top of the body of each pot, ofjust sufficient depth to remove theplating. Solder a length of tinned,single -strand wire along the top ofthe pots; that is, to the notchprepared on each one. Just to the leftof the Balance pot is a solder point onthe board and a link between thispoint and the wire over the potsshould now be made, again to help
Figure 3.Power supply circuit diagram
NOTE:LEFT-HAND CHANNEL COMPONENTSARE NUMBERED 101,102,etcIC1,2,3,101,102,103 ARE XR5534
OR NE5534
SW2
0
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MONO
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12 Hobby Electronics, April 1981
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Pre -amplifier
reduce interference.Finally, insert the six op amps into
their sockets and the board isfinished. The photograph in Fig. 5shows the completed board and youshould be able to see the earthinglinks to the pots and switch bank.That concludes the constructionalprocedure for this month. Nextmonth we describe the housing ofthe pre -amplifier and also give detailsof a suitable AC supply to run it.
Figure 5.A completed pre -amplifier board
TREBLE
R175k6
R1533k
C1847n
RV3100klin
R185k6
C171n5
RV4100klin
R1410k
C1947n
R131k5
+15v 0 C0022n
BASS1
8
4 C2322p
C21
-15V
R161k5
R1910OR
C2422u
OUTPUT TOPOWER AMPLIFIER
0V
Hobby Electronics, April 1981
O
BuylinesCapricorn Electronics, of 281 BalmoralDrive, Hayes. Middx. is offering a varietyof kits for the home constructor:
Blank, fully labelled PCB £12 PCB + switches, pots and
phono connectors £24 As above + all components
except op amps £39 XR/NE5534AN op amps
(6 off) f15
Undrilled case £12 Mains transformer, suitable to
power the pre -amplifier if you don'tintend to build the poweramplifier £4.50
Capricorn Electronics will supply a circuitdiagram and parts list with each kit ofparts.,
Please add £1.50 for p&p.
IA01
10 PCB MOUNTINGPHONO SOCKETS
r-
frEillViiiiWiefil,4LINE TAPE TAPE TUNEROUT OUT
55050IN
TAG !BOLTED TO PCBMOUNTING BOLT/
C29
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Figure 6. PCB overlay showing the positions of all components
5872
RV1
VOLUME
,c) Copyright MODMAGS Ltd.
13
Pre -amplifier
How It WorksThe main parts of an amplifier system are shown in Fig. 7 Theseseparate parts exist in any system, whether it is of modular construction(like ours) or in one case.
The pre -amplifier introduces voltage gain; ie, the output signalamplitude is larger than at the input. But it takes a large amount of powerto drive a loudspeaker (more than the pre -amplifier would be able tosupply) so the signal now has to undergo power gain via the poweramplifier.
RECORD 0
TUNER 0
TAPE IN 0
TAPE OUT 0,
Figure 7
PRE -AMPLIFIER
Figure 8 consists of a block diagram ofone channel of the HE Pre -amplifier andthis shows how the device can be brokendown into smaller sections.
Phono pre -amplifierThe output from the magnetic cartridgeof a record deck has not got what istermed a level response. In fact, thehigher frequencies (treble) have a muchgreater amplitude than the lower (bass)frequencies. The phono pre -amp includesan equalisation network to counteractthis amplitude difference and so itsoutput has a level response. The cartridgesignal is also amplified by this stage to asize similar to the signals from a tape deckor a tuner. Integrated circuit IC1 and itsassociated circuitry (IC101 for the otherchannel) provides the amplification andequalisation necessary, according to theRIAA (Record Industry Association ofAmerica) standard curve for record -playing equipment.
Input selection switchInput selection between phono, tunerand tape inputs and tape output is madeby switch SW2, and the chosen signal ispassed onto the tone control stage. Partof SW2 can be also used to directly
12
POWERSUPPLY
0 .15V
AC IN 0 0 0 OV
12 0 0 15V
TAPE O
OTAPE/TUNERIN
rRECORD DECKIPHON01 IN
INPUTSELECTORSWITCH
POWERAMPLIFIER
LOUDSPEAKER
© Copyright MODMAGS Ltd.
connect the two signals at this point sothat it functions as a stereo/mono switch.
Tone control stageThis stage consists of two op amps perchannel, the first of which, IC2 (IC102),is used as a buffer amplifier to produce ahigh -impedance input to match theoutput of a tuner, a tape player or thephono pre -amp. The buffer also has a lowoutput impedance suitable to drive thenext op amp circuit IC3 (IC103) whichhas a tone control network in its feedbackloop. The network is a standardarrangement providing bass and treblecontrol to suit individual listeningrequirements.
The power supplyMost op amp circuits (those in the HE Pre-amplifier being no exception) require athree -rail supply lie + V, 0 V, - V,) andthe power supply section uses twocommonly -available ICs to provide this.These integrated circuits need only asmoothed DC voltage at their inputs togive a stable, fixed output voltage. Anoff -board transformer provides the pre-amplifier with ± 17 VDC lie 12 V x 2).Integrated circuits IC4 and IC5 thenstabilise and regulate this voltage toexactly ± 15 VDC.
DC OUT
TONECONTROLNETWORK
PHONO PREAMPLIFIER IWITH RIAA
I EQUALIZATION
STEREO/MONO
TO OTHERCHANNEL
Figure 8
TONE CONTROL STAGE
0I OUTPUT To
POWERI AMPLIFIER
L- - -
c Copyright MODMAGS Ltd.
14
Parts ListRESISTORS *(All 3/4W, 5%)R1,101 47kR2,102,5,105 -IMOR3,103 1k2R4,104,7,107,10,110,24,124,25,125 100kR6,106 220kR9,109 22kR11,111,14,114 10kR12,112,13,113,16,116, 1k5R15,115 33kR17,117,18,118 5k6R19,119 100RR20,21 4k7R22,23 47RPOTENTIOMETERSRV1 50k logarithmic, dual
printed circuitmounting + 40 clicks
RV2,3,4 100k linear, dualprinted circuitmounting + centreclick
CAPACITORSC1,101,26,28 220n polycarbonateC2,102,16,116,24,124 22u, 16 V tantalumC3,103 750p polystyreneC4,104 3n3 polystyreneC5,105,7,107,9,109,10,110,11,111,13,113,15,115,20,120 10u, 16 V tantalumC6,106,8,108,12,112,14,114,21,121,22,122 100n polycarbonateC17,117 1 n5 polystyreneC18,118,19,119C23,123C25,125C27,31C29,30
47n polycarbonate22p polystyrene270p polystyrene470n polycarbonate1000u, 25 Velectrolytic
SEMICONDUCTORSIC1,2,3,101,102,103 NE5534 or XR5534
(see text)IC4 7815, voltage
regulatorIC5 7915, voltage
regulatorBR1 1A, 250 V bridge
rectifierLED1 red LEDMISCELLANEOUSSW1 double -pole, double -
throw, printed circuitmounting push switch
SW2 bank of three double -pole, double -throw,signal push switches
10 printed circuit mounting phonoconnectorsPrinted circuit mounting fuseholder +100 mA fuse 4 knobs to suitCase to suit (see Buylines)5 -pin DIN socket
*Note: in the series R1 to R25(channel 1) there is no R8. In the seriesR101 to R125 (channel 21 there is noR121 orR122
Hobby Electronics, April 1981
TTLA by TEXAS 741790111411111.1.110115
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SUPPORT DEVICES324232456522
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BOOKS by TEXASINSTRUMENTS
TTL Data Book (700 pages) ECM,Power Semiconductor Data Book (600pages) £4.50Linear Control Data Book (368 pages)
E3.00Software Design for Microprocessors1400 pages) E 1 1.00The Great Intl Maths on Keys (208pages) £3.50Understanding Microprocessors (240pages) E3.50Understanding Solid State Electronics1240 pages) E3.60
9000450p600p825p375p340p£16
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HEAT SINKSFor 10220 VP,age Regs andTransistors 22pFor T05 12p
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LOW PROFILE DIL SOCKETS BY TEXAS
8 P. 10 18P^ 1811 24 pn 24p14 pn 500 20 pn 206 28 pin 30p16 pn 1 1p 22 pn 22p 40 pn 46p
MODULATORS6MHz UHF 3748MHz UHF 450p
ZEROINSERTIONFORCE SILT24 Pin 47_
WIRE WRAP SOCKETS BY TEXAS8 pn 25p. 18 pn 50p 24 pn 70p
14 pin 35p 20 pn 60p 28 pn 80p16 pin 40p 22 pn 615p 40 pin 1000
HEADERPLUGS14 pin 50016 pin 60p24 pin 100p40 pin 275p
SOFTY: Ideal Software' Hardware Development tool.Using SOFTY you can develop your Programmes, De-bug/Verify and then commit them to EPROMKIT £100 BUILT AND TESTED E125Also available Expansion Board for Programmingsingle rail (+ 5v) EPROMS. Ready built £40MINI FLOPPY DISC DRIVE MECHANISM: TeaCType FD -50,4 40 track 5r%" Double/ Single Densitydrives E140FLOPPY DISC CONTROLLER: 001771 £24,FD1791 EBB, FD1691 CIS, 2143 E5.50.EPROM ERASERS: Type UV140. Will erase up to14 EPROMS in approx. 20 mins. Has slide -in tray forsafe use. MAINS and ERASE Indicators £61.50
NANOCOMP MICROPROCESSOR TRAINER. As de-scribed in WW. January 1981. A complete kit of partsavailable (secluding PCB and the case). The kit includespre-programmed 2716, sockets for all ICs and PSU parts aswell. Price E84 Inc VAT and P&P.
VEROBOARD5 0 1(copper dad)
2 5x 3 75" 65p75x5" 75p3 750 3 75" 75p3 758 5" 86p3 75017" 340p4 75017 9" 420pPkt of 100 per 50pSpot face cutter 86pPin insertion tool 118pVero Wiring Pen
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ANATOMY OF ASPACE SHUTTLE
As the dawn of a new Space Age approaches, Ian Graham reports on the fortunes ofthe first true spacecraft - the Space Shuttle
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ONCE UPON A TIME in wartime Ger-many, a number of brilliant rocketengineers developed the concept of thelong-range rocket. Von Braun's V-2 wasnot an end in itself, but merely the beginn-ing of a series of military rockets. Therewere plans afoot to upgrade the V-2 andmake provision for a pilot. It would havetaken off like a rocket and landed like aglider on an air strip. It might have beenlaunched atop a powerful booster rocket.That early idea on a drawing board is nolonger a fairy tale.
First Steps To SpaceIn the early 1950s the Bell Aircraft Cor-poration, whose X -craft had providedinvaluable experience in high speed,high altitude flight in the atmosphere,produced an interesting design - theBell Bomi. The Bomi was a two stagecraft featuring a winged booster and asmall piggy -back upper stage. Similardesign ideas appeared at about thesame time from a number of Europeanaircraft manufacturers and researchestablishments. One design proposedby the Boeing Corporation and commis-sioned by the USAF was axed in 1963before construction could begin.
In the mid -1960s several liftingbodies were flown from B-52 bombers.The lifting body was an attempt to solvethe re-entry paradox. Conventionalvehicles capable of flying in the at-mosphere and coming down to a con-trolled landing have wings andtailplanes which would burn off duringre-entry. However, blunt -nosedvehicles, which can withstand the heatof re-entry are relatively un-manoeuverable in the atmosphere. Thestubby wingless wedge-shaped liftingbody was a compromise between thetwo. A series of these vehicles wereflown right up to 1975.
Birth Of An EnterpriseThe present Space Shuttle projectbegan in 1968 with NASA's official
Hobby Electronics, April 1981
Enterprise is rolled out onto the tarmac - minus the aerodynamic cover which normally covered its engines for atmospheric test flights
adoption of the programme. The initialdesign proposal was ambitious andlacked flexibility. By the beginning ofthe 1970s it was clear that a complete-ly re -usable Shuttle system would notbe funded by the White House. To bringthe project within the cash limits set,the designers proposed that the SpaceShuttle Orbiter would be launched witha huge external fuel tank instead of amanned Booster. This also allowed thesize of the Orbiter to be reduced,because much of its fuel would be car-ried externally.
In comparison with the ambitiousdesigns that had come and gone withcontracting budgets, the configurationfinally adopted may seem to be arelatively low technology solution. Infact, nothing could be further from thetruth. The Space Shuttle is undoubtedlythe most complex project yet under-taken by NASA and its contractors.
Powerful ProblemsThe power and re-entry problems calledfor revolutionary solutions. Power issupplied by three main enginesmounted in a cluster immediatelybeneath the rear tailplane. They burn li-quid hydrogen and oxygen at a veryhigh pressure. Their thrust -to weightratio -is the highest of any engine yetdeveloped, although at just over 4 m talleach is smaller than the F-1 engine usedin the Saturn V first stage. The thrust isvariable from 65 to 109% of ratedpower to keep acceleration within com-fortable limits for different payloads.They're also responsible fcr steering thecraft. Each engine can swivel 10.5° upand down and 8.5° side to side.
Hobby Electronics, April 1981
Unlike earlier engines, the fuel is notsimply pumped into a combustionchamber and burnt. The Shuttle mainengines employ a two stage cycle. Thefuel is only partly burnt at lowtemperature and high pressure and thencompletely burnt in the main combus-tion chamber. This is about 99% effi-cient.
Cost CuttingIt's not an exaggeration to say that theShuttle main engine has broken newground in space propulsion. The enginedevelopment has been fraught withtechnical problems from the beginning.To cut costs, NASA departed from its
HRSI
LRSI
FRSI
erjoi4. .4110..
HRSI
RCC HRSIRCC
HRSI
HRSI
!eller LOWER SURFACE
UPPER SURFACE r-7-79FRSI
HRSI
RCC
LRSI
LRSI
HRSI
Fig. 1 The Space Shuttle's thermal protection system RCC - re-inforced carbon -carbon; HRSI - high temperature, re -usable surface insulation; LRSI - lowtemperature, re -usable surface insulation; FRSI - coated Nomex felt, re -usable surfaceinsulation. The carbon nose must withstand a temperature of over 1200°C again andagain, flight after flight. The leading edges of the wings reach almost 1400°C
17
The test craft 'Enterprise' made its first flight from the back of a NASA 747. The aft section was covered by an aerodynamic shroud as thiswas an unpowered glide test
A Lockheed technician examines some of the odd -shaped silica tiles that will shield theSpace Shuttle during re-entry. Each tile is carefully milled on the underside to match thecontour of the particular spot it will cover on the Shuttle. For this reason, no two tiles areexactly alike. The tiles are made in two forms - LI-900 (Lockheed Insulation, 9 pounds percubic foot) and LI-2200 (22 pounds per cubic foot). Lockheed Missiles and SpaceCompany manufactured more that 24,000 tiles for the Shuttle at its plant in Sunnyvale,California
18
usual practice of proving every in-dividual component on the test bedbefore building it into the workingsystem. Consequently, when fuel linessplit or valves blew, these otherwiseminor failures resulted in major (and ex-pensive) engine damage. In short, theengines blew up. There were a numberof serious fires. When a simplehydrogen nozzle broke, the interior ofone engine was sprayed with burninghydrogen, reducing it to an expensivemolten scrap heap.
In the silence of space the SpaceShuttle is manoeuvred, not by the mainengines, but by two orbital manoeuvr-ing engines (mounted above the mainengine cluster) and some 46 smallrockets mounted in the nose and tail.
Internal power is provided by two in-dependent electrical and hydraulicsystems. Hydraulic power for move-ment of the control surfaces, landinggear, etc. is provided by hydrazine -powered gas turbines. Electrical power(14 to 36 kW) is supplied by conven-tional hydrogen/oxygen fuel cells, pro-ducing drinking water as a by-product.
A Telling TileOnce the craft is in orbit, the next pro-blem is to get it back to Earth in onepiece. All spacecraft until the SpaceShuttle had been fitted with heatshields which could only be used once- obviously unsuitable for use on a re-usable spacecraft. The one-shot resinmixture melted and boiled, dissipating17000 C or so.
The Shuttle's thermal protectionsystem uses a number of differentmaterials ranging from a fire -proof felton part of the upper surface to the nowfamous (or infamous?) ceramic tiles.Although there are over 30,000 tiles,
Hobby Electronics, April 1981
ANATOMY OF A SPACE SHUTTLE
no two are identical. They are differentshapes and sizes designed to cling tothe subtly curved skin of the spacecraft.The main problem here was that theydid not cling to the skin. In fact, whenthe Shuttle was carried from the WestCoast to Cape Canaveral on the back ofa 747 jetplane, a total of 7,500 tileswere damaged, many of them comingaway from the skin altogether. It wasfound that, not only were the tilesthemselves mechanically too weak, butalso the method used to stick them tothe skin was not up to the job. Thisdiscovery resulted in round-the-clockwork at the Cape to re -treat, re -installand test thousands of tiles before theShuttle (named Columbia) was rolledout at the beginning of January.
Orbital TrialsUntil now, all spacecraft intended formanned operation have undergone un-manned trials to prove the system.However, Columbia's first orbital flightwill carry Commander John Young andCo-pilot Robert Crippen, so the systemhas to work first time. The test craft,'Enterprise' named after the 'Star Trek'starship, has been flown in the at-mosphere, but the complex corn-puterised re-entry navigational and con-trol programmes have only been tried insimulation.
Flight PlanBefore lift-off, the Shuttle is strapped toits external tank and two solid -fuel re-usable boosters (SRBs). It is mountedend -on on the launch pad and blasts offin the familiar way. At 44,200 m theSRBs fall away and are recovered fromthe ocean to be used again for about 20flights. The Orbiter continues to burnfuel from the external tank until justbefore it reaches orbit. The tank is thenjettisoned and breaks up in the at-mosphere.
The first mission will last little morethan two days - 54 hours, in fact.Then the Orbiter will head towardsEarth again at 14,000 MPH. Once backin the atmosphere, it will glide down to aone -and -only chance for a landing.Earlier plans had called for in -board jetengines for powered landing, but theywere axed to save money. The multi-million dollar Space Shuttle will land likean 80 -ton glider. Young and Crippenhave to get it right first time.
The Last DaysAt the time of writing, there are stillhurdles to overcome before launch. Theexternal tank has to be fuelled with atotal of over half a million gallons of li-
Hobby Electronics, April 1981
NASA's Space Telescope will be placed in orbit by the Space Shuttle in the 1980s.Lockheed Missiles and Space Company are building the basic structure for the gigantictelescope - the Support Systems Module. Operating well above any interference from theEarth's atmosphere, the telescope will be able to look seven times deeper into the heavensthan ground -based instruments. It will be able to see objects 50 times fainter and viewthem with a clarity 10 times better than ever before. Once in space, the telescope will beable to lock onto celestial objects with absolute accuracy for as long as 30 to 40 hours
quid hydrogen and oxygen. It remainsto be seen how the structure will reactto such low temperatures. The mainengines are to be fired before the bigday. It will be the first 20 -second firingof all three engines together.
Clouds On The Horizon?So, things can still go wrong even at thislate stage. It's difficult not to see cloudson the Shuttle horizon. The launch datehas been put back time and time againand the project has gone millions ofdollars over budget. But now it's on thelaunch pad on the last lap of its Earth-bound existence. It has been hailed asthe first true spacecraft, opening theway for the industrialisation of space.Many of the ambitious suggestions forelaborate space stations built frommaterials carried up into orbit by theShuttle are undoubtedly still far in thefuture - technically possible today butprohibitively expensive. However,when the Shuttle goes operational(planned for 1982) it will have provedits prime function of flying again and
again to orbit and back. It will be used asa launch platform for satellites, aresearch platform (three scientists canbe carried in addition to a crew, of four)and a repair and maintenance stationfor craft already in orbit. If it is shown tobe cost-effective to the commercialcommunity, its guaranteed flightschedule and flexible operational poten-tial are sure to be exploited. The granderplans, however, will have to remain onthe drawing board until there is an up-turn in the world economy or untilspaceflight again becomes feasible ornecessary to national security.
I have no doubt that if the rumouredSoviet Space Shuttle were to bephotographed on the launch pad, theflow of money from Washington toNASA would increase. The decisionswhich determine space project budgetsare inevitably influenced by anamalgam of constantly changing fac-tors - general economic trends, thepriorities of central government, na-tional prestige, national security, cost-effectiveness: the list is almost as in-finite as outer space itself. HE
19
MAGENTA ELECTRONICS LTD.H.E. PROJECT KITS
Make us your No. 1 SUPPLIER OF KITS and COMPO-NENTS for H.E. Projects. We supply carefully selectedsets of parts to enable you to construct H.E. projects. Kitsinclude ALL THE ELECTRONICS AND HARDWARENEEDED. Printed circuit boards (fully etched, drilled androller tinned) or veroboard are, of course, included asspecified in the original article, we even include nuts,screws and I.C. sockets. PRICES INCLUDE CASES unlessotherwise stated. BATTERIES ARE NOT INCLUDED.COMPONENT SHEET INCLUDED. If you do not have theissue of H.E. which includes the project - you will needto order the Instruction reprint as an extra 45p each.
PUBLIC ADDRESS AMPLIFIER, Mar'81 £16.56Extras - horn speakers £6.83 eachPA mic £4.40
FUZZBOX, Mar'81 £9.41WINDSCREEN WIPER CONTROLLER, Mar '81 £6.98STEAM LOCO WHISTLE, Mar'81 £11.15PHOTOGRAPHIC TIMER, Mar '81 £2.99HEARTBEAT MONITOR, Feb '81 £21.28HIGH IMPEDANCE VOLTMETER, Feb '81 £8.98AUDIO SIGNAL GENERATOR, Feb'81 £17.21BACKGRUND NOISE SIMULATOR, Feb'81 £6.43TWO-TONE TRAIN HORN, Feb '81 £4.77 less caseMEDIUM WAVE RADIO, Feb '81 £6.98BENCH AMP, Jan '81 £9.19NICARD CHARGER, Jan '81 £6.98CHUFFER, Jan '81, less case £6.44CAR REV COUNTER, Jan 81, less case £21.20
Case extra £5.98DIGITAL SPEEDO, Dec. '80 £35.89MODEL TRAIN CONTROLLER, Dec. '80 £16.86BATTERY CHARGE MONITOR, Dec.'80 £4.91JACK LEAD TESTER, Dec. '80 £1.99STEREO POWER METER, Dec. '80 £18.98PARTY GRENADE, Nov '80 £7.98TRANSISTOR TESTER, Nov '80 £5.57 inc. test leadsDOUBLE DICE, Nov '80 £13.80GUITAR PRE -AMP, Nov 80 £5.65 case (diecast) extra £2.99BATTERY ELIMINATOR, Nov '80 £14.88NOBELL DOORBELL, Oct. '80 £11.98INTRUDER ALARM, Oct. '80 £17.83FREEZER ALARM, Oct. '80 with probe £9.42TUG 0' WAR, Oct. '80 £16.98KITCHEN TIMER, Oct. '80 (2% resistors) £7.34MICROMIX, Sept. '80 £7.82AUTO PROBE, Sept. '80 £3.67 less caseTOUCH SWITCH, Sept. '80 £2.34 less case & contactsGUITAR PHASER, Sept. '80 £13.84BENCH PSU, Sept. '80 £28.50EQUITONE CAR EQUALISER, Aug. '80 £14.98OP AMP CHECKER, Aug. '80 £4.55MOVEMENT ALARM, Aug. '80 £5.68RADIO TIMER, Aug. '80 £6.98PASS THE LOOP GAME, Aug. '80 £13.98SOUND OPERATED FLASH TRIGGER, July '80, no skt £4.5918W+ 18W CAR STEREO BOOSTER, July'80 £29.98 (stereo)FOG HORN, June '80 £5.655080 PRE -AMP, May '80 £39.98SPEED CONTROLLER FOR FIX, April '80 £14.92 less caseDIGITAL FREQUENCY METER, April '80 £35.78HOBBYCOM: TWO WIRE INTERCOM, April '80 £33.95 (Master)
Sub Station £3.38 eachELECTRONIC IGNITION (CD), April '80 £20.87WIN INDICATOR, Feb. '80 (with switches) £13.92DIGI-DICE, Jan. '80 £9.98BARGRAPH CAR VOLTMETER, Dec. '79 £7.33 less caseRING MODULATOR, Dec. '79 £12.95GUITAR TUNER, Nov. '79 £10.98HOBBYTUNE, Oct. '79 £26.98ANALOGUE FREQUENCY METER, Oct. '79 £15.52MULTI -OPTION SIREN, Oct. '79 £15.98STARBURST, Sept. '79 £19.98 less caseULTRASONIC SWITCH, Sept. '79 .... £28.85 less 3 pin mains socketHOME SECURITY UNIT, Aug. '79 £28.56 less sirenSIREN £5.09 less caseLED TACHOMETER, Aug. '79 £17.98INJECTOR TRACER, Aug. '79 £4.34CONSTANT VOLUME AMPLIFIER, Aug. '79 £15.60LINEAR SCALE OHMMETER, July'79 £15.98SHARK, July'79 £25.98GSR MONITOR, June '79 £9.63ENVELOPE GENERATOR, June '79 £14.98WHITE NOISE EFFECTS UNIT, May '79 £17.74TRANSISTOR GAIN TESTER, April '79 £9.98PHOTOGRAPHIC TIMER, Mar. '79 £16.45CAR ALARM, Feb. '79 £10.98SCRATCH/RUMBLE FILTER, Feb. '79 £25.48 Mono
£29.98 StereoPUSH BUTTON DICE, Dec. '78 £6.98
80/81 ELECTRONICS CATALOGUEKITSICs
TRANSISTORSCAPACITORS
0
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P
R
CE
S
NCL
UDE
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AT
MM.HAX,,,CARO.1=1=0)
14c' a slit
Hundreds of illustrations, product data, circuitsand details of all our kits and educationalcourses. Up to date price list included, All pro-ducts are stock lines for fast delivery.Send 70p in stamps for your copy 17 x 10p or 5x 14p).
TOOLSRESISTORSHARDWARE
CASES
ADVENTURES WITH ELECTRONICSAn easy to follow book suitable for all ages, ideal for beginners. No Soldering.Uses an 'S Dec' breadboard. Gives clear instructions with lots of pictures. 16projects - including three radios, siren, metronome, organ, intercom, timer, etc.Helps you learn about electronic components and how circuits work. Componentpack includes an S Dec and the components for the projects.Adventures With Electronics £1.90.Component pack £16.72 less battery.
ADVENTURE WITHMICROELECTRONICS
Same style as above book. 11 projects based on integrated circuits - includesdice, two-tone doorbell, electronic organ, MW/LW radio, reaction timer, etc.Component pack includes Bimboard 1 plug-in breadboard and the componentsfor the projects.Adventures with Microelectronics £2.35Component pack £27.95 less battery.
H.E.LADDER OF LIGHT,JAN.'81Complete kit for this novel project includes all components and case for thecontrol module.10 individual outputsEXTRA included with our kit only: additional circuit and components forstrobe and chase features. LADDER OF LIGHT, JAN '81 £29.98 + 40p p&p.
H.E. MEMORY BANK -SYNTHESISER NOV. '80
Complete kit for this exciting project, includes i.c. with socket, 2 pcbs, caseetc. The custom designed i.c. at the heart of this project generates musicalsounds which can be stored in its own memory. Features include memoryerase, vibrato, speed and depth controls, variable pitch, chord and tremeloetc.'Synthesiser' Nov. '80 + Dec.'80 E33.95
.INTO DIGITAL ELECTRONICCurrent H.E. series Part 1 in Sept. '80. Covers digital electronics from the basics.Circuits are built on a plug-in Eurobreadboard. Reprints of back issues available45p each. Eurobreadboard and components for series £18.95 less battery. Com-ponents only £12.75.
INTO ELECTRONICS CONSTRUCTIONH.E. 6 -part Series: Feb. '80 to July'80. COVERS THE BASICS OF ELECTRONICS -LOTS OF PRACTICAL WORK. Circuits are built on a plug-in Eurobreadboard.REPRINTS AVAILABLE, 45p each part. Eurobreadboard and Components forSeries £15.63. Components only £9.43.
TOWERS INTERNATIONAL TRANSISTORSELECTOR E10.50.ANTEX SOLDERING IRON 25W £4.98.SOLDERING IRON STAND £1.98.SPARE BITS. Small, standard, large 65p each.SOLDER. Handy size 98p.EUROBREADBOARD £6.20.LOW COST LONG NOSE PLIERS 51.68.LOW COST CUTTERS £1.69.P.C.B. ASSEMBLY JIG £11.98.P.C.B. ETCHING KIT E4.98.AM -FM AIRCRAFT BAND PORTABLE RADIO£8.98.WIRE STRIPPERS AND CUTTERS £2.48.MULTIMETER TYPE 1. 1,000 o.p.v. withprobes 2" x 31,3" x 1" £6.66.MULTIMETER TYPE 2. 20.000 o.p.v. withprobes 5" x 31/2" x 11/4" £11.52.TELEPHONE PICK-UP COIL 72p.CRYSTAL MICROPHONE INSERT 58p.SPEAKERS MINIATURE, 8 ohm 87p. 64 ohm 98p. 80 ohm £1.56.PILLOW SPEAKER, 8 ohm 98p.EARPIECES. Crystal 65p. Magnetic 18p.MONO HEADPHONES. 2K Padded. Superiorsensitive 1218.HEAT SINK TWEEZERS 15p.
3 BAND S.W. RADIOSimple T.R.F. Design. Covering most Ama-teur Bands and Short Wave BroadcastBands. Five controls. Bandset, BandspreadReaction. Wavechange and Attenuater. Coilsection is by Wavechange Switch. Use withHeadphones or a Crystal earpiece. Kit con-tains all the components required includingthe P.C. Board and Case. Instructions areIncluded with this kit.KIT 818.97. Headphone extra £2.98.
SOLDER BOBBIN 30p.DESOLDER PUMP £5.98.CROC CLIP TEST LEAD SET. 10 leads with 20clips 99p.CONNECTING WIRE PACK. 5 x 5 yd. coils 65p.VERO SPOT FACE CUTTER £1.21.RESISTOR COLOUR CODE CALCULATOR 21p.STEREO HEADPHONES. 6 ohm. Padded£4.35.DESOLDERING BRAID 89p.
MAGENTA ELECTRONICS LTD.HG8, 98 CALAIS ROAD, BURTON -ON -TRENT, STAFFS, DE13OUL. 0283-65435. 9-12, 2-5 MON.-FRI. MAIL ORDER ONLYADD 40p P&P. TO ALL ORDERS. ALL PRICES INCLUDE 15% V.A.T. OFFICIAL ORDERS FROMSCHOOLS ETC. WELCOME.ENQUIRIES MUST INCLUDE S.A.E.OVERSEAS: SEND ORDER WITH 3 INTERNATIONAL POSTAL COUPONS WE WILL QUOTEEXACT PRICE BY AIR MAIL.EIRE & BFPO ORDERSU.K. PRICES - LESS 10',(COVERS V.A.T. REFUND & EXPORT DOCUMENTS). PAYMENT: STERLING U.K. BANK DRAFT,U.K POSTAL ORDERS or U K CHEQUE.ENQUIRIES: ENCLOSE 2 INTERNATIONAL POSTAL COUPONS.
20 Hobby Electronics, April 1981
B RISTOL
CENTREEXHIBITION,
B RISTOL
0 CENTREEXHIBITION,
B RISTOLEXHIBITIONCENTRE
COMPUTERS AUDIO* RADIO* MUSIC LOGIC COMPONENTS CB
HOBBY ELECTRONICS GOES WESTLondon has more than its fair share of electronics shows, but we know that
electronics enthusiasts are by no means limited to the capital. For that reason thefirst annual Hobby Electronics Show is to be held in Bristol - centre of the
South-West.
What's to see there? major electronics component suppliers
special exhibition offers Wales Et West schools' electronic project competition (*has your school
submitted an entry yet? Available from Hobby Electronics 81)TICKETS - at the door - ADULT : £1.00. CHILD, STUDENT, OAP : 50p.
GAMES KITS TEST GEAR MAGAZINES SPECIAL OFFERS BOOKSOPEN DAYS :
Friday May 29th : 10am - 7pm Saturday May 30th :.10am - 6pm Sunday May 31st : 10am - 4pm
B RISTOLEXHIBITION rCENTRE
COMPETITION ( .01\0Project Design forthe InternationalYear of Disabled PersonsCould YOU design an electronic aid for a disabled person? If you can then you could wina first prize of £200 cash
1981 has been designated theInternational Year of DisabledPersons, and HE is running acompetition to enable itsreaders to submit their designsfor electronic aids for thedisabled.
We place no restrictions onthe area of electronics that youwish to use: transistors,integrated circuits, valves (if it isimpossible for semiconductorsto do the job!),electromechanical aids(electronically controlled),computer programmes - thechoice is yours.
The only restriction we placeon entries is that ofORIGINALITY: the design mustbe original or an originaladaptation that has not beenpublished or marketed.
No Design Is Too Small, Entries can be as simple or as
complex as you like, but weenvisage that the winningentries will be ingenioussolutions to a problem orproblems encountered by adisabled person rather than anenormous (and expensive) boxof tricks.
22
We will, if necessary,segregate designs into 'classesof complexity' or specific types.We may also make someallowance for the age of theentrant (say for those receivedfrom entrants under 18).
First Prize £200 cash
Second Prize Kikusui 538Aoscilloscope
PLUS Three runners-upprizes
Closing date for the competitionis 31 July 1981 - so you haveplenty of time to get designing!No correspondence will beentered into after this closingdate.
As a guide, set out yourdesign along the lines of an HEproject - we will publish thewinning designs.
Send your design to:Project Design Competition,Hobby Electronics,145 Charing Cross Road,LONDON WC2H OEE
AND include with it thefollowing:
the completed entry form(see below)
written details of yourdesign & drawings or black -and -white photographs
suitable -sized stampedaddressed envelope (if youwish to have yourmaterial returned)
If your design is 'boxed' orbreadboarded, keep it intactuntil two weeks after theclosing date: if you haven'theard from us by then you canassume that your design is notamong the winning entries (adaytime telephone numberwould be very helpful).
rPROJECT DESIGN COMPETITION...ENTRY FORM iII certify that my design, to the best of myl'knowledge, is original and has never been""offered for publication or manufacture I'Signature IIN II CAPITALS) 111
'Address I'(CAPITALS) I
II I111
:Daytime tel.no
'Project titleMom No NE mimmssimiimmsmmosim
Hobby Electronics, April 1981
The Winner
Here we see Anthony Clarke, of Spondon, Derby, receiving the first prize in our Electronic Games Competition (HE
January 1981) from Jim Connell, managing director of Modmags Ltd. The prize was a Rowtron programmable TV game,
with an assortment of games cartridges.
SECOND -PRIZE WINNER Jeff Jones, of Risca, Gwent, received a hand-held Jet Fighters game (Computer Games Ltd.)
instead of the Space Invader game from Entex. (Our Space Invader game vanished!)
" RANKLY RAWLINGS -BIT TOO UPMARKET FOR us ...-
23Hobby Electronics, April 1981
GUITAR PHASER ZD85 Sept. '80 £9.60 HOBBYTUNE Z034 Oct. '79 £18.00BENCH POWER SUPPLY UNIT ZD87 Sept. '80 £25.00 MULTI OPTION SIREN ZD36 Oct. '79 £10.50DEVELOPMENT TIMER ZD86 Sept. '80 £8.75 ANALOGUE AUDIOTOUCH SWITCH (on Vero) Z084 Sept. '80 £4.50 FREQUENCY METER ZD35 Oct. '79 £15.00AUTO PROBE Z083 Sept. '80 £3.00 COMBINATION LOCK Z029 Sept. '79 £12.50REACTION TIMER ZD82 Sept. '80 £26.50 *STARBURST Z030 Sept. '79 £14.50MICROMIXER (on Vero) Z081 Sept. '80 £8.50 LAMP DIMMER 7031 Sept. '79 £6.50EQUITONE CAR EQUALISER ZD52 Aug. '80 £13.30 ULTRASONIC SWITCH ZD32 Sept. '79 £21.00GAS DETECTOR ZD55 Aug. '80 £22.00 CONSTANT VOLUME AMPLIFIER ZD28 Aug. '79 £11.50PASS THE LOOP GAME ZD56 Aug. '80 £12.00 INJECTOR TRACER Z027 Aug. '79 £4.50RADIO TIMER (on Vero) ZD57 Aug. '80 £5.50 LED TACHOMETER ZD26 Aug. '79 £14.75MOVEMENT ALARM (on Vero) ZD54 Aug. '80 £5.00 BABY ALARM Z025 July '79 £13.50OP. AMP CHECKER (on Vero) ZD53 Aug. '80 £4.00 POINTS SWITCH Z024 July '79 £12.50CAR BOOSTER (no speakers) Z050 July '80 £18.00 LINEAR SCALE OHMMETER ZD23 July '79 £14.00HAZARD FLASHER Z048 July '80 £10.50 SHARK ZD22 July '79 £22.75*PUSH-BUTTON VOLUME G.S.R. MONITOR Z019 June '79 £10.50
CONTROL ZD47 July '80 £19.50 ENVELOPE GENERATOR ZD20 June '79 £11.79SOUND FLASH TRIGGER (on Vero)ZD49 July '80 £3.50 DRILL SPEED CONTROLLER 7021 June '79 £7.002 WATT AMPLIFIER (on Vero) Z046 June '80 £3.90 WHITE NOISE EFFECTS UNIT ZD18 May'79 £16.85METRONOME (on Vero) Z051 June '80 £3.50 PARKING METER TIMER ZDI7 May'79 £6.70MICROBE R/C SYSTEM DIGIBELL PROJECT Z016 May '79 £5.00
(less Servos) Z045 June '80 £17.50 VARIABLE POWER SUPPLYFOG HORN Z044 June '80 £4.50 0.30V 1 AMP ZD15 May'79 £30.00*EGG TIMER ZD43 June '80 £6.50 TRANSISTOR GAIN TESTER Z076 April '79 £6j0MINI CLOCK ZD1 0 May '80 £26.00 CISTERN ALARM Z075 April '79 £51105080 PRE -AMP May '80 £32.00 MODEL TRAIN CONTROLLER ZD74 April '79 £26.00TRACK CLEANER ZD12 May '80 £7.75 PHOTOGRAPHIC TIMER ZD73 March '79 £14.50*R/C SPEED CONTROLLER ZO3 April '80 £9.60 TONE CONTROL Z072 March '79 £9.00HOBBY COM ZD8 April '80 £28.60 CASANOVA'S CANDLE ZD71 March '79 £7.50ELECTRONIC IGNITION ZD2 April '80 £18.25 SHORT WAVE RADIO ZD66 Feb. '79 £12.50DIGITAL FREQUENCY METER ZD9 April '80 £27.75 SINE/SQUARE WAVESHORT WAVE RADIO ZD80 March '80 £19.50 GENERATOR Z067 Feb. '79 £22.50TOUCH SWITCH Z079 March '80 £5.00 SCRATCH AND RUMBLE5080 PSU MODULE ZD78 March '80 £29.50 FILTER MONO ZD68 Feb. '79 £22.50SYSTEM 5080A ZD77 March '80 £15.00 SCRATCH AND RUMBLEPASSION METER ZD6 Feb. '80 £5.00 FILTER STEREO ZD69 Feb. '79 £25.00WIN INDICATOR ZD42 Feb. '80 £9.00 CAR ALARM Z070 Feb. '79 £8.50INFR RED REMOTE CONTROL ZD7 Feb. '80 £19.35 FLASH TRIGGER (less flash gun) ZD65 Jan. '79 £10.50SCALEXTRIC CONTROLLER 7041 Jan. '80 £52.50 TOUCH SWITCH Z063 Jan. '79 £5.50CROSSHATCH GENERATOR ZD4 Jan. '80 £11.25 VARI-WIPER Z064 Jan. '79 £8.00DIGI-DIE Z05 Jan. '80 £5.50 GRAPHIC EQUALISER Z062 Jan. '79 £25.00RING MODULATOR ZDI Dec. '79 £8.50 PUSH-BUTTON DICE Z061 Dec. '78 £6.00SCALEXTRIC CONTROLLER ZD39 Dec. '79 £21.50 AUDIO MIXER Z014 Dec. '78 £20.30BARGRAPH CAR VOLTMETER Z040 Dec. '79 £6.60 BEDSIDE RADIO Z058 Nov. '78 £12.50GUITAR TUNER ZD38 Nov. '79 £8.50 STEREO AMPLIFIER (HOBIT) ZD59 Nov. '78 £52.50*R2 02 RADIO ZD37 Nov. '79 £8.60 WAA-WAA PEDAL ZD60 Nov. '78 £30.00TANTRUM ZD33 OCt. '79 £37.50
IONISER KIT: Z013. This negative ion generator gives you power to saturate your home with millions of refreshing ions. without fans or movingparts it puts out a pleasant breeze. A pure flow of ions pours out like water from a fountain filling your room. The result? Your air feels like freshocean air, crisp and wonderfully refreshing. All parts p.c.b. and full instructions £10. A suitable case including front panel neon switch. etc.,available at £8 extra.
PLEASE NOTE OUR NEW ADDRESS]If you do not have the issue of H.E. which contains theProject, we can supply a reprint at 40p extra. Please add30p post and packing. Add 1 5% VAT to total order.Callers please ring to check availability of kits.
T. POW E L LADVANCE WORKS44 WALLACE ROAD, LONDON, N.1
LATE EXTRAWatchdog Intruder Alarm ZD89 OCT '80 £15.75Temperature Controlled Soldering Iron ZD90 OCT '80 £9.00Freezer Alarm (on Vero) ZD91 OCT '8C £8.50Tug 0' War Game ZD94 OCT '80 £12.50Nobel! Doorbell ZD93 OCT '80 £9.75Kitchen Timer (on Vero) ZD92 OCT '80 £5.50Light Dimmer ZD85 OCT '80 £5.00
All kits contain components as specified plus Texas I.C. sockets.where required, also connecting wire.
FAIRCHILD FLV150 red. 2 LEOS. 10 for £1.00, 100 for £7.50DALY ELECTROLYTIC CAPACITORS 2000uF 100v £1.50PHILIPS SCOPE Tube 5" CV2191/DG-13-2 £10
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24 Hobby Electronics, April 198'
Super SirenBe the first human in yourgalaxy to build this space-age siren and enjoy spurioussub -ether emissions in thecomfort and privacy of yourown home
NOW A MULTITUDE of modulationscan be yours for just a few pounds'outlay and a couple of hour's work.Thrill to the whoops, whines andsqueals as the unit responds to yourhands-on control or switch toautomatic and enjoy the dementedtwittering of an electronic aviary.Every resistor in this circuit may bevaried to adjust one of the outputparameters so there's plenty of scopefor experiment. Of course, not allcombinations of values will result in asound you can hear but it's funfinding out. Additionally there aretwo switched inputs which enableyou to select the modulating signaland the blanking pulse if required.
The heart of the circuit is theastable oscillator built around IClf(see Fig.1). This is a conventionalSchmitt trigger design which hasbeen modified by the addition of adiode in the feedback loop so that ashort positive pulse is producedwhen the voltage across C6 fallsbelow the Schmitt threshold level.The frequency of the output is variedby controlling the discharge rate ofC6. Electronic control is achievedthrough the use of a transistor. Themodulation is applied via a resistivedivider to the base of Q1 . Section dof IC 1 forms the slow -speedoscillator whose input drives Q1 .Both triangle and square -wavesignals are available and ICI e may beswitched in to blank the oscillator onselected half -cycles. Of course, therise and fall times of the slow -speedoscillator are independentlyadjustable.
Ring A Ring Of NoisesBelieve it or not we provided all the
functionsmentioned above from justhalf the chip, leaving us with threespare gates. These have beenconnected in a 'ring of three' circuit.That's just like the familiar one gateastable except that each stage nowgets its feedback via the other twogates. This results in three square -wave outputs shifted in phase by120 degrees when equal valueresistor -capacitor networks are used.
What does it do? Well with theright component values it makes anoise like a demented canary -keeps your pet budgie happy but itdrives the cat wild! Just like the restof the circuit you can experimentwith the values of the resistors andcapacitors to obtain special effects.Try connecting diodes in series withresistors R1,3,6 (anode to the ICoutput, cathode to the resistor) andsee how it modifies the output.
Pulse PowerThough the circuit will drive aloudspeaker directly, no fancyamplifiers are used. In fact a glance atthe circuit diagram will show that justone odd -looking transistor is used.This is a state-of-the-art VMOStransistor. It works just like the field-effect transistors in the CMOS chipIC1 but its special physical geometryenables large currents to be handled.The volume level and currentconsumption of the unit will dependon the supply voltage, speakerimpedance and width of outputpulse. By using a value of 1 k0 forRI 1 short (twenty microsecond)pulses are produced at the output.These may be lengthened by
TRI saOPEN
RAND
increasing thevalue of RI 1 . If Q2gets hot - use a heatsink. It's a veryrugged device so don't be afraid toexperiment.
ConstructionModular circuit design makesconstruction a cinch. f you can, werecommend you use our PCB design.It prevents wiring errors (okay - soprove us wrong if you must!) andfacilitates testing and circuitmodification. There are no specialproblems so if you're happier withsome other method - use it. Presentday CMOS chips seem very resistantto damage from static discharge butit's a wise precaution to use an ICsocket. If you use our PCB then insertthe socket and add the othercomponents working outwards fromit . . . R2,R4,C2,3,4,R 1 ,3,6 etc.It's less fiddly that way.
It would be nice to make a unitwhere all the resistors were variablebut to start you off we've designedthe board to accommodate theessential ones. Miniature horizontalpre-sets can be used or wires may betaken to panel -mountedpotentiometers for easy operation.Once the unit's working you'llprobably want to remove R9 andreplace R8 with a IMO or 2M0potentiometer so get it going and tryit out before you finalise the paneldesign. The value of Rx will set theminimum operating frequency of theoscillator so you may want to use apanel -mounted pot for that too!
Hobby Electronics, April 1981 25
VN67Af
© Copyright MODMAGS Ltd. BC109d (TAB)
Cl1000u
IC14
C210.
7
R2
C310u
Figure 1 Circuit diagram
R410k
Excepting Cl which is electrolytic,we used tantalum types for thepolarised capacitors. They cost a littlemore but they are small, pretty(?) andhave very low leakage values -provided you connect them the rightway round. Remember that atantalum cap often fails whensubjected to a reverse voltage as lowas 3 V so get it right the first time!Diodes, however, will seldom bedamaged when accidently reversedbut the circuit won't do what youexpect.
Take the usual precautions whenhandling IC1. It's the most expensivesingle component. The VMOStransistor Q2 is fully protectedagainst static discharge so noproblems there. Take care not tooverheat any component. Use a smallsoldering iron of 15 to 25 watts andyou should be okay.
Light The Blue Touch -PaperandWhen all the components aresoldered into place, insert IC 1 (theright way round), connect a loud-speaker of 3 ohms impedance up;eight or sixteen ohms is a good valueto try, and apply 9 to 12 V to thecircuit. With point SW2, A open -circuit, the result will depend on thevalue of Rx. If you used a pot tryvarying the resistance. You should be
SW? 4
R6150k
R510k
R7140
5
IC1c
1'u
13
RV247k
!Cid
SW2,2 SW2,3
ICle
OFF+ 0
SW1
rewarded with a variable -pitch tone.By connecting point SW2, A via theswitch SW2, to points SW2,2,3 and4 in turn you should obtain atwittering sequence of tones, awarbling tone adjustable by RV1,RV2 and a 'two-tone' sound.Switching SW1 to ( + ) or ( - I willblank one of the tones. Note that thisstill happens when A is modulated bythe random modulation. Use RV1,RV2 to adjust the mark -space ratio orswitch SW1 to 'centre position' toobtain a continuous output.
If you get no output check Q2. Ifit's hot switch off and make surethere are no shorts on the board.Check that D4 is connected the rightway round. If you still have problems,disconnect D3 and Ql. The circuitwill oscillate using only D4,R11,IC1,C6 and about 100k for Rx. If youdon't hear any sound from theloudspeaker, check the output of IC1by connecting a crystal earpiecebetween pin 8 and ground (0 V).
By connecting two resistors inseries across pin 8 and ground youcan provide an output for your hi-fi.Choose a ratio to provide the correctsignal level. About 100 mV shouldbe right for the 'line' input of youramplifier, and for this voltage use8k2 and 100R. Select the sirensound of your choice, switch on theafterburner, and give your ears atreat!
D3
NOTE:IC1 IS 4584 (40106)01 IS BC10902 IS VN674FALL DIODES ARE 1N4148
RV3 C6
100k 100n
Parts ListRESISTORS (All 3/4W, 5%)R1,8 100kR2,4,5R3R6R7,10,11R9
10k120k150k1k033k
SW3 4-9VON/OFF
POTENTIOMETERSRV1,2 47k miniature
horizontal preset orlinear potentiometer
RV3 100k miniaturehorizontal preset orlinear potentiometer
CAPACITORS (All 10 V working orgreater)Cl 1000n electrolyticC2,3,4 1 On tantalumC5 100n tantalumC6 100n polyester
SEMICONDUCTORSIC1 45848 (40106B,
74C14) hex Schmitttrigger
Q1 BC109, NPN transistorQ2 VN67AF, VMOS
power FETD1,2,3,4 1N4148, diode
MISCELLANEOUSSW1 single -pole, double -
throw, centre -offtoggle switch
LS1 3R or greater,miniature loudspeaker
3 position rotary switch9 V battery + clip
26 Hobby Electronics, April 1981
Super SirenSW1
Riot]]D1 D2
(3-1711d ()CI
94 .ormor. S
Q2
How It WorksSchmitt inverter IC 1 f is connected as anaudio frequency voltage -controlledoscillator. Output pulse width is set bychoice of R11. Frequency variesaccording to the value of Rx and the basedrive into Q1. Electronic control isachieved by modulating the potentialdivider connected to the base of 01. AVMOS transistor switched by IC1foutput directly drives a loudspeaker.
Modulating voltages are obtained froma slow -speed astable built around IC1 d.Rise and fall times are independentlyadjustable using RV1, RV2 and triangleand squarewave outputs are available.Care should be taken not to load thetriangle output excessively or IC1 d will beunable to drive C5 past the positive pointand oscillations will cease. There are nolimitations on the square wave output.Either half cycle may be blanked byconnecting D3 anode to IC1 pin 10 or 11via SW1. With SW1 in 'centre -off'position, continuous output will beobtained.
A pseudo -random output is availablefrom the junction of resistors R1,3,6.These are driven from the outputs of a'ring of three' oscillator built aroundIC1 a,b,c. Frequency of operation of thissection is controlled by choice of C2,3,4and adjustment of resistors R2,4,5.Change all values equally to maintainidentical mark -space ratios or experimentwith the effect of altering just one value.Capacitor Cl provides overall decouplingand the circuit should be powered from a9 to 12 V supply. Take care that themaximum voltage rating of C5 is notexceeded.
BuylinesThe VMOS transistor is available fromJW Rimmer Ltd. All other componentsshould be readily available from usualsuppliers. The total cost of components(excluding case and PCB) should bearound £1 0.
rC2
+R1G- R2
R3G-R6
R5 ...C>C5
C6-(=> 1;116\9 1
R10 \plc D3-0R9 R8
SW1Figure 2. Overlay of the PCB
SW3
Figure 3. Connection details of the project
LS1
Copyright MODMAGS Ltd.
HE
THENEWAND
EVEUNIQUROBLOC
mamma1*/tailmamma idled/1k IR
1111111 1/11111111111til IN ill til d1111111111111. WSW mama milmitdem dia1111111111111111111111111111.1.8didir di did Ni 1.11 id di id11111111111111111111111111.111111111.i 11 di at a a a$11111111 i/rmrrrarmrlt ..
V11..11111M.1.111.1 d ait d l 1d11uI
111111111111111111111111181111111111111111
IFITT1-11-11-1-("(
S
ADDS TO YOUR CAPABILITYAlready used in industry, this solderlessbreadboard is now available to the hobbyist.Unique because of its universal interlockingfacility meaning you no longer need lots ofdifferent boards.Send now for the uniqueVerobloc.Order code 200-21092G. £4.16p inclusive.
AND VERO HAVEADDED TO THEIRTRADITIONAL RANGEOF HIGH QUALITYBOARALSOEX-STOCK.
No. Order Code Description Size (mm) Price
1) 10-2845B Microboard 160 x 100 5.66
2) 10-2846H Microboard 160 x 233.4 12.41
3) 200-21084E V -Q Board 147.83 x 73.66 1.65
4) 09-2196L Veroboard 160 x 100 1.63
Carriage & VAT included.
Vero Electronics Limited, Retail Dept., Industrial Estate,Chandler's Ford, Hampshire SO5 3ZR. Tel (04215) 62829rNM NM M- NMI NMState quantity and order codes required
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extends operation to full 600 Mhz - £159.95 plus VAT. Proportional temperature controlled crystal oven
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Get full details on theseand our other models now. Why pay more?
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Book 1.Book 2.Book 3.
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Book 5. Transistor Project Circuitry
The manuals are unquestionaby the finest and most up-to-date availableand represent exceptional value.This series has been written in a fascinating, absorbing and excitingway, providing an approach to acquiring knowledge that is a veryenjoyable experience. Suitable for industrial trainees, City and Guildsstudents, DIY enthusiasts and readers of electronic journals.Each part explains electronics in an easy -to -follow way, and containsnumerous diagrams and half tone blocks with construction details andcircuit diagrams for making the following transistor projects: LampFlasher, Metronome, Wailer, Photographic/Monostable Timer, MetalLocator, Geiger Counter, Radio Receiver, Intercom., Intruder Alarm,Electronic Organ, Battery Eliminator, Anemometer, Sound Switch,Light and Water -operated Switches, Pressure -operated Switches, Lightmeter, Radio Thermometer, Ice Alarm,
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OUR 100% GUARANTEEShould you decide to return the set after 10 days exam-ination, your money will be refunded by return of post.
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28 Hobby Electronics, April 1981
Building SiteIn this month's episode, Keith Brindley offers some good advice on the tools tobuy and use if electronics is your hobby and then shows how easy capacitorcodes can be to understand
NO DOUBT, YOU will have heard theold proverb 'A bad workman blameshis tools'. Well you'll be pleased tofind out that it doesn't apply toelectronics. In our field, if youhaven't got the tools for the job youwill never be a good workman - it'sas simple as that! Electronics isn't a'hammer and adjustable spanner'hobby but an art which can be easilymastered if you have the right tools.
Two tools which I'd recommendyou buy are a pair of fine, snipe -nosed pliers and a pair of side -cutters. Both are invaluable aids tocircuit board work when projectbuilding. Remember that the circuitboard (either PCB or Veroboard) isthe 'heart' of your project and if itdoesn't work then neither will thewhole project.
Buy the best tools you can afford- it's not that the tools areparticularly expensive (reasonablepliers and cutters will cost about £6to £10) but quality is usually inproportion to cost. Those shown inFig.1 are high -quality tools forengineers at top -of -the -rangeprices. They are part of the HEworkshop toolkit and we use themevery day, so the cost is smallcompared with the usage.
A good set of such tools, treatedreasonably, should last a lifetime.But if you treat them badly theymight only last a couple of months- there's nothing moreheartbreaking than watching the tipof your prized sidecutters bounceoff all four walls of the room, as youattempt to cut 1 5 amp cable withthem. The moral is simple: never useyour tools for anything other thanwhat they're made for.
SidecuttersThe main use of sidecutters is to cutoff excess portions of componentleads after a component has been
Hobby Electronics, April 1981
Figure 1. The HE workshop's very own sidecutters and snipe -nosed pliers
Figure 2. Trimming component leads after soldering. Make sure to cut the lead as close tothe soldered joint as you can
29
Building Site
Figure 3. Snipe -nosed pliers can be useful as a heat -shunt to protect heat -damageablecomponents when soldering
soldered into the circuit board. Thistrimming of leads ensures that shortcircuits between them cannot occurand that your project has morechance of working.
Incidentally, it's bad practice toinsert all (or even just a few)components together beforesoldering them into place, for thesimple reason that once you invertthe board to start soldering,inevitably some fall out of position.By the time you have soldered all theleads and turned the board back upagain, you will find that half thecomponents are sticking out of theboard at all sorts of funny angles andplaces. Without a doubt, some ofthe leads will short together. Theonly simple answer to this problemis to insert and solder eachcomponent separately - one at atime.
Other UsesYou can use sidecutters to cut thinwire. But make sure that the wire isthin. Don't, as we've already said,use your sidecutters to cut thickmains cable. Similarly, you mustn'tuse your snipe -nosed pliers fortightening or loosening nuts andbolts or for other heavy work.Remember that they are precisioninstruments and can be damaged byrough handling.
Your 'snipes' are mainly used tobend component leads beforeinsertion into the board, or to pre-form wire links. Because they are sofine the lead can be bent, close to thecomponent body, without causingfracture.
Whenever you are solderingcomponents which can be damagedby excess heat (for example, certainsemiconductors) into the board,snipe -nosed pliers can come inhandy as heat shunts. By holdingthe component lead with the plierson the component side of the board,while soldering the lead on thecopper side, any heat beingconducted up the lead towards thedevice itself is deflected into thecomparitively large mass of thepliers and absorbed. It's an old trickbut one well worth remembering.
CapacitorsI receive a number of enquiriesregarding the coding of capacitorvalues so I reckoned that now was agood time to do a bit of brushing upon the topic. In broad terms,capacitors are normally either colourcoded or numbered (although thenumbers very often don't seem tomean much to our readers).
The colour code (for the firstthree bands, at least) is the same asthe resistor colour code; that is:
green =blue =violet =grey =white =
black = 0brown = 1red = 2orange = 3yellow = 4
56789
When used for capacitors, the codestands for the number of picafarads(1pF or 1p = 1 x 10 -12F). Let's haveen example (see Fig.4).
YELLOW
VIOLETRED
WHITEGREEN
© Copyright MODMAGS Ltd.
Figure 4. A typical colour -coded capacitor
Yellow = 4, Violet = 7 and Red = 2ie 47 followed by two zeros. So thevalue of the capacitor is4700pF = 4.7nF or 4n7.
The last two bands of colour onthe capacitor body stand for thetolerance:
black = 20%white = 10%green = 5%
and the working voltage - themaximum voltage which thecapacitor can withstand withoutdamage:
red = 250 Vyellow = 400 V
The value of numberedcapacitors is just as easy to follow.For example a capacitor of value27n (27 x 10 9F) will normally benumbered 273. The first two figuresstand for the numerical value (27),and the third figure tells you thenumber of zeros (3):ie 27000pF = 27n. Simple, isn't it!See you next month. HE
30 Hobby Electronics, April 1981
THREE FOR FREEFROM GSC
EXPERIMENTOR BREADBOARDSNo soldering modular breadboards, simply plugcomponents in and out of letter number identifiednickel -silver contact holes. Start small and simplysnap -lock boards together to build a breadboard ofany size.All EXP Breadboards have two bus -bars as an integralpart of the board, if you need more than 2 busessimply snap on 4 more bus -bars with the aid of an EXP4B.
EXP 325 £1.60 The ideal breadboardfor 1 chip circuits. Accepts 8, t4, 16 andup to 22 pin ICs. Has 130 contact pointsincluding two 10 point bus -bars.
EXP 350 E3.15 Specially designedfor working with up to 40 pin ICsperfect for 3 & 14 pin ICs.Has 270 contact points includingtwo 20 point bus -bars
EXP 300 E5.75 Themost widely boughtbread -board in the UKWith 550 contactpoints, two 40 pointbus -bars, the EXP 300 will accept any size IC arid upto 6 x 14 pin DIPS. Use this breadboard withAdventures in Microelectronics.
EXP 600 £6.30 MostMICROPROCESSORprojects in magazines I
and educational booksare built on the EXP 600 ..........
EXP 660 £3.60 Has .6" centrespacing so is perfect forMICROPROCESSOR applications
EXP 4B (2.30 Fourmore bus -bars in"snap -on" unit.
.1
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The above prices are exclusive of P& P and 15 V41.
THE GSC 24 HOUR SERVICETELEPHONE (0799) 21682
With your Access, American Express,Barclaycard number and your
order will be in the post immediatelyGLOBAL SPECIALTIES CORPORATIONMM=G.S.C. (UK) Ltd, Dept.14TTUnit 1, Shire Hill Industrial Estate,Saffron Walden, Essex CB11 3AQ.Tel: Saffron Walden (07991 21662Telex: 817477
Available from selected stockistsELECTRONICS BY NUMBERSNo. 10 SOIL MOISTURE TESTERNo more wilting houseplants with this soilmoisture test. Just place the probes into thesoil and it will light up to tell you whetherthe soil is "too wet" or "too dry". Youdon't even need green fingers.
No. 11 DIGITAL ROULETTEThe suspense and excitement of the casinoin your own home. Just press the button,the circle of lights go round and there is thesound of the roulette wheel as well, bothgradually slowing down to reveal thewinning number.
No. 12 EGG TIMERHow do you like your eggs done, hard orsoft, just set the timer and it will soundwhen the egg is done to your liking. Longbattery life because it switches itself offautomatically. So get cracking now!
Want to get started on building excitingprojects, but don't know how? Now usingEXPERIMENTOR BREADBOARDS andfollowing the instructions in our FREE'Electronics By Numbers' leaflets,ANYBODY can build electronic projects.For example, take one of our earlierprojects, a L.E.D. Bar Graph;
mow
IZE J, ;i10
Tilj?l led-CE:).
WayUP
You will need; One EXP 300 or EXP 350breadboard 15 silicon diodes6 resistors 6 Light Emitting DiodesJust look at the diagram, Select R1, plug itinto the lettered and numbered holes on theEXPERIMENTOR BREADBOARD, do thesame with all the other components,connect to the battery, and your project'sfinished. All you have to do is follow thelarge, clear layouts on the 'Electronics byNumbers' leaflets, and ANYBODY can builda perfect working project.
MI MINTO RECEIVE YOUR FREE COPY OF PROJECTS 7, 8 and 9
NUillberS
ectr,nniCS No
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ProiectsNo
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For full detailed instructions and layouts ofProjects 10, 11 and 12, simply take the couponto your nearest GSC stockist, or send directto us, and you will receive the latest'ELECTRONICS BY NUMBERS' leaflet.
If you have missed projects, 1, 2 and 3, or 4, 5and 6, or 7, 8 and 9, please tick the appropriatebox in the coupon.
PROTO-BOARDSThe ultimate in breadboards for the minimum of cost.Two easily assembled kits.
PB6 Kit, 630 contacts, four 5 -way binding postsaccepts up to six 14 -pin Dips.PROTO-BOARD 6 KIT 0.20
Pb 100 Kit complete with 760 contacts accepts up toten 14 -pin Dips, with two binding posts and sturdybase Large capacity with Kit economy.PROTO-BOARD 100 KIT f11.80
IIIIII
III
IT'S EASY WITH
Just clip the couponGive us your name and full postal address lin blockcapitals). Enclose cheque, postal order or credit cardnumber and expiry date, indicating in the appropriateboxles) the breadboard(s) you require.
G.S.C.
For immediate actionThe GSC 24 hour, 5 day a week service.Telephone (07991 21682 and give us your Access,Amercan Express or Barclaycard number and yourorder will be in the post immediately.
EXPERIMENTORBREADBOARDS CONTACT
iC CAPACITY14 PIN DIP
UNIT PRICE INCPEW Er 15% VAT
()Tyreq
EXP 325 130 1 E 2.70
EXP 360 270 3 E 4.48
EXP 300 550 6 E 7.76
EXP 800 E 8.39
EXP 660 270
use with0 6 pitch
Dip's StripBus Bar
£ 5.00
EXP 4BFour 40 Point
BusBarst 3.50
PROTO BOARDSP86 630 6 £11.73
P8100 760 10 E14.72
L
NAME
ADDRESS
1IIIII
I enclose cheque/P.O. for £Debit my Barclaycard, Access,
American Express card No.
Expiry date
If you missed project No's1 to 9 tick box.For Free catalogue tick box
GSC (UK) Ltd., Dept.14TT, Unit 1, Shire Hill Industrial Estate, Saffron Walden, Essex CB11 3AQ.Tel: Saffron Walden 107991 21682. Telex: 817477.
Mmi NM NM MI MIN III= - - - - - INS -
II
Hobby Electronics, April 1981 31
Doorbell MonitorA simple -to -build and cheap project for the home, which constantly monitors yourdoorbell and tells you if you've had a caller whilst you've been out
SOMETIMES IT CAN be helpful toknow if there has been a caller whileyou have been away from the house,and this simple gadget can be used toindicate whether or not the doorbellhas been operated. The project usesone of the cheapest and mostcommonly available ICs around in anovel circuit design which issimplicity itself to build. It has anindicator light which is normallyswitched off, but turns on and is heldin this state if the doorbell isoperated.
ConstructionA suitable 0.1" matrix Veroboardlayout for the circuit is shown inFig. 2. The board has 11 holes by 1 2strips and there ai.e six breaks in thecopper strips. These breaks shouldbe made before any components orlinks are inserted and soldered, byusing the standard cutting tool or,alternatively, a hand-held 3 mm drillbit. Hold the cutting edges of the toolor bit against the hole where thebreak is to be made and twist gentlyclockwise until a neat circular breakin the copper is made. Check thatany loose swarf is removed, thusreducing the possibility of unwantedshort circuits between adjacenttracks.
Next, insert and solder each wirelink, followed by the IC socket if youuse one, and finally the othercomponents as shown in Fig. 2. ICIis a CMOS device and can bedamaged by static discharge ifhandled incorrectly. It should be thelast component to be connected intocircuit and should be left in itsprotective packaging until then. Ifyou use an IC socket it only remainsto insert the chip into its socket,being careful not to touch the pins ofthe IC. If you haven't used a socketand you intend to solder the ICdirectly into the board then youshould use a soldering iron with aearthed bit.
32
Mt -
RESISTORS (All 3/4W, 5%)R1 1k0R2 15kR3 3k3
CAPACITORC1 15n polyester
Parts List
SEMICONDUCTORSIC 1 4001 quad, two -input
NOR gate
D1LED I
IN41 48 diode0.2" LED
MISCELLANEOUS11 hole x 12 strip, 0.1" VeroboardSW1 single -pole, single -throw toggleswitch9 V battery + clipCase to suitIC socket (if used)
R1
TO BELL
Figure 1. Circuit diagram
C115n
0+9V
NOTES:IC1 IS 4001D1 IS 1N4148LED1 IS GREEN LED
R33k3
PINS 7,8,9,12,13 OF IC1 LED1
OV
Copyright MODMAGS Ltd.
Hobby Electronics, April 1981
How It Works
The incoming signal from the bell is rectified, which provides either apositive signal (bell on) or nothing (bell off) to the electronic latch.Whenever a caller rings the bell, the latch output therefore becomespositive and holds the LED on.
INPUTSIGNAL /,
ELECTRONICRECTIFIER LATCH
FROM LEDBELL
© Copyright MODMAGS Ltd
The unit is based on a CMOS 4001 ICwhich is a quad 2 -input NOR gate. Onlytwo of the gates are used, and these bothhave their inputs connected together sothat they act a straightforward inverters.The inputs of the unused gates are con-nected to earth so that they cannotoperate spuriously.
The two inverters are connected inseries so tht the output assumes thesame logic state as the input. At switch-
on C1 will be uncharged, and thereforetakes the input to the low logic state. Theoutput assumes the same state, and lat-ches the circuit in this condition becauseof the feedback through R2. The LED in-dicator LED 1 is driven from the output viacurrent limiting resistor R3, and will ob-viously be switched off with the output inthe low state.
If the doorbell is operated, a voltagewill be fed to the bell, and this will appear
across the input of the monitor. In a nor-mal mains -operated bell circuit the bell ispowered via a step-down transformerwhich provides an AC voltage of a fewvolts to the bell. On positive -going AChalf -cycles D1 will conduct, and the inputof the circuit will be taken to the highstate. The output also goes high and thepositive feedback through R2 latches thecircuit in this state. D1 does not conducton the negative -going AC cycles, so theinput signal cannot return the circuit to itsoriginal state. The indicator lighttherefore remains switched on until theuser resets the unit by momentarily swit-ching off using SW1.
The unit will also work with battery -operated bells having a supply voltage ofabout 6 V to 9 V, but the input must thenbe connected with the correct polarity.The circuit has a negligible current con-sumption in the standby mode, and theconsumption is only about 2 mA whenthe LED is switched on.
TO BELLH
L
K
J
H
G
F
E
D
C
B
A
1 2 3 4 5 6 7 8 9 10 11
0 0 0 0 0 0 0 0 0 0 0
R3
O
R1
cvC
a
C
C
IC1
0
0i 0
00
tD
0 0 0 0
0
0 0 0 0 0 00 0 0 0 0 0 0 0 00 0 0 0 0 00 0 0 00 0 0 0 0 0 00 0 0 0 0 00 0 0 0 0
0 0 0 00 0 0 0 0
0 0 0 0 0 0 0 0 00 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0
1 2 3 4 5 6 7 8 9 10 11
Copyright MODMAGS Ltd.
Figure 2. Veroboard layout, connectiondetails and track breaks
Hobby Electronics, April 1981
BuylinesNone of these components are hard tocome by and should be found at mostcomponent stockists. The approximateprice for the parts in this project will bearound f 3.
HE
BE PREPARED WITHTHIS DETECTOR
Recommendedfor
General use. IRECIVIL
DEFENCEM ICAL
SERVICES ED
THIS DOSIMETER WILL AUTOMATICALLY DETECTGAMMA AND X-RAYS.
111 UNIT IS SIZE OF FOUNTAIN PEN AND WILL CLIP INTOP POCKET.
PRECISION INSTRUMENT, METAL CASED,WEIGHT 2oz.
CONTAINS 3 LENSES. IN RUGGED CONSTRUCTION.
MI MANUFACTURERS CURRENT PRICE OF A SIMILARMODEL OVER f25 EACH.
British design and manu-facture. Tested, calibratedand guaranteed. Ex -stockdelivery by return.
Be prepared,buy whilst available
Hemey's
Standard model0-5 or 0-50R
ONLY
95mc VAT
Post & Packing 60p
404 EDGWARE ROAD,LONDON W2 1ED
FIATHELECTRONIC
SERVICES
Packs of components (a 60p each. Post 40p + 15% VAT10 or more packs post free.
PA01 100 asstd. carbon resistors.PA02 200 asstd. preformed Resistors.PA03 20 asstd. Wire Wound Resistors.PA04 100 asstd. Mica/Ceramic Capacitors.PA04 50 Poly Capacitors.PA06 30 asstd. Electrolytic Capacitors.PAO] 10 Tantalum Capacitors .6814 50V.PA08 10 Tantalum Capacitors 4.7uF 10y.PA09 10 Tantalum Capacitors 5.6uF 6V.PAIO 20 Tantalum Capacitors asstd.PA11 6 BC107 Transistors.PA12 6 BC108 Transistors.PA13 100 0071 Transistors UM. UT.PA14 50 Germanium Diodes UM. UT.PA15 50 Silicon Diodes. UM. UT.PA16 30 1 Amp Rect Diodes UT.PA17 40 400mW Zener Diodes UM. UT.PA18 9 Variable Resistors.PA19 2 1 Amp Bridge Rect on Bd with Cap.PA20 1 Transformer 5-0-5 01, 250mA.
PA21 7 Red LEDs .125in.PA22 7 Red LEDs .2in.PA23 10 asstd. LEDs.PA24 1 Comp. Panel with useful compo-nents.PA25 15 Glass Reed switches (ex -equip.).PATE 12 asstd. Fuses.PA27 2 Plastic Toggle Switches.PA28 6 Slide type Switches.PA29 3 V3 type Micro Switches.PA30 4 asstd. Micro Switches.PA31 3 .1 matrix Blob Board 21/2 x 5.PA32 2 2p6w Rotary Switches.PA33 8 PP3 Battery Clips.PA34 60 sq. ins. of Copper Lam Board.PA35 1/21b. pkt. Ferric Chloride + 40p post.PA36 100 asstd. Transistors UT.PA37 10 1N4002 Preform Diodes.PA38 2 20 Turn Presets 200K.UT= Untested. UM-unmarked.
Full Vero range by post (Cato 40p post paid)
List of microwave devices SAE please
PCB Fotoboard + accessories
Electronic Components List 30p (Free with orders)
P.A.T.H. ELECTRONIC SERVICES369 Alum Rock Road, Birmingham B8 3DR
DO YOU EVER NEED A FEW MORE HANDS?ABSONGLEN ANNOUNCES THE NEW
MINIBENCH 11* Just a squeeze needed to clamp or release the circuit board. Adjustable minimum jaw aperture Jaws flip over for work on either side of circuit board Rubber -lined jaws for circuit board protection and maximum grip Single wing nut adjusts friction control and jaw attitude Crocodile clips mounted on flexi-arms hold components exactly where needed Crocodile clip can be used as heat shunt Lens similarly mounted is ideal for close work and spotting those solder bridges. Flexi-arms are mounted on the jaw assembly to keep station with the circuit
board. 6 separate flexi-arm mounting positions A typical configuration would consist of 2 flexi-arms with clips and one with lens. Attractive two-tone stove enamelled finish. Built to last a lifetime.
TO: ABSONGLEN LTD. DEPT. HE
Name
Address
Please supply
Minibench II 02.95
Flexi-arms with Clips (0 f4.75 each
Flexi-arms with Lens (a £5.75 each
Postage and packing £2.25
* Price applicable to Minibench purchasersonly
Remittanceenclosed for
* Trade Mark
ABSONGLEN LTD, DEPT. HETHE FORGE, STAPLOW
LEDBURY, HEREFORDSHIRE HR8 1NP
Patented
34 Hobby Electronics, April 1981
FamousNamesMichael FaradayTo follow What's In A Name, we present a new series about some of the pioneers ofelectrical and electronic science. First we look at the lives of some of the famous namesassociated with the discovery of electricity. Later we look at some of the pioneers ofelectronics, a science which grew from the understanding of the principles of electricity.We begin with one of the most practical and communicative discoverers: MichaelFaraday
EVER FELT TOTALLY baffled by a bitof theory? Ever found that you couldlearn more with a hot soldering iron inyour hand than using a book? Takeheart, for your condition is in somerespects like that of Michael Faraday,who did more for the progress of elec-tricity than almost anyone else in thehistory of this subject.
Faraday was born in 1 791, at New-ington, Surrey, the son of a localblacksmith who must have taught himmuch about the machines of the day.These, remember, were times of con-siderable and violent change. TheAmericans had successfully declaredunilateral independence (translation:they threw us out), the French werehaving a revolution (translation: killingeach other), and machines had beeninvented to do the work of three menand a boy! The results were that therewas a huge expansion of trade, a de-mand for machine -made goods, andjobs for anyone who wanted them.There's nothing new under the sun -the Luddites broke machines becausethey thought there would be less
employment, yet within a few yearsthere was such a scarcity of people todo the jobs that children were workingin factories. Our modern Luddites arebusy opposing microprocessors rightnow - with the big differencenowadays that it didn't start here, andno-one is forced to build his factorieshere in the UK.
In Faraday's youth, the blacksmithwas the man who was the machinerepairer, because his skills were wellfitted to this job. The family moved toNorth London, to take advantage ofthis new and lucrative source of in-come but Michael, at the age of 1 4,decided that he would not be ablacksmith, and was apprenticed in-stead to a bookbinder who also had abookselling business. As he bound thebooks, Faraday read them and wasfascinated by the many books dealingwith physical science. Determined toincrease his knowledge, he went tohear Humphry Davy lecture at theRoyal Institute. This experience con-vinced him that he should make hiscareer in scientific research, and he
wrote to Davy asking for a job, enclos-ing a complete transcript which he hadprepared of the lecture he had attend-ed. Davy was impressed and ap-pointed Faraday, now aged 21, as hisassistant at the Royal Institute.
Davy did not regret this step -Faraday proved to be an extraordinarilyastute experimenter, able to devise ap-paratus to prove or disprove anytheory which might be put to him.
One early opportunity occurredwhen the Danish scientist, Oersted,reported that a magnetic field existedaround any wire which was carryingan electric current. Faraday at oncerepeated Oersted's experiments toconfirm the principle, and then wenton to construct an ingenious piece ofapparatus, shown in Fig. 1, whichdemonstrated the shape of themagnetic field. By passing currentthrough the wire and the mercury,Faraday showed that the magnet mov-ed in a circular path around the wire -a path which he concluded must be theshape of the magnetic field round thewire. Davy and Faraday also saw that
Hobby Electronics, April 1981 35
METALHOLDER
TOBATTERY
COPPERWIRE
LONG BARMAGNET
FASTENEDINSIDE JAR
JARCONTAINING
MERCURY
© Copyright MODMAGS Ltd.
Figure 1. Faraday's motor experiment. A magnet was fastened inside a pot containing mer-cury. When a wire was dipped into the mercury, and current was allowed to flow through thewire, the wire rotated around the magnet
this device converted electric currentinto mechanical movement, and so theelectric motor was born.
The two men worked as a team,touring Europe with lecture -demonstrations concerned withdiscoveries which they had jointlymade. These tours put them in touchwith many of the most famous namesin electrical science, in particular Biotand Sayan, who were working on atheory of magnetism, and these sub-jects were to remain the most
fascinating of all for Faraday. In 1825,aged 34, he was appointed as Directorof Laboratories at the Royal Instituteand one of his first actions was to starta series of formal lectures, to be heldeach Friday, describing new advancesin some branch of Science. These Fri-day lectures have continued eversince, along with the Christmas Lec-tures to Schools, which Faraday alsostarted. Faraday had a gift for clear andsimple language, and his lectures wereinvariably crowded out. This is one
aspect of Faraday's work which isoften overlooked, and we may pro-bably never know how many studentswere set an excellent example both byFaraday's meticulous practical workand by his clear and concise lectures.
In 1831, Faraday published theresults of work which was to mark ahuge step in our understanding and ap-plication of electricity. The experimentwas the 'induction ring' - an iron ring(Fig. 2) with two separate windings.One winding was connected throughan on/off switch to a battery, and theother winding was connected to a sen-sitive galvanometer. Faraday waslooking for a way to convertmagnetism to electric current, and hiswas the first of many such attempts tosucceed. There were two reasons forthis. One was that Faraday had builthis own apparatus in his usualmeticulous way, and thegalvanometer in particular was verymuch more sensitive than most. Theother was that Faraday observed andnoted everything. On this occasion heobserved and noted something whichearlier researchers might not havebothered about: that the galvanometerneedle flicked each time the switchwas made or broken. Everyone ex-pected that the galvanometer wouldread continually while current wasflowing from the battery, anddisregarded these transient effects. ToFaraday, these were the importantresults, and he concluded that a cur-rent flowed to the galvanometer onlywhen the current from the battery waschanging. He had, of course,discovered the transformer principleand by doing so, laid the foundation forall our use of electricity. It was only asmall step onwards to disconnect thebattery and show that a magnet push-ed into or out of the iron ring would alsocause the galvanometer to deflect.The essential point, which no-one elsehad grasped, was that change was thekey, change of current when the ar-rangement was used as a transformer,or change of position when the ar-rangement was used with a magnet.
The next step was to produce acontinuous current from continuousmotion. Faraday realised that a prac-tical generator must use circular mo-tion, and devised the disc dynamo(Fig.3) which we now call a homopolargenerator. As shown, it consisted of acopper disc rotated between the polesof a strong magnet. Rubbing connec-tions were made to the shaft and alsoto the rim of the disc, and a small
36 Hobby Electronics, April 1981
Famous Names
TBATTERY
SENSITIVEGALVANOMETER
(c) Copyright MODMAGS Ltd.
Figure 2. The iron ring experiment. Faraday found that the arrangement, the first transformer,produced a pulse of current indicated on the galvanometer, at the instants when the switchwas opened or closed
MAGNET
CONTACTON SHAFT ---.4,
HANDLE
COPPERDISC
CONTACT ONEDGE OF DISC
TO VOLTMETER
© Copyright MODMAGS Ltd.
Figure 3. The homopolar generator. The disc revolving between the poles of the magnetgenerates a small voltage between the contacts, its magnitude depending on the speed of thedisc and the strength and size of the magnet
voltage could be detected when thedisc was spun round. Oddly enough,this arrangement, which has only everbeen a curiosity in the past, is nowcoming under investigation again. Thereason is that though the voltage isvery low, the current can be very large,and low -voltage high -current supplies
are just what we need for modernsemiconductor circuits. Since the out-put of the homopolar generator is DC,not just a full -wave rectified outputsuch as we get from most dynamos,the homopolar generator is ideal forproviding an emergency supply forelectronic equipment.
Faraday was content to move on toother topics, and leave the develop-ment of the dynamo to others, later,notably Siemens and Edison. His in-terest was still in the understanding ofthe mysterious relationship betweenelectricity and magnetism, and he wasfascinated by the representation ofmagnetism in terms of lines of force,an idea which he could express as adrawing. His intuitive feeling was thatelectrostatics, current electricity, andmagnetism must be part of the samething, but he lacked the mathematicalfacility to prove what he was suremust be true. The complete proof wasleft to Clark Maxwell just after Fara-day's death.
By 1844, Faraday was busy tyingup other aspects of electricity, still pur-suing his hunch that electricity was thekey to all science. In his early yearswith Davy,he had made manychemicalinvestigations, some of which hadbeen concerned with glass. Now glassis not a single chemical compound buta mixture, and so thousands of dif-ferent types of glass can be made. Onewhich Faraday had made and christen-ed 'heavy glass' turned out to be quiteremarkable. This particular glasspolarised any light which passedthrough it, acting in the way we allknow now from Polaroid sunglasses.What extraordinaryday's 'heavy glass' was that thepolarisation varied when a magneticfield was applied to the glass. To beprecise, the plane of polarisation wasrotated when a magnetic field was ap-plied. This was a clear indication of alink between light and magnetism, andthe 'Faraday rotation' as it is called isan effect which is used nowadays tocontrol laser beams, enablirig us tomodulate a laser beam directly by anelectric current.
Faraday retired in 1858, after acareer which had touched on and im-proved practically every branch ofscience. We've concentrated here onjust a few of his major discoveries,leaving out all his chemical and elec-trochemical work, which included thediscovery of electroplating. He died in1867, an experimenter of genius witha teacher's gift of clear explanation. Heleft behind him an extraordinarynumber of discoveries which still bearhis name, an organisation which still.delivers lectures in his name, and anew branch of engineering - electricalengineering. Few men have madesuch an overwhelming contribution toour present century.
HE
Hobby Electronics, April 1981 37
g
'PORTABLERADIO CASESize: 11 x 8 x 3% insapprox. Made from plywood, pleasingly covered.Suitable for any normalradio circuit. Has studsfor mounting 5" speakerand the front adolledto take a tuning amide,sor in the centre andnormal conti ois eitherside. E2.30 i f L Sot pa.
imonerar
LAST MONTH'S SNIP STILL AVAILABLEAnd it still dairies a tire gilt ,'r innii.ol,k r nigg gunny. veltnch exi arecur tenth selling at ed .rbr, ftnr .lull in Per btps the most useful Peakdown wire! we haw nisen ,rifer lid It is a patrol of lie.. my alldifferent eomptiter panels :ontaiiiing pan is which must Imve cost atleast £500. On these boaids sou will bird over .1(X) IC's. Own 300diodes, over 200 tiansistois and seven al thousand mho pails. iestst-ors, aondensoi, multi am. Pots, eeertnes, SCR, etc. etc. II you actProntPds loo ,.111.0, this par: el to, only 03.50, which when youdeduct the wait.e ot the desoldei inn pump, won Ls out to lust a littleover 4p per panel. Steels' this is a haigain you should not miss,When order mg please add E2.50 post and E1.27 VAT.
MAINS MOTORS Precision made asused in record players, blow heaters, etc.
Speed usually 1,400. All have amplespindle length for coupling fan blade,
pulley, etc. Power depends on stack size.5/8" stack E2.00; 0" stack E2.50: 7/8"stack E3.00; 1" stack £3.50; 10" stack£4.50. Add 25% to motor cost to cover pos-tage, and then add 15% VAT.
YOUR LAST CHANCE FOR THIS BARGAIN100 twist drills, regular tool shop price over £50, yours for only£11.50. With these you will be able to drill metal, wood, plastic, etc.from the tiniest holes in P.C.B. right up to about 0". Don't missthis snip - send your order today.
MAGNETIC LATCHLow voltage (4 - 8 volt AC/DC operation)Only f1.50 each.
PUNCHED TAPEEQUIPMENTFor controlling machine tools, etc, motorised 8 bit punch withtmatching tape reader. Ex -computers, believed Ingood workingorder, any not so would be exchanded. E17.50/pair Post £3.00
,,
STEREO HEADPHONESA' )
8 ohm impedance. padded, term1# I'Japanese made so very good quality.
41 /I.
plug. E2.99 Post hop.!noting with standard'/." lack-
BRIDGE RECIFIER1 amp 400v 30p each. /..10 for £2.50. 100 for £2000
SOLENOID WITHPLUNGERMains operated E1.9910 - 12 volts DCoperated £1.50.
MOTORISED DISCO SWITCHWith 10 amp changeover switches. Multi -
adjustable switches all rated at 10 amps,this would provide a magnificent displayFor mains operated 8 switch model
£6.25, 10 switch model £6.75, 12 switchmodel £7.25.
PANEL METERSJapanese made, full vision front, size 20i"x 20". 0 100 uA £2.85. Similar but size2" x 10" 100 uA, ualed Vu. Ditto, butscaled 0 - 100. (note: front covers easilyremovable if you want to rescale these£2.30 each) Ditto but size 1."0 1 0", scal-ed Vu, sensitivity 100 uA, E1.50.
MINI -MULTI TESTER Deluxe pocket size precision movingcoacoil instrument, jewelled bearings - 2000 o.p.v. mirrored scale.11 instant range measures: DC volts 10, 50, 250, 1000.
AC volts 10, 50, 250, 1000.DC amps 0 - 100 mA.
I Continuity and resistance 0 - 1 meg ohms in tworanges. Complete with test prods and insructionbook showing how to measure capacity andinductance as well. Unbelievable value at only£6.75 . 50p post and insurance.
FREE Amps range kit to enble you to readDC current from 0 - 10 amps, directly
on the 0 - 10 scale. It's free if youpurchase quickly, but of you alreadyown a Mini -Tester and would likeone, send £2.50.
SUPER HI-FI SPEAKERCABINETSMade for an expensive Hi-Fi outfit
will suit any decor. Resonancelie. cut-outs for 8" woofer and4" tweeter. The front material iscalved Dacron, which is thick andtit*, not need to be stuck in andthe completed unit is most pleas-ing. Colour black. Supplied in Pairs,pi ice £6.90 poi pan (this is probably less than the on inenal cost ofon,' f3.50 the pair.
LOUDSPEAKERS8" woofer and 4" tweeter, 4 ohms 35
watts power rating £6.90 Per pair.Ditto but 8 ohms, £11.50
per pair. Post £2.00.
ELECTRONIC VOLT-METER/ SENSITIVERELAYConsists of a 4'4" square dropthrough panel volt meter, 0 - 10fed. Built into the front of themeter are two screw adjusterswhich mow two pointers, up anddown the scale, to set a minimumand maximum. A unique "under"and "over" circuit inside the meteroperates one of two reed relays tobring an 'under' or 'over' circuit intoaction. The scale plate is detachable via two screws to be calibrat-ed to your own individual requirements. The 10 transistor 'under'and 'over' circuit is completely separate from the meter movementso does not have to be connected to use this as a standard 0 - 1
meter. Many uses including level controls, light controls, auto bat-tery chargers, alarm units, etc. Manufacturers list price of over£120 each. An unbelievable snip at £9.95 (less than the value ofthe meter alone.)
THIS MONTH'S SNIPVu METER Approximately 1 5/8" square, sensitivity0 500 uA suitable for use also as a recording level meter,Power output indicator or many similar applications. Fullvision front cover easily removable if you wish to alter thescale. Sac.' snip price £1, or 10 for E9. post & VAT paid.
3 wave band radio withstereo amplifier. Madefor incorporation in ahigh-class radiogram,this has a quality of output which can only bedescribed as superb. It
truly hifi. The chassissize is approx. 14". Push but-
tons select long, medium, shortand gram. Controls are balance, vol-
ume, treble and bass. Mains power supply.The output is 6 + 6 watts. Brand new and in perfect
working order, offered at less than value of stereo ampalone, namely E6.90. Post £2.50.
MULLARD UNILEXA mains operated 4 + 4 stereosystem. Rated one of thefinest performers in thestereo field this wouldmake a wonder ful gift foralmost anyone. In easy to assemble
-.701110modular form this should sell at about £30- but due to a special bulk buy and as an in-centive for you to buy this month we offer the sys-tem complete at only £16.75 including VAT and post.FREE GIFT - buy this month and you will receive a pair ofGoodman's eliptical 8"x 5" speakers to match this amplifier.
VENNER TIME SWITCHMains operated with 20 amp switch, oneon and one off per 24 hrs. repeats dailyautomatically correcting for the lengthen -Mg or shortening day. An expensive timeswitch but you can have it for only £2.95.These are new but without case, but wecan supply plastic cases (base and cover)£1.75 or metal case with window £2.95.Also available is adaptor kit to convertthis into a normal 24hr. time switch butwith the added advantage of up to 12 on/offs per 24hrs. This makes an ideal con-
troller for the immersion heater. Price ofadaptor kit is £2.30.
DELAY SWITCHMains operated - delay can be accuratelyset with pointers knob for periods of upto 20hrs. 2 contacts suitable to switch 10amps - second contact opens a few min-utes after 1st contact. £1.95.
LEVEL METERSize approximately square, scaled signaland power but cover easily removable forroweling. Sensitivity 200 uA. 75p.
J. BULL (Electrical) Ltd.(Dept. HE), 34 - 36 AMERICA LANE,
HAYWARDS HEATH, SUSSEX RH16 30U.
ADVANCE ADVERTISING BARGAINS LIST!Our FREE monthly list gives details of bargains arriving or justarrived - often bargains which sell out before our advertisement canappear - it's an interesting list and it's free - just send S.A.E.Below are a few of the Bargains still available.TRANSMITTER SURVEILLANCETiny, easily hidden but which will enable conversation to be pickedup with FM radio. Can be made in a matchbox - all electronicparts and circuit. E2.30.RADIO MIKEIdeal for discos and garden parties, allows complete freedom ofmovement. Play through FM radio or tuner amp. E6.90 comp. ki tSAFE BLOCKMains quick connector will save you valuable time. Features incluct.'quick spring connectors, heavy plastic case and auto on and offswitch. Complete kit. 0.95.LIGHT CHASERGives a brilliant display a psychedelic light show for discos, parties and pop groups. These have three modes of flashing, two ch.,patterns and a strobe el feet. Total output power 750 watts perchannel. Comlete kit. Price £16. Ready made up £4 extra.FISH BITE INDICATOREnables anglers to set up several lines then sit down and read a book.AsscroEn one has a bite the loudspeaker emits a shrill note. KitPrice
6 WAVEBAND SHORTWAVE RADIO KITBandsprearf covering 13.5 to 32 metres. Based on circuit whichappeared in a recent issue nf Radio Constructor. Complete kit in-cludes case materials, six transistors. and diodes, condensers, resist-ors, inductors, switches, etc. Nothing else to buy if you have anamplifier to connect it to Of a pair of high resistance headphones.Price £11.95.SHORT WAVE CRYSTAL RADIOAll the parts to make up the beginner's model. Price £2.30. Crystalearpiece 65p. High resistance headphone, (gives best results) E3.75.Kit includes chassis and front fair not case.RADIO STETHOSCOPEEasy to fault find start at the anal and work towards the speaker- when signal stops you have found the fault. Complete kit £4.95.INTERRUPTED BEAMThis kit enables you to make a switch that will trigger when asteady beam of infrared or ordinary light is broken. Main componants relay. photo transistor, resistors and caps etc. Circuit diagrambut no case. Price [2.30OUR CAR STARTER AND CHARGER KIT has no doubt savedmany motorists from embarrassment in an emergency you can startcar off mains or bring your battery up to full charge in a couple ofhours. The kit composes- 250w mains transformer, two 10 ampbridge rectifiers, start/charge switch and full instructions. You canassemble this in the evening, box it up or leave it on the shelf in thegarage, whichever suits you best. Price £11.50 £2.50 post.GPO HIGH GAIN AMP/SIGNAL TRACER. In case measuringonly 5%in x 3%in x 1%in is an extremely high gain (70413) solidstate amplifier designed for use as a signal tracer on GPO cables, etc.With a radio it functions very well as a signal tracer. By connectinga simple coil to the input socket a useful mains cable tracer can bemade. Runs on standard 40v battery and has input, output socketsand on -off volume control, mounted flush on the top. Many otheruses include genera( purpose amp, cueing amp, etc. An absolutebargain at only E1.85. Suitable BOohm earpiece 69p.3 CHANNEL SOUND TO LIGHT KITComplete kit of parts for a threethannel sound to light unit con-trolling over 2,000 watts of lighting. Use this at home if you wish,but it is more than rugged enough for Disco work. The unit is hous-ed in an attractive two-tone metal case and has controls for eachchannel, and a master on/off. The audio input and output are by'/.sockets and three panel mounting fuse holders provide thyristorprotection. A four -pin plug and socket facilitate ease of connectinglamps. Price £14.95, complete kit and case.8 POWERFUL BATTERY MOTORSFor models, Meccanos, drills, remote control planes, boats etc. £2.50.WATERPROOF HEATING WIRE60 ohms per yard, this is a heating element wound on a fibre glasscoil and then covered with p.v.c. Dozens of uses - around waterPipes, under grow boxes in gloves and socks. 23p per metre.COMPONENT BOARD Ref. W0998This is a modern fibreglass board which contains a multitude ofvery useful parts, most important of which are: 35 assorted diodesand rectifiers including 4 3amp 400v types (made up in a bridge) 8transistors type BC 107 and 2 type BEY 51 electrolytic condensers.SCR ref 2N 5062, 25 Ouf 100v DC and 100uf 25v DC and over 100other parts including variable, fixed and wire wound resistors, 'electrolytic and other condensers. A real snip at £1.15.FRUIT MACHINE HEART. 4 wheels with all fruits, motorised andwith solenoids for stopping the wheels with a little ingenuity you candefy your friends getting the "jackpot". £9.95. £4 carriage.DESOLDERING PUMPIdeal for removing components from computer boards as well as forservice work generally. Price £6.35.4 -CORE FLEX CABLEWhite pvc for telephone extensions, disco lights, etc. 10 metres E2,100 metres £15. Other multicore cable in stock.MUGGER DETERRENTA high -note bleeper, push latching switch, plastic case and batteryconnector. Will scare away any villain and bring help. £2.50 com-plete kit.HUMIDITY SWITCHAmerican made by Honeywell. The action of this device dependsupon the damphess causing a membrane to stretch and trigger asensitive microsvvitch. Very sensitive breathing on it for instance willswitch it on. Micro 3 amp at 250V a.c. Only £1.15.EXTRACTOR FANS - Mains VoltageEx -Computer, made by Woods of Colchester,ideal also as blower; central heatingsystems, fume extraction etc. Easy finingthrough panel, very powerful 2,500 rpmbut quiet running. Choice of 2 sizes,5" £6.60. 6" £6.60. post Et per fan.
TIME SWITCH BARGAINLarge clear mains frequency controlledclock, which will always show youthe correct time + start and stop switch-es with dials. Complete with knobs.£2.513. A
J. BULL (Electrical) Ltd - Established 25 years. MAIL ORDER TERMS:Cash with order - please add 60p to all orders under £10, to offset packing,etc. ACCESS & BARCLAYCARD WELCOMED. Our shop is open to callers.BULK ENQUIRIES INVITED. Telephone: Haywards Heath (0444) 54563.
t38 Hobby Electronics, April 1981
GuitarTremoloAmplitude -modulate the sound from yourguitar with our simple -to -build tremolo
A TREMOLO MAY NOT be the latestelectronic musical effect but, like thefuzz effect produced by the HEFuzzbox (see last month's issue) it hasremained popular. Our simple designis primarily intended for use with aguitar, and has both variablefrequency and depth controls. It givesexcellent results and has a low noiselevel.
The tremolo effect is very simple inprinciple, and just consists of anautomatic volume control that varies
Hobby Electronics, April 1981
the volume up and down at a typicalrate of a few times per second.Obviously this effect could beproduced manually, but it is usually farmore convenient to have a unit thatproduces the effect automaticallyusing an oscillator driving a voltage -controlled attenuator (VCA).
ConstructionAs this unit is likely to receive a fairamount of rough treatment it isadvisable to fit it into a very strong
case, and a diecast aluminium box isideal. However, any strong case ofmetal construction (to shield thecircuitry against interference pick-up)is suitable. Switch SW1 is a heavyduty, successive operation (ie pushon/push off switch, and this ismounted on the top panel of the caseso that it can be operated by foot. Theother controls and sockets are fittedalong two sides of the case. On ourunit SW2 is part of input socket SK2,but a separate switch can of coursebe used here is preferred.
The other components are fittedonto a 0.1" matrix Veroboard, 15strips by 37 holes, and this is cutsown from a board 3.75" wide usinga hacksaw. Then the two Y8 "diameter mounting holes are drilledand the breaks in the copper strips aremade, after which the board is readyfor the components and links to befitted into place. Integrated circuit IC1has a MOSFET input stage, and toavoid damage due to high staticcharges we strongly advise you to usean IC socket with this device. Itshould be the last component to befitted to the board and should be leftin its protective packaging until thattime. Handle the device as little aspossible.
Once the board has been wired upto the controls, sockets, and batteryclip, as shown in Fig. 2, it can bemounted inside the case using M3 or6BA fixings.
Once completed, the unit is wiredbetween the guitar and the amplifier(the circuit is automatically switchedon when the guitar lead is plugged in,and switched off again when the leadis unplugged from SK2). With RV2adjusted for zero tremolo, RV3 isadjusted by trial and error to give thesame volume with the unit switchedin or out of circuit using SW1.
39
Cl100u
R139k
R339k
R239k
IC
4
NOTE:IC1 IS CA3140E01 IS BF244B02 IS BC109
C23u3
RV147k
R46k8
C34u7
C410u
RV2+ 22k
R54k7
R121k0
RV347k
i9100n
R633k
SW2(PART OF SK2)
SVV1(3
C6
0 +9V
1u0
R84k7
+C710u
R,3k9
C10100u
OSK1OUT
(c) Copyright MODMAGS Ltd.
R101 M8
R11680R
Q2C8100n
SK2IN
SW16
Figure 1. Circuit diagram
How It WorksThe HE Tremolo consists of two main parts: a voltage -controlled amplifier and a squarewave oscillator togenerate the control voltage. The squarewave is filtered by a resistor/capacitor combination to change it into aclose approximation of a triangular wave.
The tremolo effect is produced by changing the amplitude of the guitar signal according to the rise and fall ofthe triangular wave thus producing the output waveform shown. This combined waveform consists of theoriginal guitar signal amplitude modulated by the triangular wave.
Figure 1 shows the circuit of the tremolounit, and it consists of three main sections:an oscillator based on IC1, a VCA usingQ1, and a pre -amplifier which uses Q2.
The oscillator is a well-knownconfiguration, and this generates asquarewave output at pin 6 of IC1. This isnot the ideal waveshape since it wouldresult in the output signal simply beingswitched between two volume levels,whereas we really require a smoothvariation between the two extremevolume levels. The output of the oscillatoris therefore coupled via C4 and 'depth'control potentiometer RV2 to a simple RC
1
INPUTSQUARE WAVE
SQUAREWAVEOSCILLATOR
C
filter which consisted of R5 and C5. This'smooths' the squarewave into a muchmore suitable (sawtooth-like) waveform.Potentiometer RV1 is the tremolo fre-quency control, and it gives a range ofroughly 1.5 to 10 Hz. Capacitor C3 is usedto suppress high -frequency harmonics onthe output signal of IC1 which couldotherwise leak into other parts of thecircuitry giving unwanted 'clicks' on theoutput signal.
Transistor Q2 is used as a common -emitter pre -amplifier stage withunbypassed emitter resistor R11 beingused to introduce negative feedback
VOLTAGECONTROLLEDAMPLIFIER
OUPUT
TRIANGULAR SHAPEDCONTROL VOLTAGE
Copyright MODMAGS Ltd.
which reduces the voltage gain of thestage to a suitable level (about 6 times). Italso boosts the input impedance of thestage to a level that gives a good match foran electric guitar pick-up.
The output of Q2 is coupled by C7 tothe VCA formed by R8 and the drain -to -source resistance of 01. Preset RV3 andresistor R6 are used to give a controlledreverse bias to the gate of 01 via R7, andthis is adjusted to give a drain -to -sourceresistance in Q1 that gives roughly unityvoltage gain through the circuit underquiescent conditions lie with zeromodulation signal). If RV2 is advanced togive a small modulation signal, this iscoupled to the gate of Q1 by C9. Here itvaries the gate voltage slightly, givingconsequent changes in the drain -to -sourceresistance of Q1 and the gain through thecircuit. This gives the tremolo effect.Adjusting RV2 for a larger modulationsignal gives larger and more rapid changesin the amplitude of the output signal and amore 'aggressive' tremolo effect.
Switch SW1 enables the tremolocircuitry to be bypassed when the tremoloeffect is not required, and SW2 is theordinary on/off switch. The circuit has acurrent consumption of only about 2 mA,and a small (PP3 size) 9 V battery issufficient to give many hours of operation.
40 Hobby Electronics, April 1981
Guitar Tremolo
Parts ListRESISTORS (All 1/4W 5%)R1,2,3 39kR4 6k8R5,8 4k7R6 33kR7 3M3R9 3k9R10 1M8R11 680RR12 1k0
POTENTIOMETERSRV1 47k linearRV2 22k linearRV3 47k miniature horizontal
preset
CAPACITORSC1,10 100u, 10 V electrolyticC2 3u3, 35 V tantalumC3 4u7, 10 V electrolyticC4,5,7 10u, 10 V electrolyticC6 1u0, 10 V electrolyticC8,9 100n polyester
SEMICONDUCTORSIC 1 CA3140E operational
amplifierQ1 BF244B N -channel JFETQ2 BC109 NPN transistor
MISCELLANEOUSSW1 double -pole, double -throw foot
switchSKI 'A" jack socketSK2 'A" jack -socket with double -
pole, double -throw switch(SW2)
0.1" VeroboardCase to suitKnobsBattery + connector
Buylines
0
N
M
K
H
0
O
C
B
A
C
RV2
0
RV1
SW1
SK2
......5 6 7 8 9 10 1 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 2' 30 313\0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
R11
R
+ C D C2C IC1 D
a
R2
C5R5
00 00 000.0000 R1146
C9
R6
02 b C7 R10600000000 00000
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0000000000000000000000 000000000000000000000000000 0000 0000000000000000000000000 0000 0000000000ir0000 0000000000000 000000000000000 00000000000000000000000000 00000000000000 0000000000000000000 000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000
There are two unusual components usedin this project; SK2 and SW1. These areboth available from Maplin ElectronicSupplies.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33
C Copyright MODMAGS Ltd.
Figure 2. Component positions, underneath track breaks and connection details
34 35 36 37
HEApproximate price for all parts
excluding case is £12.
Hobby Electronics, April 1981 41
First the EuroBreadBoardNow the EuroSolderBoard
vANk -70
`010
Indispensible
for the professional
42V,
Ideal
for the beginner
Design on a EuroBreadBoard - Instal on a EuroSolderBoard
First the EuroBreadBoardWill accept 0.3" and 0.6" pitch DI L IC's, Capacitors, Resistors,LED's, Transistors and components with up to .85mm dia leads.500 individual connections PLUS 4 integral Power Bus Strips alongall edges for minimum inter -connection lengths.All rows and columns numbered or lettered for exact locationindexing (ideal for educational projects)Long life, low resistance (<10m ohms) nickel silver contacts£6.20 each or £11.70 for 2
Now the EuroSolderBoardNew 100mm square, 1.6mm thick printed circuit board with pre -tinned tracks identically laid out, numbered and lettered to Euro-BreadBoard pattern.Four 2.5mm dia fixing holes.£2.00 for set of three ESB's
And don't forget the EuroSolderSuckerIdeal for tidying up messy solder joints or freeing multi -pin IC's, this195mm long, all metal, high suction desoldering tool has replaceableTeflon tip and enables removal of molten solder from all sizes ofpcb pads and track. Primed and released by thumb, it costs only£7.25 including VAT & PP
Snip out and post to David George Sales,Unit 7, Higgs Industrial Estate, 2 Herne Hill Road, London SE24 OAUems= meow
David George Sales, HE4Unit 7, Higgs Ind. Est., 2 Herne Hill Rd., London SE24 OAU.Please send me: -
42
1 EuroBreadBoardor 2 EuroBreadBoardsor 3 EuroSolderBoardsor 1 EuroSolderSucker
@ £ 6.20@ £11.70@ £ 2.00@ £ 7.25
00 Please
0 Tick0
All prices are applicable from Jan. 1st 1980 and include VATand PP but add 15% for overseas orders.
Name
CompanyAddress
Tel. NoPlease make cheques/P.O. payable to David George Salesand allow 10 days for cheque clearance and order processing
EVERCOMultiband Receiver plus 40 -channel CBMonitor. Frequency coverage-54- 87 MHz 145-176 MHz88-108 MHz Plus H1 40 CB Channels.
108-145 MHzThis unit has a telescopic antenna andsquelch control, sockets for earphoneand external DC power source.
£21.95 inc. VAT + 75p P&P
The latest from the U S A
PINBALL WIZARD*Still available *
Featured in Nov issue of E T I
Home TV Game - B/W Kit
Basic Kit £28.90Contains everything except box andcontrolsBox & Controls £6.50. P S U £3.90CEH Car Alarm Kit £18.90Chrome Chime 24 tune door chimes kit,E10.75. Built £15.95
HE MICROBE R/CBasic Kit E19.90(2 PCBs and all PCB components)
ELECTRONICGAMES
Star Chess T /V game . £63.35Database Prog T/V game £89.95Chess Challenger 7 £99.00Chess Challenger 10 £160.00Voice Challenger £230.00Chessmate 8 level E59.95Zodiac Astrology Computer £29.95Electronic Mastermind £14.90Supersonic Mastermind. New £21.00Mattel Subchase. New £17.90Mattel Armor Battle. New £17.90Enterprise 4 in 1 E22.90Galaxy Invaders. New £22.95Radio Control Models -Various
Ball Clock as H E offer. Kit £24.95, orready -built £29.95.
S a.e. enquiries. Please allow up to 21 days for delivery. ALL PRICES INCLUSIVE
UNIT 6 11.61 BROAD LANE, LONDON N.15 4DJ
11,1111 k1, 1
Day 01-808 0377; Eve 01-889 9736
itBARG. C110
LOW-COST, RUGGEDTEMPERATURE CONTROL
HIGH QUALITY
TEMP. GAUGE 0° -120°CRemote sensor on 38"capillary, panel mountingdial 55mm. diaONLY E1.85(Intl P&P)---
RELAYS BYKEYSWHITC
10A 2 -Pole C/O 240VCoil.
,
ONY 80p2 foLr E1.505 for E3.50
Panel M.E.S. Bulb HolderHigh quality. Red lens 30p
BULGUR GLASS FUSES20 mm 1A Quick Blow
10 for 40p1" (same size as 13A plugfuse but not to BS1362). Willfit most 13/4" chassis mountfuse holders. 10A quick blow5A anti -surge, 3A quick blow
10 (any mix) 40p100 foe E3
16A 240V RANCO THERMOSTATWide control range (low room temp. to over boiling point)Sensor on 22" capilliary. E2.30, including control knob.
+alRANCO THERMAL CUT-OUT 100°C15A 240V. Sensing coil on 41in. capilliary. panelmounting with reset button, £1.20.
1rGEC
CONTACTOR3 heavy duty
h,normally open
rcontacts 600V35A. 240V c.ONLY £4.50.
BUY ONE EACH OF ABOVE FOR £4.85
LIGHT DEPENDENT RESISTORS in plastic housingwith window, heavy-duty lead. Similar to ORP 61.You normally pay well over double for resistor alone.Only 30p or E2.35 for 10.
DOUBLE ENDED SMITHS BLOWERS2 output apertures, 53 x 103 mm Large flange. Only£5.50.
TOP QUALITY CHROMETOGGLE SWITCHES
2 pole C/0 centre off 10A240V, 80p, 2 for £1.50, 5for £3.50.2 Pole make, biased off 2A240V
30p. 4 fox E1
SMALL INDUCTION MOTOR (shaded pole), doubleended with 3/4" x 31/2" shafts. 240V £3.25.
BULGIN STRAIN RELIEF SLEEVE 10 FOR 30p
USEFUL RUBBER GROMMETS. Fit 3/4" hole. 10 for20p. CAPACITOR, BOOV AC.
RMS. 0.01 MFD.30p eachPOWER RESISTOR, wire -ended, 20 -watt, 4101) 5'..
Only 50p.
L.E.M. SERVICES239 RUGBY ROADLEAMINGTON SPA CV326DYPinta WARWICKSHIRE
ADD 50p P&P
ORDERS OVER
62.50 post free
Hobby Electronics, April 1981
HERE'S a second chance to own the most valu-able aid to the electronics hobbyist -AN OSCILLOSCOPE. With a screen size of 75 mmand a bandwidth of DC to 5 MHz the Kikusui 538Awill enable you to 'see' how circuits are working in-stantly.Apart from the CRT, semiconductors are usedthroughout the circuit: the 'scope is ready to operatein under 20 seconds. It comes complete withoperating manual containing full details of operation,maintenance, calibration and circuits.
All-inclusive cost of the 538A, delivered to yourdoor, is only £95. Each 'scope carries a full one-yearguarantee.We had an overwhelming demand for the 538Awhen it was first offered in the February '81 issue ofHE: the entire stock was cleared in the first twoweeks!
BRIEF SPECIFICATION
Vertical DeflectionVoltage sensitivityBandwidth
Input impedance
Ext. Horizontal AmplifierVoltage sensitivityInput impedance
CRT
Power RequirementsVoltage
Wattage
Dimensions
< 10 mV/divisionAC 2 Hz to 5 MHzDC DC to 5 MHz within - 3dBIMO ± 5% within 35 pF
< 250 mV/divisionIMO 10% within 35pF
75 mm (2.95" I round screen, greenphosphor
100, 110, 117, 220, 230, or 240 VAC,50 to 60 Hzabout 10 VA
202 mm wide by 160 mm high by305 mm deep. (7.9 by 6.3 by 12" I
Hobby Electronics, April 1981
OSCILLOSCOPEEXCLUSIVE OFFER
for HE readers
So don't miss this second chance to own a high -quality 'scope . . . and choose between TWOmethods of payment: Barclaycard or cheque
Enter your Barclaycard number in thespace provided on the coupon, add yoursignature, name and address - and we'lldo the restEnter your name, address and the amountin the coupon and send it with your che-que, made payable to Modmags Ltd.
Please also specify the number of 'scopes you require
SEND ALL ORDERS TO:HE Scope Offer,Modmags Ltd.,145 Charing Cross Road,LONDON WC2H OEE
Please note that the offer applies to UK mainland only: allow 28days for deliveryII= mi mum no MMMMMMMMMMMM
I WISH TO PAYBY BARCLAYCARD
PLEASE CHARGE TO MY ACCOUNTMY BARCLAYCARD NUMBER IS'
VISA
I enclose a cheque forfor Kikusui 538A Oscilloscope/s
SIGNATURE
NAME(BLOCK CAPITALS)ADDRESS
I= NM IMI NMI MN IM =I MN NM Ill
II
I
IIII
I
43
All theseadvantages...
Instant all-weather starting Smoother running Continual peak performance Longer battery & plug life Improved fuel consumption Improved acceleration/top speed Extended energy storage
..in kit formSPARKRITE X5 is a high performance.lop quality inductivedischarge electronic ignition system designed for the electronicsD Y world It has been tried, tested and proven to bp utterlyreliable, Assembly only takes 1 -2 hours and installationeven less due to the patented 'clip on' easy fitting
The superb technical design of theSparkntecircuit eliminates problems of thecontact breaker' There is no misfire due tocontact breaker bounce which iselaninatixtelectronically by a pulse suppressioncircuit which prevents the unit firing if thepoints bounce open at high R P MContact breaker NIP') IS eliminated byreducing the current by 95"o of the norm
There is also a unique extended dwellcircuit which allows the coil a longerperiod of time to store its energy beforedischarging to the plugs. The unit includesbuilt in static timing light, systems functionlight, and security changeover switchWill work all rev counters
Fits all 12v negative -earth vehicleswith coil/distributor ignition up to 8 cylinders.THE KIT COMPRISES EVERYTHING NEEDEDDie pressed case Ready !lolled. aluminium extrudedbase and heat sink. coil mounting clips and accessories All kitcomponents are guaranteed for a period of 2 years from date ofpurchase Frilly illustrated assembly and installation instructions areincluded
f 4
Roger Clark the world famous rally driversays "Sparkrite electronic ignition systemsare the best you can buy"
HIGH PERFORMANCEHIGH PERFORMANCEELECTRONIC IGNITION
Electronics Design Associates, Dept. HE/4/812 Bath Street, Walsall, WS1 3DEPhone. (0922) 614791Name
Address
Phone your order with Access or Barclaycard
Inc V A.7 and P P QUANTITY Rfil'D
X5KIT £16.95ACCESS OR BARCLAY CARO No.
44
I endose cheque PO's for
Cheque No
Send SAE of brochure only required.
attivofE
68LARGEPAGES
O
IP tali ORS
ViY t" ''$4001001.10
4
GCd
The largerCataloguethat means
FREE POSTAGEIN U.K.
ADDITIONALDISCOUNTS
KEEN PRICES9
GUARANTEEDSATISFACTION
9GOOD STOCKS
We pay postage
Semi -Conductors I.C.s Opto-devices Rs and Cs in great variety Pots Switches KnobsAccessories Tools Materials Connectors
ELECTROWTE foRlsEKING
ELECTROVALUE LTD. (Dept. HE4j 28 St. Jude's Road. Engletield Green, Egham. SurreyTW20 OHB Telephone: (STD 0784( (London 87) 33603. Telex. 264475
GEC AM/FM STEREO TUNERAMPLIFIER CHASSIS. Originally de-signed for installation into a music centreSupplied as two separate built and testedunits which are easily wired together.Note: Circuit diagram and interconnec-ting wiring diagrams supplied. RotaryControls: Tuning, on /off volume,balance, treble. bass. Push-button con-trols, Mono, Tape, Disc. AK, FM (VHF).LW. MW. SW Power Output: 7 wattsRMS per channel, at better than 2% THDinto 8 ohms. 10 watts speech and music.Frequency Response: 60Hz-20kHzwithin -±3dB.Tspe Sensitivity: Output- typically 150 MV. Input - 300 mV forrated output. Disc Sensitivity: 100mV(ceramic cartridge) Radio: FM (VHF),87 5MHz - 108MHz Long wave145kHz - 108kHz. Medium wave,
520kHz - 1620kHz. Short wave.5.8MHz - 16MHz. Size: Tuner - 23/4in.x 15in. x 71/2 in approx. Power amplifier -2in. x 71/2in. x 41/zin. approx. 240V ACoperation. Supplied complete with fuses,knobs and pushbuttons, and LED stereobeacon indicator. Price £21.50 plusE2.50 postage and packing.
Stereo Cassette Tape Deck Module comprisingof a top panel and tape mechanism coupled toa record/play-back printed board assembly.Supplied as one complete unit for horizontalinstallation into cabinet or console of ownchoice. These units are brand new, ready -builtand tested.Features: Three digit tape counter, Auto -stop,Six piano type keys, record, rewind, fast for-ward, play, stop and eject. Automatic recordlevel control. Main inputs plus secondary in-puts for stereo microphones. Input sensitivity100mV to 2V. Input impedance 68K. Outputlevel 400mV to both left and right-hand chan-nels. Output impedance 10K. Signal to noiseratio 45dB. Wow and flutter 01.1°,0. Powersupply requirements 18V D.C. at 300mA.Connections the left and right-hand stereo in-puts and outputs are via individual screenedleads all terminated with phono plugs (phonosockets provided). Dimensions: Top panel51/2in. x 111/4in., clearance required under toppanel 21/4in.Supplied complete with circuit diagram andconnecting diagram.Price £25.70 + £2.50 postage and packing.Supplementary parts for 18V D.C. powersupply (transformer, bridge rectifier andsmoothing capacitor) £3.
B.K. ELECTRONICS37 Whitehouse Meadows, Eastwood, Leigh -on -Sea, Essex SS9 57 tBARCLAYCARD ski for curiae kris 011..1 orders welcome * All prices
include VAT Moil order only 111 items packed 'where epplicableiis special energy ebrarbing PU ices Caters Welcome by priorappoelosol. please telephone 0702 527572.VISA
Hobby Electronics, April 1981
Short Circuit
Direct ReadingOhmmeterThis is a useful piece of equipmentfor checking unknown resistors,continuity of coils, transformerwindings etc. Designed around a741 operational amplifier it has theadvantage that once the meter dialis calibrated, resistance can be readdirectly from the scale without theusual cramping at the low -resistance end.The meter can have any intemalresistance, but it must be made upto 3k by an external resistor R7.The prototype used a meter with aninternal resistance of 100R. It is agood idea to make up the meterresistance to a round value of say,300R, by a small resistance so thatyou aren't left with an awkwardvalue for R7.The complete unit is self -zeroingand is protected against open -circuit or unknown resistance atRx by diode Dl.
1M0
SW15
R3R4
1R2 I 15100k
ZD1
R51k0
+30V
R62k7
NOTE:IC1 IS 741ZD1 IS 3V0 ZENERD1 IS 0A90/95
10k
DRx
R7(SEE TEXT)
ME11MA
© Copyright MODMAGS Ltd.
All short circuits are offered as suggestions only. To the best of our knowledge they are fully workingdesigns, but we have not tested them. If you have an original design which you would like to see published asa Short Circuit, send it to us - we will pay for all circuits published.
IPOOEWSW
RADIO
SAG
HE BACKNUMBERSr on moo me min Ns NE In miegI Please send me the following backnumbers of HE (indicate i
number required alongside the appropriate month)
1979 1980 1981Jun Feb Jan
Jul Mar Feb
aarevrio"
DISCO LIGHTSBIWA TS. SPESAsowd-Into-Ln
Scowl
tr.* Ws.
on WOW
WA.
1979JuneJulyAugustSeptember
r OctoberDecember
Any gaps in your HElibrary? There's stilltime to fill them. listedbelow are all thecurrently -availablebacknumbers.
1980February AllMarchMayJuneJulyAugustSeptemberOctoberNovemberDecember
1981
Each issue cost 1.00 (surface mail anywhere in the world).Please specify the months required in the coupon below andsend it, together with a cheque or postal order (madepayable to Modmags Ltd.) to:
HE Backnumbers Dept.,Modmags Ltd.145 Charing Cross Road, Postal Order
LONDON WC2H OEE
Hobby Electronics, April 1981
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45
RussianRouletteGameRUSSIAN ROULETTE as a gameapparently originated in the officers'mess of army posts around theworld, where shell-shocked officerswould gamble with their own livesmerely as a relief to boredom. Theidea was to load one bullet in thechamber of a revolver, then to spinthe chamber so that nobody wouldknow exactly where the bullet was inrelation to the firing pin. One of themen would then hold the gun pointedto his own head, pull the trigger and- if he was lucky (an average of 5out of 6 times) - click, if not (1 outof 6) - bang.
The HE Russian Roulette Gameharmlessly imitates the real thing. Ituses an integrated circuit to clock in acycle of six, simulating the six bulletspaces of the chamber. By operatingthe spin switch the 'bullet' isautomatically moved round - thechamber is spun. Each time the'trigger' switch is pressed, the bulletcomes one step closer to the 'firingpin', which is a LED in our game.When the bullet reaches the firing pin
46
Put the 'bullet' in, spin the chamberand take a chance with HE
This one will just kill you -a harmless electronic simulationof a dangerous game. Save the expense of redecoration:better still, save your life - with this fun -filled game from HE
the LED lights, 'killing' the last playerwho pulled the trigger. The winner ofthe game is the last one left - hebuys the next round of drinks.
As you can see, we managed to fitour prototype inside the handle of afull-sized polystyrene model of a gun(a 4" Smith 8- Wesson 44 Magnum).There is of course, no reason why an
Our prototype fitsinside the adaptedhandle of a 44Magnum model gunmade by LEtS Co., Ltd.
,iiics, pril 1981
Parts ListRESISTORS (All 1/..W, 5%)R1,2 18kR3 330kR4 470R
CAPACITORSC1,2 100n ceramic
SEMICONDUCTORSICI 555 timerIC2 4017 decade
counter/dividerLED1 red LED
MISCELLANEOUSSW1 single -pole, single -
throw miniature toggleswitch
SW2 double -pole, double -throw miniature toggleswitch
PB1 single -pole, single -throw, momentaryaction push switch
9 V battery + clip (PP3-size)Case to suit
BuylinesThe parts for this project (excluding thePCB and whatever housing you use) willcost about £6. You should have nodifficulty in obtaining components.
Any good model shop should be ableto help with a suitable model gun. Becareful to choose one which has enoughroom inside to house the project.
ordinary plastic potting box can't beused: we chose a gun simply to makeit look good. So, we'll leave thechoice of casing up to you and dealonly with the electronics.
If you are restricted by size, as wewere, then you should use our PCBdesign. The circuit shouldn't be muchbigger if you build it on Veroboardbut those extra few millimetres mightjust give you the edge. Begin byinserting the resistors, followed bythe two capacitors as shown in theoverlay in Fig.2.
At this point we normally adviseyou to use IC sockets but if you aretroubled by lack of space then solderthe ICs directly into the board. The4017 is a CMOS chip and as suchshould be handled carefully. Use anearthed soldering iron and, as withany semiconductor, solder one pin ata time, letting the device cool beforesoldering the following pin.
Next, connect the switches, LEDand battery as shown in Fig.2 using agood -quality momentary -action pushswitch for PB1. Then switch on andtry it out.
Hobby Electronics, April 1981
R2IC1 3
Ti700 T2100n
Figure 1. Circuit diagram
0SW2aSPIN
I PB1TRIGGER
0
R3330k
SW1ON/OFF cf../..
165
14 IC2 15
8 13
NOTE:ICI IS 555IC2 IS 4017LED1 IS A RED LED
LED1
R4470R
I SSWP I2Nb9V
Copyright MODMAGS Ltd.
Figure 2. Overlay of the printed circuit board, whose foil pattern is on page 65
BIASED UP
ANODE
LED1
I
PB1
R3
9V BATTERY
R2
C2 Copyright MODMAGS Ltd.
HE
How It WorksAn oscillator clocks the counter whenever the spin switch is pressed.Upon release the state of the counter is not known. Pressing the triggerswitch clocks the counter on, one step. If that is the number one output,the LED lights indicating that the bullet has been fired.
© Copyright MODMAGS Ltd.
OSCILLATOR
The oscillator is formed around a 555astable multivibrator circuit operating atabout 250 Hz. This frequency is definedby the resistor/capacitor chain R1,2 andC1 according to the formula:
1.45f = (R1 + 2R2) x C1
Switch SW2 is the spin switch, which
TRIGGER I
LED
ti
does two jobs when pressed: it connectsthe oscillator to pin 14, the clock input ofthe 4017 counter, and it isolates the LEDso that it cannot flash. Releasing SW2stops the 4017 from clocking. Eachpress of the trigger switch, PB1, providesone pulse to the clock input and thusmoves the 4017 on one step. When theoutput of the counter corresponds to theLED connection the LED lights up.
47
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er the chip.Be it a career, hobby or interest, like it or not the Silicon Chip
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48 Hobby Electronics, April 1981
0 ',Ave Q&AIt's time to talk about transducers. Nick Walton explains what they are, what they doand where you'll find them being used
We have transducers on the bill of farethis month and we will be meetingmike as well - but more of him anon.Whatever is a transducer? Well, I haveseen it described as a device whichchanges one form of energy intoanother and while that is the basicidea, it is somewhat incomplete. In thesame way you could describe yourown body as a transducer as it spendsa lot of its time changing energy of onesort into another, but as an example itjust does not feel right. So we have tosettle for a definition something alongthe lines of a device which receives asignal (or series of waves) in one formand produces a corresponding signalor series of waves in another energeticform. An excellent example of this isthe loudspeaker. It spends its timereceiving alternating currents from theoutput of an amplifier and faithfullyconverting these into movements of astiff paper cone. These movements inturn cause small changes of airpressure which our ears perceive assound. So while the energy change bitdoes take place we can also say thatthe form of the output is a faithfulreproduction (!) of the input.
Hopefully you can see the sameidea coming over from the function of amicrophone which does the reverse ofa loudspeaker: sound vibrations go inand corresponding electrical vibrationscome out and are fed usually to the in-put of an amplifier.
Today there is quite a range ofdevices all busily transducing, some inan obvious way and others not quite soobviously. Perhaps you can nowunderstand why our syllabus men-tions, apart from the speakers andmikes we've already mentioned, thefollowing things as transducers:record player pickups, the thermocou-ple (a junction of two metals betweenwhich there appears a voltage whenthe junction is heated), various lightsensitive devices which conduct bet-ter or give rise to a voltage under the in-fluence of light, and our friend the ther-mistor (pushing it a bit, you mightthink) which drops its resistance as itstemperature goes up.
If you want a really one-uptransducer, then how about thephotocoupler? This is a combination oflight -emitting diode, itself a sort oftransducer which emits its light (deriv-ed electrically in the first place) and aphoto -transistor which changes itsconduction according to the level oflight incident on it. The two parts of thecircuit can be electrically separate fromeach other. Applications of thistransducer are found in oscilloscopesfor controlling the grid of the tube andalso in the control of thyristors. Sur-prisingly, this photocoupler canoperate at frequencies in the kilohertzrange.
Usually, a transducer is what is call-ed 'passive'; that is, its energy outputis derived solely from the input energy.If it derives energy for its output from asource other than just the input wavesit is referred to as being 'active'.
Left-handed Look AtLoudspeakersLet us now look at our transducers inmore detail, and if we first consider theloudspeaker some further basic elec-tromagnetism might not come amiss.A proper understanding of theloudspeaker involves something calledFleming's left-hand rule. (This wasnamed after Sir John Ambrose Flem-ing: a physicist who lived to the ripe oldage of ninety five during which time he
Figure 1. North and south poles of perma-nent magnets attract each other
Copyright MODMAGS Ltd.
Figure 2. How a current -carrying wirebehaves in a magnetic field
invented and developed the thermionicdiode for which he coined the name -guess what - the valve.) If youremember back to the Decemberissue, we looked at magnetic field linesor lines of force. Magnetic behaviourcan be explained by regarding lines offorce wanting to shorten themselves.Thus a north pole of one magnet near asouth pole of another can result in thetwo being drawn together (Fig.1 ).Suppose we now have, going straightthrough this field, a current -carryingwire represented by the cross midwaybetween the poles with circular lines offorce round it, as shown in Fig.2. Therewill be a force pushing downwards onthe wire and you can think of this ascoming about because the north -southfield lines want to shorten themselves.It's a bit like a catapult with the wire asthe stone and the stretched field linesas the stretched elastic under tension.So we have a right angle between eachof the three quantities we are dealingwith. That is, the magnet's field (left toright across the page), the conven-tional current direction (perpendicular-ly to the page) and the force pushingthe wire towards the bottom of thepage. Any two you choose will be atninety degrees to each other.
These directions follow the wayyour left hand goes if you do a 'thumbsup'. With your hand in this position,point to someone facing you (without,of course, changing the position of
N
Copyright MODMAGS Ltd.
(WIRE CARRYING CURRENT
DOWN INTO THE PAPER
Hobby Electronics, April 1981 49
FIRST FINGER(FIELD, NHS DIRECTION)
SECOND FINGER (CURRENT,BY CONVENTION POSITIVETO NEGATIVE DIRECTION)
Figure 3. Illustrating Fleming's Left-hand rule
your thumb) and straighten out yourbig finger (see Fig. 3). The First fingerrepresents the field, the seCond fingerrepresents the current (conventionalpositive -to -negative flow, that is) andthe Thumb represents the thrust on thewire. You could use the 'm' in thumb tostand for motion of the wire exceptthat it may not always move but thereis always a thrust or force on it.
And what is the neatest example ofFleming's left-hand rule? You'veguessed. It is the loudspeaker, onceyou realise that the clever bit is theshape of the magnet. A section of thewhole speaker is shown in Fig.4, anddetails of the permanent magnetassembly are shown in Fig.5. WhileFig.5a shows a side section of themagnet,Fig.5b shows a view on -axis- in other words, what you would seeif you tore out the cone and the speechcoil. Actually I am not just being van-dalistic. If you can get hold of an oldwrecked speaker you can learn a lot bycutting it up as far as possible to look atthe coil and the shape of the perma-nent magnet. The poles are as closetogether as they can be, leaving justenough of a gap to let the coil slip in asindicated.
Now, looking at the top half ofFig.5a and putting in the x symbol torepresent the wire of the coil at thatpoint going away from you, we get toFig.6. Now give that the Fleming left-hand treatment (first fingerdownwards from the top of the page tothe bottom, second finger down intothe page) and you either discover yourthumb is pointing to the left side of thepage, or that you have dislocated yourshoulder. Try turning the magazineround instead of yourself - you'll findit's a bit lighter. So with the current inthat direction the coil is pushed to theleft. You should also check that thelower half of the coil is also pushed tothe left - otherwise you could have
RIGID FRAME
MAGNET
COIL
rn. Copyright MODMAGS Ltd.
Figure 4. Section through a loudspeaker,perhaps the best-known transducer of all
a
b COIL FITSIN HERE
Copyright MODMAGS Ltd.
Figure 5. Loudspeaker permanent magnet:a) side section showing north and southpoles and position of speech coil, b) view in-to centre pole of magnet, from cone side
Copyright MODMAGS Ltd.
Figure 6. Current -carrying wire in a magneticfield - this time between the north andsouth poles of the magnet shown in Fig. 5a
problems! Then, if a split second laterthe current flows in the other direction,further attempts to dislocate yourshoulder (it must still be the leftshoulder) should reveal the coil movingfurther into its little gap or towards theright of the page.
Mike The TransducerNow let's put mike under themicroscope as our next transducer.
The earliest type of microphone usedwas the carbon granule type. It did notexactly work as a piece of hi-fi equip-ment at the turn of the century and it isstill used by British Telecom intelephones - and it still does not workvery well. It has the great merit,however, of being cheap and simple(you can pick them up in surplus shopsfor as little as 10 to 20p) and it justworks by the sound waves squeezingthe granules a bit more tightlytogether, thus lowering their electricalresistance and so allowing more cur-rent to flow. The idea is illustrated inFig.7. Actually, they do not really do
1CURRENT
GRANULES
DIAPHRAGMRIGID
FRAME
CARBON
Copyright MODMAGS Ltd.
Figure 7. Side view of typical carbonmicrophone
such a terrible job when you considerthe high expectations we have ofmicrophone behaviour. The mike is ex-pected to respond to air displacementsof a ten millionth of a millimetre, whichcorresponds to an air pressure changeof a hundred millionth of atmosphericpressure, all this giving rise to about amillion millionth of a watt of power be-ing handled. If that is not sufficientlybrain boggling then remember that weexpect it to respond over the entire fre-quency range which our ears can hear,which is usually taken to be from alower limit of 20 Hz (ie 20 vibrationsper second) to 20 kHz (ie 20 kilohertz,which is twenty thousand vibrationsper second).
Hertz, incidentally, was a short-lived German physicist whodiscovered radio waves in 1888 aged31 and died aged 36. He will be thesubject of the new Famous Namesseries in a few issues' time.
Two mikes we need to consider indetail are the moving -coil and crystaltypes. The moving -coil bears a strikingsimilarity to the moving -coil speaker.Indeed you can use a speaker as amicrophone if you have to. The actionis that of a speaker in reverse since the
50 Hobby Electronics, April 1981
O Level 08r A
sound waves are producingmovements of the diaphragm whichmoves the coil in the field of the perma-nent magnet, thus inducing voltages init.
A not -too -distant relation is the rib-bon microphone, which uses just thesame induction principle but with acorrugated aluminium alloy ribbonwhose movement in the permanentmagnet's field does the induction bit.
A condenser microphone (morecorrectly referred to as a capacitormicrophone) gets the electrical fluc-tuations by a change in capacitor plateseparation and hence in capacitance,but the crystal mike uses a differentprinciple altogether, the piezo-electriceffect. This is an effect found in somecrystals, notably quartz, where smallstrains imposed on the crystal result insmall voltages across it.
Pick Up A TransducerIndeed the piezo-electric effect is usedin the crystal pickup of a record player- yet another type of transducer wehave to consider - where the varyingstrains are transmitted from the stylusmoving along the groove. It is a decep-tive little path that groove. Did youknow that in some highly magnifiedpictures of the grooves of unplayedrecords it is possible to see the grooveturning through a complete rightangle? No wonder they wear outquickly, especially when you considerthat early pickups had a trackingweight of up to about two hundredgrams whereas today the technologyis such that they can manage on a frac-tion of a gram. Crystal pickups usuallygive more output than magneticpickups, though this is not true for thelatest type of ceramic crystals that areused. One of the earlier difficulties wasthat the best piezo-electric crystalswere deliquescent (dissolving in waterabsorbed from the air, so unless themanufacturer took precautions youcould have the crystal picking up waterfrom the atmosphere and dissolvingitself in a little puddle by the turntable.So how about 'crystal pickup' as asuitable name for your next puppy?
Assuming that the crystal stays un-dissolved, the output is given in RMSvolts for a certain stylus velocity (RMSvolts is the 'root mean square' voltagewhich for our purposes is just a kind ofaverage voltage). For instance, youmight meet a pickup with a specifica-tion given as one mV/cm/sec. This justmeans that when the stylus is movingover the record at a speed of onecm/sec the output is 1 mV (millivolt).There can be a slight problem here
because if your disc is rotating at asteady 331/3 RPM, the rim of the disc istravelling twice as fast as a point halfway in towards the centre. Since if thespeed is halved, the output voltage isalso halved, pickup manufacturershave to build in some compensation totheir pickups. Without this compensa-tion you would get a progressive dimi-nuendo from the first groove to thelast, which might not suit everybody.
Magnetic pickups are the only othersort we have to consider, and yet againwe meet our old friend the moving coil.Small wire coils are still used and theystill vibrate in the field of a permanentmagnet, but the very latest use aprinted coil of mass about 1 50micrograms (one microgram is onemillionth of a gram) on a one millimetresquare wafer. The big advantage ofthis reduction in size and weight is thatthe magnet can be mounted sitting vir-tually on top of the stylus and this im-proves the reproduction even more(see Fig.8).
MAGNET Copyright MODMAGS Ltd.
SUPPORT
Figure 8. Modern type of moving -coil pickup
Thermocouples,Thermistors Et Light-sensitive CellsIf you bend your imagination a bit youmight be able to admit thermocouplesand thermistors into our crowd oftransducers. If you really cannot makethat leap, don't worry but you still haveto know about them! A thermocoupleat its simplest is a couple of differentbits of wire leg copper and iron)twisted together with their free endsconnected to a sensitive microam-meter. Heat them up and - lo andbehold - you see a small current flow.Strictly you should have two junc-tions, one hot and the other cold, andyou'd get a voltage developed bet-ween them, as indicated in Fig.9.
In the first example, we were usingone of the microammeter orgalvanometer terminals as the coldjunction. The thermistor, on the otherhand, is just a circuit component
HOT COLD
© Copyright MODMAGS Ltd.
Figure 9. Operation of a thermocouple
whose resistance drops when youheat it, unlike a metal whoseresistance increases withtemperature. A thermistor can bemade of carbon or some metal oxidesand can be used as the sensing ele-ment in a simple temperature alarm cir-cuit: a thermistor could have been us-ed in the HE Freezer Alarm projectdescribed in the October 1 980 issue.
Recently I was pulling an old tellyapart and found a couple of ther-mistors whose function was to offer ahigh resistance when you first switch-ed on, thus keeping current down tillthings reached their workingtemperatures.
The last class of transducers to becovered are light-sensitive devices,and these fall naturally into twocategories - those that produce avoltage when exposed to light, hencecalled photovoltaic transducers, andthose whose resistance is dramaticallyaltered by light, known as photocon-ductive cells. Selenium cells and siliconcells fit into the photovoltaic categoryand probably the best known use ofthese is in satellites where there is allthe sunlight you need to stimulate thecells to produce the electricity requiredto keep the electrical systems going. Idid hear of an American who, in sunnyArizona, built a car whose roof was en-tirely covered with solar cells . . . .
For photoconductive cells, cad-mium sulphide is probably the mostcommon compound used. A strip of itcan have a resistance of about a hun-dred ohms in sunlight but it can rise toten thousand times that value (over amegohm) in total darkness. The cellscan therefore be used as the detectorbit of, say, an automatic parking lightor in some sort of packet -on -a -production -line counting device.
At this stage my energy output isexhausted, and I hope you consideryour energy input was worthwhile andthat with all this talk of photosensitivi-ty you are well enlightened and fullytransduced. I trust the project and theessay topic are taking shape. Stuck fora topic did you say? Why notsomething on transducers . . . ?!See you next month. Cheers! HE
Hobby Electronics, April 1981 51
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20 16 pin DIL sockets 220pResistor kit. 650 resistors ;/4W10 ea value 4.7 to 1M 480pSingle potentiometers5K -1M log in lin 35pSlide potentiometers. 60mmtravel. 5K -500K log or lin 65p10 100K min. presets 70p10 lu 63V electrolytics 50p10 4u7 63V radial elec. 50p10 lau 25V radial elec. 50p10 100u 25V radial elec. 75p10 lu 35V bead tants. 100p10 0.01 C280 polyester 50p10 0.01 C280 polyester 50p10 BC107 transistors 90p10 BC108 transistors 90p10 BC109 transistors 90p10 BC2I4L transistors 90n5 2N3819 transistors 100p ,1 BDI3I transistor 45P ,1 BD132 transistor 45P i
Pack No.F33I 1 BD139 transistorF421 I MI2955 transistorF43 5 78L05 regulatorsF46A I 7805 regulatorF47A I 7812 regulatorF49A I 7905 regulatorF53 1 LM317T variable reg.F54 LM323K 3A 5V reg.H11 20 1N4002 diodesH30 2 W005 bridge rectifiersH60 100 IN4148 diodesH73 2 C10613 thyristorsJ5 10 0.2in red LEDsJ25 10 0.2in green LEDs545 10 0.2in yellow LEDs570 20 0.2in LED clips57 10 0.125in red LEDs527 10 0.125in green LEDsJ47 10 0.125in yellow LEDs572 20 0.125in LED clipsJ75 1 FND500 CC displayK5 5 741 op amps.K20 5 CA3140 op amps.K30 5 LM30IA op amps. 140pK40 1 LM324 op amps. 50pK50 I LM380 2W amp. 70pK75 I LM3914 LED bar graph 320pK85 5 NE555 timers 110pK90 I NE556 timerK100 5 TL081 op amps.L8 5 4011 CMOSL9 1 4013 CMOSLI1 1 4017 CMOSL22 1 4049 CMOS
50p175p130p40p75p45p
All prices include VAT. Please add 50p postage and packing. Send s.a.e. forour complete catalogue.
Rapid Electronics LimitedHilleroft House, Station Road. Eynsford, Kent
A NEW ADVENTURE IN COOKING! :**- : "- :"' :. . . :S S SCOMPONENTS AND CHIPS FROM
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52 Hobby Electronics, April 1981
WindscreenWasher AlarmFed up with dirty windscreens? The problem can be solved with this all -electronic circuitwhich gives you an early warning when the fluid in your windscreen -washer bottle isgetting low. It's a fun -to -build, simple and cheap project
IT IS REMARKABLE how purpose-built integrated circuits can be made,by modern-day processes, to fulfillfunctions which, only a few yearsago, would require complextransistor (or worse still, valve)circuitry. The IC used in this project isa case in point. Its official title issimply a 'fluid detector' and with onlysix other readily -available and cheapcomponents it can be used to detectwhether the level of fluid in acontainer is above or below apredetermined height. A similarcircuit ten years ago would haveused about a dozen separate
Hobby Electronics, April 1981
transistors and twenty or thirty othercomponents.
This project uses one IC, theLM1830, to automatically alert themotorist to the fact that the fluid inhis/her windscreen -washer bottle isgetting low and shortly will run out.A stop can then be made at the nextservice station, to refill the bottlebefore the car in front splatters mudon your windscreen and to yourannoyance you find that you can'tclean it off because the washer bottleis empty.
A light -emitting diode (LED) comeson whenever the fluid level is low and
tells you to refill the bottle as soon asyou can.
ConstructionConstruction of the project couldn'tbe simpler. There are only sevencomponents to fit onto theVeroboard and only eight trackbreaks to make underneath. Trackbreaks can be made with either thecorrect cutting tool for the job or asmall (about 3 mm) hand-held drillbit. Whichever you choose themethod is the same: hold the tip onto
53
the hole in question (indicated inFig.2) and gently rotate it clockwiseuntil the copper strip is cleanly broken.Check that no swarf remains lyingacross adjacent tracks because thismight cause a short circuit.
Next, insert and solder allcomponets and the single link. Usean integrated circuit socket for IC1 toplug into and check that IC1 and C3are the correct way round. The LEDcan be used to mount the board intoits case (or onto the fascia panel ofyour car) if you take care.
The probe will vary from car to carand obviously we can't providedetails for all applications. However,Fig. 5 shows one suggestion of howyou may construct yours but it alldepends on individual washbottles.All that you need to do is make surethat the probes are made of non -rusting material (stainless steel rod isideal - see Buylines) and that theydon't touch each other. Set them tobe the required distance from thebottom of the container. Then, whenthe fluid level gets below the probeheight - on goes the LED to warnyou.
The circuit draws only 10 to20 mA so the in -line fuse (which youmust use) should have a value ofabout 100 mA.
A
B
C
E
F
G
H
J
H
G
F
E
C
A
C11n0
R1470R
14
R2470R
LED1
12
IC1
13
LED1
C2
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 8 9 20 21 22 23 24
0
0TO PROBE(SEE TEXT)
O 0000000000 00000 0 0 0 0 0 0 0 0O R1 O
O
O
O
O
O
OO 000 0000000000 000000
0 R2
11
C347u .1.
0+12V
NOTE:IC1 IS LM1830LED1 IS RED LED
oV
TO +12V VIAIN-LINE FUSE
O
O
O
OTO PROBE
O
OOV
000 O 0000000000 00000 0 00000000000 000000000000000000000 000000000000000000000 0000000000000000000 00000000000000000000 00000000000000000 0000000000000000000 0000000000 0 0 0 0 0 0 0 0 0 0 000000 00 00 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0000000001 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
Copyright MODMAGS Ltd.Figure 2. Veroboard overlay, componentlocations and track breaks underneath
0
Copyright MODMAGS Ltd.
Figure 1. Circuit diagram
Parts ListRESISTORS (All '4W, 5%)R1,2 470R
CAPACITORSC1C2C3
1n0 polystyrene47n ceramic47u, 16 V electrolytic
SEMICONDUCTORSIC1 LM1830 fluid detectorLED1 red LED + mounting
clip
MISCELLANEOUS10 strip x 24 hole, 0.1" VeroboardIn -line fuseholder + 100 mA fuse
BuylinesThe components for this project shouldcost less than £4. If you have any troubleobtaining the LM1830 try TKElectronics, who stock it and advertise inHobby Electronics.
You can obtain stainless steel rodfrom:
George King Metals Ltd.224 Tooting High Street,London SW17 OSQ.
who will supply two 1ft lengths of Ye"diameter stainless steel rod for 50p in-clusive of VAT and p&p.
54 Hobby Electronics, April 1981
Windscreen Washer Alarm
How It WorksIntegrated circuit IC1 generates a small voltage atits output which is applied via the probes to the fluid(see Fig.3 below). When the resistance of the fluidincreases over a pre -determined amount (due to thewater level dropping below the height of the probes)the IC turns the LED on.
+Ve
VOLTAGEGENERATEDBY IC1
Figure 3.
s© Copyright MODMAGS Ltd.
tiLED
RESISTANCEOF WATER
+VeO
0-1\AAC---
14 12
6kHzOSCILLATOR
Rint
13k
13
REGULATOR
10
DETECTOR
11
Figure 4 (right) shows the inside sectionsof the IC in greater detail. The regulatorallows the IC to be used over a wide rangeof voltages (8 V to 28 VI. When the pro-be resistance is less than the internalresistance (R,nt - 1 3k) as it will be if thelevel of fluid is above the bottom of theprobes, then the output of the detector ishigh, turning on the transistor and alsothe LED.
If the probe resistance is above 13kthe detector turns off the transistor andthe LED goes off.
PROBERESISTANCE
Copyright MODMAGS Ltd.
TO ALARM
WINDSCREENWASHER
FLUID BOTTLE
WATERHOSE
ONE PROBE CONNECTEDDIRECTLY TO THECAR CHASSIS
PROBES
Figure 5. Electrical details of the two probes
Hobby Electronics, April 1981
SET PROBES ATREQUIRED DISTANCEFROM BOTTLE BOTTOM
HE
55
ELECTFE1111Kil
Introducing our new
CHIPSHOPKITS
Each CHIP SHOP KIT is complete in every way and contains allthe components necessary to build and operate the projectdescribed. All you need is a Soldering Iron (see Kit No. 2) and a9v battery. Each kit includes step-by-step instructions on con-struction and detailed educational notes about the individualcircuit, together with advice about soldering techniques.
Kit. No. 2 - SOLDERING IRON - contains a high qualityBritish soldering iron, a 1Amp fuse and solder together withstraightforward instructions upon how to handle your solder-ing iron and the best techniques for its use and maintenance.
Kit No. 3 - ELECTRONICS TOOLS - contains a selection ofuseful tools for anyone starting in electronics, together withinstructions about the use and care of your equipment.
SOLDER is included with every kit.
Kit. No. Price1(a) Morning Call plus1(b) Transistor Tester £5.002 Soldering Iron £5.003 Electronics Tools £4.504 Electronic Organ £3.505 Morse Code Trainer and Siren Oscillator £4.006 Light Operated Burglar Alarm £4.007 Buzzer - Aircraft £3.008 Light and Sound Alarm £3.009 Lie Detector £3.0010(a) Lamp Flasher plus10(b) Sleep Inducer £4.5011)a) Cat Sound plus11(b) Night Light Reminder £4.5012(a) Bicycle Horn plus12(b) Electronic Shocker £5.0013(a) Light Sensitive Alarm plus13(b) Electronic Lamp £5.0014 2 -Transistor Radio £4.0015 Morning Alarm £4.0016 American Police Siren £4.0017 Flashing Dual -tone Horn £3.5018 Two-way Interphone £5.0019 4 -Transistor Radio £5.0020 Clicker -Helicopter Oscillator £3.00
All kits packed individually in attractive boxes. Loudspeakersare included with each kit (except nos. 2, 3, 14 where they arenot required).
Kit nos. 1, 10, 11, 12, 13 contain two separate projects.
These kits are becoming available in Hobbyand Electronics Stores all over the Country- look out for the CHIP SHOP DISPLAY inyour local store.If you cannot locate a stockist please order direct fromElectroni-Kit Ltd. Please add 50p per kit for postage and pack-ing.
Trade and Educational Enquiries welcomes.
Cheque/P.O./Access/Barclaycard for 23p for full -colour illus-trated literature) to DEPT. HECS.
ELECTRONI-KIT LTD.RECTORY COURT, CHALVINGTON,E.SUSSEX, BN27 3TD (032 183 579)
56
Marshall'sCRIMSON ELEKTRIK HI FlMODULESCE 608 Power Amp £20.09CE 1004 Power Amp £23.43CE 1008 " " £26.30CE 1704 £33.48CE 1708 £33.48CPS 1 Power Unit £19.52CPS 3 £23.52CPS 6 £30.00CPR1 Pre Amp £32.17CPR1S II II £42.52SINCLAIR INSTRUMENTSDigital Multimeter
PDM35DM235 £DM350DM450
If
If
34.5052.5072.5099.00
Digital Frequency MeterPFM200 £ 49.80
Low Power OscilloscopeSC110 £139.00
TF200 Frequency Meter£145.00
TGF105 Pulse GeneratorNEW £ 85.00LCD Multimeter
TM351 I£99.00LCD Multimeter
TM352 £49.95Prescaler
TP600 £37.5Q
ILP HI Fl MODULESPower AmplifiersHY30 £ 7.29HY60 £ 8.33HY120 £17.48HY200 £21.21HY400 £31.83Pre AmplifiersHY6 £ 6.44HY66 £12.19Power SuppliesPSU30 £ 4.50PSU36 £ 8.10PSU60 £13.04PSU70 £13.04PSU180 £21.34MULTIPLEX NICKELCADMIUM CELLSType S101 (HP4) £0.98Type SubC (HP11) £1.75Type SubD (HP2) £1.95Friwo Chargers for abovePenlight 4: accommodates1-4 size HP7 £5.50Combibox FW611:accommodatesHP7, HP11 £13.25
NOTE ALL PRICESNET. EXCLUDINGVAT.POSTAGE/PACKING
NewPresensitised PC Boards, Developer. U.V. units.Toyo miniature Fans 230v AC £9.95Mini Metal Detector/Voltage Tester for locatingcable under plaster £9.95Flow/Speed Sensors for monitoring fuelconsumption electronically in vehicles
Just one of the exciting Leader rangeLB0508A
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bandwidth and10 my inputsensitivity on a 5"screen this universaloscilloscope issuitable for a widerange ofapplications.
Send SAE for details of full range.Marshall's 80/81 catalogue is now available bypost, UK 75p post paid Europe 95p post paid:Rest of world £1.35 post paid.
C1111111.111111111411i1.1,
£299+ VAT
A. Marshall (London) Ltd., Kingsgate House,Kingsgate Place, London NW6 4TA.Industrial Sales: 01328 1009Mail Order: 01-624 8582 24hr service.
Also rated shops: 325 Edgware Road, Lcndon W260 Encklewood Broadway, London WW2 85 West Regent StGlewow. 108A Stokes Croft Bristol.
Hobby Electronics, April 1981
Clever DickCD names HE's youngest reader andanswers a few more queries
BACK IN THE January issue of HE weasked if any of you were younger thanMartin Green (he was 13 at the time).Ask a silly question . . . get a lot ofanswers! We had to open a 'youngestHE reader' file to cope with the volumeof letters.
Right then, who is the youngestreader? Well, here's one I don'tbelieve.
Dear Educated Richard,In reply to your request for your
youngest reader, so as you can giveme a binder, it is possibly me. I am 5months old + have been reading H.E.for the last 4 months. You may thinkthat your fantastic magazine a little ad-vanced for my tender years, but per-sonally I find you style of writingperfect for my age group.R. HollandTo whom it may concern:-Icertify thatthis letter has been written by my 5month old son.R. Holland
P.S. Isn't his. handwritingremarkably similar to mine.
Sorry - don't believe you - I per-sonally think you're 500 months old.Now for the real winner (determined byall the letters received until the time ofgoing to print): Andrew Bolter, aged10 years, of Willsbridge, Bristol. He'llbe receiving this month's binder.Closest runner-up was JonathanWolff, aged 10 years, 9 months, ofBoxmoor, Herts.
Now onto some serious business.
Dear Intelligent Richard,With Reference to the NiCad Bat-
tery Charger circuit in your Januaryedition lam a little puzzled about the ar-rangement of 01 (TIP41A). Do I take itthat the terminals of this transistor are- from Left to Right - B. C.E. ?
Also, in your sister mag, E. T. I. thereare construction plans for a DifferentialTemperature Switch, on P.C. B. I have
been trying to work out how I couldadapt this for vero, but so far withoutsuccess. Please could you help?Ta MuchlyA. HarrisonCramlington, Northumberland
P.S. lam not in the habit of extrac-ting the Michael from people's names!
P. P.S. Martin Green is not H. E. 'syoungest reader (Jan. issue), I'm 12years old. Do I deserve a binder?
In answer to your first query, yes: look-ing down on Q1 (from the board side)the pins are BCE, with the emitternearest the bottom of page 51, and theheatsink tab of Q1 to the right.
As to converting a PCB design toone on Veroboard, all I can say is thatusually the simpler circuits are suitablefor Veroboard: those like the Diff TempSwitch can require too much cross -linking.
OK, Martin Green is not HEsyoungest reader but that doesn't meanthat you get a binder!
We received a mixed reaction to theletter from D.S. Nightingale, publishedin last month's CD. Only one 'nasty'letter was received, from W.H. Bid-dlecombe of Paisley, Scotland, whostarted with 'Thank goodness for N.S.Nightingale, Essex. I thought it wasjust me - now I know better' and end-ed with 'P.S. You know what you cando with your binder'. Several readerssprang to HE's defence. Cheers to allthose who wrote in expressing theirloyal support.
Nice short one next.
Dear C.D.,(1) Could you tell me where I can
get hold of ferric chloride and p.c.b.board as 1 hope to make my own.
(2) I've made the Nicad Charger inthe Jan. issue but it makes a loud buzz-ing sound. What can be done to stop it.
(3) I think H.E.s the best mag out.D. YoungEwell, Surrey
One suggestion for ferric chloride andPCB laminate is to order a complete kit:'100 sq ins copper clad board, Ferricchloride, Etch resist pen, abrasivecleaner, two miniature drill bits, et-ching dish and instructions', cost£4.95 plus 40p pEtp, fromGreenweld, 443F Millbrook Rd.,Southampton SO1 OHX (tel. 0703772501).
Buzzing noises? Either something'sshorting and the transformer is'saturating' (and overheating), or thetransformer has loose laminations. Ifthe circuit's OK, check that thetransformer is screwed down well tothe board. If you're still out of luck,send for a replacement transformer.
Just one more, this time from Spain.
Querido Ricardito el lnteligente,I'm very interested in construction
of the "Phase One", phaser publishedin HE a few months ago. My problem ismore electromechanical than elec-tronic: where can I find a miniaturefoots witch libe the one in the photos?
"Help me if you can, I'm fellingdown".
From the city of the HangingHouses, my best wishes.J. M. C. ArilloCuenca, Espana
Before you fell to your death, you canget the switch for the job (DPDT, 6amp, heavy-duty push-button switch)from Watford Electronics 35 CardiffRoad, Watford, Herts, England. Cost is£1.72 inc. VAT, plus 50p pEtp (toSpain, that is): total cost £2.22 Sterl-ing.
I must go back now to my work on therobot editor for HE (a sort ofunintelligent HEBOT). Meanwhile,keep those letters short (I print themexactly as they are written, by theway) and remember: I can't answerevery query sent in. Look afteryourselves. HE
Hobby Electronics, April 1981 57.
PRECISION PETITEMINIATURE DRILLS AND ACCESSORIESfor all your modelling needs
BAXCL.C.0
A choice of three powerdrills that fit snugly in thehand, so light they enableyou to carry out the mostintricate tasks -shaping, cutting, polishing,etc., in the minimum oftime.There are two types of drillstand, plus all the necessaryaccessories in a range thatfills every need.Send 9" x 4" S.A.E. for fulldetails.
AftS2 SI
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1.001.951.281.281.281.280.670.300.650.640.661.860.490.763.751.001.001.811.981.800.300.503.504.054.291.001.603.853.281.810.640.460.650.590.660.270.700.362.442.350.781.802.112.111.451.952.695.041.953.051.202.001.001.400.991.551.901.201.201.902.751.861.25
SL161OPSL1611PSL1612PSL1613PSL1620P011621PSL1623PSL624CSL1625PSL1626PSL1630PSL1640PSL1641PTDA2002ULN2242AULN22838CA3080ECA3089ECA3090A0CA3123ECA3130ECA31307CA3140ECA3189ECA3240MC3357PLM3900NLM3909NLM3914NLM3915NKB4400K 04406KB4412KB4413KB4417KB4420BTDA4420KB4423KB4424KB4431K04432KB4433KB4436KB4437KB4438K1344,11K84445KB4446K84448NE5044NNE5532NS06000SL6270SL6310SL6600SL6640SL6440SL6690SL6700ICL8038CCMSL9362MSL9363HA11211
1.601.601.601.892.172.172.443.282.172.441.621.891.891.253.051.000.701.843.351.400.800.900.462.201.272.850.600.682.802.800.800.601.951.951.801.092.652.301.651.951.951.522.531.752.221.351.292.751.652.261.853.752.032.033.752.75POA3.202.354.501.751.751.95
A11223A11225A12002A12017A12402A12411A12412F13741N76660N
2.15 40001.45 40011.45 40020.80 40071.95 40081.20 4008AE1.55 40090.33 40100.80 4011AE
401113401240134015401640174019402040214022402340244025402640284029403040354040404240434043AE4044404640474049405040514052405340604063
6
FREQ. DISPLAYAND SYNTH.DEVICESSAA1056 3.75SAA1058 3.35SAA 1059 3.3511C9ODC 14.00LN1232 19.00LN1242 19.00MSL2318 3.84MSM5523 11.30MSM5524 11.30MSM5525 7.85MSM5526 7.85MSM5527 9.75MSM55271 9.75MSL2312 3.94SP8629 3.85SP8647 6.0095H90PC 7.80HD10551 2.45HD44015 4.45HD12009 6.00HD44752 8.00MC145151 12.45MC145156 8.75MISCICM7106CP 9.55ICM7107CP 9.55ICM7216BP 19.50ICM7555 0.94
CRYSTALS2.768k Hz
100k Hz455k Hz1.000MHz3.27684.0004.19344.0964.0324.4336194.8005.0006.55367.0007.688.0009.00010.00010.240
2.703.855.002.952.702.002.002.002.002.002.002.002.002.002.002.002.002.002.00
0.18 4068 0.25 TTL0.18 4069 0.25 74000.24 4070 0.30 74010.30 4071 0.24 74020.80 4072 0.24 74030.80 4073 0.24 74040.58 4075 0.25 74050.58 4076 0.90 74060.24 4077 0.35 74070.24 4078 0.30 74080.55 4082 0.28 74090.55 4093 0.86 74100.95 4175 1.15 74110.52 4503 1.15 74120.80 4506 0.68 74130.60 4510 0.99 74140.98 4511 1.49 74150.82 4512 0.98 74160.96 4514 2.55 74170.25 4518 1.03 74200.76 4520 1.09 74210.25 4521 2.36 74231.80 4522 1.49 74250.79 4529 1.61 74271.04 4539 1.28 74280.59 4549 3.50 74301.20 4554 1.73 74320.98 4560 2.18 74370.85 4566 1.59 74380.85 4568 2.18 74400.93 4569 3.03 74410.94 4572 0.30 74421.30 4585 1.00 74430.99 74440.52 74450.55 74460.78 7447
0.78 0 74490.79 7448
1.54 74511.18 74530.57
0.130.130.140.140.140.180.360.380.190.210.180.260.270.320.51
0.300.300.190.380.270.270.320.350.170.320.400.330.200.740.701.151.121.051.32
0.56
0.200.20
CRYSTALS RADIO CONTROL10.245 2.0010.6985 2.5010.700 .0010.7015 2.5011.00 2.0011.115 2.0011.520 2.00
FMTX: FundHC25U8.9985 2.00 y, f 1.859.0015 2.00
2.00 PAIRS...AM 3.1024.000 2.00 PAIRS...FM 3.2525.000 2.00 CHANNELLING,26.000 2.00 27MH: 50kHz18.000 2.50 35MHz, 20kHz
XTAL FILTERS10M4131; 10.7Mhz, 15Khz OW,8 pole. 14.5010M22D, 10.7Mhz, 2.4Khz BW,SSB, 8 pole. 17.20
RC XTALSAM TX/RXFM RX:3rd ot/30pFHC25U 1.65
AMBIT international
'LON0.200.200.200.200.240.26
0.240.240.240.32
0.40
0.240.24
0.350.350.260.28
0.350.28
0.99
0.890.990.990.25
TTL7454 0.20 741287455 741327460 0.20 741367463 1.24 741387470 741417472 741427473 0.45 741437474 0.35 741447475 741457476 0.45 741477478 0.50 741487480 9.52 741507481 1.20 741517482 0.75 741537485 1.04 0.99 741547486 0.40 741557489 2.05 741567490 0.42 0.90 741577491 0.85 1.25 741587492 0.50 0.78 741597493 0.57 0.99 741607494 0.85 741617495 0.70 1.15 741627496 0.58 1.20 741637497 1.85 7416474107 0.45 7416574109 0.63 7416774110 0.54 7416974111 0.68 7417074112 0.41 7417474113 0.75 7417574114 0.40 7417674118 0.85 7417774120 1.15 7418174121 0.48 7418374122 0.46 7418474123 0.73 7418574124 1.80 7419074125 0.55 0.46 7419274126 0.57 0.46 74193
LPSN TTL 'N LPSN' TTL 'N"LPSN' MICROMARKET
0.400.300.350.350.560.41
'LSN' TTL0.300.30
'LSN' TTL 'N"LSN'0.74 74194 1.050.73 0.78 74196 1.34 1.20
0.40 74197 1.100.72 74198 1.60
0.75 74199 1.602.65 742473.12 742573.12 74260
0.97 742791.75 742831.09 1.19 742930.99 743650.55 0.90 743660.70 0.85 743671.30 743680.75 1.10 743740.80 743770.78 0.70 74379
0.71 743932.100.990.99
0.991.201.202.50
2.301.050.870.800.842.80
1.351.340.921.201.42
1.300.981.300.951.301 45
2.102.881.201.10
1502.98
1.801.80
0.931.080.890.881.201.320.660.650.640.921.801.992.151.40
VOLTAGE BEGS78 series79 series78M series78L series79L0578MGT2C79MGT2C723CNL200TDA1412NE5553NLM317MPLM337MP
0.951.000.650.350.851.751.750.651.950.751.251.481.48
MICROMARKET8080A/2821282148216
7.502.303.501.95
ALL PRICES EXCLUDE VAT - CURRENTLY AT 15%POSTAGE 50p ORDERS UNDER £12 - FREE OVER £12
Terms and condition of sale: CWO please, MA availablefor sch000ls, colleges industrial users etc. Please ask fordetails. ACCESS/BARCLAYCARD may be used for mailor phone orders (Mastercharge/Visa overseas). Please addenough for overseas airpost line catalgues pse) since theairmail rates have been dramatically increased in January.This listing gives a brief insight into the wide range of active andpassive components available from AMBIT. Our full catalogues &pricelist include the LARGEST STOCK RANGES OF COILS,CHOKES, CERAMIC/MECHANICAL/CRYSTAL FILTERS, alltypes of radio modules for AM/FM/SSB plus the most sophist.icated DIY FM tuner parts in the world. £1.85 lint) will get youfull set of catalogues Ipts. 2,3 & 4) or 75p per individual section.
8224825182556800P6810682068506852MC270821144027210221122513HM471681 LS97
3.506.255.407.505.957.454.904.856.006.505.781.703.407.544.001.25
LEDS LEDSFLAT TOP LEDS:SHAPESSQUARE 3x3rnmRECT. 2.5x5mmTRIA. 2.5x5mmTRIA. 3x3mmTRIA. 5x5mmROUND 3mmROUND 5mm
PRICED BYCOLOUR:Red 17pGreen 20pYellow 20pOrange 26p
TRANSISTORSBC237BC238BC239BC307BC308BC309BC413BC414BC415BC416BC546BC556BC550BC560BC639BC6402SC17752SA872A2SD666A250646A2SD66842SB64842SD7602SB7202SC25472S41085
8P8p8p8p8p8p
10pllp10plip12012p12p12p22p22p18p14p30p30p40p40p45p45p19p20p
LEDS LEDS
STD DOMED TYPES5mm RED 12p3mm RED clr 15p3mm RED 15P2.5x5 RED 17p5mm GRN 15p3mm GRN clr 16p3mm GRN 16P2.5x5 GRN 20p5mm YL 15p3mm YL clr 16p3mm YL 18p2.5x5 YL 20p5mm ORA 20p5mm ORA clr 29p3mm ORA 19p2.5x5 ORA 24p5mm Infra Rd 56pBPW41 IF Oct 1.51IF Opto Cplr 1.445mm Clip 5p
TRANSISTORS8E2562SK552SK168J310J17640823406733SK453SK513SK603SK 88MEM6808E9618E1948E1958E2248E2416E274BF4408E4418E36213E39513E479B F679SBFR91BFW9213E795B FY904023825137532587232SK 1342SJ492SK1352SJ502SK2272SJ83VN66AF2N3866
38p28p35p69p65p65p
3SK5149p54p58p
1.2475p70p18018p22p18p18p21p21p49p18p66p55p
1.3360p99p90p85p
2.342.343.101104.254253.553.55
95p85p
TELEPHONE (STD 0277) 230909 TELEX 995194 AMBIT G POSTCODE CM14 4SG
200 forth Seruice Road,Brentwood,ESSEH58 Hobby Electronics, April 1981
Ni-Cad BATTERYCHARGERSPECIAL OFFERfor HE readers
THE CHARGER
With the Jeckson BC -2203 three -in -one chargeryou can charge three popular sizes of Ni-Cad cell:
AA (HP7-size) - as used in radios, shavers,photographic equipment, calculators, torchesand many HE projects
C (HP1 1 -size) - as used in torches, toys, andelectric toothbrushes
D (HP2-size) - as used in large portable radios,radio/cassette players, torches and bicyclelamps
The BC -2203 is versatile too: four of the same -sizecells or mixes of two sizes can be charged together,such as two AAs and two Ds. Also, single sets oftwo can be charged, and an 'on charge' LED in-dicator is provided for each set.Operation is simple: telescopic spring -loaded con-tact heads self -adjust for each battery size, sothere's no need to fumble when inserting or remov-ing cells.
A snap -tight translucent plastic cover keeps thebattery tray dust -free.
THE OFFER
Not only a three -in -one charger, but a choice -of -three offer!
* one BC -2203 charger with four Ni-CadAA -size cells - only £9.95
* one BC -2203 charger with four Ni-CadC -size cells - only £13.60
* one BC -2203 charger with four Ni-CadD -size cells - only £15.70
All above prices are inclusive of VAT but exclusiveof post and packing, at 50p extra
AND we offer THREE methods of payment: Barclaycard, che-que or postal order
v1 111111e11:-.2Enter your Barclaycard number in the space provid-ed on the coupon, add your signature, name andaddress - and we'll do the restEnter your name, address and the amount in thecoupon and send it with your cheque or postalorder, made payable to Modmags Ltd.
cheque
Hobby Electronics, April 1981
Send all orders to:
HE Charger Offer,Modmags Ltd.,145 Charing Cross Road,LONDON WC2H OEE
Please note that the offer applies to the UK mainland only: allow 28days for delivery
ruismiummiwimmimmmmmimimmmimmosimmems.YES, I would like to take advantage of HE'Sspecial charger offer for:
No. BC -2203 charger and four AA -size Ni-Cad cells Ordered
110.45 inc. pap) I 1
BC -2203 charger and four C -size Ni-Cad cells1E14.10 inc. pErp) ( 1
BC -2203 charger and four D -size Ni-Cad cells(E16.20 inc. p&p) (
Total
I WISH TO PAYBY BARCLAYCARD
PLEASE CHARGE TO MY ACCOUNTMY BARCLA YCARD NUMBER IS
I enclose a cheque/postal order* for
SIGNATURE
NAME(BLOCK CAPITALS)ADDRESS
Delete as appropriate
L... Ell MI INN I= I= =I NM NIP
59
Books from the HE Book ServiceSPECIAL OFFER TO READERSOF HOBBY ELECTRONICSONLYELEMENTS OF ELECTRONICSBook I £2.60Book II £2.60Book III £2.60Usual price is £7.80 inc post andpacking for 3 volume set. OURPRICE £7.00 + FREE slip case for 3volumes + FREE Resistor ColourCode Disc.
28 TESTED TRANSISTOR PRO-JECTS by R. Torrens £1.50The author has designed developedand built some completely newcircuits.BEGINNERS GUIDE TOBUILDING ELECTRONIC PRO-JECTS by R. A. Penfold £1.50Enables the complete beginner totackle the practical side of elec-tronics.ESSENTIAL THEORY FOR THEELECTRONICS HOBBYIST byG. T. Rabaroe £1.50Supplies the hobbyist with a back-ground knowledge.50 PROJECTS USING RELAYS,SCR'S & TRIACS by F. G.Rayer £1.50Gives tried and practical workingcircuits which should present theminimum of difficulty for the en-thusiast to construct.
POPULAR ELECTRONICS BOOKSSinclair, I. R., Introducing Elec-tronic Systems £3.10Sinclair, I. R., Introducing AmateurElectronics £3.10Sinclair, I. R., Electronic FaultDiagnosis £4.00Sinclair I. R., Repairing PocketTransistor Radios £2.90Sinclair, I. R., Oscilloscope In Use
£4.00Sinclair, I. R., Understanding Elec-tronic Components £5.10Sinclair, I. R. Understanding Elec-tronic Circuits £5.10Kitchen, H. T., Handtools For Elec-tronic Workshop £3.25Kitchen, H. T., Electronic TestEquipment £6.20Capel, V., How To Build ElectronicKits £3.25Darr, J., How to test almost every-thing electronic ..... . £3.75Brown, R. M., How to read elec-tronic circuit diagrams . £5.60
AUDIOEarl, J., Audio Technicians BenchManual E5.00Earl, J., Pickups and Loudspeakers
£5.00Earl, J., Tuners and Amplifiers
£4.00Earl, J., Cassette Tape Recorders
£6.00Earl, J., ABC of Hi-Fi . . £6.00Capel, V., Microphones in Action
£6.00
HOW TO BUILD YOUR OWNMETAL AND TREASURELOCATORS by F. G. Rayer ..
£1.25Contains complete electronic andpractical details on the simple andinexpensive construction of Hetero-dyne Metal Locators.
HOW TO MAKE WALKIE-TALKIES by F. G. Rayer £1.75IC555 PROJECTS by E. A. Parr
£2.00Included in this book are Basic andGeneral Circuits, Motor Car andModel Railway Circuits, Alarms andNoise Makers as well as a section onthe 556, 558 and 559 timers.
PRACTICAL ELECTRONICCALCULATIONS AND FORMU-LAE by F. A. Wilson . . . £2.50'Units and Constants, Direct CurrentCircuits, Passive Components,Alternating Current Circuits, Net-works and Theorems, Measure-ments.
ELECTRONIC SECURITY DE-VICES by R. A. Penfold £1.70Includes both simple and moresophisticated burglar alarm circuitsusing light, infra -red and ultrasonicsgas and smoke detectors, floodalarms doorphone and baby alarms,etc.
ELECTRONIC PROJECTS FORBEGINNERS by F. G. Rayer .
£1.60A newcomer to electronics finds awide range of easily made projects.
POPULAR ELECTRONIC PRO-JECTS by R. A. Penfold £1.70Radio Projects, Audio ProjectsHousehold Projects and Test Equip-ment.
HOW TO BUILD YOUR OWNSOLID STATE OSCILLOSCOPEby F. G. Rayer £1.75Enables the enthusiast to simplyand inexpensively build his ownoscilloscope.
ELECTRONIC GAMES by R. A.Penfold £2.00In this book the author has designedand developed a number of interes-ting electronic game projects usingmodern integrated circuits.
COUNTER DRIVER AND'NUMERAL DISPLAY PRO-JECTS by F. G. Rayer .. £2.00Author discusses and features manyapplications and projects usingvarious types of numeral displays,popular counter and driver IC's etc.
Capel, V., Improving Your Hi-Fi£5.00
Capel, V., Creative Tape Recording£5.00
Hellyer, H. W., Tape Recorders£5.00
Sinclair, I. R., Audio Amplifiers For'Home Construction £6.00.
RADIO CONTROLDrake, J., Radio ControlledHelicopter Models £4.95Jeffries, C. R., Radio Control ForModel Yachts £3.85Safford, E. L., Radio Control Manual
£3.00
COOKBOOKSTracton, K., BASIC Cookbook
£4.10Lancaster, D., TTL Cookbook
£7.55Lancaster, D., RTL Cookbook
£4.65Lancaster, D., CMOS Cookbook
E8.20Jong, W., IC Op Amp Cookbook
£10.00Lancaster, D., T.V. TypewriterCookbook £7.75Lancaster, D., Cheap Video Cook-book £7.00Jong, W., IC Timer Cookbook
£7.65Lancaster, D., Incredible SecretMoney Machine (a how to cookbook for setting up your computeror technical business) £4.95
QUESTIONS AND ANSWERSSIMPLE AND CONCISE ANSWERSTO MANY QUESTIONS WHICHPUZZLE THE BEGINNER.Coker, A. J., Q & A On ElectricMotors £2.50Hellyer, H., Q & A On Radios andT.V. £2.50Hibberd, R., Q & A On IntegratedCircuits £2.50Jackson, K., Q & A On Electricity
£2.50Brown, C., Q & A On Hi-Fi £2.50Brown, C., Q & A On Transistors
£2.50Brown, C., Q & A On Electronics
£2.50Reddihough, J., Q & A On ColourT.V. £2.50Miller, H., Q & A On Electric Wiring
£2.50
CONSTRUCTOR GUIDESGraham. P., Simple Circuit Building
£3.40Colwell, M., Electronic Diagrams
£3.40Colwell, M., Electronic Components
£3.40Colwell, M., Printed Circuit Assem-bly £3.40Ainslee, A., Practical ElectronicProject Building £3.40Colwell, M., Project Planning andBuilding £3.40
BEGINNER'S GUIDESinclair, I. R., Beginner's Guide ToTape Recording £4.25
BEGINNERS GUIDE TOMICROPROCESSORS ANDCOMPUTING by E. F. Scott
£2.00Introduction to the basic theory andconcepts of binary arithmetic,microprocessor operation andmachine language programming.
ELECTRONIC HOUSEHOLDPROJECTS by R. A. Penfold .
£2.00Circuits range from such things as'2 tone door buzzer' Intercomthrough Smoke or Gas Detectors toBaby and Freezer Alarms.
A MICROPROCESSORPRIMER by E. A. Parr .. £2.00A newcomer to electronics tends tobe overwhelmed when first con-fronted with articles or books onmicroprocessors. This small bookwill start by designing a simplecomputer and because of its sim-plicity and logical structure thelanguage is hopefully easy to learnand understand.
50 CIRCUITS USING 7400SERIES IC'S by R. N. Soar ..
£1.65The author has compiled 50 in-teresting and useful circuits andapplications covering differentaspects of electronics using thesedevices.
Sinclair, I. R., Beginner's Guide ToIntegrated Circuits £4.25Sinclair, I. R., Beginner's Guide toAudio £4.25King, G. J., Beginner's Guide ToRadio £4.25King, G. J., Beginner's Guide ToTelevision £4.25King, G. J. Beginner's Guide ToColour T.V. £4.25Guilou, F., Beginner's Guide ToElectric Wiring £4.25
PROJECT BOOKSMarston, R. M., 110 CosmosDigital IC Projects For The HomeConstructor £4.95Marston, R. M., 110 Wave FormProjects For The Home Constructor
£4.95Marston, R. M., 110 Op Amp Pro-jects For The Home Constructor
£4.95Marston, R. M. 110 SemiconductorProjects For The Home Constructor
£4.95Marston, R. M., 110 Thyristor /SCR Projects For The Home Con-structor £4.95Marston, R. M., 110 ElectronicAlarm Projects For The Home Con-structor £4.95Marston, R. M., 110 IntegratedCircuits Projects For The HomeConstructor £4.95Marston, R. M., 20 Solid StateProjects For The Car and Garage
£4.95Marston, R. M., 20 Solid StateProjects For The Home . £4.95
Note that all prices include postage and packing. Please make cheques, etc. payable to Hobby Electronics Book Service (in sterling onlyplease) and send to:
Hobby Electronics Book ServiceModmags Ltd145 Charing Cross Road * Prices may be subject to change without notice.London WC2H OEE
60 Hobby Electronics, April 1981
Legal CB at last? Rick Maybury looks atome of the preparation required,
discusses a few more rumours and namesthe winner :if his DV27 competition
ALTHOUGH, at the time of writing the Home Office has yetto make a public announcement regarding the legalisation ofCB there can be few doubts remaining as to the final out-come. If, for one moment, we can assume CB has beenlegalised - and it may well be by the time you read this, thereare a number of things we must consider.
First and foremost must be the setting up of a nationalorganisation to oversee the running of the service. Such anorganisation should, to be absolutely effective, be non-governmental. We can, for instance, look to the radioamateur network for guidance. The RSGB (Radio Society ofGreat Britain), although possibly a little conservative in itsoutlook for CB, does manage to represent the interests of itsmembers. Hopefully such an organisation could be set upvery quickly indeed: perhaps there could be a coalition bet-ween the clubs?
Point number two concerns the method by which CB inthe UK is administered with regard to emergency channelmonitoring. Already THAMES and REACT Internationalhave proposals for an emergency service but these must beco-ordinated, particularly in terms of designated channelsfor emergency use. It may be a good idea to take a note ofsome of the emergency systems operating on the Continent.Sweden in particular is worth mentioning, because twochannels are in use, one for motorists and one for smallboats. In both cases the monitoring services have adopted aselective call facility. That means that only calls preceededby a tone burst generated by the rig will open the squelch ofthe monitoring services' equipment.
Selective call facilities in general are also worth adopting,particularly for small businesses, where the large capitaloutlay for a two-way radio system would be prohibitive. TheSwedish system allows a number of rigs with a simple
Hobby Electronics, April 1981
BreakerOneFourThe publishers of HOBBY ELECTRONICS would like to point out that itis at present a contravention of the Wireless Telegraphy Act of 1949 and1968 to use, manufacture, install or import CB transmitting equipment.It is not the intention of Modmags Ltd to incite, encourage or condonethe use of such equipment.
modification to be used only when the call is preceeded by acoded tone burst.
My last point, and one that I feel (and hope) will be sortedout before any rigs go on sale concerns type approval. Thisaspect of CB is often ignored but it is a simple prerequisite ofany kind of radio transmission system that the equipmentmust meet the specifications laid down by the Home Office.Taken a stage further it is logical to assume that rigs thathave in some way failed or gone faulty will only be repairedby personnel who have the appropriate qualifications. Beingable to give a rig 'a quick twiddle' will not be enough: ab-solute chaos will ensue if any Tom, Dick or Harry is allowedto repair rigs. One last thought though: what will happen tothe half million or so rigs that do not conform to HO type ap-proval; ie, all those that are in use today. I suspect that somekind of amnesty will be announced. This will allow anybodywith an old AM rig to hand it in at a Police Station without fearof prosecution. I feel that this will not be too successful, butwhat are the alternatives?
News Round -up
fri Al YIN? y.
MAYDAY....MAYDAY,...
.6
Back to lighter matters with a quickround up of the month's news.
In the past I have tried to giveyou the names and ad-
dresses of all theclubs that write in
to the BOFoffice. I'm
Po .
t44,46;
61
GLOBAL ELECTRONICENTERPRISES
ELECTRONIC CONSTRUCTION KITSPLASTIC INSTRUMENT CASES. 110mm x 75mm ingrey -black. 85p+ P&P 35pCAR RADIO Manual with speakerffixing kit
111 1 te.2s+ P&P 75pOCEAN CAR STEREO, with built-in auto, stop.
115.95t -P&P 95pSTEREO Headpeenes, 8 ohm .14.95POCKET RADIO AM/FM/AIR band with speaker
.E7.75* P&P 75pPOCKET RADIO AM/FM with speaker and DP
£8.95.- P&P 75pHAND ELECTRONIC Football Barns 110.95QUARTZ HALOGEN Handheld spotlemps. Plugs intocar cigar lighter 1175+ P&P 7501100 Web Mans DiMMIle with magic eye facility
£4.95SITCO CASSETTE Recorder D/C, small size 1
..£17.115-. P&P £1.508.521 C17, Auto Tearable with ceramic cartridge
.£19.95 t P&P f250B.S.R. CUR with &D.C. cartridge plinth and cover
UOYTIION Professional Ithredebenen 4-16 ohm coiledP/ Os and Cheques made payable to cord voldcontrol. 112.95+ P&P 95p
GLOBAL ELECTRONIC ENTERPRISES St..tehe's Werke, st Johns, e«nere
swine CHIP 2
Full MAN coverage, uses LC. ZN414-i-2 transistors,easy to build diagrams. Good beginners project com-plete with case and loudspeaker.
ERZ+ P&P 75pSUPER CHIP 1
Pocket earpiece radio. Performance and looks asabove, complete with easy build plans.
HRS.-P&P 65p
CRYSTAL RADIOFor beginners, no batteries required, complete withcase and easy build plans.
E2.25, P&P 60pMoney refunded it not satisfied provided goods arereturned undamaged.
Post and packing included unless stated.
All units are checked and tested prior to despatch.All items subject to availability.
OHIO SCIENTIFIC COMPUTERS New series 2Challenger C1P Cheapo 4K version E202. Ohio8K version £259. Special offer:- Superboard 3with free power supply and modulator kit andguard band kit Igives 32x32 extended display,1200 and 300 baud tape speeds, 50% highercomputing speed and 50 Hz conversion) E159the lot. Guard band kit also sold separately E10.4K extra ram E18.95. Case E27. Cassette recorderE17. Ceg mon improved monitor torn £29.50. As-sembler/Editor E25. Word processor £10. Displayexpansion kit, 30 lines x 54 characters `forSuperboard TWO E20.PRINTERS supplied with free interface and wordprocessor for Superboard and UK101. SeikoshaGP80 £225. Oki Microline 80 £329. Base 2800MST E299.
* SINCLAIR PRODUCTS only are post free.SC110 oscilloscope £139, Adaptor Ed, Re-chargeable Batteries £7.95, X1 Probe £8.05, X10Probe E8.86, Carry Case £8.80. PFM200 E54.50,Adaptor ES, Case E1.73, Connector Kit E11.27.PDM35 £32.95, Adaptor £4, Case E1.73. DM235£58.50, DM350 E78.50, DM450 £107.95, AdaptorE4, Case E8.80, Rechargeable batteries E7.95.Microvision TV E69. Adaptor OAS.MEMORIES 2114 450ns £2.15. 4116 200ns E2.83.4027 £1.30. All low current
* BATTERY ELIMINATOR KITS 100ma radiotypes with press -studs 9v E1.79, 9r -9v £2.50.Stabilized 8 -way types 3/41/2/6/71/2/9/12/15/18v100ma E3.12. 1Amp E8.30. Stabilized power kits2-18v 100ma £3.12, 1-30v 1A E8.50, 1-30v 2A£15.30. TTL and computer supplies 5V stabilized112A £9, 3A E12, 6A £20. 12v car convertor6/71/2/9v 1AE1 .62.
* T -DEC AND S -DEC BREADBOARDS s-dec£3.79, t-dec £4.59, exp4b £2.84. exp300 £8.81.
* BATTERY ELIMINATORS 3 -way type 6/71/2/9V300ma £3.50. 100ma radio type with press studs9v E4.95, 9 -9V £6.25. Car convertor 12v input,output 41/2/6/71/219v 800rna £3.04.
* TV GAMES AY -3-8600 kit £12.98. AY -3-8550kit E9.26.
SWANLEY ELECTRONICSDept HE, 32 Goldsel Rd, Swanley, Kent
Post 45p extra. Add VAT except on sectionsmarked Lists 27p post free. Phone Swanley64851. Official and overseas orders welcome.
ELECTRONIC IGNITIONSAVES PETROL
More and more new cars use elctronic ignition to give thebest performance and economy. Bring YOUR CAR up to topspecification by fitting the latest TOTAL ENERGY
'.DISCHARGE electronic system.
TOTAL ENERGY DISCHARGE gives all theadvantages of the best capacitive discharge ignitions:
* Peak Perfonnance-higher output voltage.Improved Economy -consistent high ignition performance.
* Better Starting -full spark power even with low battery.* Aexinwto Timing -prevents contact wear without 'contactless' errors-* Smooth Performance -immune to contact bounce effects.
PLUSSUPER HIGH POWER SPARK -31/2 times the energy of ordinary C.D. systems.OPTIMUM SPARK DURATION -to get the very best performance and economy with
today's lean carburettor settings.DESIGNED IN RELIABILITY -with the 'ultimate insurance' of a changeover switch to
revert instantly to standard ignition.
TECHNICAL DETAILSHIGH EFFICIENCY INVERTER. A high -power, high efficiency, regulated inverter
provides a 400 -volt energy source -powerful enough to store twice the energy ofother designs and regulated to provide full output even with the battery down to 4volts
SUPERB DISCHARGE CIRCUIT. A brand new technique prevents energy beingreflected back to the storage capacitor, giving 3'/a times the spark energy and 3 timesthe spark duration of ordinary C.D. systems, generating a spark powerful enough tocause rapid ignition of even the weakest fuel mixtures without the ignition delayassociated with lower power 'long burn' inductive systems. In addition this circuitmaintains the correct output polarity, thereby preventing unnecessary stress on theH.T. system.
SOPHISTICATED TRIGGER CIRCUIT. This circuit removes all unwanted signalscaused by contact volt drop, contact shuffle. contact bounce, and external transientswhich, in many designs, can cause timing errors or damaging un-timed sparks. Onlyat the correct and precise contact opening is a spark produced. Contact wear isalmost eliminated by reducing the contact breaker current to a low level - lustsufficient to keep the contacts clean.
IN MONEY -SAVING KIT FORM at £14.85 andp:tp.All you need is a small soldering iron and a few basic tools - everything else is suppliedwith easy -to -follow instructions.
FITS ALL 6/ 1 2 -volt NEGATIVE EARTH cars
ELECTRONIZE DESIGN2 Hillside Road, Four Oaks
Sutton Goldfield, West Midlands, B74 4D12Phone 021-308 5877
SPRING TIME IS SALE TIMEClosing date 31.4.81
6 x 555 0.006 x 741 90pIC Sockets15 x8 pin £1.0012x14 pin £1.00100 16pin E1.008 x 18 pin £1.006 x22 pin Etna
LEDs 0.2"10 each red, green, yellowLM3915 -i- 10 -element LED displayLiquid Crystal Display, 31/2 0.5" digits, d.i.I2 x TIC226D 8A/400V Triacs2 x TIC236D 12A/400V Triacs
£2.50E3.20£4.00£1.00£1.35
15 x BC182 E1.0015 x BC212 £1.00Voltage Regulators2x7805 £1.002 0 7812 E1.002 x 7812 £1.004x C106D £1.106x CD4011 £1.00
* BONUS * Further 5% discount if you buy the lot! (E24.75+VAT)
MINI KITS
These kits form useful subsystems which may beincorporated into larger designs or used alone Kitsinclude PCB short instructions and all cornponentsMKI TEMPERATURE CONTROLLER/THERMOSTATUses LM 3911 IC to sense temperature ISO' Cmax) and mac to switch heater 1 KW E4
MK2 SOLID STATE RELAYIdeal for switching rnbiors lights heaters etcfrom logic Opto isolated with zero voltageswitching Supplied without trier Select therequired truIC from our range mooMK3 BAR /DOT DISPLAYDisplays Cr analogue voltage on a linear 10element LED display as a bar or single dot Ideal forthermometers level indicators etc May bestacked to obtain 20 to 100 element displaysRequires 5 20v suppin E4.75MK4 PROPORTIONAL TEMPERATURECONTROLLERBased on the TDA 1024 Zero voltage switch this
formato burst tire powercontroller or a proportional temperaturecontroller enabling the temperature of an encvie ro be maintained to within 0 5 C
3KW MSSMKS MAINS TIMERBased on the ZN 1 034E Timer IC this kit will switcha mains load on lot off) fora preset time from 20minutes to 35 hours Longer or shorter petiodsmay be realised by minor component changesMaximum load 1 KW [4 .50
TRIACS
400V Plastic Case (Texas)3A 49p 16A 95p8A 58p
12A 85p64 with trigger 80p8A isolated tab 65p
Diac 18p
DISCO LIGHTING KITSEach unit has 4 channels (rated at 1KW at 240V perchannel) which switch lamps to provide sequencingeffects controlled manually or by an optional optoeolated audio input111.10001C. This kit features a bi.direction sequence.speed of sequence and frequency of directton changebeing variable by means of potentiometers incorpo.rates master dimming control. £14.60DLZIOOOK. A lower cost version of the abovefeaturing unidirectional channel sequence with Speedvariable by means of a preset pot Outputs switchedonly at mains xero crossing points to reduce radioInterference to minimum. E11.00Optional Opto Input OLAI £1.60
INTEGRATED CIRCUITS555 Timer741 Op AmpAV -5-1 224 Clock
AY 5.1230 2 Clock. TimerAV -3-1 270 Thermometer1017106 DVM (LCD drive,LM37 7 Duel 2 W AmpLM3 79S Dual 60. AmpLM380 2W Audio AmpLM382 Dual low nose PreampLM386 250mW low voltage AmpLM1830 Fluid Level DetectorLM2907 Ity Converter (8 pin)LM29171.v Converter (1 4in)L M3909 LED Flasher Oscillator1M39 i 1 ThermometerLM3915 Dot Bar Driver (log) .
MM 74C 91 1 4 digit display controllerMM 74091 5 7 segment -BCD convenerMM74C91 5 4 digit ca with 1 seo o pS5666 TouchdimmerSL440 A.C. Power ControlSN764 7 7 Complex Sound GeneratorTBA800 5W Audio AmpTBA810AS 7W Audio Ampt0A1024 Zero Voltage SwitchTDA2020 20W Audio AmpZN1 034E TimerAll ICs suoolied with data sheetsData Sheets only 109 each device
21p19p
E2 60[454E8.20E7 00(145(35080p
(1.0075p
E1.50(1.60E1.6060p
El 20£2.20[65096p
£4.50
C2 50£1.75E2.5268p
[1 .00
fl 20E2 85El 80
ARE YOU SITTING COMFORTABLY?Our new TDR300K Touch DimmerKit will ensure that you are. Based onour highly successful TD300Ktouch controlled dimmer kit,the TDR300K incorpo-rates an infra red re-ceiver, enablingthe lamp
In years to come everyone will beselling remote control dimmers, butyou cart have your TDR300K kit nowfor ONLY E14.30 for the dimmer unitand £4.20 for the transmitter.
brightness to be varied and switched on or off by touch orremotely by means of a small hand held transmitter.The complete kit, which includes easy to followinstructions, will fit into a plaster depth boxand the plastic front plate has no metalpads to touch, ensuring colnplete safety. Even a neon isincluded to help you locate the switch in the dark. For the more
athletic of you, theTD300K Touchdimmer
kit is still available at £8.50and the TDE/K Extension Kit for 2 -way switching, etc, is £2.
DON'T FORGET to add 50pP&P and 15% VAT to
your total pur-chase.
REMOTE CONTROL KITSMK8 - Simple Infra Red TRANSMITTER. A Pulsed infra red source which comes complete with a handheld plastic box. Requires a 9V battery. E4.20MK7 - Infra Red RECEIVER. Single channel, range approximately 20 ft. Mains powered with a triacoutput to switch loads up to 500W at 240Vac, but can be modified for use with 5 to 15V dc supplies andtransistor or relay outputs. £9.00 SPECIAL PRICE MK6 and MK7 together. Order as RC500K. £12.50MKB - Coded Infra Red TRANSMITTER. Based on the SL490, the kit includes 21R LEDs, measures only60201.3 cms. and requires a 9V IPP31 battery. E5.90MK9 -- 4 Way KEYBOARD. For use with the MKB kit, to make a 4 -channel remote control transmitter.
E1.90MK10 - 16 -Way KEYBOARD. For use with the MK8 kit, to generate 16 different codes for decoding bythe ML928 or ML926 receiver IMK12) Kit £5.40MK11 10 On -Off Channel IR RECEIVER with 3 analogue outputs (0-10V) for controlling such functionsas lamp brightness, volume, tone, etc. Other functions include an on/standby output and a toggleoutput, which may be used for sound muting. Based on ML922 decoder IC. Includes its own mainssupply E12.00MK12 - 18 Channel IR RECEIVER. For use with the MK8 kit with 16 on/off outputs which with furtherinterface circuitry, such as relays or macs, will switch up to 16 items of equipment on or off remotely.Outputs may be latched or momentary, deoendino on whether the ML926 or ML928 is specified.Includes its own mains supply. Size 90402 cms, excluding transformer. £11.95MK13 11 -Way KEYBOARD. For use with MK8 and MK11 kits. Transmits programme step - andanalogue r and - (31, mute, normalise analogue outputs, an on/standby E4.35
ALL COMPONENTS ARE BRAND NEW AND TO SPECIFICATION. ADO 50p P&P and 15% VAT TO TOTAL. OVERSEASCUSTOMERS 800 1.50 (Estropel, 01 (elsewhere) for P&P. Send sae for price list and with all enquiries. Callerswelcome 9.3175.001Mon-Fril 10.00-4.00 ISM)
TK Electronics(H.E.), 11 Boston Road, London, W7 3SJ
Tel: 01-579 9794
SW
Hobby Electronics, April 1981
sorry to say that shortage of page space now precludes thisparticular service. I now have over 200 clubs on my files soyou'll have to look at a copy of 'Citizens Band' for the latestinformation. (Sorry Mr Editor but you can't begrudge me theodd plug. *)
Video fans will be interested to know that Convoy, thefilm and record that started this whole business, is nowavailable from EMI. Both of the popular formats (VHS andBetamax) are available and the code numbers to look for are:EVH 20231 and EVX 40231.
Rumours have been flying about right, left and centreabout the issue of CB licences. One of our informants told usthat a company often called upon to print official documentswas actually printing the licences. A phone call to the com-pany concerned revealed absolutely nothing, however. Ourinformant went on to give details about the form and evenpromised to try and obtain a sample. Although we haven'tyet seen this form (nor am I too hopeful) the details we havedo sound feasible and are in keeping with what we doalready know. It will be interesting to know who will getlicence 00001: how about us Mr. Home Secretary - ?
Still with the rumours, I keep hearing about rigs that havebeen confiscated by the Customs Et Excise and being return-ed in plastic bags with seals that read something like 'Don'tOpen Till Christmas' or some such similar message. I haven'tseen one myself, nor have I met or spoken to anyone thathas: just a lot of people who know someone, etc. A genuineHE Binder to the sender of one of these elusive wrappings tothe BOF office.'Rick's main occupation now is to edit Citizens' Band -- Ed
DV27 CompetitionAnd finally, I have collated the results of my little competitionlast month to find the vendor of the cheapest DV27. Anumber of you have told us about Midland Telecom, 113Flaxey Road, Milton Keynes, which sells the redoubtableDV27 for an incredible £3.90.
First letter out of the BOF hat with this information camefrom 'Little Hitler'. Congratulations - and your Tee -Shirt ison the way.
Time's up for another month. Stay Lucky out there inCEEBEELAND and see you all next month, hopefully withsome very good news. HE
HE SUBSCRIPTIONSHaving problems hunting down your copy of HE each month?Make life easier for yourself: for only £10.00 you can have it
delivered to your door every month for a year.
Use one of three methods of payment tosubscribe to HE:
Barclaycard Enter your Barclaycard number inthe space provided on thecoupon, add your signature,name and address - and we'lldo the rest
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the amount in the coupon andsend it with your cheque orpostal order, made payable toModmags Ltd.
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Hobby Electronics, April 1981
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- - - - -63
HOBBYPRINTS
If you have never used HOBBYPRINTS before,then you don't know what you've been missing.HOBBYPRINTS are an etch -resistant rub -downtransfer. Just place the appropriate HOBBY -PRINT over a clean piece of copper clad PCBmaterial and rub. It's as simple as that. Oncethe design has been transferred, immerse theboard into the Ferric Chloride. 15 minutes lateryou will be rewarded with a perfect PCBprepared from our original artwork, so you canhave no worries about making a mistake. Bythe way, HOBBYPRINTS are ideal for makingPCBs by Ultra -Violet exposure.
WOBBYPRINTSHEETS AREAVAILABLE FOP
TO THIS ONE.ALL SHEETS COST
ISSUES FROMNOV. 78 RIGHT UP
11;
POST AND
E1.20 ALLINCLUSIVE OF
PACKING ANDVAT.ORDER BY SHEETLETTER ANDSSJJE MONTHSEE BELOW).
ISSUESHEET REF.
ISSUESHEET REF.
Nov. 78 A Sept. 79 KDec. 78 B Oct. 79 LJan. 79 C Nov. 79 MFeb. 79 D Dec. 79 NMar. 79 E Jan. 80 0Apr. 79 F Feb. 80 PMay 79 G Mar. 80 QJun. 79 H Apr. 80 RJul. 79 I May 80 SAug. 79 J Jun. 80 T
our HOBBYPRINT refer to the cT,,irt aboveid send your cheque or postal order to
riOBBYPRINTS,Modmags Sales Office,Hobby Electronics,145 Charing Cross Road,London WC2H OEE
64 Hobby Electronics, April 1981
PCB FOILPATTERNS
HE R tere 4 34
HE Russian Roulette foil pattern
The foil pattern of HE Super Siren
HE
ADVERT INDEXAbsonglen Ltd 34Ahlers Elektronika 2Ambit International 58Arrow Audio Centre 48BK Electronics 44B.N.R.S. 48J. Bull (Electrical) 38David George Sales 42Display Electronics 52Drallim Davis 28E.D.A 44Electroni-Kit 56Electronize Design 62Electro Supplies 48Electrovalue 44Global Electronics 62G.S.0 31Henry's Radio 34ILP Electronics 4&5LEM Services 42
582068564252342458525228621510
TK Electronics 62Vero Electronics 28Watford Electronics 9Wintjoy 67
Lightening ElectronicsMagenta ElectronicsMaplinMarshallsNIC ModelsParndon ElectronicsP.A.T.H. ElectronicsT. PowellPrecision PetiteRapid ElectronicsJ. W. RimmerSelray Book Co.Swanley ElectronicsTechnomaticTempus
Hobby Electronics, April 1981
SUPERBOARD IISTILL the best value in Home ComputersJust compare the features:
* 8K floating point BASIC in ROM * Full ASCII keyboard 0* Standard cassette/TV interface * RS232 printer interfaceAnin * 4K user RAMIIP * Expandable to 32K & dual mini floppy
AVAILABLE NOW from:0
C.T.S.31/33 Church Street
LittleboroughLance.
Please ring or write for latest pricesTel Littleborough (0706) 74342 any time
PARAPHYSICS JOURNAL. Russian/Czech translations. Autogenics (self -training)improves vitality. Psychotronic Generators,'UFOs, contacting extraterrestrials, Kirkli-anography, telelinesis, levitation, gravitylasers. S.A.E. 4x9": Paralab, Downton, Wilts.
E1 BARGAIN PACKSAl packs E1 each any 12 for C10. Post 25pAll top grade new components-no rubbish
PC1 12 80107PC2 14 BC108PC3 12138C109PC4 3 2N3055PC5 710'1'51PC6 16 8C182PC? 60 154148PC8 25 1 N4003
PC9 10 TO3 socketsPC10 15 0.1 /35V tantsPC11 14 3mrn red LED'sPC12 12 5mm red LED sPC13 8 741PC14 6 555PCI 5 15 12V tenetsPC16 100 lk fAW 5% R's
Send sae for 6 -page list 'enqemes Mad only
PC ELECTRONICS. 2 Thornhill, Ronuray RoodINbirowniab, Salisbury SFS 2S0
TRS-80 OR ZX80. 4 games on cassette.TRS-80, £3.50. ZX80, £3. SAE details/list.Bobker, 29 Chadderton Drive, Unsworth,Bury, Lancs.
SMALL REED SWITCHES, 10p; largemagnets, 20p; small red/green Leds, 14p;30 untested I.C.s, 35p. Postage 25p. -Grimsby Electronic Components, Lam-bert Road, Grimsby, Humberside. List15p.
BRAND NEW, not surplus. 741s at 23p;Watt Resistors, any selection, £1.60 per100. P. and p. 25p. - Systematics, HazelRoad, Woolston, Southampton SO2 7GB.
WANTED. Electronic componentsand test equipment. Good prices given.- Q Services, 29 Lawford Crescent, Ya-tely (0252) 871048, Camberley, Surrey.
If it's a case of making your projectlook good, then use one of ours.Simply send a S.A.E. forDetails and prices.
TRACE ENQUIRIESiNVITEO
H. M. ELECTRONICS271a/275a Fulwood Road.
Br oomhillSheffield S10 380
65
J ETI RATES1-3 Insertions £7.00 per scc4-11 Insertions £6.50 per scc12+ Insertions £6.00 per scc24p per word (min 15 words)Box No. £1.50Closing date 1st Friday in month precedingpublication.
Classified Advertisements must b
HE RATES1-3 Insertions £5.00 per scc4-11 Insertions £4.50 per scc12 + Insertions £4.00 per scc18p per word (min 15 words)Box No. £1.50Closing date 2nd Friday in month precedingpublication.
e prepaid.Advertisements are accepted subject to the terms and conditions printed on the advertisementLm.\ rate card (available on request).
SEND TO:- ETI/HE CLASSIFIED, 145, CHARING CROSS ROAD, LONDON WC2H OEE. TEL: 01-437 1002 Ext. 50.
PRINTED CIRCUITS. Make your ownsimply cheaply and quickly! Golden Foto-lak light-sensitive lacquer - now greatlyimproved and very much faster. Aerosolcans with full instructions, £2.25; de-veloper, 35p; ferric chloride, 55p; clearacetate sheet for master, 14p; copper -clad fibreglass board, approx. 1mm thick,£1.75 sq. ft. Post/packing 75p. - WhiteHouse Electronics, Castle Drive, PraaSands, Penzance, Cornwall.
MAIL ORDER PROTECTION SCHEMEIf you order goods from mail order advertisers inthis magazine and pay by post in advance of de-livery, this publication Electronics Today Interna-tional will consider you for compensation if theadvertiser should become insolvent or bankrupt,provided:1. You have not received the goods or had your
money returned; and2. You write to the publisher of this publicationElectronics Today International explaining theposition not earlier than 28 days from the dayyou sent your order and not later than 2 monthsfrom that day.Please do not wait until the last moment to in-form us. When you write, we will tell you how tomake your claim and what evidence of paymentis required.We guarantee to meet claims from readersmade in accordance with the above procedureas soon as possible after the advertiser has beendeclared bankrupt or insolvent to a limit of£1,800 per annum for any one advertiser soaffected and up to f5,400 p.a. in respect of allinsolvent advertisers. Claims may be paid forhigher amounts, or when the above procedureshas not been complied with, at the discretion ofthis publication Electronics Today International,DUI we do not guarantee to ao so in view of theneed to set some limit to this commitment andto learn quickly of readers' difficulties.This guarantee covers only advance paymentsent in direct response to an advertisement inthis magazine (not, for example, paymentsmade in response to catalogues, etc, received asa result of answering such advertisements).Classified advertisements are excluded.
CB SPARESJapanese original transistors and
integrated circuits.Largest selection in Britain at very
low prices.
Write or phone for free list.McLAUGHLIN ELECTRONICS44 Carlisle Road, Londonderry
N. Ireland, BT48 6JWTel: (0504) 65002
50 MIXED ICs, transistors, diodes O.Bargains list 15p. Sole Electronics, (HE), 37Stanley Street, Ormskirk, Lancs.
SHARP POCKET COMPUTERS
PC 1211 Pocket Computer with CE121 Cassette In-terface £105.95Printer not available until end of April.Free Papermate pen with all orders. All prices in-clude 15% V.A.T. and U.K. delivery.
ELKAN ELECTRONICS, 28 Bury New Road, Prest-wich, Manchester, M25 8LD.
YOUR OWN PERSONAL TOOLKITSmart zip -up case, removable tool pallet, black vi-nyl, top-quality British tools, pencil bit iron, radioside cutters and pliers, small and large screwdriver,one cross point, B.A. nut spanners 6, 4, 2 and 0.
Price £25 £1.50 p. & p.Kitonics, 7 The Meadows, Berwick-upon-Tweed
TELEPHONE ANSWERING MACHINE.Build your own for under £10 plus anycassette recorder. Send £3 for circuit andplans. S. D. Cross, 24 Thorney Road,Streetly, Sutton Coldfield, West Mid-lands.
100 IN4148, £1; 150 Resistors, £1; 100Capacitors, £1. P. & P. 25p. S.A.E. lists. -Dept. H, D.B. Products, P.O. Box 8, York,YO1 1FT.
BARGAINS FOR THE ELEC-TRONIC HANDYMAN
BRANDED L.E.D. DIGITALALARM CLOCKS
0111.00001"."(1)
Returned to ServiceDepartment withinguarantee period (2)
1 With alarm repeat. S.R.S.P. of £17.00. Offered at£3.95, inc. VAT, or 3 for £9.95, inc. VAT.
2 With luxury lamp and repeat alarm. S.P.S.P.£31.00. Offered at £7.95 inc. VAT each, or 3 for£19.95 inc. VAT.
These will he sold as received from our customers withthe existing fault(s) and without guarantee.
U KDiscounts available on large bulkpurchase.
PRESCOTT CLOCK & WATCH CO.LTD.
PRESCOTT HOUSE, HUMBER ROAD, LONDONNVV2 6ER
ELECTRIFY YOUR SALES! CLASSIFIED ADVERTISEMENT1 2 3
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Please place my advert in: Electronics Today International(Delete as applicable) Hobby Electronics
Advertise nationally in Electronics Today International/HobbyElectronics. Simply print your advertisement in the couponhere (left), indicating which magazine you require.Or telephone for more information.
Name
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Tel. No. (Day)Send, together with your cheque to:Jenny Naraine, ETI/HE,145 Charing Cross Rd., London WC2H OEE.Tel: 01-437 1002 Ext. 50.
66 Hobby Electronics, April 1981
THE CB ANTENNATHAT REALLY "ZAPS"
IT OUT
WNTJOYTHE 'CB' PEOPLE
ANTENNAS
WRITE OR CALL FOR FULL INFORMATION FROM:
WINTJOY LTD. TEL. WALTON-ON-THAMES103 HIGH STREET (STD 09322) 48145
SHEPPERTONMIDDLESEX TW17 9BL
ENGLAND
Make it fora Song!a. . a . .
The New Maplin in MatineeAmazing Value .95
For OnlyE299
+ £99.50 for cabinet if required
Easy to build. Latest technology - means lesscost, less components and 80% lesswiring. Comparable with organs selling for upto £1,000.00. Two 49 -note manuals. 13 -notepedalboard. All organ voices ondrawbars. Preset voices: Banjo, Accordion,Harpsichord, Piano, Percussion. Piano sustainSustain on both manuals, and pedalboard.Electronic rotor, fast and slow. Vibratoand Delayed vibrato. Reverb.Manual and Auto-Wah. Glide(Hawaiian Guitar Sound). Singlefinger chording plus memory. 30Rhythms! 8 -instrument voicing.Major, Minor and Seventh chords.Unique walking bass lines with each rhythm.Unique countermelody line with each rhythm.Truly amazing value for money.Full construction details in Electronics &Music Maker magazine.
The complete buyers' guide to electroniccomponents. With over 300 pages, it's acomprehensive guide to electroniccomponents with thousands ofphotographs and illustrations and pageafter page of invaluable data. Get a copynow - it's the one catalogue you can'tafford to be without.
I
I
AddressII
r is in mu ePost this coupon now for your copy of our 1981catalogue price 11.Please send me a copy of your 320 page catalogue. Ienclose 11 (Plus 25p p&p). If I am not completelysatisfied I may return the catalogue to you and have mymoney refunded. If you live outside the UK send £1.68or 12 International Reply Coupons.I enclose 11.25.
Name
rwormihnI Maplin Electronic Supplies Ltd.
All mail to: P O. Box 3, Rayleigh, Essex SS6 8LRI Telephone: Southend (0702) 554155. Sales (0702) 552911I Shops:
159-161 King Street, Hammersmith, London W6. Telephone: (01) 748 0926.HE481 I 284 London Road, Westchlf -on-Sea, Essex. Telephone: Southend (0702) 554000
MIIIIIM1111111====1111M====IMINIIIIIIM=IIN Both shops closed Mondays.
Catalogue now on sale in all branches of WHSMITH 04 Price £1.00