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Build An lnfrared Night Viewer SIMPLE FM .RADIO RECEIVER ~ c.. It uses just two chips & runs off a 9V battery z"' ~ AUfOMATIC NICAD 0 i :::, c.. ._: u, 0 c.. <( BATTERY DISCH~RGER 11 Puts new zip" into your: mobile telephone batteries ::i <( a: LOW-COST SPEED ; CONTROLLER FOR MODELS !;; :::, <( > a: w lii a w a: Compact design can handle motor: currents of up to 50 amps * A Brief Look At Liquid Crystal Displays * DC-DC Converter Circuit For The 2kW Inverter ~ ACCURATE M COMPACT RUGGED RELIABLE AFFORDABLE The reasons for choosing Tektronix stack up as well as our bench test equipment Tektronix TM 250/fM 2500 Series bench test equipment is designed to cater for a wide range of applications ranging from basic to advanced. It is equally suitable for teaching situations, industrial applications and for the advanced hobbyist. The rugged, affordable Tektronix bench test range includes: • Power supplies for lab and field work. • Digital multimeters to measure AC and DC voltage and current plus resistance and decibels. • Function generators for testing amplifiers, filters and digital circuits. • Stackable multi-function counters, especially useful standards for calibrating other equipment. • The versatile, multi-purpose basic bench set: ideal for schools, labs and production lines. Call now for full details and specification information. Tektronix h st and Measurement Free Call (008) 023342 Vol.5, No.11. November 1992 FEATURES 6 A Brief look At liquid Crystal Displays by Daniel Katznelson How they work & why they're popular BASED ON a Motorola 6BHC705CB microcontroller, this project is designed to teach the basics of programming & microprocessor control. Tum to page 34. 32 The Oriel: Jamo's Flagship Loudspeaker System by Leo Simpson Three-way system has no expense spared 79 The Story Of Electrical Energy, Pt.21 by Bryan Maher How electric lighting came to Sydney streets PROJECTS TO BUILD 16 Build An FM Radio Receiver by Darren Yates Uses just two chips & runs off a 9V battery 22 Modifications To The Drill Speed Controller by Leo Simpson Amended circuit has longer gate pulses 24 A 2kW 24VDC To 240VAC Sinewave Inverter, Pt2 by John Clarke The DC-DC converter circuitry 34 The M.A.L. 4.03 Microcontroller Board by Barry Rozema Uses a 68HC705C8 microcontroller 40 An Automatic Nicad Battery Discharger by Bernie Gilchrist Puts new "zip" into your nicad batteries 62 An lnfrared Night Viewer by Branco Justic It lets you see in the dark 74 Simplifying The lnterphone Telephone Exchange by Leo Simpson Simple modification eliminates up to 18 !Cs . SPECIAL COLUMNS 44 Serviceman's log by the TV Serviceman I did it; but it wasn't my fault 58 Vintage Radio by John Hill Converting a battery set to mains operation PUT MORE ZIP INTO your mobile telephone batteries with this low-cost device. It automatically discharges a nicad battery pack to its correct end-point voltage so that the pack can then be recharged to full capacity. Details page 40. IFYOU'RE new to electronics, here's a great project to get you started. It's a simple FM radio that uses just two low-cost ICs & runs off a 9V battery. See page 16. 66 Amateur Radio by Garry Cratt A PLL demodulator for amateur receivers 84 Remote Control by Bob Young A low-cost speed controller using discrete !Cs 88 Computer Bits by Darren Yates The PHd pocket hard disc drive DEPARTMENTS Publisher's Letter Mailbag Circuit Notebook Subscriptions Page 68 Product Showcase 2 4 B 57 96 Back Issues 98 Ask SIiicon Chip 101 Order Form 102 Market Centre 104 Advertising Index EVER WANTED TO SEE in the dark without a flashlight? This infrared night viewer will let you do just that. All you have to do is build the high-voltage supply. Tum to page 62. NOVEMBER 1992 1 Publisher & Editor-in-Chief Leo Simpson, B.Bus. Editor PUBLISHER'S LE'I*l'ER . Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Darren Yates, B.Sc. Reader Services Ann Jenkinson Sharon Macdonald Sales & Marketing Mgr. Sharon Lightner Phone (02) 979 5644 Mobile phone (018) 28 5532 Regular Contributors Brendan Akhurst Garry Cratt, VK2YBX Marque Crozman John Hill Jim Lawler, MTETIA Bryan Maher, M.E. , B.Sc. Jim Yalden , VK2YGY Bob Young Photography Stuart Bryce Editorial Advisory Panel Philip Watson , MIREE, VK2ZPW Norman Marks Steve Payor, B.Sc., B.E. SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. A.C.N. 003 205 490. All material copyright ©. No part of this publication.may be reproduced without the written consent of the publisher. Printing: Magazine Printers Pty Ltd, Alexandria, NSW; Macquarie Print, Dubbo, NSW. Distribution: Network Distribution Company. Subscription rates: $42 per year in Australia. For overseas rates, see the subscription page in this issue. Liability: Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. Editorial & advertising offices: Unit 1a/77-79 Bassett Street, Mona Vale, NSW 2103. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 979 5644. Fax (02) 979 6503. ISSN 1030-2662 2 SILICON CHIP Light pollution wastes energy The subject of this month's "Publisher's Letter" was triggered by one of the projects featured in this issue, the Infrared Night Viewer. Naturally, as part of the work involved in presenting this unit, we used it at night. And while it is more effective if used with an infrared torch, it does work quite well on moonlit nights. Interestingly, it can also work quite well on cloudy nights when the Moon is completely blocked out. How can this be so? First of all, if you live in any Australian city or major town, it no longer gets really dark at night. There is so much light around at night that we now have a major new form of pollution to contend with - light pollution. And it is the infrared portion of all this light that enables the aforesaid infrared night viewer to work. But this is not good. Most Australians, unless they have an interest in astronomy, could not give a fig about light pollution. It is now so bad in Australian cities that many city residents cannot even see, let alone identify, the symbol on our flag, the Southern Cross. Yet the Southern Cross is one of the brightest constellations in our skies. And nor should light pollution be thought of as a problem just in the inner city areas. It is particularly bad in the newer suburbs which have very bright street lighting, where the houses have so-called security lighting, plus lighting for the pool, barbecue and garden. And there is the super bright lighting used for sporting venues, shopping centres, car sales yards and so on. Maybe most people don't care whether they can see stars in the sky or not. Maybe most of them are afraid of the dark. But the level of lighting now being employed is downright wasteful. It costs a lot of money to install all that lighting and it takes a lot of energy to run it. Not only is it over-bright, most of the lighting fixtures are badly designed and aim a good portion of their light straight up into the sky instead of down at the ground. In fact, driving along roads near nighttime sporting venues can often be unpleasant because there is so much glare from the lighting. It is about time we came to our senses about this subject. While we may regard countries such as the USA as being very wasteful of energy, when it comes to light pollution we are right up there at the top of the list. In the USA and other countries , there is an organisation called the "International Dark Sky Association" and this has had considerable success in mitigating this problem. It is probably about time we had a branch of this organisation in Australia. If we start now, we could save a huge amount of fossil fuel and maybe children of the future will be able to see the stars at night, perhaps even more than we can now. If you want to write to the International Dark Sky Association, their address is: 3545 North Stewart, Tucson, Arizona 85716, USA. Leo Simpson Message Stopper This inexpensive device, which connects direct to your answering machine will automatically d isconnect your answering machine w bcocvcr ANY PHONE is answered ! If your answering machine answers your call before you do, simply pick. up any pbone, your answering mach ine will immediately disconnect and you can speak. without interference. With tbe MESSAOE STOPPER you can now leave your answering machine on and not have to worry ! Are your customers having trouble getting through to your phone/fax line ? and you've Jost the sale because your exsisting fax switch is not doing what YOU want it to do ? WE HAVE THE SOLUTION I The VSI EASY CONNECT Phone-Fax/Line Sharer The most advanced Phone-Fax (or Modem) /Line Sharing Device. Now available in Australia. Integrate ANY fax, with ANY answering machine on ANY telephone system, WITHOUT the limitations of faxswitch devices or 3 in I fax systems. l<at>r ~ Maggy Larn.p Magnify any object under a clear cool l<at>r ~ fluorescent ligbt. No more eye strain. Witb a 127mm biconvex lens, 4 dioptres, focal lengbt 245mm, sturdy l<at>r 0 1 j , ~~,~~~ftion and built Don't Pay Confusing Voice Messages Delays or Periods of Silence Unusual Dial Tones Frustrated Callers Why the EASY-CONNECT 7 lec:,use the BASY-CONNBCT la lhe moat 0 !Le.~~~~e /t,d1c:~ Nl.et,,f,_hfnne.4~:~r! today. 1 ~:!e0~ nl11 ~a ~ere~~o~~ )'.::,•e•r:r!~fhou t Ille ll m lutloni of huwltch dulce1 o r /• · ,- 11f! :l,1 ~ff JIii lfa l IYIUIIII. Other faxswltch systems ? Clum,y f11 priority operat\011 . Del1y 1. panea. t1olc:e 111e1111ea. fru1tr1ledcaller1. lnfleilble and llmlted operatlu1 •Ith otherdC\llcea. Mtut be fltled on flrat aoctet. Poor hl1tory of c:u1tomer 11t11hcllo11. The EASY-CONNECT is totally transparent. Your callers will never know it's on the line! ·. , NO NO NO NO Dedicated fax line ? _. More Aulomatic, More Flex.Ible, More Powerful tllan any 3 in I fu. ,yslcm. ~lec:om c:lur1e1 i:ffec:the Z)/6/92 •lthou1 telepho11e • _.Latest Voice Priority tccbDQ-\PU· T,of.11 J!l.c.l.ibility.. in minute, on ANY PHONE SOCKET. _.Fully Functional wilb ALL cx.tcrnion tclcpbooca. .-1.iut ■ ll1 _.No restriction lo tlac number or posi tion or c1.lcndons. .-Operate with Faa., Phone. Modem. and Answcrio1 Machine on one line. 1299. . , - / •No switches to remember (or for acl) when your otricc is unattended. .-Proven Rcliabillly bact.cd up with a 2 YEAR EXCHANGE WARRANTY. Telecom $442 SUl _.PROTECTION ror tlac Fai and other dcYiccs a1 a insl li1btnin1 or sur g es. •Austcl Approved. A!I0/148/03.C l. Ma de in U.S.A. VSI $399 U99 U99 $)14 $1124 •Save installation and renta l costs ror a separate line. :!r:;~c11~~•lt~!:, ,•1~:;:!c,~•,!/:.:3:'•r,: of ll1l,1nln111,lt,:1, IOO!f prot,:i:1lon for 11,,: fu 0 ';.!•,: The VSI Easy-Connect is not to be confused with other faxswitch systems. Our price: Onl $279.00 a~clcmar> lr,c:/c.1str-ial DM5XL Sl)U DMlOXL $89.95 -Input Lead Warnin1. ar200mA Fuse. arContinuily Beeper. - Diode Test. .,..DC Volts: 200mV -I OOOV. a.rAccu r acy: 0.11%. -Resol•tion: IOOuV. -Input Imp.: IM obm. -Ac Volts: lOOV/SOOV. .,.DC Current: lOOuA-200mA. .,.Reshtance: 200-lM obcn. -Display: 3.S Digit. 0.7• . Digital :Multimeters $117.00 =~o~ 0Bnat\:!ri~:r!i;~:.or. DMlSXL $149.95 •Locic Te st. •Input Le a d Warning. •IOA Fuse. • lOOmA F•sc:. •Continuity Beeper . •Diode Tesl . •DC Volts : 200mV-IOOOV. •Accuracy: 0.5%. •Rc:solulion : IOOuV. •l11put Imp .: IOM obm . •AC Volts: 200V/7SOV . - DC Current: 200uA-IOA. •AC Current: 200uA-IOA . .-Resistance: 200- 2000M Ohm . .-Di1play: 3.5 Diait, 0.7"" . • Low Baltcry Indicator . •12 Montbs Warranty . • Safety Tester. • Input Lnd Warnin 1 . • IOA Fuse. • 200mA Fuse. • Conllnaily Bccpc:t. .., Diode Tes t. _. DC Volts: 200111 V-IOOOV. • Accuracy: 0.79£,. • Resolution : IOOuV. • Input Imp.: IOM obm . • AC Volts: 200V /750V. • DC Current: 200uA-IOA. • Resh lance: 200-20M obm. •Display: 3.5 Dl1H. 0.7"'. .., Low BattorJ Indicator. •12 Montbs Warranty. t/.BBB Input Warning Beeper: Incorrect test lead placement will cause all three meters to IHue a warning beeper sound. The warning beeper indicates that a test lead is in an incorrect position. Safety Tester: The safety tester on the DM10XL safely detects and displays the presence of particular AC or DC voltage IPos. or Neg.) levels through a series of LED's. KJNGRAY SA214V VHF/UHF Video Comblatr Amplifier For UHF/VHF TV systtms Tbt SA214V remote powered rideo combiner bas been designed to combine and amplify a rideo output signal from a VCR with VHF/UHF signal for multipoint distribution. You can now bare rideo and TV reception from any wired distribution point in the house. output SPI.Hter. Outpat: 6dB each oatlet. ...... WI)' • KINGRAY MHW34T/ PKS02 Masthead Amplifier 40 x 20mm 60 x 2Smm 80 x 2Smm 90 x 2Smm 80 x 38mm 80 x 38mm 120 x 2Smm 120 x 38mm 120 x 38mm 120 x 38mm 12 volt DC 12 volt DC 12 volt DC 230 volt AC 110 volt AC 240 volt AC 24 volt DC 12 volt DC 110 volt AC 240 volt AC S14.9S Sl9.9S Sl9.9S S2S.S0 Sl9.9S $22.9S S23.90 $22.95 S24.9S S24.9S BeeIronies _. Suitable for city & country areas. _. Gain: 2Sd8 VHF: 34d8 UHF. _. Suitable for combincd/seperatc aerials. _.Easy insta ll a tion . _. Dui &ned &. Made in Aostralia. _. Power supply included. _. Jmprowe your TV rccc:ptioo. Only $125.00 S3.9S S3.95 S2.S0 SI.SS SI.SS $1.85 S2.95 S2.9S S2 .9S After LED's 7 Ring David Reid's First! David Reid 127 York St, SYDNEY 2000 n_ To PKS02 SJ49.00 3mm BLUE 14 mcd Smm BLUE 14 mcd Smm RED 3S00 mcd Smm RED Flashing Smm GREEN Flashing S'mm YELLOW Flashing 10mm RED Flashing 10mm GREEN Flashing 10mm YELLOW Flashing From 114.95 For UHF/VHF TV systems %I LJ--l_J-lTv was Computer Fans $19.50 SD400 Standard Smolc Alarm $28.00 SD500 Kitcben Smole Alarm S0700 Safety Ligbt Smole Alarm $37.00 A.C.N. 001-372-372 To 24°h 'Now$299.95 Smoke Detectors UHF/VHF Anl. Economical Alarm System ~ Smoke can Kill! All with Test Button S Year Limited Warranty Batteries Included (example) UHF Ant. _. S protection loops Alarm Panel. _. Di1it1I Ace en 1'.ey-Pad. _. Passive lnrra-Red Detector. _. Power Supply and Battery . _. Horn Speaker and Panic 811,tton. _. 3 paiu or Reed Switches . .-cable Sapplied. r-r-il Only$99.95 ARLEC Christmas is just around the corner, and so are the break-in's. Aroid Theft, be Alarmed! From '0.20c each. Ph: (02) 267 1385 P.O. Box Q103,SYDNEY 2000 Fax: (02) 261 8905 DCTJJO Clamp Meter "Measure AC and DC current" -AC/DC Amps (400A). _. AC/DC Volts. _. Re5ista nce. •Temperature. *Data Hold. •Peal Hold. _. Probe1 lnclo.dcd. ..-cue Included. _.lyearw a rranly. On/ $178.50 Postal Charges $5 · $25 ......... $4.00 $26 • $50 ...... $6 .00 $51 · $100 ..... $7.00 $101 · $499 .. $9.00 $500 • ........ .... FREEi MAILBAG New projects wanted As usual, the minute I saw SILICON CHIP at the newsstand I purchased it. I am usually rapt in the magazine but I was a little dissatisfied with the August edition. I agree that one sealed lead-acid battery charger is a good idea, and perhaps an update, but another? How many people who built the first one would build a second, if the first one fulfilled their needs? If you are short of ideas, how about a constructional project for the CB enthusiasts, like UHF antennas and/or a UHF SWR meter? I have been searching for something on this line for a while. I am sure there are many others who would love to build an antenna at a fraction of the cost of a commercial unit I would also love to see an antenna rotator using reasonably priced components. Any other UHF users think the same? I would also like to comment on the statement made by Leo Simpson in the April 1992 edition about Bulletin Boards being a trouble area for computer viruses. As a former BBS operator, and a co-sysop currently, I would like to mention that most BBSs nowadays scan for viruses before a file is allowed to be downloaded. Whingeing aside, I still think that the magazine is the most comprehensive in its field and look forward to further issues, perhaps with some UHF radio projects. J. Adler, Broadbeach Waters, Qld. Another fan of peanuts sticks to his blanket A fair amount of hysteria has been generated recently by articles in the media and electronic journals about the real or imagined dangers of 50Hz power lines, electric blankets, etc. I believe that case is closed as millions of people have used electric blankets etc for decades without any statistically significant effects becoming evident. However, very recently, there has come into common use a device which 4 SILICON CHIP I believe could be decidedly iffy. I refer to the mobile radio telephone, handheld, where the aerial of a UHF transmitter is about 50mm from the brain of the user! I'll stick with my blanket, thank you. While I'm at it, here's one for the design department. I believe the 9V switchmode supply idea in the August issue could have a much wider application. Many thousands (millions?) of instruments and appliances are powered by 1.5V dry cells arranged in a stack. In many cases, it would be an advantage if these were replaced by nicads, plus a switchmode supply which would produce a regulated dry cell voltage equivalent over the range of the nicad cell stack voltage. Bill Jolly, Hahndorf, SA. Video switcher for S-VHS I find SILICON CHIP as interesting and full of features as ever. Keep it up! The Video Switcher Project as described in June 1992 is a fine example and it certainly would tidy up a situation of mine. However, I have SVHS video equipment which means the project would unfortunately not be suitable. As you would know, in S-VHS and 8mm Pro formats, the video is split into chrominance and luminance signals which are processed separately. This results in a vastly superior picture. (Both formats use 4-pin miniDIN connectors for the video instead of the usual RCA or BNC connector). The audio is processed as normal using RCA plugs. Would you consider a version of the Video Switcher for use with SVHS equipment? I'm sure other readers with S-VHS or 8mm Pro would be interested. G. Suttle, Sydney, NSW. Applix microcomputer board Readers looking for a build-it-yourself microcomputer kit may be interested in attending Applix User Group meetings in Sydney or Melbourne, or SILICON CHIP, PO Box 139, Collaroy Beach 2097. logging onto one of the four Applix bulletin boards that use this computer. Although the kit comes from a garage in Yerrinbool, it is a full 7.5MHz or 15MHz Motorola MC68000 computer, built using lots of standard 74LS and VLSI chips (6821, 6545, 8530, 5380 and three PALs - nothing exotic). It can run from a serial port or provide its own CGA or EGA video, and has the entire operating system in on-board EPROM. Although you can run it without discs, it includes support for floppy drives and SCSI hard discs, via an optional Z80-based disc controller card (that can even run CP/M and MicroBee programs). User group members are attempting to fill up the four expansion slots by designing n ew hardware. An EPROM programmer has just been completed and I have seen prototypes for a Transputer card, a 25MHz MC68030 card, and an Ethernet and memory card. The free C and assembler source code available fills more than 30 discs and includes many utilities derived from Unix. It includes assemblers and disassemblers and a C-like interpreter. Software for sale includes BASIC and Forth, a C compiler from Brisbane softw are developer HiTech, plus windowing systems, com:munications packages and Unix utilities. Readers wishing to read up on this system can obtain copies of Applix manuals from the User Group. Manuals available include Users, Programmers , Technical Reference, Construction, Assembler, Disk. We must ask for $10 each to cover our photocopying costs. We can also make manuals available free in Postscript form, on IBM format discs. Please note that most manuals are so large that a high density disc mu st be used. We would be pleased to send copies of some of the Applix User group newsletters to any of your readers who may be interested in learning more. Eric Lindsay, Applix User Group, 6 Hillcrest Ave, Faulconbridge, NSW 2 776. We've recently taken on a new line in so ldering irons - Hakko - and they are excellent value for money offering features usually costing much more. We have the full range available, but check out the 926 adj ustable temperature iron, the memory card 927 and dual station 928. If you 're thinking about buying or upgrading you r soldering equipment can in and discuss your requirements. ~ :i: (..) ~ u:. § ~ ~ !:l:: G ~ u:. § ~ ~ :i: (..) (t t2 § ~ ~ :i: (..) (t t2 § ~ ~ ~ G ~ u:. • Compact unit with two 926 units Hakl<0926 Hakko 928 Dual in one station and easy to use. Cost effective and practical in Soldering Station Solder.Ing Stat"IOn •production using up less space. The Hakko 926 (above) is a super- • Two soldering irons of different • Super quick heat up and faster quick heat-up (3 sec cycle) and fast recovery iron offering high quality soldering at lower tip temperatures. The built-in ceramic heater maintains temperature to within 0.5°C of the setting. Yes this is an ADJUSTABLE temperature iron covering the range from 200°C to 480°C using a full wave zero-crossing switching system. Meets MILSTD-2000 and operates at safe 24V. Also available in ESD for antistatic environments. We stock a wide range of tips to suit. Ask for listing. Hakko927 Soldering Station Incredible memory card iron. Just look at the features • Digital adjustment/display system using built-in microcomputer. • Convenient memory cards for quick and simple tip temperature adjustment and monitoring. • Accurate Temperature Adjustment and Monitoring Simply insert the card , set the desired temperature and push the set ("S") button. Once the temperature is set, it cannot be changed without -re-inserting the card . • Temperature Memory System The tip temperature value is stored in the memory of the builtin computer allowing you to turn the power off and on without having to reset the temperature each time. The HAKKO 927 ESD Soldering Station is available for static safety and meets MIL- STD-2000 thermal capacities may be used thermal recovery, permitting simu ltaneously quality soldering at lower • Choose the exact irons you need temperatures. for your so ld ering appl1cat1ons • Separate controls for each iron • ±0.5°C dial setting • Meets MIL-STD-2000 ASK ABOUT OTHER PROFESSIONAL SYSTEMS CODE DESCRIPTION £.~195.00 EMPT $222.00 94T Solder Pot 96 So lder Pot-200W 0.85kg capacity 350.45 $399 .45 POA 152 Motor Drive for 153/154/155 POA 153 Cutting/Forming for Axial Components 11148.00 1312.00 154 As 153 but for Axial Components 5mm 1198.00 1369.20 155 Cutting for Radial Components 1324.80 1508.80 POA ,56 PdrtS Feeder for 153 and 154 POA 191 Thermometer with Large Digital Display $250.00 $278·80 191 -211 191 Sensors per Pack of 10 $17.25 $19.65 470 Desoldering Tool 1945 .00 $1079 .00 471 Desoldering Tool 848.00 $965.40 483.1 Complete Desoldering Gun 415.70 $473 .85 POA 485 Solder/Desolder Stati on with Solder Bath POA 1 493 Smoke Absorber v.i !:l:: iS ~ u:. a Solder 1.25, 0.9 and 0.71 mm 250 gm 500gm Solder Wick diameter $7.95 $14 .95 $2.95 ~ 8.30am to 5.00pm Mon to Fri. 8.00am to 12 noon Saturday. :::,. Mail Orders add $5.00 min to cover postal charges. v.l Next day delivery in Sydney add $8.00. ~ All prices include Sales tax unless stated otherwise. u Tax exemption certificates accepted if the line value ~ exceeds $10.00. u:. BANKCARD, MASTERCARD, VISA, CHEQUES or CASH cheerfully accepted. § ~ $195 .75 $233 .15 700C 50/60W Combi Solder/Desolderer $1095 .00 $1253 .00 745 Battery Powered Iron 7.2V Operation 160.00 $182 .40 804 Glue Gun with Temperature Control 279.00 $318.80 850 SMD Hot Air Rework Station with N-7 Tip 990.00 $1129 00 741 ·oo 851 SMD Station 650.00 221 :40 883 HotAirGun-1000W, 1250m 3/min 194.40 183.95 926 Solder Station - 60W Temperature Control 159.95 359.65 926ESD926 Station with Antistatic Feature 315.90 482.50 927 Key Card Station - 60W with Digital Display 423.30 532.80 927ESD927 Station with Antistatic Feature 467 .45 605 .85 928 Dual Individual Control -60W, Antistatic 531.55 a § TAX TAX PAID 1 Safewash 2000- the complete environment-friendly cleaning System The Safewash 2000 aerosol offers a break through in PCB Safewash 2000 is a unique blend of biodegradable 100% ozone friendly solvents in an aqueous blend formulated to provide effective cleaning of printed circuit boards. Safewash cleans to military standards (MIL-P-28809A) using conventional methods at room temperature. Application • Removal of flux residues and other contaminants from ~r·Inted c·1rcu·1t boards and urface Mount Assemblies • Removal of unused solder paste from sc reens • Degreasing and cleaning prior to conformal coati ng. · Features e 100% ozone friendly • Non-flammable • Biodegradable • Removes both polar and nonpolar contam inants • Removes ionic flu x residues to MIL P 28809A • Ambient temperatu, e operation • Low toxicity rework technology. There are a number of aeroso l products on the market which either still contain CFC's, or otherwise leave a sticky residue after 'cleaning '. Safewash 2000 uses a unique foaming action to break down a wide range of fluxes, in fact up to _three times more flux types than most alternatives. Once applied, the foam action 'scrubs' the b d rfr th fl ·d oar ' 1 mg e ux resi ue away from the PCB. After a few minutes the flux residues are sufficiently broken down to be rinsed away using Saferin se 2000. The printed circuit board can then be dried off using an Electrolube Air Duster or another form of forced or warm air drying. Because Safewash 2000 uses a foaming action, manual scrubbing with a brush, wh ich can cause damage, is not req uired, thereby saving money on unnecessary extras. An add itional operator benefit is that Safewash does not have the citrus smell often ~ - - - - - - - - - ~ associated with aqueous or non CFC cleaners. Safewash 2000 Electrolube Positive Photo Resist Aerosol Now in 200gm can for one to one reproduction of printed circuits and images on metals using film positive masters. Gives excellent resolution with uniform, extremely thin edge to edge coating thickness. Safe, easy to app ly an d process. Can covers approx. 5sq.m. $33 .00 Also from Ele~trolube Clear lacquer (250gm) 113.10 Freezer (550gm) 23.80 Cleaning Solvent (300gm) 10.70 i~~~w;,;;rosol 0 i~r B~st::osol 550gm aerosol $19.80 $18.10 $26 .60 We can supply Electro lube products in aerosols or in bulk. Call us for pricing A brief look at liquid crystal displays Liquid-crystal displays are everywhere these days; they're even used as TV screens. This articles describes how they work & explains why they've become so popular. By DANIEL KATZNELSON The liquid-crystal display or LCD made its commercial debut in the early 1970s. It represented a quantum leap in display technology that manufacturers of digital watches were quick to exploit. Today the LCD is the most widely used display type except, of course, for the ancient CRT, which has proven to be remarkably durable. The introduction of colour LCDs, combined with constantly improving resolution and speed, has brought about the development of highly portable flatscreen TVs and laptop computers. We are undoubtedly heading to- wards an age of "tubeless" consumer products, although that time is still a long way off. How LCDs work LCDs are amazingly efficient at performing their jobs. The smallest LED (light-emitting diode) display consumes a few milliwatts while an LCD uses power measured in microwatts. For electronics enthusiasts, the implications are obvious - a project's display-current requirements can practically be ignored. Frequently, circuits that use LEDs must be designed around the display because a glowing FRONT POLARIZER GLASS PLATE PATTERN ELECTRODE BACKPLANE ELECTRODE PASSIVATION LAYER LIQUID CRYSTAL POLYMERIC SEAL PASSIVATION LAYER ALLIGNMENT COATING GLASS PLATE REFLECTIVE COATING \ REAR POLARIZER Fig.1: this sectional view shows the physical construction of a typical LCD. Note the backplane electrode that runs behind the liquid crystal material. 6 SILICON CHIP diode demands over 1000 times more power than a liquid crystal segment. The physical arrangement of an LCD is totally different from other display devices because it does not produce light. Instead, it modifies the available ambient light to produce the required digits and characters. Liquid crystals have some of the characteristics of a liquid and some of the characteristics of a solid. The liquid crystal particles can be visualised as twisted ribbons that can be moved around. The crystalline medium in an LCD is ari organic compound that is scientifically referred to as being dielectrically anisotropic. That means that the properties of the crystals change when an electric field is present. If unenergised (ie, with no potential present), the crystals "rotate" any incoming light by go Conversely, when they are under the influence of a field, any passing light remains unaffected. For simplicity, you can imagine light as a wave moving up and down as it travels forwards . But in the real world, one light wave might be vertically polarised, while another wave is horizontally polarised. A slew of others could have any orientation between these two. A polarising filter allows only those light waves travelling with a particular orientation to pass through it. If you place one polarising filter behind another and position them so that one passes vertically polarised light while the other passes horizontally polarised light, then light will not be able to pass through both filters. But, if you take the vertically polarised light that passes through the first filter and "rotate" it through go 0 so that it becomes horizontally polarised, it can then pass through the second filter. You can do just that be placing an -unenergised liquid crystal of the right thickness between the filters. Light will travel through the first filter and 0 • v00 ___0JL~ OFF Vss __ _---..J L- CONTROL INPUT 32 TO 60 Hz. SQUAREWAVE OSCILLATOR PATTERN ELECTRODE .J'lJ'1... - - - - -- - --f ____...t.J'lJ'l... BACKPLANE LIQUID-CRYSTAL CELL - -•~ Fig.2: this is the most popular drive circuit for an LCD. The gate's control input determines whether it inverts or buffers the oscillator signal. LCD BACKPLANE (OSCILLATOR) in the shape of a display segment and consists of a grid of fine wires composed of indium tin oxide. They are etched into the glass by a process called photolithography. Another electrode (to the rear of the display) forms the backplane or common connection. As its name implies, ·it is electrically common to all segments in the display. The external connection for that electrode is brought to the front of the display to be level with the connection points for the front pattern electrodes. Voo Vss Voo LCD SEGMENT Vss RESULTANT LCD DRIVE WAVEFORM SEGMENT Off SEGMENT ON SEGMENT OFF Fig.3: these LCD drive waveforms show how the circuit works. The bottom waveform is derived by subtracting the backplane signal from the segment drive waveform. be rotated by the crystal through 90° so that it can then pass through the second filter. However, if we energise the crystals in a certain area, they will not rotate any light that passes through the first filter. This light will then "slam" into the second filter, which won't allow it to pass. Thus, if you try to look through the three layers (the first filter, the liquid crystal, and the second filter), the energised region will appear dark. And that's basically how LCDs work; each segment-forming digit is an energised region. A reflective coating is placed behind the second filter so that no light has to be generated behind the display to make the dark area apparent. This coating reflects any light making it through the assembly back towards the viewer again. How LCDs are built Fig.1 illustrates a single cell from the most common type of LCD called a Twisted Nematic Liquid-Crystal Display or TNLCD. Ambient light of the correct orientation passes through the front polariser and the front glass. It then passes through a transparent pattern of information electrodes. Each electrode is Note the passivation layer next to both electrodes. It acts to prevent current from flowing through the liquidcrystal layer, which would limit its life. The light waves continue their journey, penetrating the liquid-crystal layer and the second passivation layer. Finally, they pass through the alignment coating. That coating ensures that the crystals will line up properly when energised. The light continues to pass through the component parts of the rear glass sub-assembly, which are essentially the same as the front half of the display. Light that has not been rotated because it passed through energised regions of the liquid crystal doesn't make it though the rear polariser. The rest of the light passes to the reflector at the back, which is often a coating of highly luminescent material or may be provided with some kind of backlighting. The polymeric seal prevents the crystalline compound from leaking out In multi-cell displays, it also separates the liquid in each cell. LCD drive considerations Many readers have undoubtedly built devices that use LED displays. When LEDs are included as part of an overall design, the prime consideration is DC power consumption. If the regulator can handle the load, your problems are over. That is definitely not the case with LCDs. In fact, any DC voltages over 25mV will quickly lead to a chemical melt-down. To make matters worse, you may not be immediately aware that something is wrong until a critical measurement fails to materialise on the display. To keep from taxing the display, an LCD should be driven by an oscillator producing a clean square-wave with a 50% duty cycle. Fig.2 shows a widely accepted method that's used to drive LCDs. The basic idea is to apply a square-wave (with a frequency between 32Hz and 60Hz) to both the pattern electrodes and the backplane of an LCD. When the pulse train delivered to a pattern electrode is the same as the signal received by the common electrode (ie, the control input of the XOR gate is low), they have the same potential Thus, the segment controlled by the pattern electrode does not appear. However, if you make the gate's control input high, it inverts the oscillator's output. Thus, the pattern electrode is at some potential relative to the backplane, the crystals align, and the relevant segment darkens. The signal action for that is shown in Fig.3. LCDs are typically operated at 3-5V RMS. There are many specialised ICs designed to drive LCDs. Two such CMOS chips are the CD4543 BCD-to-7-segment latch/ decoder/ driver and its high speed equivalent, the 74HC4543. Finally, although TNLCDs are mass produced in huge quantities and can be purchased at rock-bottom prices, they are by no means the only display type that uses liquid-crystal material. Stricter requirements, such as for colour-reproduction and faster response time, have contributed to the expansion of the LCD family. Better contrast ratios combined with wider viewing angles have made necessary other LCD formats ·besides the twisted nematic. Some of those other types are ThinFilm Transistor (TFTLCD), Metal-Insulator-Metal (MIMLCD), Dynamic Scattering, and Smectic LCDs. Reprinted with permission from Popular Electronics Magazine, June 1992 issue. Copyright© Gernsback Publications, Inc, 1992. sc NOVEMBER 1992 7 CIRCUIT NOTEBOOK Interesting circuit ideas which we have checked but not built and tested. Contributions from readers are welcome and will be paid for at standard rates. Reversing light chaser for 12V lamps This low-cost reversing light chaser can drive either 12V or 24V automotive lamps and has six outputs. ICl is wired as an astable oscillator which runs at about 10Hz. This clocks ICZ which is a divide-by-10 counter. Its Q0 and Q5 outputs drive Darlington transistors Q1-Q6 via 3.3kn current limiting resistors, while the remaining outputs drive their corresponding transistor output stages via diode OR gates (D1-D8). Because of the diode OR gates, the counter first turns on transistors Q1Q6 in sequence to light the lamps (1116), then reverses the sequence so that the lights appear to run backwards. The sequence then reverses direction again and so the process is repeated indefinitely while ever power is applied. The optional light dependent resistor (LDRl) sets the chase rate according to the ambient light level. The higher the light level, the greater the oscillator frequency and the higher the chase rate. Replace the LDR with 1k 16 IC1 555 14 IC2 4017 6 07!"----HN--lf--l 9 08!"--f-N-1----.....J 09 AS 15 13 8 .,. a link if you don't want this option. Note that small heatsinks should be fitted to the Darlington transistors 8 SILICON CHIP (Q1-Q6) for lamps rated above 20W. M. Schmidt, Edgewater, WA. ($15) - A low cost crystal checker Ever needed to check a crystal to .ensure that it is operating correctly. Although this circuit won't indicate the frequency of a test crystal, it will at least show that it is capable of oscillation. Transistor Ql is configured as a Pierce oscillator and provides the test bed for the crystal. If the crystal is OK, an RF voltage appears at the emitter of Ql. This is then rectified by voltage doubler Dl & DZ and the resulting voltage across the .00lµF capacitor then turns on QZ which lights LED 1. However, if the crystal is defective , there will be no RF signal at Ql 's emitter and so both QZ and 1 TEST S1 CRYSTAL UNDER TEST ,. + 9V : ..L. .01 the LED will remain off. The prototype was built on a small piece of matrix board and shielded inside a box made ofblank PC board material. Two leads with alligator clips are used to connect the test crystal. The unit is powered from a 9V battery. P. Parker VK6BWI, Bentley, WA. ($15) 2-chip electronic blackjack game This simple electronic game uses just two low-cost ICs plus a 7-segment LED display, and can be used to play electronic blackjack. IC1 is a CMOS 7555 timer and is connected in astable mode to provide clock pulses to counter/decoder IC2. When S1 is pressed, pin 4 (reset) of IC1 is pulled high. IC1 is now enabled and its pin 3 output provides 30Hz clock pulses to counter stage IC2. After about five seconds, the 47µF capacitor is charged to 2/3Vcc and pin 4 goes low again, disabling IC1 and stopping the .----.--------...------r--..--------11-•9V 16 DEALI S1 27k IC2 4026 100k 6 b 13 4 2 15 .,. count. The 7-segment display then shows a number between O and 9. IC2 is a 4026 CMOS decade counter/7-segment decoder IC. This is used for counting and driving the 7-segment display. When IC1 stops, 16 a/ /c .,. 6 .,. 10 g 2 .,. the number displayed is the card drawn. A zero represents a 10, Jack, Queen or King and a 1 represents an Ace (1 or 11). G. Taylor, Werribee, Vic. ($15) 16 01 BC549 Q10 14 IC1 4020 011 15 10 IC2 4020 011 RESET 11 a C 9 t .,. 10 CK a 1/ g /b d 18 d 7 Timer safeguards rechargeable cells The effective life of rechargeable nicad cells can be severely shortened by over-charging. Many users save their cells from the dire effects of too high a charging rate by using a welldesigned charger, only to fall into the trap of leaving them on charge for too long. This problem can be solved by adding this simple timer circuit to the charger. It provides both 6-hour and 15-hour charging periods before automatically switching the charger off. When S1 is pressed, the commercial charger provides 8V AC for the timer, where it is rectified and filtered to provide a +12V supply rail. At this stage, the outputs from IC2 are all low and the outputs of IC3a & IC3b are high. Thus, Q1 and RLY1 turn on so that power is maintained when the S1 button is released. The timer is inactive for the first 100ms until the .033µF capacitor on pins 8 & 9 of IC3c charges and pin 10 switches low and releases the counter resets. IC1 is now clocked by a halfwave rectified signal which is derived from ,the 8V secondary of the transformer, a 1ookn resistor and D2. This provides 50 pulses per second and so the Q11 output of IC1 goes high once every 2048/50 = 41 seconds. Q11 ofIC1 in turn clocks IC2 and so Q10 (pin 12) ofIC2 goes high after 41 x 512 sees= 5.8 hours. This switches pin 3 ofIC3a low and so Q1 and RLY 1 7- - - - 11 IC1 7555 .,. 10 7x33011 12 RESET 11 6 15 D3 1N4004 S2 6 0912 8 10 IRLY1 D2 1N914 .~::---:.... 240VAC D1 1N914 100k 10k +12V --:- - - - - .... I I I N--------~ av ov I turn off to end the charging period (assuming that the 6HR setting is selected by S2). This setting is the one to use for AAA cells which require only six hours of charging. Alternatively, if the 15HR setting is selected, pin 4 of IC3b goes low and turns offQ1 and RLY1 after 41 x (1024 + 256) sees= 14.5 hours. In my case, there was insufficient room for the relay within the charger, so I mounted it on one end of the charger's plastic case. The other components were mounted on a small perf-card which slotted into a vacant internal space. The charger has LEDs to indicate which cells are charging, otherwise it would be advisable to fit an on/ off indicator. One last word - beware of the mains and keep mains wiring as far as possible from the low voltage circuitry. I put a small mound of silicone sealant over the relay contact wiring tabs and a piece of insulation card in another possible danger spot. Both the start button (S1) and the relay contacts should be rated at 240VAC and 1A. G. Wormald, Florey, ACT. ($20) NOVEMBER 1992 9 DIC THE GREATEST & IATEST BOOKS FOR THE HOBBYIST & ENTHUSIAST. Rush into your nearest store and check out these new titles and old favourites today! EDUCATIONAL SATELLITE TV (PACIFIC REGION) LEISURE SUIT LARRY BEDSIDE COMPANION NEW S2295 Cat B-6900 FUNWAY VOLUME 2. By Dick Smith KIDS BOOKS Cat B-2605 FUNWAY VOLUME 3. By Dick Smith - Cat B-2610 NEW S2995 Cat B-2321 FUNWAY VOLUME 1.By Dick Smith Cat B-2600 $695 --~ A KID'S GUIDE TO COMPUTERS Cat B-6700 For children 5 years and over, AVIATION & SPACE SCIENCE PROJECTS FOR KIDS .:--· - 1.opt.x·· . e, E-M':''.~····· o·· . · ·E.~ ·r-,-1t , .. Cat B-S?0 2 REFERENCE BOOKS HAM DIGITAL COMMUNICATIONS HANDBOOK NEW Cat B-2405 $28 OSCILLATOR CIRCUITS ENCYCLOPEDIA u~w Cat 8-17 42 IIC AMPLIFIER CIRCUITS ENCYCLOPEDIA Cat B-3670 LEARNING ELECTRONICS. Vol 2 Cat B-3672 ENCYCLOPEDIA OF ELECTRONIC CIRCUITS. Vol3 NEW $S495 Cat B-1760 ENCYCLOPEDIA OF ELECTRONIC CIRCUITS. Vol4 NEW NEW $58 95 Cat B-1762 TROUBLE-SHOOTING WITH OSCILLOSCOPES - SCANNING & SHORTWAVE THE DICK SMITH RADIO FREQUENCY HANDBOOK SPECIAL 16mm ROTARY POTS SAVINGS SCANNER FANATICS FREQ. REG. VIC SCANNER FANATICS FREQ. REG. WA Cat B-4106 S2495 $2495 SHORTWAVE LISTENING GUIDE Cat B-2040 PASSPORT TO WORLD BAND RADIO B1387 10 S1ucoN CHIP SAVE $5 CENTRE CLICK 25K DG/Linear Cat R-7810 100K DG/Linear Cat R-7820 . S2995 Priced to Clear! 95 Now Only , ~ · S29 J.~INCHMAR For more sensational savings, grab your copy of Benchmark today. Available at your nearest store. O I OW $2495 SCANNER FANATICS FREQ. REG. OLD Coming Soon! Cat B-4108 NEIN N II, Cat B-4102 Cat B-4104 All this month as a special introductory offer, save $1,00 on these new pots! Hurry prices rise in December, 41-CLICK - ENHANCE YOUR HIFI PROJECTS 50K DG/Log , C t R-7800 100K DG/Log a · Cat R-7802 . • SCANNER FANATICS FREQ. REG. NSW. 1992 Edition NEW $38 95 Cat B-4801 $1495 Cat B-9601 Cat B-2052 95 NEW $26 95 Cat B-1744 LEARNING ELECTRONICS. Vol 1 $26 95 $495 nY ea Now Only $395ea IT'S FINALLY HAPPENED! TRUE TEMPERATURE CONTROLLED SOLDERING AT AN AFFORDABLE PRICE Until now, a temperature controlled soldering station required complex sensitive, switching and control circuitry. But now, using breakthrough ceramic heating technology, Dick Smith Electronics brings you a simple, reliable and incredibly affordable temperature controlled soldering station. See this amazing station today... you'll love it! MINIMAL HEAT WASTAGE SAFETY FEATURES • Maximum heat is delivered in the tip, where you need it. • Cooler handle • Lower operating costs • Iron operates from a safety approved 16V t ransformer • Built-in iro n stand CONSTANT TEMPERATURE ENERGY EFFICIENT • Positive temperature coefficient maintains tip at a constant 310°C • El iminates overheating • .Always ready for use • 6 watt idle and 12 watt full thermal load Onl ..-Lo-NG------. LASTING FINE TIP • Quality iron clad ti p • Reduced wear & corrosion Cat T-1900 S499s REPLACEMENT TIPS AVAILABLE Cat T-1951 • LIGHTWEIGHT AND EASY TO USE • FULL 12 MONTHS WARRANTY B1387 NOVEMBER 1992 11 DIC r QUALITY TOOLS AT AN AFFORDABLE PRICE! SCOPE The Ultimate In Value & Quality PX-1 SOLDERING STATION Th is incredible station is ideal for a wide range of PCB production line, rework and maintenance applications. A three colour bargraph temperature readout, sliding temperature control (200-450 °C) and lightweight hand-piece makes using it a breeze. With the latest in Japanese PTC wngsten/zirconium ceramic element technology, it has a healthy 75W heat up and recovery power; idling at 45W. As well , it has zero swi tching and a low impedance tip grounding. Cat T-1010 5 PIECE SOLDERING KIT Beat this for value! A quality Scope soldering iron (T-1620) complete with resin core solder, iron stand, cleaning sponge and two screwdrivers. Rated at 20W 240V. Cat T-1650 Value Plus! $2995 Fast Heating! A high quality, low voltage transformer in a tough polycarbonate case made for the Scope range of irons. Saves accidental damage to sensitive components and has an electronic shield for extra protecti on . Complete with iron rest. $ Ideal for outdoor service or repair work! This amazing iron heats up in just 3 seconds. What's more, there's up to 150 watts on tap and it comes with a 6 metre lead and battery clips. Current drain is 45A. <~ ~ 100 Watts! 12V 30-150W IRON 7 9 95 Cat T-1692 ;;a ? 3.3V<at>30A TRANSFORMER 10-70 Watt Range! MINISCOPE Cat T-1635 <::::::::: r ~ Cat T-1605 s7495 60 12 $6495 SILICON CHIP :i,J- Lightweight and ideal for general service work and kit building, etc. This iron has a fingertip temperature control and requires 3.3V <at> 20A so it's best used with the scope transformer (T- 1692). Complete with spare ti p and element. SUPERSCOPE Select the temperature and the Superscope delivers it in just six seconds! With a huge 10C Watt Cc!pacity and stainless steel barrel for longer life. Requires 3.3V <at> 30A transformer (Cat T-1692) . Includes spare tip and element. s9495 ,"0" ~ ALL THIS MONTH WITH EITHER THE SCOPE MINISCOPE OR THE SCOPE SUPERSCOPE YOU'LL RECEIVE A SET OF SCOPE PCB FLUSHCUTTERS AT NO EXTRA COST p QUALITY KITS YOU CAN TRUST! No one else g ives you quality, back-up or service like us Here~s vvhy... • Behind The Scenes quality control and research & development. We build and test our own prototypes •Clear Concise Instructions and quality components. We even stock spare parts. •Professional Advice in every store and service centres throughout Australia. Help is never far away. •Added Extras include; Quality Control cards, Kit construction guides and a handy-hint booklet for Mains powered projects. NICAD BATTERY DISCHARGER Q Get the best performance from your NiCads with this stylish battery discharger. With switchable voltage (3.6, 4.8, 7.2, 9.6, 10.8 & 12V) and automatic cut-off. This easy to build kit is ideal for most types of NiCads as used in cam-corders, cordless phones, radio controlled cars, cordless drills and laptop computers, etc. The unit continuously monitors voltage and automatically cutsoff the discharge current once the battery as a whole is fully discharged . As well, there's a switchable current discharge of 50mA and 200mA and a push to start button . This full form kit has all components, hardware, case and a pre-punched (black anodised) screened front panel. Cat K-3126 NEW 0 ETO[[DN= ~ ~.. LOW COST AUDIO SWEEPER ];Hll':~~, ~ :~~~;-:, , ~ a ~,,,.- ~ I~ MIN MAX ORIL c SPEoD coarRDLLER Q · New Improved Design UNIVERSAL MOTOR SPEED CONTROLLER Q 11] This easy to build kit is designed to regulate t he speed on heavy-duty power tools. It's ideal for circular saws, electric drills, lawn edgers, jig-saws, sanders, grinders and other equipment rated at 5 amps, with a 'b rush type' motor. What's more, this improved design has a higher current rating and uses a Triac rectifier instead of a SCR. As well, it monitors t he 'back-EMF' voltage from the motor, so though the drill speed is contro lled, it won't bog down when the going gets tough . Complete with delu xe prepunched black anodised screened front panel, components, PCB and flush mounted mains socket. Cat K-3085 $4695 Here's a useful kit for audiophiles, sound experts, enthusiasts and anyone interested in sound. This affordable audio test system analyses the performance (mid, treble & bass) of speakers, speaker enclosures, filter circuits and room acoustics. It consists of a sweeping audio test signal generator and a metering amplifier which measures the results. It comes complete with a deluxe pre-punched front panel, plastic instrument case, PCB, hardware (including dB meter), components, mic insert and plug pack. s1 09 Cat K-7352 QQ <at>AUG'92 Coming Soon To A Store Near You! VHF/UHF SPECTRUM QQ [zJ ANALYSER Here's a simple yet inexpensive instrument with all the circuitry and controls you need to convert almost any standard oscilloscope or 'CRO' into a sensitive and easy to use spectrum analyser. It covers the three major segments of the VHF / UHF spectrum : 50-105MHz, 138-225MHz and 470B?0MHz. What's more you can even use it as a wideband FM monitoring receiver. A full form kit complete with deluxe case, pre-punched screened front panel, all components and hardware is supplied. ~ Cat K-7620 ~ SEP '92 $ 7 1 rP1e~se contact your nearesttiio~~-,o~availability as some kits may still be in production. I 99 EASY TO BUILD FM RADIO QQ l1J . 1 If you 're new to the world of kit building, then this one's for you! This simple FM radio receives all your favourite FM stations, uses only two low-cost integrated circuits (IC's) and runs off a 9V battery. In fact, you could even experiment and design your own tuner/ amplifier. It's easy to g\J,ild and is a great hands-on way to learn about radio .. frequency (RF) circuits and audio frequency (AF) amplifiers. This short form kit comes with FM radio IC & audio IC, PCB , speaker, components and hardware bits. Cat K-5014 s299s B1387 N O V EMBER 1992 13 I• DIC TEST EQUIPMENT 3.5 DIGIT MULTIMETER QUALITY 3.5 DIGIT MULTIMETER Here's an affordable 14 range digital multimeter for the hobbyist or student. It has a handy battery checker for 1.5 & 9 volt cells, as well as diode test. Comes complete in a safety yellow casing. Ranges: 2V, 20V, 200V, 500V DCV: ACV: 200, 500V DC(mA): 200mA Resistance: 2K, 20K, 200K, 2M Cat Q-1420 Incredibly compact and easy to use! This accurate 19 range multimeter measures DC/ AC voltages, DC current and resistance. It has a diode test, 10Amp (DC) current range and a low frequency output range. With safety yellow casing. Ranges: DCV: 0.2V, 2V, 20V, 200V, 1000V ACV: 200, 750V DC Current: 200uA, 2000uA, 20mA, 200mA Resistance: 200, 2K, 20K, 200K, 2M Cat Q-1422 995 1.25GHz HANDHELD DIGITAL FREQUENCY COUNTER LCD DIGITAL CALLIPERS This incredibly easy io use 10Hz to 1.25GHz frequency counter has an 8-digit LCD display, data hold, relative measurement and data record (min, max & average). There's also selectable resolution, period meas.urement and more. Complete with telescopic antenna and BNC to alligator clip test leads. Cat Q-1322 Ideal for engineers, designers, students and the serious hobbyist. These callipers give an extremely precise measurement of the external and internal diameter of just about anything from 0.01mm to 150mm. With metric/inch conversion, zero setting for measuring deviations, accuracy of 0.03mm and repeatability of 0.01 mm. As well, it has an automatic 'off' function and more! Complete with carry case. Cat Q-1412 Specifications Measuring Range lmpedence Accuracy Range Max Voltage Channel A: 5V P-P Channel B: 250V P-P MAJOR DICK SMITH ELECTRONICS AUTHORISED STOCKISTS: NSW: ARMIDALE: New England Electronics 711655 BALLINA: Ballina Electronics 867022 BATEMAN'S BAY: Baycity Sight & Sound 725030 BATHURST: Electronic Frontiers 323933 BOWRAL: Bowral Electrical Supplies 611861 BROKEN HILL: Hobbies & Electronics 884098 COOTAMUNIJRA: Cootamundra Music & Ute 422561 COFFS HARBOUR: Coifs Harbour Electronics 525684 DENILIOIJIN: Deni Electronics 813672 DUBBO: Chris's Hi Fi 828711 FORSTER: Forster Village Electronics 545006 GOULBOURN: Tunlive 221288 GRAFTON: Repairs &Spares 421911 GRIFFITH : Miatronics 624534 INVERELL: lnverell Electronics 221821 KEMPSEY: P&L Leonard 631134 LEETON: Leeton Audiotronic 532800 LIGHTNING RIDGE: Lightning Ridge Solar Power 29 1013 LITHGOW: Douroy Photographies 513173 LISMORE: Deere Electronic Services 214137 MOREE: Moree Electronics 522091 MUDGEE: Headware 723895 MURWILLUMBAH: Strings & Things 723684 NARRABRI: Namoi Computer Service 923274 NELSON BAY: Nelson Bay Elect & Hobbies 813685 NOWRA: Nowra Electronics 210722 PARKES: Strad MusicCtr623366PORT MACQUARIE: Hastings Computer Service 840255 RICHMOND: Silicon Crafts 784101 TAREE: Manning Electronics 512233 ULLADULLA: Coastal Electronics553989 WAGGA WAGGA: Phillips Electronics 216558 WALGm: Wal!jt!tl Electronic Centre 281116 WELLINGTON: Wellington Service 452325 WINDSOR: Hawkesbury Electronics 776722 VASS: Warmington Electrical 261116 YOUNG: Keith Donges Electronics 821279 VIC: ARARAT: Jerram Electronics 522345 BAIRNSDALE: LH & LM Crawford 525677 BENALLA: North East Electronics 622710 CASTLEMAINE: Inspect Electrics 723773 CDLAC: Colac Electronics 312847 ECHUCA: Gilmour Electronics 822956 MILDURA: Pullman Auto Pro 232882 MORWELL: Roylaine Ply Ltd 339458 SHEPPARTON: Andrew Guyatt Electronics 219497 SWAN HILL: Nyah District TV Service 329303 ST. ARNAUD St Arnaud Appliances 951069 WARRAGUL: Roylaine 234255 WARRNAMBOOL: Komit St Elec Services 627417 WONTHAGGI: South Gippsland Photo Service 721411 OU): AYR: Delta Electrix 831566 BLACKWATER: Cool Tronics 825827 BOWEN: Delpro Agencies 86 ~77 BLNDABERG: Bob Elkin Electronics 521785 CALOUNDRA: Electr(rfTlart 918533 DALBY: Hobby & Electronics 625770 DYSART: Dysart Videotronixs 582107 GLADSTONE: Electronic Enterprises 726660 INGHAM: Masons Electronics 763188 INNISFAIL: lnnisfail Hi-fi 612014 KINGAROY: MD & MM Siegle 624535 LONGREACH: Longreach Sound & Communications 583307 MACKAY: Stevens Electronics 511723 MARYBOROUGH: Keller Electronics 214559 MT ISA: Outback Electronics 433331 NAMBOUR: Nambour Electronics 411966 PIALBA: Keller Electronics 283749 STANTHORPE Granite Belt Communications 813333 TAS: BLRNIE: Electronic City 314760 DEVONPORT: Al Electronics 248322 SA: MT GAMBIER: Hutchesson's 0 ~= ~f54n:1, ~ioLW~~:i:~1h!o"~~ut~t~~~Jrio~~~~~~A~~2~YGJi:bfriFi Batavia Lighting & Electrical 211278 KALGOORLIE: Today's Electronics 215212 KARRATHA: Pllbara Office Supplies 854836 MANDURAH: Mandurah Hi Fi 5812206 PORT HEDLAND: Ivan Tomek Electronics 732531 B1387 14 SILICON CHIP $199 10Hz to 1.25 GHz 1M OHM +/- (1PPm +1d) Channel A: 500MHz/1250MHz Channel B: 10MHz (10Hz to 10MHz) Typical Sensitivity Channel A: 10-1000 MHz (3-50mV RMS) = 1-1.25GHz r10 -150mV RMS) Channel B: 10Hz-1MHz (15mV RMS) 1MHz-5MHz (20mV) 5MHz-10MHz (40mV) Dual trace, dual trigger 20 MHzCRO An affordable 20MHz oscilloscope suitable for a wide range of applications . It's a dual trace, dual trigger CAO with a fully adjustable sweep time (in 20 steps), variable hold-off, fully adjustable sensitivity, switch selectable X-Y operation, selectable trigger modes, AC/TV H/TV V trigger coupling, front-panel variable trace rotation and a sweep rate from 10nS/DIV to 1S/DIV. Specifications Vertical Sensitivity: 5 mV/ div to 5 V/div (x1 mode) 1 mV/div to 1 V/div (x5 mode) 1-2-5 sequence, 10 step attenuator. Sweep Speed: 0.1 uS/Div to 0.2 S/Div in 1-2-5 sequence, 20 steps Sweep Magnification: Rise Time: l~~roximately 17.5ns Operating Modes: Ch 1, Ch2, Alt, Chop, Add Trigger Coupling: AC, TV-H, TV-V Trigger Sensitivity Internal: 0.5 division (1 division with TV coupling) External: 500mV Trigger Source: Ch1, Ch2, Alt, Ext, line. Cat 0-1802 $699 SHORTWAVE This Month's Top Value EXCELLENCE POWER SUPPLIES frof11 SANC:i&AN & ACCESSORIES MULTI VOLTAGE CONVERTER Here's a smart alternative to batteries. This converter is ideal for battery operated toys, mini-TV's ... even shortwave radios. With six voltage selections (3, 4.5, 6, 7.5, 9, 12V DC<at> 500mA), a multi-way ouput adaptor and selectable polarity. The Go-Anywhere Receiver 10 BAND PORTABLE SHORTWAVE RECEIVER s259s Cat M-9627 Ideal for trucks! s799s 24/ 12V VOLTAGE CONVERTER The Sangean SG-789 is an incredibly compact receiver with the power to pull in broadcasts from around the world! Listen to local AM and FM stations (FM stereo with optional headphones) as well as 8 popular international shortwave bands. With bandspread tuning and an LED tuning indicator. finding the station you want quickly and accurately is easy. The SG-789 combines all this with excellent sound reproduction, a solidly built chassis, headphone and AC adaptor sockets and a soft carry case. Save $10 on this handy converter. It's ideal for CB's and stereo systems, etc in trucks and vehicles with a 24 volt system. Provides 13.BV<at> 2 amps DC continuously (BA surge rating) from a 24 volt supply. Complete with mounting hardware. Cat M-9810 Now Only s5995 Cat D-2834 12-240V INVERTER With Cassette Player! Save a massive $100 on this quality inverter! It produces 240 volts from a 12V supply and is ideal for caravans, boats, mobile workshops and even as part of a solar power system . Quality features include a low battery indicator, overload indicator and protection, power indicator, electronic/ temperature shutdown , low/high battery shutdown, 2 mains sockets and circuit breaker. ALL-BAND WORLD RECEIVER DC Input Voltage: 10.5 -14.5 (12V nominal) AC Output Voltage: 240V RMS Output Frequency: 50Hz (+/-1%) Output Power: 1500W (surge), 600W (20 minutes), 325W continuous Take your ears overseas with the stunning Sangean ATS-818CS. This fantastic receiver covers Longwave and continuous shortwave frequencies from 1.62 to 30MHz and local AM/FM stations (FM stereo with optional headphones). What's more, with a BFO (beat frequency oscillator) it receives many HF SSB transmissions including marine, aircraft, amateur and commercial broadcasts. An inbuilt tape deck with timer allows you to record broadcasts, even when you're asleep. As well, it has five-way tuning, 45 station memories, full function digital display, dual time and alarm clock. With a dual conversion receiver design it otters switchable filters and an adjustable RF gain control for optimum reception. It's brilliant! Cat D-2842 Also Available: ATS 818 (no cassette recorder) Cat 0 -2828 s349 0 ~~~i;J_~~0~ a::w Only $ 3 99 A Great Gift Idea CORD WINDER Cord Winder is neat, tidy and incredibly useful! It has a 11.5m cable with two power outlets and includes an inbuilt 10A circuit breaker. Cat M-7092 s249s DS XPRESS PHONE & MAIL ORDER SERVICE HOTLINE Outside Sydney (Free call) 008 22 6610 Sydney & Enquiries (02) 888 2105 Or write to DS XPRESS, PO BOX 321 N/RYDE 2113 FAX (02) 8051986 STORE LOCATIONS: NSW • Albury _21 8399 • Bankstown Square 707 4888 • Blacktown 671 7722 • Brookvale 905 0441 • Bondi 3871444 • Campbelltown 27 2199 • Chatswood Chase 4111955 • Chullora 842 8922• Gore Hill 439 5311 • Gosford 25 0235 • Hornsby477 6633• Hurstville580 8622• Kotara56 2092• Liverpool600 9886• Maitland 33 7866• Miranda525 2722• Newcastle611896 • North Ryde 878 3855 • Orange 618 400 • Parramatta 689 2188 • Penrith 32 3400 • Railway Square 211 3777 • Sydney City 267 9111 • Tamworth 661711 • Wollongong 28 3800 ACT • Belconnen(06) 2531785• Fyshwick 280 4944 VIC• Ballarat31 5433• Bendigo43 0388• Box Hill 8900699• Coburg383 4455• Dandenong 794 9377• East Brighton 592 2388 • Essendon 379 7444 • Footscray 889 2055 • Frankston 783 9144 • Geelong 232 711 • Melbourne City 399 Elizabeth St 326 6088 & 246 Bourke St 639 0396 • Richmond 4261614 • Ringwood 879 5338 • Springvale 547 0522 QLD • Booval 262 6200 • Brisbane City 229 9377 • Buranda 391 6233 • Cairns 311 515 • Capalaba 245 2670 • Chermside 359 6255 • Rockhampton 27 9644 • Sou1hport 32 9033 • Toowoomba 38 4300 • Townsville 72 5722 • Underwood 341 0844 •SA• Adelaide City 2321200 • Beverley 3471900 • Elizabeth 255 6099 • Enfield 260 6088 • St. Marys 277 8977 WA• Cannington 451 8666 • Fremantle 335 9733 • Perth City 481 3261 • Midland 250 1460 • Northbridge 328 6944 TAS • Hobart 31 0800 • Launceston 344 555 NT• Stuart Park 811977 STORES ACROSS AUSTRALIA AND NEW ZEALAND 81387 . NOVEMBER 1992 15 Tune your favourite stations with this low-cost _IQ RECEIVER FM If you're new to the world of electronics, then here's a great project to get you started. This simple radio tunes in all your favourite FM stations, uses only two low-cost ICs & runs off a 9V battery. By DARREN YATES Many moons ago, if you were about to get stuck into your first electronics project, the odds were that you'd start with an AM radio. There were several reasons for this. First, AM radios in the 50s and 60s were relatively expensive and you could save lots of money by building one for yourself. Often, the parts could be scrounged from the junkbox and from derelict receivers and this added to the sense of achievement when the project was completed. Building an AM radio was also a lot of fun and it was educational. The constructor could learn all about radio frequency (RF) circuits and audio amplifiers, and could carry out any r.f. input 18 17 15 ,. 13 12 11 10 1,4V TDA7000 2,2k0 Vp 1+4,SVI • 7286939 . 1 a.f. output 16 2,2k0 SILICON CHIP repairs if the set later required servicing. During the last 20 years, AM radios have become progressively easier to build with the development of-specialised ICs. One such chip is the ZN414 AM radio IC. This device is a complete tuned radio frequency (TRF) receiver in a tiny 3-pin transistor style case and it only requires a 1.5V cell to power it. It gives quite useful results and many a "matchbox radio" has been built using this device. By contrast, FM receivers were always somewhat more complicated to build, although that situation has also changed during the last decade. In particular, the Philips TDA7000 FM radio IC is virtually a complete FM radio on a single chip. All that's required is the addition of an audio amplifier stage and a few external components to produce a working FM receiver. Apart from the TDA7000 FM radio chip, the design presented here uses just one other IC to give an economical 2-chip design. This second device is an LM386 audio amplifier IC. So most of the circuit functions are taken care of by the two ICs. But why build your own when you can buy a personal FM stereo radio for less than $20? The answer is to have fun and to learn about electronics. Provided you can solder and follow a simple wiring diagram, you Fig.1 (left): block diagram of the Philips TDA7000 FM radio circuit. This device is virtually a complete FM tuner on a single chip. All that's required to make a working receiver are a few external parts plus an audio amplifier stage. PARTS LIST 1 PC board, code SC06111921, 129 x 85mm 2 SPOT toggle switches (S1, S2} 1 100k.Q log potentiometer (VR1} 1 knob to suit potentiometer 1 57mm 8.Q loudspeaker 1 F29 ferrite slug 1 5mm coil former (Altronics Cat. L-5210; Jaycar Cat. LF1224; DSE Cat. L 1010) 4 3 x 25mm-long tapped spacers 4 screw-on rubber feet 1 9V battery 1 battery snap connector 1 60-160pF tuning capacitor Semiconductors 1 TDA7000 FM receiver (IC1} 1 LM386 audio amplifier (IC2} All the parts for the FM Receiver are mounted on a small PC board & this can be installed in a plastic project case. The antenna consists of a 75cm length of light-duty hook-up wire. should have little difficulty building up the design presented here. Admittedly, our design is mono only but then most of the low-cost commercial units can only drive headphones. This unit can drive a small loudspeaker to quite useful volume levels and it can produce good quality sound from all local FM stations from 88-108MHz. Why not tackle it as your first project? Block diagram FM signals are more difficult to decode than AM signals because of the way the information is transmitted. In AM radio, the audio signal is encoded by modulating the amplitude of a fixed-frequency carrier signal. After transmission, this audio signal can be quite easily recovered from the tuned carrier using a simple diode detector. With FM, however, the carrier amplitude is kept constant and it is the frequency of the carrier that is varie.d to encode the audio frequency signal. The method of detection (or demodulation) in this case is much more complicated but, fortunately, this function is taken care of by the TDA7000 IC. Fig.1 shows the various circuit blocks inside the TDA7000, as well as the external parts required to make a complete FM tuner. It is easy to get going since only the local oscillator (VCO) requires adjustment during alignment. All the other components, with the exception of the tuning capacitor (Cvl, are fixed . The TDA7000 IC functions pretty Capacitors 1 470µF 16VW electrolytic 1 220µF 16VW electrolytic 1 100µF 16VW electrolytic 2 10µF 16VW electrolytic 1 0.15µF MKT polyester 1 0.1 µF MKT polyester 2 0.1 µF ceramic 1 .01 µF MKT polyester 2 .0033µF MKT polyester 1 .0027µF MKT polyester 1 .0022µF MKT polyester 2 330pF ceramic 1 220pF ceramic 1 180pF ceramic 1 150pF ceramic 1 56pF ceramic 1 47pF ceramic 1 39pF ceramic 1 33pF ceramic Resistors (0.25W, 1%} 1 18k.Q 1 10k.Q 1 4.7.Q Miscellaneous 30cm of 0.63mm diameter ECW, 75cm of light-duty hook-up wire for antenna. much as a conventional superheterodyne tuner. This means that the incoming signal is mixed with a local· oscillator signal to produce an intermediate frequency (IF). This IF is then filtered to remove any mixer artefacts and, finally, demodulated to produce the desired audio signal. There's just one deviation from norN ovEMBER 1992 17 ONO ANTENNA MUTE S2 POWER S1 4.70 OFF .01 10k 220 + .0033 0.15 220pF 4 0.1 330pF 18 17 16VW+ 150pF 15 OFF ON <>-'---0+6-9V 12 10 13 * 39pF * 47pF 14 10 16VW + - 180pF B IC1 TOA 7000 5 8 .,. VC1 2-&0pF .,. 33pF L1 .,. 56pF 100 + 16VW+ 0.1 + .,. 16 FM RADIO Fig.2: the circuit uses just two ICs - the TDA7000 FM radio chip & an LM386 audio amplifier. Variable capacitor VC1 tunes IC1 across the FM broadcast band (88-108MHz), while L2 & its associated capacitors form a bandpass filter at the antenna input to eliminate interference from signals outside the tuning range. mal practice. The majority of FM receivers use an IF of 10. 7MHz whereas the TDA7000 uses a very low IF of 70kHz. The advantage of such a low IF is that it can be filtered with standard active op amp circuits instead of coils or ceramic filters. Normally though, a low IF results in really bad distortion when used with wideband deviation FM; eg, the normal broadcast band FM which has a maximum deviation of ±75kHz. However, the TDA7000 successfully manages to demodulate wideband deviation (±75kHz) FM while only having a 70kHz IF. What happens is that the recovered audio is used to modulate the local oscillator so that the received FM deviation is always less than ±15kHz. In effect, the recovered audio signal is compressed to internal mixer (on pins 13 & 14) via a bandpass filter. This bandpass filter consists of inductor L2 and the 39pF & 47pF NPO capacitors. Its job is to filter signals that lie outside the desired tuning range and thus eliminate interference. Tuning capacitor VCl and inductor Ll ensure that the voltage controlled oscillator (VCO) tunes across the FM broadcast band. Inductor Ll carries a ferrite slug and this is adjusted during the alignment procedure so that VCl covers the desired frequency range (88-108MHz). Pin 1 of !Cl is the mute control line. Pulling this line high via a 10kQ resistor disables the muting functions and allows weaker stations to be tuned if desired. Switch S2 is used to switch the muting function in or out of action. When S2 is set to ON, the circuit mutes the background hiss that otherwise occurs when tuning between stations. The recovered audio signal appears reduce its dynamic range. Although this isn't desirable in a hifi FM receiver, the results are still very good and this technique considerably simplifies the circuitry required. In fact , the distortion is typically less than 2.3% at ±75kHz deviatio:n, so your favourite FM station will still come in loud and clear. Circuit diagram Now take a look at Fig.2. This shows the complete circuit diagram for our simple FM radio receiver. At the centre of the circuit is the TDA7000 FM radio IC (ICl) and this drives the LM386 audio amplifier (IC2) via volume control VRl. Let's take a quick run through the various circuit functions. The RF signal is picked up by the antenna and fed to the TDA7000 's TABLE 1: RESISTOR COLOUR CODES u Q 0 0 18 ,:•:} 470 18k No. 1 1 SILICON CHTI' Value 18kQ 10kQ 4.7Q 4-Band Code (1%) 5-Band Code (1%) brown grey orange brown brown grey black red brown brown black black red brown yellow violet black si lver brown brown black orange brown yellow violet gold brown 8 This close-up view clearly shows the construction of coil Lt. The F29 ferrite slug at the top of the former is adjusted during the alignment procedure so that the receiver tunes the required frequency range. on pin 2 and is fed to volume control VR1 via a low-pass filter consisting of an 18kQ resistor and a .0039µF capacitor. This filter stage, in conjunction with VRt , provides the necessary 50µs de-emphasis for the recovered audio signal. From there, the signal passes to the LM386 audio amplifier stage (IC2). IC2 operates with ap. AC gain of 200 by virtue of the 10µF feedback capacitor connected between pins 8 and 1. The amplified output appears on pin 5 and is coupled to a miniature 8Q · loudspeaker via a 4 70µF capacitor. Power for the circuit is derived from a 9V battery and is switched on and off using Sl. The supply rail is de~ TABLE 2: CAPACITOR CODES 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Value 0.15µF 0.1µF .01µF .0033µF .0027µF .0022µF 330pF 220pF 180pF 150pF 56pF 47pF 39pF 33pF IEC Code 150n 100n 10n 3n3 2n7 2n2 330p 220p 180p 150p 56p 47p 39p 33p EIA Code 154 104 103 332 272 222 331 221 181 151 56 47 39 33 coupled using a 220µF capacitor and a 4. 7Q resistor. Construction *MOUNTED ON COPPER SIDE Fig.3: install the parts on the PC board as shown in this wiring diagram. The wiring shown dotted is installed on the copper side of the board. All of the components for the FM Radio, including the battery and loudspeaker, are fitted to a small PC board coded SC06111921. Before starting construction, check the board carefully to ensure that it has been correctly etched. Correct any faults that you do find immediately (in most cases, there will be none). Now check that the mounting holes for coil former Ll, potentiometer VRl, tuning capacitor VC1 and the two switches (Sl & S2) are large enough to accept these parts. Enlarge the holes if necessary using a small drill. Fig.3 shows the parts layout on the PC board. Install the wire link first, then solder the resistors into place. Table 1 shows the colour codes for the resistors but you should double-check them with your digital multimeter. When you've completed that job, solder in the ceramic and MKT polyester capacitors. Table 2 shows the capacitor codes and their equivalent values. Check the value of each capacitor carefully before installing it on the board. If you get them mixed up, the tuned circuits in the front end of the receiver could be thrown off frequency and the project wont work. Note particularly that one of the 0. lµF ceramic capacitors is installed on the copper side of the board, directly beneath ICl. Keep all capacitor leads as short as possible. At this stage, the two ICs can be installed. These should be soldered directly to the PC board. Take care with the polarity of each device and make sure that you don't overheat them when soldering their pins. Pin 1 of each device is adjacent to a small notch or dot in one end of the plastic body. Tuning capacitor VC1 is installed from the component side of the board, L2 L1 Fig.4: coil Lt consists of 2½ turns of 0.63mm enamelled copper wire on a 5mm former, while L2 is made by winding 6 turns of 0.63mm enamelled copper wire on a 6mm drill bit. NovEMBER 1992 19 The pen in this photograph points to the O.tµF ceramic capacitor that's mounted directly beneath ICt on the copper side of the PC board. Note also the wire link that's used to connect VR1 's metal case to ground. coil off the drill bit and push it all the way down onto the board before soldering its leads (don't forget to scrape away the enamel from the leads first). The volume control (VRl) is installed from the copper side of the PC board. Before doing this, solder three short tinned copper wire leads to its pads (ie, install these leads on the copper side of the board). The volume control can then be mounted in position and the three wire leads soldered to its terminals. VRl 's metal case should now be earthed by connecting it via a short wire link to the adjacent groundplane on the PC board (see photo). This is done to prevent hum pickup from breaking through into the audio path. Note that it may be necessary to scrape away some of the oxide on VRl's case to ensure a good solder joint. The leads shown dotted in Fig. 3 are run on the underside of the PC board. Use light-duty hook-up wire for the loudspeaker and switch leads and be sure to wire the battery snap connector so that the supply polarity is correct. The antenna lead consists of a 75cm length of light-duty hook-up wire which is soldered directly to the PC board. Once the wir~ng is completed, secure the loudspeaker to the top of the board using a suitable adhesive. The battery can be secured using a clamp, double-sided sticky tape, or even a large rubber band. Finally, fit four 25mm-long tapped spacers to the four corner positions of the board. These spacers are then fitted with screw-on rubber feet to prevent scratches to the resting surface. Test & alignment The two toggle switches (S1 & S2) are installed from the copper side of the PC board, as is the volume control pot (VR1). The four standoffs at the corners of the board should be fitted with rubber feet. with its central shaft protruding through to the copper side. Secure it using the two small screws supplied, then mount the two toggle switches in position. The next step is to wind the two inductors. 11 is simply 2½ turns of 0.63mm-diameter enamelled copper wire (ECW) wound on a 5mm former with an F29 ferrite slug - see Fig.4. Note that each end of the coil should finish on opposite sides of the former. Strip the enamel from the ends of 20 SILICON CHIP the leads before soldering the coil to the board and use a small dab of adhesive to hold the former in position. Don't just rely on the coil to secure the former. If the former (and thus the ferrite slug) moves about, it will alter the tuning. The ferrite slug should initially be screwed about half-way into the top of the former. Inductor 12 is made by winding six turns of 0.63mm diameter ECW onto a 6mm drill bit or something similar. Wind on the six turns, then slide the To test the unit, wind the volume up to about half way, set the MUTE switch to "off", and switch on. You should immediately hear noise from the loudspeaker (if not, try setting the MUTE switch to its other position). Now flick the MUTE switch to "on"; the noise level should drop appreciably, although you should still be able to hear some hiss if you put your ear close to the loudspeaker. Now try tuning in some stations. If you're in a normal house environment and within about 40 or 50km from some reasonably strong stations, you should be able to pick them up. Sweep through the entire frequency range with the tuning capacitor and ANTRIM TOROIDAL TRANSFORMERS • • • • Now made in Australia Standard range 15VA to 2kVA Large ex-stock quantities available Competitive pricing available for OEMs & resellers • Simply the best transformers all round HARBUCH ELECTRONICS PTY LTD 90 George St, Hornsby, NSW 2077. Phone (02) 476 5854 Fax (02) 476 3231 Fig.5: check your PC board carefully against this full-size etching pattern before installing any of the parts. keep a record of the radio stations you hear. Make sure you have the MUTE switch turned off. If there are some stations that you can't pick up at one end of the band and the tuning capacitor has run out of travel,adjust the slug in coil 11 by winding it out of the former a couple of turns. This should shift the stations further tov\;ards the centre of the tuning capacitor. If, after repeated adjustments, you still don 't have enough range, try adjusting the two small screws on the back of the tuning capacitor. To do this, tune in a station and then, using an insulated screwdriver, slowly turn one of the screws to shift the station position (note: only one of screws will have any effect). Make only small adjustments at any one time before re-checking the frequency range. If you move the station the wrong way, rotate the adjustment screw in the other direction. By the way, it's important to use an insulated screwdriver for this job. If you don't, the ?,dditional capacitance provided by your hand will detune the front end of the receiver and it will be difficult to judge the effect of any adjustments. In normal use, you should find that an alkaline battery lasts about 40 hours , depending on the setting of the volume control (VR1). If you strike problems at any stage, switch off immediately and check the board for wiring errors. SC Protect your valuable issues Silicon Chip Binders These beautifully-made binders will protect your copies of SILICON CHIP. * * Each binder holds up to 14 issues * SILICON CHIP logo printed in gold-coloured lettering on spine & cover Heavy board covers with 2-tone green vinyl covering Price: $A11.95 plus $3 p&p each (NZ $6 p&p) . Just fill in & mail the order form on page 101; or fax (02) 979 6503; or ring(02) 979 5644 & quote your credit card number. NovEMBEH 1992 21 Modifications to the drill speed controller The Drill Speed Controller featured in September 1992 requires a couple of modifications in order to work reliably with all motors. These changes are incorporated on a new PC board. F1 10A A-r--0-...0----4>-------------, A2 TRIAC 1 BTA41-600 A1 GPO 240V AC D1 1N400 4 FRONT PANEL r 2 0 r1 . ~, VIEW ED FR OM BELOW A2 SPEED CONTROLLER Fig.1 : the amended circuit provides a longer gate trigger pulse to the Triac than before, to ensure reliable triggering. Two problems have arisen with the design of the Drill Speed Controller featured in the September 1992 issue of SILICON CHIP. The first is the occurrence of flash over between one of the lugs on the 2AG fuseholder and the earthed tab of the Triac when heavy duty appliances are being controlled. This has necessitated a change in the position of the fuseholder. The second problem is the occasional failure to operate on some universal motors when settings near maximum speed are used. In these cases, it appears that the inductance of the motor is such that the current through the Triac does not rise above the holding current before the end of the gate trigger pulse. If the load current does not rise above the holding current, the Triac will not maintain conduction after the trigger pulse ends. The solution is to increase the duration of the gate trigger pulse. This has meant increasing the gate trigger capacitor from .04 7µF to O. lµF and adding a 100Q resistor in series with the gate of the Triac. The amended circuit is shown in Fig, 1. Amended PC board ~ ~ ------E S8S1 - - - - - ~ II I ~- ' G Q ~ . -[JL}-ill<at>- 1• 'c§=EG I O I I TRIAC1 VR2 01 A2 A1 I I I ~.-,~ N '\ - Fig.2: the new circuit board includes the additional 100Q resistor & can accept both 2AG & 3AG fuses. The fuse has also been moved to prevent a possible flashover problem. 22 S 1LICUN C IIII' GPO The new PC board, code SC10109922, is shown on page 100. Fig.2 shows the revised wiring diagram. If you want to incorporate the necessary changes on an origin al PC board, as featured in the September 1992 issue, we suggest that the 100Q resistor be installed by first lifting the Tl leg of the SBS. The resistor can then be soldered between this lead and the pad vacated by the SBS lead. Note that this will change the position of.the lkQ gate resistor but this is immaterial. The fuse should be taken off the board and an in-line fuseho lder substituted. As noted in the original article, this circuit is suitable for universal motors with nameplate ratings up to 5 amps. Do not use it with higher rated motors. SC A unique family of full function pocket-sized digital multimeters. Large LCD Digits Large digits for easy viewing. The 0.7" high numerals allow you to easily read your measurement values from a distance. Safety Tester The Safety Tester™ on Model DMlOXL safely detects and displays the presence of particular AC or DC voltage (positive or . negative) levels through a series of LEDs. This unique feature does not use the meter's internal battery so you can always detect live voltage levels if your DMM battery is dead. Safety Test Leads Now you can safely make measurements in those dense component areas without causing shortS with long exposed test lead tips. Insulation on the probes allows only 3 1/2 mm of metal exposure at the tips, (insulation is removable, if desired). Plus, the test lead plugs are shrouded with plastic to eliminate the pos~ibility of shock. r-- -.----- ---- Fused 1 OA Current Jack Designed into the Models DMlOXL and DM15XL is another innovative feature to protect you and your meter. Fusing the lOA jack is an industry recognized safety feature which, before now, was only found in more expensive DMMs. Now a low-cost meter brings you protection from meter damage and personal injury. 1 I • ST LUCIA ELECTRONICS ·M~u: _____________ I _________ P'code: _____ I - - - - - - - - - - - - - -- - -- - - - - - - - - - - - 1 0 Bankcard 24 Campbell St. Bowen Hills Q 4006. Tel: (07). 252 7466 Fax (07) 252 2862. I I I I jI ECONOMIC ELECTRONICS: 22 Campbell St. Bowen Hills Q 4006. P.O. Box 481, Fortitude Valley 4006. Tel: /07) 252 3762. Fax /07) 252 5778. SOUTHPORT ELECTRONIC SHOP: Shop 1, 10 Welch St. Southport Q 4215. Tel: /075) 32 3632. Fax: /075) 51 0543. ACN 010 378 588. anywhere in Australia in an overnight I.Post satchel. $7.90 I Name: _______________ I 0 Visa Card O Mastercard I I I 11 I II 11 I II I ISigned___ ___ _ _ Exp. Date___ I I A 2kW 24V/240VAC sinewave inverter; Pt.2 This month, we present the DC to DC converter circuitry of our 2kW sinewave inverter. This circuit steps up from 24V DC to 365V DC & uses Mosfets to drive a high-frequency transformer. By JOHN CLARKE Converting 24V DC to 365V DC at a power level of more th an ZkW is n o simple task. If the step-up transformer is to be kept reasonably small an d light in w eight, it must run at qu ite a high frequ ency an d this presents considerable problems in making sure that the Mosfets are switched cleanly. Special measures are required. to ensure that interaction between the con- trol an d switching circuitry is kept to an absolute minimum. Befo re we dive into the full circuit description, let's have a look at a basic converter circuit so that we can get a picture of what h appens. Fig.5 shows the sch ematic of a basic converter. It uses a centre-tapped step-up transfo rmer which is driven by two Mosfets . The secondary winding of the transformer is fed to a bridge rectifier and a capacitor (Cl) to develop the DC output. The Mosfets are driven by a pulse width modulator which has feedback applied from the DC output via a voltage divider consisting of Rl and RZ. This feedback acts to reduce the width of the pulses from the pulse width modulator if the voltage starts to rise. Similarly, if the voltage starts to drop , the width of the pulses is increased. Push-pull drive Note that the centre-tap of the transformer's primary winding is connected to +24V DC, while the two legs of the primary winding are each connected to a Mosfet. The pulse width modula- tor drives the gates of the Mosfets with a complementary square w ave signal so that when Mosfet Ql is on, Q2 is off and when Ql is off, Q2 is on. Now consider what happens when Ql is on and Q2 is off. With Ql on, the full 24V DC is applied to the top half of the transformer primary winding; ie, Ql 's drain is virtually at zero volts. At the very instant that current starts to flow in the top half of the transformer winding, transformer action operates so that 24V appears across the other half of the transformer primary winding. This means that when Ql is on, the drain of QZ will have +48V applied to it. Similarly, when Q2 turns on and Ql turns off, QZ 's drain will be at OV and Ql 's drain will be at +48V. So if you can imagine a complementary square wave applied to the Mosfet gates, then the primary of the transformer will have a square wave of 48V peak-to-peak applied to it, or 24V RMS. This is stepped up by the transformer so that the secondary voltage will be 24V multiplied by the turns ratio - in this case, 18:1. The secondary voltage therefore will be a square wave of 864V peak-to-peak or 432V RMS. This AC waveform is rectified by the bridge rectifier and filtered by capacitor Cl to give 432V DC. Note that, RE CTIFIER PULSE WIDTH MODULATOR Q2 + o--------' 24V '------------+--0- Fig.5: this block diagram shows the basic converter circuit. It uses a pulse width modulator to drive complementary Mosfet stages & these in turn drive a centretapped step-up transformer. The transformer output is then fed to a bridge rectifier & to capacitor Cl to produce 365V DC. for the purposes of th is description , we have neglected any losses which occur in the Mosfets, the transformer, the rectifier or filter capacitor. If you now look closely at Fig.5, you will notice that its output is shown as 365V. Why does this differ from the figure of 432V just mentioned? Well, remember the fe edback referred to earlier? It controls the width of the pulses applied to the Mosfet gates . So the Mosfets don 't actually have a full square wave app lied to them. Instead, the pulses fed to the gates have a duty cycle that's less th an 50% (ie, they're on for less th an 50% of th e time). This means that the circuit has plenty of margin so that it can maintain the output at 365V, regardless of variations in the load an d input voltage. The full circuit Fig.6 shows the full circuit details. It uses 24 transistors, 23 ICs , 13 di- Below: this close-up view shows the DC to DC converter board, with part of the high-frequency transformer visible in the foreground. The 12 Mosfet transistors are bolted to the chassis on either side of the PC board. NOVEMBE R 1992 25 :;; n:i: z n 0 r=: CFJ N Cl PO~R L....o--:"'1 0 T OF~Ao MOTOR START 4.7k f uoo 151 IN2 1r-e 3 1l•IN1 116 ~a ; .001! +IN2 E1 1g 10k 10k f f 150k +15V ,.. f T 101 .Ii:' 35VWJ f 101 ..:- IOUT 35VWl 01t .,. E21101 I 5 112 vcc _t;_T IC1 TL494 111 C2 - T +15V ~w V#t +24V DC-DC CONVERTER j 27k : 41DEAD TIME RT ' 141VAEF 13 ~ E'...:___:JC! VIEWED FROM' BELOW• r-'\ -e- * • ♦ + r-11 ' f .,. 10 25VW ,_ 47k ; ♦ t I o.1 I T A POWER • LED1 • 18 UNDER VOLTAGE DETECT 21 Cl - IN1 . .,. 10k ~ L1 100uH 1A ...L. ~SQ5-Q16 S !:I:- 24V : F1 100A 125V -0--.0-- I +24V SWITCHED 47k .,. 385V ,- •OUTPUTI: 01I ADJUST VR1 .,. 100k -.,. V-, I CHASSIS 400VD1 0.1· IC5 IL300 i.73 4.7M (1J~37) ~ 10k 0.5W T .......,.___. D3-D6 4xMUR1560 I 561/ .0011 •12k ZD6 ( j + l 15V 1W ·0.1 r n n ~~- -----------~~----~ --- ------~ r,-----,-~) ~-- +GND ., +15V ., 680 400VW, , _ OV F4 15AI +365V OUTPUT CONTROL VCC 13 OSCILLATOR Q t--,:J-+-t FLIPFLOP CK Q~ ~ - t D RT .,. 11 10 .,. 12 VCC .,. UV LOCKOUT ERROR AMP 1 REFERENCE REGULATOR o--+--J 16 FEEDBACK PWM COMPARATOR INPUT ERROR AMP 2 15 14 REF OUTPUT Fig. 7: this block diagram shows the internal circuitry of the TL494 PWM controller. It includes a sawtooth oscillator, two error amplifiers, a PWM comparator, a dead-time control comparator & a 5V reference. Emitter followers Ql & Q2 provide the complementary output signals at pins 9 & 10. odes and 14 zener diodes. There are also several inductors and transformers, plus numerous capacitors and resistors. Many of the components are specially selected for this application, while others are relatively common. At the heart of the DC-DC converter is a dedicated switchmode integrated circuit, a TL494 from Texas Instruments. It contains all the necessary circuitry to generate complementary square wave pulses at pins 9 & 10, to drive the gates of the switching Mosfets. Facilities for output voltage regulation and under voltage dropout are provided. The TL494 is equivalen l Lu Lhe "pulse width modulator" shown in the basic circuit ofFig.5. Paralleled Mosfets While the simple circuit of Fig.5 Fig.6 (left): the full circuit for the DCDC converter. ICl is the pulse width modulation controller. It generates complementary square wave outputs at pins 9 & 10 and these drive the Mosfet switching devices (Q5-Q10 on one side & Q11-Q16 on the other) via buffer stages IC2a-IC2f & transistors Q1-Q4. IC4, IC5 & IC3 provide voltage feedback to control the pulse width modulator. shows just two Mosfets driving the step-up circuit, the real circuit uses 12 Mosfets (six per side). These drive paralleled windings of one turn on the transformer, in order to carry the very large currents required (in excess of 100A at full load). Just how you make a 1-turn winding which carries these huge currents is a story in itself and we'll give those details in a future issue. On the secondary side of the transformer, four bifilar windings drive a bridge rectifier made up of soft recovery diodes D3-D6. The output from this bridge rectifier then charges a 680µF 400VW electrolytic capacitor via a lO0µH toroidal inductor. This inductor is there to reduce the peak charging currents through the diodes in the bridge rectifier. The voltage feedback system runs along the bottom of Fig.6. The output voltage (ie, across the 680µF capacitor) is sampled by a voltage divider (4.7MQ & 12kQ) and applied to pin 5 ofIC4 which then drives optocoupler IC5. IC5 then drives op amp IC3 which in turn drives an internal error amplifier in IC1 to control the pulse width modulation. The complementary outputs from IC1 appear at pins 9 & 10 and drive paralleled Mosfets Q5-Q16 via CMOS buffer stages and bipolar transistors GND Q1-Q4. These stages provide the necessary current amplification to drive the gates of the Mosfet stages. The TL494 So that's the converter circuit description in a nutshell. Now let's look at it in more detail, starting with IC1, the TL494. A block diagram showing the internal features of this device is shown in Fig. 7. It is a fixed frequency pulse width modulation (PWM) controller containing a sawtooth oscillator, two error amplifiers and a PWM comparator. It also includes a dead-time control comparator, a 5V reference and output control options for push-pull or single ended operation. The PWM comparator generates variable width output pulses by comparing the sawtooth oscillator waveforms with the outputs of the two error amplifiers. By virtue of the di ode gating system, the error amplifier with the highest output sets the pulse width. Fig.9 shows the two output waveforms generated by IC1. Dead~time comparator The dead time comparator prevents the push-pull outputs at pins 9 & 10 from changing over at the same time. It does this by providing a brief delay between one output swinging low and the other swinging high (ie , both outputs are low for a short time at the transition points). This delay is called NOVEMBER 1992 27 PARTS LIST FOR THE 2kW 24V/240VAC SINEWAVE INVERTER 1 aluminium case, 400 x 400 x 170mm 4 170mm-long radial finned heatsinks 8 4mm-dia. screws & nuts for securing heatsink 1 self-adhesive front panel label, 230 x 170mm 2 25mm cable entry glands (Clipsal 282/25) 1 Delta 10DRCG5 mains filter 1 dual power point, 250V 10A 2 2AG 250VAC panel mount fuse holders 1 500mA 2AG fuse (F2) 1 10A 2AG fuse (F5) 1 5mm LED & bezel (LED 1) 1 panel mount rocker switch (S1) 2 80°C thermal cutouts (TH 1, TH2) 8 large rubber feet 16 6mm metal standoffs plus screws & nuts 12 12mm metal standoffs plus screws & nuts 2 6. 7mm nylon cable clamps 27 100mm cable ties 4 200mm cable ties 6 150A tinned copper cable lugs with 10mm mounting holes 47 insulated crimp lugs, 4mm stud size, 2.5mm wire size 9 insulated crimp lugs, female quick connect, 2.5mm wire size 2 solder lugs 1 50ml packet of heatsink compound Wire & cable 1 1.5m-length 130A black automotive cable , 19610.4mm (25mm 2) 1 1.5m-length 130A red automotive cable, 19610.4mm (25mm 2 ) 1 Sm-length 30A 240VAC cable, 4110.32mm (3.3mm 2) 1 2.5m -length red or brown 15A 240V mains cable 1 2.5m-length black or blue 15A 240V mains cable "dead time" and constitutes about 5% of the switching time available. Dead time is essential in a very high power push-pull circuit such as this. Without it, the Mosfets driving one half of the step-up transformer 28 SrucoN CrnP 1 50mm -length green/yellow 15A 240V mains cable 1 2.'?m-length yellow heavy duty hook-up wire 1 2m-length green heavy duty hook-up wire 1 3m-length blue heavy duty hookup wire 1 2.2m 0 1ength red heavy duty hookup wire 1 500mm-length black heavy duty hook-up wire 1 1m-length 2-core shielded cable Primary PC board 1 PC board, code SC 1130992·1 , 204 x 157mm 9 PC stakes 12 4mm brass nuts, screws & shakeproof washers 1 200mm-length 0.8mm tinned copper wire 1 100µH 1A choke (Siemens B82111-E-C25) (L1) 1 3mm screw & nut for 3-terminal regulator 12 TOP-3 mica washers, bushes, 15mm long screws & nuts 1 100kQ horizontal mount cermet trimmer (VR1) Semiconductors 1 TL494 switchmode controller (IC1) 1 4050 hex buffer (IC2) 1 LM358 dual op amp (IC3) 2 BC338 NPN transistors (01, 03) 2 BC328 PNP transistors (02, 04) 12 Siemens BUZ349 N-Channel 30A 100V Mosfets (05-016) 1 7815 3-terminal regulator (REG1) 1 33V 1W zener diode (ZD1) 2 75V 1W zener diodes (ZD2, ZD3) 2 18V 1W zener diodes (ZD4, ZD5) 2 1N4002 1A diodes (D 1, D2) 4 0.1 µF 63VW MKT polyester 1 0.01 µF 63VW MKT polyester Resistors (0.25W, 1%) 3 1Mn 1 3 .3kQ 1 150kQ 1 2.2kQ 0.5W 3 47kQ 1 82!.15W 1 27kQ 12 10!.1 3 10kQ 2 4.7Q 2 4.7kQ 24 1Q Transformer board 1 fibreglass sheet, 175 x 370mm (eg, PC board material) 2 U93/76/30 N27 cores (Siemens B67345-B1 -X27) 2 coil formers (Siemens B67345A 1000sT1) 1 sheet of aluminium, 135 x 76 x 1.6mm 2 8 x 80mm bolts plus nuts & washers 1 100A/125A motor start cartridge fuse, lug mounting, 94mm centres (Hawker Siddeley CEO100M125, GEC TCP100M125) (F1) 2 Clipsal 2DLA 12C 165A brass link bars 2 Clipsal BP165C12 165A brass link bars 2 Clipsal DLA6 165A brass link bars 14 screws for mounting link bars 2 4-way 30A PVC 240VAC mains connector strips (Clipsal BP535 or 593/30) 2 3mm countersunk screws & nuts for mounting connector strip 2 3mm screws & nuts for mounting connector strip 4 pieces of 28 x 60mm 0.6mm sheet copper 4 solder lugs Capacitors Capacitors 3 10µF 35VW PC electrolytic 2 0.47µF 63VW MKT polyester would still be switching off while the Mosfets driving the other half of the transformer were switching on. This would place a brief but direct short circuit across the 24V battery supply. As a result, the Mosfets would be 8 10µF 63VW MKT (Siemens B32523-B106-K) 1 0.1 µF 400VW polyester capacitor destroyed - they would literally blow them themselves apart. Under-voltage cutout In Fig.6 , one of the error amplifiers in IC1 is used to provide the under Rectifier PC board 1 PC board, code SC11309924, 214x162mm 1 100 x 55mm sheet of fibreglass material 2 45 x 45mm sheets of fibreglass material 2 20 x 20 x 12mm aluminium right angle brackets (1 .6mm thick) 2 3 x 10mm screws & nuts for brackets 1 8 x 80mm bolt & nut 1 6mm ID rubber grommet · 1 45mm-dia. vertical mount capacitor clamp 2 3mm screws & nuts for clamp 2 0.75mH 10A toroid chokes (L3, L4) 1 iron powdered ring core , Neosid 17-745-22 (L2) 1 500mm-length of 2mm enamel led copper wire 1 50mm -length 0.8mm tinned copper wire 2 PC stakes 4 3AG fuse clips 2 15A 3AG fuses (F3, F4) 1 4-way 30A 240VAC mains connector strip 2 $ x 10mm screws & nuts for connector strip 8 4mm brass nuts plus star washers & screws · 4 TO220 mica washers , insulating bushes, screws & nuts Semiconductors 1 LM358 dual op amp (IC4) 1 Siemens IL300 linear optocoupler (IC5) 4 MUR1560 15A fast recovery 600V diodes (D3-D6) 1 15V 1W zener diode (ZD6) Capacitors 1 680µF 400VW LL electrolytic (Siemens B43570-E0687-O) 1 25µF 370VAC motor start capacitor with spade lug connectors (Plessey P331 1340) 1 0.1 µF 63VW MKT polyester 1 .001 µF 63VW MKT polyester voltage cutout feature. This prevents the batteries fro m being excessively discharged . Pin 2, the inverting input, is connected to th e 24V supply via a voltage divider consisting of a lOkQ resistor and a 3.3kQ resistor. Resistors (0.25W, 1%) 1 4.7MQ high voltage resistor (Philips VR37) 1 56kQ 510kQ 1W 1 12kQ 1 820Q Resistors (0.25W, 1%) 4 4.7kQ 410Q 2 100Q 41 Q 1 47Q Sinewave PC board H-drive PC board 1 PC board, code SC11309922, 204 x 157mm 1 50mm-length insulating sleeving 4 4mm brass nuts, screws & star washers 14 PC stakes 1 300mm-length 0.8mm tinned copper wire 8 metal oxide varistors (Siemens S14K275) 16 TOP-3 mica washers, insulating bushes , 12mm screws & nuts 3 EFD15/8/5 ferrite transformers (T2, T3 , T4) (ie, each with 2 x Philips 4312 020 41001 cores, 1 x Philips 4322 021 35201 former & 2 x Philips 4322 121 35141 clips) 1 2.5m-length of 0.125mm enamelled copper wire 1 200mm length of insulation tape Semiconductors 4 Siemens SFH6136 fast optocouplers (IC6, IC8, IC10, IC12) 4 4049 CMOS hex inverters (IC?, IC9, IC11 , IC13) 4 Siemens BUP304 1000V 35A IGBTs (017-020) 3 15V 1W zener diodes (ZD7, ZD9, ZD11) 4 18V 1W zener diodes (ZD8, ZD10, ZD12, Z013) 3 1N4148, 1N914 switching diodes (D7-D9) 4 Siemens BYP102 1000V 50A diodes (010-013) Capacitors 3 10µF 25VW PC electrolytics 4 1µF 50VW RBLL (low leakage) PC electrolytics 1 1µF 500VW axial electrolytic (Siemens B25839~B6105-K) Pin 1, th e non-inverting in put , is conn ected the chip's 5V internal referen ce (Vref) at pin 14 , via a 4.7kQ resistor. When the voltage at pin 2 drops below 5V (ie, when the battery volt- 1 PC board , code SC11309923, 181 x 131mm 17 PC stakes 1 700mm-length 0.8mm tinned copper wire 1 miniature TO-220 heatsink (Thermaloy 6038 type) 1 3.2768MHz parallel resonant crystal , 22pF loading (X1) 1 3 x 10mm screw & nut Semiconductors 1 7555 CMOS timer (IC1 4) 2 4049 hex inverters (IC15, IC16) 1 74HC04 hex inverter (IC17) 4 74HC193 4-bit binary counters (IC18-IC21) 1 74HC08 quad 2-input AND gate (IC22) 1 NMC27C64N250 CMOS OTP PROM (IC23) 4 BC337 NPN transistors (021-024) 1 7805 3-terminal regulator (REG2) 1 33V 1W zener diode (ZD14) Capacitors 3 10µF 35VW PC electrolytic 11 0.1 µF 63VW MKT polyester 1 220pF 63VW MKT polyester 2 22pF ceramic Resistors (0.25W, 1%) 1 10MQ 1 2.2kQ 1 100kQ 4 220Q 1 47kQ 1 150Q 5W 4 2.7kQ Note: this project has been sponsored by Rod Irving Electronics (1992) & full kits will be available from this company in ea rly 1993. Copyright of th e associated PC boards is assigned to Rod Irving Electronics. age is below 20V), the output of this error amp li fier goes high (pin 3) and switch es off both outputs at p ins 9 & 10. This effectively shuts down th e circuit. Note that the voltage divider fee dNovEMBER 1992 29 Fig.8: the inverter delivers a clean sinewave, as these scope photos show. It provides 250VAC at no load (top), · 243VAC at lkW (centre) & 230VAC at 2kW (bottom). Note that the waveform improves with increasing load. ing pin 2 is connected via two thermal cutout switches. These are mounted on two of the four heatsinks in the inverter chassis and are preset to open when the temperature exceeds 80°C. Thus, when one or both of the heatsinks becomes too hot, the thermal cutout opens and the circuit is shut down. When the heatsinks cool down, normal operation resumes. Voltage feedback The second error amplifier in !Cl is used to control the output voltage of the converter. The feedback voltage from the optocoupler and IC3 is fed to pin 16 and compared to the internal 30 SILICON CHIP 5V reference, applied to the pin 15 input via a 4. 7k0 resistor. Normally, the feedback voltage from IC3 should be close to 5V. If the output rises above this, the output of the error amplifier also rises and this reduces. the output pulse width. Conversely, if the output voltage falls, the error amplifier output also falls and the pulse width increases. The gain of this error amplifier at low frequencies is set by the lMO feedback resistor between pins 3 & 15 (giving a gain of 213). At higher frequencies, the gain is set is set to 22 by virtue of the 47k0 resistor and O. lµF capacitor in series across the lMO resistor. This reduction in gain at high frequencies prevents the error amplifier from responding to hash on the supply lines. The 27k0 resistor and .OOlµF capacitor at pins 6 and 5 of !Cl set the internal oscillator to about 40kHz. This is divided by the internal flipflop to give complementary output signals from pins 9 & 10 and so the resultant switching speed of the Mosfets is ZOkHz. Pin 4 of !Cl is the dead-time control. When this input is at the same level as Vref, the outputs at pins 9 & 10 are off. As pin 4 drops to OV, the dead-time decreases to a minimum. At initial switch on, the lOµF capacitor between Vref (pin 14) and pin 4 is discharged. This prevents the output transistors in !Cl from switching on. The lOµF capacitor then charges via the associated 47k0 resistor and so the duty cycle of the output transistors slowly increases until full control is gained by the error amplifier. This provides a soft start for the converter. Complementary outputs The outputs at pins 9 & 10 of !Cl come from internal emitter follower transistors and these each drive 10k0 load resistors. These outputs also each drive three paralleled CMOS non-inverting buffers (IC2a-IC2f). These buffers stages then drive transistors Ql & QZ on one side of the circuit, and Q3 & Q4 on the other. Thus, when pin 10 ofICl goes high, Ql turns on and drives the paralleled gates of Mosfets Q5-Q10 via a 4. 70 resistor. Note that each Mosfet gate is connected via a .100 "stopper" resistor to minimise any parasitic oscillations which may occur while the Fig.9: these are the complementary pulse signals from the TL494 PWM controller. Note that both waveforms do not switch over at the same points, in order to give dead time. Mosfets are switching on and off. When pin 10 goes low again, QZ switches on to discharge the gate capacitance of each Mosfet, thus switching them off. The complementary process occurs with pin 9. Circulating currents While it is not obvious from the circuit of Fig.6 , there must be two connections to the drain and source of each Mosfet. For example, the drains ofMosfets Q5-Q10 are connected in parallel to one side of the transformer primary. In addition, each drain must be connected back to the PC board so that the zener diode protection can work. Similarly, the source connections of the Mosfets are all connected to the OV line and thence to the battery negative pole. In addition, the sources all need to go back to th~ PC board because otherwise the gate drive circuitry would not work properly. The problem with this need for double connections is that unless we take precautions to stop it, very heavy currents will flow on the relatively flimsy copper tracks of the PC board. This must be avoided because the PC board cannot carry such currents. To stop heavy currents flowing on the board, 10 resistors are used in all the drain and source connections. Thus , the gate circuitry and zener diode protection circuitry works properly but the main currents flow in the direct cable connections. But even with this precaution, the source currents from the Mosfets still tend to flow in the PC board tracks. To stop this, two grounds are provided. The first is for the load current and connects directly to the negative ter- Despite the complex circuit, the 2kW Sinewave Inverter is relatively easy to build since most of the parts are mounted on PC boards. The DC-DC converter board is at the bottom of the photograph, with the high-frequency switching transformer immediately above it. minal of the battery. The second provides the circu it earth and is connected to the n egative battery terminal via a 100µH ch oke (11). This choke prevents the load current from flowing through the parallel H2 source resistors. It does this because the inductance between the PC board and the negative battery terminal is far greater than the in ductance of the source leads. In addition , eight 10µF 63VW bypass capacitors are connected across the battery input leads , following the 100A fuse. These capacitors effectively cancel out the indu ctance of the battery cables and th ereby provide full power to the transformer and Mosfets at the switching fre quency of 20kHz. The secon dary windings of the transformer con sist of four 9-turn windings wh ich are then connected to form two centre-tapped 18-turn windings in parallel. This arrange- ment minimises the leakage inductance of the transformer. Zener diodes ZD2-ZD5 provide protection for the Mosfets. ZD4 and ZD5 are 18V zeners which protect the gates of the Mosfets against over-drive. ZD2 and ZD3 are 75V zeners which protect the drains of the Mosfets from spikes as they switch off. These zeners clamp the drains to about 80V peak and thus prevent damage. The response time of this overvoltage clamp action is about lµs which is not really fast enough. To provide protection during this initial lµs period, we have specified Mosfets which have avalanche protection. This means that at the breakdown voltage of the Mosfet (100V), an internal zener provides protection for a short time until the external protection circuitry takes over. Voltage feedback As noted above, IC4 and optocou- pler IC5 are used to provide voltage feedback to the switchmode controller (ICl). IC4 and the optocoupler must be fully isolated from the 24V input supply, which means that they must be powered from the high voltage DC output. Thus, the 365V supply is fed to a network consisting of five series 10kQ dropping resistors plus a 15V zener diode, ZD6. This provides the 15V supply for IC4 and IC5. The voltage feedback network consists of a high-voltage 4. 7MQ resistor (Philips VR37) and a 12kQ resistor connected to 0V (ie, the 0V of the high voltage supply, not the 24V battery). IC4 monitors the voltage across the 12kQ resistor and drives the linear optocoupler, IC5. IC5 provides the necessary electrical isolation between input and output. This device has high linearity and this is due to the use of two internal photodiodes, one on the isolated side to supply the output (pins 5 & 6) and a second (pins 3 & 4) to provide feedback to the LED driver circuit. The isolated photodiode output at pins 5 & 6 of IC5 is connected between the+ 15V supply rail and pin 3 of IC3. The current from the photodiode develops a voltage across trimpot VRl which is amplified with a gain of about four by IC3. IC3 then feeds pin 16 of ICl and thus completes the feedback loop. Power supply The 24V input from the battery bank is connected via heavy duty cables (ie, starter motor cables) and a 100A/ 125A cartridge fuse to the centre tap of the transformer. Because of the high currents involved, there is no on/off switch for this main supply; the 24V . input is permanently applied to this part of the circuit. Switch Sl feeds 24V to the lowpower part of the circuitry and LED 1 indicates when the power is switched on. The 24V supply from switch Sl is fed via an 82Q 5W resistor and clamped against transient voltages using ZDl. T·he 24V supply then feeds the input ofa 15V regulator (REGl) which supplies the ICs. The 10µF capacitors at the input and output of the regulator are for supply decoupling. That's all for this month. In Pt. 3, we will describe the circuitry for sinewave generation and the H-pack switching output which converts the 365V DC to 240VAC. SC NovEMBEH 1992 31 The Oriel: Jamo's flagship loudspeaker system Jamo is one of Europe's largest manufacturers of high fidelity loudspeaker systems and for some time they have been working on this state of the art design in which no expense has been spared. The result is a monumental loudspeaker with outstanding sound quality. By LEO SIMPSON When there are so many loudspeaker systems available in the marketplace, how do you set out to produce a unit which is truly outstanding? That was the target set by the Danish manufacturer, Jamo, a couple of years ago. The result is a little surprising, both in appearance and the number of drivers it uses. The Oriel system is certainly large and heavy but it is also elegant, eye-catching and nothing like conventional loudspeakers in appearance. The Oriel system stands 1.8 metres tall and weighs 72 kilograms so that once they are installed there will be very little incentive to move them. In fact, it requires a minimum of two strong men to move them safely. A major part of this weight comes from the enclosure itself and the heavy concrete base. The enclosure is essentially oval in cross-section, which ensures great rigidity, minimises diffraction effects from the drivers at medium and high frequencies and visibly reduces the apparent bulk of the system. Medium density fibreboard (MDF, also known as Customwood) is used A great deal of care has gone into the design and layout of the crossover network. Notice how the air-cored and powdered iron-cored inductors have been oriented so that the mutual coupling between them is minimised. The capacitors are of conventional foil construction (ie, not bipolar electrolytics) and have very low power factor combined with high current capability. The total number of components in the network is 22. 32 SILICON CHIP for the cabinet. The curved sections are built up from segmented sections of MDF while the flat sections are laminated from seven layers of2:Smm MDF. The curved sections are finished in matt grey while the flat sections are covered and stiffened with toughened glass - another reason why the enclosures are so heavy. The glass is trimmed with cherry wood to give a subtle emphasis to the shape. To lower the cabinet's centre of gravity and increase its stability, the widened base is cast in concrete. Three-way system At first sight, with the speaker grilles removed, the Oriels look to be a two way system, since a dome tweeter and a modestly sized cone driver are all that are visible. However, the Oriel is a 3-way system, with two bass·drivers in addition to the midrange and tweeter. The dome tweeter is perhaps the most expensive unit of its kind ever made. With a 28mm dome, a voice coil wound with hexagonal wire and ferrofluid cooled, and a magnet-weighing more than 1kg, the tweeter is claimed to be able to handle prngram transients of up to 1000 watts. It covers the frequency range from 31<.Hz to above the limit of audibility. The 18cm midrange driver is housed in its own sealed enclosure within the Oriel cabinet. Its cone is a honeycomb construction which renders it very rigid and free of any break-up over its frequency range from 100Hz to 3kHz. Again, it has a powerful magnet and its pole piece is ventilated to avoid damping the motion of the cone due to pressure build-up behind the dust cap. The two 21cm woofers each have their own sealed enclosure within the Oriel cabinet. As one of the photos accompanying this article shows, one woofer is at the top of the cabinet while the other is at the bottom. The woofer enclosures are bandpass tuned, a concept presently used in a number in the concrete base of the cabinet and it has separate terminals for the bass, midrange and tweeter. This means that the system can be bi-wired or tri-wired (ie, two or three sets of cables from the power amplifier), or bi-amped or tri-amped (ie, two or three amplifiers driving the separate sections of the network but not using an electronic crossover) . Overall sensitivity of the Oriel is quoted as 8 7dB for 1 watt at 1 metre and the recommended amplifier rating is from 70 to 300 watts. And the price for this acoustic masterpiece? Around $17,000 for a pair. For further information, contact the Australian distributors, Scan Audio Pty Ltd, PO Box 242, Hawthorn, Vic 3122. Phone (03) 429 2199 or fax (03) 429 9309. SC A pair of Oriel loudspeaker systems will require a large room to accommodate them but their rounded column shape means that their bulk is not over-powering. They stand on concrete plinths and can be set on spikes or rubber feet. of subwoofer designs , including the Bose Acoustimass. The principal advantage of bandpass tuning is that it tends to suppress any harmonics produced by the woofer and thus gives a cleaner bass response. The woofer enclosures in the Oriel are tuned to 40Hz and 75Hz, giving an effective bandpass of about 30-l00Hz. The woofers' sound output exits via angled ports above and below the midrange enclosure. Crossover network As you might expect, the Oriel's crossover network is fairly complex and uses no less than 22 components. It has five air-cored inductors , two powdered iron-cored inductors, 12 AC rated foil capacitors and three wirewound resistors. As well as providing the 6dB/octave slopes for the woofer, midrange and tweeter crossover frequencies, the network provides group delay for the tweeter. This obviates the need for "time delay compensation " which would otherwise require the tweeter to be stepped back on the baffle to match the acoustic centre line of the midrange driver. The inductors are mounted on the crossover network PC board in such as way as to minimise any mutual coupling. Mutual coupling can reduce the filter slopes and cause distortion by feeding bass energy to the tweeter and so on. The crossover network is mounted The internal construction of the Oriel system is shown in this photograph. The midrange has its own sealed enclosure while the two bass drivers each have their own bandpass tuned enclosures. Their sound output emerges via ports above and below the midrange enclosure. NOVEMBER 1992 33 MAL-4: Microcontroller Aid for Learning Here is a microcontroller design which can be used to learn programming and computer c~ntrol. It features the Motorola 68HC705CB microcontroller and has serial and parallel ports. You can program it via its own hexadecimal keyboard or via a standard IBM computer keyboard. 34 SILICON CHIP By Barry Rozema A single chip microcomputer, as the name implies, is a microcomputer in a single chip package. This means that all the building blocks of the microcomputer are in the one integrated circuit. The building blocks for most computers are the central processing unit (CPU), memory (RAM & ROM), parallel and serial input/output (I/0) ports, address decoding, clock, interrupt timer and watchdog timer. Single chip microcomputers or microcontrollers have found a very important niche in the computer industry. Due to their size and low cost, they are very effective when used for control applications such as in washing machines, microwave ovens, VCRs and burglar alarms. The microcontroller used in this project is the Motorola MC68HC705C8. It is an 8 bit microcontroller with a user programmable EPROM inst~ad of mask programmable ROM. This makes prototyping and development a reasonably easy task. Why use the MC68HC705C8? The main reasons were cost and availability plus the fact that I like Motorola's "easy to understand" data sheets and manuals. And why design and build a single chip microcontroller learning aid? I realised when I first started programming the 68 705 that it would be handy to run some small test programs to familiarise myself with the devicA. After some enquiries, I discovered that there are some development tools for the 68705 but the prices were out of my league. So the idea of designing a cheap single chip learning aid was born. Main Features • Processor - Motorola MC68HC705C8S. • Clock speed - 2MHz/2 (1 MHz internal clock). • Display - 2-l ine by 16-character alphanumeric LCD. • Keyboard - Hex keypad with option for different types. • Power supply - either 9V AC or 12V DC. • Monitor - resides in EPROM (5Kb) and includes disassembler. • Two modes - MAL-4 or single chip monitor mode. • Emulates the Motorola M68HC05PGMR programming board. • Battery backup of RAM. • Ports: A - 8-bit input port with 8-way DIP switch. B - 8-bit outpuVinput port with 8 LEDS. C - 8-bit control port with 8 LEDS. D - 7-bit input only port with 8-way DIP switch or asynchronous (RS232) and synchronous (IBM keyboard) . • Ease of construction • Stand alon e operation • Possible u se as a controller The MC68HC 70 5C8S microc ontroller is a recent addition to th e Motorola 6805 family and is similar to the 68 705P3 processor featured in the Sprinkler Controller published in the July 1992 issue and the Burglar Alarm publish ed in th e September & October 1992 issues of SILICON CHIP. The " HC " des ign ation of the 68HC705C8 signifies that it is a high speed CMOS version (ie, high speed, low power). It is one of m any versions of this chip so that once you have learnt h ow to program it , you w ill have no trouble with the other versions and indeed you will have a good grounding in programming any microprocessor. Block diagram The block diagram of Fig.1 shows MAL-4 Entitled "Microcontroller Aid for Learning, Version 4.03" or MAL-4, for short, this project is the fourth in a series which have been designed primarily as a learning tool for TAFE colleges. I paid close attention to the following points: • Low cost • Current processor technology • Simple design The MAL-4 uses a 2-line alphanumeric readout which plugs into a socket on the PC board. It is an intelligent unit which accepts ASCII code. NOVEMBER 1992 35 TABLE 1: MAL-4 MEMORY MAP Input/Output 32 Bytes· $00 Port A Data Register $01 Port B Data Register $0020 - $002F Unused 16 Bytes $02 Port C Data Register M.A.L. Zero Page Ram 144 Bytes $03 Port D Input Register $0030 - $00BF $04 Port A Data Direction Register $00C0 - $00DF M.A.L. Scratch Pad 32 Bytes $05 Port B Data Direction Register $06 Port C Data Direction Register $00E0 - $GOFF System Stack 32 Bytes $07 Unused $08 Unused $0100 - $01 5F M.A.L. Page 1 RAM 96 Bytes $0000 - $001 F Unused Serial Peripheral Control Register $0B Serial Peripheral Status Register $0160 - $12FF M.A.L. Monitor EPROM 4512 Bytes $1300 - $1 EFF Spare User EPROM 3072 Bytes $DC Serial Peripheral Data 1/0 Register $OD Serial Communications Baud Rate Register $1 FOO - $1 FOE Bootstrap ROM 223 Bytes $OE Serial Communications Control Register 1 $OF Serial Communications Control Register 2 $1FDF Option Register $10 Serial Communications Status Register $1FE0 - $ 1FEF Bootstrap ROM Vectors 16 Bytes $11 Serial Communications Data Register $12 Timer Control Register $1 FF0 - $1FF3 Unused 4 Bytes $13 Timer Status Register $1 FF4 - $1 FFF M.A.L. EPROM Vectors 12 Bytes $14 Input Capture High Register most of the significant features of the MAL-4. It leaves out essentials like the power supply, speaker driver and even an external EPROM which the unit can be used to program. The 68HC705C8 has 24 bidirectional input/output (1/0) lines and 7 input-only lines. These are arranged as three 8-bit 1/0 ports (A, B & C) while the 7 input-only lines are port D. Interestingly, while these 7 lines are specified by Motorola as input only, the first line (PD0) is also used as an output line, to provide the Tx line for RS-232 serial communications (via a MAX232 chip on the board). Port A is used to drive the 2-line liquid crystal display, along with a couple of the lines from port C. The liquid crystal display is an intelligent device and it accepts ASCII characters on its parallel data lines. Ports B and C drive a bunch of LEDs which show the state of the lines. One data line of port C also 36 $09 $0A SILICON CHIP $15 Input Capture Low Register $16 Output Compare High Register $17 Output Compare Low Register $18 Counter High Register $19 Counter Low Register $1A Alternate Counter High Register $18 Alternate Counter Low Register $1C Program Register $10 COP Reset Register $1E COP Control Register $1F Unused drives the speaker to provide the occasional beep or two, to acknowledge that the micro is receiving or feeding out data. The 16-button hexadecimal keyboard is connected to ports A and C via row and column driver ICs. Port A also provides the external parallel port. An IBM keyboard can be connected to the unit and it drives four of the lines of port D. DIP switches are also provided for data input to port A and port D. Two pushbuttons are provided for "Interrupt Request" (IRQ) and "reset" . All of _the above features can be gleaned by examining the block diagram of Fig.1 but let's face it, that will not really tell you much about how the micro works. That understanding will come gradually as you learn more about programming the device and DIPSW1 PORT-A ,I, 1,1\' l ll :\' 1/0 CONNECTOR PL2 I, I l l PORT-A PORT•B LCD J I ...< a.. .,J PORT-A INPUT BUFFER ' PC3 ,, A BUS -. E RS R/W 8-BIT DATA ca.. "'a..< .,J < a.. .,J < a.. "'< ca.. <O < a.. a.. ,, • "' a.. a.. 0 <O 0 a.. .,J ( .,J [ 0 ,, ,, , " PA7 PA6 PAS ,, < PA4 PORT-B LED MONITORS .:. ~ PAS a.. PA2 l. PA1 PAO XTAL1 2MHz [ PB7 OSC1 Ir r PBS OSC2 m P84 ,J ~ P83 ,J PB2 .,J .:. a.. RESET T P81 .,J PBO ~ PORT•C LED MONITORS PC7 .,J PC6 ,J .:. IRQ PC2 .,J PC1 ,J PCO .,J 'I 0 0 ,1, I, I, I,~\' I l I r .,J " .:. ~ PD3 a.. PD2 .,J PD1 .,J PDO ,, TXIPD1 MAX232 ]PDO RX 1 TX .I DATA IIDATA RX RS232 PLUG 8 U6 74LS139 COLUMN DRIVER II .A D BUS a PD4 ' ' "'00.. :::, "' "' < PD5 PD4 IBM PD3 KEYBOARD SOCKET PD2 8x4 X-Y KEYPAD UP TO 32 KEYS U7 74LS541 KEYPAD ROW BUFFER I Fig.1: this block diagram shows the main features of the MAL-4 microcontroller board. It has three 8-bit input/output ports (A, B, & C), while Port D has seven input lines. Two of these lines do double duty as the RS232 serial port. Data entry can be via the on-board hex keypad or via a standard IBM keyboard. how it handles data to and from its ports. Physically, the MAL-4 is constructed on a double-sided PC board measuring 223 x 153mm. It has a zero insertion force (ZIF) socket to allow an external EPROM to be used or programmed. It has a hex keyboard as u 0.. A ~\ PD7 PD5 .... IL .,J T ~ DIPSW2 PORT-D ~ PC3 a.. l C BUS r u PC4 Ir SPEAKER ,, PCS KEY6 ESCAPE ~ PB6 U2 MCUHC705C8 MCU KEYS RESET B BUS _,, already mentioned. The board is used free-standing and it only requires the connection of a 12V AC or DC plugpack to have it up and running. As a point of interest, the MAL-4 board also emulates all functions of the Motorola M68HC05PGMR "Programmer Board". The MAL-4 microcontroller board is available from the author as a complete kit and sells for $249. The address is E.S.D. Electronic System Designs, PO Box 73, Glenbrook, NSW 2773. Phone (047) 39 4039. The kit comes with a detailed assembly & operation manual which includes listings. Next month, we will continue the description of the MAL-4 board, giving the complete circuit, construction details and the parts list. SC NOVEMBER 1992 37 0-25V 1•10A PROFESSIONAL POWER SUPPLY S0003 $84.00 Profess ional Power Supp ly, S0003, is designed for use in low voltage and high current system. Its special features include short-circuit o verload protection , LED and phonic- indicators, and continuously adjustable current from 1A to 10A. It is particularly suitable for use in C.B. Transmitter, battery charger, etc .. . ADJUSTING AND TESTING: • 60W + 60W OCL DC PRE-MAIN STEREO AMPLIFIER S0309 $99.00 Th is amplifier uses no capac itors in the si gnal pa t h and has unsu rpassed low freq uen cy resp o nse. The S0309 has a pre- ampl ifier se ct ion , three band tone co ntrols, speaker protecti on circu it with anti- th ump delay and larg e heat sink for co ol op eration . SPECIFICATIONS Po wer Output 60 watts ea ch channel into 8 ohms Freque ncy res ponse: 10 Hz to 20 KH z Tot al harmo ni c distortion: Less than 0.05 % Sensiti vity : Phono: 3mV at 47K Aux an d tap e: 130mV at 47K Dimen sions: 9.07" x 8" x 2.25" Reco mmended pow er transformer is T0217 Suggested cabinet is Mark V LG192 4. After assembly, chec k the c ircu it twice before testing. Connect the voltm eter and ampere -met er as shown in fig. 2, after which power suppl y is co nnec ted. Test the voltage control by turning the VR. and noting the change from 0-25V • To test the c urrent limiting functi on , the cur re nt limiter is turned to its minimum during w hich time the LED and bu zzer wou ld be act ivated. Adjust VR1 just to make the LED and buzzer inactive again . • The outp ut vo ltage is then adjusted to about 5V while the maximum current is adjusted to 1A (v ia the VR1 ). The output term inals are then short-circuit ed, th e beeping of buzzer and flashing of LED indicate that t he cu rrent limiter is funct ional. • The output c urrent is adjusted between 1A to 10A by turning the current limiter. CHECK FOR FAULTS: Fault at output voltage : Check 723 I.C, Q1-Q5. Fault at output current: Check I.C .2, 1458. Non-functioning LED or buzzer: Check LED, Q6 , Q7, tran sistors. SPECIFICATION: 120 Wr. m.s. per ch annel into 4 ohm s load. Frequency response : 10 to 20 KHz Total harmon ic Less th an .01 % di storti on: Bass ±1 2 dB , Tone control: Mid : ±8 dB , Treble: ±8 dB. Ph ono input , 3 mv into Sensiti vity: 47K. Line , 0.3 V into 47 K. Signal to noise rat io: 86 dB Power requirement: 40V De at 6 amp . Suggested tra nsformer for power supply is T0217. Suggested rack mount cab inet: MARK V LG1924 or LG1 92 5. Output Voltage: 0-25V Output Current: 1-10A Method of protection : current limited Ind ication of overload. " BB" sound effect and LED fli c ker. Ripple and noise : <1 mV. Stability of output voltage : ,0.08 % . Power Output: LCD THERMOMETER 10301 $21.00 CLOCK FEATURES: • • • • • • 0.34" DIGITAL thermometer with Hi & Low temperature alarm function and 12 hours clock combination. Measuring range: 0°F to 160°F or -20°C to 70°C. Resolution reading : ±1.8°F. Dimensions: 3.2" x 0.86" x 2.08". T-1 with In/ Out Door sensor. T-3 with In/Outdoor all-weather proof sensor. ~,,,,,,,,,,~~ HIGH PRECISION SOUND CONTROL SWITCH S0201 $19.00 This sound activated on-off switch can be activated by a whistle or hand clap. Sensitivity is adjustable. The output can switch a 200 watt load. May also be converted to a touch switch. Uses two ICs and relay output for complete load isolation and high reliability. Dimensions: 2-7/8" x 1-7/8" x 1" . 0-SA REGULATED DC POWER SUPPLY S0002 $37.00 S0004 $37.00 When used with an external power transformer, this module makes a very stable, well filtered, well regulated power supply. It employs bui lt-in overload protection with LED indicator. Perfect for lab or shop use. There are two versions available, A and B. A. 0 to 15 VDC at 5 amps. Use with transform er T02 33 . B. Oto 30 VDC at 3 amps. Use with transformer T0234. The supplies are also current limited making them virtually failure free and foolproof. Dimensions: 5-1/2" x 2-5/8" x 1-7/8'' . 0-S0V 3A POWER SUPPLY WITH SHORT CIRCUIT AND OVERLOAD PROTECTION S0001 $42.00 This module requires an external transformer to make a high quality lab type power supply. It is short circuit proof and has overload protection also. Output voltage is var iable over a range of 0 to 50 volts and can supply up to maximum of 3 amps. Current limit trip is adjustable. Use with transformers supplying 22 to 36 VAC. A perfect match is the T0210. Dimensions: 6" x 2-5/8" x 1-7/8". ss s If you own a mobile telephone, this simple gadget will dramatically increase the life of your nicad batteries. It does this by correctly discharging the battery pack to its endpoint voltage, so that it can then be recharged to full capacity. By BERNIE GILCHRIST* An autoillatic nicad battery discharger I N RECENT YEARS, lots of people have thrown perfectly good nicad batteries on the scrap heap in the mistaken belief that they had reached the end of their useful service life. Often, however, such batteries are perfectly OK apart from having their apparent capacity drastically reduced by what is known as the "memory" effect. This memory effect is acquired when nicad batteries go through repetitive discharge cycles in which only part of their rated capacity is Research & Development Department, Dick Smith Electronics, North Ryde, Sydney. * 40 SIL/CON CH I P used before recharging. As a result, the battery acquires a "memory" so that it only discharges to the point from which is was recharged and then behaves as though it had gone flat. When you think about it, it is quite easy for this situation to occur. Acommon problem is when people recharge partially flat camcorder batteries or batteries from mobile telephones. After a number of cycles, the batteries acquire a memory effect and this drastically reduces the operational time of the equipment. So how do we prevent this memory effect? The solution is to discharge the battery all the way to its endpoint voltage (1.1 V per cell) before recharging it to full capacity. A few such deep cycles are usually required to rejuvenate a battery that is already suffering from a memory effect, after which it should deliver its full rated capacity. Automatic discharger The easiest way of correctly discharging your nicad battery packs is to use·a special discharger such as the unit presented here. It can discharge nicad battery packs ranging from 3.6V to 12V and, unlike other units on the market, switches itself off when the endpoint voltage has been reached so that no further discharge takes place. This automatic switch-off feature means that you don't have to constantly check the discharger and dis- - START S2 12V 1.2k 16k VR1 Sk 1.2k 47k 1.2k 1.2k 1M + D2 1N4002 7.3k T NICAD BATTERY I 1.2k 1.2k ..a... BATTERY VOLTAGE S1 B B 1.2k 2.2k A 3.6k 3.3k LE01 RED K PLASTIC SIDE B EOC NICAD BATTERY DISCHARGER Fig.1: the circuit is powered by the battery under discharge. When S2 is pressed, pin 6 ofIC1b goes high & turns on Q4, Q5, Q6 & Q1. As the battery discharges, IC1b compares the voltage on its pin 3 input with a reference voltage derived via S1 from IC1a. When the voltage on pin 3 falls below the selected reference voltage, pin 6 ofIC1b switches low again & Q4, Q5, Q6 & Q1 switch off. connect the leads at the appropriate time. This is important, because if discharge continues after the endpoint voltage is reached, the weakest cell in the pack can eventually be forced to reverse its polarity and this causes permanent damage and drastically reduced capacity. To avoid this risk, the Nicad Battery Discharger discharges the pack to 1.1 V per cell and then switches off before any damage can occur. Thus, for a 7.2V battery pack, the endpoint voltage is 6.6V. (Note: nicad cells maintain a virtually constant output voltage until they are fully discharged). During operation, the unit is powered by the battery under discharge. The battery pack is simply connected via two clip-on leads and the battery voltage selected by means of an 8position rotary switch. The DISCHARGING LED now comes on to indicate that the unit is operating correctly and you can set a toggle switch (CURRENT) so that the battery dis- charges at either 50mA or 200mA. When the endpoint voltage is reached, the DISCHARGING LED goes out. The battery can now be disconnected and recharged to full capacity in the usual manner. How it works At the heart of the circuit is ICl , an LMlOCL op amp and voltage reference - see Fig.1. This IC contains a stable Z00mV reference which is permanently connected to the non-inverting input of the reference op amp (ICla). ICla amplifies this reference voltage by an amount depending on the setting of VRl, so that 0. 73V is applied to the following resistive divider chain. This divider chain sets the cut-off voltages for the various battery packs. It is tapped off using switch S1 and the sampled reference voltage is then fed to pin 2 of IClb where it is compared with a sample of the battery voltage on pin 3. Let's look at this in greater detail VIEWED FROM BELOW ~ ECB When the battery pack is first connected, virtually no current flows in the circuit (except for negligible leakage current). The circuit operation is now initiated by pressing the START button (S2). When this happens, power from the battery is applied to pin 7 of IC1 via a lOmA constant current source consisting of transistors QZ and Q3. The current drawn by the LMl0 is only about 500µA at most and so most of the lOmA from the constant current source flows through LED 1. LED 1 serves two purposes. First, it acts to provide a regulated supply of about 1. 9V to ICl. Second, it lights to indicate that the battery is being discharged. Assume initially that the battery voltage is greater than the endpoint voltage. In this case, the sampled battery voltage applied to pin 3 of IClb will be greater than the reference voltage on pin 2. Thus, pin 6 of rc1b swings high; ie, to within about 50mV of the 1.9V supply. This then turns on transistors Q4 and Q5 to discharge the battery. Because Q4's emitter will be at 1.3V, Q6 also turns on and the discharge current will be either 50mA or 200mA, depending on the setting of switch NOVEMBER 1992 41 PARTS LIST 1 plastic case, 41 x 68 x 130mm 1 single pole 8-position rotary switch (S1) 1 momentary contact pushbutton switch (S2) 1 SPOT miniature toggle switch (S3) 1 T0-126 mica washer 1 10 x 3mm machine screw & nut (for transistor mounting) 4 nuts to suit toggle and pushbutton switches 1 star washer to suit switch S1 1 red crocodile clip 1 black crocodile clip 1 400mm-length of red mediumduty hook-up wire 1 400mm-length of black medium-duty hook-up wire 1 60mm length of 3-way rainbow cable 1 knob to suit rotary switch 1 5kQ miniature vertical trimpot (VR1) Semiconductors 1 LM1 0CL op amp & voltage refererice (IC1) 1 BC328 PNP transistor (01) 2 BC557 PNP transistors (Q2,Q3) 2 BC549 NPN transistors (Q4,Q6) 1 8D140 PNP transistor (05) 4 1N4002 silicon diodes (D1-D4) 1 5mm red LED (LED1) Capacitors 1 10µF 16VW PC electrolytic 1 1µF 50VW PC electrolytic Resistors (0.25W, 1%) 1 1MQ 1 2.2kQ 1 47kQ 7 1.2kQ 1 16kQ 1 100Q 1 7.3kQ 2 56Q 1 3.6kQ 1 43Q 1 3.3kQ 1 8.2Q Where to buy the parts A kit of parts for this project is available from any Dick Smith Electronics store or by mail order from PO Box 321, North Ryde, NSW 2113. Phone (02) 888 2105 or, if outside Sydney, (008)226610. The kit comes complete and includes a pre-punched & silkscreened front panel. The price is $29.95 plus $5 p&p. Quote Cat. K3126 when ordering. Note: copyright of the PC artwork associated with this project is retained by Dick Smith Electronics. 42 SILICON CHIP S3. Note that some of this discharge current flows via the constant current source (QZ & Q3} and via Q6 and its associated 56Q resistor. When Q6 turns on, its collector current is sufficient to saturate Ql and so this transistor remains on when the START button (SZ} is released. The circuit thus remains on and the battery continues to discharge at either the 50mA or 200mA rate until it reaches its endpoint voltage. When the endpoint is reached, the voltage on pin 3 of IClb falls below the reference voltage on pin 2 and pin 6 switches low. This removes the bias from transistors Q4, Q5, Q6 & Ql and so the circuit switches off, the LED goes out and the battery ceases discharging. The lMQ feedback resistor between pins 6 & 3 of IClb provides the op amp with a small amount of hysteresis so that it switches cleanly at the transition point. If the battery is already below its endpoint voltage when the START button is pressed, the output of IClb will remain low and so Q4, Q5, Q6 & Ql will remain off. However, the LED will light while ever the button is held down. As soon as the button is released, the LED will go out again and the supply voltage on pin 7 ofICl will quickly fall as the l0µF capacitor discharges. Diodes D1-D4 protect the circuit against reverse battery connection. If the battery is connected the wrong way around, a small reverse current flows via the lO0Q resistor and the base-collector junction of Ql but this cannot damage the transistor and the IC is protected by DZ. The l00Q resistor between the base and emitter of Ql ensures that it fully turns off at the end of the discharge period. Construction Fig.2 shows the wiring details for the Nicad Battery Discharger. Most of the parts, including the switches, are mounted on a PC board (code ZA1373) and this is housed in a small plastic utility case measuring 41 x 68 x 130mm. Start the construction by installing all the resistors and diodes, then install the transistors and the two capacitors. The resistor values should be checked using a digital multimeter, since the colour bands can sometimes be difficult to read. Make sure that all polarised corn- Fig.2: make sure that all polarised parts are correctly oriented when installing them on the PC board & don't mix up the transistor types. Q5 is mounted on the front panel & is connected to the board via flying leads - see Fig.a. ponents (transistors, diodes & capacitors} are correctly oriented and that the correct transistor type is used at each location. If you use the wrong transistor or install a part the wrong way around, that part could self-destruct at switch-on and possibly take other parts out with it. The IC, switches and trimpot can now be installed as shown in Fig.2. An IC socket was used for the prototype but there's no reason why the IC cannot be soldered directly to the board. Be sure to install the IC with the correct polarity. As supplied, the rotary switch will have 12 positions but it can easily be changed to an 8-position type by moving the selector ring at the end of the threaded bush. Check that the switch is seated properly against the board before soldering its pins. Switch S2 should be mounted so that it sits about 4mm above the board surface, while S3 should be pushed all the way down onto the board. At this stage, the only part not fitted to the board will be the indicator LED. We'll come to that later. In the meantime, cut two 400mm lengths of medium-duty hook-up wire for the battery connections (one red and one black} and solder them to the PC board. Similarly, solder three 60mm-long leads to the PC board for the connec- tions to the power transistor (Q5). Because it handles most of the current, Q5 requires a modest amount of heatsinking and this is achieved by mounting it on the metal lid of the case. Fig.3 shows the mounting details. Note that Q5 must be electrically isolated from the lid using a mica washer. Before mounting the power transistor, check that the contact area is perfectly smooth and free of metal swarf. If you detect any roughness, use a small file and a piece of wet and dry paper to smooth the contact area so that there is no risk of the metal punching through the mica washer when the assembly is bolted together. When you are satisfied that the contact area is OK, smear both sides of the mica washer with heatsink compound, then bolt the assembly together as shown in Fig.3. The three connecting leads from the PC board can then be soldered to the transistor pins. Finally, use your multimeter to confirm that Q5 's collector is indeed electrically isolated from the lid. Final assembly The PC board is secured to the lid of the case by the pushing the switch bushes through matching holes and doing up the locking nuts. Before doing this, however, fit the LED to the lid of the case by pushing it into its mounting bezel. This done, rotate the LED so that its anode and cathode leads will mate with the appropriate holes on the PC board (the anode lead is the longer of the two) and fit the locking ring. Two sets of mounting nuts are supplied for switches SZ and S3 and one nut should be fitted to each switch to provide support for the back of the lid. The nut for SZ should be done all the way up, while the nut for S3 TABLE 1 Battery Voltage Endpoint 3.6V 3.3V 4.8V 4.4V 6V 5.5V 7.2V 6.6V 8.4V 7.7V 9.6V 8.8V 10.8V 9.9V 12V 11V The assembled PC board is secured to the lid of the case as shown in this photograph. Note that although LED 1 is shown here mounted on the board, it is normally fitted to its bezel first & its leads slid through matching holes in board when the latter is mounted in position. should be positioned just over half way up the bush. In addition, star washers should be fitted to all the switches (see photo). The PC board can now be mounted on the lid by guiding the switch bushes through their mounting holes and making sure that the leads from the LED pass through their mounting holes in the PC board. This done, install the switch locking nuts, then solder and trim the LED leads. The battery leads exit through a hole in the top of the case. Tie a knot in these leads just before the exit point, so that the leads cannot be pulled out, and terminate their free ends with alligator clips (or some other suitable connector). Use a red alligator clip for the positive lead and a black alligator clip for the negative lead. MICA WASHER ~ NUT \ PLASTIC~r SIDE SCREW ~ -CASE LID / T0128 DEVICE Fig.3: transistor Q5 must be electrically isolated from the lid of the case using a mica washer as shown in this mounting diagram. Check that the mounting surface is smooth & smear both sides of the mica washer with heatsink compound before bolting the assembly together. Test & adjustment The unit is tested by substituting a variable power supply for the nicad battery pack. First, set the discharger to the 12V range, then connect it to the power supply and set the supply to give an output of 15V. Trimpot VR1 should initially be set to its mid-range position. Now press the START button. The DISCHARGING LED should immediately come on and should stay Qn when the button is released. If it does , the circuit is working correctly and you can check that it automatically switches itself off at some point by slowly winding the supply back until the LED suddenly goes out. Finally, the circuit can be calibrated by setting the supply to 11 V (exactly) and adjusting VR1 until the LED just goes out. Make sure that the discharger is set to the 12V range during this procedure. The remaining seven ranges can then be checked. The endpoint voltages should be very close to those listed in Tabie 1. If there are any significant variations from the listed values, check the resistors in the divider chain. SC NOVEMBER 1992 43 SERVICEMAN'S LOG I did it; but it wasn't my fault That heading probably sounds like a half-baked admission by a mayhem suspect who maintains that he was influenced by an evil spirit. In fact, it is an admission by the author but I still maintain it wasn't my fault. This all started when I was conned into a job which, in the normal way, I wouldn't have touched with 12.192metre (40ft) barge pole. Which brings me to the real background for this month's notes - the problem facing servicemen when presented with faulty appliances which are completely out of their field. They are jobs which usually result from a plea by a relative or personal friend. It matters not that the particular appliance is one that you know nothing about; that you've never seen inside one and have absolutely no technical data or circuits for reference. If it "works by electricity", you're it mate! In this case, it was a telephone answering machine, owned by an inlaw and presented to me during a FRACARRO SAVES••• ... more than $10. from every UHF television antenna you buy. Fracarro's 4PUN for better performance from weak UHF signals. Peter C. Lacey Services Pty. Ltd. P.O. Box 678 (74Fulton Rd.) Mount Eliza 3930 Tel:03 787 20TT Fax:(03) 787°3460 ACN006893438 44 SILICON CHIP social visit. And the bloke concerned introduced it with a typical con µ1an's approach; the supposedly flattering, "You know all about these things". I made a feeble attempt to disclaim such expertise but in vain. So what was the problem? Having moved beyond the "it doesn't go" stage, I learned that it had failed to deliver its "no-one-at-home" spiel (or the outgoing message as it is described in the user's manual), leaving the caller with the impression of a lifted handset but no reply. Further study of the manual put me more in the picture, at least at a general level. It was a combined telephone and answering machine and used a single tape. This latter point was important, because it meant that the outgoing message was recorded digitally in a chip. In fact, the length of the message is limited to 16 seconds; enough, but only just. Volatile recording Naturally, this is a volatile recording; it needs to be continually powered. This prompted the obvious query; had the outgoing message been lost due to power failure? The unit is powered from the mains via a 9V AC plugpack, but also takes some power from the telephone line and is fitted with a backup battery. Had the unit been left disconnected from the phone line or mains? And how old was the battery? As far as we could determine, no such failures had occurred. The batteries were fairly new and, I assumed, would be limited by their shelf life. In any case, I realised that it was possible to check the message quite readily; pressing one button (START) replays it through the speaker for checking. And it did, very faintly; so faint that I had to put my ear down to the speaker to follow it. But it was quite clear. And when I pressed the button a second time, it came forth at full bore. The next time I tried, it was at mid level. And so it went on; each time I pressed the button, the level varied and sometimes it was so faint that there was little chance it would be heard at the end of a typical phone line. A bench job Well, that was enough on-the-spot diagnosis. To have any chance of real progress, I would have to tackle it on my own bench. Not that I was very confident. The best I could hope for was an obvious faulty connection - a dry joint, a faulty plug and socket assembly, or something similar. On the bench I established that I could take it apart by releasing four screws. But one of the screws was under the backup battery - four AA cells - so I had to plug it into the mains, remove the cells, undo the screw, then replace cells to restore the backup. That done I could remove the top of the case. This carried the tape deck, the dial pad and the control buttons, plus the handset receptacle and switch hook. It was connected to the main board in the lower half of the case via a short 18-conductor flat cable, which proved quite a nuisance at times. I was even less confident when I looked at the board. Oh, it was well enough put together but the vast array of components and the complex wiring pattern, for which I had no circuit, were very off-putting; it made me realise that I was flying completely blind. Anyway, I plugged it into the mains, hoping that the backup battery had held the fort while all this was going on, and pressed the START button again. As it turned out, the message was still there but it was very erratic. In one sense, that was the good news. If it was all that sensitive, some careful prodding and tapping might find the cause. And so I started. I didn't get far at first; the whole board was touchy. I found a couple of more sensitive areas and went over them with the jeweller's loupe, looking for dry joints. I picked a couple of suspects, which I resoldered, but it didn't do any good. Nor was the job made any easier by the need to activate the message continually, with only a 16-second burst each time. Still, I persevered. Eventually I found myself in one corner of the board, near a 16-pin IC mounted in a socket. I had no idea what this IC did but it was very sensitive to even the slightest touch. Naturally, my first suspect was the IC socket - after all, I've seen enough faulty sockets in TV sets. So, as a first step, I pulled the IC out, squirted the socket with contact cleaner, and put the IC back in. Result - the unit went completely dead, at least initially. It did show some life after some more prodding but it still wouldn't deliver the message. Had the IC or the socket finally failed for good? And if the IC had failed, could I get a replacement? It was identified simply as a type 250K. I rang around my most likely suppliers but no-one could p1ace it. And the situation wasn't helped by the fact that I didn't have a clue as to its function. It was time to ask for help. I don't know where the machine is made but it is handled by a local company, which I tracked down via the phone book. I rang them and asked for the service department: No joy; the service technician was out for the day. But the young lady took my name, phone ½. Price PCBs& Panels! We have over 1,000 different printed circuit boards and screen printed front panels for kitsets from EA, ETI, AEM, HE and Silicon Chip. On special this month only for half normal price! For a complete list of available PCBs and front panels, their date of issue and price, simply send your name, address and stamped self addressed envelope. Note: Due to copyright laws we cannot supply copies of magazine articles. These are available from libraries or the magazine companies (by arrangement) ALL ELECTRONIC COMPONENTS l!l 118-122 Lonsdale St. Melbourne 3000. Ph: (03) 662 3506. Fax: (03) 663 3822. -~- ---- ------ Name Address 0 ~9:z •... l: WA.S FL-"<ING COW\~L-E.'T"E-\...Y ~L-\Nt> Postcode L-------------.J NOVEMBER 1992 45 SERVICEMAN'S LOG - CTD number, and brief details of the unit, and promised he would call nie the next day. Surprise, surprise! He did. And he was most helpful. When I related my story, he immediately identified the IC. It was the outgoing message memory chip-which explained a lot. Was a replacement chip available? Yes, it was worth only a few dollars. Crook socket But his bet was the socket. He suggested that I replace it first to see if that cured the problem and then, if that failed, replace the chip. But he ruled out a suggestion that I solder the chip directly into the board. These chips are quite temperature sensitive and don't like being soldered. He also promised to send me a circuit, which turned up in the mail the following day. Full marks all round! And so, from my local supplier, I purchased a machine pin type IC socket; beautifully made, with solid, gold-plated, contacts. This was duly fitted and bingo , that was it. I recorded a new message and it played perfectly. It was almost an anti-climax. Normally I would have returned the unit at that stage but it wasn't convenient for either of us to make the journey. So I took it home for the weekend, plugged it into a convenient extension outlet, and set it up to say its piece. Of course, no-one rang, not even a cladding salesman. At least not until late Sunday. Unfortunately, when that call did come through, the machine ignored it but not as it had done before. This time, the machine didn't respond at all; it simply didn't know that the call was there. Well, that was a real setback. As I have remarked before, there is nothing more frustrating than to cure one fault and then discover that you have apparently created another. So what had· I done? And how should I tackle it? Most importantly, I needed a ringing signal to work with. I considered a number of possibilities but settled, initially, for Telecom's own ring-back facility, as used by their technicians 46 SILICON CHIP to check ring functions (don't ask me how I know this). Back on the workbench on Monday motning, I first used the ring-back to confirm that the failure was not just a one off - which it wasn't. This also revealed something else; something which had been masked in my home set-up by the nearby regular phone. There was no ring tone being given out by the machine. At this point I fished out the circuit and began analysing it in detail. I started with the incoming phone line a standard arrangement in handset circuits; it takes power from the phone line to drive the handset. And it is necessary because although the supply is DC, its polarity reverses with certain functions, such as answering an incoming call. So I mentally wrote that one off for the moment. The other bridge would ·also have its counterpart in a handset. It can respond only to the AC ringing pulse and drives the ringing tone generator. It obviously performed this function in this circuit but did other things as well, such as instructing the answering circuit to (electrically) lift the handset and then initiate the outgoing message. So, since I was getting neither a ring tone nor the answering function, it was the obvious circuit to check. I checked the bridge diodes first but they were OK. I then went back to the incoming line and worked towards the bridge. It went through one of the hook switch contacts, then the lµF capacitor and a 4.7kn resistor. The bridge output circuit involved several more components, including a zener diode and an electrolytic capacitor. Crook joint so FO'R --root< ,.,.. 1-\0M~ 11-\e:. WG:~i<: ~NP..... ~ which is marked "R" and "T" for some reason which escapes me. Slowly it began to make sense. The first thing I realised was that the telephone circuitry, which is normally contained within the handset, formed part of the main board. This is natural enough,Isuppose,butitaddedtothe complexity of both the board and the circuit. However, I soon had the circuit mentally divided into three sections; the aforesaid telephone section, the tape recorder section, and the answering section proper with its control switches and housekeeping circuitry. So back to the incoming line. This goes to two bridge rectifiers - directly to one in the DC sense and indirectly to the other via a lµF polyester capacitor. The direct-coupled bridge is The soldered connections to the switch lugs checked out OK visually and the ohmmeter confirmed the switch function. Next was the lµF capacitor and this was where things began to happen. One soldered joint was clearly OK but the other one looked suspicious. About half of the joint was covered with flux (not unusual on this board), while the visible solder that remained just didn't look right. Although the solder extended over the track, it was tucked under, rather than flowing over the surface. Naturally, I wanted to see the rest of the joint to be sure it had flowed onto the pad proper. So I started picking away at the flux, which turned out to be a substantial lump. In fact, it was all flux; I finished up right down on the board and still no solder. More importantly, there was no copper either; I was looking at bare board. I reached for the solder wick and soaked up the remaining solder. And what a sight! The copper pad was completely missing; it had broken off at the end of the track. And the only indication of a soldered connection was a barely visible run of solder along the broken edge of the copper track, so faint as to need the jeweller's loupe to confirm it. There was no solder on the surface of the track. How this had happened I can only guess. It seems likely that the original joint had been faulty and someone had tried to repair it, but they had been too heavy handed with the iron and the copper pad had lifted and broken off. They had then tried to run the solder onto the track but it had taken only to the bare copper along the edge of the break. This had made a genuine soldered joint but a very fragile one. It may have lasted indefinitely had I not gone through my prodding and tapping routine, looking for the first fault. And I'm quite sure that the 1µF capacitor was one of the components that I had wiggled and pushed in the process. So, yes, I did it but it wasn't my fault. The repair was simple. A short length of fine tinned copper was wrapped around the capacitor pigtail TETIA TV TIP Akai VS-4E Video Recorder Symptom: can 't remember channels after power failure. The set works quite normally and remembers all settings, so long as power is kept up. And it wasn't the backup battery! Cure: With the power off, check for 3.5V on pin 41 of the "syscon" microprocessor. If the voltage is present, replace this chip. If not, replace switching transistors TR5 and TR6. TETiA TV Tip is supplied by the Tasmanian branch of the Electronic Technician's Institute ofAustralia. Contact Jim Lawler, 16 Adina St, Geilston Bay 7015. and soldered to it. This was then run directly to the switch contact at the other end of the track, only about 20mm away, and soldered to that. And from somewhere a voice muttered, "muck about with that if you can." EmonaLAB4 Four instruments in one package! The LAB4 has four full function test instruments: ■ DC POWER SU PPL V Triple output; SV, 15V, 0-S0V ■ DIGITAL MULTIMETER ■ FUNCTION GENERATOR with neatly laid out and labelled front panel controls. Also, the LAB4 is compact and on ly takes up a small space, compared to four bench-top instruments. Full function, auto-ranging FREQUENCY COUNTER 1Hz-100MHz input range INDEPENDENT INSTRUMENTS Each instrument in the LAB4 is completely independent and can be switched ON or OFF as required. The LAB4 has only one 240V mains input, saving on multiple power points. , Each instrument is clearly defined Computer illiterate As a serviceman, I long ago swore I would have nothing to do with them - computers that is. In my opinion, they were only ever invented for one reason: to provide incompetent clerical staff with an irrefutable excuse when they foul up one's account, or order, or payment. And the computer can't defend itself. Electronics Workbench® The electronics lab in a computer! A simple, intuitive and very powerful teaching tool, Electronics Workbench lets students and hobbyists design and test both analog and digital electronic circuits, without the delays and expense of a laboratory . FEATURES 0.02Hz-2MHz, with SWEEP ■ That fixed it, of course. I ran it on a workshop extension for a couple days, allowing it to answer calls, then overriding it manually. It never faltered. So it was duly returned to the inlaws. They were very grateful but obviously had no idea of the problems the monster had created. But I've no doubt I'll get the choice cut of the turkey at the next Christmas get-together. Oh well. (Just one final thought. Once it was established that the type 250K IC was a memory chip, someone made the smart suggestion that 250K meant just that: the storage capacity of the device. Why didn't I think of that?) So what was the next unfamiliar territory in which I found myself. EMONA INSTRUMENTS NSW ......................... (02) 519 3933 VIC ............................ (03) 889 0427 QLD .......................... (07) 397 7427 DISTRIBUTORS Perth .......... (09) 244 2777 Adelaide .. ... (08) 362 7548 Hobart . .. ....................... (002) 34 2233 • Quick and simple circu it entry • Digital and Analog Modules included, complete with all components • Simulated instruments : dual trace scope, spectrum analyser, function generator, multimeter, digital word generator and logic analyser • Complete control over all component values and parameters • Print: circuit schematics. parts list, instrument readings, macros • Logic conversion - truth table to Boolean formula to logic gates • Customisable hypertext help system THREE VERSIONS • Professional Version: EGA/VGA colour display; unlimited components • Personal Plus Version: Monochrome display; unlimited components • Personal Version: Monochrome display; limited to 20 components per ... EMONA INSTRUMENTS NSW ......................... (02) 519 3933 VIC ............................ (03) 889 0427 OLD .......................... (07) 397 7427 DISTRIBUTORS Perth .................. (09) 244 2777 Adelaide ........................ (08) 362 7548 Hobart .......... .... (002) 34 2233 NOVEMBER 1992 47 SERVICEMAN'S LOG - CTD ,-..,\,-\\CS F~e.:R AA"'D C?I\IE.N 1-\W\ "PgRlll\\'Ss,ol'\\ -ro us~ "™e: C.Otv\?o'f"6.R. ......_, 'c.V"\ W\-\E-N \\ E. SW rt""C\-\E-"D \T <,N ON i\i\S oC(AS\ON, ,.,WE:.N1"" ''A\.-\- FUNN'<:~-. More to the point, in the practical sense, I know nothing about them. I don't know a bit from a byte, or a ROM from a RAM, although I remember the hydraulic ram from my boyhood days in the country. (My dictionary tells me that I am "incomputerate; without a working knowledge of computers or their technology". Couldn't have put it better myself). So this is a story about my being forced into a computer service, job, and breaking my solemn oath. But, in defence, I must claim that it was only a little job, so perhaps my oath was only a little bit broken. And again, the job resulted from a plea based on personal friendship, coming from the 14-year old boy who lives next door. His father had given him permission to use the computer to write his school assignments but, when he switched it on on this occasion, it went "all funny". I started to present my stock reply; that I knew nothing about computers and could easily do more harm than good. But curiosity overcame my caution and I made the fatal mistake of asking in what manner it had failed. 48 SILICON CHIP And apparently it had presented a message saying "insert disc" - which I am given to understand is quite normal - but this message was rolling and also jittering sideways. I was caught. The assignment was fairly urgent and getting a repair through normal channels would take time. I simply didn't have the heart not to try. I said I'd take a look and see if there was anything I could do. More to the point, I had gained the impression that it was simply a monitor fault and, I told myself, a monitor is only another type of TV set. Granted, there was probably a lot of signal decoding circuitry in it which would be double Dutch to me but I was hoping for a simple power supply fault. The hula girl My first look at the screen pattern seemed to support this. When it wasn't rolling, I gained the impression of a typical hula girl fault; hum in the horizontal scan. But the rolling was less easily explained. I decided to take everything along to the workshop, where I could use the CRO an<l have time to think. The monitor carried the "Magic" brand, was made in Taiwan, and was fairly old. I opened it, found the video input, connected the CRO to it, and powered up the whole system. This seemed to clear the computer, because the video signal, with horizontal and vertical pulses, appeared normal. But further investigation was hampered by the physical layout. The power transformer was mounted on a separate rear panel and connected to the main board via a pair of very short leads and a 2-pin plug. This made it very difficult to access the main board, so I unplugged the transformer and put it and the panel to one side. Examination of the board revealed a very conventional supply; the transformer fed a bridge rectifier, which in turn fed a conventional 12V regulator IC, plus the usual filter capacitors. The next step was to restore power and check the supply. I had two options: (1) extend the transformer leads; (2) or feed in power from another source. The latter was the easiest and it so happened that a low voltage DC supply was the most convenient source. OK, so that should go straight through the rectifier and into the voltage regulator. As soon as I connected the supply, the monitor came good, with no rolling and no hula dancing. So what was the problem? I found out by accident. In order to gain better access to the circuit, I disconnected the DC supply leads, moved things around and then reconnected them. And at that point, everything went dead. I then realised that I had probably transposed the power supply leads but, of course, that shouldn't matter when feeding a bridge rectifier. If it was a bridge rectifier, that is. Well, it was supposed to be but it wasn't; one of the diodes had gone open circuit. Yes, it was as simple as that. A few cents worth of power diode and it was going like a bought one. I took it back home at lunch time and delivered it to a very grateful neigh):mur. And my fee? I didn't have the heart to charge him. He is obviously a diligent student, prepared to work hard; and youngsters like this need a break now and again. (Must be getting soft in my old age). So I wrote it off to experience. At least I can now claim - albeit tongue in cheek - that I have had some experience in servicing computers. 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Great for ANY WACUU ■ HOSE cleaning computers, typewriters, office machines, stereo and video equipment, ~lOlP~ER $29.95 s3 JAYC JAYC AF AF i.JA\CAF 3 JAYCAP ; JAY CAH 3 JAY CAfl 3 JAYCAR i JAYCAF 'J AYCAF .J ,1'C:Af1 --., JA'1 CAR ':iJAl'CA H s,JAYCAH --., JA'1CAH :i ,JAYCAR , JAY CAR , JAY CAR , JAYCAR 11 ~ : ;~g~~ ~ ~~~g:: Save $10 this month. Power handling 60 watis rms. Frequency response 55-4kHz. See catalogue for full specifications. Cat cwNormally $42. 95 2114 .Ec rno Another surplus job lot Th is time an Arlec brand supply. Input .ECTRO 240V AC output 6V AC 3 amp. .ECTRO .EC TRO TURN YOUR SURPLUS STOCK INTO CASH! It's housed in its own box with the 240V power lead from one side .ECTRO Jaycar wil l purchase your surplus stocks of components and equipment. We are continually on the and 1he 6V cable lead from th e 0ther terminating to a 2-1mm DC .ECTRO plug. Cat. MP-3023 .EC TRO lookout for sources of prime quality merchandise. O .ECTRm .E CTRO Call Mark Harris or Bruce FJoutley now (02) 743 5222 .ECTRO " ICS JA "'CS JAYC AR ELECTRONfC S JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR El l:C IRONfCS JAYCAR 1:ll:ClRONICS JAYCAR EclrClHONICS JAYCAR " ICS JAYCAR ELECTRONICS JAYC AR ELECTRONICS JAYCAR Fl FCTRONfCS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAY CAR ELECTRONIC S JAYCAR " ICS JAY CAR ELECTRONICS JAYC AR ELECTRONICS JAYC AR FLFCTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONfCS JAYC AR ELFCTRONICS JAY CAR '!_ICS JAYCAR ELECTRON ICS JA'!._~f! tlcCTRONICS JI\YCAH tc~g HONICS JAYCA8..£l_ECTRONICS .JAY CAR ELFCTRONICS .JAYCAR Elf c rnO_H!C S ,JAYCAR NLY $12.95 ea JA'r CAR 'iJ A'rCAH NOW $119 SAVE $40 9 POLYCONE WOOFER POWER SUPPLY MADNESS ~ 'i .IAYCAf1 S ,JAYCAH 'iJAYCAH S JAYCAR S JAY CAR s JA , CAn r..; JA'1 C A H Normally $159 NOW $32. 95 SAVE $10 J/\YCAH JAYCAH .JAY CAR SJ AYCAR S S SJ A,CAn Huge 50oz magnet. Frequency response 45 - 5kHz. See catalogue for fu ll specifications. Cat CG-2381 c , .J AY CAR ; Jl,YCAR ; j::g:;; . . .. ,, .,. ; .J AYCA ri , JAYCAR 3 JAYCAR '.JAY CAR -----"'71 ( :;: ,-,::::;.._ _ _ _ _~ ~g:: ; JAYCAfi ; ,JAY Cl\l l ; ,JA\ CAR ; JAYCAn ; J1\ YCAR ; JAY CAR JAYCAH J1\\CAR : IAYCAR .: JAYCAR , JAY CAR EU-CTliCNICS JAY CAR l'LECl RONIC S JAY CAR ElicCTRONICS .fAYCAR ELECT f,ONICS JAY CAn Fl fCTRONICS JAYC AR ElfC I f,ONICS JAYCAR FI f CTRON ICS .JAYC_Ar, cLF_CTHONICS JAYCAR .....,.___~., _ _ :; -C TRON; \ LC TRON I< •C TRON li '-CTROIJI< •C TR ONI( l CTRO NIC lcTRO ~h 1.:;m o N1< lc TROt < -:rno~ . -:; TRONIC -::: TRON IC -8TR0f'J!( -~ TRON IC -::: TRON !( -: TRO NI C Many of these transistors can be substituted for each other despite differences in their part numbers. The reader can easily identify these transistors from 8 major manufacturers with different type numbers but identical performances. Cat. BM-4570 $17.95 \R \R \R \R \R \R ELECTRo,::cs ELECTf,ON ICS ELFCTRON ICS ELECTRONICS ELfCTRONICS EL~CTRONICS JI\YCAR J AYCAR JAYCAR JAYCAR JAYCAR JAYCAR ELECTRONICS ELECTRONICS ELECTRON ICS EcLECTRONICS FLECTRONICS FLECTRONICS JAYCI\R JAYCAR JAYCAR JAYCI\R JAYCAR JAYCAR ELECTRON ICS ELECTRONICS ELECTRONICS FLECTRONICS ELECTRON ICS ELECTRONICS JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR ELEC TRONICS ELECTRONICS ELECTRON ICS ELECTRONICS ELECTRONICS ELECTRONICS JAYCI\R JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR ELEC TRON ICS ELFCTRONICS ELECTRONICS ELECTRONICS ELECTRON ICS ELECTRON ICS JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR ELECTRONICS ELECTRONICS ELECTRON ICS ELECTRONICS ELECTRONICS ELECTRON ICS JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR ELECTRON ICS FLFCTRONICS ELECTRONICS ELECTRONICS ELECTRONICS ELECTRONICS JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR ELECTRONICS ELECTRONICS ELECTRONICS ELFCTRONICS ELECTRONICS ELECTRONICS JAYCAR ,JAYCAR JAYCAR JAYCAR JAYCAR JAYCI\R ELECTRON! ELFCTRONI ELECTRON! ELECTRON! ELECTRON! ELECTRON! ~ICS ~ICS ~ICS ~ICS ~ICS ~ICS ~ICS JAYC AR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR ELECTRON ICS ELFCTRONICS ELECTRONICS ELECTRONICS ELECTRONI CS ELECTRONICS JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR ELEC TRON ICS ELECTRONICS ELECTRONICS ELECTRONICS ELECTRONICS ELECTRONICS JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR ELECTR ONICS ELECTRONICS ELECTRONICS ELECTRONICS ELECTRONICS ELECTRONICS JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR ELECTRONICS ELECTRONICS ELECTRONICS ELECTRONICS ELECTRONIC S ELECTRONICS J AYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR ELECTRONICS ELECTRONICS ELECTRONICS ELECTRONICS ELECTRONICS ELECTRONICS ELECTRONICS ELFCTRONICS ELECTRONICS ELECTRONICS ELECTRONICS ELECTRONICS JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR ELECTRONICS ELFCTRONICS ELECTRONICS ELECTRONICS FLECTRONICS ELECTRONICS JP ECTRO, I CTRO LCTRO l CTHO LC THO EC TRO EC TRO FCTRO FC TRO LCTRO ECTRO ECTRO EC TRO ECTRO ECTRO ECTRO ECTRO. 1:CTRO ECTRO rc mo ECTRO ECTRO EC TRO LCTRO EC TRO l'C TRO 1:CTRO 1:ClRO ECTRO ECTRO ECTRO ECTRO FCTRO ECl flO FCTRO .ECTRO .ECTRO .ECTRO .ECTRO .l:CrRO .ECTRO .ECTRO .fCTRO .ECTRO .ECTRO .ECTR _ECTR _ECTfl EC TR _EC TR _1: CTfl _£CTRC _E CTRC _ECTRC _ECTRC _cC TRC KITS KA-11 09 KA-1115 KA-11 16 KA-1117 KA-11 19 KA-1 390 KA-1550 KA-1556 KA-1 574 KA-1630 KA-1660 KA-1675 KA-1682 KA-1683 KA-1690 KA-1 692 KA-1693 KA-1696 KA-1699 KA-1702 KA-1 706 KA-1 717 KA-1 718 KA-1719 KA-1720 KA-1724 KA-1725 KA-1726 KA-1728 KA-1729 KA-1730 KA-1731 KA-1 732 KA-1733 KA-1 734 KA-1735 KA-1736 KA-1737 KA-1738 KA-1739 - Electric Fence 300W amp module 300W power supply 300W speaker protector Transistor tester Freq counter 50MHz Deluxecar alarm Ultrasonic move delector 30V 1A power supply 12V lamp flasher Electric fence Screecher car alarm Dual track power supply Baltery monitor DI box Voice operated relay Metronome Econ. Temp probe DMM Bench amp-signal trace 50MHz Dig Freq meter Cheap capacitance meter Subwoofer Adaptor Auto NiCad charger NiCad discharger RGB to PAL encoder Volt up 1.5Vto 9V Pro series 1 power amp Pro module less mosfets VHF powermatch RF probe - suit above Pro series 2 pre-amp Transistor/Fet tester Flexi timer CRO adaptor Quad 01box CROAdaptor for Monitors 18V 1A Bench Supply Speech Proc for Transceiver Karoake Box Low Voltage Cutout KITS $24.95 $89.95 $115.00 $19.95 $21.50 $169.50 $59.50 $34.95 $99.50 $12,95 $64.95 $39.95 $149.95 $14.95 $39.95 $24.95 $19.95 $19.95 $44.95 $79.00 $21.95 $29.95 $39.95 $29.95 $49.95 $19.95 $599.00 $47.95 $52.50 $7.50 $329.00 $32.00 $17.95 $24.95 $69.95 $159.50 $79.95 $29.95 $27. 95 $22.95 KA-1740 KA-1741 KA-1742 KA-1743 KA-1744 KA-1 745 KC-501 2 KC-5013 KC-5019 KC-5021 KC-5028 KC-5030 KC-5031 KC-5032 KC-5038 KC-5039 KC-5041 KC-5042 KC-5051 KC-5052 KC-5058 KC-5059 KC-5072 KC-5075 KC-5076 KC-5077 KC-5079 KC-5080 KC-5083 KC-5084 KC-5085 KC-5089 KC-5090 KC-5091 KC-5092 KC-5094 KC-5095 KC-5096 KC-5097 KC-5098 AND 240V Power Relay Dolby Surround Sound Sine/Square Wave Generator 1MHz Pulse Generator Audio Sweeper - Low Cost Flexible Speaker Protector Car radio power supply 16GHz Digilal Freq meter 100W amp module Protector car alarm Train controller High Energy Ignition Optical lacho Disco Light Universal power supply Vader Voice Mini Mitter Knightrider LEDs CD Compressor Touch Lamp Dimmer Multimeter Kit Radfax decoder Digital voice recorder CAP meter 1pF - 9999uF Reluctor high energy Stereo PRE AM P Sine/Square Wave Gen Horace the cricket 3 Digit counter VCR Remote control ext Discol ight dimmer Two Tone Siren Sinewave Oscillator 20WFluoro Inverter 12V Lighl chaser Stereo Audio Expander DTMF Decoder 4 Ch Lighting Desk Masthead Amp Digital Tacho $49.50 $39.95 $55.00 $89.50 $99.00 $29.95 $28.95 $249.00 $45.95 $49.50 $89.00 $55.00 $49.95 $169.50 $12.95 $19.95 $34.95 $17.95 $49.50 $34.95 $38.95 $44.95 $79.50 $89 .00 $46.95 $32.95 $149.50 $18.95 $23.95 $32.95 $39.95 $9.95 $16.95 $32.95 $21.95 $39.95 $79.95 $329.00 $49.95 $34.95 WHAT A FLOP! _ECTRC _Ecrnc We've made a bulk purchase of pink high quality 13/. 12 tinned hook-up wire. Not terribly exciting, but at this price grab a rol l or two, you cou ld even use pink instead of red. Note: extra postage may apply if several rolls are ordered on th eir own. Cat. WH-3018 We don't know why, but nobody wants them I They are IEC297 32 slot card frame (3U). See our 1992 catalogue page 38. BELOW COSTSAVE A FORTU NE Cat. HB-5360 WAS $129 $39 _Ecmc _ECTRC _EcTRc _ECTRC _EcTRc _EC TRC _ECTRC _ECTRC _ECTR _EcTRc _Ecrnc :~g=~ .ECTRO :~g;~o :~g;: _ECTR .f crnc _1 crnr _ECTR _EcTRc :~g;:c _Ecrnc _F CTRC NORMALLY $11 per 100mt roll This pack co ntains even more capacitors than the one it replaces. It contains about 175 assorted capacitors. Many are normal stock lines. Includes greencaps, ceramics, high voltage ceramics, polystyrene, electrolytics in RT and RB. Every pack includes one 1000µF 63V can electrolytic (Cat. RU-6743) worth $4.50 alone! At normal prices these capacitors wou ld cost over $80 1 cat. RE-6260 ON•v $10 LECT RC * SAVE $i ';:::======:::::' ..__!.:_~-S'(Jl))<'. ll(~)<'. )))<'. )) (,"J<'. J. ~ · ' -· • •• 0 VERBATIM DISC SELLOUT s f . XC-4722 3.5" DSHD XC-4726 XC-4727 5.25 ' DSOD 5.25" OSHD _ _ __ catalogue for fu ll details. Cat. KC-5071 " WAS $69 NOW SAVE $30 $39 _ _ _ _ _ _ __ JAYCAR WILL NOT BE UNDERSOLD ON GOODS OF THE SAME QUALITY ELECTRONICS ELECTRONICS ELECTRONI CS ELECTRONICS JAYCAR JAYCAR JAY CAR JAYCAR , ELECTRONICS ELECTRONICS ELECTRONICS ELECTRONICS JAYCAR JA YCAR JAYCAR JAYCAR ELECTRONICS ELECTRONICS ELECTRONICS ELECTRONICS JAYCAR JAYCAR JAYCAR JAYCAR ELECTRONICS ELECTRONICS ELECTROt, ICS ELECTRONICS JAYCAR JAYCAR JAY CAR JAYCAR ELECTRONICS ELECTRONICS ELECTRON ICS ELECTRON ICS JAYCAR JAYCAR JAYCAR JAYCAR _ELECTRONICS ELECTRONICS ELECTRONICS ELECTRONICS JAYCAR JAYCAR JAY CAR JAYCAR E E E f E E E E SJ AYCAR E l 'f, JAYCAR E S JAYCAR I· ,f. JAYCAR E f . IAYCAR I 'S JAYCAR f ;,, J/\ YC AR f :, JAYC1\H f 'S JAYCAR E ,S JAYCAR E S JAYCAR E ,S .JAYCAR E 'S J/\YCAH E ,:-, IAYC/\R f ,S JAYC AR f S ,I AYCAH E S J AYCAH E S ,JAYC AR f .c, JAYCAR I ·s .JAYC AR [ .~, IA(CAR f ,S IAYCAH f 'S JA YC AR [ S J/\YCAR f ,IAYCAR ;s r '[, 1/\YC An E ;,-, l~YCAR E ·s IA ,CARE ,:-, 1/IYCAR r _;sJ r, vc r,R r ·s J AYCA1i, ·s .JAYCAR [ 'i .1 1\YCAR F m:r,R 1 ;~, IAYCAR I s JA,CAR 1 ', :;:;g~:~; '.~ s JA ,cAR 1 ;s .JA YC:AH, ;~ ~~'.g~: i ;,, 1A, CAR E s .JA>CAR 1 -~ ~~~g~: ) ~•*~ 1111 --- ELECTRONICS ELECTRONICS ELECTRONICS tLf:CTRON ICS E E E :s JAYCAH ~l!IPl'~P!IPP""'ll"I■ . . . . . .!iii ____ E E E E :s JAYCAR E :s JAYC AR E f C ~s JA<CAR ,s :,y, CAH ~;_. ~~ r 1 :~~-ccAARR ,( -:::g~~i ~s JAYC AR E 'S .,AYCAR E ·s JA YCA R E ·;, .'AYCAR E ;~ ~ 'S ,S ,S ,S :s .::~g:: JAYCAR JAYCAR JAYCAR JA,CAfl JA\ CAR E F E t E 'S JAYCAR E :~3:~g::~ :~ ~:~g~: ~ 'S ,I AYCAR E 'S JAYCAR E . . ______________.., , '-----------------' '---- --- -------------' J JAYCAR JAYCAR JAYCAR JAYCAR ;, JAYC AR JAYCAR ;s JAYCAR .s JAYCAH ,S JAYCAR ,S JAYCAR :, JAYCAH : JAYCAR department for quantity prices 9.50 $39.50 $18.95 $14.95 $26.50 $19.50 E ;s NU A TURERS Contact our wholesale ave a ortune over normal prices. Not all types ~vailable at all stores. Limited quantities , at Type WAS NOW XC-4721 3.5" DSDO $26.50 $19.50 E E E E E E ,$ JAYCAR E $29.95 MA E ;~ J AYCAR E PRESENTS $39.95 NOVEMBER c E E E E E E E E E E 'E .JAYC AR E , S JAYCAR E 'S J AYCAR E ;s J AYCAR E ONE FOR CHRISTMAS $4 Ref: Silicon Chip March 1990 It's been replaced with a new model, but still works O.K. Short form kit. See 92 - ~~g;:~ ~~g~c ;s JAYCAR NUMBER ccoamt. pYITim-6e2nOtOanNycOelluRlarMphAoneL. LY 111\ 'l"l'l<'•. ll"• (~111\ll(,"l<'. ll fi1 f'I' ~· _ECTRC LECTRC LECTRC LECTRC LECTRC $32.95 $42.95 $19.95 $34.95 $1 10.00 $24.95 $34.50 $49.95 $99,00 $399.00 $329.00 $29.95 $84.95 $59.95 $89.50 $37.95 $129.95 $49.95 $17.95 $24.95 $27.95 $69.50 $13.95 $39.95 $22.95 $22.50 $14. 95 $27.50 $34.50 $29.50 $34.95 $11.95 $26.95 $45.00 $13.95 $37.95 $27.95 $12.95 The phone holder is like a hand and holds the phone. This "hand " can then be mounted very easily in different places in the car. It has a suction disc which allows the phone to be mounted on the drivers side window, from the cigarette lighter plug, or on the door. The phone holder fits any brand telephone and car, and there is virtually no instal lation. It is a quality, we ll made product that will BRAND NEW RUN OF MIXED CAPACITOR PACKS " PCVoice Recorder Talking Vollmeter Steam Sound Mk2 Solar Batt Charger TV Pattern Gen Baby Monitor Light Beam Relay Guitar Mixer - 4 Channel 12-240V 40W Inverter Power Supply 0-45V BA SOW+ SOW Stereo Amp Telephone CalI Timer Substation Intercom PSU Substation Intercom VHF TV Transmilter Thermostatic Switch Video Switcher 12-240V 15W Inverter Off Hook Telephone Timer 12VGel Baltery Charger NiCad Battery Discharger 240V 6/12V Gel Battery Charger 1.5V - 9V DC Converter 5A Drill Speed Control Mini Stereo Amp Si gnal Speaker protector NiCad battery charger ETl480 SOWamp module ETl480 1OOW amp mod ETl480 power supply 4 sector house alarm Mini FM transmitter Parametric equaliser Guitar preamp Solar Generator Workhorse amp RS true 232 interface FM minder bug ...J J :~g~:~ KC-5099 KC-5100 KC-5101 KC-5102 KC-5103 KC-5105 KC-5106 KC-5107 KC-5108 KC-5109 KC-5110 KC-511 1 KC-51 12 KC-511 3 KC-5114 KC-5115 KC-5116 KC-5117 KC-5118 KC-5119 KC-51 20 KC-5121 KC-5122 KC-5123 KC-5124 KE-4023 KE-4029 KE-4050 KE-4052 KE-4048 KE-4698 KE-4711 KE-4724 KE-4729 KE-4730 KM-3050 KM-3065 KM-3068 NOW SA"E A MASSIVE $90 '"'Y ~::::::::::::::::::::::::::::..- _ECTRC JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR ;s JAYCAR ,S JAYCAR S JAYCAR ,S JAYCAR ,S JAYCAR 'S JAYCAR ;s JAYCAR JAYCAR ;s JAYCAR 'S JAYCAH ;5 JAYCAR 'S JAYCAR ;,, JAYCAR ,S .IAYCAR ~t> JAYCAR ;s JAYCAR ;s JAYCAR ;s ,JAYCAR ~".'.__ L _::= = =::----------------------- .________ r SAVE 25% ON CELLULAR PHONE HOLDER NOW $3.50/l00mt _ECTRC _ECTRC LEC TRC LEC TRC ELECTRONICS ELECTRONIC S ELECTRONICS ELECTRONICS ELECTRONICS ELECTRON ICS ,S '.S MORE KITS PINK HOOK-UP WIRE! :~g~:~ JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR - :~g;:g N ICS NICS NICS NICS ,f\J_ICS JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JA YCAR JAYCAR SJAYCAR f:LECTRONICSJAYCAR ELECTRONICS JAYCAR ELEC rRON ICS JAYCAR ~ LE CTRONICS JAYCAR E E E E E SILICON CHIP AUSTRALIA'S BRIGHTEST ELECTRONICS MAGAZINE ENJOY THE WORLD OF ELECTRONICS & COMPUTERS EACH MONTH * Constructional Projects For The Enthusiast * The Serviceman's Log * Vintage Radio: Technology From The Past * Articles On Computers & Radio Remote Control * New Circuit Ideas & Techniques * Amateur Radio Projects & Features Subscribe today by phoning (02) 979 5644 & quoting your credit card number, or fill in the form below & fax it to (02) 979 6503. 0 New subscription - month to start._ _ _ _ _ _ _ __ RATES (please tick one) Australia Australia with binder(s)* Overseas airmail 2 years (24 issues) 0 $A84 0 $A105 0 $A240 0 Renewal - Sub. No.- - - - - 1 year (12 issues) Fax or mail coupon to: 0 $A42 0 $A53 0 $A120 Silicon Chip Publications Freepost 25 PO Box 139 Collaroy Beach 2097 *1 binder with 1-year subscription; 2 binders with 2-year subscription Your Name_ _ _ _ _ _ _ _ _ _ _ __ _ __ Signature (PLEASE PRINT) Address _ _ _ _ _ __ __ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ Postcode_ __ Card No. I I I Card expiry date_ _ _ / _ __ l~I~ 1 ~ 1111111111 N O VEMBER 1992 57 VINTAGE RADIO By JOHN HILL Converting a battery set to mains operation I recently completed a particular vintage radio project that had been at the back of my mind for quite some time. A fairly ambitious scheme, it involved the conversion of a battery receiver to 240V AC operation. The reason for such an insane idea is simple. I live in country Victoria and the area abounds with old battery receivers of various types. In some localities, SEC power was not available until the late 1960s, hence the abundance ofbattery sets. If these battery radios could be successfully c·onverted to mains operation, then such a conversion could be well worthwhile in some instances. Well, that was the theory anyway. There are two ways of going about such a conversion. One would be to build a power supply that would duplicate the receiver's battery requirements. Although the receiver would operate on mains power, it would still be a battery set in both design and performance. The alternative approach is a fullyfledged AC conversion whereby the set has additions such as a power transformer, rectifier valve, and a suitable complement of AC-type signal valves. An appropriate loudspeaker and output transformer would also be needed. I was to find out, however, that this approach was not without its problems and that it wasn't as easy as I originally thought. In theory, battery to AC conversion should not be that difficult and should be a straightforward project. After all, it only involves totally rebuilding about two thirds of the receiver and adding a power supply! The radio I converted was a 1935 4valve table model Radiola. I have two of these receivers and the idea was that if one ended up wrecked due to an unsuccessful experiment, then the other could still be retained as a battery set. That theory didn't work out as planned either. The project was nearly abandoned at an early stage because I could not remove the chosen chassis from its cabinet. Due to mouse infestation, the much piddled-on mounting bolts were well rusted into round brass nuts which were riveted to a turned-under flange at the bottom of the chassis. Three of the four bolts "squawked" their way free but the last one only turned the nut. The big hole A large hole had to be cut in the cabinet of the old Radiola to gain access to a rusted nut & bolt so that the chassis could be removed. Eventually, the bolt had to be cut with a hacksaw blade to free the chassis. 58 SILICON CHIP It was at this stage that I realised why there was a big hole in the bottom of the other cabinet. It hadn't been' chewed by rats as I had first assumed. Instead, it had been hacked in by some distraught serviceman so that he could obtain access to a problem brass nut that turned with the bolt. I did likewise but, despite the size of the hole and the use of a pair of locking pliers, I could not prevent the round nut from turning. Eventually, All this garbage didn't blow in during the last storm. Mouse infestation can cause serious problems when it comes to restoring old radio receivers. This photo shows one of the two 1935 Radiolas mentioned in the text. The chassis and knobs from this set were combined with the cabinet of the other. Both were originally batteryoperated receivers. adding an additional socket for the rectifier. Power transformer The coils & IF transformers were mounted underneath the original chassis, leaving the top of the chassis fairly bare. The dial drive mechanism was a friction type but this was converted to cord drive for more reliable operation. after cutting through the bolt with a hacksaw blade, the chassis was freed from its cabinet. The original Radiola circuit is typical of the early to mid-1930s. Although the tuning capacitor is a 3-gang type, the set does not have any radio frequency (RF) amplification. The extra tuning gang is for a preselector bandpass stage, which was a fairly common arrangement for a superhet of that vintage with a 175kHz intermediate frequency. The extra tuned stage was essential to avoid double spotting, a natural characteristic of the low IF. The valve complement of the bat- tery-powered Radiola was as follows: 1A6, 34, 32 and 33. The 33 output valve was one I had not encountered before and while it looks like a 1D4, it is a little different. According to the valve specification manual, the 33 has twice the output; ie, 0.7W as compared to 0.35W. Wow - what power! Replacement valves Suitable valves for the AC conversion were next on the list. The following were used: a 6A7 converter; a 6D6 IF amplifier; a 75 detector, AGC and first audio stage; a 42 output; and an 80 rectifier. Unfortunately, this meant changing every existing socket and A power transformer was the next item to be obtained and I was sure that I had an AWA type that just might fit the holes already punched in the chassis. Unfortunately, it was different and the mounting lugs did not match the hole positions. The next transformer to bt3 considered was an old "Red Line" . It had 5V and 6.3V filament windings and a 290V high-tension winding. It seemed a bit of an odd one but it would have to do. A rectangular hole was cut in the chassis to mount it and it was relatively easy to install. The 5V winding and the high-tension winding were connected to the appropriate type 80 valve socket pins. High tension filtering consisted of a 550Q resistor with appropriate electrolytics on either side. This produced a relatively hum-free DC supply of around 250V, under a 50mA load. Once into the conversion, it quickly became apparent that there would be only one complete receiver at the end of the project. An open oscillator coil and IF transformer set a pattern for stripping the other set for spare parts. What's more, one of the cabinets had been previously refurbished and the NOVEMBER 1992 59 stitution box, components of differing values can be switched in and out of circuit at the turn of a knob: IF stages The AC conversion resulted in the chassis being almost completely stripped. Note the mounting hole for the power transformer at front left. One of the end panels is from the other chassis. The IF transformers and the IF amplifier valve were the next to be wired and this was a straightforward job. What was to follow the IF stage was quite another matter, however. The AC version of this receiver uses a reflex circuit whereby a particular valve amplifies both radio frequency and audio frequency signals simultaneously. But no way was I going to invite trouble by converting to a reflex circuit! I had on hand a 5-valve Airzone circuit which uses a 6Q7 as a detector, AGC and first audio stage, ahead of a 6F6 output. This circuit was followed fairly closely and was the basis for the audio stages of the conversion. The general wiring layout underneath the chassis ended up a bit of a mess. There were connections on top of other connections, joins in the wiring and some of the components used were far from the 1935 originals. It would make any purist throw up his hands in horror, hence there is no under-chassis photograph accompanying this story. Next time, I will use a few more tag strips to make component mounting neater and more secure. One really needs to do a few of these AC conversions in order to know where best to arrange all the components. Dial mechanism This old "Red Line" power transformer worked in well with the receiver's requirements. The 80 rectifier valve is immediately behind the transformer. veneer had been rubbed down to paper thin. The plan was to retain the front end of the receiver as it was. The tuner, its associated coils and the IF transformers would remain as original. The leads to the 1A6 and the 34 valve sockets were disconnected and tagged with labels -Gl , GZ, A, etc. That way, they would be easy to reconnect to the new valves with their different socket connections. In the original wiring, the 1A6 pentagrid converter had no dropping resistors to supply the valve elements. The plate and screen grid voltages came straight from the B battery. 60 SILICON CHIP When using a 6A7 converter, grid 2 (anode grid) and grids 3 and 5 (screen) require dropping resistors from the HT rail so that they operate at the correct voltages. The old wiring cannot simply be reconnected to the new valve without these circuit modifications. A conversion of this nature requires such additions so that the substitute valves will function properly. One must be prepared to experiment a little, though. Without a suitable circuit diagram, one plays the trial and error game and a couple of substitution boxes (resi~tance and capacitance) are handy in this regard. By using a sub- Like many other receivers from the mid 1930s, the old Radiola had a friction drive dial mechanism that was chronically lacking in friction. But although I have repaired many friction drives in the past, this particular design is not an easy one to fix. For this reason, I tried a different app'r oach and converted the dial mechanism to cord drive. This involved making a new control shaft and fitting a dial drum to the tuning capacitor spindle. There were a few problems (mainly not enough room for the drum) but eventually it all went together and worked OK. When the time arrived for the big try out, it was a very exciting moment. But optimism soon turned to despair! The best the set could manage was a few squeals on some of the stronger stations. What could I expect RESURRECTION RADIO Vintage Wireless Specialists This rear view of the tuning capacitor shows the dial drum that was fitted in place of the original friction drive mechanism. Lack of space between the drum & the front plate of the tuning gang made the conversion difficult. Repairs .,.. Restoration - Sales Our skilled technicians offer QUALITY repairs and restoration. We also have a large stock of bakelite and timber radios fully restored and for SALE. Parts are available for the enthusiast, including over 900 valve types, high voltage capacitors, transformers , dial glasses, knobs, grille cloth etc. Circuit diagrams for most Australian makes and models. Send SAE for our catalog. WANTED: Valves, Radios, etc. Purchased for CASH Call in to our showroom at: 51 Chapel Street (PO Box 1116), Windsor, Vic 3181. Phone: (03) 529 5639; Fax (03) 510 4486 counter a few minor problems, and these must be tracked down and corrected. An additional resistor here and a capacitor there can make the difference between the receiver just working and working really well. Well that's the interesting part of the project finished. The cabinet work is all that remains to be done. It should be a good cabinet to work on, due to The finished battery-AC conversion - it's marvellous what a clean-up and a coat its flat ;;urfaces and small size, as comof paint can do. The speaker is an 8-inch AWA "permag" from the late 1930s. pared to a console cabinet. Note the depth of the chassis. Finally, a few words of advice. Battery to AC conversion is not as straightfrom such an outfit - part modified to blame for this and the substitution forward as one might think. If conoriginal and part Airzone? Time to boxes worked overtime. templating such a task, give it plenty The components causing most of of thought and try to pick a receiver give it a rest for a while. Tomorrow the problems were the resistors con- that's more suitable for conversion would be another day! After tracing through the web-like trolling the converter valve grids, couthan the one I chose. If it has octal mess of wiring, it transpired that I pling capacitors in the audio stages valves, it will be an advantage in that had overlooked something very im- (0.02µF seems a good all-round figall the valve sockets will be compatportant - there was no bypass capaci- ure) and the plate bypass capacitor on ible with whatever AC valves are used. the first audio valve. The Airzone cir- Using a proven circuit is also better tor on the IF amplifier's screen grid. cuit I was following used a 500pF than making up your own as you go. Adding this vital component made all the difference and the receiver burst mica bypass capacitor on the plate. Converting a battery receiver to AC This needed to be increased and a operation can be just as involved as into life. But although the conversion was value of 3300pF really smoothed out building a receiver from scratch. Unactually working, there were problems the harshness. less you are prepared for that, then When converting a battery set to . leave your battery set as you found it with harshness and distortion. Incorrect component values were mostly AC operation, one must expect to en- and enjoy it for what it is. SC NOVEMBER 1992 61 See in the dark with this low cost INF RED NI This infrared night viewer is simple to build. The viewer itself requires no assembly. All you have to do is assemble a battery powered high voltage supply and connect it to the viewer. You can then see in the night time to your heart's content. By BRANCO JUSTIC Ever wanted to see in the dark, when it's pitch black and you're sure that something sinister is lurking out there? Of course you have. Everyone would like to be able to see in the dark but humans just don't have this capability. Or at least they didn't until infrared night viewers became available. Infrared night viewers were first used by the military at the end of the second world war and were used extensively by the allied forces during the Vietnam war. These days, they are used by police forces around the world for crime detection and also for identifying marijuana crops hidden in otherwise apparently undisturbed bushland. Now you can have your own night viewer for quite a small outlay and with very little electronics assembly required. With the night viewer to be described here you will be able to see in the dark as clearly as in the day - it literally turns "night into day". There are two ways of using it. First, you can use it to observe night time scenes under moonlight. For example, you could use it to observe possums in trees. Possums can be very hard to see at night -you can often only see their shadow but with the night viewer you can see them as easily. Alternatively, you can use the night viewer in pitch darkness, together with a torch fitted with an infrared filter. This is the most dramatic demonstration. You can walk into a room in pitch darkness, turn on a torch fitted with an infrared filter and not be able to see a thing. Then if you look through the night viewer you will be able to see just as clearly as if the room was brightly lit. IR viewers such as this do have serious uses as well, such as examining the output of infrared lasers and IR LEDs in appliance remote controls, fibre optics, medical equipment and so on. By the way, you should never directly examine the output of an infrared laser or fibre optic cable. Shine it on to a flat surface and then you can safely observe the reflected IR light with the viewer. IR night viewers have been described in other magazines in the past but they have generally required some fairly specialised work in adapting lenses to an irifrared imager module. The unit described here requires none of this work. It looks just like a set of binoculars cut in half - which is effectively what it is. It has a length of shielded cable which must be connected to a suitable high voltage supply. So all you have to do is build the battery powered high voltage supply, connect it to the cable from the viewer and the project is complete. How infrared imagers work The image converter tube is powered by a high-voltage power supply (left) which develops about 13kV. This 13kV supply is derived using a single 9V battery & a special voltage multiplier circuit. 62 SILICON CHIP The special tube used in an infrared night viewer is sometimes referred to as an "image converter tube". It is a type of cathode ray tube but it does EHT TO VIEWER 680pF 3kV 680pF 3kV not have a filament. It has a cathode, an anode and a focus electrode. A lens system in front of .the tube focuses the infrared image onto the cathode face. The cathode is coated (on the inside of the glass) with a photoemissive material which responds mainly to infrared light in the region from 800 to 1200 nanometres but they also have some response in the visible light region. When the target materials are hit by infrared light, they emit electrons which are accelerated by the high voltage which is applied between the anode and cathode. The anode of the image converter tube is just like the screen of an oscilloscope. It is coated with a green phosphor which gives off light when it is hit by high velocity electrons. So what happens is that the invisible irifrared image which is focused onto + the cathode is convertT 9V I ed to a visible green ......I image on the anode screen. This image is then observed through the eyepiece lens of the viewer. The focus electrode on the image converter performs the same function as the focus electrode on any cathode ray tube such as an oscilloscope or television picture tube - it brings the image into focus. However, later model infrared image ·converter tubes such as the one used in this monocular viewer are of the prefocused type and therefore do not require an external focus electrode. Since the monocular viewer de- 680pF 3kV Fig.1: the circuit of the high voltage power supply uses a transistor blocking oscillator which produces about 1.3kV peak to peak at the transformer secondary. This is rectified by the Cockroft-Walton multiplier to produce about 13kV DC. The link in series with the 2.7kn resistor allows a small resistor to be added into circuit to adjust the high voltage output but this is not required for the tube used in this project. 680pF 3kV 680pF 3kV 680pF 3kV 680pF 3kV LINK (SEE TEXT) 680pF 3kV 01 1N914 2.7k 680pF 3kV + 10 FOCUS B 680pF 3kV EOC VIEWED FROM BELOW NIGHT-VIEWER POWER SUPPLY scribed here comes complete with lenses and is prefocused, all you have to do is build the power supply shown in Fig.1. This is essentially a one transistor blocking oscillator driving a Cockroft-Walton :voltage multiplier. Let's have a look at how the oscillator works first. It consists of a transis- · tor with its emitter connected to the centre-tap (point 4) of the transformer primary while its base is connected to one side of the primary (point 3) via a lOµF capacitor. The other side of the primary (point 1) is connected to the negative side of the 9V battery. When power is first applied, tranNovEMBER 1992 63 The voltage multiplier "stack" occupies most of the space on the power supply board. Keep all component leads short & don't handle the board after power has been applied - it can deliver a nasty shock. tor so that the base of the transistor is driven harder. The transformer core then saturates and transformer action ceases so that point 3 A special torch can be used to illuminate the collapses to 0V which turns target with infrared light when natural light off Q2. This also causes the levels are extremely low. Often though, lOµF capacitor to be dismoonlight or reflected skylight (in cities) will charged and so all action be sufficient to let you view objects with ceases. reasonable clarity. The lOµF capacitor must then charge up to the point sistor Ql obtains its base current via where the base of Ql again starts to diode Dl and the 120n resistor. The conduct and the cycle recommences. transistor conducts and applies 9V The result is a square wave signal between the centre-tap and the 0V with a frequency of about 1 lkHz apside of the transformer winding (ie, plied to the transformer primary and battery negative). Transformer action this is stepped up in the secondary to then causes +18V to appear at point 3 about 1300 volts peak to peak. This is and this "jacks up" the lOµF capaci- then rectified and stepped up in the The completed PC board is mounted "edge-on" inside a plastic utility case. Note the plastic barrier strip that's used to isolate the board from the battery & the power switch. 64 SILICON CHIP Cockroft-Walton multiplier stage to around 13,000 volts DC. Cockroft-Walton multiplier The Cockroft-Walton multiplier consists of 20 high voltage silicon diodes and associated high voltage capacitors. For those who wonder where this rectifier circuit came from, it has been around for a long time. It was first used to generate voltages as high as 200,000 volts to drive an atomic particle accelerator developed by Cockroft and Walton at Cambridge University in the 1930s. These days it can be used in a pressurised vessel containing silicon hexafluoride to develop voltages as high as two million volts. For everyday use, the CockroftWalton rectifier configuration is suitable for any application which .requires very high voltages at low currents. To understand how the CockroftWalton multiplier works, let us consider just the first few stages. Look first at the circuit consisting of diodes D2 and D3 and the two associated capacitors. The rest of the diodes and capacitors in the ladder above D3 can be ignored for the moment. In the first negative half cycle from the transformer, diode DZ conducts and charges the 680pF 3kV capacitor in series with the transformer secondary. In the next positive half cycle, the charged capacitor's voltage is added to the peak of the transformer voltage to cause diode D3 to conduct and charge up its associated capacitor to 1.3kV. So far then, what we have de- PARTS LIST Fig.2: the component wiring diagram for the PC board. Make sure that you get all the diode polarities correct otherwise the high voltage output will be reduced. scribed is the classic "halfwave voltage doubler" or "diode pump". Subsequent negative and positive half cyles from the transformer cause this step-up pumping action to continue so that each capacitor in the ladder is eventually charged to 1.3kV. After twenty or so cycles from the transformer, the voltage at the cathode of diode D21, at the top of the stack, reaches about 13kV DC. Also shown on the circuit of Fig.1 is a point marked "focus" at the junction of diodes D3 and D4. This is intended to supply the focus electrode on IR imager tubes that require it but, as previously mentioned, it is not relevant to this project. Construction The circuit of Fig.1 is built onto a PC board measuring 125 x 41mm. This is designed to fit into a standard plastic utility case measuring 130 x 70 x 45mm. The assembly of the PC board is a · repetitive job but it needs concentration otherwise you will find that some diodes are in the wrong way around. The high voltage diodes are BY509s which are normally potted into triplers for colour TV sets. The ferrite potcore transformer is supplied ready wound and the pins are marked. All you have to do insert it into the board and solder it. A battery snap needs to be soldered to the board and the job is all but finished . To finish the job, the board must be installed in the plastic case and the cable from the IR viewer connected to it. You will need to cut a square hole for the rocker switch (Sl) and drill a hole for a grommet to fit around the coax cable from the IR viewer. With these holes cut and drilled, fit the rocker switch to the case (it just snaps into place), then pass the cable from the IR viewer through the grommeted hole and solder it to the appropriate points on the PC board. This done, slide the PC board into place inside the case, as shown in one of the accompanying photographs . A sheet of 2mm thick plastic cut to size is then placed in slots above the PC board. This provides a separate compartment inside the case for the battery. This is necessary because the metal case of the battery must not come into physical contact with the high voltage capacitors. A piece of self-adhesive foam stuck to the bottom of the battery compartment will stop the battery from rattling around inside the case. The 9V battery should be an alkaline type for long life. A clip fitted to the lid of the case will allow you to fit the supply to your belt for convenient carrying. Testing With the battery fitted and the lid of the case screwed on, you are ready to try out the viewer. This can be done in a dimly lit room. Turn on the power -you should hear a high pitched w histle (provided you can hear 1 lkHz) from the inverte'r - and then look through the viewer. You should see a greenish image. Try focussing the image for increased clarity. And now for the pitch dark test. While objects such as human bodies do emit infrared radiation, the wavelengths are too long to be observed WARNING! This project generates an output voltage of 13kV & is capable of delivering a nasty shock. Always make sure that the capacitors have discharged before handling the board after switching off the power & never handle the board while power is applied. 1 monocular IR viewer assembly 1 plastic case, 130 x 70 x 45mm 1 PC board, 125 x 41 mm 1 sheet of 2mm thick plastic, 125 x 41 mm (insulating panel) 1 prewound potcore transformer 1 belt clip (with adhesive back} 1 9V alkaline battery 1 battery snap connector 1 rocker switch (S 1) Semiconductors 1 2N2219A NPN transistor (01) 1 1N914, 1N4148 diode (D1) 20 BUY509 high voltage diodes (02-D21) Capacitors 2 10µF 16VW PC electrolytic 20 680pF 3kV ceramic disc Resistors (0.25W, 5%) 1 2:?kQ 1 1kQ 1 120Q Where to buy the kit The complete kit for this project, including monocular IR viewer, parts for the high voltage power supply and 75mm infrared filter, is available from Oatley Electronics, PO Box 89, Oatley, NSW 2223. Phone (02) 579 4985. The price is $279 plus $6 for packing & postage. Oatley Electronics can also supply the power supply separately and other types of IR image converter tubes. Note: copyright of the PC board associated with this project is retained by Oatley Electronics. with the night viewer. So in a pitch dark room it is unlikely that you will see anything at all. In order to see with the IR viewer, you will need an infrared torch. "Where do I get that?" you might ask. The answer is that you will fit a supplieq infrared filter to a standard torch and that will do the job admirably. From then on, you really will be able to see in the dark. Just one thing though; after you have finished playing around in the dark, don't forget to turn off your newly acquired torch. Since you can't see the infrared beam it emits, it is all too easy to forget to turn it off. SC NOVEMBER 1992 65 AMATEUR RADIO BY GARRY CRATT, VK2YBX A PLL demodul-ator for FM • amateur receivers The use of a phase locked loop to demodulate FM signals is largely overlooked in conventional receiver designs, which normally use quadrature detectors.·By comparison, a PLL FM detector can be simpler, cheaper and easier to align. To understand why a PLL is such a good FM detector, it is necessary to first know how such a circuit operates. The basic PLL concept has been known and widely used since 1922. Since that time, PLLs have been used in instrumentation, -space telemetry, and many other applications requiring a high degree of noise immunity and narrow bandwidth. PLL block diagram A block diagram of a PLL is shown in Fig.1. Phase locked loops operate by matching their internal oscillator frequency to that of an input signal, Fin• In the "locked" condition, any variation in the input frequency appears as a phase change between Fin and the internal oscillator frequency. This phase shift acts as an error signal which causes a change in the internal oscillator frequency to "track" the input frequency. The action of locking onto the phase difference between Fin PHASE COMPARATOR and the local oscillator frequency is the basis of the name, "phase locked loop". Conventional circuitry for the reception of FM signals involves the use of a quadrature detector, such as the ever popular MC3357 and its derivatives. But although such circuits provide good performance, they invariably require the use of an external oscillator or, at the very least, a crystal to mix to a (lower) frequency before detection takes place. In addition, the bandwidth of such a circuit must be set by an external filter, incurring additional costs and complexity. In short, such circuits may be suited to mass production but they cannot easily be duplicated on the kitchen table. PLL advantages A PLL circuit has significant advantages over the quadrature detector as far as complexity is concerned. The LOW-PASS FILTER VOLTAGE CONTROLLED OSCILLATOR Fig.1: this is the block diagram for a phase lock loop (PLL). The phase comparator produces the error signal to control the oscillator. This configuration is widely used in both digital and analog circuits. 66 SILICON CHIP frequency range over which the PLL operates is controlled by a single DC voltage which sets the centre frequency. No external filter is required to produce an operational circuit. The NE564 PLL featured in this article can be configured to "detect" at input frequencies of up to 50MHz without external mixers. Hence, it is ideally suited for operation at the intermediate frequencies (IF) used in typical VHF or UHF transceivers; ie, 10.7MHz, 21.4MHz and 45MHz. Practical PLL detector In fact, a complete IF strip can be built using less than 20 passive components, with frequency adjustment controlled by a single trimmer capacitor. Fig.2 shows our circuit for a 10. 7MHz PLL detector. The input signal is fed to pin 6 of the NE564 and the audio output is produced at pin 14. Loop filtering is provided by the network attached to pins 4 and 5, while the oscillator frequency is set by the capacitance between pins 12 and 13. Apart from DC connections to pins 1, 3, 9 & 10, the only other control required is the "bandwidth" control, and this is provided by the lOkQ trimpot (VRl) feeding pin 2 of the PLL. As with all FM communications systems, use is.made of pre-emphasis and the RC network at pin 14 performs the appropriate de-emphasis. The entire circuit is designed to operate from 5V, although it can be run from 12V by changing the value of the lkQ resistor feeding pins 3 and 9 to 4700 and adding a 220n resistor in the DC feed to pin 10. The layout of the circuit is not critical at 10. 7MHz, although more care ...---------~+SV VR1 10k 1k ~--- 3 9 1 10 RF INPUT .0022 14 IC1 NE584 1k AUDIO OUTPUT 39k .0022+ .022! 8 4 22011 22011 .0022+ .0022+ ":' Fig.2: this circuit is intended to act as a demodulator following a 10.7MHz IF stage in an FM receiver. It requires virtually no alignment and is easy to build . Silicon Chip Binders 13 12 39pf VC1 0-20pf should be taken if you wish to operate the circuit at 50MHz, particularly regarding the length of component leads. At this frequency, it's important that component leads be kept short. Alignment Alignment is easy and requires only a frequency counter. The local oscillator frequency (and hence the detection frequency) can be measured at either pin 12 or 13, both of which are connected to the internal VCO circuit. Hence, to set up the PLL for operation at 10.7MHz, you simply adjust trimmer capacitor VC1 while measuring the frequency. To calculate the frequency of the VCO for a given capacitance, the following formula should be used: f0 = 1/[22Rc(C1 + Cs)l where Re is an internal 100n resistor, C1 is the external frequency setting capacitor, and Cs is stray capacitance. Comprehensive applications notes and data on the NE564 are provided in the Signetics Linear Manual, Volume 1: Communications, 1987. SC These beautifully-made binders will protect your copies of SILICON CHIP. They are made from a distinctive 2-tone green vinyl & will look great on your bookshelf. Price: $A 11 .95 plus $3 p&p each (NZ $6 p&p). Send your order to: Silicon Chip Publications PO Box 139 · Collaroy Beach 2097 Or fax (02) 979 6503; or ring (02) 979 5644 & quote your credit card number. 1 IAN J. TRUSCOTT S ELECTRONIC WORLD 30 Lacey Street, Croydon 3136 . Phone: (03) 723 3344. Fax: (03) 725 9443. Now also at: 200 Smith Street, Collingwood. Phone: (03) 419 2808. Mail and Credit Card Orders Welcome We now have a range of 5,6,8,9 & 1O pin Ask about our range of E.A.O. precision resistor networks and a comprehensive push button switches, motor start range of micra's and eproms at ridiculous capacitors and Beckman Industrial prices. Quote this ad and receive another multimeters. 5% discount. $16.80ea. 27C010-15 1 meg eprom 150ns ....... $8.l0ea. SAB8031 P Romless Micro ........ $2.50ea. MAB8049H Romless Micro ....... $2.50ea. 62256-LP S-Ram .. ................... $9.75ea. 41256 D-Ram ................................. $2.60ea. 27C020-15 2 meg eprom 150ns.... .~t1ii!ter $119 $10.00 ea. 3mw Laser Tube & inverter $99.00 ea. 6 volt 1 watt Solar Panels Infra Red Night Viewing Monocular (kit) $269.00. COMPONENT PHONE ORDER HOTLINE (03) 723 3344 NOVEMBER 1992 67 I PRODUCT SHOWCASE I measurement ranges. Alternatively, it can be configured for custom setups, using 10 save/recall states. A variety of test leads is available in the optional HP 16338A test lead kit which permits easy testing of batteries, cables, PC boards, connectors, switches and contacts. The HP 4338A has built-in HP-IB and handler interfaces for fast control of testing. It also has a comparator function for making decisions automatically for rapid results. · The HP 4338A milliohm meter is priced at $5000 while the HP 16338A test lead kit is listed at $1150. For further information, contact Hewlett Packard Australia Ltd. Phone (008) 033 821. High performance milliohm meter Hewlett-Packard has released the HP 4338A milliohm meter which offers a test measurement range from 10 microhms to lO0kQ; a 5-digit resolution for five measurement parameters; a four-terminal pair and short-correc' New·car CD player from Panasonic Those in the market for a new car sound system will be interested in the CQ-DP37 radio/compact disc player which has just been released by Panasonic. Power output from the CQ-DP37 is listed as 4 x 20W while the new "sound" feature allows the listener 68 SILICON CHIP tion function that minimises errors introduced into the test by fixtures , cables and switch parasites; and a basic accuracy of 0.4%. Instead of using a high-current source, the HP 4338A uses a lkHz test signal clamped at 20 millivolts to perform dry-contact testing. Operators can select current-source and voltage Shorted turns tester for TV servicemen , ··----~ . ., ,-:' 1 \,i i to program his/her preference for bass and treble. The new CD player has 32 times oversampling for excellent sound quality. A quick release bracket allows the unit to be removed and taken with you when you leave the car. The recommended retail price is $699. For further information, contact Panasonic Australia on (02) 986 7400. This handy little tester can save a lot of time, money and frustration by allowing suspect transformers to be tested. This means that unnecessary changing of transformers in TV repair work can be avoided. The unit will test for shorted turns as well as indicating open circuit and short circuit windings. As well as conventional transformers, it can be used to test EHT transformers (including those with triplers), as well as the vertical and horizontal windings of deflection yokes. Using the tester is quite simple - just turn it on by rotating the switch knob and then turn it clockwise until the meter indicates about 40 milliamperes. You then connect the winding of the transformer. According to the instructions, a good transformer will cause the meter reading to increase while a faulty unit will cause it to reduce or drop back to zero. The procedure is a little different when testing yokes and checking for shorts on line output transformers but again, it can be a boon in removing these components from the suspect list. The unit is available at a cost of $78 including sales tax. For more information, contact the manufacturer, J.V. Tuners, 216 Canterbury Road, Revesby NSW 2212. Phone (02) 774 1154. CCD colour camera for low light conditions A new colour CCD camera from Philips is able to produce good colour images regardless of lighting conditions. The LDH 0801/20 has high resolution and sensitivity and is suitable for safety and security applications where previously only monochrome cameras could be used. With a sensitivity enabling good colour pictures below the 1 lux level, the LDH 0801/20 overcomes the problem of picture-degrading noise at low light levels without sacrificing the colour of the image. This represents a breakthrough in its field and allows differentiation between objects and their background, even when the contrast is extremely low. The shutter sensitivity control (SSC) automatically selects a shutter speed to match ambient light conditions, which means that manual iris lenses can be fitted for virtually all indoor applications. Standard auto iris lenses are generally utilised in more demanding outdoor situations. Enhancement circuitry accentuates the picture detail both horizontally and vertically. New turbo card & data saver Astec's newly released Turbostart Card is an internal full-length card that provides full protection against loss of data due to breaks in mains power, including brownouts. The Turbostart Card and software package can be interfaced with IBM and compatible p ersonal computer systems, both of which are user installable. The card itself utilises just one slot when mounted adjacent to a half-length card. When mains power is lost or fluctuations occur, the Turbostart Card saves all memory to the system's hard disc, then parks the drive in an orderly manner and shuts down the computer. When power is restored, the automatic resumption feature will restore the system, permitting the session to be continued from precisely the same point at which the power loss occurred. For more information, contact Eltec Australia Pty Ltd, Level 7, 91 Phillip St, Parramatta, NSW 2150. Phone (02) 893 1800. For further information, contact Philips Scientific & Industrial, 25-27 Paul St, North Ryde, NSW 2113. Phone (02) 888 8222 . Genius HiPoint trackball for laptop PCs Genius Australia has released a mini trackball mouse for a variety oflaptop, notebook and portable PCs. The onebutton pointing device has 200dpi resolution and reliable opto-mechanical technology. The HiPoint can be attached to any convenient position. Its output orientation can then be changed using a graphics menu that's included in the package. You just roll the trackball in the direction that naturally serves as "up" and the system automatically sets itself to the user's choice. HiPoint's anti-slip bottom ensures a firm position, even when used on a desktop as a conventional trackball mouse. The device also features a breakaway clamp mechanism that prevents damage to delicate keyboards. The mouse mechanism is fully compatible with Microsoft and other popular brands. The HiPoint mouse sells for $131 and comes complete with 9-25 pin and 9-6· pin PS/2 adaptors, 1500mm extension cable, different size clips and clamp, Genius Mouse Driver and carrying case. It operates on DOS, Windows and PS/2 compatible computers. For further information , contact Genius Australia, 4 Briar St, Fulham Gardens, SA 5024. Phone (08) 356 7337. NOV E MBER 1992 69 110V isolation transformer New Scope soldering stations A new range of soldering stations incorporating the latest Japanese element technology has been released by Scope Laboratories. Designated the PX-1 and PC-lE, they feature a 75W tungsten/zirconium element. This is claimed to provide faster heat recovery after use, super low current leakage and extended element life. For further information, contact Scope Laboratories. Phone (03) 338 1566. Digital vernier micrometer The micrometer and vernier calliper are the two instruments commonly used for making precise measurements of physical dimensions. The micrometer is perhaps the easiest to use but the vernier calliper is more flexible since it can measure both inside and outside dimensions, as well as depth. The only problem is that many people have trouble reading the scale of vernier callipers. This problem is neatly solved by using a digital vernier calliper which has a liquid crystal display, such as the Digilog model from Dick Smith Electronics. It measures dimensions up to slightly more than 150mm (6 inches) and has a 5-digit LCD. Perhaps this instrument should now be called simply a digital calliper since the vernier scale is not used. Instead, the instrument uses a "non-contact linear cap measuring system", according to the instruction leaflet. We interpret this to mean that the unit reads its position along the scale by means of a digital bargraph with capacitive pickup. Whatever the method, it works very well. Claimed accuracy is ±0.03mm, while resolution of the 5-digit readout 70 SILICON CHIP is .0lmm. There are two buttons on the sliding portion, one to change the measuring mode from millimetres to inches (or back again) and one to zero the instrument at any portion along the scale. This is very handy when measuring deviation in dimensions from a specified figure - something you can't easily do with a conventional vernier calliper. There is no on-off switch. Instead, you close the callipers and the readout extinguishes after four minutes. Opening the jaws turns the display back on and the instrument can be used immediately. The display is powered from a single silver oxide 1.5V cell with a claimed life of 12 months in continuous use. End of battery life is indicated by a flashing display. The Digilog digital callipers are available from all Dick Smith Electronics stores at $169 (Cat No Q-1412). Many people come back from an overseas trip with audio, video or computer equipment which will only run at 110V. They get caught. But all is not lost and some of this equipment will run quite happily via a 110V isolation transformer. Pictured is one of a range of 110V isolation transformers manufactured by Harbuch Electronics. All are based on the company's toroidal transformers and thus they are compact and have a low residual hum field. Units are available with ratings of 60VA, 120VA, 300VA, 500VA and 625VA. The units up to 300VA are all housed in the same size case, measuring 125 x 75 x 185mm. The 300VA model will probably meet most needs and it sells for $127.50 plus sales tax. For further information, contact Harbuch Electronics, Pty Ltd, 90 George St, Hornsby NSW 2077. Phone (02) 476 5854. Fax (02) 476 3231. Optical drive with hard drive performance Pinnacle Micro Systems of Irvine, California, has introduced the PMO650, a rewriteable optical drive of 650 megabytes capacity. Its performance is claimed to be the fastest currently available and to rival that of many hard drives. The PMO-650 can replace existing hard drives for general data storage or can be used for vertical applications such as digital audio , digital video or multimedia. The unit is a plug-andplay optical drive that is recognised by Unix operating systems as a standard removable hard drive. Unix commands such as mount, unmount and format can be used to access the drive. For further information contact Elmeasco Instruments, 18 Hilly St, Mortlake, NSW 2137. Phone (02) 736 2888. PCB and SCHEMATIC CAD :----- -~ i I,,_ l · ···---· ---·::t__~ / TV IF AMPLIFIER ,._ . • ~~~~- U,., ~ provides recording speeds of 20Mb/ minute. It has received endorsement from numerous computer companies including Meridian Data, Digital, Young Minds and Optical Media International. Platforms supported include MS-DOS, Unix, Apple and Novell networks. According to Philips, the unit will make desktop CD-ROM publishing a reality for many corporate, government and educational bodies. It has a list price of $9750. For further information, contact Philips Components, 34 Waterloo Rd, North Ryde , NSW 2113. Phone (02) 805 4455. CD ROM ·recorder for professional use Philips Components has released an optical disc recorder that can make one-off copies of all CD formats - CDROM(XA), photo CD, CD-I and audio CD. The unit is the first CD recordable double speed drive on the market and f ---- -------- -- -l t.:l! :J! -·· " =.: : I IIT'nllll lltllll l lltllllllltlllltll l llllllll<I J.fS, l,l"Nlltllllll•.,R • t.J EASY-PC ;,,_u,onix i~~:i~t ~./ • Runs on PC/XT/AT/286/386 with Hercules, CGA, EGA or VGA. DM25lO Mtx:NL~}(h ., - Wfl/TEMP r-?A . ---&:;JEJ. AflM • • • Design Single sided, Double sided and Multilayer boards CJ.1? L/ ., . ., . e N "~-'i,lli ~ 1 ' -~ "", . . ·'<:r;:•/·;~~~:;:;c"'f' • Provides Surface Mount support • Standard. output includes Dot Matrix/Laser/Inkjet printers, Pen Plotters, Photo-plotters and NC Drill • Award winning EASY-PC is in use in over 12,000 installations in 70 Countries World-Wide • Superbly Easy to use • Not Copy Protected Options: • ~000 piece Schematic symbol library Benchtop DMMs from Tektronix Tektronix Australia has released the DM2510 and DM2510G Autoranging Digital Multimeters (DMMs). Designed for benchtop use, the DM2510 and DM2510G feature full programmability with 41/z-digitaccuracy, an integral power supply and autoranging or manual operation. The TM2500 series provide features and accuracy usually found only in higher priced instruments. Both products offer voltage, current or resistance measurements; true RMS AC volts measurements (200mV to 500V range); dB calculation; temperature measurements; DC volts from 200mV to 1000V with 0.03 % accuracy; and DC amps from lO0µA to 10A with 0.06% accuracy. For further information, contact Tektronix, 80 Waterloo Rd, North Ryde, NSW 2113. Phone (02) 888 7066. • Surface Mount symbol library • Gerber Import facility For full .info 'phone, fax or write: BTC PO BOX432 GARBUTT 4814 QLD. PH (077) 21 5299 FAX (077) 21 5930 N OV EMBER 1992 71 SILICON CHIP PRODUCT REVIEW More circuit software from Breakthrough Computers Last month, we looked at the ANALYSER III circuit design software and now we take a look at the digital half, the PULSAR digital circuit simulator. These packages run in the same manner - once you've learnt to drive one, the other is just as easy. PULSAR has a simulation speed of over 1000 gate changes per second and can pick out glitches in a circuit down to 1 picosecond. To program a circuit, you simply enter a netlist similar to that used in the many SPICE programs that are around. PULSAR then produces a screen display of all output lines over any time period from microseconds to hours. As before, the package is very easy to follow and the well-written manual has screen shots showing you exactly what happ ens. PULSAR expands as you go, allowing you to add new logic ICs and their pinouts and then combine them to produce modules, which can be linked together. This makes it easier when use you the same circuit block often. You can also use netlists generated by EASYPC's schematic program (another package from this company, reviewed below), to save more time. If you have problems generating the netlist (ie , parts list), the manual gives examples on how to do this, as well as a comprehensive listing of TTL and CMOS ICs and their printouts. Once you have the circuit's outputs displayed on the screen, you can print it either to file, to a 9 or 24-pin printer, Cont i9,,1rat ion 0.-r;ator ~1-..r File :CtJUNTDCO .NET OJ'B.IMex :8 FFEF Libniri• EASY-PC PRL"IIl!D CIRC:IJIT ROAJID LAYOIJT , AND ClRC'.UIT DIAGRAM DRAUGHTING PROGRAM IIY NumlterOne or to a HPGL LaserJet II compatible printer. PULSAR will run on anything compatible with an XT to a 486 and requires a minimum of 512Kb RAM, MS-DOS 3.2 or later. It will also drive EGA or VGA displays. EASY-PC CAD package AJ1d now we will have a look at I DOI IIESETO 110'\ll I=~~;~§:~=~E~~~~~~~~~E;~E:~=~~: ENABLELca, _ 72 1--- -- - . . . - - - - - ____ SILIC ON CHIP Ltd..1 Fig.1: reproduced from the manual, this diagram shows how the program displays waveforms from a typical digital circuit, including glitches down to one picosecond. EASY-PC, a well-known CAD package which has been around for-some time but not readily available in Australia until now. It comes very well packaged with a British Design Award label proudly displayed on the front cover. The package contains one 3.5-inch and two 5.25-inch discs and, once again, an easy-to-follow and well-written manual. The beauty ofEASY-PC is that you can do your PC board layouts and draw your circuit diagrams in the one package. Not only that but it also comes with a comprehensive symbols library the TTL library alone contains symbols for over 400 ICs. Also available is a 500 symbol surface mount library, so this is no lightweight CAD package. It Cclil produce boards up to about 43cm s·quare with up to 1500 ICs, as well as 5000 tracks on up to eight layers. You can also choose from any of 128 different track widths and pad sizes from 0.002-inch up to 0.5-inch. So what's it like to use? Well, it's quite easy, with pull-down menus in case you get lost as well as keyboard function control if you don't wish to use the mouse all the time. The schematic feature of the program was also quite good and uses the same procedure as that used for producing PC board layouts, so you don't need to learn two methods. EASY-PC will also run on anything from an XT to 486 with a minimum of 512Kb RAM and can drive Hercules, CGA, EGA and VGA displays. It also contains a number of printer and plotter drivers for 9 and 24-dot matrix printers, HPGL pen-plotters, Gerber photo-plotters and HPGL LaserJet II compatible printers. EASY-PC is priced at only $275, which is a great deal less than many other CAD packages that are currently available. The PULSAR digital circuit simulator is priced at $540. For further information on these packages, contact the Australian distributors, Breakthrough Computers, PO Box 432, Garbutt, Qld 4814. Phone (077) 21 5299 or Fax (077) 21 5930. SC ..iO LAR PANEL GIVEAWAY Brand new 6 volt 1 watt amorphous solar panels, 150m x 150mm, wi ll deliver one Watt whilst charging 6-BV batteries. Two of these in series make a great 12V battery maintainer/charger. Have weather protection , and terminating clips are provided. Incredible pricing: s10 ea or 10 for $85 CRYSTAL OSC ILLATOR MODULES LARGE LCD DISPLAY MODULE LASER TUBE BARGAIN If you always wanted a laser tub but couldn't afford it how about a BRAND NEW small 0.2-0.5 mW tube for an . incredible Brand new large Hitachi LM21 5XB display, as used in some laptop computers. Yellow-green LCD reflective type, 480 X 128 dot display, effective display area of 242 X 69 mm, has 14 LSI !Cs mounted on the rear of the PCB. Includes four pages of data sheets. Limited stock at a small fraction of their $ real value. 39 ea. Controller IC (LSI-surface mount) available $5 ea. Data sheets (28 pages): $3. $J!t I.A . BINOCULAR VIEWER GEL BATTERIES Similar to the ones used in computers. 5V DC in at approx. 30mA. TTL logic level clock output. Available in four frequencies: 4, 20, 40 and 50 MHz. Famous "high-spec" Gates brand dual cell batteries, enclosed in a plastic moulding. 4V-5AHr per pack. Connect 3 packs in series to obtain a 12V/5AHr battery. Brand new, fresh stock, fully charged. Limited stocks at a giveaway price of: s7 $ are hermetically sealed. ea or 5 for $25 LtGtH MOTION DETECTOR Small PCB assembly based on a ULN2232 IC. This device has a built in light detector, filters, timer, narrow angle lens, and even a siren driver circuit that can drive an external speaker. Will detect humans crossing a narrow corridor at distances up to 3 metres. Much higher ranges are possible if the detector is illuminated by a remote visible or IR light source. Can be used at very low light levels, and even in total darkness with IR LED. Full information provided. The IC only is worth $16' Our price for the assembly is: $6 ea. or 5 for $25 18 or 3 packs for $45 VISIBLE LASER DIODE POINTER-PEN Improve and enhance all deg. steps, coil resistance ONLY High quality military binocular IR viewer. Self powered, and originally intended to be mounted adjustable from 1 metre to infinity. Requires some IR illumination. Powered by one single 1.5V battery. Original fibreglass carry case provided. Limited stock. ON SPECIAL ssoo $12 620 INFRA RED NIGHT VIEWER ea. We have accumulated a good supply of some new and used tubes and heads with powers in the range of 0.5-2 mW. These may have some small beam geometry problems. The tubes and the heads are guaranteed for one year! You can purchase one of these tubes/heads with our Universal 12V laser inverter kits for the price of the inverter only! s79 Brand .matrix Isp ays. er size is 120 X 265mm. Buil drivers. 4 bit TTL interface required for signal and po ( +5V, -12V) . Capable of displaying characters, gra patterns, etc. 28 page information included. LIMITED SUPPLY AT A SMALL FRACTION OF THEIR REAL PRICE! Note that an LSI surface display is available. This I generator and many other with 8080 and 6800 MPU' elsewhere for about $35, information upon request. TO CLEAR Stereo Headphones. Similar to ones used for stereo "Walkmans" at $2 a pair. TV Antenna. Dual telescopic TV antenna similar to ones used on many portable TVs. At $3 each. J} These matching components were removed from brand new IR tank viewers. They include a large low light objective lens, a large prefocussed IR image converter tube, a power supply or power supply kit to suit the tube and an adjustable eyepiece assembly. Make a professional infra red night viewer at_a ridiculous price of: For the set. $199 total of 14 connections are EHT GENERA TOR PROJECTION LENS Brand new large precision projection lenses, which were originally intended for big scree n TV projection systems. Will project images at close proximity, onto walls and screens and lt has adjustable focussing. Main body has a diameter of 117mm and is 107mm long . The whole assembly can be easily unscrewed to obtain three very large lenses: two plastic and one glass. The basis of the cheapest large magnifier or projection system? Experimenters delight at ONLY $28 LASER GUNSIGHT PIEZO SIREN incredible price! ON SPECIAL AT s1so VISIBLE LASER DIODE BARGAIN LG>G>K Brand new 5mW-670nM laser diode, plus a collimating lens, plus a driver kit, plus instructions. Special introductory price for a short time only. BE QUICK SSS KIT SPECIALS ! s259 ll We have a limited supply of some 18mm fibre optically coupled 2nd generation image intensifier tubes. These are ex.military and may have some minor blemishes, but all produce'full gain. With low light lenses these will produce useful images with as little as starlight illumination. Car, also be IR assisted with IR LED's or low power torches, in rare situations where this may be required. The tubes require a 3V battery and a switch to make them operational. The viewer illustrated uses one of these tubes. It was constructed using some low cost plastic tubing and matching fittings for the case, a camera lens, and a low cost eyepiece. $ Plastic jewellers eyepieces can be used. FOR THE TUBE AND THE SPECIFICATION SHEET your presentations. Not a kit, but a complete commercial pen sized laser pointer at an THE CHEAPEST 5mW VISIBLE LASER DIODE EVER OFFERED A very small but comp lete IR telescope which only needs an EHT power supply, which is provided in kit form. PCB and all on board camp's only. Limited stock at a reduced special price. These are brand new units, main body has a diameter of 58mm and a height of 25mm. Will operate from 5V, has 7.5 : SECOND GENERATION TUBES 6.6 ohm and it is a two phase type. Six wires. on a helmet. Focus is These small TTL Quartz Crystal Oscillator modules STEPPER MOTORS Electron ic Key. Use it to activate door st rikers for entering buildings, car alarms, central locking , etc. The most secure key ever (see E.A. July '92). On special at $49.90 for two keys and one decoder kit. Stock up on this limited stock surplus item. Brand new, 6-12V (6V/50mA. 12V/150mA). Giveaway at: $6 ea or 5 for $25 NICAD BATTERY PACK A complete nicad battery power pack that was intended to be used in an emergency lighting application . Contains 17 " D" size 1.2V/4 AHr batteries which can be easily separated into individual cells. New packs in their original packing. $75 per pack UV PENS The writing of these pens is only visible under UV "Black Light". s2 ea or 5 for $18 Very small tube and inverter to suit; suit long range gunsights, laser pointers. Incredible value s1so at Includes tube, supply and ballast resistor Based on a brand new, very compact modern EHT flyback transformer which includes an EHT diode rectifier. We supply the transformer, a very simp le circuit, and the components to suit. All you need to make a very s imple EHT or DC or pulsed AC supply. Powered from 12V DC supply. Great for EHT experiments, EHT testing , plasma displays (large light bulbs can be used) etc. Total price for the transformer and the $ components ,s only: 17 Small black anodised metal body. Removable pressure switch. Vertical and horizontal adjust· ments. Battery life more than 10 hours continuous. SmW 670nM class IIIA laser. Range is about 150m, some would claim three times more. Shock tested to 2000g. One year warranty. ON SPECIAL AT $249 Price includes one rifle or pistol mount. Simplifying the Interphone telephone exchange The Interphone 10-station telephone exchange has created a lot of interest since it was published in the August & September 1992 issues. Since then though, one of our readers has pointed out that the circuit can be simplified with a saving of two ICs on each remote station board. When the Interphone was first designed by the author, Geoff Monegal, it was intended that each remote station board would be mounted in a small case near its associated extension phone. Subsequently, when it was presented ln SILICON CHIP, all the circuitry was housed in the one case. This means that there is now an opportunity to simply the circuit without prejudicing any of its functions. To explain the modification, we reproduce the remote station circuit on this page. A remote station board is required for each extension phone. The key components are IC9 (an MC14536 DTMF decoder chip) and IC10 (a 4028 1-of-10 decoder). IC9 and IC10 are there to decode the specific DTMF (dual-tone multi-frequency) code for each extension. As originally presented, the design specified that IC9 and IC10 were required on each extension board. However, one of our readers, Anthony Fouracre, of Tahmoor, NSW has Fig.1 (below): the remote station circuitry. IC9 & IC10 need only be installed on one board, since the same ICs can perform the DTMF decoding for all _extensions. +5VO-----------------------<I---------------6 4 16 3 10 1M IC9 MC1 45436 +50Vo-----~ 0.1 10 A 13 B 14 10k 12 C 11 D IC10 4028 2.2k 10k 1W 220pfJ .,. D20 + -:- PHONE ..,. ..,. STATION SET 022 1N914 -:- Off HOOKO-----------------------' 120k + 10 .,._ r-------•50V -:!:. 22k +5V RING .,. 01+ INTERPHONE REMOTE STATION 74 SILICON CHIP -: 010 -[ill]- I ---1u(;)~ Fig.2: this diagram shows the revised parts layout for a 3-station board. Note that IC9 & IC10 are only installed in one section. Flying links are then run from the decoded outputs of IC10 to the other stations. Two of these links are shown here, designated as A & B. o--CD-.....Jil.023 22k • • 06 •B •C 07 E• Il pointed out that only one MC14536 and one 4028 can do the DTMF decoding for all 10 extensions. All that needs to be done is to install IC9 and IC10 on one remote station board and then take the 10 decoded outputs from IC10 and wire each one to its corresponding D22 cathode on each remote station board. This is blindingly obvious once it is pointed out and comes under heading of "Why didn't we think of that?". Well, we didn't and we thank Anthony Fouracre for his suggestion. Wiring layout We have also reproduced the wiring layout of the remote station boards, i q I tf"' in Fig.2. This shows three remote stations on the one board. We have modified it to show just one MC14536 and one 4028 (ie, in the centre of the board). IC9, IC10 and all the associated components - ie, the 3.58MHz crystal, diodes D20 and D21, and various capacitors and resistors - have been omitted from the other two remote stations on the board. Flying links are then run from the 10 decoded outputs of IC10 to the other remote station circuits. Two of these are shown in Fig.2. If you are building the Interphone with 10 extensions, this simple modification means that you can save nine MC14536s, nine 4028s, nine 3.58MHz crystals, 18 diodes, 18 capacitors & 18 resistors. Some readers may be tempted to take this modification further and this possibility does exist. Consider that the base station board also features a 4028 and an MC14536 to decode the# and* buttons. This raises the possibility of running the four decoded data lines from that DTMF decoder chip to another 4028 IC to decode the 10 extensions. That could be done but there is the possibility that noise on the necessary ribbon cable might prejudice circuit operation. Our recommendation is to simply follow the modification to the remote station boards described above. SC YOU For many years you have probably looked at satellite TV systems and thought "one day" You can riow purchase the following K-band system for only: Here's what you gel: • A 1.6 metre prime focus dish antenna, complete with all the mounting hardware. • One super low-noise LNB (1.4d8 or better). • One Ku-band feedhorn and a magnetic signal polariser. • 30 metres of low-loss coaxial cable with a single pair control line. • lnfrared remote control pre programmed satellite receiver with selectable IF & audio bandwidth, polarity & digital readout. Your receiver is pre-programmed lo the popular OPTUS transponders via the internal memory. AV-COMM Pty Ltd, PO Box 225, Balgowlah NSW 2093. Ph: (02) 949 7417. Fax: (02) 949 7095. All items are available separately. Ask about our C-band LNBs, NTSC-to-PAL converters, video time date generators, FM2 &EPAL & Pay"TV hardware. r,-------------->{; I YES GARRY, please send me more information on K-band . Name: _ _ _ _ _ _ _ _ _ _ _ _ __ I satellile systems. I I Address _ _ _ _ _ _ _ _ _ __ __ : _ _ _ _ _ _ _ _ _ P'code: _ _ __ I Phone: - - -- - ~ - - -- - - - - ! ACN 002 1744 78 NOVEMBER 1992 75 Phone Your Order To Us Toll Free We guarantee our Jetservice Courier will deliver to your doo( faster than any other Australian supplier (including that local supplier just up the road). If we fail, I'll give you your money back plus $5.00 for your inconvenience. Mini Home PABX Telephone Exchange Kit (SC Aug/Sept '92) NEW KIT This great unit allows you to place calls on hold, intercom other I extensions. answer calls from any extension and transfer calls. It is expandable up to 10 extensions, and is compatible with all DTMF (touch tone) telephones. Operation is as !I; . simple as pressing '*' to place a call on hold , press the ex~ension_nu~ber (0-9) and the respective station rings. Once answered, you have a two way 1,· · · · . . . intercom, with which you can announce a call. To pi.ck _up the incom_ing c~II from . hold press'#'. A neat feature is that all extensions will ring when an ~nc~~ing call 1s placed on hold for 30 seconds sothat it won't be forgotten . The Basic kit Is complete with power supply, case and fac1l1t1es for 3 extensi ons. Extra extension boar~s al lo w expansion in multiples of 3. Simple operation, fantastic for ho me or small office. No more shouting from room to room. Not Auster Approved. l'111Jili!WI '':=:=:;::;:::;::::;:;i::;:.EJL.__.._"':':"-:---' K 1430 Basic Kit $189.oo K 1435 Expansion Board $79.95 3½ Digit LCD Panel Meter Kit (S.C. Sept '92) Ideal addition to power supplies, voltage meters, current meters etc. It can be calibrated to accuratel y read 2mV, 2V. 200V. Requires 9 volt power supply. Programmable decimal point. NEW 2528 $34 .95 Sub-Woofer Adaptor Kit (EA May '89) K Get an amazing bass improvement from your stereo system. This fantastic adaptor simply " samples" your stereo amp output and provides a single c hannel output to feed a separate subwoofer amp. Requires 12V AC or M 9020 plug pack. K 5560 $29 .95 2 Way Active Crossover 5250 Station Mod ule $7 4.95, K 5255 Power Supply $64.95 Ni-Cad Battery Drill Speed Controller Kit Discharger Kit ~~~~b~!pstp·::~ K Designed to rid your nicad batteries of the 'memory effect' and regain full recharge potential. It discharges your nicads correctly to enable a full recharge. Suits most battery packs. Great for mobile phones, battery drills, toys etc. 1640 $24 .95 Four Digit Combination Lock Kit . (SC Dec '90) K 1925 $44.50 KIT! K controller for 240V po wer too ls N including drills, IL power saws, " engravers etc . suitable for brushtype tools up to SA. Not suitable for globes or radiator heaters. 0 -r------- ;;...__.....;._ _ _ _T"""......,1.,;,;.::.::..:::.:.;:;;...__ _ This 4 Digit Combination Lock is bound to prove useful in many applications. Such as accessing alarm systems, electronic doors, ignition . killers or just about anything that comes to mind. Momentary or latched rela y output. This great new kit enables you to customize your sound system in your car or at home. The circuit simply connects between the audio source and the amplifiers. There are tw9 outputs, one for bass and another provides signal for the. upper range. us each amp is dedicated to a frequency range (i.e. one for bass, one for midrange and treble) . Because no passfve crossover is required in the speaker one per chan nel is require~ . Operates on+ and -15V rails. The result is a muc h better sound wit h less distortion. K (SC June/ Jul y '92) This multi-station headset intercom is designed to provide clear communication in high noise environments such as at race tracks and rock concerts. It is designed to operate with a headphone and mic co mbination. Each headset requires a station module. Stations are simply connected in a daisy-chain fashion. Up to 12 units (stations) can operate from the power supply. Features low noise circuitry and compares favourably to many commercial equivalents. Mics can be switched on continuously at one ti me for hands free operation of all stations. Also includes visual and audio call function. Ideally suited to our C 9055 headset/mic and the C 9070 noise attenuating Av iation Headset. Door Strike Apo/ogles Ideal for security access areas, thi s high quality lock will fit most door jams. Operates from 12V AC or DC. Ideally suited to K 1925 Combo Lock Kit . . In September & October ads we incorectly advertised a K 3301 Power Supply Option for $4.50 . This should read $29.50. ALTRONICS apo logises for the inconvenience. s4390$39.95 High Power Amplifier Modules Kit (SC Dec '87) All components, including o utput transisto rs mount on a single PCB. Suitabl e for high quality guitar amp, public address or in a high fidelity stereo amplifier. Kit includes ang led heatsink brack et, main heatsink and a in-built polyswitch for loudspeaker protection. Full specs available on request. $ 5140 100W Ve rsion $6j:l,efs NOW ON LY 55.oo K 5150 150W Version $9e,efs NOW ONLY $85.oo K LED Digital Tacho Kit 5570 $19.95 (SC Aug '91) This dig ital tac hometer will tell you how many revs your car's eng ine is doing. It works w ith all ignition systems and 4, 6 and 8 cyli nder cars. Indicates that 09900 RPM wit h a resolution of 100 RPM . PCB only. Digital Altimeter for Gliders This compact digital altimete r can display altitude up to 19,990 feet with 10 feet resolution . Accurate to better than 3.5 percent. A rnust for hang-gliders, ultralights etc. Operated on 9V battery . K 2580 $299.oo 1GHz Digital Frequency Meter Kit K 4320 (S.C. Nov '87 to Jan '88) Feature■: Professional mach ined and screen printed red perspex front panel, easy to a~semble and c~nstru_ct, no sp~cial t_oo ls required , bright Hewlett Pa cka rd 8 digit display, electronic switch latching, high performan ce IC's, high quality components Specifications: Operational Modes: --·· Period, freq to 10MHz, freq to 1GHz. Freq. Range: 10Hz-1GHz (1 .7GHz typical) in frequency mode; 10Hz2.5MHz (5MHz type) in period mode. Gating Times: o.o,, 0.1, 1 and 10 seconds (10MHz and 100MHz); 0.128, , 1.28, 12.8 and 128 sec (1GHz range). K 2515·$299 .00 ~ compares· ·, . pQlll!R Favourably to_ • commercial units COO""'"~ Low Cost Dual Tracking Supply Kit (SC Jan '88) Ideal for experimenting and prototyping with Memory, Logic and Op Amps Adjustable+ or - 18.SV at 1.7A, volt meter, floating ground , dropout indicator, load switch, compact sturdy "ABS" instrument case K 3325 .00 Fe ■ turea: $S 9 $31 .00 now In ,er,lce througho Inc ude Unl•erlltl••• Re,eerch E• Famous Labtech 20 Oscilloscope Get 240V AC from your car, truck or boat battery. The A_ltronics ran_ge includes an inverter for nearly every appllcat,on. Fantastic for camping, boating, farms and anywhere else 240V AC isn't available. Each size inverter is available in kit form or fully built and tested. The 300 and 600 Watt Inverters now feature new improved circuitry using multiple mosfet outputs making them even more reliable with a genuine 300 or 600 watt continuous This model is a dual trace 20MHz oscilloscope using a high brightness CRT. The vertical amplifiers have high sensitivity of 5mV/ div and ,' .·l a frequency characteristic response !j with smooth roll off exceeding 20MHz~ ' The TV sync signal operator circuit is provided to ensure stable observation of video signals. Triggering is obtained by sampling the AC power waveform, external waveform or power rating . Our latest model, the 1200 Watt Powerhouse offers excellent value for money and performance. It features crystal locked circuitry and a massive 2400 watt power surge making it ideal_for small fridges, vacuum cleaners, power tools etc. Any model an absolute necessity where 240V isn't avai lable. Call Altronlcs today for more information on freecall 008 999 007. 300 Watt K 6750 Kit Version $279 ' internally generated trigger. ;; K 6755 Built-up $379 Ideally suited to Q 0156 ( equired) . Superb quality C to 80 MHz Max 600 Olis DC Lead length prox 1.5m. 600 Wall 1 -•:• .,.. ~· .. \:··.1.:::p.::• a Mi j~.::.; . M~~ 4 9 ~ NIMROD Gas Soldering Iron Now you can solder anywhere with this new gas soldering iron. Feature,: See through gas chamber (no more guessing how much gas is left) • Built in ignition cap • Uses standard butane gas • Comes with _safety bench stand • Supplied with 2mm soldering tip and blow torch tip • Ad1ustable temperature from 400'C to 12000c • Can be easily refilled with standard butane lighter gas • Replacement tips are less than half price of some other brands. T 2455 Exhaust Port $6.50 REPLACEMENT TIPS - ALL $6.00 ea T 2451 Replacement 1mm Conical Tip T 2456 Hot Knife Tip $6.00 T 2452 Replacement 2mm Conical Tip T 2457 Hot Blower Tip $12.50 T 2453 Replacement 3mm Conical Tip T 2458 Blow Torch Tip $12.50 T 2454 Replacement 3mm Chisel Tip T 2448 Butane Gas Refill $6.95 I Car Voltage Adaptor This handy unit simply plugs into your car's cigarette lighter socket and presto! Gives you switchable 3, 4.5, 6, 7.5, 9 and 12V DC at up to SOOmA. Includes a range o( output plugs. Reversable polarity . .Great for pocket TVs, radios, portable CDs etc . As used in security systems, battery backup for computers, solar power systems etc ... Premium Grade Long Life S 50~9 S 5070 Logic Probe $37.so Probe Pulser $54.95 Our Top Selling j-. Digital Multimeter ~ •. .,1~ . With quality and features you would expect only on expensive meters the Q 1056 represents excellent value for money. 17 Ranges include DC and AC volts, resistance, diode check, DC current with 1.5V and 9V battery a 1056 t49_95 a 1057 Q 1067 Thermocouple to Suit $29.95 . a 1272 20MHz a 1280 50MHz Logic check. Q 1065 Carry Case to Suit $12.50 Turn 12V DC to 240V AC. This fantastic inverter will power lights, TV's tools, electric shavers and a whole host of other appliances. Great for camping, out in the bush and any place where 240V is not available. Featurea: Complete with over current circuit breaker • Fused 240V output • Built in panel meter to monitor output voltag_e • panel meter to monitor output voltage • Strong steel case and chassis $2 $29.95 $44.95 This fully featured meter offers performance and facilities which are normally only found on far more expensive meters. Features include DC and AC v, DC and AC current (up to 10A), transistor check, capacitance check (up to 20uF), resistance and continuity, frequency count, temperature via optional thermocouple ('C or °F) and high impact case just to mention a few. a 1064 t149.5o 300 Watt Economy · · inverter 12V/1.2AH Two models available. Both feature audio and visual 'hi' and 'low' indication, and TTL/CMOS -D - ·1 _ g_l_t_ a_l_E_n_g_1·_n_e _e_r_l_n_g ___.., compatibility: Deluxe version includes a logic pulser function making it even more versatile for •1meter fault finding, and a 50Hz logic probe. Economy Mult version includes 20MHz logic probe only. K 6770 Kit Version $499 K 6774 Built-up 12V Input $625 K 6775 Bui lt-up 24V Input S 5065 £ig,_.;;:;:::;:-"111111iiijjii,i;,i;;:;:=---.-;:;-;;;r.;:-iji;.;;j;;:~ ,, ~ -;; •·•· .. , ~ f<at> ~ -- 'j" -..-.- Carry Case To Suit $12.50 Flush/Surface Mount Alarm Paner -·With stylish compact good looks this alarm blends s_mooth ly into any residential or office decor by either flush mounting into the wall, or surface mount. 3 sectors include 24 hour panic/ fire, perimeter and internal which can ~e i.solate~ ena~Hng the ~larm to be armed at night with occupants inside whilst still protecting entries. Simple 4 digit access code for operation. See Altronics '92 catalogue for full details. S $119.oo 5490 Super Small PIA Alarm Power Su_pply Incorporates Pulse Count Triggering which virtually eliminates false alarms. Operates on 8-16V DC . Features: walk test LED, wide 12x12m detection, N.C. tamper switch, interfaces with most alarm panels. See AL TRON/GS '92 catalogue for full details. s 5302 Normally $}!f.oo This UPS (Uninterruptable Power Supply) will supply 12V at 1.2 Amps via its internal inbuilt sealed lead acid battery even when the mains has failed. Ideal for use with alarm system power supplies monitoring systems, warning systems etc . M 9090 $69,95 This Month $69.oo Siren Cover Weatherproof Horn Speaker Protects external siren from tampering, weather etc. Also ideal for . mounting strobe. Suits C 2015 horn speaker. Tamper switch available. S 5460 $28.95 10 watt, 8 ohm. Ideally suited to S 5460 siren cover and our alarm panels. Th is horn can s 5160 Tamper Switch $1.85 C 2015' Normally $ ~ This Month High Energy Siren . Absolutely ear . splitting SPL 120dB. Handy bracket for wall mounting etc. 12V 300mA. Ideal for industrial applications or alarm systems. Dlmenlfons: 100mm Diam. 125mm L. s 5177 Normally $ ~ 5 deliver in excess of 120dB when driven by an appropriate driver circuit. , • ' ' . · Alarm Strobes Uses Xenon Strobe tube for high energy flash. Output rate approx 1 per second . 12V DC, 320mA. Dimensions : 97mm diam, 50mm High. $ 12 .95 Amazing Nlcad Battery Bargain from $2.oo .. ~ u11 it1«<•,u,11'! WR At full specification premium quality. Good tor up to 1000 recharges. - , ~~,: . S 5020 S 5022 S 5023 10-24 $2.50 $7.oo $13.oo 1-9 $2.95 $8.oo $14.oo AA 500 MAH 'C' 1.8 AH 'D' 4AH Passive Infra-Red Flood Light Control ~~~~~~r S 5350 $ . .95 49 This universal infra-red remote contro l makes all other remote units superfluous. Will control CD players, videos, TV's and stereos etc. Controls up to 6 different appliances . Easy to use and programme from an existing functional remote High performance Series II. Features• Noise attenuating earphones • Noise cancelling mic • Sturdy construction • Cushioned head pad • Includes standard aircraft jacks • Over 4000 sold Australia wide • Don't pay $400 or more! $189.oo $19 .50 Case To Suit A Redford PECC Woofers This new bullet tweeter looks and sounds great. Genuine Motorola KSN 1165A. Features 400 watt maximum power capability frequency response 1.BkHz to 30kHz and SPL at 93dB (2.83v/ 1m) . 91 x 91mm mounting hole centres. Specifications available on request. Simply wires in parallel to your woofer. No crossover or capacitor required. As it presents almost no load to your amp it doesn 't effect the overall speaker system's impedance. Fantastic for hi-fi or disco speakers. C 6160 $39.95 A A 0492 $119.9s 0493 Optional Remote $24.95 Universal Remote Control Altronics Aviation Headset 9075 Carry 1------. M9000 3, 4.5, 6. 7.5, 9, 12v<at> 300mA $'95 $17.95 M 9005 6, 9, 12V <at> 500mA $pl"5o $19 .95 Telecom approved Features: Variable length outgoing message (maximum 30 seconds • Secl.}rity code access for remote • Call screening• 12 month replacement guarantee • Optional Full function DTMF Remote Control tor Playback, Reset, Save, Outgoing Message change. vT~(oafs~~:r~h~~?in~:ig~:i or even to find the keys in the dark! Features daylight sensing circuit which means unit will not activate during daylight hours (save on your power bill). Includes manual override facility to turn lights on continuously or automatically. Features movement sensitivity adjustment, and turn on period. Great for the driveway or backyard . Complete with two screw In type sockets for standard 150W floodlight globes (not included). C 9070 Headset J Telephone Answering Machine Just arrived, this new model PIA floodlight activates when it detects movement of a C 25+ $2.oo $6.oo $12.oo These multI•purpose AC-DC adapters are Just great for toys, calculators, radios, etc ■ etc Both include a range of output volta11es, a range of plugs reversible polarity and are energy authority approved. These Poly Emulsion Coated Cone (PECC) Speakers utilize the development of high grade driver components in Japan , such as Barium ferrite magnets and specially formulated paper cones impregnated with poly emulsion. The result is a driver of quite remarkable power handling, performance and extremely low distortion. C 3024 ~ Now $54.95 •• • ••'Olo\-- """••• :::: ...... ~,~ 1000 $Sg .95 Telephone Double Adaptor machine Ideal .tor answering and phone ConvP-rts sockets into a double socket to allow you to plug in two phones. P High Performance 2 Way Flush Mounting full Range 60W Speaker System Building that extension? What great speakers to install. Designed to Guitar Speaker 12" save SSS on equivalent replacement speaker 50 Watts RMS, 100 Walla Max. Attention all guitarists and keyboard musicians. This fine USA designed speaker is supplied as standard equipment to the world famous brand name series of Guitar Amps. • Impedance: 8 Ohm • Sensitivity: 101dB/W (0.5m) • Weight: 2400gm C 3102 Normally $pe'oo This Month ALTilOnlC.) 174 Roe St Perth WA 6000 Phone (09) 328 1599 PHONE TOLL FREE 008 999 007 MAIL ORDERS C/ - P.O . Box 8350 Stirling Street PERTH WA 6849 0995 $4 .95 $' · 89.oo install into ceilings or walls this slim profile attractive speaker system / grille assembly will compliment any sound system. Once installed the finished unit Front Grille Not Illustrated blends beautifully into any decor. (The grille assembly can be painted over in the same finish as walls or ceilings if required). Installation is simplified by the use of a mounting frame (which could be installed during construction) which the speaker assembly attaches to. Full mounting kit (even screws) supplied. C 0880/C 0855 Normally~O $219.oo per pair This Month HEAVY HEAVY SERVICE - All orders of 10Kgs or more must travel Express Road Please allow 7 days tor delivery. $12.00 to 10Kgs. $15.00 over 10Kgs. INSURANCE - As with virtually every other Australian supplier, we send goods at consignees risk . Should you require comprehensive insurance cover against loss or damage please add $LOO per $100 of order value (minimum charge $1) . When phone ordering please request ·•insurance". TOLL FREE PHONE ORDER - Bankcard, Visa, Mastercard Holders can phone order toll free up to 6pm Eastern Standard Time. Remember with our Overnight Jetaervlce we deliver next day. STANDARD DELIVERY & PACKING CHARGE $3 .50 to 500gms, $5.50 500gms - 1Kg, $8 ·1Kg-5Kg AUSTRALIA WIDE - We process your order the day received and despatch via. AL TRON ICS RESELLERS Chances are there is an Altronic Reseller right near Australia Post Allow approx 9 days from day you post order to when you receive goods you - check this list or phone us for details of the nearest dealer. OVERNIGHT JETSERVICE Up to 3Kg Is $10 00, 3Kg to 5Kg Is $23 00 - We process your Blue Ribbon Deelero are highlighted with a ■ These dealers generally carry a order the day received and despatch via Overnight JetNrvlce Courter for delivery ne xt day comprehensive range of Altronic products and kits or will order any required item for Country areas please allow add1tIonal 24-48 hours you . WA COUNTRY ALBANY BP Electronics ■ (098) 412681 Micro Electronics (098) 412077 BUNBURY Micro Electronics (097) 216222 ESPERANCE Esperance Communications (090) 713344 MANDURAH Lance Rock Retravision (09) 5351246 PORT HEDLAND Ivan Tomek Electronics (091) 732531 ROCKINGHAM TV Joe's (09) 5271806NT ALICE SPRINGS Farmer Electronics (089) 522388 DARWIN Ventronics (089) 853 622 VI C All Electronic Components (03) 6623506, TECS (03) 6706474 B,ORONtA Ray Cross Electronics ■ (03) 7622422 CHELTENHAM Talking Electronics (03) 5842386 COLLINGWOOD Truscott Electronics (03) 4198208 CROYDON Truscott Electronics ■ (03) 7233860 FOOTSCRAY G.B. Telespares (03) 3179100 PRESTON Preston Electronics ■ (03) 4840191 COUNTRY BAIRNS DALE LH & LM Crawford (051) 525677 BALLARAT Ballarat Electronics (053) 311947 QLD Del sound PL ■ (07) 8396155 WEST END BAS. Audiotronics (07) 8447566 WOODRIDGE David Ha ll Electro nics ■ (07) 8082777 COUNTRY GLADSTONE Gladstone Electronic Services (079) 724459. Electronic Enterprises (079) 726660 MAROOCHYDORE MALS Electroni c s ■ (074) 436119 MARYBOROUGH Keller Electronics (071) 214559 NAM BOUR Nambour Electronics (074) 411966 PtALBA Keller Electronics (071 ) 283749 ROCK HAMPTON Acc ess Elect ro nics (East St. ) (079) 221058 TOWNSVILLE Super Solex ■ (077) 724466 5A Force Electronics ■ (08) 2125505 BRIGHTON Force Electronics ■ (08) 3770512 CHRISTtES BE ACH Fo rce Electronics ■ (08) 3823366 FINDON Force Electronics ■ (08) 3471188 HOLDEN HtLL Force Electronics ■ (08) 2617088 LONSDALE Force Electroni c s ■ (08) 3260901 ENFIELD Azt ronics ■ (08) 3496340 COUNTRY WHYALLA Eyre Electronics (086) 454764 TAS HOBART George Harvey ■ (002) 342233 LAUNCESTON George Harvey ■ (003) 316533 NSW David Reid El ectronics ■ (02) 2671385 REVESBY Revesby Electronics (02) 7738087 SMITHFIELD Chantronics (02) 6097218 COUNTRY COFFS HARBOUR Gotts Habour Electronics (066) 525684 NEWCASTLE Novocastrian Elect.Supplies (049) 621358 WARNERS BAY Vi lec Distributors (049) 489405 WINDSOR M & E Elect. and Communications (045) 775935 WOLLONGONG Newtek Electronics ■ (042) 271620, Vimcom Electronics (042) 284400 WOY WOY Alphatran Electronics (043) 434919 Please note that all care ha1 been taken In preparation of these ad1, however AL TRONICS 11 not llable for errora1 typographical or otherwise. The Story Of Electrical Energy, Pt.21 Electric lighting came to Sydney's streets on 8th July, 1904. Suddenly, at 5.16pm, the city streets were a blaze of light from Circular Quay to Redfern & from Hyde Park to Darling Harbour. By BRYAN MAHER Back in the new Pyrmont power station, the Lady Mayoress, Mrs. S. E. Lees, had turned a gold presentation key. That simple act had closed the exciter field circuit of a 5.2kV alternator. This supplied 3-phase AC to new substations at Town Hall and Lang Park. At each site, a high-voltage induction motor began to spin, driving two direct-coupled 240V DC genera- tars. With the generators in series, 240/480V DC 3-wire circuits buried under the city's footpaths supplied 231 arc lamps to illuminate the streets. These 2000 candlepower electric lamps so overpowered the old gas lamps that the future of electricity was assured. Each set of 10 carbon arc lamps was connected into a series group which was supplied by the 480V DC mains. The grounded centre neutral wire was used to provide odd sets of five series arc lamps with a 240V DC supply. The carbon rods had a burning life of only 16 hours and then had to be replaced. But we have begun our story in the middle. Though practical electric lighting became possible from 1831 followfng the discoveries made by Michael Faraday in England, Sydney was then only a struggling convict Top of page: this photo shows the interior of Pyrmont power station as it was originally built, with Ferranti high speed twin-cylinder steam engines. NOVEMBER 1992 79 dangerous, that the electricity leaked away in the ground, and that it could cause fires and/or electrocution. These companies made no mention of their own dubious installations, where cables were sometimes just flung over the roofs of buildings. As well, there were numerous new entrants to the field, like the Empire Electric Company Ltd, whose advertised rate per kilowatt hour (kWh) forced the council to reduce its tariffs. And this was before the said company had even commenced operations. Commercial/domestic supply Manufactured by Belliss and Morcom, this 300 horsepower twin-cylinder steam engine measures about four metres long. The engine with its 4-tonne flywheel is direct-coupled to a Bruce Peebles alternator which once supplied 210kVA at 420V 3-phase to drive the machinery in a biscuit factory. The small generator at the righthand end is the exciter, which can produce up to 90V DC at 61A to supply the rotor field coils of the alternator. This 14-pole machine ran at 428.57 RPM & generated a 50Hz AC supply. However, the frequency would not have been all that stable, regulated as it was by a simple but fairly effective steam valve governor. The unit is today a working exhibit at the Power House Museum in Sydney. village. And even though Sir Humphrey Davy's arc light invention had illuminated the Paris Opera House in 1846, practical electric illumination had a long gestation period. The illumination of Sydney's streets was by oil lamps in 1843, then by gas three years later. But the city fathers were slow to adopt electric light. Other towns were more progressive. On 8th November, 1888, Tamworth had the honour of being the first town in the Southern Hemisphere to have electrically lit streets. The town of Young was soon to follow and then the towns ofLambton, Moss Vale, Broken Hill and Redfern got into the act. The electricity bill Moving slowly, the NSW government took 10 years.to pass a bill au~ thorising the Sydney Municipal Council (SMC) to acquire generating plant. Finally, the council appointed one Major Cardew as its consultant. He advised the building of a power station in Kent street to supply an 8km radius with illumination. The Kent Street site was resumed 80 SILICON CI-IJP by the Government due to an outbreak of bubonic plague, so Pyrmont became the second choice. With incredible foresight, the Council anticipated the coming demand from homes and private factories. However in entering the electricity supply business, the City Council faced competition from five well established private DC generating enterprises. At the forefront of this competition were th_e Oxford Street Electric Light Company, the Imperial Arcade Electric Light Company, and the Strand Electric Company whose 100-volt DC system spread like a spider's web around the Strand Arcade and adjacent shops. In the long run, the City Council's greatest competitor was the implacable Australian Gaslight Company. Well entrenched for over 60 years before the advent of electricity, the gas company was a formidable adversary. A lot of quite unethical propaganda emanated from the Council's competitors . The private electric companies spread false tales to the effect that the council's underground supply was The Council power also supplied city buildings and homes where the new incandescent filament lamps, invented by Swan in England and Edison in the USA, were a great boon. These globes were more suitable for indoor lighting than arc lamps which generated lots of heat and copious quantities of carbon dioxide and other noxious gases. City building owners immediately saw the advantages of lifts powered by DC motors. These were much cheaper than the steam powered hydraulic elevators previously used by the largest companies. Some big city stores retained their hydraulic lifts for 50 years or more, simply replacing the steam engine with a DC motor. However most new buildings went straight to electric elevators, many later changing to the Ward Leonard control system for more accurate positioning. Little did those people realise that their DC lifts would dominate electrical supply policy for the next 80 years. Home owners and tenants in city apartments quickly saw the advantages of electric appliances. After lighting, there was a big demand for electric irons and European hair curlers, as in this field gas had no equivalent. Slowly, electric heating and cooking replaced gas appliances. Sydney Municipal Council charged lighting either at a flat rate of five pence per kWh or a two-part rate which cost more for primary units and two pence for each subsequent kWh. Power for all motors, lifts, cooking and heating was charged at the lower rate. One year's operation saw 86 private and government consumers connected to the DC mains supply, in Sydney Council linesmen used to do all the work without any heavy machinery. This photo shows how the heavy cable reels were grappled off the horse-drawn drays prior to the cable being laid in the trenches. addition to the street lighting, with a total loading of just over 1MW. Generating and distribution costs were 1. 99 pence per kWh. Pyrmont power station The original Pyrmont station was equipped with three Ferranti twincylinder high speed steam engines. Each was direct coupled to a Ferranti 5200-volt 50Hz alternator. Two of these units were rated at 1000 horsepower (746kW) each, while the third was rated at 500hp (373kW). Five Babcock and Wilcocks boilers supplied steam at 160 psi (1.1 MPa) to drive the engines. Coal was brought in by rail (or ship in emergencies), while cooling water came straight from Darling Harbour. This installation was state of the art in its day, with economisers and feed water heaters to increase thermal efficiency. So fast was electricity accepted in Sydney town that within 12 months of Pyrmont opening, additional machinery was ordered to almost double the original capacity. The 45km of underground cabling around the city was extended and the existing DC substations enlarged. Today, we can only marvel at the speed at which such work progressed without the aid of heavy machinery. All trenching was done by pick and shovel and all carting by horse and dray. While the City Council was busy wiring up the city and close surrounds, a few industries further out set up their own plants. Some of these were state-of-the-art AC systems. One notable engineering effort was installed in a biscuit factory. AC/DC system True to the preferences of Thomas Edison, and with lift motors in mind, Sydney Council supplied all the in- ner city with a 240/480V 3-wire DC system. But the AC/DC rotary substations were expensive to install and operate. Therefore, the outer city areas were supplied by 240/415V AC mains from transformer substations at Darlinghurst, Athlone Place and the power station itself. This was the first normal AC supply for Sydney horn:es. In outer city regions, streets were lit by the same arc lamps as in the city, except that groups of nine lamps were arranged in series across the 415V AC mains. Thus electricity was ushered into Sydney as two incompatible systems : DC and AC. This dichotomy was to persist for more than 80 years, until 1986, often to the despair of city shopkeepers. As late as the 1950-1960 period, some business establishments in York and Clarence Streets still operated on the 240V DC supply. The custom was for electrical businesses to provide their own motor generator set to provide 240VAC 50Hz, so that radios and NOVEMBER 1992 81 DC in the inner city caused Sydney Municipal Council to upgrade its biggest and longest lasting DC substation in Clarence Street. Originally installed in 1904, this substation used high volt. age induction motors driving series connected pairs of DC generators. Later, rotary converters generating 240 volts DC were connected in pairs to give the 240/480 volt 3-wire supply. The first mercury arc rectifiers were installed in 1933. Mercury arc rectifiers This photo shows three of the 36 600kW mercury arc rectifiers installed in the Clarence Street substation in 1959. These mercury rectifiers used six anodes, for 3-phase full wave rectification. The cubicles underneath them house auxiliary equipment and the cooling fans. appliances could be demonstrated. Problems came with television, because the in-house AC supply was usually of uncertain frequency. Any deviation from the nominal 50Hz caused drifting hum bars on the screens of early TV receivers, to the consternation of shop owners and prospective customers. So fast was the electrical growth in 1904 that within three years an extension was added to Pyrmont to house new more efficient machinery, thus reducing the cost per kWh. The City Council then shocked its competitors by dropping the council's rate from 2 pence to 1.5 pence per kWh. Subsequently, each private electric company asked the council to buy it out as they could no longer compete. The goodwill of four companies was eventually purchased by the Council for a total of 110,375 pounds, each in proportion to its yearly unit sales. The largest was the Strand Electric Lighting Company which had been selling 1.24 million kWh units annually. The Council then refurbished those customers' installations to bring them up to 240V standards. Legal tussle A legal tussle, previously unheard of in Australia, ensued in 1905. The new Royal Hospital for Women, in Oxford and Young Streets, Padding82 SILICON CHIP ton, was designed and built assuming an electricity supply. It was four storeys high and electric lifts and lights were essential for safety reasons. But Paddington Council wanted to charge Sydney Municipal Council rates for the narrow land corridor occupied by the high voltage power line to the hospital. Further argument raged over a substation site. Sanity eventually prevailed; the substation was built within the hosp.ital and agreement between the councils was reached. Sydney Council mounted an intensive campaign to electrify the city. Arc lamps were hired out to commercial users who could not afford the purchase price. Similarly, businesses could rent DC motors in any size from 375 watts to 22.5 kilowatts. The small units were 240V types, while the larger units ran off the 480V supply. The conservative rates charged encouraged businesses to hire a total of 361 motors in the first two years of the scheme. More than 50 different types of factories and stores took advantage of this facility. Three years after its commencement, the Council undertaking had 1600 customers using 6 million kWh units annually. And the system was growing daily, taxing the power stations' 6.7MW installed capacity. The increased use of 240/480 volt On 1st June 1959, the substation was changed over to mercury arc rectifiers exclusively. Six sets of six 600kW glass bulb mercury arc rectifiers with main and interphase transformers and accessories were provided. When placed on load, the mercury arcs bathed the interior of the cabinets in a beautiful (but dangerous) violet glow. Together, the 36 mercury rectifiers could deliver 7300 amperes DC. The large glass bulbs came by sea from Hersham in England, the final shipment arriving in early 1959. During shipment, the bulbs were suspended in a large timber crate using ropes and steel springs. The bulbs were shipped upside down with the large quantity of mercury sloshing about in the head of the condensing chamber. In Sydney, each glass vessel was mounted within a steel cabinet, its mercury cathode at the bottom and the condensation void at the top. Each glass vessel had anode arms with external copper plated molybdenumiron alloy contacts. These connected via the glass/metal weld to join the dense graphite anodes inside. The glass arms each provided a separate pathway for the mercury arc from the cathodic pool at the bottom to each graphite anode. This isolation prevented any chance of a flashover between the AC anodes of any two adjacent phases. The auxiliaries consisted of a cooling fan and starter electrodes for each glass bulb. The fan was automatically speed controlled by passing its AC supply through a saturable reactor. These were commonly used to control AC currents before the days of gas thyratrons or Triacs and SCRs. A saturable reactor is an iron-cored inductor with two AC windings and a DC winding. The AC windings car- ried the current to the fan while the DC winding carried the output current from the mercury arc rectifier. When the rectifier was supplying little output current, the inductance of the AC windings was so high that the fan would not run. As the rectifi er was called upon to supply more current, that current passed through the DC winding of the saturable reactor. This increased the magnetising force in the iron core and so reduced the reactance of the AC windings. This in turn increased the AC voltage to let the fan run. At full DC load current in the rectifier circuit, the reactor core would be completely saturated, cancelling all the inductance of the AC windings and allowing the fan to run at full speed. Thus, the fan speed was automati cally varied to give the right amount of cooling at all times. Exciter circuit When first switched on, the rectifier bulb contained cold mercury. To initiate an arc and thus ionise the liquid metal, a magnet pulled down a spring arm within the bulb to make contact with the mercury. That passed a current into the mercury. A second magnet would then attract the spring arm upwards , drawing an arc sufficient to initiate ionisation. To maintain ionisation, even with no load current, two subsidiary electrodes continually maintained a sma 11 arc to the mercury surface. Because the cathode mercury pool must be the positive output terminal, there is no such thing as a negative output 6-phase glass rectifier. Therefore, in a 3-wire positive/zero/negative DC system, the negative 240V DC bus must originate at the transformer secondary star point. To obtain balance in the 480V /240V system, the council linesmen would connect some lighting circuits between positive 240V DC and zero. Other circuits would be connected between zero and negative 240V DC . With roughly equal loads on both sides , only a small difference current would flow in the zero line returning to the substation. Motors and other heavy loads were made for a 480V DC supply and were thus connected between the +240V and -240V lines. Because th e major lo ad current flowed out on the +240V line and returne_d via the -240V line, four recti- This photo shows smaller mercury arc rectifiers than were used in the Clarence Street substation. These units have only three anodes and a somewhat lower current rating. fiers out of the six were used in parallel to supply this current. The fifth and sixth rectifiers of a set provided a zero centre line potential. Each set of six rectifiers could supply 1215 amps continuously, or 1520 amps for a 2-hour peak period. In addition, heavy loads of up to 2430 amperes mulrl be supplied for up to 15 seconds , allowing the starting of large motors anywhere in the city. Out-of-balance current in the zero line could be as high as ·1 20 amperes indefinitely. As late as 1986, Sydney City still drew just over 4000 amperes from the last remaining three sets of glass rectifiers. Apart from their high efficiency, these mercury arc rectifiers were designed for zero maintenance. They had no moving parts, the critical components were sealed under vacuum , and neither the mercury nor the graphite anodes deteriorated during full load operation. These rectifiers thus had a very long working life. You might ask why so much DC load still existed in Sydney as late as 1986? In truth , much of that load exists to this day but it is now hidden. The advent of the AC supply in later years saw the replacement of most DC machinery with 3-phase squirrel cage induction motors. But from the very first days, DC motors were found to be superior for controlling city lifts and indeed this is still the case. Many buildings in York, Clarence, George and Pitt Streets, as well as around the waterfront area, date from early days before modern building standards were in force. Any attempt to rebuild the lifts in these buildings to modern design using AC motors would be very costly. Therefore, the DC driven lifts remain to this day, and will probably continue for years to come. By the mid 1980s, the advent of high current solid state rectifiers allowed building owners to install their own rectifier systems to run from 415V AC mains. But until 1986, the supply authority, Sydney County Council, was obliged to maintain the 480/240V DC reticulation throughout the city. Thus Clarence Street substation remained a_s a supplier of DC for 82 years. Acknowledgement Special thanks to Phil Parsonage and Des Barrett, and grateful acknowledgement to the staffs of Sydney El ectricity, Pacific Power and the Museum of Applied Arts and Sciences, and to Gordon Anderson. SC NovEMB EH 1992 83 REMOTE CONTROL BY BOB YOUNG A low-cost speed controller using discrete ICs This speed controller for electric models is very small and uses surface mount devices in the decoder circuitry. It can have up to eight FETs and will easily handle motor currents of up to 50 amps or more - all this is on a PC board measuring only 55 x 38mm. Back in the March 1992 issue, I indicated that the speed controller I would ultimately present would have all the bells and whistles, including a dynamic brake. However, the way things have worked out, the circuit presented here is quite different from that originally intended. While the circuit does not include a dynamic brake, it has provision for more FETs than originally proposed and it can therefore handle very high currents without a heatsink. may be expensive but they really are sophisticated devices. To complicate matters further, I did promise that I would use only readily available components and this precluded the use of specialised servo ICs and microprocessors, which require software drivers. And that brings me to the heart of the delay: the problems offitting all of the promised features including a dynamic brake into a small, low-cost unit using standard components. The "The design allows up to eight FETs to be fitted and these can be driven at switching rates varying from 500Hz to 2500Hz" This project has surprised me from the very beginning in just how subtly complex the problems involved with designing a speed controller really are. I take my hat off to those early pioneers who developed the commercial speed controllers of today. Let me tell you, modern FET speed controllers brake introduces more complexity into the circuit and requires a foolproof interlock and virtual duplication of the entire drive circuits. As a result, the component count soars out of sight, as does the size and cost. In hindsight, I can see that I was gradually drawn into the project while not fully understanding its complex- ity. As I researched the problems and discussed desirable features with other modellers, the design began to grow like topsy. The circuit featured this month is the design I had in mind when I accepted the project, with some added features. I called the original Speed 1. Speed 2 and Speed 3 followed in quick succession and then one day I looked at the proposed design and realised that the cost of putting it into production was far too high. Speed 3 had all of the features promised. It was a very clever, fully-digital design by Dean Herbert, using eight 4000 series logic chips. However, it would have required a 4-layer PC board to reduce its size to that required by modellers. It was also too difficult for the average modeller to construct. In other words, we had lost the plot. So it was back to the drawing board for Speed 4, a very promising design, again by Dean, with all of the features of Speed 3 and not as much complexity. We are currently working on that. By this time, however, the clamour for publication was deafening, so without further ado, here is Speed 18. Design features This design is a variable switching rate (500 - 2500Hz) single ended speed controller without a brake or reverse facility. It is intended for the experimenter who wants to know more about achieving the maximum performance from a particular speed controller and electric motor combination. As all motors vary in their inductance, capacitance and commutator speeds, they tend to respond best to a particu- R12 47k +5V R11 47k R1 100k INVERTER PULSE DETECTOR 7 R6 47k 7 +5V C2 .001 VR1 1M R19 100k J2 R2 47k R4 47k J1 C3 .01J R3 47k R18 1k PWM COMPARATOR 7 7 MONOSTABLE R9 47k ERROR INTEGRATOR 7 -------R27 R22 R28 7 R21 MOTOR DB 100V 5A M1 ----- C14 0.1 V1 + T MOTOR I SUPPLY I ..I.. Q3-Q10 8xlRFZ44 C9 0.1 M2 SPEED CONTROLLER Fig.I: this speed controller decodes the pulses from a remote control receiver and converts them into a variable duty cycle pulse train to drive the motor. The circuit can use up to eight FETs for handling motor currents of up to 50 amps. lar switching speed. To this end, the design allows up to eight FETs to be fitted and these can be driven at switching rates varying from 500Hz to 2500Hz. By monitoring motor RPM and load current, the running current can be set to the minimum by varying the switching speed, thus obtaining the best efficiency from that controller/motor combination (see previous issues for a discussion on the interaction between switching rates, motor types, commutation rates and so on). Only off-the-shelf components have been used, as can be verified by a glance at the circuit - see Fig.1. The PC board will be a surface mount unit with all the surface mount devices already soldered into place; ie, the VIEWED FROM ABOVE GDS board will be "populated" apart from the FETs. Modellers may mount up to eight FETs on the board, depending on the current rating they want. The PC board will be available from Silvertohe Electronics, PO Box 580, Riverwood, NSW 2210. Circuit description Let's now have a look at the circuit shown in Fig.1. The main components of the circuit are a voltage controlled monostable, an error integrator, a triangle NovEMBEH 1992 85 ' Speed Controller for Electric Models - ctd wave oscillator, a voltage tripler, a PWM comparator and a missing pulse detector. Most of these functions are based on an LM358 dual op amp and an LM339 quad comparator. Both of these ICs are designed for single supply operation. Op amp ICla, transistor Ql and associated components form a voltage controlled monostable. Positive pulses (RX IN) from the receiver momentarily turn on Ql via CZ and RZ, thus discharging C3. C3 then charges via resistor R4 and trimpot VRl. The op amp thus delivers a positive output until the voltage on its inverting input (pin 2) exceeds the voltage at pin 3. The pulse signal from the receiver is also inverted by comparator IC2c. The pulse output from the voltage controlled monostable (ICla) is then subtracted from the inverted input pulse by comparator IClb which also performs integration. The output of the integrator, pin 7, then feeds back to the non-inverting input of the monostable, ICla. If the input pulse is longer than the monostable pulse, IClb's output increases until the pulse lengths are equal. Similarly, if the input pulse is pin 13. The frequency is adjustable from about 500Hz to 2500Hz although, in practice, the range is less than that if a lO0kQ trimpot used for VRZ. With this value oftrimpot, the range is about 640 to 1640Hz. If higher or lower switching rates are desired, then the values for R13 or R14 will have to be changed. The triangle wave generated by IC2d is compared with the proportional control voltage from IClb by ICZa, the PWM comparator. The output at pin 2 is a constant frequency, variable duty cycle pulse train. The duty cycle determines the power output of the motor; ie, a 50% duty cycle gives half throttle regardless of the switching rate. At 100% duty cycle, the input to the FETs is straight DC, equal to the output of the voltage tripler. A set of jumpers at the inputs to the PWM comparator (IC2a) enable its sense to be inverted. This facility is necessary if the transmitter does not have a servo reversing switch. Voltage tripler Mosfets require a gate drive signal of at least 12V to ensure a low "on" resistance. Unfortunately, the drive batteries on 020 and 035 motors are "To make the Mosfets switch rapidly, they must be driven by a gate signal which has very fast transitions" shorter than the monostable pulse, IClb's output decreases until the pulse lengths match. The end result is that the duration of the incoming pulse has been changed into a proportional control voltage. This proportional control voltage will ultimately determine the length of the DC pulses fed to the motor and thus will control its speed. Triangle wave generator Comparator IC2d and its associated components operate as a Schmitt trigger oscillator with the result that a triangle waveform is produced at pin 10 (across C6) and a square-wave at 86 SILICON CH/I' only four or five cells, so they cannot be used for this. A voltage tripler, running off the +5V supply solves the problem. It consists of diodes D5, D6, D9 and DlO, plus the associated lµF capacitors. The square-wave output of oscillator IC2d drives the voltage tripler circuit and this then charges lµF capacitor C13 to close to +14.4V (assuming a fully-charged 4.8V battery). Transistor Q2 acts as a high current driver for the paralleled gates of the Mosfets. It is driven by the PWM comparator and since its output is open collector, it acts as a level converter between the nominal +5V signals and the higher voltage of the tripler. R19 sets the stick travel on the transmitter. Zener diode ZDl clamps the signal from the emitter of Q2 to prevent overdrive to the gates of the Mosfets. Resistors R20-R29 (lOQ) act as "stoppers" to prevent the possibility of parasitic oscillation. Gate capacitance One peculiar feature about Mosfets is that although they are voltage controlled devices and thus require essentially no power to turn them on, that is really only theory. In practice, when the devices are actually switching, they soak up power like a sponge. The problem is gate capacitance. In order to make the Mosfets switch rapidly, they must be driven with a gate signal which has very fast transitions, from low to high and from high to low. This means that the gate driver circuit must charge and discharge the gate capacitance of the Mosfets each time they are switched on or off. That charging and discharging process takes quite a lot of power. And the more gates you put in parallel, the more power required to drive them. The driver circuit provides enough current to drive the eight FETs. One stipulation here is that as the switching frequency increases, the effect of the gate capacitance increases. Depending upon how many and which type of FET is used, there comes a point at which the input drive will begin to fall significantly and therefore the Mosfets will not be driven hard enough. The result of this is that their drainsource resistance will not be at the absolute minimum and so the Mosfets will dissipa_te a lot more power than they should (perhaps more than they can handle). And the corollary of this is that the motor will not get as much power as it should. The data books rate the typical FET as having an input capacitance of about 1500pF, although some such as the IRFZ44 are as high as 3000pF. In my ex'perience though, they are much higher than this, or at least they certainly behave as if they are, in most of the speed control circuits I have tested. (Editor's note: perhaps a more relevant specification in this instance is Qg, or total gate charge. The specification for gate capacitance does not givt the whole picture by any means, since the capacitance actually changes dur- ing the switching process, as the drainsource voltage changes. Miller Effect is very significant. Gate charge is the total charge which must be fed to or removed from the gate in order to turn the device on or off. For the IRFZ44, the total gate charge is quoted as a maximum of 100 nanocoulombs, for a Vgs of 10V and an ID of 52 amps. Using the formula Q = CV, the effective gate capacitance is 10 nanofarads; ie, 0.01µF or four times the typical quoted IRFZ44 gate capacitance of 2500pF. This explains why Mosfets behave as though they have a much higher gate capacitance than the specified figures) . With eight FETs fitted, the limit on switching frequency will be about 1400Hz for this circuit. Another very important factor to keep in mind when choosing the size of the FET array is the behaviour of FET junctions with temperature changes. The rise in the "on" resistance of the drain-source region is linear with temperature and so there is little point in putting a few very expensive FETs in the array and then running them at an elevated temperature. It is much better to use a greater number of cheaper FETs. Remember also that the switching rate is the heart of any speed controller design. Switching times must be fast enough to prevent excessive heating of the Mosfet channels during their on-time, but slow enough to avoid serious rounding of the PWM waveform due to the gate capacitance. The ideal switching speed should be decided upon after considering the type of FET, how many, the type of motor, its current drain and commutation rate. In other words, there is plenty of scope for experimentation. • speaker that performs with equal A excellence on both classical and rdck music is a rare speaker indeed. While this is probably the ideal loudspeaker, the sad fact is that most speakers are leaning towards either one or the other type of music. So when a speaker comes along which truly performs equally well with such different types of music, it's no wonder the critics sit up . This is what Stereo Buyers Guide had to say about the new DALi 400: "The soundstage was large, very large, but unlike most speakers which give a large stage, the 400s didn 't fluff the imaging inside it. The detail was surprising in its clarity and placement- surprising because ourreference speakers didn't deliver as much on the same tracks. This doesn't happen very often! The bass was simply stunning- as clean as we've heard in a long time, yet so controlled and strong, especially in the lowest octave. No wool here; the 400s shook the foundations. The highest frequencies glistened. ... the stage showed lots of air; there was plenty of room in the image for all the musicians. The 400s won us over completely without any trouble at all. These speakers are great value in build quality, aesthetic appeal, and especially in musical temperament. We 're recommending them without reservation". Audition the new DALi 400 at your nearest DALi dealer today. DALi 400 SPECIFICATIONS: Cabinet type .. ........ ....... ... ......... Bass reflex Woofers ........ .. ... 2 x 1 70mm Polypropylene Tweeter .... .......... .. .......... . 25mm soft dome Freq 'cy response(+/- 3dB) ..... 35-18,000Hz Sensitivity .... ... .. .............. 93dB (2.83V/1m) X-over frq 'cy ............ 250GHz (Lin.Directivity) Long Term Power Handling ........... 140 Watt Timber finishes .... .. .... .... Black or mahogany R.R.P . .................. ......... ... $2500 per pair For a free information kit on the full range of DALi speakers, please contact Australian Distributor: SCAN AUDIO, 52 Crown Str, Richmond VIC 3121. Ph: (03)429 2199. Fax (03)429 9309 Missing pulse detector Comparator IC2b operates as a missing pulse detector. While ever pulses are present at the output of IC2c , diode D4 charges capacitor C5 and therefore holds pin 6 of IC2b low. · Thus, the open collector output at pin 1 will be off. If the pulse signal is lost (due to radio interference or radio or connector failure), C5 discharges via R7 and therefore pin 6 rises above pin 7. This causes pin 1 to turn on and thereby remove the base drive current to transistor QZ. This kills all drive to the Mosfets and so turns the motor off. If the pulse signal is restored, ICZb will again be disabled by diode D4 and normal circuit operation will resume. Interference suppression Electric motors with commutators are appalling sources of radio interference, so a few precautions must be taken. Capacitor C14 helps filter out commutator hash while diode DB prevents inductive spikes from destroying the Mosfets. V1 is a varistor which is rated 50% higher than the motor supply voltage and which helps hold down spikes in both directions. These components - ie, V1, DB and C14 must be mounted directly across the motor terminals. The total current drain for the speed controller is 5mA. Performance The circuit has been tested with motors drawing up to 50 amps with little or no warming of the FETs. Further test results must wait for next month's issue. SC NOVEMBER 1992 87 COMPUTER BITS ■ BY DARREN YATES Mass data storage in the palm ofyourhand This month, we take a look at the Pocket Hard Disc or PHd from KT Technology. It runs as a logical hard drive from your PC's parallel port, can be removed in seconds & can store up to 120Mb of data. If you need to transfer a large number of files from·one place of work to another, your options are fairly limited. You could back up your files to floppy disc, but as soon as your files become larger than about 1.2Mb, it starts to get messy keeping track of which disc is first, second, third and so on. Backing up large amounts of data is also very time-consuming. Alternatively, you could use your trusty modem. However, with a maximum data transfer rate of 9600 baud, it could be quite some time before you get your telephone line and your computer back again. Even with the various data compression systems, . the best serial transfer rate you can get is Pocket hard disc backing up) large files in the form of the Pocket Hard Disc (PHd). This amazing piece of technology is just 148 x 75 x 28mm in size and fits in the palm of your hand but it can store up to 120 megabytes (120Mb) of data. The beauty of the PHd is that it's fully external - it requires no internal driver card and simply plugs into the parallel printer port on your PC. The sneaky thing about it is the way it obtains its power supply - it pinches it from the keyboard socket via an adaptor which is supplied with the unit. In operation, the disc is set up as the next logical drive in your system. So if you already have a hard disc designated as your C: drive, then the PHd becomes the D: drive. It then behaves just like a normal hard disc drive, yet is removable in seconds and can then be transported to any AT/386/486 system anywhere. Pretty neat, huh? Now KT Technology has come up with the answer to transferring (or Setting it up around 57,000 bits per second or 7Kb per second, which is still slow if you have to transfer megabytes of data. Another option is to use one of the new "floptical" disc drives. These use a disc very much like a normal 3.5inch disc and can store up to 20Mb. While this may sound great, the problem is that you have to assume that the user at the other end also has a floptical drive to read the disc. It is also surprising just how quickly a 20Mb disc can be filled with just a few large files. The PHd pocket hard disc is not much bigger than a 3.5-inch floppy but, depending on the version, can hold up to 120Mb of data. 88 SILICON CHIP The Pocket Hard Disc comes complete with its own installation software. This software ensures that the drive is recognised and checked when the computer boots up. In normal operation, there is no change to any of your existing software and the unit is used just like an ordinary hard disc drive, You can copy files to and from the PHd disc drive in the normal manner, or use it as the logged drive when working in a word processor or some other application. Before you install the PHd, you need to make sure that the system is turned oft otherwise it may be damaged or the data lost. The adaptor power cable is con- This delay period is cut to about five seconds on a 386DX machine. The data-transfer rate is greater than 700Kb/ second and the maximum seek time is 19ms, which is comparable to the faster internal hard disc drives available. This can be increased by using a _h ard disc caching program such as Windows SmartDrive. Applications The PHd pocket hard disc plugs into the computer's printer port & obtains its power from the keyboard socket via an adapter cable. The device has no effect on normal printer operation & can be unplugged in seconds. nected. to the keyboard socket and one printer port and you wish to use then the keyboard plug fitted to the your printer and the PHd? No probback of the adaptor socket. The power · lem. The PHd has another 25-pin D cable is then connected to the PHd. socket at the other end and so you just This makes it independent of exterplug your printer into that. From then nal power supplies which means that on, you just print files in the normal it can be used all over the world. way as though the PHd was not there. There is also a printer port cable But back to the installation of the which is suppliedwith 25-pin D sockPHd. ets at each end tci connect the PHd to Formatting the parallel port. Before you can start using the PHd, Once the appropriate file has been there are a number of changes needed copied across, you need to format the on your C: drive, The first of these is PHd and check the data transfer to and from your printer port. Formatmade to your CONFIG.SYS file so that each time the computer boots up, it ting is done in the usual way (ie, format D:), while the supplied disc looks for the PHd. This is done by adding the following lines: contains a file called PHDINITB.COM (for the 80Mb version) which checks INSTALL=C: \DOS\SHARE.EXE the data transfer and initialises the DEVICE=PHDLPTB0.SYS PHd. The device driver you install deNote that this data transfer check pends on which model you have. For only needs to be done once. example, if you have the 40Mb PHd Once you've done that, switch off model, the relevant device driver is and reboot your machine. PHDLPT40.SYS and so on. You can make these changes using Boot-testing either EDLIN or nearly any wordprocessor. Alternatively, you could use While your machine reboots, it tests the Windows Notepad or the Winthe validity of the printer port to endows SysEdit feature. sure that it will transfer data reliably. Next, you have to take the floppy During this time, a test message is displayed on the screen. disc provided and copy the The only drawback, and it's a miPHDLPTxx.SYS file from it to the root nor one, is that if you don't have the directory of the C: drive. This is the PHd plugged in when you boot up, it only file the computer requires to contakes a 286 computer about 30 sectrol the PHd. onds to figure out that it isn't there. What do you do if you only have One area where the PHd will really excel is in backing up existing hard disc drives. In fact, when we recently upgraded one of our 286 machines to a 386DX with a new 85Mb hard drive, we used the PHd to back up the old 40Mb hard disc and then simply transferred everything over to the new system. It was that easy. Previously, you'd either have to back everything up onto floppies or load in each piece of software again, taking hours to do so. The PHd backed up the complete disc in only a fraction of the time that would have been taken for floppies, without the hassle of changing anything. The ·drop test Because the PHd is designed to be fully portable, the makers have designed it to withstand a 150G shock. That means that it will well and truly handle normal everyday bumps and knocks and then some. But no, we did not try the drop test. That would be pushing things a bit too far. The PHd also only weighs 350gm, which is really a little heavy for your shirt pocket, but the fact that it is so compact brings up another important _point - security. Because it can be unplugged so easily, you can take a back-up of your hard disc with you wherever you go. Price & availability One of the best things about the PHd is the price. The 80Mb unit has a retail price of $799. When you consider that floptical drives retail for about $850 and that floptical disks are $30 fo $40 each, the PHd is good value. The 40Mb version sells for $549; the 60Mb for $599; and the 120Mb version for $999. For more information about the PHd, contact the distributors, · KT Technology, Building 7 Central Boulevard, Portside Business Park, Port Melbourne 3207, Phone (03) 646 5755; fax (03) 646 7997. SC NOVEMBER 1992 89 5 1/4" POWER "Y" CONNECTOR 1:/:/#=i-ELECTRONIC Digital Kitchen Scales Allows you to connect two 5 1/4" drives from one power source. P19049 ....................... $9.95 KRYPTON GLOBES Whether your a professional chef or dream about being a professional chef, 7 these are the kitchen scales that you need. Don't rely on luck by throwing in a dash of this and a pinch of that. With the Arlec electronic kitchen scales , it's a simple matter of pressing a button to separate the weight of different ingredients. No need to separately weigh different ingredients in different bowls. The add and weigh facility enables the weight of the bowl and/or contents to be zeroed. This allows other ingredients to be added by weight more accurately. The digital display displays weight in kilograms and grams or pounds and ounces· and can be converted from one to the other at ·the touch of a key. The Arlec Kitchen Scales also come with a beeper timer and a plastic bowl in the form of a jug which can also double as a mixing bowl. ""::.======~ A 15076 ......................................................................$69.95. 1:1:1!'.iit,f ~ . RECHARGEABLE DRIVE AND DRILL 1000 Two Speed Cordless Drill and screwdriver. Probably one of the most handy tools you'll ever have! This screwdriver will drill or drive screws into timber, sheetmetal, and hardened plastic. • Has a powerful 4.8 volt motor. • Convenient cordless operation. • Two speed: Drill - 325 RPM Screwdriver - 150 RPM • Drilling capability - 250 holes • Screwing capability - 150 screws • Torque: 33 kg/cm • Forward or reversible operation • Quality Jacobs Chuck (1/4" or 6.5mm) • Chuck key holder on the unit • Rechargeable through an adapter which simply plugs into a regular household powerpoint (240 Volt) and reduces the voltage to a safe low level • Supplied with 4 screwdriver bits:- 2 slotted-heads & two Phillps-heads • Pilot lamps adds light to dark or confined work place • Charge indicator • 12 month guarantee T12298 .........................................................................$79.95 Indoor / Outdoor Digital thermometer You'll never have to press your nose up against a thermometer again to read what temperature it is.With this great digital thermometer the temperature can be read quickly and easily. 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Its rech argeable batter ies can be chraged over 1000 times from a regular household powerpoint (240 Volt). The Ready-light has a strong magnetic base allowing It to be clamped lo any steal or iron surface. Comes complete with wall bracket t o conveiniilntiy and recharge torch A15054 ...... . MANNESMANN TALLY MT82 ,," ~~ Mannesmann Tally have for ~ many years enjoyed International , . acclaim for the quality and functionality of their compU1er printers . The matrix printer lives up this reputation. It can offer professional printing of the highest quality. Due to the printe~s high resolution capabilities, graphics too can be printed with outstanding clarity. The computer printer can be connected to mOS1 of the more common compU1er systems by means of Its modular interlace. Even If you have had little experience with computer printers. you woni have any problem using this model because it was designed to be user-friendly. 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The MT81 Is designed to meet most of your personal computer printing requirements and will per1orm to Its highest level without the operator requiring any previous technical exper1Ise. With various character densities, line spacings and many more funci ions, this printer Is a valuable addition for your personal computlng applications (e.g. Word Processing, Graphics). SPECIFICATIONS : Printing method Serial printing with 9-needle print head Print Speed Draft 130 char./sec. NLQ 24Char/sec. Characters per line 80 char. at 1Ocpl Form length upto 22" Paper dimensions width: 3• to 1o· thickness: 0.002" to 0.004• Ribbon black 1.2 mill. draft char. Power source 120 V AC, 60 Hz; 220/240 V AC, 50 Hz Acoustic noise level below 60dB (A) Weight 4.5kg Dimensions CM xH xD) 370mm x 100mm x 250mm C93000 ................................................... $299.00 PRICES DROP LIKE A ROYAL BIKINI. 1 • 1 PRINTER CARD ..................... $29 GM RAM CARD ....................... $249 2 PORT SERIAL CARD .......... $39 GAMES CARD ........................ $19 CLOCK CARD ...... .................. $39 5121576K RAM CARD ............ $99 2 WAY FOO CONT................. $39 VGA 16 BIT 256K .................. $69 VGA 16 BIT 512K ....................$89 VGA 16 BIT 1 MEG, .............. $149 16M HO CACHE CARO .......... $529 HDD IDE /FDD ........................ $25 HOD IDE/FDD/SPG ................ $35 8 BIT ETHERNET CARD ........ $239 16 BIT ETHERNET CARD ...... $285 PRICES-A HO T PADDLE CARDS l BRACKETS 40M SEAGATE DR1Vc....----S319 85M HO 17ms ACCESS. VOICE COIL 2 YEAR WARRANTY.....................$419 105M HO 19ms ACCESS $439 120 KALOCK DRIVE. .................... $475 126M HO 16ms ACCESS. VOICE COIL 2 YEAR WARRANTY....... _ _ _ $519 170M 2 YEAR WARRANTY............ $679 212M HO 12ms ACCESS. VOICE COIL 2 YEAR WARRANTY..................... Sn9 The first book of 1•2·3 Release 2.4 The first book of Windows 3.1 2nd Ed The first book of WordPerfect 5.1 The first book of WordPerlec1 5.1 for Windows The first book of Excel 4 only $34.95 each. Handy Quick Rsfsrsncs Books Word for Windows 2 DR DOS 6 Excel 4 lor Windows PC Tools 7 :,~!~;~~~f~;=J;~:Mo;:~~t t~i~~e~!~t~=~~ ~ •: :;r~i;~ 5 :~: 5.1 1.2.3 Release } )NUHAWADING SERVICE CENTRE ) ) Norton Utllttes 6 .Only BEST WARRANTY BEST SERVICE, BEST PR/ & A FREE TRA INING COU 5Mb SYSTE 1 86-16Mhz (LM21) ....... $1199 86SX•25Mhz (LM31) .. $1299 86SX·33 (LM41) ......... $1349 86-33 LM5764KCactM.$1459 86-33128K Cache ..... $1479 86-40 (LM65)64KCecha$1459 86S X·20 (LM85) ......... $1499 86DX·33 (LM157) 56K Cache ................. $2289 86DX•50 (lm172)256K... $2889 86-33 EISA ................. $4189 NEW 1T' 286-16Mhz (LM21 )........... $1349 386SX•25Mhz (LM31) ....... $1 449 386SX-33 (LM41) .............. $1499 386·33 (LM57) 64KCache $1579 386·33128K Cache .......... $1599 386•40 (LM65) 64K Cache$1599 486SX·20 (LM85) .............. $1649 486DX·33 (LM157) 256K Cache ...................... $2339 486DX·50 (lm172)256K .... $3039 486·33 EJSA ...................... $4889 WOW. NEW 1 200Mb SYSTE 286·16Mhz (LM21) ............ $1369 16Mhz (LM21 ) ..............$1449 286-16Mhz (LM21 )......... .. 366SX•25Mhz (LM31) ........ $1469 X•25Mhz (LM31) .........$1549 386SX-25Mhz (LM31) ...... . 386SX·33 (LM41) ............... $1519 386SX·33 (LM41) ................ $1599 386SX·33 (LM41) ............... $1 386-33 (LM57) 64K Cache$1599 . 386·33 (LM57) 64K Cache.$1679 386·33 (LM57) 64K Cache.$204 386-33128KCache ............ $1609 386·33128KCache ............. $1699 386·33128K Cache ........... $212 386-40 (LM65) 64K Cache $1599 386•40 (LM65) 64K Cache $1679 386·40 (LM65) 64K Cache $214 486SX·20 (LMSS) ............... $1669 486SX·20 (LM85) ................ $1749 486SX·20 (LM85) ............... $2199 486DX•33 (LM157) 486DX·33 (LM157) 486DX-33 (LM157) 256K Cache ....................... $2359 256K Cache ........................ $2439 256K Cache ........................ $2889 486DX·SO (lni172)256K ..... $3089 486DX·50 (lm172)256K ...... $3189 486DX·SO (lm172)256K ...... $3689 486-33 EISA ....................... $4289 486•33 EISA ........ ,............... $4339 486·33 EISA ........................ 4789 11!1 4" f'fl> 1024 x 768 ~;;;;;;;;;;;:::::'J JI::::- NO~;INTERLACED 6 DOT PITCH.$1895 LET US OU~E ON~~~ o~~J/~1~~oJ~~~ REQUIRE SUPA VGA COLOUR MONITOR 1024 X 768 0.28" DOT PITCH •· • 3 VEAR WARRANTV••• $43 iiiiiiiiiiiiiiiiiiiirrr.i'im l r:::.'niiiiiiiiiiii:R':'::ITRON POWER 200 ~ y MEMORY 1·9 10:-99--100~1 41256-08 ........ $2.95 $2.75 $2.50 1 44256-08 ........ $7.95 $7.75 $7.50 I 44256-07........ $8.95 $8.50 $7.95 : SIMMS 1-9 10•24 25+ 100+ 1 1M x 9-70 $47 $46 $45 $44 : 1Mx9-60 $69 $67 $65 $63 1 1 256K•70 $23 s21 s19 s11 1 256K-80 $21 $19 $17 $15 4M x 9-80 $219 $209 $199 $179 : SIPPS 1M x 9-80 ·t $79 $6 I 9 1 • ~-. A pocket sized Inverter _ with punch. Powers :) - ·appliances Including rv·a video·a, drilla, lights, laptopa etc. · Continuous power rating Is 140 watta. But will run opptlancea with a name plaleratlngol200watta... $159.00 Genius Scanner i(6 · Black, White & Grey•Emulation ·· · Scanner with powerful Photo/ '. Image Editor & Multilingual Omnilont OCR. Windowa Compatible ...... $299.00 . 20" MONITORS Res.1280 x 1024 • - PERSONAL LAMINATOR • ... . (SAVE $10 THIS WEEK!) . Laminate those precious . 9- 0 .31 dot pitch photos, and Important • . $2 995 Display model business cards. Every club or F ' de . organization nG11ds one of these! ora a-arranged monatration . $SS OO ea 7155 This week only • . I FREE FREIGHT ANYWHERE IN AUSTRALIA FOR ORDERS OVER $25.00. OFFER EXPIRES 30/11/92. "- CHECK OUT OUR NEW RANGE OF MIXERS VE CHANNEL ECIAL FECTS MIXER SPEAKERS INDOOR SPIRAL ANTENNA • 300 ohm ribbon cable At laatl A console or lreestanding mixer with eight inbuilt special efllects. Allows sounds and ellecta to be mixed into existing soundtracks without the aid of additional external sound generators. Aa the MM6 Is designed for both DJ and studio uae the following Inputs are provided: • 2 i turntables• 4 x iine inputs• 2 x low impendance microphonea Eight special elfecta are programmed into the unit: •siren • telephone • machine gun • bombing • shooting • ambulance • thunder • laser. Studio outputs are availa ble for connection to a power amplifier and a recording tape or cassette deck. Other features include bass and treble controls headphone (cue) monitoring, CHt to CH2 crosa'tader microphone talkover switch, master volume level co~trol and left and right LED A12013 ............. $299.00 FOUR CHANNEL MICROPHONE MIXER Ila size and simplicity makes this mixer portable and easy to operate. This will accept up to lour low Impedance microphones and mix them through to one microphone output Each microphone volume can be Individually controlled and a master volume control attenuate• the overall audio output level. A12001 ................................. $69.95 antenna • Suits AM/FM tuners and portable TVs. • 1 Meter lead wtth 300 ohm spade terminals L15040......... $9.95 Ill FOUR CHANNEL STEREO AUDIO MIXER • Compact portable desk mount or panel mounting atereo mixer with 5 band equalizer and twin LED display UV meters. • 3 x stereo magnetic tunable inputs switchable • Headphone monitoring on all channels • 18 dB talk over switch • Output sockets for both the amplifier and tape deck. A12012.... $399.95 AUDIONIDEO ONE INRFA RED REMOTE CONTROL FOR YOUR VCR, TV, CD, HIFI & Aux! This unit will replace all your existing remotes & la programmable to replace Mure ones. Has Uquid crystal display, clock, alorm, and countdown Be the first In your office to have a mouse that every one will want use. This cute little mouse cover puta a bit of fun and colour onto your desk while keeping your mouse free of duotl Cr069. ]$795 timer ..... - ...........$67.95 COMPUTER ACCESSORIES 31/2" HARD DRIVE MOUNTING KIT MOUSE CLEANING KIT Keep dust and dirt from damaging your mouse with this handy mouse cleaning kit. This special rounded tool will find ita way into all the hard to get at places. The kit also comes with cleaning fluid and 5 soft cloths to keep your mouse apoueaal C21071 .................$9.95 MOUSE KIT • The MM-4 la a 4•channet stereo mixer with balanced in/output. The trim control corre ■ ponds with all Input signals. and it can control without any distortion by PEAK - . - . - . • LED. Also the EFFECT control ls provided as a kind of line. Each output level can be controlled UR independent volumes. It can be used as a DI-BOX that so the output la balanced. And it does not choose a apace because of the compact s ize. The MM-4 is a mixer designed by musician•• request. FEATURES: • CHANNEL INPUTS •TRIM control • EFFECT level control • PAN control • PEAK LEAD indicator • POWER SWITCH • CHANNEL VOLUME control • MASTER INPUT • EFFECT SEND• EFFECT RETURN • OUTPUT PEAK LED switch • EFFECT RETURN control. ECT RETURN control• EFFECT SEND control • MASTER VOLUME l & R control A 12017........... $299.00 New "wet, dry, wer· aystem cleans and dries all parts which come Into contact with the mag netlc tape. Fluid la applied direcUy on to cloth cleaning tape prior to use. It uses clean tape for each cleaning operation. low drag for use Is sensitive mechanism• - -..... A12004 .............. , .................. $169.00 c21on ...............$1&.9s Keep your computer and accessories free of dust and grime while not in use. xr• Cover Set Stanci alone 3 pin plug Plugo Into oocklt 1dJ1c1nt to the equipment thot you wont 1o·prot1ct. All ouUall on 1 power boord con be protected by ,n-Ung the Trl1ngta'Surg1/Splk1 Plug Into any of Iha flff ouuata. GrHn 11f1ty neon glowo when power 11 on. Approvot No. V88021 Total energy roUng: 225 Jouleo (10/IOOOua) Protection level: 275V Nomlnol, 475V Peok. Reoponaa Time : Better thin 10 nanoaacondo. Automatic rea•L MOUSE GIFT SET ~ X10060 .................$25.00 C21074 ...............$19.95 amount of dust, dirt, or magnetic oxide particles on your drive heada to cause problems, errors downtime or expenelve service call. Regular use of a head cleaner will keep yo..- drive free of trouble causing dirt and help keep yo..- system up and running. These disk cleaners are limple to UN and include cleaning solution and Instructions. • 3 1/2" C12560............$6.95 • 51/4" C12555............$4.95 • - 10" HIGH POWER WOOFER • With ribbed block paper con(!. • 40 wotta • Black duet cap • Cloth edge • Rubber mounting seal C10228 ...... ....$49. 95 1 0" DOPED PAPER CONE • Dark grey cone • Black dust cap • Black round frame C10238 .......... $59. 95 e) 8" FULLRANGE • Twin cone 1pe1kar with white paper cone ideal for public 1ddrea1 C10224 ....... ...$24.95 Here It Is! The Ultimate mouse kit. You get the cute little mouse cover to protect It from dust, the mouse cleanhg kit with the rounded tool & 5 cloths, the mouse house and mouse pad all In a handy black case. It takes only a minute C10233 .......... $44. 95 :1i: I C21068 ......... $16.95 HEAD CLEANER DISKS • Black round frame column speakers. • 30 watts RMS • Foam edge • Whizzer Cone C21066 .............. $14.95 AT' Cover Set . -.... u SURGE/SPIKE SAFETY PLUG they can be added to existing video tape sound tracks. Ideal for weddings. family , sporting and other recordings. ■ • Input for a video camera, VCR, CO, tape, tuner, auxiliary and turntable. • Magnetic/ceramic turntable inputs • Microphone left and right panpot • Optionally available AC power pack • Dual output monitoring VU meters • Linler sliding level fader controls • Mono/stereo microphone input • Video camera or VCA output • Headphone monitoring • Battery opertated 9 volt • Battery testing facility • Mono/atereo switch cpver. A11456 ....... $16.95 ~ A proleulonal audio mixer designed for the aerloua home .,...••■ video movle maker though to the home video camera uaer. Background music and effects can be faded In and out ao Everything you need to keep your mouse happyl You get a mouse pad, a mouse holder, a cleaning kit (previously described) and a cute little mouse VHS VIDEO HEAD CLEANERS • Dark grey cone • Black dust esp rubber ■ urround. • 60 watta RMS X1997~....... $9.95 rr • High compliance rubber surround. • 45 watta RMS • High compliance 2 Universal brackets with acrews to mount 3 1/2" hard drives Into computer cases. MM-4 4-CHANNEL BALANCED MIXER - 8 " DOPED PAPER CONE ~~ ;::' :'.$'"'~----~ ,. , - ~ l'C"'> ----·&_,, ~·:_;. ~ COMPUTER CLEANING KIT To gain optimum performance and prevent damage to valuable disks, this cleaning kit haa all you need to keep yo..computer In top notch performance. Anti-static cleaning pada, cleaning swabe, cleaning solu tion, 5 1/4" & 3 1/'l· cleaning diskettes. c21 on...............$19.95 12" HIGH POWER WOOFER • With ribbed black paper cone • 50 wotta • Black duet cap • Cloth edge • Rubber mounting seal C102291ti4.95 6" HORN & LINE x•FORMER • Weatherproof plutlc horn with 100 volt line transformer • 15 WIiia RMS • Adjustable metal bracket C10218 ...........$74 .95 ADELAIDE STORE NOW OPEN 241-243 WRIGHTST number 1 bastselling wordprocessing book-only from QUEI • Combined tutorial and reference for all levels of users. • In-depth coverage and numerous illustrations for basic and advanced operations • Extras include tear-out command map, icons, margin notes and cautions. 1,232 pages A complete, comprehensive Introduction to this popular DOS utlllty! • Covers all aspects of PC Tool's disk backup, security-and disk optimization. • Practical examples and screen shots. • Features tips, tricks and cautions. 700 pages B20204 ..........................$51.95 B20215 ...•..•.•...•.••... $57.95 USING WINDOWS3.1 SPECIAL EDITION Complete and -.• practical resource - ·- -· · for great Windows Performance! • Takes readers from installation through customization. • Provides tips on boosting windows performance and networking • Includes application techniques and integrations. 1,030 pages B21282 .................... -$51.95 USING EXCEL4 FOR WINDOWS SPECIAL EDITION The expert guide to getting the most from Excel for Windows! • Includes a Quick Start tutorial and numerous tips. • Features a tear-out ce>mmand chart • Provides complete coverage of all features. 1034 pages B20345 ..........................$61.95 3AG PACK OF 40 ($10 Value) Contains: 4 x S00mA, 8 x 1A, 6 X 1.SA, 2 X 2A, 6 X 3A, 4 X SA, 2 x 7.5A, 4x 10A The best selling book on Be>rland C++ updated for the most recent ralaasa! •Provides an overview of both C and C++ • Introduces Iha Windows application development process and explains the major components of a Windows application • Includes coverage oi Turbo C++ for Windows and a separate chapter on Borland's Turbo Debugger and Turbo Profiler 1,000 pages A comprehensive tutorial to this popular disk management and repair package! Includes step by step instruction for optimum performance. • Provides many notes and tables for at a glance reference. Teaches users how to manage flies and solve problems. Make yo;.or PC a better faster and safer place to work with Using Norton Utilities 6 from Qua. 550 pages USING 1-2-3 RELEASE 2.4 SPECIAL EDITION The performance• boosting tutorial reference for the latest version of 1·2-3 for DOS! • Provides tips and advice on how to Improve worksheet, database, and graphics performance • Includes spacial icor.s to highlight the new features of this latest version • Includes detailed instructions for using the latest features of 1·2·3. 1120 pagao B20203 ..........................$55.95 B21269 ...........................$59.95 ~~- USING QBASIC USING TURBO PASCALS 2nd EDITION Perfect tutorial and reference for all beginning QBaslc programmers! • Hands-on instruction and practical programming samples • Step by step tutorials Introduce essential QBaslc concepts Includes a comprehensive instant reference and a complete Keyword reference. 810 pages. · B21287...................... $51.95 100 per pack 1N4002 (1A 200V RECTIFIER) The most comprehensive look at Turbo Pascal 61 • Prov!des a ihorough tutorial of the Turbo Pascal language and environment. • Covers essential aspects of Object• Oriented programming with Pascal 1,800 pages B21290 .......................$61.95 LED MIXED PACK. (MIXED COLOURS) 1N4004 (1A 400V RECTIFIER) Approx 100 pieces, 5mm size Contains 50 Red, 25 Yellow, 25 green. Cat: S15992 ................$8.95 Cat: 210106...............$5.95 Cat: 210136 .............. $14.95 M205 PACK OF 40 ($10 Value) 1N4007 (1A 1000V RECTIFIER) Contains: 5 x S00mA, 10 x 1A, 10 x 2A, 5 x 3A, 5 x SA, 5 x 10A Cat: 210112................$6.95 MIXED SCREW PACK Cat: S15994 ................$8.95 1N914 i 1N4148 Cat: 210135................ $3.95 Approx 100 pieces. This pack is a must for the electronics handy person and computer serviceman. Contains screws for computer cases, _:_,.... •,u Disk Drivas ate. Cat: 210103...............$4.95 1N5404 (3amp 400V) MIXED IC SOCKETS 100 Units ($37.00 Value) Contains: 15 x 8 pin, 20 x 14 pin, 10 x 16 ,pin, 10 x 18 pin, 5 x 20 pin, 10 x 22 pin, 5 x 24 pin, 5 x 28 pin, 10 X 40 pin, Cat: P10546 .............$24.95 B21290 .....................$61.95 (STUDENT ID REQUIRED) WordPerfect {Win) Edu ...... $175.00 Coral Draw V.3 Edu ............ $340.00 MS Excel V.4 Edu ............... $240.00 PageMaker V.4 Edu ............ $300.00 d Base IV Edu ...................... $250.00 Please note: the educational software Is not kept on the shelf. It Is ordered In when you present your student ID. Cat: 210114..............$12.95 LED MIXED PACK (Red only 5mm) Approx 100 places Cat: 210138.............. $11.95 Cat: H10960 ................$3.95 MIXED POLYESTER PACK (In IEC Package) Approx 50 places Cat: R15120 ..................... $9.95 ~ ~ DIE CAST BOXES Diecast boxes are excellent mm hole, available colours 14030 Red ......... $1.20 14032 Green ..... $1.45 14034 Yellow .... $1.45 GREYFl f RIBBON CABLE 14way 16way 20way 24way 25way 26way 34way 36way 40way 50way 60way $/Mir $1.90 $2.20 $ 2 .50 $2.90 $3.20 $3.60 $3.90 $3.90 $4.90 $ 5.90 $ 6.90 10TURNWIRE WOUND POTENTIOMETER quivalent (Bourns 540S Beckman 7256) lals to suit 16-1-11, 8·1·11, 21·1·11 . 14050 SOR R14100 SK 14055 100R R1 411 0 10K 14060 200R R14120 20K 14070 SOOR R14080 1K 14090 2K 1-9 10+ $12.95 $ 10.90 14130 SOK. .............$1 6.95 14140 1001<. ........... $1 5.95 000 000 0 0 0 E]<at>J<at>) nencoded keypad, 10 igit keys plus two utility eys. Light grey in colour. UTPUT ARRANGEMENT: utput Pin No. Symbol .......................N.A_ _ _ _ Shield plate ....................... Column 2 ~- - - - .... Row 1 ....................... Column 3 1>---- .... Row ·1 ...................... Column t ~-----Row2 ....................... Row3 O..................... N.A. at. C19030 -9 10+ 2.95 $2.50 for RF aheildingand strength. Screws are provided with each box. H11451 100 x so x 25mm ........ $8.95 H11452 110 X 60 X 30mm........ $9.50 H11453 120 X 65 X 40mrn. ...... $10.50 H11461 120 x 94 x 53mm...... $13.95 H11462 188 x 120 x 78mm .... $15.95 H11464 188 x 188 x 64mm .... $29.50 ~ ~-~~:~~ PURPOSE TRANSISTORS PN100: a NPN general purpose medium power amp and awitch with continuous collector current up to SOOmA. PN200: a PNP general purpose amp at collector currents to 1 AMP. Both are T0-&2 plastic package. PN100 REPLACES: PN2221, PN2222, PN2222A, PN3585, PN3568, PN3569, PN3643, PN5133, 2N2219A, 2N2222A, 2N3414, 2N341S. 2N3416, 2N3417, 2N3700, 2N3704, 2N3904, 2N4123, 2N4124, 2N4401, 2N5088, 2N5210. PN200 REPLACES: PN2907, PN2907A, PN3638, PN3638A, PN3640, PN3644, PN4121, PN4143, PN4248, PN4249, PN4250, PN4355, PN4916, PN4917, PN5910, 2N2905A, 2N3467, 2N3702, 2N3906, 2N4125, 2N4126, 2N4291, 2N4402, 2N4403, 2N5086, 2N5087, 2N5447. PN100 ......T90001 PN200 ......T90002 1-9 10+ 100+ $0.20 $0.18 $0.15 ---------- SUPER BRIGHT LEDS • RED ................. 210146 • GREEN ........... 210147 • YELLOW........ 210148 1-9 10+ $1 .00 $0.90 Cat No. 210135 210105 210107 210110 210115 210119 10+ $0 .05 $0.06 $0.08 $0.10 $0.18 $0.20 IN4148 IN4002 IN4004 IN4007 IN5404 IN5408 100+ $0.04 $0.05 $0.06 $0.07 $0.14 $0.16 1000+ $0.03 $0.04 $0.05 $0.06 $0.13 $0.15 10K $0.02 $0.03 $0.04 $0.05 $0.11 $0.14 IES XT P.S 11f)W........... $139.00 FULL TOWER 220W P.S ............... $149.00 MINI TOWER 200W P.S ............... $89.00 BABY AT P.S 200W................. $89.00 SLIMLINE BABY AT P.S. 200W................ $89.00 I. .I Sava a small fortune on these "Dlroct Import.. low prollle IC sockets! PCB mounting solder tall. All tin plated phosphor bronze or borrylllum and dual wipe tor rellablllty. 1·9 10+ 100+ P1osso spin t5e 12e 1oe P1056014pin 20e 18e 1~ P10565 t6pin 20e 18e t&e P10567 t8pin 30e 25e 22e P10568 20pin 35e 30e 2~ P10569 22pin 35e 30e 2se P10570 24pin 35e 30e 2se P10572 28pin 45e 35e 30e BREAD BOARDS This inexpensive range of modular interlocking unita enables a quick easy way of experimenting with new circiuts and ideas. There are two main units consisting of a terminal strip or distribution and a central plug in unit. • 100 ho!eL P11000 ................ $2. 75 •840 + 100 holes · P11007............... $14.95 • 1280 +100 holes • P11010 ............ $26.95 •2560 + 700 holes • P11018 ............. $69.95 WIRE WRAP IC SOCKETS Those quality 3 level wire wrap sockets are tin plated phosphor bronze. P10579 8pin $1.50 $1.40 P10580 14pin $1.85 $1.70 Pt0585 t6pin $1.95 $1.80 P10587 18pin $1.95 $1.80 Pt0590 20pin $2.95 $2.75 P10592 22pin $2.95 $2. 70 P10594 24pin $3.95 $3.50 P10596 28pin $3.95 $3.50 P10588 40pin $4.95 $4.50 WOW! WHAT PRICES! IDC PLUGS & SOCKETS WOW I FROM $1 .00 COMPUTER CABLES • Six conductor lhlelded computer Interface cable. Wt2670 • CIC6 6 con. 1•9M 10M+ 100M+ $1.30M $1. tOM $1.00M Wt2672 • CIC9 .9 con. 1-9 M 1CJM+ 100M+ $t.60M $I.SOM $1.20M Wt2674 • CIC12 12 con. 1•9M 10M+ 100M+ $2.SOM $2.20M $1.90M W12676 • CIC16 16 con. 1-9M 10M+ 100M+ $3.SOM $3.20M $2.SOM Wt 2678 • CIC25 25 con. 1·9M 1OM+ D TYPE IDC PLUGS 1-8 10+ • DE9P llpln plug P12166 $1.50 $1.20 • DA15P 15pln plug P12168 $1.50 $1.20 • DB25P 25 pin plug P12170 $4.50 $3.95 100+ $1.00 $1.00 $3.50 DTYPE IDCSOCKETS 1-9 10+ 100+ ■ ocbt • DA15S 15 pin eocket NICADS $3.95 $4.25 $4.50 $4.95 $5.95 $6.95 D Save a fortune on expensive throw away batteries with these quality Nicad• and Rechargeral Size AA450mAH 1-9 10+ 100+ $2.95 $2. 75 $2.50 Size C 12 AH $9.95 $9.50 $8.95 P12169 $1.50 $1.20 $1.1111 • 0825$ 15 pin ■ ocket P12171 $4.50 $3.95 $3.50 $2.95 QUALITY 5mm LEDS Z10150(R). S0.15 $0.12 $0.10 $0.08 Z10151(G), S0.25 $0.20 $0.18 $0.12 Z10152(Y) .. $0.25 S0.20 $0.18 $0.12 ------ s==: 12V DC FANS BO X 80 X 25.4mm 12V OC. 1.7 Watt 0.14 Amp T12469 ................$18.95 10+ tana, only $17.95 FANS Quallty fans for use In power 1mp11 computer hotspot cooling etc. Anywhere you need plenty of air. 240V 4 518" T12461..$16.95 115V 4 518" T12A63 ..$16.95 240V 3 112" 112465.. $16.95 ""l'J"" TOGGLE SWITCHES RECTANGULAR LEDS 1-8 10+ 100+ RED ~ 15e 12, GREEN ~ 15f t2e YELLOW ~ t5e 12, 1K toe toe toe t!<at>.mo a: _)c?i. DB25 CONNECTOR SPECIALS 1-9 10+ 100+ P10880 DE9P $1.00 $0.80 $0.60 P10885 DESS $1.00 $0.70 $0.60 P10881 DA15S$1.00 $0.70 $0.60 P10882 DA15C$1.00 $0.90 $0.60 P10885 DA15S $1.00 $0.80 $0.60 P10902 D825C$1.00 $0.80 $0.60 P10904 D825P $1.00 $0.80 $0.60 P10905 D825S $1.00 $0.80 $0.60 ~ 1-9 10+ S11010 S.P.D.T$1.20 $1.10 S11020 D.P.D.T $1.30 $1 .20 MOSFET SPECIALS ICBVOLTAGE REGULATORS BARGAINS ' Deecrtption 1-9 10+ 1.00+ 7805UC $0.50 78t2UC $0.50 7815UC $0.50 7905UC $0.60 7912UC $0.60 7915UC $0.60 78L05 $0.40 78L12 $0.40 LM324 $1.00 555 $0.40 741 $0.50 $0.45 $0.45 $0.45 $0.55 $0.55 $0.55 $0.30 $0.30 $0.90 $0.38 $0.45 $0.40 $0.40 $0.40 $0.50 $0.50 $0.50 $0.28 $0.28 $0.80 $0.33 $0.39 I ,, t•~ 9 PIN D \ I SWITCH BOXES 2 WAY............... $59.95 4 WAY............... $69.95 MONITOR & KEYBOARD SWITCH BOXES $69.50 • Lever operated suction base grip for instant mounting & portability. • Mounts on smooth non-porous surfaces • Ideal for holding & other small objects • Sii ... Tp ~ S8........ IDC CENTRONICS 36 WAY PLUG & SOCKET 100+ SO.OIi Z10141(G).. $0.20 $0.18 $0.15 $0.12 Z10143(Y).. $0.20 $0.18 $0.15 $0.12 Z10145(0).. $0.20 $0.18 $0.15 $0.12 1 FLASHING LEDS RED 5mm 1-9 10+ 210159 $1.10 $1.00 $0.80 1 OOM+ $3.90M $3.40M $3.00M P12167 $1.50 $1.20 $1.00 . l"SPACING P12060 10pin P12062 20pin Pt2064 26pin P12066 34pin Pt2068 40pin Pt 2070 SOpln 1-9 10+ 2155 240V 6-15V 1A M12155 ........$8.95 $7.95 2156 240V 6-15V A2 M1215fl .......$13.95 $12.95 2851 240V 12°6V CT 250rnA M12851 ..... ...$4.95 .. $4.50 6672 240V 15 30vc 1A tapped M16672 .......$12.95 $11.95 LOW PROFILE IC SOCKETS • OE9S 9 pln CARD EDGE CONNECTORS QUALITY 3mm LEDS ECONOMY 1000+ TRANSFORMERS Z10140(R) S0.15 $0.12 $0.10 BOARD · HOLDER $6.95 I.I . ''\l,, Better than an V..extra pair of hands,.,... A must for all PCB work. T12444 .............. $9.95 1-9 $9.50 $10.00 $8.50 $9.50 $9.50 $9.50 2SJ49 2SJ56 2SKt34 2SK176 2SJSO 2SK13_5 MJ, ~ ,.a 10+ $8.00 $9.50 $8.00 $8.90 $8.50 $8.50 100+ $7.00 $8.50 $7.00 $ 6.90 $7.00 $7.00 ELECTRET MIC INSERTS With pl"9 for uey board ln ■ertton. C10170 10.es 100+ 1000+ $1.20 $1.00 $0.90 $0.70 !t TRANSISTORS BUY IN BULK &SAVEi 1-9 10+ 100+ BC 547 $0.15 $0. to $0.07 BC 548 $0.15 $0.10 $0.07 BC 549 $0.15 $0.10 $0.07 BC 557 $0.15 $0.10 $0.07 BC 558 $0.15 $0.10 $0.07 BC 559 $0.15 $0. to $0.07 BC 327 $0.20 $0.15 $0.12 BC 337 $0.20 $0.15 $0.12 BD 139 $0.75 $0.60 $0.50 BD 140 $0.75 $0.60 $0.50 II PCB MOUNTING SCREW TERMINALS (INTERLOCKING ENDS) Theae lerminala feature interlocking enda to fonn any number of coMeCtiona, . Standard 5mm apacing pina. P10520 1·9 100+ so.rs P10521 $1.00 VHF Channels 0-11 UHF Channels 28-36 Suitable for prime-good signal reception area. This antenna is used for installation on houses, flats and, because of installation simplicity, on caravans and boats. 5 ELEMENTS L15020........ $44.95 AS RIG NO.2 Included with this antenna is a gutter grip mast and 8 metres of twin feeder cable. Suitable for good signal reception areas. Ideal for houses, flats and caravans. Horizontal or vertical A small compact unit that allows transmission of video & audio signals (RF) to any TV set or VCR within range of 30 metres. Ideal for watching videos in the bedroom or kitchen without having to move the entire VCR or having long extention leads running through the house. Can also be used as a transmitter for a video camera . With power on/off switch audio and video leads and supplied with an AC adaptor. A16150 Normally.. $95.95 NOW ONLY..... $84.95 mounting is provided. L10978 ......... $49.95 WIRELESS STEREO TRANSMITTER VHF channels 0-11 UHF Channels 28-36 (AS 25) UHF Channels 36-69 (AS 25/5 Suitable for medium-fringe signal reception areas with good front to back ratio. 18 ELEMENTS L10972 ........ $109.95 This wireless stereo audio transmitter allows portable compact disc and casstte players to be used with any FM tuner/radio. Ideal for the car, boat or home Hi Fi system . Simply play the disc or cassette and tune in the signal on the FM tuner. Can also be used with radio headphones. • Mono or Stereo signals can be received. ANALOGUE WORKHORSE • Fuse and Diode protection •hFE measurements O - 1000 ( By x 10 range) • Mirror scale for more accurate reading. RANGES • DC Voltage: 0 • .1, 0.5, 2.5, 10, 50, 250, 1ooov. (20k ohm/v) • AC Voltage: 0 - 10, 50. 250, 500V, 1000V (8kohm/V) DC Current: 0-0.05, (50uA) 2.5, 25, 250mA • Resistance: 0-2K, 20K, 2M 20M ohm • Load Currant: 0-150uA, 15mA, 150mA • Load Voltage:0-3V • Volume Level: -10- + 22dB. + - 62dB • DC Current Amplification Factor: (hFE) 0-1000 ACCURACY . • DC Voltage & Current: Within +/-3¾ f.s • ·Resistance: Within :/-3¾ Of are. • Battery: 1.5V (um-3) 2pcs. 9V (oo6p) 1 pc • Fuse: o.5A, 50 x 20min • Diode: 4148 x 2 • C.C: 0.04uff x 50V • Size: 147 x 99 x 57mm • Weight: 400g approximately VHF Channels 0-11 UHF Channels 28-36 (AS 20) UHF Channels 36-69 (AS 20/5) Suitable for medium signal reception areas with • - - ••improved VHF gain. 13 ELEMENTS L10970 .......... $99.45 • Triggering Level: Positive and Negetlve 1 continuouely variable level; Pull for Auto. • Sync: AC, HF Rej, TV (each+ or- ) at TV Sync. TV-H (line) and (frame) aync are switched automatically by SWEEP TIME/Div switch. HORIZONTAL DEFLECTION • Deflection factor: 5mV to 20V/ Div on 12 ranges In 1-2-5 otep with fine control • Frequency reoponoe: DC to MHz (-3dB) • Max Input Voltage: 300V DC+ AC Peak of 600V p-p • X-Y operation: X-Y mode lo oelected by SWEEP TIME/.Div owitch. • lntenoity Modulation Z Axis : TTL Level (3Vp-j>-50V) + b<igh~. dark OTHER SPECS: • Weight: 7Kg Approx • Dimenaiona: 162 (H) x 294(W) x 352(D)mm. Q12105........................NOW ONLY $675.00 LOGIC PROBES LOGIC PROBES • Useful for TTL or CMOS hashlgh and low Indicator leds and also with pulse memory. • This Is a very handy tool for the hobbies! or serloustechnlclan for tracing those hard to find faults on logic boards. LOGIC PULSER • Can be used directly to Inject a signal Into logic circuits without removing IC • Compatible with TTL, OTL, RTL, HTL, MO. and CMOS. Q11272 ..............$19.95 Q1127 4 ................. $42.95 ANALOGUE / DIGITAL MULTIMETER 22 ELEMENTS L 10974 ........ $119.95 • Magnifier: XS at all time•. TRIGGERING • Senoitivity hit: 1 Div or more Ext: 1VJ>i> or more. • Source: INT, CH-8, LINE or EXT a11020 ..............$59.95 A16100 ............. $69.95 VHF Channels 0-11 UHF Channels 28-39 Suitable for fringe signal reception with improved front to back ratio and high gain on VHF. CTR DISPLAY:• 150 mm rectangular VERTIACAL DEFLECTION: • Deflection F,ctor: SmV to 20V / Oiv on 12 rangeo in 1-2-5 otep with fine control • Bandwidth DC : DC to 20 MHz (-3dB) AC: 10Hz to 20 MHz (-3dB) • Operating modeo CH-A, CH-B, DUAL and ADD (ALT /CHOP l202 only) • Chop Frequency: 200 KHz Approx. • Channel oeporotion: Better than 60dB at 1KHz TIME BASE • Type : Automatic & normal triggered In automatic mode, oweep ia obtained without input oignal • Sweep Time: 0.2m Sec to 0.5 Sec/ Div on rangee In 1-2-5 atep with fine control and X-Y. DIGITAL MULTMETER HC-3500T DISPLAY: 3/12 DIGIT BASIC ACCURACY: 0.5¾DC DC VOLTAGE: 0-1000V DC CURRENT: 0-20A AC VOLTAGE: 0-750V AC CURRENT: 0-20 A RESISTANCE: 0-20M OHMS TEMPERATURE:-20°C • 1200°c CONTINUITY TEST, DIODE TEST TEMPERATURE CAPACITANCE FREQUENCY, hie TEST, DATA HOLD. Q13000 ...was $169.00 now only $149.00 • HC - 50508 3 1/2 DIGIT • Basic accuracy: 0.5o/oDC • DC Voltage: 0 -1000V • DC Current: 0-10A • AC Voltage: 0 -750V • AC Current: 0 - 10A • Resistance: 0 • 20M ohms • DC AC DMS:-45dB. +50dB • Temperature: -20°c • 1200°c • AC Freq Spread: 50 Hz 2KHz Continuity Test, Diode Test. Q13020..•......... $169.00 ADELAIDE $TORE NOWOPEN 241-243 WRIGHT ST PH: (08) 211 7200 Silicon Chip BACK ISSUES July 1988: Stereo Control Preamplifier, Pt.2; Fitting A Fuel Cut-Off Solenoid To Your Car; Booster For TV & FM Signals; The Discolight Light Show, Pt.1; Tone Burst Source For Amplifier Headroom Testing; What Is Negative Feedback, Pt.3; Amplifier Headroom - Is It A Con? August 1988: Building A Plasma Display; Universal Power Supply Board; Remote Chime/Doorbell; High Performance AC Millivoltmeter, Pt.1; Discolight Light Show, Pt.2; Getting The Most Out Of Nicad Batteries; Data On Insulated Tab Triacs. September 1988: Hands-Free Speakerphone; . Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Build The Vader Voice; Motorola MC34018 Speakerphone IC Data; What Is Negative Feedback, Pt.4. October 1988: Stereo FM Transmitter (Uses Rohm BA1404); High Performance FM Antenna; Matchbox Crystal Set; Electronic House Number; Converting A CB Radio To The 28MHz Band; Queensland's Powerful Electric Locomotives. November 1988: 120W PA Amplifier Module (Uses Mosfets); Poor Man's Plasma Display; Automotive Night Safety Light; Adding A Headset To The Speakerphone; How To Quieten The Fan In Your Computer; Screws & Screwdrivers, What You Need To Know; Diesel Electric Locomotives. December 1988: 120W PA Amplifier (With Balanced Inputs) , Pt.1 ; Diesel Sound Generator; Car Antenna/Demister Adaptor; SSB Adaptor For Shortwave Receivers; Why Diesel Electrics Killed Off Steam; Index to Volume 1. January 1989: Line Filter For Computers; Ultrasonic Proximity Detector For Cars; 120W PA Amplifier (With Balanced Inputs) Pt.1 ; How To Service Car Cassette Players; Massive Diesel Electrics In The USA; Marantz LD50 Loudspeakers. February 1989: Transistor Beta Tester; Minstrel 2-30 Loudspeaker System; LED Flasher For Model Railways ; Build A Simple VHF FM Monitor (uses MC3362), Pt.1; Lightning & Electronic Appliances; Using Comparators to Detect & Measure. March 1989: LED Message Board, Pt.1; 32-Band Graphic Equaliser, Pt:1; Stereo Compressor For CD Players; Amateur VHF FM Monitor, Pt.2; Signetics NE572 Compandor IC Data; Map reader For Trip Calculations; Electronics For Everyone Resistors. April 1989: Auxiliary Brake Light Flasher; Electronics For Everyone: What You Need to Know About Capacitors; Telephone Bell Monitor/Transmitter; 32-Band Graphic Equaliser, Pt.2; LED Message Board, Pt.2. May 1989: Electronic Pools/Lotto Selector; Synthesised Tom-Tom ; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference ; LED Message Board, Pt.3; Electronics For Everyone - All About Electrolytic Capacitors. June 1989: Touch-Lamp Dimmer (uses Siemens SLB0586); Passive Loop Antenna For AM Radios; Build A Universal Temperature Controller; Understanding CAO Probes; LED Message Board, Pt.3. July 1989: Exhaust Gas Monitor (Uses TGS812 Gas Sensor); Extension For The Touch-Lamp Dimmer; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm; NSW 86 Class Electric Locomotives. September 1989: 2-Chip Portable AM Stereo Radio (Uses MC 13024 and TX7376P) Pt.1 ; AlarmTriggered Telephone Dialler; High Or Low Fluid . Level Detector; Simple DTMF Encoder; Studio Series 20-Band Stereo Equaliser, Pt.2; Auto-Zero Module for Audio Amplifiers (Uses LMC669). October 1989: Introducing Remote Control; FM Radio Intercom For Motorbikes (Uses BA 1404 & TDA7000) Pt.1; GaAsFet Preamplifier For Amateur TV ; 1Mb Printer Buffer; 2-Chip Portable AM Stereo Radio, Pt.2; Installing A Hard Disc In The PC. November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY & Morse); Sensitive FM Wireless Microphone; FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Rad io, Pt.3 ; Floppy Disc Drive Formats & Options; The Pilbara Iron Ore Railways . l ------------------------------ --- ---, .- Use this handy form to order your back issues I I Please send me a back issue for: D October 1988 D March 1989 D September 1989 O February 1990 o July 1990 O December 1990 D May 1991 o October 1991 O March 1992 o August 1992 D November 1988 D April 1989 0 October 1989 0 March 1990 O August 1990 O January 1991 O June 1991 O November 1991 O April 1992 O September 1992 0 O 0 0 0 O O 0 July 1988 December 1988 May 1989 November 1989 April 1990 September 1990 February 1991 July 1991 o December 1991 0 May 1992 o October 1992 Enclosed is my cheque/money order for $___or please debit my: o August 1988 January 1989 June 1989 December 1989 May 1990 o October 1990 O March 1991 o August 1991 O January 1992 o June 1992 O O O 0 O Bankcard Card No. Signature _ _ _ _ _ _ _ _ _ _ _ _ _ Card expiry date_ _ /_ _ O Visa Card O O 0 O O O O O September 1988 February 1989 July 1989 January 1990 June 1990 November 1990 April 1991 September 1991 o February 1992 0 July 1992 O Master Card $5.00 each (includes p&p) . Overseas order,s add $1 each for postage. NZ orders are sent air mail. Detach and mail to: Street _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROY BEACH NSW 2097 Suburb/town _ _ _ _ _ _ _ _ _ _ _ _ _ _ Postcode _ _ _ _ __ Or call (02) 979 5644 & quote your credit card details. Fax (02) 979 6503. Name ____________________________ L---------------------------------- ----96 SILICON CHIP December 1989: Digital Voice Board (Records Up To Four Separate Messages); UHF Remote Switch ; Balanced Input & Output Stages; Data For The LM831 Low Voltage Amplifier IC; Install A Clock Card In Your PC; Index to Volume 2. January 1990: High Quality Sine/Square Oscillator; Service Tips For Your VCR; Speeding Up Your PC; Phone Patch For Rad io Amateurs; Active Antenna Kit; Speed Controller For Ceiling Fans; Designing UHF Transmitter Stages. February 1990: 16-Channei Mixing Desk; High Quality Aud io Oscillator, Pt.2; The Incredible Hot Canaries; Random Wire Anten na Tuner For 6 Metres ; Phone Patch For Radio Amateurs, Pt.2; PC Program Calculates Great Circle Bearings. March 1990: 6/12V Charger For Sealed LeadAcid Batteries; Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16Channel Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC. April 1990: Dual Tracking ±50V Power Supply; VOX With Delayed Audio; Relative Field Strength Meter; 16-Channel Mixing Desk, Pt.3; Active CW Filter For Weak Signal Reception; How To Find Vintage Rad io Receivers From The 1920s. May 1990: Build A 4-Digit Capacitance Meter; High Energy Ignition For Cars With Reluctor Distributors; The Mazzie CW Transceiver; Waveform Generation Using A PC, Pt.3; ·16-Channel Mixing Desk, Pt.4; What To Do When You r Computer Goes Bung, Pt.1 . June 1990: Multi-Sector Home Burg lar Alarm; Low-Noise Universal Stereo Preamplifier; Load Protection Switch For Power Supplies; A Speed Alarm For Your Car; Design Factors For Model Aircraft ; Fitting A Fax Card To A Computer; What To Do When Your Computer Goes Bung, Pt.2. July 1990: Digital Sine/Square Generator, Pt.1 (Covers 0-500kHz); Burglar Alarm Keypad & Combi nation Lock; Simple Electronic Die; Low-Cost Dual Power Supply; Inside A Coal Burning Power Station; What To Do When You r Com puter Goes Bung, Pt.3; Weather Fax Frequencies. August 1990: High Stability UHF Remote Transmitter; Universal Safety Timer For Mains Appliances (9 Minutes) ; Horace The Electronic Cricket; Digital Sine/Square Wave Generator, Pt.2; What To Do When Your Computer Goes Bung, Pt.4. September 1990: Music On Hold For Your Telephone ; Remote Control Extender For VCRs ; Power Supply For Burglar Alarms; Low-Cost 3Digit Counter Modu le ; Simple Shortwave Converter For The 2-Metre Band. October 1990: Low-Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; . Surfsound Simulator; DC Offset For DMMs; The Dangers of Po lych lorinated Biphenyls ; Using The NE602 In Home-Brew Converter' Circuits. November 1990: How To Connect Two TV Sets· To One VCR ; A Really Snazzy Egg Timer; LowCost Model Train Controller; Battery Powered Laser Pointer; 1.5V To 9V DC Converter ; Introduction To Digital Electronics ; Simple 6-Metre Amateur Transmitter. December 1990: DC -DC Converter For Car Amplifiers; The Big Escape - .A Game Of Skill; Wiper Pulser For Rear Windows; Versatile 4-Digit Com- bination Lock; 5W Power Amplifier For The 6Metre Amateur Transmitter; Index To Volume 3. January 1991: Fast Charger For Nicad Batteries, Pt.1; The Fruit Machine; Two-Tone Alarm Module; Laser Power Supply; LCD Readout For The Capacitance Meter; How Quartz Crystals Work; The Dangers When Servicing Microwave Ovens. February 1991: Synthesised Stereo AM Tuner, Pt.1; Three Inverters For Fluorescent Lights; LowCost Sinewave Oscillator; Fast Charger For Nicad Batteries, Pt.2 ; How To Design Amplifier Output Stages; Tasmania's Hydroelectric Power System. March 1991 : Remote Controller For Garage Doors, Pt.1 ; Transistor Beta Tester Mk.2; Synthesised AM Stereo Tuner, Pt.2; Multi-Purpose 1/0 Board For PC-Compatibles; Universal Wideband RF Preamplifier For Amateurs & TV; A Look At The Config .Sys & Ansi.Sys Files. April 1991 : Steam Sound Simulator For Model Railroads; Remote Controller For Garage Doors, Pt.2; Simple 12/24V Light Chaser; Synthesised AM Stereo Tuner, Pt.3; A Practical Approach To Amplifier Design, Pt.2; Playing With The Ansi.Sys File; FSK Indicator For HF Transmissions . May 1991 : Build A DTMF Decoder; 13.5V 25A Power Supply For Transceivers; Stereo Audio Expander; Fluorescent Light Simulator For Model Railways ; How To Install Multiple TV Outlets, Pt.1 ; Setting Screen Colours On Your PC. June 1991 : A Corner Reflector Antenna For UHF TV; 4-Channel Lighting Desk, Pt.1; 13.5V 25A Power Supply For Transceivers; Active Filter For CW Rec·eption; Electric Vehicle Transmission Options ; Tuning In To Satellite TV, Pt.1. July 1991: Battery Discharge Pacer For Electric Vehicles ; CD Error Analyser, Pt.1; Loudspeaker Protector For Stereo Amplifiers; 4-Channel Lighting Desk, Pt.2; How To Install Multiple TV Outlets, Pt.2; Tuning In To Satellite TV, Pt.2; PEP Monitor For Transceivers August 1991 : Build A Digital Tachometer; Masthead Amplifier For TV & FM; PC Voice Recorder; Error Analyser For CD Players, Pt.2; Tuning In To Satellite TV, Pt.3 ; Installing Windows On Your PC; Step-By-Step Vintage Radio Repairs . September 1991 : Studio 3-55L 3-Way Loudspeaker System ; Digital Altimeter For Gliders & Ultralights, Pt.1; Build A Fax/Modem For Your Computer; The Basics Of AID & DIA Conversion ; Windows 3 Swapfiles, Program Groups & Icons; How Glass-Mount Antennas Work . October 1991: Build A Talking Voltmeter For Your PC, Pt.1; SteamSound Simulator Mk.11 ; Magnetic Field Strength Meter; Digital Altimeter For Gliders & Ultralights, Pt. 2; Getting To Know The Windows PIF Editor. November 1991 : Colour TV Pattern Generator, Pt.1; Battery Charger For Solar Panels; Flashing Alarm Light For Cars; Digital Altimeter For Gliders & Ultralights, Pt.3; Build A Talking Voltmeter For Your PC, Pt.2 ; Error Analyser For CD Players Pt.3; Modifying The Windows INI Files. December 1991 : TV Transmitter For VCRs With UHF Modulators; lnfrared Light Beam Relay ; Compact Solid-State Laser Pointer; Colour TV Pattern Generator, Pt.2; Windows 3 & The Dreaded Unrecoverable Application Error; Index To Vol. 4. January 1992: 4-Channel Guitar Mixer; Adjustable 0-45V BA Power Supply, Pt.1 ; Baby Room Monitor/FM Transmitter; Automatic Controller For Car Headlights; Experiments For Your Games Card; The GPS Satellite Navigation System; Restoring An AWA Radiolette Receiver. February 1992: Compact Digital Voice Recorder; 50-Watt/Channel Stereo Power Amplifier; 12VDC/ 240VAC 40-Watt Inverter; Adjustable 0-45V BA Power Supply, Pt.2; The Mobile Telephone Revolution; Designing A Speed Controller For Electric Models. March 1992: TV Transmitter For VHF VCRs ; Studio Twin Fifty Stereo Amplifier, Pt.1 ; Thermostatic Switch For Car Radiator Fans; Telephone Call Timer; Updating The Resistor/Capacitor Scene; Coping With Damaged Computer Directories; Valve Substitution In Vintage Radios. April 1992: lnfrared Remote Control For Model Railroads; Differential Input Buffer For CROs; Studio Twin Fifty Stereo Amplifier, Pt.2; Understanding Computer Memory; Switching Frequencies in Model Speed Controllers; Aligning Vintage Radio Receivers, Pt.1. May 1992: Build A Telephone Intercom; LowCost Electronic Doorbell; Battery Eliminator For Personal Players; lnfrared Remote Control For Model Railroads, Pt.2; A Look At Large Screen High Resolution Monitors; OS2 Is Really Here; Aligning Vintage Radio Receivers, Pt.2. June 1992: Multi-Station Headset Intercom, Pt.1 ; Video Switcher For Camcorders & VCRs; lnfrared Remote Control For Model Railroads, Pt.3; 15Watt 12-240V Inverter; What's New In Oscilloscopes? ; A Look At Hard Disc Drives; Video Edit'. ing On The Small Screen. July 1992: Build A Nicad Battery Discharger; 8Station Automatic Sprinkler Timer; Portable 12V SLA Battery Charger; Off-Hook Timer For Telephones; Multi-Station Headset Intercom , Pt.2 ; Understanding The World Of CB Radio; Electron ics Workbench For Home Or Lab. August 1992: Build An Automatic SLA Battery Charger; Miniature 1.5V To 9V DC Converter; The lnterphone Digital Telephone Exchange, Pt.1; Dummy Load Box For Large Audio Amplifiers; Internal Combustion Engines For Model Aircraft; Troubleshooting Vintage Radio Receivers . September 1992: Multi-Sector Home Burglar Alarm; The lnterphone Digital Telephone Exchange, Pt.2; General-Purpose 3½-Digit LCD Panel Meter; Track Tester For Model Railroads ; Build A Relative Field Strength Meter; Internal Combustion Engines For Model Aircraft, Pt.2. October 1992: 2kW 24VDC To 240VAC Sinewave Inverter; Multi-Sector Home Burglar Alarm, Pt.2; Mini Amplifier For Personal Stereos; Electronically Regulated Battery Charger (charges 6V, 12V & 24V lead-acid batteries) ; Internal Combustion Engines For Model Aircraft, Pt.2. PLEASE NOTE: All issues from November 1987 to June 1988 plus the August 1989 issue are now sold out. All other issues are presently in stock. For readers wanting articles from sold-out issues, we can supply photostat copies (or tearsheets) at $5.00 per article, including postage. When supplying photostat articles or back copies, we automatically supply any relevant Notes & Errata at no extra charge . N O VEMBER 1992 97 ASK SILICON CHIP Got a technical problem? Can't understand a piece of jargon or some technical principle? Drop us a line and we'll answer your question. Write to:Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. Stereo AM radio needs better alignment Could you please help me with the following questions about your stereo AM radio project as described starting with the February 1991 issue of SILICON CHIP. On my radio, only three signal strength LEDs ever light up even when tuned to the ABC stations, which in Melbourne are the strongest. I am concerned about what I had to do to fit the antenna coil to the ferrite rod. Because the supplied coil was too large for the rod I had to wrap several layers of paper around the rod to ensure a snug fit for the coil. Although the alignme.nt seemed to work OK, is it likely that this electromagnetically sloppy fit is coupling insufficient RF signal into the front end of the tuner? In the section on IF alignment, you say, "connect the multimeter between TP2 and Ground". Shouldn't that be to TPl, which is the AGC level , and not TP2 which is the tuning voltage? 1.5V power for the SteamSound Simulator In the August 1992 issue of SILICON CHIP, S. H. of Woonona, NSW, asked if it was possible to operate the SteamSound Simulator (October 1991) from lower voltages. Your answer was that it is not possible because the noise generator part of the circuit requires at least 9-lOV to produce any noise. Unfortunately, I'm not in possession of your October 1991 issue so I do not know the specifications of the unit. However, it should be possible to run it from a 1.5V cell using your 1.5V to 9V DC Converter (SILICON CHIP, August 1992). This circuit should also be perfect for passenger train lighting. The lights won't blink when you speed 98 SILICON CHIP Nevertheless, the meter response at TPl when tuning 13 and L4 is very flat - barely perceptible, in fact. Is that typical? Regarding the 3.6MHz oscillator, your instructions imply that during adjustment there is a working range within which the 3.6MHz oscillator will lock onto the 450kHz IF. I have no range - only a point. The slightest touch of the oscillator coil causes the stereo to drop out and even when it is left alone, stereo lock is intermittent on some stations and totally absent on others (which are transmitting in stereo). In describing the adjustment of the whistle filters, you specify a resistance of 32. 76kQ However, the sum of the resistances when all the trimmers are set to maximum can be no more than 33kQ (18kQ + 5kQ + 10kQ). That leaves very little room for error. Is the 32.76kQ correct? And is the accuracy implied in that specification necessary? That is, is a digital multimeter required? Do you have typical voltages for the train up, or dim when you slow down, or go out when the train stops. (T. Van der Burg, Christchurch, NZ). • This seems like an excellent idea and, although we haven't tried it, it should work. S. H. wanted to run the sound generator circuitry from batteries so that the SteamSound Simulator still made "hissing" noises when the train was stationary. As suggested by Mr Van der Burg, it should be possible to run this section from a 1.5V cell via the 1.5V To 9V DC Converter. Note, however, that the sawtooth oscillator based on Q2 & IClb should continue to monitor . the track voltage via the bridge rectifier (D1-D4) to control the "chuff' frequency. various points on the circuit other than the AGC and tuning voltage? This would help with troubleshooting. (B. F., Kew, Vic) . • Notes and Errata were published on this project in the September 1991 issue and these cover most of your questions. In particular, they answers your question on the whistle filter resistance range and the error regarding TPl in the IF alignment. A digital multimeter must be used to obtain the 32.76kQ resistance in the whistle filters since the accuracy here sets the depth of the notch filter. The problem with your tuner is likely to be in the alignment of trimmer Cl. This can be adjusted to a false peak, as detailed in the Notes & Errata. The 3.6MHz oscillator does have a quite narrow range of adjustment. However, we suspect that the stereo lock is touchy because of the low signal level. Try realigning the circuit again, taking note of the points on adjusting Cl, and this should cure your problem. The ferrite rod and coil coupling is satisfactory even though the coil diameter is larger than the ferrite rod. In fact, we used a similar technique to the one you have used to secure the coil. Incidentally, if you want to find out when or if Notes & Errata have been published on any of our projects, there is a list in the index published each year in the December issue. Track cleaner for model railroads As a model railroad buff, I read with' interest all your articles on railroad projects for sound, lighting and model control. The "Track Tester for Model Railroad Layouts" in the September 1992 issue is great. This device is handy for locating and identifying trouble spots on a layout, such as open circuits and intermittent or dirty tracks. My own problems in particular are due to car- rosion and oxidisation of the track, resulting in bad electrical contact between the track and the loco. From articles I have read in railroad magazines, mainly American, there is a commercial device available that rids us of this problem. It is marketed under the name of"RELCO". The device is a high frequency generator which converts 16VAC into 300V at 300kHz and very low current. This high-frequency 300V signal ionises the gaps caused by dirt and oxidisation on the track. My request is, do you have a circuit for such a device or could you publish something in a future edition of SILICON CHIP? (M. H., Cairns, Qld). • We have not seen the RELCO device but it seems possible that it would contravene Department of Transport and Communications regulations because it will radiate quite a high power signal at 300kHz. We would be wary of such a device anyway because it could damage any semiconductor circuitry connected to the track and may also lead to a potential shock problem. In practice, we have found that a pulse width modulation controller, as featured in the April, May and June 1992 issues, is quite effective in overcoming most of the problems with dirty track. The original PWM controller, on which this circuit was based, was published in the April 1988 and May 1988 issues. Comments on the solar battery charger I recently purchased a kit for my Solar Battery Charger from Jaycar Electronics and assembled it using the supplied parts. When initially tested, the unit drew high current but only had low output. The problem stemmed from the transistors supplied for Ql and Q2. The ones supplied were BD649/650 but when I replaced these with TIP121/ 126 transistors, as originally specified, the problem disappeared. I then went a little further and replaced these transistors with the supplied BD649/650 devices and altered the timing capacitor from 470pF to 4700pF - problem solved again. While the BD649/BD650 transistors may initially seem to be good "equivalents" they are not the same as the devices specified in my original de- Dirty heads on a Beta VCR I recently found that my old Beta video recorder has some major problems. It's fairly old and heavy and has been sitting in my cupboard for nearly five years until now. This particular model (Sanyo VTC 9300) is a top load/eject type and it has trouble loading and ejecting the tape. It also usually refuses to fast forward, rewind or even play a tape. When it does play, the picture flickers between colour -and black and white and has interference lines across the screen and looks like the picture is about to break up, all because it may have mechanical problems. I think that the heads on the VCR have a serious problem because I took the cover off and looked at the playing drum. It had a lot of grime built up on the smooth surface of the drum assembly. I spent some time with a specialised head cleaner fluid and went around with cotton buds removing grit and dirt, of which there sign. In fact, there are no equivalents to the TIP121 or TIP126 - their specifications cannot be directly matched with anything. However, the BD649/ 650 devices can be used, provided the timing capacitor value is changed. The function of this project has also been misunderstood by a few people. If a solar panel is directly connected to a 12V battery and its output is less than the battery voltage, · that solar panel will not charge the battery. The efficiency here is 0%. The Solar Battery Charger, on the other hand, allows the battery to be charged even if the output from the solar panel falls below 5V. Note, however, that the charger's efficiency is only about 50% when operating in step-up mode, increasing to a maximum of about 84% in step-down mode. Of course, if a directly connected solar panel is charging a battery, the efficiency is 100% (not counting cable losses or the efficiency of the solar cells). One also has to remember that bat- was quite a large amount. But even after this, the pictur~ still didn't change. The sound was perfect (spot on, in fact). I think that it's not an electronic fault but a mechanical fault, where the motor speed is going too fast. The motor is a 115V type in series with a winding on the transformer. I removed all of the rubber belts and found that they were all OK there wasn't any wear on them at all. Can you help me or put me on to someone who can assist me in repairing different models and types of VCRs? (J. E., Blackburn South, Vic). • From your description it is still likely that the fault is caused by dirty heads. While you may have been fairly thorough in cleaning grime off the drum, it is grime in the head gaps which will cause the problem. The reason that head dirt causes a problem with speed is that the speed control circuitry relies on the sync pulses recorded on the tape and if the heads can't reliably pick up this signal, the speed control circuitry will not work. tery voltage will change depending on the state of charge. This circuit will charge a battery from a discharged state of 10.5V to a fully charged state over a period of time and the current will vary depending on the state of charge. It also depends on the amount of power available from the solar panel. The recommended solar panel size is 6W and above. A 1W panel could only ever supply 83mA of charging current, which is not enough for charging large batteries. It would, however, charge a 830mAh battery over 10-14 hours, or just keep a 1.2Ah battery topped up if the equipment connected to it drew very little current. (Steve Calder, Parramatta,NSW). Problems with the masthead amplifier A letter from R. W. of Brunswick Heads (SILICON CHIP, June 1992) has prompted me to write to you concerning the Masthead Amplifier article NOVEMBER 1992 99 Modifying the FM subcarrier adapter I have collected all the components for the FM Subcarrier Adaptor project described in the January 1988 edition of SILICON CHIP. Hm.vever, l have now discovered that the particular transmission that I want to hear is not on the subcarrier frequency of 67kHz but on another frequency about 30kHz away. It seems that it would be easy enough to alter the VCO frequency (refer last paragraph, page 85) but what about the bandpass filter? I am not into filter design - can it be adjusted to accommodate the other frequency? The transmission referred to above is on 2SER-FM. It is a relay of the BBC from the UK. I understand it is on a subcarrier frequency of about 96kHz. The BBC is charg- which appeared in the August 1991 issue. I built four of these amplifiers but only one behaves properly. The trouble I encountered was severe oscillation throughout Band 1 to Band 5 of the VHF and UHF spectrum. This was detected by the screen of the tel evision showing herringbone patterns and blacking out of the screen, not to mention the most unusual sounds from the audio department. The OM350s became quite warm and the input voltage to pin 5 of the chip dropped to 8V DC. The use ofmy TV field strength meter was an asset. I detected up to lmV of RF on a multi- ing A$150 per year for this service and a modified FM receiver is provided to subscribers. Regarding the answer given on page 92 of SILICON CHIP, July 1992, about' resistors with six colour ban ds being "pretty rare", if you go to Geoff Wood Electronics you'll find plenty with six colour bands - at least that's the way it was the last time I was there. (W. W., Greenfield Park, NSW). • It should be possible to modify this circuit to receive the higher subcarrier merely by changing the capacitors in the twin-T filter circuit. All that should be required is to change the capacitors from 0.0022µF to 0.0015µF. No other changes to the circuit should be necessary. Thanks for your comments on 6-band resistors. It seems that they may be a little more commonplace than we thought. tude of frequencies . After a lot of fault finding, I put it down to a poorly designed PC board, with poor placement of components allowing feedback to the input of the OM350. I installed ferrite beads on some component leads, especially that long wire link on the PCB. This did help to tame the amplifiers to a certain ey' ,at but not enough. I also used mon:, '..,ypass capacitors and this also helped to eliminate unwanted resonances, but again this was not enough. I cut the long PCB track that runs from the AC input of the board to L2. I then relocated L2 under the PCB Drill Speed Controller - Amended PC Board il N N 0 0 CJ\ CJ\ .... ....u 0 0 c.? !!.1 100 SILIC O N CHIP . This is the revised PC pattern for the Drill Speed Controller featured in September 1992. The circuit modifications are detailed on page 22 of this issue. across the cut track right at the coaxial output to the power supply, th en bypassed L2 on the diode side with a 1000pF disc ceramic. Where L2 was originally located, I ran a wire link through a ferrite bead and of course bypassed it. Beauty! - the amplifiers behaved very well and I could not detect any oscillation. So after reinstalling one of the amplifiers in its proper place, everything worked fine. I was watching a video and it was raining and after switching back to watch Channel 8, I was horrified to find that the amplifier was taking off again. It makes me wonder why this design was used. I would think that dispensing with the noisy OM350s and using BFR91s or BFR94s and a properly designed double sided PCB, one side being used as a groundplan e, would give better results. Like R. W. of Brunswick Heads, all I have for my couple of hundred dollars are four power supplies, one amplifier and a heap of junk. I wonder if others have built this kit and have encountered the same problems. I now use a commercial masthead amplifier built by Kingray with 34dB of gain to boot - a very stable unit. (G. C., Ouyen, Vic). • From your letter, it seems more likely that you have experienced a number of faulty OM350s. We cannot agree that the board design is faulty and indeed the layout for the 0M350 section is quite close to that suggested in the Philips data· for this device. Nor can we agree with the addition of ferrite beads to various component leads or any of your other modifications. For example, the addition of a ferrite bead to the long link on the board will actually increase the output impedance of the regulated supply and may even lead to spurious oscillation in the LM317. It is true that many commercial masthead amplifiers do not use the OM350 and similar hybrid amplifiers but use discrete transistors. However, we believe this has more to do with reasons of economy rather than performance. Yours is the first specific complaint we have had regarding this design (apart fro m R. W. in Jun e) and so we are not aware of other readers experiencing the problems described in your letter - this despite the many hundred of kits sold. SC ~ J-J --J -- -"""'t;I ,~-;; : , ~ , - , I JL J .J J ORDER FORM Jf=J~jJ ::!.JJ~J.ll..LJ..J -...J .J ., ..... ....... _,J ..A BACK ISSUES* YEAR MONTH MONTH YEAR MONTH YEAR MONTH YEAR *Back issues are $AS each (incl. postage). Overseas orders add $A 1 per issue for postage. BINDERS Please send me _ _ SILICON CHIP binder(s) at $A14.95 each (incl. postage). Overseas orders please add $A3.00 each for postage. TOTAL PRICE $A SUBSCRIPTIONS r - - - - - - - - - - - -·, 0 New subscription - month to start D Renewal - D Sub. 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Please have your credit card details ready Fax the coupon with your credit card details 24 hours 7 days a week Card expiry date I Mail coupon to: Freepost 25 Silicon Chip Publications PO Box 139, Collaroy Beach 2097 No postage stamp required in Australia NOVEMBER 1992 101 __TCENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. ANTIQUE RADIO ANTIQUE RADIO restorations. Your one-stop radio repair shop. Specialising in restoring vintage radios, including chassis rewiring, re-condensing, quality new parts, valves, valve sockets, speakers, power & audio transformers. Secondhand radio dials & parts for most brands & models. About 400 radios in stock for sale, restoration & parts. Every restored wireless is covered by a 2year warranty on parts & labour. We restore damaged woodwork & cabinets & French polish (approx. 40 coats). Vintage car radios available for sale or restoration. Repairs done on tape decks. Open Sat. 10am-5pm; Sun. 12 .30-5pm. 109 Cann St, Bass Hill, NSW 2197. Phone (02) 645 3173 BH or (02) 726 1613 AH. FOR SALE WEATHER FAX programs for IBM XT/ ATs *** "RADFAX2" $35 is a high reso- lution, shortwave fax, Morse & RTTY receiving program. Suitable for CGA, EGA, VGA and Hercules cards (state which). Needs SSB HF radio & Radfax decoder. *** "SATFAX" $45 is a NOAA, Meteor & GMS weather satellite picture receiving program. Needs EGA or VGA plus "WEATHER FAX" PC card. *** "MAXISAT" $75 is similar to SATFAX but needs 2Mb expanded memory (EMS 3.6 or 4.0) and 1024 x 768 SVGA card. All programs are on 5.25-inch or 3.5-inch disks (state which) & include documentation. Add $3 postage. Only from M. Delahunty, 42 Villiers St, New Farm, Old 4005. Phone (07) 358 2785. SPRINKLER CONTROLLER KIT: get ready for summer with this very popular kit. Very reliable and versatile design can control eight stations and has 32 programmable START and RUN times (refer SILICON CHIP, July 1992). All settings stored in EEPROM. Can be expanded to 64 with the addition of extra memory chip and switch. Requires 24V AC to run. Complete kit including r-------------------------, CLASSIFIED ADVERTISING RATES Advertising rates for this page: Classified ads: $10.00 for up to 15 words plus 40 cents for each additional word . Display ads (casual rate): $20 per column ·centimetre (Max. 10cm). Closing date: five weeks prior to month of sale. To run your classified ad, print it clearly on a separate sheet of paper & send it with your cheque or credit card details to: Silicon Chip Classifieds, PO Box 139, Collaroy Beach, NSW 2097. Or fax the details to (02) 979 6503. Enclosed is my cheque/money order for $_ _ _ _ or please debit my D Bankcard D Visa Card D Master Card I I I I I I I I I 102 SILICON CHIP NEW 280 SINGLE BOARD COMPUTER: designed for the 1990s.Also modern kits. Local SAE for details. DIY Electronics, GPO Box 904, Hong Kong. THE HOMEBUILT DYNAMO: (plans) brush less, 1000 watt at 740 revs. $A85 postpaid airmail from Al Forbes, PO Box 3919 - SC, Auckland, New Zealand. Phone Auckland (09) 818 8967 anytime. VALVE RADIO RESTORATION BUSINESS: established 7 years. Specialising in vintage & classic car radios; sole agents in Australia for FM conversion units and solid state vibrators. Ideal opportunity for technician (ex-Telecom?) to purchase a well-established business situated in a popular, progressive Melbourne shopping centre. Long lease available. For further information contact: Nostalgic Wireless, PO Box 144, Surrey Hills, Vic 3127. x I I I I Signature_ _ _ __ _ _ _ _ _ _ Card expiry date_ __c/_ __ I I I Name _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ I I I I Street - - - - - - - - - - ~ - - - - - - - - - - - - I I Suburb/town _ _ _ _ _ _ _ _ _ _ _ Postcode_ _ _ _ __ I IL _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ JI Card No. LCD & case $135 (inc. p&p). Relays extra at $3.75 each (controller requires 9 for full kit). FROST SWITCH KIT also available. Remote temperature probe starts the above controller in a fully programmable sequence, when temperature falls to a user selectable value (controller requires modified S/W). $60 incl. reprogramming and p&p.Available from Graham Blowes, 38 Garnet St, Niddrie, 3042. Phone (03) 337 1917 AH or (03) 575 3349 BH. Fax (03) 575 3369. 8051 MICROCOMPUTER PROTOTYPING PCB $30 - similar to my ROMLoader EA Jan 92. Provision for 8255 PPI, 9346 EEPROM, 2K-32K SRAM, 2K-32K EPROM, MAX232, DIP switches & expansion header. Send A4 SAE for article. Tantau, PO Box 206, Gordon 2072. SECURITY ALARM COMPONENTS: commercial quality alarm panels, detectors, cable, everything for complete alarm system. DIY kits. Discounted prices. 4-core alarm cable $35 per 100m. 2°core alarm cable (figure-8) $15 per 100m. PIR detectors pulse count $59 ea. Horn speakers $12.50 ea. Mail order service. Send SAE for free price list to Security Distributors, 141 Todds Rd, Lawnton, Old 4501. Phone (07) 882 0002. NICAD BATTERIES: D-size 4Ah. At less than half price it's the best deal in town. $4.90 each plus p&p. Phone (052) 78 8298. KIT REPAIRS: fixed price servicing for all kits, no job too small, only quality components used. Ph (02) 649 2134 after 5pm. SURPLUS COMPONENTS: 747CJ OIL ceramic $1 ea or 25 for $20; 150Q 1OW resistors $1 ea or 10 for $8; Bourns 3386 trimpots 5kQ or 10kQ, 50c ea or 10 for $4; Eska 3AG 10A ceramic fuse, packet of 10 $1.50; ex-computer EPROMs, erased and blank tested, 2732, 2764, 27128, $2 ea or 10 for $15; · Valves, ex-government, new 12AT7 $8 ea, 5Y3GT $6 ea, KT66 $25 ea, 6AN8A · $9 ea, 6BL8 $8 ea. Many other valves and components available. Send SAE for list. Open Thursday, Friday 4pm8pm, Sat 9am-4pm. 143 Grays Rd, Enoggera Old . Ph (07) 355 1314 or (07) 855 1880 AH, Fax (07) 855 1014. Visa, Bankcard, Mastercard available for fax or phone orders over $20. Secontronics, POBox 2215, Brookside Old 4053. HARD DRIVE: Maxtor voice coil IDEAT. Factory warranty. Great bargain. New 120Mb $560, 200Mb $860. Mail MEMORY EXPANSION PRICES AT SEPT 9TH, 1992 SIMM 1Mb x 5 ?Ons 1Mb x 3 ?Ons 1Mb x 8100ns 4Mb x 9 80ns 4Mb x 8 8Qns (For SIP add $1.00) DRAM DIP 1 x1Mb70ns 256 x 4 ?Ons 41256 80ns 1Mb x 4 (slat) $46 $42 $37 $164 $152 $5 $5 $2 $23 DRIVES SEAG 130Mb 19M SEAG 44Mb 28M C'NER 200/12 C'NERS0/19 $438 $260 $750 $335 IBM PS.2 50/55/70 2Mb 70/35 4Mb $115 $180 TOSHIBA T3200SX 2Mb T44/6400 4Mb T5200 2Mb $135 $350 $135 MAC 16MbOUADRA 2MbSl&LC 4Mb P'Book $780 $83 $260 BOARDS 8MbATW2MB $232 8Mb PS2W2MB $234 4Mb HP LaserW2MB $155 8Mb PANAS W2MB $170 1Mb TI W1MB $80 Sales lax 20%. Overnight delivery. Credi! cards welcome. Ring for Latest Prices • Plans Kits and PCBs 1O0W Valve Amp PCB ......................... $30 Valve Amp PSU PCB ............... ............................ .. $25 Universal PSU (±5/±12V) Dual Supply .................... $10 Digi 125 100W amp/pair ....... $1 0 ETI 1623 PIA for PCs ........................................ .. .... $40 Max 1/0 Board ............................................... .. ........ $40 Max Kit ............................... .................................. $169 LM380 3.5 amp PCB ..................................... $7 AEM 35W amp kit .................................................... $20 ETI Audio Toolkit PCB ................ $1 0 AGC Amp PCB .................... ......................... .. ......... $7 Z-80 Miniprocessor PCB .......................................... $50 6502 Miniprocessor PCB ......................................... $50 6809 Miniprocessor PCB .............. :..... $50 8048/8049 Developers board complete B& T ........... $199 IBM PC Prototype PCB .............................................. $50 EPROM Programmer .............................................. $299 . ESL-t Electrostatic speaker kit/pair inc manual ...... $899 ESL-t Assembly Manual ........ $50 P.C. Computers (08) 332 6513 36 Regent St, Kensington SA. PELHAM Tel: (D2) 980 6988 Fax: (02) 980 6991 1st Floor, 100 Yarrara Rd, PO Box 382, Pennant Hills, NSW 2120. FIX-A-KIT KIT REPAIR & CONSTRUCTION TRANSFORMER REWINDS 3 MONTHS WARRANTY ON REPAIRS 12 MONTHS WARRANTY ON CONSTRUCTION TECHNICAL ASSISTANCE ALL TYPES OF TRANSFORMER REWINDS HVCAL ELECTRONICS TRANSFORMER REWINDS Design. Manufacture & Repair of Electronic Equipment Reply Paid No.2, PO Box 438, Singleton, NSW 2330. Ph: (065) 761291. Fax : (065) 76 1003. . order welcome. Altec Pacific. BH (03) 800 2007. Fax (03) 800 3363. AH (03) 801 4391 Wantirna. GAS LASER: a very small brand new 0.2-0.5mW visible red helium-neon laser tube, plus a kit of parts for a small inverter that will run from a 7.2V nicad battery pack. Suits laser pointers, etc. Incredible value at $50 for the tube and (02) 633 5477 supply.* VISIBLE LASER DIODE BARGAIN: brand new 5mW 670nm laser diode, plus a collimating lens, plus a driver kit plus a housing and instruc- · tions. Introductory price $85. * ELECTRONIC KEY: use it to activate door strikers for entering buildings, car alarms, central locking. The most secure key ever (see EA, July 1992). On special<at> $49.90 for two keys and one LOCAL TRADES & SERVICES JV Tuners - Repairs Transformer Rewinds 'I: A. Mowles For all types of transformer rewinds. Printed circuit boards for the hobbyist. For ser\'ice & enquiries contact: (02) 7741154 Fax (02) 7741154 (065) 761291 Fax (065) 761003 (08)3265590 Ian J Truscott 's Electronic World EEM Electronics Silicon Chip * Tuner • • • • repairs for TVs & VCRs Shorted Turns Tester lligh Voltage Probe Degaussing Wand Remote Control Tester * For sen ire~~ repair ,rnrk \Jail or credit card facilities (03) 7233344 Fax (03) 4192808 Printed cirrnit hoard assemhl~. itch mode 1>ower supplies repaired. Design ,1ork from start to finish. Ring anytime 9am-9pm Mo.n-Sun. S\\ (03) 4011393 To achertise your products or st·n ices. please call Sharon on (02)9795644(018)285532 N OVE MBER 1992 103 r-------------------------, : SILICON CHIP BINDERS l These beautifully-made binders will protect your copies of SILICON CHIP. They feature heavy-board covers and are made from a distinctive 2tone green vinyl that will look great on your bookshelf. Advertising Index All Electronic Components .. ... ... 45 Altronics .... ... ...... .... ............... 76-78 Antique Radio Restorations ..... 102 A-One Electronics ................ 38-39 Av-Comm ................................... 75 * High quality. * Hold up to 14 issues Breakthrough Computers .......... 71 David Reid Electronics .. ....... ..... .. 3 * 80mm internal width. Dick Smith Electronics .......... 10-15 EEM Electronics ........ .............. 103 * SILICON CHIP logo printed in goldcoloured lettering on spine & cover. Electronic World ..... .. .......... 67,103 Emona Instruments ................... 47 Yes! Please send me _ _ _ SILICON CHIP binder(s) at $A11.95 plus $A3 p&p each (NZ $A6 p&p). Geoff Wood Electronics ............ ... 5 Enclosed is my cheque/money order for $_ _ _ _ or please debit my Hycal Instruments .................... 103 D Bankcard O Visa Card O Master Card Harbuch Electronics .................. 21 lcom Australia .................. ........ IBC Jaycar Electronics ................ 49-56 Card No. JV Tuners ............... .. ............... 103 Oatley Electronics .. .... .... .... 73, 103 Signature_ _ _ __ _ _ _ _ __ Card expiry date_ _ _/_ __ PC Computers .. ....... ,............... 103 Name _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Pelham .... .. ... ........................... 103 Peter C. Lacey Services ............ 44 Street _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Suburb/town _ _ _ __ _ _ _ _ _ _ Postcode_ _ _ _ __ Philips Test & Measurement .. OBC RCS Radio ... ................ ........... 104 Resurrection Radio .................... 61 SILICON CHIP PUBLICATIONS PO Box 139, Collaroy Beach, NSW 2097, Australia. Phone (02) 979 5644 Fax: (02) 979 6503. L-------------------------J Rod Irving Electronics .......... 90-95 Scan Audio .. ........ ...................... 87 Silicon Chip Back Issues ..:... 96,97 Silicon Chip Binders ... ........ 21,104 decoder kit.* ULTRASONIC CAR BURGLAR ALARM BARGAIN: PCB and on-board components kit for the project featured in SILICON CHIP May 1988 edition. No screw terminals but we supply a pair of 40kHz transducers: $24.90. * LIGHT MOTION DETECTOR: small PCB assembly based on a ULN2232 IC. This device has a built-in light detector, filters, timer, narrow angle lens, and even a siren driver circuit that can drive an external speaker. Will detect human beings at distances up to 3 metres. Can be used at very low light levels and even in total darkness. With IR LED. Full information provided. The IC only is worth $16! Our price for the assembly is $6 ea. or 5 for $25. *STEPPER MOTORS: 5V, 7.5-deg., 6.6-ohm, 2-phase. Brand new $12. Major cards accepted with phone and fax orders. 104 SILICON CHIP Certified p&p Australia $5, NZ (airmail) $10. Oatley Electronics, PO Box 89, Oatley, NSW 2223. Phone (02) 579 4985. Fax (02) 570 7910. St Lucia .. .... ..... .......................... 23 T. A. Mowles ............................ 103 Tektronix ...... ........ .......... ..... ..... IFC Transformer Rewinds .............. 103 RC§ RADIO PTY LTD ~;i~1,~ ::=J ~I Ill I [lo16Jf RCS Radio Pty Ltd is the only company that manufactures and sells every PC board and front panel published in SILICON CHIP, ETI and EA. RCS Radio Pty Ltd, 651 Forest Rd, Bexley 2207. Phone (02) 587 3491 PC Boards Printed circuit boards for SILICON CHIP projects are made by: • Jemal Products, 5 Forge St, Welshpool, WA 6106. Phone (09) 350 5555. • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone 88 5730. • RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. 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While the IC-R7100 covers from 25 ~ 2000 MHz in SSB, AM, FM, wide FM modes, optional TV and FM stereo adaptor, with 900 memory IC-R7"100 channels, sophisticated timer functions and multiple scan functions. The top of the range IC-R9000 expands your listening horizons, covering 100 kHz~ 1999.8 MHz in all modes and featuring !corn's unique CRT display, intelligent scan functions and an amazing 1000 memory channels, in a unit that IC-R"IOO delivers superb high frequency stability, even in the GHz range. So tune in to the ones that professional listeners use, from the wide range of lcom wide band receivers. For further information call free on (008) 338 915 or write to Reply Paid 1009 lcom Australia Pty Ltd P. 0. Box 1162 Windsor Victoria 3181 IC-R"I Telephone (03) 529 7582 A.C.N. 006 092 575 /COM Australia's warranty is only af,plicable to tyroducts purchased from their authori.sed Australian Dealers. IC-R72 LL BROWN ADVERTISING 3907