March 1991 - Silicon Chip Online

Outer Front Cover
Contents
Publisher's Letter: Avoiding the penetrating bass beat
Feature: Electric Vehicles; Pt.3 by Gerry Nolan
Feature: Solar Electric Speed Record In Australia by Gerry Nolan
Project: Remote Controller For Garage Doors, Pt.1 by Branko Justic
Serviceman's Log: The case of the worn video heads by The TV Serviceman
Project: Transistor Beta Tester Mk.2 by John Clarke
Vintage Radio: Automatic gain control: what it is & how it works by John Hill
Project: A Synthesised Stereo AM Tuner, Pt.2 by John Clarke & Greg Swain
Back Issues
Feature: Computer Bits by Jennifer Bonnitcha
Project: Multi-Purpose I/O Board For IBM PCs by Graham Dicker
Feature: Amateur Radio by Garry Cratt, VK2YBX
Feature: Remote Control by Bob Young
Feature: The Story Of Electrical Energy; Pt.9 by Bryan Maher
Feature: Bose Lifestyle Music System Subscription Offer
Order Form
Market Centre
Advertising Index
Outer Back Cover

This is only a preview of the March 1991 issue of Silicon Chip.

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BONUS 164-PAGE JAYCAR CATALOG $3.95 MARCH 1991 NZ $5.50 :sc~ SERVICING - VINTAGE RADIO - COMPUTERS - AMATEUR RADIO - PROJECTS TO BUILD ARD FOR PCs j°Ji J i r "J !JJ'Jj_;~ ~ - '"'~ ·· . - ·. SP45l.T 4 WAY COLUMN SPEAKER 4ldlndoadlnnspealra'wilh o iO/IDvctlne wusbna. *GmhfwS"UacZr *Enudedcuniun . PMS-400 EXTENSION SPEAKER * Indoor extension speaker mounted in o block finish 125 WATT PA AW cabinet. REDFORD A2020 * Q,1p_J!: TXNine 014-16 dm. *~DlCulboblCed0tlJC bacm,d. (Slrlitddlle~ *freq. Res.: 4CHz-14cHz. llmtion: less 1tm f/4. 3 Lrit rr oc1c mcu,t CD!ile. *Metal~ *Hecr.,i~walmcmlilgbockets. *fieq.lles.20-fz- DHr. *Sn.lScR *llnensicrs 600 X138 X 60ml. ** ,,LAST ONE,, ... 1299.95 wasS599.00 now 1479.IXJ nowlB9 LAVAi.iii t.tCROPHON5 IIDFORD 8 OWHL MIXER *llllit '1' rodcmomt cmnet. * lnpus 6 nic. bdned 200-600 ohn. ut duol divarsity system * * ID' 1399.tXJ ~ onsonlJII REDFORD 100 VOLT LINE P.A. HORN SPEAKERS 10 watt 7" was $69•00 ~ 3 lt1lt/ now 149.00 15 watt 8.,, was $89•00 ~ 2 lt1lt/ now 159.00 TPA40 40 watt RMS P.A. AMPLIFIER * 202.U.t-lz 2 a\! " stock * Speaker Output: 4, 8, 16 ohm * 202.5 M-lz 1a\! in stock * Line Output: 70/100 volt. MJS $349.IXJ * 2 x oux. inputs (600 ohm). mt,, 1249.IXJ so * Boss and Treble controls. * 240 V AC or 12 V DC operation. * 270 x 225 x 88mm 2aJX.trt>cDmdm<.ohn. *0Jtput:600ohnbdned. Bai5 aid ieble conbcls. 5 pin ifllut/output sodcets. now 1289.tXJ * 8 ohm. * 5 watts RMS * 340 x 210 x 140mm. was $49. 95 so. ,. was 1399.95 PA-7300 P.A. ~ u~!f!2~!1~c~!t * Push to talk button. ** Impedance: Volume Control. 3K ohm. 19" RACK FRAMES and PANEL SETS * 4 Unit Frame .... $139.00 * 6 Unit Frame .... $149.00 * 12 Unit F10me ... $169.00 * 18 Unit Frame ... $189.00 * 30 Unit Frame .. $229.00 * 38 Unit Frame .. $269 .00 * 4 Unit Panels .... $49.00 * 6 Unit Panels .... $55.00 * 12 Unit Panels ... $89.00 * 18 Unit Panels ... $110.00 * 30 Unit Panels .. $159.00 * 38 Unit Panels .. $195.00 ** Sensitivity: -55d8. 6.5mm plug output. AVAILABLE IN BLACK or NATURAL * 9 volt bott. operation. * Rock Screws Pkt-12 .. $3.20 (Block or Noturol) 30 watt 10· was sno 00 ~ was 179. 95 * Rock Nuts Pkt-12 ...... $5.95 ~ now 179.00 ~ Nylon Protect now 144. 95 * Washers Pkt-12 ......... $2.10 ~ lo.: 1 GHz FREQUENCY COUNTER Prescaled: 10,100, 1KHz switch selectable. * 8 digit LED digital display with decimal point, gate, overflow, KHz, MHz, and uS indication. was$499.00 NOW ONLY . /Ill orgo,n MOTORAD TL-301 TIMING LIGHT with DIRECT READING ADVANCE SCALE * Resolution: Direct Counter: 1, 10, 100Hz switch selectable. * Gate Time: 0 .01 S, 0.1 S, 1 S, switch selectable. B The TL-301 Advance Scale design is for easy one-handed operation of timing advance function. Leaves other hand free to get access to those hard to see indicators. Measures timing accurately up to 6000 RPM. Test timing on all 12 volt conventional and electronic ignition systems .... 4, 6 or 8 cylinders, including rotary motors * * was$11aoo now $399.00 $79.95 HIGH VOLTAGE ELECTRO'S CASSETTE TAPE ERASER * 220uF 250V RB .......... $2.95 * 100uF 250V RB ........... $2.95 * 100uF 315V CAN ........ $4.95 Erase tapes quickly and easily. No power required was $7.95 NOW $4.95 VIDEO/AUDIO PATCH LEAD NC plug to BNC plu CA plug to RCA plu ideo lea - Easy Etch * 2 tinrnrs (coun t-clowu) * 2 1n·t,imt num1ori«m Engraves any surface * Easy Etch Engraver is supplied with * Count-up tinrnr * 12/24- hour clock * Huilt-iu alarms * I,l,ml i"<>r <m<>kll1g, IIU!<li,:11tiw1, .'JjJ()J'ts, llWf!till/f.'I, (Jt<:. a steel bit for engraving metal, wood, and plastic. Replacement tip to etch glass, ceramics and hardened metals (ET688) $18.95 why pay $43.95 elsewhere MULTIM * DC Volts: up to 1000V. * AC Volts: up to 1000V. * DC Amps: up to 10 A. * Resistance: x 1K ohm. * Sensitivity: 20K/V DC. * Continuity buzzer. * Includes batteries and probes. LABTECH - 20MHz DUAL TRACE OSCILLOSCOPE Features: Wide bandwidth and sensitivity. High senitivity X-Y mode. Z axis (intensity modulation). Front panel electrical trace rotator. Regulated power supply circuit for accuracy. Description: This model is a dual trace 20MHz CRO using a high brightness CRT. The vertical amplifiers have high senitivity of 5mV /DIV and a frequency characteristic response with smooth roll off exceeding 20MHz. The highest triggering sweep speed is 0.2uSec/DIV. t-11Q-1CRO PROBES to suit $39.95 ea. NEW MODEL FOR '91 RIPODS DMM-2 DIGITAL MULTIMETER * 100mm height. * 5/8" male screw * Autoranging. * 10 A DC. * Data Hold. <at> * 127x68x25mm adaptor. 62 X 18mm only $129.95 DSHD $25.00 ""fiTE•J.1tI *!!I now$69.95 ELECTRONIC DIARY * :i.5" All pkt.10 was$99.95 Store Telephone No's, Names and Addresses. Memo function, Schedules, 12/24 hr. Clock and Alarm, World Time, Calender, Calculator, Metric Conversion. * 10KB memory. * 3 lines with 18 characters. X * 8 levels of play. * 3 levels of coaching. * Plus more !!!! * Continuity buzzer CITIZEN ED-3800 * 147 POCKET PLUS CHESS COMPUTER (~()MPlJrl,J~ll ]:>ISK]~r1,r1,ES * 5.25" nsnn $5.oo * 5.25" DSHD $12.00 * a.5" nsnn s10.oo CITIZEN ED-4500 ZZZ CITIZEN ED-7800 ELECTRONIC DIARY ELECTRONIC DIARY Telephone Directory with Names and Addresses. Calender. Memo. Schedules, Calculator, Metric Conversion. * 32KB memory. * 6 lines with 13 characters. Telephone Directory, Schedules, Memo, 12/24 Clock with Alarm, World Time, Calender, Metric Conversion, Currency Exchanger. PC Link. * 32KB memory. * 6 lines with 32 characters. * 132 X 65 X 13mm only $179.95 *154 x 82 x 19mm POST ond PACKING SS - 525 $26 - $50 551 - $100 $101 - $499 5500 + 53.00 ss.oo $6.00 $8.00 FREE March 1991 THIS REMOTE control circuit is specially designed for operating garage doors, gates or other appliances. See page 16. FEATURES 6 Electric Vehicles, Pt.3 by Gerry Nolan Motor control - the part played by electronics 10 Solar Electric Speed Record In Australia by Gerry Nolan How the record was finally broken 38 Data On The LM383 7W Audio Amplifier by Darren Yates Plenty of power from a tiny package 82 The Story Of Electrical Energy, Pt.8 by Bryan Maher High-voltage DC transmission systems 89 Bose Lifestyle Music System Subscription Offer And the winners are ... CHECK TRANSISTORS for gain & identify their leads with this simple instrument. We show you how to build it starting page 32. PROJECTS TO BUILD 16 Remote Controller For Garage Doors by Branco Justic The transmitter comes pre-built; you build the control unit 32 Transistor Beta Tester Mk.2 by John Clarke Revised design also measures low-beta transistors 50 Synthesised AM Stereo Tuner, Pt.2 by John Clarke PC board & chassis assembly details 66 Multi-purpose 1/0 Board For IBM PCs by Graham Dicker Use your PC to control external devices SPECIAL COLUMNS 26 Serviceman's Log by the TV Serviceman WANT TO USE your PC to control external devices such as appliances & motors. Take a look at this multi-purpose 1/0 board on page 66. The case of the worn video heads 42 Vintage Radio by Jolin Hill Automatic gain control: what it is & how it works 62 Computer Bits by Jennifer Bonnitcha Config.sys. Ansi.sys & all that stuff 70 Amateur Radio by Garry Cratt A universal widr!hand RF preamplifier 74 Remote Control by Bob Young The development of digital proportional servos DEPARTMENTS 3 Publisher's Letter 4 Mailbag 46 Circuit Notebook 58 Back Issues 80 Product Showcase 2 SILICON CHIP 92 Ask Silicon Chip 94 Subscription Page 95 Market Centre 96 Advertising Index THIS RF PREAMPLIFIER can be used with shortwave receivers, for boosting signals into a frequency counter, or to boost signals from your TV antenna. Details page 70. PLEASE NOTE: the second article on amplifier design has been held over due to lack of space. This article will appear in next month's issue. Publisher & Editor-in-Chief PUBLISHER'S LETTER Leo Simpson, B.Bus. Editor Greg Swain , B.Sc.(Hons.) Technical Staff John Clarke, B.E.( Elec.) Robert Flynn Darren Yates Reader Services Ann Jenkinson Advertising Manager Paul Buchtmann (02) 979 5644 Mobile: (018) 28 5532 Victorian Representative Hugh Anderson Pty Ltd (formerly McDonald Woodside & Associates Pty Ltd) , 119 Market St, South Melbourne, Vic 3205. Phone (03) 696 5411. Contact: Ian McDonald. Avoiding the penetrating bass beat Over th e last 20 years or so, hifi system s have becom e commonplace virtually every home now has one or more systems in different rooms. If you are a music lover, then you can only regard this development as good since it brings instant music within the reach of everyone. However, there are drawbacks to th is universality of hifi systems. The first is well known and is the tendency of some people to listen to their systems at ridiculously loud levels. This really has nothing to do with hifi and is fortunately becoming less common as peop le come to realise that music does not have to be loud to be enjoyable. The second drawback is less obvious and it is related to the ability of bass sounds to easily trave l though walls, floors and closed windows an d thereby disturb people who may be quite a distance away. This can h appen even though the sound level in the person's listening room is not particularly loud. So in spite of listening at quite modest sound levels , the bass from your hifi system could well be disturbing yo ur neighbours. How does this come about'? First , some popular music is recorded with very high levels of bass. Partly, this is to overcom e the limitations of cheap radios and sound systems and partly because young people tend to like lots of bass. Second, many peopl e play their music with the loudness control switched in and with bass boost as well. This leads to unnaturally high levels of bass , which is quite unpleasant to listen to for long periods . Third, people tend to compound the probl em of excessive bass by placing th eir speakers in the corners of the room - which makes th em sound even more boomy. Lastly, some hifi dealers sell spiked feet for loudspeakers so that instead of standing on the carpet, they sit firmly on the timber floor underneath. This is claimed to make the speakers sound better (hard to jus tify) but also has the effect of making the timber floor into a giant sounding board for the speakers. That can mean that the bass from your speakers can easily travel for hundreds of metres or more. How can yo u be sure that you are not offending in this regard? Easy, just set your system for your normal listening level at n ight and go outside and listen. Can you hear the music or the bass? If so, it is time for positive action. Consider that if you are disturbing someone tonight, they may decide to disturb you on some other night. Remember, your hifi system will give the best poss ible sound with no bass boost, no loudness switched in and with the speakers not placed in the corners of th e room. And forg et spiked feet for your speakers - th ey are another gimmick. Leo Simpson Regular Contributors Brendan Akhurst Jennifer Bonnitcha, B.A. Garry Crall, VK2YBX John Hill Jim Lawler, MTETIA Bryan Maher, M.E. , B.Sc. Jim Yalden, VK2YGY Bob Young Photography Glen Cameron Editorial Advisory Panel Philip Watson, MIREE, VK2ZPW Norman Marks Steve Payor, B.Sc., B.E. SILICON CH IP is published 12 times a year by Silicon Chip Publications Pty Ltd. All material copyright ©. No part of this publication may be reproduced without prior written consent of the publisher. Printing: Magazine Printers Pty Ltd , Rozelle, NSW 2039; Macquarie Print, Dubbo, NSW 2830. Distribution: Network Distribution Company. Subscription rates: $42 per year in Australia. For overseas rates, refer to the subscription page in this issue. Liability: Devices or circuits described in SI LICON CHIP may be covered by patents. SILICON CHIP disc;;laims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. Editorial & advertising offices: Unit 39, 5 Ponderosa Pde, Warriewood, NSW 21 02. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 979 5644. Fax (02) 979 6503. ISSN 1030-2662 MARCH 1991 3 SILICON CHIP, PO Box 139, Collaroy Beach 2097. MAILBAG Commodore 64 a suitable project base Recently in the Mailbag section of your magazine there has been some discussion regarding the type of computers that you should publish projects for, IBM types versus Amiga , for example. While these computers are very popular, and each has its advantages over the other, the fact remains that these computers don't come cheap (eg, an Amiga is about $1499.00 in New Zealand). Therefore, it is unlikely that the average hobbyist interested in computer hardware would want to tempt fate with their Amiga/ IBM by modifying them in any way that might damage them. To remedy this, we need a computer that is low cost, easy to program and simple enough that if something does go wrong, it can be easily fixed. Such a computer is right under our noses, the Commodore 64. Why experiment on a littl e old C64 you say? Answer': (1) cost - I got my 64 for $125 with tape and some books; (2) ease of programming - most people know Basic and 6502 assembly is rnlatively simple; (3) the input/output is very easy to get at; and (4) popularity - in a recent school project I found that 35% of the people in my school with a computer had a C64. I currently have a C128 which is totally compatible with the C64, so I am interested in any project to do with either of these computers, especially to do with hard drive con'trollers for either (hint, hint). So I urge you, please don't leave out the peopl e with an 8-bit. Thank you for reading my letter. I like your magazine a lot ; keep up the good work. Simon Noble, Blenheim, New Zealand. High density drives not supported by DOS 3.1 I read with interest R.B.'s letter in the "Ask Silicon Chip" pages of the January issu e concerning 1.44M drives used under DOS 3.1. The an swer to RB's problem is that DOS 3.1 4 SILICON CHIP does not support high density disc drives and it is necessary to use DOS 3.3 or higher. I believe that Jennifer Bonnitcha recently wrote an article concerning this problem. If R.B. 's XT has more than 640K of memory, it may be advisable to wait until DOS 5.0 arrives (due midMarch?). DOS 5.0 not only has the capability to handle high density drives but will also free more usable memory by loading COMMAND.COM and the DOS hidden files into high memory. If not, DOS 3.3 should be quite suitable. To hook two PCs together, it is necessary to use a "null modem" cable attached to the two serial ports and some type of communications software. A standard serial cable can be used and a "null modem" adapter can be purchased for $10-15. Many computer clubs have communications software available and there are quite a few "brand name" programs available from reputable software dealers. P. Craddy, Pendle Hill, NSW. Electric vehicles might fuse the national grid! I have two comments regarding the January issue of SILICON CHIP. With regard to the article on electric vehicles, I recall reading, maybe 20 years ago, that if all vehicles in Australia were electric we would need to multiply the number of power stations by 10! Better modern motors would no doubt reduce that figure but it indicates that we don't realise the vast amount of energy used in road transport compared with that used by industry, commerce and living. The generation and distribution of electricity to fuel EVs would present enormous problems. I no longer have access to the data on these things - I hope your writer will comment. The Fruit Machine is a neat project but I conclude that this machine would lose money by the bucketful for its owner if the stake per play is 1 unit and the payouts are as shown. • The A shows on any readout once in 10 plays - on average; • The O shows on any readout twice in 10 plays - on average; • The C shows on any readout thrice in 10 plays - on average; • The L shows on any readout thrice in 10 plays - on average; • The _ (d segment) shows on any readout once in 10 plays - on average. So, the probability of three As is 0.1 x 0.1 x 0.1, or 1 in 1000 plays; the probability of three Os is 0.2 x 0.2 x 0.2, or 8 in 1000 plays; the probability of three Cs is 0.3 x 0.3 x 0.3, or 27 in 1000 plays; and the probability of three Ls is 0.3 x 0.3 x 0.3, or 27 in 1000 plays. Never mind the AA_ and CC_. So, on average , with 100 plays costing 1000 units, the payout would be: For For For For 3As 3Os 3Cs 3Ls 8 x 150 27 x 20 27 x 20 1000 units 1200 units 540 units 540 units Total= 3220 units. Costly! A. J. Lowe, Bardon, Qld. Comment: we agree with your maths; this is one poker machine that Jets the user win! Of course, the machine is just for fun ; no money is supposed to change hands. Wants circuits with the Serviceman I find the "Serviceman's Log" articles very helpful with regards to faults in colour TVs and the cartoons are quite humourous. However, I would much prefer to see any available space taken up with copies of the circuits or larger circuits as these are extremely helpful in identifying what the text is about and function of same. Perhaps you could find room for "more" of this. Even better would be two pages with the complete CTV circuit on it, as I find it hard to obtain some of the circuits from agents of certain makes, especially early models. Thank you for an interesting magazine. G. Daddy, South Kincumber, NSW. GENIUS MOUSE BRAND NAME 720K 3.5" DISK DRIVES WITH 3 MONTHS WARRANTY • 1 FOR $69 • 2 FOR $120 • 3 FOR $165 • 4 FOR $200 BRAND NAME 360K 5.25" DISK DRIVES WITH 3 MONTHS WARRANTY e 1 FOR $69 e 2 FOR $120 e 3 FOR $165 e 3 BUTTONS, MICROSOFT OR MOUSE SYSTEM COMPATIBLE, 200dpi RESOLUTION BARGAIN BASEMENT PRICE $39.95 FLOPPY DISK CONTROLLERS TO SUIT AT ONLY Will support up to 2 drives of 360/720/1.2/1.44 includes cables for both 5.25" and 3.5" drives NORMALLY $99.00 SUPER SPECIAL $49.00 SA VE $50.00 HURRY LIMITED STOCKS 4 FOR $200 MONITORS/PRINTERS MOTHERBOARDS WAS NOW $239.00 14" White/Amber/Green $535.00 14" Philips CGA $899.00 14" Multisync VGA $695.00 14" Colour VGA $499.00 Olympia NP30 Centronics Olympia NP80/24 Centronics $779.00 Olympia NP136/24 Centronics $1395.00 $499.00 $849.00 $649.00 $399.00 $699.00 $999.00 WAS NO 8088 8088 8088 8088 8088 8088 80286 80286 80386· 80386 80486 12Mhz $129.00 $109.00 12Mhz 640K installed $250.00 $199.00 12Mhz 1Mb installed . $300.00 $235.00 31Mhz $225.00 $189.00 31 Mhz 640K installed $335.00 $279.00 31 Mhz 1Mb installed $385.00 $319.00 12Mhz $350.00 $299.00 16Mhz NEAT $649.00 $449.00 25Mhz Cache $1995.00 $1495. 33Mhz Cache $2495.00 $1795. 25Mhz Cache $4395. WAS XT Case 4 Drives 150W P/S AT Case 3 Drive 200W P/S Minitower Case 200W p,s Maxitower Case 200W P/S $199.00 $299.00 $399.00 $499.00 880K Macintosh series 164K Apple 11 E 164K Apple 11Gs 720K Amstrad PC 1512/1640 1.44 Amstrad PC 2000 360K Amstrad PC 2000 1.2 Amstrad PC 2000 1.2 Amstrad Portable 720K Atari St 360K/720k 40/80 Atari ST 880K Amiga 500/1000/2000 360K Amiga 500/10p0/2000 720K IBM 1.44 IBM 360K IBM 1.2 IBM 1.2 IBM PS11 360K Toshiba/portables 1.2 Toshba/portables WAS NOW $349.00 $249.00 $269.00 $269.00 $329.00 $329.00 $329.00 $399.00 $269.00 $299.00 $199.00 $299.00 $299.00 $329.00 $299.00 $329.00 $449.00 $349.00 $399.00 $329.00 $209.00 $229.00 $249.00 $309.00 $249.00 $249.00 $379.00 $249.00 $279.00 $185.00 $285.00 $249.00 $299.00 $249.00 $299.00 $409.00 $309.00 $369.00 POWER SUPPLIES 150W XT Power Supply 200W AT Power Supply WAS WAS 3.5HH 3.5HH 3.5HH 5.25 5.25 $ 99.00 $245.00 $245.00 $299.00 $199.00 720K 1.44 4MB 360K 1.2 WAS NOW $199.00 $199.00 $299.00. $149.00 $179.00 $160.00 $169.00 $265.00 $69.00 $149.00 INTERFACE CARDS WAS . NOW EXTERNAL FLOPPY DISK DRIVES 3.5 5.25 5.25 3.5 3.5 5.25 5.25 5.25 3.5 5.25 3.5 5.25 3.5 3.5 5.25 5.25 5.25 5.25 5.25 $205.00 MEMORY CARDS Memory card PC/XT 576k Memory card 2Mb AT Memory card 2Mb XT Memory card 32Mb XT/AT Ram card for Amiga CASES INTERNAL FLOPPY DISK DRIVES $79.00 $199.00 $199.00 $279.00 $149.00 We also stock a huge range of cables, adaptors, swithboxes and chips Call today for very competitive pricing. Serial 1/0 Card 4 port Serial I/O Card 8 port Games card 2 port Parallel printer card Serial 2 port XT Serial 2 port AT Serial/Par/Games XT/AT 2Serial /2Parallel Multi 1/0 S/P/G/C/F XT/AT Proto Board with decoder Slot Extension Kit WAS NOW $199.00 $449.00 $ 29.50 $ 24.95 $ 55.00 $ 65.00 $125.00 $ 75.00 $125.00 $149.00 $199.00 $179.00 $429.00 $25.00 $19.95 $35.00 $40.00 $62.50 $50.00 $99.00 $99.00 $149.00 MOUSE/ACCESSORIES WAS GRAPHIC CARDS Mouse for PC/XT/AT/PS11 $119.00 Mighty Scanner $399.00 Sound Blaster $399.00 Mono PC/XTIAT CGA VGA8 bit VGA 16 bit 256K VGA 16 bit 512K KEYBOARDS 101 Enhanced keyboard WAS $109.00 WAS NOW $109.00 $109.00 $249.00 $349.00 $449.00 $69.00 $99.00 $199.00 $225.00 $299.00 NOW $89.00 CONTROLLER CARDS FDC 360/720/1.2/1.4 x4 FDC 360K to 2.88Mb X4 FDC 360K INT/EXT x4 FDC 360/720/1 .2/1.4 x2 HDC MFM PC/XT HDC/FDC MFM PC/XT HDC/FDC MFM AT HDC MFM AT Co-Existant FDC 2 Drives WAS NOW $129.00 $199.00 $55.00 $99.00 $139.00 $175.00 $245.00 $220.00 $119 .00 $99 .00 $179 $39. $79. $99. $149 $199 $199 $99. DEALER ENQUIRIES WELCOME WRITE OR PHONE FOR FREE CATALOGUE TRY PC MARKETPLACE SUPERFAST MAILORDER - PHONE OR FAX TODAYI Plii{ (j{eeson 's PERSONAL COMPUTER MARKETPLACE Ptv Ltd FREIGHT CHARGES PHONE (02) 418 6711 Include $10 with order for all normal itema • heavy items, e.g. monitors add $15. FAX (02) 418 6713 14 day money back guarantee Mail Order Address: Order by phone (use credit cardl by fax or by ma il. P.O. Box 1100 Lane Cove Unless insurance is declined it will be charged at 1% of total purchase. This is for your protection. NSW2066 PRICES CURREITT FOR MOITTH OF PUBLICATION OR WHILE STOCKS LAST. VISA 0 • SERVICE IS 1HE Dli:FERENCE • SERVICE IS 1HE DIFFERENCE e SERVICE IS THE DIFFERENCE • SERVICE IS 1HE DIFFERENCE - ctr,c Electronic control circuitry has a big role to play in modern electric vehicles. We look at the brain that controls the drain. By GERRY NOLAN limb in, switch on and start a conventional (ICE) motor ' vehicle and it usually settles into a steady idle. This is because the engine controller is set up to make it do just that. Basically, the accelerator is sprung to the fully closed position and idle jets in the carburettor control the fuel/ air mixture ratio and amount to produce the idle. If the engine is cold, the choke (manual or auto) is used to vary the ratio and quantity. The same result is achieved in a C different way with fuel injected vehicles. By contrast, if you climb in and switch on your electric vehicle, nothing happens until you press the accelerator. When you press the accelerator in your ICE vehicle, you increase the amount of fuel/air mixture introduced to the cylinders to be burnt, thereby increasing the amount of energy released to be converted into power and VROOM! VROOM! - engage low gear and away you go. In your electric vehicle, as you accelerate abruptly away without the benefit of gears, the complete lack of VROOM! VROOM! will make you feel even more strongly that what is happening shouldn't be happening. EV motors and controllers are so closely combined that discussing one without the other is difficult so we have arbitrarily decided to discuss controllers first and then motors in the next instalment.. Theoreticaliy, the power control of an electric vehicle is as simple as controlling the volume on your radio or television. But what about the losses Virginia? Obviously, using a whacking great rheostat would result in enormous power losses, especially at low speeds. Remember, we're talking several hundreds of amperes here. Even racing model electric cars have up to 160A pulse ratings for braking. Something with a little more finesse is called for and now power control- lers are almost all based on some form of digital, solid state circuitry, many of which use MOSFET inverters with more and more using microprocessors to completely automate motor control. Much of recent electric vehicle development is focussed on the use of laptop or small built-in computers for the collection of data over the whole charging and running regime of the vehicle. This data is then used to write software that will "tell" the vehicle what to do when particular demands are made on it. When enough data has been collected, it can be used to program a microprocessor chip to carry out all of the requirements automatically and efficiently. What are the requirements? Perhaps the most important requirement is that the control system responds quickly and smoothly to the driver's signals for higher or lower speed. While it is doing this, it should provide overload protection for the battery, drive motors, drivetrain and, not the least important, for itself. It must be able to do this while using the minimum energy, with the minimum losses and, at the same time, maximise the energy available for the vehicle and reduce battery and motor losses. Because of the very rapid acceleration capabilities of electric vehicles, the power controller should also have Pt.3: motor control - the part 6 SILICON CHIP ductors while the motor is running, the main methods of control are field and armature control, or a combination of both. DRIVER ELECTRICAL INPUT, EG ACCELERATOR PEDAL DC motor control '\V SPEED OR P0SITION / CONTROL LOGIC ' i/ ' CURRENT LEVEL \ / , I/ \V DRIVE SHAFT ' / POWER CONTROLLER '/ DRIVE MOTOR I Block diagram of electric vehicle (EV) motor control Fig .1: the motor and its controller are closely interrelated. If the driver wants to increase speed, for example, he presses on the accelerator and the control logic senses this via the output from a small potentiometer controlled by the accelerator pedal. This 'increase power' signal goes to the power controller, which increases the power to the motor. As the motor speeds up, a tachometer sends a signal back to the control logic where it is compared with the original input signal. When the motor speed reaches the desired level, the input and feedback signals will balance each other and no further 'increase speed' signals are sent to the power controller. an inbuilt "high-pedal lockout." This is a time delay so that, if the accelerator pedal is accidentally knocked down hard from fully off, the vehicle will not jerk away and injure someone. Also very important is the regenerative braking capability of the controller. This is its ability to enable energy that would normally be dissipated as heat during braking to be used to recharge the batteries - a vital factor in increasing vehicle range. How the controller works Essentially, the control logic senses the speed required by the driver, from the position of the accelerator pedal, and adjusts the amount of power going to the motors to achieve this speed. The block diagram of Fig.1 will give you a clear picture. The torque, speed and regeneration characteristics of electric motors are primarily governed by the following factors: • armature current; • magnetic flux per pole; • number of armature conductors; • number of poles; • armature speed; and • field current. As it is impractical to change the number of poles and armature con- played by electronics One way to achieve this is to vary the resistance of the armature or of both the armature and field windings by switching resistances in and out of the motor circuit with contactors. This may be achieved manually or through sensing the motor speed but, either way, the discrete changes in voltage produce a jerky motion. And of course, it produces high FR losses. A more efficient but no less jerky way is to use contactors to switch the batteries into different combinations of series and parallel to provide more or less power to the armature. These methods are rarely used now, even for model electric vehicles. High power solid-state controllers offer the most practical, reliable and efficient method of motor control, through pulse width modulation (PWM), frequency modulation and a combination of these two techniques. The PWM technique uses a constant DC voltage which is "chopped" into pulses of varying widths (see Fig.2). At low speed, the ON pulses are quite short in relation to the OFF pulses, while at high speed they are proportionally longer, right out to top speed where they are effectively 100% DC. Frequency modulation maintains a constant pulse width but varies the rate at which the pulses occur until again, at maximum speed, there is practically no time between the pulses. A combination of these two techniques may also be used. Until recently, power transistors, thyristors, SCRs and bipolar junction transistors (BJTs) were used to achieve the high switching rates needed for both PWM and frequency modulation methods. In the last few years, the development of high powered metal oxide semiconductor field effect transistors (MOSFETs), with much faster switching times and the ability to be switched directly by logic gates, has made them the preferred option. One of the reasons David Gosden of Sydney University opted for MOSFETs, despite the availability of much higher powered and cheaper thyristors and bipolar junction transistors, was because of their superior MARCH 1991 7 Fig.2(a): a constant frequency, variable pulse width (PWM) waveform. The motor slows down as the pulses become narrower & speeds up as the pulses widen. VOLTAGE VARIABLE - k: , - Tfixed ' / - - > TIME A switching capabilities. Switching times are an order of magnitude shorter than BJTs, allowing the switching frequenci es to be increased to over 15kHz. This gets it out of the unpleasant 2-BkHz range of BJT inverter switching frequ encies and al lows much quieter vehicle operation. AC motor controllers Although new developments in DC motors and controllers may change the situation at any time, at present the trend is to us e AC motors for electric vehicles. The General Motors Impact is powered by two 3-phase , AC inductiontype motors, each driving one of the front wheels. Together they develop 85kW at 6600rpm and the full torque of 1.27Nm over the whole speed range. Inverters convert DC from the batteries to AC and the whole system, which is capable of handling up to 100kW, weighs only 28kg. Pulse width modulation (PWM) and frequency modulation inverters (FMI) , and various combinations of the two , are both used in AC motor controllers. Braking During mechanical braking of a vehicle, kinetic energy is dissipated as heat in the brakes, which of course wear out over a period of time. In an EV, the life of the mechanical brakes can be increased by using the drive motor/s as a generator supplying a resistive load, thus providing a braking torque to the wheels. This type of braking, in which the vehicle's kinetic energy is dissipated in resistance, is known as "dynamic braking". Both mechanical and dynamic braking dissipate the kinetic energy as heat, which is therefore wasted. When the vehicle is travelling faster than the speed required by the driver (that is, over-running), the drive motor/s may be used as generators to convert a part of the kinetic energy loss to electrical energy which is then used to recharge the batteries. This is "regenerative braking" and is used in all modern electric vehicles in the forward direction and by some in the reverse direction. Regenerative braking is not an option that is available to internal combustion engine vehicles and, in a world where non-reusable energy resources are perceived to be running out, any means by which energy wastage can be limited obviously has valuable advantages. Nevertheless, because there is a lower speed limit to the use of regenerative braking, all EVs also have a mechanical braking system similar to that used in conventional vehicles. Energy management This photograph shows the solid state control & inverter circuitry in the Sydney University Suzuki Carry Van. (Photograph by Robert MacDonnell) . 8 SILICON CHIP An important function of the EV power control system is to provide the driver with information about the amount of energy remaining. As mentioned in the previous instalment, VOLTAGE Fig.2(b): a variable frequency constant pulse width waveform. The higher the pulse frequency, the higher the motor speed. FIXED ~ T variable > TIME B this is not quite as simple as providing a battery state-of-charge indication to replace the current fuel -remaining gauge. Some of the things an energy management system (as relate d to batteries) should do are: • provide battery state-of-charge indication; • control the maximum current drawn from the battery; • control the· depth of discharge; • control charging characteristics; The Solar Star, which recently broke the world-speed record for a solar/electric vehicle (see story this issue). actually provides a range-atpresent-rate-of-discharge readout by using a small on-board computer. When all the bugs have been worked out of the software being used in this , it is hoped that it wUl be developed into a microchip that can be used in off-the-shelf instruments . As mentioned above , microprocessors are used in conjunction with computers to facilitate the testing of various motor control strategies and combinations of strategies with few or no hardware changes. For example, Sydney University uses an Intel 80C196 processor in conjunction with a laptop computer. It has operated the motor in such a way that the stator currents are determined by the torque demand and, in another series of tests, where the motor is operated under torque control. It is safe to assume that, by the time EVs are out of the experimental stages and accessible to the motoring public , every aspect of the vehicle con- trol will be under the direction of microprocessors . Even the steering signals from the driver may be modified according to speed, gradient and so on, p erhaps even to the extent that the controller will automatically slow the vehicle down if it is going too fast for the amount of steering input indicated. The Solar Star already has a 'cruise control' selection to optimise energy usage for a given speed. Once we realise that, being electric , the EV is a fertile fi eld for all the clever ideas already developed in electronics - that we can control every aspect directly and not be restricted to controlling various valves, diaphragms an d pumps - deve lopments in EV control will take a quantum leap. SC VOLTAGE I~ ton Fig.2(c): the waveform from a variable frequency/ variable pulse width controller. VARIABLE - k T variable ' --> TIME C MARCH 1991 9 Solar electric speed record comes to Australia Runway 09/2 7 at the RAAF base Richmond, 60km north-west of Sydney, normally resounds to the roar of giant Hercules aircraft and the thump and screech of their tyres laying down long black strips of rubber. By GERRY NOLAN On Saturday, 5 January, 1991 it was quiet except for the occasional whirring of a sleek, solar powered car flashing past. Nine time_s the fleeting, low-slung Solar Star driven by Manfred Hermann, made the 2.5km run, trying to break the world speed record for a solar electric vehicle. The absolute, one-way, record of 129.0?km/h was set by the GM Sunraycer driven by Molly Brennan at GM's Desert Proving Ground in Mesa, Arizona, on 15 June, 1988. To beat 10 SILICON CHIP the official 2-way record, the Solar Star had to make two consecutive runs and achieve an average. speed exceeding 121.15km/h by at least 1 %. Before the attempt, Manfred lifted the sleek carapace of solar panels to check and adjust tyre and suspension air pressures. Then, switching on the vehicle's computer, he plugged in a 128Kb magnetic memory card to set the parameters for the day's runs. During the run, a 22cm wide by Bern deep liquid crystal display (LCD) in the instrument panel would dis- play battery voltage, current and temperature; motor voltage, current and temperature; and the temperature of the electronics. At the press of a key, it displays the voltage for each of the five sections of solar panels (60V): These panels are connected in sections longitudinally so that they receive the same level of sunlight along their length. If the sections ran across the car, half of each section would be in shadow while the sun was low. Each section has a peak power tracker to optimise the voltage against the current to obtain the higbest power for battery charging, for that section, under the prevailing conditions. From the batteries, the power goes via a frequency generator and the speed of the vehicle is actually controlled by varying the frequency of the power supply. Considerable electromagnetic interference (EMI) ;s generated by the system and several people driving the car have had their credit card magnetic strips irrevocably corrupted. The Solar Star can be run without the computer but there would be no performance indications. It may also be run without batteries, using direct solar energy, but it's not as simple as throwing a switch and the record attempt is for solar, electric vehicles. The digitally produced analog speedometer only indicates to 150 km/h, (would that be fast enough?) but the digital readout goes to 200 km/h, so Manfred will have no problems knowing ifhe is near the record. Besides, there will be three types of radar checking his top speed. Hans Tholstrup, founding father of solar electric vehicles in Australia, is there to represent Energy Promotions and the Human Powered Vehicle Association and, along with the police and John Ward from the NRMA, to make any record achieved official. At 10:30am the Solar Star is rolled out of the hangar. Actually it only needs to be guided, it is so light and rolls so easily. Manfred takes his shoes off and climbs in, being careful to step only on the strengthened parts of the body. The aramid/carbon Nomex body is contoured to support his almost prone body and his head is tucked into an extremely strong roll protection housing which has a radio aerial mounting point on top ofit. He has travelled nearly 5000km in this position, with his knees under the instrument panel and his feet at the very front, and says it's very comfortable. The controls A blue thumb-switch on the left side of the small, aircraft style , steering yoke operates the turning-indicators and there is a horn/radio press button under the right thumb. For the record attempts, the press button is wired for the radio. A small rocker "start" switch on the instrument panel is used to turn the car on. Control pedals are in the conventional positions, with the parking brake to the left of the pedal which controls the hydraulic drum wheel brakes. The accelerator pedal is on the right. Regenerative braking is implemented by a switch on the instrument panel and from then on is controlled by the accelerator. Suddenly the car is moving! No SOLAR STAR SPECIFICATIONS Length .... .. .......................................... Width .. .. .. .. .. .. .... .... .. .... .. .... .................. Height .. ................ ...................... ........ Track ........ .... .............................. .. ...... Wheel base .................... .. .................. Frontal area .... .... .......................... .. .. .. Drag coefficient .................................. Rolling resistance....... .. .... .... ..... .. ........ Weight ...... ........................ .................. Chassis .. .. .. .. .. ..... .. .... .. .. .. .... .. ... .. .. .... .. No. of wheels .... .. ........ .. .... .................. Type of wheel .................. .. ....... .. ......... Tyres .. .. .. .. ............................. .. ........... Brakes ................................................ Electric braking .. .. .. .. .. ...... .... .. .. .. .. .... .. Solar cells ...... .. ...... .. ............ .. ............ Load system .. .. .. .. .. .. .. .... .. .... .. .. .. ...... .. Motors .... .. .. .... .. .. .. .. .. ...... .. ...... .. .. .. .. .. .. Performance .... .. .. .. ......................... ... Top speed .. .. .. .. .. .. .. ..... .... .. ... .... .. .. .. .. .. Acceleration .... .............. ... ...... .. ........... noise, no fuss. One second it's just sitting there, the next second it is moving away smartly. There is an "aaaahhh!" from the small crowd. No matter how often you see it, the way it moves off so abruptly and quietly is always a surprise. Manfred claims to be able to out-accelerate a 1000cc motorcycle across an intersection and has achieved 60km/h in 4.3 seconds in acceleration tests. It is very hot out on the runway, with about six octas of fleecy white cirro-cumulus high in the light blue sky. During practice, they had problems with the electronics overheating, with power starting to drop off above 45°C, yet they were getting temperatures of 50°C while the car was stationary and up to 70°C during runs. For Saturday's runs, they have 30kg of dry ice to pack the heatsinks. If 30kg seems like overkill, it is. It's just that that's the minimum amount you can buy these days - at $6 a kg! After experimenting for awhile to find the most effective way to use the dry ice, they settled for Manfred's idea of just forcing the pellets between the heatsink fins. It worked. During most of the runs there was a cross wind from the north-west gust- 5.96 metres 1.98 metres 1.00 metres 1.12 metres 2.25 metres 0.58m 2 0.20Cd 0.004 285kg (including batteries) Aramid/carbon Nomex Four Aluminium disc Nylon belt (40.64cm x 1.5cm) Hydraulic aluminium drum 9kW Silicon in five sections Maximum power tracker AC asynchronous 4kW to 9kW (max) 135km/h (tested) 0-60km/h in 4.3 seconds ing from 5-15 knots (9-27.6km/h), giving about a 6 to 15km/h wind component directly along the runway from the west. The temperature at 1:15pm was 34°C. The Hon Neil Pickard, NSW Minister for Minerals and Energy, waved the flag and the Solar Star slipped away down the runway. For those waiting at the 1000 foot markers, by the emergency arrester net, it shimmered out of the haze and flashed past with a combination of rushing air and a low level, high pitched whine from the two AC asynchronous motors driving the rear wheels. At top speed, these were doing around 15,000rpm. Early problems The first run of just over 2km was in the 2 7 direction (into the west), with the NSW police Farey slant radar set up at about the mid-point and the police Kustom KRl0 car mounted in-line radar and RAAF police Kustom HR4 radar gun near the end of the run. But it didn't look right. At the high speeds, the aerodynamic forces on the body forced the front of the vehicle up , creating excessive drag. When it MARCH 1991 11 reached top speed on this run, the back end of the panels actually dragged on the ground.The result: a disappointing 122km/h. Obviously it was going to be harder than Leon Howes , managing director of Star Micronics, thought when he said, "We're not going to attempt to break the record, we're going to blow it away!" On the return run the police KR10 radar and the RAAF radar gun agreed precisely on 129km/h. Better, but the front was up so far it looked as though Manfred had rotated for takeoff. On the return run the Solar Star was clocked at only 113km/h by the slant radar. This was one of only three readings the slant radar was able to make during the nine runs, possibly due to its high directivity and the low profile of the Solar Star. Then again, perhaps it was because there wasn't a police car around the corner to make a booking! After the third run , the spectators and media were moved back from the runway while three Caribou aircraft took off. While this was going on, adjustments were made to the suspension to keep the car level at high speed. Manfred was hitting 131km/h on the fourth run when the cockpit suddenly filled with white smoke! For long moments he thought he was on fire. But no problem. The adjustments to the suspension had caused the body to rub on the tyre, making the smoke and slowing him down. After a wheel change he returned at 123km/h, which gave an average of 127km/h for the two consecutive runs . This beat the official 2-way record by enough to establish a new record but it hadn't exactly "blown it away". Record runs Manfred and the Star Micronics team returned to the hangar to make some serious alterations to the car's set-up. The main change was to connect another battery in series to boost the overall voltage. Interestingly, Manfred had to cut the scrutineers' tape that was put on in Darwin so that he could loosen the battery terminals. The German MOLL, 40Ah, leadacid batteries have done over 5000km and he hasn't even had to add water. Although they are rarely fully discharged, Manfred expects to get the 12 SILICON CHIP The Solar Star approaches the police radar "trap". This was on an early run as the front of the vehicle is raised. The suspension was later adjusted so that the vehicle would be level at high speed. Several different speed measuring radars were used to ensure accuracy. (Photographs by Gerry Nolan). equivaJent of over 300 deep cycles from them before rep lacement. On the sixth run, the car looked great but it only registered 121km/h on the KR10 radar and 122km/h on the HR4 radar gun. Then someone shouted, "Here he comes again!" and, as it scintillated out of the heat mirage, the white, curved front made a perfect oval with its reflection. Then it flashed past. He was obviously going faster! "135" the officer with the radar gun shouted, "and he held it for three triggerings." The crowd yelled. Jubilant. We were all part of it by now. You can't stand around on a runway for hours talking with the team, sharing their worries and their tensions, without getting involved, especially with such an empathetic vehicle as the Solar Star. The average between runs six and seven was up to 128km/h and the car was going really well, but the Caribous were due back any minute. Did Manfred have time for another run? He did, and again the car looked good. But the best he could do was 124km/h. Hans Tholstrup, the NRMA and po- lice conferred and compared notes before deciding that the 135km/h was an outright world land speed record for a solar electric vehicle and that they would allow 129.5 km/h as the official 2-way average of runs seven and eight. These records have been submitted to the Federation Internationale de l' Automobile (FAI) Category A Group 7 Class 1 (vehicles under 500 kg) for confirmation and will take their place in the Guinness Book of Records. Talking about the future of solar electric vehicles, everyone agreed that they are at about the same stage of development and public interest now as personal computers were in 1975, when the Altair 8800 appeared on the front cover of the American magazine Popular Electronics. To paraphrase Joseph K. Hart speaking about the future of electricity as oppos.ed to steam in 1924; "The reign of oil approaches its end; the next stage is solar electric power; enabling us to break away from the bonds of oil and become independent. Solar energy creates a decentralising form of power - using it, we may feel the thrill of control and freedom once again." SC 2M VHF FM Transceiver This outstanding high performance FM transceiver can be used as either a mobile or base station on the 144-148MHz amateur band. It must be one of the easiest transceivers of its kind to build yet it comes loaded with advanced features. Features like • Full PLL frequency synthesis • 24 memory channels with repeater shifts • 25W or 5W switchable output • 5kHz or 25kHz tuning steps • Microprocessor control system • Excessive SWR safety shut-down circuitry • 0.15uV sensitivity at 12d8 SINAB • 30kHz selectivity at -60d8 • -60d8 image rejection At this price you can afford to take the challenge! Kit includes all components, hardware, heatsink and a pre-punched silk screened front panel. Microphone is not supplied. YAESU D-2110 or D-2105 are recommended. Cat K-6400 Telephone Amplifier Onlys399 This telephone monitoring system is battery operated and needs no electrical connection with your telephone. Simply attach the magnetic pick-up near the earpiece and friends or business associates will be able to hear conversations as they happen. This is a complete kit with prepunched and silk screened front panel. Cat K-3104 QQ QQQ s39es ~ Jan, Feb, ~ Mar'91 <at> Nov '90 12VDC 100 Watt Converter Transistor Tester This tester is capable of checking most discrete semiconductor devices, esp-ecially bipolars and FETs. It's also an excellent way of becoming familiar with the basic operation of these components. The circuit features an overload indicator and battery check plus a quality meter. Cat K-7220 Ever wished you had the power of your home stereo in the car? Well now you can! This compact inverter will power equipment up to 100 watts. That makes it ideal for our 50 watt and 100 watt amplifier modules. It has temperature & current overload protection plus low voltage shut down to prevent your car battery going flat. This kit is supplied complete including case. Cat K-3235 QQ Q '129 s39es -<at> DEC '90 DEC '90 1.5V to 9VDC Converter With Instructions & Parts Listi Assorted Circuit Boards Here's a great way to use up leftover components! These assorted projects include 3 to 4 boards with detailed instructions and parts list - parts which you may already have! Some projects even include front panels. Cat K-9090 •·19'5 Cat K-9095 More complex boards 1 2195 MAJOR DICK SMITH ELECTRONICS AUTHORISED STOCKISTS: N.S.W.: ARMIOALE: New England Electronics 711655 BALLINA: Ballina Electronics 867022 BEGA: OZfECH Electronics 923933 BOWRAL: F.R.H. Electrical 611000 BROKEN HILL: Hobbies & Electronics 684098 COOTAMUNDRA: Cootamundra Music & Ute 422561 COFFS HARBOUR: Coffs Harbour Electronics 525684 DENILIOUIN: Deni Electronics 813672 DUBBO: Chris's Hi Fi 828711 FORSTER: Forster Village Electronics 545006 GLEN INNES: John Sommerla<I Electronics 323661 GRAFTON : Repairs and Spares421911 GRIFFITH: Miatronics624534 INVERELL: lnverell Electronics221821 KEMPSEY: P&L Leonart! 631134 LEETON: Leeton Audiotronic 532800 LIGHTNING RIDGE: Cycle & Sound 290579 LITHGOW: Oouroy 1 0 J~~~g:~:i~fc'ero9~~if.r'~c;t~13:l:1~ Electronics 210722 ORANGE: Central West Electronics 626491 PARKES: Strad Music Centre 623366 PORT MACQUARIE: Hastings Computer Service 634574 RICHMOND: Silicon Crafts 784101 TAREE: Brads Electronics 526603 WAGGA WAGGA: Phillips Electronics 216558 WELLINGTON: Wellington Service 452325 WINDOR: Silicon Cratts 776722 VASS: wannington Electrical 261116 YOUNG: Keiltl Donges Electronics 821279 VIC: BAIRNSDALE: LH & LM Crawfort! 525677 COLAC: Colac Electronics 312847 Ml LOURA: Pullman Auto Pro 232882 MORWELL: Morwell Electronics 346133 SHEPPARTON: Andrew Guyatt Electronics 219497 SWAN HILL: Nvah District TV Service 329303 TRARALGON: Traralgon Electronics 741699 WARRAGUL: Roylaine 234255 WARRNAMBOOL: KoroitSt Elec Services 627417 OLD: AYR: Delta Electrix 831566 BOWEN: Bowen Electronics 861656 BUNDABERG: Bob Elkin Electronics 521785 CALOUNDRA: Electro-mart 918533 DYSART: Dysart Videotronixs 582107 INGHAM: Masons Electronics 763188 INNISFAIL: lnnisfail Hi-Fi 612014 MACKAY: Stevens Electronics 511723 MARYBOROUGH: Keller Electronics 214559 NAMBOUA: Nambour Electronics Shop 411604 PIALBA: Keller Electronics 283749STANTHORPE Granite Belt Communications 813333 TAS: BURNIE: Electronic City 314780 OEVONPORT: A.I.Electronics 248322 SA: MT GAMBIER: Hutchesscn·s Communication Centrn 250400 PORT LINCOLN: Basshams TV & Comp WOnd 822788 WHYALiLA: E)'fe Electronics 454764 WA: ALBANY: Micro Electronics 412077 BUNBURY: Micro Electronics 216222 GERALOTON: Batavia Lighting & Electrical 211278 KALGOORLIE: Today"s Electronics 215212 KARRATHA: Daves O;citrooic 854836 MANORAH: M~ro Electron~s 5812206 PORT HEDLAND: Ivan Torr,k 1t1e Elect 732531 ~~raJt~~~~i ~~~~;i~~~J?.2m~ rl'o~\/l'.~::~. Frustrated at how quickly your 9 volt batteries go flat? Then switch over to more cost efficient 1.5 volt cells with this 1.5 to 9 volt converter. It uses just 3 components and fits on a small PC board. This is a short form kit PCB and components only. Cat K-3230 Q -<at> s14es NOV '90 rzl l.ZJ Kits marked with this symbol involve mains power wiring. Take extreme care when working with this equipment. · Degree Of Simplicity Q QQ QQQ Simple Intermediate Detailed MARCH 1991 13 ,o t!i p "" With true RMS! 1:,- ODO COMBINED ANALOG/ DIGITAL MULTIMETER ~ I , I -., If you've ever wished for an accurate digital meter with the readability of an analog meter then here is the solution-- a digital multimeter with a large 3½ digit display combined with a full sized analog meter with mirrored scale! Unit comes complete with probes and soft carry case. Ranges: • DCV 200mV, 2V, 20V, 200V, 1000V • ACV(rms) 200mV, 2V, 20V, 200V, 750V • AC(rms) & DC current 20uA, 200uA, 2mA, 20mA, 200mA, 2A, 10A • Resistance 200, 2k, 20k, 200k, 2M, 20M ohms • dB -45d8 to +50d8 (4 ranges) • Audible continuity • Diode check $199 Cat Q-1700 With Built-in Logic TBSIBTI 6-24V VOLTAGE TESTER Checks both AC and DC voltages within the range of 6, 12, or 24 volts. Cat Q-1532 PROBE TYPE DIGITAL MULTIMETER This would have to be the smallest, handiest DMM you 'll ever have the chance to buy! It features Data Hold , fixed and auto Ranging, plus a full 3½ digit LCD display. • 200mV to 500V range • 40 to 400Hz frequency range • 0 to 20M Ohms • Auto Polarity indication • Diode and continuity testing • AC/DC Current up to 200mA • Soft carry pouch Cat Q-1560 s59ss 110-500V VOLTAGE TESTER Checks for voltages in the range of 150, 300, and 500 volts DC or 110, 220, and 380 volts AC Cat0-1534 $695 WATERPROOF FUSE HOLDER It doub/BS as a F/ashlightl CONTINUITY TESTER Made from solid steel, this handy continuity tester can check for short circuits and circuit breaks, test diodes plus it doubles as a handy flashlight! Cat Q-1536 This in-line fuse holder suits 3AG(6.35x31 .8mm) fuses and is ideal for auto and marine work or in any harsh environment. Crimp connections make wiring a breeze and the large eyelet is designed to anchor the fuse holder to the wiring loom. • Rated (max) 32V <at> 30A • Resistant to water, salt spray and ultraviolet Iight • -40 to 150 deg.C temperature range • Withstands many organic solvents as wel I as rigourous shock and vibration Cat P-7917 M u L T I M E T E R s B1100/P2 14 SILICON CHIP Save over 400/o on BULK BUYSI TANTALUM CAPACITORS Cat No. uF Volts Each R-4700 R-4705 R-4710 R-4715 R-4720 R-4730 R-4735 R-4740 R-4745 R-4750 R-4752 R-4754 R-4756 R-4758 R-4760 R-4762 R-4765 R-4770 R-4775 0.1 0.22 0.33 0.47 1 2.2 3.3 4.7 6.8 10 22 33 47 68 22 100 33 47 100 35 35 35 35 35 35 35 35 35 25 25 25 25 25 16 16 10 6.3 3 80 80 80 80 80 $1.10 $1.15 $1 .25 $1.45 $1.45 $5.95 $6.95 $9.95 $12.95 $1 .75 $6.95 $1.75 $1.75 $2.25 10+ Bulk Buy Each 40 40 40 40 40 55 55 55 65 65 $2.95 $3.55 $4.15 $5.35 65 $3.55 65 65 90 50 VOLT MONOLITHIC CERAMIC CAPACITORS C at No. ~ 250V POLYSTYRENE CAPACITORS C at No. pF Each R-2807 R-2809 R-2811 R-2813 R-2815 R-2817 R-2819 R-2821 R-2823 R-2825 R-2827 R-2829 R-2831 R-2833 R-2835 R-2837 R-2839 R-2841 . R-2843 33 39 47 56 68 82 100 120 150 180 220 270 330 390 470 560 680 820 1000 90(1: 90q: 90q: 90(1: 90(1: 90(1: 90q: 90(1: 9011: 90(i; 90(1; 90(1: 90(1: 9011: 90(1; 90(1; 9011: 9011: 90(1; ., 10+ Bulk Buy Each 50q: 50q: 50q: 50(1: 50(1: 50q: 5011: 5011: 5011: 5011: 5011: 501!: 5011: 5011: 5011: 501!: 50(1: 50(1: 5011: '' 3mm LEDs Z-4077 Z-4079 Z-4081 Z-4083 Red Green Yellow Orange Each 3511: 3511: 3511: 35(1: R-1981 R-1982 R-1983 R-1984 R-1985 R-1986 R-1987 R-1988 R-1989 R-1990 R-1991 R-1994 R-1995 R-1996 R-1997 R-1998 R-1999 R-2002 R-2003 R-2000 R-2004 R-2005 R-2006 R-2007 R-2008 R-2001 R-2180 R-2181 R-2182 R-2183 R-2184 R-2185 10+ Bulk Buy Each 2011: Z-4060 2011: Z-4061 2011: Z-4062 20(1: Red Green Yellow Orange 5011: 5011: 5011: 5011: Each 10+ Bulk Buy Each 30(1: 30(1: 30q: 30(1: 30(1: 30(1: 30q: 30(1: 35(1: 35q: 40q: 40(1: 45(1; 30(1: 30(1: 30(1; 30(1: 30(1: 35q: 35(1: 40(1: 40q: 40(1: 45(1: 50q: 50q: 35(1: 45(1: 55 (1: 60(1: 65(1: 7011: 1511: 10 15 22 33 47 68 100 120 150 220 330 470 680 1000 1500 2200 3300 4700 6800 0.01uF 0.015 0.022 0.033 0.047 0.068 0.1 0.15 0.22 0.33 0.47 0.68 1uF (25v) 10mm LEDs 5mm LEDs Z-4085 Z-4087 Z-4089 Z-4091 pF 30(1: 30(1; 3011: 3011: Red Green Yellow 15(1: 15(1; 15(1; 15(1: 15q: 15(1; 15(1: 20(1: 20(1; 20(1; 20(1; 25(1; 15(1; 15(1: 15(1: 15(1: 15(1: 20q: 20q: 20q: 20q: 20q: 25(1: 25(1: 30q: 20q: 25q: 30(1: 35q: 35(1: 4011: 10+ Bulk Each Buy Each 9511: 5511: 95(1; 5511: 95(1; 55(1; 2x5mm LEDs (Rectangular) Z-4093 Z-4095 Z-4097 Red Green Yellow 35(1: 3511: 35(1; 6011: 60q: 60(1: DS XPRESS PHONE & MAILORDER SERVICE Outside Sydney (FREE Call) 008 22 6610 Sydney And Enquiries - 888 2105 FAX: (02) 805 1986 or write to DS XPRESS, PO BOX 321 N/RYDE NSW 2113 All Major Cred it Cards Accepted. 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B1100/P4 M ARCH 1991 15 Remote controller for garage doors Wouldn't it be wonderful if you could operate your garage door, gates or other devices by remote control? This unit will do the job for you. By BRANCO JUSTIC This general purpose unit will enable wireless remote control of garage doors, gates , blinds, shutters and many other devices. It features a ready-made transmitter, high security, and all of the desirable features that one would expect of such a controller! Your job is to build and install the 16 SILICON CHIP receiver/controller board described here. To this, you need to add a geared DC motor (such as an inexpensive automotive windscreen wiper motor), a power transformer and a little mechanical ingenuity. We will offer a few tips and ideas to get you started. Most people of course will want to use this project as a garage door con- troller. So, to simplify matters from here on, we'll describe the project for that application. Main features OK, lot's take a look at the main features. First, the controller has provision for both upper and lower limit switches. In operation, one of these switches (eg, a microswitch) is closed by the door at the end of its travel and this trips the circuit to stop the drive motor. In addition , the circuit also features overcurrent sensing for both the DOWN & UP modes of operation. These can be used to detect obstructions and immediately stop door operation to prevent damage to the motor or drive mechanism. In many situations, the ANTENNA r---t"-----,--....-----..-----.---..---~----....---------<1>----+8V 220k 1M L1 100k 100n 220k 4.7M 220pF E sOc 15pF VIEWED FROM BELOW GARAGE DOOR OPENER RECEIVER Fig.1: the UHF receiver front end. Ql functions as a regenerative detector stage, while Ll & Cl set the resonant frequency. The detected output appears at Ql's emitter & is amplified by ICla & IClb. The signal is then fed to Schmitt trigger stage IClc & inverted by ICld before passing to the decoder circuit (see Fig.2). overcurrent sensor could also be used to sense the "open" and "closed" limits and can thus eliminate the need for limit switches. Of course, these's nothing to stop you from using both limit switches and overcurrent sensing if you so wish. In fact, we recommend that you do use both methods for garage doors. As we've already mentioned, the unit is supplied with a ready-made transmitter and this has more than half a million possible codes - 531,441 to be exact! Press the button on the transmitter and the door goes up; press it again and the door goes down. Simple! The "open-field" range of the transmitter is over 200 metres, so lack of range will not be a problem for any normal domestic application. In addition, there is provision for manual operation using a pushbutton switch. This switch would normally be mounted on the wall inside the garage. The manual switch controls the unit in exactly the same fashion as the transmitter (ie, the unit changes direction on each subsequent press of the button). You don't have to wait for the door to reach the end of its travel either. It can be reversed at any time whilst in motion simply by pressing the remote or manual pushbuttons again. OK, so you've just opened the garage door using your fancy new controller from the luxury of your car. But who wants to drive into a dark garage at night? Wouldn't it be better if a light came on automatically as well? Our circuit takes care of this problem by including a timed relay output which switches a 12V supply rail. This relay is closed each time the controller is activated and remains on for about 2 minutes before automatically switching off. Low voltage automotive lamps and fittings can be used for the lighting, or you can use the on-board relay to trip a mainsrated relay to switch on 240V lights. Since all the inputs are filtered, inexpensive unshielded wire such as telephone cable can be used to connect the UP & DOWN door limit switches and the manual pushbutton switch. The total cost for the control board plus the transmitter is $107. To get a complete motorised garage door, you also need to obtain a suitable motor and transformer, a chain or gear drive system, a case to put it all in and other sundry hardware. All up, we estimate that the total cost of this do-it-yourself garage door opener will be about $200 . Compared to that, the cost of a commercial installation will set you back $650 or more, depending on its complexity. Interested? Then read on. How it works - receiver The control circuit is built on a single PC board. This contains the UHF receiver front end, decoding circuitry, light timing and relay driver circuitry, door operation logic, motor UP & DOWN relay drivers, overcurrent detection and a power supply. Fig.1 shows the circuit for the receiver front end. This is built around transistor Ql and quad op amp ICl. The coded signals from the trans- mitter are picked up by the antenna and are inductively coupled into a parallel tuned circuit comprising 11 and trimmer capacitor CVl. This tuned circuit sets the resonant fre quency for the self-detecting regenerative UHF receiver stage based on Ql and Dl. The detected output appears at the emitter of Ql and is AC-coupled via a 4.7µF capacitor to inverting amplifier stage ICla. A low-pass filter consisting of a lkQ resistor and .00lµF capacitor is included to prevent any RF signals from being coupled into ICla. ICla operates with a gain of about 214, as set by the ratio of the 4.7MQ feedback resistor and the 22kQ input resistor. The 15pF capacitor in parallel with the feedback resistor rolls off the response above 2.2kHz. The output from ICla appears at pin 10 and is AC-coupled to inverting amplifier stage IClb. This stage operates with a gain of 47 and a rolloff above 3.3kHz. Its output is biased at close to ground potential and so the original digital signal appears at the output (pin 9) of this stage. Next, the signal is fed to Schmitt trigger stage IClc. This stage cleans up the signal from IClb and prevents false triggering due to noise and interference. The resulting signal is then inverted by ICld to give a digital pulse train (Data) which matches the data present at the encoded output of the transmitter. Tristate decoder The recovered data signal is now applied to the pin 14 input of Tristate decoder IC2 (AX-528) - see Fig.2. This device is used to decode the 12-bit pulse signal generated by an AX-5026 encoder chip in the transmitter. It has 12 Tristate address inputs which are MARCH 1991 17 This view shows the UHF receiver/controller board, together with its companion transmitter (which is supplied ready made). Although designed to control garage doors, the unit could also be used to control gates, curtains, blinds, shutters & other mechanical devices via a motor & chain drive assembly. connected to correspond to the transmitter code. Each address input can either be tied high or low, or left open circuit (O/C). When the transmitter code matches the code on IC2's address pins (ie, when a valid signal is detected), pin 17 switches high and this drives the remainder of the circuit via two paths. Light relay First, the high from pin 17 is applied via isolating diodes D2 and D4 to a monostable made up from IC3b and IC3c. This monostable is used to operate the light relay via switching transistor Q5. The time the light remains on is set to about 2 minutes by the 1MQ resistor and lO0µF capacitor connected to pins 1 and 2 of IC3c. The circuit works like this. Initially, the lO0µF capacitor is discharged (both sides high) and so pin 3 of IC3c is low and Q5 is off. At the same time, pins 5 & 6 are held low via a 56kQ pull-down resistor. When a valid code is detected, pins 5 & 6 are pulled high and thus pin 4 ofIC3b switches low. This means that pins 1 & 2 ofIC3c also switch low and 18 SILICON CHIP so pin 3 switches high and turns on the light relay (RL5) via transistor Q5. At the same time, pins 5 & 6 of IC3b are latched high via D5. The lO0µF capacitor now charges via the 1MQ resistor and, after about 2 minutes, pulls pins 1 & 2 of IC3c high again to end the timing period. This also releases the high on pins 5 & 6 of IC3b and so pin 4 switches high again to discharge the capacitor so that it is ready for the next cycle. D6 clamps the positive side of the capacitor to the supply rail when pin 4 switches high again, to prevent damage to IC3c. pass filter. Its job is to filter out any RF signals which may be picked up by long leads connected to S1 and which could false-trigger IC3a. Similar filter networks are also used for the LOWER & UPPER limit switches (S2 & S3), for the same reason. Door logic Manual control The valid transmission line is also connected to the clock inputs (pins 3 & 11) of two paralleled D-type flipflops based on IC4. These flipflops toggle (ie, change state) on each successive clock input because of the 1MQ feedback resistor connected between the Q-bar outputs (pins 2 & 12) and the data inputs (pins 5 & 9). A time delay of about 1 second is provided in this feedback path by the 1MQ resistor and the lµF capacitor on pins 5 & 9 to prevent unpredict- Inverter stage IC3a and pushbutton switch S1 form the manual control circuit. Normally, pins 8 & 9 of IC3a are held high via a 1MQ resistor and so pin 10 will be low. When S1 is pressed, pins 8 & 9 are pulled low and thus pin 10 applies a high to the valid transmission line via D3 (just as if a valid transmission had been received from the transmitter). The 100kQ resistor and 0.1µF capacitor associated with S1 form a low Fig.2 (right): the decoding & door logic control circuit. When a valid code is detected, pin 17 of IC2 switches high & toggles D-type flipflop IC3. IC3 in turn controls RS flipflops IC5a,b & IC5c,d & these drive the motor relays via Q3 & Q4. Comparator stages IC7a & IC7b provide overcurrent sensing. g ~ ~ .... cc ::0 .- ~ I I st5. 8 IN GND VIE1ffoW M 0 eOc E CB rn ~ I OUT I DATAFROM ~ RECEIVER - ,,,.,, . A11 - 12 11 A10 10 A9 B AB 7IA7 +8V .,. 1 I I I T M 10 1~ .,. .J.t 1 I o., .,. I I 1 00kf ., 5 I '""l 330kJ t ! 1M + 56 k r.-. .,. I 0.1 7 Q I ~ 2,12 I I I ...~L I I "~ 100k 100k 2-1 ... "" +BV 22k ,, Q 0. .J 1 I ,.,.,..... ei- ~, ~• ' l- 56ki * +BV .,. i LIGHT O -. I ! ~ s&419 I ~ I 0.22n 1 . - RLA3 RLA2 RLA4 ;LA/,I, .L I I :J l I ·rI I ._ I I r +V2, <at>10 ICSc ~~ 1 +BV ,~H• ,( ~) !( ~) 10M~ ~• lE I ~ I"I •"'I r j.,. ~ *1 Dn 1W FOR 12V, 120Q 2W FOR 24V +BV ~ C '{ ,, GARAGE DOOR OPENER DECODER lUM - - - - - - - - - - - - , , .,. 10M1 .,. I I l . ~f«I I I I I '"J '"J ~ 3 11 , CLK 4M3 5,9 D IC4 14 +iv 1 -£~ ,oo I ,.::ucii ,--". +sv--fl ~ - '1' t----, -:- I ~ I 1N4148 u l'-17'-----+...... ~ • s1 MAN UAL! 100k f L_ I ""'f ...,.._,. '" ,-.,. '"f P1 I 4fA4 ~ I 3 IA3 AXS2B I " ·· 6 6JA I '~, . I f 7 I 1~1 56k UP OO~N 03 B0679 MOTOR .,. E B~ V n~ V27i r 2. 7k ¥N, * ~ ~ dJL'lo";,'~ .,.... - - S1 10k . . . . - - - - - - 1....a1 ____________00-1I,..,.-----L-1- - - - L E ~ ">-:+ 1 10uH LO T 12V .001 1 I ...L.. 4pFI RC1 3.3pF :I.,. 4pFI 17 22k IC1 AX5026 16 1M 15 .,. 14 9 GARAGE DOOR OPENER TRANSMITTER Fig.3: the transmitter circuit is based on an AX5026 trinary encoder IC. When the transmitter button (S1) is pressed, ICl generates a 12-bit code at its pin 17 output & this switches Ql which is wired as a Hartley oscillator operating at 304MHz. able operation due to short breaks in transmission. Normally, the set inputs (pins 6 & 8) of IC4 are held low by a 10MQ resistor. However, when power is first applied, a pulse is applied to the set inputs via a O.lµF capacitor. Provided the motor is connected with the correct polarity (ie, as shown in Fig.2), this will ensure that the door will be in DOWN mode if power is restored after a power failure. The Q and Q-bar outputs from IC4 are used to control two separate RS flipflops, made up from the four NAND gates in IC5. The outputs of these flipflops (pins 10 & 11) switch high when their inputs (pins 8 & 13) are momentarily pulled low (ie, while the O. lµF capacitors charge). IC5a & IC5b form the DOWN flipflop and its output (pin 11) drives switching transistor Q4 to operate the DOWN relays (RLA3 & RLA4). Similarly, IC5c 20 SILICON CHIP & IC5d form the UP flipflop and this operates the UP relays (RLAl & RLA2) via switching transistor Q3. These four relays in turn switch the power to the motor, the polarity depending on whether the door is to go up or down. For example, when RLAl & RLA2 are closed, the door goes up. Conversely, when RLA3 & RLA4 are closed, the door goes down. Note that, in either case, the motor current flows to ground via a 0.22Q current sensing resistor. Let's take a closer look at how this circuitry works by considering the operation of the DOWN flipflop (IC5a & IC5b). Normally, pin 13 of IC5a is pulled high by a lMQ resistor, pin 11 is low, and Q4 and relays RLA3 & RLA4 are off. When the paralleled Q-bar outputs of IC4 (pins 1 & 13) toggle low in response to the receipt of a valid code or at power up, pin 13 of IC5a is also momentarily pulled low via a O. lµF capacitor. This toggles the flipflop , so that pin 11 now goes high and turns on Q4 and the DOWN relays to provide power to the motor. At the same time, pin 2 of IC5b also goes high and so pin 3 switches low, which means that the flipflop latches in thi s state . The door is now driven downwards by the motor until it closes the lower limit switch (S2). At this point, pin 1 of IC5b is pulled low via a 100kQ resistor and this resets the flipflop (ie , pin 3 high & pin 11 low). This in turn switches Q4 and its associated relays off again and stops the motor. The UP RS flipflop (IC5c & IC5d) operates in similar fashion when the paralleled Q outputs of IC4 toggle low. In this case, the flipflop drives Q3 which switches the UP relays (RLAl & RLA2). The flipflop is reset and switches off the motor when the door trips the upper limit switch (S3) . The two 22kQ resistors between the outputs of IC4 and pins 1 & 6 of IC5b & IC5d allow the motor to be reversed while the door is in operation. In practice, they reset one of the flipflops if IC4 toggles again before a door limit switch is closed. For example, let's say that flipflop IC5a & IC5b is in the set condition (pin 11 high) and that Q4 and its relays are on. If the transmitter button is now pressed while the door is at mid-travel, the Q outputs of JC4 will pull pin 1 of IC5b low via its associated 22kQ resistor and reset the flipflop, thus turning Q4 off. At the same time, the other RS flipflop will be set and Q3 will turn on. Transistor Q2 makes it impossible for the outputs of both RS flipflops to be high at the same time (eg, due to a circuit fault). The way in which it works is quite simple. If pin 10 of IC5 c goes high, QZ turns on and pulls the base of Q4 low. Thus the DOWN relays will be off, even if the output of the DOWN flipflop (pin 11, IC5a) is high. This is a worthwhile precautionary measure because if all four motor-drive relays closed, there would be a short circuit directly across the power supply. Current sensing Comparator stage IC7a provides the overcurrent cutout feature for the UP mode. The voltage at its non-inverting input depends on the setting of VR1 and this can be anywhere in the range of 4-4.5V. The voltage at the inverting input is at approximately ½Vee (4V) with the motor not connected. However, when the motor is running, the voltage applied to pin 2 of IC7a rises to 4V plus the voltage developed across the 0.22Q resistor. For example, if the motor current is 1A, the voltage on pin 2 would rise to 4.22V; if the current is 2A, the voltage would rise to 4.44V, etc. Thus, if the motor current rises above a certain value, the voltage on pin 2 of IC7a will exceed the preset bias on pin 3. And when this happens, pin 1 switches low and resets the UP flipflop to stop the motor. Thus, Q3 and the UP relays turn off and the door stops if the current through the motor rises above a preset level. This typically occurs if the door encounters an obstruction or when it reaches the end of its travel. Overcurrent detector IC7b functions in exactly the same way for the DOWN mode. Trimpots VR1 & VR2 allow the trip currents to be set to the desired values for the up and down directions. The 10µF capacitors at pins 2 and 6 and IC7a and IC7b are there to slow down the response time of the overcurrent detectors so that they are not unduly sensitive to varying friction in the door 's movement or to the motor starting current. Power supply The incoming AC voltage from an external 12 or 24V transformer is rectified by bridge rectifier D16-D19 and applied directly to the motor driver relay polarity switches and the light relay. The resultant unfiltered pulsating DC is used only for driving the motor and the light. If the unit is powered from a DC supply, such as a battery which is continually trickle charged, the bridge rectifier assures that the correct polarity is applied to the circuit, no matter which way the battery is connected. A voltage dependent resistor is connected across the motor in order to minimise the possible high back EMF voltages (from the motor) which would otherwise produce sparks across the relay contacts. A 470µF capacitor is used to filter the rectified supply to drive the relay coils and diode D15 is used to isolate this filtered supply from the motor. Diode Dl 1 and a 100µF capacitor provide further filtering of a supply which is fed to IC6 , a 7808 3-terminal regulator. This provides an 8V supply for most of the circuitry. How it works - transmitter The circuit of the transmitter is shown in Fig.3. It is based on an AX5026 trinary encoder IC. When pushbutton switch Sl is pressed, this IC generates a sequence of pulses at its output, pin 17. The rate at which the pulses are generated is set by the 1MQ resistor between pins 15 and 16, while the code sequence is set by the connections of the address lines A1-A12. The pulses generated by the IC are used to switch Ql which is connected as a Hartley oscillator operating at 304MHz. Note that the transmitter will be supplied ready made and will only need to be set to your own unique code. We'll discuss this next month, along with the construction and installation of the unit. Until then , you will have to be patient and keep opening and closing your garage door by hand. Where to buy the kit A kit of parts for this project will be available in early April from Oatley Electronics. The prices are as follows: transmitter, $27.50 (built and tested); receiver PC board and all onboard components, $79.50; 12V 6.5AH Gel battery, $29.90 (limited stock). Certified postage on any of the above items is $6.00. In addition, Oatley Electronics can supply the receiver PC board in ready assembled form and is also offering a repair service for any constructor who runs into difficulties. For further information, contact Oatley Electronics, PO Box 89, Oatley, NSW 2223. Phone (02) 579 4985. Note: copyright© of the PC bocJ.rds associated with this project is owned by Oatley Electronics. PARTS LIST 1 PC board, code OE90RG, 187 x 106mm 5 SPOT relays 1 VL275A40B varistor 2 100kQ trimpots (VR1, VR2) 1 2-1 0pF trimmer capacitor (CV1) 1 5A fuse 2 fuse clips Semiconductors 1 OA90 diode (for testing) 10 1N4148 silicon signal diodes (D1-D10) 51N4004 silicon diodes (D11D15) 4 1N5402 silicon diodes (D16D19) 1 BF199 NPN transistor (01) 1 BC548 NPN transistor (02) 3 B0437 NPN Darlington transistors (03,04,05) 1 CA3401 quad Norton op amp (IC1) 1 AX528 trinary decoder (IC2) 2 4011 quad NANO gates (IC3,IC5) 1 4013 dual D-type flipflop (IC4) 1 LF353 dual JFET op amp (IC?) 1 7808 +8V regulator (IC6) Capacitors 1 470µF 35VW electrolytic 1 470µF 16VW electrolytic 1 10OµF 35VW electrolytic 2 100µF 16VW electrolytic 5 10µF 16VW electrolytic 2 4.7µF 16VW electrolytic 1 1µF 16VW electrolytic 6 0.1 µF monolithic 1 .0033µF ceramic (for testing) 3 .001 µF ceramic 1 330pF ceramic 1 220pF ceramic 1 33pF ceramic 1 15pF ceramic 1 3.3pF cermaic Resistors (5%, 0.25W) 4 10MQ 1 4.7MQ 1 2.2MQ 7 1MQ 4 330kQ 4 220kQ 8 100kQ 5 56kQ 2 47kQ 1 39kQ 1 33kQ 3 22kQ 1 10kQ 1 6.8kQ 2 4.7kQ 2 2.7kQ 1 1kQ 1 100Q 2 0.22Q 5W MARCH 1991 21 HUGE STOCK CLEARANCE PRICES DRASTICALLY REDUCED ON MOST ITEMS Jack O 'Donnell Managing Director See Altronic's new 1991 catalogue for our full range. If you haven't received your copy yet, send $1 to cover postage and packing to: ALTRONICS MAIL ORDER, PO BOX 8350 PERTH STIRLING ST, W.A. 6849. Redfo rd High End Poly Emulsion Coated Cone Woofers at Direct Import Prices Altro nic Di stri b uto rs ann o un ces the re lease of a new generat,or, of high end woofers . The development of high grade drive r com pone nts in Japa n . such as Barium ferrite magnets and specially formuiated paper cones impregnated with poly emul sion , ha ve en ab led us to offer our customers drivers of quite remarkable power handi1ri g. performance ,md extremely low di sto riti on. We b.elieve the perfo rmance exceeds that obtainab le from many Eucur,ea n ·na me" brands . and th e direct ,rnpo rt prices Cone Materials. Thi s se ries of loudspeaker features a specially selected fmre impregn ated paper cone wh, cn Is -.oa ted w:th a layer of po lypro pylene to ad d the desired rigidity. An added benefit of tt1is coa ting ,si ts resistan ce to water and moisture ingress. Voice Coil Construction. A ll vo ice co il s are wound on alum inium . th e magnet pole pie ces are ven ted fo r r1eat dissipa ti o n. Bu mp back plates are employed to allow extra voice ca ll excursion. 12" PECC Woofer 80 Watts RM S 160W Max . Rated Power .BOW Max. Power ... 160W lmped ance .... 8ohm Freq . Res p .... FO-3k Hz Res. Freq ....... 25Hz (• / -SHz) Sen sitivily .... .9Bd 8/ W(0.5m) Mag net .... ... .. 140Bgm/o 0oz . 6'h" PECC Woofer 30 Walla RMS 60W Max. Rated Power .40W Max . Power ... 60W lmpedance .. .. Bohm Freq . Resp .... FO-5kHz Res. Freq ... .... 70Hz (+/ -14 Hz) Sensiti vi ty ..... 96d 8 / W(0.5m) Magnet ....... ... 567 gm/ 20o z C 3022 $49.95 C.B. Power Microphone For professional 2 Way radios on aircraft , boats, vehicles and also industrial PA systems . 8" PECC Woofer 60 Watts RMS 100W Ma x. Rated Power .60W Max. Power ... 100W Impedance .... Bohm Freq. Resp . ...FO-4kHz Res. Freq ..... .. 60Hz (•/-12 Hz) Sensitivity ..... 9Bd6/ W(0.5m) Magnet .......... B4Bgm/ 30oz c 3024 $69.oo C0336 ~ $20.oo 21st Century entertainment fascinate your friends! c 3030 $125.oo 10" PECC Woofer 80 Walls RM S 130W Max. Rated Power .BOW Max. Power ... 130W Impedan ce .. Bohm Freq. Resp ... .FO -4kHz Res. Freq ....... 2BHz (+/ -5Hz) Sensitivity .. ... 97d8/ W(0.5m) Magnet .. ... .. 1170gm/ 41 oz C 3026 $99 .95 c 3032 $198 .oo Micron SOLDERING STATION Electron ic Temperature Cont roll ed -Temperat ure Selectabl e, Soldering Station. Now th is is really q ual ity and ve rsati lity! Now supp lied with long life cerami c cartridge heate r. The M ICRON T2440 soldering stat ion offers the ultimate in controll ed temperature , hand sold ering. Simply rotate detained rotary switch freely to selectable fi xed temperatures of: 320° C (608° F) , 350° C (662° F) , 380° C (716° F) 410° C (770° F) , 440° C (824° F) w ithout changing heater or tip. Packed with features: Temperature readout & control ; Zero vo ltage witching ; Grounded tip; ow voltage element; Chrome plated, iron clad tip. PLASMA LAMP DISPLAY Amazing! 1-'ulsating high voltage plasma discharge continually changes shape and direction . Mode selectable to either fingertip control or sound activated. For example, from voice or sound system . Provides endless fascination as it sizzles and arcs. Supplied complete wi th AC mains adaptor. A 01 20 Normally $199.00 • SAVE $50.00 Up till now similar lamps have sold for $1000 and morel/ THIS M ONTH ONLY $149.oo 15" PECC Woofer 100 Watts RM S 200 W Max. Rated Power . 100W Max. Powe r ... 200W Impedan ce .... B0hm Freq. Resp ... .FO-3kHz Res. Freq ....... 25Hz (+/-5Hz) Sensit ivi ty .. ... 9Bd 8/ W( O.5m ) Mag net .. ... ..... 1B35gm / 65o z T 2440 $,l.ff.ss This Month Only $139.ss BAG YOURSELF A KIT BARGAIN! ! FM Stereo Transmitter (See €> 1111!/!i e sc Oct ,88 ) Simply connect your CD player to the mini milter which converts the CD signal to an FM signal. This FM signal then can be tuned in via your FM walkman or your shed radio. Great for listening to your favourite CD while washing the car, mowing the lawn or doing the vacuuming etc, without blasting the neighbours. -·- .... STEIIEO FIi TRANSMITTER K 1120 ,$~o $39.50 Bench Top Power Supply FEATURES: AC/DC Millivolt Meter (See Ea Dec '87) Precision measure critical circuits. • AC/ DC range • 7M Ohm input impedance • 10mV to 30V ranges in 8 steps ·• Zero position • Battery Test position K • Output variable between 3 and 30V • Short circuit protection • Full 1 amp output over entire voltag e ra nge • Load switc hing • Curre_nt limit in g fu lly var iabletw1n selectabl e ra nges-dual scale meter • Separate earth terminal provided • Housed in our Delu xe "ABS" instrument case. }f. K 3210 $J,ff:oo $99 .oo 2670 $_pi1;0 $45.00 Door Minder (See SC Feb '88) lhis project will sense a door opening in a large or small room and will sound a two-tone chime. It does not have to be anywhere near the doorway as it uses an ingenious sensor to detect the pressure change caused when the . door opens. K 1915 $~o $34 .50 Get that atmosphere of tra nquility that only bi rds can give. The realism of this project is remarkable. Sounds for all the world like two trill ing canaries. • Saves the mess of birds • Battery powered • Easy to build K 1130 ~ 5 $19 .95 Automatic Charger for Ni Cads (See EA July 24V to 12V DC Converter (See SC Dec '87) This supply was designed to er.able 12V app liances like stereso. 2 Way Radi os. CB's etc. to ope rate from a 24V battery supply as used in trucks, 4WD's and boats. without ca using ex pensi ve damage to the ve hicle . battery system . •~~ K 3255 $,-c,.00 $ 49 .00 K 1650 ~ o $29 .95 Telephone Off Hook Indicator 50MHz Digital Frequency Meter (See EA May '88) Easy to build & construct this fantastic meter measures to well over 50MHz in 5 ranges. Features high input impedance, overflo_w LED indicator, KHz & MHz LED indicators. All componenets mount onto single PCB , even the selector swi tc h. Use where 2 or 3 phones are co nnectea on one line. !f one extension is in use a LED will flasti in each of the other extensions. Requires no external supply. Speech Synthesizer Here is a self contained Speech Synthesizer that does not require a computer to control it. K 2510 ~ o $89 .oo (ETI March '88) Low Cost Temperature Probe Here's an easy to build probe which adapts a multimeter or electronic voltmeter into a general purpose thermometer. It's Just the shot for measuring i heatsink temperatures, how hot it gets inside your car, or where little Johnny has a fever! Measurers accurately from 20 deg.C to =120 deg.C. K 2570 $21.95 '89) Get 100's more recharge cycles from your nicads. Its now well known that correctly charging nicad cells greatly extends their service life. Here is a fully automatic NiCad battery charger H1at ena bles differing charge rates as appropriate for AAA , AA. C. D cells or ce lls In series up to 9V. Once the battery is cha rg ed , the un it au to matical ly switches to trickle charge until ycu switch it off . It is fully fea tured, yet surprisi ngl y simple. K 9500 $~Qwf'I0 ~ ....... ,... -v K 9502 Pre-Programmed E rom for K 9500 $20.00 This small, simple circuit contai ns all the necessary components to make your favourite possessions speak. It ca n be con nected to almost any appliance, ve hic le or home remote co ntrol system to let you know when the kettle has switched off, the doors are locked or the water in the radiator is boiling. The inputs are coded and priority message reading means warnings are heard instead of greetings etc if two messages are sent at the same time. Blank Eprom included to allow you to program the messages you want. Terrific 18 Range Digital Multimeter Passive Infra-Red Lile Guard Floodlight Control s 5350 • 3. 5 Dig ital LCD • Compact Design 128x75x24mm • DC Voltage 5 Rang es: 100uV to 1000V • Input Im pedance: 1 M Ohm • DC Current 6 Ranges: 0 .1 uA to 10A • Overload Protectio n • Resistance Measurement 5 Ranges: 0.1 Ohm to 2000k Ohm Fantastic value and security for only $69.00 Was $135.00 a 1054 $~5 $32.s5 a 1057 Carry Case $12.50 Two Brilliant Multitesters From Altronics at Low Direct Import Prices Logic Tester, Frequency Counter, Capacitance and Transistor Tester Multimeter with Temperature Meter, Capacitance, Diode and Transistor Tester - ,...,. __ .•.,.•.~:""~>~ . -~Y a 1066 $W.oo $129.oo The !ite Guard deter; ts a moving person or vehic le by comparina the background temperature wit h a rapid c hange of temperature across the detection beams. So when Lite Guard detects movement across the coverage area, it wi ll tu rn on the floodlight(s) for 1- 20 minutes as pre-adjusted. Specifications: Detector: Dual element py roe lect ri c PIR sensor • Ra intight o utdoor all weather operation. • Photocell t o deactivate sensor during day li ght •Operating Voltage: 240V AC, 50Hz • Operation lime: Adjustable 1-20 minutes • Sensitivity: Adjustab:e 20' -50', 30 beams• .A. imab le des ,red direction with 2 ball joints• switch ing Capability: 500W max. incandescent o Operation Modes: Off. Auto, Test Manua l Ont. Passive Infra-Red Movement Detector Features: Lens simply 'snaps' to eith er wide angle (range 40ft.) for normal use or Normal angle (ra nge 80 ft pl us/ for c orridor appl 1cat1ors. • Snazzy integra moun ting brackets a1l ows corner 90 deg . moun ting as we ll as normal surface mount. • " Pulse count " r;ircuit to eliminate false-t riggering . • "Tamper" contact. • 12V DC Powe red . • Built-in test lamp. • Alarm output SPOT 30V 1a. a 1010 $l,K'oo $159.oo ~ This Month I a 1067 Temp. Probe $29.95 Temperature Range: -20° c to 750°C 0° F to 1400° F Accuracy: +/ - (3 " , 1 dgt) up to 150° C +/- 3% rdg over 150°C +/ ( 15° + 2 dgts) up to 225° F I ···-~ $79.oo . Logic Test (0 1070 o nl y) Logic 1 2.4V +/ - 0.2V , Logic O: 07V , / - 0.2v Frequency Range: 2kHz. 20kHz. 200khZ. 2MHz. 20MHz Input Sensitivity: 20MHz range 1v· rms . Other ranges 35mV rms . DC Voltage Range: 200mV, 2V, 20V, 200V, 1000V Accuracy: All ranges-.. ; - 0.5% rdg + 1dgt . ::'luJ~1':'le';,d~:~~e; ~~o~~~2v, 20v, 200v, 750V Input Impedance: 10M Ohm DC Curren t Range: 200uA. 2mA, 20mA, 200mA, 10A AC Cu rren t Range: 200uA, 2mA. 200mA, 10A Resistance Range: 200Ohm . 2k Ohm . 20k Ohm , 200k Ohm. 2M Ohm. 20M Oh m, 2000M Ohm Capacltanc~ Range: 2000pF. 20n F. 200nF , 2uF , 20uF Transistor hFE Base DC Current: 10uA, VCE: 2.8 +/ - 0.4V General: Di splay: 3 1/ 2 digit liq uid crysta l with maximum read ing of 1999 Ove rrange Indication : Highest d igit of ( 1) or (-1) 1s displayed "Vlatel" (now "Discovery") Sensation! Buy 3 for $180 save $50.00 High Energy Siren With Swivel Bracket Abos lutely ear splitting SPL 120dB. Handy bracket for wall mounting etc. 12V 300mA. BATTERY OPERATED PORTABLE P.I.R. INTRUSION ALARM Ward off thieves and intriJders at home and w hen travelling. This super handy, go anywhere P.I.R. alarm system is great for shop, office, caravan, boat, garage and whenever you are trave lling. 5177 $29.95 S Extremely eHy to /n1ta//. UNBELIEVABLE VALUE! (AROUND $250) FROM $30 Micro Piezo Siren Altronics has recentl y purchased th is quali ty siock au ctio ned by the liquid ator · of DT X Australi a LTD . Massive 11 0dB operated from 6-12V DC 150mA. You can use thi s equipment to gain limited s 5170 $24.95 access to th e "Viatel" ., information system . Each ,. unit co ntai ns a Teleco m approved m odem an d in formation decoding ci rc uits. The single PCB is a g oldm ine of q uality components for the enthusiast, incl uding the fa ntastic va luable SAA 50~0 and SAA 5050 chips. ALL STOCK BRAND NEW ~:=~~~~~~~~~~;.t7i~'W Sorry no warranty at this price. ~~:i~! 300ma • Line isolation Transformer• Teleco m approved 600/ 600 Ohm o r 600/ 150 Ohm impedance• Video/RF Modulator (Channel 0) • Low profile 12V SA SPOT Relay • Capacitor - 2.0uF 1 440V AC • Crystals • 6MHz and 4.43MHz • TTL, CMOS, Liniar and LSI ICs • SAA 5020, SAA 5050, 2516 and many more• Voltage regulators• Bridge rectif iers • Tri mpots and ca pacito rs • Filter capacitors • Flatpeck heatsink 1 Plus much , much more! VIATEL VIDEOTEX MODEM DECODER Three models to ch oose fro m; Each with a numeric keypad. X 1000 with RF output $jr.fs $25 $29 $29 X 1002 with RF o/ p & telephone hendHt $ ~ X 1004 with RF and RGB Yleleo oi p $ ~ r/ FEATURES: • Exit delay • Entry delay • Large coverage - up to 100 square metres • Low battery LED indicator• 9V A lkaline battery (not suppl ied) lasts many months. S5305"8"$49 SUPER GUARD HOUSEHOLD ALARM SYSTEM • Easy to operate Simplicity • itself - just select the switch '"' to Home, Off or Away as .,,. desired. A 45 second exiVentry delay allows you to vacate end/or re-renter your premises and disarm the system. • No key switches or code buttons to push. Thus the system is ideal for fami.l ies even the kids can operate this system. • Facility for external siren.• Battery backup (battery 8 'C' cells not included) Syatem Contenta: • Master Control unit • Front Door Bell Switch • Panic/Emergency Switch • Three Window/Door Reed Switches • Mounting Hardware • 20 Metres Wire • ln!ltt uction Manual. , Complete Sy1tem S 5'15 only SJ,N' now $85 1 Why Pay A Commercial Security Firm A Fortune To Wire Your House Or Office. This Fantastic System Installs In An Hour Or Two And Uses No Wires Hurry-Stocks Limited At This Price! Specials This Month Only Features: • Wireless reception of external or internal sensors or detectors. • Seleciable home or away modes for selecting internal and external arming or just external to allow movement inside the building. • Buil t in Piezo electric siren gives different signals to indicate different fu nctions. • Sends signal down power line to activate one or more remote sirens. • Programmable arm/disarm switch buttons. The main co ntrol receiver runs on 240V AC with a 12V 1.2AH battery for emergency backup. All other units with the excepion of the line carrier, run on a 9V battery each . The average life expectancy is approximately one year. System works around 305MHz frequency where there is less chance of false alarm . The range of the unit is normally 80 metres in open space. Main Control Receiver Take It With You If You Move Passive Infra Red Movement Detector Ideal for the loungeroom, fami ly room or hallways. Mounts up on the wall or on top of bookshelves etc. Detects movement w ithin area of 9M by 9M. s 52ao $J,291>o $89.oo Hand Held Control Transmitter Unit Keep it at the bedside ta bl e - allow s you to arm the ho use pe rimeters when you retire or yo u ca n ta ke it with you when you go o ut, arm ing your system after you lock the door. s 5275 SS81io $45.oo Remote Piezo Alarm This unit is an optiona l line carrier receive~. Receives signa l thro ug h 'AC' line i.e. it wou ld ideall y be located in, say, the roof space an d plugged into ma ins power. s 5290 $~o $89.oo s 5265 $ ~ $289.oo Complete System Special Package Price One S 5265 One S 5270 One s 5280 One S 5285 Main Controller Reed Switch S Passive 1/R Detector Wall Control Unit Accessories •c:,_,..; 5260 $_,c,:,.00 $489 .00 Detector/ Transmitter Unit (Reed Switch) Suitable for Windows and Doors This consists of an enclosed reed switch and compact UHF tra nsm itter and a removable enclosed magnet is mounted on the door or window frame with the magnet on the movi ng door or window. s 5210 $~o $45.oo MORE ALTRONICS DEALERS WANTED If you have a Retail Shop, you could increase your Income significantly by becoming an Altronics Dealer. Phone Brian Sorensen (09) 328 2199 for Details. 174 Roe St. Pe rth W.A. 6000 PHONE TOLL FREE 008 999 007 Perth Metro (09) 328 1599 ALL MAIL O~DERS Altronlc s Mall Order P.O . Box 8350 Perth Stirl ing Street W.A. 6849 STANDARD DELIVERY & PACKING CHARGE $5 .50 to 1Kg, $8 1Kg -SKg AUSTRALI A WIDE - We process you r order th·e day rece ived and despatch via. Australi a Post. A llow approx 9 days from day you post o rder to when you receive 0 ~i tJN1GHT JETSERVICE Up to 3Kg $10.00. 3Kg to 5Kg is $28 .00 - We pro cess yo ur orde r the day received and despatch via. Overnight Jets~rvlce IS Cou rier for delivery next day Cou ntry areas please allow add itional 24-48 hours. HEAVY HEAVY SERVICE - All orders of 10Kgs or more must travel E<press Road - Please allow 7 days tor delivery. $12.00 to 10Kgs. $15.00 over 10Kgs. INSU RAN CE - As with virtually every other Australian supplier. we send goods at con signees risk . Should you require comprehensive insurance cover against loss or damage please add $1.00 per $100 of o rder value (minimum charge $1 ). When ph o ne orderi ng please request .. Insurance". TOLL FREE PHONE ORDER - Bankca rd, Visa, Mastercard Holders can phone o rd er to li free up to 6pm Eastern Standa rd Time. Remember with our Overnight Jetaervlce we deliver next day. WA COUNTRY Altronics Resellers Chances are there is an Altronic Resel ler right near you - check thi s list o~ phone us for details of the nearest dea ler. Blue Ribbon Dealers are highlighted w ith a ■ These dealers generall y carry a comprehensive range of Altron1c products and kits or w ill o rde r any required item for you . 1 Don't forget our Expreea Mall and Phone Order Service - f or the co at of a local call, Bankcard, Visa or Mastercard holder1 can Phone Order fo r same day deopatch. Plea1e Note: Rese1lers have to ;:,ay the cost of freight and insurance and therefore the prices charged by individual dealers may vary s! igntly from this Catalogue - in many cases. however. Dealer prices will sti ll represent a significant cost saving from prices charged by Altronics Competitors. Blue Ribbon Dealers are highlighted with a ■ These Dealers generally carry a comprehensive range of Altronlc products and kits or wi ll order any req ui red item for you. ALBANY BP Electronics ■ (098) 412661 Micro Electronics (098) 412077 BUNBURY Micro Electronics (097) 216222 ES PERAN CE Esperance Communi cat io ns (090) 713344 GERALDTON Batavia Lighting & Electronics (099) 21 1278 KALGOORLIE Todays Electronics ■ (090) 215212 MAN DURAH M icro El ectronics (09) 581 2206 PORT HEDLAND Iva n T omek El ectronics (091) 732531 ROCK INGHAM TV Joe's (09) 5271806 NT ALICE SPRINGS Fa rmer Elec tro nics (089) 522388 DARWIN Ventroni cs (089) 853 622 ACT CITY CANBERRA Bennett Comm. Electronics (062) 805359 VICTORIA CITY All Elec tronic Componen t s (03) 6623506 T he Electron ic Compone nt Shop ■ (03) 6706474 SUBURBAN BORONIA Ray Cross Electron i cs ■ (OJ) 7622422 CHELTENHAM Talking Electronics (03) 5842386 CRO YDO N Trus cott Elect ro n ics ■ (03) 7233860 MOORABBIN Ta lking Electronics Shop (03) 5320236 PRESTON Preston Electronics ■ (03) 4840191 COUNTRY BAIRN SD AL E LH & LM Crawfo rd (051) 525677 BALLARAT Balla r at Electronics (053) 311947 BENDIGO KC Jonnson ■ (054) 411411 MILDURA McWilliam Electron ics (050) 236410 WA RRNAM BOOL Koroi t El ectronics (055) 627417 QUEENSLAND CITY Detsound PL ■ (07) 8396155 SUBURBAN CAPALABA Kingsway Electronics (07) 3902399 NEWSTE AD ECQ Electron ics (07) 2541153 WEST END B.A.S . Audiotronics (07) 8447566 WOODRIDGE Oavid Hall Electronics ■ (07) 8082777 COUNTRY BUNDABE RG Bob Elk in s Electronics (071) 721785 GLADSTONE Supertronics (0 79) 724459 MACKAY Philtronics ■ (079) 578855 MAROOCHYDORE MALS Electronics ■ (071) 43611 9 MARYBOROUGH Keller Electronics (071) 214559 PIALBA Keller Electronics (071) 283749 ROCKHAMPTON Access Electronics (East St.) (079) 221058 TOWN SVILLE Super Solex ■ (077) 724466 SA CITY Force E lectronics ■ (08) 2125505 SUBURBAN BRIGHTON Force Electronics ■ (08) 3770512 CHRISTI ES BEACH Force E l ectron ics ■ (08) 3823366 ENFIELD Force Electronics ■ (08 ) 3496340 FINDON Force Electronics ■ (08) 3471188 LONSDALE Force Electronics ■ (08) 3260901 COUNTRY MT.GAMBIER South East Electronics (087) 250034 WHYALLA Eyre Electronics (086) 454764 TASMANIA HOBART George Harvey ■ (002) 342233 LAUN CESTON George H arvey ■ (003) 316533 NSW CITY Oavid Reid E l ectronics ■ (02) 2671385 SUBURBAN CABRAMATTA M & L Electronics (02) 727443 1 CITY SO UTH Sheridan El ectro nics (02) 2817727 SMI T HFIELD C hantronics (02) 6044595 COUNTRY COFFS HARBOUR Cotfs Habour Electronics (066) 52568 4 GRAFTON East Coast Electroni cs ' (066) 431250 NEWCASTLE Novocastr ian Elect.Suppl ies (049) 62 1358 RAYMOND TERRACE Al back Electron ics (049) 8734 19 WAGGA WAGGA PHILL IPS Electroni cs (069) 216558 WARNER$ BAY Vi lec D istributors (049) 489405 WINDSOR M & E Elect. and Communications (045) 775935 WOLLONGONG Newtek Electronics ■ 042 27 1620 Vimcom Electronics (042) 284400 . SERVICEMAN'S LOG The case of the worn video heads I doubt if anyone will deny that a serviceman has to be a good detective - not in the mould of the popular fictional detectives, but a detective nevertheless, who must observe clues, probe history and find a solution to what is sometimes a very obscure problem. Just how much detective work is sometimes involved was brought home to me quite forcibly by a recent experience. More than that, it emphasised that the vital clue is often way outside one's normal line of technical thinking. The story really started about 8 years ago; and that, in itself, gives some idea of the complexity of the problem. It involved one of my long standing customers who, at that time, purchased a National NV-370 video recorder from my dealer colleague. And I hasten to add, the NV-3 70 was and still is a highly regarded machine. Many are still working with little or no service after many years of hard work. I knew little about this transaction at the time, or of the subsequent events, because I was not a National service agent until a couple of years . later. But I was able to piece the story together eventually. Faulty heads When the recorder was sold it carried a 3-year guarantee. So, when it gave trouble after about 18 months, the owner took it back to the dealer, who returned it to the National service department. The fault was diagnosed as faulty video heads and these were replaced, no charge. Some time after this, I acquired the National service centre classification. So, when the machine failed again, it landed on my bench. And it was only then that I learned of the events I have just related. A little more than another 18 months had elapsed by 26 SILICON CHIP then , so it was no longer under warranty. And again, it was video head trouble. As it came to me, the suggestion was that they needed cleaning, and there certainly was a substantial build-up of tape oxide and other foreign matter. But it quickly became clear that there was more to the problem than that. In fact, the heads had had it. I advised the owner, via my dealer colleague, and quoted for a new set of heads. Naturally, they weren't very TETIA TV TIP Hitachi CTP-229 (NP8CA Chassis) Symptom: excessive brightness and not enough control to bring it down. A "sort of" picture could be obtained by reducing the screen voltage but this revealed heavy shading on the left hand side of the screen. Cure: C719, a 4.7µF 250V electro, open circuit. This capacitor is a bypass on the 180V rail feeding the video output transistors. This fault is rather like a screen-voltage problem but the clue is that with this one there are no retrace lines visible. TETIA TV Tip is supplied by the Tasmanian branch of The Electronic Technicians' Institute of Australia. Contact Jim Lawler, 16 Adina St, Geilston Bay, Tasmania 7015. happy about this, even though they had not paid for the first job. Anyway, they eventually decided to go ahead and the job was duly done. That was OK as far as it went but I was puzzled as to why two sets of h eads had failed in such a short time. The first set, yes. Such premature failure is rare but it does happen. But the second could hardly be described as coincidence. It suggested that there was something peculiar to the machine's environment or manner of use which was responsible. But what? The question of tape quality had already been investigated - on both occasions - and all the tapes used had been well known and reliable brands. So that ruled that out. I had been to the customer's home on other service matters several years previously and my impression was one of a normal, neat and tidy, well kept house. Dirt road The only suspicious aspect was the house's location. It was on the outskirts of the suburb, alongside an unsealed road. And there was a fair amount of traffic on the road , some of it quite heavy in the form of trucks on their way to the local tip. I imagine that they would have been kept quite busy coping with the dust , particularly in dry weather. So was that it? Perhaps, but how could one be sure? And, unless I could be sure, I would have hesitated to - in effect - accuse them of not doing an adequate job of house cleaning. (It takes a brave man to do that). So that was as far as my thoughts went at that stage. Another two years went by, and then the machine was back on my bench again. And again it was the video heads. But there was more this time. The sound head and the control track head were also faulty and there was some damage to the cabinet. I gained the impression that · the ma- 1 ~~ '-J~ ~ t:i ~-- s:-.~~ ,..._ & ·-r,.u~:Rc;. ~rAINL.. '-( 0 "1/ w,qs A SUBS,-AN1"'1Al- °BUIL--D·UP OF TA'P~ OX1De &. 011H~R FO~c-f6N MA1fc-R 0 .. chine had had a pretty hard life. In fact, the customer readily agreed that it was worked pretty hard. "I reckon it would be used for at least three hours every day", he said. That adds up to a lot of.hours over two years . Nevertheless, I was still at a loss to explain this latest failure . More to the point was what to do about it. Video heads were still quite expensive and, with the sound and control heads , plus some replacement bits for the cabinet, I toted up an estimate of around $350. It was too much, of course. They wouldn't buy it and I couldn't blame them. Far better to cut their losses and put that amount of money towards a new, more modern machine. And that's exactly what they did. They went off to my dealer colleague and settled for a National Panasonic NV-G30 (significantly, they did not appear to hold any grudge against this brand). The NV-G30 is, in many respects , an updated version of the NV-370. It uses the same mechanical deck but is a more compact design and features the more modern infrared remote control system. (The NV-370 used a cord type "remote" control). And would you believe if:' - the NV-G30 was back on my bench within 18 months with faulty video heads. Strangely, the customers did not seem unduly perturbed; mainly, I imagine because the machine was still under warranty and it would cost them nothing. I also gained the impression that they now accepted that this was the norm for video recorders. A possible clue Privately, 1 was still at a complete loss to understand what was happening. But there is a severe limit to the amount of time and effort one can devote to any investigation. For the most part, one is limited to whatever information comes to hand; it is just not practical to go out and look for it. And so that's where matters rested until, quite by chance, another piece of information came to hand. In fact, two things happened almost simultaneously. First, the NVG30 came back again, exactly 19 months after I had fitted the new set of heads, and it was the same story; these heads had now failed. Shock is hardly an adequate word to describe m y feelings. For one thing I would have to confront the customer with this disturbing news and I wasn't looking forward to that. But there was also the feeling of utter frustration, knowing that there was something wrong but not knowing how to go about finding it. Th,m, even before I had passed on the bad news, the second thing happened. Another customer brought in a National NV-450, with the suggestion that the heads probably needed cleaning. This proved to be something of an understatement; it was extremely dirty. Most of the fouling was tape oxide but there' was also some suggestion of a gritty substance mixed with it which, initially, I was unable to identify. I gave the machine a thorough clean, then ran a test tape through it. It brought up a picture OK but the quality was a bit suspect; acceptable if you weren't too fussy but obviously down on new performance. Then I tried making a recording and the result here left no doubt ; it was grotty in the extreme. I decided to return the machine to the customer with a recommendation that it needed a new set of heads for any serious recording. It was then that I made the discovery. For some reason - which escapes me now - I put my fingers through the front opening into the cassette carrier area and, specifically, onto the bottom plate of the cassette carrier. And when I withdrew my fingers they were black. I rubbed my fingers over the plate again and produced more black. What was it? It wasn't tape oxide, nor did it seem to be normal house dust or fluff. I fished out the jeweller's loupe and, after some searching, found another more accessible deposit. It was on a plastic insulating strip near the power supply, covering some mains termi_nals. Getting in close with the glass - and feeling a bit like Sherlock - I studied the muck carefully. There was some house dust but this wasn't the main component. What caught my eye was a fine grey powder, almost as fine as talcum powder. Ashes to ashes What was it? It took me a while to wake up ; then it hit me out of the blue. It was some kind of ash , probably wood ash from a wood-burning room heating stove. But why were my fingers black, if the muck was grey? I suspected that, in wiping the muck MARCH 1991 27 the cause of the premature head failure, she volunteered the information that the video recorder normally sat beside the stove. So that was it; the problem was solved at last. Solved, that is, in that we now knew the cause. What to do about it was another matter and large! y in the hands of the owner. All I could do was advise. And the best advice I could offer apart from scrapping the stove - was to move the recorder as far away from it as possible and make up some kind of cover to put over the recorder when it was not in use. I also risked suggesting more frequent use of the vacuum cleaner around the general area during the winter months. The lady accepted the suggestion quite gracefully. And so a valuable lesson was learned, but learned the hard way. From now on, the first suggestion of premature head wear will send me snooping for fuel stoves of any kind . Maybe they are not all bad but one cannot be too careful. SERVICEMAN'S LOG - CTD ) ~Vi ~,, /..... ! ~I ,, The early days - -- • . ..:9a.off the carrier plate, I had concentrated it and made it look mu ch darker. Anyway, I was convinced it was wood ash . And I was almost right. When the customer came in to collect the machine, I asked him straight out if he had a wood burning stove. "We do have a stove but we don 't burn wood in it. It 's a slow combus.tion stove which burns coke. Why do yo u ask'?" I told him. And while I was explaining it all, my mind went back to the slow combustion coke stoves I had known many years ago . And as one who for a time had to clean up after them, I rated them as one of the messiest devices ever created. Perhaps that's an exaggeration but I'm convinced that they are totally incompatibl e with anything like a video recorder. So what abo ut the NV-G30 and th e 'NV-370 before it;·was this the answer 28 SILICON CHIP . here also? Now that I had been alerted, my mind went back to the visits I had made to the customer's home many years previously. And the more I thought about it, the more I was convinced that I had seen some form of room heating stove. And if I had seen it, it was most probably in the lounge room, along with the TV set, because that was where I would have been. The case cracked Of course, I had to contact. the customer eventually. The lady of the hous e answered the phone and accepted the bad n ews philosophically; I suspect she was getting used to the idea and half expected it anyway. Then I posed the question , did they have a fuel stove anywhere in the house? The answer was yes. They had a wood-burning room heating stove in the lounge room. And when I explained that I believed that this was Naturally, I have already passed this story on to several colleagues. And that prompted an interesting recollection from one of them. It goes back some 25 years, to the time when video recorders, even at top professional level, were a rarity and a very expensive one at that. After many abortive attempts to solve the problem of providing adequate tape-to-head speed - usually by the brute force method - it was Ampex who cracked the problem with a (literally) lateral approach . The result was their quadrature head system, with four heads, 90° apart, travelling at right angles across a 50mm wide tap e. I remember this well because I was privileged to see a demonstration of the first one in Australia, at Channel 7 in Sydney. This was while the local engineers and the Ampex representative were fussing around preparing the machine for its on-air debut in couple of days time (which was a complete success, incidentally). While musing thus, I realised that it now comes as a shock to think that there was a time when there was no such thing as a video recorder. Now they are nearly as popular as TV sets . We've sure come a long way. But enough of such nostalgia; let's get on with my mate 's story. He had a business in one of our country areas at the time, and was friendly with the chief engineer at the local TV station. An d this was one of the first, if not th e first, country station to invest in one of those Ampex recorders. The price tag, incidently, was well into the 6-figure mark! Special room Acting on Ampex's advice, a special room had been prepared for the machine, fully air-conditioned to contro l temperature, humidity and, particularly, dust. It had also been very well sound-proofed. So the machine was duly installed and performed right up to expectations - or at least it did initially. Then, after about 12 months of use, trouble occurred and was traced to worn heads . Nobody was very happy about this because they had been led to expect much longer life, in terms of actual playing hours. However, they shrugged their shoulders and arranged to have a new set of heads fitted. And this ran into a 5-figure sum. Anyway, the new heads were fitted and all went well fo r about another 12 months . Then the heads failed again . There was no shoulder shrugging this time; the panic button was pressed and it was all hands and the cook - plus Ampex - lined up to solve the problem. Well, it took some detective work in this case also. On the face of it, it appeared to be the perfect environment , so what had gone wrong? It turned out to be part of the soundproofing, at least indirectly. The room had been lined with acoustic tiles ; squares of Canite, or similar material, with a pattern of small holes drilled through them. The holes were supposed improve the sound absorption properties; ie, reduce reflection. In particular, these tiles had been used as the ceiling. Then, above them, for both thermal and acoustic insulation, had been laid rockwool bats. Now, as anyone who has ever handled this stuff without gloves will testify, it is h ighly abrasive. And tiny particles had been working their way through the holes in the tiles and, while not large enough to be noticeable, had found their way into the TRIM machine and played havoc with the heads. So that solved that problem. But it was a very expensive exercise, particularly by the money values of those days. Indeed, it might make the cost of domestic repairs seem trivial - until you realise that a couple of hundred dollars is still a lot of money for Bill Bloggs. Another video recorder To finish off, here is another sad tale about a video recorder. This was a Fisher FVH-P520; a model which is now some 8 or 9 years old. Truth to tell, there are not many Fisher machines about; I would probably handle about one a year. The original Fisher was made by Sanyo, in Beta format. Since this machine turned out to be in VHS format, I'm not sure whether it was actually made by Sanyo or simply marketed by them. But, as it all turned out, this was of little consequence. It was brought in by a lady, a new customer, with the complaint that it produced sound but no picture. Initially, I suspected fouled heads but I did notice one thing as I took deliv- E-1 LAMINATED POWER TRANSFORMERS PCB mount ex-stock in sizes from 2.5V A to 25VA with secondary voltages from 2 x 6V to 2 x 20V. Triple output models also available for logic circuits. Chassis mount manufactured to order in sizes from 2 .5VA to 1 KVA in E-1 and C core. PCB MOUNT STOCK RANGE CHASSIS MOUNT TO ORDER OUT ~~ '"SUl/\l lm; OUTER W H1;0: .. G - We are the largest ex-stock supplier of toroidal power transformers in Australia. Our standard range consists of the U.K . manufactured ANTR IM range in 10 VA sizes from 15VA to 625VA. All have a single 240V pr imary and dual secondary windings ranging from 2 x 6V to 2 x 55V. Our local manufacturing facilities supplement this range by manufacturing specials to order. Models are available from stock to suit most project kits. Comprehensive data sheets are ava ilable on request. Enquiries from resellers and _manufacturers are welcomed . Prices are extremely competit ive and generous trade discounts apply for quantity. 90 George St.. HORNSBY NSW MARCH 1991 29 spikes sh ould h ave ripp ed my tap e to pieces , even severed it. Yet neith er visibly or by playing it on anoth er mach ine, could I find any sign of damage. That's a mystery for whi ch I have no answer. I rang the lady and broke th e bad news. And to cover myself, I asked h er to come in and see the damage fo r h erself. When she did , I showed h er what I had found and pulled the covers off a good machine to indicate what it sh ou ld be like. She accepted my explanation readily enough. How di d it h appen? Had it been to another serviceman? No, sh e was quite adamant on that point. Her story was that they had acquired the mach in e by some kind of swap deal. It h ad worked w hen they took delivery, and for several weeks after. Then, suddenly, "it didn't go". That was all she knew. It could have been h er husband but sh e was more inclined to blame the teenagers of th e household. At least that was her story. So there it was - an otherwise good machine which will now finish up on the tip. What a waste. Here's hoping I have S()!l18 brighter stories next month . SC SERVICEMAN'S LOG - CTD . ery. This is a top loading model and one of the screws in the cassette carrier cover was missing. The alarm bells may have tinkl ed a little then but they didn 't actually ring. Later, I set it up and pushed in an odd tape I use for testing. The lady was right; not a sign of a picture, though sound was normal and seemed to be at the right pitch. I extracted th e tap e, removed the cassette carrier cover, then the main top cover, and fin ally the steel screen over the head drum (another screw missing). And what a mess I found. No, it wasn 't foul ed heads or anything like that; someone had been there before me. And if anyone qualified for a striped apron award , it was him. Whether it had been another serviceman, or just some do-it-yourself type, I had no way of knowing , but I certainly hop ed it wasn't a "professional". The two screws which secure the head drum to the main assembly were missing , the terminal board in the centre of the h ead was broken, and some of the leads to it w ere broken. But the best - or worst - was yet to come. Th e "someon e" had tri ed to remove the drum . An d, lacking both the skill and tools to do the job, h e had tried to prise it off with a screwdriver. The most obvious result was severe damage to both th e rotating drum and the matching lower drum . In fact , there were several n icks in th e edges of both drums which had left small sharp raised spikes. Nor was that all. I spun the drum and it w obbled around like a drunken sail or w ith one short leg. The shaft was bent. A total w rite-off So that was it; a total write-off. A repair would have required replacem ent of the head drum, the low er drum , and the motor assembly. An d a typi cal price tag w ould be around $500 ; a ridiculous situati on, particularly for a machine that ol d. One thing puzzled me. Those sharp TV TEST EQUIPMENT THAT WILL EARN YOU MORE MONEY MARCH SPECIALS FROM RAYTEC MOTHERBOARDS 12MHz 31MHz 12MHz 16MHz 8088 8088 80286 80286 Neat 16MHz 80386 II CASES Baby AT 200 W P/S Mini Tower 200W P/S Maxi Tower 200W P/S $109.00 $189.00 $299.00 $449.00 $899.00 (AUSTRALIAN MADE) 12 Months Warrantv SHORTED TURNS TESTER $249.00 $299.00 $399.00 Bu1lt·1n Meter to check EHT transformers inclu ding split diode type, yokes and drive transform ers. KEYBOARDS $78.00 + $3.00 p&p HI-VOLTAGE PROBE 101 Enhanced Keyboard $ 89.00 GRAPHICS CARDS VGA VGA II 256K 16Bit $225.00 512K 16Bit $299.00 I POWER SUPPLIES XT 150 Wan AT 200Wan $ 99.00 $149.00 I I . 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The ranges are from Oto 5kV Negative and from 0 to 10kV Positive. Double insulated fo r safety. MOUSE Mouse for PC XT/AT Built-in meter reads positive or negative 050kV. For checking EHT and focu s as well as any oth er Hi•tension voltages. DEGAUSSING WAND 7,700 apere turns. Strong magnetic fiel d, larger than usual coil with multicore centre. Double insulated for safety with momentary on/off switch. 240V NC 2.2 amps. This one is just about as important as ha ving a soldering iron in your toolbox! _ . _ . .- ,·-.·· . REMOTE CONTROL TESTER ~ . (INFARED OR ULTRASONIC) t,·.~---. ,_.._,-~_._,".'».:~__· ~ I _ ~ $85.00 + $4.00 p&p TUNER REPAIRS . Designed to test any ln fared or Ultrasonic control units. With the extension lead you can also test infared units which cannot be placed in fro nt of the testing unit. Requires a 9V battery . Output is via the LED diode and piezo speaker. trom only s11.oo + p&p . Cheque Money Order we also repa1r most tuners on an exchange basis. 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Model 450 offers all the capabilities of the 420 but with an extended bandwidth of 50MHz and ETS to 5ns/div (x1 Omag). Just check the basic spec alongside and call us to arrange a demonstration. GOULD Basic Model 400 Specifications Vertical Deflection Bandwidth : de to 20MHz (-3dB) Sensitivty: 2mV/div to 5Vldiv in 1-2-5 sequence Horizontal Deflection Transient Capture Sweep Rate: 500ns/div to 50s/div. 28 ranges in 1-2-5 sequence Repetitive Sampling Sweep Rate: 200, 100ns/div Delayed Sweep Range: 20ns to 5000s Display Modes: Refreshed, Roll, Interpolation, Single trace, Dual trace, Single Shot, Hold All, Hold Ch1, Hold Ch2, Hold Ref. Acquisition System Max Sample Rate: 100MSamples/s on each channel Vertical Resolution: 8 bits Record Length: 500 words/channel Acquisition Modes: Normal, X-Y, Average, Peak Detection Waveform Memories: 3 non-volatile Screen Measurements Cursors can be assigned to a trace and measurements made with respect to the datums .>1 Tand .>1 Vdisplayed on screen Trigger level indicated on screen Readout indicates instrument settings Arrow for off-screen indication Interface (RS423) Baud Rate: 75 to 9600baud Data Bits: 8 (no parity) Digital Plotter Output: HGPL format via RS423 interface • Gould 400 Series prices are from $3995 ex tax, subject to change without notice ELMEASCO Instruments Ply.Ltd. EW SOUTH WALES 18 Hilly Street, MORTLAKE P.O. Box 30, CONCORD NSW 2137 Tel: (02) 736 2888 Telex: M25887 Fax: (02) 736 3005 VICTORIA 12 Maroondah Highway, RINGWOOD P.O. Box 623 , RINGWOOD VIC 3 134 Tel: (03) 879 2322 Telex: M30418 Fax: (03) 870 8972 QUEENSLAND 192 Evans Road, SALISBURY P.O. Box 274 SALISBURY QLD 4 107 Tel: (07) 875 1444 Fax: (07) 277 37 53 SOUTH AUSTRJ LIA 241 Churchill Road, PROSPECT P.O. Box 154 PROSPECT SA 5082 Tel: (08) 344 9000 Telex: M87519 Fax: (08) 269 641 I W. AUSTRALIA 32 Teddington Road, VICTORIA PARK, W,A, 6 100 Tel: (09) 470 I 855 Fax: (09) 470 3 173 Measure & Beta This simple Beta Tester will test & measure the gain of most bipolar transistors. You simply connect the transistor, press the test button, rotate the knob until the LED lights, and read the gain from the calibrated dial scale. By JOHN CLARKE One of the more popular projects described in SILICON CHIP was the Beta Tester published in the February 1989 issue. It was a simple low-cost unit that worked very well but it did have one drawback - it could not reliably check transistors with a low beta (typically less than 50). Recently, in response to reader queries, we decided to take another look at the circuit to see if this problem coul d be solved. In fact, the solution was quite simple - all we had to do was alter the biasing arrangement around the test transistor and change a few component values. The result is the Beta Tester Mk.2. Th is version can test transistors with a beta as low as 5 which is a big improvement on the original design , especially when it comes to testing low-gain power transistors. 32 SILICON CHIP To make the unit easy to build and to avoid possible confusion, we've re-designed the PC board to accommodate the circuit changes for the Mk.2 version. This board fits into the same case as before so that, outwardly, the appearance of the instrument is unchanged. Of course, if you already have the original version, there's no reason why you can't make the necessary changes to the circuit. All you have to do is remove a few existing components and patch the new values into position on the PC board. Why check transistor beta? Nobody likes putting a dud transistor into circuit - it can cause hours of frustration. A beta tester can quickly indicate whether a transistor is good or bad (although it won't identify leaky transistors), and can thus elimi- nate a potential source of trouble. It's also useful for troubleshooting, as you can quickly remove and check any suspect transistors in a faulty circuit. Apart from providing GO/NO-GO indication, a beta tester is also useful if you want to select a transistor for a critical circuit. Some circuits will operate better with transistors that have a minimum gain figure or may require matched gain transistors for optimum performance (eg, audio amplifiers). With the Beta Tester, selecting transistors for gain is a snack. Finally, you can use the Beta Tester to identify the leads of unknown transistors and for checking whether it is a PNP or NPN device. The way in which you go about this is set out in an accompanying panel. So there are quite a few good reasons for building this handy gadget. Once you do, you'll wonder how you ever managed without it. Long battery life The Beta Tester is battery powered so that it can be used anywhere and has just three simple controls. First, there is a momentary contact pushbutton switch which applies power to the circuit while you do the test. This means that the circuit cannot flatten the battery because you've forgotten to turn it off and so the battery should last a long time. In -addition, there is a slide switch to select between NPN and PNP transistors and a knob with a scale graduated from 5-500 to provide a direct readout of beta. The circuitry is all housed in a small plastic case measuring 130 x 68 x 43mm. By the way, the Beta Tester uses an AC signal to check the test transistor's gain; it is not just a simple DC match transistors with the TesterMk.2 gain test. The frequency of operation is about 3.3kHz. Circuit operation Refer now to Fig.1 which shows the circuit details. There's nothing fancy here; just one 555 timer IC, three low-cost transistors and a few minor parts. Fig.1 can be broken down into four sections: an oscillator (IC1), an amplifier (based on the test transistor), a detector stage (Ql, D3 & D4), and a comparator (Ql, D4 & QZ). The oscillator stage is based on a 555 timer (IC1) which is wired in a somewhat unconventional manner. Normally, the free running configuration uses a timing capacitor which is charged via a resistor from the positive supply rail. In this circuit though, the timing capacitor (.OOZZµF) is alternately charged and discharged by the pin 3 output via a 68kQ resistor. The circuit works like this: at switch-on, pin 3 of IC1 goes high and charges the .OOZZµF capacitor via the 68kQ resistor. Then, when the capacitor voltage reaches 2/3Vcc (ie, 2/3 the supply rail voltage), pin 3 switches low and the capacitor discharges via the 68kQ resistor until it reaches 1/3Vcc. At this point, pin 3 switches high again and so the cycle is i:epeated indefinitely while ever power is applied. The resulting output from IC1 is taken from pin 3 and is a 3.3kHz square wave with an amplitude of close to 9V peak to peak (p-p). This signal is then clipped by diodes D1 & DZ to give a waveform with an amplitude of 1.4V p-p and AC-coupled via a O. lµF capacitor to the following amplifier stage. This stage uses the transistor under test (TUT) in a corn- ... 0.22 16VW+ U• man eniitter amplifier configuration. l To explain, a common emitter amplifier is one in which the transistor's emitter is common to both the input and output of the amplifier. In its most simple form, the emitter is connected to ground which may be : either the positive or negative rail of the circuit. The input signal is then applied between the base terminal and ground, while the output signal appears between the collector and ground. NPN/PNP transistors In this circuit, if the test transistor · is an NPN type, its emitter is connected to OV and the collector to the +9V rail via a 5.lkQ resistor. DC bias is prov~ded by the 75kQ and 27kQ . resistors, which are connected to the +9V and OV rails respectively via SZa & SZb. These set the bias to about ' T "l NPN 5.1k .,. 1'/o 9V : C B IC1 555 .., D2 TUT ..I.. D3 1N4148 ~r .,. .,. .,. B NPN .0022+ .,. EOc VIEf/fot.l'oM .,. ~- 1 TRANSISTOR BETA TESTER Fig.t: the circuit uses 3.3kHz oscillator ICt to pulse the base of the test transistor (TUT). This signal is then amplified by the TUT & fed to class-B detector stage Qt, D3 & Q2. When the output from the TUT exceeds 1.8V, Qt, Q2 & Q3 conduct & the LED lights. MARCH 1991 33 All the parts, including the two switches, are mounted on a small PC board. Make sure that the parts are installed so that they do not protrude above the mounting surface of the slider switch. Three PC stakes are used to anchor the pot lugs. 2.4V in the NPN mode to ensure that the transistor operates over its linear region. NPN/PNP selection If the test transistor is a PNP type, slide switch SZ swaps the base and emitter connections, so that the emitter now goes to the +9V rail and the collector goes to ground via the 5.1H2 resistor. SZ also swaps the bias resistors around, so that the base of th e TUT is now biased to 6.6V. This switching arrangement ensures correct bias for both NPN and PNP test transistors. In either case, the 3.3kHz oscillator signal is fed to the base of the TUT via a Z0kQ resistor and series ZMQ potentiometer (VR1). VR1 allows the base current into the TUT to be varied from a minimum of 700nA to a maximum of 70µA. As we shall see, these two figures correspond to beta ISC041 3 1 readings of 500 and 5 respectively. In greater detail, when we plug in a test transistor, the resulting collector current will simply be the base current multiplied by the beta. So, if the transistor has a beta of 500 and the base current is 700nA, the corresponding collector current will be 350µA. Similarly, if the a transistor has a beta of 5 and the base current is 70µA, the collector current will again be 350µA. What if the transistor has a beta of 100? We can again obtain a collector current of 350µA by setting VR1 to give a bas e current of 3.5µA. It follows that the voltage developed across the 5.1kQ collector load resistor will be about 1.8V when 350µA flows through it. Thus, if we have a detector that lights a LED at this 1.8V threshold , the beta of any test transistor can be read off a calibrated scale fitted to VR1 's control knob (provided of course that the beta lies bewteen 5 & 500). Q1, D3 and D4 make up the signal detector stage and this is driven by the TUT via a 0.1µF capacitor. Q1 acts as a class-B detector. It has no DC bias on its base and conducts for positive swings only of the 3.3kHz signal. The negative swings are clipped by D3, to protect the base of Q1. Thus, Q1 acts as an emitter follower for positive swings of the 3.3kHz signal but does not conduct at all for the n egative swings. This is .................. c,A \ 'wi_ __ 9V BATTERY Fig.2 (left): mount the LED so that the top of its lens is about 12mm above the board surface so that it will later protrude through the front panel by the correct amount. The capacitors should all be installed so that they lie parallel with the PC board (see photo). Fig.3 (right) shows the full-size PC pattern. 34 SILICON CHIP RESISTOR COLOUR CODES 0 0 0 0 0 0 0 0 0 0 No. 2 Value 4-Band Code (5%) 5-Band. Code 75kQ 68kQ 27kQ 20kQ 10kQ 5.1kQ 4.7kQ 2.2kQ 1kQ not applicable blue grey orange gold not applicable not applicable brown black orange gold not applicable yellow violet red gold red red red gold brown black red gold violet green black red brown blue grey black red brown red violet black red brown red black black red brown brown black black red brown green brown black brown brown yellow violet black brown brown red red black brown brown brown black black brown brown The pot lugs are slipped over the PC stakes & soldered as shown in this close-up view. w hy it is called a class-B detector because it only conducts on one half of the signal waveform. The detected signal appears at Ql 's emitter and charges a 0. lµF capacitor via diode D4. This then turns on transistor Q2 which, in turn, drives PNP transistor Q3 and the LED. Ql , D4 and Q2 together perform the comparator function. If the 3.3kHz signal fed to the base of Ql is not 1.8V p-p or more, then Ql, D4 and Q2 will not conduct, Q3 will not be turned on and the LED will not light. So th ese components also perform an important signal level monitoring function - they won't operate if the signal isn 't big enough (ie, until VR1 is adjusted to give 350µA collector curren t for the test transistor) . Self-test function An interesting feature of the circuit is the self-test function which tells you that it is working and that the battery is OK. To test the circuit, you simply select the NPN setting and push the test button. If the circuit is working correctly, the LED will flash momentarily regardless of whether or not a test transistor is connected. This happens because the 0. lµF capacitor connected to Ql 's base charges from the +9V supply rail via the 5. lkQ resistor. This causes a short pulse of more than 6V to occur at Ql's emitter and so D4, Q2 & Q3 briefly conduct and the LED flas h es. This self-test function does not work in the PNP mode because the 5. lkQ resistor is now connected to the 0V line. On the other hand, if you are testing an NPN transistor and the LED will not flash or light at all, then the transistor probably has a short between base and collector. Power for the circuit comes from a 9V battery, which can be either an alkalin e or carbon-zinc type. Either way, the battery sh ould last a year or more with normal use. Construction Construction of the Beta Tester is relatively straightfo rward. All the circu itry, including th e switches and p otentiometer, is mounted on a PC board coded SC0410391 1 and measuring 71 x 61 m m. This in turn is h oused in a compact plastic utility case measuring 130 x 68 x 43mm. Before turning on the soldering iron, carefully inspect the PC board to ensure that there are no op en cir- What is Transistor Beta? There are a number of ways of testing the gain of a transistor. The most common method is to connect the transistor in a common emitter amplifier arrangement as shown in Fig.4. A fixed current is fed into the base and the resulting current into the collector terminal then measured. The ratio of the collector current to the base current is then the DC forward gain of the transistor. This is commonly known as DC current gain, hFE or DC beta. Most digital multimeters with a beta measuring facility perform the above test. They use a base current of typically 10µA and they measure the collector current directly. Our Beta Tester uses an AC signal of 3.3kHz to measure AC beta, which is commonly referred to as the "small signal current gain" or METER T I I ...L.. I I ...L.. Fig.4: the common emitter configuration for an NPN transistor. hfe. Again, a small AC current is fed into the base of the transistor and the AC current in the collector is then measured. The ratio between the two is the AC beta (hfe). In practice, the AC beta of a transistor is generally slightly less than the DC beta. The AC beta also decreases as the signal frequency increases. MARCH 1991 35 How to Test Unknown Transistors Most of us have unmarked transistors lying in the junkbox which could be used in many non-critical circuit applications. With a little practice, the Beta Tester can be quickly used to determine whether a transistor is an NPN or PNP device, and to measure its gain. The first step is to identify the transistor leads. To begin, set the Beta knob to maximum and clip the test leads to the transistor terminals. Test the transistor on both the NPN and PNP settings and systematically swap the test leads until the beta can be measured. There are six different ways to connect the tester to the transistor and two different transistor types (NPN/PNP). This means that, at worst, you will require 12 tests to determine the pinout for a particular transistor (or to discover that it's a dud). To make life easier, here are some basic rules to follow. If you turn a small signal transistor upside down as shown in Fig.5, the leads will ei- cuits or shorts between tracks. You can check thi s by comparing your PC board with the artwork included in this article. Make sure that the holes are correctly drilled out, too. The hole for pushbutton switch Sl should be about 8mm diameter, while the mounting hol es for slide switch S2 should be 2.8mm (7 /64 inches) diameter. r C + B ... ther be in a straight line or triangular arrangement. Further, as shown in Fig.5, the leads will usually run C(ollector), B(ase) and E(mitter) from left to right, but other configurations are possible. Fig. 7: for TO-3 style transistors, the case is the collector, while the emitter & base leads are as shown. VIEWED FROM BELOW 3 cases, the case is the Collector terminal and the Base and Emitter leads are as shown in Fig.7. Reverse Gain Fig.5: possible lead connections for a small signal transistor. For small power transistors in plastic encapsulations such as TO-220 and TO-202, the leads usually run Base, Collector and Emitter as shown in Fig.6. For larger power transistors such as those in metal TOFig.6: the most common lead configuration for TO-220 & TO-202 transistors. BCE Fig.2 shows the parts layout on the PC board. The first step is to install three PC stakes at the mounting points for VRl . This done, install all the low profile components such as the wire links , diodes , resistors and the IC. Be careful with the diodes and IC since they must be oriented exactly as shown on the overlay diagram. The remaining components can Once the pin configuration is discovered , it is simply a matter of turning down the gain control until the LED goes out. Note that there is still a possibility that the Collector and Emitter leads are reversed even though you have a believable reading of Beta. This is because bipolar transistors have a reverse active mode of operation as opposed to the normal forward mode of operation. The reverse gain of a transistor is always very much smaller than the forward gain. So take the highest Beta result in figuring out whether a transistor is an NPN or PNP type. now be installed on the board. Make sure that the tops of the capacitors and transistors are less than 8mm above the surface of the PC board, as the entire assembly is mounted on the lid of the case via Sl, S2 & VRl. This will involve bending all the capacitors over so that they lie flat on the PC board or across adjacent parts (see photo) . Also, be sure to use the correct transistor type at each location (see Fig.1) . The momentary contact switch (Sl) is installed by first pushing the lug end of the switch body through the mounting hole and then bending the lugs over sideways. These lugs are then soldered to 400 ·the large pads on either side. The base of the switch should 7 E + + D PNP 100 NPN TEST + L 36 5 _J SILICON CHIP Fig.8 (left) : this full-size artwork can be used as a drilling template for the front panel if the panel is not supplied prepunched. PARTS LIST The PC board is secured to the lid of the case using the mounting screws & nuts for the switches & pot. The battery clamp can be made from scrap aluminium. sit flush with the underside of of the PC board. Mount the 5mm red LED so that the top of its lens is about 12mm above the board surface. This will allow the LED to protrude through the front panel by about 1mm when the board is later installed in the case. The PC board assembly can now be completed by installing the battery snap connector and VRl. Cut VRl's shaft to a suitable length before soldering its lugs to the PC stakes (note: the lugs should be soldered about half way down the PC stakes). Final assembly The board assembly can now be installed in the case. If you are building the unit from a kit, it is likely that the front panel will be supplied prepunched with silkscreen lettering. If not, attach the front panel artwork to the lid of the case and drill out the holes for the test leads, switches, LED and potentiometer. The slider switch requires a rectangular hole and this can be made by first drilling a series of small holes and then filing these to shape. You will also have to drill two holes for the switch mounting screws. The test leads can be made from insulated hookup wire, preferably the multistrand extra-flexible type. Use a different colour for each lead. We suggest red for the collector lead, black for the emitter lead and white for the base lead. Cut each lead about 150mm long and fit an alligator clip with an insu- lated boot to one end. The three leads can then be fed through the holes on the front panel and soldered to their respective points on the PC board. After that, the board assembly can be mounted on the lid of the case and secured using the mounting screws and nuts for S1 , S2 and VRl. The control knob should be installed by first rotating VRl fully clockwise and then tightening the grub screw for an indicated beta reading of 500. Finally, the battery can be secured to the bottom of the case using a clamp fashioned from scrap aluminium. This clamp can be attached to the side of the case using a self-tapping screw. Testing To test the unit, connect the battery, set the slider switch to NPN, and depress the test switch. The LED should briefly flash. If it does, then the circuit is operating from Q1 -Q3. The unit can now be fully tested by checking a known good transistor. To do this , connect the test leads to the transistor, rotate the control knob fully clockwise, select NPN or PNP as appropriate, and press the test switch. Now rotate the control knob until the LED just comes on. The pointer on the knob will now indicate the test transistor's beta on the scale. A word of warning here; when testing high gain transistors, the LED may extinguish again if VRl is now moved to a lower beta setting. This occurs because the test transistor saturates and thus gives false readings. Always 1 plastic case, 130 x 68 x 43mm 1 PC board, code SC04103911, 71 x 61mm 1 front panel label, 127 x 66mm 1 9V battery, Eveready 216 or equivalent 1 snap connector to suit battery 1 battery clamp 1 pointer knob, 30 to 35mm dia. 3 alligator clips 3 PC stakes 1 DPDT slider switch (DSE S2040, Jaycar SS-0821 , Altronics S-2035) 1 momentary contact pushbutton switch (DSE S-1102, Jaycar SP-0710, Altronics S-1102) 3 150mm lengths of hookup wire (different colours) 1 2MQ linear potentiometer Semiconductors 1 555 timer IC {IC1) 2 BC548 transistors (01 ,02) 1 BC558 transistor (03) 4 1N4148 diodes (D1 ,D2,D3) 1 5mm red LED (LED 1) Capacitors 1 0.22µF 16VW PC electrolytic 3 0.1µF metallised polyester 1 .0022µF metallised polyester Resistors (0.25W, 5%) 1 75kQ 1% 1 5.1kQ 1% 1 68kQ 2 4.7kQ 1 27kQ 1% 1 2.2kQ 1 20kQ 1% 1 1kQ 1 10kQ Miscellaneous Tinned copper wire (for links). use the maximum setting where the LED just glows as the correct beta reading. Another problem is that some transistors (eg, BC548s, BC549s & BC559s) have gains of more than 500, which is outside the range of the Beta Tester. However, the unit can still verify that such transistors are working OK (the LED will simply remain on at maximum beta setting). Finally, note that this unit cannot be used to test Darlington transistors. That's because a Darlington transistor will saturate even at minimum base current setting (ie, rotary control at maximum). SC MARCH 1991 37 Manufacturer's data on the LM383 7W audio power amplifier National Semiconductor's LM383 is a single medium-power audio amplifier in a 5-pin TO-220 package. It requires few external components, has built-in current limiting and is optimised for automotive use. By DARREN YATES Main features It would be fair to say that there are enough audio power amplifier ICs available on the market to meet most circuit requirements. Devices like the LM380 and LM386 are frequently used by many designers. However, when it comes to finding an amplifier IC especially suited for in-car operation , the stocks start to thin out. Low voltage operation usually implies low output power, something in the order of one or maybe two watts at most - hardly enough to get over the ambient noise levels of most cars. Not only that , since most available ICs yome in a dual inline package (or DIL) format , attaching a heatsink to the!Jl is nearly impossibl e. The LM383 from National Semiconductor was design ed to solve these problems ecconomicall y. As shown 5 +V :4 OUTPUT 3GND 2 -INPUT 1+ INPUT Fig.1: the pinout diagram for the LM38-3. This device is mounted on a heatsink using a single screw and it can deliver good power output for such a small package. in Fig.1, it comes in a 5-pin TO-220 type plastic package, allowing easy mounting onto most heatsinks. All five of its leads are cranked outwards but those for pins 1, 3 & 5 are cranked out further than for pins 2 & 4. Capable of driving loads as low as 1.6Q (or five 8Q speakers in parallel), the LM383 can deliver up to 11 watts r--- - - - - - l " l +V Fig.2: This non-inverting amplifier will operate from supply rails of up to 1°~ 0.21 ~ H! ":" 38 SILICON CHIP of audio power (at 10% harmonic distortion) from a 16-volt supply rail. The LM383 has a 3.5 amp currenthandling capability which enables the device to drive the low impedances of most car speakers with low distortion. Current limiting has also been included to protect the device during high power operation, as well as thermal protection circuitry. -:- 4U SPEAKER 20V DC. The main features of the LM383 include: • Wide supply voltage range: 5-20 volts • Output power: typically 8.6W into 2Q from 14.4V with 10% total harmonic distortion (THD). • Ability to work in a bridged configuration with another LM383 to give four times the output power. • Large output voltage swing: 11.5V (peak to peak) with a 14V supply rail. • Low distortion: 0.2% THD at 4W into 2Q. • Large bandwidth: 30kHz at 40dB gain. • Quiescent current: typically 45mA. • Input noise voltage: 2µV with a 15kHz bandwidth. Normal operation Fig.2 shows a typical application for the LM383. It shows the device running from a supply rail of up to +20V and driving a 4Q loudspeaker. Note how the gain of the amplifier is obtained. The 220Q and 2.2Q resistors form a voltage divider string. The 470µF capacitor at the junction couples a small fraction (.0099) of the output signal back into the inverting input at pin 2. This voltage divider sets the gain to 101, or just slightly above 40dB. To reduce the gain, simply increase the value of the 2.2Q resistor to a higher value . Replacing it with a lOQ resistor drops the gain down to 23 or just over 27dB. To increase the gain , increase the value of the 220Q resistor. In order to keep the number of external components to a minimum, the 1M383 has its own internal biasing for both inputs. Looking at the circuit sch ematic in Fig.3 , the non-inverting (+) input at pin 1 goes straight to the base of a PNP transistor, which is biased into co:1duction by the current source (indicated by an arrow in a circle ), diode and the 150kQ resistor. This resistor effectively determines the input impedance , which is also 150kQ. This internal configuration allows the signal to be coupled via a cap acitor directly to pin 1 without the usual external DC biasing resistors on the input. If the supply voltage of the circuit in Fig.2 is reduced to 13 .8V, w hich is the standard "nominal" voltage referred to for automotive equipment , the output power delivered is 5.5 watts into a 4Q load. This may not sound like much but mosfcar radio/ cassette players have an amplifier stage of around this power. Note also in Fig.2, the 0.1Q resistor and the 0.22µF capacitor connected to the output. These components form a Zobel network which eliminates any tendency for the amplifier to go into high frequency oscillation. The graph in Fig.4 shows the basic performance of the LM383 . Looking at the distortion vs output power graph'. the distortion increases rapidly for output powers above 3 watts into a 4Q load and above 4 watts into a 2Q load. Bridged operation With two LM383s, using the bridge circuit in Fig.5, it is possibl e to produce an amplifier that will deliver 16 watts into a 4Q load w hile operating from a 14.4 volt supply rail. If we concentrate on the left hand side of the circuit, it is identical to the circuit in Fig.2. When operating in bridge mode , however, the speaker is connected directly across the outputs of two amplifiers. This eliminates the need for a coupling capacitor and also gives a better low-frequency response. Amplifier IC1 on the left operates normally. IC2 is connected as a unity +INPUT -INPUT Fig.3: the equivalent circuit schematic of the LM383. It has internal biasing components which means that the output (pin 4) always sits at around half the DC supply voltage. Distortion vs Output Power l ;!; ' 1---+-t--++f-l-H+-l--+-4.Ji- ~ 5 ~ 4 0 J 1---+-t--++Hi D. l ID OUTPUT POWER (W ) Fig.4: this graph shows distortion versus output power of the LM383 for various supply voltages and load impedances. The distortion increases rapidly for output powers above 3W into a 4Q load. gain inverter which produces an out of phase version of the output signal from IC1. This doubles the voltage across the speaker. Since power is related to th e squarn of the voltage, we get (in theory) four times the power output. In practice , though, we get slightly less than four times the output power. This is because we are limited by the internal impedance of the LM383. This ·also means that the lowest output imp edance we can drive is 4Q, as both amplifiers "see" half the output impedance (ie, 2Q in this case) when being used in bridged mode. The LM383 has a ripple rejection of around 40 to 45dB so to be on the safe side, use a reasonably large value capacitor to decouple the supply from spikes and noise (otherwise, they may be heard interfering with the output) . The current cost of the LM383 is about $6 but you may be able to get them cheaper if you shop around.Try Geoff Wood Electronics , 229 Burns Bay Road, Lane Cove West, 2066. Phone (02)4284111. SC +14.4VO-----.....- - - - - - - - - - - - - - , - - - . , - . . - - - - ' - - - - - - , 1M 100k .,. 220Q .,. Fig.5: by using two LM383s in bridge configuration, this circuit can deliver uv to 16 watts into a 4Q load from a 14.4V supply rail. The speaker is connected directly across the outputs of the two amplifiers, thus eliminating the need for coupling capacitors & giving better low-frequency response. MARCH 1991 39 'il:~~;'>~ ·· ~ · , \\\~.._Q,}_z; ) 'f \ n\ >\\ ~. wi'-"~ ·~.~ ***GREAT RANGE! GREAT PRICE!*** ·,. \, i:;;;;i; ~r:..l~s;J-IT'F'iii:n~r.!! ,, , -iEiiiliiRiim~r , rLr~,;:!!:,;!!::~!!i.:11,ti~!!iilji!iii i&-r. tJ EVER POPULAR. 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Road fre ight bulky & frag ile items w ilt be charged at dttferent rates. FA X : (03) 639 1641 FAX: AS PHON E. FAX: (02) 519 3868 FAX: (03) 543 2648 A ll salee tax exe mpt ord ers & w holesale inq uiries to : RITRONICS WHOLESALE, 56 Renver Rd , Clayton , Victori a. P h: (03) 543 2166. Fa x, (03) 543 2648. MAIL ORDER & CORRESPONDENCE P.O BOX 620, CLAYTON, VICTO RIA.31 68 Err Ofs & omisai ons excepted. Prices & :,pocltlc,1 l ions sujttcl to change. ' IBM , PC. XT. AT, aro re gistered tr ademarks of lntern allon al Buaineas Machinea. FREE CATALOGUE WITHEVERV MAIL ORDER! ■ VISA VINTAGE RADIO By JOHN HILL Automatic gain control: what it is & how it works One of the most useful developments to come out of early radio was a special circuit arrangement known as Automatic Volume Control (AVC). The term was later modified to Automatic Gain Control (AGC) which, technically speaking, is more correct. AGC is so widely used today that most people would be unaware of its existence. It is now just one of the countless things that we take for granted, without so much as a second thought. While all modern radio (and TV) receivers have this useful control, some vintage models are less fortun- ate. Radios from the early to mid1930s may or may not have been designed with AGC. Radios prior to 1930 would definitely not have AGC. The difference between having and not having AGC was very noticeable indeed. A receiver with AGC reproduces most stations (with the exception of extremely weak or extremely strong signals) at very nearly the same volume. On the other hand , a set without AGC will vary greatly in volume from station to station, and a setting for a weak distant signal will just about split the speaker cone when the receiver is tuned to a strong local station. Tuning a set without AGC requires two hands ; one for tuning and one for constant manipulation of the volume control. Indeed, listeners who like twiddling the dial will find a receiver without AGC fairly tedious to use. In my locality, there are four local stations with the nearest one being only a couple of kilometres away. Tuning a set without AGC under such conditions can be a real pain at times. One frequently stumbles onto one of these very strong stations, which is not only nerve shattering but could do serious damage to the loudspeaker as well. As a matter of interest, I actually had a set stop dead when it encountered a local station. The reason was not difficult to find; the jolt had disconnected one of the speaker transformer connections. Admittedly, it was a poorly soldered joint but it was working OK until it was blown off. Such is the intensity of local station crashes with a receiver that lacks AGC. Summing up the situation is easy. Receivers with AGC are far more pleasant and easier to operate than those without. AGC was one of the truly great developments of the 1930s. How it works Old regenerative receivers from the 1920s never had AGC as it was technically impossible. In any case, there was seldom enough gain to make it a problem. 42 · SILICON CHIP What is the effect of AGC and how does it work? Resurrection Radio Vi tage ,re ess Soecialists Repair - estoration - S es 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 enthusiasts 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 catalogue. Valves such as the 58 (left) & the 235 were two of the early variable mu or remote cut-off types in service. These valves have specially constructed grids in which the turns are closer at the ends than in the centre. The application of progressively greater bias thus has the effect of concentrating the electron stream in the centre of the grid structure where there are relatively few turns, & this changes the amplification factor. With the manual volume control set to a particular level, variations in input signal strength (within reasonable limits) have little or no effect on the level of the audio output. This convenient situation is accomplished by rectifying a sample of the received signal and applying this negative voltage as additional bias to the preceeding valves. Thus, when the set is tuned to a strong signal, the grid bias on the AGC-controlled valves increases and this red11ces their gain. The opposite happens with a weak signal. In this case, there is less bias applied and the receiver becomes more sensitive. There are no moving parts involved and the constantly changing bias is produced electronically by the AGC circuit. One of the advantages of AGC is that it helps to smooth out station fading, as when listening to interstate stations at night, or to overseas shortwave stations. Naturally, the AGC has its limitiations. If a station fades right out or drops into the noise level, then it is beyond the set's ability to receive a non-existent signal, or change a noisy signal into a noise-free one. Circuits with AGC normally use WANTED - Valves, Radios, etc. purchased for CASH Call in to our Showroom at: 51 Chapel Street, Wlndsor,Vic 3181 PO Box 1116 Telephone: (03) 529 5639 UHF HIGH GAIN ANTENNAS antenn existing systems triangul powder coated receiving elements ensures excellent UHF reception compared to other UHF antennas of similar size and price. Two models are available: the Tit ~ 14 for Band Four and the I VA for Band Five UHF reception. Both models are supplied with back reflectors to prevent ghosting as well as a waterproof entry box designed to accept 75 ohm coaxial cable without the need for addittional baluns. They also have predril!ed holes for securing the tilt adjustable metal mounting bracket in either a horizontal or vertical position. Imported and distributed by: The old 55 was one of the first duodiode triodes. The diodes are necessary for AGC & detection and share a common cathode with the triode section of the valve. diodes to produce the rectified signal. However, some very early forms used a separate valve to vary the Available through the following retailers: Bernys. Bridgepoint. Military Road. Mosman. 2088. NSW. (02) 969 1966. Ritronics. 56 Renver Rd. Clayton. Victoria. 3168. (03) 543 2166. MARCH 1991 43 were being used for detection and AGC as early as 1932. Variable mu valves The 6H6 twin diode is sometimes used for AGC detection instead of a duo-diode triode valve. However, the basic principle is exactly the same. screen grid voltage of the IF amplifier valve. Other methods of early AGC systems also used an additional valve. However, it was used as a diode in the conventional manner. Although AGC techniques were used as early as 1930, only up-market receivers would have had such systems. Some of these arrangements were quite complex compared with later methods. Valve types From about 1932 onwards, diodes usually twin diodes - were built into various valves. One of the earliest was the type 55, a 2.5V duo-diode triode. This valve was also made in 6.3V form, as the 85. A similar valve was the 2A6, another duo-diode triode, which became the 6.3V type 75, the 6B6 in octal based form, and finished its days as the fSQ7-GT. The ,duodiode arrangem~nt, in both triode and pentode valves, was a popular one until the end of the valve era. The diodes were usually fitted to valves designed for use as first stage audio amplifiers. Typical were triode valves such as those already mentioned, plus the 6AV6 and others. However, the situation was not very favourable for the 4-valve receiver, which had no first audio stage. As a result, diodes were included in other types of valves, mainly "variable mu" types, used as IF amplifiers (more about these later). Typical types were the 6AR7, 6G8, EBF35 and 6N8. An alternative arrangement was to in- 44 SILICON CHIP elude the diodes in the power output valve, one example being the 6BV7. It matters little in which valve the diodes are located; the diode section is separate from the rest of the valve, although it shares a common cathode. One interesting valve is the 6H6. This is simply a 6.3V double diode. It was originally produced in metal form but there were a few glass versions made. Similar developments took place in Europe, where valves with diodes Many superhets from the early 1930s, such as this 4-valve Airzone, also lacked automatic gain control. Next month, we will describe an AGC conversion for this particular receiver. At a more practical level, while it is necessary to produce a negative AGC voltage to alter the grid bias of the earlier stages, this is of little use unless it is applied to the right valve types. The AGC voltage can only be fully effective if is applied to the grids of "variable mu;, or "remote cut-off' type valves. These valves have specially constructed control grids, designed to accept a wide range of bias. Varying the bias changes the amplification factor of the valve. "Vari'lble mu" means variable amplification factor. (Valves with conventional grid structures, known as "sharp cut-off" types, have only a limited range of grid bias gain control. If pushed beyond this range they can cause distortion and/or suffer interference from other strong signals). To explain further, the variable mu control grid is unlike a normal grid which has evenly spaced turns. Instead, it is wound with a variable pitch, the turns being spaced progressively closer together towards the ends , and relatively open in the centre. With this type of construction, the application of progressively greater bias has the effect of concentrating the electron stream in the centre of the grid structure, where there are relatively few turns. As a result, the amplification factor is low. In this way, the amplification factor can be varied by means of the bias. With normal bias applied, the gain of these valves is similar to that of other pentode valves; it is only when the bias is increased that the gain is reduced. Variable mu type valves are used as radio frequency amplifiers, intermediate frequency amplifiers, and frequency converters. One of the first variable mu type valves was the old 2.5V 58, which made its debut way back in 1931. It was later produced in 6.3V form as the 6D6, and then with an octal base as the 6U7G. The latter was used until the early 1950s and was a very popular valve. In most four and 5-valve receivers, the AGC operates on the first two valves, the frequency converter and the IF amplifier. With these two valves FINAL IF TRANSFORMER FINAL IF B :ff"'" V1 Cl (b) AGC VOLTAGE .,. C2! J-- TO FIRST AUDIO VALVE C2+ Fig.1: simplified AGC circuit. Resistor R1 is the diode"load. When Vl's anode is positive, current flows through R1 from (b) to (a). Thus, (a) becomes negative with respect to (b) & this negative potential varies in proportion to signal strength. This signal is then filtered by R2 & C2 to generate an AGC voltage which is then fed to the control grids of the pre-detector valves. controlled, AGC can be very effective. If a receiver has a 6-valve complement, it could have either an RF stage or an extra IF amplifier stage. In either case, the extra valve should also be connected to the AGC line, otherwise the AGC system would not be fully effective. Although AGC is easily accomplished, it can be a little mystifying, because there are many ways of incorporating it. One has only to look through a number of circuits to realise that there are quite a few variations in circuit technique. However, regardless of which circuit is used, they all give fairly similar results. Checking out old circuits shows that some receivers use the two diodes for different purposes; orie for detection and one for AGC. Other circuits tie the two diodes together as one and use them for both detection and AGC in the one circuit. Some circuits seem to use more components than others and, if you're not familiar with it all, it can be a little confusing. There are two types of AGC circuits - simple AGC and delayed AGC. Where only a single diode is used the system must, of necessity, be simple AGC. If delayed AGC is required, then two separate diodes must be available. With simple AGC, the negative AGC volta,ge begins to rise from the moment any weak signal (including Fig.2: simplified delayed AGC circuit. By applying a small negative bias (from the battery) between the diode plate and cathode, the diode is prevented from conducting and generating AGC voltage, until the signal is greater than this bias. This gives maximum sensitivity on weak signals. Practical circuits do not use a battery;. instead, the bias is derived from the cathode bias system of the audio valve. noise) is received. In other words, very weak signals are subject to some reduction in volume because they generate small AGC voltages. This means that the maximum sensitivity of the receiver can never be fully realised although, in practice, this does not amount to a serious problem unless the signals are very weak. Delayed AGC Delayed AGC is a better system in that the AGC action is delayed until the incoming signal reaches a certain level. Below this level, no AGC voltage is produced, which means that the full receiver sensitivity is available to cope with weak signals. This means that very weak stations are not robbed of any volume as is the case with simple AGC. The term "delayed" sometimes causes confusion. It does not mean a time delay; it means a level delay. This misconception can easily occur if one is unfamiliar with such systems. I touched on AGC in a previous article, where I mentioned an intended project to add AGC to an old 5-valve Airzone, a rather stylish console model but without AGC. It was my intention to relate the details of that experiment in this story but, alas, we have run out of space again. As I see it, there is little point in going into great detail about an important subject, without some preliminary discussion. In this case, the preliminaries took up a good deal more room than anticipated. Next month's vintage radio column will give a full account of the AGC conversion on the old Airzone. SC .,•••.•;11t■i;ir:.i;: RCS Radio Pty Ltd is the only company which manufactures and sells every PCB [, front panel published in SILICON CHIP, ETI and EA. 651 Forest Road, Bexley, NSW 2207. Phone (02) 587 3491. MARCH 1991 45 Interesting circuit ideas which w e have checked but not built and tested. Contributions from reade r s are welcome and will be paid for at standard rates . .0032 22k .,. Audio filter for HF receivers One of the problems with shortwave reception on the HF bands is the 5kHz adjacent channel whistle. This circuit gets rid of the whistle by using a twin-T notch filter set to 5kHz in combination with a low-pass filt er. ICl buffers the incoming signal and feeds a Sallen & Key 2nd order low pass filt er, ICZ. This filt er has poor damping so that th ere is actually a small gain at about 3kHz which reduces the effect of the notch filter at that frequ ency. Following ICZ is a simple RC network (.04µF and 10kQ) which reduces the amplitude of frequ encies below 300Hz. This RC network is buffered by IC3 w hich is connected as a voltage follo w er. The output of IC3 th en drives the 5kHz notch filter, which is fine 3MHz digital frequency counter This circuit is an extension of the 3-digit counter module published in the August 1990 issue of SILICON CHIP. It can be used to measure frequencies between lOHz and 3MHz. The input signal is fed into a xZ preamp stage form ed by inverters IC6a, b & c. The signal is th en fe d to a 46 SILICON CHIP +1 0 .,_ _ -10 / I -~~ v~ J.!)W-PA§.S_ _ T '- ,\'-~"'~ -- -- - ~ "''\ ~ ' ~ t\. \ '\ ,_ ", \ !1; -20 I ~ -30 -40 - 50 50 500 100 1k 5k 10k FREQUENCY (Hz) This graph shows the frequency response of the audio filter circuit. tuned by th e ZkQ pot VR 1. The output signal is buffered by IC4. Th e overall res ult is a frequency response of 300Hz to 3kHz w ithin 6dB (s ee graph) and the gain of the Schmitt trigger consisting of inverters IC6d & e. From here, the squared up signal is connected to the clock input of the first 4553 3-digit counter, IC3. Its carry outp ut, pin 14, is connected to th e cl ock input of the second counter, ICZ. Thus, IC3 and ICZ give a 6-digit disp lay. Th e timebase circuit uses an MM53 69 to produce a 60Hz output. Two 4017 decade counters divide this circuit is set to 3. A TL074 quad op amp could be used for ICs 14. Electronics & Wireless World, October 1990. down to produce the lOHz an d lHz timebases , respectively. The 1Hz timebase gives a frequency range of 1Hz to 1MHz while the lOHz timebase allows operation from lOHz to 3MHz, or thereabouts. Timebase switching is perfo rmed by switch Sl and NAND gates IClOa, b & c. The timebase signal is directed to IC5, a dual-D flipflop connected as two monostables which generate se- +9V t 9V b 12 6 12 C11 4 4 11 d 10 2 2 10 e9 1 ...J F 7 19 '1 2 f 15 9 g 14 10 a 1-:ib e/-/c 6 IC4 4511 1 d 9 i-=-- vw,,r--:.,:,__.,,,...,.,....,,,...,,,....q_ 10 8 6 5 17 13 7 6 a 3 IC1 4511 . 7x680ll 7 .,!§ ...1 7~fl LSD 3xFND500 3xFND500 MSD r L...r=---.,,,..- --....,,8: -- ""T.58 8 18 03 BC558 5 10k I~ 'fC./ 02 BC558 .1i.-+9V f1 01 BC558 IC2 4553 I<;'\ 1 2 6 9 7 6 5 2 +9V--.J.§ 10k I~ 7 1 10k IC3 4553 15 f1 , - - - -4 14 12 1 I ho 10 13 13 1 ,------,.---------,-,...---I r - - - -- ------J>-----+9V RESET 12 9 INPUT 100p fl o. 22 = k 470 IC6a o--;---1i:1-..,__-w,._.,_-'-l1 '" 100pF:;::: 2 4069 IC6b IC6c 14 J >0>'-4➔......::.isr7 rnf1\{~ _j!.1 ,--__.,._ _ _ +9V 100k 10M _g ls t IC5 4013 IC6d 10k s 13 IC6e 11£:>o12-- ~ 12 .....____, 13 '" 10 02 1N41 48 01 1N4148 17:\ 17:\ '-=./ + 9 V - ' - - - - - - - + - - - - - < - - - - - - - -- 1Nfi48 ~~ 04 10k --<--------- 470n f' 6 IC11 ~ H r---,if--'~10,yik,-,..7~J 1k +1'2~-r-YW~CF VR1 2k ~3 1k ·:v°UT 7805 IN GND • +9V-- ....- -- s~ 2.7k T - - - -- - - - - - - --- - - + - - - - , .,__M_M_,i_1:_9_ ___.l1 60Hz 14.._.,.,ns-=---4-'~_;7_,,,,16____.3 s ' .J!3 ~ 680!! _*--9<' 10Hz14.__l,,.,.6,-4--,lg1,,..,97,.......[,-2:3'----~r--'1c:..:Hz:__,._1_s- - ,~r-"i1-:_ 4_D·~-~\Xr,_ :3 -:),l5 ~3 ~ s1 ''a.ls 1Dk )~M ~ s5~11U"4_ _ __ 10k -quential 5µs pulses to latch and reset the counters at the appropriate time. The 1Hz timebase is also used to flash . the decimal point of the most significant digit (MSB) to indicate when the battery voltage fall s below 9V. The 7805 regulator and comparator IC11 checks for this , the output being a squarewave at 1Hz when the level drops below 9V. Bill Jolly, Nambucca Heads, NSW. ($50) .. MARCH 1991 47 IBM keyboard extension cable CIRCUIT NOTEBOOK - CTD D1 1N4002 10Q +12V + 22 16VWJ + 22 16VWJ- 0.11 1k 1k OUTPUT 1k 4.7k 4.7k .,. INPUT Direct coupled sniffer probe This circuit was developed from the RF sniffer probe published in the June 1998 issue of SILICON CHIP. Unlike the previous version, direct coupling is used throughout and there is also heavier supply decoupling. The revised circuit also uses a 1.5mH choke at the input. Simple metal detector Next time you feel the urge to head for the hills in search of gold, take a couple of these simple metal detectors along. It uses two 4011 quad 2-input NAND gate packages and little else. The detector uses the beat frequency principle and so has two oscillators - a reference oscillator and a search coil oscillator. IC1a & IC1b form the search coil oscillator, while IC1c & ICld form the reference oscillator. The signal frequencies so produced are gated together in IC2a and then passed to a Dtype flipflop comprising IC2b, IC2c & IC2d. The reference oscillator runs at about 400kHz while the search coil Ql and Q2 are used as self-biased gain stages, while Q3 clips the output signal to about 2 volts peak to peak so that it is suitable for driving the input of a frequency meter. Construction is similar to that for the original probe circuit while heatshrink tubing must be used over the input choke. Greg Freeman, Nairne, SA. ($20) ,Q, 5-PIN DIN Many of the older PCs have their keyboard input sockets at the back of the computer, which means 2 you effecitvely lose a SOCKET FACE AND PLUG REAR fair bit of the cable length before you even get to the front of the computer. With the coiled cable most keyboards have, if you stretch them any distance , and then let go of the keyboard, they recoil smack into the computer case. This idea is a simple solution - just make an extension cable. All you need is a 5-pin DIN PIN SIGNAL WIRE plug (male) and CLOCK WHITE 1 socket (female) 2 DATA YELLOW and a length of RESET BLACK 3 4-core plus braid 4 GND BRAID cable. The pin 5 RED +5V connections are shown in the diagram. Use the colour coding provided and the braid for the ground loop. Note that the maximum length will depend on the speed of your machine, but 3 metres should work well. Colin Stewart, Broken Hill, NSW. ($10) 330k +9V +9V 33!l HEADPHONE .,. oscillator runs at about 100kHz. When the search coil detects metal, its oscillator changes frequency slightly but l;?y comparing the two frequencies in the flipflop, the changes are made much more audible. When power is initially applied, the lkQ pot VR1 is adjusted for an audible beat note from the headphones. The search coil is 50 turns of SWG enamelled copper wire closewound on a circular wooden former 180mm in diameter. Darren Yates, SILICON CHIP. MARCH 1991 49 A synthesised stereo AM tuner, Pt.2 Despite the circuit complexity, our new Synthesised AM Stereo Tuner is easy to build. This month, we show you how to put it together. By JOHN CLARKE The AM Stereo Tuner is housed in a black 44mm high rack-mounting case. There are three PC boards for the tuner circuitry: a main PC board (code SC01101911 , 352 x 120mm), a display PC board (code SC01101912, 341 x 36mm), and a ferrite rod PC board (code SC0l 101913, 101 x 11mm). As can be seen from the photographs, the display PC board is soldered at right angles to the main PC board to give a neat and compact assembly. This technique greatly simplifies construction by eliminating inter-board wiring. The ferrite rod PC board is installed on an adjustable bracket on the rear panel and holds the ferrite rod assembly plus a few other smaller components, including 50 SILICON CHIP varicap tuning diode VCl. All the control switches, the indicator LEDs and the four 7-segment displays are mounted on the display board. With the exception of the 7segment displays, these all protrude through holes in the front panel and are flush-fitting to give a neat appearance. The 7-segment LED displays sit behind a bevelled grey persp ex window, while the front panel itself features gold screen-printed lettering. By the way, we recommend that you buy a complete kit of parts for this project rather than trying to buy the parts separately. That's because some of the parts are rather specialised and are not available from the usual retail outlets. Dick Smith Electronics will be offering a complete kit for around the $200 mark and this will include a pre-punched screenprinted front panel. Building it Before starting construction, make sure that you have the correct tools for the job. Most of the assembly is pretty straightforward but note that you will need a fine-tipped soldering iron when it comes to soldering in the microprocessor control chip (ICl) on the main PC board. Don't try using an iron that's too big for the job you'll damage the copper tracks on the board if you do. Before you start installing components, check the PC boards for shorts between tracks or breaks in the tracks. Also check that the holes have been drilled to the correct size and that all holes have been drilled. For example, the PC board mounting holes, regulator tab mounting holes and cable tie holes (on the ferrite rod PC board) all need to suit the mounting screws and cable ties supplied. Also, the transformer needs holes to accept its plastic mounting bushes as well as its connection pins. Finally, check that the Tako coils fit Left: the AM Stereo Tuner is built into a low-profile rack-mounting case with a pre-punched front panel & gold screen-printed labelling. The four 7segment LED displays sit behind a grey perspex window & provide the frequency readout. into the designated locations (1.2mm holes are required for their earthed case pins). Main PC board assembly Once the PC boards have been inspected , you can begin work on the main board. Fig.1 shows the details. Begin by installing all the PC stakes at the external wiring points (locations C-L, TP1 , TPZ & GND) on the top of the board. This done, install all the wire links , resistors and diodes. Because they are long and so close together, the wire links must be perfectly straight so that there are no shorts. You can straighten tinned copper wire by clamping one end in a vyce and then pulling it taut from the other end using a pair of pliers. Cut the links to length and bend their ends at right angles to form leads before mounting them on the PC board. Note that some of the resistors are 1 % types and these are marked with a star (*) on the wiring diagram (Fig.1). Use your digital multimeter to check the resistor values before installing them on the PC board. When installing the diodes, be sure to use the correct type at each location (check the parts list). Also check that each diode is correctly oriented. The ICs can now all be installed, again taking care to ensure that they are correctly oriented. IC1 is a surface-mount device and so requires special attention. Unlike the other ICs, this device is installed from the underside of the PC board. Check that it fits snugly into its rectangular cutout with its top almost flush with the top surface of the PC board, and that the leads all line up with the PC pads. The dot in one corner indicates pin 1, as shown on the overlay diagram (Fig.1). To solder the IC in place, the fine copper lands which form the solder pads for the IC leads have to be tinned with solder first. Do this with a clean fine-tipped soldering iron by applying the iron to the copper tracks and feeding on a small amount of solder. Note that if the PC board is supplied pre-tinned, you should still carry out this procedure as the tinning layer will be too thin. Once the pre-tinning operation is complete, clean the soldering iron using a damp rag or sponge to remove any excess solder and flux . This done, the IC can be placed in position and the leads soldered in place. The idea is to stroke each lead with the iron so that solder on both the lead and its underlying track melts to form a joint. You may need to push each lead down with a small screwdriver as you solder it. This simple PC board assembly holds most of the parts, including the power transformer & pushbutton switches. When installing the parts, keep the leads as short as possible & take care with the orientation of polarised components. MARCH 1991 51 orientation of the SFZ450C. It must be installed with the cross on the top of its plastic case as shown in Fig.1. You can now complete the main PC board assembly by installing the trimpots, coils and transformer. Once again, the coil types are listed in the parts list. The transformer is secured to the PC board both by soldering its pins and by burring over the two plastic bushes from the transformer body with a hot soldering iron. (We suggest you do this task last because your soldering will need a thorough cleaning afterwards). Display PC board This close-up view shows the mounting details for the microprocessor chip & 3-terminal regulator REG 2. The regulator can be bolted directly to the heatsink (ie, no isolating mica washer is required). The 7-segment LED displays & the pushbutton switches are mounted on Molex pins to stand them off the PC board. Be sure to orient the displays correctly. The three TO-220 regulators - REG 1, REG 2 & REG 4 - are all mounted horizontally and secured with a screw and nut. To keep it cool, the REG 2 device is fitted to a heatsink which mounts between the regulator tab and the PC board. Smear a small amount of heatsink compound on the mating surfaces to ensure good thermal contact (note: a mica insulating washer is not necessary). REG 3 is a smaller TO-92 plastic encapsulated device. It can now be mounted, along with the transistors 52 SILICON CHIP and varicap diodes. Once again, be sure to use the correct transistor or varicap diode at each location (check the parts list) and keep their leads short by pushing them down onto the PC board as far as they will comfortably go. The capacitors can now all be installed, along with the trimmer capacitors (Cl & CZ), the ceramic filters and the crystal (X1). The SFP450D ceramic filter can only be installed one way because of its non-symmetrical pinout, but take care with the Fig.1 also shows the parts mounting details for the display PC board. Begin construction by installing the wire links, resistors and transistors, but don't mount the LEDs at this stage. The four 7-segment LED displays and the 10 switches are all mounted on Molex pins so that they stand proud of the PC board. In the case of the switches, it's best to break the Molex pins off the strip first and push them onto the switch leads. The switches can then all be installed on the PC board (flat side as shown in Fig.1) and the pins soldered. To install the 7-segment LED displays, first install the Molex pins in strips of five . Once they are all in place, snap off the connecting strips and plug in the displays. The decimal point for each display goes towards the centre of the display board (ie, the bottom right hand corner of each display when looking at the display board the right way up). Be careful here - it's very easy to get confused. Finally, the LEDs can all be installed and held in place by splaying their leads. Don't solder the leads yet, though - that step comes later, whe_n we fit the PC board assembly in the chassis. Ferrite rod PC board Fig.2 shows the parts layout on the ferrite rod PC board. Note that the ferrite rod is secured to the PC board using two cable ties. Similarly, the external leads from the PC board are tied in place using a cable tie which passes through a hole adjacent to the 100kQ resistor. The end hole is used for mounting the PC board on a right angle bracket which is secured to the rear of the case. ~ ~ ~ :LED2 ~ ~ IC6 LM324 -{!&•LED3 --1:Iill- : LED4 . •A POWER TRANSFORMER -{JD-o~ --{TID-- :LEDS • LED6 • A 3.3k -- j •• I DD1 . ~1~ ~ . K • -<at>[lo •B w ~w 5~ :,:.. :a = Cl) <I) <I) oc i::, oc "" 0 .c u~ i::, 0 "' Cl) :::: .s"'"' Cl) .d N --- 0. oh ~ SEEK -- +Q 100uF ~ A'' l!)LED13 ~ME K --. 0 0. 0. A [;jLED7 1 K A (!}LEOS 2 K A l;jLED9 3 K (3)• 4 0. 5 A . ~LED10 K A l;jLED11 K A c. ~LEDJ2 K (3)• DOWN 0• UP Fig.I (left): parts layout for the display PC board & the main PC board. Take care with the orientation of the LED displays & note that they & the pushbutton switches are mounted on Molex pins. Use PC stakes at external wiring points C-L, TPl, TP2 & GND on the main board. MARCH 1991 53 (leads towards the centre) and secured by wedging a thin strip of cardboard between the rod and the cardboard coil former. The four leads can then be fed into their respective holes in the PC board and soldered (note: leave the leads at full length so that the coil can be slid along the ferrite rod during the alignment procedure). Finally, the ferrite rod can be strapped in place using the cable ties - see Fig.2. Metalwork The ferrite rod is secured to its PC board using plastic cable ties, while a third cable tie secures the shielded cable runs at the other end of the board. A rightangle bracket is used to fasten the assembly to the back of the chassis. The first step is to mount the two capacitors. These should lie flat on the PC board, so that the lO0kQ resistor and VC1 can be mounted on top of them as shown (ie, bend VCl's leads at right angles so that the flat of its body lies on the 4.7pF capacitor). As supplied, Ll has about 110 turns on the main coil (the plain and dark blue wire ends). Unfortunately, this number of turns gives too much inductance to allow varicap diode VC1 to tune the entire broadcast band, which means that some turns have to be removed. To do this, cut the plain wire where it runs under the main winding and take off 27 turns (the lead running under the winding can be pulled out and discarded). The new end (when trimmed) now becomes the plain wire end. Before going further though, run some wax over the end of the coil to prevent further unwinding, then run the plain wire lead back down the coil (at right angles to the windings) so that it emerges adjacent to the other three leads. This done, the coil should be slipped over the end of the ferrite rod This close-up view on the copper side of the main board shows how the microprocessor is mounted. Use a soldering iron with a very fine point to avoid overheating & damaging the tracks (see text) 54 SILICON CHIP Although the kit will be supplied with a pre-punched front panel, there is still some work to be done on the metalwork. This involves drilling the holes in the rear panel and front subpanel. The first job is to mark out the hole positions for the LEDs, switches and displays on the front sub-panel. This can be done by using the pre-punched front panel as a marking template. Once the holes have been marked out, they can be drilled (and filed) oversize to provide clearance for the front panel components. Don't bother trying to cut square holes to accept the LEDs and switches; it's much easier to drill a large round hole with plenty of clearance. These holes will later be covered up when the front panel is screwed in place. The cutouts for the signal level display and power switch can be made by first drilling a series of holes and then filing to shape. Similarly, the cutout for the 7-segment displays can Be sure to install the mains wiring in a professional manner & use heatshrink tubing to shroud the fuseholder. The paint around the earth solder lug mounting hole should be scraped away to ensure good electrical contact. RESISTOR COLOUR CODES 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 No . Value 4-Band Code (5%) 5-Band Code (1%) 4 11 1 2 2 7 6 2 4 2 1 6 1.8MQ 1MQ 330kQ 180kQ 150kQ 100kQ 68kQ 47kQ 33kQ 18kQ 15kQ 10kQ 8.2kQ 4.7kQ 3.3kQ 2.7kQ 2.2kQ 1.8kQ 1kQ 680Q 220Q 120Q 100Q 47Q 10Q brown grey green gold brown black green gold not applicable brown grey yellow gold brown green yellow gold brown black yellow gold blue grey orange gold yellow violet orange gold orange orange orange gold brown grey orange gold brown green orange gold brown black orange gold not applicable yellow violet red gold orange orange red gold red violet red gold red red red gold brown grey red gold brown black red gold blue grey brown gold red red brown gold brown red brown gold brown black brown gold yellow violet black gold brown black black gold brown grey black yellow brown brown black black yellow brown orange orange black orange brown brown grey black orange brown brown green black orange brown brown black black orange brown blue grey black red brown yellow violet black red brown orange orange black red brown brown grey black red brown brown green black red brown brown black black red brown grey red black brown brown yellow violet black brown brown orange orange black brown brown red violet black brown brown red red black brown brown brown grey black brown brown brown black black brown brown blue grey black black brown red red black black brown brown red black black brown brown black black black brown yellow violet black gold brown brown black black gold brown 5 7 1 2 1 9 6 2 2 7 4 be made by drilling a series of small holes around the perimeter of the marked area and then punching the centre-piece out and filing to a smooth finish. Once this job has been done, take a look at the rear of the sub-panel. You will find six captured nuts - two at either end and two in the middle. The rear edges of the two in the middle and the two near the tuning switches must now be fil ed flat so that the back of the display PC board can sit flush with the rear lip of th e sub-panel. Don't file the sides of the captured nuts too much though, or you could damage the threads. Fig.3 shows the layout on the rear panel. You will need to drill holes to accept the cord grip grommet, th e fuse, a mounting bracket for the ferrite rod PC board, and a small rubber grommet. In addition, you will have to make a square cutout and drill two holes to mount the RCA socket panel. Once this has been done, the case can be partially assembled by screwing the two side pieces and the rear panel to the baseplate. The fro nt subpanel and fro nt panel can then be fitted. Connecting the PC boards The next step is to connect the main and display PC boards by soldering them together at right angles. To do this , first solder five 5mm-long brass spacers to the mounting points on the copper side of the main PC board. This done, position the display board behind the front panel so that the switches and LED displays all line up correctly, th en slide the main board up to the display board and mark the intersection at either end with a pencil. Now remove the two boards and lightly solder tack them together at either end. Test the assembly by refitting it to the case, make any adjustments necessary, then solder all the CAPACITOR CODES 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Value IEC Code EIA Code 0.1 µF .068µF .047µF .01µF .0012µF .001µF 470pF 270pF 120pF 100pF 47pF 22pF 4.7pF 100n 68n 47n 10n 1n2 1n 470p 270p 120p 100p 47p 22p 4p7 104 683 473 103 122 102 471 271 121 101 47 22 4.7 matching pads together. On the prototype, we also soldered two 30mm lengths of 2mm diameter brass tubing across each end of the PC board asM A RCH 1991 55 CORO GRIP GROMMET REAR PANEL ciT~B~ EARTH •- )'4\-c F G H I J K L MAIN BOARD Fig.3: use this chassis wiring diagram to guide you in positioning the components on the rear panel & check that the cord grip grommet grips the mains cord tightly. The power switch (S1) operates at low voltage, so you can use medium-duty hookup wire here. sembly to provid e additional strength (see photos). You can use triangular pieces of scrap PC board or tinplate as an alternativ e to th e brass tubing. Final assembly At this stage , you can reposition the PC board assembly in the case and mark and drill the five mounting hole positions. You also need to drill holes to accept two earth lug mounting screws as shown in Fig.3. Before mounting the earth lugs, scrape away some of th e paint from around the holes to ensure a good electrical contact. The earth lugs can then be secured using a machine screw, star washer and nut. Because the transformer is mounted on the PC board, a pi ece of Elephantide insulation (352 x 120mm) is installed betw een th e bottom of th e main board and the chassis to prevent accid ental shorts. This can be secured by drilling holes through it at the mounting points so that it slips over the 5mm space rs on the bottom of the board. 56 SILICON CHIP Do not mount the PC board assembly in position yet, since the mains wiring still has to be conn ected to the underside of the main board . Before installing the mains wiring however, the ferrite rod PC board should be mounted in position on the rear of the case. First, bolt the rightangl e bracket to the cas e using a machine screw, washer and nut. This done, the PC board can be attached to the bracket using a machin e screw, two washers (one on either side of the PC board), and two nuts. Th e proc edure here is to tighten th e first nut so that the PC board can be still be moved smoothly under friction , then the second nut is tightened onto the first to prevent it from coming loose. The final finishing touch for the ferrite rod PC board assembly cannot be done yet since we need to align the tuner by sliding coil L1 along the ferrit e rod . Following alignm ent , L1 can be held in position with wax and a 140mm length of heatshrink tubing shrunk over the entire ass embly to prevent acc idental damage. The remain der of the rear panel components can now be mounted as shown in Fig.3. Before installing the cord grip grommet, first strip back about 130mm of outer insulation from the mains cord , then feed the cord through th e entry hole. It can now be clamped in position with the cord grip grommet. Check that the cord is h eld tightl y and that it cannot be pulled out of the grommet. The mains wiring can now be run to the fus eholder, earth lug and main PC board. To prevent accidental electric shock, w e strongly recommend that h eatshrink tubing be fitted to the fusehold er to insulate the two terminals. This invol ves slipping a piece of heatshrink tubing over the two leads befo re th ey are soldered to the fusehold er. Th e Neutral and fused Active leads connect to the transformer terminals after first passing through two hol es in th e PC board. Once these connections have been made , you can install the PC board assembly in the case and secure it using machine screws and nuts. Finally, the rest of the wiring can be install ed , along with the 0.1µF capacitor from point C to earth. Be sure to use a cable tie to clamp the shielded cable to the ferrite rod PC board as shown in Fig.2. Note that the power switch operates at low volt- age, so it is only necessary to use medium-duty hookup wire here. That completes the construction. Next month , we will conclude with the alignment details. SC These two photographs show how the main PC board assembly is mounted. It should be positioned so that the back of the display board is flush with the edge of the lip on the sub-panel. This will involve filing four captured nuts, as explained in the text. MARCH 1991 57 Silicon Chip BACK COPIES May 1988: Optical Tachometer For Aeromodellers; High Energy Ignition For Cars; Ultrasonic Car Burglar Alarm; Walkaround Throttle For Model Railroads, Pt.2; Designing & Building RF Attenuators; Motorola MC3334P High Energy Ignition IC Data. 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; Oueensland's Powerful Electric Locomotives. July 1988: Stereo Control Preamplifier, Pt.2; Fitting A Fuel Cut-Off Solenoid; Booster For TV & FM Signals; The Discolight Light Show, Pt.1; Tone Burst Source For Amplifier Headroom Testing; What Is Negative Feedback, Pt.3; Amcron MA-1200 Power Amplifier Review; Amplifier Headroom - Is It A Con? 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. 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. December 1988: 120W PA Amplifier (With Balanced Inputs), Pt.1; Diesel Sound Generator; Car Antenna/Demister Adaptor; SSB Adaptor For Shortwave Receivers; Electronics & Holden's New V6 Engine; Why Diesel Electrics Killed Off Steam; Index to Volume 1. September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Vader Voice; · Motorola MC34018 Speakerphone IC Data; National Semiconductor LM12 150W Op Amp Data & Applications; What Is Negative Feedback, Pt.4. January 1989: Line Filter For Computers; Ultrasonic Proximity Detector For Cars; Simple Computer Sound Repeater; 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 (uses LM3909); 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; 32Band Graphic Equaliser, Pt.1; Stereo Compressor For CD Players; Map Reader For Trip Calculations; Amateur VHF FM Monitor, Pt.2; Signetics NE572 Compandor IC Data; 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; I Use this handy form to order your back copies ,---------------------------------- Please send me a back issue for: O September 1988 o February 1989 O July 1989 o December 1989 O May 1990 O October 1990 o October 1988 o March 1989 O August 1989 o Jan·uary 1990 O June 1990 O November 1990 O 0 O 0 May 1988 November 1988 April 1989 September 1989 o February 1990 O July 1990 O December 1990 o 0 0 0 O 0 0 July 1988 December 1988 May 1989 October 1989 March 1990 August 1990 January 1991 O O 0 O 0 0 August 1988. January 1989 June 1989 November 1989 April 1990 September 1990 February 1991 Enclosed is my cheque/money order for $______or please debit my: O Bankcard Card No. $5.00 each (includes p&p). Overseas orders add $1 each for postage: NZ orders are sent air mail. Signature _ __ _ _ _ _ __ _ __ _ Card expiry date_ _ /_ _ Name _ _ __ _ __ __ _ __ _ __ _ _ _ __ _ _ _ __ _ Street _ _ _ __ __ _ __ __ __ __ _ _ _ _ _ __ _ _ Suburb/town _ __ _ _ __ __ __ __ _ Postcode _ _ __ __ -----------------------58 o SILICON CHIP - O Visa Card 0 Master Card Detach and mail to: SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROY BEACH NSW 2097 Or call (02) 979 5644 & quote your credit card details. Fax (02) 979 6503 7 I I I I I I I I I I I I I I I 1 -------- ---- I Electronics for Everyone - All About Electrolytic Capacitors. June 1989: Touch -Lamp Dimmer (uses Siemens SLB0586); Passive Loop Antenna For AM Radios; Universal Temperature Controller; Understanding CRO Probes ; LED Message Board, Pt.3; Coherent CW - A New Low Power Transmission Technique. 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 Electrics ; Facts On The PhaxSwitch Sharing Your Phone Line With A Fax Machine. August 1989: Build A Baby Tower AT Computer; Studio Series 20-Band Stereo Equaliser, Pt.1; Garbage Reminder - A 7-day Programmable Timer; Introduction To Stepper Motors ; GaAsFet Preamplifier For The 2-Metre Band; Modern 3-Phase Electric Locomotives . September 1989: 2-Chip Portable AM Stereo Radio (Uses MC13024 and TX7376P) Pt.1; Alarm-Triggered Telephone Dialler ; High Or Low Fluid Level Detector (uses LM1830N); Simple DTMF Encoder (uses Texas TMC5089) ; Studio Series 20-Band Stereo Equaliser, Pt.2 ; Auto-Zero Module for Audio Amplifiers (Uses LMC669) ; A Guide To Hard Disc Drives. October 1989: Introducing Remote Control; FM Radio Intercom For Motorbikes (Uses BA 1404 And TDA?000) Pt.1; GaAsFet Preamplifier For Amateur TV; 1Mb Printer Buffer; 2Chip Portable AM Stereo Radio, Pt.2; Installing A Hard Disc In The PC ; A Look At Australian Monorails. November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY and Morse); Super Sensitive FM Bug; Build A Low Cost Analog Multimeter; FM Radio Intercom For Motorbikes, Pt.2 ; 2-Chip Portable AM Stereo Radio, Pt.3 ; Floppy Disc Drive Formats & Options; The Pilbara Iron Ore Railways. December 1989: Digital Voice Board (Records Up To Four. Separate Messages, Uses Texas TMS3477NL and 256K RAMs); UHF Remote Switch; Balanced Input & Output Stages; National Semiconductor LM831 Low Voltage Amplifier IC Data; Install A Clock Card In Your PC; Index to Volume 2 (Jan-Dec 1989). January 1990: Service Tips For Your VCR; Speeding Up Your PC; Phone Patch For Radio Amateurs; High Quality Sine/Square Oscillator; Active Antenna Kit; The Latest On High Definition TV ; Speed Controller For Ceiling Fans; Designing UHF Transmitter Stages. February 1990: 16-Channel Mixing Desk; High Quality Audio Oscillator, Pt.2 ; The Incredible Hot Canaries; Random Wire Antenna Tuner For 6 Metres; Phone Patch For Radio Amateurs, Pt.2 ; PC Program Calculates Great Circle Bearings. March 1990 : 6/12V Charger For Sealed Lead Acid Batteries ; Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16-Channel Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC ; Digital Waveform Generation Using a PC; The Controls On A Model Aircraft. April 1990: Dual Tracking ±50V Power Supply; VOX With Delayed Audio; Relative Field Strength Meter; 16-Channel Mixing Desk, Pt.3 ; Simple Service Tips For Your Microwave Oven; Model Aircraft Aerodynamics; Active CW Filter For Weak Signal Reception. 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; 16Channel Mixing Desk, Pt.4; What To Do When Your Computer Goes Bung , Pt.1; Electronic Load For Checking Power Supplies. June 1990: Multi-Sector Home Burglar 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 Your 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 & Combination Lock; Simple Electronic Die; LowCost Dual Power Supply; Inside A Coal Burning Power Station; What To Do When Your Computer Goes Bung , Pt.3; Digital Waveform Generation Using A Computer, Pt.4. 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; The Tube Vs. The Microchip (Two Shortwave Receivers Compared); 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; LowCost 3-Digit Counter Module; Voice Mail For Your Computer; Simple Shortwave Converter For The 2-Metre Band; How To Make Dynamark Labels. October 1990: Low-Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; Surfsound Simulator; DC Offset For DMMs; The Dangers of Polychlorinated Biphenyls; The Bose Lifestyle Music System; Using The NE602 In Home-Brew Converter Circuits. November 1990: Low-Cost Model Train Controller; Battery Powered Laser Pointer; A Really Snazzy Egg Timer; 1.5V To 9V DC Converter; How To Connect Two TV Sets To One VCR; Introduction To Digital Electronics ; Simple 6-Metre Amateur Transmitter. December 1990: DC-DC Converter For Car Amplifiers; The Big Escape ; Wiper Pulser For Rear Windows; Versatile 4-Digit Combination Lock; 5W Power Amplifier For The 6-Metre Amateur Transm itter; The Green CD Pen . Controversy. January 1991: Fast Charger For Nicad Batteries, Pt.1; Have Fun With The Fruit Machine; Two-Tone Alarm Module; Laser Power Supply (For Tubes With Ratings Up To 10mW); LCD Readout For The Capacitance Meter; How Quartz Crystals Work; The Dangers When Servicing Microwave Ovens; Electric Vehicles - The State Of The Art. February 1991: Synthesised Stereo AM Tuner, Pt.1; Three Inverters For Fluorescent Lights ; Low-Cost Sinewave Oscillator; Fast Charger For Nicad Batteries, Pt.2; How To Design Amplifier Output Stages; Tasmania's Hydroelectric Power System. PLEASE NOTE: All issues from November 1987 to April 1988, plus June 1988, are now sold out. All subsequent issues are presently in stock. For readers wanting articles from issues out of print, 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. MARCH 1991 59 008 335757 TOLL FREE MAIL ORDER HOTLINE f9R CREDIT CARD ORDERS! ----------------, WOW! 1~ 200 MEG ULTRA HIGH SPEED DRIVES NOW A'''AILABLE y, • ~ I ._,,.. ,-.. : APPLE* COMPATIBLE I,,,~~-'/o!\ 44-1 I --~ I SLIMLINE DISK DRIVE I Compatible w1lh Apple 2+ \ ()IQ'.s)t-~ I FR~l~~~~gi ~~.}'J~KS II APPLE· IIC COMPATIBLE DISK DRIVE (including cable ..... only $189 I I FR~,~~~~gi ~~.}'J~KS 1 1·App1c 1s a reg1ste re<11raoe mar1< GET MAXIMUM PERFORMANCE ..., } '. OUT OF YOUR COMPUTER! ~ ~/, \ ~ .. I I ·:~~, A re you short of hard disk space or just sick of backing up onto flo ppi es? Then we have avai lable 200 Megabyte drives wi th IDE (pad dle) cards to plug into your IBM compat ible com puter. They are mounted in a standard I 1/4" cradle so fittin g is no problem. You will need DOS QUALITY 1 4.01 to run t hese as o ne conti guous drive (ie. as the full JAPANESE DRIVES !! 200 Meg as Dri ve C). Dos 4.01 is avai la ble for only $120 I if you purchasn o r have r,reviously purchased, a 5¼" 360K DRIVE system or m otherboard from us . The DOS is genu ine I • SOOK unformatted . • IBM" xr co mpatible I Microsott w ith G.W. Basic inte r preter and manuals. Cat.C11901 .... .... $175 Please note, these drives are already low level form att ed. You only have to use "F DISK" t o h igh level I 51 /4' 1.2 M/BYTE fo rmat th orn . I I I sl I I ~ 1 I I I I WE ALSO HAVE AVA ILA BLE 85MEGABYTE DRIVES AT $ 095.00 WITH 12 MONTHS WARRANTY• . Please see ou r las te s l 148 p ag e catalogue for I I I I I ____ ~:..b~~'=i~a.!!_o_!: __ _ _ ...I ----------- COPALDRIVE • 1.6 M/Byte unformatted • IBM• AT' C01T1>atible C1J······. · ·······'' 95 UPGRADE YOUR COMPUTER WITH A 3 1/2" DRIVE KIT , "" Y.E DATA 3.5" 1.441720/ 360 DRIVE 3½ " 144M/BYTEDRIVE • 51 /4" Mounting bracket • Power supply adapter =~~~~ (s~i~~~~~gl~/P~~~:~ed • Switchable 1·44 M/Byte formatted or n oK I0,matted 1 • Floppy Disk controller card •S ¼ .. mounted which controls 1.44/ 720/ 360/ Cat. C d rives • Cable adapter · ·· · $ 195 21 MEG HAR D DISK WITHOUT ' C,ONTROLLEF;l (STANDARD ST50B INTERFACE) ................ $449 42 MEG HARD DISK FOR XT 28 ms ACCESS WITH IDE/FDD CONTROLLER .............................$549 42 MEG HARD DISK FOR AT 28 ms ACCESS WITH IDE/FDD CONTROLLER .............................$449 85 MEG HARD DISK FOR AT 28ms ACC ESS WITH IDE/FDD CONTROLLER ..•.••.•.•.••..•.••.••.••.•.•$895 126 MEG HARD DISK FOR AT 16 ms ACCESS WITH IDE/FDD CONTROLLER .........................$1,295 All Hard Disk capacities are formatted. IDE/FDD drives are already low l evel formatted so you only have to '"F DISK'" to high level fo rmat t hem. Please note you need DOS 4.01 to fo rmat t hese to t heir maximum capacity as d rive '"C'" or· otherwise you will have to partition as "C'", "D", '"E:", etc. if you have an earlier version of DOS. ~:::;:;;::::;:;:;:;;::;:::;::;::;:;;:;:;;::;:;;;:;:;:;::::;:;::;::;::;::;::::::-::.111 SIMPLY BEAUTIFUL TECHNOLOGY! INTRODUCING THE ELEGANT &: COMPACT RITRON EXECUTIVE BASE STATION. BUILT-IN FUNCTIONALITY & FLEXIBILITY DESIGNED INTO A SMOOTH COMPACT CASE I. CONTROLLER C A RO TO SUIT X18009 Complete instructions to install a 3.5" drive in your existing compu ter. Enjoy the higher density and easy handling of 3.5" Floppy ~iskettes. 11911 C1191 5...... $325 • Absolute IBM compatabillty • 286.1 2 MHz 0 WAIT =-: : • lMBRAM • 40 MB Hard Disk/Cont. ~ • VGA Card ~ • 2 x Seri al /Parrallel/games ports • Real lime Cl ock/Calan der • Dynamic Speed Control provides Turbo Speeds • Keyboard speed sel ect • Small Footprint 304 x 330mm $139 1 FREE CATALOGUE WITHEVERY MAIL ORDER! Replace your XT for an AT. BABY 286 - 16 Mhz Landmark MAIN BOARD ~ ">--,-~,..,I Cat. X19901 . On ly $179 At home, on your desk or in the network, the Base Station Is toda y 's reliable and stunningly beautiful computer solution. A ppro ximate ly 22 x 22cm, this baby mainboard fit s hori zontally in t he base' of the syste m uni t. It uses a 4•I ayer r,r inted circ ui t boa rd . DC power & a s i'.l nal fro m the power supply ente r the boa rd t hrough 2 con nectors. Fo ur 16-bi t ca rd• edge slots & two B•bit slot s are p rov irl ed for expa nsion. X20090 ...... ....................(requlres monltor) .. .. .. .. $ 1695.00 SPECIFIC AT ION S : - , - . - . ~ - ~N -OW $795 SAVE $2 • 80286 12M Hz Microproc esso r • Dual system clock sr,eeds o f 6M Hz and 12MHz • Alterna t ive cl ock se lctab le by both hardware and software • G2 GCK1 01 PC." AT co m pati b le ch ip set • Up to 4MB RA M c an be mounted d irect ly onboa rd in a variety of combin atio ns . • 6 expansion slots; four x 16•b it, two by B•bit • Ke ylock and Ha rdwa re Reset interfaces • CMOS Realt ime cl ock/ca lander with on board battery backup • 15 levels of int eru pt • 7 cha nnels of Direct Memory Access X18201 .................. ......................... $245 COLOUR YOUR WORLD WITH THE Only 10 left. COLOUR SCANNER The GS-C105 Colour scanner scans any colour or Black & Wh ite image into your IBM PC AT, PS-2 or compatible system without loss of hue. FREE SOFTWARE! The powerfu l Colour Maestro allows you to scan an image and then do colour editing in co lours you can create yourself! You can draw different shapes, modify objects, alter colours and edit a palette of 256 colours by using the commands on your pop-up menus. You can even design yo ur ow n font type s ize. RITRON RITRON c ( 286-16*) sf 286-20 80286-12 CPU 1 MEG RAM EXPANDABLE TO 4 MEG "16Mhz LANDMARK SPEED TEST 1.2M JAPANESE BRAND F.D.D 42M HARD blSK DRIVE 28mo ACCESS 101 EXTENDED "CLICK" KEYBOARD JAPANESE KEYBOARD SWITCHES !,INI CASE & 200W POWER SUPPLY 256K VGA CARD SUPA VGA COLOUR MONITOR (1024 X 768 ree) SERIAL, PARALLEL, GAME PORTS 12 MONTHS" AUSTRALIAN " PARTS & LABOUR WARRANTY DOS 4.01 IBM• COMPATIQLE ) 80286-16 CPU 1 MEG RAM EXPANDABLE TO 4 MEG 20Mhz LANDMARK SPEED TEST 1.2M JAPANESE BRAND F.D.D 42M HARD DISK DRIVE 28mo ACCESS 101 EXTENDED "CLICK" KEYBOARD JAPANESE KEYBOARD SWITCHES MINI CASE & 200W POWER SUPPLY 256K VGA CARD SUPA VGA COLOUR MONITOR (1024 x 768 Rea) SERIAL, PARALLEL, GAME PORTS 12 MONTHS "AUSTRALIAN " PARTS & LABOUR WARRANTY DOS 4.01 IBM" COMPATIBLE ( 386SX.. 21 ) 80386SX-16 Mhz CPU 42 MEG 28mo HARD DRIVE 1.2 MEG 5 114" DISK DRIVE 1MEG RAM 16 BIT 256K VGA CARD SUPA VGA COLOUR MONITOR (1024 x 768 Reoolu1 ion) SERIAL, PARALLEL, JOYSTICK PORTS MINI CASE & 200W POWER SUPPLY 101 KEYBOARD WITH DOS 4.01 IBM• COMPATIBLE · 12 MONTHS PARTS & LABOUR WARRANTY $1,895 $1,795 RITRON EXECUTIVE ( 386-32 ) RITRON 80386SX-20 CPU 1 MEG RAM 27Mhz LANDMARK SPEED TEST 1.2M JAPANESE F.F.D 42M HARD DISK DRIVE, 28mo ACCESS 101 EXTENDED "CLICK" KEYBOARD MNI CASE & 200W POWER SUPPLY 256K VGA CARD SUPA VGA COLOUR MONITOR (1024 x 768 Reoolu1ion) SERIAL PARALLEL GAMES PORTS 1 YEAR AUSTRALIAN PARTS & LABOUR WARRANTY DOS4.01 IBM• COMPATIBLE 80386-25 CPU NO CACHE 1 MEG RAM 32Mhz LANDMARK SPEED TEST 42 MEG HARD DISK 28mo ACCESS TIME 1.2M JAPANESE F.D.D 101 EXTENDED "CLICK" KEYBOARD SERIAL, PARALLEL, GAMES PORTS 256K VGA CARD SUPA VGA COLOUR MONITOR (1024 x 768 Resolution) MINI CASE & 200W POWER SUPPLY DOS 4.01 IBM• COMPATIBLE 12 MONTHS "AUSTRA LIAN" PARTS & LABOUR WARRANTY $2,975 $2,795 RITRON EXECUTIVE RITRON Ii ( 386-56) 80386-33 CPU CACHE ON BOARD MEMORY 1 MEG RAM 56Mhz LANDMARK SPEED TEST 85 MEG HARD DISK 18mo ACCESS TIME 1.2M JAPANESE BRAND F.D.D 101 EXTENDED "CUCK" KEYBOARD SERIAL, PARALLEL, GAMES PORTS SUPA VGA COLOUR MONITOR (1024 x 768 Reoolution) 512K VA CARD DOS 4.01 MNI CASE & 200W POWER SUPPLY 12 MONTHS "AUSTRALIAN" PARTS & LABOUR WARRANTY IBM• COMPATIBLE $2,395 RITRON EXECUTIVE c 386-41 ) 80386-25 CPU CACHE ON BOARD MEMORY 1 MEG RAM 41 Mhz LANDMARK SPEED TEST ' 42 MEG HARD DISK 28mo ACCESS TIME 1.2M JAPANESE BRAND F.D.D 101 EXTENDED "CLICK" KEYBOARD SERIAL PARALLEL GAMES PORTS SUPA VGA COLOUR MONITOR (1024 x 768 Reoolutlon) MINI CASE & 200W POWER SUPPLY 256K VGA CARD (256 COLOURS) •/ DOS 4.01 IBM• COMPATIBLE ~ 12 MONTHS " AUSTRALIAN" PARTS & LABOUR WARRANTY $3,195 , , ., • I COMPUTER BITS BY JENNIFER BONNITCHA Configuring your computer Over the next few months, we will take a close look at the CONFIG.SYS file and the various installable device drivers, describe what they are, and show you how to use them. We'll also discuss some DOS environment settings that you can try on your computer. Before starting, a point on the hidden files in last month's article. Two system files in MS-DOS and PCDOS have different file types viz: MS-DOS IQ.SYS MSDOS.SYS COMMAND.COM PC-DOS IBMIO.COM IBMDOS.COM COMMAND.COM IQ.SYS contains the operating system's default device drivers and since it interacts directly with the hardware, it is highly system-specific and is generally implemented by the computer's manufacturer. MSDOS.SYS receives all requests for service functions (such as opening and reading files) and channels the requests to IQ .SYS. The command interpreter, COMMAND.COM, serves as the interface between the operating system and the user by displaying the system prompt, accepting commands from the keyboard and processing the commands so they can be executed. DOS version 2.0 and higher has the ability to use "device drivers" - programs whi'ch affect the input and/or output to a non-standard device. These drivers are read into memory (RAM) from the root directory of the boot disc and remain active as long as the computer is turned on. Since the drivers are RAM-resident, a certain amount of memory will not be available to your programs. The device drivers must be loaded through a file called CONFIG.SYS in the root directory of the boot disc . In this file are statements telling DOS what devices are going to be used. CONFIG.SYS is a text file so you can .create the file directly from DOS, or through your regular word processing program provided you can save the file as an ASCII text file. Each time the computer is booted, the statements in CONFIG.SYS are read by MS-DOS. You can easily create the CONFIG.SYS file using the COPY command's ability to copy between devices. COPY can be used to send data from one peripheral device to another. The command is used in the same way as usual, except that one device name is included as the source of the data while another device or file is specified as the recipient of the data. You can copy from the keyboard (CON) to a file or perhaps the printer (PRN). For example, the command: copy fred .txt prn copies the file FRED.TXT to the printer, while the following creates a new file on the current disc: copy con: config.sys <Enter> Type each line required, pressing <Enter> at line end. Press <Ctrl Z> then <Enter> to end the copy. CONFIG.SYS files may contain some of the following: copy con: config.sys device=c: \dos \ansi.sys device=c: \himem.sys files=32 buffers=24 "Z (you hold down Ctrl and press Z) then <Enter> 1 File(s) copied You can also use function key F6 rather than <Ctrl Z> since when using DOS, it does the same thing (ie, it produces "Z). Ctrl Z is the (lAH) endof-file character. Note that while you use the COPY CON: command, you can make corrections on the current line only. Should you need to make corrections or additions to the file, DOS version 2.0 and higher has the ability to use device drivers: programs which affect the input and/or output to a non-standard device. 62 SILICON CHIP once again use your word processor or EDLIN. The internal DEVICE command is used to give MS DOS the filename(s) of any device drivers you want to install. This command can only be used as a statement within the CONFIG.SYS file. At boot time, if any of the statements in CONFIG.SYS are DEVICE commands, MSDOS stores them in computer memory. The general syntax of the DEVICE command is: device = [drive:] [path]driver[.ext] [argument] .The standard installable device drivers provided with MS-DOS are ANSI.SYS, DISPLAY.SYS, DRIVER.SYS, PRINTER.SYS and VDISK.SYS (maybe RAMDRIVE.SYS depending on your version of DOS and computer manufacturer), together with XMA2EMS.SYS and XMAEM.SYS (if you are using PS-DOS 4.0). If you purchase a new device such as a mouse or scanner, you generally receive device driver software with the device. These installable device drivers are installed using the DEVICE command. Once you have installed a device driver, make sure the device driver is in the directory you specify, in any DEVICE command. Since the DEVICE command will accept drive and directory entries before the driver name, you may consider grouping all your installable drivers in a single directory other than the root directory. This month we will look at the installable device drivers in some detail, reserving the best till last, ANSI.SYS. elude MONO, CGA (Colour Graphic Adapter), EGA (Enhanced Graphic Adapter) and LCD (Liquid Crystal Display). HWCP is the code page supported by the hardware. Hardware code pages are ready-to-use code pages that are stored in the display deYice 's read-only memory (ROM): 437 850 860 863 865 United States (default) Multilingual Portugal French-Canadian Norway N is the number of additional code pages (1 -12) that can be supported. This number is dependent on the hardware. Code pages may also be generated using the MODE command and these are called prepared code pages. MONO and CGA do not support other fonts, so N must be O; EGA can be 2; LCD can be 1. If you purchase a new device such as a mouse or scanner, you generally receive device driver software with the device. DISPLAY.SYS This device is a code-page-switching device driver supplied with MS-DOS 3.3 and 4.x. It's job is to implement code page switching on a display adapter. A code page is a table that defines the character set you are using. A character set is a country-specific or language-specific group of characters that are translated from the code page table and displayed by your screen or printer; ie, converting stored nu·m erical data into displayable characters. MS-DOS 3.3 has five different code pages, including a multilingual code page (850) which is designed to transfer data written in 19 languages such as Norwegian, Spanish, Swiss, German, French, Flemish and UK English. The other four tables are for the US , Portugese, French-Canadian and Nordic languages. Prior to version 3.3, each copy of MS-DOS had a single fixed code page, so copies of DOS sold in the US came with the appropriate code page, copies sold in Canada came with the French-Canadian code page, and so on. Problems arose when software written to run with one code page was used with a copy of MS-DOS that had another code page. Thus the introduction of the multilingual code page. Each code page character set contains 256 characters and a typical example is the set of letters , numbers and symbols (such as accent marks) found in French. To use the DISPLAY.SYS command: device=[drive:][path]DISPLAY.SYS CON[:] =(type[,[hwcp] [,(n,m)]]) TYPE is the display adapter in use. Valid values in- M specifies the number of sub-fonts that are supported for each code page. Thus the command: device=c: \dos \display.sys con:(egl ,437,2) instructs MS-DOS to load the DISPLAY.SYS driver for use with the Enhanced Graphics Adapter, together with hardware code page 437 , and support two prepared code pages. DRIVER.SYS This device driver supports external floppy disc drives, is supplied with MS-DOS 3.2, 3.3 and 4.x, and is valuable because it can be used to drive all MS-DOS supported drives, including logical drives. Physical drives are real whereas logical drives are the product of logic stored inside a computer. At boot time, MS -DOS determines the peripheral devices attached to your computer and then checks CONFIG.SYS for any installable device drivers. During the process, DOS assigns a unique letter to each disc drive. Systems with only one internal disc drive have the letters A and B assigned to the single drive (hence the ability to DISKCOPY A: B: on single-drive computers). The first fixed disc is assigned drive letter C. The syntax of the DRIVER.SYS command is as follows: device=[drive:][path]driver.sys /D:number [/C] [/F:factor] [/H:heads] [/N] [/S:sectors] [/T:tracks] where /D:number is the physical drive number ranging from O to 255 . The first physical flopp y disc "drive is number O and referenced as drive A by MS-DOS. Drive number 1 is the second physical flopp y disc drive, while Drive number 2 (which must b e external) is the third, up to 127. The first fixed disc (CJ is assigned number 128, the second 129 and so on to 255. MARCH 1991 63 COMPUTER BITS • • • • • IC specifies that the drive detect when the drive door has been opened and closed. If the door is open, the device driver will assume that the drive does not have a disc in it yet. IF:factor specifies the device type, where the default value is 2: lf:0 lf:1 /f:2 lf:3 lf:4 lf:5 lf:6 lf:7 160K bytesl180K bytes or 320K bytesl360K bytes 1.2 Megabytes 720K bytes (3.5-inch disc) 8-inch single density 8-inch double density hard disc tape drive 1.44 Megabytes IH:heads is the maximum head number, ranging from 1 to 99 with a default of 2, while IN specifies a nonremovable block device (such as a fixed disc). IS:sectors is the number of sectors per track ranging from 1 to 99 with a default of 9. Finally IT:tracks is the number of tracks per side on the block device ranging from 1 to 99 with a default value of 80. Thus the following command: device=c:\driver.sys ld :2 lf:7 specifies physical driver number 2 as a 1.44Mbyte disc. Since the DEVICE command is read after drive letters A, B and C have already been assigned, the disc is assigned drive letter D. This command: device=c:\dos\driver.sys ld:0 lt:80 ls:15 lh:2 le lf:1 tells MS-DOS to create a new logical drive on the first physical drive (/d:0) with 80 tracks per side (/t:80), 15 sectors per track (/s:15), two heads (/h:2), detecting the door open status (le) for a 1.2 Mbyte drive (/f:1). PRINTER.SYS This driver is another code-page-switching device driver supplied with MS-DOS 3.3 and 4.x and its job is to support the switching on several IBM printers (such as the Pro printer 4201, 4202, 4207, ·etc). Since it is designed for a tight segment of the market, the syntax of the command is: device=[ drive:J [pathJprinter.sys LPTx=(type[ ,hwcp[, ... ]] [ ,n]) Included with MS-DOS 2.x, 3.x and 4.x is a virtual (RAM) disc program called VDISK.SYS. A vitrual disc has the ability to use an area of RAM or main memory as a simulated disc drive. Programs may be copied to a virtual disc as if they were a conventional disc. While virtual discs provide greater speed than conventional discs, they should not be used to store data. This will prevent the accidental loss of information in case of a power failure. VDISK.SYS performs three functions: it installs the RAM disc in memory and assigns a drive letter; it formats the RAM disc so you can store files there (FORMAT does not work with a RAM disc); and it acts as an interface between MS-DOS and the RAM disc. The general syntax of the command is: device=[ drive:] [path]vdisk.sys[bbb] [sss] [ddd] [IE[:t]]IX[t:]] BBB is the number of Kbytes put aside for the virtual disc, from 1K up to the size of your system's memory; the default disc size is 64K bytes. SSS sets the number of sectors p·e r byte, where 128 is the default value and further acceptable sizes are 256 and 512. DDD sets the number of entries allowed in the root directory where the default·is 64 and the allowable range 2-512. Each directory entry requires 32 bytes and , if necessary, VDISK ~ill adjust your request size upward to fill out a complete sector. IE directs MS-DOS to place the RAM disc in extended memory while the driver itself is placed in low memory. This switch is only applicable to the PC-AT and above. Thus, you will receive an insufficient memory message from MS-DOS is you use the switch on a machine that does not have extended memory. IX is implemented in DOS 4.x and directs the operating system to place the RAM disc in expanded memory. Note that expanded memory requires the expanded memory board and an expanded memory device driver. The optional :t parameter tells MS-DOS the maximum number of sectors to transfer to extended or expanded memory at one time. The range is 1-8 with the latter as the default. The following command creates a one megabyte virtual disc one letter above the last drive in the system. It has a sector size of 512 bytes and a directory which may contain up to 64 entries, and is in extended memory with a maximum four sectors transferred tci extended memory at one time: device=c:\dos\vdisk.sys 1000 512 64 le:4 . LPTx designates parallel ports LPTl, LPT2 and LPT3 , however you can substitute port name PRN for LPTl, the first parallel port. TYPE is the printer in use (eg, 4201), while HWCP once again is ·the hardware code page. You can specify two or more code pages, provided they are enclosed in parentheses. N is the number of additional code pages that can be supported by the printer, thus the number is dependent on the hardware. The following command instructs MS-DOS to load PRINTER.SYS for the Proprinter 4201, together with code page 850 (multilingual) and support three prepared code pages: device=c: \dos\ printer.sys prn:=( 4201,850,3) 64 VIDSK.SYS SILICON CHIP ANSI.SYS The last installable device driver, ANSI.SYS, processes all character sequences sent from the keyboard and recognises certain character sequences as being command sequences. These command sequences direct ANSIS.SYS to modify keyboard input or to modify screen output. All ANSI.SYS command sequences begin with an escape character whose ASCII value is 27. Since this is a topic well worth spending some time on; it will be dealt with in more detail next month, together with more on the CONFIG.SYS file and a look at some DOS environment commands. SC MARCH MADNESS, FACTORY PRICES-ON COMPUTER CASES ry-;;:;;s;;t;;~ill be-th;;~v;-;;;e;;;y~;;;; ithiltis-p-;.;;f-;;sio~-;i' upright case. ONLY 28 UNITS LEFT Catalog Number : CAMTP This vertical case is perfect for your new or existing XT, AT or 386 computer. It has a smoke class flip cover to keep dirt out of your disk dr ives as well as front on/off switch and keyboard socket . Pr ovision for boar ds with eight expansion slots and dual fans to keep everything cool. This case has a 230 Watt heavy duty power supply. Dimensions 16" x 15.75" x 7.75". Plus features most cases can only dream about : * Provision for 3 x 5¼" and 2 x 3.5" drives. * Speed display in MHz with two inbuit settings to suit most motherboar ds. * 4 LED indicators with wiring installed. * Turbo switch . * Inbuilt speaker. * Complete with hardware kit. * Heavy metal construction. BE QUICK, never to be repeated only $275.00 ~--------------------------------------✓ Switching Power Supply - 150W This 150 watt power supply can be used as a direct replacement for IBM XT's and compatibles. It is much more rugged than the original supply, malting it ideal for systems with a number of peripheral devices. It comes complete with power leads for both hard and floppy drives as well as power connectors for the motherboard. Has full short circuit and overload voltage protection. Dimensions 225= x 140mm x 120=. r------------ This month only $99.00 r--------:---------, 1 1.8 metre Printer Cable 1 This one is of high quality and has IBM compatible connectors I on each end. Get a spare one today for .· times when you just have to · I those print and don't want your cable to I let you down. I Only $1 O.OOea 1 I I I I 1 I I I I - ( « ~lb - RodentMat Thisrodentmatissensitiveandgivesyou accurate comfortable tracking. It also helps prevent dust, dirt and dampness from clogging up your rodent. There is also a special rubberized backing to avoid slipping. Don't let your rodent get away from you. Thismonth only $5.00ea '\ 1 1 I I I I ~-----------------✓~------------------✓ IAN'S PERSONAL GUARANTEE .L • All products carry a 14 day money back guarantee ( except software and hard disks). • All prices indude sales 1ax. • All motherboards carry a full 12 month warranty. • All cards come with full documentation • All other products carry a full 3 month warranty. Due to Technica! oovances, products we supply may in some cases vary from those pictured. In all cases the products supplied are guaranteed ID perform to an equal or higher stanaard than those pictured - WHOLESALE ENQl,JIRIE WELCOME I V/SA i ·-------------------1 Send us this coupon to receive your FREE 1991 Catalogue: : Mr/Mrs/Ms:_ __ __ _ _ _ _ _ _ __ _ __ Electronic Solutions 5 Waltham St Artarmon 2064 PO Box 426 Gladesville 2111 Telephone: (02) 906 6666 Fax: (02) 906 5222 II Address:- -- - -- - - -- - -- - 1 Suburb:_ _ __ __ _ __ State:_ ____ Postcode: _ _ _ I I Note: Please do not send back this coupon if you purchased from us in 1990 or returned the I previously issued card to be included on the mailing list, as you will receive the catalogue I I automatically. 03/91 ~--------------------------~ Multi-purpose 1/0 board for IBM PCs Ever wished you had an "add-on" board so that your PC could directly control external devices such as domestic appliances & motors? Perhaps you want to experiment with process control or robotics. If so, this plug-in board and its accompanying software could be the answer. By GRAHAM DICKER The standard IBM parallel port is an under-used facility on most computers and can provide a terrific resource as an I/O facility. The main problem is that normally you need to breadboard up an interface to' use it. That's where this I/O board comes in. The MAX-386 I/0 board contains a versatile arrangement of facilities as outlined below: • 7 SPDT relay ports, each rated at 2 amps. • 8 switch or pushbutton input lin es, each only requiring a grounding contact: TTL compatible. • 1 digital to analog converter (DAC); 4-bit precision, 0-2.5V • 1 analog to digital converter (ADC); 20-bit precision (if using a 386-based system) or 16-bit (AT) converter. Using single slope conversion. • 4 open collector outputs able to switch 1 amp at voltages up to 60 volts DC; each output reverse protected. • 4 motor drive outputs (up to 40mA each) for low voltage (3V) DC motors. These can be also used for TTL outputs. • 1 programmable timer output (by linking DAC output into ADC input). Maximum output current 200mA<at> 5 volts. What has been done with the MAX386 board (or MAX for short) is to put together a lot of interfaces in a flexible configuration on one PC board. For example, if the DAC facility is required, the relay outputs can be used to control the outside world, or if more switch inputs are required, the relays can be wired up as an input multiplexer (MUX). Also, if more ADC channels are required, the same relays can be wired as an analog MUX. In some applications, more switched outputs are sometimes needed, so some combination logic can be worked out using the relays. The printer port Usually, the IBM PC has three standard addresses available for the printer ports: LPT1=378H, LPT2=278H, LPT3=3BCH. Each of these addresses has three registers, of which not all bits are available. Port availability The multi-purpose 1/0 board features a programmable timer, seven SPOT relay ports, four open collector & four motor drive outputs, & AID & DIA converters. 66 SILICON CHIP Although the MAX board is designed to be used in conjunction with a standard parallel printer port, some ports are not as standard as others. The main differences are that some inputs and outputs for status bits are inverted. Because of this, the software examples given are for the machi nes I have tested as being compatible. To run on non-standard ports, you may have to make small software changes to invert some lines. MAX uses the first register of the parallel port for the seven relays and the select line for reading the input switches. This line also doubles as the trigger line for the Timer/ ADC. · The second register in the set is used to read the multiplexed input lines and the output of the ADC/ Timer. .12v TTL OUT J3 0AC17 01 1N914 0/C OUT J4 5D ~; PORTA 378 J1 0020---"IWr--=+--I C 011 EM401 T ~: ~: ~:: ~:: ~:: RLA7 -12V ~: 0216 4C C 010 EM401' .,. .,. 3B .,. 2A 001 C 08 EM401 .f .,. .,. •5V 0.1J PORTS 379 J1 0315 16 TTL IN J3 4 A1 0413 0512 3 A2 12 2 81 06 10 1 82 0711 8 C1 IC6 74LS157 MUX 220k 13 TIMER OUT J3-1 0 7 C2 6 01 IC5 555 5 02 AOC IN J3-9 0791 "---------------------------+--◄ B EOc VIEWED FROM BELOW ~ EC ,. + 4.7 16VW+ s; 15 .,. 8 .,. MAX 1/0 BOARD Fig.I: the MAX 1/0 board interfaces to the parallel printer port of any IBM or IBM compatible computer and uses it to control relays, motors or TTL inputs. The last port is used to output to the DAC, TTL, Motor and O/C outputs As such, individual control of the last group is not possible, but a single output of a group or an entire group can be controlled appropriately. For example, if you are using the 1 amp O/C switched outputs, you cannot use the DAC but you could use two O/C outputs and two TTL outputs. The relay and input ports, how- 1 SEL A/B ever, can be used concurrently. Now have a look at the circuit diagram of Fig.1. The relay outputs The relay outputs are driven from bits D0-D6 from register 1. A 3.3kQ resistor limits the base current of the 7 BC547 inverter transistors and another 3.3kQ in the collector of these transistors limits the base current of the following 7 BC557 relay driver transistors. 24V relays with a coil resistance of 7400 are used to reduce the total relay current drain. With all seven 24V relays , the total current drain from the combined ±12V rails is only 220mA. Since each relay coil draws only about 30 milliamps, 1N914 signal switching diodes are adequate as back-EMF suppressors to protect the relay driver transistors. The relays used are DPDT types with the contacts paralleled for inMARCH 1991 67 creased current capacity. Each set of relay connections is terminated in a 0.1-inch pitch SIP header (JZ). TTL/switch inputs A total of eight inputs connect (J3) to a 74LS157 quad 2-input multiplexer, IC6. When the logic level at pin 1 is low (O), the 1-inputs (ie, Al, B1, Cl & D1) are selected. When the logic level on pin 1 is high (1) , the 2inputs (ie, A2, B2, CZ & DZ) are selected. The outputs from IC6 are then taken to the register 2 address inputs (379H) . On some computers, these lines are inverted and will need some software to sort this out. The select line to the 74LS157 comes from register 1 address (378H) bit D7. As the inputs are TTL compatible and float high, a grounding switch is all that is required to be detected as an input. Open collector outputs MAX provides four open collector (O/C) outputs and can be provided with a second option of sinking more current by using BD679 Darlington transistors instead of the BD135 devices for Q15, Q16, Q17 & Q18. The BD135 will sink about 1 amp whereas BD679s will sink about 5 amps. A 3.3kQ resistor limits the base drive current to the output transistors, while an EM401 diode provides Where to get the kit A kit of parts for the multi-purpose 1/0 board described here is available from PC Computers, who own the design copyright on this project. · The full kit of parts, including PC board and software disc, is available as an introductory offer to SILICON CHIP readers for $149 plus $10 postage and packing (offer valid until end of June 1991 ). The fully built and tested MAX board costs $269 plus $10 postage and packing . Or you can buy just the MAX PC board, instruction manual and software disc for $39.95 plus $1 O postage and packing. For further information, contact PC Computers, 36 Regent Street, Kensington, SA 5068 . Phone (08) 332 6513 or Fax (08) 364 0902. 68 SILICON CHIP Fig.2: the MAX board is single sided so it uses a number of wire links. Assembly shouldn't take long & you should have it up & running in about an hour or so. the back EMF protection in each case. These devices are driven from the buffered outputs of the 7408/00s, ICs 1, 2, 3 & 4. (Yes, these ICs can be 7408s or 7400s, as we'll explain in a moment). A single IC is used for each bit as some printer ports invert these lines. It is an easy change to replace the 7408 non-inverting device with a 7400 inverting device and hence use standardised software. A separate ground return line is available for the common emitters on J4. By writing applicable software, the O/C outputs can be used to easily drive stepper motors and an example program is provided on the accompanying disc. TTL/motor drive outputs These outputs are individually buffered by the four 7408 devices and, as mentioned above, each one may be interchanged for non-standard printer ports to fix the problem of inverted lines. The outputs of the whole package are paralleled to provide up to 40mA capacity which is adequate to drive PARTS LIST 1 PC board (only available from P.C. Computers) 1 26-way IDC to O825M cable 7 .309-251 24V 750Q coil DPDT relays 14 T0-92 transistor insulators 1 26-way IDC DIP header 1 22-way SIP header 1 18-way SIP header 1 5-way SIP header 1 0.5-metre length of tinned copper wire 1 8-pin DIP socket 4 14-pin DIP sockets 1 16-pin DIP socket Connecting the 1/0 board to your computer is easy - you simply plug it into a vacant expansion slot. Check that nothing shorts against the other boards. small 3V DC motors or normal TTL loads. D-A converter (DAC) The DAC is a 4-bit (16 level) device using a R/2R ladder network on the outputs of the four 7408 devices. In the normal configuration using the 7408 buffers, the DAC output is in inverted mode. The maximum output voltage is approximately 2.5V DC. A-D converter (ADC) The ADC is a unique design in that the usual way computer designers, like IBM and Apple, implement the games port is to use a timer IC like the 555, but always use a variable resistance from the timing junction to ground. This is fine if all you want to use is a variable resistor between specific values for measurements, but the real world measures voltages. The principle behind this ADC is that it uses the pulse width modulation (PWM) of the 555's pin 5 to set the threshhold reference voltage on its internal comparators. The 555 (IC5) is set up as a 1-second monostable and the trigger input (pin 2) is triggered from register O bit D7 going low. This starts the timeout. As the timer is timing out, the software counter counts program loops. The faster the computer the more loops that can be counted and hence (within reason) the higher the resolution. For example, a 45MHz 386 was tested with a compiled version of the sample software (using Microsoft Basic-7) and a count of 2 22 was reached with the input vo ltage at 5 volts, at the end of th e timeout. By comparison, my slow workhorse 4.77MHz XT will only count up to about 1600 using GWBASIC, a resolution of about only 12 bits. Assembly The MAX is built on a single sided fibreglass PC board with the minimum of wire links. A double sided PC board could have been used but the only lines that are picked up from the IBM bus are the power supply rails, +5V and ±12V. As such, the MAX board can be used with any computer provided that the IBM I/O compatibility is preserved, and an external power supply is wired to the 31-way 0.1-inch pitch edge connector. Fig.2 shows the layout diagram.The first step is to insert all the wire links and the resistors which lay flat on the board. The remaining resistors and the two capacitors can now be loaded, with the three DAC 4. 7kQ resistors being mounted upright. The TO-92 (BC5 5 7/BC54 7) transistors can now be loaded, but ensure that the TO-92 spacers are placed under each transistor between the transistor and the PC board. These spacers ensure adequate ventilation, mechanical stability, and that soldering lead temperatures are not exceeded. At this stage , the IC sockets can all be installed, followed by the remaining transistors an d diodes. The assembly can now be completed by soldering in the IDC pin Semiconductors 4 74LS08 quad dual input AND gates (IC1-4; see text) 1 NE555 timer (IC5) 1 74LS157 quad dual input multiplexer (IC6) 7 1N914 diodes (01 -07) 4 EM401 diodes (08-011) 7 BC547 transistors (01-07) 7 BC545 transistors (08-014) 4 80135 transistors (015-018) Capacitors 1 4.7µF 16VW electrolytic 1 0.1 µF metallised polyester Resistors (5%, 1/4W) 1 220kQ 3 4.7kQ 510kQ 183.3kQ headers and the relays.To test the MAX board, first do a visual check to ensure that there are no splats of solder or shorts on the board. Clean off all flux and apply a sealing coat to the bottom of the PC board, making sure that the edge connector is masked off. Plug the MAX board into the expansion bus of your computer and the · DB25-M plug into a parallel printer connector. The test programs supplied with the kit are all written in BASIC and can be used in interpreted or ·compiled versions. All of the programs will display an identification header and ask for the port address location being used. If you don't know, then try them all. No exits are provided from the program so the usual CTRL-C or CTRLBreak is the easiest exit. These programs can also be used as the basis of your own application programs. SC MARCH 1991 69 AMATEUR RADIO BY GARRY CRATT, VK2YBX A universal wideband preamp Ever needed a wideband preamp to boost signals into a frequency counter? How about compensating for the long cable run from the TV antenna, or a preamp for a shortwave receiver? This simple, wideband amplifier offers usable gain, respectable noise figure and absolute simplicity. After carefully considering the OM350/360, the uPC1651 and some of the newer HP amplifiers, we selected the MWA120, one of a series of amplifier modules available from Motorola, for our RF preamplifier. Our selection was based on ease of mounting , durability and, primarily, noise figure. It would be pointless using an amplifier with a higher noise figure than the receiver with which it is to he used! Table 1 shows a comparison of the relevant parameters of the d evices evaluated for this proj ect. No doubt there exist devices with a low er nois e figure than th e MWA-120 , but ease of mounting precludes their use, as some require surface mount techniques. Fig.1 (below): use this circuit to power the preamp if you want to use it as a masthead amplifier. The lOµH choke stops the output of the 78Ll2 regulator from loading the signal output from the preamp. The MWA-120 contains a single transistor and three resistors. The construction of the device ensures good bandwidth (up to 400MHz) and stability. All that is needed externally to complete the amplifier are bias resistors, plus bypass and coupling capacitors. We did consider making a discrete amplifier, similar to the one we described in the June 1988 issue. However the temptation of using a " prebuilt" amplifier was too appealing, and considering the trouble required to build the unit from discrete components and the inevitable larger physical size of a discrete unit, we decided against it. The amplifier we built uses two MWA-120s in cascade and a minimum of parts, and is hous ed in a diecast box fitted with male and female BNC connectors . This arrangement allows the unit to be mount ed on the front of a frequency counter, directly on top of a scanning receiver, TABLE 1 TO RECEIVER uPc1651 OM350 OM360 MWA120 HPMA2135 GND 70 SILICON CHIP or using the power feed system shown in Fig.1, at the antenna end of a long run of coax cable. In fact, the unit we built was mounted directly at a discone antenna, 10 metres up . Fig.2 shows the comp lete ci rcuit. As usual, component leads should be kept as short as possible and components should be physically small. Monolithic capacitors must be used. Each amplifier is housed in a TO-39 metal can which must be soldered at several poin ts to the ground plane of the board. We used a double sided PC board, the comp onent side being the groundplane. Fig.3 shows the PC board layout for both component side and solder si de. The top and bottom sides of the board are tied together with tinned copper wire pin-throughs in several places. If the preamplifier is to be used with a scanning receiver, a "gain" control could easily he added in series with the main supply. This would allow adjustment for optimum performance by enabling the user to reduce the gain in the event of signal overload . Remember that the amplifier has gain from 100kHz to 400MHz and is wideband in every sense of the word - no filters have been included in the unit to roll off the response to interfering signals, particularly VHF television. The preamplifier is powered via a Gain Vdd Noise Bandwidth 19dB 18d8 23dB 14dB 23dB 6V 12V 12V 5V 5V 5.5dB 6.0dB 7.0dB 6.0dB 4.0dB 10-1200MHz 40-860MHz 40-860MHz 0.1-400MHz 0-600MHz PARTS LIST 1 double-sided PC board, code SC06103911, 76 x 19mm 2 F29 ferrite beads 1 diecast aluminium case , 93 x 39 x 31mm 1 female BNC chassis mount connecter 1 male BNC chassis mount connector 1 3.5mm jack socket 1 5mm LED bezel Semiconductors 2 MWA 120 hybrid amplifiers (IC1 ,IC2) 1 4.7V 400mW or 1W zener diode (ZD 1) 1 1N4001 silicon diode (01) 1 red LED (LED1) View inside the completed preamplifier. Keep all leads as short as possible & don't forget to solder the metal cans of the MWA120s to the groundplane. The PC board is suspended by the wires connecting it to the BNC connectors at either end of the case. 01 1N40D1 _lJ Capacitors 5 0.1µF monolothic capacitors 2 .001 µF monolithic capacitors L3 LED1 INPUTr ~ 0.1 0.1 ~ Resistors (0.25W, 5%) 1 560Q 1 82Q .,. ~ OUTPUT OUT Miscellaneous 1 metre of 0.125mm enamelled copper wire, hookup wire, 50Q coax cable. INOGND L1, L2 : 3T, 25B&S ECU ON F29 BEAD L2: 12T, 0.125mm ECU ON 100n RESISTOR VIEWED FROM BELOW WIDEBAND PREAMPLIFIER Fig.2: the circuit uses two MWA120 ICs in cascade to give 28dB of gain. It can be powered directly from a 12V DC plugpack or from the circuit shown in Fig.I. DC socket, allowing it to be fed from an external power supply, such as a. DC plugpack adaptor. The circuit has an onboard zener regulator which ensures +4. 7V is always supplied to both amplifiers, regardless of input voltage. Dl is a blocking diode which prevents any accidental damage to the circuit should reverse polarity be in- advertently applied. Quite a few capacitors are connected to the +4. 7V supply to provide plenty of bypassing and thereby ensure circuit stability. We did consider using a 9 volt battery inside the unit as the power source, but the current drain is too high (75mA) to allow the long term use of a battery. The circuit board can either be etched from the PC artwork provided or made by carefully scribing the outline on one side of the board, and then cutting away the copper foil with '8 I 0 0 0 0 0 0 0 Fig.3: the preamp is mounted on a double-sided PC board with one side operating as a ground plane. Both sides of the PC board are tied together at several points using tinned copper wire pin throughs. L 0 0 0 , 0 0 0 0 0 0 0 O') O') M 0 M 0 T"" c.c T"" c.c 0 u 0 u(/) 0 0 0 0 T"" T"" T"" T"" .J (/) X Fig.4: here are the full-size patterns for the PC board. MARCH 1991 71 March bargains will save you $ from Sheridan's 1.44 Mb 3.5" Disk Drives NEW Teac 1 Year Warranty ONLY $135.00 IDE & Floppy Controller Card This card controls 2 Floppy drives plus 2 Hard disk Drives . Includes Cables . 1/0 PC Card * 1 Serial Port * 1 Parallel Port * 1 Games Port $29.95 The preamplifier was built into a metal diecast case to shield it from interference & to ensure stability. IE : I -------: 1 ------,........... i---.-- 1/0 PC Card * 2 Serial Ports * 1 Parallel Port * 1 Games Port ONLY $35.00 76 DIMENSIONS IN MILLI METRES Fig.5: you can make the PC board without etching by using this plan to scribe and cut the copper pattern (note: black areas to be removed). NOW ONLY $65.00 12 Volt Fans 80mm x 80mm Mini Hobby Motor Great for those broken remote control vehicles 9 VDC 25mm x 18mm These are quality new fans and $2.95ea $27.00 in lots of 10 only $9.95 LCD Display This un it is advertised elsewhere for $65.00 Contains 160 alphanumeric characters and you can program your own symbols or characters. Great for many projects and can be used with or without microprocessor. Includes data sheet OUR PRICE $9.95 Mini PCB Momentary push to make switch. As used in popu lar alarm re mote keys. Has hundreds of other uses . MOLEX 10 way PCB plug & socket. Great fo r use in alarms . This one can be used as a replacement for many commecial models . a scalpel. Fig.5 shows the required pattern (not to scale). The unit is mounted in a diecast box, fitted with the two BNC connectors. Th e PC board can eith er be suspen ded by pieces of tinned copper wire from the centre pins of the BNC sockets, or affixed to the bottom of the diecast box using double sided foam tape . Ensure that a connection is made from each socket to the groundplane (component side) of the PC board, to ensure stability. Because the amplifier mu st remain stable over a wide range of frequencies, the bypassing components have been selected to operate at differe nt fre quencies . This is w hy the supply line to each am plifier is bypassed with both .001µF and 0. lµF capacitors . The input to the pteamp uses the fe male BNC connector wh ile the output uses the male BNC plug. Indu ctor L2 is made by w inding 12 turns of 0.125mm enamelled copper wire onto a 100Q resistor. This forms an RF choke. isolating the two amplifi er stages and ensuring stabilit y over the wide operating bandwidth. Each MWA-120 must be bonded to the top foil of the PC board as shown in the layout. Prior to appl ying the soldering iron to the can of the MWA-12 0, scrape some of the n ickel p lating from the can with either a scalpel or a small file . This will ensure a good connection . We soldered the prototype in four places on each can , ensuring a good, low impedance earth. SC Where to get the parts $0.S0ea $9.00 in lots of 20 SHERIDAN ELECTRONICS, I 328 ELIZABETH ST, . (Cnr Kippax St. opp. Central Station & Dental Hospita l) VISA SHOP SURRY HILLS, NSW, 201 O MON· FRI TELEPHONE: (02) 281 7727 .._s.AT_ _ _ _ _ _ __ . 72 SILICON CHIP The diecast box is available from Geoff Wood Electronics . Phone (02) 427 1676. The BNC connectors are available from Farnell Electronic Components, phone (02) 645 8888, part No.GE35086H (male) and GE35007H (female). The MWA-120 should be available from VSI Electronics (Australia) Pty Ltd. Phone (02) 439_8622. WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS .. . WOOD FOR CHIPS .. . WOOD FOR CHIPS ... WOOD FOF.: C Why pay up to $150 for a label? Take a cl ose look at APPA mul tim eters. Look familiar? That"s because th ey're sold unde r diffe rent brand names. Ann that means you could pay a let more than you need to. We've seen the top of the line model selling at around S150 more ~~~ho~; t~~iiist~~ffhu~ r~ r~~~i ~aii~tt ~ i5 et 0 "Cl 0 ~ ~ i et a "Cl a ~ ModBI 93 • 1999 count • Lr!~deo~fmm high contrast LCD • 8 Functions - Vdc, Vac, Ade, Aai:, Ohms, Diode, Frequency, Capacitance • 0.5% de accuracy eii~"rfimv, 2V, 20V, 200V, 1OOOV Vac 200mV, 2V, 20V, 200v, 750V Ade 200µA, 2mA, 20mA, 2uOmA, 2A, 20A Aac 200µA, 2mA, 20mA, 200mA, 2A, 20A Ohms 200n, 2kn, 20kn, 200kn, 2Mn, 20Mn Frequency 2kHz 20kHz, 200kHz Capacitance 2nF, 20nF, 200nF, 2µF, 20 AIso ,ai lable with transistor tester in place .of capacitance ran_ges, (Model 93T) $14£.80 ModBI 96 • 3 1/2 digit plus 41 segment analog bar graph • Autoranging or r,mual selection • 6 functions - Vdc, Vac, Ade, Aac, Ohms, Diode • Water resistant • Data hold • Memory offset Ade 200µA, 2mA, 20mA, 2uOmA, 2A, 20A Aac 200µA, 2mA, 20mA, 200mA, 2A, 20A Ohms 200n, 2kn, 20kn, 200kn, 2Mn, 20Mn $166.80 :i:(.) et a "Cl Cl ~ ~ ~ et a "Cl a ~ ~ ~ et a "- Cl a ~ ~ i5 et a "Cl a ~ MEMOREX GENUINE PREMIUM GRADE DISKS 51/4 2S/2D $16.95 per 10 5 1/4 2S/HD $24.95 per 10 3 1/2 2S/2D $24.95 per 1O 3 1/2 2S/HD $49.95 per 10 Comms Port 2? AT&M KITS • P:~:: t~~~Jif};f:,,!~1if;~°,,'nts • The 96 is water rssistance for industrial uss • Shockproof for a drop of 1.5ml • Built-in tilt stand • Automatic power-off • MBet /EC 348 Class II and UL 1244 standards for safB opBration eti~"rfimv, 2V, 20V, 200V, 1OOOV Vac 200mV, 2V, 20V, 200v, 750V ~ Save Problems and Cost with Look at thB fBaturss • LargB high co ntras/ display - ThB 96 and 98 havB analog bar graphs too • Colour codBd input tBrmina/s and .function switch for Basy S8tt1ng ModBI 98 • 3 1/2 digit plus 41 segment analog bar graph • Autoranging or manual selection • 8 Functions - Vdc, Vac, Ade, Aai:, Ohms, Diode, Frequency, Capacitance • Data hold • Memory offset RangBS Vdc 200mV, 2V, 20V, 200V, 1OOOV Vac 200mV, 2V, 20V, 200v, 750V Ade 200µA, 2mA, 20mA, 2u0mA, 2A, 20A Aac 200µA, 2mA, 20mA, 200mA, 2A, 20A Ohms 200n, 2kn, 20kn, 200kn, 2Mn, 20Mn Frequency 2kHz, 20kHz, 200kHz Ca~acitance 2nF, 20nF, 200nF, 2µF, OµF S214.80 ModBI 76 ComponBnt TBstBr Does the things your multimeter doesn 't! • Capacitance 200pF to 20uF • Resistance 200n to 2oMn • Transistor hfe and lceo • Diode displays Vf at 1mA e LED displays Vf at 2Ma and 1OmA • Battery tests 9V and 1.5V cells • SCA Pass/Fail test $142.80 We carry the full range of these great kits. Locally designed and aeveloped. Top quality components. Comprehensive instructions included. Why develop your own d rcuits when these building blocks are already available? Kit Description 01 02 03 04 05 06 07 08 09 10 11 12 13 14 16 17 18 19 20 21 22 23 24 25 Price 3 dig it Counter 4 dig it Cou nter 3 1/2 digit DVM 1Hz Timebase Fibre Optic Modem Reciprocal Calculator 10MHz Timebase V/F Converter FN conve rter Quad Power Supply 1OMinute Controller 6 dig Batch Coun ter 3 Digit Cou nter 3 1/2 digit LCD DVM 10kV Isolator Storage Adaptor 8 bit UART 6 dig Up/Dn Counter IR Transceiver Multi-Timebase 16Ch Tranmitte r 16Ch Receiver 2213 Com ms PCB 22/3 Radio Modem $33 .60 50. 40 59 .40 22 .40 75 .00 29. 411 45 .60 42.60 42. 60 60.60 46.20 75.00 65.40 42.60 70. 80 193.80 56 .00 69. 60 39 .60 42 .60 77.40 77.40 34.80 66.60 Warn ing - These devices are definitery NOT for beginne rs 11 you're keen to add l hat second corn ms port to your PC then take a close look at... NS16550A UART with FIFO's • Runs al l ex:sting 16450 software • ~n~l~i ~~~ff)1~tmitter and F1~6i~e!oa;;d~~~e~~~ ~{ r1 ~pyte inte rrupts presented to CPU . • Adds or deletes standard asynch comms bits to or from se rial data • Holding and shift registers eliminate need for precise • ~;Jeh~iontrol functions • ~~/M~~g~~::;~f~;fsf;~~ial • Internal diagnostics • Programmab le baud rate generator $55.60 NS16450 UART • Adds or deletes standard asynch comms bits to or from se ri al data • Holding and shift reg isters eliminate need for precise synching • Programmable baud rate • &eondei~tfontrol fu nctions • Line break gene ration and detection • Improved specification version of 8250 below $27 .00 AT &M Digital Storage Adaptor Kit INS8250 UART Low cost accessory for your scope. Converts incoming analog signals up to 20kHz into a stream of 8-bit data wo rds for storage in 2048 word memory. Ideal fo r one-shot observations. Replay as many times as you like. See description in E.A. December. Complete ki t (AT&M 17) with top quality components and full instructions is just $1 93.80 Matching case (ATM17-01) $27.60 SCOPES 60MHz 3 Channel Scope • 5mV/div de to 60M Hz • 5ns/div to 0.5s/div A and B COS5060B ($1593.90 ex tax) Popular choice UART in most PC's $20.40 DS1488 Quad Line Driver • Conve rts TTL levels to RS-232C • Current limited output ±10rnA typ • 300n powe r- off source impedance • Simple slew rate control • TTULS com patible 90c DS1489 Quad Line Receiver 40MHz 2 Channel Scope tests Logic too! No need to tum your head to read th is mu ltimeter. The reado ut is right there in tre probe' Auto and manual ranging, 3.5. digit large 1•mm LCD display - all I.n a handy probe. Logic testing function for CMOSITTL. Data Hold button, Diode. test, Continuity buzzer. Display shows all functions. Protected to 250V • DC Voltage from 200ml' to 500V • AC Voltage from 2V to 500V • Resistance from 200n to 20Mn • AC/DC Curren t to 200mA • Continuity check to 2kn • Log ic Testing to 1MHzand 1µs • Diode TeS t 2V All this fo r just $55.00 BNC ~ Terminators 51Q $6.9 SerialTest serial data analysis on your PC This is an MS-DOS software and cabling package which enables technicians and engineers to pertorm serial data corn ms analysis. It offers sophisticated problem solving fac ilities at a frac[ion of the cost of dedicated hard•,1are systems. SerialTest provides a window onto RS232 lines opera!:ng either as a passive observer or actively sending 6 ~~~~~~fg~~o r5~Bl'~iiig;mulate Triggers can be defined based on error conditions or data to initiate or terminate monitoring sequences. • Handles baud rates up to 115.2kbaud. • View each byte in ASCII or EBCDIC, decoded to hex, decimal, binary or octal vicu!Mt.. CurrentConfiguNtion: l'lyConfignratio• ~~deciNI Dda- - -- - TI ~ &C hl 6E 0D M package • Programmable thre shold • Buil l- in hysteresis e Withs tands ±30V ~ b1 b[ N bi~ br ~ ~ ~0DOATINblnn~~W~OAMbln i].:.i,bF bD 1,5 b? bi OD 00 S - Sedrch buffer by ~-1/tilit',IFur,ctionsChanr! e U~rk,'.,g Dir~ctof"j P"sh to OOS CTRL-S- Seirch huffe - -- - - - B!:,t~ Jnfornation2711, of ASCII Bi11<1"'J Oct Dec Hex Ji...,stM,p ltl1K 088HlHll 025 21 15 80 80:02 :29.178 1!,,/te Si~1w.ls: RTS X CTS 90c Errors: OOJerrun DSH X CD Frd11ing OTB Pdrit9 • Writes cap tu red data directly to disk to allow maximum capture buffer • CRC checksum calculations • Auto-configuration to any of the 20MHz 2 Channel Scope , l r comms ports 1 to 4 e 5mV/div de to 20MHz - · • Time-stamping (absolute and • 20ns/div to 0.5s/div " 4t ,, relative). including delta time COS5020 $882.90 • calculafions e Split line DTE rJVer DCE display ($756 .80 ex tax) $395 plus sales tax Send $1 Ofor a demo disk, .... .. ,_,_ _-""-'-,,""--'"-' -·"'-· refundable on purchase. COS5041 ($1176.50 ex tax) ~ a tJ -,, a )J ri ::r: ~ a a tJ -,, a )J ri ::r: ~ ~ a tJ -,, a )J ri ::r: ~ a a tJ -,, a )J ri ::r: ~ MODM~~~m~~~~fil=~Nbl ;;i::~~:~:;;i;;1 ~ ~tlitffl ~~Mm~ir b7b962b26F/,EI! bl f,C f,1 62 b! 6D: $1859.00 • Four totally separate receivers/ • 5mV/div de to 40MHz • 20ns/div to 0.5s/div Main • 0.2)!5 to 0.5ms/d iv Delayed Handy Probe Multimeter Ideal for tight spots $1372.50 ~ a tJ -,, a )J ri ::r: ~ a a tJ -,, a )J ri ::r: ~ ~ GEOFF WOOD ELECTRONICS PTY LTD 229 Bu rns Bay Road, (Corne r Beatrice St.) ING IN Nsw Lane Cove West, N.S.W. P.O . Box 671, Lane Cove N .S.W. 2066 Telephone: (02) 428 4111 Fax: (02) 428 5198. 8.30am to 5.00pm Monday to Friday, 8.30am to 12 noon Saturday . Mail Orders add $5 00 to cover postal charges. Next day deli very in Sydney add $5.00. All prices INCLUDE sales tax. Tax exempti on certificates accepted if li ne value exceeds $10.00. BANKCARD, MASTERCARD, VISA, CHEQUES OR CASH C HEERFULLY ACCEPTED Cl tJ -,, a )J ri ::r: 'ii V') REMOTE CONTROL BY BOB YOUNG The development of digital proportional servos Last month, we discussed the difficulties that arose in the very early development of proportional control and examined some of the primitive systems which preceded the modern digital R/C system. The most primitive was the galloping ghost system which ultimately led to the early analog systems. It is difficult for modern modellers, who see only digital sets which are virtual clones of each other (even down to interchangable servos), to comprehend just how many different types of systems were in operation in the early sixties. A trip to the flying field in those days was really interesting, for you never knew just what would show up next. This was enhanced by the large numbers of modellers who scratchbuilt their own equipment. Thus it was possible, on one day, to see singlechannel valve sets operating alongside tuned reed, tuned filter, galloping ghost, Walter Good, analog proportional and digital proportional CLOCK RESET CH1 OUT CH2 OUT 17. . ._____________.I J7_________________ CH3 OUT CH4 OUT Fig.1: serial to parallel conversion is performed in the remote control receiver. In this process, a series of pulses from the transmitter are converted by the receiver to servo control pulses. 74 SILICON CHIP sets, both home made and commercial. All of these early attempts were useful but far from satisfactory, lacking accuracy, speed and power in the control actuators. They also lacked reliabilty, simultaneous operation and the required number of channels. Those days have long gone and while I do not miss the unreliability, I do miss the enthus iasm generated from our quest for perfection. However, in the very early 1960s there occurred one of those quantum leaps in technology that result in one system being adopted as an industry standard, due to the fact that it delivers exactly what the application calls for. Such was the case with the development of the digital proportional system as we now know it. It cured all of the above problems in one fell swoop and gave unlimited numbers of truly proportional and simultaneous controls, coupled with unheard of reliability. Thus did the new age of R/C modelling sweep away the old. At the very heart of this revolutionary discovery - and believe me it was truely revolutionary, breaking away completely from all lines of development to that date - was the proportional servo as we now know it. So comp lete was the development by Doug Spreng and Don Mathers (USA) in the early 1960s, that the concept remains virtually unchanged to this very day. Our article traces the changes in technology that have improved the operation and reliability of the concept, but the Spreng and Mathers touch is still easily identified in the most modern PCM equipment available today. The system they developed was the Pulse Position Modulation (PPM) system in which a series of pulses are transmitted in serial form and converted in the receiver (Rx) via a serial to parallel decoder (see Fig.1). This results in a number of output pulses, usually from 2 to 8, with the pulse width directly related to the width of the transmitted pulse. This in turn is directly related to the position of the control stick on the transmitter. Usually, pulse widths run fully counterclockwise (CCW), 1.0ms; neutral 1.5ms; and fully clockwise (CW) 2ms. Full control is available over this range in steps determined by the sensitivity of the servo amplifier. This minimum step is termed the "minimum impuls e" and is typically .005ms. Thus , approximately 100 steps are available each side of neutral (centre) on a good quality servo. These steps are so small that to all practical purposes they cannot be felt, and the servo appears to be slaved directly to the transmitter stick. This is the concept of "proportional control". Herein lies the secret of success of the digital system: fantastic servo performance. Fast, powerful and extremely accurate, it fulfilled all of our dreams. Here was the most clever development in model electronics and it has yet to be surpassed. For this reason, I have chosen to present the servo first in the following series of articles. Whilst it is traditional to start with the transmitter, I feel that delivering the control pulse to the servo input is the easy part. What takes place in the servo is where the magic resides. The question which must be dealt with first is just how do these servo amplifiers work? How do they convert the pulse width information into a clockwise (CW) or counter-clockwise) CCW instruction? i-•--5 5 0 I ---6 28 3 .•~rl 11:-, •,~rlO ---+-- - -1 0 4 1,5,24,26,27 screw 2 output wheel 3 output arm 4,6 case, top 7 right rack gear 8 left rack gear 9 pot drive gear 10 second intermediate gear 11 pot shaft 12 drive gear 13 first intermediate gear 14, 15 gear pins 16 case, centre 17 motor, 1OW 18 pot wiper contact 19 pot element, 1.5kQ 20 fibre washers 21 decoder PC board 22 grommet 23 connector assembly 25 case, bottom 28 output shaft cap 1 13 ~ . 15 - -- ---,----::---- · - - -- - - 14 ~~~ 16 -------i ' ----17 ~-®·------+-1--20 20------t--~. 4 27 27---__,__; : _ _-i-----· e , 22----•o 23✓ F 24 24 Closed loop feedback Essentially, the modern R/C servo is a closed loop feedback servo in which a pulse is fed to the servo amplifier and compared to the output pulse from a reference generator on the servo amplifier board. This reference pulse is controlled by the position of the servo output arm via a potentiometer. The input pulse and the reference pulse are applied to a summing junction and the resultant 26---& KPS11-11A Fig.2: this exploded diagram shows all the parts used in a typical servo control. The key elements include the decoder PC board (21), the motor (17), a servo feedback pot (18,19), various gears & the output wheel or arm (2,3). Modern servos are built around dedicated IC servo chips (eg, the NE544 from Signetics) & are very compact & reliable. MARCH 1991 75 ,---------- -- ----- --- ----- - -- ---, \ \ I 10011 \ +5V ' I I I 22k 2.2k GNO I I I I l .,. .,. Rl 4.7k 22k .,. Cl Fig.3: an early servo decoder and drive amplifier, using discrete components throughout. Effectively, the motor drives the pot (VRl) until the pulses produced by Ql and Q2 match those at the input. error signal is then available to control the power and direction of the servo motor's rotation. The motor drive circuitry is arranged in such a manner that the servo always attempts to cancel any error (zero output to the summing junction), at which point the servo comes to rest until another error appears. Fig.2 shows an exploded diagram of a typical servo, in this case one using linear and rotary output arms. 100U As we have control over the input pulse width from the transmitter, we therefore have control over the position of the servo output arm. The accuracy of the servo is dependent upon the servo amplifier sensitivity which is termed the minimum impulse power. As noted previously, a good servo will deliver up to 100 steps each side of neutral and so we have complete control over the servo output arm. It is slaved precisely to the REFERENCE GENERATOR OUT PULSE IN SUM APPLIED TO PULSE STRETCHER ____ n'------------- .., MINIMUM IMPULSE NEGATIVE SUM WHEN INPUT SHORTER THAN REFERENCE GENERATOR Li Fig.4: this diagram shows what happens in the decoder circuitry of Fig.3. Pulses from the input and reference generator are compared to generate an error pulse which is applied to the servo motor. 76 SILICON CHIP .,. transmitter control stick, hence the name proportional control. Servo circuit Fig.3 is a circuit diagram of a very early American servo, the Orbit PS4D, manufactured by one of the pioneers, Bob Dunham. Orbit lead the way for many years in high quality radio control systems and Bob Dunham was a top contest flyer in his early years. Transistors Q1 & Q2 form a one shot multivibrator which is triggered by the leading edge of the incoming pulse from the decoder output. Interestingly enough, this servo worked on a negative input pulse, whereas the industry standard is now positive. This one shot will generate a pulse of opposite polarity to the incoming pulse from the decoder and is called the "reference generator". The width of this pulse is controlled by the position of servo feedback potentiometer VR1, which is in turn related to the position of the output arm on the servo. This pot is usually driven by the output gear of the servo mechanism. Both of these pulses are applied to the summing junction R1, R2 . Fig.4 shows the effect at this summing junction. Briefly the output of the sum- INFRA RED NIGHT VIEWER A limited purchase of some 6032A tubes which were removed from new, and near new equipment allows us to offer this Incredibly priced IR NIGHT VIEWER KIT BARGAIN! You could payover$2000foraviewer which uses a similar tube. All the tubes are "AS NEW", and are GUARANTEED not to have any blemishes! THE PRICE OF THIS UNREPEATABLE BARGAIN??: ONLY $259.00 Fig.5: Several servos are shown in this photo, with the one on the right being a currently available model. ming junction will be a pulse of either negative or positive polarity, depending upon which pulse is the longer. This pulse is then applied to the bases of Q3 & Q4, a PNP/NPN pair. Depending upon polarity, one of these transistors triggers and the output is applied to the following pulse stretcher/Schmitt trigger. The output of this network is ap plied to motor drive transistors Q7 & QlO which in turn drive the motor CW or CCW, depending upon the polarity of the longer pulse at the summing junction. The motor is driven until the potentiometer causes the Ql/Q2 one shot to deliver a pulse to the summing junction of equal length to the incoming pulse from the decoder. At this point, the motor will switch off and the servo will take up its new position until there is a change in the width of the incoming pulse, whereupon the process will start all over again. Diode pair D3 & D4 prevent both sides of the servo amplifier from switching on simultaneously which would instantly destroy the output transistors. C2 is a noise suppression filter. Notice that one side of the armature is connected to the motor case for additional shielding. Feedback resistor R3 changes the pulse width of the reference generator order to shut the motor down ahead of time, so that the servo does not overshoot and go into oscillation about neutral. This is a critical function, for if there is too much damping, the servo shuts down early and the centring accuracy is badly affected; too little damping, and the servo hunts or oscillates and servo current consumption shoots up and the output transistors start to run hot. The ideal result is called "dead beat" damping in which the servo runs to the point and stops instantly. In practice, this is very difficult to achieve and I have found that it is best for centring accuracy if the servo overshoots and moves back just once. This gives a very accurate neutral. Another problem with closed loop servo amplifiers is that a certain amount of deadband must be introduced into the system if the servo is ever to come to rest and not sit there oscillating. Capacitor Cl across the summing junction performs this function. The value of this capacitor is critical in establishing the centring accuracy of the servo. If it is too big, the deadband is too wide and the servo will be sloppy around neutral. If Cl is too small, the servo will jitter, causing excessive servo current drain, and probably damaging the output transistors and motor. As you can see from Fig.3, this amplifier had quite a large component count and could only be fitted into fairly large servos. Several such servos are shown in the photo of Fig.5. The photo of Fig. 7 shows a servo made by Silvertone Electronics. Note the double deck PC board in the Silvertone unit. This was quite a ...... includes a 6032A tube (as per sketch) electronics kit, ample plastics for the case and a 75mm round I.R. filter: Can be cut to suit your torch. All you need to finish off this kit is a good torch, and any old camera lens, small magnifying glass or an eye piece: The lenses can be obtained from camera repairers, camera shops, or can be recovered from old cameras. VISIBLE LASER DIODE POINTER - KIT Based on a "State of the art" 3mW Visible Laser diode, and a matching heatsink/collimatorassembly. The circuit even has provision for digital switching: Communications, security, etc. This complete kit includes everything you need to make the pointer illustrated except for the batteries (3 AA cells). Our SPECIAL price for the VISIBLE LASER POINTER KIT?? ONLY 239.00 Also available is a kit with the same PCB and all onboard .components, but using an Infra-Red laser diode and it's matching heatsink/ collimator assembly: This can be used for communications, security etc!! ONLY$99.00 LOOK AT THESE BARGAINS Some of these are in limited supply so be quick. All are NEW. Hall Effect IC's. data supplied ............ 1o for $20 Stepper Motors ............ ... ... ........... 2 for $20 Small 3 12VDC motors..... ................. 2 for $ 5 20VDC to 1SKVDC (S00uA) converters .......$30each 0.BmW HE-NE Laser tubes ............. .... ...... $120each Stereo (Dual) VU meters .........................•.•...$4each 150ohm 25W wirewound pots............ 2 for $ 5 [Z][B OATLEY ELECTRONICS PO BOX 89, OATLEY, NSW 2223 Telephone: (02) 579 4985 Fax No: (02) 570 7910 Certified p&p: $5 inAusl. NZ (Airmail):$1 D Fax orders are accepted with credit card payments. MARCH 1991 77 ,--- -- - --- - -- - -- ---- ~I I I I I I 330!l I I 10k - 1 Q6 AT188 I VR1 + 2.2k .,. 01 1N914 +4.BV I I 100!l 0.1 I I I I \ I I +GND 0.1 3.9k 47k100k 27k .,. .,. ... .,. 1.5I BP * ADJUST TO SET DAMPING t ADJUST TO SET DEADBANO problem to produce and service. To compound rny problems, I always used an emitter follower stage on the input to buffer the servo from the decoder, giving a transistor count of 11 compared to the 10-transistor Orbit servo . The relentless demand for lower cost and smaller servos eventually forced us to use the circuit in Fig.6 which is simpler in construction. It was used by many manufacturers but it never worked as well as the Schmitt trigger amplifier of Fig.3. It was prone to several problems, amongst which were non-linearity and changes of deadband and damping with servo position. One thing both of these discrete amplifiers shared in cornrnon how- ever was the fact that both required a centre tap on the battery pack and this type of servo was cornrnonly referred to as a "4-wire servo". Motor resistance was typically 3Q as against the 11Q motors used in the modern IC servo. The four wires were signal, usually a colour; positive 4.8V, usually red or orange; centre tap +2.4V, usually white; and ground or zero volts, usually black or brown. Note that reversing the direction of one of these servos requires the two end leads on the feedback pot to be reversed, and the two armature wires on the motor to be reversed. Do not reverse the red and black wires, for all that will achieve is a burnt out servo. One point here is that 3-wire servos can be used in 4-wire systems Fig.7: this photo shows a servo made by Silvertone Electronics. Note the doubledeck PC board with the parts crammed in to save space. Also visible is the drive motor and feedback pot. 78 SILICON CHIP Fig.6: this was a later and simpler proportional control receiver which was the first to use a DTL (diodetransistor-logic) to reduce the component count. but not the other way around. Technology finally came to the rescue of the servo manufacturer in the form of the IC servo amplifier. There were many early versions of these chips and most of them suffered serious defects of one kind or the other. Sarne of these were voltage instability, output drive latch-up in which the chip just simply melted down, non linearity and a host of other small problems, not the least of which was loss of drive voltage across the output transistors. Time and perseverence finally rid us of these little challenges and the present generation of IC servo amplifiers are immaculate in their operation. Reliable, accurate and extremely small, especially when made in surface mount form, these amplifiers have given the modeller true proportional control. I wonder how many truly appreciate the incredible cleverness of the human minds that conceived these devices? One very popular version of the IC servo is the Signetics NE544. Here in one small package are all of the features that we dreamed of for many, many years. If you ever have occasion to use one of these little devices, please take the time to marvel at the wonder of it all and spare a small thought for Don Mathers and Doug Spreng, two people who helped to make it all possible. SC Fluke 45 I ' 1• ~ f' !; 1: •:I;•; The dual disp ay bench multimeter with simultaneous display of two parameters: 16 measurement functions and two 5-digit displays for maximum versatility in a single instrument ■ Multi-function vacuum fluorescent dual display ■ True RMS voltage and current, including A.G. + D.C. ■ RS-232 interface standard, IEEE-488.2 option ■ Frequency measurement to 1 MHz ■ dB measurements with selectable reference impedances of 2n to 8,ooon and audio power from 2n to 16fl ■ Compare [Hi/Lo/Pass) function for quick in-tolerance tests ■ 0.05% D.C. current accuracy for 4-20 mA current loop service ■ Touch Hold~ Relative and Min Max ■ Audible continuity and diode test ■ Optional rechargeable battery, carrying case, rack mount kit, and PC Software Package ■ Closed-case calibration ■ D.C. Voltage 0.02% - A.G. 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Top of the range - the world's most wanted handheld multimeters with 11 functions and 40 ranges. ■ Three year warranty ■ Min Max Average recording mode with Min Max Alert™ ■ Frequency, duty cycle and capacitance measurements ■ 1000V rms input protection; Input Alert™ detects wrong input jack connections ■ 3¾ digit, 4000 count display ■ ■ Fast analog display ■ Touch Hold®and Relative modes ■ Splash proof and dust proof case; EMI shielded ■ Protective holster with Flex-Stand™ ■ Safety-designed test lead set ■ Made in U.S.A. 83 - 0.3% basic D.C. accuracy Frequency, duty cycle and capacitance $399 ex tax - $466 incl. tax 85 - 0.1 % basic D.C. accuracy $480 ex tax - $560 incl. tax 87 - True R.M.S., 4½ digit, 19,999 count mode lms peak hold, Back lit display. $580 ex tax - $676 incl. tax. Fluke 70 Series Analog/Digital Multimeters. Unbeatable performance and value ■ Three year warranty ■ 3½ -digit, 3200-count display ■ 31-segment analog bar graph ■ Single rotary dial to select all functions ■ Autoranging and automatic polarity selection ■ Batterysaving "Sleep Mode" powers-down display if you forget ■ Tough, textured case resists drops and rough handling ■ Touch Hold® (Fluke 77) ■ UL 1244 listed ■ Made in U.S.A. 73 - D.C. Voltage 0.7%, A.G. Voltage 3% Autoranging $150 ex tax - $175 incl tax 75 - D.C. Voltage 0.5%, A.G. Voltage 2% Autoranging with range hold, audible continuity/diode test $240 ex tax - $280 incl 77 - D.C. Voltage 0.3%. A.G. Voltage 2% Touch Hold® $325 ex tax - $379 incl tax Also call us for Signal Generators, Power Supplies, Counters, and any other T & M requirement. Full _range of Accessories: test leads, probes, current clamps etc. t1::r:r'1-fBs# T & M PTY. LTD. Call Tim Wortman the specialist Fluke Distributor TECH-FAST T & M PTY. LTD. 14B MAXWELL STREET, TURRAMURRA N.S.W. 2074 TELEPHONE: (02) 988 3865 FAX: (02) 988 3861 I PRODUCT SHOWCASE I is up to 30 metres. Power may be obtained either from the keyboard cable of an IBM PC via the supplied adaptor or from any 6V DC source via an optional adaptor. For further information and pricing, contact Electronic Solutions, 5 Waltham St, Artarmon, 2064. Phone (02) 906 6666 or fax (02) 906 5222. New synthesised signal generators Low cost serial to parallel converter This compact converter can be set up to work in one of two ways: serial to parallel or parallel to serial. The incoming or outgoing baud rates can be set at 110, 150, 300, 600, 1200, 2400, 4800 and 9600. DIP switches allow selection of parity, DTR and CTS open/closed and allow the RX and TX pins (2 & 3) to swapped around. Transfer distance of the serial line The HP 8664A and 8665B synthesised signal generators offer frequency coverage and spectral purity to 3GHz and 6GHz, respectively. They have excellent stability with low phase noise and low spurious outputs. Additional features are less than 1240dBc single sideband phase noise with a 20kHz offset at lkHz, spurious signals of less than 90dBc, amplitude and frequency modulation, and optional pulse modulation with 5ns rise and fall and an on/off ratio of better than80dB. The Hewlett-Packard HP 8664A is 20-inch high-resolution colour monitor for desktop publishing Computer users involved with CAD and desktop publishing systems will be interested in this newly released 20-inch high resolution colour monitor from Philips. Designated the Bril,l iance CM-5000, it can operate at any scan frequency from 30kHz to 64kHz and is suitable for use with IBM PC/XT/AT/PS-2 computers , the Mac II and SPARC workstation users. The monitor's picture tube has a .non-glare electrostatic free dark glass front surface and produces correctly sized displays for the three most commonly used formats, allowing users to move between applications without the need to adjust the picture height and width each time. Video bandwidth is 110MHz and resolution is 1280 x 1024 pixels, with excellent convergence at both centre and corners of the picture. Mean time between failures (MTBF) is 50,000 hours, which is claimed to be twice as good as similar monitors. Input connections are via a 15-pin D connector, with an optional adaptor for RGB BNC connectors. For further information, contact Philips Compo- 80 SILICON CHIP nents, 34 Waterloo Road, North Ryde, NSW 2113. Phone (02) 805 4455 . HEAVY DUTY TV/SPEAKER WALL-CEILING BRACKETS Sealed 12 and 16-button keyboards Acme Electronics has released the Grayhill series 84S 3 x 4 and 4 x 4 sealed keypads which are available in matrix and single pole . common bus circuits. The keypads feature a snap-down contact system which is gold plated to ensure low contact resistance. The legend surface can be removed from the rubber boot without jeopardising the integrity of the The MB3 and MB5 are heavy duty two platform mounting brackets • designed for securing small TV's and speakers to walls, ceilings, desks or bench tops. When mounted both units can noise with a spectral density of 140nV/root Hz; additional broadband noise filtering can be obtained by using external capacitors. For further information, contact the distributor for Analog Devices, NSD Australia, PO Box 264, Box Hill, Vic 3128. Phone (03) 390 0970. priced at $53,500 while the HP 8665B is $73,500. For further information, contact Test and Measurement, Business Communications, Hewlett-Packard Australia Ltd. Phone (03) 895 2837. Price cut on HP dual bin printer ~ 'I D ~ " ___'1fi JH ~ as well as being swivelled up or down to any viewing or listening angle. The metal platforms have predrilled holes for mounting and are easily adjusted with a large a/fen key supplied with the unit. 91 Imported and distributed by: ~ ELECTRONICS Available through the following retailers: David J Reid All Electronic Electronics. Components. 127 York Street. 118 Lonsdale St. Sydney. 2000. Melbourne. 3000. NSW. (02) 267-1385. Vic. (03) 662 3506. ~~ A VIDEO DUBBING/ ENHANCING SYSTEM THAT DOESN'T COST THE EARTH. Precision ±10V reference Analog Devices has released the first precision monolithic ±lOV refence. It has a maximum tracking error of 1.5mV, a maximum initial error of 2mV and a . temperature drift of only 1.5ppm/°C. This degree of accuracy is claimed to match that of complex hybrid designs but at half the cost. Applications include robotic, avionic and instrumentation designs, as well as 12 and 16-bit data acquisition systems. The AD688's buffered voltage outputs typically have only 0.6µV p-p of berotated seal so that custom legends can be applied. For further information, contact Acme Electronics, PO Box 264, Box Hill, Vic 3128. Phone (03) 890 0900. • • • • Those in the market for a fully featured laser printer will be pleased to learn of a substantial price cut to the HP LaserJet IID from around $7000 to $4310. HP claims that this has substantially undercut even discounted prices of any HP LaserJet lookalike products currently on the Australian market. The HP LaserJet IID printer features dual bin operation, allowing letterhead and following paper, for example , to be loaded at the same time. An optional envelope feed allows the envelope, letterhead and following sheet to all be printed and collated automatically. For further information, contact your local Hewlett Packard computer products dealer or phone (03) 895 2837. SC Enhances Video and Audio Signals. Mono/Stereo Compatible. Simple Operation. Can be used with most Video Cameras. The AVE 88L is easily installed and provides excellent results. ALL THIS FOR $49.00 (includes P & H). TO ORDER Please mail coupon to: ---------SOUNDRING PTY. LTD. I PO BOX 154, CAMM ERA Y NSW 2062 I Tel: (02) 967 2411 Fax: (02) 958 7199 Please send me _ _(Qty) AVE 88L I video dubbing/enhancing systems. I My cheque/money order for $_ _ _ is I enclosed. I Name_ _ _ _ _ _ _ _ __ I Address_ _ _ _ _ _ _ _ _ _ __ MARCH 1991 81 The Story Of Electrical Energy, Pt.8 Since AC power transmission first began, there has been a trend to higher and higher voltages, to keep resistance losses to a minimum. But there is a limit to the use of very high voltage AC and when this is reached, DC transmission must be used. By BRYAN MAHER The year was 1983, the location Foz do Iguacu, in Brazil the day overcast and hot. Watched by an assembly of invited guests, a VIP mounted a decorated dais to ceremoniously throw a small control switch. In response, giant transformer circuit breakers in an adjacent hall slammed closed, bringing on line generators of the Brazilian Itaipu hydroelectric system. Thus was initiated the first stage of the world's greatest power line which when completed would operate at 1.2 million volts and carry up to 6.3 gigawatts of electrical power. The receiving substation for this project was 800 kilometres distant on the opposite side of the country at Sao Roque, a suburb of Sao Paulo. Question: how can you economically transmit these large quantities of electrical energy over such great distances? And sell power to neighbouring nations as well? The partial answer is to use very high voltages. We have seen previously in this series the need for high voltages in long power lines. Not only are transmission losses reduced but also the corridor needed can be narrower for a given power to be carried. To transfer 7.5GW at 330kV would require about seven double circuit lines in parallel. These would occupy a corridor 250 metres wide. The same quantity of 7 __'_J I 333MVA ISOLATED , - - - TRANSFORMER I CORE AND CASE 330kV INPUT 2.255MV SUPPLY TO TEST LINE .,. FIG.1: THE TEST ARRANGEMENT used for the ASEA transformer set at the test range at Lakerville, USA. The core & case of the final transformer is alive, at 345kV above ground potential. A test cage allowed various weather conditions such as rain & mist to be simulated. 82 SILICON CHIP power could be carried by one 1200kV 3-phase line which would fit within a corridor 90 metres wide. UHV problems Ultra high voltage AC systems are, however, beset with problems. The extra insulation required can be mostly provided by the simple extension of known technology. But other difficulties emerge. Some countries, notably Russia, Sweden, the USA and Italy have been using experimental megavolt research installations for the p2.st 15 years. In the USA, west of Lakeville, Indiana, ASEA (now ABB) established a UHV test line of five spans on towers 61 metres high. Voltages up to 2.255MV are produced by a triple bank of cascaded ASEA transformers. The final transformer has its core and case alive, 345kV above ground potential, as shown in Fig. l. This complete transformer, weighing 290 tonnes , was mounted on a giant insulated pedestal. Conductor bundles of more than 1.2 metres in diameter, consisting of 18 subconductors, each 30mm diameter, have been tested. A 2.255MV disconnect switch and a test cage wherein various weather conditions such as rain and mist can be produced at will, are provided. Instruments measure voltage surges, control operation, effects of conductor height, RFI, ozone, corona power loss , audible noise, high frequency components and weather conditions. Switching surges of up to 100% overvoltage have been observed in some cases. The Ohio Brass Company contributed its laboratory facilities for insulator testing and other UHV research institutes from Canada, Italy and France cooperated. The ASEA company has always led the field in power line practice above 400kV, both in AC and DC applica- THIS HISTORIC PHOTOGRAPH shows the world's first 10kV mercury arc rectifier. It was developed at the ASEA laboratory in Ludvika, Sweden, from 1929-33. tions. That company inspired the world's first 400kV national grid system in Sweden as far back as 1952. EPRI research The Electrical Power Research Institute (EPRI) of USA contracted with the General Electric Company to conduct UHV tests at GE's facility at Pittsfield, Massachusetts. Threephase lines of 1.5MV (1500kV) and 500 metres long are used to investigate optimum design. A wide range of factors must be optimised: height, phase spacing, bundle diameter and the number of parallel subconductors. Measurements made included RFI in the broadcast band and corona effects using different types of corona shields. The test line uses gantry span towers, 71 metres wide and 21.5 metres high, with the three phases suspended below the cross member on V-shaped suspension insulator strings bf glass, porcelain and other materials. Soviet UHV The Russians possess test rigs for designs up to 5MV or even 7.5MV (7500kV). Much research and development was done into 1150kV circuit breaker design , protection systems, transformers and electric field intensity. Due to transformer leakage reactance and circuit capacitance, voltage ringing oscillations occur when switches are opened. In one Russian case, sinewaves of 400kV at a frequency of 1800Hz were found superimposed on a 1150kV 3-phase line during switching operations. The insulation on lines, equipment and particularly transformer windings must be sufficient to cope with these overvoltages. But three fundamental problems of UHV 3-phase AC lines are harder to alleviate. These are line inductance, line capacitance and the noise generated by corona discharge. Inductance and capacitance As we have previously seen, any cable has inductance which produces an AC voltage drop proportional to the product of current, inductance and frequency. Also, we have noted THE ASEA/AEP 2.255MV research substation. The high-voltage transformer is mounted on an insulated platform (bottom of photo), while the 2.255MV busbars are mounted 23 metres above ground. MARCH 1991 83 ':Qt!Q!:!Yll!:!:.!.~ 1oc-- 3-PHASE GRID SYSTEM CONTROLLED INVERTER L TRA~Wci~~ER .,. STEP-DOWN TRANSFORMER --1oc SENDING END - - - - - - i t------- RECEIVING END -------t FIG.2: BASIC SCHEME for a high-voltage DC transmission system. Either 50Hz or 60Hz AC power is generated in the usual fashion at the transmission end & this is then rectified to DC for transmission over the line. At the receiving end, the DC is converted back to AC & transformed down so that it can be fed into the system grid. that the natural phase to phase and phase to ground capacitance demands a charging curreBt. This can run to many hundreds of amperes and is also proportional to frequency. Capacitance charging current is an insurmountable problem in AC underground and submarine power cables. The close spacings of conductors and earthed shields results in huge capacitance values. In fact, inductive and capacitive effects greatly exceed the line voltage loss due to ohmic resistance of the conductors. Compensators Excessive inductance in an AC power line can be compensated for by inserting capacitors in series with the line at intervals. However, this is very expensive. Compensation by this method becomes uneconomical for lines carrying lGW or more over distances exceeding 500 kilometres. To correct for the high values of shunt capacitance in long high voltage underground cables, inductors must be used. These are connected in parallel with the line at intervals along its length. But again, the cost escalates way above the cost of cable and simple trenches. For long undersea cables though, this form of compensation is impossible. In wet and foggy weather, the corona phenomenon generates a lot of noise as well as a characteristic blue glow around the conductors. The noise , based on the system frequency (50 or 60Hz) and its harmonics, can be a loud buzzing and sputtering with components from 50Hz to many kilohertz. The DC solution Wouldn't it be nice if we could remove all these frequency dependent problems? Well, we can - just reduce the frequency to zero! Then line inductance would not be important during steady current flow. Further, line capacitance would produce no further effects after initially being energised and charged. Corona would still produce a pretty blue glow around conductors in the rain, but the generated noise levels would be vastly reduced, down to a faint hissing sound. The answer, of course, is to use high voltage DC. Thomas Edison would stand up and cheer were he still alive. Nearly a century ago, AC transmis- ISOLATED AC SUPPLY / WATER COOLER AND PUMP VACUUM TIGHT HVBUSHING - TANK ALIVE AT POSITIVE DC POTENTIAL - EVACUATED WATER COOLED STEEL TANK +15DOVDC LOAD . PERHAPS. 5kA FLOOR Corona noise Corona, as we saw in past chapters, does not cause large losses, though it does increase dramatically in damp weather, especially in wet snow. The deleterious effects of corona are RFI and acoustic noise. 84 SILICON CHIP FIG.3: A MERCURY ARC rectifier consists of an evacuated steel tank containing a mercury pool, an anode & a starting electrode. A starting current is used to vaporise the mercury to produce electrons & positive ions. When the anode swings positive, the electrons quickly accelerate towards it & a high current flows. However, when the anode swings negative, the heavier ions accelerate towards it quite slowly & so only a very small back current is produced. sion was chosen in preference to the DC systems advocated by Edison; purely because of the ease of transforming an AC voltage. The world has now turned full circle; we are facing the difficulties engendered by the frequency factor as we build higher and higher voltage AC systems. But note that it is the AC line fre quency, not the voltage, that gives trouble. Therefore, DC was chosen for that monstrous 6.3GW power line mentioned at the start of this episode. AC-DC-AC Nobody in his right mind would attempt to generate huge quantities of high voltage DC in rotating machinery. No! We still generate AC at 50Hz or 60Hz in normal alternators, at voltage in the 1 lkV to 33kV range. Transformers then raise the voltage to UHV (ultra high voltage) values around the sub-megavolt region. This is then rectified to DC for transmission over long distances. At the far end of the line, more equipment inverts the DC currents back to AC at normal system frequency (50 or 60Hz, depending on the country). This AC is usually transformed down (in a normal transformer) to feed into the system grid at the load end. The block diagram of Fig.2 explains the concept. Rectifier valves The transformers used are just extensions of known designs. But what was needed was the development of some types of valves to rectify these high AC voltages to DC, then subsequently to invert back to AC at the far end. The story starts way back before any of us were born. Though Thomas Edison discovered the vacuum diode rectifier in 1885, he saw no applications for it; nor did he give the modern theory of its operation. Physicists like Richardson (1902) explained valve rectification of AC to DC as being due to flows of negative charges to a positive anode . But a negative anode would support no such flow. So AC supply could sustain current flow in one direction only through such a valve. Rectification of AC to DC was thus achieved. As we survey the evolution of HVDC systems, it is interesting to note how early some of the techniques were known. Richardson gave the THIS IS ASEA's high-voltage DC laboratory at Trollhatten, Sweden, in 1944. Note the steam produced by the water-cooled load resistor when testing HVDC valves at full power. name "thermions" to his mobile negative charges within a valve. Today we simply call them "electrons", the Greek word for amber. His vacuum tube diode rectifiers in 1902 were called kenotrons. Around the turn of the century, scientists had perfected the use of these tubes in rectifying 100kV AC to high voltage DC. The small currents available were used for x-ray experiments. By 1932, Cockroft and Walton were producing 700kV DC supplies from voltage quadrupling diode rectifiers. Other engineers in the 1920s were using gaseous valves to rectify AC INPUT STEEL TANK ~ 'POSITIVEGRIO --,- ·PULSE SUPPLY ANO TIME'R - PULSE TRANSFORMER CONTROL GRID LOAD FIG.4: THE OUTPUT VOLTAGE of a mercury arc rectifier can be varied by interposing a control grid in the electron stream between the mercury cathode and the anode. If a sufficiently large negative potential is applied to this grid, all electrons in the mercury plasma gas will be repelled and none will pass to the anode. The valve is then in the cutoff state and no current can flow. MARCH 1991 85 V4 V6 pelled and none will pass to the anode. The valve is then in the cutoff state and no current can flow. In this way, a mercury arc rectifier can be used as a controlled rectifier, similar to an SCR. V2 Switched operation f.~ ~ I-- V1 :!,p_HASE OUTPUT TRIGGER PULSES TO EACH VALVE V3 V5 SYNC SIGNAL INPUT --i □ C HVDC LINE NEGATIVE RETURN FIG.5: BLOCK DIAGRAM of a DC-AC inverter at the receiving end. V1-V6 are controlled high-voltage mercury arc valves which are switched in turn to provide current waveforms to a 3-phase output transformer. The trigger pulse generator turns off each rectifier at the correct time by injecting a large negative pulse to the anode via a capacitor for a sufficient time to allow the arc to cease, thus giving control back to the grid much greater currents in 600V to 3kV circuits. One of the gases used was mercury vapour. Mercury arc valves Soon this technique led to larger valves in which the cathode was simply a pool of mercury at the bottom. In the late 1920s, these mercury arc rectifiers were widely used for supplying rail traction currents at . voltages in the 600 to 1500V range. The original glass envelope had then been superseded by steel tank models. Fig.3 shows a typical mercury arc rectifier which uses an evacuated steel tank. To start the rectifier, a current is passed through the mercury pool and an initial arc drawn. This vaporises some mercury to a heavy gaseous plasma of electrons and po_sitively charged mercury ions. The AC supply is connected to an anode of iron, carbon or patented alloys. Whenever the AC on the anode swings positive, it attracts electrons and, because these have only a tiny mass, they accelerate very quickly, flowing during the whole positive 86 SILICON CHIP half-cycle. Moving electrons constitute an electric current, and so many thousands of amperes can flow through the rectifier. When the AC supply on the anode swings negative, it attracts the heavy positive gaseous mercury ions. But as these ions have very great mass, they accelerate only slowly. The result is that the negative half cycle is over before any appreciable number of positive ions arrive at the anode. This back current can be measured in microamps or milliamps. Thus, a mercury arc valve rectifier passes useful current only when the anode is positive. The output is taken from the steel (cathode) case of the rectifier. Control grid The output voltage of a mercury arc rectifier can be varied by interposing a control grid in the electron stream between the mercury cathode and the anode, as shown in Fig.4. If a sufficiently large negative potential is applied to this grid, all electrons in the mercury plasma gas will be re- Once in conducting mode , the mercury valve continues passing current as long as the anode is positive, without any regard to the grid potential. We thus need a method of interrupting this current flow and this can · be achieved in two ways. The first , employed where the receiving end has no local AC supply, uses a transformer or inductance in series with the DC line to each valve as shown in Fig.5. To stop the valve conducting, the continuous DC supply must be interrupted momentarily and the grid held at cutoff negative bias. To achieve the currents in the three output phases, the appropriate pair of valves is switched on by releasing the negative bias on them at the correct timing. Then, when the output current in that phase is to be stopped, the grid is taken negative beyond cutoff and a large negative pulse injected at the valve anode. This momentarily makes the anode negative for a sufficient time for the mercury arc to cease, giving control back to the grid. Six timing circuits (3 for the anodes & 3 for grids) are required. Instead of transformers, series inductance and capacitance coupled anode pulses may be used. These methods are seldom used nowadays as systems expand. First HV mercury valve Building on their own experience and earlier German and English results in 1.5kV traction rectifiers , the ASEA company of Sweden developed a lOkV prototype from 1929-33. This, the world's first high voltage mercury arc valve, was set up in their laboratory cJ,t Ludvika for testing in 1933. Though mercury arc valves give no problems in the 600V to 3kV range, the idea of rectifying voltages up to a megavolt is frightening. In the conducting mode, the forward drop is only 15V and so there are no problems here. However, in the reverse mode, with the anode negative at hundreds of kilovolts , you would 100kV AC SUPPLY FROM TRANSFORMER ample power was available. Mercury arc valves were tested using a steaming water resistor as a high power load. METAL 1-r-..---...-.-1---- ANODE World's first HVDC line C EVACUATED - - CERAMIC HOUSING FREQUENCY COMPENSATED VOLTAGE DIVIDER TIMER SIGNAL --------++UPPER COOLING SYSTEM NEGATIVE GRID BIAS AND POSITIVE 1----1---1-- _ TRIGGER PULSE AND TIMER SYSTEM CONTROL GRID I ..!_ _ _ CIRCULATING WATER JACKET FIG.6: TO OVERCOME BREAKDOWN problems when rectifying high voltages, ASEA developed a mercury arc rectifier with a series of nine intermediate electrodes between the anode & control grid. A voltage divider connected to these electrodes thus provides 10 steps of lOkV each, which means that the field experienced by any one positive ion is drastically reduced (10kV vs. lOOkV). naturally expect voltage breakdown under such a tremendous electric field. To overcome this problem, ASEA researchers developed a more advanced valve which reduced the electric field experienced by any positive mercury ion. This was achieved by having the electron stream pass through a series of nine intermediate electrodes, each at equal smaller increments of voltage, obtained from a frequency compensated voltage divider - see Fig.6. The whole compound-anode assembly was mounted inside a ceramic extension of the water cooled steel tank. A valve with nine intermediate grating-like electrodes plus one final solid anode would have the full voltage, say lO0kV, applied to the top electrode. The voltage divider provides 10 steps of lOkV each in the space between intermediate anodes. This is sufficiently low to prevent voltage flashover or breakdown during the negative half cycle when the valve is in the non-conducting state. In 1943, an assembly consisting of four parallel mercury valves was tested in the ASEA laboratory at Ludvika. Each valve contained nine intermediate electrodes, and the whole arrangement ran successfully on 40kV at a group current up to 200 amps. Trollhattan Hydro Under a 1944 agreement with the Swedish state power board, ASEA conducted further high power mercury valve tests at Trollhattan, close to the hydroelectric power station. A point readers may not have considered is: how do you conduct a full power test on any power equipment unless you have that much power available? For this reason, ASEA shifted its research and development facility to this new location where In 1946, the many years ofresearch by ASEA engineers and scientists came to fruition. In that year, the world's first high voltage DC power line was built and put into operation. This 60 kilometre feeder operated at 90kV DC and carried 6.5 megawatts of power from Trollhattan power station northwards to Mellerud on the shores of the Vanern . So successful was this line that the concept of mercury arc rectifiers, inverters and HVDC power transmission was becoming a reality. Subsequently, a power supply was needed from mainland Sweden to Gotland, an offshore island in the Baltic Sea. An undersea cable was proposed from Vastervik on the mainland to Visby on the island, a distance of 105 kilometres. As the seabed along the route does not exceed 100 metres in depth , laying the cable was not a problem. Specifications called for 20 megawatts to be carried at lO0kV. At such a high voltage, an AC undersea cable would have been impossible due to capacitance effects. So, in 1950, ASEA was contracted by the Swedish State Power Board to develop and install suitable mercury arc valves. As there already existed a power station on the island, the DC link could in principle carry power in either direction. Thus, rectifiers and inverters were made as identical twins, and the timing sequences to the valve grids would decide the power flow direction. The Gotland Link made history in 1954, being the world's first high voltage DC undersea cable. The fame of that line is understandable as it opened the way for cross-channel power transfer anywhere in the world, a concept totally foreign to AC designs. Exhaustive tests on 140 mercury arc valve designs occupied four years of intense development. To carry the required 200 amps DC current, ASEA installed a bridge circuit at each end of the line. Each diode therein consisted of a grid controlled mercury arc rectifier having two parallel anode assemblies rated at over lO0kV. MARCH 1991 87 DEVELOPED BY ASEA at Ludvika in 1943, these four high voltage mercury arc valves contained nine intermediate electrodes (see Fig.9) & ran successfully on 40kV with a group current (anodes paralleled) of 200 amps. The nine intermediate electrodes of each rectifier are mounted inside a ceramic tube which sits atop the water-cooled steel tank. Each anode contained at least 10 intermediate electrodes. Undersea cable The single-core undersea cable was specially designed and manufactured. To achieve the greatest active conductor area in a given space, each copper strand was squashed from circular to roughly hexagonal cross section. Thus, 60 copper strands were laid up in a 5-layer pattern. The surrounding 150kV insulation was itself encircled by a neutral shielding layer, aluminium tubing, layers of steel armour stranding and a waterproof covering. Note that you cannot operate a steelarmoured single core cable on AC. If you do, the current carried by the copper will set up strong AC magnetic fields in the steel. The resulting 88 SILICON CHIP eddy currents in the armouring will overheat the cable, damage the insulation and cause breakdbwn. But the same cable carrying DC gives no problem. Sure, there are strong magnetic fields in the steel, but DC fields do not induce eddy currents! Sea return Another innovation inspired by the historic Gotland DC submarine cable is the idea of sea re.turn. In this scheme, the copper cable carries current for one half of the circuit, while the return current flows through the seawater. This practice does more than just save a copper return cable. As the ocean has an almost infinite cross section, the sea return path has almost zero resistance. Thus, cable losses are half that which would re- sult if a copper return cable were used. Electrodes of large surface area implanted in the sea at both ends of the line provide the connection to the salt water. ASEA continued their research and development of controlled mercury arc rectifiers and inverters for a further 17 years. Later valves carrying 1000 amps per anode at voltages up to 135kV established the HVDC concept beyond doubt. Installations all over the world followed and then solid state inverters appeared on the scene. We hope to cover these in a future issue. SC Acknowledgements Special thanks to ABB Australia and Sweden for supplying historic photographs and data; to ASEA Journal and Action; to General Electric and IEEE Spectrum. The Bose Lifestyle™ Music System Results of the draw First Prize: Bose Lifestyle Music System • Mr S. McDonald, 18 Harrison St, Warners Bay, NSW 2282. Runners Up: Bose 101 Music Monitor Speakers • Mr R. Ford, cl- 4 Tepko Road, Terrey Hills, NSW 2084. • Mr P. Long, PO Box 241, Richmond, NSW 2753. • Mr E. Salter, MS 694, Tara, Qld 4421. SILICON CHIP Subscription Pack winners: 1-year free subscription plus binder plus SILICON CHIP sports shirt. • Mr B. Gibson , cl- State Bank - ITS , Level 5, 223-239 Liverpool Road , Ashfield, NSW 2131. • Mr B. Laird , 35 Osprey Drive, Illawong, NSW 2234. • Mr G. White, RSD 544 , Harford , Tasmania 7307. • Ms K. A. Gluyas, PO Box 29, Doncaster East, Victoria 3109. • Mr N. Chan, 39 Forrest Road , Earlwood, NSW 2206. • Mr B. Altschwager, 27 Fitzroy Street, Sorell, Tasmania 717~. • Mr J. Farmer, 13 Keppel Road, Ryde, NSW 2112. • Mr R. Winchester, 22 Manor Road, Hornsby, NSW 2077. • Mr J. B. Prestwood, PO Box 1011, Fremantle, WA 6160. Congratulati ons to the winners of these prizes and thanks to all our subscribers for their enthusiastic support. Our thanks also to Bose Australia Inc for their support in the running of this competition over the three months from 1st September to 30thNovember, 1990. SC PHONE LINE AND MAINS FILTER/SURGE PROTECTOR ensures that lightning, pow and spikes do not reach your cos communication equipment as i constantly monitors the PHONE line a the MAINS power line. Simply connect to any existing power point, plug in your tax, phone, video, Hi Fi or any other 240 VAC operated equipment and a series of indicators shows the status of the mains power point while several MOV's and gas arrestors prevents access to damaging energy sources. The CPEP-1 is fully Telecom and Dept. of Minerals and Energy tested and approved. Imported and distributed by: ~ ELECTRONICS Available through the following retailers: Pictured above is Mr Bob Schenk, Managing Director of Bose Australia Inc, together with Leo Simpson, Publisher of SILICON CHIP, at the drawing of the Bose Lifestyle Music System prize during December 1990. Telegrafax PIL. 305-307 Sailors Bay Road. Northbridge. 2063. NSW. (02) 958 5137 Geoff Wood Elec. 229Burns Bay Road. Lane Cove. 2066. NSW. (02) 427 1676. MARCH 1991 89 '. . ~ / ·, DIGITAL MULTI METER HC -4510 DISPLAY:4 1/2 DIGIT •""-·"'"""" BASIC ACCURACY: 0.5% DC V DC VOLTAGE: 0·1000V DC CURRENT: 0-10A AC VOLTAGE: 0-750V AC CURRENT: 0-10A RESISTANCE: 0-20M OHMS CONTINUITY TEST, DIODE TEST r--.......... , DATA HOLD --- 0 13030 20 MHz DUAL TRACE OSCILLOSCOPE NOW $129.95 CTR DISPLAY: • 150 mm rectangular U•--•··. ··. ···•···.·- - - • ·- - - - - - - - - - - - - - - 1 1 VERTIACAL DEFLECTION: • Deflection Factor: 5mV to 20V / Div on 12 r?nges in 1·2-5 step with fine control • Bandwidth DC: DC to 20 MHz (-3dB) AC: 10Hz to 20 MHz (·3dB) • Operating modes CH· A, CH·B, DUAL aad ADD (ALT/CHOP l202 only) • Chop Frequency: 200 KHz Approx . • Channel separation: Better than 60dB at 1 KHz DC VOLTAGE: 0-1000V T IME BASE DC CURRENT: 0-10A • Type: Automatic & normal triggered in automatic mode, sweep is obtained without AC VOLTAGE : 0-750V input signal AC CURRENT: 0-10A • Sweep Time: 0.2m Sec to 0.5 Sec/ Div on ranges in 1·2-5 step with fine RESISTANCE : 0-20M OHMS control and x.v. CONTINUITY TEST, DIODE T EST • Magnifier: X5 at all t imes. CRO Probe to suit r ~ ~ RRP $149 95 · ~ -,m:i~ I O13010 .................... RRP $11 9.95 NOW$109.95 DIGITAL MULTI METER HC-889 t. i. DISPLAY: 3 1/2 DIGIT " DC VOLTAGE : 0-1000V DC CURRENT: 0-1 0A AC VOLTAGE : 0-750V RESISTANCE: 0-20M OHMS ,i.Tf, S~"' ot.\n. ~ \J CONTINUITY TEST, DIODE TEST, DATA HOLD, TR HFE GAIN, ✓/~..;:O•A_U_T_O_R_A_N_G_E-DM_M_W_I_T_H_B_A_R_G_R_A_P_H _ _ _ _ _ __...;;._'"""'--I 013040 ... .... ........ ...... RRP $99.95 NOW $89.95 1 ~ / ., T RIGGERING $39.50 each - Cat. 0122.01 • Sensitiv~y lnt : 1 Div or more Ext: 1Vp-p or more. • Source: INT, CH·B, LINE or EXT • Triggering Level : Positive and Negetive, continuously variable level; Pull for Auto. • Sync: AC, HF Rej, TV (each+ or•) at TV Sync. TV•H (line) and (frame) sync are switched automatically by SWEEP TIME/Div switch. HOR IZONTAL DEFLECTION Deflection factor: 5mV to 20V/ Div on 12 ranges in 1-2·5 step with fine control · Freq uency response : DC to MHz (·3d B) • Max Input Volt age: 300V DC + AC Peak of 600V p-p • X·Y operation: X-Y mode is selected by SWEEP TI ME/ Div switch. . Intensity Modulation Z Ax is: TTL Level (3Vp•p-50V) + bright, . dark • OTHER SPECS: . Weight : 7Kg Approx • Dimensions: 162 (H) x 294(W) x 352(D)mm. 012105 .......... ................ RRP $750 ~ ri,,tt>" DIGITAL MULTI METER HC-:3500T ,; .• ; ....-:" ""..i:..;.,i::11 r, ""'I ,o"' o" DISPLAY:3/12 DIGIT BASIC ACCURACY: 0.5% DC ~ ~ ( DC DC AC AC ~."'.,o~~ , (1-0 VOLTAGE : 0-1000 V CUR RE NT: 0-20A VOLTAGE0-7 50V CURRENT 0-20A ~ _,~ ,..,..._...__,11O13000 ................... RRP $169.95 o. ·I ,T ~/'i. r, J $f\."J ~..-~·I '£, ~====~'F=~~~~fia • -- g •V n, ~;,,\,~"--» .:--1 $ ;,;; _- •••• '■' -:.. :·._ ;,;.·\, ~.-.~ :. '■' '■' .), [i] :. l.=-===::::::t• .!. ;tO 11 ~ ~ = 100 MHz 3 CHANNEL 8 TRACE MODEL 5510 NOW $149.95 DC VO LTAGE : 0- 1000V DC CURRENT: 1 OA v· ~"S . ~ HC-5050DB 3 1/2 DIGIT BASIC ACCURACY: 0.5% DC AC VO LTAGE : 0-750V >::---;-- JI AC CURRENT: 0-1 OA r----nl RESISTANCE: 0-20M OHM S DC AC RMS :-45dB -+S0dB ~ T EMPERATURE: -20C-1200C AC FREQ SPREAD: 50Hz-2K Hz p_,<-, 4;'2,\) ANALOGUE/DIGITAL MULTIMETER ~ ~0 Ci ~e C. 11,,."-1'£, RESISTANCE : 0-20M OHM S TEMPERATURE: -20C -1200C CONT INUIT Y TEST, DIODE T EST TEMPERATURE CAPACITANCE FREQUE NCY, hfe TEST, DATA HO LD. NOW $695 . This instrument meets the customers needs in quality of performance, efficiency, function, design, and cost! Being rugged, highly reliable and a multi•purpose 3 • channel, 8 trace oscilloscope with a 6 inch domed mesh type 14kV post deflection acceleration cathode.r ay tube and with a fine red internal graticule. FEATURES : • Compactness, lightweig ht, ruggedness and simple design. • The diecast fra me provides compactness lightweight and ruggedness . • Easy Operation Light torque lever switches and pushbutton switches are used . High Brightness CTR, high acceleration voltage and high beam efficiency of. the 150mm rectangular CTR ensures a bright high speedsweep observation • Multi mode display system CH1, CH2, CH3, Add any combination or all the channels may be viewed simultaniously. Maximum 8 trace displaying is possible with the ALT sweep function. • High sens itivity and wide frequency bandwidth . The maximum vertical sensitivity is 1 mV!DIV (when x 5 MAG)at 20 MHz or greater 3dB and mV!DI V at 100 MHz or greater -3dB. High input impendance The input impendance of CH1, CH2, CH3, is 1Mnt2%, 25pFt3pF . 4::.i,~ ~/,,< I CONT IN UIT Y T EST, DIO DE T EST 013020 ...... .... ..... ... RRP $1 69.95 NOW $149.95 ll•...., .......,_,,.,ii,ii,,...,...;......,..."""""'"""""'"""""'..,.""""""""-----------11. - - -• LOGIC PROBE (LP-2800) USEFUL FOR TTL AND CM OS. HIGH & LOW INDICATORS PULSE. MEMORY. FOR THE HOBBIEST OR SER IOUS TECHN IICIAN FOR TRACING THOSE HARD TO FIND FAU LTS ON LOGIC BOARDS . 011272 ....... ... ........ .......... RRP$29.95 NOW $19.95 Q12109 ......... RRP $2995.00 NOW $2795.00 SCHOOLS & COLLEGES TAKE NOTE! ONLY $2395 tax exempt. ) i<✓i:QW.L1'tv~o?Pd~~;fs~~ c ~ 0 H11800 .. 10g ...... $2.00 Hl 1810.. 1 ....$14.95 BNC PANEL SOCKET 1.9 1 ~~~~i;:ss::!1~:~nsler from the device to lhe heal sink , thus increasing overall efficienc y. 10 ·99 100. ULTRASONIC TRANDUCERS BNC CRIMP PLUG Designed to transmit at 40kHz (L 19990) and recieve at 40 kHz H)('I+ P10530 SUS $2.75 S2.00 ~ BNC (L 19991 )with up to 20V 1/P on the transmitter. These units can't be SOLDERLESS TWIST ON PLU.G 1• l CANNON PLUGSj)l , 'J~f::J.O_S_9CK}j~.!tj water level detectors, . burglar alarms, motion detectors and information carriers as they can be either pulsed or used in a continues wave mode. Transmiller Receiver L19991 .... $3.95 $2.95 10+ 100+ P101162$3.50 $2.95 $2.50 CANNON TYPE 3 PIN LINE FEMALE 1·9 10+ 100+ P101164 $3.95 $3.50 $2.110 ffl 10-t- P101166 $4.95 $4.50 $3.50 < :=Ji 10+ 1·9 10 .. 100+ P10860 $4.50. $3.50 $2.50 ~ ·These quality 3 level wi re wrap sockets are tin•plated phosphor bronze. 1· 9 10+ P10579 8 pin 1.50 1.40 P10580 14pin 1.85 1.70 P10585 16 pin 1.95 1.80 P10587 18 pin 1.95 1.80 P10590 20 pin 2.95 2.75 P10592 22pin 2.95 2.70 P10594 24 pin 3.95 3.50 P10596 28 pin 3.95 3.50 P10598 40 oln 4.95 4.50 co 1·9 100+ ~~ P12170 $4.50 $3.95 $3.50 2155 9 PIN TO 25 PIN CONNECTOR ADAPTORS D TYPE IDC SOCKETS . DE9s g pin 1ocket 1·9 10 . 100 . P12167 S2.95 $2.50 $2.00 1Splnaocket · DA 155 P1 21 69 $3.50 $3.00 $2.50 Cat M1 2155 $1 6672 240V 1S 30vc 1 A tapped Cat M16672 $12.95 $11 .05 P ,2200 10. m IOO+m .20m $2.50m CIC2!i O+ m $ 3.95 Plutle boxea with plaal e lop• a nd avallable In 5 ■ .ze a. Very popular fro p,ofecta & very economlcal • 150x90 x 50rnn 10+ H10111 ..... $4.95 ELESS PHONE !! • 120 X 65 X 38mm H10120..... $2.95 $2.50 $14 .50 010533 MU52E 0•5A 010535 MU45 VUP $14.95 $14.95 010538 010540 010550 010560 MUSS 0-SOuA $16.95 MUSS 0-1mA $16.95 MUSS 0-100uA $16.9 5 MU6S0-20V $16 .95 $3 .00 $2.95 handles up to 100 Watts Sen sitivity: 100dB/ 0.5 m Frequency response: 3kHz-3~0kHz Independence: 8 ohms . Size 96 m diameter Normally ......... $12. 95 ~ MOSFET SPECIALS 2SJ49 2SJ56 1·9 $7.50 $10.00 $6.90 $9.50 10+ fans only $11 .95 each 100 . $3.95 $3.00 $2.95 FANS Ouatity, tan s lor use ,n powe r amps, computer s. holspot cooli ng etc. An ywhere you need plenty ol au. . •00 · 240V 4 5,s·· T12461 .. $12.95 115V 4 5 s·· T12463 . . $12.95 240V 3 1 r Tl 2465 .. $12.95 115V 3 1 2·· T12467 ... $12.95 $0.90 10• tans (mind) only $1Q.85 each ELECTRET MIC JHSf.RTS LWtth p,ns IOf ea sy boa,(! ,nser1 , \f C:ar C10 1 70 , $1 .20 •O · $1 .00 ON LY.........., .........$9.95 10+ $7.00 $9.50 $6.50 $8.90 VOLTAGE REGULATORS BARGAINS 12V DC FANS Tl 2469 ................ ..$12.95 · Sor:k el 10 . TWEETER Requires no cros sover and 10W HORN FAX: FAX: FAX: FAX: (03) 639 1641 AS PHONE. (02) Sl9 3868 (03) S43 2648 Oe1crlptlon 7805UC 7812UC 7815UC 71105UC 7t12UC 7t15UC 78L05 78L12 LM324 555 741 1· 9 $0.50 $0.50 $0.50 $0.60 $0.60 $0.60 $0.40 $0.40 $1.CIO $0.40 $0.50 All ules tax exempt orders and wholeule inquiries to: i'IITRONICS WHOLE SALE 56 Renve r Road . Clayton Phone (03) 543 2166 (3 llnesl Fax 03 543 2648 10+ $0.45 $0.45 $0.45 $0.55 $0.55 $0.55 $0.30 $0,30 $0.90 $0.38 $0.45 ~~ .•• . , . SPEAKERS While durable plasti c, 8 ohms Cat . C 12010 12v CC. 1.7 Wan . 0.14 Amps $4.75 H10112..... $5.75 '$5.25 • 130 x 68 x 41mm H10113 ....•$2.95 $2.50 •83x54x28mm H10115 ..... $2.25 $ 1.95 010530 MU52E 0-1A BO • 80 • 25.4mm 100 , • 195 X 113 X 60mm 100+ m 3 .40m $3.00m $12.50 i----------'I 2SK134 2SK176 2S pin aocket · Plug 16 $12.50 $12 .50 010525 MU45 0-20V $7.95 Cal M12156 $13.95 $12.95 2840 240V 9VCT Cat M12840 $4 .95 $3.95 2851 240V 12•6V CT 250mA CatM1 21151 $4.95 $4.50 2860 240 V 15VCT 250m A Cat M 12860 $4.95 $4.50 IDC CENTRON ICS 36 WAY P LUG & S OC KE T m $8.95 $12.50 P1 2171 s,t.50 $3.95 $3.50' , 100+ .t>Efil'J 1.00 S0.80 I., t-----------1 -- . oe2ss m $1 .90m 10+ 1-9 240V 6-1SV 1A Q\0510 MU45 0-5A 0105 18 MU45 0-1A 0 10520 MU45 0- 1A 2156 240V 6-1SV A.2 .OOm . P10880 /;Nfm!!II ► 10. P12168 $ 3.50 $3.00 $2.S0 , DB25P 25 pin plug WI $1. Wl 100+ 1-9 10-99 100+ If you have 2 or 4 compatable RED 20c 15c 12c devices that need to share a 20c 15c 12c GREEN thi rd or fifth, then these YELLOW 20c 15c 12c inexpencivedata tranfer will ORANGE 20c 15c 12c save youthe time and hassle TOGGLE SWITCHES of constantly changing Cables r----------➔ 1·9 10-99 and leads around . S11010 O.P.O.T $ 1.20 $ 1.10 No power required 511020 O.P.O.T $ 1.30 $1.20 · Speed and code tranparent · Two o r four position rotary switch on front panel. Switch comes standard with fema le connector. PANEL METERS NICADS RS232· 2 way . .................... $39 Save a fortune on expensive GALORE AS232- 4 way ..................... $59 throw away batteries with RS232· X over .................... $69 We have a great range of these quality Nicads and AS232· 2 way auto ............. $69 panel meters at great Rechargers! Centronics- 2 way ........... ... $49 prices! Size Desc . 1-9 10+ 100+ Centronics- 4 way .............. $69 010SOO MU45 0-1m A $12.50 AA 450mAH $1.95 $1.75 $1.50 Cenlronics• X over ..... ... ..... $69 010502 MU45 50150uA $12.50 C 1 2 A H $9.95 $9.50 $8.95 Centronics- 2 way auto ..... $79 010504 MU45 0-100uA$12 .SO 0 1 2 A H $9.95 $9.50 $8.95 • DE9P • pin plug P12166 $2.95 $2.50 $2.00 ·OA15P 1Spinpiug ~$0.60 S0.50 SOAO • P1os2, 3wav $0.80 $G. 70 $0.60 each $8.95 + P10902 0B25C $1 .00 $0.80 P10905 oe25P s1.00 so.ea 010905 oe25s s1.00 s o.ea RECTANGULAR LEDS r----------:::-"I The perfec t s olutio~! Features gold plated pin s X15668 089 Plug to 0825 Socket X15669 0B9 Socket to D825 Plug . •m 1C)t P10892 DA15C $1.00 $0 .80 P10880 OA1SP $1.00 $0.80 P10895 0A15S $1.00 $0.80 ------ DATA~ SWITCHES WIRE WRAP IC SOCKETS «6~~ CANNON TYPE 3 PIN LINE MALE $0.12 $0 .1 0 $0.25 $0.12 $0.15 $0.12 $0.15 $0.12 10-a 1·9 $1.00 $ 0.70 P10890 OA15P $1.00 $0.70 P10891 OA155 $1.00 $0.70 Z10150{R) $0.15 $0.10 $0.10 Z10151(G)$Q.20 S0.15 $0.12 Z10152(Y) SG.211 $0.1 5 $0. 12 =~~:;: : : ~:.:·: : !: PCB MOUNTING SCREW TERMINALS ,-a 100 + 1·9 , .. Theae termin1la f.ature intertodllng end• to form anv number of conectlone. Stand1rd 5mm apacing pina • P10520 2 way CANNON TYPE 3 PIN CHASSIS FEMALE P10885 OE9S 100+ ,QUALITY SMM LEOS Range: 300 feet in open field RECIEVER SPECS : (INTERLOCKJNG ENOS) ~ 1·9 1O+ L19990 .....$3.95 $2.95 CANNON TYPE 3 PIN CHASSIS MALE 1-9 1·9 Z10140(R) .... $0.15 Z10141(G) ....$0.20 Z10143(Y) ....$0.20 Z10145(01 ... $0.20 MICROPHONE SPECS : Transmitting Frequency : 37.1MHz Transmitting system : Crystal oscillation . 1CMII t - - - - - - - - - --t l---== = = = -,----f 1-1 10.fl 10G. Pl0550 8 p in ..... . 1.sc 12, toe Receiver freq : 37.1MHz HAVE YOU P10560 14 pin .... 2Qc 1~ 15,e Output level: 37mV(max) RECEIVED YOUR P10565 16 pin .. .. 20e 181 t6e Receiving sys : Super crystal ::~~ 18 pin ... :JO< 25< 22' oselllalion NEW 148 PAGE RO FLAffl1NG LJ;DS P10569 !~::~:.:·:: ~ ~ : Power sup : 9V battery · red 5mm 1·9 10+ IRVING ELECTRON! P1o57o 24 pin .. .. J.Se 30f 26e ~~:::n~~;~~~~\~~~~nxg4i:m 210159 $1.10 $1 .00 CATALOGUE ~ Weight : 220grams WITH 32 PAGES OF t-----------1 A10452 ...............$99 DATA. FREE WITH ORDERS OVER $100 ·heard so are ideal for TV remote control's , 1·9 10 99 100, P10531 S2 .50S2 .25 '2.00 1.. QUALITY 3MM LEDS :~;z,:;;.~rb7i::~~m and dual :~~';:0h5oe~e :Electret Power supply ,9V battery Cal . No. Description P10516 S2.SO $2.25 $ 1.50 1-9 10 ·99 SOCKETS S.ve • small fortu ~ on these ·wrecl Import" low prome k: sockets! PCB mounting solder tall. All lin plated phosphor D825 CONNECTOR . . SPECIALS ===t~ WIRELESS MICROPHONE & RECIEVER LOW PROFILE IC ma;ntalns a posltt,e 1·9 10·99 100.. ===1~ ====t~ CRYSTAL LOCKED liiii•-···-····•· appl ;ed to the base and ;::s~~:1o~:~ nci;;!xses.It P1051 4 $2.50 S2.25 $1 .50 ,LEDS 'i f'w'ii"iiew!i'WW-""' Hea1s;n; ?0: ~u~~?. BNC MALE PLUG ;t.ZJ-! ITT£) ( HEATSINK Normall y $11.95 MAIL ORDER & CORRESPONDENCE P.O. Box 620, Cleyton, 3168 Order Hotline: 008 33 5757 (Toll Free Sbictfy ordera on~) POSTAGE RATES $1 • $9.99..........$3.00 $10 • 24.00 ........$3.50 $25 • $49.99 ......$4.50 $50 • $99.99 ......$6.00 $100 • $199 .......$7.00 $200 • $500 .......f REE; $SOU Plus .........FREE Errors and om1ss,ons excepted Pnces and specthcattoos subfect 10 change IBM. PC · x1 · A t · il re ,e,g,11.. lldtl ldemai"kH.11 ll\19fflil!Of'ill 8u1,~ s Milchintll •A,ppe ,s ii reg,1t..-lld l•~ · o.riot.1 r1gtS1e11K1 1tildl'r_,.1 0l ~ r~ 1..,._,, 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. 386 machine hangs up in turbo mode I am the proud owner of a new 386 machine and am still trying to get used to the speed difference between it and my old JX (see "Orphan Computer To Be Disowned - page 120, September 1990). After about a month and a half of total and utter perplexity, we (me and the computer dealer) finall y ironed out the majority of the bugs (2 VGA cards, a new power supply and motherboard, a disc drive and four SIMM modules later!). There is one remaining bug though and I have asked about this. The trouble is that when I use a program that switches screen modes frequently (eg, Quick Basic), the system "hangs" after a while but only if I have the turbo on. If I run the system from boot-up with the turbo off, the error doesn't occur. Dave (the computer dealer) said that what happens is that when the turbo is on and when all the chips are getting a little warm, they could be creating errors. He said that UHF antenna for North Head translator Very shortly, I believe that the UHF television translator on. Sydney's North Head will be commissioned so that many thousands of viewers in the beachside suburbs can at last have good TV reception. Do you have any plans to publish a suitable Yagi for UHF band 5, to celebrate the event? I for one would be keen to build one as I think the commercial units are just too pricey. (S. L., Dee Why, NSW) . • Indeed you can save a worthwhile amount of money by building your own UHF antenna although we have not published a Yagi design as yet. Nevertheless, we can suggest two designs which would be suitable. 92 SILICON CHIP one way to solve the error may be to fit a heatsink to the CPU (386-20) and see what happens. Would this be a reasonable explanation of what is happening? If so, how would I go about fitting a heatsink to the CPU? (P. E., Melton , Vic). • Unless the processor is being run at a higher speed in turbo mode than it is rated for, we are not inclined to think that the problem is one of the 386 overheating. And even if it was, we would be most reluctant to try "doctoring" the unit by somehow fitting a heatsink. We are more inclined to think that either the memory chips are not fast enough or there is a problem in the software. Is the access time of the memory chips fast enough to let the processor run at the speed dictated by the turbo mode? We understand that this has been a problem in some 386 machines where the designers hav e pushed things a little too hard. Of course, you could always take the easy way out and not run Quick In the January 1988 issue of SILICON CHIP, we published a 4-bay bowtie antenna which covered both · UHF bands 4 and 5. The bowtie design has a particular advantage over an equivalent Yagi in that it is not so prone to aircraft flutter. TV signals reflected from low and high flying aircraft can be very disruptive to TV reception, particularly if you live in a hilly area which does not have strong line-of-sight signals from the transmitter. The January 1988 issue is long out of print but we can supply photocopies of the article for $5 including postage. As an alternative, we currently have a UHF corner reflector design under development and we hope to publish it soon, within the next few months . Basic in turbo. After all, as you have stated, the machine is very much faster than your old JX and it must really streak though Quick Basic, even in non-turbo mode. Wants zapper for Walkman-style radios I travel on public transport a lot and often I have to sit close to someone who is listening via headphones to a Walkman player. To be quite frank, the distorted tinny sounds coming from these phones drive me to desparation. Is there any gadget I could build which would radiate enough of an interfering signal so that the Walkman would have to be turned off? Then I could travel in blissful peace. (G. G., Gordon, NSW). • Well, G.G. , yo u are up against it but we are sure that there are man'y other people who feel the same way as you do. Leaving aside the illegality of radiating interfering signals for the moment, let us look at what would be involved. First, if the unwanted Walkman listener is playing a tape , there is no way of interfering with the unit, short of immersing it in a really intense magnetic field. While you may well feel like doing that, it isn 't really practical. Second, he or she could be listening to an AM broadcast station , although if you are travelling on a train, we don't think that is really likely, since it is not all that easy to get good AM reception on trains. However, supposing that th e person is listening to AM, it could be possible to have a transmitter which could radiate an interfering signal. But you would have to know the frequency of the received station so that you could set your transmitter accordingly. Thirdly, in the more likely possibility that the person is listening to an FM station, you really do have a problem. What you are up against is · · the "capture effect" of the Walkman 's FM tuner. This means that an FM tuner will tend to ignore the effect of an interfering signal, even if it is on the same frequency. The only way the interfering signal can break through is for it to be stronger than the wanted signal. So not only does your interference doodad have to be set to the same frequency as the Walkman is tuned ·10, it must also radiate a stronger signal. That could be a really tall order if you are near one of the FM station transmitters. In these situations, all you can really do is to count your blessings. Be thankful the person concerned is not listening to a "ghetto blaster". Still, wouldn't it be nice to have a "Thought-powered Walkman Vapouriser"? High charge at all times I have made the 60 amp-hour battery charger circuit as described on page 101 of the June 1990 issue of SILICON CHIP, using the three BD650 Darlingtons and the 3906 as shown. When connected to a flat battery it immediately supplies up to 10 amps and this current drops gradually to about 4 amps as the battery voltage rises to 15V or 16V. There is no Vtricklo or V float. I get this result again when I remove the 3906 IC from its socket and connect the charger without it. I see no sign of the chip monitoring the voltage. I have experimented with different resistors Rr, RA, RB, Re and Ro but cannot make the charger operate as described in the March 1990 issue. Please help. (G. S., Elizabeth East, SA). • Either you have connected the BD650s the wrong way around or they are faulty. We would expect that no current at all would be delivered from the charger circuit when the 3906 was .removed. This IC supplies the bias current to the three Darlingtons and if it is removed from circuit, they should not be able to turn on. You can check this out by connecting the commoned base connection of the BD650s back to one of the emitters (with the 3906 out of circuit). In this condition, the transistors should be biased right off. If they're not, check that they are connected into circuit the right way around. In fact, check this point first. If, and it seems unlikely, the BD650s More power wanted in train controller I have just bought the Train Controller Project described in the November 1990 magazine. I put the circuit together and it does not have enough output to power my Athern engine. Do you know if there is a modification to give it more output? My power supply is 18V DC at 4 amps. Also, do you know if the PC board is available separately and at what price. (W.B., Tenterfield, NSW). • As it stands, the circuit is prevented from delivering high currents by its overload protection, involving Q3. This monitors the output current via two 0.1Q resistors in parallel. This limits the maximum current to a little over 1 amp. To increase the output current, you need to reduce the current monitoring resistor. For example, you could more than double the output current by changing the two existing current resistors for a single 0.22Q 5W wirewound resistor. You can probably increase the output current to 3 amps or more but you must make sure that the TIP41 power transistor does not overheat - make sure it has an adequate heatsink. The PC board is available separately from Electronic Toy Services. Phone (08) 382 8919. are OK, you can then see why the 3906 is not operating. Again, we would suspect that it was dead or connected incorrectly. neutral" wiring was explained in an article entitled "Your House Wiring Could Kill You" in the November 1987 issue. Whatever happened to diode light dimming Notes & Errata Recently, I wanted to install a simple diode light dimmer in one of my children's bedrooms, to serve the function of a night light. However, one ofmy mates who is an electrician said that these were no longer available and had in fact been banned. Is this true, and if so, why? (B. S., Auburn, NSW). • We're not sure whether diode light dimmers have actually been banned or not but the the various energy distribution authorities have certainly banned appliances which cause DC to be superimposed on the mains. To explain a little further, diode light dimmers (which were commercially available about 20 years ago) worked by merely placing a suitably rated diode in series with the lamp. Efffectively they applied half the mains voltage to the lamps which as a result, were quite dim and, as a side effect, flickery. They were made obsolete once Triac light dimmers became cheap and readily available. Electricity authorities have banned appliances which put DC on the mains because they cause corrosion to the earthing conductors in M.E.N. systems. M.E.N. or "multiple earth IR Remote Control Extender; September 1990: some constructors are having low sensitivity problems with this unit. When re-transmitting an infrared remote control signal, the red acknowledge LED flashes to indicate reception of this signal. However, the infrared LED (IRLED1) may not provide a satisfactory output for some or all of the remote control functions. This problem is caused by ICl's AGC attack time being too short when used with some infrared remote controls. To solve this problem, the 0.15µF capacitor at pin 8 of IC1 should be changed to a larger value. Some experimentation may be required to find the best value, which should be in the range from 6.8µF to 22µF (use an electrolytic). The positive terminal of the capacitor connects to pin 8 of IC1 and the capacitor should be rated at 16VW or higher. This modification is only recommended if there is a problem with the IR Extender when it is used with your remote control unit. DC-DC Converter for Car Amplifiers; December 1990: diodes D5 and D6 are shown on the circuit diagram (Fig.1) with incorrect polarity. The overlay diagram (Fig.3) is correct. SC MARCH 1991 93 ORDER FORM USE THIS FORM FOR ALL YOUR SILICON CHIP ORDERS SUBSCRIPTION: 0 0 U RATES: NEW SUBSCRIPTION: Month To Start_ _ _ _ _ _ __ RENEWA L: Sub No._ _ _ _ _ _ Start In _ _ _ _ __ GIFT SUBSCRIPTION: Month To Start,_ _ _ _ _ _ __ ,,:c GIFT SUBSCRIPTION DETAILS o Mr/M rs/M s: _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ __ (PLEASE TICK ONE) 2 YEARS (24 ISSUES) 1 YEAR (12 ISSUES) Australia Australia With Binder NZ & PNG (Airmail) Overseas Surface Mail Overseas Airmail □$A84 □$A105 □$A130 □$A130 □ $A240 □ $A42 □$A53 □$A65 □ $A62 □ $A120 -t 0 0 ,,0 Address: _ - - ' - - - - - -- - -- - - - -- - -- -< -t :c iii _ _ _ _ __ _ _ _ Postcode, _ _ _ _ _ _ _ __ 'TI SPORTS SHIRT Please send me_ __ _ _ Sports Shirt(s) <at>$A24.95 including postage (NZ add $A3) 0 :a :1: 'TI Size: _ _ _ _ S, M, L, XL, XXL Total$"----- SILICON CHIP BINDERS ~ Yes ! Please send me; _ _ _ SILICON CHIP binder(s) at $A14.95 each C Cl 0 (including postage) TOT AL$,_ _ _ _ _ _ _ _ _ _ _ __ z (Overseas Orders add $A3 each fo r postage) .:j ~ Ill :c ~ BACK ISSUES: ISSUE SLOPPY JOE Please send me, _ _ __ _ Sloppy Joe(s) <at>$A27.95 including postage (NZ add $A3) Size: _ __ _ S, M, L, XL, XXL Total$ ' - - - - $A5.00 each (includes postage). Overseas orders add $A 1 .00 per issue for postage. YEAR ISSUE YEAR ISSUE YEAR ISSUE YEAR 0 C -t -t :c m 31: I> I:) I> TOTAL $A !:::! z m En closed is my cheque/money order for $, _ _ _ __ or please debit my Card No. O V/S4 _ !Q [i- e] _ Mr/Mrs/Ms:_ _ _ _ _ __ _ _ _ _ _ _ _ __ Add ress: _ _ _ _ _ __ _ _ _ _ _ _ _ _ __ Card expiry date Signature _ _ _ _ _ _ __ 24 Hour Fax Service (02) 979 6503 Send the coupon with your Credit Card Details. 24 Hours,- 7 Days a week. 94 SILICON CHIP _ _ _ _ _ _ _ _ _ Postcod e:_ _ _ _ __ __ Subscription Hotline Telephone (02) 979 5644 9am-5pm Mon-F ri and quote your Bankcard, Visa Card or MasterCard No. and expiry date. Detach and Mail to: FREEPOST 25 SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROY BEACH NSW 2097 No stamp required in Australia MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. r-------------------------, FOR SALE CLASSIFIED ADVERTISING RATES XT/AT HANDBOOK by Choisser & Foster. Pocket size, 92· pages. For engineers & programmers, & other serious PC/XT & PC/AT users. A collection of hardware & software facts & data on the PC-compatible & its operating system. Latest edition. This is the one advertised by Annabooks in the US mags Byte, Dr Jobb's Journal, etc. $20 including postage. 5 or more $15 each. Don McKenzie, 29 Ellesmere Crescent, Tullamarine 3043. Advertising rates for this page: Classified ads - $7.00 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. If you use a PO Box number, you must include your permanent address and phone number for our files. We cannot accept ads submitted without this information. To run your classified ad, print clearly on the lines below or on a separate sheet of paper & send the form together 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. ----- ---- - - - - -- - - - - -- - ICOM TYPE NICAD battery packs. 500mA.h 8.4V $48, 5+ $40 each. lcom type empty battery pack; fit you own nicads $12, 5+ $10 each. Xtal 3.5795 MHz NDK brand $2. 1OO0µF 16VW electrolytic 25c. Electronic flash unit, ex-equipment, $3. Add $2 p & p. Speedtronics, PO Box 538, Mirrabooka, WA 6061. - - -- WEATHER FAX programs for IBM XT/ ATs *** "RADFAX2" is a high resolution, shortwave weather fax, Morse & RTTY receiving program. Needs CGA, SSB HF radio & Radfax decoder. Also "RF2HERC", "RF2EGA" & "RF2VGA", same as RADFAX2 but suitable for Hercules, EGA & VGA cards respectively. $35. *** "SATFAX" is a NOAA, Meteor & GMS weather satellite picture receiving program. Uses EGA & IIT MATHS COPROCESSORS Enclosed is my cheque/money order for $_ _ _ _ or please debit my O Bankcard o Visa Card 0 Master Card J( I I I Signature_ _ _ _ _ _ _ _ _ _ _ Card expiry date_ _~/_ __ I I Name - - - - - - - - - - - -- - - - - - - - - - - - I I Street ------------------------ I I Suburb/town _ _ _ _ _ _ _ _ _ _ _ _ Postcode_ _ _ _ __ I Card No. 2C-08 2C-10 2C-12 2C-20 2C87- 8MHZ 2C87-10MHZ 2C87-12MHZ 2C87-20MHZ A' '1&,>: ~,s, ,,,.o "9 ( $330 $359 $430 $490 ~<S'<S' 3C-16 SC87-16MHZ $640 3C-20 3C87-20MHZ $680 3C-25 3C87-25MHZ $840 3C-33 3C87-33MHZ $990 These pices include Sales Tax. Stocks are limited at this price, so order early. PHONE (02)957 67 FAX (02)954 5550 L-------------------------~ MARCH 1991 95 r MEMORY EXPANSION SIMM& SIP 9 x256 9x1MB 9x4MB Bx1MB DRAM/DIP 4MBS\ali'.: 41256 41464 4164 1MB 414256 sons CO-PROCESSORS NTl3.. a::£1-1 NTI3..287Xl NTI3..:1!7SX16 NTI3..:!l71JX33 CYRIX$/DX20 CYRIX$/DX25 21.00 7.l.00 37500 68.00 INTEL 17500 ::B5.(X) 43200 848.(X) 51000 58.00 2.10 2.50 215 7.30 7.60 PELHAM 8J287-10 TOSHIBA LAPTOP 13m 3.13 42000 T18JJ 131a£ 131CXSX T1CXXSE ,Ml ,Ml ,Ml ,Ml ZlOI1J ZlOI1J ZlOI1J 400.00 640.00 A. M. D. SAVE 50% ON CO-PROCESSORS !0"6 ..... Prices At January 18th 16800 IBM PS/2 1M3 ,Ml ,Ml Altronics .. ... .. ... .. ... ........ ......... 22-25 Arista ... ... .. ......... ... ....... .. 43,81,89 Back Issues .................. ........ 58 ,59 CXM'Nl 386-20, 386-25, 386-2CE, 386-S, 386-33 4MB MODULES 4MB BOArds Advertising Index 490.00 580.00 135.00 :moo :moo Cad Connection ..... ..... .............. 95 David Reid Electronics .. ...... IFC, 1 Dick Smith Electronics ...... .... 13-15 Electronic Solutions ..... ... ... .... ... 65 Electronic Toy Services ......... ... 96 Sales Tax 20%. Overnight Delivery. Credit Cards Welcome 1st Floor, 100 Yarrara Road, Pennant Hills, N.S.W. 2120 Tel(02)980-6988 Fax(02)980-6991 \.. Elmeasco .. .......... ........ ... .. ... ...... 31 Geoff Wood Electronics ......... ... 73 Harbuch Electronics ..... .. ...... ... 29 Hycal Instruments ............... .. ... 96 MODEL TRAIN CONTROLLER project Silicon Chip November 1990, $19.95 plus $2.50 p&p. Plugpack, 12VAC, 1.7A, suitable for the above (use rectifier), $29.95 plus $4.00 p&p. Kits built & repaired. Prototype production board supplier to the hobbyist & supplier of SILICON CHIP project PCBs. ETS, PO BOX 491, NOARLUNGA CENTRE, SA 5168. Phone: (08) 382 8919 FIX-A-KIT $20.00 PER HOUR LABOUR Jay car Electronics ... ..... ....... ..... 48 J.V. Tuners ..... ...... ... .. .... ..... ...... . 30 3 MONTHS WARRANTY ON REPAIRS 12 MONTHS WARRANTY ON CONSTRUCTION M. Radvanyi ........................ ... ... 96 Service to most types of electronic equipment Oatley Electronics ......... ... ........ 77 TECHNICAL ASSISTANCE HVCAL INSTRUMENTS Design, Manufacture & Repair of Electronic Equipment Trading Hours 8am to 3pm, Monday to Friday (02) 633 5897 PC Computers ..... ... ... ....... ....... 96 PC Marketplace ... .. ....... ..... ..... .... 5 Pelham ....... ... ... ..... ...... ............ 96 Philips T&M ... .... .... .. ........ .. ... OBC Raytec Data Systems .. ........ .. .. 30 RCS Radio ..... ....... ... ...... ..... .... .. 45 MAX I/O Board Kit $149.00 Built & Tested $269.00 • 7 x Relays SPST 2 amps each • 8 x Switch inputs (TTL) • 1 x OAC (Digital to Analog converter) • 1 x ADC ( Analog to Digital converter) • 4 x Motor Drive outputs (40mA ea.) • 1 x Programmable timer output. MAX includes a 20 page manual with all schematics, parts layout etc., a 360K PC compatible floppy with diagnostic and sample software in GW-Basic. MAX runs from a PC compatible Printer port for full compatibil ity with a large range of computers. Same day dispatch of orders. Credit cards or personal cheques welcome. Phone: (08) 332 6513 or Fax: (08) 364 0902 (24 hours) $32.50 incl . p&p. Money order or cheque. M. Radvanyi, PO Box 49 , Kingswood, NSW 2749. Resurrection Radio .. ...... .. ........ 43 Rod Irving Electronics .. ........ 40,41 60,61 ,90 ,91 LAB LASERS. 0 .5mW to 2mW HeNe lasers complete. Ideal for students or hobbyists. Australian made. $440 to $640. Phone M.C.E. Lasers (03) 357 0055. ANTIQUE RADIO Sheridan Electronics ........ ........ 72 Silicon Chip Binders .... .... ..... . IBC Subscriptions ....... ..... .. .. .. ...... ... . 94 Soundring ..... .. .. ....... .. ...... .... .. .. 81 Tech -Fast ...... .... ... .... .... ........ ..... 79 PC Computers 36 Regent St,Kenslngtor.i, SA VGA modes, needs EGA or VGA colour monitor & card, plus "WEATHER FAX" PC card. $45. *** All programs are on 5.25-inch or 3.5-inch discs (state which) & include documentation . Add $3 postage. ONLY from M. Delahunty, 42 Villiers St, New Farm , 4005 Old. Phone (07) 358 2785. DIGITAL WAVEFORMS from a PC. As described in SILICON CHIP in March 1990, May 1990 & June 1990 .. The software can also be used for the similar project (Simple PC Function Generator) described in Electronics Australia in January 1989. Software & PC Board: $39.95 incl . p&p. Software only: 96 SILICON CHIP ANTIQUE RADIO restorations. Your one-stop electronic repair shop . Specialising in restoring vintage radios including chassis rewiring , quality new parts , valves, valve sockets, speakers , transformers, cabinet restoration . Quality secondhand radio dials & parts for most brands & models. About 400 radios in stock for restoration & parts. Every restored wireless is covered by a 2-year warranty on parts & service. French polishing of timber cabinets available. Vintage car radios in valve & transistor types available for restoration . Repairs done on tape decks, amplifiers, TVs & videos. Open Sat. 10am-5pm; Sun. 12.30-5pm. 109 Cann St , Bass Hil l, NSW 2197. Phone (02) 645 3173 BH or (02) 7261613AH. PC Boards Printed circuit boards for SILICON CHIP projects are made by: • Electronic Toy Services, 2/111 Glynville Drive , Hackham West, SA 5163. Phone (08) 382 8919. • 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. Phone (02) 587 3491. uality olds u 1 i 0mm internal wi rinted with • I .· n Sl)ID d front ' pies -of ith theiF me in, eii: own CHIP. . W-e aFe especially -pleased a quality. As soon as the first batch n,.our staff want s. ll to e store Made with a distmctive two tone green high-quality vinyl specially seleet,ed for SILICON € HIP, ai d wi h heavy board covers, each binder holds a year1s issties (the 14 issues of Vol. I or the IQ, issues of V01.2). 2fhey will look really sma~ on your bookshelf. To ordeli you11 binders, fill in the coupon on page 94 and send it to SILICON CHIP, PO Bo;x 139, Ci:ollaroy Beach, NSW 2097. A) ternativel): plione (02) 979 5644 and quote· your credit card details, or fax our orders to (02) 979 6503. Prlce $AI1.95 plus $A3 each for postage and packing. (NZ postage and pack'ing $A6.) ' ,e