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THE DIGiTAL COMPACT CASSETTE SERVICING - VINTAGE RADIO - COMPUTERS - AMATEUR RADIO - PROJECTS TO BUILD PHILIPS Fluke and Philips handheld tools ,. so advanced they're simple to use l A host of user-friendly features Many special features make the Fluke DMMs arid Philips ScopeMeter \ more convenient and easier to use. ' The display screens are easy to read. Touch Hold<at>on the Fluke 70 : ' and 80 series freezes the display on, ·vstable readings . so you can use { both hands to take a measurement. The Fluke 10 series features a time vchek'" . aFluke innovation. impressive range .of measurement capabilities for the 'price. All series feature auto and manual ranging. In short, these user-friendly tools make taking measurements a great deal easier for the on site technician. The Philips PO Series ScopeMeter . The Fluke Multimeter Series How JnUCh meter can you get into a multimeter? !I' . The Fluke series of versatile multimeters blend state-0Hhe-11rt analogue and digjtal perlo'.mance with affordability. Otfwng an The pert shootigg c TI'le Scop hign-pertorm storage osc featured 300 one, handhe It's the · a rugge MHz digi aod a 1 ltillifflf • nt. HE UN-BREAKTHROUGH . THAT WIL'L HAVE YOU SMILING FROM VOLTS TO OHMS _,,,., ·. How TO BEAT .' THE HIGH COST OF CHEAP METERS ,, ;1 Ooops! l A tool isn't very useful 1'f. ·h it won't .~It stand the hazards of everyday use . h By putting them through some of i t e . toughest simulated accidents imaginable, Fluke and Ph·1· 1 1ps meters . ,1 are as tough as they are affordable. Tough enough to work whe you work h « rever • t ey ouer a long battery I'If, And to ak e. m e sure your modest vestment in a meter is well pro cted, Fluke and Philips build the; last • ms1de and out , wit . h rugged otecti ve casings and , ign. error-proof The '.estdt? A wide choice of gh, high performance diagnost' tools for the trician on the go. tc - For further information please contact your local Philips Test &Measurement Organisation: NSW (02) 888 8222 VIC (03) 881 3666 WA (09) 277 4822 . QLO (07) 240 3700 SA (08) 384 2888 NZ (09) 849 4160 You'll measure .better performance ;r; .. L..,.,_,_,, --;~ 1 •~ • 7 --, ~-I L__ I I I lI_ - _ - -,__ I I -; 7 ,__ I --; I I "'1 . I l I l"'----I .___ ...... - - ·1 I I · I I I ,,J__ \ } , _ Vo/.6, No.4; April 1993 FEATURES DIGITAL COMPACT CASSETTE (DCC) players are now available in Australia. The format provides CD _quality & can also play conventional cassette tapes. See page 6. 6 The Digital Compact Cassette by Leo Simpson New digital decks also play conventional cassettes 8 The Story Of Electrical Energy by Bryan Maher Winning the white metal - the story of aluminium 21 Silicon Chip 5th Birthday Sweepstakes The list of prize winners PROJECTS TO BUILD . 14 A Solar-Powered Electric Fence by Branco Justic Use it to control livestock & protect vegetable gardens ELECTRIC FENCES are ideal for controlling livestock. This lowcost design can control fences up to several kilometres long & is powered by the Sun. See page 14. 22 Build An Audio Power Meter by Darren Yates Monitors power levels from 200mW to 100W 37 Three-Function Home Weather Station by John Clarke Monitors barometric pressure, temperature & relative humidity 56 12VDC To 70VDC Step-Up Voltage Converter by Darren Yates Ideal for powering battery-operated valve radio receivers 80 A Digital Clock With Battery Back-Up by Darren Yates The 4-digit display features automatic dimming SPECIAL COLUMNS 32 Serviceman's Log by the TV Serviceman The path of TV service never did run smooth 53 Remote Control by Bob Young Practical applications for the low-cost speed controller 64 Computer Bits by Joe Elkhorne · THIS WEATHER STATION has a 3½-digit LCD & can monitor temperature, barometric pressure & relative humidity. Construction starts on page 37. Upgrading to a 386 - now I know what a "kludge" is 88 Vintage Radio by John Hill Restoring an old radio chassis DEPARTMENTS 2 Publisher's Letter 4 Mailbag 30 Back Issues 63 Order Form 70 Product Showcase 72 Circuit Notebook 92 Ask Silicon Chip 93 Notes & Errata 94 Market Centre 96 Advertising Index WANT TO CONVERT 9-12V DC to any voltage up to about 70V DC? This low-cost unit will do the job. Details page 56. APRIL 1993 1 Publisher & Editor-in-Chief Le·o Simpson, B.Bus. Editor Greg Swain, B.Sc.(Hons.) PUBLISHER'S LE'I*I'ER Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Darren Yates, B.Sc. Reader Services Ann Jenkinson Sharon Macdonald Sales & Marketing Mgr. Sharon Lightner Phone (02) 979 5644 Mobile phone (018) 28 5532 Regular Contributors Brendan Akhurst Garry Cratt, VK2YBX Marque Crozman, VK2ZLZ John Hill Jim Lawler, MTETIA Bryan Maher, M.E., B.Sc. Jim Yalden, VK2YGY Bob Young Photography Stuart Bryce Editorial Advisory Panel Philip Watson , MIREE, VK2ZPW Norman Marks Steve Payor, B.Sc., B.E. SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. A.C.N. 003 205 490. All material copyright©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Magazine Printers Pty Ltd, Alexandria, NSW; Macquarie Print, Dubbo, NSW. Distribution: Network Distribution Company. Subscription rates: $42 per year in Australia. For overseas rates, see the subscription page in this issue. Liability: Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. Editorial & advertising offices: Unit 1a/77-79 Bassett Street, Mona Vale, NSW 2103. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 979 5644. Fax (02) 979 6503. ISSN 1030-2662 2 SILICON CHIP Forecasting electronic developments in cars What is likely to be the next big application of electronics in cars? Electronic ignition is now standard on virtually all new cars and engine management systems are common on all except the cheaper 4-cylinder models. On more expensive cars, antiskid brakes are becoming common while in the United States the electronically triggered air-bag system is more or less standard, largely because that country has not legislated for compulsory seat belt wearing. But what is the next big development likely to be? Some pundits are forecasting that electronic navigation systems will be the go and a lot of developmental work has been done along these lines in Europe. But do the next big applications of electronics need to be so complex and expensive? In thinking about this topic, consider what could be done to make vehicles more economical. Engines have become much more efficient but at the same time, vehicles have become a great deal heavier. Partly this is due to the use of more glass, more sound deadening and more electric motors to drive accessories. Well, how about this as a suggestion? Eliminate the rear window entirely and substitute a video camera and small screen on the dash - possibly this could double for the electronic navigation system when that comes into use. By eliminating the rear vision window there would be a considerable saving in weight, not only due to getting rid of the glass (which is much heavier than sheet steel) but also the ancillaries such as demister wiring, washer, reservoir and wipers and their motors and wiring (in the case of hatchbacks). And let's not forget the internal rear vision mirror itself. This could go and thus eliminate a dangerous blind spot for tall drivers. There would be other benefits too. The car interior would stay cooler and there would be less load on the air-conditioning. The resulting rear vision would probably be better in most cars than it is now, obstructed as it often is by head restraints, passengers and the shape of the car body itself. And it would probably make parking easier too. Would people go for it? My guess is that it would depend on how the stylists approached it. A car without a rear window coulq look incongruous because we have been so used to seeing it there but remember that the first cars had only very small windows or no rear window at all. Anyway this idea is not really new and was tried as an experiment during the sixties. But then video gear was cumbersome and not as reliable as it is now. Today's minuscule CCD cameras-would be ideal for the task. It's intriguing, isn't it? And it's all possible, right now. Leo Simpson Attention Small Business Owners I "IDI "IDI Hugie-011-llold "IDI for standard telephone systems. Yes I It's finally here ! A Music-on-Hold system for standard telephones. No need to purchase expensive PABX or Commander systems, Telecom installations, etc. Save your hard earned dollars ! Now you can give your customers a relaxed atmosphere while they are on hold. It could also give you the opportunity to promote your products ii connected to a Digital Voice Recorder or an endless loop tape via a standard tape player. Utilise your advertising time and expense every time you put your customer "on-hold". How it works:The user can press/dial 8 (Tone or Pulse) and then hang-up within 6 seconds to put incoming or outgoing call on hold. Call will remain on hold until the telephone handset is picked up. It's that simple. Note: Calls can only be put on hold or retrieved from hold with the telephone connected to the Music-on-Hold. Other telephones on the same line can be used ii these are connected by using telephone double adaptor and extension cord run directly from the Music-on-Hold. ~ System Options:- ~ Music-on-Hold Line Sharer ~ ~ ~ Line Isolation Unit Austel Approved. "IDI "IDI 8mm Video Cassette for Camcorders - 60min. $9.95 3.5" or 5.25" format (IBM) bandwidth of over 60kHz. Matching "ID1 software available allows you to "IDI display captured waveforms, zoom in "IDI on segments of interest, and also save waveforms to disk. · "IDI "IDI "IDI 1 -------:~~R.,tPL: .-i!IIP'lll-.i"ca ·t.!IIMN~I ••Iii••- I Ideal for keeping I wiring looms neat. I sizes. Available In two I I smm min. I.D. I 113mm min. I.D. I I $l95/mtr. I ~.,,, . I 1I · · · · ~ -- . I ~, Kit - eoa.50 - PC software 5.25" or 3.5" - '19.95 • """' * SHARP ZQ1200 * LABTECH 20MHz Dual Trace OSCILLOSCOPE Includes 2 probes * * =--.. "IDI $359.00 "IDI "IDI "IDI 34kB DIARY Store Name's, Address's, Phone Number's and more I * * ** ** * * ** Now Only $95.00 ** Now Only $650.00 inc. tax. Due to size and weight, we can not offer free frleght. ** * * * * * * * Please call for a quote on frieght charges. "IDI ETHERNET CABLES - BNC M/M 50 ohm "IDI 2 mtr. $ 7_95 1omtr. $16.95 BNC "T" $7.95 """"' 3 mtr. $8.95 RF Transmitter & Receiver (12 Volt) A.C.N. 001-372-372 : ~ ~~~~~~~~~~~~~********* 2omtr. $24.95 ~ - - - - - - - - - - - - - - - - - - - -"""' 5 mtr. $10 .95 ONLY$89.95 ~ ~q,~ I Record Cleaning I I Brush - $1.00 ·I Digital Storage Cro Adaptor Kit for IBM PC's $279.00 11 you need more information on this product, please call Jeffery Yager on (02) 267 1385, or by fax (02) 261 8905. A top product for '93. Remotely control just about any device up to 10-15 metres away. Complete with two key transmitters and one receiver. N.0./N.C. contacts (240V <at> 1A). Dial Cord 10mtr. - $1.00 1 gamei 9 levels "IDI "IDI Connects to the printer port of an IBM "IDI compatible PC, and converts it into a . 't I I" "II "th "IDI d191 a samp mg OSCI oscope WI a ~4. 0 VARTA •AA• NlCad 1.2V <at> 600mAH Made In West Germany "IDI "IDI ~ Music-on-Hold including ~ "IDI "IDI Wolf'"enstein 3-D Two weeks ago, you were flying for the allied air force. Now, you're a prisoner held by enemy intelligence in a castle from which nobody's escaped - ever! In a break that only comes once in a lifetime, you've overpowered the guard and taken his gun! Now, can you make it out alive I T-8 $14.50 T-10 $14.50 $3.35 ~ ~ ..,:;;;==========.;: _"'.:,e.. rm-in_a.. to;_r..,.:$.. 3 ... 90,;.__ _ TORX Drivers by VACO Joiner PLCC EXTRACTOR Only $ _9 14 5 a ma<!e In USA 2 way AUTO Parallel Switch Box For two PC's - one Printer Sell powered. :M:essage Stopper This inexpensive device, which connects direct to your answering machine will automatically disconnect your answering machine whenever ANY PHONE is answered. II your answering machine answers your call before you do, simply pick up any phone, your answering machine will immediately disconnect and you can speak without interference. MAILBAG Low cost method for PC board construction I make my circuit boards by using the magazine artworks as templates to mark the holes on a blank piece of copper laminate using a centre punch. After drilling, I then draw, using the holes as a reference, a negative pattern of the artwork onto the board with an ordinary lead pencil, showing the material to be removed and leaving the copper tracks and bands exposed. With a tiny cutter in a minidrill (Arlec tools), I then cut away the pencilled areas, ending up with an approximate copy of the artwork. After cutting the pattern, I carefully remove all the shavings using a small · stiff brush. By holding the board against the light it can be e.asily checked to see that all tracks are properly cut. When satisfied, I sand the remaining copper pattern with very fine emery paper until the copper is shining brightly and remove any dust. I don't know of any cheaper and safer way of making PC boards. You need no chemicals, no photostatic materials and no artwork materials for masking, etc. M. Schmidt, Edgewater, WA. Too much faith in computer programs It was with great interest that I read the Peerless PSK60/2 loudspeaker project in the January 1993 of SILICON CHIP. Some months ago, I decided to build a couple of compact loudspeakers and in the course of deciding on components to form the basis of my system, happened upon the very fine Peerless range. I then went on to construct these speakers and have never been the slightest bit disappointed with their performance. My speakers are virtually identical with the PSK60/ 2 units except that I chose a completely sealed acoustic suspension type enclosure. In comparing the two approaches, one wonders if we are not becoming a little bit too dependent on the results obtained from computer programs and forgetting to think out the fundamen4 SILICON CHIP tals first. The results obtained from Mr Manning's design, no doubt obtained from the ubiquitous LEAP program, show an almost identical response to my sealed design. Being unable to justify the cost of a LEAP program for one pair of speakers, my figures were derived from "The Loudspeaker Design Cookbook" in conjunction with a pocket calculator. My real point in this letter is that before the advent of programs such as LEAP, we had no choice but to consider the basics. I would contend that there are real advantages in taking the sealed approach with bookshelf-sized speakers in that the natural bass extension (12dB rather than 24dB per octave rolloff) and the ability to apply some moderate bass boost allows a slightly bigger "bass per litre" sound than an equivalent reflex enclosure. My suspicion is that by going straight to the computer and specifying a reflex design, Mr Manning has bypassed a possibly better sealed approach. A check by me (with pencil and paper) shows the responses for both sealed and vented enclosures with this particular driver and a 14litre box to be virtually identical. I'm sure I'm wrong about Mr Manning not considering philosophical alternatives. But just to be sure, I wonder if he'd mind jamming corks in the ports of a pair of his speakers and telling me if they sound different. D. Fripp, West Ryde, NSW. Comment: We agree that placing reliance on a computer program to produce a speaker design is folly indeed. Just because the computer comes up with a particular design does not mean that it will sound good. In fact, in the past we have designed a number of speakers using the Thiele/Small parameters (not using a computer though} and the results have been lousy. So just following a design procedure, computerised or not, does not guarantee good results. We assure you that the PSK60/2 speakers do not sound the same if you block off the ports - their bass output drops. The big advantage of SILICON CHIP, PO Box 139, Collaroy Beach 2097. the bass reflex design is that the cone excursion is considerably reduced at low frequencies and therefore you have more linear operation. High voltage probes - beware the dangers I have read your article "High Voltage Probes: Beware the Dangers" in SILICON CHIP for December 1992. I am surprised that neither the Coroner nor the Chief Electrical Inspector pointed out that, according to AS 1188, a standard applying to electric welders, handheld probes should not be used to measure voltages above 1000V peak. AS 1188 applies generally to all types of commercial electronic equipment, radiocommunications equipment and other equipment employing similar techniques; eg, radio and television transmitters, 400Hz aircraft equipment, power tools, electric welders, electrotherapy equipment, switchmode power supplies, radio-frequency heating and so on. George Douglas, Gosnells, WA. Question & correction on audio mixer for camcorders I am writing regarding the Audio Mixer for Camcorders published in the March 1993 issue of SILICON CHIP. First, allow me to congratulate you on a useful project which I'm sure will be very popular. Unfortunately, a small but important error has crept into the article. The component overlay on page 51 shows two of the 2.2µF capacitors used for the lower cutoff with incorrect polarity. Also, I am curious as to why the upper cutoff is so high at 72kHz. Wouldn't the circuit give better performance if this was lowered to just above the range of human hearing? Steven Merrifield, Heidelberg, Vic. Comment: lowering the cutoff frequency (eg, to 20kHz} would reduce the flatness of the passband without having any effect on the audible noise. Thank you for pointing out the error in the wiring diagram. An errata has been published in this issue. SC ~~~~~...ii GW PRODUCT SAFETY RECALL ,, - ,...ii ELECTRICAL SAFETY WARNING ,, ,...ii The following electrical testing articles are unsafe to use: ,...ii ,, CTI C86A Universal Counter ,, - ~~: ~:::i•::w~;::::~; ,...ii The above articles could cause electric shock due to inadequate insulation of live parts and a lack of earthing. -,...ii ,, ,...ii - 100MHz ,, ,...ii ,, DISCONTINUE THE USE OF THESE ARTICLES IMMEDIATELY ,...ii For repair of the articles return to: - A-One Electronics Pty Ltd, 432-434 Kent St, Sydney 2000. ,...ii ,, QUALITY SCOPES ,, 40MHz -;h~7; ;2;48~ ~ ESCORT EDM-1133 20MHz • • • • • • 3¾ Digits Autoranging 8 Functions DC V, AC V DCA,ACA Ohms Valued at $127! A look at some of the best Model Railways in Australia - * lnc!ucles Australian, European, U.S. and U.K. layouts in all scales * eo;are prot~type locations in Australia with the Mo<lel layout * Vistt a,11 the reeelit exhibitions around Australia * All technical detail explained This is a high quality Broadcast Production teaturing: CHOO-CHOO-CAM Available from: ACTIVE MEDIA IMAGES A Micro Camera mounted atop locos as they move around the layout PO Box 90, Riverwood, N.S.W. 2210 Phone: (02) 580 8525 60 minutes Running Time Cheque. Money Order, Bankcard, MasterCard or Visa GOS-6100 GOS643 GOS622 4Channels 2Channels 2Channels 100MHzBW 40MHzBW 20MHzBW 500uV • 5V/DIV 1mV-5V/DIV 1mV -5V/DIV Dual Timebase, to2ns/DIV Dual Timebase, to 2ns/DIV Timebase to 2ns/DIV Dual Timebase Trig. Auto Trigger Level Lock Auto Trigger Level Lock Variable Hold-Off Variable Hold-Off Variable Hold-Off 20kV Accel. Voltage 12kV Accel. Voltage 2.2kV Accel. Voltage EMONA INSTRUMENTS NSW (02) 519 3933 VIC (03) 889 0427 OLD (07) 397 7427 Also available from: WA (09) 244 2777 SA (08) 362 7548 TAS (003) 31 6533 APRIL 1993 5 Philips' DCC recorder is up & running On 19th February 1993, Philips officially launched the Digital Compact Cassette (DCC) in Australia. The DCC deck is being promoted as the digital successor to the compact cassette & it has the advantage that it will play all existing tape cassettes. By LEO SIMPSON DCC is a new digital recording medium which will provide sound quality comparable to compact disc standards. It uses a new tape cassette but DCC decks will also be able to play existing analog compact cassettes. To look at, the new DCC decks from Philips, Marantz, Technics and other companies do not appear radically different from existing hifi equipment and are quite similar in playback functions to a CD player - they even have a roll-out drawer. However, the digital cassette itself and the recording principles it entails are radically dif6 SILICON CHIP ferent from the analog compact cassette which is familiar to everyone. Since the new DCC decks will play existing compact cassettes, it follows that the overall dimensions of the new digital tape cassette are very similar to the analog cassette. The major difference in appearance is that the DCC has a sliding metal shield which is similar to that on 3.5-inch floppy discs. This sliding shield covers both the tape at the top of the cassette and the holes for the drive spindles. While the DCC is playable on two sides, the drive spindles are accessi- ble only from one side. To play side B, in digital or analog mode, the whole head assembly rotates and locks into position. The tape width is 3. 76mm, the same as for conventional analog cassettes but that is where the similarity ends. The digital signal is recorded on eight parallel tracks, each of which is only 185µm (microns, that is) wide and only 70µm of each of the eight tracks is scanned on playback. The large difference in effective track width between recording and playback is to reduce the sensitivity to azimuth errorwhi~h would otherwise play havoc with the system. There is also a ninth track on each Above: this is Philips DCC900 deck which has virtually all of the playback convenience features of CD players when playing DCC tapes. It can also play analog tapes with Dolby B or C noise reduction. side of the tape which is used for the data display and some control functions. As you can imagine, the heads required to track these minuscule tracks could not be made by conventional means and Philips has had to borrow from semiconductor fabrication techniques. As a result, thin film technology has been used to provide a head assembly which has three sets of head elements: (a) nine integrated heads for digital recording; (b) nine magneto-resistive heads for digital playback; and (c) two magneto-resistive heads for analog playback. The digital heads occupy one half of the head surface while the analog heads occupy the other. Thus, both digital and analog tapes can be played in both directions by the auto-reverse head assembly. The concept of magneto-resistive elements for playback heads is new to cassette decks. In a conventional magnetic playback head, the varying magnetic field on the tape causes a similarly varying electrical signal (an analog) to be produced from the head winding. By contrast, in a magnetoresistive head (MRH), the element's resistance varies according to the magnetic field stored on the tape. A constant current is fed through the resistance element and the resulting varying voltage becomes the recovered signal. According to Philips, magnetoresistive heads are excellent for reading DCC bit transitions. For analog playback, Philips claim that the inherently high bit rate capability of magneto-resistive heads allows for a wide frequency response. Data compression For digital records, three sampling rates are possible: 32kHz, 44. lkHz and These two photos of the DCC show the new format. The cassette slides into a protective case which is much less likely to be damaged than the old compact cassette case & the program information is on the cassette itself as well as on the case. The cassette ha:s a moving metal plate, similar to that on a 3.5-inch floppy disc, which protects the tape when it is out of th~ playing deck. 48kHz, the same as on DAT recorders. But whereas the effective tape speed in DAT recorders is high, in the DCC format the tape format is fixed at the snail's pace of analog cassettes, 47.6mm/second. Even by using the technique of eight parallel tracks, there is still a big problem with packing enough digital data onto the tape. If conventional data storage methods were to be used, the recording medium would just not be good enough to match DAT or CD standards. Philips has solved this problem with a new data compression method called Precision Adaptive Sub-Coding or PASC. This uses a number of techniques which are new to digital audio. First, PASC takes advantage of the fact that the human ear can only hear sounds above a certain threshold and its sensitivity is greatly reduced for soft sounds at the low and high sections of the audible spectrum. Marantz has two models of DCC deck available, both of which have essentially the same features. The DD-92 model is gold while the DD-82 model is black. Second, PASC takes full advantage of the phenomenon known as "masking" whereby a loud sound masks a soft sound. Loud sounds also modify the threshold of hearing so that the data for soft sounds can be omitted. PASC splits the audio spectrum into 32 sub-bands of equal width. Then, on the basis of the signal level in each sub-band, it calculates the masking threshold for every sub-band. Subband signals above the dynamic threshold are digitally coded with varying resolution (scale factor) proportional to their amplitude. Sub-band signals below the dynamic threshold are not encoded. There is a great deal more to the PASC technique than we have space for in this brief article but the system is so efficient that the resulting encoded data requires less than 25% of the bit rate capacity which would be required if conventional PCM (pulse code modulation) methods were used. Even so, the sound quality in terms of distortion, linearity and dynamic range is every bit as good as available from CD players or DAT recorders. Philips presently has just one model of DCC recorder available: the DCC900 which sells for $1799. The soon to be released DCC600 is expected to sell for about $200 less. A car player will be released later this year. · Marantz has two models available: the DD-82 finished in black and selling for $2499 and the DD-92, finished in traditional Marantz gold (champagne) and selling for $2999. SC APRIL 1993 7 The Story Of Electrical Energy, Pt.22 The production of aluminium is the most energy intensive of all metal refining operations. But while most readers would realise that the conversion from alumina to aluminium .involves huge amounts of electricity, the mining & alumina refining stages are also very energy intensive. By BRYAN MAHER Over the next few issues, we will trace the aluminium story from the mining of the red bauxite ore, refining it to snow white alumina and then to . the electrolytic reduction to pure alu. minium. Every Australian purchases an average of 16 kilograms of aluminium each year, in various forms. Maybe you bought lots of "tinnies", or perhaps metal furniture or kitchen appliances, or even a new alloy head for 8 SILICON CHIP your car's engine. Australia produces well over a million tonnes of pure aluminium each year, two thirds of which is exported. Our main customers are .Japan, China and South East Asia . Over 125,000 Australians are employed in the overall production of aluminium, from the bauxite ore mines to the finished metal. We begin our story at ground level, where the red bauxite ore is found. It is ironic that although aluminium is the most abundant metal in the Earth's crust, it was one of the last to be isolated. Many rocks and clays contain aluminium in combination with other elements, usually iron, silicon, and oxygen, together with trace quantities of gallium, titanium, vanadium and phosphorus. The most useful source of aluminium oxide is a red pebbly ore known as bauxite. Australia leads the world in bauxite mining, with four large mining operations at widely separated locations. Alcoa (Aluminium Corporation of America) has perhaps the largest operation in the Darling Ranges of Western Australia. Next in annual tonnage is Comalco's mine at Wei pa, on the western side of Cape York in Queensland. Third is Nabalco's operation at Nhulunbuy on the north eastern tip of the Gove Peninsula in the Northern Territory. The Reynolds organisation mines at Worsley in Western Aus- ◄ Left: this front loader can fill these 80-tonne capacity trucks in just four bites. The ore is then taken to the crushers before being placed on a long conveyor for transportation to port. tralia, and there are others. Total bauxite won in Australia is around 36 million tonnes per year (1986 figures). Bauxite is called a residual ore. It is formed by the natural weathering of rocks wherein the non-valuable materials are leached away over millions of years, leaving the residual ore. Bauxite consists of two types of hydrous aluminium oxides combined with iron, silica and other trace metals. It is the strong presence of iron oxides that give bauxite its rich red colour. Two of the largest deposits of bauxite in the world are those found on opposite sides of Australia's Gulf of Carpentaria, at Wei pa on the eastern side and at Nhulunbuy on the northwestern extremity. Early explorers The Gulf was the most visited coastline of Australia in the very early days and coincidentally Weipa is the site of the first ever landing by white men on Australian soil. Willem Jansz in the Dutch ship Duyfken (Little Dove) sailed into the eastern side of the Gulf in 1606 and landed at Albatross Bay, the site of present day Weipa. He left an embossed metal plate nailed to a tree to prove his visit. The headland on which the lighthouse today stands, guiding giant bulk ore carrier ships out of the port, is named Duyfken Point. That other famous Dutch navigator, Abel Janszoon Tasman, in his ships Zeemeeun, Limmen and Bracq, charted the Gulf in detail in 1644, naming it "Carpentaria". He sailed around the Gulf from Weipa via Groote Eylandt (which he also named) and on past the site of present day Nhulunbuy. The first written record alluding to the existence of Australia's bauxite deposits are found in the 1803 log of Captain Mathew Flinders. In circumnavigating Australia, he traced Tasman's path in the Gulf, naming two mountains, Saunders and Dunas, and Melville Bay, today the site of Nhulunbuy's harbour. In his log, he commented on the stark red cliffs of Stretching off into the distance, this 19km conveyor takes bauxite from the crushers at Nhulunbuy to the stockpiles at Melville Bay in a journey which takes about 1½ hours. the Peninsula, not realising that he was looking at vast quantities ofbauxite. Identification of the red deposits as bauxite did not come until 1949 on offshore Marchinbar Island. Three years later, the first geological survey of the ore commenced but the first lease holders abandoned their claim. In 1965, the joint venture partners Swiss Aluminium and Gove Alumina obtained a special mining lease covering 20,000 hectares which was surveyed by air. Following a feasibility study, a $320 million prospecting and construction program commenced in 1966. By 1968, the known reserves confirmed by a massive core drilling program were found to be 254 million tonnes. Each tonne of bauxite contains 50% aluminium oxide (or alumina to give it its commercial name). Pilot shipments of crushed bauxite in bags were sent to a smelter in Venice in 196 7. These were followed by two bulk shipments totalling 3500 tonnes within eight months. Two years later, the venture partners formed a compan y named Nabalco to build a full-scale bauxite mine. Nabalco also built the conveyors and loading plant, a deep water harbour in Melville Bay, a modern town to house 4500 people and the alumina refinery plant. Nabalco completed the 1300 homes and infrastructure ofNhulunbuy, including the largest primary and secondary schools in the Northern Territory, by 1972. Mining operations The bauxite deposit at Gove exists as an extensive plateau 60 metres above sea level, overlaid by less than one metre of surface soil and eucalypt APRIL 1993 9 This map of the Gove Peninsula shows the extent of the bauxite reserves for the Nabalco mine. Known reserves are at least 250 million tonnes. vegetation. The mining sequence starts with sample drilling on a 50 metre x 50 metre square grid for analysis and planning. An Edison rotary vacuum extraction drill bores a 65mm diameter hole to the bottom of the ore body which averages 3.5 metres in depth. After surface vegetation is felled by two bulldozers hauling a heavy chain between them, the topsoil is removed and stockpiled for later use in rehabilitation. A loose cover of pisolitic low grade ore is also scraped off. To break up the ore itself, a Caterpillar D11N dozer/ripper is used. It breaks up the bauxite into large chunks measuring up to 2 x 1.5 metres. This 100-tonne bulldozer, the largest in Australia, is powered by a 575kW diesel engine and was delivered by a roll-on/roll-off barge from Darwin on 9th March 1990. The arrival of this machine rendered the previously used explosives redundant, hence reducing the impact of the mine on the environment. Other large bulldozers assist in the clearing operations. Caterpillar front end loaders of 12.2 cubic metres capacity then load the ore into 80-tonne dump trucks. These front-end loaders lift 20 tonnes at a bite, thus filling each dump truck in four passes. The ore is then carried 4.6km to the primary crusher. The dump trucks use an onboard 10 SILICON CHIP computer to manage their 850hp (634kW) turbocharged VB diesel engines and to control the sequential operation of · their massive electrohydraulically operated clutches. With 85 tonnes unloaded weight, each truck tips the scales at 165 tonnes when fully loaded. Mine rehabilitation Each worked out area of the mine is rehabilitated as quickly as possible by returning the stored topsoil and planting native flora . Great care is taken to return the area to its natural state by restoring the original contours, planting ground cover and so on. The return of native fauna soon follows. A crushing power load The ore is dumped from the trucks to the primary crusher, after which it passes via selective screens to the secondary crusher. Each crusher stage is powered by a 500kW 3-phase motor. To start these wound-rotor slipring motors , resistances are introduced into the rotor circuit to minimise the initial current drag on the power station. These resistors arethen progressively reduced as the motors accelerate and, finally, shorted out so that the motors reach full speed. The power for these very large 6.6kV motors comes via the partly under- ground high voltage powerline from Nhulunbuy power station. The bauxite ore, now reduced to chunks of 25mm or less; feeds via a 1500-tonne surge bin to an overland conveyor which takes it to the port site at Melville Bay. The first section of the conveyor is a 50-metre long variable speed transporter which matches the exit rate from the surge bin to the carrying capacity of the overland conveyor. This short transporter section is powered by a 400V DC motor, hence its ability to run at virtually any speed. The main overland conveyor is 18. 7km long and consists of four separate flights. Each flight is powered by a 147kW 6.6kV 3-phase motor. Nhulunbuy is an isolated power station, without much "spinning reserve", therefore the power station must give permission before any of these very large motors are started. After it is loaded onto the continuously running conveyor, the bauxite takes 1½ hours to arrive at Melville Bay. Approximately 44% of the bauxite mined at Gove is shipped overseas to alumina refineries in every continent except Africa. The remainder is converted to alumina at the Nhulunbuy refinery. Currently, 1.4 million tonnes of alumina is exported each year. From the overland conveyor, the bauxite is stored in four stockpiles by an electrically powered jib stacker. The four stockpiles are arranged in two pairs of rows, with the belt conveyor passing down the centre of each pair. This gigantic machine runs on rails, propelled by low-geared traction motors. The feed belt of the stacker is driven by a 22kW 415V 3phase constant speed motor, while the supply comes via a 6600V trailing cable. Two of the stockpiles supply the shipping wharf, while the other two are for the Nhulunbuy alumina refinery. The stacking area measures 1. 2km long by 80 metres wide. Each of the four stockpiles can hold 100,000 tonnes of bauxite. Ore is retrieved from the stockpiles by two electric barrel reclaimers. These have a barrel 39 metres long and 4 metres in diameter and as it rotates, it swallows the crushed ore and feeds it out at the other end to another conveyor belt. The reclaimer on the export shipping stockpile is capable of moving 2200 tonnes of bauxite per hour and the other, for the refinery, 600 tonnes per hour. The bauxite ore from the export stockpiles is transferred by a shipping conveyor over the 982-metre long bridge to the loading wharf in Melville Bay which can handle ships of up to 100,000 tonnes capacity. Nhulunhuy power station All electric power for the mine, stacker, reclaimers, ship loader, the town, alumina refinery, the water supply and Yirrkala Aboriginal town are provided by Nhulunbuy power. station. This oilfired installation has three boilers, each evaporating 226 tonnes of water to steam per hour at 520°C. The steam flows through three 47,000 hp back pressure turbines, each of which drives a 35MW alternator. Exhaust steam from these turbines flows to the alumina refinery to satisfy its massive heating requirements. In addition, a 7.5MW condensing turboalternator can be run from the back pressure ~steam of the larger machines. The complete power station was purchased as a turnkey contract from Brown Boveri et Cie of Germany. Because Nhulunbuy is completely isolated, a separate emergency diesel power station was also installed adjacent to the steam plant. This power The alumina refinery & bauxite stockpiles occupy a big area. Note the barrel reclaimers which straddle the stockpiles & can move ore at up to 2200 tonnes per hour. · station houses five Allen diesel engines, each direct coupled to a 6.6kV 3-phase alternator. Each of these supercharged diesel engines is just under four metres high and is almost 10 metres long. Emergency power is essential for the alumina plant because any interruption to the flow of alumina solutions through the pipes results in solids crystallising out. Pipes and vessels must then be either scrapped or blasted out to remove the rock hard alumina. In the event of a power failure at the steam power station, the emergency diesel plant starts up automatically, restoring power within two minutes 30 seconds. Next month we will look in detail at the bauxite-to-alumina separation process at the world's largest alumina refinery. Acknowledgement Grateful thanks to Larry Davies and the staff of Nabalco, The Aluminator, QAL, Ken Cowd, C. A. Kneipp, H. L. Levin, M. McEwan and the people of Nhulunbuy. SC APRIL 1993 11 A-ONE A-ONE A-ONE A-ONE A-ONE ~ ~ ~ ~ +I• 0-50¥ 6A REGULATED PSU Output voltage: Z 0 < +/·0-35V 2.5A DUAK REGULATED PSU S0010 $159.95 +- 0-S0V DC (+- 0-35V SA RMS Regulated) Current: 2A, +2A=4A, +2+2=6A Overload Indicator: Current Limit Sharp cut out Output reset turn the selector to current limit point. I/P Transformer: Output voltage: Current: Overload Indicator: Protection method: I/P Transformer: Recommended: S0007..$48-;811'" + 0-35V/0-70V $38.40 2.5A LED Current Limited 18-24Vx2/6-8A 22+22V/225VA Recommooded • A HEAVY-DUTY REGULATED PSU S0006J;149:GIJ" $119.20 Output voltage: 0-32V Current: 20A MAX Overload Protection Ranges: CUSC Overload Induced Sharp Cutting Method (SC). Overload Induced Current Limiting Method (CL). Limiting Range: (Basic) 5A+5A+5A+5A Total 20A 18V-24Vx2/30A 24+24V/800VA ~ ~ < I 0 0-20V 20A REGULATED PSU S0005 $134.00 6.5V TO 18V DC REGULATED PSU S0011 $149.00 Output voltage: 0-20V Current: 20A Max Overload Protection Ranges: (CUSC) (Basic) 5A+5A+5A+5A Total. 20A Switch Setting. 12V-18Vx2/30A I/P Transformer: Recommeade,t 18+18V/500VA Output voltage: 6.5V to 18V DC (25V Max) Fully adjustable Output Current: 20A Max Current limit control:4 Steps (5A,10A,15A,20A) Ripple and noise: 15 mV Line Regulation: 0.08% + 20mV Load Regulation: 0.08% + 20mV Input Power: 18 to 20V AC 50-60HZ, 20-30A Recommended 18+18/S00VA Transformer: (T0238-Parallel Secondary) 1OOW CUSS 'I/ MAIN AMPLIFIER (MONO) S0313 $79.00 120W MOSFET POWER AMP (MONO) . S0329 $195.00 100W DYNAMIC CLASS ~A' MAIN POWER AMP (MONO) S0310 $89.00 Power Output: Frequency Response: Input. Impedance: Input Sensitivity: Supply Voltage: Current: Power Bandwidth: THD 1KHz 1W: Transformer: Recommended Transformer: Power Output: Frequency Response: Power Output: < 0-50V 3A PRECISION PSU S0001 $49.00 Output voltage: 0-S0V Current: 0.5 to 3A Overload Indicator: LED Protection method: Auto shut on overload , and short circuit I/P Transformer: 22V-36Vx2/3A 50Vx2/3A for High O/P Recommended: 36+36V/160VA 45+45V/160VA High 0/P ~ ~ < ~ ~ < I Recommended Transformer: 100W8 OHM 0-100KHz 22K. 0.8V DC+/-30 -42V(MAX) SA 5-S0KHz 0.001% 28Vx2/5A 30+30V/160VA. (T0209) MONO 30+30V/300VA. (T0217) STEREO 120W RMS into 8 OHMS 8Hz to 20KHz, +0 to 0.4db Input Sensitivity: 1V RMS for 120W Output Power Requirement:+/- 45 to 55 VDC at 3AMono 40Vx2/3N160VA for MONO 40Vx2/6N300VA for STERO Recommended Transformer: 40+40V/160VA. (T0212) MONO 40+40V/300VA. (T0219) STEREO Frequency Response: T.H.D.: TIO: Input Sensitivity: S/N Ratio: Power Supply: Power Consumption: Recommended Transformer: Recommended Transformer: 100W RMS into 8 OHM .150W RMS into 4 OHM 10Hz to 20KHz Less than 0,008% Less than 0.008% 0.75V- 1V Better than 80db +/-35VTO +/-45V DC 3.5A per channel. 30+30V/160VA (T0209) Mono 30+30V/300VA (T0217) STEREO ~NO-V ~NO-V ~NO-V ~NO-V ~NO-V A-ONE A-ONE A-ONEA-ONE A-ONE >. ~ ~ >. 0 DC FET SUPER CLASS 'A' PRE-AMP S0330 $145.00 FULL COMPLIMENTERY SYMMETRY FET STEREO PRE-AMP S0308 $159.00 300W HI-FI POWER AMP(MONO) . S0331 $175.00 Frequency · Response: Frequency Response: Power Output: T.H.D. : Input Sensitivity & Impedance: Phono: Output Level: Pre-AMP Output: Recording Output: Input Power: Recommended Transformer: Overall (AUX to pre output) (at rated ouput) 10 to 100,000HZ +0.5-1 db Overall (From AUX) Less than 0.01% (1,000HZ for rated output) 47K OHMS.2mV Rated Output (0.01%THD) 1.3V (20V MAX. 0.1% THD) 130mV 36+36V/0.2A 30+30V/15VA. (T0231) 10 to 100KHz +0.5db -1db T.H.D. (From AUX): 0.005% at/below rated O/P Channel Separation (at rated O/P 1 KHz) Better than 70db. Phono: HUM & Noise (IHF) Better than 70db. Phono: Better than 90db. AUX: Input Sensitivity & IMP. (1 KHz for rated Phono 47K OHM,2mV output): Output Level: Rated O/P(0.01 % THD) . Pre-AMP output 1.5V (0.1% THD) Max Output: Pre-AMP output 15V. Input PowerVol: AC 30V x 2 400mA Power Consumption: 12W Recommended 30+30V/15VA (T0231) Transformer: Frequency Response: T.H.D.: I.M . Distortion: Input Sensitivity: Power Requirement: Recommended Transformer: 300W RMS into BOHMS 500W Music Power into BOHMS 10Hz to 20KHz Less than 0.05% Less than 0.05% 1V RMS at 47K +I- 60 to 75 VDC at BA Mono 48-53x2/6-8AMP AC ~ >. ~ ~ 50+50V/500VA. (T0225) MONO -------------A-ONE NF-CR Bl•FET PREAMP/3-WAY TONE CONTROL S0307 $72.00 Frequency Response: T.H.D.: I.M. Distortion: Power Requirements: Input Sensitivity: -DC to 100KHz +- 0.5dB 0.005% at/below rated 0/P 0.005% at/below rated O/P +-15 VDC, 0.2A MAX Phono-2.5mV. Tuner, AUX and Tape-100mV Input Impedance: Phono-47 K. Tuner, AUX and Tape-100K Output Voltage: 1V Tone Control Range: BASS,+-10 db at 50Hz MID, +-5db at 1Hz TREBLE, +-10db at 15KHz RIAA Equalization: +-0.2db from 20.!::!z to 20KHz S/N Ratio: Phono,75db. Tuner, AUX and Tape, 90db. ELECTRONICS PTY LTD 432-434 Kent Street, Sydney NSW 2000. Phone: (02) 267 4819. Fax: (02) 267 4821. A. C N. 003 88 2 S13. MAIL ORDERS WELCOME: CHEQUE; MONEY ORDER, AMERICAN EXPRESS, BANKCARD,MASTERCARD AND VISA. POSTAL CHARGE $5-25 .......... $4.50 $26-$50 ...... $5.50 $51-$100 ........ $7.00 Over $100 ...... $10.00 Phone or write to us for a copy of your price list. Shop hours Mon-Fri 9-6. - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Sat 9-4. All prices include sales tax. >. ~ ~ :{NO-V 3NO-V 3NO-V 3NO-V 3NO-V ~ Build a solar-powered electric fence Electric fences are ideal for controlling livestock or protecting vegetable gardens. This low-cost design runs off a 12V battery & can power fence runs up to several kilometres long. By BRANCO JUSTIC Most electric fence controllers are expensive but this design can be built for between $60 and $130, depending on which options you choose. If you elect to power it from the Sun (via a solar cell array and voltage regulator), you can set it up in a paddock and forget about it. There's no need to worry about recharging the battery at regular intervals. 14 SILICON CHIP When switched on, the control unit delivers short high-voltage pulses to one or perhaps two lengths of bare wire that form the fence. These wires are supported by insulators which can be mounted on the existing fence posts or on temporary stakes driven into the ground. To keep costs down, the design uses an EHT transformer that was origi- nally made for use in monochrome computer m9nitors. It can deliver quite a healthy kick - 2.3kV into an open circuit and ZkV into a soon load. These voltage "kicks" are delivered at 1.5-second intervals and have a pulse . length of 250µs into an open circuit. More importantly, these figures are well within the specifications laid out by the Standards Association of Australia in AS3129. This standard specifies a maximum peak output voltage of 5kV into a lMQ load and a maximum 'pulse length of 0.ls into soon. The period between pulses is specified as greater than 0.75 seconds. Because terminal 2 of the EHT transformer has a relatively low output impedance, the unit can be used to power quite long fence runs if necessary (up to several kilometres). Its average current consumption is about 25mA but this can easily be reduced to about 15mA if the unit is used to power fence runs of less than 1km. How it works Refer · now to Fig.1 for the circuit details. At the heart of the circuit is a DC-DC inverter which steps up the battery voltage to 350V. This voltage appears at the output of bridge rectifier Dl-D4 and charges capacitors C6 & C7. These capacitors are then discharged via the primary of the EHT transformer using a trigger circuit based on UJT1 and SCR1. Let's now look at this is more detail. IC1a, Rl & Cl form a Schmitt trigger oscillator which runs at about 300Hz. Its output appears at pin 11 and drives Mosfet QZ via gates IC2a & ICZb. It also drives Mosfet Ql via gates IC1b, ICZc & ICZd. Because there is an extra stage of inversion in Ql's drive circuit, it is driven 180° out of phase with respect to QZ. Fig.1 (below): the circuit uses a DC-DC inverter (ICl, IC2, Qt & Q2) which steps up the battery voltage to 350V. This voltage appears at the output of bridge rectifier D1-D4 & charges capacitors C6 & C7. These capacitors are then discharged via the primary of the EHT transformer using a trigger circuit based on UJTl and SCRl . Thus, when pin 11 of IC1a goes high, QZ turns on and Ql turns off. Conversely, when pin 11 of IC la goes low, Ql turns on and QZ turns off. Ql & QZ are therefore switched on and off alternatively by the oscillator to provide push-pull drive for step-up transformer Tl. Tl is a 9V centre-tapped mains transformer and is used here back-tofront (ie, the 9V winding is used as the primary). When QZ turns on, the top of the primary is switched to ground and 12V appears across the top half of the winding. This means that 12V also appears across the bottom half of the primary, with Ql's drain going to +24V. Similarly, when Ql turns on, the bottom of the primary goes to ground and QZ's drain goes to +24V. Thus, Ql & QZ alternatively switch each end of Tl's primary winding between +24V and ground. The AC output from the step-up transformer is rectified by diodes D1D4 to produce a DC voltage of about 350V. This then charges C6 & C7 via R10 (180kQ). Actually, the inverter has the potential to charge C6 & C7 to over 600V if it ran continuously but this is not allowed to happen. Voltage regulation To keep the charging voltage to 350V, the inverter output is regulated The lead at the top of the EHT transformer must be cut off & the stub then fitted with heatshrink tubing & covered with a generous amount silicone sealant. using a feedback circuit based on IC1c and voltage divider R2-R4 across the bridge rectifier output. It works like this: when the bridge rectifier output reaches 350V, pins 1 & 2 of IC1c will be at approximately 6V (ie, half the 12V supply rail). The output of IC1c (pin 3) will thus switch low and disable gates ICZa & IC2c. This effectively removes the drive to Ql & Q2 and so the inverter switches off and the output voltage begins to fall. Pin 3 of IC1c then switches high again a short time later when the rectifier output drops below a critical level and this turns the inverter back on again. Thus, the inverter is rapidly .--------+------------------------0+ 12V R1 390k 4093 01-04 4x1N4004 T2 r-------7 C1 .022+ 1 EHT +12V ~ GDS PLASTIC SIDE m E B2O81 ':' R7 1.SM A OUTPUT VIEWED FROM BELOW KAO ELECTRIC FENCE cs• 1+ ':' GND ':' ':' APRIL 1993 15 ~3cJY1ACT As an option, this battery can be kept topped-up by the low-cost solar charger described in last month's issue (the 4-cell array would do the job quite nicely). Note that the unit is not designed for use with a plugpack supply. It is designed fur battery operation only. Construction FENCE TERMINALS 12V BATTERY + Fig.2: this wiring diagram shows the fence controller PC board (top) plus the optional solar panel regulator board described last month. Be sure to use heavy duty cable for the output connections & do not apply power to the unit until it is installed in a case, as high voltages are present during normal operation. switched on and off by the feedback circuit so that it produces a regulated 350V output. This regulated output charges C6 & C7 to virtually the full' 350V in less than half a second via current limiting resistor Rl0. The inverter thus operates only as necessary to maintain this charge. Unijunction transistor UJTl is employed as a simple relaxation oscillator. In operation, C5 charges via R7 towards the +12V supply rail. When the voltage on its emitter exceeds 0.67 x 12V = 8V, the UJT conducts and Cs quickly discharges via the E-B1 junction. This cycle then repeats itself at 1.5-second intervals, as set by C5 & R7. Each time the UJT conducts, it produces a positive trigger pulse at its B1 terminal and this triggers SCRl via R9. C6 & C7 now discharge via SCRl and the primary winding ofEHT transformer T2 which produces the output voltage for the electric fence. Note that the output is taken from terminal 2 of the EHT transformer (not from the EHT lead which emerges from the top of the transformer). Power supply Power for the circuit is derived from a 12V lead-acid or sealed gel battery. Most of the parts for the fence controller, including the EHT transformer, are accommodated on a PC board measuring 14 7 x 71mm. This board and the voltage regulator board are supplied as a single piece and must be separated using a hacksaw. Fig. 2 shows the wiring details. Before mounting any of the parts, the first step is to cut off the EHT lead where it emerges from the top of the transformer. The top of the "stub" must then be insulated by applying a generous coating of neutral cure silicone sealant. Apply several coatings if necessary and leave the unit to cure for at least 24 hours. The various parts can be mounted on the board in any order, although it's best to leave Tl, T2 and the two 0.47µF capacitors until last. Take care with the orientation of the two ICs and don't forget to install the wire link that runs adjacent to IC2. A second wire link is installed between Rl and ICl (a trimpot is shown on the board silk-screening but is not used), while a third link is installed in the Link A position on the PC board. Note that the Link B position marked on the board must be left vacant. Although IC sockets were used on the prototype, these are not really necessary. In fact, the circuit will be more reliable without them. RESISTOR COLOUR CODES 0 0 0 No. 2 .o 0 0 0 0 16 1 3 1 SILICON CHIP Value 4-Band Code (1%) 5-Band Code (1%) 10MQ 1.5MQ 390kQ 330kQ 180kQ 47.Q 10.Q brown black blue brown brown green green brown orange white yellow brown orange orange yellow brown brown grey yellow brown yellow violet black brown brown black black brown brown black black green brown brown green black yellow brown orange white black orange brown orange orange black orange brown brown grey black orange brown yellow violet black gold brown brown black black gold brown shown in Fig.2. The EHT transformer (T2) is secured using its integral bracket assembly - don't forget to solder its pins on the underside of the board. The PC board assembly can now be completed by connecting flying leads to the supply inputs and to the output terminals. Use heavy-duty insulated cable for the OUTPUT & GND leads (eg, mains cable or heavy-duty automotive cable). The supply leads can be run using medium-duty cable. Do not apply power to the board at this stage. That step comes only after the board has been mounted inside its case to prevent the possibility of severe electric shock (see warning panel). Solar charger . ' The control board is installed in the case after the baseplate has been installed, to allow access to the baseplate mounting screws (see text). Delete the regulator board if you don't wish to use a solar panel to recharge the battery. If you intend using the controller with short fence runs (less than 11cm), you can leave one of the 0.47µF capacitors out of circuit. This will reduce the average current consumption to about 15mA while still giving the fence plenty of "bite". The two Mosfet transistors (Ql & Q2) are installed with their metal tabs towards the adjacent edge of the PC board. Push them down onto the board 43 as far as they will comfortably go before soldering their leads. The same goes for SCRl - its metal surface also goes towards the adjacent edge of the board. Transformer Tl is now temporarily secured to the PC board using machine screws, nuts & star washers. Orient the transformer so that its lowvoltage windings face towards the ICs and terminate the leads at the points 71 HOLES: 3.5mm DIA. C, "' a, "' 145 155 MATERIAL: 1.5mm ALUMINIUM OR PCB BLANK DIMENSIONS IN MILLIMETRES Fig.3: this diagram shows the dimensions of the baseplate & the locations of its mounting holes. Not shown are the mounting holes for the two PC boards. The optional solar charger circuit consists of two assemblies: (1) a 4-cell solar panel array; and (2) a switching regulator circuit. These should be assembled exactly as described in last month's issue. Note that for short fence runs, with only one 0.47µF capacitor installed on the control board, a 2-cell array would probably be adequate for charging the battery. However, the 4-cell array would still be advisable in areas of frequent cloud cover. Case assembly Once the two boards have been completed, they can be installed in a waterproof plastic case. The recommended case is a "Bopla" wall-mounting box that's currently available from Jaycar for $14.95 (Cat. HB-6040). It is made from high-impact plastic and features a hinged transparent door with a rubber seal. The case is divided into two sections: (1) an upper section about 115mm deep with integral slots for a PC board; and (2) a lower section about 47mm deep located behind a removable front cover. As with the lid, this cover is fitted with a rubber gasket to ensure a waterproof seal. The two PC boards are mounted on an insulated baseplate which is in turn secured to integral tapped holes in the back of the case. A piece of blank PC bqard material measuring 155 x 95mm was used as a baseplate in the prototype but Perspex would do the job equally as well. Note that you will have to make a 12mm square cutout at each corner of APRIL 1993 17 Use a waterproof plastic case to house the circuit boards, to ensure long-term reliability. The case specified in the parts list is ideal for the job & comes with rubber gaskets to seal the lid & the sub-panel blow it. the baseplate to clear the mounting columns inside the box (see Fig.3). Drill mounting holes along the edges of the baseplate as shown in Fig.3, then temporarily install the baseplate in the case. Control board mounting The fence control board is mounted on the baseplate using three 6mm spacers plus an additional nut between each spacer and the baseplate. 1\vo of these spacers sit directly under transformer Tl's mounting holes REGULATOR BOARD CASE RIB 18 SILICON CHIP (just remove the mounting screws that were previously fitted). The third mounting point is drilled in the top right-hand corner of the controller board, immediately beneath the "G" of the "Danger High Voltage" warning. Drill this hole to 3mm, then install the controller board inside the case and use it as a template for marking out its mounting holes on the baseplate. The baseplate can now be removed from the case and the extra holes drilled to 3mm. This done, fit a 12mmFig.4: mounting details for the regulator PC board. Note the nut under the 6mm spacer where the board is secured to the case rib. long screw and nut at each board mounting location. At this stage, you will also have to drill two 3mm mounting holes in the regulator board - one in the corner near the input terminals for the solar panel and the other in the diagonally opposite corner (be careful not to break the continuity of the earth track). This board is mounted by securing one corner to the baseplate and the other (nearest the solar panel terminals) to a rib moulded into the back of the case - see Fig.4. The trick is to first attach the regulator board to the baseplate using a 6mm.spacer, screw, nut and washer. The assembly can then be slid into the case (regulator board first) and the extra mounting hole marked and drilled in the plastic rib. At the back of the case, behind the rib, is a narrow channel about 3mm wide and 5mm deep. You will have to file the head of the mounting screw slightly so that it fits into this chan- WARNING! PARTS LIST The internal wiring of the Electric Fence Controller is highly dangerous. There are potentially lethal voltages present on the PC board when the electric fence is running and, if there is a fault, these can remain even after the power has been switched off. In particular, be wary of the two 0.47µF capacitors. These capacitors are dangerous when charged and can only be regarded as "safe" when the voltage across them is below 20V. · As a safety precaution, never apply power to the board while it is outside its c~se. If you do have to work on the board, disconnect the power and check that the voltage across the two 0.47µF capacitors (C6 & C7) is below 20V before removing the board or touching any of the parts. You can check this voltage by measuring between the anode (centre terminal) of ScR·1 and link A. (Note: if the trigger circuit is operating correctly, it will discharge C6 & C7 as the circuit "powers down"). You should also take care with the installation of the unit. It should not be installed where members of the public are likely to come into contact with it and any installation should be clearly identified with large warning signs at regular intervals. The control unit should be moµnted in a position where it is free from mechanical damage and any wiring should be kept well away from any electrical or telephone cables. 1 PC board (Oatley Electronics) 1 9V CT mains transformer (T1) 1 EHT transformer (T2) 1 weatherproof plastic case · (Jaycar Cat. HB-6040) 2 front panel labels 1 solar charger kit - switching regulator plus solar cells; see March 1993 issue (optional) 2 large insulated screw terminals 1 cordgrip grommet 5 6mm-long spacers 5 3mm x 12-mm long screws 9 3mm nuts 5 lockwashers ELECTRIC FENCE and the latter secured using screws, nuts and lockwashers. Final wiring CONTROL BOX + METAL STAKE DRIVEN INTO GROUND II V \ ,i " Fig.5: conneciion details for the fence controller (power supply & solar panel option not shown). The GND terminal is connected to a metal stake that's driven into the ground. nel. This done, install the screw, secure it with a nut, and fit a 6mm spacer - see Fig.4. The regulator board and baseplate assembly can now be secured to the case. Finally, three 6mm-long spacers can be dropped into position on the baseplate for the fence controller board The external w1rmg can now be completed as shown in Fig.2. This involves the wiring to the solar panel, power supply and fence terminals. Run colour-coded leads for the battery and solar panel through a cordgrip grommet in the bottom of the case and fit them with a short length of plastic sleeving where they pass through the grommet to ensure a waterproof seal. The fence output leads are connected to solder lugs and terminated on two large insulated screw sockets mounted on the sub-panel. You can use the label as a drilling template for the holes for the screw terminals. Note that this label should be sprayed with a hard-setting clear lacquer to protect it from the weather. After that, it's simply a matter of fitting the external leads with suitable connectors to go to the battery and solar panel. You will also have to make up suitable leads to connect to the fence. These will typically be terminated with eyelet connectors at one end to connect to the control box and alligator clips at the other. Sleeve all connections with heatshrink tubing for weather protection. Note that the GND connection goes to a metal stake that's driven into the ground, while the "+" terminal goes Semiconductors 2 4093 quad Schmitt trigger NANO gates (IC1 ,IC2) 2 MTP3055 Mosfets (01 ,02) 1 2N2646 unijunction transistor (UJT1) 1 C1060 SCR (SCR1) 4 1N4004 silicon diodes (01 -04) Capacitors 1 10µF 16VW PC electrolytic 1 1µF 16VW PC electrolytic 2 0.47µF 250VAC polyester 1 .022µF metallised polyester • 2 .0033µF ceramic Resistors (0.25W, 5%) 2 10MQ 1 180kQ 11.5MQ 347Q 1 390kQ 1 10Q 1 330kQ Miscellaneous Medium & heavy-duty hook-up cable, alligator clips, battery connectors, heatshrink tubing. Where to buy the parts Short form kits for this project are available from Oatley Electronics, PO Box 89, Oatley, NSW 2223, Australia. Phone (02) 579 4985. Prices are as follows: Fence controller board plus onboard components ............... $40 Solar regulator board plus onboard components ............... $10 Four: 6V 1W solar cells (does not include mounting plate) ........ $32 The Bopla weatherproof case (Cat. HB-6040) is available for $14.95 from Jaycar Pty Ltd, PO Box 185, Concord 2137. Note: copyright of th~ PC boards is retained by Oatley Electronics. APRIL 1993 19 Fig.6: here are the full-size front panel artworks for the fence controller. The top label can be attached to the inside of the lid, while the bottom label is attached to the sub-panel on the bottom of the case. Make sure that the latter is suitably we~therproofed (eg, by spraying the label with a clear hardsetting lacquer). ELECJRIC FENCE CONTROLLER POWER SUPPLY: 12V DC, 25mA (BATTERY ONLY) WARNING! HIGH VOLTAGES INSIDE REFER SERVICING TO QUALIFIED PERSONNEL ONLY TERMINALS BENEATH COVER rn TO SOLAR PANEL FENCE TERMINALS GND + + + TO BATTERY to the fence wire. Fig.5 shows the details. Testing The output leads should be fastened together using plastic cable ties & the output terminal connections sleeved with heatshrink tubing., 20 SILICON CHIP To test the unit, connect it as shown in Fig.5 and apply power. Make sure you get the supply polarity correct, to prevent damage to the circuit (do not fit a reverse polarity protection diode in series with the battery leads, as it will prevent the battery from charging). If the unit is working correctly, you will hear a faint "ping" in the wire at about 1.5-second intervals. Finally, take care with the installation of the unit. It should not be installed where people are likely to come into contact with it and any installation should be clearly identified with warning signs at regular intervals. The control unit should be mounted in a position where it is free from mechanical damage and any wiring should be kept well away from any electrical or telephone cables. SC FIFTH BIRTHDAY SWEEPSTAKES: THE PRIZEWINNERS The SILICON CHIP 5th Birthday sweepstakes closed on March 1st and the prizes were drawn on March 5th. The winners are as follows: Grand Prize: Ford Festiva 3-door sedan W.R. Jongeneelen of Bargo, NSW. S. Liawatimena of Mt Lawley, WA. S. Rowcliff of Alangula, NT. S. Hain of Cooma, NSW. from Altronics: 15 temperature controlled soldering stations K. S. Jaffrey of Nelly Bay, Qld. M. J. Morel of West Melbourne, Vic. D. J. Birch of Gracemere, Qld. B. Carvey of Hammondville, NSW. J. W. F. De Vos of Prospect, NSW. L. J. Connelly of Kerang, Vic. D. Hall of Salisbury East, SA. R. C. Hilton of Mt Pleasant, WA. I. Beament of Balgowlah Hts, NSW. R. Miller of Corinda, Qld. A. Pavnovic of Christie Downs, SA. V. Caldwell of Balgownie, NSW. from A-One Electronics: 2 Mk 5 surround sound processors plus Mk 5 120W stereo power amplifiers J. H. Norton of Narellan, NSW. G. Bangerter of Belair, SA. 1 Magnet 10 vacuum tube stereo preamplifier and Magnet 120W stereo power amplifier R. Koerner of Voyager Point, NSW. from Av-Comm Pty Ltd: 1 satellite dish and receiver system R. Coleman of Leonay, NSW. The prizes for our 5th Birthday Sweepstakes were drawn by Gary Johnston (left), Managing Director ofJaycar Electronics. 2 Signal RX-550 aircraft receivers R. Morris of Bowen, Qld. R. Chan of St Albans, Vic. from Breakthrough Computers: 3 CAD software packages D. F. Crepih of Boonah, Qld. M. Flanigan of Ipswich, Qld. V. Jessup -of Maffra, Vic. from Emona Instruments: 5 logic bridges W. Dniprowyi of Woodville South, SA. P. Francis of Marrickville, NSW. D. L. Robins of Toogoolawah, Qld . B. Flanigan of Churchill, Vic. H. Nguyen of Springvale South, Vic. from Jaycar Electronics: 3 electronic security systems 0. Middleton of Liverpool, NSW. J. C. Moulder of Warwick, Qld. P. Bloomfield of Mt Helena, WA. from Pelham Pty Ltd: 3 CD-ROM packages R. G. Dunlop of Capalaba, Qld. P. Fowler of Crescent Head, NSW. P. Francis of Mandurah, WA. from Philips: 3 Philips/Fluke 50MHz Scopemeters P. Dixon of Tantanoola, SA. R. Sommerville of Charlestown, NSW. J. Bromell of Tabulam, NSW. from Scan Audio: 1 pair Jamo loudspeakers A. Perkins of Devon port, Tas. 1 pair Peerless PSK60/2 loudspeaker kits B. Bone of Mildura, Vic. 1 pair of DynAudio Image 5 loudspeakers E. Degraeve of Sunshine, Vic. APRIL 1993 21 Are you worried about burning out your loudspeakers? Build this audio power meter & worry no more With the wide dynamic range of today's compact discs, it is all too easy to over"".drive your speakers without being aware of it. By using this low-cost project, you can monitor power levels from 200 milliwatts up to 100W RMS using a LED bargraph display. By DARREN YATES Imagine that you've just whacked your favourite CD on the deck, turned up the wick and are now enjoying a golden blast of sound. But then you know that the next few bars will really make the speakers belt it out and maybe you think you should wind the wick back a bit, just to be on the safe side. If you listen in that way, the chances are that you are regularly driving your amplifier and your loudspeakers well into overload without really being 22 SILICON CHIP aware of it. And while the speakers may not protest too much if it only happens intermittently, if you do it too often you will end up with damaged tweeters at the least and possibly cook the woofers too. Paradoxically, the problem is more severe if you have a lower powered amplifier than if you have one rated at 100 watts per channel or more. You are more likely to overload a smaller amplifier and if you do drive it heavily into clipping, it can deliver a great deal more power than its nominal ratings suggest. For example, a nominal 30 watt per channel amplifier driven badly into clipping might deliver 100 watts for a brief burst and that can spell goodnight for your tweeters. By contrast, if you are using an amplifier rated at 100 watts or more, not only are you less likely to overdrive it but your spe,akers are more likely to be rated to take a lot more power anyway. So as you can see, if you are not careful in the way you use your amplifier's volume control, it can spell trouble for your speakers. Now you can end the guesswork with this simple little power monitor. It connects across one of your loudspeakers and uses a LED bargraph to indicate the . output power from your amplifier in 10 steps from 200 milliwatts to 100 watts. Circuit diagram Let's take a look at the circuit dia- gram - see Fig.1. It uses a 741 op amp (IC2) and an LM3915 logarithmic LED display driver (IC1). This latter IC does most of the work and so warrants a closer look. Inside the LM3915 is a string of 10 comparators which have their noninverting (+) inputs connected to a voltage divider string and their inverting inputs connected to an incoming DC signal. Each comparator drives a LED. If the input signal is higher than the non-inverting input for a particular comparator, then its LED will be lit. If the signal voltage is higher than the non-inverting input on all comparators, then the top-most LED will be lit. The voltage divider for the noninverting inputs is arranged so that the comparators progressively turn on their LEDs for an increase in signal level of +3dB. There are 10 LEDs, so the total signal range indicated by the display is 30dB. When we are talking about power, a 3dB increase corresponds to a doubling of power. Hence, as each additional LED is lit, it means that the power has increased by a factor of two. OK, let's now go back to the circuit diagram of Fig.1 and see how the LM3915 fits into our circuit. The signal from the power amplifier is taken directly from across the speaker terminals. This signal passes through a 100kQ trimpot and is then fed to a 741 op amp (IC2) which is connected as a precision half-wave rectifier. IC2 has diodes Dl and DZ inside the feedback loop and so allows the circuit to accurately rectify quite small AC voltages. ' The resulting DC is fed through a low pass filter consisting of a 3.3kQ resistor and a 0.15µF capacitor and thence to pin 5 of ICl. From here on, the circuit acts as described above. The DC signal at pin 5 fluctuates in proportion to the AC signal across the speaker and the LEDs are lit accordingly. The time constant of the RC filter at pin 5 is a compromise between fast attack and slow decay on the one hand and flickering with low frequency signals on the other hand. We have selected the filter components so that the display has a sufficiently fast action to catch signal transients. The lkQ and 4. 7kQ resistors on pins 6, 7 & 8 set the LED brightness. They +12V LE02-LED11 10-LEO BAR DISPLAY LE011 10 K 100W 11 K 330k + 50W 3.3k VR1 100k 12 + 0.15 FROM SPEAKER 25W 13K IC1 LM3915 13W 14 6W 15 K 10k 3W 1k 16 1.6W ~ -12V 17K 4.7k ~ S1 er-/ 12VAC INPUT 0.8W 18 0.4W 03 1N4004 0.2W OUT +12V ~ 04 1N4004 ~ LED1 4.7k OUT ~ -12V ffi ffi IGO A~K GI O AUDIO POWER METER Fig.1: the input signal is derived from one of the loudspeakers & is fed to op . amp IC2 which is connected as a half-wave precision rectifier. The resulting DC signal is then filtered & used to drive an LM3915 logarithmic LED display driver (ICt). IC1 then drives the LED display to show the power level. also set the internal reference voltage and hence the overall signal sensitivity of the circuit. Pin 9 of IC1 determines whether the LEDs are lit as a bargraph display or one at a time (ie, single LED dis- play). We've selected the single LED display mode, by leaving pin 9 unconnected, as it reduces the overall power consumption. The power supply is derived from a 12V 300mA AC plugpack. Two 3-ter- The two 3-terminal regulators must be bent against the PC board as shown in this photo so that they don't foul the lid of the case. Be sure to use the correct regulator type at each location & double-check to ensure that they are both correctly oriented. APRIL 1993 23 Before you begin construction, check the board carefully for any shorts or breaks in the copper tracks. These should be repaired before proConstruction ceeding further. Assembly can begin by inserting All of the components for the Audio Power Meter, except for the power the 'Wire link, the resistors and diodes. Follow the overlay diagram of switch and the AC power input socket, are installed on a PC board coded - Fig.2 and make sure that you install the diodes and electrolytic capacitors 01105931 and measuring 100 x 55mm. in their correct locations and the right way around. Next up, install trimpot VRl and PARTS LIST the two !Cs, followed by the 3-termi1 PC board, code 01105931, nal regulators. Don't install the 10100 x 55mm LED bar display or the indicator LED 1 plastic zippy case, 130 x 67 x for the moment. 42mm The next task is to drill the holes in 1 red 4mm banana socket the case. The mounting holes for the 1 black 4mm banana socket PC board should be fai rly straight1 SPST miniature toggle switch forward but the cutout for the LED bar 1 2.5mm DC socket display (in the case lid) will take a 4 15mm x 3mm tapped spacers little work. This is best done by using 1 12VAC 300mA plugpack the label as a template for drilling a series of small holes around the inSemiconductors side perimeter of the cutout area, then 1 LM3915 logarithmic LED knocking out the centre piece and display driver (IC1) filing the job to a smooth finish . 1 LM741 op amp (IC2) Once the holes have been drilled, 1 7812 +12V regu lator slide the LED display and the indica1 7912 -12V regulator tor LED into their holes on the board, 1 10 x red LED bargraph display then secure the board to the lid using 1 5mm green LED (LED1) four 15mm-long tapped spacers. The minal regulators produce ±12 VDC rails with LED 1 indicating that the unit is on. 2 1N914 signal diodes (D1, D2) 2 1N4004 rectifier diodes (D3, D4) 1 100kQ 5mm horizontal trimpot TABLE 1 Watts 8-ohms 4-ohms 0.2 1.26V 0.89V 0.4 1.79V 1.26V 0.8 2.53V 1.79V 3.58V 2.53V 1.6 ' 3.2 5.06V 3.58V 6.4 7.16V 5.06V 13 10.2V 7.2V 25 14.1V 10V 50 20V 14.1V 100 28 .3V 20V LED display and LED indicator can then be pushed into the lid and their leads soldered to the PC board. The on/off switch, power socket and input terminals can now mounted and the wiring completed. Now apply power and check that the supply rails from the 3-terminal regulators are correct (ie, +12V from the 7812 and -12V from the 7912). Don't expect to see the display light up yet because it won't. The only LED that should come on is the green power indicator LED. If you have an audio frequency gen- Capacitors 2 220µF 25VW electrolytics 2 100µF 16VW electrolytics 1 1µF 50VW electrolytic 1 0.15µF MKT polyester Resistors (0.25W, 1%) 2 330kO 1 3.3kQ 1 10kO 1 1kO 2 4.7kQ Miscellaneous Screws, washers, nuts, hook-up wire, solder etc. Fig.2: make sure that all polarised parts are correctly installed on the PC board. The 10-LED bar display & the indicator LED (LED 1) are not soldered to the board until after it has been attached to the lid of the case. RESISTOR COLOUR CODES 0 0 0 0 0 0 24 No. Value 4-Band Code (1%) 5-Band Code {1%) 2 1 2 330kQ 10kQ 4.?kQ 3.3kO 1kQ orange orange yellow brown brown black orange brown yellow violet red brown orange orange red brown brown black red brown orange orange black orange brown brown black black red brown yellow violet black brown brown orange orange black brown brown brown black black brown brown SILICON CHIP Fig.3 (right): this full-size front panel artwork can be used as a drilling template for the front panel (or you can attach the finished label to the lid & use that as a drilling template instead). + 0.2 0.4 0.8 1.6 3 6 12 25 50 100W SPEAKER INPUTS 12VAC IN ~~=== AUDIO POWER METER + Fig.4 (below): check your etched PC board for defects before mounting any of the parts by comparing it against this full-size artwork. erator handy, set it up to deliver about 6V on a sinewave of lkHz or thereabouts. Feed the signal into the input and adjust the sensitivity with trimpot VRl. As you rotate VRl over its full travel you should see each LED light up in sequence. If that checks out, you have a working power monitor. All that remains is to set the sensitivity so that the reading is accurate. Interestingly, no test instruments apart from a digital multimeter are necessary for this job. All you have to do is set the resistance oftrimpot VRl to 41.Zkn if you have 8Q loudspeakers and to 26.Zkn is you have 4Q loudspeakers. This done, your audio power meter should give a correct indication on all LEDs within about ±ldB. On the other hand, if you have an audio signal generator and digital multimeter and you wish to check the linearity of the power meter, the voltages that appear across a loudspeaker for different power levels are listed in Table 1. And that's about all there is to it but we'll conclude with a warning: don't wake the neighbours trying to light up the 100W LED! SC :."-'\ ~ [?~ ~ .· ; - i ~J4;,"{} t~i<,;~, ii~ - ·/4# The PC board is secured to the lid of the case on 15mm tapped spacers as shown here. Adjust the LED display so that it sits flush with the lid before soldering its leads. APRIL 1993 25 CHOOSE FROM our Wide Range of Quality Kits! Select Your Own Chime! Tests Your Sound System! AUDIO SWEEPER A useful kit for audiophiles, sound experts, enthusiasts and anyone interested in sound. This very affordable audio test system analyses the performance (treble, mid and bass range) of speakers, speaker enclosures, filter circuits and room acoustics. It consists of a sweeping audio test signal generator and a metering amplifier which measures the results. Comes complete with deluxe prepunched front panel , plastic instrument case, PCB, hardware (including dB meter), components, mic. insert and plug pack. Cat K-7352 <at>QQQ SEPT '92 $109 DISCO STROBE PROGRAMMABLE DOORBELL Lets you program your own doorbell tune. With a maximum of 14 notes possible, it can even play two different tunes - one for the front door and one for the back and, if you get sick of a tune, you can change it! The kit comes complete with all components and hardware including battery holder, PCB and a deluxe doorbell case. Back doorbell switch is optional . (Batteries not included) Cat K-3802 <at> Just the thing for your do-it-yourself disco outfit! This reliable kit provides a high-energy flash of white light which you can vary from 110 flashes/second. It's triggered by either an external source or its own internal oscillator and has both input and output trigger connectors, so that any number of these units can be linked to flash in synchronisation. Comes with all components, hardware, PCB, deluxe plastic case, screened perspex front panel, linear 100mm Xenon tube and a commercial high-efficiency reflector. Cat K-3155 <at> QQQ [1] Q DEC '92 APRIL '93 $129 Get More Out Of Your Batteries! NICAD BATTERY DISCHARGER Easy-To-Build! MOTOR SPEED CONTROLLER $4695 A kit designed to regulate the speed on heavyduty power tools. It's ideal for circular saws, electric drills, lawn edgers, jig-saws, sanders, grinders and other equipment rated at 5 amps with a 'brush' type motor. This improved design has a higher current rating and uses a Triac rectifier instead of an SCA. It also monitors the back-EMF voltage from the motor so, though the drill speed is controlled, it won't bog down when the going gets tough. Complete with deluxe prepunched black anodised screened front panel, components, PCB and flush-mounted mains socket. ~ -7/ ~/ 'J<,,ffjjji_~ f"ZI Cat K-3085 ~ 1,'; / ~,),~~~ LLI Q PLEASE CHECK YOUR NEAREST STORE FOR AVAILABILITY, AS SOME KITS MAY STILL BE IN PRODUCTION. 26 SILICON CHIP More Affordable Than Ever! 1GHz FREQUENCY COUNTER This 1GHz counter is an inexpensive variation on the 50MHz counter design published in February '93 Electronics Australia. By substituting an uprated display module and adding to the prescaler circuitry, a truly ingenious 1GHz counter can be built. The unit is designed with a seven digit 'LED' display including a 'KHz'/'MHz' status indicator and a frequency range selector so that the user can select the relevant range ie: 2MHz, 20MHz, 50MHz & 1GHz. The kit includes case, PCB, all components, hardware and a pre-punched and screened, perspex front panel. Frequency Range: Input A: Input B: 0-50 MHz 50-1GHz Cat K-7604 Input Impedance: Input A: Input B: 1M OHM 50 OHM [1j QQQ APRIL '93 $3495 Q NOV'92 Get the best performance from your Nicads with this battery discharger by beating the "memory effect". With switchable voltage (3.6, 4.8, 6.0, 7.2, 8.4, 9.6, 10.8 & 12V) and automatic cut-off. This easy to build kit is ideal for most types of Nicads as used in camcori:ters, cordless phones, radio controlled cars, cordless drills, and laptop computers, etc. The unit continuously monitors voltage and automatically cuts off the discharge current once the battery as a whole is fully discharged. As well, there's a switchable current discharge of 50mA-and 200mA and a push-to-start button. This full form kit has all components, hardware, case and a prepunched black anodised screened front panel. Cat K-3126 For The Latest In Technology... ---Col- DDQ With Large LCD Display! Ranges: 3.5 DIGIT MULTIMETER A superb 3.5 digit multimeter with large 25mm display and a 20 amp AC/DC current range. It also has auto power off, bargraph display, capacitance meter, transistor tester, diode and continu ity tester. The multimeter has side slots to fit test leads for one-handed operation and comes co mplete with ti lt stand and carry case. DC V: AC V: AC/DC current: Resistance: 200mV,2 ,20, 200, 1000 volts. 200mV,2 20, 200, 750 volts. 200uA. 2mA, 20mA. 200mA, 20A. 200 Ohm 2K, 20K, 200K, 2M, 20M s.1 59 Cat 0 -1538 Put Your Mains Circuit To The Test! AC VOLTAGE FINDER Now there's no need to put yourself at risk! This device detects the electromagnetic field surrounding cables, sensing any AC voltage above 120 volts and warns you with both an LED and an audible "buzz". At this low price, there's no excuse for not having one! Cat 0-1531 The future of Laser Technology... lt Points This Wayt LASER POINTER This new pen-sized laser pointer reaches far beyond the range of ordinary pointers and serves many useful purposes. It's ideal for med ical professionals, professors and lecturers, executives and sales people, realtors, tour guides, construction supervisors and inspectors. Complete With Holster! 3.75 DIGIT (4000 Count) MULTIMETER A rugged meter that's great for both field and workshop use, it's shock, water and dust resistant, featuring rubber a-ring gaskets on its rotary switch, input jacks and case. '° '.-, ., .-, - • C•.C• •:• The Laser pointer is also an asset for any photographer as it simplifies difficult dead corner and night shots. Specifications: Diode/ < 5mW Max at 680nm Cat T-2900 DON'T PAY $199 Supplied with a thermocouple probe for temperature measurement from -40°C to 260°C, the meter features most standard ranges plus: • Continuity • Diode test • Logic test • Frequency (Auto-ranging) • Temperature • Peak Hold • Auto Power off Cat 0-1542 s179 A PRIL 1993 27 READ ABOUT IT! .·~~~--------·-.... XTREE MS-DOS, Windows, N Hard Disk :;~~ NlW u ~-~ ~ SWITCH MINI ALARM _ A high quality alarm for the protection of up to 3 points, with a distinct sound for each. You'll feel safe with this alarm installed on windows, doors, drawers or any area requiring protection! Batteries included. Cat L-5186 s249s Management Companion,.._ Youw Got rhe Power/ UNREGULATED POWER SUPPLY A unregulated power supply ideal for portable TV's, car radios, etc. It has a power rating of 13.8V DC at 1.5A. (18V max) Cat M-9544 s499s 13.8V/1.5 REGULATED SUPPLY With screw terminals for easy connection. Ideal for CB's car stereos, small amateur transceivers etc. Cat M-9545 NEW s7 4 9 s SAVE $101 13.8V/4A PEAK FORREST MIMS' ENGINEER'S NOTEBOOK A new practical guide based on Forest Mims' years of intensive hands-on experience with IC circuits. It is an essential reference for professional design engineers, educators, technicians, students, circuit hobbyists or anyone else requiring concise, accurate information on chip applications. This one's not for the bookshelf -clear a permanent place for it next to the logic probe and multimeter in your electronics lab! Cat B-1500 $2995 HANDBOOK OF AUSTRALIAN RAILWAY FREQUENCIES s199s . THE OFFICIAL XTREE, MSDOS, WINDOWS AND HARD DISK MANAGEMENT COMPANION (3rd Edition) Xtree is the most widely used hard disk management utility for organising folders, files and directories. This book by Beth Slick is the only authorised guide to this remarkable utility program. Recommended for both beginners and intermediate users, the new third edition covers all versions including Xtree Gold and the newest release, Xtree for Windows, and features answers to the most frequently-asked hard disk management questions, straight from the Xtree Technical support team. Cat B-6606 equipment. Cat M-9547 s1 00 SAVE $201 3.5 DIGIT LCD PANEL METER by Russell Bryant The first frequency handbook on railways ever written, provides an easy to read and informative insight into the use of radio communication on government and non-government rail services throughout Australia plus locality maps for the Scanner enthusiast. This new handbook will delight both scanner hobbyists and those interested in trains and the railway system. CatB-4114 Ideal for those high current, high peak demand applications. Just the thing for 2m or small HF amateur transceivers, as a bench supply, or a supply for 'auto' s3995 'Full scale' of 200mV or 2V (user selectable) and a high input impedance (100M ohms). It can also be self-mounted. Comes with a comprehensive data sheet. Features: • Single supply rail (9V) • Low supply current (2MA max) Cat Q-2200 • Built-in auto zeroing and over range. 3.5 DIGIT LED PANEL METER Incorporates a dual-slope analogue-to-digital converter and a 100 mV reference with 200mV or 2V full scale sensitivity. 12.7 mm digit height. Auto-zeroing and overranging are provided and automatic input polarity indication available. It comes complete with full instructions. Cat Q-2210 s5995 Features: • Single + 5V operation. • Zero reading from 0V on all scales. • Decimal point selectable. • Input impedance >100M ohms MAJOR DICK SMrrH ELECTRONICS AUTHORISED STOCKISTS: IIIW: ARMIDALf: New Englar<! Ei.ctronics 711655 BALLINA: Ballina Elee1ronics 867022 BATEMAN'S BAY: BavcltvSiaht& Sound 725030 BATHURST: Ei.ctronic FrontiOIS323933 B!P-JRKE: Countrywide Ser/ices 722150 BOWRAL: Bowra1 Electri<:al Supplies 611861 BROKEN HILL: Hobbies & Ei.ctronics 884098 COOTAMIJNORA: Cootamundra Music & Lile 42t56i HARBOUR: Coifs Harbour Ei.ctronics 525684 OENILKlUl~Oeni Electronics 813672 OUBBO: Chris's Hi A 828711 FOOSTER: Hl!SterVlllage Etectronics545006GOULBOURN: Tunlive221288GRAFTON: Repairs& Spares421911 GRIFflTH: Miatronics624534 INVERELL: lnve!!II Ei.ctronics 221821 KATOOMeA: Nial!ara Plloto& 5Pot1s 822800KEMPSEY: P&KRlchards631134 LfETON: l.oeton Audiotronlc 532800 LIGHTNING RIDGE: Uahtning Ridge Solar -291013 LISMORf: Decro Electronic Ser/ices 214137 LITHGOW: 0ourov Photoarai,t,ics 513173 MACKSVILLf: Macksville Ei.ctronics 682899 MOREE: Moree Elec1ronlcs522091 MUOGEE: Headware 723895MURWILLUMBAH: Slr1ngs& Toings723684NARRABRI: -ComputerSe!vlce923274 NELSON BAY: NelsonllayEleci&Hobbies 813685NOWRA: NowraElectronlcs210722 PARKES: Strad Music Ctr 623366 PORT MACQUARIE: Hastings Computer Se!vlce 840255 RICHMOND: Silicon Crafls 784101 TAREE: Manning Ei.ctronics 512233 ULLAOULLA: Coastal Elee1ronics 553989 WAGGA WAGGA: Phillips Electronics 216558 WALGETT: walgett . Ei.ctrontcr.emr.281111 WINDSOR: HawkesburyEi.ctronics 776722YASS: warmtngtoo Elec1rical 261411 YOUNG: Keltfl DongesEi.ctronics821279 IIC:ARARAT: Jerran Elee1ronlcs522345 BAIRNSOALf: LH& LMCrawford525677BENALLA: No!1h East Ei.ctronics 622710 CASTLEMAINE: Inspect Electrics 723m COLAC: Colac Efectronics 312847 ECHUCA: Gilmour Electronics 822956 MIL.DURA: Pullman Auto Pro 232882 MORY/ELL: Rovlalne Ply Ltd 339458 ROSEBUD: Seatech Vic Ply Ltd 822225SHEPPARTON: AndrewtEElectronics219497SWAN HILL: Nyah DlstrlctTVSerilce329303 ST. ARNAUD St. Arnaud Appliances951069WARRAGIJL: Rovlaine 234255 WARRNAMBOOl: KoroltStElecSe!vices 627417 WONTHAGGI: South Gi land Phom Se!vlce n1411 : AYR: Delta Electrix 831566 BLACKWATER: Cool Trontcs 825827 BOWEN: Delpro A ·es86 3477 BUNOABERG: Bob Elkin Electronics 521785 CALOUNORA: Electro-mart918533 DALBY: Ho & Ei.ctronics ~o EMERALD: Coo!tronics 222 GLADSTONE: Ei.ctronlc Enle!prises 726660 GODNOIWINDI: CTW Elecironlcs 71~NGHAM: Masons Eloc1ronlcs 763188 INNISfAIL: lnnisfall Hi-fl 612014 KINGAR0Y: MD & MM Siegle 62~ LONGREACH: Lona reach Soond & Conrnunlcations 583307 MACKAY: Stevens Ei.ctronlcs 511723 MARYBOROUGH: Ket~ Ei.ctronlcs 214559 MOOSMAN: Mossman Electronics 982200 MT ISA: Outtlack Ei.ctronlcs 433331 NAMBOUR: Nambour Ei.ctronics 411966 PIA[BA: Ket~ Electronics 283749 STANTHORPE Granite Belt Communications 813333 TAI: BURNIE: Ei.ctronlc City 314760 OEVONPORT: Al Ei.ctronics 248322 SA: MT GAMBIER: Hutchesson's Communication 250400 PORT LINCOl.N: Basshams TV ~ ~~~75=~~~~~~f:~~v+c:oti=~:J{BIJNBIJRY:MlcroEleC1ronics216222COWARAMIJPC"'Electronlcs555448GERALOTON:OirectUghting211278KALGOORLIEToday'sElectronlcs 1 cm 28 SILICON CHIP END OF LINE CLEARANCE! 30°/o OFF! HURRY - LIMITED STOCKS!* E:; ;;;; ········ ··: .!>:::::: ;,,''........... ••······',•::•lliil] ::::: ::: *(Please contact your local store regarding availability of stock) A home for ,our equipment/ RACK FRAMES Do your instruments have a place to go at night? We have 19" rack frames that are space efficient, cost effective, easy to assemble and an absolute bargain at 30% off the normal price! They'll keep your tools from wandering! Size Cat No. Height Price 6U 12U 18U 24U 30U 40U H-2380 H-2382 H-2384 H-2386 H-2388 H-2390 358mm 625mm 893mm 1158mm 1425mm 1870mm $104.30 $111.30 $118.30 $132.30 $153.30 $188.30 Save 30% on th is 36 piece pack that includes matching screws, cage nuts and nylon washers. Cat H-2393 TRAY KIT Sa\.'8 Big Bucl<sl Added protection/ COVER SETS For an incredibly low price you can turn your rack frame into. a rack cabinet! It'll keep the dust out and provide your rack with additional strength. No. Pieces Cat. No Price 3 3 3 5 5 5 H-2381 H-2383 H-2385 H-2387 H-2389 H-2391 $41.30 $48.30 $62.30 $83.30 $97.30 $111.30 Need somewhere to mount your non-standardised equipment? You can save over $10 on this tray that fits neatly onto your rack frame. $2795 Cat H-2394 Hard To Get/ IN-LINE UHF ('M' TYPE) SOCKET In-line UHF socket for making communication cable extension leads mate with the commonly known PL259 series plugs. Cat P-2320 Pretty Neat/ $695 RACK CASES High quality cases that fit neatly into your rack for space-efficient storage. Save space and save money - now you can have them for 30% off the normal price! SWitchOnl Size Finish Cat.no Price AxBxC 44 x 34 x 38 (1U) 88 X 57 X 82 (2U) 132 x 89 x 126 (3U) Black Black Black H-2483 H-2485 H-2487 $48.00 $59.50 $69.30 A new square push-on/push-off switch with flat top. It is 11 x 12.5mm with a clearance depth of 32mm and an electrical rating of 240V AC .<at> 1amp. MINI SWITCH Black Red Gl\.'8 Your Rac/c A Break/ BLANK PANELS Bolt directly to your rack system to fill the spaces between your equipment, help keep out dust and give a neat finish. Height Finish Cat.No Price 44mm 88mm 132 mm Black Black Black H-2482 H-2484 H-2486 $9.75 $13.95 $18.85 Cat P-7540 Cat P-7542 $2.95 $2.95 SPS420 STUD-MOUNTING DIODE s1295 New 400V 20A stud-mounted SCA with mounting hardware. Cat 2-4314 DS XPRUS PHONa & MAILORNR NRVICI! Outside Sydney {FREE Call) 008 22 8610 Sydney And Enquiries - (02) 888 2105 FAX: (02) 805 1986 or write to OS XPRESS, PO BOX 321 N/RYDE NSW 2113 All Major Credit Cards Accepted. O/N~e Cou rier Available. NIW • Albury 21 83911 • Bankstown Square 707 4888 • Blacktown 871 7722 • Brookvale 905 0441 • Bondi 3871444 • Campbelltown 27 2199 • Chatswood Chase 4111955 • Chullora 842 8922 • Gore Hiil 439 5311 • Gosford 25 0235 • Hornsby 477 8833 • Hurstville 580 8822 • Kotara 58 2092 • Liverpool 800 9888 • Maitland 33 7888 • Miranda 525 2722 • Newcastle 81 1899 • North Ryde 878 3855 • North Sydney (Greenwood Plaza) 964 9487 • Orange 818 400 • Parramatta 889 2188 • Penrith 32 3400 • Railway Square 211 3777 • Sydney City 287 9111 • Tamworth 881711 • Wollongong 28 3800 ACT• Belconnen (06) 2531785 • Fyshwick 280 4944 VIC• Ballarat 31 5433 • Bendigo 43 0388 • Box Hill 890 06911 • Coburg 383 4455 • Dandenong 794 9377 • East Brighton 592 2388 • Essendon 379 7444 • Footscray 889 2055 • Frankston 783 9144 • Geelong 232 711 • Melbourne City 399 Elizabeth St 328 8088 & 246 Bourke St 839 0399 • Richmond 428 1814 • Ringwood 879 5338 • Springvale 547 0522 QLD • Booval 282 8200 • Brisbane City 229 9377 • Buranda 391 8233 • Cairns 311 515 • Capalaba 245 2870 • Chermside 359 8255 • Maroochydore 791 800 • Rockhampton 27 9844 • Southport 32 9033 • Toowoombe 38 4300 • Townsvllle 72 5722 • Underwood 341 0844 •SA• Adelaide City 232 1200 • Beverley 347 1900 • Elizabeth 255 8099 • Enfield 280 8088 • St. Marys 2n 8977 WA• Cannington 451 8888 • Fremantle 335 9733 • Perth City 481 3281 • Midland 250 1480 • North bridge 328 8944 TAI• Hobart 31 0800 • Launceston 344 555 NT • Darwin 811977 STORES ACROSS AUSTRALIA AND NEW ZEALAND . B 1470 APRIL 1993 29 Silicon Chip BACK ISSUES July 1988: Stereo Control Preamplifier, Pt.2; Fitting A Fuel Cut-Off Solenoid To Your Car; Booster For TV & FM Signals; The Discolight Light Show, Pt.1; Tone Burst Source For Amplifier Headroom Testing; What Is Negative Feedback, Pt.3. August 1988: Building A Plasma Display; Universal Power Supply Board; Remote Chime/Doorbell; High Performance AC Millivoltmeter, Pt.1; Discolight Light Show, Pt.2; Getting The Most Out Of Nicad Batteries; Data On Insulated Tab Triacs. September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Build The Vader Voice; Motorola MC34018 Speakerphone IC Data; What Is Negative Feedback, Pt.4. October 1988: Stereo FM Transmitter (Uses Rohm BA1404); High Performance FM Antenna; Matchbox Crystal Set; Electronic House Number; Converting A CB Radio To The 28MHz Band; Queensland's Powerful Electric Locomotives. November 1988: 120W PA Amplifier Module (Uses Mosfets); Poor Man's Plasma Display; Automotive Night Safety Light; Adding A Headset To The Speakerphone ; How To Quieten The Fan In Your Computer; Screws & Screwdrivers, What You Need To Know; Diesel Electric Locomotives. December 1988: 120W PA Amplifier (With Bal- anced Inputs), Pt.1; Diesel Sound Generator; Car Antenna/Dem ister Adaptor; SSB Adaptor For Shortwave Receivers; Why Diesel Electrics Killed Off Steam; Index to Volume 1. January 1989: Line Filter For Computers; Ultrasonic Proximity Detector For Cars; 120W PA Amplifier (With Balanced Inputs) Pt.1; How To Service Car Cassette Players; Massive Diesel Electrics In The USA; Marantz LD50 Loudspeakers. February 1989: Transistor Beta Tester; Minstrel 2-30 Loudspeaker System; LED Flasher For Model Railways; Build A Simple VHF FM Monitor (uses MC3362) , Pt.1; Lightning & Electronic Appliances ; Using Comparators to Detect & Measure. March 1989: LED Message Board, Pt.1; 32-Band Graphic Equaliser, Pt.1 ; Stereo Compressor For CD Players; Amateur VHF FM Monitor, Pt.2; Signetics NE572 Compandor IC Data; Map reader For Trip Calculations; Electro~ics For Everyone Resistors. April 1989: Auxiliary Brake Light Flasher; Electronics For Everyone: What You Need to Know About Capacitors; Telephone Bell Monitor/ Transmitter; 32-Band Graphic Equaliser, Pt.2; LED Message Board, Pt.2. May 1989: Electronic Pools/Lotto Selector; Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference ; LED Message Board, Pt.3; Electronics For Everyone - All About Electrolytic Capacitors. June 1989: Touch-Lamp Dimmer (uses Siemens SLB0586) ; Passive Loop Antenna For AM Radios; Universal Temperature Controller; Understanding CRO Probes; LED Message Board, Pt.3. July 1989: Exhaust Gas Monitor (Uses TGS812 Gas Sensor); Extension For The Touch-L?mp Dimmer; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm ; NSW 86 Class Electric Locomotives. September 1989: 2-Chip Portable AM Stereo Radio (Uses MC13024 and TX7376P) Pt.1; AlarmTriggered Telephone Dialler; High Or Low Fluid Leve l Detector; Simple DTMF Encoder; Studio Series 20-Band Stereo Equaliser, Pt.2; Auto-Zero Module for Audio Amplifiers (Uses LMC669). October 1989: Introducing Remote Control; FM Radio Intercom For Motorbikes Pt.1; GaAsFet Preamplifier For Amateur TV; 1Mb Printer Buffer; 2-Chip Portable AM Stereo Radio , Pt.2 ; Installing A Hard Disc In The PC. November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY & Morse); Sensitive FM Wireless Microphone ; FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Radio, Pt.3; Floppy Disc Drive Formats & Options; The Pilbara Iron Ore Rai lways. December 1989: Digital Voice Board (Records Up To Four Separate Messages) ; UHF Remote Switch ; Balanced Input & Output Stages; Data For The LM831 Low Voltage Amplifier IC ; Installing A Clock Card In Your Computer; Index to Volume 2. January 1990: High Quality Sine/Square Oscillator; Service Tips For Your VCR; Speeding Up Your PC; Phone Patch For Radio Amateurs; Ac- l r- --- - -- ----- ------- - --------------- ---, Use this handy form to order your back issues lllease send me a back issue for: O O O O o O O 0 0 0 O October 1988 March 1989 September 1989 February 1990 July 1990 December 1990 May 1991 October 1991 March 1992 August 1992 January 1993 0 0 O O o O O 0 O O 0 November 1988 April 1989 October 1989 March 1990 August 1990 January 1991 June 1991 November 1991 April 1992 September 1992 February 1993 0 July 1988 December 1988 O May 1989 0 November 1989 0 April 1990 O September 1990 0 February 1991 0 July 1991 O December 1991 0 May 1992 O October 1992 O March 1993 o Enclosed is my cheque/money order for $_ __or please debit my: Card No. 0 August 1988 0 January 1989 O June 1989 o December 1989 0 May 1990 O October 1990 O March 1991 O August 1991 o January 1992 o June 1992 O November 1992 O Bankcard ~___,__,I L__I~'---'I l~~~I L__I~ '---' Signature _ _ _ _ _ __ __ _ _ _ _ Card expiry date_ _ /_ _ O Visa Card o September 1988 O February 1989 0 July 1989 o January 1990 0 June 1990 O November 1990 0 April 1991 O September 1991 O February 1992 0 July 1992 0 December 1992 O Master Card $5.00 each (includes p&p). Overseas orders add $1 each for postage. NZ orders 'are sent air mail. Street _ _ _ _ _ _ _ __ _ _ _ __ _ _ _ _ _ _ _ __ _ _ Detach and mail to: SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROY BEACH NSW 2097 Suburb/town _ _ _ __ _ _ __ __ _ _ _ Postcode _ _ _ _ __ Or call (02) 979 5644 & quote your credit card details. Fax (02) 979 6503. Name L---- --------- ----- - - - - - - - - - - - - - - - - - - - - - ~ -30 SILICO N C HIP tive Antenna Kit; Speed Controller For Ceiling Fans; Designing UHF Transmitter Stages. RF Preamplifier For Amateurs & TV ; A Look At The Config.Sys & Ansi.Sys Files. 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. April 1991: Steam Sound Simulator For Model Railroads ; Remote Controller For Garage Doors, Pt.2; Simple 12/24V Light Chaser; Synthesised AM Sterl;lo Tuner, Pt.3; A Practical Approach To Amplifier Design, Pt.2; Playing With The Ansi.Sys File; FSK Indicator For HF Transmissions. March 1990: 6/12V Charger For Sealed LeadAcid Batteries; Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16Channel Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC. April 1990: Dual Tracking ±50V Power Supply; VOX With Delayed Audio; Relative Field Strength Meter; 16-Channel Mixing Desk, Pt.3; Active CW Filter For Weak Signal Reception; How To Find Vintage Radio Receivers From The 1920s. May 1990: Build A 4-Digit Capacitance Meter; High Energy Ignition For Cars With Reluctor Distributors; The Mozzie CW Transceiver; Waveform Generation Using A PC, Pt.3; 16-Channel Mixing Desk, Pt.4. 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 A Computer. July 1990: Digital Sine/Square Generator, Pt.1 (Covers 0-500kHz); Burglar Alarm Keypad & Combination Lock; Simple Electronic Die; Low-Cost Dual Power Supply ; Inside A Coal Burning Power Station; Weather Fax Frequencies. August 1990: High Stability UHF Remote Transmitter; Universal Safety Timer For Mains Appliances (9 Minutes) ; Horace The Electronic Cricket; Digital Sine/Square Wave Generator, Pt.2. September 1990: Music On Hold For Your Telephone; Remote Control Extender For VCRs; Power Supply For Burglar Alarms; Low-Cost 3Digit Counter Module; Simple Shortwave Converter For The 2-Metre Band. October 1990: Low-Cost Siren For Burglar Alarms ; Dimming Controls For The Discolight; Surfsound Simulator; DC Offset For DMMs; The Dangers of Polychlorinated Biphenyls; Using The NE602 In Home-Brew Converter Circuits. November 1990: How To Connect Two TV Sets To One VCR; A Really Snazzy Egg Timer; LowCost Model Train Controller; Battery Powered Laser Pointer; 1.5V To 9V DC Converter; Introduction To Digital Electronics; Simple 6-Metre Amateur Transmitter. December 1990: DC-DC Converter For Car Amplifiers; The Big Escape -A Game Of Skill; Wiper Pulser For Rear Windows; Versatile 4-Digit Combination Lock; 5W Power Amplifier For The 6Metre Amateur Transmitter; Index To Volume 3. January 1991: Fast Charger For Nicad Batteries, Pt.1; The Fruit Machine; Two-Tone Alarm Module; Laser Power Supply; LCD Readout For The Capacitance Meter; How Quartz Crystals Work; The Dangers When Servicing Microwave Ovens. February 1991: Synthesised Stereo AM Tuner, Pt.1 ; Three Inverters For Fluorescent Lights; LowCost Sinewave Oscillator; Fast Charger For Nicad Batteries, Pt.2; How To Design Amplifier Output Stages; Tasmania's Hydroelectric Power System. March 1991: Remote Controller For Garage Doors, Pt.1; Transistor Beta Tester Mk.2 ; Synthesised AM Stereo Tuner, Pt.2; Multi-Purpose 1/0 Board For PC-Compatibles; Universal Wideband May 1991: Build A DTMF Decoder; 13.5V 25A Power Supply For Transceivers; Stereo Audio Expander; Fluorescent Light Simulator For Model Railways ; How To Install Multiple TV Outlets, Pt.1 ; Setting Screen Colours On Your PC. June 1991: A Corner Reflector Antenna For UHF TV; 4-Channel Lighting Desk, Pt.1; 13.5V 25A Power Supply For Transceivers ; Active Filter For CW Reception; Electric Vehicle Transmission Options; Tuning In To Satellite TV, Pt.1. July 1991: Battery Discharge Pacer For Electric Vehicles; Loudspeaker Protector For Stereo Amplifiers; 4-Channel Lighting Desk, Pt.2; How To Install Multiple TV Outlets, Pt.2; Tuning In To Satellite TV, Pt.2; PEP Monitor For Amateur Transceivers. August 1991: Build A Digital Tachometer; Masthead Amplifier For TV & FM; PC Voice Recorder; Tuning In To Satellite TV, Pt.3; Installing Windows On Your PC; Step-By-Step Vintage Radio Repairs. September 1991: Studio 3-55L 3-Way Loudspeaker System; Digital Altimeter For Gliders & Ultralights, Pt.1; Build A Fax/Modem For Your Computer; The Basics Of AID & DIA Conversion; Windows 3 Swapfiles, Program Groups & Icons. October 1991: Build A Talking Voltmeter For Your PC, Pt.1; SteamSound Simulator Mk.11; Magnetic Field Strength Meter; Digital Altimeter For Gliders & Ultralights, Pt.2; Getting To Know The Windows PIF Editor. November 1991: Colour TV Pattern Generator, Pt.1 ; Battery Charger For Solar Panels; Flashing Alarm Light For Cars; Digital Altimeter For Gliders & Ultralights, Pt.3; Build A Talking Voltmeter For Your PC, Pt.2; Error Analyser For CD Players Pt.3; Modifying The Windows INI Files. December 1991: TV Transmitter For VCRs With UHF Modulators; lnfrared Light Beam Relay; SolidState Laser Pointer; Colour TV Pattern Generator, Pt.2; Windows 3 & The Dreaded Unrecoverable Application Error; Index To Volume 4. January 1992: 4-Channel Guitar Mixer; Adjustable 0-45V BA Power Supply, Pt.1; Baby Room Monitor/FM Transmitter; Automatic Controller For Car Headlights; Experiments For Your Games Card; Restoring An AWA Radiolette Receiver. February 1992: Compact Digital Voice Recorder; 50-Watt/Channel Stereo Power Amplifier; 12VDC/ 240VAC 40-Watt Inverter; Adjustable 0-45V BA Power Supply, Pt.2; Designing A Speed Controller For Electric Models. March 1992: TV Transmitter For VHF VCRs; Studio Twin Fifty Stereo Amplifier, Pt.1; Thermostatic Switch For Car Radiator Fans; Telephone Call Timer; Coping With Damaged Computer Directories; Valve Substitution In Vintage Radios; The AR-1500 & AR-2800 Scanning Receivers. April 1992: lnfrared Remote Control For Model Rail roads; Differential Input Buffer For CROs; Studio Twin Fifty Stereo Amplifier, Pt.2; Understanding Computer Memory; Switching Frequencies in Model Speed Controllers; Aligning Vintage Radio Receivers, Pt.1. May 1992: Build A Telephone Intercom; LowCost Electronic Doorbell; Battery Eliminator For Personal Players; lnfrared Remote Control For Model Railroads, Pt.2; A Look At Large Screen High Resolution Monitors; OS2 Is Really Here; Aligning Vintage Radio Receivers, Pt.2. June 1992: Multi-Station Headset Intercom, Pt.1; Video Switcher For Camcorders & VCRs ; lnfrared Remote Control For Model Railroads, Pt.3; 15Watt 12-240V Inverter; What's New In Oscilloscopes?; A Look At Hard Disc Drives. July 1992: Build A Nicad Battery Discharger; 8Station Automatic Sprinkler Timer; Portable 12V SLA Battery Charger; Off-Hook Timer For Telephones; Multi-Station Headset Intercom, Pt.2; Understanding The World Of CB Radio; Electronics Workbench For Home Or Lab. August 1992: Build An Automatic SLA Battery Charger; Miniature 1.5V To 9V DC Converter; The lnterphone Digital Telephone Exchange, Pt.1; Dummy Load Box For Large Audio Amplifiers; Internal Combustion Engines For Model Aircraft; Troubleshooting Vintage Radio Receivers. September 1992: Multi-Sector Home Burglar Alarm; The lnterphone Digital Telephone Exchange, Pt.2; General-Purpose 3½-Digit LCD Panel Meter; Track Tester For Model Railroads; Build A Relative Field Strength Meter. October 1992: 2kW 24VDC To 240VAC Sinewave Inverter; Multi-Sector Home Burglar Alarm, Pt.2; Mini Amplifier For Personal Stereos; Electronically Regulated Battery Charger (Charges 6V, 12V & 24V Lead-Acid Batteries); Internal Combustion Engines For Model Aircraft, Pt.2. November 1992: MAL-4 Microcontroller Board, Pt.1 ; Simple FM Radio Receiver; lnfrared Night Viewer; Speed Controller For Electric Models, Pt.1; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.2; Automatic Nicad Battery Discharger; Modifications To The Drill Speed Controller. December 1992: Diesel Sound Simulator For Model Railroads; Easy-To-Build UHF Remote Switch; MAL-4 Microcontroller Board, Pt.2; Speed Controller For Electric Models, Pt.2; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.3 ; High Voltage Probes - Beware The Dangers; Index To Volume 5. January 1993: Peerless PSK60/2 2-Way Hifi Loudspeakers; Flea-Power AM Radio Transmitter; High Intensity LED Flasher For Bicycles; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.4; Speed Controller For Electric Models, Pt.3; Restoring A 1920s Kit Radio February 1993: Three Simple Projects For Model Railroads; A Low Fuel Indicator For Your Car; Audio Level/VU Meter With LED Readout; Build An Electronic Cockroach; MAL-4 Microcontroller Board, Pt.3; 2kW 24VDC To 240VAC Sinewave Inverter, Pt.5; File Backups With LHA & PKZIP. March 1993: Build A Solar Charger For 12V Batteries; An Alarm-Triggered Security Camera; LowCost Audio Mixer for Camcorders; Test Yourself On The Reaction Trainer; A 24-Hour Sidereal Clock For Astronomers; Sanyo's Big Screen Video Projector; Sony's VGP-G?00 Colour Video Printer PLEASE NOTE: all issues from November 1987 to June 1988 plus the August 1989 issue are now sold out. All other issues are presently in stock. For readers wanting articles from sold-out issues, we can supply photostat copies (or tearsheets) at $5.00 per article (incl. p&p). When supplying photostat articles or back copies, we automatically supply any relevant Notes & Errata at no extra charge. APRIL 1993 31 SERVICEMAN'S LOG The path of TV service never did run smooth Ever had one of those jobs where nothing seemed to go right; where each lead turned out to be false? Of course; we all have. Well, I had one recently which produced just such a sequence of false leads before I finally cracked it. The story concerns a 46cm National TC-1809 colour TV set fitted with an M9 series chassis. It is one of about 12 used by a local motel and I have been servicing them since they were installed about 11 years ago. They have proven to be a very reliable set with a minimum of problems over this period. ' But, like most sets, they do have some particular weaknesses. One which I cottoned onto quite early in the piece involves C519, a lOµF 250V electrolytic smoothing capacitor on the supply rail for the RGB driver transistors. This can dry out and in some cases, one of the terminal lugs can actually come adrift. In any case, inadequate smoothing on this rail can produce some funny effects. In fact, this particular set had been FRACARRO DELIVERS•.. .. .best television antenna performance for less cost. Fracarro 10BL4, 10BL5, 10BL45, 10 element yagrs that ~ work. I Peter C. Lacey Services Pty. Ltd. P.O. Box 678 (74Fulton Rd.) Mount Eliza 3930 Tel:03 787 2077 Fax:(03) 787 3460 ACN006893438 32 SILICON CHIP in the workshop about a year ago for just this fault, at which time I had given it the usual once over for any other obvious problems. But now the motel proprietor was on the phone with a new fault which, with a bit of guesswork, I interpreted as severe vertical overscan. So I said "bring it in and we'll have a look at it". When he turned up, I plugged the set in immediately and, yes, that was the problem. And it was quite severe; on an SBS test pattern, the SBS logo at the top of the screen had all but vanished, with much the same degree of error at the bottom. This drew my attention to another point: the scan, though excessive, was still quite linear. It was almost as if the height control had simply been wound up. In fact, that was the first thing I tried - not that I believed that the problem was goipg to be solved that easily. But I wanted to check a couple of points. First, was the control working? And if it was, was it set correctly, somewhere near its mid-position? The answer to both questions was yes; it appeared to be working correctly and it was correctly set. In fact, by winding it right back, I was able to reduce the scan to almost normal but not quite. But that was not the answer. The need for such an extreme setting clearly indicated a basic fault - one which might well get worse with time. So where to from here? The horizontal scan appeared to be normal; perhaps overscanning by a whisker but nothing serious. So I went first the main HT rail, which is always a good starting point. This should have been at 111 V but was a trifle high at 115V. I reset it as a matter of routine but this had only a marginal effect. Circuit details At this stage, it was time to get out the circuit and try to come up with some ideas about the fault. The relevant section is reproduced here and I will try to give the reader a broad picture of what is involved. On the left of the diagram is the horizontal output transformer and near the bottom is a winding terminating in pin 2. This point feeds diode D503 and capacitor C517 (lO00µF 35VW} to provide a +20V rail (test point E14}. This rail supplies several sections of the set and is also used to derive a +12V rail. This is achieved using resistor R516 (immediately to the right of C517} and 6V. zener diodes D506 and D507. And that brings us to the next section of the circuit: jungle chip IC501 (AN5431}. Among other things, this chip provides the sync separator, horizontal AFC, and the horizontal oscillator, vertical oscillator and ramp generator circuits. These latter functions are accessed via pins 10, 11 & 12, while the +12V supply is fed directly to pin 13. Pin 10 is also fed from the 12V rail, in this case via R428, diode D406 and the height control (R406, a 30kQ pot}. Having digested the circuit arrangement, the first thing I did was check the +20V rail at test point E14. This was at +19.5V which was quite acceptable. My next stop was the +12V rail; this was checked at pin 13 of the IC and came out a fraction high at 12.5V, which again is an acceptable figure. Neither observation helped very much and I was pondering on my next logical move when I realised that the fault condition had changed. The degree of overscan was not constant; while I was watching the screen, the height suddenly decreased slightly. ~EIGHT 05 q408 14J l.3K C40i 16VIOO .. CSII 25V33 I ii R506 !OK l.T i zw ' Fig.1: relevant section of the National TC-1809 colour TV receiver. The +20V rail components are associated with pin 2 of the EHT transformer (lower left), while the +12V rail is derived via R516 & zener diodes D506 & D507, The height & linearity components are associated with pins 9-12 of jungle chip IC501. was further encouraged when, while probing at the diodes in an effort to measure their individual voltages, the scan began varying erratically. So did I have a faulty diode or a dry But before I could follow up on before I came back and, when I turned joint? To save mucking about, I pulled this, I was called away on another the set on again, it was no longer them both out and fitted two new matter. It was half an hour or more overscanning. In fact, it was now ones. These gave a slightly lower voltunderscanning slightly but . age than before (about 11.8V) but again Y- the fact that I had previously I didn't regard this as important. It left the height control at its did, however, reduce the overscan minimum setting partly ex- slightly and I found that I could actuplained this effect. ally set the height control to give a More importantly, as I normal scan by backing it off to its watched the screen over the extremity. next few minutes, the height That was no solution of course and slowly increased, eventu- I still suspected a thermal fault someally settling down to its pre- where in the set. In the meantime, it vious gross overscan posi- was time for lunch and so I turned the tion. So it looked like we set off to let it cool down. The lunch had a thermal problem · of break would also give me time to think some kind. about the problem. At this point, I decided to re-check the+ 12V rail, only Doubts dispelled this time I went to the two When I switched the set on again zener diodes (D506 & D507). about an hour later, any doubts I may I had tried to find these ear- have had about a thermal fault were lier without success but this immediately dispelled. The picture time I eventually tracked was now underscanning substantially, them down under the verti- by about 35mm at both the top and cal hold control. bottom of the screen. It then started to And now I seemed to be creep up and, in a few minutes, was on the track of something. back to where it had been before I For one thing, the voltage switched it off. across them had increased Fortunately, I had taken the preslightly to about 13V. While caution of leaving the meter across this increase was not im- the 12V rail, so I was able to monitor 'SO 1-r t - ~ t - 1 ~ portant in itself, I wondered it while the scan increased. For all whether it was a sign of practical purposes, it didn't vary. H~0 A. ~~~L. PROSL.E:M something that was. And I So, summarising the situation, I was OF SOW\E. \<.\tJ'O••• APRIL 1993 33 SERVICEMAN'S LOG - CTD • e~ • • • HA.)l\t-lG DlG5-STE.t> '""•r • • "' ~• '.., , • . ,.. • • ~ 1\-\E: CIR(.Ul""f A~~~NGe:N\E.N,, iHE. FlR..S, 'TH\ NG 'I 'DIP WA.'S CHE:.CK -rHE: +~OV "RA\\.A-r ,-i;.s-, 'PO\N,14- ... e: able to rule out both the +20V rail and the + 12V rail. And if there had been a fault in the zener diodes (and I was no longer sure about this), it was incidental anyway. False lead number one. Height control circuit So where to now? Pin 10 of IC501 and associated components in the height control circuit seemed to be the next best bet. As already mentioned, the main components here are R428, diode D406 and the height control pot (R406). Also connected to pin 10 is diode D403, the other side of which goes to the +12V rail at pin 13. My first step here was to measure the voltages on pins 10, 11 & 12. According to the manual, pin 10 should be at 1V, pin 11 at 6.3V and pin 12 at 7V. All these came out pretty well spot on, so there were no clues here. While making these measurements and studying the circuit, I noticed an interesting diversion. If we go back to the junction of R428 and D406, we 34 SILICON CHIP encounter another resistor - R405 . And if we trace the circuit from this point, to the right, down and left, we come back to the +20V rail, near E14. As I said, this is a diversion and, fortunately, I dicl not allow myself to be side-tracked by it. Nor should the reader, because it has nothing to do with the final outcome. But I am still wondering about its function. My best guess is that it is a belt-and-braces arrangement to ensure that the jungle chip keeps working - at least to some degree - in the event that the main +12V rail goes out. But back to the height control cir- . cuit around pin 10. Since it was obviously a thermal fault, I went over each of the components in this section with freezer spray, fully expecting that cooling one of them would cause the height to drop. Alas, no joy. Even when I went further afield, spraying C405, C406 & D404 in the linearity circuit plus several components around pins 11 & 12, there was still no response. My n ext move may seem a little unusual but was quite logical - I removed the height pot from the board. One reason was simply to check it for any funny behaviour. A Samsung set I had serviced a few weeks earlier had produced all kinds of weird intermittent symptoms. After much heartbreak, the problem was traced to a crook pot; one which measured OK when tested initially but which varied its value drastically in operation. It took quite an effort to nail it. So I gave this pot a thorough going over. And as far as I could tell, there was nothing wrong with it. My second reason for removing the pot was that I could then check a number of surrounding components without removing them. R428 checked out OK but D406 presented a query. It had a very high forward resistance reading and no reverse reading. Not only was this unusual but the diode itself was something of a mystery. Designated MA26TA, I suspect that it is a special purpose device of some kind but I could find no reference to it in the regular manuals. Nor is there anything in the parts list to provide a clue. It is quite tiny physically and is colour coded in green and cream. But since it didn't seem to be working as a diode should, I tried replacing it with a regular 1N914 small signal diode. I didn't know it then but that was another wasted effort, to say nothing of the frustration of not knowing what the device was. The other components - diodes D403, D404 & D405, capacitors C405 & C406 in the linearity circuit, and the resistors in the vertical hold circuit - all checked out OK. And this was rather significant, in view of the final outcome. No frame collapse At this point, I switched the set on again. Because the height control pot was still out of circuit, I had backed off the brightness in anticipation of total .frame collapse and the inevitable bright line across the screen. But this didn't happen; at least not totally. There was now a scan about 50mm high across the centre of the screen. And this was the first real step towards a breakthrough because, on the face ofit, it was impossible; how could we have a scan with no voltage on pin 10? But this wasn't strictly true; the meter showed that there was a voltage on pin 10. It wasn't much - a mere 0.086V - but there should not have been any voltage at all. And was it enough to give the 50mm or so of scan? Probably. Anyway, I knew I was onto something. At this point, I had to leave the set to complete another job - this time for a couple of hours. When I came back and turned it on again, there was considerably more scan than before. It now measured about 150mm and varied quite randomly. That didn't make much sense in view of the previous behaviour but I'd more or less given up trying rationalise what was going on. But the real query was the source of the spurious voltage. When I looked at the circuit, one component stood out above all the others: diode D403, between pin 10 and the +12V rail. Ifit was suffering reverse leakage, it could apply voltage to pin 10. Granted, I had already tested this component on the board and it had checked OK, but stranger things had been happening with this job. There was one quick way to find out; It took only a moment to unsolder one leg, whereupon we had total frame collapse. I fitted a replacement diode and we still had total frame collapse. I re-fitted the height pot and we had normal scan with the pot set near its mid-position. More importantly, it remained rock steady over the next couple of hours and through a couple of on-off cycles. Problem solved. But there was a bit more to it than that. When I checked D403 again on the meter, it now showed substantial reverse leakage. So why hadn't it done that when I first tested it? It would have saved me several hours and much frustration. Then there were the two suspect zener diodes. Now that I had found the real culprit, it seemed unlikely that there was anything wrong with them. It was a simple job to replace the original pair, so they went back in and behaved perfectly. And finally, the mystery diode D406, MA26TA. This was re-fitted and, again, the set continued to perform without a hitch. And it continued to behave over the next couple of days and through several on/off cycles. It has now been back with the cus- TETIA TV TIP Akai VS200 VCR (and Samsung equivalents) Symptom: Intermittent orno clock when the set is on standby. Also EE picture shows a small amount of hum. Cure: C15 in the power supply (an electrolytic capacitor on the 32V rail) is defective. The manual shows th is capacitor to be a 1OµF 50V unit but this set had a 22µF 50V fitted. It didn't matter which value replaced the faulty unit. TETIA TV Tip is supplied by the Tasmanian branch of the Electronic Tec;hnician's Institute ofAustralia. Contact Jim Lawler, 16 Adina St, Geilston Bay 7015. tomer for several weeks and, at last report, has not missed a beat. So after a couple of false leads, all ended happily. But it was not one of my most satisfying jobs. Filling in the gap Now, for a change of scene, here is something from our regular contributor, J. L. of Tasmania. He starts off with the cryptic comment, "this story started a week before it began". Well, if you say so J. L. , who am I to argue, but I must confess that these ancient brain cells had some trouble working that out. No matter; here's the rest of his story. I was asked to repair a TV set for an elderly customer and , so that she would not be without entertainment while I worked on it, I left one of my older loan sets with her. I went ahead with her job and had it completed within a couple of days. However, it wasn't convenient to take it back immediately and, before I was able to do so, she rang to say that my set had broken down. This was rather a surprise; it is an old HMV 48cm model - a B4803 fitted with a Rank Arena Dl chassis. It had given no trouble in the several years since I inherited it. Naturally I wasted no time in delivering her set and, while I was packing up the old HMV, I asked her what had happened to it. She told me that the screen had gone bright red, with even brighter lines across it. There was no sign of a picture, although the sound had continued uninterrupted. I groaned inwardly when I heard this because these symptoms in older sets often mean that the picture tube has developed a heater-cathode short. If this was the trouble , then the set would be a write-off because it wouldn't be worth fitting a new tube to the old chassis. Back at the shop, I wasted no time getting the wreck onto the bench to see ifI could rescue the situation. The first thing I did was measure the voltage on the collector of the red output transistor. This was down to 30V; over 100V less than normal. A check on the other two collectors showed a much more likely 190V. So it certainly did look like a short in the tube. There is one sure way to prove a heater-cathode short. If the collector voltage reverts to normal when the socket is pulled off the tube , then the problem has to be in the gun assembly. But when I pulled the socket off in this case, the voltage remained low. I gave a little cheer and began looking for the true cause of the problem. If the output transistor had become leaky, it could account for the symptoms. But this would be a fairly unusual fault , since output transistors usually fail completely- a dead short or an open circuit. In my experience, most leaky transistors are small signal, low voltage types. Anyway, I removed the transistor and checked it on the tester. It was perfect! No leakage and normal gain for the type. I re-fitted it to the board and hunted for any other fault that could cause a red screen. I checked the base and emitter voltages on all three transistors and found nothing amiss. Well, nothing amiss in that they were all the same but nothing like the figures given in the circuit diagram. The bases read 1V and the emitters 0.4V, instead of 2.3V and 1.8V respectively. This suggested that all three tube cathodes were drawing less than normal current. What's more, the voltages on all three transistors remained more or less the same when the socket was pulled off the tube. Where's the current going? This left me with quite a puzzle. The fact that the red collector voltage was very low suggested that excessive current was being drawn. But it APRIL 1993 35 It looked as though it was only a cou- SERVICEMAN'S LOG - CTD wasn't being drawn through the transistor, nor through the tube. So where was the current going? Nothing appeared to be getting unduly hot. There were no sparks or flames to indicate where the ergs were going. Yet the power was being dissipated somewhere. I checked all the resistors associated with the output side of the transistors and found a slight anomaly. The circuit diagram showed 10kQ load resistors and 2. 7kQ feed resistors to the tube cathodes. The values I measured were 15kQ and 10kQ respectively. But they hadn't gone high; they were the actual values fitted, so I had to accept them as correct. Leakage checks The only explanation I could suggest for the low collector voltage was that there was a leakage path somewhere on the board. I checked leakage on the red channel, using a high impedance digital meter, and compared it with the blue and green channels. There was no leakage that I could detect on any of them. Yet there had to be something that was leaky. And if it couldn't be detected with a multimeter, then perhaps it was only present when working voltages were applied. Leakage of this kind is usually found only in capacitors. Resistors go high, not low, and other devices usually short out completely. In this circuit there was only a lO00pF ceramic capacitor in the emitter circuit and a spark gap off the collector. It took no time to replace the capacitor, without any result. So next came the spark gap. I put Z0V from a bench power supply across it and it showed no sign ofleakage. Yet when I removed it from the board, the collector voltage came up to 170V and the picture returned in all its glory. The spark gap was totally enclosed in heatshrink plastic and, after I cut this away, I could see through the gap. ANTRIM TOROIDAL TRANS 0 ple of thousandths of an inch across but, by holding it up against the light, I could see that there was something inside the gap. (I trust I will be forgiven for reverting to the imperial system of measurement but it was more appropriate in this case). At first I couldn't find anything thin enough to go through the gap. Then I thought of the feeler gauge in the car toolbox. The .002-inch gauge fitted perfectly and when I looked again the gap was perfectly clear. I re-fitted the gap to the board and the picture remained bright and clear, so I declared the fault found and fixed. I finished the job by putting a short length of heatshrink tubing over the gap and shrinking it into place. I have no doubt that the gap will continue to work perfectly but I can't help wondering what it was that caused the voltage dependent short inside a spark gap that was very effectively sealed inside a thick layer of heatshrink plastic. Well thanks J. L., and another happy result. And I trust the story finished at the same time as it ended! SC AUSTRALIAN MADE TV TEST EQUIPMENT 10% discount on all test equipment. 15% discount on two or more items. Built-in meter to check EHT transformers including split diode type, yokes and drive transformers. $78.00 + $4.00 p&p ERS ~ V Built-in meter reads positive or negative voltages from 0-50kV. For checking EHT and other HT voltages. $98.00 + $5.00 p&p Strong magnetic field. Double insulated for your safety with momentary switch operation . 240V AC 2.2 amps . As important as a soldering iron! $75.00 + $10.00 p&p F 10 • Now made in Australia. • Standard range 15VA to 2kVA. • Large ex-stock quantities available. • Competitive pricing available for OEMs & resellers. • Simply the best transformers all round. Designed to test infrared or ultrasonic control units . Supplied with extension infrared detector lead. Output is via a LED and piezo speaker. $84.00 + $4.00 p&p - ::sc-- ~ ~~ ~ !UNER REPAlf!~ From $19 exchange "':'z: ~ pluspost&pack Cheque, Money Order, Visa, Bankcard or Mastercard 216 Canterbury Rd, Revesby, NSW 2212, Australia. PTYLm HARBUCH 90 George Street, Hornsby NSW 2077. Telephone (02) 476 5854. Fax (02) 476 3231. 36 SILICON CHIP Phone (02) 774 1154 Fax (02) 7741154 Humidity (%RH) Temperature (°C) ~arometer (hPa) T.HER SJI -,: Three-function home weather station This weather station allows you to monitor barometric pressure, temperature & relative humidity. It uses three separate sensors & a relatively small amount of circuitry to provide precise readings on a liquid crystal display. Design by JOHN CLARKE While this weather station uses a relatively small amount of circuitry, we must warn readers that it is not a cheap project. The sensors have turned out to be quite expensive, so . much so that retailers will not be offering a kit for this project. However, while the sensor cost certainly makes the project less attractive, we have decided to publish the article for its general interest. The Weather Station is housed in a plastic case measuring 160 x 55 x 170mm. On the front panel is a 3½digit LCD) and a switch to select baro- metric pressure, temperature or relative humidity. On the barometric setting, you can display a preset (fixed) reading or the actual reading. By comparing the actual reading with the preset reading you can check whether the pressure has fallen or risen since the fixed reading was preset. Barometric pressure is measured over the range from 931hPa to 1084hPa (hectopascals) which is equivalent to 27.5 to 32 inches of mercury. Temperature is measured from 0°C to 70°C or from -40°C to 100°c if an external sensor is used. Relative humidity (RH) can be measured from 10% to 90%. Three sensors are used in the circuit. The barometric pressure sensor is a SenSym SCX15ANC, while the temperature sensor is a National Semiconductor LM335 which has a nominal output of 10mV/°K; ie, at 0°K, (-273°C) its output will be zero. The third sensor is a Philips device which varies its capacitance in proportion to relative humidity. A brief look at the main circuit of Fig.1 will show that the heart of the Weather Station is ICl, an ICL7106 analog to digital (AID) converter which directly drives a 3½-digit LCD . ICl may be thought of as a digital multimeter which can display a full scale reading of 199.9mV. The rest of the circuitry involves interfacing the three sensors to ICl so that correct readings are displayed. Barometer connection Fig.2 shows how the pressure sensor is connected to the INHI and INLO APRIL 1993 37 ~ n ::i: :a z n 0 ;:: C/J = I /'":'\. '-.J 2 I 3 . 4 5 10k 10k 1800 SCXr95ANC PRESSURE SENSOR P1 S1b 100k 03 -- 220k 100k ~~~:e- '"e',;:ii" .,. TH1 TEMPERATURE SENSOR LM335 2 1.2k Wlr ·1 IC2 +12V --iq:r8 BX fy 82pF+ • HU MIDITY t L ZERO VR4 50k 6 68k IC3 7555 11':1 0.1! + 5 1~pF r--+- .......... , _ ' 13 I 100k ____.! 7 ___.,_, : HUMIDITY© SENSOR HI ) IC4 7555 4 12 --~,---= .,. 1N~~48 .,. 100k 0.1I 0.1I .... BAR CAL VR1 5k ~ 8 ~ 1.2k •coM 11N LO T 1 NP 33 34 0.22u 27 CREF CREF INT BUFFER r· AUTO iERO ~OSC2 '"~ 100pF 30 rlosc1 ' 0.1= 180k. .,. 26 5 +12V BP I 21 H,20 AB 19 G3 22 F3 17 E3 18 D3 15 C3 24 B3 16 1-- A3 23 G2 25 F2 13 E2 14 C2 10 02 9 82 11 6 F1 7 G1 A2 12 B1 4 3 C1 2 01 8 E1 A1 _,,► TESTI 37 t , I,. ·7"'"'"'" LO 36 REF HI 32 WEATHER STATION .,. .01+ .i. I b 10 S2a I J J • HUM .01I CAL . VR5 100k J 20 3- J 0.1 I 47k 35 REF .----1i---~----------. L!() 3 .,. 0·1I 1l~ 120k TEMP CAL VR3 20k 4·7k I·BX,J15 + 4053 ' 1cY 4.7k SET ZERO TEMPERATURE ~--t"ii" VR2 10k _ + I l l \~ I ZD1<at>) 100 12V J 1W 16VW IM.-1-11&-I-_ _ ___.,__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _.,__ _ _ _ _ _ _ _ +12v ----1---t----.----:1---t------1""""-"""'--"""'---.....- - , S2 1 : BAROMETER (hPa) 2 : TEMPERATURE ('C) 3 : HUMIDITY (%RH) S1 1 : BAROMETER FIX 2 : OFF 3 : ON SWITCH POSITIONS : - <>-i FROM 12VDC PLUGPACK + S1a 01 1N4004 /B /A B J2 140 112 /B 47k 11 D ,-, OP1 ,-, 28 138 VIEWED FROM BELOW 3 10k t----YtlM.---+12V 2 DP1 16 E/=/c /=/ • /=/ F,-G A 3·1/2 DIGIT LCD -0AoJ IS Y BP OP2 DP3 y EOc 3 .!! B. 9 19. ~ 11 ho l21 l25 l13 114 l15 124 l2s 123 122 111 118 119 120 121 Fig.1 (left): the circuit is based on an ICL7106 analog-to-digital (AID) converter (ICl) which directly drives a 3½-digit LCD. The rest of the circuitry interfaces the three sensors to ICl so that the correct readings are displayed. inputs of IC1. If the difference between the INHI and INLO inputs is 100mV, the displayed reading will be 1000, provided the reference voltage applied between REFHI and REFLO is 100mV; ie, the ratio between the input voltage and the reference voltage is 1.00. At an air pressure of 1034hPa, the voltage across pins 3 and 5 of the pressure sensor is nominally 90mV ±5%. To give a display reading of 1034, we need to change the reference voltage so that the ratio between the input voltage and the reference voltage is 103.4/90 or 1:1.149. To achieve this, the reference voltage must be reduced to 87mV. VR1 is used to set the reference voltage between REFHI and REFLO to 87mV. This is done during the calibration procedure. Temperature Temperature measurement is a little more complicated and is shown in Fig.3. The temperature sensor TH1 has a linear characteristic of 10mV/°C with the output being zero at -273°C, The humidity sensor (near pen) is a Philips device which varies its capacitance in proportion to the moisture content in the air. Also visible in the photograph is the pressure sensor (top left) & this covers the range from 931hPa to 1084hPa. or 0°K. At 0°C the sensor output is close to 2. 73V. If we were to apply this voltage directly to IC1, we would be measuring in degrees K rather than degrees C. We need t6 offset this initial 2.73V from the sensor so that the display will indicate zero at 0°C. We also need to reduce the sensitivity of the sensor to lmV/°C so that, if the display reads 0.0 at 0°C, it will read 100.0 at 100°c. To offset the initial sensor output (2. 73V at 0°C), we need to make use of a reference voltage which is available +12V - - - - - - , . - - - - - - - - - . at the common output ofICl. This is a nominal 2.88V below the positive supply rail. This is connected to the REFLO input (and INHI input), while the REFHI input connects to VR1 as for the barometer mode. Finally, the INLO input is connected to the THl sensor via a resistive divider comprising a 120kQ resistor and trimpot VR3. Trimpot VR2 is connected across sensor THl to set the sensitivity. We use this trimpot to make the display read 0.0 at 0°C. In effect, this adjusts +12V 47k 47k TEMP ZERO VR2 2.u69V BAR 1 k P1 SCX15ANC 2 180k 2.88V <at> o•c Uk REF HI TEMP CAL VR3 REF LO COMMON ICL7106 IN HI .,. IN LO 180k ICL7108 .,. ' - - - - - - - - - I N LO TEMPERATURE BAROMETER .,. Fig.2: this diagram shows how the pressure sensor is connected to the INHI & INLO outputs of the AID converter (ICl). VRl allows the unit to be calibrated. .,. Fig.3: the temperature measurement circuit is complicated by the need to offset a 2.73V output from the sensor at 0°C. This is achieved by making use of a reference voltage which is available at the common output of ICl. APRIL 1993 39 AVERAGE VOLTAGE t 00:ITT~ 1~3 r7 r7 +12V 47k VR1 '""~ 70i RH 180k HUMIDITY ZERO VR4 HUMIDITY CAL VRS ICL7108 .,. IN HI IN LO difference between Fig.1 and the separate measurement circuits of Fig.2, 3 & 4 is the use of IC2, a 4053 CMOS analog switch, to provide switching between the two barometer modes; ie, fixed and actual. When switch Slb is open, the pressure sensor voltage is fed from pins 4 & 15 ofICZ to switch SZ and thence to !Cl. When switch Slb is closed, the voltages at pins 3 & 1 of ICZ are switched through to the output at pins 4 & 15. VR6 sets the voltage at pin 3 of ICZ and thereby provides the "fixed" barometer reading. J1J7 S~~~:E OSCILLATOR IC3 TRIGGER J1JU1 .,. MONOSTABLE 100k H1 HUMIDITY .,. Fig.4: the humidity measurement circuit uses square oscillator IC3 to trigger a monostable whose period depends on the humidity sensor (H1). The outputs of the two oscillators are then filtered & fed to the inputs of the AID converter which measures the difference between them. VR5 provides calibration. the sensor voltage to be the same as the COMMON reference voltage of 2.88V at 0°C and hence negates the initial offset voltage of 2. 73V. Trimpot VR3 is then used to reduce the sensor output to around 1mV/°C (it is actually set so that the display reads 100.0 at 100°C). Humidity To measure humidity, we use two oscillators which are locked together, as depicted in Fig.4. IC3 produces an exact 50% duty cycle square-wave (waveform A) which continually triggers IC4. The latter is simply a monostable with its positive pulse duration set by the capacitance of the humidity sensor, Hl. Both oscillators run at about 100kHz and their outputs are DC pulse trains which are filtered and then applied to !Cl. In effect, IC1 measures the difference in DC voltage from the two oscillators and this is proportional to relative humidity. We can now refer back to the full circuit as shown in Fig.1. The main Decimal point drive The decimal point of the liquid crystal display is used for both the temperature and humidity modes. In order to drive the decimal point, we need a signal which is exactly out of phase with the backplane (BP) squarewave signal. Transistor Ql inverts this signal and applies it to the DP1 terminal (pin 16) of the LCD via· switch SZd. Power for the circuit comes from a 12V DC plugpack. Diode Dl provides reverse polarity protection, while the 150Q resistor and 12V zener diode ZD1 provide voltage regulation. Construction We built the Weather Station into a standard plastic case measuring 160 x 54 x 170mm. There are two PC boards; the main board measures 149 x 130mm and the display PC board 136 x 43mm. Assembly of the two PC boards is quite straightforward and all of the RESISTOR CODES 0 0 0 0 0 0 0 0 0 0 0 0 0 0 40 No. Value 4-Band Code (1%) 5-Band Code (1%) 1 1 1 4 1 1 2 1 3 2 2 220kQ 180kQ 120kQ 100kQ 91kQ 68kQ 47kW 43kQ 10kQ 4.7kQ 1.2kQ 180Q 150Q red red. yellow brown brown grey yellow brown brown red yellow brown brown black yellow brown white brown orange brown blue grey orange brown yellow violet orange brown yellow orange orange brown brown black orange brown yellow violet red brown brown red red brown brown grey brown brown brown green brown brown red red black orange brown brown grey black orange brown brown red black orange brown ~rown black black orange brown white brown black red brown blue grey black red brown yellow violet black red brown yellow orange black red brown brown black black red brown yellow violet black brown brown brown red black brown brown brown grey black black brown brown green black black brown SILICON CHIP TRIMPOT CODES 0 0 0 0 0 0 Value IEC Code EIA Code 100kQ 50kO 20kQ 10kQ 5kQ 100k 50k 20k 10k 5k 104 503 203 103 502 Parts layout & wiring diagram CAPACITOR CODES 0 0 0 0 0 0 0 0 0 Value IEC Code EIA Code 1µF 0.68µF 0.22µF 0.1µF 0.01µF 100pF 82pF 15pF 1u0 680n 220n 100n 10n 100p 82p 15p 105 684 224 104 103 101 82 15 wiring details are shown in the diagram ofFig.5. We suggest that assembly of the main board should start with the PC stakes, wire links and resis~ors. After that, the capacitors, diodes, transistors and finally the ICs can be installed. The temperature sensor (TH1) should initially be mounted on 100mm lengths of wire to allow easy calibration. Install and orient the trimpots so that their adjustment screws are positioned as shown on the wiring diagram. Now solder in the pressure sensor (Pl) and the humidity sensor (Hl) . The humidity sensor is secured with 3mm screws and nuts onto the PC board. The display PC board is next. This is a little unusual in that the display is mounted on the copper side of the board. Begin by mounting and soldering all the links on the board and cut each lead as close to the copper tracks as possible. The three 8-way rainbow cable connections (A1 -A8, B1-B8 and C1-C8) must be soldered into the display PC board before mounting the display. The "A" bus leads should be 40mm long, the "B" bus leads 60mm long and the "C" bus leads 70mm long. As before, cut off the wire ends as close to the copper pads as possible. Check your soldering carefully for Fig.5: take care with component orientation when installing the parts on the PC boards & note that the LCD is installed on the copper side of the display board after the remaining wiring has been completed. You can determine the orientation of the LCD by holding it up to the light (there's also a ridge on the edge of the glass at the pin 1 end). Where to buy the sensors & PC boards PC boards for this project will be available from our regular suppliers as listed on the back page of this magazine. The LM335 temperature sensor is available from Altronics at $3.95 plus packing and postage. Phone (008) 999 007. The Sensym SCX15ANC pressure sensor is available from NSD Australia at $64.80 plus sales tax. Phone (02) 646 5255. The Philips 2322 691 90001 humidity sensor is available from Farnell Electronic·Components to account or credit card customers at $27.76 plus sales tax. Phone (02) 645 8888. APRIL 1993 41 PARTS LIST 1 plastic case, 160 x 55 x 170mm (Arista UB-16) 1 PC board, code 04201931, 149 x 130mm 1 PC board, code 04201932, 136 x43mm 1 Dynamark front panel label, 156 x50mm 1 45 x 17 x 2mm piece of clear Perspex 1 2-pole 2-way centre off toggle switch (S1) 1 dress nut for toggle switch 1 4-pole 3-way rotary switch (S2) 418mm OD 10mm ID x 0.8mm fibre washers for rotary switch 1 3½-digit LCD, 50 x 31 mm 1 12V 200mA DC plugpack 1 2.1 mm DC panel socket 1 100kQ tuning pot (DSE Cat R1911) 2 15mm x 3mm tapped brass standoffs 4 3mm x 5mm machine screws 2 3mm nuts 2 2.5mm x 3mm machine screws 1 300mm length of 0.8mm ECW 1 400mm length of 2.54mm spaced 8-way rainbow cable 16 PC stakes Semiconductors 1 SenSym SCX15ANC pressure sensor (P1) 1 Philips 2322 691 90001 humidity sensor (H1) 1 ICL7106CPL A-D converter & 3½-digit LCD driver (IC1) 1 4053 CMOS analog switch (IC2) 2 LMC555CN CMOS timers (IC3,IC4) 1 BC338 NPN transistor (01) 1 LM335 temperature sensor (TH1) 1 12V 1W zener diode (ZD1) 1 1N4004 1A diode (D1) 1 1N4148, 1N914 signal diode (D2) Capacitors 1 100µF 16VW PC electrolytic 1 1µF 63VW MKT polyester 1 0.68µF 63VW MKT polyester 1 0.22µF 63VW MKT polyester 6 0.1 µF 63VW MKT polyester 2 0.01 µF 63VW MKT polyester 1 100pF 63VW MKT polyester 1 82pF NP0 ceramic 1 15pF NP0 ceramic Resistors (0.25W, 1%) 1 220kQ 1 43kQ 1 180kQ 3 10kQ 1 120kQ 2 4.7kQ 4 100kQ 2 1 .2kQ 1 91kQ 1 180Q 1 68kQ 1 150Q 247kQ Trimpots 1 100kQ top adjust multiturn trimpot, VR5 (Bourns 3296) 1 50kQ top adjust multiturn trimpot, VR4 (Bourns 3296) 1 20kQ top adjust multiturn trimpot, VR3 (Bourns 3296) 1 10kQ top adjust multiturn trimpot, VR2 (Bourns 3296) 1 5kQ top adjust multiturn trimpot, VR1 (Bourns 3296) shorts on the board. Once the display is mounted, there will be no chance to fix any PC board problems. The LCD is mounted on the copper side of the PC board with pin 1 located as shown in Fig.5. The pin 1 end of the display has a slight protrusion at the display edge. To be sure that the display orientation is correct, hold the display up to the light and orient it so that the digits are upright. Pin 1 is the bottom lefthand pin. The hole for the rotary switch (SZ) should be reamed out to 17mm diameter and a notch cut for the "key" of the switch. Mount switches Sl and SZ on the board, then wire the display board to the main board and complete Left: this is the view inside the completed prototype. The pressure sensor is secured by soldering it directly to the PC board & by fastening it to the rear panel using two 15mmlong spacers & machine screws. The humidity sensor is soldered to the board & then further secured using two machine screws & nuts. 42 SILICON CHIP 0 6· here are the full-size artworks for the two PC boards & the front panel. F.1g.. APRIL 1993 43 This close-up view shows the wiring details for the front panel. Use rainbow cable for the connections between the two boards & be sure to complete the wiring to the display board before mounting the LCD on the copper side. the remaining assembly work involving the front and rear panels. Testing & calibration Apply power to the circuit and check that the display gives a reading. The decimal point should appear on the temperature and humidity settings and you should be able to adjust the display reading on the "Bar. Fix" setting of S1 (do not expect any meaningful readings at this stage). The first function to be calibrated is the Barometer mode. Set VRl so that the display shows the correct barometer reading. The correct figure may be obtained by contacting the weather bureau if you live in a city. To adjust the unit so that it is correct for your location, use VRl to reduce the reading by 120hPa per 100-metres above sea level. The Temperature mode requires two adjustments to calibrate it. First ro- The ICs were all soldered directly to the PC board in the prototype but you can use IC sockets if you wish. Drill a small hole in the rear panel directly in-line with the open port of the pressure sensor to ensure correct readings. 44 SILICON CHIP tate trimpot VR3 fully anticlockwise to provide the maximum output from THl. This done, place the temperature sensor in a mixture of water and ice which is continuously stirred and adjust VRZ so that the display reads 00.0. Now insert the temperature sensor in boiling water and adjust trimpot VR3 for a reading of 100.0 degrees. Note that the boiling point of water increases by 1°C for every 39hPa increase in pressure above 1013hPa and decreases by 1°C for every 34hPa decrease in pressure below 1013hPa. Once calibrated, the temperature sensor can be installed directly on the PC board. The main board can now be secured to the base of the case using the self-tapping screws supplied. The humidity calibration also requires two adjustments. The first adjustment zeros the display at 0% relative humidity. To do this, rotate VR5 fully anticlockwise and then apply a hairdryer to both sides of the sensor for about 20 seconds. This is done to thoroughly dry the sensor and trick it into giving a reading equivalent to 0% relative humidity. Wait a few seconds after the hairdryer has been switched off and then adjust VR4 for a reading of 00.0. Now leave the sensor for five minutes or more to let it cool and stabilise, then adjust VR5 to give the correct reading for relative humidity. Again, this information is available from the Weather Bureau if you live in a city. Alternatively, if you have access to a wet and dry bulb thermometer, you will be able to do the calibration more accurately. SC REMOTE CONTROL BY BOB YOUNG Practical applications of the low cost speed controller Since the first speed controller article was published in November 1992, many readers have contacted me with questions, hints, suggestions, criticisms & applications. This column is in response to those people & shows how the speed controller can be used in other ways. The very first thing that became obvious was the number of applications people were finding for what in my mind was purely an R/C project. This led immediately to the first problem they encountered: how do you drive the SpeedlB speed controller if you have no radio control outfit? The answer to this problem is simple and requires only a few components. Fig.1 shows the pulse input timing and voltage requirements for the SpeedlB speed controller. Fig.2 shows a simple variable pulse width generator using a single 4001 or 4011 CMOS quad gate package. VRl, R2 and Cl control the "ON" time which is continuously variable. VRl can be a simple potentiometer knob or the variable resistor in a joystick controller. Remember that when you use a joystick, the stick mechanism restricts the angular rotation of the pot to under 100°, so there will be less pulse width variation available than with a simple knob. To compensate for this, increase Cl Jll t?· I .:~:-------- and decrease R2. A small trimpot in series with VRl will provide a trim control for fine adjustment of neutral. R3 controls the "OFF" time, which increases with an increase in resistance. R3 is thus an effective frame rate control. Using this circuit, the timing conditions of any of the modern R/C sets can be simulated. I might add that when fitted with a servo socket, the above circuit will make a dandy little servo tester. If there is enough reader response, I may even be persuaded to do a project on a pulse width counter with 3-decimal place resolution, to allow the setting of transmitter and servo neutrals to precise limits. Built into a box with the servo tester and a meter to indicate servo current consumption (a sure guide to the health of servo motors), this unit would be a very useful tool for all R/C enthusiasts. PC parallel port control As an interesting alternative, the parallel port of a PC could be used to Ill .I • Fig.1: this diagram shows the pulse input timing & voltage requirements for the SpeedlB speed controller. generate a suitable pulse, with control coming from either a joystick or the UP-DOWN arrow keys. This port should provide enough output to drive the SpeedlB direct although it is probably a good idea to buffer the output of the computer for safety's sake. The timing of the "ON" and "OFF" periods could be adjusted quite simply by changing the values in FOR-NEXT loops in a BASIC program. In fact, all of the above are really quite unnecessary for in reality we are doing a double conversion. The simplest fix would be to make the high frequency (2kHz) pulse width generator of the speed controller into a free running circuit and do away with the 50Hz to 2kHz conversion completely. However, this would require a completely new PC board. Twin engine control Moving on now to a more R/C oriented question, one of our readers referred to the December 1991 photo of Wes Fisher's model of the Partenavia P61, which has twin engines. This model was featured again in the December 1992 issue. The question which arises is how are the twin throttles arranged and controlled? The answer to this is not so simple and opens up many questions concerning the advantages and disadvantages ·of twin-engined models. A brief discussion on internal combustion (IC) twin-engined models may help clarify some of the advantages of electric twin-engined models. To many modellers, the sound of two motors bellowing in harmony, overlaid with the characteristic audio beat note generated when the motors are almost perfectly in sync, is music APRIL 1993 53 to the ears. To me, it conjures up visions of changing two props, two plugs and filling two tanks every time one wants to fly or tune the engines for maximum performance. I hate filling fuel tanks and at least electrics do away with this chore. It also conjures up visions of my first near disastrous experiences with twin-engined power models. Notwithstanding all of the foregoing, they are very exciting models to build and fly and are great attention grabbers on any model field. The only thing that grabs more attention than a twin is a 4-engine model. And here, Dave Masterton topped the lot with his 6engined all-electric, B36 scale model. The big problem with IC motors is that they quit for all sorts of reasons and usually at the most inopportune times, such as during take-off and when you are flying low a long way The same considerations apply should one motor suddenly lose power or even suddenly increase power. The result is an unwanted turn whose intensity will be proportional to the difference in power between the two motors. Designers (full size and model) over the years have gone to considerable trouble to produce aircraft with sufficient safety margins to overcome the problems of asymmetric flight. These measures include such devices as twin fins and rudders, lifting fins, outthrust, swept wing leading edges and so on. As a result, twin-engine aircraft today are much safer than they ever were. But caution is still required and the best fix is still good pilot training in emergency procedures. The emergency procedure for loss of power in one engine is to first reduce power if possible until you have +5V 4001 OUTPUT R1 R3 1.8M 150k out and cannot see or hear which motor has quit. Now the golden rule with multiengined aircraft is that you must never turn into the dead motor. For this reason, it is absolutely vital that you immediately identify which motor has quit, in order to take the corrective action required. The problem is, if the model is a long way away and/or out of earshot, the first indication of trouble comes when the model turns into the dead motor due to the asymmetric forces generated when only one motor is functioning. These forces are considerable and the resulting turn can be quite violent. It can also be outside the range of the normal flight controls to rectify. In this case, the model will go into a spiral dive and eventually crash if the throttles are not pulled back quickly enough. Thus, an engine failure in a multi-engined model can present real problems, even to experienced pilots. 54 SILICON CHIP Fig.2: this simple variable pulse width generator can be used to drive the Speed 1B controller. It uses a single 4001 or 4011 quad gate package. the aircraft flying straight and level. You must then identify which motor has cut and begin a turn back towards the landing area, this turn being towards the side with the functioning motor. Once the turn is initiated, you then gradually increase the throttle until enough power is established to bring the aircraft home. The last thing you want is to have to go around again with one dead motor. The other golden rule is never increase the throttle suddenly. Instead, the correct procedure is to adopt a "gently does it at all times" approach. Some models fly quite well on one engine, while some will not fly at all. In the latter case, all you can do is cut the good engine and put down as safely as possible. Electric advantages One distinct advantage of electric power is that the motors do not cut out unless something very unusual happens. The worst that happens is that one motor loses power if two separate batteries are used to supply the drive power and one goes flat ahead of the other. If a single battery is used to supply both motors, then their RPM should track reasonably well across the entire flight time. An interesting approach in regard to twin batteries would be to use a phototacho to control the RPM balance between the two motors. This could also be applied to IC motors with good effect. From the foregoing, it becomes obvious that engine management in multi-engined aircraft is a most important function. Even small variations in RPM between motors can become annoying because you constantly need to alter the trim of the aircraft. Believe me, there is nothing more annoying to a pilot than to be constantly altering the trim of his aircraft during flight. I can well remember when I was in the "Biscuit Bombers" in National Service. After the load was dropped, we used to delight in all moving down to the tail at once, giving the pilot time to retrim, and then all moving up to the front. We'd give him time to retrim again and then move down the back again. After 10 minutes of this, the pilot would burst out of the cockpit roaring "if you lot don't sit still I will chuck you all out of the back door"! After that, we would all be as meek as lambs; until the next flight. The situation for engine management in models is further complicated by the fact that we do not have tachometers on models and the transmitter stick layout makes the use of twin throttles difficult, if not impossible. One method is to use a system of bellcranks and rods to allow a single servo to drive both throttles. This is a very rigid approach and does not allow any in-flight trimming. It also requires careful planning in the building stage to get the linkages in without fouling aileron and undercarriage components. The easier, albeit more expensive approach, is to use a split lead ("Y" harness) from the throttle channel and feed two independent servos. Most modern receivers have sufficient output drive capability to do this safely. Again this system does not allow any in-flight trimming of the motors. Ideally, we would like independent throttle control to bring both motors into sync and since the mechanical arrangement of the transmitter makes this almost impossible, how can it be done? Mixed channels The answer lies in a concept known as "mixing", in which two channels are mixed to allow a composite output to be applied to two separate servos. Mixing can take two forms. The most popular these days is mixing at the transmitter (encoder) end of the tion of this device in some detail. Essentially, the mixer is an active "Y" harness with one extra lead fitted which provides the control signal for the ratio of mix. Thus, the device is fitted with two servo sockets which connect with two completely normal (unmodified) servos. If the two input leads are plugged into the throttle channel and one of the auxiliary channels, then moving the throttle lever on the Tx will move both servos in the same direction, thus applying throttle changes to both motors simultaneously and in equal pro- "For model boats, particularly electric powered boats fitted with reversing speed controllers, steering achieved by differential control of the throttles is quite useful". R/C link. The older and less popular method is to fit a mixer to the receiver output. Both systems work equally well and for those modellers who do not have modern systems with mixers in the transmitter, the receiver mixer provides quite a satisfactory solution. A typical receiver mixer provides a mix ratio over the range of 25:75 to 75:25 using a single pot, as well as a fine trimpot control for each servo neutral adjustment. The most difficult concept to grasp is the receiver mixer, so I will now concentrate on explaining the opera- portion. So far we have just a normal "Y" lead operation. The cunning part is in the operation of the second lead. This applies a differential output to each channel, thus advancing one throttle and retarding the other, again in equal proportions. The really clever part, however, is that this ratio of mix is adjustable from 25:75 to 75:25. Thus, the auxiliary lever now becomes a throttle balance control, allowing one throttle to be advanced and one retarded; just what the doctor ordered! It takes little imagination to see the uses for such a device, the most corn- man being the mixing of ailerons, elevators and flaps for trim compensation in fixed wing aircraft. Another very popular use is mixing of the collective pitch for tail rotor control in helicopters. For model boats, particularly electric-powered boats fitted with reversing speed controllers, steering achieved by differential throttle control is quite useful. In this case, the two input leads are fitted into the rudder and throttle channels. The rudder channel controls the differential input and the throttle the simultaneous input. Typically, one motor can be put into reverse and the other into forward and the boat spun on its own axis. Modern R/C equipment has developed this concept into the mixing encoder, thus doing away with the model mounted mixer. However, the concept is similar in operation. One important point to keep in mind when using any mixer is that each channel can only supply 50% of the servo throw, in order to allow the second servo to provide the last 50% of the throw. Therefore, some compensation in the mechanical linkages is required to keep the controls as effective as with non mixer use. This effect is minimised in the modern mixing transmitter, by allowing the use of 100% plus of servo travel. Keep in mind here that there are stops in the servo gear box housings and it is very easy to remove servo gear teeth if the output gear is rammed hard against these stops. SC YOU AN NOW AFFORD SATELLITE TV SYST For many years you have probably looked at sate II ite TV systems and thought "one day". You can now purchase the following K-band system for only: $995 Here's what you get: • A 1.6 metre prime focus dish antenna, complete with all the mounting hardware. • One super low-noise LNB (1.4dB or better). • One Ku-band feedhorn and a magnetic signal polariser. • 30 metres of low-loss coaxial cable with a single pair control line. • lnfrared remote control pre programmed satellite receiver with selectable IF & audio bandwidth, polarity & digital readout. Your receiver is pre-programmed to the popular OPTUS transponders via the internal memory. AV-COMM PtJ Ltd, PO Box 225, Balgowlah NSW 2093, Ph: (02) 949 7417. Fax: (02) 949 7095. All items are available separately. Ask about our C-band LNBs, NTSC-to-PAL converters, video time date generators, FM2 & EPAL &· Pay TV hardware. r--------------x I YES GARRY, please send me more information on K-band I I satellite systems. Name: _ _ _ _ _ _ _ _ _ _ _ __ I Address: _ _ _ _ _ _ _ _ _ _ _ __ : _ _ _ _ _ _ _ _ _ P'code: _ _ __ 1 Phone _ _ __ _ _ _ _ _ _ __ _ I ACN 002 174 478 10192 APRIL 1993 55 Special circuit for vintage radio restorers! Build this step-up voltage converter This little unit converts 9-12V DC from a mains plugpack up to a maximum of 70V DC at 40mA. It can be used with battery operated valve radios or any device that requires a supply voltage of more than 12V DC. rate intercom system, this project can also be tailored to provide the 50V required to operate them. In general, this circuit can be made to generate any DC voltage up to about 70VDC at modest output current levels. Circuit details By DARREN YATES If you're into vintage radio then you'll know that 'B' batteries are impossible to get for those battery-operated valve receivers. It would be a pity if melodic sounds were never to be heard again from these grand old sets for lack of a power source. In a recent Vintage Radio column (December 1991), John Hill suggested a 'B' battery eliminator using five 9V batteries. This provides a 45V supply but some old valve radios need a +6 7. 5V DC rail. Stacking seven or eight 9V batteries to provide around +7DV DC is not really practical and it would be quite expensive too. As a result, many old battery powered radios have been left to gather dust because the batteries to drive them are no longer available or the alternatives are just too expensive. This is where our little high voltage supply comes to the rescue. It allows you to run an old battery powered radio direct from the mains and it is quite cheap. If you have a couple of old Telecom phones that you wish to run as a sepa- The circuit for the High Voltage Converter is based on a Motorola MC34063A DC-DC converter IC (Fig.2). This was previously featured in the Portable SLA Battery Charger published in the July 1992 issue of SILICON CHIP. The MC34063A was designed to convert a DC voltage up to a level of about 40V maximum but by using a high voltage external pass transistor, the IC can be made to produce at least 7DVDC. The input voltage source can be just about anything from dry cells to a plugpack or your car battery but it 170 µH L r------------ --- 8I i I1 --+--◄ 180 I I I I I 12 Rsc 1N5819 0.22 V1n 0 - - - - - - l I 12 V 1.25 V Ref Reg 1100 jcrJ I 1soo : pF 14 I L-- --- -- ------------ -~ R2 Vout - - ---.,1t1,------------0 28 V/175 mA 47k The High Voltage Converter is ideal for generating the B+ rail for a battery powered vintage radio receiver, or for any application requiring up to 70VDC at 40mA. The output voltage can be adjusted by changing two resistor values. 56 SrucoN CHIP Fig.1: block diagram of the Motorola MC34063 DC-DC controller IC. It uses an internal oscillator to drive an RS flipflop & this in turn drives a Darlington transistor pair to switch an external inductor. S1 + 0.221l SW F1 2A o-/ Vin -+ 1801l 7 8 1 ~ IC1 MC34083A B 4.7k H~ K A BCE .0047+ 470 + ~ ~ 63VW+ ~ L1 : TWO LAYERS OF 0.63mm DIA ENCU ON NEOSID TOROIDAL CORE 17/732/22 RB 1k ~ HIGH VOLT AGE DC-DC CONVERTER Fig.2: the final circuit uses external pass transistor Qt to switch inductor Ll, so that the output voltage can be boosted to 70V. Resistors RA 1 & RA2 in the negative feedback network set the output voltage to the required value. must be able to supply around 250300mA. To understand how the circuit of Fig.2 works, it is useful to have a look at Motorola's own step-up circuit for the MC34063A, as shown in Fig, 1. Here there is no external transistor, as internal transistor Q1 takes care of all the load current. Briefly, the circuit works as follows. An input voltage of 12V is applied to pin 6 of the IC and also to the 170µH inductor L via resistor Rsc· This resistor provides current monitoring and the IC shuts down if the voltage across Rsc exceeds 0.3V. An internal oscillator, with its operating frequency set by the capacitor at pin 3, .drives Q1 and QZ and thus switches current through the 17DµH inductor. Each time transistor Q1 switches off, the collapsing magnetic field associated with the inductor will try to maintain the current through it but since Q1 is off, the only available current path is via the 1N5819 diode to the 150µF capacitor C0 • Thus, the capacitor charges to a considerably higher voltage than the input of 12V. Negative feedback around the circuit is used to set the output voltage to a predetermined value. This is set by a voltage divider network consisting of Rl and R2. This feeds the inverting input (pin 5) of an internal comparator, while a 1.25V reference feeds the non-inverting(+) input. Thus, when the voltage at pin 5 is just above 1.25V, Ql is not driven and when it is below 1.25V, Ql is driven at a high frequency. Typically, the circuit of Fig.2 can regulate the output voltage to within about ±50mV. Now take another look at our circuit of Fig.2 and note the differences between it and Fig.1 which we have just discussed. In the original circuit of Fig.1, pin 1 was connected to the junction of the inductor and the diode but this presented a problem for our application. Pin 1 is actually the collector of Ql inside the IC and it has a collectoremitter voltage (Vee) rating of 40V. This would be far exceeded if we pushed the circuit to produce the 70V or so we require. The solution is to use Ql inside the PARTS LIST 1 PC board, code 11102931, 100x 55mm 1 self-adhesive front panel label, 54 x 99 mm 1 plastic zippy case, 130 x 67 x 42mm 1 SPST miniature toggle switch 1 33mm OD toriodal core (Altronics Cat. L-5120) 1 3.5mm socket 1 2-pin DIN panel socket 1 2-pin DIN plug 3 metres of 0.63mm enamelled copper wire 2 M205 (2AG) fuse clips 1 2A M205 fuse Semiconductors 1 MC34063A DC-DC converter (IC1) 1 TIP31 C NPN transistor (01) 1 BY229-400 fast recovery diode (D1) 1 33V 1W zener diode (ZD1) Capacitors 2 470µF 63VW electrolytics 1 .0047µF 63VW MKT polyester Resistors (1 %, 0.25W) 2 27kO 1 1800 1 4.7kO 1 0.470 SW 1 1kO A small heatsink must be fiUed to power transistor Qt to aid heat dissipation. There's no need to isolate Qt 's tab from the heatsink but make sure that the latter does not touch any other components. · Miscellaneous Solder, screws, washers, nuts, hook-up wire . APRIL 1993 57 DC INPUT SC11102931 ~ _Qj Fig.4: check the PC board for defects against this full-size artwork before mounting any of the parts. Fig.3: make sure that all polarised parts are correctly oriented when installing them on the PC board & don't forget the wire link that sits directly under the back of the heatsink. IC as an emitter follower which then drives external transistor Ql (a bit confusing, that) . This external transistor has more generous voltage and current ratings. Pin 1 is now moved to the supply rail side of the inductor and so the internal transistor sees no more than about +12V on its collector. Apart from the use of an external transistor, the circuit of Fig.2 works in an almost identical fashion to the original circuit of Fig, 1. However, there are a few other differences which we will explain. Note the two 470µF capacitors connected in series across the output. We would have preferred to use just one output capacitor rated at 100V but 63V capacitors are much more read- ily available; ergo , we have used two in series. Connecting two capacitors of nominally the same capacitance and voltage rating does not mean that they will equally share the voltage; the actual voltage across each capacitor will mainly depend on their leakage resistance and we have no control over this factor. We solved that this problem by "swamping" the leakage resistances of the capacitors with parallel connected 27kQ resistors (RA 1 & RAz) and these do double duty by forming part of the voltage feedback network to pin 5. Output voltage As we said before, the output voltage can be adjusted to any value up to 70VDC. This is achieved simply by RESISTOR COLOUR CODES 0 0 0 0 0 0 58 No. Value 4-Band Code (1%) 5-Band Code 1% 2 27kQ 4.7kQ 1kQ 180Q 0.47Q 5W red violet orange brown yellow violet orange brown brown black red brown brown grey brown brown not applicable red violet black red brown yellow violet black red brown brown black black brown brown brown grey black black brown not applicable 1 SILICON CHIP Once the IC is in, install the 5W resistor, the fuse clips and the electrolytic capacitors. The HIGH VOLTAGE fast recovery diode (D1) and CONVERTER power transistor Ql can then be fitted. Note that Ql must be fitted with a small heatsink and this is best attached before the HVOUT DCIN transistor is installed. The last component to be installed is the toroidal inductor. ON This is wound in two layers using 70 turns of 0.63mm enamPOWER elled copper wire. Begin with a 3-metre length of wire and thread it half-way through the centre of the toroid. Now, using one half Fig.5: this full-size front panel artwork can be used as a drilling template for the of the wire, wind on 35 turns. on/off switch. Spray the finished label with a hard-setting clear lacquer before Make sure that you wind the attaching it to the lid of the case. turns as neatly as possible and keep the turns tight and close together. adjusting resistors RA 1 and RAz in the the power switch and the two power The other half of the wire is then used divider string. The equation to derive sockets are installed on a PC board to wind on the other 35 turns. Once the inductor has been wound, the correct values for resistors RA 1 measuring 100 x 55mm and coded strip and tin the wire ends, then sol11102931. and RAz is as follows: RA1 + RAz = (Vout/1.25 -1) x 1000 Before beginning any construction der the complete unit to the board. You can secure the inductor in a This is the total value for RA 1 and work, check the board carefully for RAz• You need to then divide this any shorts or breaks in the tracks by number of ways: by using a small value by two to get the value for RA 1 comparing it with the published pat- nylon cable tie that passes through and RAz• These resistors should be tern. Repair any defects that you do the toroid and two holes in the board; equal in value if possible, so that equal find, then start the assembly by in- by pouring a little hot wax over the toroid; or by using an adhesive like voltages are developed across the ca- stalling the resistors and ·wire links Blu-Tac®. see Fig.3. pacitors. The .0047µF capacitor on pin 3 sets Next, install the 33V zener diode, Switching on the switching frequency, while the the .0047µF MKT capacitor and the 33V zener diode (ZDl) protects the IC IC. It is usual to install ICs last but, in Check that all the wiring is correct this project, it's best to install it before before applying power to the board. from over-voltage. some of the bigger components go in. You will need a power supply capaConstruction Be sure to orient the IC exactly as ble of delivering 12V. This should be shown on the wiring diagram. connected via your multimeter which All of the components except for should be set to the 2A range. Make sure that you have the supply polarity correct before switching on. After an initial surge, the current should drop back to a few milliamps at most. If the current drain is appreciably more (with no output load connected), switch off immediately and check carefully for assembly errors on the board. If all is OK, disconnect your multimeter, select the 200V DC range, reconnect the power supply and measure the output voltage. You should get a reading of about 70VDC (RA 1 = RAz = 27kQ), depending on the tolerance of your resistors. Finally, the board can be mounted on the bottom of a plastic utility case and appropriate sockets fitted to accept the input and output connecThe PC board is secured to the bottom of the case using machine screws & nuts, tions. The on/off switch can be fitted with additional nuts used as spacers. A 3.5mm socket accepts the input from the plugpack, while the output is fed to a 2-pin DIN socket. to the lid of the case. SC =flW =Ui/Jl!J+ APRIL 1993 59 e A LTR. C> ~ I C COMPONENTS ~ J L,,i, L...JAJ--' 1 L,,vv e A US TRALIA WIDE A.LTRONICS 24 HOUR EXPRESS DELIVERY 'Our customers are often amazed at the speed and efficiency of our Jetservice Courier delivery. Phone your order Toll Free 008 999 007 and presto we can deliver your order next working day (country areas 24-48 hours later). Our famous 14 day satisfaction money back guarantee protects your hard earned $$$' s should ever a purchase be unsuitable for your needs. I invite you to try Australia's best electronics phone order service soon.' Regards, Jack O'Donnell Adjustable 0-45V, 8 Amp Bench Power Supply _Kit Fluorescent Light Inverter Kits (SC Jan-Feb '92) Using state of the art circuitry this supply will be a great asset to the enthusiast and professional alike. It uses switch mode principles which allows for smaller transformers, and heatsinking which means greater efficiency, less heat and lighter weight. Features: •Variable output •Variable current limit •Separate Earth Terminal •Individual Volt and Amp Meters •Constant 13.8V setting . •Short circuit proof K 3360 you to build a high power DC inverter suitable for driving fluorescent lights from a 12V source typically a car battery. Ideal for use in camping or boating as fluorescent light offers 2 big advantages over normal incandescent lights. Namely more even 360' light spread and low current drain. Two kit versions to choose from 16W and 20 to 40W. $3 75.oo . $35-.95 - - - - - - - - - - - - - - - - - - - ! K 6350 16W Versrnn igital Storage C.R.O. Ada tor 95 K 6360 20-40W Version $43· 4-Digit Capacitance Meter Kit $63· K 2806 PC 5.25" Disk Software to Suit K 2807 PC 3.5" Disk Software to Suit $19· 95 ---------------.,....--,,,..,...,,----,---:---------1 2 Way Active 2 Sector Alarm Crossover Kit System (EA Jan 92) This great Kit kit enables $89· This kit enables you to transmit TV signals from the UHF oun,ut of your VCR to a second TV set in the house. The kit is complete with box and has a range of about 20 metres. Requires 12 Volts DC. (pictured without case-included). K 5860 Normally $74 95 This Month Only $49·00 1------------1 Beat Triggered Strobe This great kit enables a P.C. user to capture a waveform and zoom in to segments of interest then save them to disc. The unit has 32K of storage memory and a sampling rate of over 600K samples per second. Input level of up to 2.5 Volt. Full sampling rate between 15K s/s to over 600K s/s. Input impedance oflMohm. 5 K 2805 0 (EA March-April '89) Features: • Includes 12V 1.2 Amp hour inbuilt sealed lead-acid backup battery • Easy to build as it all assembles on a single PCB • Two sectors - delayed and instant inputs • Entry and exit delay • Panic alarm input • Battery backup • Line monitoring • Soft pre-alarm • Lamp tell-tale output • Auxiliary relay for external siren etc • Key switch operation • Operates on virtually any type of sensor • Can be easily customised to accept Digital Keypads 00 K 1910 Video to TV Transmitter Kit you to customiseyour sound system in your car or at home. The circuit simply connects between the audio source and the amplifiers. There are two outputs one for bass and another provides signal for the upper range. Thus each amp is dedicated to a frequency range (i.e. one for bass, one for midrange and treble). Because no passive crossover is required in the speaker one per channel is required. Operates on + and - 15V rails. The result is much better sound with less distortion. 95 K5570 Improve Your Hi-Fi's $19· (SC May '90) This attractive 4-digit capacitancemeterisdesignedfortheworkshopor laboratory. It can measure capacitance from lpF up to 9999µF in seven ranges with an accuracy of better than ±1 %. An over-range LED flashes whenever the capacitance value is too large for the range selected. 95 K2524 $119· Kit (AEM July '85) Designed by Australian Electronics Monthly. Flashes in time to your music. Will also work as normal strobe. Exclusively customised by Altronics into our H 0480 Instrument Case, making construction a breeze and improving stability, safety and overall appearance. Includes silk screened panel. Two tube option available which boosts lighting output. K 5790 Strobe Kit $79· 95 K 5795 Two Tube Option $16.50 Ni-Cad Battery Discharger Kit (SC July '92) Designed to rid your nicad batteries of the memory effect and regain full recharge potential. It discharges your nicads correctly to enable a full recharge. Suits most battery packs. Great for mobile phones, battery drills, toys etc. K164o$24· 95 Rejuvenate Those Old Ni-Cad Batteries to Their Full Potential! The Powerhouse 1200W Inverter Kit (EA Feb '92) Sound Quality! Includes Heavy Duty BattenJ Leads! PHONE ORDER - FREECALL 008 999 007 A US TRALIA e ~ WIDE Jv"' ~.1\,,/-'' vvv Fax/Modem CD Cleaner We are clearing out our CD Cleaners. These cleaners use the correct motion for removing small surface scratches and general dirt and grime. A 9220 NORMALLY $17-95 .95 This Month Only $7 ----------------! Up-to-date Worlds Transistors Diodes Thyristor IC's Comparison Tables II This extremely compact book of equivalents gives brief description and specification as well as full pin assignments of 28,000 types of transistors, diodes, thyristor and IC's. An excellent reference book for professionals and hobbyists alike. 954 pages. 95 B1270$19· .ALTR. C> ~ I C COMPONENTS Anti-Static Wrist Strap The Comma Fax/Modem will turn your PC or Maclntosh into both a fax machine which can transmit faxes up to 9600 baud, as well as a Modem which supports both 1200 and 2400 baud. The Comma Fax/Modem uses the latest technology in digital signal processing to ensure lasting trouble free operation. Send faxes from home. The Comma Fax/Modem operates like a fully featured fax machine. Your faxes can now be sent directly from your PC without having to print them first.You can view incoming faxes on-screen or print them using a standard dot matrix printer. Only print the faxes you want to keep - just think of the savings on expensive fax paper. Time 5aving. The Comma Fax/Modem will also receive faxes in the background while you continue to work. When faxing out, the Fax/Modem will redial an engaged number so you can be sure your faxes are sent. The software also automatically keeps a complete log of both incoming and outgoing faxes. Also supported are cover pages, broadcast faxes, and scheduling. The software keeps a database type register of regularly used fax numbers for easy retrieval. It's a modem as well. The Comma Fax/Modem is a fully AT command compatible modem. Features include V22/V22bis standards (V21 /23 is an option) both 1200 and 2400 baud rates are supported as well as auto answer, dialling and disconnect. You will find it compatible with all popular communication software. Free Software. With each modem you will receive the New From QL2 Fax/modem software featuring both pull-down and mouse support. ALTRONICS 00 D 1590 Up-to-date Worlds Transistor A-Z Comparison Table This comparative data book contains more than 11,000 different transistors and FET's all of which are listed alphanumerically. E sections. 272 pages. Passive Infra-Red Lite Aide Floodlight Control How often have you thought there could be a prowler outside your door? Install a Lite Aide and (once armed) any "guest" will be floodlit when detected by this highly sensitive Infra-Red Detector. The Light Aide detects a moving person or vehicle by comparing the background temperature with a rapid change of temperature across the detection beams. So when Lite Aide detects movement across the coverage area, it will turn on the floodlight(s) for 10 seconds to 15 minutes as pre-adjusted. s 5350 $49· 95 Cheap Security! High-Tech Remote Car Alarm B1275$18·95 -------------------1 This fully comprehensive data book contains over 15,000 differen.t transistors and FET' s all or which are listed alphanumerically. Like volume 1 the manual is divided up into 3 sections, descriptive section, data section and replacement or equivalent section. 430 111111 asts alike! T 4001 $14·50 1---------------- $349· -------------------1 Up-to-date Worlds Transistor 0-µ Comparison Tables movement while protecting components from 1----------------------------------1 IBM :a:::o $18·95 e This amazing model features just about everything you could imagine! Multi-function keyring remote control will arm and disarm alarm (and activate central locking if fitted), chirp the horn, tum on the car headlights, panic and even open the boot (if actuator fitted) . One remote can control two alarms (in two cars). Other features include starter inhibit, valet mode, central locking interface, flashes car indicators when tripped, auto reset, user programmable options plus much more. S 5230 Normally $249· This Month Only set Includes 3 flat blades and 3 cross head screwdrivers. The screwdrivers have long shafts which make them ideal for reaching recessed screws. Handles are made from moulded plastic, and incorporate finger grips. Shafts are made from nickel chrome molybdenum. Sizes Included for Flat and Cross Blade Types: 2.4 x 75mm 3.0 x 100mm 90 T2195$9· New From ALTRONICS I ALTRONICS 1993 RETAIL CATALOGUE If you haven't received yours call us on 008 999 007 for your free copy! Rectangular Piezo Tweeter eter size of 144mm. X 67mm. Rated to 15 Watts. Clearout 00 $229· 95 Satellite Siren Connects easily into most car or house alarm systems. This self contained compact unit delivers a massive 120dB of deafening sound pressure once activated. It connects simply via 3 wires to any alarm system (car or house) that has an output that is normally negative (or low). When the alarm system is activated and the output goes positive (or high) the siren will sound. The siren will also operate if the wires to it are cut. Hence it adds extra security to your system if someone tampers with it to disable it. Simply armed and disarmed via inbuilt key switch. S 5235 Normally $69· This Month Only 6 Piece Sere This Month Only $10·00 Motorola KSN1151A/1142A 95 $59·95 PHONE ORDER - FREECALL 008 999 007 e ALTR.C>~IC COMPONENTS Portable Gas <lldcring Iron Kit working on the boat, car, farm TV antenna or anywhere in the field. One refill lasts up to60minutes. Uses standard cigarette lighter butane gas. Includes: • Hot Blower Tip • Hot Knife Tip • Polyfoam Cutter Tip • Burner Tip Sorry- Not Available from ALTRONIC Dealers at these Prices! T 2470 Normally $79· 95 ..,o ldering Iron • 370° c. • ciency patented heating element • Iron clad, chrome plated, long life interchangeable tips. Tip life expectancy is many times that of conventional plated tips. Supplied with T 2424 Tip. Energy authority approved. 95 T242o$27- Stereo Headphones with Dynamic Mic Our exciting range of head cleaners are the best we've seen and more importantly they are gentle on your heads. Why risk damaging your video or audio cassette player with inferior units. 95 A 9200 Audio Cassette Simply brilliant Mylar stereo headsets and dynamicmic combination. Includes 3.5mm stereo plug for the earphones anda3.Smm plug for the microphone. Great for hands-free dictation, intercoms etc. 95 C 9055 A 9310 VHS Video $ $3· 12·50 AUSTRALIA "WIDE Car Adaptor DC-DC must for all tool boxe ize features spring retu teel construction. 2710 Flat Nose Pliers 2720 Needle Nose Plie 95 This handy multivoltage, switch selectable adaptor enables you to run a fantastic array of DC operated devices. imply plugs into the cigarette lighter socket. Comes complete with 2m lead and universal star adaptor to suit most appliances. Output Voltages: 3, 4.5, 6, 7.5, 9, 12V Output Current: 800mA 95 M8150$lfr Metal Oxide Varistors $49· are used as pro_B_la_n;_k_ R_a_c_k_P _ a_n_e_l_s_ ..... Varistors tection devices. When its 1----------------1 Hole Punch Set Top quality blank panel clearout. All stock must go at these crazy prices. Stock is limited with definitely no backorders. at these crazy prices. 2 Unit-All 5g.oo 3 Unit-ALL S12·" 00 T 2360 NORMALLY $9700 This Month Only rated value is exceeded by a voltage spike or transient, as produced by lightning of back EMF from large motors etc its resistance changes from a very high to a very low value thus clamping the dangerous high spike to a safe level. Disc Voltage Peak Joules Diss. Size RMS Current 75 0.6W R 4110 14mm 275V 4500A R 4120 20mm 275V 6500A 140 1.0W R 4130 l4mm 130V 4500A 35 0.6W 95 ea All H 0422 Nat Alum H 0423 Nat Alum $69· H 0432 Gre H 0433 Gre 1------------------------------t $2· Assorted Battery Bargain 1---------------Be quick for this amazing battery special. All discontinued stock must go. Three types Micro Switch with Lever available - standard zinc chlo- Im-Grip Series Hand Tools LL NORMALLY $9· L.J.l\,JJ' Audio & Video Head Cleaners Cuts holes in metal upto l.6mm(16 gauge). Set of 5 punches and tapered reamer. Punch sizes, 16mm, 18mm, 20mm, 25mm and30mm. . Month Only $64·95 This e ~ L,vv JL," Cat No. S4920 S4930 S4940 S4921 S 4931 S4933 S4935 S4941 S4960 S4950 Size & Type AA Zinc Chloride AAA Zinc Chloride 9V Zinc Chloride Pk2 AA Mercury Free AAA Mercury Free C Mercury Free D Mercury Free 9V Mercury Free C Alkaline D Alkaline Pack Pk4 Pk4 Pk2 Pk4 Pk4 Pk2 Pk2 Pk2 Pk2 Pk2 Was $2.50 $2.50 $2.50 $1.80 $1.55 $1.60 $2.10 $1.25 $4.95 $5.95 NOW $2.00 $2.00 $2.00 $1.50 $1.40 $1.45 $1.90 $1.15 $4.50 $5.45 Includes 27mm lever actuator. 6A at 250V AC. SPOT. 95 s 3260 $2· Switches SPST chassis mount. With built in 240V AC Neon light. S321s.95~ea PCB Mount Terminal Super Large Instrument Cases Blocks Just the shot for wire termination to PCB for your latest project. Enables easy connection (and disconnection) of wire and cables lo a PCB. 45° type. Available in 2 and 3 way configurations. P20422WayWAS.60t,NOW ONLY ,JOit ea P20433WayWAS.85t,NOW ONLY .451t ea Des~gned to house amplifiers, inverters, power supplies micro-processor equipment etc. Builtin mounting posts for PCB's, transformers etc. Ventilated for efficient air-flow cooling. Extra tough, Super finish front and rear panels. 3 colours available. Pictured battery for size comparison only. 95 H 0490 Case $29· Phon!:'~~0j' ~\fg'g,F:·~fg~ fl[.\VY HE•\VY S[RVTCT-AJJ orders of lOkgs or more must travel Express Road-Please 2 4459 \!AIL ORDERS C/-P.O. Box 8350 allow 7 days for delivery. $12.00 to lOkgs. $15.00 over l0kgs. Slirlin Street,PERTHW.A.6849 l1''iURANCf-As with virtually every other Australian supplier, we send goods at conTJ \ RlJ D HJ \T R) & p .\ CK! NG CIH. RG ""F ~· ~$3~.~5o~,o~50~0~gms-~,~$~5.~5~0~5~00~gm-s--l~k~g-,~$8~ signee's risk. Should you require comprehensive insurance cover against Joss or damage lkg-5kg AUSTRALIA WIDE-We process your order the day received and despatch via. please add $1.00 per $100 of order value (minimum charge $1). When phone ordering please Australia Post. Allow approx 9 days from day you post order to when you receive goods. request "Insurance". O\'LRi'IC.111 JETSfR\ l(T Up to 3kg is $10.00, 3kg to 5kg is $23.00-We try to process TO I I !"RH PHOM, ORill R-Bankcard, Visa, Mastercard Holders can phone order toll free your order the day received and despatch via. Overnight Jetservice Courier for delivery up to 4pm Eastern Standard Time. Remember with our Overnight Jetservice we deliver next next day Country areas please allow additional 24-48 hours. day. \ LTRONICS RESELi t RS Chances are there is an Altronic Reseller right near you-<:heck this list or phone us for details of the nearest dealer. Blue Ribbon Dealers are highlighted with a • These dealers generally carry a comprehensive range of Altronic products and kits or will order any required item for you. WA · C OUNTRY ALBANY BP Electronics e ..................... (098) 412681 Micro Electronics ..... ...............(098) 412077 BUNBURY Micro Electronics .................... (097) 216222 ESPERANCE Esperance Comm ................... (090) 713344 MANDURAH Lance Rock Retravision ........ (09) 535 1246 PORT HEDLAND Ivan Tomek Electronics ......... (091) 732531 ROCKINGHAM TV Joe's .................................... (09) 5271806 BAIRNSDALE LH & LM Crawford ............... (051) 525677 BALLARA T Ballarat Electronics ................. (053) 311947 MILDURA Pullman Auto ..........................(050) 232882 SHEPPARTON Andrew Guyatt Elect. ...... (058) 219497 WARRNAMBOOL Kormt Electrorucs .. . .. . (055) 627 417 ENFIELD COUNTRY WHYALLA Aztronics • ······· .. ...... (08) 3496340 Eyre Electronics. .... (086) 454764 T AS QLD - C ITY HOBART George Harvey e ... ............ (002) 342233 Delsound PL ................ (07) 8396155 LAUNCESTON George Harvey e .. (003) 316533 B.A.S. Audiotronics ................ (07) 8447566 NSW C ITY NT David Hall Elect.e ................. (07) 8082777 A-One Electronics .................. (02) 2674819 ALICE SPRINGS Farmer Electronics ................. (089) 522388 COUNTRY David Reid Elect. e ... ............ (02) 2671385 DARWIN Ventronics .................... .......... (089) 853 622 GLADSTONE Gladstone Elect. Services ....... (079) 724459 SMITHFIELD Chantronics .... ..... (02) 6097218 VIC · C ITY Electronic Enterprises ............ (079) 726660 All Electronic Comp ............... (03) 6623506 MAROOCHYDORE Mais Electronics e ................ (074) 436119 COUNTRY TECS ......................................... (03) 6706474 TOWNSVILLE Super Solex e . ...... (077) 724466 COFFS HARBOURCoffs Habour Elect. ................ (066) 525684 BORONIA Rafi<Cross Electronics• ........ (03) 7622422 SA - CITY NEWCASTLE Novocastrian Elect.Supplies .(049) 621358 CHELTENHAM Ta ing Electronics ................. (03) 5842386 Force Electronics•.... ..... (08) 2125505 COLLINGWOOD Truscott Electronics• •··········(03) 4198208 BRIGHTON Force Electronics• ................ (08) 3770512 WARNERS BAY Vilec Distributors... ........... (049) 566792 WINDSOR M & E Elect. and Comm ........ (045) 775935 CROYDON Truscott Electronics• ...........(03) 7233860 CHRISTIES BEACH Force Electronics• ................ (08) 3823366 FOOTSCRAY WOLLONGONG Newtek Electronics e .......... (042) 271620 ~;!t~~r,5fe~:rtl~;· FINDON Force Electronics • ................ (08) 3471188 PRESTON 9 Vimcom Electronics .... .(042) 284400 HOLDEN HILL Force Electronics e ................ (08) 2617088 COUNTY LONSDALE Force Electronics e ................ (08) 3260901 WOY WOY Alphatran Electronics ........... (043) 434919 WEST END WOODRIDGE : :::::::::J~~i fil3~~~ PHONE ORDER - FREECALL 008 999 007 ORDER FORM ~--j)... BACK ISSUES* MONTH VEAR MONTH VEAR MONTH VEAR MONTH VEAR *Back issues are $A5 each (incl. postage). Overseas orders add $A 1 per issue for postage. BINDERS Please send me _ _ SILICON CHIP binder(s) at $A14.95 each (incl. postage). Overseas orders please add $A3.00 each for postage. TOTAL PRICE $A SUBSCRIPTIONS . 0 New subscription - month to start 0 Renewal - Sub. 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Please have your credit card details ready Fax the coupon with your credit card details 24 hours 7 days a week Card exp1ry date I Mail coupon to: Freepost 25 Silicon Chip Publications · PO Box 139, Collaroy Beach 2097 No pcstage stamp required in Australia APRIL 19 93 63 COMPUTER BITS BY JOE ELKHORNE Upgrading to a 386 - now I know what a "kludge" is! Is your computer due for upgrading but you have not known where to start? The process is fraught with pitfalls as Joe Elkhorne found to his frustration & cost. For the past couple of years, I've been perfectly happy running a modest XT compatible, an Amstrad PC20. It is perfectly adequate for simple word processing and you can't get much simpler than PC-Write 2.41. Recently, I found it necessary to provide a state-of-the-art WP document to a local book publisher. With- self-contained unit in a low-profile, plastic case. So I had the heart of a super new system and an uphill battle ahead of me. The first problem was not difficult to solve. I'd let another friend have an oscilloscope I wasn't using, again on a "pay me when you can basis". When he subsequently ac- "Right at this point, I ran into the first pitfall. Having worked with dodgy Taiwanese clones in the past, it didn't even occur to me that this board might be labelled." electronics shop in a nearby suburb. "Hi there - I need the ribbon cable that goes from a controller card to the floppy drive". The salesperson shakes her head in disgust. "They come with the controller cards". "Ifl had one, I'd not be asking for one. The thing is, I've got a secondhand card that wasn't provided with cables". "Oh yeah ... " Silence. Finally, I explicate the obvious, "So I need one". "We don't sell them". Scratching my head in perplexity, I inquire if they know who might. "You can make one yourself". "I'm game, but I need the bits. I've already got a hammer". "We sell the bits". Good, at last we're getting somewhere. At home with a bag of bits, I carefully inspect, align and assemble: ribbon cable, one, with IDC connectors, for connecting floppy drive. I do believe this technology was designed by Mr Murphy but more on this subject later. Getting it together out a platform to work on, I solicited the help of a friend with a splendid 386 system. He'd been through the learning curve with earlier versions of Windows and Word for Windows. This was an opportunity for him to show off his equipment and I was very impressed with the power of the system. When Graeme upgraded to a 486 shortly after that, he made me an offer I couldn't refuse: accept his 386 motherboard and pay him when I was abk Bonzer! There's just one trouble with upgrading the PC-20. It can't really be done. The physical architecture is not like a standard clone - it's a 64 SILICON CHIP quired a case, power supply, a CGA card and a keyboard from another person, I agreed to take these bits and pieces in lieu of cash. I think that the cashless society is already here! So, let's see where we stand. I have a 386 DX/25 motherboard with 8Mb of RAM, a "Baby" tower case with a 200W power supply which almost fits, a 360Kb 5¼-inch floppy drive, a 101key keyboard, multi-I/O card, CGA card and a PC-20 CGA monitor. Well, that's not a bad start - all the big pieces. But like any enterprise of this nature, it's always the fiddly bits that are a hassle. Fortunately, there was a discount Now my mate Rob had not only brought one case and power supply, which he was kind enough to fit, but had also mounted an old XT board in it expressly for the purpose of holding the plug-in cards in place. Right at this point, I ran into the first pitfall. Having worked with dodgy Taiwanese clones in the past, it didn't even occur to me that this board might be labelled. I looked at the mass of front panel wiring and pulled all the little connectors off without a second thought. Getting the XT board out involved compressing the nylon support posts - and holding your jaw right. Only after the board was out, in the clear light of day, did I notice that all the appropriate points were clearly stencilled. Twenty-twenty hindsight is a wondrous thing. Fitting the 386 motherboard into the case was not difficult- a couple of the nylon support posts had to be moved. But there weren't quite enough of them and some plastic from the junkbox provided additional support at a non-critical point. Nor was the power connection a problem. There's only a couple of possibilities because they're keyed and the recommended end-to-end position had already been marked with a felt pen. At this point, I truly regretted that the documentation for the 386 motherboard hadn't turned up. Oh, well, who needs a power LED anyway? None of the other front panel functions are critical to a fundamental test. I then planked the floppy drive on a magazine on top of the floppy mounting bracket for ease of testing. The multi-I/0 card was plugged into a convenient slot and my homemade ribbon cable joined up . The CGA card went alongside and the Amstrad monitor was set beside this "test jig", on the kitchen table. I'd already made a 5¼-inch boot disk. All that remained was throwing the power switch - and praying; not necessarily in that order! The smoke test Rob and his friend Liz turned up just at that point. If they expected a mushroom cloud and some gratuitous language, they were disappointed. =ftfflll/JIIJ= =U!l!l!- There was movement at the station. It's true the system didn't boot up initially but there did seem to be the proper start-up sequence. "Let's make sure the CMOS setup knows about the A: drive", said Rob. We did·this and a keyboard Ctrl-AltDel proved the system was responding properly. Unfortunately, though the floppy drive's LED came on, nothing else happened. We inspected the drive to make sure nothing had been whacked out of As well, I'd done a diagnostic/configuration dump, so I knew the port addresses (serial, printer) and interrupt vectors which had been successfully working. Again we fired up the unit and forced the system into the CMOS setup procedure. Golly, I wonder which of the 47 types I should call this beast? We exited the CMOS setup to have a think about things. Despite the obvious report that no C or D hard drive existed, the system booted up prop- "Rob & his friend Liz turned up at that point. If they expected a mushroom cloud and some gratuitous language, they were disappointed. There was movement at the station." shape. Everything looked all right but we wondered about the mysterious little jumpers. Just maybe, we decided, this drive was old and needed to be told, some way or another, that it was in an AT-style machine. Meanwhile, it was very frustrating being this close without actual operation. We decided to be daring and put the 40Mb hardcard into the system. I'd backed up all the files that morning, using the ARJ utility, to the existing 720Kb drive of the PC-20. Regardless of"finger trouble" - short of something really catastrophic like dropping the hardcard - I should be able to resume operation totally on the old machine. erly! Obviously, the system bus recognises the existence of the hardcard controller and acts appropriately. Well, this was exciting. At that point, we added the serial port cable and modem and called our favourite bulletin board. That effort was successful and we called it a night. No sense in pushing our luck, we decided. The following morning, just to be thorough, I proved that the parallel port worked. Now all I needed was to get a floppy working. Because of my BBS activities and the small hard drive setup, I do a lot of archiving on floppy disks. I proceeded to do more kitchen table tests - unsuccessfully. Position Vacant - Technical Writer SILICON CHIP has a position for an enthusiastic technical writer. This person will already be a frequent reader of this and other technical magazines and will probably have a number of hobby interests. Technical qualifications are not mandatory although a good background in electronics is necessary. Good writing skills are essential for this position and some familiarity with computers would be an advantage. Do you think you could do the job? You will mainly be involved in the writing and preparation of articles for this ~agazine. For example, you could be required to write the constructional article on the ~lectric fence project in this issue or the short feature article introducing the Digital Cassette Deck, after attendance at the recent Australian release. You will also have the opportunity to build simple electronic projects under supervision and you will be involved in proof reading and other activities involved in the day to day production of the magazine. The salary package is negotiable. If you think you could actively contribute to the improvement and growth of SILICON CHIP, send your application in writing to The Publisher, PO Box 139, Collaroy Plateau , NSW 2097. Applications close 21 st April, 1993. APR,L 1993 65 COMPUTER BITS - Upgrading to a 386 I tried the technical support telephone number for the drive manufacturer, only to learn that their local office was closed. It's amazing how many operations here in Melbourne have shut, with everything allegedly handled from Sydney. And not all of the companies have 008 numbers, unfortunately. supports 360Kb drives. This snippet of information was verified in the discount dealer's catalog. Off to the local bloke again. "Hi, it's me again. I need a high density drive, a three-and-a-half, please". This time, there's a bloke at the counter. He rummages around looking for said unit while I go over to the display and find the catalog An old adage number for the cheap controller. HavThen I recalled the old adage, "when ing perused the catalog thoroughly all else fails, read the book" and re- over morning coffee, I know there are membered that I'd seen a book on PC several to choose from. All I need, I've architecture and hardwar~ technical told myself, is one floppy and this details. I made a special trip to the controller is linkable for two drives of city. In fact, I found several compre- the same type, from 360Kb to 1.44Mb. "That's not the right controller", hensive reference books to choose from. Selecting one, I flipped to the , says the clerk. "I know that there's no table of contents and went straight to doco with it. I can see through the the chapter on floppy drives. plastic wrap. But see these links? And Right. One of the lurks is the old note the description in your catalog? cable twist - oops! - and the link for Now, can I be wrong? I've been wrong DR1 on the floppy drive itself. Fair before". He decides that maybe I'm not enough, my mistake: the straightthrough connection as I'd made the wrong and rings up the sale. I decide cable is actually the B: drive position. I'm on to a good thing because there's Hey, suppose all this fiddling has two drive cables in the packet. Wow! "The young woman takes the drive straight to one of the demo machines, kills the power, pops the top, pulls the cables and swaps it into the system It fires up, and works beautifully." done something to the drive itself? Ah, substitution test. No, I don't have a second floppy but I can put it back on the PC-20. Yes, it works. Well, the old process of elimination is one of the tried-and-true ways of troubleshooting. Now, at least, I have one less variable to worry about. Funny thing though, when I put it back in the 386, not even the LED would come on. Fiddle, wiggle, oops, the motor started. Could it be? Now I'm suspecting my cable but I don't have a spare. At this point, I'm telling myself that a 360Kb drive is old-hat anyway! I quickly justify the need for a 1.44Mb drive. Bewdy! Oh, and a controller of course, since the multi-1/O card only 66 SILICON CHIP And I've got the mounting adaptor bracket kit so I can install this beauty permanently. Racing home, I pessimistically decide to test it externally before I bolt it in place. I swap controllers, checking the stencilling on the new and deciding that yes, it does say it's set for 1.44Mb. I swap controllers, attach one of the new cables to the high-density drive and turn it on. It doesn't go. Oh, yes - I've got a formatted 1.44Mb disc in place. Well, at least the packet said they were. The LED was on, though. Unfortunately, it's always on. I wonder what will happen on the PC-20? I look at its manual. Yes ... DRIVEPARM should work. It's kitchen table time again. I'm really wondering if I could borrow a second monitor from somewhere; I'm tired of carrying the one-and-only back and forth. Never mind. Hey, power up and look at that: the system recognises there's a controller card in the slot and even knows what size it handles. But, oh dear. Why doesn't the drive work? Oh dear, what's happened now? Why is my boot disk in the A: drive corrupt? I go through every permutation that's possible. The mounting adaptor kit came with a 3½ to 5¼ ribbon cable adaptor and a power adaptor to match the usual power supply connector. By flicking a switch in the PC20, I can tell the system that the outboard drive is the A: drive. The power adaptor lets me try the edge connector on the cable, rather than the dualrow miniature connector which would be more commonly used. Aha! As I'm about to put cable to connector, something rather suspicious catches my eye. I look closely and discover, deep inside the 5¼ edge connector, a smashed contact shorting across from one side to the other. Why hadn't I seen this before? Because I was using the smaller and more appropriate connector. Score: cables 2; Joseph 0. I throw the thing aside with several rude words and find the other new cable. Double checking the "repair and upgrade" book, I confirm my understanding of the A position and B position. Now I go back to the 386 and try it. It still doesn't work! As soon as I walk into the discount electronics store, I get the impression that I've worn out my welcome. Even the laying on of plastic money might not help. I state the problem: can't get the little drive to work in two machines! The young woman is knowledgeable - she takes the drive straight to one of the demo machines, kills the power, pops the top, pulls the cables, and swaps it into the system. It fires up and works beautifully. Fair enough. Whatever is wrong is my problem, not theirs. Having seen the little drive work, I believe I can trust it. Unfortunately, back home, it still doesn't want to respond. All I'm getting is "Not Ready Error Reading Drive A (Abort, Retry, Fail)". Can it perhaps be the controller? Hey, if I'd bought the next model up, I'd be able to mix and match, put the 360Kb onto it to prove the system to that point, without any hassle. Why don't we take another drive today? They're definitely not overjoyed to see me again so soon but are more than happy to swap/upgrade. A little more money for them and maybe it will get me out of their hair. This new board is switch-selectable for four drives, independently. How can I go wrong? I start with a known the 360Kb drive - and prove that the controller and the system are happy to work together. I swap over to the 1.44Mb drive but no go. How weird can you get? Yet another foul-up Nonetheless, I'm happier with this co·n troller since there is some documentation. In fact, just as a second test, I even drop it into the expansion slot on the PC-20 and the system boots up and recognises the various switch configurations. Incidentally, in the process of all this drive testing, I've been experimenting with other facets of operation. I discover "Yet Another Foul Up" - the serial port sometimes locks up when using Telix. I spend an hour or so with a breakout box, trying to figure out what and why. Finally, I disable the XON/XOF (software) flow control, dropping back to DTR (hardware) control, and that seems to help. The original RS-232 port was a true 25-pin connection. The flying lead from the card to the backplane connector is skimpier. This needs further investigation at a later stage. Meanwhile, it's back to the drive anomalies. I'm starting to feel paranoid and begin with what should be a known working situation: the 360Kb as B-drive on multi I/O. Yes, that's OK. Now I fit the 4-way controller, set the DIP switches appropriately, reboot, and the system CMOS recognises the existence of the 360Kb drive without intervention. I do DIR B: and that's fine. Everything working. Though this might seem laborious, eliminating variables and starting with a known fully working situation at the immediate moment is a good, if pessimistic, plan. I add A: (1.44) without power, of course, and re-start the system. B: now does not work- Not Ready Error Reading Drive (Abort, Retry, Fail). Hmm, let's disconnect the ribbon cable from B and try A only, as A. Reset, CMOS COMING NEXT MONTH Remote Volume Control This project will let you adjust the volume & balance of your hifi stereo system from the comfort of your lounge chair. It's based on a dedicated microprocessor chip to simplify the circuitry and to make construction as easy as possible. It won't degrade the sound quality either, thanks to excellent specifications. Full details in the June 1993 issue. Woofer Stopper (or Dog De-Barker) Do you have trouble with barking dogs? If so, this project could be the answer to your prayers. It produces a retaliatory high-energy supersonic tone which discomforts the dogs and discourages further barking. After a few weeks of use, the dogs will be miraculously quiet. check, OK, reboot, Not Ready Error Reading Drive A. Well, all I know for certain is that the 360Kb drive on its own works. Can there be something incompatible about the 1.44Mb drive and both of my computers? Later, a call to Amstrad's technical support section elucidates the information that the PC20 will not support a high density drive, even with an external controller. "Why is the information in the manual so ambiguous?" "It's there for completeness only ... " "Groan". This was the day I went back to the PC92 show for the second time. I bought Windows 3 .1 for $95 (on 1. 2Mb which is all they had) and leaving there, went to "the local blokes" and bought a 1.2Mb drive. I raced home with all the goodies. Using the new 1.2Mb drive only and the 4-way controller set as A=l.2 and B=360, at last I had a working highdensity drive! Finally, I reset the controller for B=l.44, cobbled the thing into place and was rewarded with a proper start-up sequence. The A: drive was still perfectly happy. Asking the B: drive anything, however, still gave me a DOS error - but the LED was coming on and going off. What the heck: Format B: /s. Oh, wow! It's doing something. Presumably, somewhere along the line, the actual disk I'd been using was corrupted. I spend the afternoon and evening doing real computer things with two working high-density drives. Joy! The following morning, I turn the computer on -and the B: drive refuses to work! The LED comes on and goes off, but again I'm getting DOS error messages. The final lurk turns out to be a dicky power adaptor for the 1.44Mb drive and the forceful application of a pair of visegrip pliers ensures that the intermittent connection will never happen again. Everyt,hing now gets bolted back into place and re-tested. Two months later, the fundamental hardware is still reliable - at least at the DOS level. I've now embarked on a learning curve for Windows 3.1, DOS 5.0, Word for Windows 2 and the mysteries and frustrations of printer drivers or the lack thereof. But that's a story for next month's issue. SC APRIL 1993 67 , FM TRANSMITTER KIT Mkll 0 - This HIGH QUALITY - LOW COST FM transmitter design doesn't compromise on quality, and it should not be compared to most of the other simple design FM transmitter kits that are currently available. It features pre-emphasis for an improved overall frequency response and better overall signal to noise ratio, a very high audio sensitivity which makes it able to produce useful received outputs with the microphone being placed well away from the sound source, a range of well over 100 metres, etc. But probably the most important feature of this transmitter is its excellent frequency stability: The resultant frequency shift due to waving the antenna away and close to a human body and or changing the supply voltage by ± 1V at 9V will not produce more than 30KHz deviation at 100MHz! That represents a frequency deviation of less than 0.03%, which simply means that the frequency stays within the allocated bandwidth of the tuned frequency on the FM band. It doesn't go noisy and shift to another frequency, but it "stays put"! Transmitter Specifications X-Y LASER SCANNER KIT You could spend thousands of dollars buying commercial X-Y scanners fo r laser beam deflection. This X-Y scanner compromises by employing two suitable DC motors to achieve good results. With normal levels the motors don't actually spin but simply vibrate around the set position . The PCB and component kit include rectification and filtering (power supply), audio preamplifiers, audio filtering, and two separate power amplifiers to drive the two deflection motors. The scanner is powered by a 16V AC-900mA plugpack. In one of the modes of operation the scanner can produce a totally random two dimensional display which is depended on the actual music picked up by the electret microphone. A second mode of operation enables the power amplifiers to be driver from external oscillators and/or pre-taped signals recorded on a stereo cassette recorder. A short form kit of parts is available for the X-Y scanner. It includes a screened and solder masked PCB and all the onboard components, an electret microphone, two motors, and two lightweight mirrors. Supply voltage: 6-12V Current consumption <at> 9V: 3.5mA 240V-16V/900mA AC-DC Plugpack $16 extra. Pre-emphasis: sous Frequency response: 40Hz to greater than 15KHz UNUSUAL ITEMS AND COMPONENTS S/N ratio: Greather than 60dB Sensitivity for full deviation: 20mV Short term frequency stability (see notes): 0.03% PCB dimensions: 26mm X 42mm. Full size PCB overlay is shown below. 20KV PIV-5mA Av./1A Pk. Fast diodes ............................. $1.50 ea. 3KV PIV-300mA/30A Pk. Fast diodes ..... .. .......... .. .. .. ......... 60c ea. 30V PIV-1A/25A Pk. Schottky Barrier diodes ........... ........... 45c ea. 680pF/3KV Disc ceramic capacitors .. .... .. .. .. .. ..... .. ............ .. 30c ea. 1000pF/15KV Disc ceramic capacitors .. .. .............................. $5 ea. 0.01uF/5KV Disc ceramic capacitors .. ... .. .. .. ........ .. .. .. .. ..... $1.80 ea. Flexible DECIMAL KEYPADS with PCB connectors to suit $1.50 ea. High quality UNIDIRECTIONAL ELECTRET microphone inserts .. .. .. .......... ........ .. .. .... ............................... $8.50 Stage quality UNIDIRECTIONAL DYNAMIC microphone inserts ..................... ......... ...... ..... ......... ... .. ....... . $9.60 780nM IR diochroic filter (20nM bandpass) for IR detectors ..... $20 FRONT SURFACED MIRRORS: 10mm X 10mm X 1mm ........... $5 20mm X 20mm X 1mm .......... $6 200mm X 150mm .. .. ... .. .......... $8 Construction is easy and repeatable results are obtainable, since no coil winding is necessary. A variable inductor is provided already assembled in a shielded metal can . The double sided and solder masked PCB also makes for very easy construction. OATLEY ELECTRONICS The kit is supplied with a printed circuit board and all the on-board components, a high sensitivity omnidirectional electret microphone, and a 9V battery clip. Telephone: (02) 579 4985 Fax: (02) 570 7910 THE TOTAL COST OF THE KIT IS s11 Or you can purchase three kits for a total of $30. 68 SILICON CHIP ea. PO Box 89, Oatley, NSW 2223 MAJOR CARDS ACCEPTED WITH PHONE AND FAX ORDERS P & P FOR MOST MIXED ORDERS : AU::; I HALIA: S6: N.L. (Atr Matl): S10 VERY LARGE LCD DISPLAY MODULE UN INTERRUPT ABLE POWER SUPPLY (UPS) Contains a 24V DC to 240V AC, 50Hz Sine Wave Inverter! Use it as a portable mains power supply on boats, in c aravans, for solar powered systems, or simply for its original function: As an uninterruptable power supply for a computer. We have a limited stock of 300 watt UPSs. They are complete except for a few mounting screws. Some of these may be faulty or in need of a few modifications. A copy of the service manual (18 pages) which includes the circuits, layouts, test procedures, and modifications will be provided with each unit. All the necessary UPS electro·n ics are contained on one PCB which is easy to service. Employs modern high frequency switching techniques in the inverter section. A smal separate PCB contains a mains filter. The four mains output sockets on the rear panel are all individually switched by illuminated switches. The UPSs used two 12V 6.5Hr batteries connected in series; not provided. Inexpensive and common locally available devices are used throughout. LM324s, 40106s, TL494, 7815, LM317, IAF540s, IAF830s, etc. $60 The giveaway price for the complete unit? We may also have available -some later model UPSs for around $100. Some 600 watt new units may also be available. SOLAR CHARGER Use it to charge and or maintain batteries on boats, for lighting , solar powered electric fences, etc. Make your own 12V-4W solar panel. We provide four 6V-1W solar panels with terminating clips, and a PCB and components kit for a 12V battery charging regulator and a three LED charging indicator. See March 93 S.C. Incredible value! s42 6.5Ahr. Panasonic gel battery $35. Electric fence PCB and all onboard components kit $40: See S.C. April 93. EL-CHEAPO LASER Probably the cheapest visible red helium neon laser and power supply ever offered, AN YWHERE! The kit includes a PCB, transformer, and all the components needed to make a 12V operated laser power supply, and a used laser tube with a power rating in the 0.5-2mW range. The PCB and all the onboard assembly is the same as the one used in our EHT Generator (it also now comes with a PCB), but a few extra necessary components· and corresponding instructions are provided with the kit. Incredible value at: 550 For the 12V inverter kit and a visible red laser tube. The EHT generator kit is available separately for $23. Brand new large 640 X 200 dot matrix LCD displays, made by EpsonSeiko, screen size is 120 X 265mm, has built in drivers. Four bit TTL interface, a total of 14 connections are required for signal and power (+5V, -12V). Capable of displaying characters, graphs, patterns, etc. 28 pages of data included. Unrepeatable price: DC MOTORS We have good stocks of four different high quality Japanese DC motors. These should suit many industrial, hobby, robotics and other applications. Check out the SPECIAL prices, and compare! M4 - 3-15V, I No load = 20mA at 12V, mains body 31mm diam, 22mm long $3 MS - 3-15V, I No load = 60mA - 5700 RPM at 12V, main body 28mm diam , 40mm long $2.50 M9 - 12V, I No load = 0.52A - 15,800 RPM at 12V, mai_n body 36mm diam , 67mm long $8.50 M14 - Made for slot cars, 4-SV, I No load = 0.84A at 6V, al max efficiency! = 5.7A - 7500 RPM, main body 30mm diam, 57mm long $9.50 · This high quality Australian made PIA features true pulse count circuitry. Digital circuitry that actually counts the number of pulses, not just an R-C time constant. The pulse count is even registered by a separate green LED and the number of pulses desired is set by a DIP switch: 1-6 pulses. Both the green LED (pulse) and the red LED (detect) can be switched off after tesling. Switched by the dip switch. l' 12M range with the standard 90 deg. wide angle lens supplied or 20M range with an optional narrow angle corridor lens. SPECIAL INTRODUCTORY PRICE: LASER POINTER $69 Note that an LSI surface mount controller IC for this display is available elsewhere. More information supplied on request. IR LASERS REDUCED PRICES! This precision collimator assembly is supplied with a brand new laser diode to suit. Produces a well collimated laser beam at 780nM/5mW. Barely visible. We also supply a PCB and components kit plus instructions, for a suilable digital driver circuit lhat can be used to complete lhe laser transmitter. Suitable for communications, data links, perimeter protection , barcode reading , medical use, etc. One used 3mW Siemens tube, one used laboratory quality 2mW tube, one universal 12V laser inverter kit. for a total of: $99 PULSE COUNT PASSIVE INFRARED MOVEMENT DETECTOR High quality pen sized SmW laser diode pointer for teachers, doctors, etc. ON SPECIAL FOR $169 LARGE LENSES o. Two pairs of these new precision ground AR coated lenses were originally used to make up one large symetrical lens, for use in IBM equipment. Made in Japan by Tominon . The larger lens has a diameter of 80mm and weighs 0.5kg. Experimenters delight at only: $15 for the pair New 40mW helium neon (visible red) laser tubes: One metre long! Need approximately 3KV at 20 mA to operate. For discos, displays, holography, etc. Incredible introductory price: s990 ON SPECIAL is a set of components that can be used to make a complete passive first generation night Viewer using the XX1080 tube. Produces useful pictures in sub moonlight illumination and can be IA assisted. We provide a matching lens and eyepiece, XX1080 tube with its original connectors, and a small kit power supply. $270 At the time of publication we should also have available similar sets of matching components based on active first generation tubes. Prices for lhe sets should range between: $150-200 THE CHEAPEST 5mW VISIBLE LASER DIODE EVER OFFERED Main body has a diameter of 117mm and is 107mm long. The whole assembly can be easily unscrewed to obtain three very large lenses: two plastic and one glass. The basis of the cheapest large magnifier or projection system? Experimenter! de~ht at 3U STEPPING MOTORS s39 Note that a suilable receiver to use with these transmitters, for long range perimeter protection, was published in E.A. April 81. BIG LASER TUBES VISIBLE LASER DIODE BARGAIN ONLY We can also supply a similar kit which includes a laser diode, unmounted lens, and a driver kit: $46 NIGHT VISION COMPONENTS Brand new 5mW-670nM laser diode, plus a collimating lens, plus a driver kit , plus instructions. sas ELECTRONIC KEY KIT Use them to activate door strikers for entering buildings, car alarms, cental locking, the most secure key ever (see E.A. July 92). ON SPECIAL <at> $49.90 For two keys, and one decoder kit. DIVERGING LENS Brand new units. Diameter 58mm, height 25mm, 5V operation, simple to drive (two phase - 6 wires), 7.5 degree steps, coil resistance 6.6 ohm. 6V GEL BATTERIES Brand new Japanese 6V-500 mA Hr. Gel batteries. Fresh stock, charged, and very compact. 57 X 50 X 13mm. Limited quantity at $7 per pack or 5 packs for $30 A high quality laser beam diverging (beam expander) glass lens, mounted on an aluminium plate, with mounting screws provided. Dimensions: 25 X 25 X 6mm. Use it to expand the laser beam for Holography, Special Effects, or one of the two lenses required to fine focus a laser beam, for Surveying and Bar Code Reading. S9.90 We should also have available some fibre optically coupled , second generation image intensifier tubes, with built in power supplies. Operate off a 3V battery. To make a complete scope which will respond in as litlle a starlighl illumination , all that is needed is a 3V battery, a switch , a low light lens, and an eyepiece. The tubes are used (exmilitary) and may have some minor blemishes, but all produce full gain. Priced at a small fraction of their real value: ssoo-100 MAINS POWER SUPPLIES Brand new regulated power supplies. 240V mains in - 13.6V or 14.2V at 1.8A continuous outpul. Less than 2mV Pk-Pk ripple at 1.7A. Has additional output terminals for battery charging. 450 mA maximum . Approved Australian made units that employ a low profile Ferguson PL 18 - 40VA transformer, and a regulator ci rcuil (easily modified), in a very compact, all metal housing: 170 X 95 X 50mm. Mains lead plug attached: 1.8M long. Information/specifications provided. Limited quantities at: s30 ea. Further to the above special prices, during April-M';li we are offering b~~a8i !~i~~rfn~~~e1 EACH OF THE ABOVE MOTORS, and one of the STEPPER MOTORS ($12): l Five different motors for · a total cost of A 5mW gunsight at an unbeatab 5279 Includes one "Free" rifle or pistol mount. APR I L 1993 69 I PRODUCT SHOWCASE 4000 count digital multimeter The first 3½-digit multimeters were referred to as "2000 count" instruments, meaning that the maximum reading on their display was 1999. For some years now, 3½-digit multimeters have been available in "4000 count" versions and this means that their maximum display reading is 3999. This is a very useful increase and means that more readings can be taken before a given range is exceeded. The result is that many readings can have much better resolution; ie, four digits displayed instead of three. This 4000 count multimeter from Dick Smith Electronics has a wealth of features and includes 32 measurement ranges, all of which have overload protection. The meter is housed in a rugged yellow case and is further protected by a yellow rubber holster. The meter probes have anti-slip ribbing and a guard ring to help prevent accidental contact with the metal prods. The rotary selector switch has 30 settings: five AC voltage ranges from 400mV to 750VAC; five DC voltage ranges from 400m V to 1000V; four DC current ranges from 400µA to 400mA, with the 40mA range also serving for the 20A range; three AC current ranges from 400µA to 400mA and again, the 40mA range doubling for the 20A range; six resistance ranges from 400Q to 40MQ; a diode test range; a frequency meter setting which gives four 70 SILICON CHIP ranges (autoranging) from 4kHz to 4MHz; a logic range; and four temperature measurement ranges. A "peak hold" button can be used to hold and store the reading on any range. The meter is supplied with a standard type K thermocouple for temperature measurement in degrees Fahrenheit or degrees Celsius. If the meter range switch has not been used for 25 minutes, the meter automatically powers down to conserve the battery. Moving the range switch or pressing the power button will turn the meter on again. Battery life is quoted as 300 hours with a standard zinc carbon 9V battery. The liquid crystal display has 17mm-high digits for easy legibility and has the usual range of annunciators to indicate the mode of measurement. An interesting touch is the inclusion of the full range value underneath the decimal point on every range. For example, if you are on the 40kQ resistance range, "40" will appear under the decimal point. This is a handy reminder. All told, this multimeter has a good range of features and is ruggedly made. It is priced at $179 from all Dick Smith Electronics stores (Cat. Q-1542). High speed oscilloscope card Non-contact AC voltage probe This little probe is ideal for checking for the presence of high AC voltages in wiring or circuits. It has the distinct advantage that its probe is insulated so even if you touch the wiring directly with the probe end, there is little chance of electric shock. It is powered by two 1.5V watch batteries and has a red LED and audible beeper to indicate the presence of an AC voltage above 120V. For example, if you run along a mains power cord or place it di- I rectly over a mains switch, it will give an indication in the form of a continuous modulated tone. Recommended retail price of the probe is $16.95 and it is available from all Dick Smith Electronics stores (Cat No Q-1531.) Gage Applied Sciences Inc has released a 100 megasample/second digital storage oscilloscope card for PCs, for applications requiring high speed acquisition and storage. The Compuscope 250 runs at 100 Ms/s on channel A or at 50Ms/s on channels A and B simultaneously sampled. The Compuscope 250 is a two channel card, with AC or DC coupling, but has the capability of driving slave units to provide up to eight channels at 100Ms/s or 16 channels at 50 Ms/s. The card can trigger from channel A, channel B, externally, or from the keyboard; and with its onboard memory, will allow mid, post or pre-triggering to capture relevant waveform information, even at full sample speed. The timebase is inde- pendent on all channels and can sample from 1Hz to 100MHz in a 1-2-5 sequence. Oscilloscope software is provided with the card and will allow independent scrolling of all channels, horizontal zoom, dT & dV cursors and zero reference. Printer output is supported as well as ASCII, Asyst, DADiSP and Lotus 1-2-3 file formats. Software modules are available, to run with the oscilloscope software, which allow processing of the data acquired, including such functions as FFT, differentiation, arithmetic etc. The card fits any PC-XT/AT/386 and has available drive software for incorporating the Compuscope 250 into the users own software. More information is available on this and other Gage Compuscope equipment, with a demonstration card available for trial. For further information, contact Boston Technology Pty Ltd, PO Box 415 , Milsons Point, NSW 2061. Phone (02) 955 4765 . 64-pin test clip for microprocessors Doing any sort of voltage checks around microprocessors or other LSI chips is fraught with danger. If you short two of the pins together while trying to touch one with a meter or scope prod, you could fry the chip. The safe way is to fit one of these spring clips over it. These make it easy to make safe electrical connections to any of the pins. This one is a 64-pin job but they come in various sizes. It retails for $49. 95 and is available from all Rod Irving Electronics stores. Postcard-size interfaces for GPIB Instruments National Instruments Australia has released two new RS-232-to-IEEE 488 boxes that require virtually no desktop space, and can be considered ex- Inductance meter The Hioki 3510 HiTester measures inductance values down to 0.0lµH and dissipation (loss factor) to four decimal places, and also provides a corresponding Q indication (1/D). It includes a comparator function and a monitoring function for applied voltage and measurement current. Also available is an optional GPIB interface. For further information, contact tensions of the GPIB and RS -232 cables. Both have built-in 115 or 230V AC power supplies and built-in 256K RAM buffers. The GPIB-232CV-A is a GPIB-toRS-232 converter that links either a GPIB controller to an instrument with an RS-232 port, or a GPIB device to a computer through its serial port. It transparently converts data between the two ports so that control codes or special commands are not required. Its switch-selectable interface parameters include GPIB address, transfer rate, parity, stop bits, word length, and termination mode. The GPIB-232CT-A is an RS-232to-GPIB controller that turns any computer terminal with an RS-232 port into an IEEE 488.2 controller. It implements both normal and extended Talker and Listener, Serial and Parallel Polling, Service Requests, Pass and Receive control functions, and remote programming functions in three Nilsen Instruments Pty Ltd, PO Box 930, Collingwood, Vic 3066. Phone (03) 419 9999. Fax (03) 416 1312. modes of operation. In two of the modes, either the GPIB or the RS-232 is configured as the controlling interface. In the third mode, the GPIB232CT-A can be configured to operate in a custom application by the addition of new functions to the programmable IBCL operating system. The GPIB-232CT-A is software-compatible with the company's GPIB232CT. The GPIB-232CT-A uses the National Instruments NAT4882 chip for complete compatibility with the IEEE 488.2 standard, which defines data formats, status reporting, error handling, and common configuration commands. It performs all Controller functions specified by the IEEE 488.2 standard. High-level Nl -488.2 driver software for DOS and Windows is available. For more information, contact National Instruments Australia, PO Box 466, Ringwood, Vic 3134. Phone (03) 879 9422. VIDEO & T.V. SERVICE PERSONNEL TV & VIDEO FAULT LIBRARIES AVAILABLE AS PRINTED MANUALS $85 +P/H BOTH MANUALS T.V. & VIDEO $145 +P/H · OR AS A PROGRAM FOR IBM COMPATIBLES OR AS AN APPLICATION PROGRAM FOR D-BASE 111 PLUS FOR MORE INFO. CONTACT TECHNICAL APPLICATIONS PO BOX 137 KENMORE 4069 OR FAX/PHONE (07) 378 1064 APRIL 1993 71 CIRCUIT NOTEBOOK Interesting circuit ideas which we have checked but not built and tested. Contributions from readers are welcome and will be paid for at standard rates. Breakerless pick-up for car ignition 01 tN4004 +12V VIA .--------------+-119-+------......- -.......- - - - - - - - 1 G N I T I O N SWITCH 1k Qt TIP41C, TIP31C Two of our cars were 330ll having ignition trou100ll bles due to timing drift SW and so we decided to convert them to elec0.1 0.1 tronic ignition. The 201 J 8.2V opto-electronic conver400mW sion kits made by Piranha worked well but I wanted to save money when the time came to ....__ _ _ _ _ _ _ _ _ _ _ ___,.___ _ __..,.._ _....,.._ _.....,.._ _ _ _ _ _ _ _ CHASSIS convert a third vehicle. Fortunately, the Piranha kit comes in two CASE sections which can be The Piranha distributor kit uses a two mica washers under the Darlingpurchased separately: (1) a distribuphoto-interrupter circuit that's fed by ton output transistor to prevent hightor modification kit which is chosen to suit your particular vehicle (about emitter follower Ql. A rotating vane voltage punch-through and cover the $100); and (2) an electronic control assembly interrupts the light path transistor with a plastic cap to premodule (about $150) which plugs into across the photo-interrupter to turn vent the possibility of shorts or electransistor Q2 in the control module tric shock. the distributor kit. The accompanying circuit shows on and off. Each time Q2 turns on, it Constructors should take care to pulls pin 5 of ICl low. ICl then pulls how the Piranha distributor circuit is loop sufficient signal lead within the married to a control module based on its pin 7 output low and switches off distributor to prevent the lead from the High Energy Ignition System (SILI- Q3 to interrupt the coil current and breaking due to the constantly moving advance mechanism. Make sure CON CHIP, May 1988). There are only a fire the spark plug. The control module should be built that this lead is kept safely away from few minor modifications to the input circuit of the High Energy Ignition as described in the May 1988 issue of the rotor button and cam. Glen Host, Circuit, which means that you can SILICON CHIP (ie, in a metal case which is then earthed to the chassis). Use Doubleview, WA. ($30) use the original PC board. Dynamic noise reduction circuit Dynamic noise reduction (DNR) has been around for many years but practical circuits to implement this flmction are few and far between. Although National Semiconductor does make a DNR IC, this device is only available under license. The circuit presented here solves that problem by using only common components. Basically, the circuit reduces tape hiss during playback, with minimal affect on program quality. Each channel consists of a variable low pass filter based on a transconductance 72 SILICON CHIP amplifier (gm) within an NE572 compander/expander IC. The cutoff frequency is continually adjusted using a control signal derived from the program content. Let's take a look at the circuit. As shown, left and right signals are bled off the main inputs and summed by op amp ICla. The resulting mono signal is then attenuated below 1.6kHz by an RC network consisting of a .0lµF capacitor and a 10kQ pot which functions as a sensitivity control. From there, the signal is fed to amplifier stage IClb which also provides limiting plus filtering below 4.8kHz. The output from IClb appears at pin 7 and, after further filtering, is fed to a rectifier inside IC2 to produce a control signal for the two gm cells. These gm cells function as variable filter stages and in turn drive buffer stages IClc and ICld. When insufficient high-frequency source material is pr~sent to mask hiss, the bandwidth of the variable filters is reduced (minimum. 800Hz). The bandwidth then increases again when sufficient highs are present to mask the hiss. The only adjustment is the sensitivity pot VRl. This should initially be set to minimum and then advanced to achieve the desired effect without affecting the treble. The noise reduc- 22k 150pF LEFT INPUT 2.2 C} o. 1 1 -1 LEFT OUTPUT 7 +10~ 12k IC2a NE572 10 ~ +12V 100k 100k 22k + 12 16 +12V + 22k 0.1 ! 1 ... 0.1+ BUFFERS 1+ .01 14 , ,,.~., VR1 10k LIN 4.7+ 100k 100k + 22k 10+ f 01 ~ NR IN NR OUT~ 0.1 ~ 2x1N914 D2 22k 2.2k .015+ RIGHT INPUT - 2.2 + 150pF 22k Cf3 14 12k 1 + ~ RIGHT OUTPUT ~ tion effect can be bypassed completely simply by grounding the rectifier input via a 1kQ resistor using S1. Finally, a 572 contains two rectifiers and normal practice is to use one for each channel. In this circuit, however, one rectifier is used to set the lower cutoff frequency (using an 820kQ resistor, while the other handles the control signal. The rectifier VFO controlled transmitter for 80 metres This circuit generates almost 500mW over the frequency range from 3.5-3.6MHz using just one CMOS IC. It uses a VFO based on one inverter in a 74AC04 "6pack". This then drives the remaining five inverters (wired in parallel) to raise the power output. The frequency of oscillation is controlled by a 3.58MHz ceramic resonator and is tuned over the frequency range by a 400pF variable capacitor (VC1). This gives a frequency stability somewhere between that of an LC oscillator and a quartz crystal oscillator. The output network consisting of L1, LZ and the .0015µF capacitor serves a twofold purpose: (1) it matches the output impedance of the five paralleled inverters to a 50-ohm load; and (2) it suppresses any harmonics to better than 45dB below the carrier. The circuit operates from a 2V to 7V (max.) supply outputs are summed by bridging pins 2 and 14, thereby ensuring that they control both gm cells. D. Young, Double Bay, NSW. ($35) 10M son ·~ VC1 400pF ~ L1: 1ST ON AMIDON T44•2 TOROID L2: 23T ON AMIDON T44-2 TOROID ~ rail. Note that a 0.1µF RF bypass capacitor must be connected with minimum lead length between pins 14 & 7 (supply and earth) of ICl. John Rickard, Heathmont, Vic. ($25) Footnote: 3.58MHz ceramic resonators are available from Radiospares Components, Cat. 656-170. APRIL 1993 73 •111tu11nc• ru,n " ' " " " " 1 1 I f"'IilO I IICC DOD 10\/IIIC Cl CCT □ Or..UC(' 000 10\/1 .. IC Digital clock with battery back-up Ever fancied building a clock? Well, here's your chance to get stuck into some basic digital electronics & build yourself a useful timepiece. It has battery back-up, automatic display dimming at night, AM/PM indication & a 4-digit LED display. By DARREN YATES Digital electroni.cs is a large and diverse field. Apart from the computer industry, it's now used in everything from telephones to washing machines to the humble digital alarm clock next to your bed. However, if you look inside your clock, you won't recognise much in the way of electronic circuitry. What you will find is a PC board on the back of a LED display, with a black "blob" in the centre. Embedded inside this blob is a single large scale 80 SILICON CHIP integration (LSI) chip which contains virtually the entire clock circuit. Of course, conventional LSI clock chips are still made but, with the advent of cheap digital clocks, they are now difficult for the do-it-yourself enthusiast to obtain. These LSI chips also teach you nothing about digital electronics. This design changes that situation by not using a dedicated LSI chip. Instead, it uses nine readily available CMOS ICs, some of which you may already have sitting in your junkbox. The main features of our clock are listed in the specifications panel. Block diagram The main sections of the clock are shown in the block diagram of Fig.1. It uses an accurate frequency reference which is divided down and used to clock a number of BCD counters and a latch. There are three BCD counters in all - two to count the minutes and one to count the hours from 0-9. All three counters directly drive 7-segment LED displays. The latch provides the 10-hour count and drives two segments of a fourth LED display. Let's go through the block diagram step-by-step and explain how it all works. Basically, you can think of a clock as a specialised counter that increments once every minute. Unlike a conventional counter, it is presettable and has a somewhat unusual count sequence; eg, it counts from 59 to 00 and from 12 to 1. Let's begin with the section that generates the pulses. These have to be accurate and that means that we can't use a simple RC-type oscillator to do the job. This type of oscillator drifts with temperature and any frequency variations can translate into quite large errors. What's needed then is a very accurate frequency reference and this has been obtained by using a digital watch crystal. This type of crystal oscillates at 32. 768kHz and this is divided by 16,384 to obtain an accurate 2Hz square-wave signal. To obtain one pulse every minute, we need a frequency of 0.0166Hz and so our 2Hz signal must be further di'rided by 120. This is achieved by first passing it through a divide-by-2 stage and then through a divide-by-60 stage. The resulting 0.0166Hz signal is fed into counter 1, which is the 0-9 minutes counter. Its carry out (CO) output goes high on the 10th count and clocks counter 2 which counts the tens of minutes. Because the maximum count that the minutes counter can display is 59, we have to detect the 60th count and this is done by checking counter 2's display driver outputs. When the 60th count is reached, the first two counters are reset and counter 3 is incremented by one. Finally, the CO output from counter 3 clocks a latch when a count of 10 hours is reached. This latch not only drives the two segments of the fourth LED display but also drives a display latch to give AM/PM indication. It also provides a reset clock pulse to counter 3 for the transition from "12" to "1" (more on this later). Time setting is achieved by feeding the 2Hz clock signal directly into counters 1 and 3 so that the minutes and hours can be incremented separately. This makes time -setting a breeze. Circuit diagram Fig.2 shows the full circuit details of the Digital Clock. Note that all the IC numbers on the block diagram can be related directly to the circuit diagram. IC5 is the 0-9 minutes counter, IC6 the minutes tens counter, IC7 the 0-9 hours counter, and IC8a & IC9a the 10-hour count and latch circuit. I CRYST AL OSCILLATOR +16384 IC1 +60 IC3 +2 IC2a TIME SET MINUTES ...... 12·1 CLOCK PULSE IC9b ..._ I--- TIME SET HOURS CLK IN AM/PM LATCH IC8b '--- TEN-HOUR COUNT AND LATCH IC8a.lC9a '---- BCD COUNTER 3 IC7 L- BCD COUN TER 2 IC6 CINCO 7- • I I BCD COUNTER 1 IC5 ~ ,_,I I ,=,,-, ,_,I I DISPLAY DIMMER IC4d Fig.1: block diagram of the digital clock. It uses a crystal controlled oscillator (ICl) to generate an accurate reference frequency & this frequency is then divided down & used to clock three BCD counters (IC5-IC7) & a latching circuit (IC8a & IC9a). The counters & the latching circuit in turn drive four 7-segment LED displays, while another latch (IC8b) drives the AM/PM indicator. In greater detail, IC1 is a CMOS 4060 14-bit counter and oscillator which has its frequency set by a 32. 768kHz watch crystal. A 33pF trimmer capacitor provides the correct loading for the crystal to ensure that it starts reliably, while VCl allows Specifications • 4-digit LED readout. • 12-hour operation. • separate hours & minutes time setting. • automatic display dimming at night. • AM/PM indication. • crystal-controlled timing. • 12VDC plugpack power supply with back-up battery. the crystal frequency to be trimmed slightly so that the clock keeps accurate time. The output at pin 3 of IC1 is the required 2Hz square-wave signal (ie, the crystal frequency is divided by 214 ). This signal is divided by flipflop IC2a to produce a 1Hz signal on pin 1 which, among other things , is used to flash the two centre decimal points on the display to separate the hours and minutes digits. The 1Hz signal from IC2a is also fed to a divide-by-60 cjrcuit based on IC3 , a 4518 dual BCD counter. Both counters inside this IC are connected in cascade, with AND gate IC4a used to detect a '6' output from the second counter. Pin 4 of IC4a drives an RC network consisting of a lkQ resistor and a .001µF capacitor. Each time IC3 APRIL 1993 81 :a :i:: n :z: n 0 r: Cf.l = N +V1 "7 •• 5 VC1 3 - opF l • J 7 - .!.. 3 47 k 18k _1.8k l: er r- ) Q2 . BC5~ C _t8k 4013 Q L CK 7 .,. 7 L...--'r'J.. _r J! .,. TIM\1SET --r.,. --...E._jB_J9 1k l ... .,. .00 1 I 5 ~ 11 712 .,. 13 "IC4cL 9 1 5 DP +Vl =• )~~~ 7 l 11 9 D : 03 BC548 I 100k • • .f.~ I a -. -. 22k C ~ ~ [!__j +V2 11 0 t +V1 +V1 7 .001I s DP ,-, ...L b DISP3 HDSP5303 •Idle I Ia 78421910 a 10121391187 tak3 7x1.8k '--'-' 15 R .,..-----+--'.._----◄ ,ic::;"\B e"(-1 C 4n R 1 D IC9a Q - 3 4013 --" CK s 17 Ii 5 la I I ·r· I I . 7 001"""' . Q 13 1k .11_ 0_ ____, R IC9b S ~-- n16 _..,_◄_, 14 DISEN 1 R 20UT CLK 1 2 Q IC8a D ICT CLEN ~ 4026 2 _ 4013 3 5 8 CKl-'----+----t1CO s abcdefg _ DISP4 HDSP5303 ,, •/ MIN~:Es .001 \ "" l ...__ fu\ D1 1N914 HOSU2RS l .,. r . 3.3k 3 .,. ICS 4026 \Y .. 1J9~4 6 :V . - OUT 1k 15 R 1 ij 7 .001 I 0 '--Jg" .f ,c◄b I 10 47k 5 DP DISP2 HDSP5303 ,=, ,-, la ~ jE /';; C ~) 7 :..__ +V2 t) D5 1 CLK 0 100k .,. I +V1 .,. 100pF .,_ I E • • C VIEWED FROM BELOW B 7 1 6V T BATTERY I BACKUP.l_ 1N~g - 7 7 DISP1 HDSP5303 ,=, ,-, la 6421910 • 1012139118 +V1 I GC ~ 1-------J.---- . ~16 DISEN 2 CO CLEN ~ 15 IC5 R 4028 8 abcdelg _ 7x1.8k 5 CLASSIC CLOCK E ~05 C:3:.7k 47k 11 6 7 . 47k ~ ~ ~~ +V1 •••• 1N /'. 7812 a.;;.;"-<1.....,_\..1,,.,..a,....a.. '--' + GND ( ~ 100 ('..~ :~ 16VWi 04 D7 \ : 1N4004 ;i;. _ . Bg5~ 8 47k B/?E -a 1976410 : 1012 139 2 . - IN ------------ ♦V2 CLK 2 CLEN 6 abcdefa _ ral3 DISEN , +V1 47k 1.8k$ 7x1.8k .,. 100pFI ,l ...__ "•• J I'::'\ r- '--' + 100 25VWi °":!- 2 3 L_JIC4d 1 -■ 1 001 1J9~4 · • • ORP12, ' • U4 1N4004 i::\, +.., ~ 12VDC 300mA PLUG-PACK - _ L--------------------, L--------'31-----e■i----------------e----, 3 D IC2a Q 1 G 4 , - - - - - - - - - - - - ' ~ ~ . . +.. ,--~IMr--1-'-'ICK +V1 14 4 ,-■ 12 _ _l! ........- IC1 4060 l ------------------"-40 7 110 14 ----~ o D 12 - ICBb 11 .._µ 0 CK S R .,. 33pF'"' I 10 100k HU-- , X1 32.768kHz •• uM 11 -------'-'I 16 14 1 . - - -6..,.._ 6 Q2B 04A 03B 13 0 ENB IC3 4518 1 15 CLKA R +V1---------+----------------. The switch board carries the three timesetting switches & the light dependent resistor (LOR). It is mounted on 9mm spacers on the lid of the case & is connected to the timekeeping PC board via flying leads. reaches a count of 60, pin 4 goes high, the capacitor charges and pin 15 of IC3 is pulled high. Thus, IC3 is reset to 00 a short time after the count of 60 is reached. As a result, each time IC3 counts to 60, pin 4 ofIC4a briefly switches high. IC4a thus delivers a 0.016Hz pulse train (ie, one pulse per minute) and this signal clocks BCD counter IC5 via Dl. IC5's CO output in turn clocks IC6 (the minutes tens counter) at every lath count, as described previously. It's here that we strike the first wrinkle. When IC6 reaches a count of six, two things must happen: (1) IC5 & IC6 must both be reset to zero; and (2) a clock signal must be applied to hours counter IC7. As it turns out, we can easily detect the 6th count by monitoring the "b" and "e" outputs from IC6. When a '6' is to be displayed, the "b" output segment is low and the "e" segment out- ◄ Fig.2 (left): all the IC numbers on the block diagram can be related directly to the circuit diagram. IC5 is the 0-9 minutes counter, IC6 the minutes tens counter, IC7 the 0-9 hours counter, and IC8a & IC9a the 10-hour count and latch circuit. The timing circuit is based on a 14-bit counter/oscillator (ICl) & a 32.768kHz watch crystal. put is high. These two conditions only occur together at the 6th count. Thus, on the 6th count, transistor Ql will be off and pin 8 of IC4b will be high. Pin 9 of IC4b also goes high on the 6th count and thus pin 10 switches high and clocks hour counter IC7 via DZ. IC4b then resets IC6 a short time later via the RC delay circuit connected to its output. Because the time constant of this RC circuit is very small, the observer doesn't see the '6' appear. The output pulse from IC4b is still long enough to clock hours unit counter IC7, however. Hours counter This is where things start to get a little tricky. That's because IC7 must cycle from 1 to 9 to O (as in 1am-10am or 1pm-10pm), then from 1 to 2 (as in 11am-12pmor 11pm-12am), then from 1-0 again and so on. This sequence is impossible for a 4026 UP counter to do on its own but it can be done by adding a small amount 0f extra circuitry based mainly on IC9a. We'll look at this in some detail shortly. IC8 is a 4013 dual D-type flipflop, with IC8a connected as a latch to drive the leading display. Because this display either shows a '1' or is off, segments "e" and "f" are tied together via 1.8kQ resistors and driven by the Qbar output of IC8a via transistor QZ. When Q-bar is low, Q2 turns on and the two segments light to show a "1". Conversely, when Q-bar is high, QZ and the segments are off. IC8a is clocked by the CO output of IC7. When IC7 reaches a count of 10, its CO output goes high and Q-bar of IC8a goes low, thus turning on Q2 and the "e" and "f" segments of the leading hours digit. Now let's see how IC7 cycles through its count sequence. As already discussed, clock pulses are applied to IC7 at regular 1-hour intervals via diode DZ. Assume for the moment that the time is currently 1:59; ie, IC7 is at a count of "1". When the next clock pulse arrives , IC7 goes to a count of 2 (ie, we have 2:00 on the displays) and this causes the "2OUT" pin (pin 14) to go low. This low transition is ignored by the clock input of IC9a, since this flipflop can only change state when its clock input goes from low to high (provided its Reset input is low). When the next clock pulse occurs, IC7 goes to a count of "3" and pin 14 of IC7 goes high again This high is applied to the clock input of IC9a but IC9a ignores the clock pulse on this occasion. That's because its reset input (pin 4) is held high by the Q-bar output from IC8a. However, when the count in IC8a and IC7 reaches 13, Q-bar of IC8a is low. IC9a thus switches its Q output (pin 1) high on receipt of the clock pulse and this resets both IC7 and IC8a. Q-bar of IC8a now goes high again and turns off transistor Q2 and the leading digit (ie, the leading digit is blanked). At the same time, IC7 is reset to "0". But we don't want the hours units display to show "0"; we want it to show a "1 " instead. That's achieved by using the Q-bar output of IC8a to clock IC9b when it switches high to turn off the leading hours digit. When that happens , IC9b 's Q output switches high and feeds a clock pulse to IC7 via D3 to that IC7 immediately advances to a count of 1. IC9b then resets itself almost immediately via the RC time constant on its pin 13 output. In summary then, the hours counters (IC7 & IC8a) count to 12 and are reset to O on the 13th count. IC7 is then immediately clocked to produce a "1" on the display. This all happens very quickly so that, as far as the APRIL 1993 83 - signal derived from pin 4 ofICl. If the ambient light level is high, the resistance of the LDR is low and the output from IC4d is also low. Conversely, if the light level is low, the LDR's resistance is high and IC4d gates through the 512Hz square-wave signal from IC1. IC4d drives PNP transistor Q4 via a 47kQ base current-limiting resistor. When IC4d's output remains low (ie, the light level is high), Q4 turns on and thus Q5 also turns on and the displays are driven at a 100% duty cycle to provide maximum brightness. Conversely, when the light level is low, IC4d switches Q4 and thus Q5 on and off at a frequency of 512Hz. Q5 in turn switches the displays on and off at this frequency to reduce the display brightness . ~ Power supply - craJ , - •F""½ ~l- •---~~ -'--;~~hrJ,rtt-~t=7~ ,. : \ C> 4 :12 ,(l'-, ! ,~ U~i~H!~. .. ~ TER'Y l~ .,.., - ± F• • ./4i' • · 100uF 12VDC 25VW INPUT 0"' Fig.3: install the parts on the main PC board & the display PC board as shown here. Take care with the orientation of polarised parts & note particularly that DISP2 & DISP4 must be installed upside down on the display board (ie, with their decimal points at top left). observer is concerned, the display goes straight from "12:59" to "1:00". Q3, IC4c and ICBb are used to drive the AM/PM indicator. Q3 inverts the 2OUT output from IC7 and drives one input of AND gate IC4c, while the Q output of IC8a drives the other input (pin 12) of the AND gate. Pin 11 of IC4c thus clocks IC8b every 12 hours to toggle the AM/PM indicator. The AM/PM indicator itself is actually the decimal point on the leading digit. A very simple trick is used so that it appears in the top lefthand corner of the display - the display is LOR $2 ~ Display dimming 0 Fig.4: the switch board carries just four components: the three timesetting switches (S1-S3) & the LDR. Make sure that the flat side of each switch is oriented as shown. 84 SILICON CHIP installed on the PC board upside down! Pushbutton switches S1, S2 and S3 perform the time setting function. To set the time, S1 (TIME SET) must be held down and then either S2 pressed to set the hours or S3 pressed to set the minutes. The circuit work like this: when S1 is pressed, 2Hz clock pulses from IC1 are coupled through to S2 and S3. If S2 is now pressed, these 2Hz pulses are differentiated by a .0015µF capacitor and fed to ·pin 1 of IC7 to increment the hours display. Similarly, if S3 is pressed, the minutes 0-9 counter is clocked. IC4d, Q4, Q5 and an ORP12 light dependent resistor (LDR) provide the automatic dimming function for the LED displays. The LDR and its series 3.3kQ resistor form a variable voltage divider, the output of which depends on the ambient light level. This output is fed to one input of AND gate IC4d. The other input of IC4d is driven by a 512Hz square-wave Power for the circuit is derived from a 12V DC plugpack supply. As shown on Fig.2, the incoming DC is fed via reverse polarity protection diode D4 to a 3-terminal 12V regulator. Two separate supply rails are then derived from the output of the regulator via isolating diodes D5 and D7. The +Vl rail powers all the timekeeping circuitry, while the +VZ rails powers the LED displays via the dimming circuit (Q4 & Q5). A 6V backup battery is used to supply the timekeeping circuitry if the mains fails. This battery is isolated from the +Vl rail via D6 which is normally reverse biased. When the mains fails however, D6 becomes forward biased and the battery takes over and supplies power to the +Vl rail. During this time, D5 is reverse biased and so the LED displays are blanked. This was done to conserve the batteries in the event of a long blackout. The LED displays come back on again to show the correct time as soon as the mains power is restored. Construction All the components for the digital clock ·(except for the 3.5mm power socket) fit on three PC boards: a main board (code 04101931) which accommodates all the timekeeping circuitry; a display board (code 04101932) which holds the four LED displays; and a switch board (code 04101933) which holds the timesetting switches and the LDR. Before installing any of the parts, The display board is soldered at right angles to the main board via matching edge-connector pads & must be adjusted so that the LED displays line up with the perspex viewing window (see text). Wrap the battery in foam insulation to prevent it from shorting other components when the lid is attached. check all three boards for etching defects by comparing them with the published artworks. When you're satisfied that everything is correct, the parts can be installed on the main PC board. Fig.3 shows the parts placement details. Begin by installing PC stakes at all external wiring points, then install the wire links, resistors and capacitors. Make sure that the wire links are straight so that they don't short against other parts. You can straighten the link wire if necessary by clamping one end in a vice and then stretching the wire slightly by pulling on the other end with a pair of pliers. The semiconductors can now be installed on the PC board, followed by trimmer capacitor VC1 and the 32.768kHz watch crystal. Be sure to use the correct part at each location and check that all parts are correctly oriented. In particular, check the transistor type numbers carefully and note that all the ICs face in the same direction. The 3-terminal regulator is installed with its metal tab towards the adjacent power diodes (see Fig.2 for the pin connection details). Display board This board will only take a few minutes to assemble since it only carries the four LED displays plus two wire links. There is a catch though: displays 2 and 4 must be installed on the board upside down (ie, their decimal points must be at top left). These two displays are marked with an asterisk on the parts layout diagram (Fig.3). The other two LED displays (1 & 3) are installed in the usual manner (ie, decimal points at bottom right). Push all the displays down onto the board as far as they will go before soldering their pins. Once the display board has been completed, it can be attached at rightangles to the main board by lightly solder tacking two pairs of edge connectors together. Adjust the display board so that its bottom edge sits about RESISTOR COLOUR CODES a a a a No. 1 4 7 a a a a a 1 26 3 Value 4-Band Code (1%) 5-Band Code (1%) 4.?MQ 100kQ 47kQ 22kQ 4.7kQ 3.3kQ 1.8kQ 1kQ yellow violet green brown brown black yellow brown yellow violet orange brown red red orange brown yellow violet red brown orange orange red brown brown grey red brown brown black red brown yellow violet black yellow brown brown black black orange brown yellow violet black red brown red red black red brown yellow violet black brown brown orange orange black brown brown brown grey black brown brown brown black black brown brown APRIL 1993 85 PARTS LIST 1 PC board, code SC04101931, 154 x 88mm 1 PC board, code SC04101932, 102 x 37mm 1 PC board, code SC04101933, 82 x 51mm 1 front panel label 1 switch label 1 2.5mm DC socket 1 battery snap connector 1 ORP12 light dependant resistor 3 pushbutton !'170mentary switches (S1 ,S2,S3) 1 plastic case, 186 x 125 x 50mm (Rod Irving Cat. H-10116) 8 9mm x 3mm tapped spacers 8 25mm x 3mm machine screws 1 32.768kHz watch crystal (Rod Irving Cat.Y-11125) 1 4 x AA square battery holder 4 1.5V AA batteries Semiconductors 1 4060 oscillator/14-bit counter (IC1) 3 4013 dual D flipflops (IC2, IC8,IC9) 1 4518 dual 4-bit BCD counter (IC3) 1 4081 quad 2-input AND gate (IC4) 3 4026 decade counter/display drivers (IC5-IC7) 2 BC548 NPN transistors (01 ,03) 3 BC558 PNP transistors (02,04,06) 1 BC337 NPN transistor (05) 1 7812 3-terminal regulator 4 HDSP-5303 common-cathode ?-segment LED displays 3 1N914 signal diodes (D1 -03) 4 1N4004 silicon diodes (D4-D7) Capacitors 1 100µF 25VW electrolytic 1 100µF 16VW electrolytic 6 .001 µF 63VW MKT polyester 2 100pF ceramic 1 33pF ceramic 1 5-30pF trimmer capacitor (VC1) Resistors (0.25W, 1%) 1 4.7MQ 4 100kQ 7 47kQ 1 22kQ 1 4.7kQ 1 3.3kQ 26 1.8kQ 3 1kQ Miscellaneous • Tinned copper wire, hook-up wire, screws, nuts, washers. 86 SILICON CHTP Fig.5: this fullsize artwork can be used as a drilling template for the switches & the LOR. LDR + Time Set Hours Minutes + + + 5mm below the copper side of the main board before making these two connections and leave the remaining connections until later in case some adjustment is required. Switch board Fig.4 shows the wiring details for the switch board. Note that the three pushbutton switches must be correctly oriented, otherwise they will be behave as though they are permanently closed. In each case, the flat side of the switch body must face towards the top of the board. The only other part on the switch board is the LDR. It can be installed etther way around and should be pushed down so that its top surface is no more than 9mm above the PC board. Final assembly The prototype was built into a black ABS plastic case measuring 186 x 125 x 50mm (see parts list). This case comes with a integral screw supports on both the base and lid and these will have to be removed using an oversize drill bit. The front panel label is then attached to its panel and the cutout made for the LED displays. This cutout is best made by drilling a seri.es of small holes around the inside perimeter of the marked area, then knocking out the centre piece and filing the job to a smooth finish. This done, glue a piece ofred Perspex to the back of the panel to provide the viewing window. The front panel can now be slid into the base and the main board assembly .introduced so that the displays sit directly behind the cutout. Position the board so that the displays are almost touching the Perspex, then mark;out and dr-ill the fpur cor- ner mounting holes in the base. The main board assembly is mounted in the case on 5mm spacers. Secure the board at two diagonally opposite mounting points to begin with, then check that the displays line up correctly with the viewing window. If they don't, adjust the display board as necessary, then solder the remaining edge connector pads. Finally, the switch board can be mounted on the lid of the case, the 3.5mm power socket installed on the rear panel and the wiring completed. The exact location of the switch board is not critical but make sure that it's far enough back to clear the display board. When you have decided on the exact location, attach the label and use it as a template for drilling the holes. A small pilot drill should be used initially for drilling the switch and LDR holes and the holes then enlarged to size using a tapered reamer. This done, conneot eight 150mmlong flying leads to the switch board, then mount the board on the lid using 9mm spacers, machine screws and nuts. The wiring between the two PC boards and to the DC power socket can now be completed and the battery snap connector fitted. Testing Now for the smoke test. Connect the DC plugpack supply and switch on - you should immediately get a readout on the displays, although it might not make much sense at this stage. That's because the 4026 counters can switch on in a random mode and produce incorrect symbols. To correct the displays, all you have to do is press the time setting buttons (ie, Time Set + Hours and Time Set + 0 0 0 If all is well so far, connect the 6V b!lck-up battery (a 9V battery will also do the job), set the time and switch off the mains power. The display should now go out but the clock should continue to function. Leave the mains power off for a few minutes, then switch it back on again. The display should now come back on and show the correct time. Check that diodes D5 and D6 are correctly oriented if you strike problems here. Finally, check that the display dim- ~ flllll!J- u 00 00 ~ : 0 Fig.6: check the PC boards for etching defects against these full-size patterns before installing any of the parts. Minutes) until the counters are clocked and revert to a valid condition. If the clock doesn't work, switch off and check for wiring errors. In particular, check for incorrect parts placement on the PC boards and for shorts between soldered joints on the back of the boards. If the displays don't make much sense, check for shorts between the display segments and that the displays have been correctly oriented (displays 2 & 4 must be installed upside down). 0 04101933 ao-------o~o o0i----a00 0 0 ming feature works by covering the viewing hole for the LDR. The display should dim immediately when the hole is covered. SC I. _____. .I Classic Clock Fig. 7: the front panel cutout is made by drilling a series of small holes & then knocking out the centre piece. APRIL 1993 87 VINTAGE RADIO By JOHN HILL Restoring an old radio chassis Don't neglect an old radio chassis just because it no longer has a cabinet. Often, just restoring the chassis can be worthwhile, particularly in the case of some radiogram units. Most of my valve radio receivers are complete. I guess if one is going to collect old radios, complete sets or sets that can be easily made complete are the way to go. But things don't always work out as planned and most radio collectors soon end up with a sizable supply of bits and pieces. These often include cabinets without innards and vice versa. Murphy's Law has it that no two will ever match up. In other words, if you have 10 empty cabinets and 10 chassis, then the chances of pairing up any two are about zero. Part 3/15A of Murphy's Law states that: if any two such items do match up, it is by pure coincidence rather than by good planning, good luck or skilled ingenuity. Murphy really had very negative views! But let's not get depressed. To hell with Murphy and his infernal laws. There are three things that can be done with an old chassis. First, it can be added to the spare parts supply. It doesn't take long to strip a chassis and put away the usable parts. Second, it can be stored as is, until that long awaited day when a suitable cabinet is found. And third, it can be restored to working order and used in a number of different ways. This old HMV radiogram chassis is one of the author's favourite receivers. It has a push-pull output & three shortwave bands. The elaborate glass dial carries all the station call-signs. 88 Sn 1coN CHIP Of course, if the chassis is restored and working, it can be quickly fitted to a matching cabinet when one is found. Spare parts Let's look more closely at dealing with old chassis and incomplete receivers. If a collector is to have a comprehensive range of spare parts he must be prepared to sacrifice numerous incomplete receivers. I have stripped well over a 100 old sets for spare parts and still often find that the part I want is the one I don't have. That damn Murphy again! Any radio collector or vintage radio repairman must have spares. He needs power transformers, valves, loudspeakers, dial glasses, control knobs and many other bits and pieces. Usually, these items cannot be acquired by any means other than stripping incomplete receivers. That said, there have been many occasions when I have regretted stripping a particular radio. Sometimes, when an incomplete set is wrecked, a source of spares turns up that would have allowed the chassis to have been restored. It is for this reason that many collectors leave their incomplete receivers as they are and either strip odd parts as required or combine them with others to produce a single working receiver as the opportunity arises. It's a good idea if there is sufficient room to store them properly. However, they often end up stacked on top each other in the garage. When a spare part is eventually required, deterioration has often set in and the wanted part is no longer serviceable. I like to get some of those old chassis working again. There's no reason to shun an interesting old radio just Protect your valuable issues Silicon Chip Binders The audio end of the HMV radiogram chassis. It uses a 12AX7 to drive two 6M5 output valves & this arrangement produces more than enough audio power for normal listening. These beautifully-made binders will protect your copies of SILICON CHIP. They feature heavy-board covers & are made from a distinctive 2-tone green vinyl. They hold up to 14 issues & will look great on your bookshelf. * High quality * Hold up to 14 issues * 80mm internal width * SILICON CHIP logo printed in gold-coloured lettering on spine & cover Price: $A11.95 plus $3 p&p each (NZ $6 p&p). Send your order to: Silicon Chip Publications PO Box 139 Collaroy Beach 2097 This chassis has been converted for use with a "permag" loudspeaker by fitting the original field coil to one end. Resistors & filter chokes can also be used as substitutes for field coils. because it has lost its cabinet. Often, an unloved chassis can be made up into a really good receiver and I use some ofmy restored chassis quite extensively. Wall-mounter speaker On the wall of my workroom is a speaker box. It's just an inexpensive veneered chipboard cabinet that contains a cheap 20cm 8W loudspeaker. It was originally bought to make my daughter's radio-cassette player sound a bit better. The end of the speaker cord is fitted with a 3.5mm mono plug. This 8W speaker works quite well considering its price and the miserable box it is mounted in. When it is connected to something worthwhile , it sounds surprisingly good. It produces much better sound than a mantle radio and is quite comparable with any good table model. Any chassis that I restore to working order has a 3.5mm socket fitted to it and that eliminates all the hassles when it comes to connecting this loudspeaker. If need be, the chassis is modified to make it compatible; eg, by building in a field coil substitute, output transformer or whatever. It's then Or fax (02) 979 6503; or ring (02) 979 5644 & quote your credit card number. Use this handy form l ----------Enclosed is my cheque/money order for $_ _ _ or please debit my O Bankcard O Visa O Mastercard Card No: Card Expiry Date _ _/_ _ Signature _ __ __ _ _ __ _ Name _ _ _ _ _ _ _ _ _ __ Address_ _ _ _ _ _ _ _ __ ., ___________ ,. _ __ _ _ _ _ P/code_ __ APRIL 1993 89 This old chassis is from the early post-war era. It is a 5-valve receiver with shortwave & gives excellent performance when connected to a wall-mounted loudspeaker. are well worth keeping because they make excellent radio receivers when used in conjunction with a wall mounted speaker. This idea is by no means new or original. Over the years, I have collected many old console and radiogram chassis that had been built into home-made cabinets. Some of these conversions are quite neat while others are dreadfully rough and unappealing. I have four radiogram chassis in working order: two HMVs, a Precedent and a Philips. The Philips and one of the HMVs have push-pull outputs and they really do sound good. The 8W speaker is more than adequate in the quiet confines ofmy workshop. The other two · chassis are not so spectacular. One is from a HMV tablegram and is nothing more than a "Little Nipper" with the addition of shortwave. The Precedent is a real "el cheap(')" affair and amounts to little other than a standard 5-valve broadcast receiver with a big dial. It is not in the same class as the other units. Valve testers Rear view of the restored chassis. When they look like this, who wants to hide it in a cabinet? Note the tone control at the back of the chassis. just a matter of plugging in the speaker and the chassis will work. An old valve chassis driving a wallmounted speaker also makes a good workshop radio. There's a bit of a market for garage radios and an old 5valve chassis is a good basis for such an outfit. Radiogram chassis A number of my working chassis are from radiograms and that makes the odd one a bit better than average. Some radiograms were quite expen90 SILICON CHIP sive and the radio section was often far more elaborate than in most standard radio receivers. It is not uncommon for a radiogram chasf?is to have a few extras like a stage of radio frequency amplification, a push-pull output and two or three shortwave bands. If you're lucky, you could have separate bass and treble controls too! Personally, I'm not interested in collecting radiograms. They are just too big and heavy and take up too much room. However, I am of the opinion that some radiogram chassis There are other advantages to having a few working chassis besides listening to them on a wall speaker. In a past story on valve testers, I made the statement that if a valve tests OK in a valve tester, it is only a favourable indication that the valve is useable. To be really sure, the valve should be tested in a working receiver. Having a comprehensive range of working chassis is a great help in this regard. It is far more convenient to test valves in a working chassis than. in a complete working radio. With some receivers, valves sometimes cannot be removed without first removing the chassis from the cabinet. On the other hand, by using a working chassis, the valve can be substituted in less than 30 seconds. Another use I put my working chassis to is testing old high voltage electrolytics. I have also mentioned this in a previous story so I will reiterate only briefly. New high voltage electrolytic capacitors can be both difficult to obtain and expensive to buy. On the other hand, many secondhand electrolytics are quite serviceable but they should be carefully checked before putting them back into service. To check them, I use a working and rusty, then it doesn't generate much interest. An unusual chassis This old 5-valve receiver with its unusual dial is next on my list of chassis to be restored. They don't make them like this any more! . My next chassis restoration will be a rather novel one, even if the make and model is unknown. All I can find out about this one is that it is a relatively standard 5-valve, dual-wave receiver that has a big rotating cylindrical dial. Obviously, it has come out of a console cabinet and is all that remains of what was once someone's pride and joy. The most striking aspect of this chassis is its rather unusual dial. Apart from ,that, it is pretty average and shoufd be a straightforward job to repair. _ "My vintage radio collection consists of many interesting and desirable old receivers. However, when I decide to do a bit .of serious radio listening, it's usually one of my old radiogram chassis that supplies it. If you have a few old chassis laying around collecting dust, you may consider using them as I do. They can be very handy for test purposes and when properly set up, they make very practical receivers. SC RESURRECTION RADIO Vintage Wireless Specialists A working chassis can be a convenient high voltage DC supply for checking old electrolytic capacitors. Exercise extreme caution when testing electrolytics in this manner, to avoid receiving a nasty shock. chassis to supply the high-tension DC voltage. When a good electrolytic is connected into the high tension circuit, the voltage will drop about 10V or so and then return almost immediately to its original reading. A problem capacitor could cause a 40-50V drop and the voltmeter needle will be slow to rise again. In fact , the HT may not even climb back to its original reading. When doing this test, don't forget to discharge the capacitor when finished. Do this carefully, otherwise it could well prove to be a shocking experience! Chassis restoration When restoring an old chassis, I usually go through the normal procedures of cleaning, painting, restringing the dial cord, and replacing any paper capacitors or cooked resistors. I find the sight of a well-restored chassis quite pleasing and in some cases it would be a shame to cover it up by putting it into a cabinet. On the other hand, if a chassis is left all dirty, dusty Repairs - Restoration - Sales Our skilled technicians offer QUALITY repairs and restoration. We also have a large stock of bakelite and timber radios fully restored and for SALE. Parts are available for the enthusiast, in.eluding over 900 valve types, high voltage capacitors, transformers, dial glasses, knobs, 9rille cloth etc. Circuit diagrams for most Australian makes and models. Send SAE for our catalog. WANTED: Valves, Radios, etc. Purchased for CASH Call in to our showroom at: 51 Chapel Street (PO Box 1116), Windsor, Vic 3181. Phone: (03) 529 5639; Fax (03) 510 4486 APRIL 1993 91 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. Jitter in the Low Ohms Adaptor I'd like to share my experience concerning two of your designs: (1) the High Energy Ignition described in the April and May 1988 issues of SILICON CHIP has worked without a hiccup in a semi-competition (turbo) engine for two years. Well done! As an engineer, I have to totally agree with your choice of over-rated components, particularly in an environment such as this. (2) After buying the kit for the Low Ohms Adaptor described in the February 1988 issue, I finally got around to building it over Christmas. Whilst reasonably happy with it, there is a degree of short-term variation in the readings which concerns me. This is mainly on the "XlO0" range. Using precision 1 % resistors, I typically get a stable reading of say 1.003 ohms on the "XlO00" range, but on the "XlO0" range, a varying reading which is up to 5% out. I appreciate the need for low contact resistance in such a unit and have taken steps to reduce such resistances; eg, the Rx terminals are wired with 20A wire which is soldered to the terminals. My main question is, are there any relevant Notes & Errata on this project. Failing such a solution, I intend to rebuild it with just the top two ranges (the other two are re- Matching a car radio to a cassette deck In your very first issue (November 1987), you published an article on converting a car radio for home use. This was ideal for my situation as I live so far from the nearest transmitter. Noise from the power supply is still a problem on AM despite earthing the radio case but.as I mainly listen to ABC FM, this is of little account. My query is how do I interface this signal 92 SILICON CHIP dundant) using a heavy duty toggle switch, plus direct-wired leads terminating in large alligator clips. (R. A., Stathmore, Vic). • Based on our experience with the "Low Ohms Adaptor" the jittery readings on the high gain ranges are probable due to poor wiper contact in VRl or, similarly, poor wiper contact in S2a. Ten questions for 45 cents It's about time I dropped you guys a line. I have a few questions I'd like to ask you. (1) Do you know of any available substitute transistor for a BFX85? I have looked through substitution manuals and only found BSW66 and 2N4001, both of which I can't buy either. (2) Since you featured tb~cle entitled "Updating the Resistor and Capacitor Scene" in the March 1992 issue, I have been a little worried. Most of my resistors are 10% and 5 % types and I'm just not sure if I can work them in or not. (3) Have you ever made an automatic clock dimmer? I'd like to make one for my old clock radio which doesn't have a dimming facility. (4) Is there any way to modify the Diesel Sound Simulator in the December 1992 issue to run off 6V or 9V? (5) I recently bought a grab bag full of with a cassette deck, as 15 watts a side would obviously create an overload? (A. W., Walpole, WA). • The only way to couple the output signal from your car radio is to take it from across the volume control. If you take it from across the loudspeakers, the level will depend on ·the volume control setting: You may also need a voltage divider for signals from the volume control, otherwise the input of the tape recorder may still be overloaded. components. One of them is an IC which I don't know. Its type number is TCP4630AP-8412. If you do know it, could you give me the pin diagram? (6) I was thinking of building your TAI high energy ignition but something is holding me back. It was in an automotive book. It said that capacitor discharge ignitions are much more efficient than transistor assisted systems. Is this true? And if it is, could you design one? (7) Can a computer's parallel port 8-bit data lines be used for input and output? If not, which of the port's 8bit data lines are used for input and which for output? (8) I don't want to drive 2km just to get a 7805 regulator so could you tell me what components I could add to the output of a 7808 to produce 5V. (9) I am in the process ofrepairing a power supply. I only located half the pr9blem and want you to help me with the other half. The problem is that the 5V regulator drops down to 1V when put on load. (10) Is a 7490 almost the same as 74LS90? I asked for a 7490 at Dick Smith Electronics and I got 74LS90. I would greatly appreciate it if you answer most of these questions. (A. C., Heidelberg, Vic). • Wotta lotta questions - this is getting huge value from a 45 cent stamp. The BFX85 is an obsolete general purpose NPN transistor in a TO-39 metal e,,ncapsulation with a Vceo rating of 60V, a collector rating of lA and an FT of 50MHz. You should find that a BC638 or BC640 will be a suitable substitute. By the way, while our data library is pretty comprehensive, we are not always able to answer questions on substitute transistors. The same · applies to ICs. We don't know what a TCP4630AP-8412 is. As far as resistors are concerned, many of our circuits could get by with 5% or even 10% resistors but in any circuit there could be particular resistors which do require values within ±1 %. The solution to this problem is to measure each resistor with a digital multimeter before it is put into cir- cuit. When you do this, you will probably find that more than half of your 5% and a fair proportion of your 10% resistors will be within ±1 % of their nominal value. The answer to your question (3), regarding a clock dimmer, is featured in the "Classic Clock" project in this month's issue. Any dimmer circuit of this nature essentially consists of a light dependent resistor (LDR) in the base of a transistor which controls the current through the display. As far as the Diesel Sound Simulator project is concerned, you could run it at 9V but it would be difficult to make it run at 6V without major modifications. An easier method might be to use the 1.5V to 9V Converter published in the August 1992 issue of SILICON CHIP. The book you refer to regarding capacitor discharge ignitions was probably written in the early 1970s before reliable transistor ignition circuits were a reality. The truth is that CDI is fine for 2-stroke motors where-plug oiling is a problem but for cars CDI is not a goer. The lean fuel mixtures now required to meet pollution standards mean that a long spark duration is required. This is more easily provided with transistor ignition than withCDI. The fast spark rise-times ofCDI also present a big problem of crossfire with 6 and 8-cylinder engines. Finally, the fact is that virtually all new cars today are now fitted with some variant of transistor ignition; none have CDI. Doesn't that say something about CDI? ·We have published a number of articles in the past which make use of the fact that a parallel port can be used for input and output. For example, see the PC Voice Recorder in the August 1991 issue and the Talking Voltmeter featured in the October and November 1991 issues of SILICON CHIP. Your questions about 7805 regulators aren't really answerable. If a circuit is designed around a 7805 regulator it is not likely to work with a 7808 because it probably won't have sufficient input voltage (at least 11 V would be required for an 8V regulator) and it is not practical to reduce its output by . using four diodes in series. If your power supply output is dropping to lV, you certainly have a problem but short of saying that you have an overload, we don't know what it is. Finally, the 74LS90 can generally Dumb micros must be programmed In July and September 1992, you introduced a fantastic little black box with 28 legs called a 68705P3 microcontroller. This chip fascinates me as to its operation. The ICs are identical in the Sprinkler Timer and the Burglar Alarm. Can these EPROMs be programmed for a certain function? If so, when you buy this chip, is it "blank" and do you have to program it? If so, how do you program it? How do you erase it? In the Burglar Alarm you can transmit on two wires from the keypad to the processor board . Can you briefly explain how this be regarded as a superior device to the 7490. The LS designation stands for "low power Schottky" and means that the device is much faster than normal TTL ICs but does not have the high current consumption of Schottky TTL devices. By the way, even LS devices are being gradually phased out and at some stage you will be offered devices such as 74HC90 instead of 74LS90. In this case, the HC designation stands for high speed CMOS. Measuring temperature via a PC games card I am writing regarding "Experiments For Your Games Card", as featured in the January 1992 issue of SILICON CHIP. I cannot get a sensible reading, no matter what I try. Can you help please? My computer is a 386 and I'm running DOS 5.00 with PCTOOLS version 7.1. I have made a GWBASIC directory and put the program in there. All I get is a figure 7 or figure 8, nothing else. Is the temperature supposed to be in °C or °F? Our mean temperature here is around 30°C. I have a problem with the light measurement experiment too. The LDR supplied to me is red and marked "OSZl and GEE4". There are no electronic shops for 280km from where I live so I have to send to Australia for parts as this is quicker than trying to get them from Manila. (P. K., Manila, Philippines). works? (A. T., Everard Park, SA). • Microprocessor chips can be programmed to perform almost any function. However, this is not a task for a h obbyist, as you need the necessary software and circuitry to program the internal EPROM and there is quite a lot of code to be written. We have more projects based on the 68705P3 microprocessor in the pipeline and we will be featuring a series of articles on programming. The Burglar Alarm keypad has an internal numerical character generator and it transmits a serial code for each key press. This is recognised by the microprocessor which then produces the appropriate response. • The output from the temperature measurement circuit is not calibrated but gives relative values only. Note that the program can be made to exit more cleanly by adding the following lines to the listing: 73 locate 9.10: print "Press Q to quit.. .. " 75 a$=inkey$:if a$="q" or a$+"Q" then end. The LDR (ORP12) used in the article was obtained from Dick Smith Electronics. Notes & Errata High Energy Ignition System, May, June 1988, May 1990: a letter concerning this electronic ignition on page 91 of the March 1993 issue suggests the use of a plastic case with a metal lid, to eliminate problems with punch-through of the transistor insulating washer. We strongly recommend against this approach as the high voltage on the case lid could give a nasty shock to an unwary user. To help prevent arcing and punchthrough, we recommend that the holes in the case for the TO-3 transistor be lightly c;;hamfered to remove any swarf. The use of two insulating washers is also a good approach. Audio Mixer for Camcorders, March 1993: the 2.2µF capacitors in series with the lOkQ resistors (in the feedback network) in both channels are shown wrongly polarised on the wiring diagram on page 51. The circuit diagram is correct. SC APRIL 1993 93 _______T CENrRE Cash in your surplus gear. Advertise it here in Silicon Chip. ANTIQUE RADIO ANTIQUE RADIO restorations. Your one-stop radio repair shop. Specialising in restoring vintage radios, including chassis rewiring, re-condensing, quality new parts, valves, valve sockets, speakers, power & audio transformers. Secondhand radio dials & parts for most brands & models. About 400 radios in stock for sale, restoration & parts. Every restored wireless is covered by a 2year warranty on parts & labour. We restore damaged woodwork & cabinets & French polish (approx. 40 coats). Vintage car radios available for sale or restoration. Repairs done on tape decks. r-------------------------, CLASSIFIED ADVERTISING RATES Advertising rates for this page: Classified ads: $10.00 for up to 15 words plus 40 cents for each additional word. Display ads (casual rate): $20 per column centimetre (Max. 10cm). Closing date: five weeks prior to month of sale. To run your classified ad, print it clearly in the space below or on a separate sheet of paper & send it with your cheque or credit card details to: Silicon Chip Classifieds, PO Box 139, Collaroy Beach, NSW 2097. Or fax the details to (02) 979 6503. Open Sat. 10am-5pm; Sun. 12.30-Spm. 109 Cann St, Bass Hill, NSW 2197. Phone (02) 645 3173 BH or (02) 726 1613AH. FOR SALE WEATHER FAX programs for IBM XT/ ATs *** "RADFAX2" $35 is a high resolution, shortwave fax, Morse & RTTY receiving program. Suitable for CGA, EGA, VGA and Hercules cards (state which). Needs SSB HF radio & Radfax decoder. *** "SATFAX" $45 is a NOAA, Meteor & GMS weather satellite picture receiving program. Needs EGA or VGA plus "WEATHER FAX" PC card. *** "MAXISAT" $75 is similar to SATFAX but needs 2Mb expanded memory (EMS 3.6 or 4.0) and 1024 x 768 SVGA card. All programs are on 5.25-inch or 3.5-inch disks (state which) & include documentation. Add $3 postage. Only from M. Delahunty, 42 Villiers St, New Farm, Old 4005. Phone (07) 358 2785. THE HOMEBUILT DYNAMO: (plans) brush less, 1000 watt at 740 revs. $ABS postpaid airmail from Al Forbes, PO Box 3919 - SC, Auckland, New Zealand. Phone Auckland (09) 818 8967 anytime. TVRO NEC. C-BAND: Intelsat satellite receiver, commercial unit, rack mounted. $300.00 ono. Phone Rod (08) 387 0372. SPRINKLER CONTROLLER KITS: Enclosed is my cheque/money order for $_ _ _ _ or please debit my D Bankcard D Visa Card D Master Card Card No. Signature_ _ _ _ _ _ _ _ _ _ _ Card expiry date_ _~/_ __ Name _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Street _ __ _ _ __ __ _ __ _ _ _ _ _ _ _ _ _ __ Suburb/town _ _ _ _ _ _ _ _ _ _ _ Postcode_ _ _ _ __ x I I I I I I I I I I L-------------------------J 94 SILICON CHIP standard and enhanced versions have new PCB layout with optional program A/program B operation . Very reliable and versatile designs control eight stations and have 32 programmable start and run times. Can be used to control just about anything (refer SILICON CHIP, July 92). All settings stored in EEPROM . Kits come complete with LCD and case. Standard version: $135. Enhanced version uses 60708U3 and has built in calendar, allowing day of fortnight watering (ie, SA, SU, MO, etc}, externally triggerable cycles and rain switch capability: $175. Requires 24V AC to run. Relays extra at $3.75 each (requires 9 SURPLUS COMPONENT SALE . $TOCIH)TYS LIMITED, NO BACK ORDERS RESISTORS MOST VALUES AVAIL. 1I4W MIFILM $3/100 113W CARBON $21100 1/2W CARBON $41100 1WCARBON $51100 2WCARBON $81100 • SW WIREWOUND $0.30 10WRESISTORS $0.60 100uF 10VTANT $1.50 . C&K 120fSW $0.50 SW DIL SW $2.00 CD22100 IC $2.50 $0.80 78L12, 79L 12 $0.50 $3.00 8259 $4.00 A25 THERMISTOR $3.00 $8.00 MCT275 OPTO $1.20 $8,00 M0C3020 OPTO $2.00 $8.00 MOCS050 OPTO $1.50 $8.00 74C161 . $2.00 EL32 $8.00 74HC74 $0. 70 ONE ONLY TBL12/30 TRANSMIT TUBE $2500.00 . PHONE OR MAIL ORDERS. CREDIT CARDS ACCEPTED FOR ORDERS $20&:0VER, DISCOUNTS FO.RQUANflTY ORDERS . . 2N3055 . TIP30C TIP122 2N7000 2SC2240 . VN88 ·· 3N170 2N5954 2N3440 7906C LM3900 •···· 27C41 68681 747CJ 8251 '' VALVES .. , 3A4 417A 5651 5R4GY .. ;$1.20 $0.50 $1.20 $1.50 $0.60 $2.00 $1.50 $1.50 $1.20 · $0.50 $0.50 .$1.00 $7.00 · SECONTRONICS .·. PO BOX 2215, BROOKSIDE, OLD 4053, PHONE (07) 3551314 143 GRAYS RO, ENOGGERA, OLD 4051, FAX (07) 8551014 SHOP OPEN SATUROAY9AM•4PMAH(07)8551880 for full kit). JOCKEY PCB UPGRADE KIT: upgrade your present version (PCB SPV3 or SPV4) to the features of the enhanced version. $49. SIMPLE 68705P3/U3 PROGRAMMER PCB: needs a programmed EPROM or use it with a ROM emulator: $27. All prices include p&p. Kits and further info available from Graham Blowes, 38 Garnet St, Niddrie, 3042. Phone (03) 337 1917 (a/h); (03) 575 3349 (b/h); fax (03) 575 3369. KIT REPAIRS & CONSTRUCTION service. Fixed price servicing for all kits. No job too small. Ph (02) 649 2134 after 5pm . VINTAGE RADIO PARTS: numerous new and used valves, knobs and sundry parts. For price list, send one 45c stamp to: Airwave Radio Restoration, PO Box 333, North Hobart, Tas. 7000. A 4Mb SIMM can now be used in my Printer Buffer kit and my PC printer port driven 280 Micro Development board has a Basic Interpreter. Short form kit prices include postage. Buffer $52, 280 Dev. $76; or send $4 for my 3.5-inch promo disk to: Don McKenzie, 29 Ellesmere Crescent, Tullamarine 3034. Phone (03) 338 6286. EPROM EMULATOR: emulates 276427512, downloads 1OK bytes per second, connects to PC parallel port. Assembled & tested $160. Includes shipping. Money order only. Please ask our free catalog. Adaptive Technology, Shop 72, 1/F, Richland Garden, TMTL 333, I MEMORY & DRIVES ICL 286 Board PRICES AT MARCH 10TH, 1993 All in one board with two serial, prinler, IBM keyboard, high density floppy & IDE mono video interface. Up to 4Mb RAM, 80286-16cpu, MS-DOS compatible, 130 page manual, small size 170mm x 255mm. Laptop power supply 240V SV / 3A 12V/3A $89 $299 lnfrared sets, 1 each IR LED, diode & IDC header $1 Ampro little PC Audio IC hybrids STK043-25 or STK058-40W $9.95 SIMM 1Mbx9 70ns 4Mb (72-pin) 4Mbx9 70ns 4Mb x8 sons DRAM DIP 1 x 1Mb 256 X 4 41256 1Mbx4 $50 $220 $225 $195 70ns $6.00 70ns $6.25 sons $2.50 ZorD $24.00 DRIVES SEAG 42Mb SEAG 89Mb SEAG 107Mb SEAG 130Mb SEAG 245Mb 28ms 14ms 15ms 16ms 12ms $240 $325 $355 $390 $670 IBM PS.2 50/55170 70/35 90/95 2Mb 4Mb 4Mb $130 $220 $220 TOSHIBA T3200SX T44/6400 T5200 4Mb 4Mb 2Mb $270 $240 $150 MAC 2MbSI & LC 4Mb P'Book $108 $270 CO-PROCESSORS 387SX 20/25 IIT $130/5 387DX All Intel $140 EPROMS 27C4Mb15 $16 Sales tax 20%. Overnight delivery. Credit cards welcome. All in one NEC V40 CPU board, MS-DOS compatible, high density lloppy. SCSI hard disk, 2 serial, printer, solid state hard disk, IBM keyboard interlace, (4W), CMOS single +5V rail, up to 768Kb RAM, 384Kb ROM, 145mm x 250mm, 98-page manual. $299 Ring tor Latest Prices 1st Floor, 100 Yarrara Rd, PO Box!l82; Pennant HIiis, 21~, Tel: (02)9806988 DVTH' A 'Al Fax:{02)9806991 . J-1.lt'.l r.nL TRANSFORMER REWINDS Microbyte-PC230 v30 CPU board, 1Mb RAM inslalled, 2 serial, printer, 720Kb floppy, SCS1 hard disk, EGA video, IBM kb intertace, made in Australia, surplus $185 ea 720Kb Floppy Drives $55 TRANSFORMER REWINDS 1.44Mb Floppy Drives $89 ;!330. Ph: (065) 761291. Fax: (065) 761003. We buy surplus computer & electronic products, bankrupt stock and components. p C Computers ACTIVE DISTRIBUTORS REQ 'D AUSTRALIA & NEW ZEALAND UCANDO VCR EDUCATIONAL PRODUCTS COMPANY Unique copyrighted animated UCANDO videos for electronics & digital/computer training. USA sales US$6,000,000 year. Also sold in UK & Europe. PO Box 4603, Christchurch, New Zealand. Ph/Fax 3 379 5570. Taped components by the me· tre app 200pcs, tants, caps, zeners, diodes, resistors $5.95/metre 600-600 ohm audio output transformers PCB mount 18Hz38kHz. $9.95 Max 1/0 kil lor PCs, 7 relays, ADC, DAG, stepper driver, TTL inputs, with software $169 PC 1/0 card with 8255 chip 24 1/0 lines programmable as inpuls or outputs $69 ALL TYPES OF TRANSFORMER REWINDS Reply Paid No.2, PO Box 438, Singleton, NSW Bargains · · 1.5 watt AM broadcast transmitter XTAL locked $49 2.5 watt FM broadcast transmitter 88-108MHz. $49 Digi-125 audio power amp (over 19,000 sold since 1987) 50 walV8 $14 125 watV4 $19 New 200 watV2 version $29 lnfrared relay kit $9 Remote control tester $4 36 Regent St, Kensington , SA. Phone (08) 332 6513 FIX-A-KIT KIT REPAIR & CONSTRUCTION 3 MONTHS WARRANTY ON REPAIRS 12 MONTHS WARRANTY ON CONSTRUCTION TECHNICAL ASSISTANCE HVCAL ELECTRONICS Design, Manufacture & Repair of Electronic Equipment (02) 633 5477 Tuen Mun, N.T., Hong Kong. Fax: (852) 404 7952. PACKET MODEMS: fully built and tested $60 inc P+P. Baycom Graphic Packet Ect. Ph (02) 621 2213. Cheque or money order to J. Emery, 105 Abbott Rd, Seven Hills 2147. SPEED DEVIATION METER & Overspeed Monitor; EA Dec. 89. Set the reference speed with the potentiometer and you won't need to look at your speedo again. Monitors speed via a 7LED display, has a 3-step overspeed warning buzzer indicator, easy to install. Only three connections, an asset that adds fun to your driving and should reduce your contributions into the Public Revenue Fund. Available at a fraction of the cost of a minor speeding fine. Clearance at $20 for the PCB and components kit. IA PHOTOINTERRUPTER: an IR LED and an IR transistor in a slotted PCB mounting assembly. The discrete components are easy to separate as the assembly clips together. Great for IR experiments, $2 ea. or 10 for $15. 16-CHANNEL UHF REMOTE CONTROL: see EA Nov. 88-Jan. 89. One transmitter kit, one receiver kit and one 4-cnannel relay driver kit - priced to clear at $70. 1-INCH CAO TUBE: new 1-inch CRO tube plus a connecting diagram plus a simple experimental circuit. Very limited quantities. Clearance at $20. Ref: XXFEB9402. FIBRE OPTIC CABLE: high quality fibre optic cable, single fibre at $2/metre or 10 metres for $15; dual fibre at $4/metre or APRIL 1993 95 LOCAL TRADES & SERVICES Advertising Index Active Media Images ........ ........... 5 T. A. Mowles Transformer Rewinds Printed circuit h11ards for the hobbyist. Fur senice & enquiries contact: For all tyj)es of transformer rewinds. Antique Radio Restorations ...... 94 (08) 3265590 (065) 761291 Fax (065) 761003 Av-Comm ................. ...... .. ......... 55 Altronics ............. ............... ... 60-62 A-One Electronics ......... .... 5, 12-13 David Reid Electronics ................ 3 Dick Smith Electronics ......... 26-29 Silicon Chip EEM Electronics Tu advertise )·our products or senices, please call Sharon on Printed circuit board assembly, switch mode power supplies repaired . Design work from start to finish. Ring anytime 9am-9pm ·Mon-Sun. Harbuch Electronics .................. 36 (02)9795644(018)285532 (03) 4011393 Jaycar ....................................... IBC EEM Electronics ........................ 96 Emona ...... ....................... ............ 5 Jaycar ................ ............... ... 45-52 JV Tuners .......... ... ,.................... 36 REGULATED DC POWER SUPPLIES SPECIAL SALE Oatley Electronics ........... 68,69,96 PRICE CAT No. 10201 10202 10203 10204 10205 10206 10207 10208 10209 Special MODEL QTY GPS-1830 GPR1810H GPS-3030 GPR-3060 GPR-6030 GPS-3030D GPS-6030D GPC-1850D GPC-3030D HST-0062 2-only 2-only 2-only 1-only 2-only 2-only 1-only 2-only 2-only 8-only RANGE 0-18V, 0-3A 0-18V, 0-10A 0-30V, 0-3A 0-30V, 0-6A 0-60V, 0-3A 0-30V,0-3A 0-60V, 0-3A 2 X 0-18V/5A, 1 X 5V/3A 2 x 0-30V/3A, 1 x 5V/3A Variable Transformer WAS NOW SAVE 340.10 793.57 342.53 586.68 638.64 483.70 774.68 897.38 891.83 210.00 280.00 685.00 270.00 460.00 515.00 375.00 620.00 710.00 710.00 84.00 60.10 108.57 72.53 126.68 123.64 108.70 154.68 189.38 181 .83 126.00 A-ONE ELECTRONICS PTY LTD (02) 267 4819 267 4820 Fax (02) 267 4821 PC Computers .. .. .............. ........ 95 Peter C. Lacey Services ..... .... .. 32 Philips Test & Measurement .... IFC RCS Radio ...... .. .. ............. ......... 96 Resurrection Radio ................... 91 Rod Irving Electronics .......... 74-79 Silicon Chip Back Issues ...... 30-31 Silicon Chip Binders ...... .. .. .. ...... 89 Silicon Chip Positions Vacant.. .. 65 T. A. Mowles ............................. . 96 10 metres for $30. Ref: XXFEB9403. SWITCHED MODE POWER SUPPLIES: compact enclosed ex-Telecom supplies. Dimensions 300 x 90 x 180mm. Unregulated input 30-50V, regulated output of 12V<at> 6A or 5V<at> 40A. Two different units. Limited stocks, clearance<at> $14 ea. P & P $7 {heavy!). Specify type when ordering. Ref: XXFEB9404. Oatley Electronics, PO Box 89, Oatley 2223. Phone (02) 579 4985. Fax (02) 570 7910. I BOUGHT TOO much at a components auction and I must sell off surplus as my mother wants her lounge room back! Please send SAE for Jumbo Price List of new electronics-shop component stock at under cost price; eg: BD139/40, 10 for $5.00; 1µF/35V tant, 10 for $3.00; 5mm clear/red LED, 1Ofor 96 SILI CON CHIP $1.00; 4011, 10 for $2.00; All 74/74LS, 10 for $3.00; 555, 10 for $3.50 etc. Genuine sale. G. Cattley, PO Box N421, Grosvenor Place, Sydney 2000. Technical Applications ............... 71 Tektronix ............ .. .... ... .... ........ OBC Transformer Rewinds .............. 104 RCS RADHO PTY LTD ~i~1,~ 16ire...o I Ill :::;=I ' [I O RCS Radio Pty Ltd is the only company that manufactures and sells every PC board and front panel published in SILICON CHIP, ETI and EA. RCS Radio Pty Ltd, 651 Forest Rd, Bexley 2207. Phone (02) 587 3491 PC Boards Printed circuit boards for SILICON CHIP projects are made by: • Jemal Products, 5 Forge St, Wel 9hpool, WA 6106. Phone (09) 350 5555. • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone (09) 828 5730. • RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 587 3491. ''BELLMATE'' BURGLAR ALARMS MAIL ORDER VIA ~ FREE CALL FOR ORDERS ONLY (008) 022 888 HORINE (02) 743 6144. IIE~ \' I ~_._j ■ =··"" VISA POST & PACKING 1 24 99 3 5 $ 0- $ - $ .7 ~~~~~~rn ~~:;~ OVER $100 $8.00 MAIL ORDERS HEAD OFFICE PO. Box 185 Concord 2137. 6 Leeds Streets Rhodes 2138. Telephone (02) 743 5222. Fax (02) 743 2066, ROAD FREIGHT ANYWHERE IN AUSTRALIA (up to 20kg) $13.50 &a~~,••--1~•~, "" . =L ;~ • 1 ADELAIDE SA 190 Wright St (Cnr Selby St) (08) 231 7355. Mon-Fri 9-5.30 Fri 8.30-Sat 9-12. BURANDA QLD 144 Logan Rd (07) 393 0777. Mon-Fri 9-5.30 Thurs 8.30-Sat 9-4. COBURG VIC 266 Sydney Rd (03) 384 1811. Mon-Fri 9-5.30. Fri 8.30-Sat 9-4. MELBOURNE CITY Shop 2, 45 A'Beckett St City (03) 663 2030. Mon-Fri 9-5.30 Fri 8.30-Sat 9-2. SPRIN6VALE VIC 887-889 Springvale Rd Mulgrave (03) 547 1022. Nr Cnr. Dandenong Rd. Mon-Fri 9-5.30 Fri 8.30 - Sat 9-2. SYDNEY CITY 129 York St (02) 267 1614. Mon-Fri 8.30-5.30 Thurs 8.30pm - Sat 9-4. BANIISTOWN 363 Hume Hwy Cnr Meredith St (02) 709 2822. Mon-Fri 9-5.30 Thurs 8.30pm - Sat 9-4 - Sun 10-4pm. GORE HILL 188 Pacific Hwy (Cnr. Bellevue Ave) (02) 439 4799. Mon-Fri 9-5.30 T~urs 8.30 - Sat 9-4pm. PARRAMATTA 355 Church St (Cnr. Victoria Rd) (02) 683 3377 Mon-Fri 9-5.30 Thurs 8.30pm - Sat 9-4pm. Sunday 10am-4pm. PENRITH 199 High St. (047) 21 8337. Mon-Fri 9-5.30 Thurs 8.30 - Sat 9-4pm Sun 10-4pm. RHODES 6 Leeds St. (02) 743 5222. Mon-Fri 9-5.30.