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SERVICING - VINTAGE RADIO - COMPUTERS - AMATEUR RADIO - PROJECTS TO BUILD Control Appliances Via The Telephone Line With This .,, ~· ; 'i ·- - ~ : . . .. ~::,-:,,.. .- "4., . ··/ . ,.., .....,.. ·- -·:- -~ . ~ i DECODER r-..,. 0 cr, Cl... 2 '° ci 2 2 D ..· :·. .:: <l'. '-' ::::; '° ::, Cl... I- (/) D Cl... :;i; ....J <l'. cc I- (/) ::, <l'. >- '° D LJ.J cc LJ.J I- (/) C!J LJ.J cc 13.5V 25A Power Supply For Amateur Transceivers ~CURSORS ,.rncr.o, 1J.:·_.:.., P0SIT!0II C~l t::.i :, Cl.1 ,~s lialf . . . . . . • AU ._ ► VOLTS / D/ V · \~ ..... ~ - ot - - lUfD , • liOl!\1 S H~lf .S&UflC{~ Cl!! A; CUJPl/N§-1 :: ..,_ - 11 - ,._) t ~ ~ ; - "' - re r,--.. ""-"' - :! :; :!; 1KJ1: ? ff - """" rn~~rf ti,Yr Stu!'t H!,;ty f!l'l4" i-t'I MOOE ► """' HM.S" Hf Ai COIJFU~C'!!!!!t CH2o, tf -· ·•IA!IU: LF.Vfl SO(JJICf~ .) } :ffRTlt:Al IIHJOF (;IIZ 20 M.i;r.r~ Aall ~ CHOP l<fV $W t ~4K4,_, ... . CH1 -- ·f lr~t SI.Of'f - ,-.._,I .-1:; .._ £ ( ~~ Et Tfl!~~I ) I• • HORIZONTAL A AIU!a ,HJ B [Q] !'Wlll . . lwi !!!!'l'!!!!I MO!lf SVfff P TIME/ 0 /V J ,: • Voltage Measurement • Time Measurement • Frequency Measurement The CS-6020 has CRT readout functions which provide digital indications of settings such as vertical-axis sensitivity and sweep time on the same screen as the observed waveform, as well as cursor functions which enable digital measurements such as voltage, time, frequency, and phase of displayed waveforms. This makes the CS-6020 a 150-MHz, 4-channel, oscilloscope 150MHz 4-Channel Oscilloscope w ith CRT readout , cursors, and trigger counting • Voltage Ratio Measurement • Time Ratio Measurement • Phase Measurement usable by virtually anyone for waveform measurements and observation. It also has a wide range of advanced features such as Also new from trigger counting, cross-range Kenwood 100~ variable, and B sweep variable, and virtually all functions are logic-controlled to ensure excellent reliability and flexibility. CS 6020 100M Hz 4-Channel Oscilloscope CS-6010 - READER INFO NO. 52 ELMEASCO Instmments Ply.Ltd. N.S.W. (02) 736 2888 • Vic (03) 879 2322 • Qld (07) 875 1444 • S.A. (08) 344 9000 • W.A. (09) 470 1855 May 1991 TV DISTRIBUTION systems pose special problems for the antenna installer. Find out how to tackle these problems by turning to page 4. FEATURES 4 How To Install Multiple TV Outlets by Jim Lawler Pt.1: selecting the antenna 10 Motors For Electric Vehicles by Gerry Nolan It's "watts" under the bonnet that counts 82 The Story Of Electrical Energy, Pt.10 by Bryan Maher High-power DC transmission lines PROJECTS TO BUILD 24 Stereo Audio Expander by Darren Yates THIS SIMPLE AUDIO expander will add sparkle to your music & video cassettes by increasing the dynamic range of the signal. Construction starts on page 24. Puts the sparkle back into your audio tapes 30 Build A DTMF Decoder by Darren Yates & Greig Sheridan Control up to 9 appliances via the telephone line 42 Fluorescent Light Simulator For Model Railways by Darren Yates Simulates the "flicker" when fluoros start up 58 13.SV 25A Power Supply For Transceivers by John Clarke Features current limiting plus overvoltage crowbar SPECIAL COLUMNS 18 Vintage Radio by John Hill All about regenerative receivers 70 Serviceman's Log by the TV Serviceman YOU CAN CONTROL up to 9 appliances via the telephone line with this DTMF decoder. We show you how to build it starting page 30. I was only a little bit careless 76 Computer Bits by Jennifer Bonnitcha Colouring your PC world 79 Amateur Radio by Garry Cratt AR2500 multi-mode scanner covers 500kHz-1500MHz DEPARTMENTS 2 Publisher's Letter 17 Subscription Page 53 Product Showcase 67 Circuit Notebook 75 Bookshelf 90 Back Issues 92 Ask Silicon Chip 95 Market Centre 96 Advertising Index LOOKING FOR a really big power supply to run a highpower transceiver? This unit can deliver 25A continuously at 13.5V. Details page 58. MAY1991 1 PUBLISHER'S LETTER The Electronic Service Industry Advisory Code of Practice Late in March of this year, the NSW Government Agency of Business & Consumer Affairs launched the "Domestic Electronic Service Industry Advisory Code of Practice". Essentially, it is a code of practice which mainly covers people involved in TV and VCR service, microwave oven service and TV antenna installation. No special legislation has been enacted to enforce the new code of practice but it is backed up by the Fair Trading Act and the Trade Practices Act. It has been a cooperative effort between the NSW Business & Consumer Affairs and the following industry bodies: Consumer Electronic Suppliers Association (CESA), Television and Electronic Services Association (TESA) , the Electronic Services Industry Association and The Electronic Technicians Institute of Australia (TETIA). Now that the NSW code of practice has been introduced, it is likely that other states will follow. No-one would argue that the new code of practice is not worth having. It is likely to avoid a lot of disputes in the future, both over the nature of repairs and the cost of these services. But as Gary Wilson, the representative from CESA remarked, it is a case of "too little, too late". The fact is that the great boom years of TV servicing have long gone. Fifteen or twenty years ago, in the heyday of b&w TV and during the introduction of colour TV, was when TV service boomed. In those days, all the major retailers had large service departments to cater for the one, two or more service calls per year that most TV sets needed. Nowadays, all those service people are retired or working elsewhere because it is rare for the average TV or VCR to need a service call more than once in 5 years. And as TVs and VCRs become more and more reliable, they will need even less service. In fact, these days most appliances never require any service at all. They go for years and years and when they finally break down, they are not worth repairing anyway - you buy a new one. But, and this is worth saying, if they are worth repairing, we can be reassured by the existence of the new electronic industry code of practice. All of which leads one to conclude that any measures or legislation brought down by governments are often likely to be overdue, too late or worse, misguided. Sometimes though, governments do make the right decision, as was the case when Federal Cabinet recently debated the introduction of pay TV. It was postponed for at least two years and probably indefinitely. Without going into all the politics involved (and it had nothing to do with available technology), this was the right decision. For the moment, most people don't want, don't need and can't afford pay TV. And neither can the country. In five or ten years time, it will be a different story. Leo Simp-s on 2 SILICON CHIP Publisher & Editor-in-Chief Leo Simpson, B.Bus. Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E .(Elec.) Robert Flynn Darren Yates Reader Services Ann Jenkinson Advertising Manager Paul Buchtmann (02) 979 5644 Mobile: (018) 28 5532 Regular Contributors Brendan Akhurst Jennifer Bonnitcha, B.A. Garry Cratt, VK2YBX John Hill Jim Lawler, MTETIA Bryan Maher, M.E. , B.Sc . Jim Yalden, VK2YGY Bob Young Photography Andrew Darby 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 . All material copyright©. No part of this publication may be reproduced without prior 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, refer to 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 39, 5 Ponderosa Pde, Warriewood, NSW 2102. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 979 5644. Fax (02) 979 6503. ISSN 1030-2662 wpoD FOR CHIPS .•. WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS Now Stocking Philips Parts SerialTest serial data analysis on your PC Over the next few months, we will by expanding the range or quality Phillps components.·Remember that as with all our other IC's etc. your minimum puri:hase order is only one piece. Unlike others with minimum quantities, you can buy one 8D438I1 that's an you really want! Already in stock TDA7DOO FM Radio Clri:uit ,.60 TDA1060 SMPS Controller 4.50 SAB6456 Switched Prescaler 5.40 BYV28-100 Fast Ree Diode 1.00 88119 Var1cap Diode .55 882D48 Varicap Diode 1.05 88212 Var1cap Diode 5.50 B8809 Varicap Diode 1.00 8B405B Var1cap Diode 1.50 BT136/7/8.19 Series Triacs BR100 Dlac 2N7DOO $1.10 Watch our advertisements for further additions! Suitable for Hobby Drill, Arlecl, Dremel etc. Precision German stand with a very smooth action. Use vertically or horizontally. No excuse now for holes in the .,; wrong place! $59.95 We also have the l German Elektra Hobby Drill to go with It. 20,~~r:!~I $9i. 0 5 Handy Probe Multimeter Ideal for tight spots No need to tum your head to read this multimeter. The readout is r1ght there In the probe! Auto and manual ranging, 3.5 digit large 14mm LCD display• all In a handy probe. Logic testing function forCMOSmL Oata Hold 5utton, Diode test, Continuity ie~1,g1%iWows all functions. • DC Voltage from 200mV to 500V • AC Voltage from 2V to 500V • Resistance from 2()()Q to 20Mn • AC/DC Current to 200mA • Continuity check to 2kn f:;ntto 1MHz and ~fs.oo ~~~:6 : b?9J~ ~ ~ Q:: a lJ... Cl a ~ WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR: C Take a close look at APPA multimeters. Look familiar? That's because they're sold under different brand names. And tlla~means you could pay a lot more than you need to. We've seen the top of the line model selling at around $150 more than our price. So you're paying that much extra just for the brand label! 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(Model 93T) $14"80 Modi/ 96 • 3 1/2 digit plus 41 segment analog bar graph • Autoranging or manual selection • 6 functions - Vdc, Vac, Ade, Aac, Ohms, Diode • Water resistant • Data hold • Memory offset Ranges Vdc 200mV, 2V, 20V, 200V, 1OOOV Vac 200mV, 2V, 20V, 200V,L50V Ade 200uA. 2mA, 20mA, 2wrnA, 2A, 20A. Aac 200uA, 2mA, 20mA, 200mA, 2A, 20A OhfJJ.~fM~kn, 20kn, 200kn, $166.80 Mods/ 98 • 3 1/2 digit plus 41 segment analog bar graph • Autoranging or manual selection • 8 Functions • Vdc, Vac, Ade, Aoc, Ohms, Diode, Frequency, Capacitance • Data hold • Memory offset Rangss Vdc 200mV, 2V, 20V, 200V, 1000V Vac 200mV, 2V, 20V, 200V,J_50V Ade 200uA, 2mA, 20mA, 2wrnA, 2A, 20A Aa~~CWi\t· 2mA, 20mA, 200mA, Just Arrived The NEW SC5000A DIC Desoldering Tool. Now fitted with BOW heater, NEW Hot air nozzle makes it easier to remove su rtace mount devices. Price is unchanged at $399 ex tax $478 inc tax) ff you're working on surtace mount SMIJ°Ree;~val Kit. Comes with filter pipe, stainless ef ~a~~\~~~~ ~~ ~ht/~r $82.80 1 ~~~ 1 nozzle. AT&M KITS We carry the full range of these great kl1s. Locally designed and aeve/oped. Top quality components. Comprehensive mstn;ctions included. Why develop your own drcuits when these building blocks are already available? · Kit Description Price 11!11121 Hi1~ l i1M - • clooice wit~ tl,e uro. lo,,p , .. ,nn [DITPJ, or,..., the first letter of yoo r choice. !ho ll:SCl OC'l ..~ k u-,1 ta exit tho • • · • Writes captured data dlrectlV to disk to allow maximum capture buffer • CRC checksum calculations • Auto-configuration to any of the comms ports 1 to 4 • Time-stamping (absolute and relative) including delta time calculations e Split line DTE over DCE display S395 plus sales tax Send $10 for a demo disk, refundable on purchase. 01 3 digit Counter 02 4 digit Counter 03 3 1/2 digit DVM $33.60 50.40 59.40 04 1Hz Timebase 22.40 05 Fibre Optic Modem 75.00 06 Reciprocal Calculator 29.40 07 1OM Hz Timebase 45.60 08 Vlf' Converter 42.60 09 FN converter 42.60 10 Quad Power Supply 60.60 1t 10 Minute Controller 46.20 12 6 dig Batch Counter 75.00 13 3 Digit Counter 65.40 14 3 1/2 digit LCD DVM 42.60 16 1OkV Isolator 70.80 17 Storage Adaptor 193.80 18 8 bit UART 66.00 19 6 dig Up/On Counter 69.60 20 IR Transceiver 39.60 21 Multi-Timebase 42.60 22 16Ch Tranmitter 77.40 23 16Ch Receiver 77.40 24 22/3 Com ms PCB 34.80 25 22/3 Radio Modem 66.60 Ultrasonic Cleaner The latest high-tech W,1/ to clean PCB's, switches, watches, drafting pens· even your dentures! Let the millions of tiny cavitation bubbles clean the surtace 40000 limes per second. 165x90x50mm container holds ha~ a litre and is made of 304 stainless steel. Some people are charging a lot more. Our's are only $150 Save Problems and Cost with Ohms 2oon, 2kn, 20kn, 200kn, 2Mn, 20Mn Frequency 2kHz 20kHz, 200kHz ci~tance 2nF, 20nF, 200nF, 2µF, ~ $214.80 f~:(~r~~;½gi~~~t:ter This Is an MS-DOS software and cabting package which enables technicians and engineers to pertorm serial data comms analysis. It offers sophisticated problem solving facilities at a fraction of the cost of dedicated hardware systems. SerialTest pro~des a window onto RS232 lines operating either as a passive observer or actively sending ~i~~~~fgWo6/~i[l~e~i~mulate Triggers can be defined based on error conditions or data to initiate or terminate monitoring sequences. • Handles baud rates up to 115.2kbaud. • View each byte in ASCII or EBCDIC, decoded to hex, decimal, binary or octal MEMOREX GENUINE PREMIUM GRADE DISKS 51/4 2S/2D $16.95 per 10 $24 95 per 10 5 1f4 2S/HD 31/2 2S/2D $24.95 per 10 3 1/2 2S/HD $49.95 per 10 e Capacitance200pFto20uF • Resistance 200n to 20M'n • Transistor hie and lceo • Diode displays Vf at 1mA • • LEDdisgiar:sVfat2Maand10mA 1 : ~~e~as~~~ir~ird .SVcells $142.80 ..__ _ _ _....;._ _ _ _....;._ _ _.:.._ _ _..,, GEOFF WOOD ELECTRONICS PTY LTD 229 Burns Bay Road, (Corner Beatrice St.) INC IN Nsw Lane Cove West, N.S.W. P.O. Box 671, Lane Cove N .S.W. 2066 Telephone: (02) 428 4111 Fax: (02) 428 5198. 8.30am to 5.00pm Monday to Friday, 8.30am to 12 noon Saturday. Mail Orders add $_5.00 to cover postal charges. Next day delivery in Sydney add $5.00. All prices INCLUDE sales tax. Tax exemption certificates accepted if line va!ue exceeds $10.00. BANKCARD, MASTERCARD, VISA, CHEQUES OR CASH CHEERFULLY ACCEPTED How to install niultiple TV outlets Multiple-outlet TV distribution systems can pose special problems for the antenna installer. Here's how to tackle & solve these problems. By JIM LAWLER Most of you will already know how to distribute TV signals to two or four sets in an average home situation, using the appropriate splitters and, if necessary, a masthead amplifier. This time, we will look at the design considerations facing an installer trying to feed signals to dozens or even hundreds of sets in medium to large buildings. In these articles, I will describe the design for a motel comprising two wings of 20 units each. This month, we'll look at the antenna and the problems of getting sufficient clean signal to feed the installation. Next month, 1so· Fig.1: a simple dipole has a "figure-8" polar pattern, with two identical lobes. It picks up equally well from both front & back & provides a reference signal against which all other antennas can be compared. 4 SILICON CHIP we will cover the design of the distribution system. dBµ & all that stuff Before we go any further, it is as well to review the terms that will be used in these articles. The first term relates to signal strength. TV signals can be measured in volts, amps or watts, although these values are hardly practicable for the tiny levels encountered in TV distribution systems. A much more realistic and useful value is the decibel, derived from the logarithmic relationship of one value to another. If the db is referenced to one microvolt, then all practical db values will be positive and can be simply added together or subtracted, to establish levels at any point in the system. In these articles, I will use decibels above 1 microvolt (lµV), or dBµ, as the standard. Later on, I will mention dipoles, lobes, nulls and stubs, with only the briefest reference as to what these terms mean. They are better described in other articles, pamphlets or books on antenna theory and I would refer the reader to those sources if he feels the need for more precise detail. Checking signal strength A professional antenna installer could not do his job properly ifhe did not have a signal strength meter. This instrument can be tuned to any TV channel and the relative strength read off in microvolts or db relative to lµV. The instrument is invaluable for measuring the gain of different antennas or masthead amplifiers, or the losses in various pieces of hardware. It's not likely that the non-professional reader will have one of these instruments on hand but for any important installation, it would be a good idea to hire one for a week or two. In these articles, I will suggest typical values that I have found from experience but there is nothing to substitute for a precise level, read off on an accurate signal strength meter. Clean signals Before one can undertake the design of any installation, big or small, one needs answers to two questions: (1) Can we get a clean signal?; and (2) will that signal be strong enough? It is vital that the answer to the first question is "yes" because if it isn't, then everything that follows will be a waste of time. It would be pointless designing a good distribution system if all it can distribute are weak, ghostly pictures. All the effort put into securing a "yes" to the first question will be rewarded when the customer tunes in a clean, snow-free picture. The second question can be made into a "yes", even if it's a "not quite" to begin with. As long as the signal is free from ghosts and is reasonably steady even though snowy, it can be lifted to a usable level by a good masthead amplifier. Indeed, if you tackle the job properly, even unpromising areas can be made productive. Which antenna? Most installers use a small VHF or combination VHF/UHF antenna as their portable standard. I went one better and made up a selection of"cut to channel" dipole antennas (Fig.'1) and a collapsible 6-metre mast for my explorations. During my initial investigations of a site, this rig is moved around in the general area that the permanent antenna is to occupy and a record made of the signal levels received. I use a dipole for this job because this is the simplest antenna there is that delivers consistent and unequivocal results. It also has a very precise null in its reception pattern off the ends of the dipole elements. This makes it invaluable as a "direction finder" in areas where the direction of the transmitter is doubtful. When the dipole is "end on" to the transmitter, there will be virtually no oo Fig.2: the addition of a "reflector", as in the Channel Master 3110 or the Hills EFC1 shown here, results in an enlarged forward lobe. This antenna will show a gain of about 3 to 5dBµ over the simple dipole. reception of that channel. At all other angles, there will be some reception but experience will be needed to determine just how much signal can be expected on each channel for various locations. Commercial antennas Every commercial antenna has some level of gain over a basic dipole. Thus, once the dipole's response is determined, I am able to select an antenna Fkely to provide enough signal for that locality. The chosen antenna then becomes my standard for that installation and is coupled to a working TV set for the more practical tests. For the several standard antennas that I have used over the years, signal levels have always been around 60- 65dBµ in reasonable areas. In clear areas close to the transmitters, levels can get up to 70dBµ. On the other hand , in near fringe areas they can drop to 55dBµ but still produce areasonable picture. Next month, I will show that we must have about 65dBµ out of the antenna in order to make the distribution system work properly (ie, we must select an antenna that will deliver around this level of signal). This means a small, simple antenna if the location is close to the transmitter, or a much larger, more complicated antenna if further out. For our hypothetical motel, we'll assume that my dipole antenna produced 60dBµ. This means that I need to select a medium-gain combination Fig.3: the addition of further elements narrows the forward lobe and increases the sensitivity of the antenna. This type of antenna can show a gain of 5 or 6dBµ over a plain dipole. (Photo courtesy Dick Smith Electronics). MAY1991 5 Fig.4: the ultimate directional antenna is the "Yagi", with multiple directors ahead of the driven element. This combination VHF/UHF antenna is very sensitive, over a very narrow angle. It can have a gain of as much as 15dBµ over a simple dipole. VHF /UHF antenna that can lift signals by SdBµ over my standard dipole. The gain figure can be gleaned from manufacturers' data sheets, or determined by experiment (using that signal strength meter mentioned earlier). Thus, our selected antenna will deliver 60 + 8 = 68dBµ into the head of the distribution system. If this area had been less favourable, with a basic signal on the dipole of say 50dBµ, then I would have selected an antenna with 10 or 12dBµ gain to get the signals back into the 60-65dBµ range required. If the signal out of the best antenna available is still below the required 65dBµ, it will have to be lifted to that level using a masthead amplifier or MHA. An MHA is designed to amplify very small signals and may produce 20 or 30dBµ of gain. However, its output should not exceed 6570dBµ. It must also be able to handle strong input signals without distorting. I'll refer later to the results of distortion in amplifiers but for the moment it is sufficient to consider that an MHA should only be used in fringe areas, well away from any strong signals. Problems,problems All that I've written so far applies to installations where there are no signal reception problems. Even in 6 SILICON CHIP far fringe areas, the same selection parameters would apply. The only difference would be that a masthead amplifier would be mandatory to ensure snow-free signals at the antenna lead-in. The situation is quite different in locations where signals are subject to ghosting, or are at greatly differing levels for each channel. Ghosts are caused by signals reflected from landscape features away from the main signal path (eg, hills and buildings). The reflected signal takes longer to reach the receiver and so causes a second image displaced from the first by a time related to the extra path length. If ghosting occurs, it must be realised that no degree of amplification will clean up the picture. An amplifier can only make a bad problem worse. The picture must be cleaned up before it is amplified. Although it is true that nothing can remove a reflection from the signal once it is established, in all but very bad conditons, ghosting can be minimised by careful selection, siting and aiming of the antenna. To this end, the installer has one thing going for him: most practical antennas do not have a circular reception pattern (remember the dipole?). Often, it will be possible to orient the antenna to direct a null towards the source of the ghost. Provided that there is enough front lobe gain left to ensure reception of the main signal, the ghosts should be largely eliminated. However, it might be necessary to try several different antennas to find one that will give a good result. Another trick that sometimes works is to shield the antenna from the source of the ghost. Contrary to popular opinion, it is not always desirable to mount the antenna high on the roof of the building. Sometimes a lower mounting is preferable if this places the main building between the antenna and the source of the ghost. Finally, a high gain, highly directional Yagi type antenna (Fig 4.) might effect a useful improvement. Unfortunately, Yagi's are only practical on the high bands. On low bands, the element and boom lengths become so long as to be almost unmanageable. As a general rule, ghost busting should be done on the bare antenna, without any amplifier connected. In outer fringe areas, it may be necessary to use a masthead amplifier in order to see the ghosts, or indeed any picture at all. Even so, one should try to get the best possible signal before connecting an amplifier. Level problems Another problem that may face the installer is differing signal levels for each channel. This is less of a problem in prime reception areas but can be trot1blesome in near and deep fringe areas. And in areas with both local translators and desirable deep fringe channels, it can be a real pain. Successful signal distribution in any large installation relies on having all the channels at approximately the same strength. It doesn't matter if all channels fall in the low range from 55-65dBµ or the high range from 6575dBµ. The important point is that all channels are within the range. One often finds that Channel 2 puts out a much stronger signal than the commercial channels, for example. Or a local translator overwhelms a weaker signal on an adjacent channel. In addition, UHF is notorious for weak and patchy signals in fringe areas. There are several ways of attacking this problem. One is to use an array of "cut-to-channel" antennas for the weaker signals and rely on incidental pickup only for the local channels. Unfortunately, each of these special antennas will pick up some local signal and when these are mixed at the set, the result is chaotic ghosting. This system can be made to work but it is usually necessary to use bandpass filters on the other antennas to eliminate mutual interference on the local channel. Another method is to use a single high gain antenna to lift the weak signals to usable levels, then insert tuned attenuators to cut back the strong signals. This signal balancing has to be done right at the antenna, before any amplification is applied. This is because non-linearities in the amplifier can cause intermodulation of the weak signals by the stroriger ones. This result is an image of the strong station behind the weaker channel picture. It's sometimes called the "windscree·n wiper effect", as the nonsynchronous horizontal blanking bar of the stronger station waves backwards and forwards across tbe screen. If an MHA is necessary, yet intermodulation is a problem, there are two ways out. One is to try a lower gain amplifier. A slight loss of signal might be tolerable here if it can be made up for later in the distribution amplifier. The second way out is to use a tuned attenuator on the antenna, ahead of the input to the MHA. The simplest tuned attenuator is the "quarter wave stub", a length of coax cable attached to the antenna terminals and carefully cut to exactly a l/4-wavelength of the offending channel. The stub acts like a short circuit for that channel and can sometimes remove its signal completely. In such a case, it is necessary to fit a slightly shorter or longer stub and the art is to decide whether the desired attenuation is to be above or below the required channel. Experimentation is often the best answer. Another way of balancing signals, in areas where the differences are not too dramatic, is to use an adjustable distribution amplifier. These are often standard distribution amplifiers but with separate attenuators for each of the three bands. Thus, a strong channel 2 can be turned right back and weak UHF signal turned up, leaving the high VHF channels at normal level. However, this system will only work properly if the incoming signals have been ANTENNA & MASTHEAD AMPLIFIER VCR COMBINER MULTIPLE SPLITTER t-----rv SET 1------rv SET Fig.5: here's how to feed the output from a VCR to two or more TV sets. The combiner is actually a 2-way splitter used back-to-front. If a masthead amplifier is used, it is the output side of this device that is connected to the combiner. roughly balanced at the antenna. The risk of intermodulation is much increased if there is a weak channel in the same band as stronger channels. Mixing signals A new problem for installers has cropped up in recent years. The proliferation of video recorders has led some building owners to request that video signals be mixed with off-air signals so that their tenants can enjoy an extra "channel" or two. Mixing the signals generally works well, provided three requirements are met: (l). The incoming off-air signals are at approximately the same level as the output of the video recorder; (2). The antenna and video signals are both strong enough to withstand the losses (several dBµ) that take place in the mixing device; and (3) . The VCR output channel does not clash with any other channel detectable in the area. A weak fringe channel can interfere with the VCR output, even if it is useless for viewing. If all is well, the output of the video recorder can be taken back to the head end of the system and mixed with the incoming off-air signals. This is done in a "combiner", in reality a 2-way splitter used back to front. Fig.5 shows the details. If an MHA is being used, it is the output side of this device that is connected to the combiner. Even the best 2-way combiner will introduce a 3dBµ loss at VHF, and more at UHF. So the signals need to have at least this much level to spare before being combined. And of course, the comment about balancing the levels is probably more important here because VCR signals are less stable than off-air signals and are more subject to degradation by noise and distortion in the system. Once the video has been mixed with the off-air signals, the combined programs can be amplified and distributed around the building in the manner to be described next month. SC Fig.6: if the signal from the antenna is below the required level, it can be lifted using a masthead amplifier. The Hills MHB has a gain of about 30dB & can be fitted with a range of filters to attenuate unwanted signals. 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FAX: (02) S19 3868 FAX: (03) S43 2648 TOLL FREE MAIL ORDER t-lOTLINE F; : 1•r l\ \ , \'- "'~ <:~~ ' Errors and omrssrons excepted Pnces and specifications sut,wct to change ,BM ec " " " '"•"~"' '" "-•"'" :;:;.;::::;•,.:.:; :~ "f:!;'.~,.:.; ~~:~:~ CARD O~:~,; ~: ,~ \ ' ~ ~- ' .-- / ••=:, )~ ~ A /l,; >"1', · / ') ~ ·, Motors for electric vehicles There are many options when it comes to choosing motors for electric vehicles. Here's a guide to the various motor types, their advantages & their drawbacks. By GERRY NOLAN For petrol-heads, it's what's under the bonnet that counts - the grunt to dollar ratio. It's the horsepower that lays the rubber on the road - right? And for more horsepower, you want more cubic centimetres of engine, fuel injection, turbocharging and to hell with efficiency. Electric vehicle owners will talk 10 SILICON CHIP about "watts" under the bonnet, motor efficiency (usually in the high nineties), AC or DC, rare earth magnets, power to weight ratios, and commutated or brushless motors. But, regardless, the talk will still be about the driving force - the motor. While we're at it, the conversion from horsepower to watts is lHP = 746 watts. So your 190HP family car engine is now rated at 142 kilowatts. How electric motors work As you may know, it was Andre Marie Ampere who said that a current carrying conductor placed in a magnetic field will be deflected. The calculation of this deflecting force (F) is expressed by the "Bli" rule: F = B(li) where a conductor of length 1, carrying a current i, is located in a magnetic field B (assuming that the con~ ductor is perpendicular to BJ. The direction of the force is obtained by the left-hand rule, which is illustrated in Fig.1. The converse is also true - that is, if we move a conductor so that it "cuts" Left: the Australian-designed "Solar Star II" sports car. The kevlar front body is in place but the curved section behind the driver has yet to receive the solar panels. a magnetic field, an electric current will be generated. Faraday first defined this law and the right-hand rule that goes with it. It is this principle that we employ when using our electric motor for regenerative braking to recharge the energy source. If we make a large number of conducting loops, wrap them around an armature and connect them to a commutator so that the current is "switched" to remain in the same direction (with respect to the magnetic field), we can produce a constant deflecting force that will be converted into rotary motion of the armature and be usable as a driving force - a motor, in fact . A single coil is shown diagrammatically in Fig.3 and a cross-section of a DC commutator motor is shown in Fig.2, with all the parts labelled. From this simple discussion it will be apparent that the motor deflecting force or "power" will be increased by increasing the magnetic field strength, the number of turns on the armature and the armature current. Physical limits to these increases will be the size of the motor and the ability to cool it. Many other factors such as the number of field windings, number of poles, speed of armature (rpm), inductive losses, FR losses and so on will also help determine the motor's power output. A modified Pope motor replaces the engine and gearbox under the centre console of the Sydney University Susuki Carry Van. Force F Flux 8 -'----Current i Fig.1: the left hand rule will indicate the direction of the force when a conductor carrying current I is perpendicular to a magnetic field B. Parts of a DC motor Evolution of motors Recently, I had the somewhat bemusing experience of being told by an electrical engineer that he "did not know" if the electric motor he was using was AC or DC. What would you call a motor that ran with a DC input pulse rate of up to 12kHz? Earlier "classical" motors, millions of which are still in service, satisfy these criteria: they operate from pure DC or AC sinewave and can start and run without electronic controllers. However, it is unrealistic to talk about motors for vehicles without controllers. Much of the development on con- trollers to provide adjustable speed and power was carried out on the "classical " motors. As you can see from Fig.4, the three classical motors all have wound fields. The DC commutator and AC synchronous motors have wound armatures and require brushes, while the AC induction motor has a wound field only. The next stage of evolution is shown in Fig.5, where the field windings of the DC motor and the armature windings of the AC motor are replaced by permanent magnets (PM). This resulted in the brushless AC motor but the DC motor had to have the rotor and stator transposed, as shown in Fig.6, before it could be brushless. Why the strong push to get rid of Left-hand rule Armature core Annatuce w;,a;,g //r~··.~1~ L•:::g::(: r ( fo ,_ Field Poles .. - ~ - -- i I ·, /✓~-~I·- " \ I · ' Shaft 1 .. Rotation .._ ,' I ~ Pole core / ',·- Pole face / '• - __ , ___ . · · "'-· wlodlogs) · > / 7"-···· z------=1--------"') Trailing pole tip Field yoke (also makes stator) Fig.2: cross section of a DC motor showing the DC poles & armature. MAY 1991 11 Simple AC motor Armature winding s \ Field poles )('-~~=-.--- Brushes / To external circuit Fig.3: this diagram shows the basic principle of a simple motor. Note that that the armature winding rotates in a magnetic field. The brushes & commutator ensure current reversal in the armature winding as the armature rotates past the poles. commutators, slip-rings and brushes? Although commutator/brush systems are reliable, well-proven and resilient, they are also dirty, noisy and require regular maintenance. In addition, commutator speed is limited, they produce radio frequency interference (RFI), the brush gear takes up a lot of space and they can be difficult to cool. Anyone who has had to "bed-in" the brushes or clean the commutators on large electric motors will really appreciate the advent of brushless motors. Commutator motors are also out of DC DC This is the Swiss Brusa AC induction motor that powers the "Solar Star 11" sports runabout (see opposite page). There are many types of motors and hybrids, from tiny robot motors to the giant motors used in coal loaders. Virtually all of them can be found in one of the categories listed below and we'll look at each one briefly: • DC commutator (series, shunt and compound); • AC induction; • AC synchronous; • Brushless PM (permanent magnet) DC; • Brushless PM AC synchronous motor. The series DC commutator motor is widely used for traction applications (eg, trains, trams, forklifts) because of its high torque at low revolutions. However, because it uses brushes and a commutator and has fairly low efficiency (84% average), it is not a good 3 phase AC 3 phase AC the question when volatile gases are present as, for example, in the ventilation of fuel tank evaporation spaces, where the slightest spark will cause a disaster. Using permanent magnets instead of a wound rotor also cuts out the FR losses that inevitably occur in a conventional field winding. Types of motor LL~ . ·--, .. ~ ' Wound field DC commutator AC synchronous AC induction Fig.4: the three classical motors all have wound fields. The DC commutator and AC synchronous motors have wound armatures and require brushes, while the AC induction motor has a wound field only. 12 SILICON CHIP Solar sports car takes shape The Australian designed "Solar Star II" is the answer to critics who say solar cars are not practical. It not only doesn't look like a solar powered car but it should have performance rivalling that of conventional cars. By GERRY NOLAN My first impression of this car was one of shock. This couldn't be a solar car. Where was the familiar cockroach look and the spindly, narrow bicycle wheels? At first glance, the "Solar Star II" looks like an expensive, low-slung sports car. Then, when you look closely, you find that it really is a sports car. And it has the look of an instant classic, like the MG TF and Austin Healy sports cars. Using 10 Alco 12V, 75Ah deep cycle batteries, each weighing 19.2kg, the car will weigh about 400kg. A roomy 2-seater with hightech suspension, low profile tyres and streamlined, lightweight kevlar body, it will have a top speed of 130- This view shows the battery mounting position which is forward of the rear wheels (solar panel removed). 140km/h and acceleration equal to or better than more mundane vehicles. Designer and builder Les Pukloswski, of Huntington Enterprises, built the car in only a few months using the Ford GT40 as a body mould. This has enabled him to fit a stock windscreen and other parts, saving many thousands of dollars and months of development time. The "Solar Star II" has literally been built from a sketch Les did in few minutes when Leon Howe of Star Micronics asked him to come up with some ideas late last year. The 18kW Brusa-controlled, 3phase AC induction motor, rotating at up to 11,000 rpm will power the rear wheels through two stages of toothed belt drive, giving an 8:1 reduction to a 1:1 lightweight differential. The car has disc brakes front and rear and a fully adjustable, hightech suspension with magnesium uprights that can be raised and lowered to suit different surfaces and running regimes. At present, the car is using 24 panels of the 14% efficient ShowaArco monocrystalline solar panels from Dimitri Lajovic's 1990 World Les Puklowski demonstrates how the solar panels will fit the curve of the mounting board. At the top of the page is a computer generated artist's impression of the "Solar Star 11". Solar Challenge "Alarus", but Leon Howe is trying to obtain the 18% efficient panels developed by the University of NSW. This would save the necessity of attaching an additional solar array for long distance cruising. After being displayed at PC 91 and racing at the Gold Coast Indy Grand Prix, the car is presently undergoing registration procedures and you·r correspondent is waiting impatiently to get behind the wheel for a day. "Solar Star II" is shaping to be a really "practical" vehicle and an extremely attractive one at that. The question is, will Star Micronics go into mass production? MAY 1991 13 DC 3 phase AC ( ·. . ) ··- .. __ __ --:>"' PM DC commutator AC PM/reluctance hybrid Fig.5: these 'diagrams show how the field windings in a DC motor and the armature windings in an AC motor can be replaced by permanent magnets (PM). This gives rise to the brushless AC motor, as shown at right, but the DC motor still requires brushes. option for electric vehicles. With a fixed AC supply, induction motors run at an essentially constant speed which means that their use in traction applications has been limited. However, by using solid state controllers to produce a variable frequency 3-phase AC supply, they become a practical option. The same comments can be made about AC synchronous motors which have a DC-energised field or a permanent magnet rotor. Brushless DC motors have always been a misnomer. Originally developed by the Japanese for use in turntables and tape decks (where conventional brush motors created audio interference), they really are AC motors with the field commutation and speed control performed by switching transistors. They have always been very good for applications requiring low power. However, with the availability of new materials for use in the construction of motors , particularly rare earth magnets, and more effective electronic control systems, brushless motors are now available at much higher powers. Only a few years ago, engineers believed that the upper power limit of the brushless DC PM motor was around lOkW but now ZOkW motors are available. Brushless PM motors , both AC and DC , now use rare earth magnets such as samarium-cobalt and neodymiumiron-boron (Nd-Fe-BJ and will soon 14 SILICON CHIP 3 phase squarewave or sinewave PM brushless DC Fig.6: the brushless DC motor is obtained by going one step further and transposing the rotor and stator. be using an improved grade ofNd-FeB called " UGISTAB", marketed by Aimants Ugimag in the UK. When compared with Nd-Fe -B magnets , which are in themselves much stronger than anything else, the UGISTAB magnet has increased coercivity, greater resistance to corrosion and better magnetic stability over a wider temperature range. Brushless PM motors with peak efficiencies of up to 97% and power to weight ratios of up to 3kW /kg are now available. Of the 36 vehicles that started in the 1990 World Solar Challenge, 28 used brushless DC PM motors and three used brushless AC PM motors. UNIQ motors, mentioned in the January 1991 issue of SILICON CHIP, are produced by Unique Mobility in Colorado, USA. They achieve a high power-to-weight ratio and efficiency by a unique arrangement in which radially positioned pe,manent magnets are mounted on either or both of two hollow cylindrical rotor elements which coaxially "sandwich" a thin hollow stator. In this way, the stator windings are exposed to the entire magnetic flux. UNIQ motors were used in seven of the vehicles in the World Solar Challenge, in sizes varying from 1.5kW to 15kW. What type of motor? As indicated by our discussion so far in this article, there _is no "best" motor. The motor selection for an electric vehicle is made on the basis of efficiency, weight and cost. You could clean up that old electric motor that's been lying around in your workshop for years and build something around it, or you could decide on the type of vehicle you want, what you want to do with it, what you're going to use for energy and then decide on the motor that will best suit your requirements, for the price. Putting all this in a formal way, the vehicle factors which determine the size of motor are: the typical driving cycle; vehicle limits (type, weight and payload); and type and weight of the energy source. Typical driving cycles will vary enormously. As mentioned in a previous article, surveys show that around 90% of all daily 1-way car trips are less than 35km long with over 50% being less than 10km long. So let's look at what you would need to consider in designing a pr;i.ct'ical electric vehicle. Although we are not designing a sports car, for safety reasons, we will want to be able to stay with most other vehicles when accelerating away from the lights. This will require a motor with high torque at low speeds. On the other hand, we need to stay with traffic on the freeway too, so we don't want the power dropping off as the motor revs increase. Let's just say we want a range of 7080km with fairly snappy acceleration and a top speed of at least 80km/h. Typically, the urban vehicle carries an average of only 1.2 people but, as there aren't many 0.2 people around, In fact, Leon Howe of Star Micronics, sponsor of the "Solar Star", is so determined to prove that solar/electric vehicles are a viable alternative that he has already commissioned Les Puklowski of Huntington Enterprises in Sydney to build Report by GERRY NOLAN "Solar Star 11 ", a 2-seater solar assisted city sports runabout. was a resounding success in that it Twenty-six vehicles participated "We wuz robbed!" is the cry heard has shown clearly which questions in the event and were powered by from the solar car people. to ask and which problems must be energy sources that included elecThe 1991 Energy Challenge, solved for the next event, in January tric, solar, hydrogen , ethanol, steam, which was sponsored by the NSW 1992. compressed natural gas (CNG), Department of Minerals and Energy, No doubt the emphasis on practiliquid petroleum gas (LPG), human took place over the weekend of 18cality will ~ncourage the CNG enpower and hybrid power. 20th January. Ultimately, the award The National Roads and Motorwas to go to "the entrant which prothusiasts but the solar car people are asking why they were encourists Association (NRMA) Technical vided the most personal mobility (that is, practical and economical) aged to compete if there was never Panel, headed by John Ward, Manfor the least environmental impact." any chance that they could win. ager of Technical Services, awarded On this reasoning, the first prize Certainly, their frustration and diseach vehicle a GGI number, which appointment is a spur to prove that indicated the environmental impact was awarded to the Alsco Linen laundry truck, using compressed natural solar vehicles can be practical as the vehicle had in moving a payload well as economical and non-pollutover a distance. The perfect score gas (CNG), primarily because of its relatively large payload which put it ing. was zero, which only the solar and at the top of the class for practihuman powered vehicles were able to achieve. cality. Notwithstanding this, the so"Solar Star", the fastest solar lar cars claimed to be the clear car on earth, covered the total winners on the basis of the race distance of 373.1 km in a Greenhouse Gas Index (GGI) cumulative time of 7hrs 23min, and fuel/energy efficiency. Only giving it an average speed of one car, a CNG fuelled Toyota 50.5km/h. On several occaCamry, finished in front of the sions, the speed limit of 11 0km/ "Solar Star". h was attained on the freeway sections of the race. Figures However, to put the event and the results into perspective, recently released by the NRMA Hans Tholstrup has asked that show that the average speed people remember his statement attained on the Princes Highway, for all vehicles, is 64km/h. prior to the event: "the 1991 Energy Challenge is a world first Although the "Solar Star" only and will be a demonstration run carried one person (as did all gathering knowledge for a scithe solar vehicles, the human powered vehicles and most of entific event in 1992". In other words, neither the formula for the other vehicles), it certainly gave the driver, Manfred calculating the winner, or the methods of measuring the variHerman, "a high degree of perThe winner of the 1991 Energy Challenge, the ous parameters have yet been sonal mobility" - the basis for ALSCO Linen Mistubishi Canter, leaves the finalised. "practicality" written into the starting gate at Newcastle. It was powered by compressed natural gas (CNG). regulations. Tholstrup feels that the event Controversial results in the 1991 Energy Challenge we'll need to allow for the vehicle payload to be two people with briefcases and sportsgear or overnight bags, say about 175-Z00kg all-up. The vehicle weight itself is a major consideration. By using the lightweight, high strength fibres that are now available, vehicle weight can be kept to a mm1mum. A reasonable empty weight for a 2-seater would be about 180-220kg. With a range of 70-80km, using about 70-80Wh/km, we'll need 4.96.4kWh of storage capacity. Assuming lead-acid batteries and an energy density of 40Wh/kg (conservative but realistic), we'll require 122.5-160kg of batteries. This gives us a total vehicle gross weight of 480-5 70kg, say around 525kg. A vehicle of this weight will use about 75Wh/km at an average 60km/ h; ie, at a rate of 4.5kW. Taking into MAY 1991 15 account inefficiencies and the need for extra power to accelerate and pass, we will need a ·motor of around 56kW power output. Using these figures as a rough ruleof-thumb, you can calculate the size of motor you will require if you change any of the factors involved. But beware the snowballing effect! If you increase the range required you'll increase the battery capacity required and the weight will go up, which will require a more powerful motor, which will require a larger battery capacity, and so on. These parameters lend themselves very well to computer modelling and a lot ofresearch time and effort can be saved by optimising the motor requirements for a particular vehicle application before investing time and money in hardware. Other performance factors that will affect the choice of a motor are: regenerative braking capability, rapid and smooth motor control and braking, high torque at all operating speeds, high propulsion efficiency over the typical driving cycle, high power to weight ratio , reliability and cost. A 375 watt 24 volt electric motor powers a personal scooter made by Ormonde Engineering at Wentworthville NSW. The 1400 rpm motor is mounted under the seat and has a 13:1 reduction to the differential, Reads like an advertising copywriter's idea of the dream motor doesn't it? Well, the advances in electric motor and controller design over the last decade or so have made these at- APRIL SPECIALS FROM RAYTEC NEW! AMP HOUR METER! MOTHERBOARDS 12MHz 31MHz 12MHz 16MHz 16MHz $499 INC. PACK. AND POST. BATTERIES DON'T JUST Never again lose track of your battery condition. Our AMP HOUR meter shows total discharge of any battery bank in AMP HOURS, then returns to zero as the battery bank is charged. Overcharge condition is also shown, resetting to zero AMP HOURS when discharge commences. Suitable for 12V and above and currents up to 100 AMPS. (Higher current models available.) Current drain of meter 40mA. 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Mail coupon to: FREEPOST 25 Silicon Chip Publications PO Box 139 Collaroy Beach NSW 2097 No stamp required in Australia VINTAGE RADIO By JOHN HILL All about regenerative receivers A few weeks ago, I bought what I consider to be a rare receiver - a 4-valve Howard. This is a 240V mains-operated regenerative set of early 1932 vintage and was actually in working order. My newly acquired Howard receiver is a stately console model standing on turned legs. Unfortunately, someone has had a half-hearted attempt at restoring the cabinet but I guess it will respond OK to treatment later on. Console models with turned legs are indeed scarce and while I probably paid more than the set was worth (from an antique dealer}, I am quite pleased to have it as part ofmy collection. When something really collectable comes along I don't mind paying the price, especially when the receiver is complete, in reasonable condition and working. Most of the receivers in my collection are superhets, many of which date back to the early 1930s. While some superhets were made in the late 1920s, they were few and far between. The majority of late 1920s receivers were of the TRF (tuned radio frequency) type , either with or without regeneration. There were other, simpler, regenerative sets consisting of a detector with reaction plus one or two stages of audio amplification. This type of receiver was often described as having a "leaky grid regenerative detector". In this month's Vintage Radio column , I would like to discuss "regeneration", because it played such an important role in early radio. Regeneration is one of those rare examples where we apparently get something for nothing. (But we don't really. Ed.) Radio receivers before the valve era had only crude amplification systems. During reception, coherers and external battery-powered relays operated so that Morse signals could be recorded or heard. Later, crystal detectors and headphones increased the sensitivity of these early receiver-s by a considerable margin. But transmission distances were still relatively short, because the receiver operated only on the strength of the signal received by its aerial. When receiving valves came into general use, it was a giant step forward for the triode valve not only rectified or detected the radio fre quency signal, but amplified it as well. Regeneration Regenerative type receivers usually have bulbous-shaped valves that were a characteristic of that era. This set is an early 1932 model and is mains operated. It has been fully restored to "as-new" condition. 18 SILICON CHIP Shortly after, some clever person discovered (possibly by accident) that some receivers broke into oscillation (squeals) under certain conditions and that this effect could be controlled and used to great advantage. This was the beginning of an era when the regenerative receiver became quite popular. What happens in a simple regenerative circuit is this. Some of the radio frequency energy in the anode circuit of the detector valve is diverted through a coil (regeneration coil) situated close to the tuning coil of that same valve. This induces a stronger valve regenerative receiver operating a pair of headphones was a standard project for any lad graduating from his first home-built crystal set. A receiver of this type could almost be built from scrap parts plus a few other bits and pieces, and was always a good activity for any young radio enthusiast to embark on. The amazing aspect of such a simple radio set was the fact that, with so few components, it could pull in any station that a larger 4 or 5-valve receiver could. However, the listener was always restricted to headphones. Such performance would not have been possible from one valve without regeneration. Basic limitations This 3-valve regenerative receiver from the mid 1920s was one of the many kit types available at the time. It consists of a detector followed by two stages of transformer coupled audio. Regeneration has its limitations. Although the feedback control can often bring an inaudible station up to quite listenable volume, when it goes beyond its practical limit the set will break into oscillation and squeal loudly - and often most uncomfortably - in the headphones. When a regenerative receiver oscillates, it has the annoying habit of transmitting a signal from the set's aerial. Therefore, if the receiver is oscillating on a particular station, other receivers in the neighbourhood, tuned to the same station, will receive the signal radiated from the regenerative set. For this reason, there was plenty of radio interference from regenerative sets in the 1920s and 30s. TRF receivers Simple regenerative receivers are easily identified by their single gang tuning capacitor. Note the grid leak resistor and capacitor immediately to the left. signal on the grid of the valve and the amplification factor of the detector stage is increased many times - perhaps many hundreds of times. Also, since the signal being fed back is at the same frequency as the incoming signal, the increased gain occurs at that frequency only, resulting in much improved selectivity. So we score twice - increased gain and improved selectivity. There are numerous ways of controlling the amount of feedback to the regeneration coil. It can be controlled by swinging coils (ie, by physically altering the distance between the regeneration coil and the tuning coil), by a variable capacitor in series with the feedback coil, by a potentiometer to control the anode voltage to the valve and, in some instances, by a rheostat in the filament circuit. There were other variations and some systems worked better than others. Many exaggerated claims were made regarding various reaction circuits, but time seems to have proven that the "Reinartz" circuit was the most extensively used. Fifty to sixty years ago, a single- Mention was made earlier to TRF receivers with regeneration. A typical TRF receiver may have two stages of radio frequency amplification . prior to a detector with reaction. This would then be followed by one or two stages of audio frequency amplification ahead of the loudspeaker. A regenerative set w ith a stage of radio frequency amplification will not interfere with other radios if the set oscillates. An RF stage ahead of the detector effectively isolates the regeneration circuit from the receiver's aerial. Therefore, regenerative receivers of this type were considered better than the simple types without an RF stage. Simple regenerative detector type receivers with a stage or two of transformer coupled audio can be easily recognised by the fact that they have MAY 1991 19 The aerial taps on a regenerative receiver are used to control the receiver's selectivity. While this scheme works, it's a nuisance having to fiddle with the connections as they are at the back of the set. The most common method of controlling regeneration is by using a lO0pF variable capacitor in series with the feedback coil. Other methods involved variable coil coupling using "swinging coils" and using a potentiometer to control the anode voltage to the valve. receiver. Thus, in practice, a compromise must be struck between selectivity and volume level. As already noted, regeneration noticeably improves selectivity, particularly if it is brought up to a level where the set is just short of breaking into oscillation. On the debit side, however, when operating at the point of oscillation, a certain amount of distortion is present and thus sound fidelity is compromised when the control is used in this manner. Another oddity with a regenerative receiver is that the amount of regenAerial taps eration required varies depending on Most reaction sets had several aerial the dial position. More is needed at the low frequency end of the dial than taps and using these to advantage at the high frequency end. This means would make the set more selective. However, the looser the aerial cou- that the control cannot be left at a particular setting. Instead, it must be pling, the weaker the signal becomes, particularly if it is only a 2 or 3-valve constantly manipulated in accordance with the strength of the station and its position on the dial. REGENERATION Still another disadCONTROL FEEDBACK REGUl.j\TES vantage with a simple set COIL FEEDBACK AFC is that the regeneration control is not always capable of controlling the volume of strong local stations and often the control cannot be backed HEADPHONES off enough to permit comfortable volume levels when receiving powerful signals. This can be BB+ remedied by selecting another aerial tap, disFig.I: basic circuit for a "leaky grid" regenerative connecting the earth or receiver. Note the variable capacitor which is fitting a shorter aerial. used to control the amount of feedback. only a single gang tuning capacitor. If a set has an RF stage, it will require a 2-gang capacitor. An upmarket TRF set could have as many as four tuning capacitors, while superhets have a minimum of two. In spite of the improved selectivity provided by regeneration, regenerative receivers with only one tuned circuit were not as good as the larger TRF or superhet receivers. This limitation became increasingly evident as more and more stations crowded into the broadcast band. 20 SILICON CHIP All things considered, these "remedies" are really rather tedious. A variation of this problem involved selectivity. If the regeneration control was advanced to maximum to eliminate an interfering station, it could happen that the signal was then too loud. As before, fiddling with the aerial taps could solve the problem. The better types of regenerative receivers had two controls: a regeneration control and a potentiometer controlling the input to the grid of the first audio valve. Sets of this type were much more manageable and strong signals could be controlled without having to fiddle with the aerial coil tappings at the back of the receiver. Although regeneration was used originally with triode valves (the only types in use at the time), it is also compatible with other valve types. Many regenerative sets employing pentode valves were designed during the 1930s and 1940s and these simple receivers worked very well indeed. These valves offered higher amplification factors than the old triodes. So far I have not painted a very good picture regarding regenerative type receivers. Compared to the superhets that followed during the 1930s, the old regenerative sets left much to be desired but that doesn't mean they are not worth collecting. On the contrary - they are very collectable! Any TRF receiver with a reaction circuit is well worth having. If it is restored to good working order and is Resurrection Radio Vintage Wireless Specialists Repairs - Restoratio11 - 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. Early regenerative type receivers used "swinging coils" for regeneration control (ie, the physical distance between the coils was altered to vary the coupling). Parts are available for the enthusiasts including over 900 valve types, high voltage capacitors, transformers, dial glasses, knobs, grille cloth etc. Circuit diagrams for most Australian makes and models. Send SAE for our catalogue. WANTED - Valves, Radios, etc. purchased for CASH Call in to our Showroom at: 51 Chapel Street, Windsor,Vic 3181 PO Box 1116 Telephone: (03) 529 5639 Even during the early post war period, "Reinartz" coils could still be bought for simple regenerative type receivers. However, most experimenters were happy to hand wind their own coils. used within its capabilities, it will give more than a reasonable account of itself. So too will any other regenerative set. The lack of selectivity may, in .s ome cases, prevent some stations from being listen ed to, but there will be others that will be received quite OK. The Howard vs the Seyon One ofmy old regenerative sets is a Seyon, a receiver I have mentioned many times in the past. It's not a very exciting set and to use it in my locality really requires a wave trap to block out the swamping effect of a close local station. It doesn't sound that good either, particularly when played through a horn speaker. But that's the way they were, so why use them with anything else? It is good to have these comparisons. The Seyon's big plus is the fact that it is mains operated. That effectively makes the 3-valve set only a 2-valve set (since the third valve is used as a rectifier), so one shouldn't expect too much from it in such circumstances. A lot of cheap regenerative radios didn't have much going for them. Now back to the old Howard that I bought recently. This set is a much better receiver than the Seyon in that it has a self-conta.ined loudspeaker, an extra valve and an additional volume control. The extra valve makes a considerable difference and allows the set to be made selective, yet still retain a reasonable level of volume on distant stations. By comparison, if the Seyon is made selective, the dial becomes strangely quiet on all but the strongest signals. The Howard also has the added advantage of an 8-inch electrodynamic loudspeaker and a console cabinet which acts as a good baffle for a speaker of that size. The result is surprisingly good audio quality. While it is not as listenable as some of my later model superhet consoles, the sound is quite acceptable and when compared to the average cassette-radio of today, it sounds magnificent. That's not bad when you think about it - a 60-year old radio receiver that sounds better than those most people listen to today. We will take a closer look at the old Howard in next month's Vintage Radio column. SC MAY1991 21 merges with Electr Two of Australia's leading computer peripheral companies have merged to become the major force in supplying high quality, low cost IBM compatible computers and add on cards; for all computer users. Electronic Solutions Managing Director Ian Hardwick, has welcomed the merger with Board Solutions, and has said, "the combination of the two companies · will offer far greater value for your dollar through greater use of resoucres, and also offer what he believes to be the most awsome "Customer Service" orientated company within the computer retail market". Try us once to experience the difference. Over the next few months you will notice some changes designed to focus on you the customer and to assist you make the decision to purchase from us easier, quicker and cheaperwithoutloosing any of the value. Board Solutions Managing Director Jeremy Smith and staffwill merge with Electronic Solutions on May 1st. "We believe this merger will further .enhance consumers confidence in two of Australias leading P.C. hardware companies being able to offer high quality products, service, and even further competitive pricing". MergerMadn ( F~o~; B;a;d iocTEcE:d;~;i-D-riv; i I 1 I I I Toshiba 1.2Mb external floppy drive (Complete with cables etc.) WAS $399.00 this month $299.00 SAVE $100.00 I 1 I I I Enquire about our entire range of external drives ~-----------------~------~ VIDEOCARDS I. 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Merger Madness Specials - This month only or while stocks last YOUR GUARANTEE OF SATISFACTION: WHOLESALE ENQUIRIES * All products carry a 14 day money back guarantee ( except software and hard disks). WELCOME $1795.00 $2395.00 * All prices include sales tax. * All motherboards carry a full 12 month warranty. '' All cards come with full documentation ·* All other products carry a full 3 month warranty. Due to Technical advances, products we supply may in some cases vary from those pictured. In all cases the_ products supplied are guaranteed to perform to an equal or higher standard than those pictured $3395.00 oard Solutions P/L onic Solutions P/L ess Specials r------------------------------------: Laptop Comput~rs IAccura 328V f ·. ·, · to.. ;i,;.• :·'" - ·~/ . .::,:.•.y<•/ij'.}i:-·,,;. :;.,,c-;,"':<tt~>·-:~-::·•··.""""''"'"' 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Battery power will provide up to three hours of continious use. There is also a standby 1.mode so that power can be easily conserved. ~------------------------------------- Accura 101 If you are always on the move then this notebook computer is for you. Now for under $2,000 you need never be without your computer. The Accura uses the 80C86 processor which is nearly three times faster than an IBM XT. You will be able to store a large amount of data on the internal 20Mb hard disk. This tiny unit only weighs 3.5kgs. Other Specifications: AC adapter included. Factory installed Nicad battery pack. 640Kb of memory expandable to 1Mb. Supertwist CGA display. Dual RS-232 serial ports. Parallel and external CGA ports. Inbuilt 3.5" 720k disk drive. Only $1995.00 ~-------------------· 1 The 1991 Summer Catalogue is now available, send us this I coupon to receive your FREE copy: II Mr/Mrs/Ms:- - - - - - - - - - Electronic Solutions P/L 5 Waltham St Artarmon 2064 PO Box 426 Gladesville 2111 Telephone: (02) 906 6666 Fax: (02) 906 5222 1Address: _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ 1 Suburb: _ _ _ _ _ _ _ _ _ State: _ _ _ _ _ Postc 1 Note: Please do not send back this coupon if you pur.chased from us in reviously issued card to be included on the mailing list, you will r Add sparkle to your tapes with this Stereo Audio Expander This little project will add sparkle to your music cassettes, video or FM receiver by increasing the dynamic range of the signal. It uses only a handful of parts and runs from a 12V AC plugpack. By DARREN YATES 24 SILICON CHIP AVE you ever compared the sound from your compact disc player with your cassette deck or video? The difference is pretty much chalk and cheese! Unless you have one of the new VHS hifi video recorders, compact discs represent the closest thing to "perfect sound" by a big margin. The first thing you notice when listening to an ordinary audio or video tape is the background hiss, which is quite audible on some of the older models. And, of course, tape hiss will be quite audible if your cassette deck does not have Dolby noise reduction. What we are really talking about here is dynamic range. This is the range between the softest and loudest signals that can be reproduced by a system. In practical terms, the loudest signal is the highest level that can be reproduced without distortion while the softest signal represents the lowest level that can be discerned above the noise floor of the recording medium; ie, tape, disc, etc. Compact disc players have a dynamic range of about 90dB . This means that the ratio between the loudest and smallest signals coming out of your disc player is about 30,000:1. By contrast, the dynamic range- of an audio cassette deck with Dolby is about 50dB or about 300:1. Based on these figures, it's not hard to understand why CDs produce a far greater H OUTPUT VARIABLE TRANSCONDUCTANCE AMPLIFIEII INPUT BUFFER VARIABLE TRANSCONDUCTANCE AMPLIFIER DC BIAS' EXPANSION COMPRESSION Fig.l(a): basic scheme for an audio compressor. It consists of a variable transconductance amplifier in the negative feedback loop of an op amp. range of sound levels than audio tapes (ie, they have a greater dynamic range). Recording problems These days, most music is recorded on CDs and audio tape. But if you try to copy a CD straight onto audio tape, two things will happen. First, very quiet passages on a CD will disappear into the hiss and noise of the audio cassette; second, the loud passages will become distorted. Both of these problems occur because of the restricted dynamic range of audio cassettes. You can think of it as trying to fit a big box into a smaller one. You can't do it unless you crush it and bend it all over the place. Signal compression Fig.l(b): to achieve audio expansion, we simply swap the VTA from the feedback loop to the input circuit of the op amp stage. The larger the signal, the lower the resistance of the VTA and the higher the gain of the op amp. and a few well-known FM radio stations, you will notice that there is very little difference between the loud a.nd soft passages. It's particularly noticeable on the sound track of many video tapes , especially when there is a quiet passage, how the background hiss slowly increases as if someone is turning up the volume. You'll also notice that as soon as someone speaks, for a very short time afterwards, the sound level will be quite high and then drop to its normal level. This is an example of a compressed signal. It may squeeze more sound information onto the tape but what results is a fairly constant sound level which bears little resemblance to reality. Wouldn't it be nice if we could expand this range out again, back to its original level? This Audio Expander does just that. Essentially, it performs the reverse function of the CD Compressor project by "stretching" the compressed dynamic range out again. It can thus be used to complement the CD Compressor or to expand any music signal that has undergone compression during recording or transmission. NE572 AG C RECOVERY+ BUFFER C ATTACK+ - - t - - 1 RECTIFIER Fig.2: inside the NE572 compander IC. The incoming audio signal is fed to a gain cell (~G) & also to a rectifier stage to derive a control current. Signal-to-noise ratio (at 3Vpp & 1kHz): flat, -84.SdB; 20-20kHz, -88.SdB; A-weighted, -104d8 Fig.1 shows the basic scheme. In Fig. l(a), we achieve compression by connecting a variable transconductance amplifier (VTA) in the negative feedback loop of an op amp. The VTA acts like a voltage controlled resistor which is dependent on the incoming signal level. The larger the signal, the lower the resistance of the VTA and the lower the gain of the op amp , so that the resulting signal level remains fairly constant. In Fig. l(b), we simply swap the VTA from the feedback loop to the input circuit. It still works in the same way: an increasing voltage causes an increase in gain or a decrease in impedance in ·the VTA. The difference is that we now use this to produce an overall increase in the gain of the following op amp stage. Input impedance: 50kQ The NE572 compander IC Typical gain (at 1kHz): -17dB at 10mV input; -13.1dB at 20mV; -5dB at 50mV; 1d8 at 100mV; 6.9d8 at 200mV; 14.6dB at 500mV The Audio Expander has been designed around the NE572 stereo compander IC; the same chip used in The CD Compressor project described in the March 1989 issue of SILICON CHIP solved this problem by "shrinking the box". In other words, it compressed the 90dB dynamic range of the compact disc down to the 50dB range of audio tape by proportionally adjusting the level of the signal. ' If you listen carefully to many prerecorded video and audio cassettes Specifications Frequency response: 20Hz-80kHz (-3dB) Total harmonic distortion (THD) at 3Vpp: 0.9% at 100Hz; 0.125% at 1kHz; .08% at 10kHz; .09% at 20kHz MAY1991 25 100pF .-------------•12V 2.2 50VW - + LEFT~ INPUT .,. 18k 16 + ~ 100k 100k .,. .,. IC2a NE572N LEFT OUTPUT 4 + 10 + 50VWJ 16VWr 1 100pF 2.2 50VWI - RIGHT~ INPUT 100k 18k + 100k BYPASS 11 IC2b T" ~ S1b 10 12 t GND GND f 0--0 12VAC PLUG-PACK OUT 0.1 1k IN 470 25VW AUDIO EXPANDER Fig.3: the circuit consists of two identical channels plus a power supply. For the left channel, the incoming audio is buffered by ICla & then fed to the NE572 compander IC. The higher the input signal, the lower the impedance of the gain cell in IC2a & the higher the gain of the following op amp stage (IClb). the CD Compressor project. We published an article in the March 1989 issue which gave the details of the NE572 but we shall briefly go over it again for readers who missed it. Take a look at Fig.2 ; this shows the internal sections of the IC. The three main sections are the rectifier, a buffer stage and a variable gain cell (~G). The latter can be thought of as the voltage controlled resistor. The input signal is fed to both the gain cell (~ G) and the rectifier. Depending on the signal level, the rectifier produces a proportional DC current which becomes the control signal. This signal is then fed to the buffer stage where two external capacitors are used to independently set the attack and decay response times. The buffered signal is then used to control the gain cell and this in turn 26 SILICON CHIP .,. 14 m m OUT RIGHT OUTPUT 2 2 IN 'T EXPAND controls the gain of the following external op amp stage mentioned previously. In use, the Audio Expander is simply installed in the line between the music source (eg, a cassette player) and your stereo amplifier. Once installed, it can be left permanently in position and then switched in and out of circuit as required, using the BYPASS switch. Circuit diagram Refer now to Fig.3 which shows all the circuit details. As you can see , it consists of two identical sections, one for each channel, so we'll just explain the right channel. The input is coupled to the circuit via a 2.2µF capacitor which is grounded on both sides by lO0kQ resistors. This sets the input impedance to 50kQ + - 0.1 OUT LED1 -12V· as well as providing a DC charge path for the capacitor to prevent "pops" when you first turn it on. Cl is a 4136 quad op amp which has a very low noise level and is also quite cheap. ICla is connected as a buffer stage and provides a low-impedance source for the compander IC (IC2a) so that the rectifier section doesn't load the signal down. As mentioned earlier, the buffered audio signal is fed to both the gain cell and the rectifier inside IC2a, via pins 7 and 3, respectively. The rectifier converts the AC audio signal into a proportional DC control voltage and feeds ·it to the buffer stage inside the NE572. The two capacitors on pins 4 and 2 (lµF and lOµF) set the attack and decay time constants. After buffering, the DC signal is used to control the impedance of the gain cell between pins 7 and 5 of IC2a. The higher the signal, the lower the impedance of the gain cell. This variable impedance is con- PARTS LIST , 1 Mount the two 3-terminal regulators so that their metal tabs face each other, as shown here. The prototype board used PC stakes to terminate external wiring leads but you can solder the leads direct to the board if you wish. nected in series with the input of amplifier stage IClb, and thus controls the gain of this stage. An 18kQ resistor in the negative feedback loop sets the maximum gain ofIClb, while the parallel l00pF ceramic capacitor rolls of the response above 80kHz. Thus, as the audio input signal increases, the gain ofIClb also increases and so we get signal expansion. DC bias for the non-inverting input of IClb is supplied by pin 6 of IC2a and is about +2.5V. This is filtered by a lkQ resistor and 2.ZµF electrolytic capacitor. Because of the bias arrangement used, the output from IClb (pin 4) is at a DC level of +2.5V. It is therefore RIGHT OUTPUT fed to the output socket via a 2.ZµF DC blocking capacitor and referenced to ground via a lO0kQ resistor. Switch Sla is included in the output path so that the expander can be switched in or out of operation. Power supply Power for the circuit is derived from a 12VAC plugpack supply. This feeds positive and negative half-wave rectifier diodes Dl and DZ, and the resulting DC is filtered by two 470µF capacitors. The resulting ±17V DC rails are then fed to positive and negative 3-terminal regulators to derive ±12V supply rails. Power on/ off indication is provided ·~ 1 plastic case, 150 x 90 x 50 1 PC board, code SC01105911 , 117 x 76mm 1 front panel label, 87 x 57mm 1 rear panel label, 10 x 20mm 1 SPST toggle switch 1 DPDT toggle switch 12 PC stakes 1 12VAC plugpack 1 5mm LED bezel 4 5mm spacers 4 panel mount RCA sockets 1 3.5mm panel mount phono socket Semiconductors 1 4136 quad low noise QP amp (IC1) 1 NE572 dual compander (IC2) 1 7812 + 12V regulator 1 7912 -12V regulator 2 1N4004 diodes (D1 ,D2) 1 5mm red LED (LED 1) Capacitors 2 4 70µF 16VW PC electrolytics 2 10µF 16VW PC electrolytics 10 2.2µF 50VW PC electrolytics 2· 1µF 50VW PC electrolytics 2 0.1 µF 63VW 5mm-pitch metallised polyester or monolithic 2 100pF ceramics Resistors (0.25W, 5%) 6 100kQ 2 3.3kQ 2 18kQ 3 1kQ Miscellaneous Hookup wire, tinned copper wire, screws, nuts, washers, 600mm of shielded audio cable. 2 2uF 7812 ••• OGI LEFT OUTPUT RIGHT INPUT LEFT INPUT. Fig.4: check the orientation of each part carefully as it is installed on the PC board (see Fig.3 for pinout details). Note the use of shielded cable for the connections between the PC board, S1 & the RCA input sockets. MAY1991 27 monolithic types can be used here. This done, solder in the two 100pF ceramic capacitors and the electrolytics. Again, use the overlay diagram to make sure you install each one in the correct place and that the electrolytics are installed with the correct polarity. Construction of the PC board can now be completed by soldering in the two 3-terminal regulators and the ICs. The circuit diagram (Fig.3) shows the pinouts for the 3-terminal regulators. When they are installed on the board, their metal tabs should face each other as shown in the photographs. Check the PC assembly carefully before moving on to the next stage. Final assembly The PC board is mounted on the lid of the case on 5mm brass spacers and secured with machine screws & .nuts. Keep all wiring leads as short as possible & take care to ensure that no shorts are created when the lid is screwed down. The unit is powered from a 12V AC plugpack supply. by LED 1 which is wired in series with a lkQ current limiting resistor across the -12V rail. Construction All the components , except for the front and rear panel sockets and switches, are mounted on a PC board coded SC0l 105911 and measuring 117 x 76mm. We strongly recommend that you use this board, as the circuit layout is critical for good performance. By using the board, you will avoid problems such as ground loops whioh can cause hum. Before mounting any of the parts, check that there are no shorts or breaks in any of the PC board tracks. If you find any problems, use a sharp knife or a spot of solder to repair the fault as appropriate. Once the board is correct, refer to the overlay diagram shown in Fig.4. Begin the assembly by installing PC stakes at the external wiring points, then solder in the wire links, diodes and resistors. Check the polarity of the diodes against the overlay diagram to make sure you get them the right way around. If you're unsure of the resistor colour codes, check them on your digital multimeter or refer to the accompanying table. Next, install the two 5mm-pitch 0. lµF capacitors. Either polyester or At this stage, you can attach the Dynamark labels to the front and rear panels of the specified plastic case. Note that the case is actually used upside down, so that the lid forms the base of the Audio Expander. The front panel label has been designed so that the large block letters "AUDIO EXPANDER" sit on the top surface of the case as shown in one of the photos. The "ON/OFF" label is affixed to the top right hand corner of the rear panel. Once the labels have been attached, you can use them as templates to drill holes for the switches, LED bezel and the four RCA sockets. The holes for the LED bezel and the bypass switch are 7mm diameter, while 9mm holes are used for the RCA sockets. In addition, you will have to drill a 7mm hole directly under the ON/OFF switch to accept the power socket. You'll probably find it easier to drill out small holes to begin with, and then slowly ream them out until you get a snug fit. The PC board is mounted on the lid of the case on 5mm spacers and secured using 3mm screws and nuts. These holes can be marked out by using the PC board as a template. Af- RESISTOR COLOUR CODES 0 0 0 0 0 28 No. Value 4-Band Code 5-Band Code 6 100kQ 18kQ 3.3kQ 1kQ brown black yellow gold brown grey orange gold orange orange red gold brown black red gold brown black black orange brown brown grey black red brown orange orange black brown brown brown black black brown brown 2 2 3 SILICON CHIP AUDIO EXPANDER ~ N POWER BYPASS + + INPUT EXPAND ~ ~ OUTPUT + + + + LEFT RIGHT LEFT RIGHT SPOT A BARGAIN Fig.5: here are the full-size artworks for the front & rear panels. THEN CONTACT US FOR MORE INFORMATION UHF REMOTE CONTROL: The one and only - $49.90 for the Rx+ Tx, extra Tx $17.00 ter drilling, mount the board in position, then complete the wiring as shown in Fig.4. Since the power requirements for the Audio Expander are quite small, light-duty hookup wire is sufficient for the power supply leads, for the LED wiring and for the wiring between the RCA sockets and S 1. Check the LED polarity carefully - its anode lead is the longer of the two and goes to the lkQ resistor. The earth lugs attached to the RCA sockets are all connected together by soldering them to a length of tinned copper wire. Once this has been installed, the rest of the wiring can be run using shielded cable, as shown in Fig.4. Try to keep all the leads as short as possible. The best way to do this is to install the wiring with the lid of the case lying flat on the benchtop and the case standing upright immediately behind it. Before applying power, go over your work carefully and check for wiring errors. If everything is OK, apply power and use your multimeter to check that the regulator outputs are at ±12V. If these voltages are incorrect, switch off immediately and check the power supply wiring. Finally, you can check the circuit operation by installing the Audio Expander between your cassette player and stereo amplifier. First, select BYPASS and check that the signal from the cassette player is unaffected. If that's OK, select EXPAND --you should immediately hear clean, crisp sound with some added dynamic range! SC 1 cl SMALL D.C. MOTORS: 3-12V, 2 for $5.00 LASER: Small gunsight/pointer IR NIGHT VIEWER KIT: Large prefocussed tube plus electronics kit, a few only at $200.00 CRYSTAL LOCKED ULTRASONIC: Has relay output, assembled PCB, open transducers and circutt - Top unit! $24.90 NICAD BATTERY PACKS: 7.2V/500mAH (6 pack of penlights). easy to seperate $11 .00 LASER MOTOR DEFLECTION KIT: 2 motors, 2 small mirrors, 2 wirewound pots (Speed control), plus simple cct/diagram $16.00 , .... DUAL ELEMENT PYROELECTRIC SENSOR: Not only 1/2 price of inferior single elements units, but comes with fresnel lens and cct. $9.90ea, 1O+ $9.00ea.. We have seen elsewhere for $20.00ea. MINI NIGHT VIEWER KIT: Small electronics kit, plus small prefocussed fibreoptically coupled tube wich responds to visible and IR light $359.00 BIGGER LASER: 5SmW Large laser HEAD plus potted 12V professional power supply: 1/2 price at $500.00 DYNAMIC MICROPHONE INSERTS: High quality, unidirectional $10.00 LASER TUBE: 350mm long, 2-3mW wtth clips, ballast resistor and spec's $150.00 1 [Z] T"' T"' g:i U') OATLEY ELECTRONICS 0 T"' T"' 0 0 0 INFRA-RED LASER DIODE POINTER • KIT: $99.00 STEPPER MOTORS: Driver cct. included $12.00, driver IC available. MASTHEAD AMPLIFIER: Proven performer, complete with casing $31 .00 (No plugpack). ~tl 1I HALL EFFECT IC'S: Info supplied, 10 for $20.00 6.5AH GEL BATTERY: Brand NEW, fresh stock, $29.99 Inc. P+P (Aust. only) Testing 0 VISIBLE LASER DIODE POINTER - KIT: $220, with the casing etc. $239.00 en ~ Fig.6: check your PC board against this full-size pattern before installing any of the parts. In particular, look for shorted tracks due to incomplete etching. PO BOX 89, OATLEY, NSW 2223 Telephone: (02) 579 4985 Fax No: (02) 570 7910 Certified p&p: $5 inAust. NZ (Ainnail):$10 Fax orders are accepted with credit card payments. Melbourne Distributor • Electronics World (03) 723 3860 or (03) 723 3094 MAY 1991 29 Control equipment via the telephone line with this Have you ever thought of controlling equipment via the humble telephone line? This project allows you to do just that. It can control up to nine separate appliances and can be connected either directly to the telephone line or acoustically coupled via your answering machine. By DARREN YATES & GREIG SHERIDAN Picture this: you 've just arrived at work and remembered that you have forgotten to turn the house alarm on. Do you drive all the way home again to turn it on or do you take a punt and hope your house doesn't get robbed? Or what about this? You go out The DTMF Decoder is designed to work with commercial DTMF encoders like the "Pocket Tone Dialler" from Dick Smith Electronics. 30 SILICON CHIP somewhere and decide that you're going to come home late , but you haven't put the front verandah light on. Obviously, you're not going to drive home just to turn a light on. But will you be able to find the steps, the door and the keyhole without tripping over the cat in the dark? Now if you're really clever, you can use a little mental telepathy and your problems are solved. For us more terrestrial beings, telephony is the next best thing! If we could use the telephone system like a remote control , then it would be a simple case of ringing home , pressing a couple of buttons and the job would be done. Most phones are now connected to the ISDN network, so you could quite easily ring up from England and turn on your house alarm in Australia! This may well be an extraordinary example but it can be achieved easily with our new DTMF (Dual-Tone Multiple Frequency) decoder board. You can use it to control up to nine appliances at once. In addition to the decoder board , you need a DTMF encoder like the one pictured in this article. This features a 12-key kepad and looks rather like a small pocket calculator except that it lacks a display. Each time you press a key, the device generates a dual-tone output and this can be heard via a small loudspeaker. In use, you carry the encoder with you while the decoder sits at home , connected to your telephone line and the appliances you wish to control. To switch an appliance on, you first dial your home number and the decoder automatically "answers". After that, it's simply a matter of pressing a couple of keys on the keypad; ie, the corresponding key plus the Enter (#) key. Want to turn three appliances on (or off) at the same time? No problem - just press the three corresponding keys in turn and then the # key. Want to turn an appliance off again? - just press its key and the # key again. Up to nine appliances can be controlled in this manner. To make the circuit as versatile as possible, the decoder board features four toggle outputs (ie, outputs which turn on or off at each press of the button) plus four momentary outputs (ie, outputs which turn on for only a brief period). It's up to you how you use them to control your appliances. DTMF decoders The DTMF standard has been around for a number of years now and is used in all new phone systems. However, encoding and decoding these frequenci es has not always been an easy task. The DTMF system works like this: All the parts for the DTMF Decoder are mounted on a PC board. It can either be plugged directly into the telephone line in parallel with your existing phone or acoustically coupled to the line via a telephone answering machine. if we take a 16-key keypad like the one shown in Fig.1, we can split it into four rows and four columns. Each key ha~ a particular position in this 4 x 4 matrix. For example, key "8" corresponds to row 3 and column 2. Now a particular frequency is set aside for each row and for each coiumn. For the four columns (1-4), the frequencies are 1209Hz, 1336Hz, 1477Hz and 1633Hz. For the four COL 1 897 COL 2 COL 3 COL 4 0000 0 0 0 0 ROW 1 STO OTMF 770 (H,) 852 [?J[IJQJ0 ROW 3 941 [:]000 ROW 4 1209 1338 1477 ROW 2 1833 STD OTMF (HJ) Fig.1: the row & column arrangement for a standard 4 x 4 keypad. Each key generates a unique combination of frequencies when pressed. rows, the frequencies are: 697Hz, 770Hz, 852Hz and 941Hz. When each key is pressed, the corresponding row and column frequencies are added together and fed down the phone line. For example, if we press the "8" key, the resulting output will consist of two frequencies - 85 2Hz and 1336Hz - on top of each other. These days, all the necessary tones are generated by a single IC. In fact , we featured a DTMF encoder in Garry Cratt's Amateur Radio column in the September 1989 issue of SILICON CHIP. It produced the correct pairing of tones depending upon which key you pressed, and used a single Texas Instruments TCM5089N IC. There's no longer much incentive to build your own encoder, however not when you can now buy professional DTMF encoding units for around $25. These units include both the keyboard and a small loudspeaker, which you hold up to the microphone of your telephone receiver. We used an encoder from Dick Smith Electronics while developing this project and it worked extremely well. Decoding Generating the necessary dual tGJnes is one thing but decoding them from amongst the noise and other rubbish on the phone line is something else. To do this properly in the past meant using eight phase locked loop (PLL) tone decoders (one for each frequency), plus some noise reduction circuitry on the input - all of which meant the number of ICs required to do a decent job went through the roof! That problem was solved when Motorola came up with the MC145436 DTMF decoder IC. The internals of this IC, shown in Fig.2, contain everything we need to decode the tones into a 4-bit binary code. It includes mains frequency and dial tone rejection, as well as eight switched capacitor filters to decode each frequency. It also has the necessary decoders to produce a 4-bit binary number at the MAY1991 31 Fig.2: block diagram of the MC145436 DTMF receiver IC. It includes mains frequency and dial tone rejection circuitry in the front end plus eight switched capacitor filters to decode each frequency into a 4-bit binary code. Timing for the chip is supplied by an external, low-cost 3.579545MHz crystal. output (which corresponds to the key pressed). Note that although 16-key keypads can be used with the MC145436 , our project has been designed to use the more commonly available 12-key encoders. Block Diagram To get a better overall view of how the DTMF Decoder works, let's take a look at the block diagram in Fig.3. The DTMF signal is fed to the circuit either directly from the telephone line, using a suitable isolation transformer, or from an electret microphone placed near the loudspeaker of an answering machine. Switch Sl selects either of these inputs and feeds the signal to the MC145436 (IC3), where all the initial decoding is done. The output of this IC is, as previously mentioned, a 4-bit binary code which corresponds to the key that was pressed. This 4-bit code is fed into a 4-to-16 decoder, which produces a single high output for each key. Since most keypads have only 12 keys, and since we also need three of these keys for entering, clearing and resetting the decoder, we have nine possible output lines. These nine lines plus the master 32 SILICON CHIP reset line are then fed into a userselect matrix. This allows you to decide which keys drive which particular output. The output driver section consists of nine open-collector transistors. Four of these lines are toggle outputs; ie, pressing a key turns a particular output on and pressing it again turns the output off. The other five are momentary, ie, a particular output is on for as long as the enter key is held down. The output drivers can be used to drive relay coils or optocouplers for Triacs, for example - which ever you prefer. The keypad If you buy a standard keypad, it will have the digits 1-9 plus "*", 0 and " # " symbols. The "*" and "#" symbols are fixed but the 10 remaining keys are available for you to swap and change to different outputs. For example, you can make keys 1-4 the toggle outputs or you can make 2, 3, 5 and 8 the toggle outputs, but more about this later. Circuit diagram Let's take a look at the circuit diagram ofFig.4 and see how it all works. Starting at the input, the phone line is connected via relay contacts RL1 to a 600Q:600Q isolation transformer. This transformer not only prevents high voltage DC from entering the circuit but also prevents us from superimposing any DC on the telephone lines. The relay contacts are normally open to simulate the telephone "on hook" condition (ie, no connection). When the phone rings, an AC voltage of about 50V appears across the phone line, and this normally activates the ringer or bell on an ordinary telephone. In our case, it activates a relay to couple the phone line to the isolating transformer. A .015µF capacitor AC couples the ring signal to a full-wave bridge rectifier formed by diodes D1-D4. The resulting DC voltage from the rectifier charges a l0µF capacitor via a l00kQ resistor. This is used to set a delay time so that the phone rings a number of times before the circuit "answers" the phone. The associated 1MQ resistor discharges the capacitor when the call has been answered. Zener diode ZD1 also plays a role in setting the time delay before the circuit "answers". Because it is connected in series with the base of transistor Ql, it ensures that Ql cannot turn on until there is around +12.6V across the capacitor (ie, 12V for the zener diode and 0.6V for the diode drop at the base of Ql). Once +12.6V has been reached, Ql turns on and pulls pin 2 of IC1 low. IC1 is a 555 timer connected in a monostable role. When pin 2 is pulled low, the 555 is set and its output at pin 3 switches high and turns on relay RLY1. This closes the relay contacts to give the "answered" or "offhook" condition. The lO0µF capacitor on pins 6 & 7 now charges via the 220kQ resistor until, after about 20 seconds, it reaches 2/3rds of the supply voltage (ie, +8V). During this time, the output at pin 3 is high, which means that you only have about 20 seconds to send the desired tone (or tones) down the line. When the v;oltage across the lO0µF timing capacitor reaches 2/3Vcc , pin 3 ofICl switches low again and the relay contacts open to give the on-hook condition. In other words, the circuit automatically hangs up after 20 seconds. Diodes D5 and D6 at the output of the 555 are there to protect it from voltage spikes or a latch-up condition TELEPHONE INPUT ISOLATION & ANSWERING OTMF DECODER 4 TO 16 DECODING MEMORY REGISTER (10 USER SELECTABLE OUTPUTS) SEm~ED . __ MASTER ___. RESET OUTPUT MATRIX MICROPHONE INPUT FROM ANSWERING MACHINE FIVE MOMENTARY OUTPUT DRIVERS which can occur when driving an inductive load such as a relay. Acoustic pickup The other way of coupling the DTMF signal to the circuit is via the FET-input mic insert (ie, by acoustically coupling it to the loudspeaker of your answering machine). If this method is used, your answering machine answers the phone and hangs up afterwards. IC2 is an LF351 op amp and is connected as a simple non-inverting AC amplifier with a gain of about 48. Its job is to amplify the signal from the microphone to a usable level. Switch Sl is used to select between the two inputs. The signal is then clipped by signal diodes D7 and DB, and then fed into the MC145436 (IC3). As already mentioned, this IC decodes dual frequency tones and generates a corresponding 4-bit binary number. A 3.579MHz colour TV crys- tal is used to generate all the necessary clock signals within the IC, but these crystals are very common and are quite cheap. Depending upon the input signal, the 4-bit code appears at pins 2, 1, 14 and 13 and is then fed directly to the inputs of IC4, a 4514 CMOS 4-to-16 output decoder. Valid signal indication Pin 12 of IC3 goes high whenever a valid input signal is detected. This is buffered by NAND gates IC10a & IC10b, which are then used to drive transistor Q2 and turn on LED1 (ie, the LED stays on for as long as a key is held down). This LED also stays on for as long as you hold down the "#" key, which enters your selected output into the memory register. The output of IC10b is also used to enable IC4 (the 4-to-16 decoder) via pins 1 & 23. While these inputs remain low (ie, while ever a valid tone Fig.3: the heart of the circuit is the DTMF decoder. This decodes the tones coming down the telephone line (either directly or via your answering machine) & outputs a unique 4-bit code for each tone received. These various tones are then decoded & used to activate the output driver stages (four toggle, five momentary). is received), the selected output of IC4 will remain high. When the particular key is released, all outputs of IC4 go low. Each of the 10 outputs from IC4, corresponding to keys 0-9, are then fed to the Set inputs of 10 RS latches comprising IC5, IC6 and IC7. These are 4043 CMOS quad RS latches and form the memory register. They are also Tri-State devices, which means that their outputs can have three states: high, low or high-impedance. Code entry To enter in a particular code to control one or more of the outputs, you simply press those keys in sequence and then press the"#" (Enter) key. As you press the output-select keys (ie, keys 0-9), they are stored in the memory register (IC4-7) . You can select as many of the outputs as you like at any one time. When you press the "#" key, pin 14 ,, To send the tones down the line, you simply dial the number, then hold the encoder against the mouthpiece & press the appropriate buttons & the ENTER key. .· I --.2--,, ',a·~, This close-up view shows the user selectable matrix in one corner of the PC board. You can either use the matrix we used (as shown on the wiring diagram) or you caffwire the matrix outputs to suit yourself. You don't have to install links for all the outputs either but don' leave out the master reset link. MAY1991 33 4 pcs. Professional Electricians Insulated Screwdriver Set * 5 x 150 (flathead) * 6 x 150 (flathead) * #2 x 150 (phillips head) * #1 x 150 (phillips head) All rated<at> 1000V only $15.95/sel • A must for every hobbyist or technician • 15 pcs. -roRx- Set * Contains:- 1 x 1/2" adaptor. 7 x TORX bits in 30 and 75mm lengths. (T-20,T-25,T-30,T-40,T-45,T-50,T-55) value at $19.95 All housed in a meta/case Battery Operated DIC-DESOLDERING TOOL SC-SOOOA The DIC SC-5000A solder remover features a diaphragm pump, motor, and temperature control circuit built into the handle. The SC-5000A solder remover is a compact one-piece unit which can also be used as a hot air tool r~-----------~------, I ■ SC-SOOOABlock Diagram I '----~____,c I I I I I I I I I t -- Suc hon/ Hol A" Blower SeleCtO< 1/alvt: I I ~ Famlllartaatton wtth Major Controls and Facllltles (!) Tip ® Heater Holder <at>Filter Tube © Filter Cartridge <at> Filter Replacement Knob <at> Suction/Hot Air Blower Se!ector valve ® TemperatlKe Control ® Pow« Cord····· ·3-conduct01' ® Cleaning Pin I I ~ - - - -----,1 :1 '-----1:l'---++'V\NV\, ii ~-~ Ground L-- - - - - --~-9!!- ---------~ Heatc, SPECIFICATIONS * Power Requirements: 100V, 120V, or Engraver Pen I I I F:,, . 11 SensOI' - - .J I 240 volt AC 50/60Hz. * Suction Pump: Diaphragm-type. * Suction Motor Output: 12W. * Vacuum Attained: 6DOmmHg. * Max. Vacuum Attainable Time: 0.2sec. * Vent Volume: 15 llters/min (to open air) * Healer: SOW ceramic heater with temperature sensor. * Temperature Control System: Sensor feedback, zero-cross switching. * Temperature Control Range: 300 C - 450 C (continuously variable) . * Tip: 1.0mm hole diameter (standard). * Net Weight: 430 grams. * Scibe on Metal, Plastic or Wood. * Identify valuables to guard against * theft. Great Art's and Craft's tool. * (not Uses two •AA• batteries, included) only $3.95 $478.00 Including Tax $399.00 Ex-Tax. ,,A-3000 REMOTE CONTROL UNIT,, MODEL 1133 REMOTE ACCESS You can control just about anything with this Remote Control Transmitter/Receiver. Eg. TVs, Stereo's, Alarms etc. * N.0./N.C. relay output up to 5 amps. * Receiver operating voltage: 12V DC. * Complete with two remote keys. * Operating distance: 10 meters. was$109.95 .. now$89.95 ... KASPAROV POCKET PLUS CHESS COMPUTER * Beginner 8 levels of skill to Advanced from to Intermediate. * You set the level of help required and then play against the computer. TELEPHONE/ANSWERING MACHINE Telephone Features: Tone/Pulse switchable. Last number redial. Ringer on/ off switch. Lighted dialing keypad. Answering Machine Features: Single micro cassette. VOX recording. Call screening. Toll saver function. Tone remote control to access messages from touch tone phones. TELECOM APPROVED ATTENnON VIDEO CAMERA BUFFS II ATTENTION VIDEO CAMERA BUFFS II AVM-3 MULTI-CHANNEL VIDEO/AUDIO MIXER * Multl-Functlon mixer designed for use by the professional or amateur video camera operator. * Ideal for adding and mixing background music or * * * * voice overs to existing video tape recordings. Suits all current available video formats, VHS, Beto, Video 8, Super VHS, VHS-C, etc. Inputs available for CD Players, Camcorders, VCR's, Cossette Players, Tuners and Microphones. Easy to use controls and layout makes this unit Ideal for both domestic and commercial use. Monitor function, Stereo/Mono selectable, Left and Right VU meters, Phono Inputs, Battery test, Operates from o slngfe 9 volt battery or 9 volt DC supply (not Included) I\IC>IIV AVAILABLE NEW PRODUCT FOR 1J1 only $169.00 MS-110 SWR METER ~ for 27MHz ~ ) ~* SWR Meter. * Power Meter. * Detects Propane, Butane and * AM Modulation Meter. 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Msdium to hsavy duty two platform brackst design11d for mounting spsskers to walls, desks, ceilings, etc. Allows speaker to be rotated a lull 360 deg. as wsll as swivelled up and down. ~ ◄ "' LIMITED STOCKS only$39.95 <~ DIAL CORD ~v V~ WE'VE GOT REELS OF THE STUFF * 10 metre reel.only $Q99/reel Variable AC Trans-rorrners * HSN-0103 * HSN-0203 * HSN-0303 0-250V, o 5A 0-270V. o 7 A 0-270V, o 13A $159.00 $187.00 $314.00 An enclosed, table-top variable transformer with 4mm captivs hsad typs and sspsrate sarth connectors. Large voltage control dial snd a clearly marked scale, housed in a steel case. MB-3 SPEAKER MOUNTING BRACKET by •ARISTA• T • :0• / ~----------. DB-25 GENDER CHANGERS ~~ C ~ fivs components. Countdown timsr, can automatically turn ON/OFF any one of five components. <.A ,. ,L[)[} ([(.)~ now only $69.95 * * '--f only $99.95 , , Sate guard your family and y£ your possessions.Gas leakage .....-~~ can be fatal Ideal tor the car, caravan, boat kitchen, etc. "' " 10 volt AC o 1 amp. Complete with 2.1mm DC type plug. To suit many modems requiring 9 volt AC supply. · ,... * BK memory. ~ 10 volt AC Plug Pack * ~ RS232 l/NE BOOSTER Having trouble with long RS232 cabls lines and thsn finding out your output tsvs/ has droppsd and your not gstting snough signal down ths fins? If so, thsn you nsed a RS232 Lino Boostsr. Thu Line Boost11r can double your cable /11ngth. Requires 12V DC supply o 100mA ... $13.95 * EL E C TR O N I C PLUS CLOCK A 24 hour dual timsr/clock with; 2 count-down timsrs, 2 preset memoriBs, count-up timer and clock. ldsal for sports, msstings, msdication, cooking stc. Displays Hours, Minutss and seconds. Built-in alarms. FULL 12 MONTHS WARRANTY PIR-30 PASSIVE INFRA-RED DETECTOR * 12 meter range o 90 deg. * Walk test indicator. * 8-18V DC operated. * N.C. relay output. * N.C. tamper output. save$20.00 only $49.95 only $49.95 l ( 1ual-timer only$19.95 LABTECH - 20MHz DUAL TRACE OSCILLOSCOPE Features: Wide bandwidth and sensitivity. High senitivity X-Y mode. Z axis (intensity modulation). Front panel electrical trace rotator. Regulated power supply circuit for accuracy. Description: This model is a dual trace 20MHz CRO using a high brightness CRT. The vertical amplifiers have high senitivity of 5mV /DIV and a frequency characteristic response with smooth roll off exceeding 20MHz. The highest triggering sweep speed is 0.2uSec/DIV. t·110·1CRO PROBES to suit $39.95 ea. NEW MODEL FOR '91 7 David Reid Bectronics 127 York St. SYDNEY 2000 PH: (02) 267 1385 P.O. Box Q103, SYDNEY 2000 FAX: (02) 261 8905 SAME DAY MAILORDER DESPATCH* Post and Packing $5 - $25 ........ $3.00 $26 - $50 ...... $5.00 $51 - $100 ...... $6.00 $101 - $499 .... $8.00 $SOO + ............ FREE ai:!&l~l!,g of IC4 goes high. This enables the latches (IC5-7) via pin 5 of each IC. The selected latch outputs now go high and turn on their respective output driver stages as required. The high output generated by pin 14 of IC4 when you press the "#" key is also fed to a small delay network formed by a 0. lµF capacitor and lkQ· resistor at pin 13 of NAND gate IClOd. When the "#" key is subsequently released, pin 14 of IC4 goes low, the outputs of the latches are disabled, and pin 13 of IClOd is momentarily pulled low as the O. lµF capacitor charges via the lkQ resistor. This in turn switches the output of IClOd momentarily high and resets the latches (ie, outputs are low). This is how the momentary outputs work. They are on whenever the outputs of the memory register are high and the "#" key is held down . To produce the toggle outputs, we have used two 4013 dual D-type f!ipflops (IC8 & IC9) which are, naturally enough, connected in toggle mode. The outputs from the memory register are connected to the clock inputs of these four f!ipflops. This is done so that selecting that output with the keypad alternatively turns the output on and off. Each of these clock inputs and the common reset line have lOkQ resistors tying them to ground when the corresponding outputs of the RS latches (IC5-7) revert to high-impedance mode. This prevents the 4013s from clocking due to noise, as can occur without these resistors in place. As mentioned previously, the output drivers are BC33 7 transistors with open-collector outputs. Each has a LED indicator to show whether it is on or off, as well as a reverse-voltage protection diode to protect the transistor against large negative-going spikes when its relay turns off. Power supply Although the circuit is powered by a single 12V DC plugpack, the board splits this up into three supply rails: a non-regulated +12V rail which is fed to the output driver section (as the supply voltage here is not overly critical); a regulated +12V rail which is connected to the audio input circuitry; and finally, a regulated +5V rail which supplies the logic circuitry. Diode D18 prevents the circuit from being damaged if the power supply is connected in reverse, while the 7812 and 7805 regulator ICs produce the +12V and +5V rails, respectively. The three lOOµF capacitors provide filtering for the supply rails. Fig.4 (right): when the the phone rings, an auto-answer circuit based on Q1 & IC1 closes relay RL1 so that the tones can be fed via S1 to tone decoder stage IC3. This IC generates a 4-bit binary number in response to each tone received and feeds it to a memory register based on ICs 4-7. The 9 decoded outputs are then used to drive five momentary output stages (Q7-Q11) & four toggle output stages (IC8 & IC9). Although no prov1s10n has been made for a power switch on the board, it is quite an easy matter to connect a small SPST power switch in series with the supply line. Construction All components except for the input audio switch and the microphone are mounted on a single-sided PC board coded SC12106911 and measuring 170 x 140mm. Before you begin soldering, check the board for any shorts or breaks in the tracks, particularly where the tracks run between the pins of the ICs. If you find any problems, either use a sharp knife to cut away the excess or add a touch of solder where PARTS LIST 36 1 plastic instrument case (optional, see text) 1 PC board, code SC 1206911 , 170 x 140mm 1 600Q:600Q telephone isolation transformer (Harbuch AT-251 or similar) 1 SPOT relay 1 SPST switch (for power on-off) 1 SPOT toggle switch (S1) 1 FET-input microphone insert 1 telephone plug and cable (Telecom approved) 1 3.579MHz TV colour crystal (X1) 3 4043 quad RS latches (IC5-7) 2 4013 dual O-type flipflops (IC8IC9) 1 4011 quad 2-input NANO gate (IC10) 2 BC548 NPN transistors (01,02) 9 BC337 NPN transistors (03011) 1 7812 12VOC regulator 1 7805 5VOC regulator 16 1N4004 power diodes (01 -06, 09-018) 2 1N914 signal diodes (07,08) 1 12V 1W zener diode (ZO 1) Semiconductors 1 NE555 timer (IC1) 1 LF351 FET input op amp (IC2) 1 MC145436 OTMF decoder (IC3) 145144-to-16 decoder (IC4) Capacitors 1 100µF 35VW PC electrolytic 1 100µF 25VW PC electrolytic 2 100µF 16VW PC electrolytics 1 10µF 16VW PC electrolytic 2 1µF 50VW PC electrolytics SILICON CHIP 6 0.1 µF 63VW (5mm lead pitch) polyester 1 .022µF 63VW (5mm lead pitch) polyester 1 .015µF 63VW (5mm lead pitch) polyester 1 .01 µF 63VW (5mm lead pitch) polyester 1 .0047µF 250VAC polyester (WIMA) Resistors (5%, 0.25W) 2 1MQ 11 3.3kQ 1 470kQ 1 2.2kQ 1 220kQ 9 1kQ 4 10OkQ 1 680Q 7 10kQ 6 470Q 1 4.7kQ Miscellaneous Tinned copper wire, hookup wire, cable ties, etc. ~ >-" 18 ~ ~ I .,. .,. 61 f 10k .,. .,. 5 + v 1 ::1 l 1 +5V 1 -- ,...,,, TOGGLE 1 + : 03 .BCJJ] ,_._, 1 100 35VW ,. 12voc PLUG-PACK " -:- l 12 j 10k .,. 01 . OUT R 1 0 12 13 -t ~. 010 1N4004 ,. r 13 ~ B k \ OUT A S ~ "*" 1 K 23 I 22 __._.. 2: -• I TOGGLE 3 + ~E 12 14 18 17 I 9 0 10 8 I & 140 .,. J.. 10k I. -;:- IC9b 114 J 08 o3 4 : TOGGLE 4 'LOAD ,,. r "_ "11~ I .022 r ) I" J ) r:r-r,-m ~~ 043 4IC6 6 13 17 ~o 1 -gg LED5(~1') _ __ (+l ·- t lle~.~ iil:!Z I ~ I ,a 6 5 12 14 4 6 IB 18k 16 ~ l 1 I .12 114 _ ---- ~ •• 1C4 24 451 4 1s LED~LOAD 011 1N4004 .----11--,t---, I I ·-l- IN' ~ _3 : 2 ••.,.__ 12 ~F-"""'lr--' 8 Md~ 6 f ·-,. r l ELJc VIEWED FROM BELOW y DPTDCDUPLER Wt, ~ LOAD ' .01 10 9 o.1I .,. +5V DTMF TONE DECODER A~D DRl~ER B .,. ii Q }. ,.. MOMENTARY l : 5 TOGGLE 2 LED3 • RL ;;J -...r iiciai'' ~ N' 0 O __ lM + + 680n __ RL1 4 ...lNSl~ Wit~•· ± (I I Ml-5~ --, f +5V r: 2.2k !:- Q S1 4.7k j ~I ..- ;:. °'---o- AUDIDI L YM ·1 LINE -:- +12V UNREG O.lI AT251, 45035 ·~ ..,. 21 r~. . /: . - _. . . - ICBb ll CK S 9 D +12V REG iuwn.-=. _,ex, •-··--······ _ ..._..._.,_._-"'t +·O-_ _ _ UNREG +12V 1 I LF~51/"I" lt'--½--4'M-=t--l .,. I 5otw .I: .,. 100ki 0047 250VAC"'T"' Tllin----"11 .,. r) EHO MIC PHONE LINE 05 <at>½ ~ L I• ~ I,, 2O--=---1--4t----------------------' l .I: ,.i.r '-" 1 "'1 100 220k$ +12V REG • 2 7 5 64 3 1 2 0 B9M I Fig.5: if you intend plugging the unit directly into the phone line, IC2 & the microphone can be deleted. Alternatively, if you intend acoustically coupling the unit to your telephone answering machine, you can leave out the relay, the isolation transformer, diodes D1-D6, IC1, Ql & their associated parts. necessary. If you're not sure if you have shorted tracks or not, check the resistance between thern using your rnultirneter. Now take a look at the wiring overlay diagram of Fig.5. This shows you where each component is installed and rnust be followed exactly if you are to avoid problems. Begin the board assembly by installing the wire links. A number of these run parallel in close proximity to each other, so rnake thern as straight as you can so they don't short each other out. Don't worry about the keypad encoding links at this stage; CAPACITOR CODES 0 0 0 0 0 0 38 Value IEC Code EIA Code 0.1µF .022µF .015µF .01µF .0047µF 100n 22n 15n 10n 4n7 104 223 153 103 472 SILICON CHIP we'll corne to those later. Once you have finished installing the wire links, solder in the diodes and resistors. Sarne of the resistors are mounted upright and should be given neat rightangle folds so that they fit neatly into the board. Make sure you don't confuse the two signal diodes (D7 & DB) with the larger power diodes and check their polarity carefully against the wiring diagram. The zener diode (ZD1) is installed with a loop in one of its leads to protect it frorn thermal stress. Next, ·install the 5rnrn fixed-pitch polyester capacitors and the electrolytic capacitors. Make sure you get the polarity of the electroytics correct. Note that the .0047µF capacitor across the telephone line rnust be a 250VAC type. Now install the transistors, LEDs and ICs. Again, the overlay diagram will show you their correct orientation while the rnain circuit (Fig.4) shows the device pinouts. Note that all the ICs face in the sarne direction except for IC4 (4514) which faces the opposite way. The two regulator ICs are installed with their metal tabs towards the transformer. The 3.579MHz crystal can be soldered in next. It doesn't matter which way around it goes in. Check that the base of the crystal sits flush against the PC board. Finally, solder in the relay and the line isolation transformer. Depending upon which brands you get for these two components, you rnay have to file or drill out extra holes to rnake thern fit the board. In most cases though, the components should drop straight in and if you do have to rnake changes, they should be fairly minor. External wiring There's not rnuch to do here - just wire up the audio input selector switch (Sl) and the microphone, and install a couple of power supply leads. Note that light-duty shielded cable should be used for the microphone leads, as shown in Fig.5. Although we left our prototype in "bare-bones" state, we suggest that you install your unit inside a standard plastic instrument case. If this is done, the selector switch can be installed on the front panel, along with a polarised socket to accept the microphone leads. The optional on/off switch can be installed on the rear panel, along with a DC power socket for the plugpack supply. The power supply can be a 12V DC .1 amp plugpack. However, if you intend using only one or two of the output drivers with relays, then you could use a 300mA version. Setting up the keypad Before using the unit, you have to install the necessary links in the userselect matrix in the bottom righthand corner of the board. This matrix defines which key on the keypad operates a particular output. If you look at the grid on the board, the top row represents the keypad outputs from 0-9 but note that they are not in order. From left to right, they are: 7,5,6,4,3,1,2,0,8,9. The bottom 10 rows (from the bottom up) are as follows: MZ, Ml, R, T4, TZ, Tl, T3 , M3, M4 and M5, where M is a momentary output, T is a toggle output and R is the master reset for the toggle outputs. As an example, if you look at the overlay wiring diagram, the "9" output is connected to the 4th toggle output (T4), the "8" output is connected to TZ , the "O" output to the master reset (R), and so on. You can follow our scheme if you wish, or you can change the links to suit your own requirements. You don't have to install all the links to the momentary and toggle output rows either. For example, if you only wish to switch two appliances, then two links (plus the master reset link) are all that will be required. The completed PC board can be installed in a plastic instrument case, with the selector switch & microphone socket installed on the front panel. The telephone cable & plugpack supply leads can exit through the rear panel, via grommetted holes. An optional on/off switch can also be fitted to the rear panel. Don't leave out the master reset link; it must go in, although it can be controlled by any key you wish (except of course the"#" key). Once you have completed the board, check it thoroughly for parts placement and solder splashes. When you're happy that the board is OK, connect the power supply with your multimeter in series with one of the leads and switched to amps. Now switch on and check that the quiescent current is around 30mA or so. If the current shoots up to greater than about 60mA, switch off quickly and check your wiring. Assuming everything is OK, you can now poke around the board with a voltmeter and look at some of the voltages to check that all is well. At the Vee pins of all the CMOS ICs , including the MC145436 , you should get a reading that's close to +5V. The LF351 and NE555 IC should have close to +12V on their Vee pins. If you don't get these voltages, turn the power off and then check your wiring again, particularly the orientation of the ICs. As a final check, us e the following test procedure to mak.e sure you get the right output. Using the board So how do you operate it? Let's say you've just turned the unit on. To start with , flick switch Sl over to the RESISTOR COLOUR CODES D D D D D D D D D D D D No Value 4-Band (5%) 5-Band Code 1 1MQ 470kQ 220kQ 100kQ 10kQ 4.7kQ 3.3kQ 2.2kQ 1kQ 680Q 470Q brown black green gold yellow violet yellow gold red red yellow gold brown black yellow gold brown black orange gold yellow violet red gold orange orange red gold red red red gold brown black red gold blue grey brown gold yellow violet brown gold brown black black yellow brown yellow violet black orange brown red red black orange brown brown black black orange brown brown black black red brown yellow violet black brown brown orange orange black brown brown red red black brown brown brown black black brown brown blue grey black black brown yellow violet black black brown 1 4 7 11 1 9 1 6 MAY 1991 39 ::----, ..... ·-· ■■ D ■ D ■ DD - 0 40 SILICON CHIP a■ 0 Fig.6: before mounting any of the parts, check your finished board against this full-size artwork to ensure there are no shorted or open circuit tracks. microphone input, which is the easiest way for checking the output code. Now hold your keyboard encoder so that its speaker is next to the microphone and enter a "*" code to clear the memory register (note: you should do this each time power is applied to the board). Two things should happen. First, you should hear the tone coming out of the speaker of the encoder; and second, the VALID CODE indicator (LED 1) on the decoder board should be alight while ever you hold the key down. If you now press the enter or "#" key, LED 1 should light but all the other LEDs should stay off. This clears the memory register. The various outputs can now be tested. First, press keys 1-9 on the keypad in succession, so that LED 1 lights on each occasion. This lets you ··- ■■ DDD ■ -­ know that the circuit has "heard" your request. Now press the "#" key and check that the output LEDs all light up. When you release the"#" key, only four of the output LEDs should stay on. These should all correspond to the selected toggle outputs. The five LEDs that turn off should all .correspond to the momentary outputs. Next, we'll test the memory clear or "*" key. If you again press all of the keys from 1-9 and then press the"*", nothing should happen when you press the "#" key. That's because the "*" key clears the memory register. This means that if you make a mistake while entering the outputs you wish to select, you just press the "*" key and start over again. In our example, we used key "O" as our MASTER RESET key. If you press this and then press the"#" key, those four remaining LEDs should go out. If you have used another key for the master reset, press that key and the "#" key and you should get the same result. If you strike problems, .check the links in your output matrix to make sure that you have correctly matched the outputs to the keyboard code. What are the uses? The uses for the DTMF Decoder board are really limited only by your imagination. You can use it to turn on or off all manner of electrical items via the appropriate relays or optocoupled Triacs. Typical examples include house alarms, lights, water sprinker systems, radios, hifi systems, heaters and air-conditioners. If you are an amateur radio operator, you will already be aware of the uses of DTMF control systems. 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Features smooth slide rail with a spring lock. Is very sturdy and reliable. Fits At style keyboards. Also has pen and pin holder trays built-in. 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Call today for very delay this time, when the stock is gone new stock will increase in price competitive pricing. SAVE 50% NOW 25.00 DEALER ENQUIRIES WELCOME TRY PC MARKETPLACE SUPERFAST MAILORDER - PHONE OR FAX TODAYI You will often see these cards advertised elsewhere for around $50.00. Don't Plii{ (jfeeson s PERSONAL COMPUTER MARKETPLACE PtyLtd FREIGHT CHARGES PHONE (02) 418 6711 Include $10 with order for all normal items - heavy items, e.g. monitors add $15. FAX (02)4186713 14 day money back guarantee Mail Order Address: Order by phone (use credit card), by fax or by mail. P.0. Box 1100 Lane Cove Unless insurance is declined it will be charged at '1 % of total purchase. This is for your protection. NSW2066 PRICES CURRENT FOR MONTH OF PUBLICATION OR WHILE STCX:KS LAST. e SERVICE IS THE DIFFERENCE • SERVICE IS THE DIFFERENCE e VISA SERVICE IS THE DIFFERENCE e SERVICE IS THE DIFFERENCE Fluorescent light simulator for model railways The key word for any railway modeller and his layout is "realism", right down to the fluorescent street lights. This project "quickie" simulates the flicker you see when fluoros first start up, and it can power up to 30 mini lamps. By DARREN YATES This is one of those circuits for the model railway perfectionist. It's just the shot for controlling the lamps around your layout and will provide a realistic "fluoro-flicker " each time the lights are switched on - just like real fluorescent lights. This rapid flikering effect only lasts for a brief period, after which the lights come on and stay on. The circuit should appeal most to those who like playing "night trains"; ie, running their layout in a dimmed room to take full advantage of the When the circuit is turned on, the lamps flicker for a brief period & then stay on - just like real fluorescent lamps. It will add realism to your model train layout. 42 SILICON CHIP lighting. Best of all , the circu it is quite simple and uses just one IC and a handful of other components. It will only take you about an hour or so to build, so you'll have it up and running in no time at all. How it works Fig.1 shows the circuit diagram of the Fluorescent Lamp Simulator. When the circuit is first turned on , the lO0µF electrolytic capacitor at the base of transistor Ql has no voltage across it, so Ql is turned off. While the capacitor is charging up via the 680kQ resistor, pins 6, 9, 13 and 2 of ICl are all high. These pins are used as enable inputs for the four Schmitt trigger NAND gates (ICl a-d), which are connected as square wave oscillators. ICla is connected in a conventional manner, with a 680kQ feedback resistor from output to input, and a 0.15µF timing capacitor from input to ground. This gives an output frequency of about 8Hz. ICl b, c & d are also connected as oscillators but in a different manner. Instead of the feedback resistor going from each gate's output to its input, it is connected to the input of the next gate in the chain; eg, pin 4 of ICl b is connected to pin 8 of IClc via the feedback resistor, etc. This forms what is known as a ring counter. The reason for this arrangement is so that the outputs of the three gates, IClb-ICld, go high one at a time to produce a light chaser effect. These outputs are mixed with the output of ICla via diodes Dl to D6 , which form three OR gates. Dl and D4 form one OR gate, D5 and DZ another, and D3 and D6 the third. The result of all this jiggery-pokey is that ICla pro- 47!! r---+-----------4-------+-------''#No.----------4----.....- - - - - - - - - • 1 2 V ffJ J 1W 680k, LAMPS B 100 + 16VWJ 680k 01 1N914 .,. LAMPS 05 1N914 05 B0139 0.151 C .,. 680k B 02 1N914 .,. 4.7k 07 B0139 C B E .,. 0.15! B EOc VIEWED FROM BELOW 680k ECB FLUORESCENT LAMP SIMULATOR Fig.1: when the circuit is first turned on, Ql's collector is high & this enables a ring counter IClb-lClc & Schmitt trigger oscillator ICla. The outputs from the ring counter are OR'ed with the output from ICla using D1-D6 & the resulting signals then used to drive three Darlington transistor pairs to switch the lamps. vides a degree of randomness to the outputs, to give the lamps that flickering effect. The OR-gate outputs are then fed to three lamp driver transistor stages via 4. 7kQ isolating resistors. Each of these stages consists of a BC337 and a BD139 transistor connected in a Darlington arrangement to provide the necessary current gain. When each output goes high, its associated Darlington output stage turns on and current briefly flows through the associated lamp. During this time, the lO0µF capacitor on Ql 's base continues charging until it reaches 0.6V. At this point, Ql turns on, pulling the enable line connected to the oscillator inputs low and forcing the NAND gate outputs permanently high. The lamps now stay on continuously. The capacitor charges up in 2-3 seconds which Where to buy the kit A kit of parts for this project is available from Electronic Toy Services, PO Box 491, Noarlunga Centre, South Australia 5168 (Shop 2/111, Glynville Drive, Hackham West, SA). This kit includes the PC board & all on-board components, but does not include the lamps. The price is $14.95 plus $2.50 p&p. The PC board can be purchased separately for $5.95 plus $2.50 p&p. Payment may be made by cheque or money order, or by phoning (08) 382 8919 and quoting a credit card number. Note: copyright of the PC board artwork associated with this project is retained by Electronic Toy Services. PARTS LIST 1 PC board (available from Electronic Toy Services) 3 12V mini lamps (eg, Jaycar Cat. Sl-2639) plus additional lamps (up to 30) as required Semiconductors 1 4093 quad Schmitt trigger NANO gate (IC1) 1 BC549 NPN transistor (01) 3 BC337 NPN transistors (02,04,06) 3 8D139 NPN transistors (03,05,07) 1 12V 1W zener diode (ZD1) 6 1N914 diodes (D1-D6) Capacitors 1 100µF 16VW PC mounting electrolytic 4 0.15µF 5mm-pitch metallised polyester Resistors (0.25W, 5%) 5 680kQ 3 4.?kQ 1 2.2kQ 1 47Q MAY1991 43 ·- Fig.2: follow this diagram carefully when installing the parts on the PC board & take care to ensure that all parts are correctly oriented. The pinouts for the B0139 transistors are shown on Fig.1 (mount them so that their metal tabs face the edge of the board). Up to 10 mini lamps can be wired in parallel to each channel. UHF HIGH GAIN ANTENNAS antenn existing systems triangul powder coated receiving elements ensures excellent UHF reception compared to other UHF antennas of similar size and price. Two models are available: the for Band Four and the S for Band Five UHF • reception. Both models are supplied with back reflectors to prevent ghosting as well as a waterproof entry box designed to accept 75 ohm coaxial cable without the need for addittional baluns. They also have predrilled holes for securing the tilt adjustable metal mounting bracket in either a horizontal or vertical position. Imported and distributed by: Available through the following retailers: Bernys. Brldgepoint. Military Road. Mosman. 2088. NSW. (02) 969 1966. Ritronics. 56 Renver Rd. Clayton. Victoria. 3168. (03) 543 2166. means that the lamps only flicker on and off for this amount of time. Power for the circuit can be provided by the train controller supply. A 12V 1W zener diode is used to protect the CMOS IC against high input voltages. By the way, if you only intend using four or five lamps per output stage, you can do away with the BD139 transistors and just use the BC33 7 transistors to drive each set of lamps. Construction Is .Your Product Or Service G·etting The Exposure It Deserves? Nearly 30,000 consumers will read this page. They need to see your advertisment, if you want them to buy your product. Contact Paul today on (018) 28 5532 to reserve this space. 44 SILICON CHIP All components, except for the lamps, are installed on a small PC board measuring 73 x 63mm. Before you begin soldering, check the board for any shorted or broken tracks, particularly those running between the IC pins. Once you 're satisfied that the board is correct, start the assembly by soldering in the resistors and diodes. Fig.2 shows how the parts are installed. If you're not sure of the colour code of the resistors, use a multimeter or check the accompanying table. Be sure to match the polarity of each diode to the wiring diagram. Next, install the greencap capacitors. These all have the same value, so you shouldn't have any problems here. When you've done that, solder in the transistors. Again, check with the overlay diagram to make sure you insert them correctly. The circuit diagram (Fig.1) shows the pinout details for the transistors. Note that the BD139s are installed with the metal faces of their tabs nearest the edge of the PC board. If you aren't using the BD139 transistors (see above), install a wire link between the base and emitter holes where each BD139 would have gone. Finally, solder in the IC. Check again that you have inserted it correctly before you start soldering. When you have finished the board, check it carefully for solder splashes to ensure that there are no shorts between tracks or between IC pins. When you are connecting up the lamps, note that they all have a common line; ie, the connection to the +12V supply rail. It is then just a simple case of running the other leads from the lamps to the outputs provided on the board as appropriate. Finally, you can either install the board in a small zippy box or just hide it as is under the layout table the choice is yours. Be sure to connect the power supply the right way around. SC RESISTOR COLOUR CODES Value 4-Band Code (5%) 5-Band Code (1%) 680kQ 4.7kQ 2.2kQ 47Q blue grey yellow gold yellow violet red gold red red red gold yellow violet black gold blue grey black orange brown yellow violet black brown brown red red black brown brown yellow violet black gold brown Don1 miss this one! Irs a high quality stereo condenser electrel microphone. Phillps came lo Jaycar lo clear their excess stock. Their list price for this uni! ls $59.95!!! Features Include:• Uni-directional polar pallern -• Designed In Wlndshleld for distortion free sound • For studio and home recording • Table stand and vinyl carrying case Included Specifications Frequency Range 50-18,000Hz Impedance 6000 -47dB:!&IB Sensltivlly 6.5mm plug Connector Adaptor 6.5 lo 3.5mm supplied Cord Length 3 metres Battery Supply 1.5V M required Cal. AM4085 150 watt. Fully compallble wllh PC/XT computers. Includes metal case. • lnpul<at>47-63Hz (110/240V swllchable) • Oulpul +5V <at> 15A, -5V <at>0.5A +12V<at>5.5A, - 12V <at>0.5A • Plug compatible connectors • Built-in Ian • Size 5.5" (W) x9.5" (D) x 4.625" (H). Plnouts for leads black ground, Red +SV, Yellow +12V, While -SV, Blue -12V, Orange power good. Cal. XC-5080 $11 9 Philips list price $59.95 NOW ONLY $ 19.95 SAVE AN AMAZING $40 COUN See catalogue for full details. Cal LA-5018 $89 ATOR Cat. LA-5022 w, $119 Al lasl, areasonably priced 16 drawer parts cabinet. Designed lo hold all your 'bils and pieces':- resistors, capacitors, semlconduclors, drill bits, nuts & bolls, nails, elc. Each drawer will accept up lo 3 plastic dividers which can divide lhe drawer into 2, 3 or 4 separate compartments. 16 drawer dividers are supplied. Cat. HB-6320 $ 12.95 GENERA Cal. OT-2310 $259 L ATOR Cat. QT-2312 $249 LTMETE Cal. OT-2320 New addition to our range of hardware packs. Provides spring tension lo retain the nul, bul doesn"I damage lhe surface. $225 Pkl25 Pkl200 s Double sided fibreglass PC board at about hall normal price. SiZe 365x210mm Cal. HP-9520 Normally $14.95 50 x 1N4003300V 1A Cat. ZR-1003 $ 2.50 50 x 1N40071000V 1A Cat. ZR-1009 $5.00 $1.25 $5.55 Cat. HP--0436 Cal. HP--0437 BUY10 TAKE 10%OFF ., 'I, • Frequency counter • Capacitance meter • Logic probe 20MHz • Diode tester • 10amp • 34 ranges • One hand operation Cat. QM-1400 1. ' I ,, . L 9 pin 15 pin 15 pin High Density (In a 9D package) 23 pin 25 pin 37 pin 37 pin PC Mount PP--0800 PP--0820 $2.25 $2.50 PP--0831 PP--0836 PP--0840 PP--0850 PP--0861 $3.95 $2.95 $1.95 $3.95 30t PS--0804 PS--0824 $2.75 $2.75 PS--0832 PS--0836 PS--0844 PS--0864 $3,95 $2.95 $1.95 $3.95 )',I .., Afi Made in the USA • Cuts holes - any shape over 7/16' • Notclles clearance for plugs and wiring • Trims underslze holes to Iii parts • Suitable for steel up to 18 gauge, aluminium 16 gauge, plastic and copper Replacement punch Cat. TH-1766 $24.95 Cat. TH-1765 $34.95 WAS $99.95 NOW $79.95 SAVE $20 E' ~ Jaycar will purchase your surplus stocks of components and equipment. We are continually on the lookout for sources of !)rime gualitv merchandise. CALL MARK HARRIS OR BRUCE ROUTLEY NOW ON (02) 747 2022 9 pin 15 pin 15 pin High Density (in a 9D package) 23 pin 25 pin 37 pin Normally open (NO) and normally closed (NC) on the one assembly, Saves buying either magnets, self adhesive Cat. LA-5070 ONLY $4.95 - 5.25" DSDD 5.25" DSHD Pkt 10 1990 Price $5.10 $10.50 $9.75 $24.95 $9.50 $15.95 $15.95 $34.95 - tS Compare our everyday low prices! CHEAPEST IN AUSTRALIA? Cat XC-4730 XC-4732 XC-4736 XC-4738 AA Cat. SB-2452 $3.50 FOUR FOR $12.50 oldering stations for the hobbyist or manufactur . , _. it features a dial-up · . temperature ¾l between 111\1&,. 31s 0 c - 421°c ·"' (600°F - eoo°F). No more constant tip changing to select a different temperature. r full specs see the brand new car catalogue. Cat. TS-1600 C Cat. SB-2459 $6.50 $6.95 < • 159. erythin .I DNESS Features: • Year, month, day and date • 12 or 24 hour format • 5 daily alarm, 1 calendar alarm • 18 world city time displays • Data bank for 50 phone numbers Cat. XC-0210 .0 These batteries are encased in a black plastic housing which measures 30(L) x 16(W) x 19(H)mm. They were removed from printed circuit boards by simply cutting of the PC terminals so to use you would need to break open the plastic case . inside are two 1.2V cells. So purchase 4 of these, remove 1 cell and you have an 8.2V (9V 216 type) battery for only $4, not about $20. Ideal for Hobbyists, experimenters, etc. To buy these today they would cost about $13 ea. Cat. SB-2470 ONLY $1 each 10+ 90f! ea 100+ 75f! ea 3 way type for printers etc. See catalogue for full details. All inputs/output D25 female with $24.95 l' $49.95 L I I C Cat. XC-5072 'I tl ><.,1• ,AH, Y t •1 E ,TR )NtL ll $49:95 .,, H )~ l.., JA J F<ONIC5 JA . H ◄I fl TR •◄ N ~ A l A ► I- ! l TH! ,1l 1•-j I • Hr ' l -4.H , I' J • r t 1 ~I I~ ,. l "'41 ,\ \ I ~ " NEW KITS FOR MAY Ref: Silicon Chip May 1991 This project will add sparkle to your music cassettes, video or FM receiver by Increasing the dynamic range of the signal. The kit includes PCB, box, panel labels, In/out sockets and all specified components. Option 12V AC plugpack Cat. MP-3020 $16.95 Cat. KC-5094 $39.95 Super high quality. English made, 8mm cable clips for neat and speedy laying of insulated cables. The steel pins will driveinto wood, plaster, mortar or brick. Ruslless and shockproof. Supplied in boxes of 100 pieces. Save money by buying from Jaycar. Our SA 130 speaker kit is $200 less than other kit suppliers. Normal price $3.95 for 20 or 13~ each. Cat. HP-1177 BOX OF SA130 3WAY KIT 100 pcs ONLY $5.95 Handling power 90Wrms. Complete with cabinets. Other Vila kits available see the Jaycar catalogue. or less than 6t ea ONLY $999 This enhancer connects between two VCR's to Improve the quality of a recording of an original tape. 625 line 50 frame PAL Ddesigned in Australia. Full specs in Catalogue. t.AV~501 Up to 30% cheaper than other suppliers. Grilles pressed out of strong, perforated steel to protect Hi Fi or PA speakers in cabinets or cars, etc. Each grille has a rubber edge band and black painted finish. Grille is supplied with 4 mounting lugs, heavy duty screws and T-nuts (cabinet fixing spiked nuts.) 0 95 95 Cat. AX-3522 tor 1o· speakers $1 2 15 Cat. AX-3524 for 12' speakers $1 4 15 Cat. AX-3526 for 15' speakers $1 7 Cat AX-3520 for 8' speakers $1 Control home appliances via your telephone Ref: Silicon Chip May1991 This kit will allow you to control equipment via the telephone ltne. II can control up to nine separate appliances and can be connected either directly to the telephone line or acoustically coupled via your answering machine. You can use it to turn on and off all manner of electrical items - e.g. house alarms, lights, water sprinkler systems, radios, Hi-Fi, heaters, air conditioners, etc., etc. The kltlncludes PCB, 6000 transformer, switches, mic Insert, telephone plug and cable and all specified components. No case supplied. Cat. KC-5095 $79.95 CHEAPEST IN AUSTRALIA? Ii.OW 3.5" DSDD Cat. XC-4721 3.5" DSHD Cat. XC-4722 5.25" DSDD Cat. XC-4726 5.25" DSHD See catalogue for full details ~28.95 $57 .50 $21.95 $29.95 Cat. XC-4727 . Prices for boxes of 10 disks I WAS $46.95 $99.00 Plug into your cigarette lighter socket and transmit to another car (with identical unit) on FM. Easy to tune to your car radio. Have been tested with clear communication over O.Skm! Looks like acar phone. Cat.Al-5400 $26.00 - $39.95 8 " 80Wrms cat. cw-21so $99.50 10" 120Wrms cat. cw-21s2 $129.50 Hobbypack or reel we have them both and In two sizes 0.71mm and 1.0mm. REEL 0.71mm200g $ 7 • 25 Cat. NS-3005 1.0mm 200g per reel Cat. NS-3010 HOBBYPACK 0.71mm Sm apprx $ Cat. NS-3008 1.0mm 4m approx per pack Cat. NS-3013 1 •60 Removes solder from PCB's. 3mm wide by 5 feet long. Cat. NS-3020 $2.50 '◄ 1 x 3.5mm for PC supports and relays 2 x 1.2mm for PC pins and hook-up wire 3 x 1mm for resistors, capacitors, etc 4 x 0.8mm for IC's etc. TOTAL 10 DRILLS Cat. TD-2400 $12.95 ,,, ' '• ,\ - - - ~ - - ~ ~ - -- - -- ~~ ,.e..__.._.L..-.!..1.L...k.l~ _ 1 ~~ - - • NEW BOOKS & BARGAIN BOOKS FROM JAYCAR • Jaycar is pleased to announce that we are now distributors of a new range of books written for the hobbyist and computer • user. These books are printed in Singapore and India and are generally about 1/3rd the price of equivalent American books. •• This month we introduce 13 titles, with some real bargains amongst them . We hope to add twice this amount in the next couple ·• of months, so watch our ads. . • •• ·· ····· T~;~·~·~;:e f ~ntten in a simple ~ logical manner for users. Chapter 1 gives an insight of MS-DOS. •••. ···•·::::~:·~:~·:~:•~>:·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·•·:·· <From there the book covers Installation of MS-DOS, commands, their syntax and examples for MS- ) By f>J Stevens ( DOS version 3.3, as well as the newer versions. Also include are appendixes on the enhancement of ) This remarkable ho,y-to quickly cuts past the computer mumbo Jumbo of conventional documentation J DOS commands for version 4.01, batch me and conflg. sys file respectively. There is asection ) to reveal DOS's capabllllles and power. Veteran author Al Stevens uses non-technical language to ( exclusively on partlonlng of hard disks. The last section 1s a ready reference guide to MS-DOS (( deliver In-depth Information on MS and PC DOS commands and operations. Teach yourself to set up } version 4.01. }) fixed and floppy disk systems with easy-to-understand Instructions contained In this book. Arm • } yourself with real time-saving techniques Including Ille maintenance and file protection. Improve your Size 187 x 120mm. Cat. BM-2110 A BARGAIN $16.95 )( compute(s efficiency and effectiveness. Learn ho,y to back up and archive Illes for sale storage. }) Master easy ways lo handle tricky lile directories. Improve your disk fomnaltlng and copying s:: s:: () techniques. Experienced users will find comprehensive Information on more advanced topics slldl as } sy John Mueller )} batch files and Edlin (the DOS editor). Maximised learning - overview ot DOS for the new DOS user Spreadsheet sotlware for lhe PC. Designed for lhe 640K DOS environment, lhls version of Lotus 1-2- ...... DOS commands - Paths, Fillers, Pipes, and Input/Output Redirection Balch Flies - EDLIN - Useful / 3 allows you lo combine spreadsheets, database and graphic functions Into a single program. Written )} Commercial Utility Programs - Index to General User Needs - Glossary of Commonly Used Terms In plain English, you'll find this book overtlowlng wllh complole and concise Information on Lotus 1- •••••••••• 257 pages 153 x224mm ) 2-3 Release 2.2. Follow the logical progression ol lhe Recommended Learning Sequence to master ] \ cat. BM- ; $19.95 2 14 ) the basics quickly. A macro reference Is Included to show you how lo create your own macros. ot~er ····· ( bonuses Include appendices that sho,y source listings for sample macros and how to create and use •• ( \ / ) \ .. > ~~~~,l~~~~;~e~ ~:;~~~u~~/o further aid you In finding acommand, agraphical representation of ::<i Ji: By Edwin Rutsch •··• ) ) 339 pages, 234 x 182mm • () Wlndo,ys 386, networking, CAD, graphic Intensive programs, heavy number crunching, programming, ) • }} multitasking and 32 bit software applications. The reference section offers:- Instructions for upgrading •••• } ?) an IBM XT and AT type computer to atrue 386 system. Money saving tips on how to expand your 386 ) ] By Eric Lo,ydon )J by adding 31/2' drives, ahard disk, memory, improved BIOS, 80387 math coprocessor, VGA, •••• ) The book begins with a two chapter review of fundamental electrlctty and magnetism and the algebra }) enhanced keyboard, "Micro Channel" motherboard, modem. Illustrated instructions for assembling a j ) needed for understanding transformer theory. II then covers properties of transformers with design () 386 system and easy to understand troubleshooting Instructions. There is also abuyers guide section ) ) equations, po,yer losses, the core and windings. On to transformer types, 11 covers Inductors, power, ) ] giving explanations of computer terms and trends, hints on how to buy a computer system and ·· ( current, and impedance transformers. As well as transformers used In conveners, Inverters and }} reviews of major (US) suppliers. ? recllfler circuits. Written in an easy-to-understand manner, lhls book will be Invaluable to the •·•·•<• $24.50 ) hobbyist, experimenter and anyone wishing to learn more about transformers .:.:.: :.: 454 pages, 216 x143mm Cat. BM-2116 ·•·•· :240pages,213x273mm Y Cat. BM-2 11 2 Cat.BM-2414 . I/ For owners and prospective owners of 386 computers. In a reader friendly fashion If covers OS/2, $24 50 / 17.95 !!! ByDonL.Cannon 1 T i:~u n () Digital electronics continues to take over electrical, mechanical and electro-mechanical system } By Rudolf F. Graf ) This book has a circuit schematic for just about everything you could think of to build, nearly 1300 In } all. They are listed alphabetically and divided Into 98 basic circuit cal!lllorles. For example the \ sections starting with the letter A are:-Alarms, Amateur Radio, Amplifiers, A to Dconverters, / Attenuators, Audio Mixers, Audio Oscillators, Audio Power Amps, Audio Signal Amps, Automotive. \ This Is the hobbyists and technicians dream treasury of both analog and dlgllal circuits. From ) Amateur Radio and Crossover Networks to Fibreoplics, Test Circuits, Motor Control, Video Circuits, { Timers, etc., etc., with special emphasis on state-of-lhe-art IC circuit technology. Also included Is a ) huge index lo specific circuits. \ · A massive 760 pages. Size 175 x 230mm J cat. BM-2310 $29.95 •• < ) functions. This book provides an Insight Into this high technology world In alanguage that both } }) technicians and non-engineers can understand. II presents the basic concepts and fundamental ••• (? techniques needed to locate faults In digital systems and how to repair them. The chapters are:- Digital ••• )} System Fundamentals, Digital System Functions, Troubles hooting Fundamentals, Combinational } J) Logic Problems, Sequential Logic Problems, Memory Problems, Input/Output Problems, Basic / )} Timing Problems and Advanced Techniques. 266 pages size 176 x 222mm. ••• )( This Is agenuine Sams book In the "Understanding" range. Other books In this sell for $34.95, as this > j) one should. we have made aspecial purchase and can offer this book with a limited quantity for only ·.· ) $12.95, saving you over 60% on normal prices. ·•·•·••• ONLY $12 • 95 SAVE $22 ( Cat. BM-2416 HURSTVILLE STORE HAS MOVED TO BANKSTOWN 363 HUME HIGHWAY Cnr MEREDITH STREET BANKSTOWN Phone 709 2007 Ample parking at rear TR1'R4cr;;;;,_~ •· ·•·•·•··• 'El? LOTUS 1·2·3 'I< RELEASE 2.2 This book supplies over 13,000 American, European, British and Japanese digital integrated circuits, with electrical and mechanical specs, manufacturers names and plnouts. Recommended substitute part numbers also given. This Is an essential book for anyone engaged in service of computers or other digital equipment or the serious digital enthusiast. 244 pages. Size 178 x 247mm 1st quality book, special purchase. Cat. BM-4558 AL TRANSISTOR I Catalogue price $29.95 NOW ONLY $14.95 SAVE 50% This book Is designed lo provide In one handy volume acomprehensive body of readily accessible user slanted essential Information across the field of microprocessors. In the data tabulations will be found set out the essential basic specifications of over 7,000 commercially available microprocessor chips, Including not only the microprocessor elements themselves (e.g. MPUs and CPUs) but also the many other LSI support circuits (e.g. ROMs, RAMSs, PROMs, docks, UARTs, 1/0s) normally used In harness with the microprocessors proper lo produce complete microcomputers or mlcroconlrollers. There Is only a limited quantity of this book available and once they are gone that's II. So, If you want one, don't miss out. Cal.BM-4564 ONLY $19.95 Over 5,000 American, British, European & Japanese linear IC's with electrical and mechanical specs, plnouls, manufacturer names, recommended subslilutes etc. Manufacturers address details also given, which can be handy If you want to kna.v more about adevice. Avery comprehensive technical publication and certainly the best we have seen on llnears for the price! This book could be called a 2nd, but all the Information of the regular one is there. 192 pages. Size 180 x260mm cat. BM-4557 Normally $29. 95 SAVE $20 ONLY $9.95 Ahuge data book listing datafor thousands of transistors, as well as a large equivalent section. The book Is designed for the Engineer and Technician. Section 2 lisls manufacturers names and addresses • Section 3 ls the huge alphanumeric listing of transistors with specifications • Section 4 llsts FETs with specs • Section 5 covers unljuncllon transistors • Sedlon 6 ls the substitution guide • Section 7 covers devices with the prefix CV• Section 8 lisls 100's of transistor outline drawings and terminations. 591 pages. Size 242 x 170mm cat. BM-2342 $19.95 AN ABSOLUTE BARGAIN This book has II all. It's taken the best, most useful Information from all the manufacturers data books and lumped If all together Into this one huge manual. Sections Include - • TTL 74XX, LS, S, series • CMOS 4000 and 45XX series • 8 Bit CPUS 8000, 200, 6800, 8400, 6500 series • 16/32 bit Microprocessors 8086 up, 68000, 8000 • Memory chips RAM, ROM, EPROMS • Analog devices • Linear ICs and OP amps • Clock/Calculator chips • Voltage regulator chips. Data from manufacturers includes, INTEL, Motorola, Signellcs, National, Analog Devices, Commodore, Moslek, Rockwell , Zllog, SSS. A massive 590 pages. Cat. BM-2340 $19.95 LUXE RA ~,tf{I%--~ Every year many people diefrom smoke Inhalation caused during minor home fires. Most of' ... these deaths could have been prevented if asmoke detedor had been Installed. This unll ls a self contained detector and \ operates from a 9V battery. Simply Install the battery - attach ii lo the ceiling and forget about ii. II will start beeping when the battery requires replacing (battery life approx1 year with al kaline battery) Features: • Ionisation sensor lo warn of smoke and fire even before flames are visible • Extra loud warning horn penetrates closed doors • Installs in minutes • Self contained • Buitl-ln lest bulton • Audible beep to indicale la.v battery Size125mm diameter x 45mm deep Cat. LA-5090 These beautifully cralled rack cabinets will give your equipment a real 1st class appearance. All aluminium construction. Removable lop and bollom panels. Natural or black finish . Ventilated lid. Deluxe brush finish anodised front panel. Individually cartoned. Supplied in flat pack form and easily assembled In alew minules. Mounting hole centres conform exactly lo International Racking Specifications. Finish Front Each Panel Height Natural 44 $65.00 Natural 88 Natural 132 Black Black 44 88 HB-5414 Black 132 All boxes are 254mm deep. $19.95 ' I" ,, t ' $79.50 $89.50 $79.50 $85.00 $89.50 I I APRIL ., " " ' .. _., 1A ._◄ I• I\ .:. r r .. , :,r• • E KITS TEAM SOUND IMULATOR KIT FOR AILMA TEA TRAIN At last a low cost quality, portable butane powered flame torch. Ideal for lhe hobbyist and professional. Adjustable flame, completely portable, up to 90 minutes use per 1111, adjustable temperature control, mini size, uses standard butane gas lighter fuel. Ideal 10{ shrtnking heatshrink tubing. Cal.TS-1410 ONLY $12.95 Ref: Silicon Chip Aprll 1991 Had enough of Iha! silly whine coming oul of your HO-scale '38' loco? This steam sound simulator makes a reallsllc 'chuttlng' sound thal keeps pace wllh the loco speed. Kit indudes PC board all specified components and the expensive 82mm loudspeaker. Cat. KC-5093 SOLDERING OPTION Cat. TS-1412 $9.95 $24 115 Railmaster Train Controller kit Cat. KC-5028 $89. See catalogue for full delalls. T CHASE Ref: Silicon Chip Aprll 1991 This kll ls a4 channel light chaser. Each channel will '-"' handle up to a WM globe. Dress up your car, truck, etc. A novel approach for a brake warning lighl? Kil Includes PC board and components. no globes supplied. Cat. KC-5092 Yes, thafs correct. High quality Benelec brand 0.65mm conductor, airspace PE dletedrtc, foll shield, 5mm OD sheath, brown In colour air space, 750 coax. Save a fortune over normal prices. 70i metre for quanlllles less than 100 metre roll. Cat. WB-2002 $35 • 100 metre roll ~ $ _J Ref: Silicon Chip Feb 1991 This kit enables •., you to build a high power DC inverter suitable for driving a 20 watt fluorescent light from a 12V car battery. Short form kit. See catalogue for full details. Cat. KC-5091 $ _ 32 95 0 $21 115 0 ADAPTOR/ p Ref: EA April 1991 Using your CRO this kit and the Lissajous reference chart provided you can identify unknown devices, check whether they are defective and even identify their pin connections. Kit includes box, transformer, switches, hardware and all components. Cat. KA-1733 $24.95 Jaycar will purchase your surplus stocks of components and equipment. We are continually on the lookout for ·sources of prime quality merchandise. CALL MARK HARRIS OR BRUCE ROUTLEY NOW ON (02) 747 2022 JAYCAR WILL NOT BE UNDERSOLD ON GOODS OF THE SAMI:: QUA Li l Y Sub C NiCads are commonly used in battery packs to power RC racing cars and cordless power tools. Up til now, if a battery pack failed - you would need to purchase a new pack from the manufacturer of the product. These battery packs are very expensive. The most common voltage used is 7.2 volts which is made up with 6 x Sub C NiCads. So, instead of being forced to pay $70 - $100 for a replacement battery pack, you can now fix it yourself and save a fortune. The Sub C's are supplied with solder tab and are rated at 1.2Ah. Cat. SB-2456 $6.95 A'BECKETT STREET OPEN TILL 2pm SATURDAY '., " [ ,, . ,. TR ,. H(" f ,. <I ~I JA( Aft t JA {L;AH ~ Ill NIC TH NI JA rAR[L A Ar ~ t t t •1 ' H l I •• ' ,t I CA or the hobbyist and handyman. Our lowest price 240 uality iron has astainless steel barrel. 25 watt. 1450 240V 80mm Cat. YX-2510 $24.95 120mm Cat. YX-2514 $27.50 12V 10 of every value from 10 to 10 Meg-1/4W 5%. Cat. RR-1697 60mmcat. mm ONLY $19.95 SAVE OVER 50% c31 ==- APOLOGY Last month the Incorrect photo was inserted for the CRO Adaptor Kit. We apologise for any Inconvenience caused. Here's what you gel: • 4 slotted bits 5/32', 3/16', 1/4', 9/32' • 3 Philips bits No.1, 2 & 3 • 9 hex bits 1/16', 5/64', 3/32', 1/8', 9/64', 6/32', 3/16', 7/32', 1/4' • 3 Robertson bits No.1, 2 and 3 • 2 Posldrlve bits No. 1 and 2 • ?Tone bits T10, T15, T20, T26, T27, T30, T40 • 41/4' Star sockets ES, E6, E7, ES • 7 metric sockets 6, 7, 8, 9, 1o, 11, 12mm •? Imperial sockets 3/16', 1/4", 5/16', 11/32', 3/8', 7/16', 1/2' • 1 x 1/4' drive socket adaptor • 1 x4' extension bar • Ratchet driver And all of this is housed in atough durable metal case Cat. TD-2002 NORMALLY $29.95 These have half round smooth gripping jaws perfect for adjusting and bending components, picking up that dropped nut, etc. Cat. TH-1893 $12.95 We have purchased a large quantity of DPDT 12V, 3A high quality Japanese made Omron PC mount relays. These are Telecom approved, plastic sealed with bifurcated crossbar contacts. They conform to International 2.54mm terminal pitch and have a life expectancy of 100,000,000 operations. You would expect to pay around $10 each for these. Specifications SAVE UP Voltage DC - 12V TOSO% Current - 24mA Resistance - 5000 Contact rating - 3A 1-9 $2.95 ea Cat. SY-4055 10 • 99 $2.50 ea BUY UP NOW AND SAVE AFORTUNE MAY BARGAIN Buy both for only $19.95 SAVE $6 100+ $2 ea 1O" 65W rms Cat. CG-2376 12" 1oow rms Cat. CG-2380 12" 200W rms Cat. CG-2381 15" 150W rms Cat. CG-2382 $49.50 $99.50 $159 $129 6" 30W rms Cat. CW-2108 8" 60W rms Cat. CW-2114 12" SOW rms Cat. CW-2130 15" 120W rms Cat. CW-2131 $29.50 $39.95 $69.95 $129.50 r. 6" SOW rms Cat. CW-2140 8" 120W rms Cat. CW-2142 1O" 160W rms Cat. CW-2143 12" 200W rms Cat. CW-2145 I I ~.u: II JI(, H1,. t<jlt TF ~rn h .._ll .. t .' ' ., ' ' AR A ,\),. ' $12.95 T INLESS STEEL ONLY $24.95 SAVE $5 I High quality small side cutters that have thick (2mm) blades and comfort soft plastic handles which are spring loaded. 115mm long. Cat. TH-1890 'I $75 $109 $165 $199 ., ~ •I t I "-ih , F fl N ' A ' ' CA I' ► I ~ H ir,11( ' ' ••11 Suits both band 4 and 6, channels 21 to 69. Ideal for medium and difficult signal areas. Max gain 13dB. The 12MV Is ahigh power high fidelity woofer ulilising a 38mm diameter long throw voice coil wound on an aluminium former and high compliance suspension with a polyurethane foam roll surround, resulting in excellent linearity at very high input powers. Power handling 150 wattsrms Resonant Freq 19Hz Freq. Range fa - 3kHz Senslllvity 96<1B . . Voice coil dla 38mm ' Magnet Weight 510 grams •• I Oms 3.76 Oes 0.56 Ola 0.49 Vas SSOL Cat. CW-2125 o PL259 Plug Back to front ratio 20dB. Includes balun for 75ncable. Cat. LT-3181 1.5 metre cable Cat. AV-6512 Nonmally $8.95 NOW ONLY $3.95 SAVE $5 $89.50 to 0 This "lop of the line" UHFNHF 1V antenna will really drag In those signals. Suitable for VHF 0-11 and UHF band 4 (SBS). Corner refleclors prO\/ided for Improved UHF pertormance. Provision Is made for either horizontal or vertical installation. Batun supplied for coax. Australian designed and manufactured. 3 year warranty on workmanship. Suitable for Australian capital cities. High gain with reflector for fringe areas. Powdercoat boom with insulators. Cat. LT-3181 $139 1.5 metre cable Cat. AV-6514 Nonmally $7.95 ~ C ~ ~~,~ - ___.y / .- _,.,,--, ~~ --==- .- -- - ~:~-~- _· __ I . 1.5 metre cable Cat. AV-6516 Nonmally $5.95 ~ - NOW ONLY $2.95 SAVE $3 ~ Irs II ke a standard type 12-way , ~v-- 1991 Price $99.50 NOW ONLY $2.95 SAVE $5 An excellent antenna for medium signal reception areas with moderate signals. Receives FM, VHF and UHF band 4 (channels 21-35). Either horizontal or vertical mount, corner reflectors provided for improved UHF pertormance. Balun supplied for coax. Cat. LT-3145 $115 1989 Price $119.50 . barrier strip or terminal but ii t · •.._·. has 2 strips of 12 which can 'I;. be unplugged from each other. \_ ·. So if you have any number of .· • semi-permanent wires from 1 to 12 that you have to unplug this is the Ideal Another surplus stock buy. This lime a high quality steel box, which would make agood power supply box or for general kit work. It's painted while, has ventilation slots on the top and two sides. There is a hole on one end for a mains cable and cord grip grommet and on the other end two holes for banana terminals or switches, etc. Size 165(L) x 115(W)x 125(H)mm. You would expecl to pay about $25 for this box, but you can purchase these now from Jaycar for only $12.95 or about 1/2 normal price. Cat. HB-5470 ONLY way. Cat. HM-3202 $5.95 i ' (J RRAMAr NCORD NKSTOW RE HILL 117 York St. (02) 267 f614Mon-Fri 8.30 • 5.30 Thurs 8.30 pm• Sat 9 - 1 355 Church St (Cnr. Victoria Rd) (02) 683 3377 CO BURG VIC Mon-Fri 9 - 5.30 Thurs 8.30 pm - Sat 9- 4pm Sunday 10am - 4pm ELBOURNE Cl 115 Parramatta Rd Cnr Lloyd George Av (02) 745 3077 Mon-Fri 8.30-5.30- Sat 9.00-12 'RINGVALE VIC 363 Hume Highway Cnr Meredith St (02) 709 2007 Mon-Fri 9 - 5.30 Thurs 8.30 pm - Sat 9 • 4 ADELAIDE S. A 188 Pacific Hwy (Cnr. Bellevue Ave)(02) 439 4799Mon-Fri 9 • 5.30 Thurs 8.30 - Sat 9 - 4pm 144 Logan Rd (07) 393 0777 Mon-Fri 9 • 5.30 Thurs 8.30 - Sat 9 • 4 266 Sydney Rood (03) 384 1811 • Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 - 4 Shop 2, 45 A'Beckett St City (03) 663 2030 Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 - 2 887-889 Springvale Road Mui grave (03) 547 1022 Nr Cnr. Dandenong Road Mon-Fri 9 • 5.30 Fri 8.30 - Sat 9 - 2 190 Wright Street (Cnr Selby Street) (08) 231 7355 Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 • 12 :• :! IPRODUCTSHOWCASEJ High performance airhand receiver Have you ever wanted to listen in on what the flyboys have to say when they take to the skies? This airband receiver provides reception of the normal VHF airbands for airports but also covers the military airbands in the UHF spectrum - up to 380MHz. Designated the R535, it can hold up to and scan through 60 different channels in its resident memory. It can also be used manually or it can be used to search between two frequency limits. The sensitivity of the receiver is high at better than 0.5µV to pull in those distant stations. You can operate the receiver either from a 12VDC plug pack, your car battery or dry batteries for total portability. The unit comes complete with a built-in telescopic aerial, as well as an instruction manual, AC adaptor and listening guide. Also available is a smaller handheld unit which receives the 118-136MHz T civilian airband. It has a built-in rubber ducky antenna, internal loudspeaker, a 3.5mm earphone jack, and runs from an internal 9Vbattery or an external 9V DC source. Both units come with a 12-month warranty and an airband frequency listening guide. The R535 retails for $429 while the smaller unit retails for $199. Both are available PCB drill stand from Geoff Wood Electronics Watch stores 50 telephone numbers Does your brain have a non-functional section for telephone numbers. How many times have you wanted to ring someone only to realise that the tiny piece of paper you scrawled the number on has vanished? Or what about ringing someone overseas but you're not sure what time it is over there? This watch from Jaycar Electronics will probably save a few anxious moments! It can store up to 50 telephone numbers (5 letters and up to 12 digits) and the correct time for up to 18 cities around the world. Not bad, huh? And it has all the usual features you'd expect, including five different alarm settings. It comes complete with battery, from Av-Comm Pty Ltd, PO Box 386, Northbridge, NSW 2063. Phone (02) 949 7417. vinyl band and instructions and is priced at $24.95. It's available from all Jaycar Electronics stores. Trying to steady those tiny handPC drills is pretty tricky but this new mini-drill stand will help you drill cleaner and more correctly aligned holes in your boards. The stand is of metal and plastic construction and comes with clamps for fixing to the side of your workbench. Your mini PC drill sits in the diamond-shaped clamp and is moved MAY1991 53 up and down by pushing the springloaded lever. It is priced at $59. 95 and is exclusive to Geoff Wood Electronics, 229 Burns Bay Rd, Lane Cove, NSW. Phone (02) 428 4111. High performance bipolar op amps 9-track tape drive from Elmeasco This 9-track tape drive, the OD3210, from the Overland Data Company in the US, is designed to handle the data transfer and backup needs of a PC/AT-based network in office use and is supported by UNIX, DOS, XENIX and PICK software systems. It's only 9cm high and weighs 13.5kgs, making the OD3210 one of the lightest and smallest tape drives available. It supports both 1600 and 3200 bpi tape densities and has a built-in 1Mb of cache memory, giving tape speeds of up to 60 inches per second and 550Kb/ second data transfer. For further information, contact Elmeasco Instruments on Sydney (02) 736 2888 or Melbourne (03) 879 2322. , ~ TRANSFORMER KIT Full set of transformers & chokes for 13.5V 25A Power supply. As described in this issue of "Silicon Chip". Analog Devices has released two new bipolar operational amplifiers that possess characteristics usually only available in BIFET op amps. The AD706 is a dual bipolar 8-pin DIP package with an input offset voltage of 100µV maximum and an input bias current of 110pA. The AD706 quad bipolar package is even better R535 VHF/UHF AIRBAND RECEIVER 60 CHANNEL (BASE/MOBILE) $429 INC. PACK. AND POST. Including: 1 1 1 1 - 12 MONTHS WARRANTY ATT 96 625VA Toroidal Transformer 2851 12.6V/150mA Transformer AC116 501,1H/25A Choke AC117 1mH/25A Choke This high performance airband receiver is ideal for professional or enthusiast use as a portable, fixed or mobile station. The receiver features manual, scan and search modes. and is easily programmed. Massive 60 Channel memory caters for high traffic areas. The receiver comes complete with DC power cord, mounting bracket, telescopic whip antenna and earpiece. Full service information is also available. Spoclflcltlons: Frequlftoy Cowrage (VHF): 108 - 142.995MHz in SKHz increments (UHF): 220 - 379.975MHz in 25KHz increments Scannlog Channels: 2 to 60 pre-settable Sclnolog Rate: 10 channels every 0.8 seconds Antenna Impedance: 50 ohms Power Requirements: 12V DC, negative ground, 0.28 amps max. $214.25 Tax paid Plus Freight Sydney metro add - $5.00 All other areas add - $15.00 Payment with order please. HARBUCH ELECTRONICS P/L 90 GEORGE ST. HORNSBY, NSW PHONE (02) 476-5854 FAX (02) 476-3231 "'" 54 SILICON CHIP S■ n1IUvlty (VHF): 0.89uV for 10d8 S+N/N (UHF): 1.3uV for 10d8 S+N/N Squelch Thlllllold (VHF): 0.7uV or boner (UHF): 1.0uV or better Size: 160(W) x 46(H) x 120(0) mm Weight: 850 grams Olllliay: backlit LCD Audio Output Puwef: 300mW into 8 ohms. SEND TO: AV-COMM PTY. LTD. P.O. BOX 386 NORTHBRIDGE NSW 2063, FAX: (02) 949 7095 Please send me (qty) ....................... R535 <at> $429 ea. (Inc p. & p.) Name ........................... . .. . Address ... P/code .. I/We enclose cheque for S ............. or charge to D ~ Bankcard No I LSignature D Visa D Masten:ard · Expiry Dale . I I I Dale .. ... . J High end speakers from Onkyo The Scepter 3001 Super Labyrinth Bass System from Onkyo is designed to give extended bass response - down to 40Hz. It is a 4way system, using a 10-inch subwoofer, an 8-inch woofer to handle the low to mid bass notes, and a 2-inch midrange speaker. High frequencies are handled by a 1inch dome tweeter. Sensitivity is claimed to be 88dB/watt/metre, which means it is really more suited to higher output power amplifiers, from 60 to 250 watts RMS. Frequency response is quoted as 20Hz to 20kHz within ±4dB. The Scepter 3001 comes with a 5-year parts and labour warranty and retails for $8999 from selected audio dealers. For more information, contact Audio Insight Pty Ltd. Phone (02) 488 8184. matched with an offset voltage of less than 75µV and an input bias current of less than 150pA. Another improvement is in the base current temperature drift which is only 50% over the operating temperature range. The input noise current is rated at 3pA/✓(Hz) and each amplifier requires only 600µA , making it suitable for battery-operated equipment. For further information, contact the distributors for Analog Devices, NSD Australia, PO Box 264, Box Hill, Vic 3128. Phone (03) 390 0970. PHONE LINE AND MAINS FILTER/SURGE PROTECTOR wering machines less phones imiles Handheld LCR meter measures to 200H If you're on the lookout for a portable LCR meter that does the lot, then consider this MIC-4070D LCR meter from Meter International. This unit will measure resistance from 1 milliohm to 20MQ with an accuracy of better than 2 % , capacitance from 200pF to 20,000µF with an accuracy of better than 2%, and inductance from 200µH to 200H with better than 3 % accuracy. It also measures dissipation factor for capacitors and inductors. The unit is housed in a rugged case and has spring-loaded terminal slots to make component measurements easy. Also available is a probe for sur- to be expensive. It still is, but you can fake it pretty well with this FM car telephone system form Jaycar Electronics. It's simply an FM transmitter system built into what looks like a normal earphone. Buy two and then link up with a friend and start your own mobile party line. Simply tune your car radio to a clear frequency to receive the other phone and then you're away. The maximum operating distance is claimed to be about 500 metres and the frequency is adjustable between 88MHz and 108MHz. It costs just $39.95 from your nearest Jaycar Electronics store. SC face mount device measurements. The price of the MIC-4070D is $159 from distributors across Australia. For more information, please contact Computronics International on (09) 221 2121. FM car wireless telephone Looking like the executive about town with your own car phone used The Arista model CPEP- 1 ensures that lightning, power surges and spikes do not reach your costly communication equipment as it constantly monitors the PHONE line and the MAINS power line. Simply connect to any existing power point, plug in your fax, phone, video, Hi Fi or any other 240 VAC operated equipment and a series of indicators shows the status of the mains power point while several MOV's and gas arrestors prevents access to damaging energy sources. The CPEP-1 is fully Telecom and Dept. of Minerals and Energy tested and approved. Imported and distributed by: ARISTA ELECTRONICS Available through the following reteilers: Telegrafax PIL. 305-307 Sailors Bay Road. Northbridge. 2063. NSW. (02) 95B 5137 Geoff Wood E/ec. 229Burns Bay Road. Lane Cove. 2066. NSW. (02) 427 1676. MAY 1991 55 i:i... .-Y ~ ~ D 4 ·~, • , , / d/ .Y ,,- ~ ~ ' . - \. DIGITAL MULTI METER HC -4510 DISPLAY:41 /2 DIGIT BASIC ACCURACY: 0.5% DC V DC VOLTAGE: 0-1000V DC CURRENT: 0-10A AC VOLTAGE: 0-750V AC CURRENT: 0-10A RESISTANCE: 0-20M OHMS CONTINUITY TEST, DIODE TEST DATA HOLD 20 MHz DUAL TRACE OSCILLOSCOPE CTR DISPLAY:. 150 mm rectangu lar VERTIACAL DEFLECTION: Q13030 ........... RRP $149.95 • Deflection Factor: 5mV to 20V / Div on 12 ranges in 1·2-5 step with fine control • Bandwidth DC: DC to 20 MHz (-3dB) AC: 10Hz to 20 MHz (-3dB) • Operati ng modes CH-A, CH-B, DUAL &Ad ADD (ALT/CHOP L202 on ly) • Chop Frequency: 200 KHz Approx. • Channel separation: Better than 60dB at 1 KHz DISPLAY: 3 1/2 DIGIT BASIC ACCURACY: 0.5% DC DC DC AC AC VOLTAGE: 0-1000V CURRENT: 0-10A VOLTAGE: 0-750V CURRENT: 0-1 0A TIME BASE RESISTANCE: 0-20M OHMS CONTINUITY TEST, DIODE TEST , Type: Automatic & normal triggered in automatic mode, sweep is obtained without input signal . • Sweep Time: 0.2m Sec to 0,5 Sec/ Div on ranges in 1-2-5 step with fine control and X-Y. • Magnifier: X5 at all times. CAO Probe to suit Q13010 .................... RRP $119.95 NOW$109.95 TRIGGERING DIGITAL MULTI METER HC-889 DISPLAY: 3 1/2 DIGIT DC VOLTAGE: 0-1000V DC CURRENT: 0-10A AC VOLTAGE: 0-750V RESISTANCE: 0-20M OHMS CONTINUITY TEST, DIODE TEST, . DATA HOLD, TR HFE GAIN, AUTO RANGE DMM WITH BAR GRAPH Q13040 ..................... RRP $99.95 $39 .50 each - Cat. 0122.01 • Sensitivity lnt: 1 Div or more Ext: 1Vp-p or more. • Source: INT, CH-B, LINE or EXT • Triggering Level : Positive and Negetive, continuously variable level ; Pull for Auto. • Sync: AC, HF Rej, TV (each+ or- ) at TV Sync. TV-H (line) and (frame) sync are switched automatically by SWEEP TIME/Div switch. HORIZONTAL DEFLECTION • Deflection factor: 5mV to 20V/ Div on 12 ranges in 1-2-5 step with fine control • Frequency response: DC to MHz (-3dB) • Max Input Voltage: 300V DC+ AC Peak of 600V p-p • X-Y operation : X-Y mode is selected by SWEEP TIME/ Div switch, , Intensity Modu lation Z Axis: TTL Level (3Vp-p-50V) + bright, - dark OTHER SPECS: • Weight : 7Kg Approx • Dimensions: 162 (H) x 294(W) x 352(D)mm, NOW $89.95 Q12105 .......................... RRP $750 . ,-:" .> 1 --_, ~ ~-1= DISPLAY:3/12 DIGIT BASIC ACCURACY: 0.5% DC r.;-' .• '-, DC VOLTAGE : 0-1000V DC CURRENT: 0-20A AC VOLTAGE0-750V C. Ill.,.~~ AC CURRENT 0-20A .:,~ I RESISTANCE: 0.20M OHMS TEMPERATURE:-20C -1200C ~ CONTINUITY TEST, DIODE TEST TEMPERATURE CAPACITANCE FREQUENCY, hfe TEST, DATA HOLD, ~l" Q13000 ................... RRP $169.95 NOW $149.95 I DIGITAL METER (YF-120) • AUTORANGING OPERATION I DATA-HOLD FOR EASY READOUT • FULL RANGE PROTECTION •0-500 VOLTS AC-DC ,r......,~...,,. 1 • 0-20 M -.....;.,..J:lUiil • DIMENSION & WEIGHT= 133 x 29 x 17mm and 60g APPROX Q11270 ......................................ONLY $55.00 LOGIC PROBE (LP-2800) USEFUL FOR TTL AND CMOS. HIGH & LOW INDICATORS PULSE MEMORY. FOR THE HOBBIEST OR SERIOUS TECHNIICIAN FOR TRACING THOSE HARD TO FIND FAULTS ON LOGIC BOARDS. Q11272 ............................ RRP$29.95 NOW $19.95 .,.,, NOW $695. . DIGITAL MULTI METER HC-3500T ,c=; ~: ·~ '- 100 MHz 3 CHANNEL 8 TRACE MODEL 5510 This instrument meets the customers needs in quality of performance, efficiency, function, design, and cost! Being rugged, highly reliable and a multi-purpose 3 channel, 8 trace oscilloscope with a 6 inch domed mesh type 14kV post deflection acceleration cathode-ray tube and with a fine red internal graticule. FEATURES: • Compactness, lightweight, ruggedness and simple design. • The diecast frame provides compactness lightweight and ruggedness . • Essy Operation Light torque lever switches and push button switches are used . • High Brightness CTR, high acceleration voltage and high beam efficiency of the 150mm rectangular CTR ensures a bright high speedsweep observation • Multi mode display system CH1, CH2, CH3, Add any combination o• all the channels may be viewed simultaniously. Maximum 8 trace displaying is possible with the ALT sweep function. • High sensitivity and wide frequency bandwidth, The maximum vertical sensitivity is 1mV/DIV (when x 5 MAG)at 20 MHz or greater 3dB and mV/DIV at 100 MHz or greater -3dB. • High input impendance The input impendance of CH1, CH2, CH3, is 1 Mn-j-2%, 25pF t3pF Q12109 ......... RRP $2995.00 NOW $2795.00 SCHOOLS & COLLEGES TAKE NOTE! ONLY $2395 tax exempt. -f ~ BNC PLUGS AND SOCKETS bifiRJt Heatsink compound is applied to the base and mounting studs or transistors and diodes . It maintains a positive BNC MALE PLUG 1 -9 improves heal lransrer from the device to the heatsink , thus P10514 $2.50 S2.25 $1 .50 increasillg overall efficiency. H11800 .. 10g ...... $2.00 Hl 1810.. 1 .... $14.95 BNC PANEL SOCKET 1.9 P10516 $2.50 S2.25 $1.50 ::- 1.1 l ·9 10-99 10<'• ~ to transmit at 40kHz (L 19990) and recieve at 40 kHz (L 19991 )with up to 20V 1/P on the transmitter. These units can't be heard so are Ideal for TV remote control's , water level detectors, burglar alarms, motion detectors and information carriers as they can be either pulsed or used In a continues wave mode. Designed · BNC SOLDERLESS TWIST ON PLUG 10+ ·Transmitter 1·9 L 19990 ..... $3.95 $2.95 CANNON TYPE 3 PIN CHASSIS MALE 1·9 Receiver L19991 .... $3.85 ffl CANNON TYPE 3 PIN LINE FEMALE 1-9 10+ $3.95 $3.50 $2.90 ~ 1~ ,so.ea • P1os21 Transmitting system : Crystal oscillation. Microphone : Electret condenser Power supply:9V battery Range: 300 feet in open field wire wrap sockets are tin-plated phosphor bronze. P10579 P10580 P10585 P10587 P10590 P10592 P10594 P10596 P10598 1·9 10+ 8 pin 1.50 1.40 14 pin 1.85 1.70 16 pin 1.95 1.80 18 pin 1.95 1.80 20 pin 2.95 2.75 22pln 2.95 2.70 24 pin 3.95 3.50 28 pin 3.95 3.50 40 oin 4.95 4.50 IDCPLUGS ~ AND SOCKETS .. oscHlalion Oimmensions:115x32x44mm Weight, 220grams 10452 ...••.••... ...• $99 • DE9P o pin plug 100• P12156 $2.95 $2.S0 $2 .00 3way • DA15P 15plnplug so.ea • DB25P 25 pin plug P12170 SI.SO '3.15 $3.50 9 PIN TO 25 PIN $3.50 $2.50 CONNECTOR 0 TY PE IDC SOCKE TS ADAPTORS The perfect solution! Features gold plated pins X15668 D89 Plug to 0825 Socket X15669 D89 Socket to 0825 Plug. -~! each $8.95 , m: metre 1·9 +m 1.20m 100+ m $1 .90m 100+m .20m $2.50m CIC25 100. .. · OAl5S 15 pin aocke1 P12169 $3.50 $3.00 $2.50 . oe2ss • Plug P12200 10 , 100. $3.95 Pluac bom• with plulc Iopa 1nd avallab• In 5 alzea. Very popular fro project.a & very economkal H10111 ..... $4.95 $3 .00 $2.95 • Sor.ket , .9 P 12201 100 , ,o. $3.95 $3.00 $2 .95 10+ $4.75 3.40m $3.DOm LESS ' HONE :, H10112 ..... $5.75 '$5.25 • 130 X 68 X 41mm H10113...• $2.95 $2.50 ELECTRET MIC •83xS4x28mm H10115 .....$2.25 . IW11h pins tor eas-,, boar c, ,n!>erT ,,, . $1.95 ·r. at C10 , 70 $2.50 $1.20 • 120 x 65x 38mm H10120 ..... $2.95 INSERTS ., ,o. $1.00 P10895 DA15S $1.00 $0.80 P10902 D825C $1.00 S0.80 P1090S 0825P $1.CN) t------------1 ,\ 1-----------1 ' i-----------t J., TOGGLE SWITCHES 1·9 10-99 S11010 O.P.O.T $1.20 $1.10 S11020 0.P.0.T $1 .30 $1.20 I •Nlm!il ► PANEL METERS GALORE We have a great range of panel meters at great prices! 010500 MU45 0-1m A $12.50 010502 MU45 50/50uA$12.50 010504 010510 010518 010520 010525 MU45 (l-100uA$12.50 MU45 0-5A $12.50 MU45 0-1A $12.50 MU45 0-1A $12.50 MU45 0-20V $12.50 010530 010533 010535 010538 MU52E 0-1A MU52E 0-SA MU45 VUP MUSS 0-SOuA NICADS Save a fortune on expensive throw away batteries with these quality Nicads and Rechargers! Size Oesc. 1-9 10+ 100. AA 450mAH $1.95 $1.75 S1 .50 C l 2 AH $9.95 $9.50 $8.95 D 1 2 A H $9.95 $9.50 $8.95 $14,50 $14.9S $14.95 $16.95 010540 MU65 0-1mA $16.95 010550 MU65 0-100uA$16.95 r-----------1 · Requires no crossover and handles up to 100 Watts Sensilivity : tOOdB/ 0.5 m · Frequency response: 3kHz-3-0kHz Independence: 8 ohms . · Size 96 m diameter Normally .......... $12.95 ONLY ......... ........... $9.95 10W HORN T12469 ·········$12.95 10+ tans only $11 .95 each FANS 240V 45-s··T12461 .. $12.85 115V 4 5·8" T12463 .. $12.95 240V 31 2·· T12465 .. $12.95 115V 312"T12467 ... $12.85 VOLTAGE REGULATORS BARGAINS De■ crlptlon 7805UC 7812UC 7815UC 7905UC 71112UC 71115UC 78L05 78L12 LM324 555 741 10. $0.45 $0.45 $0.45 $0.55 $0.55 $0.55 so.40 · SCl.30 $0.40 $0.30 $1.00 $0.90 $0.40 $0.38 $0.50 $0.45 1·9 $0.50 $0.50 $0.50 $0.60 $0.60 $0.60 •• . ~~"'' SPEAKERS White durable plastic . 8 ohms Cat. C12010 12V DC FANS 0 P10905 0825S $1.00 SO.SO DEi!f'_.$1.(IO SO.SO ~ 80 r 80 • 25 .4mm 12\/ DC. 1.7 Watt , 0.14 Amps $0.80 P111180 1·9 10 • i-0_1_05_oo_M_u_•_s_o-_2o_v__s_1_•·-•_s-i 2155 240V 6-15V 1A Cat M12155 $8.95 $7.95 2156 240V 6•15V A2 Cat M12156 $13.95 $12.95 2840 240V 9VCT Cat M12840 $4.95 $3.95 MOSFET 2851 240V 12-6V CT 250mA SPECIALS CatM121151 $4.95 $4.50 2860 240 V 15VCT 250m A 1·9 10+ Cat M 12860 $4.95 $4.50 2SJ49 $7.50 $7.00 6672 240V 15 30vc 1A tapped 2SJ56 $10.00 $9.50 Cat M16672 S12.95 S11.95 2SK134 $6.90 $6.50 2SK176 $9.50 $8.90 Quality. !ans tor use ,n power imps, compulers , hotspot cooling ete . An-,,where you need plenty of air. • 195 x 113 x60mm 100+ m TRANSFORMERS 25 pin aodl.et IOC CE NTRONI CS 36 WAY PLUG & SOC KET • 150 • 80 • 50nm RECTANGULAR LEDS 1·9 10-99 100+ RED 20c 15c 12c OREEN 20c 15c 12c YELLOW 20c 15c 12c ORANGE 20c 15c 12C P12171 $,t.50 $3.85 $3.50' m 1-9 10. P12167 $2.95 $2.50 $2.00 1•9m $1 9 pin aoeket . 0E9s W1267 $1.30 W12 ,o. 1·9 100. $1.00 $0.70 P10891 DA15S $1.00 S0.70 P10892 DA15C $1.00 SO.SO P10880 DA15P $1.00 SO.SO ___, --- ::~:es~:~~!,~~~~~o Led It you have 2 or 4 compalIble devices that need to share a third or fifth, then these lnexpencivedata tranfer will 1 ::::~=~t~1~/ :~:;i~:~~!:s and leads around. · No power required Speed and code tranparent Two or four position rotary switch on front panel. · Switch comes standard with female connector. RS232- 2 way .....................$39 RS232- 4 way .................. ... $59 RS232- X over ................... $69 RS232- 2 way auto ............. $69 Centronics- 2 way .............. $49 Centronics- 4 way .............. $69 Cenlronics- X over ............. $69 Centronics- 2 way auto ..... $79 P10890 OA15P I I---T":"=:.="v:;::.;;;-----1 HAVE YOU RECEIVED YOUR FLAiffllNG ~DS NEW 148 PAGE RO red 5mm 1-9 10+ IRVING ELECTRON! 210159 s1.10 s1 .oo CATALOGUE WITH 32 PAGES 0 DATA. FREE WITH ORDERS OVER $10 RECIEVER SPECS : Receiver freq : 37.1MHz Output level: 37mV(max) Receiving sys: Super crystal t---------:::-; ~~ COMPUTER CABLES 1QUALITY 5MM LEDS 1-8 1 - 100+ Z10150(R) S0.15 S0.10 S0.10 21 0151(Glso.20 so.15 so.12 z10152(Y> so.20 so.15 so.12 SWITCHES ·These quality 3 level P12168 $3,50 $3.00 $2.50 10+ 100+ 0+ m Transmitting Frequency : 37.1MHz DATA~ WIREWRAI>. IC SOCKETS SO. 50 SOAO so.ao so. 10 CANNON TYPE 3 PIN LINE MALE , 10+ QUALITY 3MM LEDS 1-8 1 - 10G+ Z10140(Rl ...$0.15 S0.12 S0.10 Z10141(G) ....S0.20 S0.25 S0.12 Z10143(Y) .... S0.20 S0.1 5 S0.12 210145(01 ... S0.20 so.15 S0.12 1-----------1 A lntertoc:king end• to form any number of corwctlone. Standard 5mm 1paclng pine • P10520 2 way IC:7 P10860 $4.50 p10575 40 pin .....'5< 40e lSC DB25 CONNECTOR . 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Box 620, Cloyton, 3168 Order Hotline: 008 33 5757 (Toll FrM Sb1c11y ordera onty) POSTAGE RATES $1 • $9.99 •••••••••• $3.00 $10 • 24.00 ••••••••$3.50 $25 • $49.99 ••••••$4.50 $50 • $99.99 •••••• $6.00 $100-$199 ••••••• $7.00 $200 • $500 •• ••••,f REE; $500 Plus ......... FREE ·Ill 13.5V 25A power supply for amateur transceivers This massive power supply has been designed especially for running big amateur transceivers and RF linear power amplifiers. It is much more efficient than typical transistor regulated power supplies and is fully protected with fuses, current limiting and overvoltage crowbar protection. By JOHN CLARKE & LEO SIMPSON Many of the 100-150W amateur transceivers available today require an external 13.5V supply for their power. This can be either in the form of a commercial power supply unit or an automotive battery together with suitable charging facilities. Both of these methods have their drawbacks. Ready-built power supplies are often not up to the task of supplying their full power output for more than a few minutes at a time because of their duty cycle limitations. In other words, they have been de58 SILICON CHIP signed to cope with the power demands of transceivers on speech mode. When long periods of continuous transmitter operation are required, as on RTTY (radioteletype) signals, these duty cycle limited power supplies are likely to be embarrassed. That's not to say that big, continuously rated power supplies are not available. They are, but at a considerable price. They also have the drawback of considerable heat dissipation, which requires big heatsinks and perhaps even fan cooling. The new SILICON CHIP 13.5V 25A Power Supply can supply continuous loads , does not get hot and does not have big heatsinks or need fan cooling. Why? Because it is not designed along conventional regulated power supply lines. The secret of its operation is Triac control and therefore little power loss in the system ofregulation. We'll talk more about this later in the article. Features The new power supply is built into a 3-unit high rack mounting case measuring 483mm (19 inches) wide), 140mm high and 340mm from front to back. On the front panel is the power switch, the output terminals, · the 30A fuse holder and the crowbar and regulated output indicator LEDs. At the rear is the mains input lead, mains fuse and heatsinks for the stud type rectifier diodes. Specifications for the power supply are listed in the accompanying panel and are very good considering the amount of current that the unit can supply. The load regulation var- ies by about 0.26V for every lO0W change in load. This means that for a no-load output voltage of 13.5V, the full load voltage will be 12.56V at 350W. For a change in mains voltage from 240V to 220V AC , the output changes by only 9m V. The figures for regulation and hum and noise output may not seem all that marvellous when compared with a conventional regulated power supply. However, they are quite good enough for use with amateur transceivers and RF linear power amplifiers. The crowbar protection is a plus feature for any transceiver. It works to short the output if it happens to rise above 15V DC. This might occur if there is a large transient on the mains supply, if someone fiddles with the output connections from the supply while it is delivering heavy current, or (horror of horrors) the power supply has a catastrophic failure. If the crowbar protection does operate it may blow the 30-amp output fuse but a more likely result is that the power supply will merely shut down. Normal operation is then restored by switching it off, waiting a minute or so, and then switching on again. The crowbar circuit can be adjusted so that it crowbars at 15V. Similarly, the output voltage can be adjusted for Specifications Rated output voltage ........................................ .... ...... ...... .... .... 13.5V DC Continuous output current ............ ..... .. .. .. ..... .. ...... .... .. ............... 25 amps Peak output current ..... ... .. .. ... ...... .. .. .. ... .. .... .... ........... ... .. ... ...... .. 35 amps Crowbar protection voltage ...... ... .. .. .. ... .. .. ...... .. ................. .... .. .. .. 15V DC Load regulation ..... ..... .. ................... .. .... .. ... .. ... .. .. .. . <7% for 25 amp load Line regulation (260VAC to 220VAC) ... .... ...... .. .. ........ ... .... .. .. . <20mV DC Hum and noise at rated output ....... .... ... 100mV P-P (no switching hash) 13.5V no load output and the overcurrent protection adjusted for a peak current of 35A. Method of regulation One of the main problems associated with conventional regulated highcurrent power supplies is heat dissipation. This is because the circuitry usually requires an input voltage about 10-12V higher than the specified output voltage. This is needed to allow for the inevitable voltage drop across the regulating transistors and to leave some margin so that the power supply can still deliver its rated output current even if the mains supply voltage drops to 220V AC or below. And there lies the problem. If the input to output voltage drop is 12V and the output current is 25 amps, the heat which must be dissipated by the regulators is 300 watts! After you allow for the additional power losses which occur in the transformer, the rectifiers , filter capacitors and internal wiring, a 13.5V power supply rated for 25 amps (ie, around 340 watts) is likely to dissipate a maximum of 380400 watts! In other words, it will waste more power than it can deliver and its efficiency will be less than half. No wonder big heatsinks and cooling fans are Below: the 13.8V 25A power supply is built into a 3-unit high rack-mounting case. Because it features Triac control, it does not get hot & does not require big heatsinks or fan cooling. Other features include foldback current limiting & overvoltage crowbar protection. MAY1991 59 'REGULATED OUTPUT. INDICATOR 15A FUSE CROWBAR INDICATOR POWER Sl ./ A ~ I ,. PHASE CONTROLLER- I I I 240VAC MAINS I I 7kV MAINS ISOLATION 30A FUSE PRI 240V + N~D----------1--+--+---___,, CURRENT SENSE E~ CASE OUTPUT 13.5V 25A OUTPUT SENSE GROUND REFERENCE CURRENT SENSE CROWBAR Fig.1: the general arrangement for the power supply. Regulation is achieved by using a Triac (part of the phase controller) to switch the primary of power transformer Tl. The output from the bridge rectifier is then filtered using two chokes & two 80,000µF banks of capacitors. losses are reduced by other circuit measures. Block diagram a must for these conventional power supplies. When you consider the above points against conventional power supplies it is no wonder that personal computers come with much more compact and efficient switching power supplies. These are now well proven and very reliable but they present a problem when used with sensitive transceivers - interference from the switching hash. The method of regulation used in the n ew SILICON CHIP power supply reduces dissipation to a minimum and produces very little in the way of radio interferen ce. It does this by controlling the mains voltage supplied to the primary of the power transformer. This avoids the power losses in regulating transistors although there are still losses in the transformer, rectifiers and filter components. However, as we shall see, transformer and filter Most of the circuitry for the power supply is mounted on this PC board, while a second PC board holds the two 80,000µF capacitor banks. 60 SILICON CHIP Fig. l shows th e gen eral arrangement for the pow er supply. The 240VAC mains input to the transformer (Tl) is driven by a phase controller which uses a Triac as the switching element. The phase controller circuitry monitors the output voltage and current and then adjusts the amount of mains voltage which is supplied to Tl so that th e output voltage remains within sp ecified limits. If the controller sens es excess output current, then the transform er voltage is reduced to limit the current to safe levels. The secondary winding of transformer Tl drives a bridge rectifier consisting of four 70A stud mounting diodes. These really rugged diodes are mandatory in a big supply of this nature - smaller components quickly snuff it. Instead of.directly feeding a bank of filter capacitors, the output of the rectifier is fed via a 50µH smoothing choke which is quite a substantial component and then to a bank of capacitors totalling 80,000µF. Following these is another smoothing choke, this time of lmH , and then another 80,000µF capacitor bank. The use of smoothing chokes has several big benefits. First, it greatly reduces the huge peak charging currents which would otherwise need to be supplied by the transformer and rectifier diodes. Normally, these charging currents can be expected to be as much as 10 times the average output Because heatsinking requirements are minimised by the design, construction is fairly straightforward. The phase controller switches the 625VA toroidal transformer at upper left to provide output voltage regulation, while a second smaller transformer supplies all the low-voltage control circuitry. current. With a 25 amp rated output, charging currents of this order (250 amps peak) would cause very high heat dissipation in the transformer secondary, in the rectifiers and in the connecting wiring. In effect, the use of smoothing chokes in this power supply is <!throwback to the power supplies of valve amplifiers. The chokes give another advantage too - residual hum with an almost pure lO0Hz sinewave rather than the more troublesome l00Hz sawtooth hum waveform of conventional capacitor-input power supplies. So by using chokes in the smoothing network (also known as pi-section filters) and a phase-controlled Triac in the transformer primary, this power supply completely avoids the use of conventional regulators. power supply, considerable isolation is required to ensure protection of both the user and the transceiver equipment. This is provided by an optocoupler which is rated for 7.5kV isolation. Current sensing presents a problem too, at the high current ouptuts of this supply. In this circuit, the current sense resistor is only 2 milliohms so that the voltage drop across it at a current of 25 amps is only 50mV. The crowbar protection trips an SCR if the DC output voltage exceeds 15 volts. Under normal circumstances, the crowbar SCR will discharge the capacitors and the power supply will shut down. The shutdown is due to the crowbar feedback signal which tells the phase controller to stop supplying power to the transformer. High voltage isolation The complete circuit for the new power supply is shown in Fig.2. The lower section of the circuit is really quite similar to the block diagram Since there is a feedback connection between the 240V AC phase controller and the 13.5V output of the Main circuit while the rest of it is mainly taken up by the circuitry which controls the Triac. Notice that there are two power transformers in the circuit. First, there is the big 625VA job which is controlled by the Triac (down in the lefthand corner of the circuit). The second transformer, T2, is in the top lefthand corner of the circuit and supplies all the low voltage control circuitry. T2 is a 12.6V 150mA transformer which is connected to a half-wave voltage doubler circuit consisting of diodes D5 and D6 and two l000µF capacitors. This provides about 17V across each l000µF capacitor and feeds 7805 positive and 7905 negative 5V regulators. The overall voltage across the two regulators is lOV. The output from the 7905 is designated the GND reference for the circuit, while the output of the 7805 becomes the +10V rail. The reason for producing this fairly complex supply rail is so that we have a precise +5V reference or centre tap for the control circuitry and for the zero crossing detector. The AC waveform from T2 is apMA Y 1991 61 '-:I ::r:: ..... n :z: n 0 [=:: Cl) N Cl) OUT POWER GND t IN I I I : CASE .,. 1, .Iii 16VWI POWER O_N RESET AND DELAY E~ N ~ -- 240VAC I OUT 0.1 25p~AC _J •I I I I I --~--7 ~]: A GND 5 ffi' ffl IN 5 10 .,. 114 --....., !!.D RESET AT ZERO CROSSING T2 2851 I I 33on 2.2k J"lJl_ 10 ~ .,. ~ '"'I I VOLTS SET VR11QO~ 01 BC327 +lOV 10k t *0.1l cu~~Wo~ET :Sl 470k t I CURRENT LIMIT • -1 013 . ~ ~ .,. 33 .J.:" 16VWI SLOW TURN ON CROWBAR INDICATOR LE02 1k~ 4701 470k~ 470k 1N4148 47k .,~. ZERO CROSSING DETECT!)R I .022 1N4148 DlO 1N414~ +10v-~...- - - - - - - - - - - - - - - - - - , 100k +l QV -:- 2.2~ I I m I -;- +10V 2.2 BP 100k .,. I .027! ------II 470k! <at> D11 1N4148 RAMP f\.j\J 2.2k .,. *il.1I I Fig.2: the bottom section of the circuit diagram is quite similar to the block diagram (Fig.1). Triac 1 is used to switch the mains input to transformer Tl, while IC6 (MOC3021) provides the 7kV isolation for the control circuitry. In operation, ICla compares an error voltage from IC3a with a ramp voltage generated by ICld & IClc, & switches the 'Iriac via IC4b & Ql. IC5 & SCRl provide the overvoltage crowbar protection while IClb monitors the voltage across the 2mQ current sense resistor. ~ ~~~ + t-f'r.iN g- ... "'~ ... 0 > ffi _..,"' > 0 ..... 0::<0 c..,O:: ::E i ~ ~ + I c::i~ !;;~ .. ., Ei"' "' ~:,; -u ..,c ., ::E ·c plied to pin 8 ofICld (a comparator) via a lkQ resistor and is clamped to the +5V supply by diodes D7 and D8. ICld is connected as an inverting Schmitt trigger so that its output at pin 14 swings high when the AC waveform falls just below the +5V reference supply rail, and low when the AC waveform goes just above the +5V reference. ~Ii! -oca: a:<> c., ~ ·ffl ~c ~~ •..,i;~ . I· .c:3~"i ~ ~$!c: C: c. c. <O <O + .,.~1 I e"' :::, C g~g CJ) ="' eM a: w cc- ~,§ 3: :~§: 0 C:3: i.n an c. ~~£!~ !:?."' + <( I It) N C .8c~8 c- > U"! ="'M e M ,- Q==--;. ~~ g;: ·'..! -> :is- ~-~ -~ C ' a:~ <"' > .... > I GIJ=;~ < ~ .., =(J ~· ~3:: :is.,:; ~~ -g ::E ,. 3:: ~ m Ramp waveform Thus, ICld's output is a square wave which changes from low to high and high to low at the zero crossing points of the 50Hz mains AC waveform. This square wave is buffered by Schmitt NAND gate IC2c and inverted by gate IC2d. At the output of each of these two NAND gates is a differentiating network consisting of a .022µF capacitor and a 47kQ resistor tied to the +lOV rail. The differentiating networks convert the NAND gate output square waves into spike waveforms - every time the output goes high or low, a positive or negative spike occurs. Diodes D8 and D9 act as an OR gate so that their output is a train of negative spikes with a repetition rate of lO0Hz, locked to the zero crossing points of the 50Hz mains waveform. This waveform is fed to IClc which is an LM339 comparator connected as a Schmitt trigger. The positive pulse output ofIClc is used for two purposes: (1) as a reset line for IC4b (more about this later); and (2) to provide a sawtooth ramp voltage via diode D11 and its associated .027µF capacitor. The resulting waveform is synchronised to the zero crossing points of the mains waveform. It is depicted in the series of waveforms shown in Fig.3. The ramp voltage is applied to cornparator ICla at pin 6 and is compared with the error output of op amp IC3a at pin 7. Error amplifier IC3a is the error amplifier which monitors the DC voltage at the first 80,000µF capacitor bank. This amplifier has a gain of -10 due to its lOkQ input resistor and lO0kQ feedback resistor. A 2.2µFbipolar capacitor across the lO0kQ resistor sets the response time of the amplifier. IC3a amplifies the difference between the voltage across the first 80,000µF capacitor bank and the reference voltage set at its pin 12. This amplified voltage is called the error voltage and is applied to pin 7 of comparator ICla. The waveforms of Fig.3 show the error voltage superimposed on the ramp voltage. Each time the ramp voltage at pin 6 falls below the error voltage at pin 7, the output of IC la goes high. This waveform could ostensibly be used to drive the MOC3021 optocoupler and hence trigger the Triac (in the lefthand corner of the circuit). But we send the waveform through a little more jiggery-pokery before that happens. The output of comparator ICla is applied to the clock input of flipflop IC4b. This merely inverts the waveform and drives transistor Ql which inverts the waveform again and then drives optoptocoupler IC6. The optocoupler drive is shown as the third waveform in Fig.3. Power on delay Now have another look at IC4b because there is a little more to it than we've just described. It is reset by the pulse waveform from IClc (as mentioned earlier) but not before that waveform passes through NAND gates IC2a and IC2b. IC2a functions merely as an inverter but IC2a does a little more since it has a lµF capacitor connected to its pin 6. This provides the power on delay for the Triac circuitry. What happens is that when the circuit is first turned on, the lµF capacitor at pin 6 of IC2b is discharged and therefore IC2b does not gate any reset pulses through to IC4b. Hence, IC4b sits there doing nothing and Ql cannot turn on to drive IC6 and the Triac. So the big transformer gets no voltage applied to it. After a few seconds, when all the voltages for the control circuitry have MAY 1991 63 PARTS LIST 1 3-unit high rackmount case (Altronics H-0417 or equivalent) 1 AT96 18V 625VA toroidal transformer (Harbuch Electronics) 1 50µH 25A choke (L 1) (Harbuch Electronics) 1 1mH 25A choke (L2) (Harbuch Electronics) 1 Neosid 17/742/22 iron powdered toroid (L3) 1 2851 12.6V CT transformer 1 PC board, code SC14105911, 165 x 125mm 1 PC board , code SC14105912, 180 x 176mm 1 Dynamark front panel label, 120 x80mm 1 Dynamark front panel label, 100 x25mm 2 heatsinks, 75 x 105 x 25mm (DSE H-3422) 1 30A panel mount 5AG fuse holder (Altronics S-6030) 1 30A 5AG fuse (Altronics S5977) 1 3AG panel mount 240VAC fuse holder 1 15A 3AG fuse 1 large red binding post 1 large black binding post 1 neon illuminated DPDT rocket mains switch (DSE P-7706) 1 cordgrip grommet 1 mains cord with moulded 3-pin plug 2 Clipsal 563K16 insulated connectors 2 8mm cable clamps 1 2-way mains terminal strip 2 5mm LED bezels 14 PC stakes stabilised, the voltage at pin 6 of IC2b rises sufficiently to allow the reset pulses through to flipflop IC4b and so the Triac starts getting trigger pulses on every hal f cycle of the m ains waveform. But even th en there i s some trickery involved. Slow turn on Big toroidal transformers such as the 62 5VA job use d here do not like being hit with the full m ains voltage when they're first switched on. If that 64 SILICON CHIP 1 1-metre length of 3.2mm squared dual cable (DSE W2015) 1 1-metre length of 7 .5A mains rated cable 1 150mm length of 1.25mm enamelled copper wire 1 2-metre length of 0.63mm enamelled copper wire 8 6mm PC standoffs 5 cable ties 27 machine screws and nuts 4 6mm ID rubber grommets 4 insulating kits for 1/4-28 threaded stud diodes 5 10mm Utilux eyelet lugs 2 4mm Utilux eyelet lugs 1 solder lug 1 100kn miniature horizontal trimpot (VR1) 2 20kn miniature horizontal trimpots (VR2, VR3) Semiconductors 2 70HFR20 or 70HFR40 70A stud diodes (from NSD) , (01 ,02) 2 70HF20 or 70HF40 stud diodes (from NSD), (03,04) 3 1N4002 1A diodes (05,06 ,014) 7 IN4148 signal diodes (07-013) 1 MAC320A8FP insulated tab 20A mains Triac (from VSI), (Triac 1) 1 MCR69-2 25A SCR (from VSI), (SCR1) 1 BC327 PNP transistor (01 ) 1 BC337 NPN transistor (02) 1 7805 +5V 3-terminal regulator (REG 1) 1 7905 -5V 3-terminal regulator (REG 2) 2 5mm red LEDS (LED 1, LED2) 1 LM339 quad comparator (IC1) happens , they draw heaps of curren t and they blow fus es an d dim your house lights. To avoid that little pr obl em , we have a slow turn on feature . This starts out by triggering the Triac very late in each half cycle and so the transformer gets only a small portion of the mains w aveform to nibble at. After that, the Triac trigger pul ses are allowed to arrive earlier in each half cycle and the circuit stabilises at its specified output voltage. This slow turn on feature is pro- 1 4093 quad NANO gate (IC2) 1 LM324 quad op amp (IC3) 1 40 13 dual O-flipflop (IC4) 1 MC3423 overvoltage crowbar (IC5) 1 MOC3021 Triac driver (IC6) 1 V275LA20 Varistor Capacitors 16 10,000µF 50VW PC electrolytic 2 1000µF 25VW PC electrolytic 1 470µF 16VW PC electrolytic 1 33µF 16VW PC electrolytic 1 22µF 16VW PC electrolytic 2 10µF 16VW PC electrolytic 1 2.2µF 50VW bipolar electrolytic 2 1µF 16VW PC electrolytic 1 0.1µF 250VAC mains capacitor 3 0.1 µF monolithic 1 .027µF metallised polyester 2 .022µF metallised polyester · 1 .01 µF metallised polyester 1 .01 µF 250VAC mains capacitor Resistors (0.25W, 5%) 9 470kn 1 680n 1 150kn 2 680n 1W 2 100kn 1 560n 3 47kn 1 390n 9 10kn 1 330n 2 4. ?kn 1 100n 1 3.3kn 4 56n 5W 5 2.2kn 1 47n 1W 5 1kn Miscellaneous Hookup wire, heatshrink tubing (for mains switch & fuseholder), heatsink compound , solder. vi ded by the 33µF capacitor at pin 12 of IC3 and the 150kn/10kn voltage divider on pin 13. The voltage divider supplies a small vol tage to pin 13 in the absence of any voltage across the first 80,000µF capacitor bank, w hile the 33µF capacitor provides a slow ri se in the reference voltage at pin 12. The ramp, the error voltage and the Triac drive thus provide a control loop which keeps the DC output of the supply at a constant voltage, as set by VR1. If, for example, the DC output rises above · its set voltage, the error voltage drops and, as a result of comparator action by ICla, the Triac is fired later in the mains cycle. Thus, the DC output voltage will fall. On the other hand, if the output voltage falls below its set voltage, the error voltage rises higher up the ramp. Thus, the Triac fires earlier in the mains waveform to increase the DC output voltage. RAMP PIN6, IC1a Current limiting Comparator stage IClb provides the current limiting feature. This stage monitors the voltage across the 2 milliohm (2mQ) current sense resistor via a lOkQ resistor, while VR2 provides a reference voltage on pin 5. If this reference voltage is exceeded by the voltage across the 2mQ sense resistor, IClb's output goes low. This low output discharges the 33µF capacitor 1.3-t pin 12 of IC3a via diode D12. This pulls the reference voltage on pin 12 of IC3a low and consequently the DC output is reduced to a very low voltage. At the same time, because of the hysteresis effect of the 470kQ resistor between pins 2 and 5 of IClb, the reference voltage at pin 5 is greatly reduced. This has the effect of lowering the current sense threshold even further so that the trigger pulses delivered from ICla (and IC4b, Ql & IC6) to the Triac come even later in each mains halfcyle. Thus the output current is "folded back" to quite a low value which the supply can deliver without getting hot. Once the current overload is removed, the power supply voltage returns to normal. Crowbar protection The crowbar circuit operates inde- This CRO photograph shows the ramp waveform synchronised with the 50Hz AC mains sinewave. MOC3021 Pli4f!C6 LEO DRll!E Fig.3: these waveforms show how the mains input to transformer Tl is switched to achieve regulation. ICla compares the ramp voltage on its pin 6 input with the error output from IC3a. Each time the ramp voltage falls below the error voltage, ICla's output goes high & the MOC3021 switches on to drive the mains-switching Triac. pendently of the rest of the control circuit but is linked in with it, as we shall see. It is in the righthand bottom corner of the circuit. IC5 is a Motorola MC3423 overvoltage crowbar IC designed specifically for this task. It monitors the output voltage via a lOkQ resistor and trimpot VR3 which is normally set to trip at 15V DC. When the supply's output voltage reaches 15V, IC5's output at pin 8 goes high and turns on SCRl. SCRl "crowbars" (ie, short circuits) the output voltage and discharges the 80,000µF banks of capacitors. If the voltage went high as a result of a circuit defect, SCRl will also blow the 30 amp output fuse so that no further damage can result. Normally though , an over-voltage condition may not be due to a circuit defect and so the crowbar IC can shut down the control circuitry. It does The lower trace in this photo is the chopped mains waveform applied to the transformer at light loading. This photo shows the chopped mains waveform applied to the transformer with a 350W load. MAY1991 65 . The big 70A stud-mounting diodes in the rectifier (D1-D4) are bolted to heatsinks on the rear panel of the case. Because of the efficient technique used to regulate the supply, heatsinking requirements are modest compared to more conventional units which have large losses in the regulator transistors. this as follows: when the trip condition occurs, pin 8 goes high and pin 6 goes low and turns off Q2 which is associated with flipflop IC4a. Q2 causes IC4a to change state so that its Q-bar output (pin 2) goes low. This causes the 33µF capacitor at pin 12 of IC3a to be discharged via diode D13. As we have seen before, when this capacitor is discharged, the supply is shut down and so very little current passes through SCRl. When IC4a's Q-bar output goes low, its Q output (pin 1) goes high and this lights LED 2 to indicate that the crowbar circuit is on. The supply must be turned off and then on again after a minute or so, to resume normal operation. Normal supply indicator IC3b and IC3c are connected together as a window comparator to indicate when the output voltage of the power supply is within the range +11.8 to +14.4V DC. It does this as follows. The inverting inputs (pins 6 &.9) of IC3b and IC3c monitor the output of 66 SILICON CHIP the supply via a voltage divider consisting of two l0kQ resistors. Their non-inverting inputs (pins 5 & 10) are connected to the +10V rail via a vo ltage divider consisting of three resistors. This establishes a reference voltage of +7.2V at pin 5 and +5.9V at pin 10. Thus, provided the voltage at pins 6 & 9 lies between these two voltages, LED 1 will be lit, indicating that the supply output voltage is between 14.4V and 11.SV (ie, twice the reference voltages). If the voltage at pins 6 & 9 goes below +5.9V, the output of comparator IC3c will go high and so LED 1 will go out. Similarly, if the voltage at pins 6 & 9 goes above +7.2V, the output ofIC3b will go low, again causing LED 1 to extinguish. That just about concludes the circuit operation so let's recap on the story. Basically, this unit is a big brute force power supply with filtering performed by chokes and two 80,000µF banks of capacitors. The regulation process is achieved by a Triac in the primary of the power transformer so that very little power is wasted. The control circuit includes turnon delay, slow turn-on, foldback current limiting, crowbar over-voltage protection and output voltage indication, all of which we have just described. Despite all this circuit complexity the unit is very easy to build as most of the parts are mounted on two PC boards. One of these boards holds all the control circuitry while the second board holds the two 80,000µF capacitor banks. But that's all we have space for this month. Next month, we will complete the description of the power supply by giving the construction and setting up details. Acknowledgements Our thanks to the following corn panies for their assistance with this project: Harbuch Transformers, for the design and supply of the 625VA toroidal power transformer and the two iron cored filter chokes; Altronics Distributors, for the supply of the rack mounting case (Cat No. H-0418) and the electrolytic filter capacitors; NSD, for the 70HF20 stud diodes; and VSI Electronics Australia Pty Ltd, for various Motorola ICs and semiconductors. SC 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. +9V + RESET S2 100 16VW! I .10 EL 330k R 14 :c1a 12 CPD 74C14 470Q, 0.5W. 4 16 00 7 01 1 Q 6 l START/I STOP S1 03 5 .,. O.lr 16 b AO !CS 4511 a d 10 1 e/-/c -· d A3 .,. IC4 14553 ,01 270k .,. 02 15 8 .,. 82k 1% '11 CP1 IC3 7555 01 1 .,. .,. calibrated in kilometres. ICZa is half of a 4013 dual D-type flipflop connected in toggle mode. ICla provides debouncing for the START/STOP switch (Sl), which is used to start and stop the counter. You simply press it when you see the flash and press it again when you hear the thunder clap. This circuit then gives a readout of the distance in kilometres; eg, 2.35km. The output of the D-type flipflop is connected to the clock enable (CP0) pin of IC4, a 4553 3-digit counter IC. When the CPO is high , IC4 starts counting; when CPO goes low, the Toy car motor controller Have you ever needed to repair a motorised toy car with a remote control. These can be a real problem to fix but at least with this circuit you can make sure the motor itself is operating. It applies a brief burst of power which allows the motor to run but then turns it off to conserve the battery. It works as follows: transistors Ql and QZ are connected in compound 03 BC328 DO 2 0.1! Ever wondered how close a storm really is? Or, more accurately, how close that bolt oflightning was? Armed with a quick trigger finger and good reflexes, you can use this circuit to measure the actual distance to a lightning strike. Here's how it's done: The speed of sound in normal atmospheric conditions is 330 metres/ second. This circuit simply measures the time taken for the sound generated by a lightning bolt to reach an observer and gives a readout which is 02 BC328 .,. . Lightning distance meter 3xFN0500 f,-9-,b C 11 A1 A2 6 5 OP 3 13 12 et +9V 1% a 1LT 8 02 8D139 fashion to work as a switch, with the motor in the emitter circuit of QZ. 4553 3-digit counter stops. The clock pulses to be counted are provided by IC3, a CMOS version of the 555 running at 33Hz. This means that a count of 1.00 on the display (the decimal point of the most significant digit is permanently on) .represents a distance of 1km. The 4-bit binary output from IC3 is then fed to a 4511 ?-segment decoder (IC5). Each digit is driven in multiplex fashion by the DO-DZ driver outputs of IC3 and the three BC328 transistors (Ql-Q3). Darren Yates, SILICON CHIP. Pressing switch Sl pulls the base of Ql low and allows the lO0µF capacitor to charge. This turns on both Ql and QZ which stay on until the l00µF capacitor discharges. This takes about 4 seconds but the time can be increased by using a bigger value capacitor or increasing the value of the 33kQ resistor. If left on for longer periods, the BD139 transistor (QZ) may need a heats ink. D. Nicholls, North Rocks, NSW. ($15) MAY 1991 67 May is Bargain Month at Altronics. Your One Stop Electronics Shop! Jack O'Donnell Managing Director requency Counter ltlon to the labtech range wlll a1tound you with acy and 1tablllty. A truely profe11lonal t wlll erfor work1hop, Meaaurlng Mode ·Frequency Me11urement1 Channel A ! Range: 10 to 10MHz direct counter 10MHz to 100MHz prescaled by 10 • Resolution: Direct counter: 1, 10, 100Hz switch selectable. Prescaled: 10, 100, 1000Hz switch selectable• Gate time: 0.01S, 01S, 1S switch selectable• Accuracy: +/- 1 count+/- time base error x frequency. Period Mea1urement1 (channel A) • Range: 10Hz to 2.5MHz • Resolu tion: 10'S, 1o•s, 10'5 switch sell'ctable • Accuracy: +/ - count +/ - time base error x period Totallze me1urement1 (channel a) • Range: 10Hz to 10MHz • Resolution:+/- 1 count of input -• (-.~ -~-· • , ' --~/ ~ New Sensational Labtech 20 MHz CRO Au1tralla'1 Beat Value In High Rellablllty, Top Performance Cathode Ray O1cllloacope. This model is a dual trace f0MHz Oscilloscope using a high brightness CRT. The vertical amplifiers have high sensitivity of SmV div anc;t a frequency characteristic response with smooth roll off exceed ing 20MHz. The TV sync . signal separator circuit is provided to ensure stable observation of video signals. Triggering is obtained by sampling the AC power waveform, external waveform or internally generated trigger. Power consumption is only 19 watts and weight is only 7kgs. Full 12 Month• Warranty Probe Sets a 0175 $49.95 each Specification• Position x 10 Bandwidth: DC to 80MHz Max Input Voltage: 600 Volts DC Position x 1 Bandwith: DC to 3MHz Max Input Voltage: 600 Volts DC Probe Length: Approximately 1.5 meters Brilliant Multitesters from Altronics at Low Direct Import Prices Logic Tester, Frequency Counter, Capacitance and Transistor Tester Multimeter with Temperature Meter, Capacitance, Diod\¾ and Transistor Tester Q 1066 a 1010 $W.OO $:J,89".'o o - $129.oo $159.oo Terrific 18 Range Digital Multimeter • 3.5 Digital LCD • Compact Design 128x75x24mm • DC Voltage 5 Ranges: 100uV to 1000V • Input Impedance: 1 M Ohm• DC Current 6 Ranges: 0.1uA to 10A • Overload Protection • Resistance Measurement 5 1 ~hm fo"~88r8ti Temp. Probe Q 1067 $29.95 - --= & Q 1068 n Soldering Station Temperature Controlled-Temperature Selectable, Soldering w this is really quality and versatility! Now supplied with long e heater, A\ The MICRON T2440 T2440$~ $139.00 CARRY CASE TO SUIT $12.50 CARRY CASE TO SUIT Q 1057 $12.50 a 1054 $~5 $32.95 Low Coit Micron 25 Watt Soldering Iron Light-weight• efficient thermal tra nsfer from element to tip• tip temperature maintains within the limits suitable for electronic work and also small household jobs. Fully SEC IHted and approved. soldering station offers the ultimate in contro lled temperature, hand soldering. Simply rotate detained rotary :~~fa~:en;,!~ temperatures of: 320' C (608'F), 350'C (662'F), 380'C (716'F) 410'C (770' F), 440' C (824' F) without changing heater or tip. Packed with features: Temperature readout & control; Zero voltage switching; Grounded tip; ~i;o"r::!t~?:t:~~ir~~t~lad tip. REPLACEMENT TIPS $5.50 EA T2415$~ $17.95 Tip T 2416 $2.50 Multlple De-Solderlng Tool Ideal for the service tec hnician and hobbyist alike. This lightweight desoldering iron allows components to be quickly and cleanly removed w ith one hand. Naturally it's SEC approved and comes with a cleaning wand. can be uaed a1 a 1olderlng Iron. • 240V AC SOHz 30W • SEC Approval W/228 • Easy single handed action • Earthed • Simple cleaning action. Our range of adaptors are each fitted with a 1.8M lead, in line socket and M 9014 2.5mm DC connector. Should your appliance require a different connector you may select from the adaptor plugs M 9013, to M 9015 illustrated. The adaptor plug is normally set for -ve ground. This may be changed to +ve ground by simply reversing the plug adaptor to the line socket. Cat. No. Output Volt1. M 11000 3,4.5,6,7.5,9,12 6 12 9 6,9,12 15V 12V 12V 16V M 9001 M 9002 M 8004 M 11005 M 1N10t M 8020 M 8022 M 8025 Max. Current DC DC DC DC DC AC AC DC AC $19.95 $.15.95 $15.95 $15.95 $22 .50 $9.95 $1 6.95 $22.50 $19 .95 300mA 300mA 300mA 300mA 500mA 100mA 500mA 1 Amp 1 Amp * SO0mA REGULATED POWER SUPPLY Input Voltage: 240V AC 50Hz Output Voltage: 3, 4.5, 6, 7.5, 9, 12V DC Output Current: 500mA M 9040 $32.50 1 AMP POWER SUPPLY Input Voltage: 240V AC 50Hz Output Vollege: 6, ?.5 , 9, 12V DC Output Current: 1 AMP 2 AMP REGULATED POWER SUPPLY Input Voltage: 240V AC 50Hz Ouput Voltage: 12V DC +/- 0.5V Output Current: 2A DC Dlmenliono: 84x68x200m/ m Weight: 1.2 Kgs M 9030 $46.95 DC Output Adaptor Plug1 Avallable M 9013 2.1mm DC Plug M 9014 2.5mm DC Plug $1 95 $1 75 M 9015 3.5mm DC Plug All • 10 Up • FANTASTIC VALUE • •• KITS GALORE Four Digit Combination Lock This simple 4 Digit Combination Lock uses only 3 IC's, and is bound to ;,rove useful in many applications. Such as accessing alarm systems, electronic doors, ignition killers or just about ~g~~~:i'f~~~~,;11!Ji%~t 4 Sub-Woofer Adaptor Get an amazing bass improvement from your Stereo system, ~ti,;'J.7i:\~o~ ~~=~~t1~n~~1~~~f::t:[r~t: t~f;_;rnate patterns• Inbuilt microphone for beat triggering or audio modulation of lights • Direct inputs for beat triagering or audio modulation of lights • Sensitivity control • Presettable sensitivity levels f<?r each channel• Front panel LEDs mimic l i g h t . display • Altronics Kit pre-punched & silk screened Fruit Machine poker macine but without the ,t!l!!!!!!!!!!!!!!!!l■1 w _ .~ Q;) I,.., ~• · 0 &>" K 1160 l'/;i{"U>T th~eshold oo, - ,.,_,, .·,,, " ' ..._,,, _ ;~:~~:gu:~~y ;;~::=~:.=:; 00 -' ~ MAOR<NEA!! • Professional machined and screen printed red perspex front panel • Easy to assemble & . construct • No special f tools required • Bri\jht Hewlett Packard 8 digit display • Electronic switch latching • High \ Performance IC's • High \ Quality Components. This fantastic adaptor simply "samples" your stereo amp output and provides a single channel output to feed a separate sub-woofer amp Unwanted audio spectrum 1~ Control (cut-off ~ .. -":;:::;.,..,. expense of losing money. It has a jackpot and five other winning combinations. It is a good exercise in electronic principles using timers, counters and decoders. Less Cabinet. $35.00 0 1 GHz Digital Frequency Meter ;...._.....,,,..,..•.•. ::::::::--., :efi;!:r~~~~~r~~agna~fo-reversing Chas.e r patterns• Simultaneous strobe on all four This novel kit works just like a real to ~!1, a~1li1~i~iv"e~ ri!r~c~~~~~~es Compatible for 4, 6, and 8 cylinder engines. Install one into your car and start saving$$$ from the very first day. K 4015 $58.50 The Discolite flashes g:~{~i~t;;,i~c&f~~~in • Keep Your Car In To~ Tune This "state of the art' electronic ignition system uses the same semi-conductors as found in modern motor cars. Extends ~ K 1925 $39.95 $159 • 50 High Energy Ignition System , anything that comes to mind. K 5805 M 9050 $69.95 K 2515 * $iri.oo \i.f0\'1 1• _ $249.00 Two-Tone Alarm Module adJustable 60130Hz) Also inCludes an "out of phase" output enabling the use of stereo amp in a bridge configuration for those who really want to rattle the floorboards. You've just finished designing an alarm / /~ project, and you need an ear-catching ,: alarm to go with it. If that's the case, then , ·. this alarm sounder is the go. It produces kJII!' - ~ a melodic ~wo _tone sound, packs quite a T ""'.,_ k, punch for its size and uses only one X- aG' CMOS IC. · ,, • K 5560 $29.95 K194o$15.00 4tlflORl,f .) , ' C / MORE ALTRONICS DEALERS WANTED ,,.,,,._,I I I '''~ 111• ...,.174 Roe St. Perth W.A. 6000 PHONE TOLL FREE 008 999 007 Perth Metro (09) 328 1599 ALL MAIL ORDERS Altroni c Mail Order P.O. Box 8350 Perth Stirling St reet W.A. 6849 If you have a Retall Shop, you could lncreaN your lnc.ome 1lgnlflcantly by becoming an Altronlc1 Dealer. Phone Brian Soren1en (09) 328 2199 for Detall1. Bulk UNFI and O.E.M.'1 Call above number for Wholeule rate,. STANDARD DELIVERY & PACKING CHARGE $5.50 to 1Kg, $8 1Kg-5Kg AUSTRALIA WIDE - We process your order the day received and despatch via . Australia Post. Allow approx. 9 days from day you post order to when you receive goods. OVERNIGHT JETSERVICE- Up to 3Kg is $10.00, 3Kg to 5Kg is $28.00 - We process your order the day received and despatch via. Overnight JetHrvlce Courter for delivery next day Country areas please allow additional 24-48 hours. HEAVY HEAVY SERVICE - All orders of 10Kgs or more must travel Express Road - Please allow 7 days for delivery. $12 .00 to 10Kgs. $15.00 over 10Kgs. INSURANCE - As with virtually every other Australian supplier, we send goods at consigness risk. Should you require comprehensive insurance cover against loss or damage please add $1 .00 per $100 of order value (minimum carge $1). When phone ordering please request "Insurance". TOLL FREE PHONE ORDEH - Bankcard, Visa, Mastercard Holders can phone order toll free up to 6pm Eastern Standard Time. Remember with our Overn'9ht JetHl'Ylce we deliver next day. Altronlc1 Renller1 Chances are there is an Altronic Reseller right near you - check 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 wi ll order any required item for you. WA COUNTRY ALBANY BP Electronics ■ (098) 412681 Micro Electronics (098) 412077 BUNBURY Micro Electronics (097) 216222 E8PERANCE Esperance Communications (090) 713344 KALGOORLIE Todays Electronics ■ (090) 215212 MANDURAH Micro Electronics (09) 5812206 PORT HEDLAND Ivan Tomek Electronics (091) 732531 ROCKINGHAM TV Joe's (09) 5271806 NT ALICE SPRINGS Farmer Electronics (089) 522388 DARWIN Ventronics (089) 853 622 VI C. All Electronic Components (03) 6623506 The Electronic Component Shop ■ (03) 6706474 BORONIA Ray Cross Electronics ■ (03) 7622422 CHELTENHAM Talking Electronics (03) 5842386 CROYDON Truscott Electronics ■ (03) 7233860 PRESTON Preston Electronics ■ (03) 4840191 COUNTRY BAIRNSDALE LH & LM Crawford (051) 525677 BALLARAT Ballarat Electronics (053) 311947 BENDIGO KC Johnson ■ (054) 411411 MILDURA McWilliam Electronics (050) 236410 QLD. Del sound PL ■ (07) 8396155 NEWSTEAD ECQ Electronics (07) 2541153 WEST END B.A.S. Audiotronics (07) 8447566 WOODRIDGE David Hall Electronics ■ (07) 8082777 COUNTRY MAROOCHYDORE MALS Electronics ■ (074) 436119 MARYBOROUGH Keller Electronics (071) 214559 PIALBA Keller Electronics (071) 283749 ROCKHAMPTON Access Electronics (East St.) (079) 221058 TOWNSVILLE Super Solex ■ (077) 724466 SA Force Electronics ■ (08) 2125505 BRIGHTON Force Electronics ■ (08) 3770512 CHRISTIE& BEACH Force Electronics ■ (08) 3823366 ENFIELD Force Electronics ■ (08) 3496340 FINDON Force Electronics ■ (08) 3471188 LONSDALE Force Electronics ■ (08) 3260901 COUNTRY WHYALLA Eyre Electronics (086) 454764 TAS. HOBART George Harvey ■ (002) 342233 LAUNCESTON George Harvey ■ (003) 316533 NSW David Reid Electronics ■ (02) 2671385 CITY SOUTH Sheridan Electronics (02) 2817727 SMITHFIELD Chantronics (02) 6097218 COUNTRY COFFS HARBOUR Coifs Habour Electronics (066) 525684 NEWCASTLE Novocastrian Elect.Supplies (049) 621358 WARNERS BAYVilec Distributors (049) . 489405 WINDSOR M & E Elect. an_d Communications (045) 775935 WOLLONGONG Newtek Electronics ■ (042) 271620 SERVICE 'SLOG I was only a little hit careless In the context of my main story this month, that of safety, the above heading says a whole lot. The most important point is that it was said at all, because being a little bit careless can sometimes mean being a little bit dead - if you'll pardon the superfluous qualification. It is a story about a microwave oven and, in that sense, relates to the story and comments about a fatality as set out in the January 1991 issue. I will have more to say about that later. But, in terms of safety, the story I'm about to relate should never have hap pened. I am no stranger to high voltage situations; and I don't mean the nominal high voltages one encounters in ignition systems and TV sets. I mean the fair dinkum variety which mean what they say. Some of this has come from servicing microwave ovens, which I have been doing for several years. And before that I had the opportunity to work in the broadcasting field, helping to service radio transmitters; typically the ZkW types used in country commercial stations. Such transmitters would feature a valve type final stage, running at around 5000V and drawing at' least 1.5A; not the kind of power supply one would wish to tangle with but, in truth, only marginally worse than the average microwave oven. Yet consider the rules and rituals associated with servicing these transmitters. First, all power had to be disconnected from the transmitter. And in case this was overlooked, the protective panels carried interlock switches; remove any one of them and the system would shut down anyway. Then, hanging inside the cabinet, permanently connected to chassis, was an adequately insulated probe with which one was required to check 70 SILICON CHIP any high voltage point, partly to guard against a failed interlock but mainly to ensure that all capacitors in the system were discharged. Only then was the equipment regarded as safe to work on. But that was only part of the ritual. Inevitably there would come a time when measurements would have to be made with the transmitter fired up but with the panels removed and the interlocks bypassed. The first rule here was that there should always be two people present, both conversant with the appropriate switching plus proper emergency procedures. TETIA TV TIP National TC2001 A Symptom: dark band down centre of screen and small ripple on vertical lines. The band is stationary but the ripple moves in time with the video content. Cure: C533, a 3.3µF 250V electrolytic capacitor, open circuit. This capacitor bypasses the 180V supply to the video output transistors and explains the shaded picture. What it doesn't explain is the vertical wriggle but this cleared up with the new capacitor. TETIA TV Tip is supplied by the Tasmanian branch of the Electronic Technicians' Institute of Australia. Contact Jim Lawler, 16 Adina St, Geilston Bay, 7015. In addition, it was expected that everyone would exercise normal care and follow commonsense precautions; rubber soled shoes, one hand in the pocket, and so on. All of which was good training for handling microwave ovens. In fact, I have tried to follow these rules as far as practical, although the "two persons" rule is usually impractical for me, as it is for most one-man shows. But I do use a shorting probe to take care of capacitors, etc. Nor would I ever contemplate checking the power supply using the "size of spark" technique. (Quite apart from the danger, it's not very accurate). For this job, I use a professional high voltage probe, made by Fluke, which is rated at 40kV. After that, all one can do is be extra careful. As I mentioned earlier, a microwave oven power supply is only marginally less dangerous than a transmitter power supply. They typically operate at 4000V, deliver 650W of RF and, on the basis of something approaching 50% efficiency, deliver around 0.3 to 0.5A (they can deliver more than that on demand) . Slow microwaves In this case, the particular microwave oven was a commercial model, a Sharp R2340E, from a local restaurant. And as might be imagined, when commercial units like this fail, there is a fair amount of pressure to get them working again as quickly as possible. This oven is about four years old and I have serviced it several times during this period. On one occasion, the high voltage power supply capacitor failed and on another, the high voltage rectifier failed. The third fault was more unusual. It involved the connections to the filament pins of the magnetron, which are push-on clips similar to those used in the automotive industry. One of these had failed, probably because of sw, ,--------7 SW4 THERMAL CUTOUT (MAG) LATCH SWITCH A (PRIMARY) LATCH SWITCH 8 (SECONDARY) SHORT SWITCH ...L GROUNDING m- CHASSIS GROUND MAGNETRON NOTE: Door is closed. Unit is not operated. BL 220/240V SOHz SW2 r---------., I F I J. T J. RY2 FA; :::-r:: I I I I SW3 :I J/ SW1 -cn..o- FUSE 8A MF FAN MOTOR CH HIGH VO LTAGE CAPACITOR I L - - r - - SW3 I l. ___ J ~220/ I P240 I ---------I _J -MTH DIODE HIGH VOLTAGE TRANSFORMER ....... VARISTOR -.- rlrl TL TEMP SENSOR (THERMAL PROTECTOR) ~ RY1 POWER RELAY A RY2 POWER RELAY 8 TL LOW VOLTAGE TRANSFORMER DIGITAL PROGRAMMER CIRCUIT HUMIDITY SENSOR (NN-7807) -tt-14- PROTECTOR DIODE L IMPORTANT SAFE1Y NOTICE: POTENTIALS ABOVE 250V IS PRESENT ON THE PARTS AND WIRING IN SECONDARY CIRCUIT OF HIGH VOLTAGE TRANSFORMER, WHEN THE OVEN IS ENERGIZED. EXTREMELY CARE SHOULD BE TAKEN DURING REPAIR. MTT OVEN LAMP TURNTABLE MOTOR Fig.I: this circuit of the National Panasonic NN-7807 microwave oven, while differing from the Sharp model, is typical & will help you follow the story. It uses a 4000V power transformer to drive the magnetron, plus a 1.14µF high voltage capacitor, a protective diode & sundry other components. the quite heavy current involved. But this latest fault was different again. The owner complained that, while it still worked, its cooking times had increased markedly, thus largely negating the whole purpose of the device. To understand the story better, a brief description of the oven may help. It is a rather ingenious arrangement which is really two domestic oven systems combined into one, giving a rated power output of 1300W. It has two magnetrons, two power transformers, two capacitors, two stack rectifiers, two lots of plumbing and two fans. The main common item is the microprocessor controller. As I said, it's an ingenious arrangement , using existing domestic technology and parts to produce a larger unit and provide some user flexibility at the same time. For example, an economical low power mode is available by simply switching off one complete system. It also provides a degree of redundancy; even if a component fails in one system, the other system will still provide a limited service. Unfortunately, I cannot provide a circuit diagram. I have no manual and the only circuit is pasted inside the main cover. And, apart from the problem of trying to photostat it in that situation, it's showing its age somewhat. It was good enough for me to follow but a bit too grotty to reproduce. The best I can do is to present another circuit which is at least typical. It is of the National Panasonic NN7807 and variations (Fig.1). As can be seen, there is not a great deal to the magnetron circuit: a 4000V power transformer, a 1.14µF high voltage capacitor (from the magnetron filament terminal FA to chassis), a protective diode and sundry operational switches, relays and protective devices . The real complexity is in the microprocessor control system but that does not concern us here. To digress for a moment, that capacitor value - 1.14µF in this case - is worth commenting upon. It is quite critical; much more so than its superficial role - that of a smothing capacitor - would suggest. In fact, it appar- ently also forms part ofthe magnetron resonant circuit and a wrong value here, even if the capacitor is perfectly good, will result in poor performance or failure to perform at all. So back to the job at hand. Naturally, the owner was anxious to get things fixed as quickly as possible and I had promised to look at it immediately ifhe brought it around. In fact, he'd picked a bad time; I was flat to the boards with TV sets everywhere and had even shanghaied a colleague to help me out. This was a help but it also meant I was distracted from time to time when he needed to clarify a technical point or locate a spare part. Routine tests Anyway, I set it up on the bench, switched it on and made a routine preliminary check. The check I use is a well established one, issued by Sharp. There are other procedures, mostly more complicated and probably marginally more accurate, but I have found that this one is perfectly adequate at a practical level. The procedure involves measuring MAY 1991 71 SERVICEMAN'S LOG - CTD 'l)OU"&.E INSIJLATE.D CRP.SI-I 1-\tL!V\ET WIT 1-1 l-\EP,.,.-SINK RUBB,E:R ORG>A('l TRIPL.£ INSVLP..TED BIFOCAL'S DONOR CA!<:'i) QVAP 1N5VLA GA'5 /V\&\SK WI 'SNP.CI<:; 'FOO COM?P\R:Tfll\8') \.-\AND tN DovSL-E tNSV<-A,~ . POC-1<£°1* A lump of 4 x 2 Pc.e, The oven was still where I had parked it, cover off, mains plug lying on the floor, and I simply reached inside to the filament pin, pulled back the insulation over the clip, and felt for the clip with my finger. Exactly what happend next is a little unclear and difficult to describe. Being hit between the eyes with a lump of four by two would be one way to describe it; there was a violent physical reaction and I certainly saw stars. And in addition to the physical shock, there was the mental shock, the surprise and the fright. Many thoughts raced through my mind. What had I done wrong? Had I only imagined I had pulled the plug from the mains? How else could I get a shock? I had one hand in my pocket, I was wearing rubber soled shoes, and I was standing on a carpet. After a few seconds, when I had collected my thoughts, I confirmed that the mains plug really was on the floor. That meant that the shock could have come from only one source - the capacitor. But how had I completed a circuit with only one hand? The only explanation is through my arm which must have touched the chassis. I had a burn mark on my finger but nothing similar on my arm. Next question; why was the capacitor still charged? Most systems, including the one illustrated in the circuit, feature a bleed resistor (9MQ in this case) across the capacitor to ensure that it discharges. SUPPOR'fS OP•tONf\L- t::::XtAA: MICROWAV£ 'POW£R.E.{) ''I-IE.L\> N\E,I. P..M LIVE:" FLP--Sl-\lNGNf.ON SIGN 1-\EA'"\SI-\RtNK ------.SOU<-'S A.DE.QVA·H-L'-1' RU~~~R------(~~• INSVl.-AT~ LAC.ES 1-\lG,~ VOl-"TA.GE:. r"R.O&E. ,...._ EXP6:c't"W ~A"t" £VE.R.'<ONE: S\-\OuL..t> EXE.RC\ S~ NOP.M~L- C~RE: & FOU...-0\N COH\f'I\ONSENS€ ~RE"C-AvTIOI\JSo•• the rise in temperature of a quantity of water, then applying a simple formula. More specifically, I use 500ml of water, in a glass container, and measure its temperature in degrees C. This is then heated in the oven for 60 seconds and its temperature measured again: f>. typical rise would be between 15°C and 1s c. From this, the cooking power in watts can be calculated from the following formula: W = 4, 2 x ml x Cr / S where ml = quantity of water in ml; Cr = temperature rise in °C; and S = heating time in seconds. As an example, 500ml of water 0 72 SILICON CHIP anything. It couldn't raise the water temperature by even a fraction of a degree. Well that explained the owner's complaint; all I had to do was find out why. I progressed as far as getting the cover off when I had to clarify a problem my colleague had raised. It meant that I had to leave it there, at least briefly. I pulled the mains plug and put it to one side. It was a good half hour before I could turn my attention to it again. By that time, I had recalled the abovementioned fault involving a faulty clip to the magnetron filament pin. Superficially, the symptom was the same; total failure. There are other causes of total failure of course, but I just had a feeling that this might be all that was wrong. heated for 60 seconds and showing a rise of 18°C gives a figure of 630W, which is typical for a domestic type magnetron. Indeed, with a little practice and by always using the same values, one hardly needs to apply the above formula; a glance at tlte thermometer is all that is needed to tell the story. By the way, it is desirable to monitor the mains voltage during this test and to make due allowance if it is more than a few volts off normal. In this case, one magnetron could barely raise the temperature by 9°C, which meant that it was delivering less than half its rated power. And the other magnetron? - well it didn't do TV TEST EQUIPMENT TO EARN YOU A HIGHER RETURN (Australian Made) SHORTED TURNS TESTER Built-in Meter to check EHT transformers including split diode type, .yokes and drive transformers. $78.00 + $3.00 p&p DEGAUSSING WAND Strong magnetic field, larger than usual coil with multicore centre. Double insulated for your safety, also fitted with momentary on/off switch. 240V A/C 2.2 amps. Just about as important as having a soldering iron in your toolbox! $75.00 + $10.00 p&p HI-VOLTAGE PROBE Built-in meter reads positive or negative 0-50kV. For checking EHT and focus as well as any other Hi-tension voltages. This view shows the magnetron & its associated high voltage 1.14µF capacitor. Care should be exercised when dealing with these components inside a microwave oven as they can deliver a fatal electric shock. But not this model Sharp. In any case, there is always enough emission left in the magnetron filament after switch-off to bleed the capacitor, even with a sick magnetron. Not that I had ever relied Oil' this before. As I mentioned earlier, I have a well insulated earthing probe with which I normally discharge any capacitor in an oven, even if there is a bleed resistor. So why not this time? That's what I mean by being "a little bit careless". Working under pressure, I'd forgotten that the Sharp had no bleed resistor. And I'd chosen the one time when there was no magnetron operating· to discharge the capacitor. Could such a shock have been fatal? I seriously doubt it, considering the short path involved. But had I had my other hand on the chassis, instead of in my pocket, it could have been a different matter. Make no mistake, a lµF capacitor at 4000V is a very dangerous device. All of which adds up to an obvious lesson. No degree of urgency can justify taking a short cut which bypasses safety. And the irony ofit all was that, when everything was sorted out, I had one sick magnetron and one totally dead one. So , with no replacement magnetrons in stock, I had to order them and that meant a couple of days delay before I could even tackle the job again. All the sense of urgency, which had undoubtedly contributed to my mental lapse, had been for nothing. Makes you think, doesn't it? Previous story That brings me to Jim Lawler's story, the coroner's report, and the editorial comment in the January issue. In my opinion, the coroner's report is totally inadequate. One can hardly blame the coroner, who must rely on his technical advisers, but these advisers have let him down badly. It's not what the report said but rather what it didn't say that's the problem. It also highlights the ignorance of so many people, particularly the do-it-yourself types but also some who are in the commercial field. Jim Lawler clearly identified the crux of the matter: the difference between the high voltage in a TV set (anything from 15-25kV) and the much lower voltage (around 4000V) in a microwave oven. The high voltage in a TV set is relatively harmless; the lower voltage in the microwave oven is lethal. The reason is very hard to get across to some people. Everyone thinks in terms of voltage and voltage alone. We have been taught that high voltages are dangerous; low voltages are not. $98.00 + $5.00 p&p REMOTE CONTROL TESTER (INFARED OR ULTRASONIC) Designed to test lnfared or • Ultrasonic control units. With the , extension lead you can also test infared units which cannot be placed in front of the testing unit. Requires a 9V battery. Output is via the LED diode and piezo speaker. $85.00 + $4.00 p&p LASER DETECTOR PROBE A new addition to the remote control tester. Comparable with units costing $500 or more. You can test the laser pickup in compact disc players. $27.00 + $2.00 p&p LOW VOLTAGE PROBE Ideal for checking microwave ovens and TVs. The ranges are from O to 5kV Negative and from O to 10kV Positive. Double insulated for your safety. $84.00 + $5.00 p&p TUNER REPAIRS from $17.00 exchange + p&p Cheque, Money Order, Bankcard or Mastercard ~v. TUNERS) ············ ···••.•:•:•:•:•:•:•:•:•:•:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:-:::::;:;:::_;::::::-:,• 216 canterbury Road, Revesby, NSW, AUSTRALIA, 2212 ~ (02) 774 1154 [;~ (02) 774 1154 MAY 1991 73 SERVICEMAN'S LOG - CTD Yet fatalities have occurred on 32V home lighting systems while we have all had a belt off a Z0kV plus ignition system, or a TV set EHT system (uncomfortable, but nothing more). The answer is current or, more precisely, the amount of current that can flow through the victim's body. And values of l00mA - or even lower, depending on the body path - can be fatal. Unfortunately, there are so many variables - the resistance in the total path (including contact with earth), the nature of the contact with the voltage source, the body's own resistance, etc - that it is impossible to predict how much current will flow in any shock situation. The closest we can get is to consider the worst case situation; how much current can flow if all these resistances are at a minimum. And that brings us to the one factor that we can assess; the internal resistance of the voltage source or, in simpler terms, how much current the source can supply if asked. And this is where so many people become confused. Because some high voltage systems - such as TV EHT supplies and auto ignition systems have very high internal resistances, they are incapable of delivering more than a few hundred microamps or, at most, a few milliamps. And so they have been lulled into a false sense of security. High voltage warnings go unheeded; they've had a belt from an ignition or TV system and suffered no ill effect. So it's all a lot of baloney. Until you encounter a microwave oven, that is. The voltage is low by comparison, but so is the internal resistance. They can deliver half an amp 74 SILICON CHIP or more if provoked - and that's more than enough to kill. But the coroner's report makes no such distinction. It lumps TV sets and microwave ovens together, in terms of danger, thus serving to perpetuate the confusion over supply impedance. When someone finds that high voltages in TV sets are apparently not dangerous after all, they dismiss the whole warning. Nor can I agree with the safety suggestions in the report - in particular, the reference to rubber gloves. Granted, they can provide a degree of protection - if they are in good condition - but the discomfort and inconvenience they cause is such that, in practice, no one ever uses them. Recommending them may salve someone's conscience but it does little else. The editorial sums it up best. Acquire instruments and develop techniques which avoid the need to work directly on live systems. And don't forget to discharge the capacitor(s). Shark attack! Well, after all that profundity, something a little lighter would seem to be called for. So here is a complete change of scene from J. L. in Northern Antarctica. Here's how he tells it. This is not really a servicing story but it does involve several servicemen colleagues, so I suppose its presence here is justified. One Monday morning, after a particularly fine and sunny weekend, I called into a colleague's shop for a brief chat. I found him and two other technicians engrossed in watching a video tape that was running on a bench monitor. They told me that the tape had been shot the day before during a break in their water-skiing activities and I was cautioned to "be quiet and listen"! On the screen was the image of a large ocean going yacht lying a hundred metres or so offshore. On the beach there was a row of people, some in wetsuits, staring out to sea. Between the yacht and the beach was the unmistakable black triangle of the dorsal fin of a large shark. We could hear someone on the yacht calling instructions to the helmsman as they tried to manoeuvre the yacht closer to the shark. One man on deck held what appeared to be a shotgun. They were obviously trying to get close enough to at least worry the shark, if not to kill it. Unfortunately, they were on a deep keel boat and could not get too close inshore without running aground. In the meantime, the shark cruised backwards and forwards along the beach, just out of range of the seaborne shotgun. This continued for some 10 minutes, with people on the yacht and some of those on shore beginning to become very agitated. There were calls for the police, the navy, even the Prime Minister. But nobody had any idea of how to drive the shark away. Then one of the water skiers, braver or more foolhardy than the rest, waded out into the water. The shark immediately turned towards him. There were screams and gasps from the watchers on the yacht and on shore. Just as the shark reached the skier, he bent down and lifted it from the water. It was a 1-metre long radio controlled model submarine with a large triangular fin fitted to its conning tower! Most of the watchers groaned with embarrassment but the final word came from one of the people on the yacht. "Bloody brainless idiots", he shouted. Readers in other states might think this escapade was in bad taste, and you are probably right. But then, here in Tasmania, sharks are more of a psychological than practical threat. Shark attacks are almost unknown in our colder waters and a prank like this worries many but endangers none. OK J.L., apology accepted. But ya can't help larfin'. SC BOOKSHELF Valves and old time radio! How To Repair Old-Time Radios, by Clayton L. Hallmark. First published 1979, by Tab Books Inc, Blue Ridge Summit, PA, USA. Soft covers, 209 x 130mm, 249 pages. ISBN 0-8306-11487. Price $21.95. If you've just been bitten by the vintage radio bug and you're looking for some place to start (apart from our Vintage Radio column), then this book is a good place to start. The first couple of chapters will give a fairly good idea of how the various components work and a good guide as to what they look like when you come across them. Chapters 3 and 4 go into troubleshooting and how to isolate and locate various problems from the RF The best of shareware - PC utilities The Best Of Shareware - IBM PC Utilities, by Mark R. Sawusch. Published 1990 by Windcrest Books, Blue Ridge Summit, PA, USA. Soft covers, 234 x 187mm, 219 pages + 1 floppy disc. ISBN 08306-9306-8. Price $49.95. This book is basically a user manual with 75 useful utility programs for the IBM PC XT/AT, but the unusual thing about it is that the programs are already provided on a floppy disc at the back of the book. It even comes with instructions on how to download the programs onto your hard disc! The programs are too numerous to mention individually but they are split into the following categories: file management, keyboard and screen enhancement, printer utilities, disc and directory maintenance , clock and calendar utilities, programming , debugging and diagnostic utilities, operating through to the audio stages. Chapter 5 deals with testing components and describes how to determine whether they work or not. 1be.Bef,tof Shareware JBM' PC lllilitics system enhancements, batch files , and miscellaneous. There are also a number of well-known programs, including SideKick and ProKey, thrown in. Most of the programs require DOS 2.0 or later but that shouldn't be a problem. Considering it's only $49.95, it's pretty good value and worth using up some of your hard disc for! Our copy came from Dick Smith Electronics (Cat B-6050). (D.Y.) Chapter 6 goes through many of the common problems you may find with an old set while chapter 7 briefly describes how you can repair some components (obviously not the valves though!). Chapter 8 provides some information on substituting for various components, while the last few chapters describe how to correctly align radio receivers and present some of the more advanced theory. To the "old hands", this book won't be anything new but the appendix at the back provides a useful listing of some of RCA's most popular valves and gives voltage data, etc. Finally, a note of warning for beginners: because this is a US book, the power supplies mentioned will operate only from 115V, so don't try to hook one of them up out here! Our copy came from Resurrection Radio, PO Box 1116, Windsor, Vic 3181 and retails for $21.95 plus $5 postage and packing. Phone 03 529 1950. (D.Y.) Frequency reference for HF bands Frequency Spectrum Reference, Volumes 1 & 2. 0.000lHz to 29999.9kHz. Published June 1990 by Rodney M. Letts, Wantirna South, Victoria. Soft covers, 290 x 204mm, 669 pages. Price $68 plus $8 p&p. This is a privately published comprehensive listing of frequencies used in Australia up to 30MHz. Ostensibly, it covers frequencies down to DC but apart from nominating figures such as 50Hz for the AC mains supply below 10.2kHz (the Omega navigation frequency), nothing significant is listed. There is no explanatory text, just page after page of frequency listings , mostly applying only to Australia but some to the United States. Who would use it? Mostly people with scanning receivers, we would guess. If you are interested in purchasing these references, contact Rodney M. Letts, 446 Boronia Road, Wantirna South, Victoria 3152 . (L.D.S.) SC MAY 1991 75 COMPUTER BITS BY JENNIFER BONNITCHA Colouring your PC world Following on from last month's article, this month we have more adventures with the PROMPT command to set screen colours and customise your display. The DOS command PROMPT lets you change the dull, boring C> to almost anything you like - you can change the colours, location and the information shown at the prompt. PROMPT changes video attributes only. You can create a wide range of output possibilities by using symbolic replacements called metasymbols. You must precede each character with a dollar sign ($) and note that unlike the ANSI sequences, PROMPT is not case sensitive. Table 1 shows the details. PROMPT $P$G is probably the most popular way to customise the system prompt. With this sequence, you can see instantly the current drive and path, eg, C: \ WP51 \DATA>. PROMPT also lets you add instructions: any number of times through the keyboard or executed from within a batch file. Display screen attributes This command displays on one line the drive and path ($P), a space, the date ($D), a space and the time ($T). On the second line ($_), it displays the message What's Up Doc? and the greater than sign ($G). The Set Graphics Rendition command ESC[#; ... ;#m sets the screen display attributes. The command sequence may contain one or more of the parameters listed below. You should, however, check your DOS manual for any additions or alterations from your computer's manufacturer. Most monitors today support graphic functions, therefore you can call the graphic functions from the following list. The functions remain until the next occurence of a Set Graphics Rendition escape sequence. Setting and adjusting the screen colours and background intensity of the monitor is quite useful. ANSI uses the same colour codes for both the foreground and background. You start with the digit 3 for foreground colours and the digit 4 for background colours . In addition, you can specify several attributes such as high intensity (bold), reverse video etc. Escape sequences O All attributes off As noted briefly last month, you can send escape sequences to ANSI.SYS using the PROMPT command $E which represents the escape character. There are several advantages when you use PROMPT, because you can easily change the instructions you send and the commands can be used 1 High intensity display on (ie, bright) 2 Normal intensity display on 4 Underline (monochrome monitor only) 5 Blink on 7 Reverse video on 8 Concealed on, no display (invisible) PROMPT $P $D $T$_What's Up Doc?$G 76 SILICON CHIP Foreground 30 Black 31 Red 32 Green 33 Brown 34 Blue 35 Magenta (purple) 36 Cyan (light blue) 37 White Background 40 Black 41 Red 42 Green 43 Brown 44 Blue 45 Magenta 46 Cyan 47 White Note that turning on high intensity brightens the foreground colours only, with the exception that black turns to grey and brown to yellow. You can set one or more numerical values. Make sure you use only the semicolon to delimit (separate) the parameters in the escape sequence. Using the above table, you could set the following: ESC[37m - Foreground colour to white ESC[44m - Background colour to blue ESC[37;44m - Foreground and background colours simultaneously ESC[1;37;44m - Foreground to bright (1) white (37) on a blue (44) background It's good practice to use the three parameters to specify colour changes. Keep the parameters together rather than issuing one by itself. Note that changing the foreground colour doesn't turn the intensity on or off you need to do that with the O or 1 parameter - and that parameter O also clears the colours to their default value of white on black. You could build a set of simple batch files to show different coloured prompts for directories or drives so you can see at a glance what's going on, such as: <at>ECHO OFF C: PROMPT $E[36m$P$G TABLE 1 SPECIFY THIS CHARACTER $ b d e g I n p t V TO GET THIS PROMPT The $ character The I character The current date Escape character (ASCII code 1b hex, 27 decimal) The > character The < character The default drive The working directory of the default drive The current time The DOS version number Carriage return, linefeed sequence. Note that this is the underscore character. This specifies cyan as the foreground colour with the current drive and path. <at>ECHO OFF C: CD\DBASE PROMPT $E[1;37;45m$P$G This changes to the dBASE subdirectory and alters the prompt to show bright (1) white (37) on a magenta background (45). You may like to set your prompt to a different colour but have the text you type at the prompt return to normal video mode: PROMPT $E[7m$P$G$e[m Date & time display For a really fancy display, complete with date and time display (which only updates when you press the Enter key): PROMPT $e[s$e[25;56H$e[1;37;45m $t$h$h$h$h$h$h $d$e[0m$e[u$p$g Phew! Take a close look at the above command which need not necessarily be entered in this sequence. You can enter the ANSI comm~nds in any sequence, provided the parameters for each are entered correctly. $e[s Saves the cursor's current position. $e[25;56H Moves the cursor to row 25, column 56 (bottom righthand corner of the screen). $e[1 ;37 ;45m specifies bright white on a magenta background. $t displays the current time. $h$h$h$h$h$h displays the current time as hours and minutes. (space) the space character separates the time from the next parameter. $d displays the current date. $e[0m resets the text to normal. $e[u returns the cursor to its starting position. $p displays the current drive and path information. $g displays the greater than sign (> ). The space in the command is critical to the separation of the time and date display. The space character is treated by the PROMPT command just like any other keyboard character and will appear in the final DOS prompt line. You may need to set your screen colours when you exit a program, so it is worthwhile to include the prompt line in any batch files you may be using. Experiment with the following batch fil e, TEST5.BAT (the IF, GOTO and % statements will be covered in a future article): <at>ECHO OFF CLS IF !NORMAL==!%1 GOTO %1 IF !BRIGHT==!%1 GOTO %1 IF !REVERSE== !%1 GOTO %1 GOTO HELP :NORMAL PROMPT $e[0m$P$G GOTO FINISH :BRIGHT PROMPT $e[0;1m$P$G GOTO FINISH :REVERSE PROMPT $e[0;7m$P$G GOTO FINISH :HELP ECHO THE PROPER FORMAT IS ECHO either TEST5 NORMAL ECHO OR TEST5 BRIGHT ECHO OR TEST5 REVERSE ECHO MAKE SURE YOU TYPE THE REQUIRED ATTRIBUTE IN UPPERCASE GOTO FINISH :END CLS :FINISH If you type the attribute in other than uppercase, the batch file displays the help messages shown above. Naturally, you can include any additional colours as required. It sometimes helps to have the entire screen change to the new colour/ intensity, etc immediately. If you add the ESC [2J sequence to the end of any command, the entire screen is cleared and your choices are in effect. Set display mode You may also need to reset the HEAVY DUTY TV/SPEAKER WALL-CEILING BRACKETS The M83 and M85 are heavy duty two platform mounting brackets designed for securing small TVs and speakers to walls, ceilings, desks or bench tops. When mounted both units can ·· be rotated , 360 degrees ~ ~th_•::,\t_'W; ~ __--:::~rto-a-·-~ ~~4i 1l''rt-___;j I as .well as being swivelled up or down to any viewing or listening angle. The metal platforms have predril/ed holes for mounting ana are easily adjusted with a large al/en key supplied with the unit. , · ·9i Imported and distributed by: ARISTA ELECTRONICS Available through the following retailers: David J Reid All Electronic Electronics. Components. 127 York Street. 118 Lonsdale St. Sydney. 2000. Melbourne. 3000. NSW. (02) 267-1385. Vic. (03) 662 3506. MAY1991 77 THE BARGAINS CONTINUE AT SHERIDANS SURPLUS POWER SUPPLY We have secured a limited quantity of these power supplies. Input 180 - 280V AC 45 - 65 Hz. Output +5.2V at 10A, + 12V at 4A, -12V at 2A, 24V at 2A. Total output power 130W continuous, 160W peak. Efficiency - greater than 70% at fu ll load. WORTH AROUND $280.00 OUR PRICE $69.95 COMPUTER BITS ... screen mode (the screen width of 40 or 80 columns), which can be accomplished to a certain degree using the external DOS command MODE. MODE BW40 sets the display to black and white, and to 40 characters per line; MODE COBO sets the display to 80 characters per line colour. Function h of ANSI.SYS gives you much more flexibility since you can access all of the possible CGA text and graphics modes, including those which MODe ignores. Using the set mode ESC[ =#h command, you can set the display mode according to the parameter (#) specified. Reset the display mode using ESC[=#l. The character wrap functions ESC[=#h and ESC[#l (lowercase letter "el") let you decide whether the characters wrap at the end of each line. Table 2 shows the details. FORCED AIR COOLED TRIODE TABLE2 These are a quality triode and valued at nearly double the asking price. Spee sheets are available. Their type number is 3J/170E. Rated at 2KW. PARAMETER 0 1 BARGAIN PRICED AT $999.00 SUPER CAPS .047 5.5v KEEP THE VOLTAGE IN YOUR MEMORY 80 cents each 240v MOTOR BY JAPAN SERVO co~ 80mm x 80mm x 75mm 1800 rpm 100mA with 3uF STARTER CAP · THERMALLY PROTECTED 16 17 18 19 1500v 2.5a Replaces BU208 Only $4.95 .~ Character wrap 240v/110v lmput Output 14.SV <at> 5A SV<at> .SA Has internal Sheild $25.00 ea Sheridans are beginning to bring in a range of TVVideo spare parts. Please send your name & address for your copy of our catalogue. SHERIDAN ELECTRONICS, I 328 ELIZABETH ST, . SURRY HILLS, NSW, 2010 TELEPHONE: {02) 281 7727 78 SILICON CHIP colou r mono (EGA) colour (EGA) mono (VGA) colour (VGA) colour The parameters for Reset Mode are the same as for Set Mode, except for parameter 7 which resets the mode that causes wrapping at the end of each line. BU205 TOROIDAL TRANSFORMER (Cnr Kippax St. opp. Central Station & Dental Hospital) 640x200 640x350 640x350 640x480 640x480 320x200 $19.95each PROJECT CASE In . two parts amd measures 250(W) x 130(0) X 110(H), screw mounting holes . Has many uses. ONLY $14.95 2 3 4 5 6 7 DOS 4.x only 14 15 FUNCTION 40x25 black and white 40x25 colour 80x25 black and white 80x25 colou r 320x200 colour 320x'200 black and white 640x200 black and white Wraps at the end of each line ,. ~ ~ 0M . SHOP HOURS: MON - FRI SAT 9.00am- 5.30pm 9.30am-12.00pm I The ESC[=lh command activates the 40 character by 25 line black and white text mode. Another handy feature is the function ESC[#l mentioned above, which disables character wrap. When character wrap is on (which by default it is), any lines containing more than 80 characters "wrap" to the next line. When wrap is disabled, only 80 characte~s display so you can view any file using the DOS command TYPE and not be distracted by the remaining information displaying on the subsequent line. Restore character wrap using ESC[=7h, as described above. Note that the type of monitor you own will determine the success or otherwise of the various commands described this month. This is particularly true if you have a monochrome (green/black, amber/black etc) monitor. Next month, we will discuss using ANSI to control keyboard reassignment. Happy colouring! SC AMATEUR RADIO BY GARRY CRATT, VK2YBX AR2500 multi-mode scanner has memories galore! The old adage that "good things come in small packages" is becoming increasingly true due to advances in technology. These days, the more features that are added, the smaller the equipment becomes. This is particularly the case when considering the performance now achievable in amateur communications equipment. One area in which there have recently been great advances is that of scanning receivers. Until recent times, scanner enthus~ iasts have been limited to a choice of 20, 50 or 100-channel models. With the advent of "electronically erasable programmable read only memories" (EEPROMs) and the increased speed achievable with microcomputers, manufacturers are now able to produce small scanning receivers with incredible frequency coverage and memory capacity. One such product which takes full advantage of this technology recently crossed our desk for review. It is the The AR2500 synthesised scanning receiver offers contim1ous coverage between 500kHz & 1500MHz and features AM, FM, wideband FM & SSB/CW reception. It has 1984 memory channels & can he interfaced to a PC via an RS232C port. AR2500 scanning receiver from AOR, the noted Japanese communications product supplier. The AR2500 is a fully featured multi-mode synthesised scanning receiver offering continuous coverage from 500kHz to 1500MHz. The unit allows AM, FM, wideband FM and SSB/CW reception, thanks to an inbuilt BFO. It has an incredible 1984 memory channels and, in addition, allows for computer control via an RS232C port located on the rear panel of the scanner. This facility allows asynchronous communications with a personal computer for spectrum display and database compilation. Scanning speed What is so amazing about this receiver is that the high-speed microprocessor allows a scanning speed of 40 channels per second. In addition, the use of triple conversion in the receiver eliminates the majority of "birdies" commonly encountered in wide-range moriitor receivers. The unit is built into a plastic case which is approximately DIN car radio size, being 145mm wide, 55mm high and 163mm deep. This case has been used for previous models, including the AR950. One of the most important features offered by this receiver is the ability to resolve SSB transmissions. This feature, coupled with the HF coverage offered by the unit, means that it is an appealing receiver for both VHF and UHF scanning enthusiasts, as well as those interested in utility stations on the HF bands. Considering that the retail price of this unit is approx 60% of its nearest MAY 1991 79 competitor, the unit shapes up as good value indeed! However, there are some operational matters which vary from "the norm" to ensure good performance over the entire frequency range. In an extremely wide-band coverage unit such as the AR2500, the slowest component is that section of the receiver which must synthesise the various frequencies to be received. Compared to a conventional scanner, the AR2500 synthesiser must run through 10-15 times the normal frequ ency spread. Therefore, achieving a good scan speed is far more difficult than with a conventional scanner. The AR2500 microprocessor solves this problem by organising the scan frequencies in descending numerical order. This way the synthesiser can run rapidly as it is only required to make small steps instead oflarge steps between frequencies. Hence, to assure optimum operation with this unit , it is important to keep numerically close frequencies together in the same bank. For best results, we found that no more than 2-3MHz should be allowed between any two frequencies in a scan .::I::~::: \: .I $199 :· band. It's also best to use the same reception mode for all frequencies within the same bank. The same principle applies when linking two or more banks, where widely-spaced frequency jumps are required to go from one to the other. If large jumps are n ecessary between banks, the microprocessor will detect this, calculate the difference in frequencies and insert an artificial delay. Buffer frequencies Hence it may be advisable to enter a few intermediate or buffer frequencies in the lower numbered bank to allow sufficient transition time for the synthesiser. This will ensure the highest probability of locking onto weak signals. The unit will always move downwards in frequency within a bank and will move from the highest to the lowest scan bank and then back to the highest when the banks are linked. The speed will decrease, as will the probability of lock-on, if the order of frequencies requires large jumps from one to another. This scanner has 62 banks with each containing 32 positions, all of which are user program- mable. Any combination of banks can be linked, by simply using the LINK or UN-LINK keys. Sensitivity across the entire frequency range is excellent with quoted figures of lµV across the HF band which we found very conservative. When monitoring some HF frequencies, we found it necessary to use the inbuilt 20db attenuator to prevent overloading the receiver front end. With the attenuator in circuit, much of the noise associated with HF reception decreased while the signal remained at quite an acceptable level. The unit is supplied with a telescoping whip antenna which is only really adequate for VHF and UHF reception. A suitable long wire or dipole antenna should be used for HF reception. It should also be possible to use a discone antenna although the majority of these antennae on today's market suffer reduced performance below 25MHz. Despite the unconventional operation of this scanner, the unit has not given up its ease of operation for the sake of gadgetry. For example, if a bank has all 32 positions filled, the AR2500 displays "FULL" on the LCD ANTRIM TOROIDAL TRANSFORMERS INC. PACK. AND POST. This quality Japanese made airband receiver will suit student pilots, aviation enthusiasts, homebuilt '· ·• and ultralight owners. Small enough to fit in a shirt · pocket, the unit is easy to tune and is ideal for monitoring ATIS, local circuit frequencies etc. Provision for 2 crystal locked frequencies• (of your choice) is available. The receiver comes complete with 'iN battery, antenna, and an earpiece. 12 MONTHS WARRANTY Comprehenslve spare parts and technical information is held by our service department. ··.···•·•••·••••••:•••:•:•:•.•••••·••••·•:f..., • · • Crystals available at $29.95 each, plus $10 installation. Allow 3 weeks for delivery SpeclHClllona: MC 11110: Less than 10<18 audio variation from 2,,v to 10,000UV Frequency Cfflllll: 118 to 138MHz Pawer Consumpllon: 9V DC, 15mA (typical) Stnttlvtty: 1.4uV, for 10<18 S+N/N Slmlconduclall: 1 IC, 11 transistors, 7 diodes. ~~~(W)x115mm(H)x2Bmm(D) StlectlvHy: 180KHz at 8d8, 390KHz at 40<18 =:".!i-3:: SEND TO: AV-COMM PTY. LTD. P.O. BOX 386 NORTHBRIDGE NSW 2063, FAX: (02) 949 7095 Please send me (qty) . ... . . R537S <at> $199 ea. (Inc p. & P.I Please flt . .. .. . MHz, . . .. .MHz crystals <at> $29.95 ea (plus $10 lnllallatlonl I I I Name . Address .... .. P/code. I/We enclose cheque for $ ............. or charve to D No. Bankcard I D Visa D Masten:ard I I L Signature . . . . . . . . . . . . . . . . . . . . . . 80 SILICON CHIP Expiry Date I I I I _ I I ... II II . . ... Date . . . . . . . . . . . . . ... J * * * l SV A to 625V A available ex-stock l SV A to 2KV A available to order Largest ex-stock source of toroids in Australia * Competitive pricing available for OEMs and resellers HARBUCH ELECTRONICS PTY LTD 90 George St. HORNSBY. NSW 2077 Phone (02)476-5854 Fax (02)476-3231 TABLE 1 SIGNAL Transmitted data Received data Clear to send Signal Ground RS232 PIN NO ABBREV ACTION 2 3 5 7 (TXD) (RXD) (CTS) Data transfer PC to AR2500 Data transfer AR2500 to PC Data enable line to PC Ground screen. Pressing the DELETE button will remove a given frequency and allow a new one to be entered. The effect of this is that overwriting and accidental removal of frequencies is eliminated. Priority channels Instead of a single priority channel, the AR2500 allocates an entire bank to the PRiority function. When bank 1 is LINKed and the PRiority function activated, it is scanned after each successive bank. This means scanning follows the order 1,2,1,3,1,4,1,5. This is quite a useful function and considering the number of memory channels available, it's unlikely users will limit themselves to a single priority channel. In this case, 32 channels can be allocated the PRiority function. The AR2500 contains an 8K x 8 serial EEPROM which provides storage for the 78 frequency banks. There are 62 scan banks with 32 frequencies per bank, and 16 search banks with 2 frequencies per bank. The frequencies in all banks are sorted in descending order. The frequency information is stored in memory as a pseudo-BCD number occupying four bytes of data. The least significant byte contains mode information and the most significant three bytes con- tain the frequency. The AR2500 and a PC communicate asynchronously through an RS232C interface at 300, 1200 or 9600 baud with eight data bytes, no parity and one stop bit. To protect itself from data overflow, the CTS line is used by the AR2500 to signal to the PC that it is prepared to receive data. To send data, the PC must first send a signalling character such as a space (this is essentially a request to send character). After the first signalling character is transmitted by the PC, the AR2500 responds by taking whatever action is necessary and indicates completion of these actions by turning on CTS, thereby indicating to the PC that data may be transferred across the interface point on TXD. Automatic baud rate selection The AR2500 will automatically detect the correct baud rate. Initially, the PC must repeatedly send a carriage return character, until the scanner responds by returning a carriage return/line feed (CR.LF) sequence. The signals used on the RS232C port are shown in Table 1. TXD line Signals on this line are generated by the PC and are transferred to the .I.Sr...;.,;tt.■t;it:■h: RCS Radio Pty Ltd is the only company which manufactures and sells every PCB S front panel published in SILICON CHIP, ETI and EA. 651 Forest Road, Bexley, NSW 2207. Phone (02) 587 3491. AR2500. The PC holds the TXD line in marking "1" condition during intervals between characters or words, and at all times when no data is being transmitted. The PC will not transmit data unless an ON condition is present on the CTS line. RXD line Signals on this line are generated by the AR2500 and are transferred to the PC. RXD is held in the marking "1" position. As long as the PC is not transmitting, the AR2500 assumes that the PC is in the receive mode. CTS line Signals on this circuit are generated by the AR2500 to indicate whether or not the AR2500 is ready to accept data. Fortunately, this unit is supplied with a detailed 21-page instruction manual which outlines all valid computer commands recognised by the AR2500. There is sufficient information for an operator versed in microcomputer programming to generate custom software. In due course, software and connecting cables will be available to allow the scanner to be connected to a personal computer. This means the computer can be used to monitor and record activity (ie, mode, frequ ency, signal strength) for an extended length of time. This information can then be stored in the computer database for future reference. It will also be possible to display spectrum activity, illustrating those areas of the spectrum which suffer from congestion. This could be a valuable aid to frequency use and reuse planning. In summary, the AR2500 "wide range monitor" is an amazingly small but powerful receiver offering features previously available only on dedicated HF receivers and UHF /VHF scanners. The recommended retail price of the AR2500 is $999.00, with the price of additional software and connecting cables yet to be advised . All necessary mounting hardware and DC cords are included with the radio, which is eminently suitable for mobile use. The AR2500 should be available by the time this articl e appears in print from most reputable communications dealers. Our thanks to Access Communications Pty Ltd for the loan of the test unit. Phone (02) 417 5311. SC MAY1991 81 The first high voltage DC transmission line began operation in Sweden in 1946. Since that time, there has been a proliferation of DC transmission lines, operating at higher and ever higher voltages and powers. By BRYAN MAHER The Story of Electrical Energy, Pt.10 AST month, we looked at some of the early DC transmission lines which were developed to overcome the problems of AC electrical power at very high voltages. High voltage DC transmission lines became possible through the development of high power mercury arc valves. These were continually improved upon and developed by the ASEA Company of Sweden until as late as 1971. The original HVDC line from the Swedish mainland to Gotland Island used two parallel compound anodes in each mercury arc valve. Further development by the ASEA Company L 82 SILICON CHIP at their Ludvika laboratory produced the 4-anode high voltage mercury valve pictured in Fig, 1. This controlled diode, unveiled in 1958, was capable of much greater current, though it was more complex in construction and circuitry. Further research into simpler single anode mercury valves of even greater current carrying ability proceeded at the rebuilt Trollhattan laboratory. As you can imagine though, making electrical measurements on these very high voltage valves presented a host of problems. To perform the detailed voltage, current and timing tests on a bridge circuit of these valves, the scientists and engineers used oscilloscopes with their entire circuitry, case and power supply elevated to the HVDC potential. A motor generator set was specially Fig.1 (above): the world's first 4anode HVDC mercury arc valve being tested in 1958 at ASEA's Ludvika Laboratory. The four separate anode units can be clearly seen. This complex unit was effectively one controlled diode. adapted with the generator body and shaft isolated from ground by insulated mountings and shaft couplings. While this generator powered the oscilloscope, the researchers remained safe at ground potential and operated the CRO via long insulating shafts. A general view of this test setup is shown in Fig.2. These early mercury arc valves used air cooling but later higher power units used water cooling. NZ inter-island link The North and South Islands of New Zealand, originally had separate electricity supplies. Then in 1965, the two islands were joined electrically by a 125kV DC submarine cable across Cook Strait. Laid in water no more than 200 metres deep, this single-core steel armoured cable carries DC power in either direction as required. Thus excess load in either North or South Island can be supplied from the other. For this most important power link, the ASEA company installed converter bridges with mercury arc valves, each consisting of four parallel anodes with up to 10 intermediate electrodes. The photo of Fig.3 shows the original 1965 6-diode bridge at the North Island terminal. Later, the system was upgraded so that each station consisted of two bridges in series, with the centre connection earthed. In this form, the link operates at ± 250kV, at powers of up to 600 megawatts. For this level of power, the current is a maximum of 1200 amps, so high that water cooling of the valves is necessary. Thus ended the previous prevalence of air cooling for converter sets. Since the coolant is passing through equipment operating as high as 250kV above earth, this technique requires purification of the circulating water and long insulating hoses of teflon or polythene. Sweden to Denmark link A world first was celebrated in 1965 when two different countries were joined electrically by a HVDC submarine cable. Sweden and Denmark were connected by a 240kV DC cable, 86km long, between the two landfall points at Konti and Skan. This 250MW link, installed in 1965, used very large mercury valves, one of which is shown partly dissembled in Fig.4. Note here the grating-like Fig.2: high voltage testing on single anode mercury arc valves in progress at ASEA's Trollhatten Laboratory in 1962. In order to monitor the valves, the oscilloscopes were operated at the HVDC potential and were separately powered by an insulated generator. intermediate electrodes. These allow passage of the dense electron stream from the mercury pool at the bottom to the final anode at the top. As discussed last month, these intermediate electrodes, each connected in turn to ascending steps on a voltage divider, distribute the high voltage potential gradient in the cutoff mode. Thus, the valve does not flash over when in the high potential state during each negative half cycle. Fig.5 shows the Danish terminal as it appeared in 1965. As the benefits of HVDC submarine supply links became evident, many countries contracted with ASEA for such installations. In 1967, the island of Sardinia was connected to mainland Italy by a 200kV DC submarine cable 116km long. This 200MW link was at the time the world's longest. Again, a seawater return path was used. Harmonic suppression Inevitably, in any AC to DC conversion using rectifiers, harmonics are introduced into the system. So mercury arc rectifiers operating at high voltage produce harmonics of the AC mains frequency (50 or 60Hz) on a large scale. For 6-phase AC drive to a full wave group of 12 valves, the harmonics present are given by the expression (6n ± 1) where n is an integer. Thus, the harmonics produced will be the MAY1991 83 ferent frequencies; 50Hz in one , 60Hz in the other. Thus, a very short HVDC link can be used solely as a means of paralleling on multi-frequency systems. 2-way power transfer In all HVDC links, power can be transferred either way as desired (note: this operation is very different from the case of DC power interchanged between distant paralleled motor-generator sets, where we reverse the current direction for power to flow the other way). HVDC lines are unique in that the valves (mercury arc or solid state) at either end are fundamentally diodes, so they must always pass current in the same direction. By manipulating the phase triggering of the converters at either end of link, it is possible to arrange for power to flow in either direction. End of the mercury arc era Fig.3: the New Zealand inter-island link in 1965. Six diodes which constitute one 3-phase converting bridge are visible. Each diode consists of four parallel anodes, each with multiple intermediate electrodes. In its final form, this installation operates at ±250kV and can supply up to 600 megawatts in either direction. Notice that even though the valves operate at very high potentials, they are water cooled. 5th and 7th; 11th and 13th; 17th and 19th and so on. To avoid this problem, most HVDC links include filters to reduce all harmonics up to the 25th (ie, up to 1500Hz for a 60Hz AC mains input). Synchronising problems There is another point about AC powerlines which needs to be mentioned. Every AC transmission which joins areas fed by different power stations is, by the nature of AC, a synchronous link between those two power stations. Often this is desirable but it sometimes becomes a disadvantage. Should a small power transfer be desired between two large generating systems, a weak synchronous connection will not do. In times of trouble in one system, its frequency may fall slightly until corrected. During that 84 SILICON CHIP time interval, the weak interconnector will be called upon to carry very large synchronising currents in attempts to hold up the frequency of the troubled system. This overload would certainly trip off the interconnector on overcurrent, just when it is most needed. By contrast, HVDC power links do not need or carry frequency, timing or phase angle information. A DC line can only carry amperes of steady current. This fundamental asynchronous nature of HVDC links can be most useful. Cases do occur where the frequency stability of one generating system is unreliable, yet power needs to be transmitted to or from another grid which is far more stable. Here, asynchronous transfer is the only possible way. Again, the two AC systems to be joined may normally operate on dif- Development continued at the ASEA laboratories to produce larger and more efficient single anode mercury arc valves. In fact, ASEA had a 1000 amp monster mercury arc rectifier under development in 1971 but it did not go into production as solidstate high power thyristors had by then become available. Throughout the mercury arc valve era, ASEA avoided publishing any details of the valve's internal construction. Even the patent application showed nothing to indicate how they were made. No other company in the world achieved such development in mercury arc inverters. First solid state HVDC link The first HVDC thyristor installation in the world was a 50kV ZODA rectifier/inverter group. This was installed in the Vastervik converter station which was one end of the Gotland line. As a first step, an existing mercury arc valve was removed and replaced by one group of series parallel thyristors (ie, series strings of thyristors , with the strings then connected in parallel to carry the high currents). Fig.6 shows the trial installation which was in service from 1967-1969. After 15,000 hours of successful operation of the pilot solid state valve, the entire Gotland link was upgraded. A new solid state bridge was connected in series with the high voltage Fig.4: this photo gives so.m e idea of the size of the mercury arc valves from the 1965 Konti-Skan HVDC installation. Fully assembled, these valves operated at 250kV and 1000 amps. top terminal of the existing mercury arc valves. In the new addition, each diode was a series parallel group of silicon thyristors. This new bridge, supplied by its own transformer, developed 50kV DC. This, added to the 100kV of the existing original mercury arc valves, gave a total output voltage of 150kV. The original submarine cable was retained as its insulation was quite adequate for this increased voltage. Thus, the upgraded Gotland link in 1970 was capable of carrying 30 megawatts instead of the original 20 megawatt rating. However, by 1983 the electrical load on Gotland Island had so increased that a completely new HVDC system was installed. A new submarine cable, 90km long and weighing 3000 tonnes, was manufactured by ASEA Kabel of Stockholm, to a rating of 150kV. Together with the new converter stations built at each end, this cable supplied the full 130MW load of Gotland. The original cable and converter equipment and the old power station on Fig.5: this picture shows the Danish terminal of the Konti-Skan HVDC link to Sweden. The AC equipment is in the foreground while the DC converters and harmonic filters are in the background at right. MAY 1991 85 Fig.6: the world's first HVDC solid state thyristor valve group is shown at right in this picture as part of a trial installation at Gotland. It was run for 15,000 hours at 100kV and 200 amps. the island are held as reserves. The new solid state AC/DC converters shown in Fig. 7 are huge in comparison to the original Vastervik plant, now 37-years old, but still operable. Large numbers of series paral- Fig.7: the 150kV 130 megawatt HVDC installation for the Gotland Mk.3 connection. Suspended from the ceiling are the quadruple solid state valves which make up the · inverter/converter bridge. lel connected silicon thyristors carry up to 1000 amps and withstand 150kV. In 1987, to cope with further increased load, a second similar installation and cable were installed, doubling the power capacity. Suspended converters Fig.8: HVDC links are continuing to grow in size and power. This is the Konti-Skan-2 installation which was brought into operation in mid-1989. It operates at 285kV and supplies 300 megawatts. 86 SILICON CHIP Because of the multiplicity of connected components, the physical mounting of solid state HVDC converters is a critical point of design. By 1983, ASEA had installed systems in many countries, including North and South America. As some locations are subject to earth tremors, volcanic activity and other ground instability, an earthquake-proof converter mounting method was devised. Here a strong reinforced concrete building is constructed, then the complete HVDC converter units are suspended from the ceiling by tension insulators. This means that the electronic system can remain relatively stationary even though the ground and building may move laterally and vertically during earthquakes. Suspended converters have survived some violent earthquakes on the American continent, though in those disasters even powerlines, bridges and other buildings have collapsed. The first suspended HVDC convert- ers were the 1983 Gotland Mk.3 units. In the photo of Fig.7, this method of mounting is clearly seen, the bottom 1000A SUBMARINE CABLE 3-PHASE TRANSFORMER CENTRE EARTH - - - + - , T O WATER ..,. - 3-PHASE TRANSFORMER 3-PHASE GRID SKAGERRAK CHANNEL 127km WIDE - - 50Dm DEEP 25DkV CONVERTER/ INVERTER -250kV 1000A 3-PHASE TRANSFORMER SUBMARINE CABLE DENMARK Fig.9: the Skagerrak HVDC link between Denmark and Norway effectively uses two submarine cables in series to supply 500 megawatts at ±250kV. of the units hanging about two metres above the floor. World's longest DC link In 1977, Norway and Denmark were connected by the (then) world's longest submarine power link. From Tjele 3-PHASE GRID NORWAY in Denmark, two HVDC submarine cables were laid across the Skagerrak channel to Norway. Each cable is single core, steel-armoured and rated at 250kV. To carry the 500 megawatt load, these cables effectively operate in series, giving an equivalent of 500kV at lO00A. To ease the cable insulation problem, the converter stations at the ends of the line each consist of two 250kV bridges in series, grounded at their centre, as shown in Fig.9. The task of manufacturing transporting and laying one 130km length of submarine cable weighing 6000 tonnes was immense. For this purpose, a specially built ship, the M.V. Skagerrak, was equipped with a huge deck-mounted motor driven turntable (Fig.10). A loading/unloading gantry gently eases the heavy cable onto the turntable when loading and off when laying at sea. Because the cable was in one piece, no cable joining at sea was necessary and it could be voltage tested before the voyage began. In 1989, a completely new HVDC submarine link, Konti-Skan 2, was completed, carrying 300MW either way between Sweden and Denmark. With this facility, the Swedish State Power Board (Vattenfall) can exchange power with the Danish power system (Elsam) and the huge central European grid. Acknowledgement Special thanks and acknowledgements to ABB Australia and Sweden for supplying historic photographs and data; and to ABB Review, ASEA Journal and Action. SC Fig.10 (left): built especially to lay HVDC submarine cables, this ship carries 6000 tonnes of cable in one piece, 130 kilometres long. MAY 1991 87 , ~~ ~ ;) LY '~ \ /' ·-.: . \,. 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CPF CONTINUOUS POWER FILTEA SPIKE ARRESTOR The Fortran CPF Filtered Electronic Spike Protector provides a protective electronic barrier for microcomputers. printers , telephone systems and modems electronic typewriters. aud io and stereo systems and other sensitive electronic equipmen!. SPECIFICATIONS: Connectors: 0825 plug on 80m m ribbon cable and 0825 socket. Indicators: Tricolour LED's fo r TD . RD, RTS, CTS. OSA, C D, TC . AC, OTA, (E)TC . Jumper Wires: 20 tinned end pieces Power: Interface po"."'er: Enclosure: Black . high impact plastic Dimensions: 85 )( 95 )( 30mm T he CPF provides protectmn fro m d angerous electrical spikes that can cause anything from obvious damage (like immediate equipment failure) to less obvious harm that can drastically shorten a system 's life CPFs superior circuitry desig n and semi conductor technology responds instantly to any potentially damaging over-voltage , ensu ring safe trouble free operation . X 15700 ..... $99.95 Surges and spikes are caused not o nly by lightning strikes and lo.ad switching but also by other eq uipment being switch.ed on and ~ff. s uch as fluorescent lights, electric motors. fr idge freezers, air conditioners, etc For effectiv e protection suc h spikes m ust be stopped befo re the y reach your e9uipment. Simply plug The Button into an outlet and 11will protec1 all equipment plugged into a~jacent o utlets on the same branch c1rcwt T he Button employs unique met_al Q)(ide vari ster technolo gy and w ill d issipate 150 jo ul~s of electrical energy . (nearly twice that of comparable surge arre sters.) SPECIFICATIONS: Voltage : 240V Nominal Total Energy Rating . 150 Joules Response Time : 1Ons Prot ection Level : 350V peak ..... . $42.95 Additionally, CPFs filtering capability helps eliminate troublesome and annoying interference. general hash cre.ated by small motors, fluorescent lamps, and the like that threaten the performance and shorten equipment life ol unprotected electronic com ponents. ,,.. - t J Converts 5 1/ 4" single sidl'd floppy disks to double sided, by placing an appropriate notch in the floppy disk jacket. Cat X10088 c2107o .................. ss.oo DISK N OTCHER $69.95 ~/ ~ ~ .", t ~----- t ,,y - ../ '-- , ,~ 0 0 4 ◄ KEYBOARD EXTENSION LEAD ENCLO:ifJ'tlNTER • Keeps your paper and pr1nt-ou1 s 5 Pin Din plug and socket neat and ord erly • Transparent cover makes 11 easy · to check on pape r supply • Pape r can be fed from the centr e or the rear according !o the design P19038 .. .... ... .......... $9.95 ollhe pnnlec ', ~ •~~~~~~~~~~ most printers $69 .95 DELUXE PRINTER STAND • Res1ores order 10 your wo rk area withou t occupying e)( tra space • Feeds and re fo lds pape r under th e prin ter au!omat1cally • Ad1ustable paper defl ectors ensure smoo!h flow of paper • Made of mou lded plasti c • Su itable for most printers C21058 (80 column) $69.95 DATALIFE DL-600 DATA CARTRIDGE Stores up to 120 MIByte C12614 DID YOU FORGET YOUR PROTECTION? Viruses are a major problem. Our Head technician A shley rue·• the day he didn't put the write protect tabs on his t est disks. • Removable d rawer whi ch allows paper to be changed without m oving th e printer • Retr actable re ar baske1 makes pri nt-out collection last and I'.: , SPECIFICATIONS: Electrical rating: 220-260 volts (AC) 50Hz 10 Amp Spike/RF! Protection 4 500 amps lor 20ml second pulses Maximum clamping voltage 275V dtfferenhal mode ~ \ 'o~~ - ROD'S COMPUTER TIPS! $59.00 ij-- 1\ L . ', ', - l - _- -1 MAGIC STAGE A working bench for you r Mouse. •High quality ABS plastic and anti-static rubberised top The number of customer repairs that come In with viruses on their computers (hard disk s) Is very high. So like all contagious illnesses you should use protection at all times. Diskettes are supplied with write protect tabs (5114 .. ) and 3112 .. disks have a switch built into th e plastic body. I advise you to immediatly put your write protects on now! Viruses can be transmitted anytime, your children, workmates, wife, friends etc. who use your computer can easily obtain a terminal illness by inserting your "clean" disk into their "dirty" machine. So to make sure you are not a victim of the Grim Reaper put your write protects on Now! Next month we will show you what 8 write protect looks like and how to put-one on. Regards Rod Irving. A small compact unit that allows transm i ssion o f video & audio signals (RF) t o any TV set or VCR Be the f irst in your office to w ithin range of 30 have a mouse that every one metres. Ideal for will want use. This cute little watching videos In the mouse cover puts a bit of fun bedroom or kitchen and colour onto your desk without having to move while keeping your mouse free of dust! the entire VC R or having long extentlon C21069.I ... .D ::..... ;., .... $7.95 leads running through l....!i ·- . the house . Can also be used as a transmitter for a video camera . With power MOUSE on/off switch audio and video leads and CLEANING KIT supplied with an AC Keep dust and dirt from adaptor. damaging your mouse with A16150 Normally .. $95.95 this handy mouse cleaning NOW ONLY.. ... $84.95 kit. This special rounded tool will find its way into all the hard to get at places. The kit also comes with cleaning fluid and 5 soft cloths to keep your mouse spotless! UV EPROM ERASER C21071 ......... ........ $9.95 !!!) Erase your EPROMs quickly andsafely. This unit is the cost effective solution to your problems. tt will erase up to 9 x 24 pin devices in complete salety, in about 40 minutes (less time for less chips) • Chip draw er has conductive foam pad • Mains powered • High UV intensity at chip surface e nsures EPROMs are thoroughly erased Without timer X14950 ........ .... ..... .... $99 With built-in timer Xl 4955 ... ................ $169 DUST COVER Keep your computer and accessories free of dust and grime while not in use x T• Cover Set C21066 ........ ...... .... $14.95 Ar Cover Set C21068 ..... ............ .$16.95 • MOUSE KIT Everything you need to keep your mouse happyl You get a mouse pad, a mouse holder1 a cleaning kit (previously described) and a cute litUe mouse cover. C21072 ........•.....•...• $16.95 MOUSE GIFT SET Here it is! The ultimate mouse kit. You get all of the above products1 the cute little mouse cover, the mouse cleaning kit, the mouse house and mouse pad all in a handy black case. C21074 .....•............ $19.9S •Stationary holder •Includes pull-out shelf tor Mouse SURGE BUSTER 6 PROTECTED POWER OUTLETS ldeal for protecting personal computers, video equipment, colour TVs, amplifiers, tuners, graphic equalisers, CD players etc SPECIFICATIONS: • Electrical rating: 240V AC, 50Hz, 10A • 3 x Metal Oxide Varistors (MOV) • Maximum clamplng Voltage: each MOV: 71 O volts at 50 amps • Response time: less than 25 Nanoseconds. Xl 0086 ..................... $69.95 POCKET AUTO AB SWITCHES , Pocket size, auto-scanning • Allows 2 PCs to share one Printer Serial model: MS-201 - Host-powered Xl 9150 .................. $79.95 Parellel model: MP-201 Protocol transparent X19155 .................. $89.95 • 3 1/ 2" C l2560 • SI W ....... $6.95 \ '. : ':'.!~ ... ;;, l XT HD CONTROLLER .... $129 AT HD CONTROLLER .... $199 RS232/SERIAL CLOCK. ............................ $49 MONO COLOUR CARD .. $76 MULTI OL ...................... $99 VOICE MAIL. ................... $199 PRINTER CARD ............. $29 EGA CARD ...................... $149 DIAGNOSTIC ..... ::..:......... $795 TTUPRINTER.................. $89 RAM 2M AT EXT/EXP...... $225 SM AT EXT/EXP............... $325 FAX CARD ....................... $595 4 PORT SERIAL. ............. $129 2 WAY FDD CONT (360K) .............................. $39 RS232/SERIAL CARD.-.. $39 GAMES CARD ......... ........ ~29 AT S/P/G 1 SIPIG .............-$43 \\ AT SIPIG 2 S/P/G .............$49 4 WAY FDD CONT. (360-1.44M) ...................... $129 2 WAY FDD CONT. (360-1 .44M) .... .................. $80 CLOCK CARD ................ . $3.9 SMART DRIVE ADAPTER IDEIFDC........ $89 SMART DRIVE ADAPTER IDE 110 FDC ... $119 VGA CARD 16 BIT NO RAM (EXP TO 1M).................. $189 VGA CARD 16 BIT 250K (EXP TO 1M).................. $219 VGA CARD 16 BIT 512K (EXP TO 1M) .................. $259 VGA CARD 16 BIT ( 1 MEG) ..........................$299 CANON LASER CARTRIDGES - EP CARTRIDGE FOR SIDE LOADING PRINTERS ................ $189 EP-L CARTRIDGE FOR FRONT LOADING PR INTERS ................ $189 EP-S CARTRIDGE FOR TOP LOADING PRINTERS .... .......... ..$ 189 RODIRVING ELEaRONICS SYDNEY·. 74 Parramatta Ad Stanmore. 2048 . Phone (02) 519 3134 Fax (02) 519 3858 MELBOURNE : 48 AHeckett SI Phone (03) 663 6151 , NORTHCOTE:· 425 High St. Phone (03) 489 8866 CLAYTON: 56 Renver Rd Phone (03) 543 7877 MAIL ORDER& CORRESPONDENCE: P 0 . Box 620. CLAYTON 3168 Order Hotline : 008 33 5757 (Toll free, strictly orders only) Inquiries: (03) 543 7877 HEAD CLEANER DISKS · it o nl y takes a minute amount of du st, dirt or mag netic o xide particles on y our drive heads to cau.~e problems: errors, downtime or an ex per. si ve servi ce 1.:all. Reg ular u se of a h ead cll'an er will k eep your drive free o f trouble cau sing dirt and help k l'ep y our system up and runnin g . T h ese di sk cleaners are simple to u se, a nd include cleanin g solution and in struc ti o n s. !•.: " ·-:-·-- COMPUTER CLEANING KIT To gain optimum performance and prevent damage to valuable disks, this cleaning kit has all you need to keep your computer in top notch performance. Anti-static cleaning pads, cleaning swabs, ~leaning solution, 5 114.. & 3 112" cleaning diskettes. c21on ......... ........ .. $19.95 C l2555 .. ...... .... ...... $6.95 ,_ _ _ _ _ _ _ _ __ Telex: AA 151938 Fax (03) 543 2648 All sales tax exempt orders and wholesale inquiries to: RITRONICS WHOLESALE. 56 Renver Road, Clayton. Phone: (03) 543 2166 (3 lines) Fax: (03) 543 2648 For postage rate s refer to other R.I.E advertisement Er~ors and om1s_sions excepted. Prices and spec1f1cations subject to change. IBM' . PC • XT' . AT' . a..ereg1stered lrad&markso,I lnte<nat,or,al Bus,ness Machones ·Ap~ e ,s a ·oerotes •l!'9"'terecl ' f191stered Irad&mar1< 1r"""1afks ol 1he, r re spec11 v1 owner~ / Silicon Chip BACK COPIES May 1988: Optical Tachom eter For Aeromodellers ; High Energy Ignition For Cars; Ultrasonic Car Burglar Alarm ; Walkaround Throttle For Model Railroad s , Pt.2; Des igning & Building RF Attenuators; Motorola MC3334P High Energy Ignition IC Data. July 1988: Stereo Contr9I Preampl ifier, Pt.2; Fitting A Fuel Cut-Off Solenoid; Booster For TV & FM Signals ; The Di scolight Light Show, Pt.1 ; Tone Burst Source For Amplifier Headroom Testi ng; What Is Negati ve Feedback, Pt. 3; Ameren MA1200 Power Amplifier Review; Amplifi er Headroom - Is It A Con ? August 1988: Building A Plasma Display; Universal Power Supply Board; Remote Chime/Doorbell ; High Performance AC Millivoltmeter, Pt.1 ; Discolight Light Show, Pt.2 ; Getting The Most Out Of Nicad Batteries; Data On Insulated Tab Triacs. September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detecto r; High Performance AC Millivoltmeter, Pt.2; Vader Voice ; Motorola MC34018 Speakerphone IC Data; Nati onal Semi conductor LM1 2 150W Op Am p Data & Applica- lions; What Is Negative Feedback, Pt.4. . October 1988: Stereo FM Transmitter (Uses Rohm BA1404) ; Hi gh Performance FM Antenna; Matchbox Crystal Set; Electronic House Number; Converting A CB Radio To The 28MHz Band ; Oueensland's Powerful Electric Locomotives. November 1988: 120W PA Amp lifier Module (Uses Mosfets); Poor Man's Plasma Display; Au tomotive Night Safety Light ; Adding A Headset To The Speakerphone; How To Qu ieten The Fan In Your Compute r; Screws & Screwdri vers , What You Need To Know; Diese l Electric Locomotives . December 1988: 120W PA Amplifier (With Balanced Inputs) , Pt.1; Diesel Sound Generator; Car Antenna/Demister Adaptor ; SSB Adaptor For Shortwave Receivers ; Electronics & Holden's New V6 Engine; Why Diesel Electrics Ki lled Off Steam; Index to Volume 1. January 1989: Li ne Filter For Computers; Ultraso ni c Proximity Detector For Cars; Simple Co mputer Sound Repeater; 120W PA Amplifie r (With Balanced Inputs) Pt.1; How To Service Car Cas- •,. _.,.,_-10 \\le~ rf,\\.1'1.-'$ ~ sette Players; Massive Diesel Electrics In The USA; Marantz LD50 Loudspeakers. February 1989: Trans istor Beta Tester; Minstrel 2-30 Loudspeaker System; LED Flasher For Model Railways (uses LM3909); Build A Simple VHF FM Monitor (uses MC3362) , Pt.1 ; Lightning & Electro nic Appliances; Using Comparators to Detect & Measure. March 1989: LED Message Board, Pt.1 ; 32-Band Graphic Equaliser, Pt.1 ; Stereo Compressor For CD Players ; Map Reader For Trip Calcu lations; Amateur VHF FM Monitor, Pt.2; Signetics NE572 Compandor IC Data ; Electronics For Everyone Resistors. April 1989: Aux ili ary Brake Light Flas her; Electronics For Everyone : What You Need to Know About Capacitors; Telephone Bell Monitor/Tra ns- U se this handy form to order your back copies ---- -----------------------------Please send me a back issue for: O September 1988 0 October 1988 0 February 1989 O March 1989 0 Juty 1989 0 August 1989 0 December 1989 0 January 1990 O May 1990 o June 1990 O October 1990 O November 1990 0 March 1991 0 Apri l 1991 0 0 0 0 0 0 O May 1988 November 1988 April 1989 September 1989 February 1990 Ju ly 1990 December 1990 0 O 0 0 O O 0 July 1988 December 1988 May 1989 October 1989 March 1990 August 1990 January 1991 0 O O 0 0 0 0 l -__ _ Aug ust 1988 January 1989 June 1989 November 1989 April 1990 September 1990 February 1991 Enclosed is my cheque/money order for $_ __ ___or please debit my: O Bankcard Card No. $5.00 each (includes p&p). Overseas orders add $1 each for postage. NZ orders are sent ai r mail. Signature _ _ _ _ _ _ _ __ _ _ _ _ Card expiry date_ _ /_ _ Detach and mail to: SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROY BEACH NSW 2097 Name _ _ __ _ _ __ _ __ _ _ _ _ _ __ _ _ __ _ _ __ Street _ _ _ _ _ __ _ __ _ _ _ _ __ _ _ __ _ __ _ Suburb/town _ __ _ _ __ _ _ _ ____ Postcode _ __ _ __ ' ' 0 Visa Card 0 Master Card Or call (02) 979 5644 & quote your credit card detai ls. Fax (02) 979 6503 X I I - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -'---90 SILICON CHIP Computer, Pt.4 ; 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; The Tube Vs. The Microchip (Two Shortwave Receivers Compared); What To Do When Your Computer Goes Bung, Pt.4. September 1990: Music On Hold For Your Telephone; Remote Control Extender For VCRs; Power Supply For Burglar Alarms; Low-Cost 3Digit Counter Module; Voice Mail For Your Computer; Simple Shortwave Converter For The 2Metre Band; How To Make Dynamark Labels. mitter; 32-Band Graphic Equaliser, Pt.2; LED Message Board, Pt.2. May 1989: Electronic Poo ls/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; Coherent CW - A New Low Power Transmission Technique. July 1989: Exhaust Gas Monitor (Uses TGS812 Gas Sensor); Extension For The Touch-Lamp Dimmer; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm; NSW 86 Class Electric Locomotives; Facts On The PhaxSwitch - Sharing Your Phone Line With A Fax Machine . . August 1989: Build A Baby Tower AT Computer; Studio Series 20-Band Stereo Equaliser, Pt.1; Garbage Reminder - A 7-day Programmable Timer; Introduction To Stepper Motors ; GaAsFet Preamplifier For The 2-Metre Band; Modern 3Phase Electric Locomotives. September 1989: 2-Chip Portable AM Stereo Rad io (Uses MC13024 and TX7376P) Pt.1; AlarmTriggered Telephone Dialler; High Or Low Fluid Leve l Detector (uses -LM1830N); Simple DTMF Encoder (uses Texas TMC5089); Studio Series 20-Band Stereo Equaliser, Pt.2; Auto-Zero Module for Audio Amplifiers (Uses LMC669); A Guide To Hard Disc Drives. October 1989: Introducing Remote Control; FM Radio Intercom For Motorbikes (Uses BA 1404 And TDA7000) Pt.1; GaAsFet Preamp lifier For Amateu'r TV; 1Mb Printer Buffer; 2-Chip Portable AM Stereo Radio , Pt.2; Installing A Hard Disc In The PC; A Look At Aystralian Monorails. November 1989:· Radfax Decoder For Your PC (Disp lays Fax, RTTY and Morse) ; Super Sensitive FM Bug; Build A Low Cost Analog Multimeter; FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Radio, Pt.3 ; Floppy Disc Drive Formats & Options; The Pi lbara Iron Ore Railways. December 1989: Digital Voice Board (Records Up To Four Separate Messages, Uses Texas TMS3477NL and 256K RAMs); UHF Remote Switch; Balanced Input & Output Stages; National Semiconductor LM831 Low Voltage Amplifier IC Data; Install A Clock Card In Your PC; Index to Volume 2 (January- December 1989). January 1990: Service Tips For Your VCR; Speeding Up Your PC; Phone Patch For Radio Amateurs; High Quality Sine/Square Oscillator; Active Antenna Kit; The Latest On High Definition TV; Speed Controller For Ceiling Fans; Designing UHF Transmitter Stages. February 1990: 16-Channe l Mixing Desk; High Quality Audio Osci llator, Pt.2; The Incredible Hot Canaries; Random Wire Antenna Tuner For 6 Metres; Phone Patch For Radio Amateurs , Pt.2; PC Program Calculates Great Circle Bearings. March 1990: 6/12V Charger For Sealed LeadAcid Batteries; Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16Channel Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC ; Digital Waveform Generation Using a PC; The Controls On A Model Aircraft. April 1990: Dual Tracking ±50V Power Supply; VOX With Delayed Audio; Relative Field Strength Meter; 16-Channel Mixing Desk, Pt.3; Simple Service Tips For Your Microwave Oven; Model Aircraft Aerodynamics; Active CW Filter For Weak Signal Reception. May 1990: Build A 4-Digit Capacitance Meter; High Energy Ignition For Cars With Reluctor Distributors; The Mozzie CW Transceiver; Waveform Generation Using A PC, Pt.3; 16-Channel Mixing Desk, Pt.4; What To Do When Your Computer Goes Bung, Pt.1; Electronic Load For Checking Power Supplies. June 1990: Multi-Sector Home Burglar Alarm; Low-Noise Universal Stereo Preamplifier; Load Protection Switch For Power Supplies ; A Speed Alarm For Your Car; Design Factors For Model Aircraft; Fitting A Fax Card To Your Computer; What To Do When Your Computer Goes Bung, Pt.2. July 1990: Digital Sine/Square Generator, Pt.1 (Covers 0-500kHz) ; Burglar Alarm Keypad & Combination Lock; Simple Electronic Die; Low-Cost Dual Power Supply ; Inside A Coal Burning Power Station; What To Do When Your Computer Goes Bung, Pt.3; Digital Waveform Generation Using A October 1990: Low-Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; Surfsound Simulator; DC Offset For DMMs ; The Dangers of Polychlorinated Biphenyls; The Bose Lifesty le Music System ; Using The NE602 In Home-Brew Converter Circuits. November 1990: Low-Cost Model Train Control ler; Battery Powered Laser Pointer; A Really Snazzy Egg Timer; 1.5V To 9V DC Converter; How To Connect Two TV Sets To One VCR; Introduction To Digital Electronics ; Simple 6Metre 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 ; The Green CD Pen Controversy. January 1991: Fast Charger For Nicad Batteries, Pt.1 ; Have Fun With The Fruit Machine; TwoTone Alarm Module; Laser Power Supply (For Tubes With Ratings Up To 10mW); LCD Readout For The Capacitance Meter; How Quartz Crystals Work; The Dangers When Servicing Microwave Ovens; Electric Vehicles - The State Of The Art. February 1991: Synthesised Stereo AM Tuner, Pt.1; Three Inverters For Fluorescent Lights ; LowCost Sinewave Oscillator; Fast Charger For Nicad Batteries, Pt.2; How To Design Amplifier Output Stages; Tasmania's Hydroelectric Power System . March 1991: Remote Controller For Garage Doors, Pt.1; Transistor Beta Tester Mk.2; Synthesised AM Stereo Tuner, Pt.2; Multi-Purpose 1/0 Board For PC-Compatibles ; Universal Wideband RF Preamplifier For Amateurs & TV; A Look At Config.Sys & Ansi.Sys; High-Voltage DC Transmission Systems. April 1991: Steam Sound Simulator For Model Railroads ; Simp le 12/ 24V Light Chaser ; Remote Controller For Garage Doors, Pt.2; Synthesised AM Stereo Tuner, Pt.3 ; A Practical Approach To Amplifier Design, Pt.2; The Easytune FSK Indicator For HF Transmissions; Playing With the Ansi.sys File. PLEASE NOTE: All issues from November 1987 to April 1988, plus June 1988, are now sold out. All subsequent issues are presently in stock. For readers wanting articles from issues out of print, we can supply photostat copies (or tearsheets) at $5.00 per article, including postage. When supplying photostat articles or back copies, we automatically supply any relevant Notes & Errata, at no extra charge. MAY1991 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. Speed control for electric flight models I am an aircraft modeller from way back- about 28 years. Recently, I have become involved in electric flight which is a very challenging and eyeopening experience for an aeroplane (read: combustion engine) nut. I have just completed one of your projects, the Fast Nicad Charger and, to my complete amazement, it works perfectly. I built it from scratch, etched the PC board myself and had about 50% of the components in my junkbox. Thank you and your R & D staff for such a nicely presented, intelligent project. Now I face another problem - speed control. I have built an ON-OFF relay switch operated by an R/C set but the challenge of a fully proportional speed control for an electric motor in a model aircraft has set in. To date, I have destroyed numerous (and expensive) MOSFETs, one motor, four fuses and an ammeter. About 12 years ago, I built a proportional forward/reverse speed control for electric boats. The silicon bridge and transistors took about 1V out of Big new amplifier wanted On looking through your back issues, I note that it's been a couple of years since your last amplifier, preamplifier and loudspeaker projects - anything new on the horizon? I reckon a big heavyweight of about 300 watts into 4 ohms would turn a few heads. And how about a CD kit? You might import the transport mechanism and then implement a design for a digital/analog converter and other electronics with it. What do you reckon? Two-box CD players with separate D/ A converters are all the rage with the high end 92 SILICON CHIP the supply! This is not acceptable for aeroplanes drawing 7-15 amps at the 7.2-8.4V available. The NE544 servo amplifier is a great workhorse but isn't suitable for driving "expensive" MOSFETs. I am obviously not doing the right thing! A commercial speed control (imported) is in excess of $250. This is a bit too steep for the average modeller. Electric model cars obviously have the numbers, but "boaties" and R/C builders count as well. An "Aussie" developed speed control operated by an R/C set would be a boon. With environmental groups giving us (IC engine modellers) a hard time due to noise pollution, electric power is the way to go. What I and a lot ofmy flying mates are looking for is a speed control for 05 -size electric motors (buggy size), forward only, optically coupled, with a break circuit. If you can help, great. If you can't, I'll just keep the MOSFET suppliers happy and hope for the best. Thanks for a great magazine. (J. N., Hoppers Crossing, Vic) . • Thanks for your comments about the Fast Nicad Charger - it does work well. We hope to so some work on a crowd. A DI A converter project sounds good. (B. C., Grange, SA). • We have been working on a new high power amplifier for some time now, on and off, but the design has yet to be finalised. Designing a big reliable high performance amplifier is no easy task. As far as a CD kit player is concerned, it is something we considered several years ago but concluded that it was not really practical. Since that time, CD players have become a great deal cheaper and have more bells and whistles such as full remote control including volume. No, that's a project to which we'll definitely say, "Pass!" proportional speed controller for electric flight models and also for model boats in the near future - possibly in the latter half of this year. Oscilloscope user manual wanted First, let me say how much I enjoy your magazine and the information I obtain from it. I wonder if you will please ask your readers if anyone can supply me with photocopies of a user manual for a University Model UC-3 oscilloscope and a Model UAG-22D audio generator. Also, does anyone have a power supply for an ex-RAN oscilloscope, Hartley model CT436 for sale. (F. Davies, 28 Villa Road, Waratah West, NSW). • Can anybody help with the manuals and the power supply? Variations on the Nicad Fast Charger I read with enthusiasm the article describing the Fast Nicad Charger in the January 1991 issue. Having recently commenced building and flying small electric powered model aircraft, this project has appeared at just the right time. I am no electronics expert but have had some experience constructing projects from published designs. Having looked at a few other nicad charger designs, and with my own applications in mind, I wonder if you could suggest whether the following modifications are feasible and how they might be made: (1). Switchable option for 3-cell (3.6V) and 4-cell (4.8V) packs as typically used for smaller (less than 050 size) model aircraft motors (I have one each of these battery packs which I want to fast charge). (2). Selectable constant current charge rates for a given charge voltage. This could allow a slower charge when speed is not critical or when the pack is exceptionally hot. Could an ammeter or LEDs be added to monitor the charge current? (3). Could a cell discharge option be incorporated or added on? Presumably the ADC could be used to detect the drop to "end-point" voltage (ie, about 1. 1V per cell) to avoid over-discharging, thus allowing for a subsequent full charge. Presumably discharge current could be switch selectable for fast but safe discharge rates. (4). Automatically switch to "trickle" from "fast" charge once peak voltage is detected, instead of turning charger off as in the present design. The pack would then remain fully charged but would not be damaged if left attached indefinitely. (5). Some of the newer commercially available flight pack chargers sense battery temperature as a charge cut-off criterion (I understand it's high temperature that destroys cells, not the voltage as such). Presumably the ADC could be used to detect temperature using a thermistor attached to the pack. Is this a feasible and affordable option? It would be very helpful if you could provide an estimate of the total cost of this project built from scratch and also let me know if a kit is likely to be available in the future. If you are looking for ideas for future projects, how about an R/C speed controller for electric model aircraft? There are quite a lot available commercially especially from overseas but how about a simple, effective, light and economical Australian design (with the smaller 30-50 watt motors in mind as well as the standard and larger units)? Many thanks for a stimulating magazine. I have also learnt a great deal about R/C equipment and aircraft (and nicads!) from Bob Young's informative series - keep up the good work! (D. B., Townsville, Qld). • The nicad charger project should not cost more than about $80 if all new components are purchased from your local electronics retail outlet. At present, no kit supplier has decided to make this kit available. As far as the modifications are concerned, we can only give suggestions as to how they could be done. We cannot present a complete new design encompassing your modifications. Charging 3 and 4-cell packs is a Problems with UHF TV reception I live in a very difficult location for• TV reception and have built the UHF Bow-Tie Antenna described in the January 1988 issue of SILICON CHIP. The initial results are quite pleasing considering my circumstances. I have a snowy picture with colour, under the right atmospheric conditions. The antenna is mounted on a very long steel mast, with almost 20 metres of 75Q down lead to the TV set. I naturally wish to improve the reception from this system. At this stage I have not installed a masthead amplifier, as I wish to first improve both the antenna and the lead-in cable. My questions are, can I stack several of your bow-tie antennas on one mast? If I can, at what distance should they be plac.ed and how should they be coupled electrically? I found the antenna easy to build and it is far more robust than anything I could buy locally. My next question relates to the 75Q cable. I encountered a great deal of difficulty in my district identifying the cables for sale. Not one of the cables I examined was stamped with an RG number and I could not locate the Hills type SSC32 cable mentioned in your antenna project. The cables I finally purchased are marked Hills ADL 100/75 and brand 5C-2V but I have no specifications for either of these. Would it be possible for you to publish an updated listing of co- little tricky since the circuit is designed to only charge packs of 5 cells or more. This is because the voltage sensing circuitry using the ADC only starts measuring voltages above 5V. However, you should be able to charge the 4-cell pack if the charge LED (LED 1) is shorted out. This will increase the voltage supplied to the sensing circuit from the battery pack by about zv. As for the 3-cell pack, we can only suggest inserting a resistor in series with the battery pack to increase the overall charging voltage. At six amps, axial cable specifications, taking into account the variety of numbering systems on the market? I hope you can be of assistance in the above matters. (A. H., Cooran, Qld). • A number of readers have asked for details on stacking the bow-tie antennas but, as in the past, we can give no specific answers. The way to connect two stacked antennas is by means of equal length cables which ideally, should be a multiple of half a wavelength long at the main frequency of reception. To get the highest gain advantage from stacking, the antennas need to be several wavelengths apart otherwise you will not get anything like the theoretical increase in gain of 3dB (ie, a power gain of two). We think you would be much better off by going to a masthead amplifier than stacking antennas. You will get much more gain and the mechanical problems will be much less. Since you are in such a difficult reception area and have such a long run of cable, we suggest you try using 300Q ribbon rather than coax cable. While it does have drawbacks of its own, ribbon cable has far less attenuation of UHF signals than coax cable. If you do use ribbon, make sure it is twisted and spaced well away from the metal mast. In fact, with a masthead amplifier and ribbon cable, you may get quite a passable picture. Give it a go. we suggest a 0.3Q 20W resistor (eg, use three 0. lQ 10W resistors in series). Altering the charge current can be done by replacing the high current trimpot (VR1) with a front panel linear potentiometer. This will allow external adjustment and an ammeter in series with the charging cells can indicate the charge current. Note that the earlier suggestion of adding a series resistor with the 3-cell pack will prevent adjustment of the charging current unless the resistor value is increased to say 0.6Q and 40W rating. MAY 1991 93 Counter for alarm systems One drawback of today's electronic alarm systems, even homemade alarms, is that they don't have some sort of counter to tell the home owner how many times the alarm has been triggered. Usually, an alarm has a hold function which even after the alarm time has expired, keeps a flashing strobe running after the alarm period to tell the owner that his premises have been entered. Some alarm systems cannot even trigger for a second time, whereas some are connected to the phone line and tell the security installer exactly where the thief is! But what if you put a counter on the relay output? Then you would have an indication of how many times the alarm went off. You even could put a counter on infrared detec- This will allow adjustment of the charging current down to 3A from 6A without changing the resistor. The modification to discharge the cells down to 1.1 V per cell would require a completely new circuit. However, automatic switchover to trickle after full charging can be done if SCR1 is used to switch a relay which substitutes for the changeover switch S3. Detecting the fall in voltage once full charge is reached is actually accompanied by a small rise in the temperature of the cells. However, detecting this temperature rise is quite difficult since it can be masked by the ambient temperture, the temperature caused by recent discharge, and the.rmal inertia. The voltage drop detection method we have used is far more reliable. Lateral thinking on clock problem In the "Ask SILICON CHIP" column of November 1990, J.E., of Blackburn South asks for help with a digital clock with RAM and battery back up. A little lateral thinking brings another solution to mind. The use of a motorised 35mm camera and two digital 94 SILICON CHIP tars which only trip when a person gets within the zone and do not have a hold function which is left up to the main system. I came up with a simple method of buying the Dick Smith Digital Counter Module (catalog No. K2639, $12.95). By simply adding some debounce circuitry, I can now check how many times the alarm has gone off. Why don't you make yet another alarm, with a simple 0-9 counter for each sector, or just make another simple counter kit with a minimum of parts which can be connected to the main alarm system? Love the magazine. Keep up the good work. (J.E., Blackburn South, Vic). • Your suggestion for adding a counter circuit to burglar alarms is a good one and could certainly be a featwe of a future burglar alarm project. watches (one to show time and the other to show the date) could be an answer. A roll of film with 36 exposures would allow the recording of 18 power interruptions. Digital watches are about $10 each, while the camera is availc).ble from one of the big department stores for $99. Perhaps a Fresnel lens would have to be placed over the watches for magnification so that the digits can be read. On other topics, could you please explain the origin of the term "voice coil" when describing certain types of hard disk drives? Are there advantages over the use of stepper motors in these drives? Does SILICON CHIP intend reprinting in condensed form a series of articles which appeared in "Electronics World + Wireless World" in 1990 about low level non-ionising radiation and electromagnetic radiation? I believe that an issue of such social and moral importance should be at least as vigorously publicised as the dangers of Polychlorinated Biphenyls (SILICON CHIP, October 1990). (P. S., Nullamanna, NSW). • Your lateral suggestion for a camera to record time and date of power failures is an interesting one although we wonder whether the need to ex- pose and develop film might not be a sizable drawback. As far as disc drives are concerned, the term "voice coil" applies to a drive system which is very similar to that used in loudspeakers. "Voice coil" drive gives a much faster access time than previous head drive systems. As far as the series on non-ionising radiation in "Electronics World + Wireless World" is concerned, we are in two minds. We agree that it is an issue of importance but we are not sure that we could do it justice in the amount of space that we would have. "Electronics World+ Wireless World" devoted almost an entire issue to the subject - we could not do the same. It is also far from certain whether nonionising radiation really is harmful. The evidence so far is highly circumstantial. Summertime Special: chip hard to get With reference to SILICON CHIP, November 1990 and the "6 Metre Summertime Special", I have had problems obtaining the MC2831A integrated circuit. After checking out several suppliers, Radio Parts (Melbourne) finally came up with an MC2831AP. Could you please advise me if this chip is suitable for the above project and if not , if there is another that could be used that may be easier to obtain than the MC2831A? Congratulations for a fine magazine - your efforts are much appreciated. (V. T., Belgrave South, Vic). • The MC2831AP is the right chip. As far as we know, the "P" suffix relates to the plastic package. Answers on the unknown 4003 In your April issue, one of your readers asked about a 4003 chip and its function and you were unable to help. According to our data resources , a 4003 could be one of a number of chips: National Semiconductor LH4003 buffer amplifier; JCM 4003Z Television Circuit Line Selector; or a UAA4003 switching regulator circuit. Take your pick! Cheers. (A. Frolley, All Electronic Components, 118-122 Lonsdale Street, Melbourne. Phone 03 662 3506). • Thanks for the information Andrew. MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. FOR SALE WEATHER FAX programs for IBM XT/ ATs *** "RADFAX2" is a high resolution, shortwave weather fax , Morse & RTTY receiving program. Needs CGA, SSB HF radio & Radfax decoder. Also "RF2HERC", "RF2EGA" & "RF2VGA", same as RADFAX2 but suitable for Hercules, EGA & VGA cards respectively. $35. *** "SATFAX" is a NOAA, Meteor & GMS weather satellite picture receiving program. Uses EGA & r-------------------------, I I I I I I I I I I VGA modes, needs EGA or VGA colour monitor & card, plus "WEATHER FAX" PC card . $45. *** All programs are on 5.25-inch or 3.5-inch discs (state which) & include documentation. Add $3 postage. ONLY from M. Delahunty, 42 Villiers St, New Farm, 4004 Old. Phone (07) 358 2785. LAB LASERS. 0.5mW to 2mW HeNe lasers complete . Ideal for students or hobbyists. Australian made. $440- $640. Phone M.C.E. L:isers (03) 357 0055. CLASSIFIED ADVERTISING RATES Advertising rates for this page: Classified ads - $7.00 for up to 15 words plus 40 cents for each additional word. Display ads (casual rate) - $20 per column centimetre (Max. 10cm). Closing date: five weeks prior to month of sale. If you use a PO Box number, you must include your permanent address and phone number for our files. We cannot accept ads submitted without this information. To run your classified ad, print clearly on the lines below or on a separate sheet of paper & send the form together with your cheque or credit card details to : Silicon Chip Classifieds, PO Box 139, Collaroy Beach , NSW 2097. Or fax the details to (02) 979 6503. THE WORLD'S FIRST MS-DOS pocket PC at Australia's lowest price. Atari Portfolio $480 inc tax. Post & insurance free for mail orders. All accessories available at reduced prices. Uses an 80C88 CPU & is video cassette size. Data transfer to XT/AT via optional serial or parallel interface. For more information, send a 43c stamp to: Don McKenzie, 29 Ellesmere Crescent, Tullamarine 3043 . DIGITAL WAVEFORMS from a PC. As described in SILICON CHIP in March, May & June 1990. The software can also be used for the similar project (Simple PC Function Generator) described in Electronics Australia in January 1989. Software & PC Board: $39.95 incl. p&p. Software only: $32.50 incl. p&p. Money order or cheque. M. Radvanyi, PO Box 49, Kingswood, NSW 2749. Enclosed is my cheque/money order for $_ _ _ _ or please debit my O Bankcard o Visa Card 0 Master Card ? I I Signature_ _ __ _ _ _ _ _ _ _ Card expiry date___/_ __ I I Name _ _ _ _ __ _ _ _ _ _ __ _ __ _ _ _ _ _ _ __ I I Street _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ I I Suburb/town _ _ _ _ _ _ _ _ ___,_ _ Postcode_ _ _ _ __ I L _________________________ J Card No. IBM SOFTWARE: "Morse Tutor" $9. 5.25-inch or 3.5-inch (please specify) or call for price list. Disk Emporium, PO Box 780, Baulkham Hills 2153. Phone (02) 639 0615. CIRCUIT DESIGN SOFTWARE. Design your own .008% THD Sinewave Generator from 90Hz-30kHz using the PCB in SILICON CHIP, February 1991 . $20 inc. p&p. Design & build you own Audio Power Amplifier up to 20W. On-screen circuit diagram and hardcopy facilities. Instructions included. $30 inc. p&p. Custom-make your own SLA Battery Charger using the UC3906 IC (4-30V). Designed by the author of the SILICON MAY1991 95 MEMORY EXPANSION Advertising Index Altronics .. ... .......... .......... .. ..... 68-69 IIT 4164 41256 41464 411000 2.20 2.10 2.35 2.20 2.50 7.00 1MB x 4 (Static 256K X 9 1MB x 9 4MB 20.50 65.00 x9 120.00 8087 175.00 8087-1 175.00 8087-2 2.30 2.40 272.00 80287-8 2.75 802-87-10 275.00 178.00 287XLT 285.00 7.60 7.90 285.00 287XL 46 .00 387DX20 550.00 510.00 480.00 21.00 22.50 387DX25 693.00 640.00 600.00 76.00 81 .00 848.00 780.00 670.00 387DX33 387SX16 432.00 406.00 395.00 46.00 387SX20 510.00 440.00 Sales Tax 20%. Overnight Delivery. Credit Cards Welcome 1st Floor, 100 Yarrara Road, Pennant Hills, N.S.W. 2120 PELHAM Tel(02)980-6988 Fax(02)980-6991 Antique Radio Restorations ...... . 96 Arista ...... ......... .. .............. 44,55,77 Av-Comm ....... .. ... .. .... ....... 16,54,80 Back Issues .. .... ....... , ............ 90,91 David Reid Electronics ...... .. . 34,35 Electronic Solutions .... .. .... .... 22,23 Electronic Toy Services ............. 96 Elmeasco ............................. .... IFC Geoff Wood Electronics ............... 3 Harbuch Electronics .... .... ..... 54,80 Hycal Instruments ........ .. ......... .. . 96 MODEL TRAIN CONTROLLER project, SILICON CHIP, November 1990, $19.95 plus $2.50 p&p. Plugpack, 12VAC, 1. 7A, suitable for the above (use rectifier), $29.95 plus $4.00 p&p. Kits built & repaired. Prototype production board supplier to the hobbyist & supplier of SILICON CHIP project PCBs. ETS, PO BOX 491, NOARLUNGA CENTRE, SA 5168. Phone: (08) 382 8919 FIX-A-KIT Jaycar Electronics ... .. ........... 45-52 $20.00 PER HOUR LABOUR J.V. Tuners ................................. 73 3 MONTHS WARRANTY ON REPAIRS 12 MONTHS WARRANTY ON CONSTRUCTION Service to most types of electronic equipment M. Radvanyi .... .......... .. .. ..... .. ..... 95 TECHNICAL ASSISTANCE HVCAL ELECTRONICS Design, Manufacture & Repair of Electronic Equipment Oatley Electronics .................... . 29 PC Computers .. .... .. .... ...... ......... 96 Trading Hours 8am to 3pm, Monday to Friday PC Marketplace .. .:... .... .............. 41 (02) 633 5897 Pelham .. .... .. ...... .. .. .................... 96 Philips Test & Measurement .. OBC TRANSFORMER REWINDS Raytec Data Systems ................ 16 MAX 1/0 Board Kit $149.00 Built & Tested $269.00 ALL TYPES OF TRANSFORMER REWINDS RCS Radio ....... .. .. ..... ......... .. ..... 81 • 7 x Relays SPST 2 amps each • 8 x Switch inputs (TTL) • 1 x DAG (Digital to Analog converter) • 1 x ADC ( Analog to Digital converter) • 4 x Motor Drive outputs (40mA ea.) • 1 x Programmable timer output. MAX includes a 20-page manual with all schematics, parts layout etc., a 360K PC-compatible floppy with diagnostic and sample software in GW-Basic. MAX runs from a PC compatible printe r port for full compatibility with a large range of computers. Same day dispatch of orders. Credit cards or personal cheques we lcome. Reply Paid No. 2 PO Box 438, Singleton, NSW 2330. Ph:(065) 761291 Fax: (065) 761003 Phone (08) 332 6513 or Fax (08) 364 0902 (24 hours) PC Computers, 36 Regent St, Kensington, SA CHIP March 1990 project. $20 inc. p&p. Buy all three for $50 and save $20! IBM/XT/AT compatible, 5.25-inch 360K disc only, CGNEGNVGA, MS-DOS 3.2 or later. Send cheque/money order to: D. Yates, PO Box 134, French's Forest, NSW 2086 . SIGNAL GENERATOR, HP-606, 50kHz-65MHz, $320. Signal generator, HP-608D, 10-420MHz, $320. Sweep generator, Jerrold 900C, 500kHz-1200MHz, $380. SSS adapter, RA 121, $75. Cable fault locator, Bicco Test T215 (Cossor), $240. Logic analyser, HP1610, $860. D. Dauner Elec- 96 5ILICON CHIP TRANSFORMER REWINDS tronics, 51 Georges Crescent, Georges Hall, NSW 2198. Phone (02) 724 6982. Fax (02) 725 7850. Resurrection Radio .................... 21 Rod Irving Electronics ........ ...... 8,9 56,57,88,89 Sheridan Electronics .. ........ ... .... 78 Silicon Chip Binders ........... ..... IBC Subscriptions .. ........ .. .. .......... .. ... 17 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 & amplifiers. Open Sat. 1Oam-5pm ; Sun. 12.30-5pm. 109 Cann St, Bass Hill, NSW 2197. Phone (02) 645 3173 BH or (02) 726 1613 AH. SC Transformer Rewinds ................ 96 PC Boards Printed circuit boards for SILICON CHIP projects are made by: • Electronic Toy Services, 2/ 111 Glynville Drive, Hackham West, SA 5163. Phone (08) 382 8919. • Jemal Products, ·5 Forge St , Welshpool, WA 6106. Phone (09) 350 5555. • Marday Services, PO Box 19-189, Avondale , Auckland , NZ. Phone 88 5730. • RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 587 3491. NO * High _quality * Holds up to 14 issues * 80mm internal width * Gold printed with SILICON logo on spine and front cover CHIP . h,ese beautifullJy mad€ binders will protect your copies of SILICON CHU>. We are especially pleased with their look and quality. As soon as the first batch came in, everybody on our staff wanted them to store their own personal issues. You will too. How To Phone (02) 979 5644 Fax (02 979 6503 ORDER: - ;;...-;...-~ ·.,.__..,~~ Made with a distinctive ,two tone green high-quality vinyl specially selected for SILICON CHIP, and with heavy board covers, each binder holds a year's issues (the 14 issues of Vol. I or the 12 issues of Vol.2). They will look really smart on your bookshelf. To order your binders, fill in the coupon on page 17 and send it to SILICON CmP, PO Box 139, Collaroy Beach, NSW 2097. A!lternatively phone (02) 979 5644 and quote your credit card details, or fax your orders to (02) 979 6503 . .Brice $All.95 plus $A3 each for postage and packing. (NZ postage and packing $A6.) J