July 1990 - Silicon Chip Online

Outer Front Cover
Contents
Publisher's Letter: The story of electrical energy
Vintage Radio: How to solve unusual problems by John Hill
Review: AR950 100-Channel Scanner by Garry Cratt
Project: Digital Sine/Square Wave Generator; Pt.1 by John Clarke
Project: Alarm Keypad & Combination Lock by Greg Swain
Project: Build An Elegant Electronic Die by Darren Yates
Serviceman's Log: The dangers of a quick fix by The TV Serviceman
Back Issues
Feature: The Story Of Electrical Energy by Bryan Maher
Feature: Waveform Generation Using A PC, Pt.4 by Steve Payor
Feature: Computer Bits by Jennifer Bonnitcha
Project: Low Cost Dual Power Supply by John Crichton
Feature: Amateur Radio by Garry Cratt, VK2YBX
Market Centre
Advertising Index
Subscriptions
Outer Back Cover

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Hard Disk Cache and P rinter Buffer etc. Motherboard only $125 Motherboard plus 640k $250 Motherboard plus 1MB $300 THIS MONTH ONLY $199 EXTRA VALUE!!! If you buy IBM RAM utilities disk too you get the whole lot for an incredibly low $375 TRANSDATA 3.5" Hard Disk Assembly Fixed Bracket Dimension:208mm x 145mm x 41 mm (L x W x H) Weight :1040gm net Material :Alum inium alloy Keyswitch:Two -position pull CAM switch Buzzer :Pulse sound LED :Power ON (Green) steady: HO RN/ (Yellow) trigger :Alarm (Red) pulse SLOT EXTENSION KIT - Compatiable w it h PC/XT/AT slots - M5890 includes on e extender card plus f lat cab le extensio n for f our extend ed s lo t s on one external module - Exce llent for te st and repair of PC add-on cards - Th e on board po wer supply conn ector allow s usage of extenal power sourc es for add on cards on the extension module. The power fuses on M5890 must be removed in this case t o disconnect the +SV/ + 12V pow er supplies from PC - All pin-s ig nal assignment of PC-bus are clearly marked o n s lot No 4 for easy testing/moni1oring BACK IN STOCK! ONLY $199.00 M5s9o - Write or phone today for your FREE copy of our Catalogue! Over I 00 produds shown with full details and specifications! EXTERNAL DISC DRIVES Out pertorm s PS 11 model 50 Comes with utility software to allow you to use additional memory as print spooler, disk cache or virtual disk. Cannol use old RAM (ie 41256) chip co unt and increase th e speed and reliability • ~:iirif} t::fbr4~cki~l~uminium alloy Warning alarm fo r indicating wrong operation LEDs for indication RN/ operation and system status Easily assembled into the case Includes 1 X H3636 removeable bracket H3635 - WAS $179 NOW $125 Removable H3636 - WAS $129 • ~!1:c:~:,1:xrc,~~i~1nf~)Cc6ug~~ e ~~~s~ ~~a;Ip~~~errupt • • Game port Cables and manual included M5865 - WAS $125.00 NOW$62.50 SAVE50% , GAMES \ ·. CARD .)> TWOPOR.t M5850 Runf:t;C• Joyst ick s .••.:.,. WAS $29.50 .· NOW ONLY $19.95 > SAVE 33% PROTOTYPE DEVELOPMENT CARD Designed for the PC add-on card designers as an excellent alternative to pure breadboard card for daveioping prototype of add-on cards. 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WE HAVE AUSTRALIA'S LARGEST RANGE OF EXTERNAL DRIVES PART# SIZE D2930 D2932 D2938 3.5" 5,25" 3.5" AMSTRAD D2904 3.5" 720K ATAR I ATAR I IBM IB M IBM IBM IBM PSII IBM PS II D2916 D2918 D2946 D2948 D2950 D2952 3.5" 5.25" 3.5" 3.5" 5.25" 5.25" 5.25" 5.25" 720K 3601720K 720K 1.4MB 360 K 1.2MB 360K 1.2MB TOSH IBA TOSHIBA D2970 D2972 ZEN ITH ZEN ITH COMPAQ COMPAQ D2976 D2978 5.25" 5.25" 5.25" 5.25" 360K 1.2MB 360K 1.2MB D2980 D2982 5.25" 5.25" 360K 1.2MB PHONE (02) 418 6711 FAX (02) 41867 13 Mail Order Address : P.O. Box 1100 Lane Cove NSW2066 NOW ONLY $90 • Parallel printer port RS232C seri al communicat ion port (expandable to two by user CLOCK CARD ONLY $45 - INCLUDING SOFTWARE COMPUTER Pfii[ (j[eeson 's SAVE 30% Dime nsion:206mm x 117mm x 41 mm (L x W x H) Weig ht :2159m net (w/o hard disk) Material :Plastic Capacny :3.5" hatt-he ight disk ST506/412 intertace type Transferable to another computer system Convenient for transport and storing AMIGA AM IGA AM IGA NEW NEW • r CAPACITY 880 K 36 0/BB0K 880 K COMMENTS PRICE WITH ON/OFF SWITCH WITH ON/OFF SWITCH INTER NAL KIT FOR A2000 249.00 299 .00 229 .00 FOR PC1512/1640 WI TH POWER SUPPLY SW ITCHABLE , W ITH POWER SUPPLY W ITH ADAPTER INTERFACE & CABLE WI TH ADAPTER INTERFACE & CABLE WITH ADA PTER INTERFACE & CABLE W ITH ADAPTER INTERFACE & CABLE W ITH ADAPTER INTERFACE & CABLE W ITH ADAPTER INTERFACE & CABLE 269 .00 269. 00 299 .00 299 .00 329 .00 299.00 329.00 349 .00 399 .00 SUIT TOSHIBA LAPTOP SUIT TOSHIBA LAPTOP SUIT ZENITH SUPER SPORT SUIT ZENITH SUPER SPORT SUIT COMPAQ SLT 286 SUIT COMPAQ SL T 286 349. 00 399.00 349.00 399.00 PERSONAL COMPUTER MARKETPLACE PtyLtd FREIGHT CHARGES Includ e $10 wit h order fo r all normal items - heavy items, e.g. monitors add $15. 14 day money back guarantee Order by pho ne (use credit card), by fa x or by mail. Unl ess insura nce is declin ed it w ill be charged at 1% of t ota l purchase . This is for your protection. PR ICES VALID AT 1 JULY 1990 349.00 349.00 JULY 1990 FEATURES 8 Review: AR950 100-Channel Scanner by Garry Cratt Mobile unit covers many bands 52 The Story Of Electrical Energy by Bryan Maher Pt.1: coal burning power stations This sine/square wave Generator uses high speed CMOS ICs & a digital filter IC to produce sine & square waves from 0.1Hz-500kHz. It also features a 4-digit frequency readout. Turn to page 16. THIS KEYPAD combination lock can be used to control a burglar alarm or activate a solenoid-operated door strike - see page 28. 64 Waveform Generation Using A PC, Pt.4 by Steve Payor PC board plus software PROJECTS TO BUILD 16 Digital Sine/Square Wave Generator by John Clarke Covers the frequency range from 0.1Hz-500kHz 28 Alarm Keypad & Combination Lock by Greg Swain Turns your house or car alarm on & off 34 Build An Elegant Electronic Die by Darren Yates Simulates the roll of a real die & turns itself off 78 Low Cost Dual Power Supply by John Crichton Provides switched outputs from ± 3V to ± 18V SPECIAL COLUMNS IF YOU KEEP anything long enough .. .. well, you know the rest. The Serviceman's hoarding tendencies sure came to the rescue this month. His stories start on page 40. 6 Vintage Radio by John Hill Remote Control How to solve unusual problems 40 Serviceman ' s Log by the TV Serviceman The dangers of a quick fix 72 Computer Bits by Jennifer Bonnitcha What to do when your computer goes bung; Pt.3 Space restrictions have prevented us from publishing Bob Young's Remote Control column this month. The column will return with the next issue. 88 Amateur Radio by Garry Cratt Weather fax - list of frequencies DEPARTMENTS 2 Publisher's Letter 3 37 60 50 Mailbag Bookshelf Circuit Notebook Back Issues 94 100 103 104 Product Showcase Ask Silicon Chip Market Centre Subscription Page HAS SOMEONE PINCHED the dice from the Monopoly game? Replace them with this electronic die. It uses just two CMOS ICs and simulates the roll of a real die. See page 34. JULY 1990 1 Publisher & Editor-In-Chief Leo Simpson, B.Bus. Editor Greg Swain, B.Sc.{Hons.) Technical Staff John Clarke, B.E.{Elec.) Robert Flynn PUBLISHER'S LETTER Advertising Manager Paul Buchtmann (02) 979 5644 Mobile: 018 28 5532 Victorian Representative McDonald Woodside & Associates Pty Ltd, 143a Como Parade East, Parkdale, Victoria 3194. Phone (03) 587 5155. Contact: Cameron McDonald. Regular Contributors Jennifer Bonnitcha, B.A. Garry Cratt, VK2YBX John Hill Jim Lawler, MTETIA Bryan Maher, M.E., B.Sc. Jim Yalden, VK2YGY Darren Yates Bob Young Photography Bob Donaldson Editorial Advisory Panel Philip Watson, MIREE, VK2ZPW Norman Marks Steve Payor, B.Sc., B.E. SILICON CHIP is published 1 2 times a year by Silicon Chip Publications Pty Ltd. All material copyright {c). No part of the contents of this publication may be reproduced without prior written consent of the publisher. Typesetting: Magazine Printers Pty Ltd, Rozelle, NSW 2039. Printing: Macquarie Print, Dubbo, NSW 2830 . Distribution: Network Distribution Company . Subscription rates: $42 per year in Australia. For overseas rates, refer to the subscription page in this issue. Liability: Devices or circuits described in 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 2 SILICON CHIP The story of electrical energy This month, we introduce a new series entitled "The Story of Electrical Energy" which will tell all about the generation and major uses of electrical energy. Written by Bryan Maher, we hope it will be just as popular as his previous long-running series, "The Evolution of Electric Railways", which concluded in the March 1990 issue. When that series started, in our very first issue, there' was some critical comment from readers who did not see why such material should appear in an electronics magazine. This was probably because the initial chapters largely dwelt on steam locomotives. As the series developed though, readers began to see just why we had elected to run it - because there is a great deal of technology in electric transportation that you just don't get to read about anywhere else. Towards the end of the series, we had readers commenting that they really looked forward to reading each chapter even though they were not interested in trains! Some were even beginning to worry that they might be becoming train buffs! Heaven forbid. What's wrong with train buffs, anyway? We have high hopes for this new series on electrical energy and we think that readers will find it just as engrossing as the story of electric railways. Bryan Maher is, above anything else, an enthusiastic storyteller and his extensive engineering background gives each article solid credibility. As the person who usually sub-edits this material, I look forward to each chapter too. Not just because I enjoy reading about the subject matter but because I also enjoy delving into our library to check the technical material. As the series was being planned, I wondered why it had not really been done before, either in a book or in magazines. When you think about it, there are any number of articles, books and magazines devoted to the subject of electronics which, for the most part, is engineering on a miniature scale. Silicon chips are the prime examples of this. By contrast, the generation and transmission of electrical energy is engineering on a truly vast scale and with far reaching effects and consequences in the lives of all of us. Without cheap electrical energy, how would we function today? I look forward to Bryan Maher's Story of Electrical Energy and hope that you enjoy reading about this fascinating subject. Leo Simpson OUR NEW ADDRESS: Unit 39, 5 Ponderosa Pde, Warriewood, NSW 2102. Phone (02) 979 5644. Fax (02) 979 5644. Our postal address remains: PO Box 139, Collaroy Beach, NSW 2097. .MAILBAG The elevator is the speed controller Having held a commercial pilot certificate for nearly 40 years, I found it incongruous that, in his cogent article on flight [SILICON CHIP, May 1990), Bob Young treated the throttle as the speed controller, yet went on to note that "without power, the nose must be pushed down to maintain speed ... " The latter alone should have taught him that, regardless of the power [throttle) setting, the misnamed "elevator" always controls speed, making the throttle the "up and down thing". Even during, say, an ILS approach, the elevator is used to set the speed as power is varied to keep the airplane on the glide slope. A glider in calm air inexorably descends regardless of airspeed since it lacks a throttle to make everything go up all of which proves that the "elevator" label is as queer as a $3 bill. It wasn't clear why "stalls are very dangerous in piloted aircraft ... " They shouldn't be if there's enough room to recover from them. They are mandatory maneuvres for licencing so they can't be all bad. Certain designs will "deep stall" however, and that can be worse than bad news from home. Lastly, it was the US Army Air Corp which operated the P-26 [alias "the Old Goat"), not the Army Air Force which was not yet extant. George Lindley Redfern, NSW In defence of the IBM PC & its clones I would like to write in reply to the two letters published in the May 1990 edition of SILICON CHIP. Would the person who honestly believes that the IBM computer and its clones are a less popular alternative to the Commodore Amlga please raise his/her hand? Here's a simple test. Name three brands of computers that worked in their own language four years ago and now are compatible with the IBM PC. Now name any computer - other than Commodore - that is designed to perform with full capability to the Amiga system. The answers to the first question are the Apple [using the II Blu adaptor card), the Tandy range of computers, and the Amstrad. There is no answer to the second question. I can't deny the fact that I know quite a few Amiga owners but when I asked them the advantages of their computer over an IBM, the only legitimate answer they gave me was, "It's got better colours". Big deal. If you want good colours on your games, then be less serious about your computing future and buy an Atari. It's nice to see that an electronics magazine has finally given IBM owners the chance to learn new things about their computer, explained in simple English [unlike some computer magazines which rave on about some Lotus 1-2-3 system that most computer owners can't afford). In fact, I discovered only three weeks ago the statement "Lost clusters found in N chains" when I ran my CHKDSK command. I've found the meaning of this but I'm sure that other computer users would like to know, too. I'm looking forward to future issue of Ms Bonnitcha's column, when this will probably be explained. We don't want to know what's inside a crummy Amiga. All in all, I believe Ms Bonnitcha and the SILICON CHIP team are doing an excellent job. Please ignore the whining of Amiga owners. Alan Brand Sunnybank, Qld On the other hand ... I would like to continue the argument put forward by M. Riley in Mailbag (May 1990) regarding projects for computers other than the IBM PC and its clones. I am also a very satisfied Amiga owner and would like to see some projects for this machine as its success cannot be denied. As M. Riley wrote, projects such as a hard drive controller would be appreciated by readers who own this machine since the cheapest hard SILICON CHIP, PO Box 139, Collaroy Beach 2097. drive (20Mb) available comes at a price of $1000 and an 8Mb board without memory fitted costs approximately $1200. So I am sure you can see how much such projects would be appreciated by your readers [myself included). Other projects you might like to try are a processor accelerator and coprocessor on a single board. Tony lngrisano Matraville, NSW VLSI chips should have carrier sockets In the April 1990 issue of SILICON CHIP, Mr Ian Hardwick of Electronic Solutions mentioned that boards with surface mounted VLSI chips were virtually un-repairable in this "throwaway society" [mainly concerning computer motherboards and add-on cards). It makes one wonder what the extra cost of chip carriers would be at production level. Especially when you are talking approximately $500 for an AT-compatible motherboard. Even if the chip carriers added $50 to the price of a motherboard, I for one, think it would be well worth it just knowing you have some chance at least of repairs being effected. Although it is rare for one of these chips to fail, like all man-made products they can and will. This also applies to add-on cards. Take, for instance, a multisync monitor and VGA card advertised in the same issue for $995. Considering what you get [including 256K for display memory), this card is good value for money. But, and this is a big but, what if the card fails after the 3-month warranty period and it turns out to be a VLSI chip. What do you do - throw it away and buy another one? By the way, this letter is no reflection on Mr Hardwick or Electronic Solutions. All criticism is directed at the manufacturers, whether they are in Japan, Taiwan, Silicon Valley or where ever. Keep up the good work on your excellent magazine. R. Hobson Glenreagh, NSW JULY 1990 3 VINTAGE RADIO By JOHN HILL How to solve unusual problems When one's hobby is restoring old radio receivers, it is inevitable that every now and then a set comes along with an unusual problem. Solving some of these odd problems is often easier said than done and the new chum to the vintage radio scene may find some repairs quite difficult. Some time ago, I reworked a few of the sets in my collection. These receivers were ones that l had restored several years ago but, in some instances, the restoration work was not as good as I would do today. The reasons are many. First, I did not know then what I know now. Second, some recently acquired test equipment (such as a valve tester, a radio frequency generator and an output meter] now makes it possible to perform much more precise tune-ups than in the past. These reworked sets included a number of 4-valve receivers , several of which responded extremely well to the fine tuning they received. A 4-valve radio, in particular, requires spot on alignment if it -is to perform well. There was still another set that needed attention and I had been well aware of its shortcomings for quite some time. While it looked a nice enough receiver, it was a terrible performer due to poor alignment. This mid-1950s 5-valve Mullard was so far out of tune it was "double spotting". As the dial pointer was moved across a station, Small JOpF trimmer capacitors can be used to tune an IF transformer when the normal tuning slugs are immovable. The alternative is to replace the IF transformer but suitable replacements are not always available. 4 SILICON CHIP the station would tune in, tune out, then tune in again, thus occupying two side-by-side positions on the dial. It was a problem I could not handle at the time because the iron cores in the IF transformers had been butchered. The screwdriver slots had been gouged out by someone trying to get the rather stiff slugs to move. When I last worked on the Mullard, I did manage to move the slugs a little but it appears that they were moved in the wrong direction because the alignment got worse. In desperation, the chassis was put back into the cabinet and the set placed in the "too hard basket". Alignment techniques Anyone familiar with old radios will know that IF transformers can be tuned by two methods. The method used in the Mullard and most other more recent receivers is by means of adjustable iron cores. However, back in the early days of superhets, the IF transformers were tuned with small trimmer capacitors. It therefore seemed reasonable to assume that the Mullard could be pulled back into alignment by adding some 30pF trimmer capacitors to the base connections of the transformers. Four trimmers were soldered into the circuit to see if the theory would work - and work it did! As it happened, four trimmers were unnecessary and two were removed from the circuit for the better. Such a modification is a bit of a trial and error affair. To cut a long story short, the set tuned up really well and the double Besurreetion Radio The original vintage wireless specialists Our skilled technicians offer QUALITY repairs & restoration. We have a large stock of bakelite and timber radios fully restored and for sale. Valves, high voltage capacitors and other specialised parts available. Intermediate frequency (IF) transformers can be tuned by either adjustable iron cores (left) or adjustable capacitors (right). Correct alignment of the IF stages is vital if the receiver is to perform correctly. ADDITIONAL SERVICES COPIES OF: CIRCUIT DIAGRAMS $5.00 SERVICE MANUALS $10.00 AVAILABLE FOR MOST MAJOR AUSl . MAKES FROM 1934 ONWARD. 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 ACTIVE SHORT WAVE ANTENNA TECHNIKIT AT4SW 't (SEE SC JAN '90) COMPLETE KIT $59 BUILT and TESTED $119 (BATTERIES INC) CASE $10 This is the rear view of the old Seyon receiver mentioned in the text . Note the 2.5V SX245 output valve (centre) in the 4V socket (see text). You should always be prepared to improvise to restore an old set to full working order. spotting disappeared. While there were other ways of solving the problem (eg, replace the IF transformers), the simple capacitor trick got me out of trouble and that is what this story is all about. Harsh sound Another problem often encountered when restoring valve radios is harsh sound in a set that lacks a tone control. Quite often a set will restore OK but the tone is either harsh or, at the other extreme, dull and lacking treble response. This change of tone is often noticeable after a loudspeaker has been replaced and so some tone adjustment is necessary in order to give the set a more pleasant sound. This is easily done by installing a high voltage capacitor between the anode of the output valve and the chassis. A capacitor in this position has the ability to bypass the harsher high frequencies and they are shunted off to earth instead of going through to the loudspeaker. The larger the capacitor, the greater the effect. By simple trial and error, the LOOP ANTENNA Q TECHNIKIT PX1 COMPLETE KIT $44 BUILT and TESTED $69 (SEE SC JUNE 89) Improved signal strength & signal quality in a portable tunable antenna. PACKING & POSTAGE IN AUSTRALIA INCLUDED IN PRICES QUOTED. WRITE OR RING FOR BROCHURES ORDERS ACCEPTED ANYTIME PAYMENTS BY BANKCARD, VISA, MASTERCARD, CHEQUE or MONEYORDER TRADE ENQUIRIES WELCOME JILOA PTY LTD (TECHNIKIT DIVISION) P.O. BOX 73, GLENHUNTL Y, VIC 3163 Phone (03) 571 6303 ]ULY 1990 5 This is the Mullard receiver with the butchered IF transformers. It lived in the "too hard" basket for quite some time until a remedy was found. Always use a high voltage capacitor (400V minimum) in the plate circuit of the output valve. By changing the capacitor value, you can alter the tone of the radio to give the best result. These heavy wattage wirewound resistors are the types to use as filament resistors when using a 2.5V valve in a 4V or 6.3V socket. You can calculate the resistor value using the technique described in the text. tone can be varied by trying capacitors of different sizes. A 0.022µF capacitor would be a good starting point. On the other hand, if a set sounds dull and lifeless, then it is most likely due to too large a capacitor in this anode to chassis position. When this is the case, the capacitor must be located (it could also be on the first audio valve) and replaced with one of less capacitance. Most receivers without a tone control have a bypass capacitor which serves as a fixed tone control. In some instances, it may be switched in or out of circuit by a tone switch. However, remember that a set 6 SILICON CHIP sounds a good deal different on the bench compared to when it is in its cabinet. The baffling effect of the cabinet greatly improves the sound, so any adjustments to the tone should be done with this point in mind. The old Seyon One of my very early sets is an old Seyon, an electric model with 4V valves (not counting the 5V rectifier). Replacement valves for such radios can be a problem for they are indeed a rarity today. When I first bought the set, the output valve was a B406. Being fairly green about such things at the time, I didn't realise that the B406 was in fact a battery valve and as such, was not suited to an AC filament supply. The original output valve could have been any of a number of valves and I have since discovered that an E406 works quite well. However, before the E406 came along I was faced with the problem of using an appropriate output valve. Although the B406 worked, it didn't look the part and it produced a certain amount of hum due to its lightweight battery filament. It so happened that I had several SX245 and CX345 valves in my collection. These were appropriate output triodes for such a radio except that they had 2.5V filaments instead of the required 4V filament. To solve this problem, a resistor was placed in series with the filament, after which the 2.5V valve worked quite happily in the 4V socket. Mind you, there was a surprising amount of heat generated in the resistor but it did get me out of trouble and that's what this particular article is about. Now if you are clever and know the filament or heater rating of the valve, the value of the resistor required can be worked out by Ohm's Law. On the other hand, if you're not clever or have no specifications on ancieut valves, there is another way. All one needs is an old wirewound rheostat (a 200 one or less) and a multimeter. The rheostat and the valve filament are connected in series and placed across the filament supply voltage, making sure that the rheostat is set to maximum resist- If you want to use a 2.5V valve in a 4V socket, the required resistance can be determined using a rheostat and a multimeter. You simply connect the rheostat (set to maximum) in series with the valve heater, and connect the multimeter (set to AC volts) across the valve heater. The rheostat is then wound back until the meter indicates 2.5V and its value measured to obtain the resistance. odes in the form of a fairly heavy filament. Because these valves used an AC supply, a special centretapped cathode resistor was used across the filament to reduce mains hum. The amount of resistance used on a 4V valve would be different to that used on a 2.5V or 6.3V valve and the resistor should be replaced if the filament voltage is changed. Substituting a 4V valve with a 2.5V valve, as was done in the Seyon, would require a centretapped resistor of a slightly lower value. Not having the appropriate resistor meant that it wasn't changed at all and that didn't seem to make the slightest difference. It also meant that no alteration was necessary when the set was converted back to 4V operation. There are numerous situations whereby one can get out of trouble by using a resistor and a valve with a lower filament or heater voltage. Such a method is quick and easy and does not involve separate transformers or other inconveniences. It is also applicable to both AC and DC-powered receivers. Warning signs Some radios, such as this 5-valve Philips mantle set, have a tone switch at the back which cuts in a capacitor that is used as a fixed tone control. Altering the size of the capacitor affects the degree of tonal response. ance. This done, the multimeter (set to AC volts) is connected across the filament of the valve. The rest is straightforward: you simply adjust the rheostat until the meter reads 2.5V. The rheostat resistance is then measured with the multimeter to get the required value for the filament resistor. In the case of my valve substitution in the Sey on, there is a 4V supply with 1.5 amps flowing through the filament resistor and the 2.5V valve. Therefore, the potential across the resistor is 1.5 volts. Since Watts = Volts x Amps, the wattage of the resistor required must be 2.25 watts. A 5W wirewound resistor would do nicely, even if the valve drew two amps. The 10W one I used was more than adequate. Most of the old 2.5V output triodes had directly heated cath- Although this story is about getting out of trouble, ignoring certain warning signs can also get one into trouble. For example, my old Seyon has a potential problem that I have ignored for years - one that could give rise to a serious short circuit. The 240 volt supply to the power transformer is platted rubber covered wire and over the years the insulation has decomposed, merged into a single mass and gone quite brittle. Just how close those wires are to each other is anyone's guess and if there is a big zap one day and a fuse blows then I will know that they were a little closer than I thought. In my defence, there are two reasons why I have not replaced this old wiring. First, it has not been disturbed and is in working order. Second, the wires are not just rubber covered but also cotton covered. That layer of cotton seems to make all the difference and I doubt if it will ever give trouble. Only time will tell. ~ JULY 1990 7 100-channel scanner for home or mobile use Last June, we reviewed the AR900, a 100-channel handheld scanner manufactured by AOR in Japan. Now AOR has produced a mobile version, the AR950, which covers the same bands. By GARRY CRATT It is pleasing to see that after our review of the AR900, AOR has taken some of our comments to heart and made several important improvements to the design. First, the AR950 receiver produces significantly more audio which is a necessity for mobile applications. In addition, there is provision for an external speaker to be used, further enhancing mobile operation. Other improvements have been made to the instruction manual (which is now easier to read) and to the receiver squelch action, which 8 SILICON CHIP suffered from "popping" in the first AR900 sample submitted for review. Basic functions The basic functions of the AR950 are the same as for the AR900 handheld unit. There are 100 channels available for user selected frequencies and these are grouped in 5 banks (each of 20 channels). Each bank is labelled A to E. Banks can be added or deleted from the scan list by pressing the relevant bank key. These keys operate as a toggle. When the band has been selected for inclusion in the scan list, the relevant letter is displayed in the LCD panel. When the bank has been deleted, the letter disappears from the display. Frequencies to be scanned can be directly entered into memory while frequency bands are being searched. This is quite a useful feature because it allows a particular band of frequencies to be searched and when an interesting signal is found, it can be located in any of the 100 memory channels. The advantage of having 5 banks is that frequencies of similar interest can all be stored in the same bank. For instance, all aviation frequencies can be stored in one bank while mar ine frequencies can be stored in another. It is then quite easy to scan 20 frequencies relating to the same service. In ad- dition to the aviation and VHF marine bands, other bands of interest include the VHF or UHF amateur band, the UHF commercial band, the UHF CB band, and the cellular telephone band. In addition, the AR950 has a "priority" function which allows a user programmable priority frequency to be toggled while scanning a bank of frequencies. It also has a "lockout" function which allows unwanted channels to be bypassed during scanning, and a "hold" function which disables either the scan or search functions once a transmission has opened the receiver squelch. One of the more important and often overlooked features of such a scanner are the scan and search increments. The AR950 has increments of 5kHz, lOkHz and 25kHz on VHF high and low band; 12.5kHz and 25kHz on the airband, UHF bands, and trunked 800-900MHz bands; and 30kHz on the cellular telephone bands. This should cover all frequency allocations on all bands! Another plus for this particular scanner is the use of EEPROM (Electronically Erasable Programmable Read Only Memory) technology which means that there is no need for nicad batteries to back up the frequencies programmed into memories. With EEPROM technology, all data programmed into memory is stored until it is updated or deliberately deleted by the user. Even if the power source is removed, the frequencies in memory will be retained. Antennas The AR950 is supplied with two antennas, one of which is a dedicated 800-900MHz ¼-wavelength whip for improved reception of the trunked radio and cellular bands. These bands are becoming increasingly popular with scanner enthusiasts and radio technicians alike. The other antenna is a telescopic whip which is designed to cover the VHF bands. Most fixed point or "home" installations will, of course, use an external antenna such as a discone. Because of this, the AR950 has an inbuilt switchable 20dB attenuator for use when strong adjacent channel signals are present. During testing of our sample, we experienced interference of this type from four Sydney television transmitters which are located within 1km of our test laboratory. Switching in the attenuator reduced this interference to a level which allowed us to set the squelch so that all desired channels were received without problems. Protect Your Electronic Equipment & Valuable Data Files from a Power requirements The AR950 operates from 12V DC and is supplied with a polarised power lead with inline fuse. Also, the unit has an inbuilt series diode to prevent possible damage from reverse polarity of the power supply. One criticism we do have of the unit is that, when placed on a flat surface (such as a desk) and when viewed from above, the LCD is a little difficult to read. If the unit is tilted upwards by raising the front edge by 25mm or so, the problem disappears. A simple wire stand would have cured this problem but this seems to have been overlooked by the manufacturer. Despite this shortcoming, the AR950 represents good value for money at the recommended retail price of $399, especially when the country of origin (Japan) is taken into account. The unit is distributed by Access Communications, 33 Alleyne St, Chatswood, NSW 2067. Phone(02)417 5311 for the name of your nearest dealer. ~ With COMPUTER PROTECTOR A definite must for all electronic office equipment Available in the folloWing Current Ratings: I Amp, 3 Amp, 6 Amp, & I O Amps ..------Cl.l'l.l:IJJ ■ ~ ~5!Lng~se I SYSTEMS Wanted: Your Circuit Ideas Have you got a good circuit idea languishing in the old brain cells? If so, why not send it to us for publication in Circuit Notebook? We'll pay up to $70 for a really good circuit, depending on how much work we have to do to knock it into shape. So transfer your idea to paper, write a brief circuit description and send it to SILICON CHIP, PO Box 139, Collaroy Beach, NSW 2097. WESTINGHOUSE BRAKE & SIGNAL COMPANY (AUSTRALIA) LIMITED SIGNAL DIVISION 80-86 Douglas Pde, Williamstown. Victoria. (PO Box 267, Williamstown. Victoria 3016) Phone (03) 397 1033. Fax (03) 397 1861 Telex: 37 477 Wessys Vic (03) 397 1033. NSW (02)5451322, Old (07) 275 3188 SA (08) 212 3161 , WA (09) 446 8844 COM/1 JULY 1990 9 LookTD WITH A 386S1 FROM ~li . = = ~ w1n~1~fa{~ 32 Bit Computing Power without The 5 digit Price Tag! HERE ARE 4 GOOD REASONS WHY YOU'LL BUY YOUR FUTURE COMPUTER FROM DICK SMITH ELECTRONICS .... 2 THE QUALITY TWinhead computers are constructed using the latest surface mount technology for improved reliability. All controls are conveniently located on the front panel and the AT keyboard has a smooth, bounce-free design to keep up With the fastest typists. Your Superset-590 Computer has undergone extensive testing before it leaves the factory. To ensure it has arrived safely, our own Quality Control Department then puts EVERY Twinhead computer through 24 hours of rigourous testing and has given your new computer a 100% diagnostic test ... even formatted and tested your Hard Drive. Yes, you can trust your business to the computer you buy from Dick Smith Electronics! ·,jj 1 • • • • • • • • • • THE COMPUTER • Twinhead -590 AT compatible • Super fast 16MHz 80386SX processor with socket for 80387SX Maths co-processor Keyboard switchable processor speeds 1Mb RAM expandable to 5Mb on board Shadow RAM feature 40Mb Hard Drive & high density 5¼" Drive 2 x 1" and 1 x half height drive bays 4 free expansion slots MS.DOS 4.01 Operating System 2 serial & 1 parallel port Paradise VGA graphics adaptor with 256k (expandable to 512k) Graphics Memory VGA monochrome Monitor 3 - i THE SUPPORT Think of a computer question and our support staff will know the answer! If you have a problem using any of our computers or software, or just need some good advice, our support staff are waiting for your call. Computer Service Hotline 888 2002 SERVICE TOO! Service is not a problem with a computer you buy from Dick Smith Electronics. We have a computer service plan lo suit YOUR needs• Take your computer to the nearest Dick Smith Electronics Store and we'll rush it to our Service Department. • For a small fee, your 12 months warranty can become a 24 month warranty. • Enquire about a Field Service Contract. Available nationally, a Field Service Technician will come to you and in most cases your computer will be repaired on the spot! • We can even tum your 12 or 24 month warranty into a Field Service Warranty for just a little extra! including VGA Monochrome Monitor Add $500 for VGA Colour Monitor 20MHz Neat AT Motherboard Faster, and more versatile, the 286 NEAT motherboard represents a significant advance over conventional 80286 designs. The NEAT (New Enhanced AT) chip set enables the user to control the relationship between microprocessor, expansion bus, and on-board memory, giving greater flexibility than ever before. The NEAT Motherboard suits any IBM compatible case from AT to tower and runs at 8, 10, 12, 16 or 20MHz with any version of MS-DOS above 3.0. It has onboard support for Lotus-Intel-Microsoft (LIM) Expanded Memory Spee. Version 4.0. Using the ROM based setup program provided, you can set CPU, BUS, and OMA speeds, memory wait states, even install custom hard drive specs. Comes socketed for the 80287 Math co-processor and three 8-bit plus five 16-bit expansion slots, as well as the capacity to hold 8 megabytes of memory (DIP and SIP memory modules). Ok memory supplied . cat X-1003 Only se99 More Colours! More Options! VGA Graphics Adaptor! More colours, higher resolution and more options are just some of the outstanding features of our VGA Graphics Adaptor! Fits into any IBM compatible (XT or AT) and comes with 256K RAM on board that's easily expandable to 512K for even more amazing colour and graphic capabilities. Super VGA is supplied with utilities which allow emulation of EGA, Hercules, and CGA. Supplied with software drivers and comprehensive manual. 8 Bit Version. Cat X-2018 s24g 16 Bit Version Cat X-2019 s299 Twin Port Game Card 8MB Memory Board This 8MB IBM compatible memory board can grow with your needs. Start out with just 2MB then expand it in lots of 2MB up to a full 8MB as your memory needs grow. It uses standard 1MB RAM chips and can be configured as expanded or extended memory. EMS version 4.0 drivers come with the board along with user selectable 1/0 ports for page selection. Ok RAM on board. Cat X-1020 Want a friend to share the fun of your computer games? This card will allow you to fit two joysticks to your IBM compatible computer for twice the action! Cat X-2040 $ 3995 RS-232 Quick Tester Ao m-uo, """ wdh 25 p;o mal, aod 25 p;o fomal, cooo,cto,s. 3 switches and 6 LED's allow quick selection of the most popular RS-232 configurations. Simply set the switches to select the connection you need $ Cat X-2652 3.5" Disk Drives These 720K and 1.44Mb disk drives come complete with 5¼" mounting kit, hardware, manuals, power and 34 pin adaptors, bezels ... the lot! 1.44Mb Version. Needs DOS 3.3 or higher. 5 219 5 199 Cat X-2221 720K Version. Needs DOS 3.2 or higher. Cat X-2220 Co-Resident Floppy Controller Allows you to add a third and forth floppy disk drive to your IBM compatible. Designed to co-exist with your current floppy controller card. Cat X-2025 s99 Q ;s; e1 3995 ~" :~: :! RS-232 Serial Breakout Box A complete in-line tester/adaptor which makes complex and time consuming serial connections a breeze! Comes with 25 pin male and female connectors. Also comes with jumper pads and wires, as well as 24 in-line switches for quick selection for any RS-232 configuration . The tester has 8 bi-colour LED's which monitor the lines and tell you at a glance when you've got it right! Cat X-2654 * """ "- ...,,..,.. $1 .95 $2.75 $2.95 $3.75 $4.50 $4.75 $2.95 Bench Voltmeter Bench Ammeter An ideal bench-top Voltmeter. More convenient than a multimeter, this meter is perfect for the classroom as well as the work bench. It measures voltage in two ranges - 0 to 1OVdc and Oto 20Vdc at · 2.5% accuracy. The large 80 x 80mm scale is perfect for taking measurements in vehicles. Cat Q-2140 s299 The perfect partner for your Benchtop Voltmeter. This Bench Ammeter measures current in two ranges - 0 to 5Adc and Oto 1OAdc. The easy to read 80 x 80mm scale is great for demonstration work while the 4mm banana terminals make connections a breeze. Cat 0-2130 s299s $ 3 9 5 ~ -~ Square Fuseholder Attractive 18mm square faced fuseholder with black casing and coloured insert. Accepts standard 3AG fuses. $195 • Cat P-7900 - These easy access fuseholders are ideal for use in test equipment or any low voltag e device. They accept 3AG fuse s and require a 13mm mounting ~~\eP-7902 s130 ~ ~ In-Line Fuseholder N.S .W.: ARM!OAL[ New Englcmd Electronics i116558ALLINA Bal lina Electron1cs867022 BOWRAL F R.H . Electr1ca l 611 861 BROKEN Hill Hobbies & Electromcs 884098 COOTAMUN0RA Coo1amund,a Music & Lile 422561 C0FFS HARBOUR Colts ~r;:,~~~l~~ei!~io~i ~~~~ 1e~l~~!~i;~~~~~l~;6;~3i~~ 83RA~h{b5N5~~b~1~s ~~~ l~~;;~~1;~;s~~l~~/1~e 2 1 Miatrorncs 624534 INVEA ELL lnverell Eleelronir,s 22 182 1 LEETON Li;~ ·rir, A.ud101rornc 532800 uiHTNING RIDGE Cycle & ~nd 290579 LITHGOW Douroy Pho1ograph1cs 513173 LISMORE Decro Eleci;.:., .•cServ1ces 214137 MOREE. Moree Electronics 522091 MUDGE E Headware 723895 NARRABR1 Namo1 Gompu1er Se1v1ce 923274 NELSON BAY Ne bon Ba y Elec1 & Hobbies 813685 N0WRA Nowr a Electronics 210722 ORANGE Ce n!rn l West Elec11omcs 62&49 1 PARKES Strad MUSIC Centre 623366 PORT MACQUARI E Hastings Compurer Secv 1ce 83 4574 TAREE Brads Electronics 526603 WAGGA WAGGA Ph 1l1Jps Elec1romcs 216558 VASS Warmmqtori E1ec11,cal 261116 YOUNG Ketlh Donges Eleclrorncs 821279 VIC : BAIRNS0ALE LH& LMCrawfo1d 525677 C0L AC CoJ;ic E1ec1romcs 31 284 7 MILDURA Pu!!man Auto Pro 232882 M0RWELL Morwe!I Electt0n1cs 346133 SHEPPAR TON Andrew Guyan Elect ronics 219 497 SWAN HILL Nyah D1s1r1ct TV Service 329303 WARRAGU L Roylame 2342!:15 WARRNAMBO0L Koro1! St Elec Services 62741 7 OLD: AVA Delta Elec1r11 831566 BUN DABE.AG Bob Elkm Etectron 1cs 721785 CAL0UNDRA E.leClfo-m;in 918533 DYSART 0ys;;n V1deo1rom • s 582107 INGHAM Masons Elec1ron,cs 763188 MACKAY Stevens Elec!ron1c ~ ~1 172] MARY BOROUGH Ke!!ei Elec1ron1cs 21 4559 NAM BOUR Namborn Elec1ror11 cs Shop 411 604 PI ALBA Ke ller E!ei.;tronics 28]749 TAS: BURNIE Elec rromc (; iry .31 4760 0EV0NP0RT A I Electronics 248322 SA : MT GAM B!ER Hu1chesson s Commun1r:;i t10I"! Centre 250400 PORT LINCOLN Basshams TV & Comp World 822788 WHYALLA Eyre Elecl!omcs 454 764 WA: ALBANY M1c:10 E. lee1romcs 4120 77 BUNBURY Micro E1ec1,omcs 21ti222 GE RAL0iON B;it;ivrn Llghtmq & Electr1c.:il 2i 1966 KARR ATliA D.:iv~~ 0<;r.1tron 1c: 8~4836 MANORAH M1r.10 (ler.tron 1C<:: ~812206 PORT H(OL AND lv;in Tomek the EIW 732~31 PCB Mount Fuseholders Ideal for Hobbyists and enthusiasts. AC/DC movement iron meter in oval style case measuring approx. 55mm wide x 58mm long . Note - moving iron meters are not highly accurate but give good relative indication. Cat Q-2080 '\ s199s .· · Miniature Led Bezel Easy to mount fu seholders in both popular sizes. ~ Cat P-7910 M205 $120 A low current drain , highly visible in a chrome bezel. Available in red and green . 5 50 • Cat P-8104 Red ii1; Cat P-8106 Green ~ ' LED l 12V Mes Bezel Cat P- 7908 3AG 95c [D0<at>) MAJOR DICK SMITH AUTHORISED STOCKISTS: Moving Iron .-eter 0-20V (AC & DC) /;"====1======#1 The right fuseho lder for car Keypad Matrix Switch accessories... radios, CBs,etc. Takes 3AG fuse s and comes with 600mm of Use it for electronic ~o~mnirl\'li::;l:,]oi:( cable a t t a . c t ~ 1 e d<. locking devices Cat P-7912 :,· or numeri c input for any di gital device . 0 ~~ Cat P-7804 ,;;;;;.,_.-._-1 s110 -~ 0 8 ~~~~ll~~~~Nso ~; Just what you need for Tuner or Receiver projects to give accurate tuning indication. The meter scale is 35mm x 15mm, impedance is 1k, and the straw coloured meter face looks great mounted with a back-lit display. Cat 0-2095 s295 Bayonet Fuseholder Th ese fuseholders are designed to keep 240V connection s safely out of re ach of roam ing fingers! Cat P-7914 suits M205 fuses Cat P-7916 suits 3AG fuses Tuning Meter With Centre Zero Attracti ve bezels with bright, flat topped lenses for a smart, modern appearance. Available in red or 5 50 8~;e~:8100 Red 2 Cat P-8102 Green ~r ,t f ~ ~ ~ Dual Colour Led Bezel Ideal for two- state indication especially in logic circuits. Mounted in a chrome plated bl.e - e Cat P-8108 10~~ [B<at>J <at>J ,,_,______ $495 t NEW KITS SOON TO BE RELEASED Secure Start Need more sectors? 2 Sector Alarm Control Module 2 Sector Module The basis of an effective 2 sector home burglar system. Just add an arm/disarm keyswitch, horn speaker, sensors and a 12V DC power supply and you are in business, not the thieves! Supplied in shortform - components and PCB only. Cat K-8401 - . - . . ~J.!J~!J~ JUNE '90 ~!jJJJ· =---=;:: By adding these modules to K-8401 you can expand your system to secure your entire house or business. Shortform kit - PCB and components only. Cat K-8400 $3995 4 Digit Capacitance Meter ~-1 /lffj:f_ •i ~ ~ 1JJ. ..,, -~ ~ --r i tiJ:1.' L ., ,,.~ . - $1295 ~ JUNE '90 MAV'90 Measures capacitance from 1pF up to 9999uF in 7 ranges. Accuracy better than + /- 1% + /- 1 digit. Supplied with all components, hardware, PCB, pre-punched silk screened front panel and case. $129 Cat K-7500 KIT CLEARANCE - HURRYI LIMITED STOCKS! Batteries tired? Nicad Fast Charger Wl ~ No more flat batteries with this Mains powered fast charger. Complete with all components, cose ond PCB. It can't overcharge (if set correctly) and you'll save money! Cat K-3476 · · ·· · · · · ·.. ·, ; · · . ,i)J, · $6995 Remote Alert/Doorbell Eliminates the need for unsightly wiring, pleasant two tone chime. Ideal for the sickroom and elderly. Complete with Transmitter Cat K-2730 Tilt Alarm So Easy To Build! Bookshelf Speakers Low cost compact Bookshelf Speaker Kit uses a Magnavox 6MV 15cm driver and 3AC Tweeter. Buy the complete kit and SAVE! Got a leaning towards this 'go anywhere alarm' which sounds when it's tilted? Ideal as an alarm for bikes! Short Form - Case not supplied. Cat K-3248 Cat K-4000 Sleeves, baffles x-overs etc. $126 Pair Cat K-3999 Speaker Woofer 6MV Cat K-3998 Speaker Tweeter 3AC $29.75 ea. $6.75 ea. Brake Lamp Monitor A low cost, easy to build project that warns (44 you if your vehicle brake lights aren't working. ,I Complete with all components and case. ~ .,.R--v1.t11 Cat K-4500 ,.. Revive Your Old 7V UHF to VHF Converter See UHF channels 28 to 63 including SBS, with this easy to build low cost converter. Complete with pre-punched case. Cat K- 3236 Low Cost! Battery Power Supply Variable supply - ideal for beginners. No messing with Mains, can be powered from a battery. Includes all components, hardware and case. No metering, no frills, but economical. Cat K-3460 I ·: I . Due to limited stocks some stores may not carry all of these items. We can arrange transfer to your nearest store. please phone ahead to check availability. EXTRUDED CASES Ultra strong, ultra reliable cases based on a specially made 18 gauge aluminium extrusion. The extrusion measures 76 x 102 x 102mm and is available in three different lengths each with four slots for insertion of PCBs without the need for screw mounts. 76mm Cat H-2420 102mm Cat H-2425 153mm Cat H-2430 '-='.::====-~ $22.95 $25.95 $29.95 ZIPPY BOXES The box most preferred by electronics magazines because of its quality and versatility! With Dick Smith Electronics Zippy Boxes you get a better finish witH a tight fitting plastic and recessed aluminium lid- Yes, two lids with every box ! 28x54x83mm Cat H-2855 41 x 68 x 130mm Cat H-2853 50 x 90 x 150mm Cat H-2851 . 60 x 113 x 196mm Cat H-2852 METAL CABINETS Beautifully made cabinets to suit a huge range of projects, especially r-::::::-"---.!l_ those with meters and controls which ~,:::: need to be panel mounted. They -:::::: consist of an aluminium base, <> metal sides with cooling slots, and self- tapping screws. All in an attractive two-tone finish. 102 x 56 x 83mm 150 x 61 x 103mm 150 x 76 x 134mm 185 x 70 x 160mm RACK MOUNTING CASES Cat H-2741 Cat H-2742 Cat H-2743 Cat H-2744 ALUMINIUM BOXES .-----. ~ Just the thing for those weekend ·ect that t left I ·ng di prOJ S ge YI aroun · These boxes come in two pieces which slide together and come complete with screws. Versatile and in a wide range of sizes. Natural finish. 110 x 51 x 70mm 104 x 60 x 46mm 127 x 102 x 76mm 133 x 76 x 54mm 152 x 132 x 103mm 180 x 158 x 118mm Cat H-2300 Cat H-2305 Cat H-2320 Cat H-2325 Cat H-2330 Cat H-2335 $2.95 $3.95 $4.95 $6.95 , . , $6.95 $8.95 $9.95 $11.95 Just what your equipment needs for space efficient storage and that clean, professional look. All cases are 430mm wide and 554mm deep (international standard), and have a black -= a~:disedfinish. . A=Front Ponel height (mm> B=Mounting Hole centres (mm) C=lnternol Case Height (mm) A B 44 34 88 57 132 I 89 C I 38 Cat H-2483 I $69 82 Cat H-2485 , $89 126 Cat H-2487 I $99 RACK MOUNTING BLANK PANELS Designed to bolt directly onto you r rack system and neatly fill the spaces between equipment. They come with predrilled mounting ho les and black anodised finish. 44mm Cat H-2482 $15.95 88mm Cat H-2484 $25.95 132mm Cat H-2486 $29.95 LOW VOLTAGE IRONS Quality Spring Loaded Pliers/ Fast Heating 3 o-15ow Nippers High quality handtools help make work easier! Specially selected for project work they're all high carbon steel, drop forged, hardened and tempered with insulated handles. 127mm Needle Nose.cot T-3290 115mm Diagonal Nipper. Col T-3291 115mm Long Nose. Col T-3292 153mm Needle Nose. cot T-3293 125mm Flot Nose. ColT-3s 96 125mm Bent Nose. Cot T-3297 11 smm End Nipper. cot r. 3298 $895 12 Volt 1 0.10 watt Miniscope Lightweight, finge rtip control gives precise temperature. Requires 3 _3v <at> 30A Comes 995 v with spare tip &~ le ment _ · pack. Col T-1660 · ·· ·. · :·Connects toyourcarbattery _/_.- ___ · ,. ~ ~ · & heats in 3 sees. Comes wit~ · 6m (20ft) lead with clips. ~ Current drain 45A. Cot T-1635 Spare Tip & Element Pack CotT-1601 I $ 7 $69 $1 Q9S 3.3V<at>30A (lnt) 150 Watts. Transformer Low Voltage transformer for Superscope. scope irons with electronic shield for extra protection. Cat T-1 692 Select temp. Heats to required in 6 sees! Requires 3.3V <at> 30A. Comes with spare tip & . element. c~ 1 s59 Spare Tip & Element $1 Q95 Pack Cat T-1603 ~ ~~ - 4 Blade Scraper 'G' Clamp Set Three handy 'G' C lamps that are perfect forrnost hobby work, etc. All fit the 30mm (diam.) magnetic base supplied. Sizes include 40mm x 35mm, 30mm x 30mm & 20mm x 25mm. Cal T-4755 This handy sc raper has a blade with four purpose designed surfaces on it for deburring and cou ntersinking holes as well as general finish ing work. Cal T-3625 s59s (lO.o. (S Store Locations • NSW • Al bury 21 8399 • Bankstown Square 707 4888 • Belconnen (06) 253 1785 • Blacktown 671 7722 • Brookvale 905 0441 • Bondi 387 1444 • Campbelltown 27 2199 • Chatswood Chase 4111955 • Chullora 6428922 • Gore Hill 439 5311 • Gosford 250235 • Hornsby 477 6633 • Hurstville 5808622 • Kotara 56 2092 • Liverpool 600 9888• Maitland 33 7866 • Miranda 525 2722 • Newcastle 61 1896 • North Ryde 878 3855 • Parramana 689 2188 • Pen rith 32 3400 • Railwa y Sq uare 211 3777 • Sydney City 267 9 111 • Tamworth 6617 11 • Wollon gong 28 3800 •ACT• Fyshwick 80 4944 •VIC ·• Ballarat 3 1 5433 • Belmon t 43 8522 • Bend igo 43 0388 • Box Hill 890 0699 • Coburg 383 4455 • Dandenong 794 9377 • East Brighton 5.92 2366 • Essendon 379 7444 • Footscray 689 2055 • Frankston 783 9 144 • Geelong 232 711 • Melbourne City 399 Elizabeth St 326 6088 and 246 Bourke St 639 0396 • Ric hmond 428 161 4 • Ringwood 879 5338 • Springvale 547 0522 • OLD• Brisbane City 229 9377 • Buranda 391 6233 • Cairns 311 515 • Chermside 359 6255 • Red bank 288 5599 • Rockham pton 27 9644 • Sou thport 32 9033 • Toowoom ba 38 4300 • Townsv,lle 72 57 22 • Undenwood 341 0844 • SA• Adelaide City 2234 122 • Beverl ey 347 1900 • Elizabeth 255 6099 • Enfield 260 6088 • St. Marys 277 8977 • WA • Cannington 45 1 8666 • Fremantle 335 9733 • Perth City 48 1 326 1 • Mid land 250 1460 • Northbridge 328 6944 • TAS • Hobart 31 0800 •NT • Stu art Park 81 1977 PHONE ORDERS OUTSIDE SYDNEY - FREECALL ~n~ui!~~~888 2105 Sydney Cu~~m~ r~ ld Fax: (02) 805 1986. MAIL ORDERS: DS XPRESS, Freepost 100, P.O. Box 321 North Ryde NSW 2113 Digital Sine/Square Wave Generator; Pt.1 This new Digital Sine/Square Wave Generator uses high speed CMOS ICs and a digital filter IC to produce sine and square waves over the frequency range from 0.1Hz to 500kHz. It also features a 4-digit frequency readout and an output level control. By JOHN CLARKE In the past, if you wanted a high quality sine and square wave generator, you would have chosen a Wien Bridge oscillator design such as the one featured in the January & February 1990 issues of SILICON CHIP. This has very low harmonic distortion, a rated output of up to 10 volts RMS, and a frequency coverage from lOHz to lOOkHz. For many applications though, a much wider frequency range and a rock solid amplitude is desirable. To get these qualities, you would 16 SILICON CHIP previously have chosen a function generator. These can certainly give a wide frequency range but often have the drawback of a relatively high harmonic distortion on sine waves. Now there is a third choice, with this new Digital Sine/Square Wave Generator. You can think of it "as the function generator to use when you want something better than a function generator". Like most audio function generators, it covers a very wide frequency range - from O. lHz to 500kHz - and it does so with rock solid amplitude stability. There is no bouncing about of the amplitude as you change frequency (as is inevitable with thermistor stabilised Wien Bridge designs). Why would you want such a wide frequency range? Well, there are any number of reasons. If you are doing logic design, a clock frequency down to O. lHz (ie, one pulse every 10 seconds) can be very handy, since it lets you see the circuit work as each clock pulse arrives. And if you are working on audio or analog circuitry, the wider frequency range of this generator can be very useful. For example, it can allow you to check the low frequency response of amplifiers and loudspeakers. Similarly, the higher frequencies are available for checking the upper response of power amplifiers and other analog circuitry. The generator has a 4-digit LED readout so you can set the frequen- cy exactly. The output frequency is selectable in four ranges, with a slight overlap between each: 0.1-10Hz; 10-1000Hz; 1-100kHz; and 100-500kHz. Presentation The styling of the new Digital Sine/Square Generator is similar to that of the 1GHz Frequency Meter (SILICON CHIP; Nov-Dec. 1987 & Jan. 1988) and the Capacitance Meter (May 1990). It is housed in a plastic instrument case and uses a 4-digit LED display behind a red perspex panel with a Dynamark label covering the lower half of the panel. It has two knobs for the range selection, two knobs for frequency setting (fine and coarse), and a knob for the output level. There is also a pushbutton ON/OFF switch, a miniature toggle switch to select sine or square wave output, and a BNC socket for the output terminal. Waveform synthesis So what's special about this new generator design? So far we've told you what it isn't. It isn't a Wien Bridge and it isn't based on conventional function generator circuitry. Incidentally, it does not produce the more exotic waveforms found on some function generators, such as triangle and sawtooth ramps. In our experience, these waveforms are seldom used and are provided simply because the circuit produces them rather than because they have any real use. Our new generator produces its sinewaves by a process which can Specifications Frequency Range 0.1 Hz-500kHz in four ranges : 0 .1-1 OHz; 1 0-1 OOOHz; 1-1 OOkHz; & 100-500kHz Output Waveforms Sine & square Harmonic Distortion Square Wave Rise Time Less than 0.1 % from 0 .1 Hz-50kHz; 0 .27% at 80kHz 1Ons Square Wave Fall Time 1 Ons Output Level Sine wave : variable from 0 -1.2V RMS Square wave: variable from 0-5V p-p Output Impedance 6000 nominal Load Impedance 6000 to infinity Protection Short circuit protected (indefinite) Display Accuracy ±2% + be called waveform synthesis or more accurately, "piecewise linear approximation". In this process, the circuit builds up the sinewave in little steps which are quite accurate in their absolute level but then we need filtering to remove the discontinuities due to the steps. The block diagram of Fig.1 shows the main components of the generator circuit. The key to the circuit is an up/down counter and a staircase generator. The up/down counter runs from O up to 9 and then back down again to 0, repeating the sequence continuously. The counter drives the staircase generator which produces one half of a sinewave (from trough to crest) 1 digit on the count from 0-9. Then, as the counter counts down from 9 to 0, the staircase generator produces the next half of the sinewave, from crest to trough. This process is continuous and the result is a sinewave approximation, with 9 steps from trough to crest, and 9 steps from crest to trough. You can see this stepped waveform in one of the oscilloscope photos accompanying this article. Naturally, before we can use this waveform, it must be filtered and this is done in a switched capacitor filter and a tracking RC filter. These two filters effectively remove all the switching hash associated with the waveform synthesis and VR2a ,VR3a SWITCHED CAPACITOR FILTER S1 : 1 : O.1HZ·1OOkHz 2 : 1OOkHz-SOOkHz - -TIMEBASE -.166.6ms 1 5410 LEVEL CONTROL FREQUENCY READOUT 55.55ms 2 Fig.1: the up/down counter controls a staircase generator which produces one half of a sinewave on the count from O to 9 and the other half on the count from 9 down to O. This signal is then filtered & fed to the output. The square wave signal is derived from the up/down counter circuitry. JULY 1990 17 COARSE ANE VR2b 500k LIN VR3b 1Ok LIN +5V 0.1+ gggg MAX VR4 5k 16 ------1 16 IC8 74HC390 11 4 IC9 4518 10 IC10 74LS192 (74HC192) 12 15 10 9 .,. +100 MASTER CLOCK OSCILLATOR VR6 100k FREQUENCY DISPLAY 4xHOSP5303 VR7 20k a ,, g 1 I I •/_Jc 12 CK 10 15VW TANT ,_, f d ,-, I I I I I_I 10 + T- COM OP 3,8 5 IC12 74C926 OIUL+ +5V COM DP 3,8 5 COM 3.8 A7 TIME BASE OSCILLATOR 16 B8 14 K· 15 R 10 31 1 R C 0 IC13 4017 4 24 13 E 5 0 11 LE 18 OS 6 .,. 'I' .,. +5V 1 16VW r· POWER 471l + 10 16VW+ S1 : 1 : 0.1Hz-100kHz 2 : 100kHz-500kHz OUT -1---+sv 1 16VW S2 : 1 : 0.1 Hz-1 OHz 2: 10Hz-1kHz 3: 1kHz-100kHz + eo----i . DIGITAL SIGNAL GENERATOR the result is a very clean sinewave which is fed to the output buffer and level control. Other features of the block diagram need not concern us now but they are included for completeness. They include the master clock generator, a number of divider stages to drive the up/down 18 SILICON CHIP counter, and the timebase and digital frequency readout circuits. Circuit details Now let's have a look at the circuit of Fig.2. ICl is the up/down counter referred to above. It is a 741S190 (or 74HC190) high speed decade counter which has 4-bit BCD outputs: QA, QB, QC & QD. These outputs are decoded by IC2, a 74HC42 BCD-to-decimal decoder. IC2 has 10 outputs, from O to 9, but we don't use the "O" output in this circuit. Because ICl counts in BCD (binary coded decimal), each successive output of IC2 goes low ( + 5V) for one clock period. 16 0.1+ 1 2 01! 16 34 11 LOAD +3 15 A 2 14 B QC 6 13 C 7 12 D 45 * 270k *3.3k * 82k 1 OD UPI DOWN 5 IC2 74HC42 10pF +10V * 10k *1k * 39k * 22k * 2.2k * 18k 56 EN 8 OA 3 OB IC1 74LS190 (74HC190) 15 10 9 23 * 47k 0.1 4.7 OFFSET ADJ~r---10k + 25VW .,. * 120k SUMMING AMPLIFIER 6 7 -10V 0.1 ~ 79 +5V * 33k 14 10 PR 09 IC6 11 CK 74HC74 08 * 10k CLR 7 13 DECADE DECODER CLOCK INPUT +5V *10k +5V 11 12 8 *1 % ~---------5v 0.1 10 STAIRCASE SINE WAVE SQUARE WAVE 0.1 SQUARE BUFFER 16 15 IC4 LMF100CCN 17 * 20k * 10k * 20k .,. 19 18 COARSE VR2a 500k LIN 20 +10V * 10k * 10k FINE VR3a 10k LIN OUTPUT 4.7 + 25VW-r -10V 22pF 22pF SOUA'RE S3a SWITCHED CAPACITOR FILTER (HOLE LOW-PASS) OUTPUT SINE S11 S2c ffi ffi 5 5 IN OUT GNO GND OUT B ELJc VIEWED FROM BELOW IN 1 ' j_ "! .,,; """I One of the crucial circuit functions is to change ICl 's mode from counting up to counting down, and so on. This is achieved by IC6, a 74HC74 dual-D flipflop. We use only one flipflop in this chip and it is clocked by the minimax output, pin 12, of ICl. So when ICl gets a clock pulse which would cause it to count S3b 11 TRACKING RC FILTER beyond its maximum count of 9 [ie, overflows), its minimax output goes high and toggles IC6 which then changes state at its Q output, pin 9. Pin 9 of IC6 is connected to pin 5 of ICl. When pin 5 is low, IC2 counts up; when it is high, ICl counts down. So IC6 is hooked into ICl to automatically change its LEVEL VR5 1k LIN SOUARi SINE .,. 10k SINE BUFFER Fig.2: ICl is the up/down counter shown in Fig.1. Its minimax output clocks flipflop IC6. When Q of IC6 is low, ICl counts up (0-9); when it is high, ICl counts down (9-0). ICl 's outputs are decoded by IC2 & summed by IC3 to produce a stepped sinewave. This waveform is then filtered by switched capacitor filter IC4 and the RC tracking filter. ICs 7-11 provide the timebase while ICs 12 & 13 drive the frequency display. JULY 1990 19 Despite the circuit complexity, the construction is straightforward. All the parts (except the mains switch) are mounted on two PC boards which are soldered together at right angles via edge connector pads. The completed assembly then fits inside a plastic instrument case. mode from counting up to counting down and so on. So we have seen how ICl & ICZ, together with IC6, count from Oto 9 and then back down again. Nine outputs of ICZ are coupled to IC3, an LM318 high speed op amp which functions as a summing amplifier, although the "O" output does play a part, even though it is not physically connected. It is IC3 and its associated resistor network which actually produces the stepped sinewave from the outputs of ICZ. Notice that the resistors connected to the nine outputs of ICZ reduce in value as they go from 1 to 9. For example, pin 2 of ICZ (the "1" output) has a total of 317Hl connected to it (270kfl + 47kfl), whereas pin 11 (the "9" output) has only 10kfl connected to it. Thus, when the (uncon20 SILICON CHIP nected) "O" output of ICZ is high, the circuit produces the trough (ie, the minimum peak) of the stepped sinewave. When pin 11 is high, it produces the crest (ie, positive peak) of the stepped sinewave. So IC3 produces a stepped sinewave at its output. Because the signal is summed from ICZ, the signal would normally have a DC offset of - 2.5 volts. This is because all the outputs of IC2 switch between OV and + 5V. This DC offset is cancelled out by feeding a DC signal of + 2.5V from the wiper of trimpot VRl to the non-inverting input of IC3. The waveforms shown in Fig.3 demonstrate how the sinewave is generated. The top waveform is that present at pin 3 of ICl , the QA output. It is half the clock frequency fed to pin 14 of IC1. The next 10 waveforms are those present at the decoded outputs of IC2. Now look down to the second lowest waveform which is present at pin 6 of IC3. This shows how the steps of the generated sinewave coincide with the pulses from IC2. Switched capacitor filter Another crucial factor in obtaining the high performacne of this circuit is the use of a National Semiconductor LMF100 dual switched capacitor filter. The beauty of this device is that it allows the design of a filter with variable cutoff frequency and that is just what is needed here. Consider that the hash to be filtered out of the sinewave output is essentially a square wave with a frequency 18 times higher (than the sinewave). And since the sinewave output ranges from 0.1Hz to 500kHz, the switching frequency (actually the clock frequency to ICl) will range from 1.8Hz to 9MHz. So what is needed is an effective filter which will track the oscillator frequency - a filter with a fixed cutoff frequency would be useless. This is where the LMF100 from National Semiconductor comes into the picture although even it cannot cover the whole operating range it covers the oscillator frequency range up to l00kHz. We don't plan to explain just how the LMF100 works in this article we just don't have the space. In essence though, it can be considered as a number of cascaded low pass filters in which the capacitors are varied by switching them rapidly in and out of circuit. This has the effect of varying the amount of capacitance in each of the filter stages and thereby causes the filter's cutoff frequency to track the clock frequency - just as we want. What actually happens is that IC4, the LMF100, is fed with a signal which is 3 times the clock signal fed to ICl, or 54 times (3 x 18) the ultimate sinewave frequency. This 54 times clock signal comes from IC7f, a Schmitt trigger buffer stage following IC9. RC tracking filter While the LMFl00 filter removes just about all the switching hash from the sinewave, some hash still remains and that is the reason for a further RC tracking filter. It consists of potentiometers VR2a and VR3a and a 4.7kQ resistor, along with the capacitors connected to S2c and Slf. The switches select the 2.2µF capacitor for the 0.1lOHz range, the .022µF capacitor for the 10-lO00Hz range, the 220pF capacitor for the 1-lO0kHz range and the lO0pF capacitor for the 100-500kHz range. VR2a & VR3a are ganged with VR2b & VR3b respectively. The latter control the frequency of the master clock oscillator. Thus, as the frequency of the generated sinewave varies, so does the the rolloff point of this passive RC filter. Output buffer Since the output of the RC tracking filter is essentially a high impedance, it needs to be followed by a high impedance buffer stage 18 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 OA. IC1 u u 1SLJ LJ LJ LJ LJ LJ IC2 LJ LJ LJ LJ LJ LJ LJ7J u~~□1N 7..______ co_uN_r_uP_ _ _ _ PIN6, IC3 L c□uNT o□wN n MINIMAX ,_ J IC1 __,I n '--------------'~-------------'ll ---..~_.,--...r-_,..___r-~...r--r--;-::;-..__...,_~--,, ~6 _J SINE WAVE SQUARE WAVE .____ _ ____.r Fig.3: these waveforms show how the stepped sinewave is generated. Each successive decoded output of IC2 goes low for one clock period as IC2 counts from 0-9, then from 9-0 & so on. These decoded outputs are summed by IC3 to produce the stepped sinewave (second from bottom). The square wave is derived from Q-bar of IC6. before being coupled to the output. This function is performed by IC5, Ql & QZ which together can be thought of as a power op amp with a gain of unity. D1 & D2 provide a small amount of bias to the output transistors, Ql and QZ, to ensure that crossover distortion is eliminated from the output. After all, there's not much point in generating a low distortion sinewave and then spoiling it in the buffer stage. Square wave generation So far we have not mentioned how square waves are generated by the circuit but in fact they come very easily, from the Q-bar output of IC6 (the same IC that generates the up/down control signal for ICl). Hence, IC6 produces a square wave which is always locked to the sinewave output from IC3. Toggle switch S3a selects either the sinewave signal from the buffer or the square wave signal from paralleled Schmitt trigger inverters IC7c, IC7d & IC7e which buffer the Q-bar signal from IC6. From there, the output signal goes to a lkQ level pot (VR5) and then to the output socket. Note that S3 is a double pole single throw (DPST] switch and that S3b (the second pole] appears to be doing nothing, switching between earth and earth! However, it does have a purpose and it selects the best earth point for the cold end of VR5, so that the output signal is free of extraneous noise, in either sinewave or square wave modes. Master clock IC7b, a high speed CMOS Schmitt trigger, is connected to function as the master clock oscillator. It is varied in frequency by two potentiometers in series, VR2b & VR3b, which function as the coarse and fine frequency controls. Depending on the range selected by Sl, the master clock oscillator is either 54 JULY1990 21 PARTS LIST FOR THE DIGITAL SINE/SQUARE GENERATOR 1 PCB, code SC04108901, 162 x 225mm 1 PCB, code SC04108902, 225 x 75mm 1 display mask film, 248 x 75mm 1 Dynamark front panel label, 248 x 42mm 1 grey plastic instrument case, 263 x 1 90 x 84mm 1 red perspex front panel, 250 x 75 x 2.5mm 1 2155 15V centre-tapped 1 A mains transformer 1 mains cord & plug 1 mains cord grip grommet 5 knobs 1 T0220 U-shaped heatsink, 25 x 27 x 34mm 1 DPDT toggle switch (S3) 1 1OOmm-length of 1 0mm heatshrink tubing 1 240VAC push-on/push-off switch (S4; DSE Cat. DSE P-7566 or Altronics Cat. S-1090) 1 6-pole 2-position rotary switch (S1; DSE Cat. P-7502 or Altronics Cat. S-3002) 1 4-pole 3-position rotary switch (S2; DSE Cat. P-7504 or Altronics Cat. S-3003) 1 BNC panel socket 40 Molex pins 4 HDSP5303 13mm red 7 -segment common cathode displays 2 metres of 0.8mm tinned copper wire 10 PC stakes 1 1 50mm length of medium duty hookup wire 550mm length of heavy duty hookup wire 3 machine screws, nuts and washers 4 self-tapping screws 1 solder lug Semiconductors 1 7 4HC190 or 7 4LS190 decade up/down counter (IC1) 1 7 4HC42 decade decoder (IC2) 1 LM318 high speed op amp (IC3) LMF1 OOCCN switched capacitor filter (IC4) LF351 FET input op amp (IC5) 1 7 4HC7 4 dual-D flipflop (IC6) 1 7 4HC1 4 hex Schmitt trigger (IC7) 1 7 4HC390 dual decade counter (IC8) 1 4518 dual decade counter (IC9) 1 7 4HC192 or 7 4LS192 decade up/down counter (IC10) 1 7 4HCOO quad NANO gate (IC11) 7 4C926 4-digit counter (IC12) 1 4017 decade counter (IC13) 5 BC338 NPN transistors (01 ,03,04,05,06) 1 BC328 PNP transistor (02) 2 7805 3-terminal +5V regulators (REG1, REG2) 1 7905 3-terminal -5V regulator (REG3) 4 1 N4002 1 A diodes (D3-D6) 2 1 N41 48 signal diodes (D1 ,02) Capacitors 2 1000µ,F 16VW PC electrolytic 1 1 Oµ,F 16VW PC electrolytic 1 1 Oµ,F 1 6VW low leakage electrolytic or tantalum 2 4.7µ,F 25VW PC electrolytic 1 2 .2µ,F 16VW PC electrolytic 3 1µ,F 1 6VW electrolytic 10 0. 1µ,F monolithic 1 .022µ,F metallised polyester 1 220pF ceramic A lkHz stepped sinewave as it appears at pin 6 of IC3 (0.2ms/div). The lkHz waveform after digital filtering by IC4 (0.2ms/div). The lkHz waveform after passing through the tracking filter (0.2ms/div). The sinewave output at 480kHz (timebase setting .03µs/div). The square wave response at lkHz (0.3ms/div). The square wave output at 90kHz (5V p-p; risetime l0ns). 22 SILICON CHIP IC7a, PIN2 R, IC13 1 1 2 1 1 1 1 OOpF ceramic 22pF NPO ceramic 22pF ceramic 12pF ceramic 1 OpF NPO ceramic 1OpF ceramic Potentiometers 1 500k0 dual gang PCBmounting linear pot (VR2) 1 1 OkO dual gang PCBmounting linear pot (VR3) 1 1kO linear pot (VR5) Trimpots 1 1 OkO miniature horizontal trimpot (VR 1) 1 5k0 miniature horizontal trimpot (VR4) 1 1 OOkO miniature horizontal trimpot (VR6) 1 20k0 miniature horizontal trimpot (VR7) Resistors (0.25W, 1 330k0 1 % 1 1 270k 1 % 3 1 120k 1 % 8 1 82k0 1 % 3 2 47k0 1 % 1 1 39k0 1 % 1 1 33k0 1 % 1 1 22k0 1% 9 2 20k0 1 % 2 5%) 1 8k0 1 % 15k0 1 % 1OkO 1 % 1OkO 4 .7k0 2 .2k0 2700 470 330 times the sinewave frequency (ie, up to 5.4MHz for a l00kHz output) or 18 times the sinewave frequen~y (ie, up to 9MHz for 500kHz output). IC8 and IC9 are dual decade counters set to divide by 100 so that the output of IC9 gives an overall division of 10,000. IC8 is a 74HC390 high speed CMOS counter to cope with the 5.4MHz master clock frequency for a sinewave output of lO0kHz and the 9MHz master clock frequency for the 500kHz output. IC9 is a standard 4518 CMOS counter which can easily cope with its maximum input clock frequency 90kHz (from IC8). Range switch SZb selects the clock signals for IC7f & IClO, from either the master clock, IC8 or IC9. IClO and ICl 1 act as a divide-by-3 circuit which is necessary when the LMFlO0 switched capacitor filter is in use. Otherwise, the divide-by-3 circuit is bypassed by Sle, at the input to ICl. _J .....___ ___.1 CK, IC12 LE, IC12 R, IC12 Fig.4: the counter circuit waveforms, IC7a produces a gating pulse to gate through pulses from the timebase to the clock (CK) input of counter IC12. The count is then latched (LE) and the counter reset (R). IC13 is then disabled by the high on its CE input until reset by the high from IC7a. CE, IC13 Digital display The 4-digit display circuit has the same fast update time for all the frequency ranges. This is achieved by having the display circuit count the "master clock divided by 100" output from IC8. The counter circuit requires its own fixed clock timebase, although two clock frequencies are required to cope with either the 0. lHzlO0kHz range or the 100-500kHz range. IC7a, another Schmitt trigger in the IC7 package, functions as the timebase oscillator with the two frequency settings selected by Sla. Trimpots VR6 & VR7 allow precise calibration of these frequencies. A 74C926 4-digit counter (IC12) is used to count and display the frequency, while IC13, a 4017 decade counter, is used to provide the necessary reset and latch enable signals. The way the counter circuitry works is illustrated by the waveforms of Fig.4. What happens is that the timebase oscillator from pin 2 of IC7a and the divided clock signal from IC8 are applied to the two inputs of NAND gate ICl la. This gates through a 166 or 55 millisecond portion of the divided clock signal, depending on the setting of switch Sla (see Fig.1). This gated signal is applied to pin 12 of IC12 which then counts it in its four decade counters. At the end of the timebase period, a short pulse is applied from pin 4 of IC13 to the latch enable input, pin 5, of IC12. This latches the contents of the four internal counters into the display registers so that they can be displayed by the LED readouts. Shortly after the latch enable pulse, another pulse is applied from pin 7 of IC13 to the reset input, pin 13, of IC12. This resets the four internal counters, ready for the next gated clock signal. IC13 is then stopped from further counting by the high signal from its pin 4 to pin 13 and it is reset the next time the timebase signal from IC7a goes high. IClla then gates through another 166 or 55ms period of clock signals to be counted. You can see the sequence of counter operation in Fig.4. The top waveform is the timebase signal from IC7a. The second waveform is the gated clock signal fi:om pin 3 of ICl la. The remaining three waveforms are the latch enable, reset and chip enable pulses, in that order. Power supply The supply uses a 15V centretapped transformer which feeds a bridge rectifier (diodes D3-D6) and two 1000µF electrolytic capacitors. The resulting ± 10V supplies provide power for the op amps, IC3 & IC5, and also for the 3-terminal regulators. There are two + 5V regulators (REGl & REG2) and one - 5V regulator (REG3). REG 1 is used to power most of the generator circuit while REGZ is used to power the LED display and IC12. The two separate positive regulators are used to ensure that the hash produced by the display counter circuitry is kept out of the sensitive generator circuitry. Next month we will conclude the description of this project with the construction and setting up details. JULY 1990 23 _t:.L,INU l'IIL,.'.). -· · · -- ·· · - - - - · · · -· ·· - --· · · - · · · · - - - - · ·-· ··- - -· · · -· ·· · - - - - ·· · - •• · - -• • · ~• •• • --- - • • ,...,, . ,...,....,..,. • • ...... "• --- - • • ,._., .,...,...,._., • • ...,, "• ._.__._..., •• , .._.,.,._,...,.,,, • • ._,," • ,__.._.__._,,, ,._, , . , ...,.._,v,-..1 uru, l.... LLVI nv1,1vv Vr"\ I _ECTRONICS JAYCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICS JA\ JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS JA\ JAYCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICS JA\ -~gi~g~:g~ =ECTROi _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO ECTRO _ECTRO _ECTRO ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECfRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO _ECTRO I AVf""' A □ c 1 Cf"'TD/"\"-llf"'O 1Avf""'A □ c, cr,Tonu1,-.o 1Avf""' AD c1 Cf""'Tnn i 11f"'lo JAVf"' AD c1 Cf"'TD/"\"-Jtf""'O IAVf""'A □ r:1Cf""'T Dr\"-11 ,-. 01Avf"' A □ c 1 cr,TOn ,._ 11,...c.- 1 A vf"'A □ c1 cf""'T □ /"\"- ll f"'lo 1Avf""' A □ A 1.5 to 9V DC/DC converter Ref: EA May 1990 Replace those expensive 9V batteries with an economical 1.5V D cell. Lasts much longer and saves you the cost of the kit in no time. Shortform kit - PCB. potcores. battery holder, heatsink and all electronic components supplied (excluding optional receiver parts). No box or box hardware supplied. Cat KA-1724 $19.95 Specifications Type: Output Voltage: Output Current Tracking Accuracy: Load Regulation: Line Regulation: Ripple output Protection: _ECTRO _ECTRO _ECTRO .ECTRO _ECTRO _ECTRO .ECTRO .ECTRO .ECTRO .ECTRO, .ECTROI .ECTROI .ECTROI .ECTROI .ECTROI .ECTROI .ECTROI ~g~g; .ECTROI ECTROI ECTRO, ECTROI ECTROI ECTROI ECTROI ECTROI ~gi~g: ECTROI ECTROI ECTROI ECTROI ECTROI ECTROI ECTROI ~gi~g: $229 Dual tracking with switchmode pre-regulators for high efficiency 0 to+/-50V 1.7A from Oto 87V; 1.5A at 91V; 1A at 100V Better than 30mV Better than 500mV at +/-V and 1A Better than +/-5mV for mains voltages from 'lJ.0.200/ AC Less than 3mV p-p at full load Fully protected against output short circuits and forward and reverse voltages connected to the output fuse protection for the power transformer. Only $59.95 ea1. Kc-so14 Specifications Signal delay: 16.4 miliseconds • Clock frequency: 15.7kHz • Frequency response: 100Hz to 43kHz within (pm) 3dB • Maximum output signal: 800mV RMS • Maximum input sensitivity: 0.7mV RMS Ito actuate relay) • Harmonic Distortion: <0.5% at 250mV and 1kHz <1.5% at 800mV and 1kHz • Signal to noise ratio: (ms) 66dB unweighted with respect to 500mV RMS at the output PRO SERIE 140 WATTS o··- . "1$W'""'""''C> s.t'< ~;,,;;<a 0<-<1/l-tft ff · ~ <OX • wm• Otl.AV _ECTRO •:::,;>'-'====="'"'"'":=========~<fl :~gi~ _ECTRO Ref: Silicon Chip April '90 This magnificent switchmode type laboratory power supply has great professional features but costs around 1/2 of inferior built up units. This kit features high efficiency toroid power transformer. professional high resolution 10tum wire wound voltage control potentiometer, latest I.C. technology, excellent line load regulation. lc,,v ripple voltage, apart from a smart plastic case! (for more information see specs below}. The Jaycar kit is complete down to the last nut and screw as well as all hard-to-get I.C.'s. Cat No. KC-5073 First Syllable Dropped Off VOX Relay Kit ICSJA, ±50V (0-1 00V) 1.5A Dual Tracking Power Supply Kit ONLY Ref: Silicon Chip April '90. At last a VOX (Voice Operated Relayj that does not cut off the first bit of speech! This clever project uses an acoustic delay to prevent the common fault in all but the most expensive VOX circuits• the 10mS or so of that is lost by relay operating time. It may not sound much but it is very annoying and a long time in speech terms. This kit is supplied by Jaycar in a short form. i.e. without case. front panel. plug adaptor etc. This saves you over $20 on the price otherwise, as we believe most of these projects will be built into other equipment anyway. All other parts (including all PCB parts) included. c 1 Cf""'TD:.) N BARGAIN LED PACK Ref: EA Dec 1989/Jan 1990 NEW• UJY.lraded design - now gives 140W nms channel into 8 ohms. Dual toroidal transformers supplied. Cat. KA-1725 $599 100 assorted LED's 5mm, 3mm. rectangular plus others. Normal value about $35 · ONLvSS.95 ADELAIDE STORE NOW OPEN 190 Wright Street Ph: (08) 231 7355 FIBREGLASS PC BOARD MADNESS!! Stock up now. Well under 1/2 normal price. SIZE 1 505 x 205mm Cat. HP-9522 $4.50 SIZE 2 400 x 170mm Cat HP-9523 $3.00 EXPERIMENTERS PLUG PACK BARGAIN SIZE J 500 x 90mm Cat. HP-9524 $2.00 Don't miss this one. Primary - 220V 50hz (will work OK on 240V) lead length 1.8mt long - bare ends ( no 240V plug supplied). Secondarys - 16V AC at 800mA -9VACat1.5AMP Lead length 1.7mt long terminated in a strange plug Supplied in a maxi box style. Measures 75 (W) x 85 IL) x 60 (H)mm -----.... 1-9 $5. 95 10-49 $5.50 0-99 $4. 5 95 100 + $4,50 3 ■ 75 DIGIT 4000 COUNT 39 RANGE • Inductance : ~u~~;ce • Temperature • Peak hold • Logic ,_____ ...,_._....,_ See catalogue for full details Cat. OM-1475 Cat No. MA 2618 $179 NOTE! This item is sold strid/y_ for parts only. It is not approved • th I • • ror connection to e e,ednc,ty ECTROI ECTROI L EcTROI _ ECTROI :; ECTROI \ ECTROI ___ _ 1 Jaycar now stocks an increased range of fuse. New additions include: JAG FAST BLOW 2.5A 4A 7A' 8A Cat Sf.2195 Cat. SF-2197 Cat. SF-2201 Cat. Sf.2203 ALL 25e ea 10+ 20e ea JAG SLOW BLOW 250mA 750mA 1.5A 2.5A 4A Cat. Sf.2223 Cat. SF-2225 Cat. SF-2227 Cat. SF-2229 Cat. SF-2231 6A 7.5A 10A Cat SF-2233 Cat. SF-2234 Cat. SF-2236 ALL$1 .20 ea 10+ $1 ea M205 FAST BLOW 50mA 1.6A 4A Cat. SF-2147 Cat SF-2161 Cat. SF-2164 ALL 25e ea 1O+ 20e ea M205 SLOW BLOW 200mA 250mA 1.5A Cat. SF-2169 Cat. Sf.2171 Cat. Sf.2173 ALL $1 .20 ea 10+ $1 ea Headphone/Microphone Set High quality headphone/microphone set. Supplied with a pair of 32 ohm quality dynamic headphones and a noise cancelling electret microphone. Insert is mounted on a flexible boom with windscreen. Supplied with separate stereo 3.5mm plug for headphones and 3.5mm mono plug for insert. (Mic insert requires 3-5 volts power for operation. This headphone would easily be worth $50. We have a limited quantity available at the absolute bargain price of$2995 Cat. AA-2022 ON Ly $29.95 , NICSJAY1 " ICS JAj ECTRONICS ~Av~;~ ~~~~~~~~;~~~A ~~;~ ~~~~~~~~;~~A~~;~ ~~~~i~~;~~A ~c;~ ~~~~~~~~;c~A ~c;~ ~~~c~~~~;~~; ~CA~ E~ECTRQ~;c~A~CAR E~ECT~O~iCSJA~CAR ELECTR0~1 cs .d 9fl • ): . _ JA ECTRON ICS JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ~~J~~~!~~ JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRON ICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR El ECTRONICSJAVCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR El FCJBONIGS IAYGAB ELECTRONICSJAYCAR ELECTRONICS JA ELECTRONICSJAYCAR ELECTRONICS JA ELECTRONICSJA YCAR ELECTRONICSJA El ECJBQNICS IAYCAB El JCCIBONtCS I4Y w o se Power Supply Load Protection Kit n versa AR ELE< AR ELE< AR ELE< AR ELE< AR ELE< AR ELE< AR ELE< AR ELE< AR ELE< Cat KC-5077 AR ELE< AR ELE1 AR ELE1 AR ELE• AR ELE, AR ELE• AR ELE VARTA 2.4 V 100mA/H Ni-CAD AR ELE These batteries are encased in a black plastic housing which measures 30 {L) x 16 (W) x 19 (H) mm. They were removed from AR ELE printed circuit boards by simply cutting of the PC terminals so to use you would need to break open the plastic case. Inside AR ELE AR ELE are two 1.2 V cells. So purchase 4 of these, remove 1 cell and you have an 8.2 V {9V 216 type) battery for only $4, not about A large transformer ideally suited to computer power AR ELE $20. AR ELE• supplies. Size 115 (L) x 10 (W) x 86 (H) mm. Ideal for Hobbyists, experimenters, etc. AR ELE Primary To buy these today they would cost about $13 ea. AR ELE 2 x 120 V 50hz (240 V) AR ELE 1 x 110V AR ELE Secondary AR ELE 16 V Regulated to+ 12V DC 5A AR ELE 16 V Regulated to -12 V DC 5A AR ELE 9.3V Regulated to 5 V DC 5. 7A AR ELE Cat. SB-2470 AR ELE AR ELE These transformers would normally cost about $80 each. AR ELE We have a limited quantity available for only $30 each. -AR ELE -AR ELE An amazing 3000 MCD of brightness in a LED! Lights up red, clear to look at. ,AR ELE 10+ $3.65 CatZD-1796 :AR ELE Cat. MM-2040 :AR ELE :AR ELE Due to huge weight mail order customers add $8 extra to AR ELE normal P& Pcharges. :AR ELE 'AR ELE :ARELE Refer Silicon Chip May 00 -AR ELE This attractive 4 digit capacitance meter kit is designed for A medium size transformer measuring 96 (L) x 96 (W) x BO (H) :AR ELE workshop, laboratory or serious hobbyists. It can measure :AR EU mm. 'AR ELE capacitance from 1pf up to 9999uf in seven ranges with an Primary AREU accuracy of better than+/· 1%+/· 1 digit. Kit is complete with 2 x 120 V 50hz (240 V) .ARELE all components required to finish construction. 1 x 110V 'AREU Secondary :AR ELE Cat KC-5075 10.5V 3A AR ELE 16V3A AR Elf AR EU &~ AREU Normally $70 each s . 'AR EU Limited quantity available AR EU 'AR EU 'AR EU Mail orders add $4 extra P & P. 'AR EL£ Texas brand, save a fortune on normal prices. Cat. MM-2045 l\REU AREU Normally about $25 ea AR EU Cat. RU-6714 AR ELI 'AR ELI AR ELI AR ELI Jaycar will purchase your surplus stocks of components AR EU and equipment. We are continually on the lookout for AR ELI sources of prime quality merchandise, AR ELI AR ELI AR ELI 10+ $11.50 ea AR ELI AR ELI AR ELI AR ELI AR ELI :AR ELI Full range available AR ELI 10' 65WRMS Cat. CG-2376 $59,50 AR ELI 12' 65W RMS Cat. CG-2379 $59.50 :AR ELI $89,50 12' 100WRMS Cat. CG-2380 :AREU 12' 200WRMS Cat. CG-2381 $159.00 AR EL: Refer silicon Chip May 90 15' 150WRMS Cat. CG-2832 $129.00 -AR EL Designed for cars with Reluctor distributors, this ignition kit :AR EL Importers distress, your gain! features improved protection for the coil and main switching :AR EL 220mm long, yellow handles, super high quality. Normal trade transistor. :AR EL price is $35.04 including tax. Kit includes PCB, die cast box and all components to finish :AR EL Cat. TH-1875 :AR EL the kit :AR EL KC-5076 :AR EL 'AR EL AR EL AR El AR EL AR EL AR EL AR EL AR EL :;AR ELE(;.,,_.,,_w,,,_,,, , LLL~"'- " ' __ , ,, _,,,. ____ ,,, _ , ,. ___, ,._, ,,, ____ __ ,_,_ , _ _____ _, .. , ___ _ __ _, •_ _ .. CTROI CAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONI CSJAYCAR ELECTRONICSJAYCAR ELECTRONICS JA YCAR ELECTRO! CAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS JAYCAR ELECTRO! CAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS JA YCAR ELECTRO! CAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS JA YCAR ELECTRO! ~ ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS JA YCAR ELECTRO! ... --.. ,-,____.,,.__,.,,,.,.,._......_u._..,._""~ ...,.., 0 • o r , rc:r:n o111cc I AVC AD Ci CCT0O II. II CC: IAYC AP F I FCTPO I\.IICS IAYCAR Ft _ECTA() N.JCSIAYCAB El FCTRCllilCSJAYCAB E._LECTRONICSJAYCAR ELECTRO! Refer Silicon Chip June 90 Ideal for a magnetic cartridge, tape player or microphones. Shortform kit, includes PCB swi cable and all electronic components. No box front panel or panel hardware supplied. Refer Silicon Chip June 90 This add-on board prevents dangerous voltages from being delivered to a load by any dual trackng power supply when it is turned on or off. Shllft form kit Includes PCB. relay and all specified components. $17.95 $32.95 Ferguson Transformer Bargains VARTA BATTERY MADNESS PF-4725 ONLY $1 each 10+ .90~ each 100+ . 75~ each 5mm 3000 MCD LED A bargain at $30 each ONLY $3.95 1p F · 9999uF Capacitance Meter Kit PF-4766 $109 Only $20 each TURN YOUR SURPLUS STOCK INTO CASH!! Philips Computer Capacitor Bargain 84 Pin PLCC Socket SALE 15,000uF 40V Can 1.9 10 • 99 100 up $2.95 ea $2.50 ea $2.00 ea THIS LOT ONLY $12.95 ea CALL BRUCE ROUTLEY OR MARK HARRIS NOW ON (02) 747 2022 Guitar Speakers I I I I I I $46.95 I High Quality Electricians Pliers Sale GRAB A PAIR FOR YOUR TOOL BOX ONLYS12.95 ~ --~~ . _ _ _ . .. - • · · - - , , - , " , 1-1...Lv __.. - · .. . ____ . . ·-· .. - ~ , -nn L'-'-", m,m~" r """ tU:l; 1HUNlc;SJA YCAR I nVl~t \..,.;),JM. f\.,I\N t:Ltc.; I HC>NIC ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS.JAYCAR ELECTRONICS.JAYCAR ELECTRONIC ~ ~~~;~~:~JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS.JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS.JAYCAR ELECTRONICSJAYCAR ELECTRONIC R ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONIC R ELECTRONICSJAYCAR ELECTRONl~YC~~ ~~CTRONI~~~~ ~~~TA~~!~~~~~ ~LECTRO~!C~~CAR ELECTRONICSJAYCAR ~~~TR()NIC!l.JAYCAR ELECTRONICSJAYCAR ELECTRO~:g ~ ·\tf.. · · ... ... .. · ·· · · ....................................................,,,,tr=···..... .......................... · ....... · .. ... .. ..........,,,,=<at> mg:: · · Magnavox BMV 8/30 Replacement R ELECTR< ELECTR< ELECTR< ELECTR< ELECTR< R ELECTR< R ELECTR< R ELECTR< R ELECTR< R ELECTR< R ELECTR< R ELECTR< R ELECTR< R ELECTR< R ELECTR< R ELECTR( R ELECTR< R ELECTRC R ELECTR< R ELECTR< R R R R ndled Update your B/30 woofers • today! The old B/3()'s ha 120 30 watts these watts rms. No need to·buy new cabinets - the BMV mounts in the.same hole. High quality and high performance woofer for most applications. Power Handling 120 watts rms Resonant Freq. 31 Hz Freq. Range fa. 4kHz Voice Coil Dia. 38mm Magnet Weight ~s 510 grams Oto 080.3L7 ~:!~ ____.,.~!'.:'\!! ~ ~t~g:; '99.50 NOW •59 50 • ■ A VE '40 WAS r Magnavox 12MV :: d.The 12MVis a high power high fidelity woofer utilising a 38mm I th · ·1 nd I ·· f : 'f Magnavox SW Woofer . The 'iJN Mk6 is a high fidelity woofer utilising a 25mm diameter long thrrm voice coil wound on an aluminium former and a high compliance suspension with a .polyurethane foam roll surround, resulting in excellent linearity at high power. Power Handling 65watts rms Resonant Freq. 39.5Hz Freq 39.5Hz • 5khz · range 96d8/1w/1mt Sensitivity Voice Coil Dia. 25mm OMS 2.317753 QES 0.5470474 0.4425861 OTS VAS 3.241097 Iameter ong rrm voice COi wou on an a ummIum armer and high compliance suspension with a polyurethane foam roll surround, resulting in excellent linearity alVBIY high input powe,3. Power Handling Resonant Freq. Freq Ra ·.. nge SenSJIMly . Magnet Weight Oms 0es Oto Vas C "'" 2125 at.,,.. 150 watts rms 19Hz fa. 9(Hz WAS '119 • 50 1 96d 8grams 510 3.76 0.58 '--------~ 0.49 580L NOW 79.50 SAVE S4Q I ,, Cat CW-2109 WASS39.50 NOW '24.50 SAVE 1 15 o;;;a=-::----~ RELECTR< ; R ELECTR< R ELECTRC R ELECTRC R ELECTRC R ELECTRC R ELECTRC R ELECTRC: 111::}::::,.,.,.,.,., .......•. , ,,,,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,·,····=''~::::::,,,....,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,,,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,.,,..·':..,,,:,,,,,,,::: ~ ELECTR< ~ ELECTRc' ~ ELECTRC: l ELECTRC: Unbelievable Distress Stock Purchase Unbelievably cheap but there's a catch! ~ ELECTR< 1 ELECTR<: We have obtained a quantity of new (removed new from brand new eq_uipment) These were i~luded in our 1987 Catalogue and were selling for $39.95 each. 1 ELECTRc' computer switchmode type power supplies. They have outputs of +SV 2A. +12V 30mA. • We have purchased the entire quantity from the importer who was told to clear all stocks at any · 1 ELECTR( 12V 30mA. & 12V 2A. The problem is that they are 110\/ powered and NOT 24fN. You price! l ELECTR< can use them for parts at this bargain price. Cat MP-3000 ■ The unit is not the most accurate in the world, but it will give you sorre idea of the pH and l ELECTRC Chlorine lfMJls. The two prooos are inserted in to the water to be tested. An instant reading of the l ELECTR( l ELECTRc' Chlorine lfMll and pH value is given on the panel meter display. • I ELECTRC We emphasise that this offer is more a bargain for the parts. The meter for I ELECTR< example,isworth$10alone.Thecase/probe I ELECTR< could be used for all sorts of things! I ELECTR< I ELECTR( CatOM-6135 WAS $39.95 ••eh il I ELECTR< : ELECTR( ELECTRC ELECTR(. ELECTR( ELECTR( ELECTRC ELECTRC ELECTRC Machine Pin Type ELECTRC 16 Pin normally $1.50 each ELECTR( ,:.: SolderType Now 3 for $2 Save $2.50 ELECTRC . 20 Pin normally 48' each Cat No. PI 6456 J SWITCHMODE POWER SUPPLY pH CHLORINE METER sg 95 NOW ONLY , s9_95 :, .. IC SOCKET MADNESS ~~g;~~ ELECTRC ELECTR( ELECTR( ELECTRC ELECTRC ELECTRC ELECTRC ::LECTRC ::LECTRC ::LECTRC ::LECTRC :LECTRC ,LECTRC :LECTRC 'LECTRC :LECTRC :LECTRC II\,. ....................................,,,fiill!! Probe Type Digital Multimeter 3 .1/2 Digits• Manual or Auto Range with Loaic Probe ~gi~~ t~g:g _ECTRC 1gi~g _ECTRC :~gi~g CTRON f ~'7'N~4tf~7 Saves1.ao $59.95 t~gi~~ :, LECTRC LECTRC LECTRC LECTRC 7~ ea:~ SS.SB This fantastic 31/2digit meter is actually easier to use than a conventional hand-held unit The readout is in the body of the 'probe' itself so you don"! have to avert your eyes to get a circuit reading. The unit has most of the features of conventional meters as well! Logic Probe Bonus. This TTL/CMOS compatible feature will test-logic 'HI' or logic 'LO'. The circuit is protected to 250\/. All electrical symbols are shown in the large (42mm x 18mm) windDIN. · Cat OM-1420 :tigi=~ It,!·!•.•. •·· · · ·•·•·•·•· ···· ·•·•·•·•·••·•··•·•·• LECTRC ~~%~:: .·.·•·•·•···•··•·····•·•·•w····· .·.•·•••·•·•···· ·.·.·.·.·.•.•.•···.·.·.·•.•.w.·.·.•.•.•.·.·• 18 Pin normally $1.65 each Now 4 for $2 Save $4.60 Cat No. PI 6458 20 Pin normally $1.90 each Now 3 for $2 Save $3.70 Cat No. PI 6460 22 Pin normally $2 each Now4for$2 Save$6 Cat No. PI 6462 24 Pin normally $2.30 each Now 3 for $2 Save $4.90 Cat No. PI 6464 28 Pin normally $2.60 each Now 4 for $2 Save $8.40 Cat No. PI 6466 40 Pin normally $3.25 each Now 3 for $2 Save $7.75 Cat No. PI 6468 Iii: CODE-A-PHONE REMOTE ANSWERING MACHINE The Code-A-Phone is a top quality remote control answering machine which is simple to use. It features Digital Recording whereby your voice is recorded on a microchip. Special features include: • dual recording • personal greeting • call screening • personal memo record • one touch playback • digital message counter • answer only/message limit• ring selector• tape saver• automatic on • fast forward and rewind • easy to replace microcassette • expanded message length • REMOTE CONTROL FEATURES: 13 function beeperless remote control • remote on • personal 3 digit security code • fast forward/rewind • greeting change • greeting breakthrough • save messages • cancel :::~~::,11 saver • last message indicator • full tape retrieval • repeat playback • personal • This answering machine has fMlry feature that you will fMJr require in an answering service. One year 89 warranty. A qua,ir u ':'-. Cat YT-7032 CTRON. _ ___. . -· ,.1,,.1',. i, . ,:._ ;o;;,;; ;;; ,•.,;; ;,;; i...i...i..v ; ;;v, . ,.;,.,~;..,;n,; ; i....i....i.....;...,· ;;ov·• • .....,•..;•.iF. i.;_,,ni; LL._,v,.,..,, ,.,...,-.M'"'\ 1vr11, "-'-._...,, ,,..,, ,.. ' - ' ~ '"""" 1.-LLv1nv1'u'-'......,"' ' ...,l'Vl 1-LCv 1nu 1't1v,;:,,.,,n1 v l"\n c 1-cv 1 MV Nl v .:>.»\ TVl"\M CTRONICSJA YCARJAYCAR ELECTRONICS.JAYCAR ELECTRONICSJAYCAR CTRONICSJAYCARJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR CTRONICSJAYCARJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR CTRONICSJA YCARJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ...,TD"~llr"'C' IAVr-A n '"''"'" n rt ,-,..,-n,...• ,.,...,... •• ._.,,... • n ,-, .-,...-,..r,,... .... ,..,.... , • ...,,,....,., CTRO c.LECTRO ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRO ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRO ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRO ELECTRONICSJA YCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRON!~ ELECTBQ r , ,..,..."TT"'l,....,11,-.,-. •• vr-A n .-, ,-,...,..n,..., 11,-.,-. ••v,... An ,-, ,..,...~ .. u ;AR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS.JAYCAR ELECTRONICS.JAYCAR ELECTRONICSJAYCAH l:Ll:t; I HO N IG::i.JA YG AH tLtLl I H U Nl <.;<;JA YLlAH t:L t:v I HUNl'-"' ELECTRONICSJAYC, :AR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS.JAYCAR ELECTRONICS.JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS ELECTRONICSJAYC, ;AR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSELECTRONICSJAYC, : AR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSELECTRONICSJAYC, ;AR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSELECTRONICSJAYC, :AR ELE•, SJAY_C, ELECT ELECT fLECT ELECT ELECT ELECT ELECT ELECT ELECT ELECl The release of several major competitors product catalogues recently ELECl enabled us to check our prices against theirs. We were not suprised ELECl ELECl when on identical items we found we were over 60% cheaper than our ELECl competitors on some products. ELEC' ELECELEC" ELECJaycar has built up an enviable reputation of providing good quality ELECproducts at very reasonable, realistic prices. We won't be undersold on ELECELEC" items of the same quality but, frankly, why bother? Our prices are lower ELEC. anyway. ELEC ELEC ELEC Jaycar Them Jaycar Them % % ELEC Savings Savings ELEG ELEG Heatshrink Tube 10mm 3.00/1 mt 4.50/1.2mt20% Audio lead 5 Pin Din - 5 Pin Din 4.50 5.95 24% ELEG Power Supply 3-6-9-12 V 1 Amp 34.95 39.95 12% Outdoor Balun 75/300ohm 3.75 5.95 37% ELEC 1.9 AH Gel Battery 18.95 32.95 42% ELEC TV Set Balun 2.25 3.95 43% ELEC CSize Nicad Battery 1.2 Ah 6.50 9.95 35% Indoor 75ohm Splitter- 2 Way 5.95 7.95 25% ELEC 555 Timer Applications Book 16.95 24.95 32% Balun Socket -Line 2.25 4.95 55% ELEC 23% Design of PLC Circuits Book 22.95 29.95 Burglar Alarm Pressure Mat 19.95 24.95 20% ELEC Magazine Binder 7.95 8.95 11% Digital Therm - Body Temp 14.95 19.95 25% ELEC Budget Disks 5.25 DSDD Pk 10 6.50 9.95 34% Telecom Phone Plug 2.95 4.95 40% ELEC 15% Budget Disks 3.5 DSDD Pk 10 16.95 19.95 Computer Printer Cable 18.95 24.95 24% ELEC 18% ELEC 14 - 16 Pin IC Inserter 8.95 10.95 Freezer Spray (vol may differ) 9.00 22.95 60% ELEC IC Extractor 2.95 25% 3.95 Air Duster (vol may differ) 7.95 24.95 68% ELEC 8000 UF 75 V CAN 17.75 24.95 29% Desoldeiwick 2.50 2.95 15% ELEC 25% BC547. 548. 549 .15 .20 18m Roll Insulation Tape 1.00 1.95 49% ELEC PN100, PN200 .25 .35 28% Tweezers - Pointed 1.95 2.95 33% ELEC 23% 2N3055 2.25 2.95 Neon Test Scl'e'Mlriver 2.75 3.95 30% ELEC 2732A 10.95 15.95 33% Pack 300 1/4W Resistors 6.50 9.95 35% ELEC ELEC 555Timer IC .70 .95 26% Pack 60 Greencaps 7.95 15.95 50% ELEC Blank SS Rbre/g PCB 300 x 300 9.95 15.95 37% Pack55 Electrolytics 7.95 15.95 50% ELEC Pack 100 5mm Red Leds 15.50 28.95 46% ELEC 5600UF 40 V Capacitor 9.50 24.95 62% ELEC Pkt 50 PC Pins 1.90 3.95 52% ELEC Pk! 25 PC Sockets 3.50 5.95 41 % ELEC 75mm Sid Heatsink 6.95 9.95 30% ELEC ELEC 4' 240 V Fan 24.95 29.95 16% ELEC Pkt 4 T03 Insulating Mica/Bush 1.30 1.95 33% Ideal for the hobbyist and ELEC T0220 Clip Dn Heatsink 1.20 1.95 38% handyman. Our lowest price ELEC T03 Powerfin Heatsink 2.50 3.50 28% ELEC 24W quality iron has a Brass Spacers - Clearance 9mm 1.30/8 Pcs 5.50/10 70% ELEC stainless steel barrel. 30 ■ Quality Electrophone Brass Spacers - Clearance 25mm 1.40/4 Pcs 5.50/6 Pcs 62% ELEC watt. Brand 5mm LED Mt Bezels 1.90/20 1.95/15 27% ELEC Cat. TS-1450 ■ Two way htercom ELEC Pkt 4 Big Rubber Feet 1.75 2.50 30% ELEC Pk! 8 3AG Fuse Clips 1.20 1.95 38% paging facility ELEC Cable Joiners - Scotchlok 1.25/4 Pcs 1.'15/2 Pcs 50% ■ Recharge socket on ELEC Metal Box 150 x 76 x 134mm 7.50 9.95 24% handset ELEC Hoiwod 6' Box 33.95 39.95 15% , ELEC ■ Pulse/fone dialling 25 Pin D Plug 1.95 3.95 50% , ELEC ■ 12 months warranty{ , , ELEC 'l5 Pin D IDC Plug 5.95 7.95 25% ■ Superb sound, a , ; it , ELEC 9 Pin Din D IDC Plug 4.95 6.95 28% qua! ity product \:< f, , ELEC 8 Pin IC Socket .20 .25 20%. , ELEC Cat. YT-7068 Multi Turn Trimpots 1.95 2.95 34% , ELEC SP Bedlamp SWitch 1.50 1.95 23% , ELEC 4 POT Mini Toggle SW 6.75 13.95 51% , ELEC Mercury SWitch 2.25 4.50 50% , ELEC , ELEC Heatshrink Tube 5mm 2.25/1 mt 3.50/1.2mt23% , ELEC , ELEC ELE< MAIL ORDERS POST a PACKING ELE< You can save over When buying at Jaycar! Jaycar Soldering Iron 10 MEMORY CORDLESS PHONE ·----- $16.95 » ONLY $279 •~ ~~ ;1;• ~, . ; n -•:(■--'.::'. iLI ··a-· 0 21 37 .JP~.Ou. .!:!Bollx.1r.l.1.1u..Cou.7.:1a~~i. ~!£:d5!li . !..._ $ 3.75 4 50 $ 6 50 "''ER $lOO $ · -=:::::;:=:=::::::::::=:=:::::::::::::!__:u:'.!,::•:!.!,!~--_,!$8!;!.00~~====!!!!!!::==~ Telephone (02) 747 2022 FOR ORDERS ONLY FACSIMILE (02) 744 0767 TOLLFREE 008 022 888 ___________ GORE HILL $10-$24.99 ::::: !~!l ELE< ELE< ELE< ~t~: 188 Pacific Hwy (Cnr. Bellevue Ave) (02) 439 47999 5 30 9 4 -Mon-Fri - . sat - pm ELEt 144 Logan Rd (07) 393 0777 ELE1 PARRAMATTA Mon-Fri 9 • 5.30 Thurs 8.30 • Sat 9 - 12 ELE1 l!!!ll;;;;;;;l!'-!!!~;;;;;;;;:::::.:;=::..J Shop 2, 45 A'Beckett St City (03) 663 2030 ELEI Mon-Fri 9 _5_30 Fri 8.30 • Sat 9 • 12 ELE< CONCORD ELE• ..,......., ~zrrA 887-889 Springvale Road Mulgrave (03) 547 1022 1 rA ~ HURSTVILLE Nr Cnr. Dandenong Road Mon-Fri 9 - 5.30 Fri 8.30 - Sat9- 2 190 Wright Street (Cnr Seib'( Street) (08) 231 7355 ELE• Mon-Fri 9 • 5.30 Fri 8.30 • Sat 9 • 12 ELE• ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRON! YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELEC ONICSJAYCAA ELECTRONICSJAYCAR ELECTRONICS •~ • ELE ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICS JAYCAR ELEE ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS JAYCAR EL IIIEEB JAYCA JAYCAR JAYCAR JAYCAR 85 1 ~ ~a~ a~:tfa ~o~ d Concord 2137 SYDNEY - CITY 117YorkSt(02)2671614Mon-Fri 8.30 • 5.30 Thurs 8.30 pm. Sat 9 -12 BURANDA QLD 355 Ch urc h st (C nr. Viictoria Rd ) (02) 683 3377 MELBOURNE-CITY Mon-Fri 9 - 5.30 Thurs 8.30 pm · Sat 9 · 4pm 115 Parramatta Rd (02) 745 3077 Mon-Fri 8.30. 5.30. Sat 8.30. 12 SPRINGVALE VIC Forest Rd (02) _ 121 5707000 Mon-Fri 9. 5.30 Thurs 8.30 pm. Sat 9. 4 ADELAIDE S.A. ~t~: ~~~~~ ~~~!~~NI~~~~~~~~~~!~~~!~~~~~~ ~~~:~~!~~;~~~ ~~~~~~~!~~~~~~ ;L~~~!~~~~~~ ~~~~:~~!~;~~~ ~~~~!~~~!~~~~~ ~~~ ~~~~~t~ Burglar alarm keypad & combination lock This keypad combination lock can be used to arm/ disarm your house or car alarm, or to activate a solenoid-operated door strike. It will also trigger the alarm when it detects seven consecutive incorrect entries, to defeat unauthorised tampering. By GREG SWAIN Although burglar alarms are a good idea, they can also be very inconvenient to operate. In particular, you always have to be sur8 to leave or re-enter the house during the fixed exit and entry delay periods to avoid falsely triggering the alarm. Another drawback is having to fumble around for the alarm key each time you want to switch the alarm on or off (ever accidentally set off your alarm and 28 SILICON CHIP couldn't find the key?]. Now you can have all the advantages of a home burglar alarm without the disadvantages . This easy-to-build Burglar Alarm Keypad is designed to mount near your front door and lets you turn the alarm on or off by pressing a few buttons. With this device, there's no need to make a mad dash for the front door as soon as the alarm is armed. Although designed for the MultiSector Burglar Alarm described in the June 1990 issue of SILICON CHIP, the Burglar Alarm Keypad will suit just about any house alarm circuit. It uses easy-to-get parts and is a snack to build and get going. Typically, the keypad would be mounted just inside your front door but it could also be mounted in a weatherproof case just outside the door. In the latter case, you could get rid of the exit and entry delay periods altogether and just wire the alarm for instant triggering. Other possible applications of the device include switching mains power to a computer or some other appliance to prevent unauthorised use, switching a telephone line, arming/disarming an ignition killer circuit in a car and controlling power doors on garages. 22k ------------....------- ------0+12VDC INPUT 14 01 7 4 CK 03 04 10 2 g CK IC2d 4093 IC1 4017 01 12 01 CE 3 00 RST CE 15 8 13 02 BC548 ':' .,. .,. +V MONO B ALARM TRIGGER IC3a 04 EO c +v 16 1D CE 02 03 WIRE LINK PRE SET S (758 #) 011 16 ,, LATCH 330k +V VIEWED FROM BELOW BURGLAR ALARM KEYPAD Fig.t: initially, decade counter ICt is reset & QO is high. If the correct code keys (758#) are pressed, the counter is clocked and the Qt, Q2, Q3 & Q4 outputs switch high in sequence. The high on Q4 then turns on transistor Qt for monostable operation or toggles counter IC3b for latched operation. IC3a counts the number of incorrect entries. Operation To activate the lock, you just press four keys on the keypad in the correct sequence. When this happens, the circuit switches a relay whose contacts are wired across the ARM/DISARM switch of the burglar alarm. However, if you strike an incorrect key during the code entry, the circuit automatically resets and you have to start again. A LED indicator at the bottom of the keypad lights whenever the circuit is armed (ie, when the relay contacts close). This LED could also be mounted at some remote location or it could be left out altogether if you don't want it. You select your own 4-digit code when building the unit, by installing wire links on the PC board. You also have the option of wiring the circuit to provide latched or monostable relay operation. This involves installing a single resistor in one of two positions. In the latched mode, the relay changes state each time the correct 4-digit code is entered. If you want to turn a burglar alarm on and off, this is the mode to use. Alternatively, in the monostable mode, the relay contacts close for only a short period to activate a door strike or whatever. put open circuit to set off the alarm. y OU can ignore the ALARM TRIGGER output if you don't wish to make use of this feature . It can be regarded as a useful optional extra in security applications. Coding How it works As can be seen from the photographs, there are 12 keys on the keypad: the digits 0-9, plus * and # keys. Any four of these keys can be used for coding while pressing any of the remaining keys will clear (or reset) the circuit. In practice, you would normally decide to use one key only to reset the circuit if you run into any problems during code entry. For example, you might decide to always use * as the reset key and choose the code 09#5. Alternatively, you could choose an all digit code (eg, 7581). Because they can be included as part of the code, the * and # keys dramatically increase the odds against someone guessing the correct code. And what are those odds? Well, assuming the person knows that he must enter a 4-digit code, the odds are greater than one in 20,000. Even if he knows that the same number cannot be used consecutively (which it can't), the odds are still approximately one in 16,000. What's more, if the circuit detects seven incorrect key entries, it switches its ALARM TRIGGER out- The circuit is simple yet ingenious - see Fig,1. There are just three low-cost CMOS ICs, two transistors, a relay, a small keypad and a few other minor components . Let's see how it works. IC1 is a 4017 decade counter with 10 decoded outputs. Its Q0-Q3 outputs are connected to lines 1, 2, 3 & 4 via isolating diodes D1-D4. Each of these lines in turn connects to one side of a single key while the remaining keys all go to the Clear [C) line. The other sides of the keys are commoned and connected to the clock (CK) input of IC1. Fig.1 shows the circuit configuration for a code of 758#. That's because line 1 is connected to key 7, line 2 to key 5, line 3 to key 8 and line 4 to#. The code can be changed simply by connecting different keys to each of these lines. Initially, IC1 is reset which means that Q0 is high and its other outputs are all low. Now let's assume that the correct code is entered. When key 7 is pressed, a positive going clock pulse is applied to pin 14 of ICl via D4 and the closed key contacts. This clocks the ]UL Y 1990 29 PARTS LIST FROM ALARM KEYPAD _.....:----0----<>-----<>--->---0 1 TO SECTOR INPUT 1 1 HO AHO NC SWITCHES Fig.2: here's how the ALARM TRIGGER output is connected to the alarm sensor wiring loop. Note that some circuits will require a different value of load resistor. In that case, just substitute the required value for the 10kQ resistor shown. 1 4 4 4 4 PC board , code ZA-1450, 105 x 50mm (copyright DSE) PC board, code ZA-1451 , 85 x 50mm (copyright DSE} keypad , DSE Cat. K-8403 12V SPOT relay, DSE Cat. S-7120 6-way PC terminal block 6mm spacers 6BA x 1 2mm machine screws 6BA nuts 3mm nuts (for use as keypad spacers) Semiconductors counter which clears QO (ie, switches it low) and sets Ql high. Pressing key 5 now applies a further clock pulse to pin 14, this time from Ql via D3. This clears Ql and sets QZ high. Similarly, Q3 switches high when key 8 is pressed, while Q4 switches high (and Q3 clears) when # is pressed. Thus, Q4 switches high each time the correct 4-digit code is entered. However, if an incorrect key is pressed at any time (ie, any key connected to the clear line), pin 1 of Schmitt NAND gate ICZa will be pulled low by the 22krl resistor on pin 14 of ICl. This switches pin 3 of ICZa high and resets ICl, which means that you have to start all over again. When Q4 of ICl switches high (when the correct code is entered), Below: the parts are all assembled on two PC boards which are connected by short wire links. The keypad board is then folded over & mounted on the back of the main circuit board. it clocks IC3b which is one half of a dual BCD counter. This sets QO (pin 11) of IC3b high. If the circuit is wired for latched operation, this high turns on transistor Ql which then switches on the relay and the LED indicator (LED 1). The high on Q4 also charges the O. lµF capacitor on pins 5 & 6 of ICZb via a 330krl resistor. After a brief delay (33ms with the values shown), pin 4 of ICZb switches low and resets ICl via ICZa (ie, QO high and all other outputs low). The O. lµF capacitor (Cl) then discharges via the 330krl resistor (Rl) into Q4 to remove the reset signal from ICl after about 33ms. This resetting procedure has no effect on IC3b as it responds only to positive-going clock signals. Its QO output can only be cleared by entering in the correct code again. When that happens, Q4 of ICl switches high again and IC3b switches its QO output low. Thus, QO of IC3b changes state each time the correct code is 1 4017 decade counter (IC1) 1 4093 quad Schmitt NANO gate (IC2) 4518 dual BCD counter (IC3) 2 BC548 NPN transistors (01,02) 4 1 N4148 diodes (D1 -D4) 1 1 N4002 diode (D5) 1 5mm red LED (LED 1) Capacitors 2 0. 1 µF monolithic 1 1 µF (C 1 , monostable operation only) Resistors (0.25W , 5%) 1 1 Mrl (R 1 , monostable operation only) 2 330krl 1 1 Okfl 3 22k0 1 1.5krl entered, to switch the relay either on or off. For monostable operation, output Q4 of ICl drives transistor Ql directly via its zzkn base current limiting resistor. As we 've already seen, Q4 goes high each time the For Features and Perl ormance ... YOUR COMPLETE ALARM SUPPLIER DOMESTIC RADIO REMOTE CONTROL SYSTEM. This unique system comes in 2 models - a single channel and a dual channel. the single channel can be used to trigger the alarm's 24 hour/panic sector. These remotes have a user programmable code, are crystal locked so they never need adjusting, and have an incredible range of up to 200 metres. Each system comes with 1 receiver and 2 key ring mount transmitter keys. DOMESTIC SINGLE CHANNEL REMOTE $228.00 DOMESTIC DUAL CHANNEL REMOTE $288.00 ADDITIONAL KEYS SINGLE CHANNEL TRANSMITTER KEY $66.00 DUAL CHANNEL TRANSMITTER KEY $78.00 CAR REMOTE CONTROL. We also have a Car Remote Control that can be added to most brands ol car alarms. The remote pulses your car's indicators 3 or 4 times and isolates the ignition, fuel pump or starter motor as it turns the alarm ON. The remote gives 1 long pulse when the alarm is turned OFF and again these remotes have a range of up to 100 metres. CAR REMOTE CONTROL $132.00 DOMESTIC ALARM SYSTEM. Our DA3-1 M is an Australian made, 4-sector, keyoperated Domestic Alarm System. It features user programmable Home or Away mode; Reset or Latch mode; Handover mode on sectors 1 to 2, 1 to 3 or 1 to 2 & 3; Adjustable Entry delay time; Entry Buzzer with pulsed, constant or silent mode; 24-hour tamper on Sector 4; plus a separate 24 hour Panic monitor with a panic button on the front panel and input for an optional external panic button. Our alarm has a built-in siren and seperate siren driver for an external horn speaker, a strobe light output, a trigger output to operate a dialler and a low battery indicator. The alarm comes with an AC adapter and a 6.5A back-up battery. The unique feature of this alarm is its low standby current when operating on a battery. Requiring less than 20mA, the alarm is ideally suited for Battery Only or Battery and Solar Panel operations in Marine, Caravan or Remote area uses. D3-1M HOUSE ALARM $288.00 PASSIVE INFRA-RED DETECTOR. The ASPIS 10 Passive Infra-red detector has superb RF protection, 110 degree coverage, 25-metre range and a dual element pyroelectric detector. There is also a programmable pulse count, adjustable sensitivity, and vertical adjustment zone pattern. The detector uses sealed chamber technology so it can be used with fans, air conditioners or in a semi-open location. You can also install the detector flat or corner mounted at varying angles. ASPIS 10 PIR DETECTOR $78.00 COMPLETE PACKAGE SPECIAL OFFER 1 x DA3-1 M Domestic Alarm System (includes 6.5A battery & AC adapter) 2 x ASPIS 1O Passive lnfa-red Detectors 2 x Surface Mount Reed Switches 1 x Siren Cover With Tamper Switch 1 x 8 ohm 1OW Horn Speaker 1 x Large Blue Strobe Light 1 x 4-core 7/0.20 1OOM Roll of Cable 1 x Fig 8 14/0.14 1OOM Roll of Cable $288.00 TOTAL PACKAGE DISCOUNT $569.40 49.40 SPECIAL PACKAGE PRICE $520.00 WE ALSO SELL A RANGE OF ALARM ACCESSORIES Large Blue Strobe light Telephone Dialler Surface Mount Reed Switch Roller Door Reed Switch 8 ohm 1OW Horn Speaker lnfa-red Auto light Globes for Auto Light 12V 15W Warble Siren Horn 12V 11 OdB Screamer Tamper Switch 4-Core 7/0.20 1OOM Cable 6-Core 7/0.20 1OOM Cable Fig-8 14/0.14 1OOM Cable 12V 6.5Ah Gel Cell Battery 1.5 amp 18VAC Plug Pack Siren Cover W/Tamper Switch Automotive Digital Ignition Disabler DAS 20BL 8-Sector Alarm Panel DAS 208M 8-Sector With Built-In Dialler OTHER SYSTEMS AVAILABLE INSURANCE RECOMMENDED MODELS $ 27.00 $168.00 . $ 7.20 S 36.00 S 13.20 S 70.00 $ 6.60 S 22.20 S 20.40 $ 1.80 $ 30.00 $ 48.00 $ 16.80 $ 36.00 S 30.00 S 24.00 S 60.00 $420.00 $600.00 VISA Ring for a FREE complete brochure pack Cheque or Money Order $156.00 $ 14.40 $ 24.00 $ 13.20 $ 27.00 $ 30.00 $ 16.80 ffi AUTOMATIC ALARMS & ELECTRONICS C/- TARRAWANNA POST OFFICE NSW 2518 Call us FREE on (008) 02 4897 9am to 8pm A.H. (042) 84 0403 Freight FREE lor orders over $200.00 High sensitivity- 1mV/dlv 8tab/e low drltt design 8 divisions of displayed dynamic range with accurate distortion-free waveform measurement Special TV sync separation circuits for measurement of video signals Delayed sweep function Convenient XY operation to, measuring phase dlg,rent:ill. between two waveforms Variable sweep control Incorporating x10 magnifier Uncal and trigger warning lights TV-V& TJ(·H triggering Trigger hold-off OS1020A $85llu1u1111.••tar• (0S7040A) OS104IJA $1045 :t3% accuracy • Cursors for direct measurement of waveform voltage, time and frequency • 20MHz bandwidth n,.,,.,,,-,.. • 1mV max sensitivity • Similar performance to 0S7020A OS8020R $1045 n•$1ZO.S51111:IB" Supported & Serviced Australia-wide by Elmeasco Instruments pty Ltd Dealer enquiries welcome. Call {02)736 2243 ·Recommended prices only You've Gotta Getta Goldstar from: A.C.T. John Pope Electrical 80 6576 N.S.W. Ames Agency 699 4524 • D.G.E. Systems (049) 691625 • W.F.Dixon (049) 69 5177 • Macelec (042) 29 1455 • Newtek (042) 27 1620 • Novacastrian Electronic Supply (049) 62 1358 e Obiat Ply Ltd 698 4776 e Digitel 709 6511 e Geoff Wood 427 1676 . N.TERRITORY J Blackwood (089) 84 4255, 521788 e Thew & McCann (089) 84 4999. QUEENSLAND St Lucia Electronics 252 7466 e BAS. Audiotronics 844 7566 e The Electronics Shop (075) 32 3632 • Solex (Townsville)(077) 72 4466 • Xanthos Electrical (079) 27 8952 $.AUSTRALIA Elmeasco (08) 344 9000 VICTORIA G.B. Telespares 328 4301 • The Electronic Components Shop 670 6474 • Factory Controls (052) 78 8222 • Mektronics Co 587 3888 • Truscott Electronics 723'3094 W AUSTRALIA Atkins Carlyle 4811233 e Leda Electronics 361 7821 PAPUA NEW GUINEA T E (P.N.G.) Pt Moresby 25 6322 Lae 42 6246 LEOl K (!) A [] □ EJ [:] □ □ [] [:] 7 • .. • [:][:JC:JG Fig.3: for latched operation, connect the 22kn resistor adjacent to Qt to point L; for monostable operation, connect the resistor to point M and change Rt & Cl. The diagram shows how the wire link presets are installed for a code of 095# but you should devise your own code. correct code is entered. This switches transistor Ql on to close the relay contacts for the period set by the RlCl time constant (note: these values are increased for monostable operation}. Incorrect entries IC3a counts the number of consecutive incorrect entries when the circuit is armed (ie, when QO of IC3b is high}. Each time an incorrect number is pressed, pin 1 of IC2a is pulled low and pin 3 switches high to generate a reset pulse for ICl. This reset pulse also clocks IC3a (pin 1}. After eight reset pulses (one pulse from entering the correct _,_,.,.,, ...__ _ 'C · .. ) \ combination plus seven pulses from incorrect entries}, Q3 of IC3a switches high and IC2c turns off transistor Q2. It also pulls the clock enable (pin 2) low to disable the counter, so that the Q3 output (pin 6} stays high. Transistor QZ functions in the same way as a set of normally closed sensor contacts. When it turns off on the seventh incorrect entry, it immediately triggers the external alarm circuit. Fig.2 shows how the ALARM TRIGGER output is wired to form part of the resistive wiring loop to the alarm sector input. The circuit is simply substituted for the 10k0 load resistor that's normally included in the loop to the MultiSector Burglar Alarm. (Note: some alarm circuits may require a different value load resistor. In this case, the required value should be substituted for the 10k0 resistor shown}. IC3a is reset when the correct code is entered to disarm the circuit (and switch off the alarm}. As soon as the correct code is entered, QO of IC3b goes low and IC2d pulls IC3a's reset terminal (pin 7) high. This switches Q3 of IC3a low and turns on transistor Q2 via IC2c to simulate closed sensor contacts. IC3a is held in the reset state for as long as the circuit is disarmed. Construction All the parts are mounted on two small PC boards coded ZA-1450 and ZA-1451. The ZA-1450 board holds all the active circuitry while the ZA-1451 board holds only the keypad and the LED indicator. Fig.3 shows the assembly details for the two boards. The parts can be mounted in any order but we suggest that you leave the relay and output terminal block until last. Make sure that the ICs, transistors and diodes are all installed with the correct polarity. Pin 1 of each IC is adjacent to a notch in one end of the plastic body. Note particularly that D3 faces in the opposite direction to D1, D4 & D2. Note also that D5 is a 1N4002 type. Where to buy the kit The completed assembly can be installed in a weatherproof case or mounted on a electrical switch plate. The LED indicator beneath the kepad lights when the circuit is armed. 32 SILICON CHIP This project was developed by Dick Smith Electronics and is available from all DSE stores or by mail order from PO Box 321 , North Ryde , NSW 2113 . You can also order by phone on (02) 888 2 105 or, if you are outside the Sydney area, on (008) 22 6610 . The kit consists of two etched PC boards plus all the necessary components (including the keypad). Alternative-values for R1 & C1 are supplied so that the kit can be built for either latched operation or monostable operation (one second relay pull-in time). The price is as follows: Burglar Alarm Keypad (Cat. K-8 403) ..... .. .. .... ... .. .. .. .. ..... ... .. . $29.95 Postal orders should add another $4.50 for p&p. Please quote the catalog number when ordering. Note: copyright of the PCB artworks associated with this project are retained by Dick Smith Electronics. This circuit hoard has been assembled to give latched operation from an entry code of 095#. Note that the coding lines are not in sequence but run C3421 (see Fig.3). There are two options when it comes to installing the 2 2kQ resistor adjacent to Ql. Connect this resistor to point L for latched relay operation or to point M for monostable operation. The values shown on Fig.3 for Rl & Cl are suitable for latched operation but this time constant will have to be increased for monostable operation. It's simply a matter of choosing a suitable time constant to give the required relay turn-on period. For example, if Rl = lMQ and Cl = lµF, the time constant (and hence the relay turn-on time) would be 1 second. Other possible values are 2.2MQ & 33µF (72 seconds); lMQ & 22µF (22 seconds); and 330kQ & 22µF (7 seconds). The keypad is mounted on its board using four 3mm nuts (one on each mounting post) as spacers. Check that all the pinouts from the keypad protrude through the holes in the board, then secure the keypad by using your soldering iron to "burr over" the plastic mounting posts. The keypad terminals can then all be soldered and the LED installed. Watch the polarity of the LED the flat side of the plastic body is adjacent to the cathode (K) lead. Install the LED so that its top is level with the tops of the keys. Coding links The coding links (wire link presets) are best installed before the two PC boards are hooked to- The keypad hoard is mounted on the back of the main circuit board on 6mm spacers and secured with machine screws & nuts. Four 3mm nuts are also used as spacers when mounting the keypad on its board. gether. These are installed down the lefthand side of the ZA-1450 board. You can use any 4-key code you like (including * and #) and you can use the same key twice but not consecutively. For example, you can program in the code 1525 but not 1552. To program in the code, connect the four selected key outputs to the 1, 2, 3 & 4 lines. The outputs of the remaining eight keys are then all connected to the C (clear) line. Fig.3 shows how the circuit is connected for a code of 095#. That's because key O is connected to line 1, key 9 to line 2, key 5 to line 3, and key # to line 4. Note that the coding lines run 1, 2, 4, 3, C (from left to right). The two boards can now be connected together using 15 25mm-long insulated wire links. Finally, fold the keypad board over and mount it on the back of the circuit board using 6mm spacers and 6BA machine screws and nuts. Testing To test the unit, connect up a 12V power supply and press a clear key (any key that's not part of the code). Now enter in the correct code and check that the relay operates and that the LED comes on. The relay should latch on if you have installed the 22kO resistor in the latch (L) position or pull in for the preset time if you have chosen the monostable (M) position. Now check that the relay turns off again when you re-enter the code (latched mode only). This done, rearm the circuit (ie, LED indicator on) and use your multimeter to monitor pin 10 of IC2c while you press a clear key seven times. Pin 10 should start off high but should switch low on the seventh press of the key. Depending on your application, the completed unit can be mounted in a plastic zippy box or you might like to consider mounting it on a standard electrical switch plate. In either case, you would have to make a neat cutout to suit the keypad and drill a hole to accept the LED. The switch plate idea is the one to go for if you intend mounting the unit inside your house. ~ JULY 1990 33 How many times have you opened up that favourite board game to find that someone has pinched the dice? In that case, why not build this electronic die which uses just two CMOS ICs? It simulates the roll of a real die and even turns itself off. Build this elegant electronic die By DARREN YATES Die or dice - which is correct'? Let's straighten that question out right at the start. "Die" is the singular form of 'dice" so it is correct to term a unit which will randomly indicate 1 to 6 as a die. There have been a number of designs over the years for simulating a 6-sided die but most either use a 7-segment display to show up the numbers 1 to 6, or a row of 6 LEDs to indicate the die number rolled. But although these circuits are simple, they don't give a realistic display. When you roll a 6-sided die, it rolls along with the initial momentum of the throw, and then slows down until it stops. How many times have you almost seen a "6" turn up on the die, only to see it turn over into a lousy "1 " '?. This circuit cycles through the numbers 1 to 6, and slows down until it stops on its final number. This is far more realistic than pressing a 34 SILICON CHIP button and having the final number instantly staring you in the face. Another feature of a real die is the dots on the faces. This has often been a tricky task to achieve electronically, and most circuits don't bother about it. Our circuit has this built in, with all the displays matching the faces of a real die, including the diagonal "2" and "3". Fig.1 shows how all numbers are displayed. Another problem with electronic die circuits we have seen in the past is that it is all too easy to leave them switched on so that they flatten the battery. This design has no on/off switch - it turns itself off automatically, after 50 seconds. The circuit Now let's have a look at the circuit diagram - see Fig.2. It uses only two low-cost CMOS ICs, seven light emitting diodes (LEDs) and not much else. ICl is a 4015 dual 4-bit .. ,.. Fig.1: here's how all the numbers are displayed by the LEDs. Note that the displays match the faces of a real die, including the diagonal "2" and "3". +6V 100 + 16VWJ ROLL S1 I C2 33 10VW + 70 ~ 1 C ,o.::.-4,___ _;:1---."fg C 4~c,1s"e R~6_ _ 15 D 16 R3 f-...,1Y,Ok~+----'14 R IC1 ! 02 11 00 .,. 00 LED1 LE07 R2 LE03 180k LE01Q LE02Q LED3Q QLED5 LED4 Q QLE06 QLED7 CMOS LED DIE Fig.2: when the ROLL button is pressed, Cl & C2 discharge and oscillator IC2a clocks 4-bit shift register ICla. ICla in turn clocks IClb and their outputs drive the display LEDs. As C2 charges, IC2a slows and eventually stops to give a static display. The LEDs then turn off after 50s. register while IC2 is quad NAND Schmitt trigger. The circuit works as follows . If you press the ROLL button Sl, capacitor C2 is shorted out while Cl is shorted via diode D2. Once the ROLL button is released, capacitors Cl and C2 begin to charge again and while they are doing so, the rest of the circuit can function. Also, when the ROLL button is pressed, capacitor C4 quickly charges via the 560kn resistor R4. These two components are part of an oscillator associated with Schmitt trigger NAND gate IC2a. C4 is charged via R4 as just noted but once the capacitor voltage reaches the positive threshold of IC2a, its output flicks negative and then C4 is discharged via diode Dl and the series lOkQ resistor. This happens repeatedly and results in a series of short negative going pulses (at pin 3 of IC2) which decrease in frequency until they stop altogether after about 5 seconds. This 5-second time period is set by the charging of capacitor C2 and the negative threshold of IC2a. The pulses from IC2a clock the circuit and simulate the roll of a real die, whereby the LEDs cycle very rapidly at first and then slow to a complete stop to give one of the static displays shown in Fig.1. The clock pulses are fed to pin 9 of ICla, a 4-bit shift register which is connected as a D-type flipflop. ICla is made to function as a flipflop by connecting its Q0 output at pin 5 to the D input at pin 7 via inverter IC2b. The Q0 output of ICla is also used to drive LED 4 which is on for all the odd-numbered displays; ie, 1, 3, and 5. The output of IC2b is also used to clock the second 4-bit shift register, ICl b. The D input of IC1 b is tied to the positive rail so that on each clock pulse, a "high" is shifted to each output from Qo to Ql to Q2 (pins 13, 12 & 11, respectively). Pin 11 drives LEDs 6 & 2, pin 12 drives LEDs 1 & 7 and pin 13 drives LEDs 5 & 3. These LEDs produce the even-numbered displays 2, 4 & 6. When Q0 of ICl b goes high, LEDs 5 & 3 come on to produce the displays 2 & 3. On the next clock pulse, Ql now also becomes high so that the displays 4 & 5 are produced as LEDs 1 & 7 are now also lit. On the third clock pulse, Q2 goes high as well, lighting LEDs 6 & 2 to produce the displays 5 & 6. Die sequence Let's just go through the sequence whereby the circuit produces the die displays. SC08107901 Fig.3: here is a full-size reproduction of the PC artwork. JULY 1990 35 PARTS LIST 1 PC board, 105 x 57mm, code SC08107901 1 momentary contact pushbutton switch, DSE Cat. S-1201 4 1 .5V alkaline AA cells 1 4 AA-cell holder 1 9V battery snap 4 PC standoffs (plus screws and split washers) Semiconductors 1 4015 dual 4-bit shift register (IC1) 1 4093 quad NANO Schmitt trigger (IC2) 2 1 N914 silicon diodes (01 ,02) 7 red LEDs Capacitors 1 1OOµF 16VW PC electrolytic 1 47µF 25VW LL (low leakage) electrolytic (C1) 1 33µF 25VW LL electrolytic (C2) 2 .O1µF metallised polyester (C3 ,C4) Resistors (0.25W, 5%) 1 1 MO 2 10kQ 1 560k0 1 3 .3k0 1 180k0 1 1.8k0 The first clock pulse to ICla causes its pin 5 to go high and light LED 4 - the display for "1 ". The next clock pulse causes LED 4 to go out and pin 13 of IClb to go high, to light LED 5 & LED 3 - the display for "2" . The next clock pulse causes LED 4 to come on again while LEDs 5 & 3 remain alight, giving the display for "3 " . The next clock pulse causes LED 4 to go out while LEDs 5 & 3 remain on and pin 12 of ICl b goes high to light LEDs 1 & 7, giving the display for "4". With the next clock pulse, LED 4 comes on again while LEDs 5, 3, 1 & 7 remain alight to give the display for "5". Next, LED 4 goes out again and pins 11, 12 & 13 of ICl b are all high to light LEDs 5, 3, 1, 7, 6 and 2 to give the display for ''6''. The next bit is devious. In order for the die to cycle from a "6" back to a "1 ", IC2c and IC2d form an AND gate to check when Q2 of ICl b is high, indicating a 6 on the display, and when Q0 of ICla goes high again. When this occurs, the output of IC2c goes high, resetting ICl b and forcing all its outputs to go low. This now makes the output of IC2c go low again since the Q2 output of ICl b is no longer high. The resulting output of the AND gate IC2c/d is a brief positive pulse. The output of IC2c also drives the reset pin of ICla via a time constant consisting of R3 & C3. The pulse is not there long enough to cause ICla to reset while the display is cycling, allowing the display to go from a "6" back to a "1" again. If we removed R3 & C3 and then replaced R3 with a wire link, the display would cycle through 1, 2, 3, 4, 5, 6, 0, 1, 2, etc. Of course, you would have to slow down the clock pulses considerably to be able to see this sequence of events as we have described it. Auto turn off As noted previously, the circuit turns itself off automatically, to save the battery and to avoid the need for a separate on/off switch. The 47µF capacitor Cl and the lMO resistor Rl are used to provide this auto turn-off feature. As Cl charges slowly through resistor Rl, the voltage at their junction, pin 8 of gate IC2c, slowly . F ~ .01; I . e-{J]I}-e ~ rf°_rqb~'::,j__ + - 6V BATTERY Fig.4: install the parts on the PCB as shown here. Make sure that all the parts are correctly oriented and note that LED 1 faces in the opposite direction to the other LEDs. decreases. About 50 seconds after the ROLL button is released, the voltage at pin 8 reaches the lower threshold level of the gate, forcing its output at pin 10 high. Register ICl b is reset instantly and when capacitor C3 is sufficiently charged via 10k0 resistor R3, ICla is also reset, forcing all outputs low and turning off the display. The current consumption of the circuit then drops from about 3mA to approximately lµA. Construction The board is designed to sit as either a unit on its own or to fit into a small zippy box, such as DSE Cat. H-2851. All the components, including the pushbutton switch, fit onto a PC RESISTORS No □ □ □ □ □ □ 36 1 1 1 2 1 3 SILICON CHIP Value 1MO 560k0 180k0 10k0 3 .3k0 1.8k0 4-Band Code (5%) 5-111~ Coda (1'1,) brown black green gold green blue yellow gold brown grey yellow gold brown black orange gold orange orange red gold brown grey red gold brown black black yellow brown green blue black orange brown brown grey black orange brown brown black black red brown orange orange black brown brown brown grey black brown brown board which measures 105 x 5 7mm (code SC 08106901). Before you begin assembly, check that there are no shorts or breaks in any of the tracks. Fig.4 shows the wiring details of the circuit board. Start by installing the wire links and then follow with the lower profile components such as the resistors and diodes. Make sure you check the resistor values with your multimeter as you install each one. This done, the capacitors can all be installed (watch the polarity of the electrolytics ). Next, install the seven LEDs and the two CMOS ICs. Make sure they are inserted the right way around before you power up, otherwise they may be damaged. Finally, solder in the pushbutton switch (note the flat on the switch body) and the battery snap connector. If you intend to mount the die in a zippy box, we suggest that you solder in four PC stakes in the position of the switch and then solder the switch to the PC stakes to raise it off the board. This way, the board can then be screwed to the lid of the box with the switch protruding through it. Once the board has been completed, connect up the battery pack and press the button. You should see a flash of LEDs as the circuit fires into action. When you release the button, you should see the cycling rate begin to decrease until it stops on the final number. After about 50 seconds, the LEDs should go out. All that remains to be done is to pull out that favourite board game and enjoy the fruits of your labour. Troubleshooting If it doesn't work, check carefully for wiring errors. Are all the parts in the right way around? Have all the wire links been installed? Are there shorts between adjacent IC pins or PC tracks? If any of the LEDs fails to light, check that it has been correctly installed. Note that if you do install a LED the wrong way around, its series partner also won't light (eg, if LED 1 is the wrong way around, LED 7 will also remain off). Finally, don't just rush out and replace the !Cs. That seldom solves anything. ~ BOOKSHELF Music Applications of Microprocessors Musical Applications of Microprocessors, by Hal Chamberlin. 2nd edition published 1985 by Hayden Books, Indianapolis, Indiana, USA. Hard covers, 162 x 238mm, 802 pages. ISBN O 672 45768 7. Price: $59.95. While there are any number of books available on computers and microprocessors, there are precious few books on electronics in music and of those that are available, very few are of any real use. This book, by contrast, is excellent, and worth every cent of its price. Having said that , I must point out that this second edition was written in 1984 and there have been a few developments in electronic music since then. Where to start? There is so much in its 802 pages that it is difficult to know which sections to highlight in this necessarily short review. Therefore I'll start with chapter 5 which is the last of the introductory background section of this text and it is the first devoted to microprocessors. It covers microprocessor terminology and gives the early history, particularly with respect to the first personal computers such as the Commodore PET, TRS-80 and the Apple. Also covered in this chapter are peripheral devices such as printers, plotters and modems. This is very good background and worthwhile reading for anyone who was not into electronics or computing before the 80s. All told, there are 21 chapters, divided into four sections, the first of which I have already mentioned. The second of these sections, which has 6 chapters, is devoted to " Computer Controlled Analog Synthesis". Chapter 6 starts with basics such as voltage controlled oscilla tars, amplifiers and filt ers and chapter 7 goes on to treat digital-to-analog (DI A) converters. Chapter 8 is on computer control and chapter 9 on keyboard interfaces, while chapters 10 and 11 round out the section with coverage of other input devices and displays. This is very well written. The third section is entitled "Digital Synthesis and Sound Modification" and a large part is devoted to digital tone generation techniques. Fourier transforms are covered in detail, as are Fast Fourier Transforms (FFTs) and FFT Algorithms. Chapter 14, the third in this section, is devoted to digital filtering, which will be of great interest to anyone involved in digital technology, particularly as it covers reverberation simulation (as used in the Yamaha DSP-1 and similar products). Chapter 15 covers percussive sound generation, again using digital techniques, while chapter 16 is on source signal analysis, mainly spectral analysis, in 2 and 3dimensional form. Chapter 17 is on digital hardware while chapter 18 complements this with coverage of digital software. The last section of the book, with three chapters, is entitled " Product Applications and the Future " . Chapters 19 & 20 mainly cover music synthesisers while chapter 21 looks to the future . Quite frankly , as I write this continued on page 95 JULY 1990 37 JOYSTICK FOR IBM• Features selectable ''spring centring '' or " tree floating " . 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Box 620, CLAYTON 3168 Order Hotline : 008 ;13 5757 SERVICEMAN'S LOG The dangers of a quick fix A quick turnaround is something every serviceman aims for. It minimises the number of devices cluttering up the shop, it helps cash flow, and .it provides a certain sense of satisfaction. What's more, the customer expects it. But it isn't always the best approach, particularly with older sets. IC provides a number of functions, including the horizontal oscillator, sync separator, etc. I quickly found that R458 needed only a minor adjustment for the system to jump back into lock, after which the set produced a good picture. In fact, on a quick turnaround basis, I could probably have regarded the set as fixed. But a couple of things made me suspicious. One was the owner's attempt to describe the fault which, garbled though it was, hinted at more than one symptom. The other was that, now that the picture was locked, it was obviously overscanning horizontally. Not grossly - and the customer might well have accepted it - but enough to warrant investigation. That little bit of philosophy was prompted by a recent experience involving a Kriesler 59-4 colour set. This model is now about 12 years old and is about the last of the "true" Kriesler sets; ie, before they became a Philips chassis in a Kriesler cabinet. And of course, at that age there is always the question as to whether a lot of expense can be justified. In this case, the Kriesler was a "second" set, having been replaced by a more recent model a few years ago. But it still had its place in the household and the owner was keen to keep it going. Unfortunately, he was unable to provide more than a very garbled description of the trouble which, boiled down, was best summed up in his own words, "It doesn't go properly." Fortunately, he and his family were going on holidays for several weeks, so there was no rush for at least that period, or even longer if necessary. He just wanted to be sure it was fixed. TETIA TV TIP Philips 14CT2006 etc (CTXA-1 S chassis) Symptom: No sound . Voltages around output IC 7181 (TDA 2611 AO) are all wrong but some No sync When I eventually switched it on, one fault was immediately obvious; the horizontal system was out of lock. This could mean either a loss of horizontal sync pulses or serious horizontal oscillator drift, such that the sync system could no longer control it. Removing the back of the set, I sought out the horizontal hold preset pot (R458), a 47k0 trimpot connected via R459 to pin 15 of IC450 (TDA2590) - see Fig.1. This 40 SILICON CHIP are more wrong than others. Audio output on pin 8 of SIF chip 7164 seems to be OK but nothing reaches the power chip. Cure: C2177, a 22nF 50V ceramic capacitor, has gone leaky and shorts the signal to ground. i TETIA TV Tip is supplied by the Tasmanian branch of The Electronic Technicians' Institute of Australia. Contact Jim Lawler, 16 Adina St, Geilston Bay, Tasmania 7015. The width control, R687, 10k0 (lower right of Fig.1 ), had no effect, suggesting that the overscan was more than a maladjustment. In fact, I decided to bypass that problem for the moment and simply let the set run while I attended to more urgent jobs. In particular, I was anxious to make sure that the horizontal hold problem had really been solved and was not intermittent. In fact, the set ran perfectly for the rest of the day. But next morning there was a new fault. As the set warmed up, all it presented was a 50mm high band of picture across the centre of the screen; ie, partial frame collapse. And I had a feeling that this was only the beginning. On the off chance that this might be a faulty height control pot, R637, lkO (lower left of Fig.1), I tried adjusting this but it had only a minor effect. There is a waveform (64) given for the signal feeding this pot, indicating a p-p value of 3V. But a check with the CRO showed only a fraction of this value. From there it was a fairly simple step to transistor TR636 which feeds the pot. This transistor had dropped its gain and replacing it brought the scan back to normal. . So back to the width problem. This turned out to be due to R688 (47k0) which connects to the moving arm of the width pot. The resistor was found to be open circuit, so that problem was easily fixed. More trouble By now the set was beginning to look pretty good. I tidied it up a bit, then put it to one side where I could let it run in case anything else decided to show up. For the next three days it went like a bought one but then the picture started to tear, as though it was about to lose horizontal lock. It didn't actually lose lock but the 1sae1 .. u I ~£ ~~ To R-425. R.416. L501 . UU : IT. R47S . SK2:42 Pin 6, I SK211 Pin I . I , :::, I : Lrn , C4U ~ ' - - - - - - - - - -1 - lDo_ - .3;- - - - :~v FRAME S FRAME FLVBACK PULS 46 J; -~:::1 JOV DEFLECTION SOARD to-1U55 CIS1 'r-{Il]---.-- -,-~22~~v R&St ;;J; 35V 7TR65i 80213 cna 1:: RH5 TCH3 n'n 1Hn rlHF'-tl~l1?,'z51. fRAMf OUTPUT RH4 OEFUCT10N YoKE - - FRAME OSCII LATOH , J Fig. 1: section of the Kriesler 59-4 circuit. IC450 (TDA2590) is at the top, the vertical oscillator stage at bottom left, and the width control at bottom right. tearing action was accompanied by loss of colour. My first reaction was to suspect a fault in either the sync circuitry or the horizontal oscillator. And I assumed that the loss of colour was probably due to misplacement of the burst gate and its effect on the colour killer. In any case, either fault would be in the TDA2590 IC. So the only real test was to replace the IC. I was lucky in this regard. I had such an IC on hand and the IC in the set was mounted in a socket. So it was only a few moments work to make the change. And that was it; the picture came up perfectly stable, with steady colour. So, again, the set went back into "soak corner" where it ran perfectly for several more days. Then, one morning, it came up with the picture rolling. I let it run in this mode just to see what would happen and after about half an hour, when the roll rate had slowed appeciably, it suddenly locked. And it remained that way for the rest of the day. It rolled again the next morning at switch-on and I immediately reset the vertical preset pot (R622) until the system locked. Of course, I knew what would happen; after about half an hour the picture started rolling. So it seemed like a thermally sensitive fault in the vertical oscillator circuit. I let it cool and tried again. Again the picture was stable at first, then began rolling as it warmed up. I reached for the can of freezer. The vertical oscillator consists of two transistors: TR621 (BC548) and TR622 (BC558). I froze each of them, one at a time, but this had no effect. I sprayed the surrounding components and even the sync amplifier transistor, TR615 (a BC548), all to no effect. But I still suspected one or both of those two oscillator transistors. So out they came and in went two new ones. And I was right; that fixed it. After that, the set ran for several more weeks before the customer called for it. In the meantime, I checked. the two transistors. Both seemed OK on a rough "continuity" test, even when frozen or heated. But it was a different story when I tried them on a curve tracer. I could find nothing wrong with the BC558 but the gain of the BC548 was all over the place. But strangely, heating or freezing had no effect, one way or the other. Naturally, all this had chalked up a fairly substantial account and I was a little apprehensive as to how this would be received. After all, it was an old set. But the owner didn't quibble; in fact, I think the list of faults convinced him that I had done a thorough job. This all happened several months ago, and a recent check confirmed that all was well. So everyboby's happy. But it was lucky that I had plenty of time to run the set. Had it been a rush job, the set would have bounced more times than a rubber ball. A thorny Thorn And still on the theme of not-soyoung sets but from a slightly difJUL Y 1990 41 apart from the condition of the picture tube. So I wasn't too happy when this set turned up. The owner said that the picture had gone but the sound was OK and the screen lit up. That absolved the power supply and made the job a little less discouraging. So I agreed to take it on. The first thing was to test the picture tube emission. This was a real surprise. Most of these tubes now test in the 10% to 30% range well into the red on the meter. This one read 105%, only a little below full scale, and the same on all three guns. It would be a shame to junk such a set, so it seemed to be worth a couple of hours of labour and a moderate figure for parts. The owner set $100 on the repair and I imagined that I could do it for that much. So I set to work. Blue screen ferent angle, here is a story from my Tasmanian colleague, J.L. Just how much is an old TV set worth? It's one of the more unpleasant duties of a television serviceman to have to tell a customer that his TV set is too old to be economically repaired. He might have paid nearly $ 1000 for it 15 years ago and finds it hard to accept that his investment has gone sour. Sets of that age are usually worthless but there are exceptions. A Thorn 9104 came in recently and at first glance I didn't want to have anything to do with it. Although it was still in excellent mechanical condition, I had no doubts about what it would be like to service. Over the years I have repaired many of these sets and have also 42 SILICON CHIP written off just as many with worn out picture tubes. Most of the repairs involved the switchmode power supply and so long as this could be fixed easily, the repair was worth doing. Unfortunately, this chassis was built in the UK, to the usual UK standards of complexity and inconvenience. The power supply is extremely awkward to work on, being a three layer assembly with very short leads linking the various parts. The supply cannot be operated while it is open for service so one is continually unsoldering and resoldering leads if chasing a difficult fault. This alone is enough to turn me off the model but other parts of the set are just as confusing and any obscure fault is all it takes to write off the set, quite When I switched the set on, it came up with a blue screen, retrace lines and a faint trace of picture. It seemed at first like a screen (G2) supply problem and I checked the screen voltages on the tube base. This didn't help because they were all about normal and the same on each gun. Next, I tried the grid voltages and again, all were normal and equal. Finally, I measured the cathode voltages and found only the red cathode to be normal, with the other two only about half of what they should have been. I removed the video output board and began a systematic check of the transistors in the blue and green channels. I could find no fault there so I began a check of the diodes, inductors and finally resistors in both channels. In fact, I found the fault among the latter components without having to measure them. I happened to touch the heatsinks on all three output transistors and only the red one was warm. The blue and green heatsinks were stone cold. This could only mean that the transistors had not been turned on, or were only just turned on. And, if so, then it could only be due to a high resistance collector load. And so it turned out to be. The special thick-film network carrying the load resistors for all three transistors had gone funny and the two transistors were trying to work with loads six times higher than normal. Suddenly, something occurred to me. " Whoa there! Back up a moment!" I said. " If the green and blue channels are turned off, how come we have a blue screen?" I went back to the screen controls and gun switches on the convergence board. Switching off the green and blue guns made not the slightest difference, while switching off the red gun removed the blue screen! So the main problem seemed to be gross impurity and I'd have to get that right before I went any further. And this is where my problems really began. I started the process by manually degaussing the tube. This removed the nice even blue screen and produced a varied mass of uneven colour similar to that which usually follows the next procedure - moving the yoke to the end of its travel. At this point I wondered if that was all that the trouble was - just the yoke out of position. But try as I might, I could not find any combination of yoke and purity ring positioning that would give an all over red screen. The best I could get was reasonable red down the centre half of the screen, with a wide band of blue on one side, and the same of green on the other. For the moment, I returned to the video output board. I patched a couple of 12k0 1W resistors across the faulty thick-films, replaced the board, and restored the three gun switches. When I turned the set back on, the nice, pure centre screen that I'd had earlier had become all blotchy again. I degaussed the screen again and this restored a monochrome picture down the centre, with the green and blue bands down the sides. In fact, this procedure was repeated three more times and on each occasion the tube somehow altered its purity each time it was allowed to cool down. It was very puzzling, and I had almost come to the conclusion that the tube had an internal fault. A loose shadow mask was about the only thing I could think of and I began to wonder if we would have to write it off after all. Degaussing circuit Then I realised that whenever I degaussed the tube, the central red band became a little wider. If I kept this up, then I might have a good red screen by tomorrow morning! And this led to the realisation that in all probability, the automatic degaussing circuit was not working. One of the idiosyncrasies of English design is that nothing is where you'd expect it to be. The auto degaussing circuit is not on the power supply board, or the vertical output board, or even the convergence board. It's on the video IF board! Fortunately, it is easy to get at and I soon determined that the coils were OK. I wasn't so sure about the rest of the circuitry because they gave some funny readings. The cir- TV TEST EQUIPMENT PCB POWER TRANSFORMERS (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 HI-VOLT AGE PROBE Built-in meter reads positive or negative 0-50kV. Can also be switched to check negative voltages. For checking EHT and Focus voltages as well as TVs and Microwaves. Hi-tension voltages. $89.00 + $5.00 p&p LOW-VOLTAGE PROBE Ideal for checking microwave ovens and TVs. The ~ ranges are from Oto 5kV and from Oto 1 OkV. Double insulated for safety. $79.00 + $5.00 p&p DEGAUSSING WAND • Proudly manufactured in Australia by HARBUCH ELECTRONICS Pty Ltd 90 George St. , HORNSBY, N.S.W. , 2077 Phone (02)476-5854, Fax (02)476-3231 Strong magnetic field, larger than usual coil with multicore centre. Double insulated for safety with momentary switch operation. 240VA/C 2.2 amps. As important as having a soldering iron! $75.00 + $10.00 -,&p TUNER REPAIRS . We repair most tuners on an exchange basis. From only $17 .00 + p&p . ... , . . . . Cheque, Money Order, Bankcard or MasterCard Y.V.TuNERs) 216 Canterbury Road, Revesby, NSW 2212 Phone (02) 77 4 1154 JULY 1990 43 WOOD FOR CHIPS ... WOOD FOR CH IPS .. WOOD FOR CH IPS ... WOOD FOR CHIPS . . WOOD FOR CHIPS .. WOOD FOR CHIPS ... WOOD FOF · Emtek E-301 Logic Probe • • • • • • . Level Detector Pulse Detector Pulse Memory HVLow/Pulse Leds Suits TTUCMOS/HTL etc Operates from 4.5 to 20Vdc Specifications Max Input Frequency Min Pulse Width Input Impedance ,3!> - . Over-Voltage Protection ~ . ·:, Pulse LED flash time 17MHz 30nS 1Mn 220Vac 500ms ": . • $31.50 ~,,~ :~~si=~~~:!~s NEW Digital Engine Analyser ~ ::r: (.J cc a lJ.. Cl a ~ ~ ::r: (.J cc The APPA23 gives you 8 functions dwell, tacho, duty cycle, continuity, volts, amps, ohms and diode testing. Huge 20mm high contrast 3 1/2 digit LCD readout. Auto-poweroff to save battery life. Large rotary switch to simplify function selection . Case is drop-proof and water resistant. Brief Spees DC Voltage. 200mVto 200V Tacho: Oto 10000rpm and Oto2000rpm Duty Cycle: Oto 100% Dwell : Oto 90" (4cyl) Resistance : 200 to 20Mo. DC Current: 15A Great value at $119.00 inc tax ($99 .00 ex tax) -::, L: . ~ ~ i(.J a lJ.. Cl a 2 .,. ~ i (.J cc a lJ.. Cl Cl ~ ~ ~ cc Cl lJ.. Cl a ~ Fluke 80 Series ... Top of the line Multimeters The Fluke 80 series offers a huge range of extra features like a 200kHz frequency counter, capacitance meter, combined analog and digital scales plus the ability to automatically record max/min and average readings and store them for u2 to 36 hoursf c:. a cc Proven the best under all conditions from -100°C to +300°C. Laminated cage springs on solid brass pin to ensure virtually non-resistive contact. Sliding action is self cleaning. Soldering irons won't burn them. Highest quality and flexibility. 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A must for electricians . $49.50 Individual screwdrivers available Flat• 2.5mm $4.20, 4mm $5.40, 5.5mm $7.80, 6.5mm $10.50 Philips Head • No 1 $6.40, No 2 $8.40 Wire Wrap We carry exte_nsive stocks of wire and tools. Wire Wrap comes in two pre-cut lengths - 10.16cm and 12.7cm 30AWG at $4.80 and $5 .60 per 100 lengths. Also on spools of 30m for $9.95 . We also have a wire kit consisting of 200x 6.25cm, 250x7.62cm, 100x8.89cm, 100x10.16cm 100x11.43cm and 100x13.97cm. All 30AWG and colour coded for$34 .80 Tools The OK MST hand wrap tool is just $19 .50 The OK Cutter and Stripper is $28.50 Enquire about wire wrap sockets. Our range is too extensive to list here. .,.... """.,."' ""'"' ' l. .,. .,..,,.,~"' .~~ AilJ!!!'i;ill""' AT&M KITS We carry the full range of the ureat kits. Why develop your own circuits when these building blocks are already available? 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Consists of Male and Female D25 to Male and Female D25. Ideal for service technicians and installation people. A very versatile piece of cable! $34.00 NEW 2-Way' /,"" Automatic !/ Data II' Switch ............ Now two PC's can share one printer automatically. it The printer (or other peripheral) is allocated on a first-come-first-served basis. LED indication tells you which PC is connected. No external power and can be easily attached to any surface using velcro pads supplied. Suits any PC and Printer with parallel (Centronics) connections using DB25 connectors. $99 .50 la .,.,Cl a ::0 "::r: ~ la a .,., a ::0 "::r: ~ lCl Cl .,., a ::0 ":i:: ~ lCl Cl .,., Manual Data Switches a Total flexibility at very modest cost. 2 Way Seriaf (RS232) $45.00 Parallel (Centronics)$55 .00 4 Way Serial (RS232) . · $70.00 Parallel (Centronics)$80 .00 "'ii::r: ::0 V) lCl 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. Man Orders add S_5 00 to cover postal charges. Next day delivery in Sydney add $5.00. c Cl .,., a ::0 ~ "":"' 1 . ro GLADESVU.E Tax exemption certificates accepted if line value exceeds $10.00. BANKCARD, MASTERCARD, VISA, CHEQUES OR CASH CHEERFULLY ACCEPTED "'ii::r: V) SERVICEMAN'S LOG -CTD cuit consists of just three components. Only one has a logical part number - R199, a 6800 5W wirewound resistor. The other parts are X199, the usual PTC thermistor, and Z199, a device which looks like a 40mm diameter disc ceramic capacitor. This latter device was in series with the degaussing coils, and had a resistance of several megohms. This seemed to be all wrong and for the moment, I couldn't identify its symbol on the circuit diagram. So I had to find out what it was, and if it was indeed faulty. In some respects, I'm glad I'm a hoarder. Although it is hard to live among all the junk, there are times when it becomes invaluable. Like when I want an old Thorn IF board complete with degaussing components. In fact, I found three such boards and all three gave readings similar to the suspect one, which seemed to clear Z199. I still wasn't sure what Zl 99 was but was beginning to recall that the symbol could mean a voltage dependent resistor, which would have a high resistance at low voltage - including the voltage ap- plied by the ohmmeter. On this basis, a theory as to the circuit's purpose and operation began to evolve. It seemed most likely that its purpose was to reduce the residual current in the degaussing coils to a minimum, following the degauss function. This theory was eventually proved correct but more on that later. Anyway, since the circuitry seemed to be OK, the next test was X199 PTC THERMISTOR 200V'--.\oliliill.J.-----, Fig.2: the degaussing circuit used in the Thorn 1904. The VDR (Z199) and the 6800 resistor (R199) network was an early refinement to the conventional degaussing system. to see if it actually passed any current. For this I used an AC clamp meter. I hooked the clamp around one of the AC leads and switched on. The needle didn't move. This meant that there was either a break in the circuit that I hadn't found, or no voltage was being applied to it. A check across the degauss network showed only BOV, whereas the circuit diagram indicated there should be at least 200V. There were no less than three plug and socket connections between the degaussing circuit and the power transformer. None of these was easy to test but I soon found myself at the relevant terminals on the transformer. And there was the trouble - the winding was open circuit. This was quite a puzzle because, according to my circuit , the degaussing system is fed from the same winding that supplies the HT to the chopper transistor. The chopper was working quite normally, so I had to assume that there was a second secondary, so to speak. Then my magpie tendencies came to my salvation - again! Just outside the workshop was the latest of these Thorn sets to be junked. It was only a few minutes work to remove its power transformer and fit it in place of the faulty one. At the next switch-on, the degaussing coils gave out a good solid "boing" and the last of the impurity disappeared. The next thing this set needed was a thorough convergence setup. These old delta gun sets never had enough convergence adjustments; it always seemed that the one you wanted was on a different brand of set. This one needed at least four controls which were not provided. But I perservered and eventually produced a reasonably well converged picture. But it was still only in monochrome. By this time I had spent much more than the two hours I had budgeted for the job. I had replaced the load resistors on the video board and the power transformer. I had no idea what would be involvcontinued on page 99 JULY1990 45 Dear Customer, _r- Once again we have put together a really exciting lot of products for you. -And look at these very competitive prices! LABTECH has produced a terrific 40MHz Scope and their NEW Audio Oscillator will be a winner. Don't waste your time and hard earned a-•ca•s•h•·•D•o•y•o•u•r•sh•o•p•p-in•g•a•t•A-lt.ro•n-ics_-_T•O•D•A•Y•!-----W-it•h•k-in•d•r•e-ga•r•d•s•, t) ~ Two Brilliant New Multitesters From Altronics at Low Direct Import Prices Q 1066 Multimeter Temperature Meter with Capacitance, Diode and ate for Design Engineer and Bench Technician apacltance Meter • Logic Tester • Transistor and Diode Testers Transistor Tester. a 1070 Engineering Multimeter Tester/Counter Five Range Frequency Counter. Specifications For a 1066 / a 1070 DC Voltage Range: 200mV, 2V, 20V, 200V, 1000V Accuracy: All ranges+/- 0.5% rdg + 1dgt Input Impedance: 10MOhm • AC Volta go Range: 200mV, 2V, 20V, 200V, 750V Input Impedance: 10MOhm DC Current Range: 200uA, 2mA, 20mA, 200mA, 10A AC Current Range: 200uA, 2mA, 200mA, 10A Q 1070 Rosistanco Range: 200Ohm, 2kOhm, 20kOhm, 200kOhm, 2MOhm, 20MOhm, 2000MOhm Frequency ID 1070 o•ly) Range: 2kHz, 20kHz, 200kHz , 2MHz, 20MHz Input Senoitivity :20MHz range 1V rms. Other ranges 35mV rms. C1p1cit1nco Range: 2000PF, 20nF, 200nF, 2uF, 20uF TomperabJro (Q1066 only) Range: -20'C to 750'C 0'F to 1400'F Accuracy : +/· (3' + 1 dgt) up to 1S0'C +/- 3% rdg over 1S0'C +/(15' + 2 dgts) up to 225'F Logic Test (Q1070 only) Logic 1: 2.4V +/- 0.2V, logic 0:07V +/- 0.2V Transistor hFE Base DC Current: 10uA, VCE: 2.8 +/- 0.4V General: Display: 3 1/2 digrt liquid crystal wnh maximum reading of 1999 Overrange Indication: Highest digit of (1) or (-1) is displayed $12.50 (suit a 1066 & a 1070) Digital Capacitance Meter •• t#:>l1,h <:A~<'< Clfm( f - ----~------····· .. .. . "May '90 it • Mains powered 9999µ.F in scve a 1067 Temp. Probe tor a 1066 $29.95 2 Amp Regulated Power Supply Input Voltage: 240V AC-S0Hz Output Voltage: 12V DC +/-0.5V Output Current: 2A DC Dimensions: 84 x 68 x 200mm Weight: 1.2kgs M9050 Normally $69.95 This month only $59.95 SAVE $10.00 The Days Of Tape Decks Are Numbered This Digital Recorder delivers astonishing reproduction of voice and/or music without one single moving part! Digital Voice Recorder (Silicon Chip Dec'89) Here is a digital voice recor der that can store 4 ditterent signals, voice, sound or a music source of up to 30 seconds each or one recording of up to 2 minutes. This new digital voice recor der uses a special voice recorder/playback IC and 7 other IC's making it bot h simple to construct and incredibly economical. Separate 256K Ram chips are used tor each channe l. These memories can be ganged to provide a total of 2 minutes of message time. There are 4 trigger inputs so that a message can be stored when a certain cond ition occurs. Battery backup is provided so that the messages are retained when main power is ott. Typical applications include: • Alarm system messages • Sales. messages for customers put ''on hold"• Experimental telephone answerin g machine• Door station announcer• Talking displays for shops• Emergency warning message announcement • Operation instru ctor for machinery etc. For those who want a professional appearance• stand alone product, we can supply with K 9550 Kit complete - PCB Format $129.00 our Deluxe H 0483 Instrument case and fully punched and screen printed fro nt panel. K 9555 Kit complete · with Inst. case $} 49.00 40M Hz D ual Trace Oscilloscope • CRT Display 150mm rectangular, domed mesh and 12kV post accelerator type. e Vertical Amplifier (CH1 and CH2 identical) Operational Modes: CH 1, CH2, ADD, DUAL, ALT, CHOP Sensitivity: 5mV-5V/Div 3% in 1-2-5 steps, 1mV- 1VIDiv 5% X5 Mag • Horizontal Amplifier Operating Modes: X-Y operation CH1-X axis, CH-2 Y axis Sensnivny: 5mV - 5V/Div +/- 3% in 1-2-5 steps Input Impedance: 1MOhm +/- 2%, 25pF +/- 3% e Time Base Sweep Method: AUTO, NORM, SINGLE Magnified Sweep: 10 times+/- 5%, Max 20nS Delay Method: Continuous delay and adjustment e Synchronization A, B, B Triggered, Internal V-MODE, CH1 , CH2, LINE, EXT e Trigger Coupling: AC, DC, HF Rej, TV-H (Line), TV-V (Frame) Triggering Sensitivity: INT. DC 20MHz 1.0 Div, 20MHz - 40MHz 2.0 Div, EXT. DC - 20MHz 150mVp-p, 20MHz - 40MHz 300mVp-p • Vertical Amplifier Signal Output: 50 mVIDiv. - 50 Ohm • Intensity Modulation Z Axis Bandwidth: DC - 1MHz, Sensitivity:3Vp-p • Probe Calibrator Output : 1 kHz square wave 1V II Q 0160 $ 1495 .00 Price includes TWO X1/X10 Probes worth $100.00! ''l DUAL TRACKING POWER SUPPLY + /- 50V DC AT 1.0AMP SILICON CHIP APRIL '90 17 Range Digital Multimeter Voltage output: 0 to +/-SOV or Oto 100V Current output: 1.7 A from 0 to 'olV (+/-43.5V) lAfrom0to IO0V (+/-50V) Load regulation, hen.er than 500mV at +/-50V, lA Drop out indicator (5mV of ripple) Short circuit protection Load switch - no need to switch off when switching load. K3380 with Overload Protection Australia's best value, less than $50 II $229.00 Speclflcallon: DC Voltage Range: 2V, 20V, 200V, 2000V AC Voltage Range: 200V, 500V DC Current Range: 'Z 200mA, 20 mA, 2mA, Laboratory Series Audio Oscillator 10A ReslstanceRange: 200Ohm, 2k0hm, 20kOhm, 200k0brn, 2MObrn Diode Test Test Current: 1.0 +/· 6mA Test Voltage: 3.2V Max. Batt,ry Test Range: 1.SV, 9V Q1547$ 4 8 O • Frequency Range: 20Hz to 200kHz in 4 ranges • Sine Wave Characteristics: Output voltage: 5V RMS or more at no load Distortion factor (at max output) 0.5% or less Output impedance: 600 Ohms +/-10% Output attenuator: 0 to greater than 50d8 oontinuously variable, • External Synchronisation Characteristics Input impedance: approx. 10kOhms Max. allowable input voltage: 10V RMS • Reading Accuracy 0.01%, +/-1 count • Frequency Counter Characteristics Display: 4 digits, 7mm red LED display Frequency range: 10Hz-1 Mhz (square wave) Sensitivity: 25mV RMS Max. input: 150V pp Input impedance: 1MOhm Square Wave Characteristics (TTL Out) Overshoot: 2% or less (at 1kHz) Rise/fall time: 200n sec or less • Power requirements: 100I120I220V +l-10%240V +5%, Another Altronics Direct Import Price Breakthrough Carry Case Q 1057 $12.50 INVERTERS INVERTERSINVERTERSINVERTERSINVERTERS Get 240V AC Mains Power from your battery with these handy inverter kit sets POWERHOUSE 600W Many combinations to choose from: 300 WATT I NVERTER (See EA Dcc''ol) This inverter has the capacity to produce 600 watts of mains power which will run a fantastic array of appliances. Ideally suited to rurming power tools, lighting (including fluros) elcctr · motors and much more. It can be used either as a portable or a pcnnancnt fixture. • Manual or Auto Start facilities • Low battery Kit version K 6770 $425.00 Fully built and tested 12V Input K 6774 $525.00 24V Input K 6775 $525.00 WITH AUTO START Operates from 12V Car Ban.cry 1 Auto Stan draws power from your battery only when appliance is plugged in and "turned onM ie, battery can be left permanently connected if required. • Voltage Regulated • Current Regulated• Current Overload unit self limits Complete Kit K 6750 $279.00 Fully built and tested K 6755 $379.00 Laboratory Power Supply Single printed circuit board construction • Deluxe instrument case • Attractive silk screened front panel • Fully drilled and punched chassis - No holes to drill • Front panel supplied to accommodate K 3302 option if requi red SPECIFICATION: • Output Voltage - 3 to 50 volts • Output current up to 5 Amps (max. 175W) • Floating outputs isolated from ground • Ripple less than 90mV p-p at max. (See EA May'85) 3 - 50 Volts at up to 5 Amps 10 TURN OUTPUT VOLTAGE CONTROL OPTION. (K 3300 is normall y supplied with standard pot) K 3301 $29.50 AUXILIARY+ AND - 12V OUTPUT TERMINALS OPTION Fixed Outputs Independent of Variable Main Output K 3302 K33oo$195 .oo T1HI really exciting new• Ill that ell of these epeeker• ere available et euch a low d/ecount price for thi• month - but be quick - etocka are limited. 15" (375mm) WOOFER $14.50 Ultra High Power Capacity Polypropylene Bass Drivers Our ALL NEW "Black" polyprop ccne Bass Drivers exhibit qune astonishing low register reproduction. Power ratings quoted are conservative. Not the cheapest but definitely the BEST VALUE we know of· ANYWHERE. 10" WOOFER 60Watt RMS 100W Max. C 3065 12" (300mm) WOOFER Huge 120 Watts RMS Massive 200 W Max. C3075 1O0Watt RMS 150W Max. Normally $129 Normally $99 NOWONLY$99 YOU SAVE $30 NOWONLY$89 C3070 Was$69.00 NOW ONLY $49.00 HUGESAWNGSONSPEAKERS 8"WOOFER 60Watt RMS 1OOW Max. c 3060 Was $49.95 61 /2" WOOFER/Midrange 30Watt RMS SOW Max. C 3055 WAS $29.95 Now $39.95 SAVE $10.00 NOW ONLY $24.00 Multiple De-soldering Tool Ideal for service technician and hobbyist alike. Can alao be used aa a aolderlng iron. I 240V AC 50Hz I SEC Approval W/2228 I Easy, single-handed action I Earthed I Simple cleaning action. 61/2" Mid Range 30Watt RMS SOW Max. with sealed fram e c 3045 Was $27 .50 NOWYOU SAVE AT$22.00 TO 3 HEATSINK GIVE-AWAY FROM 50 cents each! H 0503 50c EACH 10 UP 4OcEACH NORMALLY $1 . S0EACH r12so Normally $59.95 Th is month $49.95 SAVE $10.00 TOP VALUE Replacement Tip T 12551.5mm $4.95 Spare Tip T 12521 .2mm $4.95 Why pay $400 or more for a David Clark set? AVIATORS HEADSET WITH OIL FILLED EA R CUSHIONS • High pcrformanc.c, noise attenuating earphoms. • Noise cancelling microphon:: • Cushioned head pad • Super sturdy • Great performance• Superb, professional pilot's headset will last a lifetime with reasonable treatment. • Includes standard aircraft jacks. ONLY $189.00 C9070 Now available f rom Altronics Dealers VALUE OUR DIRECT IMPORT PRICE LESS THAN $100! Pocket Sized Personal Audio Signal Generator Qune the fi nest portabel audio oscillator we have ever seen. Ran ge switch and multiply enable selecti on to 46 preset freq uencies from 20Hz to 1S0kHz , eg 20H z, 28H z, 32Hz, etc. Sine Wave and Sq ua.re Wave o utput. Output control -20db to 0db Internal 9V battery Q 1542 Oscillator • · . Harris Four Channel Digital Recorder/Announcer • The Harris A2100 provides 4 channels of natural speech recording and play-back. • Record time for each channel Is Internally selectable to 10, 15, 20 or 30 seconds. • Channels can be used separately or linked to provide one long recording/announcement. Facilities/Features • Microphone Input - balanced line, low Z, Input 5 PIN DIN socket (mates with Redford C 0372 desk m1c) Auxilliary Input· 100KOhm 0.2V sensitivity, e.g . for CD, tape deck, Tuner, BGM line. Timer Switch - automatically initiates the play back of the selected channel. Intervals are 10, 20, 30 seconds, 3, 6, 12 and 30 minutes and off. Line In/Line Out · zero gain circuit 1 :~~~ :: ~GuJ oftt~~~ :~~~tf~~~ck 08 0 through the recorder. This line will interupt with the recorded announce- etc ments as desired. Literally dozens of applications • Music on Hold Adviser· Over 50% of phone calls are • • • placed on hold - use thi~ time to promote your business or products. Information Guide - Great for displays, trade shows, self guided tours and even art galleries. PA System Feedback Eliminator· Wth the Harris Announcer, feedback is eliminated. Just operate on 'instant replay' mode and once the announcement is recorded it wtll automatically page. Self resets ready for the next message. Emergency Signals • and/or security warnings can be 0 \p.~~::i;,=<,\'' II ~ ··---· . Lttera · IIY hUn d(e dSO f app1·!Ca t·!OnS. Dea d easy tOUS e. • 1,~~=~~~<l,,,!~; f,;'~~i~~:,rf~i~!tm~ ~~;~~n~~~record 0 Designed around the TMS 3477 digital recorder IC, this brilliant Australian made recorder has no moving parts and will play Indefinitely. $7g g A 2100 Great Value you own ads or have them commerco!.lly produced • play thro_ugh your PA/BGM system as often as desired with .00 50MHz Logic Probe with Logic Pulser LOGIC PULSER {Model Q 1280) Synch input impedance ............................ 1MOhm Pulse rate ................................................. 0.5/400Hz Pulse width ................................................ 10uS Output current ......... .. ... ......... ..... ................ 1OOmA sink/source Maximum input signal frequency .. .................. Input impedance .... .. .. .. ...................... ............ Opperattng ..s~ppl( range ................................ TTL. LoijtC 1 (H LED) .................................. Logic "0 (LO LED) ........................................ Square wave output current ...................... 5mA sink/source CMOS: Logic"1" (HI LED) .............................. Power suply range .................................... 5 • 15V DC Logib "0" (LO LED) ........................................ Power supply protection ............................ 20V DC (30seconds max) Mimimum detectable pulse width .................. Synch input protection ........................ ...... 120V DC {30 seconds max.) Maximum signal input protection .................... Test point protection .................................. 35V DC (30 seconds max.) Power supply protection .... 50MHz 120kOhm 18V DC maximum > 3.0+/-0.25V < 0.75+/-0.25V > 60% Vcc+/-5% < 15% Vcc+/-5% 10 Nanoseconds +/-70V AC/DC (for15seconds) +/-20V DC II Bench Top Power Supply (See EA Jan'85) VALUE • Short circuit protection • Load switching • Current limiting fully variable-twin selectable ranges-dual scale meter • Separate earth terminal provided • Housed in our Deluxe "ABS" instrument case SPECIRCATIONS: • Output Voltage - 3 to 30V • Output Current Oto 1 amp (fully variable) • Load Regulation - Better than 0.2% from Oto full load • Output Ripple• Less than 2mV RMS e BANKCARD e VISA e MASTERCARD e PHONE TOLL FREE 008 e NEXT DAY JETSERVICE DELIVERY a 1280 $54.9s 3-30V to 1 Amp Max. With Variable Current Limit. K3210 $90.oo 999 007 Country clients please allow an additional 48-72 hours MORE AL TRONICS DEALERS WANTED If you have a Retail Shop, you could increase your income significantly by becoming an Altronics Dealer, Phone Chris Campbell (09) 328 2199 for Details. 17 4 Roe St. Perth W.A. 6000 PHONE TOLL FREE 008 999 007 Perth Metro (09) 328 1599 ALL MAIL ORDERS P.O. Box 8350 Stirling Street Exchange Perth W.A.6000 AL TRONICS RESELLERS Chances are there is an Altronics Reseller right near you - check this list or phone us for details of the nearest dealer. PI••• Note: Resellers have to pay the cost of freight and insurance and therefore the prices charged by individual Dealers may vary slightly from this Catalogue - in many cases, however, Dealer prices will still represent a significant cost saving from prices charged by Altronics Competitors. Don't forget our ExprH1 Malt and Phone Order Service - for the coat of a local calf, Bankcard, VIH or M•terc■ rd holder• can phone order for 1 ■ me day deapatch. Blue Ribbon DHler. are highlighted with a ■. These Dealers generally carry a comprehensive range of Altronic products and kits or will order any required item for you. STANDARD DELIVERY & PACKING CHARGE $5.50 to 1Kg $8 over 1Kg 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 3 Kg is $8.00 • 3Kg to 5Kg is $20.00- We process your order the day received and despatch via. Overnight JetHrvlce Courier 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 consignees risk. Should you require comprehensive insurance cover against loss or damage please add 1% to order value (minimum charge $1). When phone ordering please request "Insurance". TOLL FREE PHONE ORDER - Bankcard.Visa, Mastercard Holders can phone order toll free up to 6pm Eastern Standard Time. Remember with our Overnight Jetaervlce we deliver next day. WA COUNTRY ALBANY BP Electronics ■ 412681 ESPERANCE Esperance Communications 713344 GERALDTON Bird Electronics 641631 KALGOORLIE Todays Electronics ■ 212777 KARRATHA Daves Oscitronic 854836 PORT HEADLAND Ivan Tomek Electronics 732531 WYALKATCHEM D & J Pease 811132 NT ALICE SPRINGS Ascom Electronics 521500 Farmer Electronics 522388 DARWIN Ventronics 853622 ACT CANBERRA Bennett Commercial Electronics 805359 VICTORIA CITY All Electronic Components 6623506 SUBURBAN CHELTENHAM Talking Electronics 5842386 CROYDEN Truscott Electronics ■ 7233860 PRESTON Preston Electronics 4840191 COUNTRY BENDIGO KC Johnson ■ 411411 MORWELL Morwell Electronics 346133 Tattersal Sounds 8212892 QUEENSLAND CITY Oelsound P/L 8396155 SUBURBAN CAPALABAKingsway Electronics 3902399 WOODRIDGE David Hall Electronics 8082777 COUNTRY BUNDABERG Bob Elkins Electronics 721785 GLADSTONE -Supertronics 724459 MACKAY Philtronics ■ 578855 ROCKHAMPTONAccess Electronics (East St.) 221058 TOOWOOMBA Hunts Electronics ■ 329677 TOWNSVILLE Solex ■ 7724466 MAROOCHYDOREMals Electronics 436119 SA CITY Force Electronic ■ 2125505 SUBURBAN BRIGHTON Force Electronics ■ 3770512 CHRISTIE& BEACH Force Electronics ■ 3823366 ENFIELD Force Electronics ■ 3496340 FINDON Force Electronics ■ 3471188 LONSDALE Force Electronics ■ 3260901 COUNTRY MT.GAMBIER South East Electronics 250034 WHYALLA Eyre Electronics ■ 454764 TA.SMANIA HOBART George Harvey ■ 342233 LAUNCESTON George Harvey ■ 316533 NSW CITY David Reid Electronics ■ 2671385 CARINGHAH Hicom Unitronics 5247878BLACKTOWN Sheridan Electronics 621 1494 COUNTRY COFFS HARBOUR Coffs Habour Electronics 525684GOSFORD Tomorrows Electronics 247246 GRAFTON East Coast Electronic 431250 NEWCASTLE Novocastrian Elect.Supplies 621358 RAYMOND TERRACE Alback Electronics 873419 WINDSOR M & E Electronics 775935 WOLLONGONG Newtek Electronics ■ 271620 Vimcom Electronics 284400 WAGGA WAGGA Phillips Electronics 216558 February 1988: 200 Watt Stereo Power Amplifier; Deluxe Car Burglar Alarm; End Of File Indicator For Modems; Low Ohms Adaptor For Multimeters; Line Isolation Unit For Phone Patch; Easy Tips On Headphone Repair. March 1988: Remote Switch For Car Alarms; Telephone Line Grabber; Endless Loop Tape Player; Build Your Own Light Box; New Life For RadioCassette Players; Old-Time Crystal Radio. April 1988: Walkaround Throttle For Model Railroads, Pt.1; pH Meter For Swimming Pools; Slave Flash Trigger; Headphone Amplifier For CD Players ; What Is Negative Feedback, Pt. 1 ; Mobile Antennas For The VHF & UHF Bands. May 1988: Optical Tachometer For Aeromodellers; High Energy Ignition · For Cars; Ultrasonic Car Burglar Alarm ; Walkaround Throttle For Model Railroads , Pt.2; Designing & Building RF Attenuators; Motorola MC3334P High Energy Ignition IC Data. June 1988: Stereo Control Preamplifier (Uses LM833), Pt.1; Breakerless Ignition For Cars Using Hall Effect Pickups; Mega-Fast Nicad Battery Charger; Automatic Light Controller Uses PIR Detector ; RF Sniffer Probe & Preamplifier; What Is Negative Feedback, Pt. 2. July 1988: Stereo Control Preamplifier, Pt.2 ; Fitting A Fuel Cut-Off Solenoid ; Booster For TV & FM Signals ; The Discolight Light Show, Pt.1; Tone Burst Source For Amplifier Headroom Testing; National Semiconductor LM833 Op Amp Data; What Is Negative Feedback, Pt.3. August 1988: Building A Plasma Display ; Universal Power Supply Board; Remote Chime/Doorbell; High Performance AC Millivoltmeter, Pt.1; Discolight Light Show , Pt. 2; Getting The Most Out Of Nicad Batteries; Data On Insulated Tab Triacs. September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Vader Voice; Motorola MC34018 Speakerphone IC Data; National Semiconductor LM 1 2 1 50W Op Amp Data & Applications ; What Is Negative Feedback, Pt.4. October 1988: Stereo FM Transmitter (Uses Rohm BA 1 404); High Performance FM Antenna; Matchbox Crystal Set; Electronic House Number; Converting A CB Radio To The 28MHz Band; Electronics & Brock's BMW Blaster; Queensland 's Powerful Electric Locomotives. November 1988: 120W PA Amplifier Module (Uses Mosfets); Poor Man 's Plasma Display ; Automotive Night Safety Light; Adding A Headset To The Speakerphone; How To Quieten the Fan In Your Computer; Screws & Screwdrivers , What You Need To Know; Diesel Electric Locomotives . December 1988: 120W PA Amplifier (With Balanced Inputs), Pt.1; Diesel Sound Generator; Car Antenna/ Use this handy form to order your back copies ~ I I I - ---- ----- - --- - Please send me a back issue for: D May 1 988 LJ June 1 988 n - -- - - February 1 988 □ July 1 988 - - ----------- •--7 D March 1 988 o O September 1 988 April 1 988 I □ October 1 988 D November 1 988 D December 1 988 D August 1 988 D January 1 989 I I □ March 1 989 D April 1 989 D May 1 989 D June 1989 □ July 1989 O August 1989 D September 1989 0 October 1989 0 November 1989 D December 1 989 □ January 1990 D June 1990 D February 1 990 D April 1 990 □ May 1990 I I I I I I I I I I I I D March 1990 O February 1 989 Enclosed is my cheque /money order for $ _ _ _ _ _ _ or please debit my □ Bankcard D Visa Card ----,------r---. _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ D MasterCard Card No. I II ]I II Signature. _ _ _ _ _ _ _ _ _ _ _ _ Card expiry date_~-Name _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ (PLEASE PRINT) Stree.______________________ Suburb/town, _ _ _ _ _ _ _ _ _ _ _ _ Postcode____ Price: $A5.00 each (includes postage) . Overseas orders add $A 1 .00 per issue for postage NZ & PNG orders are sent by air mail. Detach and mail to: SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROY BEACH NSW 2097 OR FAX: (02) 982 95 53 l I ~ - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -J50 SILICON CHIP Demister Adaptor ; SSB Adaptor For Shortwave Receivers; Electronics & Holden's New V6 Engine ; Why Diesel Electrics Killed Off Steam; Index to Volume 1 . January 1989: Line Filter For Computers; Ultrasonic Proximity Detector For Cars; Simple Computer Sound Repeater; 120W PA Amplifier (With Balanced Inputs) Pt.1 ; How To Service Car Cassette Players; Massive Diesel Electrics In The USA. February 1989: Transistor Beta Tester; Minstrel 2-30 Loudspeaker System ; LED Flasher For Model Railways (uses LM3909) ; Build A Simple VHF FM Monitor (uses MC3362), Pt.1; Lightning & Electronic Appliances; Using Comparators to Detect & Measure. March 1989: LED Message Board , Pt.1 ; 32-Band Graphic Equaliser , Pt.1 ; Stereo Compressor For CD Players ; Map Reader For Trip Calculations ; Amateur VHF FM Monitor, Pt.2; Signetics NE572 Compandor IC Data; Electronics For Everyone - Resistors . April 1989: Auxiliary Brake Light Flasher; Electronics For Everyone: What You Need to Know About Capacitors ; Telephone Bell Monitor/ Transmitter; 32-Band Graphic Equaliser, Pt. 2; LED Message Board , Pt.2. May 1989: Electronic Pools/Lotto Selector; Synthesised Tom-Tom ; Biofeedback Monitor For Your PC ; Simple Stub Filter For Suppressing TV Interference; LED Message Board , Pt.3; Electronics for Everyone - All About Electrolytic Capacitors. June 1989: Touch-Lamp Dimmer (uses Siemens SLB0586) ; Passive Loop Antenna For AM Radios ; Universal Temperature Controller; Understanding CRO Probes; LED Message Board , Pt.3; Coherent CW - A New Low Power Transmission Technique. July 1989: Exhaust Gas Monitor (Uses TGS812 Gas Sensor) ; Extension For the Touch-Lamp Dimmer; Experimental Mains Hum Sniffers ; Compact Ultrasonic Car Alarm; NSW 86 Class Electrics ; Facts On the PhaxSwitch Sharing Your Phone Line With A Fax Machine. August 1989: Build A Baby Tower AT Computer; Studio Series 20-Band Stereo Equaliser, Pt.1; Garbage Reminder - A 7-day Programmable Timer; Introduction To Stepper Motors; GaAsFet Preamplifier For The 2-Metre Band; Modern 3-Phase Electric Locomotives . September 1989: 2-Chip Portable AM Stereo Radio (Uses MC13024 and TX7376P) Pt.1; Alarm-Triggered Telephone Dialler; High Or Low Fluid Level Detector (uses LM1830N); Simple DTMF Encoder (uses Texas TMC5089) ; Studio Series 20-Band Stereo Equaliser , Pt.2 ; Auto-Zero Module for Audio Amplifiers (Uses LMC669) ; A Guide fo Hard Disc Drives. October 1989: Introducing Remote Control; FM Radio Intercom For Motorbikes (Uses BA 1 404 And TDA7000) Pt.1 ; GaAsFet Preamplifier For Amateur TV ; 1 Mb Printer Buffer; 2-Chip Portable AM Stereo Radio , Pt.2 ; Installing A Hard Disc In The PC; A Look At Australian Monorails. Novem ber 1989: Radfax Decoder For Your PC (Displays Fax , RTTY and Morse) ; Super Sensitive FM Bug ; Build A Low Cost Analog Multimeter; FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Radio , Pt.3 ; Floppy Disc Drive Formats & Options; The Pilbara Iron Ore Railways . Decem ber 198 9: Digital Voice Board (Records Up To Four Separate Messages, Uses Texas TMS34 77NL 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 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. February 1990: 1 6-Channel Mixing Desk ; High Quality Audio Oscillator, Pt.2 ; The Incredible Hot Canaries ; Random Wire Antenna Tuner For 6 Metres; Phone Patch For Radio Amateurs, Pt.2; PC Program Calculates Great Circle Bearings. March 1990: 6/ 12V Charger For Sealed Lead-Acid Batteries; Delay Unit · For Automatic Antennas; Workout Timer For Aerobics Classes; 16-Channel Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC; Digital Waveform Generation Using a PC ; The Controls On A Model Aircraft. April 1990: Dual Tracking ± 50V Power Supply; VOX With Delayed Audio; Relative Field Strength Meter; 16-Channel Mixing Desk, Pt.3; Simple Service Tips For Your Microwave Oven ; Model Aircraft Aerodynamics; Active CW Filter For Weak Signal Reception. May 1990: Build A 4-Digit Capacitance Meter; High Energy Ignition For Cars With Reluctor Distributors ; The Mazzie CW Transceiver; Waveform Generation Using A PC, Pt.3 ; 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; Fitting A Fax Card To Your Computer; Off-Shore Oil Rigs ; What To Do When Your Computer Goes Bung , Pt.2. Note: November 1987, December 1987 & January 1988 are now sold out. f ULY1990 51 PT.1: COAL BURNING POWER STATIONS In Australia, as in all industrialised nations, our whole lifestyle - work, homes, meals, relaxation, transport - presupposes the ready availability of cheap, reliable electrical energy. Just how electricity is generated, transmitted and used in large industries is the subject of this new series. We begin with a look at modern coal-burning power stations. By BRYAN MAHER For cities, electricity must be generated on demand, as it cannot be stored in large quantities. Power stations generate the electricity we need, then transmission lines, substations and distribution circuits bring it right into our homes. Almost all electric power used is generated as 3-phase AC by rotating machines called alternators. These are mechanically driven, most often by a turbine powered by either steam or water (hydro). In this first episode of our new series we look into the works of a typical modern steam power station. Siting is important. The boilers require huge supplies of fuel, usually coal, together with copious quantities of water. An ideal site would be an area with generous coal THIS AERIAL VIEW shows the Callide B power station which is located near Biloela in Central Queensland. This station was completed in March 1989 at a cost of $830 million & generates 700MW. • deposits beside a lake or harbour. Lake Macquarie, near Newcastle, is a large body of tidal water surrounded by deep coal mines. The Hunter River Valley, north west of Newcastle, is rich in coal and has ample fresh water. Little wonder then that the greatest concentration of electric power stations in Australia are found in the Newcastle region. Victoria has long used the Yallourn coalfields for power generation. Central Queensland has enormous coal supplies in the Blackwater-Moura-Middlemount areas, far from the sea. Therefore Gladstone power station, the largest in the state at the time, was built on the Calliope River beside Gladstone Harbour. Coal is transported 300km to the power station by electric train from the mines. Typical power station A typical coal burning power station is shown in our simplified flow diagram, where numbered sections are referred to in the text. Coal mined in open cut or deep underground mines is conveyed by rail, truck or conveyor belt systems (1), to the coal storage stack (2). From the storage stack, coal is elevated to the top of the bunkers (3) and from there it gravitates down to the pulverising mill (4). Here the coal is ground to a micrograin powder, so fine and smooth that it flows like dry dust. Air, drawn in at (5), passes through a heat exchanger (6) where it is preheated by the hot flue gases and then mixed with the powdered JULY 1990 53 THIS SIMPLIFIED FLOW DIAGRAM shows the basic processes in a coal-burning power station. Pulverised coal is burnt in a boiler (8,9,10&11) to produce superheated steam at 540°C. This superheated steam then drives the turbines (16,17&18) which in turn drive the alternator (21) to produce electricity. The exhaust steam from the turbines is then condensed by cooling water & pumped back to the boiler drum (15) for re-use. ASH AND DUST O coMsusT10N GASES COMBUSTION AIR COMBUSTION ZONE coal (and sometimes a little oil) to form a highly combustible mixture. This air-coal mixture is blown by a large fan (7) into the boiler furnace chamber (8). The boiler (8,9,10,11) is a huge vertical structure up to 20 metres square and 80 metres high, which is filled with thousands of steel highpressure water tubes. Each tube forms an endless loop beginning and ending at the steam drum (15) located at the top of the structure. The air-coal dust mixture burns intensely in the furnace chamber (8) to continuously turn the water in the tubes to high pressure steam. In the largest NSW Electricity Commission power stations, each boiler turns more than half a tonne of water to saturated steam every second! BOILER WATER Superheater SATURATED STEAM Saturated steam is forced from the boiler drum (15) and through SUPERHEATED STEAM HOT COOLING WATER COLD COOLING WATER CD the superheater (10). This consists of tubes at the top of the boiler where even more heat is added to the steam. By this procedure, the pressure is raised to 16,550kPa (2400psi) and the temperature to 540°C. If the steam pipes from the boiler were not lagged, they would glow a dull red! Superheated steam contains much more energy than saturated steam as superheating allows the pressure to be increased a hove the gas-liquid critical point. High pressure turbine From the superheater (10), the steam flows at a rate of 1800 tonnes/hour through the turbine steam control valve into the high pressure 25 turbine (16). Here the steam impinges upon the hundreds of radial blades, pushing them and their main shaft around at 3000rpm. The higher pressure turbine has the shortest blades. Longer blades are used in the intermediate pressure turbine and even longer blades in the low pressure turbine. Exhaust steam from the high pressure turbine passes back to the boiler for reheating to the original temperature (this is not shown in our simplified diagram]. Reheated steam then enters the intermediate pressure turbine (17). Exhaust steam from the intermediate pressure turbine enters both ends of the low pressure turbine (18). By the time it has reached the last blades of the low pressure turbine, the steam pressure and temperature has dropped close to atmospheric conditions but the steam velocity has reached values up to Z000km/h. The final bladewheels in modern turbines may be two metres or more in diameter. (continued next page) ~ QEGB 1300MVA or amps). 1.3GVA (gigavolt- Thermal efficiency LIDDELL POWER STATION in the NSW Hunter Valley has four 500MW turbogenerators for a total installed capacity of 2000MW. This view shows one of the turbo-generators which has been uncovered for maintenance. Alternator The turbine drives the alternator (21), wherein the electricity is actually generated. The alternator may be up to 15 metres long · and consists of a laminated silicon alloy steel stator (the outer stationary section) with the rotor inside. The laminated steel core of the stator has many axial slots which carry heavy insulated copper conductors, wound in a triple set of coils. Each coil set generates one phase, so the whole alternator generates a complete 3-phase AC 50Hz supply. In a 660MW alternator, such as at Bayswater and Eraring in NSW, the output is 21,000A at 23kV. The turbine shaft is direct coupled to the alternator rotor shaft, driving it at 3000rpm. The rotor is wound with very heavy insulated copper conductors. These form the 56 SILICON CHIP excitation circuit which is fed with thousands of amps, typically at a voltage in the range 200V to 500V, to create an intense DC magnetic field which rotates with the rotor. The interaction of this rotating magnetic field with the stator windings generates the electricity. Alternator transformer The electrical output of each alternator goes directly to the transformer (22). This steps up the voltage to a much higher potential for connection to the state grid system. Obviously the electrical rating of this alternator transformer must match the power capability of the alternator which supplies it. In Australian power stations, we find transformers as large as 830MV A (megavolt-amps), while in the USA some are as large as For greatest efficiency and power output of any steam turbine, we need to maximise the steam pressure differential between entry and exhaust. This is achieved by using very high steam pressures at the input of the turbine and by having virtually a vacuum at the turbine exhaust. To produce this vacuum, the condenser (19) is situated immediately below the low pressure turbine. The condenser is a heat exchanger consisting of a very large vessel up to 12 metres in diameter and up to 12 metres long. It contains thousands of thin-walled copper or brass tubes through which cold water is circulated. The exhaust steam from the low pressure turbine enters the condenser and flows over these tubes, whereupon it condenses to pure water. This water is immediately removed by the condensate pump, leaving a near vacuum. This condensing of steam and removal of condensate water goes on continuously, so the turbine exhaust steam is always at a very low . level (about 1115th of atmospheric pressure). A copious supply of cold water is fed through the condenser tubes by the circulating pump (23). In some power stations, a large dam provides ample water but most power stations have to make other arrangements. If you think for a moment, you will realise that some heat is continuously transferred from the turbine exhaust steam to the coolant water in the condenser. This commonly raises the temperature of the circulating coolant water by about 10°C. Cooling towers This relatively large amount of heat must be dissipated and those power stations which are not situated close to a large dam, lake or ocean must resort to huge concrete cooling towers (24). The towers may be 130 metres high, 100 metres in diameter at the base and 50 metres in diameter at THE VENTURI SHAPE of cooling towers produces a strong updraft of air which cools the water from the condenser. These towers can be 100 metres across at the base & 130 metres high. the top, and they may weigh as much as 20,000 tonnes. Their venturi shape provides a strong updraft of cooling air which occurs because of natural convection - no fans are used. The coolant water from the condenser, typically at 40°C, is sprayed upwards inside the tower and falls onto hundreds of vertical PVC sheets. The updraft of air then causes cooling by evaporation. Most of the water falls to a pond at the tower base. The condensate [ie, condensed steam) from the condenser is pumped to a holding tank, often called the hotwell (not shown on our TURBINE OVERHAUL AT the Gladstone power station in Queensland: this 300MW alternator rotor is 1.2-metres in diameter & spins at 3000rpm. simplified diagram). From the hotwell, the water must be pumped back into the steam drum, inside the boiler. That means pumping water against the 17 ,000kPa steam pressure in the boiler! Therefore, the boiler feed pump (20) is driven by the largest motor in the power station, anything from 3 megawatts to 15 megawatts. In some power stations, an auxiliary lOMW steam turbine is used to drive the boiler feed pump. Economiser On its path back into the steam drum, the boiler feed water is preheated in the economiser (11). This is a set of high pressure water pipes lying within the path of the very hot furnace gases, to extract most of their remaining heat. The flue gases also preheat the intake air (11), as noted previously. The flue gases consist mainly of water vapour and carbon dioxide, together with unburnt dust, fine grit and fly ash which must be removed before being expelled from the smokestack. This is done by the electrostatic precipitator (12). Electrostatic precipitator AERIAL VIEW OF THE TARONG Power Station, 180km north-west of Brisbane. This 1400MW station is one of Queensland's newest and employs four 350MW turbo-generators. Note the two large cooling towers. The precipitator consists of a large box-like structure containing lots of fabric filter elements. The fly ash and grit are stopped by the filters and are collected in an ash bin at the bottom of the precipJULY 1990 57 that when a furnace chamber inspection peephole is opened, air blows into the fire rather than flame spurting out. This point is a safety essential, as the furnace chamber walls have access manholes for use when the boiler is not in use. Any positive pressure within the fire chamber would be extremely dangerous as it might blow out a manhole and cause a firestorm outside. Heavy ash falls from the bottom of the furnace chamber and is mixed with water to form a slurry. The same thing happens to the fly ash and solids caught by the precipitator. This slurry is pumped (25) to an ash dam for disposal. Overall results ONE OF THE 28 COAL MILLS installed at Bayswater Power Station in the NSW Hunter Valley. These mills pulverise the coal to the consistency of talcum powder prior to combustion in the station's boilers. The generation of electricity is carried out on such a vast scale that efficiency of operation is essential. However, despite the best state-of-the-art design, the overall thermal efficiency, from fuel input to electrical output, does not exceed 40%. Electrical losses in a large station amount to about 6% of total power generated. These electrical losses include the resistive power losses that occur within alternators and transformers. Auxiliaries THIS 660MW TURBO-GENERATOR is one of four at Eraring Power Station (south of Newcastle). It generates 23kV at 21,000 amps. itator. A high electrostatic potential is applied to the fabric elements to attract the dust and grit out of the flue gases. Induced draught fan The flue gases must be drawn from the top of the boiler furnace, through the superheater (10), the economiser (11) airheater (6) and precipitator (12), then blown up the smokestack (14). This task is performed by the induced draught fan (13). Maximum efficiency in the boiler comes from complete combustion of the coal. The flue gases should contain no unburnt combustible mater58 SILICON CHIP ial. This is not only an efficiency requirement but is also demanded by environmental considerations. Complete burning of the pulverised coal demands a precise balance between the performance of the inlet forced draught fan (7) and the exit induced draught fan (13). Fire safety Furthermore, for safety of operators and plant in the boiler room, the induced draught is stronger than the forced draught, so that air pressure within the furnace chamber is slightly below atmospheric pressure. This means All power used to drive the six main auxiliary motors we have described (ie pump and fan motors) must, from an overall station viewpoint, be considered a power loss. Nevertheless, these very large motors are essential to the operation. In a large power station where, say, 2600MW (ie, 2.6GW) is generated, typically 130MW or 5% of alternator output is used by the station itself. Of this, the six main auxiliary motors associated with each alternator could add up to lO0MW of necessary station loading. Next month we will look further into these fascinating power stations. Acknowledgements Grateful thanks to the Electricity Commissions of New South Wales and Queensland, and to Dr Habibulah. ~ SELF CONTAINED WIRELESS PIR ALARM SYSTEM CROSSOVER 2WAY DATA SWITCH BOX Control two computers and two printers. • DB-25 and Centronic type available. Complete with two wireless key transmitters, this little system •will cover up to 12m <at>90deg. NOW ONLY $59.95 was $199 NOW $129 AUTO SCANNING A/B SWITCH BOX *DB-25 Type NOW ONLY $69.95 VIDEO CAMERA LENS SET MS501 3 WAY MINI SPEAKERS * 1 . 6 X teleconverter *0.5X wide angle lens Will suit camcorders with 46mm, 49mm, 52mm screw theads. - - • Supplied with lens caps and hard case. *20 watt RMS * 80Hz to 18kHz *SUIT IBM XT/AT * 200mm/sec · • 195 d . 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Contributions from readers are welcome and will be paid for at standard rates . ...------..,...__..+2ov Driving stepper motors from a parallel printer port The parallel printer port on an IBM-style PC provides 12 latched bits of output (see Computer Bits, SILICON CHIP, February, 1990 for pin connections and other details). This allows up to three stepper motors to be driven quite easily, if we assign four bits to each motor. The circuit presented here uses two bits to drive each motor coil. There are three possible states for each coil: " + ", " - " and "off". The coils are driven in bipolar mode; ie, the current through the entire coil is reversed and the centre tap is not used. This allows more torque to be developed than with the usual unipolar drive, where only half of each coil is energised at any given time. (Refer to "An Introduction to Stepper Motors'', SILICON CHIP, August 1989 for a more complete discussion of these drive schemes). For bipolar drive we need a power driver chip which can both source and sink large currents. Such ICs have been around for quite some time, disguised as audio amplifiers. The humble LM:380 audio amplifier makes an excellent stepper motor driver. It can source and sink currents up to 1.3A (with proper heatsinking). Such a current, through both windings of an 89mm stepper motor, can produce arm-breaking torque. The circuit shows two LM380s, each driving one of the stepper motor's coils in a half-bridge configuration, with a centre-tapped DC power supply. The coil drive voltage is ± 8V, which limits the maximum speed to only a few hundred RPM but keeps the static power dissipation within reasonable limits. The current limiting resistors R should be chosen to limit the coil 60 SILICON CHIP PARALLEL PORT DATA BITS 10k ooo---w.1.----.....- - - - - - 1 +10V 10k 01 O--Wt~~--+--......----,1 1k .01 1k 01 '""' .01 SIGNALo-----<..,__ _ _ _ _ _ _ __ .,. GND 89mm STEPPER MOTOR MOTOR COIL PHASE 2 ~-------+2DV o.,I .,. 10k 03 1N4001 R *4 .7!:J 020--~~--...-------=-t ,ow 10k D30-"IIW-+--~----1k .01 1k .D1 * SEE TEXT ., A 2155,215,....6_ _ _ __, ._+.:........_...,--·+20V 240VAC + N E~ 4700 16VW '--------+---ov ., TABLE 1 STEP 0 1 2 3 4 5 6 7 PRINTER PORT OUTPUT BITS 03 02 01 DO 0 0 0 0 1 1 1 0 1 1 1 0 0 0 0 0 0 0 1 1 1 0 0 0 PHASE 1 CURRENT. (Amps) PHASE 2 CURRENT (Amps) 1 1 0 0 0 0 0 1 1 0 1 1 1 1 1 0 1 0 1 1 1 1 0 current to around 1A (ie, the DC coil resistance plus R should be greater than or equal to 80). The audio amplifier inputs are driven from the TTL output bits of 1 the printer port via resistive voltage dividers. The (lightly loaded) TTL output levels of + 0.1 V and + 3.8V are reduced to a 0.35V differential signal at the LM380 in- puts, which is sufficient to drive it to saturation in either direction. When both TTL bits are the same, the LM380 output will sit somewhere around the half-way point, and the coil is effectively deenergised. The drive sequence, for a halfstep clockwise drive is shown in Table 1. For a full-step drive, simply omit steps 1, 3, 5 & 7. Alternatively, for a full-step, half-power drive, omit steps 0, 2, 4 & 6. If this looks a little complicated to program, it needn't be, if you take the trouble to set up a small array with the appropriate bit patterns for each step. In GWBASIC, this can be achieved as shown in Table 2. Once the drive table has been set up, the motor can be stepped forwards or backwards as shown in Table 3. Delay loops should be inserted within the above code to control the speed. A second motor can be driven from the top four bits of PORT.A. Simply multiply the COIL.DRIVE.CODE for this motor by 16, add it to that of TABLE 2 DEFINT A-Z DIM COIL.DRIVE.CODE(?) FOR MOTOR.STEP=0 TO 7 READ COIL.DRIVE.CODE(MOTOR.STEP) NEXT MOTOR.STEP DATA 5,4,6,2, 10,8,9, 1 the first motor, and OUTput the eight bits to both motors simultaneously. A third motor can be driven from PORT.C but the COIL.DRIVE.CODE should be XOR-ed with 11 [decimal) before outputting it, since bits DO, Dl and D3 of PORT.C are inverted. Finally, on IBM PC-XTs or similar compatibles, it helps if you turn off the 18.2Hz DOS clock interrupt. Use the instruction: OUT &H21,INP[&H21) OR 1 to disable the clock interrupts, and OUT &H2 l,INP[ &H21) AND &HFE to restore the interrupt when you have finished stepping the rnotor[s). This will ensure smooth stepping at the higher speeds. Steve Payor, Kogarah Bay, NSW ($35) TABLE 3 REM Go forward 1000 half steps FOR MOTOR.STEP=0 TO 1000 OUT PORT.A,COIL.DRIVE.CODE(MOTOR.STEP AND 7) NEXT MOTOR.STEP REM Go backward 500 full steps FOR MOTOR.STEP=1000 TOO STEP -2 OUT PORT.A,COIL.DRIVE.CODE(MOTOR.STEP AND 7) NEXT MOTOR.STEP Switching mains with your computer A Siemens BRTl 1 optically isolated Triac AC switch [or SITAC for short) can be used to directly drive a mains load provided the load is less than or equal to 60W. A 5V signal derived from your computer port drives the internal LED of the BRTl 1 via a 3.3k0 resistor. This 1.5mA drive current is sufficient to turn on the internal optical Triac of the BRTl 1 and thus allows current to flow to the load. Under normal loads [eg, a lightbulb or transformer), no snubber network [series resistor & capacitor) is necessary as the internal Triac has a very good dV/dT rating of lOkV/µs. The Triac can handle a 3A surge current and a continuous current of 300mA. For higher load currents, an external Triac will be required. All wiring to the mains side of the BRTl 1 must be run using 240V ACrated wire and the IC should be mounted with 15mm of clearance between the low voltage side [pins 1, 2, 3} and the mai:o.s side [pins 4, 5, 6) of the IC. This will ensure that the full 5.3kV isolation provided by the IC is maintained. SILICON CHIP One-chip DC volume control It is often useful to be able to control the output level of an audio signal with a DC voltage, particularly if hum voltages are likely to get into a standard volume control. DC level control is also useful where the volume control is remote from the signal. This circuit is based on the MC3340P DC volume control IC. The audio signal is applied via an AC coupling capacitor to the pin 1 input [maximum level of 0.5V RMS), while the output is extracted from pin 7 and fed to the output via a 0.47µF capacitor. Potentiometer VRl forms part of a voltage divider network and sets the DC voltage on the control input [pin 2}. When the control voltage is at a minimum, the output is at its maximum gain of 1 ldB. When the control voltage is at a maximum, the output is attenuated ------------+B-16V 10 16VWI 2.2k .,. VCC ~.,.U .T 0.47 16VW ~i\l-"J-i----11 IN MC~~OP OUT 7 •~PUT CONTROL GNO ,ROllOFF 2 J 6 2~RL1N~--. . 1k 47 + 16VW+ .,. 47kf ~ i -:- 680pFI. .,. by BOdB. The 680pF capacitor at pin 6 provides high frequency rolloff of the signal and the distortion is less than 1 % for a 0.5V RMS input signal. The circuit could also be used to provide sound effects by feeding a modulated control voltage to pin 2. SILICON CHIP JULY1990 61 ~5wut4,4, There's one mailrea//y trust . .. BOARD SOLUTIONS Pty Ltd I I ***NEW!!! 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E1000 E1030 E1010 E1040 E1050 E1060 E1070 E1080 E1090 E1105 E1110 E1120 55.00 134.95 99.00 349.00 425.00 245.00 275.00 249.00 285.00 275.00 134.95 154.95 C1000 C1005 C1010 C1020 C1030 C1040 C1050 C1060 C1070 C1080 C1090 139.00 199.00 249.00 275.00 99.00 115.00 125.00 25.00 189.00 325.00 399.00 C1100 C1120 549.00 399.00 C1130 C1140 549.00 95.00 • 14 Day money-back guarantee (except software) • At least 6 months warranty on all our products. • Mail orders are our speciality! • Road Freight on normal size items is $9.00 • Insurance $1.00 per $100 of order value • All prices INCLUDE sales tax • We accept Visa, Bankcard, Mastercard and Post Office COD • Call for latest price list • Special prices apply until June 30, 1990 - or while stocks last! • Leasing facilities available: just ask! • Government pricing available on request 48 Line 1/0 Card F1130 Serial RS-422 Adaptor F1140 Industrial 1/0 Card F1150 Universal Wire-wrap Card F1030 Dual Serial RS-422 Card F1040 80286 Speed-up Card F1050 IEEE 488 Interface Card F1060 IEEE 488 Interface Card- National Compatible F1070 A-D/D-A Converter, 12 bit, 1 Ch. 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We also have a 5-¼in floppy disc full of upgraded software so that you can use your computer as a function generator or tone burst generator. By STEVE PAYOR This series started out as a simple example of computer interfacing; a practical demonstration of how a little bit of electronics could enhance your PC, and vice-versa. On the way, we created a log/linear frequency sweep generator, a tone burst generator, and a sine/triangle/square wave function generator. That's not bad value, really, for a handful of resistors, a 64 SILICON CHIP 36-pin socket and some optional filtering components. PCB and floppy disc In this final article, we will put it all together with the introduction of a PC board (to make the filter easy to build) and a floppy disc with fully executable programs. But first, let's recap the story so far : The February 1990 issue, pages 68-71, described the parallel printer port and showed how to access the various bits directly. We also showed how a binary-weighted resistor network could turn the 8 data bits into an analog voltage. In the March 1990 issue, pages 80-84, we showed how a low-pass filter could remove the "steps" from the digitally generated waveform. On page 83, we gave a listing of a log/linear frequency sweep program, which proved very useful for adjusting the "flatness" of the filter passband response. The frequency sweep program is written in TURBO BASIC and has data rate of 20k samples/sec. When combined with the simple third-order LC filter , it can generate high quali- a HXACT VALUES ALL RESISTORS 1% OUTPUT S1b--------, S1a * 2. 769k : FIL TEA .._ LOAD 68[1 2.7k J. ---, (9) 07 * 5.583k 5.6k 50pF. 3.3k (8) 06 -!- C1 * 11.21k 5.6k 5.6k (7) 05 22k OUTPUT tRIM VR1 2.2k <5kf .,. 470!1 (6) 04 FILTER TYPE 180k (4) 02 3RD ORDER CHEBYSHEV : -0.1d8 AT 4.4kHz I 5TH ORDER CHEBYSHEV -0.1dB AT 36kHz C1b L2 C3 .0047 .01 38.3mH .033 .001 .001326 5.943mH .006308 7.618mH .005537 + 50pF LOAD 100k SAMPLES/ SECOND .001 297pF 4.415mH .005782 8.335mH .006424 + 50pF LOAD 100k SAMPLES/ SECOND L4 C5 SUITABLE DATA RATE C1a 20k SAMPLES/SECOND 180k 180k (3) 01 (16,19) TO (30,33) GND 5TH ORDER BUTTERWORTH -0.1dB AT 22kHz o---~Mr--- 7 (1) - S T R O B E 0 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 0 CRO TRIGGER CENTRONICS PIN NUMBERS ty waveforms up to 4.5kHz. In the May 1990 issue, pages 92-97, we presented two more programming examples. The program on page 93 is for generating IHF standard audio tone bursts. It is also written in TURBO BASIC and has the same data rate and frequency limitation as the frequency sweep program. The program on pages 94-96 is a wide range (20kHz plus) sine/triangle/square wave function generator. The program itself is in GWBASIC but it uses a high speed subroutine, written in 8088 machine code, to achieve a data rate of 100k samples/sec. OUTPUT D-A CONVERTER/FILTER Fig.1: this D-A converter & filter circuit plugs into the Centronics port of your computer. Note that you have a choice of filters: 3rd or 5th order Chebyshev, or 5th order Butterworth (see text). In most cases, the 3rd order Chebyshev filter will be adequate (see text). programs which can be run directly from DOS. The executable versions of these programs have been considerably enlarged, to make them more "user friendly". For example, they will automatically locate the 1/0 ad- dress of your parallel printer port. The data rate compromise You may well ask, why not use the highest possible data rate in all the software? Well, for short, repetitive waveforms, like sine, No compiler needed All these programs [and more) are on the floppy disc. The source listings of these programs are exactly as published. However, the source listings of the TURBO BASIC programs are mainly for information only. Since most readers will not have a copy of the TURBO BASIC compiler, we are including compiled and executable versions of these The 5th order Chebyshev filter is suitable for the function generator program but not for the frequency sweep & tone burst programs. The 36-pin Centronics socket is soldered directly to the PC board. ]ULY 1990 65 data rate, the filter components can be calculated to suit. Filter choices The 3rd order filter is easier to build than the 5th order types. Note that the Centronics socket fitted to this board is the "solder bucket" type which has a pin spacing of .085-inch. triangle and square waves, the highest data rate of took samples/ sec is fine. However, for the long waveforms produced by the frequency sweep and tone burst programs, the number of bytes required becomes excessive. For example, a 0.5s tone burst would require 50,000 bytes at a data rate of 100k bytes/sec. Not only is this getting close to the maximum allowable array size (64k bytes) but you would also have to wait an awfully long time for the program to set up this waveform. A data rate of 20k samples/sec is much more realistic for this task. Execution speed If you have an 8087 mathematics co-processor, the compiled programs will use it, resulting in a considerable saving in the time re- quired to set up the waveform. For example, setting up a 0.5s tone burst takes 4 seconds with the coprocessor and 41 seconds without it. Note: the data rate during waveform output remains unaffected by the presence of the coprocessor. What will affect the data rate is the speed of your CPU and/or 1/0 card. The programs allow you to enter sample times other than 50µs. So, for example, if you have a toMHz Turbo XT, you may find that a tkHz waveform comes out as 2. tkHz. To correct this, try entering a sample time of 23.85µs at the start of the program. The best way to determine the actual sample time on your machine is by experiment, so the first thing to do is get the D-A converter working. Once you have determined the Where to buy the PC board & software An etched PC board plus a 360K 5 ¼-inch floppy disc of the software are available from M. Radvanyi, PO Box 49, Kingswood, NSW 2750. The price is $39.95 (includes instructions on running the programs plus packaging & postage) Note: does not include on-board components. Please make payment by cheque (to M. Radvanyi) or by mail order. The floppy disc includes three separate executable programs which can be run from DOS: frequency sweep, tone burst generator and function generator (sine, triangle & square waves). Also included are some GWBASIC programs for those who wish to create their own waveforms. The software is easy to use and all frequencies and functions for each program are simply entered into the opening menu. Note: copyright of the PC pattern and the software is retained by the author. 66 SILICON CHIP The low-pass filter is only required if you wish to remove any visible traces of the D-A steps from the waveforms. With the machine code software, you certainly won't hear any difference because the lowest alias frequency will be 50kHz. So, if you don't have a CRO, you can leave the filter section of the PCB empty, and replace the switch with a wire link. Capacitor CtA can still be fitted, if you wish, to absorb the D-A glitches. You have a choice of filters from 1st order to 5th order in fact. We have listed the component values for suitable 3rd and 5th order filters on the circuit diagram. In most cases, the 3rd order Chebyshev filter will be adequate. This only requires one inductor and is easy to align (see the CRO photo on page 81, March 1990}. Unless you are an experienced constructor, we suggest you stick to the 3rd order filter, even for the higher data rate. (In this case, simply get out your calculator and divide the values for Cl, 12 and C3 by 5). Don't forget to fit a link in place of 14. The main advantage of the 5th order filters is that their steeper cutoff allows a passband which extends closer to the theoretical limit of half the sampling frequency. For example, with a took samples/sec data rate, the 5th order Chebyshev filter allows a frequency response up to 36kHz ( - 0.tdB). However, the very steep cutoff results in some ringing on square and sawtooth waveforms. The 5th order Butterworth (maximally flat) filter will give slightly cleaner waveforms. However, the - 0.tdB bandwidth is reduced to only 22kHz. Its principal advantage is that it can be adjusted to be dead flat up to 20kHz. In practice however, such precise alignment is rather difficult. Changing the parameters You can scale the 1 & C values, to take into account different source impedances or to move the cutoff frequency. PARTS LIST 36 . WAVEFORM OUTPUT GNO GND 19 CRO TRIGGER OUTPUT 36-PIN CENTRONICS SOCKET Fig.2: parts layout for the 3rd order filter. C3 consists of three capacitors connected in parallel to give the required value. The circuit values shown are for a data rate of 20k samples/sec but the filter can also be built for the higher data rate by dividing the L & C values by 5. 1 PC board, code PC-Driven Waveform Gen. 1 5.25-inch 360K floppy disc, "Silicon Chip Digital Waveform Generation Software" 1 36-way IEEE-488 type Centronics socket 1 2k0 or 1 OkO miniature horizontal trimpot (see text) 4 PC stakes Resistors (0.25W, 1 %) 5 1 1 1 3 1 1 1 1 180k0 27k0 22k0 18k0 5.6k0 (one selected for 55830 ± 1 00, two selected for 11,2100 ±500) 3.3k0 2.7k0 (selected for 2,7010 ±50) 4700 680 Optional .components for low-pass filter CRO TRIGGER OUTPUT PINS 1 TO 18 SOLDERED TO COPPER SIDE OF PCB 36 PIN CENTRONICS SOCKET Fig.3: parts layout for the 5th order filters. The winding details for the inductors are given in an accompanying panel. You wHI need a CRO to accurately align the filters (by adjusting the inductors) to give a flat response across the passband. For example, to change the 3rd order filter to accommodate a 1.200k0 source impedance, multiply all the L values by 1.200/1.083 and divide all the C values by this same amount. This gives ClA + ClB = 13.lnF, 12 = 42.44mH and C3 = 29.8nF. Now let's say you have a compiled "C" program which has a data rate of 60k samples/sec. Dividing the above L & C values by 3 will make the filter suitable for this data rate. Assembling the PCB The PCB is designed to be soldered directly to a 36-pin "Centronics'' socket. There are two types of socket available. The "solder bucket" type has a pin-topin spacing of .085-inch, while the JDC type has a 0.1-inch pin spacing. If you have the latter type of socket, cut the finer connector pattern off the end of the PCB. Solder pins 1-18 directly to the PCB pads and connect the signal ground pins (19-30 & 33) using three tinned wire links on the component side of the board, as shown in the wiring diagram (and photograph). Sorting the resistors Before fitting the resistors, it is desirable to check them with a digital multimeter. The most important ones are those at the top of the ladder - in particular, the resistor for the MSB should be within 0.2% for an accuracy of 1/2 LSB. Therefore, try to get the resistors for bit D7 to add up to 2.769k0. Of the three 5.6k0 resistors, put the one closest to 5.583k0 in the D6 position and try to get a pair which add up to 11.2 lkO in the D5 position. Normal 1 % accuracy will do for all the lower bit positions. By the way, the resistor values 1 DPDT slide switch 1 or 2 RM 1 0 ferrite core assemblies (each consisting of two matched core halves, inductance adjuster, two mounting clips and coil former.) AL values to suit required inductance (see text) length of 0.25mm, 0.315mm or 0.4mm grade 2 enamelled copper wire (see text) Miscellaneous Assorted polystyrene, silver mica, or high-stability foil/film capacitors for C1 a, C1 b, C3 & CS (see Fig.1 ). have been optimised for standard TTL output source and sink impedances. If your printer port is driven directly from a custom LSI chip, some modification of the resistor network may be necessary. The most likely scenario is insufficient drive to the high-order bits. If you have access to a CRO, run the 0-255 test ramp program and you will probably see small "backward" steps 1/4 and 3/4 of the way up the ramp and a larger backward step at the half-way JULY 1990 67 Pins 19-30 of the Centronics socket are all joined together using a tinned wire link. These pins, along with pin 33, are then connected to earth on the PC board. This is the opening menu for the tone burst generator program. The default parameters give the IHF standard but you can change any parameter simply by typing in a new value and hitting RETURN. point. Take a large value resistor (eg. 330kn) and temporarily shunt the resistor for the second-mostsignificant bit (D6). Note the effect and keep trying different shunt resistors until the waveform is perfectly straight at the 1/4 and 3/4 points. Below: the 5th order filter also uses parallel connected capacitors to give the required values. Note how the pot cores are mounted. 68 SILICON CHIP Now trim the MSB (D7) until the gap at the half-way point disappears, and that's it. The secret is to start trimming from the lower bits up. Output level trimming The D-A output can be trimmed to lOmV per step with the 3.3kQ resistor and the Zkn trimpot. This gives an output voltage range of 0.1 V to 2.65V for a digital input of 0 to 255. For audio applications. you may wish to fit a lOkQ trimpot. which will allow you to trim the output to 2.828V peak to-peak (ie. exactly 1V RMS for sine waves). The output trimming circuit may seem a little unusual but it performs a vital role in maintaining the linearity of the D-A converter. The heavy DC load to ground helps to stabilise the TTL "high'· level output voltages. The output impedance is approximately l.083kQ when trimmed for 2.55V p-p and l.200kQ when trimmed for 2.8V p-p. (You will need this information later when calculating the filter components). At this stage. the D-A converter is complete and you can test it using a digital voltmeter and the DC How To Wind The Inductors The inductors are wound on PCB-mounting RM 1 0 ferrite core assemblies. Use AL 400 cores for inductors greater than 1 0mH and AL 250 cores for inductors less than 10mH. If you are using a different core type, you will need to know its AL value in order to calculate the number of turns required . The calculation is quite l:limple: (1 ) . Express the desired inductance in nH; eg, 38.3mH = 38,300,000nH (2). Divide this by the AL value of the core; eg, 38 ,300,000 -+- 400 = 95,750 . (3) . Take the square root; eg, (93,250)½ = 309.4 = the required number of turns (309 and a half will be near enough) . If the core has an adjuster, find out how much it can increase the inductance and subtract half this amount before doing the above calculation. For example, the AL 400 core has an adjustment range of 0 to +20% while the AL 250 voltage software, or a pair of headphones and the signal generation software. Note that the D-A network will produce a current output (eg. 0 to 2.55mA) when used with a short circuit load, such as a pair of headphones. However, with the filter in circuit, the load should be higher than 2k0 to maintain a flat frequency response. Winding the inductors Full instructions for calculating the number of turns are given in the accompanying panel. Note that RM10 cores are recommended. For preference, use A1 400 cores for inductors greater than 10mH, and A1 250 .:ores for inductors less than 10mH. The coil formers for both cores will accommodate up to 400 turns of 0.25mm grade 2 enamelled copper wire, 250 turns of 0.315mm wire, or 180 turns of 0.4mm wire. The A1 400 core has an adjustment range of Oto + 20%, while the A1 250 core has an adjustment core has an adjustment range of 0 to + 1 7 % . Thus, when calculating the number of turns, reduce the desired inductance by 10% and 8.5% respectively. This will put you in the middle of the adjustment range . Thus, to obtain 38.3mH on an AL 400 core, we have to calculate the number of turns for an inductance of 38.3mH less 10% = 34.47mH. This gives 293.5 turns. We used 0.25mm enamelled copper wire, for which there is ample room within the core window. Alternatively, if you don't want to bother with aligning the filter, leave out the adjusters and the inductance will be accurate to within ±2% as is, provided you count the turns correctly. Suitable cores, formers, mounting clips and adjusters are available in boxed sets from Radiospares Components for $6 .83 each, plus sales tax. The AL 400 set is stock number 228-258 and the AL 2 50 set is stock number 228-242. range of O to + 17%. So, when calculating the number of turns, reduce the desired inductance by 10% and 8.5% respectively. This will put you in the middle of the adjustment range. Alternatively, if you don't want to bother with aligning the filter , leave out the adjusters and the inductance will be accurate to within ± 2% as is, provided you count the turns correctly. On the subject of accuracy, it is well worth selecting the exact capacitor values with the aid of a digital capacitance meter, especially if you intend to use fixed inductors. With adjustable inductors, the filter "flatness" can easily be restored, even if the capacitors are 5% off. Note that the PCB will accommodate up to three capacitors in each location, so that standard values can be combined to give the exact value required. For best results use polystyrene, silver mica or similar low temperature coefficient capacitors. ~ Problems? ... and you don't have our NEW 1990/91 148 page electronic parts and accessories catalogue ... Its our latest TRADE catalogue for the consumer ARISTA ... Your one-stop problem solver. ... Stylus ... ... Plugs, Jacks and Sockets... .. .Batteries .. . ...Cable .. . ...Tools and Technical Aids .. . ...Plug and Power Packs .. . ...Car/Auto Accessories .. . ... Boxed Hi Fi Speakers .. . ... Raw Replacement Speakers ... ...Speaker Accessories ... ... Telephones and Intercom ... ...Public Address Accesso ries .. . ... Security and Alarm Accessories .. . ... TV/Video/ Antenna Accesories .. . ... 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(Includes Timer D1sk J $895 5 WITH 20 MIBYTE HAR D DISK: & single 360K Disk Drive $1195 & dual 360K Disk Drives $1395 WITH 40 M/BYTE HARD DISK: & single 360K Disk Drive $1575 . & dual 360K Disk Drives $1725 WITH 80 M/BYTE HARD DISK : & sing le 360K Disk Drive CALL & dual 360K Disk Drives CALL CONTROLLER CARD TO SUIT $80 -~ ~ , ____ Ji#-~JJlj • Final assemb ling an d testing in Aust raha! • 4 M By1e Main Board 2 M' Byte in st alled • Sw1tchable 8 10 f2 MH z • l .2 M Byte Floppy Disk Onve • 80286 CPU • Colour Graphics Display Card • 8 Slots • Floppy & Hard Disk Controller • Pri nter Card and RS232 • Keyboard • 200W Power Supply • Manual • 6 Months Warranty • Size: 360(W) x 175(HJx 405(DJmm With 20 M/Byte Hard Disk $1995 With 40 M/Byte Hard Disk $2195 With 80 M/B e Hard Disk DISK STORAGE UNITS • 80 x 3 1 2"' · Lockable C16038 .. ...... .. ... ..... $16 .95 • 40 x 3 1'2 .. · Lockable C16035 .. .. .. ... .... ... .. $14 .95 • 40 x 3 1 '2 ·· ·· Ec lipse "" C16040 ..... .... .. .. ....... $8.99 • SO x 5 1•4 ". Lockable • Fullycompat1bleWTth SMC PC 21 0 • Bus topology througn RG·62 A U coaxial cable • Zero-Wall at 20 MHz • h gher 80386 ac h1ne • 2 5 Mbps transm ss,o,.. •a1e C16025 .... ............. .$14.95 Cat. Xl 8156 · 120 x 3 1 '2 ··. Lockable C16039 .... ...... ........ $21.95 C16042 ............. .. ..... $9.95 • 100 x 51 4 ··. Lockable C16020 ... .. .... ,.. ...... $15.95 • 120 x 5 1 •4 ··• Lockable C16028 ............. ..... $19 .95 PRIAM HARD DISK DRIVES LANS UPS NETWORK CARD Iii • Fully compatible with NoveW UPS monitor boara • Built-in RS232 port s1ereo pnone iack and LAN UPS connecto· • Suppons power r:;onitor LAN PS t.Xl 1 High capacity, Th o 700 s eries d isk drlv os otte r unform a1od capac it ies ran g ing from 178 MB y tes to 382 Mbytes of s tora ge wllh ln • compact 5 \ 2" pa c kage s lu . SCSI. The 700 Series d rives offe r tho Ind us try · and AN SI S1an dard SCSI Inte rlace lor oasy sys1ems inlergratlo n. The Inte rface Is an embedd ed (w i th in d rlV o form factor) SCSI Imp leme ntat ion . SCS I Is an emerg in g standard for opll m lzed system . Integration and porfonna nce. H fros your system from dov lc ► un l que _ characteris tic s, such as hoad and track ktentlllca tfon.W llh !ho 700 series PRIAM now offe rs the be nll llol u s ing an omb9ddod SCSI In s m all m ic rop rocessorbased systems requiring high capac ity, high porlorma nco d is k d rives . Hig h per1ormance. With 1 20 msoc. av erage seek t!m e and a dat a transfer rate ol 10 Mb l! s: soc, tho 700 serlu ollers the speed requ ired for mu lt i user, mu!11 tasking appl lca tlons . Advanced Technology Tho 700 series d isk drlvci has an advanccid lin ear vo!ce-eoll and c losed loop dGd lc ated servo t ec hn o logy and can be lntergra ted Into wortc s111Ho ns, muHI user sysltms, and network app llcatfons. Reli ability Every 700 series consi sts ol loatu res dn l gned to maximize re lfab!lity and data Integrity. Fea tures suc h as an automatic 1c1u ator, land lng ·sh lpplng zone and Integral shock mounts guard agatnst acc ldent al toss of valu ab le data . 380 M! byte X20048 ............................ ....................... $2495 SCSI In terface card .................................................... $129 Save a small fortune with these quality 20 minute tapes . We import direct so we can pass en the savings Cat. D11141 1·9 10+ 25 + $1.95 $1.85 $1.75 240 VAC MAINS SURGE PROTECTOR / LINE FILTER This unrt has inbuil1 M.0.V circui1ry preventing any AC power spikes or surges entering the product rt is protecting. An addrtional fea!ure has been added to this unit. Line fi11ering and cond itioning circuits have been Included wrth the use ol a 1orrid coil which su~resses electro magnetic interference (EM I) caused by other appliances operating In the AC sys1em ie: con,:,uters, neon starters. refrigerators etc. The PAC 18 is sufficient for roost domestic and some commercial applications. • Approved by the Australian Dept of rrinerals and Energy. • Appoval # N11361 X10092 ..................$69.95 25 MHZ TOWER SYSTEM The 386 Tower PC IS a high pertormance system thaf s IBM· AT' compatible . However. the 386 Tower PC gives you 4·8 times the pertormance FEATURES : • ln1el 80386· 25 Mhz microprocessor • Switchable 25 Mhz • 2 M/Byte fi"ed . To1al memory expandable up to 16 M/Bytes. . • Up to 2 M/By1e or 8 M/By1e RAM modules on system board or on RAM card • Op1ion tor 80287 & 80387 co-processor socket • Operates in page mode with interleave memory subsystem • Shadow RAM supported to allow system 8 1OS to be executed on system memory instead of slower EPAOM • Fou r 16•bit 1/0 slot. Three 8-bit 1/0 slot. and one 32•bit memory slot. • 8042 keytx>ard controller 1nter1ace for AT· compatible keyboard • Seven direct memory access (DMA) channels • Chips and Technology chip set • AMI 386 BIOS/Phoenix 386 8105/ t.WARD 386 BIOS (AMI fi"ed) • SO M/Byte hard disk . 42 M/By1e formatted . Fast access. • VGA card .. .... ... . Prtam presents the 700 series d!slc. dri ves, m embers cf a pc worlul PA tAM fam il y cl ad vanced 5 1/4 .. d isk d ri ves . 170 M /byte X20046 ..... ........................... .......... ........$1690 DATA CASSETTES S330 , 100 x 5 114 '"'Eclipse .. • Fully compatible with Novell NE-1000 Ethernet c ard • Built-in 15 pm D type connector • 10 Mbps transm ission rate • Meets the IEEE 802 ·3 standard Cat.X18160 $295 R-NET/S INTERFACE NETWORK CARD • Fully com pat ible wi1h SMC . Novell Arenet card • Star -burst topology through RG-62 AIU coaxial cable • Zero wait at 20MHz or higher 80386 machine • 2·5 Mbps transmission rate Cat.X18162 .. .... ... .. $195 150W SWITCH MODE POWER SUPPLY FOR IBM* PC*/XT* & COMPATIBLES DC OUTPUT: + S/13A. •SV/0 SA + 12V/4.5A · 12V/0.5A Cat. X11096 .. ........ $129 200W SWITCH MODE POWER SUPPLY FOR IBM* AT" & COMPATIBLE DC OUTPUT: + 5/16A. ·SV/0 .5A + 12VISA · 12V/O.SA Cat.X1 1097 ...... $199 180W SWITCH MODE POWER SUPPLY FOR BABY AT"COMPATIBLES Cat. X11098 . $169 TOWER COMPUTER CASING Features security key switch. and mounting accessories etc. Size : 165(W) x 600(H) x SOO(D) Cat.X11105 $249 ~ BABY AT* STYLE COMPUTER CASING Compa9t foot space . Features security key switch. 8 slots. and Si~~n~~/~:;)~s157;(~) x 405 (D) IBM* XT* COMPATIBLE CASE WITH AT" STYLING ONLY $99 IBM* XT* COMPATIBLE CASE Cat.X11093 Now you can have Ar styling in. a xr size case . Features security key switch. 8 slots. and mounting accessories. Size: 490(W) x 145(H) x 400(D) s;~~n~~/~!;): 3~('1,'°J x 140(H) Cat. X11091 ........... $99 Cat. X11090 xr size and styling. Features security key switch, 8 slots , and 5 CONSUMER PREMISES EQUIPMENT PROTECTOR This unique unrt has been developed over the past 12 mon1hs to offer the maximum possible external protection to user equipment such as fax machines , computer modem; and 1elephone answering machines. Both line and power lnpu1s are protected. The CPEP 1 substantially reduces the damaging effeC1s of a!mospheric discharge (l;ghtning) which can occur in equipment connected into the telephone ne1work. In addition power spikes and surges tha1 are sometimes present in power lines are reduced. only $69 X10089 ....... .... ........$64.95 ~ You get more for your dollar with Rod Irving_ Electronics! ~ ,, .M,,._•I --r 1J • • CENTRONICS CONNECTORS • 14 Way plug .P12205 • 24 Way plug . ... P12207 • 36 Way plug .... P12210 ,o. 100+ $2.95 $2.50 $2.00 .. , SOLDER CENTRO NICS IN-LINE SOCKET P12211 • 36 Way t-9 ,o. $4.50 $4.95 I I IDC SOCKETS 1" SPACING 11!± Ll! • 10 Pin $1.95 $1.75 • 16 Pin P12101 $1 .75 • 20 Pin P12102 P12103 Cat A10450 $1.95 $1.75 $1.95 $1.75 iiii . These superb ra ck mount cabinets w1tl give you, proIecIs a real professional appearance' Just look at these fea tures • All dimensions conform to tile International Standard • All aluminium construction • Chrnce of black or natural finish • Deluxe brush hrn sh anodised front panel • Removeable 1op and bottom hd • Ventilated lid Horizontal Depth: 254mm A External Front Panel Height mm 8 Mounlmg Hole C&ntres mm C Internal Chassis Height mm $2.00 $1.80 B C 44 88 132 44 Finish Cat.No. Price $59.50 $69.50 34 38 Natu ral Hl 0401 57 82Natural H 10402 89126Natural H10403 34 38 Black H 10411 88 57 82Black H10412 132 891 26 Black H10413 $79.50 $65.00 $75.00 $85.00 • 34 Pin ?12104 $3.00 BNC PANEL SOCKET 1-9 10-99 100. P10516 $2.50 $2.25 $1.50 BNC CRIMP PLUG D TYPE IDC PLUGS 1-9 10+ 100+ • DE9P 9 pin plug P12166 $2.95 $2.50 $2 .00 • DA 15P 15 pin plug P12168 $3.50 $3.00 $2.50 • DB25P 25 pin plug P12170 $3.95 · $3.50 $2.95 Absotut<?ly 1op quahty unhke our opposI11on s' 6G 40 Resin COll?d Pnce Cat.No . Oescript10n $8.95 131000 7 1mm 250gm $15.95 T31002 71mm 500qm $7.95 n101 0 91mm 250gm $14.95 r310 12 91mm 500gm $7.50 T31020 1 6mm 250grn TJ\022 l 6mm SOOgm TJ1030 71mm 1 me!re T3103 2 91mm 1 me1rc TJ1Q34 1 6mm 1 meire $13.95 $1.50 $1.25 $1.00 PASSIVE INFA-RED DETECTORS lhete du ■ I element P1Hlve lnf■ -ffd detector ■ are ■ very reliable way to enaure Ncurity and protection when u.ed In conjunction with an al ■ rm D TYPE IDC SO CKETS • DE9S 9 pin aocket 1·9 10+ 100+ :-_::~::,:~;~;:';",,:i:,:r:v'~• ■re intruder. They In• compact beige coloured ~abinet deaigned for either P12167 $2.95 $2.50 $2.00 ~~~%:,~;';';;~~~~.;~t■mper ~~~g:~~~':!~;~°'- socket ~=:ti~r;t... P12169 $3.50 $3.00 $2.50 • Cunont .,.,w, 20mA 15 pin ~ BNC CANNON TYPE 3 PIN LINE FEMALE 1-9 SOLDERLESS TWIST ON PL UG 10+ 100+ P10ll64 $4.50 $4.20 $3.20 :i ~:~~ P l 1010 1280. P11011 300Holes$32.SO 1280, MINI MOMENTARY PUSH BUTTONS 8 CANNON TYPE 3 PIN CHASSIS FEMALE 1-9 10+ 100+ P108&6 $5.115 SS.50 $4.00 (EX SCOTCHCAL) All p11ces per box and include lax 8007 REVERSAL FILM 250 • 300mm f 10 shee!s I JOO• 600mm !5 shee! sI • Fem ale to Female • Saves moo1ty1ng o r :eplac1ng non -ma11r.g Centron•cs c.Jbles • All 36 pms wired ~1raIgllI Ir.,m,gf'1 Cal X 1 5663 Male to Male e a, x, 5€61 Male to Female $39 .95 $54 .95 LNkproof and in 3 comvenient aizea, these long MNic• He batteriN are ideal for burgular systema, emargency lighting or as a co~tar backup power supply idf'.1I for many power n...:ls. Ca1s1502912V12AH $29.50 Ca1S1503112V26A!-I $39.50 CatS1503312V4 5 AH $49 .50 $79 .95 8009 BLUE ALUMINIUM 250 • 300mm ( 10 shee1sI 300 • 600mm (5 sheets : 8011 RED/WHITE ?50 x 300mm 110 sheeIs I 300 • 600mm {5 sheetsl $69 .95 S79.95 $64 .95 $74 .95 ~~~ x $64 .95 8015 BLACK/WHITE 250 x 300mm I 1O sheets 1 300 • 600mm 15 sllee!S I $64 .95 $74.95 3 ~~i!;~~Ls~~:is1 300 x 600mm (5 sheetsl 8016 BLUE/WHITE 250 x 300mm (10 sheets i 300 • 600mm (5 stieets i 80~8 GREEN/WHITE 250 k 300mm ( 10 shet::s, 300 x 600mm /5 sheets ) RECH A RGE AB LE 12V GELL BATTE RIES TEXTOOL IC SOCK ETS (ZERO INSERTION FORCE) CENTRONICS GENDE R CHAN GERS 3M DY NAMAR K PHOTOSENSITIVE 300 • 600mm (5 sheets) 100+ 10+ LJ RS232 GENDER CHANGERS • Saves modifying or replac ing non -mat ing R S232 c ables • All 25 pms wi red stra ight !hrougll Cal X 15650 Male to Male Cat x 1565 l Male to Female 8005 BLACK ALUMINIUM 250 x 300mm l 10 sheels ) $69 .95 1-9 10-99 100• P10531 S2.50 $2.25 $2.00 $74 .95 $64.95 S74.95 $64 .95 $74.95 UV EPROM ER ASER Era se your EPROMs qu,ckly and safety This unit i s the cost ettecI1ve so!u!1on to your p1 obiems II will erase up lo 9 x 24 pin devices m complete safety In abou! 40 mmuIes (less ro, less cll1psJ Fea lures mcludf! e C t11p {l1,1wo1 11.is conduc t1vp lo.im p,1(1 • • Ma 111!, powo11•{1 ~~~~!~~ E'.~!{O~s·~.~'i·~~~~~~iy er,;sed • Engmce,ed to p1event UV e•posure • Dunf!n~ions 21 7 • 80 • 6flmm WITHOUT TIMER $119 4 ( ,1 1 X. \ 4 9~0 TELECOMMUNICATION CU RL CORD • U.S plug to U S plug • Replacement hand set cord • Length 4.5 me!res Cat. Y16023 ...... ... $7.95 Tlw• ZI F eockete are cw perfect for ln•rtlng and removing EPROMS eo •• not to damage 1h11 IC pine. 1-9 10+ • 1& pin P17016 $16.95 $13.95 • 24pln 3 MINIATURE HEATSI NK 1 A grea ! hllle lello w 1! you are shon 0 1 ..,pace Greai price too becau<;e we import direct so you sa-.,e' Drmens,ons 19 1L 1, 131 W 1,91H1rrnn C a1No ' 9 10H"OhOfi S0 .40 $0.35 P17024 S19.95 S18.50 • 28 pin P1702S S26.95 $24.95 VOLT AGE REGULATORS B ARG AINS • 40 pin ,. ~:~ -~ $69.95 ~~isHo les $17.50 100Holes $26.95 kYt - -.a 1-9 10-99 100. P10530 $2.115 $2.75 $2.00 P1 7040 $34.95 $32.95 Protecta norm .. siad roon-... • Cov■ r• ■n are ■ 12m x 12m :: :~~; ::~ p,;ce 2.75 $ P ll OOO 100 Holes 1-9 10+ 100+ P10ll62 $3.115 S3.50 $2.90 S11070 S0.70 S0.60 $0.50 $3.25 c'!~ ~!DB~ ~: ;~,:," CANNON TYPE 3 PIN CHASSIS MALE • pueh off $3.50 lI P11012 1280•400Holes $39.95 P1101s 1920•500Holes $59.95 P1 1Q18 2560 • 700Holcs $69.95 S11060 S0.60 S0.50 $0.40 $2.50 [ P11009 640• 200 Holes SOLDER ROLL S • DA15S 10+ 100+ • puehon • 40 Pin · P12108 1-9 P10ll60 S4.75 $3.IIO $3.00 1-9 • 36 Pin P12106 1-9 10-99 100+ P10514 $2.50 $2.25 $1.50 $24.95 . A • 26 Pin ~ CANNON TYPE 3 PIN LINE MALE Tuneabte : 92 - 104MHz Freq. Response: 50 1SkHz Range: Over 300 lee! in open field Modulation: Fl.-1 Power Source : 9V Battery Type: Electret Conden ser DlmenaiOf\l : 185 x 27 x 38mm Weight : 160 grams MASTER RACK MOU NTING CABINETS ii P12100 OMNI-DIRECTIONAL WIRELESS MICROPHONE GU - BNC MALE PLUG 10dB IN-LINE COAXIAL AM PLIFIER Reduces loss !rom spllners and long cable runs Su1!able !or use ...,tth antennas. coax ial reed lines and VCR s A.JC adaptor included SPECIFICATIONS : ~r~~~~i Range : 5 -900MH1 Power Requirements : 12v A C Adaptor (included) Input Impedance : 75 ohm Output Impedance : 75 ohm Cat I. 15043 $39.95 Descnpt1on 7805UC 7812UC 7815UC 7905UC 7912UC 7915UC 78LOS 78L12 LM324 555 741 1-9 10 SO.SO S0.45 so.so $0.45 $0.50 $0.45 $0.60 $0.55 $0.60 $0.55 $0.60 $0.55 $0.45 $0.40 $0.45 $0.40 $1.00 $0.90 $0.40 $0.38 $0.50 $0.45 Z 1 SPECT ROL 64Y MULTI TU RN TRI MPOTS Cat No Descnp1on 1-9 A14 700 10A SJ 50 A 14 710 A 14 720 R\4730 A 14 740 A14 750 A14760 Al-4770 Al-4780 A14790 A 14800 Al4810 Rl-4820 Rt48.)0 A 14840 Al4850 1O • $3 .20 20R SJ SO SJ .20 50A IOOR S3 50 SJ SO S3 50 Sl 50 S3 50 Sl.50 $3 .20 $3 .20 $3 20 $3 20 S3 .20 S3 .20 S3 .20 S3 20 S3 20 $3 20 $3 20 $320 S3 20 $-l .20 200H SOOR IK 2K SK I0K 20K SOK 100K 200K SOOK 1M - $3.50 $3 .50 S3 50 $3 .50 SJ 50 $3 .50 $3 50 $3.50 INSULATION DISPL ACE MENT TYPE HEA DER PLUG S Gold plated r,bbon <..able p!ug tha1 plugs l:rectly In10 PCB rnounIIng IC sockels All include press -11 1 cap tha1 tits In10 t1011on1 hall ot pluq over IDC c.ihle 10 $1 .40 S1 .50 S2 .75 S5 .75 MAIL ORDER & CORRESPONDENCE: P.O. Box 620. CLAYTON 3168 Order Holline : 008 33 5757 (Toll free. strictly orders only) POSTAGE RATES . $1 - $9.99 $ 10- $24.99 $25- $49.911 $50- $99.911 $100- $199 $200- $500 $500 PLUS ~:=i~~~~:g~s~~1;. $3.00 $3.50 $4.50 $6.00 FR EE FREE FREE ~~~~ ~r:~:~1. ~~~~~:~:t'~~~~~~~~':1a~e:i.ll be All sales tax e1empt orders and wholesale inqui rie s to : RITRONICS WHOLESALE . 56 Renver Rd, Clayton . Ph. (03) S43 2166 (3 lines) COMPUTER BITS By JENNIFER BONNITCHA What to do when your computer goes bung; Pl.3 Faulty disc drives are a common cause of computer malfunction and can lead to loss of data or even complete files. Similarly, it's all too easy to unintentionally delete wanted files. Here's what to do when disaster strikes. Computers and accidents were made for each other so backup your data regularly. I know that you know that DEL*.* is something only simpletons do. Likewise FORMAT C: ~ you would never do something so ridiculous would you? Don't bet on it. Everyone has moments of stress, anxiety and just plain stupidity. If (read when) the inevitable occurs, reach for one of the excellent software utilities containing an "undelete" program. Mace Utilities, PC Tools and Peter Norton's Norton Utilities are probably the best known but there are many other highly reliable programs available both commercially and in the public domain. These programs also often contain software which will undelete a formatted disc. If you accidentally delete files don't do anything more with that disc until you can run a utilities pro- gram. If you have a hard disc, find the most recent set of backup discs and use them. If you work in a floppy disc only environment, always make extra backup copies. The floppy disc is no less susceptible to corruption and data loss than the hard disc. Following a hard disc disaster, some companies elect to store all data on floppy discs. This is fine except that they usually make no provision to backup the diskette contents, leaving them just as vulnerable but on a smaller scale. Viruses & the common cold When your computer catches a virus, it is usually the result of running an infected program on your computer. The system files like IQ . COM, DOS.COM and COMMAND.COM are favourite targets. Often the code can take control and destroy information on your disc. Vaccine programs exist to help detect these insidious heartbreakers. You should find that all reputable software is 100% virus free but be wary of public domain programs, particularly the games programs. System backups can sometimes help to eradicate the virus but it really depends on the type of virus your computer has caught. Hard disc head crash DON'T USE PAPER CLIPS to attach labels to floppy discs. The clips may have become magnetised and may destroy valuable data. Always hack-up your data and protect the discs from liquids, dust and fingerprints. 72 SILICON CHIP If everyone backed-up, imagine how peaceful life would be! Discs mostly fail for two reasons - old age and mechanical problems such as a head crash. A head crash occurs when the read/write heads touch the disc surface, thus scratching it and usually destroying forever the information on that part of the disc.) The heads themselves can also be damaged through carelessness, particularly when relocating your computer. Be sure to use your computer's pARK, RETRACT or sometimes SPINDOWN program to move the hard disc heads to a "safe" zone before the move. Voice coil drives usually park automatically when you finish using the computer. Parking - no, not that kind An alternative method of parking or locking the heads on some hard discs is an airlock feature which is activated when the power supply detects an interruption. Airflow is vital to disc operation. The cushion of air causes the heads to operate just above the surface of a hard disc and actually on a floppy disc surface (which is one reason why floppy discs don't last as long). \!\Then the computer is powered down, the read/write heads are parked and locked in a non-data area. A spring engages the airlock arm so that the heads remain in the non-data area until the airflow is once again sufficient. Some hard discs have their own kind of rubber shock absorbers. They suspend the head and disc assembly inside the hard disc case to provide protection from unexpected bumps and jolts. When a hard disc reaches the correct operating speed, a head actuator moves the read/write heads across the various platters. Stepper motor drives (the most common form of hard disc) move the heads in a series of steps from one track to another. The head actuators of the more expensive voice coil drive move the heads in one sweep to the right track using a magnetic field. Voice coil drives operate at around twice the speed of stepper motor drives. Hard disc hiccups A common indication of hard disc failure is the inability to boot the computer. At system startup, the BECAUSE THEY ARE MECHANICAL devices, disc drives eventually wear out and fail. In this drive, the read/write head (at end of pen) became detached from its support and damaged the floppy disc in the process. The discs themselves also wear out from repeated use. computer's BIOS performs a series of operations, culminating in a call to the hard disc for the final loading sequences. How you take the loss of a boot record depends a lot on your inner strength - and how long it has been since your last backup. Most problems with hard discs in particular can be traced to mechanical failures such as the stepper motor, worn out read/write heads, faulty drive controllers and faulty connecting cables. Sometimes the read/write heads and the platter surface can move slightly out of alignment. The end result is a disc drive which "thinks" it is reading from one track when in fact it is reading something completely different. The hard disc itself is just a recording device with connectors at the back for power and the hard disc controller board. It is the controller board which actually handles the task of formatting the disc for later use. It also "decides" where to place the read/write heads, where to write or read data, and when to report the success or failure of like operations to DOS. Generally the hard disc will experience one of the following problems: (1). Whining and screaming (no, not from the operator) from the hard disc. Make sure you backup your data now. Death is imminent. (2). Continual Abort Retry messages from DOS mostly indicate either operational problems (like typing the wrong command) or, when associated with drive specific!}tions, perhaps a damaged read/ write head. Run one of the diagnostic utility programs to show up any head errors. (3). Continual or increasing Abort Retry messages can also mean that bad sectors are causing problems. You could try running a low level format to lock out the bad sectors. (4). Sector or Address Not Found messages from DOS can indicate a chip failure on the logic board attached to the drive. The low level format is performed using the PC manufacturer's diagnostic or setup routines and it performs two important tasks. First, it sets the interleave for the disc and second, it formats every JULY 1990 73 sector on the disc to test it for reliability. Troublesome sectors are locked out by the controller to ensure that DOS can't store data in suspect sectors, no matter how hard it tries. The low level format also writes new sectors and sector ID headers but at the same time, like the DOS format, it overwrites existing information on the hard disc. There can be no recovery after the low level format but it can fix troublesome sectors. Frazzled floppies Some disasters are unavoidable but others can be avoided by using plain common sense. Take the humble can of soft drink - yes, take it right away from the computer. Any liquid, including tea or coffee, can mean death for floppy discs. Please be careful where you place the next cup, glass or can. I know you can all be adult about these things and can be trusted - but can you trust the other inhabitants of your office or home'? There is not a great deal you can do about spilt liquid except mop it up and hope for the best. A speck of dust, a biscuit crumb, cigarette ash, a drop of water and even fingerprints can all render a disc useless. Some disc manufacturing companies, recognising the frailty of human operators, offer disc recovery services. How they manage to resurrect some discs is close to a miracle. Liquids can affect more than discs (look around the office any Friday afternoon). Portable computers are often the victim of an untimely drowning. Their very nature means that they are often used balanced on the knees of their owners . Spilt liquid can cause a serious chain reaction in a laptop since liquid spilt ·on the keyboard drains straight into the system unit. Floppy disc drive alignment When you insert a disc into the floppy disc drive and close the latch, a spindle clamps the centre hold and starts turning the disc inside the jacket at between 300rpm and 360rpm depending on the disc type. A read/write head is also pressed 74 SILICON CHIP TABLE 1: FORMAT OPTIONS Disk Type Valid Switches 160/180K 320/360K 720K (5 .25) 720K (3+) 1.2M 1.44M /1 /1 /7 /N /N /N /4 /4 /V /T /T /T /8 /8 /S /V /V /V /B /V /S /B /V /S /S /S /S Formats a single side of the disc. /1 /4 Formats a 5.25-inch , doublesided disc in a high capacity disc drive. /7 Formats a 5.25-inch, 720K disc in a high capacity disc drive. /8 Formats 8 sectors per track. /8 Formats the disc, leaving enough space to copy an operating system. This was very popular in the good old, bad old days of software protection . /S Copies the operating system files. /T: Enables the specification of the number of tracks. This switch formats 3 + inch floppy discs to the number of tracks specified - 80 tracks for 720K and 1.44Mb discs (/T:80) . Specifies the number of sectors per track. The 3 +inch floppy disc formats the number specified ; for 720K discs, the value is 9 /N: (/N :9) . /V Format prompts you for a volume label at completion . against one or both sides of the disc. When all's said and done, it is most often use rather than abuse which spells the end for your floppy discs. The surface just wears out from a lifetime of having the read/write heads re-arranging the magnetic oxide coating. The most common problem with a disc drive occurs when it is out of alignment. One note of caution, however . If your disc drive is diagnosed as having an alignment problem, make sure you can read the contents of the discs on another machine. The discs can also be out a little and may read reasonably reliably on your disc drive but not on another computer. Preventative maintenance for discs Head cleaning kits are available for floppy disc drives. Generally they contain items such as antistatic cleaners, cleaning solution, dust removers, cleaning wands, cleaning wipes and a cleaning diskette. The value of these kits is debatable and falls into the same category as video head cleaners many manufacturers actively discourage their use. The best thing to do is to check with your computer's manufacturer. No cleaning at all is often preferable to over-zealous use of these products. Personally, I remain to be convinced of their worth, although I do know of some installations who swear by them - only you can judge. Disc capacity Two common problems with diskettes today are firstly the different sizes available and secondly, the different densities. While one 5.25-inch diskette may look like the next, they can be poles apart. Discs now come as either double density or high density. The problem is that while the double density disc traditionally has a capacity of 360K, the high density disc can have from 1.2Mb to 1.44Mb of storage space. In between, you can also find the quad density disc which stores 720K - although this is mostly confined to the 3 + inch format. You can only tell which does what by looking closely at the disc drive for an identifying label or by formatting a disc to find out the exact capacity. This procedure can, however, create further problems. Discs are upwardly compatible. This means the data on a 360K disc can be read by the high density drive but not vice versa. If you attempt to read a high density disc in a low density drive, depending on your DOS version, something like the following displays: General Error Failure. Error Reading Drive X. Abort, Retry, Fail'? Typically this indicates a wrong match of diskette and drive density. Check the disc label and, if available, format a blank disc, noting the results. Most computer manufacturers provide several options with the FORMAT command. Note that if you format single or double sided discs in the high density drive, you may not be able to reliably read those discs in their "native" drives. Table 1 is based on the options available on the NEC PowerMate: For example, the command: FORMAT A:/N:9/T:80 formats a 720K 3 + inch diskette in a high capacity 1.44Mb drive. You will also find that a lower density disc can format to a higher capacity in the appropriate drive. Although FORMAT will take a few tries to complete the process, you will generally find an increased disc capacity. Don't be fooled. Double density discs are not manufactured to the same standard as high capacity discs and usually contain some bad sectors. As the disc drive attempts to use those sec- tars, it retries the format operation many times. If your format program shows you the head and cylinder count, watch it next time you try to format' a double density disc in a high capacity drive. At completion, which can sometimes take a very long time as the drive tries to format those "dud" sectors, you will certainly end up with more available sectors. And you will almost certainly end up with ongoing problems. The disc drive won't use any bad sectors but it will attempt to use sectors which are only slightly better. It stands to reason that since the marginal sectors have a weaker signal, they will more than likely fail more rapidly. Since files are often segmented on a disc, you could also end up not being able to recover the rest of the file. In addition, the incorrectly formatted disc has data recorded at twice the recommended strength and density so that, over time, the adjacent magnetic domains on the disc begin to affect each other. What happens is that the disc seems to erase itself - although some would like to blame the ubiquitous computer virus. The result is inevitable - data loss which could be more than a little annoying. In addition, the low density disc is ruined since the high density format places a recording on the disc at twice the normal strength. You can try reformatting the disc in a low density drive but the drive cannot fully overwrite the stronger recording. Using the /4 format option in a high density drive is of little use since the high density drive goes into "reduced" mode to format at 360K. At this stage, you've got two choices. You can throw the disc away [what a waste) or you can put it through a bulk eraser which erases all magnetism from the disc and returns it to almost factory freshness. Next month, we'll look at the CHKDSK command and tell you what to do when errors are detected. We'll also take a look at power supply and keyboard problems. ~ Protect your valuable issuesl SILICON CHIP BINDERS These beautifully made binders will protect your copies of SILICON CHIP. In 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.1 or the 12 issues of Vol.2). It will look great on your bookshelf. * High quality Hold up to 14 issues 80mm internal width Gold printed with SILICON CHIP logo on spine Price: $All.95 plus $A3 p&p each (NZ p&p $A6). Send your order to SILICON CHIP Publications Pty Ltd, PO Box 139, Collaroy Beach, NSW 2097; or use the handy order form on page 104. Fax 979 6503. ]ULY 1990 75 PRICES THAT WILL DRIVE OUR High performance AT/386Hard Disk/Floppy Disk Controllers Parallel Centronic Printer Cables Data Switches CAT. ACDS21 CAT. LACPP3 3 metre cable CATIC256K10 CAT. LACPP5 5 metre cable 41256-10 CAT. LACPPl0 10 metre cable Standard printer cables with DB25 pin plug to 36 pin Centronics plug. Suits all popular parallel printers and computers printer ports. CAT. LACPP3, only $18.00 CAT. LACPP5, only $22.00 CAT. LACPPlO, RAMat Ridiculous prices!! only $30.00 $7.95 CATIC1M10 41100-10 • Suits all parallel printers • 2 computers to one printer or one computer to 2 printers • 36 pin centronics connector $19.95 CATIC4256K10 414256-10 $19.95 ONLY$29.95 Lowest Price EGA CAT.ACDS22 Speed up the disk performance of your AT or 386 machine by a factor of around 2:1 with tl1ese fast caching disk controllers 1:1 sector interleaving, using the latest Western Digital 1006 chip set greatly increases performance with most drives. Features: • Capable of addressing hard disks with up to 16 heads and 2408 cylinders 1 or 2 drives are supported. • Will run on a 16MHz BUS on a suitable '."igh speed machine, delivering a massive 200% improvement in throughput from this feature alone I • The DCAHF is available with a built-in floppy disk controller, supporting up to 2 drives which may be any mix of 360K or 1.2MB 5¼" or 720K or 1.44MB 3½" drives. CAT. DCAH ONLY $245 SAVE $24 CAT.DCAHF ONLY $275 SAVE $24 Universal Wirewrap Card For connection between serial devices. All pins straight through. • Suits all parallel printers • Crossover switch • 36 pin centrnnics connectors Serial Printer Cables- 3 Metres Hardware Control CAT.LACSP25 CAT. LACSP9 Type3 Computer Computer End 25 Pin End 25 Pin Type4 Female Male 2 Printer End 9 Pin Female 3 568 1,6,8_ _ _ 19 19 7 20 Printer End 25 Pin Male 3 7 5_ _ _ 7 568 4 CAT. LACSPX25 Printer Computer Printer End 25 Pin End 25 Pm End 9 Pin Female End 25 Pin Male 20 2 Female Male 2_ _ _ 3 16 2 3 3 4 68 7 7 5 8_ _ _ 4 ONLY $15. 75 each AT Cases, going for a Song! Mini Tower Case with 200WAT Power Supply CAT.CATBP Normally $349 Only $299, SAVE $50 Modem Accessories CAT. LAGC25M, CAT. LAGC25F Modem cable 25 pin plug to 25 pin socket. All pins are wired straight through. ONLY $9. 75 each Modem cable 9 pin socket to 25 pin plug . The appropriate pins are connected (TXD to TXD, RX to RX etc) Adaptors This compact case is the same as used in the-famous Silicon Chip Project AT It has plenty of room for a full XT, AT or 386 system , and has drive bays for 2 x 5.25" and 2 x 3.5" drives. Front power switch, reset, turbo and disk drive light and keyswitch. And being a "mini-tower" it takes up very little space. ONLY $325.00 This is Australia 's best price on a top quality EGA video card. Usmg the most advanced ASIC chip technology, it provides high performance with maximum reliability. And you get a FREE printer port (1/0 selectable) Features include: Full compatibility with XT, AT, 386 Full 256K display memory Award EGA BIOS, fully hardware compatible with IBM EGA Completely backward compatible with CGA, MDA and Hercules with intelligent ·· switching software. ONLY$149 This card provides complete register level compatibility with the IBM Video Graphics Array standard (VGA), while being backwards compatible with EGA, CGA and Hercules Graphics/MDA monochrome standards. The VC1024 is fitted with an additional 256K of display memory for up to 1024 x 768 pixel resolution LACM9 NORMALLY $129 ONLY $99, SAVE $36 1: ONLY$69.95 CAT.LACSPX9 Type2 Typel Computer Use 7 (or 8) wire cable ONLY $9. 75 each Used to test and re-wire RS-232 interfaces VGA CARD 5~ - - 4 20 7 20 68 CAT. LA9M25F 9 pin plug to 25 pin socket. CAT. LA9F25M 9 pin socket to 25 pin plug. The appropriate pins connect internally c0 allow for matching of serial equipment using a mixture of 9 pin and 25 pin connect.ors (eg. a 9 pin serial. connector on a sen al mouse to a 25 pin serial port on a PC) CAT. LAAB Serial Printer Cables- 3 Metres x on/x off Hardware Control 4 This universal wirewrap card is ideal for engineers and other technical people developing hardware add-ons for IBM PC/XT/AT/386 or compatibles The card provides a complete built-in data bus, address bus and 1/0 line buffer circuit. It incorporates a universal address decoding chip (0-3FF, step 8 or 16) and a D25 female connector. Buffering of the inputs and outputs makes damage to the PC's bus from faults on the card impossible. The wire-wrap area is 4000 holes which are plated through fo. r easy prototyping work. The card is built to a very high standard and can withstand heavy use. RS-232 Break-OutBox 5 68 Use 4 wire cable card in Australia has FREE printer · $9.75 each CAT. LANULL Null Modem Adaptor $9.75each CAT.LAOT Serial Quick Tester LEDs monitor the lines to give instant feedback. Great for fault finding. ONLY$19.90 Designer 3 Butto~ Mouse CAT. With free pocket and 2mousepad. LIMITED OFFER.$75 Modem Cables - 2 Metres CAT LACM25 Type 5 Computer end25 pin Female 1 Modem end 25 pin male Mcdem end 9 pin end 25 pLri female male 1 2 3 4 CAT.LACM9 Type 6 Computer 4 5 2 3 4 5 6 6 20 7 8 20 20 7 6 7 8 4 $15.75 each CAT.LAAPS2 PS2 to AT keyboard connector adaptor. Enables AT style keyboards to be used on PS/2 computers. AMERE$9.75 CAT.LAAVGA VGA graphics card adaptor. 9 pin to 15 pin adaptor enables multisync monitors to plug into the 15 pin analog output of VGA graphics cards. ONLY$9.75 COMPETITION TO DRINK!!! 11 12MHzPC/AT Motherboard with the lot!! Magic Colllbo" Mono/ Colour Graphics Card + High-Resolution Monochrome Monitor CAT VCCOMBO/CAT ACJV!.A This is the video card to suit all occasions I The Magic Combo Card drives monochrome monitor in both EGA and Hercules modes Colour Graphics Adaptor (CGA) standard. When using the TTL monochrome monitor, grey tones are used to simulate colours . Now you don't need to put up with gritty CGA graphics for your text - switch to high quality 720 x 348 pixel MDNhercules. Nor do you have to miss out on all the games software because you can't run CGA graphics. You get the best of both worlds with the Magic Combo. A BARGAIN AT ONLY $129.00 Play your CGA games on your monochrome monitor NEAT Chipse t PC/AT Mothe rboards CAT MB28612N The Cheapest XT Turbo Motherboard on the Planet!! CATMBXCI 00 Ifyou ~antthe • performance and flexibility of a 386 machine without the pricetag, you need our new NEAT Chipset motherboard. It out-pertorms 16MHz 386SX systems costing much more yet offers supenor flexibility The board is superbly engineered, with top quality surface mount components for the ultimate in reliability Features: • Rechargeable battery backup on the motherboard • Clock speeds of 12 or 16MHz (0 wait state) • Page interleaved memory uses DIL (44256 , 41256, 411000) or SIP memory chips Up to 5MB of main board memory Can be configured as any combination of DOS, Extended or Expanded (EMS) memory • Shadow RAM function. System ROM and Video BIOS can be mapped to fast RAM for lightning fast response • Expansion slots: 16 bit x 5, 8 bit x 3 • Fast-Landmark 20.5 (16MHz) , 14.8 (12MHz) • Password protection in ROM • Calculatorand Timer in ROM • User definable hard disk support. Dnves not in the BIOS table can be entered by the user and stored m CMOS RAM . 47 disks in ROM plus a user definable place (No 48) This fantastic little XT motherboard has a full 8 expansio slots and uses just 5 low cost 1MB RAM chips to provide a full 640K of memory The use of advanced ASIC chips means incredible reliability. The CPU is a state-of-the-art NEC V20 running at 4.7110MHz (switchable) with zero wait states. Size is just 208 x 161mm Memory Size DRAM 128K Bytes 424256 X 1 256K Bytes 424256 X 2 384K Bytes 512K Bytes 640K Bytes 424256 X 3 424256 X 4 or 421000 X 4 424256 x 5 or 421000 x 4 + 424256 X 1 Se lling for a limite d period at only $119.00 (12MHz/0WS/0KRAM) CAT MB28616N (16MHz/0WS/0KRAM) $499.00 $599.00 This brand new Tower case is perfect for any XT, AT or 386 machine. Superb styling and heavy duty construction make this an open and shut easel A flip down smoked perspex cover protects the drives and power switch from accidental knocks. The power supply is a heavy duty 230W output unit - don't settle for less. Feature s include: ~ • Drive bays for 3 x 5¼" FDDs or HDDs, "l two 3½" FDDs and one 3½" HDD ·"; • 4 LED indicators and Turbo switch · • MHz display (2 settings to tie m. wit.'l -. .Cli.: ~ "normal" and "turbo ' modes) lba.,-• Heavy 1.44mm steel constructmn t.=.=_ • Dimensions: 71/s'' x 16" x 153/'4" Introductory Special ONLY $399.00 (OK RAM fitted) ONLY $499 The World's fastest XT Turbo 31MHz XT Motherboard ONLy $225.00 ~ 1 re. CAT MBXC2 If you want the fastest XT on planet Earth, this is it Our MBXC2 comes in at a staggering 10.9 on Nortons SI - that's 31MHz compared to 4.77MHz on your standard XT · The board is fully XT compatible and runs with all standard XT cards. Speed is switchable between standard 4.77MHz and turbo speed · Up to 1MB of RAM can be fitted on-board. For even faster operation, the memory above 640K can be used as "shadow RAM " for speedmg up BIOS operations or as a RAM disk. The board provides software selectmn of wait-state. MBXC2 IBMXT IBM PS2 Model 30 10MHz XT A t.YilK IBM AT (A Membe: o! the Nc1Comm Group ~ Comp~n,cs) MEGA MODEM 1234 NEW•Io;-;x-i;,~ 1; Inte;nal software & cable. $399.oo ;;,ciud-;;; ~:0Ji~2400 MEGA MODEM 24 Includes software & cable $349.00 300, 1200, 2400 COMMODORE 64/128 Includes software & cable $1 75.00 CAT MB28612N This high performance PC/AT motherboard has everything! Others charge the same for boards with nothing I I This top quality motherboard uses state-of-the-art VLSI technology and surface mount design for best performance and reliability. Don't accept less I • 12MHz zero wait-state CPU (15 9 MHz Landmark speed rating) • Up to 1MB of RAM on the motherboard (OK fitted) 80nS or 120nS RAM can be fitted. • 4 x 16 bit and 4 x 8 bit expansion slots • 2 serial and 1 parallel port built m , including cabling • Rechargeable on-board battery backup Professional Look" Vertical Case 11 We accept: Bankcard, Mastercard & VISA Mail orders our specialty Freight on smaller items is now $9.00 + $2.50 P&P • All prices include sales tax • All products carry a 14 day money back guarantee (software and hard disks excepted) • All products carry a full 3 month warranty • All cards come with full documentation • Ring for quantity discounts and tax free prices Owing to technical advances, products we supply may in some cases vary from those pictured. In all cases they are guaranteed to perform to an equal or higher standard . •• I I w The prototype was built into a plastic zippy case but could also be built into a 2-piece aluminium box. It provides a fixed + 5V output and 6 switched outputs from ± 3·18V. Build this low cost dual power supply Since completing this project, I wonder how I ever got along without it. It has lots of uses, is simple to build, safe, reliable and almost foolproof. Above all, it is cheap and could save you a fortune in batteries. By JOHN CRICHTON This power supply was originally designed to power op amp circuits which require balanced positive and negative rails, with the option of simultaneously driving TTL circuitry (5V logic) as well. It provides six switchable voltages: ± 3V, ± 6V, ± 9V, ± 12V, ± 15V and ± 18V (the maximum recommended for many op amps) and has an independent + 5V output which can be used with or without the dual rails. Of course, if you feel you will never need the 5 volt supply and wish to power a radio or something similar instead, the 5V regulator could be replaced by a 6, 8 or 12V 78 SILICON CHIP unit on a drop-in basis. This option will be discussed later. Other uses include driving the family Walkman (typically + 3V), trannie ( + 9V), bench amp (say + 12V), 9V battery projects, smoke testing power amplifiers and recharging gel and nicad batteries. Some of these uses will be referred to again later. The circuit is powered by a 16VAC 900mA plugpack transformer and since no separate transformer or mains wiring is required, the project is suitable for the complete beginner as well as those who like to have projects up and working in only a couple of hours. The great advantage of this kind of switched voltage supply over a "wind up the wick" style is that there is no need to tie up a voltmeter to make the voltage selection. With this unit, once you've set the switch you know what the voltage is and that it will remain constant while you work. Voltages can also be changed very quickly merely by using the switch. Two versions are possible and which to build depends on the space available on your workbench. A medium-sized zippy box makes a unit about the size of the average W alkman radio which could be fixed to a shelf or a wall, while a two-piece aluminium case would make a nice free-standing unit on your bench. Both units have identical performance and are equally easy to build. The design is not intended necessarily to be followed in every detail but can be tailored within limits to your precise requirements. The circuit is shown in Fig.1 and is based on the use of three 3-terminal voltage regulators. An LM7805 provides the fixed + 5V output while the LM317 and LM337 provide the balanced rails. If the 5V output is not required, the + 5V regulator can be omitted completely or replaced with another value. Regulators designed to supply 6, 8, 12 or 15V can be used as pin for pin replacements. The plugpack voltage of 16V AC is half-wave rectified by D1 , D4 & D7 and filtered to obtain open circuit voltages of about + 24V on Cl & C5 and - 24V on C3. The balanced ± 24V supplies are fed directly to the LM317/337 regulators while C5 feeds C6 via R7, a 150 5W resistor, to reduce ripple and lower the power dissipation in the 5V regulator. The LM7805 contains active circuitry which maintains close to 5V between its OUT and COM terminals for inputs greater than about 7.5V. C7, a 2.2µ,F tantalum capacitor, is required to maintain stability and improve the transient response of the regulator at high frequencies. DB and D9 are protection diodes, reverse biased in normal use, which protect the regulator against reverse polarity or heavy reverse currents if the output voltage were ever to exceed the input (eg, if the input were shorted). Other components associated with the adjustable regulators play the same roles. The LM317 and its negative counterpart the LM337, are of more recent design than the 78XX series regulators and have better specifications. The pinouts of these regulators are shown on the circuit diagram of Fig.1 (as are the pinouts for the 7805). They develop 1.25V between their OUT and ADJUST terminals and typically only 50µ,A flows between ADJUST and ground. Other housekeeping (chipkeeping?) currents are diverted to VOUT. Consequently, a minimum output current of some 10mA is necessary or the output voltage will rise. In this design, each adjustable regulator is set up to generate a constant current which is passed through a set of 2 700 resistors switched by a 2-pole 6-position switch to "jack up" the output voltage in accurate 3-volt steps. D9 + +v r--<--~>Nr+-'IWr.. &80 ~ VR1 VR2 10011 ...__ _ _ _ __, 1D00 D1,09 9x1N4002 Rl 7805 FROM 16VAC D3 PLUGPACK + Cl 2200uf C2 + --...,.,_ _ 2.2af· S1a .~.. COM 0 +18V AC2 0----+-----------------------0 DV LM317 -18V 0 oom,~• OUT CJ + S1b 2200uf C4 2.2uf + 06 LM337 VR4 1000 '--~~Nr+-•.,,,,,,,... :~! D4 --~.. IN LOW-COST DUAL POWER SUPPLY Fig.I: a 7805 3-terminal regulator provides the fixed + 5V output while LM317 & LM337 adjustable regulators provide the variable plus & minus rails. Power comes from a 16V AC plugpack. In the prototype, 5 % resistors were selected from a bandolier but these days 1 o/o metal film resistors are widely available if you feel you need that kind of accuracy. The current-setting resistors associated with each regulator are adjusted so that 3V appears across each resistor in the chain (about 1 lmA). Because the number of resistors through which the current passes can be adjusted with switch S1, the JULY 1990 79 cuits! The regulators are mounted on the copper side of the board with their leads bent at rightangles. An ON/OFF switch was deliberately omitted as otherwise the plugpack could be left turned on for long periods with possible dangerous consequences. Instead, a LED indicator on the front panel serves to remind users to turn the supply off at the wall socket. The power supply is not connected to mains earth but is isolated by the plugpack tranformer. Consequently, it may be used without restriction on both earthed and double insulated equipment without any fear of hum loops and the problems they can introduce. Assembly of the PCB The completed PC board is secured to the lid of the case by the regulator mounting screws. The lid, together with an external heatsink, provides the necessary heatsinking for the regulators. voltage at the output can be switched to plus and minus 3, 6, 9, 12, 15 & 18V. If the switch is at the 3V setting, about 1.25V of this will be due to the regulator and the remaining 1.75V to the first resistors in the chain (about 1570). Ideally one would use a combination of fixed resistors here but the tolerance on regulators seems to be about ± 4% so a trimpot is necessary for accuracy. For the same reason, trimpots are required to set the constant currents (about 1120). The fixed resistors associated with the trimpots allow the design settings to be achieved more quickly and with greater accuracy than if trimpots were used alone. Construction As already mentioned, there are two basic versions of the supply with a couple of options which you can select to suit your own application. The same PCB is used in both units. In the zippy box version, the regulators are mounted on the metal lid to remove heat. An external T0-3 heatsink is also recommended but may not be required if only low output currents are drawn and you guarantee no short cir- If~ The PCB design is very simple but it is worthwhile inspecting the board to ensure there are no patchy copper lands or unwanted bridges between tracks. Repair these if necessary and make sure all holes are drilled. Because the PCB is a tight fit in the zippy box, the filter capacitors and trimpots must be small in size. Recent stock from most suppliers is suitable but parts from your junk box are unlikely to fit. PC pins or stakes are used to terminate external wiring connections and these should be mounted first. The resistors and diodes are mounted next, followed by the tantalum capacitors and trimpots. Use the component overlay diagram of Fig.2 as a guide when installing the components. The 5W resistor should be I ~~ ~---rk\ o• .i::,. . . . . . . . The three regulators are mounted on the copper side of the PC board as shown here. Smear the regulator tabs with heatsink compound before bolting them to the lid. 80 SILICON CHIP 1=..: Fig.3: this is the full-size PC pattern. re}. PARTS LIST F / A / g ~~ 1 plastic zippy box, 41 x 68 x 130mm, (DSE Cat. H-2583 or equivalent) 1 PC board, code SC 04107901, 70 x 60mm 1 16V 600mA AC plugpack 1 2-pole 6-position rotary switch 1 knob to suit switch 2 red binding post terminals 1 green binding post terminal 1 black binding post terminal 1 U-shaped heatsink, 60 x 35 x 30mm (Jaycar Cat. HH-8511) 1 2. 1 mm DC power socket 1 2. 1 mm DC power plug +v LEDl(;YB K FROM 16VAC PLUGPACK DV -v Fig.2: check that all parts are correctly oriented during assembly and use PC stakes at external wiring points. The three regulators are mounted on the copper side of the board (see photo). Install the 5W resistor so that it sits off the board by 5mm to aid cooling. mounted so that it stands about 5mm off the board to improve cooling. Carefully check the polarity of the electrolytic capacitors against the overlay diagram before soldering them to the board. Leave the regulators until the box is ready and you get a chance to fit parts together for a dry run. MICA WASHER BUSH NUT \ SCREW i \ :~~~ :s-1 ~ DEVICE 1 METAL REAR PANEL ' FINNED HEATSINK Fig.4: mounting details for the LM317 & LM337 3-terminal regulators. The metal tabs of these devices must be electrically isolated from the metal lid & heatsink. You can now solder the 10 2700 range resistors between the 12 terminals on the rotary switch, as in the photograph and the overlay diagram of Fig.2. Front panel hardware The front panel, and specifically the spacing of the binding posts, was designed with finger room in mind. However, most multimeters use a standard 19mm spacing and matching dual plugs are available. If you wish to use 19mm spacing, use the appropriate front panel layout as a starting point. In the plastic version, clearances dictate that the + , - and common terminals need to lie along a line near the centre (the line of the switch is recommended). Mark up, drill and ream the holes in the front of the zippy box for the output terminals, LED and switch. Remember to drill a hole for the 2.5mm power socket in the side of the box. Fit the binding posts and the range switch with its resistors in position and drop the PCB in on top so that the filter capacitors fit Semiconductors 1 7805 5V 3-terminal regulator (REG1) 1 LM31 7 adjustable 3-terminal regulator (REG2) 1 LM337 adjustable 3-terminal regulator (REG3) 9 1 N4002 silicon diodes (D1-D9) 1 red LED (LED 1) Capacitors 3 2200µF 25VW PC electrolytics 3 2.2µF 35VW tantalum Resistors (0.25W, 5%) 1 1.2k0 1W 12 2700 2 1200 2 820 2 680 1 150 5W Miscellaneous Insulated hookup wire , screws, nuts, lockwashers, Dymotape or white Letraset for labelling, heatsink compound, solder. snugly between the switch and the terminals. The PCB must be recessed about 10mm into the box so that the lid will fit when the regulators are in place. You will need to cut away some of the plastic ribs in the box with a wood chisel or a hot knife to do this. Leaving just enough clearance to reach the lid screws at the side of the T0-3 heatsink, mark the line of the regulator fixing holes and drill them in the aluminium lid. They will ]ULY1990 81 DISKS! LIFEIIME WARRANTY 0. 0150210 01 50220 0150310 0150320 1-9 BOXES 1 O+BOXES $7.40 $6.95 $19.50 $18.95 $22.50 $21 .50 $49.95 $47.95 DESCRIPTION NO BRAND 5.25 DISKS DSDD NO BRAND 5.25 DISKS DSHD NO BRAND 3.5 DISKS DSDO NO BRANO 3.5 DISKS DSHD C201100 DISK STORAGE CASE (1 Ox5. 25 disks) C201200 DISK STORAGE BOX (100x5.25 disks) C201300 DISK STORAGE BOX (80x3.5 disks) H230100 DISK HEAD CLEANER H230200 DISK HEAD CLEANER $3.50 $15.95 $17.95 $7 .95 $7.95 5.25 DISKS 3.5 DISKS FD45010 5.25 360K DISK DRIVE HALF HEIGHT FD45020 5.25 1.2Mb DRIVE HALF HEIGHT FD45030 3.5 SWITCHABLE 760K OR 1.44Mb $159.50 $179.50 $219.50 FC45000 4 WAY DISK CONTROLLER 360K/760K/1 .2Mb/1.44Mb $139.00 MT23010 $3.00 DIGIT AL MULTIMETER Measures DC 0-1 OOOV, AC 0-500V Current 0-10 amps, Resistance 0-2MEG Includes: Test Leads, Manual , Spare Fuse and Battery MT23020 DIGITAL MULTIMETER AUTORANGING $169.50 -::~t\ Measures DC 0-1 OOOV, AC 0-700V Current 0-1 0 amps, Resistance 0-2MEG Continuity Buzzer. Includes: Test Leads, Manual, and Carry Case. ~.~ ~ · STANDARD MAIL RATES WITHIN AUSTRALIA $1.00-$9.99 ........ . .......... . . . . ......... $3.00 $10.00-$29.99 .................... .. ....... . $3.50 $30.00-$99.99 .......... . ................... $5.50 $100.00-$200.00 . ........................... $6.50 ~ 1 ::11R:Rc:~RR:A~~RP~:!~~::Ec~~ ~::E:F :::~:~~CREDIT CHARGE ORDERS MINIMUM PURCHASE $10.00 ~ ~ /)/\ AUST-TEK L/b F• EC• RONICS PO BOX 1422 CAMPBELLTOWN, NSW, 2560 You've Gotta Getta Goldstar from: A.C.T. John Pope Electrical 80 6576 N.S.W. D.G.E. Systems (049) 69 1625 e W.F.Dixon (049) 69 5177 e Macelec (042) 29 1455 • Newtek (042) 27 1620 • Novacastrian Electronic Supply (049) 62 1358 e Obiat Pty Ltd 698 4776 e Digital 709 6511 e Geoff Wood 4271676 N.TERRITORY J Blackwood (089) 84 4255, 52 1788 e Thew & McCann (089) 84 4999 QUEENSLAND St Lucia Electronics 252 7466 e B.A.S. Audiotronics 844 7566 • The Electronics Shop (075) 32 3632 • Solex (Townsville)(077) 72 4466 • Xanthos Electrical (079) 27 8952 S.AUSTRALIA Force Electronics (08) 212 5505 VICTORIA G.B. Telespares 328 4301 • The Electronic Components Shop 670 6474 e_Factory Controls (052) 78 8222 • Mektronics 587 3888 • Truscott Electronics 723 3094 W AUSTRALIA Atkins Carlyle 4811233 e Leda Electronics 361 7821 PAPUA NEW GUINEA T E (P.N.G.) Pt Moresby 25 6322 Lae 42 6246 Now for the smoke test! Set all trimpots to their mid-positions and the switch to minimum, then connect a voltmeter between the adjustable outputs. Switch on and monitor the temperature of each regulator tag with your fingers. If any of the regulators gets hot, switch off at once and recheck everything. If the voltages are high but stable and nothing else seems to be wrong check that the switch is wired in the correct sense. It is all too easy to connect the wrong ends of the resistor chains to ground. If all is well, check that the outputs of the variable regulators are similar, positive and negative, and breathe a sigh of relief. Now switch the voltages up a click or two and check that the outputs change in sympathy. This close-up view shows the mounting details of the 3-terminal regulators. Use your multimeter to check that the tabs of the adjustable regulators have been correctly isolated from the heatsink. Note the cardboard insulator between the regulators & the PC board. be about 25mm from one end. Now use the lid as a template to modify the central hole in the T0-3 heatsink to fit the regulator positions. Remove any burrs from the holes and ensure that the lid and heatsink will fit tightly together to conduct heat away from the regulators. Spread a little thermal paste between them. You can now mount the regulators on the board and then attach them to the lid using insulating kits and thermal paste (LM317 & LM337 only). The metal tab of the 7805 regulator can be bolted directly to the metal lid. Tighten the fixing bolts carefully to ensure that the regulators cannot rotate and check that there are no shorts between adjacent pins. Now use a multimeter (switched to a low "Ohms" range) to ensure that the adjustable regulator tabs are correctly insulated from the lid and from each other. Note that the lid is connected to ground on the PCB via the tab on the 7805. Now that the PCB is attached to the lid, cut a piece of cork or card as an insulator/spacer to fit between the PCB and the lid and glue it in position near the filter capacitors. This done, cut a piece of thick card about 25 x 60mm and slip it between the board and the regulators to prevent shorts between the PCB and the fixing nuts. Tighten the switch and the terminals on the inside of the plastic box and wire diodes between each terminal and ground. These will protect the regulators against reverse connected charged capacitors in the external circuitry. Setting up The PCB assembly should be' checked out and adjusted before mounting it in the box. To do this, connect up the LED and the input sockets to the board with suitable lengths of hookup wire and connect the 2.5mm connector to the plugpack. On the switch, make sure that the "common" sides of the two resistor chains are connected together and to the two poles of the switch and to earth on the PCB. The other ends of the chains go to the trimpots associated with each adjustable regulator. Use short lengths of suitable colour-coded hookup wire to connect the PC stakes to the output terminals (wrap one turn round each stake before soldering to obtain a durable joint). Use thicker wire (or two lengths of hookup wire) to connect the earth on the PCB to the common terminal. Check all the wiring. Adjustments The next step is to adjust the constant currents. Connect your voltmeter across the first 2700 resistor on the switch at the "hot" end of the chain associated with the negative regulator. Adjust trimpot VR4 carefully to obtain 3.0 volts. Now repeat this step for the corresponding positive regulator resistor and its triinpot (VRl}. Now that the currents are set, you can adjust the other trimpots (VR2 & VR3} associated with each regulator to obtain the plus and minus 3V outputs at the minimum switch setting. That's all there is to it. When you are ready to fit everything together, put a dab of superglue on the side of the LED before fitting it into its hole and mount the power socket firmly. Pack the wiring carefully into the box and fit the lid. Check that you get the expected voltages from each terminal before connecting anything to your new power supply. As it stands, the unit is a sealed system which contains heat generating components. If you expect to drive the 5V supply hard for hours at a time, fit a 2-4mm thick washer under each fixing screw or' the lid to allow air to circulate over the 5W resistor and both surfaces of the lid. This small modification will improve heat dissipation and continued on page 99 ]ULY1990 83 ELECIBONICS JAYCAR ELECTRaNicSJAvcAR ELECTRaNic&JAYCAA ELEcmaNic&JAvcAR ELECTRONICSJAvcAR ELECTR0~1c~AYCAR ELEcmo~1c~YcAR ELE~~Ra~:~~;~~;R EtE~~R~~:~~ ~; ~t~g:g~:g~ JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICS JI JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS JI ONl)C~ S~. ~- •,•-~ •~ -~ - -~-~-~-~-~-•~•-~-~•~•~•~ •~ - - :• :-i~ :-!"i'!!i"!-1 -~"~'"!-~'~"!r~,~ -~ -!~!-!'~"i_!_t"~'i'"~•~-~-~•~-i"!l~~ -~ -~ .,~ •-i":•~ --~•-!•~-~-•~-~-~T~~"i'"~"~:''!"i"!!!'-~-!•-~-!=~ -~'i"~""~'•jvi"~•~n~,c~,~- ~- ~T.o~"i '~"""~~,_.~_vi "~'~"~rij•,-,- ;T~ONICS JI ~t~g FAX· PHONE· MODEM LINE PROTECTOR<=3<=3<=3<=3<=3<=3 mgf ELECT ELECT ELECT ELECT ELECT ELECT ELECT ELECT ELECT ELEC ELECT ELECT ELECT ELECT ELECT ELECT ELECT ELECT ELECT ELECT ELECT ELECT ELECT ELECT ELECT ELECT ELECT ELECT ELECT ELECT ELECT ELECT ELECT ELECT ELECTF ELECT ELECT ELECTF ELECTF ELECTF ELECH ELECH ELECH ELECH ELECH ELECT ELECH ELECT ELECT ELECTI ELECH ELECT ELECTF ELECT ELECT ELECT ELECT ELECT !:LECT cL[CT ::LECT ::LECT ::LECT ::LECT :LECT : LECT : LECT :LECT : LECT : LECT :LECT :LECT :LECT :LECT :LECT :LECT :LECT ' LECT :LECT :LECT :LECT :LECT :LECT :LECT :LECT :LECT :LECT :LECT :LECT :LECT :LECT :LECT :LECT :LECT :LECT ,LECT PLEASE READ THIS We are all becoming aware that lightning in storms can severly damage sensitive electronic equipment connected to 'phone lines. Voltage spikes on phone lines are the most common reason why FAX machines, answering machines, modems, cordless 'phones etc .• are damaged. Induced voltage spikes on telephone lines can be unbelievably high! The best way to protect 'phone equipment during a stonm is to actually~ the appliance from the wall socket. This is sometimes not possible of course. The next best thing is to instal a device between the Telecom line and your expensive equipment to protect the equipment from spikes. The big problem with such a filter is that owing to the magnitude of the voltage spikes no practical filter could b e ~ to catch~ r:Nery time. The Jaycar Telephone Line Filter attenuates the enormous bulk of line spikes whilst remaining effectively transparent to the audio band used by modems, FAX machines, etc., A number of Telecom grade spike attenuators are used including a quality German Siemens gas arrester. The big factor in the efficiency of this filter, however. is earth impedance. This filter must be connected to earth and the lower the impedance between the unit and earth the better the filter works. The filter plugs into a Telecom socket and a standard 240V mains socket. {The mains earth is the only connection used). We cannot guarantee that this filter will solve lightning induced telephone line spikes destroying your equipment. Some things {like the impedance of your earth system) are totally beyond our control. We can say, hOWr:Ner, that this drNice will give your equipment a reasonable chance of survival in a storm. We are so confident of this product that we are quite happy for you to use the unit for one month without obligation. If you are not hapP\I with this product in any way return the unit in its original condition along with your receipt for a full refund. • Protect your expensive telephone, etc., equipment from storm damage • Transparent to normal communications This charger is designed to charge 12V lead acid batteries in cars, trucks, boats and • lnstal in minutes motorbikes. It is protected internally by a thermal overload switch which shuts off the • Uses no power current if something goes wrong Cat. XF-7080 Features: • 4 amp rms • Charging meter • Overload and short circuit protection • Plastic case • 2 year guarantee Cat. MB-3520 ARLEC CAR BATTERY C HARGER $99.00 $42.50 POWER WINDOWS Squeeky Clean Mains Filters PROTECTION FOR: MICROPROCESSORS, TERMINALS, MICRO COMPUTERS, PRINTERS, DISK DRIVES AND TELEMETRY EQUIPMENT Used by Government Departments, Schools, Universities, Banks and TV Stations Most modern personal computers and peripheral equipment are fitted with basic type filtering components. In most instances this protection offers only minimal protection and is not capable of handling many mains supply problems. The problems facing the personal computer user includes high levels of RF {radio frequency) interference, voltage spikes and FM modulation. The supply authority actually superimposes a range of frequencies from 1kHz to over many MHz for the control of hot water systems, and other industrial remote control services. Additionally both industrial and domestic motors turning on and off can induce large spikes into the mains supply. For you to ensure maximum safeguard to both your hardware and software against RF noise, control tones and voltage spikes the equipment should be pre-filtered by a SOUEEKY CLEAN MAINS FILTER Many unexplained errors. programme corruption aoo general inconvenience are eliminated by a Squeeky Clean. SPECIFICATIONS: Approval Na's: N10716/N10717 Load Rating: Cont 10 amps, with circuit breaker at 240VAC Clamping Voltage: 300V peak or 275V rms Peak Impulse Current: 2000A (Bx 12u); 2 outlet (8 x 20u) Protection Modes: Active-Neutral Earth Leakage: Will not trip a 20mA Earth leakage breaker Cable length: 1 metre (approx) Cat MS-4020 2 OUTLET Cat. MS-4025 $109 Co1Nert your normal hand operated window winders to power windows. They are really easy to connect, simply remove the manual handle, choose the correct adaptor and connect the motor drive. The screw the drive to the door. A metal bracket is supplied which mounts inside the door for added strength. All cables for connecting are supplied. Driver unit has a second switch which controls passengers window. Also included is a special relay which shuts the motor down when the window is completely up or down, which saves wear and tear on the motor. There is even a courtesy light builtin which is connected to the door pin switch and lights up when the door is open. Colour is grey. Kit includes - 2 window winders, relay, 4 metal adaptors which cover most cars, complete wiring harness and full wiring instructions. BRAND NEW MODEL Cat. LR-8812 $239 ~~!~n~c~!;~~! SOLENOID <=<<=< If you don't Iike the idea of fitting a burglar alarm. what about a fuel cut-off solenoid! Supplied with two threaded nipples, rubber fuel hose, hose clamps and a DPDT switch. In the energised condition the fuel is cut off. In cars with carburettors, the solenoid can be installed between the fuel pump and the filter. In diesel powered vehicles it should be before the pump. There are a number of options for wiring in the solenoid. Add a KJ-7000 red light flasher kit ($19.95) for total protection. Cat. XC-2050 $69.95 4 DOOR CAR POWER DOOR LOCK KIT If you own a four door car and want the convenience of power door locking, this is the kit for you. It consists of 2 master solenoids and two remote solenoids. {Masters for the front doors, opening either will unlock the other 3 doors). Full wiring harness to connect all 4 solenoids to the doors of even the biggest cars, all hardware included. Also included is the controller relay circuit (Cat. LR-8835 $29.95) which will also adapt to our remote controller (Cat. LR-8820 $109.50) so the system can be remote controlled. Cat. LR-8830 $169.95 ECTRONICSJ CARJAYCAR ECTRONICSJA YCARJAYCAR ::CTRONICSJA YCARJAYCAR ::CTRONICSJAYCARJAYCAR : CTRONICSJAYCAR JAYCAR :CTRONICSJA YCARJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR - CTAON JCS IAYCAP c, tAVClt.0 ccroo ► 1 1 cc EL CTRONICSJAYCAK ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR t:Lt:C I NIC AYC K t: Cl A <.. A ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ,,.Hren r e ro:roo•1100 11 , ,010 c:, rr":rn.l"'t..u1.r1.~ . ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR LECTROt LECTROt ELECTROt ELECTROt ELECTRO! ELECTRO! ELECTROI rCAR (CAR (CAR rCAR !CAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRON ICSJAYCAR ELEGinN "~~ "v~ • P c, L ~TPf'>~otr.c lA"'r AC i:1 i:r.n>l"l•Ur."- IAVf"'.AC i:1 i:r.TAnNIC'-'-.IA YC:AR FI FCTRONICSJAYCAR Another Jaycar direct import. All disks are supplied with envelope, index labels and writeprotect tabs. Remember. these disks might be cheap but they are good quality. We are so impressed by the quality we are happy to offer a lifetime guarantee. 5 1/4" DSDD 48TPI DOUBLE SIDED/DOUBLE DENSITY Cat. XC-4730 ELECTRONICSJA YCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICS ELECTRONICSJAYCA ELECTRONICSJA YCAR ELECTRONICS ELECTRONICSJAYC/> ELECTRONICSJAYCAR ELECTRONICS ELECTRONICSJAYCA ELECTRONICSJAYCAR ELECTRONICSELECTRONICSJAYCA ELECTRONICSJA YCAR ELECTRONICS ELECTBQNICSJAYCA ELECTf ELECT! FLECTI aycarwill not be undersold on quality leads and con re our rices! ELECT! ELECTf EADS - ALL 1 8 metres long ELECT! 825 Male - 36 way Centronics plug ~ ELECT! at PL-0854 ELECT! 825 Male - D825 Fem ale " \ ELECT! ELECT! at PL-0855 o ELECT! 825 Male - Male ELECT! at PL-0856 ELECTI ELECTI ELECTI Just a few from our comprehensive range ELECT D825 Male solder Cat. PP-0840 ELECT ELECT D825 Male IDC Cat PP-0842 ELECT Cat. PS-0844 ELECT ELECT Cat. PS-0846 ELECT 1 ELECT ELECT ELECT 150 watt fully compatible with PC/XT computers. EL[CT Includes metal case. • lnput <at>47-63Hz (110/240V ELECT ELECT switchable) • Output +SV <at> 15A, -SV <at>O.SA, +12V ELECT l1ll 5.SA, -12V <at> O.SA • Plug compatible connectors 1 ELECT • Built-in fan • Size 5.S'(W) x 9.S'(D) x 4.625'(H). ELECT Cat. XC-5080 , 1 ELECT 1 ELECT ELECT R ELECT ELECT ELECT ELECT ELECT ELECT ELECl 101 keys • Enha R ELECl luminated LED indi ELECl refile design • Swit ELECl 9'(W) X 8'(D) X 1.33' R ELECl R ELECl at. XC-5090 R ELECl R ELECl R ELECl R ELECl R EL~CI R ELEC I R ELECl R ELECl R ELECl R ELECl R ELECl R ELECl See our catalogue for full specs \R ELEC fr $18.95 ea $19.95 ea $6.50 for 10 51/4" DSHD 96TPI DOUBLE SIDED/HIG H DENSITY $19.95 ea $15.95 for 10 SAVE $3 Cat. XC-4732 f ' ..........-.: CONNECTORS $1.95 e . $5.95 ea 10+ $5.75 ea $1.95 ea 1O+ $1.75 ea $5.95 ea 1O+ $5.65 ea 3 1/'l' MF2DD 135TPI DOUBLE SIDED/DOUBLE DENSITY Cat. XC-4736 $16.95 for 10 SAVE $10 RMAT TO 1.4Mb! lfyourcomputerhasthenewfonnat ng then you can store up to 1.4Mb on the one disc. ,.• ·., , .. · ··-:._,_,...... WAS $49.95 , : • . ,,, $34.95 :~(' _.,. .. ::,. , DC TO DAYLIGHT SCANNER? Not really but, this fantastic little hand held unit covers most bands fr om 60 - 950MHzl The unit works normal 25kHz spacing and also the new 12.SkHz offsets. You can also programme up to 20 selected channels in this unit. You can also programme the unit to "search" a band of frequencies. When the scanner finds a transmission. it locks to it and displays that exact frequency on its clean LCD display. The ·Road Runner" AR-880 measures 190mm high x 50mm wide and 45mm deep. It has a sturdy stainless steel belt clip and BNC connected rubber duckie antenna 150mm long. It is powered by 4 x AAA batteries. If ever you thought of buying a scanner, this is the one! Specifications: 60 -90MHz Freq . Coverage 138 -174MHz 406-525MHz 800-950MHz 0.4mV Lo. Hi, VHF Sensitivity: 1mV 830 - 950MHz at 12dB SI NAD Channels: 20 13 channels per second Scan Speed: Search Increments: 5. 10, 12.SkHz. Lo, Hi, VHF 12.SkHz UHF 25kHz 830 - 950MHz fN DC <at> 60mA (squelched) Ant Conn : BNC LCD Display Type: Cat. DS-6000 ONLY $399 PC/XT COMPUTER POWER SUPPLY $119 ►►► 12V DC BRUSHLESSFAN I=~t~g: A proud addi lion to our range. 00mm square x 32mm deep. 120mA. Cat. YX-2512 $24.95 240V 120mm (5") 16 drawer cabinet to hold all of your bits and pieces - resistors. capacitors, semis. drill bits. nuts & bolts. etc. Drawers have a stopper that stops the drawer from coming out completely and spilling all over the place. Each drawer can be split into 3 with the dividers supplied. Drawer size 11 O{L) x SO(W) x 34(D)mm. Total size 185(H) x 242(W) x 124(D)mm Cat. H8-6320 Cat. YX-251 4 240V 80mm (31/4") Cat. YX-2510 Cat. YX-2511 $2.20 Solder type plug suits RG58 coax. Used with cellular phones. VHF transceivers. etc. Cat. PP-0664 $3.50 ea SUPER LARGE INSTRUMENT CASE Su~r large size 355mm wide x 250mm deep x 122mm high. Ideal for amplifiers, invertors, power supplies, microprocessor equipment, etc. Mounting posts are provided for PCB's and transformers. Unit is vented in both top and bottom panels for efficient air fl ow cooling. Case is extra tough with super finish front and rear panels. Grey colour. Made in Australia. Cat. HB-5905 $39.95 10+ $36.50 ea ***** "°"'"°""== ====~~=~====': ELECTRONICSJ YC R ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR El ECIRQNICS IAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRON ICSJAYCAR El ECJRQNICSIAYCAR .~ ~~ Cat. SK-0760 JAYCAR JAYCAR JAYCAR JAYCAR JAYC:AR $2.20 FOR 120mm FAN )~UMERIC KEYPAD Catalogue Price $3.50 ea FIVE FOR $10 CS CS CS CS CS $24.95 FAN FINGER GUARD FOR 80mm $12.95 i:S JAYC CS JAYC $27.50 ~==="'""~"="",:<:: ELECT11ONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELE-CTRONICSJAYCAR El ECJBONICSJAYCAR =~t~g c"==========================6: LECTRONICSJAYCM ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJ,AfCAR ELECT ICSJA CA ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR El ECTRONICSJAYCAR R ELEC' RELEC R ELEC RELEC R ELEC" R ELEC R ELEC. R ELEC" R ELEC. RE LEC" R ELEC" R ELECR ELEC" R ELECR ELEC" R ELEc· R ELEC' R ELEc· R ELEC" R ELECR ELEC" R ELEC R ELEC R ELEC R ELEC RE LEC" R ELEC R ELEC R ELEC R ELEC R ELEC R ELEC R ELEC ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR El ECTBONIGSIAYGAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR El ECTRONJCSJAYCAR ~mg R ELEC ELEC ,R ,R ELEC ELECTRONICS JAYCAR ELEC ELECTRONICS JAYCAR ELEC ELECTRONICS ~ EL.ECIBQlliCS .. v~.Aa. c , c:r ~g~= ~t~g ECTRONICS JA YL,AH t.Lt:L, I HUNIL,;).JA Tl....,AH t: L CL, I NUN11....,i:>JATL,AH t:. L C.L, I MUNll...,,:>,JA J L,f-\l i CLC I..., I M.VNIL,.:>,.JJ--\ TL,f-\M C LC V I MV l'II IL,v.Jf-\ I l...,J-\M C.LCV I t1U""1 LV.:>.JI-\ J\..,1-\M C L C\., L NVNIL.,.:>.JA TVAH C: L CL, I HUNI~ JAY £CTRONICS JAYCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICS JAY ..ECTRONICS JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS JAY ..EC """ " JAYCAR ELECTRONICs,,IAYCAR ELECTRONIGSJAYGAR ELEGTRONIGSJAYGAR ELEGTRONIGSJAYGAR ELEGTRONIGSJAYGAR ELEGTRONIGSJAYGAR ELEGTRONIGSJAYGAR ELECTRO NICS JAY . EC~nm:=~===:::::~!!:!l!:!!!:!!!!:!!ij:fflm~~~~~~~~!!!~-i~=~~~~~~~~~~~~~i~~~~~~ji igiR< igT MOTOROLA KSN 1141A PIEZO TWEETER 400W RMS IR Doorway/ Mini Alarm ..EC ..ECT ..ECT ..EC Brand new Motorola Powerline horn.Includes a protection circuit internally which allows the new horn to handle 400N rms. It uses a miniature light bulb and a PTC resistor. Under eJ<treme high power surges, the PTC opens up allowing the speaker to continue to play at a somewhat compressed power level. The resulting product is virtually blow-out proof. Replaces the KSN1025A. See catalogue for specs. 3 year warranty. Cat CT-19 12 This pocket size alarm has a built-in PIA sensor to detect human movement. It has a built-in swivel mounting bracket which allows it to be mounted on a wall. and aimed in any direction. It is ideal as a personal alarm. or more igr ..ECT .ECTR< ..ECTR •ECT .ECT ..EC ..EGT .ECT ...EGT ...ECTR< ..ECTR< ..ECT ...ECTR • ECT . ECT ...ECT .ECT LECT LECT LEGT LECTR LECT LECT LECT LEGT LECT LECT LECTR LECTR< LECTR LECTR LECTR LECTR LEGTR LEGTR LEGTR LECTR LEGTR LEGTR LEGTR LEGTR cECTR LECTR ...ECTR ..EGTR ..EGTR • ECTR . EGTR . EGTR ...ECTR .EGTR ..ECTR .EGTR ..EGTR ...EGTR ..EGTR ..ECTR .EGTR .ECTR ..ECTR ..ECTR< ..ECTR .ECTR< ..ECTR ..ECTR< ..ECTR< ..EGTR< .ECTR ..ECTR ..ECTR £CTR .ECTR £GTR .ECTR< ..ECTR .ECTR< £CTR £CTR .ECTR< £CTR £CTR .ECTR £GTR .EGTR .ECTR .ECT~ $3 7 9 5 • importantly an excellent entry sensor to announce customers. 11 will either give a pleasant chime for five seconds or a siren sound which persists until the unit is turned off. It measures only 108 x 67 x 35mm and ,., ba operates on a~• ttery . Cat LA-5012 $49.95 )NICSJAY, Ferrite Potcore Bargain Due to en amazing stock buy we can offer a beg of ferrite cores leach core styrene foam pecked) for a sensationally low price. The cores range from 45/ 29 & 36m potcores down to 14/8 and smaller! Other cores supplied include some RM cores, EP cores and X (cross) cores. A selection of bobbins is supplied including multicheek & PCB pin types. !Note: we cannot guarantee that there is enough and a correct bobbin supplied for every core!). A random selection of clips and other mounting/fixing hardware is also supplied! FREE BONUS: a sm all number of prewound inductors is thrown in for FREE . There were 35 PAIRS (i.e. 70 helves) in the peck opened to write this description. Consider that a 36/22 potcore would cost you around $18 - this pack represents top value. Strictly limited quantities of this genuine bargain . NOTE 1: Data not supplied - you must use your own resources for this mainly TDK. NOTE 2: Due to the massive weight extra P&P $3 ._ willapply.Cat.LF-1270 ON''Y $l 9 . 95 BARGAIN BAGS Contains approximately 3kg of assorted electronic goodies - 'JUNK' if you like . but all brand new components etc. Ideal to fill up your junk box . Unfortunately due to the massive weight P&P is normal rates plus $5 $1°4.95 <<<<< ISOLATED TAB TRIAC •E Rated at 8A f1XN in T0220AB package. BT 137F600 Cat. ZX-7149 $2. 75 ea 10+ $2.so •• If, Designed -for CD use. Cat AA-2010 $19.9~ OPEN AN ACCOUNT WITH JAYCAR MINI BENCH VICE Jaycar is now accepting account applications from all established companies who can exhibit good trade references . For application details see our store managers or phone Top quality mini vice Cat TH-1850 $13.95 (02) 747 2022 6 WATT MICRO AMP 1 CHANNEL AMPLIFY YOUR WALKMAN! Provides up to 6 watts into 4 ohms from a 15V power supply". Mighty midget measures 50mm square. On-board volume control. Accepts high or low impedance inputs. i.e. low headphone output of cassette deck. Walkman type unit etc .. and high for standard line level sources such as tuners . VCRs. etc .. !regarded as AUX). Output short circuit protected . • A copper heatsink fin must be soldered to the top of the IC to achieve this. 24mm High . Specifications: Power Out fN/ lmax) into 4 ohms Input Sens 100mV ,T.H.D. 0.3% Gain at 6V 38dB 4-16V<at> 1-2A Power Supply Cat AA-0340 ·. -.· $17.95 Note: 2 required for stereo - .::: £GT~ £GT .ECTRONICS JAYGAR £GTRONICS JAYCAR £GTRONICS JAYGAR £CTRONICSJAYGAR BUSHING STRIP $3.95 ea (I~ $1.95 KIT Contains motor. brass cog, gearbox housing and all other parts to make various combinations of motor from 2rpm to 1150. Works from 1.5 - 4.5V DC. Depending on load draws from 200SOOmA. See catalogue for full details. Cat. YG-2712 $18.95 ©I Anodised black aluminium stands suitable for most speakers. Supplied with castors and spikes lfor carpet) and adhesive pads for wooden floors. Speaker sits off floor approx 250mm with castors. Width adjustable from 148mm IID) to 250mm 11D). Depth approx 225mm. Enhance the look and sound of your speaker system. Cat. CS-2700 $49.95 pair ·:==•:-.fl!.~· . JAYCAR - STOCKS SPEAKER KITS TOO! See catalogue £crn £CT~ .ECT~ NiCad BATTERY ADAPTERS If you al react)' have AA Ni Cads and you find you then need a C or D size you can use these adapters and use your AA's you already own. Or; if you need 4 x D cells that will cost $27.80- 4 x AA and 4 adapters will only cost $17.45- OVER $10 SAVED! 4 x AA's will not last as long as 4 x D because of the lower rating !Ahl of the AA NiCads. C size packet of 4 Cat. SB-2462 D size packet of 4 Cat SB-2464 Thios bushing strip is ideal for covering dangerous edges of panel holes. i.e. cut-outs Designed to suit panels 1-1.Gmm thick. The strip can easily be cut to length with a sharp knife or scissors. 1 metre_ pack Cat HP-0730 _. _ _ _ _ _ _.., ~"'~~"'~~~~~~ ~ ~~~i!ii~!li~~~~9Pffljijiji~~ii!ji~iiie)~~1tNINICSJAY CS JAY I'! ELECTRONIGSJA YGAR ELECTRONICSJAYGAR ELEGTRO NICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRO NICSJAYCAR ELECTRONICSJAYCAR ELECTRO NICSJAYCAR ELECTRONIGSJAYCAR ELECTRONIGSJAYCAR ELEGTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRO NIGSJAYGAR ELEGTRONIGSJAYGAR ELEGTRONIGSJAYGAR ELEGTRONIGSJAYGAR ELECTRONIGSJAYCAR ELECTRONICSJAYCAR ~~R ELECTRONIGSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONIGSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJA YGAR ELEGTRONICSJAYGAR ELEGTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONIGS JAY ELECTRONI CSJAYCAR ELECTRONICS JAY ELECTRONICSJA YCAR ELECTRONICS JAY ELEGTRONIGSJAYCAR ELEGTRONICSJAY ELECTRONICS,JAYCAR El ECTRONICSJAJ, "'" c.u :::,._, , nv1"i 1,._,o'-""' ,,._,M n CLC.V I nVl'll l V~J-\ TVJ-\M C.L C.V I M Ul"4 1V ~ TV A H t. L t.V I HUN IV tiJA Y(..;AH t.Lt.(..; I HUNl{.;:s.JAYCAH t ltC I HO N ICSJA YCAR ELECTRONlCSJAYCAR ELECTRONICS ELECTRONICSJAYCAR ~R ELECTRONICSJAYCAR ELECTRONI CSJAYCAR ELECTRON ICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS ELECTRONICSJAYCAR ~R ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS ELECTRONICSJAYCAR ~R ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELEC-..,ONI CSJAYCAR ELEClRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS ELECTRONICSJAYCAR I\.R ELEC-r............ ,..,.. ... ~,,.. ... ... ,..., ........-r"" ..... ... ........ , ,a,,.. ...... ,..., BARGAIN ISOLATING TRANSFORMER ,...,..~,.,.II,..~,,.~,,.. ... ... r , ,- . C '" ",.. ,. ... r 1 rr,-rrv"\t,.11,...(' r • c;..... -rn l'"\", llr C" c:c -roau •c£ IA yr- • o C f I A.Vr"AQ c;: 1 CCIOr.\l HC..c;-.fil.r....:rQC\....MCS:JAYCAR I ELECTR ! ELECTR ! ELECTR SAL! Designed for general purpose soldering. This kit includes a 30 watt 240 volt soldering iron. a quality metal stand with sponge, a length of solder and roll of solderwick. Cat. TS-1650 Arlec model 45065 600 ohm:600 ohm. PC mounting transformer. Telecom approval RA83/119. 25.4 x 19 x 20.5mm. $29.95 $7.95 10+ $6.50 •• Cat. MA-1508 IA V r"A Q TEMPERATURE ADJUSTABLE Portasol Professional The Portasol Professional is a fully comprehensive portable gas powered heat tool. It incorporates a soldering iron, hot knife, blowtorch and hot blow which is ideal for heatshrink tubing. FEATURES • No cords or batteries• Heavy duty, tip temperature adjustable up to 400°C • Equivalent to 10 • 60 watts• 90 mins use on one fill of gas • Uses standard butane gas lighter fuel • Soldering iron is static free • Blow torch operates up to 1300°C, perfect for heavy soldering jobs, brazing or silver soldering • Hot blow is ideal for our heatshrink tubing, adjustable up to 500°C • Hot knife cuts and cauterises synthetic materials such as plastics, ropes. Adjustable to 450°C The complete kit comes in a compact and rugged polypropylene case (230 x 80 x 36mm) which contains: 1 x Portasol Professional heat tool with 2.4mm soldering tip 1 x Hot Blow tip 1 x 81owTorch tip Replacement Tips 1 x Hot Knife tip 1mm Tip Cat. TS-1426 1 x Cleaning Sponge 2.4mm Tip Cat. TS-1427 1 x Safety Stand Hot Blow Cat. TS-1428 1 x Igniter Cap Blow Torch Cat. TS-1429 Cat. TS-1425 i / !!2:4~ ir! ~cr! ! ~: ; rature adjusta~e beween 240°C and 450°C enabling very delicate soldering on low settings with surprising heat energy reserves on i :~i~~~ ~~:~~;i~;l:!~fo~mperature is indicated by LED lamp brightness !;~;,;;~;~,~~~M ~~~.'!!L IRON • 240 volt operating • 370°C fixed temperature• High efficiency patented heating element• Iron clad chrome plated, long life interchangeable tips. Cat. TS-1550 $27.95 ll'l(.1'}- / ~ ALL $15.95 ea $79 Portasol Portable Gas Soldering Iron New generation soldering iron. Why bother with rechargeable batteries or chargers any more. The Portasol needs no cords or gas bottles. All you need is a can of Ronson type Butane cigarette lighter fuel. A full tank will last about an hour, and it refills in seconds. Portasol has an adjustable dial. You can vary it from the equivalent of 10 to 60 watts. A BRILLIANT NEW CONCEPT IN SOLDERING IN THE FIELD • No cords. batteries or bottles • Heavy duty, tip temperature up to 400°C • Adju stable temperature -equivalent to 10 • 60 watts• Hard working, up to 60 minutes continuous use• Refills in seconds. uses standard Butane gas lighter fuel • No leakage current to sensitive circuits • Made in Ireland Cat. TS-1420 $39.95 TIPS TO SUIT Cat. TS-1421 $15.95 Cat. TS-1422 $15.95 • 1mm TIP • 2.4mm TIP FREE GAS! Purchase either Portasol iron this month and receive a f ree can of Portasol gas ,: /~~ .,,,.-. --IRON CLAD TIPS TO $14.95•.·. ···· SUIT TS- 1460 & TS-1550 JAYCAR Cat TS-1552 Cat. TS-1553 c::::::1J=::Il STOCKS $6.95 ea A ~ LARGE SOLDER SPECIAL RANGE 200 gram reel 1mm 00/40 resin cored Cat. NS-3010 OF Normally $7 .25 ea IRONS, THIS MONTH & j ONLY $5.95 ea ACC'S .I\**** Sim~y insert your cables and crimp with a pair of pliers. Nylon insulated casing. Pack of 8 pieces. . $1:25 ~ ....... • ast ard.! ___x_ __,J mg: pE::zA ~Sm Y= C=Rm lfilM mP =W = l"R """E ~?IT~::::TUR:::::::.=N=YmOmU=R=:6i.\ '=R ELECTf SURPLUS STOCK • ,RELEcn CONNECTOR INTO CASH" •· lR ELECTf ·• · (l___.LV 11 MINIJT 1mm Micro Chisel 1.5mm Mini Chisel DIGITAL THERMOMETER Measures body temperature from 32-43°C. Easy to use, push button to switch on, place in mouth or under arm and when body temp is reached the unit will'beep'. Don't pay $29.95! Cat. OM-6300 Much lower l ELECTR l ELECTR 1 ELECTR 1 ELECTR 1 ELECTR 1 ELECTR 1 ELECTR 1 ELECTR 1 ELECTR 1 ELECTR 1 ELECTR 1 ELECTR 1 ELECTR '1 ELECTF '1 ELECTF '1 ELECTF '1 ELECTF il ELECTF R ELECTF R ELECTF R ELECTF R ELECTF R ELECTF R ELECTF R ELECTF R ELECTF R ELECTF R ELECTF R ELECTF R ELECTF R ELECTF R ELECTF R ELECTF R ELECTF R ELECTF H ELECTF R ELECTF R ELECTF R ELECTF R ELECTf ,R ELECTf ,R ELECTF ,R ELECTf ,R ELECTf ,R ELECTf ,R ELECTf R ELECTf ,R ELECTf R ELECTf lR ELECTf 'RELECTf R ELECT! ~R ELECTf fR ELECTf R ELECTf R ELECTF ,R ELECTf 'R ELECTf IR ELECTf ,R ELECTf ) } ~ ·.• · ~J .£ . . Jaycar will purchase your "surplus stocks of components and •·• ,R ELECTf R ELECTf •• R ELECTf •·m~Il ~:~~eO~Ri~B~R:icuu::LciiEi~~;~s . :~ \RELECTf 'J, :: ROUTLEY NOW ON ) '.= ~~~g;: .••••• \R ELECTf .•.·.·.·. \R ELECTf R ELECTI \ R ELECTf MAIL ORDERS POST & PACKING M A IL ORDER V I \R ELECTI HEAD OFFICE P.O. Box 185 Concord 2137 \R ELECTI 115 Parramatta Road Concord 2137 HOnlNE (02) 747 1888 $10 -$24 99 $ 3.75 \R ELECTI 11 \ R ELECTI • Telephone (02) 7 47 2022 FOR ORDERS ONLY $25-$49.99 $ 4.50 ROADFREIOHT ANYWHERE \R ELECTI ~ , F_A_c_s_1M_1L_E_<o t _2_>_7_4_4_ o_7_6_ 7...!:::T=O=LL=FR=E=E=I0=08=)=02=2=88=8=-$~0~'...:.ER'.!..:.~~~~~ ·99'.___ ___!~~600~·50...blN=A=U=ST=RAU~A!!!!(u=p=t•=20k=g.::::)I \R ELECTI \R ELECTI GORE HILL 188 Pacific Hwy (Cnr. Bellevue Ave) (02) 439 4799R ELECTI • Mon-Fri 9 • 5.30 Thurs 8.30pm • Sat 9 • 4pm R ELECTI SYD NEY · CITY 117 York St. (02) 267 1614BURANDA OLD 144 Logan Rd (07) 393 0777 \R ELECTI Mon-Fri 8.30 - 5.30 Thurs 8.30 pm• Sat 9 • 12 Mon-Fri 9 • 5.30 Thurs 8.30 - Sat 9. 12 \R ELECT! PARRAMATTA 355 Church St (Cnr. Victoria Rd) (02) 683 3377 Shop 2, 45 A'Beckett St City (03) 663 2030 \R ELECT• MELBOURNE-CITY Mon-Fri 9 • 5.30 Thurs 8.30 pm• Sat 9 • 4pm Mon-Fri 9 • 5.30 Fri 8.30 • Sat 9 • 12 ~~~g: CO NCORD 115 Parramatta Rd (02) 745 3077 SPRINGVALE VIC 887-889 Springvale Road Mulgrave (03) 547 1022 \R ELECT Mon-Fri 8.30 - 5.30 • Sat 9 - 12 Nr Cnr. Dandenong Road Mon-Fri 9 • 5.30 Fri 8.30 - Sat 9 - 2 R ELECT HURSTVILLE 121 Forest Rd (02) 570 7000ADELAIDE S.A. 190 Wright Street (Cnr Selll'y' Street) (08) 231 7355 ~R ELECT Mon-Fri 9 - 5.30 Thurs 8.30 pm - Sat 9 • 4 Mon-Fri 9 • 5.30 Fri 8.30 • Sat 9. 12 'TRONICS I[ .. . ]} (02) 747 2022 ff = VISA ~• ~ :ARELE -~ ---···-- ~·-·-·--·-·· - ··· - ··-··· ·----· ··-· ··--·· -· ____ :AR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRON ICSJAYCAR :AR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRON ICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ;AR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRON ICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR :AR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRO NICSJAYCAR ~RELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONI CSJAYCAR EL~CTRONI CSJA:,'CAR ELECTRONICSJAYCAR ELECTRONl<;:~ ~ ~TRONICS ELECTRONICSJAYCAR ELECTRONICS TRONICS ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS ELECTRONICSJAYCAA ELECTRONICS JA YCAR ELECTRONICS ELECTRONICSJA YCAR ELECTRONICS JA YCAR ELECTRONICS !S~:,S~~ ~~~s~~~~~~ ~~~g~~~:~~ AMATEUR RADIO By GARRY CRATT, VK2YBX Weather fax - what frequencies to listen to Our Radfax Decoder project in November has aroused much interest in the reception of weather fax signals from both amateurs and meteorologists alike. This article sets out to explain the origin of both HF and satellite signals and lists where and when they can be heard. Facsimile, in comparison to other modes of image transmission, offers a significantly higher degree of resolution than other less used modes such as slow scan TV (SSTV) and fast scan TV. This resolution, often between 1000 and 2000 lines per frame, means that extremely high quality images can be transmitted within the limitations of audio bandwidth, either down a telephone line or, of more interest to amateurs, via HF radio. As the time taken to transmit each frame is really of no consequence, detailed pictures can be received using a communications receiver and either a decoder for use with a computer, or a dedicated "receive only" fax unit. As a result, HF fax transmission is used in many countries for the distribution of weather charts for use by aviators, mariners and other interested parties. A modern fax transmitter electronically scans the sheet of text inserted and uses the voltage variations obtained to modulate an audio subcarrier, using either AM or FM modulation. Some transmitters use positive modulation, where the amount of modulation is determined by the amount of white (100% is all FIG.1: LIST OF SATELLITES TRANSMITTING WEATHER INFORMATION 88 FREQUENCY TYPE 137.500MHz 137.620MHz 137.300MHz 137.400MHz 137.850MHz 137.850MHz 1691.00MHz 1691.00MHz 1691 .00MHZ 1694.50MHz POLAR POLAR POLAR POLAR POLAR POLAR GEOST GEOST GEOST GEOST SILCON CHIP ORIGIN LINE RATE USA-NOAA 6 USA-NOAA 9 USSR-METEOR 2-14 USSR-METEOR 2-14 USSR-METEOR 2-14 USSR-METEOR 3-1 USA-GOES 5 USA-GOES 2 USA-GOES 3 ESA-METOESAT 2 120 120 120 120 120 120 240 240 240 240 INCLINATION 98 98 82 82 82 82 75 114 135 180 DEGREES DEGREES DEGREES DEGREES DEGREES DEGREES DEGREES DEGREES DEGREES DEGREES PERIOD W W W E 102MIN 102MIN 104MIN 104MIN 104MIN 11 OMIN 24HRS 24HRS 24HRS 24HRS white), while others use negative modulation, which is the reverse relationship to the material scanned. Typically, FM subcarrier modulation is used for HF transmissions as it offers some immunity to fading problems. Critical parameters The critical specifications for all fax transmissions are drum speed and scanning density. The subcarrier modulation type must also be known. Drum speed is expressed in RPM and relates to the original mechanical scanning systems used years ago. Most dedicated fax receivers allow selection of the two most commonly used speeds: 60 lines per minute and 120 lines per minute. Other rates sometimes used are 100 1pm, 180 1pm and 240 1pm. Scanning density refers to the number of lines per inch, which determines the linearity of the display. These values are often expressed as the IOC value (index of co-operation) and relate to the height to width ratio of the image. In addition to the HF fax broadcasts, there are a number of geostationary and polar orbiting weather satellites transmitting picture information in the VHF and SHF bands. The broadcasts that interest most amateurs are the APT or automatic picture transmissions. These are capable of an image resolution of 2-3km under good lighting conditions and are relatively easily received on modified 2-metre equipment or scanning receivers. Fortunately, all major users of cc ~· a co co ,-..,. -< t- c::: .._ CANBERRA AUSTRALIA CHINA CHILE BULGARIA CANADA BRAZIL BUENOS AIRES ARGENTINA BEIJING SANTIAGO BELLOTO RESOLUTE HALIFAX FROBISHER BAY SOFIA ESGUIMALT RIO DE JANEIRO BRASILIA DARWIN CITY COUNTRY BAF6 BAF36 ccs ccs ccs ccs ccs ccs ccs ccs ccs LR069 LR072 LR074 AXM31 . AXM32 AXM34 AXM35 AXM37 AXl32 AXl33 AXl34 AXl35 AXl36 PPN9 PPN9 PWZ PWZ LZJ2 CKN CKN VFF VFF CFH CFH CFH CFH VFR VFR CCV6 CCV6 CCV6 CCV6 CCV6 CALLSIGN IOC 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 5185.00 10720.00 18093.00 2628.00 5100.00 11030.00 13920.00 19690.00 5755.00 7537.00 10555.00 15615.00 18060.00 10225.00 18080.00 12025.00 17140.00 5093.00 4268.00 6946.00 3235.00 7710.00 4271 .00 6330.00 10536.00 13510.00 3253.00 7710.00 4766.00 6418.00 8594.00 13525.00 22071.00 2716 .00 2886.00 4063.00 6418.00 8692.00 8776.00 12600.00 13525.00 22070 .00 5525.00 8120.00 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 FREQUENCY RPM ITALY ROMA NEW DELHI OUICKBORN ATHENS GREECE INDIA PINNEBERG HELSINKI PARIS GERMANY FINLAND FRANCE NORTHWOOD BRACKNELL CAIRO EGYPT ENGLAND COPENHAGEN CITY DENMARK COUNTRY FIG.2: LIST OF CURRENT HF FAX TRANSMISSIONS BAF4 BAF8 BAF33 OXT OXT OXT OXT SUU36 SUU2 GFA21 GFA22 GFA23 GFA24 GFA25 GFE25 GFE21 GFE22 GFE23 GFE24 GYA1 GYA6 GZZ2 GZZ3 GZZ40 OFB28 FTE4 FTl8B FTM30 DDK3 DDK6 DDH3 MGR MGR MGR ATP38 ATP38 ATA55 ATA57 ATV65 ATV65 IMB51 IMB55 IMB56 CALLSIGN 10115.00 14365.00 18235.00 5850.00 9360.00 13855.00 17510.00 4526.00 10123.00 3289.50 4610.00 8040.00 11086.50 14582.50 2618.50 4782.00 9203.00 14436.00 18261.00 2813.85 3436.85 4247.85 6436.85 8494.85 8018.00 4047 .50 8185.00 12305.00 7880.00 13882.50 3855 .00 5206.00 8100.00 12903.00 18227.00 18233.00 4933.50 7405.50 14842.00 14772.00 4777.50 8146.00 13600.00 continued IOC 120 576 120 576 120 576 120 576 120 576 120 576 120 576 120 576 120 576 120 576 120 576 120 576 120 576 120 576 120 576 120 576 120 576 120 576 120 576 120 576 120 576 120 576 120 576 120 576 120 576 120 576 120 288 120 288 120 576 120 576 120 288 120 576 120 576 120 576 120 576 120 576 120 576 120 576 120 576 120 576 120 576 120 576 120 576 next page FREQUENCY RPM :!:: -c n r=: 0 0 :z: CJ) C0 0 I AUCKLAND MONSANTO ST DENISCHAUDRON DAKAR PRETORIA MADRID NEW ZEALAND PORTUGAL REUNION SENEGAL SOUTH AFRICA SPAIN SWEDEN FORT DE FRANCE MARTINIQUE NORRKOPING ROTA NAIROBI TOKYO JAPAN KENYA CONTINUED CITY FIG.2 COUNTRY CALLSIGN JMH JMH JMH JMH JMH JMH JMJ JMJ JMJ JMJ JMJ 5YE 5YE 5YE3 5YE3 FFP FFP ZKLF ZKLF ZKLF ZKLF CTV4 CTW8 CTU2 HXP FZS63 6VY41 6VU73 6VU79 ZR05 ZR02 ZR03 ZR04 AOK AOK AOK AOK AOK AOK AOK AOK AOK SMA4 SMA6 SMA8 3622.50 7305.00 9970.00 13597 .00 18220.00 22770.00 3365.00 5405.00 9438.00 14692.50 18130.00 9044.90 10115.00 17366.90 22867.00 5013.00 14521.50 5805 .00 9459 .00 13550.00 16220.00 4235.00 8526.00 13002.00 8176.00 16335.00 7587.50 13667.50 19750.00 4014.00 7508.00 13773.00 18238.00 3650.00 6918.50 10250.00 4053.50 4704 .00 7453 .00 8506.00 9075.00 12759.00 4037.50 6901.00 8077.50 FREOUENCY 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 RPM IOC 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 USSR MOSKVA MOLODEZHNA YA KHAVAROVSK SAN FRANCISCO PEARL HARBOUR NORFOLK MOBILE LA JOLLA KODIAK GUAM BOSTON USA CITY ANKARA COUNTRY TURKEY CALLSIGN YMA5 YMA5 NIK NIK NMF NMF NPN NPN NPN NPN NPN NPN NOJ NOJ WWD WWD WLO WLO WLO NAM NAM NAM NAM NPM NPM NPM NPM NPM NPM NMC NMC NMC NMC RHO RHB RHO RHO RUZU RUZU RUZU RUZU 3377 .00 6790.00 3502.00 12750.00 3242.50 7530.00 4975 .00 7894.00 10255.00 15990.00 19860.00 22910.00 4298.00 8459.00 8646.10 17410.60 6852.00 9157.50 11145.00 3357.00 8080.00 10865.00 16410.00 2122.00 4855.00 8494.00 9396.00 14826.00 21837 .00 4346.00 8682.00 12730.00 17151.20 19275.00 7475.00 9230.00 14737.00 9280.00 15830.00 17660.00 18490.00 2815.00 5355.00 7750.00 FREOUENCY 90 90 120 120 120 120 120 120 120 120 120 120 120 120 12.0 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 120 60 90 120 60 120 120 120 120 60 90 120 RPM IOC 288 288 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 576 288 576 576 576 576 576 576 576 288 576 ~ ~ z z z <:!) z z <:!) c.. c.. <( z z <:!) Ill"' cr.i ...J ...J <( u ...J ...J <( u z ~ c.. ~ c.. Ill ...J ...J 0 (,) 0 N ..... cr.i cr.i II: 1- N ..... ► :c a. ◄ II: Ill"' (/) I- c.. II: <.O z U") c., O: :E ◄ ::) c., Cl L.lJ L.lJ r-- ...J ...J <( u ~ c.. ...J 0 N ..... Cl L.lJ w c.. (/) <.O r-- LI") Ill (,) - Z ◄ (,) Ill ◄-◄ :c a. z II:"' II:::) 0 g:c ◄ II: c., z Ill 0 t-m Cl) II: ◄ Ill (/) (/) (/) (/) (/) :::> :::> :::> :::> :::> ..... 0 0 0 0 0 5 :::> :::> :::> :::> :::> 1:11 ~~~ ~~ .... I- I- I- I- I- :z::zzzzz ~◄ ~:c uooooo (,) u,uuuuu -I -I -I >- 0 fil N N::t!::t!::t! ◄ m: >cc ◄ .... :::r: :::r:-'"'-'"'-'"' > =◄ z ◄ Ill ~ z z <:!) cr.i z 0 cr.i (/) ~ z An example of a weather fa x picture received on HF from AXM (Canberra) is shown in Fig.5 . (/) <( C: Further reading .,...r--C'lNC:00 ...J ...J <( (1) ARRL Handbook, 1989; (2) Weather Satellite Handbook, Ralph E. Taggart; (3) Schedule of Australian Meteorological Radfax Broadcasts (available from the Director of Meteorology, Bureau of Meteorology, Attention SRCM, GPO Box 1289K, Melbourne, Vic. 3000). a=C'lC:OOC'lM ._ ~ r-,... .,- .,..... N u (/) ::::::,-'"'-'"'u;O-=t LI") '<t LI") <.O <.O za. u Q these satellites use the same picture format, making reception of these pictures relatively easy. Fig.1 shows a list of current satellites and their frequencies while Fig.2 shows a list of current HF transmissions. The National Oceanic and Atmospheric Administration [NOAA) Weather Service broadcasts numerous weather satellite photos taken by GOES (Geostationary Environmental Satellite) spacecraft as shown in Fig.3. Also, the US Naval Oceanography Centre transmits weather information by HF fa x for use by US naval vessels and stations and for use by the US Military Sealift Command. Although designed for navy use, these charts are also of interest to private and commercial marine interests (see Fig.4). t- Fig.5 (below): this weather fax was received on HF from the Bureau of Meteorolgy in Canberra. It is just one of many different weather maps transmitted by the Bureau. ...J ...J <( u ~ c.. ...J 0 N ..... Cl LJ.J L.lJ c.. (/) <.O >- ...J r-- LI") z 0 >...J (/) z 0 z 0 (/) cr.i :::> :::> (/) ...J ...J -:::>:::>~ z 0 (/) N SQ ~ N (/) z LI") LI")<( (/) '<t '<t C: zMMt<CNN ~g:oo~ ::::::, t-t-<:!) u Q e~U")U")~ (/) ~5,2:;:!::;:!:<( z 0 u,zoo □ cr.i (/) N ~ :::r: (/) fil::t!::t!~~ ~..:::.:::..:::.:::0.,..- <( ...,."Q"cor,.....,a=M<.ONI"- ...J ...J <( >c::::1- <.O N N M u; ... ~co.,......,- z C: t- JULY 1990 91 NEWCROtS This inexpensive rang of modular Interlocking units enables a quick, easy way of experimenting with new circuits and ideas. There are two main units consisting of a terminal strip or distribution and a Central plug•in unit. • 100 holes INSIDE THE IBM PC (Revised and expanded edition} •Peter Norton f he widel y acclaimed gUtde to the IBM PC s inner workings The latest ed1t1on now covers every model of lhe IBM mrcro PC XT and A T. and every ver sion ol DOS from 1 1 to 3 O .. .... $44.95 B20080 VERTICAL DEFLECTION • Deflection Factor: SmV to 20V/ Div on 12 ranges in .1•2·5 step with fine control • Bandwidth DC : DC to 20MHz (·3dB) AC: 10Hz to 20MHz (·3d8) • Operating Modes: CH·A, CH·B, DUAL and ADD (ALT/CHOP L202 only) • Chop Frequency : 200KHz Approx. • Channel Separation: Better than 60dB at 1KHz P11000 .................... $2.75 • 640 + 100 holes P11007 ... ............... $14.95 • 1280 + 100 holes P1_1010 .................. $26.95 12V DC FANS • 2560 + 700 holes P11018 .................. $69.95 80 x 80 x 25.4mm • 12V DC, 1.7 Watt, 0.14 Amps T12469 .................. $12.95 10+ fans only $11 .95 each ===Ill RECTANGULAR LEDS 1·9 10-gg 100+ 1._2c RED 20c 15c GREEN 20c 15c 12c YELLOW 20c 15c 12C 12c ORANGE 20c 15c .f ~ QUICK MOUSE GOLD INSERT LOW PROFILE IC SOCKETS • Gold machined pins • Extremely high quality • Anti•wicklng • Ideal for professional use or where field service components is required. Cat .no. Descriptio n P10620 P10624 P10626 P10628 P10630 P10632 P10634 P10640 P10644 Spin 14 pin 16 pin 18 pin 20 pin 22 pin 24 pin 28 pin 40 pin 1-9 1 O+ $1 .20 $1.60 $1.90 $2.00 $2.20 $2.40 $2.60 $2.90 $2.95 $1.10 $1.40 $1.80 $1 .90 $2.00 $2.20 $2.40 $2.70 $2.75 LOW PROFILE IC SOCKETS Save a ·s mall fortune on these "Direct Import" low profile le sockets! PCB mounting solder tall. All tin plated phosphor bronze or berrylllum and dual wipe for reliability. Cat. No. 10+ P10550 P10560 P10565 P10567 P10568 P10569 P10570 P10572 P10575 Description 20MHZ DUAL TRACE OSCILLOSCOPE CRT DISPLAY • 150mm rectangular 1·9 $0.20 $0.20 $0.35 $0.35 $0.30 $0.30 $0.40 $0.40 • Sweep Time : 0.2µ Sec to 0.5 Seel Div on 20 ranges in 1·2·5 step with fine control and X·Y • Magnifier: X5 at all ranges TRIGGERING • Sensitivity lnt: 1 Div or more Ext : 1Vp·p or more • Source: INT. CH·B, LINE or EXT • Triggering Level: Positive and Negative, continuously variable level; Pull for Auto • Sync: AC, HF Rej, TV (each+ or·) at TV Sync. TV•H (line) and TV•V (Frame) sync. are switched automatically by SWEEP TIME/Div switch . Th,s spectacular rugged and compact DMM has a bnght yellow :Irr:~:~~~;:i~!~~%~e g~:~~U/8S 2 diode and transistor test. contInuIty (w 11h buzzer). capacitance meter . up to 20 amp current measurement and comprehensive ACtOC voltage curr en1 and resistance ranges CHECK THESE FEATURES .... • Push•button ON/O FF SWl!Ch • Audible con ttnuIty test · • Single !unction. 30 posItIon easy to use rotary switch for FUNCTION and RANG E selection • Transistor test • Diode ICSI • • • • • • • Ouallty probes 1-2"' High conlrast LCD Full overtoad pro1ec11an 20Amp Bwlt IO hltIng ball Capacitance meler lnsttuct1on manu al 09 1550 . Normally $ 165 Special , only $129 HORIZONTAL DEFLECTION • Deflection factor : 5mV to 20VI 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 600Vp•p • X·Y Operation: X·Y mode is selected by SWEEP TIME/ Div switch • Intensity Modulation Z Axis : TTL Level (3Vp•p - 50V) + bright. • dark OTHER SPECIFICATIONS • Weight : 7Kg Approx • Dimensions : 162(H) x 294(W) x 352(0) mm 012105 ... . ...... ...... ....... ..... ... ... ........ .... ... ... .. ... $750 X19952 ......... .. .. ..... $79.00 WITTY MOUSE • Three buttons, user definable • Silicone coate<! steel ball • High resolution movement of 195 dots/Inch . Smaller table space and less hand movem_ent required • Optical rotary encoder • Max. tracking speed: 200m/sec • Mouse resident firmware • Size: 116 x 66 x 34mm • Mouse Driver Software included . allowing you to Install with all popular software packages. Also included Is the handy Pop-up mer, u software that allows the user to integrate the mouse with the keyboard. DOS. and other popular software packages - X19950 ....................... $59 8 pln ......... ...$0.20 $0.18 14 pln ..........$0.25 16 pin ......... $0.25 18 pin ......... $0.40 20 pin ........ . $0.40 22 pin ......... $0.40 24 pin ......... $0.40 28 pin ......... $0.50 40 plr. ..... .... $0.50 MICROSOFT' COMPATIBLE! • Auto•selection and auto• transfer between mouse system system PC mouse mode and Microsoft serial mouse mode • Microsoft Serial Mouse and Mouse System compatible • Super high tracking speed : 600mm/sec • Super high resolution : 200 0.P.I. (0.12mm/dot) • Silicon rubber coated ball • Optical rotary encoder TIME BASE • Type: Automatic and normal triggered in automatic mode, sweep is obtained without input signal 20A, 3 112 digit frequency counter multimeter with capacitance meter and transistor tester. ---=- FLASHING LEADS • Red,Smm 40MHZ READ-OUT OSCILLOSCOPE CRT DISPLAY • 150mm rectangular VERTICAL AMPLIFIER (CH1 and CH2 Identical) • Operational Modes : CH1, CH2, ADD . DUAL, ALT, CHOP • Sensitivity : SmV•SV/ Div 3% in 1-2·5 steps -------~ 1mV•1V/ Oiv x5% x5MAG • Bandwidth DC: DC to 40MHz (·3dB) AC : 5Hz to 40MHz (·3dB) • Rise Time : Less than 8.7nS HORIZONTAL AMPLIFIER • Operating Modes : X· Y operation CH1·X axis. CH2· Y axis • Sensitivity : 5mV•5Vt Div± 3% in 1·2·5 steps • Input Impedance 1Mll :':2%, 25pF±3% • Bandwidth DC DC to 1MHz (·3dB) AC 5Hz to 1MHz ( ·3dBl ,;>tO'o0 G'yl,.0 1$39 s\li\ \ \O Q\ '2.'2-Q ~ _ea.\ so ea.C TIME BASE • Sweep Method : AUTO , NORM , SINGLE • Sweep Time (A) : 0.2µs•0.5S/ Div±3% in 1·2•5 steps (X1 only) (B): 0.2µS-0.5mSI Div±3% in 1·2•5 steps (X1 only) • Magnified Sweep : 10 times ±5%, Max 20ns • Linearity: t 3% or better 012107 ..... .. .. Compact. ru~ged , banery operated. hand held 3 k digit multimeter. Features ... • 1/ 2" high contrast LCD. • Automatic over-range indication with the ·· 1" displayed. • Automatic polarity mdicat1on on DC ranges . • Capacitance measurements to 20uF • Diode te stmg with 1 mA fi xed current. • Audible Continuity Test. • Transistor hFE Test. SPECIFICATIONS Maximum Di splay: 1999 counts 3 1/2 digit type with automat1c polarity indication . Indication Method: LCD display. Meaaurlng Method : Dual·slope in A·D converter system. Over-range Indication: " 1" Figure only in the display . Temperature Ranges: Operating 0-C to + 40-C Power Supply: one 9 volt banery (006P or FC· 1 type of equivalent) Cat. 091540 ..... Normally S139 SPECIAL $99 :·~,r~ ='=1 ll1 fl ~ L ,__r""' • -·, AIR IONS ' I ·Q •-L,f•! !JL GENERATOR i ,. ,., 0 ·•, - M;um (l>l>le ,::: Magk So~ / telephone handset and a fax to the same telephone line • Detects whether an A STATIONARY BREAK THROUGH !!! Now you can use your fingers Instead of your mouse. and compatible's, Operates under Microsoft I mouse system mode. FEATURES: on the 58 X 48mm front panel of the touch mouse control the on screen cursor movement. · With no ball, the touch mouse requires no desk space for movement. · No pad to get dirty and take up desk space. One finger can do all the users drawing. · Compatible with all existing mouse software. · RS- 232 serial port No need for air freshners · -- 0 Just plug It Into the cars cigarette fighter and ,t releases negative air ions into the vehicle .... making a .iiifJJ!llt ~f~~~~1:;~~~ :~1e!~st are PC- SHARE ~~~sp~;;,~ CGA, EGA, RGB. Keyboards - PC-XT or work. X1~ $'2f9 The Trackball keyboard is a palm d riven mouee w hich la built into your NEW keyboard. Above the ball I• 3 key• - w hich allow y ou, y our aelectiona and zooming In and out on work. The Trackball allows you to keep the feel of your work in the centre of your palm. feeling prevails. The product is also good for the respiratory and blood systems. u:~~i=~~ :~nochrome, power 101 KEY TRACKBALL KEYBOARD fresh driving environment. surges, created by lightning striking telephone lines. - Especially suitable for laptops, the touch mouse saves on desk space. .. th e phone or th e lax 88 you wish • It Is protected against lightning strikes- your lax switch has built In protection against phone or use the tax to make an out going call • Lets you override the au tomatic switching and connect the line to either · User's finger movements . 1 The PC- SHARE Magic Box enables two user workstations (monitor & keyboard) to be connected to one PC. SPECIFICATIONS: · Magic box 20mm X 100mm X 20mm · Master cable - 600mm I 1 ;i~t!n:e ~:.:~ desks • so metres Power supply - none required · Compatible computers - PC, PC-XT, PC-AT 286, PC-AT 386, PS/2 Model 25, PS/2 Model 30. · Compatible operating systems· Supports MSDOS, OS-2, MS-WINDOW, Incoming call Is for the phone or the lax and automatlcally puts It through to the correct unit • It automatically switches when you pick up the MODELS: ATM-110 Touch Mouse for IBM PC/ XT/ AT · ~:~e~~; ~ative Air Ions .Jfiljifle • lets you connect a normal TOUCH MOUSE v,... , _,,~ . • FAX SWITCH X19960 ....................$149.00 9 A1son Advantage• of the Trackball mouae: • It la more accurate th an other cursor con1rola • It has more flexibility than other device•. ::~:::.rrr ~~r:: ih~=~i: ! h: ~ rio.i:=::.i"::: working In another area. ' • Dietortion free drawing ability. • Compadabillty w it h other major mouae ayateme • Dynamic resolution. :':;'!~,,:' :~::~.~~..~~'.".'1~:....$299 PRINTER BUFFER PB - 42P PRINTER BUFFER The printer buffer Is for offices or schools which have high volume data to process. Its a time saver. It accepts data from your computer and stores the data in its memory, then feeds the data to your printer =::r ~.~~~our X12030 _ ·:::;,·::. - sw; - - - - - ~ ROD IRVING ELECTRONICS UJ.1U##;l--t\2U<at>ll$%liU##;l-t\21?t¾1i:$ - ~~~~~: . •rI , OKI LASER PRINTER ;~:aarramatta Rd . . , Phone (02) 5193134 ~ ~---.,/;_! ~ .$169 95 00 lo - 2- K FITTE .. D CAN-TAKE UP TO . X19160 fM EGOFIIAII * SpecHlcetlona: ,Microaolt aerial mou• and PC mouae compatible •Tracklng speed- 900mm/aec. • Resolution- 200 dpl (dot s per") Dynamic reaolution-100-1200 dpl • Opto mechanical encoder. AUSTRALIAS CH EAPEST PRINTER MICROLINE 172 I ... I I I • Compact, reliable, economical I Thia OKI dot matrix printer is a great investment for the office or I home • The Microline 172 fits anywhere you need it, and OKJ exclusive bottom feed helpe improve your workftow. • 180 CPS Printer I • NL030 CPS YOU WON'T FIND IT CHEAPER! I I ONL5i3 I I .a,ctn..._......c:::t±r-i j ONLY $1995 ~ ~- SPECIACATIONS Ol400 Printing speed : 4 pages/minute Resolution : 300 x 300 DPI Emulation : HP Laser Jet Series II Data Buller : 512K Byte (standard) 1M Byte expansion (option) 2M Byte expansion (option) Max. 2.5M Byte Interlace Centronica Parallel or * RS232C Serial Resident Fonts : 25 •kinda Standard Pap.,r input : 200 sheeta Standard Paper output : 200 sheeta f ace up 100 aheeta face up Introducing the new generation In page printers, the OKILASER 400. The affordable LED page printer designed tor the amall busineaa. Reliable and compact, the OKJLASER 400 fita neatly into the smallest of office• . Highly reliable due to the latest LED imaging technology, the OKI LASER 400 offera excellent print quality, superior paperhandling, and a variety ol lonta which rival.some of the more expensive laaer printara on the market. .. • • • • • • • • • • • • • • • DATA TRAN SFER SWITCHES 2 WAY RS232 X19120 ONLY $39 4 WAY RS232 X19125 ONLY $59 2 WAY Centronics X19 130 ONLY$49 4 WAY Centronics . .. .. X 19135 ONLY $59 easy to check on p•per supply • Paper can be fed from the centre or the rear according to the design of the printer · • Removable drawer which allows paper to be changed without moving the printer • Retractable rear basket makes print-out collection fast and convenient • Suitable tor maost printers C21055 ........... ...... $29.95 • • • • • • I I I NORTHCOTE : 425 High Phone (03) 489 8866 I 620 Order Hotline : Phone (03) 663 6151 s1. ORDER & I MAIL CORRESPONDENCE : P.O . Box , CLAYTON 3168 I I 008 33 5757 (Toll free , strictl y orders only) Inquiries : (03) 543 7877 Tele x: AA 151938 Fax · (03) 543 2648 I All sales tax exempt orders and w holesale inquiries to: RITRONICS WHOLESA LE 1 56 Renver Road , Clayton . I ~:~n~1~~4;4;6~~66 (3 lines) ORDER HOTLINE 008 33 5757 (TOLL FREE) STRICTLY ORDERS ONLY LOC AL ORDERS & INQUIRES (03) 543 7877 POSTAGE RATES: $1 - $9.99 ............... .......... $3.00 ~#~ • Transparent cover makes it • PRINTER PAPER ~~~ ENCLOSED PRINTER STAND (inc tax) Fax:( 02) 5193868 MELBOURNE: 48 A'Beckett St The new Z-NIX Super Bua Mouae 2 allow• you to get the moat out of your computer and enhance your productivity. It give• you the abUity to expand the veraltiltty of your computer through the uae of g111ghlc aoftware ouch u plllnt, draw and CAD programs. The • 100% Mlcroaoft Compatible • IBM or APPLE Family Computer Compatible. • Free Software with Pop-up Menue. • LIie time Warranty. Aleo aupplled with the SUper Bua Mouae are two FREE Telepalnt Super Mouae 2 all owe you to run diak• which al Iowa the uaer to program• like GEM ond Windo- pertorm high reaolutlon graphl with the mouae.Great Valuel .X19951 .......................$ 11 Which make• all operations of the computer eaaler and faaler. Many popular Spreadaheata, databoaea, word proceaaora and other program• can alao bo -,keel with the SUper Moues 2. HURRY! THIS OFFER CAN'T LA I I I I I COMPUTER PAPER I Quality paper at a low price! I 2,000 sheets of 60 gsm bond I paper I . 11 x 9 1/2" I C21001 .... ... ,.............. .$41 I . 15 x 11" I 2 1 11 59 95 •• • •••• • ••••• • •••· • $10 • $24.99 ········ ···· ······ ···$3.50 $25 - $49.99 ................. ... $4.50 $50 - $99.99 ······ ·· ·· ·········· $6.00 $100 + ........ ..... . ............ . .. FREE The above postage rates are for basic postage only. Ro ad Freight, bulky and frag ile items wi ll be charged at ditt erenl rates Errors an d omissions excepted . Prices and specifications subject to ch ange IBM" PC" xr· AT" are ,eg,stereo Jrc1d em a1ks cl i "lernd! •oria 1 8u s ,ne~~ Ma cM,,.,es ·Appl e ,s a •eg ,stereo !•ademark Tel1on · ,s a , ,,.g, ~tere<I 1r c>oe m an, 01 Du po nl ·oe no ntes reg ,s1 er eC lf;iOema,~s ol 1ne" res pec t,ve owriers IPRODUCT SHOWCASE I Sheridan Electronics Redfern store to close Fast memory board for the Amiga Whether or not you are a fan of the Amiga computer, the memory available in the standard machine is a real problem. They come standard with 512K of RAM but by the time "Workbench" is loaded, only 340K is available for other software. Now that problem has been addressed with the release of a 1.8 megabyte memory card designed to fit the expansion socket inside the After many years in the electronics parts retail business, Mike Sheridan is to close his Redfern store. Mike informs us that he is now running his closing down sale and that there are many bargains to be had. For those of you who have not ventured down to Redfern, the address is 226 Cleveland Street and the phone number is (02) 699 6912. In the meantime, its business as usual at Sheridan Electronics' other store, at Shop 30, Patrick Street, Central Plaza, Blacktown, NSW 2148. Phone (02) 621 1494. base of the computer housing. The board comes with 512K of RAM and sockets for the remainder. A nicad battery powers the on-board real time clock and there is an extra memory disable switch. The memory board comes with fitting instructions and a 12 month warranty. For further information and prices, contact Flinders Electronics, Unit 2, 11 Flinders Ave, Lara Lake, Vic 3142. Phone (052) 82 2550. Desoldering tools from Jaycar Giant size instrument case This new large instrument case was designed and is manufactured in Australia for Altronics of Perth. It is considerably bigger than instrument cases that have been available up till now. Dimensions of the case are 355mm wide, 122mm high and 250mm deep and there are plenty of ventilation slots so that heatsinks can be mounted inside. There are strong mounting positions for transformer bolts and adequate numbers of pillars for mounting large printed boards. The front and rear panels of the case are of the same material and are in fact moulded at the 94 SILICON CHIP same time as the top and bottom sections. They are well finished and suitable for silk screening or Dynamark labelling. Three colours are available black, grey and blue - and the front panels can be either black or grey. The price of the case is $39.95 and they are available from Altronics Distributors Pty Ltd, 174 Roe Street, Perth, WA 6000. Phone (09) 328 2199 . Sick of burning your fingers when using desoldering braid? If so, one of these desoldering tools is a painless alternative. There are two models to choose from, an economy model and a deluxe version, both with a long lasting Teflon tip. The economy model is made from a heavy duty plastic and has a plunger thumb rest and guard so that your thumb can't slide over the top of the tool. It has a large barrel, is able to take a fair amount of solder and costs only $9.95. The deluxe model has a heavier metal construction and has a very smooth plunger operation. The tip is easily unscrewed to allow removal of built up solder. It retails for $16.95. Both tools are available now from any Jaycar Electronics store. Telephone microphone inserts from D. Dauner Need the odd telephone microphone or speaker insert? You can get them from Dauner Electronics for the piffling price of $1 each. Yep, just $1. Dauner Electronics is at 51 Georges Crescent, Georges Hall, NSW 2198. Their phone number is (02) 724 6982. New plastic cases have two mounting options These new plastic cases from Geoff Wood Electronics come with the standard vertical ribbing inside the box but they are also supplied with small moulded plastic sections which allow boards to be mounted horizontally, and even stacked if necessary, without having to drill holes in the lid to screw them down. Also, the countersunk screws for the lid are machine screws fastened into metal inserts - not the usual self-tapping screws into plastic pillars. You will be able to remove the lid as many times as you Hot air desoldering station Removing surface mount chip carriers from printed boards can be a real chore for service personnel. To help solve this problem, Scope Laboratories has released this hot air desoldering/soldering system. It directs hot air at the IC pins through an array of tiny pipes like, without having to worry about stripping the thread inside those plastic pillars. The cases are a little more expensive than the standard jiffy boxes but they're worth it if you require that extra versatility and quality. The sizes are 50 x 100 x 25mm (small) which costs $7.95, 80 x 150 x 50mm (medium) for $13.95 and 110 x 190 x 60mm (large) which costs $22.95. They're available from Geoff Wood Electronics, 229 Burns Bay Rd, Lane Cove, NSW. Phone (02} 428 4111. Bookshelf in each clip-on nozzle. Different nozzles are available to suit all the common SMD IC packages. A desoldering time of around 7 seconds is typical and the air flow temperature is adjustable between 100°c and 390°C. For further information contact Scope Laboratories, PO Box 63 , Niddrie, Vic 3042. Phone (03) 338 1566. C & D size nicad cells from Altronics s., If you want more current than standard 1. 2V AA size cells can delvier, then have a look at these little beauties. The C size is rated at continued from page 3 review, I have not had nearly enough time to absorb all the information in this very comprehensive text. However, I can state that it is very well written and covers a very complicated subject in great detail. For anyone who is interested in the subject, whether directly via music or via digital signal processeing, this book is an important reference. Our sample copy, in hard cover form, came from Jaycar Electronics and it is priced at $59.95. It is well worth it. (L.D.S). JULY 1990 95 . ~I:, High capacity lithium cells for computer clock back-up Premier Batteries has released a range of backup batteries to suit most personal computers on the market. Among the brands catered for are IBM, Epson, NCR, Tandon, Compaq, AST Research and many more. They are direct replacements for bat- 1800 milliamp-hours (1.8 amphours) and has a standard charge rate of 180 milliamps for 15 hours. The D size is rated at 4000 milliamp-hours (4 amp-hours) and has a standard charge rate of 400 milliamps for 15 hours. The C size cells are priced at $12.00 each while the D size goes for $19.50. They are available from Altronics Distributors Pty Ltd, 17 4 Roe Street, Perth, WA 6000. Phone (09) 328 2199. teries made by Eagle Picher, Panasonic, Rayovac, Sanyo and Tadiran. These replacement batteries are assembled from high capacity hermetically sealed lithium cells which have an operating temperature range from - 40°C to + 85°C. For further information, contact Premier Batteries, 7/27 Childs Road, Chipping Norton, NSW 2170. Phone (02) 726 7701. The number of pin grid array (PGA) ICs used in state of the art equipment is steadily increasing. The main problem with these ICs is trying to remove them from a socket or board without damaging the pins. This extraction tool from Energy Control International is designed for 10 x 10 up to 25 -x 25 pin ICs. It RCS Radio Pty Ltd is the only company which manufactures_and se lls eve ry PCB[, fr o nt panel publi shed in Sil .ICON CHIP. ETI and EA. 651 Forest Road, Bexley, NSW 2207. Phone (02) 587 3491. SILICON CHIP Plastic project boxes from Arista Extraction tool for PGA ICs .,.•~.,~1;f.:.;.: 96 has thin walled construction to allow for a minimum of clearance from nearby components. For more details, contact Energy Control International Pty Ltd, 26 Boron St, Sumner Park, Qld 4074. Phone (07) 376 2955. These new project boxes are externally similar in appearance to the jiffy boxes sold by most retailers but are an interlocking design held together by four long screws. Inside, there are four pillars to mount PC boards instead of ribs on the box sides. There are two sizes, the UB-6 pictured, which is 90 x 50 x 25mm and sells for $5 .95 and the larger UB-8 which is $7.95. Both are currently available from Arista Electronics outlets. Precision screwdriver set It's quite easy to damage those small machine screws on equipment if you don't use a screwdriver which fits the screw head exactly. This set from Arista contains three flat-blade and three Philips-head screwdrivers with sizes of 2.4, 3.0 and 3.8mm for each type. All have insulated non-slip handles which are colour-coded by type. The driver tips are made of nickel chrome molybdenum steel for extra strength. Suitable for all types of work, this screwdriver set is available from Arista Electronics outlets for $22.95. Special crimp tool for Ethernet connectors Increasingly, large and small businesses are installing computer networking systems and quite a few of these are based on Ethernet. Until now, if you were installing such systems, you needed separate crimp tools for the Ethernet and Thin Ethernet systems. Now, that problem has been solved with the release of a new crimp tool from Greenpar. Made in Sweden, the new crimp tool has a die arrangement which enables the user to crimp the centre and outer contacts of both N and BNC connectors. Designated B86-57, the new crimp tool is available from agents and branches of Acme Electronics, 205 Middleborough Rd, Box Hill, Victoria 3128. Phone (030) 890 0900. Audio signal generator for automated testing "~#.!it:~'$tl l'<(>A(~~M~f~ '°"""'" -"'O:l _.._,, -- .... ,... - ii D ED Ill II g _ _,.. "' - ~, __ = -~ _! -"~- -~-· • ~-]i _, ! ..L ~- Measuring the performance of a studio, transmitter or satellite uplink is now possible within 30 seconds. How so? Use the Tektronix ASG-100 Audio Signal Generator in High performance mini loudspeakers Audiosound Laboratories has introduced a new speaker system to meet both domestic and professional requirements for high performance from a very small enclosure. According to the designer, they are intended for critical listening in small listening rooms. They are claimed to be ideal for digital source material and live music monitoring. Measuring only 305mm high, 190mm wide and 190mm deep, this new Australian made system is a 2-way system with a 25mm dome tweeter and 165mm woofer. Frequency range is quoted as 65Hz to 20kHz at the - 6dB points. The system impedance is a nominal 80 and sensitivity is quoted as 85dB at 1 conjunction with the VM700A Option 40 Audio Measurement Set. The ASG-100 creates tone sequences for testing audio performance to ANSI Tl.502-1988, EIA/TIA-250-C and CCITT 0.33 standards. Each type of tone sequence starts with a unique one second FSK signal which identifies and communicates to the VM700A the appropriate stored measure- watt at 1 metre. Power handling is stated at 50 watts on program material. Two cabinet styles are available, designated 8012 and 8013. The 8012 version is finished in black simulated woodgrain while the 8013 comes in a high gloss Eurothane and is available in any colour to suit a particular surrounding. Also available is a B version of both cabinet styles which has a higher power rating (up to 75 watts on program material). This is gained by a modified version of the crossover network which has steeper slopes. Prices range from $629 a pair for the 8012s to $889 for the 8013B. For further information, contact Audiosound Laboratories, 148 Pitt Road, North Curl Curl, NSW 2099. Phone (02) 938 2068. ment program to use. Up to 4 seconds of voice may be recorded in the ASG-1 OOs nonvola tile voice memory using the front panel microphone and this can be useful for indentifying test sequences. For further information, contact Tektronix Australia Pty Ltd, 80 Waterloo Road, North Ryde, NSW 2113. Phone (02) 888 7066. ]ULY1990 97 For further information on the monopod or tripod, contact Arista Electronics Pty Ltd, PO Box 191, Lidcombe, NSW 2141. Low-cost RGB monitor Budget 6-channel microphone mixer This liftle unit allows four 600!2 . and two 50kn impedance microphones to be mixed together and fed to one tape deck ·or power amplifier. ·Each microphone input has its own level control and there are m§lster treble and bass controls New IC sockets have disposable carriers Recently released by Energy Control International, these new low profile sockets feature a disposable carrier system that peels away after insertion into the board. They enable better air flow around the IC and easy inspection of solder joints. They are available in a large number of pin formats. For further information, contact Energy Control International Pty Ltd, 26 Boron St, Sumner Park, Qld 4074 or phone (07) 376 2955 or Sydney (02) 555 7659. Monopod & tripod from Arista OK, so what's a monopod when it 's at home. It's the tripod you have when you don't want a tripod. It is a one-legged "tripod" which gives improved stability for your new video system or camera. The VCS2 monopod has a 3-section telescoping single leg which extends to 165cm but can be clamped at any length. It is much easier to set up than a tripod and more easily car98 SILICON CHIP as well as a master volume control. All the inputs and outputs are via 6.35mm jack sockets on the rear panel. Frequency response is quoted at 20Hz~ 20kHz while harmonic distortion is less than 0.3%. The mixer is priced at $149.50 from any Jaycar Electronics store. ried from place to place, while fully extended. A useful feature is the removable camera plate which allows easy removal of the camera from the stand without having to worry about locking screws. The whole thing comes in an attractive shoulder carry case and retails for $99.95. But when you do want a tripod for greater stability, then the VCS4 tripod could be the answer. It has a lockable horizontal movement control which is smooth in operation as well as a removable panning arm. It sells for $199.95. If you're looking around for a low-cost RGB monitor to either experiment with or to hook up to your computer system, then this open frame monitor from Force Electronics may be the answer. It comes with connecting leads and data (ie, specifications and circuit diagram). Resolution is quoted as 720 dots x 200 lines. The power supply required is 12V at 1.6 amps . Priced at $169, it is available from Force Electronics, 203 Wright Street, Adelaide, SA 5000. Phone (08) 212 5505. Autoranging DMM with RMS indication This new digital auto-ranging multimeter from Metex measures true RMS voltages and currents as well as frequencies up to 400kHz. Designated the Metex M-818, the unit has a large 4-digit liquid crystal display as well as a 41-point bargraph for analog indication. It is housed in a bright yellow plastic impact-resistant case and comes complete with an attractive vinyl carry case. There are five voltage ranges from 400mV to 1000V for DC ( ± 1.0% accuracy on 400V & 1000\T. ranges), and 4V to 750V in four ranges for AC volts, with an accur.acy of ± 1.5 % . The input impedance is 9MO for DC and approximately 5M!l for AC. Current ranges fo r AC and DC are 4mA to lOA in five ranges with accuracy of ± 1.2% for DC and ± 1.8% for AC. When measuring resistance, the accuracy is ± 0.8% for the three Dual power supply: ctd from page 83 hence reliability. A larger heatsink may also be necessary. Performance This unit can be thought of as two power supplies in one. As a dual voltage variable supply it is capable of delivering up to 150mA at ± 18V and in excess of 250mA at ± 15V or less at very low ripple, and with excellent line and load regulation. The Serviceman's Log: ctd from page 45 ranges from 4k0 to 400k0, ± 1.2% for the 4MO range and ± 3.0% for the 20MO range. The accuracy for frequency measurements is ± 2 % on the three ranges from 4kHz to 400kHz. The unit also has a continuity and diode test range with audible alarm and a data-hold feature which stores the last measurement. Priced at $169.50, the Metex M-818 is available from all Jaycar Electronics stores. 48V switchmode supplies from Amtex ed in restoring the colour, and was beginning to regret ever having started the job. Then I thought, "Damn it! I'm never likely to need the chroma board out of this junked set. Why not swap it for the one in this set?" And it was no sooner said than done. That fixed it and the old Thorn went home with a new lease of life. Its picture tube is likely to last another 15 years but whether the circuit boards will last that long is another matter. Then again, there are likely to be more of these old Thorn sets coming in with dud tubes, so perhaps I can keep this one going beyond my retiring age! How it works This new range of switchmode supplies provide an output of 48 volts DC with output currents ranging from 1A to 10A. Each unit has short circuit and output overload protection as well as switchable 110/230 VAC inputs. Also included is soft start power up circuitry and input surge protection. For further information, contact Amtex Electronics Pty Ltd, 13 Avon Road, North Ryde, NSW 2113. Phone (02) 805 0844. With time to think, I evolved the following theory about the workings of the degaussing circuit. At the moment of switch-on, the PTC thermistor, X199, is cold and its resistance is low. This allows almost the full voltage to be applied to the degaussing coils and Z199 which, at the high voltage, offers minimum resistance. In its fixed voltage guise, it can provide in excess of 550mA at 5V with short circuit protection provided by R7 and internal foldback current limiting. As a combination unit, with both supplies in use, the 5V specifications still stand but, as you might suspect, the 18V output may not be usable depending on how much current is drawn from the fixed supply. The lower voltage supplies are unlikely to be affected if current demands a re reasonable. ~ As Xl 99 heats up and its resistance rises, the voltage applied to Z199 and the coils will fall and the reduced voltage across Zl 99 causes its resistance to rise. But this would allow X199 to cool and increase the current through the coils. So the function of R199 is to maintain sufficient current through Xl 99 to keep it warm and its resistance relatively high. At the same time, most of the current it does pass will flow through R199, rather than the coils. Subsequently, a colleague came up with two text books which confirmed this theory: "Colour Television;' by R. N. Patchett, and "PAL Colour Television for Servicemen" by W. C. Cook. That leaves one point still unexplained; the 80V I measured across the degaussing circuit, connected to an open circuit transformer winding. How come? It was another of those (expletive) digital multimeter misreadings. Apparently there was enough capacitance, or leakage, across the break in the transformer winding to develop 80V at the picoamps needed to drive the DMM. Later, using a 100,0000/V analog meter, I could not detect any voltage. ~ Is Your Product Getting The Exposure It Deserves? Consumers need to see your product if you want them to buy it Contact Paul To Reserve This Space - (02) 979 5644 ]UL Y 1990 99 ASK SIUCON CHIP Got a technical problem? Can't understand a piece of jargon or some electronic principle? Drop us a line and we'll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. VCR & VGA: are they compatible? I have two questions to ask you. The first concerns a secondhand oscilloscope I have purchased. It works very nicely, except that the vertical calibration is about 10% out (ie, with the variable control in the CAL position, a DC voltage measured with the oscilloscope is about 10% lower than that measured with a digital meter). My problem is that the original owner lost the manual. There are plenty of trimpots (one of which I am sure will be the vertical calibration) but I do not wish to fiddle without knowing what they do. The oscilloscope is a Leader LBO-512A. I would appreciate it if you help me obtain a copy of the manual. Second, I have a suggestion for a project. I have an old VCR in which the heads have gone but the audio and video circuitry still works nicely. Additionally, I will soon have a new computer with a VGA monitor. It has occurred to me that, if I can display the video signal on the monitor, I will have a very nice TV for practically zero cost. This would involve taking the composite How to dope loudspeaker cones First of all I love your great magazine and I can't wait to read it when I see it in the stores. How about two editions a month? When I was reading the Ask Silicon Chip pages of the February 1990 edition, I came across an item entitled "Amplifier Couplers: Do You Need Them?" It included a question about doping for speakers. I work in the hire industry and this involves repairing loudspeakers of all shapes and sizes. To dope a speaker cone we have found PV A woodworking 100 SILICON CHIP video or the original RGB signal (with a little prodding around the VCR circuit boards) and converting it to a VGA format. All I know of VGA is that it uses analog RGB signals and a high horizontal scanning frequency. The main problems I can think of are having the wrong voltage levels and incompatibility in scanning frequency but I am sure there are many more. If you have any suggestions about the practicality of this, I would be interested to hear them. (W.K., Macquarie, ACT). • To obtain a manual for your oscilloscope, we suggest you contact the current distributors for Leader products, AW A Distribution, 112-118 Talavera Road, North Ryde, NSW 2113. Phone (02} 888 9000. As far as your proposed VCR to VGA monitor hookup is concerned, we don't think it's a goer. Unless your VCR already has RGB outputs (the large majority don't), you have Buckley's hope of finding RGB signals inside it. Normally, VCRs only break the incoming TV signal down into composite video and audio - there is no need to process down to RGB signals. glue (such as Selleys Aquadhere) to be the best. All you have to do is apply one coat with a paint brush, allow it to dry and then apply a second coat. Both coats need to be quite liberal for best results and care must be taken not to get the glue on the suspension ribbing as this needs to be quite flexible. The end result is a cone with more strength and stiffness and less likely to tear. (D.H., Manunda, Qld). • Thanks for your comments on doping although we were under the impression that doping compounds for speaker cones should never dry out. Aquadhere dries fairly hard, doesn't it? Aside from that, we don't think there is any easy way of solving the incompatibility of the horizontal scanning rates. However, maybe one of our readers can throw more light on this subject. Substituting pots in the Studio 200 pre amplifier I would like to suggest a resistance meter as a project, similar to the capacitance meter published in the May 1990 issue. This would come in handy when constructing a project. Instead of using your multimeter and selecting the range, you just connect the resistor to the device and it automatically gives the value. A LED indicator could be used to tell you whether it is in the kilohm or megohm range. Such a device would immensely aid older (and colour blind) enthusiasts who perhaps now find it difficult to read the colour code on constantly shrinking resistors. I also have some miniature lOkO pots (both log and linear) which I would like to use in an integrated amplifier I am working on. I would like to use the Studio 200 preamplifier circuitry in this amplifier. Is it possible to change the pot values to lOkO and, if so, what other circuit changes are needed? (T.I., Matraville, NSW). • As far as your suggestion for a resistance meter is concerned, we don't think it is really a viable project since digital multimeters are so readily available at low prices. The more expensive multimeters are also autoranging for resistance measurement. We are not really very keen on the idea of substituting lOkO pots for those in the tone controls and, presumably, the volume and balance controls of the Studio 200 preamplifier. However, you can substitute a lOkO dual (log) pot for the volume control and a dual (linear) pot for the balance control, although the latter change will mean a 6dB loss in gain. For the tone controls, you can substitute dual ganged 10k0 (linear) pots by scaling the associated component values. For example, when substituting for the 100k0 bass control the associated 22k0 resistors should be reduced to 2.2k0 and the .OlµF capacitor should be increased to O.lµF. Similarly, for the treble control, the 3.9k0 resistors should be reduced to lkO and the .0047 µF capacitors increased to .047 µF. We must emphasise that we have not tried the circuit with these values so we cannot be sure whether it would be completely stable and free of distortion. Run on problem with high energy ignition Let me congratulate you on the excellent article on the High Energy Ignition presented in the May 1988 issue of SILICON CHIP. I have built the unit and it has performed faultlessly in my car [Mazda 626, late 1982 model). Fuel consumption is down by 10% and cold starting, idling and acceleration can only be described as "sweet". There is one problem, however. When I switch the ignition off after a long enough run for the engine to reach its normal operating temperature, I experience a 2-4 rev runon. On the assumption that this may be due to the long on-current through the ignition coil at low revs (caused by the constant lms off period regardless of revs), I obtained a copy of the Motorola datasheet for the MC3334P. It appears that the device has been designed to allow a reduction of the on-time at low revs, although your circuit does not make use of this feature. As you mention in the article, ignition coils can readily accommodate the increase in temperature at low revs. The overrun is a different matter and I would like to get rid of it. Clearly, you chose not to use the feedback controlled variable dwell reference voltage capability of the MC3334P for the sake of simplicity. However, I cannot see why it should not be possible to additively mix the RPM dependent output of the "dwell • Thermal runaway In Studio 200 pre amplifier Recently my brother (who lives in Brisbane} built the Studio 200 control unit as described in the June and July 1988 issues of SILICON CHIP. At initial switchon, after about one minute, the headphone amplifier transistors get excessively hot. He has implemented the modification described in the September 1989 issue of SILICON CHIP but the trouble still exists. I am quite experienced at kit construction so I constructed the headphone circuit, minus the LM833 (IC4) and I experienced the same problem. After one minute, the current through the two transistors was 40 milliamps and rising rapidly. Can you provide a solution? (R.C., Avoca Beach, NSW). • A small number of people have experienced this problem reference buffer" with the differentiated square wave pulses utilised by your circuit to drive the chip. All my endeavours were thwarted however, by a different problem. As soon as I applied sufficient feedback to achieve a significant reduction in on-time, the chip broke into high frequency oscillation at around 10MHz. All conventional remedies having failed (improved bypassing, elimination of earth loops, phase lead or lag in the feedback path, etc), it occurred to me that you may have some experience with this part of the chip function, before you decided not to utilise it in your final circuit. I would greatly appreciate any info in this regard. (P.G., Linden Park, SA). • The reason we did not use a variable dwell angle was simply that we could not get it to work with the non-reluctor circuit. We also could not get it to work reliably with the reluctor version published in the May issue. We tried a number of circuit arrangements but when they proved unreliable, we abandoned them in favour of the and so did we when we used a similar circuit with different transistors (BC338/BC328 instead of BD139/140) in the 16-channel mixer described recently. We had a couple of the headphone drivers (out of the 18 employed) blow out transistors. In view of this, we took a " boots and all" approach and incorporated emitter resistors as well as the two diodes, to stabilise the collector current. You could take the same approach and duplicate the headphone circuit in the mixer. The relevant circuitry is shown on page 61 of the March 1990 issue. The best way to incorporate the 330 emitter resistors would be to desolder the emitter lead of Ql and Q2 and bend it out at rightangles from the other two leads. Next, solder one end of each 330 emitter resistor to the vacant PCB hole.s-Finally, attach the free end of each emitter resistor to the associated emitter lead of the transistor. simple approach - it works and has proved very reliable. Having said that, we do not think the long coil current on-time has anything to do with the "run-on" in your car. Once the ignition key is turned off, the ignition coil can only deliver one more spark, at most. After that, the coil is not fed with any current and therefore cannot deliver any sparks. Maybe the hotter spark from the high energy ignition is causing the spark plugs to run slightly hotter and thereby cause the run-on problem. However, that seems like an outside possibility. We are more inclined to think that you have coke deposits on the pistons or on the spark plugs themselves and it is these deposits which are causing the run-on. If that proves to be not the case, you might try a set of "cooler" spark plugs. (Editor's note: after we had prepared this answer, this reader wrote again and informed us that the "run-on" problem was caused by a sticking solenoid valve in the carburettor. However, we have inJULY 1990 101 Another way to stop blowing lamps I have just read the April 1990 edition of SILICON CHIP and noticed an article on "How to stop blowing expensive lamps". This is by no means a recent problem. About 28 years ago I modified a slide projector which used a 300W 240V lamp which seemed to have a very limited life. The first solution was to use a Brimistor which is a device that has a high resistance when cold and a low resistance when hot. It certainly did the trick but suffered from the Brimistor failing. This was obviously because it was not quite suited to the load. It is very difficult to purchase one to exactly suit the requirement. The solution finally settled on was to use a resistor to limit the inrush current and a relay to switch the resistor out after a eluded the whole answer here because it is still applicable to cars without a solenoid fuel cut-off). Why have the input coupling capacitor? I noticed you made a point of mentioning the size of the input capacitor on the universal preamplifier published in the June issue. I agree that if a large capacitor is used, the preamplifier will "see" a low source impedance at low frequencies and therefore low frequency noise will be minimised. But why not eliminate the capacitor altogether and direct couple the magnetic cartridge to the preamplifier? After all, the bias current flowing into the inputs of the LM833 must be very low and therefore any effect of that current flowing through the cartridge would be negligible wouldn't it? And wouldn't it be better to eliminate the 47µF capacitor because it is an electrolytic and therefore a source of distortion? I would be very interested to know the answer to this question. (N.H., Blayney, NSW). 102 SILICON CHIP short time delay. The relay is powered from the 240V AC mains via a diode, filter capacitor and resistor to limit the voltage across the relay coil. The resistor in series with the lamp filament is chosen to be about the same as lamp's hot resistance and it needs to be rated at about 50 watts, as its peak power can burn it out if a lower power unit it used. (T.T., Para Hills West, SA). • While we agree that your system will work, we think it is rather crude. Having to use a 50 . watt resistor is a definite drawback as is having to use a resistor to limit the voltage across the relay coil. The latter resistor •will also have quite a high power dissipation. If sufficient readers are interested, we will produce a Triac based circuit which will do the job automatically, with very little power dissipation. OK? • That's a very interesting topic you raise. In theory, the argument against letting any current flow through a magnetic cartridge is that the current would magnetically "bias" the cartridge and therefore make it non-linear, at least for large stylus deflections. But let us look at the subject in more detail. A look at the specs of the LM833 shows that the maximum input bias current is 1000 nanoamps which is the same as 1 microamp. So if we direct coupled a cartridge to the input (ie, instead of having an input coupling capacitor), the maximum DC current that could be expected to flow through the cartridge would be lµA. That does not seem like a large current but when you compare it with likely signal currents, the picture changes. Consider a cartridge generating a signal of 10mV peak into the nominal load impedance of 50k0 a fairly standard set of conditions. This would cause a peak signal current of 200 nanoamps or 0.2µA - 5 times less than the fixed DC current. Clearly, this means that there could be a problem because the DC current is higher than the peak signal currents that are normally likely to occur. We thought we would investigate this matter further. If indeed the DC current does "bias" the cartridge then it should cause a mechanical deflection of the stylus. And if it does cause deflection then that means that there will be less deflection capability available for the cartridge to follow the record groove. So how do you put it to the test? Simple, we thought. Just feed a DC current through the cartridge and see if the stylus is deflected. We started with a current of lµA (3.5V fed through 3.3MO) which is the worst case mentioned above. We set a cartridge up on the bench, clamped it in an upside down position for easy inspection and then observed it with a magnifying glass. We then switched the current on and off. The result was absolutely invisible. Which is probably pretty much what you could expect. After all, magnetic cartridges have a response which declines at a rate of 6dB/octave which means that the response at DC is negligible. And even if the expected deflection of the stylus was in line with normal groove deflections, you would need a microscope to see it and even then, you would probably need to watch very carefully to detect it. Fair enough, we thought. Let's make the current quite sizable, much larger than would ever occur when tracking a disc but not enough to cause any damage. So we fed a current of lmA through one coil of the cartridge - this is 1000 times the current suggested above. This time, careful inpection showed a small but definite deflection of the cartridge each time the current was switched on. That proved the principle, at least. So if you don't want to prejudice the signal handling of your cartridge in any way, you should include the input coupling capacitor. Finally, we have seen one phono preamplifier using an OP27 op amp which eliminated the input coupling capacitor. This was possible because this op amp has a much lower input bias current of around 150 nanoamps (max). T CEN·1· Cash in your surplus gear. Advertise it here in Silicon Chip. 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 own classified ad, put or.e word on each of the lines below and send this form with your payment to: Silicon Chip Classifieds, PO Box 139, Collaroy Beach, NSW 2097. MEMORY IC's & SIMM's From Japans Largest Manufacturer of Computers the Quality you expect.. SIMM MODULES 1 Mb X 9 80ns $115.00 DRAM 1 Mb X 1 80ns $10.50 80ns $10.50 PLEASE PRINT EACH WORD SEPARATELY, IN BLOCK LETTERS DRAM 256K X 4 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ($7.00) • Add 20.~: Sales Tax/ SS.00 P & P PACIFIC MICROELECTRONICS PTY. LTD. 'CENTRAL PARK' UNIT A20, 4 CENTRAL AVENUE, THORNLEIGH N.S.W. 2120 PHONE : 02 481 0065 FAX : 02 484 4460 o) Name FUJITSU Street Postcode Suburb/Town .. or please debit my Enclosed is my c neque or money order for $ D Bankcard Card No D Visa Card D MEMORY CHIPS MasterCard Prices at May 1 st, 1990 I~~-~~~~-~-~~~~~~~-~~~~ Signature .. Card expiry date ...... ./ ..... .. . Speed Chip type SIMMS (MACS) (IBM) SIPPS DIP 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 & VGA modes, FIX-A-KIT $20 PER HOUR LABOUR NO CHARGE FOR KITS THAT CAN ' T BE REPAIRED 3 MONTHS WARRANTY ON REPAIRS CONSTRUCTION AVAILABLE HYCAL INSTRUMENTS DESIGN, MANUFACTURE, REPAIR OF ELECTRONIC EQUIPMENT (02) 633 5897 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, Old 4005. Phone (07) 358 2785 . ZIP 9 X 256 9 x 1Mb 8 x 1Mb 9x1MbPS2 9 X 256 9 x 1Mb 411000 414256 41256 41464(256) 4164 414256 (1 Mb) 41256 411000 (1Mb) 4400 (4Mbl Sales Tax 20¾ 12Dns 100ns 80ns Prices (excluding tax) 30.00 34.00 36.00 116.00 120.00 108.00 112.00 165.00 38.00 40.00 112.00 116.00 10.80 11 .40 11 .80 10.80 11 .80 12.20 2.85 3.40 3.95 3.40 3.95 2.70 3.00 13.50 15.00 4.40 12.80 13.20 98.00 Overnight delivery Credit cards welcome DISCOUNTS FOR DEALERS Phone for pricing on ?Ons, 60ns, Toshiba. Compaq & Laser Printer PELHAM Tel (02) 427 0011 - Fax (02) 418 6831 DIGIT Al WAVEFORM GENERATION: as described in SILICON CHIP in March, May, June & July 1990. PC board and software to generate waveforms . Both for only $39.95 including p&p. Instructions included. PC Board $16.00, Software $32.50 including postage. Send cheque or money order to M. Radvanyi, PO Box 49, Kingswood, NSW, 2750. AUDIO TV VIDEO repair business for sale . $40,000 . Phone (02) 664 1804. VCR MAINTENANCE supplies. This month's special - video belt kits only $9.50; professional chamois head cleaning tools & cleaning fluid $ 7. 50; quality head cleaning cassettes $13.00. Send SSAE for full catalog. We accept Bankcard & Mastercard. To order, please supply VCR brand & model number, item quantities, name & address, plus credit card details. Please include $3.00 for post & packing. Makrun Computer Technology, PO Box 458 , Merrylands 2160. WHOOPS! MY 280-BASED PBUFF printer buffer just doubled its memory capacity again. Over 3000 kits now sold. Combinations of DIP/SIPP/SIMM DRAMs in 9 memory sizes up to 2Mb. Rev J board, Ver 4 .2 EPROM and in]UL Y 1990 103 r~--------------------, SILICON CHIP BINDERS Yes 1 Please send me _ ___ SILICON CHIP binder(s) at $A 11.95 plus $A3 p&p each {NZ p&p $A6). Name _ _ __ _ _ _ __ _ __ _ _ __ _ _ _ _ _ _ _ __ (PLEASE PRINT) Street_ _ __ __ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Suburb/town _ _ _ __ _ _ _ __ _ __ Postcode _ _ _ _ __ Enclosed is my cheque /money order for $ _ _ _ _ or please debit my ~ I Bankcard I J Visa Card [ J MasterCard Signature _ _ ___________ Card expiry date_~-- L-----------------------J structions $39. Cable board $9. P&P $3. Serial board and many other options available. Send a 41 c stamp for a free catalog to: Don McKenzie, 29 Ellesmere Crescent, Tullamarine 3043 . brand & model number & $12 .00 for · each kit required . Prompt dispatch assured. James Cotterill, PO Box 44, Farrer, ACT 2607. 60W Valve-1 $99, 200W Valve-2 $199, Audio Toolkit Tool-1 $69, FET-1 super quality stereo preamp $20, Bass & Treble $23. ROBOTICS: experimenter's kit. Includes IBM-PC controller, PSU, stepper motor, manual, software $99. Digital voice recorder TMS-334 7 chips $25. PC Computers, 36 Regent St, Kensington, SA. Phone (08) 332 6513. PROJECT PCBs: ETI-DIGI 125 audio amp $9/pair, ETl-1623 IBM PIA card $39.95, 6502/Z80/6809 miniprocessor $49 . PRE-BUILT AUDIO AMPS: 3 .5W LM380 $20, LM1875 $30, 150W IC-150 $99, 300W IC-300 $179, SMARTWORK POST-PROCESSOR: if you own a HP7475 or compatible flat bed plotter you can plot your own PCBs direct on blank board ready to etch. PP plots 1: 1 and mirror image. Only $99 . PC Computers (08) 332 6513 . BOOKS LOGIC ANALYSER. Gould Instruments BELT KITS FOR VCRs. Please supply Electronic Kit Constructor's Manual Everything you need to know to make your electronic kit constructing successful and satisfying ... • Preparing your workplace• Tools required • Component recognition, descriptions and codes • Reading circu it diagrams• How to solder and fix solde ring problems• Assembly hints• Troubleshooting tec hniques• Technical terms and definitions. 36 pages The best there is, ONLY $4.9S Digital Voice Recorder Board Silicon Chip December 1991 Complete. fully detailed. step-by-step assembly instruct ions with nearly 100 diagrams and installation illustrations. World standard instructions similar to Schlumberger/Heathkit books. 40 pages Top Quality $9.9S MOTORISTS - Trouble-shooting Guide Let Mick Annick and his mate Alec Auto help you get back on the road when your motorists' service is not available. Bright, easy-to-read and understand with all original drawings. Convenient size to fit your glovebox. 30 pages ONLY $3.9Sea S up $3.00ea Plus $2.50 P&P for all orders. Send your cheque or money order to: Nolan Project Services Pty Ltd K40 stand alone analyser. Eight nonvolatile memories, 7-inch CRT, 4 x 2K sample memories, 2 x 16-channel, probes up to 1 00MHz, asynchronous capture. Weighs 7.7kg. $975.00. Import Technologies (07) 372 5138. PB0 PORT ABLE battery rechargeable 80-column printer. Serial interface. Very compact & light. 1.1 kg. Uses normal or thermal paper. $1 7 5. Import Technologies (07) 372 5138. EPSON TOSHIBA LCD SCREEN. Originally to suit T1500 desktop. 240 x 180mm, 640 x 200 pixels. Uses 5V supply & TTL drive signals. Suit experimenter. $150 . Import Technologies (07) 372 5138. PO Box 681 North Sydney NSW 2059 All books are publlshed by Nolan Project Services Pty Ltd, 148 Wycombe Road Neutral Bay NSW 2089 Deafer enquiries welcome - wholesale prices. Phone (02) 953 0810 104 SILICON CHIP TOSHIBA T3100 CO-PROCESSOR kit. This piggy-pack board enables the fitting of a 80287-8 to the early T3100. Advertising Index Altronics ........................ 46-49 Arista .... ...... .... .. ................. 69 Aust-Tek Electronics .......... .. 82 Automatic Alarms ........ ...... ... 31 Board Solutions .... ...... ... . 62,63 David Reid Electronics ..... .. .. . 59 Dick Smith Electronics .... . 1 0-1 5 Electronic Solutions ........ 76 , 77 Elmeasco .... .. ................ 31,82 Geoff Wood Electronics ... ..... 44 Harbuch Electronics .... ......... 43 Hycal Instruments .............. 1 03 Jaycar Electronics .......... 24-27 84-87 Jiloa ..... ..... ... .. .... ..... .... .... ..... 5 J.V. Tuners ......................... 43 Pacific Microelectronics ...... 1 03 PC Marketplace .... ............ .. IFC Pelham ...... ........... ............ 103 RCS Radio ...... .. ......... ......... 96 Resurrection Radio ...... ... ....... 5 Rod Irving Electronics ..... 38,39 70,71,92,93 Silicon Chip Binders .... 75,0BC Subscriptions .. .. .. ............ .. IBC Westinghouse ...................... 9 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. Two types available, solder in & plug in. Solder version $190.00. Plug-in version $335.00. Import Technologies (07) 372 5138. WANTED EARLY ISSUES OF SILICON CHIP wanted. Must be in good condition. November 1987, December 1987 & January 1988 only. Up to $10.00 per issue if in mint condition. Phone Terry (08) 382 8919. Don't miss a single issue IF YOU'RE THE KIND OF READER that can't wait to get the next copy of SILICON CHIP, then why not have the magazine delivered direct to your door? Each month, we'll bring you the best and brightest electronics magazine in the business, put together by Australia's most experienced team. Here's what to look for in each issue: * Constructional Projects For The Enthusiast * Amateur Radio: Theory & Projects * The Serviceman's Log * Computer Bits: Getting The Most From Your PC * Vintage Radio: A Fascinating Hobby 24 Hour Fax Service (02) 979 6503 Send the coupon with your Credit Card details. 24 Hours, 7 Days a week. r----------------------Freepost * Subscription Coupon □ □ New subscription Renewal Start in, _ _ _ _ _ __ Name _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ (PLEASE PRINT) Subscription Hotline Telephone (02) 979 5644 9am-5pm Mon-Fri and quote your Bankcard , Visa Card or MasterCard No. and expiry date. 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