November 1990 - Silicon Chip Online

Outer Front Cover
Contents
Publisher's Letter: Things go better with natural gas
Feature: How To Connect Two TVs To One VCR by Jim Lawler
Feature: Introduction To Digital Electronics by Joseph Carr
Project: Battery Powered Laser Pointer by Leo Simpson
Feature: Win A Bose Lifestyle Music System
Vintage Radio: Testing old radio valves by John Hill
Project: Low-Cost Model Train Controller by Greg Swain
Serviceman's Log: The customer takes a holiday by The TV Serviceman
Project: A Really Snazzy Egg Timer by Darren Yates
Feature: Amateur Radio by Garry Cratt, VK2YBX
Project: Build A 1.5V To 9V DC Converter by Darren Yates
Project: Modifications To The 16-Channel Mixer by Silicon Chip
Feature: Computer Bits by Jennifer Bonnitcha
Back Issues
Feature: The Story Of Electrical Energy; Pt.5 by Bryan Maher
Feature: Remote Control by Bob Young
Feature: Turn Your CRO Into A Spectrum Analyser by Alex Eades
Subscriptions
Order Form
Market Centre
Advertising Index
Outer Back Cover

This is only a preview of the November 1990 issue of Silicon Chip.

You can view 61 of the 120 pages in the full issue, including the advertisments.

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Can not use o Id RAM 0e 41256) MOUSE MAT USUALLY $119.00 NOW ONLV $99.00 YOU SAVE $20.00 ONLY $225.00 BUY WITH 1MB OF RAM FOR $395.00 AND GET A FREE MOUSE COVER AS WELLI POWER UP WITH OUR 1SOW POWER SUPPLY Normally $125 NOW $89 YOU SAVE $36.00 SPEED UP YOUR OLD XT WITH A NEW MOTHERBOARD MINI TOWER CASE 12MHz XT MOTHERBOARD wrTH 200W POWER SUPPLY VGA CARDS ONLY $249.00 SAVE $80.00 16 BIT NOW $249.00 8 BIT NOW $178.00 NORMALLY $75.00 - e CPU-Ultra high speed V20 e Clock speed 12MHz, 0 was state memory access • 4. 77112MHz Hardware,' Software selectable • Uses advance VOL-C1 system control eh., to reduce the eh., count and increase the speed and reliability • Wait state for memory and l,O (On-board/ExtemaQ are programmable by Hardware,' Software • 8087 co-processor socket and 8 1,0 expansion slots • 512KBl640K811024KB on board (384KB virtual disk) • tt purchased woh IBM RAM we include; utility disk, which contains softwara drivers to make use of the 384KB (1024KB models only) for RAM Disk, hard disk cache and printer buffers etc. THIS MONTH ONL V $50.00 Motherboard only $125 1/0 WITH 2 SERIAL AND 2 PARALLEL PORTS FITTED 286 NEAT MOTHERBOARD e 16MHz e Expandable to I MB RA<\1 using 256k DRAM chips or 4MB using 1MB DRAM chips• 8/12 or 8/16MHz hardware or keyboard selectable• Six 16--bit and two S-bit expansion bus slots e AMI 8105 ROMs included e Supports all NEAT functions including shadow RAM.. 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NOW ONLY $14.95 At these prices it will BLOW you away MAIL ORDERS: P.O. BOX Q103, SYDNEY 2000 PHONE ORDERS: (02) 2671385 FAX: (02) 2618905 NORMALLY $4.95 1 1 i l i #2 250 volt AC 0.47uF NOW $1.95ea 10+ $1.75ea 100+ $1.50ea WAS$3.95 NOW$1.80ea 10+ $1.60 100+ $1.40ea POST & PACKING $5. $25.......... $3.00 $26. $50 ....... $5.00 $51 • $100 ......... $6.00 $500 + $101 _.$499 ...... $8.00 FREE 1 1 November 1990 FEATURES 6 How To Connect Two TVs To One VCR by Jim Lawler Avoiding ghosts & other hassles 16 Introduction To Digital Electronics by Joseph Carr Learn about logic gates & flipflops 98 The Story Of Electrical Energy, Pt.5 by Bryan Maher Gas turbine power stations in the Northern Territory 110 Turn Your CRO Into A Spectrum Analyser by Alex Eades A $399 accessory probe does the job THROW AWAY that primitive rheostat model train controller. This simple unit offers much improved running characteristics & has simulated inertia as well. Details page 42. PROJECTS TO BUILD 24 Battery Powered Laser Pointer by Leo Simpson Explore the fascinating technology of laser light 42 Low-Cost Model Train Controller by Greg Swain Build it for improved starting & low-speed running 56 A Really Snazzy Egg Timer by Darren Yates It ticks away the seconds & sounds a chime 72 Build A 1.5V To 9V DC Converter by Darren Yates Uses just three components & fits on a small PC board 75 Modifications To The 16-Channel Mixer Revised circuit has even better performance SPECIAL COLUMNS 38 Vintage Radio by John Hill Testing old radio valves 48 Serviceman's Log by the TV Serviceman The customer takes a holiday 66 Amateur Radio by Garry Cratt The 6-metre summertime special 80 Computer Bits by Jennifer Bonnitcha Computer cables & all that rot 104 Remote Control by Bob Young Nicad cells for high rate discharge EXPLORE THE fascinating world of laser light with this battery powered laser. Our article on page 24 shows how to build it. ~ ~ fl'o-4,, ~ ) r-. "~ ' . --. ' . - i~ . ,.·-/-- X ~,-,l'r,,"-"V/~ 0 ~ .. THE SERVICEMAN took so Jong to fix this month's fault that the customer went on holiday. There weren't really any Eskimos but the Serviceman did try a spot of freezer. See page 48. DEPARTMENTS 3 Publisher's Letter 4 Mailbag 32 Circuit Notebook 90 Product Showcase 96 Back Issues 2 SILICON CHIP 113 115 116 119 120 Subscription Page Bookshelf Ask Silicon Chip Market Centre Advertising Index WANT TO HOOK two (or more) TV sets up to one VCR? Our article on page 6 shows you how it's done. Publisher & Editor -In-Chief Leo Simpson, B.Bus. PUBLISHER'S LETTER Ec"ltor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Darren Yates 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 Things go better with natural gas As most people are aware, most of Australia's electrical power is generated by coal burning power stations. There is one overwhelming reason for that; we have enormous reserves of coal. But burning coal does have its drawbacks, some of which are obvious and some of which are not. Without thinking too hard about it, we can consider the drawbacks of mining coal: it takes a lot of energy to extract and transport it and coal mines have a very large negative effect on their immediate environment, particularly if they are open cut mines. Then when coal is burned, it produces huge amounts of ash which must be disposed of and there are also the nasty pollutants which go up the stack; for example, radioactive trace elements. For now, and for a long time into the future, we'll probably have to live with these drawbacks of coal fired power stations, because they present less problems than, say, oil fired or atomic power stations. Fairly recently though, a new development in power generation has been introduced in remote parts of Australia, chiefly in the Northern Territory. Because these regions don't have reserves of coal close by, they have in the past relied on expensive diesel powered stations. Now though, gas turbine powered stations are being installed, fuelled by natural gas. Wh&t an excellent idea! Natural gas is a much cleaner burning energy source than coal, does not require large amounts of energy to extract and again, we have enormous reserves of it. The full story is told in this month's episode of "The Story Of Electrical Energy" by Bryan Maher (see page 98). There's an interesting twist to the story too, because it is possible to greatly increase the efficiency of power conversion, as has been demonstrated in Darwin's power station. It's a concept that we 'll possibly see a great deal more of in the future. Consider for example, the concept of garbage and sewage being processed to produce methane which could then drive gas turbine powered alternators. It's an interesting thought, isn't it? Leo Simpson Eirenaan Akhursi Jennifer Bonnitcha, B.A. Garry Cratt, VK2YBX John Hill Jim Lawler, MTETIA Bryan Maher, M.E ., B.Sc . Jim Yalden , VK2YGY Bob Young Photography Glen Cameron Edltorlal 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 NOVEMBER 1990 3 MAILBAG Audio coupling capacitor should be replaced This note refers to the excellent series on vintage radio by John Hill. For the benefit of those restorers who have had little experience in valve radio service, I would like to comment on a statement made by John on Page 67 of the September issue: "if the rectifier valve is weak there is a good possibility that the output valve will be in a similar condition and may also require replacement". What needs to be stressed here is that the probable cause of the failure of these particular valves is a leaky audio coupling capacitor. There is little point in replacing these valves unless the cause of the problem has been fixed. It is unfortunate that paper capacitors manufactured in this part of the world, prior to the introduction of polyester caps, almost without exception became "leaky" electrically speaking. The capacitor became the equivalent of a capacitor with a resistor across it. Paper capacitors were commonly used for audio coupling and a leaking one applied a positive potential to the grid of the output valve, causing excessive current flow. This resulted in severe stress on three items: the output valve, the rectifier valve and the power transformer, and failures of one or more of these items were common. Sonie reslorers seem Lo Le reluctant to replace faulty capacitors for ,reasons which entirely escape me. When I was employed in radio service after WWII, a typical service of a 10-year old set consisted of replacing all the paper capacitors and in most cases this was all that was necessary to bring the set back to "as new" performance. E. G. Baker, Bathurst, NSW. NE602 article strikes the right note The NE602 article in the October issue of SILICON CHIP (Amateur Radio, p82) struck a responsive chord in me. Just what I needed to sort out the oscillator in my Collins 618T 4 SILICON CHIP (tunes in lkHz steps) and to tune/ modulate my Collins 618S in SSB mode! Sadly, at the time of writing, Stewart Electronics have no stock of the device, nor do they have the relevant Signetics data sheets. Perhaps you can help with (a) data sheets and (b) a source of supply; ie. "wherejagetit?" A recent convert to SILICON CHIP, I bought my first copy because of the Collins 51J4 article. How about more of the same? J. Mackesy, VK3XA0, Mt Evelyn, Vic. Comment: Stewart Electronics has in formed us that the shortage of NE602s was only temporary, no doubt caused by Garry Cratt's article. Their present price is $4.32 plus 20% sales tax plus postage and packing. If you are buying the chip, they can also supply data for the NE602, at a nominal charge. Video cameras don't have external sync In the October "Ask SILICON CHIP" page, as part of your answer to A. C. of Groote Eylandt, NT, you state that " ... most video cameras have facilities for external sync ... " Oh, how I wish that were so! In fact, almost no domestic or industrial grade video cameras ever had provison for external sync. The only one I have ever found was the Sony AVC-3250CE monochrome camera. I hunted high and low for a colour camera with provision for external sync but the only ones available were professional and studio cameras, with 50 to 100 thousand dollar price tags. (If I am wrong about this, I would be delighted to hear from you!) There are ways to slave old monochrome cameras to modern video recorders or cameras but to my knowledge no domestic camera can be genlocked to another camera or recorder. Some micro-computers can be genlocked to domestic colour cameras but the reverse is not possible. Unfortunately, A. C. is looking to do what is only possible with very SILICON CHIP, PO Box 139, Collaroy Beach 2097. expensive professional equipment. Editing amateur video is possible but a much less sophisticated end result is all that can be expected. I am working on an article on this subject for SILICON CHIP. If the editor accepts it for publication, I hope that I can explain to A. C. and others just what they can expect from their home video productions. Jim Lawler, Hobart, Tasmania. What was wrong with the transformer? I am a regular reader of SILICON CHIP and usually enjoy reading the Serviceman's Log feature which often contains very useful information. This month, however, I was most disappointed (October 1990 issue) in the story of the repair of the National Colour TV set TC-2656 which left the fault still not clear. On page 53 the Serviceman asks: "What kind of transformer fault would produce a gradual temperature fault like this?" Yes, what fault indeed? And he does not answer that question. What was the transformer fault that was affected by cooling? With regard to the charging, it seems to me that the customer should not have been charged for the ZSC1573 (Q501) which was apparently replaced unnecessarily and in my opinion he should not have been charged for the second 2SD951 (Q551) unless he was instructed or advised not to use the set further when he rang on the second occasion. These are my thoughts on the matter and I would like to know what was wrong with transformer T501. R. W. Henning Mount Rumney, Tasmania. Comment: the Serviceman wasn't witholding information. He doesn't know what was wrong with the transformer; only that it caused problems. Send it by fax Want to have your say? Why not fax your letter to us on (02) 979 6503. You can send any orders or subscriptions by fax too, for quicker service. wpoD FOR CHIPS ... WOOD FOR CHI PS ... WOOD FOR CHIPS ... WOOD FOR CHI PS ... WOOD FOR CHI PS ... WOOD FOR CHIPS ... WOOD FOR: C Comms Port 2? ~ . 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Pane I Case Cal No Price He~hl Holl Space Haight Depth Width Natural Black 44 1RUi 34 38 254 430 H0401 H0411 1?9.95 88 2RU 57 82 254 430 H0402 H0412 79.95 13 (3R ) 89 38 254 430 H0403 H0413 . 89.95 '"1:;;:.~;;.,.',";;:;' ''"''""'"'""' .,'"''"'""''"'.' ''.•o! , ~ec°de:~°riontroi functlons Line break generation and detection ~nmio:~o:eciflcatlon version of $27.00 • • • • • $55.00 How to connect two TV sets to one VCR In September, we ran a project that could extend a video recorder's IR remote control to allow operation from another room. It was a great little project but it didn't explain just how the remote TV set was also connected to the VCR. Here's how to do it. By JIM LAWLER So how does the VCR in the lounge room feed its picture to a second TV set in the bedroom? Well, it's quite easy to arrange a simple two-TV set-up in any home of average size. The first thing to understand is that the RF signals at the output of your VCR are at a very high frequency and very low voltage. The signals are measured in microvolts which means that special care must be taken with distribution if they are not .going to be lost along the way. First and foremost, it is necessary to understand that high fre- quency transmission lines are not like ordinary power cables. They have to be properly matched to the VCR and the TV if the signal is not to be dissipated in the wiring. Second, if a cable is not properly terminated, it can set up reflections along the line which show up as ghosts on the picture. To avoid signal losses and ghosts, it is important to match the impedance of the transmission line to the output of the VCR and to the input of the TV. For convenience, this impedance has been standardised at 75 ohms and all domestic equipment is designed for this value. So, provided that you select cable and hardware suited to this application, no problems will be encountered. To avoid complex mathematics in signal level calculations, engineers and technicians have adopted the use of decibels as a convenient measure of signal level. For TV signals, most antenna installers use dBµV, or decibels above 1 microvolt. By using dBµ V values, it is only necessary to add together all the losses in the system and subtract them from the signal level available to arrive at the level that will be available at the TV. Or working the other way, one adds the calculated losses to the required signal level at the TV, to arrive at the necessary input level from the VCR or other source (eg, an antenna). If that sounds confusing, don't worry. We'll give you a few examples to show how it's done, For the rest of this article, we will talk about dBµV on the understanding that older TVs need 60dB of signal to give a good picture. Modern sets need only around These TV signal splitters are made by HPM Industries Pty Ltd and are available from large hardware stores (eg, BBC Hardware & Mitre-10). The unit at left is a 2-way splitter box (Cat. 406/2S/TV) while at right is boosted 4-way splitter (Cat. 406/B4S/TV) which has an overall gain of 8dB at each outlet. 6 SILICON CHIP L.....______.1 VCR VCR TWO-WAY SPLITTER i----- □ LOCAL TV (b) ------.0 Dc::::::::::l REMOTE TV VCR Ct:::=::J LOCAL TV (c) 1 2 3 TO REMOTE RECEIVERS Fig.1: here's how to split the output from your VCR to feed two or four TV sets. In the arrangement shown in (b), a simple 2-way splitter is used to split the output from the VCR, while at (c) the output from the VCR is amplified before being fed to a 4-way splitter. The amplifier & splitter may be separate units or combined in a single box. 55dB for the same result but it's wise to use the higher level to leave a good margin of safety. For difficult or critical applications, it is often necessary to measure the available signal with a signal strength meter. However, for domestic applications, an approximation of signal strength will usually give satisfactory results. Most video recorders have an output level of about 65dB. This represents the level of signal that would reach a TV set fed from an average antenna in an average reception area. Thus, if the VCR output is fed to a single TV at this level, the picture should be just about perfect. Even allowing for poor contacts in the plugs and sockets, enough signal should still be left over to give an excellent picture. Splitting the signal If one wants to split the signal between two TV sets, certain precautions must be taken. As already mentioned, the impedance must be matched and maintained throughout the system. This means that the leads to the TV sets cannot simply be cut and twisted together, as this would result in a gross mismatch of impedances. If this were done, you would get ghosts and a very noisy (or snowy) picture. Instead, a splitter umt must be used which allows accurate matching and a minimum of signal loss at the split. Fortunately, splitters are readily available from electronics retailers and even from most hardware stores. Splitters come in many styles, some square and boxy and others similar in appearance to the common mains power outlet. Depending on your application, you can get 2-way splitters (to feed two TV sets), 3-way splitters and 4-way splitters. In-line splitters that connect to the cable with common coax plugs are also available but these are not the best choice because the plugs and sockets can work loose after awhile. The wall mounted, screw fixing type are much more reliable. The main necessity is that the splitter be designed for 75-ohm systems. It must also be a wideband type if it is to handle UHF signals. In the normal domestic VCR installation, a lead is taken straight from the VCR's "RF Out" socket to the TV's antenna socket (Fig.la). For a two-TV system, we need to split the single output cable from the video using a 2-way splitter. One output from the splitter is then connected to the local TV while the other is connected to the remote TV in the other room (Fig.lb). The cable to the remote TV should be as short as possible otherwise cable losses may become a problem. If the cable length is 10-20 metres or so, the losses can usually be ignored (except in difficult cases). But 40 or 50 metres of cable will cause a loss that must be allowed for in most installations. The need to keep the lead short means that it is best run under the floor. This way, the cable can be run in a straight line from a point near the VCR to a spot immediately under the outlet in the other room. The best procedure is to pull the carpet back, drill a 10mm hole for the cable hard up against the skirting board, and then fit the splitter (or outlet socket) just above the hole. When the carpet is pushed back, the cable will be almost invisible and the whole assembly is neat and inconspicuous. Calculating signal levels The best place to start this kind of installation is to fit an outlet socket at the remote TV end of the cable. To get a good picture, you will need 60dB of signal at this point. The next step is to measure the cable length back to the VCR and add the loss represented by this length of cable. Let's say it was 2dB, which is an average figure for a bout 15 metres of domestic grade coax. This means that there must be at least 62dB of signal fed into the cable. We now need to take into account the losses in the splitter. A NOVEMBER 1990 7 4-way splitter. The losses in these items can amount to 5, 7 or even 9dB, so they become quite important in the calculations. Note that you can use a 4-way splitter to feed three TV sets, although it will have somewhat higher losses than a 3-way type. If you do use this kind of setup, the unused output should have a 75-ohm resistor connected across it to ensure correct matching. Do not leave the unused output open circuit. Distribution amplifiers These splitter units are sold by Dick Smith Electronics but similar units are also available from other retailers. The units shown are a 2-way splitter, a 4-way splitter & a 2-way plug-type splitter (bottom). This photo shows the 2-way & 4-way splitters with their covers removed. All you have to do is connect the lead from your VCR to the input terminal, then run coaxial cable from the outputs to your TV sets. good quality 2-way splitter will have an insertion loss of 3dB on each leg. This means that the input to the splitter must be + 3dB above its calculated output, or 65dB. Notice how the losses are added all the way from the output to the input. In this exercise, we have calculated that we want 65db into the splitter and this is just about what 8 SILICON CHIP is supplied by the average VCR. If the cable loss was higher (as it might be for a large house or if the cable could not be run via a direct route), then there could be too little signal at the remote TV. In this case, some kind of amplifier would be needed. Also, if you want to send your VCR signals to more than two TV sets, you will need to use a 3 or For anything but the most compact systems, you will almost certainly need a small distribution amplifier to compensate for the higher losses in the multi-way splitter. Various manufacturers have recognised this need and have provided a series of small distribution amplifiers for domestic use. These give from 10 to 25dB signal gain and can compensate for the losses in any reasonable home situation. Mostly, they are powered from the mains, usually via a 6-12 volt plugpack supply. The amplifier can be mounted close to the back of the VCR or on the skirting board close to the power point. The "RF Out" from the VCR goes to the amplifier input, while the amplifier output is fed to the splitter (Fig.le). Do not install the amplifier after the splitter. (Some years ago I made my own distribution amplifier from a disused masthead amplifier. I modified the input to suit 75-ohm coax and arranged a 12-volt power feed from within the VCR itself. This amplifier provided 26dB of gain following the VCR output and allowed me to reticulate signal to the TV set in the lounge, as well as to the kitchen, a bedroom and to four outlets in my workshop downstairs!) The simple distribution system described here will suit up to about four TV sets. If more sets are needed on the system, or if long ea ble runs are necessary, then another system of distribution will be needed. This is the "Main Trunk" system which is simple enough in principle but somewhat beyond the scope of this article. Maybe another time. ~ Nothing Ov,r $3.00 SCREWDRIVER SPECIALS 15W SOLDERING IRON 20W SOLDERING IRON • Ideal for project building • Mains powered 15 watt iron • Light duty with pencil grip • Air cooled finger grip for continuous use • Earthed tip & barrel for added safety • Lightweight and ,.---._ comfortable to use Cat T-1310 s259s Blade 6mm 3.2mm 5mm 6mm 8mm Cat T-1620 s299s Weller® Flat Blades: Cat No. T-6020 T-6030 T-6040 T-6052 T-6060 -- Price $1.95 $1 .95 $1 .95 $1 .95 $2.95 Cat No. Blade T-6028 T-6032 T-6050 T-6058 T-6062 3.2mm 4mm 5mm 8mm 8mm Price $1 .50 $1 .95 $1 .95 $2.95 $2.95 Price 11 .95 1.95 $1 .95 $2.95 Cat No. T-6035 T-6045 T-6055 Blade 3.2mm 5mm 6mm Price $1 .95 $1 .95 $1 .95 STACKABLE C0MP0NE~ NEW! STORAGE TRAYS CASE Cat H-2477 s39s $595 With 14 compartments under a clear plastic lid Cat H-2499 Phillips Head: Cat No. Blade T-6025 T-6037 T-6047 T-6065 6mm 5mm 6mm 8mm 111B Ons Tool 11lat DOBS It All/ 3-IN-1 MODULAR TOOL Savs $3.00 a pair/ PLIERS Cat T-3296 Cat T-3297 Cat T-3298 Flat Nose Bent Nose End Nipper -------· ■ • It's a drill plus drill bits - - - ~ • It's a Soldering Iron plus solder • It's a Screwdriver plus drivers • And it's rechargeable too! ~ s799s Cat T-5712 Reduced from $991 NOVEMBER1990 9 4lillllJ ALL RACK CASES REDUCED! Just what your equipment needs for space efficient storage and a clean, professional finish. All are finished in black anodised brushed aluminium and conform to standard sizes so they're sure to bolt straight into your rack system with NO DRILLING! Cases: - Blank Panels: (All cases are 430mm wide & 254mm deep) Cat No. Height Price H-2483 44mm $54.95 H-2485 88mm $75.95 H-2487 132mm $84.95 Cat No. H-2482 H-2484 H-2486 Save over $14.00 on every case! Save $6.00 on every panel! Height 44mm 88mm 132mm Price $9.95 $19.95 $23.95 HARDWARE SAVINGS! Power Heatsink • It's interlockable - join as many as you need! • Holds 2 x T0-3 packages • Size: 78x110x33mm qng;. a1r:r:1 Cat H-3461 0",:R "Cl ,u iO rr. Wisher TB-1 02 Tool Box Plastic Instrument Case A sturdy plastic tool box with two full width trays, metal latches, and large carrying capacity. • • • • Cat H-2570 Attractive black ABS case With carry handle Ideal for portable devices such as test gear Size: 200x95x140mm t.'Allt: $1".I 11n"c ., cat H-2506 ~ S!j95 Economy. Power Heatsink · • Flag mounting design with fins top and bottom • Holds 2 x T0-3, T0-26, or T0-220 ICs • Cat Size: 74x102x25mm Cat H-3471 =• s4e5 OVER 2O0/o OFF/ MAJOR DICK SMITH ELECTRONICS AUTHORISED STOCKISTS: N.I.W.: ARMIOAl.E: New England Elecironics 711655 BALLINA: Ballina Electronics 867022 BOWRAL: F.R.H. Electrical 611861 BROKEN HILL: Hobbies& Electronics 884098 COOTAMUNORA: Cootrnundra Music & lit! 422561 COffSHAR80UR: Coifs tetxJur Eleclronics 525684 OENILJQUIN: Deni Electronics 813672 OUBBO: Chris's Hi Fi 828711 FORSTER: Forster VIiiage Electronics 545006 GLEN INNES: John Sommer1a:I Electronics 323661 GRAFTON: Repairs and Soares 421911 GRIR'ITH: Mlatn>nlcs 62<4534 INVERELL: lnvmfl Elecironics 221821 LEETON: Leeton Audiotronic 532000 LIGHTNING RIOGE: Cycle & Sound 290579 LITHGOW: Douroy ~raphics 513173 LISMORE: Oecro Electronic Services 214137 MOREE:Monie E1ec1ronics 522091 MUOGEE: Headwa!? 723895 NARRABRI: temli Com~r Service 923274 NELSON BAY: ='1:k~'=1==::ir~~~10122=~T~l'li':~1~=~~~ WN',J;A WN';J;A: PhiHips Elec1ronics216558YASS: ~ngton~ 261116YOUNG: Kei111 Donoes Eltctronics821279 VIC: BAIRHSDALE: Ui & 1M Crawfool 5256TT CO!AC: (;)lac Electronics 312847 MILOURA: P\JITman Au1D Pro 232882 t.Q!WELL: MorweH E1octronics 348133 SHEPPARTON: And~ Guyatt Electronics 219497 SWAN HILL: Nvah District TV Seritce 329303 WAIIIAGUL: ~aioe 234255 WARRNAMIIOIJI.: Koroit SI Elec Services 627417 OLD: AYA: Delta Electrix 831566 BUl()AllERG: Bob Elkin Electronics 721785 CALOUNORA: Eleciro;nart 918533 DYSART: Dysart Videotronixs 582107 INGHAM: Masons Electronics 763188 MACKAY: SleYens Elecironics 511723 MARYBOROUGH: Keller Electronics i1:m =~~~J PI~~,~~~~~ ~~604MT 2="~eu:! =i~~ U ~: 11ass18ns TV & Comp Wor1d 822788 WHYALLA: Eyre Electronics 454764 WA: ALBANY: Micro Electronics 4120TT BIMBURY: Micro Electronics 216222 GERALDTON: Ba1avia l..iQhting & Electrical 211966 KARRATHA: Daves Cllcltronlc 854836 MANORAH: Micro Electronics 5812206 P(JIT HEOLAND: Ivan Tomek the Elec1 732531 10 SILICON CHIP s14e5 Weather- proof Switch Cover $ 4995 Weatherproof your toggle switches with these screw-on rubber covers. Ideal for marine use or any outdoor situation. Cat H-1914 Snap On Heatsinks The fast, efficient and economical way to control heat dissipation. Cat H-3416 Suits T0-220 case cat H-3417 Suits T0-126 case 75c FUN KITS FOR SERIOUS BUSINESS HOME SECURITY KITS GOING AWAY FOR CHRISTMAS? 4 SECTOR HOME ALARM Q With 4 sectors, this one board can control your complete home or office alarm system . It features separately adjustable entry and exit delays and LED entry status display. 2 SECTOR BURGLAR ALARM CONTROL UNIT Q Cat K-3254 This Control Unit features variable entry and exit delays, LED status indicators, alarm driver circuitry, timed and latched outputs, two separate sector inputs, and the provision to add extra sector boards as required . Cat K-8401 s39es SophisticatBd SBcurity For Your Hom, Alarm! Expand your K-8401 Burglar Alarm Control Unit. Add as many of these Sector Modules as you need . They hold two sectors, each with LED status indicators and isolating switches. ALARM PHONE DIALLER QQ UHF TRANSMiTTER KEY Q An amazing device that can be fitted to almost any alarm system. If your alarm is triggered, the Phone Dialler calls the number you have programmed into it and emits a distinctive tone. The kit even includes a pushbutton telephone • and Plug-pack power supply. This new design uses a SAW filter for improved frequency stability and eliminates the need for transmitter alignment. It features a flashing LED to indicate the button is being pressed and an automatic cut-out after 10 seconds if the button is accidently held down. - ~ . CatK-8300 s79es Cat K-8400 s12es · ··- · --- - - · ···· (1111' ,\lJ\J.:M f'l fl 'NI ;::: U Cat K-3259 s29es BURGLAR ALARM Q ~ POWER SUPPLY UHF REMOTE CONTROL SWITCH QQ Finally... a sophisticated BURGLAR Alarm Power Supply you can build yourself! It not only provides a 12 volt supply for your alarm, but rechar~es your back-up battery and automatically switches the supply between battery and mains should their be a power interruption. Use it for switching security systems, lights, or doors. This kit includes a frequency locked transmitter along with the switching unit which contains a receiver, decoder, and relay driver all on the one board . s39es .UGWO "' -~~ O -<:::> oc.. I~.; 0 114"~ Qhio)ri11 ~ C Kits marked with this symbol involve mains power wiring. Take extreme care when working with this equipment. Degree 01 Slmpllclly I§ ® ~ Cat K-3258 . s79es Cat K-8402 [t) Mains Q Simple QQ Intermediate QQQ Detailed n ffiJ . B1035/ BL NOVEM BEH 199 0 11 PORTABLE POWER SOLUTIONS Do you need to run battery operated devices from the mains? Do you need to run mains equipment from batteries? Do you even need to run 11 0V American gear m Australia? What ever your power needs you 're sure to find a solution at Dick Smith Electronics! RECHARGEABLE NICAD BATTERIES - THE DSE CHARGING CABINET • Charge up to 8 batteries at once! Cat S-3305 AAA $3.95 • Even charge 3 9V batteries simultaneously Cat S-3300 AA $3.95 Cat S-3301 C $9.95 • Features charge lights for each cell and test meter Cat S-3303 D $9.95 High Capacity Nicad Charging Cabinet Cat M-950~ . BATTERY TESTER catY-5018 s595 Cat S-3315 1.2Ah $29.95 Cat S-3316 1.9Ah $32.95 Cat S-3320 2.7Ah $37.95 Cat S-3322 6.5Ah $49.95 ft) Adapt overseas connectors to standard Australian power plug SLIMLINE CHARGING CABINET • Charges up to 8 AA or AAA Nicad batteries • Can also charge 2 9volt cells $2295 Cat M-9508 MICROWAVE OVEN LEAKAGE DETECTOR • Checks your oven door seal • Meter measures as low as 0.1mW psc • Needs no batteries Cat Y-4100 DIGITAL TYRE PRESSURE GAUGE It's fast, efficient, and highly accurate with a lifetime Lithium battery. Cat Y-5034 12 s249s HIGH PERFORMANCE POWER INVERTOR • 12 volts DC to 240 volts AC at 600 watts • Compact design housed in a robust alloy enclosure • Attach it to your car battery to run TVs, VCRs, or even a small refrigerator 525 ~~~SILICON CHIP 12V BATTERY CHARGER • Del ivers a powerful 500mA • Ideal for charging Sealed Lead-acid or Gel-cells as used in burglary alarm • Can be left running continuously . I Cat M-9531 . C Run Am,rican equipment in Australia! 115VAC STEPDOWN TRANSFORMER Includes an American style 2-pin plug , fuse, and 2m power cord Limited Stocki AUDIO COUPLING TRANSFORMER Ideal replacement part for radios or in any oscillator circuit Cat M-0224 25c 6-WAY POWER BOARD Comes with overload protection Ideal for Hi-Fi gear Cat M-7170 s499s ELECTRONIC NUMBER MUNCHER SMART PHONE s29e5 Cat M-9526 Cat M-5000 Cat M-7302 '2495 Cat M-9570 Cat M-1156 AUSSIE REVERSE ADAPTOR S895 3, 4.5, 6, 7.5, 9, or 12 volts selectable at up to 300mA 5 12V GEL CELL RECHARGEABLE BATTERIES - Supplies 12 volts DC at 1 amp • Rings by itself and gives voice instructions • Asks your child questions then responds in dozens of different ways - even corrects wrong answers • Sound effects match each button • For children aged 3 and up Cat Y-7107 s4995 • 5 maths activities including a mixed quiz • Plus it's the perfect kiddies fi rst calculator Cat Y-7129 'JC' MY JUNIOR COMPUTER • Just like a lap-top computer • Includes 17 educational games • Activity cartridges available Cat Y-7266 - 00 CB RADIOS SCANNERS UNIDEN BEARCAT 1OOXL uniden. HAND-HELD SCANNER Listen to the exciting world of VHF and UHF transmissions with the Uniden 1OOXL Scanning Receiver. • 9 bands covering 66-88MHz, 118-174MHz, 406-512MHz • Keyboard frequency entry, 16 memory channels, Band scan and memory scan • Includes in-built NiCad batteries, and AC charger • 2 year Uniden Warranty Cat 0-2813 Limited Stocks' 249. SCOOP PURCHASE/ $ UNIDEN BEARCAT 200XLT HAND-HELD SCANNER One of the most sophisticated scanners available! • 200 memory channels with scanning by auto search or keypad • Includes a high capacity NiCad battery pack and charger • 2 year Uniden Warranty s499 Cat 0-2810 * 200XLT Model Illustrated HEAT SHRINK TUBING Radiation cross linked, flame retardent, heat shrinkable, military grade polyolefin tubing. Now with that sort of description it has to be good! Sold in 1.2m lengths; shrinks in diameter by approx. 2: 1 ratio. SIZE 1.2m x 1.6mm 1.2m x 1.6mm 1.2m x 3.2mm 1.2m x 3.2mm 1.2m x 4.8mm 1.2m x 4.8mm 1.2m x 6.4mm 1.2m x 6.4mm 1.2m x 9.5mm 1.2m x 9.5mm 1.2m x 12.7mm 1.2m x 12.7mm 1.2m X 19.1mm 1.2m X 25.4mm CAT NO W-4100 W-4102 W-4104 W-4106 W-4108 W-4110 W-4112 W-4114 W-4116 W-4118 W-4120 W-4122 W-4124 W-4128 COLOUR Black Colours Black Colours Black Colours Black Colours Black Colours Black Colours Black Black Certified to U.S. Mil spec #MIL-1-23053/5 PRICE $2.50 $2.50 $2.95 $2.95 $3.50 $3.50 $3.95 $3.95 $4.50 $4.50 $4.95 $4.95 $6.95 $8.95 10 UP $2.00 $2.00 $2.45 $2.45 $3.00 $3.00 $3.50 $3.50 $4.00 $4.00 $4.50 $4.50 $6.25 $8.05 With Electronic Tuning/ SLIMLINE AM CB The elegant style of this Dick Smith Electronics CB will compliment your dashboard. At just 140x30x130mm, it fits exactly where you want it. • Touch control electronic tuning • LED signal strength/power output display • Built-in noise limiter • External speaker jack • Complete with mic and mounting kit Cat 0-1200. DOTC Approved Only $8 g Extra Va/us/ 'SUPER LION' AM SSB CB At this low price you weren't expecting all thes.e quality features, but here they are! • Inbuilt SWR meter t · PEARCE-SIMPSON • Emergency channel 9 switch • Squelch/Mic gain/RF gain/ Clarifier controls • LED channel display $ • PA facility Cat D-1711. DOTC Approved Only IDC GRADE CABLES Cat W-2750 26 way $2.95/m 30m pack only $60 SAVE $15! Cat W-2752 34 way $3.50/m 30m pack only $80 SAVE $8.50 ...... 199 10 BAND SHORTWAVE RECEIVER CHILDREN'S WALKIE-TALKIES • At last... a stylish two-way radio for the kids to enjoy! Operates from 9 volt batteries (not supplied) 0. 0.T.C. approved Cat D-1075 $1995/pair. • Your local AM/FM stations plus 8 shortwave bands • Includes a soft carry case • Battery operated with sockets for an AC adaptor and headphones Cat D-2834 s799s Bring The World Into Your Home! SANGEAN MULTIBAND RECEIVER • AM/FM plus Long Wave, Medium Wave & Short Wave (150kHz to 30MHz) • Digital fre quency display, with keyboard or dial tuning • 24 hour clock with sleep timer • Plus a host of other features $ 299 Cat D-2831 TWO FOR ONE SALE! PERMAGARD •Penetrates, lubricates, and displaces moisture •Protects metal tools & parts from corrosion sggs Cat N-1120 ELECTRONIC CLEANING SOLVENT • Ideal cleaner for any electronic equipment • It's non corrosive and leaves no residue Cat N-1100 14 SILICON C H I P TAPE HEAD CLEANER • An efficient magnetic tape head cleaner • Will not harm plastics or rubber Cat N-1155 THERE'S SURE TO BE AN OZONE SAFE SERVICE AID TO HELP YOU TOOi SPRAY FREEZER AIR DUSTER • Use it to detect fau lty components and solder joi nts • The safe way to cool small components • High pressure inert gas for cleaning circuit boards and delicate equipment Cat N-1 110 s229s Cat N-1 150 D E V E L 0 p M E If ' Design Your Own Circuits Fast & Easy! Wishmaker II ~ Prototype Design Station ~ With the Wishmaker II you can quickly and effortlessly build prototypes of your digital designs without the need for soldering , then test them with the vast array of test and measurement equipment built into this impressive unit. A rugged and portable design make the Wishmaker II a must for engineers, technicians, students, and hobbyists who need a device that can get their designs up and running fast! The Unit comes with a removable solderless breadboard , wire jumper kit with 350 assorted lengths, probes, and detailed manual. s499 Cat 0-1435 With Inbuilt Component Checker! 60MHz Dual Trace/ Dual Timebase CRO If you 're a technician or engineer then you'll be stretching most CROs to their limits with the kind of work you do. The DSE 60MHz CRO, however, has the performance and features to tackle CB radios, high frequency transceivers, and the newer high speed computers with ease. Its dual traces, along with dual timebase, will deliver all the information you need to make decisions fast. With features like these plus trigger holdoff, delayed sweep, and beam finder, you should have on~ now! S 1595 Cat Q-1290 20MHz Dual Trace/ Dual Trigger CRO Value, features and performance make this CRO an ideal choice for general service, design, and TV work. With an inbuilt component checker, X - Y Operation , high sensitivity, dual trigger and large 6" screen, it's well suited for professional applications and affordable for the hobbyist. Features include: • 20MHz bandwidth (-3dB) • Single or dual trace modes • 2 probe sets • Inbuilt component checker s799 Cat Q-1285 DSXPRESS PHONE & MAILORDER SERVICE Outside Sydney (FREE Call) 008 22 6610 Sydney And Enquiries - 888 2105 FAX: (02) 805 1986 or w rite to DS XPRESS, PO BOX 321 N/RY DE NSW 2113 All Major Credit Cards Accepted . O / Nite Courier Available. PHONES SECURITY AUDIO . COMPUTERS 24 HOUR DESPATCH OF ALL ORDERS NSW • Albury 21 8399 • Bankstown Square 707 4888 • Blacktown 671 7722 • Brookvale 905 0441 • Bondi 387 1444 • Campbelltown 27 2199 • Chatswood Chase 411 1955 • Chullora 642 8922 • Gore Hill 439 5311 • Gosford 25 0235 • Hornsby 477 6633 • Hurstville 580 8622 • Kotara 56 2092 • Liverpool 600 9888 • Maitland 33 7866 • Miranda 525 2722 • Newcastle 611896 • North Ryde 878 3855 • Parramatta 689 2188 • Penrtth 32 3400 • Railway Square 211 3777 • Sydney City 267 9111 • Tamworth 66 1711 • Wollongong 28 3800 • ACT• Belconnen (06) 253 1785 • Fyshwick 80 4944 • VIC • Ballarat 31 5433 • Bendigo 43 0388 • Box Hill 890 0699 • Coburg 383 4455 • Dandenong 794 9377 • East Brighton 592 2366 • Essendon 379 7 444 • Footscray 689 2055 • Frankston 783 9144 • Geelong 232 711 • Melbourne City 399 Elizabeth St 326 6088 and 246 9ourkeSt 639 0396 • Richmond 428 16 14 • Ringwood 879 5338 • Springvale 547 0522 •OLD• Brisbane City 2299377•Buranda 391 6233 • Cairns 311 515 • Chermside 359 6255 • Red bank 288 5599 • Rockhampton 27 9644 • Southport 32 9033 • Toowoomba 38 4300 • Townsville 72 5722 • Underwood 341 0844 •SA• Adelaide City 223 41 22 • Beverley 347 1900 • Elizabeth 255 6099 • Enfield 260 6088 • St. Marys 277 8977 •WA• Cannington 451 8666 • Fremantle 335 9733 • Perth City 481 3261 • Midland 250 1460 • North bridge 328 6944 • TAS • Hobart 31 0800 •NT• Stuart Park 81 1977 The Largest Australian Electronics Retailer! 63 Stores Across Australia 81035/PB NOVEMB ER 1990 15 Digital electronics has moved from the outskirts to the forefront of our hobby. Beres your chance to learn about or refresh your knowledge ·o f some of the basic elements of that technology. By JOSEPH J. CARR An Introduction to Digital Electronics You don't have to be too old to remember when digital electronics was the province of a few esoteric specialists who worked in forsaken realms of electronics. Everyone in those days "knew" that analog electronics was "real" electronics. But times changed; digital electronics eventually became easily accessible to all because of the introduction of integrated-circuit logic elements. The costs of digital technology have also dropped precipitously over the years. Originally, there was one fly in the digital ointment: price. This author can recall paying $5 for a NAND-gate chip in 1967 and nearly $14 for a 7490 BCD-output decade counter. Today the 7490 is less than $2 (and a great deal less in terms of 1967 dollars). Reliability has improved over the past two decades as well. At one time, a large digital project was unreliable by default. But today, chips hold up well and projects can be expected to last a long time. Copyright (c) Gernsback Publications, USA. Reprinted with permission from Popular Electronics, April 1990. 16 SILICON CHIP Even "green" chips, which by definition have no factory burn-in, perform as well as many highreliability devices. In this article we will take a look at the most fundamental building blocks of digital electronics: gates and flipflops. All larger digital circuits, whether a simple BCD counter like the 7490 or a largescale integration (LSI) microprocessor chip, ultimately boil down to a very few, different forms of digital-logic gates. We will learn about those basic-circuit elements below. Logic Families Digital-logic families are devices using the same technology and the same general circuit elements. They are designed so that it is easy to interface them using only electrical conductors (eg, wires and printed-circuit traces). The interfacing chore is thus eliminated because we don't need to worry about matching signal levels and . LJ o-----{>o----o B A LOW+ HIGH INPUT A OUTPUT B 0 1 1 0 INPUT A I I I I I I I I I I ouT[UT~ HH r-- 'LOWLJ LJ L_j D Fig.1: the inverter or NOT gate's schematic symbol is given in A. The circuit in B will mimic the gate's operation whose truth table is given in C. Typical waveforms for the device are shown in D. INPUT INPUT anything from - 15 to O volts for low, and O to + 15 volts for high. In general, one of two situations are standard in CMOS circuits. Either low is zero and high is + 5 volts (when TTL compatibility is needed), or low is a negative voltage and high is a positive voltage of the same value. The terms "positive logic" and "negative logic" sometimes confuse people who are just learning digital electronics. In positive-logic systems, a high will be a more positive voltage than a low. In negative-logic systems, a low will be more positive than a high. OUTPUT A B C 0 0 0 0 1 1 1 0 1 1 1 1 IN~UT--i__Jl_ I I I I I I I I I I INPUT B / I t I I I I I I I I OUi:"UT 1 1 I I I I L_]1_Jl_ D Fig.2: the 2-input OR gate (A) can be simulated by the circuit in B to yield the results shown in C. When operating in a circuit, it acts as shown in D. impedance values. The two modern digital-logic families consist of the transistor-totransistor logic (TTL) and complementary metal-oxide semiconductor (CMOS) devices. TTL devices are based on NPN/PNP bipolar transistors while the CMOS devices are based on field-effect transistors (MOSFETs). You can recognise CMOS devices by their "4xxx-series" part numbers (eg, 4049). TTL devices carry part numbers of 74xx (eg, 7490) or 74xxx (eg, 74161). Military (Mil -spec) TTL devices are sometimes seen in hobbyist parts suppliers as industrial surplus. Those devices carry the same number as the civilian version, except that the first "7" is replaced with a " 5" . In other words, a 5490 is a 7490 that's been drafted. Digital vs. Analog Digital electronics differs from analog electronics in the nature of the signals processed. In an analog circuit, a signal can have any value within a certain range. For example, suppose we have an operational amplifier connected for analog oper ation. Further, suppose that the output voltage can swing from - 12 to + 12 volts DC. In an analog circuit, the output voltage can take on any value between - 12 volts and + 12 volts; no values are forbidden . In digital circuits, on the other hand, the signals can take on only one of two permissible values - all Gates The most basic digital elements are gates. All digital circuits can be formed from only three such basic elements: the NOT gate, AND gate, and OR gate. Although these three gates can do it all, we also include the NOR, NAND and XOR gates among the basic elements. While discussing each gate, we'll show you its schematic symbol, an equivalent circuit made of switches that operate a lamp, and its truth table (in which 1 = high and o = low). Finally, we'll present a wavetrain example. other values are forbidden. Because only two values are permitted, we say those circuits are binary in nature. The two levels are often called 1 and O (or logical 1 and logical 0), true and false, or high and low. In this article, we will use high and low to denote the different states, except for a few cases where 1 and O seem particularly appropriate. The two families of digital devices use different voltage levels for high and low. For example, the TTL family uses + 2.4 to + 5 volts for high, and O volts to + 0.8 volts for low. In the CMOS family, on the other hand, it is possible to use Inverters Inverters, also called NOT gates, get their name from the fact that they produce an output that is the v+ :~c A .,. INPUT A INPUT B OUTPUT C 0 0 1 0 1 0 1 0 0 1 1 0 IN P l T 7 - - - 1 U L I , IN~UT I I I I I I I I I :in : LJnL.lJJ l ~ I I I I I I I I I I I I I 11 I I I II I I 11 I I I ouyu~ D Fig.3: the NOR-gate circuit symbol (A) is the same as the OR gate but with a circle at the output to indicate inversion. It is functionally equivalent to the circuit in B. Its truth table output is just the inverse of the OR gate's. Shown in D are some typical waveforms for the gate. NOVEMBER 1990 17 A ~ B~ C A B (output) is on (high) if either switch A or switch B is high. That's why they're called OR gates. A truth table for the OR gate is shown in Fig.ZC. What it says is that the output is low only when all inputs are also low. A high on any or both inputs produces a high output. The circuit action of those rules is shown in a practical form in Fig.ZD. Both inputs receive a series of pulses, and the change in output reflects the operation of the gate in response to those input levels. C '-o--<at>-i.,. v+-0~ IN~UT_Il__J7_ INPUT A INPUT B OUTPUT I I I I C I I I 0 0 0 I I 0 1 0 1 0 0 1 1 1 INPt iI I in ; n,I I I I I I I I I I I I I I I _J___u LJ.J I [J__ t 1, 1 11 1 1 1 OUTPUT C D Fig.4: the AND-gate's circuit symbol (A) should not be confused with the OR· gate's. A simple equivalent circuit can be constructed with two switches and a lamp, as in B. The device produces the truth table shown in C while typical waveforms are given in D. opposite of the input. A high input yields a low output and vice versa. The letter ''A'' is an expression that represents the input, so "A" can equal a high or a low. In like fashion, the letter ''B'' represents the output. An inverter is represented by a triangle on its side with a circle at the output (see Fig.lA). Whenever a circle appears at any lead (input or output) of a digital circuit it indicates inversion, as we'll see with some of the other gates. We can sometimes get better insight into a circuit's behaviour by looking at a simple equivalent circuit. In Fig. lB we have a simple DC circuit that represents the operation of an inverter. Switch Sl selects either a high signal (V + ) or a low signal (ground or O volts) as the input to the circuit. The lamp indicates the output - it's on for a high output and off for a low output. When the switch is in the high position, both sides of the lamp have the same potential so the lamp is not illuminated. That indicates a low output. When the switch is in the low position, the lamp receives both ground and V + so the lamp lights to indicate a high output. The truth table for the NOT gate is shown in Fig.lC. If the input is A and the output is B, we find that a low input produces a high output, and a high input produces a low output. This circuit action is shown in Fig. lD. In this case, the input is A while the output is called B or Abar. The line above the input or out18 SILICON CHIP NOR Gates The NOR gate is made by combining an OR gate with an inverter. (Note the circle on the output terminal in Fig.3A). The gate might be considered a NOT-OR gate. The NOR gate produces a low output if any or both inputs is high. An equivalent switch circuit for the NOR gate is shown in Fig.3B. As long as both switches are open, the lamp is on, but if either switch is closed then the lamp is turned off. The truth table for that type of circuit is shown in Fig.3C, which can be summarised by the following rules: the NOR output is high if, and only if, both inputs are low (ie, the output is low if any input is high). Those rules are presented in a more dynamic form in Fig.3D. put in logic notation indicates that the signal is the opposite of whatever the "unbarred" signal is. For example, if A is high, then Abar is low. We can use that notation to indicate the relationship between the input and the output: B = A-bar That is an expression used in Boolean algebra, which is the mathematics of digital logic. OR Gates An OR gate (Fig.ZA) produces a high output if at least one input is high. So if A, B, or both A and B are high, then the output is high. Another, perhaps simpler, way to put that is to say both inputs must be low to get a low output. Fig.ZB shows a simple equivalent circuit for the OR gate. The lamp AND Gates The AND gate (see Fig.4A) produces a high output if and only if both inputs are high. The AND-gate :~c A INPAUT__IL___fL INPUT A INPUT B OUTPUT C 0 0 1 0 1 1 1 0 1 1 1 0 I I I I I I INPUT B ii I I I I n LJ:f!liL!__ __!_l_.j I I I I ] I I I I I I I I I I II II I I I I I I OUTPUT C D Fig.5: here we present the NAND-gate circuit symbol (A) an equivalent circuit (B), its truth table (C), and some typical waveforms (D,). v + ~~ h ~ ✓"-o A B 0 0 -:- IN~uTSl__Jl_ INPUT A INPUT B OUTPUT C 0 0 0 0 1 1 1 0 1 1 1 0 INPUT B ouyuT I I I I I I I I I I I I i ~ I I I I nl_J_J_ i I _u I LJ I I I I I I I I -1lJ1fL_Jl_ tle or nothing to do with computers. Most flipflops have two outputs called Q and Q-bar. The Q output is the main output, while Q-bar is said to be a complementary output. That is, when Q is high, then Q-bar will be low, and when Q is low, then Qbar will be high. Also, when an input line on a schematic diagram is shown with a small circla at the flipflop body, then that input is active when low. Otherwise, the input is active when high. RS Flipflops The RS, or "Reset-Set", flipflop is Fig.6: the XOR-gate (A) requires a more complex equivalent circuit, as shown in B. It generates the unique truth table given in C. The waveforms in D are characteristic of its behaviour. are high. As in our previous cases, a dynamic example of those rules is given in Fig.5D. A XOR Gates A SET INPUT RESET o I ii 0 INPUT 0 OUTPUT OUTPUT 0 1 0 1 0 1 1 1 msALLOWEO NO CHANGE I I 1 0 Fig.7: the circuit for a NOR-logic RS flipflop is shown in A while its truth table is given in B. equivalent switch circuit is shown in Fig.4B. The lamp is on only if switch A and switch B are closed. The truth table of Fig.4C can be summarised as follows: The output will be low if either input is low (ie, the output will be high only if all inputs are high). Those rules are summarised by the timing diagram of Fig.4D. NANO Gates The NAND gate (see Fig.5A) is made by combining an AND gate with an inverter. An equivalent circuit is shown in Fig.5B; if either switch is open the lamp is turned on and it will only go off if both switches are closed. The rules of operation are given in the truth table (see Fig.5C) and can be summarised as follows: the output is high if one or both inputs are low, which is to say the output is low only if both inputs The last basic gate that we will consider is the Exclusive-OR (XOR). That gate (shown in Fig.6A) is a little unusual but it has a lot of different applications. An equivalent circuit for the XOR gate is shown in Fig.6B. The switching circuit has two SPDT switches cross-connected as shown. The truth table (Fig.6C) reveals some interesting behaviour: if both inputs are low, then the output is low. If both inputs are high, then the output is again low. If one input is high, and the other is low, then the output is high. In other words, a low output occurs anytime that both inputs are at the same level (regardless of whether they're high or low). The output goes high only when one input (but not both together) is high. That behaviour is displayed in Fig.6D. o I o SET INPUT RESET INPUT 0 0 NO CHANGE 0 1 1 I 0 1 0 0 I 1 1 1 OISALLOWEO OUTPUT OUTPUT B Fig.8: the circuit for a NAND-logic RS flipflop appears in A while B shows its corresponding truth table. Fig.9: a clocked RS flipflop can only operate when the clock input goes high. The circuit then behaves in the same manner as the circuit shown in Fig.BA. SET Flipflops Once an electronics buff progresses beyond an understanding of elementary digital-logic gates, it's time to tackle the next order of circuit organisation - flipflop circuits. A flipflop is a one-bit memory device made of basic gates, although it is rarely thought of as such in this day of 256KB and 1MB dynamic-memory chips. But flipflops are still commonly used in digital electronics, both in computers and in circuits that have lit- RESET INVERTER LOAD/TRANSFER INPUT Fig.10: the master/slave flipflop circuit consists of two clocked RS flipflops, designated here as A and B. The circuit is configured so that the outputs of A drive the inputs of B. The two clock lines are driven out of phase from a common clock, through the load/transfer input. NOVEMBER 1990 19 _r· _r INACTIVE ACTION HERE 0 0 CLR CLK CK 0 0 SET 1 ACTION HERE a 0 A Fig.11: in a level-triggered flipflop, the circuit action happens when the level is either high (positive-level triggering) as in A or low (negativelevel triggering) as in B. Edge triggering occurs if the circuit changes state when the input signal is in transition from either low-to-high (at the positive edge) or high-to-low (at the negative edge) as illustrated in C and D, respectively. a flipflop circuit that has two inputs: set and reset. When the reset input is made active, the Q output is forced low (if a Q-bar output is available, then it is forced high). The set input has just the opposite effect: an active input signal forces the Q output high and the Q-bar output low. There are two forms of RS flipflop: NOR-logic and NAND-logic. The NOR-logic RS flipflop circuits are configured with 2-input NORgates such as in the 7402 devices. The NAND-gate circuits are built using 2-input NAND-gates such as in the 7400 chips. The NOR-logic flipflop circuit is shown in Fig.7 A, while the truth table is shown in Fig.7B. The NOR logic circuit uses active-high inputs. In other words, a low on both inputs at the same time will result in no output change. But if either input is made high, while the other is low, then the result will be an outputstate change. Which state occurs depends upon whether it was the set or reset input that was made active. The condition of both inputs being simultaneously high is disallowed because the results will be unpredictable. The NAND logic circuit (Fig.BA) uses 2-input NAND gates instead of NOR gates to form a flipflop. They act just the opposite of NOR-gate flipflops (compare Fig.SB with Fig.7B). There are two RS flipflop chips available in the CMOS family of 20 SILICON CHIP B Fig.12: the D-type flipflop (A) is a 1-bit data latch. It will transfer the data on the D input line when the clock line switches high. The waveform timing· diagram (B) shows how the Q output switches with the D input and clock pulses. devices. The 4043 is a quad NORlogic RS flipflop ("quad" because four RS flipflops are in the same package). Similarly, the 4044 device is a quad NAND-logic RS flipflop. Clocked RS Flipflops One of the problems inherent in the design of the RS flipflop is that noise on the inputs can trigger an output transition. Also, the RS flipflop is asynchronous - it is not time-dependent and will operate whenever a valid input is applied. A solution to those kinds of problems is the clocked RS flipflop circuit of Fig.9. The two gates on the right form a NAND gate logic RS flipflop in the same manner as in Fig.BA. The inputs of this flipflop are controlled by the outputs of the other two NAND gates. As long as the clock input remains low, the outputs of both left gates are locked high, so the RS flipflop cannot operate. However, if ffii the clock-input goes high, then the inputs of the RS flipflop will respond to the inputs applied to the set or reset inputs. Master-Slave Flipflop The so-called "master-slave" flipflop is shown in Fig.10. This circuit consists of two clocked RS flipflops, A and B as shown. The circuit is configured such that the outputs of the left flipflop drive the inputs of the right one. The two clock lines are driven out of phase with one another but from a common clock line, now called the load/transfer (or LIT) input. If the LIT line is high, then the clock of the A flipflop is low and the B one is high. Under that condition, B is active and A is inactive. Whatever levels appear on the outputs of A are automatically transferred to the outputs of B by virtue of CLK2 being high. But when the LIT line goes low, B is disabled (but its outputs remain the same) ffmi SET 0 0 OISALLOWEO 0 1 0 1 0 1 1 NORMAL FOR CLOCKED OPERATION 0 CLK 0 SET 1 J K 0 0 0 1 1 0 1 1 CLK OUTPUT 0 OUTPUT Q CLOCKm l NO CHANGE T1 T2 T3 T4 I I I I I 0 1 FLIPS TO THE OPPOSITE STATE ou1fUT / I I I T5 T6 I I i I I I:j C Fig.13: the JK flipflop (A) can be operated in either of two modes - direct and clocked. The logic truth table for the direct mode is shown in B while the truth table for clocked operation is shown in C. A JK flipflop is useful for binary division as illustrated in D. 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LTD. 14B MAXWELL STREET, TURRAMURRA N.S .W. 2074 TELEPHONE: (02) 988 3865 FAX: (02) 988 3861 Fo1 = F/2 Fo2 CLOCK = F/4 Fo3 CLK WITH F/8 Fo4 = F/16 03 02 PULSES = CLK CLK CLK FREQUENCY F A 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 CLOCK 01 02 L 03 04 Fig.14: shown in A is a 4-bit binary counter made from four JK flipflops. The timing diagram for the circuit is shown in B. Note that each successive stage divides the input frequency by 2. and A is enabled. Any changes on the S and R inputs are reflected on the Qt/Qt-bar outputs of A. When the LIT line goes high again, those new levels are transferred to the outputs of B. The master-slave flipflop is used where noise or synchronisation is a problem. In some flipflops, we see a difference between various types of clock triggering. Figs.11A & 11B show the difference between positive and negative-level triggering. In level triggering, the circuit action happens when the level is either high (positive-level triggering) or low (negative-level triggering). Edge triggering occurs when the input signal is in transition from either low to high (called positiveedge triggering) as in Fig.11C, or high to low (called negative-edge triggering) as shown in Fig.11D. Type-D Flipflops The D-type flipflop , also sometimes called a 1-bit data latch, is a digital circuit (Fig.12A) that will transfer the data on its D input line to the Q output when the clock 22 SILICO N CHIP (CLK) input goes high. Thus, the Dtype flipflop is said to "latch" the data on the D input for one clock cycle. Fig.12B summarises the operation of the D-type flipflop. When the clock pulse goes from binary O to binary 1, the latch stores the input state (ie, if D is high, then Q will go high; if Dis low, then Q will switch low). Note also that if the clock input remains high, the Q output will simply follow the signal applied to the D input. Examples of D-type flipflops include the 7474 dual edge-triggered TTL flipflop and the 4013 CMOS device. JK Flipflops The JK flipflop (Fig.13A) can be operated in either of two modes: direct and clocked. This device has five inputs and two outputs. The set and clear (CLR) inputs are similar in operation to the set and reset inputs on a basic latch. The J and K inputs are synchronous inputs and are similar to the set and reset inputs of a clocked flipflop. "J" means set while " K" means reset. Finally, the device also has a clock input and the standard Q and Q-bar outputs. The set and clear inputs are asynchronous in nature. They are normally held high and in that state have no affect on the operation of the flipflop. However, to set or reset the flipflop as you would an ordinary latch , momentary low signals are applied as required. For example, to reset the flipflop, a binary O would be applied to the clear input. The Q output would then go to the binary O state. The logic truth table for the direct mode of operation is shown in Fig.13B. When both clear and set are low, the JK flipflop does not know what to do , so that state is disallowed. The results are unpredictable if this occurs, so avoid that combination of inputs. When the clear input is low and the set input is high, then the Q output immediately goes low and the Q-bar output is high. However, when the clear input is high and the set input is low, the opposite action takes place: Q = high and Q-bar = low. Finally, note the action when both clear and set are high: the JK flipflop is set up for clocked operation and a different set of rules applies. Note also that the clear and set inputs override the J, K and clock inputs. Their main application is to preset the flipflop to one state or the other prior to another operation taking place. Now let 's consider the synchronous inputs. The truth table for clocked operation of the flipflop is shown in Fig.13C. The JK flipflop is a negative-edge triggered device; ie, the circuit's output transitions only occur during high-to-low transitions of the dock (CLK) line. If both the J and K inputs are low, then there will be no change in the output state during clock transitions. But if J is low and K is high, then a clock transition forces Q low and Q-bar high. Similarly, when J is high and K is low, the opposite occurs: Q goes high and Q-bar goes low. If both J and K are high, the Q output will flip to the opposite state when the negative-going clock transition occurs. A depiction of that is shown in Continued on page 93 TM* THE UEXT CEUERHTIOU Genexxa, the dynamic new sound in audio has arrived. The components are designed to perfection. The performance is uncompromising. The sound is brilliant and the quality unparalleled. They are the finest we can produce. For the home. 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OVER 400 STORES AUSTRALIA-WIDE 42-84os ..... . .. . . . .... . . 499.95 his laser is housed in a length of plastic electrical conduit which protects the laser tube and the high voltage power supply. To operate it, you press the pushbutton, just like a torch. You hold the button down to operate it, and take your finger off to stop. Simple. This conserves the batteries and reducesthe possibility of accidents. T Warnings Speaking of accidents, we need to stress a couple of safety points before we go to much further. (1). Looking directly into the laser tube while it is operating could damage your eyesight. The tubes used in this project are of low power, around a milliwatt or so, but they still could cause damage to your eyesight. So don't even think of looking into the tube while it is operating. Ever. (2). The power supply of this project is potentially LETHAL. Yes it could kill you, or at the very least, give you a very unpleasant electric shock. It may be battery powered but it contains a DC-to-DC inverter which steps the voltage up to very high levels. You can't even trust it when it is turned off, until it has had time for the capacitors to discharge. What is a laser? Lasers are becoming so commonplace now that it is easy to forget that they are using some pretty exotic technology. Laser stands for Light Ampli- fication by Stimulated Emission of Radiation. The important characteristics of lasers are that they produce very pure monochromatic light (ie, a single wavelength or frequency), that all the light waves are coherent (ie, in phase) and that the beam has very little divergence (ie, it is concentrated into a small spot). There are many different types of lasers. The first laser, demonstrated in July 1960 by Theodore Maiman, was a crystal laser (actually a rod of synthetic ruby with the ends finely ground and polished so that they were optically flat and exactly parallel to each other). Both the polished ends are silvered to act as mirrors but one is partially silvered so that some light passes through. This very precisely . Build this Battery Powered Laser Pointer By LEO SIMPSON Want to explore the fascinating technology of laser light? Now you can, with this battery powered laser. Completely portable, it could be used as a laser pointer for lectures or for laser experiments. 24 SILICON CHIP dimensioned ruby rod was resonant at one particular light frequency. All that it needed was some external stimulation and it would emit light at that particular frequency - see Fig.1. FULLY SILVERED END FLASH LAMP PARTIALLY SILVERED END LASER BEAM Pumping the laser Those early crystal lasers were stimulated or "pumped" by an external Xenon flash tube. They could not operate continuously, for two reasons. First, an Xenon flash tube will not operate continuously and secondly, a laser needs to dissipate a lot of heat when it is operating and crystals do not conduct or dissipate heat very well. Other types of lasers The most common types of laser are either gas or semiconductor. Gas and semiconductor lasers are not optically pumped but are stimulated or energised by passing a current through them. For gas lasers, this means a high voltage DC power supply is needed, capable of delivering many thousands of volts. Laser applications So what are some typical laser applications'? These days, you name it, it's got a laser in it. Well almost. The most common applications are in CD players and CD-ROM drives, in laser printers, and in barcode readers for supermarket checkouts and lending libraries. They're the everyday consumer applications but they also have lots of applications in industry, surveying, medicine and science. Now that lasers are so widespread, it is not surprising that low power laser tubes have become a great deal .l:.. Fig.1: the first laser was a synthetic ruby rod which was optically "pumped" by a high power Xenon discharge tube. By contrast, gas lasers are "pumped" by passing a current though the tube with a high voltage DC power supply. (Courtesy Radio-Electronics). cheaper in the last few years. Combine that fact with the use of other existing cheap technology and you can build a laser for not much more than $200.00. We're talking about a low power Helium-Neon laser, with a tube rated at 0.5-0.8 milliwatts or a slightly larger tube, rated at 1-1.SmW. The tube is energised from a 12-volt rechargeable battery pack via a DC-to-DC inverter. The whole lot - batteries, inverter and laser tube - is housed in a length of 40mm OD electrical conduit (in a nice bright orange colour) with suitable end pieces. Now let's have a look at the circuit which is shown in Fig.2. As will become more apparent when you look at the diagrams of Figs.3 & 4, the circuitry is in two parts: the transistor inverter and the rectifier circuit. Fluorescent light inverter Fig.2: the complete circuit of the laser. It is basically a small fluorescent light inverter driving a rectifier board to develop the high voltage. The two test points (TPl & TP2) are provided for checking the laser current (at 3.5 to 3.4mA). If necessary, the current is adjusted by changing the 68kQ and 33kn ballast resistors. With the supplied kits, this should not be necessary. The transistor inverter, built around Ql, Tl and Dl, is directly out of a battery powered fluorescent light. It comes already assembled on a miniature printed circuit board. Essentially, it is a "ringing choke" inverter. Transistor Ql oscillates by virtue of the positive feedback from the secondary of transformer T1 back to its base. It oscillates at about Z0kHz or so and steps the 12V DC input up to many r -- - - - - - - - - - -------7 SWITCHED~ _ _ _ _....,._ _ _ _ _ _ _ _ _ _ _ _ _ _ __ , • I , - - - - - - - - - - - - - ------7 I I LINK DIRECT~---' +1 0• 1JV .01 3kV 1M 0.25W 680pF 3kV J I 47 I' 1k 0.25W I I VOL 1~g\~,ml~LIER L ___ ____ __ _ I L _ _ __ _ _ _ _ _ _ _ _ DC-AC • SEE TEXT CONVERTER j ~ TP2 I ___ __ _ J LASER TUBE TP1 ECB DC POWERED LASER HEAD NOVEMBER 1990 25 TO LASER TUBE 10-14V +~ - 47~ Dl lA• l~ * SEE TEXT Fig.3: the wiring diagram for the two printed boards, showing also how they are linked together. Be sure to use the components specified since they operate at high voltage. [~ ....... !II ~I c:::,, z } ,.......--..... 12V NiCad BATTERY PACK I :9 ~ I------~ 1--- - - - -- - - - - - -- - - - ---JlOmm----- - - - - -- - - - - -- -~~ Fig.4: these "see through" diagrams shows how the laser and the battery pack are mounted in their respective lengths of electrical conduit. The endplates are made of 10mm-thick Perspex. hundreds of volts AC (depending on the loading). Normally the output of the transistor inverter would be fed to a small fluoresc ent tube (say around 8 to 10 watts rating) via the .0015µF capacitor from the transformer secondary winding. However, this circuit bypasses the .0015µF capacitor with a link to feed the rectifier circuit. Rectifier circuit There are two stages to the rectifier circuit. DZ and D3, together with two Close-up view of0.5-0.BmW laser tube, showing the 33kf2 2W ballast resistor wired to the positive electrode of the tube. 26 SILICON CHIP .0lµF capacitors, form a conventional halfwave voltage doubler circuit. Then, stacked on top of that is a Cockcroft-Walton voltage multiplier circuit comprising diodes D4, D5, D6 & D7 and their associated capacitors . When the circuit is firs t turned on, both the halfwave voltage doubler and the Cockcroft-Walton voltage multiplier work together to produce a voltage of between 3.5kV and 6kV to fire the laser tube and establish a discharge current of several milliamps through it. With the discharge current flow ing, the Cockcroft-Walton multiplier can no longer function prop erly because its high impedance is heavily loaded by the laser tube. This high internal impedance of the multiplier is artificially provided by the two 680pF high voltage capacitors and the 1MQ resistor. So what happens is that the halfwave voltage doub ler, DZ and D3, supp li es the laser tube via th e series path provided by th e diod es D4 to D7. Even so, th e voltage across the la- PARTS LIST Close-up view of the finished printed board assembly. The smaller board is from a portable fluorescent lamp and is su pplied ready assembled. 1 PC board, 78 x 26mm (for the rectifier circuit) 1 assembled fluorescent light inverter board (see text) 1 laser tube (see text) 1 304mm length of 40mm OD electrical conduit 1 184mm length of 40mm OD conduit 4 10mm th ick Perspex endplates to suit conduit 1 polarised male socket (2 or 4pin) 1 polarised female socket to suit male socket 12 small self-tapping screws to fasten endplates and polarised sockets 10 AA size nicad cells 1 pushbutton momentary contact switch 6 VG2X 2kV silicon diodes 3 .01 µF 3kV ceramic capacitors 2 680pF 3kV ceramic capacitors 1 1Mn 0.25W resistor 1 68kn SW wirewound resistor 1 33kn 2W resistor 1 1kn 0.25W resistor Miscellaneous Hookup wire , solder, etc. This view shows the completed assembly, ready for mounting in the electrical conduit. Remember that the circuit operates at high voltage so never touch any of the parts while power is applied. ser tube is still quite high, at close to 1000 vo lts DC. The current through th e tube is set by the "ballast res istors", a 68kn 5W and 33kn 2 watt type. And that 's just about it , as far as the circ ui t is con cerned. It runs from 12 volts DC as already ment ioned, provided by a "battery" of nicad ce lls or from an externa l 12 V battery. Construction This w hol e pro ject is avail ab le as a ki t from Oatl ey Electron ics so corn- ponent availability w ill not be a problem (see the panel on prices elsewhere in this article). As already noted, there are two PC boards, one of which (for the transistor inverter) w ill be supplied already assembled. All you have to do is fit two links to the board, although it is li ke ly that these, too, w ill already be fi tt ed . You w ill need to check your samp le board against the com ponent w iring d iagram of Fig.3 to confi rm thi s poin t. The rectifi er board takes 6 di odes, 6 capacito rs and 3 res istors. Note th at the diodes an d capacitors are far from ordinary in that they have high voltage ratings. The diodes are rated at 2kV w hile the ceramic disc capacitors are rated at 3kV. When assembling th is board, install the 6 diodes first , fo ll owed by the capacitors. Note that diode D3 hangs off the board slightly on one side, to clear one of the .0lµ F capacitors . The 1Mn resistor is mounted vertically, to save space. The 33kn 2W ballast resistor is not wired in at th is stage - that is done later wh en the circuit is co nnected to the laser tube. Wh en the rectifi er board is complete, it can be connected to the inverter board with two short links of tinned copper w ire. Th e d iagram of Fig.3 and the photos show how they go together. Initial tests By thi s time , you 'll probably be itc hing to do a test ru n an d yes, you can do so, prov ided yo u have a 12V NO\' f•:/1 1/lE/l 1990 27 laser tube are laid out on your workbench or table which must have a safe insulating surface. Connect the two input leads the battery and the laser tube should fire up immediately. If not, disconnect and leave the unit for a few minutes, to allow the high voltage capacitors to completely discharge. Remember, they can give you a substantial shock, even if no power is applied to the circuit. Once the capacitors have discharged, you can safely check your work and rectify any mistakes. Battery pack The laser & the two PC boards are simply slid into the electrical conduit. Note the special cutout for the pushbutton switch. Wrap the laser tube in a small piece of corrugated cardboard to centre it in the conduit & hold it in position. power supply which can deliver about an amp or so. Before you think about connecting the power supply though, the laser tube must be connected, together with the in-line 33kQ ZW ballast resistor. Notice that the laser tube is polarised. The negative electrode is the one connected to the internal metal shield. The negative wire from the rectifier board goes to the negative electrode. The positive wire, from the 5W resistor end of the rectifier board, connects to the positive electrode of the laser tube via the 33kQ ZW ballast resistor. That done , check all your work carefully. The unit is now ready for testing. Before you do that though, make sure that both boards and the The 12V battery pack is made up from 10 1.2V AA size cells. These are soldered in series, in two groups of four and one group of two, as shown in the battery pack diagram in Fig.4. These are then packed (squeezed tightly is probably a better description!) into a 184mm length of 40mm OD electrical conduit. The endplates are made of 10mm-thick Perspex, drilled to take small fixing screws. One of the end plates is drilled to take a polarised male socket for the DC connections. Before the batteries are finally inserted into the electrical conduit, a layer of card or other insulating material is placed between each group of cells, to avoid the possibility of shorts. Laser head As an alternative to the nicads, you can use a 12V sealed lead acid battery housed in a plastic case as shown here. This will give longer battery life than the nicads but the arrangement is not as convenient. 28 SILICON CHIP The laser tube and its driving circuitry are also mounted in a section of 40mm OD electrical conduit, 304mm long. This also has 10mmthick Perspex end plates. One of these, mounted at the laser tube end, has a 6mm hole drilled right through it, to avoid any obstruction of the laser light. The other end plate carries a female polarised socket, to match the one on the battery pack. A hole needs to be cut for the pushbutton switch 100mm from one ertd of the conduit. The switch is a pushfit into a specially shaped cutout, roughly 13mm by 12mm. You'll need to do it by drilling the outline and then finishing with a small rectangular file. The laser tube and the accompanying printed boards are a comfortable fit into the conduit. Before they are inserted though, you'll need to pack some pliant insulating material, such as pieces of corrugated cardboard, around the laser tube so that it is Thia computer and electronic game Joyaliclr la c/4WJt1y t»algned for two handad oparalion. Th/a not only helf» to lncre- control and accuracy but a/ao prolong• playing tin» by reducing hand fatigue that can be auociaflHI with nonnal eing/a hand operated unlla. The JSC-5 la e/ao t»elgned .a the handgripe can eaeily be reated on a fable or olhH flat ~~:::;..' eurfece for .,abilizing the unit during uee. It la compatible with moat computera Including -.-+-,,Ametrad, Atari, Commodore •nd ~ E LECTRONICS SOUND AUSTRALIA Your P.A. Accessory Specialist The end plates for the plastic conduit are made from lOmm-thick Perspex, drilled to take small fixing screws. This particular end plate carries the polarised DC power socket. centrally located in the conduit. Next, the wires for the switch are fed through the conduit and out through the switch hole. The wires are soldered to the switch and then the laser tube and the PC boards are installed in the conduit. The DC input wires are soldered to the polarised female socket and the two endplates are fitted. Finally, the laser head and the battery pack are fitted together by a standard double female plastic fitting which has an internal diameter of 40mm - a snug fit over the conduit. Now plug the two units together, push the switch and your Laser Pointer STEEL SPEAKER GRILLES CHROME CATCHES 5'· $ 8.95 6"- $ 9.95 Large Lockable $9.95 8'- $11.95 10' - $15.95 Small Lockable $4.95 12'- $19.95 15"- $23.95 STEEL SPEAKER 18"- $34.95 Clamps for GRILLES Grilles Pk4- $2.95 5' $8.95 STEEL DISHES Suit 1 x Male XLR + Female XLR $4.95 As above also 2 x 1/4" Sockets Suit 2 x 1/4' Sockets PLASTIC DISHES Suit 2 X 1/4' Sockets $3.95 $5.95 $4.95 PLASTIC CORNERS Large Corner/Foot$2.95 Large Stackable$2.95 Large lnterlocking$1.95 Medium lnterlocking$2.95 Extrusion for above $5.95/M 6' Strap $ 1.95 8' Strap 10· Strap $ 4.95 8' Nylon Briefcase Style Chest Handle Metal Recessed Spring Handle $ 2.45 $ 2.95 $ 2.95 $ 5.95 $12.95 HEAVY DUTY CARPETED ROAD CASES 4 Unit $100 .00 6 Unit $115.00 8 Unit $135.00 10 Unit $155.00 12 Unit $175.00 This photo shows how the AA nicad cells are shoe-horned into the electrical conduit. Rack Cases can be made to order in any size and any colour carpet. MICROPHONE WINDSHIELDS BLACK, YELLOW, REO , BLUE, ORANGE ALL $5.50ea RACK HANDLES. GOOSE NECKS, CABLES. CONNECTORS and lots more available Please Call for a Catalogue SOUND AUSTRALIA 28 Walker S~. Dandenong, VIC, 3175 Telephone: (03) 791 1622 Where to get the kit Kits tor this project are available from Oatley Electronics. The complete kit for the laser head, including a 0.5-0.8mW tube, is $189.00. With a 1-1.5mW tube, the price is $209.00. The battery pack is $29.90. Certified postage and packing for the above items is $8.00. Also available is a 12V 6.5A.h sealed lead acid battery for $27.90. You can contact Oatley Electronics by phone on (02) 579 4985 or by post at PO Box 89, Oatley, NSW 2223. At Last!!! Public Address & 11 ,It1 Hi Fi Combined Ill This is the business end of the laser, showing the Perspex end plate with a hole drilled though it. should "laze" away. Have fun but remember our warnings about looking into the laser tube while it is operating. Remember too that the circuit operates at high voltages and that some of the capacitors can remain charged for quite some time after the power is turned off. ~ It t\ . 'I Now you can havw Hi R qulllity audio anywhe,.., The SP352L T -,,.llkera haw, their own on board 100 \'OIi IIM x'forme,.. to Ol!WrC~ long, crowded cab/a ruM. Theee speaker• can be connected up to eny 700 11011 line output on moet mono public •ddratul amp/lW.,.. If true etereo ie required they can ew,n be hooked up to a domealic Hi R amplifier with the aid of euy to lnela/1 step up tranefonnera. lt»al for office and warehouee eetupe or even if you llimp/y want H R audio piped through to your ewimming pool and backyard. The SP352L re ere t»eigned around a high Impact black cabinet with ~ I, mete/ n»eh gr/I,. and coma ELECTRONICS with mounting bracketa. I' ' ''. 'l .aD Tl.'1111\. ft NOVEMBER 1990 29 * FINANCIAL SUBSCRIBERS ON 12TH DECEMBER WILL BE INCLUDED OVER _, , $6500 Bose's radical new Lifestyle Music System is the great prize to be won. It comprises the Music Centre and one RF remote control (pictured), the Bose Acoustimass Powered Speaker System and a pair of Bose Lifestyle Powered Speakers (pictured). By taking out a subscription you could enjoy the benefits of this radical new music system which does not clutter up your living space with bulky hifi equipment and enables you to listen to two program sources at the- same time, in two zones, in your home. OFFER ENDS 30TH NOVEMBER 1990 30 SILICON CHIP WORTH OF PRIZES MUST BE WON - TM ® PLUS EACH MONTH ONE PAIR OF HIGH PERFORMANCE BOSE 101 MUSIC MONITOR SPEAKERS 3 SUBSCRIPTION PACKS FROM SILICON CHIP As part of this promotion, one pair of Bose 101 Music Monitor speakers, valued at $450, will be given away each month to a lucky subscriber. And even if you do win a pair of these speakers, you still go into the draw for the Bose Lifestyle Music System. Also each month, 3 new subscribers will get a SILICON CHIP subscription pack for free. This comprises a one year subscription to SILICON CHIP, one SILICON CHIP binder and one SILICON CHIP T-shirt in your size. Effectively, you get your annual subscription fee of $42 back and still go into the draw for the Bose Music System. HOW TO ENTER All current subscribers to SILICON CHIP at 1 2th December 1 990 are already in the draw. By taking a further one or two year subscription, they get another one or two entries . New subscribers enter by filling out the subscription coupon elsewhere in this issue and sending it together with their remittance of $42 (cheque, postal note or credit card authorisation) to SILICON CHIP, PO Box 139, Collaroy, NSW 2097. Or fax it with a credit card authorisation to (02) 979 6503. (1). The compell!1on 1s open only to Australtan residents with a aur rent_ renewed or extendecl subscr1 pt 1on received by the last mar! en 30th November t 99 0. (2) Subscnbe1s extendmg for an additional year arc entitled to two entries. (3). Subscribers wit h a two year subscrIptmn are ent itl ed to !wo entries (4) En tries received after the closing date wil l not be 111cluded . (5) Employees of Siheon Chip Pu!Jl1cat1ons Ply Ltd c1nd Bose ,%stralia lnG and their larnilles are not eligible to enter (6). Soutt1 Au stI alIan residents do not tiave to purnt1ase a subscr1p t10J1 to enter but may enter on1y om:e by subm1ttmq th eir mime . ad RULES & CONDITIONS di ess ano a hand drawn lacsm11le of the subscnptmn to Silicon Ch ip Publlcalrons Pl v Ltd. PO Box t 39. Collaroy. NSW 2097 (7). Prize s are not tran sferable or exchangeable and may not be con verted to cash (8). l he Judge s· decision 1s !1m1I and no conespondence will be entered into (9) The description ol the competItmn and mstrw;tIons on t1ow 10 enter form a part of the ccmpetIt Ion cond1t1c~s . (1 0) The com-pet 1tIon beqins on 29th Augu st 1990 and closes w ith the last mail on 30th November. 1990. The draw will take place in Sydney on 17th December, 1990 and the wInnc1 will be notified by lettergram . The winner w,1 I also be announced in The Australian on 20th Decembe1. 1990 and in a late1 issue of SIucoN CH!P. (11 ). The maior prize 1s one Bose Lifestyle Music System and the total value of all prizes offe red is $6735.00. The promoter is Silicon Cl11p Publications Pty Ltd , Unit 39/5 Po nderosa Parado. Warriewood NSW 2102 Permit TC90l2565 issued under the Lotteries and Art Unions Act. 1901: Raffles Bingo Permrt Board Perm it 90/1668 issued on t 618/90 . ACT Permit No 90/1077 issued under !he Lotteries 01 dinance, 1964. NT Perm it NT093 4l90 issued undeJ Lotteries and Gam ing Act NOVEMBER 1990 31 CIRCUIT NOTEBOOK Interesting circuit ideas which we have checked but not built and tested. Contributions from readers are welcome and will be paid for at standard rates. r-----------------------------T-----------------------~ I 10k I I PEAK DETECTOR I ,------.....--.w,,~----------, I I I I I 15k : I INPUT + 1~ I I IOUTPUT ><-+-t_,...1-''l'M--.-----, I I I ~------::1 I _ I I r15 v____ I ~i 1~ -15V L___________ I I I : _ ___ _____ J SAMPLE AND HOLD I +15V I L ---------------------- r---.t * : I I I I _j +15V 08 +15V 1N914I -15V 1M 10k 5.6k 03 1N914 .,. -15V 1M 3.3k .,. IC6 * SEE TEXT Low frequency sample & hold circuit This sample-and-hold circuit was designed specifically to measure the amplitude of very low frequency signals (below O. lHz) and to provide a steady reading on a moving coil meter. It should in fact give an accurate reading of the peak value of almost any signal with a frequency of O. lHz to lOkHz, although square waves might cause problems. The circuit can be broadly divided into three sections: a peak detector based on ICl & ICZ , a sample and hold circuit based on IC4 & IC5, and some control circuitry involving IC3 & IC6. The peak detector captures negative going peaks and stores the voltage in the O.lµF capacitor on ICZ's input. This peak value is then sampled by the sample and hold section (IC4 & IC5) when the input sig32 SILICON CHIP t nal is still negative but swinging positive. This sampled value is then held while the input signal is positive and during the next peak detect period. At positive going zero crossings, the peak detector is reset by Ql which is driven by IC3 and QZ to prepare it for detection of the next peak. Comparator IC6 keeps the sample and hold circuit (IC4, IC5 & Q3) in the hold mode while the peak detector is capturing the next peak. The result is a flicker free meter reading at all but very low frequencies. The circuit should perform well with almost any .periodic signal (except possibly square waves) with input amplitudes from 0.1 V to 10V. The prototype used FET-input op amps (LF351s) for IC1-IC6 but for higher operating frequencies, comparators (eg, LM393) are recommended for IC3 and IC6. The O. lµF "hold" capacitors at the inputs of ICZ and IC5 must be low leakage types so low voltage ceramics are not recommended (ordinary old greencaps seem to work just fine). Phil Denniss, University of Sydney, NSW. ($30) Single chip low battery alarm Here are a couple of handy circuits for use with 12V batteries. Fig.1 is just about the simplest lowbattery alarm you can get. It's based on the lntersil ICL 821 lCPA IC (from Geoff Wood Electronics). Multi-turn trimpot VRl sets the trip point for the circuit, while the lMQ resistor between pins 2 and 3 sets the hysteresis. When the low voltage point is reached, pin 4 goes low and transistor Ql turns on and sounds the piezo alarm (eg, DSE Cat L-7024). +5V ANTENNA ZD1 -, 3.3V 1W .01- .01- + + 4.7pF'- 47pF .001 100k 47pF F II IC1 BA1404 X1 38kHz~= 10pF I .0033 14 10 03 1N4001 FDU=-'-T_ _ _ _ +5V 0--0 240VAC VAR1· 270V 0.1 2.7k 13 12 330pF100k .001.J. ,. FM stereo test tone transmitter This FM stereo test tone transmitter could be useful for testing and aligning FM stereo receivers. It uses two transistor oscillator circuits to drive the left and right inputs of the BA1404 Stereo FM Transmitter IC originally featured in the October 1988 issue of SILICON CHIP. Ql and QZ, together with their associated RC feedback networks, form two phase shift oscillators. Using the values shown, Ql oscillates at 1.5kHz while QZ oscillates at 550Hz to provide the test tones. The frequency of these tones can be altered by changing the .00BZµF and .0033µF capacitors, if necessary. The outputs of these phase shift oscillators appear at the emitters of Ql and QZ and are fed to the BA1404 stereo FM transmitter stage (ICl) via switch SZ. This switch allows the tone frequency fed to each channel to be swapped over. Switch Sl selects between either the left or right tones, or can be used to select both tones. It does this simply by switching the supply rail to each phase shift oscillator via isolating diodes D1 and DZ. Power for the oscillator circuits is derived via a mains transformer, D3 .------...------------o+V ,-------...-----------0+12v 100k 39k and a 5V 3-terminal regulator (7805). A 1.7V rail for ICl is derived via zener diode ZDL Construction and alignment of the transmitter stage (ICl) is exactly as described in the October 1988 issue, except that Cl, VRl and VRZ are removed from the original circuit. The remainder of the circuitry can be built up on a small piece of Veroboard. The antenna for the prototype consisted of a' piece of blank PCB material mounted face down inside the plastic case. LZ should then be adjusted after the antenna is in place. Greg Freeman, Nairne, SA. ($20) 100k 01 BC55B ~~~~-----_,,_.. IC1 ICL8211PA 1M • O TO ~LOAD ALARM --------------+--oov Fig.1 The point at which the alarm trips will depend on your application but 11.5V will suit most situations. Once tripped, the alarm continues sounding until it is disconnected or until you start charging. 01 BC327 01 1N914 Fig.2 Fig.2 shows how the circuit can be modified to automatically disconnect the load when the low-voltage trip point is reached. It will be especially useful where the battery is used to power appliances that always seem I to be accidentally left on. In this case, when pin 4 goes low, Ql turns on RLYl and so the relay contacts open. Peter King, Airlie Beach, Qld. ($25) NOVEMBER 1990 33 t: L t:.\,,., I HVI \ I I L , ~ TL,l-\t1 CL C V t M Ul',I IL,v,JM l L,t v , C: L CV L M Vl \1 1\.,.::),.,.11-\ TL,f-\M C LC \., I n Vl 'l l '-'.:>,.JI-\. I \.,Mn C LCV I t1 Vl\lll..,v,,Jf-\ I 1..,/-"\M CL C V I n V l \1 11..,0vM T V M n C:L C \., I nVl\1 11..,v,,J/"\ 1\.,/"\n L LC V I MVl '\1 1\.., .,;:, \JI"'\ I Vf"\n C::..L CV J nV l \111.., ..:: ..,, ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJA YCAR ELECTRONICS JAYCAR ELECTRONIC~ J ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ~LECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONIC~ J I11i11 l~v·············· ·TH,.N°r<ING··-_1F ·auv1·Nti'•A··ca··RA010··AND . 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Full single sideband upper and lower operation • Noise blanker as well as a • SWR meter • scanner • supplied with DC power lead. quality dynamic mic and mic clip plus mounting bracket. • Dimensions 180(W) x 256(D) x55(H)mm Cat. DC-2015 :LECTROf' . • Dimensions 131(W)x 140(D) x 31(H)mm (compact!) • Supplied with dynamic mic, DC power lead. mic clip, mounting :LECTRor. brackets ett :LECTROf' Cat. DC-2000 • • Dimensions 146(W) x 100(D) x 51(H)mm :LECTROf' Cat DC-2010 :LECTROf'. :LECTROf' ALL THIS FOR ONL GREAT VALUE :LECTROf' /l:\11; ~)\'~v'i"'/ I /27,; '!h ,._,,, S /.-/< v y '>: :LECTROf'. h,,,,_ ,,~,,,,,,,.,,,,.,,..,,,,..,,,,_,,,, "'-'.<611' : LECTROf', -lM' o/ :LECTROf' ~ ~ £ ~.'' , '.'' I' ' , ., , ,,,(t,,J ~ ;}J :LECTRO!' ,, ... ,, . . . . .. . . , , _ j "" , ' ......... , ,_ : LECTRO,' :. ,.: ', _.; "'"""~9 i»-. • , , - ; ; _, \_, ,_ :LECTRDr. :LECTROf' :LECTRO~ : LECTRO~ : LECTRDr. High perfonmance helical fibreglass mobile whips designed and manufactured in Australia to suit our most rugged conditions. All with standard 5/16' 28 TPI thread :LECTROf' :LECTROf' Cat. DC-2030 :LECTROf' :LECTROf' cat. Dc-20so :LECTROf' ':'. :LECTROf' .. $89 95 y $129 -.< :· ~ z ,_ . \._:~ :, ': - $<JA;!.',« N,, s AT $279 ~}'° ,, ~(:It =:; Vo':."-.',._:.. .,,~..:. I 27MHz Antennas $14.95 =-==-====·===========::::i.c:C $17 .95 3 foot Helical Whip 5 foot Helical Whip 10 1 1 1111 ~ ~!~::::M• '" •~~~::~::~:~: ;:'.::~,::SION ~PRl:6.• .. •.Q;1~K.;iS~ ,LEcrnm !~i ,.. l_i,i. :LECTRO~ MOUNT BASE ~i~)~~~!:r ~O ~,g:___ _G'> -. - luggage racks. ~!f ' LECTRO~ !:.: ~~-~e/DC-3065 ' LECTRO~ . :LECTRO~ Cat. DC-3075 :LECTRO~ :LECTRO~ :LECTRO~. $39.9!,; r. · ·:___ __ _. .- . $8.95 \t~g;=~ a o, Heavy duty die cast construction with locking adjustable tilt. \ligi~g~ Complete with alien key. Cat DC-3070 -LECTRO• ::LECTRO~ " . $16 • 9 5 l~ffii I;~;1s~~~ =~ \t~g=~ \! -:itJ i' '• __..- Add extra flexibility to your antenna with this 16' 28TPI spring. Cat DC-3084 ., 4 ❖ ~ :!,... _ ' ·· $7.95 Q ff;f~~moo;,oo~ FILTER "" ELECTRO . ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR El ECJBQNJCS.JAVCAR EIEC1ROI\IJCSIAYCAR - ""'" -~~· Cat. AS-3185 $24 95 Designed for use with AM and SSB transceivers. Ideal replacement complete with curly lead fitted with 4 pin plug. Cat. AM-4050 -------- 00 :LECTRO~ ·· :LECTRm /: UNIVERSAL DYNAMIC MICROPHONE Simple to use meter reads standing wave ratio to enable accurate matching between transmitter and antenna. Can be left in-line to Heavy duty- up to 25 watts with 8 ohm ,.L. ~ 50cm RGSB/U cable fitted with 2 x PL259 plugs. Use with SWR. etc. Cat. WC-1095 $12.95 f $12.95 ~ SWR METER !:?iit:r10NS for cable connection PATCH LEAD Push button breakoverfitting. Standard 5/16' 28TPI male/female fittings. Cat DC-3082 Standard 5/16' 28TPI base complete with 3 metres RG58/U coax terminated via a Pl259 plug Cat DC-3065 Simply press sown and twist to remove your antenna in a hurry. Standard 5/16' 28TPI male/female fitting Cat. DC-3080 $12.95 - - $13.95 ~ i i i:;~ ~: ~J;;:: !1l~i~~:~ ]:~~~:~~=~E :L : ~~:-~95 )~~g;=g~ 5/ FLIP FLOP SNAP-DOWN " GUTTER MOUNT BRACKET ' LECTRO~ :LECTRO~ :LECTRO~ :LECTRO~ Super strong magnet that won't let go. Don't be caught with the whimpy magnets that don't stick, Includes standard 5/16' 28TPI mount and . 5 metres of RG58/U coax fitted with PL259 plug Cat. DC-3072 SWA-1 ~ $22.95 fWl! Cf=J RU u r MICROPHONE CLIPS Mounting clips suit most microphones. . . __ .. . . . ELECTRONICSJA YCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS,JAYCAR El ECTRONICSJA'fCAR El ECIBONICSJAYCAR Prevents static high voltages damaging your equipment. . , Cat. PP-Q692 $3.95 ELECTRONICSJA YCAR ELECTRONICSJA YCAR ELECTRONICS JAYCAR ELECTRON ICE ._ ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICS JAYCAR ELECTRONIC~IJ, ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICS JAYCAR ELECTRONICE J, ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICS JAYCAR ELECTRONIC~!J, ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS JAYCAR ELECTRONIC~ U ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS JAYCAR ELECTRONIC~IJ, ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS JAYCAR ELECTRONICEjJ, ELECTRONICSJAVCAR El ECTRONICSJAYGAR fl ECTRONICS IAYC ACl i:1 i=rIAQNIC<,li This bushing strip is ideal for covering dangerous edges of panel holes. i.e. cut-outs. Designed to suit panels 1 1.5mm thick. The strip can easily be cut to length with a sharp knife or scissors. 1 meter pack. Cat. HP-0730 $1.95 II"\' ....,,..,n CLC:.\., I MVl 'fl\.,Ovf-\ T V/-\n CLCI.., I MUl'II\.,~ T\.,1-\M C LC\., I MVl'O\ . , ~ TVAN t:.LCl., I MUl'lll\.,OvA f\.,1-\M CLC\., I MUl"-411,..,\),J/-\ T\.,l\t1 c u :1..., I HUNIL,,:,.JI-\ T\.,AH t:.LJ:l., I HUNfl.,;')JA JL,I\H t:Lt:V I HUN I~ Yl,;A H t:LtC I HC JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS.JAYCAR ELECTRONICSJAYCAR ELECTR< IAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJA YCAR ELECTRONICS.JAYCAR ELECTRONICSJAYCAR ELECTR( \ ........ ........... .... .... ........................... ... .. ............. ...... ...... ..... .................................................................... ;!!1!1!1!1!1!1:1:BB BBBBB!lJR ·cAR ELECTR< i~i:i;~ ;;nE,,v-,,.:,.:, 11 ~.~~;;~;h:ri~.. 16 CHANNEL AUDIO MIXERS ~A, R ErL;E;C~T:R:( Cat KC-5065 Ref: Silicon Chip March 1990 Comprehensive battery charger for GEL batteries. Charges both 6 & 12 volt batteries. Charging rates: 1.2Ah (250nA), 2.5Ah (520mA). 4.5Ah (!nlmA). 5Ah (1.2A). 15Ah (3A). arges our range of GEL batteries. Includes PCB and all rd components. No box or front nel. Transormer not $1399 12 CHANNEL PANEL KIT Cat. KC-5064 $999 CONSOLE CHASSIS/POWER SUPPLY1I Cat. KC-5070 £. :.: if~~:~RD :;:: Dam rn1 !\ EQUALISER/METER BOARD ! ~~:C"80MD A JAYCAR = .......-"-' U~·=•,u=y ~~~.~~.~·~·~··~·~..... . . . .... ........... 1 i.i.j,l..i. . .J ffill ·:mr FM RADIO INTERCOM .,. mr Pro Series Power Amp Kit ;$,f5[9~:9r::::"~~~::: ' I~f§~~~~;E~n: ii CAR ELECTRC 1 ICiA~R\E\L1E!c~:T;R;C1 at a time. It operates on FM and even includes an FM · tuner. Kit includes PCB. box, front panel, tuning label, mic inserts, speakers. plugs and sockets. mic cable and all ·:::::::::::::m~: :•,:.:::: CAR ELECTRC CAR ELECTRC CAR ELECTRC CAR ELECTRC ULTIMETE I KIT Ref: Silicon Chip Nov 1989 An excellent way to learn about electronics and the result will be a quality analogue multimeter you can use for years. Ideal for educational areas. schools. etc. The unit is partially assembled with some soldering required. The 20V/ohm unit has everything included plus leads/probes and battery. Cat. KC-5058 $34.95 ~::::her :t 14095 $ 'f~MiNiATUREFM ;;; Car Alarm Kit THOUSANDS ( TRANSMITTER :if Ref EA Aug 1988 SOLD f KIT Ref: ETI December 1985 :,: [; The car alarm that goes ·.•·,':,' • ~~:ii~~ii:·l~~~n~es~~~~ t KA 1675 :Jij!! :,:•:: C ::i $34 .95 :i~~~:~ !~:~:~ t~~ ~c~~~! ~~I ·:·: •:fb·•·•·•·";:.-:-:❖:•:•:•:•:•:•:•:•:•:•:•:•:•:•:·:❖:•:•:•:•:•:,:,:,:-: ,,:❖:·:•:•.❖:·:,:•:•:••··.. CONCORD VISA This unit is a 2 transistor, 2 stage I HURSTVILLE specified parts and makes an ideal, mexpensive begmners kit ...','.. ,. CAT KE-7411 ifit"::l':~r _:.:..,:. .....•,::::::::::,,•,.• ·•·•·••:•:•:':,:,:,:.:,:.:,:,:•:•:•:•:•:·:·:,:,:·;W .,.;,:,:-.·:,:,•·:•:•:•:•,•:' :AR ELECTRO :AR ELECTRO 3~= ~~~g=g ~Iii -,1 :r=·DIGITAL VOICE jjj RECORDER · i i compatible computer on your TV. Cat KA-1720 $ i,.: $9.95 .,:. ,. :AR ELECTRC : AR ELECTRO : AR ELECTRO 39095 )! :,.I,':,.; Refer EA August 1989 Use your IBM :AR ELECTRO ;1= :t:g~=g f ~1= ~~~g;~g i1 ~1~ ~t~g;=g )j Ref: Silicon Chip DEC 1989 ~~:;~:~~ 0 ;~~~~ it:~o~ ~~~::!ges or ganged together for 2 minutes. Ki t includes PCB and all ;:;:; ;AR ELECTRO components. Sf)8aker, mic. insert and box not included. ] :AR ELECTRO Cat.KC-5072 ;AR ELECTRO $125 \(:=:::::::::::,::....,.;❖:❖:-:,:,:-:,:,:,:,;❖.: :-:-:-:-:-:❖:❖:•:-:,: ,:,:,:❖:•:❖•• -<.. ::-:,:-.(·· ·•·•·•·•· ·•·: :.;;.;.,.:•:•:•:•:•:•X•, • .. •:❖•❖ .t ::-.,; :❖:-:,:,: ................. .... ....... ,,:-:,:.. ~...,..... 117YorkSt.(02)2671614Mon-Fri 8.30 - 5.30 Thurs 8.30 pm - Sat 9 - 12 355 Church St (Cnr. Victoria Rd) 102) 683 '3377 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 9.00 - 12 121 Forest Rd 102) 570 7000 Mon-Fri 9 - 5.30 Thurs 8.30 pm - Sat 9 - 4 BURANDAQLD MELB OURNE-CITY SPRINGVALE VIC ADELAIDE S.A. .i i - ~~w s~= ~t~gi=g 188 Pacific Hwy (Cnr. Bellevue Ave) (02) 439 4799- Mon-Fri 9 - 5.30 Thurs 8.30 - Sat 9 - 4pm 144 Logan Rd (07) 393 0777 Mon-Fri 9 - 5.30 Thurs 8.30 - Sat 9 - 12 Shop 2, 45 A'Beckett St City (03) 663 2030 Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 - 12 887-889 Springvale Road Mulgrave (03) 547 1022 Nr Cnr. Dandenong Road Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9- 2 190 Wright Street (Cnr Selby Street) 108) 231 7355 Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 - 12 ; AR ELECTRO ; AR ELECTRO ;AR ELECTRO :AR ELECTRO ;AR ELECTRO ;AR ELECTRO ;AR ELECTRO ;AR ELECTRO ;AR ELECTRO ;AR ELECTRO :AR ELECTRO ;AR ELECTRO ;AR ELECTRO ;AR ELECTRO ;AR ELECTRO ;AR ELECTRO ; AR ELECTRO ; AR ELECTRO ;AR ELECTRO .. 11 Q 1=1 crTnr. !CARELECTRI '":''-' !l~M~n":'!c~LC~'-'"'!,~n\"! v!'!' , .,!'!"v~<>J"l'lM!"!,'!"'-'~ ""!!"!!'cL!"!c!!''-'~'~ " v~,~"~ "~ "'-"' '!'!"!'''-'~"~"!!"c!'!!L'!'L~V'!'!,n!!!v'-'"!!!''-'~"'-"' '!!!!!!'!'!,v"M"n!'l!L'!'L"!"'Lv!'!'!'!! ,n'!'!'v!!'l,.!!'!,v'!!!~ !'!!M"'•!"!'v!!!= !!'t""!'L"!"'LL!■,v~,,n~ v■,.9.'!'[l ,v!!.!!-,,.,n ~,"!"'v~M\!! nl!'lc!■ .Lcl-l'v!"!',\!!nv !"!',!'!.,l!"!v'!!!!'!!!"l!!!ell!l'!lll~l'!!"!!!!'!!~~~C"'L'C'!ll! 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YCAR ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICS.JA YCAR ELECTRONICSJAYCAR A.YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR A.YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ~LECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS.JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRI ELECTRONICSJAYCAR ELECTRI ELECTRONICSJAYCAR ELECTRI ELECTRONICS.JA YCAR ELECTRI ELECTRONICSJAYCAR ELECTRI ELECTRONICSJAYCAR ELECTRI VINTAGE RADIO By JOHN HILL Testing old radio valves The best way to check old valves is to use a valve tester but these are now difficult to obtain. Fortunately, there are other methods that will allow you to sort your valves into good & bad categories. One problem with radio valves is that while they may look OK on the outside, it can be rather difficult to assess what they are really like on the inside - and that's where it counts. Most vintage radio enthusiasts are forced to use secondhand valves and there is often no means available to find out just how good or how bad these old valves may be. As mentioned in previous articles, a valve tester is a very useful instrument that has been specially designed to measure cathode emission. Unfortunately, a valve cathode do.es not emit electrons indefinitely and only has a limited useful life. Gradually, over a period of years, valves get weaker and weaker until they finally cease to work efficiently. Many an old worn-out valve will still light up and function , but that doesn 't necessarily mean that it is in good condition. A valve tester will check this aspect of valve performance. Valves can have other faults apart from poor cathode emission. The heaters can burn out or internal elements can warp with the heat and alter the valve 's characteristics. Sometimes, the parts can distort to such an extent that adjacent electrodes touch If you don't have a valve tester, you can check whether or not a valve still works by plugging it into a working receiver. However, this method won't reveal weak valves in the RF stages due to the compensating action of AGC (automatic gain control). 38 SILICON CHIP and short circuit. Dropping a valve can also initiate any of these problems. What with one thing and another, untested secondhand valves are a bit suspect and can present a few headaches for vintage radio enthusiasts. Valve testers A valve tester can pick up most of these problems. A good tester has a switch connected to each base pin so that all individual elements can be checked. Internal short circuits can also be detected and are indicated by a light on the control panel. As stated earlier, a valve tester is a very useful instrument. Valve testers are relatively simple in principle, but somewhat complex in construction regarding switching and wiring. Basically, a tester ties all the grids, anodes and diodes of a valve together and measures the strength of the cathode emission to all of these elements collectively. Disconnecting any one element should cause the meter needle to drop, thus proving that it is both operative and connected into circuit. A valve characteristics tester is a similar instrument to a valve tester but is considerably more complex. In simple terms, a valve characteristics tester sets up the valve so that it is tested under actual working conditions. Screen grids and anodes are loaded up to normal working voltages and control grids can also be set up with their specified negative bias. A valve set up in such a manner can be properly checked under working conditions. This is not the case with a standard valve tester. Finding a working valve tester of any type is not an easy task. So far, I have collected four testers but only one is in good working order. An- Service Tip Symptom: valves light up. HT is present but no audio response when the grid of the audio valve is touched. Cause: the most common fault is an open circuit primary on the output (speaker) transformer. The output valve gets excessively hot and the screen grid may glow if the set is left switched on. Replace the output transformer. The audio output valve should also be replaced as the heat distorts the valve elements. and this changes the characteristics of the valve. Vintage radio service tip is supplied by Resurrection Radio, 51 Chapel St, Windsor, Vic 3181. This Heathkit Tube Checker is the author's only working valve tester. Its main disadvantage is that it is unable to accommodate European-type valve bases, although suitable adaptors could be made up with very little effort. This AVO Valve Characteristic Meter is a very up-market instrument (what a shame it doesn't work). A valve characteristics tester checks a valve under simulated working conditions. other problem frequently encountered with valve testers is that their instruction manuals have long been lost and if you are unfamiliar with these instruments, you simply won't know how it functions or how to use it. My working tester is an American Heathkit unit which is of comparatively recent vintage. It was originally bought in kit form and has been assembled very professionally. It is a useful and well made instrument. Being of American design , the Heathkit valve tester has the disad- vantage of not having sockets that will test British and European valves; eg, British 4-pin and 5-pin types and those horrible P-base or side contact valves. Adaptors could be made without too much effort but the small volume of "foreign" valves requiring testing has not made this worthwhile. The Heathkit scroll Suitable test data was also a problem with my Heathkit tester. This particular tester uses a "scroll" which is located inside the unit behind a nar- row window on the control panel. The idea is to wind the paper scroll around until the valve type to be tested shows in the window, after which all the necessary information relating to that valve can be read off. But although that sounds a reasonable idea in theory, it did not work so well in practice. First, the scroll was not tracking straight and one edge of it was beginning to crumple up. Second, being a relatively late model tester, the scroll had mostly late model valves on it. Common vintage radio valves such as 6A8, 6D6, 687 and dozens of other valves from the 1930s and 1940s were simply not on the scroll. Fortunately, the instruction manual on how to assemble the Heathkit came with the tester and the manual also included information on how to set up the instrument for newly developed valves that were not listed on the scroll. Naturally, the same technique could be used for the older valve types not listed. Compiling a comprehensive data test sheet was a long and drawn out process. The tester was set up to read 100% with new valves. Wherever possible, three new valves (preferably of different manufacture) were used and an average reading decided on - not that new valves vary much from one brand to another. In cases where no new valves were available for comparison, the "intelligent guess" method was used instead. That statement may sound a trifle NOVEMBER 1990 39 While a valve tester is simple in theory, it can be quite complicated regarding internal wiring and switching. Wasn't the printed circuit board a great invention? unscientific but is not as bad as it may appear. I had 23 number 42 output valves to test and no new valve as a guide. It seemed reasonable to assume that some of these valves could well be in as new condition so the tester was set up to read around 95 percent on the better valves. Some time later when a couple of new valves were tested, the guesstimated test data was found to be spot on. For smaller batches of valves, the intelligent guess method of establishing emission levels becomes less accurate. Even so, it does give some indication and provides ·a comparative figure to work with until a new valve becomes available. Providing one has reasonably accurate valve data, a valve tester is an extremely convenient device when servicing a broken down radio. Testing a set of unknown valves is a good starting point and will either clear each valve of suspicion or indicate good reasons for their replacement. Substitution checks In the days before the valve tester, the best test that could be arranged was to plug the valves into working radios to find out if they would operate (the substitution test). This was This is the scroll from the Heathkit valve tester. Very few vintage radio valves were on it and a comprehensive test data sheet had to be compiled for the older types. 40 SILICON CHIP accompanied by giving the glass envelope a few dongs (with a rubber danger) to show up any near short circuits between the valve elements. Sometimes a valve will arc internally when struck in this manner, indicating that some of the high voltage elements are uncomfortably close together. While such a test is better than no test at all, it gives little indication as to the degree of cathode emission. It simply tells you whether or not the valve is working. Whether it is working well or is only in fair condition is often difficult to determine. One of the reasons for this is the fact that the AGC (automatic gain control) circuit compensates for weak signals and, to some extent, weak valves. This is particularly the case with valves used in the front end of a receiver; ie, radio frequency amplifiers, intermediate frequency amplifiers and frequency converters. When checking valves by the sub-. stitution method, make sure that the receiver is tuned to a relatively weak but steady signal; eg, a distant station in daylight hours. Checking valves under these conditions may be a little more meaningful. Another reason why substituting a valve may not be a reliable test is that the characteristics of a particular valve type must vary a little from valve to valve. Replacing a frequency converter, a radio frequency amplifier or an intermediate frequency amplifer valve can easily alter the tuning of Tapping a valve with a suitable donger often reveals internal faults and short circuits. You can make your own donger by fitting a couple of grommets to a pencil. Audio output and rectifier valves can be tested for serviceability using a working radio and a multimeter as described in the text. Although this won't give you a percentage readout, it does allow valves to be sorted into good and bad categories. flowing in the anode and screen grid circuits of an output pentacle are considerably greater and meter variations are much more obvious. Power rectifiers are also easy to check by the substitution method and this can be done with a DC voltmeter connected between the high tension supply and earth. Checking the voltage means that the receiver wiring does not have to be unsoldered as is the case when using a milliampere meter for measuring current flow. Again the testing process is quite simple. Rectifiers with good cathodes and plenty of emission will produce a much higher output voltage than rectifiers with poor emission. Although a percentage read out is not possible, the good performers can be easily separated from the bad, depending on the voltmeter reading. When it comes to valve testing, everything points in favour of a valve tester. But even these useful instruments are not infallible. A tester will . only indicate the emission level of a valve and whether or not it is likely to work. Whether it really works well can only be determined by further testing in a receiver. ~ Resurrection Radio This box of odd valves and other radio junk was obtained from the local flea market. Testing indicated that all but three valves were serviceable. the receiver and a perfectly good valve may appear to be worse than it is simply because the set is not aligned to suit that valve. Valves used in the audio section of a receiver respond to substitution testing better and a weak output valve that tests at about 30% will sound like a 30% valve when substituted for a good valve. Current measurements There is another technique that can be used to test valves and, once again, a working receiver is used. With this method, a milliampere meter is placed in the plate or cathode circuit and comparative readings on the meter will indicate differences in valve efficiency. A good valve will have more current flowing than a poor valve. Although such a set up will not give a percentage read out, it will at least allow a quantity of valves to be sorted into poor, good and excellent categories. Unfortunately this method of checking can get a bit vague with some valve types. In the case of a 6B6 triode, the anode or plate current is only about one milliamp, so the meter would need to be a very sensitive type with a digital readout if any significant variation in current is to be detected. On the other hand, the currents Vintage Wireless Specialists Repairs - Restoration - Sales Our skilled technicians offer QUALITY repairs and restoration. We also have a large stock of Bakelite and Timber radios fully restored and for SALE. Parts are available for the enthusiasts including over 900 valve types, high voltage capacitors, transformers, dial glasses, knobs, grille cloth etc . Circuit diagrams for most Australian makes and models. Send $5.00 plus SAE for our catalogue. WANTED - Valves , Radios , etc . purchased for CASH Call in to our Showroom at: 51 Chapel Street, Windsor,Vic 3181 PO Box 1116 Telephone: (03) 529 5639 NOVEMBER 1990 41 Low-cost model train controller Throw away that primitive rheostat controller. This low-cost unit offers much improved running for your model trains and features simulated inertia as well. By GREG SWAIN Most model train sets come supplied with a simple rheostat controller but this must be the worst type of throttle you can have. OK, so they 're cheap but that's about all they have going for them. On the debit side, they result in poor low-speed running characteristics, jack rabbit starts and a model that frequently slows (and even stalls) on curves and gradients. Why does the rheostat controller cause these problems? It's all to do with the fact that this type of controller simply consists of a variable resistor in series with the supply voltage to the track. It's job is to control the armature current of the motor. This in turn controls the torque produced by the motor and thus the speed of the model. This scheme works fine at high running speeds because the control resistance is quite small. It's mainly the back EMF produced by the motor that determines armature current in this situation, and so the speed will be virtually independent of load variations (due to gradients and curves, etc). It's at the low speed settings that we strike problems. The reason for this is simply that, to get the train to run at a lower speed, the resistance in series with the supply is increased. At very low speeds, the rheostat con- +12·1 8 V ~ - - - - - - - - - - - - - - - - - 1 . . . . . - - - - , B 01 BC337 1N4001 SPEED C VR1 5k 0 EOc VIEWED FROM BELOW BRAKE ~ BCE S1a S1b Constant voltage source 4700 FORWARD SZa FOR S2b 4700 TO TRACK BRAKE LEVEL VR3 1k REV SIMPLE TRAIN CONTROLLER WITH INERTIA Fig.t: the circuit is based on Darlington transistor pair Qt & Q2. These form an emitter follower which buffers the output of speed control potentiometer VRt. VR2 & the 4700µF capacitor provide throttle inertia while VR3 and the 470Q resistor set the braking inertia. Q3 provides overload protection by removing the drive to Qt when the voltage across the tQ resistors exceeds 0.6V. 42 SILICON CHIP troller behaves as a constant current source and this swamps out the otherwise beneficial effect of reduced back EMF as the motor slows. Let's take a closer look at this situation. Normally, when a motor slows down, its back EMF falls and the armature current rises, thus increasing the torque. However, because our rheostat controller is now behaving as a constant current source, it prevents the armature current from rising in response to this reduced back EMF. This reduces the torque of the motor just when we most need it and leads to the poor low-speed control characteristics mentioned earlier. Another problem with the rheostat controller is its poor voltage regulation. If the motor attempts to draw additional current in response to an increased load, the voltage across the resistance increases and so the track voltage falls. This reduced track voltage adds further to the low-speed running problems encountered with rheostat-type controllers. Finally, it's impossible to start a model train smoothly with a rheostat controller. That's because a motor requires a much larger armature current to start than it does to keep running. So what happ ens as the throttle is advanced? At some point, the motor suddenly starts and, once started, it quickly gathers speed. The result is a jack-rabbit start which hardly makes for realistic control. The answer to these problems is to use a controller that behaves as a constant voltage source at any given control setting. And that's precisely what this circuit does. It's really nothing more than a variable voltage power supply with a low output impedance. Because the controller has a low output impedance , the current through the armature now varies according to the back EMF and this leads to much improved torque at low run- Most of the parts are mounted on a small PC board which can be hidden under the layout. The controls can be mounted in a small plastic case to give a walkaround throttle or they can be mounted on the main control console. A substantial heatsink should be fitted to transistor Q2 (at the back of the board). ning speeds. This in turn leads to much improved control characteristics , eliminating the tendency for the model to slow down and stall on curves and gradients. A constant voltage source also overcomes the problem of jack rabbit starts. Unlike the previous situation, the armature can now draw significant current at low throttle settings (ie, at low track voltage) and so starting is much smoother and more realistic. Inertia & braking As a bonus , this new controller includes a couple of features to make your model behave just like the real thing. When you open the throttle on a real train, it doesn 't speed up immediately. Instead, it gradually builds up speed to match the new throttle setting. Similarly, when the brakes are applied, the train does not come to a "brick-wall " stop but slows down gradually. So , to make things more realistic , this low cost controller includes simulated inertia circuitry so that the track voltage builds up slowly when the throttle is wound up and drops slowly when the brake is applied. A couple of preset pots allow you to independently adjust the amount of inertia for throttle and brake to suit your layout. Finally, the controller includes output short circuit protection. This is necessary because short circuits can occur quite frequently in a model train layout; eg, if a loco becomes derailed. It's also easy to accidentally short circuit the track when you modify your layout. To overcome this problem, the con- troller automatically current limits when the track is short circuited and lights a LED to indicate the overload condition. How it works Now take a look at Fig.1 which shows all the circuit details. It's uses just three trarisistors plus a few other components. The input ·to the controller is unsmoothed DC of15-18Vand this voltage is tapped off by VR1 which is the throttle control. This voltage is then applied to the base of transistor Q1 via S1a, D1 , the inertia trimpot (VRZ) and the series 5.6kQ resistor. The voltage change on the base of Q1 is not instantaneous when VR1 is adjusted to a new setting, however. That's because it takes time for the 4700µF capacitor to charge up to the throttle voltage via D1 and VRZ. Instead, depending on the setting of VRZ , the train will build up speed gradually until the capacitor is full y NOVEMBER1990 43 less than 0.6V and so Q3 is off and has no effect on the circuit operation. However, if a short circuit occurs, the output current shoots up until there is 0.6V across the two H1 resistors. At this point, Q3 turns on and reduces the drive to the output stage, thus limiting the output current to about 1.2A. It also turns on LED 1 to indicate the overload condition. At the output, double-pole switch SZ is used to provide forward/reverse switching. It simply switches the supply polarity to the track. Diode DZ is included to protect the transistors from any spikes which may be generated by the loco motor or by track switching. Power for the circuit can be derived from any 12-18V unsmoothed TO TRACK Fig.2: install the parts on the PC board as shown here. Take care with component polarity and note that the metal tab of Q2 goes towards the edge of the board (see Fig.1 for transistor & LED pinouts). charged. Diode Dl prevents the 4700µF capacitor from discharging through VRl when the throttle setting is reduced. So VRZ and the 4700µF capacitor PARTS LIST 1 PC board (available from Electronic Toy Services) 1 5kQ linear potentiometer 2 1kQ PC-mounting trimpots 2 DPDT miniature toggle switches 1 heatsink (see text) 1 TO-220 mounting kit (mica washer plus insulating bush) Semiconductors 2 BC337 NPN transistors (01,03) 1 TIP41 NPN transistor (02) 2 1N4001 silicon diodes (D1 ,D2) 1 red LED (LED 1) Capacitors 1 4700µF 25VW PC electrolytic 1 47µF 25VW PC electrolytic Resistors (0.25W, 5%) 1 5.6kQ 1 470Q 21Q, 1W provide the simulated inertia feature for the throttle. Similarly, brake switch Slb and VR3, in conjunction with the 4700µF capacitor, provide the braking feature. When brake switch Slb is closed, the 4700µF capacitor slowly discharges via the 470Q resistor and VR3. Thus , the voltage on the base of Ql gradually reduces and so the train slows to a stop. Note that Sla switches out the throttle control (VRl) when the brake is applied. That's done for two reasons: (1) to eliminate the need to reduce VRl's setting to zero in order to stop the train; and (2) so that the train will gradually build up speed to its previous setting when the brake is released (assuming that VRl is not touched). VR3 sets the level of braking inertia. Transistors Ql and Q2 form a Darlington output stage and this stage is forward biassed as soon as the voltage on Ql 's base reaches 1.3V. These two transistors together function as a compound emitter follower, with QZ supplying current to the load via two parallel lQ resistors. Q3, LED 1 and the two parallel lQ resistors provide the overload protection feature. Nmmally, the voltage across the two lQ resistors will be MICA WASHER BUSH NUT \ \ :~~~ :s-1 scrw ~ DEVICE ' FINNED HEATSINK Fig.3: mounting details for the TIP41 transistor. Smear all mating surfaces with heatsink compound before bolting the assembly together, then use your multimeter to confirm that the metal tab of the transistor & the heatsink are correctly isolated. TO CONTROLLER Fig.4: if you don't already have a suitable power supply, this simple circuit will do the job. Use a power transformer with a 12V secondary that's rated at 60VA or more & take care with the mains wiring. RESISTOR COLOUR CODES D D D D 44 No. 1 1 2 SILICON CHIP Value 4-Band Code (5%) 5-Band Code (1%) 5.6kQ 470Q 1Q green blue red gold yellow violet brown gold brown black gold gold green blue black brown brown yellow violet black black brown brown black black silver brown DC supply. Most model enthusiasts will already have a suitable supply but if you don't, the circuit shown in Fig.4 will do the job. Construction There are a couple of choices when it comes to building this unit. Many modelling enthusiasts will prefer to retain their existing control console and so will bury the PC board under the layout. Others may want to fit VRl and the two switches into a small case to provide a walkaround throttle. This would then be linked to the PC board via a multi-way cable. Because each individual's requirements will vary, we'll simply show you how to assemble the PCB. Fig.2 shows all the details. You don't have to follow any particular order when installing the parts on the board but it's generally easier if you mount the smaller components first. Many of the components are polarised so be sure to orient them exactly as shown in Fig.2. These include the transistors, diodes, LED and electrolytic capacitors. Q2 is installed with its metal tab towards the edge of the board. Check the resistor values with your digital multimeter before installing them on the .board. Alternatively, refer to the accompanying table to read off their values from the colour codes. We mounted the LED directly on the board but it could also be mounted in some other location and connected by flying leads if that's more convenient. Rainbow cable can be used to wire up LED 1, S1 and VRl but use medium duty hook-up wire for the connections to S2, the track and the power supply. The prototype used trimpots to preset the throttle and braking inertia but you can substitute a couple of full-size potentiometers if you wish. These could be mounted on the front panel and linked to the PC board via flying leads. Heatsinking Because it can be required to dissipate quite a lot of power, a substantial heatsink must be fitted to Q2 (TIP32). A commercial finned heatsink with a rating of 2°C per watt would be satisfactory or you could bolt it to a sheet of aluminium (about 200 square cm should be OK). In either case, it's advisable to iso- To keep it cool, the metal tab of the TIP41 transistor (Q2) should be bolted to a substantial heatsink. Use a mica washer & insulating bush to electrically isolate the transistor from the heatsink as shown in Fig.3. late the metal tab of Q2 from the heatsink using a mica washer and insulating bush to prevent accidental short circuits (see Fig.3 ). However, you can bolt the transistor directly to the heatsink provided you make absolutely sure that the heatsink touches nothing else. If you elect to mount the board in a metal case, the case itself can be used for heatsinking. Be sure to isolate the tab of Q2 from the case though, otherwise the supply will be shorted out. Note: the metal tab of the transistor is connected to its collector. Testing To test the unit, connect up a power supply and check that the track voltage slowly increases (or decreases) to a new value each time the throttle (VRl) is varied. You can do this by monitoring the output across DZ. If this checks out, check that LED 1 lights if you momentarily short-circuit the output. It should go out again when the short-circuit is removed. If you strike problems, first check the voltage across the 4700µF capacitor. No voltage here? - check that Dl is oriented correctly, that Sla is closed and that Slb is open. Ql and Q2 can be checked by measuring their baseemitter voltages. In each case, you should get a reading of about 0.6V (assuming that there's at least 1.2V on Ql's base to start with). IfLED 1 stays on, check DZ , the wiring to S2 and for track shorts. Finally, check that the output swaps polarity each time the forward/reverse switch (S2) is operated. Naturally, you should always make sure that the loco has come to a complete stop before operating this switch. Flicking this switch while the model is still moving will only lead to a derailment and could even damage the gearing. ~ Where to buy the kit A kit of parts for this project is available from Electronic Toy Services, PO Box 491 , Noarlunga Centre , South Australia 5168 (Shop 2/111, Glynville Drive, Hackham West, SA). This kit includes the PC board, all on-board components , the throttle control pot. and the two switches, but does not include a mains transformer or case. The price is $19.95 plus $2.50 p&p. Payment may be made by cheque or by phoning (08) 382 8919 and quoting a credit card number. Note: copyright of the PCB artwork associated with this project is retained by Electronic Toy services. NOVEMBER 1990 45 1-9 ao,.. 10+ 31/2"0D $19.95 $18.95 31 /2"DD 3 1/2"HD $39.95 $37.95 31 /2"HD 51/4"0D 51 /4"0D $9.95 $8.95 51/4"HD $19.95 $17.95 5 1/2"HD $24.95 $22.95 DYSAN , VERBATIM 1-9 ao,.. 10+ 31/2"OD $22.95 $21.95 1-9 Bo,.. 10+ 3 1/2"OD $29.95 $27.95 1-9 ao... 10+ 31 /2"OD $32.95 $31.50 3 1/2"HD $39.95 $37.95 31 /2"HD $49.95 $47.95 31 /2"HD $59.95 $57.50 3 1/2"HD $69.95 $67.95 51/4"OD $19.95 $18.95 5 1/4"OD $19.95 $17.95 51 /4"OD $24.95 $23.95 5 1/4"OD $19.95 $18.95 51/4"HD $31.95 $29.95 51 /4"HD $29.95 $27.95 5 1/4"HD $32.95 $29.95 5 1/4"HD $39.95 $37.95 ALL PRICES PER PKT/BOX OF TEN ~...... , ~// -----=-----------.. . --- ~S_TAGE BATES PH: PH: PH: PH: (03) (03) (02) (03) 663 6151 489 8866 519 3134 543 7877 FAX: (03) 6 39 1641 FAX: AS PHONE. FAX: (02) SI~ 3868 FAX: (03) S43 2648 .$1 • $9.99..........$3.00 $10 • 24.00 ........ $3.50 $25 • $49.99......$4.50 $50 • $99.99......$6.00 $100 • $199 .......$7.00 $200 • $500 ....... FRE E $500 Plus ....... .. 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But there was no hint of the frustration to come when she first approached me. Her description of the fault was that, on odd occasions, there would be lines across the screen. And, in answer to my questioning, she described what I took to be a couple of noise bars, such as can occur with faulty tracking. Then she went on to explain that she planned to visit relatives in Queensland and would be away for about five weeks This meant that I could have the machine during that time and work on it at my leisure. It was a very convenient arrangement and she duly delivered the machine on the eve of her holiday. The NV-G7 A first appeared about four years ago and it transpired that this particular machine was still within its 3-year warranty period; it was now May and the warranty expired in July - a point of some importance, as things turned out. I set the machine up at the end of the bench, connected it to a monitor and proceeded to put it through its paces. I played pre-recorded tapes, I recorded programs off-air and replayed them, for hours on end - sometimes almost continuously all day. And did it play up? Not on your Nellie, as the saying goes. In fact, the whole five weeks went 48 SILICON CHIP by and I hadn't seen even a hint of the trouble the customer had described. Had she been a less reliable person I would have been tempted to doubt its very existence. In any case, all I could do was explain what had happened - or not happened - and suggest she take the machine back and see how it performed. With any luck, the fault might become continuous and thus easier to deal with. That didn't happen but within a week she was on the phone to report its brief appearance once again. And this time she had an additional observation. On this occasion, at least, she was convinced that the fault had occurred during recording. She had recorded a program and the lines had appeared on playback. She had immediately extracted the TETIA TV TIP Kriesler 59-01 Symptom: Total lack of horizontal hold. Line oscillator running slow and although its speed can be varied with R719 in CU701 , it cannot be brought up to correct speed. Cure: R729 (4.7kQ 1W) gone low. Metal film resistors rarely lose resistance but this one had been coated with carbon from a nearby burn-up on the main board. TETIA TV Tip is supplied by the Tasmanian branch of The Electronic Technicians' Institute of Australia. Contact Jim Lawler, 16 Adina St, Geilston Bay 7015. cassette and substituted a pre-recorded one, which played perfectly. Swapping the cassettes again produced the fault, which meant that it was recorded on the tape. In fact, she had put the tape aside for me. But did the fault occur only during record? Or had it also shown up during playback, on previous occasions? Naturally, we had no way of knowing and the tapes that had been involved had long since been re-used. Nevertheless, it was an important clue. Second attempt Of course, I was quite happy to have another go at it but it transpired that the customer was planning another interstate trip, again for about five weeks, and this would start in a few weeks time. In the meantime, she wanted to keep the machine. It did not always play up and even when it did, the results were watchable, albeit with some irritation. So a few weeks later, the machine was back in the workshop . We were into August now and, technically, it was out of warranty. But I had been careful to record the date when the complaint had first been made. I didn't want there to be any argument about what I felt was a genuine claim. Again, I set the machine up for testing, only this time I had the faulty tape to assist me. I viewed it at length and came to the conclusion that it was a typical tracking problem, probably involving a servo fault of some kind . But that was as far as I could go; nothing I could do would make the fault occur on my bench. So it was a repeat of the first episode. The customer returned, I explained the situation (which she accepted), and I returned the machine to her. Thankfully, she was very patient. And thankfully also, she was planning another holiday. This was to be even longer than before, starting in November and running until late January (it actually ran into Febru- THIS TESTER CAN PAY FOR ITSELF IN LESS THAN ONE DAY ~ □ ~CHECK™ ,., . i1 i 4 f~~lv'""" 11111! SIMM/SIP MEMORY MODULE and DRAM TESTER ~ * * . • * r, * ' ~ * * * * * * * ary). So I could have another go then. But, significantly, she had been home only a few days when she rang to say the the fault had re-appeared. And, again, it had happened in the record mode. She had played another tape but there was no sign of it. All I could do was make a note of it. Third attempt Thus began episode number three, in early November. I put it through its paces as before and, for a while, no joy. Then one day, when I recorded a 3-hour tape , then played it, there were the noise bars. I played a pre-recorded tape and the picture was perfect. I crossed my fingers and made another recording. And there were the noise bars again; it was still in fault condition. Well, at least I had proved the point. The fault occurred in the record mode only. But that really only complicated the problem. Still convinced that it was a tracking fault, I could not, by any stretch of the imagination, work out what kind of a fault would create a tracking error only in the record mode. Also, why had it taken so long to show up on my bench and how significant was this? Completely at a loss, I decided to put the thing aside for a few days, think about it, and hope for inspiration. In any case, there was pressure of more urgent jobs , plus the need for some extra bench space, so I disconnected it and pushed it aside. The inspiration idea didn't work. When I was able to set the machine up again, several days later, I was no nearer an explanation. But Murphy was on holidays and fate was on my side. When I first ran it, there was no sign of the fault and after a couple of abortive attempts to make it misbehave, I gave it away but left it switched on. Pressure of other jobs predominated for the rest of the day and I left it that way overnight. The next morning I tried it again and, lo and behold, it was in the fault condition. Then the penny dropped with a bang! Suddenly, a number of apparently unrelated facts came together and began to make sense. The explanation was - in a word temperature. It was summer now, but all my previous tests had been during the winter, when the workshop temperature would seldom exceed 20 All chips are tested simultaneously. Tests 64K x 8/9, 256K x 8/9, 1M x 8/9, 4M x 8/9 and 16M x 8/9 bits. Stand alone and portable - no need for a computer interface. User friendly LCD interface shows clear instructions and results. Zero insertion-force sockets for fast and easy operation. AC adaptor included. Expansion slot for add on products. Current measurement terminals. Two programmable voltage sources. Automatic current limiters provide full protection for your modules. High speed 16 Bit processor generates complex test algorithms. $1499.00 Plus Tax BONUS - SINGLE CHIP ADAPTER FOR TESTING 64K x 1,256Kx 1, lMx 1,and4Mx 1 DRAM chips PACIFIC MICROELETRONICS PTY LTD 'CENTRAL PARK' UNIT A20, 4 CENTRAL AVENUE THORNLEIGH, NSW, 2120 Telephone: Fax: (02) 481 0065 (02) 484 4460 Australian Representative FUJITSU MICROELECTRONICS PACIFIC ASIA LTD. o) FUJITSU NOVEMBER 1990 49 SERVICEMAN'S LOG - CTD degrees C; comfortable enough for me but a bit chilly for some people. And one of those would have been the machine 's owner. I knew she was a cold mortal, who liked to keep her house well warmed during the winter and was always glad of an excuse to go north at this time. I don't suppose the difference between the two locations would have been more than a few degrees at most, yet I was convinced that this was the vital point. In fact, I put it through a couple of cycles by unplugging it overnight, which invariably cured the fault . Similarly, leaving it turned on for 24 hours was enough to restore the fault . So I could now create it, more or less on demand. But apart from that, I wasn't really any closer to finding the fault. I simply could not envisage the kind of fault which would create a tracking error - or servo fault - in the record mode only; which was what seemed to be happening. Well, I know when I need help. I called one of my contacts at the National Panasonic service section and put the problem to him, giving him all the clues I had collected so far. He was as helpful as he could be, fishing out a manual and pouring over it with me at length. But in the end, he had to admit that he was battling; he could think of nothing that would fit the symptoms. In fact, his summary of the situation was really more helpful than he imagined. Regardless of what the noise bars looked like, he was adamant that they could not be due to a servo fault if they occurred only on record. As he put it, "It's got to be a signal path fault." And while he admitted it was a long shot, he suggested that I check the vertical sync pulses and associated circuitry. Apart from that, I was on my own. The only good point was that the weather was getting warmer and the fault was present most of the time. So, at the next slack period, I decided to try the freezer approach. After all, it was definitely a temperature fault and, with a bit of luck, I might just hit the spot. Half a can of freezer later, I gave up. I'd been over almost all of the main board, paying particular attention to the areas mentioned by the National technician, plus the servo circuitry which, in spite of his reservations , I still felt needed to be cleared. The best I could say for that exercise was that I had found a lot of things that weren't wrong. So it was back to the think tank. Whenever I had a spare moment I fished out the manual, read and reread anything which I thought might help, poured over the circuit and prayed for inspiration. I even took the manual home at night - which wasn 't looked upon very favourably by Mrs Serviceman. But time was slipping by. It was after Christmas and the owner would be back in a few weeks. Finally, I dropped everything else, opened the manual and went over the circuit, section by section. This was quite an operation in itself, because the circuit gets quite a spread on. On the basis of the symptoms and TV TEST EQUIPMENT Is Your Product Or Service Getting The Exposure It Deserves? (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-VOLTAGE PROBE Built-in meter reads positive or negative 0-50kV. ··· · ;· For checking EHT and focus as well as any other , •· • •· HI-tension voltages . ,:· · $98.00 + $5.00 p&p ·ill ' . . .. . . LOW VOLTAGE PROBE Ideal for checking microwave ovens and TVs. The ranges are from 0 to 5kV negative and from 0 to 10kV positive. Double insulated for safety. $84.00 + $5.00 p&p Consumers need to see your product if you want them to buy it ~ DEGAUSSING WAND Strong magnetic field , larger than usual coil with multicore centre. Double insulated for safety with momentary on/off switch. 240V A/C 2.2 amps. This one is just about as important as having a soldering iron in your toolbox! $75.00 + $10.00 p&p REMOTE CONTROL TESTER , (INFARED OR ULTRASONIC) Contact Paul To Reserve This Space (018) 28 5532 $85.00 + $4.00 p&p TUNER REPAIRS from only $17.00 SILICON CHIP + p&p We also repair most tuners on an exchange basis. Cheque, Money Order, Bankcard or Mastercard Y. V TUNERS~ • 50 Designed to test any lnfared or Ultrasonic control units. With the extension lead you can also test infared units which cannot be placed in front of the testing_unit. Requires a 9V battery. Output is via the LED diode and p,ezo speaker. • 216 Canterbury Road, Revesby, NSW, 2212 Telephone (02) 774 1154 everything I had checked so far, I mentally wrote off each section as it appeared not to be relevant. In particular, I was looking for any circuitry exclusive to the record function. I won't bore you with the details, but I finished up looking at a section called the "Luminance & Chrominance Pack Schematic Diagram". More specifically, it was at a section of this, designated as IC301, VEFY014 (see Fig.1). Now this IC is unlike any regular IC. It is a complete printed circuit board carrying two conventional IC chips: a 32-pin chip (AN3321) and a 24-pin chip (AN3215S), plus a swag of resistors, capacitors, etc, all surface mounted. And IC301 is novel in another respect; it is not even a conventional PC board. It is built on what is called "3D" board; a thin, flexible, translucent film. I have seen equipment - not in our field - in which such boards were even rolled up to conserve space. This particular board measured about 75 x 40mm and was folded in two lengthwise, making a package measuring 75mm by something less than 20mm. It is located underneath the main board, which is horizontal. Under this is a sub-board, attached to the main board at right angles, so that it protrudes downwards. And IC301, in its folded configuration, fits into a slot in this board, so that it sits parallel to and below the main board. There is a total of 78 connections to IC301, 39 on each edge. They are soldered to 78 copper tracks on the sub-board. Circuit details So much for the physical layout. Getting back to the circuit, one of the features of this section is the use of distinctive arrows to mark the record and replay circuits; pink for the record circuits and grey for replay. (Unfortunately, this difference is lost in the circuit reproduced here, although the pink tends towards a lighter grey). This distinction proved invaluable in my search for any record-only cir- .. •• w 0 0 4 w ::.::: u 0 0 <( a:, '.l: >- u w a: <( ....J z z 0... :c: :c: f- f- <( 0... <( 0... ....J <( ....J <( z z <..!l <..!l (/) (/) z z <( <( L 4 ' ! ~ < ~ i C, < ~ 0 0 ~ < ~ ~ = 0 00 ~ 0 < ~ ~ 0 z < z ~ 0 ~ = 0 ~ ~ 0 z z< ~ Fig.1 (right): the luminance & chrominance circuit for the NV-G7 A. Unfortunately, the colour coding indicating the record and playback paths cannot be shown here, although in practice they helped considerably in tracking down the problem. 0 ~ N . ~ I ~ :I: CJ NOVEMBER 1990 51 ing some nice remarks about these notes , he goes on to describe an unusual fault in his TV set. Mr R. T. describes himself as a "fixer" of electronic equipment in a radio station, so it was natural for him to tackle the fault himself. This is how he tells it. SERVICEMAN'S LOG - CTD Philips K11 ~ 0 O- ~ ONL"( SOM~~ Wl-\0 1-\~CS BatJ 11-\l;R~ Wll-(.... APPR~C\~.,..E:, 11\E:: SA,tSFAc,,o~ t Fe:t-i'" A, HAVING NAI t..£D n\E. C.Ul-f'Rl1"' APTER AL.-L11-\0$ MONTI-\S OF F'RUS"t'RAT\ON cuit which could be the culprit. And in a sense I suppose, I worked backwards. In the extreme top left of the diagram is a connection (13) marked "Picture VR", which runs directly to the video recording heads. Backtracking from here , we find that it connects to pin 78 of IC301 and carries a pink arrow. From here it connects to pin 28 of chip AN3215S, then to a block marked "FM Mod", and then out of the chip via pin 23, with pink arrows all the way. Was this "FM Mod" the temperature sensitive record-only circuit I was seeking? Hardly daring to hope, I hit the AN3215S with a smidgin of freezer. And that was all it needed; a 30 second recording confirmed that the fault had vanished. I let the machine run and in about 20 minutes - it was a hot day - the fault was back. Another smidgin of freezer (even less than before) produced another clean recording. The culprit nailed Only someone who has been there will appreciate the satisfaction I felt 52 SILICON CHIP at having nailed the culprit after all those months of frustration. Words cannot express it. (Well, I did mutter a few words!) And the repair? It did not involve, as one might imagine, replacement of the AN3215S, but replacement of the whole 3D board, IC301. This turned out to be relatively inexpensive and, in terms of labour, cheaper than attempting to repair it. That fixed it, of course. And now that I knew what was involved it was easy to confirm this, which I did over many cycles. So, when the customer returned I was able to announce with ill-concealed satisfaction - that I had cracked it. Naturally, she was delighted; the more so when I was able to tell her that there was no charge. Yes, National did the right thing about the warranty, without a quibble. But I was glad I had been so meticulous about recording the vital dates. It's a point worth remembering. To finish off, here is an interesting contribution from a reader, Mr R. T. of Wollstonecraft, NSW. After mak- The story in the July issue, about being misled by test equipment when repairing the degaussing circuit in a Thorn 9104, reminded me of a similar occurrence which I experienced. The TV set in question was the family's 1978 vintage Philips Kl lA. The initial fault was that it was unable to remain tuned to any station. It could be temporarily fixed by tapping gently - and sometimes not so gently! - on the cabinet in the vicinity of the preset tuning controls. The fault was obviously one of mechanical origin but despite several attempts at cleaning the controls with cleaning lubricant and checking for dry joints and hairline cracks in the PC board, the module eventually had to be replaced. We now had excellent pictures - for a fortnight - then the old trouble returned. This time we established that the problem was purely electronic. Monitoring the output of the voltage regulator, IC203 (TAA550), at G2 (see . Fig.2) showed that the voltage remained constant. But the voltage at the output of the channel-select switches (SK9) , at Dl2, was varying by 200-300m V. Faulty module? What was causing this? A faulty, brand-new tuning control module? At this point, the investigation went a bit haywire. In an attempt to determine whether it was the tuning control module or the actual tuner (U200) that was at fault , the lead to the tuner from D12 was broken and the tuner fed with voltage from a variable power supply. With this setup , the tuner worked perfectly and could not be made to mistune. The lead to D12 was reconnected , the lead to G2 opened, and the variable power supply substituted for the internal regulated supply from IC303. The fault immediately returned. As a further attempt to isolate the fault , an 1 ___l, __ - CHAf.NEL SELECTOR- - I F AMPLIFIER - FOR EXCLUSIVE KITS AT AFFORDABLE PRICES: OATLEY ELECTRONICS +12c L UHF ***VISIBLE LASER DIODES*** Brand new 3mW visible Laser diodes, supplied with a high quality collimator, ·. ' and heatsink assembly. g Simple to use, since it requires a cu rrent of about 85mA, with a vo ltage of only 2.3V across it. We include the specifications, instructions and a suggested driver and digital switch circuit. This circuit is also suitable for driving our Infra Red Laser Diodes ! U200 r SPECIAL introductory offer: We will supply the diode, the collimator, the PCB and the components (complete Kit) for the driver for ONLY: $270.00 PCB and components kit for the driver and digital switch can also be purchased separate!\~~-~: I SEE IN THE DAR,K! . with our INFRA RED NIGHT VIEWER at a SPECIAL price, while stocks last! We have good stock of the 6032A tubes. This is your opportunity to build a product which commercially cost 1OOO's of dollars at a fraction of the cost. We supply the electronic kit, a 6032A Image Intensifier tube, and the case components for only. ONLY $339.00 BRAND NEW TUBES Fig.2: relevant section of the Philips Kl lA circuit, showing the tuner and its associated switching circuitry. external pot was connected between Gl and G2, with the moving arm to D12. I was not really surprised to find that the fault was still there. What was going on? Up to this point, everything had been done on the control panel, which can be accessed from the front of the TV set. Delving into the innards of the set, to pin 2 of the tuner, it was found that the voltage on it was varying by 700-B00m V. Sense at last Now things were starting to make sense. It seemed most likely that something inside the tuner was intermittently loading the control voltage. And the reason why the tuner had performed perfectly when operating from the external power supply was that the latter has a very low output impedance, so that any variation in loading would have been masked. Had the power supply been connected via a resistor, say 47kQ, then this would have simulated the resistance of the tuning pots, and the fault would not have caused as much confusion as it did. Having Scottish blood in me , I did not want the further expense of a new tuner for a 12-year old TV set, if it could be avoided. Fortunately, a few squirts from a freezer can revealed that one of the tuning diodes had an intermittent short. A new diode restored operation and the set has now been working perfectly for several months. Had the set belonged to a paying customer, a new or reconditioned tuner would have been fitted but, for an in-house repair, it was felt that the end justified the means. Well, that's R. T. 's story, and a very interesting one too. It shows just how easy it is to be deceived if all asp ects of our test equipment - in this case the power supply - are not taken into account. Thank you, R. T. The 6032A tubes are BRAND NEW and perform well with a good infra red torch. Torch and Lenses are not supplied STILL ON SPECIAL: Till the end of 1990!: Single Channel UHF Transmitter/ Receiver at $49.90, the pair! PIR detector with commerical case at $39.90, interface at $7.90! A 'SPECIAL BONUS' For all readers who observe lhis advertisment: FREE PACK AND POST on all our kits, purchased by mail order. Applie s for the month of publication only: SIM PLY MENTION THI S AOVERTISMENT! HAVE YOU GOT OUR NEW KIT LISTING? If interested simply ask us to send you our current listing. We have many kits and ready made items. Our kits include: SINGLE AND MULTI CHANN EL UHF REMOTE CONTROLS, MASTHEAD AMPLIFIERS , TEMPERATURE CONTROLLERS, CAR ALARM S. PIR MOVEMENT DETECTORS, ULTRASONIC MOVEMENT DETECTORS, BIKE ALARMS. FM TRANSMIT· TERS, 'M USIC ON HOLD ' FOR TELEPHONES. MAINS ANO BATTERY POWERED LASERS etc. etc. OATLEY ELECTRONICS PO BOX 89, OATLEY, NSW 2223 Telephone: (02) 579 4985 Fax No: (02) 570 7910 Certified p&p $4-$6 Aust. NZ add $2 NOVEMBER1 990 53 eremy s NEARLY 10% of has been REDUCED BOARD SOLUTIONS Pty Ltd SIMM Module , 1 MB 80ns SIPP Module, 1MB 80ns MOTHERBOARDS 10MHzXT, (640K)OKRAM 10MHz XT, (1MB) OK RAM 31MHz XT286 OK RAM Baby 286 12MHz OK RAM Baby 286 12MHz OK RAM VLSI Baby 286, 12MHz VLSI OK Neat 286, all-in-one, OK RAM 16MHz NEAT 286 OK RAM 20MHz 286 OK RAM 16MHz 386SX, OK RAM M1010 M1000 M1020 M2015 M2030 M2020 M2010 M2040 M2045 M3000 20MHz 386 NEAT, OK RAM 25MHz 386 NEAT, OK RAM 20MHz 386SX, OK RAM M3002 M3004 M3005 1645.00 1795.00 895.00 25MHz 386, 32K Cache , OK Neat M3010 33MHz 386, 32K Cache , OK M3020 2395.00 449.00 499.00 545.00 599.00 545.00 895.00 1995.00 1 M RAM Chip - 80nS 256K RAM Chip - 1OOnS 256K RAM Chip - 80nS 4 X 256K RAM Chip, 1OOnS 4 X 64K RAM Chip , 120nS For VGA card 64K RAM Chip - 120nS NEC V20 Chip NEC V20 Chip, 10MHz NEC V30 Chip, 10MHz 80387SX 16MHz Co-Processor 8087-2, 8MHz Co-Processor 2C87-8MHz (equiv 80287/8) 2C87-10MHz (equiv 80287/ 10) 2C87-12MHz (equiv 80287/ 12) 2C87-20MHz 3287-16MHz (equiv 80387/ 16) 3287-20MHz (equiv 80387/20) 3287-25MHz (equiv 80387/25) 3287-33MHz (equiv 80387/33) . 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FLOPPY DISK DRIVES 115.00 149.00 199.00 299.00 Z9680 Z9690 14in 14in 14in 14in 14in 14in TTL, Amber TTL, Green TTL, Paper White EGA VGA 640 x 480 Multisync M9000 M9010 M9020 M9030 M9040 M9050 249.00 249.00 249.00 599.00 749.00 899.00 Monitor 14in VGA 1024 x 768 M9060 799.00 1/0 CARDS 2 Ser. 1 Parallel Games, Parallel & 2 x Serial Chip Set & Cable suit 11040 Multi 1/0 Card XT only Multi 1/0 Card , 2 Ports all 4 drive types supported (XT Only) Paralle l Printer Card (XT/AT) Serial PortCard X 1 (XT/ AT) Serial PortCard X 2 (XT/AT) 1/0 Plus Card - XT Only Serial/Parallel Card - XT/AT 2 Serial , 2 Parallel , AT Multi-Serial Card , 4P-AT i1080 i1110 i1041 i1000 i10 10 i1020 i1030 i1040 i1050 i1060 i1070 i1090 69.95 74.95 24.95 129.00 164.95 29.95 54.95 64.95 99.00 64.95 84.95 245.00 VIDEO CARDS VGA Card , 800 x 600 (256K) VGA Card , 1024 x 768 (512K) Magic Combo CGA Card EGA Card Mono Hercules Card , 16MHz operation+ Parallel Port I V1000 V1010 V1020 V1035 199.00 299.00 V 1040 89.95 129.00 179.00 POWER SU PPLI ES 200 Watt PSU Suit Tower Case P2020 195.00 PHONE OR FAX NOW FOR LATEST PRODUCTS. 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RAM TYPE 1MB 100nS DIL 1MB sons DIL 256K 100ns DI L 256K 80ns DIL 4x 256K 1 00ns chip 4x 64K 120ns 1 MB 80ns SIMM module 1 MB sons SIPP module BOARD·SOLUTIONS Cat No 29300 29380 29400 29480 29200 29212 29680 29690 Was NOW! $29.95 $32.95 $7.95 $8.95 $32.95 $12.00 $295.00 $295.00 $1 9.95 $21 .95 $6.95 $7.95 $21.95 $9.95 $225.00 $225.00 YOUR ONE-STOP PC our product range IN PRICE! 200 Watt PSU Suit Baby T Case 150W PSU, Circuit Board 150W Switching PSU - XT 200W Switch PSU - Baby AT 200W PSU, Baby AT, L Type 220W Switching PSU - AT 200W PSU With Battery Backup 150W PSU Cap. 220nF/200V P2030 P1500 P1510 P2000 P2010 P2200 P2040 P9000 149.00 85.00 124.00 149.00 149.00 195.00 695.00 3.95 KEYBOARDS 84 Key Keyboard XT/AT 101 Key Keyboard, XT/AT 101 Key Keyboard+ TrackBall K1000 K1010 K1020 95.00 99.95 174.95 I. RAM CARDS RAM Card, OK RAM , XT only 2MB RAM Cd, OK LIM/ EEMS AT 2MB RAM Cd, OK LIM/ EEMS XT 6MB RAM Card, -OK RAM 4MB Fast Card Suit 20MHz +SX 32 Bit RAM Card 25 + 33MHz R1000 R1010 R1020 R1030 R1040 R1050 99.00 265.00 245.00 295.00 299.00 349.00 DISK CONTROLLER CARDS Floppy Disk Card, 4 Ports 360K Disk Cont 4 port, 2In 2Ex or 4In Floppy Disk Card All Drives ESDI Hard Disk Cont Card -AT ESDI HDD/FDD Card - AT Hard Disk Cont, 1 :1 lnt. AT HDD/FDD Cont, 1 :1 lnt. AT Hard Disk Cont, 1: 1 lnt. RLL, AT HDD/FDD Cont, 1 :1 int, RLL , AT SCSI HDD/FDD for AT Hard Disk Controller, XT Hard Disk Controller, RLL-XT 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 CASES Hinged , Baby AT Full Size Hinged AT Case C1000 C1005 Hinged Baby AT w/200W PSU Slimline 'XT' or 'AT' with PSU 3.5in Hard Disk Ext. + Cable 5.25in Floppy Disk Ext. + Cable 5.25in Full Height Ext. + Cable Baby Tower Case AT Baby Tower Case+ 200W PSU Tower for 6 Dev. (4 front, 2 rear) Tower for 6 Dev. (4 front, 2 rear) & 200W PSU Tower for 6 Devices, (6 front) Tower for 6 Devices, (6 front) + 200W PSU Case, hinged XT 125.00 I C1010 C1020 C1030 C1040 C1050 C1070 C1080 C1090 249.00 295.00 99.00 134.95 125.00 189.00 325.00 399.00 C1100 C1120 499.00 C1130 C1140 499.00 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-DID-A Converter, 12 bit, 1 Ch. F1080 Clock Card - XT F1100 EPROM Writer Card F1110 Games Card- 'XT'& 'AT' F1120 If you're looking for the ultimate in quality, reliability and value,look no further than these outstanding models from Panasonic - a brand to trust! 144cps 9 pin 80 col P5000 $349 192cps 9 pin 80 col P5010 $449 240cps 9 pin 80 col P5020 $499 330cps 9 pin 132 col P5030 $949 192cps 24 pin 80 col P5040 $649 192cps 24 pin 132 col P5050 $1099 240cps 24 pin 132 col P5060 $1249 95.00 110.00 135.00 445.00 125.00 195.00 495.00 445.00 8K Ethernet 8 bit with 'T' Adaptor 16K Ethernet 16 bit with 'T' Adaptor Ethernet 50 Ohm Terminator Thin Ethernet Cable, 25 feet Thin Ethernet Cable, 50 feet Thin Ethernet Cable, 75 feet Auto Boot ROM for NEE1 HIGH QUALITY JSE SYSTEMS BUILT, TESTED AND FULLY GUARANTEED! 286 12MHz SYSTEM Includes • • • • • • • 8112MHz (Landmark 16MHz) 1 MB RAM on board 1.2MB (5-1 /4in) Floppy Disk Drive Serial, Parallel and Games Ports Floppy Controller Enhanced 101 Key Keyboard Hinged "Baby AT" case and 200W power supply • 14in Paper White Monitor & Mono Hercules Card $ X2859 All this for only 1195 Add $695 for 40MB 28ms + controller 386SX 16MHz SYSTEM Includes 595.00 199.00 49.95 245.00 35.00 NETWORK N1000 399.00 N1017 N1020 N1030 N1040 N1050 N1060 499.00 12.75 35.00 55.00 75.00 CALL (02) 906 5696 FOR THE DEALER NEAREST YOU! 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ENHANCEMENT COMPANY 4195 PO BOX 1120, LANE COVE NSW 2066 TEL (02) 906 5696 FAX (02) 906 4592 Build this really snazzy ••• EGG TIMER How many eggs have you seen that could keep time? This one can - it ticks away the seconds and then plays a musical chime. We must admit it looks a bit weird for an egg, with a switch at its pointy end and a knob on its side, but what do you eggspect? By DARREN YATES They say one of the best things in life is a perfect 3-minute egg; that nottoo-hard, not-too-soft, just right edible wonder that has had man searching the globe for centuries. However, unless you 've had the time to sit and watch the water boil as you count away the minutes, the results may have ended up anywhere between a sloppy, watery mess or something that resembles the solidity of your average golf ball! But man, in his usual adaptive style, invented the egg timer, that marvel of modern engineering, to save him from this time-consuming chore of creating the perfect egg! Here at SILICON CHIP, eggs for lunch have never been high on the menu, but we realised that the humble egg timer is well overdue for a facelift both on the inside and the outside. As you can see, what we've come up with resembles something like an egg although most eggs won't sit on their big end. This one does. That's all well and good but what if you hate eggs? Well, we've catered for other applications by providing an extended timing range up to 17 56 SILICON CHIP minutes. You could use it as a move timer for a game of chess, for example (and completely scramble his game at the same time)! The biggest bonus about this proj- The Egg Timer is built into an eggshaped case that normally contains a Pavlova mix. You can vary the time from 15 seconds to about 17 minutes. ect is that the egg-shaped case can be bought from just about any supermarket for just over $2 - and you get a free Pavlova mix thrown in! To be specific, it is a Pavlova Magic egg. Buy one today and have a pavlova on the weekend. Well, that's what the outside of the timer looks like. Now we'll delve inside and see how the circuit works. Circuit details If you look at the circuit diagram in Fig. l, it may appear at first to be a little complicated. But as we will soon show, it is fairly simple. The circuit uses three ICs: a 4093 quad Schmitt trigger NAND gate, an LMC555 CMOS timer, a 4001 quad NOR gate and not much else. Most circuits based on the 555 timer IC use two series resistors to charge and discharge a capacitor. This works well but when when long time delays are wanted (more than 10 minutes for example), the resistors and the capacitor have to be quite large in value. This gets to be a real problem when the capacitor value has to be around lO0µF or more because capacitor leakage becomes the limiting factor. You get to the point where the capacitor leakage is much the same as the charging current and so the timer circuit does not work. The technique we've used instead is to dump small discrete amounts of current into a charge pump circuit several times per second. Because it's no longer a continuous current flow, it takes a lot longer to charge up the capacitor. So if we make the number of r;urrent pulses per second quite D2 ,--_.,._._+9V IC2 LMC555 3.3k +9V 56k E 100 16VW ·~ ~+9V ~ S1a T 9V : ...L.. l 56k ... B EOc ... VIEWED FRDM BELDW TICKING EGG-TIMER Fig.1: ICla operates as a variablefrequency pulse generator & is used to charge the 6.8µF timing capacitor on pins 6 & 2 ofIC2. IC2 is a CMOS version of the 555 timer. When the voltage across the 6.8µF capacitor reaches 2/3 Vee, its output goes low & triggers the chime generator circuit (IC3a,b,c & IClc,d). The chime generator circuit then drives complementary output stage Ql & QZ. All the King's horses & all the King's men ... yes, it really does all fit inside the Pavlova Magic case. Power comes from a small 9V battery. small , we can also reduce the size of the capacitor needed and still produce a sizable time delay. The technique works because we can use a relatively small capacitor which has a much lower leakage. To make this a bit clearer, imagine you're filling a big bucket of water from a tap. If you leave the tap running continuously, it will take a certain amount of time to fill it. Now if you try to fill it again, but this time turning the tap on, off, on, off, so that for half the time it's on and for the other half it's off, it will take twice as long to fill it. In this circuit, the length of time that the tap is on is kept constant, say a second if you like. The time the tap is left off, though, is varied. So if the tap is on for one second in every 10, obviously it must take 10 times as long to fill the bucket than if the tap was left on continuously. This holds true whether it's a half a second in every five or a quarter of a second in every two and a half. The important thing is the ratio of how long the tap is on compared to it being off. This is called the "mark/space ratio". By varying this ratio, we can vary the time it takes to fill the bucket; or in our case, the time delay before the alarm sounds. This technique allows us to use a small low leakage tantalum or aluminium electrolytic capacitor and still generate a time de~ay of up to 17 minutes. NAND gate ICla is connected as a variable-frequency pulse generator. It produces pulses of fixed width, no matter what the frequency, and we actually change the mark/space ratio by changing the frequency. Mark/space ratio In our circuit, diodes Dl and D2 and variable resistor VRl do the job of changing the mark/space ratio. If we assume that the output of ICla has just gone high, then a current flows through diode D1, through the 3.3kQ resistor, and charges up the O. lµF capacitor. The voltage across the capacitor increases until it reaches the threshold voltage. ICla now sees a high on its inputs , and so its output NOVEMBER 1990 57 Because the charge can take anywhere up to 17 minutes to develop across the capacitor, if we put too heavy a load on it, the voltage will drop and the timing will be out. The CMOS 555 has inputs with an impedance of 10 12 ohms (or one million megohms) and so does not upset the circuit. While the 6.8µF capacitor is charging up, the internal flipflop of ICZ is reset and the output at pin 3 is high. This output directly controls two low frequency oscillators formed by Schmitt NAND gate IC1b and IC1c and two NOR gates, IC3a and IC3b. Clicking oscillator While ICZ's output is high, IC1b is enabled and oscillates at a frequency of about 0.5Hz. This produces a "click" about once a second to indicate that the timer is running. When the 6.8µF capacitor voltage at pin 6 of ICZ is charged to 6 volts, the output at pin 3 goes low. This disables the ticking oscillator ICl b and allows the oscillator formed by NOR gates IC3a and IC3b to begin oscillation. This is another low-frequency oscillator which drives a 2tone alarm, indicating that the time delay has expired. Tone oscillators Here's how everything fits together inside the case. Use small pieces of foam rubber or plastic insulation to ensure that there are no shorts from the loudspeaker or battery to the PC board. The two halves of the case are simply clipped together & are held by matching grooves. goes low. The capacitor now discharges back through the 3.3kQ resistor, diode D2 and the 500kQ potentiometer, VRl. Depending on its setting, it takes a longer time for the capacitor to discharge than to charge, resulting in the output staying low for a longer period. Also connected to the output pin of ICla is diode D3, a lMQ resistor and a 6.8µF capacitor (for th.:- time being we'll ignore the 555) . This part of the circuit represents our "water bucket" analogy. Whenever the output of IC1a is high, a current flows through D3 and the lMQ resistor, charging the 6.8µF capacitor. When the output is low, 58 SILICON CHIP the diode no longer conducts and the capacitor stores the voltage across it. Next time the output goes high, the capacitor charges up a little more and so on. This part of the circuit is called a "charge pump" because we are pumping and storing a charge in the capacitor. The lMQ resistor and the 6.8µF capacitor set the base time constant of the circuit. Increasing the value of either component increases the base time delay. ICZ is a CMOS version of the 555 timer, connected here as a threshold detector. It also acts as a controlled time delay for repeating the alarm, which we'll talk about a little later. The output of IC3a is connected directly to NAND gate IClc and to gate IC1d via NOR gate IC3c. IC3c acts as a switched inverter. It is turned on via a low output from pin 3 of ICZ (the 555) and inverts the drive signal from the output of IC3a. This allows the two tone oscillators, IC1c and ICld, to operate alternately. NOR gate operation The reason that NOR gate IC3c is in the circuit is that both tone oscillators need to switch off at the same time, but operate alternately to produce the two tones. When the output of ICZ is high, the output of gate IC3a is held low and so is the output of IC3c. These hold one input of both IClc (pin 8) and ICld (pin 13) low, so both oscillators are off. However, when the output of the 555 goes low, IC3a is enabled and so is IC3c, which now acts as an inverter, providing the opposite phase enabling signal for ICld. The outputs of the three oscillators, IClb, IC1c and IC1d, are mixed PARTS LIST 1 Pavlova Magic shell case 1 PC board, code SC08110901 1 Dynamark clear label artwork 1 DPDT pushbutton switch 1 57mm 8Q loudspeaker 2 PC stakes 2 pieces of double-sided foam tape (see text) 1 9V battery (Eveready 216 or equivalent) 1 9V battery snap connector 1 500kQ log potentiometer 1 knob to suit pot Semiconductors 1 4093 quad Schmitt trigger NANO gate (IC1) 1LMC5~,~55CMOStim~ (IC2) 1 4001 quad NOR gate (IC3) 1 BC338 NPN transistor (01) 1 BC328 PNP transistor (02) 3 1N4148, 1N914 signal diodes (D1,D2) Fig.2: make sure that all parts are correctly oriented when installing them on the PC board & take care not to confuse Qt & Q2. The external wiring leads should be made long enough so that everything can be correctly positioned inside the case. together via three lOkQ resistors and coupled to the output stage. This stage is formed by transistors Ql and QZ which drive the speaker. Once the output of ICZ goes low, causing the 2-tone oscillator to sound, the 6.8µF timing capacitor is discharged via the 470kQ resistor, until it reaches 3 volts. This causes the output of ICZ to go h igh again , and so the alarm tone stops and the cycle starts again. The end result is that the alarm CAPACITOR CODES 0 0 0 0 Value IEC Code 6.8µF 6u8 100n 0.1µF .018µF 18n EIA Code 685 104 183 rings for approximately 3 seconds after the circuit reaches its preset time and then rings every half time setting after that; ie, if the time setting is 10 minutes, the alarm rings after 10 minutes and then every five minutes after that. Why is that? Because the 6.8µF capacitor takes twice as long to initially charge to 6 volts as it does to charge from 3 volts to 6 volts in the succeeding cycles. The circuit is reset by switching it off and then on again. Construction When you buy or make the printed circuit board, check that there are no shorts or breaks in any of the copper tracks, particularly around the pads of the ICs. If there are any, correct them now. You may also need to trim Capacitors 1 100µF 16VW PC electrolytic 1 6.8µF 25VW tantalum or low leakage electrolytic 1 2.2µF 63VW PC electrolytic 4 0.1 µF metallised polyester 2 .018µF metallised polyester Resistors (0.25W, 5%) 3 1MQ 2 56kQ 1 470kQ 3 10kQ 1 120kQ 1 3.3kQ 1 100kQ Miscellaneous Solder, washers, nuts , hookup wire, etc the board, so· that it will fit into the Pavlova Magic egg case . Once you're sure the board is OK, insert the PC pins and solder in the TABLE 1: RESISTOR COLOUR CODES 0 0 0 0 0 0 0 0 No . Value 4-Band Code (5%) 5-Band Code (1°/!') 3 1MQ 470kQ 120kQ 100kQ 56kQ 10kQ 3.3kQ brown black green gold yellow violet yellow gold brown red yellow gold brown black yellow gold brown blue orange gold brown black orange gold orange orange red gold brown black black yellow brown yellow violet black orange brown brown red black orange brown brown black black orange brown brown blue black red brown brown black black red brown orange orange black brown brown 2 3 NOVEMBER 1990 59 i:7 10 I~., E E 3 }IME (MINS)___ --- i EGG~ Figs.3 & 4: here are actual size artworks for the PC board & front panel. wire links and the resistors. Use a multimeter if the resistor band colours are not very clear. Next, install the polyester capacitors. Remember to keep their lead lengths as short as possible because of the tight fit. After that , solder in the electrolytics capacitors, making sure that each has correct polarity. The 6.8µF capacitor can be a tantalum or low leakage aluminium electrolytic. Now insert the semiconductors , again making sure of their correct polarity. Once you've completed the board, check over it again for any solder splashes or dry joints. Add one egg Got your pavlova egg? Had your pavlova? Good, now drill the egg shells. When drilling holes through the egg shell, do it slowly as the shell has a tendency to bend and may crack if you go too hard, too fast. If you prefer, use a small drill first and then finish the holes to size with a tapered reamer. The hole for the switch goes straight through the top. The holes for the pot and the speaker simply go on either side of the upper section and there are a couple of holes in the bottom half of the shell for the speaker as well. The 2-pole pushbutton switch is fairly easy to wire up as it doesn't matter which way round you use it, so long as you keep the lead orientation the same. The second pole is used to short out the capacitor when the timer is turned off, so that when it 60 SILICON CHIP is restarted, the capacitor has no voltage across it, and we get a correct time delay. If you find that 2-pole pushbutton switches are hard to obtain, then you can do away with the second pole and just use a single pole pushbutton switch. The 6.8µF timing capacitor will discharge through the circuit but it will take about half a minute to get close to zero volts. Filling the egg When putting the whole thing together, the magnet side of the speaker faces the component side of the board. To stop any shorts from occurring, we suggest you use a piece of double- sided foam tape to attach the speaker magnet directly to the board. The 9-volt battery goes on the other side of the board, again spaced by a piece of foam tape or something similarly non-conductive. Note that it's easier to wire up the pot and the switch before mounting them into the egg shell case. This done, take hold of the board, with the battery and the speaker on either side, and place them in the bottom section of the egg shell so that the copper side of the board faces the front panel area. In order to connect the two shell halves together, you'll need to tilt the board forward about 10°, to clear the base of the switch. If you do it correctly, the base of the switch should just fit over the top of the 555 IC and be perpendicular to the 0. lµF capacitor alongside it. The lid should then just squeeze together with the bottom section, making a good, tight fit. Operation Drill several holes in the back of the case to allow sound to escape from the loudspeaker. It's best to use a small drill first & then finish the holes to size with a tapered reamer. To use the Egg Timer, set the time control to the desired length and then press the button. You should now hear it ticking away merrily. Once the alarm has sounded and you need to use it again, turn it off, set the time, and turn it on again. If you strike problems, switch off immediately & check for wiring errors. Note that the accuracy of the calibrations will depend on your particular potentiometer. Now, all you need to do is start enjoying the eggs of your labour! ~ The Q 1050 Breaks New Ground For An Advanced, Precision Analogue Meter Of This Quality Below $100.00 Pocket Sized Sine/Square Signal Generator • Froquoncy Rang •: 20H z to 150 KHz. limos 1: 20Hz to 1.5KHz. limos 100; 2KHz to 150KHz. 23 Position Pre-selected Range Switch Laboratory Quality Electronic FET Volt/Ohm Meter w ith Center Save Zero • Sine/Square Wave Output • Output Attenuator : 2 Position OdB and " 3.5 Digit LCD • Automatic Rang ing • DC Voltage : 1OOuV to 750V • AC Voltage; 1mV to SOOV • Resistance; 2000 to 20MO • Continuity Tester • Comes in Folding Wallet • • • ' • • • 20d8 with Fi ne Adjust Control Output Impedance : 6000 Slnowave: 1.2V RMS Max (No Load) Squ arowavo : 8V PTP Max (On Load) Sync Pul se: 1.2V RMS (No Load) . Impedance: 1Kn Compact Size : 820 x 21 Ox 21 mm Battery Indicato r $12.5 Tuck This Fsntsstic Sine/Square $65.00 01060 Fantastic for the glovebox, too/kit and, of courae, your top pocket. Excellen t for mobile field worlc. A great gift idea for your budding genius student Great New Inductance Capacitance Digital Multimeter NEW FOR CHRISTMAS Terrific New 18 Range Digital Multimeter From World Famous Labtech Instruments • 4.5" Mirrored Sca le. 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The large LCD digits msk• tak ing measur• msnts quick and efficient. e 3.5 Digit LCD• Bar Graph Display • Continuity Check With Buzzer • Tilt Stand on Desktop • Data Hold Fu nction • Minus Memory to Nullify • DC $99 • 00 At Last! A True Rms Analog Digital Multimeter At A Very Competitive Price Another Altronics Price Breakthrough Great For The Christmas Stocking! This popular 3.5 digit Mull/meter Is slmp//clty c ap acitance and Inductance ranges, enables you to test a wide variety of components . lndlspenslble for the design engineer, t ech nicia n and enthusiast alike. e e Tiltstond on Desktop Voltag e 5 Ranges 1OOuV to 1OO0V DC Curren t 6 Range& 100nA lo 20A AC Voltag e 5 Ranges 100uV lo 750V AC Curren t 6 Ranges 100nA lo 20A Resistance 7 Ranges 1oomn to 200Mn lnpul Im pedance 10Mn Capacitance 5 Ranges 1pF to 20uF Inductance 5 Ranges 1uH to 20H Diode Test• Continuity Test With Bouer Transisla- Test (hF E) 3.5 Digit LCD e DC • • • • e • • • • ~ " -:i.... a 1062 Multimeter $149.00 Includes Deluxe Carrying Case VolVAC Voll. 100uV10OOV e 1OMO Input Im pedance • Low 1 8 +:i:e Per Secon d e DC/AC ;:~e;re R:t~ Current 100uA-1 0A • Resistance: 0.1n to Each Meter Comes With Free Carrying Case Worth $12.50 . 20MO • Transistor G ain · hFE: e Diode Checker e Tru e RMS AC e dB Meler •45dB to+ Impedance• 3.5 Di gital Display• 4.5" An AC Volt 100uV-1000V e DC Amp/AC Am • Resistance 0.1O-20MO • Diode Check Buzzer• Au tomatic Polarity Reversal • L New Prod ,,_~HIGH TECH Company Collapse Brings Fantastic Bargains for the Electronic Enthusiast *''V.10t e I'' (now D1scovery") · SENSATION! 11 UNBELIEVABLE VALUE/ Around $250.00 value for as low as $24.00! Altronlcs has recently purchased this quality stock from the liquidator of DTX AUSTRALIA LTD. You can use this equipment to gain limited access to the ·•viatel" information system. Each unit contains a Telecom approved modem and information decoding circuits. The single PCB is a goldmine of quality components for the enthusiast, including the fantastically valuable SAA 5020 AND SAA 5050 chips. ALL STOCK BRAND NEW PREMIUM QUALITY INDIVIDUALLY TESTED BY THE MANUFACTURER (in our rush to get this amazing SCOOP PURCHASE to you we have not had time to check each unit so we cannot offer any warranty) " VIATEL" · Now known as " DISCOVERY" What is " DISCOVERY"? Worth well over $150.00 for the salvage value of the " bits" alone! Look at this list of component parts! • Mains Transfo rmer - 240-9/15/24V 300mA • Line Isolation Transformer - Telecom approved 600/600 Ohm or 600/150 Ohm impedance. • Video/RF Modulator (Channel 0) e Low profile 12V 5A SPDT Relay • Capacitor - 2.0uF 440V AC • Crystals - 6MHz and 4.43MHz e TTL, CMOS, Linear and LSI ICs - SAA 5020, SAA 5050, 2516 and many more • Voltage regulators • Bridge rectifiers• Trim pots and capacitors • Filter capacitors • Flatpack heatsink I Plus much, much more! Telecom "D ISCOVERY" is a sophisticated information service whereby subscribers may access essential business and leisure information and transaction services. With the "VIA TEL" Videotex Modem Decoder and your own TV receiver or computer monitor, you can look up any telephone number in Australia via the electronic whrte and yellow pages; connect up to news services; check airline schedules ; pay bills or go shopping. You can even go to the bank without leaving the comfort of your own home. 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For component tests, a special circuit is designed, with which a single component or components in or out of actual circuit board can be easily tested, requiring no power to drive the circuit. The display shows fault of component value, characteristics of component, and half-dead components under dynamic test. Audio Oscillator & Function Generator Fantastic Hi Tech • Hi Soec (See EA Dec '86) This ultra low distortion oscillator is comparable with the 6est laboratory standard sine wave oscillators. As well as having very low distortion it has excellent envelope stability, square wave output and output metering. SAVE $50.00 K3380 Specifications ~;~~~:~~ti~.~tto~~g~~ :1~~ 1'.Jt~~9 9~,~~ ;l ':; rbtie,.~~~i;CZ~r~:t.::i~;~isov HEADPK>NES Normally Why pay $400 or more for a David Clark set? month only WITH OIL FILLED EAR CUSHIONS $105.00 • High performance, noise attenuating earphones. • Noise cancelling microphone • Cushioned head pad • Super sturdy• Great performance • Superb, professional pilot's headset wlll last a lifetime with reasonable treatment. • Includes standard aircraft Jacks. Max. adjustable• Attenuator 0db -10db. OOW unbalanced a single PCB. Kit comes complete with K 2540 Passive Infra-Red Lite Guard C9070 ONLY $189.00 Floodlight Control WAS $135.00 CHRISTMAS SPECIAL ONLY $99.00 SAVE $36.00 100W and 60W 40hm -100V line Output Transformers Below Cost Priced to clear Converts 4ohm Amplifier output to 100V line Great for Public Address, Background music applications All Brand New Perfect Condition. 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Thus the system is ideal for families - even the kids can operate this system. • Facility for external siren • Battery back-up (bat\9ry 8 'C'cells not included) System Contents • Master Control Unit • Front Door Bell Switch• Panic/Emergency Switch • Three Window/Door Reed Switches • Mounting Hardware • 20 Metres Wire• Instruction Manual FANTASTIC VALUE Complete System S 5465 Normally $129.00 THIS M ONTH ONLY $99.00 NORMALLY $129.00 THIS MONTH ONLY $119.00 SAVE $10.00 Esrns its cost hunderds oftimes over In cleaning connectors, PCB'a, switches, jewellery, g/seeee, watches, drafting f»nB, etc. Awarded the Good Product Design Award for CETDC in 1987 CLEANER With Wireless Remote Control HIGH POWER CAR ALARM Pin Point U LTRASQN IC WIii even clean your teelhl Won't scratch or damage - uses ordinary tap water and creates millions of super-penetrating bubbles. Hospital tests show that t.ntruonic cleaning produces better results safer than conventional methods. 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Comes complete with Mo face plates for either concealed or visible fitting. S4390 $39.95 21 st Century entertainment - fascinate your friends this Christmas! PLASMA LAMP DISPLAY AMAZING SAVINGS ON 4BA <at>UD <at>mzD SPACERS AND SCREWS!!! ~ ~ ( Item FANTASTIC! SOLENOID OPERATED DOORLOCK Clear out Price 10 or Amazing! Pulsating high voftage plasma diaeharge continually changes shape and direction. Mode selectable to either fingertip control Of 50Und activated. For example, from voice or sound system . Provides endless fascination as it sizzles and arcs. Supplied complete with AC mains adaptor. more Imagine getting one far Christmas/ 100 $1.20 $2.30 $1.30 $ 2.30 8 $1.20 100 $6.00 $1.20 $1.00 $2.00 $1.20 $2.00 $1.00 $5.00 $1.00 $5.50 $9.00 Oty per pack 25 100 25 8 100 100 Normally $6.50 $10.00 A o120 Normally $199 SAVE $50.00 Up till now similar lamps have so for $1000 and more!! THISMONTHO WANTMOREPOWERFROMYOUR AMPLIFIER? - LOOK AT THIS!! BRIDGE ADAPTOR FOR STEREO AMPLIFIERS (SeoEAJune"B5) Many combinations to choose from 300 Watt Inverter with Auto Start Operates from 12V Car Battery Auto start draws power from your battery only when appliance is plugged in and ·turned on• , that is battery can be left permanently connected if required. • Voltage regulated • Current regulated• Current Overload unit self limits. Co mplete kit K 6750 $279.00 Fully built and t ested K 6755 $379.00 100's of uses at home and away. POWERHOUSE 600W INVERTER (See EA Dec "87) NEW THIS MONTHI This nverter has the capacity to produce 600 watts od mains power which will run a fantastic array of appliances. Ideally suited to running power tools, lighting (including fluros) electric motors and much more. It can be used a, a portable or permanent fixture. • Manual or Auto Start faciliti,es • Low battery cut-out. This simple circuit makes it possible for any stereo amplifier to deliver four times the single channel power into the same single load. Frequency response is 1OHz to 300k.Hz end harmonic distation is less than 0.001 o/o atBV RMS. K5565 Kit Version K 6770 $42S.00 GREAT Fully built and t ested 12V Input K 6774 SAVINGS I I I 24V Input K 6775 $525.00 $15.95 VALUE Beat Triggered Strobe <SeeAEMJuly1885) • • • Great for parties, shop displays and special lighting effects The DISCOLITE flashes party lights on and off in beat with the music from your sound system.• 4 tight channels contrlled by 4 seoarate audioe channels • Forward, reverse & auto-reversing chaser patterns • Simultaneous strobe on all 4 channels• Alternating light patterns• Music modulation available on chaser strobe and alternate patterns • inbuilt microphone for beat triggering or audio modulation of lights• Direct inputs • Sensitivity control • Presattabte sensitivity levels for each channel • Front panel LEDs mimic light display • Altronics kit prepunched and screened. DISCOLITE (See SIiicon ChlpJuly/Aug"88) K 5805 e BANKCARD e $1 S9.50 Add some life to your next party Designed by Auetralian Electronics Monthly. Aaah• in time to your music ph.Js it will work as a normal strobe. Exclusively customised by Altronics into our H 0480 instrument case, making construction a breeze and improving stability and overall appearance. Includes silk screened panel. K 5790 Was $79.95 Now $70.00 SAVE $10.00 For Increased power two tube option K 5795 $16.50 VISA e MASTERCARD e PHONE TOLL FREE 008 999 007 e NEXT DAY JETSERVICE DELIVERY 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. 174 Roe St. Perth W.A. 6000 008 999 007 Perth Metro (09) 328 1599 PHONE TOLL FREE ALL MAIL ORDERS P.O. Box 8350 Stirling Street Exchange Perth W.A.6000 ALTRONICS RESELLERS Chances are there is an Altronics Reseller right near you - check this list or phone us for detai Is of the nearest dealer. PIHH 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 - ,n many cases, however, Dealer prices will still represent a significant cost saving from prices charged by Altronics Competitors. Don't forget our Exprna Mall and Phone Order Service- for the coat of a local call, Bankcard, VIH or M•tercard holder• can phone order for Hme day deapalch. Blue Ribbon DHlen, are highlighted with a ■. These Dealers generally carry a comprehensive range of Altronic products and kits or will order any required item for you. WA 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 Jellervlce Courier for delivery next day Country areas please allow additional 24-48 hours. HEAVY HEAVY SERVICE - All orders of 10Kgs or more musttravel 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 11oods 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. COUNTRY ALBANY BP Electronics ■ 412681 ESPERANCE Esperance Communicatiuns 713344 GERALDTON Bird Electronics 641631 KALGOORLIE Todays Electronics ■ 212777 PORT HEADLAND Ivan Tomek Electronics 732531 WYALKATCHEM D & J Pease 811132 NT ALICE SPRINGS Farmer Eleclronlca 522388 DARWIN Ventronics 853622 ACT CANBERRA Bennett Commercial Electronics 805359 VICTORIA CITY All Electronic Components 6623506 The Electronic Component Shop ■ 6706474 SUBURBAN CHELTENHAM Talking Electronics 5842386 CROYDEN Truscott Electronics ■ 7233860 PRESTON Preston Electronics ■ 4840191 COUNTRY BENDIGO KC Johnson ■ 411411 SHEPPARTON Tattersal Sounds 8212892 MILDURA McWilliam Electronics 236410 WARRNAMBAL Kovoit Electronics 627417QUEENSLAND CITY Delsound 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 CHRISTIES 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 TASMANIA HOBART George Harvey ■ 342233 LAUNCESTON George Harvey ■ 316533 NSW CITY David Reid Electronics ■ 2671385 CARINGHAH Hicom Unitronics 5247878BLACKTOWN Sheridan Electronics 621 1494 CO UNTRY COFFS HARBOUR Coifs 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 AMATEUR RADIO BY GARRY CRATT, VK2YBX The 6-metre summertime special With the 6-metre season now upon us, we are presenting a low power, crystal locked exciter. When used with a suitable power amplifier, it can take advantage of the favourable ionospheric conditions normally encountered during the summer months on this band. Each summer, you will notice that TV reception on channel 2 becomes a problem, particularly around sunset. The most common symptom is a "venetian blind" effect which is usually co-channel interference from another channel 2 transmitter, perhaps many hundreds or even thousands of kilometres away. But while these summer conditions, due to atmospheric "ducting", temperature inversion, and improved ionospheric conditions, mean that TV reception is a problem, it's a wonderful time for working 6-metres over incredibly long distances. With that in mind, we decided on the "6-metre summertime special". The criteria for such a project should be economy (after all, the exciter may only be used for several months of the year) and simplicity. This left us To ensure stability, the 6-metre transmitter is built on a PC board with a ground plane. Take care with component orientation & keep all leads as short as possible. The circuit should be housed in a metal case. 66 SILICON CHIP looking for a single chip FM transmitter, without too much additional circuitry. During this "search", it dawned on us that there might be an integrated circuit, normally intended for the 49MHz cordless telephones used in the USA, that could be the perfect answer. Sure enough, Motorola have such a device , the MC2831A. This chip is a complete 49MHz transmitter and includes a variable reactance modulator for FM, a pilot tone oscillator, a low-battery indicator, and an audio amplifier with limiting - see Fig.1. The complete circuit, using the MC2831A chip (IC1) and an OM361 hybrid amplifier (ICZ), is shown in Fig.2 Third harmonic crystal The onboard RF oscillator for IC1 is an internally biased Colpitts type, which can be used for crystals in the fundamental mode or the L/C standard configuration. The crystal selected should have a frequency of exactly one third the desired 6-metre channel, as the third harmonic is g1merated (amongst others) by the output buffer, at pin 14. The crystal should be calibrated for parallel resonance, with a 32pF load capacitance. Table 1 shows a list of 6metre repeaters and popular simplex frequencies. Inductor L1 is used to provide compensation for the reactance of the modulator and for fine frequency adjustment. The modulating signal, either from a test oscillator or dynamic microphone, is applied via pin 3 of the IC. Our circuit uses the microphone preamplifier, with the signal going via zokn potentiometer VR1, and then to pin 5 via a lµF capacitor. The output of the preamplifier is then coupled from pin 6 to pin 3 via a lOkQ resistor and 2.2µF capacitor. This gives plenty of gain. We found that about 2m V from the microphone is all that is required to drive the exciter to 3kHz deviation. This is the internal limit set by the IC, at the crystal frequency. As we are using a harmonic which is three times the fundamental frequency, the maximum deviation possible will be 9kHz - too much for narrow band FM use. VRl allows the deviation to be set to the desired level. We found that 5kHz corresponded to the midpoint of the potentiometer travel on our prototype. Capacitors C5 and C6 should be selected to have the same value, in order to . minimise residual amplitude modulation (AM). We have not used the pilot tone oscillator or the low battery indicator features in our circuit since they are not required for this application. As previously mentioned, the MC2831A buffer generates harmonics, one of which we require and the others we do not. Hence, the output (pin 14) of ICl is fed to a bandpass filter, centred around 50MHz, which attenuates signals below 50MHz by 30dB. L2, L3 and VCl are the filter components. Note that these two coils are located at 90° to each other on the PC board, to prevent any mutual coupling. By carefully choosing the value of the coupling capacitors on both VARIABLE REACTANCE OUTPUT (1) (16) DECOUPLING (2) (15) MODULATOR INPUT (3) (14) RF OUTPUT vcc VCC2 (4) (13) GND ... MIC AMP INPUT (5) (12) VCC1 MIC AMP OUTPUT (6) (11) BATTERY CHECKER vcc TONE SWITCH (7) (10) LED .,. TONE OUTPUT (8) (9) OSCILLATOR COIL MC2831A Fig.1: block diagram of the MC2831A FM transmitter IC. the input and output sides of this filter, the fundamental and second harmonic of the crystal oscillator can be significantly further reduced. Using the values shown on the circuit, the fundamental and second harmonics of the crystal are attenuated by 30dB, while all frequencies above the desired 6-metre frequency are attenuated by 40dB. The trap formed by L5 and VC2 serves to reduce the 65MHz output component (twice the second harmonic of the crystal). 82!l +9V +12V 4.7 + 16VWr .001I 3.3k RF OSCILLATOR RF DSC 12 y 20kr,M MICvCJ . -~I-• ... .001+ 2701l . .001+ IC1 MC2831A 56pF Fii~JE( 15 2.2 56pF! 12DpF 470!! VC1 100k ._..,..._......,.........14 I L4 5uH II 11 II .001 ~OUTPUT 1 8 t7-50pf tpF 18pF .,. 13 .,- L2 ...0047l l2. l3 : 4T. 25 B&S TCW ON 5mm BOLT l5 : 6T. 25 B&S TCW ON 12mm BOLT L3 ':' 100!!.,. VC2 -, 7-50pf .,. 6-METRE AMATEUR TRANSMITTER Fig.2: most of the circuit functions are performed by IC1 which is the Motorola MC2831A FM transmitter stage. NOVEMBER 1990 67 We also experimented with an output lowpass filter, to further reduce the harmonic output, but found that the improvement of 6dB was not worth the effort. Any tuned power amplifier which follows this exciter will attenuate these unwanted signals even further. The IC has an RF outpu t of -40dbm, which of course is insufficient for our needs. We decided that an output level of lm W or so (0dbm) would be a good starting point. RF amplifier Out initial choice for the job of RF amplification was another Motorola device, the MWA120. This is a DCDC SUPPLY AND RF OUTPUT ,-----,----n vcc 2 DECOUPLING z MWA120 COUT >,.:..--t-o .,. .,.3 GNO Fig.3: the RF amplifier stage in the transmitter circuit (Ql) is similar to-the MWA120 hybrid amplifier from Motorola. It's a common emitter circuit based on a BFR91 or MRF571 RF transistor. TABLE 1: 6-METRE BAND REPEATERS FREQUEN CY 50.010MHz 50.075 50.090 51.020 51 .030 52.013 52.020 52.100 52.200 52.225 52.250 52.310 52.320 52.325 52.345 CALL SIGN JA21GY VS6S IX KH6EQI ZL1UHF ZL2MHB P29BPL FK8AB ZK2SIX VK8VF ZL2VH2 ZL2VHM ZL3MHF VK6RTT VK2RHV VK4ABP LOCATION Nagoya Hong Kong Honolulu Auckland Hawkes Bay Loloata Island Noumea Niue Darwin Taranaki Manawatu Christchurch Wickham Newcastle Long reach FREQUENCY 52.350 52.370 52.418 52.420 52.425 52.435 52.440 52.450 52.460 52.465 52.470 52.485 52.490 52.510 CALL SIGN VK6RTU VK7RST VKOMA VK2RSY VK2RGB VK3RMV VK4RTL VK5VF VK6RPH VK6RTW VK7RNT VK8RAS ZL2SIX ZL2MHF LOCATION Kalgoorlie Hobart Mawson Base Sydney Gunnedah Hamilton Townsville Mt. Lofty Perth Albany Launceston Alice Springs Blenheim Mt. Climie Where to Get the Parts The MC2831A is available from VSI Electronics (Australia) Pty Ltd in Sydney & other capital cities. The BFR90 or BFR91 transistors can be obtained from VSI or Dick Smith Electron ics. A suitable crystal (code GC05E) can be obtained from HY-0 Crystals. Phone (03) 783 96 11. The OM361 can be obtained from stockists of Philips components and Radiospares Components (all states) . A suitable microphone, complete 68 SILICON CHIP with plastic case and PTT switch (Model "07702" or "07704") can be obtained from Benelec Pty Ltd; phone (02) 693 5111. Additional information on the MC2831A can be found in the Motorola data book "Linear and Interface Integrated Circuits", DL 128 Rev 2 1988. Also in application notes AN-HK-02 "Low Power FM Transmitter System" and AN-HK-09 "A Fundamental Transmit Frequency Design in a 46149MHz 10-Channel Cordless Phone". 400MHz hybrid amplifier containing a single transistor with good power gain, a simple 3-pin package and, best of all, 50Q input and output impedances. However, after several enquiries we realised that the device, although still current on the manufacturer's production list, was not available in Australia. The prototype we had built used a device obtained directly from the USA. Nevertheless, we were undeterred. The data sheet for the MWA120 showed the internal circuit as having a single transistor and three resistors. Surely by opening up the device, we should be able to measure these resistors, then choose a likely transistor and duplicate the circuit. This is in fact what we did. By grinding off the top of the IC, we were able to identify and measure the resistor values, as shown in Fig.3. We selected two possible candidates from the transistor data book, either the BFR90/91 device or the MRF5 71. Both devices exhibit lOdB or so of power gain in this application, which is sufficient to drive the output amplifier, an OM361 hybrid amplifier (IC2). This brings the output level up to our target. The PCB layout for the exciter will accept both types of driver transistor. The output stage of the exciter comprises an OM361 hybrid amplifier, normally seen in television masthead preamplifiers, which has a gain of 28dB when operated from 12 volts. This stage provides sufficient gain to achieve an output power of lm W. Due to the high gain of this IC, particular care must be taken to ensure that the amplifier remains stable under all conditions. This means keeping the component leads of C13, C14, C15, L4 and C16 as short as possible. The main DC supply pin is fitted with an F29 ferrite bead to ensure that RF does not get into the supply rail. Construction Construction of the exciter is quite simple. The unit is built on a doublesided PC board measuring 92 x 64mm. The upper (component) side of the PCB is a ground plane, ensuring a good low impedance earth where needed. Component leads that are connected to ground should be soldered on both sides of the PCB. Three in- PARTS LIST 1 double sided PC board, 92 x 64mm , code SC06111 901 2 5µH inductors (L 1, L4) 1 17 .50833MHz crystal 1 F29 ferrite bead 1 20kQ trimpot (VR1 ) Semiconductors 1 MC283 1A FM transmitter (IC1) 1 OM361 hybrid amplifier (IC2) 1 BFR91 , MRF571 NPN RF transistor (Q1 : see text) TO MIC + 12V Fig.4: when installing the p arts, be sure to solder the leads on both sides of the board if the groundplane comes right up to the edge of the hole. The coils are made by winding tinned copper wire onto bolts (see Fig.2 for details). 0 Resistors (0.25W, 5%) 1 1MQ 1 270Q 1 100kQ 1 100Q 1 10kQ 1 82Q 1 3.3kQ 1 3.9Q 1 470Q 0 en ..... ..... ..... 0 Miscellaneous 2 metres of 25 B&S tinned copper wire, 50Q coax cable . (,!;) 0 ..... 0 en o• :o 0 0 0 -- 0 00 00 0 0a a - 0 0 00 0 0 0 0 00 0 0 ..... ..... ..... 0 0 0 00 00 00 0 <.O 0 ..... g ct,0 8 0 0 O'> 0!c)c,! oo• :o oo: 0 () 0 00 00 00 000 Capacitors 1 22µF 16VW electrolytic 1 4.7µF 16VW electrolytic 1 2.2µF 16VW electolytic 1 1µF 16VW electrolytic 1 .0047µF disc ceramic 5 .001µF disc ceram ic 1 120pF disc ceramic 2 56pF disc ceramic (should be closely matched : see text) 1 47pF disc ceram ic 2 18pF disc ceramic 2 7-50pF trimmers 0000 0 Figs.5 & 6: here are the two full size artworks for the PC board. The bottom pattern is the groundplane and is necessary to ensure a good low impedance earth. ductors - 12, 13 and 1 5 - need to be wound. We made ours fro m 25 gauge B&S tinned copper w ire (shown as TCW on the circuit diagram). All three inductors are air cored. You can wind them on a 5mm or 12mm bolt and the bolt's threads w ill give precise spacing for each of the turns . The RF output on the prototype was terminated in a BNC connector, for easy connection to an add-on power amplifier. The exciter should be housed in a metal box to ensure minimum oscillator leakage. The microphone can either be permanently connected, or a suitable plug/ socket combination can be used to incorporate a push-to-talk switch. The circuit draws almost lOOmA when fed from a 12V supply, so battery operation is not recommended. Next issue, we will describe a power amplifier for the unit. ~ NOVEMBE R 1990 69 . i · ~IBM*. CARDS . . \~ 1· ·e·,-' ·-··-l l , D. 2&4WAY RS232 DATA TRANSFER SWITCHES ::, w , z' 0 RS232 BREAK OUT BOX ~ C,.) ' a: \ei~~a~~!~~;J ~~g~a~~~ing. 2 spares. 24 switches enables you to break out circuits or reconligure and patch any or all the 24 active positions SPECIFICATIONS : Connectors : D825 plug on 80mm ribbon cable and DB25 socket. Indicators: Tncolour LED's for TD. RD. RT$. CTS, DSR. CD. TC . RC . OTA. (E)TC Jumper Wires : 20 linned end pieces Pow er : lnlertace power. Enc losure: Black . high impact plastic. Dimensions: 85 x 95 x 30mm The Fortron CPF Filtered Electronic Spike Protector provtdes a protective C z electronic barrier !or m1crecomputers. printers, telephone systems and modems electromc typewriters, audio and stereo syslems and other et rn w a: 0 I- . rn a: ::, 0 , g ~ C et rJ> A simple way ol monitoring RS232 interface lead activity. Interface powered, pocket size !or circuit CPF CONTINUOUS POWER FILTER SPIKE ARRESTOR I i: I- ' Cl Z · ci: al a: a: 0 UJ C a: : D .J ~ :E ► ::c .1J > .1J :c a: .1J .1J ::c ...z .L sensitive electronic equipment. The CPF provides protection from dangerous electrical spikes that can cause anything from obvious damage (like immediate equipment tailure) to less obvious harm that can drastically shorten a systems life CPFs superior circuitry design and semi conductor technology responds instantly to any potenti ally damaging over-voltage. ensuring safe trouble free operation. X15700 .............. $99.95 g Additionally. CPF's filtering capabihty helps eliminate troublesome and annoying interference, general hash cre.ated by small motors. fluorescen1 lamps, and the like that threa ten the performance and shorten equipment life of unprotected electronic components. SPECIFICATIONS: Electric al rating : 220·260 volls {AC) SOHz 10 Amp Spike/RF! Protection : 4.500 amps lor 20m/second pulses Maximum clamping voltage : 275V differential mode • Cat. X10088 THE BUTTON SPIKE PROTECTOR Surges and spikes are caused not only by lightning strikes and load switching but also by other equipment being switched on and ~tt. such as fhorescent lights. electric motors. !ridge freezers. air conditioners, etc. For effective protection such spikes must be stopped before they reach your equipment. Simply plug The Button into an outle t and it will pro1ect all equipment plugged into adjacent outlets on the same branch circuit. The Button employs unique metal oxide varister technology and wiU dissipate 150 joules of electrical energy. (nearly twice that of comparable surge arresters.) SPECIFICATIONS : ¥~:~ie~e~~~VR~~~~f~o ioules Response Time: 1Ons Protection Level: 350V peak ........... $42.95 RIBBONS ... .. ~ ~ AlJ\,! COMPUTER PAPER Quality paper at a low price! 2,000 sheets cl 70 gsm bond paper . Cat. 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X15663 Male to Male Cat . X15661 Male to Female Cat. X15664 Fem ale to Female Normally $33.95, Only $24.95 m " ··•" 4 PORT SERIAL. ............. $89 VGA 256K. ......................$199 VGA 512K....................... $299 VGA 1MEG ......... $495 i~i· ~!,,,.>"!:,lb;I VOICE MAIL.. ................. $245 PRINTER CARD.............. S35 EGA CAR D......................$139 2 WAY FUD CONT. RS232 GENDER · CHANGERS • Saves modifying or replacing non.mating RS232 cables • All 25 pins wired straight through Cat. X 15650 Male to Male Cal. X 15651 Male lo Female Cat X1 5652 Fem ale to Female Normally $14 .95 each Onlv$8.95 MOTHERBOARDS (360K) ............................ .. 549 RS232 SERIAU CARD..... ......................... 549 GAMES............................ $29 AT SIP GAMES ............... $35 4 WAY FOO CONT. (3S0-1 .44M) ... ..... ..........•.• :$ 129 2 WAY FOO CONT. (360-1 .44M)..................... $80 CLOCK CARO ................. $49 SMART DRIVE ADAPTER IOEIFOC .......... $89 SMART DRI VE ADAPTER IDE 1/0 IFOC ... $119 ~; £t.~i.~'.:.-.-.-.-.:::·::.::::::.::~~~~~ XT 12M STD. SIZE............. S199 SUNTEC AT 12M................ S375 80386-25 ... .~£~.'itt~ .... $2,695 80386- 33 ... !!'.1:!£'!!\....$2,995 RODIRVING ELECTRONICS SYDNEY: 74 Parramatta Rd . Stanmore. 2048 RS232 MINI TESTER • Male 10 female connec11ons • All ptn wired straight lhrough • Dual colour LED tnd1ca1es achvtly and direction on 7 lines • No battenes or power required T D. Transmrt Data D.S R. Data Set Ready R D Receive Oa!a C D C ctmt!rOt!lt:.'{;I Keep your computer and accessories free of dust and gri me while not in use A w o rk ing bench for your Mouse. •Stationary holder ' i R T S. Request lo Send D T A Data T erm1nal Ready C.T S Clear to Send Cal. X 15656 Nor mally $39.95 ~ :a:·. · •High quq,l i~y A BS plastic and ant i•static rubberised ,op i .-"' .:;.. SPECIAL ONLY $32.95 MAGIC STAGE ,-/ ''::~e~o;~:~~~r20 2 only 4 WAY CatX19125 only DUST COVERS 'I) et :., II you have two or lour compatible d evices that need to share a third or fi fth, then these inexpensive data tr ansfer switches will save you the li me a~d hassle of constantly changing cables and leads around. • No power required • Speed and code transparent • Two/Four position rotary switch on front panel • Three/Five interface conneclions on rear panel • Switch comes standard with . fl COPYHOLDE 7 (YU-H32) /4 • Adjustab.1~ ar ~s allows. easy pos 1t1oning • C o py area 9 112" x 11 .. • Sl id ing line g uide • Clam p mou n ting C21062 .. ... ...... $39.95 Phone (02) 519 3134 Fax (02)5 193868 MELBOURNE: 48 ABecken St Phone (03) 663 6151 NORTHCOTE: 425 High SI Phone (03) 489 8866 CLAYTON : 56 Renver Rd. Phone (03) 543 7877 MA!L ORDER & CORRESPONDENCE: P.O. Box 620. CLAYTON 3168 Order Hotline : 008 33 5757 (Tall lree , strictly orders only) Inquiries: (03) 543 7877 Telex: AA 151938 Fax (03) 543 2648 MAIL ORDER & CORRESPONDENCE P.O. Box 620, Clayton, 3168 Order Hotline: 008 33 5757 (Toll FrN Sb1cdy ordera onty) POSTAGE RATES $1 • $9.99 .. ........$3.00 $10 • 24,00 ........$3 .50 $25 • $49.99 ......$4.50 $50 • $99.99 ... .. .$6.00 $100 -$199 .. ... .. $7,00 $200 • $500 , ......$8 .00 $500 Plus ....... .. FREE The above poetage r•IB• aN t« bHIC postage only. Road freight, bulk,- and fragile IIIIHTW will be charged at dltterent rain. All sales tax exempt orders and wholesale inquiries to: RITRONICS WHOLESALE . 56 Renver Road , Clayton. Phone: (03) 543 2166 (3 lines) Fax· (03) 543 2648 For postage rates ref er to o ther R.1. E ad vertisem en t Errors and omissions excepted . Prices and speciftcations sub1ect lo change . 1BM· PC' Kl ' ,',l' are 1eg,~1e,«11,a<M>n"1arks or 1n1e,na1,ona1 Bu,;iness Mad>Klt!S · Apple 1s a reg,51&red trildemarl<. ·~tes <4'glMl!fl'<l Uadmatk sol trll!tr •est>l!Ct•~e owne rs / ' / '> .J / r: ~ ,'---------~:-~:---::---:=--~=-===~~~----:::=·~·--==:--=~'~-~/-=-~-~;;;;..-·--:=~'~'~-~~~=~·~"'~--~~...;....;....;'~-----◄·~ QUALITY COMPONENTS 2'::. ·. ' ..:. . • 1·9 10 ·99 100. ~ ~ -,~~. C: ·~ BNC PANEL SOCKET 1.9 I<( \ ~ ~ ~! BNC CRIMP PLUG Cl) •10530 $2.95 $2.75 $2.00 ::::, - 0 1~ 0 "" 1- 1·9 . · O '-- Designed to transmit at 40kHz (L 19990) and recleve at 40 kHz (L 19991 )with up to 20V 1/P on the transmitter. These units can't be heard so are ideal for TV remote control"s , water level detectors, burglar alarms 1 motion detectors and information carriers a~ they can be either pulsed or used in a continues wave mode. BNC SOLDER LESS TWIST ON PLUG ~ / ULTRASONIC TRANDUCERS ~ . \ . a: 10 -99 100• P10531 S2.50 $2.25 $2.00 <( - ~!!! . :c l! 0 iJ; ..._ t ·Transmitter 1 ·9 1·9 u;r:=- 1-9 -~ L.L ~ , - _-_ <.:>offi ___ ~ <( Q. M ~ ' ~ ; : -• !:: °'J--.., ~ . I > • ::::, ,,.,-~ <.:) Q ~I- '<(~ . ~ 1/ <.:) <( 1-9 3way ~~ ' I ADAPTORS The perfect solution! Features gold plated pins X15668 0B9 Plug lo 0825 Socket X15669 099 Socket lo 0B25 Plug. each $8.95 - m : melre W12672 1·9 m S1.60m 1 674 : ; ;o:":. we;ght , 220grams $2.SOm 1 676 : ; $3.SOm W12678 S220m $1.90m 1 1 ,°0: ~ • 100• m $3.20m $2.50m . CIC25 1·9 10+ P10579 8 pin 1.50 P10580 14pin 1.85 P10585 16 pin 1.95 P10587 18 pin 1.95 P10590 20 pin 2.95 P10592 22pin 2.95 P10594 24 p;n 3.95 P10596 28 pin 3.95 P10598 40 oin 4.95 1.40 1.70 1.80 1.80 2.75 2.70 3.50 3.50 4.50 IOC PLUGS ANO SOCKETS 1·9 WIRELESS MICROPHONE· 10450 ........... $24.115 100. $2.95 $2.50 $2.00 TRANSFORMERS $3.50 $3.00 $2.50 • O825P 25 pjn plug P11170 M.50 $105 $3.50 2840 240V 9VCT Cat M12840 $4.95 D TYPE IDC SOC KETS Iii pm 1ocke1 1·9 10 . · DE9S 100. P12167 $2.95 $2.50 $2.00 15 pin IOCket . 0A15S P12169 $3.50 $3.00 $2.50 Cat M 12860 H1O115...•. $2.25 .$1 .95 0-5A 0-1A 0·1A 0·20V ~,1v2~~~ st~o s~'.~·5 ,,:'"','oo. $14 .50 $14.95 f MOSF ET S P ECI ALS 1·9 $7.50 $10.00 $6.90 $9.50 10+ $7.00 $9.50 $6.50 $8.90 Requires no crossover and handles up to 100 Watts Sensitivity : 100dB/ 0.5 m Frequency response : 3kHz-3•0kHz Independence: 8 ohms. Size 96 m diameter Normally .................... $12.95 m ONLY .................... $9.95 11MIHIOIIIN -4·\ SPEMERS~ White durable plastic . 8 ohms Cat . C12010 VOLTAG! REGULATORS 12V DC FANS 80 • 25.4mm 7 Normally $11.95 UC 7905 7 ~ 2 UC $0.60 $0.60 $0.55 LM324 $1.IIO $0.90 •OO· $12.95 SSS $0.40 $0.38 $SOU Plus ........• FREE 115v 31 r T12467 .·$12.85 741 $0.50 $0.45 The .......... go,•to••rofor bulc poe11ge only. Roed "eight, 240V 3 1 rT12465 10, tans ( m1led) ;:::~g :~:: :::: $0. 55 v;:: ~mr :E :: 115v 458 T12463 $12.95 S0.90 P.O. Box 620, Cloyton, 3168 Order Hotline: 008 33 5757 BARGAINS $0\~ ~~5 P00STAGe°'RAT'es ~r~~~:o:::'. ~~y;4::• EL ~~J:~uAI C MAIL ORDER & CORRESPONDENCE =:~~Ion ~~~0l4A;:;.95 amps. computers . ho lspol 1r ~:ht~;,t~ eas yboatd,n!.ef'!,lt •O · HORNS 010550 MU65 0-100uA$16 .95 S4.95 FANS Ouol,ly Ions lo, us• m powe, ~ $1 .00 , I., 010538 MU65 0-50UA $16.95 010540 MU65 0-lmA $16.95 $3.95 10+ fans only $11.95 each $3.95 $3.00 $2 .95 S1 .20 $0.80 $0.80 $0.80 $0.80 8087CHIPS 8087•3 (4.77MHZ) $175 8087•2 (8MHZ) $265 8087•1 (10MHZ) $395 80287•6 (6MHZ) $295 80287-8 (8MHZ) $395 80287•10 l10MHZ) $495 • · 80387•16 (16MHZ) $795 80387-20 (20MHZ) $895 80387•25 (25MHZ) $1.095 .,_80_8_38_7_3_3_ _ _ _ _s_1._ ◄ 115--1 \I $12.50 $12.50 $12.50 $12,00 $14.95 rl $~;5 ,._ $2.50 $0.80 $0.80 r-----------1 100+ 010530 MU52E 0-lA 1----------"f 2SK:76 BO • •~~r.ket - P10880 10-+ $ 0. 70 $0.70 $0.70 $0.80 . ~;~~268·:~;~·$5.25 H10120 ..... $2.Q5 10+ $1.00 010535 MU45 VUP $4.50 SJ 2 49 6672 240V 15 30vc 1A tapped 2SJ 56 Cat M16672 $12.95 $11.95 2SK 34 IDC CENTRO NICS 36 WAY PLUG & SOCKET · Plug •• noo a 00mm •120x65x38mm MU45 MU45 MU45 MU45 2851 240V 12-6V CT 250mA P12171 $,1.50 $3.95 $3.50- ~~;-:::::;:,:::-n•n;i~:• H10111 ..... $4.95 $4.75 $2.50 1·9 $1.10 010533 MU52E 0-5A CatM12~51 $4.95 $4.50 2860 240 V 15VCT 250m A 25 pin IOdlet . 0825S uA :~::::... ::::~:.;•;::,:~::}~! 5 red 5mm 210159 2156 240V 6-1 SV A2 Cat M12156 $13 .95 $12.95 ~ 1 --- ,.:.:;... S0.10 so.12 so. 12 .9_5-4 1·9 1o+ t-0_1_05_60_M_u_s_5_o-_,_ov__s_,_s_ 2155 240V 6-15V 1A Cat M12155 $8.95 $7.95 ~ ~~~~ ~·~~~! m 1G-II Z10150(R)$0.15 $0.10 z,0151(G>so.20 so.15 Z10152(Y) $0.20 $0. 15 1-9 DE9S $1.00 DA15P $1.00 DA15S $1.00 DA15C $1.00 DA15P $1.00 DA15S $1.00 DB25C $1.00 0B25P $1.00 DB25S $1 .00 DE9~ $1.00 If you have 2 or 4 compatable 12c devices that need to share a 12c third or fifth, then these 12c inexpenclvedata tranter will 12C save youthe time and hassle T OGGLE SWITCHES of constantly changing Cables t----------➔ f.9 10-99 and leads around . S11010 O.P.O.T $0.90 $0.80 · No power required S11020 D.P.D.T $1 .10 $1 .00 · Speed and code tranparent Two or tour position rotary switch on front panel. · Switch comes standard with female connector. PANEL METERS RS232· 2 way ..................... $39 Save a for1une on expensive G ALORE RS232· 4 way .. ................... $59 throw away batter~s with RS232· X over. ................... $69 We have a great range of these quality Nicads and RS232- 2 way auto ............. $69 panel meters at great Rechargers! Centronics- 2 way ..............$49 prices! Size Oesc. 1-9 10• 100+ Centronics- 4 way ........ ......$69 010500 MU45 0-tm A $12.50 AA 450mAH $1.95 $1 .75 $1.50 Cenlronics• X over .............$69 010502 MU45 50/50uA $12.50 C 1 2 A H $9.95 $9.50 $8.95 Centronics- 2 way auto . $79 010504 MU45 0-100uA$12 .50 D 1 2 A H $9.95 $9.50 $8.95 · OA1SP 15plnplug wl1h~ ~~.ES s·;.90m $~.;Orn ;~oom 1--1 LEDS 1-9 10-99 RED 20c 15c GREEN 20c 15c YELLOW 20c 15c ORANGE 20c 15c • DE9P • pin plug 100 • m S1.50m S1.20m !:, 10, P10890 P10895 P10902 P10905 P10905 ,QUALITY 5MM LEDS 010510 010518 010520 010525 , • 185 x 113 Z10140(R) .... $0.15 $0.12 $0.10 Z10141(G) ....$0.20 $0.25 $0.12 Z10143(Y) .... $0.20 $0.15 $0.12 Z10145(0l ... $0.20 $0.15 $0.12 RECTANGULAR SWITCHES IC SOCKETS · c,c, 10 • m 100.m 100. FLAfflffiG ~DS Volume control : Tuning Led Oimmensions :l15x32x44mm ~ W12670 •CIC6 1.g m 10• m 100• m $1.30m._s1.1om 11.Qom .. oscUlaUon Power sup, 9V battery P10885 P10890 P10891 P10892 QUALITY 3MM LEDS Receiver freq: 37.1MHz Output level : 37mV(max) Receiving sys : Super c rystal IDATA( R~ NS F El These quality 3 level wire wrap sockets are tin-plated phosphor bronze. C ONNECTOR , Si• conductor shielded computer m1ert1ce cabl A 40< 35< 9 PIN T O 25 PIN ~COMPUTER . .-"Ii ,. • • - • · CABLES ~, . , 30< 35< 30< P1 2 168 10+ 100+ 12 12< 10< 15< 18< I<;< 25< 22< 30< 25< 30< 26< WIREWRAI> P12166 so.so $0. 70 $0.60 P10860 $4.50 $3.50 $2.50 · _ ... :30< 100+ eSO.&O $0. 50 $GAO CANNON TYPE 3 PIN LINE MALE 1- ,o. • P10521 100+ c::::i1 L.L . ,.. P108M $4.95 $4.50 $3.50 -w' ~ 1~ <( 1- 10+ 8 pin ······ 1.SC 14 pin .... 20< 16 pin .. ..20< 18 pin 20 pin .... 35< 22 pin .... 35< 24 pin .... 35< 28 pin .... 45< 40 pin .... 45< \Ill), MICROPHONE SPECS : Transmitting Frequency : 37.1MHz Transmitting system : Crystal oscillation . Microphone : Electret condenser Power supply:9V battery Range : 300 feet in open field RECIEVER SPECS: TheN terminal• future intertocking enda to form any number of conectione. Standard 5m,,, 1paclng pine • PtOS20 2 way CANNON TYPE 3 P IN CHASSIS FEMALE ......... P10550 P10S60 P10565 P10567 Pt0568 P10569 P10570 P10572 P10575 PCB MOUNTING SCR EW TE RMINALS (INTERLOCKING ENDS) tc / ~ . / ,/ $2.115 10+ 100+ CANNON TYPE 3 PIN LINE FEMALE f-9" H1+ 100+ P10864 $3.95 $3.50 $2.90 / i; : Cl) Receiver P10862$3.50 $2.95 $2.50 < zw $2.115 L19991 .• •• $3.85 . ,. ,., ,, DB25 CONNECTOR . SPECIALS t----------~ A10452 ............... $99 1O+ L 19990 ..... $3.85 CANNON TYPE 3 PIN CHASSIS MALE :E ~~I~ 3: Cal . No. Descriplion ==I~ =====IE 1-<I 1N8 RECIEVER Save • small fortune on these ··oirec1 Import .. low profile le sockets! PCB mounting solder 1111 . All tin plate-d phosphor bronze or berryllium and dual wipe tor reliability. It 10 99 100. P10516 $2.50 $2.25 $1.50 Cl) . (:':1 MICROPHONE & LO W PROF ILE IC S OCKETS H11800 .. 1 Og .... ..$2.00 H11810 .. 1 ... .$14.95 ==la; WIRELESS n n n )\ ~::s~~~~:~un~,:i~des.11 •10514 $2.50 S2.25 $1 .50 C ~ £Rn maintains a positive heats ink seal !hat improves heat transfer from the device 10 the healsink, thus increasing overall efficiency . BNC MALE PLUG .; z ,; ~ :+: ~ ~ ~•.:- - !, 'Ii C RYSTAL LOCKED ...,,......_..,.,....,._., ~ .. )(',.,.~ •••';ed lo the base and i.::, w LEOS )~ HEATSINK COMPOUND Heatsink compound is ,Q. ~ ~ BNCPLUGS ANO SOCKETS • .- J , only $1Q.85each $ 1 • $ 9 •99 •••••••.. . $ 3 .00 $10 • 24.00 •••••••• $3.50 $25 • $49.99 ...... $4.50 $;2~~00~;$$995190.909~.·.··.·.: •••••·.:F:~R:~E~E bulky •nd t,,glle l18mo wUI bo r~ ~/' lw>~ ' - - - - - - -R~O ~D : -:I~R~V~IN =-=G- E ~L ~E - CT ....&.R - O_N_IC -S -"7,1/r --....J..------L....,-----....L!•=hu~g~~·~··~'~~n~t,~•-~~-~~ ,if- ;:,, . Z 5 CITY: 48 A'BECKETT ST, MELBOURNE NORTHCOTE: 425 HIGH ST, NORTHCOTE SYDNEY: 74 PARRAMATIA RD, STANMORE . MAIL ORDER: 56 RENYER RD., CLAYTON --.~ -')1 / ~ Y v , PH: (03) 663 6151 PH: (03) 489 8866 PH: (02) 519 3134 PH: (03) S43 7877 ~~~ ..~ · FAX: (03) 639 1641 FAX: AS PHONE. FAX: (0 2 ) 519 3868 FAX: (03) 543 ~648 - #? ~ - - 1 All sales tax exempt orders and wholesale inquiries to: nlTRONICSWHOLESALE . 56 Renver Road, Clay1on Phone (03)5432166 (31ines ) Fax 03 5432648 .l l,. □ ~ \~ Errors andom,ss,ons excepled. , Pncesandspecilicalionssubjectlo change. IBM" PC ' Ill ' A T' .11er"9'sl.. .cU,..,.,,..,.., o1 ••-""""' """M" ""'"'"" ·- := ,.(~ "• ,;=:. ,,..,.,,. -1 ~ .:/ .-.... ~ _.. P. ~ ,.. -, "-• ~·~·•••.fllli :;?.~ Build this 1.5V to 9V DC converter get it going and can be operated from an AA, C or D-size cell. What's more, the TL496 only costs about $2. Sick of how quickly your 9 volt batteries go flat? Then switch over to more cost-efficient 1.5 volt cells with this 1.5V to 9V DC converter. It uses just three components and fits on a small PC board. Block diagram By DARREN YATES There's nothing worse than when you're using a piece of electronic equipment and you're just at a crucial moment when suddenly the rotten 9-volt battery goes flat! They're not cheap either. Don't you just hate paying the prices for a 9-volt alkaline or even just carbon-zinc 9V batteries? And what about the price of 9-volt nicads? Some retailers are charging more than $24 for these things, and when you consider they're only rated for lO0mA.h, that's pretty pricey. Even when you take into consideration the fact that they are rechargeable, you have to wait for up to 16 hours before you can use them again! As the man said, "there has to be a better way"! Well, there is, thanks to the Texas Instruments TL496. The TL496 is a very compact DC step-up switching converter IC which provides a regulated 9V DC output from a 1.5V DC input. It only requires a filter capacitor and an inductor to ~ The block diagram in Fig.1 shows the internal operation of the TL496 IC. An input voltage can be applied to either pins 2, 3 or 4, but each has a separate purpose. If you want to use just one 1.5V battery, then you apply this to pins 2 and 3. Or you may prefer to use two 1.5V cells in series, in which case you just connect them to pin 2 and leave pin 3 floating. Both ways have their benefits. If space is a problem, one cell definitely makes more sense, but the tradeoff is more current drain. Because it's stepping the voltage up six times (from 1.5 to 9V) and because the IC is not perfectly efficient, it uses about eleven times the current we get at the output; eg, we may get lOmA at the output but the circuit consumes 114mA from the battery. If you want to talk about efficiency ratings, the circuit is about 50% efficient. Even so, it is a much cheaper way of powering a circuit from 9V than to use 9V batteries. If you were to use two cells ·in series, the IC needs to step the voltage up three times and so requires only about six times the current. This doesn't change the efficiency of the circuit - it just means that two cells will last about twice as long as one cell. Our circuit uses the single cell option which we think is the most economical overall. High frequency oscillator This 1.5V to 9V DC converter is incredibly simple, thanks to the use of a dedicated switching converter IC from Texas Instruments (the TL496). There are just three components on the board, plus four PC stakes! The circuit can be housed in a separate case or built into the equipment to be powered. 72 SILICON CHIP Returning to the block diagram, the switching voltage regulator control uses a high-frequency oscillator to drive the output transistor, which has an inductor connected between its collector (pin 6) and the supply input. T INPUT (4) 2C INPUT (3V) (2) 1C INPUT (1.5V) (3) ELECTRONICS WORLD 9V SERIES REGULATOR SWITCHING VOLTAGE REGULATOR CONTROL 1----- NOVEMBER SPECIALS (6) SWITCH USED 'AA' 700mAH NICAD BATTERIES $ 0.50 TEMPERATURE CONTROLLED SOLDERING STATION $135.00 GND (5) GND (7) UNIVERSAL NICAD BATTERY CHARGER $ 29.95 Can do 4 at a time (AA, C, D, or 9V Nlcads) Fig.1: block diagram of the TL496 switching converter IC. It uses a high frequency oscillator to drive a switching transistor. D1 REVERSE BIASED 40 CHANNEL AM CB RADIO $ 79.00 + + VIN Fig.2: how a switching regulator works. When S1 is closed, current flows & energy is stored in the inductor. Note that diode D1 is reverse biased during this time. There may be some readers for whom switching regulators are new territory, so let's briefly go over the principles of operation. Basic principles If you take a look at Fig.2, we have an inductor, a switch, a diode and a capacitor. The inductor represents our coil, switch Sl takes the place of the output transistor in the IC, the diode is the zener diode shown in-the block diagram of Fig, 1, and the ea pacitor is our output capacitor. When the switch is closed (corresponding to the transistor being turned on in the IC), a current flows through the inductor as it stores energy. The anode side of the diode is now effectively connected to ground, so it is reverse biased and no current flows through to the load. In Fig.3 , we open the switch again to stop the current flow but the inductor tries to maintain the current. The voltage across the inductor rises sharply as a result of this. The diode now becomes forward biased and the inductor dumps its stored energy into the capacitor. The TL496 has an internal oscillator which drives the output transis- I 1 -0 VOUT 0- Fig.3: when S1 is opened, the voltage across the inductor rises. D1 is now forward biased & so the inductor dumps its stored energy into the capacitor. tor, switching it on and off at a rate which depends on the load current. The higher the load current, the higher the switching frequency. At any particular load current, the switching rate is not an absolutely steady frequency though; it hunts back and forwards. In fact, what actually happens is that the internal transistor is always turned on for roughly the same period of time, around 0.3 milliseconds. Then, depending on the load current, the switching rate can be anywhere from a few Hertz up to around ZkHz. SMOKE DETECTOR $ 49.95 PIEZO SIREN WITH BACKUP BATTERY $ 59.95 Ideal for Car Alarms DIGITAL DISPLAY AM/FM STEREO CAR RADIO $ 49.95 PORTASOL GAS SOLDERING IRON $ 35.00 ARLEC SUPER TOOL KIT $ 69.50 LOGIC PROBE $ 35.00 SCANNER FANATICS FREQUENCY REGISTER OF VIC. $ 24.95 PHILIPS INFRARED REMOTE CONTROL $ 35.00 COMMON CATHODE 7-SEGMENT DISPLAY $ 1.00 VIDEO DUBBING KIT $ 15.95 ARLEC 2 SPEED CORDLESS DRILL AND SCREWDRIVER $ 69.95 2-CHANNEL FM WIRELESS INTERCOM $ 89.95 SINGLE CHANNEL UHF TRANSMITTER KIT $ 18.00 SINGLE CHANNEL UHF RECEIVER KIT $ 34.90 VULTURE CAR ALARM KIT $ 39.90 ,c 2 2C GNO 1.5V T~~4S 8 OUT>-- - - - . . - , +9V GNO 470 16VW OUTPUT .___ _..___ _ _ _ _ _ _ _ _-<lOV * l 1 : 5JT .0.6J mm OIA . ENCU WIRE WOUNO ON A NfO SIO 17 747 10 TOROIO 1.SV TO 9V DC CONVERTER Fig.4: the complete circuit for the 1.5V to 9V converter. Note that you can also use two 1.5V cells in series, in which case the connection to pin 3 is deleted. INFRA RED NIGHT VIEWER KIT $239.00 TALKING ELECTRONICS ULTIMA FM BUG KIT $ 12.50 M ail Orders Welcome 30 Lacey St, Croydon VIC, 3136. Telephone: Fax: (03) 723 3860 (03) 723 3094 (03) 725 9443 NOVEMBER 1990 73 I I 7 uF 0 _... 9V --- Fig.5: inductor L1 consists of 53 turns of 0.6mm enamelled copper wire on a Neosid toroid core. Fig.6 at right shows the full size PC pattern. The maximum output current from the circuit is about 40 milliamps. At this current, a typical 9V battery would not la.st long at all. By contrast, a 1.5V D-cell will last for about 20 hours at this output current. Circuit diagram The circuit diagram in Fig.4 shows how few components are required one IC, one capacitor, one inductor and that's it! The inductor is a Neosid 17-742-10 toroid core, wound with 53 turns of 0.6mm diameter enamelled copper wire. The exact number of turns is not really important since the IC selfregulates. So as long as there are somewhere between 45 and 60 turns, the circuit will work. The efficiency will tend to vary by a small amount depending on the number of turns, but we found a figure of 53 turns to be about optimum. The 470µF filter capacitor is used to smooth the DC output on pin 8. The ripple output is generally around 50mV peak-to-peak, except at very PARTS LIST 1 PCB, code SC11111901, 60 x 38mm 1 TL496CP 9V switching inverter (IC1) 1 470µF 16VW electrolytic capacitor 1 Neosid 17-742-10 toroid core, 28mm OD, 15mm·ID 2 metres of 0.6mm enamelled copper wire 4 PC pins 1 AA, C or D size 1.5V battery 1 holder to suit battery Miscellaneous Solder, hookup wire, etc. 74 SILICON CHIP :::1 ~: -21 .,.... .,.... Constructing the DC Converter should only take about half an hour. We have designed a small board for the job. It is coded SC11111901 and measures 60 x 38mm. Whether you buy or make the PC board, check that there are no shorts or breaks in the tracks. If there are, touch them up now before you do any soldering. Begin the assembly by installing the four PC pins. These are used to connect up the 1.5V supply and the 9V DC output. Next, wind the inductor. This is the most time-consuming step in the assembly process. You will need just over 2 metres of 0.6mm enamelled copper wire. Winding the wire is a matter of threading the wire through for the required number of turns (53). Be careful not to kink the wire as you do the job. Make sure the turns are reasonably tight and spread evenly around the core. Bring both ends of the finished winding to the same spot so they can be easily soldered into position. Clean the two ends of the winding of enamel, by scraping it off with an old razor blade or utility knife blade. This done, tin the ends with solder, position the toroid on the board and solder the leads to the board. You will also need to use an anchor wire to stop the inductor from moving about on the board. The anchor wire is soldered to two unconnected pads on the board. Next, solder in the 470µF capacitor. Remember to check that its polarity is correct - the negative pin should go towards the inductor. Finally, solder in the TL496 IC. Again, make sure of the correct polarity - pin 1 (indi- 0 ,,- ,- .,.... u(f) low load currents. It can be reduced by substituting a larger capacitor. Construction 0 0 O'l TABLE 1 LOAD CURRENT <at>9V OUTPUT INPUT CURRENT <at>1.5V no load 0.1mA 0.5mA 1mA 2mA 5mA 10mA 20mA 40mA 50µA 1.3mA 5.2mA 11.7mA 25mA 57mA 114mA 230mA 460mA cated by the dot on top of the IC) should be closest to the outer edge of the board and furthest away from the capacitor. Finally, wire up the battery holder to the board, making sure that the polarity is correct. Insert the battery and then measure the output voltage from the board. It should be close to 9 volts DC. The completed board and the battery holder can be housed 'in a small plastic zippy case or, in some instances, built into the equipment it is to power. Don't forget to cut the track to pin 3 of the TL496 if you intend using two 1.5V cells in series. Current loads As mentioned before, depending upon your situation you can use either AA, C or D-size batteries with this circuit. Table 1 shows the expected load and input currents. Ideally, if you require large input currents, say more than 100mA, use a C or D- size cell for best economy. And if you use an alkaline cell rather than a carbon zinc type, it will last considerably longer. ~ Modifications to the 16-channel mixer In February, March, April & May of this year we published a 16-channel mixer design which has been very well received by enthusiasts. Predictably, many people are modifying the design to suit their own purposes and equally predictably, some have found that the performance can he improved. Whenever we publish a new design, we do so in the expectation that at least some of our readers will closely check through the design parameters to see what it achieves, to see if there are any mistakes and to see if it can be improved. And every now and again, some of these readers are moved to tell us the results of their endeavours. One such reader is Phil Denniss and we'll let him take up the story: I was filing away my back issues of SILICON CHIP when I came upon the articles for your 16-Channel Mixing Desk that were printed earlier this year. As I have a great interest in audio electronics I decided to read through the articles. Before pursuing this much further I would like to say that while I have not read the entire set of articles, I found the presentation very good, particularly the setting up procedure. But it is a shame to see such a lot of effort messed up by a fairly small but important mistake. However, the situation is very easily fixed without any need to change the circuit board. Basically, the problem is that the resistor values chosen do not yield the specified differential input impedance, nor do they give very good common mode rejection with any S1 : 1 : MIC 2 : LINE BALANCED 3 : LINE UNBALANCED 10DpF 10k 1°/, 1k 1% MIC ZO-....-'r--......- - - l l t - -......---w,1,,----...,_-"1 AND LINE INPUT 30---'-::+---+---tlr--4t----"WiAc--+----t--.......- - - - : : I S1b 2,~ _. • DENOTES CHANGE FROM ORIGINAL CIRCUIT "1' ia'l 0 REVISED PREAMPLIFIER FOR 16-CHANNEL MIXER Fig.1: revised circuit for the 16-Channel Mixer preamplifier stage. The component values that have been changed are highlighted with a star. Compared to the original, this circuit offers better common mode rejection and therefore is less prone to hum & noise pickup. source that does not have zero source impedance; ie, most real sources. I have done some calculations to establish what the input impedance and common mode gain are for the general case using the published circuit. I checked the results by lashing up the circuit and measuring the relevant circuit parameters. I initially used an LF351 op amp at DC without coupling capacitors because it was easier for me. I found that the 9H2 resistor should be 1kQ and the 427Q and 483Q values should total 10kQ, to balance the values in the inverting arm of the circuit. This will yield an input impedance of 1.07kQ and give a common mode gain determined by the matching between the resistors around this stage and the balance in the source resistance. I reckon there should be a 100pF capacitor to ground from the non-inverting input of the op amp as well, to keep a lid on the common mode gain at high frequencies, and I feel that the 10kQ resistors just after the input coupling capacitors do not do anything worthwhile either, though I might be persuaded otherwise. Initially, when considering the noise performance using the suggested modifications, I reckoned that maybe it would be 6dB worse because the input resistance was roughly doubled, or perhaps 3dB because the noise currents in the two op amps were perhaps correlated (it turns out that they are not). Well anyway, I figured that I had better check it out properly with an LM833, to find out the real answer. It sure surprised me. I figured that with the inputs shorted to ground, the difference in S/N between the two circuits would be less than 1.5dB. With 300Q to ground on each input (ie, a 600Q source), the difference would be about 1.15dB. This is because the input noise depends hardly on the NOVEMBER1990 75 11le MB3 I•• n»dium to ,,.•vy duty two pl•tfonn mounting br•ckel spec/flc.lly de•igned for •curing •peak,,n, ate lo wall• and eel/Ing•, deab or bench tape. Once mounted lhe br•cket can be rotated• full 360 degree• u _, u l»lng •wfve/led up or down until lhe required viewing or ll•tening •ngle I• •che/ved. I~ Both pl•lfor1T111 have predrllled hole• for mounting and •II moving parla and jolnta are eaai/y re/eaaed or locked with an large a/Ian key aupplied with lhe unit ~ ELECTRONICS CHRISTIAN BLIND MISSIQ~ ·J R,,gtoriKf[;~~e, bt1« COUPON Please cut and send to: CHRISTIAN BLIND MISSION INTERNATIONAL. P.O. _Box 5, 1245 Burke Road, KEW. Vic. 3101 Phone: (03)817-4566 e D Please send me further information about CBMl's work. As long as it is possible for me. I will help: D monthly D quarterly D annually D lo prevent blindness CJ to restore eyesight CJ to rehabilitate the blind Enclosed is my gift of$ _ _ _ _ __ Mr1Mrs, Miss, Street, __ _ City : __ . . l'aslcode : The MB5 i• • heavy duty IWO platform mounting bracket de•lgned for securing alTIIIII TV'• and speaker• lo walls, ceiling3, desks or bench Iopa. When mounled It can be rotated• full 360 degrees •• -11 n being swlw,lled up or down to any viewing or listening angle. Both p/sl -forlTIII have predrilled holes a'D , ~ .n.&\.liJ ,I ft ELECTRONICS 76 for mounting and sreenily adjusted with •large •llen keysupplledwlthlheunit. SILICON CHIP noise current of the op amp at all but depends mostly on the input noise voltage and to some extent on the bias and feedback resistors. While studying the LM833 data, I noted a graph of "Input Referred Noise Voltage vs Source Resistance" and this plot clearly shows that the noise does not rise 6dB above the zero Rs level until the source resistance exceeds 3kQ. For my circuit this does not happen until the source resistance actually reaches lkQ. At this value of source resistance, the original op amp will start to seriously load the source and this will in turn increase the SIN ratio more than my proposed circuit will. Just to make sure, I decided to lash up the circuit and measure the noise. The results were not too satisfactory because I used a protoboard which left the circuit open to pick up noise and hum. The exercise mostly showed how quiet the LM83-3 is and how easy it was to pick up a lot af unwanted garbage. However, it did show that the equivalent input noise voltage was about lµV and that the difference in noise performance between the two circuits is very small. Generally the published circuit is not a very good performer because of this very problem. The performance of the preamp is too dependent on the source impedance and the source impedance presented to the preamp is unknown. The ideal solution to this is to use a circuit that provides much higher input impedance, such as the two op amp instrumentation amplifier, so that the source impedance has much less effect. This will change the noise performance of the preamp. At worst, the noise may increase by 3dB but it may provide better performance because the preamp will effectively see a lower source impedance. It will see only the impedance of the source and not the input resistors. Another less important point I would like to discuss is the extensive use of electrolytic capacitors for coupling. I appreciate that circuit designers are pretty well up the creek when it comes to good high value (470nF and upwards) capacitors, and it is very hard to find an acceptable alternative to the old electro in terms of size, cost and capacitance. Bipolar electros seem to have disappeared. I think it would have been safer not to use so many electros, although this may compromise frequency response and/or noise performance. But more importantly I think you have specified the incorrect polarity for some of the coupling capacitors in the mixer and this may degrade the performance of the mixer somewhat. My reasoning is this: the LM833 has a fairly high input bias current, 500nA typical and lµA max according to the National book, and this can produce quite a high offset voltage (5m V or more) at the inputs of the op amp. This is amplified by the op amp (if it has a DC gain of more than one) and can reach 100mV or so at the output. Now the input transistors of the LM833 are PNP (for low noise I guess) so the current flows out of the input and will therefore produce a positive voltage across the input biasing resistor, or feedback resistor for the inverting input. It is important to note that the offset so caused may be positive or negative at the output, depending on the configuration of the stage, but is usually positive at the input. In the mixer, nearly all the electrolytic coupling caps have their positive terminal connected to the source and their negative terminal connected to the load. A quick check over the circuit indicated that the input capacitors of ICs la, 2b, 6a, 6b, 7b, 8b & 9b, and the output capacitors for ICs la, lb, 2a, 7a, 8a & 9a, are the wrong way around. I cannot tell the extent to which this will affect the performance of the mixer but I think that it is advisable not to reverse bias electrolytic capacitors if possible. (P. D., Chippendale, NSW). • How do you answer an onslaught such as this? Well, as we have done, you publish it. We quite agree that our single op amp balanced input will not give as good common mode rejection as the classic twin op amp design: In designing the balanced input stage for the mixer, we were deliberately trying to minimise the op amp count and obtain the best signal/noise ratio. However, as Phil Denniss points out, the circuit can be modified to improve the common mode rejection, particularly with real source impedances such as 600Q, without a significant increase in the residual noise. We calculated the noise performance for both single op amp circuits Fig.2 (left): this is the amended wiring diagram for the preamplifier board. The changes are all at the top of the board, near switch S1. and confirmed that the suggested modifications will provide only a 1.3dB increase in noise while changing the common mode rejection from -16.2dB for our circuit to better than -48dB with the modifications. We also tested the alterations and found the S/N ratio to be -99dB with respect to a 2V output and 600Q source impedance. The original arrangement produced -90dB under the same conditions, although this measurement was masked by hum pickup. The results indicate that Phil's modifications give superior results since the hum pickup is considerably less due to the improved input balance. Making the changes The revised circuit for the preamplifier is shown in Fig.1. By comparing this to the original circuit on page 61 of the March 1990 issue, you will see where the changes are. To help you spot the changes, we have highlighted each changed component value in Fig.1 with a star. Most of the circuit changes are associated with the section involving pin 3 of ICla. To help those who have already built the mixing desk, or those who intend to build it, we have produced an amended wiring diagram for the preamplifier board - see Fig.2. This will take the place of the wiring diagram shown on page 72 of the April 1990 issue. Note that the wiring to the switch is now simplified. The shielded cable from the pole of Slb to point "x" on the original diagram has been removed entirely. So has the shielded cable from the very top of the switch wafer. If you intend making changes to the original switch wiring, follow the new diagrams very closely. Six components along the switch end of board are altered. If you look at the top of the board you will see a line of 7 components, with two 33µF capacitors at the end. The changes to these are tabulated below: The 91Q resistor adjacent to these components is also Old 1.2kQ 10kQ 560Q 1.8kQ 470Q 13Q 0 New 1.1kQ 10kQ 100pF 10kQ link link changed, to lkQ. Note also the 1. lkQ resistor added across the switch and the earth from point 12 on the switch to the board. In addition, as noted by Phil Denniss, a number of electrolytic capacitors in the circuit are reversed in polarity. These are now correctly shown on the diagram of Fig.2. However, capacitors on the other boards should also be reversed. The capacitors in question are the input capacitors of IC2b, IC6a, IC6b, IC7b, IC8a & IC9b and the output capacitors of IC2a, IC7a, IC8a & IC9a. Ideally, these capacitors can all be bipolar types which are readily available, although they do cost a little more.~ NOVEMBER 1990 77 Prices to keep our Champ 360dpi Hi-Resolution Mouse. More squeak for your dollar! CAT /\CCM CHRISTMAS SPECIAL reduced from $99 While stocks last at $75 Pin plug to 25 pin socket. { '.t\T 1,ADr-Jl/.hF If you want a superb quality mouse that is fully MicroSoft and Mouse Systems compatible, this is it! The Champ Mouse is a precision pointing device, suitable for all Mouse driven software, including Windows, Word, WordPerfect, Ventura, CAD packages etc. The Champ features double the resolution of lesser rodents, with 500mm/sec tracking. Software allows software selection of resolution from 60 to 1080 dpi. Excellent tactile response and three button design are complemented by the FREE software that provides mouse support for a huge range of non-mouse driven programs. A MOUSE MAT and MOUSE POCKET are also included, but stocks are limited at this price so order early to avoid disappointment I r_ EGA Card with monochrome mode The World's fastest XT Turbo 31MHz XT Motherboard CAT.MBXC2 If you want t he fast es t XT on pl anet Earth.this is it . Our MBXC2 comes in at a sta gge ri ng 10.9 on Norton s SI - that 's 31MHz compared to 4.77MHz on your standard XT. The board is fully XT compatible and runs with all sta nd ard XT ca rds . Speed is switchable betw een standard 4.77MHz an d turbo spe ed. Up to 1 MB of RAM can be fitted on -boa rd. For even faster ope rati on, the m emor y abov e 640K can be used as "shadow RAM" for speeding up BI OS op era tions or as a RAM disk. T he boa rd provides software selection of wait-state Only $225, or , 1MB RAM fitted, only $395! Performance Index MBX C2 IBMXT s:J 10MHzXT 9 pin socket to 25 pin plug. IBM AT t 'AT I J\9F2!JM Tlic dp propnnte pins connect internally w aUow for mRtching of serial equipment llS!n<:J a mixture of 9 pin and 25 pin connectors (eg 9 pm serial connector on s,-,r 1RI mouse to 25 pm serial port on PC). :T Chipset PC/AT High perfonnance AT/386Hard Disk/Floppy Disk Controllers VGA CARD This graphics adpator is designed to upgrade the IBM PC/XT. 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The display uses the latest supertwist technology and provides excellent viewing in bright or dim light. The VGA colours can be mapped to 10 different grey scales for best viewing results. L------------------------..J r 1--1 :::fo*:~=•211,-, - •- - - • Fax (02) 906 5222 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 Motherboards carry a full 12 month warranty • All products carry a full 3 month warranty • All cards come with full documehtation • 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. L______________________________ _J COMPUTER BITS BY JENNIFER BONNITCHA Computer cables and all that rot Modem and serial cables bear a striking resemblance to each other. How can you tell the difference? What really is the difference between serial and parallel printer cables? Why do you need different cables for hard and floppy disk drives? We'll answer these questions and more as you read on. The PC world is full of cables. Apart from generating lots of paper, computers are really good at strangling you with all types of cables - serial and parallel printer cables, video cables, keyboard cables , modem cables, adaptor cables - the list goes on and on. The sad fact is that unless you use the correct cabfe for the job, you can end up feeling very frustrated with little to show for your effort. Cables come in two basic varieties round and flat ribbon. That's pretty trite but one thing is certain - your computer won 't work properly unless all the appropriate cables are correctly attached. A major problem for many people is how to tell the difference between the male and female ends of the cable. The photo of Fig. l shows the differences. On the left is a male connector; it has pins in the centre while the female connector on the right has pin receptacles or sockets. The male pins on a multiple-pin line plug are Fig.1: this photo shows two 25-pin D plugs. The one at left is a male plug while the one on the right is a female plug. 80 SILICON CHIP connected with the appropriate fe male counterparts at the other end of the cable to close a circuit. If you are still confused, think of the typical power outlet - the power plug is a male connector while the power point itself is a female socket. Be aware also that many cables will have the same type of connector at each end, depending on the configuration of the computer and the device you want to attach. So it is possible to have a cable with a male plug at each end. Once you understand the basics of cables and connectors, you will certainly feel more at home with your computer. Parallel cables The parallel printer cable (also known as a Centronics printer cable) enables you to connect a standard parallel printer to your computer. The connection is made by a cable with a multiple-pin plug at each end. The most common is a 36-pin Centronics plug at the printer end (named after the American printer company that pioneered this parallel interface) and a 25-pin "D" type connector to the computer end. The photo of Fig.2 shows these plugs for a typical printer cable. Your computer will probably have only one parallel port which DOS knows as LPTl. A parallel port has eight lines for sending all the bits for one byte •Of date simultaneously across eight wires. This interface is fast and is usually reserved for printers rather than computer-to-computer communications. The main problem with parallel ports is a limit on cable length of about 4-5 metres. Cables longer than this may require amplification (signal buffering) to reduce the risk of introducing errors into the signal. Extender cables are Fig.2: these are the connectors on a typical parallel printer cable. The connector on the left is a 36-way Centronics type while that on the right, which plugs into the computer, is a 25-pin D type. used to extend the length of an existing cable (funny about that!) and usually have a female connector at one end and a mating male connector at the other end. With this type of cable, all wires are straight through as appropriate. Generally extender cables are not recommended for the parallel printer. However, I have used a 6-metre cable with extender without any problems. You can try a longer cable on your computer but remember - you have been warned! The parallel port of most PC, XT and AT computers is unidirectional; that is, data will travel only one way, from the computer to the port, to the parallel device. The newer PS/2 computers have a bidirectional parallel port which enables data to travel to or from the port. This bidirectional capability is not currently used in most applications. Future uses for the parallel port may include taking input from high speed data transfer devices like scanners, bar code readers and video cameras. Pin arrangements Fig.3 shows the pin arrangement of the typical 36-pin parallel connector socket. Note that the pins are numbered from right to left. Some early model computers may have Centronics connections at both the system unit and printer ends. When this is the case, the cable often has the same male connectors at each end since printers always have female connectors. In the case of the Centronics connector, the female connector is a 18 1 (0----------0) "o---------0) 38 19 Supported & Serviced Australia-wide by Elmeasco Instruments Pty Ltd N S W (02) 736 2888 Vic (03) 879 2322 Old (07) 875 1444 S.A. (08) 344 9000 W.A. (09) 470 1855 You've Gotta Getta Goldstar from : A.C.T. John Pope Electrical806576N.S.W. D.G.E. Systems (049) 69 1625e W.FDixon (049) Fig.3: this diagram shows how the pins are numbered on a typical 36-pin Centronics socket. The pins on the mating 36-pin plug are numbered from left to right. You can see the numbers moulded in to the plastic, right next to the four outside pins. 69 5t 77 • Macelec (042) 29 1455 • Newtek (042) 27 1620 • Novacastrian Electronic Supply {049) 62 1358 • . Obiat PJy L)d 6~8 477f; 9 _Digitel 709 §511 e Geott Wpod 427 1676 QUEENSLAND St Lucia Electronics 252 7466 • BAS. 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 e The Electronic Components Shop 670 6474 • Factory Controls (052) 78 8222 • Mektronics 587 3888 • Truscott Electronics 723 3094 W AUSTRALIA Atkins Ca rlyle 48 1 1233 • Leda Electronics 361 7821 PAPUA NEW GUINEA TE (P.N.G.) Pt Moresby 25 6322 Lae 42 6246 ·Recommended prices only NOVEMBER 1990 81 36-PIN CONNECTOR - PRllfTER 25-PIN CONNECTOR 1 STROBE 1 2 DATA 1 2 3 DATA2 3 4 DATA3 4 5 DATA4 5 6 DATAS 6 7 DATA6 7 8 DATA 7 8 9 DATA8 9 10 ACKNLG 10 11 BUSY 11 12 PE 12 13 SLCT 13 14 AUTO FEEDXT 14 COMPUTEB GROUNDS18THROUGH25 31 - INPUT PRIME 16 32 FAULT 15 36 SLCTIN 17 Fig.4: if you are not sure about the details of your printer's parallel interface you should look at the instruction manual. Included will be a diagram like this which shows the exact pin assignments. socket-type - examine your parallel printer if you are still unsure. The standard parallel connector from your computer is more likely to be the 25-pin D-shell socket-type (DB25S). This connector conserves space since it is smaller than the Centronics connector (see Fig.2). Thus the "standard" parallel printer cable commonly has a male 36-pin Centronics connector at one end to mate with the SECONDARY RECV'. DATA DCE TRANB:r.nTTER SECONDARD RCV'. DATA RECEIVER SIGNAL SECONDARY R.T .S. DATA TERMINAL READY SIGNAL QUALITY DETECT RING INDICATE DATA BIG. RATE SELECT. DTE TRANS. BIG. ELE. TIM. 14 15 16 17 18 19 20 21 22 23 24 25 printer's socket-type printer connector, and a 25- pin D-shell (DB-25P) connector at the other to mate with the computer's parallel port. The D-shell connector is so named because it is "D" shaped - although one could argue that the Centronics connector is shaped likewise. Common D-shell connectors are the 25pin variety which have the DB-25 prefix and the DB-9 connectors corn1 2 3 4 5 6 7 8 9 10 11 12 13 PROTECTIVE GROUND TRANB:r.nTTED DATA RECEIVE DATA REQUEST TO SEND CLEAR TO SEND DATA SET READY SIGNAL GROUND RECEIVED LINE SIGNAL DETECT + VOLTAGE -VOLTAGE SECONDARY RECV. LINE DETECT SECONDARY CLEAR TO SEND Fig.5: this is the pin assignment for the RS-232 interface on a modem. Be aware though that they are by no means standard. If you are connecting a modem or other serial device, make sure you find out the exact pin assignment otherwise you could have lots of hassles with plugs and cables. 82 SILICON CHIP manly used for serial connections (eg, modems.) Note that in all cases, the "P" suffix stands for pin (male) while the "S" suffix stands for socket (female). Problem - if one end of the cable has a connector with 25 pins and the other end a connector with 36 pins, how does the message get through? Answer - not all wires are connected. Fig.4 shows a typical parallel interface line diagram. Although there is considerable standardisation, you must check your computer and printer manuals for specific information. As mentioned earlier, while the parallel connection is by far the most popular for printers, the main problem is the limit on the length of the cable. Solution - use a serial print connection instead. Serial cables The Reference Standard number 232 version C or RS-232C serial port (also called RS-232) on your computer is primarily used for devices that must communicate bidirectionally with the system, such as modems, mice, scanners, digitisers - or any device that "talks" as well as receives information from the PC. The asynchronous serial interface is, in fact , the primary system-to-system communication device. It is character oriented and thus has about 20% overhead for the extra information needed to identify each character. Data is transmitted through the cable one bit at a time, with each individual character framed by a standard start and stop signal as opposed to a parallel transmission of eight or more bits at a time. The recommended cable length is 15 metres, however much longer cables generally work without any problems. Your computer may have no serial ports or several. DOS numbers them consecutively as COM1, COM2, COM3 and so on. The original PC and XT computers and most clones of that era used the DB-25P connector and so required a serial cable like the one shown in Fig.1. The introduction of the AT computer saw a change to the computer connector with the advent of the DB-9P connector which has 9 rather than 25 pins for the serial port. Fun with RS-232 The serial port requires a communications or RS-232 cable to connect Table 1: Modem Pin Assignments and Description PIN NAME DIRECTION DESCRIPTION 2 T.D. To DCE Transmit Data: data is transmitted out from the terminal to the modem etc 3 R.D. From DCE Receive Data: data coming into the terminal from the device 4 R.T.S. To DCE Request To Send: the signal form the DTE informs the device that the terminal has data to send 5 C.T.S From DCE Clear To Send: indicates to the computer or terminal that data may be sent to pin 2 for transmission. Signal appears in response to asserting RTS 6 D.S.R. From DCE Data Set Ready: indicates to the terminal that the device is connected 7 Gnd Both Signal Ground: all signals on other pins are referenced to this level 8 C.D. From DCE Carrier Detect: indicates that a valid carrier has been received 12 H.S. From DCE High Speed: signal is low when the device has established communications 15 TCLK From DCE Transmit Clock 17 RCLK From DCE Receive Clock 20 D.T.R. To DCE Data Terminal Ready: signal from the computer or terminal which enables/disables operation of all inputs/outputs of the RS-232 22 R.I. From DCE Ring Indicate: changes level when a ring signal is detected 24 XTCLK To DCE External Clock input to device a serial port to another serial device and here is where the fun really begins! The "standard" serial cable can be either straight-through or a nullmodem cable. Most IBM/clone systerns use pin-type connectors for the serial port so you must use a serial cable with a mating socket-type connectar (DB-9S or DB-25S) at one end and at the other a connector suitable for connecting to the other device. Most devices have the socket-type connector (DB-25S). so the cable usually has a mating DB-25P connector. When you connect one PC to another, the cable needs to have a sockettype connector at both ends. What happens when you want to connect serial devices with differing connectars? You use either an adapter cable or one of the many "gender benders " supplied by most electronics stores. Fig.6: this is a typical RS-232 "gender bender", suitable for adapting male to female connectors or two cables with the same male or female plugs. They can save you the trouble of having to change a plug or the expense of buying a new cable. Fig.6 shows a typical example of the gender changing devices available. Armed with your serial cable and assorted adaptor devices, the other important information is the serial interface itself. Data terminal equipment The source or destination of signals on a communications network is known as Data Terminal Equipment (DTE). A device such as a modem which establishes, maintains and terminates transmission while possibly converting signals - is a Data Communications or Data Circuit-terminating Equipment (DCE). The main difference between the two is how the signals at the DB-25 connector are arranged. When you connect two DTE devices (ie, computer-to-computer), you need a null-modem cable, while DTE to DCE (ie computer-to-modem) requires a "normal" straight through modem cable. Fig.5 shows the standard computer RS-232 pin assignments while Table 1 provides a brief description of a typical serial connection - a modem. What it all boils down to is that cables are part and parcel of cornputer life. Confusion is overcome by asking questions, experimenting and labelling your cables as required. Acknowlegement Our thanks to Phil Gleeson of PC Marketplace for the illustrations used in this article. ~ NOVEMBER 1990 83 , ,_,_.._..., , o , ...... ,,.,,._,....,...,r, ,...,,_, 1 , _ , _ ,_ ,__, o, , ....., , u ,._, ~ ,-., , ,._,~, , ,_ ,_,_ ,._, ,, ,.._, .,.,,._,.......,,-., ,,__, ,-., , , l - LL- \,,,1 ,,,._,., .. .......... ....,,-., l \,,,r'\ I\ L L Lv,.,.._, , ,. , ....,.......,r'l f \,,,MI\ LL LV lf l V t .. l V uVn , ._,,-., , , L- L L \,,, 1 1 , v , .. , v ,..hJI"'\ I V r'l ll LL L V I 1 1\.J I .. I V'-' Ul"'\ I V l"'\1 1 LLLV I , ,,._,, .. I\." , ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONI CSJAYCAR ELECTRONI CSJA YCAR ELECTRONICSJAYCAR ELECTRONICS JAYCAR ELEC TRONIC, , ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONI CSJAYCA R ELECTRONICSJAYCAR ELECTRONICS JAYCAR ELECTRONIC, , ELECTRO~ ECTRONICS. l;::::'::::::::::;;';il'lfil ECTRONICS. ECTRONICS. ECTRONICS. ECTRONICS. ECTRONICS ECTRONICS ECTRONICS ECTRONI CS ECTRONI CS ECTRONICS ECTRONICS ECTRON ICS E:CTRONICS ECTRONICS ECTRONICS ECTRONICS ECTRONICS ECTRONICS ECTRONICS ECTRONICS ECTRONICS ECfRONI CS ECTRONICS ECTRONICS ECTRONICS ECTRONICS ECTRONI CS ECTRONI CS ECTRONICS ECTRONICS ECTRONICS ECTRONICS ECTRONICS ECTRONIC S ECTRONICS ECTRONICS ECTRONICS ECTRON ICS .ECTRONICS ECTRONI CS ECTRONI CS ECTRONICS ECTRONICS .ECTRON ICS .ECTRONICS .ECTRONICS .ECTRONICS ECTRONICS ECTRONICS ECTRONICS ECTRONICS Note: this picture of Model ECTRONICS ECTRONICS ECTRONI CS .ECTRONICS .ECTRON ICS .ECTRONI CS ECTRONI CS .ECTRONI CS .ECTRONICS .ECTRONICS .l:C I HONICS .ECTRONICS .ECTRONICS .ECTRONICS .EClRONICS .ECTRONICS .ECTRONICS .ECTRONICS .ECTRONICS .ECTRO NI CS .ECTRONICS .ECTRONICS .ECTRONICS .ECTRONICS .ECTRONI CS .ECTRONICS .ECTRONICS .ECTRONICS .ECTRONICS .ECTRONICS .ECTRONICS .ECTRONICS .ECTRONICS .ECTRONICS .ECTRONICS 7 .ECTRONI CS .ECTRONI CS ..ECTRONI CS .ECTRONI CS . ECTRONI CS .ECTRONICS .ECTRONICS . ECTRONICS .ECTRONICS .ECTRONICS . ECTRONICS . ECTRONICS ...1 SENSATION! You will never be able to get into VIATEL this cheap ever again. Jaycar have jumped on the bandwagon and have purchased DTX Australia Ltd 'Directronics' brand Videotex (VIATEL) terminals. These terminals enable you to connect your phone (some models even have phones supplied!), TV or RGB colour monitor to set up a VIATEL system in your home of office! Just think, you can access all of that fantastic information on VIATEL without having to pay a fortune for an exp€lnsive terminal. You will still need to pay the VIATEL service fee of course!! Each videotex terminal contains a fully Telecom approved modem and all electronics to decode VIATEL signals and display them on your TV or RGB monitor. We have roughly the same quantities of 4 fairly similar models. Model #1 ..... .... (the cheapest) features full console, au• numeric keypad (for entering into and operating the Videotex system), RF \ out (to your TV) but no phone. You can plug any phone into the socket provided of course, The phone is only used to . . access the Videotex a #2 number anyway (some phones can be used as key pads however). This machine is all you really need. ••• Cat. YV-7075 $29.95 That's right under $30 - HURRY, HURRY, HURRY!! Worth around $250 less than a few ye~us ago . Customers have been disappointed before when we have run out. Make sure you get in quick so that you won't be disappointed. Quantities are strictly limited but once sold, they are gone forever! Model #2 - identical to above but with a dedicated phone which can be used as a keypad. Cat. YV-7076 $34.95 This is one of the greatest bargains we have ever seen!! Model #3 ·-as per model #1 but with RF and RGB video output (for better quality colour on a suitable RGB colour monitor). Cat. YV-7077 Info on VIATEL $34.!15 Model #4 - as per model #3 but with a phone as well. Cat. YV-70 9 $39.85. SOLD OUT NOTE! All models are brand new in cartons with instructions. They are worth far more than this for the parts alone. They contain valuable Philips SAA5020 and 5050 chips . Because we are selling these at such a ridiculously low cost warranty is only one month from receipt. If you are worried about this buy a model #1 as a spare! There are two available entries into VIATEL. They are 'Discovery 40' or 'Discovery 80' depending on the level of service you require. You only need Discovery 40 with this special offer. There is a $60 joining fee and a $15 per month subscription plus Access Charge. Once you subscribe to the service you will get a pin number which will access you into the system. For more information call 'Discovery' (Telecom trademark) on 008 033 342 lt.~W'?~lY~ l l l l l l l ELECTRON ICSJAYCAR ELECTRONICSJAYC R ELECTRONI CSJAYCAR ELECTRONICSJAYCAR ELECTRON ICSJAYCAR ELECTRONICSJAYCAR ELECTRONI CSJA YCAR ELECTR ONI CSJAYCAR E:LECTRO NICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCA R ELECTRONICSJAYCAR ELECTRO NI CSJAYCAR ELECTRO NI CSJAYCAR ELECTRO NI CSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRON ICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELFCTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRO NICSJAYCAR ELECTRO NI CSJAYCAR ELECTRO NI CSJAYCAR ELECTRO NICSJAYCAR ELECTRO NICSJA YCAR ELECTRONICSJAYCAR ELECTRO NICS ELECTRONICSJAYCAR ELECTRON ICSJAYCAR ELECTRO NICS ELEC TR O NICSJA YCAR ELECTRONI CSJAYCAR ELECTRONI CS ELEC TRO NICSJA YCAR ELECTRONICSJAYCAR ELECTRONICS ELEC TRO NI CSJA YCAR ELECTRONICSJAYCAR ELECTRONICS ELEC TRO NICSJAYCA R ELECTRONICSJAYCAR ELECTRONICS ELECTRO NICSJA YCA R ELECTRONI CSJAYCAR ELECTRON ICS JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR ELECTRONIC ELECTRONIC ELECTRONIC ELECTRONIC. ELECTRONIC\ ELECTRONIC) ELECTRONIC, ' ,..., ,-....,.,...,.., ,.... ,,,..,,.... . • , ,,.... .. ,..., ,- , ,- .............. ,... • ., ,..,... , .. ,,,... ....... ,- , ,....,... ......... ,.. . ,, ,..,,... , . ,,,.., ....... ,- , ,...,... ................. ,,,..,,.... , .. ,,,... ....... ,... , ,...,...,- r, ,... • .,,...,... ' .. ,,,.... ...... ,- , ,... ,... .....,..,.,..... ,. ,... ,... , . ,,,... . ..... ,-, ,-,....,...r,,..., ,, ,...,,., •• , ,,,.., .. ,.... ..... .- .................... . ,, ,....~ . • . · - ' - -· - - - - - · ··-, I HU Nll,;:;JA YGAH t LtC I HONI CSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAl1 ELECTRONICSJA YCAR ELEC JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELEClllONICSJAYCAR ELEC JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTl1ONICSJAYCAH ELEC "" " ' " " C:LC:L, 1 t1u1.i1.,;:,._,ATL,A t1 t:Lt v JA'nm:mmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm!!!mm===========m=mmmmmmmimn(CAR Australia's Cheapest Telephone Answering Machine The public aren't ready for this one yet! This product was launched on the Australian market last year. It was state-of-the-art. reliable and low cost. It was a flop. Why? Because market feedback indicated that people did not like the 'sound' of the outgoing message This sound was. in fact, an electronic reproduction generated from a computer chip, not quite as' warm' as an outgoing tape message. Importers dilemma: The importer knew they had a good product but did not know how to sell it to an unsophistica ted public. They called Jaycar. Benefit from your sophisticated knowledge. As ti me goes by the public will get used to computer generated voice messages. Most overseas ·opera tors' (especially in the USA) are computer voices - as many of you would know. In the meantime, Jaycar bought the stock at a bargain basement price, and now we are offering it to you at a crazy price! But fi rs t. you must be hapl1( with the prod uct at any pri ce. Quite frankly, we think that there is nothing wrong with the reproduction sound of thi s machine. r,Ne really cannot unders tand why it 'frightens' the public. but that's what they tell us) We have tested the machine out and all the guys here have no problem with the sound. Extended Satisfaction Guarantee. Prove to yourself that it's OK though. Buy one of these machines and try it for 14 days (21 days for mail order). If you are not completely satisfied with this product for any reason, send it back in original condition and we will refund your money in full (less post & packing costs). We can't be any more genuine than that! Superi or fea tures: Most of the sophisticated machines comi ng out today are single tape units. The public's perception lags behi nd this fact. This machine has other great features too:J • • • • • - Advanced VOX system that stops recording when Incoming caller hangs up Flashing LED that Indicates number of massages that have bean left Answers to 2 or 4 rings Memo record faclllty Massage save option Battery backup to retain your outgoing message (battery not supplied) AUSTEL (Telecom) permit A89/16A/0057 12 month - yes! - 12 month warranty VIFA SPEAI{ER KITS BACK IN STOCK! We all know how fantastic the VIFA SA-Series speaker units sound. It wo ul d not be an exaggeration to say that they genera lly perform as well as bui ld equivalents that cost twice as much . VIFA SA-50 2 way kit 30 watts RMS full kit only $369 VIFA SA-70 2 way kit 50 watts RMS full kit only $449 VIFA SA-100 2 way kit 70watts RMS full kit only $699 VIFA SA-130 3 way kit 90 watts RMS fuII kit only $999 Cat. CS-2450/52 Cat. CS-2471/72 Cat. CS-2460/62 Cat. CS-2465/67 Ii ~iiiil~~--iliii;;;~ii;;lii~-.;ii.iiii~~~~ili1ilii.lili-~~~:~ ;JA\ 1;JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR 1;JMCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR 1,JA YCAR ELECTRONI CSJAYCAR ELECTRON ICSJAYCAR ,JAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR 1 ;JAYCAR ELEC TRONICSJAYCAR ELECTRONICSJAYCAH 1 iJAYCAR ELEC TRONICSJAYCAR ELECTRONICSJAYCAR liJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR , ______;: ELECTRONICSJAYCAR ELE AR ELECTRONICSJAYCAR ELECTRO YCAR EL[CTl1ONI CSJAYCAR ELECTRONICSJAYCAR ELECTRON ICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONI CSJAYCA R ELECTRONICSJAYCAR ELEC IAYCAR EL IAYCAR EL IAYC/\R EL JAYCAR EL IAYCAR EL IAYCAR EL JAYCAR EL JAYCAR EL JAYCAR EL JAYCAR EL JAYCAR EL JAYCAR EL JAYCAR EL JAYCAR EL J/\YCAR EL JAYCAR EL JAYCAR EL JAYCAR EL JAYCAR EL J/\YCAR EL JAYCAR EL JAYCAR EL JAYCAR EL JAYCAR EL JAYCAR EL JAYCAR EL JAYCAR El JAYCAR EL JAYCAR EL JAYCAR EL JAYCAR EL JAYCAR EL JAYCAR EL JAYCAR EL JAYCAR EL JAYCAR EL JAYCAH EL JAYCAR EL J/\YCAR EL JAYCAH EL JAYCAH EL JAYCAR EL JAYCAR EL JAYCAH EL JAYCAH EL JAYCAR EL JAYCAR EU JAYCAR ELI JAYCAR ELI JAYCAR ELI JAYCAH ELI JAYCAH ELI JAYCAR ELI JAYCAR ELI JA " CAH ELI JAYCAR [ LI JAYCAR El I JAYCAR ELI JAYCAH ELI JAYCAR ELI JAYCAR ELI JAYCAH ELI JAYCAR ELI JAYCAR ELI JAYCAR ELI JAYCAR El I JAYCAH ELI JAYCAR ELI JAYCAR ELI JAYCAR EU JAYCAR EU JAYCAR EU JAYCAR ELI JAYCAR EU JAYCAR ELI JAYC/\R EU JAYCAR EU JAYCAR EU JAYCAH [U JAYCM EU JAYCAR EU .IAYCAR EU JAYCAf1 [LE JAYCAR ELE JAYCAR tL[ JAYCN1 EU JAYCAR ELI JAYCAR ELE JAYCAR ELE JAYCAR ELE JAYCAR [L[ JAYCAI~ ELE JAYCAR ELE JAYCAR t LE JAYCAR ELE JAYCAl1 t Lf JAYCAR ELE JAYCAR ELE JAYCAR ELE iiliiiiiiiiiiii•==--===:wi )tX\:ii'L~\ ELECTRON ICSJAYCA ' LECTRONICSJAYCAR ELEClRON ICS ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTF1ON ICS ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECll1ONICS ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS ELECTHONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICS ELECTRONICSJAYCAR ELECTRON ICSJAYCAR ELECTRONICS ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELEC TRONICS JAYCAR ELECTRONICSJAYCAR ELEc ·r JAYCAR ELECTRONICSJAYCAR EL[ C I JAYCAR ELECTRONICSJAYCAR ELECl JAYCA R ELECTRONICSJAYCAR ELECl JAYCAR ELECTRONI CSJAYCAR ELECl JAYCAR ELECTRON ICSJAYCAR ELECl JAYCA R ELECTRONICSJAYCAR ELECl Piezo tweeter ith built in speaker protection at. CT-1912 3 7.95 :,.....•.•, .• ..•.•······•·· . TES 2360 DMM 3.75 digit 4,000 count . 39 range • inductance • frequency • temperature • peak hold ' logic See page 5 of 1990 catalogue for full details. All this and more for only $179 ATTENTION CUSTOMERS!! Cat. OM-1475 Make a purchase from any Jaycar store on Saturdays during Novembe r and receive absolutely "FREE" a sample of "WD-40". Offer valid for this month only. The box is made by Lume in Italy. It's waterproof/hoseproof, grey ABS with clear lid. The lid actually has a rubber gasket to ensure a watertight seal. · Size 150(L) x 110(W) x 70{H)mm. This type of box is in other catalogues for $70. Normally $29.95 Hi Quality Inner Ear CD Digital Headphones Supplied with Gold plated 3.5mm stereo plug and comes wi th a handy carry case. Try them. You will be amazed ~ with the sound!!! Only $9.95 Cat. AA-2015 This month only ~~ $19.95 Save $10 .,_. Protection for: Microprocessors, terminals. micro computers. printers. disk drives and telemetry equipment. Used by government departments. schools, universities. banks and TV stations. See catalogue for full details. 4 OUTLET Cat. MS-4020 $269 2 OUTLET Cat MS-4025 3.1~ $109 nf ra Red Remote Control Dimmer Update to electronic dimming! Cat. HB-6250 , ;"'~ This dimmer wiU repl_ace your normal large size light switch and •J1!¥~~:::::;~~~=::i~~=~:.;;::·· ·give you touch d1mm1ng/sw1tchmg and remote control I igital Capacitance \. Meter . At a touch of the button on the wall plate you can dim your light and the light will stay dimmed at whate1er level you lift your finger off. This function is repeated on the remote control. Wall unit colour- white with fawn panel. Two year warranty if installed by licensed electrician. Cat. XR-0800 r ·t.--· --· ·--····· · . , , Quality Disks at Silly Prices , , Lifetime Guarantee 5.25'DSDD 5.25' DSHD MF2DD $6.50/1 0 $1 5.95/10 $16.95/10 $34.95/10 Only $55 , Quality Dynamic ,;;,,,,======== ==~·-<,/ CD Stereo ·. Headphones XC-4730 XC,4732 XC-4736 XC-4738 , • .....,r,. , , ...._....._L....__, • , \ \.J r ,.,.....,._.,.,_,ro. I '--'r"II \ ...._ , _L .._, 1n\.Jl 'll\,., ..;>,.Jr\ l \,.,J>V l L L C. \,., I nVl'IP,., V.JI'"\ 1\,.,1'"\M CL C \.., t M V l\lll...,v,./1"\ f\..,l"\t"\ CL C I..., l t"\Vt\l l \..,v,./1'"\ TVAM C LC ..... I nVl\111....,.:),JM. fl....,1-\t'I C L CI...., I t1.Vl\lt\,.,V JM lVM n CLC\.., ln V l 'l l\,., -.>,..11" ... I '--'Mn L LLV , .,,._, ~YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRC \YCAR ELECTFlONlCSJAYCAR ELECTRONICSJA YCAR H ECTRONICSJAYCAR FI FCTRONICS.JAYCAR FI FCTAONICS. IAYCAR f'I JCr.TRONlr.<::. IAYrA R f' I f'r'.Tl>OtJ tr<:: IAVrAR f' I FrTAOtJlrS. IAVCAR ELECTRC . - ' CAR ELECTRC ,,\ YCAR ELECl IAYCAR ELECl IJA YCAR ELECl Ref: EA Oct 1990 onwards JAYCAR EL[Cl Ref: Silicon Chip August 1990 JA YCAR ELECl IAYCAR ELECl New digital unit uses high speed CMOS and a digital filter IC to At last! A totally new design preamp to match up to the spectacularty successful Pro-Series I power amp! This exceptional tA YCA R ELECI produce waves over a large frequency range • from 0.1 Hz to SOOkHz. performer is. as you would imagine. housed in a 1 x rack unit cabinet The Jaycar kit features a fully punched professionally JA YCAR ELECl The Jaycar kit includes PCB. box. punched and screened front panel Australian made cabinet. Absolutely no holes to drill or punch! Be wary of other kits which may only include an unpunched JA YCAR ELECl and all specified components. HK made box_ JA YCAR ELECl Cat. KC-5079 FEATURES: The main feature of this unit is its performance capability. In line with state-of-the-art design philosophy JA YCAR ELECT JAYCAR ELECl extraneous control have been eliminated from the signal path. The design totally avoids the use of screened hook up wire. IA YCAR ELECl It is consequently very easy to build. Signal-to-noise performance is staggering - up to 115dB! This machine is basically a IA YCAR ELE:C l wire with gain! Max distortion is 0002%. 1IAYCAR FLECI 11A YCA R ELECl Inputs for phono. line. CD, etc. abound with the ability to record from source to tape and monitor another source at the !A YCAR ELECl same time. In keeping with the serious nature of the equipment. the only front panel control is for volume. If you think that IAYCAR ELECl you need 'tone· controls forget this product It is for serious audiophiles only_ IAYCAR ELECl IA YCAR ELECl IAYCAR ELECl Jaycar collaborated with EA on both the Pro-Series I power amp and this exciting new preamp. Because of this. we are IAYCAR ELECl uniquely qualified to provide you with the best possible kit! As usual, nothing is spared til compromise quality. So if you IAYCAR ELECl want the best. this is it! IAYCA R ELECl Cat KA-1730 1IA YCAR ELECl Ref: Si Iicon Chip October 1988 •JAYCAR ELECl Stereo FM transmitter many uses. See catal JAYCAR ELECl Cat KC-5041 IAYCAR ELECl IAYCAR ELECl JAYCAR ELECl IA YCAR ELECl JAYCAR ELECl IAYCAR ELECl IA YCAR ELECl IA YCAR ELl:Cl IAYCAR ELECl IAYCAR ELECl !AYCAR ELECl IA YCAR ELECl Ref: Si Iicon Chip August 1990 IA YCAR ELECl This compact unit provides a precise voltage to IA YCAR ELECl IA YCAR ELECl Refer. EA September 1990 give a higher resolution of voltage readings from IA YCAR ELECl Kit includes PC board and all components; your DMM. Top multimeters such as Fluke 85 IA YCAR ELECl except 1 x 80mm length 16mm brass tube include this voltage measurement feature. IA YCAR ELECl Cat KA-1729 Kit includes PCB, box. label and all specified IAYCAR l:LECT IA YCAR ELFCl components. Cat KC-5082 IA YCAR ELl:Cl IAYCARELEC I IAYCA R ELECT IAYCAR ELECl Ref: Silicon Chip October 1990 IAYCAR FI EC ! This kit enables the Discolight {as described in IAYCAR ELECl Ref: Silicon Chip ASug 1990 SC July and August 1988) to be used simply as a IA YCAR ELECl Horace is a great project that is fun IA YCAR ELECl four channel dimmer_ Basically you can vary the to use once you've built it. Horace AYCAR ELECT intensity of the light on all Discolight functions. can sit anywhere and hwne he hears AYCAR ELECT Kit includes PCB. all components and hardware. AYCAR ELECT a sound he will chirp back. Small and Cat. KC-5085 AYCAR ELECT easily hidden_ Kit includes PCB, mic AYCAR ELECl insert and all components. AYCAR ELECT AYCA R ELECl AYCAR ELECT AYCAR ELECT AYCAR ELECT AYCAR ELECT AYCA R ELECT AYCA R ELECT AYCA R ELECT AYCAR ELECT The sneaky alarm - the alarm you have when you don· ·1 A.YCAR ELECT Ref: Silicon Chip September 1990 Ref: Silicon Chip September 1990 have an alarm! Red light flasher installs in dash and you A.YCAR ELECT Looking for a cheap module for event counting or o tie There's no need to buy a second VCR for the bedroom. This turn it on when you leave the car. Kit includes 2 BONUS A.YCA R ELECT used as part of a larger project? If so. consider thi s 3-digit simple kit will allow you to operate your VCR using its remote A.YCA R ELECT alarmstickers. counter module. It uses only two low cost CMOS IC's and control from any room in the house. Cat. KJ-700'.l . / . 0,YCAR ELECT can be put together in a couple of hours. Buy 2 kits and 0,YCA R ELFCT Kit includes all standard components. PC board and box. gang them together and get 6 digits and so on !! 0,YCAR ELECT ·. ! ' ' • I Cat Short form kit includes PC board and components. WCARE LECT WCARELECT Cat.KC-5083 \YCA R ELEC T \YCAR E:LECT \YCAR ELECT \YCARE LECT WCAR ELECT WCAR ELECT WCARELECT WCARELECT \YCARE LECT \YCARELECT \YCARFLECTI 188 Pacific HIN'{ {Cnr_ Bellevue Ave) {02) 439 4799\YCA RELECT - Mon-Fri 9 - 5.30 Thurs 8.30 - Sat 9 · 4pm SYDNEY - CITY 117YorkSt.{02)2671614\YCAR El [Cl , BURANDAQLD 144 Logan Rd {07} 393 0777 Mon-Fri 8.30 - 5.30 Thurs 8.30 pm - Sat 9 - 12 \YCA R ELECl ' Mon-Fri 9 - 5.30 Thurs 8.30 · Sat 9 · 12 \YCA R ELECT! PARRAMATTA 355 Church St {Cnr. Victoria Rd) {02) 683 'J!,77 MELBOURNE-CITY Shop 2. 45 A'Beckett St City {03) 663 2030 \YCA R ELEC-1I Mon-Fri 9 - 5.30 Thurs 8.30 pm - Sat 9 · 4pm Mon-Fri 9 • 5.30 Fri 8.30 · Sat 9 - 12 \ YCA R ELECT! CONCORD 115 Parramatta Rd {02) 745 3077 \YCAR ELECTI SPRINGVALE VIC 887-889 Springvale Road Mulgrave {03} 547 1022 Mon-Fri 8 30·-5.30 · Sat 9.00-12 \ YCAR ELECTI Nr Cnr. Dandenong Road Mon-fri 9 - 5.30 Fri 8. 30 • Sat 9 - 2 HURSlVILLE 121 Forest Rd {02) 570 700'.l IYCA R ELECTI ADELAIDE S.A. 190 Wright Street {Cnr Selby Street} (08} 231 7355 I Mon-Fri 9 - 5.30 Thurs 8.30 pm - Sat 9 - 4 \YCA R ELECT! Mon-Fri 9 - 5.30 Fri 8.30- Sat 9- 12 1YCA R ELECT! , ..'"''-'Vf"'\1vr..n L L L VI r lV l'I IV V-.JM \YCAR ELECTI ELECTRONICSJAYCAR ELECTRONI CSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAJAYCAR ELECT/ ELECTRONICSJAYCAR ELECTRO NICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTR ONICSJAJAYCA R ELECT! ELECTRONICSJAYCAR ELECTF1ONICSJA YCAR FLECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELEC TRONICSJAYCAR ELECTRONICSJAYCA R ELEC TRONICSJA JAYCAR ELECT! ELECTRONICSJAYCAR ELEC TRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTR ONICSJA JAYCAR ELECT/ ELECTRONICSJAYCAR ELECTRONICSJA YCAR ELECTRONICSJA YCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRON ICSJAYCAR ELECTR ONICSJAJAYCAR ELECT! ELECTRONICSJAYCAR ELECTRO NICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJAYCAR ELECTRONICSJA JAYCA R ELECT! J:"I i:::rTArif\urc::_ IA Yr AR 1=1 i= rTPrif\11r__ c::_ IA Y rAR i:::1 i=r"TQr\f\11r c:: 1/J..Vr J:J. Q i:-1 J:r T Rril\11rc:: 1AvrAo i::1 i=r T□ rH..1rrc 111vr110 c1 crT □ n11.11rc- 1 11vr11 □ c1 cr-Tnn~11rc- , • . ,,,.... . ......... . ..- ,,.... .... .......... ... ,,....~ . • JAYCAR FI F r.Tf SINE/SQUARE WAVE GENERATOR Pro Series II High Performance Stereo Preamp. THE ULTIMATE HI-FI PREAMP WAS $179.50 NOW $149.50 SAVE $30 $329 Normally 34.95 COFFSET KIT FOR DIGITAL MULTIMETERS e $39.95 RF Voltmeter Probe to Suit UHF Powermatch. MK2 This month only $29.95 SAVE $5 $7.50 DISCOLIGHT DIMMER $ 3 9 .9 5 s ·-ic&.95 Remote Control Extender for VCR's Deluxe Red Light Flasher Low Cost 3-Digit . Counter Module ~ ~ KC-5084 $29.95 $19.9 5 ~ $23.95 VISA • ,YCAR ,YCAR ,YCAR ,YCAR ,YCAR ,YCAR ,YrlJ.A I t!l I PRODUCT SHOWCASE I Low-cost 20MHz CRT readout oscilloscope from Goldstar In the May 1989 issue of SILICON CHIP, we reviewed a 20MHz dual trace oscilloscope from Goldstar. It was a good performer and available at an attractive price - so much so, that we purchased one for our own laboratory. Since then it has been a reliable workhorse. Now Goldstar has released a version with CRT readout, again at an attractive price. It does not offer all the "bells and whistles" of much higher performance CRT readout CROs, such as the Kenwood 150MHz model reviewed in the September 1990 issue, but the features it does offer are very welcome. All the control features, with the exception of those to do with the CRT readout, are identical to those on the standard Goldstar OS7020 model referred to above. The difference is that 88 SILICON CHIP the horizontal trace position and Holdoff controls, at the top of the panel, have been shifted to the right, to accommodate the six pushbuttons associated with the CRT readout. Goldstar's CRT readout features are quite simple and easy to come to terms with. Essentially, you have two cursors on the screen and they can be moved up and down with respect to each other and sideways with respect to each other. Both cursors can also be moved as a pair, up, down or sideways. At the bottom of the screen are displayed the vertical attenuator settings for the two input channels and the setting of the timebase. If one of the variable vertical attenuator or timebase control knobs is not in the calibrated setting, the readout will indicate that too; eg, >0.ZV or >50µs. In each case, the readout refers to the voltage per division or time/division; ie, 0.2V /div or 50µs/div, corresponding to the knob settings. At the top of the screen, there are · two readouts. The one on the left indicates the vertical displacement between the cursors and reads in volts or millivolts . For example, if the Channel 1 attenuator is set at 0.ZV/ div and the cursors are 3 divisions vertically apart, the readout will be "!1V1 0.600V". If channel 2 is being used at the same setting, the readout will be "!1V2 0.600V". On the righthand top portion of the screen, the readout will indicate the horizontal displacement between the cursors and reads in milliseconds or microseconds. For example, if the timebase switch is set to 50µs/div and the cursors are horizontally 5 divisions apart, the readout will be "!1T 250µs". If you then push the "1/!1T" cursor button, the lefthand readout will then display frequency; ie, "1/!1T 4.000kHz". Interestingly, you can have two different cursors on the screen, one for channel 1 and one for channel 2, although if both channels are in use (in alternate sweep or chop mode), the cursor setup for channel 1 is displayed. Moving the cursors is easy. First you have to select the cursor to be moved and this is done by pressing the SEL button to brighten the cursor to be moved. Pushing it once brightens the first cursor, allowing it to be moved in any of four directions with the arrow buttons. Pushing SEL again dims the first and brightens the second cursor, so it can be moved. Pushing SEL a third time brightens both cursors and they can then be moved simultanesously to match up with points on a displayed waveform. In some situations you may want to turn the CRT readout off completely. This may be to obtain an uncluttered screen or perhaps to obtain maximum trace brightness (it does dull the traces very slightly). To turn the CRT readout off, or turn it on again, press the SEL and 1/D.T buttons together. Why would you want CRT readout anyway? There are several good reasons. They make it that much easier to take precise measurements of waveforms off the screen, for pulse durations, rise and fall times, voltage swings and so on. Combined with a Polaroid oscilloscope camera, they make it unnecessary to write down the CRO settings - they're already on the photo. In short, if you want a CRT readout oscilloscope but don 't need the extra wide measurement bandwidth which usually comes with such instruments, then this 20MHz dual trace Goldstar model, the OS-8020R, is well worth considering. It comes with a comprehensive, well-written instruction manaul and two switchable probes and is priced at $1045 plus tax where applicable. For further information, contact the Australian distributor for Goldstar products, Elmeasco Instruments Pty Ltd, PO Box 30, Concord, NSW 2137. Phone (02) 736 2888 or their offices in other states. starting mode. As well, they are claimed to improve the life of the lamp by automatically adjusting the tube preheat time according to the wattage rating and thereby producing the optimum starting condition. The new electronic starters also incorporate an automatic cutout which means that they will not try to restart a failed lamp - a common cause of ballast overheating and failure. For further information, contact Thorn Lighting, PO Box 188, Smithfield, NSW 2164. Phone (02) 604 4300. Passive infrared lighting controller ·-Jl'll'TC..1111'&. ft detect when someone is moving around within 15 metres of the door. The unit then switches on any 240V lights for presettable times between 5 seconds and 10 minutes. It can also be used near stairways, garages, storerooms, etc and is great where security may be a problem. It is priced at $69.50 and you can check it out at any Jaycar Electronics store. Loudspeaker enclosure analysis program If the current crop of speakers on the market don't meet your requirements and you're ready to build your own, then this CAD package, called LEAP, may be just what you need. It was designed in the US and is IBM XT/AT compatible. It produces graphs of sound pressure levels, power responses, cone excursions, speaker impedance and amplifier current, all with respect to phase and amplitude. Two separate packages are available. First, you can purchase a demonstration package with six fixed Solid state fluorescent' lamp starter While fluorescent lamps are a great deal more efficient and last much longer than ordinary incandescent lamps, they do have one big weakness - the starter. As they age, they become unreliable and generally lead to flickering of the lamps. In some cases, their contacts can stick, which leads to burnout of the ballast and an expensive repair. Now there is a range of four plug-in electronic starters which are compatible with most fluorescent tubes. Called the Fluoropulse, they are claimed to give a much more reliable start because of their "multi-pulsed" lightning, power aurgee do not reach your coeuy equipme conetanlly monitoring the PHONE line the MAINS power lifHI. Simply contu1ct to an exletlng power point plug In your fex etc end a 1111rlee of indicator• ehowe the etatue of the malne power point. Fully Telecom •nd Dept of Mineral• and ~I, Energy approved. ELECTRONICS How many times have you come home early in the morning, and walked into low-flying flower pots while you fumbled around looking for that rotten verandah light switch? Well, you can avoid bruises to your person by getting one of these "people-sensor" light controllers. The Thromatic Security Sensor is installed near the door and in parallel with the existing light switch. It uses a PIR (passive infrared) sensor to enrenns existing Unique powderc receiving elernente 1/1 enaure11 excellent UHF reception compared to other UHF anlennM of eimilsr eize •nd price. Two model• are •wllsbla: TVA 14-Bsnd Four end TVA 15-Bsnd Rve. Both •tw aupplied with back reflectors to prevent ghoeting u well H • welerproof entry ~I, box and• till adjuet•ble ELECTRONICS metal mounting bracket Jl'II Tt.'lll'ft.. ft NOVEMBER1990 89 Super VGA monitor from Philips Known as the Brilliance, this monitor can operate in both standard 640 x 480-pixel VGA mode as well as the 800 x 600-pixel super VGA mode. It has a 60Hz refresh rate to reduce flicker and minimise user fatigue and it can operate with EGA, CGA, MDA and Hercules cards. The unit also comes with its own VGA card which is claimed to be 50% faster than most standard cards because it has true 16-bit throughput and memory caching. Software drivers for major applications such as AutoCAD, Ventura and Microsoft Windows are also designs which have been fully analysed. The $29.95 cost of the demonstration package is then refunded when you buy the full package. The full package comes with three discs and includes a tutorial and a 200-page manual with all the instructions you need to create your own enclosures. It retails · for $499 plus postage and packaging. For further information, contact the Australian distributors, Speaker Technologies , on (065) 50 2254 or by mail to PO Box 50, Dyer's Crossing, NSW 2429. provided with the package. For further information, contact Philips Components, 11 Waltham St, Artarmon, NSW 2064; or phone (02) 439 3322. blade and can cut through most soft materials such as plastic sheets and boards, plywood, leather, rubber sheets, cardboard, urethane and nylon sheets. It is priced at $16.95 from Jaycar Electronics. Uninterruptible power supply seem like much but when you consider that when the mains fails you generally lose your lighting and airconditioning too, there is a practical limit to how long you might want to continue in the dark. Three models are available, rated at 250VA, 350VA and 550VA, and they are very compact by virtue of not requiring a large storage battery. The 250VA unit, for example, designated the PC Might-25, measures 85 x 150 x 240mm and weighs less than 5kg. It uses a 12V 4Ah storage battery. The transfer time from failure to the UPS is typically 4 milliseconds and the output waveform is a quasi sinewave. The two larger models have a computer interface socket which can allow for automatic shutdown of unattended computers - great for systems which are permanently on-line. Prices start at $299 for the 250VA model. For further information, contact Lumen International Electronics (Australia) Pty Ltd, PO Box 543, Dandenong , Vic 3175. Phone (03) 791 3719. Fax-phone modem line filter Panel cutter from Jaycar This panel cutter is just the thing for cutting neat holes in plastic front panels for LEDs, switches and other panel hardware. The cutter is used like a chisel and has a blade adjustable to suit different material thicknesses. It is supplied with two 10mm and one 5mm 90 SILICO N CHIP Are you troubled by an unreliable mains power supply which is prone to fail at the most inconvenient times? Now there is a new range of uninterruptible power supplies which are much lower in cost than previous models on the market. These new units from Lumen International don't maintain the power for long after a failure but they do give you plenty of time to save your data and log off about six minutes. That might not Voltage spikes from electrical storms can easily damage your phone line communications equipment, leading to big repair bills. This phone line filter from Jaycar is claimed to give your equipment a good chance of surviving an electrical storm. The filter is simply connected between the phone line and your modem. The unit is priced at $99 from Jaycar Electronics and is presently available on a 1-month trial basis - if you're not satisfied with it after one month, they'll give you your money back. Check it out at your nearest Jaycar store or contact their head office at PO Box 185, Concord, NSW 2137. Large electroluminescent monitor is only 7.5cm deep Most monitors occupy a large amount of workbench space, especially the large 19-inch monitors used in drafting and desktop publishing. This electroluminescent display from Amtex Electronics is only three inches deep and even comes with its own power supply. With 1024 x 864-pixel resolution, it only requires a particular interface card to run with IBM XT/ AT PCs or with the Apple Mac II. Each of its 884,736 pixels is also individually addressable, allowing high resolution graphics and text. It has a wide viewing angle of more than 120 degrees and its amber display is easy on the eye. It also comes built into its own 432 x 394 x 75mm enclosure. For more information, contact Amtex Electronics, 13 Avon Rd, North Ryde, 2113; or phone (0 2) 805 0844. Supported & Serviced Australia-wide by Elmeasco Instruments Pty Ltd N S W (02) 736 2888 Vic (03) 879 2322 Old (07) 875 1444 S.A. (08) 344 9000 W.A. (09) 470 1855 Palm-sized VHS-C camera from JVC You've Gotta Getta Goldstar from: Weighing only 750 grams, the new JVC GR-AX7 is claimed to be the light est fully-featured camera produced to-date. Its chassis is 30'¼, sma ll er than the standard VHS camera and it fits in the palm of your hand. It is equipped with a 6:1 power zoom and a variable shutter speed from 1/50s for normal shots to 1/4000s for A.C.T. John Pope Electrical806576N.S.W. D.G.E. Systems(049) 691625e W.F.Dixon (049) 69 51 77 • Macelec (042) 29 1455 • Newtek (042) 27 1620 • Novacastrian Electronic Supply 049) 62 1358 e Obiat Pty Ltd 698 4776 e Oigitel 709 6511 e Geott Wood 427 1676 EE LAND St Lucia Elec1ronics 252 7466 • BAS. Audiotronics 844 7566 • The E:lectronics Shop (075) 32 3632 • Solex (Townsville)(077) 72 4466 • Xanthos Elec1rical (079) 27 8952 $.AUSTRALIA Force Electronics (08) 212 5505 VICTORIA G.B. Telespares 328 430 1 e The Electronic Components Shop 670 64 74 • Facto Controls (052) 78 8222 • Mektronics 587 3888 • Truscott Electronics 723 3094 AU THALIA Atkins Carlyle 48 1 1233 • Leda Electronics 361 7821 PAPUA NEW GUINEA TE (P NG .) Pt Moresby 25 6322 Lae 42 6246 'Recommended prices only NO\'l•:r-.1 BEil 1990 91 suit experimenters using a Commodore Amiga while the 15-pin connector is suitable for both PS2 and multisync cables. The 19 and 23-pin connectors retail for only $3.50 each while the smaller 15-pin connector costs $7.45. For further information, contact Geoff Wood Electronics on (02) 428 4111 or see them at 229 Burns Bay Rd, Lane Cove, NSW 2066. RMS reading analog & digital multimeter IEEE-488 controller board for the Mac This board, from Elmeasco Instruments, will turn your Macintosh SE/30 into an IEEE-488.2 bus system, capable of transferring data at rates up to lMB/ s. It can control up to 14 separate devices or instruments. Applications for this can include laboratory testing, production testing and process monitoring, as well as communicating with engineering, sci- fast action work. Also included is JVC's autofocus system, a digital superimpose system for adding in graphics and titles over the picture, and time and date insertion. Another interesting feature is backlight compensation for adjusting exposure to avoid "silhouetting" effects. For more information, contact the distributors for JVC products, Hagemeyer (Aust.) BV, on (02) 750 4188. entific and medical equipment. The board itself uses Turbo488 and NAT4882 custom chips, which were designed for the job and are extremely reliable. The unit comes with National Instruments Corporation's NI-488 software driver and requires no configuration jumpers. All settings are performed by software. For further information, contact your nearest Elmeasco office or phone Sydney (02) 736 2888 or Melbourne (03) 879 2322. DB connectors from Geoff Wood Now available from Geoff Wood Electronics are these 15, 19 and 23pin connectors. The 23-pin unit will I.E...;. t■i;~~:.;;: RCS Radio Pty Ltd is the only company which manufactures and sells every PCB f, front panel published in SILICON CHIP, ETI and EA. 651 Forest Road, Bexley, NSW 2207. Phone (02) 587 3491. 92 SILICON CHIP There are times when you need the accuracy of digital and the continuity of analog measurement. This new multimeter from Altronics combines the best of both worlds and has true RMS indication as a bonus. The Hung Chang HC-5050DB has a mirror-backed moving coil meter and a 3½-digit (1999 count) LCD panel meter to give simultaneous analog and digital measurements. It will measure from 200m V to 1000V DC with ±2.5% analog and 0.5% digital accuracy in five ranges, and AC voltages between 200m V and 750V with ±3.5% analog and 0.75% digital accuracy. Also included are dB, current to 10 amps, resistance to 20MQ, continuity and diode measuring capabilities. The true RMS indication is good for AC and pulse waveforms with crest factors up to 5 for up to 1000 counts and crest factors up to 2.5 for up to 2000 counts. The unit comes complete with probes and instruction manual which has an internal schematic and parts list for the meter. Considering all its features, the price is a bargain at $199.50. You can get yours from Altronics in Perth or one of their distributors. Dual DACs in a single chip This series of new ICs from Analog Devices provides two digital-to-analog converters (DAC) in a single 24pin DIL or surface mount package. Having 12-bit resolution, the AD7237 and AD7247 each contain their own internal reference and can be loaded either serially or in parallel, depending on which device. With linking options, the output voltage can be changed to one of three ranges: 0 to +5V, 0 to +lOV or ±5V. Introduction to Digital Electronics - from p.22 clock pulses and the resulting outputs are shown in Fig.14B. Fig.13D. There it would appear that the input frequency is being divided in half. At time T1, the clock is positive-going so no change occurs. But at time TZ, there is a negative-going change, so the output snaps from low to high. The next negative-going transition occurs at T4, so the output line snaps low again. The result is that two input pulses (A and B) must be applied to the clock line to create one complete output pulse, therefore: fm = 2fout If JK flipflops are connected in cascade, as in Fig. 14A, their outputs form a binary division chain. In the 4-bit case shown, the input frequency of the clock is f. The frequency at Ql is f/2, at QZ it is f/4, at Q3 it is f/8, and at Q4 it is f/16. An example series of Conclusion Output accuracy is guaranteed to ±1 LSB. The power dissipation is 165mW from a 15V supply and the output buffering amplifier can provide a 10V output swing across a ZkQ load. ANTRIM TOROIDAL TRANSFORMERS Logic gates and flipflops are very useful electronic devices. Clearly understanding the rules governing each one allows the experimenter to use them in both traditional and non traditional circuit applications. By using your imagination, you will be able to solve a remarkable variety of electronics problems. Footnote: readers who want a more detailed course on Digital Electronics should refer to the 10part series entitled "Digital Fundamentals" by Louis Frenzel which was featured in the November 1987 to September 1988 issues of SILICON CH IP. For further information, contact the distributors for Analog Devices, NSD Australia, 205 Middleborough Road , Box Hill, Vic 3128. Phone (03) 890 0970. E-1 LAMINATED POWER TRANSFORMERS PCB mount ex-stock in sizes from 2.5VA to 25VA with secondary voltages from 2 x 6V to 2 x 20V. Triple output models also available for logic circuits. Chassis mount manufactured to order in sizes from 2.5VA to 1 KVA in E-1 and C core. PCB MOUNT STOCK RANGE QUALITY TOROIDAL POWER TRANSFORMERS, MANUFACTURED IN U.K. NOW AVAILABLE EX-STOCK AT REALISTIC PRICES. General Construction We are the largest ex-stock supplier of toroidal power transformers in Australia. Our standard range consists of the U.K. manufactured ANTRIM range in 10 VA sizes from 15VA to 625VA. All have a single 240V primary and dual secondary windings ranging from 2 x 6V to 2 x 55V. Our local manufacturing facilities supplement this range by manufacturing specials to order. Models are available from stock to suit most project kits. Comprehensive data sheets are available on request. Enquiries from resellers and manufacturers are welcomed. Prices are extremely competitive and generous trade discounts apply for quantity. CHASSIS MOUNT TO ORDER HARBUCH ELECTRONICS PTY LTD 90 George St .. HORNSBY NSW 2077 Phone (02)476-5854 NOVEMBER 1990 93 A-3000 REMOTE CONTROL SYSTEM "You can control just about anything with this remote control transmitter/receiver. TV's, Stereos, Alarms etc. * Receiver relay output: N.0./N.C. up to 5 amps. • Receiver operating voltage: 12 volts DC • Complete with two (2) remote keys (batteries included) • Operating Distance: 1Ometers • Frequency: 300 - 31 OMHz * GOODWILL GOS-622 20MHz 2CH. OSCILLOSCOPE * Display: CH1 , CH2, DUAL, CH2, X-Y * Sweep Modes: Auot, Normal Single Shot. * Auto Trigger Level Lock, Variable Hold-off. * Sensisitivity: 5mV/DIV to 5V/DIV to 20 mHz ·'l NORMALLY$109. * Includes 2 x 1:1 & 10:1 PROBES ,::; NOW $89.9 ONLY $799.00 12 MONTHS WARRANTY CB SWR METERS BELL-QUARTZ DIGI-THERMO DIGITAL THERMOMETER CB-005 SWR/POWER and FIELD Strength Meter 1OWatt/ 100 Watt Switchable * Temperature Range: -40°C to +50°C NORMALLY $39.95 Selectable 1sec or 15sec Sensing Time. ' * Presettable Hi/Lo alarm. * Stainless steel probe with 1mtr Cable * LED Display * NOW$24.95 CB-100 SWR/POWER and MATCHER 1 Watt/ 10 Watt/ 100 Watt Switchable Slim-line Design "Only 3cm High" ONLY$44.50 NORMALL y $29.95 CARREPLACEMENTSPEAKERS $11.95ea $ 4.95ea $ 4.95ea $ 4.95ea $ 6.95ea $ 9.95ea SK46-4 4" x 6" 4ohm 20Watt SK5-8 5" Bohm 5Watt SK5-4 5" 4ohm 5Watt SK6-4 6" 4ohm 8Watt 5K14-4 4" 4ohm 25Watt 5K44-45" (Low Profile) 4ohm 10Watt !a .... a.a •1111 1111 e •-• tll 11...a "W * HDS-90 PROBE TYPE DIGITAL MULTIMETER • Auto and Manual range operation. AC/DC ampere measurement. * Logic test function (CMOS/TTL) • Data hold and diode test functions . . • Fast response continuity buzzer. • Large 3.5 digit LCD display. * 12 Months warranty . Ni-Cad BATTERY PACKS * ea To suit most cordless phones NOW ONLY $55.00 T.V. VIDEO R.F FLYLEAD - 75 ohm COAX For most cordless phones and ~ battery~back-ups NOW $19.95 * roclType# 2 , 20 meter length - Low loss cable Male to Female PAL connections • Includes Male/Male PAL adapter * * NORMALL y $18.95 To suit most computers for battery back-ups. NOW $9.95 VIDEO LEAD - 75 ohm COAX BNC/RCA to BNC/RCS plugs NOW ONLY • 1.5 mtr Length $9.95 a•-----------Iii '1~ A .. 9.6 volt $24.95 3.6 volt $13.95 PLAYMASTER "PRO SERIES ONE" HIGH POWER AMPLIFIER KIT NORMALLY $599.00 Now $549•00 SAVE $50.00 Output Power: 140Watts RMS into Bohm 200Watts RMS into 4ohm Distortion: 0.005% at 1OOWatts into Bohm Frequency Response: 1OHz to 1OOkHz KASPAROV- "CONQUISTADOR" 16KCHESSCOMPUTER • 17 Playing Levels • 4 tournment Levels with clock controlled play • 3 Specialist Levels (Problem Solving, Infinite, Analysis and 10 second chess) * 9 Casula Levels (including MAKES A Beginners Levels) GREAT GIFT ONLY $199.00 "Offers a Tough Challenge to over 92% of all Chess Players" MULTI-LINGUAL POCKET TRANSLATOR *Ideal for travellers, students, business people and holiday makers. • Instant word conversion of ENGLISH, FRENCH, GERMAN, SPANISH and ITALIAN. • 1,400 words in each language. • Light and easy to carry. 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BOX Q103, SYDNEY 2000 PHONE ORDERS: (02) 2671385 FAX: (02) 2618905 NOW ONLY $21.95 Ideal for computers, TV and videos etc. MORE SPECIALS IN THE FRONT OF THIS MAGAZINE POST & PACKING $5 - $25 ..... ,.. ,. $3,00 $26 - $50 ....... $5.00 I $51 _$100 ......... $6.00 $500 + $101 -$499 ...... $8.00 FREE 1 1 Silicon Chip BACK COPIES ~ reo Power Am.!tirm; End Of File ; -,-..,.,-'-'",,.,s Adaptor For Multimeters ; · o ation 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 Radio-Cassette Players ; Old-Time Crystal Radio. ttle For Model wimming Pools ; e Amplifier For Feedback, Pt.1; HF & UHF Bands. April 1988: Railroads, P Slave Flash CD Players; Mobile Ante 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 C~ plifier (Uses LM833) , Pt.1 ;-BT'eakar~ ,iesftOYi"61ii1ion For Cars Using Hall Eff · -Fast Nicad Battery Charg , utomatic Light Controller (Uses PIA 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 12 150W Op Amp Data & Applications ; What Is Negative Feedback, Pt.4. October 1988: Stereo FM Transmitter (Uses Rohm BA1404) ; High Performance FM Antenna; Matchbox Crystal Set; Electronic House Number; Converting A CB Radio To The 28MHz Band; Queensland's Powerful Electric Locomotives. November 1988: 120W PA Amplifier Module (Uses Mosfets); Poor Man's Plasma Display; Automotive Night Safety Light; Adding A Headset To The Speakerphone ; How To Quieten The Fan In Your Computer; Screws & Screwdrivers, What You Need To Know; Diesel Electric Locomotives. December 1988: 120W PA Amplifier (With Balanced Inputs), Pt.1; Diesel Sound Generator; Car Antenna/Demister Adaptor; SSB Adaptor For Shortwave Receivers ; Electronics & Holden's New V6 Engine; Why Diesel Electrics Kil led 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 Elec- , Use this handy form to !!rder_vour _back _copies_+ --, I Please send me a back issue for: I □ May 1 988 □ October 1 988 I I I I I ·I I I I I I I I I I D D D D March 1989 August 1989 January 1990 June 1990 □ dul'le 1 §8~ D D D D D November 1 988 April 1 989 September 1989 February 1 990 July 1990 .[] Feerua, y 198~ □ July 1 988 □ December 1988 D D D D May 1 989 October 1989 March 1 990 August 1990 □ March 1988 □ August 1 988 D D D D January 1989 June 1989 November 1 989 April 1 990 □ September 1 990 -Id Pep, ii 19~8" □ September D February 1 989 D July 1989 D December 1989 D May 1990 D October 1 990 Enclosed is my cheque/money order tor $ ______ or please debit my D Bankcard D Visa Card D MasterCard Card No. Price: $A5.00 each (includes postage) . Overseas orders add Signature _ _ _ _ _ _ _ _ _ _ _ _ Card expiry date_~'--$A 1 .00 per issue for postage. NZ & PNG orders are sent by air mail. Name _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ (PLEASE PRINT) Detach and mail to: I II ]I II Stree.______________________ Suburb/town _ _ _ _ _ _ _ _ __ _ _ Postcode____ SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROY BEACH NSW 2097 OR FAX: (02) 979 6503 l _ I ~------ ------------------ --------------~ 96 SILICON CHIP tries In The USA; Marantz LOSO Loudspeakers. February 1989: Transistor Beta Tester; Minstrel 2-30 Loudspeaker System ; LED Flasher For Model Railways (uses LM3909) ; Build A Simple VHF FM Monitor (uses MC3362), Pt.1; Lightning & Electronic Appliances ; Using Comparators to Detect & Measure. March 1989: LED Message Board, Pt.1 ; 32Band Graphic Equaliser, Pt.1 ; Stereo Compressor For CD Players; Map Reader For Trip Calculations ; Amateur VHF FM Monitor, Pt.2 ; Signetics NE572 Compandor IC Data; Electronics For Everyone - Resistors. April 1989: Auxiliary Brake Light Flasher; Electronics For Everyone: What You Need to Know About Capacitors; Telephone Bell Monitor/ Transmitter; 32-Band Graphic Equaliser, Pt.2 ; LED Message Board, Pt.2. May 1989: Electronic Pools/Lotto Selector; Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference; LED Message Board, Pt.3; -Electronics for Everyone - All About Electrolytic Capacitors. June 1989: Touch-Lamp Dimmer (uses Siemens SLB0586) ; Passive Loop Antenna For AM Radios; Universal Temperature Controller; Understanding CRO Probes; LED Message Board , Pt.3 ; Coherent CW - A New Low Power Transmission Technique. July 1989: Exhaust Gas Monitor (Uses TGS812 Gas Sensor); Extension For The Touch-Lamp Dimmer; Experimental Mains Hum Sniffers ; Compact Ultrasonic Car Alarm; NSW 86 Class Electrics ; Facts On The PhaxSwitch Sharing Your Phone Line With A Fax Machine. August 1989: Build A Baby Tower AT Computer; Studio Series 20-Band Stereo Equaliser, Pt.1; Garbage Reminder - A 7-day Programmable Timer; Introduction To Stepper Motors; GaAsFet Preamplifier For The 2-Metre Band; Modern 3-Phase Electric Locomotives. September 1989: 2-Chip Portable AM Stereo Radio (Uses MC13024 and TX7376P) Pt.1 ; Alarm-Triggered Telephone Dialler; High Or Low Fluid Level Detector (uses LM1830N); Simple DTMF Encoder (uses Texas TMC5089) ; Studio Series 20-Band Stereo Equaliser, Pt.2; Auto-Zero Module for Audio Amplifiers (Uses LMC669); A Guide To Hard Disc Drives. October 1989: Introducing Remote Control; FM Radio Intercom For Motorbikes (Uses BA 1404 And TOA 7000) Pt.1 ; GaAsFet Preamplifier For Amateur TV; 1Mb Printer Buffer; 2Chip Portable AM Stereo Radio, Pt.2 ; Installing A Hard Disc In The PC; A Look At Australian Monorails. · November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY and Morse); Super Sensitive FM Bug; Build A Low Cost Analog Multimeter; FM Radio Intercom For Motorbikes, Pt.2 ; 2-Chip Portable AM Stereo Radio, Pt.3; Floppy Disc Drive Formats & Options; The Pilbara Iron Ore Railways. December 1989: Digital Voice Board (Records Up To Four Separate Messages, Uses Texas TMS3477NL and 256K RAMs) ; UHF Remote Switch; Balanced Input & Output Stages; National Semiconductor LM831 Low Voltage Amplifier IC Data; Install A Clock Card In Your PC; Index to Volume 2. January 1990: Service Tips For Your VCR; Speeding Up Your PC; Phone Patch For Radio Amateurs; High Quality Sine/Square Oscillator; Active Antenna Kit; The Latest On High Definition TV; Speed Controller For Ceiling Fans; Designing UHF Transmitter Stages . February 1990: 16-Channel Mixing Desk; High Quality Audio Oscillator, Pt.2 ; The Incredible Hot Canaries ; Random Wire Antenna Tuner For 6 Metres ; Phone Patch For Radio Amateurs, Pt.2; PC Program Calculates Great Circle Bearings. March 1990: 6/12V Charger For Sealed LeadAcid Batteries; Delay Unit For Automatic Antennas ; Workout Timer For Aerobics Classes; 16-Channel Mixing Desk, Pt.2 ; Using The UC3906 SLA Battery Charger IC; Digital Waveform Generation Using a PC ; The Controls On A Model Aircraft. April 1990: Dual Tracking ±50V Power Supply; VOX With Delayed Audio; Relative Field Strength Meter; 16-Channel Mixing Desk, Pt.3; Simple Service Tips For Your Microwave Oven; Model Aircraft Aerodynamics; Active CW Filter For Weak Signal Reception. May 1990: Build A 4-Digit Capacitance Meter; High Energy Ignition For Cars With Reluctor Distributors; The Mazzie CW Transceiver; Waveform Generation Using A PC , Pt.3; 16Channel Mixing Desk, Pt.4; What To Do When Your Computer Goes Bung, Pt.1; Electronic Load For Checking Power Supplies. June 1990: Multi-Sector Home Burglar Alarm; Low-Noise Universal Stereo Preamplifier; Load Protection Switch For Power Supplies; A Speed Alarm For Your Car; Design Factors For Model Aircraft; Fitting A Fax Card To Your Computer; What To Do When Your Computer Goes Bung, Pt.2. July 1990: Digital Sine/Square Generator, Pt.1 (Covers 0-500kHz); Burglar Alarm Keypad & Combination Lock; Simple Electronic Die; LowCost Dual Power Supply; Inside A Coal Burning Power Station; Weather Fax Frequency List; What To Do When Your Computer Goes Bung, Pt.3; Digital Waveform Generation Using A Computer, Pt.4 (PC Board Plus Software) . August 1990: High Stability UHF Remote Transmitter; Universal Safety Timer For Appliances; Horace The Electronic Cricket; Digital Sine/Square Wave Generator, Pt.2; The Tube Vs. The Microchip (Two Shortwave Receivers Compared) ; What To Do When Your Computer Goes Bung, Pt.4. September 1990: Music On Hold For Your Telephone; Remote Control Extender For VCRs; Power Supply For Burglar Alarms; LowCost 3-Digit Counter Module; Voice Mail For Your Computer; Simple Shortwave Conve.rter For The 2-Metre Band; How To Make Dynamark Labels. October 1990: Low Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; Surfsound Simulator; DC Offset For DMMs ; The Dangers of Polychlorinated Biphenyls; The Bose Lifestyle Music System; Using The NE602 In Home-Brew Converter Circuits. PLEASE NOTE : November 1987, December 1987, January 1988, February 1988, April 1988, & June 1988 are now sold out. All subsequent issues are still available but stocks of March 1988 are now low. Order now if you want this issue. NOVEMBER1990 97 The Story Of Electrical Energy, Pt.5 Until now, this series has dealt with very large coal burning power stations but there are many regions which are far from natural energy sources. A prime example is Darwin which is now using a highly efficient gas/steam combined cycle system. By BRYAN MAHER Though Darwin is the smallest of our capital cities, it shares with its harbour the longest and most romantic history. The magnificent inlet we know as Port Darwin was discovered in 1644 by Captain Abel Janszoon Tasman of Lutjegast, Holland, who was exploring our northern waters. 98 SILICON CHIP Sailing in the Zeemeeun, he mapped our coastline from Cape York to North West Cape with incredible accuracy. He named Van Diemen Gulf and visited areas around present day Darwin. The first Englishman to enter what is now Darwin's harbour was Captain Phillip Parker King, gamely sailing in 1819 with his tiny 85-tonne ship , HMS Mermaid. Electrical beginnings For many years , the batteries of the overland telegraph line were the only sources of electrical energy in the Northern Territory. Then in 1914, the first engine-driven generator in the Territory was installed to service Darwin government offices and drive a freezer. By 1920, the Town Hall and Victoria Hotel boasted electric lights and a few town streets were lit. Then in 1922/23, Felix Holmes built an oil engine driven power station to supply energy to all Darwin. When he died , his station was taken Left: this is the Channel Island Power Station in Darwin. Fuelled by natural gas, it has five gas turbines. The five stacks for the gas turbines can be seen next to the main turbine hall but two of these stacks are not normally used. Instead, the exhaust gases for the two associated turbines are fed into heat exchangers to power two steam turbines. The exhaust gases are then vented from the two stacks between the buildings. over by the Town Council in 1930 and seven years later by the NT Administration. In 1939 this, the only generating plant in Darwin, had a capacity of 160kW. By mid-1940, a second station equipped with twin English Electric alternators lifted Darwin's total capacity to 660kW. These were driven by 6-cylinder, liquid cooled, vertical stroke diesel engines. Within two years, additional machines were installed. A lMW Fullager and two smaller Crossey diesel-alternators raised the station's capability to 2.5MW as the city grew during the war years. To supply military needs, one of the units was moved to Alice Springs and a smaller machine to Katherine. Additional electricity supplies for armed forces establishments were provided by a multiplicity of smaller generating plants, some semi-portable. Ex-US Army diesel generating sets were given to the NT Administration at the end of World War 2 but they proved troublesome due to poor wartime maintenance. As late as 1960, the Administration operated power stations at Darwin, Katherine and Alice Springs. Peko mines supplied their own needs plus the town of Tennant Creek. Around 1961, Darwin's electricity situation became critical and a new power station at Stokes Hill was planned. This was completed in 1962 and supplied the city's needs until 1987. All machines up to 1987 were diesel powered but the need to freight in expensive diesel fuel kept the price of generated electricity a lot higher than in other states. Another factor on the minds of the administration was Darwin's history of destructive hurricanes sweeping in from the Timar Sea. The new Channel Island power station uses gas turbine driven alternators, fuelled by natural gas from the Amadeus Basin, 1600km to the south. This view of the station shows the large exhaust stacks for three of the turbines. In the foreground is the metering equipment for the natural gas. In 1974, Cyclone Tracy destroyed most of the overhead electricity distribution network, and damaged substations and some of the generators in the power station. However, most of the high voltage lines and all underground lines remained intact. After the devastation of Tracy, electricity authorities from all over Australia and the defence forces sent approximately 500 electricians and linesmen to assist the Northern Terri- tory Administration staff in restoring power. Cyclone proof underground power transmission was installed in the suburbs of Tiwi, Anula, Wulagi and Wanguri, as well as the city central business district. Berrimah power station Following the development of gas turbines of megawatt capability in Europe and the USA, the Northern NOVEMBER 1990 99 Not all natural gas fuelled generating sets in the Northern Territory are gas turbines. This new installation at Tennant Creek uses a 340kW spark ignition prime mover made by Waukesha. Territory Electricity Commission, formed in July 1978, began construction of the Berrimah power station. The installation was to use two gasturbine driven alternators, a departure from the prevailing system of diesel driven units. Gas turbines will run on just about any fuel. However, that statement should be modified by saying that the efficiency of a gas turbine is a function of the type of hydrocarbon on which it is fed and is very dependent on the ambient temperature. This factor is important in the tropical climate of Darwin. However, the efficiency of an engine is not the only factor in the price of generated electricity. Just as important is the fuel cost per kilogram, delivered to the site. Therefore, the existence of natural gas below Central Australia is today a vital factor in the Northern Territory electric energy story. Natural gas from deep wells in the Amadeus Basin in Central Australia, 300km south-west of Alice Springs, is now reticulated by a 2000km underground pipe system. The Darwin power stations receive their fuel from this source and gas is also laid on to smaller stations at Tennant Creek, Katherine and the privately owned 100 SILICON CHIP Cosmo Howeley power station. Liquid natural gas (LNG) is supplied to the power station at Pine Creek. However, most installations also retain some distillate fired machines. Channel Island Because of the city's continual growth, a new and larger coal-fired power station was planned in 1981 for Channel Island. Originally used as a quarantine station and leprosar- . ium, this small land mass, roughly 1.7km long and 900m wide, is situated within Port Darwin harbour, 13km south of the city. Naturally, a coal-fired power station in a state without coal deposits would pose an economy problem. Approximately 500,000 tonnes of coal would have been needed annually. Then, in 1984, very large gas turbines became available and so site preparation was stopped and the power station re-designed to use this new technology. Gas supply is by reticulation from the Amadeus Basin wells. Physics of gas turbines Basically, a gas turbine consists of an air compressor stage and a power turbine section on the one shaft which drives the external load. Air is drawn in, compressed, then mixed with combustible fuel gas. To start the engine with the shaft turning, an electric spark ignites the air-fuel mixture, creating a flame which reaches very high temperatures - 800-1400°C. The resultant sudden expansion produces high pressures within the combustion chamber. The hot gases escape by flowing through the turbine blade wheels, driving them around to produce mechanical power. The turbine shaft must drive the compressor stages and the rotary mechanical load; ie, the alternator. The power turbine may consist of four or five blade-wheels with fixed blade assemblies between them. The air compressor section {;an have as many as 9-12 blade-wheels and complementary fixed blade sets. The fixed blades direct the flow of gases onto the rotary blades. The largest blades are found in the air inlet and exhaust gas outlet areas where pressures are lowest. Conversely, small blade wheels are used near the centre of the machine where pressures are highest. High temperature materials Gas turbines were known in principle but not used for decades until machine parts capable of withstanding the high temperatures could be manufactured. The flame in the combustion chamber is far too hot for many metals. The resulting corrosion, added to the abrasive action of extremely fine dust entering with the air supply, can play havoc with blades and bearings. The metals now employed include alloys of titanium (a metal won by beach sand mining), and also chromium and vanadium. Research in the past three years has produced turbine blades and bearings made from ceramics such as silicon nitride and boron carbide. The efficiency of any steam or gas engine is maximised when the temperature of the gas entering the power turbine blades (or cylinder, as the case may be) is highest and that of the exhaust gas is lowest. This is expressed by the equation shown in Table 1. One big disadvantage of gas turbines is that the heat content in the exhaust gases is very high. Exhaust temperatures may be as much as 4006000C. However, this heat does not have to be wasted. It can be used to turn water into steam to drive another turbine and alternator. This is the 13.6MW ASEA gas turbine installation at the Ron Goodwin Power Station at Alice Springs. The Northern Territory is gradually changing to natural gas for electric power generation, using the rich gas fields of the Amadeus Basin in Central Australia. Combined cycle systems Because the gas turbine's waste heat indirectly drives a steam plant, the total power output is higher for the same fuel input. Thus, the combined cycle system (gas turbine + associated steam turbine) has increased efficiency. The first use of this system in Australia was in the Channel Island power station, Darwin. Here the exhaust heat · from two 32MW gas turbo-alternator sets is used to boil water in two water-tube heat exchanger boilers. The steam produced drives a 34MW steam turbo-alternator. Thus, the combined cycle system generates a total of lO0MW of electrical power using only the fuel supplied to the gas turbines. Gas turbine section The combined cycle system at Channel Island uses two of the five John Brown (UK) Ltd gas turbines. The 550°C hot exhaust gases from each flow via horizontal 5-metre square ducting to a heat exchanger. In this large compartment, 15-20 metres high and 6 metres wide, filled with three sets of water pipes, the hot exhaust gases boil water to steam. The steam pipes then re-enter the heat exchanger at the point where the flue gasses are hottest, so the steam is Looking not much more imposing than a deluxe caravan, this is actually the ASEA FT35C 13.6 megawatt gas turbine generating set which was installed at the Ron Goodwin Power Station at Alice Springs at the end of 1987. It supplies base load power to the township. NOVEMBER 1990 101 Table 1: Efficiency of Rankine Cycle Turbine Efficiency = Work Output = Heat Input - Heat Output Heat Input Heat Input Note 1: this simplified equation does not take into account superheating and reheating in the case of steam systems. Note 2: all temperatures are in the absolute scale; viz: zero degrees absolute= -273.16°C. As absolute zero cannot be reached, engine efficiency is always less than 1 (ie, <100%). Note 3: being a Rankine cycle (rather than a theoretical Carnot), the above equation cannot reduce to (T(in) - T(out))/T(in). superheated to 485°C at a pressure 4.2MPa. After passing through the heat exchanger, over superheater and HP tubes, economiser, LP and feedwater tubes, the flue gases have given up most of their heat to the steam system. The exit flue gases, now down to 145°C, pass up a large vertical vent to the atmosphere. The steam derived from the two heat exchangers drives a 3000rpm Mitsubishi steam turbine, directcoupled to a Brush 2-pole 34MW alternator. rel cage pony motor supplied from the station auxiliary AC busbars. This motor drives the gas turbine shaft via an hydraulic torque converter coupling with variable slip. As the speed builds up , the fuel gas is ignited, increasing the speed to the full 5100rpm, whereupon the starter motor is shut down. Should some electrical calamity such as a severe lightning strike or a major breakdown stop the whole power station, a "black start" is necessary. Under this very rare condition, the station auxiliary bus would also be dead and the only lighting would be from batteries. To overcome this problem, black starts at Channel Island use a Norwegian Kongsberg gas turbine. This machine has no electric pony motor but is started by compressed air. Once up and running, this emergency generator supplies the station lights and auxiliary AC busbars, enabling the other machines to be electrically started in the normal way. The compressed air reservoir is always kept up to pressure by an electrically driven compressor, though in an emergency a separate diesel driven compressor provides the air supply. Should all this fail, electrical supply is available for a black start from Berrimah power station, 40km away. Here, two Stal Laval gas turbines can supply Darwin via the 132kV powerline system. Hudson Creek substation As well as providing steam from their exhaust heat, each gas turbine, running at 5100rpm, also drives a 3000rpm 32MW alternator via a helical gear box of 51:30 ratio. These 11.5kV 50Hz alternators, made by the Brush Company of England, use the brushless excitation method, outlined in chapter 3 of this series (September, 1990). An inverted exciting-alternator on the same shaft has its AC output rectified by a diode wheel to provide the low voltage heavy DC current needed to excite the main alternator rotor. As the excitation currents run via cables inside the hollow shaft, no sliprings or brushes are needed. The 220MW output of Channel Island power station runs via three 132kV lines to Hudson Creek substation. Each line is capable of carrying the entire 1300 amps load in an emergency. Two of these lines use the bundle-of-two conductor arrangement. The construction of this substation was the major part of the $7 million works implemented during 1989. At Hudson Creek, a 125MVA autotransformer provides a 66kV supply for Pine Creek and other mining areas. At Alice Springs, new ABB Stahl Laval GT35 gas turbines and generators run on a mix of 97% natural gas and 3% distillate. A total generating capacity of 53MW is installed and the gas is supplied by a separate pipeline from Palm Valley wells. Control system High voltage lines The machines at Channel Island power station are each controlled by a General Electric Speedtronic electronic speed, power and voltage regulator. A distributed computer bus system oversees excitation, and controls load and reactive current sharing between generators . The usual starting procedure for each gas turbine is via a 3-phase squir- The new 132kV transmission line, completed and put into service on 12th November, 1989, now supplies power from Channel Island to Katherine. As well as augmenting the Katherine power station, this power line also supplies electricity to consumers along the 350km route . In normal operation, Channel Island is used as a base load station Gear driven alternators 102 SILICON CHIP This photo shows a 30MW gas turbine during assembly at the ABB works in Switzerland. The blades, shaft and bearings of gas turbines are subjected to extreme temperatures from the burning gases. To combat the corrosion and abrasion from the high temperature gases, the blades are usually made from titanium alloys. have complex redundancy built in because there are many alternative lines feeding each area. But in the vastness of the Northern Territory, this would be totally uneconomical. So, in common with many other electric supply authorities worldwide, live line maintenance is undertaken as a routine operation in the NT. To perform live line work, linesmen must be specially trained. Long manipulation rods, jib poles and lifting tackles made of non-hygroscopic plasticised non-conducting materials are used. One of the photos in this article shows a crew on a transmission tower changing a faulty strain insulator set on a 66kV line. The power is on and full load current is flowing through the cables. The red insulated manipulation rods shown in the photograph can be fitted with special tool ends such as spanners, nut drivers, hooks and cable clamps. Working from a safe distance, the linesman, holding one end of the long rod, hooks the other end into the live bolt, nut or cable clamp. A twisting motion can then unscrew or tighten, insert or remove the part as required. Changing insulators Live line maintenance at 66kV! And you thought that 240VAC was hazardous. Specially made insulated manipulating poles and highly trained staff means that live line maintenance is a routine procedure, not only in the Northern Territory but all around Australia. because of the much higher efficiency of its lOOMW combined-cycle output. Katherine's generators assist in times of peak load or if a breakdown occurs at Channel Island. Among the new power lines are an 80km lightweight 66kV line to Pine Creek, plus others to Jabiru town, the Ranger uranium mine and the Alligator River region. A 22kV line feeds the Jindalee Over-the-Horizon Radar Station north of Alice Springs. In total, the Northern Territory has built 2290km of overhead and 400km of underground high voltage lines, plus 2200 substations. These service 43,000 consumers who consume 900GWh annually. Live line maintenance On any electrical system, power interruptions are a cause of annoyance to householders and lost production in industry. Some systems Tension insulator strings are under tonnes of strain due to the weight and tightness of the span conductor, plus wind forces. To change such an insulator set, as is being done in the photo, first the mechanical strain must be taken up by a temporary jury rig. Then, working carefully, the linesmen uncouple and remove the damaged insulator string. A new insulator set is then bolted into place and the jury rig removed. All this is achieved with the line fully alive but the workmen safely at ground potential. Other live line work which can be carried out includes attaching or removing tee junctions, using liveline cable clamps. Also, new power lines can be erected above existing live high voltage lines. Acknowledgements Special thanks to the Northern Territory Power and Water Authority, to Public Relations manager Michael Nott, and to Max Wagland, Ian Campbell, ABB and ASEA Journals, Action and Review and Electricity Trust of SA. ~ NOVEMBER 1990 103 REMOTE CONTROL BY BOB YOUNG Nicad cells for high rate discharge and the jetpipe temperature shoots up into the dangerous area. As a result, a complex battery analyser is used in order to determine the state of charge and performance of each individual cell in the battery pack and great care is exercised in order to keep those batteries in top condition. As it is, there is just enough capacity in a good battery pack to effect a start on one engine. The second engine cannot be started until the battery has picked up sufficient charge from the operating engine. In fact, the instructions state that a start must not be attempted on the second engine until the charging current has fallen below 100 amps. As stated previously, these batteries need to be good. The aircraft itself is of Brazilian design and manufacture and is intended for use in South America. The middle of the Amazon Basin is no place to have a flat battery. All in all, it is a very demanding situation. Radio control modellers do not place such stringent demands on their battery packs with regard to life threating situations. However, the poor long suffering R/C serviceman who fails to get his customer's R/C into tip-top shape for that competition very defi- High discharge rates can cause real problems for nicad batteries. This month, we look at those problems and discuss the solutions. In September we dealt with nicad cells for transmitter and receiver use in aircraft and discussed the difficulty in determining what constituted a correct rate of discharge for a 500 mAh cell. This month we will not face this difficulty for we will be dealing with awesome capacity/discharge ratios that may result in run times of as short as 15 seconds to 5 minutes. No confusion here. This is high rate discharge with a capital "H''. I would like to open the discussion with a little tale of an aviation application of nicads in a light twin-engine aircraft called a Bandierrante. This is a 20-seat commuter machine powered by Pt-6 turbo props. Now starting one of these little turbines is quite a trick as they must be spooled up to 12-15% of normal rpm with the starter motor before in.troducing fuel. The higher the rpm on the starter, the lower the jetpipe temperature and the less the thermal stress on the hot parts of the engine, - -100 ae 0 -~ 80 1.6 r---__ - ?: 60 ·c::; "'a. 0"' 40 20 particularly the power turbine. The problem is that a sufficient mass of cooling air is required before the fuel is introduced. Any pilot foolish enough to disregard the instruction prohibiting the application of fuel before the 12% rpm figure is on the clock is liable to find his power turbine dripping onto the tarmac. The problem is that this calls for starter engagements of quite long durations, typically 10-12 seconds. This demands the best batteries available and nicads are the order of the day. The Bandierrante battery consists of 20 cells of 36Ah capacity (Ah stands for ampere-hours) which gives some inkling of the discharge current involved. The start up surge is 1500 amps, falling as starter RPM increases. This whole situation is extremely complex for batteries are heavy and must be carried at the expense of payload. Thus, the smallest battery possible is carried. However, if these batteries sag in voltage or the motor is slow to start, the start-up rpm falls - - - --- 1.5 1-------,1------,---;------t-1 .4 ,_ 2 .0 3 .0 4 .0 Discharge rate (C mA ) Fig.1: capacity vs discharge rate. High discharge rates increase cell stress and give shorter cell life. 104 SILICON CHIP Q) 1.2 ~ 1.1 > 1.0 0 Charge . C / 1 OX 15hrs. 20°C(68 °F) Discharge : Cut off voltage 1 OV , 20°C(68°F) 1 .0 1.3 CJ> 0 0 ~ Charge 900 mA X1 .5hrs. --;-Temp. : 20°C(68°F) - 0.9 A ~ _,,.-/' I',.,......___ 18 A 0.8 07 - O 200 IX"- /r-,.... I""\\.' ~r--- 0.9 2 .7A ~ 400 5.4A 'l\ 11 600 800 1000 1200 1400 Discharge Capacity <mAh> 1600 1800 Fig.2: the cell terminal voltage at various discharge currents. At 18A, the average voltage is about 1 V. Electric propulsion technology has come a long way in the last few years. At left is the Geist 150 electric motor which employs samarium cobalt magnets while at right is the Hecktoplett 355/5 motor which has a rated power output of 860 watts (1300 watts input). Photo courtesy Moore Park Model Supplies, Armidale. nitely faces a life threatening situation, and it seemed to me at times that the middle of South America jungle, anacondas, piranhas and all would have been a much safer place to be. Such is the day-to-day-life of the R/C manufacturer or serviceman. Model cars, boats and aircraft do not call for such heavy duty or large capacity batteries but they do call for a reliable cell with a good capacity to weight ratio. Standard cell The standard cell for model car, boat and aircraft use is the 1.2Ah model but recent developments in battery and motor technology have introduced a host of new cell sizes into the R/C field. Indeed, the ever present demand for higher performance and thus lighter weight is forcing modellers back to the smaller cell sizes (800 and 900 mAh). This results in much higher capacity/discharge ratios and a subsequent increase in cell stress, lower terminal voltages and shorter cell life - see Fig.1 . Once again we are faced with determining the capacity/discharge ra- tios to establish which are the best cells for our particular application and again this calls for a precise understanding of what the cells will be called upon to deliver in operation. Electric motors for model propulsion fall broadly into four broad categories: 05 , 15, 25 and 40-size motors. These four styles come in a bewildering range of case configurations and armature windings and we'll delve more into this subject in a future article. The windings fall into two categories: stock and modified. One of the most popular sizes for electric cars is the 540 size case with the stock winding drawing about 23.5 amps free running and giving adequate performance on a 6-cell 1.2Ah battery pack for a 6-minute race time. The modified 540 draws about 2.54.5 amps free running and on a 1.2Ah battery is raced for 5 minutes. Electric flight The situation for model aircraft is quite different, with enormous powers being involved in the top level contest models. A little sports model using the 540 stock motor will require about 110 watts per kilogram. A 7-cell battery (ie, 8.4 volts nominal) driving a 540 fitted with a 9-inch (diameter) x 4 (pitch) prop will deliver about 8000 rpm. This is sufficient for models weighing up to 1.5kg. The loaded current on this prop is approximately 20 amps. Compare this with the high performance contest model fitted with one of the exotic European motors. All figures are quoted from the "Electric Flight Newsletter" from Moore Park Model Supplies. The model was fitted with a Hecktoplett 355/5 wind motor and a 27cell SCR/N 900mAh battery pack. An electronic speed control was fitted as a throttle device and the performance figures are given as follows: prop Bally 13 x 7; revs 11,200 at 51 amps. This is equivalent to a power input of about 1400 watts! Compare this to another of the expensive German motors (Geist) and some idea of the power involved is quite clearly indicated: prop 13 x 7; revs 11,500 at 72 amps. Notice also the improved efficiency of the first motor, which of course, was the most expensive and the heaviest. Now I would like to draw your attention to the cell capacity/load ratios (BOC) which leave absolutely no doubt that here we are dealing with high rate discharge and that the batteries involved had better be good. Notice also the tremendous wattages involved. At these currents, the average terminal voltage is about 1 volt per cell (Fig.1) giving 2 7V x 72 amps (1.944kW). Electric propulsion technology has come a long way in the past few years. The electronic speed controller alone is a major development in its own right. No weight is quoted for this model but a brief description of the test flight stated that it climbed like a scalded cat and was well up under the cloud base in 25 seconds. I would estimate the weight to be around the 3.5kg mark which works out at around 550 watts per kilogram. That's equivalent to a power to weight ratio of 550 kilowatts per tonne! It makes our 110 watts per kilogram sports model look like a kitten. The average speeds of this type of model are around 120150km/h. NOVEMBER 1990 105 r~~~===~====~s,~s,=+====::i:..----.-_-+·--_-_-_-_-+·--_-_-_-_-+·--_-_-_-_-_~·---~-~~--,--~ ..... Temperature: 20 ' C(68" F) 10 , 8 1 - - -- " " ~ - - + - -- ""'----""'~- voltage: 1.0V /cell Charge: Full charge +--+---+--- - - + - - -- - + - - - - - + E n d "' Q. E < 2 -...... 800 C Cl) 600 ::, (.) Cl) ...Cl 400 Cll ~ (.) Ill c 200 1 50SC E 1 40SCR/140SCRC 1 30SC R/130SCRC 120SGRP / 120SCPC I u, ' a.I +-~- ~i----+-.-,----J',,,.--f---f"oc+-'~~g~~:s11OOAS/1 OOC 100 E' ml : I -~---+---+-..._,--,...,.-__---l",ci80AAR 80 1------1--- + -- - - ii f - - -- - f - - - - , - -- - - - - t -- 60 I - + - - - t - --+-----"'-.:l--- - -_,,,..c -___,,,,i.:--+---.::--f'.....,_-+-+--""'c-"""',-,,..,;:-1 7QAR - +---+-----+--'- -- -+---'----------'-..__..,,l,---+----l-""...-""""'""60AA / 60SC i60SCR/60AS I 50AA / 50AAR I !----- - - + - - - - - - r------- - - - - >----+----+ . ! +--- - - -------t-- .. - -- 40 !----- - - + - - - - - + -- - · ··----ri - - · - +- ' I . l . -- - - ----+--- ~-~---- t - - ------+-->o.-i 30A AE 27AA ~ ---- · -7-- 20 I __L --- - - - - - -- + - - -- +--+~"lo.---+---P-...+--3'1180AAA 1 5 N/ 15NC 11AA 1 10 10 15 I◄,________ 20 40 1.5 4 2 6 8 10 -- - ·- Hours Minutes Typical duration time Fig.3: this graph of discharge current vs duration time can be used to aid cell selection. The cell types listed down the right hand side are from Panasonic. The batteries involved are of course very good and battery technology has leapt ahead in recent years. Fig.3 shows a graph used to aid in cell selection, while Fig.4 is a discharge characteristic graph for the Panasonic P-90 SCR cell. Fig.2 is a high rate discharge graph showing the terminal voltages at various discharge currents. Notice that the terminal voltage shows an average 1V at 18 amps, a long way short of the 72 amps in the model quoted above. This raises a terribly important point in the selection of electric flight batteries, that being the compromise 106 SILICON CHIP between using less cells of a higher capacity or more cells of a lower capacity. Reference to Fig.2 shows quite clearly that the higher the capacity/ load ratio, the lower the terminal voltage. Thus, in a 20-30 cell pack, great gains can be had by using less cells of a higher capacity and more suitable construction. The "Electric Flight Newsletter" confirms this when it states that a change from 30/800mAh cells (AR) to 27/900 SCR cells gave quite a large increase in 00mph. In this particular case, we see improved cell construe- tion and a better capacity/load ratio combining to give a result well in advance of what could be expected. Cell reversal Incidentally, running large numbers of cells in series like this is not really recommended as it increases the risk of cell reversal in the weaker cells, especially in applications where very deep discharge at very high rates is anticipated. Panasonic recommend that a low voltage cut-off be provided for packs of this type. It is for this reason that some specialist firms provide what they call "pushed cells". These are battery packs in which all of the cells have 1 ooi:=====i===:::i:==i=::::i=+=+=+=++==----~---~ C t, arg e : 900 mA X 1.5 hr ... s. 1--- - 1--- + -......_.--+---+-+-++- 1--c..._ ~ - -+--+--+--+- +-++++-~ Tern p ;A_ 20' C -+1-+-+-+-+-< 0 .8V ~~ 100 ? i- 80 0 --- .... ....... A B -~ 60 - ' ~ 40 u g. u C/10 x 15 hrs· Charge. Discharge C/5 Cut ott voltage . 1.0V 20 0 - 20 -10 - 4 - 14 ;;; a, :i '= E , t---------------+---+--+--++++ k --+----+--i, a, E .= 0) :".' ro .c +--+--+--+-+-+; 0 32 10 50 20 68 30 86 ·"'0 ~a::::J=::l=t:::1::tW !--- -+ --+--+ 1----+--+--+-+--t-+++-!- - -- M-+-+-1-+-++-H ~a, ~ --..:-- 1.2 -- - - ---- -- - Ol ~ 1 .1 -L . ' - - ' " \ I \ I 0 .9 - " R" type "S" type P-80AAR _ P-100AAS_ · 0 2 4 3 Discharge time (hours> I - ' I I 1 .0 - - ·c Charge: 1 C x 1.5hrs, 20 °C(68°F) Discharge: 0.3A, 20'C(68 ' F) > I-------- 60 140 'F I 1.3 --+-- 50 122 Fig.5: the effect of temperate on cell capacity. If the temperature during charge & discharge is high, the capacity decreases. 1 .4 u I - -- 40 104 + Fig.6: the "S" series Panasonic cells have 40% greater capacity than comparable "R" type cells. I 0 · 1 ':--1---'---'---'---'---'-'-...1...J..-'-:10:-----L--'--L-L--"-L....J...J...J100 Discharge Current IAI been matched as closely as possible in capacity to eliminate the problem of the weak cells collapsing in advance of other cells in the pack. In addition, a pushed pack is selected for maximum capacity, so a nominal l.2Ah pack may deliver in excess of l.5Ah. A "matched pack" is only graded on capacity. As you may have guessed by now, nicad cells in this type of application receive a hammering and fail reasonably often, hence all of the precautions in an effort to eliminate failures while at the same time pushing performance to the limit. The prime culprit for any failures · that do occur is heat and this problem is appi;oached by the manufactures in several ways. First, they warn the customer of the dangers and shortcomings of exceeding the temperature limit. Panasonic state flatly that discharge temperature ranges are -20° C to +65 °C and that because service life will be decreased by repeated discharges at extreme temperatures, discharges between 20°C and 30°C are recommended. Fig.5 shows the effect of temperature on cell capacity. Fig.4 (left): discharge characteristics for the Panasonic P-90 SCR cell. Now one sure way to raise the temperature of a cell is to subject it to extremely high rates of charge and discharge, exactly what modellers are now doing. Manufacturers go to great lengths to produce special cell types which will stand these extremely high charge and discharge currents. The Panasonic "R" type cell, designed for rapid charge, has a specially improved negative plate for example, with an increased gas absorption characteristic. It can be subjected to controlled charging at the 1C rate; thus a rapid charge in 1 to 1.5 hours is possible. The emphasis on the word "controlled" is mine because I often see modellers trying to cram a full charge into a cell in 15 minutes or less. This will result in excessive heating, and premature cell failure. The moral here is to use several packs and the longest charge time possible. For those with the necessary funds or dedication, there are the high capacity "E" series cells. These combine a high capacity density positive plate with a high capacity paste negative plate, resulting in a 20-30'¼, capacity increase over standard types. Next are the "RIP" high rate discharge and rapid charge cells which feature edge welded plates and terminals. This results in a sharp reduction in internal resistance and a subsequent improvement of the voltage characteristics during high discharge rates. This is combined with excellent gas absorption for high rate charging. Finally, we have the "S" series cells which feature a high density positive plate made of foam nickel and a paste negative plate. The resulting battery has a capacity 40% higher than the comparable "R" cell - see Fig.6. Again , it can be fully recharged in one hour as with the "R" type. All in all, there is now an impressive array of batteries, showing the great strides in battery technology during recent years. Without this technology Blectric flight models would still be just a dream. Acknowledgement The author thanks Malclom Wilson of Premier Batteries Pty Ltd, Chipping Norton, NSW and also "Electric Flight Newsletter" from Moore Park Model Supplies. ~ NOVEMBER 1990 107 \0J ~ ~ ~ •~ \ ~ -~ ~-~~· ~ ~ - -~ <at> ,. ~ ~ -. - ~ ,~\ / l:ii If! ) ........ ,~ - 088 335757 TOLL FREE MAIL ORDER HOTLINE FOR CREDIT CARD ORDERS! ... -------------.. tiiii, "NEW" 1 AUTOMATIC TELEPHONE I II SLIMLINE APPLE* COMPATIBLE ANSW ER/ CALL CARD DISK DRIVE TURN YOUR IBM* PC, XT, AT INTO A I CompatiblewithApple2 + Cat. X19901 Only $179 FULLY FUNCTIONAL ANSWERING I FR~r~~~~gi ~~~J~KS MACHINE!!! I APPLE* IIC COMPATIBLE I DISK DRIVE 1,nclud,ng cable ..... only $189 I . A Sophisticated Voice coil mail system I FREE PACK OF SIS DISKS 1· Auto answering I Dialing 11· WITH EACH DRIVE! I·.100 voice mail boxes .· · Password protect ion I · Message mailing ,, .... · Auto r!!dialing I ..,,, · Beeperless remote control '~ , I · Toll saver ·.~ I · Call screening ~ · Electronic .Phone book . 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Fits most 6502 ''compatible'' computers. C14200 ............ .... . $29.9 Turn your CRO into a spectrum analyser for just $399 Have you ever dreamed of owning your own spectrum analyser? If you're an amateur, TV technician or electronics teacher, we'll bet you have. The $20,000 plus price tag would certainly have dampened your spirits. But now there is a probe which turns your CRO into a spectrum analyser. By ALEX EADES This little gem is called the VOS-107 Spectrum Probe and at a price of $399 it is a magic accessory. When an opportunity to review the VOS-107 came my way, I jumped at the chance. Having spent years building ham radio projects - where an analyser would have been a wish come true - I needed no convincing of the value of such a device. For the uninitiated, a spectrum analyser is an essential test instrument for any equipment designE)d to process frequency information and there is plenty of that! Take for example entertainment electronics. TVs, radios, VCRs, cameras and music systems are all involved in processing the frequency components of signals. The enormous amount of this equipment in use generates a growing need for spectrum analysers. The VOS-107 Spectrum Probe looks for all the world to be just another logic probe, but it is nothing like that at all. A normal oscilloscope displays how a voltage changes with time. A spectrum analyser displays the amplitudes of signals separated on the basis of 110 SILICON CHIP their frequencies. The VOS-107 converts the latter into the former (a handheld Fourier Analyser!). And that's no mean feat, especially for $399! What is a spectrum analyser? It is a device which looks much like an ordinary CRO but with a quite different method of display. It shows the frequency components in a signal along with their strengths at very good accuracy. To get an idea of this, imagine a display like the dial of your radio with vertical lines showing all the strengths of the stations in their respective positions. Sound over the top? Not really, such devices have been around for 30 years or so. The snag has always been the cost $20,000 to $50,000! Winning Lotto was the only way the average bloke could get one in the past. Measuring frequency There are several methods commonly used to measure frequency and they are testimony to the ingenuity (desperation?) of souls needing to quantify frequency information. The first is to display the signal on the CRO and measure the time taken for the pattern to repeat. The frequency is then found by dividing 1 by the time using a calculator. The second method is to use a digital frequency meter (DFM) which provides a reading in Hertz directly, while the third technique involves using a communications receiver or absorption wavemeter. Other devices such as slotted lines and lecher wires are somewhat esoteric and will not be discussed further. The CRO method will give the fundamental frequency and an experienced operator a gut feel for what others (harmonics or otherwise) may be present. The DFM will latch onto the largest amplitude signal and ignore the rest. The receiver or wavemeter method is probably the best as they can be tuned to a certain frequency and provide a measurement on a signal strength meter. By tuning across a band, an idea of the frequencies present can be obtained. These devices have been the mainstay of frequency analysis by hams for years. The difficulty with all these methods is that they display only one frequency at a time. It's like reading a newspaper one letter at a time instead of in whole words. This makes adjusting circuits a painstaking process when several frequencies need to be monitored simultaneously. CROs & spectrum analysers Most readers are familiar with the display of an oscilloscope - a pattern of how voltage on a circuit changes with time. We have grown to rely on the bounty of information then brings up dozens of spikes on the horizontal line, representing short wave, amateur, TV and FM signals. Evaluation This is the VS-107 Spectrum Probe in its case. It also comes with an AC plugpack and a brief instruction manual. It can be used with virtually any oscilloscope with a bandwidth of 5MHz or more. these bright green traces provide. Oscillation, switching, ringing, clipping, glitching, drooping, overshoot spikes, rise time, fall time, lumps and bumps are all familiar beasties encountered on the oscilloscope screen. The CRO's main drawback is its inability to provide detailed information on the frequencies of the signals being monitored. As a great deal of circuitry is designed to manipulate signal frequencies, this limitation is restrictive. With the VOS-107 spectrum probe, these waveform lumps, bumps, lines and spikes become fundamentals, harmonics, sidebands and intermodulation products, allowing spectral purity and bandwidth to be easily seen and measured. Connecting the probe Virtually any CRO has adequate performance for use with the VOS-107. The normal vertical sensitivity setting is 50mV/div (or 50mV/cm), while the timebase setting is 0.5ms/div (or 0.5ms/cm). Connecting the probe to the CRO is simple. The probe has a figure-8 shielded output cable. One half of the cable is terminated with a BNC plug and this goes to the CRO's vertical input socket. The other half of the cable is terminated in a 3.5mm line socket and this is for the 12V AC power input from a plugpack transformer. To monitor a signal, either the probe tip is used or an adaptor for coax cable is supplied - essential for VHF work. Remember to use a terminating resistor on the cable, otherwise reflections will cause inaccurate results. The manual recommends a simple arrangement to achieve this. For high power sources such as radio transmitters, the earth lead can be clipped to the input to form a "sniffer loop" which can be placed near the transmitter output. When connected and powered up, the screen displays a waveform which looks like a video signal. There is a negative-going sync pulse on the far left, closely followed by a vertical zero reference line, a 'noisy' horizontal line and, on the far right, the beginnings of the next sync pulse. The zero line represents minimum frequency and its height a level of 50dB a hove the noise floor. The vertical trace position and horizontal timebase controls are adjusted so that the sync pulses are off screen. Now the horizontal line represents frequencies from 1MHz to 100MHz. Touching the probe tip The essential specifications for the probe are: frequency range 1-lO0MHz; dynamic range 50dB; vertical output 5mV/dB; IF bandwidth 180kHz; and horizontal linearity ± 10%. These performance specs are moderate when compared to a laboratory grade spectrum analyser but still quite useful. To check these specs, I connected the probe to a CRO, RF signal generator and a spectrum analyser so that comparisons could be made. The overall frequency range of the sample probe was 1MHz to 103MHz which is slightly greater than the specifications. The horizontal frequency scale is linear within the specification, covering about 10MHz per division on a CRO with 10 divisions. Vertical scale accuracy was tested at 10, 50 and 100MHz with excellent results throughout, each vertical division measuring l0dB. You'll have more error just reading the CRO than from the probe! The easiest vertical set-up is to adjust the zero reference line for 5 divisions, which automatically gives lOdB per division. Comments The probe does not offer a direct reading in say dBm, however the vertical scale is useful for relative measurements which after all are the most common type. (For example, harmonics on a radio transmission are specified relative to the carrier level). A reliable lOdB/div scale is all you need. To simplify use, I attached a horizontal scale to the screen of the CRO using masking tape and a ballpoint pen. It's a bit rough I guess, but certainly effective, making frequency measurements a breeze. Minimum sensitivity of below 40/lV is plenty good enough to sniff out the majority of signals. The most serious limitation in my opinion is the IF bandwidth as this NOVEMBER 1990 111 Turn your CRO into a spectrum analyser ..• This is the normal oscilloscope display at 0.5ms/div and 50mV/div, here showing harmonics produced by an RF oscillator. determines the resolution of the display. The 180kHz bandwidth means that the spe.c trum monitor is unable to resolve the sidebands of a typical narrowband voice modulated signal from a CB or amateur transceiver. Sidebands determine the width of the signal in the band and contain the information in the transmission, so the monitor's inability to display them is an unfortunate limitation. The manual specifies the probe's resolution as 0.5MHz, a figure my measurements support. Amateur radio uses To monitor the output of my SSB transceiver, I placed the probe's sniffer loop near the coax to the dummy load. Only 5 or 10 watts were needed to produce a useful display - a very good result. The object of an oscillator is to have a pure single frequency at the output. Viewing this output on a CRO will give some qualitative idea of the purity. Is it a good looking sine wave or one containing lumps and bumps? With the probe, the main signal peak (the frequency we are trying to generate) is visible along with any other frequencies (usually harmonics) - a greatly improved display. The effect of your adjustments to the circuit can be easily seen. 112 SILICON CHIP This CRO photograph shows the video format of the Spectrum Probe's output waveform. Notice the negative sync pulses. A "mixer" is a circuit designed to change a signal of one frequency to another and in the early days of radio was called a "frequency changer". The tuner in a TV set and the "front end" of a radio are usually mixers. Mixers require careful adjustment to obtain the best results input levels, balance and output tuning need to be spot on. The adjustment can only be performed accurately in the frequency domain, hence the need for a spectrum analyser. The aim is to maximise the desired output and minimise the unwanted signals - difficult with a CRO alone but a breeze with the VOS-107 probe. TV technicians could also find the VOS-107 probe a great tool in their efforts to track down and nail circuit gremlins. TV IF performance, especially bandwidth and linearity, is clearly displayed. How about viewing the frequency spectrum of the signal from video heads or actually seeing the modulator working? Teaching Fourier Analysis Fourier analysis is a mathematical process of taking a time dependent signal (as on a CRO displayj and turning it into its frequency components. For example a square wave consists of the fun- damental (or clock frequency), 3rd, 5th and all odd harmonics with strengths inversely proportional to the harmonics number. The 3rd harmonic is 1/3 the strength of the fundamental, the 5th, 1/5 the fundamental, and so on. If all these signals could be generated and added together in the correct phase relationship, the original signal would be regenerated. If you think this sounds all very dry, you're not alone - thousands of students would agree. Enter the VOS-107. The device is of such low cost that institutions could afford to teach students "hands on". You simply feed various signals into the analyser and note what comes out and compare it to the theory. I wish these devices were around when I did Fourier analysis! Conclusion All in all, I am impressed with the performance of the VOS-107 and am sure that it will become common in the near future. (I'll have to ring Leo and tell him it'll take me a few months to finish evaluating the probe - should give me enough time to complete a few ham projects!) Our review sample came from David Reid Electronics, 127 York Street, Sydney 2000. Phone (02) 267 1385. ~ AUSTRALIA'S DYNAMIC ELECTRONICS MAGAZINE They said we'd go broke but we didn't! Did you have doubts when we started SILICON CHIP? Many people shook their heads and said we were headed for disaster! It may not seem all that long ago but it's now almost three years since SILICON CHIP came onto the scene. According to most people, we had NO chance at all of succeeding. To tell the truth, we probably were a little foolhardy but we started off anyhow. We thought there would be enough readers out there who would appreciate what we were trying to do. Thankfully, enough of you have made the decision each month to buy SILICON CHIP for us to survive and grow. Our special thanks to those readers who took out a subscription in our early days - they helped us enormously. In fact, they probably made the difference between our survival and failure. So now it's three years down the track. You might have noticed how the issues have been growing, bit by bit, starting first at 96 pages, then 104, then 112 and now, with this issue, 124 pages and with a growing colour content too. Some readers have even commented that they were amazed that we have kept the price of SILICON CHIP so low for so long. After all, the price of everything else has gone up in the last 3 years hasn't it? What about SILICON CHIP? "Uh oh", I can hear you muttering, " He's just about to announce a rip-off price increase for SILICON CHIP". Well NO. We plan to hold the price of SILICON CHIP constant for as long as possible. Yep. We know that you like to see SILICON CHIP on sale at a good price each month. But we need you to help us with that. To help us hold the price of SILICON CHIP for as long as possible, we're asking you to take out a subscription. Presently, you may like SILICON CHIP but maybe you don't buy every issue. Possibly you like to flick through each issue and • •• then decide to buy. Well, if you think SILICON CHIP is good, why not buy it every month? That way, you'll have access to all the articles and you won't regret having missed an important issue. If you decide to take out a one-year subscription, you'll be helping us a lot. For our part, we'll have SILICON CHIP delivered to your door in mint condition, generally a few days before it goes on sale in newsagents. You'll know about the specials from SILICON CHIP advertisers, before they run out! And to sweeten the deal, there is our big subscription promotion, starting this month, featuring a Bose Lifestyle Music System as the grand prize. It's well worth being in the draw by becoming a subscriber. And another point. If you work in electronics, a subscription to SILICON CHIP could be partly paid for by Paul Keating (yes, a ta:x deduction). Check your eligibility for a deduction with your accountant. Your Guarantee of Satisfaction And what about if you take out a subscription and then decide that you don't want SILICON CHIP delivered every month? That's OK. We understand that this might happen with some readers. So, to overcome any reluctance you might have on that score, we will refund the balance of your money if at any time you decide the cancel your subscription. Please take a few moments now to fill out the coupon on the back of this page. Send it with your remittance to us and we will start your subscription with the next issue. I know you will enjoy reading SILICON CHIP for the next 12 months and I thank you for your enthusiastic support. 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Telephone (02) 979 5644 9am-5pm Mon-Fri and quote your Bankcard , Vi sa Card or MasterCard No. and expiry date. SILICON CHIP Detach and Mail to: FREEPOST 25 SILI CON CHIP PUBLICATIONS PO BOX 139 COLL ARO Y BEACH NSW 2097 No stamp required in Australia 11 /90 BOOKSHELF Diode substitution handbook International Diodes Equivalents. Published by Tech Publications, Singapore. Soft covers, 305 x 170mm, 135 pages. ISBN 9971 84 567 9. Price $14.95. If you're an electronics enthusiast, technician or repairman, you can never have too many semiconductor substitution handbooks. Luckily, there are quite a few substitution handbooks available for transistors and integrated circuits but diodes are generally not well catered for. This book fills that gap. As well as covering diodes of all types, this handbook covers zener diodes, thyristors, triacs, diacs and light emitting diodes. It covers American, European and Japanese type numbers. Be aware though, it is not like most semiconductor substitution handbooks. It does not quote any specifications or ratings at all. It just lists each device and its closest equivalent - nothing else. For example, the BY127 is listed as being equivalent to a 1N4006. There is no other information to tell you the current rating, PIV rating or anything else. Still, when you are looking for some component substitutions, this book might be the only act in town. It could just be the one that gets you out of trouble. For that reason alone, it gets the nod of approval. Smart cards, radio tags and all that Integrated Circuit Cards, Tags and Tokens: New Technology and Applications. Edited by Peter Hawkes, Donald Davies and Wyn Price. Pub- Handy reference for electronic equations Electronic Equations Handbook, by Stephen J. Erst. Published 1989 by Tab Books Inc, Blue Ridge Summit, Philadelphia. Soft covers, 303 x 186mm, 245 pages. ISBN 0 8306 3241 7. Price $29.95. This book is exactly what it claims to be. It is filled with equations which pertain to just about every aspect of electronics. It does not tell you how to use the equations; it just lists each equation, its variables and its constants. Is it useful? Yes. To many hobbyists and technicians who do not have access to a large technical library, it will be quite useful. It is available from all Dick Smith Electronics stores - Cat. B-1790. (L.D.S.) lished 1990, BSP Professional Books (Blackwell Scientific Publications Ltd), London UK. Hard covers, 240 x 164mm, 181 pages. ISBN 0 632 01935 2. Price $112.00 This is one of those books that you can read right through and end up not feeling any the wiser about the subject. If 'you are wanting to know about the technology of smart cards and radio tags, you had better look elsewhere. While its subtitle mentions "new technology" it is almost written entirely on the applications of smart cards. There is nothing on the technology of tags used in animal husbandry, libraries or in retail stores. Nor is there any mention of the very latest in security systems, involving computer finger-printing (see "Fingerscan Personal Identification", SILICON CHIP, May 1990). That is not to say that finger and palm prints don't get a mention but clearly the authors did not know of any viable system at the time of writing. As an up-to-date reference on the title subject therefore, this text leaves a lot to be desired. Our review copy came from Blackwell Scientific Publications (Australia) Pty Ltd, PO Box 378, Carlton South, Victoria 3053. Phone (03) 347 5552. ~ NOVEMBER 1990 115 ASK SILICON CHIP Got a technical problem? Can't understand a piece of jargon or some technical principle? Drop us a line and we'll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. Digital clock with battery backup I am in need of a digital electronic clock with up to one month or more of battery backup and RAM so that if the power fails, the time it failed is stored in memory along with the length of time the power was off. It would have to accept up to 8 power failures in memory. I have been looking around and have found nothing! Can you help me? (J. E., Blackburn South, Vic). • That's a pretty fancy circuit you are talking about there. We have not seen such a circuit. Can any of our readers help? AM radio needs careful alignment I recently completed the AM Stereo Radio (SILICON CHIP September, October, November 1989), which was bought as a kit. Although it worked at first switch on and I have been carefully through the alignment procedure several times, the results are disappointing. In making this comment, I am mindful of the commercial and fully built up combination AM/FM stereo sets one can buy for about $80 (the price of this kit), or even less. The main problem is lack of stabil- Which CDs are digitally mastered? With reference to compact discs, are all modern recordings made from digital masters and if not how does one determine which ones are? I have read in a scientific magazine that the layer of aluminium in a CD degrades with time from oxidisation. If this is the case, will my shiny new discs (which incidentally seem to be rather overpriced in this country) produce music of the same quality in 20 years time as they do today? Perhaps an article on compact 116 SILICON CHIP ity of the stereo mode. Movement of the set, or a slight bump, causes it to drop in and out of stereo. The two main uses I planned for the set were: (1) on public transport to and from the city; and (2) while jogging. The results from a 25-year old mono transistor radio are less distracting. On the SILICON CHIP set, I can only obtain 3AR (621kHz, ABC Melbourne) in stereo in some parts of the city centre but not from home. The Melbourne city centre can be seen from the front of my house and is about 13km away. The sound quality of the SILICON CHIP AM Radio on good headphones is OK but if connected to a high quality domestic stereo, it comes nowhere near that of my modest old FM tuner. Incidentally, the "el-cheapo" headphones provided with the kit were a complete waste of time - yet presumably contributed to the high price of the kit. They should have been a separately priced option. I make the following observations in the hope that it may assist you to help me. I've trimmed the aerial leads as short as possible, "pre-loaded" the tuning capacitor shaft, and the alignment seemed straightforward. I used the plastic lid of the box as originally described in SILICON CHIP (for appearance), rather than using the prediscs would make interesting reading. (W. A., Paraburdoo, WA). • It is easy to tell where CDs have been made from digital masters; they have the coding DDD. Those that are coded ADD have used analog masters. As far as oxidisation of aluminium is concerned, it should not happen if the plastic coating maintains its integrity. Even so, no-one really knows whether CDs will deteriorate over long periods of time. Presumably, the correction circuitry will take care of any problems that occur and so the music quality should be the same. punched aluminium alternative supplied in the kit. I did notice a number of apparent "cost-cutting" measures with the components provided in the kit. I do not know how these might affect the performance. The tuning capacitor was the specified Toko type but coils L2, L3, L4, and L5 were unbranded. The 2% capacitors were ordinary unbranded greencaps, said to be selected. The "full-size" dual gang pot was unbranded and, even with 330Q series resistors, the mismatch of the two channels at low volume is quite audible. (For about $1 or so more, one can buy a good quality, branded, Japanese miniature pot that matches perfectly without buffer resistors). The antenna coil (Ll) seems insubstantial in construction when compared with older commercial transistor radios and too large a diameter for the 3/8-inch ferrite core. I have wedged it firmly, but there is a gap between coil and ferrite. There were other problems too, like·the two separate AA battery holders (instead of the specified side-by-side 2-cell holder) and no materials for fixing them into the box. The kit instructions suggested "glue" (none provided) but the plastics involved are very difficult to glue. I would appreciate any advice you can give me to help with this particular project. (B. W., Bulleen, Vic). • We are concerned that your AM Stereo Radio kit and its performance are not to your expectations. We can assure you that the prototype unit had excellent sensitivity and stability. The stereo sound quality was also excellent, particularly on local stations , and the unit had to be severely bumped to knock the reception out of stereo. We have also examined a built up kit from Dick Smith Electronics and found the performance equal to our prototype after it had been carefully aligned. That is the key to the success of this project. We are confident that your radio can equal the performance of our prototype provided that careful attention is paid to the alignment. Similarly, the susceptibility to dropping out of stereo is dependent upon the lock range of L5, the 3.6MHz oscillator. The slug of L5 must be set to the centre of its lock range as described in the instruction manual. Regarding the comments that you have made concerning the quality of the Dick Smith kit, their kit department has gone to considerable lengths to match the quality of the prototype. The cheap headphones were supplied only to complete the kit and better headphones should be used for serious listening. Genuine Tako coils are supplied with the kit and although not marked with the Tako brand, are marked with their type designations. The 2% values for the capacitors were selected by the DSE kit department using standard metallised polyester capacitors and a capacitance meter. The volume control supplied is a standard DSE potentiometer, similar to that used in our prototype. The 330Q padding resistors can be adjusted in value for best results at low volume. Similarly, the antenna coil used in our prototype was a DSE coil and was wedged to the ferrite rod using thick cardboard as described in the article. The use of two separate AA battery holders instead of a dual holder is quite OK. We recommend using contact adhesive to fix these in place. Replacement SCR for a timing light I was asked to fix a professional timing light which had failed and found what appeared to be an SCR (2N6565) shorted on all three terminals. I have since searched through various catalogs and substitution guides, all to no avail. This leaves me at a loss as to what to do, as the light comes from overseas. A new one costs about $50 and I don't fancy telling my friend to ditch it and buy a newie. Could you possibly advise me where I may be able to get a replacement that might take the place of this? As there was no circuit diagram with it I am unable to give you any idea of its function. (A. M., Taree, NSW). • We have searched through all our data books for any information on the 2N6565 SCR. Unfortunately, we have Dual point distributor system I have been running the transistor assisted ignition (SILlCON CHIP, May 1988) successfully on my Holden Monaro V8 for a number of years now and am very pleased with it. However, I have been told I can get a dual point conversion for my distributor which will improve the performance further. Apparently it does this by increasing the ignition dwell time and thus enables the coil to deliver a much hotter spark. (D. T., Moruya, NSW). • What heresy! Seeking to improve upon the unimprovable! As far as we are aware, the dual point conversions you refer to have two sets of points which are connected in parallel to a single coil. In operation, the two sets of points open and close at different times (because they are offset on the distributor cam) and therefore extend the "dwell" time. Perhaps we should explain that a little further. "Dwell" is measured in degrees of rotation (of the distributor cam) and refers to the time the points are closed. During drawn a complete blank. Normally, these timing lights use a transistor inverter to boost the car's battery voltage to several hundred volts DC. This is stored in a dump capacitor which powers the Xenon discharge tube. The discharge tube is normally triggered directly by a lead from the number one spark plug. So where does the SCR come in? We dunno. All we can suggest is that you disconnect the SCR, connect the unit up to the power and measure the DC voltage produced by its inverter. Having done that, it should be possible to select a suitable SCR - we assume that the 2N6565 is a "sensitive gate" SCR. Therefore, if the voltage is 400V or less it should be possible to use a C106D as a substitute. Switchmode power supply has hot zeners I would like to thank you for the current range of test equipment that this time, the points are not lifted by the cam and they are in the "dwell" position. Normally, a 6cylinder motor has about 40° of dwell which means that the points are closed for about two thirds of the time. How do we figure that out? Well, a 6.- cylinder motor has a 6-lobe cam in the distributor and each lobe represents 60° of rotation. Therefore, for 40° of dwell, the points are closed for two thirds of the time. The problem for conventional points is that while the dwell is fixed, the points actually are closed for less and less time the faster engine goes. Thus, there is less time for the coil current to build up. The transistor assisted ignition we published solves this problem by using "dwell extension". The main transistor feeding the coil is on most of the time, as explained in the article, and so the coil delivers a really hot spark. All of which is a long-winded way of saying that any mechanical means of dwell extension, such as dual point distributors, is unnecessary. You are already getting the hottest possible spark with the coil you are using. your magazine is publishing. At last the enthusiast can get excellent test gear at kit prices. I have just completed the switchmode power supply (April 1990) and digital capacitance meter (May 1990) and have found them to be good performers. However, I must make comment on some aspects of the power supply. On my unit, the zener diodes (ZD2ZD5) ran quite warm, in fact too hot to touch! On calculating the current through both 560Q resistors in the supply lines feeding them and ignoring the current taken by the LM344 which I would imagine to be quite small, the resulting value is 53.6mA. This represents 800mW in a 1W zener. While this would be within the device specification, it leaves little "headroom" and the results of a failure of these devices would put the full 60V on the low voltage circuit, with disastrous results. I replaced these zeners with 3W types to be on the safe side and would NOVEMBER 1990 117 Increasing battery charger output I am writing to ask for help with your DC-to-DC battery charger published in the September 1988 issue of SILICON CHIP. I have constructed the project to the letter twice and the maximum output voltage I can get is 11. 75V with an output current of 1.56 amps. I have checked and rechecked every step and still get the same results. On my first attempt at the project, I used a BUZ71L power FET which blew when the circuit was connected. On the next attempt I used a BUZ71A with no dire results. I wondered if in the first attempt I could have damaged the PWM IC. be interested in your comments concerning this. Also when supplying current to a load (0.5A or more), the toroids get quite warm and I wonder if this happened in your prototype? One other point concerns the LM317 and how voltage is fed to its adjustment pin. If the voltage adjust pot becomes noisy or open circuit, the LM317 will have an open circuit between it and ground and will be destroyed. This happened to me while trying the supply out with a pot I had on hand. Perhaps a useful modification would be a higher value shunt resistor between the lO0Q resistor and 15kQ resistor mounted on the board? Finally, for your Notes and Errata the supply lines are reversed on the wiring diagram going to points C and D. Luckily I noticed this or I would imagine that the 470µF caps would have complained quite loudly! My next project will be the digital sine/square wave generator and I hope that it also may become an equally useful instrument. Also, I too would be interested in a slow start circuit for higher power lamps so could you please put that project on your drawing board. Perhaps a general article on making PCBs and making front panels would also be a good idea. Thank you again for an interesting and informative magazine. (R. P., Salisbury East, SA). • It is true that two of the zener diodes (ZD2 and ZD5) do run quite 118 SILICON CHIP When I connected a 20W 12V globe to the output and adjusted VRl for minimum current drain, the LED seemed to not really change, except that in the fully clockwise VRl position the LED goes off completely. I have put an ammeter in series with the globe and get only 1.56 amps - adjustment of VRl makes no difference. (B.A., Croydon, Vic). • It is relatively easy to increase the output voltage of this charger circuit to the desired figure. The output voltage is a function of the internal 5V reference (pin 16), Rl, RZ, R3 and R7. You can easily increase the output voltage by increasing R7 to 1 lkQ or 12kQ. It's unlikely that you have damaged the IC or any other components. Battery charging for Digital Voice Recorder I have recently purchased a Digital Voice Recorder from Altronics. I noticed that the value for Rl is not marked on the circuit diagram. Instead, there is a note saying "see text". Unfortunately, I could find no reference to Rl in the said text. Could you advise me please? (M. C., Groote Eylandt, NT). • Rl is intended to trickle charge the standby batteries, if they are nicad types. If alkaline (ie, non rechargeable) cells are used for the standby batteries, Rl is not used. If you are using nicad batteries, Rl needs to be selected to give a low trickle charging current. We suggest a value of lkQ with a 0.25W rating. Higher resolution for the pH meter warm to the touch and are, in fact, dissipating close to 800mW as you calculated. If you regard this as too close to the wind, there is nothing wrong with replacing them with 3W types as you have done. The toroids do get warm when supplying large currents to the load. This is quite normal. We specified a multiturn pot for the adjustment to the LM317. This would not normally present any problems with an open circuit wiper. Pulling a pot. out of your junk box always represents some sort of risk to circuitry as far as open circuit wipers are concerned. In other words , if you are in doubt about a pot use a new one. I have built the pH Meter described in the April 1988 issue of SILICON CHIP and am happy with its performance. Would it be possible to modify the circuit to read from 4 to 10 for higher resolution? - 4 being zero, 10 being full scale. (G. F., Dandenong, Vic). • It is possible to modify the circuit to read from 4 to 10. All you have to do is to modify the meter scale to cover the range 4-10 and then adjust trimpot VR4 for the correct range. Ideally, VR4 may need to be changed to a lower value, such as 5kQ, for easier adjustment. The calibration procedure will be the same as described on page 64 of the April 1988 issue. Computer batteries not rechargeable Notes & Errata In Jennifer Bonnitcha's Computer Bits column in the September 1990 issue of SILICON CHIP, there is a reference to the "rechargeable battery" which maintains the computer's real time clock. My understanding is that these batteries are lithium cells and therefore not rechargeable. Am I correct? (P. W., Sutherland, NSW). • Tch, Tch. That was an oversight on our part. You are right, they are not rechargeable although perhaps it would be a good idea if they were, because then they would not be so inclined to die after a year or so. Studio 200 Stereo Control Unit, June, July 1988: in spite of the notes published regarding Dl and DZ, a number of constructors have still experienced overheating problems with Ql and QZ in the headphone driver amplifiers. To cure this problem, 33Q emitter resistors should be installed for Ql and Q2. To do this, disconnect the emitters of Ql and Q2 from th e PCB and wire the 33Q resistors in series, between the PCB and the fre e emitter leads. This will slightly reduce the available headphone drive level. If this is critical, reduce the 82Q resistor to 47Q. ~ MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. CLASSIFIED ADVERTISING RATES Advertising rates for this page: Classified ads - $7.00 for up to 15 words plus 40 cents for each additional word. Display ads (casual rate) - $20 per column centimetre (Max. 10cm). Closing date: five weeks prior to month of sale. If you use a PO Box number, you must include your permanent address and phone number for our files. We cannot accept ads submitted without this information. To run your classified ad, print clearly on a separate sheet of paper & send it together with your cheque or credit card details to : Silicon Chip Classifieds, PO Box 139, Collaroy Beach, NSW 2097. Or fax the details to (02) 979 6503. If paying by credit card, fill in the details on the order form included elsewhere in this issue. IIT MATHS /:' "l.s,-e-, COPROCESSORS 2C-08 2C87-8MHz 2C-10 2C87-1 0MHz 2C-12 2C87-12MHz 2C-20 2C87-20MHz 2C-20H HYPERBOARD 3C-16 3C87-16MHz 3C-20 3C87-20MHz 3C-25 3C87-25MHz 3C-33 3C87-33MHz ~J:-o ~{~ .S.s 476 528 618 645 130 890 915 1148 1380 - - FIVE YEAR WARRANTY CAD CONNECTION PHONE (02) 957 6719 ...... FAX (02) 954 5550 FOR SALE BEGINNER'S GUIDE To The IBM PC. Gives new users a flying start & saves money. $12 posted. Bruce Collins, 234 Tor St, Toowoomba, Old 4350. 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, needs EGA or VGA col~ our 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, KIT REPAIRS Kits repaired from all magazines. PCs and peripherals also repaired. Ring anytime 9am-9pm EEM ELECTRONICS 10 Bouverie Place Epping, Vic. 3076 Phone (03) 401 1393 42 Villiers St, New Farm, 4005 Old. Phone (07) 358 2785. KITS AVAILABLE for the ETI Digi125 $17.95 plus $2.50 p&p. Heatsink not supplied. Kits built and repaired. Repairs to radio control equipment. Model railway projects designed and built. Prototype and production board supplier to the hobbyist. Supplier of PCBs for projects in SILICON CHIP. Electronic Toy Services (08) 382 8919. DIGITAL 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. BARGAIN OF a lifetime. Retiring hobbyist has for sale an enormous quatity of new components (20,000+) cataloged & in over 300 capstan drawers. 250 magazines, test equipment, UV light box, tools, wire, circuit diagrams, etc. Best offer. For details, phone John (065) 85 2150 BH, (065) 85 3321 AH or fax (065) 85 2331. XT/AT HANDBOOK by Choisser & Foster. Pocket size, 92 pages. For engineers & programmers, & other serious PC/XT & PC/AT users. A collection of hardware & software facts & 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 data on the PC compatible family & its operating system. Latest edition. This is the one advertised in the US mags Byte, Dr Jobbs Journal, etc. $20 including postage. 5 off $15 each. Don McKenzie, 29 Ellesmere Crescent, Tullamarine, 3043. ANTIQUE RADIO ANTIQUE RADIO restorations. Your one-stop electronic repair shop. Specialising in restoring vintage radios including chassis rewiring, quality new parts, valves, valve sockets, speakers, transformers, cabinet restoration. Quality secondhand radio dials & parts for most brands & models. About 400 radios in stock for restoration & parts. Every restored wireless is covered by a 2-year warranty on parts & service. French polishing of timber cabinets available. Vintage car radios in valve & NOVEMBER1990 119 C ..1 N Adroit Electronics ........... ... ...... 120 ►~ IC") ·oi 0 0 C: .c a. en u Q) f06 Ol C: "O Q) Arista .... .. ..... .... ............... 29,76,89 ll) (.) >< CU Z LL Back Issues ...... .. ......... ....... .. 96,97 Board Solutions ... ...... .... ..... .. 54,55 Q) ·~ ... I-,.... Cad Connection .. .. .... ... .. ... ...... 119 (.) -=:I' David Reid Electronics ....... . IFC,1 w Q) (/) ..I Bose Australia .. ... ................. 30,31 ll) wr::o::I' !: e. 0 ..c: a: c. 0 §, Cl.·Cl. (/) ::::, Altronics ........ .. ........ ..... ....... .. 61-65 -=:I' or.: a: ;; (/) ~ a: Advertising Index 1- (/) Q) Q) (/) 0 94,95 Dick Smith Electronics .. .......... 9-15 EEM Electronics ... .. ..... ... .. ..... 119 Electronic Solutions .............. 78,79 C ea: Electronics World .... .... .... .......... 73 Elmeasco ........... .. .... ............. 81,91 MEMORY EXPANSION SIMM & SIP 9 X 25.6. 9x 1MB 8 x 1MB(MAC) 9x4MB -120ns -100ns - 80ns - 70ns - 60ns -100ns - 80ns - 70ns - 80ns - 70ns - 80ns NIA 23.00 23.80 24.70 30.00 79.00 81 .50 89.50 76.50 82.00 528.00 -100ns - 80ns - 80ns - 80ns - 80ns 2.10 2.40 2.50 7.65 7.65 INTEL 8087-2 80287-10 80C287-12 387SX-16 387DX-16 387SX-20 387DX-20 3870X-25 3870X-33 175.00 308.00 390.00 435.00 478,00 490.00 538.00 680.00 835.00 387SX-16 3870X-20 3870X-33 400.00 490.00 750.00 CYRIX TOSHIBA LAPTOP T1000SE T1600 T3100E T3100SX T3200SX T3200 T5100 T5200 2MB 2MB 2MB 2MB 2MB 3MB 2MB 2MB 51 5.00 340.00 340.00 340.00 340.00 570.00 340.00 340.00 COMPAQ 386-20, 386-25, 386-20E, 386-S, 386-33 4MB MODULES 680.00 4MB BOArds 798 .00 PELHAM WEITEK 3167-20 3167-33 4167-25 4167-33 820.00 1010.00 1500.00 1780.00 30/286,50 70E61 ,121 70A21 2MB 2MB 2MB Harbuch Electronics .......... ...... 93 Hycal Instruments .. .......... .. .. .. 119 Jaycar Electronics .... 34-37,84-87 Jiloa ....... ... ..... .... .. ....... ..... ....... 120 J.V. Tuners .... .. ... ... ..... .. ..... ....... . 50 Oatley Electronics ......... ...... ..... 53 Pacific Microelectronics ............ 49 PC Marketplace ....... .. ...... .. ..... IBC IBM PS/2 DRAM/DIP 4164 41256 41464 4 X 256 1MB Geoff Wood Electronics ......... ... 5 Prices At Sept 13, 1990 CO-PROCESSORS 250.00 280.00 280 .00 Sales Tax 20%. Overnight Delivery. Credit Cards Welcome 1st Floor, 100 Yarrara Road, Pennant Hills, NSW 2120 Tel (02) 980 6988 Fax (02) 980 6991 Pelham ..... .. ..................... .... .. 120 RCS Radio.................... .. .......... 92 Resurrection Radio .................. 41 Rod Irving Electronics .... ...... 46,47 70,71, 108,109 Silicon Chip Binders ....... ..... OBC Silicon Chip Subscriptions 113, 114 TOROID POWER TRANSFORMERS From quality UK manufacturers. Available from stock at discount prices, 15VA to 625VA. Send SSAE for data & prices to: Transformer Discounters, PO Box 542, Wahroonga 2076. ACTIVE SHORTWAVE ANTENNA SILICON CHIP, JAN 1990. Complete kit $59.00, Built and Tested $119.00, Case $10.00. LOOP ANTENNA Improve signal strength & quality with this portable antenna. Kit $44.00, Built and Tested $69.00 COMPACT INDOOR FM ANTENNAS Two models to choose from, Terk FM2000 a passive loop FM antenna for $69.95 or the Terk PI2 powered FM antenna with wideband low noise filter for $199.00. We can also provide assembly facilities for small production runs at competitive prices JILOA (TECHNIKIT DIVISION) transistor types available for restoration. Repairs done on tape decks, amplifiers, TVs & videos. Open Sat. 10am-5pm; Sun. 12.30-5pm. 109 Cann St, Bass Hill, NSW 2197. Phone (02) 645 3173 BH or (02) 726 1613AH. WANTED 120 SILICON CHIP Tech-Fast ..... .. .. .... ........ ... .......... 21 Transformer Discounters ... ... .. 120 PC Boards Printed circuit boards for SILICON CHIP projects are made by: PO Box 73, Glenhuntly, VIC 3163. Telephone: (03) 571 6303 • Electronic Toy Services, 2/111 Glynville Drive, Hackham West, SA 5163. Phone (08) 382 8919. Phone (03) 789 5145. 50 Edward St, Langwarrin 3910. • Jemal Products, 5 Forge St, Welshpool, WA 6106. Phone (09) 350 5555. WANTED CIRCUIT: Pye power supply • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone 88 5730. PS775. $10 for lend of & return . Phone (067) 36 1078. WANTED: IC MBL8243M P/N ElWANTED VALVES: 1A7, 1H5, 105, 1P5. Pay $10 each. W. Kilpatrick. Sound Australia .... .......... .... ... ... 29 Tandy Electronics ........ ........ ... . 23 347766 for Akai VS-3 VCR (on Mechaeon PCB). Phone (049) 48 6087. • RCS Radio Pty Ltd, 651 Forest Rd , Bexley, NSW 2207. Phone (02) 587 3491 . WELLER A DIGITAL MULTIMETER FOR UNDER $40.00 ?? SELF-IGNITING CORDLESS PYROPEN * HAS SOLDER TIP PLUS HOT BLOW TIP * APPROX. 4 HOURS WITH EACH FILL * USES STANDARD BUTANE GAS • SOLDERING TEMP - 250° to 500°G, HOT BLOW 650°G LABTECH Q105H DIGITAL MULTIMETER $169.95 WeUer'PYRoPEN · *D.C. VOLTAGE UPTO 1000Volts *A.G. VOLTAGE UP TO 750 Volts *D.C. AMPHERE UP TO 1OAmp * DIODE TEST * RESISTANCE UP TO 2Mn INCLUDES TEST LEADS & MANUAL * BONUS FREE CAN OF WELLER GAS !! KASPAROV POCKET CHESS COMPUTER HSA4330P WEATHER-PROOF OUTDOOR SPEAKER SYSTEM *8 LEVELS OF SKILL TO ADVANCE FROM BEGINNER TO INTERMEDIATE. "TRUL Y VERSATILE, TEACHES CHESS TACTICS, SHOWS THE BEST MOVES, AND WARNS OF DANGER." * 3 WAY ACOUSTICSUSPENSION * 30 WATTS RMS * COMPLETE WITH MOUNTING BRACKETS ' * COiviPACT DESIGN • YOU SET THE LEVEL OF HELP REQUIRED AND THEN PLAY AGAINSTTHE COMPUTER. SAVE $20.CXJ NOW $149.95/PAIR _ ONLV $49.95 -~~-!i!""'\!1'11' _. -.•· -.. . ·sTUDIO 200 CONTR UNIT KIT • SLIM ONE RACK PROFILE * FULLY PUNCHED AND PRINTED PANELS $199.00 . STUDIO 200 SERIES 1OOW PER CHANNEL AMPLIFIER $359.00 DELUXE COMPACT DISC CARRYING CASE • Removable tray. (Holds 20 discs) • Attractive leatherette cover. (Black) • Felt Lined interior. • Locable case with carry handle. DIALCQRD We've got reels of the Stuff!!!! !! 10 metre reel ... only 99 cents That's AUDIO TAPE TX-60 $2.45ea TX- 9o $2.95 ea BOX of 10-$22.00 BOX of 10 - $26.00 MOUSE MAT for your MOUSE 260mm x 220mm ONLY $14.95 NITE-WATCH MOTION DETECTOR with TWIN FLOODLIGHT KIT * Coverage: 90° <at> 15 Metres • Timing & Sensitivity Adjustment • Lights can be operated manually WAS$99.95 TOP VALUE! ONLY $21.95 VIDEO CASSETTE STORAGE CABINET NOW $79.95 ,. * Holds 8 VHS or BETA tapes. Now only $14.95 (Floodlights not included} i QUARTZ HAND-HELD SPOT LIGHT * 12 Volt operation via cigarette lighter * 12 feet of cord. * 55 watt Beam. · WAS$19.95 NOW$12.95 "Great for around the field, property, for the kids, or just for fun. It even has a morse code function and belt clip.,, • Transmitting distance: 50 100 mts open field . • Operated by six (6) "AA batteries (not included) • DOC approved (27 .145 m Hz). $19.95 /pair