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BABY ROOM MONITOR & FM TRANSMITTER AUSTRALIA'S DYNAMIC _ - ELECTRONICS MAGAZINE~ - ~~ '0 • V • PROJECTS ... Build A 4-Channel Guitar Mixer Automatic Controller For Car Headlights Adjustable 0-45V BA Power Supply COMPUTERS ... Experiments For Your Games Card What To Do When Things Go Wrong Plot your position to less than 100 metres! The revolutionary GPS satellite navigation system lets you do just that & much more. We take a look at how the system works. ~ ij Microsoft~ t~ , MS-DOS:, ; Upgrade · Word Perfect V5.1 r- : ~iP~ ;~~~~ 11:t SPREADSHEETS SAVE $100 Lotus 123 V2.3 $569 n CAD PROGRAMS Autosketch V2. .. .............. .... SAVE $50 $99 Autosketch V3.0 .. ..... ...... .... .SAVE $50 $249 Generic CAD ....................... SAVE $100 $599 Turbo CAD 30 V1.8 .... ... ......... SAVE $50 $149 PARADOX MS DOS 5 Upgrade ·· · s129 I SAVE $100 Pa rad ox V3.5 WWW ~ j .,,_.• • i_If\ :e.:: ''""" ummn" Sl99 ~ ,i} _. :. ~ Works Lotus Works s199 $899 0 and A V4 D.Base IV R. 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SAVE $50 $299 MS Word V5.5 ................. SAVE $1 20 $499 MS Word for Windows ..... .SAVE $100 $549 Lotus 123 for Windows .... ... .. SAVE Supercalc V5 .... ......... ......... SAVE Lotus 123 V3.1+ ................ SAVE MS Excel for Windows .......... SAVE DATABASES SAVE $30 Harvard Graphics V3. Microsoft Works . . .............. SAVE $50 $229 Lotus Symphony ..... SAVE $170 $829 First Choice V3 .. .. .. .... . . . .. SAVE $40 $179 MS Office for Windows ......... SAVE $100 $849 DESKTOP ,;.. :t~Y·':_l~f 1 :. 0 .... $599 Animator .. . . ...... ...... ..... SAVE $100 $269 MS Power Point for Windows .... SAVE $70 $819 your computer. Fast Back Plus V2.1 ............. ... SAVE $50 $189 Window V3/Microsoft Mouse .... SAVE $50 $269 MS Mouse/Paintbrush ............. SAVE $80 $179 Norton Desktop ......... .. .......... SAVE $50 $169 Central Point Back-up . . ..... SAVE $50 $149 Ouemm Memory Manager ....... SAVE $30 $109 Desqview Dos Multi-tasking ...... SAVE $50 $149 Norton Back-up for Windows .. ..SAVE $30 $129 ACCOUNTANCY Attache 4. . .... SAVE $200 $679 The Business Manager ... .... ... SAVE $100 $199 In House Accountant .. .... ... ..SAVE $50 $249 la§!l / PFS:fo-st Publisher SAVE $40 First Publisher V3 s159 Excellent publishing features. Market leading presentation package. ~ ~ Essential utilities for ~ Express Publisher .... .. ...... SAVE $100 $299 Ventura Gold V3/Windows . ... SAVE $100 $1095 Carel Draw for Windows ........ SAVE $100 $599 •wit 1!l aa 111M:tirn a&1 1 On Target... .. . .... SAVE $20 $129 MS Project for Windows ..... ... SAVE $100 S699 Je1r1uee savE . SAVE $650 ·>---> ' .·• """"'' '"' ;,,~ QUATTRO PRO ~" •., Lotus Freelance PLUS , ~~ s1gg ~ <0~ ~!~~l:fiate SAVE $530 Quattro Pro MultiMate 4 SAVE $630 Applause II s149 s149 -s49 WILEY PARK STORE ONLY 1018 CANTERBURY RD. WILEY PARK 2195 Framework Ill s149 PHONE: 740 4462 or 740 6055 $5 DELIVERY AUSTRALIA WIDE TOLL FREE: (008) 02 2116 30 DAY ACCOUNTS AVAIL. OR FAX YOUR ORDER: 740 4463 MOST CREDIT CARDS ACCEPTED HN0365 .... .VOLUME 5 NUMBER1 •I ., .. .. .. .. ..• ..·.--..-. .. ...-.-- ........ ........ --- .. ir ii- ii- ii- !!! ii- ~ January 1992 DO YOU NEED a really big power supply? This switchmode design is adjustable from 0-45V DC & can deliver currents up to 8 amps. See page 64. FEATURES 8 The Story Of Electrical Energy, Pt.17 by Bryan Maher Giant hydroelectricity schemes in Brazil 42 Experiments For Your Games Card by Darren Yates Some simple circuits plus programs 82 New Blood Steriliser Uses Microwaves by Leo Simpson Radical process has Australian patent PROJECTS TO BUILD 16 Build A 4-Channel Guitar Mixer by Darren Yates Features bass, midrange & tone controls 28 Automatic Controller For Car Headlights by Jeff Monegal Turns your lights on & off automatically 53 Baby Room Monitor & FM Transmitter by John Clarke YOU CAN DO MUCH more with a games card than just play games. This month, we show you how to use the various inputs for temperature & light measurements, or for a simple burglar alarm. The program listings are included - see page 42. Lets you monitor the baby on an FM radio 64 Adjustable 0-45V 8A Power Supply by John Clarke Uses switchmode regulation for low power dissipation SPECIAL COLUMNS 34 Serviceman's Log by the TV Serviceman Same set, same symptoms, but ... 40 Computer Bits by Jennifer Bonnitcha What to do when things go wrong 58 Vintage Radio by John Hill Restoring an AWA Radiolette receiver THIS NEW 4-CHANNEL MIXER boasts separate bass, midrange & treble controls & has very low noise & distortion. It's ideal for use with musical instruments such as electric guitars. Details page 16. 74 Amateur Radio by Garry Cratt The Global Positioning System 78 Remote Control by Bob Young Motors for electric flight models, Pt.2 DEPARTMENTS 4 6 22 81 84 Publisher's Letter Mailbag Circuit Notebook Subscription Page Computer Update 87 Product Showcase 92 Ask Silicon Chip 94 Market Centre 96 Advertising Index 93 Notes & Errata THE SERVICEMAN tangled with some Mitsubishi TV sets this month & one of them bounced. His troubles start on page 34. JANUA RY 1992 1 AVL-5 Video Camera Light ill VBR-400 Battery Reconditioner MP-100 Charger Specifically designed to tackle the problem caused by memory effect displayed by most rechargable batteries. The VBR-400 will discharge and recondition the battery to an optimum level before use. This ensures the battery capacity will be used efficiently and lengthen the overall life of the battery. (suit many SONY, JVC & SHARP cameras) The MP-100 can be used as a direct DC/DC voltage convertor power supply or as a NiCad charger. The DC input is via a fuse protected cigarette lighter plug so the unit can be operated from cars and trucks. Suits many 6V, 7.2V, & 9.6V batteries. Short cicuit and overcharge protection with LED status indicator. Complete with vinyl carry case and multiplug adaptors. Only $59.95 Only $59.95 Simply clip lightweight on a battery, attach to •••••••••••I•••••••••••••••••••••• light. A New portable video camera } the top of the video camera and switch ( on. No long cables or heavy battery I ~~Ji!~~;f~ •··•· •••·•· · ·•·•· · · •· · · • ~~~ksse t~o~!~~i~~u~~ttery not included. ~~v3:t!;!r5 Ill 1!111' === AVM-3 Professional Audio Video Mixer This professional audio video mixer is designed for the serious home movie maker through to the professional video camera user. Background music and effects can be faded in and out through turntable, CD player, tuner or cassette inputs. Other features include individual fader controls for each channel, master output volume, cue monitoring, left/ right pan pot control, Mic inputs, VU meters and more ! ! Freq. Res. 20Hz to 20KHz. Output level: 775mV. Power Supply: 9 V DC battery, or optional power adaptor. Dimensions: 265 x 195 x 60 mm Only $169.95 Data Switch Boxes Computer Data Cables DB-25 M to Cent. (36) M Cent.(36) M to Cent.(36) M DB-9 or 25 M/M or F /F $9.90/1.8mtr $39.95/5mtr $8.50 each DB-25 M to Cent. (36) M Cent.(36) M to Cent.(36) F DB-9 M to DB-25 M $19.95/3mtr $29.95/3mtr $9.50 DB-25 M to Cent. (36) M DB-9 M to DB-9 F DB-9 M to DB-25 F $36.95/5mtr $9.95/2mtr $9.5Q DB-25 M to Cent. (36) M DB-9 M to DB-9 F DB-9 F to DB-25 M $69.95/10mtr $16.95/5mtr $9.50 DB-9 M to DB-9 M DB-9 F to DB-25 F $19.95/2mtr $19.95/2mtr $9.50 DB-25 M to DB-25 F VGA (15) M to VGA (15) F $19.95/2mtr $29.95/2mtr DB-25 F to DB-25 F VGA (15) M to VGA (15) M $19.95/2mtr $29.95/2mtr DB-25 M to DB-25 M VGA (15) F to EGA (9) M $29.95/5mtr $24.95/2mtr DB-25 M to DB-25 F 5 PIN DIN M to 5 PIN DIN F $29.95/5mtr $9.95/2mtr DB-25 M to DB-25 M DB-25 M/F NULL MODEM $59.95/10mtr $19.95/2mtr Cent.(36) M to Cent.(36) M DB-25 M to DB-9 F $24.50/2mtr $16.95/2mtr , DB-25 M to DB-25 M II Ji ill ;::.o~B-25 crossover type A/B/C/D VGA and PS-2 i ::SB-25 Auto (P /S not ;nc) IIII ;;::,,s2s P/B A.C.N. 001-372-372 (CAs-1•1 Adaptors VGA (15) M to EGA (9) M $14.95 VGA (15) F to EGA (9) M $14.95 VGA (15) M to EGA (9) F $14.95 VGA (15) F to EGA (9) F $14.95 PS-2 M to 5 PIN DIN F $9.50 PS-2 M to DB-9 M $9.50 David Reid Bectronics ELECTROLUBE Service Sprays =? Electronic Cleaning Solvent Electronic Cleaning Solvent P.C.B. Cleaner P.C.B. Cleaner Freezer Spray ti Contact Cleaner Lubricant Contact Treatment Oil Permaguard Ultraclene Airduster Clear Protective Lacquer Tape Head Cleaner Conformal Coating Anti-Static Spray * (ECS200) (ECS400) (PCC200) (ECS400) (FRE400) (EML200) (SOB200) (EPE200) (EUL200) (EAD400) (CPL200) (VID100) (DCA200) (SCS250) 200ml 400ml 200ml 400ml 400ml 200ml 200ml 200ml 200ml 400ml 200ml 100ml 200ml 250ml VSI Easy-Connect $11.95 $14.95 $8.50 $14.50 $14.95 $8.95 $9.75 $7.50 $8.95 $19.95 $13.50 $7.95 $39.95 $10.95 4pc. Spirit Level Set Transfomer Torpedo Level: Reads horizontal, vertical & 45° surfaces. Line Level: Attaches to a piece of string for longer distance readings. Surface Level: Reads horizontal surfaces in all directions. Angles Level: Reads surfaces angles and gives readings in degrees. M 2156 Transformer 240 V AC primary, 6 V, 9 V, 12 V, 15 V AC secondary <at> 2 A. was $17.95 Only $19.95 Computer Diskettes 240 volt AC input to 10 volt AC output <at> 1 amp. As used on modems, phones, etc. A very rare product ! ! Now $10.95 MINI VAC Great for cleaning keyboards, camera lenses, audio equipment, etc. 9 V battery operated. Now $9.95 This NEW mains filter protects your computer, HiFi, office equipment, TV & video, etc. against Surges, Spikes, RF, Transients, Lightning. The LF-8 contains 2 high performance filter networks protecting the 8 outlets. The outlets are arranged in 2 banks of 4, with the 1st bank in series with the 2nd. This arrangement allows B bank to give DOUBLE filtration for more sensitive equipment. The filter includes a power analyser circuit that continually monitors the incoming power alerting the user to the ACTIVE, NEUTRAL & EARTH connections. r-Fll.1'11:1---i LF... Only $239.00 127 York Street, SYDNEY 2000 P.O. Box 0103, SYDNEY 2000 A.C.N. 001-372-372 :;:;:;:"-:"':: Our "IIOT'' new product for '92 Plug Pack LF-8 Squeeky Clean Mains Filter ==~ :II Save installation and rental costs for a separate line. Switches incoming Fax calls automatically on receipt of calling Fax tones. Latest VOICE PRIORITY technology. Installs in minutes on ANY PHONE SOCKET using supplied connecto r s. DOES NOT REQUIRE EXPENSIVE TELECOM INSTALLATION. Adds HOLD FACILITY to all phones. Puts a call on hold from any phone. Manual Transfer to Fax before, during or after voice conversation . Can interupt a voice conversation, to send or receive a Fax, then res ume. Works with or w ithout an Answering Machine. Pulse/Tone dial compati able. WIii operate with Fax, Phone, Modem and Answering Machine on one line. No restriction to the number of extensions or other devices connected to it. Compact Design, being a little larger and heavier than a packet of cigarettes. Proven Reliability backed up with a 2 YEAR Exchange Warranty. Also works with Commander, Keyphone or PABX (technical installation requ'd) The EASY-CONNECT is compatible with the changing needs. Provides Lightning protection for the Fax and other devices connected to it. Made in the U.S.A. Telecom Austra lia Permit Number : A90/14B/0342. Size: 85mm x 90mm x 33mm. Wgt: 225g . Now $10.95 5.25" D.S.D.D. 360K $4.20/ pkt-10 5.25" D.S.H.D. 1.2M $7.60/ pkt-10 3.5" D.S.D.D. 720K $7.80/ pkt-10 3.5" D.S.H.D. 1.44M $16.95/ pkt-10 The First Truly Intelligent PHONE-FAX LINE SHARING DEVICE NO Confusing Voice Messages. NO Periods of Silence. NO Unusual Dial Tones. NO Delays. NO Frustrated Callers. The EASY-CONNECT is totally transparent. Your callers will never know it's on the line ! I Only $399.00 2 YEAR Exchange Warranty my-power 200 inverter What is my-power ? My-power is a sensational breakthrough that converts 12 volt power from a battery, to 240 volt mains power. By simply plugging my-power into your cigarette lighter socket, a host of standard electrical appliances can be used where mains power is unavailable. What will my-power run? My-power 200 has a continuous rating of 140 watts when connected to a fully charged battery. For intermittent periods 200 watts can be drawn and for starting motor driven appliances, my-power will supply up to a massive 400 watts for short bursts. As a guide, most appliances with a name plate rating of up to 200 watts should be suitable for operation with my-power. Continuous power: 140 watts, 200 watts peak. Protection: Overload, Undervoltage, Overvoltage, Fused Input & Output. Low battery indicator /audio buzzer. LED indicators monitor IN/OUT volts. Size: 50mm x 13.5mm x 7 4mm. Only $199.00 Ph: (02) 267 1385 Fax: (02) 261 8905 Sh>r• hours: Post ond Packing Mon-Ftl 8:30 to 5:30 Thur5 8:30 to 7:00 Sat 9:00 to 1:00 Cr • dlt Card5 Ac: c: •pt•d Frl • ndl1i,1 S • rvl<• SS - S 25 . . . . .. S4.00 126 - •so ...... 16.00 151 - SlOO ...... 57 . 00 5101 - S499 .... S9.00 SSOO • ......... .. . FftH Publisher & Edit or-in-Chief Leo Simpson, B.Bus. Edit or Greg Swain, B.Sc.(Hons.) PUBLISHER'S LETTER Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Darren Yates Reader Services Ann Jenkinson Sales & M ark eting Mgr. Angela Clarke, B.A.(Comm.) Phone (02) 979 5644 Mobile phone (018) 28 5532 Regular Contributors Brendan Akhurst Jennifer Bonnitcha, B.A. Garry Cratt, VK2YBX Marque Crozman John Hill Jim Lawler, MTETIA Bryan Maher, M.E., B.Sc. Jim Yalden , VK2YGY Bob Young Photography Stuart Bryce Edit orial Advisory Panel Philip Watson, MIREE, VK2ZPW Norman Marks Steve Payor, B.Sc. , B.E. SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd . A.C.N. 003 205 490. All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Magazine Printers Pty Ltd, Alexandria, NSW; Macquarie Print, Dubbo, NSW. Distribution: Network Distribution Company. Subscription rates: $42 per year in Australia. For overseas rates, see the subscription page in this issue . Liability : Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. Editorial & advertising offices: Unit 1a/77-79 Bassett Street, Mona Vale, NSW 2103 . Postal address : PO Box 139, Collaroy Beach , NSW 2097. Phone (02) 979 5644. Fax (02) 979 6503 . ISSN 1030-2662 4 SILICON CHIP Appliance safety is a concern Are you concerned about the safety of your home appliances? Of course, you are. Everyone is. But you probably do not worry too much when buying a new appliance because most electrical appliances are subject to stringent approval testing by electricity authorities. In the past, such approval testing was (and still is) the bane of manufacturers and importers but most people would have felt that if it ensured appliance safety then it was a good thing. But now it turns out that electrical safety is not guaranteed by approval testing. For quite a few years now we have been concerned that the power cords and plugs of appliances such as heaters have not had adequate ratings. And we can point to one glaring example - the Mistral GyroAire range of fan heaters. In fact, a few years ago we had one of these in our lab to replace the power cord which was clearly inadequate. This was a 10-amp 2400 watt appliance and the power cord became very hot in normal operation. We replaced both the cord an d the plug. In fact, we even wrote it up as a 3-page story entitled "Making Your Electric Radiator Safe" in the October 1989 issue. We thought we had made a big enough issue of it at the time but it turns out that we should have made a big stink. Why? Because it turns out that the Mistral GyroAire GA12 and GA16 fan heaters (units made before 1979) have caused the deaths of two children and at least 100 fires! Furthermore, according to the coroner's report on the deaths of the two children, the company involved, Kemtron Pty Ltd (now in liquidation), knew the risks and engaged in a "cover-up" operation. So if you have one of these fans in your household, take a hammer to it and smash it u p. Clearly then , the present process of appliance testing does not stop all the crook on es going to market. Or perhaps it does not stop previously approved appliances from being downgraded by the manufacturers so that they become unsafe. How many other unsafe appliances are out there? Nobody knows. We think that the whole process of approval testing and standards should be reappraised. Perhaps there are too many appliances to be tested. Maybe the testing should be more rigorous for room heaters and hairdryers and less so for oth er appliances. Or do we just leave the system of testing as it is and say that two deaths an d 100 fires is not a bad result, given the present cost of testing? I don't think so. Leo Simpson Portable DC Calibrator for Precision Source and Measurement Functions Hybrid Panel Meters Combine Analog and Digital Functions with Excellent Readability v v v Provides Vdc, mAdc and thermocouple emfs (type K, E, J, T and R) v Compact NiCad powered with EL back lighting and weighs only 1.2kg v Auto-stepping output function for repeated adjustments and calibration procedures v Output division function from 1 to 15 for checking linearity v 20 output-values storage memory v Direct thermometer calibration v Outputs from ±1 OOmV to ±36V, 0 to +24mA v Max resolution of 10µV, 10µA v High accuracy- ±(0.5% of rdg + 0.06% of range) v v v v v v Colour liquid crystal displays - green, yellow, blue and red Analog bargraph in 90° quadrant format with 31 segments - length of segments emphasises analog change rate. Analog scale indicates% of full scale Digital read-out uses 3 1/2 digit format Cold cathode fluorescent back lighting provides clear bright colours with minimal heat output Models for AC and DC voltage or current. Scaling option for direct readout of values Analog 0-1 mA or 4-20mA output option Over-range, decimal point and unit indication 92mm square cut out Model 2433 Tong Tester Measures True RMS v Measures voltage to 600Vrms, Current to 200Arms, Power to 200kW v Suitable for single phase or balanced 3-phase v Jaws accept conductors or bars up to 25mm diameter/wide v Analog output READER v Autoranging v Ideal for noisy waveforms INFO NO. 21 v Measures ac and de voltage, ohms and continuity v 3 1/2 digit 5mm high LCD display v Data hold function v Measures to 500V, 2Mn max v Convenient pocket size v Continuity buzzer v Analog battery and hand driven, digital battery driven Pocket Sized Digital Thermometers v Compact and exceptionally reliable v 150mm chart width v One or two pens v Z-fold or roll chart v Vertical or flat bed v AC, DC or Internal battery operation v 12 calibrated ranges from 1OmV to 50V full v AC voltage measurement ranges v Constant voltage types v Ranges to 5000Mn v Automatic hold function v Seven different basic models v Semiconductor or thermocouple types v Choice of probes (standard screw terminal connector) v ±0.5°C accuracy, 0.1 °C resolution v Ranges from -50 to 99.9°C (semiconductor) v or -50 to +600°C (thermocouple) Built-in time display scale 60cm/min to 2cm/hr crystal controlled chart speeds v 300mm/s max response .-'. Remote control option v YOKOGAWA Yokogawa Australia Pty Ltd Centrecourt 03, 25-27 Paul Street North, North Ryde Fax : (02) 888 1844 A.C.N. 003 888 364 v New South Wales Victoria Queensland S. Australia ~ W. Australia 'tl Tasmania Auckland N. Z. Specialist Reps J Yokogawa 02(805 Yokogawa 03 819 0699 1500 LE Boughen 07 369 1277 Trio Electrix 08 212 6235 Leda Electronics 09 361 7821 Meacon Systems oo 44 7575 N.E.I. (AKL 64 2732 Tech Fast (02) 988 3865 A.T.E. (03) 543 8041 l MAILBAG Fax modem will be a boon Thanks for the exciting Fax-Modem project in the September 1991 issue of SILICON CHIP. I've just picked up my ordered copy of the magazine from the newsagent and feel inspired to write to you. I've been a loyal reader since the beginning of 1990 and the owner of a AT-286 clone since May this year - not an area of electronics I would have foreseen getting into. So now I find all of your magazine of interest, not just most of it. Jennifer's articles have been of considerable help in an accelerating area in a technology I knew nothing about. The Fax-Modem will be of immediate use to my business - I'm a self-employed engineer-metalworker - and when I get it running I'll sell the Taiwanese 2400 baud modem I've just bought ($NZ230). G. Goldfinch, Auckland, NZ. Do-it-yourself flash meter wanted As a builder of practical kits plus being a keen underwater photographer too, may I offer a suggestion for a kit that I feel will appeal to many? This would be a flash meter using perhaps a solar cell for the sensor with a small meter to show F-stop readings. Flash meters are very expensive to buy for those who wish to just check their flash outputs. I struck this problem while wanting to check the output of my underwater strobes (flashes) before an overseas trip . I feel a meter would not only help me but other amateur underwater photographers plus any photographers who read SILICON CHIP. By the way, I love the magazine. A. I. Masszauer, Ipswich, Qld. Satellite dish project should be a priority Garry Cratt's excellent 3-part series on the basics of TVRO satellite systems was very timely in view of the recent Federal Government decision to give the go-ahead to pay TV. In the past, I have lamented at the lack of opportunity for TVRO experimenters vis-a-vis Aussat. Unfortunately, Garry Cratt's series is also heavily biased towards commercial systems. Since the introduction of pay TV is at least one year away, you should as a matter of urgency start some serious projects for the TVRO experimenters. At the very least, you should start experimenting with a low cost dish either circular or "squarish" - using simple materials. Already some prospective pay TV licensees are talking of $500-600 just for the dish. No doubt every Tom, Dick and Harriet will have a commercial dish on their roof within a few years, so a home-made dish which is different and eye-catching is just what is needed for the electronics enthusiast. S. Kamaldeen, Hobart, Tasmania. Cartoon brilliance in November issue I regularly enjoy the cartoons as featured in The Serviceman but have only just been moved to put toner to paper, as it were. The cartoon on page 40 of the November issue is very clever and deserving of a special credit to your cartoonist. Keep up the great work. Greig Sheridan, Ashfield, NSW. AM stereo - the problem with synchrodyne detection In response to D. Stringer's comments in Mailbag, October 1991 , regarding the AM Stereo Tuner, the decoding method used by Motorola is really the simplest way to do it. If synchrodyne detection is used, the resulting decoded in-phase and quadrature components must be further processed (in non-linear fashion) to retrieve L and R signals. For instance, the L+R signal (or envelope shape) could only be retrieved SILICON CHIP, PO Box 139, Collaroy Beach 2097. from the outputs of the synchrodyne detector by using a function generator of: L+R = ✓ (F+Q2 ), where I and Q are the in-phase and quadrature outputs of the synchrodyne detector. The L-R signal would need a function generator of L-R = (Q/I)✓ (I2+Q2 ) The complication arises due to the carrier phase shift. For mono broadcasts, the synchrodyne detector is OK - Q above is zero, so L+R = I (the synchrodyne detector in-phase output) and L-R = 0. In the ideal "quadrature" system, (L+R) should equal I and (L-R) should equal Q, so only linear adding and subtracting would be required after the synchrodyne detector to retrieve the L and R signals. However such a signal would not be compatible with envelope (diode) detectors. The modulator at the transmitter first of all produces a true quadrature modulated carrier for the L+R and L-R signals, however the resulting envelope is not L+R, which would be required for compatibility. This envelope is therefore stripped from the carrier and replaced with an L+R modulated envelope; the signal is then ready for transmission. Unfortunately, this need for compatibility makes it difficult to make a low distortion detector and in fact the system itself, due to its 'non-linear' nature, will inevitibly produce more distortion and crosstalk than a true quadrature system, even if a perfect detector could be made. Jim Woodhead, Paddington, Qld. Reader input wanted for spectrum analyser design As a result of numerous reader requests, I am in the process of designing a 10-band spectrum analyser project for readers to construct. The device is intended to complement 1octave graphic equalizers such as the one that was published in SILICON CHIP in an earlier issue. To assist in designing the analyser to meet readers expectations, I am quite happy to accept any reader's suggestions as to what features they would like to have on the unit. There is a choice of display formats available, notably a LED matrix, backlit LCD or vacuum fluorescent. The choice will also depend on how many readers express interest in the project, and what price range they expect the parts to cost. The preliminary prototype is already built but due to its modular design, can quite easily be modified if there appears to be a trend towards certain features. Any readers wishing to contribute any ideas on the project are most welcome to write to me at their earliest convenience. Stephen McBride, GPO Box 737, Townsville, Qld. Class A amplifiers not practical I would like to respond to the letters in August 1991 and November 1991 about the suggested Class A amplification project. I am an electronics technician and have for many years designed and constructed many audio amplifiers of very high quality and have had the privilege of reviewing some of the socalled best amplifiers in the world on very high resolution speakers (eg, Alan Moss electrostatic speakers). Some of these have been class A designs. Quite frankly I have to agree with the Editor on this one that such a system would be completely over the top. In my opinion, Class A is highly over-rated and the power supplies needed would have to be very large, not to mention that the power dissipated across the output devices would be in the order of 300 watts per voltage rail. If you used Motorola devices such as the MJ15003, MJ15004 which have a power rating of 250 watts, you would have to derate them to at least 130 watts and that's with hope you can keep the devices at 60° C or below. To get 50 watts we are going to need an output stage rating of at least 700 watts. That's about 12 output devices. At current retail prices, that's about $114 worth of output transistors and remembfr guys, at best, class A amplifiers have an efficiency of 25% . But this is just the beginning of some of the things you have to consider when designing such an animal. For example, the transformer would have to be rated at a minimum of 800VA. This is for just one power module by the way, not stereo. To give you an example of part of the cost involved, I have just designed and built a 900 watt power amplifier of very high quality. The transformer it uses is a 2kVA toroidal unit which cost almost $400.00 wholesale. And believe me, that is just the beginning of the cost involved in designing and building a beast such as this. The $2500 .00 quoted as an acceptable price to pay for amplifiers and speakers would be quickly eaten up by the cost of a stereo Class A amplifier. I'm sorry guys but I would be surprised if the Editor-In-Chief would go for such a project considering the cost and the technical headaches that would be encountered. Anthony Holton, Launceston, Tasmania. Black♦Star Video Monitor Tester 1410 e Checks MDA, CGA, • • e • Class A amplifier supported I am writing in to support R. L. 's request for a pure class A amplifier system. Although I cannot afford $2500, I think I should be able to start with one unit, then gradually build the rest when finance allowed. Would it be possible to make the above system using all FETs? If FETs have more advantages than bipolar transistors, why are they usually only used in the input and output stages? I cannot find any amplifier project using all FETs. Is there any reason for this? T. Tong, Sydney, NSW. Comment: Generally, it is not good practice to design amplifiers using FETs throughout. While FETs do have their advantages, their generally lower voltage gain and the fact that they are a voltage sensitive device makes the overall circuit design harder than if bipolar devices are used. SC • • • • e • EGA, Hercules, PGA, VGA, SVGA, 8514A, XGA and TV formats Microprocessor controlled Intelligent alpha-numeric display Analog RGB, TTL-IRGB, Secondary RGB, Horizontal/ Vertical/Composite syncs Colour Bars, Test Card, Crosshatch, Dots, Ramp, Focus, Horizontal Lines, Vertical Lines, Raster and Checkerboard Full control of output signals 15.625 to 48.5kHz Line and 49.9 to 87Hz Frame Frequencies Inverse Video Separate Analog and TTL Outputs 1V and 0. 7V Video Easy to use via 9- and 15-way 'D' and BNC Connectors $1155.00 ex tax $1328.00 inc tax Detailed brochures and specifications available. We are factory trained to advise on your requirements for general purpose Test & Measuring Instruments. Ask for our FREE 20 page 1992 catalogue <at>IB3Il.£1r JP1rW &6frJ]) 129 Queen Street, Beaconsfield, NSW 2014 P.O.Box 37 Beaconsfield NSW 2014 Tel: (02) 698 4776 Fax: (02) 699 9170 JA NUA RY 1992 7 The Story of Electrical Energy, Pt.17 When people think of Brazil they tend to think of huge rivers and rainforests but this country is also the greatest industrial nation and exporter of manufactured goods in the southern hemisphere. In recent years, Brazil has built a hydroelectric power station and high voltage DC link which is the largest in the world. By BRYAN MAHER Brazil, the largest country in South America, is exceeded in size only by the USSR, China, Canada and the USA. With over 130 million people, Brazil has half the population of the Latin continent. By any standards, it is a major industrial nation. Brazil has huge mineral resources, including iron ore reserves of 60 billion tonnes. Naturally, it has an extensive railway system, with 33,000 kilometres of track, of which 1400 kilometres is electrified. In 1945, Brazil's total electricity consumption was less than 1.6 gigawatts. Today, industrial growth has pushed consumption above 43GW with no sign of slackening. Of this, hydroelectric plants supply 40GW (93%). Projections forecast a 160GW demand by the year 2010 and meeting this demand could cost about $100 Itaipu's alternators are among the biggest in the world, as this photo of a 2060tonne rotor shows. It has 66 poles and rotates at more than 90 RPM to generate 715 megawatts. 8 SILICON CHIP billion over the next 20 years. The megalopolis of Brazil, indeed of all South America, is the Greater City of Sao Paulo. This massive urban area sprawls about 80 kilometres wide and is home to 11 million people. Situated on the Tropic of Capricorn, up on the southern escarpment 770 metres above sea level, it is 53 kilometres west of its port Santos and 320 kilometres southwest of Rio de Janeiro. The Amazon & hydro power The Amazon, the world's greatest river by far, is navigable for the full 3 700km east-west width ofBrazil. This enormous watercourse, more than 100 metres deep and 80 kilometres wide in parts, discharges water into the sea at the phenomenal rate of 160,000 cubic metres per second. The Amazon region has 47% of all drainage basin area in Brazil. But because of the low gradient of the river (10mm per kilometre or 0.001 %) and its slow speed (3-8km/h), the main Amazon stream has only 7% of Brazil's hydroelectric potential. Table 1 shows the total calculated hydroelectric potential of Brazil to be an enormous 210 gigawatts (equivalent to about 200 times that of all of Tasmania's hydro stations). But of the total, more electricity could be generated by the Southern Parana system than by the sum of all others including the Amazon. Fed by voluminous tributaries, the Parana forms the second largest water drainage in the South American continent. Flowing southward in the hinterland, the Parana near the town of Guaira is 4.2km wide. Beyond this point, at Salta del Guaira, the water drops over the escarpment in the mighty Guaira falls, one of the most breathtaking sights on the continent. ltaipu power station The obvious energy potential of this This artist's impression shows the great sweep of the Itaipu dam project. At left are the spillways which must handle almost the full flow of the river in flood times. To the right of the curved section is the power station which has 18 turboalternators giving a total output of 12.6 Gigawatts, more than the total grid capacity of New South Wales! mighty river system prompted an investigation of the hydroelectric potential in 1966 at an isolated spot on the Parana known as ltaipu. Plans called for the building of a colossal dam and power station. With a generation capacity of over 14GVA (12.6GW), this plant alone is larger than the sum of all power stations in New South Wales! However, it is 800km from the industrial suburbs of Sao Paulo, so long power lines were inevitable. To complicate matters further, the Parana River runs through other countries and forms the border with Paraguay. Cooperation between Brazil and Paraguay resulted in the ltaipu Treaty, signed on April 26th, 1973. This described the project to be built and acknowledged the joint ownership by both countries. Within 12 months, topography studies were complete, together with predictions of the power level and time schedule. The bi-national construction authority, now called Itaipu Binacional, contracted for the purchase and installation of machinery, materials and services. Preference was given to tenders from Brazil and Paraguay. So vast were the civil engineering works, that thirteen companies from both countries cooperated in their execution. The manufacture and installation of the giant turbines and generators was carried out by a consortium of six Brazilian, one Paraguayan and six European firms, including Brown Boveri/ ASEA (later ABB), Alsthom, Bordella, Voith and Siemens. The sequence of construction Consider the size of this massive undertaking. At the location of the proposed dam, the Parana was (and still is) a massive swift flowing river, more than half a kilometre wide, 30 to 90 metres deep, with the water racing past at two million tonnes per minute (33,000 tonnes per second). How on earth would you start building a dam to block it? There is no way a coffer dam could hold back that torrent even if you could get in there to build one! That was the first problem the builders faced. Their method solved the problems in an ingenious sequence of construction covering 13 years: (1) Between 1975 and 1978, they dug a 2km-long diversion channel, 150 metres wide and 90 metres deep. It was blocked upstream and downstream by temporary concrete arch dams and two rock plugs. In just under two years they dug out 2,600,000 cubic metres of sand and gravel, plus 30 million tonnes of hard rock. Simultaneously, outside the rock plugs, underwater excavation of 1.5 million tonnes of rock was performed using special equipment. In the dry space between these temporary coffer dams, the permanent concrete diversion structure was then built, incorporating 12 sluice openings. jA NUAR Y 1992 9 (4) When all walls were built up to full height, the spillway gates were closed. So great is the water flow in the Parana River that the reservoir filled to capacity in 12 days! Installation of the power house machinery then proceeded. The first turbogenerator became operational in 1983 and the 18th unit by 1988, provision being left for two future machines. Size comparison Drainage Basin Fraction of Brazil's Area Hydroelectric Potential Amazon 47% 15GW Sao Francisco 7% 38GW The entire dam wall measures 8km long, with the highest section being 196 metres above the riverbed at its centre. To gain a realistic appreciation of the height and length of this giant structure, let us compare it with something we all know well. If the Itaipu Dam were placed across Sydney Harbour, it would be a solid wall one and a half times the height of the Harbour Bridge and over 250 metres thick at its base. This immense barrier would extend all the way from Redfern on the south side to St Leonards on the north. Itaipu Dam raises the river 120 metres above it1? natural level, forming a lake 170km long on the upstream side and up to 16km in width. Its maximum surface area is more than 1400 square kilometres. Of this, 57% is in Brazilian territory and the rest is in Paraguay. From the total catchment area of a little less than a million square kilometres, the Parana River inflow to the dam varies with the seasons from about 33,000 tonnes per second to 72,000 tonnes per second at peak flood times. Of this, 14,000 tonnes per second flows through the 18 715-megawatt Francis water turbines in the power station. The spillway, rated at a maximum flow of 62,200 tonnes per second, must be capable of passing all excess water in flood times. Such is the bulk of water flowing down the Parana river that the power plant is essentially a run-of-the-river operation, with the reservoir water level r€Jmaining approximately constant. East Coast 7% 21GW 50Hz & 60Hz generation Parana 11% 121GW All Others 28% 15GW Total 100% 210GW This photo shows a 2000-tonne alternator stator being lowered into place during construction of the Itaipu project. Note its size in relation to the men below. (2) With the rock plugs removed, the concrete coffer dams at both ends of the diversion channel were simultaneously l>laslecl oul, allowing water to enter the diversion channel. For the next four years, the river flowed via the diversion channel and through the diversion structure sluices. The main river channel was then blocked upstream and downstre,a m by coffer dams. Construction of the main dam, power station and spillway then proceeded in the dry river bed. At the same time, the left and right wing dams were completed. (3) Filling of the reservoir occurred in 1982. To effect this, the steel sluice gates of the diversion structure were closed and plugged with concrete. The diversion structure was then enlarged until it became part of the main dam and power house. TABLE 1: HYDROELECTRIC POTENTIAL IN BRAZIL 10 SILICO N CHIP Because the Paraguayan electricity system works on 50Hz and the Brazilian on 60Hz, Itaipu generates power at both frequencies. Nine alternators with 66 poles and running at 90 RPM (actually 90.9091 RPM) produce the conductors are concentrically enclosed in (but insulated. from) continuous grounded pressure-tight metal outer pipes. The whole assembly of large diameter piping is filled with sulphur hexafluoride gas at high pressure. This SF 6 gas is extremely inert chemically, non-toxic, non-flammable and has very high dielectric strength. Each of these properties is essential for switchgear applications. So even at the extremely high voltages of 525kV at Itaipu, gas insulated busbars and switchgear result in a compact indoor installation instead of the huge outdoor switchyard which would otherwise be needed. As the circuit breaker contacts are completely encased in grounded metal, RFI generated during switch openings is suppressed. Therefore, microelectronics may be used for control circuits and can be mounted close to the high voltage equipment. This is just not possible with conventional high voltage switchgear. And being always immersed within dry unreactive gas , the conductors, insulators and contacts will not be corroded by the warm humid atmosphere expected around a hydro power station. 50Hz to HVDC conversion The size of the ltaipu project is so large that it is difficult to comprehend. Here we see a 525kV gas insulated conductor (looks just like a big pipe) and behind that is a 525kV lightning arrestor. In the background are some of the penstocks that feed the turbines. Each penstock has an inside diameter of 10.5 metres (more than 34 feet) 50Hz supply. The other nine alternators have 78 poles each and run at 92RPM (actually 92.30769 RPM) to produce the 60Hz supply. So no fancy frequency changing is required to produce both power frequencies. But the story becomes much more complicated with regard to distribution, as we shall see. Each machine develops its output at 18kV but the currents are enormous - more than 26,000 amps per phase. Enclosed hollow conductors carry the huge currents from each alternator to 18kV /525kV step-up transformers. These very heavy 18kV conductors are hollow for two reasons. Firstly, the currents are so enormous that skin effect is appreciable and thus solid conductors would give no benefit. Secondly, it allows the circulation of cooling fluids. The 60Hz units supply the Brazilian national system by transformation from 525kV to 765kV. Most of this AC power is transmitted by 3phase lines to Sao Paulo. The 50Hz machines send power to the Paraguayan state grid at 525kV and, by further transformation, at 220kV. Gas insulated switchgear The 525kV AC outputs from each transformer are carried by gas insulated busbars and switchgear. The live While the generating capacity at Itaipu is evenly split between 50Hz and 60Hz, not all the 50Hz power is required by Paraguay. The excess 50Hz power is sold to Brazil to supplement the supply to Sao Paulo. But, as we have seen, the Brazilian system runs at 60Hz. Therefore , the 50Hz power is converted to high voltage DC at Itaipu, transmitted over the 800km to Sao Paulo, then converted from DC to 60Hz 3-phase AC supply. To achieve this, they built the world's largest high voltage DC transmission system, between 1984 and 1987. Two DC power lines, each rated at 3.15 gigawatts , run in parallel over the route. Each line consists of two multi-bundled conductors rated at 2650A; one conductor at +600kV (with respect to earth) and the other at -600kV. This centre-earthed arrangement effectively gives a 1.2 million volt link while limiting the potential stresses at insulators and equipment to half this voltage. To convert the AC to DC, multiple JA N UARY 1992 11 light-triggered water-cooled silicon thyristors are used. These third generation GTO units are a far cry from earlier gear. Thyristor ratings This photo of the ltaipu project shows the turbine hall section of the dam. Notice the huge penstocks feeding each turbine. The turbine hall is about 1km long. The capability of a thyristor to handle large currents is governed mainly by its cathode area. Today, silicon wafers 100mm in diameter are commercially available. This makes possible the manufacture of thyristors with a cathode area about 13 times larger than the active area of the first HVDC thyristors used in the Gotland DC link in 1970, as described in the March 1991 article of this series. The thyristors used each carry about 3300 amps under normal conditions but under fault conditions they must safely carry up to 30,000A during the four or five cycles that elapse before the overcurrent circuit breakers can open. The very high fault current capability of these modern GTO thyristors allows optimisation of the accompanying transformer design. No longer need transformers possess high reactance in order to limit short circuit currents. A transformer with lower output impedance means less copper loss in the windings and a big saving in transformer cooling equipment. Third generation thyristors also have much improved voltage capability. Off-state voltage ratings are now as high as 7kV per unit. This is two or three times the value possible in earlier designs. ASEA now make thyristors which are capable of carrying the full current of all present and projected HVDC systems. Thus, no paralleling of thyristors is required. Light-triggered thyristors Looking more like a chemical plant than a power station, these are some of the gas insulated (sulphur hexafluoride) bus bars and switchgear inside the ltaipu project. Because it uses gas insulated switchgear throughout, there is no large high voltage switchyard; just miles and miles of big pipes! 12 SILICON CHIP However, even with voltage ratings of 5kV or 6kV per thyristor, hundreds of such units must be connected in series to withstand the full 600kV of the Itaipu line. They are clamped into water cooled heatsinks, with teflon hoses connecting them to an external source of distilled water. Naturally, all thyristors in the series stack must be turned on and off simultaneously, even though some thyristors will be elevated at plus or minus 600kV above earth. Therefore, all the thyristors are triggered optoelectronically with laser light pulses via optical fibre glass cables. This photo shows the Parana River in full flood, with the spillways handling more than 62,000 tonnes of water per second. At the same time, the total flow through the 18 turbines is 14,000 tonnes per second! In the centre of the silicon wafer is a second auxiliary thyristor. The infrared light signal first switches on the auxiliary thyristor which then electrically triggers the main power thyristor. For the entire ltaipu project, ASEA used 20,000 high power thyristors rated at 7kV off-state voltage and 4kA on-state current. So ltaipu stands as the world 's biggest power station, running the world's biggest and heaviest alternators and feeding the world's biggest high voltage DC link over the greatest distance. Truly, ltaipu is a mind boggling engineering project on a vast scale. sc Acknowledgements A view inside the Valve Hall at ltaipu, showing two of the 16 valve assemblies. Each valve assembly contains 384 thyristors in a full-wave bridge configuration; as needed for a 600kV DC line. ltaipu is the starting point for the biggest and longest high voltage DC link in the world (800km to Sao Paulo). Special thanks to Ms Maria Nicholl, the Embassy of Brazil, for photos, diagrams and data. Acknowledgements also to IEEE Spectrum, ABB/ASEA Journal and Action, Phillip Vaughn-Williams, Goverflo do Estado Sao Paulo, Dr Geoff Cochran, Dr Mike Gore, ltaipu Binacional. JANUARY 1992 13 ·RITRON POWER RITRON QUALITY OPTIONAL EXTRAS RITRON RITRON ADD PRICE TO BASE SYSTEM COST. 512K VGA CARD •••••••••••••••••••••• $50 lM VGA CARD ......................... $150 TO CHANGE A ~•• • • ~ ~.§ 7•; • • 2 • • • • • • •Y 80286-12 CPU 1 MEG RAM EXPANDABLE TO 4 MEG 16Mhz LANDMARK SPEED TEST 1.2M JAPANESE BRAND F.D.D 42M HARD DISK DRIVE 28ms ACCESS 101 EXTENDED "CLICK" KEYBOARD JAPANESE KEYBOARD SWITCHES MINI CASE & 200W POWER SUPPLY SUPA VGA COLOUR MONITOR (1024 x 768 res) SERIAL, PARALLEL, GAME PORT 3 YEAR "AUSTRALIAN" PARTS & LABOUR WARRANTY 256K VGA CARD. IBM• COMPATIBLE SPREADSHEET, WORDPROCESSOR & DATABASE SOFTWAREINCLUDED. ASSEMBLED & . . TAX INC. $1,199 TESTED IN AUSTRALIA -· ' $1,050 80286-16 CPU 1 MEG RAM EXPANDABLE TO 4 MEG 21Mhz LANDMARK SPEED TEST 1.2M JAPANESE BRAND F.D.D 42M HARD DISK DRIVE 28ms ACCESS 101 EXTENDED "CLICK" KEYBOARD JAPANESE KEYBOARD SWITCHES MINI CASE & 200W POWER SUPPLY SUPA VGA COLOliR MONITOR (1024 x 768 Res) 2 SERIAL, PARALLEL, GAME PORTS 3 YEAR "AUSTRALIAN" PARTS & LABOUR WARRANTY 256K VGA CARD. IBM• COMPATIBLE SPREADSHEET, WORDPROCESSOR & DATABASE SOFTWAREINCLUDED. ASSEMBLED & TESTED IN AUSTRALJA $1 ' 249 TAX INC. $1,090 TAX EX. ...................................,..,.,..............,,..,.......... ..,,.,.~,,,_.............,.,.,.,.,.....,,.,... TAX EX 40M HARD DRIVE TO A 85M HD add ........................ $175 126M HD add .......................... $350 200m HD add ......................... $750 EXTRA RAM l MEG add ........................... $75 2 MEG add ........................... $150 PLEASE NOTE SYSTEMS DO NOT COME WITH DOS. 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'SHAREWARE SOFTWARE ' TAX INC. WITH 200MEGORIVE $2,995 TAXINC. $2,450 TAX EX. ASSEMBLED & TESTED IN AUSTRALIA. $2,195 ~:; TAX INC. $1,875 TAX EX WITH 200 M.EG DRIVE $2,595 TAXINC. $2,295 TAX EX. TAXEX. RITRON EXECUTIVE c48s-1s.1 ) 80486-33 CPU 128K ON BOAR D CACHE. 1 MEG OF RAM 157Mhz LANDMARK SPEED TEST 43 MEG HARD DISK 1.2M JAPANESE BRAND F.D.D 101 EXTENDED "CLICK" KEYBOARD SERIAL, PARALLEL, GAMES PORTS 512K VGA CARD. IBM• COMPATIBLE VGA COLOUR MONITOR (1024 x 768 Resolution) MINI CASE & 200W POWER SUPPLY 3 YEAR "AUSTRALIAN" PARTS & LABOUR WARRANTY SPREADSHEET, WORDPROCESSOR & DATABASE SOFTWARE. ASSEMBLED & TESTED IN AUSTRALIA. $2 095 80386-40 CPU 64K CACHE ON BOARD MEMORY 1 MEG RAM EXP TO 16 MEG 65 Mhz LANDMARK SPEED TEST 126 MEG HARD DISK 12ms ACCESS TIME 1.2M JAPANESE BRAND F.D.D 101 EXTENDED "CLICK" KEYBOARD SERIAL. PARALLEL, GAMES PORTS 512K VGA CARD SUPA VGA COLOUR MONITOR (1024 x 768 Resolution) MINI CASE & 200W POWER SUPPLY 3 YEAR "AUSTRALIAN" PARTS & LABOUR WARRANTY SPEADSHEET, WORDPROCESSOR & DATABASE SOFTWARE INCLUDED. "SHAREWARE SOFTWARE •$2,495 $2,095 WITH 200 MEG DRIVE TAXINC. TAXEX. ROD IRVING ELECTRONICS Est. 1977. MAIL ORDER HOTLINE: 008 33 57 57. (ORDERS ONLY) ENQUIRES : (03) 543 7877 HEAD OFFICE: 56 RENVER RD, CLAYTON. PH: (03) 543 2166. FAX (03) 543 2648 CITY 48 A'BECKETT ST. MELBOURNE. PH. 663 6351 / 6391640. FAX: 639 1641. OAKLEIGH: 240C HUNTINGDALE RO, OAKLEIGH. PH: (03) 562 8939 NORTHCOTE 425 HIGH ST. NORTHCOTE, PH. 489 8866. FAX: 489 8131. SYDNEY:74 PARRAMATTA RD, STANMORE. PH: (02) 519 3134. FAX: (02) 519 3868 MELBOURNE DEALER: BLUESTAR COMPUTERS: 271 MAROONDAH HWY, RINGWOOD, 3134, PHONE: (03) 870 1800 FAX: (03) 879 3927 $3,095 $2,595 TAX INC TAX EX 80486-33 CPU 128K ON BOARD CACHE. 4 MEG OF RAM 157Mhz LANDMARK SPEED TEST 200 MEG HARD DISK 12ms ACCESS TIME 1.2M JAPANESE BRAND F.D.D 3.5" 1.44M JAPANESE BRAND F.D.D 101 EXTENDED "CLICK" KEYBOARD SERIAL, PARALLEL, GAMES PORTS 1 MEG VGA CARD. IBM• COMPATIBLE VGA COLOl;IR MONITOR (1024 x 768 Resolution) TOWER CASE & 220W POWER SUPPLY 3 YEAR "AUSTRALIAN" PARTS & LABOUR WARRANTY SPEADSHEET, WORDPRCESSOR & DATABASE SOFTWARE. ASSEMBLED & TESTED INAUSTRAUA. IDEAL CAO MACHINE! TAX INC. II -=-~· . --~ FREIGHT CHARGE BASED ON 35KG COMPUTER SYSTEM Melb-Metro.$12.00 Adelaide ..... $17.00 Bribane...... $17.00 Canberra .... $18.00 Darwin........ $40.00 Perth........... $31.00 Tasmania .... $53.00 l~- $ Vic country.... $19.00 NSW country.$39.00 S.A country... $39.00 OLD country.$55.00 W.A country.. $74.00 lnaurance:$1 / $100 Value. • ·..,,; 9 3 '7 5 $3 , 295 TAXEX. All sales tax exempt orders to : RITRONICS WHOLESALE 56 Renver Rd, Clayton, Victoria. Ph: (03) 543 2166 Fax: (03) 543 2648 MAIL ORDER & CORRESPONDENCE P.O BOX 620, CLAYTON, VICTORIA. 3168. Error• & omml•eona excepted. Prtcn & apecltlc1tlon1 11Ubjaet lo change. "IBM, PC, XT, AT, are regl•leted trademark ■ of lnlemadonal BualneH Machlnee. VERBATIM DATALIFE 1·9 boxes 10+ ISKS 1-9+ 5 1/4" 5 1/4" 31/2" 31/2" 3 1/2"DD $19.95 3 1/2"HD $45.95 5 1/4"OD $14.95 5 1/4"HD $23.95 TY 10+ 50+ 100+ 500+ DS/DD $4.30 $4.20 $4.10 $3.75 $3.50 DS/HD $8.50 $8.25 $8.10 $6.95 $6.50 DS/DD $7.90 $7.70 $7.50 $7.00 $6.00 DS/HD $15.95 $15.75 $15.50 $12.00 $11.00 1-9 boxes $18.95 $42.95 $12.95 $22.95 31/2"DD $28.50 3 1/2"HD $53.50 5 1/4"OD $22.95 5 1/4"HD $27.95 10+ $27.95 $52.50 $21.95 $26.95 1-9 boxes 10+ 3 1/2"DD $23.95 3 1/2"HD $39.95 5 1/4"OD $12.95 5 1/4"HD $19.95 $22.95 $37.95 $11.95 $18.95 HARD DRIVES •=1-1~1w;<at>;1•1•1<at>t1i•1;ra • 42 MEG HARD DISK FOR XT 8ms ACCESS WITH IDE/FDD CONTROLLER FAST STEPPER .......... $549 18 ms ACCESS WITH IDE/FDD.,........,,.,,.,........., Y AR CONTROLLER VOICE COIL.. .. 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SPECS: Keyboards: Int&rnaI 83-key keyboard Microprocessor: CPU 80386SX-20 10 function keys Memory: Fitted with 4Mb I/O Ports: External 15 i:,ln VGA BIOS: 128KB ROM Pheonix BIOS analogmonitor port, Centronics 25-pin Storage Devices: One 1.44MB 3.5" parallel port, Extarnal 5.25" floppy floppy disk drive connector One 60MB 2.5" Hard Drive Weight: 3 Kg includin~ battery Displa y: VGA compatible display 640 x 480 pixal resolution 32 grey scales Backlit Paper White LCD extax • Intel 80486 Microprocessor • IBM, XT and AT • Direct support for the Weitek 167 coprocessor • Built~n cache controller: Optional 32-KB, 64-KB, 128-KB or 256KB cache memory • 128Kcache fitted. • Supports interleaved cache RAM for high speed CPU as well as 80486 burst mode • • Flexible DRAM 1-32MB • Sophisticsted DRAM controller • AMI BIOS with built~n SETUP program • Support shadow RAM • Synchronous AT bus clock with programmable clock • Support fast A20 Gate & fast CPU reset to boost performance of software utilizing 80486 protected mode, such as OS/2, UNIX.. etc. ' • Eight expansion slots. Six 16 bit, Two 8-bit $3495 X18131 .......................................................... $1,795 31 /2" DRIVE KIT. Y.E DATA 3.5" 1.44n20/360 DRIV l;O~ • 51 /4" Mounting bracket • Power supply adapter • Cable adapter $115 d ~ _ -~ - , • Floppy disk controller card which co~t rols 1.44/7~/360 drives E . th h' he'<>.j • Complete instructions to install a 3.5 I n your existing computer. nIoy e 19 r density & easy handling of 3.5'' floppy diskettes I C11915 ....... ............ $295 $2950 _ MATH CO-PROCESSOR SPECIALS 80287XL... replaces 80287-6 80287-8 80287-10 ..............$295 . 80387DX-33.................... . ..................................... $595 80387SX-1 6................... • .....................................$450 80387SX-20................... .. .................................... $495 LOOK! NEW CARDS 4 PORT SERIAL CARD "MegaRAM" Memory board This new generation memory enhanced board offers O wail state high speed operation. It can take up to 6M8ytes of 4 x 256K or 1 x 1 M DRAM chip. Up to 7 cards can be used together (42MB EMS). It is 100% EMS 3.2 & 4.0 compatible, and best of au it can be used in an XT, AT or 386 because it is 8 bit, 16 bit configerable. So get yourself a Mega for the price of a Mini. X18051 ........, .................................................... .......... .......... ................ $299. 00 ROD IRVING ELECTRONICS Pty. Ltd. (Software Output cables included.) The PE-514A has 4 aerial ports for asynchronous communication. These ports can be used to connect your PC with a aerial printer, MODEM. aerial mouse or other aerial devices which uae an RS232C interface. The interface ia a DTE type with a male DB25P for 4 aerial port output it supports DOS & XENIX. ACN.005 428 437 HEAD OFFICE: 56 RENYER RD, CLAYTON. PH: (03) 543 2166. FAX (03) 543 2648 CITY 48 A'BECKETT ST. MELBOURNE. PH. 663 6351 /6391640. FAX: 6391641 . OAKLEIGH 240C HUNTING DALE RD OAKLEIGH PH: 562 8939 NORTHCOTE 425 HIGH ST. NORTHCOTE, PH. 489 8866. FAX: 489 8131 . SYDNEY:74 PARRAMATTA RD, STANMORE. PH: (02) 519 3134. FAX: (02) 519 3868 BLUESTAR COMPUTERS: 271 MAROONDAH HWY. RINGWOOD. PH: (03) 870 1800 Postage rates $1 • $9.99 ...... $3.00 $10 -$24.99 .. $3.50 $25 • $49.99 ..$4.50 $50 • $99.99 .. $6.00 $100 • $199... $7.00 The N pootago ram• a,o bulc poa tago only up to !~~ky I toms ~·::g~lgh, wlU be $200 - $ 500••. FREE ch arged at different $500 PLUS .. FREE X18155 .........$199 .' ••-:..:J~t>~., TOLL FREE MAIL ORDER HOTLINE: 008 33 5757 Build this low-noise 4-channel guitar mixer Fancy building a guitar mixer but don't like the units that are currently available? Well, why not take a look at this 4-channel mixer? It has separate bass, midrange & treble controls and has very low noise and distortion. By DARREN YATES These days, most musical instruments have higher quality audio outputs than the average cassette deck. This particularly applies to keyboards that use digital voice synthesis but electric guitars have picked up their game as well and now provide high quality outputs. An audio mixer, therefore, must meet certain minimum standards if it is going to faithfully reproduce the music and not add unwanted coloration of its own. Although there are a couple of mixer kits still currently available, these 16 STI,ICO N CHIP were designed many years ago and don't take advantage of the very lownoise, low-cost op amps now available. This new design features National Semiconductor's LM833 dual low-noise op amp to achieve excellent performance, plus board-mounted potentiometers to ensure easy con. struction. In addition to the tone control facilities already mentioned, the unit features separate input level controls plus an output level control. It is ideal for use with most musical instruments, from keyboards to guitars to tape decks. In fact, you can feed it with just about any audio signal - it's not just limited to guitar outputs. The accompanying specifications shows the performance of the new 4Channel Mixer. Two specifications are quoted for the signal noise ratio: (1) with all inputs closed, and (2) with all inputs open. In practice, since the four input level controls will neither be all fully open or fully closed but at some intermediate setting, the signal to noise ratio will be somewhere around 90dB. This is a very good figure. Block diagram To see how the 4-channel mixer works, refer now to the block diagram of Fig.1 . Each input has its own preamplifier stage which provides a fixed 26dB of gain for the input signal. The four outputs are then resistively mixed together and connected to the mixer preamplifier. This stage has 12dB of gain to overcome some of the inherent loss in the resistive mixer. Fig.2 shows how this loss comes about. Each output is effectively connected to a 47kQ resistor and the opposite ends of these resistors are all joined together. Thus, as Fig.2 shows, each output is effectively connected to a potential divider consisting of one 47kQ resistor (the one connected to its output) and three other 47kQ resistors in parallel (these correspond to the other input stages). The audio is taken from the tap and fed to the mixer preamplifier stage. Because the bottom three resistors are in parallel, the signal level applied to the mixer preamplifier is only a quarter of that at the output of the input preamplifier stage. This loss is overcome by giving the mixer preamplifier a gain of 12dB (ie, we amplify the mixed signal by four). The output of the mixer preamplifier is thus approximately equal to the sum of the four input preamplifier outputs. This mixed signal is then passed through a 3-band graphic equaliser which provides separate bass, midrange and treble controls. These allow you to tailor the sound to suit your own tastes, whether you like beefy bass or squeaky-clean treble. Each frequency band is individually tailored by a single control which operates around a common inverting op amp configuration. The bass control provides about ±14dB of gain at lOOHz, while the midrange and treble controls provide ±1 ldB of gain at lkHz and lOkHz respectively. These figures mean that the tone controls should provide more than adequate boost or cut in most situations. PREAMP 1 PREAMP 2 BASS MIXER PREAMP INVERTING BUFFER TREBLE PREAMP 4 .,. INVERTING STAGE Fig.1: block diagram of the 4-Channel Mixer. Each input is first preamplified, then resistively mixed and fed to a mixer preamplifier stage.-The output from this stage then drives the tone control section which in turn drives an output buffer stage. MIXER PREAMP gain of-1 and, in addition to buffering the tone control output, ensures that the output signal is in phase with the signal inputs. Circuit details 47k 47k .,. Fig.2: each input preamplifier effectively drives a potential divider consisting of a 47kQ resistor & three other 47kQ resistors in parallel. Finally, the signal output from the tone control stage is fed to an inverting buffer. This stage operates with a SPECIFICATIONS Signal to noise ratio: {at 50mV input<at> 1kHz) All inputs closed : -96dB All inputs open: -82dB Distortion: (at 1kHz and 100mV input)< 0.0075% Graphic equaliser: Bass: ±14dB<at> 100Hz (±1dB interaction with midrange); ±19dB<at> 50Hz (±0.3dB interaction with midrange) Midrange: ±11dB<at> 1kHz (±0.8dB interaction with bass, ±2dB interaction with treble) Treble: ±11dB<at> 10kHz (±2dB interaction with midrange) Maximum output: approx. 23V p-p before clipping Frequency response: 18Hz-35kHz {±3dB) Fig.3 shows the complete circuit details for the 4-Channel Mixer. It uses four LM833 dual low-noise op amps which can be directly related to the various stages shown in Fig.2. Because the four input stages are identical, we'll save some time by describing the channel 1 input stage only. The input signal is coupled into the circuit via a 2.2µF electrolytic capacitor, while a lOkQ resistor to ground sets the input impedance. A lkQ stopper resistor is also included in the input stage to protect the circuit against RF radiation. What happens here is that long audio input cables can act as radio antennas. When combined with the residual circuit capacitance, this can produce a tuned circuit which couples radio signals straight into the sensitive first junction of the op amp. This junction can act as a detector and thus detected radio signals will be amplified and fed through the mixer! By adding the lkQ stopper resistor, we greatly reduce the sensitivity of the first stage to RF signals while JANUARY 1992 17 2.2 INPUT 25VW 1 er-=t1-·-.-"",Ntr-"1 .022 +15V 10k 10k 10k 6.8k TREBLE VR7 100k LIN 6.Bk 10k .0015 39pF VO}~:E~~~~ 10k LOG -15V +15VREGO ovo INPUT 4 2.2 25VW 1001 6x0.1l +15V • -15V 25VWI 100 + 25VW! o--:a1--·......-Wilr--"I --!- 3,0.1I -15V REGO 10k .,. 1.2k FOUR CHANNEL MIXER Fig.3: the main circuit can be directly related to the block diagram shown in Fig.1. ICta, ICtb, IC2a & IC2b all function with a gain of about 19. Their outputs are mixed via the level control pots and the resulting signal amplified by IC3a and fed to tone control stage IC3b. Finally, the output from IC3b is fed to unity gain buffer stage IC4a via volume control potentiometer VR8. still allowing through the wanted audio signals. Following the stopper resistor, the signal is fed into the non-inverting input (pin 3) of ICla. This stage is configured as a non-inverting amplifier with a gain ofabout 19.3, as set by the 22kQ and 1.2kQ resistors (ie, Gain = 1 + 22kQ/1.2kQ). The 100pF feed- 18 SILICON CHIP back capacitor across the 22kQ resistor set the upper 3dB frequency response to about 72kHz, while the 1.2kQ resistor and 22µF capacitor set the lower 3dB frequency response to about 6Hz, thus ensuring good wideband audio response. The output from IC1a appears at pin 1 and is coupled via a 2.2µF elec- trolytic capacitor to a 10kQ pot (VR1), which acts as the input level control for that channel. Similarly, VR2 , VR3 & VR4 act as the input level controls for the other three channels. Not.e that, because these level controls follow the input preamplifiers rather than precede them, we can reduce the amount of noise present in the final output in the event that a particular channel is not required. By simply rotating the unwanted level control(s) to minimum, we remove the associated input preamplifier .022 ~.t-2_--1:~:k~OS_T_..__W,,H,__-Wfr---, BASS SECTION noise from the rest of the circuit. Following the level controls, the signals are mixed together via four 47kQ resistors, as described previously. The signal is then fed to noninverting op amp stage IC3a which operates with a gain of about 4.3 to make up for mixing losses. Graphic equaliser Next, the signal is fed into the 3band graphic equaliser section. This is based on IC3b and potentiometers VR5, VR6 & VR7. These pots, plus their associated resistors and capacitors, form an AC negative feedback loop around the op amp. To understand how the tone controls work, let's consider the bass boost/cut circuitry based on VR5. Fig.4 shows the basic arrangement. In addition to the pot, this circuit consists of two lOkQ resistors (one on each side of the pot) and a .022µF capacitor across the pot. The capacitor and the 1ookn pot set the frequency response, while the two lOkQ resistors limit the amount of boost and cut. Because VR5 forms part of the feedback loop and part of the input network, we can change the low frequency gain ofIC3b by simply varying the pot. , For example, if the pot is adjusted so that the feedback loop has minimum resistance, the result is an amplifier with a gain of approximately 10kQ/110kn or .09 (ie, the low-frequency output is cut). Conversely, if the pot is fully wound the other way, then we have maximum resistance in the feedback loop and minimum resistance in the input stage. The gain is now 110kn/10kn or 11, which results in a boost in the low frequency output. The midrange section works in a similar manner except that there is now a .0lµF capacitor in series with the inverting input. This, along with the .0022µF capacitor across VR6, Fig.4:: basic arrangement for the tone control section, showing the bass boost/cut circuitry only. The .022µF capacitor & the pot (VR5) set the frequency response, while VR5 also allows the low frequency gain of the op amp to be varied. The midrange & high ranges work in similar fashion. gives a bandpass filter arrangement. The .0lµF capacitor sets the lower frequency limit, while the .0022µF capacitor sets the upper frequency limit. Again, the pot is connected so that it forms part of the both the input and feedback circuits, which allows the gain to be varied as before. The treble control (VR7) works in similar fashion on the high audio frequency range , as set by the .0015µF capacitor in series with the inverting input of IC3b. Finally, a 39pF capacitor is included in parallel with the feedback network across IC3b. This reduces the overall response ofIC3b to very high frequencies to ensure stability. The output from the graphic equaliser appears at pin 1 ofIC3b and is fed to VR8, which forms the master volume control. IC4a is an inverting amplifier with unity gain. It buffers the output from the volume control and, as a bonus, provides a 180° phase shift to bring the signal back into phase with the input signals. This phase-corrected signal appears at pin 1 of IC4a and is AC-coupled to the output via a 2.ZµF capacitor. PARTS LIST 1 PC board, code SC01102921, 249 x 113mm 3 100kn linear potentiometers 5 10kn log potentiometers 13 PC stakes 1 ±15VDC power supply board, DSE Cat. K-3435 or Jaycar Cat. KC-5038 (see text) Semiconductors 4 LM833 dual op amps (IC1-IC4) Capacitors 2 100µF 25VW electrolytics 4 22µF 16VW electrolytics 11 2.2µF 25VW electrolytics 9 0.1 µF 63VW 5mm-pitch polyester 1 .022µF 63VW 5mm-pitch polyester 1 .01 µF 63VW 5mm-pitch polyester 1 .0022µF 63VW 5mm-pitch polyester 1 .0015uF 63VW 5mm-pitch ceramic 5 100pF 5mm-pitch ceramic 1 39pF 5mm-pitch ceramic Resistors (0.25W, 5%) 5 47kn 2 6.8kQ 1 33kQ 4 1.2kn 8 22kn 41kQ 11 10kn 1 4700 Miscellaneous 5 audio sockets to suit, 1 piece of blank PC board measuring 149 x 113mm (see text), solder, screws, nuts, washers, hookup wire, shielded cable, tinned copper wire. Power supply Because of the mixer's very low noise characteristics, we elected to keep the power supply off the main board. This reduces the amount of mains hum and interference picked up by the circuit, since we no longer have the unregulated supply on the board. The circuit is designed to run off ±15VDC but will work with slightly reduced specifications down to ±12VDC. If you include this circuit with another piece of audio gear, you should be able to find ±15VDC somewhere. If not, you can use the universal power supply board published in the August 1988 issue of SILICON CHIP. You can buy this kit from Jaycar Electron- ics (Cat KC-5038) or from Dick Smith Electronics (Cat K-3435). Construction All components for the 4-Channel Mixer are mounted on a single PC board measuring 249 x 113mm and coded SC0l 102921. Before you start construction, check the board carefully for defects by comparing it against the published pattern. If you find any, use a small dash of solder or a small artwork knife as appropriate to repair the problem. Once the board is OK, check that the PC-mounting potentiometers (VR1-VR8) fit snugly into the holes on JANUARY 1992 19 INPUT 1 GND _ INPUT 2 _.fil!!! _ INPUT 3 _fil!!l _ INPUT 4 _fil![I _ -------------------"" F ;?!;?!~ ., ) . - -~ -:.-:.-:.,-_-_ ..._-_-ii . ,. ...L..J, _ _ 0 22uf • GAIN 2 VR2 GAIN3 VR3 • GAIN 4 VR4 BASS VR5 Fig.5: follow this parts layout diagram carefully when wiring up the 4-Channel Mixer. For best results, the unit should be equipped with a groundplane by mounting it in a metal case or on a piece of blank PC board (see text). the board. If they don't, enlarge the holes with a slightly larger drill bit until they do fit. While you're still at your rough workbench, you can hammer in the PC stakes. These go into the 13 external wiring points at the back of the board - see Fig.5. Solder them in, then install the 13 wire links. If necessary, you can straighten the link wire by clamping one end in a vice and then stretching it slightly by pulling on the other end with a pair or pliers. Next, solder in the resistors. The table below shows the resistor colour codes. If you cannot make out the colour bands clearly, use your multi- meter to check the resistor values. The 5mm fixed-pitched capacitors can now be installed, followed by the electrolytics. Make sure that you install the electrolytics with the correct polarity, as shown on Fig.5. The same goes for the four ICs which can also be installed at this stage. You can identify pin 1 of an IC by an adjacent dot or notch in the plastic body at one end of the device. All four ICs face in the same direction. Finally, install the eight potentiometers along the front of the board. Take care to ensure that you don't get any of the pots mixed up. Logarithmic pots have the letter "A" stamped into the metal casing, while linear pots are MID VR6 TREBLE VR7 VOLUME VRB stamped with the letter "B". Because of the circuit's sensitivity, we suggest that you earth the potentiometer casings. This can be done by soldering a single length of tinned copper wire to the back of the pots and then soldering one end to the earth pattern underneath the board (see photo). A groundplane will greatly reduce the circuit's sensitivity to hum. For CAPACITOR CODES Value IEC Code EIA Code 0.1µF 100pF 39pF 100n n10 39p 104 101 39 RESISTOR COLOUR CODES 0 0 0 0 0 0 0 0 0 20 No. Value 4-Band Code (5%) 5-Band Code (1 %) 5 1 8 8 2 4 4 1 47kQ 33kQ 22kQ 10kQ 6.8kQ 1.2kQ 1kQ 470Q yellow violet orange gold orange orange orange gold red red orange gold brown black orange gold blue grey red gold brown red red gold brown black red gold yellow violet brown gold yellow violet black red brown orange orange black red brown red red black red brown brown black black red brown blue grey black brown brown brown red black brown brown brown black black brown brown yellow violet black black brown SILICON CHIP this reason, we suggest that you install the board in a metal case. Alternatively, you can fashion a suitable groundplane from a piece of blank PC board. Don't forget to connect the circuit earth to the groundplane (or to the metal case). Testing Before you hook up your power supply, check the board assembly carefully to ensure that all components are at their correct locations and are correctly oriented. When you're sure that everything is OK, connect your power supply to the board, with your multimeter (switched to amps) in series with the positive supply rail. Now switch on and check the current flow. If it is greater than about 30mA, switch off immediately and check the board carefully for solder splashes, shorts between tracks and other possible wiring errors. Assuming everything checks out so far, use your multimeter to check the supply voltages to the ICs. Pin 8 of each IC should be at+ 15V while pin 4 of each IC should be at -15V. To test that each audio channel is working, simply feed in an audio signal of about 100mV or so (a tape deck RCA output is fine) and connect the output from the mixer to your hifi gear or to a bench amplifier. If you now wind up the level control for the relevant channel, along with the master volume control, you should hear the audio at the output. The bass, midrange and treble controls should also be checked for correct operation. To do this, set the tone controls on your amplifier to the flat position (or switch them out of circuit), then check that the mixer tone controls have the desired effect on the low, mid and high frequencies as appropriate. All that remains now is to mount the mixer board in with your existing audio gear or mount it in a case of its own. Note that, for optimum performance, you should use shielded audio cable for both the input and output connections. Finally, remember to turn the level controls for any unused channels down to minimum when you are using the mixer. This will eliminate noise from the preamplifier stages in the unused channels and give the best signal-to-noise ratio for your music or recordings. SC l----0 0 __..; ru (J\ __..; C) __..; __..; 0 C) u (/) ..... Cl) Cl) :.s cc .....00 ~ 0 > 0 > a--•---D9 lQ. JANUARY 1992 21 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. - - - - - - T W O ENGINE LENGTH-- ----- □ I I TRACK TRAIN DIRECTION I Cl r SIGNAL PHOTO INTERRUPTER SY-508 IRL1 12V .,.. +12V -:- ~ 1son +12V 9x1N914 01 16 15 ST 180k 10 4 +12V RESET S1 FROM PIN 4 OF IC2b OF FINAL CONTROL SIGNAL UNIT IC1 4017 I1 . -+-----. 12 4 +12V 7 CLOCK INPUT ONE CONTROL SIGNAL UN,IT Signalling for model trains This circuit is a single-track closedloop model train signalling system. Each control signal unit can be powered directly from the track if using a command control system or any other system which provides a constant track voltage. Alternatively, it may be powered from a 12V external DC supply. The signalling sequence is as follows: upper red with lower red, upper green with lower red; upper green with lower orange and upper green with lower green. This sequence can 22 SILICON CHIP be arranged to include an upper orange as well, or just a single red, orange and green as used on side tracks, by using more or less outputs of the 4017 (ICl). Reset switches can be located alongside the main train controls. One use for-the reset switches can be to allow trains to enter or exit the loop via points. One 40106 Schmitt trigger IC is used per six reset switches. Each control signal can be reset to any signal in its sequence, by repeated pressing of the reset switch, without affecting following units. When a control signal has reached the end of its sequence (upper green with lower green), it blocks clock pulses to itself and following units. Different length sequences can be mixed as long as they are the same length. For example, if a 5-step sequence followed the above 4-step sequence, then you add a fifth step to the above sequence that duplicates the fourth step (ie, upper green with lower green) , so that it appears as a 4step sequence. This is done as follows: (1) disconnect pin 12 of ICZd from pin 10 of ICl and connect it to pin 1 (output 5 of IC1); (2) disconnect pin 9 ofIC3c from pin 7 ofICl and connect it to pin 10 of ICl; and (3) connect a duplicate of the drive circuit connected to pin 7 to pin 10 ofICl. No control signal unit can be clocked (by the units ahead of it) from the start of its sequence until the control unit ahead of it has been reset by its photo-interrupter. This allows two trains to be in consecutive sections. If, at power on, all of the signal LEDs for any control signal are off, then ICl has come on with a higher output than normally occurs in the sequence. The solution is to either repeatedly press the reset switch or incorporate a power-on reset circuit at pin 15. Brian Boogs, St Andrews, NSW ($40) Automatic night light timing circuit ► How often have you fallen asleep in bed while reading and left the light on? This circuit will turn a reading light off after one hour and;gives a warning flash about six seconds before shut-down, thus giving you time to reset the circuit if necessary. The low voltage supply for the circuit is derived via transformer Tl, bridge rectifier D1-D4 and a 7812 3-terminal regulator. When power is applied, binary counter IC3 is reset via the lOµF capacitor on pin 11 and is clocked by 555 timer IC4. NAND gates ICla-ld and ICZa-Zc then decode IC3's Q output and in turn drive transistor Ql. ICZa controls the warning flash, while IClc controls the final shut-off. These gates cannot change state until QlO, Q12 & Q14 all go high after about 1 hour. When they do, pin 9 ofICZa goes low and pin 11 ofICld switches high. Ql thus switches off and turns offTriac driver IC5 and Triac 1 for the next two clock cycles. For the next six clock cycles, either QZ, Q3 or both are high and so the light turns back on again. Q4 then goes high on the next clock cycle, pin 10 of IClc switches low, pin 11 of ICld switches high again and the light turns off. At the same time, the low output from IClc resets the 555 timer and so IC3 stops. Pushbutton switch S1 allows IC3 to be reset at any time, while S2 effectively functions as an OFF switch. It does this by switching out the lOµF timing capacitor on ICl, thus greatly increasing the clock speed and effectively reducing the timing period to zero. Arthur Hand, Saratoga, NSW. ($35) ... 0 a: ........_..,,,__~-+--11---ll· ~ ~ C C ACS Radio Pty Ltd is the only company that manufactures and sells every PC board & front panel published in SILICON CHIP, ETI & EA. RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 587 3491. JANUARY 1992 23 AL TRONICS 24 HOUR EXPRESS DELIVERY 'Our customers are often amazed at the speed and efficiency of our Jetservice Courier delivery. Phone your order Toll Free 008 999 007 and presto we can deliver your order next working day (country areas 24-48 hours later). Our famous 14 day satisfaction money back guarantee protects your hard earned $$$'s should ever a purchase be unsuitable for your needs. I invite you to try Australia's best electronics phone order service soon.' · Regards, Jack O'Donnell For Homea and Smell ComnMrclal PremlMa Keyless 4 Sector Alarm Control Panel This is a 3 zone alarm control panel designed for the protection of homes and small commercial premises. It employs the latest advanced electronic circuitry offering the highest degree of quality and reliability . It will accept either active or passive normally open or normally closed sensors making it both a versatile and effective protection system . 12V battery charger inbuilt. See Altronics '91 catalogue for full details . This 4 zone panel has been suitably designed for the protection of both commercial and residentail properties . It employs the latest electronic circuitry and the most up-Iodate security technology. It has 4 independent individually lsoltable protection circuits accepting both normally open or normally closed sensors. The panel is easily armed and disarmed via the integral inbuilt keypad. 12V battery c harger , inbuilt. See Altronics '91 catalogue for full details. ' Economy Alarm Panel s $249.oo s 5490 $129'.oo 5485 Flush/SuHace Mount Alarm Control Panel Economical Alarm System Kit The kit comes complete with the following components: • One Alarm Panel • One Passive lnfrared Detector (P.1.R.) • One AC Power Pack • One 8 Ohm Horn Speaker • Three pairs of Magnetic Reed Switches • One 12V/ 1.2AH Rechargeable Back Up Battery. Feature•: • 5 Protection Circuit Loops • Independent Connections for N.C . and N.O . Sensor Switches • Arm - Disarm ~Y ~~W/-~t:t~~~s~eK,;bt~ad Control • Warble Tone Steady Tone Siren Driver • Adjustable Timers for Entry Delay and Siren Duration • " Latch" and " Timing " Output Relays • Remote and Local Alarm Status Indicatio n • See Allronics '91 catalogue for full details. s 5470 • With atyllah compact good looka thla alarm blenda amoolhly Into any reatdenllal or ofllca decor. This compact 3 sector alarm panel has been designed to either surface mount or flush mount into a standard 3 gang electrical wall box. In order to provide the maximum amount of security and operation convenience the panel is operated via a 4 digit access code rather than a key. For ease of installation and service, the panel is provided with a plug in wiring harness. See Altronics '91 catalogue for full details. s 5490 $119.oo Optional Accessories: • M 8020 Charger $12.50 • S 5085 Battery Backup $29.95 (see Below) $349.oo ~~ '::"~~~-''f"' ~ ~ c"/j_ ~ •· Alarm Stickers Ext ra large for home . 200x75mm. s 5400 $1.ssea For your car (fixes to inside of window). 70x25mm. s 5410 • A ready to use system, no installation • Fully automatic operation , very user friendly • Large coverage, over 100 square metres • Portable or wall mounted • Long life 9V batter')' operation • Battery low ~~;;~~i~e• ;i~~~~~~!~~~~ri;t and home, shop, caravan or when travelling . Be quick . Normally $i9'.3o This Month $49.oo Am■zln11 price for an Alarm Syetem offerln11 th••• f■c/1/tlea Audible warning with a 125 decibel loud siren and visible warning of flashing headlights when the alarm system is triggered . Keyring remote c~ntrol. allows arming with 'beep' sound and disarming with a headlights flashing signal. The alarm system will be triggered by unauthorised entrance through the car doors, boot , bonnet or removal of the car sound unit. The siren will sound and the headlights flash for 60 seconds. EHy to ln1tall. sonu• ol' ~r S 5220 .00 fr..Al■rm StlckJ~yl Thi• Mon 111 $99 $3.es Mt of 4 This Month Only Ideally suited to above CRO. DC to 80 MHz. Max 600 Volts DC . Lead length approx 1.5m. $599 _ _ _ _ _ _ _ _ _ _ _ _ ___. a 1015 17 Range Digital Multimeter Our Top Selling Autoranging LCD Multimeter With Memory Function With overload protection DC Voltage to 2000V 4 ranges AC Voltage to 500V 2 ranges DC current to 10A 4 ranges Resistance to 2 meg other 5 ranges Plus diode and battery tester. Includes 9V battery and probe set, Q 1056 and Bar Graph Dlaplay This popular 3.5 digit Multimeter is simplicity itself. Full auto ranging on· voltage and Normally great value at ~ 5 $39.95 $12.50 Th is month for the very quick only Q 1057 Carry Case to Suit Awarded the Good Product Design Award for ¥ii!?;,,i;s;i~s1 Ultrasonic Cleaner can earn its cost a hundred times over in cleaning Computer Connectors , PCB's, Switches. Relays, Jewellery, Tuck 1h11 lantutlc alne/aquare wave oaclllator away In your toot box Pocket Sized, Personal Audio Signal Generator resistance measurements. The large LCD digits allow quick and efficient reading of measurements. • 42 Segment Bar Graph Display • Auto-ranging on voltage and Resistance • Memory Mode • Low OHM Range • Hold Facility • Automatically indicates negative inputs • Low Battery Ind icator• Continuity check with Buzzer. Pin Point Ultrasonic Cleaner This pocKet sized oscillator has all the features of a large bench oscillator. 46 preset switched frequencies ranged lrom 20Hz to 150kHz, eg: 1kHz, 1.2kHz, 1.5kHz, 1.SkHz, 2kHz etc. Smaller than most multimeters, this is ideal for technicians, servicemen , students and hobbyists who require an 1 accurate and reliable osci llator ready to use anywhere . 0m2$--oo Thi• $80.oo Q 1075 Normally $ ~ 0 0 Now only $49.s5 $99.oo Month Only Sensational Value On UHF Alarm Systems Main Control Receiver "' 6 The main control receiver runs on 240V AC with a 12V 1.2Ah battery for emergency backup. The range between the transmitters and the receiver is normall y 80 metres in open space . Feature,: • Wire less reception of external and internal sensors & detectors• Selectable home or away modes for selecting internal or external arming or just external to allow movement inside the bu ilding• Built in piezoe lectric siren gi ves different signals to indicate different functions • Sends signal down power line to activa t e remote siren • Programmable arm/ disarm switch buttons tlo Glasses, Watches etc. Power Supply: 240V Capacity: 570ml With 3 Minute Auto Timer Passive Infra Red Movement Detector Ideal for the loung eroom , family ro om or hallways. Mounts up on the wall or bookshelf. Detects movement within an area of 9 x 9m. Powerful 6000 RPM Mini Drill Front Door Rem ote Keypad This handy unit vi rtuall y duplicates th e function ot the main cont rol unit but at a more convenient location, ie. just inside the front or rear door etc. System can be armed or disarmed without the need to go to the main co ntrol unit . $15 .00 Replacement Drill Bit• for PCB Work T 2320 0.8mm $3.50 T 2325 1.0mm $3.50 This consists of an enclosed reed switch and transmitter w ith a magnet . This unit is a line ca rrier rec eiver , ie. plugs into 240V AC and rece ives signal through AC line . For PCB Work Tons of torque. Just the shot for PCB work. 12V DC operation from optional power pack. Comes with 0.8mm and 1.0mm chucks. Plus one 1.00mm drill bit.$ T 2302 ~ 5 0 Thll Month Only Remote Reed Switch S YSTEM 2 SYSrEM 1 SYSTEM 3 lncludet: 1 x Ma 111 Cont roller 3 x Remote Reed Sw,tche~ 1 x Remo te PIA Movemen~ Oeter:tor 1 x Rem o te Keypad 1 x Remote S1 ren Plus 4 Bonus La rge Ala rm Warn in g Stic kers This Month Only Includes: 1 1< Ma ir Cont roller 3 x Remote Reed Sw1lches Plus 4 Bonus large Alarm Warning Sticke rs This Month Only Th is Month Only NORMALLY~ NORMALLY NORMALLY~ $ 399 $249 $SJ6- tn c1uc:1e1; 1 x Ma, n t;on1ro11er 1 x Rem ote Reed Switch 1 x Remote PIA MovemP.nt Detector 1 x Remo te Keypad Plus :\ Bonu .s Large Al ar rn warning Sticker s $299 Nicad Battery Super Sale! ack Cases to clear t Crazy Prices/ Were $35.oo $4O.oo $45.oo $45.oo $48.oo 1 unit'Grey Panel 2 unit Silver Panel 3 unit Silver Panel 3 unit Grey Panel HS0413 Now 3 unit Black Panel MU Metal Shielded Audio Transformers Microphone Type: Primary: 200 Ohm Secondary: SOK Ohm. A high quality item eminently suited to mixers, PA amplifiers and where an ultra low "hum" pickup level is desired. M0701 Normali~ $~95 Thi• Month Only $25.oo · 10 up$23.oo ~ Bridging/Isolating Type: Use for coupling audio modules. Prevents earth loops, hum etc. Essential coupling device where DC isolating is required. Nominal impedance ratio 10K: 10K (1:1). M 0702 Normally $~95 Thi• Month Only $25.oo 1oup$23.oo Attention Audiophiles/ ? Optimise Your Sound System With This Oxygen-Free Cable Twin Jumbo Twin Mega ~ Cable .._ · - Jumbo Cable 204 x 16 AWG. ~ 504 x 12 AWG. --..... 10+ 1-9 ~ 5020 AA 500 mAH $2.so $2.20 S 5021 AAA 180 mAH $3.so $3.20 S 5022 "C' 1-SAH $7.so $6.oo S 5023 'D' 4 AH $12.oo $11.oo Super Heavy Duty S 5024 9V $16. $12.so $11 .so New Portable Gas Soldering . 1• ~ Iron - - - . . . , . , ; _. This fantastic new iron Is fully sell powered and portable. One easy refill by a standard butane can allows up to 60 minutes of continuous S • • r c•11 • ~ use with a temperature range up to 40CJOC (equivalent to 60 watts). Features clear reservoir to see exactly how much gas is left. A perfect tool for engineers, electricians and hobyists. T 2450 $39.50 T2452 Replacement 2mmTip $4.95 T 2455 Replac ement C.talytlc Converter$4 .95 Superb Dome Tweeter Quality Panel Bargain of 1991 Meter Clearance Less Than ½ Price! MU52E Type. Overall Dome Tweeter Wi t h Ferro Fluid dimensions BOW x 60 Watt Max. Power. Silky smooth 66H. Bolt mounting centres frequency response 1.5Hz to 20kHz . Wide angle dispersion. Massive $58'.'oo 64W x 48H. Hole power handling capacity. Diam. required 50mm. 94mm. High spectrum. Purity. Nuts and washers Thl1 Month $20 r:: ROLL Thl1 Month $45,~:: ROLL Incredible low price! provided. c3012.$28:so $12 .00 WERE NOW High Performance 2 Way Flush Thi• Month 1A 0531 $15.oo Mounting Full Range 60W 10up$1O.oo "Highly recommended. I found II SA .02 $2 .95 $15.oo 0533 Speaker difficult to pick the difference between the A/Ironic• C 0880, the 0538 sov 200 1. 5 $15 .00 Amer/can Sonance and Botton SYstem Huge Reductions on Sy1tem1, a Discontinued Transformers High Energy What great speakers to install. Designed to install into ceilings or Siren Hurry limited quanitities. Output speaker system / grille assembly will W 0136 Normally $~95 w 0138 Normally Q 3 $!. Q Q Acoual/c both coating around $600 pair" John Negus leading WA Audiophile walls this slim profile attractive voltages: 6.3V, 7.SV, 8.SV, 9.5V, 12.6V and 15V at 1 Amp. Sorry - Not Available From Altronic Dealers at These Prices compliment any sound system. Once installed the finished unit blends beautifully into any decor. (The grille assembly can be painted over in the same finish as walls or ceilings if required) . Installation is simplified by the use of a mounting frame (which could be installed during construction) which the speaker assembly attaches to. Full mounting kit (even screws) supplied . c MA2155 w••~ s $29.s5 Now $8 .00 10 up $7.00 CLEARANCE BARGAINS ON FAMOUS VIFA SPEAKER KITS! These Fine High Fidelity Speaker Systems With 0880 $%,oo ea This Month'• Special High output. Very loud 12Ddb Sound Pressure Level. 12V 300mA. Danish Made Speakers Represent Excellent Value For $99.oo Front Grille Not Illustrated Money and Compare Favourably With Many Other Commercial Units Costing Much More! Plasma Lamp VIFA SA-5O C 3250 Were $ ~ 0 0 Display Brilliant 2 way bass reflex system 5.3 litre enclosures, Now Only $299.oo 72Hz - 18kH, . sow peak. Amazing! Pulsating high voltage plasma discharge continually changes shape VIFA SA-1OO and direction. Mode selectable to either fingertip control or sound activated . For example, from voice or sound system. Provides endless fascination as it sizzles and aros. Supplied complete with mains adaptor. A 0120 Normally $JH.oo Thl1 Month Only $99 .00 Incredible performance from this 2 way loudspeaker system. 42 litre enclosures 35Hz20kHz, 100 Watt peak . VIFA SA-13O Superb floor standing 3 way bass reflex speakers 72 litre enclosures, sealed mid range 28Hz-20kHz, 130 watt peak. C 3270 W e r e $ ~ Now Only $55O.oo c 3280 Were $ lJ,89'.'"oo Now Only $799.oo 5177 C 3280 //luatreted FAMOUS AL 240V Power Relay Low Voltage Cut-Out For Cars And Boats NEW FOR '92 NEW FOR '92 Here's a simple project that monitors the power drawn from a 'master' socket and automatically switches on a 'slave' socket. It is versatile, because it can monitor one or several appliances plugged into the 'master' and switch on one or several devices pi ugged into the 'slave'. Ideal for Hi-Fi's and computers . 6370 $59.95 Four Digit Combination Lock ICS KITS K • Build this simple little gadget, and avoid getting caught out with a flat battery during your holidays. It simply connects into a 12V accessories power line, and shuts off the flow if the batteries voltage drops to a dangerously low level. Great for the car fridge or just about anything else that is powered by your car or caravan battery. K 4328 $ .95 24 1GHz Freque Hurry 1tock1 llmlted at thl• prlcel SAVE $50. • Professionally machined and screen printed red perspex front panel • Easy to assemble and construct • No special tools required • Bright Hewlett Packard 8 digit display• Electronic switch latching• High performance IC's • High quality components. Laboratory Power Supply Bridge Adaptor for Stereo Amplifiers 3 Fits easily to std. electrical 4 switchplate cat. P 8040. Use with 7 8 electric door strike/release cat. S 4930. This 0 simple 4 Digit Combination Lock uses only 3 IC's, and is bound to prove useful in K many applications. Such as accessing alarm systems, electronic doors, ignition killers or just about anything that comes to mind. Operates from 10-30VDC (or 8xAA cells). 1925 $39.95 2515 $299.oo $249.oo Sub-Woofer Adaptor K 1000's Now In oervlce In unlveraltleo, collegea, lndu1trle1 and the home work bench throughout Auotralla. Variable adjustable voltage O to 50 Volts at up to 5 Amps. Our superb version incorporates the latest refinements and is now housed in an attractive, tough "ABS" instrument case. This all new compact version uses high efficiency toroid power transformer. Includes voltage and current meters. Ask about our optional + & - 12V and 10 turn pot accessories! $195.oo Studio 200 Stereo Control Unit .a: K 3300 • The sound quality and overall specifications of this amplifier will compliment any sound system. The overall mechanical design and pre-drilled chassis means that this kit virtually falls together and should only take the average constructor about 6 hours to build. Why pay hundreds of dollars when you can build it yourself and end up with a quality professionally finished amplifier? · Feeturea: • In Built speaker protection • Torodial Transformer (Low Hum)• Black Satin Finish • Low leakage power supply capacitors • Housed in Rugged Custom Chassis. The Studio 200 Stereo Control unit is companion to the studio 200 stereo power amplifier (and other power amps). It features slim 1u rack mount profile, trebel, stereo mono switch and volume control. Inputs include phone, tuner, V.C.R. and tape. Virtually all components mount Dn PCB's, making assembly and construction a breeze. Altronics kit includes fully professionally punched and printed panels. K 5015 $229.oo Buy Both Kits for $599 And Save! 4tlft0Pllf) (\~ I:,19.... l_.,,,Allf'I I H 174 Roe St. Perth W.A. 6000 Phone (09) 328 1599 PHONE TOLL FREE 008 999 007 MAIL ORDERS C/- P.O. Box 8350 Stirling Street PERTH W.A. 6849 STANDARD DELIVERY & PACKING CHARGE $5.50 to 1Kg, $8 1Kg-5Kg AUSTRALIA WIDE - We process your order the day received and despatch via. Australia Post. Allow approx 9 days from day you post order to when you receive goods. OVERNIGHT JETSERVICE Up to 3Kg Is $10 00, 3Kg to 5Kg Is $23.00-We process your order the day received and despatch via. Overnight Jetoervlce Courier for delivery next day Country areas please allow addItIonal 24-48 hours HEAVY HEAVY SERVICE-All orders of 10Kgs or more must travel Express Road- Please allow 7 days for delivery .. $12.00 to 10Kgs. $15.00 over 10Kgs. INSURANCE - As with virtually every other Australian supplier, we send goods at consignees risk. Should you require comprehensive insurance cover against loss or damage please add $1.00 per $100 of 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 Jetoervfce we deliver next day. AL TRON ICS RESELLERS Chances are there is an Altronic Reseller right near you - check this list or phone us for details of the nearest dealer. Blue Ribbon DHlera 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 COUNTRY ALBANY BP Electronics ■ (098) 412681 Micro Electronics (098) 412077 BUNBURY Micro Electronics (097) 216222 ESPERA'NCE Esperance Communications (090) 713344 KALGOORLIE Todays Electronics ■ (090) 215212 MANDURAH Lance Rock Retravision (09) 5351246 Micro Electronics (09) 5812206 PORT HEDLAND Ivan Tomek Electronics (091) 732531 ROCKINGHAM TV Joe's (09) 5271806 NT ALICE SPRINGS Farmer Electronics (089) 522388 DARWIN Ventronics (089) 853 622 VIC All Electronic Components (03) 6623506 The Electronic Component Shop ■ (03) 6706474 BORONIA Ray Cross Electronics ■ (03) 7622422 CHELTENHAM Talking Electronics (03) 5842386 CROYDON Truscott Electronics ■ (03) 7233860 PRESTON Preston Electronics ■ (03) 4840191 COUNTRY BAIRNSDALE LH & LM Crawford (051) 525677 BALLARAT Ballarat Electronics (053) 311947 BENDIGO KC Johnson ■ (054) 411411 MILDURA McWilliam Electronics (050) 236410 OLD Del sound PL ■ (07) 8396155 NEWSTEAD ECQ Electronics (07) 2541153WEST END B.A.S. Audiotronics (07) 8447566 WOODRIDGE David Hall Electronics ■ (07) 8082777 MAROOCHYDORE MALS Electronics ■ (074) 436119 MARYBOROUGH Keller Electronics (071) 214559 PIALBA Keller Electronics (071) 283749 ROCKHAMPTON Acceaa Electronics (East St.) (079) 221058 TOWNSVILLE Super Solex ■ (077) 724466 SA Force Electronic.;"' (08) 2125505 BRIGHTON Force Electronics ■ (08) 3770512 CHRIITIII BEACH Force Electronics ■ (08) 3823368 FINDON Force Electronics ■ (08) 3471188 HOLDEN HILL Force Electronics ■ (08) 2617088 LONSDALE Force Electronics ■ (08) 3260901 ENFIELD Aztronics ■ (08) 3496340 COUNTRY WHY ALLA Eyre Electronics (086) 454764 TAS HOBART George Harvey ■ (002) 342233 LAUNCESTON George Harvey ■ (003) 316533 NSW David Reid Electronics ■ (02) 2671385 SOUTH Sheridan Electronics (02) 2817727 SMITHFIELD Chantronics (02) 6097218 COUNTRY COFFS HARBOUR Coifs Habour Electronics (066) 525684 NEWCASTLE Novocastrian Elect.Supplies (049) 621358 WARNERS BAY Vilec Distributors (049) 489405 WINDSOR M & E Elect. and Communications (045) 775935 WOLLONGONG Newtek Electronics ■ (042) 271620. Ever forget to turn your car's headlights on at night? Or have you ever left your headlights on & flattened the battery? This automatic headlight controller eliminates both those problems. Automatic controller for car headlights By WALLY HAMMER & JEFF MONEGAL NY ONE who owns a car knows what it's like to turn the key in the ignition only to be greeted by a horrible clicking noise from under the bonnet. Yep, flat battery. Frustrating, isn't it? You grit your teeth, get out, kick the car, mutter and wish that there was some electronic device that would automatically turn your car's lights on when they are needed and off again when they are no longer required. The project presented here will do just that and more. It senses the ambient light level and automatically A switches the parking lights and the headlights on or off to suit the conditions. It is simply wired in parallel with the existing lighting circuit, which means that you can still switch the lights on manually using the existing switch if necessary. To operate the unit, you simply do nothing. Once installed correctly, the project will make the operation of your car's lights fully automatic. When the ambient light drops below a preset level, the parking lights will come on first, followed two seconds later by the headlights but only if the en- gine is running. If you switch the engine off, the lights will also go off. Similarly, the lights will switch off if the ambient light rises above a certain level. Another feature that has been added is a "temporary on" mode. Provided it is dark, the driver can switch the lights on for about 30 seconds by pressing a switch, after which time they will automatically turn off. This feature is useful for providing light to find your way to the front door, for example. All car batteries should be able to power the lights for over 30 minutes, so 30 seconds won't cause any problems with battery charge. How it works The prototype was built into two plastic jiffy cases, with the larger unit mounted behind the dashboard. The smaller case contains only the indicator LED, the "TEMPORARY ON" switch, and the LDR (on the back panel). 28 SILICON CHIP Refer now to Fig.1 for the circuit details. Schmitt trigger stage ICla and its associated components shape the pulses from the negative side of the coil primary to produce a series of square-wave pulses on pin 2. When the engine is off, pin 1 of ICla is held high py a lO0kn resistor and pin 2 stays low. However, when the engine is running, negative going pulses from the coil pass via Dl to ICla's input, which then switches its output high and low according to the pulse frequency. The resulting square-wave pulses on pin 2 ofICla are differentiated by a .00lµF capacitor and then inverted by IC1b to produce a train of short positive going pulses at pin 12. These pulses are detected by D5 and used to charge a lµF capacitor. If the engine is running, there will be enough pulses (even at idle) to charge the 1µF capacitor sufficiently to produce a logic high on pin 1 of ICZa. However, if the engine is stopped or is only being cranked over with the starter motor, then the pulses coming into the circuit will not be fast enough to prevent the lµF capacitor from discharging via the parallel 220kQ resistor. Thus, pin 2 of ICZa will be high and this high is then inverted by ICZb after a brief delay to produce a low on one input of a wired OR gate consisting of D7 & D8. If either input of the wired OR gate is low, pin 9 of IC1e is also low and transistors Q1-Q4 are all off. And when the transistors are off, the parking light and headlight relays (RLYl & RLYZ) are also off. i! ~ ~~~s ... C> <Oc, a:Es ~WMW c ... ;! ~S: v--+---~ti~5 -i---e~~~ QX a: ) c.:> ,. -✓ -, ca;3 N-- + ... I ~g C> C> c;:1; ::!: ffi~ a:,-.. Q ,- "' ::, :: o=:::;. z 0 + + I ....... . > + I ~ ~; c., ~E <O :!: u ., :5"' C>. .... N ~ "' !,! + c., "' H•· ~ I . ► a: 5. H•· M =(] 0 ~ C> C> ~ 0 == ~ 0 il: ::l+ ,- ~~.~~ Light sensing circuitry 8 '-' Now let's consider the light level sensi11g circuitry. During daylight hours, the resistance of the LDR is low and this holds pin 9 of IC1e low via inverters IC1c, IC1d and diode DB. Thus, pin 8 ofICle will be high, which means that the transistors and relays will all be off as before. When the light level falls, the resistance of the LDR increases and a logic high is now applied to pin 3 of IC1c. Pin 10 of ICld now switches high (after a delay set by the RC time constant on pin 11) and thus pulls the cathode of D8 high. If the engine is off, the other input of the wired OR gate (ie, the cathode ofD7) will be held low and no further circuit action takes place. However, if the engine is running, D7's cathode will also be pulled high and so pin 9 of IC1e will be pulled high by its --- ::l · + ,,,. I-to :::l M .., ., N !,! _H•· 0 a: w Q!... .... ..J ..J 0 a: I- z ~ 0 0 ... .,._ ea> en z I- ::c ..c;... c., :J C <( w ::c 0 + ~ I ....... Fig.1 (right): the circuitry from D1 to IC2a determines whether the engine is running, while the LDR, IClc & ICld monitors the light level. If the engine is running & the light level is low, the cathodes ofD7 & D8 are both held high & ICle turns on Ql & Q2 to activate the parking lamps relay (RLYl). This also turns on Q3 which then switches on Q4 & RL Y2 after a 1.5-second delay via IC2c & IC2d. :E 0 I::> <( . + > + I ~ w ~~g~ ~ff:c.:>ffi z ,- --' a: ::z:wOa: ; 35ffig ., JA N UARY 1992 29 ~~ ~1®·~7re~· lG ~='"Tte®~~~®~•! ·TC :;! TO _.,__. LOR ........!.... :;! ~o F ffl1 -l:::!i I~ I To~O S1 - - - ~ Q _001 - Q+t1 47uF + (e(_}• 1uF ~ - --<e:::>-eoa 1M~- • -0:::U D7.-cl)1 ~ 1 Ie eQD ~2 - N • +12V FROM BAITTRY VIA 15A FUSE C• ~Lti1 BJ• 0001 + A----, {:illJt ~ <Clt '-f ~ ~ 01 ~~---~ ~ '-,J.0,33 • tOli]e RELAY RLY1 · k D11.a::::::,..~ D 10k ~ •01 ill 4584 N • t I •041 uF ~ t;) f'!\REG1 I ~ +~j01 100.F-1 TD PARKING LIGHTS TO C ASSIS Fig.2: install the five wire links on the board first & note particularly the link underneath IC1. The remaining parts can be installed in any order but take care with the orientation of polarised components. Transistor Q4 must be mounted with its metal face towards IC2 (see Fig.1 for pinout details). associated 100kO resistor. Thus, pin 8 of ICle switches low and turns on Ql, Q2 and relay RLYl to activate the parking lights. Now let's see how the headlights are turned on. When Q2 turns on, Q3 also turns on and takes pin 5 of IC2c high. This in turn switches pin 8 of IC2d high after a 1.5-second delay, as set by the RC time constant on pin 9. Thus, Q4 turns on and activates RLYZ which then supplies power to the headlights. Q4 also turns on LED 1 to indicate that the lights are on. The reason for the 1. 5-second delay is to limit the surge current that occurs when the lights are turned on. This would obviously be very much higher if both sets of lights were turned on at the same time. The RC time constant at the output of IClc provides about 20 seconds of delay when night/day transitions are detected. This eliminates false trig- gering due to short variations in the light level falling on the LDR. Further filtering is provided by the l0µF capacitor on pin 3 of IClc. Switch S1 and IClfprovide the 30second "temporary-on" feature. When pushbutton switch S1 is pressed, the associated lO0µF capacitor quickly charges via a 1.5kO resistor. The resulting high is then inverted by IClc and pulls pin 3 of ICZb low via Dl 1. This logic low makes the circuit think that the engine is running and so, if it is night time, the lights turn on. The lO0µF capacitor then begins discharging through its parallel 330kO resistor and, after about 30 seconds, pin 6 of IClf switches high again and the lights turn off. Power is derived from the 12V car battery via reverse polarity protection diode D6 and 3-terminal regulator REGl. This gives a regulated +8V rail to power the circuit but note that the relays are powered directly from the +12Vrail. ZDl and its associated 1000 resistor provides protection against spikes which may be present on the supply rail from the battery. Relay ratings Tests on several makes of car showed that the parking lights draw from 4-9A, depending on the number of lamps in the circuit. For this reason, RLYl is specified with 10A contacts. The headlights, however, are a different proposition. Most high-beam lights are rated at 60-lO0W. Ifwe consider that there are two of them and the supply voltage is around 14V, it follows that together they draw around 14A. That is why a separate headlight relay with 30A contacts is used to switch the headlights. Construction Fig.2 shows the wiring details for the Automatic Headlight Controller. Check the PC board carefully to ensure that no track faults exist before you start construction. In particular, check for shorts between close tracks and for breaks in tracks. Once this has been done, start the assembly by installing the five wire links. One link runs under ICl, so ensure that it is installed before the IC is soldered into place. This done, install the resistors and capacitors but take care with the electrolytic capacitors as they are polarised. Next, install the diodes, transistors and ICs. Once again, take care with the polarity of these components and be sure to use the correct device at each location. Note that the metal face RESISTOR COLOUR CODE 0 0 0 0 0 0 0 0 0 0 0 0 30 No. Value 4-Band Code (5%) 5-Band Code (1%) 1 1 2 1 4 470kO 330kO 220kO 150kO 100kO 47kO 15kO 10kO 2.2kO 1kO 1000 yellow violet yellow gold orange orange yellow gold red red yellow gold brown green yellow gold brown black yellow gold yellow violet orange gold brown green orange gold brown black orange gold red red red gold brown black red gold brown black brown gold yellow violet black orange brown orange orange black orange brown red red black orange brown brown green black orange brown brown black black orange brown yellow violet black red brown brown green black red brown brown black black red brown red red black brown brown brown black black brown brown brown black black black brown 3 1 3 1 4 1 SILICON CHIP PARTS LIST 1 PC board, code CE 91 AL 1 12V PC-mounting relay (MR301 12HS) 1 12V 30A automotive relay 1 momentary contact pushbutton switch 1 plastic jiffy case, 130 x 68 x 41mm 1 plastic jiffy case, 83 x 54 x 28mm (to house S1 & LED; optional, see text) 1 light dependant resistor (LOR) The PC board can be held in position in the case using foam rubber. Use plastic cable ties to bind the leads into neat bundles & make sure that you wire the unit into your car in a professional manner, as described in the text. of the BD437 transistor (Q4) fac es diode D10. The 3-terminal regulator and the relay are the last components to go on the board. Once these are on, go over the board carefully and check that all parts are in their correct locations and are correctly oriented. The external leads can now be soldered to the board. Make sure that all leads have sufficient length to reach the relevant parts of the vehicle when the project is installed. For the prototype, we installed the pushbutton switch (S1), the LED and the LDR in a separate small zippy box which was then mounted on top of the dashboard. Bench testing Before installing the project in the car, it should be tested on the bench using the following procedure: . (1). Connect the unit to a 12Vbench power supply (more than likely nothing will happen) and make sure that the LDR is in bright light. (2). Wait 45 seconds for the circuit to stabilise, then press S1. Again nothing should happen. Now cover the sensor with a dark cloth, wait for another 45 seconds and again press S 1. This time RLYl should come on, followed about 1.5 seconds later by headlight rely (RLYZ) and LED 1. Check that the relays automatically switch off after about 30 seconds (first RLYl and then RLYZ 1.5 seconds later). (3). If all is well so far, connect an audio oscillator to the input and feed in a 50Hz 5V (approx.) pulse waveform. If the LDR is in bright light, the relays should remain off. Cover up the LDR and check that the relays and LED 1 switch on after the 45-second delay. If this is OK, disconnect the pulse generator and check that th e relays switch off after a short delay. If everything checks out as d escribed above, the project can be installed in the car. If you strike trouble , then refer to the troubleshooting procedure at the end of this article. Installation The position of the LDR is very important and will determine the effectiveness of this project. In the prototyp e installation, the LDR was mounted on the back of a small plastic case that also contained the pushbutton switch (S1) and the LED. This box was then mounted on top of the dashboard so that the pushbutton switch could be easily reached by the driver. One thing to watch is that the LDR must be shielded from oncoming headlights an d overhead street lights, otherwise the unit could switch the lights off at the w rong time. Similarly, it should also be shielded from any instrument lights, from the lights of following vehicles and even from the headlight indicator LED on the front panel. The final position of the LDR will, of course, vary from car to car. In stubborn cases, try mounting it under the dashboard to the right of the steering column. Semiconductors 2 4584 hex Schmitt trigger inverters (IC1 ,IC2) 1 78L08 3-terminal regulator (REG1) 2 BC558 PNP transistors (Q1-Q3) 2 BC548 NPN transistors (Q2-Q4) 4 1N4004 power diodes (D1,D6,D9,D10) 7 1N914 signal diodes (D2D5,D7,D8,D11) 1 15V 1W zener diode (201) 1 green LE:D (LED1) Capacitors 2 100µF 16VW electrolytic 2 47µF 16VW electrolytic 3 10µF 16VW electrolytic 1 1µF 16VW electrolytic 4 0.1 µF 5mm-pitch monolithic 2 .0033µF ceramic Resistors (0.25W, 5%) 1 470kQ 1 15kQ 1 330kn 3 10kQ 2 220kQ 1 2.2kQ 1 150kQ 41kQ 4100kQ 1 100Q 1W 347kQ Miscellaneous Automotive connectors, hook-up wire, 30A hook-up wire (for headlight wiring), nuts and bolts. The PC board can be housed in a plastic jiffy case and installed behind the dashboard, with the necessary wiring run through the firewall via a suitable grommet. To connect the parking lights into circuit, simply connect the lead from the PC board to the positive lead running to one of the lamps (the parking lamps are all in JANUARY 1992 31 Headlights Reminder Circuit If you don't like the idea of automatically switching your lights on and off, or you just want to save money, why not use the circuit as a Headlights Reminder instead? The modifications are straightforward and, as a bonus, the installation is much easier. A practical Headlights Reminder should sound a warning buzzer when three conditions are satisfied: (1) the engine is running; (2) the light level is low; and (3) the headlights are off. We already have the engine and light level sensing circuitry, so all we need to do is detect whether the headlights are on or off. This can be done using IC1f. The modifications to the circuit are as follows: . , . , . parallel, so energising one energises the lot). The external 30A headlights relay (RLY2) can be mounted in the engine bay, preferably adjacent to the existing headlights relay. It's then simply a matter of identifying the leads and connecting the normally open contacts ofRLYl across the normally open (1 ). Disconnect the anode of D11 from pin 3 of IC2b and connect it instead to pin 9 of IC1 e. (2). Reduce the 100µF capacitor on . pin 5 of IC1f to 0.1 µF and increase the 1.5kQ resistor to 100kQ. Delete switch S1. (3) . Substitute a 12V buzzer for RLY1 (ie, connect it between the + 12V rail and the collector of Q2). Leave diode D9 in position. (4) . Delete all components following Q2 and the buzzer, except for the 47kQ resistor on pin 5 of IC2c and the 150kQ resistor on pin 6 (these resistors are left in circuit to prevent the Schmitt triggers from oscillating). If you are uncertain as to which parts to leave out (or are too lazy to work it out), just leave out Q3, Q4, LED1, D10 and the external relay (RLY2). contacts of the existing relay. You can do this quite easily by using double adapter automotive spade clips. Note that any wiring between the two relays must be run using 30A automotive cable. Don't forget to connect the leads from the PC board to the coil terminals of RLYl. The connection to the ignition coil That's all there is to it. To install the unit, connect it to the ignition coil as before and connect the free end of the 100kQ resistor at IC1f to the switched side of the headlights switch. The + 12V supply for the circuit should be picked up from the switched side of the ignition switch, via one of the existing fuses (this is possible because the circuit now draws negligible current and doesn't have to be permanently powered). Now, when it's dark, your engine is running and the lights are off, the cathodes of D7, D8 & D11 are all high and IC 1e turns on Q1 & Q2 to drive the buzzer. When you turn your headlights on, IC1 f's output goes low and pulls pin 9 of IC1 e low via D11. IC1 e's output thus switches high, Q1 & Q2 switch off and the buzzer stops. can be made by terminating the input lead with an automotive eyelet lug. Power for the circuit must be obtained directly from the battery side of the fusebox via a 15A in-line fuse. Don't use any of the existing fuses and make sure that the supply remains at+ 12V even when the ignition is switched off (note: once installed, the circuit is powered continuously). Also, don't leave out the 15A in-line fuse; if you do, you run the risk of a fire if there is a short circuit. If you are joining wires to existing cables, it's best to solder the junction and then insulate the soldered joint with a few layers of insulation tape. Make sure that no strain is placed on any cables running through the car and that no metal can wear through the cable insulation. Troubleshooting We mounted the LDR on the rear panel of the control case but this can be varied to suit your situation. Note that the LDR must be mounted where it will not be exposed to oncoming car headlights, or to street lights or instrument lights. 32 SILICON CHIP Hit doesn 't work, the first step is to check component placement, orientation and soldering. If these checks don't reveal anything, the next step is to isolate the faulty circuit section. The procedure is as follows: (1). Check the supply voltages, You should get a reading of +8V at the output of REGl and on pin 14 of each IC. Check also that +12V is being supplied to each relay coil. Switch off immediately and clear the fault if you don't get the correct readings. (2). If the supply voltages are correct, remove diodes D7 & DB and check that both relays turn on. If neither relay turns on, check the circuitry around ICle, Ql and Q2. IfRLYl turns on but not RLY2, check the circuitry around Q3, IC2c, IC2d & Q4. (3). If both relays turn on in step 2, you've cleared the circuitry following ICle. Now install DB and check that the relays are off when the LDR is exposed to bright light (note: you may have to wait while the 47µF capacitor on pin 11 of ICld discharges) . If the circuit passes this test, cover up the LDR and check that the relays switch on after 45 seconds. Check the circuitry around the LDR, IClc, ICld & DB if you strike problems. (4). If everything is OK so far, then the fault lies in the engine sensing circuitry. Install D7 and try pulling pin 1 ofIC2a high (ie, connect it to the +BV rail). Provided the LDR is covered up, the relays should close after a short delay. If they don't, check the circuitry around IC2a & IC2b. If they do, try pulling pin 13 of IClb low. If the circuit still works, check ICla and Where to buy the kit A kit of parts for this project is available for $32.95 plus $3.50 p&p from CTOAN Electronics, PO Box 33, Condell Park, Sydney, NSW 2200. Phone (02) 708 3763. Orders may be placed using Bankcard, Mastercard, cheque or money order. The kit includes the PC board, all on-board components, the pushbutton switch, the LED, the LOR and the on-board parking lamp relay. It does not include the plastic cases, headlight relay, cable or automotive connectors. These parts may be purchased from electronics retailers and automotive accessory shops. If you are unable to get the project going, CTOAN Electronics offers a full baekup repair service. The cost is $15.00 plus $5.00 return postage. Please note that only kits built as described in this article and with good qualit soldering can be accepted for repair. Note: copyright of the PC board associated with this project is retained by CTOAN Electronics. its associated components, otherwise check the circuitry around IClb. Finally, there are a few simple adjustments you can make to the circuit if necessary. If the circuit turns the headlights on too early, increase the value of the lOOkQ resistor in series with the LDR. Alternatively, decrease the value of this resistor if you want the lights to come on earlier. The "TEMPORARY ON" period can be adjusted by changing the 330kQ resistor on pin 5 of IClf. Increase the value of this resistor to obtain a longer period and decrease it to obtain a shorter period. For example, reducing the resistor value to 150kQ will give a period of about 15 seconds. SC Introducing the Protel advantage. Protetf or Windows': Protelfor Windows is an entirely new Printed Circuit Board design system createdf or Windows 3. 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Adva11ced PCB and Professional Schematic are registered trademarks of Prate/ Technology Ply Ltd. \Vinduu,'S is a registered trademark of Microsoft Co,poration Inc. 1 JANUA RY 1992 33 SERVICEMAN'S LOG Same set, same symptoms, but. .. Usually, we welcome a set of symptoms we've seen before; it can mean a quick cure for what, originally, might have been a sticky one. It's what we call experience and it's what the customer pays us for. But sometimes two different faults can produce identical symptoms. My stories this month demonstrate the confusion and red herrings this possibility can sometimes cause. The first one involved an AWA Mitsubishi 34cm colour TV set, model C-3423. It was a new set, only about nine months old and, of course, still under warranty. I was .making a house call on a different matter when the teenage daughter asked me if I would look at her TV set. According to her, it had simply failed in the middle of a program and was completely dead. Could I fix it? I assured her that I should be able to and, if she had the necessary documents to cover the warranty, it should noi cost her anything. In fact all these were in order, so I loaded the set into 105 the van and headed for the shop. When I set it up on the bench and switched it on, the result, superficially, was as she had described it: no picture, no raster and no sound. But it was not quite dead. At the moment of switch-on, I had heard a faint "boing" as the de-gauss circuit activated. This meant that the mains fuse was intact, eliminating one initial check. I pulled the back off and switched on again, looking for any obvious damage. I found none but I was able to observe that the picture tube heaters were up and running, which ruled out a lot more possibilities. Delving a little deeper, I established that the main HT rail was spot on at 103V. I pushed the EHT probe in under the ultor flap and came up with a 1N•9'& T 40 2 F BT C421 IOOOfliF 2~V Fig.1: the horizontal output transformer circuitry in the Mitsubishi Model C3423, The 16.5V rail is derived from pin 5 ofT402 via resistor R435, diode D406 and capacitors C422 & C421. similar answer - EHT spot on. So where to now? I began imagining all kinds of weird and subtle faults, involving a faulty IC or something similar. Fortunately, calmer thoughts prevailed. There are always other voltage rails and it is essential to check all of these before suspecting individual components. And so I very soon discovered that what should have been a 16.5V rail was actually sitting at only 3V. I'm not sure of all its functions but one is to provide another rail - a 12V rail via a voltage regulator, 1502. In any case, it was the most likely cause of the failure and had to be fixed. There is very little to this circuit (Fig. l). It is derived from a tapping, pin 5, on the horizontal output transformer (T402) and consists of a lQ fusible safety resistor (R435), a diode (D406), a 1500pF capacitor (C422) across the diode, and a lO00µF 25VW electrolytic capacitor (C421) as the filter. Well, . with only four components involved, it didn't take long to find the culprit. It was C421, the lO00µF filter capacitor, which was virtually open circuit. In fact, it couldn't even struggle up to lµF on the capacitance meter. Anyway, it was easy enough to fix; a new electro and the set was up and running like new. I rang the house, spoke to the girl's mother and told her that the set was ready. She said she would be in to pick it up the next day. In the meantime, I left it running. And so the next day the lady collected the set and I completed the necessary warranty claim forms and sent them off. · All of which added up to a perfectly routine exercise involving a relatively simple fault. In fact, the reader is probably wondering why I bothered to relate the story. Mum returns There is a very good reason; the set 34 SILICON CHIP bounced - and bounced in a particularly nasty way. Mum was back the next day with the set and rather testily complained that it had run for only 15 minutes, than failed with exactly the same fault as before. (It's always the "same" fault when a set bounces). Naturally, I apologised, tried to explain that these things do happen occasionally, and assured her that the warranty conditions would still apply. This mollified her somewhat but she wasn't laughing when she left. Why did that crucial 15 minutes have to happen in the customer's home rather than on my bench? And so I started all over again. I switched the set on and there was the reassuring "boing" from the degauss circuit. And with the back off I could see the picture tube heaters were alight. And the main HT rail was spot on, as was the EHT. Of course, it couldn't be the 16.5V rail again but it was. It was down to 3V, exactly as before. I was starting to pinch myself now, expecting to wake up and find it all a horrible dream. (I do have such dreams!) But it was real enough. And, with Fig.2: power supply circuitry in the Mitsubishi model CT-1447AM. The bridge rectifier is at centre and the voltage regulator, IC901, at lower right. Note the voltage on pin 4 and the incorrect voltages shown for Q902. identical symptoms, I was totally confused. On the one hand, it appeared that the brand new capacitor I had fitted had lasted only a few hours. On the other hand, the odds on such a coincidence seemed too long to consider. Nevertheless, I felt that it had to be the capacitor, so I pulled it out and checked it on the tester. But I felt a bit foolish when the tester showed that it had the full lOOOµF plus; there was nothing wrong with it. So what was wrong? With the capacitor cleared, the wasn't much left. The lQ safety resistor? A likely culprit - only it wasn't. That really left only the diode. The only snag was that an in-situ check with the meter showed it also was OK. I was getting the horrors now. Was it a faulty tapping on the transformer? I put that idea to one side and decided to try a long shot. In spite of the test, I was having second thoughts about the diode. I grabbed another diode, tacked it across the existing one and tried again. Bingo! That was it. The 16.5V reappeared, and the set began to play. I pulled the original diode out and checked it again, but couldn't fault it. Yet it wouldn't work; it obviously could not handle the voltage and/or -~---·· ij~t<t )I. . . <at>?)o~=--· cs~-r :BOUNC..E:..D 11-\e:. NE:.X, PAY WHF;.N ~UM "RA~E.~ 1"E.S1iLY COM?LA\Nl::P.u .. 11-\~ JANUARY 1992 35 SERVICEMAN'S.LOG - CTD current conditions off the circuit. I fitted the new diode properly, ran the set for a couple of days, crossed my fingers, and advised the owner that it was ready. That was several weeks ago and all is well so far. But why did those two components fail in quick succession? I've tried to think of some reason why the capacitor failure may have contributed to the diode failure but without success. I have finally concluded that it was sheer coincidence - but I wish that the diode had chosen -to fail in the workshop rather than in the customer's home. So that was the first example of two faults with identical symptoms. It was another case of a totally dead set. As before, preliminary observa1 .---t-lJol-, tions, indicated that the mains fuse .,.bi ~ was intact but there the similarity ~--~ I ® !l!l!il ended. There was no HT rail voltage and, not surprisingly, no EHT. I went back to the bridge rectifier (Fig.2), which is directly across the mains, and measured its output across the main filter capacitor, C906 (l00µF). The reading was around 300V, which was a little on the high side and suggested a lack of load. From there, I went to pin 4 ofIC901, a voltage regulator package which provides the main HT rail at 115V. (Incidentally, some of the voltages quoted around this part of the circuit are quite strange. Pin 4 of IC901, . More Mitsubishis c________ , j shown as 115V, connects directly to The second example involved two the collector of Q902 where, miracuQ more 34cm Mitsubishi colour sets, lously, it becomes 165V. The other models CT-1447AM and CT-1440A. voltages on this transistor are equally Fig.3: horizontal output transformer And perhaps I should add at this point strange.) But there was no voltage at pin 4. circuitry in the Mitsubishi Model CTthat any apparent emphasis on Mitsubishi by these stories is purely So, was it a regulator failure or was 1447 AM. The collector of the horizontal output transistor, Q503, coincidental. In no sense do I intend something loading the circuit? In fact, connects to pin 1 of the primary to imply that they are more prone to it appeared to be the latter because a winding, while the 115V rail goes to faults than any other set. It is just that resistance check from pin 4 to chassis pin 2. · the need to present these stories in showed only 3.5Q. Aha!, I thought, sequence may give a wrong impres- I'll bet that's the horizontal output sion. transistor broken down - this being mary, pin 1, while the 115V rail conThe first set appeared a couple of one of the more common causes ofHT nects to the other end, pin 2. weeks after the incident described rail loading. So it was off down to the other end A wobbly diagnosis above. The owner was going on holidays for several weeks and the set had of the circuit (Fig.3) to Q551, the tranAnd this was where my snap diagnosis began to look a bit wobbly. A failed a couple of days earlier, so they sistor in question. In typical fashion, decided to leave it with me while the collector connects to one end of resistance measurement from the colthey were away. That suited me fine. the horizontal output transformer pri- lector ofQ551 to chassis gave a virtually identical reading to that at pin 4 of the regulator IC. I tended to over11ao• look the full significance of this iniHK(lll 112W tially, regarding it as no more than a confirmation of the load on the HT rail. But it suddenly struck me that there was the resistance of the transformer C802 primary winding in between these two oaoe Rf-I 6 points. Granted, it is quite low - only AIOI$ 11011 about JQ - but it is measurable and HO should have shown up as a difference between the short at one end of the winding and that at the other. So how M:.2,r.'.., JVOI come they both read the same? How come both ends of the transformer PI04 OICIIUI- coi. primary were showing the same resistance to chassis? Fig.4: power supply circuitry in the Mitsubishi Model C-3423. The power supply If the fault was in Q551, it was a bridge rectifier is at left, the chopper transformer (T801) at centre, and the voltage regulator (Q801) at right. The 103V HT rail is derived from pin 4. very funny one. Either that or we had 36 SILICON CHIP OS!5 more than one fault; or the fault was in the horizontal output transformer. That was a nasty thought because there are some 10 pins connecting the transformer into the PC board and, together with the physical layout, this could make getting it out rather tedious. On the other hand, it was a simple job to lift Q551 to clarify the position. And as far as I could determine from a rough check, the transistor was OK. However, it is important to realise that these transistors have an internal resistance of about 400 between base and emitter, plus a diode between collector and emitter. This can sometimes confuse simple tests. But the more important check was from pin 1 of the output transformer to chassis and this still showed 3.50. So it wasn't Q551. It had to be the transformer- or was it a "funny" somewhere else in the set? I felt that the latter possibility was a long shot and, in any case, tracking it down (or disproving it) could be a long and involved business. Among other things, it would probably involve cutting various copper tracks. This is not always as easy as it sounds if the tracks are crowded to- gether and is something I try to avoid if possible. So before pulling the transformer, I decided on one more check. One of my more valuable pieces of test gear is a shorted turns tester. I wasn't sure how well it would work in this situation because the transformer second.ary winding was pretty well loaded with, among other things, the picture tube heater winding. Nevertheless, I connected it across pins 1 and 2 and made the test. And the indication was that there were no shorted turns in the transformer. Well, that was a useful piece of information but not really conclusive. So where to now? After some cogitation, I decided that in spite of the work involved, the quickest and most satisfactory approach was to remove the transformer. Granted, if it wasn't the culprit, the work of pulling it out and putting it back might appear to be wasted but at least it would settle the question once and for all. I set to work with the iron and solderwick and, after about 15 minutes, was able to lift the transformer clear of the board. This finally gave me a clear go. A quick check at the pin AUSTRALIAN MADE TV TEST EQUIPMENT Happy New Year Specials. 10% discount on all test equipment. 15% discount on two or more items SHORTED TURNS TESTER Built-in meter to check EHT transformers including split diode type, yokes and drive transformers . $78.00 + $4.00 p&p TETIA TV TIP Princess 14CT8 (PC-02X chassis) Symptom: weak vertical hold. Video input to the sync separator (IC301) is normal but the vertical oscillator is inside the same chip so it is not practical to see if the sync pulses are normal. Cure: the clue is that the voltage at the input to the sync separator is lower than specified. The cause is that the first video amplifier, (0201 2SC1815) is slightly leaky collector to emitter. This does not seem to affect its gain but does put a wrong bias on the sync separator. TETIA TV Tip is supplied by the Tasmanian branch of the Electronic Technician's Institute ofAustralia. Contact Jim Lawler, 16 Adina St, Geilston Bay, 7015. 1 and pin 2 positions on the board showed that there was no short to chassis, which meant that it had to be PRESTON ELECTRONICS 217 High Street, Preston, Melbourne Victoria 3072 (Cnr of Bell & High Street) TEEPROM PC Eprom Programmer Card, Cable + Software $250.00 HIGH-VOLTAGE PROBE Built-in meter reads positive or negative voltages from 0-50kV. For checking EHT and other HT voltages. $98.00 + $5.00 p&p 1991 European/Jap Transistor Equivalent Book, 790 Pages $39.95 DEGAUSSING WAND Strong magnetic field. Double insulated for your safety with momentary switch operation. 240V AC 2.2 amps. As important as a soldering iron! $75.00 + $10.00 p&p REMOTE CONTROL TESTER Designed to test infrared or ultrasonic control units. Supplied with extension infrared detector lead. Output is via a LED and piezo speaker. $84.00 + $4.00 p&p ~~ ~ From$19exchange plus post & pack Cheque, Money Order, Visa, Bankcard or Mastercard 216 Canterbury Rd, Revesby, NSW 2212, Australia. Phone (02) 774 1154 Fax (02) 7741154 Economy Soldering Iron - 240V Fine Point Tip $19.95 Video Recorder Replacement Belt Kits (Specify Make & Model} $12.95 CB Radio Power Amp, 35W AM, 70W SSB Output $199 Fujitsu 12V 1A PC Relays $1.00 ea. Mail Order Hot-Line 8 /Card-Mast/Card-Visa-Cheque Phone (03) 484 0191 JANUARY 1992 37 SERVICEMAN'S LOG - CTD the transformer. Fairly obviously, there had to be a short between the primary winding and one of the secondary tappings. A resistance measurement between pins 1 & 2 and pins 9 & 10 (the picture tube heater winding) gave the all clear. But from primary pin 2 to pins 3, 4, 5 & 7 (which are all part of one winding), there were very low resistance readings. And the lowest was 3.5Q to pin 7, which connects to chassis. Also significant was the fact that the readings from pin 1 were almost identical. Conclusion: the breakdown between primary and secondary must have been at, or very close to, the centre of the primary winding. And that makes it one of the dirtiest tricks that Murphy has pulled for a long time. And the shorted turns test? No, it didn't fail; the fault was not a shorted turn. On the other hand, it was areasonable try as faults in output transformers commonly result in shorted turns. Anyway, these thoughts aside, I had finally tracked down the fault. A call to AWA for a replacement transformer was handled with commendable speed and it was on its way in few hours. And that, apart from the routine fitting, was the end of the story. I ran it regularly each day until the customer returned from holidays and have heard nothing from him since. The twist to the story But now comes the twist to the story. While that set was still in the workshop waiting to be collected, another 34cm Mitsubishi arrived, this time a model CT-1440A. Although a different model, with some superficial differences, it uses essentially the same circuit and chassis as the CT1447 AM. The complaint was the same; completely dead. I started at the bridge rectifier as before and found a similar situation; a slightly higher than normal voltage of about 300V. I then moved to pin 4 of the regulator, IC901, only to find no voltage. Almost automatically I made a resistance check to chassis. And what did I find? Yes, you've guessed it; 3.5Q I could hardly believe it. More to the point, I hardly knew what to do. Remembering how I had been caught in the first story, I had a horrible feel- ~MONG 011-1~ 11-lt~G'E> rf WOUl.--D PROBABL-V \NVOL-VE'. CV"'\I\NG VA'R\OUS COP'P6:.'R -.1RAC.KSon 38 SILICON CHIP ing that Murphy was having a lend of me. On the one hand, the symptoms seemed so obvious - perhaps too obvious - while, on the other hand, the odds against two such identical faults landing on my bench within a week or so of each other seemed pretty long. I couldn't escape the feeling that which ever way I jumped, it would be wrong. IfI pulled the transformer out, there would be nothing wrong with it. If I didn't, I would spend hours looking for an elusive fault with the same symptoms, while it was the transformer all the time. Either way, I couldn't win. But, of course, I had to start somewhere. I went over the circuit in fine detail, repeating every measurement I had made on the first set, looking for something that didn't match and which might provide a clue. It was a vain effort; as far as I could determine everything was exactly as it had been in the first set. So, finally, there was nothing for it but to pull the transformer. And it really was the same fault. So I'd been caught out by my own caution. But I still reckon it was long odds for those two faults to turn up in such quick succession. Or have I latched on to an inherent fault in a batch of these transformers. Well, only time will tell but, if I encounter these symptoms again, I reckon I'll take a punt on the transformer. Postscript Well, that was supposed to be the end of this month's contribution. However, shortly after I had finished bashing it out on the computer, another dead Mitsubishi turned up. It was a model C-3423, the same as the first one with the failed 16.5V rail. And, like that one, it was a new set, only about one month old and still under warranty. In view of the previous stories, my first reaction was to suspect that 16.5V rail. But then another thought crossed my mind; I realised that this set uses the same horizontal output transformer as the models CT-144 7AM and CT-1440A. So I couldn't overlook the possibility that this was going to be number three with the primary/secondary breakdown. I checked the 16.5V rail first. It was completely dead whereas previously there had still been about 3V. Next, I checked the 103V HT rail and this You can now afford a sate II ite TV system For many years you have probably looked at satellite TV systems and thought "one day". You can now purchase the fol lowing K-band system for only: $995.00 Here's what you get: * A 1.8-metre prime focus dish antenna, complete with all the mounting hardware. *or better). One super low-noise LNB (1.4dB *magnetic One Ku-band feedhorn and a signal polariser. * 30 metres of low-loss coaxial cable with a single pair control line. * A 99-channel infrared control This horizontal output transformer is from the CT-1447AM (second story), although it is also used in the C-3423. It had shorted from the centre of the primary winding to one of the secondary windings. was also dead, a symptom more like that of the output transformer fault. It looked even more like it when I checked around the voltage regulator package, Q801 (Fig.4). Voltage is applied to pin 1 of this from a chopper transformer, T801, and was sitting at around 300V. But at pin 4, which delivers the 103V rail, there was nothing which indicated that the voltage regulator wasn't working. A resistance check from pin 4 to chassis showed only 2.6Q. And hard alongside the voltage regulator on the circuit were two likely culprits: a lO0µF electrolytic capacitor (C807) and a 160V zener diode (D807) which protects against excessive HT voltage. It was easy enough to disconnect both of these but I drew a blank; the 2.6Q remained. Another possibility was a breakdown in the voltage regulator. But while not ruling it out, I felt it was most unlikely considering the symptoms. A breakdown of the transistor in the regulator would most likely put 300V on pin 4. So was it the previous transformer fault? This still seemed like a possibility until I took a closer look at the circuit. Between the HT rail and pin 2 of the output transformer primary (Fig.1) is a diode, D408. It seemed to me that it would be most unlikely that I would be able to get a reading of 2.6Q through this diode, considering the low voltage of the meter. Nevertheless, I made some readings at the transformer and this quickly ruled it out. So it was back to the circuitry around pin 4 of Q801. The HT rail also connects to a tap on the lower winding of the chopper transformer. So was it a fault in the chopper transformer? I had a lucky break here; using solderwick, I was able to soak up the solder around the tapping pin until it was isolated from the copper pattern. This cleared the fault from the HT rail, which was my first real breakthrough. So it could be the chopper transformer. But then I spotted something else; the left hand end of this winding connects to chassis via diode D805 and choke L802 in series, and also via a parallel 2200pF capacitor, C808. So it could be either the diode or the capacitor. I pulled the capacitor out first and, of course, drew a blank; nothing wrong with it. But the diode was a different story; it had broken down and the 2.6Q was mostly from the choke (L802) and the transformer winding. So I finally cracked it, in spite of the red herrings. But that's all part of the game. SC satellite receiver with adjustable IF and audio bandwidth, polarity and dual digital readout. Your receiver is pre-programmed to the popular AUSSAT transponders via the internal EEPROM memory. This unit is also suitable for C-band applications. Call, fax or write to: AV-COMM PTY LTD PO BOX 386, NORTHBRIDGE NSW 2063. Phone (02) 949 7417 Fax (02) 949 7095 All items are available separately. Ask about our C-band LNBs, NTSCto-PAL converters, video time date generators, FM 2 and EPAL. I I ----------YES GARRY, please send me more information on K-band satellite systems. I I : Name ... ... .... .......... .. .. ................ ...... : I Address.. ... ... .. ... .. .. ....... .. ............. .... I I ...........................P/code ..... .. .. ..... .. II Phone ..... ...... .. ............. ............. ..... .. I I I II . ___________ .I I AC N 002174478 01 /92 JANUARY 1992 39 COMPUTER BITS BY JENNIFER BONNITCHA What to do when things go wrong Most times when you use your computer, things go according to plan and the desired result is achieved. From time to time, however, things go horribly wrong and knowing how to fix the problem is quite an art. You can divide most computer problems neatly into two categories: (1) those causing physical damage, and (2) those which are logical. Physical damage in terms of computer files means that something affects the physical location of the file on a disc, thus preventing a part of the file from being written to or read. Logical damage, on the other hand, is contentrelated and this can mean that a DOS area (for example the File Allocation Table - FAT) or the contents are corrupt. Most computer users have at some time had the experience of a program terminating unexpectedly- for example the Unrecoverable Application a little data loss through to corrupted files. Graceful program termination generally closes any open files, deletes any temporary files created during the session, frees-up allocated memory and restores the original hardware/ software interrupt table values, if altered. In order of importance, the first process - closing open files - is vital. Deleting temporary files is a neat and tidy way to end a session, while releasing memory and restoring the interrupt table are very important unless you decide to turn the computer off or perform a restart. If DOS and your program don't cooperate in the removal of temporary "If DOS and your program don't co-operate in the removal of temporary files, then you most definitely should remove them yourself so that they don't tie up disc space." Error from Windows 3. Programs which terminate in a graceful, orderly manner seldom, if ever, cause problems. Inelegant, awkward terminations can occur when you choose the Abort option from DOS during a critical stage of the program, the system locks up or you lose power or reboot your computer during program execution. You may end up with anything from 40 SILICON CHIP files, then you most definitely should remove them yourself so that they don't tie up disc space. Open files When DOS closes a file, any information or instructions pending for the file are written, the directory time/ date stamp is updated, as is the FAT, and finally the file handles are freed. It is imperative that DOS and the pro- gram cooperate when closing files since when a program closes a file it directs DOS to write all information the program holds in its buffers. DOS, on the other hand, writes all information and updates the directory entry and FAT. If only DOS closes a file, there is the chance information may be "trapped" in the program's buffers. If a program stops before it closes a file, you lose information, the subdirectory information may not be correct and the FAT may not be updated correctly. IfDOS stops during file closing, information may or may not be recorded, the subdirectory entry may not be correct and the FAT may or may not contain the correct chain entries for the file. In combination, disagreement between the file, subdirectory entry and FAT causes logical inconsistency, thus the disc is logically damaged. While this can cause considerable problems, there is hope! Unexpected program termination has one saving grace - you can usually guess how much data may have been lost. Word processing and spreadsheet programs generally lose the most recent revisions while database and accounting programs may have pieces lost. You may find that the file has been corrupted or is littered with garbage. In the case of a database, you may also find that any related files could be affected. The most important question in this instance is: could DOS and the program clean-up prior to termination? While the current information is lost, the system's integrity should be intact. Memory disagreements As mentioned above, when a program terminates in an orderly fashion, memory used by the program is freed for further use. Memory (or RAM) is used both by DOS (and freed automatically) and a program (which it should free on termination). Note that DOS 5 handles memory allocation in a different way. This article describes earlier versions to avoid complication. A future article will describe the differences in DOS 5. When a program starts, DOS , depending on the program type, allocates conventional RAM to the program: COM: first 64K EXE: whatever is established by the linker that creates the EXE file. This information is stored in the file's preamble. Any other memory used by the pro- mer. If the problem was a disc error, the program halts immediately and DOS bypasses the clean-up stage! The Ctrl C/Ctrl Break combination may cause a program to terminate prematurely. DOS will restore any changes to the, interrupt table, however if the program made any modifications, you should restart DOS to reset the interrupt table. This is not a bad idea in any case, just to be sure. How far is too far? Knowing when to turn off your computer or restart DOS is part of the art. Try to make sure all foreground and background programs have terminated, the system is at the DOS prompt and that the disc drives have completed any writing "Unexpected program termination activity. Remember, however, that the has one saving grace - you can system prompt is usually guess how much data may not always a guarantee of completion. have been lost." When you run backgram is requested when necessary, ground programs, including TSRs then freed. Since DOS can't automati- (Terminate and Stay Resident procally free any other memory when a grams), the DOS prompt won't indiprogram ends, memory must be freed cate an idle system. explicitly by the program. Thus, if a Since the computer is processing program stops suddenly, RAM can be in the background, any work taking trapped. Although programmers by place is out of view. The DOS prompt and large are careful to include a is an indication that any foreground "clean up" routine for unexpected work is complete, while the backprogram termination, programs can't ground program could still be chugging away. Don't always trust the disc handle all problems. activity light either, since this is meant Why is_it so? as an indicator rather than the absoYou can put the blame on three lute truth. You may notice the light remains on when audible disc access different occurrences: critical errors, CPU exceptions and the Ctrl C/Ctrl is complete. This is particularly true for floppy Break key combination. Badly behaved programs usui).lly disc drives. When a disc is selected cause the CPU exception, giving help- the drive light is turned on and then ful responses like divide by zero, di- turned off again when deselected. The vide overflow and unrecognised in- difference between light on and acstruction errors. The price you pay is tual activity is between half to one the loss of any un-saved work and the second; likewise when deselected. possibility of inconsistencies between The light may stay on until the motor stops completely. the FAT and directory entries. The hard disc drive, on the other Critical errors are generated by devices such as open disc drive doors hand, spins continuously, so the light and off-line printers. The DOS com- is a better indicator of use. Also, since mand processor, COMMAND.COM, in- the light only goes on during actual tercepts the problem and displays the read and write operations, you may device not ready message together find the inte:i;nal processing is taking with the option to Abort, Retry, Ig- place between read/write operations nore or Fail. Should you decide to and so the light is extinguished. Abort or Fail, DOS returns control to We'll look at more troubleshooting the program; the next reaction de- tips next month and discuss ways of SC pends on the ability of the program- repairing damaged files. GAS LASER INTRODUCTORY KIT 8 :~i~i ~~~~d a"~l~!:f:~ : t~~s~~~i~~i.~7n°:hrs~~~eC?t~ LASER INTRODUCTORY OFFER". The tubes are used but have plenty of life left in them. They are GUARANTEED! You I~~~~:~~:·ann!i7:u~ 0 i~~~;•1i:~\~!.';~:~~hst~~~~~ at about 3mW, and one of our reliable and efficient 12V UNIVERSAL LASER POWER SUPPLY KITS. A tube and the supply will easily slide into inexpensive 50mm SWV pipe, which makes for a compact self powered laser head. Casing is not supplied. Several of our customers reported that AT NIGHT, THE BEAM FROM THE SIEMENS WAS VISIBLE UP TO 4km AWAYI The kit comes with full instructions and it even includes a prewound transformer. The unlimited applications include laser pointers, surveying, optical experiments, medical field, holography, and fascinatinR laser dis~lays. Wr, are still offering this "TRIO $149 ~.ft~1~i~1~ 6~:R PICTURE) PASSIVE INFRARED SENSORS Experimenters delight! A brand new SmW 780nM• 820nM infra red laser diodes supplied with a collimating lens, heatsink, laser diode data, a suitable driver circuit and the components for this circuit. Visible in low light. Excellent for IR sights, data links, high quality audio links, ~~~t~~ro~~~~.eter s59 What are the expensive parts in a Passive element movement detector, as per ~u~iiiaJu:r:1eme:t htY~ sensor, plus a fresnet lens plus a white filter. We can supply these three components for: 5 ONLY or 10 for $80 9,90 For all the abovemen• tloned components! We can supply the same kit with a used, tested laser diode for $35. Limited stock. DECIMAL KEY PADS Positive snap action switches on a self adhesive backing. No connectors provided. Limited quantity. BIGGER LASER TUBES For the more serious applications we have some brand new, large 4mW and l0mW tubes. Both the tubes are of exceptional quality and would normally cost about three times this price. Call for a special deal for a tube and supply s155 10mW ONLY $386 co~~~ag~•tv 5 1,30 EA. or 10 for $10 LCD DISPLAY MODULES ~ ~~~ul~~~i\t s~~.':,. ~~~::l!~ !1~~!~u::ricb[~~di~~:y control circuitry already mounted underneath the PCB. Both the units have provision for backlighting, and only require a few milliamperes at SV to operate. We include comprehensive information. AT A SMALL FRACTION OF THEIR REAL VALUE. ~~t~hb'::~~lt:h~~: line module (16 X 2), s22 .50 s35 !1u;'~'::t~~~~~g2 (~~exd~flay module, We will atso have other LCD modules available, at similar low prices. A backlighting inverter kit is also available for $8. Melbourne Distributor: Electronics World (03) 723 3860 or (03) 723 3094 Closed from 24/12/91 till 14/ 1/ 92 OATLEY ELECTRONICS PO BOX 89, OATLEY , NSW 2223 Telephone: (02) 579 4985 Fax : (02) 570 7910 Certified p &p : S6 in Au st. NZ (Airmail) : S10 JANUARY 1992 41 ~ COMPUTER EXPERIMENTS =INJ#- By DARREN YATES Experiments for your games card You may not have realised it but you can do much more with your PC's game card than just play games. In this article, we'll show you how you can use it to detect various inputs and provide a few GWBASIC routines so that you can start experimenting. If you have a good look at the computer adverts in SILICON CHIP, you will notice that there are all manner of plug-in cards available that you can install in your PC to make it do just about anything. There are clock cards, memory cards, video driver cards, I/O cards and diagnostic cards, plus a host of others. There are even cards that will allow your computer to act as a facsimile machine. However, many people think of the humble games card as a "keep the kids happy" item. That's little unfair because, for just $30 or less, a games card can be a very cheap alter- a native to some of the dedicated input cards currently available. A typical example of the current generation of games cards is the one on offer from Rod Irving Electronics. It sells for just $29 and has inputs for two joysticks via DB15 sockets. It's also easy to install-you just whip the top off your computer and plug it into one of the expansion ports on the motherboard. Let's see what's involved in using one of these cards. SILICON CHIP +5V X·PLANE CONTROL OF~,__._.. JOYSTICK 2.2k TRIGGER 1/41558 OUTPUT Card circuitry The games card contains four !Cs, a handful of passive components and little else. Our main centre of interest on !' the board is an NE558 quad timer IC, which is basically four inde- This games control card is available from Rod Irving Electronics & sells for just $29. It plugs into an expansion slot on the motherboard & has inputs for two joysticks via DB15 sockets. 42 pendent 555 timers in the one package. This IC interfaces to the joystick controls, while the rest of the card can be accessed only by the computer. Fig.1 shows a partial circuit diagram of the NE558 quad timer IC circuitry. In reality, this part of the circuit is replicated four times to cover the controls in both joysticks, so we'll just look at one section. If we take a look at the average joystick, it contains two variable resistors (potentiometers) and a couple of switches. The two potentiometers Fig.1: the input control circuitry for the games card. There are four such circuits to cover all the controls on the joysticks. take care of direction, one in the xplane and the other in the y-plane. The two pushbutton switches, which most joysticks have, allow us to blow F18s out of the sky and other things. We can use these inputs too, as we shall explain shortly. By moving the joystick around, we move the wipers of the potentiometers and thus change their resistance values. As shown in Fig.1, each potentiometer forms an RC time constant with a 2.ZkQ resistor and a .0lµF capacitor, and so this time constant X s1 I ( tlV_I_ \ • 1 2 \ \._ 9 _ +SV s21 lL 3 I10 __ GJ!D_ G_!!!I_ 4 ,5 11 _ X L-I- - -., 6 12 __ 13_ GND S41 Y 7 I14- 08 I 01:.;' S31 y Fig.2: the pinout details for the DB15 sockets on the card. The joystick potentiometers can be replaced with resistive sensors, while the switches can be replaced with relay contacts. varies according to the resistance of the control. In normal operation, the computer sends a signal to the trigger input of the 558 timer and the capacitor charges up via the joystick pot and the 2.2kQ resistor. During this time, the computer clocks an 8-bit counter. When the capacitor voltage reaches the threshold voltage, the output of the timer changes state and the computer stops counting. The value in the counter when it finishes counting is available in a register and we can access this number using a couple of simple GWBASIC commands. Obviously, the larger the value set by the potentiometer, the longer it take for the .0lµF capacitor to charge up and the larger the value in the counter. This gives us a type of analog to digital (AID) converter. In fact, it is really a resistance to digital converter since it is the resistance, and not voltage, that is changing. larly, one side of each of the switch inputs is connected to the circuit ground. This is all the information we need to adapt the card for other applications. In fact, we can replace the joystick with just about any resistancevarying device we choose and we will give you a few examples. Temperature measurement If we replace the joystick with a thermistor, we can produce a very simple but effective thermometer. Fig.3 shows the circuit diagram for this. You simply connect the thermistor leads to pins 1 & 3 of the DB15 socket. Now isn't that easy? The circuit works because the resistance of the thermistor changes with temperature, which also changes the time constant of the timer circuit. Thus, the value in the counter will be proportional to the temperature. The small BASIC routine in Listing 1 prints the value on the screen. The STICK(0) functi_on in GWBASIC returns the counter value for the x-plane controller of the first joystick, which is where our thermistor is located. This program is quite small since it just gives an on-screen reading, but could easily be expanded to record temperature over time, save data to disc, or do other jobs. Light measurement By using a light dependent resistor PIN1-----. TH1 NTC 0815 SOCKET Fig.3: the replacing one of the joystick controls with a thermistor, we have a simple thermometer. The small BASIC routine in Listing 1 prints the value on the screen. PIN1-----~ L0R1 0815 ORP12 SOCKET PIN6 osi~o1 (0SE CAT Z-4801 Fig.4: by using an LDR instead of a thermistor, we can monitor changes in light level. (LDR) instead of a thermistor, we can measure changes in light level. Fig.4 shows the circuit details. Note that, this time, the sensor has been connected between pins 1 & 6 (ie, to the y-plane input). If you now look at the program shown in Listing 2, you can see that it is identical in structure to Listing 1 except that the STICK(0) statement has become STICK(l). The program thus looks at the y-plane control of the joystick where our LDR is located. You could use this simple set-up to monitor light levels in a greenhouse or for any other application where LISTING 1 - TEMPERATURE MEASUREMENT PROGRAM 10 REM Temperature Measurement 20 REM copyright 1991 SILICON CHIP magazine 30 CLS: KEY OFF 40 LOCATE 1,26:PRlNT"SILICON CHIP THERMOMETER" 50 T =STICK(0) 60 LOCATE 3,30: PRINT"Temperature = "; 70 PRINTT 80 GOTO 50 DB15 sockets The pinout diagram for the DB15 sockets on the card is shown in Fig.2. Pins 1 & 9 are the +5V supply pins which we can use to power our projects, provided we only draw low currents. Pins 4, 5 & 12 are the ground pins. As we can see in Fig.1, because one side of each pot is tied to the +5V supply rail, the number of input connections required is reduced. Simi- LISTING 2 - LIGHT MEASUREMENT PROGRAM 10 REM Light Measurement 20 REM copyright 1991 SILICON CHIP magazine 30 CLS: KEY OFF 40 LOCATE 1,26:PRINT"SILICON CHIP LIGHTMETER" 50 T =STICK(1) 60 LOCATE 3,30: PRINT"Light Reading = "; 70 PRINTT 80 GOTO 50 JANUARY 1992 43 Experiments for your games card 0B15 SOCKET TD GAMES CARD PIN 1 0 - - - - - - - - , PIN 2 LDR1 DRP12 SECTOR 0 PIN 3. ,-_---,0---- - PIN 6,0--+-- ---, SECTOR 1 PIN 110-- MINI REED SWITCH (DSE CAT P-7 856) SECTOR 4 RS1 SECTOR 6 RS3 LDR2 DRP12 + -- Fig.5: these sensors & the program shown in Listing 3 can be combined with the games card to produce a simple 8sector burglar alarm. The reed switches can be used to monitor doors & windows, while the LDRs monitor light level changes. The thermistor can be used as a fire monitor. ----, SECTOR 2 PIN 1 3 n - - - + - - - ~ SECTOR 3 house burglar alarm TH1 NTC SECTOR 7 RS4 measurements of light level are necessary. The beauty of this system is that we require next to no hardware at all apart from some wire, an LDR and a DB15 male plug. Home burglar alarm We can now expand on the ideas presented so far and make an 8-sector house alarm. The games card has eight inputs altogether: the four variable resistor control inputs plus the four switch inputs. We haven't used the switch inputs before but again these are very easy to use. The switch inputs can only detect two states - ie, open and closed - and so they are ideal for relays, pushbut- ton switches, reed switches, etc. The circuit diagram for the house alarm is shown in Fig.5. It contains three LDRs, four reed relay switches and one thermistor input, all of which are connected to a single DB15 connector. The reed relay switches replace the joystick buttons and can be used to monitor windows or doors; one section has a small magnet while the other section contains the relay. When the window is lifted, the relay opens and it's then simply a matter of using a suitable GWBASIC program to detect this happening. The LDRs detect light level changes, while the thermistor detects changes in temperature (eg, due to a fire) . Note that we're not interested in the exact values here - just detecting a change is good enough! Listing 3 shows the BASIC program for the house alarm. If we go through it, the program proper begins at line 50. Now if we look at the circuit diagram, we can see that each sensor has LISTING 3 - HOUSE ALARM PROGRAM 1O REM House Alarm Project 20 REM copyright 1991 SILICON CHIP magazine 30 CLS: KEY OFF: DIM A(?) 40 LOCATE 1,2'7 :PRINT"SILICON CHIP HOUSE ALARM" 50 FOR NUMBER = 0 TO 3 60 VSECJOR(NUMBER)=STICK(NUMBER) 70 SSECTOR(NUMBER)=STRIG(NUMBER*2) 80 IF ABS(OLDVSECTOR(NUMBER)-VSECTOR(NUMBER})>4 THEN PRINT TIME$": Sector"NUMBER"alarm .... " 90 IF SSECTOR(NUMBER)=-1 T_HEN PRINT TIME$": Sector"NUMBER+4"alarm .... " 100 OLDVSECTOR(NUMBER)=VSECTOR(NUMBER) 110 NEXT NUMBER 120 GOTO 50 44 SILICON CHIP been given a sector number. Lines 60 and 70 allow the computer to check all of the inputs; ie, the four switches and the four directional control inputs. The variable VSECTOR contains the count for each of the four sensors and these are obtained by using the STICK(x) statement, where "x" represents the sector number. GWBASIC also has a very useful function called STRIG which allows us to check if a particular button has been pressed at any time since we last looked at it. If it has, the function returns a value of " -1 ", otherwise it is "0". Line 90 checks this and prints out an alarm message, along with the time at which it occurred. STRIG statement The reason for the STRIG(NUMBER * 2) argument is that we are only interested in looking at the STRIG(0), STRIG(2), STRIG(4) and STRIG(6) arguments. If you have a GWBASIC manual, you may like to look this up for yourself. Line 80 checks to see if there is a difference of 5 or more in the last two readings from the variable sensors. If there is, it prints the alarm message. Note that because the sensor resistance values can vary widely, the counter can cycle from 0 to its maximum count of 255 a number of times. This can cause false alarm messages in some circumstances if the counter stops near its maximum ·or minimum count. For example, if the counter stops on 255 on one cycle and on 0 the next, a false alarm message will be printed even though there is only a difference of one count. This problem could be solved with fancier software. The program continually loops through each sensor until we press "control-break". Conclusion Although this has only been a brief introduction and the examples we have given are only very simple, it should whet your appetite and encourage you to experiment. There are many other possible project ideas if you are prepared to use more hardware and spend some time writing the software. It's all up to your imagination. SC ',I t-41 JA' CAR El f CTRONtrc JAYCAR [·cECTRONIC S 1AYCAR , LFCTHO'!l( JA \'CAR ELE CTRO'Jll c I C11REIEC.,.f--iCJ~11""~ IA (,;!lf F TW "Jl( JAY h LFCTF~Q\JI('· AY1Af1FL r: R(1',JJ( c C.A1 ELECT, 'ill., JAtCA" .... E: lHi JA GAF Lr,;l.TI-K"-11C JA (ARl: _::.(·H f\J( Ai f-L~L lf.~\.JC JA'r'lA/\ I · ""IH(I\J(c- JA C'AHl:.:1.. CH 1\il( T fl r CI 'Tf ,, I( ,., \h f f i... m., i AH lR ~ IC )JA, ~ L vfi0 '~1l JAY M{F f'" t ,IC, '-, (,AH l d C THv t'>:IC, JAY( ~f t L>- I 10NtC, JA'rCAl1 ElE-C J1(lN I( H 1\1( ._, JA T Al- f- ~ l HI )' .,( A, ',! 1A I Ar A r Al- rl l NIC A, 1, ST EO AUDIO MIXER ® □ ~[J)CtDu<at> ~ <at>CtDu[J)CtDu<at> BRAND Brand new model This mixing console is packed wilh features. It combines the qualifies of a broadcasting or mixing console with the features needed by adisc jockey, sound amateur or home mixer. Will accept inputs from microphones, turntables, tuners, lape decks, CD, video etc. FEATURES • lwo microphone inpuls • 4 slereo inpuls • level control for each slereo input • VU melers, headphone sockel • 240 voll operaled SPECIFICATIONS Inputs Sensitivily Impedance Mic1&2 1mV · 600n Phono 1 & 2 3mV 50kn Line 1 & 2 150mV 100kn Oulpuls • Amplifier oulpul - max 3.5V rms (1 kHz) • Recording oulpul - max 3.5V rms (1 kHz) • Headphoneoutpu 200mW Frequency Response • Mic - 20Hz - 20kHz :!2dB • Phono - 20Hz - 20kHz (RIM) ±1dB • Line - 20Hz - 25kHz :12dB Signal lo Noise • Mic- 60d8 • Phono - 60dB • Line - 70dB THD • Mic - less lhan 0.1 % • Phono - less lhan 0.1 % • Line - less than 0.05% Dimensions • 382(L) x 200(W) x 75(H)mm Cal. AM-4202 $169 Less 15% NOW $143.65 STEREO AUDIO MIXER WITH EQUALISER, AUTO TALKOVER AND SOUND EFFEC S ® O~[;)(!JJ'u'<at> ~ <at>(!JJ'u'[;)(!JJ'u'<at> 19" RACK MOUNT • Ideal for professional DJ's etc FEATURES• two microphone inpuls • six stereo inputs• level control for each stereo input-switchable • LED bargraph VU meters• rack mount• lalkover •fader• bass and treble control (Equal iser)• masler outpul volume conlrol • headphone monilor volume conlrol • cue monitor• sound effects - bombing, laser, ambulance, shooting, siren, machine gun, telephone, slorm • 240V operaled. SPECIFICATIONS. same as AM-4202.• Dimensions 482(L) X200(W) X75(H)mm. Standard 19' rack mounling. Cat. AM-4208 I l j $249 Less 15% Now $211 .65 F b I 1, , L 15~ OFF EVERYTHING PROFESSIO AL AUDIO MIXER AND OUTPUT 5 BAND EQUALISER SW TCHABL INPUTS AND TALK VER. 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Conlrol range-= Boost, cul 12dB (+/- 2dB) • Power source 240V AC • Dimensions 340)L) x 240(W) x 65(HR) x 35(HF)mm CalAM-4210 $329 N Less 150/o "JI NI f 4 · ( \~ t A:li...t ..l f-:1. J:.l F-C , L , , C ~I r co ~ I ,_ /\ AC I cc JQQ,.-11 ' r: r_r_po r-,,1 r • l 11 , NI< Portasol Professional catTs-142 $74.95 Less 15% r 15% OFF ALL SOLDERINC IRONS $63.70 OK Soldering t tlon CatTS-1600 159.50 Less 15% $135.57 .I 20w Prof s Portable cas soldering Iron Cal TS-1420 i( $39.95 Less 15% CatTS-1550 $27.95 Less 15% al $23.75 on $33.95 71mm diamete 200 gram reel. Cal NS-3005 f $7.95 Less 15% $6.75 I ,~;,:;i~)~ ~t- ~f~ ~~:,~~~ ;~~~. ·. .. · UyoijfnparestJaycarshowrqomijassold outof the item you want to purchase, you can phone (02) 743 6144 and they will advise which isfores Jfa~ _th~t ij~~icu1ar·11rri~ui:t ·i.~sfoi:k~!J~fbeijinnlny rif .th~salar Yifo ~.an then phonearoundyours!l.f, or you can place an order . . .. Vlith outman ~rder de~f~ on (02)74~ ,144 using' c:~edit card ~nd We'H do the finding f~r you and send you the goods. > for full specifications alid~esctiptiij~s chec~ ourJ990/91 catalogues ..•Be quick; stock is limited and won't last. .· PLEASE t-161'e: A~ THESE ITE;i .A~E A(~EAI)~ HEAvil.y·• oisc6uNTE:I>, .. ~~i OFF DOES NOT APPLY. Lt· L L, I I L Lr I lt 1, T Description Cat AA2090 Lockdown car antenna AS3050 Redford stereo ceiling spkr kit BS0416 Book: Macintosh Prog BS0418 Book: Computer Aided Logic Design BS0430 Book: Understanding CAD/CAM BS0514 Book: Audio IC Op Amp Applic · BS0739 Book: Best - Lotus 1-2-3 BP1208 Book: Home Recordings Make Money BP1212 Book: Intro Digital Audio BP1214 Digital Logic Gates BP1216 Computers and Music BP1218 How to set up Home Recording Studio CX2613 2 Way x'over 60W 5kHz CX2617 Philips x'over 600/4000 3 way - pair HP121 0 Crimp wire connector pkt 8 HM3204 4 Way PCB terminal HR5210 Rack frame 6 unit HR5215 Panel set for 6 unit HB5380 Black rack box see cat page 44 HB5381 Black rack box see cat page 44 HB5382 Black rack box see cat page 44 l 't Now 3.95 9950 50.00 39.95 20.00 44.95 20.00 34.95 16.95 34.95 19.95 44.95 24.95 17.95 17.95 22.95 19.95 7.95 9.95 12.95 9.95 19.95 9.95 7.95 4.95 59.00 39.00 1.50 150 149.00 59.95 .50 .50 110.00 30.00 35.00 25.00 45.00 30.00 45.00 30.00 HB5383 Black rack box see cat page 44 KA 170 7 Powermate 2 KA 1714 Beat me metronome KA 1715 Car brake lamp monitor KC5044 Car safety lights KC5053 Extension touch dimmer KC5060 Balance in/out KC5073 50V Dual track power supp KC5078 PSU load protector KC5.()82 DC offset for DMM KC5086 DC-DC converter car KC5087 Big escape game KC5088 Poker machine game KC5093 Steam Sound Simulator KJ7900 Etching Kit LR8812 Power car window winders MF1030 Trans! PL12/20VA MM2020 Ccone TIf suit P/M 00/60 MS4020 4 outlet squeeky mains fill Ml5010 OO0W inverter 12-240V NA 1015 WD40 150g spray can PP0247 RCA plug- rapid PS0357 7 Pin Din Chassis skt PS0615 TV Coax Plug - Rapid, Solder less PS0619 Wire Joiner - Rapid, Solder less PP0642 F59 Coax Ski PP0685 PL259 Rapid Solderless · PP0810 9D Rightangle Plug PP0822 15D Rightangle Plug PA0885 RS232 surge suppressor 55.00 119.00 29.95 24.95 29.95 14.95 27.95 199.00 17.95 39.95 149.50 34.95 26.95 24.95 13.95 239.00 34.95 79.50 269.00 639.00 3.95 2.95 1.85 39.00 79.00 14.95 10.00 10.00 9 95 14.95 159.00 8.95 22.95 99.50 18.95 16.95 14.95 9.95 189.00 18.95 40.00 189.00 499.00 2.00 1.00 .80 2.95 100 3.50 140 3.50 2.95 4.25 19.95 1.20 .20 1.20 100 150 9.95 I ,~ t ( CL 'fl <I Was 8.95 I ( ,. ~11 :--..11 l '"JII C'lf >Nil C A1lAH h . . l-l H ~ll Avr .'i.CJ t:: r::r T~nr,,.111 I ,.,,. PP1052 Canon 5 pin male line PP1080 Utilux Line Spk Conn PA3588 Adaptor 6.5 mon plug > 6.5 ster skt PA3595 Adaptor 6.5 ster plug > 2x ster skt PA3597 Maptor 6.5 ster plug > 2 x 3.5 ster skt PA3650 PL259 plg > RCA skt Pl6496 22 pin IC skt w/wrap Pl6522 24 Pin ZIF Socket OM1500 Metex M818 Auto DMM OM7206 8K Databank/calc QM7210 World time credit card OM7240 Metronome - electronic SB2464 AA to D NiCad adaptor pkt 4 SL2900 12V inspection lamp ST3005 Arlec smart lite torch SY 4002 2 c/o cradle relay skt SY 4004 4 c/o cradle relay ski TS1428 Rotblow tip portasol pro TS1429 Blowtorchportasol pro TH1882 6" linesman cutter/plier TH1920 Arlec easy etch engrav TH1952 Caulker Sticks 10" x 2" WW4040Earth Braid 50g Roll XC0101 24 hr clock movement XC0102 Backward clock movement XW0405 Arlec 7 day timer XF7080 Phone/fax/modem line prot YS5520 12V Bug killer YT7010 Answ machine 1800 ZD1772 Dual Colour Rect Led 8.95 3.95 5.00 2.00 1.95 .75 4.95 1.50 4.95 3.95 4.15 24 .95 169.95 59.95 19.95 39.95 3.95 6.95 22.95 150 2.50 15.95 15.95 7.95 43 .95 4.95 2.50 14.95 14.95 34.95 99.00 29 .95 79.95 .50 1.50 100 40 14.95 99.50 20.00 995 19.95 1.50 2.95 14.95 .50 100 9 95 9.95 3.95 26.95 3.50 100 9.95 9.95 21 .95 50.00 17.95 50.00 .30 Ad CLEC.: R ~IC~ .JAYCJ.H E:LECTRONICS sJA','C,iH b .. ~ !HONIC ,,,, AH JA C 'F1 , L[CTR<JNICS JA'1CAF1 EU-C-RONICS J,\', CAR b.Lrl !RONI< c ',\,CAR ' JAYCAR ELECTROI\IC~ JA <'CAR F-LEC rn· J,:.,~ ~F· '.L ( "'R(V-.1r \f ' • 'NIC . 1s·%0FF VIFA SPEAKER KITS All in stock now. On demonstration in all stores Ideal if you are running large size speaker cable to your speakers . Size 92(W) x 79(H)mm . Cutout size 74(W) x 54(H)mm * 6A 8A 800mA 1.2A 2.4A 2.7A 6.5A 15A 24A 38A sers Guide to Cellular T lephones • Asia/ IC By N Boucher This book addresses the features, myths and lhe facls that are an importanl parl of cellular radio. With !his informalion you should be well equipped to choose the best mobile phone for your purposes. Knowing how cellular radio works, you will be able to get the most oul of your investment. Chapter headings include: • Choosing aphone• Cellular systems • The network • Anlennas • Balleries ·• Faults • Functions and features • Coverage • Fax and other devices • Privacy• Roaming • Digital cellular. II then covers each counlry separalely including Australia, NZ. Hong Kong and other Asian counlries. An excellenl book. See review In EA Sepl 91. CalBC-1140 SA-70 2 Way kit, 50 Walls RMS Spks/cabs normally $449 Cal CS-2471 /72 150/o OFF EVERY i 15% ()7"? GEL BATTERY I $313.65 Was Now Cat ~ 6V $8.95 1A $7.69 SB-2479 ; SA-100 $4.95 Cat PT-3006 j SA-50 , 2 Way kit, 30 Watts RMS \ Spks/cabs normally $369 , Cal CS-2450/52 6V 6V 12V 12V 12V 12V 12V 12V $14.95 $16.95 $16.95 $26.50 $29.95 $32.95 $43.50 $79.00 $99.95 l 2 Way kil, 70 Watts RMS $12.70 $14.40 $14.40 $22_52 $25.45 $28.00 $36.97 $67.15 $84.95 $127.45 SB-2477 [ Spks/cabs normally $699 SB-2478 '. Cat CS-2460/62 SB-2482 \ 15% SB-2480 ; $594.15 SB-2483 t; ()7"? 15% tJ7"? $381.65 SA-13 3 Way kit, 90 Walls RMS Spks/cabs normally $999 Cal CS-2471/72 15% tJ";"? $849.15 $9.95 .L&SS 15% $8.46 .I 15% OFF EVERY INVERTER I The very latest in sirens. Use it on your car alarm or just for fun. This amazing siren has six different siren sounds which can be wired up through a rolary swilch to swilch between lhem. Any combinalion can be connected togelher to give different sounds in a rotating manner. If you were lo describe the sounds you would say whoop whoop, laser gun, two lone warbler, screamer, beep beep. Give your car or house alarm a unique sound lo others. Operaled on 12 volt DC and sound pressure level on most sounds is around 115dB. Size 105(H) x 105(W) x 110(L)mm Cat. LA-5705 12V DC To 240V AC WAS NOW 100 Watt $189.50 300Watt $419.00 $161.07 $356.15 $211.65 $381.65 $424.15 300 Watt economy $249.00 300 W sine wave $449.00 500Watt $499.00 511411 DSDD 511411 DSHD from 115 Parramatta Road Concord to 311211 DSDD 311211 DSHD 6 LEEDS STREET RHODES NSW 213B Cat Ml-5050 Was Now $550 $4.67 $10.50 $8.92 $9.75 $8.29 $18.50 $15.72 Cat XC-4730 XC-4732 XC-4736 XC-4738 r· (02) 743 -5222 NEW FAX NUMBER (02) 743 2066 Only $99 95 NEW MAIL ORDER HOTLINE Business card size Photo size (02) 743 6144 ORDER LINE 008 022 888 , CAI Ml-5020 LAMINATOR Price breakthrough! Below $100! NEW PHONE NUMBER T Cat Ml-5040 Up until now, if you wanted to purchase a laminating machine to laminate business cards, it would cost you upwards of $400. Jaycar is proud to announce the arrival of our own directim orted laminator that will not only do business .cards, it will also ;rrG ' laminate photographs as well. It's so simple to use, you can protect and preserve your favourite photos (up to 4" x 6") (100 >/ 150mm), business cards, recipes, membership cards etc. I , Operates on 240V AC. Will heat up in 2-3 minutes. Come into any store for a demo._ Cat XL-2500 LamInat1ng cards available. • Larger warehouse and full showroom T Cat Ml-5000 15% OFF OUR ALREADY CHE $34.95 JAYCAR HAS MOVED Cat Ml-5030 95 x 57mm Pk! 100 Cat XL-2504 156 x 112mm Pkt 24 Cat XL-2505 $19.95 $12.95 ...., tlt. f-,' ~ -s AR A Ah ELE( ~ (l'-11! J CAR "''',I < Ar< F FC lf1l)'ilr', IAYCAR Lf'l Trll "Jll' .J, C ,\RF cC IHO'llU JAYCAR tlr- J." 1 \Ill~ 1-1. {· F HC':'\i!C '\Y( ARE_ f:_.._ flf T (l\ll( ;\'n. . AH LE n 'NI f-LEC TF•.)NIC" JAYCAR llc.C rnm,1cc "' ,Al L, C RONI< 'LfC 'HONICS JAYCAR FLrC~RONIC l,JAYCAR Elf V lRONI< (Akf- ~(fF~ •\Ill..½ .AYC:AR!U:C"'RON ICS.JAYCARFLFl.TRONIC~ JAYCARrL<- C.,.RQ 1rc il PHILIPS DOME Cat CT-2012 [ $26.50 Now $22.52 ! MOTOROLA 400W RMS PIEZO i Cat CT-1912 $37.95 Now $32.95 ~ VIFA D25 Cat CT-2020 I $74.00 Now $62.90 I• • T S MULTIMETER METEX Frequency counter, capacitance, logic Cat OM-1400 Was $79.95 Frequency capacitance , transistor, 20A, case Cat OM-1555 Was $129.50 Now $67.95 · ,.. Now $110.07 T M TE DIGIT JAYtAR 2 RANGE Cat OM-1410 Was $49.95 Now $42.45 T Frequency, transistor, capacitance, data hold, 20A Cat OM-1560 Was $189.00 IDRANGE Now $160.65 T ® WHITE CONE MID Cat CM-2080 1$28.50 Now $24.22 RESPONSE DOME MID Cat CM-2090 I $49 .95 Now $42.45 ; PHILIPS DOME MID Cat CM-2088 if $79.50 Now $67 .57 1 1 ! wooFERS it 8"$42.95 POL YCONE Cat CW-2114 Now $36.50 110" POLYCONE METEX 3650 CR Cat CW-2116 i $52.50 Now $44.62 f MAGNAVOX 12W Cat CW-2122 [ $59.95 Now $50.96 MAGNAVOX 12MV Cat CW-2125 t $119.95Now $101.96 i . f.,,:.:,,,-,.,.,.-.,...':, ,--;..;:;::::,;,~::,,,)...,:,:.:~::-,~'-::·, -~~-.. -. .-.-.:::.::.::.:::::,:::-:-..,-,.':-.,-:;~::.:~~~:::::,:.:«:.:•:~~:,:-::.:;;;,,:~=~:::--:.-:;.,,,~,,~,,,:.:;;~;;;;;;;;;;so;;: ·•:;;;:-::,'\'-,~'-~~ ,.,.,,,;;;-;,,..,} Cat OM-1420 "."""~=- Computer i ntertace bargraph, frequency, transistor, logic, relative offset, 20A, case, dalahold, min/max hold plus more. Cat QM-1450 Was $199.50 I Was $59.95 Now t $50.95 Grmder/Mmi Dr.II/Engrave h One of the most powerful small tools we have seen! This unit fits neatly into the palm of your hand (11 0mm long}, yet it's powerful 12V DC motor enables you to drill PCBs up to 2mm 0. It can also be used as an engraver as well as a miniature grinder. The unit is supplied with 2 grinding wheels, one engraving burr, a 10mm HS steel PCB drill and 2 brass collet chucks. A 9-18V DC, 1-2A power source is required. Cat. TD-2485 Fantastic value at $24.95 'Throw away' mini engraver P' TF T · r This very powerful but low cost dedicated engraver has a 1.8mm 0 ball-head burr interference fitted onto the motor drive shaft. We have engraved literally dozens of metal objects with this tool and the burr seems as sharp as ever! Obviously a quality HS steel bit. Once the burr wears out, however, it may be difficult to replace the bit, so we are calling it a 'throw away' engraver. We must emphasise that the fitted burr may be able to be removed and replaced bui we can't guarantee it. Who cares anyway at this price. This engraver will probably last a normal user lifetime! Requires 12V DC at 1-2A. CatTD-2480 Only $16.95 NEW MINI FAN ~ 40mm x 40mm x 20mm (dia}; (1.57" x 1.57" x 0.79"}. Ideal where size is a factor. Specifications: Bearing Sleeve and ball bearing Voltage 12V nom, 10.2 - 13.8 volts Current 100mA Input power 1.2watts Max air flow 0.15 (m3tmin} Max air pressure 3.50 (mm-H20} Noise 30dB(A} Weight 35mm CatYX-2502 $22.50 * GREEN ~ THUMB ~ ATTENTION POT LANT 0 ERS The green thumb will advise you when to water your pot plants. Put one in each pot plant and when they are dry, Green Thumb plays a tune. II requires one AAA ballery which lasts more that a year. Size 220(L) x 32(Dia)mm. Green Thumb is not a gimmick. IIWOfkS well. AAA BATTERY PKT 2 CAT SB-2375 $1.95 , I I 'JI ' KA-1702 50MHz Dig Freq meter $79.00 KA-1706 Cheap capacitance meter $21.95 KA-1707 Powermate 2 $119.00 KA-1717 Subwoofer Adaptor $29.95 KA-1718 Auto NiCad charger $42.50 KA-1719 NiCad discharger $27.95 KA-1720 RGB to PAL cncoclcr $39.95 KA-1736 18V 1A Bench Supply $79.95 KA-1737 Speech Proc for Tran $29.95 KA-1738 Karoake Box $27.95 KA-1739 Low Voltage Cutout $22.95 KA-17 40 240V Power Relay $49.50 KC-5012 Car radio power supply $28.95 KC-5013 16GHz Digital Freq meter $299.00 KC-5019 100W amp module $42.95 KC-5021 Protector car alarm $79.50 KC-5028 Train controller $89.00 KC-5030 High Energy Ignition $55.00 KC-5031 Optical tacho $49.95 KC-5032 Disco Light $159.50 ' KC-5033 Studio 200 Preamp $229.00 KC-5038 Universal power supply $12.95 KC-5039 Vader Voice $19.95 KC-5041 Mini Mitter $34.95 KC-5042 Knightrider LEDs $17.95 KC-5050 1/3 Graphic Equaliser $239.00 KC~5051 CD Compressor $49.50 KC-5052 Touch Lamp Dimmer $34.95 KC-5055 Stereo 1/2 Octave. Eq. $349.00 KC-5058 Multimeter Kit $38.95 KC-5059 Radfax decoder $44.95 KC-5060 Bal in/out for EO $27.95 KC-5071 Gel batt charger $69.00 KC-5072 Digital voice recorder $99.50 KC-5074 VOX with delay $59.95 KC-5075 CAP meter 1pF - 9999uF $109.00 KC-5076 Reluctor high energy $46.95 KC-5077 Stereo PRE AMP $32.95 KC-5079 Sine/Square Wave Gen $149.50 15% OFF EVERY KIT KA-1724 KA-1725 KA-1726 KA-1728 KA-1729 KA-1730 KA-1731 KA-1732 KA-1733 KA-1734 KA-1735 KA-1109 KA-1115 KA-1116 KA-1117 KA-1119 KA-1390 KA-1392 KA-1430 KA-1550 KA-1556 KA-1574 KA-1598 KA-1610 KA-1630 KA-1652 KA-1660 KA-1675 KA-1682 KA-1683 KA-1690 KA-1692 KA-1693 KA-1696 A-1699 h Volt up 1.5V to 9V $19.95 Pro series 1 power amp $599.00 Pro module less mosfets $47.95 VHF powermatch $52.50 RF probe - suit above $7.50 Pro series 2 pre-amp $329.00 Transistor/Fe! tester $32.00 Flexi timer $17.95 CRO adaptor $24.95 Quad DI box $69.95 CRO Adaptor for Monitors $159.50 Elect'ric Fence $24.95 300Wamp module $119.95 300W power supply $115.00 300W speaker protector $23.50 Transistor tester $21.50 Freq counter 50MHz $169.50 Prescaler 500MHz $46.50 Vocal canceller $24.95 Deluxe car alarm $89.50 Ultra sonic move detector $34.95 30V/1A power supply $99.50 40W inverter 12/230V $99.95 300W inverter 12/230V $269.00 12V lamp flasher $12.95 Blueprint 60/60 $369.00 Electric fence $62.50 Screecher car alarm $37.50 Dual track power supp ly $149.95 Battery monitor $14.95 DI box $39.95 Voice operated relay $24.95 Metronome $19.95 Econ. Temp probe DMM $19.95 Bench amp-signal trace $44.95 KC-5080 Horace the cricket $17.95 KC-5083 3 Digit counter $23.95 KC-5084 VCR Remote control ext $32.95 KC-5085 Discolight dimmer $39.95 KC-5089 Two Tone Siren $9.95 KC-5090 Sinewave Oscil lator $16.95 KC-5091 20W Fluoro Inverter $32.95 KC-5092 12V Light chaser $21.95 KC-5094 Stereo Audio Expander $39.95 KC-5095 DTMF Decoder $79.95 KC-5096 4 Ch Lighting Desk $329.00 KC-5097 Masthead Amp $49.95 KC-5098 Digital Tacho $34.95 KC-5099 PC Voice Recorder $32.95 KC-5100 Talking Voltmeter $42.95 KC-5101 Steam Sound Mk2 $19.95 KC-5102 Solar Batt Charger $34.95 KC-5103 TV Pattern Gen $110.00 KC-5105 Baby Monitor $24.95 KC-5106 Light Beam Relay $32.50 KE-4014 Mixer preamp $44.95 KE-4023 Signal Speaker protector $22.50 KE-4029 NiCad battery charger $14.95 KE-4033 Temperature probe $32.95 KE-4050 ETl480 50W amp module $27.50 KE-4052 ETl480 100W amp mod $34.50 KE-4048 ETl480 power supply $29.50 KE-4666 RS232 Centronics inter/f $32.50 KE-4690 ETl342 CDI $79.50 KE-4698 4 sector house alarm $32.95 KE-4711 Mini FM transmitter $9.95 KE-4724 Parametric equaliser $24.95 KE-4729 Guitar preamp $45.00 KE-4730 Solar Generator $13.95 KJ-7000 Red light flasher $19.95 KM-3044 6000 Mosfet Module ·$139.95 KM-3050 Workhorse amp $35.00 KM-3065 RS true 232 interface $27.95 KM-3068 FM minder bug $11.95 4 CHA NEL GUITAR Ml E /PREAMP KIT Rei: Silicon Chip Jan 1992. This kit re places our very popular ET1467 Mixer PreAmp released way back in 1980. This project lakes advantage ol lhe new low no:se, low cosl_op amps available. This unit lealures se parate bass, midrange and treblecontrols, ve ry tow. noise and d1 slorl1on, separate input level controls plus an output level control. Ideal tor use with most musical instruments lrom keyboards lo gu itars lo lape decks. In lacl, you can feed ii wilh jusl about any audio signal - il's not just limited lo guitar outputs SPECIFICATIONS: . Signal to noise ratio: (al SOmV inpul <at>1kH7)-AII inpuls cl osed: -96118 / All inputs oprn: -8211B Distortion: (al 1kHz and 1OOmV input)< 0.0075% Graphic equaliser: Bass: +/-14dB<at>1OOH_ 1(+/- 1dB inlcraclion wilh midra11uc); ,/-19118<at> SOH; (, /-0.3118 inleraclion with midrange) Midrange: ,/-11dB<at>1kHz (; /-08dB mteraclion w1 lh bass, +/-2dB inleraclion with treble). Treble +/-11 dB<at> 1OkHz ( ,/-2d 8 interaction wilh midrange). Maximum output: approx 23V p-p bclore clipping. Frequency response: 18Hz-35kHz(+/-3dB). The kit includes PC Board, polenliomelers, inpul sockets and all specilied cornponenls The kil does nol include the optional ground plane nor the 15V power su pply board (Cal KC-5038 - $12.95) ' /,~i l *********** ':."- -:-----:-~~1~,-:---=-".'"'"".-=--7--::~~~~~~-~~~:....:;.!.::...:.!..:______________J $4-9:95 , 'I ' I • L I- • ' , 11 ,I C 1 It T- 11J'. ( r IC Nii ., - r .' I ,,-.J ~ L I l, . ~ I f J;., I I C At \ /,r~ , T f 1 !r 1',JIC 1.\ .,r :n "J1 F SCOPE PROGRAMMABLE ALARM MODULE Eprom conlroll ed • 6 seclors plus 6 x 24 hour sectors. See previous ads for ful l detail s. Panel in abox is $199. Wehave aquantity without the boxes. Includes .1r===~iiiii■--==~ 7_____.1] 6:(~~i1;rual \.., Was $129.50 Now $99.50 _"1e44, 15% $84.57 ~ R . I, 1, ,I I ,•,., 15% OFF EVERY BURGIAR ALARM AND ACCESSORIES - . ' '- r.1,·.1, . H: !h . ~.I fie ·t'-,1 ,, Jli 'JI I Hi quality Zeus brand directl y imported by Jaycar. Why wail unlit afler you are robbed lo install !he alarm. Do ii now! See catalogue for full de tails. Complete systemincludes: _ __ _ _ _ 1 xControl panel 1 xpassive infra red detector/TX Normally 1 x Door/WindowReed delecior/TX i $599 1'X Hand held remote conlrol/TX : 1 x Horn speaker - 1Owallf.vired · 15% 1 x 240VAC adaptor 1 x 1.2Ah back-up battery 1 x Set of batteries for all TX Cal LA-5200 OPTIONAL EXTRAS: Door/Window Reed Wi reless Passive Switch -wireless Infra Red Detector Wireless Remote Keypad Control Cal LA-5210 Cal LA-5205 Cal LA-5215 Cal LA-5208 Was $69 15% tJ77 Was $129.95 15% ()77 Was $129.00 15% ()77 Was $59.00 15% tJ7'? $58.65 $1 10 .45 $ 109.65 $50.15 Cal LA-5170 _"1e44, 15% $21 1.65 it ·lflf !I N<, :. s (:iL;;~.- '. .__,:~'<_. ~: iI -•-•-•-------•-•-----•-•-•-•-•;_. ,_._.,,_.,._ •- --• . .. - .. · • -• _,,.._., ,_ • . •. i ,·.w.w1.•··0N.·.····•wM,.·mE.···mM.w.•.wo.w.·.Rw.•my.•..• $1 18.15 T.w.·E .·.·.·.•··,·········E _ ·.·.·.·..p·.-·.•··•H "·······o · "····~N··········E ..·.·.·.······, w .... : I.OW COST l :::: :::.:. :: :.:·;:::::.:::::.::: ~~-;~-~~: ::;:~<::·;;_,; _ ~,~-_.: :.: .: ;~;::.~.:~ ! , CA.It .• / .>·· ·.·.·•·•· <•··· - · JltiJlRMS SEE _<: ou~ ~~tVlllUS A~~- OR CALL IN FOR FULL > INFORMATION .. .I , L REMOTE CONTROL CAR ALARM cat LA-s9oo $129.50 Less 15% $1 10.07 Sirens extra on all models Cat LA-8908 or Backup Siren Cal LA-8910 $49.95 . .. ''" "'-; ke44, l 5% ON LY $84.96 1 •;n , I $ 11~rp·Fa:; i DURNEW 'I Hand Held Remote - wireless Was $249 .•.•.•.•-•.•-•-•.•••-•.•.•,,•.•,•,•.•;.•,•,.,•.•,,v.._._.,,_.,,,•.•.•., v .•,.•.v.-.•,-..,,•.,,,,,,•,•.-.---.v .•.w-----•-••'"-'•"-'-"'•"•'•-•. I 'I, tJ77 $509.15 -~ ... ,·, .. --:(;: --·~.0':'"1"~- _.,_. f GME ELECTROPHCiN"ifl ;··· REMOTE f \f I UHF WIRELESS BURCLAR ALARM Terminator Sector ,:__ Puls Count 4 . ''"", Keyless · Cal LA-5018 Was $89.00 Alarm Le44. 15% $76.65 Panel :: 1 • $19.95 L= 15% $16.96 L= . 15% $42.46 With Drivers Door Central Locking Cat LA-8902 $179.50 L e,u, 15% $1 52.57 With 4 Door Central Locking Cat LA-8905 $269.50 Le,u, I 5% $229.07 •, ,a,::•,u __:•:•-•- ;, - \_, ,_•; \ ••·•:-,.- ~--1-•i1 i . . : : 11 0 ' l=O Power Relay CalKA-1 740 0 , Cat KA-1739 SA BOATS $ 22.9 5 ~ $ 3 2.5 0 :rY~~J9Y~!~PwssrocK 1Nro cA~~n: r I 1 (J~YCAR) VILL)'URCHASE YOUR SURPLUS. STOCKS ? I 8ii e&iit8iiMmsAND EOliiPMENT. We ARE- t l d:Wl'tiil6Ad.'v ONTHE l.OOKOUT FOR SOURCES) ? , I \ ?f PRIMEOUALITYMERCHANDISE.••·. ( : ~i1;,tl:;~~;;;,~f;~s:z~2t:~~~J $49.50 T Ref: Si licon Chip December 1991 This simple project al lows you lo monilor a doorway or a palh using an infra red lighl beam. When someonewal ks lhrough !he beam, ii !riggers an alarm for a1 second period. Kil includes PC board, case, panel and all specified parls. Pfugpack and oplional relay are no! supplied Plugpack Cat. MP-3006 $15.95. Cat. KC-5106 ~ r-~""'-- "~~-~-~-~:--- '-;-- ---- -~--- ----.-~:~~-"'1 TERN CENERATOR KIT Rei: Silico n Chip Novem ber 1991 Thi s new co lour TV pa lt ern generalor produces seven sepa rale pa lterns: checke rboa rd, crosshalch , dot, greyscale, white raste r, red ras ter and co lour bars. II wil l enabl e you lo sel your TV's con verge nce and puril y for !he bes t possible picture. Th e Jaycar kil includes PCB punched and sc reened fronl panel, modulator and all specified componenls . 12V AC plugpack nol suppl ied. Cal. MP-3020 $16.95 Cat. KC-51 03 CA Ref EAJanuary 1992 Build thi§ simplekil and avoid gelling caught out wilh aflat car ballery. It simply connecls inlo a 12 volt accessory's powe r line and shuls off theflow if !he ballery's voltage drops lo a dangerously low level, where ii won't slarl !he vehicle TheJaycar kil includes PCB, box, relay and all specified components. Ref EA Jan 1 1992. This , sim ple kil will monilor lhe power drawn froma ·masler· sockel and aulomalically swilch on a slave socKel. lls very versalile because ii can monitor one or several appliances plugged inlo the ·master· and switch one or seve ral devices plugged into the slave. An ideal use for !his project would be to swilch on your HiFi system. Wilh a 4 outlet board plugged into lhe slave socKe,I lurning on your amplifier (in masler) will swilch on your luner, !ape deck, CD player, turntable. TheJaycar kit includes PCB, box, 240Vsockels, lead and plug and all specified componenls. $11 0 a er - c or. 1 Ref: Silicon Ch ip November 1991 A Jaycar homegrown kit. If you need lo operate any eq uipmenl from solar power, you will need a charger. This unit wi lt stepdown the vollage lo the balleries when !he solar panels put oul more lhan 15V and stepup the vollage when there less than 12 volts available. Wi ll work with any solar panel regardless of waltage, but kit will limit currenl lo 2 amps which is equivalenl lo around a 25 wall panel. Kil includes PCB, polcores, healsink and all specified componenls. •• ·u t: $34.95 The OP-2230 is a compacl, 20MHZ, 16-channel logic monilor wilh unique, cuslomIC design. Aulodeleclion of power and ground pins makes inslrumenl usage an easy, clip-on-and-view operalion. Aulodeleclion of bolhTTL and CMOS logic levels is also provided. The pulse lalch funclion easily delecls and displays shorl-duralion pulses. Functionall y equivalenl to sixleen 20MHz logic probes, the UT-2020 also provides indical ion of high, low and pulsing inpuls. 11 lhe pul se repelil ion raleis over eighl herlz, lhe pulseLED flas hes al an 8Hz rale. The cuslom ICdesi gn allows use ol lhe uni! a clock rales of up lo 20MHz. Specilicalions: ICs lesled CMOS & TTL digital, 16-pin DIP max imum Config uration Dual in-lineclip-on package wilh oulputs for scope mon itoring lnpul impedance 1Mn (approximate) Display Hi gh LED on Low LED off Pulses LED blinking Operational frequency DClo 20MHz Laich mode Lalches first pulse detected until manually reset Operational vollage 4 10 15 volls DC . Cal QP-2230 Overvoltage proleclion 20 volls absol ule maximum Tempe ralurerange -10° to+70°c ONLY Dimensions 8.6 X3.4 X3cm(H XWXD) * NE M DEL 20MHz C 0 Quality Hung Chang Model 3502 INTRODUCTORY PRICE $699 .4t!44 15% $594 .15 Features include: • TV signal lriggering • High reliabilily • Low power consumplion (19 walls) • Lightweight (6.5kg) • Wide bandwidth and high sensi livily • Front panel electrical trace rotator CRO Cal. OC-1900 PROBES Cat. OC-1902 $39.50 ea Leu 15% $33.57aa (2 required) $79.95 hE D OFFICE 6 Leeds Street Rhodes 2138 Telephone (02) 743 5222 FAX (02) 743 2066 ~ c ·- -- -- VISA EY - CITY PARRAMATTA HHODES BANKSTOWN GORE HILL POST & PAC ING $10 - $24.99 $25 - $49.99 $50 - $99.99 OVER $100 $ 3. 75 $ 4.50 $ 6.50 $ 8.00 117 York St. (02) 2671614 Mon-Fri 8.30 - 5.30 Thurs 8.30pm - Sat 9 - 1 355 Church St (Cnr. Victoria Rd) (02) 683 3377 Mon-Fri 5.30 Thurs 8.30pm - Sat 9 - 4pm Sunday 10am - 4pm 6 Leeds SI (02) 743 5222 Mon-Fri 8.30 - 5.30 - Sal 9-1 2 363 Hume Hwy Cn r Meredith SI (02) 709 2822 Mon-Fri 9- 5.30 Thurs 8.30pm - Sal 9 - 4-Sun 10 - 4pm 188 Pacific Hwy (Cnr. Bellevue Ave) (02) 439 4799 Mon-Fri 9 - 5.30 Thurs 8.30 - Sat 9 - 4pm 9- MAI P.O. Box 185 Concord 21 37 FREE CALL. FOR ORDERS ONLY ROAD FREIGHT ANYWHERE IN AUSTRALIA (up to 20kg) $13.50 BURANO D COBURG VIC MELBOURNE CIT SPRINGVALE VI ADELAIDE SA \ (008) 022 888 HOTLINE (02) 743 61 44 144 Logan Rd (07) 393 0777 Mon-Fri 9- 5.30 Thurs 8.30 - Sat 9- 4 266 Sydney Rd (03) 384 181 1 Mon-Fri 9 - 5.30 Fri 8.30 - Sal 9 - 4 Shop 2, 45 A'Beckelt St Cily (03) 663 2030 Mon-Fri 9- 5.30 Fri 8.30 - Sat 9 - 2 887-889 Springvale Rd Mulgrave (03) 547 1022 Nr Cnr. Dandenong Rd Mon-Frl 9-5.30 Fri 8.30 - Sal 9 - 2 190 Wright St (C nr. Selby St) (08) 231 7355 Mon-Fri 9 - 5.30 Fri 8.30 - Sal 9 - 12 Baby room monitor & FM transmitter This Baby Room Monitor allows you to listen to your baby from a remote location using a conventional FM receiver. It runs from a single 1.5V AA battery & includes a muting facility so that it only transmits sounds above a certain level. By JOHN CLARKE The SILICON CHIP Baby Room Monitor is an ideal aid for busy parents wanting to keep a check on their baby at all times. It's basically a simple FM transmitter fitted with a microphone. In use, it's positioned close to the baby and broadcasts to a standard FM receiver while you get on with the gardening or washing the car. This project will also be useful if you have a large house and the baby's room is some distance away from the main bedroom or the living room. The useful operating range is about 30 metres, so it will have no trouble broadcasting from one end of the house to the other. As can be seen from the photos, the project is housed in a small plastic case. There's just one control - a small slider switch on the side to turn the power on or off. The remaining parts are mounted on a small PC board and include a trimpot to adjust the sensitivity of the unit and two coils to adjust the transmitting frequency. The receiver can be any FM radio ranging from a personal portable to a mantel or "ghetto blaster" style receiver, or even a stereo hifi tuner. You simply preset the monitor to transmit on an unused frequency of the FM band and then tune the receiver to match. Block diagram Fig. l shows the block diagram of the Baby Room Monitor. The circuit is based on an FM stereo transmitter IC, the BA1404 made by the Rohm Corporation of Japan. This IC includes left and right channel amplifiers, a multiplexer which can be locked to a crystal, a mixer, an RF oscillator and an RF amplifier which drives the antenna circuit. These circuit blocks can be connected to produce a stereo FM transmitter, as described in SILICON CHIP, October 1988. In this application, however, the left and right channel amplifiers are effectively connected in cascade so that the BA 1404 only transmits a mono signal. This is done for two reasons: (1) to provide sufficient gain for the microphone signal; and (2) because no-one really wants to listen to a baby wailing in stereo. The signal from the electret microphone is applied to the input of the right channel amplifier which operates with a nominal gain of 30. Because its output is connected internally to the multiplexer switch and is not available on any pin of the IC, we have derived the amplified signal from the right channel balance output. This output is a high impedance and so is buffered using Ql to prevent loading by the gain control (VRl). From VRl, the signal is applied to the left channel amplifier which also has a nominal gain of 30. The balance JANUARY 1992 53 output of this amplifier is connected to a voice operated switch (VOX) which controls the internal multiplexer switch via the oscillator input at pin 5. When the signal level from the microphone is low, the signal from the left channel balance output and thus from the VOX is also low. Thus, the multiplexer diverts the right channel output through to the following internal buffer stage. Because the right channel output provides only the first stage of amplification, the signal level from the multiplexer buffer is thus effectively muted. Conversely, when the signal level from the microphone goes high, the output of the vox also goes high and the multiplexer switches the left channel output through to the following buffer stage. Because the signal has now been through two stages of amplification, it is at quite a high level. This signal is AC-coupled via C3 into the RF mixer oscillator stage. 11 and Cl are used to tune the mixer output, while the two 15pF capacitors on pins 9 & 10 provide positive feedback to ensure that the mixer oscillates. Its output drives an RF amplifier stage which in turn drives the antenna via C4. 12 & C2 tune the RF amplifier output and effectively filter out any sidebands generated by the mixing process. Circuit details Fig.2 shows the final circuit for the Baby Room Monitor. Supply de- This close-up view of the assembled PC board clearly shows the winding details for Ll & L2. Note also the orientation of multi-turn trimpot VRl. The PC board clips into guides running down each side of the plastic case. coupling for the electret microphone is provided by a 1kn resistor and lOOµF capacitor, with the microphone then fed via a second lkQ resistor. Its output is coupled via a 10µF capacitor into the right channel amplifier input at pin 1. The right channel balance output is buffered using transistor Q1. This is wired as an emitter follower and provides a gain of close to 1. The output at the emitter is tapped using VR1 to provide gain control and the signal then applied via a lOµF capacitor to the left channel input. The left channel balance output appears at pin 17 and is applied to the base of Q2 via a O. lµF capacitor and lOkQ resistor. Q2 & Q3 form the vox. When the signal from the left balance output is low, Q2 is biased on and so Q3 is off. Thus, the vox output at Q3's collector is low and so the output of the right channel amplifier inside ICl is switched through to the internal buffer, as described previously. Conversely, when the signal from the left balance output swings high (ie, when the baby cries), Q2 turns off and Q3 turns on. Q3's collector is now high and thus the output of the left channel is switched through to the buffer. The lOOµF capacitor on Q3's collector filters the vox output +1.5V C1 BUFFER 15pF .p 15P.F C2 10 RF MICROPHONE ELECTRET ] ANTENNA BUFFER AMPLIFIER ,__.......,.~ ]l_.,.1 _,..._c,• Rf MIXER OSCILLATOR OSCILLATOR IN 17 5 IC1 OUT BA1 404 13 14 12 C3 vox Q2,Q3 54 SILICON CHIP Fig.1: block diagram of the Baby Monitor. The circuit is based on the BA1404FM stereo transmitter IC which has been adapted here for mono operation. 1k 100. +1.5V + - 16VW+ C3 10 .01I + 14 C1 47pF _NPO .,. 16VW 12 vc OSC'-"O.___ _ 1k 15pF NPD GAIN VRk1.l!l--------t 1 10 osc--15pF NPOl .,. 16VW - IC1 BA1404 + 1 RIGHT IN BAl L 7 ELECTRET MICROPHONE RF 8 GN RF OUT AUDIO BIAS 2 + 10 16VW:r ANTENNA · ~ · .. :f ----NPO .0011 0.1 LOW• RIGHT CHANNE AT MPX OUT HIGH • LEFT+ RIGHT CHANNELS AT MPXOUT 10k .,. C2 47pF NPO 02 BC558 E VIEWED FROM BELOW 100k L1, L2: 1.5T0.62mm ECW DN 5mm FORMER WITH F29 CORE 100 ROOM MONITOR + 16vwr- .,. Fig.2: the circuit uses Ql to buffer the right channel balance output while Q2 & Q3 form a VOX circuit. When the signal level from the microphone goes high, the output of the VOX also goes high and the multiplexer inside ICl switches the high gain left channel output through to a following buffer stage. This signal is then ACcoupled via C3 into an RF mixer stage & thence to an RF amplifier which is tuned by C2 & L2. to prevent rapid cycling of the multiplexer switch. Strictly speaking, Q2 & Q3 do not form a vox circuit at all. Instead, this part of the circuit is really a threshold switch which is used to select between two levels of gain. However, its effect is exactly the same as a true VOX circuit, in that it effectively "kills" CAPACITOR CODES 0 0 0 0 0 0 0 0 Value IEC Code EIA Code 0.1µF .033µF .01µF .001µF 47pF 15pF 4.7pF 100n 33n 10n 1n 47p 15p 4p7 104 333 103 102 47 15 4.7 the output under no-signal conditions. Power for the circuit is derived from a single 1.5V battery and is switched by Sl. The remaining components depicted on the circuit (except for the lOµF audio bias and .OlµF decoupling capacitors) are exactly as depicted on the block diagram (Fig.1). Construction Fig.3 shows the construction details. All the parts except for the switch arid the electret microphone are mounted on a small PC board coded SC06210911 and measuring 62 x 46mm. This is housed in a standard plastic case which is fitted with & self-adhesive dress label to indicate the switch positions. Start construction by checking that the PC board fits neatly into the case and that it is supported on the stops of the PC guides. These stops enable the PC board to be mounted horizon- tally but they must be lowered by about 4mm so that there is sufficient clearance for the battery. You can achieve this by carefully cutting away the guides with a pair of side cutters. If the PC board is too wide, it can be filed down to size until it fits neatly into the case. This done, check that the two coil formers can be fitted.into their respective mounting holes. Enlarge the holes if necessary (using a tapered reamer), then install the two coil formers from the copper side of the board and glue them into position using 5-minute epoxy. The IC can now be installed on the board, followed by the three transistors. Note that Ql is an NPN type while Q2 & Q3 are both PNPs, so don't get them mixed up. The next step is to wind the coils on each former. Each_coil is wound by · first stripping the enamel from one end of the enamel copper wire and JAN UA RY 1992 55 SINGLE CELL HOLDER (SEE TEXT} PARTS LIST Fig.3: here's how to.mount the parts on the PC board. Keep all leads as short as possible & note that most of the resistors are mounted end-on to save space. The coil formers for Ll & L2 are installed from the underside of the board. 1 plastic case, 82 x 54 x 30mm 1 PC board, code SC06210911, 62 x 46mm 1 electret microphone 1 miniature double-throw slider switch 1 AA cell holder 2 5mm screw core formers 2 F29 ferrite screw cores 1 100mm length of 0.62mm enamelled copper wire 1 750mm length of medium duty hookup wire 1 1kn 25-turn top adjust trimpot, Bourns 3296W (VR1) Semiconductors 1 BA 1404 stereo FM transmitter (IC1) 1 BC548 NPN transistor (01) 2 BC558 PNP transistors (02, 03) The microphone is secured to the case by carefully reaming its mounting hole to size until it is a tight fit. Note that the switch terminals must be splayed outwards as shown here to provide clearance for the PC board. soldering it to the board. You then wind on 1.5 turns and solder the free end into the remaining pad. The remaining parts can now be installed as shown in Fig.3. Note that all but one of the resistors are mounte.d end-on to save board space. Make sure that the five electrolytic capacitors are all correctly oriented. If you can't obtain a single AA-cell holder, you can make one by cutting a dual cell holder in half. The spring at the negative end is soldered directly to the board, while the positive termi- nal is connected to the board using a stout piece of tinned copper wire. Once the PC board is complete, the case can be drilled to accept the microphone and on/off switch. These parts are both mounted on one end of the case. Drill a small pilot hole for the microphone to begin with, then carefully ream it to size until the microphone is a tight fit. The square cutout for the switch can be made by first drilling a series of small holes and then filing to get the correct shape. The switch is then Capacitors 2 100µF 16VW PC electrolytic 4 10µF 16VW PC electrolytic 1 0.1 µF monolithic 1 .033µF metallised polyester 3 .01 µF ceramic 1 .001 µF metallised polyester 2 47pF NP0 ceramic 2 1SpF NP0 ceramic 1 4.7pF NP0 ceramic Resistors (0.6W, 1%) 1 100kQ 2 1kQ 310kQ secured to the side of the case using two small self-tapping screws. It will be necessary to splay the switch terminals to clear the edge of the PC b'oard (see photo). A small (2mm) hole can now be drilled in the other end of the case for the antenna wire. This done, connect the microphone and switch to the PC board using light-duty hookup wire and connect a 750mm length of medium-duty hookup wire for the an- RESISTOR COLOUR CODES 56 0 No. Value q 1 0 0 3 100kQ 10kQ 1kQ SILICON CHIP 4-Band Code . brown black yellow gold brown black orange gold brown black red gold 5-Band Code brown black black orange brown brown black black red brown brown black black brown brown C06210911 1IJl!!!f BABY ROOM MONITOR ON OFF Fig.4: actual size artwork for the front panel. Fig.5: actual size PC artwork. tenna. Tie a k:hot in the antenna wire before passing it through the case to prevent it from coming adrift. Finally, push the PC board into the case and attach the adhesive dress label to the base (which now becomes the front panel). Be sure to attach the label so that the switch markings are adjacent to the on/off switch. Check your work carefully for assembly errors, then install the battery, switch on and check the supply voltage to the IC. You should get a reading of 1.5V between pins 15 & 3. Tuning adjustment The unit can now be adjusted for correct operation using an FM receiver set to an unused frequency near the centre of the band (around 100MHz). Set VRl to minimum gain (ie, rotate the adjusting screw clockwise until you hear a click), then screw the slugs into the coils. Initially, set Ll so that its slug is level with the top of the former and L2 so that its slug is about 2mm above the top of the former. Now adjust Ll until the transmitter frequency matches the receiver. This will be indicated by the level meter on the receiver (if it has one) and by a sudden drop in the hiss level. When the correct point has been found, wind The completed PC board fits inside a small plastic zippy case to give a really compact assembly. Oscillator tuning coil L1 at top right is used to tune the unit to the desired frequency, while L2 tunes the RF amplifier for maximum range. VRl slowly anticlockwise until you hear a signal from the radio (make sure that the microphone is picking up sound) and adjust L2 for maximum signal. To set the transmitter to a lower frequency, wind the slugs further into the coil formers. Conversely, to set Specifications Operating voltage ............................................ 1.5V Quiescent current ... .. ....................................... Typically 3mA Frequency range ............................................. 88-108MHz Range .............................................................. 30 metres (approx.) Dimensions ...................................................... 82 x 54 x 31 mm the frequency to the high end of the band, wind the slugs further out of the formers. Note that both slugs should be set to similar positions in the formers to get the best result. The coils are also slightly interactive which means that adjusting one will affect the other. Always use a plastic alignment tool to adjust the coil slugs. Don't use a metal screwdriver as this will damage the slugs and give misleading results. Finally, adjust the gain control so that the unit transmits only those sounds that reach the required threshold. Don't advance the gain control too far though, otherwise you'll get instability which will give a highpitched whistle from the receiver. SC JANUARY 1992 57 VINTAGE RADIO By JOHN HILL Restoring an AWA Radiolette receiver In the mid 1930s, AWA produced a popular series of mantle radios under the tradename "Radiolette". The Radiolette appeared in various shapes and sizes and was still a popular receiver during the immediate post-war era. The early versions were mainly in black or brown bakelite but some coloured cabinets were also made. These were mostly in "ivory" or "jade". The coloured models have not survived in the same numbers as the bakelite models - perhaps there were not as many made? These early Radiolettes were nicknamed "Skyscraper" models because their shape was vaguely similar to that of the Empire State building in New York. There was also another version of this little mid-1930s receiver. Although the chassis was virtually the same, it was housed in a timber cabinet (still with skyscraper lines) but with a small round dial instead of the square dial that characterised later models. All of these mid-1930s Radiolettes are very collectable items and are much sought after by vintage radio collectors. For this reason, I was quite pleased when I recently obtained a 1934 timber cabinet version for a very reasonable price. Although the set was Radiolettes were still being produced in the early post-war years. This 4-valve model has octal valves and is oflate 1940s vintage. 58 SILICON CHIP not working, it was all there, in excellent condition and completely original throughout. This month's Vintage Radio story is about restoring the old Radiolette to working order. As with most early superhet receivers, there were plenty of things to check and replace, but that is fairly normal when working on a radio receiver that is nearly 60 years old. Routine checks In keeping with my usual routine procedure, I started the job by checking out a number of vital components - the ones that often break down in a receiver of this age. Continuity tests on the power transformer primary and high tension secondary windings showed that they were OK, as were the radio frequency (RF), oscillator and aerial coils. The intermediate frequency (IF) transformers also tested OK. Preliminary checks of this nature are very worthwhile, as they will quickly locate any trouble spots. The loudspeaker was the first major component to fail the test. While the field coil checked out OK, the output transformer primary winding was open circuit. This is not an uncommon fault with valve radios and the output transformer should always be a suspect component until proven otherwise. Fortunately, luck was on my side for a change as a search through my spare output transformers revealed a similar unit in working order. It was quickly fitted to the loudspeaker mounting and wired up accordingly. That was one problem taken care of. The valves were next and they were cleaned and tested. All were in excellent condition with the exception of the 80 rectifier which was very sick The 1934 Radiolette in unrestored condition. The set had been well cared for in its 57 years and was completely original throughout. indeed. This suggested that there could be a problem somewhere in the high tension circuit, a suspicion that proved correct later on. These early Radiolettes vary considerably in their under chassis construction. Some have little component boards with numerous capacitors and resistors attached, while others have a big bundle of parts which are taped together and attached to one endplate of the chassis. Neither arrangement is particularly easy to work on. My little Radiolette was of the bundle type and if readers care to check with the appropriate photograph, the word "bundle" is about the only word one can use to describe this type of construction technique. Obviously, the printed circuit board hadn't been invented in the 1930s. Replacing components in the bundle must be done carefully in order to maintain the existing circuit. Capacitors should be removed one at a time and appropriate replacements fitted in their place. With a receiver of this age it is advisable to replace all of the paper capacitors, whether they be in the bundle or elsewhere. Now most old capacitors are well marked. If a capacitor has a value of O. lµF, then it usually says so somewhere on the casing. Not so with the Radiolette's capacitors. These particular paper capacitors are colour coded with three colours, This 1936 bakelite Radiolette is a more common version of this popular range ofmid-1930s receivers. Unlike the timber version, it carried a square dial. The high voltage electrolytics are installed in a square metal can on top of the chassis where the thin asbestos heatshield does little to protect them from the hot rectifier valve. The asbestos was made safe by sealing it with clear Estapol®. similar to the way a resistor is marked. In this case the colours have the values of the standard colour code and the capacitance is in picofarads . For example, consider a capacitor that is marked red, green and yellow. The capacitance is worked out as if it were a resistor; ie, the first colour represents the first digit, the second colour the second digit and the third colour the multiplier in tens. Thus, red is 2, green is 5, yellow is 4 = 250,000pF or 0.25µF. I hadn't come across this system before and, initially, I could only assume it was similar to that used for resistors. After checking some of the capacitors with a capacitance meter, my assumption was confirmed. Electrolytic capacitors The paper capacitors weren't the only capacitors in need of replacement - the electrolytics were also on the sick list. Time treats old electrolytics most unkindly and as these particular capacitors were approximately 5 7 years old, it seemed logical to reJANUARY 1992 59 There's not much room underneath the chassis of a mid-1930s Radiolette. Taking up most of the available space are the IF coils and the 3-gang tuning capacitor. The inaccessible volume control potentiometer is to the left of the IF cans. It has a somewhat unnecessary friction drive reduction connecting it to the control knob shaft. place them all without question. There were two 25V cathode bypass electrolytics in the bundle which needed to be replaced. One carried a value of 25µF, the other 5µF. Both were totally inoperative and judging by the cracks in the ends of them, they had dried out many years ago. The replacement electrolytics were modern types rated at 22µF 63VW and 4. 7µF 63VW. As ail the replacement capacitors were small modern types, the bundle looked a bit gutless when the change over was completed. That's one good point about replacing old capacitors with new units - the modern varieties take up much less room. The two 8µF high tension electros were next on the list. These are housed in a steel can which is bolted to the chassis next to the rectifier valve. This w~uld be about the worst possible place to mount the electrolytics, since A front view of chassis. The large metal container at the near end houses three of the five valves. The loudspeaker is an electrodynamic type and was still in working order. 60 SILICON CHIP it subjects them to a considerable amount of heat. The thin asbestos heatshield becomes quite ineffective after the set has been operating for several hours. Removing the top of the can revealed that the original capacitors were sealed in a mass of black wax. They were quickly released by gently heating the can, so they were not as difficult to remove as first thought. One of the electrolytics was completely short circuit, which could have been the reason for the almost defunct rectifier valve. Any short circuit or high leakage situation in the high tension line will over-work the rectifier. The high tension electrolytics were replaced with modern 450VW units. They were reluctantly installed inside the chassis mounted can and the hot working conditions ignored. There is little room under the chassis for additional parts. Getting it going A quick check of the resistors with an ohmmeter showed that they were all OK and within tolerance. The end was near; all that remained was to clean and lubricate the dial mechanism, and fit a new power cord. The set was now ready for a trial run. The little receiver worked surprisingly well and required very little in the way of re-alignment to bring it to peak performance. Even the loudspeaker sounded OK which isn't always the case with an old Radiolette. The little AWA's output transformer was in need of replacement (primary open circuit). Fortunately a spare transformer was discovered lying in my junkbox. RESURRECTION RADIO Vintage Wireless Specialists All of the original paper and electrolytic capacitors were replaced. This procedure can solve a multitude of problems and is a must if a trouble-free restoration is required. Repairs - Restoration - Sales Our skilled technicians offer QUALITY repairs and restoration. We also have a large stock of bakelite and timber radios fully restored and for SALE. Parts are available for the enthusiast, including over 900 valve types, high voltage capacitors, transformers, dial glasses, knobs, grille cloth etc. Circuit diagrams for most ~ustralian makes and models. Send $5.00 plus SAE for our catalog. HOLIDAY SPECIAL: 10% OFF ALL ORDERS IN JANUARY Call in to our showroom at: 51 Chapel Street (PO Box 1116), Windsor, Vic 3181. Telephone: (03) 529 5639 Silicon Chip Binders The infamous bundle: this mass (mess) of components consists of paper and electrolytic capacitors, carbon and wirewound resistors, and insulating pieces of cardboard. The bundle need not be removed from the receiver and is best left hanging on its many connecting wires while individual components are replaced. These small electrodynamic speakers frequently have a buzz or rattle in them and often sound every bit their age. I was very pleased to note that the volume control was smooth and quiet in its operation. Replacing a volume control in one of these radios is one "helluva" job. In fact, when it comes to servicing, there are few sets worse to work on than a mid-1930s Radiolette. Running the set continually for a number of hours proved that everything was working well. No overheating of the power transformer or the loudspeaker field coil was evident, which is a good indication that nothing is being overloaded or working abnormally. The mid-1930s Radiolettes are very collectable radios and have an appeal that many other receivers of that era lacked. I'm quite sure that most collectors would consider them, as I do, to be "classic radios" of their era. SC These beautifully-made binders will protect your copies of SILICON CHIP. They are made from a distinctive 2-tone green vinyl & will look great on your bookshelf. Price: $A11.95 plus $3 p&p each (NZ $6 p&p). Send your order to: Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Or fax (02) 979 6503; or ring (02) 979 5644 & quote your credit card number. JANUARY 1992 61 FECTS MIXER A conaol or freestanding mixer with 8 i11built special effectL Designed for both DJ and studio use. The following Inputs are provided: 2 x turntables • 4 x line Inputs • 2 x low impendance microphoneL Eight special effects: siren, telephone, machine gun, bombing, shooting, ambulance. thunder, laser. Other features: bass & treble control, Headphone Cue monitoring. CHI to CH2 cross fader. mic talkover switch. master volume level control and left & right LED VU meters. INDOOR SPIRAL ANTENNA • 300 ohm ribbon cable antenna • Suits AMtFM tuner• and portable rv·s. • 1 metre lead with 300 ohm spade termi1a1a L15040.............. ~9.95 A12013 .............................................$299.00 VIDEOCAM / VCR AUDIO MIXER A professional audio mixer designed for the serious home video movie maker through to the home video camera user. Background music and effect• can be faded in and out to existing video tape sound tracks. Ideal for weddings, family. sporting and other recordings. • Input for a video camera, VCR, CD, tape, tuner, auxiliary and turntable. •·Mic panpota • Mic faders• Turntable faders• VU meters • Mono/stereo switches • CD/Tape fader & more. A12004 ....... .... ............... ............ .......$169.00 ~..iit ~ SURGE/SPIKE SAFETY PLUG Stand alone 3 pin plug Plugs into socket adjacent to the equipment that you want to protect. All outiets on a power board can be pro1ected by inserting the Triangle Surge/Spike Plug Into any of the free ouUets. Green safety neon glow• when power is on. Approval No. VB8029 Total energy rating: 225 Joules (10l1000us) Protection level : 275V Nominal. 475V Peak. Response nme: Better than 10 nanoseconds. Automatic to eix batteries similtaniously. Charges UM3. UM4. & UM5 nicads. Charging circuits are automatically selected depending on the pt,ysical size of the battery and the charger . charging time 10-14 hrs. 240V AC mains operated. Requires NM4 or NM5 charging modules if UM4 or UM5 batteries are to be charged. M23523 ............. $22.95 C HEADPHONES) ~ c::::~ .,i?.€= SURGE/SPIKE SAFETY CORD SET 3 pin MAINS plug to 3 p in IEC plug Plugs directly into your equipment and replaces your existing cor~•set. Clear moulded plugs at both ends with green safety neons that glow when power ia on. Approval Numbers: VBB029, V900297, VB5006. Total Energy Rating: 225 Joule ■ (10l1000ua) Protection level : 275V Nominal. 475V Peak. Response Time: Better than 10 nanosecond&. Automatic reset X10080 .................. $39.50 • Compact portable deak mount or panel mounting stereo mixer with 5 band graphic equalizer and twin LED display VU meters. • 3 x atereo magnetic turntable inputa awitchable • 3 x stereo line inputs• switchable • Headphone monitoring on all channels • 18 dB talk over switch • Output sockets for both the amplifier and tape deck A1 201 2 . ......... $399.95 VIDEO ACCESSORIES VHS VIDEO HEAD CLEANERS New "wet .dry. we!" system cleans and dries all parts which come into contact with the magnetic tape. Fluid is applied directly on to cloth cleaning tape prior to use . It uses clean tape for each cleaning operation . Low drag for use in sensitive mechanisims . A11456 .. .. ......... ........ S16.95 ONE INFRA RED REMOTE CONTROL FOR YOUR VCR, TV, CD, HIFI, & Aux! This unit will replace all your existing remotea & is programmable to replace future ones. Has liquid crystal display. Clock, alarm & countdown timer•••$67.95 AUDIO ACCESSORIES COMPACT DISC CASES Packet of 3 standard replacement compact disk cases. (\~ ; \ \~ ,' 410030 ..... . HS-3000 HANDY SCANNER INCLUDES FREE SOFTWARE! PC PAINT BRUSH & IMAGE TOOL • Wide 4.13" (105mm) Scan width • 100/200/300/400 awitchable DPI resolution • Four encoded mode•: 8/W and three half tone patterns. • Thrity-two lh•de• of grey. • Built in scanner view window for accurate scanner placement. X19945 ... .. .... .. ....... . r· ~ POPULAR DELUX HEADPHONES These headphone• have large soft ear cushions ■ a well aa having individual left & right channel volume control. A14005•... .....•. $34.95 - :,----- $269 l: !' . .. . $7.95 L., MOU SE CLEAN ING KIT Keep dust and dirt from damaging your mouse with this handy mouse cleaning kit. This special rounded tool will find its way into all the hard to get at places. The kit also comes with cleaning fluid and 5 soft cloths to keep your mouse spotless! a C2 1071 ... ...... .... .... $9.95 . . MOUSE KIT Everything you need to keep your mouse happy! You get a mouse pad, a mouse holder, a cleaning kit (previously described) and a cute little mouse cover. C21072 .. ............... .. $16.95 -~-.> ~ VIDEO / AUDIO TRANSMITTER MOUSE GIFT SET Here it is! The ultlmate mouae kit. You get the cu1e little mouse cover to protect it from dust, the mouse cleaning kit with the rounded tool & 5 cloths,-the mouse house and mouse pad all In a handy black case. C21074 .................. $19.95 A small compact unit that allows transmission of video & audio signals (RF) to any TV set or VCR within range ol 30 NOW ONLY.. ... $84.95 free of dustl · C21069... .. ,=--· y ·- ' xT• Cover Set C21066 .................. $14.95 AT• Cover Set C21068 .. ... ...... ....... $16.95 metres. Ideal for watching videos in the bedroom or kitchen without having to move the entire VCR or having long extention leads running through the house. Can also be used as a transmitter for a video camera. With power on/off switch audio and video leads and supplied with an AC adaptor. A16150 Normally .. $95.95 MOU S E COVER Be the first in your office to have a mouse that every one will want use. This cute little mouse cover puts a bit of fun and colour onto your desk while keeping your mouse 1,~~~~il,' Keep your computer and accessories.. free of dust and grime while not in use MINI STEREO EARPHONES lmpendance: 32 ohms Sensitivity: 96dB Freq. response: 40· 10,000Hz Cord length: 1.2m A14006 .•....• .. ..... $4 .95 ......... $6.99 DUST COVER ;'_:::I ~ C SPEAKERS) - 8" DOPED PAPE_R CONE • High compliance rubber aurround. • 45 watta RMS • Dark grey cone • Black dust cap • Black round frame C10233 .......... $44 .95 • - 10" HIGH POWER WOOFER <1 ·~ ~(s;r-1-4,;l FOUR CHANNEL STEREO AUDIO MIXER NBC-2 BATTERY CHARGER Nickel cadmium battery charger for charging up MOUSE I HOUSE WITH THESE GREAT NEW PRODUCTS! HL \D C I. EA:\E R DISKS It 11nh· takl'\ a minutt.• amount of du~t. dirt or mai,:nelit· nxidt' partide, on your drive ht•ad\ to t·au\t' prohlt'm\ : t'rror,. downtimt• or an t·x1lt.'1Hin• \t'r\" i u · rnll. Rt'gular uu• nf a. head dl'itnt·r will kt·ep your driH fn·e of ~muhlt· rausini,: dirt and help keep your ,ystem up and running . Thest· dhk t·ll'anl'f\ art· ,imple to u\e, and indudt· deaning rnlutiun and in,truction\ • .\ 1/ 2'" C!2S60 ... •~t<'l]] -3-~;i; • With ribbed black paper cone. • 40 watta • Black dust cap • Cloth edge • Rubber mounting seal C1022 8 .... ... ... $49. 95 1 0" DOPED PAPER CONE • High compliance rubber aurround. • 60 watts RMS • Dark gr41y cone• • Black dust cap • Black round frame C10238 ....... .. .$59. 95 8" FULLRANGE • Twin CON1 epeaker with white paper cone ideal for public addrea• column apeakera. • 30 watts RMS • Foam edge • Whizzer cone C10224 ..........$24. 95 • 12" HIGH POWER WOOFER • With ribbed black paper cone • 50 wotta • Black dual cap • Cloth edge • Rubber mounting aeal C10229~ 4 .95 COMPUTER · CL EANING KIT To gain optimum performance and prevent damage to valuable disks, this cleaning kit has all you need to keep your computer in top notch performance. Anti.static cleaning pads, cleaning swabs, cleaning solution, 5 1/4" & 3 112" cleaning diskettes. c2 107'7 6" HORN & LINE x •FORMER • Weatherproof plaatic horn with 100 volt line tronaformer • 15 watts RMS • Adjustable metal bracket . C10218 .•.•.......$74 .95 'T1 CD ROM DRIVE UNIT. ANNOUNCING THE ~ NEW RITRON ~ , - -MULTIMEDIA ~ ~ COMPUTER ~ ~~ ~ Open up a whole new world of sight and sound user Interaction with a CDROM Drive Unit. (!..:!~ :,"liil w :; .l';JV' You have never seen such a wealth of infomation and entertainment with ::JJ m m Laser ROM ~ n . ;, ~ I 64K CACHE 386-33 MB RITRON SUPA VGA MONITOR (.28"D.P 1024x768) 89M HARD DISK (85M FORMATTED) 1MVGACARD 2MRAM CD ROM DRIVE WITH MASSIVE CAPACITY 2S,P,G PORTS MICROSOFT COMPATIBLE MOUSE DOSS.O 1.2 DRIVE MINI CASE & 200W P-S 101 EXTENDED KEYBOARD 2 EXTERNAL SPEAKERS FREE CD SOFTWARE. $3450 STELLAV. CD ROM GAME 3 YEARS PARTS & LABOUR WARRANTY MICROSOFT WINDOWS -........ C") :c Q z C :E en w a: 0:: X w a: w u.. u.. CD ROM CAN PLAY NORMAL CDs WHILE PROCESSOR IS WORKING. i,. YOU CAN LISTEN TO YOUR CD WHILE THE SYSTEM IS NUMBER CRUNCHING. ($3,495) C SCSI-2 Hard Disk Drive. J> C audio and visual response that will truly astound you. You can even play and listen to your audio CD'S while contlnuning to use your computer The world of the CD-ROM makes available to you over 1,500 CD-ROM Titles produced by more than 1,800 companies which support this fast growing Information and entertainment facility. Read the following specifications and see why similar disc based software pails Into Insignificance. Comes complete with CD ROM DRIVE UNIT, controller card for Installation In an IBM PC.2 SPECIFICATION PERFORMANCE "C 0 ~ 'T1 0 ::JJ s::J> F ($795 ) 0 Discdiameter..............................12cm Disc speed ..................................200-530rpm (CLV) Data capaclty............................... 540 MBytes Data transfer Rate Sequential... ................................. 150KBytes/sec. (Mode 1) 171KBytes/sec. (Mode 2) ::JJ C m ::JJ U) ~ m ::JJ MICROSOFT WINDOWS 3.0 & Z-NIX SUPER MOUSE II PACKAGE. The Piranha SP4200 Intelligent drive provides high capacity data storage using the Small Computer System Interface (SCSI). It la designed for aingle-uaer. multi•uaer. multi-tasking. CAD. engin-ing. deak top publishing and network systems that require advanced processing power and high performance. It uses state-of-the-art voice-coil drive technology and CacheAow; a third generation adaptive disk caching system which uaea a dynamically partitioned 64Kbyte buffer and automatic mode switching. Piranha performs with a 14.4 millisecond average aeek time and a12.66 megabit-peraecond media transfer rate. The ayncronous SCSI interface operates at 5.0 megabyteaper-aecond and 10 megabytes per second for the SP4200F. Anally the piranha haa a full complement of defect management features to ensure defect-free operation. SPECIFICATIONS Average Seek Tlme ....................Sub-1S milliseconds Track-to.Track...........................S milliseconds Data Transfer Rate Buffer to disk ..............................12.66 Mbits/sec Buffer to Host... ......................... S.O Mbytes/sec (SP4200) "z $1,195 ... -En 0 ~ What a package! 0 M.lcro1of't® Window■"', the 1of'twan that tran1form1 the way you uae your penonal computer and the Z-NIX Super Mou1e 11. Together at la1tl Window■ tlve ■ you the ability to run more than one application at a time and tran1fer Information between appllcatlon1. the 1uperlor way It Ule■ the full power of your computer. and lt1 rich ,raphlcal interface provide a more Intuitive. more efficient work environment than ever before available on a PC. The Z-NIX Super Mou1e I■ de ■l,tned and en,lneered to enhance your productivity. With feature 1uch a1 bJah re■olutlon. bJah 1peed traclr.lnt. and variable traclr.lnt parameters It let■ you tet your work done fa■ter and more efflclenUy. With thl1 treat paclr.ate you will find more 1treamllned way■ for you to work your penonal computer. When you combine the 1peed and accuracy of the Z-NIX Super Mou1e 11 with Microsoft Window■ 3.0 It unleash•• your computer 10 It can operate at lt1 full power, unhampered by prevlou1 memory re1tlctlon1. ~ a: ~ LX-850 80 Col, 9 Pin Dot Matrix. 240 Cps Draft ~ 48 Cpa NLO. Push Tractor. W Smart Park Feature C c22074. _ _ _ .$365 ~ FX-850 80 Col. 9 Pin Dot .J Matrix. 264 Cps Draft CC - 54 Cps NLO Push Tractor Smart Park Feature ~ u.. FX• 1050 136 Col. 9 Pin Dot ::i ············-··..··············$750 I- u, 0 Matrix. 264 Cps Draft. 54 Cps NLO. Push Tractor. Smart Park Feature. .....................................$925 ~ '®f D. SQ-850 80 Col. 24 Nozzel C Z CC Ink jet, 600 Cps Draft, 198 Cpa LQ. Push Tractor. Smart Park Feature. 1 225 $ • o------···. if LQ-200 80 W Col. 24 Pin Dot Matrix 192. Cpa Draft, 64 LO. Pull Tractor. ~ ~.~.'.'..~~~.'.~.~.~: ..............$475 1.1. ~J ll: .;,· ·-·z':'_· . I■■••· LQ-570 80 Col. 24 Pin Dot Matrix. 252 Cps Draft. 84 Cpa. NLO Scalable Fonts 8 to 32 points. 11 LO Fonts 360 x 360 DPI. Top. Rear, Bottom and Front paper feed paths. Convertable Push/Pull Tractor. - - - -.• $575 LQ-1170136 Col. 24 Pin Dot Matrix. 350 Cps Draft. 110 Cps NLO. Scalable Fonta. 8 to 32 point, •11 LO Fonts. 360 x 360 DPI. Top. Rear. Bottom. and Front Paper Feedpaths. Convertable Push/Pull Tractor · - -- -...............$1.149 LQ-870 80 Col. 24 Pin Dot Matrix.330 Cps Draft, 110 Cps NLO. Scalable Fonta. 8 to 32 points. 11LO Fonts. 360 x 360 DPI. Top. Rear. Bottom. & Front paper Feed paths Convertable Push/Pull Tractor. ·----·$895 • "C jj m U) ~ C z c5 <D N LQ• 1070 136 Col. 24 Pin Dot Matrix. 252 Cps Draft. 84 Cpa NLO. Scalable Fonts. 8 to 32 point, 11 LO Fonts. 360 x 360 DPI. Top. Rear. Bottom. and Front Paper Feedpaths. Convertable Push/Pull Tractor _ _ _ _ ..................... $775 LQ•400 80 Col. 24 Pin Dot Matrix. 180 Cpa Draft. 60 NLO Pull Tractor C22070 .....................$439 X ... -... LQ-860 80 Col. 24Pin Dot Matrix' 295 Cpa Drsft,98 CPS LO. Colour Standard.Push Tractor Smart Park Feature ...................................$1095 SQ•2550 80 Col. 24 Nozzel ink jet, 600 Cpa Draft, 198 Cps LO. Push Tractor. Smart Park Feature. .................................... $1995 m ~ SAVE ON OUR GREAT RANGE OF EPSON PRINTERS LX-400 80 Col, 9 Pin Dot ;:i; Matrix, 180 Cpa Draft 30 Cps NLO, Pull Tractor W C22054 •...•.•••..•••••••• $249 ::JJ w 0 80 m :I: $189.00 10.0Mbytealaec (SP4200f) 'T1 'T1 - LQ• 1060 136 Col. 24Pin Dot Matrix' 292 Cpa Draft, 98 Cpa LO. Colour ~ Standard.Push Tractor. Smart Park Feature. -............... - ........................... $1.395 LQ-2550136 Col. 24Pin Dot Matrix• ,,:i.1 400 Cpa Draft, 133 LO Colour Standard,Push Tractor, Smart Park Feature: .......... - ......$2•049 L FREE PACK AND POST FOR MAIL ORDERS OVER $10.00. OFFER EXPIRES MIDNIGHT 31 / 1 /92 '- 1 . ....., ;i<at>ijj:MiA l•I . ,.k\ 1 DC VOLTS DC AMPERES Adjustable 0-45V 8-amp power supply Do you need a really big power supply? One that's big enough to allow you to do .away with the car batteries on your workbench? Well this is for you. Its output is adjustable from 0-45V DC & it can deliver currents up to 8 amps. Design by JOHN CLARKE In the past, a power supply rated at 0-45V and 8A would have been much bigger than this unit. It would have needed really big heatsinks and possibly fans as well to keep it cool. It would also have needed a much bigger transformer and more filter capacitors, and would generally have been a much more expensive unit. 64 SILICON CHIP So why is this unit not as big as those older designs? Because it is a switchmode power supply, using the same principle as the millions of power supplies used in personal computers. These are light in weight, compact in size and highly efficient. Because it uses the switchmode principle, this new supply has no large heatsinks yet always runs cool or only slightly warm to the touch. The new supply is housed in a large plastic instrument case and has meters for voltage and current. There are two knobs to adjust the output: one for voltage and one for the current. Just below the voltage knob is a toggle switch which allows the supply to deliver a fixed 13.8V output - handy if you are working on any automotive device. There is also a pushbutton switch to allow the maximum output current to be set an d a toggle switch to connect the supply output to the front panel terminals. The supply has three binding post terminals on the front panel: red for positive, black for negative (OV) and green for Earth. Neither POWER A o--o"""a---.-S1 240VAC 35V ►-----r--------------1t-----O+ + Nu----,--+--~ Cl-CS DC OUTPUT 50VDC ~ARTH OUT +12V CURRENT CONTROL CIRCUITRY VOLTAGE Fig.1: this simplified block diagram shows how the circuit works. The control circuit monitors the output voltage & current & drives an optical fibre link. This optical fibre link in turn controls FET Q1 which functions as a switching regulator. D2, L1 & C6/C7 filter the pulsed waveform from Q1 to produce a steady DC output voltage. the positive or negative terminals are internally connected to the power supply chassis so it may be used as a fully floating supply or with one side connected to Earth. There is a red LED above both adjusting knobs and these indicate Regulator Dropout and Current Overload. These will normally not come on unless the supply is overloaded or for a brief moment at switch-on. Inside, the new supply has a large PC board and two power transformers (one a large toroidal unit and a smaller unit). On the rear panel there ~s a finned heatsink and two semiconductor devices. These devices are a fast recovery diode and, at the heart of whole circuit, a 33-amp 100V FET (field effect transistor). The supply dimensions are 352 x 129 x 280mm (W x H x D), including knobs and rear projections. It weighs 5.5kg, which is surprisingly light for a supply of this rating. Now let's have a look at the circuit details. Simplified circuit While switchmode supplies have the advantage of lightness and efficiency, they tend to be more compli- cated in circuitry than conventional linear power supplies . In the case of this power supply, the situation is more complicated because we have used a FET as the main switching device rather than paralleled bipolar transistors. The FET is much more rugged but requires more complicated drive circuitry. Never fear though, because the basic concept is relatively simple, as we shall now describe. Fig.1 shows the simplified circuit for the new power supply. Transformer T1 (the big toroidal type) has a 35VAC secondary which is rectified by bridge 1 and filtered by capacitors C1 -C5 (a total of 23,500µF). This results in an unregulated 50VDC source for the switchmode supply. Switching transistor Q1, diode D2, inductor L1 and the output capacitors C6 & C7 comprise the stepdown switching regulator circuit. Q1 is switched on and off at about 20kHz. If the pulse switching waveform has a short duty cycle (ie, Q1 is off most of the time), very short pulses of current will be fed to L1 and the resultant DC voltage across C6/C7 will be low. Conversely, if the pulse duty cycle is high, Q1 will be on for most of the time and the DC voltage across C6/C7 will be high. By varying the pulse duty cycle from zero to 100%, the output voltage can be varied from zero to close to 50V; ie, around 45V or a little higher. Control circuit The 20kHz pulse switching waveform is produced by the control circuitry. This monitors the output of the switching circuit and therefore needs its own supply voltage which is provided by the small transformer Specifications Of Prototype Output Voltage ...................................................... .. . 0-45V Output Current .. .. .................... .................... ..... ........ 8A below 35V 6A at 40V Load Regulation ...... ........................ .... .......... .... ........ 1% Ripple and Noise .. .......... .. ........................... ...... ....... 5mVp-p at 6A 13V 10mVp-p at 8A 18V 40mVp-p at 8A 35V Current Limit ...... .... .... ................ ............................ .. 800mA to 8.6A Overcurrent Limit ............................... .. .................... 9A Fold back Current ........ .... .. .............. ...... .... ...... .. ..... .. < 2A JA NUA RY 1992 65 Despite the apparent circuit complexity, the supply is easy to build as most of the parts are mounted on a single large PC board. The circuit employs switchmode regulation, so relatively little heatsinking is required. T2, the bridge rectifier comprising diodes D3-D6, and the associated 7812 regulator. The control circuitry feeds its pulses to Ql via a light link. This consists of a LED and photodiode detector pair which are coupled via a short length of optical fibre cable. Both the detector and the LED are contained in neat little packages which attach to each end of the short optical cable. Made by Siemens, they provide complete electrical isolation between the control circuitry and Ql. Ql is a Philips 33A Mosfet which has a very low on resistance of about 0.052Q. This means that its dissipation is very low, even when the supply is delivering currents of 8 amps. Now let's have a look at the complete circuit as shown in Fig.2. Circuit description The whole circuit of Fig.2 looks 66 SILICON CHIP pretty daunting but if we deal with it in sections it becomes easier to understand. First, let's recognise the similarities between the whole circuit of Fig.2 and the skeleton circuit introduced in Fig.1. In the top lefthand corner ofFig.2 is the transformer Tl and its associated bridge rectifier and filter capacitors. It provides the 50V DC which feeds Ql (in the centre top section of the circuit). Ql is driven by a bank of paralleled inverters (IC2), driven in turn by Q2 and the optical fibre link comprising ICl and LEDL The light path is depicted by a dotted line between the ICl and LEDL LEDl is controlled by IC3, Q3 & Q4 and, together with all the other ICs shown on Fig.2, these comprise the control circuit shown on Fig.1. Ql is connected in series with the negative supply rail, with D2, inductor Ll and capacitors C6 & C7 forming the switchmode arrangement shown in Fig.2. The switching action of Ql can cause large voltage transients at its drain electrode and to protect against excessive voltages here, a 75V zener diode (ZD3) connects from the drain of Ql to its gate, via diode D1. Thus, if the voltage at the drain of Ql exceeds 75V, Ql is turned on again to shunt the transient. As noted above, the gate signal for Ql comes via IC2, Q2 and the light link, ICl . IC2 and Q2 are powered from a 15V rail derived by 15V zener diode ZDl from the 50V supply via Fig.2 (following pages): FET Ql & the optical fibre link (ICl & LED 1) form the heart of the circuit, while oscillator IC3a, comparator IC3b & error amplifier IC5d form the control circuit depicted in Fig.1. VRl, IC5b & IC5c provide the adjustable current limit feature while IC3c provides foldback current limiting protection. CJ-118A 20MHz Dual Trace C,s~UJ♦ ♦S~c:>pe SPECIFICATIONS: Operating modes Yl, Y2, Yl and Y2 added are swltchable alternately and Intermittently. Bandwidth, MHz: ■ DC coupled input: at -3dB .. 0-20 ■ DC coupled input: at -6dB .. 0-35 ■ AC coupled input: at -3dB .. 3xl0·'-20 ■ AC coupled input: at -6dB .. 2xl0·'-35 ■ input with external divider in position 1:1 , .. 0-7.0 Transient response built-up time, ns, max.: ■ ■ DC coupled input: .. 17.5 with external divider in position 1:1 .. 50 Deflection factor (11 calibrated steps with 1-2-5 seq.) ■ ■ ■ mV /DIV: Accuracy,%: Max. input (AC/DC) V: .. 5-10' .. +/- 4 .. 250 Input Impedance, Mohm/pf: ■ ■ ■ DC coupled input: with external divider in position 1:10 with external divider in position 1:1 .. 1/20 .. 10/15 Dimensions: .. 1/100 212 x 133 x 336mm Sweep speed (21 calibrated steps with 1-2-5 seq.) ■ ■ ■ .. 20-50xl0 .. +/- 4 .. +/- 8 ns/DIV: Accuracy, %: 50ns/DIV+ Accuracy,%: 20ns/DIV Screen Size: 4" 3 Trigger modes: ■ Auto, turning to triggered upon application of trigger signals HOPM (NORM). Trigger source: ■ Includes 2 x 1:1 10:1 probes, and screen protection cover. Internal (from channel Yl or Y2), external. Sensitivity for Internal synchronization, V: ■ ■ 50Hz to 4MHz, DIV., Max.: .. 0.8 4MHz to 20MHz, DIV, Max.: .. 2 Sensitivity for external synchronization, V, Max.: ■ lOHz to 20MHz .. 0.2 Typical external synchronization ■ Input imp. kohm/pf .... , Note: for Government Dept's, Schools, Sales Tax No. holders, etc only $430.43 ea. (ex-tax) - official order must be produced .. 70/15 . Available from: ··· ····.·.• · David Reid Electronics >/127 York Street,> Universe Computers 127 Melbourne St, .· ....... ... •···· ·.· . SYDNEY "-cS.W.2000 Nth ADELAIDE S.A. 5007 Ph:(02)2671385 Fax: (02)2618905 Ph: (08) 2391577Fax: (08) 239 1221 {Mai/orders ·welcome} A.C.N. 001-372-372 {Mai/orders welcome} +50V +15V 3900 0.5W +4.7V 0.1 1k C1-C5 5x4700 50VW + - Z01 15V 3W Z02 4.7V 1W 0.1 3 j 2 \ \ \ LEVEL SHIFTER \ \ o~rb~\L i~:E \ \ \ OUT \ 6.8k \ 100k 100k \ \ 100k 03 BC338 C11 1000 25VW + - + 1 16VW \ 10k 2.2k \ \ \ 10 16VW 100k B 04 BC328 820pf 10k 470k B_ _ _ _ _ ___..__-4----___.__ _.___ _ __..._ RAMP OSCILLATOR _._4_.______J...__--l..._L--l--L--COMPARATOR VOLTAGE ERROR INPUT 09 1N4148 +12V CURRENT 08 1N4148 S2: 1: CURRENT 2: SET CURRENT 47k 2.2k 270k 10 16VW CURRENT M2 1mA CURRENT 100k 10~~1N~--4---+------'.___J LE03 CURRENT LIMIT 0.1 - 0.1.I. 1k 10 + C 47n 68 SILICON CHIP >-. K 1.5k 16VW CURRENT LIMIT AMPLIFIER A OVERCURRENT LIMIT LOAD S3 ~+ .001 A +12V 18k 100k S4: 1: ADJUSTABLE 2: 13.BV FIXED 02 MUR1515 K C6,C7 2x1000 50VW 47k +2.5V + 0.1 250VA1 CB-C10 3x1000 50VW - + - A 13.BV VR6 50k AOJ - VOLTAGE;;i,,,.,.._---l'""""<□ S4 VR4 10k LIN 1k + 1 16VW L1 VOLTAGE ERROR AMPLIFIER FILTER =]J= VOLTAGE REFERENCE 0.1 250VA1 EARTH Jn A - - - - - e - - - -- -- - - - - - - - ~ . . -- - - - -- ---4----e- - -- -- - -..---+---+----+----+--+--.-+12v 2.2k 4.7k 22k 100k 1 18k 100k 16VW _ 13 10!2 5W 07 1N4148 1 16VW + - 1k 5W 2.2k 2.2k 470!2 05 BC639 10k 0.1 14 100k 8 C LE02 OROPOUT K 1k 470n DROPOUT DETECTOR MINIMUM LOAD SWITCHING 10V OFF 5V OFF L1: 10T 1.2mm DIA ENCU ON NEOSIO 17-745-22 IRON POWDER CORE L2: 6T 1.2mm DIA ENCU ON NEOSIO 17-742-22 OR PHILIPS 4330 030 60210 CORE . . .,,.1 C a<at>c BF199 BC328,338 aOE 8C639 VIEWED FROM BELOW 1 23 m,.,,.~ AK 40V BA POWER SUPPLY JA NUARY 1992 69 Vp (a) Vp (b) Fig.3(a): the triangle waveform VT from IC3a is compared with the error voltage VE from IC5d to produce the gate switching pulses for Qt. When VE is high, comparator IC3b delivers wide pulses as shown in (a). Conversely, when VE is low, the comparator delivers narrow pulses as shown at (b). two lkQ resistors in parallel. ICl, the light detector, is powered from a 4.7V rail derived by zener diode ZDZ from the 15V rail via a 390Q resistor. Light detector ICl, the light detector, has an integral photodiode and an amplifier with an open collector output at pin 3. This is loaded with a lkQ resistor and drives transistor QZ, a voltage level shifter which drives ICZ. Five inverters in ICZ are paralleled so that they have sufficient drive for the gate of Ql. The inverters are connected to the gate via a 470Q resistor which effectively slows down the turn-on and turn-off times for Ql by a slight amount. This has been done deliberately to reduce the amount of high frequency filtering needed for the final DC output. Control circuitry The core of the control circuitry comprises the triangle waveform generator IC3a, the error voltage amplifier IC5d and comparator IC3b. IC3a is a comparator which is connected as a Schmitt trigger oscillator running at Z0kHz. The output waveform, a triangle (or sawtooth), is taken 70 SILICON CHIP from across the 820pF capacitor and fed to the inverting input of comparator IC3b. IC3b then compares the triangle voltage with the error voltage fro m IC5d and generates switching pulses to drive LEDl and, ultimately, the gate of Ql. This process is illustrated by the waveforms of Fig.3. Have a look at how the triangle waveform VT is compared with the error voltage waveform VE in the comparator IC3b. When the error voltage is relatively high as in Fig.3(a), the comparator delivers wide pulses from its output at pin 1. On the other hand, when the error voltage is relatively low, the comparator delivers narrow pulses as shown in Fig.3(b). The output of IC3b feeds transistors Q3 & Q4 which form a buffer stage to drive LED 1 via a 270Q resistor. LED 1 is the transmitting end of the optical link which drives ICl and, ultimately, the gate of Ql. We now flick across to the top righthand corner of the circuit (Fig.2) to have look at the section involving IC5d, the error voltage amplifier. This op amp monitors the output voltage of the power supply to make sure that it is controlled within close limits. IC5d compares a portion of the output voltage, applied to its inverting (-) input at pin 6, with a reference voltage applied to its non-inverting (+) input at pin 5. The reference voltage at pin 5 is tapped off ZD4 by VR4 or VR6 (depending on the setting of switch S4). ZD4 is an LM336Z -2.5V precision reference diode. IC5d amplifies the difference between the voltage at its Main Features • 0-40V adjustable output • 800mA to 8A adjustable current limit • Short circuit proof with foldback cu rrent limit • Separate voltage and current metering • Regulator dropout and current overload indication • Output load switch • 13.8V output switch setting • Switchmode design • Minimal heatsinking pin 6 (representing the output voltage) and the voltage at pin 5 (representing what the output voltage should be). This voltage is then applied to pin 7 of IC3b (as discussed previously) via diode D9. Current monitoring If you have a look just to the left of ZD4, you will see two arrows pointing down, marked B and C. This break in the negative supply line from Ql goes to the current monitoring section, shown in the bottom lefthand corner of the circuit. IC5b, IC5c & IC3c provide the current monitoring functions of the circuit. IC5c detects the current flowing by monitoring the voltage developed across the two paralleled 0. lQ 5W resistors (Rl & RZ). But there's quite a bit more to it than that, brought about by the need to adjust the current limit value, which is done by VRl. One of the problems with a large supply is how do you set the current limit? You can't just bung a temporary load across the output and then twiddle a knob to set a current which may be as much as 8 amps. If you did so, there would be enormous heat produced in your temporary load and also in the supply itself. There is also the voltage setting to consider. While it may relatively easy to set a current limit value when the supply is set for a relatively high voltage, it becomes more difficult to do so when the supply is set for a low voltage because the temporary load must then have a very low resistance - and then that would not suit if a high voltage output was required. Clearly, the current setting cannot be done by connecting a temporary load on the supply. We have to arrange to have the ammeter show the current limit being set at up to 8 amps (by VRl) without having any large current flowing. This is achieved by pushbutton switch SZ. In the normal setting oI SZ (position 1), the ammeter (MZ) is effectively connected across the two eurrent monitoring resistors Rl and RZ. When SZ is pushed (position 2), the ammeter is connected to the output of op amp IC5b, a voltage follower connected to VRl, the current adjust control. So when SZ is pushed, IC5b feeds a current through the ammeter which is identical to what it would get for a given current from the supply. So PARTS LIST 1 instrument case, 355 x 250 x 122mm (Altronics Cat. H-0492) 2 aluminium front & rear panels to suit above case 1 steel baseplate to suit case 1 PC board , code SC04201921, 189 x 167mm 1 Dynamark front panel label, 340 x 117mm 1 0-50V meter scale 1 0-1 0A meter scale 1 M-3092 35V+35V, 300VA toroidal mains transformer 1 2851 12.6V 150mA mains transformer 1 72mm long heatsink (Altronics Cat. H-0522) 2 MU65 1mA meters 1 panel-mount mains 3AG fuse holder 1 3AG 7.5A fuse 1 7.5A mains cord & plug 1 cord grip grommet to suit mains cord 1 3-way mains terminal block 1 2-way mains terminal block 2 21 mm diameter collett knobs 1 panel-mount illuminated mains switch (S1) (Altronics Cat. S3218) 1 15A toggle switch (S3) (Altronics Cat. S-1057) 1 SPOT or DPDT momentary action pushbutton switch (S2) (Altronics Cat. S-1092) 1 SPOT toggle switch (S4) (Altronics Cat. S-1210) 1 green binding post 1 red binding post 1 black binding post 2 5mm LED bezels 1 TO-220 mica washer & in~ulating bush 1 SOT-93 mica washer & insulating bush 1 Neosid iron-powdered core, 17745-22 1 Neosid iron-powdered core, 17742-22; or Philips 4330 030 60210 1 50mm-length of 2.2mm OD plastic optical fibre pushing the "Set Current" switch S2 doesn't actually cause any load current to flow. Neat, huh? IC5b's output also goes to IC5c, th e current limit amplifier. It amplifies 7 solder lugs 33 PC stakes 1 length of insulating sleeving for fuse holder and mains switch 10 plastic cable ties Wire & cable 1 500mm-length blue mains-rated wire 1 750mm-length brown mainsrated wire 1 250mm-length green/yellow mains-rated wire 1 2m-length yellow hookup wire 1 2m-length red hookup wire 1 2m-length blue hookup wire 1 2m-length orange hookup wire 1 400mm-length 0.8mm tinned copper wire 1 1m-length 1.2mm enamelled copper wire Screws & nuts 4 6mm untapped brass spacers 4 screws & nuts to mount PCB 5 screws, nuts & star washers for earth term inals 3 screws & nuts for terminal block 4 screws & nuts for mounting 2851 transformer, bridge rectifier & heatsink 2 screws & nuts for mounting 01 & D2 7 self-tapping screws (for mounting metal baseplate) Semiconductors 1 BUK436-1 00A 32A N-channel Mosfet (01) 1 BF199 NPN RF transistor (02) 1 BC338 NPN transistor (03) 1 BC328 PNP transistor (04) 2 BC639 NPN transistors (05,06) 1 SFH551V Siemens light link receiver (IC1) 1 74C14, 40106 CMOS hex Schmitt trigger (IC2) 2 LM339 quad comparators (IC3, IC4) 1 LM324 quad op amp (IC5) 1 SFH750V Siemens light link transmitter (LED1) the difference between the voltage at its non-inverting input, which is the current setting voltage, and the voltage across the paralleled 0.1Q resistors , Rl & RZ. 2 5mm red LEDs (LED2,LED3) 1 FB3502 35A rectifier bridge 1 15V 3W zener diode (ZD1) 1 4.7V 1W zener diode (ZD2) 1 75V 1W zener diode (ZD3) 1 LM336Z-2.5 zener reference (ZD4) 5 1N4004 1A diodes (D1 ,D3-D6) 1 MUR1515 15A, 150V ultrafast recovery diode (D2) 5 1N4148 switching diodes (D7-D11) 1781212V regulator (REG 1) Capacitors 5 4700µF 50VW PC electrolytic (C1-C5) 5 1000µF 50VW PC electrolytic (C6-C10) 1 1000µF 25VW PC electrolytic (C11) 3 10µF 16VW PC electrolytic 4 1µF 16VW PC electrolytic 6 0.1 µF monolithic 1 0.1 µF 50VW ceramic or polyester 2 0.1 µF 250VAC metallised polycarbonate 1 .001 µF metallised polyester 1 820pF ceramic Resistors (1 % 0.25W) 1 470kQ 6 1kQ 1 270kQ 4 1kQ 5W 9 100kQ 1 820Q 3 47kQ 3 470Q 1 27kQ 1 390Q 0.5W 5% 2 22kQ 1 270Q 1W 5% 2 18kQ 1 220Q 410kQ 2 100Q 2 6.8kQ 1 47Q 1 4.7kQ 1 39Q 5W 6 2.2kQ 1 10Q 5W 1 1.5kQ 2 0.1Q 5W 1 1.1 kQ Trimpots 2 50kQ enclosed horizontal trimpots (VR5,VR6) 2 10kQ linear pots (VR 1, VR4) 1 ?00Q enclosed horizontal trimpot (VR2) When the power supply delivers current to a load, there is a voltage developed across the. 0. lQ resistors. If this voltage exceeds the setting ofVRl , then the output of IC5c will go low JANUARY 1992 71 IC5a's output goes high to turn on LED 2, indicating that the supply is out of regulation. Minimum loading resistors This view show~ the fibre-optic light link that's used to isolate the control circuitry from the switching circuitry. It uses a LED & a photodiode/amplifier in separate packages, with the two joined by a short length of optical cable. and shunt the error voltage signal from the input of comparator IC3b via diod e DB. This will throttle back the duty cycle of Mosfet Ql until the current delivered equals the current set. Also, when IC5c's output goes low, it causes comparator IC4d to turn on LED3 , the current overload indicator. Foldback current mode · In addition to the current limit mode, this power supply has current foldback. This is a very worthwhile feature and acts to limit the current to a safe value in the event of a short circuit. It acts independently of the adjustable current limit mode so that even if you have the current limit set at maximum (nominally B amps), the fo ldback mode still works. What happ ens is that if the output current rises to a figure of 9 amps, because of excessive loading or a short circuit , the current is quickly reduced to a much safer value of less than 2A. Co mparator IC3c provides the foldback mode. Its non-inverting input is connected to a voltage divider string consisting of 22kQ, 2 7kQ, BZOQ an d 1. lkQ resistors. The voltage input corresponds to a 9A current. IC3c monitors the difference between the voltage at its non-inverting input and that developed across the current sensing resistors Rl & RZ. When the 9A current figure is exceeded (corresponding to 0.45V), pin 72 SILICON CHIP 13 of IC3c goes low and pulls the error input ofIC3b low via diode D10. This throttles Ql right back and so the output current is greatly reduced. At the same time, diode Dl 1 pulls the junction of the 22k0 and 27k0 resistors low which effectively reduces the overcurrent limit input at pin 11 of IC3c to a figure well below the initial 9A setting. This condition is maintained until the cause of the overload is removed. Regulator drop out Comparator IC4a and op amp IC5a provide a visible indication that the supply is not regulating; ie, not delivering the voltage which it is supposed to . IC4a monitors the output of Q3 & Q4 (the stage which drives LED1, the light link transmitter). Whenever LED 1 is driven, the output of IC4a is low and when LED 1 is off, the output of IC4a goes high. When it's high , the O. lµF capacitor at pin 2 of IC5a is charged via diode D7. When the output ofIC4a is low, the O. lµF capacitor can discharge via the 10k0 resistor connected across it. Since the 0. lµF capacitor is kept charged while ever pulses are sent to LED 1, IC5a has a low output. If LED 1 is on continuously, then Ql is fully on and the supply is out of regulation since there is no more means of control. When this happens , the 0.1µF capacitor discharges and Comparators IC4b & IC4c and transistors Q5 & Q6 provide minimum current loading for Ql , the switching Mosfet. This is necessary because a switching regulator such as this does not work reliably at very low values of load current; the switching pulses become extremely narrow and they tend to become irregular as the circuit tries to throttle itself back sufficiently to maintain a given output voltage. The solution to that is to have a certain minimum load current at all. times. This is achieved with three sets of resistors. Firstly, the two lkO 5W resistors in parallel are permanently connected across the supply. These provide sufficient current drain at voltages above 10V. For voltages between 5V and 10V, Q6 is used to switch in a 390 5W resistor and for voltages below 5V, an additional 100 5W resistor is switched in by Q5. Comparators IC4b & IC4c control the switching of Q6 & Q5. The noninverting inputs (pins 9 & 11) are tied to a divider string consisting of a 22k0 resistor and two 4700 resistors. The inverting inputs (pins B & 10) of each comparator monitor the supply output voltage via a voltage divider oonsisting of an 1BkQ resistor and a lkO resistor. Thus, when the output voltage is reduced below 10V, IC4b's output goes high and switches on Q6. Similarly, when the supply voltage is reduced below 5V, IC4c's output goes high and switches on Q5. Final filter The filter network consisting of toroidal inductor Ll and capacitors C6 & C7 removes most of the switching spikes from the output voltage but an extra stage of filtering is required to obtain the low output noise and ripple quoted in the specification panel. This is provided by another toroidal inductor (LZ) and capacitors CB, C9 & C10. This is augmented by the 0. lµF capacitors connected between earth and the positive and negative rails of the supply. Next month we will describe the construction and setting up of the supply. SC BUILD YOUR OWN FAX/MODEM This is a fully featured kit The Comma Fax/Modem is a commercially designed kit you can build. It will turn your PC (or Macintosh) into both a fax machine which can transmit faxes up to 9600 baud, as well as a Modem which supports both 1200 and 2400 baud. You get all the necessary components as well as a professional case, and power supply . You also receive FREE Fax/Modem software . All this for less than $300. The Comma Fax/Modem uses the latest technology in digital signal processing to ensure lasting troublefree operation. Also supported are cover pages, broadcast faxes, and scheduling. The software keeps a database type registerofregularly used fax numbers. for easy retrieval . Send faxes from home The Comma Fax/Modem is a fully featured fax machine similar to units costing over $1000, which will transmit faxes at up to 9600bp. Your faxes can now be sent directly from your PC without having to print them first. Programs supported such as Ventura Publisher, Wordperfect, Windows, TIFF and Dr Halo to name but a few. You can view incoming faxes on-screen or print them using a standard dot matrix printer. Incoming files can also be exported in either TIFF or PCX format for use in most popular graphic packages. Only print the faxes you want to keep - just think of the savings on expensive fax paper. Now Available MNP and V42bis option. V21/25 option. Time saving The Comma Fax/Modem will also receive faxes in background while you continue to work. When faxing out the Fax/Modem will redial an engaged number so you can be sure your faxes are sent. The software also automatically keeps a complete log of both incoming and outgoing faxes. As well it's also a modem The Comma Fax/Modem is a fully AT command series V compatible modem. Features include V22/V22bis standards (V21/23 is an option) both 1200 and 2400 baud rates are supported as well as auto answer, dialing and disconnect. You will find it compatible with all popular communication services including most bulletin boards. $99.00 $39.00 FREE Software With each kit you will receive the QL2 Fax/Modem software featuring both pull-down menus and mouse support. Value packed kit Each kit has been specially prepared to ensure you are able to build the Comma Fax/Modem with a minimum of specialised skills. We have also weighed each kit to ensure every component is included. There is also a step-by-step guide to testing your Fax/Modem throughout the building process. ONLY $299.00 Note: This device does not have an Austel permit in force. Connection to Teleoom lines is an offence. New Years Specials AT only Floppy Disk Drive Controller 360K and 720K. These Floppy Drives are now back in stock at the super price of only Card - Can be used on 360K - 1.44Mb drives. These were $99.00. $69.00 Now only $25.00 IBM External Floppy•Disk Drives 3.5". These drives would normally sell for $329.00. We also st.ock a range of motherboards, external disk drives, hard disk drives, add-on interface cards, as well as a huge range of cables, adaptors, switch boxes and chips. Call today for competitive pricing. These are a super special at $179.00 DEALER ENQUIRIES WELCOME TRY PC MARKETPLACE SUPERFAST MAILORDER - PHONE OR FAX TODAY! Plii{ {jleeson's PC MARKETPLACE Pty Ltd ...-------------------------------------------.•= -. PHONE (02) 418 6711 FREIGHT CHARGES FAX Include $1 Owith order for all normal items. Heavy items e.g . monitors add $15. 14 day money back guarantee. (02)4186713 Mail Order Address: P.O. Box 1100 Lane Cove NSW2066 e Order by phone (use credit card), by fax or by mail. Unless insurance is declined it will be charged at 1% of total purchase. This is for your protection. I ua I e SERVICE IS THE DIFFERENCE e =Al 1191 I==. ...... 1i ~il:◄ ~i~(~ PRICES CURRENT FOR MONTH OF PUBLICATION OR WHILE STOCKS LAST SERVICE IS THE DIFFERENCE I SERVICE IS THE DIFFERENCE e SERVICE IS THE DIFFERENCE AMATEUR RADIO BY GARRY CRATT, VK2YBX The Global Positioning System Amateur radio operators now accept satellite communications as a normal and regular mode of operation. But perhaps few realise how farreaching satellite communications are becoming. This article describes the revolutionary satellite navigation system which is now in use: the Global Positioning System (GPS). The Global Positioning System, when fully implemented, will consist of a constellation of 21 operational (plus three spare) navigation satellites, funded by the US Department of Defence, which will replace the now aging Transit satellite navigation system. It can be used by both military and civilian operators for the navigation of aircraft, boats, submarines and land-based vehicles. The service is free of charge and can provide civilian users with accuracy typically in the order of 30 metres. GPS can provide precise and continuous global, all-weather navigation data. It is capable of providing latitude, longitude, altitude and time, and hence (by computation) the speed and direction of motion in real time. Presently there are 16 operational satellites in orbit. The entire complement of 24 satellites should be in place by mid 1993. Known also as NAVSTAR, the GPS system will comprise a constellation of satellites in six orbital planes, with each group of four satellites circling the globe at about 20,200km. This arrangement will give an orbital period of 12 hours, or two orbits per satellite, per day. Each satellite transmits navigational signals with special coding, unique to each "bird", on two frequencies simultaneously. These signals are 11 (1575.42MHz) and 12 (1227.6MHz). The 11 carrier is modulated with a "coarse acquisition" (C/ A) code which has a frequency of 1.023MHz. Both the 11 and 12 frequencies are also modulated by a second code, called the P-code, which has a much faster switching rate of 10.23MHz. Both codes carry information at a data rate of 50 bits per second. This information gives the precise position of the satellite in space, plus clock data and other information, allowing a GPS receiver to determine the range to the satellite. The Micrologic Expl~rer GPS Designed specifically for use in boats, cars and aircraft, the Micrologic Explorer can accurately respond to changes in position and speed in less than two seconds. In addition to showing latitude, longitude and altitude, the unit can also display the local time (accurate to one second) and the distance and speed in either nautical miles and knots, statute miles and mph, or kilometres and km/h. All receiver functions and navigation functions are completely automatic and up to 100 waypoints can be entered into the unit's memory, either by entering the latitude and longitude or the present position. There are audible and visual alerts for waypoint arrival, crosstrack error and anchor watch, and the unit can display the direction to a waypoint at the press of a key. The claimed accuracy of the unit is 50 metres RMS, 0.1 knots RMS and 75 metres RMS for altitude U!lder the 74 SILICON CHIP current system of selective availability. For further information, contact Coursemaster Autopilots Pty Ltd, 7 Smith St, Chatswood 2067. Phone (02) 417 7097. Each spacecraft is equipped with two caesium-beam clocks, to ensure that each satellite transmits the code at exactly the same time. Hence, a GPS receiver on Earth can tell not only from which satellite the navigation data is being transmitted, but the distance to that particular satellite. This is done by measuring the time that the signal takes to travel from one satellite to the GPS receiver, using a second satellite as a time reference. Because the speed of light (and radio waves) travels at 300,000 kilometres per second, we can calculate that the signal travels 30cm per nanosecond. Hence, by measuring the time taken for the signal to arrive at the receiver, the range to the satellite can be computed. In order to calculate the precise position of the GPS receiver, some logic must be employed. If only one satellite were used, it would be true to say that the location of the receiver must be somewhere on a sphere centred around the satellite at a distance equal to the "range". If a second satellite is also used, and the range measured from it to the receiver, the location of the receiver must be somewhere along the line of intersection of the two overlapping spheres. If a third satellite is used, the probable location of the receiver can be determined even more accurately. This kind of computation is called a 3D "fix", and requires three satellites for navigation data plus a fourth for precise timing. The receiver must also be able to calculate the exact location of each satellite. Because only 16 satellites are currently available, this sometime gives rise to a situation where only two satellites are visible at one time, and hence no fix can be obtained. While these outages only last for a few minutes, they can occur at any time, day or night. In such instances, where the GPS receiver is being used for mobile navigation, a back-up system must be used, such as Omega, Loran C (where available), or manual navigation. This shortcoming is now being overcome, through the regular launching of additional satellites. Almanac data In order for the receiver to be "loaded" with sufficient data to enable it to calculate the exact location Called the "Pyxis", this portable GPS system from Sony packs the electronics and antenna into one compact hand-held unit. It allows you to check and store your latitude & longitude; check your direction, speed & altitude; check the distance & direction to your destination; plan & store up to nine routes & destinations; & track distance, direction & altitude of points passed. It also tells the time and can graphically compare your current direction with the most direct route to your destination. For further information, contact Sony Australia or Navigation Management Systems, 89 Cheryl Crescent, Avalon Beach 2107. Phone (02) 997 5117. of all satellites, a general "Almanac" is transmitted constantly, which gives the approximate location of each satellite. This data is transmitted slowly and it takes up to 13 minutes for the receiver to acquire it. This data is accurate for up to six months and gives the receiver sufficient information so that it knows roughly where to look for satellites. Information that pinpoints the exact location of the satellite is transmitted every 30 seconds and is referred to as "ephemeris" data. This data is a set of equations that produce the exact location of that particular satellite. This is quite a complex task and the gravitational effect of the Moon and the solar wind must be taken into account. Once the location of each satellite is known and the range to each satellite is known, a complete position fix is possible. Because the satellites are constantly moving, setting and rising, and because it requires four satellites to give a position fix, the ideal receiver should be able to receive and process five satellites. Four of these receiver channels will be tracking satellites, whilst the fifth will be searching for the next satellite, which will be needed when one of the others disappears over the radio horizon. Differential mode When used in the differential mode, a 1-3 metre accuracy can be achieved. Basically differential operation is achieved by placing reference receiving stations at fixed sites. Such stations can monitor GPS signals, calculate errors, and then broadcast correction factors to properly equipped maJANUARY 1992 75 Boasting a large liquid crystal display, the Magnavox MX100 GPS Navigator uses graphics to convey a wide range of information. A useful safety feature is the man overboard button (MOB) which instantly logs the exact latitude & longitude. The unit then provides steering data back to that point. Contact Coursemaster Autopilots Pty Ltd, 7 Smith St, Chatswood. bile receivers. This approach could be used to circumvent some of the deliberate errors introduced by the operators of the GPS system. Deliberate GPS errors Basically, the US Government offers two different levels of service. Military users have access to the "Precise Positioning Service" (PPS), which is generally capable of providing accuracies of up to 16 metres or better. Non-military commercial users, will have open and unlimited access to the "Standard Positioning Service" (SPS), which can provide accuracy to 100 metres for 95-98% of the time. The US Department of Defence introduces artificial errors into the GPS signals to degrade the accuracy for SPS users. This is done to deny any The Magnavox MX100 comes with a high-gain antenna that can be mounted in any convenient location & connected to the unit via a 15-metr.e cable. potential adversary access to the full system accuracy. Considering the recent "Gulf War" conflict, where GPS played a vital part in Allied military operations, this is understandable. There are two techniques used to introduce errors. They are Selective Availability (SA), and Anti-Spoofing (AS). Under SA, the orbital parameters are offset and the satellite clock signals are dithered slightly, thus giving the user an incorrect value for time and range. Anti-Spoofing involves encryption of the P code so that it becomes impossible to interfere with GPS operation by transmitting false signals. From a user's point of view, the affect of AS is to deny access to the LZ frequency. Authorised military users can be given decryption keys that cancel out [,tf.fC6ffE:"~:··i·~ Vo1...1r p,:,:::.i t.ic,n ~-~ 4oa52. 728 1.,.1 73a3,3, ?OE: ·~·. ; I..Jel,:11:.i t•-1 I ~ COG ' II SOl3 I'::._::, ~..::.I ·::.11,,:' _::, I'::. Ui. '':/ ...! ' ' .. The "Plotter" mode on the MX100 provides selectable gull's-eye views of the boat or waypoints, along with important navigational data (including current position, speed and course. 76 SILICON CHIP The "Navigate 2" screen displays the next waypoint, plus position, time & ETA. Other display modes include the "Position" mode & the "Sailplan" mode which lets you enter up to 200 waypoints over 20 routes. the artificial errors to give the maximum accuracy. Apart from artificially introduced errors, factors such as satellite clock error, ephemeris errors and ionospheric errors can also degrade GPS accuracy. Absorption of satellite signals can also cause propagation errors, introducing geographic errors of up to 75 metres. A GPS NAVIGATION ~NM S..-- v For the right advice at the best price ... PYXIS IPS-360 Private networks Main Features: Presently, there are several privately operated differential networks operated on a subscription basis, in locations such as the North Sea and the Gulf of Mexico. These applications are intended for offshore oil exploration. Some countries are looking at the possibility of providing public broadcast differential GPS services. Finally, there are surveying applications for GPS where , by measuring the phase difference on the satellite carrier signal, from one position to the other, over a long period of time, (typically one hour), an accuracy of 5mm or so can be achieved for stationary receivers. • Displays latitude, longitude & altitude. • Displays speed & direction, plus distance & direction to your . destination. • Let's you plan & store up to 9 different routes (50 waypoints, 50 destinations). Further reading: • Compares current direction with the most direct route to the destination. (1). "GPS Reference Guide". Navigation Management Systems, cl- Aviation Business and Commercial Operations Network Pty Ltd (suppliers of GPS receiving equipment). Phone (02) 997 5117; fax (02) 997 8729. (2). "Marine Navigation With The Global Positioning System, Questions and Answers". Available from Coursemaster Autopilots Pty Ltd. Phone (02) 417 7097; fax (02) 417 7557. (3). "Differential Operation of the Global Positioning System". IEEE Communications, July 1988, Vol. 26 No 7. • Tracks distance, direction & altitude of points passed en route & displays time to 1-second accuracy. • Accuracy: position 30-100 metres; velocity 0.3 knots (0.56km/h). NAVIGATION MANAGEMENT SYSTEMS 89 Cheryl Crescent, Avalon Beach 2107. Phone (02) 997 5117 Mobile (018) 22 2804 INTRODUCING THE NEW MXIOO GPS NAVIGATOR FROM MAGNAVOX. The unerring accuracy of six-channel continuous satellite tracking. Dazzling displays of navigational data. Turn it on and the double supertwist LCD screen fills with bright, high-resolution data. Position. Speed. Headihg. Cross- track error. Time and distance to the next waypoint. All updated at one-second intervals. Enter up to 200 waypoints with complete descriptions. Plus 20 routes with as many as 20 waypoints each . There's even a Man Overboard button that plots a return course to the exact spot. See a demonstration of the new MXlOO today. • • • • • • • • • 7 Smith Street, Chatswood NSW 2067 Australia Tel: (02) 417 7097 Fax: (02) 417 7557 Telex: AA89426 Unique Magnavox Features: • • • • Six-Channel continuous satellite tracking. • Advanced double super-twist LCD screen . • Features no other GPS Navigator offers. • Man Overboard feature plots a return course to the exact spot. • Legendary Magnavox reliability. • • • • • • • • COURSEMASTER AUTOPILOTS - Austral ia's world lead e r in auto pilot t e chn o lo gy REMOTE CONTROL BY BOB YOUNG Motors for electric flight models, Pt.2 Last month, we discussed the can size and bearings of motors intended for electric flight. This month, we continue with a detailed examination of the armature, brushes and associated items. The armature, from the user's point of view, is the one area in which great changes can be made to improve system performance and also the one that will influence the design of our proposed electronic speed controller the most. The range of options is staggering, with armature winds varying from three turns to 27 in 1-turn steps. The big problem from the motor manufacturer's point of view is that the range of applications is so diverse that it is impossible to provide a true stock motor. The main consideration is the bal- At the point of switch on, the motor armature is stationary and thus the armature winding provides a purely resistive load, the value of which is the DC resistance of the armature coil itself. Thus, a 3-turn armature provides a virtual short circuit. This is an important factor in the design of electronic speed controllers, for the electronics must be capable of delivering the full instantaneous starting current or a very serious complication arises. As a motor begins to turn, the back EMF from the windings rises and starts "The big problem from the motor manufacturer's point of view is that the range of applications is so diverse that it is impossible to provide a true stock motor. The main consideration is the balance between motor output power and run time". ance between motor output power and run time. Four factors - battery capacity and weight, armature winding and run time - must all be considered very carefully and the scope for some clever system design and development is unlimited. This is one of the things about electric propulsion that makes the field so fascinating. Now the really important thing here is to understand how an electric motor works. 78 SILICON CHIP to oppose the voltage applied to the brushes, with the result that the armature current begins to fall. The final running current depends largely upon the voltage applied, armature resistance, timing of the brushes and the motor load or RPM. The lowest running current in a correctly timed motor occurs when it is unloaded and when the revs are at their highest. Loading the motor will begin to slow it down and cause an increase in armature current. Out of this simple observation arises the concept of the correct gear ratio or prop size to suit the application. If we use too low a gear ratio or too fine a pitch on the prop, the revs will be high, current low and thus run time high, but the speed will also be low. Conversely, a high gear ratio or coarse pitch prop will load the motor. Revs will be lower, current higher and thus run times shorter, but the speed of the model will be higher. The motor in this case will also run at a much higher temperature, as will the speed controller. This loading factor also raises the problem of starting current. As stated previously, the maximum current is drawn with the armature stationary. If the load is high, then the time taken for the motor to accelerate to full RPM is lengthened with the result that large amounts of current are used for a considerable length of time. This will heat the motor, batteries and speed controller and considerably reduce run times. Now we can see the importance of gear ratios and prop pitches. If there is constant starting and stopping, average current consumption will be increased dramatically. The correct driver or pilot style also has a great deal of influence. For example, the driver who thinks ahead, never lets the forward speed fall to zero, and who uses minimum throttle changes will always achieve longer run times than his lead-thumbed mate. It is also obvious that an aircraft enjoys a real advantage here, as there are very few rocks, twigs and pranged cars in the sky. Thus, the throttle can be set at one speed and left there for a considerable length of time. Here the prime consideration is the pitch of of the modelling business with lots of scope for the clever and/or innovative modeller. The complications involving armatures do not end here. Delving deeper into the black art of electric motor theory, we find some very interesting factors involved. Multi-wound armatures Fig.1: this Futaba speed controller from the 1970s was rated at 12V & 10A, a flea-power rating by modern standards which require controllers rated up to hundreds of amps. the propeller. Applications calling for constant climb demand a fine pitch prop to keep the revs high. The need for speed calls for a coarse pitch prop with some sacrifice in current at take off (here a variable pitch prop would be really nice) and once at speed, you never allow the nose to go up. There is a second complicating factor in regards to starting which affects the design of the speed controller. If we do not supply the full start-up current required for the stationary armature, then the time to run the armature up to the correct operating speed is extended with attendant heating problems. For this reason, speed controllers are quoted at instantaneous and sustained currents. For example, the state-of-the-art Tekin TSC 41 lP is rated at 1050A maximum current, a staggering figure by previous standards but a necessary one if 3-turn armatures are going to be used to full effect. Compare this to the 1970's era Futaba 12V 10A speed controller in the photo of Fig.1. There is another problem which involves the number of poles on the armature winding. A 7-pole motor provides a greater mechanical advantage at start-up than a 5-pole motor and a 3-pole motor is approaching the bottom of the barrel. This problem is compounded when starting under heavy loads and for this reason the European manufacturers tend to prefer 5 and 7-pole armatures whereas the Americans and Japanese tend to stay with the 3 and 5-pole layout. Now we are beginning see where the enormous complexity in providing a motor to suit all applications begins to arise. For starters, a compromise must be struck between starting torque and cost (3, 5 or 7-pole). From here we move rapidly into a bewildering array of compromises involving armature winds, battery run times, brush material, bearings, and thermal considerations. Again, all of these factors influence the cost. Obviously an application involving lots of starting, stopping and accelerating would tend to call formultipole motors and cost becomes a secondary consideration. Track and offroad vehicles fall into this category. On the other hand, in applications such as aircraft, where the run time is lengthy and the motor RPM never varies, we can live with the slower acceleration of the 3-pole motor. Average current Even here , the position is by no means clear cut for the number of poles also affects the average current for any given load and thus affects the run times (for any given battery size). As a general rule, the greater the number of poles the lower the running current. Which is the most important in your application: acceleration, cost, RPM, run times or any one of a myriad of considerations? As stated before, electric propulsion is an intriguing branch One would think that an armature wind is an armature wind but not so in this mad, highly competitive world, where everybody is looking for that small edge. Trinity (America) quote their armature winds as singles, doubles, triples and quads. What does it all mean? The answer to this little question lies in the problems (or as the positive thinkers would have us believe, challenges) involved in coil winding. Copper wire has mass, volume and resistance and the heat dissipation takes place on the surface of the wire. Now the problem is that a single strand of say 19-gauge wire (American) is very stiff and will not bend easily around the armature contours. The large diameter also leaves diamond shaped spaces between winds, thus wasting valuable volume. This space is vital to another factor involving the magnetic flux density and that is the concept of amp-turns. The magnetic field will increase with a constant current if we increase the number of turns. All of these factors play an important part in the final wound armature. Coil winders have always faced these problems and one simple method of improving efficiency is to use parallel windings of two or more strands of wire which will give the same mass and resistance. Thus, two strands of 22-gauge wire will give the same mass and electrical resistance as a single strand of 19-gauge wire. Triples consist of a 3-strand winding and a quad winding uses four strands of a very fine wire indeed. There are two benefits that accrue from using this method and these are of great interest to the electric motor enthusiast. One is the fact that because the diameter is smaller on each strand, they fill in the spaces between winds much more readily. Thus, there is less wasted volume and this results in a better amp-turns ratio. These finer wires also follow the armature contours more readily, again saving space. JANUARY 1992 79 MOTORS FOR ELECTRIC MODELS - CTD The second factor is that two strands of wire have a greater surface area than an equivalent single strand, thus assisting in the heat dissipation of the armature windings. (Editor's note: the reduction of"skin effect" may also be an important factor. The speeds at which these motors run means that the currents through the armature constitute a relatively high frequency which may be 5kHz or more. Clearly, at the very high currents involved, skin effect could be very important. It would be minimised by trifilar and qµadrifilar windings; ie, triples and quads). Now the importance of doubles, triples and quads becomes crystal clear. There is another factor of importance in this issue and that is the more snugly wound coils using smaller diameter wire tend to throw off armature winds less than the heavier single strand windings. This is an important factor when the RPM of some of these motors is considered. Trinity quote 52,000 RPM for their 9-turn, double wind "Nuclear Assault" 4.9 wet magnet motor. I assume this is unloaded and presently I can offer no explanation of what a "wet magnet" is. "Everybody" can tell me that the "wet magnet" is better than a "dry magnet" but "nobody" can tell me why! Does this mean that if we drop a "dry" magnet into a bucket of water it becomes "wet" and works better? The mystery continues. Stay tuned to this magazine for further episodes of this intriguing little mystery. As you can well imagine, motors spinning at these revs and drawing the amount of current that they do, generate a large amount of heat - so much so that parts of the motor are seriously in danger of melting down. The brushes and motor "endbell" are two such components. High brush wear A complicating factor for the brushes is the fact that most modern motors allow the timing of the commutator to be advanced or retarded. This can result in severe arcing at the com mut ator/b rush junction and brushes will just simply melt or at best wear extraordinarily quickly. 80 SrucoN CHIP For this reason, brush design has become a major factor in modern motor design, so much so that some classes of car racing are almost a motor and brush tweaking competition instead of a drivers' event. There is a bewildering array of brush types available in a variety of materials and physical shapes. As a general rule, a soft brush material will allow a higher RPM but will wear more quickly. The harder materials withstand heating better and thus last longer but wear the commutator more quickly. The usual brush composition is a mixture of copper/graphite which will boil off the copper if they overheat, leaving just the graphite riding on the armature. The resistance of the graph- "The endbells carry the brush housing and rear bearing and can get very hot. The usual composite plastic endbells can actually melt". ite is much higher than copper and this is why the brush goes black at the end and the motor slows noticeably. Trinity offer a special brush alloyed from copper/silver which gives excellent results but wears very quickly. Using this type of brush, the commutator stays cleaner and does not burn at the commutator slots. These brushes are very soft and are usually changed every two runs on modifieds and every three runs on stock motors. Another popular trick is to cut the brushes to reduce the surface area in contact with the commutator. This increases the cooling area of the brush and reduces friction . The shape of the cut also effects the timing of the motor. By cutting one side from -the brush, an effective increase in timing of 2-3 degrees may be achieved if they are inserted the normal way. This will result in an increase in RPM. If they are installed in the reverse mode, an effective retarding of the timing is achieved, resulting in more torque and lower battery drain. One point here is that the brush width to commutator diameter ratio must be kept realistic. Brush timing With regard to the timing, the normal method of timing an electric motor is to advance or retard the brushes so that the motor will deliver equal performance in either direction of rotation. If the timing is advanced or retarded, the motor will become unbalanced and run more efficiently in one direction or the other. As there are not too many races run fully in reverse, it is usual to time the motor to work the way you want it in the forward direction only. The usual timing angle range for modern car motors is from 8-37 degrees. Some motors come pre-timed and others feature a fully adjustable endbell, which allows any timing angle to suit all manner of applications. The endbells carry the brush housing and rear bearing and can get very hot. The usual composite plastic endbells can actually melt. To prevent this and to improve motor cooling and thus efficiency, some manufacturers offer aluminium endbells. Keep in mind here also that magnets do not like getting hot and most will demagnetize very quickly if the heating gets out of hand. One final word on the brushes. Spring tension also plays a major role in establishing the RPM/torque ratio of your motor. Again as a rough rule of thumb, the lighter the spring, the higher the RPM and the less the brush wear. The heavier the spring the higher the torque and the greater the wear on the brushes and commutator. The final word is on shunts (the braid connecting the brush to the battery terminals). Once again, dual and triple shunts are the go. These braids must carry the full motor current and if they are too light, this will result in a loss of power. What you must always keep in mind when working with very high currents is that a lQ resistance in the wiring at 12 amps will result in a 12volt drop. If your supply battery is 12V then there is nothing left for the motor. At 120 amps, we are now talking 0. Hl Just make sure that your wiring is thick and all connections are sound; that is if you want any current to reach your motor. SC - - ORDER FORM USE THIS FORM FOR ALL YOUR SILICON CHIP PURCHASES SILICON CHIP BINDERS: Yes! 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Mail coupon to: FREEPOST25 Silicon Chip Publications PO Box 139 Collaroy Beach NSW 2097 No stamp required in Australia New blood steriliser • uses microwave energy One of the real scourges of the nineties is the AIDS virus. No one who develops full blown AIDS survives more than a few years so there is a huge research effort in developing drugs for its treatment. Now a Sydney engineer has hit upon using microwave energy to sterilise AIDScontaminated blood - a development which may become very significant in the next few years. This new process for the sterilisation of AIDS contaminated blood is the subject of a patent application (Application PK 7302 - Australian Patent Office - assigned to Jamiri Holdings Pty Ltd). It relies for its effect on nuclear magnetic resonance. Electromagnetic energy can be used to selectively excite atoms, molecules or cells with great precision. Nuclear magnetic resonance (NMR) has been used to study cancer cells for almost 20 years, specifically for the measurement of proton density. The proposer of this new blood treatment, Graham Rogers, has drawn upon his expertise in the use of microwaves for heating and sterilisation, to make it quite specific - namely, to treat human blood. The process is aimed specifically at viruses, namely HIV, AIDS and Hepatitis A & B. His patent application details the theory of resonance and the concept of resonant ionisation spectroscopy using tuneable pulsed lasers. Basic concept The concept of his device is to selectively ionise or remove cells or a virus from blood by the use of microwave energy. This is to be accomplished by passing the blood through a spiral coil into an RF chamber where it will be irradiated at a specific resonant frequency and power level. After being irradiated, the blood is removed from the chamber where it is cooled rapidly to avoid any deterioration of the blood itself. No other treatment of the blood would be necessary although it might have to be passed through the sterilisation process more than once to be 100% effective. Nor would there be any degradation of the blood cells Coming Next Month In SILICON CHIP* 40W 12VDC To 24VAC Inverter This 12VDC to 240VAC 50Hz inverter uses a transformer, two low cost power Mosfets and a minimum of other parts to drive electric shavers and other small appliances. It can also be used to provide a variable frequency drive to telescopes. 50 Watt Per Channel Stereo Amplifier After a long period of development, we hope to publish the first article on this high performance midi-sized amplifier next month . It is very quiet and is modular in design. Coming Soon - Transmitter For VCRs With VHF Modulators . Our TV Transmitter can now be used with VCRs that have a VHF modulator. We've simply added a UHF modulator in front of the amplifier stage & the device now accepts the direct video from the VCR. Details in the March issue. *While these articles are in an advanced state of preparation, their inclusion in the nominated issue will depend on space availability. 82 SILICON CHIP the microwave chamber, the blood will be rapidly cooled by passing it through a vortex tube powered by compressed air. Prototype blood reactor A prototype sterilisation unit was brought to the premises of SILICON CHIP magazine for a photographic session. It was not as described in the patent application but many of the principles were similar. Essentially, the prototype is an industrial microwave oven with microprocessor control of power level, fluid temperatures and pumping rate. Instead of using an air-driven vortex for cooling, :the prototype employed a Seebeck semiconductor cooling device. The unit was not demonstrated and even it had been, we had no access to testing facilities to verify the process. Field tests This prototype sterilisation unit looks much like a microwave oven with an extra chamber below. The latter holds the Seebeck semiconductor cooling device, a pump, cooling fans and air filters. themselves or any effect on blood antibodies. The close control of the process is supposed to see to that. The patent application goes on to detail the construction of the microwave chamber, the pumping and cooling equipment and the source of the microwave energy. The microwave source is to be based on a conven- WHERE DO YOU GET IT? o~ (f.~ tional magnetron and a mains power supply except that the power level will be able to be set very precisely and the microwave frequency set by a tuneable waveguide. The temperature of the blood will be closely controlled at all times by a microprocessor based monitoring system. After it has been removed from At the time of writing, full scale tests of the process had not been carried out and so it is not possible to state whether the process is effective or not. However, undertakings had been obtained for tests to be carried out in the first quarter of 1992 at a major Sydney teaching hospital. Graham Rogers also has offers to run full scale tests in a number of countries. He expects to begin Australian tests soon. We hope that the process does prove to be effective. If so, it could be of major benefit in controlling AIDs and other blood related diseases. SC QLD'S LARGEST SUPPLIER OF MICROWAVE OVEN PARTS & ELECTRONIC COMPONENTS SHARP REPLACEMENT PARTS DISTRIBUTORS FOR Panasonic . .n • AKAi e CAR STEREO e TV e VCRs e STEREO e BUSINESS EQUIPMENT e WHITEGOODS e VIDEO CAMERAS e PHONES e MICROWAVE OVENS A RANGE OF MAGNETRONS, DIODES, CAPACITORS & SHEET MICA TO SUIT MANY MODELS & BRANDS OF MICROWAVE OVEN IEBI EDSONFIELDPTYLTD (A.C.N. 010378588). Trading as: ll lll • ECONOMIC ELECTRON/CS, 24 Campbell Street, Bowen Hills, Old 4006. PO Box 481, Fortitude Valley, 4006 Telephone (07) 252 3762. SOUTHPORT ELECTRONIC SHOP, Shop 1/ 10 Welch St, Southport, Old 4215. Telephone (075) 32 3632 Fax (075) 51 0543 I VISA I e VAST RANGE OF COMPONENTS e TEST EQUIPMENT e TOOLS e SOLDERING EQUIPMENT e DATA BOOKS e AUDIO/VIDEO ACCESSORIES e CABLE & CONNECTORS JANUARY1992 83 DiskTwin 2.0 - continuous backup for Macs Hard disc failures are something that we all have to come to terms with. But the havoc they cause can now be eliminated with the DiskTwin. Up till now, backup systems only made periodical backups of your hard disc to tape or floppy disc . DiskTwin runs continuously, making updates every time the disc is written to. If the disc crashes , it automatically takes over, handles all reads and writes, and informs the user that a hard disc crash has taken place. Downtime is thereby eliminated. If the system is operating as a file server, DiskTwin provides no degradation in performance and can even send error messages to the network administrator if the server is unattended. Once the problem with the disc has been corrected, or a new one fitted, it can rebuild the disc (at up to 85Mb per minute) and fix bad blocks. When using removable media, such as erasable optical and SyQuest drives, the system can provide both continuous and archival backup. For more information, contact Scott Lidgett at Lidcam Technology, 505 St word processor or spreadsheet . application. The text then appears in your word processor as if you'd just typed it in. There are no file format conversion programs or any need for file saving . . Text entry is as simple as pressing a button and scanning the material to be entered. The text then appears in your word processor, ready for editing and formatting. Two versions of the Typist are available. The Macintosh Typist consists of the scanner, a SCSI box, ao external power supply and the software. Data can· be entered into any Mac program that handles text or numbers such as Word, Excel or Page Maker. The PC Typist consists of the scanner, an interface card and the software. When used with Windows 3.0, it will input data into any Windows 3.0 application that handles text or numbers such as Word for Windows, Excel and PageMaker. When used straight with DOS, it can input data into most popular word processing and spreadsheet programs. A special feature lets you scan text as an ASCII file for importing into a non-supported program or database application. Scanned images may also be saved as TIFF, PICT or PCX formatted fi les. For more information, contact Chris Franklin at Omnipage Australia on (02) 906 4900. Ethernet over phone lines Kilda Rd, Melbourne 3004. Phone (03) 820 9077. Typist personal scanner has OCR Th e Typist is claimed to be the first scanner specifically designed for optical character recognition (OCR). With 300 dpi (dots per inch) resolution, it can read 11 Western European languages and can separate graphics from text. All non-stylised fonts from 6-72 points can be read, including dot matrix. When a document is scanned, it recognises the text, then turns it into a format suitable for your particular 84 SILICO N CHIP The PhoneNet StarController allows Macintosh users to get the speed .and throughput of Ethernet over a standard twisted pair. It takes advantage of the spare wires already running to most phone jacks, thus allowing users to move around the network without spending hours running leads to new offices. The StarController hub is a multiport LocalTalk repeater that mounts in the telephone wiring closet. It connects all network devices together in a star configuration, repeating Ethernet and LocalTalk signals over 12 ports, and monitors network traffic and error rates . Each port can support up to a 100-metre branch at 10 megabits per second. The system complies with the IEEE 10BASE-T standard and will support a variety of Ethernet devices from PCs to VAX minicomputers. Unused ports are automatically shut off to prevent disruptive signal errors. If jamming errors occur, the port is disconnected and re-activated after jamming clears. An interface allows connection to coax based Ethernet LANS. For further information, contact Nick Verykios at NetComm Australia, Block A, 25 Paul St North, North Ryde 2113. Phone (02) 888 5533. Postscript compatible laser printers Just released from Practical Peripherals are the Newgen Turbo PS/ 1200T and Turbo PS/600T printers. Both are fully Postscript compatible and handle up to A3 size paper. They are the first high resolution printers to incorporate IET (image enhancement technology) and ART (automatic recognition technology) that automatically selects interfaces and · emulations as needed. The machines are based around the 4-page per minute Canon LBP-LX engine and use IET to smooth characters , figures and curved images. Each machine is controlled by a RISCbased processor. 10Mb of memory is standard in the 600T and 18Mb in the 1200T. Enough memory is present to print a full A3 page, or to perform double buffering with A4 pages for greater throughput speed. These printers are designed with a feature that allows the control program for the printer, emulations and fonts to be updated directly from a host computer. Hence, future Computer circuit board design package Emona Instruments has just released a CAD (computer aided design) package for PC boards which is low cost and easy to use. Called PADS-PCB, its features include .001-inch design resolu tion, 32 x 32-inch maximum board size, 30 routing layers and up to 150 (equivalent) 14-pin ICs. Other features include intelligent connection structure; top and bottom SMT (surface mount technology) placement; complete flexibility in defining pads, track shapes and sizes; and support for blind, buried and micro vias (connections between layers). CAM options in PADS-PCB offer board drilling, plotting and artwork layout. Solder masks, silkscreen films, assembly drawings and artwork layers can be produced at the push of a button. Autorouting options include a low cost router, a super router that will completely lay out a board, and an interactive router for analog and critical circuitry. For more information, contact Mark Breznik at Emona Instruments, 86 Parramatta Road, Camperdown, NSW 2050. Phone (02) 519 3933 . enhancements are made easy. Options include an Ethernet interface, memory expansions, memory cards that store fonts and emulation programs, and various size paper trays and paper handling devices. For more information , contact Greg Ducquet at Practical Peripherals, Level 11, 231 North Quay, Brisbane, Old 4000. Phone (07) 236 1433. Panasonic scanner has 400dpi resolution Roland has just introduced the FXRS505U image scanner which is capable of 400 dpi resolution. It can easily be connected to any IBM or Macintosh compatible computer and used in applications such as word processing, desktop publishing and CAD. It can also be used with in-built FAX cards. Line drawings and photographs can easily be imported into desktop publishing programs via TIFF and PCX file formats , whereas text may be imported into any word processing package through the use of optical character recognition (OCR). With a scanning area of 216 x 356mm and a scan time of just 13 seconds per A4 sheet, documents can be fed into any application quickly and easily. At just under $2500 including sales tax, the Panasonic scanner will prove invaluable for those users looking for fast text and graphics input into their software applications. For more information , contact Adrian Stephens at the Roland Digital Group, 233 Burwood Road, Hawthorn, Vic 3122. Phone (03) 818 0633. Mini 12MHz XT motherboard This 12MHz XT motherboard uses the NEC V20 processor and measures only 212 x 217mm, making it suitable for small footprint cases. It has separate switch selectable wait JANUARY 1992 85 386SX upgrade for IBM PS/2 states for both onboard RAM, ROM and expansion slot 1/0 . Provision is made for up to 640Kb. Connectors provide switching for turbo/normal operation with LED indication, key lock and speaker connection . It comes supplied with Juko ST 810S (developed by NEL Electronics) and eight expansion slots. The card comes with no RAM fitted and retails for $99. For more information, contact Rod Irving Electronics, 74 Parramatta Rd, Stanmore NSW, or their Melbourne stores. Windows 3.0 driver for Canon colour system Hypertec has just made available its Hyperace 386SX accelerator/processor upgrade boards for the IBM PS/2 model 30286 and 50 computers. These cards provide the functionality of an 80386SX processor, along with a significant increase in processing speed. The Hyperace 386SX includes a 20MHz Intel 386SX processor, 64Kb zero wait state cache and support for the 80387SX maths co-processor. No cables , installation software or software drivers are required. All that is needed is to remove the 80286 processor from the mother- may be limited. This way, text may be printed at 400 dpi while graphics and icons may be printed at 200 dpi or less. In addition, the TCP driver includes a special 400 dpi font generator that supports any typeface from the Bitstream Facelift utility. For further information, cor:itact David Cartwright of Alkira Pty Ltd. Phone (02) 975 4423. 32-channel PC-based logic analyser Alkira has released the True Colour Printer (TCP) driver, the first Windows 3.0 driver for the Canon Colour Imaging Systems. The driver allows Windows 3.0 applications such as Arts & Letters , CorelDraw, Aldus PageMaker and Word for Windows to print directly to the Canon CLC-500 or PS-300 colour imaging systems. Because it is the first program to separately address the text and graphics memory of the Canon system , the TCP allows text to be printed at 400 dpi (dots per inch), even though the graphics memory 86 SILICON CHI P The PCL-512 is a 100MHz 32channel logic analyser which plugs into any IBM PC or compatible. Samples up to 100MHz can be made with the internal clock using eight channels, each with 8Kb memory. At 25MHz, with either internal or external clock triggering , the PCL-512 can accept up to 32 inputs each with 2Kb memory. Each input has an input impedance of 500kQ shunted with 5pF capacitance. Acquired data can be displayed as a timing diagram or state format. Data can be recorded before or after triggering. Over 4000 trigger conditions and eight data qualification channels give excellent data recording flexibility. Cursors are available to make precision timing interval measurements. board and plug the Hyperace 386SX board into the 80286 socket. Recommended retail price is $825 (ex tax). For more information on the Hyperace 386SX, contact Katherine Doric at Hypertec, 408 Victoria Road, Gladesville, NSW 2111. Phone (02) 816 1211. For further information, contact Tony Coward, Priority Electronics, Suite 7, 23-25 Melrose St, Sandringham, Vic 3191. Phone (03) 521 0266. P~!~!d Computer Watchdog & 48-llne 1/0 Card: $318.00 • Provides 48 TTL inputs or outputs. • On-board watchdog (PC fails, dog will hardware reset the bus) • Useful for unattended computers so that if they stop you can have the watchdog independently reset your PC. • Fully addressable & programmable by the user (even in Basic). • eg , Turn ON/OFF devices in your home, office, workshop , industry. • Address & examples of software or hardware supplied. 24-lnput Opto-lsolator Board: $229.00 • 24 opto-coupled inputs. • Either transistor pull-down or current loop input. • Pin compatible with 1/0 Watchdog Card (optional leads available) • High voltage isolation. • Prov ides immunity from EMI , RFI & earth loops. • 16-output & 8-input board also available. AC/DC Interface Card .................... $185.00 Relay Board With 8 Relays ............ $259.00 Temperature Board (4 Inputs) ...... $189.00 PO Box 628 Willoughby, NSW 2068. Phone (02) 809 1083 Fax (02) 808 1432 I PRODUCT SHOWCASE I tures and displays stable measurements, allowing technicians to take readings in hard to reach places while keeping their eyes on the circuit. Other standard features include auto-ranging, range hold and optional manual ranging. All 70 Series II meters retain the simple one-handed operation for which Fluke is famous. For further information, contact Tom Nealon at Philips Test and Measurement (02) 888 0417. Extended range port for . optical fibre tester New range of Fluke multimeters The current series of Fluke multimeters has been upgraded and extended. Known as Series II, the new range introduces three new models: the 79, 29 and 70. The 79 and ruggedised 29 models can check capacitance from l0pF to 9,999µF. When measuring voltage, they can display frequency, while the analog bargraph shows the AC voltage across the test point. This allows users to see how much potentially hazardous voltage is present when making frequency measurements. The analog bargraph has 63 segments and updates as fast as the eye can follow. A new feature on these models called "smoothing" displays the running average of eight readings, providing stable readings , even with fluctuating signals. The Model 70 is similar to the familiar 73 but has no current inputs. It is ideal for many utilities, schools and computer field service applications. A 300mV function allows the use of a variety of current, temperature and high voltage accessories. The entire 70 Series II family includes as standard many features once considered optional. Fluke's patented automatic Touch Hold is now available on all models. Touch Hold cap- Multi-function fax/copier Canon has just released a combination fax, answering machine and copier nicknamed "The Works", offering ultra high quality (UHQ) imaging. UHQ imaging enables it to transmit in 64 shades of grey. This means that photographs and detailed diagrams can be transmitted with greater definition. When used as a copier, "The Works" produces clean, professional copies. The answering facility can be programmed to phone out when a message is received. Using a touch phone, incoming messages can be replayed, or erased, the outgoing message can be changed, and the paging function can be toggled. As each message is replayed, the time and date it was received is displayed on a liquid crystal display. Printouts of times and dates can The Tektronix FiberScout optical fibre tester is now available with a new 1500nm single mode long range port. This port allows testing of fibre links up to 64km. 1550-nanometre wavelength systems are extremely vulnerable to cable bends or kinks which cause system degradation or even failure. The also be made. The unit can also be set to take longer to answer if no messages have been left. Speed-dialling allows access to up to 15 fax and 15 telephone numbers at the press of a key. A further 100 fax/phone numbers with names can be stored in the electronic phone directory, featuring alphabetical search. A FAX/TEL switch can teli if the call is voice or fax and switch accordingly. Thus, all calls to the number are answered appropriately. For more information, contact Tony Poynton at Canon Australia, 1 Thomas Holt Drive, North Ryde, 2113. Phone (02) 805 2000. JANUA RY 1992 87 ·DC supplies with built-in protection Imark Communications has rele ased a range of Australian design ed and man ufactured regulate d power supplies. They are intended for use with high-powered trans ceivers or in service workshops and manufacturing app lications. There are four basic models in the series, ranging from 10-40 arhps current rating. They feature short circuit, overload and over-voltage protection. Depending on the model, they come,w ith meters for battery voltage, battery current, DC output voltage and DC output current. Other features include rem ote load sensing, over-voltage protection, low voltage battery release w ith indicator, fo ldback current limiting above th e preset voltage, and circuit breaker protection. Each model has excellent regulation and ripple rejection and com es in either a ben chtop model or a 19-inch rack mounting model. For further information , contact Owen Smart at Imark Communications , Unit 2, 75 Mark St, North Melbourne, Vic 305 1. Phone (03) 329 5433. FiberScout, with its new port, can easily identify bends and faults, their distance and related dB losses. Introduced in 1990, the FiberScout was the first handheld fault finder on the market. Other ports available for this unit are the multimode short range (3km), universal short range, and the long range (27 .5km). For more information, contact Kryssia Taggart at Tektronix on (02) 888 7066. work on breadboards etc, these will certainly save you many hours of stripping and tinning wires. The kit consists of 25 wires of each length in a perspex case. It is available from Rod Irving Electronics, 74 Parramatta Rd, Stanmore NSW, or from their Melbourne stores. Jumper wire kit for prototyping The MGI Solitare 8xp film recorder is capable of reproducing images at up to 8,000-line resolution in a fraction of the time such machines have taken to date. It can produce a 35mm slide image in less than 30 seconds, making it faster to produce original slides than duplicates. Up to 68 billion colours may be scanned and through the use of digital geometry control, cameras can be aligned automatically. Colour correction, image adjustment and positioning are controllable via the front panel. Solitare can reproduce images on any of 17 different camera modules, the most popular being 35mm slides, 70mm, 35mm cine film and 8 x 10 and 4 x 5-inch transparencies. A variety of computer systems may be interfaced to the Solitare including: Silicon Graphics, MicroSun, DEC Micro- This jumper kit consists of 14 different lengths of wire from 0.1 -inch to 5-inches long, suitable for use in prototyping or experimental boards. All ends are pre-tinned and the wires are colour coded to make identification easy. If you are doing any design 88 SILICON CHIP vax, IBM and Apple Macintosh (through its SCSI or GPIB interface). Because of its high speed, the system has found a niche in animation and special effects applications by companies such as Imax, Omnibus, and American Film Technology. For more information, contact David Kidd at PBS Images, 10 Aquatic Drive, Frenchs Forest 2086. Phone (02) 451 8111. Smoke detector for households High-speed image recorder Many of the deaths caused by household fires are a result of the occupants being overcome by smoke inhalation. A battery operated smoke detector can help in.alerting people to the dangers before they become life threatening. The Smoke Signal from Universal uses an extremely small amount of radioactive material that ionizes in the presence of combustion particles; ie smoke. This causes the unit to alarm. Using this method of detection, false alarms are scarce and usually due to smoke products being produced by some other means. Smoking will not normally set off the unit unless smoke is blown directly into the detector. The Smoke Signal retails for $19.95 and comes from Jaycar Electronics. Phone (02) 743 5222. NTSCtoPAL video converter The CN-lO0P subcarrier converter allows an NTSC video signal to be displayed on a PAL video monitor. It is suitable for viewing NTSC signals from international satellite TV transmissions, NTSC laser disc players and VCRs. The unit operates from an AC adapter and has RCA connectors for inputs and outputs. Without going through the usual difficult process of standards conver- sion, this clever little device does it very simply but with the compromise that the pictures are displayed with slightly reduced height-just like wide screen movies on SBS. At $200, it is an easy way to view NTSC signals. For more information, contact AvComm Pty Ltd, PO Box 386, Northbridge, 2063. Phone (02) 949 7417. Build it yourself digital multimeter The MIC-7S is a 3½- digit DMM with ranges for AC and DC voltage and current, resistance and diode/ continuity. It is an ideal kit for schools, TAFEs and colleges. The instructions cover the assembly, the theory of operation, and component coding. Soldering and component handling are also discussed. Everything down to the last nut and bolt is included to get a complete digital multimeter up and working. At $79.95 ($62.50 ex tax), it is good value as a test instrument and a learning experience. For further information, contact Tom Onishi at The Electronic Component Shop, 1st Floor, 289 Latrobe New operations centre for Jaycar Street, Melbourne 3000. Phone (03) 670 6474 . High performance filter for phone lines The EM2000 is a new high perfomance common-mode filter for data and telephone lines. It offers 40dB attenuation of common-mode noise over the range of lO0kHz to 20MHz. Packaged as a 14-pin DIL device, it provides 1700V RMS isolation between lines. At $3.53 (250+), the EM2000 is an ideal choice for cost-effective EMI suppression. For more information, contact Peter Dau at Alpha Kilo Services, 1/144 Burns Bay Rd , Lane Cove, NSW 2066. Phone (02) 428 3122 . SC ANTRIM TOROIDAL TRANSFORMERS Jaycar Electronics has recently moved to a new 15 ,000 sq. ft . warehouse and operations centre in the Sydney suburb of Rhodes. The new centre incorporates a well-stocked retail store with plenty of parking nearby. Their store at Concord has now closed. Gary Johnston , Managing Director, said that the n ew centralised wareh ouse facility will enable Jaycar to increase its range of components and products, as well as improving service to customers. The n ew address is just off Concord Road at 6 Leeds St, Rhodes , NSW 2138. Phone (02) 743 5222 or fax (02) 743 2066. • • • • Now made in Australia Standard range 1SVA to 2kVA Large ex-stock ·quantities available Competitive pricing available for OEMs & resellers • Simply the best transformers all round HARBUCH ELECTRONICS PTY LTD 90 George St, Hornsby, NSW 2077. Phone (02) 476 5854 Fax (02) 476 3231 JA N UARY 1992 89 DIGITAL MULTI METER HC -4510 DISPLAY:41 /2 DIGIT B.ASIC ACCURACY: 0.5% DC V DC DC AC AC VOLTAGE: CURRENT: VOLTAGE: CURRENT: 0-1000V 0-10A 0-750V 0-10A RESISTANCE: 0-20M OHMS CONTINUITY TEST, DIODE TEST DATA HOLD (z,'ocf:, 20 MHz DUAL TRACE OSCILLOSCOPE NOW $129.95 CTR DISPLAY:· 1so mm rectangular 013030 . RRP $149.95 ,......,_._,, _ _ _.......... ___ __ _ _ _ _ _ _ _ _ _ _ _ _....;;;;;;;._..II VERTI ACAL DEFLECTION: DIGITAL MULTI METER HC-5010EC c. f\."J~ ~ · • Bandwidth DC: DC to 20 MH.z (-JdB) AC: 10H.z to 20 MH.z (-JdB) • Operating modes CH-A, CH-B, DUAL aRd ADD (ALTICHOP L202 only) • Chop Frequency: 200 KHz Approx. • Channel separation: Better than 60dB at 1 KH.z DISPLAY: 3 1/2 DIGIT BASIC ACCl)RACY: 0.5% DC DC VOLTAGE: 0·1000V DC CURRENT: 0-10A AC VOLTAGE: 0-750V AC CURRENT: 0-10A RESISTANCE: 0-20M OHMS CONTINUITY TEST, DIODE TEST • Deflection Factor: 5mV to 20V , Div on 12 r~nges in 1-2-5 step with fine control S\~ 013010 .................... RRP $119 .95 NOW $99.95 TIME BASE • Type: Automatic & normal triggered in automatic mode, sweep ,s obtained without input signal • Sweep Time: 0.2m Sec to 0.5 Seel Div on ranges in 1,:.2-s steo with .line _______ , control and X-Y. • Magnifier: X5 at all limes. TRIGGERING • Sensitivily lnt: 1 Div or Tl)ore Ext: 1Vp-p or more. •Source:INT,CH-B,LINEorEXT 1 I : : T HIS M O N TH ONLY I · 2 FREE CRO PROBES I Pull for Auto. • Sync: AC, HF Rej, TV (each+ or-) at TV Sync. TV-H (line) and (frame) sync are switched automatically by SWEEP TIMEIDiv switch. HORIZONTAL DEFLECTION • Defleclion factor: SmV lo 20VI Div on 12 ranges in 1-2-5 step with fine control • Frequency response: DC to MHz (-JdB) • Max Input Voltage: 300V DC+ AC Peak of 600V p-p • X-Y operation: X-Y mode is selected by SWEEP TIME/ Div switch. • Intensity Modulation Z Axis: TTL Level (3Vp-p- 50V) + bright, - dark OTHER SPECS: • Weight: 7Kg Approx • Dimensions: 162 (H) x 294(W) x 352(D)mm. DC VOLTAGE: 0-1000V DC CURRENT: 0-10A AC VOLTAGE: 0-750V RESISTANCE: 0-20M OHMS CONTINUITY TEST, DIODE TEST, DATA HOLD, TR HFE GAIN, AUTO RANGE DMM WITH BAR GRAPH -..on 013040 ... .. ..... ........... RRP $99.95 NOW $89.95 012105 .......................... RRP $750 NOW $695 DIGITAL MULTI METER HC-3500T DISPLAY:3/12 DIGIT BASIC ACCURACY: 0.5% DC , , - -~ •' • DC VOLTAGE: 0-1000V DC CURRENT: 0-20A AC VOLTAGE0-750V AC CURRENT 0-20A RESISTANCE: 0-20M OHMS IJ-,-..-tii-1 TEMPERATURE:-20C -1200C CONTINUiTY TEST, DIODE TEST TEMPERATURE CAPACITANCE FREQUENCY, hfe TEST, DATA HOLD. - - ~ - 013000 ....... .. ... ....... RRP $169.95 ,......_OIE,\.,-, ANALOGUE/DIGITAL MULTIMETER HC-5050DB 3 1/2 DIGIT ·BASIC ACCURACY: 0.5% DC -..a.JlU tt---iil" This instrument meets the customers needs in quality of performance, efficiency, function, design, and cost! Being rugged, highly reliable and a multi-purpose 3 channel, 8 trace oscilloscope with a 6 inch domed mesh type 14kV post deflection acceleration cathode-ray tube and with a fine red internal graticule. FEATURES: • Compactness, lightweight, ruggedness and •(~pie design. • The diecast frame provides compactness lightweight and ruggedness. • Easy Operation Light torque lever switches and push button switches are used. • High Brightness CTR, high acceleration voltage and high beam efficiency of the 150mm rectangular CTR ensures a bright high speedsweep observation • Multi mode display system • CH1, CH2, CHJ, Add any combination or all the channels may be viewed aimultaniously. Maximum 8 trace displaying is possible with the ALT sweep function. • High sensitivity and wide frequency bandwidth . The maximum vertical sensit ivity is 1 mVIDIV (when x 5 MAG)at 20 MH.z or greater JdB and mVIDIV at 100 MHz or greater -JdB. High input impendance The input impendance of CH1, CH2, CHJ, is 1Mnt2%, 25pFt3pF _ _ ...,;"'I DC VOLTAGE: 0-1000V DC CURRENT: O-iOA ...-u..-,.-,,. 100 MHz 3 CHANNEL 8 TRACE MODEL 5510 NOW $149.95 AC VOLTAGE: 0-750V AC CURRENT: 0·10A RESISTANCE: 0-20M OHMS DC AC RMS :-45dB ·+S0dB TEMPERATURE: ·20C-1200C AC FREQ SPREAD: 50Hz-2KHz CONTINUITY TEST, DIODE TEST .................. RRP $169.95 NOW $149.95 !!l-'_013020 ,,_....,.,_.,...,..~...,.----------------1 • LOGIC PROBE (LP-2800) .,._ ail Q12109 ......... RRP $2995.00 NOW $1,995 USEFULFORTTLANDCMOS. HIGH & LOW INDICATORS ~~~\EH~~~~~iESTORSERIOUSTECHNIICIAN - - : . 6~RL6~~g~iA1:o~E HARD To FIND FAULTS -..o::;..ari,11 011272. ......... ............ .. .:.. RRP$29.~5 NOW $19.95 SCHOOLS & COLLEGES TAKE NOTE! ONLY $1,695 tax exempt. • I 1 L-- ---- -----• ___j • Triggering Level: Positive and Negetive, continuously variable level; DISPLAY: 3 1/2 DIGIT I : -SOME BNC MALE PLUG 1-9 11;-99 100+ ""'" ~ ,,.~ QUALITY 3mm LEDS 1-9 10-99 100+ Z10140(R) $0.15 Z10141(G) .. $0.20 Z10143(Y) .. $0.20 Z10145(0) .. $0.20 $0.12 $0.18 $0.18 $0.18 $0.10 $0.15 $0.15 $0.15 QUALITY 5mm LEDS BNC PANEL SOCKET - 1-9 10+ 100+ P10516 $2.50 $2.25 $1.50 :: ii• •· --- Z10150(R). $0.15 $0.12 $0.10 Z10151(G). $0.25 $0,20 $0.18 Z10152(Y) .. $0.25 $0.20 $0.18 ------ FLASHING LEDS BNC CR IMP PLUG 1·~ 10-99 100+ P10530 $3.95 $3.75 $3.00 RED5mm Z10159 Designed to transmit at 40kHz (L 19990) & recieve at 40kHz (L19991) withup to 20V 1/P on the transmitter. These units can't be heard so are ideal for TV remote controls, water level dectectors, burglar alarms, motion dectectors & information carriers as they can be either pulsed or used in a continuous wave mode. Transmitter 1-9 10+ L19990....... $2.95 $1.95 I only II L----- ----- 9 PIN D SWITCH BOXES , THIS MONTHS TOP TEN GAME SPECIALS! THEIR FINEST HOUR. ........................... $59.95 SEARCH FOR THE KING ...................... $59.95 LINKS CHALLENGE GOLF.... ."......-........ $59.95 ELVIRA ................................................... $69.95 JET SET PACK ...................................... $59.95 KINGS QUEST FIVE .............................. $69.95 SECRET OF MONKEY ISLAND ............ $59.95 HEART OF CHINA ................................. $69.95 RED BARON ........... ............................... $69.95 TEST DRIVE ll.. ...................................... $69.95 BNC SOLDER LESS TWIST ON PLUG PANEL METERS CANNON PLUGS AND SOCKETS 2 WAY................ $59.95 4 WAY................ $69.95 MONITOR & KEYBOARD SWITCH BOXES only $69.50 Save a fortune on expensive throw away batteries with these quality Nicads and Rechargersl Size AA 450mAH 1-9 10+ $2.95 $2 75 100+ $2.50 Size C 1 2;.. H $9.95 $9.50 $8.95 Size D 1 2 AH $9.95 D TYPE IDC PLUGS 1-9 CANNON TYPE 3 PIN CHASSIS MALE 1-9 10-99 CANNON TYPE 3 PIN LINE FEMALE 1·9 10-99 100+ P10964 $3.95 $3.50 $2.90 0 CANNON TYPE 3 PIN CHASSIS FEMALE 1-9 P12166 $1.50 $1.20 $1 .00 10-99 100+ · P10966 $4.95 $4.50 $3.50 DB25 CONNECTOR SPECIALS 1~9 • DA15P 1Spln plug 100+ P10962 $3.50 $2.95 $2.50 10+ , DE9P 9pln plug P12168 $1.50 $1.20 $1.00 LOW PROFILE IC SOCKETS Save a small fortune on these "Direct Import" low profile IC sockots ! PCB mounting solder tail. All tin plated phosphor bronze or borrylllum and dual wlpo for rellablllty. 1-9 10+ 100+ P10550 8 pin 15e 12e lOC P10560 14pin 20e 18C 15C P1056516pln 20C 18C 16C P1oss11apin 30e 25e 22e P 1oss8 20pin 35e 30e 25e P10569 22pin 35e 30e 26e P1os10 24pin 35e 30e 26e P1os12 28pin 45C 35e 30e P1os1s 40pin 45e 40e 35e • 0825P 25 pl11 plug •• P12170 $4.50 $3.95 $3.50 P10880 DE9P P10885 DE9S P10891 DA 15S P10892 DA15C P10ll95 DA 15S P10002 DB25C P10904 DB25P P10005 DB25S 10+ $1.00 $0.80 $1.00 $0.70 $1.00 $0. 70 $1.00 $0.90 $1.00 $0.80 $1.00 $0.80 $1.00 $0.80 $1.00 $0.80 DTYPE IDCSOCKETS 1-9 • DEBS 8 pin 110cket P12107 $1.50 $1.20 $1.00 • DA15S 15 pin aocket P12169 $1.50 $1.20 $1.00 , 0825S 15 pin aocket w 1·9 10-99 1·9 100+ WIRE WRAP IC SOCKETS Theso quality 3 lovol wire COMPUTER CABLES • Six conductor ahlelded computer Interlace cable. W12670 • CIC6 6 con. 1-BM 10M+ 100M+ $1.30M $1 .10M $1.00M W12672 • CIC9 9 con. wrap sockets are tin plated phosphor bronzo. P10579 Spin P10580 14pin P1058516pin P10587 18pin P10590 20pin P10592 22pin P10594 24pin P10596 28pin P10598 40pin $1 .50 $1.85 $1.95 $1.95 $2.95 $2.95 $3.95 $3.95 $4.95 $1 ,40 $1.70 $1.80 $1.80 $2.75 $2.70 $3.50 $3.50 $4.50 10+ • Plug P12200 $3.95 $3.00 • Socket P12201 $3.95 $3.00 L FANS C =:) 12V DC FANS 80 x 80 x 25.4mm Oeacrlptlon 1.9 10+ 7805UC 7812UC 7815UC 7905UC 7912UC 791 SUC 78L05 78L12 LM324 555 $0.50 $0.50 $0.50 $0 30 $CJ.60 $0.60 $0.40 $0.40 $1.00 $0.40 $0.50 ~ $9.50 $8.00 $8.90 TOGGLE SWITCHES CANNON TYPE 3 PIN LINE MALE P10960 $4.50 $3.50 $2.50 We have a great range of HEATSiNK panel meters at great prices I COMPOUND 010500 MU45 0•1n,A $9.95 010502 MU45 5()150uA $9.95 010504 MU45 0·100UA $9.95 010533 MU52E 0-SUA $12.95 010538 MU65 0-sOuA $12.95 010540 MUSS 0-lmA $12.95 Heatsink compound is 010550 MU650-100uA$12.95 applied to the base and 010560 MU650-20V $12.95 ' mounting studs of transistors & diodes. It MOSFET maintains a positive SPECIALS heatsink seal that improves heat transfer from the device to the heatsink, thus increasing overall ~O+ efficiency. $9.50 $8.00 $10.00 $8.50 $9.50 P12171 $4.50 $3.95 $3.50 $0.45 $0.45 $0.45 $0.55 $0.55 $0.55 $0.30 $0.30 $0.90 $0.38 $0.45 12V DC. 1.7 Watt 0.14 Amp T12469 ................ $18.95 10+ fans, only $17.95 FANS Quality fans for use In power amps, computer hotspot coollng otc. Anywhere you neod plonty of air. 240V 4 5/8" T12461..$16.95 115V 4 5/8" T12463 .. $16.95 240V 3 112" T12465 .. $16.95 115V 31 /2" T12467..$16.95 10+ fan ■ (mixed) Only $14.95. $9.50 H11800 .. 10g ... $2.00 H11810.150g. $29.95 L/:.iijiii''iiiii 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. Updating old Magnavox speakers I am about to update my speakers as they are getting a bit long in the tooth. They were originally Magnavox MV50s using an 8-30 midrange, 10-40 woofer and two 15Q tweeters and I think were of 60-litre capacity. As the cabinets are in excellent condition and I'd like to save a buck, could I make your new speaker system in these? How do you work out box size in litres? My enclosures are 435mm wide by 670mm high by 295mm deep and are made of 19mm pineboard. The rear panel is flush while the front baffle is recessed 13mm in from the front edge of cabinet. I will replace the baffle with a new one as my cutouts aren't compatible with yours. It's a pity you didn't give details of the crossover network as I like to make my own - the bought ones are usually inferior unless you pay "lotsa dough" for them. If the increased internal volume of mine causes problems, I could soon eliminate it but possibly it would give a lower bottom end? My tweeters are no longer original and neither are the woofers as both 1net with a blown amplifier. I was wondering why you didn't try the Peerless range from Dick Smith Electronics which are excellent value compared to say Vifa speakers and I as- sume would be in good supply? I must say I really enjoy your excellent magazine and have never missed a copy. There's always at least one project of interest each month and often more. Why do you have such long part numbers for your PC boards? - all the other magazines have nice simple ones. Please let me know what your opinion is regards the above. (P. G., Orient Pt, NSW). • Calculating the volume in litres is done as follows. Take the internal dimensions and convert them to centimetres. Your enclosure therefore has internal dimensions of 39.7 x 63.2 x 24.4cm. Multiplying these together gives a volume of 61220 cubic centimetres. You then divide this figure by 1000 to get the result in litres. Your enclosures have a volume of 61.2 litres. They could be used without any change for the system described in the September 1991 issue of SILICON CHIP. The standard crossover networks specified are not expensive so you would not save much money there. We could undoubtedly have used Peerless loudspeakers but the overall system would then have been more expensive. Our PC boards have a long number because they are directly related to our filing system for project articles. It works as follows. The first two numbers give the project category (eg, 01 means an audio project). The next number identifies the number of the project because there might be more than one audio project that month. The next four numbers give the month and year of the project while the last number gives the board number because there may be more than one board for a given project. Hence, in last month's issue, the light beam relay project has a board number of SC03112911. The "03" gives the project category of "security" and there's only one project in that category, hence 031. The 1291 figure is the month and year and there is only one board for the project so the last number is 1. Got it? Zenith radio at the nadir I ask if you could help me find a circuit diagram and component layout for a "Zenith" brand radio, via your magazine's readers. The radio is a portable, DC only, AM-FM-SW receiver. It has six shortwave bands, extending to 18.4MHz. Its full model ID is "Royal 3000-1". Date of manufacture is 1968. Country of manufacture is the USA. Any help would be greatly appreciated. (David Tindall, c/o Alcorns Communications, 3/690 Nicklin Way, Currimundi, Qld 4551). Hall Effect pickup for ignition system Recycling aluminium from an old antenna I am wishing to build the UHF TV antenna described in your June 1991 issue. I have an old VHF antenna withxound tubular elements (approx 6-7mm). Could these be used for the reflectors, and could pipe (approx 20mm) be used for the reflector booms? Also were could I get the kit for the balun box? (D. F., Pittsworth, Qld) . 92 SILICON CHIP • There is no reason why you cannot use the round tubular elements from your old antenna to make the new one. Similarly, you can use larger aluminium for the reflector sections. The only disadvantage will be that the antenna will be somewhat heavier and will have more wind resistance (windage) . No kit is available for the balun box as such, although you can buy the PC board from one of our listed suppliers on page 96. I wish to know if it is possible to use a Siemens Hall Effect sensor in , place of the reluctor for the ignition system published in the May 1990 edition, of SILICON CHIP. I want to try to use the above as I do not know where to buy a reluctor and I can get the Hall Effect sensor from Jaycar. (K. M., North Booval, Qld). • We would recommend you use the version of the circuit published in SILICON CHIP in June 1988. This was specifically designed for the Siemens Hall Effect device. Back copies of this issue have been sold out for some time now but we can photocopy the article for you for $5.00, including postage. Reliable reception with the Radfax Decoder I have recently purchased and assembled the Radfax Decoder as described in the November 1989 issue of SILICON CHIP. The decoder appears to be operating but I have been unable to tune the unit properly to a fax signal, or to have the software respond to the decoder input. The instructions only say to check for +5V on the designated IC pins, then "the LED will tell you that the decoder is working." The 5V rail is active and the LED does respond to audio inputs (ie, it flashes in time with a Morse signal and lights in response to voice or noise on a received signal). I cannot tune the decoder to give a steady LED from a fax and the LED appears to respond more to the noise on the signal than to the signal itself. The software does not respond at all to the decoder input. To assist me, could you please provide the following information: (1) What should the LED do when a fax is "tuned" (both on the preliminary signal and when the fax transmission starts)? (2) What is the centre frequency and baud rate for the Melbourne weather faxes? (3) Is there a positive test that I can do to prove that the decoder is working correctly? (B. L., Wynnum, Qld). • The LED should light continuously when tuned to a weather fax transmission when there is a preliminary signal sent and should flash on reception of a fax picture signal. For information on the transmission frequency and baud rate of Melbourne weather faxes, we suggest that you to contact the Melbourne Bureau of Meteorology. The actual transmission frequency is varied to best suit current atmospheric conditions. To reliably receive a fax picture, you must have a noise-free signal and your BFO must be critically adjusted for best results. Keep the receiver away from your computer to void picking up noise from that source. Also, it is very difficult to pick up fax signals during the day. You will get the best results at night. Questions on the UHF corner reflector Could you please give more information on the UHF corner reflector antenna which appeared in the June 1991 of SILICON CHIP? Can the air core balun be used in other applications where a 300/75 ohm vnbalanced transformer is required? How does it fare against the commercial balun wound on a ferrite core? Are th~te splitters with less than 3.SdB loss available commercially? Could I use a diplexer the other way around as a splitter? Could you give me the length of the dipole to get the VHF channels?. What ~ould be the dB gain and back to front ratio? Could I use expanded mesh aluminium as a reflector on the above antenna? How well will a VHF version of the antenna perform (at least theo- Higher power version of Mosfet amplifier I would like to make some changes to your 120 watt PA module, as described in the November 1988 issue of SILICON CHIP. I have used this module in many projects of mine and I have made many more for friends. All are still working flawlessly with plenty of punishment I assure you. Lately, I have found the need for higher power output from a mosfet power module. What I would like to do is replace the output devices with 2SK176 and 2SJ56 Mosfets and then raise the supply rails to as high as ±70V using a 50+50V 300VA toroidal transformer. Will this module handle this or, if not, is it an easy job to change other components to allow for the higher supply? If the basic design of the 120watt module is beyond this, is there a new design on the drawing board, capable of 250-300 watts into 4 ohms? Also, is there any chance of doing an article on the Carver Pro range of power amplifiers and how they achieve such incredible power from so little weight. (A. J., Nowra, NSW). • Your concept of increasing the rating of the output devices is OK but you will have to use more paralleled retically) and if you don't recommend it, please explain why not. (G. D., Morwell, Vic). • The air core balun can be used in other applications where a 300/ 75Q balun is required. It should be at least as good as commercial baluns. We don't know of any splitters with less than 3.5dB loss. You can use a diplexer in the reverse direction as a splitter. We would not advise building the corner reflector for VHF reception. For a start, the dipole would be very large and have a lot of windage and it would be difficult to cover the whole band. In fact, the reflector elements would need to be about 2.5m long. You can use expanded mesh aluminium as the reflector for the UHF version. It will perform better than the rods as a reflector but may not last as long. output devices to get sufficient output current rating to obtain your required power. We would suggest that you will need eight devices (ie, four N-channel and four P-channel) in the output stage. In principle this should work but in practice it there may be a big problem laying out a suitable PC board. We don't have a new design on the drawing board but we hope to do a design later this year. We have no plans to describe the Carver amplifiers but essentially they use the same principle as the NAD power amplifier - it uses thermistors in the power supply so that it can deliver lots oipower in the short term but not so much on a continuous basis. This means you get an amplifier with lots of headroom and a relatively cheap power supply, considering the peak power rating. Notes & errata Digital Altimeter for Gliders & Ultralights; September, October and November 1991: the wiring diagram on page 33 of the November 1991 issue shows the two outer wires to the Barometer Adjust potentiometer (VR6) transposed. The circuit diagram is correct. SC JANUARY 1992 93 MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. r-------------------------, 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. To run your classified ad, print it clearly on the lines below or on a separate sheet of paper & send it with your cheque or credit card details to : Silicon Chip Classifieds, PO Box 139, Collaroy Beach, NSW 2097. Or fax the details to (02) 979 6503. I I I I I I ANTIQU E RADIO ANTIQUE RADIO restorations. Your one-stop radio repair shop. Specialising in restoring vintage radios including chassis rewiring , re-condensing , quality new parts, valves, valve sockets, speakers, power & audio transformers. Secondhand radio dials & parts for most brands & models. About 400 radios in stock for sale, restoration & parts. Every restored wireless is covered by a 2year warranty on parts & labour. We restore damaged woodwork & cabinets & French polish (approx. 40 coats) . Vintage car radios available for sale or restoration. Repairs done on tape decks & amplifiers. Open Sat. 10am-5pm; Sun. 12.30-5pm. 109 Cann St, Bass Hill, NSW 2197. Phone (02) 645 3173 BH or (02} 726 1613 AH. FOR SALE Enclosed is my cheque/money order for $_ _ __ O Bankcard 0 Visa Card 0 Master Card ~ - II_ __II·I or please debit my XI I I Signature_ _ _ _ _ _ _ _ _ _ _ Card expiry date_ _~ /_ __ I I Name _ __ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ I I Street _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ I I Suburb/town _ __ _ __ _ _ _ _ _ Postcode_ _ _ _ __ L _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ JI Card No. 94 SILICON CHIP WEATHER FAX programs for IBM XT/ ATs *** "RADFAX2" $35 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" $45 is a NOAA, Meteor & GMS weather satellite picture receiving program. Uses EGA & VGA modes, needs EGA or VGA colour monitor & card, plus "WEATHER FAX" PC card. $45. ••• All programs are on 5.25inch or 3.5-inch discs (state which) & include documentation. Add $3 postage. Only from M. Delahunty, 42 Villiers St, New Farm, 4004 Old. Phone (07) 358 2785. COMP.ONENTS SPECIALS available until end April 1992. MC14433 digital panel meter chip $15.00 (new stock). MC45512 memory telephone dialler chip $10.00. 4001, 4011, 4071, 4081 $0.40 ea for 10 up. 4013, 4017, 4024, 4040 $0.80 ea in lots of 10 up. 7805, 7808, 78L05, 78L08 $0.40 ea. 1N914 $0.05 ea, 1N4004 $0.07 ea. 2114 static RAM chips $1 .50 ea, data available. P&P on components $4.00 up to order value of $200.00. Ring for postage rates on higher order values. CTOAN Electronics, PO Box 33, Condell Park, NSW 2200. Phone (02) 708 3763. r Prices at December 1, 1991 SIMM 1MBx9 1MBx 8 IBM COMPATIBLE computer kits & accessories. Button spike protector $37.00. 6-socket power boards with surge/spike protection $49.00. Pack/ post $3.00. Send for a free price list. M.T.S. Electronics, PO Box 1013 Taree, NSW 2430. Phone (065) 53 1296. DIGITAL SPEEDO kit $50.00. Digital tacho with 10RPM resolution $49.00. Memory telephone dialler with single button dialling $30.00. 40kHz crystals $12.00. Hall effec;t sensors $4.00. Certified P&P $5.00. CTOAN Electronics, PO Box 33, Condell Park, NSW 2200. Phone (02) 708 3763. GARAGE DOOR REMOTE control kit: see SILICON CHIP March/April 1991. For orders received before the end of January 1992, we are offering one complete receiver kit and one ready made transmitter for the special price of $94. Oatley Electronics, PO Box 89, Oatley, NSW 2223. Phone (02) 579 4985. GREEN LASER TUBES: we have a limited supply of 1.5mW laser tubes with a green output beam. These appear as bright as 5mW red lasers because of the relative response of the human eye. Priced at about 1/3 their real value at only $399. Oatley Electronics, PO Box 89, Oatley, NSW 2223. Phone (02) 579 4985. VISIBLE LASER DIODE BARGAIN: we supply a used & tested 3mW visible red laser diode with its own high-quality collimator assembly, a simple constant current source circuit & components to suit. Only $94. Oatley Electronics, PO Box 89, Oatley, 2223. Phone (02) 579 4985. CHEAPEST LASER EVER? We have a good supply of some new & near new laser heads with minor beam geometry problems. They produce outputs from 1-2mW. We can provide our 12V laser supply & one of these tubes for only $89. Oatley Electronics, PO Box 89, Oatley, 2223. Phone (02) 579 4985. UNIVERSAL TEMPERATURE control: as per SILICON CHIP June 1989. We provide the complete kit including hard- "'I MEMORY EXPANSION 4MB x9 256 X 9 (For SIP 100ns 80ns 100ns 80ns 80ns 80ns add $1) DRAM-DIP 1MBx 1 80ns 256 X 4 100ns 80ns 41256 120ns 100ns 80ns 55.00 57.00 48.00 53.00 225.00 16.00 6.40 6.30 6.50 1.80 2.00 2.20 PELHAM \.. COPROCESSORS 80387-DX 25 80387-SX 16 8028710MHz 80287 To 20 173.00 142.00 95.00 156.00 FLOPPY DRIVES 3.5 Panasonic 1.44 3.5 Teac 1.44 5.25 Panasonic 1.2 80.00 86.00 92.00 EXPANSION CARDS LS 866N 32Mb OK 240.00 AST RAM plus 8Mb 350.00 BOCA AT plus 8Mb 250.00 SPECIALS Sun SLC Sharp 6220 Sharp 8081 PS/2(ALL) PS/2(ALL) Mac FX/NIX Laser Printers 4Mb 1Mb 1Mb 2Mb 4Mb 4Mb 2Mb 250.00 160.00 100.00 150.00 295.00 230.00 206.00 SOCKETS Simm Sockets 30 x 1 Vert Simm Sockets 30 x 2 Ang Simm Sockets 30 x 2 Vert 1.70 3.50 3.20 Sales Tax 20%. Overnight Delivery . Credit Cards Welcome 1st Floor, 100 Yarrara Road, Pennant Hills, NSW 2120. Tel (02) 980 6988 DIGI-CART DSP BOARD For 16-bit IBM compatibles. Broadcast quality 44.1 kHz/16-bit stereo audio with audio recorder software. $1599 + tax Custom software service for applications available. PC Computers (08) 332 6513 36 Regent St, Kensington SA. ware but no case. Clearance at $20. Oatley Electronics, PO Box 89, Oatley, 2223. Phone (02) 579 4985. FOR SALE: OVER 250 brand new television valves. Reasonable offers accepted. Sell complete or lots. E, Cunningham, 310 Brazil St, Broken Hill 2880. Phone A.H. (080) 87 6460. UNUSUAL BOOKS. Fireworks, locksmithing, radar invisibility, surveillance, unusual chemistry and more. Send SASE for catalog to: Vector Press, Dept. S, PO Box 434, Brighton, 5048 SA. SOLAR PANELS, wind generators, batteries, inverters, etc. Our 50-page Fax (02) 980 6991 ~ FIX-A-KIT KIT REPAIR & CONSTRUCTION 3 MONTHS WARRANTY ON REPAIRS 12 MONTHS WARRANTY ON CONSTRUCTION TECHNICAL ASSISTANCE HVCAL ELECTRONICS Design, Manufacture & Repair of Electronic Equipment (02) 633 5477 TRANSFORMER REWINDS ALL TYPES OF TRANSFORMER REWINDS TRANSFORMER REWINDS Reply Paid No.2, PO Box 438, Singleton, NSW 2330. Ph: (065) 761291. Fax: (065) 761003. Solar Engineering catalog is the definitive statement on equipment and price! Send $15 to Solar Technology, PO Box 1129, Esperance 6450. Phone (090) 71 3719. 2.8Mb BACKPACK external disk drive for PC/XT/AT/PS1/PS2/etc. No internal connection. Runs off compatible printer port. Printer still supported. Simple in- WANTED: YOUR CIRCUIT & DESIGN IDEAS Do you have a good circuit idea languishing in the ol' brain cells? If so, why not sketch it out, write a brief description & send it into us? Provided your idea is workable & original, we'll publish it in Circuit Notebook & you'll make some money. You'll also help save us from the dreadful "circuit burnout" syndrome which afflicts anyone who has to generate too many circuit ideas in too short a time. We'll pay up to $60 for a really good circuit (not too big please). So transfer your circuit to paper & send it to Silicon Chip Publications, PO Box 139, Collaroy Beach, NSW 2097. JANUARY 1992 95 r-------------------------, SILICON CHIP BINDERS Protect your valuable issues with a special binder from SILICON CHIP. Our binders feature heavy board covers, are made from a distinctive two-tone green vinyl, and have the SILICON CHIP logo printed in gold-coloured lettering on the spine and front cover. They hold up to 14 issues and will look great on your bookshelf. Price: $A 11.95 + $A3 p&p or buy a subscription and get a discount on the first binder (see the subscription order form in this issue).To order, simply fill in & mail this coupon or phone or fax your order to Silicon Chip Publications. x Yes! Please send me _ _ _ SILICON CHIP binder(s) at $A 11.95 plus $A3 p&p each (NZ $A6 p&p) . I I I I I I I I I I Card No. D Visa Card Altronics ... .... .. ... ... ... ........ .... . 24-27 Antique Radio Restorations ... ... 94 Av-Comm ..... .... ..... .. .. ... ............. 39 Bose Australia ...... .................. OBC Coursemaster Autopilots ... .... .... 77 David Reid Electronics ...... .. 2,3,67 Harbuch Electronics .................. 89 Harvey Norman Discounts ....... IFC Hycal Instruments .. .. ... ...... ........ 95 Jaycar Electronics .. .. ... ...... .. . 45-52 Enclosed is my cheque/money order for $_ _ _ _ or please debit my 0 Bankcard Advertising Index J.V. Tuners ...... ...... ... ...... ........ ... 37 D Master Card Nav. Management Systems .... .. 77 Oatley Electronics ... .. ....... .. .. 41,95 ~ __,__,I I'----''--'------'--'I l'--'------'__,__,I ~I~__, Obiat ....... ..... .......................... ..... 7 Pat ex Systems ........ ..... ... .......... 86 Signature_ _ _ _ _ _ _ _ _ _ _ _ Card expiry date_ _ _/_ __ Name - - - - - - - - - - - - -- - - - - -- -- - - Street _ __ _ _ __ _ _ _ __ _ _ _ _ _ _ _ _ _ _ __ PC Computers ........... ....... ..... ... 95 PC Marketplace .. ... ... ...... .... .... .. 73 Pelham .. ... .. ... ... .... ...... .... ... ........ 95 Preston Electronics .. ....... ... ....... 37 Protel Technology .. .. .. ....... ... ..... 33 Suburb/town _ __ __ _ _ _ _ _ _ _ Postcode_ _ _ _ __ RCS Radio ............. ... ....... .. .... ... 23 Resurrection Radio ................... 61 SILICON CHIP PUBLICATIONS PO Box 139, Collaroy Beach, NSW 2097, Australia. Phone (02) 979 5644 Rod Irving Electronics .... .. .. .. 14, 15 Fax: (02) 979 6503. 62,63,90,91 L-------------------------~ stallation. Suit laptops or any PC upgrade. 3.5-inch 2.8Mb drive accepts 1.4Mb and 720Kb disks. $599. 5.25inch 1 .2Mb drive accepts 360Kb disks. $499 . Prices include tax, postage and insurance. Don McKenzie, 29 Ellesmere Crescent, Tullamarine 3043. PC TALKING VOLTMETER software. For project published in SILICON CHIP, Oct/Nov 1991. Plugs into the printer port of any IBM PC/XT/AT/386 or compatible. Displays voltages up to ±128V on screen, takes voltage samples over time, 8-bit accuracy to within 1%, combines with the PCVOICE RECORDER to give a talking voltmeter. Available on 5¼inch 360Kb disc plus documentation and instructions for $35 plus $3pp. Also available PCVOICE RECORDER software - turn your computer into an audio recorder $25 + $3pp (VGA/EGA/CGA/ MONO) . MS-DOS required. Send your cheque or money order to Darren Yates, PO Box 134, French 's Forest, NSW 2086. 96 SILICON CHIP Silicon Chip Binders ...... ........ .... 96 Stewart Electronics ... ... ...... ... .... 96 Forty pages of dreams! z ID I: St Lucia ..... ..... .......... ... ... ... ........ 83 Subscriptions ...... ....... .. .... ......... 81 Transformer Rewinds .. .............. 95 Yokogawa ................ ... ...... .. .. ...... 5 Zcomp ..... .. ... ..... ....... .... ..... .. .... IBC PC Boards Printed circuit boards for SILICON CHIP projects are made by: • Electronic Toy Services, 2/111 Glynville Drive, Hackham West, SA 5163. Phone (08) 382 8919. • Jemal Products, 5 Forge St, Welshpool, WA 6106. Phone (09) 350 5555. • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone 88 5730. • RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 587 3491. 1 WHO SKIDDING WHO? THE NOTEBOOK IS ALREADYHERE!! ... and for 3 years has been an unparalleled success for 3,420 wise and canny Z88 Notebook owners in Australia. At under $1000 and 1kg - can you afford to NOT be one of them? READ ON and increase your productivity and leisure time the clever way for ever. For some time now there has been a lot of hype about the arrival of a new notebook computer (or three). If you don't know the facts you could be under the impression that th ese new notebooks are the first with any Macintosh capabilities to hit the Australian marketplace. WRONG!! BUT WHO'S KIDDING WHO? The Cambridge Z88 Notebook Computer has been the NUMBER 1 CHOICE WORLDWIDE _FOR OVER 3 YEARS, with full size QWERTY keyboard and the ability to talk to both Mac's and PC's - not to mention Amiga's, Atari's, Amstrad's etc. With the proven Z88 Notebook at under 1kg and under $1000 plus 20 hours use on 4AA batteries - who needs anything else? Oh - we almost forgot the lifetime guarantee. That's right, we give you a LIFETIME GUARANTEE with your Z88 Notebook computer FOR NO EXTRA CHARGE. Who else thi nks that much of you - or indeed their computer?? ORDER YOUR Z88 NOTEBOOK NOW BY CALLING ZCOMP ON (008) 244 328 A FREE CALL OR (02) 958 2797 POSTAL ADDRESS: PO BOX 106, NEUTRAL BAY, NSW 2089