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Tracking Lightning Strikes In Australia E=mc2 ,rigl,t/ So a 20MHz Cro Dual Trace 111itl, 2 x 1:110:1 probe, for under 1500.00 ? Tbat formala does'at seem to 111orl, oat. But after ,,eavJI calculatioa I've fouad t,,at it's t,,e be5t value 20MHz Cro arouad to111a. Cl-118A 20MHz Dual Trace Cro ONLY 1195,00 Noa1 in •~oclzl 12 moatbs 111arraat,Y SPECIFICATIONS: Frequency range up to 20MHz. Sensitivity: 5m V/D!V to IOV/ DIV. Sweep rate: 0.05us/ DIV to 50ms/DIV. Dual Trace; Yl Y.2, YI Y2. Dimensions: 212x/33x336mm /with cover). 4" screen. Includes 2 x 1:1 10:1 probes. IC-DESOLDERING TOOL HAKKO 926/50 SOLDERING STATION SC-SOOOA * Temperature adjustable: 200 * 24voll Ci> 50 wall element. The DIC SC-5000A solder remover features a diaphragm pump, motor, and temperature control circuit built into the handle. The SC-5000A solder remover is a compact one-piece unit which can also be used as a hot air tool - 480 deg. C. * Ceramic heating element. * Control accuracy : +/ - 5 deg . 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(3/16, 7 /32 ,1/ 4,9/32,5/16, * ■ SHORT WAVE RECEIVER * 1pc. T-Bar driver handle. * * FLUKE 7 9 SERIES II MULTIMETER $295.00 save $22.00 The meter you all been waiting tor!! ■ - ■ ~ -.: ·111if7 ~ r ~ ' ■ ■ ■ 11/32,3/8,7 /16,1/2"). lpc. 1/4" socket adaptor. lpc. bit adaptor. lpc. 90 deg. adaptor. - ■ -~-~ - =--,,. -- - Capacitance measurement. Frequency measurement. Fast analog bar graph. 4,000 count display. Automatic Touch Hold. 0.3% basic accuracy. Continuity beeper. All inputs protected. 3 year warranty . '--:.- Normally $290.00 on/y$19.95 Now $259.00 save $40.00 CDA 1 FM Stereo NYLON CALIPER * 150mm TrE:ar1.smitte,r * Input: 3.5mm plug. * Tuneable 89 - 91 MHz. only$4.95 * Range: 15 meters. * Power: 1 x AAA battery. The ·sutane Pencil Torch"' will melt solder, silver solder, small brazing rod, glass tubing, and many other materials. Now$49.95 save $20.00 only$9.95 ·why buy a kit at this price• 4 ZONE •KEYPAD• CONTROLLED ALARM SYSTEM "'fhe Control Panel has 4 sectors fol' N.O. and N.C. i nputs, a 5 amp relay output, horn speakel' output. and more. It is all controlled via a remote keypad, (four wire hook-up). 'fhat means yon can hide away the main control panel, on1. of veiw, and ope1·a1.e all your functions via the key1rnd. All yon have 1.o do is 1.o remember your PIN number. A ver y versitial, bu1. simple to use alarm system." • .. ····..· f/!:'-1?. . 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Box QI03, SYDNEY 2000 FAX: (02) 2618905 Ci: ~ ~~I E'iilli SAME DAY MAILORDER DESPATCH* ~\L:.al $5 - $25 ........ $4.00 $26 - $SO ...... $6.00 SSl - $JOO ...... $7.00 $101 - $499 .... $9.00 $SOO• ............ FREE lnltmlllional' - · September 1991 FEATURES 4 The Highs & Lows Of AID & DIA Conversion by Darren Yates Discover the basics of AID & D/ A conversion techniques 12 Plotting The Course Of Thunderstorms by Leo Simpson How lightning strikes are tracked LOOKING FOR a great pair of speakers to complement your hifi system? If you can follow a simple wiring diagram, you can build this exciting 3-way system for just $499. Details page 16. 88 The Story Of Electrical Energy, Pt.13 by Bryan Maher The Tumut 3 & Murray 1 power stations PROJECTS TO BUILD 16 Studio 3-55L 3-Way Loudspeaker System by Greg Swain Build them from a kit for excellent sound quality 28 Digital Altimeter For Gliders & Ultralights by John Clarke Portable unit has LCD readout & works to 19,990 feet 58 Build A Fax/Modem For Your Computer by Leo Simpson Assemble it yourself for just $299. 70 Ultrasonic Switch For Mains Appliances by Jeff Monegal If you stop moving, it switches the appliance off THIS COMPACT digital altimeter can display altitude up to 19,990 feet, has a barometric pressure offset adjustment & is ideal for use in ultralights, gliders, hang-gliders & balloons seepage 28. SPECIAL COLUMNS 40 Serviceman's Log by the TV Serviceman I'd never seen that one before 66 Computer Bits by Jennifer Bonnitcha Swapfiles, program groups & icons 78 Amateur Radio by Garry Cratt How glass-mount antennas work 82 Vintage Radio by John Hill Transistor radios are worth collecting HERE'S YOUR CHANCE to get a fax & modem all in one go. This combination fax/modem is available as a kit for just $299. Turn to page 58. DEPARTMENTS ' 3 36 53 55 2 Publisher's Letter Circuit Notebook Subscription Page Product Showcase SILICON CHIP 86 Back Issues 93 Ask Silicon Chip 95 Market Centre 96 Advertising Index Note: space restrictions this month have prevented us from publishing the Remote Control column & part 3 of the CD Error Analyser. These articles will be published in the October issue. Publisher & Editor-in-Chief PUBLISHER'S LETTER Leo Simpson, B.Bus. Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Darren Yates Reader Services Ann Jenkinson Sales & Marketing Mgr. Angela Clarke, B.A.(Comm.) Phone (02) 979 5644 Mobile phone (018) 28 5532 Regular Contributors The future of electronic mail This month, as usual, we have a mixture of projects and technical articles designed to tickle your electronics fancy. For those who are keen on high fidelity systems, we have an article on a 3-way loudspeaker system which can be built for a very reasonable price. It has been quite some time since we last described a loudspeaker system and in view of the number of different speaker combinations we have tried over the last few years, in the quest for good sound at a reasonable price, we are very pleased to finally present this system. For those who have an abiding interest in thunderstorms and lightning, and who doesn't as the thunderstorm season comes round once again, we have an article about a radio system which actually plots lightning strikes as they happen. This system will shortly be installed in Australia and will be a big advance in monitoring storms as they progress. But perhaps the most interesting project article this month is the one on the Fax/Modem, beginning on page 58. Whether or not you have a computer and whether or not you are interested in having a fax or a modem, this unit will be of particular interest. Why? Because it's so cheap. When you consider how expensive both modems and facsimile machines were just a few years ago, this under $300 unit represents another benchmark in the declining prices of computer-based equipment. As this trend continues, it's not too hard to see where this technology is likely to lead. Ultimately, many homes will have their own fax machines in fact many people already have a fax machine at home. But the machine of the future is likely to be much cheaper and will combine the capabilities of a plain paper fax, photocopier and modem for computer hookup. In fact, it is likely that s0me of these fax wonders will eventually have full sized computer keyboards so that you can sit down, dash off a short letter and then fax it anywhere, down the street or across the world. All this will probably be available in the not too distant future at a price of less than $500 in today's money. And what of the consequences of this technology? Well the postal service as we know it will probably cease to exist. Why bother going down the street to post a letter when you can zap it off without leaving your home and at less cost? It is well to remember that, ultimately, technical change comes about not because new technology is discovered but because it makes it possible to do things more easily, quickly and more cheaply. So read the Fax/Modem article on page 58 and take a look at a portent for the future. Leo Simpson Brendan Akhurst Jennifer Bonnitcha, B.A. Garry Cratt, VK2YBX John Hill Jim Lawler, MTETIA Bryan Maher, M.E., B.Sc. Jim Yalden, VK2YGY Bob Young Photography Stuart Bryce Editorial Advisory Panel Philip Watson, MIREE, VK2ZPW Norman Marks Steve Payor, B.Sc., B.E. SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. All material copyright ©. No part of this publication may be reproduced without prior written consent of the publisher. Printing: Magazine Printers Pty Ltd, Alexandria, NSW; Macquarie Print, Dubbo, NSW. Distribution: Network Distribution Company. ' Subscription rates: $42 per year in Australia. For overseas rates, refer to the subscription page in this issue. Liability: Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such e_quipment. 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 SEPTEMBER 1991 3 The highs & lows of AID & DIA conversion If you're new to electronics, then the idea of turning analog signals into digital highs and lows is probably ~ little hard to understand. In this article, we'll explain some of the basics behind this important area in electronics. H ple like talking in TLAs, or threeletter acronyms?) A microprocessor is one of those reasonably long ICs you'll see if you look inside your CD player. It controls the opening and closing the CD tray, the motor that spins the CD and where the laser diode sits to play the next track. However, microprocessors and computers in general can only deal with information that is in the form of a series of 1's and By DARREN YATES O's (or binary digits), yet very few scribed is an example of converting real life situations produce their redigital data (you pressing the switch) sults in a neat series of 1 's and O's. Most electrical parts such as mointo analog voltages (the CD player operating a motor which opens and tors, amplifiers and the like are operated by applying some known voltage closes the tray). It is an example of what is often to them. For example, the motor in a called a microprocessor-controlled toy car spins when the battery is condevice or MCD. (Isn't funny how peo- nected to it. Computers and microprocessors cannot generate these voltages on their own, nor can they understand these voltages if they are from sensing devices such as thermometers. This is where analog-to-digital and digital-to-analog converters come into play. Say you were going to take temperature measurements every couple of hours or so and you wanted to store the readings in a computer. We'll assume that you'll be using an electronic temperature measuring device that produces some voltage for a given temperature. If we feed this analog voltage, through an analog-to-digital converter (ADC), we get a digital row of l's and O's, known as a "word". The computer can now take this data in and recognise what it means through some software. If you were going to control a motor AVE you ever considered how your CD player works? You take the compact disc out of its protective jacket, you press the OPEN/CLOSE button on your CD player and the CD tray rolls out. You then place the CD in the tray, press the OPEN/CLOSE button again, and the player swallows your disc and produces clean, crisp stereo sound. The very process we have just de- .__..___ _ _ _ _ _ _ _ _ _ _ _--0 2.5V ANALOG 0 VOLTAGE 4R OUT EACH BIT: 1 =VREF (+SV) 0 = ov Fig.1: an R-2R-4R ladder network is the simplest DIA converter available. The resistor network simply behaves as a voltage divider. 4 SILICON CHIP SR 16R 32R 64R 128R LSB 0 Fig.2: the equivalent circuit for an R-2R ladder network when a logic 1 is applied to the MSB & all other inputs are at logic O. -L- - - - - - - DIGITALDATAIN-58 - - -- -M-S~ ANALOG :>----0 VOLTAGE 2R OUT Fig.3: this DIA converter uses just two resistor values & allows for easy expansion of the number of inputs. The output is buffered by an op amp wired as a voltage follower stage using your computer, connecting the digital data straight to the motor won't do the motor or the computer any good. A computer on its own, can only supply an ON/OFF control because of its digital nature. If we want to use computer data to vary the speed of the motor, we have to feed the digital output into a digital-to-analog converter (DAC), which produces a fixed voltage for a given word. The output of the DAC is then fed to the motor. Binary weighting Before we start talking further about ADCs and DACs, let's discuss how the conversion scale works. Let's say our computer can produce TABLE 1 (8) (4) (2) LSB (1) FRACT. 0 0 0 0 1/16 0 0 0 1 2/16 0 0 1 0 3/16 0 0 1 1 4/16 0 1 0 0 5/16 0 1 0 1 6/16 0 1 1 0 7/16 0 1 1 1 8/16 1 0 0 0 9/16 1 0 0 1 10/16 1 0 1 0 11 /16 1 0 1 1 12/16 1 1 0 0 13/16 1 1 0 1 14/16 1 1 1 0 15/16 1 1 1 1 16/16 MSB an output of four bits in a row; eg, 1111 (it could be any combination of 1's and 0's). To get precise values from this 4-bit word, we give each bit a numerical weighting. If we take our 4-bit word, the least significant bit (LSB) is the one on the righthand side and the most significant bit (MSB) is on the lefthand side. The LSB is worth 1, the next lowest is worth 2, the next 4 and the MSB is worth 8. If you look at Table 1, you can see how we can get individual values from 0 to 15 by just changing the pattern of 1 's and 0's. How it works In operation, an analog-to-digital converter takes the analog voltage we give it and compares it to an analog reference voltage. Let's say we feed in a voltage of 2.5V and our reference voltage is 5V. The ADC compares the two and produces the digital word "1000" at its output. If you look back at our chart in Table 1, this word corresponds to the decimal number 8. So how does this happen? Our input voltage of 2.5V is exactly half that of our reference voltage of 5V. The ADC then produces the dig- ital equivalent in its range; ie, half of 16 is 8. We then send this off to the computer, which recognises the value as half its maximum possible value. In this case, the LSB is worth 1/16 of the maximum value or in other words, we can get one of 16 possible readings. In most real situations, this isn't enough and so the number of bits is increased to 8 or, for really precise measurements, to 16 bits. Ifwe consider 16 bits and give each bit a weighting of double the previous one (ie, 1, 2, 4, 8, 16 etc), the 16th and most significant bit will have a weighting of 32,768. If we add all of these together, we get 65,536 possible combinations (zero to 65,535) . Your CD player uses 16 bits to turn the digital data back into a smooth analog voltage which then goes to your stereo amplifier. DIA converter types We'll start by looking at how we can make a DAC and by explaining how they work, as they are crucial to understanding how an ADC works. There are a number of different types of DAC, each differing in size, speed and cost. R-2R-4R DIA converters The simplest way to produce a DAC is to connect resistors to the digital output lines, join them all together and then take the analog voltage from the junction. If you look at Fig.1, the resistor connected to the MSB has a value of R, the next smallest bit has a resistor of value 2R, and so on. Since each bit has the same output voltage - ie, either 5V or 0V - the resistor network LSB 2R 2R 2R R 2R//2R = R 2R//(R+R) =R (1/4) (1/2) 2R 2R .,. 2R 2R R Fig.4: these three diagrams show how the resistor values in Fig.3 are built up. Note that the output impedance at each node in the resistor string is simply R. R 2R(R+(2R//(R+R))) =R (1/2) . SEPTEMBER 1991 5 "UNITS" 1 D 20R 40R 0 LSB MSB 10R "TENS" 64 D D 1 D MSB LSB 2R R SOR BR 4R Fig.5: basic scheme for a (BCD) binary coded decimal DIA converter. Note that each resistor in the tens digit is 10 times greater than its corresponding bit resistor in the units digit. This DAC works the same way as a binary DAC, except that we only use the first 10 possible values (0-9). the R-2R DAC shown in Fig.3. Let's see how this circuit works. If you look at it, each bit is half the value of the next significant bit. In order to get the correct voltage ratio, the resistors between two consecutive bits must appear as half. The circuit in Fig.3 achieves this even though it may not be apparent at first glance, so let's build it up a bit at a time. Fig.4 shows the progression as the circuit is built up. If we work out the parallel resistance in each stage, the total value should come to a value of acts like a giant voltage divider. If we feed in the word "1000000", we have a potential divider consisting of resistance R in series with the parallel combination of the seven other resistors. You can see this in Fig.2. Because all the other bits are zero, it's as if we connected the resistors to ground. These seven resistors in parallel give a value of R (or very close to R). In effect then, we have a potential divider with two resistors of value R. Basic electronics tells us that the voltage at the junction of the two resistors will be half the applied voltage. In our case, 5V was fed in, so we get 2.5V at the junction . The MSB has a weighted value of half the total range. In this case, the MSB has a weighting of 128 and the total range is 256. So with our initial 5V going into resistor R, we get 2.5V at the output. The problem though, is finding a suitable value of resistor. If we make R a value of 1kQ (a normal digital output should have a much greater load than this), then our largest resistor needs to be 128kQ. Now you can't buy a 128kQ resistor. The DAC we've just described is only an 8-bit version. If we extend it to 16 bits, then the largest resistor has to be 32,768 times the value we specify as R (a 32. 768MQ resistor?). R. This means that the voltage we get from each bit is half that of the next significal).t bit, which is just as we want. The value in brackets shows how much each bit contributes to the overall voltage if that bit is high. We can then feed the output of the DAC to an analog buffer to produce a low-impedance analog voltage as shown in Fig.3. BCD DIA converter On many occasions, particularly in digital multimeters, simple binary weighting is replaced by a binarycoded-decimal (BCD) number. This is a 4-bit binary word which goes from 0 to 9. If you go back to Table 1 and ignore the last six lines , any one of the first 10 lines constitutes a BCD number. Fig.5 shows a practical circuit of a 2-digit BCD DAC. If the binary equiva- R-2R DIA converter A clever solution to this problem is r--MSB R r-- "UNITS" ~ LSB 2R 4R MSB R BR 4.8R LSB 2R 4R R BODOR. The solution, shown in Fig.6, is similar to the R-2R solution we have already explained, except in this case a resistor of value 4.8R is placed in series between each digit. This allows us to make the resistors in each corresponding digit the same, so that we only have a ratio of eight between the highest and lowest resistor values. Switches In each case above, we have assumed that the digital bit coming into the DAC is the reference voltage; ie, if a high is represented by 5V, then 5V is the reference point. In practice, each bit is used to operate a switch which switches in the correct reference voltage, and not just the digital input to the DAC. This way, a much more accurate and precise reference level is produced. Fig. 7 shows an example of this. AID converters So how about AID converters then? Well, there are a number of wellknown and some not-so-well-known types of ADCs, differing in size, speed and cost. Counter AID converter The slowest and best-known type is the counter ADC. A block diagram of this type of counter is shown in "HUNDREDS"~ MSB BR lent of the number 64 is applied to the DAC, the output will be 641100 x VREF (ie , 5V), which is 3.2V. The way this works is that each bit of the tens digit has a resistance of 10 times Jess than the corresponding bit in the units digit so that it supplies 10 times the voltage. Each digit works the same way as the normal binary DAC, except that we only use the first 10 possible values (0-9). Again, though, we have the problem that as we go up in the number of digits, the resistance in the lower digits must go up in response. So if we had a 4-digit number, the resistance in the LSB of the units digit would be LSB 2R4R BR 4.BA ANALOG ,.........--ovoLTAGE OUT 6 SILICON CHIP Fig.6: the solution to the problem in Fig.5 is to install a 4.8R resistor in series between each set of digit resistors, as shown here. This allows us to use the same value resistors for each digit. Fig.7: in a practical DIA converter, the incoming digital data activates CMOS switches. These then switch a reference voltage to the resistor network to ensure accurate levels. .-----'Ylfll'r----- - - --OOUTPUT -:- Fig.8. It works as follows: When the circuit is first switched on, the counter output is zero. The digital word, containing all zeros, is fed to a DAC, such as shown in Fig.3. The analog output is fed into the inverting input of the op amp, which compares the DAC output to the incoming voltage. If the incoming voltage is higher, the output of the comparator goes high, enabling the counter to count up. As the digital word increases, the DAC output rises correspondingly until the DAC output is higher than the incoming voltage. At this point, the comparator output goes low, disabling the counter. The digital word at the counter output is then the digital value of the incoming voltage. Because they can only increment at the rate of the LSB , counter ADC's are very slow and so are not used where conversion speed is important (eg, in DAT recorders). Sample and hold circuitry also has to be added into circuits like this to hold the analog value RESET while the counter works its way up to the correct value. Tracking AID converter Fig.9 shows a simple but more useful variation of the counter ADC. Instead of an ordinary up counter, an up/down counter is used, and the output of the comparator is fed to the up/down control input. Let's look at how it works. Again, we assume that the counter reads zero when the circuit is first turned on. The output of the counter is fed into the DAC, whose output is fed back into the inverting input of the comparator. If the DAC output is lower than the input voltage, then the output of the comparator will be high, allowing the counter to count up. So, up to this point, it is similar in operation to the first ADC we considered. However, when the output of the DAC is higher than the input voltage, the comparator output goes low and this now forces the counter to count I UP COUNTER COMPARATOR I I I Another type of ADC, often used in digital multimeters, is the integration or dual-ramp ADC, an example of which is shown in Fig.10. These are used in systems requiring moderate cost and high accuracy but where speed of conversion is not a priority. It works like this: The analog signal is applied to the integrator and, at the same time, a counter is enabled and begins counting the incoming clock pulses. When the counter reaches a certain count (after a predetermined time, T), the control logic switches from the input voltage to a reference voltage, which is opposite in polarity. The counter at this time is reset and begins counting again, while the integrator begins slowly ramping down to ov. This is a very linear ramp because DIGITAL OUTPUT MSB UP/DOWN COUNTER I I Integration AID converters RESET DIGITAL OUTPUT MSB down. It continues to count down until the DAC output falls below the input voltage, at which point the counter is forced to count up again. As you can see, this type of ADC tracks the input voltage automatically and continuously. In the first ADC we described, the counter had to be reset after each conversion . Although Fig. 9 represents a big improvement in performance, we still have the problem of it incrementing at the LSB rate. So for an 8-bit ADC, it will take 256 clock cycles to go from minimum to maximum value. This is too slow for a CD player, for example, but this type of ADC is often used in less critical applications. DAC DAC OUTPUT DAC LSB LSB CLOCK Fig.8: the simplest AID converter is based on an UP counter, a DAC & a comparator. When the output of the DAC is lower than the input to the comparator, the counter counts up. It stops when the DAC output rises above the incoming voltage, at which point the counter is disabled. The digital word at the output of the counter then represents the incoming voltage. ANALOG t-----OOUTPUT CLOCK Fig.9: basic scheme for a tracking AID converter. It uses an UP/DOWN counter instead of the UP counter shown in Fig.8. This means that the counter can be clocked in either direction in response to the signal from the comparator stage & thus the counter accurately tracks the input. The advantage of this scheme is that the counter does not have to be reset after each reading. SEPTEMBER 1991 7 START CONVERSION RESET OMPARATOR CONTROL LOGIC l +1/2:21\(v;;,+VREF)T /RC -VREF t,t/RC ~ COUNTER COMPARATOR IS TRIPPED WHEN +1/2('v,;;+VREF)T/RC = VREFt,t/RC of the reference voltage, so that when the voltage of the integrator reaches OV, the value on the counter represents the digital proportion of VrN/ VREF· Integrating ADCs are often used in digital multimeters as their accuracy is independent of clock frequency and the capacitor value in the integrator. This is because the up and down slopes are equally affected. Successive-approximation When speed and accuracy are important, the successive-approximation ADC is the most cost-effective and requires only the number of bits plus one or two clock cycles to complete a conversion. In a 16-bit converter, for example, something like 17-18 clock cycles are required, regardless of the input voltage range. A block diagram and a basic timing interval are shown in Fig.11. Instead of comparing the input voltage to the entire range of values (which depends on the number of bits}, it compares it to each of the bits in turn. Starting off with the MSB, if the input voltage is higher than the DAC output with that bit being set (which would give a DAC output of half the full scale}, then the MSB becomes a "1". If the input is lower than that bit, then it is set to "O". The next least bit down, which is COMPARATOR ANALOG INPUT 0 - - - - - - - - t SIGNAL FS ANALOG INPUT +1/16FS __ l __ 618 ANALOG REFERENCE 4/8 218 STATUS (BUSY) SERIAL OUTPUT CLOCK >-----CLOCK OUTPUT ~--==TE=sT,.._---'=TE==s-=!-T--'-:T=es=T~-TIME MSB BIT 2 BIT 3 (b) (a) Fig.11: the successive-approximation AID converter is the most cost-effective scheme where speed & accuracy are important (eg, computer interfaces). In a 16-bit converter, it requires only 17-18 clock cycles to complete a conversion, regardless of the input voltage range. Unlike other AID converters which compare the input voltage to the entire range of values, this AID converter compares the input voltage to each of the bits in turn. 8 SILICON CHIP DIGITAL OUTPUT (OFFSET BINARY OR 2's COMP.) j t,t/T(PROPORTIONAL TO FS COUNT): 1/2 ((v,°w'/REF) +1) START CONVERSION CLOCK Fig.10: an integrating or dual-ramp AID converter. Integrating ADCs are often used in digital multimeters where speed of conversion is not a priority, as their accuracy is independent of clock frequency and the capacitor value in the integrator. 1/4 full range, is added to the previous bit and their combined value compared against the input voltage. If the DAC voltage exceeds the input, then that second bit is set to "O", but if it doesn't exceed the input, it is set to "1". You can see this in the timing interval diagram. The process continues until the LSB is tried and set. After that, the value of the digital output register is the digital value of the input. Because it must repeatedly compare each bit with the input voltage, a sample and hold input stage is re quired to keep the input from changing. The speed and accuracy of this type of ADC allows it to be used in computer interfaces and in high-speed data acquisition systems such as digital storage CROs. The foregoing is essentially a brief overview of what analog-to-digital and digital-to-analog conversion is all about. It is by no means complete as there are some schemes that have not been included due to space restrictions. But, as a starting point, it should set you in the right direction. It's even possible to build up a couple of the simpler ADCs and DACs using common op amps and a few CMOS counters and gates. Why not experiment with them yourself? 0 References (1) "Analog-Digital Conversion Handbook", 3rd edition, PrenticeHall, 1986. (2) "Digital/ Analog and Analog/Digital Conversion Handbook", Motorola 1980. SC SERIES II FLUKE® The Multimeters Professionals Prefer! The all new Series II Fluke professional quality multimeters give you better value, better performance and more features than ever before. All of the '70 Series' meters now have 'Touch Hold', Diode Test, Continuity beeper, Automatic Self Test, Sleeper Function and exceptionally long battery life as standard features. MULTI METERS Fl1xibility Plus! It's NBW! FLUKE 70 SERIES II FLUKE 77 SERIES II A Bargain priced multimeter that offers the ultimate in reliability, quality and accuracy and is the ideal entry level multimeter. It has all of the incredible 70 series features including large 3200 count digital display, 31 analogue segment Bar Graph and 'Touch Hold' which locks the readinQS into the display until you're ready to read it. You wont buy a more rugged , more reliable meter at the price! It's difficult to believe that the old Fluke 77 multimeter could be improved upon ... but it has. The new Fluke 77 Series 11 has an improved DC range of 4mA to 1OA (20A intermittent) on both AC & DC as well as outstanding accuracy. Add to this the new design which makes it even easier to use than before, the comprehensive LCD display which gives you visual confirmation of most features and incredibly rugged construction and you've got the ideal meter ior tradesman and technician alike. Cat Q-1601 s149 Cat Q-1607 s349 An Ex~BJ..tional Buy/ FLUKE 79 SERIES II Even More Accurate/ FLUKE 73 SERIES II Improved functional design, and now even greater accuracy with the superb Fluke 73 Digital Multi meter with 31 segment analogue Bar Graph. Not only does it host an amazing range of features, including auto range ·and auto polarity, but it's designed to make operation as easy as possible. With a current range up to 1OA and voltage ranges up to 1000V (AC) & 750V (DC) it's an ideal meter for tradesmen or serious hobbyist. 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With accuracy levels now at 0.4% for DC voltage, 2.0% for AC voltage, 1.5% DC current (32mA to 1OA) and basic resistance at 0.5%, it's just what you need when tight tolerances are essential to your work. You won't find a meter that's easier to use nor one that's better constructed. Cat Q-1 605 s315 FLUKE 87 DIGITAL MULTIMETER Once you've used the sensational Fluke 87 multimeter ... you'll wish all your test gear performed so well. It's without doubt the ultimate multimeter with an unsurpassed level of features, accuracy and reliability. Some of it's many features include fast 3¾ digit 4000 count mode, high resolution 4½ digit 20000 count mode, backlit display with fast, high resolution analogue bar graph , 0.1% basic DC accuracy, 20kHz bandwidth true RMS, Min/Max/Average (up to 36 hours) recording, 1000V RMS input protection, 'Touch Hold', Min/Max Alert and much more! Cat Q-1610 s&99 All FLUKE multimeters come with a 3 Year Warranty 81190/ PB Addsd Insulation for Extra Safety/ FAN SPEED CONTROLLER DC-DC (12V-100W) CONVERTER Q [t] Warmer weather is fast approaching, so while you're thmkmg about dusting off the old fan you might like to make it m?re effe9tive by building this Fan Speed Controller. Its easy to build and comes as a full form kit with PCB,_all components, plastic case with prepunched & silk screened front panel, mains plug and socket and a plastic pot so there's maximum insulation for added safety. <at> Cat K-3086 7191 $ 3 QUAD 'DI' BOX 995 ~~~~,;;;;::;~) 7995 QQQ[z] ~----iJ.!l'i.!.,~~ ~ljjjj~ ~ i ! Save $20 6/91 s329 PORTABLE AM STEREO RADIO Small , lightweight, superb stereo sound and incredibly easy to tune. This Wide Band AM Stereo Radio is quite simple to build and requires no fancy tools or equipment. Comes with case, economy stereo headphones pre-punched front panel & label and all components .. . all you do is assemble it. 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It comes with a fully pre-punched black case with silk screened front panel and all components Cat K-3165 .,,,. f f,j_,j~ ~')_ Q 4 CHANNEL LIGHT CHASER DIMMER 12 Cat K-3235 At last, a practical solution to the problems confronting stage and studio performers needing to connect several devices to a mixing box! This mains powered (requires M-9527 plug pack) Quad 'DI' box kit has significant ad.vantages o.ver battery • powered versions and will replace up to four separate direct injection (DI) boxes ... at a fraction of the cost. It's easy to build and comes with all components, PCB, case and silk screened & pre-punched front and pre-punched rear panels. £':\ $ Cat K-5012 ~ 6/ 91 Intended For Professional Use! A DC-DC converter which allows you to use a high power audio amplifier in the car! It has split supply rails which can be adjusted to suit virtually any amplifier module. Ideal for twin SOW amp modules for stereo set-u p or perhaps a single 100W amp module. Suitable for use with our K-3440 and K-3442 amp modules. Comes with PCB, all components and case. An attractive 4-di~it. capacitance me.ter that's su itable for workshop or lab~ratory, etc . Its ideal for 1dent1fymg capacitors where the markings are difficult to follow or for selecting matched values in critical filter and timer circuits. Seven ranges are available allowing measurements from 1pF to 9999uF. Also has over-range indicator and null control for pF range Comes with all components, _ _ _ _ _ ________. PCB's, case and prepunched silk screened front panel. Cat K-7500 s 12 QQQ [z] 9 ffft-1/f[,{_,j,i# fi!L'JJ · IZ'1 LZJ 5/90 Kits marked with this symbol involve mains power wiring . Take extreme care when working with this equipment . Q Degree Of Simplicity Simple QQ Intermediate QQQ Detailed SAVE$1000 At last. an inexpensive. high power computer that you can fit in your briefcase. 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Suits most IBM AT compatibles and will run at 8, 10, or 20MHz. It's socketed for 80287 Math co-processor with 3 x 8-bit & 5 x 16-bit expansion slots. Has capacity for up to 8 MB RAM. Ok memory supplied. cat x-1003 Now Only $449 12MHzAT COMPATIBLE MOTHERBOARD Save $100 Building your own computer or upgrading your old one? Our 12MHz motherboard. Holds up to 4Mb RAM, has keyboard or hardware selectable 8/ 12MHz operation. six 16-Bit and Two 8-Bit expansion slots and it's socketed for an 80287 Co-processor. Ok RAM ~~~!\~~2 Computer Support Hotline... (02) 888 2002 Solving Your Computer Problems! DIC~MITH PHONES SECURITY AUDIO COMPUTERS Now Just $199 MINI VERTICAL CASE A space saving, floor-mount case to fit XT, AT. and 386 baby size motherboards. Features a back plane with 8 expansion slots. switches for turbo & reset, indicator lights for power. turbo & hard disk operation, digital speed indicator, keyboard lock, and 4 disk drive bays (2 x 3.5" & 2 x 5.25"). Cat X-1006 $299 200W AT POWER SUPPLY A 200W switching power supply, suitable for AT style computers. High output ensures there will be enough power to run a large number of expansion options. Comes complete with built-in fan. Cat X-1012 DS XPRESS PHONE & MAIL ORDER SERVICE Outside Sydney (FREE Call) 008 22 6610 Sydney And Enquiries - 888 2105 FAX: (02) 805 1986 or write to OS XPRESS, PO BOX 321 N/RYDE NSW 2113 All Major Credit Cards Accepted. O/Nite Courier Available. 24 HOUR DESPATCH OF ALL ORDERS NSW • Albury 21 8399 • Bankstown Square 707 4888 • Blacktown 671 7722 • Brookvale 905 0441 • Bondi 387 1444 • Campbelltown 27 2199 • Chatswood Chase 4111955 • Chullora 642 8922 • Gore Hill 439 5311 • Gosford 25 0235 • Hornsby 477 6633 • Hurstville 580 8622 • Kotara 56 2092 • Liverpool 600 9888 • Maitland 33 7866 • Miranda 525 2722 • Newcastle 611896 • North Ryde 878 3855 • Parramatta 689 2188 • Penrith 32 3400 • Railway Square 211 3777 • Sydney City 267 9111 • Tamworth 66 1711 • Wollongong 28 3800 ACT • Belconnen (06) 253 1785 • Fyshwick 80 4944 VIC • Ballarat 31 5433 • Bendigo 43 0388 • Box Hill 890 0699 • Coburg 383 4455 • Dandenong 794 9377 • East Brighton 592 2366 • Essendon 379 7444 • Footscray 689 2055 • Frankston 783 9144 • Geelong 232 711 • Melbourne City 399 Elizabeth St 326 6088 & 246 Bourke St 639 0396 • Richmond 4281614 • Ringwood 879 5338 • Springvale 547 0522 QLD • Brisbane City 229 9377 •Buranda 391 6233 • Cairns 311 515 • Chermside 359 6255 • Redbank 288 5599 • Rockhampton 27 9644 • Southport 32 9033 • Toowoomba 38 4300 • Townsville 72 5722 • Underwood 341 0844 • SA • Adelaide City 223 4122 • Beverley 347 1900 • Elizabeth 255 6099 • Enfield 260 6088 • St. Marys 277 8977 WA • Cannington 451 8666 • Fremantle 335 9733 • Perth City 481 3261 • Midland 250 1460 • Northbridge 328 6944 TAS • Hobart 31 0800 NT• Stuart Park 811977 STORES ACROSS AUSTRALIA & NEW ZEALAND YOUR EIGHT SPECIALTY STORES IN ONE DICK SMITH ELECTRONICS (WHOLESALE) ACN 000 456 956 B1190/ PB Each day of eve.zy year, there are an average 44,000 thunderstorms and 8 million lightning flashes. A big storm will have many thousands of lightning strikes and these can cause great damage. Hence, it is important to be able to plot the course of thunderstorms. Plotting the course of As you read this article, a lightning monitoring system for the states of New South Wales and Victoria is in the process of being set up, in time for the next "lightning season" in the coming summer. Lightning monitoring re- By LEO SIMPSON TrT2 = a • R2 Fig.1: LPATS receivers record the precise time that they detect a lightning strike. When two receivers detect a lightning strike simultaneously, the time difference between the two is zero and the lightning can be assumed to be anywhere on a straight line equidistant from the two receivers. When receiver 1 detects the strike before receiver 2, the strike has occurred on a hyperbola which passes around receiver 1. 12 SrucoN CHIP ceivers placed up to 500km apart will be able to plot each lightning strike, virtually as it happens, with an accuracy of as little as 200 metres. The information provided by the lightning monitoring system will be of great importance to government bodies such as the various electricity commissions, Telecom, state railway authorities and defence establishments, as well oil refineries, large chemical plants and organisers of sporting events where large crowds of people are expected. There is already some monitoring of thunderstorms being done in Australia apart from that provided by weather radar. For example, the Northern Territory Power and Water Authority uses the Stormscope system to monitor the progress of thunderstorms in the Katherine region. If a large storm threatens the area and the 132kV transmission line in particular, additional gas turbines in the Katherine power station are brought on line, so that an interruption to power transmission from Darwin will not cause blackouts . And dui;ing the particularly damaging thunderstorm which hit Sydney last summer, Prospect Electricity (previously known as Prospect County Council) had prior warning of the storm's extent from a direction finding storm location system and thus had alerted all its line crews. Sydney Electricity (previously known as Sydney County Council) did not have this warning and thus did not learn the full extent of the storm damage until many hours later. The system to be installed for monitoring NSW and Victoria is a great deal more involved than the Stormscope system which works in conjunction with weather radar. The problem with weather radar is that while it can give a good indication of cumulo nimbus clouds and heavy rain, it does not detect lightning. Stormscope does, but not with any great accuracy. The new system is known as LPATS, which stands for Lightning Positioning & Tracking System. It is a Time of Arrival (TOA) system whereby the time when a lightning stroke is detected at a number of remote radio receivers is precisely recorded. Then, with the position of each the remote receiver being fixed and known, the position of the lightning strike can be calculated. Basic principle The principle of the Time of Arrival system is illustrated in Fig.1. Here we see two radio receivers which are lo,cated a considerable distance apart which may be up to 500 kilometres. Now consider a lightning strike which is recorded at exactly the same time by the two receivers. A moment's thought will reveal that the strike must have been somewhere on a straight line equidistant between the two receivers. This line is depicted in Fig.1 as (Ti-Tzl = O. Now consider another lightning stroke which is somewhat closer to receiver 1 than to receiver 2. Receiver 1 will detect the stroke at a time before receiver 2. Again, by a similar process of deduction, the lightning stroke must have occurred somewhere along a curved line shown as (T 1 -T 2 ) = a. Other lightning strikes can be shown to have occurred anywhere along a hyperbolic line which circles receiver 1 or receiver 2. Now if we add another receiver as shown in Fig.2, we get more information about the possible location of a lightning stroke. Receivers 1 and 2 give a "time difference line" of T1 -T 2 while receivers 2 and 3 give a time difference line of T 2 -T 3 . Receivers 1 and 3 give a third time difference line. The location where all three intersect is the position of the lightning strike. Or is it? In fact, there are some thunderstorms situations where three receivers are not enough to give a clear result so four receivers is the practical minimum in an LPATS network. And in practice, to give a degree of redundancy, five or six receivers are used. Timing In order to give precise location of lightning strikes, all of the receivers in the system must have the same very precise time reference. In the USA, the LORAN navigational system has been used but now the Navstar Global Positioning Satellite (GPS) system is the preferred reference. LPATS makes use of the civilian access standard positioning service of GPS which has an accuracy of up to 100 metres. This is used to establish the location of the receivers at installation. After that, in normal operation, the GPS signal is used to continually synchronise the 10MHz time clock. The receiver itself uses a simple whip antenna to pick up the lightning signal. An enclosed helix antenna is used to receive the GPS satellite timing signals. The detection receiver has a bandwidth of 2kHz to 500kHz and apparently uses an AM detector although the manufacturers, Atmospheric Research Systems, Inc. are coy about giving any details. However, the detection process is good enough to produce a good approximation of the waveform of the lightning strike. T1-T2 • a Lightning and thunderstorms can do tremendous damage in Australia. With a precise system for plotting thunderstorms and lightning strikes, the hazards can be minimised and any damage more quickly repaired. Fig.2: with three receivers, three "time difference" hyperbolas can be plotted although only two are shown here. 'l\vo hyperbolas will intersect at two points or (rarely) touch at one point. Three hyperbolas are needed to plot a single unambiguous location for every lightning strike. SEPTEMBER1991 13 Fig.3: how lightning is located by time of arrival: (1). The signal will be detected at each receiver at a different time relative to the event, dependent on the distance from the event. (2). Time is measured at each site with a resolution of 100 nanoseconds (±50 nanoseconds). (3). Each receiver has a 10MHz timebase which is typically synchronised 20 times a second from a precise source such as the Navstar GPS satellites. (4). A minimum of three receivers are required for a solution. Achievable accuracy is 1 microsecond and within 200 metres, dependent on the size of the network. This is fed to an 8-bit analog to digital converter with a 200 nanosecond sample rate. The waveform is then stored in memory with 100 microseconds of storage. Two characteristics of the strike waveform are important - the peak current of the strike and its risetime. The exact peak of the waveform is crucial because that is used tu define the time of the strike. If a preset signal threshold was used to define the time of strike, there would be timing errors because of the large range of magnitude of lightning strikes - they can range from a peak current of less than 1000 amps to more than 100,000 amps and they can have a duration of 500 milliseconds. Since the peak of the lightning strike is timed with an accuracy of ±0.1 microseconds, any inaccuracies which could occur due to the differing magnitudes of lightning strikes are eliminated. The digitising and storage process also allows other information such as the stroke polarity and total stroke energy to be determined. All this information about the time of the strike and its amplitude is sent by a serial 14 SILICON CHIP data link such as a phone or radio modem to a central computer which calculates the exact location of the strike. This information is stored for later analysis and is also available for immediate display on area maps by the users of the LPATS service. They can plot the progress of storms as they develop and, with experience, they can predict where they are heading and the likely amount of lightning damage. If necessary, vital equipment can be shut down or otherwise protected, sporting events can be cancelled, crowds evacuated from golf courses and so on. Noise rejection You might wonder how a receiver with a bandwidth of 2kHz to 500kHz would be able to discriminate between local radio interference noise and a lightning strike. After all, a lightning strike which may be 200km or more away from the receiver will not produce a very strong signal. Local radio interference can easily be much stronger. The answer is that the detection receiver really does not have to perform the discrimination process. Why? Because the only naturally occurring electromagnetic event that can be simultaneously detected by four or more LPATS receivers which are many hundreds of kilometres apart is a lightning strike. Hence, if less than four receivers in an LPATS system detect an electromagnetic discharge, it is not recorded as a lightning discharge by the central computer. This method has led to a high degree of detection accuracy. Naturally, each receiver needs to be sited away from strong sources of radio interference but apart from that, the installations are quite uncritical. In fact, if a receiver site does become noisy, its threshold of detection is automatically adjusted, under software ~ontrol. Accuracy In practice, the LPATS system can locate lightning strikes to within 200 metres at the centre of the network (depending on its overall size), ranging out to a kilometre for strikes well outside the region covered by the reC!')ivers. You might wonder if the ac- curacy could be improved, down to say 50 metres or less. In practice, the answer is no. For a start, the Navstar GPS enables positioning only within 100 metres; although the military capability of GPS enables targets to be located to within less than 10 metres! Second, there are inevitable errors, both random and systematic, which add up to give the ultimate positional accuracy for lightning strikes of within 200 metres. But there is a third reason why lightning strikes cannot be located with better accuracy and that has to do with the path of the strike itself. This is usually several thousand metres long and is rarely over a straight vertical path. So while•LPATS could perhaps locate the centre of a discharge to within better than 200 metres, the exact point where it hit the ground would still be unpredictable. In practice, where a lightning strike causes substantial damage, it will usually be fairly easy to locate the exact point, once the LPATS system has done its work. In practice too, the users of the information provided by an LPATS network will know precisely where any damage prone installation is, given the locality of a lightning strike. Suffice to say that the information on lightning strikes and thunderstorms from LPATS is far more precise than from any other lightning detection system previously developed, especially those based on direction finding antennas. A very good example of the efficacy of an LPATS system was given during a thunderstorm in the USA, on 13th June 1991. This took place during the 1991 US Open Golf Tournament at the Hazeltine National Golf Club. A spectator was killed by lightning during this storm and several people were injured. A subsequent inquiry into this tragedy was able to obtain archived data which showed the initial development of the storm, its path and even the strike which killed the player. Had the event's organisers had access to this information during the storm, it is likely that no-one would have been hurt. Acknowledgement Our thanks to Ken Ticehurst of Kattron Pty Ltd, Ourimbah NSW and to Dr Rodney Bent of Atmospheric 40.273N 9'J.675W 132 mi 170° _ 10381 Strokes in 1:07 18:21 USA NATIONAL LIGHTNING DATA - □ 12Clx120 Magnified Magnified - Normal Comm Connected Fig.4: this is a screen display from an LPATS network covering the United States. There is a facility to zoom in on thunderstorms & lightning strikes are plotted virtually as they occur. The system can locate lightning strikes to within 200 metres at the centre of the network, depending on its overall size. 11 5. 0 0 119 .00 12J.00 127 . 00 1J 1 .00 1J5.00 1J9,00 14J.00 147 .00 * -12.00 - 16 . 00 -12.00 Darwin ~1.0~ 1.0 1.0 -20.00 *~ Da~ r w C ::::, Ij:: < ...I -24 . 00 -28 . 00 - J 2.00 *Alice l. 0 ~ ~~rt 1.5 ~ 1.0_1.o -28.00 _J -J6.00 * -20.00 -24.00 1.0 Springs 1.0 L~ -16.00 -]2 .00 Adelaide -]6.00 - 40. 00 ~ ~ ~ ~~ ~ ~ ' - - ' - - ' - ~ - ' - - ~ ~ ~ ' - - ' - - ' - ~ . , . , _ ~ L . . . . L . ~' - ' - - ' - ~ ~ -40. 00 115. 00 11 9. 00 123.00 127 . 00 1]1 . 00 135 . 0 0 139.00 14J.00 147.00 LONGITUDE Fig.5: this is a plot of location accuracy for an LPATS network covering the whole of Australia. In this notional system, lightning receivers are located at Dampier, Darwin, Townsville, Adelaide, Perth and Alice Springs. Note that in spite of the huge distance between the receivers, there is a large area for which lightning strikes could be pinpointed to within a kilometre or better. Research Systems Inc for their assistance in preparing this article. Thanks also to Michael Nott of the Northern Territory Power and Water Authority for information on their Stormscope warning system. SC SEPTEMBER 1991 15 If you can wield a screwdriver & follow a simple wiring diagram, you can build this exciting full-size loudspeaker system. It uses three drivers which you install in a readymade enclosure for excellent sound quality. By GREG SWAIN Studio 3-55L 3-way loudspeaker system W E HAVE been keen to describe a full-size loudspeaker system for some time now. Basically, we wanted a system that produced good quality sound when driven by ·amplifiers rated at up to SOW or more, but which didn't cost the earth. Good quality commercial loudsp eaker systems are quite expensive, so the do-it-yourself enthusiast can save quite a few dollars by building his own. In deciding on the type of system we wanted , it didn't take long for the basic design parameters to emerge. The first thing we decided was that 16 S1ucoN CHr P the system had to have three drivers, to ensure a smooth frequency response right across the range. This is in keeping with most other full-size loudspeaker systems currently on the market. Next, we wanted a 12-inch (30cm) woofer to ensure reasonable efficiency and good power handling. We also specified a good quality tweeter, since the top end response is a very important parameter in any loudspeaker design. And finally, we needed a good match between the tweeter, woofer and midrange drivers. Unfortunately, not all of those aims are easily reconciled. In the first place, the enclosure cannot be too small if we want sustained bass response down to about 50Hz, or so. If the enclosure is made too small , the woofer resonance shoots up from around 30Hz to 80-lOOHz. We eventually settled on an enclosure volume of 55 litres as the ideal size for the selected woofer. Selecting the drivers OK, so much for the basic design parameters. The n ext task was to select suitable drivers. Initially, we investigated the possibility of using one of those fancy polypropylene cone woofers in a sealed enclosure designed to Thiele/Small parameters. We tried a number of combinations of various drivers but the results were always disappointing. Most of the woofers that we tried looked good on paper but when installed in a cabinet, they lacked bass response. We also had trouble matching the woofer sensitivity to the midrange and tweeter. So they just didn't stack up. Finally, we decided to try a locallymade woofer -the Magnavox 12W099. We teamed it with a Philips AD1160/ T8 tweeter and a 5-inch midrange unit selected from the Jaycar catalog, and the results were irpmediately encouraging. Unlike the earlier polypropylene units that we tested, the Magnavox woofer gave good, tight bass response which was well sustained down to below 50Hz. Its sensitivity was also a good match to that of the midrange unit, although the tweeter clearly needed backing off. In terms of construction, the Magnavox 12W099 woofer uses a large pressed steel chassis, a ceramic magnet and a heavy paper cone. Paper cones are now regarded by some as being old-fashioned but correctly designed paper cones are still far superior to polypropylene cones that don't happen to perform. The 12W099 is fitted with a synthetic rubber roll surround for the outer suspension. This is now a common form of construction since it helps maintain linear operation at high cone excursions and is also useful for damping cone induced resonances. The free-air cone resonance for the 12W099 is quoted at 30Hz ±5Hz. Other specifications include a 25mm hightemperature voice coil, a nominal power handling capacity of 80W (on progra..'11 signals), a frequency response up to 4kHz and a sensitivity of 95dB at 1Wand 0.5 metres (89dB at 1 metre). The 5-inch midrange unit we eventually settled on is of Taiwanese origin and has a quoted frequency response of 350Hz to 5.5kHz. It features a white paper curvilinear cone and closed back construction. This latter feature is important since we don't want the necessity of a separate enclosure for the midrange to stop it being pumped by the woofer. By contrast, we didn't have any The crossover network used in the Studio 3-55L loudspeaker system is a 3-way LC unit with crossover frequencies at 800Hz & 5kHz. It is supplied ready assembled & features clip-on spade terminals. trouble deciding on the tweeter. The Philips AD11610/T8 dome tweeter was the natural choice, both in terms of price and performance. It features a 1-inch textile dome and is specified to operate over the range from 750Hz to 22kHz with good off-axis dispersion. By the way, both the tweeter and midrange units are listed in the Jaycar catalog. The tweeter (Cat. CT-2012) is prir.P.rl at $28.50 while the midrange unit (Cat. CM-2080) normally sells for $26.50. The 12W099 woofer is avail- able separately for $59.95. (Cat. CW2022). To keep costs to a minimum and to make construction as easy as possible, it was desirable to use a commercial crossover network. But while this is a good idea in theory, it's not always possible to use an off-the-shelf crossover network without any need for modifications. Fortunately, we were able to pick a crossover that worked although we did have to provide some attenuation for the tweeter, as already noted. The unit selected is Tr-ansfer Function Mag - dB volts/volts (0.10 oct) M .o L 5.0 A 10 s s 0.0 -5 . 0 -10 .0 -15.0 -20.0 -25.0 -30.0 -35.0 -40.0 I 100 .0 1000.0 10000 .0 log Frequenc~ - Hz Fig.1: the frequency response of the completed system (level controls set to zero). As can be seen, the frequency response is fairly flat (within ±5dB) from about 45Hz up to around 15kHz or so. SEPTEMBER1991 17 This photograph shows the main components of the Studio 3-55L loudspeaker system. They are (clockwise from top right): the Magnavox 12W099 12-inch woofer, the 5-inch midrange, the Philips AD11610/f8 tweeter, the crossover network, the recessed input terminal panel & the level attenuators. again straight out of the Jaycar catalog (Cat. CX-2616) and is listed at $22.95. It's a fairly simple LC unit with crossover frequencies at 800Hz and 5k.Hz. Having decided on the crossover network, we also decided to add a couple of level controls (or faders, as they are commonly called) for the midrange and tweeter. These level controls are basically constant impedance attenuators and they enable the user to independently adjust the levels of the midrange and tweeter. Many hifi enthusiasts want the facility to adjust their loudspeakers in this fashion, either to compensate for room acoustics or to better tailor their loudspeakers to suit particular kinds of music. Testing the design At this stage, we decided to seek Magnavox's cooperation to check the 18 SILICON CHIP design validity and to fine tune the system. In particular, we wanted to check the system on Magnavox's computer-controlled acoustical analyser. This system goes under the fancy name of"Maximum-Length Sequence System Analyser" (or MLSSA for short). Among other things, MLSSA plots impedance, frequency response and crossover response curves, as well as 3D cumulative spectral decay plots based on impulse response measurements. These tests soon revealed that the tweeter was somewhat more sensitive than the other two drivers, as we had already found from initial listening tests. The solution was simple - a resistive attenuator to reduce the tweeter's level by about 3dB. Apart from that, the acoustic tests confirmed that the design concept was virtually spot on. Fig.1 plots the frequency response of the completed system (level controls set to zero). As can be seen, the frequency response is fairly flat (within ±SdB) from about 45Hz up to around 15kHz or so. This is quite a good result, with good overall balance between bass and treble response. In practice, we felt that the system was slightly on the bright side with the level controls set for a flat response (ie, to zero). We thought that the system sounded best with both level controls set to -3dB but that will depend on your personal preference and your listening room's acoustics. Fig.2 plots the impedance curve for the Studio 3-55L. It is fairly constant between l00Hz and 20kHz but below lO0Hz, it rises steeply to a maximum of 18Q at 65Hz. This corresponds to the low frequency resonance of the system and results from intera_ction between the enclosure and the woofer cone. Note the dip in system impedance 20 to a minimum of about 4.5Q at 5kHz. This dip occurs at the midrange/ tweeter crossover frequency but should not cause any problems with today's solid state amplifiers. ' .;, 15 ::E :c !:!. J w u z cc Where to buy the kits fz 10 Although we haven't mentioned it yet, Jaycar were keenly involved with this project right from the beginning. Most of the parts were already in the Jaycar catalog and the company has been able to produce a complete kit priced at just $499 for the pair, including cabinets and all hardware (but not including the optional spade connectors). Considering the performance of this loudspeaker system and the cost of comparable comni~rcial systems, $499 represents excellent value for money, in terms of overall sound quality and power handling. We've also gone to considerable trouble to make sure that these loudspeakers look the part. Unlike earlier kit loudspeakers, the cabinets are supplied fully assembled to ensure a high standard of finish . You don't need any messy PVC glue or woodworking tools for this loudspeaker project unless you elect to make the cabinets yourself, that is. · As supplied, the cabinets are cut from 18mm-thick particleboard and are professionally finished in black simulated-woodgrain veneer. They come complete with clip-on speaker grilles and with the holes already cut in the baffle. All you have to do is mount the crossover, install the Innerbond filling and wiring, and screw the drivers, faders and input terminal panel into position. Alternatively, you can make the cabinets yourself and buy the various components separately from Jaycar. The loudspeaker cabinets are available for $250 a pair while the hardware pack costs $279. This hardware pack includes the loudspeakers, crossovers, terminal panels, level controls , resistors, innerbond filling material, cable and screws. ~ Crossover design Fig.3 shows the circuit of the crossover network, together with the additional components that have been added to produce a working design. For those who are unfamiliar with crossover networks, their job is to divide the audio spectrum so that each a. - _/ ffi ,. \ \I---,-- -- ' 'r--r-- ~ a. "' _/ V 5 0 20 I\ r--... - ,.Y vv I I I 10k 1k 100 20k FREQUENCY (HERTZ) Fig.2: the impedance curve for the Studio 3-55L loudspeaker system. The 18Q peak at 65Hz corresponds to the low frequency resonance of the system, while the dip at about 5kHz corresponds to the midrange/tweeter crossover frequency. driver is fed with its optimum range of frequencies. Because we are using three drivers here, we need a 3-way crossover network. As already mentioned, the network used has crossover frequencies at 800Hz and 5kHz. ThiJ, means that the woofer handles frequencies below 800Hz, the midrange frequencies from 800Hz to 5kHz, and the tweeter frequencies above 5kHz. As shown in Fig.3, the crossover network uses 1C filter sections to rolloff the response at the designated frequencies at 12dB/octave. For the woofer, 11 & Cl form a low pass filter with a -3dB point at 800Hz. For the tweeter, the equivalent components are 14 & C4 but, in this case, these form a high pass filter with a -3dB point at 5kHz. The midrange filter network looks somewhat more complicated but is · simply two LC filter sections connected in cascade. C2 & 12 form the high pass filter section, while L3 & C3 form the low pass filter. In reality, of course, it's not quite as simple as that since there is some interaction between the two filter stages and the load. The end result, however, is a bandpass filter which channels the middle frequencies to the midrange driver. Fig.4 plots the response of the crossover filter sections while Fig.5 shows the low frequency response of the woofer. Note the peak in the response in the region of 65-70Hz which corresponds to the system resonance. Below this figure, the woofer output drops away steeply but there is still plenty of bass down to about 45Hz. The low output from the crossover network is coupled directly to the woofer, while the middle & high out- ,- - - - - - - - - - - - 7 j Fig.3: the crossover network uses LC filter sections to roll off the response at the designated frequencies at 12dB/octave. Note the resistive attenuator fitted to the tweeter. I C4 I I I L4 I I TWEETER I I I INPUT C2 L3 I MIDRANGE I I I I I I WOOFER I I L. _ _ _ CROSSOVER BOARD _ _ _ I _j SEPTEMBER 1991 19 Transfer Function 11ag - dB volts/volts (0,10 oct) -4.0 M L -5.0 A s s -6.0 -7.0 -8 .0 -9, 0 -10.0 -11.0 -12.0 -13.0 -14.0 10000 .0 1000.0 100.0 log Frequency - Hz Fig.4: this graph plots the response of the crossover filter sections. The woofer handles frequencies below 800Hz, the midrange frequencies from 800Hz to 5kHz, and the.,tweeter frequencies above 5kHz. Transfer Function 11ag - dB volts/volts (0 .10 oct) 29.0 M L 27.0 A s s 25.0 23.0 21.0 19.0 17.0 15.0 13.0 11.0 9.0 10.0 100.0 log Frequency - Hz Fig.5: the low frequency response of the woofer. Note the peak in the response in the region of 65-70Hz which corresponds to the system resonance. Below this figure, the woofer output drops away steeply but there is still plenty of bass down to about 45Hz. puts are fed to their respective drivers via the level controls. Although they might look like it, these level controls are not simple potentiometers but are constant impedance pads. These vary the signal fed to the drivers while maintaining a constant input impedance as seen by the crossover network. As mentioned earlier, the tweeter output is also attenuated by -3dB to improve the overall balance of the system. This attenuation is provided by the 4. 7Q and lOQ 10 watt wirewound resistors associated with the tweeter. Construction We'll assume here that you've purchased the ready-made cabinets but, if you have the necessary woodwork20 SILICON CHIP ing skills, there's nothing to stop you from making your own cabinets from the dimensions shown in Fig.6. That way, you can save even more money and you can choose a veneer to suit your existing furnishings. The first step is to make up the wiring looms using the 2-way cable supplied. Fig. 7 shows the details. Cut each loom to the length indicated, then strip about 6mm of insulation from the ends and tin them using your soldering iron. Alternatively, the leads can be fitted with spade connectors, as shown in Fig.7. Note, however, that Jaycar will not be supplying the spade connectors as part of the loudspeaker kit, since most constructors will prefer to save money be soldering the various connections. On the other hand, the spade connec- tars do make the wiring looms somewhat easier to install and you may consider them worthwhile for this reason, despite their extra cost. Make sure that the spade connectors are crimped tightly to the leads if used. Also, be sure to fit the correct size of connector to ·each wiring lead - see Fig.7. Note that the wiring looms to the midrange and tweeter consist of two sections. Twist the ends of the common (black) leads together before soldering them, or terminate them in a common spade connector. The 4.7Q and lOQ resistors are soldered to the tweeter wiring loom to ensure troublefree connections. Bend the leads of the lOQ resistor so that it can be soldered directly to the tweeter terminals. Alternatively, you can fit the lOQ resistor leads with spade connectors. After crimping, these spade connectors should also be soldered to ensure reliability. The next step is to drill the mounting holes for the loudspeakers, level controls and input terminal panel. This isn't a difficult task but take care when handling the woofer and midrange drivers, otherwise you could end up with a screwdriver through one of the cones. The woofer and the twe~ter are secured using 10-gauge x 20mm selftapping roundhead screws, while the midrange is secured using 10-gauge x 12mm self tapping screws. The level controls, crossover and input terminal panel are all fastened using the smaller 12-gauge x 12mm screws. Use the drivers and the various other components as templates for marking out the positions of the screw holes. These holes must be slightly smaller than the core of the screw threads, to avoid the risk of stripping out the holes when the screws are tightened. Before drilling, check that the marked hole positions are not too close to the rims and that, for the sake of appearance, they are all symmetrical in relation to the baffle centre line. It's also a good idea to centre-punch each hole position before drilling, so that you don't accidentally scratch the veneer with the drill bit. The crossover network is mounted on the inside rear panel, just above the input terminal panel. Don't try drilling the holes with any of the components in position. PARTS LIST \ ~ REAR MOUNTED IN 18 x 5 GROOVE IN TOP, BOTTOM AND SIDES .., "' "' 115 115 «> «> "' A = N N A' 390 .I BAFFLE MOUNTED IN 18 x 4 REBATE IN TOP, BOTTOM ANO SIDES 10 280 DIMENSIO NS IN MILLIMETRES HOLES:- A 282 DIA. SECTION A'·A' B 110 DIA. C 84 DIA D 52 DIA . CHAMFERED 3 x 3 ON FRONT E 50 DIA. IN BACK PANEL INSIDE DIMENSIONS: - 650W x 354W x 2340 INSIDE VOLUME MUST NOT BE REDUCED MATER IAL:· BAFFLE : 658 x 362 x 18 PLAIN PARTICLE BOARD BACK : 660 x 364 x 18 PLAIN PARTICLE BOARD TOP, BOTTOM ANO SIDES : 18 VENEERED PARTICLE BOARD Fig.6: if you have the necessary tools & woodworking skills, you can probably save quite a few dollars by building your own cabinets. You can vary the assembly details to suit yourself but don't alter the internal dimensions. That's just asking for trouble. When the pilot holes have been drilled, mount the input terminal panel on the rear panel and secure it using four 12-gauge x 12mm screws. This done, cut the Innerbond mate- The 5-inch midrange driver features closed back construction so that it cannot be "pumped" by the woofer. rial into two equal pieces and use one piece to line the back, sides, top and bottom of the cabinet. There's no need to secure it - when the crossover network is screwed into position , it will sit in place quite naturally. The crossover network can now be installed. It sits on top of the Innerbond material, which means that a certain amount of patience is necessary to align the mounting screws with the pilot holes. However, once the first screw is in, the rest should be easy. Next, use a sharp utility knife to cut a slit in the Innerbond material to give access to the input panel terminals. This done, connect (or solder) the input wiring loom between the input terminals and the crossover. Make sure that the positive lead (red) goes between the"+" connection of the input terminal panel and the "IN" terminal of the crossover network. The tweeter, midrange and woofer wiring looms are now connected to 2 pre-built 55-litre cabinets plus clip-on covers 2 12W099 Magnavox 12-inch (30cm) woofers (Jaycar Cat. CW-2122) 2 5-inch midrange loudspeakers with sealed backs (Jaycar Cat. CM-2080) 2 Philips AD1161 0ff8 dome tweeters (Jaycar Cat. CT2012) 2 tweeter level controls (Jaycar Cat. AC-1682) 2 midrange level controls (Jaycar Cat. AC1680) 2 3-way crossover networks (Jaycar Cat. CX-2616) 2 recessed input terminal panels (Jaycar Cat. PT3004) 1 1.5-metre length of lnnerbond 1 ?-metre length of colour-coded medium-duty figure-8 speaker cable (eg, Jaycar Cat. WB1706) 2 10Q 1OW wirewound resistors 2 4.7Q 10W wirewound resistors 8 10-gauge x 20mm roundhead self-tapping screws 4 10-gauge x 12mm roundhead self-tapping screws 14 12-gauge x 12mm roundhead self-tapping screws 36 mini female spade connectors (Jaycar Cat. PT4520); optional , see text 8 medium female spade connectors (Jaycar Cat. PT4522); optional, see text Where to buy the kit Complete kits for the Studio 3-55L loudspeaker system are available from Jaycar Pty Ltd , PO Box 185, Concord 2137. The kit comes complete with fully assembled cabinets (with all holes cut), loudspeakers, lnnerbond material and all hardware but does not include the optional spade connectors. The price is $499 for the pair. The loudspeaker cabinets are also available separately for $250 a pair, while the hardware pack costs $279. the crossover network and the far ends of the looms pulled through the holes in the baffle. Fig.8 shows the wiring details. Pull the tweeter leads through SEPTEMBER199 1 21 The woofer should be installed last so that you have access to the crossover network while installing the other parts. * TO CROSSOVER (W)C>-.__ RED ~(+) BLACK "------<:::J (-) 700mm LONG * (CI r::::>-'"" TO WOOFER WOOFER WIRING LOOM * TO CROSSOVER 700mm LONG (MID---._ RED * --<](3) (Cl&--- BLACK~ l·Ii::::>---.. TO MIDRANGE LOUDSPEAKER (+) • * BLACK (1) TO MIDRANGE LEVEL CONTROL (2) RED 500mm LONG MIDRANGE WIRING LOOM TO CROSSOVER * (T) ,......._ (Cl 700mm LONG RED ~--=======================:;;;;;_BLACK ~(3) BLACK 500mm LONG TO TWEETER RED TWEETER WIRING LOOM *MINI SPAOE LUG • MEDIUM SPAOE LUG TO CROSSOVER * * * 240mm LONG (IN)~(+) * (C)~(-) TO INPUT TERMINALS INPUT WIRING LOOM Fig.7: the wiring looms can either be fitted with the optional spade connectors or soldered directly to the various components. The numbers on the level controls are stamped into the terminals. 22 SILICON CHIP the tweeter .hole, the tweeter level control leads through the HIGH level control hole, the midrange leads through the midrange hole, and so on. It's now simply a matter of clipping the various connectors to the drivers and level controls, then securing each component to the baffle with its mounting screws. The logical approach is to install the tweeter first, then the level controls and the midrange driver. Leave the woofer until last, so that you can check the various wiring connections back to the crossover network. Exercise great care when connecting the leads to the level controls, since it's all too easy to transpose the two red leads that run to terminals 2 and 3. These numbers, by the way, are stamped into the terminals of the level controls, just below the eyelets. You can use your multimeter to assist you in identifying the leads, if necessary. Be sure to match the level controls with the tweeter and midrange. The HIGH level control (for the tweeter) is mounted on the righthand side of the baffle, while the MID level control is mounted on the lefthand side. Sealing the components The crossover network sits on top of the Innerbond material & is screwed to the back of the cabinet. Note the slit cut in the Innerbond to the left of the crossover network to give access to the lugs on the input terminal panel. Fig.8: follow this diagram carefully when installing the wiring & pay particular attention when connecting the level controls as it's easy to make a mistake here. The 10Q & 4. 7Q 10W resistors can be mounted directly on the back of the tweeter. Solder the resistor leads to ensure reliable connections. We didn't bother to use gaskets or sealing compound around the drivers or level controls, since these proved totally unnecessary. All you have to do is do the screws up firmly to get a good airtight seal to the baffle. Don't overtighten the screws though, otherwise you'll strip the hole. The only component which might be a bit suspect in this regard is the woofer, because it has such a large diameter rim and because its mounting holes are so far apart. If you're worried about sealing, then we suggest that you run a strip of thin draught excluding tape around the bottom rim of the woofer before screwing it down. Do the same for the midrange and fader controls if you wish. The tweeter comes with its own gasket, so sealing is not a problem. After you've assembled one cabinet, the second cabinet can be assembled in exactly the same fashion. You can then connect them to your amplifier, select some music and sit back and enjoy the sound. We're sure you'll be impressed. Finally, although we've specified the power handling capacity of the Studio 3-55L's as BOW program, they can be used with amplifiers rated up to 100W or more - provided that you're sensible. They can produce quite prodigious sound levels, so lack of power handling capacity will not be a problem. SC Constant Impedance Attenuators - How They Work As noted in the circuit description, the 3-55L loudspeaker system uses constant impedance attenuators which have the advantage of not altering the action of the crossover network. If conventional potentiometers were used, the crossover frequency to the tweeter or midrange would alter according to the setting and this could have undesirable effects on the sound quality. These "constant impedance" attenuators have two concentric wirewound elements which are internally connected to the common wiper. For proper action, an 8Q attenuator must be used in conjunc- INo--- an LOUDSPEAKER COMo----.....__ _ ___:;;_, Fig.9: the circuit of the constant impedance attenuators. tion with an 8Q driver. To understand the control action, consider what happens when the attenuator is wound fully up so that the tweeter (or midrange) gets the full signal. In this case, the driving source "sees" just the voice coil of the driver, in parallel with the lower 36Q resistive element which has a negligible effect on the loading. At the other extreme, for maximum attenuation, the driving source "sees" just the 8Q resistive element of the attenuator, in series with a small portion of the lower resistive element which is itself in parallel with the· speaker driver; thus the signal to the driver is heavily attenuated. For in-between settings, the driving source "sees" a series/parallel combination, of the attenuator's resistive elements and the tweeter's voice coil - all adding up to close to the nominal figure of 8Q. SEPTEMBER1991 23 Phone your order to us Toll Free. We guarantee our Jetservice Courier will deliver to your door faster than any other Australian supplier (including that local supplier just up the road). If we fail I'll give you your money back plus $5.00 for your inconvenience.~ 6 ~ Flush/Surface Mount Alarm Control Panel rm System Kit mponent1 to With 1tyll1h compact good looks this alarm blends smoothly Into any realdentlal or office decor. The kit comes complete with the following components: • One Alarm Panel • One Passive lnfrared Detector (P.I.R .) • One AC Power Pack • One 8 Ohm Horn Speaker • Three pairs of Magnetic Reed Switches • One 12V/ 1.2AH Rechargeable Back Up Battery. s5410 $349.oo Fealu19o: • 5 Protection Circuit Loops • Independent Connections for N.C. and N.O . Sensor Switches • Arm - Disarm by Digital Access Key-pad • MultiStation Remote Control • Warble Tone - Steady Tone Siren Dri ver • Adjustable Timers for Entry Delay and Siren Duration • " Latch" and "Timing" Output Relays • Remote and Local Alarm Status Indication • see Altronics '91 catalogue for full details. This compact 3 section 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 t he panel is operated via a 4 digit access code rather than a key. For ease of insta llation and service, the panel is provided with a plug in wiring harness. s 5490 $119 .00 FREE THIS MONTH ONLY100m ROLL ·CABLE and 4 LARGE WARNING STICKERS WITH ANY PURCHASE OF THE ABOVE SYSTEMS Jt THATS A SAVING OF OVER $40/ Battery Operated 4 Core Portable Passive Security Cable Infra-Red Quality 14/.20 for professional security/alarm Intrusion Alarm systems. t A ready to use system, no installation ,required' \.OCompletely self SO contained - No .JI ~~~~~a~us~~~~ ,'s11\fl. fl.'-1\-,:ll"oi,o~I\ \_\fl. ooO '\ f1.U , _ S 5305 $49 or required Large coverage, over 100 sq metres Portable wall mounting Long life 9V battery operation (not included) . Battery low warning . Recommended for home, shop, .oo caravan or when Telephone Type Cable t-antastic for any alarm instal lation. Ideally suited to our control panels above. PERM Y/ 0302 2 pair W 0303 3 pair W 0306 6 pair $1 .50 W 0310 10 pair $2.40 .60 .60 0354 Grey 80 0355 Black • per m W 0356 White Passive Infra-Red Lite Guard Floodlight Control W W The Lite Guard detects a moving person or vehicle by comparing the background temperature with a rapid change of temperature · across the detection beams. So when Lite Guard detects movement across the coverag e area, it will turn on the floodlight(s) for 1-20 minutes as pre-adjusted. $ Strobe Signal Lamps Uses Xenon Strobe tube for high energy flash output at a rate approx. 1 per seconds. Fantastic light energy output for the DC power used. DC input 12V 320 mA. s 5455 Blue $34.95 S5450 $34 .95 Digital Access Keypad Red This digital access keypad is a 12-button electronic coded comb ination lock. It provides two sets of secret codes tor the owner. There are 11880 different comb inations possible for secuirty key and 132 different combinations possible for panic. The secret codes may be in stantly changed by the owner by just simply rearranging the el I I ~110 code jumper pins on the PCB. co•· See Altronics '91 catalogue for full details. s 4200 $69 .95 Alarm Stickers 200mm x 75mm 70mm x 25 mm S5400 $1.e5 s 5410 $3.9s S5350 69 .00 UHF Microprocessor Controlled Wireless Security System travelling. Apart from the flawle11 operation of the 1y1tem one of the great features Is lt1 appllcatlon with rented or leased premises - let's face It, money spent on lnatalllng a wired 1y1tem In your home or office, factory, etc 11 Irrevocably lost when you move on. With this 1y1tem you almply take It with you. Wlrele11 Complete System Includes: Remote Keypad 1x 1x 1x 1x 1x 1x 1x 1x Control Panel Passive Infra Red Detector/ Transmitter Door/ Window Reed Switch/ Transmitter Hand Held Remote Control/ Transmitter Horn Speaker - 10 watVwired 240V AC adaptor 1.2Ah Back-up Battery Set of batteries for all transmitters S5240$649.oo sm5$129.oo Personal Remote s52so$59.oo Door/Window Reed Switch s 5247 $69 .00 8 Ohm Economy Weatherproof Horn Speakers A superb oacllloacope for technicians and englneen working on projects where other Instruments would be stretched beyond their capabllltlea. Where precise measurements of computers, CD' s, digital videos, RF applications, high speed digita l.and other high speed equipment is a must. With Features Like: • Delayed sweep for partial waveform expa nsion. • Channel 1 sign~! output for use with a frequency counter • CH2 polarity inversion switch • Vertical deflection magnification, XS • Switchable chopping frequency • Scale illuminating system• B Intensity contro l for bright. magnified waveforms • Variable hold-off for observation of waveforms wit h complex periods• Single sweep mode for one time or other suddenly occuring events• Sweep magnfication , X10 • Signal delay line for accurate vie w of high frequency pulse leading edge • Trigger preset function . C 2015 10 Watt This Month's Special Disk Cleaners .95 Alumlnlum Construction sa~e400/o 10 H 0400 3 Unit Black Economy Case H 0404 1 Unit Case Grey F/ Panel H 0405 2 Unit Case Grey F/ Panel disc cleaners. D 1007 3'/," Kit D 1809 5'!.'' Kit C 2025 15 Watt ~ 5 0 Thll Month Only Rack Case Clearance uP Now-a-<lay·s computer hardware and software doesn't come cheap, and is often difficult to replace. So protect you r valued investments w ith our 5%'' floppy $13 .95 Sorry not aval/ab/e from A/Ironic Dea/era at thete price, H 0406 3 Unit Case Grey F/ Panel $5.95 $35.oo Rack Shelf SM Telephone TO3 Heatsinks Extension Leads SPECIAL THIS MONTH OHL Y 1-9. 40 ,..'I' (Non A ustal Approved ) 10.99. .., 30... $5.oo 100 up .20~ P 0991 \t\ a.afga ,.., p.('l'a1-'""' Plasma Lamp Display 21st Century Entertainment Fascinate Your Friends/ Amazing! Pulsating high voltage plasma discharge continua ll y changes shape and direction. Mode selectable to either fingertip control or sound activated. For example, from voice or sound system . Provides endless fascination as it sizz les and arcs. Supplied complete with AC mains adaptor., A 0120 Normally ~ 0 0 Save $100 Up t/11 now a/ml/er /amps have sold for $1000 and morel/ This sturdy 3 unit high rack shelf is designed to accommodate a vast range of equipment wh ich does not have rack mounting capability. Fantastic for videos, tuners , CD players, amps, tape decks and anything else that is under 3 unit high and 300mm deep. It even has an adjustable bracket which stops the appliance moving backwards. Supplied in flatpack form - easily assembled in minutes. Hardware supplied. 5359 $49 .95 Super Guard Household Alarm System H Super Guard la a comprehensive low cost alarm system . Simple to Install and operate, thl1 system 11 great tor home or small office. Three sets of door/ window reed relay proximity switches are supplied . Ad ditional switches can be installed as desired. These switches can be connected to the " Instant alarm " circuit (windows) or "Delayed Alarm" circuit. eg front or rear door thus enabling you to disarm the system when reentering the house. Ideal for the Shed or Garage $99.oo A Crazy $30.oo VIFA 2 Way 100 Watt Weatherproof High Performance 2 Way Flush Mounting Full Range 60W Speaker Speaker Redford and Scan Audio have System " Highly recommended. I found It d/11/cult to pick tfle combined resources to develop this Audio Purists. difference between the A/Ironies C 0880, the Amer/cen Thi• Month Only This Is For You! C 0970 Black C 0972 White Normall~ $ ~ s o· ea This Month $31 0 .00 PR high performance weatherproof speaker system . The heart of the system is the now famous S'' V IFA Woofer/ Midrange, computer optimised for use in a 5 litre Bass reflex cabinet. The classic VIFA 19mm ferro fluid Dome Tweter is incorporated with the crossover network as employed with the SA-50 bookshelf system. The system is fitted w ith a unique overdrive protection device enabling amplifier input of up to 100 Watts without damage. The combination of the internationally acclaimed VIFA drivers with the rugged Redford extruded aluminium enclosure give an overall performance and appearance that is superior to any competitive weatherproof speaker on the Australian market. Each speaker la supplied with mounting brackets. Sonance and Bo,ton Acouat/c Sy1tem1, both coating around S600 a pair'" - John.Negus feeding WA Aud/ophl/e Building that extension? What great ~peake!~ to install. Designed to install · into ce,lrngs or walls this slim profile attractive speaker system / grille assembly will compliment any sound system. Once installed the finished unit blends beautiful ly into any decor. (The grille assembly can be painted over in the same finish as wa lls 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 . C0880 $)25".oo ea Thl1 Month's Special $99.oo ea High Performance Digital Sine/Square Wave Generator Get 24OV AC Mains Power From Your 12V Battery With These Handy Inverter Kit Sets Depending on power capacity the various models wlll power TV Sets, HI FI Turntables, AC Lighting, Electric Drills, Angle Grinder and 100 and 1 Appliances (ETf March '88) Here 11 e nll contained Speech Syntheolzer that doH not require a computer to control It. . This small , simple circuit contains all the necessary components to make your favourite possessions speak . It can be connected to almost any appliance, vehicle or home remote (See SC July '90) This new digital Sine/ Square Wave Generator uses high speed CMOS ICs and a digital filter IC to produce co n tro l system to let yo u know when the kettle has switched off, the doo rs are locked or the water in the rad iator is boiling. The inputs are sine and square waves over the frequency range from 0.1Hz to S00kHz. It also features a 4-digit frequency readout and an output level control. ike most high quality audio function coded and priority message reading means warnings are heard instead of greetings etc if two messages are •nerators, this digital generator sent at the same time. Blan k Eprom 1ers a very wide fre~uency range ·om 0.1Hz to S00kHz - and it s so with rock solid amplitude included to all you to programme the messa ges you w ant. of the amplitude as you change K95oo$95.oo frequency (as is inevitable w ith termistor stablised Wien Bridge K 9502 Pre-Programmed Eprom for K9500 $20.00 ~taoility. There is no bouncing about designs) . improves the comfort level of the civi lised ca mper. Similarly, it has uses in boating . Typically, it can be used to power an electric shaver, electric blanket. electric can opener or a 40W light bulb. K 6705 $99.oo 300 Watt Inverter with Auto Start (See EA April '88) • Super Compact - ki t is supplied with tough ABS case • UM1 High Efficiency Toroid Tren1former thus keepi ng down heat dissipation . battery drain and we ig ht •A uto start when appliance is plugged in and " turned on " ie battery can be left permanently connec ted if req • Voltage regulated • Current regulated • Current overload. Here's an easy to ouild probe which & Powerhouse 6OOW Inverter D'l C ~21.95 -Touch Lamp Dimmer K 2570 (See EA Dec '87) Th is inverter has the capabili ty to produce 600 watts of mains power (See SC June '89) which will run a fantastic array of applian ces . It would be ideally suited to runni_ng lmpre11 your next dinner gue1t1 with thla nifty "Touch" Lemp Dimmer power tools, lighting (inc lud ing fluros ). electric motors_ Are you still persisting w ith on~ of t~ose <;>Id knob a light 6750 Complete Kit $279.oo K 6755 Fully Built Teoted $37O.oo K STOP PRESS - 300 WATT INVERTERS NOW INCORPERATE NEW IMPROVED CIRCUITRY. EVEN BETTER VALUE/I adapts a multimeter into a general purpose thermometer . Mea1ure1 accurately from -20 deg C to type light Dimmers? Well here Is (See EA Aug '85) This in ve rter is ideally suited for powering low wattage mains appliances from the car battery while camp ing . This cconside rab ly draws power from your battery only 2547 $175.oo Low Cost Temperature Probe K =120 12/240V 40 Watt Inverter and mUch more. It ca n be either used as a portabl e unit or permanent fixture . A must for fa rm ing , camping , mining , boating , remote settlements an~ where ever else 240V power isn't available . Can be configu red to o perate dimmer whi c h can turn your lights on and off or Just dim them by touch ing the decorative plate. Extremely sa fe operation Normally $~.00 K K Thll Month 6329 gold plate 6330 with with 1llver plate $30 .00 off either 12V or 24V DC . K 6770 Kit Verolon 50MHz Logic Probe with Logic Pulser 20MHz Logic Probe with Audio Indicator $625 .00 K 6775 24V Fully Built $625 .00 K 6774 12V Fully Built $499 .00 Palm Grip Tools Diagonal Cutter T 2100 $9.95 Flat Nose Pller T 2110 $9.95 Needle Nose Pller T 2120 $9.95 Curved Needle Nose Pller T 2130 $9.95 Buy The Set For $30.oo HU/(RY THIS MONTH ONL YI e , ersonal nal Generator Hobby Pack Heatshrink Include,: ( Internal Diame ter ) 1.6mm. 2.4mm, 4.8mm , 6.4mm , 12.7mm , 19mm . w 0567 $4.95 Now you can have a full function audio 1lgnal generator for le11 than $1001 This pocket sized oscillator has all the features of a large bench oscill ator. 46 preset switched frequencies ranged from 20Hz to 150kHz . eg . 1kHz, 1.2kHz , 1.Sk Hz, 1.8kHz, 2k Hz, 2kHz etc . Smaller than most multimeters, this is ideal for technicians , servicemen, students and hobbyists who require an acc urate and reliable oscillator read y to use an y where . 01542$99.oo BONUS/ With ( Worlh $1 2.50) Fre• Carry CaH Thi• llfonlh An absolute necessity for radio servicing . With provision fo r both internal and ex!ernal mod ulation Frequency Range l00kHz-150 MHz in 6 ranges a 1550 $2~.oo Thll Month $249.oo Quad 'DI' Box for Stage And Studio See E.A. June '91 DC-DC Converter For Car Amplifiers Simple 12 or 24V Light Chaser See S.C. Dec '90 See S.C. April '90 Deli vers a hefty 1.5A at O to 50V. T his dual tracki ng power supply is a must for your workbe nch. The two rails track each other exactly on any voltage. Precise vo ltage is ob tained with the multi -tum rota r y co ntrol. It also has a clear display and m eter movement, a dropout indicator and load ON/ OFF switch. Hou sed in a medium sized instrumen t case with a silver anodised pre-pu nched and screened front panel. $. K 3380 .00 Th is simple unit will replace four separate direct injection (D I) boxes, but at a fraction of the ir total cost. It offers excellent performance, and is ideal for connecti ng a bank of electronic musical instruments to a standard mixing desk. . K 5555 .95 $79 Fast Charger For Nicad Batteries This DC-DC converter will allow you to use a hifi power audio amplifier in your ca r to provide good quality sound. It provides spl it supply rails which can be adjusted to suit your ampl ifier. K 4100 .50 $139 Inverters for Fluorescent Looki ng for a simple circuit to sink your teeth into? Th is 12V light chaser has four separate c hannels , variable chase rate, fuse protec tion and uses just two ICs. There are four channels and each channel can handle up to 36W. K 5810 .95 22 9 FM Radio Microphone $39 Transistor Gain Tester See s.c. March '91 ,._e>! ~ See S.C. Jan/Feb '91 This Nicad Fast Charger is designed to operate from a 12V car battery. It can charge nicad battery packs from 6-12V at currents up to 6A, or you can wire the circuit to charge battery packs up to 30V at reduced current. These DC-AC inverters, are suitable for fluorescent lights rated up to 16 and 40 watts. Fantastic for camping. back yard sheds etc. K 6350 16W Version .95 $35 $129 .oo 6360 40W Version $43.95 Two Channel Pro Power Amp 90 Watts Per Channel K 1660 This simple Beta Tester will test and measure the gain of most bipolar transistors . You simply connect the transistor, press the button, rotate the knob until the LED lights, and read the gain from the calibrated dial scale. K 2534 K This stereo amp Is Ideal for background/foreground applications. Fantastic for restaurants, shops, disco's, aerobics, PA sound systems and home. · $25 .00 AM/FM PLL Tuner »- 174 Roe St. PERTH W.A. 6000 Phone (09) 328 2199 PHONE ORDER TOLL FREE 008 999 007 MAIL ORDER Cl · P.O . Box 8350 Perth Stirling St. W.A. 6849 $-1 ~O ~$:Q 1 This Mo nth This fantastic tuner is the Ideal add-on to any sound system. Can be used as background of music In restaurants, shops etc or any PA application. Also a great upgrade for the home HI-FI. ,)>! "" ,! . : .. ,eat1,,"' ! $~.oo INTRODUCTORY OFFER $599 $11.so Charging cur,ent 300mA M 9020 at 12V. Great for any Gell Cel l. "'". A 2040 K 11 06 Gell Cell Charger ~ma,., ___,..,,, ,.,., , • 90 watts RMS per channel minimum in to 8 Ohms from 20 to 20 ,000Hz with less than 0.05% THD • 2 large power meter indicators• EI A panel with handle device • XLR socket for speaker term inal • Output relay to eliminate turn -on and off transients • Dimensions: (W x H x D) 482 x 92 x 295mm • Weight: 10.5kgs • l~e~ suited to A 2210 stereo tuner. This simple FM Microphone Kit can be built in next to no time and only requires an ordinary FM radio for reception . • Works in the standard 88-108MHz FM range• Ru ns from a single 9V battery • High sensitivity microphone supplied • Long ra nge transmission (up to approx 30m) . ' . •;, ~~'-+~•-. , ""' - . "' -,~''\+'~' ,,,,_ ' "' " - . '''''" ».'<>........,,.,,,,_,,.,,,,.,,,_ • Digital LED frequency readout display • FET FM front end for high image rejection •Phase-linear ceramic filters are incorporated in both AM and FM IF section• 20 station memory • Phase-lock loop (PLL ) IC for FM multiplex stage • Dimensions: (W x H x D) 435 x 60 x 232mm • Weight: 3kgs. A2210$~.oo INTRODUCTORY OFFER $199 HEAVY HEAVY SERVICE - All o rders of 10Kgs or more must travel Express Road •Please allcN 7 days tor delivery. $12 .00 to 10Kgs. $15.00 over 10Kgs. INSURANCE - As with virtually every other Australian supplier , we send goods at consignees risk . Should yo u require comprehensive insurance cover against loss or damage please add $1 .00 per $100 of order value (minimum cha rge $1) . When phone ordering please request " Insurance". TOLL FREE PHONE Ok DER - Bankcard , Visa Mastercard Holders can phone order toll free up to 6pm Eastern Standard Time . Reme"1ber with our Overnight Jetoervlce we deliver next day. STANDARD DELIVERY & PACKING CHARGE $5.50 to 1 Kg , $8 1Kg-5Kg . AL TRONiCS RESELLERS- Chan,es are there is an Al troni c ResellP.r right AUSTRALIA WIDE - Via . Austra lia Post allow approx 7 days for delivery . near you - check this list or phone us for details of '. he nearest dealer . OVERNIGHT JETSERVICE Up to 3Kg is $10.00. 3Kg to 5Kg is $28.00. Overnight Blue Ribbon Dealers are highlighted with a ■ These dealers generally carry a Jetaervlce Courter for delivery next day Country areas please allow additional 24 -48 comprehens ive range of Altronic products and kits or we 'll order any required item hours. for you . 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It has a barometric pressure offset adjustment for heights up to 5000ft & is ideal for use in ultralights, gliders, hang-gliders & balloons. By JOHN CLARKE An altimeter is one of the most useful instruments on board any aircraft but, unfortunately, they are expensive. A brand new altimeter for general aviation will typically cost about $800, while secondhand units in working order usually start at about $300. For this reason, many recreational flyers of gliders and ultralights do without an altimeter, or use a secondhand instrument of doubtful accuracy. 28 SILICON CHIP Many old altimeters can be as much as 30% out and often have sticking dials and a slow response time as well. Most also suffer from significant hysteresis- ie, they give different readings at the same heights, depending on whether the aircraft is climbing or descending. Even new altimeters are only guaranteed to an accuracy of about 10% and can suffer significant hysteresis problems. Another problem with some mechanical altimeters is that they only provide barometric pressure offset for altitudes up to about 2000 feet. This offset adjustment is necessary to compensate the unit for the altitude of the landing strip and to compensate for daily variations in air pressure. Unfortunately, an offset adjustment of 2000 feet is inadequate for some landing strips if you want to zero the altimeter at ground level. By contrast, the SILICON CHIP Digital Altimeter does not suffer from any of these mechanical problems. It is accurate to better than 3.5% and responds quickly to changes in height with insignificant hysteresis. And because it has a fast response time, it can easily indicate rising thermals which should make it particularly attractive to glider pilots. But perhaps the best news is the cost of this unit. We reckon that a complete kit of parts should set you back no more than about $250. Digital display Unlike a conventional altimeter, this unit features a 3½-digit liquid crystal display (LCD) that's very easy to read. All the pilot has to do is multiply the reading on the display by 10 to get the height (or altitude) in feet. There are just three user controls on the front panel: two toggle switches to the left of the display and a rotary control knob (BAR ADJ) to the right. The top toggle switch is used to select the display mode for the instrument. When ALT is selected, the unit functions as an altimeter with a resolution of 10 feet. When BAR is selected, the unit displays the barometric setting with a resolution of lhPa (one hectaPascal). The barometric reading is set using the BAR ADJ control, which provides a calibrated adjustment from 1051hPa to 842hPa. This corresponds to a height adjustment from -1000 feet to +5000 feet when compared to the standard sea-level pressure (1013hPa). This means that the altimeter can easily be set to show altitude (ie, height above sea level), height above a local aerodrome, or flight level (ie, height above the standard mean sea-level pressure of 1013hPa). In most cases, where takeoff and landing are from the same strip, the BAR ADJ control is simply adjusted (in ALT mode) so that the altimeter displays zero feet when the aircraft is on the ground. After that, the altimeter will indicate the height of the aircraft above the landing strip, provided of course that the BAR ADJ control is h=;ft untouched. Alternatively, the pilot can set the altimeter before takeoff so that it displays the altitude of the aerodrome. Thus, the BAR ADJ control functions in exactly the same manner as the barometric (or sub-scale) adjustment control found on a conventional altimeter. It can be used either to set the height or the barometric pressure. Incidentally, the hectaPascal (hPa) is the standard metric unit for atmospheric pressure. It is directly equivalent to the old millibar unit which was in common usage until a few years back; ie lhPa = lmb. The second toggle switch is for powering up the Digital Altimeter and ,.,..-· .. ,-·,.,- An SCX15ANC solid state pressure sensor (lower, right) forms the heart of the Digital Altimeter. This device is designed for measuring air pressure from about 1033hPa down to a vacuum & provides an output voltage which is proportional to air pressure. for checking the battery condition. This toggle switch has three positions: down for ON; centre for OFF; and up for battery check (BAT). A light emitting diode (LED) positioned immediately above this switch indicates the battery condition. It shines brightly if the battery is in good condition but goes dim if the battery is flat. The expected life of a 9V alkaline battery is approximately 50 hours of continuous usage. Maximum ceiling To keep the design as simple as possible, the Digital Altimeter is limited to a maximum reading of 20,000 feet (19,990 feet to be precise). We don't really regard this as a limita- tion, since most recreational aircraft don't get above 10,000 feet and even gliders seldom exceed this altitude. In any case, oxygen is necessary above 10,000 feet and the temperature goes well below freezing above this altitude. These environmental limitations should keep even the most enthusiastic recreational fliers to altitudes well below 10,000 feet. How an altimeter works An altimeter is really a barometer. that's been calibrated to display air pressure changes directly in feet. It relies on the fact that the air pressure drops by about lhPa for every 30ft rise in height. However, this figure is only approxi- Specifications Range .................................................................. -1000ft to+ 19,990ft Barometric offset range ....................................... 843-1051hPa calibrated (-1000ft to +5000ft) Readout ....................................... ........................ 3½-digtt LCD Resolution ............................................................ 1O~in ALT. mode, 1hPa in BAR. mode Accuracy .............................................................. 3.5% (typically better than 2%) Operating temperature range .............................. -5°C to +50°C Current consumption ........................................... 1OmA Power requirements ............................................ internal 9V DC battery; or 12V DC external supply (with optional regulator) Battery life ............................................................ 50 hours Dimensions .......................................................... 140 x 110 x 46mm Weight .................................................................. 0.4kg SEPTEMBER 1991 29 mate because, in practice, the change in pressure with altitude is non-linear. For example, from sea level to 1000ft, the pressure drops by lhPa for every 27.7ft rise, while at about 5000ft the pressure drops by lhPa for every 31ft increase in height. This non-linearity is mainly due to the compressibility of air and the drop in air temperature with altitude. To ensure accuracy, the non-linearity of the pressure vs altitude curve must be taken into consideration. The SILICON CHIP Digital Altimeter has the necessary correction factors built in to the circuit. We'll talk more about this later on. In practice, the air pressure at a given height in a standard atmosphere can be calculated from the following formula: TABLE 1 2.5 2.4 2.3 Altitude (Feet) Pressure (hPa) Temp. (OC) -1000 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10,000 11 ,000 12,000 13,000 14,000 15,000 16,000 17,000 18,000 19,000 20,000 1051 1013 977 942 907 875 843 812 782 752 724 697 670 644 619 595 572 549 527 506 485 466 17.0 15.0 13.0 11.0 9.1 7.1 5.1 3.1 1.1 -0.8 -2.8 -4.8 -6.8 -8.8 -10.8 -12.7 -14.7 -16.7 -18.7 -20.7 -22.6 -24.6 P = 1013.25(1 - 73.999 x 10·6 x Height) 5 -2563 Table 1 shows the air pressure values for various altitudes from -1000 to 20,000ft, together with the expected temperatures. This table assumes a standard atmosphere (1013hPa and 15°C at sea level), whereas the actual pressures and temperatures will depend on the weather· and ground temperature conditions on the day. As can be seen, the air temperature drops at a rate of approximately 2°c/1000ft. Note that although we usually think of an altimeter as a device that measures height above ground, it is really a device that 2.2 2.1 20000 1.9 19000 AMPLIFIED PRESSURE SENSOR OUTPUT (WITH RESPECT TO 2V) 1.8 18000 "' 1.7 1.6 • A-0 OUTPUT CHANGE POINTS 17000 16000 1.5 15000 1.4 14000 "' ~ 1.3 13000 > 12 12000 1.1 11000 E 10000 ...g 0 0.9 9000 0.8 8000 0.7 7000 0.6 6000 0.5 5000 0.4 4000 0.3 3000 0.2 2000 0.1 1000 0 1013 963 913 863 813 763 713 663 613 563 513 5 "" 0 463 PRESSURE (hPa) Fig.1: unlike the amplified pressure sensor output, the altitude vs. pressure curve is non-linear, as this diagram clearly shows. For this reason, the sensor output is fed through a curve shaper (actually, a weighted AID converter) to obtain a corrected response. This corrected response is represented here by the stepped graph & has a maximum error of 1.1 %. 30 SIL/CON CHIP All the parts for the Digital Altimeter (except for the LCD & switches) are mounted on two PC boards which sit one above the other to give a compact assembly. Power is derived from a 9V battery or you can add the optional 9V regulator board & power the instrument from an external 12V battery. -measures height above a set pressure level. For example, let's say that the air pressure at ground level is 1025hPa. If the instrument is set to this value using the BAR ADJ control, it then displays the height above this pressure level. So what happens if the air pressure at ground level changes (eg, due to changing weather patterns)? Our altimeter will no longer display the height above ground level; instead it will continue to display the height above the 1025hPa pressure level. The way around this problem of course is to set the altimeter to the new ground pressure level using the information transmitted by the aerodrome's local weather beacon. Pressure sensor Unlike conventional altimeters, the SILICON CHIP Digital Altimeter derives its accuracy from a solid-state pressure sensor. This device is designated the SCX15ANC and is made by SenSym in the USA. It is designed for measuring air pressure from about 1033hPa down to a vacuum - just the shot for altimeter air pressure measurements. In operation, the SCX15ANC produces an output voltage which is proportional to air pressure. It is supplied calibrated to within ±5% and is also temperature compensated, which means that its output voltage remains relatively constant with changes in temperature. This is important for an altimeter pressure sensor, since the temperature difference between sea level and 20,000ft is about 40°C. Because the sensor output voltage increases linearly with increasing pressure, it must be corrected so that we get a true altitude reading. This is done by feeding the amplified pressure sensor output through a curve shaper. Fig.1 shows the details. The bottom curve in Fig.1 is a plot of altitude vs pressure for altitudes up to 20,000ft. From this, it can be seen that any altimeter which did not correct for this non-linear curve would be extremely inaccurate. In fact, we could expect errors of 25% or more, depending on how the output of the sensor was amplified. The top graph in Fig.1 plots the amplified pressure sensor output, while the stepped graph shows the corrected response after it has been fed through the curve shaper. This clearly shows the accuracy of the in~ built correction circuitry. Note that the corrected response from the curve shaper tracks the required altitude vs. pressure curve in a stepwise linear fashion. The tracking error is less than or equal to 1.1 % but this is not the overall accuracy of the altimeter since we must also take the non-linearity of the sensor into consideration (±1 %). Verification So how did we verify the design in practice? We did this in two ways: (1) by flying the unit in a glider; and (2) by comparing it against a conventional altimeter of known accuracy in a vacuum chamber. For the flight test, the Digital Altimeter was compared with a conventional altimeter up to a test ceiling of about 6000ft. Because of its fast reSEPTEMBER 1991 31 sponse, the electronic unit quickly became the pilot's preferred reference. In particular, the pilot reported that this fast response enabled him to track thermals without recourse to a variometer. The Digital Altimeter also gave the . same reading on the ground at takeoff and landing. By contrast, the conventional unit was nearly 50ft out. The vacuum chamber was used for design verification and for calibra- tion. One of the accompanying photographs shows the test rig. It used a small vacuum pump to evacuate air from a glass bowl placed upside down on a rubber seal attached to an old turntable platter. As shown in the photograph, the mechanical altimeter was placed inside the vacuum chamber while the Digital Altimeter's sensor was connected to the vacuum chamber via a plastic hose. By using this test setup, we were able to calibrate the Digital Altimeter so that it tracked the commercial unit to within 1 %. Finally, we used two methods to check the Digital Altimeter for temperature variations. First, we used spray freezer to test the temperature sensitivity of various parts of the circuit. When these tests were complete, the unit was placed in a freezer for several hours and then tested on the vacuum chamber setup. i-:+.::..:3V~-------------------tREF REFERENCE l-'-+-'-'1.2=5V'--------, VOLTAGE +ZV LIQUID CRYSTAL DISPLAY BAROMETER ADJUST PRESSURE SENSOR CURVE SHAPER BAROMETER/ ALTIMETER SELECT INH1 3·1/2 DIGIT DISPLAY DRIVER +2V Fig.2: block diagram of the Digital Altimeter. The pressure sensor produces a voltage which is a function of air pressure. This voltage is then amplified & fed to the curve shaper to correct for the nonlinearity of the altitude vs. pressure curve. The curve shaper output is then applied to a 3½-digit LCD display driver via a mode selection circuit & this in turn drives the liquid crystal display. 32 SILICON CHIP The prototype was tested by comparing it with a conventional mechanical altimeter placed in a vacuum chamber. This vacuum chamber used a small pump to evacuate air from a glass bowl which was placed upside down on a rubber seal attached to an old turntable platter. You can now afford a satellite TV system For many years you have probably looked at satellite TV systems and thought "one day". You can now purchase the following K band system for only These tests showed that the main temperature variations came from the pressure sensor itself, while any variations produced by the remaining circuitry were negligible. For the prototype, the reading varied by only 100ft over a 30°C temperature range. Block diagram Refer now to Fig.2 which shows the general arrangement of the altimeter. In addition to the pressure sensor, it includes an amplifier, a curve shaper, a voltage reference, a display driver IC and the 3½-digit LCD. There is also the barometer adjustment control and a switching circuit to select either the altimeter mode or the barometric adjustment mode. The output from the pressure sensor is first amplified to increase the signal to a usable level and then applied to the curve shaper. Although shown as a single stage in Fig. 2, this amplifier actually consists of three separate op amps. Its job is to amplify the differential output from the bridge circuit in the sensor and provide a noise-free output with stable gain over a wide temperature range. To ensure temperature stability, the reference voltage block provides a stable +6V supply for the pressure sensor. This reference voltage block also provides +3V, +2V and +1.25V reference voltages for the curve shaper circuit and 3½-digit display driver IC. If you now refer back to Fig, 1, you will see that the amplified output from the pressure sensor is a straight line. Its output (with respect to 2V) is 0V at 1013hPa barometric pressure and +2.5V at 463hPa (20,000ft). As explained previously, this straight line response has to be shaped (by the curve shaper) so that it follows the altitude vs. pressure curve. This curve shaping function is performed using a 32-step staircase approximation. Although not shown here, this circuit uses a resistive divider network which reduces the amplified output from the sensor so that it is within 1.1 % of the required altitude vs pressure curve. It works by switching in a different divider ratio for every 0.078V (2.5/32) increase in the amplified pressure sensor output as the aircraft gains height. The 1.25V reference voltage ensures that the correct divider ratios are switched in at the correct positions on the altitude vs pressure curve. In the altimeter mode, the output from the curve shaper is switched through to the INm input of the 3½digit display driver (IC13) . This device is an Intersil ICL7106CPL and it contains all the circuitry necessary for A/D conversion and for driving the LCD. Note that there are four external inputs applied to the display driver: REFm, INm, INw and COM. The REFm input is set to +3V (which sets the input voltage range), while COM is set to +2V. All input voltages applied to INm and INw are with re- $995. 00 This is about 1/3 the price of comparable systems Here's what you get: .. A 1.8 metre pressed steel prime focus dish antenna, complete with all the mounting hardware - as well as a self supporting ground stand. .. One super low noise LNB (low noise block converter) l.4d:B or better. .. One KU band feedhorn and all the mounting hardware as well as a magnetic signal polariser. .. 30 metres oflow loss coaxial cable with a single pair control line. .. A 99 channel infrared control satellite receiver with adjustable IF and audio bandwidth, polarity, and dual digital readout. The IR control unit has a range of approx. 10 metres. Before you receive your system the unit 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 seperately. Ask about our low noise 'C' band LNB, and other interesting products. All systems are provided with dish pointing details. ----------- 1 Yes Garry, Please send me more information I on your K band satellite systems. I Name.. ... ... ....... ....................... . I I Address ..... .......... .. .................. I ................................................... I ..... .......... ............ P/Code ........ .. I I Telephone ............................... I I I I I I I I I .. ~N~2~!:------0~ .. SEPTEMB ER 1991 33 PARTS LIST 1 plastic case (SY-110), 140 x 110 x 46mm (Arista UB14) 1 PC board, code SC04108911 , 114 x 97mm 1 PC board, code SC04108912, 97 x 102mm 1 PC board, code SC04108913, 87 x 40mm 1 front panel label , 98 x 36mm 1 SPOT centre-off toggle switch, C&K 7103 (S1) 1 SPOT toggle switch, C&K 7101 (S2) 2 C&K toggle switch dress nuts 5 9.5 mm ID x 19mm OD fibre washers 1 Sensym SCX15ANC pressure sensor (Farnell , NSD) 1 3½-digit LCD (Farnell Cat. H1331CC) 1 9V battery holder 12 PC stakes 1 clear Perspex panel, 45 x 18 x 2mm 1 knob, 14.5mm outside diameter, 0.25-inch shaft 1 34mm-length of plastic right angle strip, 19 x 19mm 2 25mm 4BA nylon screws 2 12mm 4BA brass screws 4 48A nuts 3 2mm x 5mm-long screws 3 2mm nuts 1 6mm ID grommet 1 piece of polyurethane packaging for heat insulation, 200 x 130 x 2mm thick 1 200mm-length of light duty hookup wire 1 1-metre length of 0.8mm tinned copper wire Semiconductors 1 LM10CN op amp and reference (IC1) 6 OP77GP precision op amps (IC2-IC6,IC11) 1 ADC0804LCN 8-bit AID converter (IC?) 1 4093 quad Schmitt NANO gate (IC8) 2 4051 8-1 analog multiplexers (IC9,IC10) 1 4053 triple 2-1 analog multiplexer (IC12) 1 ICL7106CPL 31/2-digltA/D LCD driver (IC13) 1 BC548 NPN transistor (01) 1 BUZ71 N-channel Mosfet (02) 1 LP2950CZ-5 5V regulator (REG1) 1 3mm red LED (LED 1) 1 4. 7V 400mW zener diode (ZD1) 11N4148, 1N914diode (D1) Potentiometers 2 100kQ 25-turn top adjust trimpots, Bourns 3296W (VR2,VR4) 1 1OkQ 25-turn top adjust . trimpot, Bourns 3296W (VR3) 2 5kQ 25-turn top adjust trimpots, Bourns 3296W (VR1 ,VR5) 1 10kQ 10-turn pot, Bourns 3590S-1 Ok (VR6) Resistor networks 2 100kQ 4-resistor 8-pin SIL thick-film resistor networks, Bourns 4608X-102 (R2,R4), (Farnell 107-064) 3 22kQ 4-resistor 8-pin SIL thick-film resistor networks, Bourns 4608-102 (R1 ,R3,R5) , (Farnell 107-062) Resistors (all Philips MRS25 0.6W 1% metal film) 1 1MQ 1 3.3kQ 1 470kQ 1 1.2kQ 1 360kQ 2 1kQ 1 200kQ 2 330Q 1 160kQ 1 300Q 4 100kQ 2 270Q 1 75kQ 2 240Q 1 51kQ 1 220Q 2 47kQ 1 200Q 1 27kQ 4160Q 2 20kQ 2150Q 1 13kQ 1 100Q 2 10kQ 1 24Q Wire & cable 1 80mm-length of 6-way 0.1-inch spacing rainbow cable (Farnell 150-432) 1 200mm-length of 8-way 0.1 inch spacing rainbow cable (Farnell 150-433) Capacitors 1 10µF 16VW tantalum 2 10µF 16VW PC electrolytic 1 4.7µF 16VW PC electrolytic 1 1µF 16VW PC electrolytic 1 0.47µF polyester (Wima MKS2) 1 0.22µF polyester (Wima MKS2) 8 0.1 µF monolithic ceramic 6 0.1 µF polyester (Wima MKS2) 1 .047µF polyester (Wima MKS2) 2 .01 µF polyester (Wima FKC2) 1 220pF ceramic 1 100pF ceramic Where to buy the kit A complete kit of parts for the Digital Altimeter will be available from Altronics Pty Ltd, PO Box 8350, Perth Stirling St, WA 6000. Phone (09) 328 4459. sp ect to this +ZV common voltage. Thus, any voltage above ZV applied to the IN8 1 input will give a positive reading, while voltages less than ZV will give n egative readings. The IN10 input works a little differently. When the input voltage is greater than ZV, it subtracts from the voltage on the INH1 input. Conversely, when the voltage on IN10 is less than 2V, it adds to the voltage on IHHJ. Thus, if both INHI and IN10 are at +ZV, the display will read zero (ie, 000). In this circuit, the INLo input is used for the barometer setting and to provide the required offset adjustment in the altimeter mode. We've already covered the function of the barometer adjust (BARADJ) control. It allows the barometric reading to be set anywhere in the range from 843-1051hPa (calibrated); or it can be used for height adjustment. Finally, the LCD sp ec ifi ed has 12.7]Jlm-high digits which are easily read , even in bright sunlight. Unlike a conventional instrument, it can b e read at a glance and the digital display avoids any possible confusion. That's all we have space for this month. Next month, we will publish the circuit details and tell you how it works. SC 34 SILICON CH IP WOOD FOR CHIPS... WOOD FOR CHIPS... WOOD FOR CHIPS... WOOD FOR CHIPS... WOOD FOR CHIPS... WOOD FOR CHIPS... WOOD FOR CHIPS... WOOD ~ TDA1520 Complete 20watt Hi-Fi Audio Amplifier IC • Ideal for mains powernd applications using a 44Vdc supply. but operates down to 15V. Quiescent current 54mA (tvp). • Power bandwidth from 20Hz to 20kHz giving 22W into 4U • 74dB open roop voltage gain gives 260mV input sensi!ivity for 16Woutput • Signal to noise of 80dB (typ) • · Suits symmetrical or a~ymmetrical power supplies • Thermal protection • Very low intermodulation and transient intermodulation distortion • Built-in output current limiter • Low input offset voltage • Low crossover distorti on in output stage • AC short circuit protection • Minimum number of external compone nts Comes in SOT-131A 9 lead SIL package ONLY $8.35 "When it comes to using Serial/est to diagnose a practical senal communications set-up, most users will find the package easy-to-drive, yet a powerful diagnostic tool... " . Rob Evans E.A. Ma-, 91 Why pay up to $150 for a label? Take a close look at APPA multimeters. Look fam iliar? Thars because they're sold under different brand name_s. And that means you fgu~{.;t fe~~ ~~rt~ihirt~~~ig:ed model selling at around $150 more than our price. So you're payi ng that much extra just for the brand lalJel ' Look at th• featums • Large high contrast display The 96 and 98 havs ana/og bar • lo'ft/}/c~3ed input tsrminals and function switch tor sasy sstting • Probs storags clips built in tor sasy two handsd msasursm•nts • ThB 96 is water msistancs for industrial uss • Shockproof tor a drop of 1.5ml • Built-Jn tilt stand : 'J'UL%1i1244~WJi i'?i~-:f~1 and standards for sats '"n TDA7000 FM Radio Circuit Monolithic IC fo r mono FM portable radios. Uses absolute minimu m of external components ye t has frequency-locked -l oop system with 70kHz i.f. with selectivity obtained by RC filters. Oscillator Is only function which needs align ment. Spurious reception is automatically muted . The IC contains RF input Mixe r, Local Oscillator IF amplifi er/ limiter, Phase demodu1ator, Mute ..::.~+-~ - ~ -~ ~ -~ -----,...' detector and mute switch . See FM Radio Intercom article in Silicon Chip Oct 89 for more details. ONLY $3.40 National CMOS LOGIC Data Books Covers CD4000 74 HCOO, 74 HCTOO and 74COO families. If you're quick you'll get one. We can never get enough - So Hu rry $15.00 Crimping Tools TakB your pick! We also have ttie connectors to suit ModularTelephone Plug Crimper 4way, 6 way or 8 Wo>J 129 .95 D-Sua Crimper 88.00 Coax CrimpertorRGSB/59 88.00 Lug Crimper fo r Red, Blue and Yellow $88.00 We stock a wide range of high quality tools suitable for the professi onal serviceman through to hobbyists Squeeky Clean Mains Filters Provide comprehensive protection for PC's, videos, tv, office eq ui pment etc against surges and interterence. Response time is less than 20ns! Peak impulse current is 2500A for 20µs!Clamps at 250Vrms. 10A continuous rating. Will not trip earth leakage devices. Made in Australia and fully ~'fo0a~~~~I~ [~~£~ii1i ~witched power point $110.00 LF-4 has 4 independent filtered outlets and 1OA breaker $235.00 Variabls Transtormsrs Easy way to 'adjusr the mains. 1.2A open $97 .70 2.SA open 1122.20 SA enclosed 159.60 7A enclosed 187.30 13A enclosed 314.65 Save Problems and Cost with MEMOREX I GENUINE PREMIUM GRADE DISKS 51/4 2S/2D $16.95 per 10 5 1/4 2S/HD $24.95 per 10 3 1/2 2S/20 $24.95 per 1O 3 1/2 2S/HO $49.95 per 10 op•ration Model 93 • 1999 count • Large 20mm high contrast LCD readout • 8 Functions - Vdc, Vac, Ade, Aac, Ohms , Diode, Freq uency, Capacitance • 0.5% de accuracy $142.80 Ranges Vdc 200mV, 2V, 20V, 200V, 1OOOV Vac 200mV, 2V, 20V, 200V,J'S_OV Ade 200uA, 2mA, 20mA, 2wmA, 2A, 20A Alie 200uA, 2mA, 20mA, 200mA, 2A, 20A Ohms 2000, 2kn, 20k0, 200kQ, 2MQ, 20MQ Frequency 2kHz 20kHz, 200kHz Ca~acitance 2nF, 20nF, 200nF, 2µF, SerialTest serial data analysis on your PC This is an MS-DOS software and cabling package which enables technicians and engineers to pertorm serial data comms analysis. It offers sophisticated problem solving fac ilities at a fraction of the cost of dedicated hardwarn systems. SerialTest provides a window onto RS232 lines operating either as a passive observer or actively sending ~i~~~~fgWo6/~Bt~etiig~m ulate Triggers can be defined based on error con ditions or data to initiate or terminate monitoring sequences. • Handles baud rates up to 115.2kbaud. • View each byte in ASCII or EBCDIC, decoded to hex, decimal, binary or octal Also°!:!'ai lable - Mods/ 93t with transistor tester in place of 2A range $142 .80 Mods/ 96 • 3 1/2 digit plus 41 segment analog bar graph • Autoranging or manual selection • 6 functions - Vdc, Vac, Ade, Aac, Ohms, Diode • Wate r resistant • Data hold • Memory offset ~ti~~mv, 2V, 20V, 200V, 1000V Vac 200mv, 2v, 20v, 2ooy,7_sov Ade 200uA, 2mA, 20mA, ,wmA, 2A, 20A Alie 200uA, 2mA, 20mA, 200mA, 2A, 20A Ohms 2oon, 2kQ, 20k1l, 200kQ, 2MQ, 20MO $166 .80 Mods/ 96 • 31/2 digit plus 41 segment anal og bar graph • Au torangi ng or manual selection • 8 Functions - Vdc, Vac, Ade, Aac, Ohms, Diode, Frnquency, Capacitance e Data hold • Memory offset Ranges Vdc 200mV, 2V, 20V, 200V, 1OOOV vac 200mv, 2v, 2ov, 2oov,7sov Ade 200uA, 2mA, 20mA, 2wmA, 2A, 20A Alie 200uA, 2mA, 20mA, 200mA, 2A, 20A Ohms 200Q, 2kn, 20kO, 200kn, 2MO, 20Mn FreAuency 2kHz 20kHz, 200kHz ciacitance 2nF, 20nF, 200nF, 2µF, OµF $214.80 Modal 76 Componsnt Tsstsr Does the things your multimeter doesn't! ., Capacitance 200pF to 20uf • Resistance 2000 to 20Mo • Transistor hfe and lceo • Diode displays Vf at 1mA • LED disr,Iar; Vf at 2Ma and 1OmA = -~ie~as~~aimrd 1.5\J"cells $142.80 • Writes cap tu red data di rectlv to disk to allow maximu m cap(ure buffer • CRC checksum calculations • Auto-configuration to any of the comm s ports 1 to 4 • Time-stamping (absolute and relative) including delta time calculati ons e Split line DTE over DCE display $425 1$395 ex lax) Send $1 Ofor a demo disk, '!1~ () ;;i;; ;\;!'· ,,, ~ 8c:::, re~ ~ .kl~ ; ·J\3}~=1~ 8 u1IHn Fhn1 L1gh1er • AdIu5lable from 10-60V. PORTASOL PROFESSIONAL !R~DAp~ i~~~o!IJ batteries yet it gives the equivalent of a 10 to 60W iron. Up to 90 minutes continuous use from a ~nit~g ~~ ~ttenw:e~tas high includes one soldering tip, a hot knife, blow torch and hot blow. Cap contains a flint lighter. Comes in a handy case (with stand tor the iron\ almost fits in your pocket. $69.95' PORTASOL STANDARD SOLDERING IRON We've sold hundreds of 'em to servicemen and technicians. Complete and ready to use with just the iron and bit $39.95 Spam tips are each $12.95 Portasol gas specifically designed for PORThSOL 1SOg $ 5.95 Geoff Wood Electronics Pty Ltd tine 1n N s W) 229 Burns Bay Road, (Corner Beatrice Street), Lane Cove West N SW Mail Orders to - P O Box 671, Lane Cove N S W 2066 Telephone : (02) 428 4111 Fax : (02) 428 5198 8.30am to 5.00pm Monday to Friday. 8.00am to 12 noon Saturday Mail Orders add $5.00 min to cover postal charges Next day delivery in Sydney add $5.00 All prices INCLUDE sales tax unless stated otherwise Tax Exemption Certificates accepted if the line value exceeds $10.00 BANKCARD, MASTERCARD, VISA, CHEQUES or CASH cheerfully accepted. \'PO c:::, ~ () ! ~ a ::0 ~ ..._ °a § ,_r.ti ~ ...., () ;;i;; ~ § £ 2 ~ § CIRCUIT NOTEBOOK Interesting circuit ideas which we have checked but not built and tested. Contributions from readers are welcome and will be oaid for at standard rates. Soft start for 240V lamps The life expectancy of a 240VAC incandescent lamp can be greatly increased by slowly increasing the voltage applied to it at switch-on to limit the in-rush current. This circuit slowly increases the power at switch on so that full lamp brilliance is reached after 10 seconds. It should prove useful for use with projector lamps. IC1a is an LM339 op amp which is wired as a comparator. Its non-inverting input is biased to just above 0V, while the inverting input is wired to a voltage divider connected across the unfiltered output of the bridge rectifier. IC1a thus operates as a zero crossing detector. Its output is pulled high by a 1.8kQ resistor at each zero crossing point of the mains and this pulls Voltage regulator for alarm backup battery Most car alarm systems use a backup battery and this is usually isolated from the main battery by a diode. The problem with this scheme is that the backup battery never fully charges. For example, if the regulator output is set to 13.BV, then the battery will charge to 13.BV minus the voltage across the diode (ie, to about 13.2V). This could affect both the volume and sound quality of the alarm. It 36 SILICON CHIP pin 9 of IC1b high via D6 (ie, the .047µF capacitor is quickly discharged). When IC1a's output goes low a short time later, the voltage on pin 9 of IC1b falls as the .047µF capacitor charges. The resulting sawtooth voltage on pin 9 ofIClb is compared to the voltage across the 33µF capacitor on pin 8. Initially, this voltage is low but increases as the capacitor charges via its associated 100kQ resistor. The higher the voltage on pin 8 of IC1b, the longer pin 14 is switched low during each mains half cycle. IC1b drives a MOC3021 optoisolator and this in turn drives an SC151D Triac which switches power to the lamp. Thus, the greater the charge on the 33µF capacitor, the longer the MOC3021 is on and the longer the lamp turns on after each zero crossing point. Eventually, the voltage across the 33µF capacitor exceeds the peak voltage on pin 9 of IC1b and so the lamp stays on continuously to give full brilliance. Power for the circuit is derived from a mains transformer and this drives a bridge rectifier consisting of diodes D1-D4. The output of the bridge is then fed to D5 , filtered by a 470µF capacitor and applied to a 12V 3-terminal regulator (REG1). D5 isolates the unfiltered output of the bridge rectifier from the filtered regulator input. When building the unit, exercise extreme caution on the 240VAC side of the optocoupler. Inductor Ll can be made by winding 29 turns of 0.63mm enamelled copper wire on a Neosid 17-732-22 iron powder toroid. Power dissipation in the Triac is about 1W for every 240W of lamp load. could also reduce the effective range of pager signalling and could cause difficulties with RF operated keys. This simple voltage regulator circuit overcomes that problem by first doubling the voltage from the mai.n battery and then feeding it to a regulator circuit to obtain the desired output (13.8V). When the alarm is activated (or the main battery is disconnected), it operates a relay which then switches the backup battery into circuit to drive the alarm siren/pager at full power. The circuit uses a 555 timer (IC1) wired in astable mode to drive pushpull output pair Ql & Q2. These transistors provide a voltage doubling action in conjunction with capacitors Cl & C2 and diodes D3 & D4. This works as follows: when Ql turns on, it charges C2 via D4 to about 11 V. When Ql turns off and Q2 turns on, Cl is charged via D3 to about 11 V. This action takes place continuously so that Cl & C2 apply around 22V DC to the input of the LM317K adjustable regulator (REG1). VR1 is used to G. Freeman, Nairne, SA. ($35) 01 1N4007 +12V 0--+-11.....+----, + 200 16VWI 0.1 16 8.2M 12 11 .,. 820k 10 IC1 4060 LEDS GREEN .,. 0.47 014 01 BC548 02 BC548 3 LE04 GREEN + T , 5x1 .2V -MAX I ..L.. i .,. LE01 RED .,. Simple nicad charger with 16-hour timer Nicad cells can be easily damaged by overcharging but this circuit helps prevent that problem. It works by shutting off power to the cells after about 16 hours. The heart of the circuit is ICl which is a 14-stage binary coun° ter. This functions as a 16-hour timer. The RC timing components on pins 9, 10 & 11 set the frequency of the on-board clock to one pulse every 7 seconds, while the O. lµF capacitor and lOOkQ resistor on pin 12 provide power-on reset so the counter starts from a count of zero. At switch-on, Ql & QZ are off and the LM317 applies a constant charging current to the nicads via two parallel paths. The first path is via DZ and a 27Q resistor (AA cells only), while the second path is via LED 5 and its series 27Q resistor. Sl switches an additional 18Q resistor into circuit to increase the charging current for C cells. At the end of the 16-hour timing period, Q14 (pin 3) of ICl goes high and turns on Ql and QZ. Ql then disables the timing circuit by pulling pin 9 of ICl low, while QZ disables the constant current source (REGl) by pulling its ADJ terminal low. During the timing period, LEDs 1, 2 & 3 turn on in sequence to indicate elapsed times of 4, 8, 12 (LEDs 1 & 2 on together) and 16 hours respectively. LED 5 indicates that the battery has been connected correctly, while DZ prevents the batteries from discharging into REGl if the supply is disconnected. LED 4 flashes while ever the clock circuit is running to indicate that charging is in progress. B. Dumuid, Aldgate, SA. ($25) 01 1N4004 FR~~~~AR:--------1 -:-------------11-+1-+----------------- BATTERY D3 1N4004 D2 1N4004 I 3 I IC1 555 2200 16VW _ + T 13.SV : 0.1 2200 16VW 04 ..I.. I I I 2200 16VW ~I~" I : + _ TO ALARM SUPPLY RAILS ALARM OUTPUT 1N4004 set the voltage on the output of the regulator to 14.4V. REGl charges the backup battery via DZ, the normally closed relay cim- tacts and a 4 70Q 1W resistor. This resistor may have to be varied to suit your backup battery which should b13 charged at a C/10 rate. The resistor value shown is suitable for a l.ZA.h battery. B. Adams, Dee Why, NSW. ($25) SEPTEMBER1991 37 10+ $4.95 $9.90 $9.25 $18.95 RS232i'sERIALcARo~..~ .$39 XT HD CONTROLLER. AT HD CONTROLLER .. . RS232/SERIAL CLOCK .................. $49 MONO CO LOUR PRINTER CARD $76 MULTI l/0 ................ ~ -···· $99 PRINTER CARD...... . .... $29 EGA CARD.... ......... ~ . ..... $179 DIOGNOSTIC ............................. :.... $795 FAX CARD.... ....................... .... $595 2 WAY FDD CONT (360K) ............. $39 SMART DRIVE ADAPTOR IDE/FDC . . GAMES CARD ........................ $25 AT S/P/G 2 S/P/G .......... ........... $45 4 WAY FDD CONTROLLER (360-1.44M) ..... ................... .. .... $129 2 WAY FDD CONTROL ER (360-1.44M) .......................... .... $80 VGA CARD 8 BIT 256K ..........$139 VGA CARD 16 BIT 256K (EXP TO 1 MEG) ........ ...... . VGA CARD 16 BIT 512K (EXP TO 1 MEG).. ..$239 /21....................... anon P.LE JET P~ I N TER ,'- VGA CARD 16 BIT (1 MEG)$269 ~ ~•! ' RITRON EXECUTIVE 486 TOWER with 42M HDD • 80386SX-20 • 2 SERIAL, PARALLEL JOYSTICK PORTS • 43 MEG 28ms HD • 101 KEYBOARD • 1.2 MEG 5 1/4" DRIVE • 1 MEG RAM • 256K VGA CARD 3 YEAR PARTS & LABOUR WARRANTY • VGA COLOUR MONITOR 1024 x 768 DOS 5.00 AN EXTRA $100. , EVER POPULAR, LOW ~~ BUDGET. DRIVER & POP UP MENU ~ SOFTWARE. X19950 .......... $49.95 c·-. . ,r / GENIUS MOUSE INCLUDES DR GENIUS SOFTWARE, MENU MAKER, MENU LIBRARY, MOUSE HOUSE & MAT, 9-25 PIN ADAPTOR .. $115 QUICK MOUSE MICROSOFT MOUSc:? MICROSOFT COMPATIBLE. FREE MOUSE HOUSE & MAT PLUS FREE POP UP SOFTWARE. X19955 .... $69.95 THE TOP OF THE RANGEi \ SUPPORTS 1oo·s OF APPLICATIONS. FREE PAINTBRUSH SOFTWARE ............... $169 FAX ROLLS MEMORY UPDATE YOUR RAM WITH THESE GREAT PRICES! 1-9 10-99 100 + 1256-08 ..... $4.95 $4.50 $3.9 4256-08 ..... $13.95 $12.95 $11. 1-9 10+ $130 $120 $34.95 $32.50 ~ ~:-, ~.,. 210 210 210 216 216 210 X 11.5 X 30m................................ $9.95 50m ...~.......... ..$9.95 ...... $19.95 ............. $9.95 X 24.4 X 50m... ~ ••:............ $11 .95 X 30 X 25m ................................... $9.95 X 25.4 X X 25.4 X 100m....... X 25.4 X 30m... ~ Lt llll!r .:' tfjjjJ/ 43M 1 • VOICE COIL IDE HARD DRIVE 17ms ACCESS TIME. SAVE $30 ...... $449 PRINTER STANDS ENCLOSED PRINTER STAND ... $39.00 DELUX PRINTER STAND ............ $89.00 WIRE PRINTER STANDS.. 80 COLUMN ... $24.95 132 COLUMN ...$34.95 QUAU T GREAT VALUE ---------- • 486-25 MOTHERBOARD • 1 MEG VGA CARD __ -::;::-~ • 1 MB RAM • MASSIVE 42 MEG HD 12ms .... • 1.2 M FLOPPY • TOWER CASE & 200W PS • SUPER VGA (1024 x 768) COLOUR MONITOR • 2 SERIAL, PARALLEL & GAMES PORTS • 3 YEARS PARTS & LABOUR WARRANTY • 101 EXTENDED KEYBOARD WITTY MOUSE 7--cAN~ -lOe ............. s6 CLOCK CARD ...... ... .......... .... $39 I ............ . , RITR ON 386SX-26 27M Landmark $1 999 . SX-20/27 .................. :. · • .. ........... $6 -33 128K CACHE. . ,.. . ................... $1 $ 3895 FREE DOS 5.00 THIS WEEK! TOP SELLING SOFTWARE PRODUCTS MICROSOFT WINDOWS VERSION 3 ..... . MICROSOFT WORD ........................ .... . MICORSOFT WORD FOR W INDO MICROSOFT FLIGHT SI MICROSOFT WORKS ... WORD PERFECT.......... .. XTREE GOLD ... ... ........... PC TOOLS VERSION 7 .. NORTON UTILITIES .... .. 1·9 10-99 Y11007 2.304 MHz $2 .00 $1.50 $1.00 Y11009 2.7648 MHz $2.00 $1.50 $1.00 Y11018 3.93216 MHz BNC PANEL SOCKET 1-9 10+ 100+ P1051 6 $2.50 $2.25 $1.50 $1.50 $1.00 $0.75 Y11025 4.75 MHz $1.50 $1 .00 Y11033 5.0688 MHz $1.00 $0.75 $0.50 Y11045 6.667 MHz BNC CRIMP PLUG 1-9 10-99 100+ P10530 $2.95 $2.75 $2.00 ~ \ ~ $0.75 $0.50 Y11061 10.6445 MHz $1.00 $0. 75 $0.50 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 10-99 100+ $1.00 $0.75 1·9 Z10140(R) $0.15 Z10141(G) .. $0.20 Z10143(Y) .. $0.20 Z10145(0) .. $0.20 Y11105 32MHz $1.00 $0.75 Y11110 36 MHz $1.00 LOW PROFILE IC SOCKETS Savo a sma ll fortune on theso "Direct Import" low profile IC sockets! PCB mounting solder tall. All tin plated phosphor bronze or P10964 $3.95 $3.50 $2.90 ~ CANNON TYPE 3 PIN CHASSIS FEMALE 1·9 10-99 100+ P10966 $4.95 $4.50 $3.50 borrylllum and dual wipe for rollablllty. 1·9 10+ 100+ P10550 a pin 1~ 12e 1oe P105so 14pin 2oe 1ae 15e P1056516pln 20e 1ae 16e P1056718pin 30e 25e 22e P1oss8 20pin 3Se 30e 25e P1ossg 22pin 35e 30e 26e P10570 24pin 35e 30e 26e P10572 28pin 45e 35e 30e P10575 40pin 4Se 40e 35e CANNON TYPE 3 PIN LINE MALE 10-99 100+ P 10960 $4. 50 $3. 50 $2. 50 WI1EWRAP IC SOCKETS Those quality 3 level wire wrap sockets are tin plated COMPUTER CABLES • She conductor •M•lded computer Interface cable. W12670 • CIC6 6 con. Sensitivity: 100dB/0.5 Frequency reapol\!MI: 3kHz-3-0kHz lndependance: 8 ohms. Size 96mm diameter. Normally.......... $12.95 Now on special at.$9.95 10-99 $0.12 $0.18 $0.18 $0.18 100+ $0.10 $0.15, $0.15 $0.15 phosphor bro nze. 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MOSFET SPECIALS DTYPE IDCSOCKETS • Plug P12200 $3.95 $3.00 • Socket P12201 $3.95 $3.00 1-9 $2.95 010500 MU45 0•1mA $9.95 010502 MU45 5Q/50uA $9.95 010504 MU46 0·100., A $Q.95 010533 MU52E O·SUA $12.95 010538 MU65 o.souA s12.95 010540 MU65 0•1mA $12.95 010550 MU650-100uA$12.95 010560 MU650-20V $12.95 •• -- Rechargersl Sia A.A 450mAH u~·1 ~ FLASHING LEDS Save a fortune on expensive throw away batteries with theae quality Nicada and ~ Z10150(R). $0.15 $0.12 $0.10 Z10151(G). $0.20 $0.15 $0.12 Z10152(Y).. $0.20 $0.15 $0.10 CANNON TYPE 3 PIN CHASSIS MALE 100+ Requirea no crossover & handlea up to 100 W. $0.75 D TYPE IDC PLUGS 10..99 I ; PER HORN EETER 10w HORN SPEAKERS $0.75 CANNON PLUGS AND SOCKETS 1-9 10+ $0.80 $0.70 $0.70 $0.90 $0.80 $0.80 $0.80 $0.80 Y11100 27MHz P10531 $2.50 $2.25 $2.00 1-9 1·9 DE~P $1.00 DE9S $1.00 DA15S $1.00 DA1SC $1.00 DA15S $1.00 DB25C $1.00 DB2SP $1.00 DB2SS $1.00 ,Y11 082 18MHz $1.00 BNC SOLDER LESS TWIST ON PLUG 1-9 $1.00 controls, water level dectectora, burglar alarms, motion P10880 P10885 P10881 P10892 P10895 P10902 P10904 P10905 12VDCFANS 80 x 80 x 2&Amm 12V OC.1 .7 Watt 0.14 Amp T12469............... $16.95 10+ lane, only $15.95 FANS Quality Iona for UN In power ampa, computer hotspot cooling etc. Anywhere you need pi.nty of air. 240V 4 518" T12461 .. $16.95 115V 4 5/8" T12463 .. $16.95 240V 3112" T12465 .. $16.Q5 115V 3112'' T12457 .. $16.95 10+ fana (rnlHd) Only $14.115. TOGGLE SWITCHES • pocket aize, auto• acanning. • Allows 2 PCa to ahare one printer. Serial model: MS-201 - Host powered X19150 ................ $79.95 Parellel model: MP·201 Protocol traneparant X19155.••......•.•••• $89.95 SERVICEMAN'S LOG I'd never seen that one before To some extent, I suppose, that heading would apply to most stories that warrant telling - if it isn't unusual, it's hardly worth relating. But this one, I feel, is more unusual than usual- if you know what I mean. It concerns a Panasonic video recorder, model NVG-30A, purchased by one of my regular customers, just two years before this episode. And this short life was just one of several confusing factors and red herrings that had to be bypassed before the real culprit was unmasked. The complaint was a very noisy picture; so noisy as to be virtually unwatchable. It was also intermittent, which didn't help, but this point was not fully appreciated initially. The story really began when the machine was only about one year old. At that time, it appeared to be nothing more than a routine fault. When the owner brought it in, it certainly was behaving very poorly. In fact, to illustrate his point, he had brought in a tape that he had recorded. This tape was very noisy on playback and was also noisy when played back on another machine. Fouled heads? My natural reaction was to suspect fouled heads and a visual check confirmed that they were pretty grotty. However, I was a little surprised that they were bad enough to create the symptoms we had observed. Still, it's hard to be as precise as one would like when making such judgements. Anyway, the first job was to give it a routine clean and lubricate, which I did, at the same time checking for anything else which might need attention. In fact , it appeared to be in excellent condition in all other respects, so I simply put everything back together and gave it a run on the bench. It turned in a first class perform40 SILICON CI-IIP ance, on both record and playback, thus seeming to confirm my original diagnosis. And, on that basis, the machine was returned to its owner. But I did take the opportunity to discuss with him the quality of the tapes he was using, because it did appear that there was more fouling than there should have been after only 12 months ' use. It transpired that some of his tapes, while of well known brands, were quite old, this not being his first machine. So I suggested that he cull out the oldest ones, particularly any showing noise in the first minute or so. TETIA TV TIP General Electric TC20T1 (Hitachi PAL3-A chassis). Symptom: Excessive width. The height is not affected so heads on screen look like footballs. The width control has a small degree of affect but not enough to correct the fault. Cure: One or other of C758 (0.33µF 400V) or C759 (0.22µF 400V) open circuit or dry jointed. These caps effectively earth the bottom end of the horizontal deflection yoke and without them the yoke circuit impedance becomes excessive. TETIA TV Tip is supplied by the Tasmanian branch of the Electronic Technician 's Institute of Australia. Contact Jim Lawler, 16 Adina St, Geilston Bay, 7015. It was about six months before I heard from him again and then it was much the same story. But this time, along with the machine, he also brought in a batch of seven tapes for me to check. A visual check of the heads confirmed that there was some build-up of oxide, though not nearly as much as on the first occasion. But it was more than I would have expected in such a short time. This prompted some questions, from which I learned that the machine copped a lot of use. It was used mainly to record the late night movies and this happened almost every night. When I checked his tapes on another machine, I found three out of the seven which I rejected. Not only were they noisy at the beginning but they exhibited odd streaks and bursts of noise throughout. They had obviously had a pretty hard life on the previous machine, which seemed to explain the head fouling. So I cleaned everything up again and returned the machine, along with the tapes and some appropriate advice concerning them. And as before, I heard nothing more from him for about another six months, which brings us up to the time of writing. Then the owner was on the phone with the lament, "This recorder is really playing up now. I made a recording last night and it's really crook. I'll bring the recorder in and the tape". I said OK, but I wasn't as confident as I tried to sound. Twice was bad enough but three times meant real trouble. When he arrived, I set things up and played the tape he had brought. And there was no doubt about it; it was crook, with all the symptoms of fouled heads. But when I replaced his tape with one of my own, it played perfectly, which didn't tally with the fouled heads theory. The final blow to this idea came when the owner wound his own tape forward some distance to where it was a perfect recording. In fact, this random on-and-off behaviour was repeated several times throughout the tape. Murphy's conspiracy All this put a different complexion on things. Not only had it ruled out dirty heads as a major problem, it had also - for the first time - clearly indicated that it was an intermittent fault, probably in the record mode. Until now, Murphy had skilfully organised the symptoms so as to disguise this fact - at least from me. So I suggested he leave it with me, and warned him that it might take some time. He accepted this philosophically; after all, as he put it, it wasn't much good as it was. I set the machine up in a corner of the bench, pushed in the customer's tape, and set it to record while I went on with other jobs. At the end of three hours it rewound automatically and I set it to replay. It came up with a perfect picture and I let it run, glancing at the monitor from time to time. It ran like that for at least an hour then, suddenly, it was into noise. I pulled the tape out, put it in another machine, and it was still noisy. The fault had occurred during recording. Investigating further, I went back to where the noise started and checked the onset more carefully. This revealed that it was quite gradual; taking about five minutes from the first noticeable effect until it was in full bloom. But the change back to normal was immediate; as if it had been switched off. I didn't have any real clues at that stage and pressure of other work prevailed. I simply put it through repeated record and replay cycles, in the hope that some further clues might emerge. And one did. During one test, I suddenly realised that the noise was not on the tape, which played perfectly on another machine. This time it was occurring in the replay mode. Well, that was a real turn-up. It meant that the fault had to be in a section which was common to both record and replay modes and there are not many of these. In fact, the only one that came to mind was the head amplifier pack, a small PC boa~d assembly in a metal can, which comes immediately after the head drum. It handles both the record and replay signals - separately, admittedly - but I suspected that there could be sufficient common circuitry to allow it to fail in both modes. Fortunately, I had a unit in stock and it is a plug-in device, so it was obviously worth a try. And the machine did come good. It ran almost continuously for several days, with- · out so much as a flicker - until I was about to give it back to the customer, that is. Then it was back to its tricks. That was a real blow because there was little else to suspect. But, as it happened, the solution came by pure chance. Have you ever performed some seemingly innocuous act which has suddenly revealed all? Well, I have - and that's what happened this time. I was watching a noisy replay of a known good tape when, for no reason that I can explain, I switched the machine from the normal mode to the still frame mode. The result was a perfect still picture! I then switched back to norm'al and it was noisy as before. A couple of more checks confirmed that this was no fluke. What did it mean? This is a 3-head machine, the third head being used in. the so-called "trick" mode. So what it meant was that one of the other two heads was intermittently noisy; something I had never heard of before. Nor has anyone else, as far as I can determine. Fortunately, I had a spare head drum in stock which I promptly fitted . And that did fix it - and confirmed the diagnosis. So ended what had been a most frustrating exercise. After all that trauma, I'm happy to sit back and gloat over someone else's problems. So here's a tricky one from J. L., south of the border. The fisherman's TV This story began when one of the local fishermen brought in an Hitachi CWP-131 colour set. This is a mains/ battery type with twin rotary tuners and a 30cm screen. It was popular many years ago and there are still a lot SEPTEMBER1991 41 R702 . ,o ""'" C702 0.01 '" H,(L)AFC ;~a, CR701 IN34A TR701 2SC45B<at>I<at> 2SC l740<at>!<at> C70 1 0 .0 1 W2W) R707 12K ( 703 CR702 0 .0 1 1N34A R 720 68 0 R72 3 680 C765 1/ 5 0 0 D06 at!00 R76!, 4.7K + TR6 0 11 TR602 2SC458 <at>/<at> 2 SC l740<at>/<at> R 60 3 4 .7 1( R601 6 .8K + C605 2 20/16 R614 R6 t9 220 C6 19 4 + + TR603 2SA673<at>/<at> '" V,(F) PRE DRIVE 10 R6 !8 27K J; ci'. ~ R6 ! 5 <8 R6 0 ~ ~ Q I( C60 • 3 _V.'.! ' HOLO J .068 RGO-. CR602 M V-1 3 C6 0 9 10/50 7 100 I 3 471 16 R60 4 1/ 50 1 C +'' 2 3 R6 20 22 K R6 l 7 2 .7 K 22 K R62 1 2.2K R60 9 820 C6 02 :r l 112Wl "" ( 74 4 - :~& R706 9 5 M60IL!I. HM6233 V.!FIOUT R60 8 2 ,71( '" R6 2 2 3.6 Fig.1: the vertical oscillator & vertical output stages of the Hitachi CWP-131. The vertical oscillator stage is based on transistors TR601 & TR602 on the left, while the HM6232 thickfilm output stage (shown on the circuit as HM6233) is on the right. of them around. Not many, though, spend most of their lives at sea, and this may have had some bearing on the multiple problems presented on this occasion. The first time the set came in it was a simple "no-go "; the lOA fuse in the 12V line had dropped its bu ndle. The owner said. " .. .it worked last night, but wouldn't go this morning". It's rare to find fuses open circuit without being blown. This one had simply broken in the centre, probably the night before as the set cooled after being switched off. I fitted a new fuse and the set worked as well as ever. It went back to sea that night and I hyard nothing more about it for about three months. Then it was back, again with an open circuit lOA fuse. This was too much of a coincidence so I asked him to leave the set so that I could investigate why it was so hard on fuses . By this time it was the off season for fishing and he· wasn't going back to sea fo r several weeks. So he was quite happy for me to keep the set and, hop efully, find the cause of the troubl e. Then , as a passing comment, he mentioned that the picture had sometimes bri efly collapsed to a few centimetres high, then returned to normal. Even less frequently, it collapsed to a 42 SILICON CHIP bright line but alw ays recovered quickly, usually as the ship rolled to port - or was it starboard; I never can remember! (Simple J. L. The words "port" and "left" both have the same number of letters. So port is the lefthand side when looking towards the sharp end. No charge for that. Serviceman.) So, it looked as though we had two problems, not obviously related. It was not going to be an easy task and, in the event, the minor complaint became the major problem. Fishing for faults To open the account, I fired up the set on AC. The sound came up immediately but, when the screen lit up, I could see that the vertical scan problem had now become permanent. All we had was a line across centre screen. A quick check on the several rails showed that all voltages were close to normal, so I replac ed the lOA fuse and tried again, using the 12V battery I keep under the bench for such occasions. This time, the set came good with a full picture. When I restored the AC supply, the picture continued for an hour or so , then collapsed to about 25mm high. When I changed back to the 12V supply, the.fuse werit open circuit. So it appeared that something was shorting in the vertical stage and this was taking out the fuse in the 12V supply. It seemed strange, though, that the AC supply did not appear to be so critical and its fuse could withstand whatever overload was being imposed by the defective component. The vertical stage in the Hitachi NP6C chassis is a rather strange setup. Transistors TR601 and TR602 are designated as the vertical oscillator in a configuration that I cannot recognise. (One day someone is going to say, "That's easy! It's a so-and-so oscillator". And I'll say, "Of course it is. I just wanted to see if you knew!") The oscillator is followed by a simple series height control (R612), then a PNP pre-drive amplifier, TR603. This feeds the main driver amplifier and an output pair on a thickfilm unit, HM6233. The curious thing about this whole vertical stage is that the so-called oscillator stage appears to require substantial feedback from the output of the thickfilm unit (pin 8, normally 60V p-p) before it can produce the required voltage at this unit's input (pin 2, normally 1.2V p-p). I found the thickfilm module to be extremely sensitive to vibration. I took a long, soft knitting needle I keep for this sort of investigation and very gently prodded around and over the mod- ule. I couldn't find any part of it more sensitive than any other part, but the gentlest touch anywhere on its surface would toggle the unit in and out of operation. The picture was bouncing between normal and a bright line, and was very hard to stabilise in either state. One thing I have learned about these Hitachi chassis over the years is that these thickfilm units are subject to faulty soldered joints. The problem appears to be due to the ceramic substrate being extremely rigid, while the transistors and other components attached to it are far less rigid. These components have a tendency to change their size as they heat and cool, but the ceramic substrate refuses to move. So, over time, the assembly develops cracks in the joints. It's always worth trying to resolder the modules. I have been successful in perhaps half of my attempts but the only guaranteed solution is to replace the unit. This time it was to be one of my unsuccessful attempts. I removed the module and tickled it with a No.8 (400°C) bit in my Weller soldering iron. It took quite a long time to cool after that but, when I replaced it in the chassis, there was no sign of any activity. I tried all kinds of prodding and poking but it appeared to have failed completely. Oh well; it was worth a try! I have a colleague who is the local Hitachi agent, so I rang him, hoping he had an HM6233 in stock. I was out of luck, but he offered to include one in an order he was sending off that night. So , in a couple of days, I had a new unit; an HM6232. It looked the same as the HM6233 and virtually identical to a secondhand HM6231 which I had dug up from a junked set in the store room. When I had a closer look at the unit in the set on the bench, I found it was an HM6232, not the 6233 as shown in the circuit. I wish manufacturers could make up their minds - they make the life of your average serviceman truly a hell on Earth. Australian Made TEST EQUIPMENT YOU CAN TRUST Built-in Meter to check EHT transformers including split diode type, yokes and drive transformers. $78.00 + $3.00 p&p Appeals to Heaven I fitted the new module and switched the set on. I stamped my foot and thumped the bench, I called down from Heaven all kinds of imprecations on the designers of electronic equipment; all to no avail. All I had was a thin white line across the centre of the screen. At this point, I made the same mistake that I have made in the past. I reached for the high-tech tools of my trade and tried to deduce the cause with frequency counters, oscilloscopes and other assorted state-of-the art devices. If I had used my multimeter, I would have solved the problem hours earlier. I have already mentioned the peculiar nature of the vertical oscillator in this chassis. The oscilloscope showed only lO0mV at the input to the height control (it's normally 2.4V p-p) and also that the oscillator was running slow. The sync pulses were arriving at the oscillator at the correct intervals, but were obviously incapable of pulling the oscillator up to speed. The waveform vanished on the other side of the height control until I adjusted this to its maximum position, which produced a tiny trace of signal (about a lmV) at the base of the pre-drive transistor, TR603. There was no sign of any signal at the collector of this stage. Since the voltages on the oscillator transistors, the pre-drive transistor, and the input to the thickfilm module were all close to correct, I decided Strong magnetic field, larger than usual coil with multicore centre. Double insulated for your safety, also fitted with momentary on/off switch. 240V A/C 2.2 amps. Just about as important as having a soldering iron in your toolbox! $75.00 + $10.00 p&p 0 Built-in meter reads positive or negative 0-50kV. For checking EHT and focus as well as any other Hi-tension voltages. $98.00 + $5.00 p&p (INFRARED OR ULTRASONIC) Designed to test lnfrared or Ultrasonic control units . With the ( extension lead you can also test infrared units which cannot be placed in front of the testing unit. Requires a 9V battery. Output is via the LED diode and piezo speaker. $85.00 + $4.00 p&p E A new addition to the remote control tester. Comparable with units costing $500 or more. You can test the laser pick-up in compact disc players. $27 .00 + $2.00 p&p NEW PRODUCT Save time and money with this tester. Helps you determine if you have a tuner problem, an AGC problem or a fault in the IF stages. $250.00 .,.~~.;r.~i;:r:.;;~ RCS Radio Pty Ltd is the only company which manufactures and sells every PCB [, front panel published in SILICON CHIP, ETI and EA. L 651 Forest Road, Bexley, NSW 2207. Phone (02) 587 3491. (Tax inc.) from $17.00 exchange+ p&p Cheque, Money Order, Bankcard or Mastercard ~v. TUNERS). ·· · ·· · ··· · ····• •.•-•:-:-:-;-;.;.:-:-:-:•:•:•:•:•:•:•:-:-: :-:-:-:-:-:-:-:-:-:-:-:-:-:-:;:::::;:;::::::;::::-- 216 Canterbury Road, Revesby, NSW, AUSTRALIA, 2212 '"2:::r (02) 774 1154 (02) 7741154 ~A i SEPTEMBER 1991 43 SERVICEMAN'S LOG - CTD ~ 'R~~\/E-t:> -rt-\~ MOPUL,..~ & ,1c::Kt..-e:D 1--r w,-rl-\ ~ No.~ Br'f" \N M'-f WEU..ER 1~01'-.\oo••· that the only possible fault must be an open circuit capacitor in a feedback loop. There were several parts of the circuit that looked like feedback loops, and they all included electrolytic capacitors. So, with a sad heart and a weary hand, I began to extract all the electros that might conceivably figure in the vertical function. · An hour later I had checked every capacitor and most of the resistors in the relevant part of the chassis. There was nothing wrong with any of them. I then removed the transistors and diodes and tested them exhaustively but couldn't find any that were in any way doubtful. And that didn't leave much to test. I had already checked the voltages on the transistors and at the input and output terminals of the module and had found nothing dramatically wrong. So if there were no faulty ea- · pacitors or transistors in the circuit, then the trouble had to be a faulty resistor. But which one? I checked 44 SILICON CHIP every resistor from R601 onwards but they were all OK. That left only the output module - which I had already replaced. I had another look at the voltages around the module. I had already checked the supply on pin 1 and found 107V. This was high by about 30V but was accounted for by the fact that the output stage was not drawing any current. The voltage on pin 5 sets the bias on the driver transistor and this was correct at 0.6V. And the voltage on pin 11 was also correct at 0.1 V. At first glance, these had seemed to be the important voltages on the module. Pin 5 should turn on the driver, which should then turn on the output pair. But I had overlooked the network around pins 2, 3, 4 & 10. I had checked the resistance values for this network but had paid no attention to the voltages. This very soon revealed an anomaly which enabled me to solve the problem. The voltages should range from 54 V on pin 2 to 34. 7V on pin 10. In fact, they were all within 0.1 V of 9V. Since this voltage is derived from the 54 V rail which feeds the horizontal oscillator - which was working - then the low voltage on pin 2 could only be the result of an open circuit feed resistor. This turned out to be R636, a l0Q 0.5W metal oxide resistor which is shown on the circuit but not on the PC board pattern. I hunted all over the board pattern in the manual but couldn't find a trace of R636. Fortunately, Hitachi boards are quite clearly labelled so I was eventually able to find it. But it took some doing. It looked as though R636 had been added as an afterthought because it had been mounted high above the other components, on tubular supports, and the silkscreened part number appeared to have been handwritten after the overlay mask had been prepared. A quick check revealed that R636 was indeed open circuit and so it was immediately replaced. All the voltages around the output module then came good and I had a full scan - more than a full scan, in fact, because the height control was still turned up full bore. Legless trimpot It was then that I became aware of yet another fault in the vertical stage. As I adjusted the height trimpot, the picture collapsed to a bright line. I removed the trim pot and the two outer legs fell off. They had been riveted to the ceramic base but the rivets had corroded away. This may have been the result of the set's many sea voyages yet, strangely, there were no other signs of sea air corrosion. So the Hitachi was finally fixed but it leaves unexplained the sequence of original faults. I suspect that the faulty height pot was responsible for the intermittent nature ofthe original vertical collapse, ·while the demise of R636 accounted for the final failure. I'm not sure how all this related to the blown fuses - it might have been just coincidence, especially since the AC fuses showed no signs of distress . Or perhaps the ship's voltage regulator is out of adjustment, putting more than the usual 13.5V on the line. That's an idea I must put to the skipper, next time he comes into port. Thank you J. L., and congratulations on a happy ending - even if you were "all at sea" there for a while. (Ouch! Sorry about that). SC Unbelievable scoop purchase of top quality alarm panels. Jaycar has purchased the Importers entire stock of SCOPE brand state of the art programmable alarm panels. This alarm panel has 6 separale sectors plus 6x 24 hour sectors. The features and facilities this panel has Is simply amazing, the manual fists 51 separate facilities thal can be programmed, some of lhese include: • when standard alarm zones are required, no programming is required • permanenl memory hold up facility • separale limed exit, enlry and PA circuils • any zone can be limed (0-99 sees) as an exit/entry • final door set • digital communicator oulpuls, arm/disarm, alarm, personal allack, fire/lamper • these can be Inverled • hand over zones, programmableon any zone • isolale lacllily (exce pt PA, lire and tampers • soak lest (on any zone) • • operator memory slores 8 events , - • • siren lest (tests all sirens for 1Oseconds) ~ • • will drive a combination of sirens, piezo ~ ·. ' ' • zone paring • key terminal - 6 options • automatic reset - 1Ooptions • end of line resistors programmable on any alarm zones • pulse count on all zones This alarm has a digital 7 segment des play on the panel to show sector conditions and system informafion. There is also a12 dlgil keypad on the front. Each unit is supplied with a114 page installation/service manual and an operating manual which covers about everything you will ever need to know. Speclltcalfons: Operaling vollage -16-1 SV AC Ouescenl current consumpfion -125mA Oulpul voltage -13.6 V DC Power output max current -1A DC No of sectors - 6 x burglary Stand by ballery- up to 6.5 Ah End of the line resislor -1 Kn Sector loop current -1 mA Key switch Input- programmable for either latching or Sector de-bounce lime - 300 msec pulse input Size - control box 330 x 255 x 82mm Entry lime- prog 0-99 sees Exit lime - prog 0-99 sees Siren lime- prog 1-1 Omin $22.50 Power supply to suite 16V AC Cat MP-3021 Gel battery to suit 1.2Ah $26.50 CatSB-2480 Cal LA-5180 II s - Ideal for warehouses, factories and large houses. This 'slaie of the arl' alarm panel has 12 seclors plus 5 tamper zones. The features and programming lunclions are similar to the smaller lunil. The scope 6.30 is conlrolled lby a separate digital keypad with an alpha/numeric LCD display. We supply two of these with each unit (one for the front door and one for the back door). The unit is housed in ametal box measuring 355W x 290H x 120D. This can be hidden away as all access is done via the keypads. When standard and lamper zones are required all zones are end of line resistor supervised and can also be programmed so that both lamper and alrm circuits can use the same cable pair. 114 page installation/service manual and operallng Instructions supplied. SpecHlcatlons: Operating vollage -1 6-1SV AC Operating current-150mA End line resistor - 1K Current de-bounce lime - 200m sec Output vollage - 13.65V DC Memory type - Eprom programmed through keypad Keypads - LCD with aplh/numeric characters Plug pack to suit -16V AC Cal MP-3021 $22.50 Cal SB-2486 Back up battery to suit 12V 6.5Ah $43.50 Supplied with two keypads Cal LA-5185 ONLY $599 ONLY$199.50 Also available without case for $129.50 Cat LA-5182 lntelllgenl remote keypad to program and arm/disarm the system, 7 segment readout. You can use up to three per panel. Cat LA-5183 Special price $59.95 This is an ideal"alarm syste mfor home units and small houses. 11s easy to operate and install. Simply screw the unit on the wall. It has an inbuill PIR (range up lo 15ml) as well as a12V rechargable 700mA gel ballery. The unit requires 12V DC to charge the ballery, a power supply can be plugged in permanenlly or for 1Ohours when the power light llashes (approx every 2 weeks). II has an inbuilt 115dB piezo screamer, and wow is it loud, as well as a 12V output sockel for an external piezo of required. Once the uriil is switched on by the keyswilch they keys are then hidden and normal day lo day on/ott operation is by two RF transmiller key fobs. This is awell engineered alarm system, ii is easy to use and install and ii works very well. lls made in Italy and there is only a limited quantity. Cat LA-5140 ONLY $179.50 240V power adaptor to suit 12V DC 300mA We have purchased a large quantily of National brand gel balleries. Stock up now al these crazy low prices. Some well below normal wholesale prices. 6 Volt 8Ah 12 Volt 2.4Ah 12 Volt 24Ah Cal SB-2478 Cal SB-2483 Cal SB-2492 Only $16.95 Only $29.95 Only $99.95 (wholesale price $132) 12 Volt 38Ah Cal SB-2495 Only $149.95 (Wholesale price $228) Cal MP-3006 $15.95 A C SURGEBUSTER Jaycar proudly announce lWo new quallly plasllc toolboxes to our range. Two sizes are available, medium and large and both are Ideal not only for hobbyists, but anyone who needs to carry and care for tools. L SZ Has two fold-out trays to store small components/parts and room In the bottom for tools. Size: 320(L) x 140(H) x 16qD)mm. Cal. HB-6330 Tray size: 290(L)x 130(W)x25(D)mm Includes carry handle and locklng clip. A Top quallly US made 240V 50Hz 1300rpm molor whlch was used lo power acylindrical blower fan for an air condlllonlng system. Taiwan made motors sell for around $40 - US made motors would cosl $60 or more plus lax. We have a limited quanUly. Dimensions 85 dla, 100 heigh! including mounting bolls and drive shaft. Cal. MM-5050 Safely assured surge prolec;led power oullel plus $5,000 FREE Insurance agalnsl damaging vollage spikes and power surges. Cal MS-4010 $29.95 ONLY $24.95 $14.95 0 AR Ideal for !he professional or lradesperson. Has lwo fold-out trays with adjustable compartment dividers, twin locking clips and twin carry handle Size 415(L) x 160(H) x 170(D)mm Cal.HB~ Tray size: 375(L) x 155(W) x 28(D)mm High level prolection against damaging power surges plus provides line noise lillerlng to minimise eleclrical lnler1erence. 4 protected oullels and overload cul-out. Recommended for PC's, HI FI and other valuable elecimnlc equipment. Plus $5,000 FREE Insurance Cal. MS-4012 $99.95 $ 24.95 duck TV wilh overload prolecllon Cal. MS-4040 This brand new design Indoor anlenna will pick pal almosl anything! Well, almosl! II ls omni dlrecllonal and polarised and will pick up AM/fMNHF and UFH. Frequency range Is 100MHz - 960MHz. II ls easily adjusled tor either horizontal or vertical polarisallon signals - jusl lurn II around. II ls supplied with 12 velcro sllcky pads on the underside for easy mounllng on awall or window. Size Is 280(W) x 240(L) x 12(D)mm. Supplied with 3 metres of coax and aslandard 750 TV plug. ;;;;v$2s:95 BI $12.95 V Double A tors Cal. PP-4035 $4.25 NOW AVAILABLE 1 e/ telephone answering (model #915) Guitar speaker 12" 10 w tt See calalogue for lull delails Normally $99.50 Cal CG-2380 Only $79.50 Features Include Phone: • 1Omemory • Pulse and lone • Easycall compallble • 3 way calling • Call diversion • Call waiting • Reminder calls • Call baring Answering machine: • Remole conlrol • Interrogate machine from away • Telecom approved Cal. YT-7040 $ 24 9.00 JS Last year we were forced to increase our prices on 3 and 4mm nuts and bolts because the local importer we bought from increased their prices. We really weren't happy about this, so we've been on the lookout for a new supplier, which we have found . We can now REDUCE our everyday prices back to somewhere near where they were last year. Description Oty Cat Old Price New 3x6mm screw 25 HP0400 $1.20 $1.00 3x6mm screw 200 HP0401 $4.20 $3.50 3x10mm screw 25 HP0403 $1.20 $1.00 3x10mm screw 200 HP0404 $4.75 $3.75 3x15mm screw 25 HP0406 $1.30 $1 .1O 3x15mm screw 200 HP0407 $4.95 $3.95 3x20mm screw 25 HP0410 $1 .40 $1.20 3x20mm screw 200 HP0411 $6.20 $4.95 3x25mm screw 25 HP0414 $1 .50 $1.25 3x25mm screw 200 HP0415 $7.50 $5.95 3x32mm screw 25 HP0418 $1 .60 $1 .50 3x32mm screw 200 HP0419 $8.95 $7.50 Flat washer 25 HP0430 $1.25 $1.00 Flatwasher 200 HP0431 $4.75 $3.50 Shake washer 25 HP0433 $1.40 $1.20 Shake washer 200 HP0434 $7.50 $5.95 3mm nut 25 HP0425 $1 .50 $1.20 3mm nut 200 HP0426 $7.25 $4.95 4x10mm screw 25 HP0450 $1.40 $1.30 4x10mm screw 200 HP0451 $7.20 $6.50 4x15mm screw 25 HP0453 $1.50 $1.40 4x15mm screw 200 HP0454 $7.95 $6.95 As used In many 240 volt appllcallons, e.g. halrdryers, healers. hol rollers, Irons elc. 12a0 c cat. sT-3804 $2.50 1s2°c 22a 0 c 240°C $ 2 .50 $2.50 Cal. ST-3815 $2.50 cat. ST-3808 Cal. ST-3812 Another surplus bargain. These are a piezo Hi FI lweeler, but in a strange shape. They were used In a Kangaroo scaring device, but the manufacturers had a model change and these became surplus. The specllicallons are similar lo our economy piezo lweeter(Cal. CT-1905), but lhe shape is ralher different. SPECIFICATIONS Frequency Response 800- 40k Peak Power 75 walls inlermillenl Use wilh or wllhout crossovers. Size 50mm diameler, 60mm mounting holes, lenglh 75mm Including bullel. Cal.'fT-1906 ONLY $2.95 10+ less 100/o 100+ $2.00 e a p wehad a quantity of these some time ago, and we still get asked If we have any more available. They are used In televtslons. They have roll surrounds and are QUALITY small speakers. Oval speaker, rubber roll surround. Size: length 68mm, width 34mm, height 33mm. lmpedanai 7n. Power handling 1 wall. Cal. AS-3020 A Cat No Description PL-0870 09 female to 025 male, 2mt PL-0871 09 male to 09 female, 2mt PL-0872 Centronics plug to centronics PL-0873 $3.95 PL-0874 plug, 2mt Hi-density 150 male to female, 2mt Keyboard ext 5 pin DIN to DIN Prial $19.95 $12.95 $19.95 $14.95 $ 9.95 Oval speaker, but with 4 holes for standard type mounting. Roll surround. Size: lenglh 70mm, width 40mm, height 29mm. Impedanai 120. Power handling 3walts. $ Cal.AS-3021 R Save your car for less than $5! Were selllng for $19.95! ll's a black box wlth 12 digits on the top and a flashing LED. It looks very similar to the controller on a very expensive car alarm (the one lhat guarantees your car won't be stolen.) So, wllh !his sitting on your dash, would be thieves will think you have a high quality alarm, and move on. Can be used on !Is own, or to complement any exlsllng alarm system. Use on cars, around the home, on boats, elc. Easy to inslall, size 70 x 50mm, sllcky tape already supplied on back. Includes alarm sticker. Requires 2 xAAA batlerles (not Included) Cat. SB-2375 $1.95 for two. Cal. LA-5105 ONLY $4.95 3.95 .,, Oscillometric method Oval speaker wllh 4 holes for mounting. Same dimensions as type 2. Impedance 80. Power handling 5 walls. Cal. AS-3022 $5.95 PC mount- pins are 15mm apart. Also includes mounllng holes for panel mounllng. Operates anywhere from 6 to 12 volls DC. Size 28mm dlameler, 35mm mounting holes, 14mm high excluding pins. Cal. AB-3460 CRAZY PRICE $99.95 1-9 $2.95 10-99 $2.00 100 up $1.50 Quality ABS black plasllc box. Ideal for use In cars as can be supplied with underdash mounting bracket II may look familiar to many people as ll's a radar detector enclosure. The front panel has a square hole and the rear panel has some odd shaped holes, bul cables can be run through and In a car they won't be seen anyway. Dimensions 39(H) x 125(W) x 127(D)mm. Available two ways: Box AIncludes lop, bollom, front and rear panel, mounting bracket and two lhumb screws. $ Cat HB-5942 ■ Box Bincludes lop, botlom, front and rear panels only. 5 95 Cat HB-5940 Keep an eye on your blood pressure at home wllh this easy lo use digital electronic blood pressure meter. It uses the highly accurate oscillometric method lo give systolic and diastolic pressure as well as pulse. Features include • Easy operation Designed for quick and simple one-touch operation • High accuracy High precision wllh osclllometrlc method and artllect reject algorllhm • Memory Convenient memory funcllon for previous reading Supplied complete with comprehensive lnstrucllons, case and batteries (4-AA). Cal. QM-7250 $2.95 240V mains to 15V AC 1OOmA. Supplied with 2 metre cable lo a 2.1 mm DC plug. Cal. MP-3022 L.: I BARGAIN Speaker Is a 3'foam suspension lypeand has a metal grille over the front. CatAS-3185 Normally $26.95 ONLY $4.95 T 240V primary, solder lugs. Size same as 2851 types Cal. MM-2012 $5.95 An excellent way to learn about electronics and lhe result will be a qualify analogue multimeter you can use for years. Ideal for the educational area, schools, elc. The unit ls supplied partially assembled, there Is however, some soldering required. Kit Includes everything lo gel the unit operational Including leads and probes and ballerles. SPECIFICATIONS • 20,000 ohm,,\'olt • Continuity buzzer • 1.SV battery check • dB measuremenls • Diode & fuse protected • 19 ranges Cat. KC-5058 $38.95 NORMAL PRICE is $9.95 STOCK UP NOW • Wholesale enquiries contact Bruce Routley (02) 747 2022 ER Sept $21.95 A A $ave a fortune e Delays lhe inlerior lighl from swilching off for 13-17 seconds. Simply inserts between lhe door swilch and globe. 2mA currenl draw. 1988 Cat price $13.95 The ullimale car accessory swilch. II conslsls of a black !ouch plale wilh a LED which mounls on/under lhe dash lhrough a 1(2' hole. Touch plale size 25 Wx 38 H mm. This connecls wilh cable and plug/ski lo a relay (relay supplied). SWilch is SPST on/off Ideal for spoflighls/driving lights, or virtually any car accessory. Raled al 30 amp 10-15V DC. Also supplied wilh 6 slick on symbols lo indicale lighls, flashes elc. Made in England. A DP relay cos! $16.95 on ils own! These are nol very common so slack up while they are available and al lhese prices you can allord lo. Gold plaled conlacts. PL UQ Aris la price S16.95 Cal PP-0862 Jaycar price $ 2 each SOCKET Arisla price $17.50 Cal PS-0865 Jaycar price $ 2 each 1988 Cat price $32.95 CAT SP-0700 ONLY $8.95 II you have lrouble charging the small 'N' and 'AAA' size balleries in your charger, lhese adaplors will solve lhe problem. Simply insert !he balleries into these adaptors, !hen inlo your charger. 1988 SAVE A FORTUNE Pul one of these on your rear parcel shell and avoid rear end collisions. Easy lo inslall wilh sell adhesive rubber mounling and 2 ml cable. 12 V DC. Arisla price $13.35 Cal M -2085 Jaycar price $4.95 E Cat price $5.95 AAA adaptors (4 pieces) Cal PH-9280 Only $1.95 N adaptors (4 pieces) Cal PH-9282 Only $1.95 Conlrol lhe speaker volume between Iron! and rear speakers In your car. All uni ls designed for 4 speakers. 1988 This carry case will accepl a 6.5Ah gel! ballery. II is ideal for video camera users or for hand held 12 voll spollighls for shoolers, nigh! bush walks elc. II has leads for connecling lo ballery inside case (posilive is fused) and acigarelle lighter sockel is mounled on lhe side. ahas aslrap for hanging on shoulder (removable) and a bell loop. The lop has a zipper lo hold !he ballery in. Llmlled quanlily. Cal HC-6500 About 1/2 price Cat price $27.95 $14.95 10 wall rms in dash uni! Cal AA-2082 ONLY Jaycar price $14.95 This Is asmall lead wilh a 90 sockel on one end lo a 9 way sized 15 pin D plug (wilh only 7 pins connecled). Lenglh 10cm. Arisla price $14.95 Cal Pl-0876 Jaycar price $2.95 These are not lypical Jaycar producls, bul al lhese crazy prices we won'! have !hem for long. $8.95 30wall rms in dasn unil Cal AA-2083 Slandard vinyl case Iha! holds up lo 12 casselles in !heir cases. Arisla price $5.95 Cal AR-1480 ONLY $14.95 3Q wall rms wilh facial brackel Cal AA-2084 Jaycar price ONLY $2.50 $15.95 You don'! see Ihis very oflen. These are 8' honeycomb woofers designed for car HiFi use. They have a melal grill over lhe cone, a huge 20 oz (.57kg) magnel, loam roll surround, black frame and silver honeycomb diaphragm. Power handling 35 walls rms, sensilivily 93d8, lrequency response 60Hz lo 12kHz, impedance 4n. Now less than half price Cal CW-2117 $49.95 a pair 36 Pin cenlronics plug lo 34 pin edge conneclor. 2.4 long ribbon (flat) cable. Computer equivalenl lo Tandy 26-1401. Used wilh many prinlers. Limiled quanlily. Arisla price $25.95 Cal PL-0878 · Vinyl attache slyle case which will hold up lo 40 casselles Includes plaslic inserls for holding casselles and handle. Arisla price $24.95 Cal AR-1485 1988 Ja_ycar price Cat price $119.95 $9.95 A "RS232" 25 pin D plug lo plug, 2 ml lead wilh DIP swilches for simple wiring conliguralion changes for TXD (lransmilled dala), RXD (received data) and HS (hand shake). Supplied Wilh 1988 dala. cat PL-0877 Cat price Jaycar e_rice $41.95 :i,27.95 * Made for video. Pins are reversed. lenglh 1.5 melres. Arista price $5.95 Cal AV-6525 Jaycar price $1.50 :iili1r::i==~,B AP E I Don't miss this opportu nity to stock up with qual ity cable at crazy crazy low prices. We've bought thousands of packs of Arista cable, and you can save a fortune. There are 5 ditterent sizes and 5 colours of each-size. All the cable is packaged in bliste r packs. They are available in large packs of one roll of each colour. One large pack for each cable. size. To give you some comparison as to the thickness of the conductors you simply multiply the number of conductors by the thickness of each one. For example HUW5 is 14 x .25 = 3.5mm. Our light duly hook up wire is 10 x .12 = 1.2mm. So the HUW5 is almost 3 limes the thickness of wire. Th is product consists of an AM/FM radio and a pair of stereo wal kman style headphones. The catch is that the radio doesn't wQrk very well, the reception range is not very tar. The headphones are line, they have a 3.5mm stereo plug lilted. We sell headphones like this for $8.95. The radio may work better if ii has a better ae rial or ii is ideal for hobbyists lo experiment with. The normal price for these Is $19.95 Hook up 1410.25mm, 18 gauge OD 2.4mm. 5 colours - black, green, red, while, yellow. 12mls per colour. Total length 60 metres. Arista catalogue price $5.95 per colour. Total $29. 75. Cal WH-3019 Jaycar's price 10 amp hook up wire. Size 16 x .3 = 4.8mm, OD 2.6mm, 16 gauge. This is eq uivalent lo our WH-3040 heavy duly hook up. 8.6 metres of each colour. Total length 43 metres, 5 colours. Arista price $29.75. Cal WH-3020 $10.95 12 amp hook up wire. Size 19 x .36 = 6.8mm, OD 2.9mm, 14 gauge. Equivalent lo our WH-3050 extra heavy duly hook up wire. Cal WH- 3050, 6melres of each colour. Total length 30 metres, 5 colours. Arista price $29.75 Cal WH-3021 Jaycar's price $9.95 25 amp auto cable. 11.21mmOD 4.4mm, 10 gauge. Suitable tor the heaviest jobs. 2.4melres each colour, 5 colours. Total length 12 metres. Arista price $29.75 Cal WH-3023 Jaycar's price $7.95 Shotgun microphone with built in amplifier. Recording and headphone output sockets use as a hearing aid. Supplied with micro ear headphones for direct monitoring microphone. Inbuil t amplifier allows output and headphones connection direclly lo the microphone '" '· without an external amplifier. Complete with detachable sound colleclng tube. Max power gain 49dB, freq resp 200Hz-8kHz, power source AAA x 1. Arisla price $79.95 Cal AM-4040 Jaycar price $34.95 Was $89.50 NOW ONLY $ 49 ■ 50 $5 Designed for Walkmans. Has an inline volume control for each channel and a right angle 3.5mm stereo plug. Supplied with 3.5 lo 6.5mm adaptor. Freq response 20-20,000Hz, sensilivily 100dB<at> 1kHz. Cord length 1.2ml. Arista price $9.95 Cal AA-2026 Jaycar price $4.95 e Lightweight television headphor.e with 6 ml of cord and an in line volume control. Supplied with 3.5mm mono plug. Frequency respcnse 20' 20kHz, sensitivity 100dB , <at>1kHz. Arista price$14.95 CalAA-2027 nt Spees - Gain: 15-19dB, Channels: 21-69, Frequency: 470862mHz, Boom: 20mm square, Overal length 2214mm, Finish: elements and boom anodised. Cal LT-3182 Was $139 NOW ONLY $79.50 Z'.} ::,~}-)\~\~ $9.95 15 amp auto cable. Size 19 x .45 = 8.55 OD 3.5mm, 12 gauge. this is equivalent lo about 4mm auto cable. 3.6melres of each colour. Total length 18 metres, 5 colours. Arista price $29.75 Cal WH-3022 Jaycar's price ent Spees· Gain: 13dB, Channels: 21-69, Frequ: 470-862mHz, Boom: 20mm square, Overall length: 1234mm, ~ Finish: elements and boom anod ised. ~ Cal LT-3181 $12.95 Save well over 50% , Jaycar's price Cal AA-2025 A bargain at We were sick and tired of paying loo much for antennas. We have found our own supplier and can now reduce the prices by up lo 45%. Bui don't worry, the new ones are imported but so were !he ones they replaced. New everyday low prices. Wholesale enquiries: phone (02) 747-2022. ~)~~J\\\ ~ ,-.::~~ , ,>· - • ' I MOS Dynamic Jaycar price $6.95 256kx4bil80nS ~ --. Cal. ZZ-8436 $15.95 Ullra lighlweight mini phones with accurate wide frequency range. Supplied with lwo spare soil loam earpads and gold plated stereo right angle plug and a storage case. Freq response 20-20kHz, sensitivity 1OOdB <at>1kHz. Arista price $16.95 Cat AA-2015 Jaycar price $7.95 1 211 h Jaycar price $18.95 , , rr· - AUDIOLINE TELEPHONE S EM We worked hard lo gel Ihi s great answe ring machine in our stores for under $100. II is simple lo use and Auslel permilled. Features include: • Electrodynamic microphone for high quality reading • Volume control for incoming messages • Playback call screen ing • Micro-processor controlled • Message received indicator/counter • Variable lenglh outgoing message • Remote !urn on, rewind, playback and fas! forwa rd • Twelve months exchange guarantee. * CalYT-7020 HiFi honeycomb woofer incorpcrates loam edge, silver cone, black frame and blue · dress ring. Specilicalions, freq resp 48Hz-12.7kHz, sensitivity 88dB, im pedance 8 oh ms. Power handling 30W RMS, magnet weight 10oz. Arista price $34.95 Cal CW-2107 _ .• $99.95 .,.... .,..,.,,.., ... \.,: , . , . .•.•,,, u .,, ••., ,,,:+. ► ,nb'-: • . • n,n ,· •..... •,-,. , .. •,•,n.•,., ... ,r,,y ,_,n_,N · ,•,•u,;,. -,•. ,un , , _.,,,, · u u,-,·• · . ,u · r ,·.·u, · " . un, ,. .. v,u.•,•n n u · ,,,,,-.• :: . nN~ . . ~uu· · . n A --- - ·- • .,._ .... • • - · ., ._ . . ._,J •I ....... .. .......... .,,• ..., " • ....... 'U, 1 ,...,... ,...,.., un t VMII r..LL-V I nu1,,v.., Jf'\ I '-'Mj'I C:LC.\,.,I nU1'41\., 1 ELECTRONICS JAYCAR ELECTRONIC, JAYCAR ELECTRONICS JAYCAR ELE 1 ELECTRONICS JAY CAR ELECTRONIC JAYCAR EL CH ONK JAY AR 1 ELFCTRQNI( c, JAYCAR ELECTRONIC A AR EL C FONII " A 1 EL! rn, •"I( . ·, ,1 .1.C'TRONIC JA C' 1 El l - . I EL IE TP: I I EL It I -F : F\ \ F: I I T If- - '\ Professional cable cutter I :rr 1 : ELET', 1 · Elf T~ \ EL r •{t E'l CT I EL CT,11 EL TP \ EL m1 EL r 1 EL H oc 32 way. Normally $6.95 Cal DC-4000 September special Anolher surplus slock buy which will save you heaps. This lime it's a cable culler. They are designed lo cul copper and aluminium cable up to 38 sq mm. They will slice lhrough cable wilh lhe grealesl of ease and slrip as well. Lenglh 215mm (81• ' ). Every loolbox needs one. Trade price $21.89 plus tax. Cal TH-1823 Jaycar price $9.95 I I $2- •, 30 mt rolls of cable. Super convenient! L GH I I - L E ' 1 I L I "I E L I tLF r F- : TF: Pkl200 T l I EL C a l H P - 0 6 ~ ~ ~~ I . 1-'l~ffl . u::1"1~Hi IJC..:JCLJ ,•· ~ , - ~ It ~ 1 ti ~~ ~~l~i~/~ 1~hl l•,---~-m_lA_t:m_r_i_~_~_~_w:r_ ,Z',.:_m_,_•~-~ _-.._.~ ::::_ : ·:::_ -:_(Sfl.:_~: - _""../ lI ( ~ ' I GT I LI 1 Cellular phone antenna ~, replacement I l. F- : L"rff- Mounls inside lhe car! ll's exlremely small, measuring only 63(W) x 114(L) x1.6(D)mm designed lo suil most cellular phones • inlerior mounled lo slop lhefl and breakage • high performance omni-direclional • high performance omnldireclional • bandwldlh 800MHz · 1000MHz • 12 monlh warranly • used by Brilish Telecom. Supplied wilh 3.8 melres of cable, filled wilh plug and lnslallallon inslruclions. Normally $69.95 Cal DC-4000 TYCO cat. WB-199930 metre roll NORMAL PRICE 00~ metre $17.95 SAVE $6.05 0 25D male lo 25D male. ~ Normally $19.95. Cal PL-0856 · / tXED C I A And it's bigger lhan lasl time. Over 200 capacilors supplied (lhe lasl run of lhis pack had only 150). The pack includes: Tanlalums · 2.2µF 16 and 25V. Polyesler 0.82µF, 1µF, 0.47µF, 0.56µF, 0.68µF, o047ff voltages from 100 lo 400V. 630V Polyester in 0.022µF, 0.047µF and 0.22µF Ceramics 2.2pF, 5.6pF, 12pF, 15pF, 82pF, 680pF, 2200pF, 4700pF, 0.022µF, plus some high voltage ceramics Eleclrolytics 1000µF, 220µF, 100µF, 47µF, 470µF PLUS MORE Cat. RE-6260 0 RIME SPEC APACIT CIGARETTE L Ideal for running a12 voll appliance from your cigarelle lighler. Consisls of afused · cigarelle lighler plug wilh 1.4ml of cable lerminated lo a2.5mm DC plug. Includes 2A fuse. Cal PP-2008 ONLY $2 LE~ T EC' ECTfi ECTR ECTHO ECTRONIC ECTRONICS R ELECTRONICS JAY • • 5 1/4" KIT Cat. XC-4792 $6.95 ea Every year many people die from smcke lnhalalion caused during minor home tires. Mosl of ~ lhese dealhs could have been "- / / prevenled if asmoke _ .t. deleclor had been _ inslalled. This unil is aself contained delector and operates from a9V ballery. Simply Install !he ballery. allach II to lhe celling and forget about II. II will start beeping when lhe ballery requires replacing (ballery life approx 1 year wilh alkalineballery) Fealures: • lonlsallon sensor lo warn of smoke and fire even before flames are visible • Extra loud warning horn penetrates closed doors • fnslalls In mlnules • Self contained • Bulll-ln test bullon • Audible beep lo indicate low ballery Size 125mm diameter x 45mm deep Cat. LA-5090 $19.95 F - ·. / ~ ll's a1.4ml length of lwln fig 8 polarised cable wllh a line fuse holder and a2A 3AG fuse, Ideal for running a 1'N piece of equipment from the car, wilh the added bonus of being fused. A fuseholder on a300mm single wire wllhoul a fuse sells for $1.10. So slack up now! Cat SZ-2014 ONLY $1 each Tf; Ltr , ' \ i;s~j.~ EL L L With these cleaners you can keep your drives In top shape and save your dlskelles from damage. ■ x · ,. 3 1/2" KIT Cal. XC-4790 $13.50 SAVE $3.00 7 < 3 2 Refer SIiicon Chip Nov/Dec 1987. See cal for full delails. Normally $299 September special Cal KC-5013 $249 Save $50 T ~ ERC 8 1 GHZ digital frequenc meter kit fl CT EL EL ii ONLY$9.95 CA 24/0.20mm Cat. WB-1709 30 metre re II NORMAL PRICE 55t metre 4~~~"~~ f EL ~r E $7.50 SAVE $1.50 I? ,ii I ,.. T E P NORMAL PRICE 30~ metre Al last you can now buy black phi lips head chipboard screws lo mounl your speakers from Jaycar. These are very dlfflcull lo obtain. Two sizes available. L•ge No. 1Dx 30mm Ideal for woofers • ~ j ,. Pkt 20 Cal HP-0624 ,, ' $3. 50 .... ~ Pkl 200 Cal HP-0626 $27 ■ 50 L•ge No. 6 x 15mm Ideal for lweelers, mldranges, crossovers Pkl 20 Cal HP-0620 $2.95 , fl F i EL "' L <LE( f· ur TF hE F DUTY 14/0.14mm Cal. WB-1703 30 metre roll Speaker mountin screws "\ SAVE OVER 50% ON NORMAL PRICE The Elesen vibrallon sensor ii top quality and Is made in Europe. ft features aLED which Illuminates when lhe sensor detects vibrallon, which makes ii exlremely easy to set lhe sensilivity. Supplied with Instructions. CaL LA-5063 Sub C NiCads are commonly used in battery packs to power RC racing cars and cordless power tools. Up til now, if a battery pack failed you would need to purchase a new pack from the manufacturer of the product. These battery packs are very expensive. The most common voltage used is 7.2 volts which is made up with 6 x Sub C NiCads. So, instead of being forced to pay $70. $100 for a replacement battery pack, you can now fix it yt>urselt.and save a fortune . The Sub C's are supplied with solder tab and are rated at 1.2Ah. Cat. SB-2456 $6.95 ea We will not be undersold on goods of the same quality . ·• , .... '· A A '· Home sentry provides the same level of protection as many other expensive systems, but with on fraction of the cost system is wireless and can be set up within few minutes. When you move, take ii with you. The system consists of: 1) The Control Alarm Unit. II incorporates 4 sectors and includes the inbuill 110dB siren, mains plua pack, alarm period switch, backup ballery and siren Lo/HI switch. 2) The Door Protector. This unit mounts just inside the front or back door and incorporates a keypad for turning the alarm on and off and a reed and magnet which guard the door. 3) Passive lnfrared detector. One supplied with the kit and more can be purchased separately if necessary. Range is 1Ometres. 4i Remote Controls. Two key fob remote controls are supplied in the kit for easy arming and disarming before entering the protected area. HOME SENTRY MUST BE THE LOWEST PRICED, QUALITY WIRELESS ALARM SYSTEM ON THE MARKET. The system 1 x Control alarm unit with 240V adaptor 1 x Door protector with Reed and Magnet Cal LA-5230 1 xPassive lnfrared detector 2 xRemote controls ONLY $259.00 Aller purchasing the kit you mind you need more components lo fully cover your house/unit etc. _ o e This unit is NOT included in the full kit. II ls wireless and incorporates areed/magnel and glass break detector. Cat. LA-5234 $49.50 As supplied In the kit, available separately for large homes where more than one is needed. Great price! Cal l.A-5232 $49.50 t Includes keypad and reed/magnet. You will require a second one of these if you enter/exit from the back door, as well as the front. Cal l.A-5236 $79.50 l:J. 1:)- Thal's exaclly what this pack is - The Ullimale This pack gives you every resistor in the E48 range from 0.5 ohm lo 9.1 Meg. The E48 range goes like this: 10, 11,12, 13, 15, 16, 18, 20, 22, 24, 27, 20, 33, 36, 39, 43, 47, 51, elc So, you get 1Oof every value, a total of 170 values, 1700 resistors in all and they are bandoleered for easy sorting. The resistors! They are top quality, guaranteed 1/4 wall 5% miniature sized. In fact they look like 1/SW they are so small. Buy this pack and you will NEVER be short of any resistor again. To buy all these resistors on an Individual basis (i.e. St ea) ii would cost you $85. This pack costs well under 1(2. that price and there is alimited quantity. Cat. RR-2000 ONLY $29.95 Less than 2~ ea CJD CO BARGAI ERTER Another surplus stock bargain. This lime a high quality ASTEC brand fully buill DC/DC converter wilh specifications. Input +36V DC nominal, 31 to 40V RMS range Output +12\/ DC or +SV DC, nominal ±1 % Vollage limil at 13.0 to 15.0VDC or 6.010 7.0V DC res peclivel y. Current +12\/ DC, 3.0 amp DC max +SV DC, 5.3 amp DC max Efficiency +12\/ DC 75% minimum +SV DC 70% minimum Size 160(L) x 53(W) x 39(H mm supplied on melal plate Cal. MP-3040 STRICRY LIMITED QUANTITY ONLY $14.95 ea Refer Silicon Chip Aug 91. This masthead amplifier kit is easy lo build install. II will give around 1BdB of gain from 40MHz lo 1GHz which is right across the UHF and VHF bands plus FM bank (8S-108MHz) as well. The Jaycar kit includes the special 24V AC power supply. Beware ol other kits which don't supply this. Also includes PCB, jiffy box, .!l!a§.1 clarl_lll, OM 350 and all specified componenls. Cal KC-5097 :i;44.85 Reier Silicon Chip Aug 91. This LED digital tachometer features a 4 dig ii readout lhal indicates from O9900 RMP. II works from Kettering to Hall Effect systems and with 4, 6 and 8 cylinder cars. The Jaycar kit is a short form version, everything is supplied except lhe box and front panel - as we feel many constructors will want lo mount ii in the dash. CatKC-5098 $34.95 A Refer Silicon Chip Aug 91. Can record messages up to 20 seconds long. Store themon hard or floppy disc and then replay them when you wish. The Jaycar kit includes all specified components except lhe, plug pack and zippy box. The software is available from Silicon Chip. CalKC-5099 $32.95 TE DIGI AL ULTI METER HCOMP ER T RFA Yes , the Metex M3650CR will interface with your computer via RS-232. Connecting lead and software disk supplied. Monitor store and print out the output of the DMM on computer. It will take readings over time and find and hold mimimum and maximum readings. PLUS: • Bargraph • Frequency • Transistor • Logic • Relative offset • 3.5 digit • 20 Amp current ••Carry case • Overload Indicator • Data hold • Mimimum/maximum hold • Diode and continuity • Range selector beeper Cal. QM-1450 $199.50 Refer EA Sept 91. Increase your talk pONer. Connects in linewith existing mic, and acts as a preamp, compressor and speech filter. II also automatically generates a 'beep' each lime the press lo talk button is released; lo signal the end of your "over"! Short form kit. Includes PCB, mic socket, relay and all specified components. No box supplied. Cal KA-1737 ~ Refer SIiicon Chip Sept 1991. At last, a high quality ( . speaker kit at avery reasonable price using quality components. Jaycar and Silicon Chip proudly announce the Studio 3-55L 3 way speaker kit. The kit incorporates the Magnavox 12W, 12' woofer, sealed 5' midrange driver and the fabulous Philips AD11610/TS dome tweeter. Power handli~g is 80 watts programme. Drop into any Jaycar store for a demonstration (not Concord) The kit is available in two parts. Part one includes the drivers, crossovers, terminals, faders, innerbond, screws, cable etc. Part two includes the two fully build black cabinets with all holes cut and speaker grill fitted. ST 18V 1A BENCHTOP Ref: EA August 1991 This economy priced power supply features: • variable output vollage from 2.5 to 18V • swilchable current limiting• both vollage and current metering. The Jaycar kit includes PCB, all specified components, Scotchcal panel and meter scale. This 12 volt motor driven siren really let out a blast! In fact, it's almost deafening. It's very small compared to most si rens measuring only 82(H) xSO(L) x74(D)mm. Limited QUanlily, Cat LA-5252 Part 2: Cabinets Cat CS-2480 Cat CS-2482 $279 $250 TOTAL $529 B H TOGETHER FOR ONLY$499 4-CHANNEL C' C' $79.95 Cat. KA-1736 Part 1: Speakers etc BU IG T $24.95 PRO GRADE 19" RACK 1 unit enclosure Cat HB-5120 2 unit enclosure Cat. HB-5125 3 unit enclosure Cat. HB-5130 4 unit enclosure Cat. HB-5135 5 unit enclosure Cat. HB-5140 G Refer Silicon Chip June 1991 This 4-channel lighting desk is intended for theatre, disco and music group applications. II has heavy duly circuitry and is able to cope with spotlights rated up to 1000 watts or more. Operating features • Four channels• 60mm slider pots • Click action flash switches with integral LEDs • Separate dimming for each channel• Master dimmer control • Flash on each channel • Master dimmer for flash • 4-channel chaser• Adjustable chaser rate • Single slep for chaser• Chaser on and off• Flash switch LEDs mimic lamp display The Jaycar kit includes pre punched and silk screen case, original Cand Kswitches, original slider pals (Jaycar supplied the samples lo Silicon Chip) and all specilied components. Beware of kits with non original parts. Cat. KC-5096 TUR Jaycar wi ll purchase your surplus stocks or components and equipment. We are continually on the lookout for sources of prime quality merchandise. CALL MARK HARRIS OR BRUCE ROUTLEY NOW ON (02) 747 2022 $329 • i • ~' ~ $29.95 ~I[ I POST & PACKING ff $10-$24.99 $ 3.75 P.O.Box185 Concord2137 FREE CALL-FOR ORDERS • Telephone (02) 747 2022 $25-$49.99 S 4.50 ROADFREIGKT $50 $99 99 $ 6 50 ANYWHERE IN AUSTRALIA ONLY (008) 022 888 7 44 0 7 6 7 ~ , _FA_x_1°_2 _,__ _ _ _ _ _ _-=o=vE=R=s1=00==$8=00==~1•.:...P,_02011_a1_s,_3_so _____ Ho_ru_N_E_(o_2_ 17_47_1_s0_0_ YONEY- CIT" RRAMATT CONCORD ANKSTOW GORE HIU 115ParramattaRoadConcord2137 117YorkSt.(02)2671614ND Mon-Fri 8.30 - 5.30 Thurs 8.30 pm - Sat 9 - 1 355 Church St (Cnr Victoria Rd) 102) 683 3377 COBURG VIC Mon-Fri 9 - 5.30 Thurs 8.30 pm - Sat 9 - 4pm Sunday 10am - 4pm LB OUR NE CIT 115 Parramatta Rd Cnr Lloyd George Av 102) 745 3077 Mon-Fri 8.30 -5.30 · Sat 900-12 INGVALE VIC 363 Hume Highway Cnr Meredith St (02) 709 2822 Mon-Fri 9 - 5.30 Thurs 8.30 pm- Sat 9- 4 DHAIDE SA 188 Pacific Hwy (Cnr Bellevue Ave) 102) 439 4799Mon-Fri 9 - 5.30 Thurs 8.30 - Sat 9 - 4pm 144 Logan Rd (07) 393 0777 Mon-Fri 9 - 5.30 Thurs 8.30 - Sat 9 - 4 266 Sydney Read (03) 384 1811 Mon-Fri 9 - 5.30 Fri 8.30- Sat 9 - 4 Shop 2. 45 A'Beckett St City (03) 663 2030 Mon-Fri 9 - 5.30 Fri 8.30- Sat 9 - 2 887-889 Springvale Road Mulgrave (03) 5471022 Nr Cnr. Dandenong Road Mon-Fri 9 - 5.30 Fri 8.30 - Sat 9 - 2 190 Wright Street (Cnr Selby Street) (08) 231 7355 Mon-Fri 9 - 5.30 Fri 8.30- Sat 9-12 ~ ='II/JIJl!J-- The electronics magazine for the enthusiast Four good reasons why you should subscribe to SILICON CHIP 1. You get a 12.5% discount on the newsstand cover price. Recently, we had to increase the cover price of the magazine because of rising costs but we have held the subscription to the old price so you get the benefit. 2• You'll never miss an issue. Sometimes it can be very hard to find SILICON CHIP in the. newsagents because it sells out early or gets buried under other magazines. By taking out a subscription you don't have to search for it - it arrives in your letter box in mint condition. We wrap it in tough plastic to make sure of that. JUNK MAIL 3 • Get a discount on the binder too.soYou'll want to store and protect your issues of SILICON when you take out CHIP a subscription you get a further discount on the binder. By taking out a 2-year subscription and buying two binders at the same time, you get even bigger savings. And we despatch the binder(s) with your first issue so you have it right from the start. 4• From time to time, we will have special promotions and offers in the magazine, like the Bose Lifestyle competition featured in the September to December 1990 issues. When you are a subscriber you are automatically eligible for these and you get the chance to benefit. Interested in these savings and benefits? Just fill in the coupon on the following page and send it with your remittance. You'll be glad you did. Why not do it today? I hope to see you as a supporter soon. Leo Simpson, Publisher Just fill in the coupon on the following page ~ Most magazines sell their subscriber lists to mail order companies, to earn extra income. Be assured that we will not do this. Your privacy will be respected and you will not be deluged with unwanted mail. SPECIAL NEWSLETTER Subscribers will receive a special newsletter at least twice yearly which will contain information on Upcoming S1ucoN CHIP projects and special offers, available only to subscribers. MAGAZINE BINDERS Spedally designed binders for SILICON CHIP are always available. Made with a distinctive high quality 2-tone vinyl, you can obtain them at a discount when you take out or renew your subscription. The price details are on the coupon overleaf. SEPTEMBER1991 53 ~~~ORDER FORM / USE THIS FORM FOR ALL YOUR SILICON CHIP PURCHASES SILICON CHIP BINDERS: Yes! Please rush me _ _ _ SILICON CHIP binder(s)<at> $A14.95 each including postage. (Overseas orders please add A$3.00 each for postage). Total $A_ _ _ __ SPORTS SHIRT: Please send me _ __ Sport Shirt(s)<at> $A24.95 including postage. (Overseas orders please add $A3.00 for the additional postage). Size(s): S(Qty)__ M(Qty)_ L(Qty)_ XL(Qty)__ XXL(Qty)_. Total $A._ __ SLOPPY JOE: Please send me _ _ Sloppy Joe(s) <at> $A27.95 including postage. (Overseas orders please add A$3.00 for the additional postage). Size(s): S(Qty)_M(Qty)_L(Qty)_XL(Qty)_XXL(Qty)_. Total A$ _ _ _ BACK ISSUES: $A5 .00 each (including postage). Overseas orders add $Al.GO per issue for postage. ISSUE YEAR ISSUE YEAR ISSUE YEAR ISSUE YEAR TOTAL $A SUBSCRIPTIONS .. RATES: □ NEW SUBSCRIPTION: Month to Start □ RENE WAL: Sub No. (PLEASE TICK ONE) Start In Australia □ GIFT SUBSCRIPTION: Month To Start Your Details Mr/Mrs/M s: Address: Postcode 2 years (24 issues) 1 year (12 issues) O$A84 O$A42 Australia with Binder(s) O$A105 O$A53 NZ & PNG (Airmail) O$A130 O$A65 Overseas Surface Mail O$A130 O$A62 Overseas Airmail O$A240 O$A120 Daytime telephone number: _ _ __ _ _ _ _ Enclosed is my cheque/money order for $_ __ or debit myDIEBI DIE JIJDi v1sA I 1 1111 11 1 11 1 1 1 11~11~~ Card expiry date Signature _ __ _ _ __ _ __ _ _!_ _ -'='a Fax the coupon with your Credit Card details 24 Hours, 7 Days a Week Gift Subscription Details Message: _ __ __ _ _ _ _ _ _ _ _ __ Mr/Mrs/Ms: _ _ _ _ _ _ _ _ _ _ _ _ __ Address: _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ __ _ __ _ __ Postcode_ _ __ (02) 979 5644 9am - 5pm Mon-Fri. Please have your Credit Card details ready. Mail coupon to: FREEPOST 25 Silicon Chip Publications PO Box 139 Collaroy Beach NSW 2097 No stamp required in Australia I PRODUCT SHOWCASE I Handy timer doubles as a clock Screwdriver set has 36 hits This screwdriver set is one of the handiest we have seen and is ideal for the car or home toolkit. The T-handle has a magnetic hex drive holder and one side of the handle could be used as a soft-face hammer. There are four straight screwdriver bits, three Philips heads, four Allen screw and six Torx bits. In addition, there are straight and rightangle 1/4inch adaptors to drive the socket spanners in the kit. Metric and Imperial sizes are covered, from 5 to 13mm and from 3/16-inch to 1/2-inch. It all comes together in a grey plastic case which slips easily in the glove compartment or toolbox. Priced at $19.95, the screwdriver/ socket set is available from David Reid Electronics, 127 York Street, Sydney, NSW 2000. Phone (02) 267 1385. Aviation headset has noise cancelling mic. This aviation headset from Altronics has a number of worthwhile improvements over the previous model. It is more comfortable, with a better handband and foam-filled ear seals for better attenuation of cockpit noises. Figures for sound attenuation range from-14.3dB at 125Hz up to -37dB at 8kHz - it is very good in this respect. The universal boom assembly is easily adjustable and is fitted with a noise cancelling electret microphone fitted with a windshield. It is compatible with microphone preamplifiers with nominal impedances ranging from 150Q to 10kil The headphones are very rug- This handy timer is ideal for cooking, as a reminder to take medicine, for timing sports events or meetings and as a 12 or 24-hour clock. It has a 6-digit liquid crystal display and operates from a single dry cell which is included in the purchase price. In effect, the unit incorporates three timers as well as the clock function and all functions can run in parallel. There are two individual timers which can be set to go off any time in a 24hour period while the third timer is a stopwatch, counting in seconds up to 24 hours. The unit is easy to set and the instructions are on a label on the back of the unit so you'll never lose them. It's priced at $19.95 from David Reid Electronics, 127 York Street, Sydney, NSW 2000. Phone (02) 267 1385. Crimp connectors for semi-rigid RF cable gedly made and well finished and should last a long time in everyday use. They are priced well below competitive brands at just $189. They are available from Altronic Distributors Pty Ltd, 174 Roe Street, Perth, WA 6000. Phone (09) 328 2199. RF semi-rigid cables have presented problems in the past because there has been no suitable connector which can be installed in the field without complex soldering equipment. SEPTEMBER 1991 55 Protel for Windows now available Prnld f" m Vlh,ilowi, ·Od ;;~;u;~- -6[,tiou; The Australian-designed Protel software for circuit design and PC board layout is very successful both here and overseas. In the USA, it is widely sold under a different brand name. Now Protel for Windows is available as a PCB layout module in two versions: Professional PCB and Advanced PCB with auto placement and auto routing. Some of features of Protel for Windows include: 16 routing layers, four power plane layers, four mechanical drawing layers, and four editable solder and paste masks. Items can be selected by layer, connectivity and area. Selected items can be cut, copied, pasted, moved , deleted, rotated in one degree increments and read or written from and to a file. Undo and redo commands are available, as are multiple libraries. IEEE library symbols are supported. The program runs under Microsoft Windows version 3 or later. It takes advantage of the 386 enhanced mode in Windows and thus uses the virtual memory capability provided. This means that the user can load boards of any size, with no restrictions on the number of components, tracks and nets. It also supports the hdn multiple document interface (MDI) standard. This allows the user to load different boards simultaneously and to move tracks , pads and components between designs. For further information, contact Protel Technology Pty Ltd, GPO Box 204, Hobart, Tasmania 7010. Phone (002) 73 0100. To solve this problem, Huber & Suhner has recently released a new crimp connector designed for operation up to 18GHz. Termination is by means of a crimp connection between the outer cable conductor and the connector body. The inner conductor of the cable acts as the centre mating pin. For further information, contact David Pilley at Huber & Suhner (Australia) Pty Ltd, PO Box 3 72, Narrabeen, NSW 2101. Phone (02) 913 1544. IEEE-488.2 controller board for PCs This new GD-GPIB can be used to monitor, control and interface with over 4000 engineering, scientifi~ or medical instruments and represents a cost-effective way of crossing over to the IEEE-488.2 standard. Most of the tasks are performed by the new NAT4882 chip, including both IEEE-488 and IEEE-488.2 standards. Data transfer rates for the board are 400Kb/second in both read and write modes. It has an RF-shielding receptacle, six interrupt lines with enabling and disabling, and three DMA channels. The board can be programmed using either National Instruments' NI56 SILICO N CHIP 488.2 Windows 3.0 or MS-DOS software, as well as LabWindows. For more information, contact Paul Twigg at Elmeasco Instruments Pty Ltd, PO Box 30, Concord 2137. Phone (02) 736 2888. Differential microphone from Crown Crown's new close-talking microphone overcomes the problem of feed- back in large and loud concert venues by isolating the vocalist from other on-stage sounds. The Crown CM-310 model has a differential noise-cancelling electret module which allows higher-thannormal sound levels before feedback occurs. It has a smooth frequency response from 60Hz to 17kHz and a sound pressure level of 151dB for 3% total harmonic distortion with 48V DC phantom power. The signal to noise ratio is quoted at 72.5dB at 94dB SPL. Phantom power requirements are from 12-48V DC at 1.5mA. The Crown CM-310 retails for $403 .00. For further information, contact David Adams at Bose Australia Inc, 11 Muriel Avenue, Rydalmere 2116. Phone (02) 684 1022. Battery packs for 2-way radios Premier Batteries has introduced a range of high performance battery packs to suit most current 2-way radios. The batteries are direct replace·ments for packs used in Motorola, GE, Maxon and Philips equipment. They have high-impact plastic cases and nickel cadmium cells which are suitable for rapid charge and discharge. Premier also provide a comprehensive testing service to check and analyse ,b atteries of doubtful serviceability and can recondition packs suffering from memory effect. For further information, contact Malcolm Wilson at Premier Batteries Pty Ltd, 7/27 Childs Road , Chipping Norton, NSW 2170. Phone (02) 727 0565 . Automotive amplifier from Analog Devices The AD22050 difference amplifier is designed to extract, amplify and low-pass filter small differential signals from large common mode voltages, replacing previously complex circuitry. Operating from a single supply of between 2.5V and 36V, it has a common mode range from ground to 6x (Vs - 1) volts and a low-frequency common mode rejection of 97dB. The gain is normally to x20 but this can be varied from x1 to x160 with the addition of an external resistor. The output stage will drive a 1kQ load to 4V with a 5V supply. Applications for the AD22050 include load and current sensing, motor control, and interfacing with pressure, strain and low-level output transducers. For further details, contact Leo Nyhoff at NSD Australia, Locked Bag 9, Box Hill, Vic 3128. Phone toll free on (008) 335 623. SC Satellite TV Demonstration A full demonstration of the $995 PAL satellite TV system will take place at Altronics Pty Ltd, 17 4 Roe St, Perth, on Saturday, 21 st September, 1991; time 9am-2pm. Garry Cratt from Av-Comm Pty Ltd will be present to answer any questions on the system. ANTRIM TOROIDAL TRANSFORMERS j ib&&L&ti!L EE&Etu -~ 2kW power supplies from HP Hewlett-Packard has released two 2kW power supplies using compact switc'h ing technology. The HP 6671A has an output peak-to-peak noise of less than 7m V under all operating conditions and it can deliver up to 220 amps at DC voltages from 0-8V. The HP 6674A has a noise rating of 15mV with a maximum output of 60V and 35 amps. Both models are only 13.3mm high in rackwidth housing and are designed for ATE applications. They also include built-in IEEE-488 voltage and current programmers and a multimeter capable of sending readings to a controller. The IEEErecommended standard commands for programmable instruments (SCPI) are also used. For further information, contact Hewlett-Packard Australia Ltd, 31-41 Joseph St, Blackburn, Vic 3130. Phone (03) 895 2869. • • • • Now made in Australia Standard range 15VA to 2kVA Large ex-stock quantities available Competitive pricing available for OEMs & resellers • Simply the best transformers all round HARBUCH ELECTRONICS PTY LTD 90 George St, Hornsby, NSW 2077. Phone (02) 476 5864 Fax (02) 476 3231 SEPTEMBER1991 57 Build this fax/modem for your computer Have you been holding off on buying or building a modem for your computer? You have? It's just as well because you can now build this combination fax and modem for less than the cost of a modem alone. It's a freestanding unit that's fully software driven. By LEO SIMPSON Th ese days , everyone who has a computer probably has a yen for a modem - so that yo u can access bulletin boards and exchange programs and correspondence with fri ends, and so on. In parallel with this , more and more people are getting their own fax machin e - they're so convenient for leaving messages at any time, ordering goods from suppliers , etc. Some time ago, people recogn ised that there was a problem with fax machin es and that was junk faxes . Thermal fax pap er is not cheap to buy and if yo ur fax machine automat58 SIUCCJ .'c C II II' ically prints out every silly message that comes through, including those wasteful cover sheets that tell you that you are getting a fax message , you quickly go through a lot of paper. To get around this problem, faxcards were developed. We reviewed one of these units in the June 1990 issue of SILICON CHIP. With a faxcard installed in your computer, you can receive all the faxes and then review them on screen before deciding to print them out on your printer, which can be just about any old dot matrix machine printing on ordinary paper. So potentially, faxcards can give big savings on fax paper and they have the advantage that you don't have to print out a message before you fax to someone else. But technology moves on. Since a fax is really just a glorified modem linked to a thermal printer (with a few bells and whistles thrown in), it was inevitable that there would be a melding of the two technologies hence a fax/modem. We are very pleased to present one of the first examples of this new combined technology, by courtesy of Comma Corporation and PC Marketplace. And the good news is that this technology comes to you quite cheaply by virtue of being supplied as a complete kit. What you get Alright , what do you get with this box of tricks? The Fax/Mo dem is housed in a compact extruded aluminium case measuring 150mm wide, 38mm high and 173mm deep. There are no controls on the front of the unit , just a bunch of LEDs in a row. On the back, there are US modular phone sockets, a 25-pin D socket for RS-232 connection, a miniature on/ off switch and a male socket for connection of an AC plugpack supply. The reason there are no controls on the Fax/Modem is that it is completely driven by software, which is also supplied as part of the deal. You just boot this software up on your machine (it practically does this itself - we're not kidding) and away you go, guided by menus. This Fax/Modem has been designed as a free-standing unit rather than as a card to go inside a PC. This means that it can be used with any PC or Macintosh which has a spare RS-232 port. Computer requirements If you are using a PC , you need to have at least 640Kb of RAM, a free serial RS232 port, preferably a mouse (this means you probably need two ports), and a hard disc drive (although strictly speaking you can install it on a floppy only machine). The display can be CGA, EGA or VGA. A monochrome display can be used but you won't be able to display any graphics from incoming or outgoing faxes. So let's go through what you can do with the Fax/Modem. First, it allows your PC (or Macintosh) to work as a fax machine which can receive and transmit faxes at up to 9600 baud. When receiving faxes it works in the background, without interrupting the programs you are using. Then, when The Fax/Modem is a standalone unit so that it can be easily transferred from one computer to another & doesn't tie up an expansion slot. A double-sided PC board accommodates all the components, including the RS-232 input socket. you are ready, you can have a look at any received fax on the screen and, if you want to, print .it out on any printer which can be a dot matrix, laser printer or inkjet. The quality of these fax printouts will be every bit as good if not better than that from a conventional fax machine. And you will have the advantage of a permanent record , rather than one which will fade with Specifications V.29/ V.27ter/ V.21 Ch2 fax modes; V.22bis/ V.22/ Bell 212A/ Bell 103 data modes; V.23/ V.21 optional. 9600/ 7200/ 4800/ 2400/ 300 baud half-duplex fax operation; 2400/ 1200/ 300 baud full duplex data operation. Group Ill fax compatible send & receive . TR29 class 2 fax command set compatible (EIA PN2388). "AT" series V modem command set compatible . Automatic answer; tone & decadic dialling; analog, remote & local digital test facilities; automatic adaptive equalisation ; guard tone generators; call progress monitoring . Note: please check your serial 1/0 card. It must have a 16C450 UART, not an 8250 or 82C50. If it has either of the latter, it must be replaced. If it is not socketed, you may have to replace the 1/0 card . The 16C450 is available from PC Marketplace for $14.50. time, as thermal fax printouts do. Second, the Fax/Modem will work as a conventional modern at rates up to 2400 baud. When set up by the software (it uses the Hayes command set), it does auto dialling, auto answer and disconnect. It is compatible with most communications software programs and most bulletin boards. What's in the kit Basically, you get everything bar a soldering iron and solder. The kit comes with a screen printed, solder masked, double-sided PC board; all the ICs and IC sockets ; and all the other parts. Plus, you get the software and documentation , as already men- H.g.1 (following page): the key devices in the circuit are U10 & Ull - a fax/modem chipset, made by Exar (XR2901 and XR-2902). Microcontroller U4 & its associated EPROMs provide the control signals. The line isolation circuitry is in the top lefthand corner, while the circuitry at top right provides interfacing to the RS232 socket. S1•:l'TE 1\IHE/l ·1991 59 Vo□ l R18 22k C40I.L 01 R28l:~ 01 "'1 ~ ' m E L1 INDUCT .I I R22 10k 20--- • r JM7 3PLINK Voo 0 - XR-2900 C49I,l;-· 10 - Vooo ' , I 47 RCVIN1~!.!.~f--!}' - - - - - - - - - - 7 - 3 f -;;r--7---;~rTT7-;i'7n TXOUTl!'45~~*1_ _ _ _ _ _ _---;l~l~(t---;r-,r-7-t-" 1 2 C1 TXCLK!f.--':)-➔----------r--r--,t---, 1 I R22 2.2k R23 100k 30 Voo 41 ..__] MCl*MP _ _ _ _ ___, 7 X1 Y1 20 .2752MHz --j □~_J! C14 •• 20pFI cso.i4 RXCLK iNf 35 PAO AO/PAOll-'2' - - - - - - - 9 1 A1 /PA111-' - - - - - - - " "3I ' PA1 A2/PA21"4"-0- - - - - - "37, PA2 U11 TO DO 26 25 TOO XR-2901 C13• 20pFI GNO I '----=r---------------:r-------;j--j~-+--+--;--- TX01~ I WR14 U10 XR-2902 RO 12 3--~------------------,-;r--7""T7""77-Rxo,µ21ALE 13 I HOO~ 26 TOl H01~ T2 27 T02 H02 ~ 03 23 T3 28 T03 H03 04 22 T4 29 T04 HD4~ 05 21 T5 30 T05 HOS~ 06 20 T6 31 T06 H06~ H07~ T7 32 T07 T8 33 TOB 09 12 T9 RESET I ~± ---.----...----v □ o T1 07 19 I I 01 25 08 11 I I 7 31 4 WENl-'"-- - - - - - 0 WEN 2 - - - - - - - =39t DENl-"3"'DEN 6 38 CLKIN CLKOUTl'' - - - - - - - 9 X2/CIN I lR 5 ~--------........-v,, I. ~ GF124 AGNO 6 34 T09 VssA Vss□ RESET ;-.-~r.1:c'o=1r.18__, 42 4 XR-2 1 0 0 r - i B 60 SILICON C HIP Voo ALEL ,)lM--1 RXO.!l.._ v1181--? ROl'B--~ 7 ~ WR ~ A 0 3 XRUi321 TXOll-'1.:.9_ _ _ _._. 11 5 TXC:1-' .:.-------:r---, ~ Rei cs:rg'-----:t----' 47T C46""' a 13 Rxc:F----1-----~ ..--J-!l RCO 7 .l,, 0C433.I.,. FAX/MODEM 20 JM40_ __ _ _ _1--18 FREQ 3PLINK 0 ADO XR-2321 ADl ' EL J c 02 VIEWED FROM BELOW I 1 EXTXC:l-"6'--➔'~+-----------r --r--r--- i1~~f _ _43 C2 0. 2400 I Vao ..EsPKO ~ C23.L 1 OxR- ( 5 MSCLKt-- - - - , Vss G GND µ □ 114. r J - . 1 2 ' 0.1 -I Vss ( 14 U14 J3 RS 232 ll S 12 11 C27 C48 0.1 01! C43 0.1 I 74 04 U19 14 DSR SEIZE 16 Vee ooie2- - - - -~ --'l>-4---l----'l..--+--l----..:i,-, 011-5- - - -021-6- - - -- A14 A15 2 1A 3 18 U17 74HC139 CD +----;>----+--+---;>----+--+---;>--~ +---;1----+--+---;>----+--; 9 U7 0 3l-'- - - - -+---ll---+-+---ll---+---' 74HC374 1-1~2_ _ _ _~ 04 05 15 5 1v11-- + - + - - - ~ TX CLK .,. 3 06 16 --+-+--· OA7 Q1 __J 18 07 1 EXTCLK 024 XR-1489 3~N~K u-=---+-~1-'11 CLK 1Y3...7 GNO 15 a 6 RXC LK 17 0 7 19 GNO U14c 10 OE TXO RXO RTS RI 22 f<' 7 ADDRESS BU Voo C29 01+ + '!1 9 40 Vee RESET EA/UP 31 MASK UP JM5 3PLINK 28 0 Vpp 20 :i: C12 01 1 2 R21 8.2k.,. NON-MASr UP 12 INTO 13 INT1 1 0 RXO 16 4 5 6 7 8 DA4 15 T1 3 Voo iNR 17 RO U4 P07 32 DA7 1 11 TXO XR-2903/8031 20 3t~~K 2 GNO JO ALE/P .,. U9 272 56/ 27128 9 10 A11 12 13 14 OE 22 PSEN 29 GND 14 A8 P16 P2 2 23 p ~--l>--,t----"IP14 23 24 A10 A11 A12 ----;>---+--"P1 3 XL-9~i46 0011'4'--t-----'l----"1 3 P1 2 - - - ~ 1 - - + - - 2- P11 CS•.-1-------~l---'I-P10 14 01 3 X1 19 ADDRES S BU S X2 18 A14 Y2 11 .0592MH z a~ 20pf:i: JM3 2~ 3PLINK ~ ~15 1 SEPTEM BER 1991 61 IC sockets are supplied for all the chips except for the 48-pin chip (U10) for which machine pin IC socket strips will be supplied. Note how the miniature loudspeaker is mounted above the PC board on plastic pillars. tioned, and a plugpack power supply. Most important, there is a repair service available. If you do assemble the kit and, horror of horrors, it doesn't work, you can get it fixed for a very reasonable fee. More about that later. Before going any further though, let's make a number of important points. First, this is no project for a beginner. If you have not already built a number of reasonably complex projects in the past, don't decide to have your initiation on this one. Second, it uses an expensive double sided board with tracks and pads that are very close together. Even though the PC board does have a green solder mask, you can still short out tracks and do other damage if you are not proficient with a soldering iron. Third, and this is most important, you will need a temperature controlled soldering iron with a small tip. It should be cleaned regularly - keep 62 SILICON CHIP that foam pad clean and moist, and use if often! Finally, if you buy the kit and then decide that it really is too complex for you to attempt, then you can return it for a refund (less shipping charges), provided certain conditions are met. These are spelt out in instructions which come with the kit. OK, happy with all that? Let's proceed to describe the circuit. It really consists of just three main chips which are the fax/modem chipset (two) and the microcontroller. All the rest is the interfacing, RAM, ROM and other incidentals to make it all operate. Circuit diagram The whole circuit, minus the power supply section, is spread out over two pages (Fig.1) and looks pretty daunting but really, most of it just shows all the connections to and from the big black chips. At the top lefthand cor- ner is all the circuit to do with the interface to the phone lines - the LIU or line isolation unit. Below that is an amplifier and speaker which enables you to hear dial tone and all the other beeps and cheeps that faxes and modems make when they are operating. In the bottom lefthand corner are the key devices, U10 and Ul 1. These are the fax/modem chipset, made by Exar (XR2901 and XR-2902). Ul 1 is the DSP or digital signal processor while U10 is the analog processor. To the right of these is U3, another Exar chip which is presently the only option with this kit. U3 provides V21 and V23 modem standards which are 300 and 1200/75 baud rates. In the bottom righthand corner of the circuit is U4 (the microcontroller) and its associated RAM and EPROM chips, U2 and U9, respectively. U8, to the left of U4, is a nonvolatile RAM chip, a so-called NOVRAM. This chip has all the information the processor needs at power up. At the top righthand corner is all the circuitry to do with the RS232 port and the front panel LEDs. It consists of address decoding chips U17 and U7, together with U5 (to the right ofU9), plus U6 (an octal buffer/driver for the LEDs) and U14, U15 and U16 which are two 1488s and a 1489 to provide the RS232 port. Well, to be candid, we can't say a lot about how most of this circuitry works since it is all locked up inside the three key chips already mentioned. In fact, when you come right down to it, we can't say anything except that all the signal levels will be 5V logic signals. The exception is the LIU which we'll now proceed to describe. Line isolation unit At the top left of the circuit are shown two sockets, Jl and J2 . These are US modular sockets which are connected in parallel, so that a phone can be connected together with the Fax/Modem. From the modular connectors, the incoming lines go via linking connectors JM9, JM10 and JMl 1. These allow correct connection for Australia or New Zealand. After these, the lines go though inductors 11 and 12 to bridge rectifier D4-D7 and also to the ring detect circuit consisting of 10kQ resistor R35, lµF capacitor C52, 27V zener Z7, diode Dl and optocoupler U21. U21 couples through the de- +13V 14 U16 C31 0.1 ! 14 U15 C5 0.1 ! DB 1N4001 t---------voo + C37 2200 _ C3B 2.2 + - + CB 0.1 C34 0.1 09 1N4001 C36 1000 + - C35 2.2 wave rectifiers D8 & D9 and associated capacitors to provide positive and negative rails of ±13V to ±18V. These in turn are fed to 3-terminal 5V regulators to give ±5V rails. While the power supply circuit is shown on a separate page, that was purely because we did not have space for it on the main circuit. It is on the PC board along with all the other circuitry. Construction -13V C1 01! 1 U15 1 U16 C2 01I . ~ 123 Fig.2: the power supply uses a 9-12VAC plugpack to drive half wave rectifiers D8 & D9 to produce ±13-18V rails. These rails in turn drive positive & negative 3-terminal regulators to give ±5V supplies. t ected ring signal to the microcontroller U4, to tell it that the phone is ringing. After the diode bridge, the line sig. nal goes via the relay contacts for relay RLl. This relay "seizes" the line when it is energised via latch IC U7 which is controlled by that master of events U4 (yep, the micro). When the line is "seized" - a fancy way of saying that it is connected - it is coupled to a gyrator circuit consisting ofQl , QZ, 10µF capacitor C55 and associated resistors. QZ and Ql look like a Darlington transistor pair which is exactly what they are but they act as a current sink controlled by the voltage across the 10µF capacitor. The whole circuit thereby acts as a gyrator or quasi inductance. The gyrator acts in concert with 4. 7µF capacitor C54 and transformer Tl to provide the required 600!.1 load impedance to the incoming lines. Back to back zener diodes ZZ and Z3 provide clipping of the input signal so that it does not damage the following circuitry which is the "hybrid". Op amps U13a and U13b form · the "hybrid", a circuit which formerly was provided by a bridge transformer. Its purpose is to separate the incoming signal from the outgoing signal. The core of the circuit is really op amp U13b together with the resistors at its input and its 22kQ feedback resistor. U13a acts simply as an inverting amplifier with a gain of 1. It takes the output signal from U10 (and U3 if fitted) and feeds them to transformer Tl via 464!.1 resistor R16 and lµF capacitor C51. U13b discriminates against the outgoing signal from U13a by virtue of the resistors at its input. As far as the incoming signal is concerned, it sees U13b as a non-inverting amplifier with a gain of 2, as set by resistors R18 and R19. The incoming signal is also loaded by 4640 resistor R16 and the virtual zero output impedance of U13a. Because of the low impedance of U13a, virtually none of the incoming signal appears at pin 5, the noninverting input ofU13b, so it operates as a straight inverting amplifier. Outgoing signals from U13a, on the other hand, see U13b as having no gain because the signal appears at both inputs. So both the incoming and outgoing signals are passed in the correct directions through the circuit and they do not interact. Critical to the circuit operation are the values of the resistors around U13b - they are all 1% tolerance. Virtually, the only other analog part of the circuitry is that associated with U18, the audio amplifier which drives the speaker for dial tones and so on. Power supply Compared with the rest of the circuitry, that for the power supply is dead simple. It consists of a 9-1 ZVAC plugpack transformer feeding half Since this project is all based on one compact PC board, by the time you have finished assembly of the board you have finished the project ! Start the assembly by carefully checking the board for any etching errors, track breaks or shorts. There should not be any but check thoroughly anyway because once all the parts are on, fault-finding is very difficult. This done, install all the resistors , diodes and zener diodes - see Fig.2. Check each resistor with your digital multimeter before it is installed and soldered into place. Next, solder in all the capacitors, making sure that the polarity of the electrolytics is correct, then install the sockets. These will be supplied for all except the 48-pin chip, U10. For this, machine pin IC socket strips will be supplied. You may to have snap these off to length before soldering each section in. Install the sockets according to the wiring diagram. Ignore the fact that the photographs of our prototype show vacant sockets - these are not necessary, so don 't install them. This means that you don 't need to install sockets for Ul, U3 or UZO. These components, plus transistor Q3, relay RLYZ and some resistors and capacitors, are reserved for future enhancements of the product and also the NZ version. Note also that the board has provision for two overlapping sockets, U10 and U12. Only U10 is used in this circuit, so don't put in the socket strips for U12. Do not put any of the ICs in yet. That has to wait until you've completed the initial power checks. Now install the 2-link, 3-link and 4-link jumper blocks. Note that unless you are building a version for New Zealand, jumper JM11 is not needed. JM4 is also not needed unless U3 is to be installed. The miniature loudspeaker is inSEPTEMB ER 1991 63 w ...J <I: ::E w u.. XR2902/XR2402 Fig.3: this wiring diagram shows the top PC pattern only. U10 & U12 are shown overlapping but only U10 is used here. Refer to the text regarding the various jumper link options & for details on component omissions. stalled on a couple of pillars and connected by two wires which drop down onto the board. You can now install the rest of the hardware , including the two crystals (don't get them accidentally swapped around), the two regulators, the US modular sockets and DC input socket, the female 25-pin D socket and the miniature toggle switch. Finally, you can install the eight rectangular LEDs. Note that there is provision for 12 LEDs in all and 12 are shown in the photographs but this circuit uses only eight. Those labelled Al to A4 on the wiring diagram are omitted. The LEDs need to be installed flat on the PC board so that they just touch the back of front pan el when it is 64 SILICON CHIP mounted. The best way to do this is to bend the leads of each LED at rightangles 3mm from the body. This is done by holding the LED so that the anode lead is on the right and then bending both leads down. Don't make a mistake here otherwise all the LEDs will be installed back to front! Warning! The Fax/Modem is not an Austel approved device. It has been designed so that when it is submitted as a commercial product, fully assembled , it should pass all Austel requirements. In the meantime, connection to Telecom lines is an offence. The front panel is a piece of screen printed Mylar film with double side adhesive tape. You peel off the backing and then stick it to the moulded front panel escutcheon. This whole assembly can then be pop riveted or secured to the board with screws, nuts and lock washers. There are also two rightangle metal brackets which need to be pop riveted to the board. At this stage, your Fax/Modem is almost complete but don't rush along to finish it. Carefully check your work against the wiring diagram and the circuit. Any mistakes need to be fixed now. Power up Now connect the AC plugpack and check the voltages to the inputs of the Although not shown here, inductors L1 & L2 will be supplied with kits. Note, however, that only eight LEDs are required, so omit LEDs A1-A4 (top right). Use a fine-tipped temperature controlled iron to solder the parts to the PC board. 3-terminal regulators. They should lie in the range of ±13V to ±18V, depending on the particular plugpack supplied. Now check the outputs of the 3-terminal regulators. They should be +5V or -5V, as the case may be. Now check that the correct supply voltage (+5V or -5V) is present at the supply pins for each IC socket and at the anodes of the eight LEDs. Note that the positive supply on some chips is labelled Vdd or Vee and is +5V. Vpp, pin 1, on the EPROM (U9) is also +5V. Vss, the negative supply, is -5V. On U15 and U16 (the 1488 RS232 line drivers), pin 14 should be the unregulated positive supply rail (+13V or above) , while pin 1 is the unregulated negative supply (-13V or below). Similarly, on U14, the 1489 line receiver, pin 14 should be +13V. There is no negative supply to U14. With all the supply voltage checks complete and correct, you can insert all the ICs. Make sure, whatever you do, that they all go in the right way around. They all face to the front of the board except for U21, the optocoupler. Now power up the circuit. Nothing should happen except that LEDs MR and HS should light up. If not, turn off the power again and check your work very carefully. If you can't get the two LEDs to light up, check that they are definitely wired in correctly and that the +5V rail is present at their anodes and at pin 20 of U5. You should have done this before but never mind. Failing that, you can always return it to the suppliers, PC Marketplace, who will be happy to fix it for their prescribed fee. On the other hand, we expect that the unit will perform exactly as it should and so you can proceed to connect the Fax/Modem to your computer and install the software. The software comes supplied on two 360Kb floppy discs. To load the software, insert the first disc in the drive and type install. After that, it's simply a matter of answering the questions. Don't try simply copying the files to your hard disc, as they are all compressed. The software, by the way, features drop-down menus, is easy to operate, and can be either mouse or keyboard driven. Have fun. SC Where to buy the kit The full kit of parts and the software is available from PC Marketplace Pty Ltd, PO Box 1100, Lane Cove, NSW 2066. Phone 02 418 6711. The price is $299.00. The kit will be available early in September. SEPTEMBER 1991 65 COMPUTER BITS BY JENNIFER BONNITCHA Swapfiles, program groups & icons After you have instal~ed Windows, you can easily customise it to suityour requirements. This month, we show you how to create new program groups & items. Windows 3.0 probably has the smartest installation routine around - but it's not always as smart as it could be. Setup scans the CONFIG.SYS and AUTOEXEC.BAT files to disable utilities it thinks will conflict with Windows and where possible it replaces them with its own Windowscompatible versions. If you use TSRs (Terminate and Stay Resident programs) such as SideKick, you should remove the appropriate lines from AUTOEXEC.BAT. You can use TSRs with Windows but you should load them after Windows is running. Before installing Windows, it's a good idea to make a copy of the AUTOEXEC.BAT and CONFIG.SYS files so that you can check them against the installed versions. Once you have installed Windows .Eile 66 .Qptions Window New program groups The Program Manager's menu bar contains four options: File, Options, Window and Help. Rather than having Windows separate your applications into Windows and Non-Windows applications, you may want to group all your frequently used applications together. You can easily create a new Program Group by selecting File then New from the Program Manager menu bar. Fig.1: the Program Manager window gives you access to the other Program Groups (along the bottom of the screen) & is central to the operation of Windows. It runs continuously in the background,evenif other applications are selected. !::felp rnifil rnifil Games Non Windows SILICON CHIP and started the program, you are presented with a desktop containing many icons (pictures). These icons are the items you select to perform various tasks. You will usually see the Program Manager and any associated Program Groups. You can think of the Program Manager as a kind of shell for Windows because all applications run under and are controlled by the Program Manager. It is from this main window that you are able to access other Program Groups and options (Fig.1). Thus, the Program Manager is central to those operations that enable the execution of Windows and Non-Windows Applications and utilities. It also manages your computer resources so you can have more than one application running at the same time. Although you can minimise the Program Manager, it is always running in the background until you exit from Windows. The Program Manager is responsible for setting up and supervising any applications you want to run under Windows - a set of related applications or programs is called a Program Group. The Program Manager initially contains five Program Groups - Main, Accessories, Windows Applications, Non-Windows Applications and Games. All the applications in the Accessories window, for example, form a Program Group (Fig.2). ffi Applications ~ ~ ffi Main Accessories Fil ~ • ~ Write Win Paintbrush Terminal ll!J!D Uillil. Calendar Calculator 6 Cardfile ~ mm mm Games Non Windows Windows then displays the New Program Object dialog box (Fig.3) which allows you to create either a new Program Group (a collection of related applications) or Program Item (a single application within a Program Group). Select Program Group if necessary, then click on OK. Next, Windows needs to know about the intended purpose of the Program Group (Fig.4) by means of a Description (Windows normally fills in the Group File section for you) such as My Apps. Once you choose OK, you are ready to place Program Items into your new Program Group. Copying & moving icons You can move program icons according to your own preferences. You could group all your commonly used applications in the above My Apps Program Group rather than using Windows ' separate groups. You could also place commonly used accessories such as the card file or calculator into My Apps. You can move icons from one group to another by pointing to ~ 1111111 0 e Recorder kJ[) Clock mm Friim1 lliMJ Applications Aldus PIF Editor the icon, then dragging with the mouse to the new group window; if you hold down the Ctrl key while you drag, you will leave the icon in its original group window and copy it to the new window. New program icons When you purchase a new application and you want it to run under Windows , you will probably want to add it to a Program Group. One of the options from the Program Manager file menu is Run - you are advised to run all Windows applications installation programs in this way as Windows will not only install the new program but also place the appropriate icon in the current Program Group for you. Supposing you want to place a Program Item for an existing application into a Program Group. First, activate the appropriate Program Group (such as My Apps) then select File New from the Program Manager menu bar. Since a group window is already open,Windows assumes you want to add a Fig.2: a set of related programs or program applications is called a "Program Group". This figure shows the programs normally available in the Accessories window. . The programs in the remaining Program Groups at the bottom of the screen can be displayed by doubleclicking on the icons. Program Item and so automatically selects it (Fig.5). After choosing OK, you then need to give Windows a short Description of the Program Item and tell it where to find the application and how to start it (Fig.6). Possibly the easiest method is to type the Description, press the Tab key to place the typihg bar on the Command Line and then choose the Browse button to locate the program's directory and the name of the file that loads it into memory. Once the application's (generally) .EXE file is located, choose OK then you can try to Change the icon that displays in the Program Group - although not all programs provide a special icon. Deleting icons & groups If you decide a Program Item is no longer needed to run a particular application in Windows (you may decide to group your favourites in My Apps for example), you can remove the item. Deleting the Program Item does not actually delete any of the program files - only the program icon New Program Object New <at> )ir.ciiir.ain.:iiro.up·: 0 Pro gr am ltem OK Cancel ~oup File: OK Fig.3: a new Program Group is created by first selecting File & then New from the Program Manager menu bar: Windows then displays this New Program Object dialog box. Select Program Group as shown, then click OK. I Cancel Fig.4: after you click OK in the previous dialog box, Windows displays the J>rogram Group Properties dialog box. This allows you to assign a name to the Program Group, while Windows fills in the Group File section for you. SEPTEMBER1991 67 Fig.5: to add a Program Item to an existing Program Group, you first activate the appropriate Program Group (such as Applications), then select File New from the Program Manager menu bar. Since a group window is already open, Windows assumes that you want to add a Program Item and so automatically selects it in the dialog box New Program Object New 0 OK Program Group <at>:rr'i:i\irii"mlfein"; Cancel is removed. Select the required icon then press Delete or choose File Delete from the Program Manager Menu Bar. Windows asks you to confirm the deletion. When you delete a Program Group, first minimise the group window then use the same procedure described above. If you want to remove all associated files, you need to use the File Manager to delete the files and remove the directories. Of course, you could also delete the files from the DOS prompt, but that defeats the purpose of the exercise, doesn't it? Swapping files One important way you can speed up Windows ' operation is to defragment your hard disc prior to installation with a utility such as the one included in Norton Utilities. There are not many applications performing such disc-intensive activities. Computers with 386 processors or higher can use virtual memory when in 386 enhanced mode. When Windows requires more memory it swaps information from memory to a swap file on the hard disc. This permanent or temporary hidden file reserves space on the hard disc for Windows to use for swapping. Windows automatically sets up a temporary swap file when running in 386 enhanced mode although a permanent swap file is desirable since it stays on disc and consists of contigu- . Command Line: OK Fig.6: this dialog box allows you to name the new Program Item & provide Windows with the necessary information to find & start the program ous disc blocks. The temporary swap file is created dynamically each time you start Windows. If you want a permanent swap file, Setup calculates the optimal size for the file based on the largest contiguous space it finds on the disc, thus it is advisable to defragment prior to installation. The permanent swap file dramatically increases the performance of the system because the file is stored in contiguous clusters, thus reducing the access time significantly. Should you decide to stay with the temporary swap file, regular defragmentation is a good idea so Windows can find sufficient space to create a large enough dynamic swap file . Temporary or permanent ? If you did not create a permanent swap file during Setup, a temporary swap file is created each time you start Windows. Windows determines the optimum size, but always leaves at least 512Kb free on the hard disc. You can set aside a portion of your SwaplileSwapfile has lound a suitable location for a swap lile on drive C: Largest ponible swap file size: Total lree dislt space: i llrowse... Cancel , Creilte 8194K bytes 16554K bs,tea Cilncel Reco-.ded awai, lile size: Fig.7: when Windows is running in 386 enhanced mode & gets low on memory, it swaps information from memory to a swap file on your hard disk. Although you can use a temporary swap file (Windows will create one each time it boots up), a permanent swap file will give noticeably improved performance. 68 SILICON CHIP hard disc for a permanent swap file after installation. As suggested above, make sure you defragment your hard disc first for the best results. Start Windows in real mode by typing WINIR at the DOS prompt. Make sure only the Program Manager is active, choose File Run, type swapfile then choose OK. Windows then displays the Swapfile dialog box (Fig. 7) which suggests the size of the largest swap file (contiguous disc space) that can be created on the current disc and the total amount of disc space available (contiguous and discontiguous). You can then make any necessary changes although as a general rule larger is better (make sure you leave enough disc space for normal operations) then choose Create. Exit from Windows then start Windows in 386 enhanced mode by typing WIN. When low on memory, Windows will now swap information from memory to the permanent swap file you just created. The swap file can be changed back to a temporary file by following the above procedure and choosing Delete from the Swapfile dialog box . Choosing disc drives If your computer has more thaJ.l one hard disc, for optimum performance place the swap file on the disc drive with the most available space. You can set the size and location of temporary swap files in the SYSTEM.IN! file as well as limit the disc space actually used. Next month, we look at the SYSTEM.IN!, WIN.IN! and PIF files, to see how you can further customise your window to the world. SC Was 8088-12 8088-31 286-12 286-16 286-16Neat 386SX-16 386SX-20 386-25 ~~t~~ OK RAM OK RAM OK RAM OK RAM OK RAM OK RAM OK RAM OK RAM Now $ $ $ $ $ $ $ $ $ 135 $ 199 $ 245 $ 449 $ 499 $ 695 $ 795 $1495 ~~ ~ !!~~~ 486-33 OK RAM 99 149 199 299 325 525 625 895 :~~:~ $4495 $2795 I I I I I I I I I : $4495.00 \ . : _ _ _ _ _ _ _ _ _ !Illa _ _ _ _ _ _ _ . / \ . - - - ~ - ~--11!111 ~ SEPTEMBE SPECIAL $279.00 Includes 1Mb I · r 256K carv 512K card € o 1Mb) 8514A $87 4 $549 $649 $925 $995 $699 $799 O <) SAVE$ \. - - ~!!.n.!!1!~ - -~----------' . er Warranty s DOS Ver 4.01 at no additional charge (Value $155.00) ~~ MHz d2 ~~E z p. oo2Mb) 1.2Mb r 1. Floppy, 42Mb ard Drive 256K 16 Bit VGA card, 14" Super VGA Colour Monitor - 1024 x 768 2 S, 1 P, lG ports. Enhanced 101 keyboard ~ lu '-,Jb- ~ Speed 21Mhz -(Exp. t,o 4Mb) .__..= ...•u or 1.44Mb Floppy, 42Mb Hard Drive 256K 16 Bit VGA card, 14" Super VGA Cplour Monioor - 1024 x 768 2 S, 1 P, 1 G ports. Enhanced 101 keyboard $1795.00 $2195.00 386-25MHz 386-33MHz Landmark Speed 41Mhz Includes: (No Cache) 1Mb RAM - (Exp. to 8Mb) 1.2Mb or 1.44Mb Floppy, 42Mb Hard Drive 256K 16 Bit VGA card, 14" Super VGA Colour Monitor - 1024 x 768 2 S, 1 P, lG ports. Enhanced 101 keyboard Landmark Speed 56Mhz Includes: 64kCache 1Mb RAM - (Exp. t,o 8Mb) 1.2Mb or 1.44Mb Floppy, 42Mb Hard Drive 256K 16 Bit VGA card, 14" Super VGA Colour Monitor - 1024 x 768 2 S, 1 P, G ports. Enhanced 101 keyboard $2995.00 $3395.00 Larger Hard Drives for all Systems: Western Digital 85Mb add $350.00 Conner 104Mb add $495.00 Conner 120Mb add $645.00. Extra Memory (per 1Mb) add $125.00. Electronic Solutions Sales P/L YOUR GUARANTEE OF SATISFACTION: 5 Waltham St. Artarmon 2064 *Allproductscarrya14daymoneybackguarantee (exceptsoft.wareandchips). prices include sales tax. * All computer systems carry afull24 month warranty. Po Bo X 426 Gladesv.ille 2111 •• All All cards come with full documentation • All other products carry a full 12 month warranty. Telephone: (02) 906 6666 Fax . (02) 906 5222 •All specials are for the month of magazine inserted or until stocks are exhausted [Z] - Due to Technical advances, products we supply may in some cases vary from those pictured. In all cases the products supplied are guaranteed to perform to an equal or higher standard than those pictured -• TIMEOUT ULTRASONIC APPLIANCE MINDER Ultrasonic switch for mains appliances Are you one of those people who goes to sleep while watching TV or who inadvertently leaves mains appliances on? This project monitors an area using ultrasonic sensors & if no movement is detected for a preset period, it switches the controlled appliance off. By JEFF MONEGAL Switching a lamp off after the baby has falle n asleep is just one of the many uses for this proj ect Other possible uses include automatically switching off outdoor lights along a path, or turning off an iron, a radiator or a desklamp. And why leave the TV going while you drift off into slumberland? After all, the life of a TV tube depends on the hours of use. This project can automatically switch your TV off if you pass out on the couch or if the kids lose interest and abandon the set. 70 SILICO N CH IP To op erate the project, you simply plug it into the mains , plug the appliance to be controlled into the mains socket mounted on one end of the case, and press the ON/ OFF button. The green STANDBY LED now goes off, the appliance turns on and the red MOVE LED flash es each time movement is detected. The movement detector used h ere is a proven design but instead of triggering an alarm system , it simply resets a timer. If this timer is reset before its time limit expires , the controlled appliance remains on. However, if no movement occurs for a preset time , then the detector will not reset the timer and the applianc e turns off. The time for which no movement can occur before the appliance is turned off is set during construction and can be anywhere in the range from 230 minutes. Once the controlled appliance has been turned off, it can only be turned on again by pressing the ON/OFF button. Repeated pressings of the ON/OFF switch simply toggle the appliance between on and off. A small warning lamp on the front panel flashes just before the time-out expires. This is useful for those times when no movement has occurred in front of the TV (eg, during a gripping susp_ense movie) and you want the TV to remain on. Alternatively, the lamp can be replaced with a buzzer so that you get an audible indication that the time-out period is about to expire. How it works Refer now to Fig.1 which shows the circuit details of the Ultrasonic Ap pliance Minder. It can be roughly split into four sections: an ultrasonic receiver (ICl, ICZ & IC3a); an ultrasonic transmitter (IC3d, IC3e & IC3f); a timer circuit & relay driver (IC4, IC5, Q3Q5, etc); and a power supply (Tl, D8D12, REGl) . Ultrasonic waves generated by the transmitter bounce around the room and eventually find their way back to the receiving transducer. Its output is fed to ICla which is connected as a variable gain amplifier due to the presence of trimpot VRl in the feedback loop. The non-inverting input of ICla is biased to half supply (½Vee) by two lO0kQ resistors, while the associated lOµF capacitor provides decoupling. This sets the outpl!lt at pin 1 to half supply when no signal is applied, so that we get maximum signal swing in both the positive and negative directions. VRl varies the gain ofICla from about 13.5 (at maximum resistance) to about 4.5. Following ICla, the amplified signal is coupled to inverting amplifier stage IClb. This stage has a gain of 39, thus giving the total maximum gain of approximately 500. From there, the signal is applied to a level detector circuit consisting of Dl, Rl, RZ and Cl. Cl charges on the positive going peaks of the amplified signal and discharges at a slower rate through RZ on the negative signal peaks. What happens is that a DC paten- tial is established across Cl. This potential remains steady as long as the signal picked up by the receiving transducer is at a steady level. However, if an object disturbs the ultrasonic field, the varying signal levels reaching the transducer cause the DC potential across Cl to vary. These signal variations are coupled through CZ to pin 2 of IC2 . This stage operates as a high-gain inverting amplifier with its bias set to about 1V by the lMQ & 150kQ resistors on the non-inverting input (pin 3). If the detected voltage across Cl rises above this 1V reference, pin 6 of ICZ swings low, thus turning on Ql and QZ. The 4.7µF capacitor at the input ofIC3a now quickly charges via QZ and its 470Q collector resistor. Thus, pin 2 of IC3a switches high and so Q7 turns on and lights the MOVEMENT LED to indicate that movement has been detected At the same time , the high on pin 2 of IC3a resets counter stage IC4 via DZ. When movement ceases, Ql and QZ switch off and the 4. 7µF capacitor at the input of IC3a discharges via its parallel lO0kQ resistor. Pin 2 of IC3a then switches low again and Q7 and the MOVEMENT LED turn off. Refer now to IC5a; this is one half of a dual 4013 D-type flipflop which operates in toggle mode due to the lO0kQ resistor connected between its Q-bar output and the Data (D) input at PARTS LIST 1 PC board, code ACT ONE 1 plastic utility case 1 pushbutton switch 1 12V miniature relay with 240VAC 1OA contacts 1 11 VAC mains transformer 1 pair 40kHz ultrasonic transducers 1 12V miniature lamp or buzzer 1 mains plug and mains cord 1 surface-mount mains socket 1 1OA fuse and fuseholder 1 miniature 40kHz crystal 2 200kQ miniature vertical trim pots (VR 1,VR2) 4 rubber feet 4 6mm-long standoffs 11 nylon screws & nuts 12 plastic cable ties Semiconductors 1 TL072 dual op amp (IC1) 1 TL071 op amp (IC2) 1 40106 hex inverter (IC3) 1 4040 binary counter (IC4) 1 4013 dual flipflop (IC5) 1 78L08 8V regulator (REG1) 2 BC558 transistors (Q1 ,03) 3 BC548 transistors (Q2,Q5,Q7) 2 80437 transistor (Q4,Q6) 61N4148 diodes (01-06) 61N4001 diodes (07-12) 1 5mm red LED (LED1) 1 5mm green LED (LED 2) Capacitors 2 1OOµF 16VW electrolytic 2 22µF 16VW electrolytic 2 1OµF 16VW electrolytic 1 4.7µF 16VW electrolytic 2 1µF 16VW electrolytic 7 0.1 µF monolithic 1 .001 µF ceramic 2 680pF ceramic 1 220pF ceramic 1 1OpF ceramic 1 4.7pF ceramic 1 2.2pF ceramic Resistors (0.25W, 5%) 21MQ 1 560kQ 1 390kQ 1 270kQ 2 150kQ 13 100kQ 1 47kQ 1 27kQ 4 22kQ 7 1OkQ 3 4. 7kQ 3 1kQ 1 470Q Miscellaneous Most of the parts are mounted on a small PC hoard & this in turn is secured to the lid of the case using nylon screws & washers. The relay is mounted on a separate outrigger board if mains appliances are to be controlled. Insulated hookup wire, mainsrated cable, heatshrink tubing . SEPTEMBER 1991 71 signals then drive the 40kHz transducer for high power operation, or the transducer can be connected between pin 10 of IC3e and ground for low power operation. Power for the project is derived from the mains via transformer Tl. Its secondary output is applied to bridge rectifier DB-Dl 1 which then drives an 8V 3-terminal regulator (REG1) via D12 . D12 is there is isolate the current pulses drawn by the lamp and relay from the regulator circuit. Construction ·{' The bodies of the two ultrasonic transducers, the pushbutton switch and the fuseholder are sheathed in heatshrink tubing to provide additional mains isolation. Mount the fuse lower down than shown here, to clear the PC board. pin 5. Actually, the two flipflops inside IC5 are connected in parallel but that doesn't affect the way the circuit operates. The RC timing circuit on the D input (pin 5) provides debouncing for the switch contacts. Each time Sl is pressed , it pulls the clock (CK) input high and the flipflop toggles. Assume initially that IC5 is set with its Q output (pin 1) low and its Q-bar output high. When Sl is pressed, IC5's clock input (pin 3) is pulled high and so the Q output switches high and Qbar goes low. This turns Q5 and the STANDBY LED off. At the same time, Q6 turns on and the relay closes to power the external appliance. The low on Q-bar (pin 2) now reverse biases D3 and thus pin 11 of IC4 is pulled low by the associated 100kQ resistor. IC4, a 12-stage binary counter, is now free to count the pulses on its clock (CK) input from Schmitt trigger oscillator of IC3b. If movement is detected by the ultrasonic receiver, IC4 is reset by IC3a and counting starts again. However, if no movement is detected, IC4 continues to count the clock pulses from IC3b until eventually its Q12 output (pin 1) goes high. This reverse biases D6 , thus enabling Schmitt trigger oscillator IC3c. IC3c operates with a frequency of about 1Hz. It drives Q3 which then drives Q4 to flash the TIMEOUT lamp 72 SILICON CHIP (or pulse a buzzer). This indicates that the timing period has almost finished, which means that you must move (if you are still awake) to prevent the appliance from switching off. If movement is still not detected, then a short time later pin 13 of IC4 will also go high. When this happens, the associated 100kQ resistor (on the anodes of D4 & D5) pulls the RESET pin ofIC5 high. IC5 now resets with Q low and Q-bar high and so the STANDBY LED turns on and the appliance switches off. Trimpot VR2 sets the period for which no movement must be detected before the appliance switches off. By using the component values shown, that time can be varied from about 2 minutes to 30 minutes. If longer or shorter times are required, it's simply a matter of changing the value of the timing capacitor. Fig.2 shows the parts layout on the main PC board. Begin construction by inspecting the PC board for any open or shorted tracks. When this has been done, install the two links on the top of the board but don't install the three bottom links at this stage. If you have decided to use IC sockets , now is the time to install them. This done, install the passive components (resistors and capacitors), then the diodes and transistors. Check that all polarised components are correctly oriented. Fig.1 shows the pinout diagrams for the transistors. When installing the transistors , push them down onto the PC board as far as they will comfortably go before soldering their leads. Be sure to use the correct transistor at each location, as the circuit uses a mixture ofNPN & PNP types. Note also that diodes D8D12 are 1N4001 types, while the remaining 'diodes are all 1N4148s. The remaining components can now be installed, along with the insulated links on the underside of the board. Make sure that the ICs are correctly oriented and don't overheat the crystal, otherwise it could be damaged. Although there is provision on the main PC board for the relay, it must be mounted on a small "outrigger" board if mains appliances are to be switched Ultrasonic transmitter IC3d and IC3e are wired as a standard 2-gate oscillator. This operates at 40kHz due to the 40kHz crystal in the feedback path. Note that the crystal is fed from a voltage divider network (100kQ and 22kQ) to keep the drive within safe operating limits. IC3finverts the output from IC3e so that we get complementary output signals (ie, signals that are 180° out of phase). These complementary output Fig.1: the circuit consists of an ultrasonic receiver (ICl, IC2 & IC3a); an ultrasonic transmitter (IC3d-f); a timer circuit & relay driver (IC4, IC5, Q3-Q5, etc); and a power suppy (Tl, DB-D12 & REGl). VR2 on IC3b sets the timing period. If no movement is detected, QB & Q12 of IC4 eventually both go high & reset IC5, thus turning off the appliance. +BV !+ luF 10pF 4.7pf 1M 4.7 100k 10k 390k ULTRASONIC RECEIVER 10D~ 1!220p R2 , 47k Cl 0.1 100k 02 0.1 ·sc54B E 100k 101 .. t I D2 1N4148 D3 I~· l ">o• ' T T • ) ) ,olcK as 13 __. VR2 200k IC31 ~ EICIB ULTRASONIC tri -0 tri ::0 HIGH POWER I TRANSMITTER (/) tri 0. 680p Q LOW ,POWER ELJc o(1_) I co co '-' ULTRASONIC APPLIANCE REMINDER w 0 4 0.1' +BV fi'h -012 , .... 01 l ) 8< r > •iM "( I 17 100k + F1 A 10A --0--.0---.---- 8 '-' ""-I ~- IC5a 4013 !!ISET 22'' ~ 0:, 5 100k 1 I 1 3:: J 8D437 -6. PLASTIC SIDE -3 Tt - t ' 680pf'! 3 1cK 04 TI MEOU T' r - ---------, T 14 LAMP OR BUZZER 150k 0.1 T 0.1I "I 11,R ~~4~0121 • · ~ 10k 22 T + l 116 1N4148 IC3b T T 100..: 11V 240VAC VI EWED FROM BELOW N • f ) 1our , 10 I , +Bv r--- - - - - - - -7 I <at> I i- - - - - - - - - - - - l I I I : I I I I I ELEPHANTHIDE MAiNS COVER I I <at> * \ f ~ V E T°WN) MAINS PANEL SOCKET Fl~ CORD GRIP GROMMET ULIBASOlilC * fj) <at> CASE LID LINKS UNDER PCB - - - * COVER WITH HEATSHRINK TUBING Fig.2: take care with component orientation when installing the parts on the PC board & use mains-rated cable for all 240VAC wiring. Don't forget the links under the PC board. (see Fig.2). This is done to keep dangerous main voltages away from the main board. Alternatively, for switching low voltages, the relay can be installed on the main PC board. The relay contacts are then used as a normally open switch. If you are using this option, 74 SILICON CHIP delete the mains socket and all associated mains wiring. When the boards have been completed, the case can be drilled to accept the hardware. Use the front panel label as a marking temr,late to locate the holes for the two LEDs, the pushbutton switch, the warning lamp and the transducers. The holes for the transducers are best made by first drilling small pilot holes and then reaming them out until the transducers are a tight fit. The main board is mounted on the lid of the case on 6mm plastic standoffs and secured using nylon screws and nuts. You will also have to drill holes in the base to mount the power transformer and relay board , plus l I!. . AM il ~1'"N'1'1:I I - - - - - - - - - ~ - C•i)' This view inside the completed prototype shows how the mains cables are bound so that if a lead does come adrift, it cannot short against anything. Note that nylon screws are used to mount all the hardware items in the case. holes in each end to accept a cordgrip grommet, fuseholder and surfacemounting mains socket. Mount the fuseholder down near the bottom of the case, to keep it away from the PC board (note: it should be further down than on the prototype). The front panel label can now be attached, the hardware mounted in position and the wiring completed as shown in Fig.2. Note that nylon screws & nuts are used to secure the relay board, mains terminal block and power transformer to provide isolation from the mains. As a further safety measure, the bodies of the two ultrasonic transducers and the pushbutton switch must be sleeved in heatshrink tubing (see photo). The front panel items are all wired using light-duty hookup wire but you must use mains-rated cable for all connections to the power transformer, fuseholder, mains socket and relay contact terminals. The mains cord enters through one end of the case and is anchored by the cordgrip grom- CAPACITOR CODES 0 0 0 0 0 0 0 0 Value IEC Code EIA Code 0.1µF .001µF 680pF 220pF 10pF 4.7pF 2.2pF 100n 1n 680p 220p 10p 4p7 2p2 104 102 681 221 10 4.7 2.2 RESISTOR COLOUR CODES 0 0 0 0 0 0 0 0 0 0 0 0 0 0 No. Value 4-Band Code (5%) 5-Band Code (1%) 2 1MQ 560k.Q 390k.Q 270k.Q 150k.Q 100k.Q 47k.Q 27k.Q 22k.Q 10k.Q 4.7k.Q 1k.Q 470.Q brown black green gold green blue yellow gold orange white yellow gold red violet yellow gold brown green yellow gold brown black yellow gold yellow violet orange gold red violet orange gold red red orange gold brown black orange gold yellow violet red gold brown black red gold yellow violet brown gold brown black black yellow brown green blue black orange brown orange white black orange brown red violet black orange brown brown green black orange brown brown black black orange brown yellow violet black red brown red violet black red brown red red black red brown brown black black red brown yellow violet black brown brown brown black black brown brown yellow violet black black brown 1 1 2 13 1 1 4 8 3 3 SEPTEM BER 1991 75 met. Leave sufficient cord inside the case to reach the fuseholder and mains terminal block. Install about 45mm of heatshrink tubing over the leads to the fuseholder before connecting them to the terminals. After soldering, push this tubing over the body of the terminals and shrink it to a tight fit using a hot airgun. Do not install the Active lead between the mains terminal block and the relay board at this stage. This lead is only installed after the unit has been checked for correct operation. Don't forget to connect the earth lead between the PC board and the terminal block - see Fig.2. After the wiring has been completed, use plastic cable ties to bundle the wires together, as shown in the photographs. In particular, you should ties the mains leads together so that if one lead does come adrift, it cannot move and short against anything. Final checkout To test the unit, first check your mains wiring carefully, then close the lid of the case and apply power. The STANDBY LED will usually now come on, while the MOVEMENT LED should flash briefly if there is movement in front of the transducers. Adjust the sensitivity control, VRl, to ensure that the ultrasonic range can be varied. Now press the ON/OFF button. The STANDBY LED should go out and the relay contacts should close. If this checks out, set VR2 to minimum (fully anticlockwise) and check that the relay drops out after about two min- Because there are exposed mains connections on top of the transformer, it should be covered with insulation to prevent accidental contact. This piece of insulation is secured by one of the transformer mounting screws & to the side of the case using a nylon screw & nut. utes if there is no movement in front of the sensors. Note: you can simulate this by disconnecting a lead to one of the transducers. Finally, install the active mains lead between the transformer and the relay board. The controlled appliance should now toggle between on and off when you press the ON/OFF button and should automatically switch off if there is no movement during the timing period. Troubleshooting If it doesn't work, first use your multimeter to check the supply rails. You should get +8V from the regulator and this voltage should also be present on the positive supply pins of Where to buy the kit Kits for this project are available from CTOAN Electronics, PO Box 33, Condell Park, NSW 2200. Phone (02) 708 3763. There are three variations : • Kit 1: includes PCBs, mains transformer, relay, 40-kHz crystal & ultrasonic transducers. Price $39.95 plus $4.00 p&p. • Kit 2: includes all of Kit 1 plus on-board components, pushbutton switch, LEDs & lamp. Cost $54.95 plus $4.00 p&p. • Kit 3: includes all of Kit 2 plus plastic case, adhesive front panel label, fuseholder, mains socket and mains cord & plug. Cost $69.95 plus $4.50 p&p. CTOAN Electronics offers a full repair service for this kit. The cost is $20.00 plus $5.00 return postage. Only kits built as described in this article and with good quality soldering will be accepted for repair. Note: Copyright of the PC board for this project is retained by CTOAN Electronics. 76 SILICON CHTP the ICs. A low rail indicates that either the regulator, a supply diode or an IC has been incorrectly oriented. It often helps if you can pinpoint the fault to a specific section of the circuit. Assuming that the supply rails are correct, here's what to look for: • Symptom: relay doesn't close on each alternate pressing of Sl. Check circuit around IC5 & Q6 and check D4 & D5 for correct orientation. If the Q output of IC5 goes high on alternate presses of Sl, check Q6. • Symptom: circuit times out regardless of movement; MOVE LED does not flash. Check that pin 6 of IC2 swings low when movement is present. If OK, check Ql & Q2. Ql's collector should swing high if movement is detected, while QZ 's collector should go low. If no signal is present at pin 6 of IC2, use a CRO to check for signal at the output of the transmitter. If this is OK, check for signal at the outputs of ICla & IClb when there is movement. • Symptom: MOVE LED flashes but circuit times out regardless of any movement. Check orientation of DZ & D3, • Symptom: warning lamp flashes continually during timing period. Check orientation of D6. • Symptom: warning lamp does not flash just before timing period expires. Check around IC3c, Q3 and Q4. • Symptom: circuit does not time out if there is no movement. Check circuit around IC3b & IC4. Check D4 & D5 for correct orientation. SC For Features, Price and Performance, there's no other choice [fuai1j OMS 35 Multimeter with Bargraph e 3 1/2 digit large LCD display • Memory for relative measurements • Data hold function • Diode and Transistor testing DM824 Multimeter with Frequency nte e 4 1/2 digit large LCD display • Measures capacitance • 200kHz frequency counter • Diode and Transistor testing Gotta Gatta 0S7020A 20MHz & 0S7040A 40MHz Osei Iloscopes D 3 Multimeter with hermometer 3 1/2/digit large LCD display • Measures capacitance • Measures Temperature -20 to +15{l'C DM6 Mui imeter fits your shirt 3 1/2 digit LCD display Memory mode for relative measurements Data hold function I • High sensitivity - 1mV/div • Stable low drift design • 8 divisions of displayed dynamic range with accurate distortion-free waveform measurement • Special TV sync separation circuits for measurement of video signals • Delayed sweep function (0S7040A ) • ±3% accuracy • Convenient XY operation for measuring phase differences between two waveforms • Variable sweep control incorporating x10 magnifier Uncal and trigger warning lights e TV-V & TV-H triggering • Trigger hold-off • Includes TWO x1/x10 switched probes ar 0S8020R Readout Cursors for direct measurement of waveform voltage, time and frequency 20MHz bandwidth 1mV max sensitivity Similar performance to 0S702GA hZJ1lh34~.,(Y(J /11strume11t\' PI)·. Ltd. Australia's Leading Test & Mea uring Instrument Compa11y Contact your nearest Elmeasco Office for name of your local supplier and special pricing if you mention this magazine Tel : (02) 736 2888 Fax : (02) 736 3005 NEW SOUTH WALES Fax : (03) 870 8972 Tel : (03) 879 2322 VICTORIA Tel : (07) 875 1444 Fax : (07) 277 3753 QUEENSLAND Fax : (08) 269 6411 Tel : (08) 344 9000 SOUTH AUSTRALIA Tel : (09) 470 1855 Fax : (09) 470 3173 W. AUSTRALIA AMATEUR RADIO BY GARRY CRATT, VK2YBX How glass mount antennas work One of the status symbols on cars today is a small antenna mounted on the rear window for a mobile \elephone. These antennas have the advantage that they can be installed without the need to drill holes for cables but are they as effective as conventional body mounted antennas? This article gives the answer. One of the dilemmas facing today's amateur is how to mount mobile antennas without permanently marking or modifying the exterior of a motor vehicle. In the past, tradition has dictated that a 1/4-wavelength whip antenna mounted in the centre of a vehicle roof provides optimum performance. .These days, people are far more reluctant to drill a hole in the centre of the roof of a brand new motor vehicle for the sake of antenna performance, particularly when they are informed that the performance of a suit- ably sited glass mount antenna can be just as good. Glass mount antennas are available for a wide range of frequencies, including the now more commonly used cellular bands (830-890MHz). This kind of mounting system has considerable appeal to operators using rental or company vehicles where any modification to the exterior of the vehicle would be out of the question. Many communications retailers now stock glass mount antennas for VHF, UHF and other radio bands. This type of antenna is unobtrusive, easily This photograph shows a typical glass-mount antenna coupling box that has been modified to form a test probe. The centre conductor of the coaxial feedline is connected to a conductive plate whose area is the same as that of the mounting foot of the antenna on the other side of the glass. 78 SILICON CHIP removed, weatherproof, broadband, and an ideal alternative to bumper or boot mounted systems which cannot provide a good omnidirectional radiation pattern. If an antenna is to be used without a groundplane, then theory dictates that it must be a 1/2-wave antenna rather than a shorter 1/4-wave whip which requires a groundplane to form the symmetrical half of the antenna. Another consideration when designing a glass mount antenna is the mechanical "foot" that must be used to mount the radiator. This must be mechanically stable and easily affixed to any window of a motor vehicle. Ideally, it should also allow some adjustment of the angle of elevation of the antenna to compensate for the slope of the window, ensuring that the antenna remains vertical in all mounting situations. How they work To analyse the theory of glass mount antennas, it is best to consider the external radiator first. The whip section and the mounting foot comprise a 1/2-wave resonant radiator. However, due to the loading capacity caused by the mounting foot and the dielectric loading resulting from mounting the foot on glass, the physical length of the radiator will be somewhat shorter than the theoretical value. However, the radiator will still be presented as an electrical 1/2-wavelength with voltage loops occurring at both ends. The foot can be mechanically mounted onto the windscreen or rear window in the motor vehicle using a suitable adhesive. This has negligible effect on the performance of the antenna. The impedance of the exterior radiator is around 2-3kQ. As the patent theory of coupling through glass is much the same as that of an interstage coupling capacitor, and since the coupling is done at a high impedance point, very little loss occurs, and only a small amount of capacitance is needed for efficient coupling through the glass. Fig.1 shows the equivalent circuit of a glass-mount antenna. In most modern applications, a 2-element colinear radiator has been chosen which provides some gain over a standard 1/4-wave whip , and also radiates a fairly omnidirectional pattern. Theoretically, two 1/2-wave radiators spaced approximately 0.7 of a wavelength between centres produce some gain above that of a 1/4-wave radiator if they can'1be kept in phase. Practical experience has shown that the airwound phasing coil is the best trade off between the electrical requirement and mechanical robustness. Most designs use a 5/8-wavelength upper radiator and a quarter wavelength lower radiator, separated by an airwound phasing coil. This design is known as a "3dB" gain antenna. By stacking and correctly phasing these two elements, the radiation pattern is compressed, resulting in a lower angle of radiation. The major lobe of a 1/4-wavelength antenna is approximately 30° above the horizon, while a "3dB " antenna has an angle of radiation of 8°. Under test conditions , it has been shown that a properly sited "3dB " glass mount antenna can be made to perform ldB better than a roof mounted quarter wavelength antenna and, at the same time , provide a radiation pattern with relatively low distortion. Interestingly, one of the design criteria is that a glass-mounted antenna should be able to survive going through a car washing system. The RF energy is coupled through the glass by placing a coupling box cl I SOURCEl I GENERAWR I I L- A---------,.1---]l . iJI, _ _ _j inside the window and then affixing the mounting foot precisely over the same area on the outside of the window. The coupling box contains a tunable LC network, with a high-Q air dielectric capacitor, formed from a piece of brass sheet, providing the means for varying the resonant frequency. A non-conductive screw is adjusted to distort the brass sheeting, thereby varying the capacitance. The bottom end of this sheet connects to the coaxial cable braid. The centre conductor of the coaxial feedline is connected to a conductive plate whose area is the same as that of the mounting foot on the other side of the glass. These two parallel 9onductive plates, together with the glass of the window, form the capacitor which couples energy through to the outside antenna. Typically, the value of capacitance is about 2 to 3pF. At the resonant frequency, the "hot" end of the parallel LC circuit is at a high impedance, whilst the coaxial cable is tapped to an impedance point of 50Q. Fig.2 shows the circuit represen- · tation of this arrangement. Locating the antenna Since we know that the optimum capacitance for good coupling of RF energy through the glass is around 23pF, it is obvious that incorrect loca- TRANSFORMER I I I L-=, . , J G-_1-S-H-IE-LO-- y I-' .,. GROUND "'I" Fig.1: equivalent circuit for a glass-mount antenna. Only a small amount of capacitance (2-3pF) is required for efficient coupling through the glass. a,----, z l I I I I : : 11 11 11 50tl TRANSMISSION · LINE TO TRANSMITTER AND/OR RECEIVER Fig.2: the circuit representation of a glass-mount antenna. The energy from the antenna (A) is coupled through the glass by placing the mounting foot over the coupling box located inside the window. OATLEY ELECTRONICS IFOR No.1 KITS I ~ ~ I INFRA RED NIGHT VIEWER A very small complete ki t • Includes both an adjustable lens and an eyepiece • The matching tu bes, lenses an d eyepieces were removed from 5 ~~1/iTHE 2mW PHILIPS head, 12V supply kit, warning labels, ballast resistor and the instructions: KIT No. LK13. 299 EXPERIMENTAL E.H.T. POWER SUPPLY Includes the IR tube, lens eyepiece, electronics kit and th e case ki t: KJT No. tRNW5. 75mm round IA plastic fil te r: $16. o 2mW PHILIPS LASER HEAD WITH 240V POWER SUPPLY Uses a brand new visible red He-NE LASER HEAD: Encapsul ated He-Ne tube • Ve ry tight beam (0.95mR ): More suitable for most applications • Head dimensions: 37mm diameter by 260mm long • Supplied with a very small pro fessional 240V power supply, that even has a TTL inte r lock: Needs 3-5V <at> approx 3mA, ac ross two isolated term inals to swi tch the laser on: Opto isolator built into the supply• Use it for surveying , science experiments, laser displays, holography, etc.• Priced at about 1h of the ex pected price and ONLY WHILE STOCKS LAST AT: s210 ~~1/i!THE 2mW PHILIPS head, the com mercial power supply, warn ing labels, ball ast resistor and the instr uct ions: KIT No. LK14. VISIBLE LASER DIODE Similar story to the IR diode but this one is very visible: 3mW <at> 670nM ON LY $210. For a 3mW visi ble laser diode, collimator/heatsink assembly, a suitable drive r/digital switch kit and the instructions. Same head as the LK14, but thi s unit is supplied with our newest 12V lase r inverter kit , which will power most laser tubes • The supply is easy to con struct and comes wilh a totally prewound transformer, and simple instructions • The sw itched mode power supp ly wit h MOSFET outpu t is very efficien t and a gu aranteed design • THE INCREDIBLE PRICE? s175 new Ge rman night vision equipment • Simple construction: Instructions provided • For a limited time only the kit is supplied with a high quality mi litary inverte r: Draws on ly 25mA from the 9V battery • IR ill umin ation is req uired in the dark, and good ranges are possible with just med ium powered foc ussabte to rches, fitted with an IR fil ter • You wou ld normally pay over $3000 for a view like this! DON ' T MISS OUT! ONLY 2mW PHILIPS LASER HEAD WITH A 12V POWER SUPPLY Can produce sparks about 1cm long, whilst drawing approximately 35mA from a small 9V battery! • Great for many high voltage experi me nts • 3-1 6V operation_and very low power consumption • E. H.T. voltage output depends on DC supply voltage: Approx 16KV output with ~4V s~pp ly • As a bon us, th is unit will power all the IR tubes! Ask abo ut some unusual and well priced tubes we will have in stock • Professional unit wi th a sealed voltage mult iplier section • Circui t provided • Approx imate dimensions: 105 X 56 X 37mm . s39 ONLY For ~ -H·'.· powe r supply and the c1rc u11/mstructions. IR LASER DIODE A 5mW/780nM laser diode mo unted in a prec ision made adjustable coll imator asse mbly • Removed from new and near new equ ip ment • Very ti ght bea m and is just visible to humans in a darkened room • Requi res only a constant current source to operate : Approx 80mA/2V • Use ii for communications, securi ly. medical research. scientific experiments, invisible lase r pointer: Very visible 10 an IR Nig ht Viewer! • Suitab le low voltage dr ive r/d igi tal kit is inc luded in our SPECIAL INTRODUCTORY PRICE: ONLYsg g For t he collimated assembly illustrated, and a su itable expe rimental driver/dig ital switch kit and the instructions. Melbourne Distributor: Electronics World (03) 723 3860 or (03) 723 3094 SE PTEMB ER 1991 79 Amateur Radio - glass mount antennas CHRISTIAN BLIND MISSH{~ ·J Re,$totiK! :;~~t, be1K This view inside the coupling box shows how the adjustment screw is used to distort the brass plate to change the tuning capacitance. She is just one of the 2.5 million blindnessthreatened people treated every year by CBMI health care workers and eye specialists. Millions more are still waiting for sightsaving treatment. tion of either the antenna or coupling box would severely degrade the performance of a glass mounted antenna. In an effort to accurately determine the optimum location for both coupling box and antenna mounting foot, a simplified test set up has been devised. This allows the measurement of the capacitance of the glass at any location on the vehicle. If the capacitance of the glass falls within the set limits, the location is suitable for the mounting of a glass mount antenna. If capacitance is high, and this can be the case if the area of glass to be measured contains demister wires, mesh or sun screen tinting, the location will not be optimum. Test set-up Please help CBMI to transform your gift into eyesight! COUPON Please cut and send to: CHRISTIAN BLIND MISSION INTERNATIONAL, P.O. Box 5, 1245 Burke Road, KEW, Vic. 3101 Phone: (03)817-4566 D = Please send me further information about CBMl's work. As long as i_t is possible for me, I will help: D monthly D quarterly D annually D to prevent blindness D to restore eyesight D to rehabilitate the blind Enclosed is my gift of$ _ _ __ __ Mr/ Mrs/ Miss: _ _ _ __ _ __ _ Street: _ _ __ __ __ _ __ City: _ 80 _ _ __ _ Pnstcode: _ SILICON CHIP _ _ The test set up itself is made from the coupling box of a standard glass mount antenna. The box has been modified so that the centre conductor of the coaxial cable is fed directly to the PC board coupling plate and the braid of the coaxial cable goes to the brass foil sheath inside the coupling box. This box may then be connected to a digital multimeter which measures capacitance. Typically, the DMM should be switched to its 200pF range, as this will provide resolution of 0.1 pF. An additional test lead connected to the braid of the coaxial cable at the multimeter end and terminated with an alligator clip at the other end may be used as an optional vehicle earth connection. With the probe connected to the digital capacitance meter, the meter will give a particular reading in free space. By placing the test probe against the glass, this reading will increase by several pF. Placing the probe across demister wires or window tinting, or even close to the chrome surround of vehicle windows, will cause the capacitance to be higher than optimum for good RF performance. Hence the probe can be used to verify that the preferred mounting location is unaffected by any of these factors. If a genuine coupling box from a glass mount antenna is unavailable, the test probe may be made from a zippy box with a PC board in place of the lid. Patent protection Glass mount antennas are protected in many countries of the world by patents. The principle of coupling RF energy through glass dates back as far as 1929, and developments of this technique have transpired since that time until the 1980s. US Patent 4238799 covers a glass mount antenna system designed for the 2 7MHz CB bands. Since that time, other variations and improvements have been made for virtually all radio bands utilised today. In particular, Australian patent 535273 covers the application of this technology for cellular use. The information presented in this article is for technical interest only. Readers should be aware that any use of the information contained in this article on a commercial basis may breach intellectual property rights protected by these patents. A commercial version similar to the glass mount capacitance tester described in this article is available from the Antennas Specialist Company, Cliffland, Ohio, and possibly from their representative in Australia, RF Industries Pty Ltd - phone (02) 749 1488. Radio Convention Radio amateurs who will be in the "top end" during September should make it their business to drop in for the 1991 Radio Convention presented by the Townsville Amateur Radio Club. The venue will be the James Cook University in Townsville, on 27th, 28th and 29th of September. For further information phone (077) 73 3487 or (077) 74 0211. SC BUILD YOUR OWN FAX/MODEM This is a fully featured kit Time saving The Comma · Fax/Modem 1s 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. The Comma Fax/Modem will also receive faxes in background while you continue to work. 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 ensur~1asting troublefree operation. 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. with all popular communication services including most bulletin boards. Available soon When faxing out the Fax/Modem will reaial 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. MMP and V42bis option. FREE Software With each kit you will receive the QL2 Fax/Modem software featuring both pull-down menus and mouse support. Also supported are cover pages, broadcast faxes, and scheduling. The software keeps a database type register of regularly used fax numbers for easy retrieval 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. As well it's also a modem The Comma Fax/Modem is a fully AT command series V compatible modem. Features include V22N22bis 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 There is also a step-by-step guide to testing your Fax/Modem throughout the building process. ONLY $299.00 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. Note: This device does not have an Austel permit in force. Connection to Telecom lines is an offence. 42Mb Voice Coil HOD with Controller/AT Bus Normally this unit would SELL for $750.00 THIS MONTH ONLY $425.00 SAVE43.3% DEALER ENQUIRIES WELCOME We also stock a range of motherboards, external disk drives, hard disk drives, addon interface cards, as well as a huge range of cables, adaptors, switch boxes and chips. Call today for very competitive pricing. ASK FOR A COPY OF OUR FREE CATALOGUE TRY PC MARKETPLACE SUPERFAST MAILORDER - PHONE OR FAX TODAY! Pfii{ (jkesons --- PERSONAL COMPUTER MARKETPLACE Pty Ltd FREIGHT CHARGES PHONE (02) 418 6711 Include $10 with order for all normal items. Heavy items e.g. monitors add $15. 14 day money back guarantee. FAX (02)4186713 Mail Order Address: Order by phone (use credit card), by fax or by mail. Unless insurance is declined it will be charged at P.O. Box 1100 Lane Cove 1% of total purchase. This is for your protection. NSW2066 PRICES CURRENT FOR MONTH OF PUBLICATION OR WHILE STOCKS LAST e SERVICE IS THE DIFFERENCE e SERVICE IS THE DIFFERENCE e SERVICE IS THE DIFFERENCE j • • - I e • • ~ SERVICE IS THE DIFFERENCE :::l VINTAGE RADIO By JOHN HILL Transistor radios are collectable Early transistor radios are now considered collectable items by many vintage radio enthusiasts. They can also be used to "restore" irrepairable and incomplete sets to some form of working order. "Solid state" and "transistorised" are words that do not often appear in this column. When it comes to transistors, yours truly would have to look up a book before attempting to wire one of those tiny components into a circuit. As far as electronic technology is concerned, I am at least a quarter of a century behind the times. However, solid state equipment was not invented yesterday and some transistor radios have now been around long enough to wear the vintage radio classification. They have been with us for 30 years now and there is no reason why some of the older sets should not be preserved with the same enthusiasm that collectors bestow on valve type receivers. Many early transistor radios were very good. They performed well and were made to last, so why not collect some of them while there are still a few to be found? The foregoing should be sufficient justification for bringing transistor radios into this month's Vintage Radio column. Early transistor radios can be both interesting and collectable. Granted, many have battery problems but these are relatively easy to solve. In fact, perfectly usable transistor These two old HMV transistor radios are part of the author's collection. The one at the front has been converted to mains operation using a 9V DC adaptor. 82 SILICON CHI P radios are often discarded for no other reason than the non-availability of a suitable battery. Most early transistor radios were designed for battery operation only and were powered by one of several types of large dry batteries. While some of these batteries can still be purchased, they are not readily available and their cost is prohibitive. Also, because they are now made in India and are not date stamped, the chances of buying a fresh one are fairly remote. The following story is an example. The $24 battery My friend Ron came to see me with an old Kriesler transistor radio in one hand and an Indian battery in the other. He had bought the battery at a hardware shop in a remote country town while he was on holidays. After arriving home he found that the battery had clip-on connectors instead of the usual 2-pin socket. He hoped that I could do something to sort out the problem. Upon examining the battery, two things came to notice. First, the price tag of $24 nearly took my breath away. Second, the battery felt all lumpy inside, which immediately suggested that all was not well. A check with a multimeter confirmed that the "new" battery was very sick indeed. Ron had been sold a brummy battery and it would cost him more than $24 worth of petrol to take it back to where he bought it. What really surprised me was the fact that Ron apparently didn't think that the battery was expensive. "They usually last six to eight months, so that's not too bad really", was his comment. Compared to the price of six torch cells, it seemed outrageous to me. Anyway, my immediate problem Why not collect some old transistor radios while they are still available? This neat little set is an AWA Radiola Eight which was a very early 8-transistor radio. Many early transistor radios were quite good performers. was to get Ron out of trouble and I did what anyone else would have done. I converted the set to accept a 9V "AA" pack consisting of six "AA" cells in a plastic 6-pack holder (see photo). This involved nothing more than replacing the 2-pin plug with a snap connector and adding a piece of foam plastic to take up the extra space and prevent the battery pack from rattling around inside the case. The disadvantage of such a conversion is that the battery capacity is considerably reduced. However, the choice of heavy duty alkaline cells would help offset this. Anything is better than paying megabucks for a stale Indian battery. Now one would expect Ron's battery story to end there - but not so! The very next day after doing the battery pack conversion, I was telling a friend about the $24 battery and where it was bought. As he was going there the following week, he offered to take the battery back and try to get a ·. refund. Which he did - successfully. You can imagine how pleased Ron was to have his money refunded. Perhaps the most interesting aspect of this part of the story was the fact that the battery was on the shelf when Although now difficult to obtain, batteries for early transistor radios can still be purchased - if one can afford them. This type of battery is now made in India and, because they are not date stamped, the state of the battery is questionable even when new. the current owner bought the business some two years previously. It is anyone's guess as to just how old the battery was when it was purchased. Some 25 years ago I was interested in flying radio-controlled model aircraft and, at the time, used dry cell powered single channel equipment. Oh boy, is that a story in itself - and a vintage radio story too! However, the point I am trying to make is this: I never bought batteries without checking them in the shop with a multimeter first. There was too much money flying around in the sky to lose it all because of a faulty battery. There is nothing like a "flyaway" to ruin a good afternoon on the flying field. Observing the experiences of others taught me that just one faulty battery can have very expensive consequences. Converting to mains power Making up a suitable battery pack for an early model transistor radio is not the only way out of trouble. Converting them for 240V operation is another alternative and this can be done in a number of ways. Back in the days when these receivers were popular, a special power supply could be bought that fitted straight into the battery compartment. This power pack contained a power transformer, diodes and smoothing capacitors to give a hum-free output. It was approximately the size of the original battery and had a 2-pin socket at one end to accept the standard 2-pin plug of the receiver. Converting a battery Conversion to AA-size battery packs is the easiest way to overcome battery problems in early transistor radios. Because most sets run off 9V, the 6-cell pack is the most useful. Heavy-duty alkaline cells will give the best life and should be used if possible. SEPTEMBER1991 83 This old Philips "Power Pack" made it easy to convert a battery radio to mains operation. It fitted directly into the battery compartment and contained a mains transformer, diodes and filter capacitors to give a hum-free output. Any 100mA power pack of the appropriate voltage can form the basis of a supply for a transistor radio. In some cases, it is simply a matter of making the appropriate connections, either by soldering direct to the battery leads or by fitting appropriate plugs and sockets. However, not all such supplies (eg, plugpacks) can be used directly - at least not without some modification. Those designed to power appliances other than radios may not have adequate filtering. This can result in severe mains hum, which is very much out of place in what is supposed to be a battery receiver. In some cases, it may be sufficient to add an electrolytic capacitor across the output, typically around 220µF or more. Be sure to use a capacitor with the appropriate voltage rating. A more elegant approach might be to add a voltage regulator which, in addition to ensuring that the voltage remains constant, provides some additional filtering. (The Universal Power Supply Board described in the August 1988 issue of SILICON CHIP should also prove useful for anyone wanting to make up such a supply. Ed.) As previously stated, many of the older transistor radios worked very well. If such a receiver is connected to a large loudspeaker, it can deliver quite good volume and quality of sound. These radios can thus be useful in their own right, as well as being collectable items. The Trojan horse This AWA "Transistor Seven" is similar to the one that was used as a transplant in two old valve radio cabinets. Although the transplants worked satisfactorily, each cabinet was later re-converted as soon as valve chassis became available. radio for mains operation was as easy as fitting one of these units. It is unlikely that such a power pack would still be available today, as modern transistor radios no longer use the large batteries of yesteryear. Today's pocket size devices use the much more convenient torch cells. Another way to solve the problem is to use an adaptor or power pack of the type used to run small low power battery appliances. These were very popular when calculators used LED 84 SILICON CHIP displays instead of the now more common liquid crystal displays. The old LEDs consumed a considerable amount of power and most calculators of that era were fitted with a socket so that a power pack could be used to operate them independently of the battery. However, many of these old calculators ran on three or six volts, so one needs to check the power supply before using it for a radio. Some early radios operated on 6V but a 3V supply would be of little use. In my opinion, some valve sets are not worth restoring simply because they are battery models . Whether straight battery sets or vibrator types, battery valve radios do little for me. Although I have restored several to working order, I am not enthusiastic about battery valve receivers. It is possible (usually with some difficulty) to install a transistor radio inside an old valve radio cabinet. I have done this on two occasions and it is one way to get a dilapidated old battery valve set working again. My first conversion was on a 1940 AWA battery receiver with a timber cabinet. The radio was beyond repair. The transistor chassis implant used in this project was from an old AWA ?-transistor leather-cased portable that I had bought about 28 years ago. While Resurrection Radio Vintage Wireless Specialists Repairs - Restoration - Sales Our skilled technicians offer QUALITY repairs and restoration. We also have a large stock of Bakelite and Timber radios fully restored and for SALE. This 1940 battery-operated radio was fitted with a "transistor transplant" but was later reconverted to valve operation when the opportunity arose. Fitting a transistorised chassis presents quite a challenge if the original dial and dial mechanism are to be retained. it seemed like a good idea at the time, fitting this radio to the old cabinet did have its problems. Perhaps the most difficult aspect of such a conversion is connecting the original dial and dial drive mechanism to the transistor receiver and getting it to track accurately. The best way to achieve this is to discard the transistor radio's tuning capacitor and use the original one. That's easy to say but not so easy to do! In this case, the set was also converted for 240V operation by the inclusion of a small transformer, diodes Small DC plugpacks are ideal for running battery-powered transistor radios but note that additional filtering may be needed in some cases to avoid mains hum. and filter capacitors. The finished receiver worked quite satisfactorily, but it needed a plywood cover at the back of the cabinet to hide all the horrible and unsightly things inside. However, when the opportunity came to reconvert the set to a 240V 5valve receiver, the transistor innards were soon removed and now the old AWA is a 5-valve Hotpoint. The old AWA transistor chassis then had a second chance at life. It was later recommissioned for use in a very old console cabinet. The old set's valve chassis hardly had a component left on it, hence the need for the transplant treatment. Once again, the set's original tuning capacitor was used, along with the original dial. No sooner had this job been completed when along came a suitable 5valve chassis that fitted the cabinet almost perfectly. So, once again, the transistorised conversion was reconverted to valve operation. Although the old transistor set now lives in limbo in a back corner of the garage, it has proved the point that a transistor radio can be used in an old valve cabinet if you are desperate enough. To succeed in getting a transistor radio to work in an old valve radio cabinet, while retaining the original dial setup, is a challenge worth meeting. Try it sometime - just for the hell of it, if for no other reason! SC Parts are available for the enthusiasts including over 900 valve types, high voltage capacitors, transformers, dial glasses, knobs, grille cloth etc. Circuit diagrams for most Australian makes and models. Send SAE for our catalogue. WANTED - Valves, Radios, etc . purchased for CASH Call in to our Showroom at: 51 Chapel Street, Windsor,Vic 3181 PO Box 1116 Telephone: (03) 529 5639 The book offacts! FERROMAGNEIIC CORPS • Materials • Design • Applications Complete data on over 500 types of Iron Powder and Ferrite cores and assemblies, al l available in Australia! paid from : $1C 5'/'I U. U post STEWART ELECTRONIC COMPONENTS Pty. Ltd. ACN 004 5 18898 P.O. Box 281 Hunt1ngdale 3166 PH (03)543-3733 FAX (03)543-7238 SEPTEMBER1991 85 Silicon Chip BACK COPIES July 1988: Stereo Control Preamplifier, Pt.2; Fitting A Fuel Cut-Off Solenoid; Booster For TV & FM Signals; The Discolight Light Show, Pt.1; Tone Burst Source For Amplifier Headroom Testing; What Is Negative FeedQack, Pt.3; Amplifier Headroom - Is It A Con? August 1988: Building A Plasma Display; Universal Power Supply Board ; Remote Chime/Doorbell; High Performance AC Millivoltmeter, Pt.1; Discolight Light Show, Pt.2; Getting The Most Out Of Nicad Batteries; Data On Insulated Tab Triacs. September 1988: Hands-Free Speakerphone ; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Vader Voice ; Motorola MC34018 Speakerphome IC Data; National Semiconductor LM12 150W Op Amp Data & Applications; What Is Negative Feedback, Pt.4. tomotive Night Safety Light; Adding A Headset To The Speakerphone; How To Quieten The Fan In Your Computer; Screws & Screwdrivers, What You Need To Know; Diesel Electric Locomotives. December 1988: 120W PA Amplifier (With Balanced Inputs), Pt.1 ; Diesel Sound Generator; Car Antenna/Demister Adaptor ; SSB Adaptor For Shortwave Receivers; Electronics & Holden's New V6 Engine; Why Diesel Electrics Killed Off Steam; Index to Volume 1. January 1989: Line Filter For Computers; Ultrasonic Proximity Detector For Cars; Simple Computer Sound Repeater ; 120W PA Amplifier (With Balanced Inputs) Pt.1; How To Service Car Cassette Players; Massive Diesel Electrics In The USA; Marantz LD50 Loudspeakers. October 1988: Stereo FM Transmitter (Uses Rohm BA1404) ; High Performance FM Antenna; Matchbox Crystal Set; Electronic House Number; Converting A CB Ra.dto To The 28MHz Band; Queensland's Powerful Electric Locomotives. February 1989: Transistor Beta Tester; Minstrel 2-30 Loudspeaker System ; LED Flasher For Model Railways (uses LM3909) ; Build A Simple VHF FM Monitor (uses MC3362), Pt.1; Lightning & Electronic Appliances; Using Comparators to Detect & Measure. November 1988: 120W PA Amplifier Module (Uses Mosfets); Poor Man's Plasma Display; Au- March 1989: LED Message Board , Pt.1 ; 32-Band Graphic Equaliser, Pt.1 ; Stereo Compressor For CD Players; Map Reader For Trip Calculations; Amateur VHF FM Monitor, Pt.2; Signetics NE572 Compandor IC Data; Electronics For Everyone Resistors. April 1989: Auxiliary Brake Light Flasher; Electronics For Everyone: What You Need to Know About Capacitors; Telephone Bell Monitor/ Transmitter; 32-Band Graphic Equaliser, Pt.2; LED Message Board, Pt.2. May 1989: Electronic Pools/Lotto Selector; Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference ; LED Message Board, Pt.3; Electronics For Everyone - All About Electrolytic Capacitors. June 1989: Touch-Lamp Dimmer (uses Siemens SLB0586); Passive Loop Antenna For AM Radios; Universal Temperature Controller; Understanding CRO Probes; LED Message Board, Pt.3 ; Coherent CW - A New Low Power Transm ission Technique. Use this handy form to order your back copies r---------------------------------Please send me a back issue for: 0 October 1988 0 November 1988 O March 1989 0 April 1989 O August 1989 0 September 1989 O January 1990 O February 1990 O June 1990 0 July 1990 O November 1990 0 December 1990 0 April 1991 0 May 1991 0 0 0 0 O 0 0 O July 1988 December 1988 May 1989 October 1989 March 1990 August 1990 January 1991 June 1991 0 0 O O 0 0 0 0 August 1988 January 1989 June 1989 November 1989 April 1990 September 1990 February 1991 July 1991 O O 0 0 0 O O O l -__ _ September 1988 February 1989 July 1989 December 1989 May 1990 October 1990 March 1991 August 1991 Enclosed is my cheque/money order for $_ __ ___or please debit my: 0 Bankcard Card No. $5.00 each (includes p&p). Overseas orders add $1 each for postage. NZ orders are sent air mail. Signature _ _ _ _ _ _ _ __ _ _ __ Card expiry date_ _ /_ _ Detach and mail to: SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROY BEACH NSW 2097 Name _ _ _ _ __ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ __ _ Street _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Suburb/town _ _ _ _ _ _ __ ______ Postcode _ _ _ __ _ 0 Visa Card 0 Master Card Or call (02) 979 5644 & quote your credit card details. Fax (02) 979 65o3 X ________________________________________I __ ..__ 86 SILICON CH IP How To Connect Two TV Sets To One VCR ; Introduction To Digital Electronics; Simple 6Metre Amateur Transmitter. December 1990: DC-DC Converter For Car Amplifiers; The Big Escape - A Game Of Skill ; Wiper Pulser For Rear Windows; Versatile 4-Digit Combination Lock; 5W Power Amplifier For The 6Metre Amateur Transmitter; The Green CD Pen Controversy; Index To Volume 3. January 1991: Fast Charger For Nicad Batteries, Pt.1; The Fruit Machine; Two-Tone Alarm Module; Laser Power Supply; LCD Readout For The Capacitance Meter; How Quartz Crystals Work; The Dangers When Servicing Microwave Ovens; Electric Vehicles - The State Of The Art. July 1989: Exhaust Gas Monitor (Uses TGSB 12 Gas Sensor); Extension For The Touch-Lamp Dimmer; Experimental Main_~ Hum Sniffers; Compact Ultrasonic Car Alarm ; NSW 86 Class Electric Locomotives; Facts On The PhaxSwitch - Sharing Your Phone Line With A Fax Machine. August 1989: Build A Baby Tower AT Computer; Studio Series 20-Band Stereo Equaliser, Pt.1 ; Garbage Reminder - A 7-Day Programmable Timer ; Introduction To Stepper Motors; GaAsFet Preamplifier For The 2-Metre Band ; Modern 3Phase Electric Locomotives. September 1989: 2-Chip Portable AM Stereo Radio (Uses MC13024 and TX7376P) Pt.1; AlarmTriggered Telephone Dialler; High Or Low Fluid Level Detector; Simple DTMF Encoder; Studio Series 20-Band Stereo Equaliser, Pt.2 ; Auto-Zero Module for Audio Amplifiers (Uses LMC669); A Guide To Hard Disc Drives. October 1989: Introducing Remote Control ; FM Radio Intercom For Motorbikes (Uses BA1404 & TDA7000) Pt.1; GaAsFet Preamplifier For Amateur TV; 1Mb Printer Buffer; 2-Chip Portable AM Stereo Radio, Pt.2; Installing A Hard Disc In The PC; A Look At Australian Monorails. November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY and Morse) ; Super-Sensitive FM Wireless Microphone; FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Radio , Pt.3; Floppy Disc Drive Formats & Options ; The Pilbara Iron Ore Railways. December 1989: Digital Voice Board (Records , Up To Four Separate Messages) ; UHF Remote Switch ; Balanced Input & Output Stages; Data For The LM831 Low Voltage Amplifier IC; Install A Clock Card In Your PC; Index to Volume 2. January 1990: Service Tips. For Your VCR ; Speeding Up Your PC ; Phone Patch For Radio Amateurs ; High Quality Sine/Square Oscillator; Active Antenna Kit ; The Latest On High Definition TV ; Speed Controller For Ceiling Fans; Designing UHF Transmitter Stages. February 1990: 16-Channel Mixing Desk; High Quality Audio Oscillator, Pt.2; The Incredible Hot Canaries; Random Wire Antenna Tuner For 6 Metres; Phone Patch For Radio Amateurs, Pt.2; PC Program Calculates Great Circle Bearings ; A Look At Computer Interfacing. March 1990: 6/12V Charger For Sealed LeadAcid Batteries ; Delay Unit For Automatic Anten- nas; Workout Timer For Aerobics Classes; 16Channel Mixing Desk, Pt.2 ; Using The UC3906 SLA Battery Charger IC ; The Controls On A Moc:Jel Aircraft. Apri l 1990: Dual Tracking ±50V Power Supply; VOX With Delayed Audio ; Relative Field Strength Meter; 16-Channel Mixing Desk, Pt.3; Simple Service Tips For Your Microwave Oven; Model Aircraft Aerodynamics ; Active CW Filter For Weak Signal Reception. May 1990: Build A 4-Digit Capacitance Meter; High Energy Ignition For Cars With Reluctor Distributors ; The Mazzie CW Transceiver; Waveform Generation Using A PC , Pt.3; 16-Channel Mixing Desk, Pt.4; What To Do When Your Computer Goes Bung, Pt.1. June 1990: Multi-Sector Home Burglar Alarm; Low-Noise Universal Stereo Preamplifier; Load Protection Switch For Power Supplies ; A Speed Alarm For Your Car; Design Factors For Model Aircraft; Fitting A Fax Card To A Computer; What To Do When Your Computer Goes Bung, Pt.2. February 1991 : Synthesised Stereo AM Tuner, Pt.1 ; Three Inverters For Fluorescent Lights; LowCost Sinewave Oscillator; Fast Charger For Nicad Batteries, Pt.2; How To Design Amplifier Output Stages; Tasmania's Hydroelectric Power System . March 1991: Remote Controller For Garage Doors, Pt.1 ; Transistor Beta Tester Mk.2; Synthesised AM Stereo Tuner, Pt.2; Multi-Purpose 1/0 Board For PC-Compatibles ; Universal Wideband RF Preamplifier For Amateurs & TV; A Look At Config ,Sys & Ansi.Sys ; High-Voltage DC Transmission Systems. April 1991: Steam Sound Simulator For Model Railroads; Simple 12/ 24V Light Chaser ; Remote Controller For Garage Doors, Pt.2; Synthesised AM Stereo Tuner, Pt.3; A Practical Approach To Amplifier Design, Pt.2; The Easytune FSK Indicator For HF Transmissions ; Playing With the Ansi.Sys File. May 1991: Build A DTMF Decoder; 13.5V 25A Power Supply For Transceivers; Stereo Audio Expander; Fluorescent Light Simulator For Model Railways; How To Install Multiple TV Outlets, Pt.1; Motors For Electric Vehicles; High -Power DC Transmission Lines. July 1990: Digital Sine/Square Generator, Pt.1 (Covers 0-500kHz); Burglar Alarm Keypad & Combination Lock ; Simple Electronic Die; Low-Cost Dual Power Supply; Inside A Coal Burning Power Station ; What To Do When Your Computer Goes Bung, Pt.3; Weather Fax Frequencies. June 1991: A Corner Reflector Antenna For UHF TV; Four-Channel Lighting Desk, Pt.1; 13.5V 25A Power Supply For Transceivers; Active Filter For CW Reception; Electric Vehicle Transmission Options; Tuning In To Satellite TV , Pt.1. August 1990: High Stability UHF Remote Transmitter; Universal Safety Timer For Mains Appliances (9 Minutes) ; Horace The Electronic Cricket; Digital Sine/Square Wave Generator, Pt.2 ; The Tube Vs. The Microchip (Two Shortwave Receivers Compared); What To Do When Your Computer Goes Bung, Pt.4. July 1991: Battery Discharge Pacer For Electric Vehicles; CD Error Analyser, Pt.1; Loudspeaker Protector For Stereo Amplifiers ; Four-Channel Lighting Desk, Pt.2; How To Install Multiple TV Outlets, Pt.2 ; Tuning In To Satellite TV, Pt.2; PEP Monitor For Transceivers ; The Snowy Mountains Hydroelectric Scheme. September 1990: Music On Hold For Your Telephone; Remote Control Extender For VCRs ; Power Supply For Burglar Alarms; Low-Cost 3Digit Counter Module; Voice Mail For Your Com puter; Simple Shortwave Converter For The 2Metre Band ; How To Make Dynamark Labels. August 1991: Build A Digital Tachometer; Masthead Amplifier For TV & FM ; PC Voice Recorder; Error Analyser For CD Players, Pt.2; Tuning In To Satellite TV, Pt.3 ($1000 Satellite Ground Station Reviewed); Installing Windows On Your PC; StepBy-Step Approach To Vintage Radio Repairs . Octo ber 1990 : Low-Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; Surfsound Simulator; DC Offset For DMMs; The Dangers of Polychlorinated Biphenyls; The Bose Lifestyle Music System; Using The NE602 In Home-Brew Converter Circuits. November 1990: Low-Cost Model Train Controller; Battery Powered Laser Pointer; A Really Snazzy Egg Timer ; 1.5V To 9V DC Converter; PLEASE NOTE: All issues from November 1987 to June 1988 are now sold out. All subsequent issues are presently in stock. For readers wanting articles from issues out of print, we can supply photostat copies (or tearsheets) at $5.00 per article, including postage. When supplying photostat articles or back copies , we automatically supply any relevant Notes & Errata at no extra charge. SEPTEMBER19 91 87 The Story Electrical I Left: ever wondered how big the insulators on 330kV lines are? This photo, taken during the construction of the 330kV line from the Murray 1 power station, gives the answer. Most power stations in the Snowy Mountains scheme are underground but the two largest are above ground, at Tumut 3 & Murray 1. Tumut 3 is also used during off-peak times for pumping water for energy storage. Leaving behind the Snowy uplands and Cabramurra (Australia's highest town), the discharge water from the underground power stations plunges downhill to fill Talbingo reservoir w~ich is 544 metres above sea level. Lying in the steep gorges of the upper Tumut river valley, the waters are impounded by Talbingo Dam, the most 88 SILICON CHIP massive structure in the Snowy system. Talbingo Dam is 162 metres high and over 600 metres thick at its base, and contains over 20 million tonnes of earth and rockfill. Its capacity is 921 gigalitres. The function of this reservoir is to provide the water head for Tumut 3 power station, the largest by far in the Snowy scheme. From the darn, water flows via a 945-rnetre long headrace channel to the pressure pipeline inlet structure. This channel, 92 metres deep and up to 190 metres wide, took three years to complete. The headrace channel feeds water into the six pressure pipelines which feed the power station. Each pipeline, 5.56 metres in diameter, is big enough to drive a doubledecker bus through. The pipes were constructed of rolled medium-tensile steel plate up to 30.2mm thick, manufactured in sections and joined by electric welding on-site. Each pipe has to withstand enormous forces in service - the pressure of the 150.9-rnetre head and the inevitable turbulence from the water flowing at up to 189 cubic metres per second. Therefore, the welding of pipe sections was a critically controlled operation. For stress-free welds, the pipes were heated to 66°C and held at that temperature, while electric welding was performed. Imagine, if you will, a tradesman arc welding inside that hot pipe section! But it had to be done at every joint in more than 10,000 tonnes By BRYAN MAHER of Energy, Pt.13 of steel pipe. N0 1 wonder the construction of the six pipelines took 4½ years! Tumut 3 power station Largest by far in the Snowy scheme, the above-ground Tumut 3 power station generates up to 1500 megawatts. The six 250MW alternators were the largest water-driven machines in Australia at the time of installation (between 1968 and 1972). Of the vertical shaft salient-pole type, each rotates ever so quietly at only 187.5 RPM. They have 32 poles and produce 15.4kV which is transformed up to 346kV for statewide transmission. The huge machine hall is 154 metres long and 60 metres high. The alternators are on original ground level, with the Francis type water turbine equipment extending 33 metres below. Two 130/20 tonne capacity overhead travelling cranes, used to construct the machines, are now used only for maintenance operations. For heavy lifts such as on the enormous generator rotors, both 130-tonne hoists are used in tandem using a special lifting beam. Unlike all the other power stations in the Snowy, the tailwater from the Tumut 3 water turbines flows uphill against a small head - 16.5 metres maximum. This water forms Jounama pondage, captured by the small Jounama Dam, a rockfill/ earthfill wall 44 metres high, 5.8km downstream from the power station. Pumped storage The eternal problem in all electricity generating systems is the daily cycle of peak and off-peak loads. Demand in NSW may be as high as 9 gigawatts during winter evening peaks but may fall to as low as 4.4 gigawatts around 4-5am the next morning: Steam-driven generating plants, with their slow thermal stabilisation time, cannot cope with such large variations. Start-up time is usually many, ma:µy hours and it is very difficult and inefficient to have boilers up to temperature, ready for load, but not yet needed. Large modern boilers have a minimum load value and cannot be operated at lower demand. Ideally, the thermal power stations should be used for supplying the constant base load 24 hours per day. The Snowy power stations can then be used at their full capacity only during the large morning and evening peaks. They can be brought on line very quickly, within a few minutes, and then taken off line just as quickly. Water turbines are large machines as this photo of a turbine spiral casing shows. Ten of these 97MW machines are installed in the Murray 1 power station. Water flows through each turbine at a rate of 241 cubic metres/second. SEPTEMBER1991 89 Tumut 3 power station is notable not only because it is the biggest power station in the Snowy scheme but because it also pumps water back up into Talbingo reservoir for use at peak times. It uses six 250MW alternators. Obviously, in dry times, there may be a limit to the amount of water available. We don't want to empty the dams just to supply peak hour electricity demands. To get around that problem, the Snowy scheme uses pump storage. To this end, three of the six machines at Tumut 3 power station are provided with extra equipment. As the cross section diagram shows, the three units at the western end of the station have much longer vertical shafts. In generating mode, the alternator is driven by the 254MW water turbine immediately below it. Further below 90 SILICON CHIP this , at the bottom of the shaft, is a huge centrifugal pump capable of pumping 100 cubic metres of water per second uphill against a 155-metre head. In pumping mode, the alternator is operated as a 250MW synchronous motor, driven by electrical power drawn from the state grid. This is done only during early morning, around 1-4am. In this mode the machine rotates in the same direction and at the same speed as it does when generating. Force pumping Lift pumping with the pump above water is unsatisfactory and severely limited due to cavitation (ie, water vaporising around the pump blades). Force pumping (with the pump below the water supply) is the only solution. It was for this reason that Jounama Pondage was provided. A section diagram of Tumut 3 shows that although it is an outdoor power station, when Jounama Pondage is at full service level (FSL), the alternators and much of the power station are actually lower than the level of the water outside, separated by a thick concrete wall. The sequence to start pumping is an interesting one. It goes as follows: (1) The turbine water inlet valve is opened and water flows down from Talbingo reservoir to drive the turbine and alternator, thus generating full voltage. (2) The alternator is synchronised with the state grid. (3 ) The turbine inlet valve is closed but the machine continues to rotate, the alternator now acting as a motor driven by the state grid. (4) The pump valve is opened and water is pumped from Jounama Pondage back uphill to Talbingo reservoir. Power to drive the machines when they are acting as motors is supplied (via the 330kV state grid) from the thermal power stations located in the Newcastle region. This pumping operation is only undertaken very early in the morning, when the state load is very light. In these dark hours , it is economical to keep the thermal stations running to provide the 750MW pumping power, as large boilers cannot be operated below some minimum load. Thus, the steam turboalternators and boilers at Eraring and Bayswater are kept thermally stabilised, ready for the morning peak which begins around 6am. In effect, electricity is being stored for later use. Snowy/Murray system To find the greatest water head of all hydroelectric plants on the Australian mainland, we must look to the Murray 1 power station. This is part of the southern half of the Snowy scheme - the Snowy-Geehi-Swampy Plains-Murray development. During wet seasons, the Murray 1 and Murray 2 power stations are driven by water caught in the precipi- ,\ TWO 130,'20 TON OVERHEAD TRAVELLING CRANES '- EARTHFILL FOUNDATION - ' EXCAVATION LINE RL 1197 PUMP SCA l f 01 i lf . SECTION ALONG TUMUT 3 POWER STATION RL 1152 Above: this cross-section diagram of Tumut 3 power station shows how three of the alternators double as pump motors. The turbines are immediately below the alternators, while the three centrifugal pumps are right at the bottom. Note that the tailwater from this power station is above the turbine, so that the pumps can operate. tous gorges of the Geehi River catchment. Geehi Dam, a rock/earth wall 91 metres high, impounds 21.1 gigalitres of water 1106 metres above sea level (higher than the Blue Mountains). The overflow spillway for this dam is unusual. A 32 -metre diameter bellmouth opens into an 8.84-metre diameter underground tunnel which passes under the dam wall. On the downstream side, this overflow tunnel exits to open air in a flip bucket which spouts the escaping water upwards to prevent erosion. Snowy-Geehi tunnel Another view ofTumut 3 power station, this time from above the headrace. The high voltage switchyard is in the background. At times , insufficient rain/snow falls on the western side of the ranges but the eastern Snowy River may be running full. In such circumstances, water pumped up from Lake Jindabyne flows via the 14.4km Island Bend-Geehi transmountain tunnel to refill Geehi reservoir. In still dryer periods, water is allowed to flow from the Lake Eucumbene mass storage via the EucumbeneSnowy tunnel to Island Bend; thence under the Great Divide (1000 metres SEPTEMBER 1Y91 91 provided for two pipes but the third was added during construction. These three pipes weigh 13 ,000 tonnes, plus the weight of water inside. At any one moment, those pipelines contain 43,000 tonnes of water rushing downhill at an average velocity of 93km/hour. At a bifurcation before the power station, the three pipelines divide into 10 conduits, each leading into a turbine. The 10 vertical shaft Francis turbines, each driven by water at the rate of 24 tonnes per second, provide a total of 950MW. Murray 2 power station Water is discharged from Murray 1 into the Murray 2 pondage, thence through a tunnel and pipelines to the Murray 2 power station, the last and most western on the Snowy scheme. This Murray 2 pressure tunnel is one of the largest in cross section, 7. 5 metres in diameter, steel reinforced and concrete lined throughout. Four machines, each rated at 137.5 megawatts, produce 17kV to feed the stepup transformers. Interstate electricity This is the Murray 1 power station which has the highest head of any hydroelectric station in Australia. It has 10 vertical shaft Francis turbines which provide a total power output of 950MW. below the mountain peaks above) to Geehi. From Geehi reservoir, water flows westward via the Murray 1 pressure tunnel towards the Murray power stations. The flow of water into and out of Geehi reservoir is controlled by separate valves, immense 7.6 x 3.7-metre bulkhead gates, stoplogs and guard gates. The mind boggles at the immense size of these valves - such is the amount of water used by the Snowy scheme. Murray 1 pressure tunnel The Murray 1 pressure tunnel carries water from Geehi to the heads of 92 SILICON CHIP the Murray 1 pressure pipelines. Steel and concrete lined throughout its 11. 7km length, this 6. 93-metre diameter conduit carries 250,000 litres of water every second! An 8.2-metre diameter vertical surge-relief shaft, 114 metres high, is situated half a kilometre back from the western end of the pressure tunnel. The top of this shaft opens to atmosphere into a 61-metre diameter surge pool situated on the mountainside above. The pressure tunnel leads through valves into the three pressure pipelines running 1.5 kilometres down the mountainside to the Murray 1 power station. The originai design The Murray power stations were designed to supply the first major interstate transfer of synchronous electric power in Australia. The Murray Switching Station is an immense array of 345kV busbars, circuit breakers and protection equipment. From here, the outputs of both Murray power stations are carried by three powerlines to Dederang, where they join the Victorian grid. In addition, 330kV interconnections join the Murray power station to the Upper Tumut and Yass substations. These links allow power to be interchanged between the thermal power stations of NSW near Newcastle and those in Victoria near Yallourn and Morwell. This, the first interstate synchronous interconnection, has since been extended to South Australia. SC .Acknowledgement Grateful acknowledgement and thanks to Libby Langford and the Snowy Mountains Hydroelectric Authority for data, photos and permission to publish. 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. Wants a subwoofer kit I am a person who respects high fidelity sound equipment and would love to see a decent subwoofer kit. With recent technology, subwoofers produce excellent bass response. There is a subwoofer with case for $349.00 at Tandy and other stores but I would like to se'e one as a kit with some guts behind it, say 100 watts. Unfortunately, to get power like that, you are obviously going to need suitably rated speakers. What if you were to design a vented enclosure using Jaycar's new HF1001 10-inch 120 watt subwoofers (Cat. CW2152), plus a 100 watt amplifier with say the subwoofer adaptor kit (Altronics Cat. K-5560) and a loudspeaker protection kit (Altronics Cat. K-5051 $35.00)? I would also like some sort of auto power up/down with delay so that when a signal is first applied the speaker powers up after five seconds and when no signal is present for 30 minutes, it powers down. Problems with the VCR Extender I have constructed the "Remote Control Extender for VCRs" and have a number of problems with it: (1). The "receiver acknowledge" LED flickers except when the room is in total darkness! (2). The Extender will only "extend" the VCR remote signals when the room is at a reasonable light level; ie, if the room is totally dark, the extender will not function (not even the "receiver acknowledge" LED will operate). I have checked the circuit and components. I think they are correct. Any ideas as to why it operates as it does? Maybe I need to adjust some of the filter values. In addition, some sort of Dolby noise reduction circuitry or filters or both to dispose of unwanted hum from the mains or signal source could be added. You might even want to improve one of your earlier amplifiers and add the above. The Altronics Active Subwoofer Project (Cat. K-5000) is a fine example of this but lacks power and you would be afraid to turn up the volume. Have a go at it - I think it would be very popular! (J. E., Blackburn South, Vic). • A subwoofer project is on our list but is still some way off. Noisy AM stereo tuner Recently, I built up the AM Stereo Tuner (Feb-April 1991) and I am now experiencing problems with very noisy reception after alignment. The alignment procedure went well until the IF section was tackled. I found that there is very little change at TP2 when peaking the L3 and L4 IF coils. Much better joy resulted from Can I have a copy of the data and application sheet please? The unit functions at a distance of about two metres in a well lit room but the red LED flickers like crazy all the time, so this tends to swamp the VCR's receiver. (M.A., Melbourne, Vic). • We suspect that the infrared diode is connected in reverse so that it is forward biased rather than reverse biased. Also check that you are using a BPW50 as the infrared diode. A number of kits have been supplied with clear LEDs and these will not work properly. We have been informed that the BPW50 diode is no longer in production. The Siemens BP104 is a suitable replacement. Make sure you obtain the pinout diagram from your retailer when you buy it. adjusting the IF from TP1 rather than TP2. When aligning the RF section, Cl hardly provided any voltage variation at all at the TP1 test point. The L5 adjustment is fine but very touchy with about 2-3° of slug rotation over which this oscillator locks. With the notch filters , I needed to increase the 18kQ resistors in series with VR1 and VR3 to 22kQ in order to get the specified 32.76kQ across the 18kQ resistor and 5kQ and lOkQ VR3 and VR4 trimpots in the left channel, and VR1 and VR2 trimpots in the right channel. Dick Smith Electronics have a note in their kit suggesting that the 4. 7pF capacitor across VC1 may need to be reduced to obtain the final high fre quency test voltage maximum of 8.5V. I found that after alignment, the TP2 voltage was only 7.34V. After all that, the sound quality is lousy so I hope you can tell me what is wrong. Finally, why the preoccupation with rack mount cabinets? They do not match commercially built shelf mount equipment and it is usually necessary to lop off the ends of the panel or put up with the mismatch. (P. S., Nerang, Qld). • Evidently, your tuner is still not aligned correctly otherwise you would not be experiencing noisy reception. However, your letter has prompted us to clarify a few points in the alignment procedure which should help you to solve your problems. First, there is an error in the text under the heading of IF alignment (page 58 of the April 1991 issue). The text should read "To align the IF stages connect the multimeter between TP1 and GND and select the 2V range". The reference to TP2 is wrong. Aligning the IF stages by measuring the TP1 AGC voltage rather than the TPZ varicap tuning voltage should solve a lot of a your problems. Second, when adjusting Cl, be sure that the dip in the AGC at TP1 is not the minimum capacitance point of Cl since this will give a false peaking SEPTEMBER 1991 93 How to dim fluorescent lights to use a "rapid start" tube and a "rapid start" ballast. You cannot dim fluoros in parallel, for the following reasons: (1) you need a separate filament transformer for each tube; (2) each tube will tend to come on or go out at different levels; (3) each tube will have a different brightness characteristic. Because the filaments need to be energised permanently, dimmed fluorescent tubes will tend not to last as long as normal , will use more power and the inductance of the ballast can caus e commutation problems with the dimmer circuitry at low settings (ie, intermittent or random flickering). An ad- I have been told by an electrical contractor that to use a light dimmer successfully on my fluorescent lights I must replace the ballasts with special "dimming ballasts". Is this true or is there some other way around the problem? If so, how about a project/article on the subject? Also, if one of these "dimming ballasts " is used , can your "Touch Lamp Dimmer" then be used to dim the lights? (W. A., Paraburdoo, WA). • As far as we know, there is no such thing as "dimming ballasts" but special d}cuit arrangements are needed to dim fluorescent lamps. Briefly, the lamp DIMMER filaments must be maintained at full 033 1k 250VAC voltage regardless of whether the tube is dimmed or fully alight. This is acRAPID START TUBE complished by usA--0 ing a separate filament transformer which is energised from the full 240V 240VAC AC supply (ie, not RAPID START affected by the dimN-----+-------r mer setting). Th e filament E • transformer must have two separate ditional problem 'is that fluoro low voltage windings w hich can tubes tend to rectify at low brightwithstand the full 240VAC between them (to supply the filaness settings and this also causes flicker. ment at each tend of the tube). An exampl e of a suitable filament You can't use the TouchLight transformer is the HPM FD238 Dimmer because the filaments which is available from electrical would have to be energised perand lighting wholesalers. manently, since there is no on/off Fig.1 shows a typical dimming switch. On the whole, we do not circuit arrangement for a fluores- recommend dimming fluorescent cent lamp but note that you need lamps. • point. To be sure that Cl is peaked correctly, its capacitor plates should at least be partially closed. Note: there are two positions where Cl w ill give the correct setting. If the peaking point cannot be obtained in the correct manner, then the 4. 7pF capacitor across VCl may need to be reduced as indicated in the Dick 94 SILICON CHIP Smith Electronics kit notes. The L5 adjustment is fairly critical but should not present a big problem. With regard to the notch circuits, the 18kQ resistors in series with VRl and VR3 may need to be increased to 22kQ should the respective trimpots be low in value, as you have found (for example, when 4. 7kQ trimp ots are used for VRl and VR3 instead of the 5kQ types specified). We also recommend initially setting VR2 and VR4 fully clockwise. Finally, we use rack mounting cases because they are readily available and affordable. Omitting the midrange control from the mixer I want to use the treble and bass controls of the 16-channel mixer (SILICON CHIP, Feb-May 1990) in the Studio 200 Preamplifier (described in June, July 1988) because I have the required lO0kQ slider pots. Would you please advise how I can eliminate the midrange control to achieve this? (D. G. , Port Douglas, Qld). • All you have to do is leave out the parts associated with the midrange control; ie, 2 x 12kQ, 1 x .0027µF, 1 x .0lµF and the lO0kQ slider pot. The circuit will then work as a conventional bass and treble control. Notes & errata Stereo AM Tuner; Feb-April 1991: some clarification of the alignment procedure has become necessary following a number of letters on this subject. First, there is an error in the text under the heading of IF alignment on page 58 of the April 1991 issue. The text should read: "To align the IF stages , connect the multimeter between TPl and GND and select the 2V range". Second, when adjusting Cl, be sure that the dip in the AGC at TPl is not the minimum capacitance point of Cl since this will indicate a false peaking point. To be sure Cl is peaked correctly, its capacitor plates should at least be partially closed. Note: there are two positions of Cl which will give the correct setting. If the peaking point cannot be obtained in the correct manner, then the 4. 7pF capacitor across VCl may need to be reduced. The 18kQ resistors in series with VRl and VR3 should be increased to 22kQ should the respective trimpots be low in value (eg, when 4.7kQ trimpots are used for VRl and VR3 instead of the 5kQ types specified). We also recommend initially setting VR2 and VR4 fully clockwise as mentioned in the alignment procedure. SC MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. FOR SALE WEATHER FAX programs for IBM XT/ ATs *** "RADFAX2" is a high resolution, shortwave weather fax, Morse & RTTY receiving program. Need& CGA, SSB HF radio & Radfax decoder. Also "RF2HERC", "RF2EGA" & "RF2VGA", same as RADFAX2 but suitable for Hercules, EGA & VGA cards respec tively. $35. *** "SATFAX" 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 5.25-inch or 3.5-inch discs (state which) & include documentation. Add $3 postage. Only from M. Delahunty, 42 Villiers St, New Farm, 4004 Old. Phone (07) 358 2785. 0 MY AUSTRALIAN DESIGNED lowcost super fast Z80 micro-controller development system has gained acceptance already with educational institutions. Pop it on the end of any PC MS-DOS or Z80 machine & away you go. Boards, EPROM & 360Kb disc $76 including postage for a short form kit. Gee, I wish I had this when I was a kid. For more information send a 43c stamp to Don McKenzie, 29 Ellesmere Crescent, Tullamarine 3043. 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. PC VOICE RECORDER SOFTWARE. Project published in SILICON CHIP, August 1991. Plugs into the printer board of any genuine IBM PC/XT/AT/ 386 or compatible. Record up to 20 seconds of sound, save it to disc & replay it in the future. Software only available on 5.25-inch 360Kb disc plus documentation & instructions for $25 plus $3. Talking Clock software also available - turns your computer into a talking timepiece. $15 plus $3 p&p. r-------------------------7 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 a separate sheet of paper & send it with this form & 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. Enclosed is my cheque/money order for $_ _ _ _ or please debit my O Bankcard O Visa Card 0 Master Card I I I I I I I I I iI I I Signature_ _ _ _ _ _ _ _ _ _ _ Card expiry date_ _~/_ __ I I Name _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ I I Street _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ I I Suburb/town _ _ _ _ _ _ _ _ _ _ _ _ Postcode_ _ _ _ __ L _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ JI Card No. (VGA, EGA, CGA, Mono). Send cheque or money order to Darren Yates, PO Box 134, French's Forest, NSW 2086. PROFESSIONAL KITS & products. Amplifiers, power supplies, test equipment, PC driven devices & surplus parts. Send SASE for list to: Al Younger, 5/22 Albert St, Edgecliff, NSW 2027. ULTRASONIC BURGLAR Alarm Kit. See S.C. May 1988. Crystal locked. Can be used as a detector or as a selfstanding alarm. Provision for bonnet/ boot protection, flashing light & backup battery. Easily combined with our UHF remote control. Save 100s of dollars on equivalent commercial alarms. Clearance priced at only $29.90 for the PCB and all parts, except the screw terminals. A pair of ultrasonic transducers is included! Don't miss out. P&P for any one or more kits listed: $5. Oatley Electronics, PO Box 89, Oatley, 2223. Phone (02) 579 4985. SINGLE CHANNEL UHF Remote Control. EA Jan.89 & April 89. Use it to switch car alarms, central locking, activate door openers, etc. Up to 50-metre range. Has separate switch & indicator relays. More than 19,000 code combinations. Features a compact transmitter. Only $49.95 for a complete transmitter kit & the receiver PCB and all on-board components. Extra transmitters are priced at $17 each. P&P for any one or more kits listed: $5. Oatley Electronics, PO Box 89, Oatley, 2223. Phone (02) 579 4985. LASER ASSEMBLY. Not a kit but a complete commercial HeNe visible red laser contained in a small plastic case. Dimensions 160 x 60 x 35mm . 7-14V DC operation at approx. 300mA. Includes a brand new 1mW tube. Very limited quantity at $135 each. P&P $5. Oatley Electronics, PO Box 89, Oatley, 2223. Phone (02) 579 4985. LOW-COST PIR Movement Detector Alarm. EA, May 1989. Now supplied with commercial case. Reliable unit that features a dual element pyroelectric SEPTEMBER 1991 95 ...._ r MEMORY EXPANSION Advertising Index Prices at July 10th 1991 DRAM DIP. ZIP SIMM & SIP SPEED (ns) TYPE 120 100 70 80 4164 2.20 2.35 41256 1.80 2.00 2.20 2.40 41464 2.50 2.75 411000 6.10 7.30 7.90 1MBx4 (Static) 36.00 256K x 9 14.00 20.00 21.00 1MBx9 58.00 68.00 78 .00 4MB x 9 272 .00 299 .00 Simm Sockets 30 x 1 Vertical 1.70 Simm Sockets 30 x 2 Angle 3.50 Simm Sockets 30 x 2 Vertical 3.20 PELHAM \.. INTEL 8087 (fits all 8088's) 80287-10 ' 80287-XLT (laptops) 80287-XL (up to 20MHz) 387SX16 387SX20 387DX16 387DX20 387DX25 387DX33 387DX40 Antique Radio Restorations ....... 96 Av-Comm ... ............ .. .. .... .. ......... . 33 120.00 125.00 160.00 150.00 180.00 188.00 185.00 265.00 265.00 300.00 350.00 Back Issues .......................... 86,87 David Reid Electronics ...... ... IFC, 1 Dick Smith Electronics .... ..... ... 9-11 Electronic Solutions ............. ... ... 69 Electronic Toy Services ...... ....... 96 Elmeasco ... ......................... ....... 77 Geoff Wood Electronics ............. 35 Sales Tax 20%. Overnight Delivery. Credit Cards Welcome 1st Floor, 100 Yarrara Road, Pennant Hills, NSW 2120 . Tel (02) 980 6988 PRINTED CIRCUIT BOARDS Altronics ................................ 24-27 CO-PROCESSORS CYRIX IIT Fax (02) 980 6991 Harbuch Electronics .................. 57 Hycal Instruments ...... ...... .... ...... 96 Jaycar Electronics ................ 45-52 .J FIX-A-KIT $20.00 PER HOUR LABOUR PCBs for all SILICON CHIP projects made to order. Prototype & kit repair service available. Hours 10-5 Wednesday to Friday, 9-12 Saturday. ETS, PO BOX 491, NOARLUNGA CENTRE, SA 5168. Phone: (08) 382 8919 MAX 1/0 Board Kit $149.00. Built & Tested $269.00. • 7 x Relays SPST 2 amps each • 8 x Switch inputs (TTL) • 1 x OAC (Digital to Analog converter) • 1 x ADC ( Analog to Digital converter) • 4 x Motor Drive outputs (40mA ea.) • 1 x Programmable timer output. MAX includes a 20-page manual with all schematics, parts layout etc., a 360K PC-compatible floppy with diagnostic and sample software in GW-Basic. MAX runs from a PC compatible printer port for full compatibility with a large range of computers. Same day dispatch of orders. Credit cards or personal cheques welcome. Phone (08) 332 6513 or Fax (08) 364 0902 (24 hours) PC Computers, 36 Regent St, Kensington, SA. sensor. Optional interface kit enables uses such as self-standing alarms, automatic light control, shop entry detector, etc. Over 1O metres range. Don't miss out at the clearance price of only $29.90 for the PCB & the PIR detector components kit. Interface components kit $9.00. P&P $5. Oatley Electronics, PO Box 89, Oatley, 2223. Phone (02) 579 4985. ANTIQUE RADIO ANTIQUE RADIO restorations. Your one-stop radio repair shop. Specialising in restoring vintage radios including 96 SILICON CHIP J.V. Tuners .... .... .. ....... ...... .. ........ 43 Oatley Electronics .. .... ............... 79 PC Computers .... ..... .................. 96 3 MONTHS WARRANTY ON REPAIRS 12 MONTHS WARRANTY ON CONSTRUCTION PC Marketplace ............ ............. 81 Service to most types of electronic equipment TECHNICAL ASSISTANCE Pelham ... .. ........ ......................... 96 HYCAL ELECTRONICS Design. Manufacture & Repair of Electronic Equipment Trading Hours 8am to 3pm, Monday to Friday (02) 633 5477 Philips Test & Measurement .. OBC RCS Radio .. .. ... ..... .. .. ................ 43 Resurrection Radio .................. .. 85 Rod Irving Electronics .......... 38,39 Silicon Chip Binders ................ IBC Stewart Electronics .................... 85 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. Subscriptions .... ... ...... ........... 53,54 TopCom Radio Comm . .............. 96 Transformer Rewinds ................ 96 PC Boards Printed circuit boards for SILICON CHIP projects are made by: SCANNERS • Electronic Toy Services, 2/111 Glynville Drive, Hackham West, SA 5163. Phone (08) 382 8919. Top quality Uniden, factory authorised dealer. Range from $210.05 for 50XL, covers 10, 6, 2, 70cm , 10 memories, ideal for amateur, to $475.52 for 200XLT, 200ch , covers all major bands, including 800-900MHz. Also the cheapest prices on marine equipment. Update to SSB for $238.26. Fibreglass 27MHz antenna $40.1 3. Post & pack $1 0 under $250. Cash, cheque & credit card accepted . TopCom Radio Communication, PO Box 336, Greensborough, Vic 3088. Phone (03) 883 9535. • RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 587 3491. 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. 1 Oam-5pm; Sun. 12.30-5pm . 109 Cann St, Bass Hill, NSW 2197. Phone (02) 645 3173 BH or (02) 726 1613 AH. SC • Jemal Products, 5 Forge St, Welshpool , WA 6106. Phone (09) 350 5555. • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone 88 5730. SILICON CHIP BINDERS NO * High quality * Holds up to 14 issues * 80mm internal width * Gold printed with SILICON logo on spine and front cover CHIP These beautifully made binders will protect your copies of SILICON CHIP. We are especially pleased with their look and quality. As soon as the first batch came in, everybody on our staff wanted them to store their own personal issues. You wiU too. How To Phone (02) 979 5644 Fax (02) 979 6503 ORDER: Made with a distimctive two tone green high-quality vinyl specially selected for SILICON CHIP, and with heavy board covers, each binder holds a year's issues (the 14 issues of Vol.l or the 12 issues of Vol.2). They will look really smart on your bookshelf. To order your binders, fill in the coupon in this issue and send it to SILICON CHIP, PO Box 139, Collaroy Beach, NSW 2097. Alternatively phone (02) 979 5644 and quote your credit card details, or fax your orders to (02) 979 6503. Price $All.95 plus $A3 each for postage and packing. (NZ postage and packing $A6.)