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Especially For Model Railway Enthusiasts Order Direct From SILICON CHIP Order today by phoning (02) 9979 5644 & quoting your credit card number; or fill in the form below & fax it to (02) 9979 6503; or mail the form to Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. This book has 14 model railway projects for you to build, including pulse power throttle controllers, a level crossing detector with matching lights & sound effects, & diesel sound & steam sound simulators. If you are a model railway enthusiast, then this collection of projects from SILICON CHIP is a must. Price: $7.95 plus $3 p&p Yes! Please send me _______ copies of 14 Model Railway Projects Enclosed is my cheque/money order for $­_________ or please debit my  Bankcard    Visa Card    Master Card Card No. Signature­­­­­­­­­­­­_________________________ Card expiry date_____/_____ Name _________________________Phone No (____)_____________ PLEASE PRINT Street ___________________________________________________ Suburb/town __________________________ Postcode____________ Vol.8, No.1; January 1995 FEATURES FEATURES   6 The Latest Trends In Car Sound by Julian Edgar It just depends on your budget THE OLD PUSHBUTTON radio driving two dual-cone speakers has been left way behind by the latest car sound gear. Our feature starting on page 6 looks at the latest trends. 53 Volkswagen’s Golf Ecomatic by Julian Edgar A new meaning for stop/start driving PROJECTS PROJECTS TO TO BUILD BUILD 14 Build A Sun Tracker For Solar Panels by Nenad Stojadinovic Increases solar panel output by 30% or more 24 Simple Battery Saver For Torches by Marque Crozman It turns the torch off when you are not using it 32 Dolby Pro-Logic Surround Sound Decoder; Pt.2 by John Clarke The full construction details 56 A Dual Channel UHF Remote Control by Bernie Gilchrist Use it to control alarms & other devices 65 Build A Stereo Microphone Preamplifier by Darren Yates Simple circuit provides 10dB of gain THE ADDITION OF A SOLAR tracker to control a rotating frame can increase the overall energy output of a solar panel by 30% or more. This design can be used to control any size panel – see page 14 SPECIAL SPECIAL COLUMNS COLUMNS 40 Serviceman’s Log by the TV Serviceman Symptoms don’t seem to help much any more 62 Computer Bits by Darren Yates A low-cost emulator for Zilog’s Z8 microcontroller 72 Remote Control by Bob Young Working with surface mount components 78 Vintage Radio by John Hill Basic tools & test equipment 82 Amateur Radio by Garry Cratt Wideband preamplifier has response to 950MHz DEPARTMENTS DEPARTMENTS   2 4 22 71 85 Publisher’s Letter Mailbag Circuit Notebook Book Reviews Order Form 86 92 94 96 Product Showcase Ask Silicon Chip Market Centre Advertising Index THIS UHF REMOTE control can switch two devices independently of each other. It comes with a ready-made transmitter & is just the shot for controlling burglar alarms. Details page 56 IY YOUR DYNAMIC microphones don’t have enough output, try this portable stereo mic preamp. It has low noise & distortion, runs off two 9V batteries & is built into a rugged diecast case – see page 65. January 1995  1 Publisher & Editor-in-Chief Leo Simpson, B.Bus. Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Reader Services Ann Jenkinson Advertising Enquiries Leo Simpson Phone (02) 979 5644 Regular Contributors Brendan Akhurst Garry Cratt, VK2YBX Marque Crozman, VK2ZLZ John Hill Jim Lawler, MTETIA Bryan Maher, M.E., B.Sc. Philip Watson, MIREE, VK2ZPW Jim Yalden, VK2YGY Bob Young Photography Stuart Bryce SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd. A.C.N. 003 205 490. All material copyright ©. No part of this publication may be reproduced without the written consent of the publisher. Printing: Macquarie Print, Dubbo, NSW. Distribution: Network Distribution Company. Subscription rates: $49 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 34, 1-3 Jubilee Avenue, Warrie­ wood, NSW 2102. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 979 5644. Fax (02) 979 6503. ISSN 1030-2662 PUBLISHER'S LETTER Loud car stereos are a menace Not so long ago, the loudest vehicles on the road were trucks, buses and the occasional large motorbike. But now there are vehicles which challenge them for the title and they can often be quite small, such as Daihatsu Charades and Holden Barinas. The reason these and other cars are so noisy has nothing to do with their engines and everything to do with their sound systems. By now, most people will have experienced the noise of these machines. It is most unpleasant. For example, you may be sitting at the lights or stuck in bumper-to-bumper traffic when suddenly you will be immersed inside a giant drum which is being beaten mercilessly Boomp Boomp Boomp... You immediately say "What the (expletive deleted)!" and check your windows to see that they are wound up tight. If you are lucky, the cretin will move on and relative peace will reign again. Or perhaps you have been sound asleep at night and have been woken by an almighty tribal drum pounding out a primitive rhythm which then thankfully passes by - you don't hear the car, just the sound of the drum. You softly mutter an incantation, hoping that the driver soon meets his destiny and then try to go back to sleep. Now I am not against people spending money on good sound systems for their cars. If I was, this month's article on car sound systems would not appear. But clearly, immensely powerful car sound systems have become the latest toy of some anti-social, inconsiderate and straight-out stupid motorists. Sooner or later, these people will become the target of police, just as people in hot cars, on motorbikes or those with CB gear used to be. It wasn't that the gear that these people were using was bad in itself, it was just that some of them were anti-social. I and many other people object stenuously to loud car stereos. It is stressful enough to drive in today's fast and heavy traffic without being subjected to that sort of noise. Nor do I believe that anyone driving with that level of noise in their car could possibly be driving safely – it is bad as being affected by drugs or alcohol. And the damage to these persons' hearing doesn't bear thinking about. Sooner or later governments will get around to legislating against this sort of behaviour. When they do, it might be a blanket prohibition against car stereos above a certain power, or a certain number of knobs or something equally arbitrary. Or maybe they will confiscate the equipment after the first warning. Now that I could agree with! So if you are one of these people who like to turn up the wick so everyone within 500 metres can hear your taste in music, please cool it. You will be doing everyone, and yourself, a big favour. Leo Simpson WARNING! SILICON CHIP magazine regularly describes projects which employ a mains power supply or produce high voltage. All such projects should be considered dangerous or even lethal if not used safely. Readers are warned that high voltage wiring should be carried out according to the instructions in the articles. When working on these projects use extreme care to ensure that you do not accidentally come into contact with mains AC voltages or high voltage DC. If you are not confident about working with projects employing mains voltages or other high voltages, you are advised not to attempt work on them. Silicon Chip Publications Pty Ltd disclaims any liability for damages should anyone be killed or injured while working on a project or circuit described in any issue of SILICON CHIP magazine. Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. SILICON CHIP also disclaims any liability for projects which are used in such a way as to infringe relevant government regulations and by-laws. Advertisers are warned that they are responsible for the content of all advertisements and that they must conform to the Trade Practices Act 1974 or as subsequently amended and to any governmental regulations which are applicable. 2  Silicon Chip MAILBAG Feedback on making PC boards I liked John Clarke’s article on “How to Plot Patterns Directly to PC Boards” in the November issue. I picked up a minor point concerning the caption to the photograph on page 82. It mentions the use of Ajax® and steel wool for cleaning the blank board. Many years ago, Doug Rees of Circuit Components told me I should use Ajax and not steel wool. I have found Ajax to be the only satisfactory commercially available cleaning compound. Steel wool is not as good as using a stainless steel pot scourer, or better still, as Doug recommended, one of the non metallic pot scouring mitts, such as 3M Scotch Brite® (use rough side if a double sided mitt). Steel wool always gave me a 1020% reject rate, mostly because the resist lacquer did not stick to the copper surface properly. I believe that this is because the Ajax® solution provides a medium for electrolysis between the copper of the board and the iron of the steel wool, leaving copper or iron salts behind which do not seem to wash off. Also Doug pointed out that steel wool is coated with a very fine oil so that it will resist rusting until used. This oil may be left behind on the copper. I felt an affinity with your “Publisher’s Letter” about spectacles. I use them too, with several different magnifications on hand for different tasks, using a headband loupe at 4X for tiny work. I have spoken to an ophthalmic surgeon about them. He said they are OK if your eyes are equal and you have no astigma­tism. If the specs give you headaches, make you feel nauseous, or giddy, you should consult a specialist. Interestingly, ophthalmic shops will sell headbands but not specs. Bob Nicol, Microzed Computers, Armidale, NSW. Tape dropout mystery unravelled I refer to the mysterious problem with dropouts on compact cassettes mentioned in the Mailbag pages in the June 1994 issue. You will be pleased to hear that I have found the 4  Silicon Chip explanation and in fact it turns out to be a “flaw” in the system of cassette manufacture. As you may recall, the problem was if you record a new cassette straight out of the wrapper there are no dropouts of audio. If you fast-forward that same tape to the other end then record for up to the first five minutes you can and do get drop­outs. After that tape has been used for some time the problem is at both ends. The cause of the problem lies in the method used to clamp the tape to the inner hub reels. The way it is done is to use a plastic insert to clamp the tape between itself and the hub. The result is that the tape forms a bump which, under the pressure of being wound or rewound, leaves a periodic indentation through the layers of the tape. These bumps in the tape cause loss of head contact and thus a dropout. Because a new tape has not been wound over one of these clamps the beginning of a new tape has none of these creases, and hence performs OK. Thinner LP tapes exhibit the problem more than thicker base tapes. To prove my theory, I removed the tape from the clamp, discarded all defective tape then used some cassette splicing tape at both ends to secure the tape in place. I have made a large number of tests over the last three weeks without any dropouts. My case rests. Do we call this syndrome the clamp cramp? G. Dicker, Kensington, SA. Comment on bogus SIMMS Regarding your recent article, entitled “The Great RAM Scam of 1994”, I am trying to determine if this was written in sincer­ity or “tongue-in-cheek”. The reason I ask is who really gives a damn? I don’t mean to be sarcastic but my experience over the last 10 years has been as follows: (a) Yes, the IBM was equipped with memory parity checking and if it detects a parity error it locks up and reports, rather clever­ly, PARITY ERROR! This is really not much better than having the machine lock up as it probably would anyway because the SILICON CHIP, PO Box 139, Collaroy, NSW 2097. last opcode fetched put it into hyper-­ space or in an infinite loop. (b) As a general rule, we have found that nasty memory chips have been around for a long time prior to the birth of parity-less SIMMS. As a supplier of PCs for small office networks, we run all new machines for 48 hours straight and have found that a number of early PC problems are definitely RAM related. Our experience has shown that these problems can usually be remedied by RAM replacement and, more often than not, are not reported by the parity checking. (c) Parity checking, by today’s standards, is akin to determining that a person is a witch because they float. It would be happy days if more common problems such as general protection failures from Windows caused less headaches than the Parity Error Checker. (d) Virtually ALL wholesale outlets that we purchase machines from advertise the fact that two different style SIMMS are avail­able (ie, with and without parity). As a supplier and system supporter, it is definitely not in our interest to supply ma­chines where there is a shadow of doubt that mem­ory may cause a problem. (Your referenced supplier Pelham also supplies both types and states that fact). (e) Our rule-of-thumb has always been BUY THE GOOD RAM which generally means purchasing RAM which is speced to the faster speed although I am not certain that the extra bit (parity) is worth the additional cost (ie, we could have machines which have eight extra bits of Checksum or CRC for each byte if it was deemed so necessary). (f) Error checking of any sort required on the RAM component of ANY PC must cast aspersions on the design philosophy relating to the dynamic RAM architecture of that particular computer. After the brickbats, a bouquet is due: an enjoyable and informative magazine. I have been a reader since its inception but until today, not an active contributor. W. Maier, Manager, Scorpia Design, Northgate, Qld. Printing PC patterns on a laser printer Your article on plotting PC boards in the November 1994 issue follows the same problems that I had with the black areas not being black enough, until I started to use a shareware pro­ gram called Print GL. This enables the laser printout to be reversed. Any circuit board program must be output in the same HPGL format you are using to the Print GL program and then printed to the transparency. I have found the type of transparency called Celcast LP100 to work well. This means the lack of complete darkness has less effect but the quality control has to be exact, so I have used the Riston board. The Print-GL program only reverses on a laser printer and many types of printer drivers are included in the program. The problem of warping boards, while being under the ultra­violet was corrected by using two 6mm sheets of plate glass, clamping the negative and board together so they could be more easily turned over when doing double sided boards, which is what I have mainly done. A book called “Making Printed Circuit Boards” by Jan Axel­son (ISBN 0-8306-3951-9) makes two comments of interest: (1) The voids on page 152 (holes in the tracks) which with negative resist become marks on the non-copper areas; (2) The use of Graphics toner cartridge for the laser printer. I have enclosed two transparencies of a board I did for controlling the UHF Repeater system in the Auckland District, using the ISD90 voice chip controlled by an 1802 microprocessor. These transparencies gave me good quality circuit boards but the timing and cleanliness have to be exact. Regarding the odd comment on battery charging that has been mentioned over the last twelve months: none of the charging voltages can be taken as right unless the temperature of the lead acid car type battery is taken into account. Trade experience of the following case proved this in a very positive way. A 24V truck had four 6V batteries, mounted under the tray in a rack off the chassis with the long side of one battery to the front of the vehicle, thus getting cold air direct onto it. This truck did an overnight run of approximately 450km and each morning the front battery was flat and the other three batteries fully charged. Each day the front flat battery was removed and recharged and before being refitted, all the other three batteries were moved forward by one position. Next night, the same thing – front battery flat. This fault of the colder battery not accepting the charge was fixed with insulation in front of the front battery. In most cases of car battery failure, the cell which re­ceives the most heat in the car engine area will fail first. This is most common where the charging regulator does not receive the same heat as the battery; eg, boats, trucks, etc. If in a stable situation like a solar charging system, first set the battery in a position where its heat will be as constant as possible. Dig it into the ground if you have to and alter the location of the solar regulator to obtain the full charge of the battery. Heating up the regulator will usually drop the charge rate if it is temperature compensated and placing the regulator in a colder place than the battery, the reverse. A good guide to maintaining a lead acid battery on a trickle charge for a long period of time is 1mA for every amp/hr at the 20-hour rate; eg, the average car battery of, say, 50A/hr at the 20-hour rate would, if in reasonable condition, stay charged with a trickle charge of approximately 50 milliamps. This is roughly equal to the self-discharge rate. M. Passau, Papakura, NZ. Comment: we have used Celcast LP­100 transparency material and have used both a laser printer and photocopier for our boards. Some come out well, comparable to your patterns, and some come out poorly and have to be done again. Why do valve amplifiers sound different? About 15 years ago, some academic at the Physics Department of the University in Helsinki published a paper with the above title. I can’t recall his name but it sounded as if this gentle­ man was Japanese. I read his paper in Germany, where I was in­volved in sound production. Apparently, he was determined to find an answer to the argument and started by investigating the human ear. What he found was that the human ear distinguishes instru­ments at the first few milliseconds of rise time. This gave him a handle to look at the electronics side and compare the risetime processing. He found, of course, a great deal of difference. His argument was that any leading edge must be processed without any distortion. This, of course, is a tall task as every­body knows. He called this the “TIM” effect ( for transient intermodu­lation). Valves have a soft input; ie, high impedance and, there­fore, require low coupling capacitors. Transistors, on the other hand, have a low impedance and need to be pushed with current. The time constant for a feedback loop is as different as using a hammer against the tickle of a feather. In the real world, sound has a relatively slow rise time. This is complemented by valve amplification, which does not overshoot. Transistor and operational circuits, however, create with their infinite gain at the first microsecond or so quite a handful of unwanted harmonics. If those harmonics are present, they sit right at the leading edge and there is no way of remov­ing them. Therefore, a circuit has to have provision to prevent any overshoot. This is not a problem today. We are now using extremely well designed circuit layouts in comparison to 15 years ago. However, one should beware any amplifier that has a large bandwidth. Anything more than 20kHz is not a benefit; it may only sound hard. Professional equipment has a roll-off at 15kHz. The paper also provided a theoretical description of a test pulse, suitable for the testing of amplifier stages: a squarewave modulated with a sine­ wave. The sinewave has three times the fre­quency of the squarewave and is 12dB down. I hope I haven’t opened another Pandora’s Box. W. Melchhart, Westmeadows, Vic. Comment: we well remember the paper on transient intermodulation by Matti Otala. It caused quite a stir at the time but while valve amplifiers usually do not suffer from TIM (they don’t have enough feedback) they don’t necessarily sound better, just dif­ferent, as you say. January 1995  5 The latest trends in Car Sound Car sound has come out of the dark ages during the last few years & a staggering range of new gear is now available to the enthusiast. It just depends on your budget. Pt.1 by JULIAN EDGAR Car sound systems have undergone a revolution in the last few years. The use of high quality compact discs has meant that amplifiers, speakers and other in-car components have become vastly more sophisticated to take full advantage of the digital sound source. Some manufacturers, such as Ford and Mazda, are now fitting subwoofers and powerful amplifiers in their topline cars. And in the aftermarket area, enthusiasts are squeezing in 15-inch sub-woofers, active crossovers and as many as three dual-channel amplifiers in their search for the ultimate sound. Competitions pitting enthusiast’s car sound systems against each other are 6  Silicon Chip being held around Australia. In short, the old manual pushbutton radio powering two dual-cone speakers screwed into the door trims has been left a long way behind. Front-end systems While the formerly ubiquitous AM/ FM radio-cassette unit has remained popular, CD players now dominate premium systems. CD changers which feature provision for six, 10 or even 12 CDs, are mounted in the boot, under a seat or in the glovebox, and allow the playing of up to 12 hours of music. A controller is normally integrated into the dash-mounted radio-cassette head-piece or the changer can use a separate remote control. The performance and ease of use of multi-CD systems has made it impossible for cassette players to compete. The Philips DC082 changer, for example, features a response of 5Hz - 20kHz ±1dB, total harmonic distortion (THD) of 0.03% at 1kHz, and a signal-to-noise ratio of 95dB. The Alpine 5952Z has even better specifications, with a THD of only .0008% (1kHz). CD players incorporated into a dash-mounted unit are also available, most capable of playing only one CD at a time. Howev­ er, Alpine’s dashmount­ed CD player will accept three CDs which are loaded into a magazine before being inserted into the unit. Of course cassette-based systems are still available. The Alpine 7620E, for example, has a claimed frequency response of 20Hz - 20kHz with metal tape, although no deviation figure is attached. Signal to noise ratio is up to 75dB with Dolby C and wow and flutter is just 0.06%. Most of these top-line units have an inbuilt amplifier, although the Alpine unit mentioned above is designed to be used with a separate amplifier and so has only line-level RCA outputs. Kenwood’s “cassette receiver” includes a 25W x 4-channel amplifi­er, while the Philips DC521 unit has a 12W x 4-channel amplifier. Signal processing It’s immediately following the signal source that some of the more recent innovations in car sound technology can be seen. Chief among the units positioned in the path between the signal source and the amplifier are equalisers and digital signal pro­ cessors (DSPs). Included in the range of sophisticated parametric equalis­ ers now available is the EQQ unit from Audio Control. This features full equalisation controls for both the front and rear speakers. All four channels can be individually equalised by seven bands of control and the unit also provides half-octave bass equalisation at 31.5Hz, 45Hz, 63Hz, 90Hz, 125Hz and 180Hz. Also included in the package are individual level adjustments for each stereo input and an 18dB/octave subsonic filter. DSP units can be used to provide surround sound, parametric graphic equalisation, listening position selection, and distinct­ ly different music environments. The equalisation system employed by the Pioneer unit, for example, allows one-third octave equali­sation and the unit can move the apparent focus of the music around the inside of the car by using audio delay techniques. The acoustics of five listening environments ranging from a studio to a stadium can also be re­ created and the effect is quite uncanny. Another interesting item is the Audio Control Epicenter, a device for those who like gut-wrenching bass. This unit searches for low frequency harmonic artifacts in the recording and then digitally restores the underlying fundamental which may have been lost through poor recording techniques. A control knob allows the effect to be tailored to your taste. A 36dB/octave subsonic filter is includ­ ed in the device. The unit produces extreme bass but it sounds quite different to the normal effects of bass boost, being much more natural. Amplifiers The boot was the only place in this car with sufficient room & ventilation for this Coustic 45W RMS x 4-channel amplifier. The amplifier is mounted on a hinged carpeted panel which can be swung out to give access to the car’s jack which is located in a recess behind it. This photo was taken during the installation process, with the wiring later tidied away. This end view of the Coustic amplifier clearly shows the RCA sockets for the left & right line-level inputs. A third set of RCS sockets provide a single mixed output with variable output level. Also located on this end panel are the variable high & low pass filter controls, the “peak” indicator LEDs, & the bass & treble boost switches. The “parallel” switch allows the input to the front channel to be internally fed to the back channel as well. CD changers, such as this Kenwood unit, can be mounted in the boot as shown here or under a seat inside the car. They provide good sound quality specifications, with some units ac­cepting up to 12 discs to provide 12 hours of music. Using (or having available) high January 1995  7 These Jaycar Super Tweeters can be mounted on the door sail panels (the triangular part of the door behind the wing mirrors). This location gives good stereo imaging. The rear deck of this demonstration car uses a new moulded fibre­glass parcel shelf. The mid-bass, midrange and treble drivers are located here. On one side, the speaker grilles are all in place while on the other side the grilles have been removed to show the individual loudspeakers. sound pressure levels (SPLs) is now the norm, with some systems capable of generating SPLs of over 125dB(A). Even those people who don’t want to suffer hearing damage specify high-power amplifiers to overcome road and wind noise and to achieve reasonable output levels from small, inefficient speakers. Multi-channel amplifiers are generally used, with some amplifiers featuring three stereo pairs. A 6-channel amplifier, for example, could be used in the following way: two channels driving front mid-bass speakers and tweeters, two channels driv­ing rear 2-way split or coaxial systems (typically 6 x 9-inch or 6-inch), and two channels driving twin subwoofers. A typical car amplifier of this sort is the Coustic AMP-660. It features a power output of 50W RMS x 6, with a maximum THD of 0.09%, a frequency response of 10Hz - 50kHz, and an A-weighted signal-to-noise ratio of better than 95dB. Maximum input current is a staggering 70A! For this system, you would be wise to significantly upgrade your car’s battery and alternator or use a separate battery and alternator to power the amplifier. The cost of quality amplifiers can be quite low, with a 4 x 45W amplifier boasting specifications similar to that quoted above retailing for around $500. A sophisticated equaliser has been fitted to the glovebox lid of this car. It might look impressive but glovebox utility is sub­stantially reduced! 8  Silicon Chip The trend in car amplifiers is towards multiple speakers in each channel being driven by a single high-current amplifier. Car speakers typically have an impedance of four ohms and so a series/parallel wiring arrangement can be used to allow a large number of speakers to be driven. In fact, many modern amplifiers are capable of working into speaker loads as low as two ohms. There are obviously problems in fading the levels from front to rear if the speakers on the left or right are driven from just one amplifier channel, though. Loudspeakers When it comes to loudspeakers, all top-line car audio systems use a mixture of tweeters, midrange drivers and woofers. The tweeters can be mounted on the A-pillars, within the dashboard, on the sails (the triangular areas on the doors where the mirrors mount), or even in the dashboard air vents. The directional nature of high audio frequencies means that tweeter positioning is critical in obtaining good staging effects. The front doors can obviously be used for speaker en­closures and this space is frequently used for midrange speak­ ers. This can involve fitting new inner door trims and these can be constructed of medium density fibreboard (MDF), or more re­cently be moulded from fibreglass. Once made, the new panel is covered in velour or cloth so that it matches the rest of the car’s interior. If the car is a traditional “threebox” sedan, the rear deck is generally used to mount 6 x 9-inch, 7 x 10-inch, 6-inch or 8-inch speakers. These can be coaxial types or two- or three-way designs, or can use separate drivers for the bass, midrange and treble. Of A standard dashboard speaker location (under the grille) can be used to house a midrange speaker or tweeter if you decide to upgrade to a high-quality system. The original loudspeaker that was used in this location is discarded. All is not what it seems here. While the top-of-the-line Kenwood KDC-9100 CD receiver is obvious, what isn’t so clear is the function of the cigarette lighter. It controls a hidden Epicenter bass accentuator. Pulling on the knob switches the device on, while rotating it controls the amount of bass. these, the three-way 6 x 9-inch loudspeakers are the most commonly used in this location. Cars that don’t have a suitable separate boot volume present greater problems when it comes to rear speaker placement. Common in hatchbacks is the replacement of the luggage cover with a strongly-braced MDF substitute, with the speakers mounted on that. Station wagons and other cars in which there is no other option sometimes use tube-mounted woofers, with the carpeted tube placed laterally or longitudinally within the cabin. SC This Earthquake 12-inch subwoofer is typical of some of the speakers now being squeezed into cars. It has a power handling capability of 300W RMS. This door has had a new fibreglass inner panel made to incorpo­rate new loudspeakers. They are located behind the grille cloth in the lower lefthand corner of the door. With the grille panel on, the door looks like this . . . . . . and with the grille panel removed, it looks like this. In this particular case, a 6-inch (150mm) mid-bass driver has been fitted, along with a separate tweeter to provide good quality sound. January 1995  9 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: dicksmith.com.au Build a Sun Tracker for Solar Panels The addition of a solar tracker to control a rotating frame can increase the daily energy output of a solar panel by 30% or more. This tracker frame is built around a 60W panel supplied by Dick Smith Electronics. 14  Silicon Chip This simple design will increase the daily output of your solar panels by around 30% or more. It was designed to suit a 12V 60W panel but it can be used without circuit modifications to control any size panel. By NENAD STOJADINOVIC Imagine the scene: an alternative energy expo with all sorts of nifty gadgets to make one’s life away from the power companies just a little easier. As I wander around, I can’t help noticing the large numbers of solar panels bolted immovably to their stands. “Surely they would deliver more power if they followed the Sun around?”, I ask. “Yes they would,” they answer, “but solar trackers are expensive items”. I checked around and let me tell you, they are not kidding. Everyone complains about the weather but nobody does any­ thing about it. Thinking these sage thoughts, I sat down at my desk and came up with a circuit that eventually evolved into the design you see before you. Tracker fundamentals When a solar panel is aimed directly at the Sun its output is at a maximum but for a fixed panel this only happens for a short time each day; before and after that the output drops off markedly. Ideally, the complete tracker would follow the Sun in both altitude and azimuth but that means two motor drive circuits would be required. It is more practical to just track from east to west (ie, altitude) and have a fixed azimuth which can be changed manually from time to time to account for the changing position of the Sun from summer to winter. Most pub- lished designs use this approach and this one is no exception. Not only should a tracker follow the Sun from east to west but at the end of each day the panel should be swung back to the east so that it faces the sunrise next day. Most published designs that we have seen do not do this. Apart from that, the tracker should incorporate limit switches so that the panel is not driven against the stops if a fault occurs. Finally, the tracker should only run intermittently, swinging the panel by just a few degrees from time to time and then consume very little power at other times. The circuit The design is based on an LM324 quad op amp where IC1a and IC1b are configured as a “window” comparator. A window comparator works on the principle that when the input to the two comparators is at the desired level, the output of both will be low Fig.1: the circuit is essentially a “window” comparator involving IC1a & IC1b. Whenever a shadow falls across LDR2, the output of IC1a goes high & the motor drives the panel westward until both LDRs are once again fully sunlit. +12V R1 10k 0V RE 4.7k LDR1 EAST ORP12 VR1 5k IC1a 3  1 D3 1N914 R8 VR2 10k 9 LDR3 ORP12  10 6 4 IC1c LM324 8 2 C1 4.7 11 3 LDR2 WEST 1 ORP12  IC1b E B VIEWED FROM BELOW C R9 D4 1N914 100k G D S D Q3 G S M 7 RM 2. 7  5W C2 0.1 D1 1N914 6 R2 10k C R5 100k D2 1N914 +4.8V 5 E 2xMTP3055 S 14 IC1d 13 RW 4.7k B D 12 8 IC2 555 Q2 G R7 22k A 7 R3 1k B 100k R10 1M Q1 S1 BC548 HG C E WEST +7.1V 2 S2 HG EAST R4 1k R6 100k Q4 D G S 2xMTP3055 D Q5 G S SOLAR TRACKER January 1995  15 Fig.2: the PC board is straightforward to assemble. Note that mercury switches S1 & S2 must be angled to set the limits on panel rotation, as detailed in setting-up procedure. Take care with component orientation. SHIELD LDR2 LDR2 S1 Q1 10k 4.7k 100k 1k D3 22k G D S VR2 LDR3 D1 D2 Q3 12V 0.1 1M 1 D4 G D S 2. 7  5W IC2 555 10k 100k IC1 LM324 VR1 Q2 1k 4.7uF G D S Q4 100k 4.7k 100k G D S Q5 S2 MOTOR The PC board has a blackened cardboard light shield placed between LDR1 & LDR2. Note that the mercury switches are fairly fragile & will break if roughly handled. Warning: do not handle mercury ­it is poisonous. (off). In this case the input voltage at point A (pins 3 & 6) is to remain between the upper and lower trigger voltages of say, 7.1V and 4.8V, re- spectively. If the voltage at pin 3 rises above 7.1V, the output of IC1a jumps to around 10.7V (on). Similarly, if the voltage on pin 6 falls to below 4.8V, the output of IC1b jumps to 10.7V (also on). Why a window comparator? Why not a simple feedback device? The answer lies in the zone of non-operation while the input voltage is in the window – the so called “dead zone”. A propor­ tional device will attempt to follow the Sun exactly and conse­quently the motor will always be either running or on the verge of running. The input voltage signal for both comparators is provided by two light dependent resistors, LDR1(E) and LDR2(W), connected in a resistive divider configuration. It can be seen that when equal sunlight falls on both LDRs they will have (roughly) equal resistances and the supply voltage will be dropped in two equal increments, leaving point A somewhere around +6V. We will pretend that RE and RW are not there for the moment. As the Sun moves west, the cardboard divider panel between the two LDRs throws a shadow onto LDR2(W), causing its resistance to rise, and so the RESISTOR COLOUR CODES ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ No. 1 4 1 2 2 2 1 16  Silicon Chip Value 1MΩ 100kΩ 22kΩ 10kΩ 4.7kΩ 1kΩ 2.7Ω 5W 4-Band Code (1%) brown black green brown brown black yellow brown red red orange brown brown black orange brown yellow violet red brown brown black red brown not applicable 5-Band Code (1%) brown black black yellow brown brown black black orange brown red red black red brown brown black black red brown yellow violet black brown brown brown black black brown brown not applicable voltage at point A rises correspondingly. As soon as this voltage rises above +7.1V, IC1a switches on and drives the panel motor westward. LDR1E and IC1b together are there to drive the panel east­ward. Normally this function is not used since the Sun does not travel east, but is provided in case of whoopsies such as the family dog crashing into the panel. If the panel is moved too far west, a shadow falls on LDR1 and this causes point A to fall below +4.8V. This causes IC1b to switch on and drive the panel east until normal conditions are restored. The threshold voltages for IC1a and IC1b are set by R1, R2 and VR1 acting as a three-way voltage divider. Reducing the resistance of VR1 will bring the threshold voltages closer to­gether and thus reduce the size of the non-operation “window”. SC13101951 Fig.3: this is the full size etching pattern for the PC board. END OF SPINDLE THREADED TO ACCEPT MATCHING NUT ON CIRCUITRY CASE V-PULLEY H-pack output stage The drive side consists of a set of four Mosfets in an H-pack arrangement. A west signal from IC1a causes Q2 and Q5 to switch on and an east signal switches on Q3 and Q4. R5 and R6 are included to make sure that the Mosfets switch off. At the end of the day, rewind to the east is taken care of by IC1c which works as a simple comparator. As darkness falls, the resistance of LDR3 increases until the voltage on pin 9 reaches the voltage on pin 10. The reference voltage at pin 10 can be any arbitrary value above zero and so is tied to pin 5 of IC1b; ie, 4.8V. The actual darkness threshold is set by VR2. The output of IC1c is fed to a IC2, a 555 timer wired as a monostable with an ‘ON’ time of about 10 seconds. As the light faded it was found that shadows from trees and things would start to trigger the dark sensor but the west sensor would argue the point, resulting in the panel hunting back and forth. IC2 prev­ents this by fully rewinding the panel to east the moment the darkness sensor triggers. When IC2’s output goes high, it does two things. First, via diode D2, it switches on Q4 and Q3, driving the whole show eastward. Second, it causes IC1d’s output to go low and thus removes the base drive from Q1. This shuts off any possible drive to transistors Q2 and Q5, ensuring that the tracker will not follow the (D) SUB-FRAME (C) TELESCOPING PROP SECTION (B) PIVOTING PROP (E) SOLAR CELL CARRIER FRAME 12.7 PILLOW BLOCK (A) BASE (D) SUB-FRAME Fig.4: this diagram shows the tracker frame in perspective view. The dimensions of its various parts are given in Figs.5-8. Moon, car headlights, or other such light sources. The mercury switches are there to set the travel limits of the panel. S1(W) disconnects the gate signal to the west drivers as the panel tilts to its westerly limit; similarly, S2(E) cuts off gate signals to the east drivers as the panel tilts to its easterly limit. Some refinements The tracker will function with January 1995  17 12.7 DIAMETER SPINDLE WELDED TO FRAME END ON CENTRE LINE 12.7 DIAMETER SPINDLE WELDED TO FRAME END ON CENTRE LINE 140 232.5 85 555 232.5 25 x 2.5 FLAT IRON LUGS WELDED TO FRAME TO SUPPORT SOLAR CELL MODULE. POSITIONS AND DIMENSIONS MAY NEED ADJUSTMENT TO SUIT YOUR MODULE 305 305 1162 (E) SOLAR CELL CARRIER FRAME MATERIAL: 25.4 SQUARE MS TUBE 1.6 WALL THICKNESS ALL CORNERS WELDED DIMENSIONS IN MILLIMETRES HOLES 7 DIAMETER Fig.5: the solar cell carrier frame on the prototype was designed to suit a standard 60 watt panel from Dick Smith Eec­tronics (Cat. MSX-64). twitching back and forth but not quite running. It took some time to figure it out but this is the result of the com­ parators being switched on by a very slowly changing input. Comparators have extremely high gains. As the voltage on the input pin approaches that of the comparison pin, peaks of noise on the input will be amplified tremendously and cause the comparator to rapidly switch on and off. Unfortunately, the driver transistors will do the same with consequent wastage of power. The solution is to 30 just these components but is not as efficient as it could be. I found a few small modifica­tions reduced current consumption dramatically – never a bad thing with alternate energy. The first mod came about when I bought some LDRs that had a very low resistance in bright sunlight. It seems that not all ORP12 equivalents are the same. The addition of RE and RW reduced the current through the LDRs and kept them a lot cooler to boot. The second mod came about when I noticed the drive motor rapidly 30 25 27 10 703 (B) PIVOTING PROP MATERIAL: 30 SQUARE MS TUBE 2 WALL THICKNESS Building the tracker 45 97 107 85 104 85 707 106 53 25.4 45ø x 6mm CHAMFER 12 (C) TELESCOPING PROP SECTION MATERIAL: 25.4 SQUARE MS TUBE 1.6 WALL THICKNESS DIMENSIONS IN MILLIMETRES ALL HOLES 7 DIAMETER Fig.6: construction details for the pivoting prop & telescoping prop sections. 18  Silicon Chip introduce some hysteresis. On IC1a, the first instant the comparator switches on causes a high signal to travel through D3 and R8 to the junction of the LDRs. The nett effect is to cause the input on pin 3 to suddenly rise about 0.4V, thus well and truly turning the comparator on. The same system is used on IC1b via D5 and R9. The hystere­sis circuit also causes IC1a to turn off a trifle later then it otherwise would, thus causing the panel to turn a bit further before the motor switches off. This is a handy thing in prevent­ing the input voltage from sticking too near the upper limit. (Note: the current drain of the tracker is around 10mA when the panel is stationary, rising to about 1.5A when the motor is running. Most of the 10mA quiescent current can be attributed to the 555 timer and this could be reduced to under 2mA by using a CMOS 555 (ie, a 7555). The circuit for the solar tracker is wired on a PC board measuring 125 x 73mm and coded 13101951. There is nothing at all tricky about the board assembly. Make sure that the diodes are all in the right way around or strange things will happen. Use sockets for the two ICs but don’t install them just yet. PARTS LIST 2.5 87 TWO PIECES OF 25 x 2.5 FLAT IRON, 87 LONG WELDED TO TOP OF UPRIGHTS TO SUPPORT PILLOW BLOCKS. HOLES DRILLED TO MATCH PILLOW BLOCKS 25.4 25.4 25.4 HINGE TANG WELDED TO UNDERSIDE 25.4 TWO PIECES OF 25 x 2.5 FLAT IRON WELDED TO BOTTOM OF HORIZONTAL FOR PIVOT 1220 (D) SUB FRAME DIMENSIONS IN MILLIMETRES HOLE DIAMETER 7 Fig.7: this diagram shows the dimensions of the frame pivot support. 25.4 Miscellaneous Hookup wire, solder, blackened cardboard for LDR shield. Testing Before you power up the board, remove the ICs from their sockets and make sure that your power is supplied via a 2A fuse. Alternately, use a current limited supply if you have one. Hook up the power and make sure that the correct voltage is going to pins 4 & 11 of the IC1 socket and pins 1 & 8 25.4 SQUARE MS TUBE WALL THICKNESS 1.6 HINGE TANG WELDED TO BOTTOM END OF SUB FRAME 505 Be careful with the Mosfets. These little fellows are really rugged once in the circuit but are easily damaged when being handled beforehand. Do not ever touch the pins with your fingers and if they come wrapped in foil, just peel a bit back around the pins and solder them in like that. The villain is static electricity and standard precautions include grounding yourself and your soldering iron, etc. 25.4 225 x 140 T-HINGE CUT TO CLEAR SQUARE TUBE AND WELDED TO ANGLE IRON 32 Resistors (0.25W, 1%) 1 1MΩ 2 4.7kΩ 4 100kΩ 2 1kΩ 1 22kΩ 1 2.7Ω 5W 2 10kΩ 15 Capacitors 1 4.7µF 16VW electrolytic 1 0.1µF monolithic HORIZONTAL AND TWO UPRIGHTS 25.4 SQUARE MS TUBE WITH 1.6 WALL THICKNESS UPRIGHTS WELDED TO ENDS OF HORIZONTAL 8 Semiconductors 1 LM324 quad op amp (IC1) 1 NE555 timer (IC2) 5 1N4148 diodes (D1-D5) 4 MTP3055 Mosfets (Q2-Q5) 1 BC548 NPN transistor (Q1) 3 ORP12 light dependent resistors (LDR1,2,3) 305 1 photovoltaic solar panel (see text) 1 tracker frame to suit panel 1 3V barbecue spit motor 1 weatherproof box with transparent lid 2 pillow blocks 2 V-belt pulleys 1 V-belt to match pulleys 1 4-way insulated terminal block 2 mercury switches (S1,S2) 1 8-pin IC socket 1 14-pin IC socket 1 5kΩ trimpot (VR1) 1 10kΩ trimpot (VR2) 2 OFF 25.4 x 25.4 x 3 ANGLE IRON WELDED TO SQUARE TUBE (A) BASE DIMENSIONS IN MILLIMETRES HOLE DIAMETER 7 25.4 1250 25.4 Fig.8: the hinge details for the frame pivot support. of the IC2 sock­ et. Measure around the various other pins, especially the driver transistors, for the same reason. When finished, power down and put the ICs in. The circuit falls naturally into west and east drives, and so that’s the way testing proceeds. Power up and measure the voltage on pin 3 or 6; it should be about +6V. Place your finger alternately over LDR2(W) and LDR1(E) and the voltage should swing up and down in unison. It seems logical that putting one’s January 1995  19 This view shows the tracker frame with the solar panel removed to reveal the barbecue spit motor which is driven by the tracker circuitry. finger over LDR2(W) should result in the tracker going west. Try it; pin 7 of IC1b should immediately jump to around +10.5V (high) while pin 1 stays low and vice versa. Put your finger on LDR3 and confirm that pin 14 jumps to the same high level and then low again when uncovered – you may need to adjust VR2. Note that once IC2 seizes control of the system it doesn’t let go for about 10 seconds and that S2(E) will stay high during that time. If you want to disable IC2 while you check other parts of the circuit, short out LDR3 with an alligator clip. If all is well, hook up a motor to the output pins. Covering LDR2(W) will now drive the motor one way (mark it on the motor) and LDR1(E) the other. 20  Silicon Chip LDR3 will always drive the motor east, regardless of any other LDR you have covered. The mechanicals Being primarily a mechanical engineer, I decided to try doing a little better than some of the jury rigged trackers I had seen around. The tracker illustrated in the diagrams was designed to suit a standard 60 watt panel from Dick Smith Eec­tronics (Cat. MSX-64; price $599.) This is encased in a welded frame which, in turn, is mounted on pillow blocks so that it can be rotated. The stand is hinged at its base, allowing the panel to be raised and lowered to account for seasonal variations in the Sun’s altitude. The PC board was mounted in The tracker circuitry is mounted in a weatherproof plastic box with a transparent lid. The box is mounted on the same shaft which drives the solar panel via a V-belt. a weatherproof plastic case with a transparent lid. A blackened piece of cardboard is used as a light shield between LDR1 and LDR2 so that as the Sun moves across the sky, it repeatedly throws a shadow across LDR2(W). The weatherproof box then is mounted at the end of a belt-driven shaft and in the same plane as the solar panel, as shown in the photos. Motive power was a problem, with the commonly available windscreen wiper motors being found to have not enough torque and too much power. The best solution comes in the form of a cute little spit motor from the local barbecue place. The speed is low, torque is high and they’re cheap. The only glitch is that the actual motor is a 3V unit while the Mosfets put out about 7.5V. The answer is to use a current limiting resistor but the value has to be chosen carefully. Too much and starting torque ends up too low, while too little fries the motor. Around 2.7Ω is about right. Commissioning If everything has checked out on the bench, commissioning should be fairly simple. Point the LDR’s directly into the Sun and turn on the power. The PC board is mounted in the weatherproof box so that when the frame is rotating from east to west, LDR2 will have a shadow cast upon it as the Sun moves further west. Nudge the panel so that LDR2(W) is about half shaded and the motor should immediately scream to life. If it doesn’t, carefully turn VR1 clockwise until it does. Switch off the power and wait until sunset. Darkness level is set by VR2; start with it fully anti­clockwise. When it’s reasonably dark, adjust VR2 until the motor starts up. Watch that the panel frame does not hit the stand at the end of its travel. At the fully rewound position, check that S2(E) has switched off. If not, gently bend the glass case down until the mercury falls from the contacts. Do the same with S1(W) for the westerly limit. There are two things to be aware of before you sit back and enjoy watching your panel do its sunflower routine. First, putting a plastic lid over your LDRs can alter their light level settings and you may need to make some fine adjustments. Second­ , overcast days are bad news as there is no clear target for the LDRs. Instead, the tracker will orient on any patch of lighter sky it sees, meaning it spends all day winding itself back and forth. In that case, it is best to switch it off. (Editor’s note: as an alternative to turning the tracker off on overcast days, the output of IC1b could be disabled to prevent the unit from tracking east. This is easily accomplished by placing a toggle switch in series with SC diode D1). Is A Solar Tracker Worthwhile Having? In presenting this article on a solar tracker we should comment on whether it is worthwhile for all solar panels. In our opinion, it is probably not worthwhile for panels rated at less than about 18 watts. This is because the cost of the tracker itself, which could be $100 or more, depending on how much of it you build yourself, has to be added to the overall cost of the installation. Clearly, if you add $100 to the cost of a 10 watt panel, you could buy an 18 watt panel (using Dick Smith Electronics catalog prices as a guide) and thereby increase the output by 80%. However, for the bigger panels the use of a tracking mechan­ism is clearly worthwhile. January 1995  21 CIRCUIT NOTEBOOK Interesting circuit ideas which we have checked but not built and tested. Contributions from readers are welcome and will be paid for at standard rates. Using 3-wire railway crossing lights This modification allows the Level Crossing Lights and Bell circuit as described in SILICON CHIP in April 1994 (and in “14 Model Railway Projects”) to be used with 3-wire LED railway crossing lights. The #450 UNEEK brand HO level crossing signals use two miniature LEDs which are internally wired in series. The leads connect to the free anode of the first LED, to the common junc­tion between the cathode of the first LED and the anode of the second and finally, to the free cathode of the second LED. The modified circuit (see Fig.1) comprises the original 2-input Schmitt NAND gates but with the output transistors deleted. The outputs of IC1b and IC1d are now used to directly drive the LEDs. The output of IC1b is complementary to the output of IC1d so that when pin 11 of IC1b is high, IC1d’s pin 10 is low. Conversely, when pin 11 is low, pin 10 is high. With pin 11 high, current flows via LED1 and LED3 and their respective 2.2kΩ resistors to pin 10. LED2 and 1 TO PIN 2 OF IC2a (LEVEL CROSSING LIGHTS AND BELL CIRCUIT) 4093 IC1a +10v 13 2 FLASHER RATE VR1 50k 2.2k 5 6 14 12 3 IC1c 4 9 11 IC1b 2.2k LED1 IC1d 8 10 COM 2.2k A1  LED3 COM  7 LED2 2.2k 47 LED4 are off. When pin 11 is low, the high pin 10 output drives LED2 and LED4 via their respective 2.2kΩ resistors to ground. LED1 and LED3 are now reverse biased but with a negligible current flow­ ing from the cathode to the anode. Fig.2 shows the modified component overlay for the PC board (code 15203932). Note that Q1 and Q2 have been removed and links replace the original 22kΩ base resistors. The 2.2kΩ pullup resistors are also removed from the PC board. Also the 1kΩ resistors for the K2 and K4 connections have been in­creased to 2.2kΩ, while extra 2.2kΩ K2 A3   LED4 2.2k K4 Fig.1: the modified circuit uses the original 2-input Schmitt NAND gates but with the output transistors deleted. The outputs of IC1b & IC1d are now used to directly drive the LEDs resistors are required for the A1 and A3 connections. Note that the UNEEK level crossing signals are wired with a grey lead for the common and two black leads for the free LED connections. If only one LED flashes in a signal crossing assem­bly, you will need to swap the two black connections to produce the correct lead polarity. For further information on UNEEK HO railway crossing lights, contact CIL Distributors Pty Ltd, PO Box 236, Castle Hill, NSW 2154. Phone (02) 634 3475. Silicon Chip staff +12V GND TO SPEAKER 2.2k 2.2k A1 A3 COM K2 K4 2.2k 2.2k Fig.2: Q1 & Q2 are removed from the original board & links replace the original 22kΩ base resistors. The 2.2kΩ pullup resistors must also be removed from the board. Also the 1kΩ resistors for the K2 & K4 connections are in­creased to 2.2kΩ & extra 2.2kΩ resistors are required for the A1 & A3 connections. 22  Silicon Chip The UNEEK level crossing signals are wired with a grey lead for the common & two black leads for the free LED connections. If only one LED flashes in a signal crossing assem­bly, simply swap the two black leads to produce the correct lead polarity. S1 68k Q1 BC549 16 16 10k 3 0 X1 4MHz VC1 60pF D1-7 15 1N914 330pF 10 120pF CLK 1k 12 IC1 4040 +1517 ö1517 1 14 CLK 13 4 9 2 5 15 3 IC2 4017 +8 ö8 5 8 6 RST 6 7 9 8 8 RST 11 Electronic guitar tuning fork Anyone who has played a guitar will know that as long as one of the strings has been tuned to a reference, the rest can be accurately tuned by plucking adjacent strings and listening for zero beat. This circuit generates a 329.6Hz sinusoidal signal of high accuracy. This frequency is the frequency of the first string on a guitar and corresponds to the first E above middle C on a piano keyboard. A BC549 transistor forms a simple 4MHz crystal oscillator with a trimmer capacitor to bring it exactly on frequency. The 4MHz signal is then divided by 1517 by the 4040 binary Level translator for PC games port As previous articles in SILICON CHIP have shown, the PC games port can be used for a variety of applications. However, it does present a problem if you wish to interface with a standard TTL or analog circuit which has an output in the range of 0 to 5V DC. This is because the games port expects voltages in the range 4.8V to 7.2V DC. This circuit solves that problem; it translates a 0-5VDC voltage swing to 4.8-7.2V DC. IC1 is an LM358 dual op amp IC and IC1b is connected as a unity gain buffer. The incoming DC voltage is applied to a vol­tage divider consisting of 11kΩ and 10kΩ resistors. However, instead of being connected to 0V, the other side of 4 470 18k 2 56k 18k 7 56k 10 18k 1 12k 5 10k 6 12k 0.1 0.1 0.1 6 3 IC3 LM386 4 5 7 10  0.1 0.1 100 8W 8W .047 10k 13 VOLUME VR1 50k 2 0.1 0.1 Fig.3: the circuit uses three ICs & is powered from a 9V battery. counter and associated diodes. The diodes form an 8-input AND gate; the junction of the diodes and the 10kΩ resistor goes high when the count reaches 1517, resetting the counter to zero. The output from pin 15 clocks a 4017 decade counter/decoder. The outputs of the 4017 go high in succession and due to the choice of resistor values, a five-level stepped sine wave is produced at their junction. Low pass filtering is provided by the 0.1µF capacitors and the 18kΩ resistor. A reason­able quality sine wave is available across the volume control and this is amplified by an LM386 to drive a speaker. Calibration is done by connecting a frequency meter across 11k 0-5VDC INPUT the volume control and adjusting the trimmer capacitor until the frequency is 329.6Hz. To use this unit, turn it on and adjust the volume to a suitable level. Pluck the first string on the guitar and listen for a beat signal. Tension the string up and down until the beat frequency is zero. As shown, the unit is powered from a 9V battery and this is quite ade­quate for occasional use. However, the LM­ 386 draws considerable current at high volume, so if it is required to be used at high volume for extended periods it may be wise to use a 9V DC plug­pack instead of a battery. L. Williams, Bungendore, NSW. ($30) 3 2 +12V IC1b 1 56k 4.8-7.2VDC OUTPUT 10k 680  5 ZD1 9.1V 400mW 9V 8 IC1a 6 LM358 4 7 Fig.4: this simple circuit uses a single dual op amp & translates a 0-5V DC voltage swing to a 4.8-7.2V DC swing. This makes it ideal for interfacing external circuitry to the games port of a PC. the voltage divider is connected to the output of IC1a which acts as a unity gain buffer for the 9.1V zener diode. Hence when the input vol­ tage is at 0V, pin 3 of IC1b is set to +4.8V. The voltage divider values are selected so that when the input voltage increases to +5V, pin 3 rises by only 2.4V. The resultant output at pin 1 is a DC voltage ranging from 4.8 to 7.2VDC. The 56kΩ resistor at the output of IC1a provides the cor­rect amount of current feed to the 555 timer inside the games port. Silicon Chip staff January 1995  23 We fitted our Battery Saver into a standard Eveready® Dolphin torch. These take an Eveready® No. 509 lantern battery but still have plenty of room inside. Simple battery saver circuit for torches How many times have you gone to use a torch only to find the battery flat because it had been inadvertently left on? Too many, right? Well, curse no more. This little project will save the life of your precious battery by turning it off when you’re not using it. Design by MARQUE CROZMAN The suggestion for this project initially came from a nurse who works at night. She was always coming across torches that had been left on or were flat as a result of being left on. In these times of being environmentally aware, she felt that wasting batteries needlessly just added to pollution, increased land-fill and so on, let alone the cost of having to replace them! The problem then was to come up with a project that turned the torch 24  Silicon Chip off when not in use, without being too expensive. In principle, the concept is simple enough and is the same as the “automatic power down” feature now present on many digital multi­meters and calculators. These turn the power off if the unit has not been used (ie, buttons pressed) with a given time, typically 15 minutes or so. Torch batteries have a much shorter life than the batteries in calculators or multimeters and they are usually used for shorter periods at a time. Therefore, we decided to come up with a circuit which would turn off the torch after a period of six minutes or so, unless it had been moved. So our circuit would have to have a timer which was reset each time the torch was moved. How to do that? Use a movement sensor, that’s how. If the torch is to be switched off, it stands to reason that any switching device used must have a negligible effect on the lamp brightness and it must also consume very little current in itself, whether the torch is on or powered down. That turns out to be a pretty stiff challenge. Read on to find out the solution. Circuit description The circuit is shown in Fig.1. When you turn the torch on, the circuit monitors its move­ment as you move around. When you put the torch down, there S1 TORCH 10M 470k 1M 0.1 MOVEMENT SENSOR 1M Q1 BC547 C B E 33 LL 2.2M TORCH BATTERY SAVER 8 4 RS Q2 7 DIS IC1 IRF540 7555 6 3 G THR OUT TRIG 2 1 6V 6V D S 0.1 B E C VIEWED FROM BELOW GD S Fig.1: the circuit is essentially a 7555 monostable timer with a period of six minutes (T = 1.1RC seconds). If the movement sensor ball makes & breaks contact, the 33µF capacitor is discharged & must charge to +4V before the torch is extinguished. ceases to be any movement. About six minutes later, the torch will turn off. IC1 is a CMOS 7555 timer which is configured as a mono­stable. The timing period is set by the 10MΩ resistor and 33µF low leakage capacitor at pins 6 & 7. When the torch is turn­ed on, the capacitor at pin 2 is initially discharged and this provides the trigger condition for the circuit. Pin 3 goes high and stays that way until the 33µF capacitor charges above +4V. When this occurs, pin 3 goes low. Pin 3 drives the gate of FET Q2 and this turns on to feed the torch globe. When pin 3 of IC1 goes low, Q2 turns off and extinguishes the torch globe. All this presupposes that the torch has not been moved after it was first turned on. If movement has occurred, the sequence of events is different. Any motion of the torch is monitored by the movement sensor. As shown in the photos, the movement sensor is TO-5 size metal can with eight pins around the periphery and one in the centre which connects to the can. Inside is a metal ball with a roughened surface. As the sensor is moved, the Fig.2: this component overlay diagram shows how to assemble the PC board. The movement sensor can be oriented in any direction. PARTS LIST 1 PC board, code 11101951, 30 x 35mm. 1 6V or higher voltage torch 1 movement sensor (available from Oatley Electronics) 1 piece of PC board, 17 x 7mm 1 3mm diameter x 12mm long screw & nut 1 33µF 16VW tantalum or LL electrolytic capacitor 2 0.1µF MKT polyester capacitors Semiconductors 1 TLC555C or 7555 CMOS timer (IC1) 1 IRF540 or BUZ71 N-channel Mosfet (Q2) 1 BC547 NPN transistor (Q1) Resistors (0.25W, 1%) 1 10MΩ 2 1MΩ 1 2.2MΩ 1 470kΩ metal ball makes and breaks contact between the can and one or two of the peripheral pins. Fig.3: here is an actual size artwork for the PC board. The heart of the Torch Battery Saver circuit is this movement detector. We’ve removed the top of one of these to show the roughened metal ball inside which makes & breaks contact between the case & any one or two of the outside pins. Note: photo is larger than life size. This intermittent contact charges and discharges the 0.1µF capacitor in series with the base of transistor Q1. So each time the ball inside the sensor makes and breaks contact, transistor Q1 discharges the 33µF capacitor at pins 6 & 7. This stops the 7555 from timing out and so the torch stays on. The Mosfet specified for Q1 is an IRF540 or a BUZ71. Both of these are cheap and readily available and more than capable of carrying the lamp current which will typically be about one amp or so for a large torch. The critical factors are the drain-source resistance of the FET and the gate voltage required to turn it fully one. In practice, these Mosfets require a gate voltage of at least 5V to get their drain-source resistance below 0.1Ω and thus reduce the voltage losses to below 0.1V. This makes the circuit practical only for torches with battery voltages of 6V and higher. It also means that once the battery voltage drops below, say, 4.75V, the losses across the Mosfet become quite significant. However, at 4.75V, a 6V torch battery has just about “had it” anyway. Table 1 sets out the operating conditions of the prototype Torch Battery Saver, as the battery voltage is reduced. As you can see, when the battery voltage is at 5V or more, the voltage losses across the Mosfet are quite low. Once the circuit goes into standby mode, the current is reduced to around 120µA which is mostly due to IC1. When the 7555 does time out and the torch turns off, the only way to turn it back on is by switching the torch off and on again. When you switch off, the triggering capacitor at January 1995  25 This view of the PC board shows the Mosfet bent upwards to reveal the 7555 timer IC. Note that our proto­type used a tantalum timing capacitor. This view of the PC board shows the Mosfet with its leads bent over & obscuring the 7555 timer underneath. pin 2 discharges through the 2.2MΩ resistor so that the 7555 can be triggered if you immediately switch on again. Construction We designed a small PC board for the Torch Battery Saver and it should be possible to install it in any of the larger torches. We installed it in an TABLE 1 Battery Voltage Current Drain Voltage Across FET 6V 750mA 0.061V 5.5V 720mA 0.068V 5.25V 700mA 0.074V 5V 680mA 0.086V 4.75V 670mA 0.114V 4.5V 640mA 0.200V 4.25V 540mA 1.032V 4V 370mA 2.610V 26  Silicon Chip Eveready® Dolphin torch and this had plenty of room inside. Fig.2 shows the parts layout on the board. Note that the IC must be installed before the Mosfet and the latter has its leads bent to lie over the IC. Mounting the unit in the Dolphin torch was relatively easy but we had to modify the central contact on the switch assembly. We did this by drilling a 3.5mm hole through the central contact and then made a new contact assembly which could be isolated from it. This was done by taking a small piece of copper PC board measuring 17 x 7mm. This had a hole drilled through the centre and a 3mm dia­ meter x 12mm long screw was soldered to the copper surface. This was then fitted with a transistor mounting bush and fitted to the central battery contact of the torch. The screw was fitted with a nut on the underside of the torch switch assembly and this then became the This photo shows how the central contact of the switch assembly was modified with a separate contact made from a piece of PC board. This was mounted with a 3mm screw (with its head buried in solder). This screw retains the small PC board which is on the underside of the switch assembly. negative supply contact for the battery saver PC board. The +6V supply to the board comes from the positive side of the switch assembly while the central contact to the torch bulb connects to the drain of Q1. Other torches will require different connection arrangements but we have designed the board with large positive and negative terminals to make this easy. Have a look at the photos to see how we did it. Note that when assembled, the retaining nut for the PC board will more than likely make contact with the case of the movement sensor. This is not a problem because the case is at 0V potential anyway. Testing The easiest way to test the device is rig it up to a 6V power supply or assemble it into your torch and turn it on. After six minutes or so, it should extinguish. On the other hand, if you move or shake the torch at least once every five minutes, the torch should not go out until you switch it off. Note that you can provide a longer timeout period by in­creasing the 33µF capacitor although for values larger than 100µF the leakage will become significant and ultimately will limit the period that can be achieved. You can also shorten the period, if you wish, by reducing the 33µF capacitor. For example, a value of 2.2µF will give a time of about 25 seconds. You could use a small value like this for testing, so that you do not have to wait SC out the full 6-minute period. SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Rod Irving Electronics Pty Ltd SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Rod Irving Electronics Pty Ltd SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Rod Irving Electronics Pty Ltd SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Rod Irving Electronics Pty Ltd SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Rod Irving Electronics Pty Ltd DOLBY PRO-LOGIC SURROUND SOUND DECODER; PT.2 Dolby Surround Sound is the biggest thing in hifi in the 90s & now you can have it in your home without spend­ing big dollars. In this second article on our Dolby ProLogic* Surround Sound Decoder, we give the construction details & show how to connect it to your hifi system. By JOHN CLARKE Although the SILICON CHIP Surround Sound Decoder is complex in operation, it is easy to construct and requires no internal adjustments. The unit is built into a plastic case measuring 255 x 80 x 180mm. Virtually all of the circuitry is mounted onto a PC board coded 02311941 and measuring 204 x 151mm. 32  Silicon Chip You can begin construction by checking the PC board against the published pattern. Check that there are no open circuits or shorts between tracks. If there are any, they should be fixed before proceeding further. Note that the appropriate size holes have been drilled to take the power transformer mounting screw, the mounting screw for the mains terminal block, the screws for the two 3-terminal regulators and for the six self-tapping screws to secure the PC board into the case. The component overlay for the PC board is shown in Fig.5. This shows all components as viewed from the top of the board and the tracks are shown as if you were looking through the board from the topside. We suggest you begin the assembly of the board by inserting all the PC stakes required for the wiring to the switches, pots, sockets and other external components. Install the links using tinned copper wire. To produce a neat job, we recommend that the wire be straightened by holding each end of the wire with a pair of pliers and pulling them until the wire is slightly stretched. Cut the wire to a length suitable for each link A single large PC board accommodates most of the parts, so the construction is quite straightforward. Note the heatshrink tubing used to insulate the terminals on the fuseholder. The terminals of the power switch on the front panel must be insulated in similar fashion, to prevent accidental contact with the mains. and bend each link with pliers so that it fits neatly. Now you can install the five ICs, taking care with the orientation of each device. Take particular care when soldering in IC1 (the Dolby decoder), since its pin spacing is much closer than on normal ICs (.07-inch instead of 0.1-inch). Make sure that solder does not bridge between pins. The resistors can be installed next. Use the colour code table to guide you in selecting the resistor values. A digital multimeter can be used if you are in any doubt about the value. Note that the two 1W resistors are mounted above the PC board by about 3mm and their leads are bent inwards to accommodate the hole spacings on the PC board. Now mount the four reed relays, the diodes and transistor Q1. Take care with the orientation of the diodes and note that diode D4 is a different type to D1-D3 and D5. Regulator REG1 requires a heatsink which is secured to the PC board with a 3mm screw and nut, while REG2 (7805 or LM­340T5) bolts directly to the PC board (no heatsink needed). Bend the regulator leads so that they can be inserted into the board holes before securing with the screw and nut. The heatsink for REG1 does not need to be insulated from the regulator but smear a little heatsink compound on its mount­ing surface (the 7812 or Where To Buy A Kit Because of the licensing requirements associated with this design, it is available only as complete kit of parts from Jaycar Electronics Pty Ltd. Please note that the M69032P Dolby Pro Logic decoder IC is not available as a separate item &, for this reason, it is not possible to construct the unit by separately purchasing individual parts. LM340T12 type) before it is mounted. The capacitors can now be installed. Take care to ensure that the correct value capacitor is installed in each position. For the non-electrolytic types, the accompanying table shows the various markings which may be on the capacitor body. For example, a capacitor of .0047µF could be labelled 4n7, 472 or 0.0047. Electrolytic capacitors must be mounted with the polarity shown on the overlay diagram. The 1000µF capacitor is mounted on its side with the leads bent at right angles. We recommend that this capacitor be secured to the PC board with a dab of silicone rubber to prevent its leads from breaking. The toroidal transformer mounts using a long bolt through its centre and a large metal washer at the top. Between the transformer and the metal washer is a neoprene rubber washer and a second neoprene washer is fitted under the transformer to provide a cushioned mounting. Connect the two mains wires of the transformer (two orange) to the mains terminal block as shown on the overlay diagram. Now check your work to make sure January 1995  33 GND S4 47k 180pF 15k 15k 47k 7.5k 7.5k 0.22 0.22 .068 39k 0.1 39k 10uF 180pF 10k 100uF IC2 M65830P 8.2k 8.2k 10k D4 1 X1 10uF 1k 22k 0.1 2.7k 1M 2x100pF 22 25VW VR1 10k 1M 100k D3 RED D2 A 47  1W WHT YEL REG1 47  1W PINK T1 POWER TRANSFORMER 470pF 100uF K 10uF D1 470  8.2k 470pF A 22uF 25VW 1000uF 25VW REG2 LED2 LED1 470  1 IC3 TDA10748A 15k 15k 39k IC5 LM358 0.1 VR3 8.2k 39k IC4 TLO74 1 4.7k 180pF 10k .068 10uF 10uF 0.1 4.7k 1.8k VR2 180pF 1uF .0056 10uF 15k 22uF 100uF 47uF 18k 10uF 10uF 1uF 15k .0056 7.5k 10uF 10uF .0033 .0022 .047 10uF 10uF 10uF 10uF 82  Q1 4.7uF 15k 18k D5 100  0.1 22k 47uF 470pF 0.1 0.22 RELAY 4 25VW 47k .0056 0.1 100  0.22 0.18 47k +4V 0V 4.7uF 10uF RELAY 2 100k 0.1 0.68 100  SURROUND OUT 1 IC1 M69032P 100uF 47k 220uF 0.1 0.1 10uF RELAY 1 100k 10uF LL .0047 2x.022 680pF 330k 100  CENTRE OUT 680pF .047 .047 15k 100k 10M 22uF 15k LEFT OUT 10  10uF RELAY 3 0.1 5.6k 30  100  0.1 0.1 100k 100k 100k 22k 47k 22k 0.1 10uF 22k 22k RIGHT OUT S4 22k 8.2k LEFT IN 10  S5 RIGHT IN 10uF 240VAC Fig.5: install the parts on the PC board exactly as shown here, taking care to ensure that all polarised parts are correctly oriented. Take care also with the transformer connections & note that REG1 is fitted with a small heatsink. that all the components are correctly installed. When you are sure that the PC board assembly so far is correct, the board can be mounted in the base of the case using the self-tapping screws. 34  Silicon Chip Now it may not be immediately apparent but there is a right way and a wrong way of doing this because the case has a slightly larger opening for the front panel than for the rear panel. The correct orientation for the PC board is with the reed relays and power transformer mount­ed above the ventilation slots. Grounding the rear panel Before affixing the front panel label, attach the counter­ sunk earth screw so that it mounts flush with the front EARTH TERMINAL ACTIVE BROWN REAR PANEL FUSE SURROUND OUT LEFT OUT LEFT IN CENTRE OUT RIGHT OUT RIGHT IN EARTH GREEN/YELLOW CLAMP GROMMET BROWN NEUTRAL BLUE 5 7 4 8 6 6 2 1 5 3 4 .001 250VAC S1 EARTH TERMINAL 1 2 0.47 K A LED1 10 C S2 3 K A LED2 A VR3 VR2 VR1 1 S5 7 S3 S4 8 FRONT PANEL Fig.6: be sure to use mains-rated cable for all 240VAC wiring (ie, to the fuseholder, power transformer, mains switch & earth terminals) & note the use of shielded audio cable between the board & potentiometers VR1-VR3. January 1995  35 This close-up view shows how the power switch & its associated .001µF capacitor are insulated using heatshrink tubing. The leads to other components in the vicinity should also be insulated to prevent any possibility of accidental shorts. panel. Now attach the labels to the pre­ punched front and rear panels. The holes can be cut out with a sharp knife, reamer and small file. Now cut the pot shafts and rotary switch shaft to a length suitable for the knobs supplied. This done, install the switches, pots, LEDs (and bezels) and earth terminal on the front panel. On the rear panel, the RCA sockets, the fuse holder and earth termi­nal can be secured in place – see Fig.6 The outer sheath of the mains lead should be stripped back by about 50mm to expose the three wires. Be careful not to cut the wire insulation when doing this. Secure the mains lead into the cord grip grommet and press the grommet into the rear panel hole. The cord should be gripped securely so that it cannot be pulled out of the grommet. Connect the green/yellow (Earth) wire to the solder lug on the rear panel. The brown (Active) wire is terminated at the end lug of the fuseholder but before soldering it in position slip a length of heatshrink tubing over the wire so that the fuse termi­nals can be insulated afterwards. Now solder another brown wire to the side terminal of the fuse holder. Pass this lead through the heatshrink tubing and then push the tubing over the fuse­ hold­er body. Connect the blue (Neutral) mains wire to the mains terminal block on the PC board and another mains wire to the second termi­nal on the terminal block. Again, slip a length of heat­ CAPACITOR CODES ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ Value IEC Code EIA Code 0.68µF 680n 684 0.47µF 470n 474 0.22µF 220n 224 0.18µF 180n 184 0.1µF 100n 104 .068µF 68n 683 .047µF 47n 473 .022µF 22n 223 .0056µF 5n6 562 .0047µF 4n7 472 .0033µF 3n3 332 .0022µF 2n2 222 .001µF 1n0 102 680pF 680p 681 470pF 470p 471 180pF 180p 181 100pF 100p 101 shrink tubing over the wires, ready to shroud the front panel power switch, S1. Now solder the .001µF 250VAC capacitor across S1’s terminals, then solder the two mains wires to their respective terminals and cover the switch with the heatshrink tubing. RESISTOR COLOUR CODES ❏ No. ❏  1 ❏  2 ❏  1 ❏  7 ❏  6 ❏  4 ❏  7 ❏  2 ❏  9 ❏  4 ❏  5 ❏  3 ❏  1 ❏  2 ❏  1 ❏  1 ❏  1 ❏  2 ❏  5 ❏  1 ❏  2 ❏  1 ❏  2 36  Silicon Chip Value 10MΩ 1MΩ 330kΩ 100kΩ 47kΩ 39kΩ 22kΩ 18kΩ 15kΩ 10kΩ 8.2kΩ 7.5kΩ 5.6kΩ 4.7kΩ 2.7kΩ 1.8kΩ 1kΩ 470Ω 100Ω 82Ω 47Ω 1W 5% 30Ω 10Ω 4-Band Code (1%) brown black blue brown brown black green brown orange orange yellow brown brown black yellow brown yellow violet orange brown orange white orange brown red red orange brown brown grey orange brown brown green orange brown brown black orange brown grey red red brown violet green red brown green blue red brown yellow violet red brown red violet red brown brown grey red brown brown black red brown yellow violet brown brown brown black brown brown grey red black brown yellow violet black gold orange black black brown brown black black brown 5-Band Code (1%) brown black black green brown brown black black yellow brown orange orange black orange brown brown black black orange brown yellow violet black red brown orange white black red brown red red black red brown brown grey black red brown brown green black red brown brown black black red brown grey red black brown brown violet green black brown brown green blue black brown brown yellow violet black brown brown red violet black brown brown brown grey black brown brown brown black black brown brown yellow violet black black brown brown black black black brown grey red black gold brown not applicable orange black black gold brown brown black black gold brown Use cable ties to bind the mains wiring & the wiring to the front panel, as shown here. All ICs, including IC1 (the Dolby Pro Logic decoder), can be soldered direct to the PC board. Make sure that the mains cord is securely anchored. Both the fuse­holder and switch heatshrink tubing can now be shrunk down with a hot-air gun. The front panel is earthed to the rear panel using a length of green/yellow earth wire terminated into the solder lugs at front and rear (see Fig.6). Do not leave this lead out – it is necessary to ensure electrical safety. Take care when wiring up the rotary switch S3 since there are many connections to be made. Use hook-up wire for this. We used rainbow cable for wiring the LEDs and from S5 and S4 to the three PC pins on the board near the relays. Standard hook-up wire was used for the remaining connections. There is no need to use shielded cable for the connections to the rear panel RCA sockets. Shielded cable, however, must be used for the wiring to pots VR1, VR2 and VR3. Voltage checks Now check all your wiring carefully against the diagram of Fig.6. When complete, the Surround Sound Decoder is ready for testing. Before plugging into the mains, insert the 250mA fuse into the fuse holder if you have not already done so. Connect the negative lead of your multimeter to the 0V test point near IC1 (see Fig.5). Apply power and check that the power LED lights. Check that the output voltages of REG1 and REG2 are +12V and +5V, respectively. Actually, for REG1, the voltage should lie between +11.5V and +12.5V and for REG2, between +4.8V and +5.2V. If the voltage is low or not present, turn off the power and find the fault before switching on again. Check that there is +12V at pin 37 of IC1, pin 11 of IC3, pin 4 of IC4 and pin 8 of IC5. There should be +5V at pins 1 and 24 of IC2. Check also for +4V at pins 43 and 44 of IC1, and for +6V at pin 8 of IC3. Check that the relays operate about 10 seconds after power is applied. This can be checked by measuring the voltage at the collector of Q1. Initially, the voltage should be about +16V and when the relays switch on, the collector vol­tage should fall to less than +0.5V. Noise tests Switch on the noise test switch, S2, *Trademarks & Program Requirements Note 1: “Dolby”, “Pro Logic” and the Double-D symbol are trade­marks of Dolby Laboratories Licensing Corporation, San Francisco, CA 941034813 USA. Note 2: this Surround Sound Decoder requires a stereo program source such as a stereo television or hifi stereo VCR. For sur­round sound, the program must be Dolby Surround encoded as indi­cated in the movie credits by the Dolby Double-D symbol. For unencoded stereo signals, the Dolby 3-stereo selection will provide the centre front channel. The decoder will not operate from a mono signal. January 1995  37 The rear panel carries the left & right input sockets, plus sockets for left out (L), right out (R), surround out (S) & centre out (C). STEREO AMPLIFIER 1 L STEREO TV OR VCR PRO-LOGIC DECODER R FRONT LOUDSPEAKERS L L R R S STEREO AMPLIFIER 2 REAR LOUDSPEAKERS LEFT SURROUND RIGHT SURROUND Fig.7: the easy way of connecting the Surround Sound Decoder to your hifi system is to use a phantom centre channel. All you need, apart from the source, is another stereo amplifier & an extra pair of loudspeakers. STEREO AMPLIFIER 1 Connecting the system L L R R L STEREO TV OR VCR PRO-LOGIC DECODER FRONT LOUDSPEAKERS MONO AMPLIFIER C C R STEREO AMPLIFIER 2 REAR LOUDSPEAKERS LEFT SURROUND S RIGHT SURROUND Fig.8: this is the preferred method of installing the Surround Sound Decoder. In this case the centre channel is used & a total of five power amplifiers (& five loudspeakers) is required. 38  Silicon Chip and check that LED 2 lights. If all these tests show no problems, the decoder is ready for a listening test using the noise signal. To do this, connect an amplifier and loudspeaker to the left channel output and check that noise is present when S2 is switched on and the left channel is selected with S3. Make sure that the surround mode is selected with S5. Check the volume control operation from minimum to maximum rotation. At minimum volume, nothing should be heard from the loudspeaker while at maximum volume the noise signal should be quite loud. This done, do the same checks for the centre, right and surround channel outputs. If all is well, you can connect up to your stereo TV or stereo VCR. In general, there are two ways in which you can use the SILICON CHIP Dolby Surround Sound Decoder in your system. The easiest way is to use a phantom centre channel so that no centre channel loudspeaker or amplifier is required. This setup is shown in Fig.7 and essentially all you need, apart from a stereo TV or VCR as the source, is two stereo amplifiers and four loudspeakers. The left and right channel outputs from the decoder connect to a pair of line inputs (ie, tuner, aux) on a stereo amplifier. The rear channel signal then connects to the second stereo amplifier which is switched to mono mode so that both channels get the same signal. The rear channel amplifier does not need to be a high power unit – a unit rated at 10 watts per channel or more will be adequate. Similarly, the rear speakers can be quite modest and do not need to be full range units. Centre channel options SILICON CHIP SOFTWARE Now available: the complete index to all SILICON CHIP articles since the first issue in November 1987. The Floppy Index comes with a handy file viewer that lets you look at the index line by line or page by page for quick browsing, or you can use the search function. All commands are listed on the screen, so you’ll always know what to do next. Notes & Errata also now available: this file lets you quickly check out the Notes & Errata (if any) for all articles published in SILICON CHIP. Not an index but a complete copy of all Notes & Errata text (diagrams not included). The file viewer is included in the price, so that you can quickly locate the item of interest. The Floppy Index and Notes & Errata files are supplied in ASCII format on a 3.5-inch or 5.25-inch floppy disc to suit PC-compatible computers. Note: the File Viewer requires MSDOS 3.3 or above. ORDER FORM PRICE ❏ Floppy Index (incl. file viewer): $A7 ❏ Notes & Errata (incl. file viewer): $A7 ❏ Alphanumeric LCD Demo Board Software (May 1993): $A7 ❏ Stepper Motor Controller Software (January 1994): $A7 ❏ Gamesbvm.bas /obj /exe (Nicad Battery Monitor, June 1994): $A7 ❏ Diskinfo.exe (Identifies IDE Hard Disc Parameters, August 1995): $A7 ❏ Computer Controlled Power Supply Software (Jan/Feb. 1997): $A7 ❏ Spacewri.exe & Spacewri.bas (for Spacewriter, May 1997): $A7 ❏ I/O Card (July 1997) + Stepper Motor Software (1997 series): $A7 POSTAGE & PACKING: Aust. & NZ add $A3 per order; elsewhere $A5 Disc size required:    ❏ 3.5-inch disc   ❏ 5.25-inch disc TOTAL $A Enclosed is my cheque/money order for $­A__________ or please debit my ❏ Bankcard   ❏ Visa Card   ❏ MasterCard Card No. Signature­­­­­­­­­­­­_______________________________ Card expiry date______/______ Name ___________________________________________________________ PLEASE PRINT Street ___________________________________________________________ Suburb/town ________________________________ Postcode______________ Send your order to: SILICON CHIP, PO Box 139, Collaroy, NSW 2097; or fax your order to (02) 9979 6503; or ring (02) 9979 5644 and quote your credit card number (Bankcard, Visa Card or MasterCard). ✂ The second way to wire the system is to use the setup shown in Fig.8. In this case the centre channel is used and a total of five power amplifiers will be required. The extra power amplifier is for the centre channel and it can drive a full range loud­speaker which should ideally be of similar quality to the left and right channel speakers. This is the preferred option and for this you set the centre channel switch (S4) to “wide band”. Alternatively, you can choose to have a small centre channel speaker which has a restricted bass response. For this option, you set the centre channel switch to “normal”. This rolls off the centre channel signals below 100Hz but they are not lost and are added to the left and right channels. Warning! If a centre loudspeaker is used, do not place it on top of or underneath your TV set unless you are sure that the loudspeak­er magnets are shielded. Severe colour distortion and loss of purity will result from placing a normal speaker near a television screen or monitor. We should mention a third option which can involve two stereo amplifiers and still drive the centre channel. In this case, one power amplifier is used to drive both rear speakers which are simply connected in parallel. This prevents you from easily changing the balance between the rear speakers but this would normally not be a problem. Once the system has been installed, balance adjustments will need to be made so that the sound output is equal in all channels. This is done with the noise switch on. Start by select­ing the left channel output and the surround sound mode, and adjust the volume to a comfortable level. Now select the right channel and adjust the balance in the stereo amplifier so that the left channel and right channel outputs are the same. This done, select the centre channel and adjust the centre trim con­trol for the same sound level as the left channel, then do the same for the surround channel. That concludes the setting up. Switch off the noise test and your Dolby Pro-Logic Surround Sound Decoder SC is ready for use. January 1995  39 SERVICEMAN'S LOG Symptoms don’t seem to help any more Is it my imagination or is it becoming more & more difficult to relate the symptoms to the fault? Time was when most symptoms gave at least a hint as to the area involved. But in both this month’s stories, they were no help at all. This is the third story in the Contec saga and must be regarded as weirder that most, if only because even the customer’s complaint was weird. And, as I’ve already hinted, the symptoms gave no clues at all. As usual, it was the motel proprietor himself who fronted up to the counter, lugging the offending set with him. And in answer to my query as to the nature of the problem, he replied (somewhat facetiously I now realise), “It’s the remote control system – it only half switches the set off”. 40  Silicon Chip My private reaction was, “Don’t be silly – how can you half switch a set off? It’s either on or it’s off”. However, when I spoke to the customer, I was a little more circumspect: “How do you mean?” He grinned. “Turn it on and I’ll show you”. So we hooked the set up to a power point, connected an anten­na and turned it on. And up came a first class picture. I flicked through all the channels, tried the various controls, and everything seemed fine. So it was over to the customer to explain further. He produced the remote control unit and pressed the OFF button. And I had to admit the his description of what happened wasn’t all that silly after all. There was still a picture on the screen but there was a total loss of colour. There was also some loss of brightness and a noticeable shrinkage in picture size, amounting to about 12mm on all four sides. Pressing the ON command on the remote control unit brought everything back to normal. There is no standby control on the set itself, as with some sets; only a normal ON/OFF switch directly in the mains circuit. And of course, this functioned normally. Well, I had no quick answer to that one. So the set was left with me to tackle when I felt a little stronger. Power supply checks I went first to the power supply and to the HT rail coming from it – see Fig.1. This is derived from pins 5 and 6 of T502, the switch mode transformer, via diode D516, 100µF capacitor C523, and series transistor Q507. It goes out on pin 1 of plug/socket C. This rail is shown as 114.9V – a rather unnecessary order of precision, I felt, but at least we did have a figure. Checking this when the set was operating normally confirmed that it was very close to this value. I then tried to turn the set off via the remote control. This should have reduced the HT rail to zero but it didn’t. That in itself didn’t surprise me but I did imagine that it might drop by some amount. But no; it actually rose very slightly, by about 1.5V. The amount was not significant in itself but the fact that it was the opposite of what one would expect made the whole situation that much more puzzling. With no obvious clues, I decided to trace out the remote control path and check for possible faults in this section. It wasn’t a particularly dif- -31V TO PIN 27 OF IC 801 5V 4 F 3 F 1 F 12V 2 F 1 E 2 E 8 1 D510 C514 47 7 6 240V D511 3 4 2 5 R519 1k IC 510 IC502 330 C515 470 0.1 Q506 T501 Q505 T502 Fig.1: the Contec MSVR-5383 power supply again. The on/ off control signals from pin 27 of IC801 come in on pin 1 of socket F & go to the base of transistor Q509. This transistor then controls Q508 & Q507. When pin 27 goes high, Q507 turns on & delivers the HT voltage to pin 1 of socket C. Conversely, when pin 27 goes low, Q507 turns off & removes the HT rail. ficult exercise. Infrared pulses from the remote control unit are picked up and processed by the in­frared receiver, IC601. The resultant signals come out on pin 2 of this IC and go to pin 35 of IC801, the central processing unit. This, in turn, toggles pin 27 between 4.5V and 0V at each press of the ON/ OFF button on the remote control to switch the HT rail on and off respectively. In fact, this is the only function that this signal performs. Jumping ahead a little, the actual switching is performed by series transistor Q507. This, in turn, is controlled by tran­sistors Q508 and Q509. When the voltage from pin 27 of the CPU goes to +4.5V, Q509 turns on and so Q508 & Q507 also turn on to provide the HT rail. At the same time, Q505 & Q506 also turn on to provide the 12V rail. Conversely, when the voltage on pin 27 of the CPU goes low, Q509, Q508, Q507, Q505 & Q506 all switch off and the HT and +12V rails are removed. At least, that is what should happen. In fact, there was no change of voltage Q507 114.9V C 5 6 D516 C C523 C 1 2 3 Q508 Q509 at the base of Q507 as the on/off function was initiated. I was able to trace the signal to the collector of Q509 and from there to the base of Q508 but no further. There was no change at the collector of Q508 and, of course, none at the base of Q507. So it looked as though either Q508 or Q507 was faulty. I pulled Q508 out and checked it and it appeared to be OK. I then did the same with Q507 and found that it appeared to be a dead short. But I must confess that, as a result of subsequent think­ing, I did wonder whether the fault was more subtle than that. But more on that later. The immediate requirement was for a replacement transistor. I didn’t have the Q807 type (a 2SC3310) or any of its direct equivalents in stock but I finally settled for a 2SD841 which has slightly higher ratings. This, I felt, should be a suitable substitute. And that was the answer. It wouldn’t have surprised me if there had been more than one fault, considering the various symptoms, but the set came good immediately, and responded quite positively to the remote control signals. So, at a practical level, that was the end of the exercise. Puzzling symptoms But I couldn’t help wondering why the set behaved as it did. Why the loss of colour, the reduced brightness and the picture shrinkage? And why the slight increase in HT voltage, in response to the remote control signal? And the truth is, I’m still wondering. I spent a lot of time going over the circuit – and the set itself, before I re­ turned it – analysing the circuit and making measurements in an effort to rationalise its behaviour. I didn’t make much progress. At one stage, I wondered whether the slight increase in HT voltage was due to some subtle aspect of the transistor failure but I was eventually forced to discard that theory. I am now convinced that Q807 was simply a dead short and was not able to respond to the signal from the CPU in any way. The observed symptoms were due to some other mechanism and had nothing to do with the voltage on pin 27. As I mentioned earlier, the line from January 1995  41 SERVICEMAN’S LOG – CTD pin 27 of the CPU goes only to the base of Q509. Granted, there is another function derived from this. The 12V rail, derived from the 50Hz transform­ er T501, is turned on and off from the HT rail by means of tran­sistors Q505 and Q506. Unfortunately, as far as any explanation goes, it doesn’t help; the 12V rail supplies only the audio IC, IC904. And that apparently leaves only one possible explanation; that the signal coming out on pin 27 performs a number of switch­ing functions within the CPU or comes out on some other pin(s) and controls other external functions. A prime suspect here would be IC701, which handles most of the video and colour processing. Building on this theory is the idea that, if some functions were turned off (colour processing, for example), then there could be a reduction in HT current drain. This could be suffi­cient to cause the extra 1.5V or so which I observed. And the picture shrinkage? Again, this could be tied to the higher HT rail voltage. I had my doubts about this idea initial­ly; doubts that such a small change in HT voltage could have such an obvious affect on picture size. So I pulled a swifty. The HT rail voltage is set by a regulator network within the power supply and, more specifically, by potentiometer VR501. So, with a crosshatch pattern on the screen, I fiddled VR501 to produce an increase of around 1.5V. And the result was a degree of shrinkage very close to that which accompanied the fault. So there it is; these are the best theories I can advance. If anyone is closer to this circuit and can offer a more detailed explanation, then be my guest. That’s enough from me for this month. I’ll now pass you over to my colleague, J. L., from latitude 42 degrees south, or there­abouts. This is how he describes his latest weirdo. Just a stereo amplifier Now here’s one you are going to find hard to believe! Most stereo amplifiers are just that – stereo amplifiers. But not when it’s a Sony STR-AV1070X. 42  Silicon Chip The 1070X is an integrated AM-FM stereo receiver, with no less than six speaker outlets, left and right for front, centre and back! And for inputs, it can accept two phono players, two cassette tape decks, a CD player, a digital audio tape deck, an external equaliser, and three video decks! The entire system can be remote controlled with a “Remote Commander”, featuring buttons to work the radio and amplifier, as well as TV and VCR, CD player and DAT recorder! It can operate Sony equipment with builtin codes and can also learn the codes of other brands if one should be so crass as to connect them to such an elaborate unit. The remote control carries two small slide switches and 80 buttons. Yes, that’s right, 80 function buttons! And its all packed on a handpiece just 200mm long, 70mm wide, and 20mm thick. That’s hardly larger than an ordinary TV/VCR controller! Pardon the exclamation marks, but this amplifier has every­thing!! My customer spent half a day removing all the input and output connections, then staggered into my workshop with the monster cradled in both arms – it weights something like 20kg – and gingerly placed it on the bench. I had been alerted to his approach with what was supposed to be “... just a stereo amplifier”. But I expected nothing like this and I very nearly asked him to take it somewhere else. Later, when I had heard a list of all his problems, I was even more convinced that if he wouldn’t take it elsewhere, then I would. It appeared that he had an intermittent problem. Sometimes when he tried to adjust the volume with the remote control, the process would start normally but then the controller would apparently lose contact with the set and the volume would continue to increase up to maximum. And since this amplifier has an output rating of 250W + 250W into 4-ohms, his neighbours were thinking of taking up a petition. But there was more. At the same time as the volume control took off on its own, the front panel display would go crazy, indicating wrong functions or no functions at all. Similarly, there were times when nothing at all would work and the set had to be switched off at the mains to restore normal operation. On the basis of his description of the symptoms, I suspect­ed that the entire system was microprocessor controlled and that it was this section that was causing the problems. And since it was intermittent, with the system working normally for much of the time, I guessed the fault was going to involve dry joints or something like that. The owner brought along a 44-page user manual for the unit and although it gave lots of detail about operating the set, there was nothing at all of a technical nature. Fortunately, I am on good terms with the local Sony specialists so next day I visited their workshop and was able to consult their service manual. A real eye-opener This was a real eye-opener. It included several 6-page foldout schematic diagrams, as well as minutely detailed PCB diagrams. The “circuit board location” diagram reproduced here – see Fig.2 – gives some idea of the complexity of this amplifier. There are no less than 18 separate PC boards (and I can’t even find one labelled “tuner board”!). Honestly, I’ve seen video cassette recorders with less complexity than this stereo amplifier. And a colour TV set is a snack after this thing! A quick glance through the manual convinced me that I was going to have to study the circuitry long and hard before I could ever come to grips with it. So I made arrangements to borrow the manual for the weekend and was about to leave for home when their audio technician entered the work- shop. After exchanging greetings and other pleasantries, I asked him if he had ever had to work on an AV1070X. “Not often”, was his reply, “but what’s wrong with yours?” I started to explain that the volume control ran up to full and he continued “... when you use the remote commander, and the displays go crazy and the set has to be turned off to reset everything?” It was almost word for word as my customer had explained it. Quite obviously, it was a fault that had been around for a while. The 1070X is not a common stereo amplifier, so January 1995  43 TRANSFORMER-3 BOARD (1070X : E MODEL) SPEAKER OUT BOARD VOLTAGE SELECTOR BOARD (1070X) : E MODEL POWER BOARD TRANSFORMER-1 BOARD (970X0) TRANSFORMER-2 BOARD (1070X) REAR BOARD SURROUND SPEAKER BOARD HEADPHONE BOARD VIDEO BOARD SURROUND BOARD DISPLAY BOARD MAIN BOARD POWER IC BOARD EQUALISER BOARD MUTE BOARD RELAY BOARD BALANCE VR BOARD VOLUME BOARD Fig.2: this “Circuit Boards Location” diagram for the Sony STR-AV1070X audio/video amplifier gives some indication of the physi­cal complexity of the assembly. The main board, identified on the right, is underneath everything else. it’s not surprising that only the Sony specialists knew about the fault. What is surprising is that the fault should be so common as to be instantly recognisable, even to a specialist. Washers & wire For all that, my colleague’s next statement was probably the most unexpected thing I’ve ever heard. He said, “all you need to cure the problem is five spring washers and a piece of wire!” He went to a drawer and took out an A4-sized plastic bag containing, as far as I could see, one sheet of paper. The paper carried a Sony heading and outlined a list of symptoms, just like those my customer had reported. The document gave no indication as to what causes the problem but it proceeded to give details of where and how to fit five spring washers and a short length of wire. I asked if I could have a photocopy of the paper and was told I could have that one. Then I started to remove it from the plastic bag, only to be told that I would “... need that because the washers are special!” It was only then that I noticed the five tiny internal star washers in one corner of the bag. And on the other side of the paper was a 150mm length of wire to 44  Silicon Chip complete what must be the simplest modification kit I’ve ever seen. I thanked my friend for the information and the kit, then returned to my workshop to see if I could complete the job before lunch. The five spring washers were to be fitted under the heads of two of the self-tapping screws that secured the main circuit board to the chassis and between the circuit board and the chas­ sis where it was secured by three more self-tapping screws. The length of wire was to link an earth track on the front display panel to the main earth track near the microprocessor. That sounds easy enough but when I pulled the cover off the chassis, my heart sank. One end of the frame was occupied by an enormous power transformer and the rest of it was filled with circuit boards and massive finned heatsinks. The main board, the one secured by the aforementioned screws, was at the bottom of all that lot and virtually inaccessible. There is no point in trying to tell exactly how I did the job. Suffice to say that I had to remove three of the power transistors and their associated heatsink to get at two of the screws. The other three were almost as difficult, since the washers had to go between the board and the chassis – pushed into position through a small hole in the side panel of the chassis. Lining them up was a nightmare but the job was eventually done and the screws retightened. I then had to remove the front panel to get at the track that was to be connected to one end of the length of wire. The points to be joined by the wire were only 30-40mm apart and I wondered why Sony had packed a 150mm length of wire in the modification kit. I soon found out! With the wire attached to the front panel and the panel replaced on the chassis, there was absolutely no way I could reach the wire to pull it through to the main board. I had to remove the front panel, thread the wire through a gap some dis­tance from the actual earth points, and then replace everything and pull the wire up to reach the second point. I could then cut off the surplus and make the joint. Fitting three of the spring washers and the wire link had taken me something over an hour. I then had to test the thing! Fortunately for my neighbours, I don’t have six large loud­speakers, so I couldn’t do a dynamic test. However, the owner had suggested that the intermittent front panel display always accom­ panied the volume problem and, since the volume control was motor driven and one could see if it was operating correctly, I was happy enough to sit there pressing the remote control buttons and watching for any signs of distress. No more malfunctions Fortunately, there were no malfunctions and the customer has reported no problems in the three months since he took the monster home again. So I’d say it’s cured. But what a tale of woe about something as supposedly simple as a stereo amplifier! I still don’t know exactly what was wrong with the unit but it was obviously something to do with ineffec­tive chassis connections for the circuitry associated with the microprocessor. And what an awkward, fiddly process it proved to be to fit such a simple modification kit. Thanks J. L. Your story only confirms my impression that the game is getting harder all the time. And, of course, the hills are getting steeper, the print’s getting smaller, and everySC body’s mumbling! SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.jaycar.com.au The Ecomatic Golf is entirely conventional in ap­pearance & is available in Europe in two & four-door forms. It’s what’s under the skin that makes this car so interesting. By JULIAN EDGAR Volkswagen’s Ecomatic: a whole new meaning to stop/start driv­ing Recently, Volkswagen brought a uniquely-specified demon­stration model to Australia. Called the Golf Ecomatic, it has a lot of relevance to future cars – especially those which spend most of their time in cities. At first glance, the specifications of the Ecomatic Golf don’t look very exciting – a Diesel engine with just 47kW (but 124Nm), a 0-100km/h time of 18 seconds, and a top speed (even with the car’s good aerodynamics) of only 156km/h. But it’s the fuel economy – and how VW obtains it – which is the intriguing aspect. Diesels always have good economy but with a city cycle of 4.6 litres/100km (about 62mpg) this car’s something else again! Emission levels January 1995  53 The drivetrain is based on the standard Golf Diesel, with a few additions. On the right is the huge battery which powers the heater water flow, vacuum & power steering when the engine is off, & just to the left of that is the bellows which controls the clutch movement. are also greatly reduced over a conventional diesel engine. So how do they do it? The basic approach is that the engine is switched off whenever it’s not needed. In urban use, that can amount to as much as 60% of the time. The resultant fuel saving is about 40% over a conventional car of the same type, with obvious reductions in pollution and noise emissions. The Ecomatic Golf uses a conventional Golf Diesel power­ train, from its 4-cylinder 1896cc engine to its single-disc dry-plate clutch and five speed manual gearbox. However, the car is driven in a way that’s quite different compared to a conven­tional Dash warning lights are used to indicate aspects such as the need to change gear for best fuel economy & to warn if the wrong gear is selected (for example “second” when the car is station­ary). The button on the end of the right-hand stalk switches the Ecomatic system off. 54  Silicon Chip car. For a start there’s no clutch pedal. The clutch is operated pneumatically, being triggered by a micro-switch in the (conventional looking) gear lever knob and activated only when the throttle is released. To move off, first gear is selected and the accelerator is depressed. The car drives off with a slight jerk and as revs rise the gear lever can be moved into second and so on. At the first throttle liftoff – eg, when ap­proaching a red light – the engine dies completely and the clutch automatically disconnects the engine and transmission. Changing back down through the gears is pointless – the engine is switched off and there’s no connection between it and the wheels anyway. While sitting at the lights the car is quiet and still, although all of the usual electric and engine-operated equipment, such as the brakes, heater and radio, continue to work normally. When the lights turn green, pressing on the accelerator immediately starts the engine and the car moves off – if you’ve selected first gear, that is. If you’re in the wrong gear, a warning light glows. Another warning light is used to indicate when a gear change should be made if best fuel economy is to be realised. When driving around in first gear, the engine takes five seconds of zero throttle application before it dies. This means that, for example, if you’re leaving the driveway of a petrol station and you’ve waited more than five seconds for traffic to clear, the engine will have switched off by the time you wish to join the flow. In order to maintain engine-dependent functions when the engine is off, the Golf uses a huge 92 amp/ hour battery and a 90-amp alternator. Electric motors are used to circulate coolant for the heater when the engine is stopped, while vacuum for the brakes is supplied by an electric pump. The power steering also uses electrics rather than an engine-driven pump. The electric power steering system is also more fuel-efficient than a conven­ tional hydraulic system, saving 0.1 litres/100km. A potential problem with this system is that voltage-dependent devices could be upset by the large drop in battery voltage each time the engine is started. These ancillaries include the headlights and the airbag trigger This diagram shows the layout of the control system. Note the electrical operation of the power steering, coolant & vacuum pumps. control unit. VW solved this problem by using a second, much smaller, battery to supply these ancillaries during the actual starting process. Since this typically takes less than half a second (according to VW), this battery needs only a very small capacity and in fact looks like a motorcycle battery. Electronic control system The Ecomatic electronic control system (horribly dubbed by VW the Digi-Swing) uses 13 input sensors. Coolant temperature, load, gearbox speed, road speed, gear position, brake operation and Ecomatic switch position are just some of the inputs. The amount of torque being applied to the steering wheel, whether or not the driver’s hand is in contact with the gear lever knob, and whether the bonnet is open or closed is also monitored. The latter input is necessary to avoid the possibility of automati­cally running over a mechanic working under the bonnet! The control system decides when to start and stop the en­gine, engage and disengage the clutch, switch on the pumps for power steering and vacuum, and when to switch to the auxiliary battery during engine starting. A dedicated ECU controls the Ecomatic functions. Input sensors include load, coolant temperature, gear lever movement, road speed & nine others! A range of control behaviour is built into the system. If the coolant temperature is below 40°C, the engine will not au­tomatically switch itself off, nor will it do so when the car is in reverse gear. Before the clutch is (automatically) engaged, the electronic control unit checks engine speed against output shaft speed and waits until the two are identical. VW claims that this allows the fully-laden car to move off up a one-in-five incline with no problems. Driving the Ecomatic Once you get over the shock of the engine constantly switching itself off, it takes only a short time to adapt to this car. In city use, apart from the problem of inattentive pedes­ trians who can’t hear you coasting up to them, the car works well. On open roads, the fact that the engine switches off the moment you lift the accelerator could cause a few problems when it comes to ensuring smooth cornering lines. However, this prob­lem is easily overcome by activating the override button. This disables the system so that the engine runs constantly as in a conventional car. The car is on sale in Europe now and, given the positive reaction to the demonstration car, it’s probably only a matter of time before it’s on SC sale here. January 1995  55 Control car burglar alarms with this . . . Dual channel UHF remote control This UHF remote control can control two devices indepen­dently of each other. It’s just the shot for controlling car burglar alarms & for switching other devices, such as house alarms, on & off. By BERNIE GILCHRIST Last month, we described a comprehensive car burglar alarm that you can build and fit yourself. In this article, we are present­ ing the companion remote control unit. It uses a commercial keyring transmitter plus a ready-made (and aligned) front-end receiver module so that it’s easy to build and get going. Although it’s mainly intended for 56  Silicon Chip controlling car burglar alarms, this unit can also be used for switching other electri­ cally-operated devices; eg, garage door motors, lights and model cars. The receiver board carries two relays – one for each chan­nel – and these have both NO (normally open) and NC (normally closed) contacts. They can be wired independently of each other in either latched or momentary (pulsed) mode to suit your appli­cation. Selecting latched mode simply means that the relay alter­nately operates and releases with each press of the corresponding transmitter button. Alternatively, if pulse operation is select­ed, the relay only operates while its corresponding transmitter button is held down. The companion UHF transmitter has one button for each chan­nel and transmits a coded signal to operate the receiver (and activate one of the relays) when ever a button is pressed. The code is selected using a combination of up to six wire links, which must be the same in both the transmitter and receiver (otherwise the unit will not work). Both channels can be operated at the same time, if required, by press- ing halfway between the two buttons on the transmitter. In all, there are some 4096 different code combinations and this should be sufficient to prevent interference from other users, particularly as the range is limited to about 20 metres. All connections to the remote control receiver are made via a single 9-pin nylon plug and socket. ANTENNA 12V CH1 (A) Q1 11 4TH GND 2 3 Circuit description The keyring transmitter uses an AX5026S-4 surface mount 4-state encoder IC which works with a complementary AX5027 decoder IC in the receiver. Note, however, that the decoder IC has 18 pins and provides seven address bit inputs (A1-A7) and four data bit outputs (D0-D3). By contrast, the encoder IC is a 16-pin device and only provides address bit inputs A1-A6 and data bit inputs D1-D3, with A7 and D0 not accessible. In this circuit (see Fig.1), address bits A1-A6 are used for code selection, while data bits D2 and D3 are used for channel selection. To set the security code, the six address inputs (A1-A6) can each be connected in one of four possible ways: to ground, to V+, to the 4th state pin (pin 1) on the IC, or left open circuit. This results in 46 or 4096 possible code combina­tions. (Note: a terminal has been provided to code A7 in the receiver in case a different keyring encoder is used in the future, thus giving 16,384 code combinations. However, for the transmitter used here, it must be left disconnected). The transmitter is activated by pressing either the CH1 or the CH2 button. If the CH1 button is pressed, for example, tran­sistor Q1 turns on and this does two things: (1) it lights LED 1 to indicate that the unit is transmitting; and (2) it pulls the D3 input (pin 11) of IC1 high to set the channel information Similarly, if the CH2 button is pressed, Q2 turns on, LED 1 lights (as before) and the D2 input is pulled high. The encoder IC has a single output (DOUT at pin 15) which generates a stream of pulses containing both the code and the channel information. These pulses then modulate (ie; switch on and off) a 304MHz transmitter stage. The data is sent continuous­ly while ever a button is being pressed. If both buttons are pressed, the code LED1 LED1 4 5 6 7 V+ A2 CH2 (B) Q2 16 VDD 4TH A1  IC1 AX5026 A3 VCC 11 D3 D2 10 DOUT 15 O/P 304MHz TRANSMITTER GATE OSC1 14 A4 A5 GND 470k A6 VSS 8 OSC2 13 TE 12 KEY-RING TRANSMITTER Fig.1: the transmitter is based on an AX5026 encoder IC, with data bit inputs D2 & D3 used for channel selection. Coding is achieved by connecting each address input (A1-A6) to V+, Gnd or the 4th state input, or by leaving it open circuit. information for both channels is generated by IC1 and transmitted. Receiver Fig.2 shows the receiver details. The pre-built UHF receiver front-end is a small module that uses surface mount devices. It is tuned to 304MHz and is supplied aligned and test­ed. In operation, the front-end module processes the received RF signal via a bandpass filter, an RF preamplifier, a regenera­tive detector, an amplifier and a Schmitt trigger. Its input is fed by a short antenna while the output (at pin 5) is a copy of the serial data stream that was produced by the encoder IC in the transmitter. Main Features • Dual channel – can control two independent devices • Good security – 4096 possible code combinations • Compact ready-made keyring trans­mitter • Ready-made & pre-aligned front-end receiver module for stable tuning & ease of construction • Latched or momentary relay output for each channel • A range of about 20 metres in open air The output from the front-end module is fed to the AX5027 4-state decoder (IC1) which then compares the transmitted code with the code on its own address pins (A1-6). If the codes are found to be the same, the VT (valid transmission) pin goes high, along with one (or both) of the two data terminals (D3 and D2). D3 (pin 13) goes high when channel 1 is selected, while D2 (pin 12) goes high when channel 2 is selected. Resistor R1 sets the data decoding rate so that it matches the transmis­sion rate. NAND gates IC2a-IC2d are used to decode the channel select outputs (D2 & D3) from IC1. Let’s assume that the CH1 button in the transmitter is pressed. In this case, D3 of IC1 in the re­ceiver goes high, which means that pin 3 of IC2a goes low and pin 11 of IC2c goes high. Similarly, pin 10 of IC2d goes high if the CH2 button is pressed, while both NAND gate outputs go high if both the CH1 & CH2 buttons are pressed together. These NAND gate outputs (pins 11 & 10) then drive the output stages of the circuit via one of two possible paths, to provide either latched or pulsed relay operation. Latched operation For latched operation on channel 1, the output from IC2c is fed to the clock input of 4013 D-type flipflop IC3a. This IC has its Q-bar output connected to its data (D) input to January 1995  57 +6V D3 1N4004 Q1 E BC547 C C3 0.1 V+ R4 1.8k B ZD1 1N4736 6.8V C1 0.1 +6V UHF 2 RECEIVER 5 MODULE 14 DIN 4TH GND 1,3,6,8, 10,11, 12 1 2 3 4 5 6 7 8 V+ 4TH A1 VT IC1 AX5027 A2 1 17 D3 13 A3 5 6 R1 470k OSC2 15 A6 3 IC2a 12 13 IC2c 4011 OSC1 16 A7 14 2 D2 12 A5 4 IC2b 4 14 R 1 D Q IC3a 3 4013 2 CLK Q S 6 LATCH PULSE 8 A 9 C K 4 2 E 3 1 8 V+ A 9 CH 2 LED2  6 D2 1N4004 LATCH PULSE 10 R6 R 13 1.5k D Q RLY2 R8 1.5k B IC3b 11 12 CLK Q S 7 8 B C R5 1.5k K R3 1M RLY1 R7 1.5k 7 C2 0.1 IC2d D1 1N4004 Q2 BC337 +6V 10 VIEWED FROM BELOW 11 7 9 VSS 9 E  5 18 VDD A4 A CH 1 LED1 K R2 1M 7 C4 10 C 9-PIN PLUG Q3 BC337 E RECEIVER Fig.2: the incoming RF signal from the transmitter is picked by a UHF frontend module & the detected signal fed to IC1 for decoding. IC2 & IC3 process the signals from IC1 to provide either latched or pulsed relay operation. Transistors Q2 & Q3 are used to drive the two relays. provide toggle operation. Each time IC3a receives a clock signal, its Q output at pin 1 chang­es state and remains in that state until the next clock signal is received. Assuming that the circuit has been wired in latch mode, IC3a’s Q output drives transistor Q2 via R5. Thus, if IC3a’s Q output goes high, Q2 turns on and activates relay RLY1 to operate a set of changeover contacts. At the same time, LED 1 lights to indicate that the relay is on. The relay now remains on until the transmitter button is pressed again. When that happens, IC3a’s output switches low and Q2, RLY1 and LED 1 switch off. D1 is there to quench any high-voltage spikes generated by the relay switching action. Momentary operation If the circuit is wired in pulse mode, IC2c’s output is fed directly to Q2 via 58  Silicon Chip R5, thus effectively bypassing IC3a. When the CH1 transmitter button is pressed, pin 11 of IC2c goes high and so Q2, LED 1 and RLY1 turn on as before. However, when the trans­ mitter button is released, pin 11 of IC2c switches low again and so Q2, LED 1 and RLY1 turn off. As a result, RLY1 only remains on for as long as the trans­mitter button is held down if the pulse mode linking option is selected. IC3b, Q3, LED 2 and RLY2 all function in exactly the same manner as their corresponding channel 1 components if the CH2 button is pressed. As before, either latch or pulse mode can be selected for the relay. Power supply Power for the circuit can be derived from any DC source capable of supplying 10-15V DC and 100mA (eg, a 12V car battery or a 9V plugpack supply). D3 provides reverse polarity protection for the circuit, while C4 provides supply decoupling. The result­ing +12V (nominal) rail is used to power the relays, transistors Q2 & Q3, and the LEDs. The remainder of the circuit, including the UHF front-end module, is powered from a 6V rail and this is provided by a series regulator consisting of Q1, ZD1 and R4. The circuit consumes about 5mA in the quiescent state (both relays off) and about 55mA when both relays are on. Note that when power is first applied to the circuit, IC3a and IC3b have their reset inputs pulled high via capacitors C1 and C2 respectively. This ensures that the circuit initially switches on with both relays off. The two capacitors then charge via R2 and R3 respectively and so the reset pulse ends after about 0.1 seconds, after which the circuit functions normally. Construction All the parts, including the frontend module, are mounted on a small 250mm LONG INSULATED WIRE ANTENNA 10uF 1.5k 7 NC D2 9 COMM 2 NO 3 COMM RLY1 0.1 LED1 D1 1M  P 1.5k 1 NC  P L IC3 4013 L 1 1 1M 0.1 470k 4TH GND V+ ANTENNA A7 A6 A5 0.1 Q1 1.5k IC1 AX5027 RLY2 Q3 1.8k 4 +12V 8 NO UHF RECEIVER MODULE ZD1 IC2 4011 LED2 D3 Q2 6 0V 1.5k PC board measuring 105 x 40mm. Fig.3 shows where the individual parts go on the board. Begin construction by installing the resistors (R1-R8). These can be mount­ed either way around but it is good practice to mount them with their colour codes all in the same direction as this will make them easier to check. Next, install the wire link that runs parallel to the IC2, then install the two wire links which determine latch (L) or pulse (P) operation for each channel. In fact, it’s a good idea to initially wire both channels for latch operation, just to make sure that the flipflops (IC3a & IC3b) are working. This done, install diodes D1-D3 and zener diode ZD1. These can be mount­ed in one direction only, with the stripe on the very end of the diode corresponding to the striped end on the overlay diagram. The three ICs can now be installed on the board. Make sure that you don’t get IC2 (4011) and IC3 (4013) mixed up and check that all the devices are correctly oriented. The next step is to mount the three transistors (Q1-Q3). Install each transistor so that its flat side is facing the direction shown on the overlay diagram and push them down onto the board as far as they will comfortably go before soldering their leads. Don’t press the transistors down too far though, as this stresses their leads and can damage internal connections. Note that Q1 is a BC547 device while Q2 & Q3 are BC337s, so don’t get them mixed up. Once the transistors are in, install the capacitors at the locations shown on Fig.3. The three 0.1µF (100n) MKT capacitors can be installed either way around but note that the 10µF electro­ ly­tic capacitor is polarised and must be correctly oriented. The two LEDs can either be installed directly on the board or con­ nected via long flying leads if you want to mount them at a remote location. Make sure that the LEDs are correctly oriented. In each case, the anode lead is the longer of the two while the cathode lead is adjacent to a flat edge on the body. Finally, complete the board assembly by installing the two relays and the front-end module. Note that the front-end module is oriented with its component side facing away from board. It comes fitted with a 12-pin header and these pins must be bent at A4 A3 A2 1A1 WIRE LINK FOR PULSE (P) OR LATCH (L) MODE Fig.3: the two wire links marked with an asterisk (*) are either connected to “L” for latched operation or to “P” for pulsed operation. The coding pads are at the righthand end but note that A7 must be left open circuit. The completed board assembly is mounted on the lid of the case using 12mm tapped spacers & machine screws. Note the coding links at the righthand end. right angles so that it mounts vertically as shown in the photos. In order to obtain a decent range, an insulated wire anten­ na must be connected to the EXT ANT input. This antenna should be 250-300mm long but can be increased to about 500mm to obtain a slightly greater range. Testing When the assembly is completed, connect the receiver to a 12V DC power supply and press the CH1 (A) transmitter button. If the unit is working correctly, relay RLY1 will immediately latch on. Check that this relay can now be turned off by again pressing the CH1 transmitter button. The second channel is checked out in exactly the same fash­ion (ie, RLY2 should toggle each time the CH2 (B) button is pressed). If everything is working OK, you can also check the effective range of the unit. It should operate reliably up to about 20 metres in open air. This range will be somewhat reduced if the receiver is placed inside a car, depending on the location of the antenna. Once these initial checks have been made, switch off and reconfigure the links (if required) to obtain the required relay operating modes (ie, either latch or pulse for each channel). Note that you will have to configure channel 1 so that it oper­ates in latch mode if you intend using this unit to control the Car Burglar Alarm described in last month’s issue. Coding As supplied, the transmitter comes with its A1-A6 address pins (pins 2-7) all open circuit (ie, the transmitter is not coded). Fortunately, the job of coding is fairly straightforward although you do need good eyesight and a soldering iron with a fine tip. An eyeglass or a magnifying glass will be handy for this job. January 1995  59 leaving the address pin open circuit. Note that address pin A7 must be left open circuit to suit the transmitter used here. Be careful not to link any of the three columns closest to the end of the board together, otherwise damage may result. Apart from that, it’s simply a matter of matching the re­ceiver’s code to that programmed into the transmitter. Check your work carefully here – if the two codes are different, the unit won’t work. Final assembly Mount the UHF front-end module with its component side facing outwards, as shown here. Note that the module is supplied pre-aligned to 304MHz & requires no further adjustments. 1 2 3 4 5 6 7 8 9 9-PIN PLUG ALLOCATIONS 1 CHANNEL 1 RELAY OUTPUT NC 2 CHANNEL 1 RELAY OUTPUT NO 3 CHANNEL 1 RELAY OUTPUT COMMON 4 +12V INPUT 5 NOT USED 6 0V INPUT 7 CHANNEL 2 RELAY OUTPUT NC 8 CHANNEL 2 RELAY OUTPUT NO 9 CHANNEL 2 RELAY OUTPUT COMMON 9-PIN NYLON PLUG VIEWED FROM BACK The transmitter case consists of two half sections which are simply clipped together. They are separated by lightly squeez­ing the sides of the bottom section, then prising the two sec­ tions apart. This done, remove the battery and the PC board from the case. All you have to do now is connect each A2-A6 address pin (pins 2-7) of the IC in one of four possible ways: (1) to a strip on the top surface of the board labelled 4TH; or (2) to a strip on the bottom surface of the board labelled V+.; or (3) to a strip on the bottom surface of the board labelled G; or (4) leave the pin open circuit. For example, you might decide to tie A2 to 4TH, A3 to G, A4 to V+ and leave A1, A5 & A6 open circuit. That’s just one possi­ble code combination – you should use a different combination to ensure that you have a unique code. The completed PC board can now be installed in a plastic zippy case measuring 41 x 68 x 130mm. As shown in the photos, the board is mounted on the lid of the case and is secured on two 12mm tapped spacers using four machine screws. You can use the board as a template for marking out the two mounting holes. An additional hole will also have to be drilled in one end of the case to provide an exit point for the 8-wire cable and for the antenna. The external wiring cable can be made up from eight 200mm lengths of medium-duty hook-up wire. Connect the leads to the PC board as shown on Fig.3, then sleeve them with a 170mm length of heatshrink tubing. The cable can then be passed through the hole in the plastic case and the various leads connected to a 9-pin plug. A plastic cable tie can be secured to the cable just inside the case to prevent the leads from being pulled out of the board. Fig.4 shows the wiring details for the 9-pin plug, as viewed from the back. Each lead is terminated by first soldering it to a special pin which is then pushed into its appropriate location from the back. Make sure that you install each pin in its correct location, as they are impossible to get out if you make a mistake. Fig.5 on page 40 of the December 1994 issue shows how to connect the unit to control the Dick Smith Fig.4: this diagram shows the pin allocations for the 9-pin plug as viewed from the back (or wiring side). Short links of fine wire can be used to make the connections. Be sure to keep a record of the code, since you will need to code the receiver with exactly the same combination. Import­ant: do not make any connections to pins 1 & 16 of the IC during the coding procedure. Once coding has been completed, the transmitter can be carefully reassembled by installing the parts and clipping the two halves of the case together. Make sure that you install the battery with the correct polarity – the positive terminal is indicated by a moulded “+” sign on the bottom section of the case. If everything is OK, the LED should light when one of the transmitter buttons is pressed. The same code can now be programmed into the receiver by linking each A1-A6 address pin of the decoder IC (AX5027) to 4TH, G or V+ at one end of the board, or by TABLE 1: RESISTOR COLOUR CODES ❏ ❏ ❏ ❏ ❏ No. 2 1 1 4 60  Silicon Chip Value 1MΩ 470kΩ 1.8kΩ 1.5kΩ 4-Band Code (1%) brown black green brown yellow violet yellow brown brown grey red brown brown green red brown 5-Band Code (1%) brown black black yellow brown yellow violet black orange brown brown grey black brown brown brown green black brown brown The transmitter is disassembled by carefully prising the two halves of the case apart. The 4TH state line is clearly visible to the right of the IC. Electronics Car Bur­glar Alarm. There are just four wire connections: the two power supply connections, a connection between the NO contact of RLY1 and the ARM/DISARM input of the alarm, and a connection between the common contact of RLY1 and the 0V rail. If you intend using the unit for some other purpose, note that it is suitable for switching low-voltage equipment only (up to 28V DC at a few hundred milliamps). Do not try to switch mains voltages using the on-board relays – the relays are not rated sufficiently to do this job, nor is the board designed to accommodate mains voltages. If you do need to control high voltage equipment, then this may be done by using the unit to control external heavy-duty relays which are rated to do the job. Troubleshooting If it doesn’t work, the first step is to check that the transmitter and receiver are identically coded. If this checks OK, check the supply rail to the frontend module and to the three ICs in the receiver. You should find +6V on pin 7 of the front-end module, on pin 18 of IC1, on pin 14 of IC2 and on pin 14 of IC3. If this voltage is incorrect, check D3, Q1 and ZD1. If the supply rail is OK, set your DMM to a low AC range and connect it between pin 9 of the front-end PARTS LIST 1 2-channel UHF keyring transmitter 1 PC board, code ZA1307, 104 x 40mm 1 UHF front-end receiver module 2 12V miniature SPDT relays, DSE Cat. P-8007 1 9-pin nylon plug & socket 1 plastic zippy case, 41 x 68 x 130mm 2 200mm lengths of mediumduty hookup wire (red & black) 3 400mm lengths of medium duty hookup wire (white, blue & yellow) 1 170mm length of 12mm-dia heatshrink tubing 2 12mm-long tapped spacers 4 3mm x 5mm-long machine screws 1 plastic cable tie Semiconductors 1 AX5027 decoder (IC1) 1 4011 quad NAND gate (IC2) 1 4013 dual D flipflop (IC3) 1 BC547 transistor (Q1) 2 BC337 transistors (Q2,Q3) 3 1N4004 silicon diodes (D1-D3) 1 1N4736 6.8V zener diode (ZD1) 2 3mm LEDs (LED1,LED2) Capacitors 1 10µF 16VW electrolytic 3 0.1µF (100nF) MKT ceramic This close-up view clearly shows the V+ & Gnd coding lines on either side of the A1-A6 address pins on the underside of the transmitter board. module and ground. Apply power and check that the DMM reading increases when you press one of the transmitter buttons. If it doesn’t, then either the transmitter is suspect or the front-end module is faulty. If the reading does increase as expected, switch off, set the DMM to measure DC volts and check that pin 17 of IC1 swings high when either button is pressed. Check the timing resistor (R1) and the coding if this does not occur. If the reading does go high, check that pin 11 of IC2 goes high when the CH1 button is pressed and that pin 10 goes high when the CH2 button is pressed. If either relay still refuses to operate, check its asso­ c iated driver Resistors (0.25W, 1%) 2 1MΩ 1 1.8kΩ 1 470kΩ 4 1.5kΩ Where to buy a kit A complete kit of parts (Cat. K3260) is avail­ able from all Dick Smith Electronics Stores or by mail order from PO Box 321, North Ryde, 2113. The price is $99.95 plus $7.00 p&p (includes one trans­ mitter). Additional transmitters (Cat. K­3261) are $39.95 each. Note: copyright of the PC board artwork for this design is retained by Dick Smith Electronics. transistor (Q2 for channel 1, Q3 for channel 2). If either relay works OK in pulse mode but not in latch mode, check the connections around IC3. Try changing the IC only as a last SC resort. January 1995  61 COMPUTER BITS BY DARREN YATES A low-cost emulator for Zilog’s Z8 microcontroller Creating your own microcontroller projects is not as hard or expensive as you may have thought. GEC Electronics now has available Zilog’s new low-cost emulator for their Z86C04/ E04 & Z86C08/E08 8-bit microcontrollers. We take a look at the IceBox to see what it can do. Microcontrollers either have you interested or totally bored but whatever your persuasion, they represent the “now” generation of electronics. They are more often than not seen as little “do-everything” boxes capable of solving just about every circuit problem. Now while that may be the case for industry, for the aver­age hobbyist they are still pricey, particularly the programming systems. Let’s take a look at the pros and cons. Programmer vs Emulator It used to be that code was hand-programmed into the chip but now all programming is done via the PC, which can make for a much more convenient approach. The convenience depends on what path you follow. While microcontroller programmers are relatively cheap (ie, around a few hundred dollars), they do present someth­ing of a problem. If you are debugging code and trying to fine-tune your project, you are forced to erase and reprogram your EPROM microchip each time you wish to change the code. This may sound fairly simple but it is a time-consuming exercise. This is also an expensive approach. Most distributors will tell you that their micros are cheap but that’s so long as they’re only talking about One-Time Programmable (OTP) devices. When you start to talk about the EPROM versions, which you need if you only have a programmer, the price skyrockets – you can expect to pay 5-10 times the cost of an OTP part! In real terms, this could be anywhere up to $35 more. The better alternative is to have an emulator. This is a board which can actually emulate or take the place of a chip. The board has a socket and a cable is connected between it and your circuit. The cable has a header on it which takes the place of the chip in your project. You now simply program the board to act like the chip and you no longer need the expensive EPROM part. The beauty of this system is that you can modify your code and check it instantly – there’s no waiting to erase the UV PROM in the chip which means that you can get your project up and running a lot sooner. The IceBox The register windows allow you to not only see all registers at a glance but also to edit any one by simply wiping over the register you wish to edit & typing in the new value. The ASCII equivalent of that code is displayed on the right. 62  Silicon Chip So what’s so good about Zilog’s IceBox? Firstly, it is low cost. For an emulator from most other micro­ controller manufactur­ ers, you can Zilog’s IceBox emulates the Z86C04/E04 & Z86C08/E08 devices & costs just $285 plus tax. It comes with two manuals which include application notes & the software is designed to run under Windows. All you have to add is a 9V DC power supply & a DB25 serial cable. can quickly compare code from two different applications as well as open multiple windows. You can open a memory map window as well as output port status windows – in fact, you can open every option available at the same time if you so wish. Thirdly, the Zilog Z86E04 chips which it emulates are very competitively priced at around $2.75 each in quantities of a hundred. In OEM quantities, the masked-C04 part price can be as low as $1.20. This rises to around $4.55 for one-off but it is still quite cheap when you consider what they can do. It will also emulate the Z86C/E30 and 31 devices (among others) which have more I/O lines. The IceBox will run quite happily on an old 286 PC but Zilog recommend that you use a 386 PC to get maximum performance. You’ll also need at least DOS 5 and Windows 3.0. There are two manuals which include applications notes and ideas, as well as code examples to get you going. All you need to add is a 9VDC 500mA power supply, a serial DB25 cable and the ideas. Now while the IceBox emulator is well worth a look, what about the devices themselves? The Z86E04/08 This shows both the code & data memory windows. Again, each one is shown in hexadecimal format (which can also be switched to binary). The data memory has no meaningful data in it & displays its default settings; ie, FF hex. Both can be edited by wiping over the particular byte & writing in the new value. expect to pay over $700. The IceBox is available for only $285 plus sales tax, and that includes a sample chip and all software. Secondly, the software itself is well designed and runs from Windows. The software programmer is very well written and is much easier to use than most DOS-based programmers. By operating from Windows, you The Z8 micros are 8-bit standard instruction code set devices but they have a very high proportion of input/ output (I/O) lines compared to the number of device pins (14 I/O lines for an 18-pin package). However, some of the more unusual features are within the chip itself. The Zilog range starts with the Z86E03 which has 512 bytes of ROM and continues through up to the Z86­ E63/64 which has 32K of ROM. I/O lines also can range from 14 for the smaller devices up to a whopping 52 for the Z86E64. The particular OTP devices of interest are: (1) the E04 which has 1K x 8 of read-only memory (ROM) and 124 x 8 random-access memory (RAM); and (2) the E08 which has 2K of ROM and 124 x 8 RAM. Each of these bytes of RAM is individually addressable so you don’t need to waste time working through an accumulator to get to a particular piece of data. Another good feature is that all software is transferrable to other members of the Z8 family. This makes it easy to upgrade from one device to another to suit your particu­lar needs. January 1995  63 Each device has two comparators which can accept analog signals and produce a high or a low, referred to a common exter­ nal reference voltage. This reference voltage can be anywhere between 0 and 4VDC (the supply voltage is 5VDC). What this does is make it very easy to interface outside analog circuits with the micro. The two on-chip comparators also allow you to create anal­og-to-digital converters (ADCs). Since eight of the 14 I/O lines are arranged into an 8-bit register address, you can easily pro­ gram an 8-bit digital-to-analog converter (DAC) and create a fairly quick 8-bit ADC using the microcontroller as a successive approximation register. The comparators can also link to internal program inter­ rupts which allow you to tell the micro to execute a certain portion of code upon receiving an external voltage level of some kind. This should give plenty of scope for experimentation. Timing For timing considerations, there are two on-board 8-bit counters, both of which run as a function of the main clock but one can also be programmed to work from an external clock source. This can be very handy if you’re working on a frequency counter, for example. Each counter has a 6-bit programmable prescaler to allow you to define a start position. This is useful for working on time-critical applications where you want a specific time to pass before executing some program branch. These counters can also be linked to internal interrupts and the current value of the counter is available in a specified register which can be read at any time. They are also reasonably fast, with the E04 capable of clocking at 8MHz and the E08 at 12MHz. Current consumption is in the order of 5-10mA, depending on the device, application and speed. Each device also has two sleep modes; one turns the device off, while the other also turns the main clock off. In this latter mode, current consumption falls to just 1µA which makes them entirely suitable for battery operation. By programming one of the external interrupts, you can easily wake the device back up again, even from this almost “dead” position. Both devices have power on reset, which starts the 64  Silicon Chip If your code isn’t working quite write, this is where you come. The debug window allows you to see each line of code and allows you to step through the code by any number of lines, which you can specify. The trace code box displays each line of code executed after its completion. You can also set break points though the code to find a particular error condition. Downloading hex code from the PC into the emulator is easy. You simply click on the DOWNLOAD option and you are presented with this screen. When you click on OK, the code is automatically loaded. The file format can be in either standard INTEL hex or binary. micro and enables it to begin executing code from location 000C(hex). OTP capability The E04/08 OTP option allows you to mass-produce low cost proprietary software fairly easily and, most importantly, these devices can be ROM protected. This feature enables the programmer to lock away the code so that it can’t be copied. Overall the Zilog IceBox emulator is a winner. It brings together a low-cost emulator system with a good all-round micro from one of the oldest manufacturers in the game. It certainly is the lowest-cost, most efficient programming system I have yet come across. For $285 + tax, it is excellent value for money. The package includes cross assembler, graphical user inter­ face (GUI) software and object utility files, as well as an emulator operating manual and a Zilog technical reference man­ual. For more information on the Zilog range of devices, contact Russell Lemon at GEC Electronics in Sydney. SC Phone (02) 638 1888. Build this stereo microphone preamplifier . . . and get the most out of your tape recordings By DARREN YATES If your dynamic microphones don’t have enough output, try this portable mic preamp. It has low noise & only .008% distortion. What’s more, it runs off two 9V batteries for about 100 hours & is built into a metal diecast case to shield out un­ wanted hum. If you do any outdoor audio recording, then you’ll be familiar with how microphones work and how to get the best sound possible with your gear. The major problem these days is that most microphones are dynamic types. But while these have a superior noise performance compared to other types, they are usually not very sensitive, most being somewhere around -75dBV. By comparison, the older elec­tret and condenser microphones were often as sensitive as -60dBV which is quite a big difference in output. This lower sensitivity for dynamic microphones is usually of no consequence when you are recording sources close-up. Howev­er, if you are trying to record distant sounds, such as bird calls, it can make things quite difficult. Although a recording will still be possible, it will have a great deal more noise due to the necessity to drastically increase the gain of the recorder’s preamplifier stages. Naturally, the results will vary from recorder to recorder but even some well-known professional recorders will introduce noise if the preamplifier gain is advanced too far. The way around this problem is to increase the signal from the mi- crophone before it is fed into the recorder mic input. And that’s the job of the Stereo Microphone Preamplifier described here. It is simply inserted into the audio path between the micro­phone(s) and the tape recorder and provides a fixed amount of gain in each channel. This, in turn, enables much lower set­tings of the gain controls and so drastically reduces recording noise. In the prototype, the gain has been fixed at 10dB but this can be altered for each channel simply by changing a single component. The signal-to-noise ratio is 90dB with respect to 10µV, which is very quiet, while the distortion is just 0.008%. In addition, the unit is built into a diecast aluminium case which not only makes for a rugged design but stops any stray hum from getting into the circuit. The circuit Take a look now at the circuit details – see Fig.1. As can be seen, it is based on a single LM833 dual op amp. Each channel uses one section of the op amp package and this is connected as a non-inverting amplifier. The 2.2kΩ and 1kΩ resistors in the negative feedback network set the gain to 3.2, which is just a tad over 10dB. The .001µF January 1995  65 S1a 0.1 0.47 RIGHT INPUT 1k 22k 8 3 2 IC1a LM833 1 10 16VW 100  RIGHT OUTPUT 22k B1 9V 2.2k .001 1k 0.47 LEFT INPUT 1k 22k 5 7 IC1b 4 100  LEFT OUTPUT 22k 4 B2 9V 2.2k .001 1k S1b 0.1 10 16VW STEREO MICROPHONE PREAMPLIFIER Fig.1: the circuit is based on a single LM833 dual op amp. Note that each section (IC1a & IC1b) wired as a non-inverting amplifier with a gain of 10dB. capacitors ensure that the frequency response rolls off above 72kHz, while the two 1kΩ stopper resistors at the non-inverting inputs reduce the sensitivity to RF noise. To ensure that the preamp can be used with any microphone, the inputs are AC-coupled via 0.47µF capacitors, giving a fre­quency response down to 15Hz. When you consider that most dynamic microphones start at around 60-80Hz, this is more than adequate. The outputs from the op amp stages appear at pins 1 & 7 and are fed to the right and left output sockets respectively. Final­ly, ±9V supply rails are derived from the two 9V batteries via douple-pole on/off switch S2. If alkaline batteries are used, they should provide about 100 hours of continuous operation. The supply rails are decoupled using 10µF electrolytic capacitors. Construction All of the components except for the power switch, the four 6.35mm sockets and the batteries are installed on a small PC board measuring 48 LEFT OUTPUT x 58mm and coded 01111941. Fig.2 shows the wiring details. Before you commence construction, check the board thorough­ly for any shorts or breaks in the PC tracks. If you find any, use a small artwork knife or a dash of solder to fix the problem where appropriate. When you’re sure that the board is OK, begin the assembly by installing PC stakes at the external wiring points (12 in all). This done, install the three wire links, followed by the resistors, capacitors and the IC. We recommend that you check the value of each resistor on your multimeter, as some of the colours can be difficult to decipher. Take care with the orientation of the two 10µF capacitors and the IC. The notched end of the IC is adjacent to pin 1 and must face towards the two 0.1µF MKT capacitors. If performance is critical, you can substitute the OP275GP dual op amp from Analog Devices or the NE5532AN device from Signetics/Philips. These devices are slightly more expensive and not as easy to obtain as the LM833, however. Once the board assembly has been completed, position it inside the case at one end (see photo) and mark out its corner mounting holes. Drill these holes to 3mm, then attach the front panel artwork to the lid of the case and drill the hole for the power switch. The lid should now be fitted to the case and the front panel label used as a guide for marking out the locations of the input and output sockets (two on either side of the case). These holes should be located about 12mm from the top rim of the base. Drill these four holes using a small pilot drill initially, then carefully enlarge them to size using a tapered reamer until LEFT INPUT IC1 LM833 1k 22k 1k 22k 10uF 100  1k -B1 2x0.47 1 2.2k +B2 S1 1k 0.1 .001 0.1 10uF 2.2k 22k 100  22k .001 -B2 RIGHT OUTPUT +B1 66  Silicon Chip RIGHT INPUT Fig.2: install the parts on the PC board & complete the wiring as shown here. Take care with the orientation of IC1 & the two 10µF electrolytic capacitors. PARTS LIST 1 PC board, code 01111941, 58 x 48mm 1 diecast aluminium box, 121 x 61 x 39mm 1 self-adhesive front-panel label 4 6.35mm panel-mount sockets 1 DPDT toggle switch 2 9V battery snap connectors 2 9V alkaline batteries 12 PC stakes 4 15mm x 3mm dia. machine screws 8 3mm nuts 4 self-adhesive rubber feet 1 200mm-length of medium-duty figure-8 cable Semiconductors 1 LM833 dual op amp (IC1) The circuit is housed in a diecast metal case which provides shielding against stray hum fields. Note that shielded cable must be used for the input & output connections to the preamplifier sockets. INPUT OUTPUT L L the sockets are an exact fit. The PC board is secured to the base of the case using ma­chine screws and nuts, with an additional nut under each corner acting as a spacer. Make sure that the board is oriented so that its input terminals are to the right. This done, complete the battery switch wiring, then connect short (40mm) lengths of figure-8 cable to the input and output terminals. The four 6.35mm sockets can now be mounted in position and the wiring to them installed. Note that the centre terminal of each socket must go to the earth pattern on the PC board. On the prototype, the batteries were secured using double-sided adhesive tape. A piece of foam rubber is subse­quently wedged into position when the lid is closed to prevent the batteries from coming adrift. Finally, four rubber feet should be fitted to the bottom of the R R POWER ON PORTABLE MICROPHONE PREAMP Fig.3: here are full size artworks for the front panel & the PC board. Capacitors 2 10µF 25VW electrolytic 2 0.47µF 63VW MKT polyester 2 0.1µF 63VW MKT polyester 2 .001µF MKT polyester Resistors (0.25W, 1%) 4 22kΩ 4 1kΩ 2 2.2kΩ case to prevent scratches to desktops and other surfaces. Testing Before switching on, go over your wiring carefully and check that all is correct. This done, apply power and check the supply rails to the IC. Pin 8 should be at +9V (measured between pin 8 and ground), while pin 4 should be at -9V. The quiescent current should be about 7mA and this can be checked by connecting a multimeter in series with one of the supply rails. If everything checks out OK so far, you can now check that the unit works in practice. To do this, connect the microphones and the tape recorder and check that the gain controls on the recorder can now be set to a much lower level than before for a given sound level. If you need more gain, simply increase the 2.2kΩ feedback resistor in each channel. Finally, if only one channel is to be used, the input of the other channel should have a 1kΩ resistor connected across it. This is best done by soldering a 1kΩ resistor across a spare plug and SC plugging this in as required. January 1995  67 SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings. Please feel free to visit the advertiser’s website: www.altronics.com.au BOOKSHELF Sound & Recording: An Introduction Sound and Recording – An Introduction, by Francis Rumsey & Tim McCormick. Published 1992 by Butterworth Heinemann, London. Soft covers, 318 pages, 234 x 156mm, ISBN 0-24051313-4, $85.00. If you’re looking for a good general introduction to the world of sound recording, then you’ll definitely need to look at this one. “Sound and Recording” is a good reference book which covers just about every issue related to sound recording, from audio perception through to the latest digital techniques. Chapter 1 covers the basics of how sound travels, units of measurement and the frequency spectrum. Chapter 2 continues on how we hear sound, from the mechanics of the ear to how we perceive sound direction. Chapter 3 deals with the signal path from source to speakers and introduces the basic components of sound record­ing. Chapter 4 deals with these in detail, starting with micro­phones, how they work, how their responses are measured and plotted, as well as looking at the various types available. Chapter 5 progresses to loudspeakers, giving basic mechani­ cal theory that relates to today’s common systems as well as ideas on positioning speakers for best response. Chapters 6 & 7 deal with mixers and they cover various features from fade to pan and how each of the controls works. Chapter 8 talks about the world of analog tape recording, giving some brief history and then discussing the recording process, including equalisation and biasing requirements. Various recording formats are also looked at as well as different types of recorders. Chapter 9 moves on to noise reduction and gives background information on the well-known examples; ie, Dolby A/B/C and dbx. Chapter 10 explains the basics behind digital recording and explains quite well some of those sometimes confusing topics of sampling and quantisation. Various formats are also presented including R-DAT and Nagra-D and Sony’s PCM system. The chapter then moves on to discuss hard disc recording techniques including discussion on how hard discs are built and finally, optical discs. Sony’s Mini Disc is not covered, as you might expect, since it is so recent. Chapter 11 covers the principles of operation of the record player, including lateral tracking of the tonearm, RIAA equalisa­ tion and arm design. Discussion then carries over to turntable design. Chapter 12 looks at power amplifiers and topics such as distortion, crosstalk, signal-to-noise ratio and frequency re­sponse, while chapter 13 looks at the important area of signal lines and interconnections, covering topics such as hum loops, transformers and balanced line systems. Chapter 14 looks at add-on equipment which can improve the apparent quality of sound from graphic equalisers, dynamic range limiters and compressors as well as effects such as reverb and echo. Chapter 15 takes a brief look at MIDI, what it is and where it’s used, as well as explaining how it works from a user’s perspective. All throughout the book, little “fact file” panels concisely explain common concepts relevant to the current chapter and are ideal for those looking for more in-depth information. Overall, this is quite a good book and ideal for anyone who wants to find out more about audio or for those who want a basic reference for their bookshelf. (D.B.Y.) In Marconi’s Footsteps: Early Radio In Marconi’s Footsteps – Early Radio by Peter Jensen. Pub­lished 1994 by Kangaroo Press, Sydney. Hard covers, 176 pages, 286 x 220mm, ISBN 0-86417-607-4, $49.95. If you’re looking for a good read on how radio began, then this is the book! It follows the early steps of one Guglielmo Marconi and how his idea of a “wire-less” telegraphy system transformed the European stage. The first half of the book is an historical perspective on Marconi. It covers his childhood, his arrival in England as a young man with ambition, through to his chance meetings that helped to establish “wire-less” as the newest form of mass commu­nication. Other areas covered include the Clifden Radio station, the first transmission from England to Australia in 1918, and the effect that the sinking of the Titanic had on wireless. The second half of the book is of a more technical nature, with circuits and diagrams of some of the early transmitters and receivers, including the coherer detector and the crystal set. The schematics and mechanical diagrams presented are quite detailed continued on page 88 January 1995  71 REMOTE CONTROL BY BOB YOUNG Working with surface mount components – easier than you think The introductory article on the new radio control system last month has really put the cat amongst the pigeons. Readers have reacted with horror & revulsion at the thought of using surface mount components so it seems appropriate to discuss these devices in detail before we go any further. I know, I know. I promised that this month would see the circuit of the receiver for this R/C series but the best laid plans of mice and men and all that . . . I have found it neces­sary to make a few revisions to the design which has now been test flown over quite a few weekends and before I go into print with these, I want some more test flying done. So to stop the editor from taking a fit of apoplexy, I olution is no longer so quiet, for the movement towards surface mount is now rolling along at full steam ahead. Everyone, it appears, is now climbing on the SMD bandwagon. So much so that the usual ridic­ulous 8-12 week component delivery times have blown out to the insane. Surface mount devices for model work, and model aircraft in particular, offer many advantages over “I can now hand-assemble a surface mount PC board in a fraction of the time it took me to complete a comparable through-hole assembly. And, as an added bonus, the finished result is a much better unit all round”. am bringing forward this article which would otherwise have been presented in a couple of months’ time. One of the revolutions that has quietly overtaken the elec­ t ronics industry over the past few years has been the introduc­tion of surface mount PC board assemblies. This quiet rev72  Silicon Chip conventional leaded (through-hole) components. To begin with, the components are very small and thus quite light. More important, however, is the fact that the components sit flat on the PC board and thus in a crash will not bend or shear off at the lead/body junction. Thus, the final assembly is much more robust and gives fewer failures in service. For these reasons, I have chosen the surface mount format for the R/C project to be presented in the coming months. Therefore, I feel that it is appropriate to present a de­tailed article on how to handle surface mount components by hand, in anticipation of the requests I will receive for this sort of information. Most people I have spoken to over the past few years regard surface mount with some apprehension, if not active dislike. This is a pity actually for as I will demonstrate, surface mount offers many advantages, even from a hand assembly point of view. Obviously the major thrust towards surface mount comes from the fact that it was originally designed for rapid machine assembly, with the cost savings that accrue from automation. But even from a hand assembly point of view, surface mount has much to offer and I have now arrived at a point where I would sooner work with surface mount components than through-hole. When working with surface mount, you just simply solder each end of the component to the PC pads and that is it; no spending hours bending and shaping leads. There is no fumbling around trying to push leads through holes or working in a forest of leads, or trying to get solder and iron into an almost impos­sible to reach location. Nor is there any going back and snipping leads which fly around the room, turning the workshop into a safety goggle area. When I look back at that form of assembly, I shudder these days. I can now hand-assemble a surface mount sembled in this manner in the future. Thus, it is not too difficult to envisage a situation in the not too distant future where some components will only be available in surface mount form. For these reasons, it is important that people involved in electronics start to come to grips with the techniques involved in building and repairing in surface mount. What is surface mount? Fig.1: this is a typical surface mount assembly machine. Note the large reels which take a minimum of 3000 components. PC board in a fraction of the time it took me to complete a comparable through-hole assembly. And, as an added bonus, the finished result is a much better unit all round. Disadvantages Possibly the major disadvantage is the fact that some components are not marked and this forces upon people working in surface mount an almost fanatical sense of discipline with regard to storage of components and recording of components placed. Service is likewise a little more difficult when dealing with unmarked components. For our prototype and service work, we use a tray drilled to accept pill bottles. Both the lid and the bottle are marked and we even punch holes in the lids so that they do not have to be removed from the bottle. Components are removed from the bottle with tweezers. The worst situation is one such as I encountered with the receiver front end developed for this current project. Here I was working with up to six prototypes simultaneously, all using a large number of unmarked components (mainly capacitors). Every receiver had to be numbered and every component change had to be recorded, because once you put that unit down, five minutes later it was impossible to remember what was on that board. The real problem arose when I got tired and forget to record a change. What was on the board? There was no way of knowing except by removing the component and measuring the ca­ pacitance or replacing it with a known value. This is all very tiresome and consumes a lot of time. Capacitors can be purchased with markings but are more expensive and thus few and far between. Once the unit is in production, then document control becomes extremely important from a service point of view. These disadvantages are minor though when compared with the benefits obtained from this very important development in component technology. From the electronic enthusiast’s point of view, the import­ant point is that surface mount is here to stay and more and more equipment will be as- Surface mount is a system of assembly utilising components which are designed to be placed by machine flat onto the surface of a PC board which has already been prepared with a screened solder paste. This PC board and its components are then run through an oven or wave solder machine to complete the soldering process. There are many forms of soldering techniques and it is not proposed to delve too deeply into this aspect of surface mount. Our concern today is with the hand assembly of these components. However, it is important for servicemen to know that one very important difference between wave soldering and infrared reflow, for example, is that infrared reflow does not require the compon­ ent to be stuck to the PC board with epoxy adhesive before it is soldered. This makes servicing just that much easier than dealing with components stuck down with epoxy. The reason for the epoxy being needed for wave soldered SMDs is that the solder wave will wash the components off the PC board unless they are stuck down first. It is interesting to note that we regularly assemble doubled-sided surface mount boards without epoxy, using infrared reflow. In this case, the solder paste is sufficiently tacky to hold the components in place on the underside of the PC board while it moves through the reflow oven. The automated PC board assembly process begins with the preparation of a PC board with specially shaped pads. These are designed to ensure that the resultant soldering process results in a satisfactory bond without skewing the component around. The shape of the pad and the way the tracks meet the pad are very important because we are dealing with very light compon­ents in a fluid (molten solder) with very high surface tension. This is doubly important when using infrared January 1995  73 reflow without epoxy. Always keep in mind here that we are dealing with compon­ents sitting flat against the PC board with no lead through a hole to stop movement. Poorly designed PC board layouts can result in components skewing around and shorting out on the component next to them. As our usual component spacing on tight PC boards is 0.020-inch, even a small movement can have serious consequences. Square pads with heavy tracks coming in at 45 degrees are notorious for pulling components around. Some PC board manufacturers appear to have difficulty understanding this, for I have often rejected PC boards from manufacturers when they have substituted square pads for our rounded rectangles. Component assembly The physical assembly process begins with the screening of the solder paste onto the PC board. The solder paste mask is etched into brass shim and the thickness of the shim determines how much solder will be applied to the join, the usual thickness being 0.008”. The solder paste mask is 0.005” less in diameter than the pad size, to stop solder from spilling over the edge of the pads. The screened PC board is then run through a surface mount assembly line. There are a myriad of these machines and Fig.1 shows a typical example. Note the reels holding the components. Ordering components for surface mount is not for the faint heart­ ed as the minimum reel size number of vias in the PC board. I am very reluctant to put a track under an 0805 using rounded rectan­gle pads. However, the Japanese do it regularly and appear to have no problems. Other components we will encounter in this project are the SOT23 transistor and diode packs, a little 3-prong package and the SO14 and SO16 surface mount IC packages. Kit presentation Fig.2: this shows the receiver board with all components soldered at one end. Each component is soldered at one end first while being moved into position with a pair of fine tweezers. Note that the board is shown here slightly larger than actual size. run through the soldering station. The finished product is a joy to behold, with bright solder joins which are fully wetted and with good meniscuses. That is provided nothing goes wrong, which it very easily can do if the entire process is not monitored very carefully from PC board design to soldering. The basic building blocks in the surface mount component range are of course the resistors and capacitors. These are usually little rectangular blocks and are often defined by their size in inches. Thus, a 1206 resistor, the most commonly used size in our component range, measures 0.120” x 0.060”. There are many sizes in the range, however in this project we will only encount­er a few of them. Fig.2 shows some of the more common components in surface mount. The small “Hand assembly of a surface mount PC board is very easy provided you have a good magnifying lamp or glasses, a soldering iron with a very fine tip, a pair of tweezers, a solder sucker & a steady hand”. holds 3000 components. Resistors come in reels with a minimum of 5000 per reel. Surface mount does not lend itself very well to small runs, as the setup costs are high. On long runs, it is the only way to go. Once the PC board is loaded with components, it is then 74  Silicon Chip capacitors in the receiver, for exam­ple, are 0805 (0.08” x 0.05”). The Japanese manufacturers have virtually standardised on 0805 and most Japanese equipment uses this size component. I find 1206 more practical as two tracks can be slipped under a 1206 safely, thus reducing the The kit will be presented in two forms: (1) an assembled surface mount PC board leaving the through-hole assembly to the customer; and (2) a full kit which will feature a bare PC board and packs of surface mount components. A note here on component marking. The resistors are always clearly marked in the usual 3-digit format (4-digit for close tolerance components). Thus, a 100kΩ resistor will carry the marking 104 or 1003 for close tolerance. The capacitors may or may not be marked (most commonly not). If they are marked it will be in a 2-letter code (usually) which will look something like AO. The manufacturer’s code list is necessary if you wish to decode this symbol. Likewise, the markings on the SOT23 packages are in a 2-digit format and again the manufacturer’s list is needed to decode it. For example, a BAS16 diode carries the marking A6 and the BFT25 transistor, V1. So be very careful when handling those unmarked components. You have been warned! Hand assembly of the surface mount PC board is very easy provided you have the correct tool kit. Do not under­take hand assembly unless you have the following equipment: a good magnifying lamp or glasses, a soldering iron with a very fine tip, a pair of tweezers with points less than 0.020” thick, a solder sucker and a very steady hand. To begin, lay the bare PC board down flat on the table with the surface mount pads facing upwards. You will notice that the pads are already tinned but they have been levelled so that there is not enough solder to hold a component in place. Thus, the first step is to pre-tin the pads. Align the PC board so that the diode and transistor packs (SOT23) present the single pad to your soldering hand. Tin one pad only on each component and this pad should Fig.3: the essential components you need for hand assembly of a surface mount board are magnifying spectacles (or a magnifying lamp), a fine tipped soldering iron & tweezers with very fine tips. be the pad closest to your soldering hand. Tin the single pad only on the SOT23 packages and only one pad on any IC packag­es. Now using tweezers, pick up the first component and slide it into place near the appropriate pre-tinned pad. Apply the tip of the soldering iron to the pre-tinned pad and slide the compon­ent into the wet solder, stopping at the correct location on the pad. This is usually with the component centred on the pad. It is very important to pick up the component from a flat surface so that the points of the tweezers do not protrude below the bottom of the device. This can otherwise result in a component sitting above the PC board and thus prone to cracking. This is also the reason that we solder one leg only. If both pads were tinned, the component would not sit flat against the PC board. Let the solder cool before removing the tweezers. You now have your first surface mount component on the board. That wasn’t too painful was it? Continue placing components until all of the surface mount components have been mounted. By this stage you will have all the components in place but with only one pad soldered on each de­vice. Now align the PC board so that the unsoldered pads are facing your soldering hand and apply the tip of the iron and the solder simultaneously to the pad. Watch the heat, as these com­ponents are quite delicate. A quick dab will do it. At this point you may like to touch up the original join if you feel it needs it. At some stage in the assembly, particularly for the receiv­ er PC board, you will have had to place two components side by side which are only 0.02” apart (PC board programs such a Protel Autotrax work best in inches, hence the Imperial measurements). Care should be exercised to ensure that these components are parallel to avoid shorts. You may also have to file the points of your tweezers to get them in between the components. File the points so that they are of equal length and less than 0.02” thick. In case you are wondering how thick 0.02” is, don’t worry. You will soon find out when you try to assemble the receiver. If you cannot place R8 and C11 for example, because your tweezers won’t fit, then they must be thicker than 0.02”. Probably the most difficult component to solder is the SOIC package. The legs on these packages are only 0.05” apart and there are lots of them. It is very easy to get a solder bridge on these leads. If this happens, use a solder sucker and a minimum of heat to clear the bridge. Also keep the iron tip clean and make sure it stays pointy. Removing components Finally, a word or two on removing components. On a general level when servicing surface mount equipment, it must be kept in mind at all times that some components may be fixed with epoxy as well as with the solder. This makes removal more difficult, howev- er epoxy will let go at elevated temperatures and on small components the epoxy is not usually a problem. Larger components are a different matter. In our project, epoxy will not be encountered, but you may still have some difficulty removing components unless you know the tricks. As you cannot snip one end and lift the component away from the board as with through-hole components, you must use quite a different technique. Packages such as the 1206 can be removed by quickly heating each end in turn two or three times until the component moves. Once it moves, slide the component sideways and upwards with the tip of the iron. Usually the surface tension will cause the component to adhere to the iron tip. As a result, at the end of the day you end up with a sponge tray full of components. The SOT23 package presents more of a problem. Begin by heating all three legs in succession and then hooking the single leg upwards with the tip of the iron. Once the single leg is up the other two will come away easily. Alternatively, the legs may be cut with a sharp knife and each leg removed individually with the tip of the iron. There are, of course, specially shaped sol­dering iron tips for all of these components but they are very expensive. The IC packages are by far the biggest headache. A sharp knife is the next best to a dedicated iron tip. Run the knife along the legs close to the IC body. These legs are quite thin and will cut through easily. Care should be taken to ensure that too much downwards pressure does not translate into sideways force which will lift the tracks. Likewise, when tracks are warm do not lift upwards with too much force or the bond between the tracks and the fibreglass substrate will be broken. One big problem is replacing a device on pads that have solder on them from a previous component. It is very difficult to get the component to sit flat against the PC board unless the pads are properly cleaned first. Solder wick is a help here but my old mate Boris has the most elegant solution. He solders in stereo, with an iron in each hand. Removal and replacement is quick and easy in this manner but the board must be anchored and you SC must watch the heat. January 1995  75 SPECIALS BY FAX If your fax has a polling function, dial (02) 579 3955 and press your POLLING button to get our latest specials, plus our item and kit listing. Updated at the start of each month. FIBRE OPTIC COMMUNICATOR Transmitter and Receiver PCB (two separate PCBs) and all on-board component kits. The kits also include Motorola fibre optic couplings, 1.5M of fibre optic cable, an electret microphone and a speaker. These are all the parts needed to experiment with the transmission of audio over fibre optic cable, at a low total price of: $29.00. The optic fibre optic couplings are also available separately at $12.00 per pair, fibre optic cable $1.50 per metre. 27 MHz TRANSMITTERS These new Australian made transmitters are assembled (PCB and components) and tested. They are Xtal locked on 26.995 MHz and were originally intended for transmitting digital information. Their discrete component design employs many components, including 5 transistors and 8 inductors: circuit provided. A heatsink is provided for the output device. Power output depends on supply voltage and varies from 100mW to a few watts, when operated from 3-12VDC. These are sold for parts/experimentation/educational purposes, and should not be connected to an antenna as licensing may be required: $7 Ea. or 4 for $20 DIGITAL RECORDING MODULES Small US designed 12 second digital recording modules. Complete units that include a speaker and a battery: $18.50 PRINTER MECHANISMS Brand new Epson dot matrix printer mechanisms. Overall dimensions are 150x105x70mm. These are complete units and contain many useful parts: 12VDC motor (50mm long - 30mm diam.) with built in tachometer, gears, solenoid, magnet, reed switch, dot matrix print head etc.: $12 VISIBLE LASER DIODE KIT Just the basics: a 5mW/670nM visible laser diode plus a collimating lens, plus an APC driver kit (Sept. 94 EA). UNBELIEVABLE PRICE: $35 CD MECHANISMS Brand new compact disc player mechanisms. Include IR laser diode, optics, small conventional DC motor, gears, stepping motor, magnets etc. The whole assembly is priced at less than the value of the collimating lens, which is easy to remove: $8.50 HF ELECTRONIC BALLASTS Brand new “slim line” cased electronic ballasts. They provide instant flicker free starting, extend tube life, reduce power consumption, eliminate flicker during operation (high frequency operation), and are “noise free” in operation. The design of these appears to be similar to the one published in the Oct. 94 SILICON CHIP magazine. One of the models 76  Silicon Chip even includes a DIMMING OPTION!! Needs external 100K potentiometer or a 0-10V DC source. We have a good but limited stock of these and are offering them at a fraction of the cost of the parts used in them! Type A: Designed to power two 32W - 4' tubes, will power two 40W - 4' tubes with no noticeable change in light output, has provision for dimming: $26 Type B: Designed to power two 16W - 18" tubes, will power two 18W - 18" tubes with no noticeable change in light output: $18 WELLER SOLDERING IRON TIPS New soldering iron for low voltage Weller soldering stations and mains operated Weller irons. Mixed popular sizes and temperatures. Specify mains or soldering station type: 5 for $10. PLUGS/SOCKETS 3 pin chassis mounting socket and a matching covered three pin plug. Good quality components that will handle a few amperes at low voltage: $5 for 4 pairs. DYNAMIC MICROPHONES Low impedance dynamic microphones with separate switch wiring, 3.5mm mic. plug, 2.5mm switch plug, as used on most cassette recorders: $4 Ea. 40mW IR LASER DIODES New famous brand 40mW-830nM IR laser diodes, suit medical and other applications: $70 Ea. Constant current driver kit to suit: $10. LOW COST 1-2 CHANNEL UHF REMOTE CONTROL Late in October we will have available a single channel 304MHz UHF remote control with over 1/2 million code combinations which also makes provision for a second channel expansion. The low cost design includes a complete compact keyring transmitter kit, which includes a case and battery, and a PCB and components kit for the receiver that has 2A relay contact output! Tx kit $10, Rx kit $20. Additional components to convert the receiver to 2 channel operation (extra decoder IC and relay) $6. INCREDIBLE PRICES: COMPLETE 1 CHANNEL TX-RX KIT: $30 COMPLETE 2 CHANNEL TX-RX KIT: $36 ADDITIONAL TRANSMITTERS: $10 FIBRE OPTIC TUBES These US made tubes are from used equipment but in excellent condition. Have 25/40 mm diameter, fibre-optically coupled input and output windows. The 25mm tube has an overall diameter of 57mm and is 60mm long, the 40mm tube has an overall diameter of 80mm and is 92mm long. The gain of these is such that they would produce a good image in approximately 1/2 moon illumination, when used with suitable “fast” lens, but they can also be IR assisted to see in total darkness. Our HIGH POWER LED IR ILLUMINATOR kit, and the IR filter are both suitable for use with these tubes. The superior resolution of these tubes would make them suitable for low light video preamplifiers, wild life observation, and astronomical use. Each of the tubes is supplied with an 9V-EHT power supply kit. INCREDIBLE PRICES: $120 for the 25mm intensifier tube and supply kit. $180 for the 40mm intensifier tube and supply kit. We also have a good supply of the same tubes that may have a small blemish which is not in the central viewing area!: ameter by 40mm long. Have APC driver built in and need approximately 50mA from 3-6V supply. For a blemished 25 or 40mm (specify preference) image intensifier tube and supply kit. Matching good quality eyepiece lens only, $7 Extra! That’s almost a complete night viewer kit for $57. $25 !!ON SPECIAL!! $50 HIGH POWER LED IR ILLUMINATOR This kit includes two PCBs, all on-board components plus casing: Switched mode power supply plus 60 high intensity 880nM IR (invisible) LEDs. Variable output power, 6-20VDC input, suitable for illuminating IR responsive CCD cameras, IR night viewers etc. Professional performance at a fraction of the price of the commercial product. COMPLETE KIT PRICE: $60 SIEMENS VARISTORS 420VAC-20joule varistors that are suitable for spike protection in Australian 3 phase systems: 10 for $5. TAA611C ICs TAA611C Audio power amplifier ICs, no more information: 5 for $5. INTENSIFIED NIGHT VIEWER KIT SC Sept. 94. See in the dark! Make your own night scope that will produce good vision in sub-starlight illumination! Has superior gain and resolution to all Russian viewers priced at under $1500. We supply a three stage fibre-optically coupled image intensifier tube, EHT power supply kit, and sufficient plastics to make a monocular scope. The three tubes are supplied already wired and bonded together. $290 for the 25mm version $390 for the 40mm version We can also supply the lens (100mm f2: $75) and the eyepiece ($18) which would be everything that is necessary to make an incredible viewer! MAINS POWERED GAS LASER Includes a professional potted mains power supply and a new 3mW red tube to suit. One catch, this supply requires a 4-6V (TTL) enable input which is optically isolated, to make the unit switch ON. Very low consumption from a 4.5V battery. $100 for a new 3mW tube plus a TTL mains power supply to suit. LASER POINTER SPECIAL A complete 5mW/670nM pointer in a compact plastic case. Uses a more efficient laser diode that results in a battery life of 10 hours. Powered by two AA batteries (supplied). $99 VISIBLE LASER DIODE MODULES Industrial quality 5mW/670nM laser diode modules. Overall dimensions: 11mm di- $60 VIDEO TRANSMITTERS Low power PAL standard UHF TV transmitters. Have audio and video inputs with adjustable levels, a power switch, and a power input socket: 10-14V DC/10mA operation. Enclosed in a small metal box with an attached telescopic antenna. Range is up to 10m with the telescopic antenna supplied, but can be increased to approximately 30m by the use of a small directional UHF antenna. INCREDIBLE PRICING: TDA ICs/TRANSFORMERS We have a limited stock of some 20 Watt TDA1520 HI-FI quality monolithic power amplifier ICs, less than 0.01% THD and TIM distortion, at 10W RMS output! With the transformer we supply we guarantee an output of greater than 20W RMS per channel into an 8ohm load, with both channels driven. We supply a far overrated 240V-28V/80W transformer, two TDA1520 ICs, and two suitable PCBs which also include an optional preamplifier section (only one additional IC), and a circuit and layout diagram. The combination can be used as a high quality HI-FI Stereo/Guitar/P.A., amplifier. Only a handful of additional components are required to complete this excellent stereo/twin amplifier! Incredible pricing: $25 for one 240V-28V (80W!) transformer, two TDA1520 monolithic HI-FI amplifier ICs, two PCBs to suit, circuit diagram/layout. Some additional components and a heatsink are required. CAMERA FLASH UNITS Electronic flash units out of disposable cameras. Include PCB/components and Xenon tube/reflector assembly. Requires a 1.5V battery. $2.50 LIGHT MOTION DETECTORS Small PCB assembly based on a ULN2232 IC. This device has a built in light detector, filters, timer, narrow angle lens, and even a siren driver circuit that can drive an external speaker. Will detect humans crossing a narrow corridor at distances up to 3 metres. Much higher ranges are possible if the detector is illuminated by a remote visible or IR light source. Can be used at very low light levels, and even in total darkness: with IR LED. Full information provided. The IC only, is worth $16! OUR SPECIAL PRICE FOR THE ASSEMBLY IS: $5 Ea. or 5 for $20 GAS LASER SPECIAL We have a good supply of some He-Ne laser heads that were removed from new or near new equipment, and have a power output of 2.5-5mW: very bright! With each head we will supply a 12V universal laser power supply kit for a ridiculous TOTAL PRICE of: $89 TWO STEPPER MOTORS PLUS A DRIVER KIT This kit will drive two stepper motors: 4, 5, 6 or 8 eight wire stepper motors from an IBM computer parallel port. Motors require separate power supply. A detailed manual on the COMPUTER CONTROL OF MOTORS plus circuit diagrams/descriptions are provided. We also provide the necessary software on a 5.25" disc. Great “low cost” educational kit. We provide the kit, manual, disc, plus TWO 5V/6 WIRE/7.5 Deg. STEPPER MOTORS FOR A SPECIAL PRICE OF: that enables the tube to be operated from a small 9V battery. The tube employed is probably the most sensitive IR responsive tube we ever supplied. The resultant viewer requires low level IR illumination. Basic instructions provided. IR LASER DIODE KIT For the tube, lens, eyepiece and the power supply kit. $42 BRAND NEW 780nM LASER DIODES (barely visible), mounted in a professional adjustable collimator-heatsink assembly. Each of these assemblies is supplied with a CONSTANT CURRENT DRIVER kit and a suitable PIN DIODE that can serve as a detector, plus some INSTRUCTIONS. Suitable for medical use, perimeter protection, data transmission, IR illumination, etc. $40 We can also provide “just the basics” for this kit: a 5mW/780nM IR LASER DIODE plus a COLLIMATING LENS, plus a CONSTANT CURRENT DRIVER KIT, plus a PIN DIODE. UNBELIEVABLE PRICE: $35 BIGGER LASER We have a good, but LIMITED QUANTITY of some “as new” red 6mW+ laser heads that were removed from new equipment. Head dimensions: 45mm diameter by 380mm long. With each of the heads we will include our 12V Universal Laser power supply. BARGAIN AT: $170 6mW+ head/supply. ITEM No. 0225B We can also supply a 240V-12V/4A-5V/4A switched mode power supply to suit for $30. 12V-2.5 WATT SOLAR PANEL SPECIAL These US made amophorous glass solar panels only need terminating and weather proofing. We provide terminating clips and a slightly larger sheet of glass. The terminated panel is glued to the backing glass, around the edges only. To make the final weatherproof panel look very attractive some inexpensive plastic “L” angle could also be glued to the edges with some silicone. Very easy to make. Dimensions: 305x228mm, Voc: 18-20V, Is-c: 250mA. SPECIAL REDUCED PRICE until the end of 94!: $20 Ea. or 4 for $60 Each panel is provided with a sheet of backing glass, terminating clips, an isolating diode, and the instructions. A very efficient switching regulator kit is available: Suits 12-24V batteries, 0.1-16A panels, $27. Also available is a simple and efficient shunt regulator kit, $5. CCD CAMERA Monochrome CCD camera which is totally assembled on a small PCB and includes an auto iris lens. It can work with illumination of as little as 0.1Lux and it is IR responsive. Can be used in total darkness with Infra Red illumination. Overall dimensions of camera are 24x46x70mm and it weighs less than 40 grams! Can be connected to any standard monitor, or the video input on a Video cassette recorder. NEW LOW PRICE: $199 IR “TANK SET” A set of components that can be used to make a very responsive Infra Red night viewer. The matching lens tube and eyepiece sets were removed from working military quality tank viewers. We also supply a very small EHT power supply kit $140 SOLID STATE “PELTIER EFFECT” COOLER-HEATER These are the major parts needed to make a solid state thermoelectric cooler-heater. We can provide a large 12V-4.5A Peltier effect semiconductor, two thermal cutout switches, and a 12V DC fan for a total price of: $45 We include a basic diagram-circuit showing how to make a small refrigerator-heater. The major additional items required will be an insulated container such as an old “Esky”, two heatsinks, and a small block of aluminium. INFRA RED FILTER A very high quality IR filter and a RUBBER lens cover that would fit over most torches including MAGLITEs, and convert them to a good source of IR. The filter material withstands high temperatures and produces an output which would not be visible from a few metres away and in total darkness. Suitable for use with passive and active viewers. The filter and a rubber lens cover is priced at: $15 MINIATURE FM TRANSMITTER Not a kit, but a very small ready made self contained FM transmitter enclosed in a small black metal case. It is powered by a single small 1.5V silver oxide battery, and has an inbuilt electret microphone. SPECIFICATIONS: Tuning range: 88-108MHz, Antenna: Wire antenna - attached, Microphone: Electret condenser, Battery: One 1.5V silver oxide LR44/G13, Battery life: 60 hours, Weight: 15g, Dimensions: 1.3"x0.9"x0.4". $25 REEL TO REEL TAPES New studio quality 13cm-5" “Agfa” (German) 1/4" reel to reel tapes in original box, 180m-600ft: $8 Ea. MORE KITS-ITEMS Single Channel UHF Remote Control, SC Dec. 92 1 x Tx plus 1 x Rx $45, extra Tx $15. 4 Channel UHF Remote Control Kit: two transmitters and one receiver, $96. Garage/Door/Gate Remote Control Kit: Tx $18, Rx $79. 1.5-9V Converter Kit: $6 Ea. or 3 for $15. Laser Beam Communicator Kit: Tx, Rx, plus IR Laser, $60. Magnetic Card Reader: professional assembled and cased unit that will read information from plastic cards, needs low current 12VDC supply-plugpack, $70. Switched Mode Power Supplies: mains in (240V), new assembled units with 12V-4A and 5V-4ADC outputs, $32. Electric Fence Kit: PCB and components, includes prewound transformer, $28 High Power IR LEDs: 880nM/30mW/12deg. <at> 100mA, 10 for $6. Plasma Ball Kit: PCB and components kit, needs any bulb, $25. Masthead Amplifier Kit: two PCBs plus all on board components: low noise (uses MAR-6 IC), covers VHF-UHF, $18. Inductive Proximity Switches: detect ferrous and nonferrous metals at close proximity, AC or DC powered types, three wire connection for connecting into circuitry: two for the supply, and one for switching the load. These also make excellent sensors for rotating shafts etc. $22 Ea. or 6 for $100. Brake Light Indicator Kit: 60 LEDs, two PCBs and ten Rs, makes for a very bright 600mm long high intensity Red display, $30. IEC Leads: heavy duty 3 core (10A) 3M LEADS with IEC plug on one end and an European plug at the other, $1.50 Ea. or 10 for $10. IEC Extension Leads: 2M long, IEC plug at one end, IEC socket at other end, $5. Motor Special: these motors can also double up as generators. Type M9: 12V, I No load = 0.52A-15,800 RPM at 12V, 36mm Diam.-67mm long, $5. Type M14: made for slot cars, 4-8V, I No load = 0.84A at 6V, at max efficiency I = 5.7A-7500 RPM, 30mm Diam-57mm long, $5. EPROMS: 27C512, 512K (64K x 8), 150ns access CMOS EPROMS. Removed from new equipment, need to be erased, guaranteed, $4. Green Laser Tubes: Back in stock! The luminous output of these 1-1.5mW GREEN laser diode heads compares with a 5mW red tube!: $490 for a 1-1.5mW green head and a 12V operated universal laser inverter kit. 40 x 2 LCD Display: brand new 40 character by 2 line LCD displays with built in driver circuitry that uses Hitachi ICs, easy to drive “standard” displays, brief information provided, $30 Ea. or 4 for $100. RS232 Interface PCB: brand new PCB assembly, amongst many parts contains two INTERSIL ICL232 ICs: RS232 Tx - Rx ICs, $8. Modular Telephone Cables: 4-way modular curled cable with plugs fitted at each end, also a 4M long 8-way modular flat cable with plugs fitted at each end, one of each for $2. 12V Fans: brand new 80mm 12V-1.6W DC fans. These are IC controlled and have four different approval stamps, $10 Ea. or 5 for $40. Lenses: a pair of lens assemblies that were removed from brand new laser printers. They contain a total of 4 lenses which by different combinations - placement in a laser beam can diverge, collimate, make a small line, make an ellipse etc., $ 8. Polygon Scanners: precision motor with 8 sided mirror, plus a matching PCB driver assembly. Will deflect a laser beam and generate a line. Needs a clock pulse and DC supply to operate, information supplied, $25. PCB With AD7581LN IC: PCB assembly that amongst many other components contains a MAXIM AD7581LN IC: 8 bit, 8 channel memory buffered data acquisition system designed to interface with microprocessors, $29. EHT Power Supply: out of new laser printers, deliver -600V, -7.5kV and +7kV when powered from a 24V-800mA DC supply, enclosed in a plastic case, $16. Mains Contactor Relay: has a 24V-250ohm relay coil, and four separate SPST switch outputs, 2 x 10A and 2 x 20A, new Omron brand, mounting bracket and spade connectors provided, $8. FM Transmitter KIt - Mk.II: high quality - high stability, suit radio microphones and instruments, 9V operation, the kit includes a PCB and all the on-board components, an electret microphone, and a 9V battery clip, $11. FM Transmitter Kit - Mk.I: this complete transmitter kit (miniature microphone included) is the size of a “AA” battery, and it is powered by a single “AA” battery. We use a two “AA” battery holder (provided) for the case, and a battery clip (shorted) for the switch. Estimated battery life is over 500 hours!!: $11. High Power Argons: the real thing! Draw pictures on clouds, big buildings etc., with a multiline water-cooled Argon laser with a few watts of output. “Ring” for more details. Argon-Ion Heads: used Argon-Ion heads with 30-100mW output in the blue-green spectrum, will be back in stock soon, priced at around $400 for the “head” only, power supply circuit and information supplied. BATTERY CHARGER: S2 accessory set for Telecom Walkabout “Phones”. Includes cigarette lighter cable, fast rate charger, and desktop stand. Actually charges 6 series connected AA Nicad batteries: $27. BATTERY PACKS: Contain 6 AA Nicad batteries wired in series, can easily be pulled apart, used units, satisfaction guaranteed: $2 per pack. LITHIUM BATTERIES: Button shaped with pins, 20mm diameter, 3mm thick. A red led connected across one of these will produce light output for over 72 hours (3 days): 4 for $2. CIGARETTE LIGHTER LEADS: Cigarette lighter plug with 3 metres of heavy duty fig. 8 flex connected. Should suit load currents up to 20A: 5 for $5. SUPERCAPS: 0.047F/5.5V capacitors: 5 for $2. HOUR METER: Non resettable, mains powered (50HZ), WARBURTON FRANKI, 100,000 Hours maximum, 0.01Hr resolution: $15. PCB MOUNTED SWITCHES 90 deg. 3A-250V, SPDT: 4 for $2. AC POWER SUPPLY: Mains in, two separate 8.5V/3A outputs, in plastic case with mains power lead/plug and output leads/plugs: $15 Ea. MONITOR PCB’s: Complete PCB and yoke assembly for high resolution monochrome TV monitors (no tube). Operate from 12V DC, circuit and information provided: $15. MODEMS: Complete mains powered non standard 1200 baud Telecom approved modems. We should have brief information available. Limited stock at below the price of the high quality case that these are housed in: $20 for 2 modems. OATLEY ELECTRONICS PO Box 89, Oatley, NSW 2223 Phone (02) 579 4985. Fax (02) 570 7910 Bankcard, Master Card, Visa Card & Amex accepted with phone & fax orders. P & P for most mixed orders: Aust. $6; NZ (airmail) $10. January 1995  77 VINTAGE RADIO By JOHN HILL Basic tools & test equipment An important part of vintage radio collection involves restoration & repair work. For that, you need a good workbench, a few basic tools & some basic test equipment. It is surprising the number of vintage radio collectors who do not do their own repairs. In my opinion, people who simply collect radios and do not repair or restore them are missing out on most of what vintage radio has to offer. Of course, buying, selling, trading and scrounging old radios are all part of the deal and those activities can be exciting too. But nothing matches the thrill of hearing an anci­ent receiver burst into life after being mute for 20 or 30 years. Such a moment is truly rewarding. Vintage radio would have little appeal to me if someone else did my repairs. What’s more, if that were the case, what I consider to be a relatively inexpensive hobby would suddenly become fairly unaffordable and I would perhaps change my inter­ests and go in for breeding budgies, white mice or something like that. White mice? I think I’d have to go for the budgies. I occasionally do repairs for other collectors and it has been to my advantage to do so. First, these repairs, along with my own, have given me interesting material for my Vintage Radio column. Second, the extra repairs, particularly in the early days of my vintage radio activities, gave me additional experience (and headaches) which were helpful in acquiring some basic skills in this field of repair work. This basic equipment for the workbench includes several sets of jumper leads, a small pocket knife & a pair of wire strippers. 78  Silicon Chip Sometimes, of course, I bit off more than I could chew and that was good experience too, as it curbs overconfidence. Learn­ing radio repair techniques from scratch was interesting work and lack of experience should not deter those who would like to do their own repairs. The third big advantage of doing repairs for other collec­tors is the fact that most of these repairs are done, not for money, but in exchange for something else – a box of old valves or spare parts, a few derelict receivers or a wanted chassis or cabinet. It’s a good way to operate and trading is often a much better arrangement than dealing with that filthy money stuff. Now some of the guys I do work for don’t even own basic tools. I can think of four who do not even possess a multimeter or a soldering iron. Speaking from my own experience, I had both of these items long before I became interested in vintage radio. I have always maintained that almost nothing can be repaired unless you have a good selection of tools and equipment and I am not just referring to radio repairs. In the past month, I have put new springs in the oven door, fixed a rattle in a heater, repaired a fault in my electronic organ and done a valve regrind job on my motor cycle. Now that is not meant to be a thinly veiled brag. It is simply a statement of fact to illustrate a point. If you don’t have the right attitude and tools, then there is little that can be done when it comes to fixing things. While the stove, heater and valve regrind were really routine jobs, the organ was unfamiliar territory. However, some circuit board pushing and flexing revealed a crook solder joint in a board socket and the problem was easily rec- SATELLITE SUPPLIES Aussat systems from under $850 SATELLITE RECEIVERS FROM .$280 LNB’s Ku FROM ..............................$229 LNB’s C FROM .................................$330 FEEDHORNS Ku BAND FROM ......$45 FEEDHORNS C.BAND FROM .........$95 DISHES 60m to 3.7m FROM ...........$130 These two soldering irons can handle just about any vintage radio soldering job. They include an old-style Scope soldering iron & transformer (left) & a modern temperature controlled iron. Tube & ring spanners are handy when adjusting some of the trimmer capacitors found on old radio sets. While these trimmers may be awkward to adjust, once set they stay that way. tified with the soldering iron – without the big bill that a professional techni­ cian would have charged. Sure, I was lucky, but my investigations saved several hundred dollars because the organ technician would have charged two hours travelling time before he even looked at the job. However, being able to fix things does not happen instant­ly. It is something that slowly develops over a long period and the sooner one starts the better. If you never have a go you will never know what your capabilities are. In some instances, you could not do a worse job than some of the so called “experts” who are, at times, incompe- tent and dishonest. If you saw some recent current affairs programs on VCR servicing and automotive repairs you will know what I mean. The workbench All this rambling has been leading up to the theme of this month’s column and that is the setting up of a workbench suitable for vintage radio repairs. I intend listing what is on my bench (which I consider to be fairly adequate) and those readers think­ing of doing their own radio servicing can weigh up the pros and cons as to whether or not it is worth the initial outlay. So here we go! LOTS OF OTHER ITEMS FROM COAXIAL CABLE, DECODERS, ANGLE METERS, IN-LINE COAX AMPS, PAY-TV DECODER FOR JAPANESE, NTSC TO PAL TRANSCODERS, E-PAL DECODERS, PLUS MANY MORE For a free catalogue, fill in & mail or fax this coupon. ✍     Please send me a free catalog on your satellite systems. Name:____________________________ Street:____________________________ Suburb:_________________________ P/code________Phone_____________ L&M Satellite Supplies 33-35 Wickham Rd, Moorabin 3189 Ph (03) 553 1763; Fax (03) 532 2957 January 1995  79 be the most useful. A small pair of locking pliers may also come in handy at odd times. Pliers with insulated handles are a good choice when work­ ing with electrical equipment but not all types are available with this safety feature (eg, locking pliers). Two pairs of side cutters would also be considered a ne­cessity for any vintage radio workbench – a very small pair for those out-of-the-way awkward places and a larger pair for general purpose work. Spanners & sockets The old analog multimeter on the left is used by the author for most generalpurpose work, while the digital multimeter is re­served for jobs that the analog meter cannot handle (eg, measur­ing capacitance). Having two meters is often an advantage, espe­cially when one wishes to measure voltage & current at the same time. My workbench is, in fact, an old kitchen table with a Lami­nex top. It serves the purpose quite well and the Laminex top is durable and splinter free, which is something that cannot be said of a timber-topped bench. Above the bench and within easy reach is the best place to have a tool board of some sort. Too many items on the bench clutters the work area, whereas tools that have a place to hang when not in use are out of the way. So what tools do we need on the board? A selection of small to medium-size screwdrivers would be a good start and that must include one small enough to fit the little grub screws often found in old-style control knobs. A small Phillips head screwdriver could also be handy at odd times when working on more modern equipment. Pliers are always a useful tool and a variety of three or four different types will not go astray. A small pair of long nose, a large pair of long nose, plus a pair of combination or slip joint pliers for more powerful gripping jobs would A couple of small chests of drawers gives ready access to minor spare parts & keeps the work area un­cluttered. They are ideal for storing resistors & capacitors. 80  Silicon Chip There is always a need for a few spanners and a small 6-inch (150mm) shifting spanner will cover most situations. Howev­ er, a couple of tube spanners will also be handy when adjusting a particular type of trimmer capacitor that was commonly used in AWA and HMV receivers during the late 1930s and early post-war period. A scriber is a useful tool for valve radio repairs and it has a number of uses. First, it is just the right instrument for marking the bakelite bases of the older style valves. Once the base is inscribed, it doesn’t matter whether the original type number remains legible or not. Loose valve sockets can also be tightened with a scriber. Seven and nine-pin sockets, plus a particular octal type, have split socket connections which can be sprung back into position with a scriber point, thus restoring socket tension and giving firm contact with the valve pins. A scriber is a very useful tool! A good variety of pliers & side cutters are necessary for vin­tage radio repairs. One can never have too many tools when it comes to working on old radio chassis. RESURRECTION RADIO VALVE EQUIPMENT SPECIALISTS Repairs – Restoration – Sales for RADIO & AUDIO Equipment This photo shows the author’s valve tester & radio frequency (RF) generator, both of which were originally built from kits. Valve testers are hard to come by these days, although RF genera­tors can be readily purchased from electronics retailers. So too is an old bicycle spoke. The head of a spoke can reach into inaccessible places and hook out the dial cord when nothing else will reach. No radio workbench would be complete without a bike spoke or two. Radio repairs are fairly ineffective unless one can replace a few capacitors and the odd resistor. For this reason, a couple of miniature chests of drawers full of capacitors and resistors should be within easy reach on the workbench. A full range of both high-voltage and low-voltage capacitors plus electrolytics can be stored in a single set of drawers if the drawers are peti­tioned off so that each has two compartments. A small vice, a hacksaw and a selection of files (round, half round, square, flat, etc) are also handy tools to have. It is perhaps better to mount the vice in some other work area as it could be a hindrance on the radio repair bench. A packet of drills and a pistol drill would complement these other tools. Soldering irons & test gear Now for the more-expensive items. First of all, a good soldering iron is a must for the vintage radio repair man and on my bench there are two. One is an old Scope iron with its 3.3V transformer. The iron itself has been restored to as-new working condition by fitting it with a new carbon element and copper soldering tip. This soldering iron gets very little use and is called upon only when heavy-duty work is to be done. The other soldering iron is a tem- perature controlled type and is ideally suited for vintage repairs. With the large tip and a 310°C temperature setting, it is perfectly adequate for making most solder joints. Extra large joints and even those chassis soldering jobs can usually be done quite well if the temperature is turned up another 50°C. Only on rare occasions is the variable heat iron inadequate for the job and that’s when the Scope iron is used. Another relatively expensive item is a multimeter and these can range from $20 to $400, depending on choice. While a budget priced meter may be a bit limited in its use, there is really no reason to spend mega-bucks on a meter for vintage radio repairs. Having two meters can be an advantage, especially if they are different types; ie, one digital and the other an analog type. If the analog meter has an output socket and the digital meter has a capacitance range, then they should cover most situa­tions. But why have two meters? You will only have to damage one to make the other worth having. What’s more, try measuring volts and amps in a circuit at the same time with just one meter. The final items that are worth having include a radio fre­ quency (RF) generator and a valve tester. While the former can be bought new from electronics suppliers, the latter may be more difficult to acquire. And although many vintage repairers get by without these instruments, they do take the guess work out of valve testing and SC receiver alignment. S VE L VA BOUGHT SOLD   TRADED Send SSAE for Catalogue Visit our Showroom at 242 Chapel Street (PO Box 2029), PRAHAN, VIC 3181. Phone: (03) 510 4486; Fax (03) 529 5639 Silicon Chip Binders These beautifully-made binders will protect your copies of SILICON CHIP. They are made from a dis­tinctive 2-tone green vinyl & will look great on your bookshelf. Price: $A11.95 plus $3 p&p each (NZ $6 p&p). Send your order to: Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Or fax (02) 979 6503; or ring (02) 979 5644 & quote your credit card number. January 1995  81 AMATEUR RADIO BY GARRY CRATT, VK2YBX Wideband preamplifier has response to 950MHz You can build this versatile amplifier for quite a range of amateur applications. It uses one tiny surface mount device on a PC board only 30mm square and will produce a gain of up to 18.5dB at 500MHz. A wideband amplifier can be a useful tool in any amateur shack. Apart from the obvious applications of improving receiver sensitivity and compensating for coaxial line losses, there are also instrumentation applications where this handy little device can improve the sensitivity of frequency counters and field strength meters. In fact, it could even be used as a masthead preamp for television use. We last described a wideband preamplifier in March 1991. Since then, the price of monolithic amplifiers has dropped dramatically. One leading supplier worldwide is Mini-Circuits, located in Brooklyn, USA. And fortunately for amateurs in Austra­lia, they have a new agent, the well known component supplier, Clarke and Severn Electronics, located in Sydney. Mini Circuits has an extensive 400page product catalog, of which 50 pages are dedicated to their range of amplifiers. For this project, we selected the MAR-6, a device with useable gain, adequate noise figure, 50Ω input and output impedances, and cap­able of being cascaded easily with a minimum of external compon­ ents. For such a reasonable price, these devices certainly do a great job! Even though there are a minimum of components used in this design, there are a number of important The prototype preamplifier was mounted in a small diecast box & the BNC input & output connectors are soldered directly to the PC board. construction techniques which must be observed if the amplifier is to live up to expecta­tions. Firstly, transmission lines must run flush to the IC package. This means that a 2.5mm hole must be drilled in the PC board to accept the plastic body of the amplifier, allowing the connection leads to be soldered directly to the transmission lines for both input and output connections. In addition, to minimise what is called the “step discon­tinuity” (the impedance mismatch) which is typically the equival­ent of adding 0.2nH of series inductance, the transmission lines feeding the amplifier should be tapered. Also, corners of trans­mission lines should be minimised and where bends are necessary, the corners should be chamfered to minimise extra shunt ca­pacitance. The standard rule of keeping lead lengths as short as possible also applies and this is why the design uses chip ca­pacitors. Ground planes should be kept as large and solid as possible to ensure a low impedance ground return. Gain, compres­sion and high frequency rolloff will all be degraded if proper grounding techniques are not used. If the amplifier is to be used in a 75Ω situation, the input and output SWR will increase from an ideal 1:1 in a perfect 50Ω system to 1.5:1 , a mismatch loss of 0.18dB per port. Internal circuit details Fig.1 shows the internal circuit of the MAR-6 amplifier. The internal resistive networks determine the individual transistor operating points and all we need to do is supply the correct voltage to the DC input terminal. Rc is an external bias resis­tor. This resistor 82  Silicon Chip Rbias V+ RF RF IN 11 IC1 MAR6 RC Q1 Q2 3 RF OUT INPUT Cblock 11 Rb Cblock OUTPUT 4 2 RS RFC OPTIONAL 3 Fig.2: the MAR-6 must be used with input & output coupling capacitors & an output inductor to isolate the DC supply. If the (optional) inductor is omitted, the available gain will be re­duced. V+ 4 RE 1 DOT OR TRIANGLE INDICATES PIN 1 2,4 GND Fig.1: the internal circuit of the MAR-6 monolithic amplifier, shown with its collector biasing resistor, Rc. compensates for increases in device Beta with temperature, by dropping the collector voltage as the amplifier attempts to draw more current. Mini-Circuits recommend the use of resistors with a positive temperature coefficient, such as carbon composite types. For bias stabilisation over the temperature range of -10°C to +100°C, a drop of at least 1.5V is necessary. The larger the voltage drop, the more stable the bias voltage will be, the optimum being about 2V. As the optimum DC condition for the device is achieved at 16mA at 3.5V, we used 100Ω from a 5V source. Other voltage /resistor combinations are 9V/344Ω, 12V/531Ω, and 15V/719Ω. Fig.2 shows more connection details for the MAR-6. An RF choke is used in series with the bias resistor, to ensure that the resistance does not appear in parallel with the load, and hence degrade the output match. At HF the value of this choke can be 10µH or so, but at high frequencies several turns of wire on a high permeability ferrite bead should be used. If the choke is omitted, a gain loss of several dB could be expected. 2 us to use monolithic ceramic types in the prototype. Some designs use a combination of low and high pass filters on input and output ports, and this may be desirable if the amplifier is to be used on a dedicated band. However, the wideband version presented here offers greater versatility as a general purpose unit. Our proto­ type produced a high frequency 3dB point of 950MHz, sufficient for most amateur needs. a pair of tweezers is mandatory during construction, to hold the components as they are soldered. The PC board we used is single sided and the components are wired directly to the top of the PC board which in this case is the copper side. To assist in physically locating the components before soldering, we drilled the PC board, just as if the components were going to be inserted from the non-copper side. The component leads can be cut off flush with the underside of the PC board after soldering. Begin assembly by drilling the diecast box to take two BNC sockets. Use internal tooth lockwashers 5/16-inch) between the sockets and the box to ensure a good conductive bond. The input and output connections on the PC board must be soldered directly to the centre pin of the BNC sockets and at the same time the PC board ground connections must be able to be soldered to each side of each BNC socket. To ensure that the PC board mechanically fits, use a rat-tail file, to carefully file away the exposed fibreglass between the Construction The suggested PC board layout is shown in Fig.4. The entire unit can be wired into a diecast metal box, and fitted with BNC sockets (either male or female or a combination of both). The active device is mounted on top of the PC board (copper side up), and is located in a 2.5mm hole drilled in the centre of the PC board. Power for the unit should be supplied from an external source via a socket on the side of the amplifier enclosure. Because we have endeavoured to keep lead lengths as short as possible, 100  180  .01 L1 ZD1 5.1V 400mW 0.1 11 3 2 0.47 K 560 0.1 4 1 DOT OR TRIANGLE INDICATES PIN 1  LED1 IC1 MAR6 INPUT +12V A L1: 3T, 0.25mm DIA ENCU WOUND ON FERRITE BEAD Final circuit Fig.3 shows the complete circuit of the prototype. In addi­tion to the choke, a .01µF bypass capacitor has been used to ensure a low impedance path to ground for any signal that does get past the choke. The circuit is powered from 12V with a zener diode used to regulate down to +5.1V. In addition, a LED has been included as a power indicator. Surface mount DC blocking capacitors can be used to ensure the best possible impedance match. In practice, the difficulty in obtaining 0.1µF chip capacitors in small quantities forced 3 OUTPUT 4 3 A K 2 WIDEBAND PREAMPLIFIER Fig.3: the complete circuit of the prototype amplifier has a 5.1V zener diode regulator & LED power indicator. January 1995  83 GND +12V K INPUT SOCKET LED1 A 560  180  ZD1 .01 100 L1 0.47uF OUTPUT SOCKET 0.1 1 0.1 IC1 Fig.4: the component layout of the preamplifier. All components are mounted on the copper side & a 2.4mm hole must be drilled to allow the MAR-6 device to sit flush with the copper surface. Fig.5: actual size artwork for the PC board. turns of 0.25mm enam­ elled copper wire around a UHF ferrite bead. Allow about 3mm of connection wire either side of the bead and tin these leads prior to soldering. Before wiring the amplifer assembly into the metal box, connect a 12V DC power supply and check that the current consump­tion is about 30mA (15mA for the LED and 15mA for the IC). Once soldered into the box, it is quite difficult to remove the PC board cleanly, should there be a wiring error. Testing edge of the PC board and the input/ output pads. The result will be two “half moon” notches, adjacent to each connection pad. Once the mechanical considerations have been attended to, the circuit can be assembled. We found it easiest to fit the MAR-6 first, keeping the leads as short as possible. It is quite easy to hold the amplifer chip in place with a pair of tweezers with one hand, and solder one of the connection leads. After this, the other leads can be soldered without any need to hold the device. 84  Silicon Chip Preparation of each device is important prior to insertion to ensure a good clean bond. Due to the very short lead lengths, soldered joints must be made quickly to ensure that no damage occurs to the components, due to excessive heat. It may be necessary to scrape off some of the insulating material on resistor and capacitor leads to ensure the shortest leads possible and to produce good soldered joints. Pay particu­lar attention to the polarity of both the zener diode and the LED. The RF choke is made by winding three After final assembly, the unit is ready for testing. In our case, we connected a signal generator to the input and a spectrum analyser to the output. The prototype amplifier exhibited a flat response from 1MHz to about 850MHz. The only special components required are the diecast box, obtained from Farnell Electronic Components Pty Ltd (phone (02 745 8888) and the MAR-6 device from Clarke & Severn Electronics (phone 02 482 1944). All other components are commonly SC available. ORDER FORM BACK ISSUES MONTH YEAR MONTH YEAR PR ICE EACH (includes p&p) TOTAL Australi a $A7.00; NZ $A8.00 (airmail ); Elsewhere $A10 (airmail ). Buy 10 or more and get a 10% discount. Note: Nov 87-Aug 88; Oct 88-Mar 89; June 89; Aug 89; Dec 89; May 90; Aug 91; Feb 92; July 92; Sept 92; NovDec 92; & March 98 are sol d out. All other issues are currently i n stock. $A B INDERS Pl ease send me _______ SILICON CHIP bi nder(s) at $A12.95 + $5.00 p&p each (Australi a only). N ot avail abl e elsewhere. Buy five and get them postage free. $A SUBSCRIPTIONS ❏ New subscription – month to start­­___________________________ ❏ Renewal – Sub. No._______________   ❏ Gift subscription ☞ RATES (please tick one) Australia Australia with binder(s)* NZ & PNG (airmail) Overseas surface mail 2 years (24 issues) 1 year (12 issues) ❏ $A90 ❏ $A49 ❏ $A114 ❏ $A61 ❏ $A135 ❏ $A72 ❏ $A135 ❏ $A72 ❏ $A240 Overseas airmail ❏ $A120 *1 binder with 1-year subscription; 2 binders with 2-year subscription GIFT SUBSCRIPTION DETAILS Month to start__________________ Message_____________________ _____________________________ _____________________________ Gift for: Name_________________________ (PLEASE PRINT) YOUR DETAILS Your Name_________________________________________________ (PLEASE PRINT) Address___________________________________________________ Address______________________ _____________________________ State__________Postcode_______ ______________________________________Postcode___________ Daytime Phone No.____________________Total Price $A __________ ❏ Cheque/Money Order ❏ Bankcard ❏ Visa Card ❏ Master Card 9am-5pm Mon-Fri. Please have your credit card details ready ______________________________ Card expiry date________/________ Card No. Phone (02) 9979 5644 Signature OR Fax (02) 9979 6503 Fax the coupon with your credit card details 24 hours 7 days a week Mail coupon to: OR Reply Paid 25 Silicon Chip Publications PO Box 139, Collaroy 2097 No postage stamp required in Australia January 1995  85 PRODUCT SHOWCASE High-voltage oscilloscope probe The first high-voltage (above 1.5kV) oscilloscope probe to win safety certi­ fication from Underwriters Laborat­ory (UL) has been introduced by Tektronix. UL certification also quali­fies the Model P5 100kV probe for safety certification by two internation­al standards-setting bodies: the Euro­pean Economic Community’s IEC (In­ternational Electrotechnical Commis­ sion) and Canada’s CSA (Canadian Standards Association). The P5100 high-voltage probe com­ bines unprecedented safety ratings, a bandwidth of 250MHz and the lowest input capacitance (less than 2.75pF) of any probe in its class. It lets users exploit the high bandwidth capacity of Tektronix TDS300-400- and 500- series digitising oscilloscopes or max­imise the performance of other manu­ facturers’ scopes. Combined with Tektronix’ scopes, the P5100 probe For further information, contact Tektronix Australia Pty Ltd, Test and Measurement Products, 80 Waterloo Road, North Ryde, NSW 2113. Phone (02) 888 7066. CD-ROM based shopping system enables safe, accurate measurement of high-frequency, high-voltage sig­nals. The P5100 probe has accessories designed for safely gripping large high­ voltage test points. One P5100 acces­ sory is a retractable hook tip, useful for gripping large bolts (up 1/4-inch diameter) and hooking the probe in place while making signal measure­ ments. Using the hook tip rather than securing the probe with wires elimi­nates a high-voltage testing safety haz­ard. InfoMagic Australia has announced InfoExpress, a free CD-ROM based shopping system that gives informa­ tion on more than 2000 software prod­ucts. InfoExpress includes profes­ sional product reviews to help shop­ pers evaluate products before buying. If the shopper wishes to make a purchase, they simply click on the ‘order’ button to add the product to their shopping list. Pricing and order­ ing details are displayed at the bottom of the screen and orders can be made by telephone or fax. Phone advisers are available seven days a week be­ tween 8am and 8pm to fulfil orders and supply additional information. Speak to program your VCR There are currently over four and a quarter million remote control VCRs in Australia and most of their owners have difficulty programming them. Accord­ing to Dick Smith Electronics, the solution is now at hand. The new VCR/TV Voice Programmer is a handheld infrared remote control which makes child's play out of programming a VCR. Forget trying to work out which buttons to press - all you have to do is simply "tell" it to change channels, fast forward, play, record, etc and it will do as you say! Programming your VCR will become as simple as talking. The features incorporated in the "VCR Voice Pro­ grammer" include: Voice command to change chan­nels, operate the video functions, play, rewind, fast­forward, pause, record, stop etc; up to 15 recording periods may be programmed for up to six days in advance; ability to recognise and respond to four different voices; the voice command "Zapit" quickly disposes of advertisements in a recorded program. A single "VCR Voice Programmer" will replace existing TV or VCR remotes for up to two complete VCR/TV systems. The VCR/TV Voice Programmer is available at all Dick Smith Electronics stores for $199. 86  Silicon Chip InfoExpress offers discounted prices for volume purchases or smaller discounts plus ‘frequent buyer’ points. Once registered, customers will automatically receive updated versions of the CD-ROM every 3 months. InfoExpress is available for Apple Mac­intosh computers with a Windows version, due for release in the first quarter of 1995. An Apple Macintosh 68020 based computer is required to run InfoExpress, running System 7.0 and above, with 2Mb available in RAM and 3Mb available on the hard disc. The Macintosh will need to have Ap­ple QuickTime 1.6 software loaded to run the demonstrations, be fitted with a 13inch colour monitor for easy view­ing of InfoExpress scenes and have an internal or external CD drive con­nected. The InfoExpress CD-ROM is avail­able now free from InfoMagic resellers or by calling (008) 804 895. Quadruple speed CD recorder Yamaha Music Australia has announced the new CD Expert Series Compact Disc recording system, claimed to be the world’s first quadru­ ple speed CD recorder. The Expert Series by Yamaha represent the organisation’s third genera­tion recordable CD product, a CD re­corder/ reader supporting SCSI-2 that operates in real time, 2-times (double speed), and 4-times (quadruple speed) modes for data, text, image and audio applications. It handles all standard Compact Disc formats including CD-ROM (Read Only Memory), CD-ROMXA (ex­tended Architecture), CD-I (Interac­tive) and CD-DA (Digital Audio). Three recording modes are available: (1) Disc-at-once, recording the entire disc in one session with no data added later; (2) Track-at-once, recording only part of the disc, adding data later (up to 99 times, as defined by the Orange Book specifications) but not reading from the disc in the interim, New CD-ROMs from TDK TDK has a new line-up of CDROMs for both recordable CD and computer data storage applica­ tions, available in 74/63 and 21/18 minute playing times. The new CD ROMs have been designed with convenient Title/ Date/Contents labels for easy identification and employ a pro­ prietary protective back coating so ink or marker pens will not and (3) Multisession, recording part of the disc in one session, reading in the interim and adding data later until the disc is fully recorded. Available in 8cm/18 minute, 12cm/ 63 minute and 12cm/74 minute formats, the CDM Series discs are guaranteed for accurate data reading, even by players employing ‘Phase Differ­ential Tracking’. The Expert Series is available in internal mounting or external ver­sions. The CDR100 is a single, half­-height 5-1/4 inch FDD format unit for internal mounting and powering by the host computer. The CDE100 is supplied in an external case with in­tegrated power supply, while the CDE100H10 also includes an internal 1 gigabyte hard disc drive, to prevent buffer under-run experienced with transfers from some hard drives. All are linked to the host computer through an advanced SCSI-2 data transfer interface for fast handling of large volumes of data. penetrate into the disc substrate. TDK are also marketing their 74 and 63 minute recordable CDs with a printable surface. Both the labelled and printable CD-ROMs feature quadruple speed recording capa­bility with guaranteed playback stability for over a million plays and life expectancy of over 10 years. For further information on these and other TDK commercial and professional products, contact Mark Gribble on (02) 437 5100. For further information contact Mitsui Computer, 14 Aquatic Drive, Frenchs Forest, NSW 2086, phone (02) 452 0433, or SCSI Corporation, 19/9 Hudson Avenue, Castle Hill, NSW 2154. Phone (02) 894 6033. High-energy tape eraser Amber Technology has announced the new Weircliffe BTE220 High-Energy Degausser, a shielded bulk eraser complying with the recommended magnetic field emission levels currently being considered in the EC January 1995  87 Physical Agents Directive. The BTE220 is designed to erase Hi-8, 8mm, VHS and S-VHS video cassettes, as well as all formats of audio cassettes and cartridges, includ­ ing DAT and DCC. The new BTE220 incorporates a powerful erase coil, enabling Hi-8 and 8mm video cassettes to be erased at a rate of six per opera­tion. The BTE220 is compact, with dimensions of 383 x 364 x 177mm. With Weircliffe’s magnetic shielding, the unit requires no additional free space surrounding it and may be located in close proximity to sensitive instruments. In addition, the BTE220’s internally shielded degaussing compartment gives enhanced protection to the operator from extraneous magnetic fields, in line with current NRPB recommendations. The BTE220 offers better than -80dBR erasure with Hi-8/8mm me­dia coercivity and features simple and efficient operation. The easily acces­sible media degaussing compartment is electromagnetically interlocked with the unit’s semi-automated erase head assembly and automatically en­gages the dual pass erasure cycle when the compartment is closed. For further information, contact Amber Technology Pty Ltd, Unit B, 5 Skyline Place, Frenchs Forest, NSW 2086. Phone (02) 975-1211. Fischertechnik robotic construction kit Fischertechnik has released a new robotic construction kit for use with the IBM-PC, PS/2, Amiga and Atari computers. Known as PROFI COMPUTING, the kit provides 888 parts with a 164-page manual describing the construction of 12 computer-controlled models. These include a CD player, a parcel-turning machine and a robot with a motor-driven gripper. Book Reviews – continued from page 71 and will probably spark some to head off for the tool shed and workbench. While some of the larger designs may be impracticable for most people, there is enough to interest the more determined. The book also contains many photos, some in colour, of the earliest Marconi equipment. 88  Silicon Chip This kit is useful for educational and training purposes in the fields of computer control, factory automation and mechanical and electrical engineering. It is also useful for simula­tion and prototyping applications. The Fischertechnik interface provides eight digital and two analog in­puts and four bidirectional motor out­puts. It connects to any parallel printer port and allows a second unit to be connected for a total of 16 digital in­puts and eight motor outputs (or 16 lamp outputs). The analog inputs may be used with potentiometers (for position control), light dependent resis­tors (for measuring light), thermistors (for measuring temperature), or with any resistive device from 0 to 5kW. Fischertechnik software called Lucky Logic provides an interactive, mouse-driven, user interface that is similar to a Sequential Flow Chart (SFC) style of control that is used by major industrial equipment suppliers such as Allen Bradley. Also available is a Programmable Control Language (PLC), developed by Procon Technology, that simulates the operation of relay-ladder-logic control. Finally, ex­ample programs are also available in C.BASIC and Pascal. The kit provides three motors and gears, six microswitches, two phototransistors, a 20-pin connection socket and construction base plate. For further information, contact Peter King, Procon Technology, PO Box 655, Mount Waverley, Vic 3149. Phone (03) 807 5660. Some of the more interesting photos include a look at a couple of early Australian transmitters at Queenscliff, Victoria and Devonport, Tasmania. There are seven appendixes which include letters between Marconi and his long time supporter, Sir W M. Preece, the first two technical reports on the Marconi system, two early pat­ents and a report made by Capt. H. B. Jackson to the Admiralty on the worthiness of the Marconi system for the Royal Navy. There is also an extract from the 1912 New York Times from the wireless operator on board the Titanic. Overall, this is a great read. For anyone who has ever been captivated by the thought of transmitting their voice over the air waves, this book will serve as a good reminder of how it all began. (D.B.Y.) SC SILICON CHIP BOOK SHOP Newnes Guide to Satellite TV 336 pages, in paperback at $49.95. Installation, Recept­ion & Repair. By Derek J. Stephen­son. First published 1991, reprinted 1994 (3rd edition). This is a practical guide on the installation and servicing of satellite television equipment. The coverage of the subject is extensive, without excessive theory or mathematics. 371 pages, in hard cover at $55.95. Servicing Personal Computers By Michael Tooley. First pub­ lished 1985. 4th edition 1994. Computers are prone to failure from a number of common causes & some that are not so common. This book sets out the principles & practice of computer servicing (including disc drives, printers & monitors), describes some of the latest software diagnostic routines & includes program listings. 387 pages in hard cover at $59.95. The Art of Linear Electronics By John Linsley Hood. Pub­lished 1993. This is a practical handbook from one of the world’s most prolific audio designers, with many of his designs having been published in English technical magazines over the years. A great many practical circuits are featured – a must for anyone inter­ested in audio design. Optoelectronics: An Introduction By J. C. A. Chaimowicz. First published 1989, reprinted 1992. This particular field is about to explode and it is most important for engineers and technicians to bring themselves up to date. The subject is comprehensively covered, starting with optics and then moving into all aspects of fibre optic communications. 361 pages, in paperback at $55.95. Digital Audio & Compact Disc Technology Produced by the Sony Service Centre (Europe). 3rd edition, published 1995. Prepared by Sony’s technical staff, this is the best book on compact disc technology that we have ever come across. It covers digital audio in depth, including PCM adapters, the Video8 PCM format and R-DAT. If you want to understand digital audio, you need this reference book. 305 pages, in paperback at $55.95. Power Electronics Handbook Components, Circuits & Applica­ tions, by F. F. Mazda. Published 1990. Previously a neglected field, power electronics has come into its own, particularly in the areas of traction and electric vehicles. F. F. Mazda is an acknowledged authority on the subject and he writes mainly on the many uses of thyristors & Triacs in single and three phase circuits. 417 pages, in soft cover at $59.95. Surface Mount Technology By Rudolph Strauss. First pub­ lish-ed 1994. This book will provide informative reading for anyone considering the assembly of PC boards with surface mounted devices. Includes chapters on wave soldering, reflow­ soldering, component placement, cleaning & quality control. 361 pages, in hard cover at $99.00. Electronics Engineer’s Reference Book Edited by F. F. Mazda. First pub­ lished 1989. 6th edition 1994. This just has to be the best reference book available for electronics engineers. Provides expert coverage of all aspects of electronics in five parts: techniques, physical phenomena, material & components, electronic design, and applications. The sixth edition has been expanded to include chapters on surface mount technology, hardware & software design, Your Name__________________________________________________ PLEASE PRINT Address____________________________________________________ _____________________________________Postcode_____________ Daytime Phone No.______________________Total Price $A _________ ❏ Cheque/Money Order ❏ Bankcard ❏ Visa Card ❏ MasterCard Card No. Signature_________________________ Card expiry date_____/______ Return to: Silicon Chip Publications, PO Box 139, Collaroy NSW, Australia 2097. Or call (02) 9979 5644 & quote your credit card details; or fax to (02) 9979 6503. semicustom electronics & data communications. 63 chapters, in paperback at $140.00. Radio Frequency Transistors Principles & Practical Appli­ cations. By Norm Dye & Helge Granberg. Published 1993. This timely book strips away the mysteries of RF circuit design. Written by two Motorola engineers, it looks at RF transistor fundamentals before moving on to specific design examples; eg, amplifiers, oscillators and pulsed power systems. Also included are chapters on filtering techniques, impedance matching & CAD. 235 pages, in hard cover at $85.00. Newnes Guide to TV & Video Technology By Eugene Trundle. First pub­ lish-ed 1988, reprinted 1990, 1992. Eugene Trundle has written for many years in Television magazine and his latest book is right up date on TV and video technology. 432 pages, in paperback, at $39.95.  Title Price  Newnes Guide to Satellite TV  Servicing Personal Computers  The Art Of Linear Electronics  Optoelectronics: An Introduction  Digital Audio & Compact Disc Technology  Power Electronics Handbook  Surface Mount Technology  Electronic Engineer's Reference Book  Radio Frequency Transistors  Newnes Guide to TV & Video Technology $55.95 $59.95 $49.95 $55.95 $55.95 $59.95 $99.00 $140.00 $85.00 $39.95 Postage: add $5.00 per book. Orders over $100 are post free within Australia. NZ & PNG add $10.00 per book, elsewhere add $15 per book. TOTAL $A January 1995  89 Silicon Chip 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. BACK ISSUES 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; Weather Fax Frequencies. September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Build The Vader Voice; Motorola MC34018 Speakerphone IC Data. plays Fax, RTTY & Morse); 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. April 1989: Auxiliary Brake Light Flasher; What You Need to Know About Capacitors; 32-Band Graphic Equaliser, Pt.2; LED Message Board, Pt.2. 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; Installing A Clock Card In Your Computer; Index to Volume 2. May 1989: Build A Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference; LED Message Board, Pt.3; 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.4. July 1989: Exhaust Gas Monitor (Uses TGS812 Gas Sensor); Extension For The Touch-Lamp Dimmer; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm. September 1989: 2-Chip Portable AM Stereo Radio (Uses MC13024 and TX7376P) Pt.1; 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). January 1990: High Quality Sine/Square Oscillator; Service Tips For Your VCR; Speed­ing Up Your PC; Phone Patch For Radio Amateurs; Active Antenna Kit; 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. March 1990: 6/12V Charger For Sealed Lead-Acid Batteries; Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16-Channel Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC. October 1989: FM Radio Intercom For Motorbikes 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. April 1990: Dual Tracking ±50V Power Supply; Voice-Operated Switch (VOX) With Delayed Audio; Relative Field Strength Meter; 16-Channel Mixing Desk, Pt.3; Active CW Filter For Weak Signal Reception; How To Find Vintage Receivers From The 1920s. November 1989: Radfax Decoder For Your PC (Dis- June 1990: Multi-Sector Home Burglar Alarm; Low- 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. September 1990: Music On Hold For Your Tele­ phone; Remote Control Extender For VCRs; Power Supply For Burglar Alarms; Low-Cost 3-Digit Counter Module; Simple Shortwave Converter For The 2Metre Band. October 1990: Low-Cost Siren For Burglar Alarms; Dimming Controls For The Discolight; Surfsound Simulator; DC Offset For DMMs; The Dangers of Polychlorinated Biphenyls; Using The NE602 In HomeBrew Converter Circuits. November 1990: How To Connect Two TV Sets To One VCR; A Really Snazzy Egg Timer; Low-Cost Model Train Controller; Battery Powered Laser Pointer; 1.5V To 9V DC Converter; Introduction To Digital Electronics; Simple 6-Metre 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 6-Metre Amateur Transmitter; Index To Volume 3. January 1991: Fast Charger For Nicad Batteries, Pt.1; Have Fun With The Fruit Machine; Two-Tone Alarm Module; LCD Readout For The Capacitance Meter; How Quartz Crystals Work; The Dangers When Servicing Microwave Ovens. February 1991: Synthesised Stereo AM Tuner, Pt.1; Three Inverters For Fluorescent Lights; Low-Cost Sinewave Oscillator; Fast Charger For Nicad Batteries, ORDER FORM Please send me a back issue for: ❏ September 1988 ❏ April 1989 ❏ May 1989 ❏ June 1989 ❏ July 1989 ❏ September 1989 ❏ October 1989 ❏ November 1989 ❏ December 1989 ❏ January 1990 ❏ February 1990 ❏ March 1990 ❏ April 1990 ❏ June 1990 ❏ July 1990 ❏ August 1990 ❏ September 1990 ❏ October 1990 ❏ November 1990 ❏ December 1990 ❏ January 1991 ❏ February 1991 ❏ March 1991 ❏ April 1991 ❏ May 1991 ❏ June 1991 ❏ July 1991 ❏ August 1991 ❏ September 1991 ❏ October 1991 ❏ November 1991 ❏ December 1991 ❏ January 1992 ❏ February 1992 ❏ March 1992 ❏ April 1992 ❏ May 1992 ❏ June 1992 ❏ July 1992 ❏ August 1992 ❏ September 1992 ❏ October 1992 ❏ January 1993 ❏ February 1993 ❏ March 1993 ❏ April 1993 ❏ May 1993 ❏ June 1993 ❏ July 1993 ❏ August 1993 ❏ September 1993 ❏ October 1993 ❏ November 1993 ❏ December 1993 ❏ January 1994 ❏ February 1994 ❏ March 1994 ❏ April 1994 ❏ May 1994 ❏ June 1994 ❏ July 1994 ❏ August 1994 ❏ September 1994 ❏ October 1994 ❏ November 1994 ❏ December 1994 ❏ January 1995 Enclosed is my cheque/money order for $­______or please debit my: ❏ Bankcard ❏ Visa Card ❏ Master Card Signature ____________________________ Card expiry date_____ /______ Name _______________________________ Phone No (___) ____________ PLEASE PRINT Street ________________________________________________________ Suburb/town ________________________________ Postcode ___________ 90  Silicon Chip Note: all prices include post & packing Australia (by return mail) ............................. $A7 NZ & PNG (airmail) ...................................... $A7 Overseas (airmail) ...................................... $A10 Detach and mail to: Silicon Chip Publications, PO Box 139, Collaroy, NSW, Australia 2097. Or call (02) 979 5644 & quote your credit card details or fax the details to (02) 979 6503. ✂ Card No. Pt.2; How To Design Amplifier Output Stages; Tasmania's Hydroelectric Power System. Remote Control For Model Railroads, Pt.3; 15-Watt 12-240V Inverter; A Look At Hard Disc Drives. March 1991: Remote Controller For Garage Doors, Pt.1; Transistor Beta Tester Mk.2; Synthesised AM Stereo Tuner, Pt.2; Multi-Purpose I/O Board For PC-Compatibles; Universal Wideband RF Preamplifier For Amateurs & TV. July 1992: Build A Nicad Battery Discharger; 8-Station Automatic Sprinkler Timer; Portable 12V SLA Battery Charger; Multi-Station Headset Intercom, Pt.2; Electronics Workbench For Home Or Laboratory. April 1991: Steam Sound Simulator For Model Railroads; Remote Controller For Garage Doors, Pt.2; Simple 12/24V Light Chaser; Synthesised AM Stereo Tuner, Pt.3; A Practical Approach To Amplifier Design, Pt.2. August 1992: Build An Automatic SLA Battery Charger; Miniature 1.5V To 9V DC Converter; Dummy Load Box For Large Audio Amplifiers; Internal Combustion Engines For Model Aircraft; Troubleshooting Vintage Radio Receivers. May 1991: 13.5V 25A Power Supply For Transceivers; Stereo Audio Expander; Fluorescent Light Simulator For Model Railways; How To Install Multiple TV Outlets, Pt.1. September 1992: Multi-Sector Home Burglar Alarm; Heavy-Duty 5A Drill speed Controller (see errata Nov. 1992); General-Purpose 3½-Digit LCD Panel Meter; Track Tester For Model Railroads; Build A Relative Field Strength Meter. June 1991: A Corner Reflector Antenna For UHF TV; 4-Channel Lighting Desk, Pt.1; 13.5V 25A Power Supply For Transceivers; Active Filter For CW Reception; Tuning In To Satellite TV, Pt.1. July 1991: Battery Discharge Pacer For Electric Vehicles; Loudspeaker Protector For Stereo Amplifiers; 4-Channel Lighting Desk, Pt.2; How To Install Multiple TV Outlets, Pt.2; Tuning In To Satellite TV, Pt.2. August 1991: Build A Digital Tachometer; Masthead Amplifier For TV & FM; PC Voice Recorder; Tuning In To Satellite TV, Pt.3; Step-By-Step Vintage Radio Repairs. September 1991: Studio 3-55L 3-Way Loudspeaker System; Digital Altimeter For Gliders & Ultralights, Pt.1; Build A Fax/Modem For Your Computer; The Basics Of A/D & D/A Conversion; Windows 3 Swapfiles, Program Groups & Icons. October 1991: Build A Talking Voltmeter For Your PC, Pt.1; SteamSound Simulator For Model Railways Mk.II; Magnetic Field Strength Meter; Digital Alti­meter For Gliders & Ultralights, Pt.2; Getting To Know The Windows PIF Editor. November 1991: Colour TV Pattern Generator, Pt.1; Battery Charger For Solar Panels; Flashing Alarm Light For Cars; Digital Altimeter For Gliders & Ultralights, Pt.3; Build A Talking Voltmeter For Your PC, Pt.2; Modifying The Windows INI Files. December 1991: TV Transmitter For VCRs With UHF Modulators; Infrared Light Beam Relay; Solid-State Laser Pointer; Colour TV Pattern Generator, Pt.2; Index To Volume 4. January 1992: 4-Channel Guitar Mixer; Adjustable 0-45V 8A Power Supply, Pt.1; Baby Room Monitor/FM Transmitter; Automatic Controller For Car Headlights; Experiments For Your Games Card; Restoring An AWA Radiolette Receiver. February 1992: Compact Digital Voice Recorder; 50-Watt/Channel Stereo Power Amplifier; 12VDC/240VAC 40-Watt Inverter; Adjustable 0-45V 8A Power Supply, Pt.2; Designing A Speed Controller For Electric Models. March 1992: TV Transmitter For VHF VCRs; Studio Twin Fifty Stereo Amplifier, Pt.1; Thermostatic Switch For Car Radiator Fans; Telephone Call Timer; Coping With Damaged Computer Direct­ories; Valve Substitution In Vintage Radios. April 1992: Infrared Remote Control For Model Railroads; Differential Input Buffer For CROs; Studio Twin Fifty Stereo Amplifier, Pt.2; Understanding Computer Memory; Aligning Vintage Radio Receivers, Pt.1. May 1992: Build A Telephone Intercom; Low-Cost Electronic Doorbell; Battery Eliminator For Personal Players; Infrared Remote Control For Model Railroads, Pt.2; Aligning Vintage Radio Receivers, Pt.2. June 1992: Multi-Station Headset Intercom, Pt.1; Video Switcher For Camcorders & VCRs; Infrared October 1992: 2kW 24VDC To 240VAC Sine­wave Inverter; Multi-Sector Home Burglar Alarm, Pt.2; Mini Amplifier For Personal Stereos; Electronically Regulated Lead-Acid Battery Charger. January 1993: Peerless PSK60/2 2-Way Hifi Loudspeakers; Flea-Power AM Radio Transmitter; High Intensity LED Flasher For Bicycles; 2kW 24VDC To 240VAC Sine­wave Inverter, Pt.4; Speed Controller For Electric Models, Pt.3. February 1993: Three Simple Projects For Model Railroads; A Low Fuel Indicator For Cars; Audio Level/ VU Meter With LED Readout; Build An Electronic Cockroach; MAL-4 Microcontroller Board, Pt.3; 2kW 24VDC To 240VAC Sine­wave Inverter, Pt.5. March 1993: Build A Solar Charger For 12V Batteries; An Alarm-Triggered Security Camera; Low-Cost Audio Mixer for Camcorders; Test Yourself On The Reaction Trainer; A 24-Hour Sidereal Clock For Astronomers. April 1993: Solar-Powered Electric Fence; Build An Audio Power Meter; Three-Function Home Weather Station; 12VDC To 70VDC Step-Up Voltage Converter; Digital Clock With Battery Back-Up; A Look At The Digital Compact Cassette. May 1993: Nicad Cell Discharger; Build The Woofer Stopper; Remote Volume Control For Hifi Systems, Pt.1; Alphanumeric LCD Demonstration Board; The Micro­soft Windows Sound System. June 1993: Windows-Based Digital Logic Analyser, Pt.1; Build An AM Radio Trainer, Pt.1; Remote Control For The Woofer Stopper; Digital Voltmeter For Cars; Remote Volume Control For Hifi Systems, Pt.2 July 1993: Build a Single Chip Message Recorder; Light Beam Relay Extender; AM Radio Trainer, Pt.2; Windows Based Digital Logic Analyser; Pt.2; Quiz Game Adjudicator; Programming The Motorola 68HC705C8 Micro­ controller – Lesson 1; Antenna Tuners – Why They Are Useful. August 1993: Low-Cost Colour Video Fader; 60-LED Brake Light Array; A Microprocessor-Based Sidereal Clock; The Southern Cross Z80-based Computer; A Look At Satellites & Their Orbits. September 1993: Automatic Nicad Battery Charger/ Discharger; Stereo Preamplifier With IR Remote Control, Pt.1; In-Circuit Transistor Tester; A +5V to ±15V DC Converter; Remote-Controlled Cockroach Servicing An R/C Transmitter, Pt.1. October 1993: Courtesy Light Switch-Off Timer For Cars; Wireless Microphone For Musicians; Stereo Preamplifier With IR Remote Control, Pt.2; Electronic Engine Management, Pt.1; Programming The Motorola 68HC705C8 Micro­controller – Lesson 2; Servicing An R/C Transmitter, Pt.2. November 1993: Jumbo Digital Clock; High Efficiency Inverter For Fluorescent Tubes; Stereo Preamplifier With IR Remote Control, Pt.3; Siren Sound Generator; Electronic Engine Management, Pt.2; More Experiments For Your Games Card. December 1993: Remote Controller For Garage Doors; Low-Voltage LED Stroboscope; Low-Cost 25W Amplifier Module; Peripherals For The Southern Cross Computer; Build A 1-Chip Melody Generator; Electronic Engine Management, Pt.3; Index To Volume 6. January 1994: 3A 40V Adjustable Power Supply; Switching Regulator For Solar Panels; Printer Status Indicator; Mini Drill Speed Controller; Stepper Motor Controller; Active Filter Design For Beginners; Electronic Engine Management, Pt.4. February 1994: 90-Second Message Recorder; Compact & Efficient 12-240VAC 200W Inverter; Single Chip 0.5W Audio Amplifier; 3A 40V Adjustable Power Supply; Electronic Engine Management, Pt.5. March 1994: Intelligent IR Remote Controller; Build A 50W Audio Amplifier Module; Level Crossing Detector For Model Railways; Voice Activated Switch For FM Microphones; Simple LED Chaser; Electronic Engine Management, Pt.6. April 1994: Remote Control Extender For VCRs; Sound & Lights For Model Railway Level Crossings; Discrete Dual Supply Voltage Regulator; Low-Noise Universal Stereo Preamplifier; Build A Digital Water Tank Gauge; Electronic Engine Management, Pt.7. May 1994: Fast Charger For Nicad Batteries; Induction Balance Metal Locator; Multi-Channel Infrared Remote Control; Dual Electronic Dice; Two Simple Servo Driver Circuits; Electronic Engine Management, Pt.8; Passive Rebroadcasting For TV Signals. June 1994: 200W/350W Mosfet Amplifier Module; A Coolant Level Alarm For Your Car; An 80-Metre AM/ CW Transmitter For Amateurs; Converting Phono Inputs To Line Inputs; A PC-Based Nicad Battery Monitor; Electronic Engine Management, Pt.9 July 1994: SmallTalk – a Tiny Voice Digitiser For The PC; Build A 4-Bay Bow-Tie UHF Antenna; PreChamp 2-Transistor Preamplifier; Steam Train Whistle & Diesel Horn Simulator; Portable 6V SLA Battery Charger; Electronic Engine Management, Pt.10. August 1994: High-Power Dimmer For Incandescent Lights; Microprocessor-Controlled Morse Keyer; Dual Diversity Tuner For FM Microphones, Pt.1; Build a Nicad Zapper; Simple Crystal Checker; Electronic Engine Management, Pt.11. September 1994: Automatic Discharger For Nicad Battery Packs; MiniVox Voice Operated Relay; Image Intensified Night Viewer; AM Radio For Aircraft Weather Beacons; Dual Diversity Tuner For FM Microphones, Pt.2; Electronic Engine Management, Pt.12. October 1994: Dolby Surround Sound – How It Works; Dual Rail Variable Power Supply (±1.25V to ±15V); Talking Headlight Reminder; Electronic Ballast For Fluorescent Lights; Temperature Controlled Soldering Station; Electronic Engine Management, Pt.13. November 1994: Dry Cell Battery Rejuv­enator; A Novel Alphanumeric Clock; UHF Radio Alarm Pager For Cars & Boats; 80-Metre DSB Amateur Transmitter; Anti-Lock Braking Systems: How They Work; How To Plot Patterns Direct To PC Boards. December 1994: Dolby Pro-Logic Surround Sound Decoder, Pt.1; Easy-To-Build Car Burglar Alarm; Three-Spot Low Distortion Sinewave Oscillator; Clifford – A Pesky Electronic Cricket; Cruise Control – How It Works;Index to Vol.7. PLEASE NOTE: all issues from November 1987 to August 1988, plus October 1988, November 1988, December 1988, January, February, March & August 1989, May 1990, and November and December 1992 are now sold out. All other issues are presently in stock. For readers wanting articles from sold-out issues, we can supply photostat copies (or tear­sheets) at $7.00 per article (incl. p&p). When supplying photostat articles or back copies, we automatically supply any relevant notes & errata at no extra charge. January 1995  91 ASK SILICON CHIP Got a technical problem? Can’t understand a piece of jargon or some technical principle? Drop us a line and we’ll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. Universal preamp is noisy I have built your Low Noise Universal Stereo Preamplifier which was published in the April 1994 issue. To provide the ±15V rails required I have also built a power sup­ply, as published in the August 1988 issue. Both units were built from kits supplied by Jaycar Electronics in Melbourne. I built the microphone version of your design. Having built and tested it, I was very disappointed to find that the noise generated by the preamplifier was much greater than that of my old audio mixer/amp. What was even worse, the amplification provided by the preamp was insufficient either for a dynamic or for an electret microphone. Both channels of the preamp performed in the same fashion, which reduced the probability of some resis­ tor or capacitor being defective. Suspecting the IC (LM833N), I replaced it with another one but this made no difference to the preamp’s performance. I remeasured the volt­ ages at all pins of the IC with respect to ground and found, as before, that they matched those specified in your arti­cle (ie, +15V at pin 8, -15V at pin 4, +3mV at pin 1, and 20-30mV at other pins). A tone, generated by a signal injector and applied to the input terminals, came through to the outputs with some Weather beacon frequencies I must congratulate your staff for designing and publishing so many great and interesting projects for the electronics enthu­siast. I say to myself every month when I receive my SILICON CHIP that they can’t keep these coming indefinitely but you do and they are of great personal interest! I do have a question for you about the AM weather radio though. Are these weather beacons operating all 92  Silicon Chip amplification, which as I mentioned previously, was quite inadequate for use with a microphone. To reiterate, I was very disappointed that the claims made in your design article were not met. I checked and rechecked the PC, all connections and all soldered joints, but could not find anything wrong. Is, there, perhaps, an error in the design? I would appreciate your comments. (J. R., Glen Wav­erley, Vic). • We are very surprised that you have found the design noisy since it is fundamentally a very quiet and well-proven design. It is essentially the same design as published in our June 1990 issue. Have you managed to make a measurement of the signal to noise ratio? We would expect that it would be in excess of 60dB with respect to a 100mV output signal. Note that the signal to noise ratio must be measured with the input loaded by a resistor equal to the source impedance of the microphone, say around 470Ω or less. You have not indicated what sort of noise comes from the preamplifier. Any noise generated by this design is essentially white noise. If you have hum, then you have a layout problem in either the earth or signal wiring or the unit is too close to a power transformer or mains wiring. We are also surprised that you the time or just at certain times? I have a multiband radio that picks up LW but have picked up nothing at all when the airwaves are sampled randomly. Where could I find out the frequencies used by these bea­cons? (N. P., Ermington, NSW). • The frequencies are as follows: Sydney 317kHz; Richmond (RAAF base) 347kHz; Bankstown 212kHz. Sydney and Richmond are repeat­ ers and operate 24 hours a day. There are other frequencies for other states but you’re not likely to pick them up. have found the gain insuffi­cient. The nominal gain, as set by the 200kΩ and 390Ω resistors, is 514 which is a very high figure. Have you confirmed that the gain is correct? We would expect the gain to be more than ade­quate for a typical electret microphone. A 2mV input signal will result in an output signal of 1V which should be more than enough for your mixer/amplifier. The fact that you have low gain and poor signal to noise ratio really does not add up and we wonder if your input coupling capacitors are partially open circuit or the wrong value. You can test this point by shorting the input capacitors out temporarily. If the gain comes up and the noise goes down, that is the prob­lem. Perhaps you should also check the other input components for open circuits as well. Kanga hammer too fast I have always enjoyed reading your magazine especially ‘The Serviceman’ and the varied projects which you have presented over the years, some of which I’ve constructed. My brother, working on the opal fields, complained to me of his Kanga jack-hammer running marginally too fast and as a consequence the hammer action was not working very well. This complaint is often heard at White Cliffs and the way miners have compensated has been by using a product from Arlec which re­duced the incoming voltage and is controlled by a dial on the front of it. Apparently, they are no longer available although from comments I got from various electrical suppliers that I spoke to, one would assume there is still quite a demand for this item. Then I suggested that I could assemble for him the “Univer­sal Motor Speed Controller” as featured in the September 1992 issue of SILICON CHIP. So he put his money down and I purchased a kit from Dick Smith Electronics and assembled it according to the instructions. My test run at home in Melbourne seemed to indicate it was working so, when on holidays, I delivered the unit to him for approval. Alas, he was not satisfied. His complaint is that although it varies the speed of his hammer, the range is not from the maximum down but leaves a gap between the performance of the hammer without the speed con­troller to the maximum setting with the unit in line. I altered the inboard pot to see if I could change anything but without success. Am I expecting too much from the unit or have I done something wrong? Perhaps you could suggest an alternative. (R. W., Montrose, Vic). • The problem with using the speed control with such a power hungry device as a Kanga hammer is that it reduces the voltage too much. The maximum RMS voltage from any SCR speed control is only about 170 volts RMS for which the waveform is halfwave rectified AC. This effectively reduces the maximum power of the tool by half. Indeed, electric drills and other appliances which have inbuilt electronic speed controls use motors which are designed to give their maximum performance at around 180 volts RMS, not 240V AC. It sounds as though your brother’s Kanga hammer needs a voltage reduction of as little as 5-10%. This cannot be achieved with an SCR speed control. However, it should be possible to achieve the result you want with the 2400W dimmer published in the July 1994 issue of SILICON CHIP. This will allow very slight reductions in the mains voltage to be achieved and its Triac is rated for the very high surge currents which can be expected. The circuitry also includes a “snubber” to allow the Triac to commutate properly (ie, turn off properly at the end of each AC half-cycle). If you do decide to take the approach of using the 2400W dimmer to control the speed of the Kanga hammer, we suggest you restrict its operation so that the maximum voltage reduction is no more than say, 20%. Since the dimmer has a linear voltage versus power control characteristic, (ie, 0 to 10V, 5V gives half power), this can be easily done by substituting a 10kΩ pot for the main dimmer control (VR2) and then connecting a 47kΩ resistor in series with the low voltage end of the pot. Low-cost data logger wanted Might I suggest that your boffins develop a project for the construction of a small, single or dual channel data logger. I am aware that there are commercial units available, such as the mini unit from R.S. Components, but the R.S. units do not have a voltage input version, so voltage and current monitoring are not possible. Head lamp battery problem A few years ago, a friend gave me six old head lamp sets of the underground mining type. The head lamps consist of a twin filament bulb (GE BM32) surrounded by a silver reflector that can be moved in and out by a knob, focusing the light beam, all of which is housed in a water and-gas proof plastic case. This is fitted with an adjustment knob that has several positions and off for one or both filaments. It also had contact points for re­charging the battery without disconnection. A clip arrangement at the back of the lamp fits onto the safety helmet holder. The power supply was a lead acid battery, Exide Triclad Type F2, with nominal voltage of 4V. I could not find any capaci­ty rating on the battery but it stated that the nominal bulb rating was 1A. This head lamp set is no longer available in Australia and the battery is made in India but it costs more than the new updated replacement head lamp set with its own battery. The lamps can be obtained but are costly. I have been able to obtain a few different bulbs (from 12V garden lighting systems) but I am still looking for a better bulb to fit the 4V bulb housing. After looking at many gel cell rechargeables, I found one (NPG18-12 Yuasa) that gave me good power capacity but it was large and very heavy – too much weight and space to carry in a backpack. I now have this idea of using a series (say 3 x 12V) of high voltage batteries of low to reasonable capacity and converting the voltage through a stepdown transformer to the desired voltage. I would suggest that a unit the size of a matchbox and having a logging capacity of at least 250 samples would be most useful. The proliferation of micro­ controllers should make the construction of such a system rather straightforward. • Thanks for your suggestion of a compact data logger as a possible project. We cannot promise anything but we will have a look at the idea to see if it is viable. The transformers convert voltages and current with very little loss (about 6% or less). I could increase the capacity by two to six times, depending on the battery and bulb I used for the lamps. This will give me more running time for the lamp, as well as reducing the number of recharging cycles. As the voltage goes down, the ampere hour capacity goes up. Is this correct for this situation? How do I convert the DC to AC and how do I construct the transformer to convert say 12/24/36V to 4V, with a possible 1A maximum current. What frequency would be best to use? I was thinking of 75-100Hz as the final AC frequency to avoid flicker­ing in the light beam. (T. F., Nambour, Qld). • Unfortunately, your proposal is not very practical since the inevitable losses in the converter circuitry and transformer would mean a considerable loss in efficiency. At best, you could not expect the efficiency of your proposed system to be better than 80%. As far as battery capacity or energy capacity is con­ cerned, the important parameter is the number of watt-hours stored. This is obtained by multiplying the amp-hour rating by the battery voltage. In fact, you will find that the watthour capacity of any type of battery is more or less the same, regardless of the voltage. So there is no real advantage in using a high battery voltage and then stepping down. The most efficient approach would be to match the filament voltage to the battery voltage. Apart from that, you can obtain more efficiency by using Krypton torch globes which are claimed to be 70% brighter than normal globes. Krypton globes are available from Jaycar Electronics. SC January 1995  93 MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. CLASSIFIED ADVERTISING RATES FOR SALE Advertising rates for this page: Classified ads: $10.00 for up to 12 words plus 50 cents for each additional word. Display ads (casual rate): $25 per column centimetre (Max. 10cm). Closing date: five weeks prior to month of sale. To run your classified ad, print it clearly in the space below or on a separate sheet of paper, fill out the form & send it with your cheque or credit card details to: Silicon Chip Classifieds, PO Box 139, Collaroy, NSW 2097. Or fax the details to (02) 979 6503. DON’S SHORT FORM KITS: PIC­ 16C54-58/71/84 Universal PCB $23; Basic Stamps $65; Serial Driven 18 I/O $70; Parallel Driven 64 I/O $38; Relay8 PCB $10-$20; Z80 Dev. $38-$52; 8K-4Mb Print Buff. $38-$52. Promo Disk for all projects $2. Don McKenzie, 29 Ellesmere Crescent, Tullamarine 3043. Phone (03) 338 6286. _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ TINY VIDEO CAMERAS $20 off! This month from $179. Previous buyers get DOUBLE $40 off. MATCHBOX SIZE PCB MODULES from 32 x 32 x 23mm with lens. 16 types. Optional lenses, C lens mounts, cases & technical manuals. ALLTHINGS. Ph/Fax (09) 349 9413 TENDER ESTATE, military radios, military pamphlets, transceivers, linears, PSUs, genemotors, general catalogue 85c stamp. Hadgraft, 17 Paxton St, Holland Park Qld 4121. AH (07) 397 3751. VALVES: all types for radio, audio and industrial use. For sale and wanted to buy. SSAE for list. Electronic Valve and Tube Company, PO Box 381, Chad­ stone, Vic 3181. Fax (03) 571 1160. Ph (018) 557 380. INFRARED AUDIO CONTROL KIT based on the Intelligent Infrared Receiver kit (ref. Silicon Chip, March Enclosed is my cheque/money order for $­__________ or please debit my RCS RADIO PTY LTD Card No. ✂ ❏ Bankcard   ❏ Visa Card   ❏ Master Card Signature­­­­­­­­­­­­__________________________ Card expiry date______/______ Name ______________________________________________________ Street ______________________________________________________ Suburb/town ___________________________ Postcode______________ 94  Silicon Chip RCS Radio Pty Ltd is the only company that manufactures and sells every PC board and front panel published in SILICON CHIP, ETI and EA. RCS Radio Pty Ltd, 651 Forest Rd, Bexley 2207. Phone (02) 587 3491 ELECTROSTATIC LOUDSPEAKERS • • 3-Panel Full Range Design. Available in kit form or fully assembled. • Locally designed & manufactured. For information brochure, Phone (09) 397 6212 Fax (09) 496 1546 Or write to: E. R. AUDIO, 119 BROOKTON HWY, ROLEYSTONE, WESTERN AUSTRALIA 6111. N.S.W. Ph. (02) 804 6859 S.A. Ph. (08) 332 6513 TAS. Ph. (002) 31 2403 1994) to control volume, treble, bass, balance, inputs, and select between two inputs (CD, VCR, etc). Also available infrared transmitters, preprogrammed and learning models. For details call BENETRON P/L (02) 963 3868 or (018) 200 108. WEATHER FAX programs for IBM XT/ATs *** “RADFAX2” $35 is a high resolution, shortwave weather fax, Morse & Rtty receiving program. Suitable for CGA, EGA, VGA and Hercules cards. Needs SSB HF radio & Radfax decoder. *** “SATFAX” $45 is a YUGA ENTERPRISE BA, LA, LB, LC, UPA, UPB, UPC, TA, Buy TBA, TDA, TEA, & 2SA, 2SB, 2SC, Sell ese 2SJ, 2SK, SAA, Japan STA, STK, STR, ICs & tors HA, AC, KA, KIA, Transis IX, LM, MN, PA TEL: (65) 741 0300 FAX: (65) 749 1048 705 Sims Drive #03-09 Shun Li Industrial Complex Singapore 1438 MicroZed Computers PO Box 634 (296 Cook’s Rd), ARMIDALE 2350 V (067) 722 777 F (067) 728 987 Credit cards accepted. SIMM (all 70ns) Parity/No Parity 1Mb 30-pin $57/55 4Mb 30-pin $192/185 2Mb 72-pin $130 4Mb 72-pin $230/210 8Mb 72-pin $480/440 16Mb 72-pin $740/670 32Mb 72-pin $1520/1340 MAC 8Mb P’BOOK CO-PROCESSORS 387S/DX to 40 $405 $90 LASER PRINTER HP with 2Mb $200 COMPAQ CONTURA 8Mb $550 DRAM DIP 1Mb x 1 256 x 4 70ns 70ns $7.20 $7.20 IBM PS.2 THINKPAD L40/N33 90/95 8Mb 8Mb 4Mb $655 $513 $230 TOSHIBA 3100SX 44/6400 4Mb 4Mb $285 $265 SUN SPARC 10/20 16Mb SPARC 10/20 64Mb $965 $4080 DRIVES – SEAGATE 261Mb 16ms 3yr wty $230 545Mb 14ms 3yr wty $335 1052Mb 9ms 5yr wty $695 Sales tax 21%. Overnight delivery. Credit cards welcome. RING FOR LATEST PRICES 1st Floor, 100 Yarrara Rd, PO Box 382, Pennant Hills, 2120. Tel: (02) 980 6988 Fax: (02) 980 6991 NOAA, Meteor & GMS weather satellite picture receiving program. Needs EGA or VGA plus “WEATHER FAX” PC card. *** “MAXISAT” $75 is similar to SATFAX but needs 2Mb expanded memory (EMS 3.6 or 4.0) and 1024 x 768 SVGA card. All programs are on 5.25-inch or 3.5-inch disks (state which) & include documentation. Add $3 postage. Only from M. Delahunty, 42 Villiers St, New Farm, Qld 4005. Phone (07) 358 2785. MicaSOFT Electronics and Computing tutor program, written in UK, ideal for TAFE, schools or individual use. Now Parallax “BASIC STAMP”: 8 I/O pins and proto­ typing area. Program it with a PC, 33 simple instructions. Development kit includes one “BASIC STAMP” ($270). Extra modules ($79.85). Chipset and Resonator to make your own $30.25. STAMP Stretch­ er 16 I/O 1 A/D $91.96. Serial input LCD display $102.85. Scarce com­ponents need­ed for Application notes now in stock. Small items XPress post $5, kit $8. Send four 45c stamps for details. Parallax Distributor and technical support in Australia. MEMORY & DRIVES PRICES AT DECEMBER, 1994 PELHAM available in Australia. Send 4 x 45c stamps for demo disk (tell us what size). MicroZed Computers, PO Box 634, Armidale 2350. U N U S UA L B O O K S : E l e c t r o n i c Devices, Fireworks, Locksmithing, Radar Invisibility, Surveillance, SelfProtection, Unusual Chem­ istry and more. For a complete catalog, send 95 cents in stamps to Vector Press, Dept S, PO Box 434, Brighton, SA 5048. BINARY CLOCK - OCTOBER 1993: complete documentation supplied, includes introduction to binary, how it SILICON CHIP FLOPPY INDEX WITH FILE VIEWER Now available: the complete index to all SILICON CHIP articles since the first issue in November 1987. The Floppy Index comes with a handy file viewer that lets you look at the index line by line or page by page for quick browsing, or you can use the search function. All commands are listed on the screen, so you’ll always know what to do next. Notes & Errata also now available: this file lets you quickly check out the Notes & Errata (if any) for all articles published in SILICON CHIP. Not an index but a complete copy of all Notes & Errata text (diagrams not included). The file viewer is included in the price, so that you can quickly locate the item of interest. The Floppy Index and Notes & Errata files are supplied in ASCII format on a 3.5-inch or 5.25-inch floppy disc to suit PC-compatible computers. Note: the File Viewer requires MSDOS 3.3 or above. Price $7.00 each + $3 p&p. Send your order to: Silicon Chip Publications, PO Box 139, Collaroy 2097; or phone (02) 979 5644 & quote your credit card number; or fax the details to (02) 979 6503. Please specify 3.5-inch or 5.25-inch disc. January 1995  95 SECONTRONICS Advertising Index COMPONENTS, COMPUTERS, ELECTRON TUBES S/H TEST EQUIPMENT, COMPUT­ ER REPAIRS Altronics ..........................IFC,24-25 RECYCLED EPROMS: ALL ARE CLEANED, ERASED AND BLANK TESTED. Av-Comm.....................................85 2716 2732 2764 27128 27256 Avico Electronics.........................59 $1.50 ea or 10 for $12 $1.50 ea or 10 for $12 $2.00 ea or 10 for $16 $3.00 ea or 10 for $26 $3.50 ea or 10 for $32 David Reid Electronics ..............90 TRANSISTORS, ICs, DIODES 2N3440 $0.50 ea or 10 for $4 2N7000 $0.80 ea or 10 for $6 TIP122 $1.20 ea or 10 for $10 74HC04 $0.60 ea or 10 for $5 1N5060 diodes 100/$10 or 1000 for $70 7406 $0.25 ea or 25 for $5 LM380N $2.50 ea or 10 for $20 DAC O8EP $5.00 ea or 10 for $45 VALVES: 12AV7 $4 1B3GT $5 6J6WA $5 works, PLD source list­ings, conversion tables. Kit with PC board and all components $75 plus $5 p&p. Optional Z frame stand (includes spacers and chassis DC connector) $25 plus $5 p&p. Available from Prototype Electronics, 1/29 Stewart St, Parra­ matta, NSW 2124. Phone (02) 890 2960; Fax (02) 630 3148. Pay by cheque, money order, credit card. PRINTED CIRCUIT BOARDS for the hobbyist. For service & enquiries contact: T. A. Mowles (08) 326 5590. QQV07/50 $15 6SG7 $6 1S2 $3 6AS7 $8 3D21 6U8A 6080WA 6X5GT $6 $6 $9 $5 Phone, mail or fax your orders. Credit cards accepted for orders $20 & over. Mail orders to PO Box 2215, Brookside, Qld 4053. Or shop sales at 143 Grays Rd, Enoggera Qld. Hours: Thursday 4pm-9pm; Sat 9am-4pm. Phone (07) 353 4919, Fax (07) 855 1014. Microprocessor For Stereo Preamplifier Now back in stock: the 68HC705-C8P pre-programmed micro­pro­cessor for the Infrared Remote Controlled Stereo Preamplifier (Silicon Chip, Sept.-Oct. 1993). Also suits the Remote Volume Control (May & June, 1993). Price: $45 + $6 p+p Payment by cheque, money order or credit card to: Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. Phone (02) 9795644; Fax (02) 979 6503. 68705 DEVELOPMENT SYSTEM: In Circuit Simulator/Emulator and programmer board. Suppor ts all 68HC705 range including C4, C8, J2, K1, P9, C9, D9 & 68705P3, U3, R3 microcontrollers. For more information contact Oztechnics, PO Box 38, Illawong NSW 2234, Phone (02) 541 0310, Fax (02) 541 0734 Email oztec<at>ozemail. com.au. "garage sale". LASERVISION, Australia's largest laser system manufacturer is selling equipment to make way for new models. Please contact Stephanie for a list of items available. Ph (02) 651 1511. LASER TUBES, systems and parts DEAD OR ALIVE: LEAK TL 50/PLUS. Ph (02) 452 1724. Emona Instruments.....................89 E.R. Audio....................................95 Instant PCBs................................95 Jaycar ................................... 45-52 Kalex............................................93 MicroZed Computers...................95 Oatley Electronics.................. 60-61 Pelham........................................95 RCS Radio ..................................94 Rod Irving Electronics .......... 67-71 Secontronics................................96 Silicon Chip Binders....................96 Silicon Chip Bookshop.................23 Silicon Chip Projects Book......OBC Silicon Chip Wallchart................IBC Tortech.........................................77 WANTED WANTED: YOUR CIRCUIT & DESIGN IDEAS Do you have a good circuit idea. If so, why not sketch it out, write a brief description of its operation & send it to us. Provided your idea is workable & original, we’ll publish it in Circuit Notebook & you’ll make some money. We’ll pay up to $60 for a really good circuit but don’t make them too big please. Send your idea to: Silicon Chip Publications, PO Box 139, Collaroy, NSW 2097. 96  Silicon Chip Dick Smith Electronics........... 10-13 Yuga Enterprise...........................95 _________________________________ PC Boards Printed circuit boards for SILICON CHIP projects are made by: • RCS Radio Pty Ltd, 651 Forest Rd, Bexley, NSW 2207. Phone (02) 587 3491. • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone (09) 828 5730. • H. T. Electronics, 35 Valley View Crescent, Hackham West, SA 5163. Phone (08) 326 5590.