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GHOST BUSTING FOR TV SETS NOW FEASIBLE $4.50 AUGUST 1993 NZ $5.50 INCL GST REGISTERED BY AUSTRALIA POST – PUBLICATION NO. NBP9047 SERVICING — VINTAGE RADIO — COMPUTERS — AMATEUR RADIO — PROJECTS TO BUILD Z80-BASED SINGLE BOARD COMPUTER Build A Super Bright 60-LED Brake Light Array SILICON CHIP If you are seeing a blank page here, it is more than likely that it contained advertising which is now out of date and the advertiser has requested that the page be removed to prevent misunderstandings.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 Vol.6, No.8; August 1993 FEATURES FORGET THOSE MESSY edits on your VCR. This project smoothly fades any composite PAL video signal to black & can also wipe left or right across the screen for special effects. Details page 18.   4 Ghost-Busting for TV Sets Now Feasible New system from Philips cleans up the signal   6 The Keck Optical Telescope, Pt.2 by Bob Symes The world’s biggest optical telescope PROJECTS TO BUILD 18 Low-Cost Colour Video Fader by Darren Yates Fades to black or wipes left or right across the screen 30 A Microprocessor-Based Sidereal Clock by John Western THIS STAR CLOCK is micro­ processor controlled & has two 6-digit displays which show sidereal time & either local or universal time. See page 30. Shows sidereal time plus local or universal time 56 Build A 60-LED Brake Light Array by Leo Simpson The LEDs light from the centre outwards 82 The Southern Cross Computer by Peter Crowcroft & Craig Jones A single-board Z80-based computer for the 1990s SPECIAL COLUMNS 40 Serviceman’s Log by the TV Serviceman Little things can be big time wasters 53 Remote Control by Bob Young Unmanned aircraft – Israel leads the way YOU’VE SEEN THOSE fancy brake light arrays on late-model sports cars & now you can build one for your car. It uses 60 highbrightness LEDs that light from the centre outwards. Construction starts on page 56. 62 Vintage Radio by John Hill How to deal with block capacitors 72 Amateur Radio by James Morris, VK2GVA A look at satellites & their orbits DEPARTMENTS   2 28 75 79 Publisher’s Letter Circuit Notebook Order Form Product Showcase 90 92 95 96 Back Issues Ask Silicon Chip Market Centre Advertising Index THIS SINGLE-BOARD Z80-based computer is designed for the 1990s generation of students. It comes with a fully commented monitor & is designed to teach microprocessor & microcontroller programming techniques. August 1993  1 Publisher & Editor-in-Chief Leo Simpson, B.Bus. Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Darren Yates, B.Sc. Reader Services Ann Jenkinson Sharon Macdonald Marketing Manager Sharon Lightner Phone (02) 979 5644 Mobile phone (018) 28 5532 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: $42 per year in Australia. For overseas rates, see the subscription page in this issue. Editorial & advertising offices: Unit 1a/77-79 Bassett Street, Mona Vale, NSW 2103. Postal address: PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 979 5644. Fax (02) 979 6503. PUBLISHER'S LETTER Pay TV will boost optical fibre technology Since I wrote about the "Pay TV Farce" back in the August 1992 issue, the story has had more twists and turns than any fiction writer could have dreamed up. The big players missed out on getting a satellite TV licence while two unknowns, Ucom and Hi-Vision, got the prizes. Now that the Australian Broadcasting Authority has approved the licences, there remains the matter of about $400 million to be paid. However, the satellite TV licences may yet turn out to be the "booby prizes" if the Packer/Murdoch/Telecom pay TV consortium looks seriously at the other way open to it – optical fibre transmission and what it terms "Asymmetric Digital Subscriber Lines". While we don't know exactly what Telecom is planning, it is an obvious move. Having lost its monopoly on telephone traffic and having been told by the Federal Government to go out and behave like a commercial corporation, it is starting to do just that, to the consternation of some politicians within the Government. Not only has it aligned itself Packer and News Corporation in the Pay TV consortium, it has also taken the unprecedented step of taking a shareholding in the Seven TV network. This last step is of particular significance because of the Seven Networks' experiment in interactive television in Adelaide. Let's just crystal-ball on how the Packer/Murdoch/Telecom Pay TV system might work and remember it will probably be interactive. Therefore, the subscriber could use his set to dial up the exchange and select whatever program he wants or switch between any of dozens of programs. This would be no problem for the optical fibre system, especially since only one video program would need to be sent from the exchange to the subscriber at any one time. Think about it? A choice of maybe dozens of programs, always with high signal quality and with no need for a dish on the roof. Satellite pay TV is unlikely to be able to offer the same range of choice. So really, at some stage in the next decade, a satellite TV licence could just be a millstone around a company's neck. Remember also that the optical fibre system will probably also support video telephones and data services of all sorts – education, banking, shopping, TAB, you-name-it. When you think of the huge potential of an optical fibre network, it could well be that Telecom is quite happily contemplating its prosperous future. And why shouldn't it? After all, it was told to go out and play with the big boys and that's what it is doing. Leo Simpson ISSN 1030-2662 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 Ghost-busting for TV sets now feasible However much we might like watching TV, a great many viewers are plagued by ghost reception. This is caused by signals which have travelled by reflection rather than the direct path. A number of ghost cancelling circuits have been mooted over the last 10 years but none has come to fruition. Now Philips has succeeded where others have failed. At the recent National Association of Broadcasters (NAB) Conference in Las Vegas, Philips Research Laboratories demon­strated the world’s first prototype TV receivers with built-in ghost cancellation circuitry. The demonstration consisted of live Ghost-Cancelling Refer­ ence (GCR) signals beamed to the convention centre by five local TV stations. At the convention centre, delegates compared heavily ghosted pictures with specially prepared large screen TVs incor­porating Philips ghost cancellation technology, on which there was not the slightest hint of a ghost. 4  Silicon Chip At the heart of the system is a special Ghost Cancellation Reference signal which the broadcasters transmit in a hidden portion of the TV field. By the time the GCR signal reaches a receiving antenna, it has undergone the same ghost distortions as the tele­ vision picture. The received analog signal is then changed into digital form using an inexpensive 8-bit converter. Once the signal is in digital form, it can be easily manipulated. The signal is then compared to the original GCR signal. Based upon this analysis, settings are made for a ghost cancelling filter. The filtered signal, with ghosts removed, is then converted back to analog for normal viewing. This whole process is done electronically and the process­ing speed is what makes the Philips system so effective. The ghost cancelling filter chip is produced by Philips, as are the mathematical algorithms and processing software that control the system. This system has out-performed all others in trials to win the “ghostbuster” title, and has an internal clock speed of 57MHz. The USA’s Federal Communication Commission (FCC) has approved use of the Philips ghost cancelling signal by TV broadcasters, effective from 30th June, 1993. The immediate objective at the Philips Briarcliffe Laboratories is to reduce the power supply require­ ments and make the chips sufficiently cost effective for main­stream production. Helen Freeman, Philips TV and video product marketing manager in Australia, says that we can expect the “ghostbusting” option to be available SC in TV sets from 1995. 8MM VIDEO CASSETES These 120-minute 8mm metal oxide video cassettes were recorded on once for a commercial application and then bulk erased. They are in new condition but don’t have the record protect tabs fitted. The hole in the upper right corner will have to be taped over. $9 Ea. or 5 for $38 LARGE NIGHT VIEWERS One of a kind! A very large complete viewer for long range observation. Based on a 3-stage fibre optically coupled 40mm first generation image intensifier, with a low light 200mm objec­tive mirror lens. Designed for tripod mounting. Probably the highest gain-resolution night viewer ever made. ONE ONLY at an incredible price of: $3990 BINOCULAR EHT POWER SUPPLY This low current EHT power supply was originally used to power the IR binoculars advertised elsewhere in this listing. It is powered by a single 1.5V “C” cell and produces a negative voltage output of approximately 12kV. Can be used for powering prefocussed IR tubes etc. $20 IR BINOCULARS High quality helmet mount, ex-military binocular viewer. Self-powered by one 1.5V “C” size battery. Focus adjustable from 1 metre to infinity. Requires IR illumination. Original carry case provided. Limited stocks, ON SPECIAL AT: $500 IR FILTERS A high quality military grade, deep infrared filter. Used to filter the IR spectrum from medium-high powered spotlights. Its glass construction makes it capable of withstanding high temper­atures. Approx. 130mm diameter and 6mm thick. For use with IR viewers and IR responsive CCD cameras: ON SPECIAL $45 12V OPERATED LASERS WITH KIT SUPPLY Save by making your own laser inverter kit. This combination includes a new HeNe visible red laser tube and one of our 12V Universal Laser Power Supply MkIII kits. This inverter is easy to construct as the transformer is assembled. The supply powers HeNe tubes with powers of 0.2-15mW. $130 with 1mW TUBE $180 with 5mW TUBE $280 with 10mW TUBE MAINS OPERATED LASER Supplied with a new visible red HeNe laser tube with its matching encapsulated (240V) supply. $179 with 1mW TUBE $240 with 5mW TUBE $390 with 10mW TUBE GREEN LASER HEADS We have a limited quantity of some brand new 2mW+ laser heads that produce a brillant green output beam. Because of the relative response of the human eye, these appear about as bright as 5-8mW red helium neon tubes. Approximately 500mm long by 40mm diameter, with very low divergence. Priced at a small fraction of their real value $599 A 12V universal laser inverter kit is provided for free with each head. ARGON HEADS These low-voltage air-cooled Argon lon Laser Heads are priced according to their hours of operation. They produce a bright BLUE BEAM (488nm) and a power output in the 10-100mW range. Depends on the tube current. The head includes power meter circuitry, and starting circuitry. We provide a simple circuit for the supply and can provide some of the major components for this supply. Limited supplies at a fraction of their real cost. $450-$800 ARGON OPTIC SETS If you intend to make an Argon laser tube, the most expen­sive parts you will need are the two mirrors contained in this ARGON LASER OPTIC SET. Includes one high reflector and one output coupler at a fraction of their real value. LIMITED SUPPLY $200 for the two Argon LASER mirrors. LASER POINTER Improve and enhance all your presentations. Not a kit but a complete commercial 5mW/670nm pen sized pointer at ONLY: $149 LARGE LENSES Two pairs of these new precision ground AR coated lenses were originally used to make up one large symmetrical lens for use in IBM equipment. Made in Japan by TOMINON. The larger lens has a diameter of 80mm and weighs 0.5kg. Experimenters delight at only: $15 for the pair. EHT GENERATOR KIT A low cost EHT generator kit for experimenting with HT-EHT voltages: DANGER – HIGH VOLTAGE! The kit also doubles as a very inexpensive power supply for laser tubes: See EL-CHEAPO LASER. Powered from a 12V DC supply, the EHT generator delivers a pulsed DC output with peak output voltage of approximately 11kV. By adding a capacitor (.001uF/15kV $4), the kit will deliver an 11kV DC output. By using two of the lower voltage taps available on the transformer, it is possible to obtain other voltages: 400V and 1300V by simply adding a suitable diode and a capacitor: 200mA - 3kV diode and 0.01uF 5kV capacitor: $3 extra for the pair. Possible uses include EHT experiments, replacement supplies in servicing (Old radios/CRO’s), plasma balls etc. The EHT generator kit now includes the PCB and is priced at a low: $23 LED DISPLAYS National Seminconductor 7-segment common cathode 12 digit multiplexed LED displays with 12 decimal points. Overall size is 60 x 18mm and pinout diagram is provided. 2.50 Ea. or 5 for $10 BATTERIES Brand new industrial grade PANASONIC 12V-6.5AHr sealed gel batteries at a reduced price.Yes, 6.5 AHr batteries for use in alarms, solar lighting systems, etc. Dimensions: 100 x 954 x 65mm. Weight of one battery is 2.2kG. The SPECIAL price? $38 PIR DETECTORS What are the expensive parts in a passive movement dector as per EA May 89? A high quality dual element PIR sensor, plus a fresnel lens, plus a white filter. We include these and a copy of PIR movement detector circuit diagram for: $9 MASTHEAD AMPLIFIER KIT Based on an IC with 20dB of gain, a bandwidth of 2GHz and a noise figure of 2.8dB, this amplifier kit outperforms most other similar ICs and is priced at a fraction of their cost. The cost of the complete kit of parts for the masthead amplifier PCB and components and the power and signal combiner PCB and components is AN INCREDIBLE: $18 For more information see a novel and extremely popular antenna design which employs this amplifier: MIRACLE TV ANTENNA - EA May 1992: Box, balun, and wire for this antenna: $5 extra SODIUM VAPOUR LAMPS Brand new 140W low pressure sodium vapour lamps. Overall length 520mm, 65mm diameter, GEC type SO1/H. We supply data for a very similar lamp (135W). CLEARANCE AT: lenses: two plastic and one glass. The basis of a high quality magnifier, or projection system? Experimenters’ delight! $30 CRYSTAL OSCILLATOR MODULES These small TTL Quartz Crystal Oscillators are hermetically sealed. Similar to units used in computers. Operate from 5V and draw approximately 30mA. TTL logic level clock output. Available in 4MHz, 4.032MHz, 5.0688MHz, 20MHz, 20.2752MHz, 24.74MHz, 40MHz and 50MHz. $7 Ea. or 5 for $25 FLUORESCENT BACKLIGHT These are new units supplied in their original packing. They were an option for backlighting Citizen LCD colour TVs. The screen glows a brilliant white colour when the unit is powered by a 6V battery. Draws approximately 50mA. The screen and the in­verter PCB can be separated. Effective screen size is 38 x 50mm. $12 MAINS FILTER BARGAIN For two displays - one yellow green and one silver grey. SOME DIFFERENT COMPONENTS 1000pF/15kV disc ceramic capacitors ..............$5 20kV PIV - 5mA Av/1A Pk fast diodes .........$1.50 3kV PIV - 300mA / 30A Pk fast diodes ........... 60c 0.01uF /5kV disc ceramic capacitors ...........$1.80 680pF / 3kV disc ceramic capacitors .............. 30c Who said that power MOSFETS are expensive?? MTP3055 N-channel MOSFETS as used in many SC projects ............................$2 Ea. or 10 for $15 MTP2955 P-channel MOSFETS (complementary to MTP3055) ..........................$2 Ea. or 10 for $15 BUZ11 N-channel MOSFETS $3 Ea. or 10 for $25 Brief DATA and application sheet for above MOSFETS free with any of their purchases (ask) Flexible DECIMAL KEYPADS with PCB connectors to suit ...........................................................$1.50 1-inch CRO TUBES with basic X-Y monitor circuit CLEARANCE <at>..............................................$20 Schottky Barrier diodes 30V PIV - 1A/25A Pk. 45c 100 LED BARGRAPH DISPLAY Note that we also have some IEC extension leads that are two metres long at $4 Ea. Yes 100 LEDs plus IC control circuitry, all surface mounted on a long strip of PCB. SIMPLE - a 4-bit binary code selects which one out of the 10 LED groups will be on, whilst another 4-bit binary code selects which one of each group of 10 LEDs will be ON. Latching inputs are also provided. We include a circuit and a connecting diagram. VERY LIMITED QUANTITY WEATHER TRANSMITTERS FM TRANSMITTER KIT - MKll A complete mains filter employing two inductors and three capacitors fitted in a shielded metal IEC socket. We include a 40 joule varistor with each filter. $5 These brand new units were originally intended to monitor weather conditions at high altitudes: attached to balloons. Contain a transmitter (12GHz?) humidity sensor, temperature sensor, barometric altitude sensor, and a 24V battery which is activated by submersing in water. The precision all mechanical altitude sensor appears similar to a barometer and has a mechani­cal encoder and is supplied with calibration chart. Great for experimentation. $16 Ea. SOLAR CHARGER Use it to charge and or maintain batteries on BOATS, for solar LIGHTING, solar powered ELECTRIC FENCES etc. Make your own 12V 4 Watt solar panel. We provide four 6V 1-Watt solar panels with terminating clips, and a PCB and components kit for a 12V battery charging regulator and a three LED charging indicator: see March 93 SC. Incredible value! $42 6.5Ahr. PANASONIC gel Battery $35, ELECTRIC FENCE PCB and all onboard components kit $40. See SC April 93. $7Ea. This low cost FM transmitter features pre-emphasis, high audio sensitivity as it can easily pick up normal conversation in a large room, a range of well over 100 metres, etc. It also has excellent frequency stability. The resultant frequency shift due to waving the antenna away and close to a human body and/or changing the supply voltage by +/-1V at 9V will not produce more than 30kHz deviation at 100MHz! That represents a frequency deviation of less than 0.03%, which simply means that the fre­quency stays within the tuned position on the receiver. Specifications: tuning range: 88-101MHz, supply voltage 6-12V, current consumption <at>9V 3.5mA, pre-emphasis 50µs or 75µs, frequency response 40Hz to greater than 15kHz, S/N ratio greater than 60dB, sensitivity for full deviation 20mV, frequency stabil­ity (see notes) 0.03%, PCB dimensions 1-inch x 1.7inch. Construction is easy and no coil winding is necessary. The coil is preassembled in a shielded metal can. The double sided, solder masked and screened PCB also makes for easy construction. The kit includes a PCB and all the on-board components, an electret microphone, and a 9V battery clip: $11 Ea. or 3 for $30 LARGE LCD DISPLAY MODULE - HITACHI These are Hitachi LM215XB, 400 x 128 dot displays. Some are silver grey and some are yellow green reflective types. These were removed from unused laptop computers. We sold out of similar displays that were brand new at $39 each but are offering these units at about half price. VERY LIMITED STOCK. $40 OATLEY ELECTRONICS $15 Ea. PO Box 89, Oatley, NSW 2223 STEPPER MOTORS Phone (02) 579 4985. Fax (02) 570 7910 $12 MAJOR CARDS ACCEPTED WITH PHONE & FAX ORDERS These are brand new units. Main body has a diameter of 58mm and a height of 25mm. Will operate from 5V, has 7.5deg. steps, coil resistance of 6.6 ohms, and it is a 2-phase type. Six wires. ONLY: PROJECTION LENS Brand new large precison projection lens which was original­ly intended for big screen TV projection systems. Will project images at close proximity onto walls and screens and it has adjustable focussing. Main body has a diameter of 117mm and is 107mm long. The whole assembly can be easily unscrewed to obtain three very large P & P FOR MOST MIXED ORDERS AUSTRALIA: $6; NZ (Air Mail): $10 August 1993  5 KECK OBSERVATORY The world’s biggest optical telescope; Pt.2 Last month, we gave the background to the site selection and segmented design of the 9.84-metre Keck Telescope. The guid­ing force for the project was Jerry Nelson who had the job of promoting the concept & convincing enough people to give finan­cial grants to allow it to proceed. By BOB SYMES Ultimately, he was successful in convincing the astronomers and accountants that the challenge could be met, and the problems overcome. Armed with a $US70 million grant from the W. M. Keck Foundation, Nelson and his collaborators set to work. The Cali­fornia Institute of Technology and the University of California made up the difference in the projected cost of $US94 million. These two institutions will run the telescope through the California As6  Silicon Chip sociation for Research in Astronomy (CARA), an association inaugurated specifically for this purpose. Through CARA, they will allocate the major part of observing time, though the University of Hawaii will receive 10% of the time as co-ordinator of the science reserve atop Mauna Kea. On September 12th, 1985, the ground-breaking ceremony took place on the summit and the dome and associated complex was completed in October 1988. The tube and supporting structure was contracted out to the civil engineering firm of Schwartz and Hautmont of Tarragona, Spain and was also completed in 1988. It was erected on the summit in 1989. Understandably, the mirrors caused the major headaches. At every step of the way problems arose and had to be overcome. Since multiple mirrors, when used together, cause optical diffraction effects if they remain as individual round segments, it was necessary to construct hexagonal segments that nestle into each other to minimise the effect. Under certain circumstances, such as when two telescopes are used as an optical interferome­ter, it is these very diffraction effects that are used to ex­tract information about the object under study, but when the telescope is used on its own, the diffraction spikes can hide details that might otherwise be observed. A further effect of diffraction is that contrast is re­duced, thus further hiding subtle detail. Squares, triangles and hexagons are the only shape of mirror that can nestle together in this fashion. From the point of view of wasted material and keeping the shape as nearly round as possible to make figuring easier, a hexagon shape was chosen. And this is where the problems began. Normally, a mirror is ground and polished in its final (usually circular) shape. But a new technique, known as stressed mirror polishing, was to be attempted. In this method, the polishing table has a series of suction pads and rams which distort the blank before polishing begins. The mirror is then polished to a spherical figure, and when it is released from the table, the correct hyperboloidal figure would be obtained. Terry Mast, the University of California optician who over­ s aw most of the design and construction of the mirrors, deter­mined that the correct shape would not be realised unless the blanks were polished in the round and then cut to hexagons, rather than the other way around. The danger was that when cut, internal stresses in the blank would be released, thus throwing out the carefully created profile. Less of a problem, but still requiring careful attention, was that since each of the 36 mirror segments has one of six possible different surface profiles, dependent on where it will be in the final mosaic, the radial position of the hexagonal sides had to be in exact relationship to the figure. Optics fabrication Itek Optical Systems of Lexington, Massachusetts was chosen to fabricate the optics, as they had much experience in satellite optical systems. The first six segments were to be delivered by late 1987 and the following 36 (which included six spares – one for each position) were to be made available within two years. However, by late 1987, work was still being done on the first segment and by mid- 1988 the second was giving trouble. The feared stress-relief distortions had materialised and each segment had to be individually touched up under computer control, optically tested using a laser interferometer, and then touched up again, until the residual errors were within the ability of the This diagram shows the location of the 36 segment primary mirror, the secondary (2) and tertiary (3) mirrors and the Nasmyth (4) & Cassegrain (5) foci. The tertiary mirror is required for the Nasmyth focus but is removed to allow light to pass through a hole in the primary mirror to the Cassegrain focus. warping harness on the tele­ scope mirror mount to correct. As a result of this delay, in 1989 CARA contracted another optical laboratory, Tinsley Laboratory of Richmond, California, to take over the construction of half the mirror segments. Work was under way by February. Both the Tinsley and Itek blanks were “hexagonised” at the Itek works, and by mid-1989 two segments per month were being produced between the two contractors. By this time, it had been decided to forego the computer controlled zonal refiguring, since this was proving too slow, and it was hoped that the warping harness could cope with the now greater residual aberrations. In fact, the after hexing deformations have been reported to be as great as 1 micron. The warping harness is a series of adjustable springs on the support structure of each mirror. There are 30 such springs for each segment and when correctly set, they can reduce the residual aberration by a factor of up to 15. At least the delivery was easy, unlike the delivery of the great primary of the 5-metre Hale telescope which made a slow journey from the Corning Glass works in New York to the west cost on a specially constructed flatbed railcar. By contrast, the mirror segments for the Keck were shipped from Lexington, Mas­ sachusetts to Honolulu by Federal Express! They were then sent by barge to Hilo on the windward side of the Big Island and by truck to the summit. The relatively low weight of each segment made this method quite feasible, something that couldn’t be said of the massive Hale mirror. In common with most observatories, there is a re-aluminis­ing facility in the building, so that the mirrors do not need to leave the mountain when the reflecting surfaces need to be refur­ bished. In fact, they were delivered from the mainland uncoated and were aluminised just prior to installation. Each mirror is housed in a complex support that includes adjustable pads, feedback sensors and actuators, as well as the preset warping components. The requirement is that every segment is supported in such a way that all act together to form one 10-metre mirror. Each segment be in perfect collimation with all the rest in the mirror support framework and must be able to correct for the inevitable tube flex­ure of a structure as large as this when the August 1993  7 movement is in the order of 1mm, in increments of 0.004 microns. The position actua­tor consists of a precision ground screw of 1mm pitch. Shaft encoders allow the screw to be turned in increments of one ten-thousandth of a revolution. This 1mm per revolution displacement is further reduced by a factor of 24 by a ratio-reducing hydrau­ lic bellows unit. Capacitive feedback sensors This view, taken from within the tubular structure of the tele­scope, shows all the mirror segments in place. In all, some 36 hexagonal segments are used to create the primary mirror. telescope is slewed from one part of the sky to another. Flexure of the tube has been estimated to be in the order of 0.5mm as the telescope is pointed in different directions, and this flexure has to be reduced by a factor of 10,000 in order to maintain the perfect collimation required to give the sub arc-second images that the site is capable of producing. The actua­tors are also capable of detecting and correcting thermal changes in the mirror and support structure. Mirror support system In order to provide this required collimation, the mirror support system comprises passive and active support. The passive support is made up of a stainless steel hub and disc (the flex disc), which sits in a circular cutout in the rear of the mirror and prevents the mirror moving laterally from its assigned posi­ tion. Support for the mass of each mirror is by means of three “whiffletrees” evenly spaced about the mirror, and about two thirds 8  Silicon Chip of the way out from the centre – at the radial centre of mass of the segment. Each whiffletree contains a further 12 floating supports, giving a total of 36 floating supports per segment. The principal is similar to the technique used by thousands of amateurs for their home-made telescopes, only mechanically far more complex and, of course, on a completely different scale. Effectively, each mirror segment is able to tilt or shift to counteract the previously discussed errors. By the way, the word “whiffletree” comes from the days of stagecoaches, where the whiffletree was the pivoting wooden cross-arm attached to the drag spar. By pivoting, it compensated for any uneven pull by the horses on either side of the spar. Each mirror segment, thus being able to move freely within its lateral confinement, allows the active control system to tilt or move it toward or away from the focus in order to maintain collimation. Each segment has three position actuators associated with it, one on each whiffletree. The total Feedback for the actuators is supplied by temperature com­ pensated displacement sensors, consisting of parallel plates mounted on each mirror, with a third plate, called the paddle, attached to the adjacent mirror, placed between the first two. The change in capacitance induced by any relative shift between the two mirrors is detected and the resulting corrective commands are sent to the position actuators. Each internal segment has 12 sensors attached to it and each peripheral segment has six or eight, depending on wheth­er it is a corner or side segment. The sensitivity of this system is such that displacements of the order of 0.001 microns can be detected. Jerry Nelson states that there are actually 63 more sensors than are required to define the mirror shape, so there is sufficient redundancy to keep the telescope functioning to speci­fication even if there are some sensor failures, assuming those failures are randomly distributed around the various mirrors. This also gives the ability to switch out a (faulty) sensor that is returning readings that are substantially different from its neighbours, whilst still allowing the tele­scope to operate normally. This is similar to the multiple sensor “democratic” systems used on aircraft computer controls. He further comments that a great advantage of the active control chosen is that it relies on no external source to define its parameters. When the telescope is switched on, it corrects itself and is ready for work. This can be done at any time, day or night, or even with the dome slit closed. Thus, engineering calibration or work can be carried out when ever it is convenient. This contrasts with some active systems, where a star or artificial equivalent has to be viewed and its image analysed before the appropriate commands can be issued to the correcting mechanism. False incoming data, such as air-column or dome turbulence that scatters the incoming star image, is therefore entirely eliminated. The information received from the 168 sensors, the correc­ tive calculations and the correction commands to the 108 actua­tors are handled by 12 microcomputers under the overall command of a DEC Micro-VAX. Corrections are performed every half second, with a 10-second settling time required after a major slew of the telescope. One of the computers is dedicated to maintaining a log of all readings and subsequent actions, so that if anything goes wrong, its data can be analysed to isolate the problem. An example would be where a wire or actuator rod breaks. The computer would sense an alignment problem, send a corrective command, and fail to see a response from the displacement sen­sors. Obviously a runaway condition is then likely. Whilst such conditions can be trapped by the software, by keeping an activity log, the actual source of the problem can be quickly identified. Secondary mirrors There are two interchangeable secondary mirrors that result in overall focal ratios of f/15 and f/25. The f/15 secondary is 1.45 metres in diameter and is intended for work in the visible spectrum. The f/25 secondary is 51cm in diameter and is designed for observation in the infrared region. The f/15 secondary mirror was ground and polished at the Lick Observatory optical laboratories in Santa Cruz, California, under the guidance of master optician David Hilyard and astronom­ e r Joseph Miller, who described it as the most difficult grinding job they had ever undertaken. The mirror is made of Zerodur, is hyper­boloidal in figure and, because of the very small focal ratio of the optics, is highly convex (the radius of curvature is only 4.7 metres). As a result, special flexible polishing laps had to be devised, and progress constantly monitored with a laser profilometer, which could detect aberrations of the order of λ\2. After final figuring, testing by more elaborate optical methods indicated a figure of better than λ\15. The finished mirror was shipped to Hawaii on July 19th, 1991. The optical Great care must be taken in polishing & figuring the mirror blanks & this is done before they are hexagonised. Here an optical techni­cian uses a laser profilometer to check a mirror blank. combination of the f/1.75 primary and the secondary yield a final f/15 focus. This secondary will be used for observations at visible wavelengths. A further complication that occurred during the polishing of this mirror was its distur­bance on the polishing table during the San Francisco earthquake in October 1989. Luckily no damage was sustained and re-align­ment was successfully carried out. The f/25 secondary is made of nickel-plated beryllium. It was figured at the Lawrence Livermore National Laboratory near San Francisco, tested and finally plated with gold. It will be used exclusively for work in the infrared spectrum and has the ability to be used as a “chopper”, mechanically moving to alter­nately provide a view of the object being studied and the back­ground sky. In this way, sky readings can be subtracted from “object + sky” readings to give an “object only” output from the detectors. Each secondary mirror is housed in its own secondary sup­port which can be placed interchangeably forward of the prime focus as required. Both supports have the same external August 1993  9 This photo shows the complex support structure of the main mir­ror. Each mirror segment is monitored & adjusted by the comput­er control system twice every second. shape as the main mirror mosaic to minimise the effects of diffraction and also to minimise the central obstruction. They block only 9% of the incoming light. Both secondaries will deliver their light to either the Cassegrain focus behind the primary mirror – the central hexagon being left out to provide access to this focus – or via a flat ter- tiary mirror placed in line with the mechanical axis, and at 45 degrees to the light path, to a focus at one of six locations around the telescope. Two of these locations pass through the axis bearings to two Nasmyth platforms, where bulky or heavy equipment can be accommodated without affecting the fine mechani­ cal balance of the system. The other four are for lighter Table 1: Telescope Facilities on Mauna Kea Facility Size Primary Use University of Hawaii 24-inch Telescope #1 0.61m Optical University of Hawaii 24-inch Telescope #2 0.61m Optical University of Hawaii 88-inch Telescope 2.24m Optical/Infrared NASA Infrared Telescope Facility 3.0m Infrared Canada-France-Hawaii Telescope 3.6m Optical/Infrared United Kingdom Infrared Telescope 3.8m Infrared Carltech Sub-Millimetre Observatory 10.4m Millimetre/sub-millimetre James Clerk Maxwell Telescope 15m Millimetre/sub-millimetre W. M. Keck Telescope 10m Optical/Infrared Table 2: Facilities Planned Or Under Construction Facility Size Primary Use Second keck Telescope 10m Optical/Infrared VLBA Facility Subaru Telescope US-Canada-UK National Optical Telescope Radio 8.3m Optical/Infrared 8m Optical/Infrared Smithsonian 6-Antenna Array Galileo National Telescope 10  Silicon Chip Radio 3.5m Optical/Infrared instru­ments that can safely ride in the tube itself. In addition to standard observatory instrumentation, five major instruments are being built specifically for use on the Keck telescope to take advantage of its unique capabilities. They are: (1). The Low-Resolution Imaging Spectrograph (LRIS), a collimated array of four 2048 x 2048 CCDs imaging an area of 6 by 8 arc-minutes at prime focus. Used in the 0.4-1.0µm region of the spectrum, its angular resolution is 0.15 arc-seconds. (2). The High Resolution Echelle Mosaic Spectrograph (HIRES). This is similar in construction to the low resolution spectro­graph but the spectral resolution is 10 times higher and it work­s in the 0.3-1.0µm region. (3). The Long Wavelength Spectro­ graph (LWS), a 96 x 96 BIB (Bumped Indium Bond) array used in the 8-20µm region. (4). The Near Infra-Red Camera (NIRC). Covering the 1-5µm spec­trum, it uses a 256 x 256 indium antin­omide array with an angular resolution of 0.15 arc-seconds. It was developed at Caltech. (5). The Long Wavelength Infrared Camera (LWIC) for use in the 8-14µm spectrum. It uses a 20 x 64 BIB array from Hughes and, de­pending on wavelength, the angular resolution is 0.08 to 0.32 arc-seconds. On November 7th, 1991, the telescope was officially dedi­cated at a ceremony at the summit. At this stage, only nine mir­rors were in place but already the first official observation and concept-proving run had been made. The first image obtained was a CCD image of the galaxy NGC 1232 (Arp 41) in Eridanus. The re­sults were as encouraging as the design and construction team had hoped, fully vindicating the optimism they had shown in this radical new telescope. The image showed detail that had not been previously seen from ground based telescopes, and was a portent of what was to come once all segments were in place and the telescope fully commissioned. Although the warping harnesses had not yet been fully ad­justed, and seeing was less than perfect, Airy disc star images were obtained with dia­meters of 0.61 arc-seconds at the 50% energy level, and 80% of the light fell in a circle 1.6 arc-seconds AUSTRALIAN MADE TV TEST EQUIPMENT 12 Months Warranty on Parts & Labour SHORTED TURNS TESTER Built-in meter to check EHT transformers including split diode type, yokes and drive transformers. $95.00 + $4.00 p&p HIGH-VOLTAGE PROBE Built-in meter reads positive or negative 0-50kV. For checking EHT & focus as well as many other high tension voltages. $120.00 + $5.00 p&p GW QUALITY SCOPES 100MHz DEGAUSSING WAND Great for computer mon­­­it­ors. Strong magnetic field. Double insulated, momentary switch operation. Demagnetises colour picture tubes, colour computer monitors, poker machines video and audio tapes. 240V AC 2.2 amps, 7700AT. $85.00 + $10.00 p&p TUNER REPAIRS From $22. Repair or exchange plus p&p. Cheque, Money Order, Visa, Bankcard or Mastercard TUNERS PLUS FREE DMM 40MHz 216 Canterbury Rd, Revesby, NSW 2212, Australia. Phone for free product list Phone (02) 774 1154 Fax (02) 774 1154 CEBus AUSTRALIA KITS CEBus Australia has opened the Circuit Cellar door to bring you a range of high quality, educational electronics kits. There are three types of kit available: an Experimenter’s Kit which includes the PCBs, manuals, any key components that are hard to find and the basic software required by the finished product. Then there is the Complete Kit which includes everything above plus the additional components required to complete the kit. Finally, there is the complete kit with Case & Power Supply. Regardless of which kit you purchase you get the same high quality solder masked and silk screened PCB and the same prime grade components. Our range of kits includes: HAL-4 4 Ch, EEG Monitor, Complete kit only ................... $356.00 Experimenter’s Kits: SmartSpooler, 256K print spooler ..................................... $214.00 IC Tester, Tests 74xx00 family ICs .................................... $233.00 Serial EPROM Programmer, For 27xxx devices ............... $214.00 Ultrasonic Ranger Board with Transducer.......................... $194.00 NB: The above prices DO NOT include sales tax. Don’t forget we also have the HCS II, Home Control System, available, Its features include: Expandible Network, Digital & Analog 1/O, X-10 Interface, Trainable IR Interface and Remote Displays. Call fax or write to us today for more information. Bankcard, Mastercard & Visa accepted. CEBus AUSTRALIA. Ph (03) 467 7194. Fax (03) 467 8422. PO Box 178, Greensborough, Vic 3087. ESCORT EDM-1133 20MHz • • • • • • 3¾ Digits Autoranging 8 Functions DC V, AC V DC A, AC A Ohms Valued at $127! GOS-6100 GOS643 GOS622 4 Channels 2 Channels 2 Channels 100MHz BW 40MHz BW 20MHz BW 500uV - 5V/DIV 1mV - 5V/DIV 1mV - 5V/DIV Dual Timebase to 2ns/DIV Dual Timebase to 2ns/DIV Timebase to 2ns/DIV Dual Timebase Trig Audio Trigger Level Lock Audio Trigger Level Lock Variable Hold-Off Variable Hold-Off Variable Hold-Off 20kV Accel. Voltage 12kV Accel. Voltage 2.2kV Accel. Voltage EMONA INSTRUMENTS NSW (02) 519 3933 VIC (03) 889 0427 QLD (07) 397 7427 Also available from: WA (09) 244 2777 SA (08) 362 7548 TAS (003) 31 6533 August 1993  11 Table 3: W. M. Keck Telescope Specifications Optical Design: Ritchey-Chretien Primary Mirror Secondary Mirror (f/25) Effective aperture 8.2m Figure Convex hyperboloid Maximum diameter 10.95m Shape Circular Light-collecting area 75-76 sq.m Diameter 0.51m Limiting magnitude ±28 Radius of curvature 1.82m Figure Concave hyperboloid Distance from primary 16.6m Number of segments 36 Focus behind primary 4.54m Radius of curvature 35m Equivalent focal length 250m (f/25) Focal ratio 1.75 Gap between segments 3mm Site Mauna Kea, HI Total weight of glass 14.7 tonnes Longitude West 155 deg 28 min 3 sec Position actuators 108 - 3 per segment Latitude North 19 deg 49 min 6 sec Whiffletrees 108 - 3 per segment Elevation of dome 4150m Displacement sensors 168 - 6-12 per segment Dome height 31m Active-control 0.5 second cycle Dome width 37m Setting time after siew 10 seconds Dome moving weight 635 tonnes Dome air exchange 5 minute cycle Observatory Individual Segments Number of aspheric types 6 Telescope mounting Altazimuth Number of each type 6 Max. telescope height 24.6m Spares of each type on hand 1 Telescope moving weight 270 tonnes Focal length tolerance 0.2mm Project cost $US94 million Shape Hexagonal Construction time 7 years Greatest diameter 1.8m Project headquarters Kamuela, HI Thickness 75mm Glass type Schott Zerodur Mean annual temperature 0°C Mass 400kg Average wind velocity 25km/h Clear night per year 250 Environmental Secondary Mirror (f/15) Figure Convex hyperboloid Average relative humidity Less than 10% Shape Circular Sub-arc-second seeing Greater than 50% of time Diameter 1.45m Radius of curvature 4.73m Distance from primary 15.41m Focus behind primary 2.5m Equivalent focal length 150m (f/15) across. These images were obtained at the prime focus since the secondary and tertiary mirrors had not yet been in­stalled. After these test images, the nine mirror segments, already greater in light collecting capacity than the 5- metre Hale telescope on Mount Palo­mar, were removed for safety so that work could continue on the as yet unfinished support structure. At this same November ceremony, 12  Silicon Chip the ground was turned for a second, identical telescope, the Keck II. If all goes according to schedule, Keck II is expected to be operational some time in 1996. In October 1991, the Schott Glassworks began delivery of the first of the 42 1.9 metre blanks required for the Keck II. Used alone, the second telescope will double the available observing time. Just as important, the two tele­ scopes, 85 metres apart, can potentially be used as an optical interferometer, giving a light grasp equal to a single 14.1-metre mirror but with the resolving power of a mirror 85 metres in diameter. In practice, however, this theoretical resolving limit is unlikely to be achieved but confidence has been expressed that a resolution of better than 0.01 arc-seconds is feasible. The light collecting area of the two mir- An optical technician monitors a diamond-edged circular saw as it cuts a mirror blank to a hexagon. Thirty six of these hexagonal seg­ments are used in the Keck mirror & the gaps between them are less than 3mm. rors will be greater than the world’s current 10 largest optical tele­scopes combined! By early 1992, when 18 of the segments were in place, the telescope already ranked as the largest optical reflector. Work had been slowed down by a snowstorm in November, hampering access to the summit and pro­gress once there, but finally, on April 14th, 1992, the last of the 36 segments was lowered into position. Designer Jerry Nelson, project manager Jerry Smith, facilities manager Ron Laub and Don Hall from CARA were all present for the final mirror positioning, the culmination of a 15year dream. Although the telescope is officially completed, shake-down engineering tests, alignment, tracking and ironing out the bugs inevitable in a project of this size are continuing before it is finally commissioned. The same can be said of the fine tuning required to optimise the new instruments to the telescope. This is expected to take about a year and will be under the watchful eye of operations director Peter Gill­ing­ham, recent­ly moved to Mauna Kea from the Anglo-Australian Observatory at Coonabarrabran, NSW. Most of the problems encountered earlier in the telescope pointing software seem to have been solved but further work is required to iron out troubles in the segment active control computer. From concept to completion, the Keck telescope has taken nearly two decades to come to fruition, during which time many valuable technological lessons have been learned. Its commissioning will have lasting implications for astronomy. New horizons have been opened up to keep researchers and theoretical astro­ physicists occupied for years. It also comes at a time when new and exciting data is being returned from the orbiting Hubble Space Tele­ scope. Both telescopes have the same limiting magnitude of about 28 but they can work independently or in concert to push the fron­tier of knowledge forward an order of magnitude from anything that has gone before. Hubble’s great strength is its superb location; Keck’s is its massive light collecting power. And Keck does it at 1/16th the construction and operational costs! Hard on the heels of the now proven design concepts comes confirmation that other telescopes of this kind are to follow – from the US, Japan and Europe. This is perhaps the greatest contribution of its designers, builders and the telescope itself – the heralding SC of a new era. Acknowledgments “Sky & Telescope” magazine; CARA; Caltech; Itek Optical Systems; Summit & facility support staff - especially Andy Pera­ la, Jerry Smith and Mary Beth Murrill. August 1993  13 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 By DARREN & GARY YATES Low-cost colour video fader Forget those messy edits on your VCR! This project uses readily available components & smoothly fades any composite PAL video signal to black level to enhance your home movies. It can also wipe left or right across the screen for special effects. Let’s face it – editing home movies is not easy. Have you ever tried to get your VCR to do a clean edit from one scene to the next? It’s virtually impossible unless you have one of the top-of-the-line models. Often, the only result you get is the brief flash of a “snowy” screen as you cut from one scene to the next. It not only looks unprofessional and messy but is annoying to look at as well. This Colour Video Fader solves that problem. It accepts any colour or black-and-white composite PAL video 18  Silicon Chip signal and can fade it smooth­ly down to a black screen and back up again. This makes it easy to fade one scene to black, set your cam­corder for the next scene and then bring that scene up from black to full brightness again. Result – a profession­al transi­tion from one scene to the next. Since no movie is complete these days without some special FX (movie lingo for “effects”), we’ve also added a screen wipe facility. This allows you to wipe the screen to black from leftto-right or from right-to-left. Again, once the screen is black, you can make your cut, move on to the next scene and wipe the video back on again by turning the control in the other direc­ tion. What could be easier? In addition to these features, the Colour Video Fader also features an external control input. This input is for a future project that will allow you to wipe a scene to black in over 50 different ways; eg, from top to bottom, diagonally, disappearing squares, and so on. This optional add-on project will be de­scribed in SILICON CHIP in a few month’s time. By now you’re probably thinking, “OK, so what expensive chips have been used?” Well, we haven’t used any. The circuit uses just two common CMOS ICs, a few transistors and a handful of other components. Fading video signals Before we dive straight into the circuitry, let’s take a look at a typical Colour burst signal Immediately following the sync pulse is the colour burst signal, which is nominally 10 cycles of 4.43MHz sinewave. This signal provides a phase reference so that your TV can decode the colour (or “chrominance”) information in the video signal. (Note: this signal does not appear in blackand-white TV systems). Both of these signals are vital to your TV set. If the horizontal sync pulse disappears, your TV picture will start to tear horizontally and the picture will break up. And if the colour burst signal disappears, then so will the colour from your TV screen. No amount of knob-twiddling on the front of your TV will help if either of these two signals has disappeared. One signal that doesn’t appear in Fig.1 but which is also vitally important is the field (or vertical) sync pulse. This occurs once every 20ms and has a 250µs duration. It synchronises the TV to the field rate – each time a vertical sync pulse is received, the set begins BLUE RED MAGENTA GREEN CYAN WHITE 100% YELLOW video signal – one that we would like to fade down to black. To fade down the audio level, you simply reduce the amplitude of the audio signal and that’s about it. But that’s not the case for a composite video signal. Fig.1 shows a typical PAL composite video signal from a colour bar pattern generator. This waveform represents just one of the 625 horizontal lines on the TV screen and has three main features: (1) a line sync pulse; (2) a colour burst signal; and (3) the picture information (luminance & chrominance). The line sync (synchronisation) pulse is used to signal the start of a new line on the screen. This pulse lasts for 5µs and occurs once for every line. Since there are 625 lines on the screen and they are updated 25 times per second, the sync pulse frequency is 15.625kHz (more commonly called the horizontal line frequency). In a colour TV receiver, the 625 lines are interlaced into two groups or fields, each containing 312.5 lines. Thus, one field consists of lines 1, 3, 5, 7, etc, while the other field consists of lines 2, 4, 6, 8, etc. Each field is displayed alter­nately at a 50Hz rate and this virtually eliminates the flicker that would otherwise be apparent at a 25Hz rate. 30% BLACK VIDEO SIGNAL 10-CYCLE COLOUR BURST 0% LINE SYNC PULSE Fig.1: a typical PAL composite video signal from a colour bar pattern generator. This waveform represents just one of the 625 horizontal lines on the TV screen and has three main features: (1) a line sync pulse; (2) a 10-cycle colour burst signal; and (3) the picture (or video) information. scanning a new field. The video component of the waveform follows the colour burst signal and it is this that determines what appears on the screen. In the case of the waveform shown in Fig.1, the result will be a set of vertical colour bars, starting with white on the left­hand side of the screen and going through yellow, cyan, green, magenta, red, blue and finally black on the right­hand side. The sync pulses ensure that all the horizontal lines match up so that the bars are vertically aligned. If we reduce the video section of the signal in amplitude, we reduce the “brightness” of the display and we can fade all the way to black. However, we must leave the sync pulse and colour burst signals at their original amplitude otherwise the picture will lose sync and colour during the fade. In practice, what we have to do is reduce the amplitude of one part of the waveform (the video information) and keep the rest the same (sync pulse and colour burst). This may sound difficult but in the end it is fairly simple due to the repeti­tive nature of a composite video waveform. The trick is to first extract the sync pulse and colour burst signals from the waveform, play around with the video information that remains, and then mix the sync pulse and colour burst signals back in. Block diagram Block diagram Fig.2 shows the bas­ics of the circuit. As shown, the incoming video signals are fed into a The Colour Video Fader can smoothly fade a video signal from full brightness to black & back up again, or can wipe left-to-right or right-to-left across the screen as shown on the facing page. It uses only low cost parts. August 1993  19 INPUT VIDE0 + SYNC MIXER Q2,Q3 Q1 SYNC + COLOUR BURST ENABLE IC1c DC CLAMPING VIDEO ENABLE FADER IC2a,IC1a IC1b VR1 VIDEO BUFFER VIDEO AMPLIFIER SYNC + CB ONLY +10dB Q4,Q5 VIDEO ONLY SYNC + WIPE GENERATOR IC2b,IC2d,IC1d D1,D2 buffer stage, after which the signal is fed three ways: (1). to a DC clamping stage (IC2a & IC1a). This clamps the bottom of the video signal to a steady DC voltage regardless of the video amplitude. In this case, it’s the bottom of the sync puls­es; ie, the level corresponding to 0% in Fig.1. (2). to the sync and colour burst enable circuitry (IC1c); and (3). to the video enable circuitry. The job of the sync and colour burst enable circuitry is to allow just the sync and colour burst signals to pass through to the final mixer stage. It blocks out all other video signals. Conversely, the video enable circuit only allows the pic­ture information to pass through and rejects the sync and colour burst signals. Once the composite video signal has had the sync and colour burst components stripped from it, it can be manipulated in the fader stage (ie, faded up or down). The signal is then fed to the mixer stage which mixes the sync and colour burst signals back in to produce the modified composite PAL signal. This signal is then fed to your VCR. At this stage, we haven’t mentioned the sync and wipe generator circuit. This part of the circuit is a bit more SYNC + COLOUR BURST ENABLE IC1c DC CLAMPING IC2a,IC1a TO MIXER SYNC SEPARATOR TO MIXER VIA FADER VIDEO ENABLE IC2a IC1b D1,D2 IC1d COLOUR BURST PULSE GENERATOR IC2b VARIABLE WIPE PULSE MONOSTABLE IC2d EXTERNAL INPUT DRIVE Fig.3: this expanded block diagram shows the sync & wipe generator circuitry in greater detail. The output from the colour burst gating pulse generator (IC2b) is used to trigger a variable wipe pulse monostable (IC2d). Its output is ANDed with the pulses to the sync & colour burst enable circuitry via diodes D1 and D2 & fed to the video enable switch. 20  Silicon Chip OUTPUT Fig.2: block diagram of the Colour Video Fader. The incoming composite video signal is stripped of sync & colour burst signals before being applied to the fader section (VR1). After fading, the sync & colour burst signals are mixed back in & the resulting signal amplified to make up for losses in the circuit chain. in­ volved and needs another block diagram to explain fully – see Fig.3. The first thing to notice is that the incoming signal from the video buffer doesn’t go directly to the DC clamp but via a sync separator. This separ­ates out the horizontal and vertical sync pulses and generates positive-going pulses which switch in the DC clamping circuit. The output of the sync separator is also fed to a colour burst gating pulse generator (IC2b). This produces negative-going pulses about 7µs in length, which cover the length of the colour burst. The sync separator and colour burst pulse generator outputs are then ORed together and the resulting signal fed to the sync and colour burst enable circuitry. Thus, the sync and colour burst enable circuit allows only the colour burst and the sync signals to pass through to the mixer. The output from the colour burst gating pulse generator is also used to trigger a variable wipe pulse monostable (IC2d), which produces variable-length pulses. These pulses are then ANDed with the pulses to the sync and colour burst enable circuitry via diodes D1 and D2 and fed to the video enable switch. The outputs of both enable circuits are then fed into the video mixer as before. Circuit diagram Let’s now take a look at the complete circuit – see Fig.4. All the major circuit elements depicted in the two block diagrams can be directly related to this diagram. As shown, the incoming video signal is AC-coupled to the base of tran­sistor Q1 via a 0.1µF capacitor. The 82Ω resistor connecting the input +5V Q2 BC548 B 10k VIDEO IN Q1 BC558 0.1 C E B C 82  IC1b 4066 E 1.2k 1.2k 10k C B 14 3 Q4 BC548 4 470  1.5k 5 Q5 BC548 B E 1.2k FADE VR1 1.5k 10k 0.1 Q6 BC558 B 6.8k 2.2k C E 100  680  IC1a E C 100 16VW 2.2k 150  VIDEO OUT 470  1 13 100 16VW +5V 1M 2 VR3 20k 1.2k 10 16VW +5V IC2a 4070 1 3 IC1c 1k 10 Q3 BC548 6.8k B 11 2 47pF 12  C E 10k 470  +5V 4.7k 75k 100pF 13 5 IC2b 6 6 4 270pF EXTERNAL INPUT +5V L TO R EXTERNAL WIPE S1 IC2c D1 1N914 B 4.7k 11 E C VIEWED FROM BELOW 7 I GO 7 9 4.7k 100k 12 IC1d 8 14 SET BLACK LEVEL MAY NEED ADJUSTMENT 8 WIPE VR2 500k LIN D2 1N914 IC2d 10 D3 1N4004 9 9VDC 300mA PLUG-PACK 100 16VW IN 7805 GND OUT 100 16VW +5V 0.1 0.1 5.6k R TO L COLOUR VIDEO FADER Fig.4: the various elements in the circuit diagram can be directly related to the two block diagrams. IC2a functions as a sync separator, its output switching high for the duration of each sync pulse. The video signal (minus the sync & colour burst signals) passes through IC1b & is faded by VR1. The signal is then buffered by Q4 & mixed with the sync & colour burst signals from IC1c & Q3. to ground provides the correct terminating impedance so that “ghost” or reflected signals do not occur. Transistors Q1 & Q2 form the buffer stage. Because a PNP/NPN arrangement is used, the required level of input im­pedance has been achieved with negligible voltage difference between the base of Q1 and the emitter of Q2. This is important for the correct functioning of the DC clamping circuitry. From the emitter of Q2, the signal path is split three ways, as mentioned before. First, it goes to IC2a via a lowpass filter consisting of a 1kΩ resistor and a 47pF capacitor. This reduces the amplitude of the colour burst signal so that it doesn’t cause IC2a to false trigger. IC2a is an exclusive-OR gate and is used here as a very high gain ampli­ fier/comparator. By tying one input to the supply rail, we have also made it work as an inverter. IC2a and CMOS analog switch IC1a together form the DC clamping circuit. Q2’s emitter is set to +2.7V by virtue of the bias voltage applied to the base of Q1. A video signal applied to the base of Q1 will swing high and low but each time a sync pulse arrives it will cause IC2a to switch its output high. This will cause CMOS switch IC1a to close and thus “clamp” the bottom of the sync pulse to +2.7V. This happens for every sync pulse that arrives at the base of Q1. Thus, the incoming video signal at the base of Q1 (and therefore at the emitter of Q2) can only swing between +2.7V and +3.7V (approx.). At the same time, IC2a effectively August 1993  21 10-CYCLE COLOUR BURST BLUE RED LINE SYNC PULSE MAGENTA GREEN CYAN YELLOW WHITE 100% 30% BLACK 0% +5V PIN 3 IC2a 0V PIN 4 IC2b produce the wipe pulse. IC2d triggers on the rising edge of the pulse from IC2b, as shown in Fig.5, and its output pulse length is set by VR2. By varying VR2, we can vary the pulse length from almost zero to 64µs (ie, the length of a screen line). Because IC2d is triggered once for every line, we can thus create the effect of a wipe from one side of the screen to the other. In order to eliminate sync and colour burst signals from the video signal we wish to modify, IC2c is used to invert the signal at pin 8 of IC1d. Its output at pin 11 is then ANDed with the wipe control signal at pin 10 of IC2d, using diodes D1 and D2, and the resulting output applied to the control input of IC1b. Typical waveforms PIN 8 IC1d PIN 10 IC2d WITH PIN 8 = GND PIN 11 IC2c PIN 5 IC1b Fig.5: this diagram shows the waveforms produced at various points in the sync & wipe control circuitry. The width of the screen wipe is controlled by the pulse width on pin 10 of IC2d & this in turn is set by VR2. functions as a sync separator, its output switching high for the duration of each sync pulse. These sync pulses are used to trigger the colour burst monostable, made from IC2b. IC2b is triggered by the falling edge of the sync pulse appearing at pin 3 of IC2a, so that the colour burst pulse fol­lows the sync pulse. This monostable produces a brief negative-going pulse about 7µs long, as set by the RC time constant on its pin 5 input – see Fig.5. The colour burst pulses are applied to the control input (pin 6) of IC1d, while the sync pulses are applied to pin 9. Its output (pin 8) is high for the combined duration of the sync and colour burst pulses, and is low while ever video infor­mation is present. 22  Silicon Chip The output at pin 8 is used to control IC1c which is anoth­er CMOS switch. Thus, by feeding in the control signal from IC1d, only the sync and colour burst signals pass through IC1c, while the picture information is eliminated (ie, the video is blanked). The output from the colour burst gating pulse monostable (IC2b) is also used to trigger monostable IC2d to CAPACITOR CODES ❏ ❏ ❏ ❏ ❏ Value 0.1µF 220pF 100pF 47pF IEC Code 100n 220p 100p 47p EIA Code 104 221 101 47 Fig.5 shows the results of these machinations. The waveform applied to pin 5 of IC1b begins with a low-going pulse that covers the sync pulse and colour burst signals. This is then followed by a variable length positive-going pulse that is con­trolled by VR2. As a result, IC1b blanks out all of the sync pulse and colour burst signals and only passes video information while the output of the diode AND gate is high. Thus, if VR2 is set so that each positive pulse covers only half the line length, then only that half of the picture will be shown while the other half of the screen will be blacked out. In other words, the amount of picture shown is determined by the length of the positive pulse and this can be continuously varied using VR2. Switch S1 controls the wipe direction. If pin 8 of IC2d is pulled high, then the black is wiped from left to right (L-R). Conversely, if pin 8 is pulled low, the black is wiped from right to left (R-L). S1 also makes another interesting effect possible. If the WIPE potent­i­ ometer (VR2) is turned fully in one direction, the picture can be instantaneously flicked on or off using S1. This facility is much more versatile than it may first appear at first sight, as it allows us to create a myriad of wipes including diamonds, centre-splits, diagonal wipes and more using a plug-in external controller. At this stage, we have produced the wipe function by modifying the control signal to pin 5 of IC1b. What POWER SOCKET EXTERNAL INPUT VIDEO IN VIDEO OUT 11 10 4.7k 1.5k 1.2k 0.1 10k 6.8k 5.6k 7 6 100uF 680  Q6 150  9 10 4 100uF 470 5 2 3 ▼ S1 remains of the video signal is now fed to a resistive divider network that includes 10kΩ potentiometer VR1. This is the FADE control and it allows the picture to be smoothly varied from full brightness at one extreme to full Q3 8  SEE TEXT Above: view inside the completed prototype. Keep the wiring neat & tidy & use PC stakes to terminate all wiring connections to the PC board. Fig.6 (right): be careful when installing the transistors on the PC board, as both NPN & PNP types are used. The 7805 3-terminal regulator is mounted with its metal tab towards the adjacent 10µF capacitor.  470W 100uF 0.1 100uF 5 270pF 75k 6 7 8 Q5 2.2k 10uF 7805 D3 4 1 4.7k 0.1 VR3 IC2 4070 100pF 10k 100  1k 2.2k Q4 6.8k IC1 4066 1 47pF 11 1.2k 1M 82  470  Q2 D1 1.5k 1.2k 0.1 1 2 100k 3 D2 10k 4.7k 1k Q1 9 black at the other extreme. The video signal from VR1’s wiper is fed to buffer stage Q4, after which it is mixed with the sync and colour burst infor­mation coming from IC1c and buffer stage Q3. The combined 1 VR1 VR2 com­posite video signal is then fed to transistors Q5 and Q6 which together act as a wide bandwidth amplifier with a gain of about 3.2. This gain compensates for any losses in the buffer stages and CMOS switches and RESISTOR COLOUR CODES ❏ No. ❏   1 ❏   1 ❏   1 ❏   1 ❏   1 ❏   4 ❏   2 ❏   1 ❏   3 ❏   1 ❏   2 ❏   2 ❏   3 ❏   1 ❏   3 ❏   1 ❏   1 ❏   1 Value 1MΩ 100kΩ 75kΩ 22kΩ 12kΩ 10kΩ 6.8kΩ 5.6kΩ 4.7kΩ 2.2kΩ 1.5kΩ 1.2kΩ 1kΩ 680Ω 470Ω 220Ω 150Ω 82Ω 4-Band Code (1%) brown black green brown brown black yellow brown violet green orange brown red red orange brown brown red orange brown brown black orange brown blue grey red brown green blue red brown yellow violet red brown red red red brown brown green red brown brown red red brown brown black red brown blue grey brown brown yellow violet brown brown red red brown brown brown green brown brown grey red black brown 5-Band Code (1%) brown black black yellow brown brown black black orange brown violet green black red brown red red black red brown brown red black red brown brown black black red brown blue grey black brown brown green blue black brown brown yellow violet black brown brown red red black brown brown brown green black brown brown brown red black brown brown brown black black brown brown blue grey black black brown yellow violet black black brown red red black black brown brown green black black brown grey red black gold brown August 1993  23 is set by the 2.2kΩ and 680Ω resistors. The result is that the overall peak amplitude of the video signal is the same at the output as at the input (provided that the signal has not been faded). This video output can then be fed into your VCR which provides the output termination. Power for the Colour Video Fader is derived from a 9V DC plugpack supply. PARTS LIST 1 PC board, code 02107931, 103 x 57mm 1 plastic case, 130 x 68 x 41mm 2 self-adhesive labels 1 single-pole 3-position toggle switch 3 panel-mount RCA sockets 1 2.5mm chassis-mount DC power socket 1 10kΩ linear pot. (VR1) 1 500kΩ linear pot. (VR2) 2 knobs to suit 15 PC stakes 4 rubber feet Semiconductors 1 4066 quad analog switch (IC1) 1 4070 quad 2-input OR gate (IC2) 2 BC558 PNP transistors (Q1,Q6) 4 BC548 NPN transistors (Q2-Q5) 2 1N914 signal diodes (D1,D2) 1 1N4004 silicon diode (D3) 1 7805 3-terminal regulator Capacitors 4 100µF PC-mount electrolytic 1 10µF PC-mount electrolytic 4 0.1µF MKT polyester 1 220pF MKT polyester 1 100pF ceramic 1 47pF ceramic Make sure that all polarised parts are correctly oriented when installing them on the PC board. Pin 1 of each IC is adjacent to a notch or dot at one end of the plastic body. Diode D3 provides reverse polarity protection, while a 7805 3-terminal regulator is used to derive a regulated +5V supply rail for the circuit. The 100µF and 0.1µF capacitors fitted to the input and output terminal of the regulator provide filtering and supply decoupling. Construction If you’ve had trouble following the circuit, don’t worry – construction is a cinch. That’s because most of the parts are mounted on a single PC board (code 02107931) and the external wiring is straightforward. Fig.6 shows the parts layout on the PC board. Begin the assembly by installing PC stakes at all external wiring points, then install the wire links and resistors. The accompanying table shows the resistor colour codes but it’s also a good idea to check them on a digital multimeter just to make sure (the colours on some resistors can be difficult to decipher). Note that two of the resistors are installed end-on (near IC2) to conserve board space. Once the resistors are in, the remaining parts can be in­stalled on the board. These include the transistors, diodes, capacitors, the two ICs and the 3-terminal regulator. Be sure to install the correct part at each location and make sure that all polarised parts are correctly oriented. In particular, make sure that you don’t get the transistors mixed up, as both NPN and PNP types are used in the circuit. Take care also with the orientation of the 3-terminal regu­lar. It should be installed with its metal tab towards the centre of the board. This done, the completed board should be carefully checked for missed solder joints and solder splashes. A little time spent Resistors (0.25W, 1%) 1 1MΩ 1 2.2kΩ 1 100kΩ 2 1.5kΩ 1 75kΩ 2 1.2kΩ 1 22kΩ 3 1kΩ 1 12kΩ 1 680Ω 4 10kΩ 3 470Ω 2 6.8kΩ 1 220Ω 1 5.6kΩ 1 150Ω 3 4.7kΩ 1 82Ω Miscellaneous Light-duty hook-up wire, tinned copper wire for links, machine screws & nuts. 24  Silicon Chip Fig.7: check your etched PC board against this full-size artwork before mounting any of the parts. COLOUR VIDEO FADER L➙R EXT. R➙L WIPE DIRECTION FADE WIPE + VIDEO OUT VIDEO IN EXTERNAL INPUT 9VDC IN Fig.8: these full-size artworks can be used as drilling templates for the case. checking at this stage can save a lot of frustration later on. The assembled PC board is housed inside a standard plastic case measuring 130 x 68 x 41mm. This will have to be drilled to accept the PC board and the various hardware items. Before drill­ing, attach the front and side panel labels to the case so that they can be used as drilling templates. The various hardware items can now be installed in the case and the wiring completed as shown in Fig.6. The connections to the front panel components are run using light-duty hook-up wire, while the power and RCA socket connections are run using light-duty figure-8 cable. Once all of the connections have been made, the PC board can be secured to the bottom of the case using machine screws and nuts, with additional nuts used as spacers. Complete the con­struction by fitting four self-adhesive rubber feet to the bottom of the case. is correct, check the current consumption by connecting your multimeter in series with the positive supply rail between the DC power socket and the PC board – you should get a reading of about 50-60mA. Now for the big test – you’ll need either two VCRs or a camcorder and a VCR. The Colour Video Fader is wired into circuit as follows: (1). Connect the VIDEO OUT from the camcorder (or one of the VCRs) to the VIDEO IN of the Colour Video Fader. (2). Connect a lead from the VIDEO OUT of the Colour Video Fader to the VIDEO IN on your VCR (note: if you are using two VCRs, this connection goes to the VIDEO IN of the second machine). (3). Set your camcorder or first VCR to either view a scene or replay an existing tape. The second VCR should be set to AUX IN or AU and the TV connected to its RF OUT socket. (4). Rotate the FADE and WIPE controls fully clockwise, and set the WIPE DIRECTION switch to R-L. This sets the fader to maximum luminance and the wipe function to show a full picture (note: if the screen is black, flick the switch to the L-R position. If the picture now appears, the switch is upside down). The FADE and WIPE controls can now be varied to check that they operate correctly. If everything is OK, set the FADE control to full brightness and set the WIPE control for half-picture/ half black. This done, flick the switch to its alternate setting and check that the picture and black areas of the screen are imme­diately transposed. Finally, most camcorders and VCRs have RCA sockets for their video and audio outputs but some older model VCRs have a BNC socket for their VIDEO OUT connection. If your VCR has a BNC socket, then it’s simply a matter of purchasing a BNC plug-toSC RCA socket converter. Testing To test the unit, first apply power and check for +5V on pin 14 of both ICs. If the reading is 0V, check the plugpack polarity – it’s probably reversed. Assuming that the supply rail The external input accepts signals from an external control unit to create a myriad of fancy wipes. This external controller will appear in a future issue. August 1993  25 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. Low-cost isolation amplifier It is often necessary to provide electrical isolation between one part of a circuit and another either simply to AC INPUT remove earthing problems or because one part of the circuit is at a different voltage potential to the other. This is a common re­quirement in switchmode power supplies, public address systems and when connecting transducers to industrial equipment. This circuit will accept a signal of ±1V and provide the same signal (inverted) at the output with 0.01% linearity and 7500VAC isolation. Bandwidth is about 100kHz. The circuit is based on the IL300 linear optocoupler (IC3). This IC comprises one infrared LED and two photodiodes. One photodiode is on the isolated side of the package and the second photodiode is on the non-isolated side. The two photodiodes are manu­factured to match within 0.01% linearity so that the output can closely match the signal applied at the input LED. Feedback is applied using the second photodiode to monitor the received light from the LED. This means that the signal across the isolated photodiode is almost the same as the signal across the diode in the feed­back path. IC1 receives the applied signal which is divided by two so that the resulting signal is ±0.5V peak-to-peak. IC1 is biased on due to diode D1 which applies -0.7V to the inverting input at pin 2. The resulting output at pin 6 of IC1 powers the LED in IC3 via a 100Ω resistor. Since the LED is always biased on with no signal applied, a negative signal can be applied to IC1 with­out the LED turning off. The feedback from the non-isolated photodiode connects to the inverting input of IC1. The second and isolated photodiode at pins 6 and 5 of IC3 28  Silicon Chip +15V 22pF IC3 IL300 +12V 3 27k 27k 2 IC1 LF351 4 6 100  2 5 220pF +1.4V 1 10 33k 10 D1 IN4148 15k 7 3  -12V -0.7V +15V 6 4 7 3 56k 15k D2 1N4148 3 6 IC2 LF351 4 AC OUTPUT -15V D3 1N4148 -12V INPUT connects to op amp IC2. A +1.4V bias voltage set by diodes D2 and D3 offsets the bias initially produced by the biased LED. The 56kΩ resistor across the negative feedback path of IC2 converts the current output from the photodiode to a voltage. Note that to obtain the required voltage isolation, the power sup­plies for IC1 and the non-isolated side of IC3 must be completely separate from Low distortion oscillator Here is a low distortion oscillator which uses only a single variable resistor to change the frequency over a 3:1 range. Thus the circuit has an advantage over the Wien bridge oscillator where two elements have to be changed to alter the frequency. IC1a functions as a unity gain inverting amplifier which is fed from the output of IC1b. IC1b is connected as a notch filter with capacitors C1 & C2 and resistors R1, R2 & R3 forming a “T” filter section across the feedback and output terminals of the op amp. To maintain oscillation, a feedback signal from IC1a is applied to the filter ISOLATED OUTPUT the power for IC2 and the isolated side of IC3. You can use batteries or separate transformer power supplies to obtain this isolation. When designing a PC board, make sure that there are no tracks run down the centre of IC3 and maintain adequate separation between the isolated and non-isolated PC tracks. John Clarke, SILICON CHIP. via a 100kΩ resistor. The inverted sinewave signal at the output of IC1a is clipped to 7V peak to peak using zener diodes ZD1 and ZD2. This sets the sinewave output level. Assuming C1 = C2, the frequency of oscillation is set by the equation: F = 1/2πC1√R3.(R1+R2). If C1 & C2 are 560pF, the frequency can be set to any value between 4.7kHz and 15.6kHz. Other values of C1 can be selected to provide different frequency ranges. The maxi­mum oscillation frequency is limited to about 20kHz using the LF353 or TL072 op amps. The lowest operating frequency is limited only by the capacitor size. Distortion of the sine wave is about 0.3%. John Clarke, SILICON CHIP. +5V 100k .01 100k +5V 4.7k 4 Q1 BC548 3 V1 2xBAW62 1M D1 2 D2 10k 1 IC1a TLO74 11 6 IC1b 5 7 .01 IC2a 74C14 1 16 14 6 2 3 5 7 J CK Q 10k 1 4027 KR S -5V INPUTS IC3a 4 TO DIGITAL MULTIMETER 7 100k .01 100k +5V +5V 12 V2 2xBAW62 1M D3 13 D4 10k 14 IC1d IC1c 10 8 0.1 11 11 IC2f 13 12 13 13 10 10 J CK R IC3b Q KS 9 Phase adapter for digital multimeters I am often required to construct a Bode plot for a particu­lar circuit, requiring a log-magnitude and phase response. Find­ing the gain is usually pretty simple but the measurement of phase can often be difficult. The circuit presented here measures the phase difference between two signals, and displays the result in degrees on a digital multimeter. Essentially, the circuit consists of two analog to digital converters, whose output is “mixed” in a T-type flipflop. The advantage of this technique over the more usual XOR gate, is that both the magnitude of the phase and its sign (either leading or lagging) can be measured. When one signal is leading the other, the relevant flipflop will be toggling, whilst the other output will be high. Swapping the inputs reverses this process. Each input is attenuated and clipped before being buffered and amplified by 10 (IC1), then converted into a digital signal by Schmitt inverters IC2a & IC2f. The operation of the cir­cuit is fairly self-explanatory, with the multimeter measuring the average value of the digital waveform appearing between the outputs of the flip­flops (IC3a & IC3b). In practice, the multimeter is set to the 2mA range, so a reading of say, +0.163 would correspond to a 10k R3 330k 10k +15V 2 3 7 6 IC1a 4 4.7k -15V C1 TL072 LF353 4.7k C2 R1 10k 100k R2 1k ZD1 6.8V ZD2 6.8V 5 220k 15 10k Q2 BC548 8 phase measurement of +163°. Measurement of phase dif­ference using an oscilloscope is usually accurate to around ±5° whereas this adapter can display to ±1°. Note that this is the phase resolution and is not a claim for accuracy which will depend on calibration. In order to utilise the adapter, it must be calibrated. To do this, first set VR1 to its maximum resistance and adjust VR2 so that the multimeter reads the desired value (as calculated from an oscilloscope). This done, swap the input probes and adjust VR1 for the same magnitude but different sign; eg, if the first reading was adjusted to +0.045, then adjust VR1 for a display of -0.045mA. It should be noted here that a phase difference of ±180° will actually produce a reading of 0.000 because of the combination technique used with the flipflop. The prototype circuit was constructed on Vero­board and powered from a 9V battery driving a 555 charge-pump oscillator to provide the -5V rail. Banana plugs spaced at 19mm were used to provide an easy interface to the multimeter. Steven Merrifield, Heidelberg, Vic. ($30) Handy hint 6 IC1b VR1 10k 12 9 VR2 10k 7 SINE OUTPUT This low distortion sinewave oscillator uses notch filter IC1b to drive unity gain inverting amplifier IC1a. Capacitors C1 & C2 & resistors R1, R2 & R3 form a “T” filter section across the feedback & output terminals of IC1b. Quite often, projects and alarms use pulsating piezo beep­ers. Elaborate circuits can be built just to pulse the beeper or, if you want, you can use a pulsing beeper. Try connecting a continuous tone beeper in series with a flashing LED – it works. R. Barham, Cairns, Qld. ($5) August 1993  29 A microprocessor based sidereal clock Are you an amateur astronomer who needs to know the position of the stars in the sky? If so, you need a sidereal clock. This microprocessor controlled clock has two 6-digit displays which show sidereal time & local or universal time. By JOHN WESTERN A sidereal clock measures time relative to the stars as opposed to a normal clock which measures time relative to the Sun. A star’s position relative to the Earth is measured in sid­er­eal days. A sidereal day is the time taken for the Earth to spin once on its axis relative to the stars. This is about four minutes shorter than a solar day. The ratio, as listed in “The Astronomical Almanac” is a factor of 1.00273790934, accurate to 12 decimal places. This clock has two displays: the left-hand display indi­ cates sidereal time while the right-hand display can display universal or local time. Each mode is referenced to a common temperature controlled crystal oscillator. 30  Silicon Chip Five keys on the front panel give universal/local time selection, display brightness, time setting and regulation (ie, setting the long-term accuracy of the clock). The clock can be set to provide a tone on the minute for either universal or sidereal time. Circuit description The circuit is based on a Z80C microprocessor running at 4MHz, together with a 6116 RAM, a 27C32 EPROM, an 82C55 PIO chip, two 7447 display drivers and 12 7-segment LED displays as the other major components – see Fig.1 & Fig.2. The circuit is divided among three PC boards, one for the CPU, one for the 12-digit display and one for the temperature controlled oscillator – see Fig.3. The CPU board (Fig.1) provides the functions of a frequency divider, a power-off detector, a reset circuit, an address decod­er and the power supply. A 4020 14-stage binary counter, U6, divides the 4MHz clock by 29 (512) to give a frequency of 7812.5Hz. This is then used to interrupt the Z80C on its NMI input (pin 17, U1). The correct universal time is determined by counting to a figure close to 7813 for each second that passes. Reference divider numbers In fact, the division process is a little more complex because if the clock is to keep accurate time for a long period, the precise division factor can only be determined by trial and error over a period which may span weeks or months. This design allows the user to actually program in the division numbers. There are four division numbers for universal time and these are designated as U1, U2, U3 and U4. U1 is the division number used at the end of each second; U2 is used at the last second of each minute; U3 is used at the last second of each hour; and U4 is used for the last second of each 24hour day. In this fashion, a change in the value of U4 will allow the accuracy of the clock to be altered by one part in 675 million. The sidereal division factors are designated as S1, S2, S3 and S4 and these are used in the same way as the division factors for universal time. To keep track of sidereal time, the clock simply subtracts the value S1 from U1, S2 from U2 and so on. The numbers are calculated from the measured timing error using the Basic program accompanying this article. The measured timing error is calculated by reference to a precise clock such as Telecom’s time service or Radio VNG. Ultimately, the reference numbers are stored in RAM when they are fed via the keypad buttons on the front panel. The stored program in the EPROM then uses these numbers for correct time keeping. Supply monitoring U7E, a Schmitt inverter, is used to monitor the +12V supply and whenever this is present, its output at pin 10 is low. When the +12V supply is removed, such as when the clock is in transit or not being used, pin 10 of U7E pulls PC3 of the 82C55 high (pin 17, U2). The Z80C then sets all the ports of the 82C55 to the input condition and this prevents current being sourced to the display board from the stand-by battery BT1. Thus, the oscillator and CPU boards keep functioning but the display board is effectively disabled. Even so, the time for which the stand-by battery can keep the clock going is limited to a few hours at most. This is because the current drawn by the oscillator heater is fairly substantial at around 250 milliamps. U5 is a 74HC138 3-to-8 line decoder. It monitors the A12, A13 & A14 address lines which are used to select memory blocks of 4096 bytes. The EPROM is located at address 0000H, the RAM at address 1000H, the 82C55 at address 2000H and the keyboard beeper at address 3000H. The power-on reset circuit is based on Schmitt inverter stages U7a and U7b. When power is first applied, C1 charges to +5V via R1. Schmitt trigger inverter U7a detects the transition from low to high on pin 1. Its output at pin 2 then goes low and resets the This view inside the completed prototype shows how the CPU board, display board & the oscillator (inside small box) fit together inside the case. Note that the piezo buzzer is mounted on the solder side of the display board, while 5V regulator U8 is heatsinked to the rear panel. The display board accommodates two groups of LED displays plus the five pushbutton switches. One group of displays show sidereal time, while the other group shows either local or UTC time. 82C55 (U2) and the 4020 (U6). At the same time, U7b inverts this signal to reset the Z80C (U1). Clock signal The 4MHz clock signal for the CPU board is generated on the oscillator board and appears on pin 5 of JP3. Inverter U7d buff­ers and squares up the signal which is then applied to the Z80C and the 4020. Power for the clock can be supplied from a 12V battery or a 12V 1A DC plugpack. Diode D1 protects the circuitry from reverse polarity while zener diode D5 prevents voltage spikes from inter­fering with or damaging the circuit. The 12VDC is then applied to +5V regulators U8 and U9. They provide separate +5V supplies to the display and CPU boards. If the +12V supply is not present, diodes D2 and D3 allow the CPU and oscillator boards to continue functioning from the battery. Ports PA0-PA5 and PB0-PB7 on the 82C55 peripheral interface are config­ ured as outputs and they drive the 7447 7-segment decoder drivers (U1 & U2) on the display board. Ports PC0-PC3 are configured as inputs to monitor the power-off detector (PC3) and the keyboard matrix (PC0-PC2) on the front panel. Ports PC4-PC7 are configured as outputs; PC4 and PC5 drive the keyboard matrix August 1993  31 PARTS LIST CPU board 1 L-shaped double-sided PC board 1 9V battery & snap connector (BT1) 1 14-pin IC socket 2 16-pin IC sockets 1 24-pin IC socket 1 28-pin IC socket 2 40-pin IC sockets (see text) Semiconductors 1 Z80C microprocessor (U1) 1 82C55 programmable interface (U2) 1 6116 static RAM (U3) 1 27C32 or 27C64 programmed EPROM (U4) 1 74HC138 decoder (U5) 1 4020 14-stage binary counter (U6) 1 74HC14 hex Schmitt trigger (U7) 2 7805 3-terminal regulator (U8, U9) 1 1N5404 rectifier diode (D1) 2 1N4001 rectifier diodes (D2,D3) 1 1N4733 5V zener diode (D4) 1 1N4746 18V zener diode (D5) Capacitors 1 220µF 25VW electrolytic 1 100µF 25VW electrolytic 2 1µF 25VW electrolytic 6 0.1µF 63VW monolithic ceramic Resistors (1%, 0.25W) 1 22kΩ 1 5.1kΩ 8 10kΩ 1 330Ω Oscillator PC board 1 PC board, 1 4MHz crystal 1 1mH inductor 1 brass block (see Fig.7) Semiconductors 1 LM358 dual op amp (U1) 1 LM334 current source (U2) 1 78L05 3-terminal regulator (U3) and PC7 indicates whether the righthand display is showing universal or local time. Display board The display board accommodates the 12 7-segment displays, the key32  Silicon Chip 2 2N5485 N-channel FETs (Q1,Q2) 1 TIP31 NPN transistor (Q3) Capacitors 2 0.1µF 63VW monolithic ceramic 1 68pF ceramic 2 27pF ceramic Resistors (1%, 0.25W) 1 10MΩ 3 10kΩ 1 1MΩ 1 8.2kΩ 2 100kΩ 1 1kΩ 1 18kΩ 1 220Ω Display board 1 double-sided PC board 1 piezo beeper (Tandy Cat. 273065) 5 panel switches (E.S.Ruben Cat RF19 3.14001.006) Semiconductors 12 TIL312 common anode LED displays (DIS1 to DIS12) 2 7447 decoder/drivers (U1,U2) 1 555 timer (U3) 10 BC548 NPN transistors (Q1,Q3,Q5,Q7,Q9,Q11, Q13-Q16) 6 BC337 NPN transistors (Q2,Q4,Q6,Q8,Q10,Q12) 2 1N4148 signal diodes (D1,D2) Capacitors 1 10µF 35VW tantalum 2 0.47µF 16VW electrolytic 3 0.1µF 63VW monolithic Resistors 6 10kΩ 6 4.7kΩ 1 3.9kΩ 16 27Ω Miscellaneous 1 3AG 1A slow blow fuse 1 in-line 3AG fuseholder 1 can Electrolube nickel screening paint (DSE N-11138) 2 RF suppression beads (DSE R-5425) board switch matrix, a beeper, a pulse detector and driv­ ers for the heater on indicator and the universal/local indicator – see Fig.2. The displays are multiplexed two at a time. The Z80 feeds a BCD number via the 82C55 to the two 7447 decoder Fig.1 (right): the CPU board is based on a Z80C microprocessor (U1) running at 4MHz, together with a 6116 RAM (U3), a 27C32 EPROM (U4) & an 82C55 PIO chip (U2). It acts as a frequency divider, a power-off detector, a reset circuit & an address decod­er. drivers, U1 & U2. The appropriate digits (say DIS1 & DIS7) are then en­abled by turning on one of the six Darlington pairs (Q1 & Q2). The process is then repeated for the other five pairs of digits. The bright­ness of the display is changed by reducing the on time for each digit, via the Z80C. The keyboard matrix is scanned by taking ports PC4 or PC5 low and then reading the condition of ports PC0PC2. If one of the switches has been pressed, then one of ports PC0-PC2 will be low. Switch debouncing is achieved via the software. Each time a key is pressed, the beeper sounds. A CPU write or read to any address in the range 3000h-3FFFh causes pin 12 of U5 (74C138) to go low momentarily and trigger 555 timer U3, which drives the piezoelectric beeper. The decimal points of displays DIS7 and DIS12 are used as indicators. The decimal point of DIS7 indicates when the oscilla­tor heater is on. This decimal point is driven by transistor Q13 which is turned on by the “heater output” (HO) line from the oscillator board. The decimal point of DIS12 indicates whether universal or local time is being displayed on the right-hand 6-digit display. This same decimal point also has the function of indicating that the power has been off. If the power goes off, the decimal point begins flashing. It is driven by transistor Q14 which is turned on by the PC7 line from the 82C55. Diodes D13 and D14, together with transistors Q15 and Q16, form a missing pulse detector. This is used to disable the dis­plays if the microprocessor stops running normally. This prevents a particular display from being provided with a continuous high current. The pulse detector monitors the 5V pulses on the O1 line from the CPU board. With pulses normally present, Q15 will be on and Q16 will be off so that pin 4 on each of the 7447 decoder/ drivers will be high. If the pulses on +5V FROM U8 JP2 VCC R5 330  9 R3 10k R4 10k 16 8 16 10 CLK U6 4020 25 U7c 74HC14 12 Q9 14 5 8 R1 22k NMI 11 U7a U7b 2 1 4 3 26 RESET 30 C1 100 A2 33 C8 0.1 C9 0.1 39 HO 4 40 GND 3 1 +9V 2 2 +12V 1 32 D3 31 D4 30 D5 29 D6 28 D7 27 A12 A11 RD A13 WR D3 PC4 D4 PC2 D5 PC1 D6 PC0 D7 A0 PA5 A1 8 D3 PB7 7 D4 PB6 9 D5 PB5 10 D6 PA2 13 D7 PA1 PA0 21 5 22 36 17 A14 PB1 RD PB0 WR PB2 PC3 RST CS 29 35 PB3 6 R9 10k 13 VCC R10 10k 12 VCC 11 TO 10 10 LO 9 HO 12 8 S5 13 7 S4 16 6 S3 15 5 S2 14 4 S1 3 GND U2 82C55 PB4 D7 A10 PC5 12 D2 D6 A9 D2 PA3 D5 A8 4 D2 D1 15 D1 D4 A7 3 33 PC7 PA4 D3 A6 37 38 D1 D0 14 D0 D2 A5 36 JP3 TO OSCILLATOR 4MHz 5 D1 A4 35 C10 0.1 D0 A3 34 VCC 34 A1 8 U1 Z80C A1 32 D0 A0 9 AO 31 C7 0.1 WAIT BUSRQ 17 R8 10k 26 11 7 RST VCC 6 24 INT CLK 6 U7d R2 10k 2 GND 39 1 O6 JP1 40 1 13 O5 12 04 22 11 1C 25 10 8C 24 9 4C 23 8 2C 2 7 O3 3 6 O2 4 5 O1 19 4 2D 18 3 1D 20 2 4D 21 1 8D TO DISPLAY 7 C2 0.1 VCC +5V D3 1N4001 IN BT1 9V U9 7805 GND OUT C5 1 D2 1N4001 JP4 +5V TO JP2 D1 1N5404 IN +12V 1 0V 2 R11 10k D5 1N4733 C6 220 U8 7805 GND OUT C4 1 U7e 11 R12 4.7k VCC VCC 24 24 A0 8 A1 7 A2 6 A3 5 A4 4 A5 3 A6 2 A7 1 A8 23 A9 22 A10 19 WE A0 A1 D0 A2 D1 A3 D2 A4 D3 U3 6116 A5 D4 A6 D5 A7 D6 A8 D7 A9 OE A10 CE 10 21 D0 9 10 D1 D1 10 11 D2 D2 11 13 D3 D3 13 14 D4 D4 14 15 D5 D5 15 16 D6 D6 16 17 D7 D7 17 9 D4 1N4733 D0 A1 D0 A2 D1 A3 D2 D3 U4 27C32 D4 A4 A5 A6 D5 A7 D6 A8 D7 20 A9 18 A10 OE/ VPP 12 C11 0.1 A0 20 A11 8 A0 7 A1 6 A2 5 A3 4 A4 3 A5 2 A6 1 A7 23 A8 22 A9 19 A10 21 A11 CE 18 12 VCC R6 10k 6 I GO A12 1 A13 2 A14 3 16 G1 Y1 A B C U5 74HC138 G2A G2B SIDEREAL CLOCK - CPU 4 5 Y2 Y0 Y3 14 13 15 12 8 August 1993  33 34  Silicon Chip C2 0.1 1 2 6 2D 4D 8D 6 8C O6 1 8D 1 4D 2 1D 3 2D 4 O1 5 O2 6 O3 7 2C 8 4C 9 8C 10 1C 11 O4 12 O1 2 4C GND 2 FROM CPU BOARD JP1 O5 13 1 2C GND 3 D1 1N4148 C5 0.5 4 7 1C S1 4 5 4 7 1D 5 3 S2 5 C4 0.1 3 VCC C3 0.1 S3 6 S4 7 S5 8 HO 9 LO 10 TO 11 VCC 12 FROM CPU BOARD JP2 VCC 13 VCC C 1 R21 10k HO C6 0.5 D2 1N4148 G BI/RBO E D F 8 U2 7447 C B A 8 4 2 1 RBI LT 16 8 F G 8 BI/RBO E 4 E C R7-13 7x 27  E C 7 8 10 13 1 6 R28 10k E E C VIEWED FROM BELOW B E Q16 BC548 C B DIS7 TIL312 HEATER ON LED DRIVER R22 27W 11 2 7 8 10 13 1 SW1 11 2 7 8 10 13 1 S1 Q4 BC337 B 11 E C 11 R29 10k O2 Q3 BC548 B 2 14 DIS1 TIL312 14 E C R2 4.7k 2 7 8 10 13 1 B Q2 BC337 Q15 R27 BC548 C 10k B VCC B Q13 BC548 14 15 9 10 11 12 R14-20  13 7x 27 VCC 14 15 9 10 11 12 13 VCC Q1 BC548 B D B RBI 2 A LT U1 7447 16 O1 R1 4.7k O3 SW3 1 14 E C DIS3 TIL312 Q6 BC337 B 11 2 7 8 10 13 1 DIS9 TIL312 14 SIDEREAL DISPLAY 11 2 7 8 10 13 E C S3 S4 SW4 UNIVERSAL/LOCAL DISPLAY B Q5 BC548 SW5 O4 R4 4.7k S5 Q7 BC548 B SIDEREAL CLOCK - DISPLAY SW2 S2 DIS8 TIL312 14 DIS2 TIL312 14 E C R3 4.7k 11 2 7 8 10 13 1 11 2 7 8 10 13 1 E C TO 14 E C R25 10k DIS10 TIL312 14 DIS4 TIL312 Q8 BC337 B O5 R5 4.7k C1 10 R26 3.9k LO 6 7 11 2 7 8 10 13 1 11 2 7 8 10 13 1 E Q9 BC548 C B KEYBOARD BEEPER 2 U3 LM555 4 DIS11 TIL312 DIS5 TIL312 Q10 BC337 B 1 8 14 14 E C 3 VCC VCC R23 10k O6 R6 4.7k 1 E C PIEZO BEEPER R24 27  Q14 BC548 B 11 2 7 8 10 13 1 11 2 7 8 10 13 Q11 BC548 B E C 6 14 14 E C UNIVERSAL/ LOCAL LED DRIVER DIS12 TIL312 DIS6 TIL312 Q12 BC337 B JP1 TO CPU BOARD 1 +9V OUT R7 10M R3 8.2k R6 10k R U2 LM334 R1 220  2 1 U1a LM358N 5 8 6 R4 18k R8 390 7 U1b 3 +12V 4 HEAT ON IND 5 4MHz OUTPUT 3 R5 10k R2 10k C4 0.1 2 GND IN U3 78L05 GND Q3 TIP31 B SEE TEXT 4 C E U2, Q3 AND Y1 ATTACHED TO BRASS BLOCK OUT L1 C1 1mH 27pF Y1 4MHz Q1 2N5485 G R9 1M R12 100k C3 27pF D S C2 68pF R10 100k C5 0.1 Q2 2N5485 G U4 78L05 GND Fig.3: the crystal oscillator circuit. Crystal Y1 & transistor Q1 form a Pierce oscillator which operates at 4MHz, while FET Q2 buffers the 4MHz signal to the CPU board. U2 is an LM334 adjustable current source & functions here as a temperature sensor. It is monitored by U1a & U1b & these in turn control Q3. When Q3 is on, it dissipates several watts to heat the interior of a small plastic utility box which houses the oscilla­ tor board. IN D TIP31 S R11 1k 78L05 LM334 I G O R VIEWED FROM BELOW 2N5485 G S D B CE SIDEREAL CLOCK - OSCILLATOR O1 are missing, Q15 will turn off, Q16 will turn on and the displays will be disabled. Oscillator board The oscillator PC board features a 4MHz crystal oscillator and a temperature controller – see Fig.3. Crystal Y1 and transistor Q1 form a Pierce oscillator. FET Q2 buffers the 4MHz signal to the CPU board. U2 is an LM334 adjustable current source connected as a temperature sensor. It causes a voltage drop, proportional to the Absolute temperature, to be developed across R2. This resistor is connected to the inverting input of op amp U1a which is connected as a comparator. Pin 3 of U1a is connected to a reference voltage divider across the 5V supply and this effectively sets the oper­ating temperature of the circuit. Fig.2 (left): the display circuit is controlled by the CPU board & uses two 7447 display drivers (U1 & U2) plus 12 7-segment LED readouts. U3 drives a piezo beeper to provide the keypad beep function. When pin 3 is more positive than pin 2, the output (pin 1) of U1a goes high. This output is buffered by U1b and is used to drive transistor Q3. This transistor is connected across the +12V supply and functions as the heater in the circuit. When the transistor is on, it dissipates several watts to heat the interior of a small plastic utility box which houses the oscilla­tor board. As the temperature inside the box rises, the voltage at pin 2 of U1a increases to the point where it is more positive than pin 3. This causes pin 1 (and thus pin 7 of U1b) to go low and therefore transistor Q3 is turned off. The circuit then cools down to the point where the transistor is switched on again. Q3, Y1 and U2 are all attached to a brass block which is maintained at a constant temperature of 70°C. Pin 7 of U1b is also routed to the display board to light up a “heater on” indicator, as mentioned above. Construction The three PC boards should be assembled and then linked together –see Figs.4-6. The CPU and display boards are double-sided but without plated through holes. This means that any holes in the board not associated with components should have pinthroughs installed and these should be soldered on both sides of the board. You can use tinned copper wire for all pin-throughs. Once the pin-throughs have been installed, the IC sockets can be inserted. They provide additional pin-throughs for the board so their pins must be soldered on both the component and solder sides. The use of machined pin or wire wrap IC sockets is recommended because the pins on these are longer than normal, allowing soldering on both sides of the board. Sockets which are too close to each other to allow soldering on the component side will need to be split into two halves and installed separately. There are no sockets used on the display board. Once the IC sockets have been installed, the other compon­ents should be added. All components must be soldered on both sides of the board except the displays which are only soldered on the copper side. The piezo­electric buzzer is mounted on the solder side of the display board (see photo). August 1993  35 U9 7805 D2 D1 R5 C11 JP3 C5 R4 +12V R2 +9V R11 GND R12 D4 HO U1 Z80C CLK R3 1 C8 U5 74HC138 1 U3 6116 C9 R6 1 U6 4020 1 U4 27C32/27C64 C7 U7 74HC14 R9 R8 1 1 R1 C10 R10 U2 82C55 C1 1 JP1 JP2 Fig.4: this diagram shows how the parts are installed on the CPU board. Note that pin throughs must be installed at all vacant hole positions, while all components & IC sockets must be soldered on both sides of the board. R15 R19 R20 R16 R17 R18 D2 U1 7447 R29 1 Q9 R5 1 1 Q10 The correct operation of all functions should be estab­lished by using them as described below. In normal mode, the SELECT key Q11 R6 1 1 Operation Q12 Q14 1 R27 R28 SW1 SW2 SW3 SW4 SW5 R23 R26 C3 C1 JP1 36  Silicon Chip Q13 R21 R24 C6 D1 Q16 Q15 C4 1 D11 TIL312 R14 Q8 D10 TIL312 1 Q7 D9 TIL312 1 R4 D8 TIL312 1 Q6 D7 TIL312 1 D6 TIL312 D2 TIL312 D1 TIL312 1 Q5 R3 C5 1 C2 1 Q4 D5 TIL312 1 R8 R12 R13 R9 R11 R10 Q3 R2 D3 TIL312 R7 Q2 D4 TIL312 Q1 R1 functioning. The oscillator board can now be placed in a standard plastic box measuring 28 x 54 x 83mm (DSE H-2855 or equivalent). The board is insulated by surrounding it with pieces of 10mm thick polystyrene. The three boards can now be linked together. The connec­ tions between the CPU and display boards can be of tinned copper wire, with every second link insulated. The connections between the CPU and oscillator boards should be made with about 80mm of insulated wire. Note that the pin numbers for each wire differ on each board. The boards are installed in a standard plastic instrument case measuring 200 x 65 x U2 7447 The brass block (see Fig.7) on the oscillator board should be installed at the same time as the components. Transistor Q3 is screwed to the block while the crystal and temperature sensor are held in place using strips of metal as clamps. Heatsink compound should be used to ensure a good thermal bond to the brass block. The heater current must be set before the three boards are connected together. Apply +12V to the oscillator board and meas­ure the current drain. Choose a value of R8 which gives a supply current of about 250mA. Monitor this current until it drops to a low value. This indicates that the temperature control circuitry is 160mm (DSE H-2505 or equivalent). You will need to make several cutouts in the front panel for the two 6-digit displays and the five pushbutton switches. You will also need two small pieces of red transparent plastic and these are glued behind the dis­ play cut­outs. A 1A slow-blow fuse should be installed in series with the +12V supply line. The fuseholder can be an in-line type or mount­ed on the rear panel. The whole assembly can now be fitted in the case. Voltage regulator U8 should be heatsinked to the rear panel using a piece of aluminium plate bent into an L shape. The display board can be fixed to the front panel using the holes either side of the switches. The spacing between the board and the front panel is determined by the height of the switches and displays. Appro­priate spacers need to be used to provide this clearance. The CPU board can be fixed in place using the mounting holes provided in each corner of the board. Once the three boards have been installed, power can be applied. If all is working correctly, the beeper should sound and the display should show all eights (lamp test mode). The SELECT switch can now be pressed to acknowledge that a reset condition has occurred. The right and left displays should now indicate time in hours, minutes and seconds. The battery should not be installed until the operation of all functions is veri­fied, as the CPU can not be reset with the battery in circuit. To reset the CPU, turn the power off for 10 seconds. R22 D5 D3 D12 TIL312 JP4 BT1 9V C4 U8 7805 U3 555 C2 GND +12V C6 JP2 R25 BEEPER Fig.5: the parts layout on the display board. As with the CPU board, the parts must be soldered on both sides of the board & pin-throughs installed at vacant hole locations. switches between universal and local time for the right-hand display. The decimal point on digit six of the righthand display lights up to indicate that universal time is selected. The BRIGHT key changes the display brightness through five levels. The DISPLAY key switches the right and left-hand displays on or off. The SET TIME key starts and stops the set time mode of operation. The SET REF key starts and stops the set reference mode of operation. In “Set Time” mode, the SELECT key selects the digits which are to be set. The + key will then increment the hours or minutes that are flashing. When the seconds are flashing, the + key will zero them. The seconds on universal/local time can only be set in universal mode. The TONE key enables the buzzer to sound and indicate the occurrence of each minute that passes. To indicate sidereal minutes, the tone key must be pressed when any sidereal digit is flashing and vice versa for universal/ local. To stop the tone function, press the TONE key again. The BATTERY key causes the display to indicate the length of time that the battery has been used. If the power has been off and the decimal point is flashing, pressing the battery key will terminate flash mode. When a new battery is installed, the “-” key can be used to zero this display. In “Set Reference” mode, the SELECT key selects the refer­ence number to be changed. The left-hand display will cycle through an indication of U1-U4 or S1-S4 when the SELECT key is operated. The + and - keys are then used to adjust the particular reference number chosen. This close up view shows the oscillator board in its case, with the cover & insulation removed. The power transistor (Q3), constant current source (U2) & crystal are attached to a brass block near the centre of the board. its accuracy against an accurate time signal such as Telecom’s time service or radio station VNG on one of the following frequencies: 2.5MHz, 5MHz, 8.638MHz, 12.984MHz and 16MHz. The error obtained after 24 hours needs to be recorded and entered into a PC running the program STAR­TIME.BAS. The program will calculate and display new values for U1-U4 and S1-S4. These updated reference values should be entered into the clock using the set reference mode. This process of adjustment may have to be performed a number of times, with the accuracy being checked over longer periods. The sidereal time is referenced to Where to buy the kit Readers can buy a short form kit of this project from the author. The kit comprises the three PC boards, a programmed EPROM and the five keypad switches for the display board. The kit is priced at $95 plus $5 for postage and packing, anywhere in Australia. The author can also provide a repair service on completed sidereal clock kits for $60 plus the cost of any parts replaced. Payment can be made via cheque or money order to John Western, 81 Giles Ave, Padbury WA 6025. Phone (09) 401 2733. 6 14 Time setting 5 2.6 Set the universal time and check R3 C2 R12 Q2 R10 R11 +9V C4 GND R7 R4 R6 R5 R2 R1 B +12V 1 U2 L1 C3 BRASS BLOCK C1 Q1 R8 15 U3 R9 B HO U1 LM358 U4 Y1 C5 Q3 A A +12V HARD WIRED TO Q3 JP1 CLK Fig.6: the parts layout for the oscillator PC board. Keep all component leads short & note that R8 must be chosen to give a supply current of about 250mA – see text. 3.5 20 27 2.5 5 HOLES A = COMPONENT MOUNTING TAPPED M2.5 B = BLOCK MOUNTING TAPPED M2 MATERIAL: BRASS DIMENSIONS IN MILLIMETRES Fig.7: this diagram shows the dimensions of the brass block. August 1993  37 10 ‘********************************************************* 20 ‘* STARTIME.BAS by JOHN WESTERN 12/06/91 This program * 30 ‘* calculates new values for the sidereal clock reference * 40 ‘* numbers. The error in seconds/day and the values of U1-U4 * 50 ‘* are entered by the user. * 60 ‘********************************************************* 70 DEFDBL A-Z 80 CLS:PRINT “ SIDEREAL CLOCK CALCULATION PROGRAM” 90 ‘ 100 ‘ GET CURRENT VALUES OF U1-U4 110 INPUT “Enter current value of U1”; U1 ‘get current values 120 INPUT “Enter current value of U2”; U2 130 INPUT “Enter current value of U3”; U3 140 INPUT “Enter current value of U4”; U4 150 ‘ 160 ‘CALCULATE TOTAL NUMBER OF PULSES PER DAY 170 PCD = (U1 * 59 * 60 * 24) + (U2 * 59 * 24) + (U3 * 23) + U4 180 ‘ 190 ‘GET ERROR FROM USER 200 INPUT “enter number of seconds per day error”;TIMERR 210 WHILE ANSWER$ <> “f” AND ANSWER$ <> “F” AND ANSWER$ <> “s”     AND ANSWER$ <> “S” 220 INPUT “Is clock fast or slow? (F/S)”; ANSWER$ 230 WEND 240 ‘ 250 ‘CALCULATE PULSE DIFFERENCE FOR EACH REFERENCE VALUE 260 PD = (TIMERR / 86400!) * PCD 270 IF PD >= 84960! THEN PPS= INT(PD/84960!):PD = PD - (PPS * 84960!) 280 IF PD >= 1416 THEN PPM = INT(PD/1416):PD = PD - (PPM * 1416) 290 IF PD >= 23 THEN PPH = INT(PD/23): PD = PD - (PPH * 23) 300 IF PD >= 1 THEN PPD = INT (PD) 310 ‘ 320 ‘CALCULATE AND DISPLAY NEW VALUES OF U1-U4 330 IF ANSWER$ = “f” OR ANSWER$ = “F” THEN GOSUB 2010 ELSE     GOSUB 1010 340 PRINT 350 PRINT “New U1 =”; U1 360 PRINT “New U2 =”; U2 370 PRINT “New U3 =”; U3 380 PRINT “New U4 =”; U4 390 ‘ 400 ‘ CALCULATE AND DISPLAY NEW VALUES OF S1-S4 410 PCD = (U1 * 59 * 60 * 24) + (U2 * 59 * 24) + (U3 * 23) + U4 420 SIDCNT = PCD / 1.00273791#:PULSDIF = PCD - SIDCNT 430 S1 = INT(PULSDIF / 84960!): PULSDIF = PULSDIF - (S1 * 84960!) 440 S2 = INT(PULSDIF / 1416): PULSDIF = PULSDIF - (S2 * 1416) 450 S3 = INT(PULSDIF / 23): PULSDIF = PULSDIF - (S3 * 23) 460 S4 = INT(PULSDIF) 470 PRINT “S1 =”; S1 480 PRINT “S2 =”; S2 490 PRINT “S3 =”; S3 500 PRINT “S4 =”; S4 510 END 1000 ‘ ROUTINE TO CALCULATE NEW VALUE OF U1-U4 FOR CLOCK SLOW 1010 U1 = U1 - INT(PPS) 1020 U2 = U2 - INT(PPM) 1030 U3 = U3 - INT(PPH) 1040 U4 = U4 - INT(PPD) 1050 RETURN 2000 ‘ ROUTINE TO CALCULATE NEW VALUES OF U1-U4 FOR CLOCK FAST 2010 U1 = U1 + INT(PPS) 2020 U2 = U2 + INT(PPM) 2030 U3 = U3 + INT(PPH) 2040 U4 = U4 + INT(PPD) 2050 RETURN 38  Silicon Chip Fig.8: this full-size artwork can be used as a marking template for the front panel. universal time and should be correct once universal time is adjusted. In the event that the sidereal time is not accurate, the values S1-S4 allow it to be adjusted. The sidereal time should now be set following normal astronomical procedures. The prototype clock has been operating for two years with universal time giving an error of less than one SC second per month. SILICON CHIP AUSTRALIA’S BRIGHTEST ELECTRONICS MAGAZINE ENJOY THE WORLD OF ELECTRONICS & COMPUTERS EACH MONTH ★ Constructional Projects For The Enthusiast ★ The Serviceman’s Log ★ Vintage Radio: Technology From The Past ★ Articles On Computers & Radio Remote Control ★ New Circuit Ideas & Techniques ★ Amateur Radio Projects & Features Subscribe today by phoning (02) 979 5644 & quoting your credit card number, or fill in the form below & fax it to (02) 979 6503. ❏ New subscription – month to start­­___________________________ ❏ Renewal – Sub. No._______________ RATES (please tick one) Australia Australia with binder(s)* Overseas airmail 2 years (24 issues) ❏ $A84 ❏ $A105 ❏ $A240 1 year (12 issues) ❏ $A42 ❏ $A53 ❏ $A120 *1 binder with 1-year subscription; 2 binders with 2-year subscription Your Name________________________________________________ Fax or mail coupon to: Freepost 25 Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Signature (PLEASE PRINT) Address__________________________________________________ ______________________________ _______________________________________Postcode__________ Card expiry date________/________ Card No. August 1993  39 SERVICEMAN'S LOG Little things can be big time wasters Frustration & annoyance is the theme of this month’s notes. It’s about the many & varied things that can contrive to slow the job & which collectively can add up to a lot of wasted time. As most readers will appreciate, most faults that turn up on the service bench are fairly routine. Generally, they are faults that have been seen before in the same model set or faults which, by their very nature, can be recognised in any set. These are the ones that provide the bread and butter – and a smidgin of jam occasionally. The real stinkers – the ones that call for a lot of patience and electronic detective work – may make it into these notes but seldom earn much income. In between these two extremes are those which, in spite of being relatively straightforward in a technical sense, can be quite frustrating – often for all kinds of silly reasons. This is one such story and it has a very silly twist in the tail. It is about a Panasonic model 2970V TV set, a 73cm model with stereo 40  Silicon Chip sound. This set is fitted with the M15D chassis which has been very reliable. Incidently, the “D” in this type number indicates a “dead” chassis; ie, one which is isolated from the mains. There is also an M15L model, the “L” signifying a live chassis. This set is only about three years old but it had been used for only part of that time. The owner had just moved into a new home and the set has been in storage for about 15 months while he and his family were living in smaller temporary accommodation. Obviously, the storage period may have had something to do with the problem. The owner was typically vague about the nature of the fault, saying only that the set was still working but that there was something funny about the picture. This was confirmed when I set it up on the bench. Yes, the set was working and, yes, there was something funny about the picture; it was suffering from severe pincushion in the east-west mode; ie, it bowed inwards on each side. This was one of the first frustrations, because it is quite a rare fault these days. Worse still, it was one I had never encountered before in this model chassis. I wasn’t quite sure where to start. Another frustration involved the complexity of the service manual. While the material in it is very well presented, the circuit and other data are spread over many sheets, making it difficult if the circuit has to be traced from one sheet to another. On the other hand, it is much better than having the circuit reduced so much that essential detail is lost. Getting back to the fault, the pincushion circuitry is on a separate board – designated the K board – and this same module is used in several models. Initially, I was unable to find the circuit and wasted a lot of time searching for it. I eventually ran it to earth in the section for the M15L chassis (of course – where else would it be?). It is reproduced herewith and at least I don’t have to apologise for the quality. But this only moved me on to the next stage of frustration. The circuit did not carry any waveforms or even any voltages on the transistors. I did eventually track down the voltage data – on yet another sheet – but not before I had wasted more time trying to rationalise the voltages as I found them. I also searched through the manual for any explanation as to how the pincushion circuit functioned, but in vain – I was on my own. So, all in all, I wasted a good deal of time before I even started. The K board The K board is about 150mm long by 100mm wide and slides vertically between two rails mounted on the right-hand side of the cabinet (as seen from the back). It connects to the rest of the set via two plug and socket assemblies, K1 and K2, on leads long enough to allow the board to be removed and worked on while still in circuit. This, at least, was a plus. Pin 1 of K2 connects to the 113V main HT rail, while pin 2 carries vertical pulses. These were traced back to a network connected to pin 2 of IC401, the vertical output chip. Pin 3 has no connection and pin 4 goes to chassis. Plug K1 connects directly to the horizontal scan coils via pin 1 (H-) and pin 3 (H+). Pin 4 connects to chassis. The hori­zontal amplitude here is quite substantial. The lower part of the circuit shows three transistors: Q701, Q702 and Q703. Q703 is the first one in the chain and is fed with vertical pulses from pin 2 of plug K2. The output from Q703, at its collector, goes via the pincushion Fig.1: the K-board (pincushion) circuitry for the Pana­sonic TC-2970V. Vertical pulses come in on pin 2 of plug K2 & are fed to the base of Q703 (lower right). Q703 drives the pin­cushion control, the output of which then drives Q702 & Q701. Finally, Q701’s output is coupled to the horizontal scan coil circuitry to provide the necessary pincushion correction. Note the absence of waveforms and transistor voltages. control to the base of Q702 which, in turn, drives Q701. Q701 is a power transistor (TO66 package) and is mounted on a heatsink. Its output is coupled into the horizontal scan coil circuitry to provide the necessary pincushion correction. Waveform checks I tried checking various waveforms, hoping I might find an obvious dis­ crepency, but without success. The vertical pulses appeared to be making their way through the chain OK but, without any waveforms for reference, I had no way of knowing whether the amplitude and waveform shape were correct at every stage. The only hint was that the gain of Q703 was not what I would have expected from a superficial assessment of its configuration. But then, I couldn’t be sure. Also shown in this part of the circuit is width control R708 (5kΩ) and pincushion control R710 (20kΩ). I tried adjusting the width control and this behaved as expected; it varied the width and nothing else. But when I tried the pincushion control, August 1993  41 circuit. But no, it was spot on value. Next, I lifted C707 and measured it. It was down to around 700µF, which made it bad enough to need replacing, even if it wasn’t the main fault. And it wasn’t, because a new one made little difference. My next stop was C708 (47µF) and this was where I struck oil; it was extremely leaky, which could easily account for the weird voltages and the failure of the pincushion circuit. And it did, because a new one immediately cured the pincushion problem. Having located the fault, I checked the voltages again, more or less as a matter of routine. I didn’t refer to the manual list this time, having memorised the values well enough – I thought – to satisfy such a check. And so it seemed; I measured 1.85V on the emitter, 2.5V on the base, and 9.3V on the collec­tor, near enough to the figures I recalled from the manual. SERVICEMAN'S LOG – CTD The final twist it behaved in a less logical fashion; it also changed the width and nothing else! That suggested that the fault was in this section of the circuit. Transistor checks My next step, was to check all three transistors but, as far as I could determine, all were OK. I had not at this stage unearthed any voltage data for these transistors but I made a few voltage measurements anyway, hoping that they might provide a clue. And they did, in a way. The voltages on Q701 and Q702 at least seemed reasonable, by rule-of-thumb guess­ timation. But Q703 was another matter; unless it was being used in a very unusual way, I couldn’t make any sense of it. I measured 17V on the collector, 17V plus on the emitter and 17V on the base. But, while this didn’t make much sense, it did remind me of the appar­ent low gain of this stage. But what should the voltages be? I found them listed quite by chance when, as so often happens, I was 42  Silicon Chip searching the manual for something else. At a quick glance I registered that those for Q703 were not only nothing like the values I had measured but seemed to be much more reasonable. All of which simply confirmed my idea that whatever was wrong was in the immediate vicinity of Q703, the transistor itself having already been cleared. There aren’t many components directly associated with Q703. I started with R712, thinking it might be open COMMON TEST POINT VOLTAGES E B C Q701 0.025 0.62 13.8 Q702 11.9 11.3 0.62 Q703 1.85 9.3 2.5 Q802 0 0.01 16.5 Fig.2: this is the relevant portion of the transistor voltage table from the Panasonic TC-2970V manual. The collector & base vol­tages shown for Q703 are transposed. And so, after a routine check and adjustment, the set was duly returned to the customer, putting an end to my time-wasting frustrations. Or so I imagined. My final frustration came as a nasty twist when I later took a second look at the voltage table in the manual. It was then I suddenly realised that the voltages were not listed as I had recalled them. Oh, the values were correct but not the transistor connections. The manual listed them as 1.85V on the emitter, 9.3V on the base and 2.5V on the collector. I did a double take on that. Those figures did not make sense and, had I been more observant, I would have realised this when I first saw the table. Instead, I read them as I imagined they would be, rather than as they were. The point about these figures is that – apart from anything else – they imply a base-emitter voltage of around 7.5V – an impossible condition according to my understanding of solid state theory. When I went to (solid state) school, the maximum voltage which could normally be developed across such a junction would not exceed 0.7V, and would be more like 0.65V in practice. So what had gone wrong. My immediate reaction was to sus­pect that the figures in the manual were a mistake; that they had been wrongly set out Fig.3: this diagram shows the front-end circuitry for the High Energy Ignition System, as published in the May 1988 issue of SILICON CHIP. The constructor’s problems were at the very front of the circuit. with the base and collector values trans­posed. I spent a lot of time, on and off, thinking about the problem and the longer I thought about it, the more convinced I became that the manual was wrong. Note particularly that, if we transpose the base and collector values as given in the manu­al, we then have 0.65V across the base/ emitter junction, exactly according to the rules. Finally, at the first opportunity, I rang my colleague in the Panasonic service department and put the problem to him. It didn’t take him long to fetch the manual and look up the circuit and chart. His reply was brief, to the point: “Ah yes, a typo” (typographical error). Anyway, that was the end of story as far as the various problems and frustrations were concerned, But I do suggest that anyone who is likely to be dealing with the M15 chassis, or the manual, make a note of the mistake. Finally, I do have some other comments on the fault itself. While electrolytic capacitor failures are not un­usual, I was surprised that one as large as C708 should deteriorate to this extent in only a few years. The fact that the set was stored for so long may have been a factor, although it should not have been. And what about C707? This, I think, might have been a vic­tim. Rated at only 6.3VW, it had about 17V applied across it while ever the fault was present. The wonder is that it didn’t break down completely. In addition, there is another electrolytic capacitor in this part of the circuit – C716 (10µF 50VW). This was also checked and was found to be down to about 5µF. It was replaced along with C707 and C708. While on the subject of electrolytics, I find that if one reads lower than its rated capacitance, by even a small amount, it is time to replace it. New capacitors invariably measure higher than their marked value. If they drop below that figure, they are generally on the way out. Kit projects To change the scene, but still on the subject of frustrat­ing situations, I am reproducing a letter from a reader, Mr R. S. of North Melbourne, Victoria. It is not a servicing story in the usual sense, nor was it a particularly profound exercise, but it is an excellent example of the problems which can arise from the supposedly simple job of building a kit project. Assuming a well-designed project and a properly prepared kit, it is reasonable to expect that it will work at first switch-on (provided, of course, that the kit has been correctly assembled). But it doesn’t always happen that way. And when it doesn’t, kit builders react in a variety of ways. Some simply regard the design as a bomb, curse the designer, and chuck the whole thing in the garbage bin. Some strip it down and rebuild it; a time wasting and usually futile procedure. One enthusiast, in the days of build-your-own TV sets, stripped down and rebuilt a complete 17-inch TV set, in an attempt to cure a relatively simple fault – the pic­ture was transposed left to right. More enlightened souls, like our reader, assume that the design is capable of working and that its failure must be due to a construction fault –which is usually the case. They then set about finding it in a methodical way. Just how simple some of these faults can be is shown in this example. Here’s how he tells it. The night before Christmas Some months ago, my son-in-law to be raised the question of fitting an electronic ignition system to his motor vehicle. Because I had built a number of CDI (Capacitor Discharge Igni­tion) and TAI (Transistor Assisted Ignition) units, I was consid­ ered a suitable consultant. Although very pleased with the performance of all units tested, I have never been able to detect either an increase in fuel economy or engine power. Perhaps this is because I always cleaned and adjusted the ignition system on a regular basis – about every 3000km. What I have noticed is that the electronic systems require virtually no manitenance or adjustment, unless I disassemble the distributor for some other purpose. Since CDI is currently out and TAI is in, the choice was simple. I did not experience any crossfire with CDI but the inverter squeal could be objectionable. My last TAI circuit is dated at 1982 but the “High Energy Ignition System” unit produced by SILICON CHIP in May, 1988 was available in kit form. And, as his training was in the field of electronics, a kit was purchased and he assembled the unit. A few days before his initiation to son-in-law, he invited me to install the TAI in the vehicle, as he knew that I would be more familiar with the automotive side of things (self-trained also). However, I put this off while he August 1993  43 SERVICEMAN'S LOG – CTD was being moulded into married life during the next two weeks and I waited for his return. A telephone call was subsequently received on December 23rd and arrangements were made to perform the change over on the night before Christmas. He had already mounted the box in the engine bay and all that should have been necessary was for me to find a suitable 12V supply and make the appropriate connections to the ignition system. This particular vehicle incorporates the ballast resistance in the loom but I was able to find a suitable power supply con­nection at the fuse panel and run a wire to the unit. Laying out the wiring to the coil in a secure fashion came next. Suitable checking took place and I felt that we were ready for the all-im­portant smoke test. Switching the ignition to the run position produced no problems but switching to the start position failed to produce any fire in the engine. This enabled me to demonstrate how easy it was to revert to the old faithful 44  Silicon Chip Kettering system, if it was required. We had begun the work in the open and in dry conditions, but by now a light rain had become a heavy downpour and daylight had vanished, so we called it a night. No smart comments about Melbourne’s weather thanks; we aren’t overjoyed either! The next day, my daughter rang and invited me to lunch with the family. No great arm twisting was necessary, as it would give me the opportunity for further fault finding. After a pleasant meal, off came the lid and the investigation began. I was expect­ing to find a fault with D5 but it still behaved as a diode and was oriented correctly. Transposed resistors The resistors were checked next and it was found that the 22kΩ resistor to the input (pin 5) of IC1 was 2.2kΩ. A search was made for a suitable resistor and we were able to find two 10kΩ units. My son-in-law has a very limited stock of components, as electronics is not his hobby. I was concerned that the additional current through the zener diode in IC1 might be too much for it. A re-test took place but the engine did not start. At this point, it was not noticed that the 22kΩ resistor which should have wired into the input of IC1 had been placed in the collector circuit of Q2. In other words, the 2.2kΩ and 22kΩ resistors had been transposed. The unit was removed from the vehicle and, because there was the possibility of serious damage to IC1, I decided to take the unit with me for further testing and repair. The 22kΩ resis­ tor problem was corrected the next day. I then proved that Q1 was intact and with the aid of a spare coil connected, produced a spark when the output of IC1 was taken to chassis using a jumper lead. Since waveforms were going to be traced, the CRO was fired up. This was an overkill, as will be seen. The action of the points opening and closing was mimicked by connecting a flying lead to the power supply chassis. This produced a step at the 47Ω resistor, as was expected. Unfortunately, when the CRO probe was transferred to the other side of diode D5, the pulse vanished. On turning the board over to the track side, it came to my attention that there were more tracks and holes than were necessary for this project (as a last resort read the text fully). The constructor had placed the anode lead of D5 into the next hole up the board. Once this correction had been made, a pulse could be traced to pin 7 of IC1. By now reconnecting the test coil and spark plug, I was able to view a nice healthy spark. When installed the next day, the system worked perfectly. The constructor did emphasise that he had performed “high reliability hand soldering” techniques as his employer instructs. And to his credit the soldering could not be faulted. But my warped sense of humour considers that suitable connectivity is required before conductivity can take place. Fair enough, R. S. and thanks for the story. It emphasises one very important point – the difference between field servic­ing, where a device originally worked but has now failed, and production line servicing, where the device has never worked. Production line servicing is a completely different SC ball­game. 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 REMOTE CONTROL BY BOB YOUNG Unmanned aircraft – Israel leads the way UMAs have developed over many years from craft that have showed promise to devices which are important in the modern defence arsenal, as shown by their extensive use in the Gulf War. However, the country which has really shown the way has been Israel with its Mastiff & Scout aircraft. This month, we will look at some of the more exotic modern UMA systems but first a few observations. I am forever amazed at the reader reaction to each monthly column and to some extent my own views of each column. Columns that I am happy with often pass unnoticed or even attract adverse comment. On the other hand, some that I am not happy with, despite my best efforts, can attract a favourable reaction. By far the most persistent cause of headaches is the choice of topic. When I settled upon the subject of UMAs for a purely electronics magazine, I did so with some trepidation and they were difficult columns to write. I had to spend weeks in the NSW State Library researching the subject, bringing my knowledge of the subject up to date. It appears that my fears on this series of articles were unfounded for they have attracted possibly the most reader reac­tion of all of the columns I have written to date, with the exception of the speed controller articles. This is not to say that all readers agree with what I have written, so here are a few comments from readers who felt moved to communicate their The IAI Scout is a notable Israeli UMA that began operational flying with the IDF in 1981. Its wingspan is 4.96 metres, maximum take-off weight is 159kg & its maximum speed is 176km/h. The endurance time is quoted as seven hours. interest. My thanks to them and all of the others who wrote or otherwise commented on the articles. First, Tony Mott of Blackburn, Victoria sent me a very interesting extract from the book “German Aircraft” by J. R. Smith and Antony Kay. It gives the most detailed description of the Mistel (Mistletoe) composite aircraft (mentioned last month) that I have yet encountered. Tony pointed out that according to Smith and Kay, not only did I get the name of this project wrong but I also gave incorrect details of the operation of this intri­guing unit. What can I say, except “OOPS!” Contrary to what I stated in the June 1993 issue, the upper fighter unit of the pair was the mother ship and the larger, lower (bomber) unit was the disposable missile. Here is a classic example of not checking the facts. The details, sadly, came from my own (faulty) memory. Despite all the research I did, the one thing I did not refresh my memory on was wrong. Whilst on the subject of the Mistel project, Smith and Kay give some very interesting details of this and similar weapons. They claim the earliest use of a guided UMA in combat was when the Italians launched a Savoia Mar­ c hetti S.M.79 bomber packed with explosives and fitted with radio control against British warships off the Algerian coast on the 13th August, 1942. This aircraft was set on course by the pilot who then bailed out but the mission failed due to a radio malfunction. Further to my comments on the improvements in warhead design in the June 1993 issue, the Mistel was fitted August 1993  53 The IAI Helstar from Israel is one of the most notable UMAs flying. It has twin co-axial rotors some two metres in diameter & its maxi­mum take-off weight is 500kg. It can stay airborne for six hours & has a maximum speed of 185km/h. with a 3500kg hollow charge warhead made up of 1725kg of high explosive and a 1000kg steel core. This core had a theoretical armour penetration of 7.5 metres. In actual tests, it burst through some 18.5 metres of concrete, a staggering result. As stated previously, men have an absolute genius for de­signing ways to kill each other. The thing that really impressed me in regard to the Mistel was just how advanced the German technology was in those days. The original Mistel was aimed at the target and launched, under control of the autopilot, at the target. This left much to be desired as regards accuracy and a proposal was put forward to fit a wire guidance system similar to that designed for the Henschel Hs 293D. In this system, television cameras in the bomber relayed pictures back to the fighter. Wire guidance was used very successfully in many early missiles. It is easy to see where the inspiration for the smart bomb, used to such great effect in Iraq, came from. Wallace Beasley of Hillbank, SA sent in a fascinating tale he picked up on the rumour mill whilst working for the RAF at Lympne as a young lad. Several British fighter pilots were al­ leged to have been arrested because 54  Silicon Chip they planned to fly to Spain in their Hawker Fury fighters to fight against Franco in the Spanish civil war. Not only that, but it was rumoured that they had managed to get hold of a Queen Bee complete with ground control equipment and had planned to load it with explosives and use it as a guided missile against some strategic target. As primitive as all of the foregoing appeared, they were to spawn a deadly breed of UMAs and guided missiles in a very short space of time. All of this reminds me of Charles Fort and his theory on the steam engine. Fort held that when it came time to invent the steam engine it would appear spontaneously around the world. This certainly seems to have been the case with UMAs. New breed UMAs Returning now to the Middle East and the 1990s, we come face to face with the new and very deadly breed of UMAs. As stated previously, the Israelis now hold the dominant position in the design and supply of UMAs, so we will have a quick look at some of these and their uses. The leading Israeli UMA company is Israeli Aircraft Indus­tries (IAI), which absorbed the Tadiran UAV division in 1984. Tadiran developed the Mastiff series of UAVs and Mastiff III was Israel’s first generation production mini-UAV. Mastiff is now fairly primitive by modern standards but it served Israel well for almost a decade. The experience gained from this UMA and its evaluation by the USMC led directly to the US Navy requirement for Pioneer, more of which later. Mastiff does not have a preprogramm­ ed opera­ tion option and is purely operator controlled. It is due to be re­ placed by the new IAI Searcher. Mas­tiffs were bought by the US Navy in 1984-85. Mastiff has a wing span of 4.25 metres and weighs in at 138kg at take-off. Its maximum speed with a 16.4kW (22hp) engine is 186km/h, while its operational ceiling is 4480 metres (14,700ft). In 1976, IAI started development of the Scout and in 1981 Scout II began operational flying with the Israeli Defence Forces. Scout is slightly larger than the Mastiff but has the same basic appearance. Most IAI UMAs feature a short fuselage fitted with a pusher propeller. The wing is shoulder mounted on this pod. The tail­plane is mounted on twin booms which attach to the wing. All are fitted with a tricycle non-retractable undercarriage – very basic stuff by modelling standards. The pusher propeller leaves the nose free for TV cameras and other sensors, and keeps the air­craft and camera lenses free from exhaust waste. Scout has a wingspan of 4.96 metres and maximum take-off weight is 159kg. Its speed with a 16.4kW motor is 176km/h (95 knots) and the ceiling is 15,000 feet. The endurance of the Scout is quoted as seven hours. Takeoff is via a truck-mounted catapult (standard), but wheeled take-off is also an option. The Scout has been the Israeli Defence Force’s mainstay UMA since 1982 when it was introduced over the Beka Valley with some outstanding results in defence suppression missions. Scout has the option of being able to switch between pre-programmed and operator-controlled flight. This allows the uplink (the radio control channel from ground to aircraft) to remain silent during most of the mission except for any unforeseen events which need operator intervention. The sensors fitted vary and include a daylight TV camera, FLIR and laser rangefinder/target designator. Recovery is by net in standard configuration but wheeled landings are an option. Scout has been exported to Sing­apore, South Africa and Switzerland and, like Mastiff, will be replaced by the Searcher. Interestingly enough, both Switzerland (IAI joint venture) and South Africa have since developed their own versions of the Scout, both a little larger but with the same basic layout. However, the 6-metre South African Seeker is far and away the more elegant looking vehicle. It has a very interesting “return to base” mode in the event of the primary or backup UHF control links being broken or jammed. The Swiss Ranger has a parachute recovery for peace-time emergencies or, for normal operations, a wheeled or skid under­carriage which can be used in conjunction with an arrester cable. Pioneer In 1985, the US Navy purchased the first of nine Pioneer units from IAI. Developed by IAI and produced as a joint IAI/AAI venture, Pioneer is derived from the earlier Scout and maintains the same basic layout. Its wingspan is 5.11 metres and maximum take-off weight is 200kg. Power is by a Sachs SF 350 2-cylinder, 2-stroke engine rated at 21kW. The service ceiling battleships Missouri and Wisconsin. Pioneer flew more than 500 missions during Desert Storm, totalling in excess of 1700 hours. Its missions included mine-hunting, naval OTH (over the horizon) targeting and route recon­ naissance for AH-64 helicopters, as well as the more commonplace overland surveillance and target location. Sensor options include TV, FLIR, EW/ECM, decoy, communica­ tions relay and laser rangefinder/designator. The guidance system is either pre-programmed or it can be flown by an operator. Recovery is either by wheel­ed undercarriage with an arrester or, on ship, by net. Since 1986, IAI has developed a stream of more and more advanc­ ed UMAs including Ranger, Impact, Search­er (wingspan 7.22 metres, speed 204km/h, ceiling 7620 metres), Hunter and the very interesting Helstar. Helstar (Heliborne Loitering System with Thermal imager and Radar) is an unmanned maritime helicopter featuring twin co-axial rotors some two metres in diameter (not much larger than the usual model helicopter). Designed to operate from Israeli naval corvettes and other missile carrying boats, the Helstar take-off weight is a staggering 500kg. It is fitted with an Allison 250C20B turboshaft engine rated at 313kW (420hp) and can stay airborne for six hours. Its maximum speed is over 185km/h (100 knots) and the mission radius is 185km. Pioneer flew more than 500 missions during Desert Storm. Its missions included minehunting, naval over the horizon targeting & overland surveillance & target location. is 4575 metres (15,000ft), while the endurance is six hours. It is launched using wheels, catapult or rocket boost along a rail. The EI-Op TV or FLIR camera is carried in a ventral turret and EW (electronic warfare), decoy or other payloads are option­al. The USN and USMC now have nine Pioneer units, each comprising up to eight air vehicles. Six of these were deployed before and during the Desert Storm operations, with two operated from the I have chosen to devote some considerable time in describ­ing the IAI aircraft for one simple reason. In essence, they are little more than typical model aircraft, yet they form the nu­cleus of the practical UMA movement. Here are front-line minia­ture aircraft, the likes of which can be found on model flying fields anywhere in the world. This really is no accident as many of the designers are active modellers who spend their weekends on model flying fields. Of course, UMAs are much more sophisticated and expensive than model airplanes. Teledyne UMAs Two other UMAs of interest before we close for this month are the Teledyne Ryan Model 410 and the Teledyne Ryan Scarab/BQM-145A. The Model 410 is large enough (9.55 metres wingspan) to carry fullsized payloads but looks for all the world like a grown-up IAI twin boom UMA. It was designed for long-range or long-endurance missions and was first flown on 27th May, 1988 with an on-board check pilot under a tear-drop canopy. Here the circle is complete, for we finally have what is little more than a man-carrying model aircraft. The Model 410 has a take-off weight of 816.5kg and the 119kW (160hp) flat 4-cylinder Lycoming engine pushes it along at 322km/h (174 knots). Its maximum endurance is 22 hours, the service ceiling is 30,000 feet and the range is 2300km. Here is the ultimate modeller’s toy – just hop in and fly to the field, then whip out your transmitter and have a nice day of R/C flying. At the end of the day with your Model 410, you could then stow the Tx, change back to manual control, hop in and fly home. What a way to go! For the ultra-sophisticated, we have the Teledyne Ryan Scarab BQM-145A. It has a wingspan of 3.35 metres, a length 6.15 metres and weighs in at 1077kg. Fitted with a Teledyne CAE 373-8C turbojet engine rated at 970lb thrust, the Scarab can nip along at a handy 851km/h (459 knots). Its mission radius is 966km, while the service ceiling is 43,000ft. The Scarab was designed primarily for Egypt in the mid-1980s as a groundlaunched reconnaissance UMA and 56 were subse­ quently delivered. It is launched by booster rocket from a truck-mounted “zero length” rail and recovery is by parachute or airbag landing. Here we have left the model movement far behind and on this note we leave this most fascinating field of human endeavour. Acknowledgement My thanks to Bill Herbert, Flynn, ACT for the photo of the Jindivik aircraft featured in the May 1993 issue SC of SILICON CHIP. August 1993  55 By LEO SIMPSON BUILD You’ve seen those late-model Japanese sports cars with a row of pinpoint red lights in the spoiler. They look snazzy & they draw immediate attention to the brakes being applied. Now you can have one for your car. This Brake Light Array uses 60 high-brightness light emit­ting diodes and a few other components. The LEDs are installed on two narrow PC boards and they are driven so that they light up from the centre of the array and spread out till all LEDs are alight. This takes place in a fraction of a second and looks even more eye-catching than the brake light arrays on Japanese cars. The Brake Light Array, or BLA for short, is housed in a thin aluminium channel which is 500mm wide. It can be mounted on the parcel shelf of your car and power can be taken from one of the brake lights. The total current drain of the BLA is about 260mA which is minuscule compared to the current of several amps drawn by your existing brake lights. In fact, the BLA is so bright for such a small current that it seems likely that brake lights in the future will not use incandescent lamps – they will use high-brightness LEDs. 56  Silicon Chip Interestingly, because the circuit has a regulated supply voltage, the brightness of the Brake Light Array will always be constant, regardless of any variations in the battery voltage. Flasher circuitry Now have a look at the circuitry of the BLA – see Fig.1. This looks fairly complicated considering that it merely lights up a bunch of LEDs. However, the circuit could be used for other purposes and so can be made to flash several times in succession before the LEDs stay on permanently, until the power is removed. Power for the circuit comes from one of the brake lights. The positive supply (+12V) is fed through a 500mA in-line fuse and then to a 2.2Ω resistor and 15V zener diode which protects the circuit from any high voltage transients which could come, for example, from door solenoids or motors. The +12V supply is regulated to +8V by a 7808 3-terminal regulator which feeds all the circuitry. IC2, an LM3914 dot/bar display driver, is the heart of the circuit. It drives 30 LEDs in 10 groups of three and each group of three LEDs is in series with its particular output from the LM3914. The LM3914 is operat­ed in bar mode (pin 9 connected high) and the current through each set of three LEDs is set at 10mA by the 1.2kΩ resistor at pin 7. Normally, an LM3914 is used to A 60-LED BRAKE LIGHT ARRAY FOR YOUR CAR drive a bargraph display of LEDs in response to a signal voltage applied to its pin 5; the more signal, the more LEDs light up. And so it is in this design. The signal voltage is applied to pin 5 via transistor Q3 which is connected as an emitter follower. Its base signal comes from the emitter of Q1, a unijunction transistor. Q1 is connected as a relaxation oscillator to produce a sawtooth waveform at its emitter. What happens is that the 22µF capacitor at the emitter is charged up to about +5V via the 10kΩ resistor and 100kΩ trim­pot, VR1. Each time the capacitor reaches the threshold voltage of around +5V, the unijunction (Q1) discharges the capacitor and the cycle begins again. So Q1 is the source of signal voltage applied to pin 5 of IC2 via Q3. If we neglected the effect of Q2 and IC1, the action of the circuit presented so far would be to repeatedly light up the full row of LEDs. Clearly, this would be no good for brake light use as it would send the drivers of following cars mad (as well as being illegal). This is where IC1 comes into the picture. Each time Q1 discharges the 22µF capacitor at its emitter, it produces a brief positive pulse at its base 1 (B1) terminal. This pulse is amplified, inverted by transistor Q2 and fed to the clock input of IC1, a 4017 decade counter. With the aid of a link on the PC board from its pin 13 (enable) input, IC1 can be made to count any number of pulses up to six whereupon it will stop counting and its selected output will go high. This selected output is fed via diode D1 to the emitter of Q3 and to pin 5 of IC2. This stops Q3 from responding to the sawtooth signal from the emitter of Q1. Thus, IC1 will turn all LEDs on until power is removed from the circuit. Master & slave circuit The description so far tells how LEDs 1-30 are driven. LEDs 31-60 are driven by IC3, another LM3914 which is “slaved” to the signal from the emitter of Q3. Thus, IC3 is forced to mimic Below: this close-up view shows the master board of the LED Brake Light Array. It carries 30 high-brightness LEDs, while the slave board carries another 30 LEDs. August 1993  57 58  Silicon Chip B 4.7k Q3 BC548 E 10k 100k VR1 22 16VW C 100W B1 3 1k MODE 6 RHI 9 Q1 2N2646 E B2 8.2k +V1 1 B K K A K A A    K K A K A A    K K A K A A    K K A K A A 1.2k E C REF OUT 7 CLK 16 2 Q1 4 2 Q2 IC1 4017 Q3 7 15 10 15 RST Q4 1 Q5 5 Q6 EN 8 13 14 14 5.6k RLO 4 LED1LED30    K K A K A A BRAKE-LIGHT ARRAY 100k 0.1 REF ADJ 8 IC2 LM3914 18 17 16 15 14 13 12 11 10 10k    Q2 BC548 SIG 5 K K A K A A 6 5 4 3 2 1    K K A K A A SELECT SWEEPS K K A K A D1 1N914    A    K K A K A A    8.2k    CHASSIS +12V FROM BRAKE LIGHTS K K A K A A 6 9 F1 500mA +V2 ZD1 15V E 2. 2  RHI MODE 3 B 1       K K A K A A    K K A K A A    K K A K A A C 22 16VW 1.2k REF OUT 7 B2 IN 5.6k E B1 REG1 7808 GND REF ADJ 8 IC3 LM3914 22 16VW OUT RLO 4 I GO +8V 2 18 17 16 15 14 13 12 11 10 K K A K A A VIEWED FROM BELOW SIG 5 K K A K A A    22 16VW K K A K A +V1 LED31LED60    A K K A K A A IN K K A K A REG2 7808 GND    A 22 16VW OUT    K K A K A A +8V    +V2 K K A K A A    CHASSIS 500mA IN-LINE FUSE +12V FROM BRAKE LIGHTS ZD1 VR1 REG1 10k 22uF Q1 22uF 100 1k 10k Q2 Q3 8.2k 4.7k 1.2k 5.6k D1 1 IC2 LM3914 100k COMMON 0.1 22uF 2. 2  IC1 4017 1 2 3 4 5 6 SWEEP LED1-LED30 K A 22uF REG2 8.2k 1.2k 5.6k 1 IC3 LM3914 22uF LED31-LED60 K A everything done by IC2 in driving its LEDs. IC3 and its 30 LEDs are fed by their own regulator (REG2). Note that we do not recommend that this circuit be set up to provide more than one sweep of the LEDs before they turn on fully. Multiple sweeps of the LEDs will be quite distracting to following drivers and is illegal in Australia, as far as we know. Construction As noted above, the LED Brake Light Array is built on two narrow PC boards which each measure 230 x 27mm. These boards are supplied with a full component overlay so assembly is quite straightforward. One board has LEDs 1-30 on it and it becomes the “master” while the second board accommodates IC3 and LEDs 31-60 and is the “slave”. We suggest you build the master board first and get it going before doing the slave board. Assemble the small components such as links, diodes and resistors and capacitors first, then the transistors and in­ tegrated circuits. The highbrightness LEDs come last. ▲ LED polarity trap Fig.1 (left): the circuit uses two LM3914 dot/bar display drivers which respond to the ramp voltage generated at the emitter of unijunction transistor Q1. Decade counter IC1 controls the number of times that the LEDs are swept before they come on fully. You will need to use care in assembling the LEDs so that they are all lined up – if even one is not lined up with the others it will stick out like a sore thumb. The way to line them up is to install each LED so that its leads are just long enough so that they can lie flat on the top surface of the board, with the LED body butted up to the edge of Fig.2: install the parts on the two PC boards as shown in this wiring diagram. Note that the leads used to connect the boards together must be long enough to allow the boards to be mounted end-to-end. the board – the accompany­ing photos show the general idea. Before we leave the LEDs, there is a big trap to watch. We normally show a pinout diagram on the circuit which shows the LED polarity. The normal convention is that the longer lead is the anode and the lead adjacent to a flat on the side of the lens is the cathode. However, it is not always the case and it could be most frustrating to assemble 30 LEDs onto the board and find that they are all the wrong way around. In particular, the LEDs supplied with this project kit will be the reverse of normal convention – the shorter lead will be the anode. To be sure that you assemble them correctly, check at least one LED with a 9V battery and RESISTOR COLOUR CODE ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ No. 1 2 2 2 1 2 1 1 1 Value 100kΩ 10kΩ 8.2kΩ 5.6kΩ 4.7kΩ 1.2kΩ 1kΩ 100Ω 2.2Ω 4-Band Code (1%) brown black yellow brown brown black orange grey red red brown green blue red brown yellow violet red brown brown red red brown brown black red brown brown black brown brown red red gold gold (5%) 5-Band Code (1%) brown black black orange brown brown brown black black red brown grey red black brown brown green blue black brown brown yellow violet black brown brown brown red black brown brown brown black black brown brown brown black black black brown not applicable August 1993  59 These two views show how the master & slave boards are mounted end-to-end so that the LEDs form a single bargraph. This version used a channel made from two angle aluminium sections. a 4.7kΩ limiting resistor. You have been warn­ed. Finally, fit the short link adjacent to the 4017 which selects the number of sweeps at six; ie, install a link connect­ ing “common” to “6”. After having checked your work carefully, connect a DC power supply set to 12V. The row of LEDs should sweep towards the regulator end of the board six times before all flick on and stay on until power is removed. You can change the rate at which the LEDs sweep by adjusting trimpot VR1. We suggest you set it for a sweep rate of several times a second. This then completes your work on the master PC board. Now you can assemble the slave PC board. As can be seen from the photos and the wiring diagram of Fig.2, the slave board has quite a few components omitted. To be specific, those omitted are the 2.2Ω resistor and zener The slave board is mounted upside down on the aluminium channel, so that the LEDs light from the centre outwards. Ignore the resistor shown tacked on the back of this prototype board – the final version has the resistor mounted on the component side (see Fig.2). 60  Silicon Chip diode at the input to the regulator, transistors Q1, Q2 & Q3, IC1, diode D1 and all of the associated resistors except for the 4.7kΩ and 1.2kΩ values associated with the LM3914. Begin the slave board assembly by installing the two resistors, the two wire links, the two 22µF capacitors and the 3-terminal regulator, then install the LM3914 and the 30 LEDs. To complete the slave board, you will need to run three insulated wires from it to the master board. These include the common ground wire (0V) and a wire from the input terminal of the 3-terminal regulator on the master board to the input of the regu­lator on the slave board. Finally, a lead must be run from the emitter of transistor Q3 on the master board to the same position on the slave board; ie, the emitter pad of Q3. This is the control signal wire for the slave board. Now check all your work carefully again and apply 12V DC once more. The LEDs on both boards should now sweep towards the regulator six times in identical fashion before flicking on perma­nently. Now we strongly suggest that the BLA be set for only on sweep of the LEDs before they come on permanently. To accomplish this, remove the link between pins 13 and 5 of IC1 that was installed previously and connect a short link underneath the master PC board between pins 2 and 13 of IC1. This done, apply power again and check that the LEDs make one sweep and then flick on fully. Finally, set the rate at which the LEDs sweep on by ad­justing trimpot VR1. Mounting the boards To make up the Brake Light Array, the two assembled PC boards must be positioned end-to-end with the regulators on the outermost ends. Mounted in this way, the resulting display will start in the centre of the two boards and spread out to the ends until all LEDs are alight. We had two prototypes of the BLA. One had the PC boards mounted in an aluminium channel measuring 40 x 25 x 500mm long. The boards were glued together and then secured in the channel with small blocks of foam plastic. The channel was mounted on a short upright made from metal towel rail fittings. The whole assembly was then sprayed with flat black enamel. The second prototype BLA used a channel made from two angle aluminium sections measuring 25 x 50 x 500mm and secured together with self-tapping screws. The boards were mount­ed end-on on the bottom section using suitable screws, spacers, Protect your valuable issues Silicon Chip Binders PARTS LIST 1 aluminium channel, 500mm wide (see text) 2 PC boards, 230 x 27mm 1 in-line 3AG fuseholder 1 500mA 3AG fuse 1 100kΩ trimpot (VR1) Semiconductors 60 5mm high brightness red LEDs (LED1-60) 2 7808 8V 3-terminal regulators (REG1,REG2) 1 4017 CMOS decade counter (IC1) 2 LM3914 dot/bar LED drivers (IC2, IC3) 1 2N2646 unijunction transistor (Q1) 2 BC548 NPN transistors (Q2,Q3) 1 15V 1W zener diode (ZD1) 1 1N914, 1N4148 silicon diode (D1) Resistors (0.25W, 1%) 1 100kΩ 2 1.2kΩ 2 10kΩ 1 1kΩ 2 8.2kΩ 1 100Ω 2 5.6kΩ 1 2.2Ω 0.5W 1 4.7kΩ ★ High quality ★ Hold up to 14 issues Miscellaneous Aluminium channel mounting hard­ ware, hook-up wire, screws, nuts, spacers, washers. ★ 80mm internal width Where to buy the kit A kit for this project with all parts except the metalwork is available from Oatley Electronics, PO Box 89, Oatley, NSW 2223. Phone (02) 579 4985 or fax (02) 570 7910. The kit price is $65 plus $3 for postage & packing. Note: copyright of the PC artwork for this project is retained by Oatley Electronics. Price: $A11.95 plus $3 p&p each (NZ $6 p&p). Send your order to: ★ SILICON CHIP logo printed in gold-coloured lettering on spine & cover Silicon Chip Publications PO Box 139 Collaroy Beach 2097 Or fax (02) 979 6503; or ring (02) 979 5644 & quote your credit card number. Use this handy form ➦ Capacitors 5 22µF 16VW electrolytic 1 0.1µF monolithic These beautifully-made binders will protect your copies of SILICON CHIP. They feature heavy-board covers & are made from a dis­ tinctive 2-tone green vinyl. They hold up to 14 issues & will look great on your bookshelf. Enclosed is my cheque/money order for nuts and washers. A similar support assembly was made from towel rail fittings and again the whole assembly was sprayed with flat black enamel. The assembled BLA can be mounted on the parcel shelf of your car, as close to the rear glass as possible. You will then need to make a connection to the chassis for the 0V supply line and to one of the brake light wires to pick up the +12V supply. This can most conveniently be done using a “Contact” connector. This connector is simply wrapped around and new wire and the wire to the brake light and then the connector is squeezed to make a safe and insulated connection. These connectors are available in a pack of four for $1.50 from Jaycar Electronics (Cat. HP-1206). Points to note Two important notes about the connection to the brake light: (1). Make sure you make the connection to the stop light filament line, not the tail light; and (2). Don’t forget to fit a 500mA inline fuse to the +12V line, as specified SC on the circuit diagram. $________ or please debit my ❏ Bankcard   ❏ Visa   ❏ Mastercard Card No: ______________________________ Card Expiry Date ____/____ Signature ________________________ Name ___________________________ Address__________________________ __________________ P/code_______ August 1993  61 VINTAGE RADIO By JOHN HILL How to deal with block capacitors As a young lad, I saw quite a few radio sets come and go from my bedroom. Each one was the ultimate receiver – that is, until something better replaced it. My first sets were a couple of crystal sets which served me well for many years. Following these were the regenerative receivers: several 1-valvers, a 2-valver and even a 2-valve shortwave set with plug-in coils. I spent a fair amount of my time building receivers and listening to them. There is nothing quite like the satisfaction of making something that actually works. Looking back, I have very fond memories of those bygone days. After the home-made battery sets had run their course, I spent up big and bought a mains-powered set – my first big pur­chase. It was only half a set really, just a chassis and speaker that I bought from a kid at school for 30 shillings. Unfortunate­ly, my mem­ory is not good enough to recall all of the details and I wish now that I could remember them more clearly. The set involved was a 4-valve regenerative detector type receiver. I still have the single gang tuning capacitor, so that aspect of it is fairly clear in my mind. There was no dial, just a knob fitted to the tuner shaft. It took a steady hand to tune it to stations at the high frequency end of the dial. I distinctly remember that one of the valves was very large, blue in colour and extremely hot when it was working. I would just about bet a week’s This tuning capacitor is all that remains of the au­thor’s first mains-powered receiver. The set used large block capacitors for smoothing the high tension rail – common practice prior to the advent of the electrolytic capaci­tor. 62  Silicon Chip wages that it was an E406. A couple of other valves were silvery looking 5-pin triodes and there must have been an old 280 rectifier or the like in the line-up as well. The chassis was a metallic bronze colour which seemed to be pretty classy at the time. No doubt, it was just one of those cheapies that were made in the early depression years. Block capacitors This old AC receiver had two volume controls (one being the reaction control), a feature that was not uncommon in those days. It also had two large pressed steel covers mount­ed on top of the chassis and these housed the power transformer and block capacitors. It was that can full of capacitors that finally caused the demise of my pride and joy and the set was eventually cannibalised for spare parts. This block capacitor contains three separate 0.5µF capacitors & their capacitance is clearly marked on the side. In this in­stance, each capacitor is separate & none is connected internally to the case. VINTAGE RADIO We are moving in February 1994 MORE SPACE! MORE STOCK! Radios, Valves, Books, Vintage Parts BOUGHT – SOLD – TRADED Block capacitors were usually housed in large metal cans. The “Chanex” can at left houses three 0.5µF capacitors, while to its right are a 4µF capacitor (middle) and two 1µF capacitors. Chanex capacitors were made in Australia. Send SSAE For Our Catalogue WANTED: Valves, Radios, etc. Purchased for CASH RESURRECTION RADIO Call in to our NEW showroom at: 242 Chapel Street (PO Box 2029), Prahran, Vic 3181. Phone: (03) 5104486; Fax (03) 529 5639 EXCITING CAREER OPPORTUNITY IN Sales Management FOR THE ELECTRONIC COMPONENTS INDUSTRY This old block capacitor has suffered a terminal internal disor­der. No doubt something like this happened to many block capaci­tors when the paper dielectric broke down and allowed them to short circuit. Many early sets used block capacitors. These units were nothing more than paper capacitors in metal cans instead of the cardboard tubes that were to become the norm in later years. Although the term “block capacitor” strictly refers to metal-cased paper capacitors of quite large size, the comments made in this article include all metal-cased paper capacitors, even the smaller sizes. AC-operated receivers required much larger capacitors than any battery set had needed up until that time. Mica capacitors of relatively small sizes were adequate for battery sets but this situation changed with the advent of mains-powered radios. Initially, paper capacitors were used in the high tension filter instead of the electrolytics that were to become common a few years later. A pair of 4µF paper capacitors did a reasonable job of smoothing out the mains hum when used in conjunction with a loudspeaker field coil (the latter acting as a choke). Unfortunately a pair of 4µF paper capacitors take up a sizable amount of space. It was common practice at this stage of receiver development to place all the big bulky capacitors in a large pressed steel can instead of having them situated through­out the circuit as would be the case a few years down the track. When hot wax, smoke and ominous rumbling sounds poured forth Location: Chatswood, Sydney, NSW Sales: Territory NSW and Qld. Altronics Distributors of Perth, Western Australia have a position for a dynamic young person for their Sydney Office. Applicants should be conversant in general purpose electronics and be familiar with common electronic components. Formal qualifications in Sales and/or Management would be an advantage. A current drivers' licence and a reliable vehicle is required. The successful applicant will be appointed initially as Assistant Sales Manager with a view to promotion to the position of Manager NSW and Qld in approximately 12 months. This is an exciting and rewarding career in Electronics. Apply to Colin Fobister, Sydney Office. Phone: (02) 417 8938; Fax: (02) 417 2670. August 1993  63 This view shows the contents of a typical block capacitor. This one contained five individual units which could only be connected as a single unit into the circuit. The can formed a common chas­sis connection for all five capacitors. from my old regenerative’s capacitor box, it appeared as though the end had come. Knowing what I know now, I guess it wouldn’t have been a difficult problem to repair but as a 14-year old, it seemed like the end of the world. What a terrible feeling to see 30 shillings self-destruct before your eyes. At a rough guess, I would say that the input capacitor on the high tension filter developed a short circuit. This is not an unknown happening, even with electrolytics, and a sure sign of this problem is the rectifier anodes glowing red. Block capacitors are no different to any other old paper capacitor and require exactly the same treatment. The difference in size between a 4µF block capacitor and a couple of modern 22µF 450V electrolytics is illustrated by this photograph. Fitting modern capacitors into an old can is easy as far as space is concerned but getting the cans apart without wrecking them can be another matter. That’s right! Discard them completely and replace with modern equivalents whether they be polyester or electrolytic. There is no room in any of my receivers for leaky, troublesome 60year old paper capacitors. Early paper capacitors were made in two types: inductive and non-inductive. The inductive type was suitable only for some applications and could not be used if the capacitor was required to pass RF signals. Rolled foil capacitors were made non-inductive by a very simple trick. The metal foils were made slightly wider than the paper dielectric and offset slightly relative to each other, so that each protruded from one end of the roll. A connection was then Despite its age (at least 60 years), this capacitor still reg­isters it true capacitance on the meter. How it would perform with 250V across it is quite another matter. 64  Silicon Chip made to each foil by means of a rivet which connected all the turns of the foil together. Block capacitors vary greatly in size. Some are relatively small in size and capacity while others, as previously discussed, are quite large. Many of the larger capacitors are not singular in construction but have multiple units inside them. In fact, they can have as many as four or five separate capacitors in the one casing. Some electrolytic capacitors were also built into metal cans, usually in pairs. In other instances, they were packaged in cardboard containers. Common problems There is a reasonable possibility of encountering block capacitors in any mains-powered radio from the late 1920s to the end of the 1930s. A 1939 German SABA receiver I worked on recent­ly used quite a large block capacitor. One problem frequently encountered when replacing block capacitors is that, in some instances, there are no identifying markings on the can to indicate the capacity or the voltage rating of the capacitor. Some are clearly marked but others are not. This can be a problem at times but usually a solution can be found. Often, particularly where quite large capacitances are involved, it doesn’t make a great deal of difference if the replacement capacitor is half or double that of the original value. I have cut 0.5µF capacitors out of circuit while a receiver is working only to find that their removal makes no apparent difference to the set’s operation. In this case, virtually any size replacement capacitor would work OK. On the other hand, capacitors from some parts of the circuit need to be of a partic­ular capacitance or fairly close to it. Usually however, the capacitance is not critical and a ballpark value will work just as well. A substitution box can be a great help when replacing capacitors of unknown value. One way out of the unknown value dilemma is to measure the old capacitor with a capacitance meter. Although an ancient paper capacitor may be leaky, it will usually register its value with reasonable accuracy on a ca­pac­ itance meter. A capacitance meter tests a capacitor at a potential of only a few volts and any leakage at those levels is usually only slight. It can behave quite differently when 250V is applied to it, however. If a capacitor fails the meter test, its value can often be guesstimated by its physical size. The capacitance meter can also be very handy when replacing those larger blocks which contain four or five separate capaci­ tors. If the capacitance value of each unit can be determined, then their substitution is much easier. Multiple block capacitors come in two types: some have a number of different leads coming from them, while others have connection lugs at the top. With the first type, each wire con­nects to one contact of an internal capacitor, while all the other contacts share a common connection to the inside of the can. In other words, bolting the can to the chassis effectively grounds one side of all the capacitors. Thus, if there are four wires coming from the can, then there are four capacitors in the block and the can is the chassis connection. The other type does not have an internal common connection to the can and individual units can be connected singularly or in parallel as required; eg, the 1.5µF block capacitor shown in one of the photographs can be wired into the circuit as a single 1.5µF capacitor, as three 0.5µF capacitors, or as two capacitors with values of 1µF and 0.5µF. When replacing block capacitors, there is no reason why the new capacitors cannot be placed inside the old These two block capacitors have values of 4µF (left) & 6µF. Block capacitors were very large by today’s standards & they took up a considerable amount of space. Many early tubular paper capacitors carried the inscription “non inductive” to distinguish them from earlier inductive types. They used an extended foil construction similar to that used for modern paper & polyester capacitors. can if so desired. Sometimes, however, this is easier said than done because the can may prove difficult to open without wrecking it. In my old 3-valve Seyon, the 280 rectifier originally teamed up with two 1µF paper capacitors which were used in the high tension filter. Unfortunately, such a small amount of ca­ pacitance does not do the job particularly well and the hum level is quite objectionable. When restoring the set, the original Philips capacitors showed considerable leakage when tested and they were replaced with modern 1µF 350V electrolytics. Being relatively inexperienced in valve radio repairs at the time, it never occurred to me to increase the capacitance. There was plenty of room inside the cans to accommodate larger units which would have greatly reduced the mains hum. In summary then, block capacitors should not present any real problems for vintage radio repairers. They are simply paper ca­pacitors that should be replaced if a restoration is to be effec­tive and reliable. Whether or not the original can is used to house the replacement capacitors is entirely up SC to each individu­al restorer. August 1993  65 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 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 AMATEUR RADIO BY JAMES MORRIS, VK2GVA A look at satellites & their orbits Amateurs are in the privileged position of having access to experimental satellites which provide a range of techni­cal & operational challenges. This month’s article discusses some of the basics of satellite orbits. The laws of planetary motion were first described by Kepler and Newton in the 17th century and they also apply to the motion of satellites around the Earth. Kepler’s first law states that the orbit of a satellite is an ellipse (Fig.1a). The satellite’s closest point of approach is called the perigee, while the apogee is the orbital point furthest from the Earth. The shape of the ellipse is determined by the semi-major axis (a) and the eccen­tricity (e). When the eccentricity is zero, the shape of the orbit is circular. Kepler’s second law states that equal areas are swept out in equal times by the satellite’s radius to the Earth, so that the satellite’s velocity as seen from the Earth will vary, being maximum at the perigee (Fig.1b). For circular orbits, the veloc­ity of the satellite is constant. Kepler’s third law describes the way in which there is a fixed relationship between a satellite’s height and its orbital period, with smaller orbits containing faster moving satellites – see Fig.1c. Kepler’s laws, in conjunction with Newton’s laws, can be used to fully describe the orbit of a satellite around the Earth, resulting in a mathematical model with six constant terms. These constants are called orbital or Kepler­ ian elements. The inclination of an orbit is the angle between the orbi­tal and equatorial planes (Fig.2a). When a satellite moves in the same direction as 72  Silicon Chip the Earth’s rotation, it is said to be in a prograde orbit. Satellites which follow retrograde orbits move in the opposing direction (Fig.2b). The most commonly used orbit is geostationary, where the satellite moves at the same speed as the Earth’s rotation, and has an inclination of 0 degrees. A geostationary satellite appears at a fixed location in the sky, so that it can provide a continuous communications link between ground stations within its “footprint”. The use of satel­lites in geostationary orbit for global communications was envis­ aged by the scientist Arthur C. Clarke in 1945. His calculations, based on Kepler’s laws, showed that geostationary satellites would orbit the equator at a height of approximately 35,786km. This unique orbit is known as the Clarke belt, and contains many satellites which are “parked” in “slots” above the equator. The Optus series of satellites are located in the assigned slots: 156°, 160° and 164° east. Recently, there have been proposals made by amateur groups to establish geostationary communications links with the develop­ment of the Phase IV series amateur satellites. This new genera­tion of Hamsats could provide some very interesting possibilities for long distance voice, packet and image communication. Polar orbiting satellites pass over the north and south polar regions (Fig.2b). The NOAA weather satellites follow polar orbits which are also sun-syn- chronous, passing over the same points at the same local times each day. This allows the same areas of the Earth to be imaged under reasonably consistent lighting conditions. The footprint of a sun synchronous polar orbit satellite overlaps itself during successive passes. SARSATS (search and rescue satellites), which often share a common space platform with weather satellites, utilise this footprint overlapping to obtain accurate readings for the position of ELT (emergency locator transmitter) and EPIRB (emergency position indicating radio beacon) devices. A rather specialised orbit is used by the Russian Molniya satellites, which are inclined at approximately 64°. Their orbits are optimised to provide telecommunications for areas located at high northern latitudes, as geostationary satellites cannot be seen from locations above 81° north or south. Moln­iyan orbits are also highly eccentric, and remain within view of targeted regions for many hours; a specific appli­ c ation of Kepler’s second law. Low Earth orbits Low Earth orbit satellites (LEOS) follow fast, almost circular orbits and are relatively inexpensive to implement (approximately 1/20th the cost of geostationary). LEOS orbits are used extensively by small satellites which gather atmospheric and other scientific data. Many amateur satellites make use of near-polar low Earth orbits with an inclination of greater than 80°. Amateur LEOS are able to rapidly upload and download information around the world, making them ideal vehicles for packet BBS (bulletin board systems), which have been used for primary international communications during disasters. The excellent MAJOR AXIS, A ORBIT SATELLITE EARTH PERIGEE APOGEE SEMI-MINOR AXIS, b MINOR AXIS, B world-wide coverage and low cost of LEOS also provides a strong commercial potential. Currently, there are a number of proposals for global personal communications on the corporate drawing boards. A disadvantage of LEOS is the amount of tracking required at the ground, as they tend to move rather quickly. This is partially offset by the fact that the satellites are closer to the Earth, with the associated increase in signal strengths. Lower gain antennas may be used, which often have broader direc­tional characteristics and less critical aiming requirements. Orbital perturbations The Earth has a slight bulge at the equator and a flatten­ing of the poles; its true shape is as an oblate spheroid. This complicates the determination of satellite motion, as Kepler’s laws assume the Earth to be perfectly spherical. The Earth’s mass is not evenly distributed, producing minor variations in the gravitational forces acting on its satellites. The difference in gravity experienced at two points in an orbit produces a ‘gravity gradient’ or slope. A satellite will be more attracted to one of these points, and accelerate towards it. Geostationary satellites are attracted towards the positions of 75° E or 105° W, and require regular ‘station keeping’ to prevent their inevitable slide towards what are commonly referred to as satellite graveyards (orbital points situated between gravitational ‘bulges’). A recent example of this effect occurred in 1992, when two ARABSAT series spacecraft suddenly ran out of station keeping fuel. They began to drift along the Clarke belt towards 75° E and although still otherwise operational, were eventual­ly powered down to prevent interference to other satellites. The gravitational fields of the sun and moon significantly affect geostationary satellites, by inclining their orbits away from the equator. The LEOS are less affected, due to the in­creased effect of the Earth’s gravitational field at close range. Again, station keeping is required to correct the orbit of satel­lites affected, by the firing of onboard thrusters in the op­posite direction of the drift. At heights of below approximately 1000km, satellites are affected by atmospheric drag, which serves to reduce the eccen­tricity and apogee height of their orbits. Atmospheric drag can be a particular problem for low Earth orbiting satellites. Attitude The orientation of a satellite in its orbit with respect to the Earth is its attitude, which is maintained through attitude control. This differs from station keeping in that the shape of the orbit is not of prime concern. Attitude control is used for local stabilisation. To simplify the stabilisation of satellites in low orbits, the gravitational field of the Earth is utilised. After launch, the spacecraft gradually aligns itself vertically with the Earth, so that the antennas are pointing in the desired direction. During this time, amateurs monitoring the satellite’s beacon may notice periodic fading as the satellite ‘oscillates’ around the stable attitude. This effectively modulates the beacon, an effect used to help determine the status of the satellite in the initial orbit stage. SEMI-MAJOR AXIS, a 2 a b a ECCENTRICITY OF ORBIT, e = 2 PERIGEE HEIGHT = a(1 - e) 6378km APOGEE HEIGHT = a(1 + e) 6378km (a) SATELLITE NEAR PERIGEE V2 A2 T2 A1 PERIGEE T1 APOGEE V1 SATELLITE NEAR APOGEE EARTH ORBIT (b) PERIOD ~= 105 MINUTES HEIGHT = 1000km r V ~= 26000km/h EARTH r= 6378km LOW ORBIT HIGH ORBIT HEIGHT = 35786km VELOCITY ~= 11000km PERIOD = 24 HOURS (c) Fig:1: this diagram illustrates Kepler’s Laws of planetary motion which also describe the orbits of satellites around the Earth. Note that at apogee the satellite is travelling at its slowest speed. Geostationary satellites, which generally carry telecom­ munications and broadcasting, are too far from the Earth for gravitational torque stabilisation to be efficient. These satel­lites are stabilised by two basic methods. An entire satellite may be set spinning, in the manner of a gyroscope. The antennas must then either have circular symmetrical radiation patterns, or be placed upon a non spinning (despun) platform. Alternatively, internal stabilisers may be used, in the form of momentum wheels, which provide the necessary overall stabilising torque. Satellites which use this August 1993  73 N The point directly underneath the satORBITAL PLANE ellite at the Earth’s SATELLITE surface is called the sub satellite point (SSP). Radio frequenEQUATORIAL cies received at the PLANE EARTH i°  ground appear to vary from high to low i° = INCLINATION during the satellite’s pass overhead, due to the effect of Doppler (a) shift (Doppler shift is a phenomenon N associated with the POLAR ORBIT behaviour of waves HEIGHT ~= 1000km pro­p­a gated from a mov­ing transmitter). The nominal freORBIT quency of a particular beacon or transponder (transponders are HEIGHT 35786km EQUATOR devices which, upon receiving signals, 5F 8 180 o 164 o automatically issue 160 o responses) is given 156 o for the TCA, when the Doppler shift is B2P 113 o zero. (b) In the case of satFig.2a illustrates the inclination of a satellite orbit, ellite AO-21, with a while Fig.2b shows the geostationary orbits of the Optus satellites at around 160°E, the Intelsat 5F8 nominal downlink satellite at 180°E & the Palapa B2P satellite at 113°E. of 145.987MHz (FM voice), the received method are called three-axis or body frequency may vary from approximatestabilised. ly 145.990MHz at AOS to 145.984MHz To correct for errors in spacecraft at LOS. The effect of Doppler shift attitude, a variety of techniques are is greater for passes which are more used, such as firing thrusters, accel- directly overhead. erating the momentum wheels, and AO-21 is a LEOS with a near polar employing reaction wheels to absorb orbit of 83° inclination. Apogee and the effects of disrupting forces. perigee heights are 1000km and 958km respectively. The orbital period is Tracking about 105 minutes, and a good pass Tracking a satellite involves locating may last for 20 minutes. The FM voice transponder uses an its position in orbit and determining its motion. This information is referred experimental digital pro­cessing systo the Earth’s motion, so as to provide tem which is used to regenerate weak pointing coordinates (look angles) for or distorted signals. The downlink a station’s antenna system. Times at frequency, as mentioned, is approxiwhich the satellite will be visible to mately 145.987MHz. the station are calculated, and the A beacon on 145.822MHz (CW) is feasibility of communications with quite useful for tracking, even with the satellite during these times are an FM receiver. Due to the relatively evaluated. wide­band nature of the FM signal, it is The time at which a satellite appears not necessary to use an expensive mulover the radio hori­zon, and beacons timode rig to tune in. Try 145.990MHz or other transmissions are received, as a starting frequency on which to is known as the acquisition of signal monitor the satellite. (AOS). The time of closest approach Some handheld transceivers can (TCA) and loss of signal (LOS) then be tuned in 5kHz and 12.5kHz steps, describe the completion of the pass. giving a series of three frequencies 74  Silicon Chip (145.990MHz, 145.9875MHz and 145.985MHz) to track Doppler shift. Receive antenna requirements for this satellite are mini­mal and a ¼-wave ground plane should give good results. The uplink frequency for this transponder is 435.016MHz, making it “mode B” in hamsat terminology. The uplink requirements are a little more involved. Power levels in the range of 25W are con­sidered the minimum useful level, although AO-21 has been worked with a dual band hand-held (WA5ZIB/KB8KVY). By using a predictive tracking program, it would be possi­ble to determine the best time to listen out for the satellite, although it is also possible to just tune in and wait. After the first pass, add 105 minutes to the AOS to give an indication of when the next pass might be (given that the satellite will be in view at the next pass). For those with a computer, a tracking program is essential for detailed orbital analysis and more advanced satellite experimentation. These programs require a set of up-to-date Keplerian ele­ ments for each satellite being studied, which are available from bulletin boards in a standard format. Further information Amateur satellite information is avail­­able from AMSAT Aus­tralia. Their HF net meets on Sundays at 1000z (UTC). Net frequencies are 7.064MHz and 3.685MHz, depending on conditions. AMSAT Austra­lia is at GPO Box 2141, Adel­aide 5001. Public domain satellite track­ing programs and NASA-issued Kep­ler­ian elements are available from the Satcom Australia BBS on (02) 905 0849. References (1). The Inclined Orbit Satellite Tracking Guidebook, M. Long & J. Keating, MLE Inc, 1993 (available from AvComm Pty Ltd, PO Box 225, Bal­gow­ lah, NSW 2093). (2). Satellite Communications Systems, G. Maral & M. Bousquet, John Wiley & Sons, 1986. (3). Satellite Communications, T. Pratt & C. Bostian, John Wiley & Sons, 1986. (4). Advanced Electronic Communications Systems, W. Tomasi, Prentice Hall, 1987. (5). Satellite Communications, D. SC Roddy, Prentice Hall, 1989. 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) ❏ $A84 ❏ $A42 ❏ $A105 ❏ $A53 ❏ $A130 ❏ $A65 ❏ $A130 ❏ $A65 ❏ $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 August 1993  75 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 PRODUCT SHOWCASE Acorn’s 16-bit PocketBook If you’re always on the move but still need information at your finger tips without the bulk of a portable PC, then take a look at the new PocketBook from Acorn Computers. It measures just 63 x 43 x 6mm and runs off two ‘AA’ cells or an optional 9VAC 150mA plugpack. It’s small enough to fit inside your coat pocket yet powerful enough to handle a wide range of tasks. The PocketBook comes with several software packages built-in including word-processor, spelling checker, spreadsheet, clock with alarm, scientific calculator and database. Any of these can be selected by using eight softkeys which form part of a graphical user interface similar to Microsoft Windows. It uses a CMOS variant of the 8086 running at 3.54MHz and also includes optional internal hard disc storage and 256Kb of main memory. Designed with students at school and university in mind, the Acorn PocketBook is aimed at bringing the world of computers closer to students who can not only do their homework and assignments at home but down­ load them with an optional serial link to other Acorn 32-bit micros at school. Low cost pH meter This low cost pH meter is not much larger than a bulky felt-tip pen. It has a small liquid crystal display and comes with a buffer solution for calibration. Using it is simple. Pull the protective cap off the bottom of the unit and switch it on. Dip it in the solution to be measured and stir gently for a few seconds. Then read the LCD, turn the unit off and replace the protective cap. Calibration is done with the supplied buffer solution and adjustment is via a small screwdriver which is supplied. The unit will read pH from 0-14.0 with resolution of ±0.2pH. It uses four 1.4V mercury batteries (675H or equival­ent) and battery life is estimated at 1000 hours. The serial link can transfer data at a fast 1.54Mbits/second. It’s also suitable for professionals who need access to numbers and data without the bulk of even a laptop PC. The unit has a 58-key softkey QWERTY keyboard, an 8-line x 40- character LCD and a back-up battery to retain data when you change the main batteries. You can also install solid-state drives on which you can save your files using the menu button on the keyboard, which brings up a menu system similar to Windows. Files are saved in MS-DOS format with directories and 2-part filenames, allowing users familiar with PCs to be quickly up and running. You can also print out files with the optional Centronics parallel printer interface and include infor­mation such as page set-up and fonts. The PocketBook comes with two well-produced and comprehen­ sive manuals and retails for $695. For schools, the deal is $599 which is a great price for what essentially is a computer, not a pocket organiser. If you’d like more information on the Acorn PocketBook or other Acorn products, call Peter Revell at Acorn Computer Australia on Melbourne (03) 419-3033. Surface mount transistors for radios The unit will have wide application in pH measurement of swimming pools, aquariums, water quality, aquaculture and so on. The unit is available from all Dick Smith Electronics stores and is priced at $129.00 (Cat. Q-1403). These new SOT-323 and SOD-323 surface mount transistors and diodes are only 1.25mm wide and between 1.7mm and 2mm in length. Siemens is the first company in Europe to supply tuner diodes of this design. The components are also available on 8mm tape for series equipment production. August 1993  79 For further information, contact Mark Walsh, Siemens Ltd, Electronic Components Department, 544 Church St, Richmond, Vic 3121. Phone (03) 420 7345. Weatherproof loudspeakers Pictured above are a pair of weatherproof loudspeakers which are made in Australia. The enclosure is based on a very strong aluminium extrusion which is finished in powder-coat enamel, while the end-caps are made of Luran UV-resistant plastic. The speaker grille is made from steel mesh that is also powder coat­ed. Inside, the two speakers are coax­ ially mounted – a small dome tweeter and a carbon-fibre woofer, both with Kaptan high-temperature voice coils and Barium ferrite magnets. The enclosure is ported and its stated frequency response is from 110Hz to 15kHz. Branded Redback, these rugged loudspeakers may be used in a wide range of applications such as inside or outside the home, in hotels, clubs, 80  Silicon Chip schools and other public address uses. Several models are available with either 30 or 60 watt power handling. For domestic use there is a model with 8-ohm impedance, while for PA use a unit with an in-built 100V line transformer is available. This has multiple taps to allow it to be used at maximum power levels of 10, 20 or 30 watts in the case of the lower power model, or 20, 30 or 60 watts for the higher power model. All models are also available finished in white rather than black. Further information on the Redback range of weather­proof loudspeakers can be obtained from any Altronics stockist or from Altronics Distributors, 174 Roe Street, Perth, WA 6000. Phone (09) 328 2199. Digital sound level meter How often have you wanted to measure the loudness of sounds you are experiencing? Perhaps you have wanted to measure the sound level of passing traffic (especially those noisy garbage trucks late at night) or perhaps you have wanted to know just how quiet your hifi listening room is. And for your neighbours’ sake, you might also want to know how loud it is when you turn up the volume on your amplifier. For more serious applications, you might want to measure sound levels inside and outside factories, or you may want to measure the exhaust noise from trucks to make sure they comply with noise regulations. For all those tasks you need a sound level meter and this model from TES is just the ticket. The Tes 1350 sound level meter has a 3½-digit liquid crystal display which indicates sound levels in dB. The instru­ment has two ranges: 35-100dB (LO) and 65-130dB (HI). Measurements can be taken with either A or C weighting and the response can be set to fast or slow. In the fast mode, the meter averages sound over a period of 0.2 seconds, while in the slow mode it averages sound over a 1.5-second period. More importantly, the meter has a “max hold” facility so that you can record the loudest sound over a short period of time; the stored reading reduces by less than 1dB every three minutes. An internal calibration signal at 1kHz is also provided, allowing you to calibrate the meter for a level of 94dB. Quoted accuracy is within ±2dB and resolution is ±0.1dB. Frequency response from the electret microphone is typically from 30Hz to 12kHz. For acoustic analysis applications, the meter has AC and DC outputs available via a 3.5mm stereo jack socket. The meter is powered from a 9V alkaline battery and the battery life is quoted as approximately 100 hours. It is supplied with a foam-lined carrying case and comes with a miniature screw­driver for calibration. The TES 1560 digital sound level meter is available from Jaycar Electronics stores at $259.00 (Cat. QM-1580). CD-ROM database for all semiconductors IC/Discrete, the world’s largest semi­­­ conductor database, is now available on CD-ROM at a subscription price of $4,500. This price includes the IC/Discrete parameter database and 52 CD-ROM image discs containing scanned manufacturers’ data sheets (scanned at 300 dpi). Any page of information can be printed out on any standard laser printer. Images may also be downloaded to disc for use in CAD systems. The database contains around 1,500,000 devices and their parameters (940,000 currently available and 530,000 discontinued devices), 1,900,000 suggested alternatives, 1200 manufacturers and 664,000 data sheet pages. It also includes Australian and overseas distributors, pinout information and the ability to add in-house part numbers. The database may be searched using eleven different criter­ ia, including part number, generic number, characteristic parame­ters, function, keyword, manufacturer’s part number and so on. System requirements to run IC/Discrete are an IBM or compatible 80286 AT or better, 640Kb RAM or more, a hard disc drive with at least 3Mb free, a VGA monitor, DOS 3.1 or later and a CD-ROM drive with controller card. For further information, contact Greg Jenkins, Hintons Information Services, 10 East Parade, Eastwood NSW 2122. Phone (02) 804 6022. Hewlett-Packard’s colour inkjet plotter CAD users will be interested in the new HP DesignJet 650C plotter, a colour and monochrome inkjet plotter, intended for people who typically plot 20 or more designs per day. The HP DesignJet 650C plotter is available in two models – the AO size (36 inches wide) for $16,999 and the A1 size (24-inches wide) for $13,998. Prices have also been reduced on the AO and A1-size HP DesignJet 600 mono­chrome inkjet plotters to $12,688 and $10,688, respectively. The plotter’s four ink cartridges, in cyan, yellow, magenta and black (CYMK), let users create a full range of colours. Users can design detailed plots that use colour to differentiate data and highlight specific areas. For instance, colour can be used to show various layers of electronic circuits or changes to an existing design plan. The plotter features three modes of operation – draft, final and enhanced – for monochrome and colour, so users can choose from a variety of levels of speed and print quality. The highest print quality is 300 dots per inch (dpi) colour and addressable 600 dpi monochrome. In the enhanced colour mode, the plotter takes a second pass to produce smooth, even area fills. For further information, contact an authorised dealer or Hewlett-Packard by phoning (03) 272 2651. VIDEO & TV SERVICE PERSONNEL TV & VIDEO FAULT LIBRARIES AVAILABLE AS PRINTED MANUALS $90 EACH + $10 DELIVERY BOTH MANUALS VIDEO & TV $155 + $15 DELIVERY OR AS A PROGRAM FOR IBM COMPATIBLES $155 + $10 DELIVERY FOR MORE INFORMATION CONTACT TECHNICAL APPLICATIONS FAX / PHONE (07) 378 1064 PO BOX 137 KENMORE 4069 August 1993  81 THE SOUTHERN A single board Z80-based compute Here is a single board computer designed especially for the 1990s generation of students. With a series of addon boards, smart sockets, fully commented Monitor & an intelligent EPROM emulator, it can teach many aspects of microprocessor & microcon­troller techniques of programming. By PETER CROWCROFT & CRAIG JONES 82  Silicon Chip board computer (SBC) in the early 80s will remember how quickly their limitations were met. The worst was that when you had written a program of about 6080 lines of code, the calculation of forward and backward subroutine jumps and the actual data entry became a real chore. Second, there was no easy way to store your work when you turned off the power to the board. Third, some SBC suppliers did not publish their Monitor and so disregarded a whole area of teaching programming and worked against the very aim that the SBC was supposed to promote. With the advances in electronics over the last few years there was an opportunity to launch a modern, updated SBC. It had to meet all the above objections. But it had to be more; it had to be able to introduce students to the real world of current day µP and µC programming techniques. We wanted to be able to take a student who had never programmed before and after a few hours (after the kit was constructed) have them writing programs using Monitor system calls and software and KEYBOARD DISPLAYS Z80 POWER SUPPLY MEMORY DECODER ROM RAM Fig.1: the concept of the Southern Cross is simple with a Z80, RAM, EPROM & decoding. also look at how to use the routines in the Monitor for your own programs and how to do software and hardware single stepping to debug your own programs. Full documentation on programming the Southern Cross SBC is contained in the user manual which comes with the kit. Features The Southern Cross comes on a large, single-sided PC board measuring 248 x 130 mm. It is designed around a Z80 microproces­s or and nine CMOS ICs. The system runs at 4MHz but a speed con­ trol has been built into the board for those times that speed control is more efficiently carried out in hardware than in software. All the circuit features of the Southern Cross are shown in the block diagram of Fig.1. The complete circuit is shown in Fig.2. In the bottom lefthand corner of the circuit is the 5 x 4 keypad and 74C923 keyboard encoder (IC9). The 74C923 continuously monitors the keypad matrix, looking for a keypress. When one is detected, it produces a 5-bit number and its pin 13 output (Data Available) is set high. Two capacitors are connected to the 74C923. C9 sets the speed at which the chip scans the keypad matrix while C11 provides keypad de­bounc­ing. The 5-bit data from IC9 is buffered by IC8, a 74HC244 octal Tristate buffer, which feeds the data bus. The Z80 N CROSS er for the 1990s hardware interrupts, almost before they knew it. In the first article of this series, we will introduce the Southern Cross SBC, its features, its circuit diagram and de­scribe the construction. In future articles we will look at how to connect it to a Personal Computer to aid in code development and introduce two add-on boards which give the Southern Cross SBC access to the outside world. Further on, we will introduce an EPROM emulator and look at how it can be used with a PC for program development. We will I/O DECODER CLOCK controls IC8 through the I/O address decoder chip IC3. The keyboard buffer chip (IC8) has two unused input lines. These have been taken to connector CN4 where they are available for other uses. Output interface The output interface consists of six 7-segment common cathode LED displays and an 8-ohm loudspeaker driven by transis­ tor Q7. Latch IC1 drives the display segments and decimal points via two resistor networks, SIL1 & SIL2. Latch IC4 drives the common cathodes of each display as well as the speaker via seven NPN transistors. Both latches IC1 & IC4 are controlled by I/O decoder chip IC3. IC4 has one unused output line (pin 16) which is taken to connector CN4, as is the speaker output line. The core of the Southern Cross consists of the Z80 (IC6), the I/O address decoder (IC3), memory decoder (IC2), RAM (IC7) and EPROM (IC6). The reset circuit consists of pushbutton switch S21 in conjunction with resistor R19 and capacitor C15. Pressing the reset button resets the Z80 CPU and the display latch IC4. R19 and C15 also provide the power-on Fig.2 (following page): this is the complete circuit of the Southern Cross comput­er. It has a 5 x 4 keypad for data entry & program execution & a 6-digit display as the major output interface. August 1993  83 ▼ A NYONE WHO USED a single 84  Silicon Chip August 1993  85 CN1 K 1uF SIL1 LED1 0.1 1 SW1 100pF Memory decoding The Z80 has a full address space of 64K and 16K of this is used for memory, 8K for the EPROM and 8K for RAM. Depending on which section of memory is being addressed, the EPROM or RAM must be selected and this is done by IC2, a 3-to-8 line decoder. Three address lines, A13, A14 & A15, are used as input to IC2 and two of its output lines become CHIP SELECT signals for the memory chips; the EPROM from 0000H to 1FFFH and RAM from 2000H to 3FFFH. Each input/output (I/O) device needs one I/O port address for itself. To get this unique address, we need to decode one of the 256 I/O addresses provided by the Z80 and this is done by IC3, another 3-to-8 line decoder. The connection of address line A7 to the enable (E3) pin 6 of IC3 effectively divides the memory map into two halves. If A7 is low, the decoder is disabled and no I/O ports on the Southern Cross are selected. The upper half of this memory map is further divided in half by 86  Silicon Chip 1k 1k Q6 1k Q5 CN4 0.1 100  100k 100k S17 S1 S2 S3 S4 S18 S5 S6 S7 S8 S19 S9 S10 S11 S12 S20 S13 S14 S15 S16 IC9 74C923 IC8 74HC244 0.1 3.3uF P1 0.1 1uF S21 Fig.3: this is the component overlay of the Southern Cross. It uses a single sided board & 54 links to keep costs low. Take care with the orientation of the keypad switches (S1-S20) – see text. reset circuit. It holds the reset line at ground immediately power is applied to the board. C15 then charges up via R19 and the line goes high (and the reset is removed) after several milliseconds. Q4 1 22k 10k 2.2k RESET PAD 74HCU04 560  10M 22k 22k 22k 22k 22k 33pF Q3 B1 0.1 1 DISP6 1k 1 XTL1 DISP5 Q7 IC7 6264 IC5 Z80ACPU IC6 27C64 1 33pF Q2 IC4 74HC273 1 DISP4 1k SIL2 1 CN3 DISP3 1k 10uF Q1 0.1 1k 0.1 DISP2 IC1 74HC273 1 IC3 74HC138 1 IC2 74HC138 DB1 10uF 330  7805 CN2 AC/DC DISP1 1 1000uF address line A6, connected to enable pin 4 (E1) of IC3. Thus, 64 locations from 80H to BFH are available to the Southern Cross. If A6 is high, then a quarter of the address space, from C0H to FFH, is available for use by other devices. To get eight I/O ports from this 64 block, address lines 0, 1 & 2 are decoded by IC3. You can see seven decoded ports, 80H to 86H, on the diagram. Ports 80H to 83H are taken to the expansion port. Ports 84 and 85 communicate with the displays; port 86 connects to the keyboard. Port 87H is not used. Clock circuit As mentioned above, the clock frequency for the Z80 is 4MHz and this is provided by an oscillator built around a 74HCU04 inverter and a 4MHz crystal. For those applications where a slower clock is desirable, a second variable oscillator is pro­vided. This is built around three inverters (IC10d-f) and is varied with trimpot P1. The change over from the fixed to the variable clock circuit is via the Fast/Slow switch SW1. Expansion connectors There are three expansion sockets. On the right of the board is CN4. This contains two input lines and two output lines, as well as ground and +5V lines. As we shall see later in this series, serial downloading of programs from a PC comes via this socket. Experiments which can use single bits can also use this connector. At the top centre of the board is the I/O connector CN1 which has connections to ports 80h to 83h, the reset line and supply connections. Finally, on the left of the board all the address, data and Z80 control lines are taken to a 40-pin header connector, CN3. Expansion projects too big to be accommodated at the other sock­ ets can be performed using the signals available here. Monitor program The Southern Cross SBC can do nothing on its own. It re­quires a set of instructions in the form of a program to tell it what to do. This is stored in the 27C64 EPROM and is called a “monitor”. The basic function of a “monitor” is to allow memory locations to be viewed and changed and to allow program execu­tion. It also contains many useful programs which you can use to develop your own programs. This use of the monitor will be dis­cussed in detail later in this series. The fully commented monitor for the Southern Cross SBC is supplied on a floppy disc with the kit. It can be printed out for study. It is a deliberately simple monitor without program tricks or cryptic code. Its purpose is to teach, not to impress or confuse the beginner. Programming of the Southern Cross begins with the simple examples listed in the User Manual which comes with the kit. First, one LED segment in one of the six segment displays is turned on. Gradually, the student is shown how to assemble code and enter it into the Southern Cross. Several demonstration programs are built into the monitor. Function 8 (pressing the ‘Fn’ function key then the ‘8’ key) will play a tune. You can then enter your own tune, press Function A and the tune you entered will play. Function C brings up a random 4-digit hex number which you must be find within 20 tries (9 tries is our best). Other Function key assignments include: • Function 0 – start program execution. • Function 1 – ready to receive Intel hex file in serial download. • Function 4 – move a block of memory defined by Function 2 (begin block) and Function 3 (end block) to the address displayed. • Function 5 – calculate a check sum on the block of memory defined by Function 2 (start) & Function 3 (end). • Function 6 – relative branch calculator. • Function B – toggle the speaker off/on. If you get tired of the speaker beeping when you press a key, you can turn it off and have a variable off period of the displays instead. • Function D – test the Relay Board if attached. • Function E – test the 8 x 8 LED dot matrix board if attached. • Function F – brings up the time/ day/date in the Smartwatch socket if attached. Saving programs One of the big problems with SBCs in the 1980s was that when you turned off the power, your programs in RAM were lost. The solution in those days was to build a battery-backed RAM board but these days Dallas Semiconductor has neatly solved the problem with their Smartsocket DS1213B. This can be fitted in the RAM socket underneath the 6264 RAM IC. It has a battery life of 10 years. When power is turned off, the Smartsocket senses this and the built-in battery takes over and all your programs are safely kept in the RAM. Time & date option Dallas Semiconductor also has a Smartsocket of the same physical size which incorporates a time and date function. This is the DS1216B. You can set the time and the date and it is permanently saved in the chip until you alter it. Two simple changes to the board allow the DS1216B to be used. Function F then brings up the time and date on the dis­plays. The date comes up in the standard DD/MM/YY format or you can change a single bit in the Monitor Where to buy the kit The Southern Cross computer kit was designed in Australia for DIY Electronics, GPO Box 904, Hong Kong. The kit containing all the components, documentation and floppy disc with the moni­tor program may be ordered in Australia from Alpine Technology, PO Box 934, Mt. Waverley, Vic 3149. Phone or fax (03) 751 1989. You may pay by Bankcard, Mastercard, cheque or money order. Buyers outside Australia should contact DIY Electronics in Hong Kong. Phone (852) 725 0610. The kit costs are as follows: Southern Cross Computer..............................................................$172.00 Dallas DS1213B SmartSocket..........................................................$55.00 Dallas DS1216B SmartSocket..........................................................$74.00 Technical manual of IC data sheets................................................. $10.00 The kit will be sent to buyers from Hong Kong by registered airmail and this is included in the purchase price. Note that there is no copyright on the PC artwork, program code or documentation and buyers are encouraged to copy and modify the software provided. PARTS LIST 1 PC board, 247 x 130mm 21 keypad switches 1 miniature slide switch (SW1) 1 4MHz crystal 1 5V buzzer Semiconductors 2 74HC273 8-bit latches (IC1,IC4) 2 74HC138 3-to-8 line decoders (IC2,IC3) 1 Z80A microprocessor (IC5) 1 27C64 8K EPROM (IC6) 1 6264 8K static RAM (IC7) 1 74HC244 octal Tristate buffer (IC8) 1 74HC923 keypad encoder (IC9) 1 74HCU04 hex inverter (IC10) 7 BC547 NPN transistors (Q1-Q7) 1 5mm red LED (LED1) 1 7805 5V regulator (REG1) 1 bridge rectifier (DB1) 6 CM1-5615S red 7-segment common cathode displays (DISP1-6) Sockets & connectors 1 40-pin socket 2 28-pin sockets 4 20-pin sockets 2 16-pin sockets 1 14-pin socket 1 16-way rightangle socket (CN1) 1 2.5mm DC socket (CN2) 1 40-way rightangle socket (CN3) 1 6-way header & socket (CN4) Capacitors 1 1000µF 35VW electrolytic 2 10µF 16VW electrolytic 1 3.3µF 16VW electrolytic 2 1µF 16VW electrolytic 7 0.1µF monolithic 1 100pF ceramic 2 33pF ceramic Resistors (0.25W, 5%) 1 10MΩ 7 1kΩ 1 100kΩ 1 560Ω 6 22kΩ 1 330Ω 1 10kΩ 1 100Ω 1 2.2kΩ 2 4 x 100Ω SIL resistor arrays (SIL1, SIL2) 1 20kΩ trimpot (P1) Miscellaneous Heatsink for regulator, tinned copper wire, rubber feet. August 1993  87 The Southern Cross single board computer is intended as a learning tool for those who want to know more about microprocessors. It uses the Z80 8-bit microprocessor & all the other parts are readily available. program to use the Ameri­can MM/DD/ YY format if you wish. The day of the week can also be indicated using the decimal points. Construction The Southern Cross computer is built on a single-sided PC board. The top is screen printed with the component overlay diagram while the copper pattern on the underside has a solder mask which covers all the board except around the solder pads. This makes soldering easier and reduces the risk of solder shorts on the copper pattern. The first thing to do is to place all the components into a container and then check them off against the parts list. The component overlay shows where all the parts go. First, there are 54 links to be inserted. Next, insert the resistors and we sug­gest you check each one for correct value with your multimeter. Your can also insert the two resistor packages, SIL1 and SIL2, at this stage. Sockets are used for all the ICs and they all oriented the same way, with the end notch pointing to the top of the board. Watch the polarity of the electrolytic capacitors, C1, C2, C3, C5, C11 & C15. The buzzer B1 must also be correctly oriented. There are seven BC547 transistors to 88  Silicon Chip be inserted and their case orientation should match the shapes shown on the board overlay. The six LED displays are oriented with their decimal points adjacent to the driver transistors. For LED1, the cathode lead is the shorter of the two and should be at the top of the PC board. The bridge rectifier, DB1, should be inserted so that the “+” symbol on the package is adjacent to the “+” on the PC overlay. The 7805 voltage regulator’s leads should be bent with pliers before it is soldered in place. It is assembled on the board together with its heatsink, as shown in the photograph. Each keypad switch has a flat part on one of its sides. This faces towards the bottom of the PC board as shown in Fig.2. All 21 key switches are identical. Sixteen of the same colour are supplied for the hex numbers 1-F. Now insert all the miscellaneous components such as the Speed and Reset switches, the 20kΩ trimpot P1, the various con­nectors and the 4MHz crystal. Lastly, insert the integrated circuits in their sockets, making sure that they are oriented correctly. When all the components have been installed on the board, check your work very carefully. In particular, check the follow­ing points: electrolytic capacitors around the correct way; ICs in their sockets the right way around; and all the links on the board. We also suggest that you fit four rubber feet to the corners of the Southern Cross PC board. This will prevent the component leads on the underside from damaging your bench or desk surface and will prevent any shorts if you place the board on a metal surface. Now set the Speed switch to the F (fast) position and con­nect a 9V or 12V AC or DC plugpack. The Southern Cross should then beep, the power LED should light and the numbers ‘2000’ should appear in the group of four Address displays. If the board does not work when you turn it on, remember that the problem is almost certainly a mistake you made during construction. The most common cause of kit failure is bad solder­ing or forgetting to solder a pad. Also common is incorrect insertion of components or solder shorting across two pads. Use your multimeter to check that +5V is present at the respective pins of the ICs, as shown on the circuit diagram of Fig.2. If the Southern Cross is completely dead when the power is connected (and LED1 does not come on), then clearly the place to look for faults is around the bridge recti­ fier and the 7805 regulator. Similarly, if some of the board is active and some parts are not, then this will indicate where to SC direct your attention. LED BRAKE LIGHT INDICATOR This “brilliant” brake light indicator employs 60 high intensity LEDs (550-1000mCd) to produce a display that is highly visible, even in bright sunlight. The intensity produced is equal to or better than the LED brake indicators which are now included in some late model “upmarket” vehicles. The LED displays used in most of these cars simply make all the LEDs turn on every time the brakes are applied. The circuit used in this unit can perform in this manner and, for non-automotive applications, it can be customised to produce a number of sweeps (110) starting at the centre of the display and with a variable sweep rate. It not only looks spectacular but also attracts more attention. All the necessary “electronics” is assempled on two identical PCBs and the resulting overall length of the twin bargraph dis­play is 460mm. It’s simple to install into a car since only two connections are required: Earth and the brake­ LASER SCANNER ASSEMBLIES These are complete laser scanners as used in laser printers. Include IR laser diode optics and a very useful polygon scanner ( motor-mirror). Produces a “fan” of light (approx. 30 deg) in one plane from any laser beam. We provide information on polygon scanner only. Clearance: $60 400 x 128 LCD DISPLAY MODULE – HITACHI These are silver grey Hitachi LM215XB dot matrix displays. They are installed in an attractive housing and a connector is provided. Data for the display is provided. BRAND NEW units at a low: $40 LASER OPTICS The collimating lens set is used to improve the beam (focus) divergence. The 1/4-wave plate and the beam splitter are used in holography and experimentation. All are priced at a fraction of their real value: 1/4 wave plate (633nM) ..............................$20 Collimating lens sets ..................................$45 Polarizing cube beam splitters ....................$65 GREEN LASER TUBES We have a limited supply of some 0.5mW GREEN ( 560nm) HeNe laser tubes. Because of the relative response of the human eye, these appear as bright as about a 2mW red tube: Very bright. We will supply this tube and a suitable 12V laser power supply kit for a low: $299 CCD ELEMENT BRAND NEW high sensitivity monolythic single line 2048 element image sensors as used in fax machines, optical charachter recognition and other high resolution imaging applications: Fairchild CCD122. Have usable response in the visible and IR spectrum. Supplied with 21 pages of data and a typical application circuit. $30 INFRARED TUBE AND SUPPLY These are the key components needed for making an INFRARED NIGHT VIEWER. The tubes will convert infrared light into visible light on the phosphor screen. These are prefocussed tubes similar to type 6929. They do not require a focus voltage. Very small: 34mm diameter, 68mm long. All that is needed to make the tube light connecting wire. The case for the prototype unit which would be suitable for mounting on the rear parcel shelf, was mainly made from two aluminium “L” brackets that were screwed together to make a “U” section. A metal rod and its matching holders (commonly available from hardware shops) are used for the supporting leg. $60 for both the PCBs, all the onboard components & instruc­tions: the 60 LEDs are included! We also have available a similar kit that does not have the sweeping feature. It produces similar results to the commercial units installed in cars: all the LEDs light up when power is applied. $40 for both the PCBs and all the onboard components. This kit is also supplied with the 60 LEDs and it uses different PCBs, that have identical dimensions to the ones supplied in the above­ mentioned kit. operational is a low current EHT power supply, which we provide ready made or in kit form: powered by a 9V battery and typically draws 20mA. INCREDIBLE PRICING: $90 For the image converter tube and an EHT power supply kit! All that is needed to make a complete IR night viewer is a lens an eyeiece and a case: See EA May and Sept. 1990. ALUMINIUM TORCHES – INFRARED LIGHTS These are high quality heavy-duty black anodised aluminium torches that are powered by four “D” cells. Their focussing is adjustable from a spot to a flood. They are water resistant and shock proof. Powered by a krypton bulb – spare bulb included in cap. $42 Note that we have available a very high quality INFRARED FILTER and a RUBBER lens cover that would convert this torch to a good source of IR: $15 extra for the pair. PASSIVE NIGHT VIEWER BARGAIN This kit is based on an BRAND NEW passive night vision scope, which is completely assembled and has an EHT coaxial cable connected. This assembly employs a high gain passive tube which is made in Russia. It has a very high luminous gain and the resultant viewer will produce useful pictures in sub-moonlight illumination. The viewer can also be assisted with infrared illumination in more difficult situations. It needs an EHT power supply to make it functional and we supply a suitable supply and its casing in kit form. This would probably represent the best value passive night viewer that we ever offered! BECAUSE OF A SPECIAL PURCHASE OF THE RUSSIAN-MADE SCOPES, WE HAVE REDUCED THE PRICE OF THIS PREVIOUSLY ADVERTISED ITEM FROM $550 TO A RIDICULOUS: $399 This combination will be soon published as a project in EA. NOTE THE REDUCED PRICE: LIMITED SUPPLY. Previous purchasers of the above kit please contact us. 24VDC TO MAINS VOLTAGE INVERTERS In the form of UNINTERRUPTABLE POWER SUPPLIES (UPS’s).These units contain a 300W, 24V DC to 240V 50Hz mains inverter. Can be used in solar power systems etc. or for their original intended purpose as UPS’s. THESE ARE VERY COMPACT, HIGH QUALITY UPS’s. They feature a 300W - 450W (50Hz) SINEWAVE INVERTER. The inverter is powered by two series 12V 6.5Ahr (24V). batteries that are built into the unit. There is only one catch: because these NEW units have been in storage for a while, we can not guarantee the two batteries for any period of time but we will guarantee that the batteries will perform in the UPS’s when these are supplied. We will provide a 3-month warranty on the UPS’s but not the batteries. A circuit will also be provided. PRICED AT A FRACTION OF THEIR REAL VALUE: BE QUICK! LIMITED STOCK! $239 ATTENTION ALL MOTOROLA MICROPROCESSOR PROGRAMMERS We have advanced information about two new STATE OF THE ART microprocessors to be released by Motorola: 68C705K1 and 68HC705J1. The chips are fully functional micros containing EPROM/OTPROM and RAM. Some of the features of these new LOW COST chips include: *16 pin DIL for the 68HC705K1 chip * 20 pin DIL for the 68HC705J1 chip * 10 fully programmable bi-directional I/O lines * EPROM and RAM on chip * Fully static operation with over 4MHz operating speed. These two chips should become very popular. We have put together a SPECIAL PACKAGE that includes a number of components that enable “playing” with the abovementioned new chips, and also some of the older chips. IN THIS PACKAGE YOU WILL GET: * One very large (330 x 220mm) PCB for the Computer/Trainer published in EA Sept. 93; one 16x2 LCD character display to suit; and one adaptor PCB to suit the 68HC705C8. * One small adaptor PCB that mates the programmer in EA Mar. 93 to the “J” chip, plus circuit. * One standalone programmer PCB for programming the “K” chip plus the circuit and a special transformer to suit. THE ABOVE PACKAGE IS ON SPECIAL AT A RIDICULOUS PRICE OF: $99 Note that the four PCBs supplied are all silk screened and solder masked, and have plated through holes. Their value alone would be in excess of $200! A demonstration disc for the COMPUTER/TRAINER is available for $10. No additional software is currently available. Previous purchasers of the COMPUTER/ TRAINER PCB can get a special credit towards the purchase of the rest of the above package. PLASMA BALL KIT This kit will produce a fascinating colourful changing high voltage discharge in a standard domestic light bulb. The EHT circuit is powered from a 12V supply and draws a low 0.7A. We provide a solder masked and screened PCB, all the onboard components (flyback transformer included), and the instructions at a SPECIAL introductory price of: $ 25 We do not supply the standard light bulb or any casing. The prototype supply was housed in a large coffee jar, with the lamp mounted on the lid – a very attractive low-cost housing! Diagrams included. LASER DIODE KIT – 5mW/670nm Our best visible laser diode kit ever! This one is supplied with a 5mW 670nm diode and the lens, already mounted in a small brass assembly, which has the three connecting wires attached. The lens used is the most efficient we have seen and its focus can be adjusted. We also provide a PCB and all on-board components for a driver kit that features Automatic Power Control (APC). Head has a diameter of 11mm and is 22mm long, APC driver PCB is 20 X 23mm, 4.5-12V operation at approx 80mA. $85 PRECISION STEPPER MOTORS This precision 4-wire Japanese stepper motor has 1.8 degree steps – that is 200 steps per revolution! 56mm diameter, 40mm high, drive shaft has a diameter of 6mm and is 20mm long, 7.2V 0.6A DC. We have a good but LIMITED supply of these brand new motors: $20 HIGH INTENSITY LEDs Narrow angle 5mm red LED’s in a clear housing. Have a luminous power output of 550-1000mCd <at> 20mA. That’s about 1000 times brighter than normal red LED’s. Similar in brightness SPECIAL REDUCED PRICE: 50c Ea or 10 for $4, or 100 for $30. IR VIEWER “TANK SET” ON SPECIAL is a set of components that can be used to make a complete first generation infrared night viewer. These matching lenses, tubes and eyepieces were removed from working tank viewers, and we also supply a suitable EHT power supply for the particular tube supplied. The power supply may be ready made or in kit form: basic instructions provided. The resultant viewer requires IR illumination. $180 We can also supply the complete monocular “Tank Viewer” for the same price, or a binocular viewer for $280: Ring. MINI EL-CHEAPO LASER A very small kit inverter that employs a switchmode power supply: Very efficient! Will power a 1mW tube from a 12V battery whilst consuming about 600 mA! Excellent for high-brightness laser sights, laser pointers, etc. Comes with a compact 1mW laser tube with a maximum dimension of 25mm diameter and an overall length of 150mm. The power supply will have overall dimensions of 40 x 40 x 140mm, making for a very compact combination. $59 For a used 1mW tube plus the kit inverter. OATLEY ELECTRONICS PO Box 89, Oatley, NSW 2223 Phone (02) 579 4985. Fax (02) 570 7910 MAJOR CARDS ACCEPTED WITH PHONE & FAX ORDERS P & P FOR MOST MIXED ORDERS AUSTRALIA: $6; NZ (Air Mail): $10 August 1993  89 Silicon Chip Preamplifier For Amateur TV; 1Mb Printer Buffer; 2-Chip Portable AM Stereo Radio, Pt.2; Installing A Hard Disc In The PC. November 1989: Radfax Decoder For Your PC (Displays 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. BACK ISSUES September 1988: Hands-Free Speakerphone; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Build The Vader Voice; Motorola MC34018 Speakerphone IC Data; What Is Negative Feedback, Pt.4. November 1988: 120W PA Amplifier Module (Uses Mosfets); Poor Man’s Plasma Display; Automotive Night Safety Light; Adding A Headset To The Speakerphone; How To Quieten The Fan In Your Computer; Diesel Electric Locomotives. December 1988: 120W PA Amplifier (With Balanced Inputs), Pt.1; Diesel Sound Generator; Car Antenna/Demister Adaptor; SSB Adaptor For Shortwave Receivers; Why Diesel Electrics Killed Off Steam; Index to Volume 1. January 1989: Line Filter For Computers; Ultrasonic Proximity Detector For Cars; 120W PA Amplifier (With Balanced Inputs) Pt.1; How To Service Car Cassette Players; Massive Diesel Electrics In The USA; Marantz LD50 Loudspeakers. March 1989: LED Message Board, Pt.1; 32-Band Graphic Equaliser, Pt.1; Stereo Compressor For CD Players; Amateur VHF FM Monitor, Pt.2; Signetics NE572 Compandor IC Data; Map reader For Trip Calculations; Electronics For Everyone –Resistors. April 1989: Auxiliary Brake Light Flasher; Elec- tronics For Everyone: What You Need to Know About Capacitors; Telephone Bell Monitor/ Transmitter; 32-Band Graphic Equaliser, Pt.2; LED Message Board, Pt.2. May 1989: Electronic Pools/Lotto Selector; 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; NSW 86 Class Electric Locomotives. September 1989: 2-Chip Portable AM Stereo Radio (Uses MC13024 and TX7376P) Pt.1; Alarm-Triggered Telephone Dialler; High Or Low Fluid Level Detector; Simple DTMF Encoder; Studio Series 20-Band Stereo Equaliser, Pt.2; Auto-Zero Module for Audio Amplifiers (Uses LMC669). October 1989: Introducing Remote Control; FM Radio Intercom For Motorbikes Pt.1; GaAsFet 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. 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; PC Program Calculates Great Circle Bearings. March 1990: 6/12V Charger For Sealed Lead-Acid Batteries; Delay Unit For Automatic Antennas; Workout Timer For Aerobics Classes; 16-Channel Mixing Desk, Pt.2; Using The UC3906 SLA Battery Charger IC. April 1990: Dual Tracking ±50V Power Supply; 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 Radio Receivers From The 1920s. May 1990: Build A 4-Digit Capacitance Meter; High Energy Ignition For Cars With Reluctor Distributors; The Mozzie CW Transceiver; Waveform Generation Using A PC, Pt.3; 16-Channel Mixing Desk, Pt.4. Please send me a back issue for: ❏ January 1989 ❏ March 1989 ❏ July 1989 ❏ September 1989 ❏ January 1990 ❏ February 1990 ❏ June 1990 ❏ July 1990 ❏ November 1990 ❏ December 1990 ❏ April 1991 ❏ May 1991 ❏ September 1991 ❏ October 1991 ❏ February 1992 ❏ March 1992 ❏ July 1992 ❏ August 1992 ❏ December 1992 ❏ January 1993 ❏ May 1993 ❏ June 1993 ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ September 1988 April 1989 October 1989 March 1990 August 1990 January 1991 June 1991 November 1991 April 1992 September 1992 February 1993 July 1993 ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ November 1988 May 1989 November 1989 April 1990 September 1990 February 1991 July 1991 December 1991 May 1992 October 1992 March 1993 ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ❏ ➦ Use this handy form to order your back issues December 1988 June 1989 December 1989 May 1990 October 1990 March 1991 August 1991 January 1992 June 1992 November 1992 April 1993 Enclosed is my cheque/money order for $­______or please debit my: ❏ Bankcard ❏ Visa Card ❏ Master Card Card No. Signature ____________________________ Card expiry date_____ /_____ Name ________________________________________________________ Street ________________________________________________________ Suburb/town ______________________________ Postcode _____________ 90  Silicon Chip Note: all prices include post & packing Australia (allow 2 weeks for delivery) .......... $A6 Australia (by return mail) ............................. $A7 NZ & PNG (airmail) ...................................... $A7 Overseas (surface mail) ............................... $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. Fax (02) 979 6503. June 1990: Multi-Sector Home Burglar Alarm; Low-Noise Universal Stereo Preamplifier; Load Protection Switch For Power Supplies; A Speed Alarm For Your Car; Design Factors For Model Aircraft; Fitting A Fax Card To A Computer. 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. 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 Telephone; Remote Control Extender For VCRs; Power Supply For Burglar Alarms; Low-Cost 3-Digit Counter Module; Simple Shortwave Converter For The 2-Metre 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 Home-Brew 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; The Fruit Machine; Two-Tone Alarm Module; Laser Power Supply; LCD Readout For The Capacitance Meter; How Quartz Crystals Work; The Dangers When Servicing Microwave Ovens. February 1991: Synthesised Stereo AM Tuner, Pt.1; Three Inverters For Fluorescent Lights; LowCost Sinewave Oscillator; Fast Charger For Nicad Batteries, Pt.2; How To Design Amplifier Output Stages; Tasmania's Hydroelectric Power System. March 1991: Remote Controller For Garage Doors, Pt.1; Transistor Beta Tester Mk.2; Synthesised AM Stereo Tuner, Pt.2; Multi-Purpose I/O Board For PC-Compatibles; Universal Wideband RF Preamplifier For Amateurs & TV. 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; Playing With The Ansi.Sys File; FSK Indicator For HF Transmissions. 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; Setting Screen Colours On Your PC. 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; Electric Vehicle Transmission Options; 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; PEP Monitor For Amateur Transceivers. August 1991: Build A Digital Tachometer; Masthead Amplifier For TV & FM; PC Voice Recorder; Tuning In To Satellite TV, Pt.3; Installing Windows On Your PC; 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 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; Error Analyser For CD Players Pt.3; 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; Windows 3 & The Dreaded Un­ recov­erable Application Error; 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 Direct­ ories; 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; Switching Frequencies in Model Speed Controllers; Aligning Vintage Radio Receivers, Pt.1. Alarm; The Interphone Digital Telephone Exchange, Pt.2; General-Purpose 3½-Digit LCD Panel Meter; Track Tester For Model Railroads; Build A Relative Field Strength Meter. October 1992: 2kW 24VDC To 240VAC Sine­wave Inverter; Multi-Sector Home Burglar Alarm, Pt.2; Mini Amplifier For Personal Stereos; Electronically Regulated Battery Charger (Charges 6V, 12V & 24V Lead-Acid Batteries). November 1992: MAL-4 Microcontroller Board, Pt.1; Simple FM Radio Receiver; Infrared Night Viewer; Speed Controller For Electric Models, Pt.1; 2kW 24VDC To 240VAC Sine­wave Inverter, Pt.2; Automatic Nicad Battery Discharger; Modifications To The Drill Speed Controller. December 1992: Diesel Sound Simulator For Model Railroads; Easy-To-Build UHF Remote Switch; MAL-4 Microcontroller Board, Pt.2; Speed Controller For Electric Models, Pt.2; 2kW 24VDC To 240VAC Sine­ wave Inverter, Pt.3; Index To Volume 5. 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; Restoring A 1920s Kit Radio February 1993: Three Simple Projects For Model Railroads; A Low Fuel Indicator For Your Car; 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; File Backups With LHA & PKZIP. 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; Low-Cost Mini Gas Laser; The Micro­soft Windows Sound System. May 1992: Build A Telephone Intercom; LowCost Electronic Doorbell; Battery Eliminator For Personal Players; Infrared Remote Control For Model Railroads, Pt.2; A Look At Large Screen High Resolution Monitors; OS2 Is Really Here; Aligning Vintage Radio Receivers, Pt.2. June 1993: Windows-Based Digital Logic Analyser, Pt.1; Build An AM Radio Trainer, Pt.1; Remote Control For The Woofer Stopper; A Digital Voltmeter For Your Car; Remote Volume Control For Hifi Systems, Pt.2; Double Your Disc Space With DOS 6. June 1992: Multi-Station Headset Intercom, Pt.1; Video Switcher For Camcorders & VCRs; Infrared Remote Control For Model Railroads, Pt.3; 15-Watt 12-240V Inverter; What’s New In Oscilloscopes?; A Look At Hard Disc Drives. July 1993: Build a Single Chip Message Recorder; Light Beam Relay Extender; Build An AM Radio Trainer, Pt.2; Windows Based Digital Logic Analyser; Pt.2; Low-Cost Quiz Game Adjudicator; Programming The Motorola 68HC705C8 Micro­ controller – Lesson 1; Antenna Tuners – Why They Are Useful. July 1992: Build A Nicad Battery Discharger; 8-Station Automatic Sprinkler Timer; Portable 12V SLA Battery Charger; Off-Hook Timer For Tele­phones; Multi-Station Headset Intercom, Pt.2; Understanding The World Of CB Radio. 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. September 1992: Multi-Sector Home Burglar PLEASE NOTE: all issues from November 1987 to August 1988, plus the October 1988, February 1989 & August 1989 issues, are now sold out. All other issues are presently in stock, although stocks are low for older issues. For readers wanting articles from sold-out issues, we can supply photostat copies (or tearsheets) at $6.00 per article (incl. p&p). When supplying photostat articles or back copies, we automatically supply any relevant notes & errata at no extra charge. August 1993  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. AND or OR gates with diodes V+ A Z 1k I was very interested in the Quizmaster circuit B A Z featured in the July 1993 issue of SILICON CHIP but I was confused over the use C B of diode gating. According to your text on page 71, 1k diodes D1-D4 make up an C AND gate. I am used to seeing diAND OR odes and a resistor used A B C Z A B C Z to make an OR gate and it 0 0 0 0 0 0 0 0 seems to me that the func0 0 1 0 0 0 1 1 tion of your circuit really is 0 1 0 0 0 1 0 1 an OR function too. After 0 1 1 0 0 1 1 1 all, if any of the Q1-Q4 out1 0 0 0 1 0 0 1 puts go low, the output of 1 0 1 0 1 0 1 1 the diode gate will also go 1 1 0 0 1 1 0 1 low and operate the buzzer 1 1 1 1 1 1 1 1 and so on. Z = A.B.C Z = A+B+C Surely, that describes an to label a gate with the AND or OR OR function since Q1 or Q2 or Q3 or Q4 going low will cause function. In the case of the diode logic gate in something to happen. Am I right? (B. the Quizmaster, all inputs being high S., Rooty Hill, NSW). • That’s a good question, B. S, and result in a high output at the junction one that has perplexed many people of the four diode cathodes. This is the trying to come to grips with the rules AND function without a doubt. Howof logic. The truth is that the AND ever, since we are more interested in and OR functions are closely related, the condition when one of the inputs as are the NAND and NOR functions. goes low, you could argue that it’s an It depends on what logic conven­tion OR function but the voltage output is you apply as to whether you decide the wrong polarity for positive logic. Skippy not easily frightened With your Woofer Stopper still on my mind, I saw just the right few minutes of a TV travel program. I see that commercial “Electronic Kangaroo Warners” cost over $200 to fit to cars and off-road vehicles. Your Woofer Stopper circuit would be ideal as a roo stopper too. I also need an “electronic mouse trap”. When can we build one? (P. T., New Norfolk, Tas). • The Woofer Stopper can be quite 92  Silicon Chip effective at stopping dogs from barking when used as a teaching system, as described in the article. However, we have serious doubts as to whether it would be of any use as a kangaroo scarer to prevent collisions with cars. Because of the limited range, we just cannot see it being a viable project. We have not described an electronic mouse trap and also cannot see the point of one either since the good old mechanical spring type is quite effective. It’s much cheaper too. On the other hand, if the junction of the diode cathodes had a “pull-down” resistor instead of the 10kΩ “pull-up” resistor used in our circuit, it would be more clearly an OR gate. The two gate diagrams and their truth tables show just how close the functions can be. It all depends on the logic convention you adopt in thinking about the circuit. To build or not to build I am interested in building the Car Digital Voltmeter de­scribed in the June 1993 issue of SILICON CHIP. However, the price of the advertised kit is about the same as for an economy digital multimeter advertised in the same issue. Also you can buy a digital panel meter for around the same price. Faced with this choice, I wonder if I should bother build­ing the voltmeter and just buy a meter to do the job. I want it to monitor the battery in my boat by the way. (P. S., Leichhardt, NSW). • On the face of it, the obvious choice is to just buy a meter and not bother with building a kit. However, meters with liquid crystal displays may not be the best choice if they are to be used in cars or boats, unless you can guarantee that they will not be exposed to sunlight for more than short periods of time. Intense heat and sunlight kills liquid crystal displays. It is also true that the more money you pay for an instru­ment with a liquid crystal display, the more reliable it is likely to be. So if you spend $30 or so on a digital multimeter, it may not have a very long life if used permanently in a car or boat. Bird scarer wanted You’ve done the Woofer Stopper in the May 1993 issue of SILICON CHIP. Now how about extending the idea to produce a bird scarer. There must be plenty of people with fruit trees who would want such a system as well as those who are plagued by damage from sulphur crested cockatoos. (R. G., Punchbowl, NSW). • We have tried the Woofer Stopper on birds such as rainbow lorikeets and it has no effect whatsoever. As far as we can determine, birds will only respond to a loud sound such as a gun going off or a distress call from one of their number. On this basis, an ultrasonic device such as the Woofer Stopper would be useless. It might be better to record the distress call of the birds you want to scare using the single chip Voice Recorder described in the July 1993 issue. You could then feed this recording to a power amplifier and speaker to broadcast it to the birdies. Woofer Stopper doesn’t work I built the Woofer Stopper as described in the May 1993 issue of SILICON CHIP but I’ve found it to be ineffective on the little dog next door. It doesn’t seem to affect it in the least. I’ve measured the signal at both sides of the tweeter with my oscilloscope and have found it to be 20kHz and 10V peak to peak. So why doesn’t it work? (B. M., Campsie, NSW). • The fact that you have measured a 20kHz square wave at both sides of the tweeter indicates that the circuit is probably working as it should but that the tweeter might be faulty. When you switch the circuit on and off, you should at least hear a fairly loud click from the tweeter and while it is running you should be able to hear some hiss. If you have young children in the household they should be able to hear it too. Don’t subject them to it at close range because it will hurt their ears. You can also test a piezoelectric tweeter by connecting a resistor across it (virtually any value will do) and then briefly connecting a 9V or 12V battery across it. Each time you do so, the tweeter will click fairly loudly. The reason for connecting a resistor across the tweeter for this test is to discharge its capacitance which can be as much as 0.3µF. If the capacitor is not discharged by a shunt resistor, it will only click once when initially connected. If your tweeter does not click, it’s prob­ably faulty. By the way, the Woofer Stopper can Problem with TV reception Because I am located behind a hill and approximately 100km from Brisbane, my TV reception leaves a lot to be desired. I have had to run a 300-ohm ribbon cable from the house to the top of a hill 500 metres away to get any reception at all and, for this reason, I am anxious to build the masthead amplifier described in the August 1991 issue of SILICON CHIP. However, I note that it is designed for 75-ohm cable. I would be grateful if you could advise me of the modifica­ tions necessary to make the unit suitable for use with 300-ohm cable. (B. B., Maleny, Qld). • We do not think that our mast- be made to work with virtually any speaker but a tweeter will naturally work better because of its extended high frequency response, whether or not it is a piezoelectric or dynamic type. If you use an 8-ohm speak­ er, the circuit can be expected to draw a lot more current, around 1.5A or so, rather than the 100mA or less with a piezo tweeter. Finally, there’s no guarantee that the Woofer Stopper will work with all dogs. The dog next door might be deaf or just too stupid to know that he is being reprimanded. Puzzling problem with National VCR I have a puzzling problem with sound on my National NV300 VCR. I find that when I buy a new good quality tape and record on it from any source, I get a very low sound level. However, if I go to my collection of older tapes and repeat the same route and playback the finished recording, both picture and sound are perfect. By the way, the picture on the new tape is perfect; only the sound drops down. When I turn the TV volume up, I can just hear it in the background. If I put one of my older tapes back in, everything returns to normal. I have taken some of the new tapes back to the store I purchased them head amplifier would be suit­able for driving such a long cable length. In fact, you could have problems sending the signal over such a long run with any masthead amplifier. An alternative suggestion is to use your existing antenna mounted on the hilltop to drive another identical antenna close by which faces down the hill. You would then have a third antenna at your homesite pointing up the hillside. You may find it beneficial to drive the downward pointing antenna with a masthead amplifier and our August 1991 design would be quite suitable for that, driving 75 ohm cable. This concept is not new and was originally suggested in “Wireless World” magazine many years ago. It should work well. from. When these were tried on another VCR, all seemed to work OK. Recently a workmate approached me with an identical problem in his VCR, which carries the General brand. He uses good quality video cas­settes and some or most of his older recordings have a better sound than a newly bought tape. Unfortunately, I could not help him. I cannot seem to solve the mystery with my own machine. I’ve examined and thoroughly cleaned around the audio head assembly and checked to ensure that the new tapes are not out of alignment. Perhaps another reader may help with a valuable clue in this matter. Sure I could take my VCR to a service centre but I would never get to know the real reason for this annoying prob­ lem. (R. P., Sheffield, Tas). • This is a fairly common problem with old National VCRs, R. P. Replace the audio/control head and your problems should be fixed. It won’t be cheap though – it’ll cost you about $140 to have the part replaced. Coil information for metal locator I have come across your simple metal detector circuit in the March 1991 issue of SILICON CHIP and have completed the circuit as detailed. However, I am at a loss as to the gauge August 1993  93 Problem with the Baby Room Monitor I have written to you previously about a problem I have getting the Baby Room Monitor described in January 1992 to trans­ mit. Your suggestion on that occasion was to disable the VOX circuit by removing Q2 and Q3 but unfortunately this had no effect. I am a relatively experienced kit constructor and am con­fident that there are no solder bridges, dry joints, wrongly inserted polarised components, etc. I have even replaced IC1, a rather expensive stabin-the-dark, but no transmission. of the enamelled copper wire used for the search coil and the dimen­sions of the former. I would be grateful if you could supply this information. I find great value from the magazine and wish more simple circuits could be included. Perhaps a yearly compilation of all circuits could be included in a magazine. Keep up the good work. (M. G., Glendalough, WA). • The gauge of the wire is not overly critical – 24 or 26 SWG (approx. 0.5mm diameter) would work equally as well. The diameter of the coil itself is also not critical but a good size would be around 15cm. Optical illusion with car voltmeter I just noticed on the cover of your June edition that the LED display of your depicted Car Voltmeter has the least signifi­cant digit showing a “mirror image” of a 6! Since I am going to build this project, I was wondering if there is a possible wiring error in this design or just a malfunction of the “f” segment actually showing an 8! Or perhaps you used too slow a shutter speed when taking the picture while the display was changing? Either way, could you please clarify this before I proceed with building the project. My worries were triggered by a differ­ent and simpler design published by another magazine where the display constantly switched (flickered) between two values when the input voltage varied slightly or was halfway 94  Silicon Chip I have now discovered that I can tune the transmitter and transmit expelled breath sounds if a probe is touched to pin 12 or 14 of IC1. Any attempt at transmitting speech is muffled and distorted, regardless of VR1’s setting. If I remove the probe, the transmission ceases. (R. O., Waverley, NSW) • On re-reading your first letter, we noticed that you are using an IC socket. This socket will prevent the transmitter from operating at its correct frequency due to the extra capacitance. If you solder the IC directly onto the board, the transmitter should then work as published. between the least significant digit numbers. To my knowledge, this can be caused by an inconsistent up-count when the display is blanked. Is your design also prone to this? Why can’t the voltage to frequency converter in your design be used outside your specified range of 8-17V? Is it caused by non-linearity occurring outside the range and how bad is it? Could you please tell me how to modify the design to read down to at least 4V fairly accurately without major surgery, or could the range be shifted by changing just one component? (M. S., Edgewater, WA). • You should be awarded full marks for observation but there is nothing wrong with the kit. Your analysis regarding shutter speed is correct. We were unable to use a high shutter speed because it was a time exposure, in order to be able to display the digit. Note that any digital display can be subject to jitter of the least significant digit, especially if the quantity being measured is itself varying. The circuit can not easily be modified to read down to 4V. That’s because the circuit is powered by the battery it is meas­uring and needs a regulated rail of at least 5V. Test procedure for clocks I repair clock radios as a hobby. I don’t have much trouble with the radio portion, if I can get parts. However, I have problems with IC clock chips and the display. In most cases, one or more segments of the LCD fail to illuminate. Can you suggest a test or procedure for determining whether the fault lies in the display or in the clock chip? I have most of the test equipment of a small service shop. Also, can you suggest a book that might be helpful in understanding the function of clock ICs? I enjoy SILICON CHIP very much and have been a subscriber for the past four years. (T. G., Lavender Bay, NSW). • There is no simple test to diagnose whether the fault lies in the display or in the clock chip when you have missing seg­ments on an LCD. The only thing you can do is to check for continuity between the relevant pins of the LCD and the clock chip. Failing that, it is a lottery as to whether the fault lies in the clock chip and the display. Our experience though suggests that the liquid crystal displays are far less reliable than the clock chips. Unfortunately, we cannot refer you to any books on the subject and data on clock chips is now quite hard to get since most of them are sourced from Asia. Drifting around the Greek Islands I am writing to ask for your help with the VHF FM Monitor Receiver that was published in SILICON CHIP in March 1989. I recently built this project and have had a lot of trouble with it. I can only pick-up a couple of Greek stations which transmit on about 151.75MHz. If I take my hand off the tuning pot after I finish tuning, I lose the station or I get a very distorted sound. I have ob­ served all precautions regarding earthing of components on the double-sided board. I also tried to earth the body of the tuning pot but with no success. It seems that this project is very temperamental. If I even move the board in a different direction, I get distortion and I lose the signal. (P. T., Canterbury, NSW). • It seems likely that your receiver is working as it should but it needs earthing and shielding. We suggest you assemble the receiver board onto an earthed metal baseplate and fit the tuning shaft with an insulating knob. This should greatly reduce the effect of hand capacitance when you are SC tuning. MARKET CENTRE Cash in your surplus gear. Advertise it here in Silicon Chip. CLASSIFIED ADVERTISING RATES ANTIQUE RADIO 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): $20 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 both with your cheque or credit card details to: Silicon Chip Classifieds, PO Box 139, Collaroy Beach, NSW 2097. Or fax the details to (02) 979 6503. ANTIQUE RADIO RESTORATIONS: specialist restoration service provided for vintage radios, test equipment & sales. Service includes chassis rewiring, recondensering, valve testing & mechanical refurbishment. Rejuvenation of wooden, bakelite & metal cabinets. Plenty of parts – require details for mail order. About 1200 radios within 16,000 square feet. Two-year warranty on full restoration. Open Saturday 10am-4.30pm; Sunday 12.30-4.30pm. 109 Cann St, Bass Hill, NSW 2197 Phone (02) 645 3173 BH or (02) 726 1613 AH. _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ _____________ FOR SALE WEATHER FAX programs for IBM XT/ ATs *** “RADFAX2” $35 is a high resolution, shortwave fax, Morse & RTTY receiving program. Suitable for CGA, EGA, VGA and Hercules cards (state which). Needs SSB HF radio & Radfax decoder. *** “SATFAX” $45 is a 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. ❏ Bankcard   ❏ Visa Card   ❏ Master Card Card No. ✂ Enclosed is my cheque/money order for $­__________ or please debit my RCS RADIO PTY LTD Signature­­­­­­­­­­­­__________________________ Card expiry date______/______ Name ______________________________________________________ Street ______________________________________________________ Suburb/town ___________________________ Postcode______________ 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 August 1993  95 TRANSFORMER REWINDS ALL TYPES OF TRANSFORMER REWINDS TRANSFORMER REWINDS Reply Paid No.2, PO Box 438, Singleton, NSW 2330. Ph: (065) 76 1291. Fax: (065) 76 1003. ICL 286 Board Kits All in one board with two serial, printer, IBM keyboard, high density floppy & IDE mono video interface. Up to 4Mb RAM, 80286-16cpu, MS-DOS compatible, 130 page manual, small size 170mm x 255mm. Max I/O kit for PCs, 7 relays, ADC, DAC, stepper driver, TTL inputs, with software $169 PC I/O card with 8255 chip 24 I/O lines programmable as inputs or outputs $69 1.5 watt AM broadcast transmitter XTAL locked $49 2.5 watt FM broadcast transmitter 88-108MHz. $49 Digi-125 audio power amp (over 19,000 sold since 1987) 50 watt/8 $14 125 watt/4 $19 New 200 watt/2 version $29 Infrared relay kit $9 Remote control tester $4 $299 Ampo little PC All in one NEC V40 CPU board, MS-DOS compatible, high density floppy. SCSI hard disk, 2 serial, printer, solid state hard disk, IBM keyboard interface, (4W), CMOS single +5V rail, up to 768Kb RAM, 384Kb ROM, 145mm x 250mm, 98page manual. $299 P.C. Computers MEMORY & DRIVES PRICES AT JULY 10th, 1993 SIMM 1Mb x 9 70ns 1Mb x 3 70ns 4Mb (72-pin) 4Mb x 9 70ns 4Mb x 8 80ns $63 $60 $245 $235 $210 DRAM DIP 1 x 1Mb 70ns $6.25 256 x 4 70ns $6.25 1Mb x 4 Z or D $26.00 DRIVES SEAG 42Mb SEAG 89Mb SEAG 107Mb SEAG 130Mb SEAG 214Mb 28ms 14ms 15ms 16ms 16ms $205 $292 $310 $335 $470 IBM PS.2 50/55/70 70/35 90/95 2Mb 4Mb 4Mb $145 $235 $235 TOSHIBA T3200SX T44/6400 T5200 T5200 4Mb 4Mb 2Mb 8Mb $265 $245 $150 $575 MAC 2Mb SI & LC 4Mb P’Book $110 $270 CO-PROCESSORS 387SX to 25 $110 387DX to 33 $110 Sales tax 20%. Overnight delivery. Credit cards welcome. All Electronic Components..........80 Altronics .....................IFC,63,76-78 Antique Radio Restorations.........95 A-One Electronics.................. 26-27 Boston Technology......................39 Cebus Australia...........................11 David Reid Electronics ................3 Ring for Latest Prices Dick Smith Electronics...14-17,OBC 1st Floor, 100 Yarrara Rd, PO Box 382, Pennant Hills, 2120. Emona Pty Ltd.............................11 Tel: (02) 980 6988 Fax: (02) 980 6991 PELHAM 36 Regent St, Kensington, SA. Phone (08) 332 6513. THE HOMEBUILT DYNAMO: (plans) brushless, 1000 watt at 740 revs. $A85 postpaid airmail from Al Forbes, PO Box 3919 - SC, Auckland, NZ. Phone Auckland (09) 818 8967 any time. Advertising Index Instant PCBs................................96 Jaycar ................................... 45-52 JV Tuners.....................................11 Oatley Electronics.....................5,89 PC Computers.............................96 UNUSUAL BOOKS: electronic devices, fireworks, locksmithing, radar invisibility, surveillance, self-protection, unusual chemistry and more. For a complete catalog send 95c in stamps to: Vector Press, Dept S, PO Box 434, Brighton SA 5048. Extra BASIC STAMP modules $66 incl p&p. Reprogram­ mable for reuse. For more info send SAE for data sheet & circuits. Quantity prices available. Bank­ card, Master, Visa or cheque with order. Parallax of USA products distributor & technical support in Australia. MicroZed Computers, PO Box 634, Armidale 2350. Fax (067) 728987. PAY TV & SATELLITE Scrambling News Monthly, with the latest on descrambling techniques & addresses, where to buy the latest descramblers. Send stamp for info. John Papp, Box 37885 Winnel­lie, N.T. 0821. GLOBAL ELECTRONIC SERVICES: kits; consultancy; sales & design. Please write/fax requirement to: Mr Lucas, PO Box 755, Saint Helier, Jersey JE4 8ZZ, Channel Islands (UK). Fax (0 534) 80570. Silicon Chip Back Issues........90,91 PRINTED CIRCUIT boards for the hobby­ist. For service & enquiries contact: T. A. Mowles (08) 326 5590. A 4Mb SIMM can now be used in my Printer Buffer kit and my PC Printer Port driven Z80 Micro Development board has a Basic Interpreter. Short form kit prices include postage. Buffer $52, Z80 Dev. $76, or send $2 for my 3.5-inch promo disk to Don McKen­zie, 29 Ellesmere Crescent, Tullamarine 3043. Phone (03) 338 6286. Transformer Rewinds...................96 _________________________________ SOLVE YOUR SMALL circuit development problems quickly, try this one. Parallax BASIC STAMP. A general purpose small circuit modu­le, it is really a 25 x 50mm board with a computer chip (4MHz PIC 16C56), EEPROM, 8 I/O sink 25mA or source 20mA board space includes 6 x 10 pad prototyping area. Has 216 type battery con­nections. Program it on a PC with our development kit which includes one BASIC STAMP $245 incl p&p. Commands in­ clude POT (crude A/D), PWM (crude D/A), BUTTON , SERIN, SEROUT, SOUND & SLEEP. 96  Silicon Chip WANTED Do you have a good circuit idea? If so, why not submit it for publication in Circuit Notebook and earn yourself some money? Send your idea to Silicon Chip Publications, PO Box 139, Collaroy Beach, NSW 2097. Pelham........................................96 Peter C. Lacey Services..............40 RCS Radio ..................................95 Resurrection Radio......................63 Rod Irving Electronics .......... 66-71 Silicon Chip Binders....................61 Silicon Chip Order Form..............75 Technical Applications.................81 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.