March 1990 - Silicon Chip Online

Outer Front Cover
Contents
Publisher's Letter: UHF translators and environmentalists
Feature: The Evolution of Electric Railways by Bryan Maher
Feature: The UC3906 SLA Battery Charger IC by Darren Yates
Vintage Radio: Wave traps - a useful vintage radio accessory by John Hill
Project: 6/12V Charger For SLA Batteries by Darren Yates
Project: Delay Unit For Automatic Antennas by Greg Swain
Serviceman's Log: A bit of a snag with the sausage rolls by The TV Serviceman
Project: Workout Timer For Aerobics Classes by Steve Calder
Subscriptions
Back Issues
Project: 16-Channel Mixing Desk by John Clarke & Leo Simpson
Feature: Amateur Radio by Garry Cratt, VK2YBX
Feature: Computer Bits by Steve Payor
Feature: Remote Control by Bob Young
Market Centre
Advertising Index
Outer Back Cover

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

You can view 44 of the 104 pages in the full issue, including the advertisments.

For full access, purchase the issue for $10.00 or subscribe for access to the latest issues.

BONUS 148-PAGE JAYCAR CATALOG SERVICING - HIFI - Registered by Australia Post. Publication No NBP 9047 6/12-Volt Charger For Sealed Lead-Acid Batteries PLUS: * Wave Trap For Vintage Radios * Using The UC3906 Battery Charger IC * Understanding SSB Transmissions COMPUTER PART# SIZE AMIGA AMIGA AMIGA AMSTRAD ATARI ATARI IBM IBM IBM IBM TOSHIBA TOSHIBA D2930 D2932 D2938 D2904 D2916 D2918 D2946 D2948 D2950 D2952 D2970 D2972 r 3.5" 5.25" 3.5" 3.5" 3.5" 5.25" 3.5" 3.5" 5.25" 5.25" 5.25" 5.25" CAPACITY 880K 360/880K 880K 720K 720K 360/720K 720K 1.4MB 360K 1.2MB 360K 1.2MB COMMENTS COLOUR GRAPHICS ADAPTER FOR IBM PC/XT/AT The M5752 is a colour graphics adapter card capable of operating with either IBM RGB or composite monochrome monitors and features the following: • Parallel printer port • Text modes: 40 x 25or 80 x 25 • Graphic modes; 320 x· 200 or 640 x 200 • Light pen interface e Includes composita video monitor adapter • Manual included M5752 - wAS $115.00 NOW $69 • V20 processor • Can be expanded to 256k, 512k, 640k or 1mb • Uses combinations of 414256, 41464 and 41256 • 4. 77 or 12MHz hardware or keyboard selectable operation• Front panel LED ind icators supported • Eight expansion slots • Legal BIOS ROMs included • 8087 maths co-processor capability • Norton SI rating of 2.5 • Size 8.5" x 8.5" e Weight 1.1 lbs M5500- XT 1MB 12MHz TURBO MOTHERBOARD WAS $129 NOW $110 YOU SAVE! GREEN SCREEN MONITOR - TTL - HIGH RESOLUTION AMERICAN/MEXICAN MANUFACTURE A qualrty product by a major American company. These would normally sell for $200 to $300 but we (ONLY 200 UNITS) this month only $69.00 14" flat screen, including till/swivel base. Extremely high quality Memorex brand. LIMITED STOCK AT $125.00 EACH AT(16 BIT) HARD/FLOPPY/DISK CONTROLLER Will control 2 DEALER ENQUIRIES WELCOME x ST 506 Interface hard drives AND 2 x Floppy drives; 360k/720k/1 .2M/1 .44M. Normally sells for $245, this month we offer 50 only at $145.00 YOU SAVE $100 Have you seen our catalogue? Write or phone today for your FREE copy. PERSONAL COMPUTER MARKETPLACE Ptyud PHONE (02) 418 6711 FAX (02)4186713 Mail Order Address: P.O. Box 1100 Lane Cove NSW2066 249.00 299.00 229.00 269.00 269.00 299.00 299.00 329.00 299.00 329.00 349.00 399.00 XT1MB 12MHzTURBO MOTHERBOARD 84 KEY KEYBOARD have a limned amount of stock available PRICE WITH ON/OFF SWITCH WITH ON/OFF SWITCH INTERNAL KIT FOR A2000 FOR PC1512/1640 WITH POWER SUPPLY SWITCHABLE, WITH POWER SUPPLY WITH ADAPTER INTERFACE & CABLE WITH ADAPTER INTERFACE & CABLE WITH ADAPTER INTERFACE & CABLE WITH ADAPTER INTERFACE & CABLE SUIT TOSHIBA LAPTOP SUIT TOSHIBA LAPTOP FREIGHT CHARGES Include $10 with order for all normal items - heavy items, e.g. monitors add $15. 14 day money back guararrtee Order by phone (use credit card), by fax or by mail. Unless insurance is declined it will be charged at 1% of total purchase. This is for your protection. VISA WHERE SERVICE /S THE DIFFERENCE THIS NEW BATTERY CHARGER can charge both 6V & 12V sealed lead acid batteries with capacities of up to 15Ah. Construction starts on page 20. MARCH 1990 FEATURES 4 The Evolution of Electric Railways by Bryan Maher Pt.29: the Australian VFT project 10 The UC3906 SLA Battery Charger IC by Darren Yates Using it in practical circuits 96 The Technology Letters by Richard Kopf Adventures in UHF TV land ARE YOU INTO A strenuous aerobics exercise program? Our new Workout Timer will tell you when to change exercises by flashing a light & sounding a buzzer. Details page 44. PROJECTS TO BUILD 20 6/12V Charger For SLA Batteries by Darren Yates Charges SLA batteries of up to 15A.h capacity 30 Delay Unit For Automatic Antennas by Greg Swain Stops the antenna jitters 44 Workout Timer For Aerobics Classes by Steve Calder It flashes a light & sounds a buzzer 60 16-Channel Mixing Desk by John Clarke The full circuit details SPECIAL COLUMNS 14 Vintage Radio by John Hill Wave traps - a useful vintage radio accessory 34 Serviceman's Log by the TV serviceman A bit of the snag with the sausage machine 72 Amateur Radio by Garry Cratt Understanding single sideband transmission .a: THE SERVICEMAN really went through the mincer this month but the snags were eventually sorted out. His battle starts on page 34. 80 Computer Bits by Steve Payor Digital waveform generation using a PC 86 Remote Control by Bob Young The controls on a model aircraft DEPARTMENTS 2 Publisher's Letter 42 Circuit Notebook 56 Subscription Page 57 Bookshelf 58 Back Issues Product Showcase Ask Silicon Chip Notes & Errata Market Centre IBC Silicon Chip Binders 90 100 102 103 MANY AUTOMATIC ANTENNAS go through multiple stop/start operations when you go to start your car. This simple unit will stop the antenna jitters. See page 30. MARCH 1990 1 SILICON CHIP Publisher & Editor-In-Chief Leo Simpson, B.Bus. Editor Greg Swain , B.Sc.(Hons.) Technical Staff John Clarke, B.E.{Elec.) Robert Flynn Advertising Manager Paul Buchtmann (02) 982 9553 Regular Contributors Bryan Maher, M.E. B.Sc. Jim Yalden, VK2YGY Garry Cratt, VK2YBX Jim Lawler, MTETIA John Hill Jennifer Bonnitcha, B.A. Bob Young Photography Bob Donaldson Edltorlal Advisory Panel Philip Watson, MIREE, VK2ZPW Norman Marks Steve Payor, B.Sc., B.E. SILICON CHIP is published 12 times a year by Silicon Chip Publications Pty Ltd . All material copyright (c). No part of the contents of this publication may be reproduced without prior written consent of the publisher. Kitset suppliers may not photostat articles without written permission of the publisher. Typesettlng/makeup: Magazine Printers Pty Ltd , Rozelle, NSW 2039. Printing: Macquarie Publications Ltd, Dubbo, NSW 2830. Distribution: Network Distribution Company. Subscription rates: currently $42 per year (12 issues) inside Australia. For overseas rates, refer to the subscription page in this issue. Liability: Devices or circuits described in SILICON CHIP may be covered by patents. SILICON CHIP disclaims any liability for the infringement of such patents by the manufacturing or selling of any such equipment. Address all mail to: Silicon Chip Publications Pty Ltd, PO Box 139, Collaroy Beach, NSW 2097. Phone (02) 982 3935. Fax (02) 982 9553. ISSN 1030-2662 2 SILICON CHIP PUBLISHER'S LETTER UHF translators and environmentalists One of the most radical changes to the Australian political scene in recent years has been the great increase in the influence of environmentalists. And seeing how the electorate seems to be moving, politicians of every party are jumping onto the environmental bandwagon. As this process goes on, it is becoming more and more difficult to get worthwhile engineering projects underway because of the overriding concern for the effects on the environment. Now some engineering projects have very large and deleterious effects on the environment. Under this heading come dam building projects, mines and mineral refining processes, and any operation which requires large scale clearing of the natural landscape. All of these need to be looked at carefully so that a balance is obtained between a desirable engineering development and minimising any long term damage to the landscape. Few people could argue with such a thoughtful process but there is little doubt that the trend is getting out of hand when there is vehement opposition to the installation of UHF TV translators. Right at this moment, for example, a UHF translator is about to be installed on Sydney's North Head. This is badly needed to improve the TV reception of tens of thousands of residents around Sydney's northern beaches. But the well-intentioned local Manly Council is opposing this development tooth and nail. Now this is just plain silly. UHF translator masts are nothing like the massive towers used by the TV stations in Sydney and Melbourne. By contrast, UHF translator towers are almost invisible and require very little land space. They don't cause pollution and have no known effect on wildlife apart from possibly providing a convenient perch for the odd bird or two. In other words, there is no logical reason to oppose them, apart from wanting to appear " environmentally sound". On the positive side, there are real benefits when UHF translators are installed. Apart from the great improvement in TV reception, there is also the visual benefit in the disappearance of all those large and unsightly TV antennas from every home, to be replaced by small and insignificant UHF antennas. A visit to the Gosford district, north of Sydney, really emphasises this improvement. So far from opposing UHF translators, loca.1 councils should support and call for their installation. There are very few parts of Australia which don't have at least one or two localitiEJs, large or small, which could benefit from a UHF TV translator. Leo Simpson PRCCESS COMMUNICATIONS PTY LTO MS-101 9-Band Shortwave Recei ver Ideal for Travellers: • Miniature size. • Complete with personal stereo headphones. • Includes short wave listening guide. • Great " leather look" carry case. • AM broadcast and FM stereo coverage. Cat # C6000 $119.00 • Optional AC adaptor Cat # T0321 $19.95 ATS-803A Portable Communications Receiver: • Continuous coverage from 150KHz to 30MHz. • AM/CW/SSB, Inbuilt RF gain control, BFO. • PLL synthesised tuning , LCD display • Scanning , 14 memories, AM broadcast & FM stere o coverage, 12 short wave bands. Cat # C5020 $299.00 • Optional AC adaptor Cat # T0941 $24.95 SG-796 9-Band Economy Shortwave Receiver: • 6 short wave bands. • AM broadcast. • FM stereo. • Protective carry pouch and shortwave guide. Cat # C6020 $79.00 • Optional AC adaptor Cat # T0320 $19.95 ATS-802 Synthesised Shortwave Receiver: • Continuous shortwave coverage 5.8MHz to 15.5 MHz. • 25 memories. • Auto timer functions. • Up/down tuning control in SKHz steps. • AM broadcast and FM stereo coverage. Cat # C6028 $199.00 • Optional AC adaptor Cat # T0630 $24.95 MS-102: • Slightly larger than MS-101 but with 10 short wave bands. Cat # C6010 $119.00 • Optional AC adaptor Cat # T0321 $19.95 Road Runner AR-880 Hand-Held Scanner: • Scan , search, lock-out, hold, delay functions. • Frequency coverage 60MHz-90MHz, 138MHz-174MHz, 406MHz-525MHz, 830MHz-950MHz. • Selectivity: 7.5KHz at 6d8. • Audio output: 120mW. • Size : 140mm (H) x 55mm (W) x 44mm (D) . Road Runner Cat # C5020 $399.00 40-Channel • Optional AC adaptor 27MHz AM CB: 2 • Up/down push Cat # T0620 $19.95 button channel control. • Easy to read red LED channel display. • Miniature size suits installation in modern vehicles. • Maximum legal power output. Cat # C5100 $79.00 SPECIAL INTRODUCTORY OFFER - SAVE $10.00 Road Runner RR-477 Compact Hand-Held UHF Transceiver: • Scanning , lock out , Hi-Lo power controls. • Pro grammable repeater operation. • Optional tone squelch available. • Back-lit LCD display. • Maximum legal 5 watt output. • Includes rechargeable ni-cad battery. Cat # C5047 $599.00 Availabl e Ac ce ssories: a) Speaker microphone Cat # CSOSO S49.50 b) Drop in desk charger (including tast and slow charge rates) Cat # C5052 $129.00 c) Glass-mount half wave antenna no holes to drill! Cat # K3095 $79.00 d) Mobile transceive r adaptor - adapts i~~X your AR-477 to mobile configuration. Includes full mounting hardware ideal for use with a) & c) above. Cat # C5054 $129.00 e) Spare 10.8 volt. S00mA ni-cad battery. Cat # K3090 $69.00 f) Communications headset Cat # K5060 $49.00 ' g) Vax-unit - allows handslree operation using headset f) above Cat# C5055 S69.00 h) Trickle charge AC adaptor Cat# T0120 $19.95 SG-792AL: • Similar to SG-796 above, but includes 6 shortwave bands, VHF air band and long wave band. Cat # C6025 $79.00 • Optional AC adaptor Cat # T0320 $19.95 I ... ---- . .~~g~~ - --..,,.__-----...........____ ~ Seamaster International VHF Marine Transceiver: • High/Low power switch . • Scan, priority, dual watch , up/down channel control. • Auto seaphone compatible. • 54 transmit and 57 receive channels. • DOTC Approval # 274B0090. Cat # C7000 $299.00 SPECIAL INTRODUCTORY OFFER Auto Seaphone Microphone: (lo suit above): Cat# C7005 $159.00 Wired to suit C7005 transceiver. Seamaster VHF Marine Antenna: • Includes 4-way polycarbonate UV stabilised base and coaxial cable. • Weather-proof fibreglass radome. • Ground independent half-wave design . Cat # K3162 $69.00 !~ - ";;';~ Mobile Scanner AR-950: • Suits mobile or desk-top installation. • Frequency coverage : 60MHz-90MHz, 118MHz-174MHz 430MHz-512MHz, 830MHz-950MHz. • Search increments: 5KHz, 10KHz, 12.5KHz, 25KHz, 30KHz. • Search, scar. , priority, lock-out, delay/hold, AM/FM function s. • Supplied with 2 antennas for optimum UHF and VHF reception . • Inbuilt 20dB local/DX attenuator. Cat # C5015 $499.00 • Optional AC adaptor Cat # T/230 S24.95 - ~ -,,:.r-- ~ · PT.29: TIIE AUS'FRALIAN VFT PROJECT THE EVOLUTION OF ELECTRIC RAILWAYS In the last episode in this series, we look at recent developments in fast trains overseas. We then conclude with a discussion of the Very Fast Train proposed to link Sydney and Melbourne, and later other capital cities and population centres. By BRYAN MAHER As might be expected from their considerable past experience with electric traction, the Swedes are working with experimental high speed trains. They consider new dedicated tracks too expensive in their crowded country. Therefore, in August 1986, Swedish Railways (SJ) let a contract to ASEA Traction for 20 high-speed trainsets capable of 200km/h on the existing tracks. Each trainset consists of one lightweight Bo-Bo electric locomotive hauling five passenger coaches. Additional coaches can be added when necessary. The rear coach contains a driver's cabin and full console from which the train can be driven when running in the reverse direction. Each train is equipped with a buffet car and carries 288 passengers. The aim is to reduce the present travelling times by 25% on all main lines and recapture the passenger traffic currently lost to road and air travel. To achieve this, consistent running at 200km/h is required. At this speed, the 457km journey from Stockholm to Gothenburg will shrink from the present 4 hours and 5 minutes to a tidy 3 hours. The current traffic is 2,700,000 passengers annually, a figure which is expected to rise to 4,400,000 by mid 1990. This increase will fully occupy the first 20 trainsets delivered. SJ has an option with ASEA for a further 32 similar trainsets, destined for the Stockholm-Malmo, Gothenburg-Malmo and StockholmSundsvall routes. ASEA's experimental train ASEA has based the design on their class Xl 5 experimental mainline train. This has been running on SJ mainlines since 1977, assisting in the development and testing of new motor drive systems, bogies and train controls. The excellent results of SJ's XlO commuter trains running in the cities of Stockholm and Gothenburg and the southern districts of Sweden since 1982 have confirmed much of ASEA's research. AN ARTIST'S IMPRESSION of the Australian VFT streaking through the countryside. We think the artist must have let his/her imagination run riot about the gradient though. Maximum gradients are planned to be 3.5%, not 20% or more as shown in this view. 4 SILICON CHIP Gate-turn-off thyristors (GTOs) and 3-phase variable frequency variable voltage induction traction motors have been a valuable result of this concentrated R&D effort. Add to this new motor control systems, suspension and coupling techniques and we have the great advance in technology now being exported from Sweden to the rest of the world, including Australia. ASEA Brown Boveri are even now developing a more advanced GTO, with the promise of inverters using less semiconductors, at lower cost and weight. 15kV 16.6Hz supply The Swedish fast trains operate from the standard single phase 15kV 16.6Hz overhead voltage. In each locomotive, the main transformer has six secondaries; four of these supply the traction system, one feeds the auxiliaries and the sixth secondary is dedicated to harmonic and power factor control. Each traction secondary winding feeds a 4-quadrant GTO rectifier GERMANY'S VERY FAST ICE (Intercity Experimental) trains held the world speed record until just recently. When they begin full operations, the trains will be fully sealed, so that passengers will not experience uncomfortable pressure variations when passing through tunnels. bridge, the outputs of pairs of bridges being paralleled to form a DC link. Each DC link supplies power to a 4-quadrant GTO DC/AC 3-phase inverter which then drives two of the four 3-phase inductiontype traction motors. Because 4-quadrant controlled GTO bridges are used throughout, full regeneration of power is possible, allowing traction and regenerative braking with the one switchless system. When the driver wishes to slow down or stop, he reduces the frequency of the inverter output. While the induction motors are pulling the train they normally run at about 97% of synchronous speed but when running (under momentum) faster than this sync speed they act as asynchronous alternators, to apply braking to the train. This regenerated power returns via the inverters, the rectifying bridges and the transformer to the whole SJ railway grid. Germany's ICE train Until just recently, the official world rail speed record of 406km/h was held by the German Federal Railways (DB) Inter-City Experimental (ICE) train. Designed with optimised aerodynamics, the new ICE train has improved high speed power and trailing bogies and a total train power of 8.4MW (11,260 hp). Two locomotive designs are being tested, one built by ABB and one by AEG and Siemens. The 114m long train consists of a Bo-Bo electric locomotive at each end, with three passenger coaches carrying a total of 261 passengers. Each 4.2MW loco weighs 78.2 tonnes and passenger coaches weigh 46.6 tonnes, giving a total weight of 296 tonnes for a 5-car train. Though each locomotive is equipped with a lightweight pantograph, MARCH 1990 5 haul the VFT at 330km/h. ABB are building Bo-Bo-Bo locomotives to haul the train from the French Coast through the tunnel and on to London. While in the tunnel the locomotives will run on 25kV 50Hz. Once on English soil, the loco will draw power from the British Rail south line 750V DC 3rd rail current system. The Australian VFT ANOTHER VIEW OF GERMANY'S high speed ICE train. Normally these travel with only the rear locomotive's pantograph in the raised position. This is done to keep drag to an absolute minimum. only the rear loco runs with its pantograph raised, similar to the French TGV described last month. This reduces slipstream drag. A high-voltage cable runs the length of the train to connect both pantographs. Each loco carries a 5.12MVA transformer, GTO rectifiers and a 7.6MVA inverter to supply 3-phase variable voltage variable frequency drive to the four induction type traction motors. To minimise that gremlin of all high-speed trains, unsprung weight, special suspension methods are used for the heavy motors. The locomotive body carries 2/3 of the weight of motors and gear box, the remaining 1/3 of their weight being suspended from the bogie frame. Flexible lateral suspension units perform this mass-juggling miracle which leaves the driven axles to carry little more unsprung weight than the running wheels and axle. Complete with hydraulic dampers to modify vertical and lateral movement, this clever construction results in minimum track stress at very high speed, and a high degree of train rolling stability. Florida's VFT project This American very fast train is proposed to run on a dedicated line 6 SILICON CHIP from Miami on the Atlantic coast to Tampa on the Gulf of Mexico. To avoid formidable civil engineering work, this new line will not cross the Everglades but will detour northwards. From Miami, the train will run through Palm Beach to Orlando, serving the Florida Disneyland, a potential source of considerable passenger patronage. From Orlando, the route will take a south westerly path to Tampa. The total run will be 480km. The Florida trains will consist of a 3.2MW 25kV 60Hz Bo-Bo electric locomotive at each end, with three 1st class and five holiday class passenger coaches and a diner between, giving a capacity of 480 passengers. Eight 3-phase induction motors will propel the train at 240km/h. When the green light is given for construction, ABB will provide the locomotives and rolling stock. English Channel VFT The Trans Manache Link (TML) Company is constructing a pair of tunnels beneath the English Channel to directly link England and Europe by rail. Tunnel users will rent pathways at set times. One user will be the London-Paris very fast train. Between Paris and the coast, the French locomotive will Originally proposed by the eminent Australian scientist Dr Paul Wild, the concept of a very fast train carrying passengers from Sydney Central to Melbourne Princes Street in less than three hours is quite realistic. Consider that by jet plane the trip from city to city takes 1 hour and 15 , minutes flying time plus delays at the terminals and travel by car from city to airport and vice versa. All up, in peak hours, the total travelling time can easily be 3 hours 30 minutes or more. Then there are many people unwilling to travel by plane. And what of freight? The Australian VFT is presently in the advanced design stages, sponsored by a consortium of private industry: BHP, Elders IXL Ltd, Kumagai Gumi Ltd and TNT Australia Ltd. The proposed train will run from Sydney past Mascot airport, to Bowral, Goulburn, Canberra, Cooma, Bombala, Orbost, Bairnsdale, Dandenong and then Melbourne. The system will be entirely double track, of standard gauge, (1435mm), using advanced wheel and rail technology, with electric traction. Estimated to cost $4.8 billion to construct, the project should provide employment for 25,000 Australians in the building of permanent way and civil engineering works, rollingstock, power supply and support facilities. As well as providing SydneyMelbourne travel, the system will give access to Canberra and the Snowy Mountains. Fares are expected to be competitive with air travel and two classes of coach seating arrangements will suit all travellers at a variety of charges. The no- FLORIDA'S FAST TRAIN PROPOSAL looks similar to the French TGV hut if it is given the go-ahead, all locomotives and rolling stock will be supplied by ABB of Sweden. tional design calls for a running time for non stop trains of 2 hours and 56 minutes, with less than 8 minutes longer if two stops are made along the way. Two locomotives The proposed train will probably consist of two 4MW Bo-Bo electric locomotives, one at each end, with six intermediate cars between. On passenger trains, the cars will consist of first and economy class cars, some with food preparation galleys. There will be 80 passengers per first class coach and 98 per economy car. These numbers will be reduced to 64 and 79 respectively in the case of cars incorporating a galley or baggage compartment. The total train is expected to be 210m long and will carry about 400 passengers. Each locomotive is planned to be 20m long, 3.2m wide and 4.4m high, weighing 80 tonnes. Passenger cars will be 6.2m longer than a locomotive, the same width, but 300mm less in height, and weigh 40 tonnes empty. Freight cars will be only 18m long, weighing 80 tonnes. The high train power of at least BMW (10,700 hp) is necessary to accelerate the train to the 360km/h operating speed on the high speed track section. Fast and suburban sections The route may be assumed to consist of three speed sections. Within 20 to 30km of terminal stations (Sydney and Melbourne), the track will parallel existing SRA and VR suburban lines. Here speed will be restricted to within 90 to 200km/h for two reasons: track curvature and power supply. Both the NSW and Victorian Railways use 1500V DC supply for their electric traction and 120V AC for signalling and interlocking systems. When running on parallel tracks in these regions, the VFT will also be powered by the 1500V DC supply but the (approximately) 1 lMW required per train will not be available - hence the restriction in speed. Once clear of suburban areas, the VFT high speed tracks will be powered by high voltage single phase AC. Whether 25kV or 50kV will be used is still to be decided. Between cities, a steady 350 or 360km/h running speed is envisaged. To allow such continuous speed, track curvature will be limited to 7km horizontal and 22km vertical. The track will be BHP headhardened 60kg/m rail on 270kg prestressed concrete sleepers, laid on a heavy ballast bed. In all, 860-900km of electrified double track will be constructed on a 30-metre wide easement, but this will be wider where earthworks, culverts and railway stations are built. With the high power/weight ratio proposed, (8MW/460t or 17.4kW/t), the VFT will be quite capable of racing up 3.5% grades at full speed. Therefore the design philosophy is to run straight up and over hills rather than curve around them. Aerodynamics At a speed of 350km/h, aerodynamic design is paramount. The total resistance to motion of a train must (obviously) be overcome by the locomotive power. On flat track in still air, the motion resistance of any vehicle can be expressed by the standard polynomial equation: MARCH 1990 7 train on the system is using current. Excess power generated by the train during braking can readily be absorbed by the state electricity grids. This facility will not always be available while the VFT is running on 1500V DC within the Sydney and Melbourne suburban areas, as the suburban DC supply is sometimes unreceptive. But regenerative power will also be absorbed by the train's own auxiliary load - adequate for braking at the low suburban speeds. Eddy current brakes AUSTRALIA'S VFT (VERY FAST TRAIN) is currently in the process of an $18.9 million dollar feasibility study. It is being planned to take advantage of the high potential passenger traffic between Sydney, Canberra and Melbourne and will run at speeds of 350km/h. Expected travelling time between Sydney and Melbourne is 3 hours. Resistance = A + Bv + Cv2 + ... where: v = velocity; A = mechanical bearing friction plus the rolling friction of wheel on rail (not a problem using roller bearings). Rolling friction is minimised by using heavy rail rigidly laid; B = that part of rolling resistance which is proportional to velocity, plus the momentum of any air volume carried forward by the train. The first part is a function of weight per axle, while the second part is minimised by streamlining. Bogies, pantographs, coach joins and air intakes of diesel or gas engines all trap air, adding drag. Successful streamlining minimises these factors and rejects the use of diesel or gas propulsion. Electrification using a single pantograph running knuckle-forward, enclosed bogies, flush fitting windows and doors and continuous profile vestibule coach joins are thus mandatory; C = (train aerodynamic frontal area) x (air density) x (frontal, bogie and pantograph air pressure effect + train skin friction). The C term can be reduced to: skin friction, 50%; bogie and undercarriage air drag, 25%; pan- e SILICON CHIP tograph 6% ; airconditioning intakes 6 % ; front end 6 % and rear end 6% Though smaller than A or B, C is vital as it is multiplied by the square of the velocity. At high enough speeds, the air resistance of the train skin can predominate over all other considerations (assuming optimum aerodynamic shape). Skin air resistance can be minimised by smooth construction using unpainted stainless steel, welded, not riveted. Motive power To keep the unsprung mass per axle down to 1.6 tonnes, it will be necessary to body-mount the traction motors and gearboxes. Hollow quill drive shafts will transmit traction and braking forces between motors and driven wheels. Total load per axle will be 20 tonnes. Three phase induction motors will be used for traction. The benefits of high power to weight ratio and rugged, simple, maintenance free rotors make induction motors the top choice. As a bonus, the use of GTOs allows 4-quadrant power transfer, for full regenerative brakes at all times. This electric brake facility will be fully operative even if no other Out on the high speed section of the track, because of the limits on wheel-rail adhesion at high speed, even a combination of electric regenerative brakes and pneumatic disc brakes will be insufficient. The train specification is stringent, calling for an emergency stopping distance of 3500m for a train running down a 3.5% grade at 350km/h! Therefore eddy current brakes will also be used to assist in stopping the train. A controlled current flowing in electromagnets train-mounted close above (but not touching) the rails will produce eddy currents in the rails. This dissipation of energy generated by motion causes a braking effect. Thus, the train will be brought to a stop by a force which does not require wheel-rail adhesion. To ensure compatibility with VR and SRA locomotives should towing of a VFT ever be needed, and to provide a parking brake, a standard air brake and train pipe will also be available. Noise emission There should be no fear of excess noise within the suburbs. The German ICE train at 150km/h is quieter than existing VR and SRA suburban trains at 80km/h. Logistics The proposed Sydney-Melbourne VFT will generate (directly and indirectly) 25,000 jobs for 5 years during construction. At least 32 trainsets will be built in Australia, including 200 passenger cars, 20 freight cars and 64 locomotives. The complete construction will cost $5 billion in today's values. Passenger traffic of 14,000,000 trips, equivalent to 6,600,000 full Sydney-Melbourne journeys, annually is expected. The 900km double track will need 217,000t of steel rails, 3,000,000 sleepers, 9 million tonnes of ballast and 6600t of copper overhead contact wire. All these materials are available from Australian manufacturers. Between 4000 and 8000ha of land will need to be purchased, 50 to 100m wide over 800 kilometres. A total of 326 bridges, totalling 18km are planned, mostly in the Dandenong section. Besides the two terminals, 16 railway stations are proposed to cater for tourists to the Snowy Mountains ski resorts and other intermediate stops. Tunnels will be unavoidable in the city suburban areas, probably 6 in Sydney and up to 10 in the precincts of Melbourne. Frequent trains An average of one SydneyMelbourne non-stop train every 30 minutes is proposed, with one intermediate stopping train per hour. Peak hours will see extra express ANOTHER ARTIST'S IMPRESSION of the Australian VFT running through the countryside. As with the TGV, the VFT will run with just the rear locomotive's pantograph raised. And since the supply voltage will be 25kVAC or 50kVAC, the height of the catenary is likely to be somewhat greater. trains added to the route. The Sydney-Melbourne fare is expected to be approximately $100. The consortium is hoping to start construction within 12 to 18 months. First, the Sydney-Canberra section will be constructed to enable full-speed testing of rolling stock, power and in-train signalling systems. The Canberra-Melbourne leg will commence construction the following year, with the entire railway to be completed by 1996. Feasibility study The first report of a $18,900,000 feasibility study delivered in November 1989 predicted that the VFT would generate $1 billion in ticket and freight charges annually. The report also costed an alternative inland route via Albury. The consortium presently favours the coastal route because it has greater scenic and tourist attraction. On the coastal route, stations are proposed at the following centres: Sydney, Mascot, Campbelltown, Bowral, Goulburn, Canberra, Cooma, Bombala, Orbost, Bairnsdale, Maffra, Traralgon, Moe, W arragul, Dandenong and Melbourne. Inland route stations The inland alternative route proposes stations at Sydney, Mascot, Campbelltown, Bowral, Goulburn, Canberra, Yass, Wagga, Albury, Wangaratta, Benalla, Seymour, Tullamarine and Melbourne. This route is more than 100km shorter than the existing Sydney to Melbourne railway. Perhaps the day of great electric railway progress is indeed dawning in Australia. On this optimistic note we end our series on "The Evolution of Electric Railways". Acknowledgements Special thanks to Dr John Nicolson (technical manager) and Dr Paul Wild (chairman) of VFT Australia; to Lars Persson of ASEA Brown Boveri Traction (Aust). Also to Comeng of Granville and Dandenong, ASEA Journal, ABB Journal, BBC, AEG, SJ (Sweden), DB (Germany), CFF (Switzerland) and Deutsche Eisenbahn Consulting (Frankfurt) for photographs, data and permission to publish. ~ MARCH 1990 9 A look at the UC3906 SLA battery charger IC The Unitrode UC3906 is designed to correctly control the charging of sealed lead acid batteries so that over-charging is avoided and life is maximised. It compensates for the change in battery voltage with temperature so that overcharging is avoided, regardless of the ambient temperature. By DARREN YA TES In the July 1989 issue of SILICON CHIP, Garry Cratt featured the UC3906 battery charger in his Amateur Radio column. The circuit presented was suitable for 12V sealed lead acid (SLA) batteries and the article created quite a lot of interest. Since then, many readers have wanted to know how to use the circuit to charge 6V batteries and how to add other features . With this in mind, we are presenting this follow-up article on the maSINK 16 jor characteristics of the UC3906. We have also designed a more comprehensive charger circuit which is featured elsewhere in this issue. With careful use, sealed lead acid batteries can be expected to give a service life of 5 to 10 years. But if they are over-charged, which happens all too often with most charger circuits, their service life will be only a fraction of this figure. A typical car battery charger is not suitable for SLA batteries and will SOURCE COMPENSATION f5 14 +VIN 1---+--013 VOLTAGE SENSE , - - - - - - - U 1 1 TRICKLE I VREF BIAS 1----012 CHARGE ENABLE VREF POWER 7 INDICATE 9 OVER-CHARGE INDICATE OVER-CHARGE 8 TERMINAL Fig.1: internal circuitry of the UC3906. It monitors the battery voltage and switches to one of three charging modes: trickle, charge or float. 10 SILICON CHIP almost always result in overcharging. By the way, there is some confusion about "sealed lead acid" and "gel" batteries. Most manufacturers now call them sealed lead acid but still refer to the term "gel". Since the electrolyte in a SLA battery is in the form of a gel, we don't think there is much wrong with referring to them as gel batteries but since that term now seems to have fallen out of vogue, we will call them SLA batteries from now on. OK? Now back to the UC3906. Charge states Fig.1 shows the schematic diagram for the internal circuitry of the UC3906 while Fig.2 shows the chip connected into a circuit which is suitable for charging a 12V SLA battery. You need to look at both of these circuits together to understand how the chip works. Essentially, the UC3906 has three main modes or states of operation and these depend on the voltage of the battery under charge. These are shown in Fig.3. State 1 is called "bulk charge" whereby the battery is charged at close to or the maximum charge rate. This can be seen on the plot for charge voltage in Fig.3. As the battery voltage builds up to V12, the circuit changes to State 2, the "over-charge" state (point C on the charge voltage curve). When the battery reaches point D on the voltage curve, the charging current begins to taper off. Upon reaching point E, the battery voltage is equal to Voc (overcharge voltage) and the charger circuit switches abruptly to State 3, the "float" state. From here on, the battery may be charged at any level up to 1/lOth the maximum charge rate but it will not be allowed to exceed the "float voltage", Vp. D2 1N4DD7 + + SUPPLY INPUT -i D3 1N5404 .,.. 5 3 4 2 RA 180k 1% 15 6 BATTERY .,. i- 12 1) VT = VREF (1 + 2)-VOC 3) VF = VREF (1 + = = D.95VOC = 0.9VF = B) IT WHERE RX = R: :c RB + RA R~ RB ) :c .t~c 0 RB) o,::v = .o::v = VIN - VB - 2.5V RT Fig.4: all the key voltages and currents can be designed into the circuit using these equations. RC 39k 1% 14 .,. R: RX ) RA + RA 5) V31 6) IMAX IC1 UC3906 VREF (1 4) V12 7) IOCT RB .D39+ Fig.2: basic circuit for charging a 12V SLA battery at currents up to 500mA. For practical applications, both the positive supply input and the output positive lead should be fused to protect D1 & D3. Also shown at the start of the charge voltage curve of Fig.3 is the "trickle charge" condition (points A and B). In this condition, the battery is completely flat and below the trickle voltage, VT, which is typically 10.5V for a 12V battery. When a sealed lead acid battery is in this flat condition, it cannot accept a high charge rate. Therefore, the circuit trickle charges it at IT, until the voltage rises above VT whereupon the circuit switches into State 1, bulk charge. All the key voltages and currents mentioned above can be designed into the circuit using the formulas shown in Fig.4. Four resistors in the circuit determine the three voltage levels, VT, Voc and VF, These resistors are Ra, Rb, Re and Rd and to ensure accuracy, they should be ~~-~---:,,;-VOC C D .__IFF"i~VgF=..V:!131 G CHARGE VOLTAGE - A ------ -- -------- CHARGE CURRENT mc_:_ __ IT --------- STATE LEVEL OUTPUT 1 ::=-i 0 oc TERMINATE INPUT (C/S OUT) I - ~- STATE 1 I I I '1 ON-i---- • OFF -ri I I___ .I.__ I oc INDICATE OUTPUT l __ _ I I I STATE 2 ... I~ ---t--___ . _ _ , _ I- STATE 3 • I. STATE 1 Fig.3: voltage and current waveforms for the various charge states. If the battery is flat, it is triclcle charged until voltage VT is reached. The circuit then switches to State 1 (bulk charge), followed by State 2 (over-charge) & State 3 (float). 1 % tolerance. Using the formulas in Fig.4, you can check that the circuit has a VT of 10.6V (formula 1), Voc of 14.6V (formula 2), and a VF of 13.8V (formula 3). Formulas 4 and 5 are of academic interest only, since they are controlled by the internal functioning of the IC. As it stands, the circuit of Fig.2 will give a ma ximum charging current of 500mA , as may be calculated with formula 6. If you want a lower charge current, the resistor Rs should be varied according to the formula . As a practical example, if you want a maximum charge current of 250mA, resistor Rs should be increased to rn. However, if you want a higher charging current, say 1 amp, the circuit must be upgraded by changing Ql to a higher gain transistor such as a Darlington BD650. This is because the UC3906 can only deliver a maximum base current of 25mA from its pin 16. So for higher charge currents, Ql must be changed as well as Rs. And since diode D2 has a rating of 1 amp continuous, it should be upgraded to, say, a 3-amp 1N5404, if currents of more than 500mA are required. For charging currents of 1A or more, Ql should be mounted on a heatsink. If a load is applied to the battery while it is connected to the charger (which is how we envisage the unit would be used), the charger will contribute its full output to the load. If the battery drops 10% below the float level, VF, the charger will MARCH 1990 11 Charge & Discharge Currents the battery could be expected to deliver around 450 milliamps for 10 hours. Now what do we mean by terms such such C/4 and C/5? When we start bandying about figures of C/4 or C/5, we are talking about charge and discharge rates based purely on the battery capacity and with none of the derating mentioned above. C is the battery capacity in ampere-hours. C/5 refers to a 5-hour rate of discharge or charge. So C/5 for a 5 amp-hour battery is 1 amp. C/4 for a 5 amphour battery is 1.25 amps. Let's make it clear again that rates such as C/4 and C/5 do not Many people are confused about battery capacity and what it means as far as charge and discharge currents are concerned. Battery capacity is rated in ampere/hours. For example, you might have a 5 ampere-hour battery. Now this does not mean that the battery is supposed to deliver 5 amps for one hour, although it might not be far short of it. The capacity is normally rated for 10 hours or 20 hours. At the 20-hour rate, a 5 amp-hour battery could deliver 0.25 amps (250 milliamps) for 20 hours. At the 10-hour rate, the capacity would be reduced by about 10%, so that reset itself to State 1 and full charge current will be delivered. An interesting aspect of the circuit is that it does not drain any power from the battery via the sensing resistors, Ra to Rd, when the input power is off. This is because the chip senses whether the input voltage is low (see "UV sense" section on Fig .1) and if that is the case, the internal transistor at pin 7 is off. Consequently, no current flows through Re and battery loading is negligible. circuit published in July 1989. They have been included because the UC3906 has been found to be vulnerable to reverse voltages. D2 protects the circuit against reverse current flow which can occur if a battery is connected to the output when no power is connected to the input. D3 protects the circuit against reverse connection of a battery and should itself be protected by a fuse (see our complete charger circuit elsewhere in this issue) otherwise it can be destroyed. Dl protects the circuit against reversed input supply connections and could be eliminated if the circuit is permanently wired. Diode protection By the way, diodes D2 and D3 were not included in our original D3 1N5404 RT 470fl ., 5 3 4 1% 16 2 .,. 11 12 RB 18k 1% IC1 13 UC3906 RD l0 390k 1% 7 14 .039-+ RC 43k 1% 15 470fl.,. Fig.5: basic charger for 6V SLA batteries (500mA max). As before, the positive input & output lines should be fused to protect D1 & D3. 12 SILICON CHIP refer to the recommended discharge current of a battery. If you discharge a battery at a C/5 rate you will only get about 85% of its quoted capacity (assuming that is quoted at a 20 amp-hour rate). Finally, regardless of the capacity, SLA batteries can deliver very high discharge currents for short periods (20 seconds or less). For example, a 5 amp-hour battery may well be able to deliver a short term current of 50 amps or more. However, such a rate of current should not be maintained for very long as not only will it discharge the battery very quickly but it may also cause internal damage. Fig.5 is a version of the charger which is suitable for 6V SLA batteries. Its over-charge level, Voc, is 7.4V. VF is 6.9 volts and VT is 5.1 volts. Again, you can check that these voltages are obtained by substituting the values for Ra, Rb, Re and Rd into formulas 1, 2 and 3 in Fig.4. Maximum charging rate As noted above, the UC3906 controls the maximum charging current delivered to the battery, according to formula 6 in Fig.4. If you have access to the specifications for a battery, you will see a figure quoted for maximum charging current. If you don't have access to the specs, you are safe to assume that you can charge any SLA battery at C/5. To give an example, if you have a 10 amp-hour battery, you can safely charge it at a maximum current of 2 amps. For an explanation on charging rates and terms such as C/5, see the panel accompanying this article. Above VT, the battery is charged at the maximum current recommended by the manufacturers. This is another area of confusion as different manufacturers set different maximum charging rates fOi their batteries. Typically though, the maximum charge current is C/5 or C/4 or higher. ~ Super Selections, Super Values - Come In Today! Cordless Screwdriver. This rechargeable driver has all the power of an electrical screwdriver, without the cords! Comes complete with an adapter recharger, 1 drill bit, charging stand, 1 phillips and 1 slotted screwdriver bits. Also features forward/reverse switch and adjustable handle for finding just the right position. Maximum torque 25kg/cm. s4.9s20 . . .69.95 1. Economy Styrene Case. 15.2x8.1x4.8cm. Reg 6.95 Sale! 3.95 2. Balance Control. 211-261 Reg 2.99 Sale! 1.99 210223 3. SPST Rocker Switch.215.590 Reg 3.99Sale!1.99 4. Three-Conductor ¼"Plugs. 274.139 Reg 4.49 . Sale! 2.49 5. Halogen Globe. A long life replacement globe. HPR 52 type, pkt of 1, 2.8 volts. m-1 190 Reg 6.95 Sale! 4.95 10. SK Ohm Linear Potentiometer. Has 43mm long, ¼" diameter shaft, and mounts in a o/,s" hole. Sale! 99c 6. Magnetic Wire. 21s.1 345 7. BNC Male to Phono Jack. Video and RFadapter. 278-254 5.95 11. W/W IC Tool. 2151 510 Reg 11.95 Sale! 7.95 12. 28 Position W/W IC Socket. 215 1993 Reg 2.99 Sale! 2.49 13. 8 Pos.W/W IC Sckt. 2161988 Reg 2.99 . 2.49 14. 14 Position W/W IC Socket. 2161993 Reg 2.99 . Sale! 2.49 15. 1ttin W/W IC Socket. Square 0.025" posts accept three levels of wire. 215.1994 Reg 3.49 .Sale! 2.49 16. DPDT Slide Switch. 215.403 Reg 2.99 Sale! 1.49 17. Instrument Case. 210250 Reg 9.95Sale! 6.95 18. 9V Battery Holder. 210.325 Reg 99cSale! 49c 19. 1/a" Open Circuit Jack. 214.251 Reg 3.49 . Sale! 1.99 20. Auto Plug YAdapter. Power two 12V DC accessories from one lighter outlet. 210-1535 Reg 11.95 Sale! 6.95 With Over 400 Stores Australia Wide You 'll Find One Near You Wherever You Are! --=an.lg IC a - - - - - - - - - - - - - - - ELECTEl&NICS Prices Apply at All Tandy Stores and Participating Dealers Tradema rk ol Tandy Corpo1a11on --------------- VINTAGE RADIO By JOHN HILL Wave traps - a useful vintage radio accessory A "wave trap" was a common radio accessory in the 1920s and can still he of use today for those who dabble in vintage radio. This month's column delves into the mysteries of this long forgotten device. Back in the days when most domestic receivers were of the "reaction type", selectivity (the ability of a radio to separate out adjoining stations) was something that left much to be desired. Early radio sets were not very selective. A simple reaction type receiver is reasonably selective on distant stations but nearby stations will literally swamp the dial, being audi- ble from one end to the other. Selectivity can be improved by altering the aerial tappings in order to1tighten the coupling to the tuning coil but any improved selectivity by this method will be at the expense of distant station volume. Selectivity can also be increased by removing the earth wire from the receiver or by using a shorter aerial. Again, both methods will reduce the long distance performance of the set. The regenerative receiver's lack of selectivity was just one of many reasons why superhets rapidly took over from reaction types. In my childhood days I had a 1-valve·reaction set in my bedroom. In those days I was living approximately 6km from 3BO's transmitter at Bendigo and from memory, I'd say that 3BO completely obliterated about one third of the dial. Stations within that particular zone were unlistenable because of local station interference. It is this type of situation that lends itself to a wave trap for such a device can almost completely tune out a local station, thus making more stations available for listening. A wave trap is about the most uncomplicated electronic device one can make. It consists of nothing more than a coil of copper wire and a tuning capacitor (see Fig.1}. VC1 15-415pF L1 TO ANTENNA ~--TERMINAL OF RECEIVER L1 : 60T, 0.5mm ENAMELLED COPPER WIRE CLOSEWOUNO ON 40mm DIA FORMER Fig.I: a wave trap consists of a tuned circuit in series with the aerial input. A basic wave trap is nothing more than a tuned circuit made up of a coil and a variable capacitor. The capacitor need not be a single gang unit. Instead, you can use a 2 or 3-gang unit salvaged from a derelict radio. 14 SILICON CHIP A quick glance at Fig.1 shows it to be nothing more than a simple tuned circuit which is identioal to the tuning coil and tuning capacitor of a radio receiver. Ideally, it This is the author's wave trap. It need not have been so large but the box was available - it previously housed a crystal set. A much smaller unit could be built using more modern components. This superhet receiver has an intermediate frequency of 175kHz. A wave trap helps to reduce the number and intensity of the heterodyne whistles that occur when such a set is operated in close proximity to a powerful local station. should cover the same frequency range. Adding a diode and a set of earphones to a wave trap would convert it to a crystal set. When using a wave trap it must be placed in series between the aerial and the aerial input on the receiver. If the wave trap is tuned to the local station, the tuned circuit of the trap resonates at the station frequency, allowing only a reduced signal to pass through to the receiver. All other radio frequencies pass through unhindered. Perhaps that last statement is not quite correct. Almost unhindered would be a more accurate statement for there is a slight drop in volume on other stations when a wave trap is in use. Also, frequencies close to the one being trapped are diminished to some extent. Unfortunately, every convenience has its price. TRF receivers We will digress for a moment and discuss a particular type of early radio, for it may help to make the operation of a wave trap more clear. One way that early receivers were made more selective was to introduce more tuned circuits. This was the way the first TRF (tuned radio frequency) receivers operated and it was common to see radios in the mid to late 1920s with two or three tuning dials on the control panel. In the case of a 3-dial set, there were two stages of radio frequency amplification prior to the detector. This involved three separately tuned circuits and such a set up increased selectivity by a considerable degree. Incidentally, those old TRF receivers with independent dials were quite difficult to tune for it was most unlikely that a radio station could be received with all the dials set at the same numerical position. In order to listen to a particular station, each dial had to be set to a position where each tuned circuit was correctly aligned with the others. If the circuits were not properly synchronised, the operator would hear nothing. A special log chart was usually supplied with multi-dial radios so that station positions could be recorded for future reference. It is little wonder that single knob tuning became popular. However, this required far greater accuracy in the manufacture of coils and tuning capacitors. Now the reason for the foregoing paragraphs on TRF receivers is this: installing a wave trap is, in effect, the same as adding another tuned circuit to the radio being used. When using a wave trap, the tuned radio frequency circuit of the trap does not track with the rest of the receiver and is only effective at one particular frequency - the frequency of the local station that it is designed to suppress. Under these circumstances, the wave trap makes the set more selective because it reduces the signal strength of the station it is tuned to restrict. MARCH 1990 15 Wave traps were common when this old Martin receiver was the latest thing. Reaction type receivers, such as the Martin, often needed an additional tuned circuit to minimise the swamping effect of a strong local station. A 3-dial TRF receiver such as this unit was quite tricky to tune so it was little wonder that single-knob tuning eventually took over. Multiple tuned circuits helped these old receivers to be more selective. Unlike the first tuned circuit of a TRF receiver, the resonant frequency in a wave trap is not passed on to other stages for further amplification. It works in a similar way but no use is made of the resonant energy, although enough signal passes through so that the trapped frequency can still be heard on the receiver at a much more restrained level. The term "wave trap" has been around for a long time and although the name explains the function on the device, I think that it should have a more scientific name. In actual fact, I believe a wave trap 16 SILICON CHIP should be called a "series connected, variable resonance, radio frequency choke". Now doesn't that sound a whole lot better than wave trap? However, for the convenience of readers, I shall continue to use the term wave trap. Early superhet problems Readers can be excused for thinking that a wave trap is only of use when using an ancient reaction type receiver in close proximity to a local station. While this is the most obvious application for a trap, it can also be used to advantage with early superhets which had low in- termediate frequencies. Although the standard IF for domestic receivers has been around 455kHz for about 50 years, this was not always the case. Many of the sets from the early to mid 1930s operated on much lower intermediate frequencies. One such frequency was 175kHz and this IF was quite common in early superhets. The peculiarities of these particular receivers becomes obvious when they are used close to a powerful station. In my own situation, I live approximately 4km from 3CV's 5kW transmitter and this causes con~ siderable local station problems with all of my vintage radio listening, including my early superhets. There are several types of receiver malfunctions caused by such strong interference. Firstly, heterodyne whistles appear at numerous points on the dial there are not just a few whistles but dozens of them. Secondly, harmonics of the local station frequency also appear at various places around the dial. One of my old superhets tunes in about three 3CV's and two 3BA's (a more distant local station). It is under these annoying circumstances that the old wave trap can be of assistance for it can help control the previously mentioned problems. Using a wave trap will eliminate many of the whistles and harmonics because it reduces the local station signal strength to more manageable levels. AGC problems Another situation where a wave trap can be an advantage is with a radio that lacks automatic gain control. If such a receiver is used carelessly and is tuned onto a local station without backing off the volume, the speaker can be severely overloaded and possibly even damaged. Again, a wave trap will help reduce the signal strength to more normal levels. A practical wave trap Although a wave trap is basically just a coil and a variable capacitor, it is far more convenient to use if properly housed. The one shown in FRONT PANEL VINTAGE RADIO REPAIRS 1 =~ REAR PANEL EARTH _ _,_ TUNING CAPACITOR (VC1) 15•415pF - ~ - LAWSON RADIO has been in the business of repairing radios for 40 years. If John Hill"s column has rekindled the memories, but you are not confident enough to carry out your own repairs then call us now, for an obligation free quotation . Should you want to sell or purchase a vintage radio contact Michael today. EARTH ANTENNA L1 : 60T, 0.5mm ENAMELLED COPPER WIRE CLOSE WOUND ON 40mm DIA FORMER Fig.2: here's how to wire up a practical wave trap with IN/OUT switching. Use one section of a 2 or 3-gang tuning capacitor if that's what you have available. 298 GREAT WESTERN HWY LAWSON, NSW 2783 (047) 59 1254 the accompanying photographs has been placed in a wooden box (an earthed metal box may be even better). It has both aerial and earth connections, plus a double pole double throw (DPDT) switch which either switches the aerial straight Although this old 4-valve Airzone is a superhet, it lacks AGC. Using a wave trap on this and similar receivers helps to throttle back the overwhelming effect of a local station. through to the set or to the set via the wave trap. The earth connection just goes straight through the box from the terminal on the back panel to the terminal on the rear panel - it is more convenient to have both the aerial and earth leads coming from the same position on the work bench. It is also very convenient to be able to switch the trap in or out at the flick of a switch rather than having to connect the trap into the aerial lead when it is required. Fig.2 shows a wiring diagram that completely cuts out the trap when the aerial is switched straight through. The number of turns on the coil will vary according to the gauge of the wire, the diameter of the former and the capacitance of the tuning capacitor. 60 turns on a cardboard tube from a toilet roll may be a reasonable starting point. If that local radio station is spoiling your vintage radio fun, then trap it out with an old fashioned wave trap. If you decide to build one, the convenience of the switchable model is well worth the ex~ e~ct. ~ ~esurrection !Jadio The original vintage wireless specialists Our skilled technicians offer QUALITY repairs & restoration. We have a large stock of bakelite and timber radios fully restored and for sale. Valves, high voltage capacitors and other specialised parts available. SPECIAL - this month only: 1O & 15µF 450 volt electrolytic caps $3.00 plus p&p WANTED - valves, radios, etc. , purchased for cash. Call in to our showroom at: 51 Chapel Street, Windsor, Vic 3181 PO Box 1116 Telephone: 529 5639 MARCH 1990 17 MORE DEALS TO MAKE THE High performance AT/386Hard Disk/Floppy Disk Controllers Universal Wirewrap Card CAT. IF054 CAT. DCAH (HDD) or CAT. DCA HF (HDD & l'DD) This universal wirewrap card is ideal for engineers and other technical people developing hardware add-ons for IBM PC/XT/ AT/386 or compatibles. ·1 The card provides a complete built-in i;; data bus, address bus and I/O line buffer ··. circuit. It incorporates a universal address decoding chip (0-3FF, step 8 or 16) and a D25 female connector. Buffering of the inputs and outputs makes damage to the PC's bus from Speed up the disk performance of your faults on the card impossible. AT or 386 machme by a factor of around 21 with these fast caching disk The wire-wrap area is 4000 holes w hich controllers. are plated through for easy prototyping work. The card is built to a very high 1:1 sector interleaving, using the latest standard and can withstand heavy use. Western Digital 1006 chip set greatly increases performance with most d rives . NORMALLY $129 Features: • Capable of addressing hard disks with u p to 16 heads and 2408 cylinders. 1 or 2 drives are supported • Will run at u p to 16MHz on a suitable high speed machine, delivering a massive 200% improvement in throughput from this feature alone I • The DCAHF is available with a built-in floppy disk controller, supporting up to 2 drives which may be any mix of 360K or 1.2MB 5¼" or 720K or 1.44MB 3½" drives. ONLY $99, SAVE $36 CAT.DCAHF ONLY $225 SAVE $24 Data Switches CAT. ACDS21 CAT LACPP5, only CAT LACPP10, only Serial Printer Cables- 3 Metres WAS $95 NOW $59, SAVE $3o CAT. LAAPS2 PS2 to AT keyboard connector adaptor. Enables AT style keyboards to be used on PS/2 computers. ,. graphics card adaptor. 9 pin to 15 pin adaptor enables multisync monitors to plug into the 15 pin analog output of VGA graphics cards. AMERE$9.75 CAT. LACM9 Modem cable 9 pin socket $9.75 each CAT. LANULL Nu ll Modem Adaptor $9.75 each $18.00 $25.00 Modem Cables - 2 Metres CAT LACM25 Type5 Computer Modem end 25 pm end 25 pm Female male 1_ _ _ _ 1 CAT.LACM9 Type6 Computer Mod em end 9 pm femal e 1 end 25 pm ma!e 8 Hardware Control CAT.LACSP9 CAT.LACSP25 Type3 Computer End 25 Pm Type4 Computer Printer Printer End 25 Pm End 9 Pin End 25 Pin Female Male 2 Male 3 3 3 568 19 1.6,8 19 CAT. LAAB Used to test and re-wire RS--232 interfaces ONLY $29.95 5,6,8 568 Use 4 wire cable Serial Printer Cables- 3 Metres xon/xoff Hardware Control CAT.LACSPX25 Type 1 CAT.LACSPX9 Type2 Pnntei Computer End 25 Pm Printer End 25 Pm Computer End 9 Pin End 25 P1.'"l Female 2 Male Fem ale Male 3 16 20 68 7 20 AT Cases, going for a Song! Mini Tower Case witb200WAT Power Supply 5 7 20 20 CAT. LAOT 20 68 8_ _ __ 4 Use 7 (or 8) wire cable Serial Quick Tester LEDs monitor the lines to give instant feedback Great for fault finding RS-232 Break--OutBox For connection between serial devices. All pins straight through. CAT. LAAVGA VGA to 25 pin plug. The approriate pins are connected (TXD to TXD, RX to RX etc.) ONLY$39.95 CAT. LACPP3 3 metre cable CAT. LACPP5 5 metre cable CAT. LACPP10 10 metre cable Standard nrinter cables with DB25 pin plug to 36 ,;in Centronics plug. Suits all popular parallel printers and computers printer ports. CAT LACPP3, only $15.00 Serial Printer Cables ONLY$9.75 Modem cable 25 pin plug to 25 pin socket All pins are wired straight through . ONLY$29.95 • Suits all parallel printers • Crossover switch • 36 pin centronics connectors Parallel Centronic Printer Cables Fem ale Modem Accessories • Suits all parallel printers • 2 computers to one printer or one computer to 2 printers • 36 pin centronics connector ONLY $9. 75 each CAT. ACDS22 EXTRA SPECIAL!!! DISK BOX WITH 100 DISKETTES CAT.DCAH ONLY $175 SAVE $50 Adaptors CAT. LA9M25F 9 pin plug to 25 pin socket. CAT. LA9F25M 9pinsocket to 25pin plugThe appropriate pins connect internally to allow for matching of serial equipment using a mixtureof9 pin and 25 pin connectors (eg. a 9 pin serial connector on a serial mouse to a 25 pin serial port on a PC). ONLY $15.75 each CAT. CAT.BP This compact case is the same as used in the famous Silicon Chip Project AT. It has plenty of room for a full XT, AT or 386 system, and has drive bays for 2 x 5.25" and 2 x 3.5" drives. Front power switch, reset, turbo and disk drive light and keyswitch . And being a "mini-tower" it takes up very little space. Normal price is $299, but for this month only Reduced to $199 while stocks last! SAVE$100 USE 9 (OR 101 WI RE CABLES ONLY $19.90 $15. 75each CALL US NOW FOR OUR GREAT CATALOGUE WITH ALL OUR PRODUCTS LISTED! OPPOSITION HAl'E OUR GUl'SI BABY AT CASE + POWER SUPPLY MULTISYNC CAI'.CAATBP CARD MONITOR + VGA CAT ACMM & CAT VC0800 This compact PC/AT case features a flip -top bd and fa cibties for expans10n for up to 8 slot mother boards . The internal drive mounting tray will accept up to 3 half height 5¼ hard or floppy dnves. LEDs and switches for Reset/Turbo/Power are provided A keylock and key are also provided . Dimensions are: 360mm(W) x 165mm(H) x 400mm(D) · Need more ports on your PC? This compact half slot card comes complete with 2 serial and 1 parallel power and all the connectors . plus a 9 pm to 25 pm DB adaptor cable for the senal port. Normally $85 Limited stock: ONLY$45,SAVE$25!! The cards provide complete register level compatib1lrty with the IBM Video Graphics Array standard (VG A ), wlule bemg backwards compatible with EGA. CGA "'ld Hercules Graph1cs/MDA monochrome standards. The VC1024 1s htted with an add1t1onal 256K of display memory for up to 1024 x 768 pIXel resolution. Prices the competition can't match!! 12MHz 0-wait state Normally $1,298 "half-size" AT Only $995, SAVE $303 motherboard Includes a heavy duty 200W AT Power Supply. Limited Stock Save $246 on 12MHz ONLY $175, SAVE $74 0-wait-state Monitor Madness!!! 14 11 EGA MONITOR + EGA CARD Save 40% on 2 Serial/1 parallel Port Card CAT IOPS2 Great Deal with TheTurboXT Motherboard CAT MB1 600 CAT MB286HS1 M "Baby-Size" AT Motherboard The MB1600 IS an IBM PC/XT compatlble motherboard. It measures only 81/i' x g· The board runs at 10 MHz or 4.77MHz, providing complete compat1b1lrty with the IBM standard Eight 62 pm edge connectors are also mounted to the board . The 1/0 channel 1s bussed across the eight expansion sloes The heart of the MB1 600 1s an 8088 ·3 CAI'. AC MECA & CAT VCEGA The ACMEGA is a full EGA colour monitor, providmg both text and graphics display with all EGA and EGA compatible graphics cards. It features a 0.31mm dot pitch tube with anti-reflective coating. A tilt and swivel stand is provided . This !ugh performance AT motherboard features ultra-fast performance and a full 8 slot expansion bus. It is switchable to 6, 8, 10 and 12MHz and can accept 256K , 512K 640K or 1MB of memory on the motherboard T he range of speeds allows slower memory LO be used when available The design uses the powerful CHIPS & TECHNOLOGY clup set (12 5MHz vers10n) for very high performance and relrability. It outperforms other 12MHz designs by a vvide margm . Normally $848, now only $675. SAVE $173 Normal price $595. But while current stocks last: only $349 "Magic Combo" Mono/ Colour Graphics Card + High-Resolution Monochrome Monitor CAI' VCCOMBO/CAT ACMA This is the video card and morn tor to smt all occasions ' The Magic Combo Card dnves both your old CGA colour morutor and tlus bnllrant new monochrome monitor to the two most popular standards 1. Colour Graphics Adaptor (CGA) standard When usmg the TTL monochrome monitor. grey tones are used to simulate colours 2. M onochrome Display adaptor with H ercules graphics (720 x 348 pIXeLs) when driving it as a TTL monochrome morutor Now you don't need to put up with gntty CGA graphics for your text - .s witch to !ugh qualrty 720 x 348 pixel MDNhercules. Nor do you have to miss out on all the games software because you can't run CGA graphics You get the best of bo h worlds with the Magic Combo. Normally $328, now only $275. SAVE $53 perform ance motherboard has a full 6 expansion slots (5x16 bit, 1x8 bit) and a full 1MB of BOnS memory for maximum performance - 13.7 on Nortons SI rating I 8 or 12MHz operation 1s keyboard selectable The small size of the board makes 1t ideal for reolacement m both XTs and slower ATs. The mounting holes match those of both XT and AT machmes. microprocessor The system board supports both ROM/EPROM and R/W memory It has space for 32K x 1 and BK x 1 of ROM or EPROM A full 640K of h1g h speed RAM can be fitted on the motherbrnmi Normally $495 plus $295 for 1MB of RAM. Sale Price $495 complete, SAVE $295!! NORMALLY $149 ONLY $99, SAVE $50 with V20 chip $109 Only while stocks last! ! ................................. ~~ :37] ~~~;o:~::•:~:: ·• L ~----•■-----■-•■• ElectrnnkSolution, Fax(02)9065222 We accept Bankcard , Mastercard & VISA Mail orders our specialty. Freight on smaller items is now $9 00 + $2.50 P&P • All prices include sales tax • All products carry a 14 day money back guarantee (software and hard disks excepted) • All products carry a full 3 month warranty • All cards come with full documentation • Ring for quantity discounts and tax free pnces Owing to technical advances products we supply may in some cases vary from those pictured In all cases they are guaranteed to perform to an equal or higher standard . ................................. A charger for sealed lead acid batteries This new charger is designed especially for 6 and 12 volt sealed lead acid batteries and is based on the Unitrode UC3906 charger IC. It is suitable for charging batteries of up to 15 amp-hour capacity and can deliver up to 3 amps. By DARREN YATES Elsewhere in this issue we have produced a comprehensive article on the characteristics on the Unitrode UC3906 battery charger IC. Here we present the IC in a circuit which will cope with 6 or 12V batteries and has five switchable charge rates. Most sealed lead acid (SLA) battery chargers on the market are quite simple affairs and are relatively cheap, but (and this is an important "but") most do not correctly charge a battery at either the correct current or to the correct 20 SILICON CHIP voltage. Not only that, many do not provide an "end-of-charge" condition and continue to belt current into the battery whether it's fully charged or not. This can do considerable damage to sealed lead acid batteries and greatly shorten their service life. Our charger maintains the battery at a constant float voltage once it has been fully recharged. This means it can remain connected to the battery indefinitely and still keep it in peak condition. This charger will charge either a 6 or 12V SLA battery and has charge rates set to suit capacities of 1.2, 2.6, 4.5, 6 and 15Ah. The maximum charge currents for these settings are 250mA, 520mA, 900mA, 1.2 amps and 3 amps, respectively. If you have a battery which does not quite match one of those batteries listed, that does not matter just select the nearest suitable current. For example, if you have a lAh battery, select the 1.2Ah charge rate. If you have a 3Ah battery, select the 2.6Ah rate. The charge currents provided are at the rate of C/5. C is the battery capacity in amp-hours. So the C/5 rate is C divided by 5. Hence, 15 amp-hours divided by 5 gives a charge current of 3 amps. However, many SLA battery manufacturers quote or recommend a maximum charge rate of C/4 (we took a more conservative approach). So if your battery is not among those quoted, you can divide its amp-hour rating by 4 and select the nearest charge rate provided. For example, if you have a 12 amphour battery, you could charge it on the 15Ah setting provided on our charger (ie, maximum charge rate would be 3 amps). The new charger is housed in a relatively large metal case, measuring 306mm wide, 204mm deep and 96mm high. On the front panel, it has two terminal posts for the charging leads to the battery and two rotary selector switches. The first selects either 6 or 12 volt charging while the second selects the rate of charge. There are four LED indicators. The first, on the righthand side of the panel, is a power LED, to indicate that the circuit is on. On the lefthand side there is a group of three LEDs to indicate the float (red), main (green) and trickle (yellow) charge modes. We will explain these modes a little later in this article. On the rear panel of the charger is the mains switch and two fuseholders, one for the primary of the power transformer and one in the positive output lead. The charger is short circuit proof and cannot be damaged by reverse connected batteries (except for blowing the fuse). How it works Now have a look at the circuit diagram of Fig, 1. As already mentioned, the heart of the circuit is the UC3906 (IC2) and this is teamed with an LF347 quad op amp (ICl) and a BD650 Darlington transistor, Ql. What the circuit does is to continuously monitor the battery voltage and then adjust the charge rate to suit. If you have a 12V battery connected and it is flat, say below 10 volts, the charger will only deliver a small trickle charge. This is because "flat" sealed lead acid batteries should not be charged at a high rate - it can cause damage. While the circuit is in trickle mode, the yellow LED is lit. Once the battery voltage rises above 10 volts, the charger then delivers its maximum charge rate, according to the setting of the charge switch, S2. While the charger is delivering a high cur- PARTS LIST 1 PCB, code SC14103901, 190 x 102mm 1 front panel label, 302 x 90mm 1 metal case, 302 x 200 x 90mm 2 knobs 1 2-pole 5-position rotary switch 1 4-pole 2-position rotary switch 1 red 4mm binding post terminal 1 black 4mm binding post terminal 1 240VAC mains switch 1 9mm rubber grommet 1 8mm cable clamp 2 3AG safety fuseholders (Jaycar Cat. SZ-2036) 1 3AG 5A fast-blow fuse 1 3AG 1 A fast-blow fuse 4 1 0mm 3mm-tapped metal spacers 3 solder lugs 1 2-way insulated terminal strip 1 18V 6A transformer (Jaycar Cat. MM-2000 or equivalent) 1 insulating kit to suit T0-220 transistors 1 insulating kit to suit stud mounting diode Resistors ( 1/ 4 W) 1 1MO 1% 1 2 560k0 1 % 4 3 220k0 1 % 1 3 180k0 1 % 1 1 47k0 1% 1 1 18k0 1 % 1 3 10k0 5% 1 2 3.9k0 5% 2 1 2.7k0 1% 2 Semiconductors 1 LF347, TL074 quad op amp (IC1) 1 UC3906 charger IC (IC2) Miscellaneous Screws, nuts, washers, heavyduty hook-up wire, heatsink compound, solder. rent, the green LED will be lit. Once the battery is fully charged, which usually takes four hours or so depending on how discharged it was, the charger will change over to the "float" mode. This maintains the battery at a constant terminal voltage, dependent on temperature. And as you would expect, this is when the red (float) LED is lit. All the charge functions are controlled by the UC3906 while the three LEDs are driven by op amps in the quad package. Power for the circuit comes from a transformer with an 18 volt secondary which feeds a bridge rectifier and 4700µF capacitor to give about 24 volts DC. This supply is fed to pins 3 and 5 of the UC3906 (IC2) and to the emitter of the Darl- 1 BYX98-300 or equivalent 1 OA stud mount power diode (D1) 1 1N5404 3A power diode (D2) 1 BD650 Darlington transistor (01) 1 PA40 rectifier bridge 1 3.3V 400mW or 1 W zener diode (ZD1) 2 5mm red LEDs (LED 1 , LED 4) 1 5mm yellow LED (LED 2) 1 5mm green LED (LED 3) 4 5mm LED bezels Capacitors 1 4 700µF 35VW pigtail electrolytic 3 0.1 J,tF metallised polyester (greencap) 1 .0012µF metallised polyester 2.2k0 5% 1 kO 5% 1 kO 1 % 6800 1 % 4700 5% 4 700 1 % 3900 1% 4. 70 5% 5W 3.30 5% 5W ington transistor, Ql, via a paralleled group of four 5-watt wirewound resistors which have a resultant resistance of 0.970. This composite resistance is monitored by IC2 via switch S2. This part of the circuit looks a little confusing but is quite straightforward really. What happens is that switch S2 is used to "tap off" part of the voltage developed across the composite resistance and feed it to pin 4 of IC2 . IC2 then turns on Ql just hard enough to ensure that the voltage between its pins 4 and 5 does not exceed 250mV. This is how the circuit maintains the selected charge rate. By using S2 to "tap off" the voltage across the composite resistance, there is no need to MARCH 1990 21 The SLA Battery Charger uses a large power transformer so that it can deliver the maximum 3-amp charging current. Take care with the mains wiring and sleeve all exposed terminals with plastic tubing to prevent electric shoclc. switch the charging current. Hence a light duty rotary switch can be used instead of one with heavy duty contacts. Because the UC3906 can only supply a maximum current of 25mA, Ql is specified as a BD650 Darlington transistor which has a minimum gain of 750 at a collector current of 3 amps. This means that the maximum current that the UC3906 will ever have to deliver is a tiny 4 milliamps. Typically, the current from the UC3906 will be much smaller, less than one milliamp. The collector of Ql is connected to the positive output terminal of the charger via a 10-amp stud mounting diode, Dl. This prevents any damage to the circuit which could be caused when a battery is connected to the output while no 22 SILICON CHIP power is applied to the circuit. Diode D2 and the 5A fuse provide protection against batteries connected the wrong way around. Voltage switching S3, a 4-pole 2-position rotary switch, is the voltage selector. All four poles of the switch work by switching shunt resistors in and out of circuit, depending on whether the 6V or 12V mode is selected. Note that all the resistors associated with S3 are 1 % types. This is necessary to ensure that the circuit provides correct voltages across the battery at all times. The two 0. lµF capacitors at pins 8 and 14 on IC2 and the .0012µF capacitor between base and collector of Ql ensure that the circuit is stable and not able to oscillate at supersonic frequencies. LED indication Three op amps in ICl drive three light emitting diodes, as mentioned previously. All three are connected as comparators. ICla is driven from pin 9, the "over-charge indicate" output of IC2. When pin 9 goes low, the output of ICla goes high to turn on LED 3 and indicate that the charger is delivering full charge. IClc is driven from pin 10, the "state level control" of IC2. When pin 10 goes high, the output of IClc goes low to turn on LED 4, the float charge indicator. Fig.1 (right): the circuit is based on the UC3906 charger IC. This monitors the battery voltage and switches between three charge states: trickle, charge & float. The output of ICl (pin 16) drives Darlington transistor Qt to control the charging current. c.) N 0 co ....::r:co ("'J ::c > ~ :::>IC:'.:W ___ - r _ CASE nh, V+ • i ~K BCE ; 0.1 I • • - - 4700 35VWI ...r:=<!A40y J:• ~ N-~-------~ ~-----~ 240VAC A ~ S1 POWER 680!:J 10k I -r I I SAH ¾-fri ..~. 1 390!l t. 1k _4.5AH 4.7!l 5W I 3.3!:J SW I .,. v+ .,. MAIN A CHARGE LE03 GREEN K t- 6 IC2 UC3906 I Ll8 Ll2 D3 I I 2.7k tt'h" I.~·:. 1 ·~ .t4 0.1+ 116 ~ r 13 10 12 ll 15 ---, "00" K_ 01 BYX98300 O~IM UNIVERSAL 6/12V BATTERY CHARGER V+ -!:- POWER~ LE01 REP . . . n.l!·. o 470!:J r;. r . t / '- 6V SJd __ 12V ~A 1'/o 47k ~ 220k 1¾ 1% S3c 012" ~ , 1M ~ 560k 1 1/o I S3b 12V 6V 1~0k~80k 11, 1'/, S3a v+ v+ ' -:, 1k 7 • - I 1Dk1 -t ~ - + LE04 REo - CHARGE v~~ TRICKLE CHARGE BATTERY r+ 1N5404 02 1 220k 1 1/a '8 1.. k1 Vo \ 2•0 f 18k 1% 1'Ak f 18D - RESISTORS D D D D D D D D D D D D D D D D No 1 2 3 3 1 1 3 2 1 1 4 1 1 1 1 1 Value 1MO 560k0 220k0 180k0 47k0 18k0 10k0 3 .9k0 2 .7k0 2.2k0 1 kO 1 kO 6800 47 0 0 4 700 3900 4-Band Code (5%) not applicable not applicable not applicable not applicable not applicable not applicable brown black orange gold orange white red gold not applicable red red red gold brown black red gold not applicable not applicable yellow violet brown gold not applicable not applicable 5-Band Code (1%) brown black black yellow brown green blue black orange brown red red black orange brown brown grey black orange brown yellow violet black red brown brown grey black red brown brown black black red brown orange white black brown brown red violet black brown brown red red black brown brown brown black black brown brown brown black black brown brown blue grey black black brown yellow violet black black brown yellow violet black black brown orange white black black brown Note: where 5% tolerance resistors are called for in the parts list, 1 % types may be used . IC1 b drives " trickle charge" indicator LED 2. When IC2 is in the trickle mode, current is supplied from pin 11 and via the 4700 resistor to the battery. While this is happening, the voltage at pin 11 of IC2, and hence pin 6 of IClb, will be above the reference voltage at pin 5. This causes IClb's output to go low and light LED 2. When the battery voltage rises sufficiently, IC2 switches off its output at pin 11 and turns on the charge output at pin 16, to drive Q l. When this happens, the voltage at pin 11 drops from around + 24V to the battery voltage. This causes pin 6 of IC1 b to drop below its reference input at pin 5 and LED 2 goes out. Some readers may think that pins 9 and 10 could be used to drive LEDs directly, eliminating the need for ICla and IClc. However, these "open collector" outputs cannot sink very much current, typically 5mA or less, and so the op amps are necessary. By the way, the unused op amp in the IC1 package is not shown. On the printed circuit board, its inputs (pins 9 and 10) are tied to the OV line while its output, pin 8, is left with no connection. Putting it together Light duty hook-up wire can be used to wire the front-panel switches since they switch low currents only. Bind the leads together as shown. We used sockets for the ICs but you can solder them directly into circuit. 24 SILICON CHIP All the circuit components except the LEDs, the stud mount diode, switches and power transistor are mounted on a printed circuit board measuring 190 x 102mm (code SC14103901). Both the stud mount diode and the transistor are bolted to the rear wall of the chassis for heatsinking. You will need to drill holes in the chassis to mount the four LEDs, two rotary switches, power switch, two fuses, the transformer, the Darlington transistor, bridge rectifier, stud diode, the printed circuit board and any other hardware. We suggest you drill all these holes before any assembly work takes place. Use the Scotchcal front panel, if available, as a template for drilling the front panel. The GROMMET I (n) POWER TRANSFORMER ~- LED3 MAIN BATTEAY CHARGE g ~ 10 _ ( : ~ 0 ;) "~j ,3 14 Fig.2: Q1 and D1 must be isolated from the chassis (see Figs.3 & 4) while the four 5W resistors and D2 should he mounted proud of the PCB to aid heat dissipation. Use heavy-duty cable to wire the output terminals. printed board can be used as a template for its mounting holes. Before beginning assembly of the board, check it carefully for breaks or shorts in the copper pattern. It's much easier to find and correct any defects at this stage. Although we did not use them for our prototype, we suggest you use PC pins for all the wire connections to the board. They should be installed first. Use the wiring diagram of Fig.2 as a guide during assembly of the printed board and subsequent wiring of the chassis. With the PC pins installed, you can start soldering in all the small components such as the resistors, diodes, links and small capacitors. Elsewhere in this article is a table showing the colour codes for 5 % MARCH 1990 25 The BD650 Darlington transistor is mounted on the rear panel which provides heatsinking. Use heavy-duty cable to wire the emitter and collector leads. and 1 % resistors. While the table will help you select the right resistor, particularly when 1 % types are involved, we do suggest that you check each value with a digital multimeter before it is soldered into place. Note that where the parts list calls for resistors with a 5 % The BYX98300 diode is also mounted on (but isolated from) the rear panel to ensure adequate heatsinking. Fig.3 shows the mounting details for this device. tolerance, you may naturally use 1 % types instead. When soldering in the power resistors, make sure they sit a few millimetres above the board, as they get quite warm when charging at 3 amps. Check the polarity of the 4700µ.F filter capacitor, diode DZ and zener diode ZDl when they are being installed. Insert the two ICs last. Check that they are correctly oriented [both in the same direction) before soldering their pins. When the board is complete, check your work carefully and then set it aside so that work can proceed on the chassis. Wiring the chassis ~ - SOLDER LUG (§)- e~ MICA WASHER INSULATING BUSH C) (9.)(<at>cQ) MICA WASHER PLAIN WASHER -LOCK WASHER ®-NUT Fig.3: mounting details for the BYX98300 diode. After mounting, use your multimeter to check that the body of the diode is correctly isolated from chassis. 26 SILICON CHIP Both the transformer and the bridge rectifer must be bolted to the base of the case. This done, you can run all the wiring to the primary and secondary of the transformer. The mains cord should pass through a grommeted hole in the rear of the chassis and be secured with a cable clamp [or you could use a cord grip grommet). The Active [brown) and Neutral [blue) leads of the mains cord should be stripped and tinned and secured in the insulated terminal block. The earth lead should be terminated at the solder lug adjacent to the transformer. Both the mains power switch and the two fuses should have shrink-on sleeving fitted over their contacts, INSULATING BUSH \ T~ SCREW T0220 DEVICE MICA WASHER ! I NUT { - § HEATSINK (REAR OF CASE) / Fig.4: mounting details for the BD650 Darlington transistor. Use your multimeter to check that its metal tab has been correctly isolated from chassis. after the wires have been soldered. This will help prevent any accidental shorts or electric shocks. We used miniature bezels to mount the four LEDs. To use these, you clip the front section of -the bezel into the panel, then insert the LED and then fit the locking clip onto the back of the bezel. You can then use a length of 6-way ribbon cable to wire the three charge indicator LEDs. When installing the stud mount diode, an insulating kit must be used to isolate the device from the chassis (see Fig.3). This consists of two mica washers, plastic bl!.sh, flat washer, lock washer and nut. A solder lug needs to be fitted over the threaded stud to make the cathode connection. Make sure that the mounting hole is deburred Problems? ... and you don't have our NEW 1990/91 148 pf1ge electronic parts and accessories catalogue ... Its our latest TRADE catalogue for the consumer ARISTA ... Your one-stop problem solver . 'I"'" 0 CJ) C") 0 'I"'" -:t' 'I"'" (.) en Fig.5: here is an actual size artwork for the PC board. before mounting the diode, otherwise the mica washer may be damaged. The Darlington power transistor also needs an insulating kit and this consists of a screw, rectangular metal washer, mica washer, plastic bush, flat washer, lockwasher and nut. Fig.4 shows the mounting details for this device. When mounting both the stud diode and the Darlington transistor, use a little heatsink compound on both sides of the mica washer to im- ...Stylus .. . ... Plugs, Jacks and Sockets ... ...Batteries .. . ...Cable .. . ... Tools and Technical Aids .. . ... Plug and Power Packs .. . ... Car/Auto Accessories .. . ... Boxed Hi Fi Speakers .. . ... Raw Replacement Speakers ... ... Speaker Accessories ... ... Telephones and Intercom .. . ... Public Address Accessories .. . ...Security and Alarm Accessories .. . .. .TV/Video/Antenna Accesories .. . ... Videocam Accessories ... ...Audio Accessories ... ... Headphones ... ...Computer Accessories .. . . .. Microphone Accessories .. . ... Mixers, Amplifiers, Equalizers ... Just about anything you want. .. Get your catalogue complete with "Recommended Retail Prices" free from your local ARISTA dealer or send $2.50 P & H and your return address to: ARIST~ ELECTRONICS PTY LTD PO BOX 191, LIDCOMBE, NSW, 2141 MARCH 1990 27 The rear panel carries the on/off switch, two fuses, and mounting hardware for D1 and the Darlington transistor (Ql). prove heat conduction to the chassis. Before making any connections to the stud diode and the Darlington transistor, check that they are isolated from chassis. You can do this by switching your multimeter to a high "Ohms" range and then checking the resistance between the device (diode stud or transistor collector) and chassis. You should get an infinite ohms reading, confirming that the device is isolated from the chassis. Before mounting the front panel hardware, the Scotchcal panel The four 5W resistors and diode D2 are mounted a few millimetres proud of the PC board as they get quite warm when charging at 3A. 28 SILICON CHIP should be fitted, if you have obtained one (from the printed circuit manufacturers listed at the back of this magazine). Before fitting the panel, make sure that all the holes are thoroughly deburred. For the rotary switches, wire the voltage selection switch first. The best way to do this is to measure out the distance from each connection point on the board to the corresponding position on the switch so that all the leads can be laced or tied together neatly. The leads for the current selection switch are much easier to wire up as all but one of them come from adjacent positions on the board. The wiring should then be looped around behind the voltage switch so as to keep them separated. Note how we have used cable ties to keep the wiring tidy. Once the wiring has been completed, check it against the wiring diagram of Fig.2. With this done, you can apply power and check the voltages. The voltage across the 4700µF capacitor should be about 24 volts DC. Set the charger to 12V and connect a 3300 resistor across the output terminals. This should cause the trickle LED to light, indicating that the voltage at the terminals is less than 10.5V. Disconnecting the resistor should cause the trickle LED to go out and the float LED to light. Now set the charger to 6V and connect a 1200 or smaller resistor across the output terminals. Again, the trickle LED should light, indicating that the voltage at the output terminals is less than 5.1 V. Disconnecting the resistor should cause the trickle LED to go out and the float LED to light. You can now simulate a battery across the output terminals by connecting a large electrolytic capacitor across the output terminals, together with a parallel 2.2kn (or thereabouts) bleed resistor. We suggest a capacitor of 4700µF or higher. Now when the charger is turned on, the trickle LED should light for a few seconds and then, all of a sudden, there should be a very fast sequence through the LEDs from the trickle to float. As a final check, measure the voltage across the capacitor when the float LED is alight. When 6V is selected, the voltage should be close to + 6.9V. When 12V is selected, the voltage should be 13.BV. All that remains now is to secure the lid and the charger is ready to recharge all those flat SLA batteries lying around the place. ~ wpoD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS .. . WOOD FOR CHIPS ... WOOD FOR C TOOL BOX MC13024 AM Stereo The Bubble-Etcher· a clear acrylic tank, holding the Telephone Plug Radio Chip .•• etchant in a narrow vertical slot. An Basis of the tiny 2 chip radio project electric heater raises the etc;hant to Crimaer Tool in Silicon Chip, the MC130224 First Supplies Due In of Make your own PCBs with contains sensitive mixer, VCLO, IF amp, AGC and AFC circuitry, stereo pilot detector, signal quality detector and complete AM stereo decoder! With a handful! of additional parts you have a quality AM STEREO radio. Hurry though • this one will be popular at only $5.95. -----------. working temperature, and bubbles are introduced by a pump. Movement of the fluid rinses away the dissolved copper from the board, etching it clean in a few minutes. The air increases effectiveness by providing additional oxidising power and regenerating the etchant. Using ammonium persulphate allows you to see the etching process as it is a c1ear so1u1ion. Just dissolve crystals in hot water, pour into the tank and off you go! Features • PC Boards are etched hands free, no stirring required. • Over or under etching are eliminated, as you can see when to stop. • You can leave the liquid etchant in the tank permanently. • Suits PC boards up to 30.5mm x 25.4mm. • Double insulated 240V pump and heater. $ 238.50 Discount Disks 51/4 Bulk Paclcl 51/4 Filesafe OS OD 51/4 Fllesafe OS HO 3 1,Z Fllesafe OS OD 31,Z Filesafe OS HO $6.50 $18.50 $34.95 $39.95 $69.95 All Prices per Pack of Ten Disks. ~ G et Coaxial Test Leads a i._ Q a ~ Disk Cases DDSOL DD100L DD40L DDSOL DD10 50 x 5 1/4 100 x 5 1/4 40 x 3 1/2 80 x 3 1/2 10 x 5 1/4 $25.80 $29.95 $25.40 $29.95 $2.95 Approximately 1metre long with hooded alligator clips one end. Available in two types BNC Connector $16 .00 Banana plugs $10. 75 5 1/4 31/2 $6.95 $6.95 ~ et 0 Ideal for switching one printer between two computers or one computer between two printers. Total flexibility at very modest cost. Serial (RS232) $45 .DO Parallel (Centronics) $55.00 i._ Q a ~ Homeguard Alarm ~ ~ et 0 i._ Q 0 ~ Wireless Passive lnfrared Alarm Yes a genuine Aussie alarm and it's self contained. No complicated arming and disarming routines. Simple press the coded wireless key (two supplied) and you're in business. Has built-in panic function (via the same key). 110dB siren. No wiring - just stick up on the wall! PIR detector works on body heat. Green light shows movement. Builtin battery indicator. Alarm resets after two minutes. $129.95 Nibbling Tool Culs up lo 18 gauge steel or 1.5mm aluminium or other unhardened metals. Make square holes for . connectors • or any shape. Just drill a 10mm holes and away you go 1 Value at $19.95 TMoU~IMi•"~h... VARIABLE TRANSFORMERS Our range includes free standing and panel mounted types with ratings up to 2kVA. Ideal for situations where the mains is 'sagging' or you want to check the effects of mains variations on equipment. FTN sllndillfl $345.00 13amps at up to 250V 7amps at up to 270V $206.00 $175.00 SA at up to 250V P1n1/Typ1 1.2A at up to 250V $97. 70 2.5A at up to 250V $122.50 Other sizes to sp1ei1/ artier eACAdaptor • Spherical milling cuner • Wire brush • Grinding wheel • 4 Drill bits - 0.6, 0.8, 1.0, 1.2mm • 5 Chuck collets • 6 Eraser sticks $69.50 ~ 0 t::l ~ 0 t::l .,, SUPERTOOL ACCESSORIES 0 Pack of 4 high speed drill bits 0.6, 0.8, 1.0 and 1.2mm $6.50 Milling cuners Set of 3 $7.95 Wire brushes Set of 3 $14.40 Grinding bits Set of 3 $10.95 Cuning discs Set of 6 $10.95 Eraser sticks Set of 1o $3.50 a :l) -~iiiiiiiiiiliijiiili~ilil'\ · L!;J!!!_.!!!~~~ ._ o t::l 0§~ Now Fmro wrrH PRaPm cHucK... ~ C.K. brand highest quality. Set of six, round, flat, triangle, square, halfround and tappered flat. ideal for PCB and metal finishing $33.00 DRILL 'N DRIVE 0 Rechargeable two speed drill and screwdriver 2 The SC-5000 gun incorporates a motorised diaphragm pump. There are no tubes or separate compressors. A built-in thermosensor circuit controls the 60W ceramic heater to ensure rapid warm-up. Exact temperature control prevents damage to sensitive circuitry. The gun can also be used as a hot blow tool. $399.00 ex tax ($479.50 inc tax) Optional Stand $42.50 • Drills timber, metal, hardened Features • TwoScrew-driver Speeds Drill - 325 rpm, - 150 rpm •• Forward and reverse operation Pilot light for dark areas plastic Supplied with Rechargeable Baneries AC Adaptor 0 ~ ~: 2 Philips Screwdriver Bits Incredible Value at only 4. Filter cartridge 5. Filt&r removing lever 6 . Suction / Hot air change lev1t 7. Thermo sensor control 8. Electric outlet cord 9. Cleaning pin GEOFF WOOD ELECTRONICS PTY LTD et 229 Burns Bay Road, (Corner Beatrice St.) INC IN Nsw Lane Cove West, N.S.W. P.O. Box 671, Lane Cove N .S.W. 2066 ~ a t::l $69 • 95 .,, 0 :l) () J:: ~ ~ 1. T ip 2. Hut8'" holder 3. Filter pipa :l) ~ ~f~:t:t~~~ci~~; '" ~ t Operates from safe 12V via AC adaptor. It can Drill, Engrave, Erase, Grind, Mill, Polish, Sand Etc. Supplied with ~j; ! Dlc •5000 Desolder·mg Tool ~ ARLEC SUPER TOOL All for a low Need le Files Disk Cleaners FDC1 FDC3 Do the job properly with these handy tools - ideal for professional installers. Strips the cable to the exact size. Holds modular connector in place and correctly aligns wire with pins. Squeeze and the job's done! 4pin US plug $13.95 6pin US plug $13.95 Spin US plug $29 .95 0 t::l Features • Dual 400/600 •c Temp Range e1600 Wan output • Built-in safety handle • Hanging hook for storage 1 • 12 month warranty A necessity at $59.50 .,, 0 :l) () J:: 'ii t,) ~ 0 t::l .,, 0 :l) 0 Telephone: (02) 428 4111 Fax: (02) 428 5198. () Q 0 8.30am to 5.00pm Monday to Friday, 8.30am to 12 noon Saturday. Mail Orders add $5.00 to cover postal charges. Next day delivery in Sydney add $5.00. ~ i._ ~ All prices INCLUDE sales tax. Tax exemption certificates accepted if line value exceeds $10.00. BANKCARD, MASTERCARD, VISA , CHEQUES OR CASH CHEERFULLY ACCEPTED J:: Delay unit for automatic antennas You move the ignition key to the ON position and your car's antenna starts up. Then when you move to the START position, the antenna retracts again. This simple delay circuit will stop the antenna jitters. By GREG SWAIN Ever tried to buy a replacement automatic antenna for a Holden Commodore? I'll bet that you got the same shock that I did. Oh yes, they're readily available but the $220 asking price is really "over the fence ". I didn't go ahead with the purchase. Instead, I took the alternative approach and bought an aftermarket antenna from an auto accessory shop for about 1/3rd the price of the GM part. "We sell lots of these for Commodores", the salesman assured me. "It's easy mate. You just plug straight into the existing wiring". Oh yeah? To cut a long story short, it's not quite as simple as that. Mounting the antenna was no problem but there was no way it would work with the existing wiring. I eventually solved the problem by unplugging the antenna control box inside the car and installing a couple of jumper leads across the plug. Antenna control When the radio was turned on, the original antenna would rise to about half-height after a delay of +12 V VIA IGNITION SWITCH O Ii 1 1 1 1 11 IO SWITCHED +12 V r-_CO_NT_RO_L_LI_NE--i AUTOMATIC ANTENNA Jt·- ---- +12V FROM BATTERY CAR RAOIO Fig.1: how the antenna is normally wired up. The antenna extends when the control line from the radio switches to + 12V. +12V VIA IGNITION SWITCH +12V FROM BATTERY t AUTOMATIC ANTENNA CO NTROL LINE CAR RADIO Fig.2: the delay unit is installed in the control line between the radio & the antenna. It holds the control input to the antenna low for 4 seconds after the control line switches high & high for 11 seconds after it switches low. 30 SILICON CHIP .-------i.,..__ 100 10P. ____,.~,W,,.-------0+12V FROM BATTERY + 16VW+ D1 1N4002 SWITCHED +12V CONTROL LINE C>--1-+l-+---"\M\---"f FROM RADIO 01 BC328 IC1 555 s__.,____ TO CONTROL LINE 0 OF ANTENNA ,---eC 220k .,. ~ l .01 D2 1N4002 I RmY .,. 180!1 .,. ANTENNA DELAY UNIT .,. B eOc VIEWED FROM BELOW Fig.3: 555 timer ICt is wired as a monostable. When the control line goes high, pin 3 switches low after 4 seconds and turns on Qt and the relay. When the control line goes low, pin 3 goes high 11 seconds later and Qt and the relay switch off. four seconds. It could then be raised or lowered to any height required using pushbutton up/down switches mounted on the dashboard. Similarly, when the radio (or the ignition) was turned off, the antenna would fully retract after a delay of about seven seconds. Because the control box has now been removed, the dashboard switches no longer work and the new antenna is either fully up or fully down (which is really more convenient). Fig.1 shows how the antenna is wired up. It has three leads: one goes to + 12V from the car's battery, one goes to ground and the third goes to a switched + 12V output from the radio. The way in which the antenna works is quite straightforward. When the radio is turned on the control line goes high and the antenna extends. Conversely, when the radio (or the ignition) is switched off, the control line drops to 0V and the antenna retracts. The control line, by the way, controls a changeover relay inside the antenna base. This in turn switches the direction of the current through the antenna motor to provide up or down operation as required. There's just one problem with the circuit of Fig.1: the antenna starts up as soon as the ignition is switched to the ON position when starting the car [assuming the radio switch is on), but then immediately retracts when you go to the ST ART position. If the engine doesn't fire quickly, the antenna can have several false starts as the ignition switch is moved between the ST ART and ON positions. All this stopping and starting inevitably causes wear on the motordriven nylon rack inside the antenna and can lead to premature failure of the drive system. Antenna delay unit Our Antenna Delay Unit solves that problem. As shown in Fig.2, it is installed in the control line between the radio and the antenna. It works by holding the control input to the antenna low (ie, at 0V) for a further four seconds after the ignition has been turned on. At the end of this 4-second delay period, the output of the Antenna Delay Unit goes high (ie, to + 12V) and the antenna then extends in the conventional manner. This 4-second delay period gives you ample time to switch through the ON position and get the car started before the antenna is activated. Conversely, when the ignition (or the radio) is switched off, the Antenna Delay Unit holds the control input to the antenna high for a further 11 seconds before dropping to 0V. This means that the antenna now stays extended for 11 seconds after the ignition has been switched off before retracting. This feature is useful if the engine stalls soon after starting or if you switch off the ignition but immediately decide to restart the engine to move the car. It also allows you to switch off the engine and switch through to the ACC (accessory) position without having the antenna start retracting as you go through OFF. In practice, the Antenna Delay Unit will greatly reduce the number of antenna operations. This translates into less wear on the nylon rack and greatly extended antenna life. It also means more convenient operation - it's quite annoying having the antenna stop and change direction after moving only a few centimetres. Circuit details PARTS LIST 1 PCB, code SC05103901, 57 x 65mm 1 1 2V SPOT PC-mount relay 4 PC stakes Semiconductors 1 555 timer {IC1) 1 BC328 PNP transistor {01) 1 15V 1W zener diode (ZD1) 2 1 N4002 diodes {D1 ,D2) Capacitors 1 1 OOµF 25VW electrolytic capacitor 1 4 7 µF 16VW electrolytic capacitor 1 .01 µF metallised polyester Resistors {0.25W, 5%) 1 220k0 1 4700 1 47k0 1 100 Fig.3 shows the circuit details of the Antenna Delay Unit. It uses a 555 timer IC (what else?), plus a transistor, a relay and a few other minor components. The 555 timer (ICl) is wired as a monostable oscillator and is powered directly by the + 12V rail from the car battery. Let's assume initially that the control line from the car radio is low (ie, the ignition is off). This means that the 4 7µF timing capacitor on pins 2 & 6 will be discharged and thus pin 3 of ICl will be high. Pin 3 of ICl controls Ql which is a BC328 PNP transistor. When pin 3 is high, Ql and the relay are off, and the control input to the antenna is low. Assume now that the ignition is MARCH 1990 31 0 ASSIS I ~ NTROL LINE ANTENNA 1 HED + 12V CONTROL E FROM RADIO •+ ,LO V FROM TTERY 100uF 0 u Z01 en 1 .2.1 Fig.4: parts placement on the PCB. You can install the parts in any order but leave the relay until last. Fig.4 (right) shows the PCB artwork. suddenly switched on. When this happens, the control input jumps to + 12V (assuming that the radio was on in the first place) and the 47µF capacitor charges via Ill and the 47k0 resistor. After about 4 seconds, the voltage across this capacitor reaches 2/3Vcc (ie, 2/3 of the supply rail) and pin 3 of !Cl switches low and turns on Ql. Ql, in turn, switches on the relay which connects the + 12V rail to the control input of the antenna. The antenna now extends in the conventional manner (ie, 4 seconds after the ignition was switched on). Switching off If the ignition is now switched off, the control line from the radio goes low again and the 47 µF timing capacitor on pins 2 & 6 discharges via its parallel 220k0 resistor. After about 11 seconds, the voltage across the capacitor reaches 1/3Vcc and pin 3 switches high and the relay turns off. This switches off the + 12V supply to the antenna control line and so the antenna now retracts. Diode Ill prevents the timing capacitor from discharging into the switched control line from the radio, while D2 protects Ql from any back EMF generated by the relay. Power for the circuit is derived directly from the car battery. A 100 resistor and lOOµF capacitor provide decoupling and filtering of the + 12V supply rail, while ZDl protects !Cl and Ql from any high voltage spikes that may be on the line. 32 SILICON CHIP Construction The parts for the Antenna Delay Unit are all mounted on a small PCB coded SC05103901 and measuring 57 x 65mm. Fig.4 shows the parts layout on the PCB. Before starting construction, take a good look at the copper side of the PCB and compare it with the published pattern. Any board defects such as open circuit or shorted tracks are best corrected at this stage. You can now install the parts on the board. Install four PC stakes at the external wiring points first and leave the bulky relay until last. Note that many of the parts are polarised so be sure to install them the right way around. These parts include the IC, transistor, diodes and electrolytic capacitors. It's easy to identify pin 1 of the IC - it's adjacent to a notch on one end of the plastic body. The PCB can be installed inside the car behind the kick panel or housed in a watertight plastic and mounted with the antenna. To test the unit, apply power and connect a clip lead between the control input and the + 12V rail. The relay should pull in after about 4 seconds and drop out 11 seconds after the clip lead is removed. Installation The Antenna Delay Unit can either be mounted inside the car or installed adjacent to the antenna under the mudguard. If you choose to mount the unit inside the car, we suggest that you install it behind the kick panel, adjacent to the access hole for the antenna leads. On most modern cars, the antenna will be hidden behind a plastic panel secured to the inside of the mudguard by self-tapping screws. Remove this panel, then use your multimeter to identify the leads to the antenna. In most cases, you will find that the connections to the antenna are made via bullet connectors. A splashproof plastic case should be used to house the PCB assembly if you decide to mount the unit with the antenna. This can be secured either to the antenna mounting bracket or directly to the antenna body itself (possibly by using plastic cable ties). Seal all holes in the case with silicone sealant to prevent water entry. Finally, use an automotive crimp connector kit to terminate the four leads from the PCB. That way, it will simply be a matter of unplugging the existing wiring and then plugging the Antenna Delay Unit into circuit. ~ David Reid Electronics ''PHAXswitch'' . --!llllllllffif!mRIII!<at>!-.. The PHAXswitch is an automatic switch that allows you to run a phone and a fax on one telephone line. • Three (3) operation modes: automatic phone/fax selection manual fax; manual phone • PHAXswitch answers an incoming call (silently). decides if the incoming call is for the phone or the fax, automatically puts it through to the correct unit, and rings the phone or fax as usual. LASER "102" KEY "XT" KEYBOARD • IBM "XT" compatible • Standard 5-pin din connector EXCELLENT VALUE AT ONLY NORMAL R.R.P. $69.95 NOW ONLY HURRY!!! DON'T MISS OUT ON THIS ONE • Multitap: 1 2V <at> 5A 15V<at> 4A 24V<at> 2.5A 27V<at> 2.2A 30V<at> 2A • 240 volt PRIMARY SCOOP PURCHASE $16.00 ea 30 watts RMS ·, Freq. response: T0-3kHz. ~·- -_ ~ Res. freq: 36Hz. . . Sensitivity: 87d8. 8 ohms. ~ r l ONLY • Range: 50 to 500 volts • Weight: 28 grams • Batteries: 2 x 1.5 volt button cells (LR4 4/SR44) supplied • Size: 135mm (length) x 155mm (wide) $21.95 Simply fantastic as Hi-Fi extension speakers for the Den, Games Room or Kitchen. Looks just like a down light. Excellent reproduction. Save floor space. ea • lnsu.lated handles with spring return. I : j~!h sl~e~~ b:~:m for inner conductor crimp pins • Jaw sizes: 5.4, 6.48 and 8.2mm for shielding crimp collars • Length: 226mm tJt ONLY VIDEO TRANSMITTER AVS30 $89.95 ~ ~ , , ASSORTED PRINTED CIRCUIT BOARDS Double Sided Boards Oly Avail Price 335mmx120mm 505mmx205mm 605mmx120mm Single Sided Board$ 75 113 23 $3.45ea $5.95ea S4.50ea 305mmx110mm 310mmx185mm 335mmx100mm 200 65 24 $3.00ea $3.45ea $3.15ea 375mmx 90mm 405mmx 95mm 20 60 S3.15ea S3.45ea 405mmxl10mm 30 $3.45ea 405mmx170mm 40 505mmx 90mm 505mmx105rnm 505mmK110mm JO 4S 55 $3.BSea $J.45ea $3.SOea $3.60ea "VULCAN" GAS SOLDERING IRON KIT 57mm MINI SPEAKER 200mW 8 OHM WAS NOW ONLY UI ARLEC 6 VOLT LANTERN BATTERY KLT • 6 volt <at> 5000mAH • Safety cut-out for short circuit protection • Supplied with two chargers (1) 240 volt charger (2) 12 volt charger with cigarette lighter plug • 12 months guarantee MINI VAC CLEANER FOR DELICATE DUSTING ea boards, or hard to get _at electronic equ,pment. Also good for camera or computer equip. ~ · . -, __ . ·• , 1J · · 4' $14.95 HAVE YOU GOT YOUR NEW ARISTA CATALOGUE YET? IF NOT WE'LL SEND YOU ONE UPON REQUEST. WE KEEP IN STOCK A WIDE RANGE OF ARISTA PRODUCTS, BUT WE WILL ALSO ORDER IN ANY PRODUCT OF THEIRS THAT WE WOULD NOT NORMALLY KEEP AS A STOCK LINE. DAVID REID ELECTRONICS, YOUR OFFICIAL ARISTA STOCKIST. "XITEL" XM-12E MODEM • • Complete with 3 soldering tips, blow torch , hot blow sponge and solder EXCELLENT VALUE AT ONLY A SET $59.95 CCITT V.22 (B,li) (1200 bps) and W.21 (300 bps) Bell 212A (1200 bps) and 103 (300 bps) • Asynchronous • • • • • • Full duplex • Tone and Pulse dialling Auto-Dial • Call progress monitoring Auto-Answer • Loopback for remote diagnostics Internal speaker with manual and software volume control 8 status and activity indicators NOW Communicate via RS232 port. "SAVE ON KITS THIS MONTH" 50 VOLT 5 AMP POWER SUPPLY. . .. . was $195.00 30 VOLT 1 AMP POWER SUPPLY . . .... was $90.00 FUNCTION GENERATOR. . ... was $155.00 STUDIO 200 AMPLIFIER. . ..... was $399.00 STUDIO 200 PRE-AMP. . .. was $229.00 TRANSISTORIFET/ZENER TESTER ... . was $55.00 12V to 240V INVERTER .600W ....... ... . . .... was $425.00 12V to 240V INVERTER 300W . . . . . . . . . . . . . . . was $279.00 $2.30 ea $1.00 iroirn~ Ideal for cleaning model train layouts, tiny PC LAST CHANCE AT THIS PRICE NOW ONLY $8.00 ea DUE LATE MARCH COMPUTER DISK STORAGE BOXES 1•9 $7.00 ea 10+ $6.30 ea ONLY $59.95/SET DB-25 PLUG to CENTRONICS PLUG 1.8MTR LONG Video Input: 0.8Vp-p to 2Vp-p. Audio FM Deviaton: Max. 40kHz. ONLY $69.95 ~ e12ons IBM PRINTER CABLES Output Channel: UHF channel 30 Tuning Range: UHF from 512 to 612MHz Transmitting Distance: 10 metres RF Output Level: Below 500uV/M at 30 metres Antenna Imp: 75 ohm. Power: 2 watts. 15 WATT 8 OHM LIGHT GREY INNER $29.50 15 WATT 8 OHM DARK GREY INNER $29.50 3.5" STORAGE BOX (HOLDS 40) . NOW ONLY $8.95 5.25" STORAGE BOX (HOLDS 100) NOW ONLY $10.95 $14.95 NOW ONLY Bonus 2 Nicads FREE DOWNSOUND DOWN-LIGHT SPEAKERS $24.00 COAXIAL CABLE CRIMP TOOL ARLEC NICAD CHARGER • Compact size • Recharges 2 or 4 AA Nicad Batteries • Two (2) charging rates - 4 hours, 15 hours • 2-year guarantee 41256 256K x 1 RAM CHIP AS USED IN SUB-WOOFER KIT (E.A. SEPT '89) • • • • • HURRY!!! LIMITED STOCKS $299.00 INCL. POWER SUPPLY 6.5" POLYPROPYLENE WOOFER 200 WATT BABY AT POWER SUPPLY M2175A TRANSFORMER $350.00 now $170.00 now $79.00 now $135.00 now $350.00 now $180.00 now $45.00 now $360.00 now $250.00 • Auto-Disconnect WAS ONLY $299.00 $199.00 500 WATT UNINTERRUPTABLE POWER SUPPLY Output Rating (Under Load): 500 watts Voltage Unit Switches To Backup: 204 and 260 volts AC Voltage Unit switches To Normal: 212 and 252 volts AC Input/Output Frequency: 50Hz or 60Hz Typical Recharge Time: 10-12 Hours Overload Protection: 3.15 amp Time Unit Takes To Switch Over: Internal DC f-use: 4D amp · 4mS (typicalVBmS (max) Dimensions: 144 x 242 x 436mm Voltage Regulation: +i-5% Weight-20.5kgs Audible Alarm: Buzzer and LED indicators Safety: According to IEC 380 and AS3250. $1799.00 lncl. tax $1564.34 ex. tax ~ PHONE NOW!!! (02) 267-1385 TO PLACE YOUR ORDER David Reid Electronics 127 York Street SYDNEY 2000 Ph: (02) 267 1385 MAIL ORDERS P.O. BOX 0103 SYDNEY 2000 FAX: (02) 261 8905 POST & PACK $5-$25 ... . $4 $26-$50 ... $5 $51+ ..... $8 BUSINESS HOURS Mon-Fri 8.30-5.30 Thur 8.30-7 .00 Sat 9.00-1.00 IC~'. Ill VISA A bit of a snag with the sausage rolls With a heading like that, one can assume there is an unusual story to follow. But what is a serviceman doing mixed up - if that's the right phrase - with sausage rolls? Well, everything's gone electronic these days, so it had to happen eventually. Truth to tell, this is not my story. It comes from a colleague who lives up the NSW north coast, in an area renowned for its tourist attractions and large holiday population. This is how he tells it. My mate's story Ordinarily, this is the last kind of job I would want to become involved in. It's hard enough keeping track of all the new model TV sets, video recorders, etc that seem to breed like rabbits in a 40-acre paddock but at least you know what they're supposed to do. With this device I hardly had that much to go on. So how did I become involved? It was one of those social links which is hard to ignore. The owner of the appliance - Charlie - lives only a couple of doors down the road, so we see each other frequently on that basis. In addition, we both own boats and belong to the local sailing club, so we see a lot of each other at that level too. And Charlie's a pretty decent bloke anyway, who has done me a few favours - all of which adds up when someone is in strife. Charlie is the local pastrycook and his business is quite large for a country area. It employs about 20 people in a factory on the edge of town and supplies a range of outlets up and down the coast for 50km or so, as well as his own outlet in the town. As well as the aforementioned sausage rolls, his products include meat pies, and a wide range of cakes and pastries. 34 SILICON CHIP One of his latest appliances is what might best be described as a sausage mince dispenser. It set him back some $6000 but, on the basis of what it was supposed to do and his needs, he considered it a sound investment. That may sound surprising but with a daily turnover of around 3000 pies and rolls, doling out dollops of mince with a spoon is hardly a proposition. And that's about all I knew about the thing up to this point. It was only recently that I first learned of his troubles. His reply to my "Ow yer goin' mate?" - politely translated - suggested that things weren't "goin"' too good. "It's that blankety blank sausage mince machine. Always packing up in the middle of a production run. Costs me a fortune in lost production time". I went through the motions of suggesting the appliance maker's service department or even the local electrician but it was a losing battle. It had already been back to the makers on two or three occasions - an expensive and lengthy procedure in itself - with little long term satisfaction. And the electrician freely admitted he was out of his depth. "It's the electronics in the thing", Charlie went on. 'Tm sure of that. Right up your alley really. Could you possibly have a look at it?" Put like that, how could I refuse? Thus it was that I found myself face to face with the machine while the factory was idle during the day. The main part was a heavy gauge stainless steel box, about 60cm square and 30cm high, mounted on castors for mobility. This contained an electric motor and pressure pump. Mounted on top of it was a funnel, about a metre high, with a top diameter of around 45cm, narrowing to about 6cm at the bottom where it entered the box. This was the input to the pressure pump and in use, would be loaded with raw mince. A post on the side of the box, about the same height, provided support for the top of the hopper. Emerging from the side of the box was a plastic hose, about three metres long and 5cm in diameter, with strands of reinforcing fabric moulded into it. This was the pump outlet. The other end of the hose terminated in a stainless steel nozzle, about 30cm long, slightly angled, and tapering to about 2.5cm at its outlet. There was also an operator's control button on the nozzle. In operation, the mince was forced out through the nozzle and applied to whatever pastry was involved. In making sausage rolls for example, the pastry would be laid out in strips about a metre long, a run of mince laid along it, the pastry rolled, then cut into lengths prior to baking. Up to this point everything described - bar the control button - was robust, well designed and ideal for an industrial application. Not so the control button and its associated cable which was supposed to control everything. The control button was a micro switch mounted in a plastic housing and was connected to the main control unit via a cable taped to the hose. The control unit The control unit was in a box mounted on the side of the machine. ~ "I know that it's rough", he admitted, "but it got us out of bother a few weeks ago. Now the whole thing's gone erratic again; I think it's about to pack it in completely". It certainly sounded like a more deep seated fault. Closer inspection showed that the control unit had its own power supply and could be easily detached from the machine. Having done that I disconnected the hose, then dumped the whole lot in the van and took it back to the workshop. I had several ideas about the button and cable but first I had to check the control unit. I Crude etching . . .~ff~ 1:. M"'ca~Asr.m• ~ e: U~G. 'RI N\lNC€- \ S \?.UT ;:;£ ___ ,__ 0 It appeared to be a small micro- processor and timer which controlled a relay in the pump motor circuit and offered the operator a number of options, selected by a button pad on the box. These included continuous feed with the nozzle button held down, a single delivery of a measured amount, or repetitive measured amounts, as used to fill a batch of pie crusts. Electronically, this was quite clever; mechanically, it left much to be desired. The control button housing was of flimsy plastic and the cable was a lightweight microphone variety, only about 2.5mm in diameter, taped to the underside of the hose. Since the hose and cable would be dragged across the concrete floor, and the nozzle would often be dropped on the concrete, it was no surprise that both had given trouble. The plastic housing and micro switch had been replaced several times, cracks in the housing allowing water to reach the micro switch when the nozzle was washed after each production run. The cable was badly worn and if not already faulty, was not far from it. In desperation Charlie had ditched the micro switch and substituted a fairly robust spring loaded pushbutton switch from the local service station. He had simply taped this to the side of the nozzle. I had no circuit of the thing but a visual inspection failed to reveal any obvious fault. But I was shocked at its appearance. The printed copper pattern was the crudest piece of etching I'd seen for a long time; the kind of thing you'd expect an experimenter to draw freehand with a resist pen. Beauty may be only skin deep but this was clearly indicative of the rough and ready approach to the whole electronic design. On the other hand, having disconnected the flimsy microphone cable and substituted a couple of clip leads, I couldn't fault its performance. I let it run while I worked on the button housing and fresh cable, tested it in all modes at regular intervals and it never missed a beat. So all I could do was press ahead with the obvious requirements and hope it wasn't a deep seated intermittent. My main concern was to get it all going for that night's shift. I decided to retain the auto switch Charlie had bought. It was a single hole mounting type, robust and reliable and while not totally waterproof, was no worse in that respect than the original micro switch assembly. The original plastic box was mounted on a metal plate which was then secured to the nozzle. I was lucky enough to have on hand a diecast aluminium box which was only slightly larger and this was easily fitted to the plate. With the switch mounted in the box it only remained to fit a new cable back to the control box. I was lucky here too; I had on hand an odd MARCH 1990 35 SERVICEMAN'S LOG -CTD length of professional microphone cable, two conductor plus shield, with a tough outer coating, about 6mm in diameter. Then it was back to the factory to reassemble everything. In the process I took the precaution of taping the cable in such a way that it would normally sit on top of the hose, rather than underneath it. A dummy run indicated that everything seemed to be working correctly and I left Charlie to organise the real thing later in the evening. As I learned the next day, it all went without a hitch - and has kept on going for the many weeks leading up to my writing these notes. Even so, I don't regard the setup as ideal. I'm hoping it will last 12 months or so while I find something better. I'd like a better switch and have been toying with the idea of a reed switch actuated by a permanent magnet. I've heard rumours of commercial versions of such an assembly and would like to track them down. I'd also like a better cable, perhaps an armoured variety if I can find one, that was light enough and flexible enough. In the meantime, Charlie is delighted, regards me as an electronic wizard, and happily paid me for my time. (There was never any suggestion that he wanted any favours in this regard; all he wanted was to get the thing fixed). Looking back I can't escape the feeling that the mechanical part of the appliance was a well established and proven design long before anyone decided to add the electronic features. And whoever did it may be very clever electronically but has a lot to learn about the practical side of industrial electronics. It doesn't work - but don't get me sta'r ted on that subject or I'll go on forever. So here's a complete change of scene - in more senses than one. From the north coast to the south coast, where another colleague is battling to cope with the vagaries of UHF transmissions - as have been dealt with extensively elswhere and problems unique to UHF equipment. As might be imagined, the main section unique to UHF - apart from the antenna - is the tuner, and that is what this story is all about; tuners and the problems of service. This is how he tells it. My other mate's story This all started with a fairly routine job involving a Sharp VCR, type VC9300. The owner's main complaint was that it had chewed up a couple of tapes. Then he added, almost as an afterthought, that he couldn't get it to work on UHF. The cause of the tape destruction was fairly obvious; it needed a new idler wheel, plus the usual routine cleaning, lubrication and adjustment of the various torques. That done I put it through its paces, making several recordings with a varie- Change of scene Well that's my mate's story and I couldn't agree more with his comments about industrial electronics. A common but misguided concept is that one can simply take the hardware of entertainment electronics and use it for industrial electronics. 36 SILICON CHIP TH~ 'Pf<l~EJ:> COPPe-R_ PA1f'ERl'l w~:s nu~: C.ROP6"S1"' Pf~C(; OF e.-rcttlNG l'l) SEEN FQ~ A LONG TIMG:-., ... ty of cassettes, and satisfied myself that the tape chewing problem was solved. Now for the tuner. I went over the VHF channels but found little to worry about, apart from a slight touch-up here and there. There was certainly no lack of sensitivity. Next, I tried the UHF channels. The owner was right; there wasn't even a flicker - just snow. I tuned right across the band but couldn't raise a sign of anything; and this in the presence of at least one local signal which delivers a millivolt or more from the antenna. The two possibilities here were that either the UHF tuner itself was faulty or that another fault was depriving it of correct operating voltages. In particular, the voltage on pin 8, which is a switching voltage to bring in the UHF section, is a prime suspect, failure of the associated transistor which switches this voltage on and off being a common fault. (The normal value is about 10V in the "on" position). I checked this and other appropriate voltages and all were correct. So it was the tuner. Tuners are quite complex things to service; it is a specialist job, undertaken by a number of independent organisations. Very few company service departments will handle them. Even worse, the latest designs are virtually non-repairable; chuck it away and buy a new one. Fortunately, this one didn't fall into that category and I deal with a repair organisation in the city for such service. On past experience, I expected this to take a bout three weeks; longer than I would like but about the best available. I advised the customer accordingly, adding a week for safety in case something went wrong. If only I'd known then what I know now. These things tend to slip one's mind with pressure of other jobs but after about five weeks the alarm bells started ringing. A phone call didn't produce a very satisfactory answer. The truth is that this firm is only an agency; they farm the work out to another organisation, which makes it just that much harder to chase things up. They were extremely vague WE:: KeP-r '-fOUR TH\ 'S U'°'F -r\l~R UHF 11J~R. ftJ A C.OP'&OA'RO R:'R 3 "(OU SEN'\ \JS 'BUR."11"' OUR it>AST' N\ONT\-\~ ... .& ,-r ,.._ SO "<OU CAN - f-\AVE:. 1-t'" ~~C.K FA\l--E'D -rt) S~OIJJ A S\NGt.-e: FAUL.1'" )/ V F\RM about the situation at first but after I made some jumping up and down noises - at STD rates - they said that it had been passed on to the service company and was still there. In reply to my request to hurry things along, they promised faithfully to do so. In the meantime, I had to do what I could to placate the customer. Spattered chips Three weeks later - still no tuner. Another phone call - I was spitting chips by now - and this time I insisted on speaking to a particular person who has been helpful in the past. Their answer was a real stopper; that person was on holidays and nobody else knew anything about the tuner. I'm afraid I blew up. In no uncertain language I demanded that they find someone who knew something about it and ring me back promptly, adding that I had no intention of holding onto an STD call while they waffled about. Three days went by and no response. I made another call and demanded to speak to the manager. With an effort I managed to remain calm long enough to explain the problem and request that he do something about it. He appeared to be sympathetic and promised to look into it and call me back. Two days later he called me. The tuner had been fixed, was on its way back to them and they would despatch it immediately. After another week, making the total count about 10, the tuner finally arrived. End of story? Not a bit of it! Brown dog You're not going to believe this; it was no better than before - absolutely dead. Fuming, I pulled it out and sent it back with a stiff note, saying do something about it and do it fast. And they did; it took only a week to get it back this time. And yes it did work but it was as sick as the proverbial brown dog. More precisely, I measured it as being at least 25dB down on normal. It needed a 5mV signal from the colour bar generator to produce even a snowy picture. This was so C bad that even I began to doubt my diagnosis. Was there another fault in the recorder? As luck would have it, an identical recorder came in for routine service. I pulled the tuner out - the tuner alone without its board and fitted it to the suspect machine. It worked perfectly. I rang the manager again and demanded that he do something about it. His reply was apologetic but not very informative. In the meantime, my customer was jumping up and down - and I couldn't blame him. So I pulled another trick; I gave the customer the manager's name and phone number and said, "Here, you give him a blast - two blasts might be better than one". It's a good trick. If nothing else, it convinces the customer that you are genuine. And in this case it might have helped. Anyway the manager rang back in a couple of days but only to say that the repair department claimed that there was nothing wrong with the tuner. How glad I was that I had tried MARCH 1990 37 SERVICEMAN'S LOG -CTD that substitute tuner. I was able to shoot that claim down in flames. I felt a bit sorry for the manager; he was the meat in the sandwich but I had to keep the pressure on. Anyway, he rang back in a couple of days, saying that the service department still claimed there was nothing wrong with the tuner but that they were sending me a replacement one. This duly arrived, was fitted, and worked perfectly; the final justification of my diagnosis and persistence. So, after about three months, I finally had a less unhappy customer. With hindsight I am convinced that nothing was done to the tuner the first time around. Something was fixed the second time, but performance was judged purely subjectively, probably using a strong signal from a nearby transmitter. On the basis of that episode, I had had a gutful as far as that firm was concerned. So, when faced TETIA TV TIP with a faulty tuner in a HMV colour set, C221 chassis, I sought the advice of a colleague. He recommended another company, firm B. I rang them. Yes, they knew the tuner and could provide a reconditioned replacement for a very reasonable fee. So I despatched the tuner, with a cheque, and crossed my fingers. Everything looked good at first - the replacement arrived in less than a week. You beaut! The joy was short lived. Sensitivity at the bottom end of the band SBS (Ch.52) and ABC (55) - was very poor. The next channel up WIN (59) - was suffering extreme cross modulation, and only Capital (62) and Prime (63) were worth watching. It had to be the tuner. So I pulled it out and sent it back, with a covering note detailing the faults. This time the round trip took about 10 days. Then the tuner arrived with a letter claiming that there was nothing wrong with it and that I Is Your Product Or Service Getting The Exposure It Deserves? Consumers need to see your product it you want them to buy it Contact Paul To Reserve This Space (02) 982 9553 Pye T30 chassis Symptom: No picture or very dark picture. Colour appears to be OK when turned up high and contrast control has some effect but brightness control does nothing. Collectors of the video output transistors are some 20V higher than normal. Cure : Plug and socket connection from brightness control, at bottom right corner of small signals board, either loose or suffering from corrosion on the pins. TET/A TV Tip is supplied by the Tasmanian branch of The Electronic Technicians' Institute of Australia. Contact Jim Lawler, 16 Adina St, Geilston Bay, Tasmania 7015. should check the antenna or the circuits supplying the tuner in the set. I regarded that as a classic "out" and something of an insult, to boot - particularly when I realised that this was not the same tuner (no AUDIO TRANSFORMED FOR PROFESSIONAL, OEM OR AMATEUR Broadcast quality aud io transformers ex-stock More than 70 standard types ava ilable Fast prototyping se rvice for non-standard types Comprehensive data available on request Loca ll y manufactured Competitively priced HARBUCH ELECTRONICS PTY LTD 90 George St.. HORNSBY NSW 2077 Phone (02)476-5854 38 SILICON CHIP mention of this), and even more so when I fitted it and it worked perfectly. Need I say more? My next experience involved several UHF tuners of the so-called mechanical variety. These are a continuous tuning type employing a variable tuning capacitor, made by General, but also used by other makers. I am currently holding a General (GC18A), a HMV and a Healing receiver, all needing service for this model tuner. In an effort to avoid more intestinal distress, I sought further advice. Firm C, a colleague assured me, was the one to deal with. I rang them and was assured that they could handle this model. So, cautiously, I sent one tuner for starters. It was back within week with a note saying that it could not be fixed, as it had been "bodgied". On closer inspection I had to agree that this was probably right. Fair enough. So I checked the other two, but they seemed clean, and I sent them off. These also came back in short order, with the advice that they were not repairable, but with no further explanation. But at least I must say this for that firm; they were honest and didn't muck me about. But I'm stuck with three sets which may have to be written off due to lack of adequate tuner service. All of which adds up to a rather grim outlook for this and other UHF areas as they are brought in. A major problem arises from the fact that all the tuner service centres are remote from these UHF regions and so have little knowledge of the practical problems, or the means to test tuners in the field. At best they are relying on instrument measurements but, more likely I suspect, often lack even this facility, depending on limited off-air observations. SILICON CHIP BINDERS quality * High up to 14 issues * Hold internal width * 80mm printed with * Gold SILICON CHIP logo on spine ,;;: /:~•.,•"::··,. . ,. >~}e-. ~" ,:'"' ,. ,~ ,.v · These beautifully made binders protect your copies of SILICON CHIP. In distinctive two-tone green high-quality vinyl specially selected for SILICON CHIP, and with heavy board covers, each binder holds a year's issues (the 14 issues of Vol.1 or the 12 issues of Vol.2). It will look great on your bookshelf. -------------------~-Yes! Please send me ____ SILICON CHIP binder(s) at $A11.95 plus $A3 p&p each (NZ p&p $A6). Name _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ (PLEASE PRINT) Street_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Suburb/town _ _ _ _ _ _ _ _ _ _ _ Postcode _ _ _ _ __ End of story Enclosed is my cheque/money order for $ _ _ _ _ or please debit my Well that's it for this month. While both stories are a little out of the ordinary, the fact that they both come from country areas should help broaden our outlook and make us appreciate some of the problems D Bankcard D Visa Card D MasterCard faced by our country colleagues.~ Signature_ _ _ _ _ _ _ _ _ _ _ _ Card expiry date_---'--- L--------------------------' MARCH 1990 39 ** MOTHERBOARDS ** 10MHz XTM/Board, OK RAM 149.00 Baby 286 M/Board, 20MHz/0K 845.00 Baby 286 M/Board, all-in-1 545.00 Baby 286 M/Board, 12MHz 399.00 Half-size 286 M!Board, with 1MB RAM 695.00 Baby 386 M/Board, 33MHz 2795.00 Baby 386SX M/Board, 20MH z 1095.00 **CHIPS** 1M RAM Chip - 100nS 1M RAM Chip - 80nS 256K RAM Chip - 100nS 29.95 32.95 8.95 Floppy, YE-Data, 720K/1 .44M 175.00 Floppy, YE-Data, 720K/1.44M +Frame 199.00 Floppy, YE-Data, 1.2MB 175.00 Hard, NEC 42MB, 28mS 3.5in 695.00 Hard , NEC 42MB, 28mS 5.25in Frame 745.00 Hard,NEC 42MB 22ms AT BUS 795.00 Hard , NEC 3.5in 134MB 23mS ESDI 1595.00 Hard , NEC 3.5in 134MB 23mS SCSI 1795.00 Hard, NEC 5.25in 179MB 18mS ESDI 1995.00 Hard, NEC 5.25in 380MB 18mS ESDI 3995.00 Hard, NEC 5.25in 760MB 16mS ESDI 5995.00 Hard , NEC 5.25in 380MB 18mS SCSI 4195.00 Hard, NEC 5.25in 760MB 16mS SCSI 6195.00 Hard, Miniscribe 20MB, 65mS 349.00 ** ROCTEC EXTERNAL FLOPPY DISK DRIVES ** 256K RAM Chip - 80nS 9.75 8087-2, 8MHz Co-Processor 275.00 80287, 6MHz Co-Processor 315.00 80287, 8MHz Co-Processor 450.00 80287, 10MHz Co-Processor 499.00 4 X 256K RAM Chip, 100nS 32.95 4 X 64K RAM Chip, 120nS -for VGA card12.00 64K RAM Chip - 120nS 4.95 NEC V20 Chip 24.75 NEC V20 Chip, 10MHz 34.95 NEC V30 Chip, 10MHz 49.00 ** DISK DRIVES ** Floppy, YE-Data 360K 140.00 For Amiga 500, 1000, 2000, 3.5in 880K For Amiga 500, 1000, 2000, 5.25in 360/880K 249.00 299.00 For TOSHIBA laptop series, 5.25in 1.2MB 399.00 ** MICE & JOYSTICKS ** 30.00 120.00 Logitech Mouse, 2 button serial + PaintSNJ Logitech Bus Mouse, 2 button + PaintSNJ Mouse Mat 130.00 140.00 7.50 ** MONITORS** Monitor, 14in TTL, Amber Monitor, 14in TTL, Green Monitor, 14in TTL, Paper White Monitor, 14in EGA Monitor, 14in VGA Monitor, 14in Multisync Monitor, NEC 14in Multisync 199.00 199.00 199.00 599.00 749.00 899.00 1049.00 ** MICRO CHANNEL ** For Commodore PC1 , 5.25in 3601720K 40/80 track For Atari ST series, 3.5in 720K For Atari ST series, 5.25in 3601720K 40/80 track For Amstrad PC1512/1640, 3.5in 720K For IBM XT, 3.5in 720K XT For IBM AT, 3.5in 1.44MB For IBM XT, 5.25in 360K For IBM AT, 5.25in 1.2MB For TOSH IBA laptop series, 5.25in 360K 299.00 299.00 299.00 269.00 299.00 329.00 299.00 329.00 349.00 Dual Sync Adaptor, PS/2 Compatible 2MB RAM Card for PS/2, OK RAM 8MB RAM Card for PS/2, OK RAM 349.00 349.00 599.00 ** 1/0 CARDS ** Multi 1/0 Card XT only Multi 1/0 Card, 2 Ports all 4 drive types supported Parallel Printer Card Serial RS232 Card Serial RS232 Card X 2 1/0 Plus Card - XT Only Serial/Parallel Card - XT 2 Serial, 2 Parallel, AT 99.00 145.00 27.00 55.00 79.00 85.00 55.00 75.00 Quality Roctec external floppy disk drives suitable for most brands of computers. Why pay a fortune for manufacturer's drives? It could well be a Roctec anyway! Supplied with Interfaces as required. AMIGA: ATARI 5.25in 360/880K 40/80 track, suits Amiga 500, 1000 & 2000. ED5201 ..... ... .. .......... $299.00 AMSTRAD: 3.5in 720K suit PC1512/1640 .................... $269.00 IBM: 3.5in 720K suit XT.. ........... $299.00 3.5in 1.44MB suit AT ......... $329.00 5.25in 360K suit XT.. ....... .. $299.00 5.25in 1.2MB suit AT ......... $329.00 TOSHIBA 5.25in 360K suit laptop series .... .......... ............... ... . $349.00 5.25in 1.2MB suit laptop .... .... .. COMMODORE: 5.25in 3601720K 40/80 track, suits .. .. Commodore PC-1 . ED5201 ............. .. .... .... ... ....$299.00 ATARI: 5.25in 3601720K 40/80 track suits Atari ST series. ED5202 ............................. $299.00 3.5 in 880K, suits Amiga 500,1000 & 2000. ED3051 ................ ..... ..... .. $249.00 3.5in 720K suits Atari ST series. ED3503. ............ .$269.00 . ■ promises . . . deliver the goods . . . Try us! Games, Parallel Printer, Serial Card, 'XT'& 'AT' Multi-Serial Card, 4P-AT 99.00 199.00 ** VIDEO CARDS ** VGA Card, BOO x 600 VGA Card, 1024 x 768 Magic Combo CGA Card EGA Card, with Hercules Mode Mono Hercules Card, 16MHz operation 349.00 499.00 129.00 249.00 115.00 ** POWER SUPPLIES** 150W PSU, Circuit Board 150W Switching PSU - XT 200W Switch PSU - Baby AT 200W PSU, Baby AT, L Type 220W Switching PSU - AT 200W PSU With Battery Backup 150W PSU Capacitor, 220nF/200V 85.00 124.00 145.00 145.00 195.00 495.00 2.60 Floppy Disk Card Disk Controller, 4 port, 2In, 2Ex, or 4In ESDI Hard Disk Cont Card - AT ESDI HDD/FDD Card -AT Hard Disk Cont, 1 :1 Interleave, AT HDD/FDD Cont, 1 :1 Interleave, AT Hard Disk Cont, 1:1 Interleave, RLL, AT HDD/FDD Cont, 1:1 interleave,RLL, AT SCSI Card for AT Hard Disk Controller, XT Hard Disk Controller, RLL-XT 99.00 130.00 349.00 399.00 225.00 249.00 249.00 275.00 219.00 125.00 145.00 Case, hinged, Baby AT 95.00 115.00 199.00 99.00 265.00 245.00 295.00 ** DISK CONTROLLER CARDS ** Floppy Disk Card, 4 Ports . 1.2M/360K, 720K/1.44M 55.00 Case, hinged Baby AT w/200W PSU Slimline 'XT' or 'AT' with PSU 3.5in Hard Disk External+ Cable 5,25in Floppy Disk External+ Cable 5.25in Full Height External+ Cable 5.25in Case for 3.5in Drive Baby Tower Case AT Baby Tower Case+ 200W PSU Tower for 6 Devices, Switches at Top Tower for 6 Devices,+ 200W PSU Switches at top Case, Tower for 6 Devices, Switches in Middle MAJOR AUTHORISED DEALERS Adelaide Albany Broken Hill Cannonvale Chariestown Coffs Harbour Deniliquin Devonport Glen Innes lnverell Leaton Lightning Ridge Lismore Mackay Maryborough Morwell Mount Gambier Mt Isa Mudgee Nambour Narrabri Port Lincoln Taree Townsville Wagga Wagga Warnabool Windsor Microtronics Micro Electronics Hobbies And Electronics Whitsunday Decor Newtronics Gaffs Harbour Electronics Deni Electronics A 1 Electronics John Summerlad Electronics lnverell Computer Bits Leeton Audiotronics Cycle & Sound Decro Electronics Steven's Electronics Keller Electronics Morwell Electronics Hutchesson's Communic. Outback Electronics Headware Nambour Electronics Namoi Computers Bassham's TV & Computer Brad's Electronics Suf?er Solex PhIllip's Electronics Maartronics Windsor Communications ** INTERFACE CARDS ** 48 Line 1/0 Card Serial RS-422 Adaptor Industrial 1/0 Card 110.00 135.00 445.00 Universal Wire-wrap Card Dual Serial RS-422 Card 80286 Speed-up Card IEEE 488 Interface Card IEEE 488 Interface Card- National Compatible A-D/D-A Converter, 12 bit, 1 Channel A-DID-A Converter, 12 bit, 2 Channels Clock Card - XT EPROM Writer Card Games Card- 'XT'& 'AT' 125.00 195.00 495.00 299.00 125.00 ** RAM CARDS ** RAM Card, OK RAM , XT only 2MB RAM Cd, OK LIM/EEMS AT 2MB RAM Cd, OK LIM/EEMS XT 6MB RAM Card, -OK RAM 499.00 95.00 **CASES** ** KEYBOARDS ** 84 Key Keyboard XT/AT 101 Key Keyboard, XT/AT 101 Key Keyboard + Mouse Case, Tower for 6 Devices, + 200W PSU, Switches in middle Case, hinged XT 2121799 412 077 884908 466898 439600 525684 813 672 248322 323 661 223 769 532 081 290579 214137 511 723 214559 346133 250400 433 475 723 895 411604 923 274 822788 526603 724466 216558 629870 775935 NEW DEALERS REQUIRED IN ALL AREAS: PLEASE CALL OR FAX FOR DETAILS • 14 Day moneyback guarantee (except software) • 3 month warranty on all our products • Mail orders are our speciality! • Freight on small Items is $9.00 • Insurance $1 .00 per $100 of order value • All price INCLUDE sales tax • We accept Visa, Bankcard, Mastercard and Post Office COD • Call for our latest price list • Special prices apply until March 30, 1990-or while stocks last! 249.00 249.00 99.00 115.00 125.00 25.00 160.00 299.00 299.00 449.00 299.00 549.00 199.00 449.00 50.00 245.00 35.00 ** NETWORK ** BK Ethernet Adaptor, 8 bit with T Adaptor 16K Ethernet Adaptor, 16 bit with T Adaptor Ethernet 50 Ohm Terminator Thin Ethernet Cable, 25 feet Thin Ethernet Cable, 50 feet Thin Ethernet Cable, 75 feet Auto Boot ROM for NEE1 Auto Boot ROM for NEE2 Workstation , 12MHz Diskless, with 1MB RAM 399.00 449.00 12.75 35.00 49.00 62.00 35.00 35.00 2495.00 fl~S~ ~ BOARD SOLUTIONS PO BOX 1120, LANE COVE NSW 2066 TEL (02) 906 5696 FAX (02) 906 5222 CIRCUIT NOTEBOOK I -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. 100xRED LEDS 100-sequence LED chaser 16 +9V IC3 4017 12 Although many chasers use lots of LEDs to give an interesting display, the number of LEDs in a sequence is invariably quite small (typically three or four). As shown, this LED chaser has a sequence of 100 but you can easily set it to a lower figure if you wish. The circuit is quite straightforward and uses two 74C14 Schmitt trigger !Cs (!Cl & IC2) and two 4017 decade counters (IC3 & IC4). IC2e & IC2f form a simple square wave oscillator with a frequency of approximately 20Hz. This clocks decade counter IC3, the outputs of which go high in turn on each subsequent clock pulse. These outputs drive the anode lines to the 10 x 10 LED matrix array. In addition, IC3's divide-by-10 output (pin 12) clocks decade counter IC4. Its 0-9 outputs in turn drive the cathode lines low via inverters IC1a-IC2d. Thus, at any one time, there is only one LED with Pulse width modulated signal compressor This novel signal compressor circuit is based on three common ICs and will cost just a few dollars to build. It's designed to make loud audio passages softer and soft passages louder (ie, it compresses the dynamic range). Referring now to the circuit, the audio signal input is coupled via two 10µF capacitors to op 42 SILICON CHIP 14 CLK 13 CLK EN +10 12 IC4 4017 CLK EN 13 + 9V on its anode and OV on its cathode. Each LED of each column lights in turn as the outputs of IC3 cycle through, with IC4 switching the columns. To alter the number of LEDs in amp stages IC2a and IC2b. IC2b functions as a voltage follower and simply passes the input signai onto IC2c. IC2a, together with D1 & D2, functions as a halfwave rectifier and produces a proportional DC voltage which is fed to the control input (pin 5) of 555 timer stage IC1. ICl is connected as a monostable, with the control voltage on pin 5 used to modulate the pulse width of a clock signal fed into pin 2. The clock is rather RST 15 ND 8 the sequence, disconnect the reset (pin 15) from GND and connect it to one of the outputs. You can do this with IC3 or IC4 or both. Darren Yates, French's Forest. ($25) unusual and consists of two CMOS analog switches (IC3b & IC3c) connected as inverters. It runs at about 85kHz, as set by the .001µF capacitor and the 56k0 and 5.6k0 resistors. When the control voltage on pin 5 of IC1 is low, then so is the mark/space ratio of the output on pin 3. This mark/space ratio increases as the control voltage increases and in turn controls analog switch IC3a. IC3a is wired in parallel with 01 1N4002 +12V Bm~YO---t-ff-t-7r-------11---.----------------11----, 470n 2.2M t:::: a....., 03 1N4002 14 IC3 555 .001 IC2b 13 04 1N4002 IC1 LM1830 + .047 P~g~E0----1"'10 ......,_9--11-' + BOTTOM1 PROBE 22+ Bilge pump with 15s sloshing delay This circuit is similar to the 30-second bilge pump described on page 27 of the February 1990 issue but also includes a 15 second sloshing delay. This delay period is useful in situations where there is considerable sloshing (eg, in high speed vessels) and increases pump life by eliminating unnecessary running. Here's how the circuit works. Initially, Ql is off, both inputs of ICla are high, and thus pin 4 of .,. 10! 02 1N914 RELAY + 22+ Schmitt NAND gate IClb is high and the pump circuit is disabled. When water reaches the top probe, pin 12 of IC1 switches high and turns on transistor Ql. This pulls pin 2 of ICla low and thus pin 3 goes high and the 22µF capacitor charges via the 560k0 resistor. After about 15 seconds, the charge on the capacitor exceeds the upper threshold of IClb and so pin 4 switches low. Note that for this to happen, Ql must be on continuously for 15 seconds. If water only sloshes against the probe, Ql will turn off again, pin 3 of ICla will switch low, and the 22µF capacitor will discharge via Dl. Pin 4 controls the pin 2 trigger input of 555 timer IC2 which is wired as a monostable. When pin 2 is pulled low, pin 3 of IC2 goes high and switches on the relay to activate the bilge pump. The 10µF capacitor connected to pins 6 & 7 now charges via the 2.2MO resistor and, after about 30 seconds, resets the 555 timer. This then turns off the relay until water again contacts the top probe for a full 15 seconds. Peter King, Airlie Beach, Qld. ($20) r----------+-+---------+9V the 470k0 feedback resistor connected to op amp stage IC2c. When the control voltage to IC3a is high, the switch is closed and the feedthrough resistance is about 600. However, because a pulsed waveform is applied to IC3a, the average feedthrough resistance will appear to be 1200 with a 50% duty cycle, and will vary according to the mark/space ratio. Thus, by varying the mark space ratio, we vary the gain of IC2c. This means that if the signal input level increases, the DC control voltage increases and this increases the mark/space ratio which in turn decreases the gain of IC2b. Conversely, as the signal input level decreases, the gain of IC2b goes up. Darren Yates, French's Forest, NSW. ($25) IC1 555 10k 1 +9V + SIGNAL~ 0 IN +9V +9V 10 470k .·.1· O 1 .,. COMPRESSED .,. MARCH 1990 43 Workout timer for aerobics classes Are you into a strenuous exercise program involving aerobics? This Workout Timer will tell you when to change exercises by flashing a light and sounding a buzzer. By STEVE CALDER We have a confession to make. None of the slobs at SILICON CHIP are actually into aerobics - as such. But if you're one of those people who gets dressed up in tight leotards with contrasting (preferably vertically striped) leg warmers, then this Workout Timer is for you. The whole idea behind aerobics (or so we're told) is to do a series of 44 SILICON CHIP different exercises in quick succession. These exercises are usually accompanied by ear-splitting music, which probably serves some purpose although we're not too sure what. Maybe it dulls the pain of the exercises. Anyway, the idea is to get nice and sweaty and to give those muscles a real workout. And to do that, you've got to do lots of dif- ferent exercises that would put a contortionist to shame. So assuming that you're an aerobics type person, how much time should you give to each exercise and when should you switch to the next? Our Workout Timer solves this vexing problem. It sounds a buzzer and flashes a light when it is time to change exercises. No more do you have to rely on the instructor. You can vary the time between "beeps" (or flashes), and thus the time for each exercise, from 10-75 seconds by means of a rotary control on the front panel of the unit. Each beep lasts about 2 seconds and then the timer automatically begins the next cycle. For example, let's say that you've PUSH-ON PUSH-OFF T 2x1N4004 01 I A---0 +12V s, 1000 + 25VW+ 240VAC 10 ,. o.,I + 16VWr LED1 BUZZER .,. 150mA 03 1N4004 MAX .,. IC1 555 56k RLY1 47 + 16VWI LL . GNO WORKOUT TIMER Fig.2: the circuit uses a 555 timer IC which has been wired as an astable oscillator with a long duty cycle. Its output (pin 3) drives a 12V buzzer and relay RLY1 to flash the lamp. VR1 adjusts the period between "beeps" from 10-75 seconds but you can vary this if you wish simply by changing the 47µF timing capacitor. set the rotary control to 20 seconds. This means that the buzzer will briefly sound every 20 seconds for as long as power is applied to the unit. When you hear the buzzer, it's time to change to the next exercise (or collapse in a heap!). A mains socket mounted on one end of the case allows a 240V lamp to be plugged into the unit and this flashes when the buzzer sounds. After all, you might not be able to hear the buzzer above all that loud music! How it works Fig.1 shows the circuit details. As can be seen, the Workout Timer is based on a 555 timer IC and this has been wired as an astable oscillator with a high duty cycle. VRl and the 270k0 and 56k0 resistors determine the charging period for the 47 µF timing capacitor, while the 56k0 resistor sets the discharge period. These periods correspond to the exercise time (ie, the time between beeps) and the buzzer time respectively. Let's see how the circuit works. At switch on, the 47 µF capacitor begins charging via VRl. During this time, pin 3 of ICl is high and so the buzzer and the relay (RLY1) are both off. When the voltage across the 47 µF timing capacitor reaches 2/3Vcc, pin 3 immediately switches low and the buzzer and relay turn on. This closes the relay contacts which are wired in series between the mains active lead and the power socket, and so the lamp also turns on. The 47µF capacitor now discharges via the 56k0 resistor until it reaches 1/3Vcc. When it reaches this voltage, pin 3 switches high again and the buzzer and relay are turned off. The 47µF capacitor now starts charging again and so the cycle is repeated continuously while ever power is applied. By varying VRl between its minimum and maximum settings, we can vary the charge time from 10 seconds to 75 seconds. The discharge time (Td) is about 1.8 seconds, as determined by the equation Td = 0.693RC, where R = 56k0 and C = 47µF. Power for the circuit is derived PARTS LIST 1 PC board, code SC08102901, 132 x 87mm 1 plastic zippy box, 1 50 x 90 x 50mm (Jaycar HB-6021 , Altronics H-01 51 ) 1 surface-mount mains socket 1 24V centre-tapped mains transformer (Altronics M-7124) 1 12V buzzer (Arista AB2, available from David Reid Electronics; Jaycar AB-3454) 1 mains cord and 3-pin plug 1 cord grip grommet 1 2MO linear potentiometer 2 25mm-long spacers 1 pushbutton mains on/off switch 1 12V DPDT relay 3 plastic cable ties 10 PC stakes 1 large solder lug 4 3 x 1 0mm machine screws 2 3 x 1 5mm machine screws 4 3mm nuts Semiconductors 1 3 1 1 555 timer IC (IC 1 ) 1 N4004 diodes (01 -03) red LED (LED 1) 7812 3-terminal regulator Capacitors 1 1 1 1 1 1OOOµF 25VW electrolytic 4 7µF 16VW LL electrolytic 1 OµF 16VW electrolytic 0. 1µF polyester .01 µF polyester Resistors (0.25W, 5%) 1 270k0 1 56k0 1 1k0 Miscellaneous Heatshrink tubing, 240VAC rated hookup wire MARCH 1990 45 Most of the parts are mounted directly on the PC board but note that the buzzer is stood off the board on 25mm pillars. Use plastic cable ties to bind the 240V AC wiring and sleeve all exposed terminals with heatshrink tubing. from the mains via a 24V centretapped transformer. This feeds a full-wave rectifier circuit consisting of Dl and D2 to produce an unregulated supply rail of about 17V DC. This rail is then filtered by a 1000µF electrolytic capacitor and regulated to + 12V using a 7812 3-terminal regulator. A 10µF capacitor is used to filter the regulator output while LED 1 provides power on/off indication. A 1k0 resistor is used to limit the LED current to 12mA. Construction An earth lead must be run from the power socket to a large solder lug which fits over the pot shaft. This ensures correct earthing of the pot metalwork. As an additional precaution, fit the pot with a plastic knob. 46 SILICON CHIP A printed circuit board has been designed to accommodate most of the parts, including the mains transformer. This board is coded SC08102901, measures 132 x 87mm and fits into a standard plastic zippy box. Fig.2 shows the wiring details. Begin construction by installing PC stakes at all the external wiring points (10 in all), then mount the parts on the PC board. It's best to install the small components first, before moving on to the buzzer, relay and power transformer. Note that many of the parts are polarised so be sure to install them the right way around. It's easy to POLYSTYRENE CAPACITORS -----,~.......- - - - CORO CLAMP GROMMET E (GREE YELLO A (BROWN) POWER TRANSFORMER Made here in Australia? Made Special to Type? Polystryrene Capacitors - 10pF to 1mF Voltage Range - 63VDCW to 10,000 VDCW Tolerance - 0.25% to 10% Allied Capacitors Australia manufactures capacitors to the specification of the customers using high quality, imported polystyrene 240VAC POWER SOCKET Fig.2: be sure to use 240V AC rated cable for all connections between the PCB, switch St and the power socket. The 7812 regulator is installed with its metal tab adjacent to the lO00µF capacitor. identify pin 1 of the IC - it's adjacent to a dot or notch in one end of the plastic body. Install the 3-terminal regulator with its metal tab towards the 1000µ.F capacitor. The buzzer must be stood off the board using two 25mm spacers and two 3mm nuts (see photo). This is necessary to ensure that the buzzer protrudes slightly through the front panel when the lid is screwed down. The flying leads from the buzzer are then run back to the PCB, with the red lead going to the positive supply rail. At this stage, you should be ready to drill the case to accept the external hardware. You will have to drill holes in one end of the case to accept the mains switch and the surface mount mains socket, and another hole in the other end of the case for the cord clamp grommet. Use the front panel artwork as a guide for drilling the front panel. There are three holes to be drilled here: one for the LED bezel, one for the potentiometer (VR1), and one for the buzzer. Use pilot drills to start the holes for the pot and buzzer, then carefully ream them out to the correct size. and aluminium foil with a tolerance of 1 micron. Our capacitors are manufactured to the system of Total Quality Control. We can provide Just In Time delivery if required, together with a Certificate of Conformance if requested. Specific values between 10pF and : 1uF are no more expensive than standard value components. You can now design circuits to use a single capacitor rather than a number in parallel or series to achieve a desired value. Personalised labelling is available at no extra cost. Your component code or name can be built into the capacitor. Minimum runs of on ly 25 allow you to specify a particular value for a prototype run. Delivery lead time for short runs is 3 to 4 working days, and for longer runs is less than 2 weeks. We are also able to produce capacitor styles for applications such as dual mount, end filled and mini style capacitors . INTERESTED? Call us now on: (02) 938 4690 ALLIED CAPACITORS AUSTRALIA PO Box 740 Brookvale, NSW 2100 M ARCH 1990 47 ....a: ....<Cen 0 0 + ,... 1/1 0 co 0 a, 1/1 N "' 0 ,... ~ 00 0 + CJ CJ) 1/1 0 ,- 1/1 0 N a: w :E - II- ::::, 0 a: 0 L == Fig.3 & 4: here are actual size artworks for the front panel and the PC board. You can use the front panel artwork as a drilling template if you wish. ~ Now check that the PCB clips neatly into the case. File the edges of the board until it fits, if necessary. Don't use metal pillars to mount the PCB. If you do elect to mount the board on pillars, you must use insulated types to provide the necessary isolation from the mains. Next, fit the mains switch, then strip back 180mm of outer insulation from the mains cord and clamp it in position. Connect the earth lead (yellow/green) to the power socket and the active lead (brown) to the switch. It's a good idea to fit heatshrink tubing over the switch terminals to eliminate the possibility of electric shock. The remainder of the wiring can 48 SILICON CHIP 0 now be run from the PCB to the mains socket and S 1 as shown in Fig.2. Be sure to use 240V AC rated cable for these connections. In addition, an earth lead must be run from the power socket to a large solder lug which fits over the pot shaft. This ensures that the pot metalwork is correctly earthed and is a necessary safety feature. Once all the wiring has been run to the power socket, it can be secured to the case using machine screws and nuts. Use plastic cable ties to bind the 240V AC wiring so that if any lead comes adrift, it will not short to the low voltage circuitry. Construction can now be completed by installing the LED and the potentiometer on the front panel and wiring them back to the PCB. Fit a plastic knob to the pot shaft (not metal) and carefully align the indicator before tightening the grub screw. Testing This is the easy part - just switch the unit on and if it doesn't work you've got a fault. After all, there's not much that can go wrong with a 555 timer circuit! If you do strike problems, check for incorrect wiring, faulty soldering and incorrect component orientation. Finally, you can change the timing range of the Workout Timer simply by changing the 47 µF timing capacitor. For example, to double the range to 150s, just increase the capacitor value to lOOµF. ~ EVERYTHING FOR YOUR LIBRARY You'll find a fantastic range of reference and source books at your nearest Dick Smith Electronics store. When you need accurate information, fast... you're better-off having it on-hand! THE 1990 HA:~fg,91< • · 1 ARRL RADIO HANDBOOK t_-_~'.·__ ":'"' "' ---;-, ~ ,_ , \ NEW 1990 EDITION •. .. _. c dJ ~1 k ~;-•. ' "'•· - --·, . \;~ --·:"'· It's the bible according to Amateur operators! The all new ARRL Handbook is updated with all the latest information for the avid amateur radio operator. Keeping up its outstanding tradition with new and fascinating projects to build, a wealth of highly informative articles and morel A quality hard-back publication which turns your amateur-shelf into a library. The first shipment has just arrived , so you'd better grab your copy before they all go! It has to be the best amateur reference sources you'll get all year. 5 Cat B-2223 ' Outstanding Value! i~~s iNsTRUMENTs ~ l\ 99 -m - T_e_x_a _s -In_s_t-ru_m _ e_n-t s-!---, TTL LOGIC DATA techni~22t~ LINEAR DATABOO K Just on twelve hundred pages of on standard TTL circuits, Schottky TTL circuits, low power LS, ALS, high speed CMOS, VLSI Processors .... the lot. With a general information section giving comprehensive tables and covering parameter measurement information and typical information. You get everything including mechanical data and measurements. Another invaluable tool for your library. Incredible value and a must for the experimenter, technician and project builder. You'll get the complete 3 volume set of Tl's Linear Circuits Data Book at this incredible low price. All the important technical information you need for amplifiers, comparators, special function IC's , data acquisition and conversion , voltage regulators and supervisory circuits ... everything I You won't find a handier reference source or better value. Over 2300 Pages ~ Cat B-5520 $ Cat B-5521 Qnl~~~I- PRACTICAL DIGITAL HANDBOOK By Mike Tooley A fantastic publication which provides a practical introduction to digital electronics. The book introduces digital circuits, logic gates, bi stables and timers as wel l as microprocessors, memory and input/output devices then looks at RS-232C interface and IEEE-488/IEEE-1000 microprocessor buses. There's also a section on digital test gear projects, append ices on test equipment and a useful reference data section. ,'___--;~$\'f95--'9 :~ Cat B- 1270 i»XPRESS PHONE OR MAIL ORDER SERVICE Outside Sydney (FREE Call) 008 22 6610 Sydney And Enquiries 888 2105 FAX: (02) 805 1986 or write to DS XPRESS, PO Box -321 N/Ryde NSW 2113 All Major Credit Cards Accepted. O/Nite Courier Available 24 HOUR DESPATCH OF ALL ORDERS DIGITAL LOGIC GATES & FLIP FLOPS By Ian R. Sinclair The by-line for this title is "What they do and how to use them " and you'd be hard pressed to find a more practical or better presented publication on the subject. It's a great aid to design and troubleshooting of digital circuits and ideal for students, enthusiast and technicians. It assumes only a basic knowledge of electronics and the more theoretical topics are explained from the beginning. A worthwhile addition to your bookshelf. Cat B-1271 ~~~i~~~ COMPUTER ACCESSORIES! 3-WAY SWITCH BOXES RS-232 MULTILINK ADAPTOR A complete in-line tester/adaptor which makes complex and time consuming Serial connections a breeze! Comes fitted with 25 pin male connector and 25 pin female connector. With jumper pads and wires, 24 in- line switches and 8 bicolour LED's for line monitoring. A great idea! The switch box allows the switching of a common input or output to an y one of three other devices. All lines are switched. Ideal for sharing a printer or modem with more than one computer or connecting several printers to one Centronics port. 25 Pi n With OB25 Connectors. Cat X-3575 36 Pin X 36 Pin Conn ectors. Cat X-3576 y s49gs °"~ - Cat X-2654 S4995 ea RS-232 QUICK TESTER RS-232 SERIAL 9 LINE TESTER An in-line tester which has both 25 pin male and 25 pin female connectors . Three switches and 6 LED's allow quick selection for the most popular RS-232 configurations . You simply set the switch to select the connection you need. Cat X-2652 An easy to use line tester with 25 p in male and 25 p in female connectors. 18 bright LED 's monitor the lines so you'll know immed iately where the problem lies. A great time and headache saver! Cat X-2650 S} 995 GENDER CHANGERS/ ADAPTORS PRINTER AND SERIAL CABLES 25 PIN FEMALE GENDER CHANGER Changes th e configuration of any 25 pin ma le connector to 25 pin CHANGER fema le. Wired pin for pin . An in-line gender changer wh ich Cat X-3566 has DB9 male connectors at RS-232 25 PIN TO 9 PIN ADAPTOR each end. A line adaptor with OB25 pin Cat X- 2657 fema le connector one end and 9 PIN FEMALE GENDER DE9 male at the other. Cat X-266 1 9 PIN MALE GENDER CHANGER 25 PIN MALE GENDER CHANGER r.entronics Printer cable Standard printer cable suits PC compatibles and Atari ST computers. Cat X-8614 25 Pin M/F Serial cable Ideal for modem connection to 9 Pin Serial port. Fitted with OB9 female connector and OB9 male connector. Cat X-8007 RS-232 9 PIN TO 25 PIN ADAPTOR In line adaptor with OB9 fema le conn ect ors one end and DB 25 male at the other. Cat X-2660 S95ea NULL MODEM/ JUMPER BOXES \ RS-232 Null Modem Adaptor With OB25 connectors at ea ch end . Wired for fu ll haridshaking . Al lows the connection of two computers 'back to back'. Cat X-2664 RS-232 Serial Jumper Box s299s Fitted with 36 Pin Centronics connectors at each end . Cat X-9005 ~ 9 Pin(Fl - 25 Pin(MI Serial cable Changes the gender on any 25 pin plug from female to male. Wired pin for pin. Cat X-3565 ONLY 36 Pin Centronics cable s249s.. Fitted with 25 pin female and 25 pin Male 'D' connectors. Cat X-3564 With OB9 female connectors on each end . Cat X-2656 5 You 'll find a complete range of cables and accessories for .all your computer needs at your nearest store. $995 25 pin male and 25 pin fema le connectors . With jumper pads and wires which allow permanent soldering for RS-232 connec tions. Cat X-3569 .............. ............ 25 Pin M/M Serial cable Fitted with 25 Pin 'D' connectors. Cat X-3574 KEYBOARD/MONITOR EXTENSION CABLES 295 A great way to save desk spacet Allows you to get the keyboard and monitor away from the CPU . Monitor Extension cable A 2 metre extension cable fitted with 9 pin 'D' connectors. Cat X-2602 Keyboard Extension cable A 2 metre coi led extension cable with 5 pin DIN connectors. Cat X2600 /; HIGH PERFORMANCE FOR YOUR COMPUTER! 20MHz NEAT AT MOTHERBOARD It's New! Only $699 Faster, more versatile and vastly more efficient! The 286 NEAT motherboard is speed and function enhanced and represents a significant technological advance over conventional 80286 designs. The NEAT (New Enhanced AT) ch ip set enables the user to control the relationship between microprocessor, the expansion bus and on-board memory giving greater flexibility than ever before . Improved memory structure design allows super-fast operation up to an incredible 20MHz, using optional memory interleaving. Suits any IBM compatible case from AT to tower cases and will run at 8, 10, 12, 16 or 20MHz. Uses any version of MSDOS above version 3 and has on board support for Lotus-Intel-Microsoft (LIM) Expanded Memory Specification Version 4 .0. Wait state selectable from zero to one-wait. Using the ROM based setup program provided, you can switch between high and low speeds, setting at the lower speed allows the use of slower, less expensive memory chips. The 286 NEAT board is socketed for the 80287 Math co-processor. With three 8-bit and five 16-bit expansion slots, up to 8 megabytes of memory (DIP and SIP memory modules) , shadow RAM capability, independently programmable CPU and AT bus clock rates , programmable Memory and 1/0 wait states, programmable Memory and 1/0 command delays and more. Astounding performance and versatility from the ultimate 80826 motherboard! Cat X-1003 Mini XT Motherboard Super small, top performing and amazingly inexpensive! Perfect for hackers and anyone building a system from scratch or getting a previously deceased XT system on the road again. Superbly constructed using multi-layer PCB board and quality workmanship throughout. With 8 expansion slots and up to a fast 8.9MHz clock speed. Socketed for 640K RAM. Fits any standard IBM compatible XT but takes up much less space. It's a great one for experimentation and exceptional value to boot! Just add a case, RAM , a video and disk controller and you're up and running . Cat X- 1001 NEW/.Just $} 49 Super VGA Graphics Adaptor! IBM AT Compatible 80286 Motherboard More colours, higher resolution and more options are just some of the outstanding features of our super VGA Graphics Adaptor! Enhances AutoCAD, games, text, paint programs, graphics, charts, desktop publishing, business software ..... astonishi ng clarity and versatility at the touch of a button. With additional memory you can get up to an astonishing 1024 x 768 resolution in 16 colours! Fits into any IBM compatible (XT or AT) and comes with 256K RAM on board (expandable to 512K). It's supplied with utilities which allow emulation .of EGA, Hercul es and CGA with boot disk option. All standa rd IBM VGA modes are supported, in fact, there are so many graphics modes available there's just no room to list them all here! Comes complete with drivers for Lotus (release 2), AutoCAD (Versions 2.18) , GEM , Word Perfect (Version 4.2), Framework II (release 1.1 ), Wordstar (release 3 & 4), Ventura (Versions 1 & 2) and MS Windows (Version 2). Building your own computer or upgrading the old one? Our 12MHz motherboard is the way to go for the ultimate computing power. DRAM not inc luded. • Expandable to 4Mb • Selectable 8112MHz operation • Six 16-Bit and Two 8-Bit expansion slots. • Selectable tor RAM speed 80 or 100 nanosecond Cat X-1002 • Selectable from O wait states on read operations (with 80 nanosecond RAM) • Socketed tor 80287 Coprocessor • Performance - 13. 7 using Norton S.I. • Battery backed rea l time clock on board • AMI Bios ROM's included • OK RAM supplied 8 BIT VERSION. Fitted with 256K (expandable to 512K) Cat X-2018 $299 Just 16 BIT VERSION Faster graphics/text update on screen for 286/386 machines. Cat X-2019 $349 Now Just s399 COMPUTER PROBLEMS? Call our exclusive COMPUTER HOTLINE on (02) 888 2002 for the solution! KITS ·· KITS ·· KITS ·· KITS ·· KITS SIMPLE FM RECEIVER FOR THE 6M BAND What Colour Is Your Music? / Cat K-6005 Full form kit with ... • Deluxe Pre-punched Front Panel Label • High Quality Case • Components, speakers ... everything! CHROMA-VOX $}39 Cat K-3162 Here's a great new project that's very simple and produces amazing results! An easy to build receiver which lets you listen to amateur radio on the 50 to 54MHz banci. It uses a low noise MosFet front-end and a single IC performs most of the receiver functions (The new MC3363). It will even form a basic 'tuneable IF receiver module for future converters to cover other amateur bands. Add colour to your music at parties and dances! Our new Chroma Vax uses the latest technology in Triac Driver IC's and gives you three channels which can be connected directly to speaker or headphone outlet. There's a master level control and each channel has adjustable sensitivity. With a high level of insulation between mains and signal output, insulated case and front panel, and specially selected potentiometers for the maximum safety. Will drive up to 2400W of incandescent lamps. Kit comes complete with a pre-punched, silk screened front panel and prepunched rear panel. IMPROVED LIGHT CHASER lncrBdibly Small/ FM WIRELESS MICROPHONE $}695 Cat K-5006 Cat K-3161 Our new Light Chaser is low in cost, easy to build , incredibly flexible and it's designed with safety in mind. With 6 chasing patterns, 8 speeds, an enhanced front-panel monitor display and the ability to run lamps to a total of 2400 watts. It's been designed as a 'dedicated' chaser for the ultimate in safety. This also allows many more functions without getting into complex construction techniques. Comes complete (full form). right down to the last bolt' UNIVERSAL UHF REMOTE CONTROL SWITCH VK POWERMATE 25 SHORT FORM KIT CASE (CAT H-2481) & TRANSFORMERS (CAT M-2010) NOT INCLUDED V K P o w<i/T ... OU': The FM Wireless Microphone is small enough to be inserted into a matchbox, can be tuned to operate at around 90MHz (On your FM receiver), it's incredibly stable with extremely sensitive circuitry and relatively easy to build. It's fantastic! Comes as a short form kit with components and PCB. Also includes batteries. Cat K-3210 ~ C The perfect kit for amateurs with all the grunt you need to get the most out of your shack . A high power 13.8VDC supply giving a huge 25 amp continuous current rating with a peak of 35 amps. ft 's capable of running transmitters and amplifiers in the 100-1 SOW class. And it's fully protected with both foldback current limiting and an over voltage crowbar circuit. Short Form Only - Includes PCB components and necessary hardware. $?,,?,,:s ~ ; It's easy to build and can be used for switching security systems, lights, doors ... almost anything you can think of! The kit consists of a 304MHz receiver, decoder IC and output relay driver on a single board. Full form kit including pre-punched panel , panel label, PCB and all necessary components. Also comes with Department Of Communications (DOC) approved transmitter! What Makes Our Kits Best? The Hot Canaries 1. We use only brand new , prime spec components. 2. We guarantee the quality! 3. We build a prototype of every kit. 4. We re-write the instructions in clear , easy to ur;iderstand terms. 5. We carry spare parts for all current kits. 6. We make it as easy for you as possible~ 7. Our service department can get you out of trouble. 8. You can return the kit if it's too difficult (Before the inner packs are opened) 9. We have the largest and best range. It's easy to see why most people prefer Dick Smith Electronics kits! Here's a great kit that is not only easy to build but can give you hours of fun with your friends. It produces the sounds of two birds singing. They start off slowly and build up ... and up ... competing for virtuoso supremacy. The period of trilling, chirping and pitch of each bird is different, creating a random effect as the birds come in and out of chorus. Think of all the great gags you can have with this one! Besides, it beats keeping birds in a cage and there are no seeds or droppings to clean up. Kit comes complete with all components and hardware, it's battery operated (not supplied). K-3530 1GHZ Digital Frequency Meter • • • • • • Full Form Front Panel Label Case Battery Holder Speaker IC Sockets I'- "" NEW KIT SOON TO BE RELEASED! With Period Counter! This should be at the top of your list for workshop equipment. A truly intelligent frequency counter - PLUS a period counter - at an exceptionally low price that's highly accurate and quality built. Superbly constructed , with a range of unique features that are nothing less than astounding. It actually measures subsonic frequencies in fractions of a second with amazing accuracy. Measures right across the range from 0.1 Hz to 1GHz. Check out these specifications .... Cat Q-1314 -~-. -i oooa~ 8 <at>b~~.a· s499 Input Characteristics CH.A (0.1Hz-100MHz)Frequency Range: DC couple 0.1 Hz to 80MHz AC couple 30Hz to 80MHz Sensitivity: 15mVrms 0.1Hz to 50MHz 25mVrms 50MHz to 80MHz Coupling: AC/DC Filter: Low Pass( 100KHz, -3dB) Input Impedance: 1Mohm/ /40PF Attenuator: X 1, X20 Trig Mode: Auto or Manual Period Range: 10nS to > 10S Input Characteristics CH.B (50MHz-1GHz) Frequency Range: 50MHzto 1GHz Sensitivity: 20mV to 650MHz 55mV to 1GHz Coupling: AC only Input Impedance: 50 ohms Max. Input: 3Vrms Resolution: At least five digits at minimum gate time. Resolution depends on setting gate time control. Timebase Frequency: 1OM Hz Aging Rate: < 1PPM / Month Coefficient: < 10PPM, 0 C - 40 C Accuracy: < 50PPM Line Var.: < 0.1 PPM for line voltage + I- 10% Gate Time: Continuously Variable from 60mS to 1OS or 1 period of input signal, whichever is longer. MAJOR DICK SMITH ELECTRONICS AUTHORISED STOCKISTS: N.8,W.: AAMIDALE : New England Electronics 711655 BALLINA : Ballina Etectromcs 867022 BOWAAL: F.R.H. Electrical 611861 BROKEN HILL: Hobbies & Elec1ron1cs 884098 COFFS HARBOUR: Gotts Harbour Electronics 525684 DENILIQUIN : Deni Elec1ron1cs 813672 OUBBO: Chr1s·s Ht F1828711 FORSTER: Forster Village Electronics 545006 GLEN INNES: John Sommer!ad Electronics 323661 GRAFTON: Repairs and Spares 421911 GRIFFITH: Miatron ics 624534 INVEAELL: lnvere ll Electroni cs 221821 LEETON : Leeton Audiotron 1cs 532800 LISMOAE: Decro Electronic Services 214137 MOREE: Moree Electronics 523458 MUDGEE: Headware 723895 NAARABAt: Namo1 Computer Service 923274 NOWRA: Nowrn Electro nics 210722 ORANGE: Central West Electronics 626491 PARKES : Strad Mus ic Centre 623366 POAT MACQUARIE: Comdox 834574 TA REE : Brads Electronics 526603 WAGGA WAGGA: Ph1ll1ps Electronics 216558 VASS : Warmington Electrica l 261116 VIC: BAIANSOALE: LH & LM Crawford 525677 MILDURA: Pullma n Auto Pro 232882 MOAWELL: Morwell Electro nics 346133 SHEPPAATON: Andrew Guyal1 Electron ics 219497 WAAANAMBOOL: Marrtronics 629870 QLD: AYR : Della Electr1x 831566 BUNDABERG: Bob E1krn Electron ics 721785 MACKAY: Stevens Electronics 511723 MARYBOROUGH: Keller Electronics 214559 PIALBA: Keller EleC1ro n1cs 283749 TAI: BURNIE: Electronic City 314760 DEVONPOAT: A.I.Electronics 248322 SA: MT GAMB1EA: Hu!chesson·s Communication Ce ntre 250400 POAT LINCOLN: Basshams TV & Computer World 822788 WHY.ALLA : Eyre Electronics 454764 WA: ALBANY: Micro Electronics· 412077 BUNBURY: Micro Electronics 21622~ GEAALDTON: Batavia Light ing & Electrical 211966 KAAAATHA: Daves Oscitron1c 854836 MANDURAH: Micro Electronics 581 2206 Neutrik Pro-Quality Plug & Sockets (te}NEUTFIIK The ultimate in plugs and sockets, particularly for professional and /or industrial use, you won't buy better than Neutrik. Type Line Socket with switch Line Socket R/Angle Heavy duty Line Plug Heavy Duty Line Socket 6.5mm Line Plug Mono 6.5mm Line Plug Stereo 6.5mm Line Plug R/Angle 6.5mm Line Socket Stereo 6.5mm Panel Socket Stereo 2 x RCA Plug Chassis Plug Plastic Chassis Socket Plastic PCB Mount Straight PCB Mount R/ Angle Cat No. P-1570 P-1572 P-1574 P-1576 P-1578 P-1580 P-1582 P-1584 P-1586 P-1587 P-1588 P-1589 P-1590 P-1591 Price $11.95 $10 .95 $9.95 $9.95 $5.95 $8.75 $10.95 $8.95 $9.25 $24.95 $2.50 $3.00 $1.25 $1.25 COMPONENTS AND TOOLS SCREWDRIVERS CAPACITORS Great value and range! Our range of capacitors is bigger and better than ever. It's one stop shopping for all your component needs at your nearest Oick Smith Electronics store. Value In uf 1PF 1.5PF 2.2PF 2.7PF 3.3PF 3.9PF 4.7PF 5.6PF 6.8PF 8.2PF 10PF 12PF 15PF 18PF 22PF 27PF 33PF 39PF 47PF 56PF 68PF 82PF 100PF 120PF 150PF 180PF 220PF 270PF 330PF 390PF 470PF 560PF 680PF 50VCeramic Cat No. R 2215 R 2217 R 2219 R 2221 R 2223 R 2225 R 2227 R 2229 R 2231 R 2233 R 2235 R 2237 R 2239 R 2241 R 2243 R 2245 R 2247 R 2249 R 2251 R 2253 R 2257 R 2259 R 2285 R 2287 R 2289 R 2291 R 2293 R 2295 R 2296 R 2297 R 2299 R 2301 R 2303 Price $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 820PF 0.001MF 0.0022MF 0.0033MF 0.0047MF 0.0056MF 0.0068MF 0.0082MF 0.01MF 0.022MF 0.033MF 0.047MF 0.1MF 0.22MF R 2305 R 2307 R 2309 R 2311 R 2313 R 2315 R 2317 R 2319 R 2321 R 2323 R 2325 R 2327 R 2360 R 2370 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.18 $0.30 $0.45 3KV Ceramic/NEW Value In uf CatNo. Price 100PF 120PF 150PF 180PF 220PF 270PF 330PF 390PF 470PF 560 PF 680 PF 820PF 0.001MF 0.0022MF 0.0033MF 0.0047MF 0.0056MF 0.0068MF R 2375 R 2376 R 2378 R 2380 R 2381 R 2382 R 2383 R 2384 R 2386 R 2387 R2388 R 2389 R 2390 R 2392 R 2393 R 9394 R 2395 R 2396 $155 $155 $155 $1.55 $155 $1.55 $155 $1.75 $1.75 $1.85 $185 $1.95 $195 $1.65 $185 $2.05 $2.25 $2.45 0.0082MF 0.01MF R 2398 R 2400 Get your tool box in order with these high quality, great value screwdrivers. All have insulated handles and Chrome Vanadium shanks for long life. $2.65 $2.85 50V Monoli1hic/NEW $0.30 10PF R 1981 $0.30 R 1982 15PF $0.30 22PF R 1983 $0.30 33PF R 1984 R 1985 $0.30 47PF $0.30 R 1986 68PF R 1987 $0.30 100PF R 1988 $0.30 120PF R 1989 $0.35 150PF $0.35 220PF R 1990 R 1991 $0.38 330PF $0.40 470PF R 1994 $0.45 680PF R 1995 $0.30 1000PF R 1996 $0.30 1500PF R 1997 $0.30 2200PF R 1998 $0.30 3300PF R 1999 $0.30 4700PF R 2002 $0.35 6800PF R 2003 $0.35 0.01mf R 2000 $0.38 0.015mf R 2004 0.022mf $0.38 R 2005 $0.40 0.033mf R 2006 0.047mf R 2007 $0.45 $0.48 0.068ml R 2008 0.1ml R 2001 $0.50 $0.35 0.15mf R 2180 0.22ml R 2181 $0.45 0.33ml R 2182 $0.55 $0.60 0.47mf R 2183 0.68mf R 2184 $0.65 10ml R 2185 $0.70 Philips Head Size 6 x 38mm 3.2 x 75mm 5 x 75mm 5 x 100mm 6 x 100mm 6 x 125mm 8 x 150mm Cat No Price T 6025 T 6035 T 6037 T 6045 T 6047 T 6055 T 6065 $2.95 $2.95 $2.95 $3.95 $3.95 $3.95 $5.95 Flat Blade Size 6 x 38mm 3.2 x 50mm 3.2 x 75mm 4 x 100mm 5 x 100mm 5 x 150mm 6 x 125mm 8 x 150mm 8 x 200mm 8 x 250mm Cat No Price T 6020 T 6028 T 6030 T 6032 T 6040 T 6050 T 6052 T 6058 T 6060 T 6062 $2.95 $2.50 $2.95 $2.95 $3.95 $3.95 $2.95 $5.95 $5.95 $5.95 GENERAL PURPOSE SOLDERING IRON 30-150 WATTS/ SCOPE 12V SOLDERING IRON Only$79 95 Just $2995 CatT-1635 Cat T-1620 Ideal for outdoor work. Rated at 30-150 watts, so it's suitable for a wide variety of applications. Lightweight, easy to handle and beautifully balanced to make work easier. Comes with 6 metre power cable fitted with 2 alligator clips for easy connection to car battery, etc. Pack also contains spare elements and tip. It's fantastic value! Rugged and reliab le from Scope! It's rated at 20 watts which makes it ideal as a general purpose iron for around the home, workshop, etc. Plugs straight into the mains and it's fitted with air cooled handle to make work more comfortable. Tips and elements are easy to replace so maintenance is a breeze. DSE SOLDERING STATION Ideal For SitB Work/ Only $}35 Cat T-2000 A professional quality soldering station at an affordable price! Ideal for hobbyist or technician. Features fully variable temperature control (from around 200 - 500 degrees Celsius). temperature meter, iron holder, tip cleaning sponge, comprehensive instructions and full service manual. You won't buy better at the price' 3-IN-1 MODULAR TOOL • • • • It's a DRILL It's a SCREWDRIVER It's a SOLDERING IRON It's RECHARGEABLE CatT-5712 ~ ~ ~ Just $99 ALL NEW SOLDER AND ACCESSORIES You'll on ly get the best job done when you use quality solder and accessories to assure yourself of the best possible joints and connections. We stock a complete range of Multicore soldering products for all your soldering needs - you won't find better quality at the price! Solder Tape - Low temperature Spray Flux Remover Emergency solder, melts with a match with resin core. A highly efficient flux remove r. In handy 200g spray 34 grams. Cat N-1 632 $3.95 pack. Yes, it's ozone safe ! Cat N- 1160 $6.95 General Purpose Resin Core Solder Alu-Sol 40/ 60 5 core solder. 1.2mm X 14 grams. Cat N-1634 Aluminium based solder for joining dissimilar metals . $2.50 Makes a normally difficu lt job, easy! 100g X 1.6mm. Solder Cream Cat N-1625 $11 .95 8 grams X 1.6mm Cat N- 1640 $2.50 96/ 4 Tin / Silver. This lead free solder is ideal for stainless steel. Uses Arax acid flux so not Solder 95/5 Tin Antimony recommended for electrical work. Great for metal Idea for copper, brass, tin , jewellery etc. 7 grams. project boxes etc . Cat N-1644 $4.95 Cat N-1624 $2.50 Tip Cleaner/Tinner Solder For General Metal Repair In 15 Gram Tin. A fast and efficient method for Arax acid flux cored, not recommended for electrical cleaning and re-tinn ing soldering iron tips . Cat N-1648 work. 75 gram roll of 40/ 60 solder. Cat N- 1630 $4.95 $2.95 PLUGS AND SOCKETS WIRE AND CABLE Transistor Sockets - German 'Assmann' Types TO-3 Cat P-4023 $2.25 TO-5 Cat P-4015 $1.40 TO-18 Cat P-4018 $1.25 IC Sockets - New machine pin types 8 Pin. Tin/ Gold. Cat P-408 1 $1.00 14 Pin Tin / Gold. Cat P-4141 $1.50 16 Pin. Tin / Gold . Cat P-4161 $1.75 OIL Plu9s - Component Carrier Type 16 Pin. DIL Header Cat P-4164 Plug $3.50 14 Pin. DIL Header Cat P-4144 Plug. $2.95 Cat P-4300 32 Pin Socket Strip. $3.95 Jack Sockets for 'D' Connectors (mixed pack Cat P-2725 of 14 sets) $3.95 You 'll find the right wire and cable for just about any application at your nearest Dick Smith Electronics store. Our easy Cable Selection Bar saves time and you can make fantastic savings when you buy in bulk (100m or more)! Here are just some! MAINS CABLE 24/ 020 Figure-8. White Cat W- 2020 60c/m 24/ 020 6 Core. Grey. Cat W-2042 Save $1 / m! Now $1.95/m 7.5 Amp 3 Core Textile covered. Cat W-2054 $1.95/rn 24 / 020 light Duty 3 Core 7.5 amps. Grey. Cat W-2055 $1.00/m 24/ 020 Ord inary Duty 3 Core. 7.5 amps. Grey. Cat W- 2056 $1.75/m 32/ 020 Ordinary Duty. 3 Core. 1O amps. Grey Cat W-2058 $1.95/m 30/ 025 Ordinary Duty. 3 Core. 15 amps. Orange Cat W-2059 $2~50 FIGURE 8 CABLE GLUES AND ADHESIVES SUPER GLUE. Quick drying, super strong . In 2ml tube. Cat N- 1218 $1 .50 Superlastt SUPER GLUE Make repairs in seconds ! 10ml conta iner. Cat N- 1219 $6.95 PVA GLUE Ideal for wood, cloth, paper, etc. In 50ml bottle. Cat P- 1223 $3.50 5 MINUTE EPOXY Two mi x epoxy glue for filling and extra strong bonding. In easy to use 24m l syringe. Cat N- 1228 $5.95 F 1 , :;;;;;;;::::::: . . dstockis s.. . . . . . . . ~···························•·1~ Genume US Galla Tape Authonse • . PHONES SECURITY AUDIO _ : 26/ 030 Heavy Duty. Rated at 20 amps. Ideal for automotive use. Cat W- 2025. $85c/m 26/ 032 2 Core. Rated at 20 amps. Insulated and sheathed. Cat W-2027 $1.35/m 26/ 030 New marine cable. 15 amp rated -double insulated for super corrosion for super corrosion protection. Cat W-2029 $1.95/m 1/ 060 Bell Wire. White. Cat W-2005. 40c/m But you'll find a million and one uses for GAFFA tape around the home, workshop ... anywhere! You'll find a great range now at your nearest Dick Smith Electronics store. Heavy Duty Black/Silver Sticks to almost anything and an ywhere. Easy to remove , long wearing. 5 Metre Roll. Black. Cat N-1400 $9.95 40 Metre Rol l. Black. Cat N- 1405 $15.95 25 Metre Silver. Cat N-14 10 $9.95 ,i( • ••••••••••••••••••••••••••••••••••• Double Sided Indoor. 12mm x 2 metre roll. Acrylic foam, white, suitable for indoor use. Cat N-1380 $2.95/roll Double Sided Outdoor 12mm x 5 metre roll. Butyl foam , black, hard wearing, super sticking for outdoor use. Cat N-1382 $6.95 SUBSCRIBE SUBSCRIBE SUBSCRIBE r~ ,,1} Have SILICON CHIP delivered direct to your door at no additional cost. Each month, we'll bring you the best and brightest electronics magazine, put together by Australia's most experienced team. • • • • • • '1 d l! Police radar: it's not always right r) Intelligent charger for 12V gel batteries CONSTRUCTIONAL PROJECTS AMATEUR RADIO VINTAGE RADIO COMPUTER BITS THE WAY I SEE IT INFORMATIVE ELECTRONIC STORIES ~-----------------------------------FREEPOST* 24 Hour Fax Service (02) 982 9553 Send the coupon with your Credit Card details. 24 Hours, 7 Days a week. SUBSCRIPTION COUPON D Renewal D New subscription Start in _ _ _ _ _ __ Name _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Subscription Hotline Telephone (02) 982 3935 9am-5pm Mon-Fri and quote your Bankcard , Visa Card or MasterCard No. and expiry date. (PLEASE PRINT) Street_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Suburb/town _ _ _ _ _ _ _ _ __ _ _ Postcode _ _ __ 1 year (12 issues) D $A42 2 years (24 issues) D $A84 NZ & PNG (airmail) D $A65 0 $A130 Overseas surface mail D $A62 D $A130 Overseas airmail D $A120 D $A240 Australia Detach Coupon and Mail to: FREEPOST 25 SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROY BEACH NSW 2097 *No postage stamp required in Australia. 56 SILICON CHIP Enclosed is my cheque/money order tor $ _ _ _ or please debit my D Bankcard Card No . I D Visa Card D MasterCard I I I I I i I I I I I I I I I I Signature _ _ _ _ _ _ _ _ _ Card expiry date_/_/_ _ ~ oi L-----------------------~ BOOKSHELF Antenna construction with PVC pipe Easy-up Antennas for Radio Listeners and Hams, by Edward M. Noll. Published 1988 by Howard Sams & Company, Indianapolis, Indiana USA. Soft covers, 279 x 216mm, 162 pages. Price $27.95. If you're a keen shortwave listener or an amateur radio operator, you are sure to be interested in this book on build-ityourself antennas. This book features a great many antennas and a lot of these are based on PVC pipe which is a readily available and corrosion free material. The construction details for each antenna are relatively sketchy with each usually only having a dimensional diagram and a photo or two. However, there are lots of photos throughout the book so the general construction methods are fairly obvious once you have been right through the text. Most of the antennas featured are variations on dipoles and long wire antennas and there are a few simple yagis given too, but no quads. Still. I suppose quads hardly rate as "easy up antennas", do they? The book is weak on antennas for the VHF and UHF bands mainly because the relevant chapter features only two designs, a discone for scanners and a very simple 2- element dipole for FM reception. It also lacks any details on performance for any of the antennas - so there is nothing on radiation patterns, relative gain, impedance or VSWR and hence there is no basis for comparison. However, if these details were to be included, the text would be a good deal larger and perhaps a lot more expensive than it is. Essentially, the text should be regarded as a good source of ideas for antennas for shortwave listening and for amateurs operating in the HF bands. Our copy came from Jaycar Electronics (Cat. BS-0735) and is priced at $27.95. (D.B.Y). Basic principles of music synthesisers description of how various sounds are produced using AD (attack/decay) and ADSR (attack, decay, sustain, release) and other forms of modulation. Voltage controlled filters, amplifiers and oscillators are all explained in detail, as are vibrato, tremolo, portamento and ring modulation. Other circuit techniques such as sample and hold are also well covered. In summary, the book is easy to read and explains the basic principles of synthesisers well, without getting down to actual circuit examples. As the title suggests, the book is for musicians, not for circuit designers. Our sample copy came from Jaycar Electronics (Cat.BP-1206) and is priced at $19.95. (D.B.Y). Bring back the valves! 70 Years of Radio Tubes and Valves, by John W. Stokes. Published 1982 by the Vestal Press Ltd, Vestal, New York, USA. Soft covers, 280 x 217mm, 247 pages. Price $32.95. Many of the younger generation think that electronics has always been ICs, transistors and what have you, and don't realise what they've missed out on! We're not going to get involved in continued next page Synthesizers For Musicians, by R.A. Penfold. Published 1989 by PC Publishing, Kent, England. Soft covers, 215 x 137mm, 167 pages. ISBN 1-870775-01-5. Price $19.95. If you enjoy listening to Bruce Hornsby or other synthesiser players and you'd like to know in a general way how these things work, then this is the ideal book. It's not a typical overview of the different synthesisers that were in vogue 10 years ago, but a useful MARCH 1990 57 Silicon Chip · BACK COPIES ·. February 1988: 200 Watt Stereo Power Amplifier; Deluxe Car Burglar Alarm ; End of File Indicator for Modems; Door Minder Alarm ; Low Ohms Adaptor for Multimeters; Line Isolation Unit for Phone Patch; Electronics In The Jaguar XJ40 ; Easy Tips on Headphone Repair. March 1988: Remote Switch for Car Alarms ; Telephone Line Grabber; Endless Loop Tape Player; Build Your Own Light Box; New Life for Radio-Cassette Players; Old-Time Crystal Radio. April 1988: Walkaround Throttle for Model Railroads, Pt. 1 ; pH Meter for Swimming Pools; Slave Flash Trigger; Headphone Amplifier for CD Players ; What is Negative Feedback, Pt.1 ; Mobile Antennas for the VHF & UHF Bands. May 1988: Optical Tachometer for Aeromodellers; High Energy Ignition for Cars; Ultrasonic Car Burglar Alarm ; Walkaround Throttle for Model Railroads , Pt.2; Designing and Building RF Attenuators; Motorola MC3334P High Energy Ignition IC Data. June 1988: Stereo Control Preamplifier (uses LM833). Pt.1 ; Breakerless Ignition For Cars Using Hall Effect Pickups; Mega-Fast Nicad Battery Charger; Automatic Light Controller Uses PIR Detector; RF Sniffer Probe & Preamplifier; What is Negative Feedback, Pt.2 . July 1988: Stereo Control Preamplifier, Pt. 2 ; Fitting a Fuel Cut-Off Solenoid; Booster for TV & FM Signals; The Discolight Light Show, Pt.1; Tone Burst Source for Amplifier Headroom Testing; National Semiconductor LM833 Op Amp Data; What is Negative Feedback, Pt.3 . August 1988: Building a Plasma Display; Universal Power Supply Board; Remote Chime/Doorbell; High Performance AC Millivoltmeter (uses OP-27). Pt.1; Discolight Light Show, Pt.2; Getting the Most Out of Nicad Batteries ; Data on Insulated Tab Triacs. September 1988: Hands-Free Speakerphone; Switchmode Charger for 12V Gel Batteries; Electronic Fish Bite Detector; High Performance AC Millivoltmeter, Pt.2; Vader Voice; Motorola MC34018 Speakerphone IC Data; National Semiconductor LM12 150W Op Amp Data & Applications; What is Negative Feedback, Pt.4. October 1988: Stereo FM Transmitter (uses Rohm BA1404); High Performance FM Antenna; Matchbox Crystal Set; Electronic House Number; Converting a CB Rad io To The 28MHz Band; Electronics & Brock's BMW Blaster; Queensland's Powerful Electric Locomotives. November 1988: 120W PA Amplifier Module (uses Mosfets); Poor Man's Plasma Display; Automotive Night Safety Light; Adding a Headset To the Speakerphone; How To Quieten the Fan In Your Computer; Screws & Screwdrivers, What You Need To Know; Diesel Electric Locomotives. December 1988: 120W PA Amplifier (With Balanced Inputs). Pt. 1 ; Diesel Sound Generator; Car Antenna/Dem ister Adaptor; SSB Adaptor for Shortwave Receivers; Electronics & Holden's New V6 En gine; Why Diesel Electrics Killed Off Steam; Index to Volume 1. January 1989: Line Filter for Computers; Ultrasonic Proximity Detector for Cars; Simple Computer Sound Repeater; 120W PA Amplifier (With Balanced Inputs) Pt.1 ; How to Service Car Cassette Players; The Goalkeeper Gatling Gun; Massive Diesel Electrics In the USA. February 1989: Transistor Beta Tester; Minstrel 2-30 Loudspeaker System; LED Flasher for Model Railways (uses LM3909) ; Build a Simple VHF FM Monitor (uses MC3362 ), Pt.1; Lightning & Electron ic Appliances; Using Comparators to Detect & Measure. March 1989: LED Message Board, Pt.1; 32-Band Graphic Equaliser, Pt.1; Stereo Compressor for CD Players; Map Reader for Trip Calculations ; Amateur VHF FM Monitor, Pt.2; Signetics NE5 72 Compandor IC Data; Electronics for Everyone - Resistors. April 1989: Auxiliary Brake Light Flasher; Electronics for Everyone: What You Need to Know About Capacitors; Telephone Bell Monitor/ Transmitter; 32-Band Graphic Equaliser, Pt.2 ; Led Message Board, Pt.2. May 1989: Electronic Pools/Lotto Selector; Use this handy form to order your back copies "Ill\ r-- - -----------------------------+-- 7 1 Please send me a back issue for: February 1 988 March 1988 April 1988 □ I □ May 1 988 □ I □ October 1 988 I □ March 1 989 I I l I I I I I I I I I I □ □ □ July 1 988 □ August 1 988 □ [l November 1 988 □ December 1988 □ January 1989 D February 1 989 ii April 1 989 □ May 1 989 D June 1989 □ D August 1989 □ September 1 989 D October 1989 □ November 1989 □ December 1989 □ January 1990 0 February 1 990 June 1 988 September 1 988 July 1989 Enclosed is my cheque/money order tor $ _ __ ___ or please debit my □ Bankcard □ Visa Card □ MasterCard Card No Price: $A5 .00 each (includes postage). Overseas orders add $A 1 .00 per issue tor postage. Signature, _____________ Card expiry date _ ___._ _ NZ & PNG orders are sent by air mail. Name______________________ _ ___ (PLEASE PRINT) Detach and mail to: SILICON CHIP PUBLICATIONS Stree.__ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ __ _ __ PO BOX 139 COLLAROY BEACH NSW 2097 Suburb/town _ _ _ _ _ _ _ _ _ _ _ _ _ _ Postcode _ _ __ OR FAX: (02) 982 9553 .I..___.___,___.__,II..___.____.___..__ ] .I. .---'----'----'--I l_l---'----'-----'--_, I I I I l I 'I I I I I I I * ~---- -----------------------------------'-- 58 SILICON CHIP Synthesised Tom-Tom; Biofeedback Monitor For Your PC; Simple Stub Filter For Suppressing TV Interference; LED Message Board, Pt.3; Electronics for Everyone - All About Electrolytic Capacitors. June 1989: Touch-Lamp Dimmer (uses Siemens SLB0586); Passive Loop Antenna For AM Radios; Universal Temperature Controller; Understanding CRO Probes; Led Message Board, Pt.3; Coherent CW - a New Low Power Transmission Technique. July 1989: Exhaust Gas Monitor (uses TGS812 Gas Sensor); Extension For the Touch-Lamp Dimmer; Experimental Mains Hum Sniffers; Compact Ultrasonic Car Alarm; NSW 86 Class Electrics; Facts On the PhaxSwitch - Sharing Your Phone Line With A Fax Machine. August 1989: Build A Baby Tower AT Computer; Studio Series 20-Band Stereo Equaliser, Pt.1; Garbage Reminder - A 7-day Programmable Timer; Introduction to Stepper Motors; GaAsFet Preamplifier For the 2-Metre Band; Modern 3-Phase Electric Locomotives . September 1989: 2-Chip Portable AM Stereo Radio (uses MC13024 and TX7376P) Pt.1; Alarm-Triggered Telephone Dialler; High Or Low Fluid Level Detector (uses LM 1830N); Simple DTMF Encoder (uses Texas TMC5089); Studio Series 20-Band Stereo Equaliser, Pt.2; Auto-Zero Module for Audio Amplifiers (uses LMC669); A Guide to Hard Disc Drives. October 1989: Introducing Remote Control; FM Radio Intercom For Motorbikes (uses BA 1404 and TDA7000) Pt.1; GaAsFet Preamplifier for Amateur TV; 1Mb Printer Buffer; 2-Chip Portable AM Stereo Radio, Pt.2; Installing A Hard Disc in the PC; A Look at Australian Monorails . November 1989: Radfax Decoder For Your PC (Displays Fax, RTTY and Morse); Super Sensitive FM Bug ; Build A Low Cost Analog Multimeter; FM Radio Intercom For Motorbikes, Pt.2; 2-Chip Portable AM Stereo Radio, Pt.3; Floppy Disc Drive Formats & Options; The Pilbara Iron Ore Railways. December 1989: Digital Voice Board (Records Up To Four Separate Messages, Uses Texas TMS3477NL and 256K RAMs); UHF Remote Switch; Balanced Input & Output Stages; National Semiconductor LM831 Low Voltage Amplifier IC Data & Applications; Install a Clock Card In Your PC; Index to Volume 2. January 1990: Service Tips For Your VCR; Speeding Up Your PC; Phone Patch For Radio Amateurs; High Quality Sine/Square Oscillator; Active Antenna Kit; The Latest On High Definition TV; Speed Controller For Ceiling Fans. 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. Note: November 1987, December 1987 & January 1 988 are now sold out. BOOKSHELF - CTD FROM PAGE 57 the "valves-sound-better-thantransistors" argument, nor is the book written in that vein. Instead, it presents a general history of valves and vaccuum tubes. It's a well produced introduction into what was the era of wireless. It covers many of the developments that occurred during the 1920s, 30s and 40s, giving a pictorial display of many of the valves that were popular with constructors. There are 27 chapters, too numerous to outline in detail here. However, some examples of the subject matter discussed are developments in tetrodes and transmitting tubes, and outlines on some of the major manufacturers like Mullard, Philips and Amalgamated Wireless (Australasia) Ltd are given. There is even discussion on some of the major valves that subsequently became well known to radio collectors. An example is the 6V6, certainly one of the most-used valves in the world. It also gives you the atmosphere of the period by showing many of the contemporary advertising posters from England, America and Australia. Whether you're a fan of valves or not, this is certainly interesting reading about an era that was wireless, and would certainly be a worthy piece to add to any vintage radio collector's shelf. The book is available for $32.95 from Resurrection Radio, PO Box 1116, Windsor, Vic 3121. (D.B.Y). Making money from audio recording Make Money From Home Recording, by Clive Brooks. Publishe d 1989 by PC Publishing, Kent, England. Soft covers, 216 x 137mm, 105 pages. ISBN 1-870775-25-2. Price $17.95. Many people are interested in home recording in one form or another, and probably quite a few are interested in the business opportunities too, so this book is assured of a wide readership. Whether it will give you enough background to make good home recordings is quite another matter though, because the book is not very technical. Chapter 1 gives some basic information on using a room or a garage as a home studio and touches on the essential topics of sound-proofing and ventilation. However, it gives no information on how the equipment should be set up or how the room might be laid out. Chapter 2 is devoted to studio equipment and talks about cassette decks and four track recorders. It also makes some mention of microphones and their general characteristics but that's about as far as it goes. There is nothing on mixers or equalisers, and the barest of mentions of midi systems and keyboards, all of which would be used these days by the serious home recordist. This would especially apply if the reader was considering recording advertising jingles (one of the suggested business opportunities). We could go on about the nontechnical nature of the book but the point is made - it really is more on the subject of business opportunities. On that basis, the book provides interesting background which is well worth reading. Our review copy came from Jaycar Electronics (Cat BP-1208) and sells for $17.95 . [L.D.S). [!tl MARCH 1990 59 16-Channel Mixing Desk, Pt.2 In this second article on our new 16-Channel Mixing Desk, we present the details of the circuitry. The design is based largely on the LM833 low noise dual op amp instead of the 5534 used in previous mixer designs. By JOHN CLARKE & LEO SIMPSON To be able to easily follow the circuit description, you will need to refer to the description of the block diagram, Fig.1, in the first article in this series. Now let's look at Fig.2 which is the circuitry used on each of the 16 input channel boards. This is depicted schematically along the top of the block diagram, Fig.1. The input signals come from pins 2 and 3 of a 3-pin XLR socket and are fed via 33µF capacitors to the inputs of ICla which is half of an 60 SILICON CHIP LM833 dual low noise op amp. Switch S1, a 3-pole 3-position switch, switches the feedback network (Slc), the input attenuator (Slb) and pin 2 of the input socket for the balanced or unbalanced input condition (Sla). Let's see how these conditions come together. When switch S1 is in setting 1, the input channel is connected to suit balanced microphone outputs. In effect, ICla operates as an inverting amplifier for signals from pin 2 of the XLR socket and as a non-inverting amplifier for signals from pin 3 of the XLR socket. In both cases, the gain is determined by the two resistors connected to the noninverting input, pin 2; ie, 10k0 and lkO. Gain for the inverting signal path is 10k0/1k0 = 10 while gain for the non-inverting signal is 100/lkO + 1 = 11. To compensate for this difference in path gain, a resistive attenuator is connected in series with the signal to pin 3 of ICla. This attenuates the signal by a factor of 0.909. When multiplied by the nonFig.2 (opposite): this is the circuitry for each of the 16 input channels. IC1a & ICtb are input preamplifier and buffer stages, IC2a a 3-band tone control stage, IC2b the post fade buffer and IC3a, D1, D2, Qt & Q2 the headphone driver stage. IC4, IC3b & IC5 provide overload indication. ~ ~ 0) 0 CD ....CD :r: n !Jl 10kVR6 LOG ~ - · FADER~• ■ - 16VW 100 - ' . " WI+ ' . 0.1! o•.w.I I l 4.7!! IC1 t8 0.1 IC2 I- \, .,. 6.8k ':'" 0. 1 I v- POST FADE BUFFER 1 OF 16 .,. 16VWI - I 1 V+ 011 1 2 ~ BUS EFFECTS CH2/CH4 BUS HEADPHONE MONITOR 1 OF 16 j 100pF EFFECTS~10k VR7 10k LOG S2b . DlI .,. I ~ 1L ., r . r r- 0·1 10k Sl: 1: MIC 2 : LINE BAL 3: LINE UNBAL 1.2k 1¾ 2k 1°1. CH1/CH3 BUS ATTE~~~TOR 10k LOG INPUT .,. "~h L 330 ~ .,. PEAK DETECTOR 1 OF 16 INPUT BUFFER AND AT~E~~WR -- -i. 1 OF 16 v- 3-BANO EQUALISER .0027 33k VIEWED FROM BELOW B ' EOc v+ .. ,. S2a ' .~- S2 : 1 : CHANNEL OUT 2 : CHANNEL IN 10k LOG FOL~i~CK~ FOLDBACK BUS All the circuitry ,shown in Fig.2 is accommodated on a single PCB. There are 16 of these boards altogether - one for each input channel. Note how the pots are mounted directly on the board to cut down on the internal wiring. inverting gain of 11, it gives an overall gain of 10, the same as for the inverting gain. Hence, the circuit provides a perfectly balanced input. The input impedance is 1.BkO which comprises the lkO input resistor network in the inverting signal path and the lkO input divider in the non-inverting signal path, with both shunted by lOkO resistors to earth. Line balanced & unbalanced In position 2 of switch S1, the input channel is connected to suit balanced line inputs. The gain is reduced by a factor of 10 by switching the 1.2k0 resistor across the 1OkO resistor between pins 1 and 2 of ICa (Slc). This provides a gain of 1.07 for the inverting signal path and a gain of 2.07 for the non inverting signal path. This disparity of gain is compensated for by the switched attenuator (Slb) in the non-inverting signal path which reduces the signal by a factor of 0.4825. When multiplied by the non-inverting gain of 2.07, the overall gain is 0.999 which is pretty close to the inverting gain of 1.07. Thus, by virtue of This board accommodates all the effects send, effects return & foldback circuitry shown in Fig.3 .. There are two such boards in the mixer. As before, the pots are soldered directly to the PCB to simplify the wiring. 62 SILICON CHIP the selection of feedback resistors and the attenuator associated with S1b, the circuit gives balanced input conditions for both line and microphone sources. In position 3 of switch S1, the input channel is connected for unbalanced inputs. The feedback and input attenuator is the same as for the balanced condition while the difference is that pin 2 of the XLR socket is grounded. Pre-fade attenuator Following the preamplifier stage is a non-inverting op amp stage comprising ICl b. This is labelled on the circuit as an input buffer and attenuator but most mixer operators would think of it as a "prefade attenuator". It enables the signal levels to be set up on each input channel. The gain of this stage is variable from 100 to unity by means of VRl. This stage is followed by IC2a which is a 3-band Baxandall tone control stage. VR2 provides the bass control function and has no effect on frequencies above about 300Hz by virtue of the .015µF capacitor shunting it. VR4 provides the treble control function and has little effect on frequencies below about 2kHz, by virtue of the .0015µF capacitor in series with the pot wiper. VR3 provides a midchannel control by virtue of the .002 7µF capacitor shunting the control and the .012µF capacitor in series with the pot wiper. 2.2 16VW o-4 ..---.~w.-....---"1 EFFECTS RETURN + CH1/CH3 BUS EFFECTS RETURN AND PAN (2) CH2/CH4 BUS . 22k PAN VR10 10k LIN 15k 6.Bk 2.2k 39k EFFECTS jjlJs +15V EFFECTS SUM AND LINE AMPLIFIER (2 ) 2.2k 100k 47 16VW ,. + -15V EFFECTS SEND LINE OUTPUT 39pF + 6.8k 39k FOLOBACK BUS F-0 1k .,. 2.2k FOLOBACK SUM AND LINE AMPLIFIER (2) 100k • +15V0 l 0.11 t 1001 16VW+ IC6 - 15V0 I o.,I 47 16VW + 7 F-o +15V FOLDBACK LINE OUTPUT ,. iB 6.8k IC8 r ,oo -I r .a + 1k -15V e- 16VW+ .,. Fig.3: the effects and foldback circuitry. IC6a & IC6b process the effects return signal while VR10 pans the signal between the CH1/CH3 and CH2/CH4 buses. IC7a & IC8a are the effects sum and foldback sum amplifiers, while IC7b and IC8b function as line amplifiers. Headphone driver The output of IC2a then feeds the foldback send control VR5 and the main fader control VR6 (bottom, left of the diagram). Following VR6 is the post fade buffer, IC2b, which has a gain of 2. It feeds the effects send control VR7, the pan control VRB and the headphone monitor stage, IC3a. This uses two transistors, Ql and QZ, to boost the output current to give sufficient drive for any stereo headphones, high or low impedance, that may be used. Diodes Dl and D2, in conjunction with the 330 emitter resistors, set and stabilise the quiescent current through Ql and QZ, to eliminate crossover distortion. Peak detector As well as driving the headphone monitor for each channel, the signal from the emitters of Ql and Q2 also feeds the peak detector which monitors for signal overload. IC4 and D3 function as a precision full wave rectifier. Its output is fed to the inverting ( - ) input of IC3b which functions as a corn- parator with hysteresis set by the 220k0 feedback resistor from pin 7 to pin 5. The non-inverting ( +) input is fed from a lOkO trimpot. This is adjusted to set the input signal level above which the comparator output, pin 7, goes low. When this happens, the 7555 timer, IC5, is triggered and turns on LED 21 for around 24 milliseconds which is quite long enough to be seen. Thus even the briefest of overloads will be registered by the circuit. And because IC4 functions as a full wave rectifier, peak MARCH 1990 63 There's quite a lot of wiring inside the mixer, despite the fact that all rotary pots are directly soldered to the boards. Most of this wiring is repetitive and includes power supply connections, wiring to the 20 slider contr.ol~, and input/output socket connections. Note that several boards are m1ssmg from this photo. overloads on both positive and negative half cycles of the audio waveform will be registered. Power supply connections Note that the positive and negative power supply connections for ICl and ICZ are not shown on their respective op amp symbols. They were omitted for clarity. However, these connections are shown on the supply rails, on the lefthand centre of the diagram, together with the various bypass capacitors on the rails. Note the 4. 70 resistors in series with both the positive and negative supply rail inputs. These provide a degree of supply decoupling, in conjunction with the 100µF bypass capacitors. As well, the 4.70 resistors will act as fuses in the unlikely event of a short on the board. If this happened, only one input channel would be disabled rather than possibly the whole mixer circuit. Effects and foldback The effects and foldback buffer stages are shown in Fig.3. Note that all of Fig.3 is accommodated on one printed board, of which there are 64 SILICON CHIP two. These stages are all based on the LM833 dual low noise amplifier. They are all quite straightforward but you should look at the block diagram, Fig.1, to understand how they fit into the overall scheme. IC6a, the effects return circuit, is a non-inverting unity gain buffer. IC6b, the effects pan driver, is a non-inverting amplifier with a gain of 2. IC7a and IC8a, the effects sum and foldback sum amplifiers, are inverting amplifiers, each with a gain of 17. IC7b and IC8b, the effects and foldback line amplifiers, are non-inverting amplifiers, each with a gain of 7.8. Note that the supply connections to IC6 and IC8 have again been omitted for clarity but they are shown on the supply bus, at the lower lefthand corner of the circuit. Now let's have a look at the 2-page circuit diagram, Fig.4. This is the circuitry for the 5-band equalisers and LED VU monitors. It also includes the master fader, the sum and post fade amplifiers and the headphone monitor stages. All of Fig.4 is accommodated on one printed circuit board, of which there are four. IC9a is shown as the "sum amplifier" connected to the CHl bus but remember that there are four of these boards so it could equally apply to the other three output channels. That is why it is shown as 1 of 4. You will find this note on several parts of the circuit as a reminder that the same circuit is on four boards. IC9a is an inverting amplifier with a gain of 34 (ie, 75k0/2.2k0). It drives the master fader VR13 and then the post fade amplifier IC9b which is a non-inverting amplifier with a gain of 4 (ie, 6.8k0/2.2k0 + 1). Five band equaliser IC10b, IC12 (a TL074 quad Fetinput op amp) and IC13 (a single Fet-input op amp) make up the five band equaliser. The five op amps in IC12 and IC13 are all connected as gyrators which are the equivalent of inductors. The gyrators act together with a series capacitor to form broad tuned circuits centred on 60Hz, 240Hz, lkHz, 3.5kHz and lOkHz, and give boost and cut of ± 12dB. Fig.4 (overleaf): the circuitry for the 5-band equalisers, output channel monitors and LED VU meters. The VU meter uses cascaded LM3915s (IC14 & IC15) and these are multiplexed between dot and bar modes to display peak and average signal levels. . drasticallY ust be . ,, Everything d -- stocks rn . of profit! .. reduce d irrespective cleare SH1 SH2 SH3 SH4 SH5 SH6 SH7 SH8 SH9 SH10 SH11 SH12 SH13 SH14 SH15 SH16 SH17 SH18 SH19 SH20 SH21 SH22 SH23 SH24 SH25 SH26 SH27 SH28 SH29 SH30 SH31 SH32 SH33 SH34 SH35 SH36 SH37 SH38 SH39 SH40 SH41 SH42 SH43 7 400 Quad 2-lnput NANO Gate 10 for 7 403 Quad 2-lnput Open Drain NANO Gate 10 for 7 404 Hex Inverter 10 for 7 408 Quad 2-lnput AND gate 10 for 7 41 0 Triple 3-lnput NANO gate 10 for 7 442 BCD to Decimal Decoder 10 for 7476 Dual J-K Flipflops with Preset and Clear 10 for 7 41 56 Dual 2-Line to 4-Line Decoder/Demultiplexer 10 for 7 4188 256-Bit PROM, Open Collector Output 10 for 75136 10 for 75451 Dual Peripheral Driver Positive AND Gate 10 for 7 4LS02 Quad 2-lnput NOR Gate 10 for 7 4LS04 Hex Inverter 10 for 74LS27 Triple 3-lnput NOR Gate 10 for 74LS51 Dual 2 Wide 2-lnput AND/OR Invert Gate 10 for 7 4LS86 Quad 2-lnput Exclusive OR Gate 10 for 7 4LS92 Low Power Divide By 12 Counter 10 for 7 4LS113 Dual J-K Flipflop with Preset 10 for 7 4LS1 23 Dual Monostable Multivibrator 10 for 74LS157 Quad 2-lnput Multiplexer 10 for 74LS161 Synch 4-Bit Binary 10 for Counter 7 4LS 1 63 Synchronous 4-Bit Binary 10 for Counter 7 4LS169 Synchronous 4-Bit Binary 10 for Up/Down Counter 74LS175 Quad D Flipflop 10 for 74LS367 Hex Bus Driver With 3-State 10 for Outputs 7 4S04 Ultra High Speed Hex 10 for Inverter 7 4S112 Fast J-K Flipflop With Preset and Clear 10 for 7 4S113 Fast J-K Flipflop With 10 for Preset 7 4S188 Schottky, 256-Bit PROM, 10 for Open Collector Output 7 4S241 Octal Buffers/Line Dr/Rx, 3-State Outputs 10 for 4020 CMOS 1 4-Bit Binary Counter 10 for 4049 CMOS Hex Inverter/Buffer 10 for $ $ $ $ $ 2.00 2.00 2.00 2.00 2.00 $ 2.00 BLACKTOWN i ,~2, STORE ~~ENING SOON SH44 SH45 SH46 SH47 SH48 SH49 SH50 SH51 SH52 $ 2.00 $ 2.00 $ 2.50 SH53 SH54 SH55 SH56 $ $ $ $ 2.50 2.00 2.00 2.00 $ 2.00 SH57 SH58 SH59 SH60 $ 2.00 SH61 $ 2.00 SH62 $ 2.00 $ 2.00 $ 3.00 SH63 SH64 SH65 SH66 $ 2.50 $ 2.50 $ 3.00 $ 2.00 SH67 SH68 SH69 $2.00 SH70 $ 2.00 SH71 $ 2.00 SH72 $ 2.00 $ 3.00 $ 2.50 $ 2.00 $ 2.00 6800P IC-CMOS 8-Bit Microprocessor, $ 1.50ea 1MHz 6821 IC-CMOS PIA Peripheral Interface $ 1.50ea Adaptor 2114P20 IC-MOS Static 4K RAM, 200ns $ 0.80ea $ 0.60ea 2114P30 IC-MOS Static 4K RAM, 300ns ML8205 Dual Tone Ringer 10 for $ 1.00 TR1865 Disc Controller $ 1.00ea WD2795A Disc Controller $ 1.00ea 10 for $ 1.00 8T26AN HT1-201-5 10 for $ 1.00 $ 0.60ea 7805/LM309, T03 Voltage Regulator $ 0.60ea 7815, T03 Voltage Regulator AMPLE PARKING IN ADJACENT STREETS ~ $ 2.00 SH73 SH74 SH75 SH76 SH77 SH78 SH79 SH80 SH81 SH82 SH83 SH84 SH85 SH86 Transistor, B0679 NPN, T0220 10 for Transistor, B0680 PNP, T0220 10 for IC, LM348 Op. Amplifier 10 for Benelec Analog Multimeter 20kohm Per Volt, With Case and Leads IEC Panel Mounting Socket IEC Switched & Fused Panel Mounting Plug IEC Panel Plug with Filter & Fused PSU Smoothing & Filter Unit 'Amiga' Computer Lead, Centronics to 25 'D' Female Hand Held Cassette Microphone-Stop/Start 5-pin 'DIN' In line Male Plug 10 for 5-pin 'DIN' In line Female Plug 10 for 5-pin 'DIN' 2-metre Lead, Male to Male, Flat Cable 5-pin 'DIN' 5-metre Lead, Male to Male, Flat Cable 5-pin DIN 9-metre Lead, Male to Male, Flat Cable IEC Mains Lead, Female In-Line to 2-Pin Plug 9-Way 'D' Female Plug Lead to 7-Pin Fem.Ski. 2 Metres Telephone 'Curly-Cord' with US Telephone Plug Transformer, 240V to 15V 200mA Power Pack, 240VAC to 15VDC 500mA ('OZ' Adapt. Req) 50-Way 'D', Male & Female Connectors 1 2 Assorted Multi-turn Trimpots SONY 3.5-inch Single Sided Disc Drive 400K MITSUMI 3.5-inch Single Sided Disc Drive 360K CROUZET Syncronous Motor, 240VAC 60 RPM Motorized Paper Tape Assy. With 30VDC Motor (OK for 1 2V) Telecom 'Commander' Interface Boards, Lots of 1 2V Relays 1 2-Digit Numeric Array Displays , MFTD by NSD Burroughs 12-Key Keypad in Case With Lead 'SHURE' Precision Stylus Force Gauge SUPER PACKS 1 OO's 1/4, 1/2 and 1 watt resistors SUPER PACKS 1 OO's Assorted Electro's SUPER PACKS Approx. 30 Assorted Potentiometers SUPER PACKS 1 OO's Assorted Disc Ceramic Caps SUPER PACKS 100 Power Diodes, 100V 1.5A Mini Relays, 5V DPDT Changeover Mini Relays, 12V Single Pole Changeover 'SAFT' Sub 'C' Nicad Batteries, 1.5Ah 'SAFT' 'AA' Lithium Batteries, 3.6V, Wire Ends 30 Assorted Resistor Networks, SIL & DIL Philips Drive Motors, Dual Spindle, 15V DC 40 x 40mm BNC Male to Female Leads, 3 Mir Length 41 64 DRAM, 1 50 n/sec Mail Charges: $15-$19.95 . . .. . . ..•.... $5 $20·$39.95 ... .. .•...... $7 $40·$69 .............. . $8 $70-$99 ..... . ........ $10 $100 and over ... ...... $15 Large or overweight articles sent Skyroad Freight Forward, Trading Hours: Mon-Frl . . . . . . . 9am•5.30pm Sat ........... 9.30am-1 pm $ 0.95 $ 0.70 $ 3.75 $33.00 $ 1.00ea $ 3.95 $ 6.00 $ 6.95 $ $ $ $ 6.50 2.50 1.50 1.50 $ 2.75 $ 3.25 $ 4.75 $ 2.00 SH47 Benelec 20kohmlvolt " '=t~· IEC switched & fused panel mounting plug V. ' H50 IEC panel plug with filter & fuse $ 1.25 $ 1.00 $ 1.95 · SH66 Sony 3.5-lnch single sided disc drive (400K) $ 9.50 $ 0.75pr $ 4.00 $12.50 $15.00 . 7 Mitsumi 3.5-lnch single sided drive (360K) $ 3.00 $13.50 $ 6.00 $ 0.50 ~ ';;' >'' $ 4.00 $ 2.50 ... _ _h ..... - - - - - - ' _ ,...., "' ,0 12-diglt numeric dlsp~~~ 1 $ 3.00 $ 5.00 . ' $ 3.00 2 $ 3.00 $ $ $ $ 3.00 1.00 1.00 2 .00 Burroughs 12-key keypad ·-a-·· · · .. SH84 Philips dual spindle drive motors $ 3.50 $ 2.00 $13.50 $ 3.00 $ 2.95 S~51 PSU smoothing & filter unit SHERIDAN ELECTRONICS 286 Cleveland Street, Surry Hills, NSW 2010 Ph: (02) 699 5922 or (02) 699 6912. Fax: (02) 698 3694 Mail orders to: PO Box 226, Strawberry Hills, NSW 2012 NOTE: Wo accept Bankcard, Mastercard and Visa. Howerer, we cannot glre quantity discounts on credit card purchases or account orders, Minimum tor account orders Is $15 excluslre of postage and packing. All prices Include Salos Tax. All prices quoted are tor this month only or unt/1 stocks last :r: ::a z n n 0 t""' gi C) C) .,. f CH1 BUS I I r ' -15V 1n1, -15V 910\l 60Hz VR14 100k LIN 16VWi ~ I .,. 1nr.1 240Hz VR15 100k LIN 2.2k .,. I FIVE BAND EQUALISER 1 OF 4 r 9100 CUT I .,. .018 T 4.7k:S I l - 100kl .,. .047 ~ 1kHz VR16 100k LIN BOOST 4.7k 100k i F :-i .,. 33pF.I I .0012: µ 1 011 -=:= I .022 0.22 47k SUM AMPLIFIER ANO POST FADE AMPLIFIER 1 OF 4 16VW:r: 100 r--------~-+15V 100 -... 75k 22pF _,,- -- ■■ T I I I I T _J_ I 1.,. 100k 560pF1 .0047 HEADPHONE MONITOR 1 OF 4 rV I I I l + T _.91011 ........ ¥hi 3.5kHz VR17 100k LIN ■ 33pF ..\D_.k_. I\, I UU 10kf ,. 10k I +15V BALANCED LINE AMPLIFIER 1 OF 4 I ., .,. II 3 -- BALANCED LINE OUTPUT ~ J I CHANNEL MONITOR 16VW+ 10 "ii L----~---+-+------15V ~ 16VW 10 ,------tl------------- +15V .......... 910[) h'h 10kHz VR18 100k LIN -15V .... ..,. ?"'-- +15V s::: > (") :r: "-I Cf) C) co ....co !Jj + + ":" EOC VIEWED FROM BELOW 8 I w >- v2 18 117 10 .J.i" 16VW+ f""" +15V 3.9k +A¥, ± 1% 30k 0.11 SIG K -57dB -15V , PEAK/AVERAGE LED VU METER 1 0F4 ~ 10 10 16VWI 16VWI +5V hs -:- +15V -:- RL0 4 115 - 680!! 1% 113 REF ADJ 8 .011 + 10 .,JJ' .,. 16VW.I 10 111 IC20 7555 ""=' 1% 1k 13 16VW:r } 112 ), t--L l 100k 0.1-I RHI 6 REF OUT 7 IC14 LM3915 114 ), -:- l l 1% l I 1k v+ 3 MODE g 110 }- ~ 11 + 1 16VWI v+ 3 g MOOE sGtl,c21c 100k !- ~ V2 l1a 1% 910!! ~ 8 REF ADJ 680!! 1'/, l1s 10 16VWi -: RL0 4 In ~ 5 r:i\11c21b 10kt +15V REF OUT 7 RHI 6 1,4 IC15 LM3915 l1s 113 IC21d 12 l,2 (ll (10 SIG ~,//wI 0dB '1~rn 2ol,o , tlf l f l f l f ... LED1-20 The power supply board provides ± 15V rails to power the op amps, together with a + 5V supply to run all the LEDs in the VU meters. The three 3-terminal regulators are bolted to small heatsinks. For a detailed description of how gyrator and equaliser circuits work, see the articles on the Studio Series 1/2-Octave 20-Band Stereo Equaliser described in the August and September 1989 issues. Balanced output stage The output of the 5-band equaliser, at pin 7 of op amp IC10b, feeds the balanced output stage which comprises op amps ICl la and ICl 1b. This acts in the following way: ICl 1b acts as a non-inverting unity gain buffer which feeds pin 3 of the XLR output socket. It also feeds IClla which is connected as an inverting op amp with a gain of 68 SILICON CHIP - 1. This gives a signal 180° out of phase with the input. It drives pin 2 of the XLR socket. Both output signals are coupled via 4 7µF capacitors. As well as driving the balanced output stage, the output of IC10b also drives the headphone monitor, comprising IC10a, Q3, Q4, D4 and D5. This stage is identical to those used for each input channel, as described above. VU metering The signal metering circuitry is based on the National Semiconductor LM3915 dot/bar display driver. Used by itself, the LM3915 is capable of driving 10 light emitting diodes to give a moving dot or bargraph display with a signal range of 30dB. To give a moving dot display (ie, only one LED on at a time), pin 9 is pulled below the V + line at pin 3. To give a bargraph display, pin 9 is connected directly to pin 3. In the circuit under discussion, we have two LM3915s cascaded to cover a signal range of 60dB. To enable them to display a bargraph for the average signal level and a dot (single LED) for the peak signal level, the LM3915s are switched rapidly between the two modes and . the signal fed to their inputs (pin 5) is switched at the same rate. This switching, or multiplexing, is accomplished by a 4066 4-way analog switch, IC21. Its four switch sections are opened and closed by the square wave signal generated by IC20, a 7555 timer. This is connected to give a 50% duty cycle square wave by charging and discharging the .0lµF capacitor at pin 6 via the 100k0 resistor connected from pin 3. The frequency of this waveform is about 450Hz. Signal detection The signal from the output of the equaliser (pin 7, IC10b) is fed to IC16, a non-inverting amplifier with gain adjustable by trimpot TRIM2. IC16's output is fed to ICl 7 which is Below: four of these 5-band equaliser plus LED VU meter boards are used · in the mixer (one for each output channel). This board carries all of the circuitry shown in Fig.4. OUT 2500 25VW 2500 25VW 240VAC + 2500 25VW + - - 1 25VW - 1 25VW + + - .,. - 2500 25VW OUT E • +15V -1 5V FO"-'-UT_ _ _ _ _ ___,,_ +5V nh, CASE 012-015 4x1N4002 2200 16VW + 2200 _ 16VW + - 1 16VW .,. Fig.5: the power supply uses a large toroidal transformer with two secondary windings. A 30V centre-tapped secondary feeds bridge rectifier D8-D11 and this drives positive and negative 3-terminal regulators to give ± 15V supply rails. The other secondary feeds bridge rectifer D12-D15 and this drives a 7805 3-terminal regulator to give a + 5V supply. another fullwave precision rectifier (ie, it responds to both the positive and negative half cycles of the waveform and it has very good linearity). Its output is fed via a 68k0 resistor to a lµF filter capacitor to give a DC voltage which is proportional to the average signal level over any time period of approximately 68 milliseconds. This DC voltage is the one used to produce the bargraph display. To obtain the peak signal level at any time, the rectified signal from the cathode of D6 is fed to IC18 which functions as a sample and hold circuit. The l0µF capacitor, combined with the 36k0 and 62k0 resistors, has a time constant of one second so that even brief signal peaks are "caught" and displayed. Switching between display modes To understand how the switching between the two modes occurs, essentially all you need to know is that each 4066 analog switch is switched on when its control pin is taken high. Hence, when the output of IC20 is high, switches IC21a, IC21b and IC21c are on and IC2ld, is off. This places the LM3915s in bargraph mode and the averaged signal from the lµF capacitor on pin 8 of IC21c is fed to pin 5 of IC15, the LM3915 displaying the top 30dB of signal range. The same DC signal is fed to ICl 9, an op amp with a gain of 31 ( + 30dB) to drive pin 5 of IC14, the LM3915 displaying the lower 30dB of signal range. When the output of IC20 is low, switches IC2la, IC21b and IC21c are all off (ie, non-conducting) while IC21d is on. This feeds the peak DC signal through to the LM3915s, which are now in dot mode. Power supply Fig.5 shows the power supply which has more in common with a power amplifier than a small signal device. It uses a hefty toroidal power transformer and a substantial amount of filter capacitance. A centre-tapped 30V (15V + 15V) secondary feeds a bridge rectifier consisting of diodes DB to Dl 1. The positive and negative outputs of the bridge rectifier each feed two 2500µF filter capacitors. The resulting positive and negative DC rails feed 3-terminal regulators to obtain balanced supply rails of ± 15V. A separate regulated 5V supply rail is required to run all the LEDs of the four dot/bargraph displays. This is obtained from an BV winding on the transformer which feeds a bridge rectifier consisting of diodes D12 to D15. The DC output is filtered by two 2200µF capacitors which then feed a 7805 3-terminal regulator. RF breakthrough To minimise RF breakthrough in all parts of the circuitry, you will notice that many of the feedback resistors of the op amps are shunted with capacitors ranging between 39pF and 220pF. This is to roll off the response a hove the audio range. You will also note a number of rolloff networks involving lkO series stopper resistors and 150pF shunt capacitors. Again, these are there to roll off any supersonic and RF signals so that they do not break through into audibility. This is most important for a professional mixer design which is often used in proximity to vicious electrical noise sources. Next month we will describe the construction of the printed circuit board modules and, if space permits, describe the wiring of the mixer control panel. ~ MARCH 1990 69 .11 ELC:CTR ONI CS JAYCAR ELECTRONICS JAYCAR ELECTR ONICS JAYCAR R ELECTR ONI CS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR .R ELECTR ONI CS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR .R ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR R ELECTR ONI CS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR .R ELE R ELE ,R ELE .R ELE ,R ELE R ELE .R ELE .R ELE .R ELE .R ELE .R ELE .R ELE RELE ELECTRON ICS JAYCAR ELECTRONICS JAYCAR ELECTRON ICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICSJAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR - ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR .. -· ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR .. " ._,, '"' ................. , ,.,. . ,., ........ ELECTRONICS JAYCAR ELECTRONIC JA ELECTRONICS JAYCAR ELECTRON IC JA ELECTRONI CS JAYCAR ELECTRONIC JA ELECTRONICS JAYCAR ELECTRONIC JA ELECTRONICS JAYCAR ELE CTRONIC JA R ELE R ELE RELE R ELE R ELE R ELE R ELE R ELE R EL R ELE R ELE R ELE R ELE R ELE R ELE 'l ELE R ELE 9 EL 9 ELE ~ ELE ~ EL HLE H L 'IELE HLE 'IELE 'IELE 'IELE 1 ELE 1 ELE 1E LE 1 ELE 1 ELE 1 ELE l ELE l ELE l ELE I ELE I ELE I ELE I ELE :E LE : ELE ELE ELE ELE ELE ELE ELE ELE ELE ELE ELE ELE ELE EL E ELE ELE ELE ELE ELE ELE ELE ELE ELE ELE ELE ELE ELE ELE ELE ELE ELE EL EL EL ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR tltC I KVNIC::, JA YL.Al'1 CLCl- I n v " " ' " ' " • - n LLL~ ' .. v .. •~- _," - · '" - - - .. · - --· - - ELECTRONICS JA YCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONIC JA ELECTR ONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONIC JA Fl t=CIBONICS IAYCAB FI ECIBQN/CS IAYCAB Fl.FCIROMICS IA'rTAR Cl FCIBONICS IAYCAR &:1..FCIRONICS IA YCAB C:I F-CIBONICS IAYCAR Cl CCIRONI CC ~J ►rTQO h U C C' IAYCA P c • . c c ~ . -- JATL,,..,M t::l-1:L.. INUl'll\...,.;) . - - - - .. , _,, .,_,...,. -· ' ' ....,. ................ . ............... ...,. ...,.. ' ........... , J ,.,., J \...,>-\n C LC\.., I nv1'111.., .:, ,J,-,,.1\.,Mn C: L.C:\.,I nv,-.11..,,:1.;,-.. , .....1"\11 L.1..L.\.,I , ,-..,,.,..., ....... ,..., • ...., ... • - - - - - · • · --· ...... _ - · • • -- .. - -- · YCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR EL YCAR ELECTRONICS JA YCAR ELECTRONICS JA YCAR JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JA YCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR EL YCAR ELECTRONICS JA YCAR ELECTRONICS JA YCAR JAYCAR ELECTRONICS JAYCAR ELECTRONICS JA YCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR EL YCARELEc~-• .. -- ••---•--·----- .. -- ·· ··-·· · · ·· :AREL :AR EL :AR EL ;AR EL ;AR EL :AR EL Ref: Silcon Chip Feb/Mar/April ·90 :AR EL :AR EL In keeping with the incredibly successful 8002 :AR EL channel Jaycar mixer technology, Jaycar and :AR EL Silicon Chip have come up with two fantastic :AR EL new designs: 12 in 4 out and 16 in 4 out stage/ :AR EL studio audio mixers. These mixers have even :AR EL higher performance than the 8002 which is in :AR EL :AR EL keepng with their more professional :AR EL applications. Each input is capable of accepting : AR EL balanced mic. balanced or unbalanced line :AR EL inputs I Each has an overload/clipping LED :AR EL indicator (a must) input attenuator and similar :AR EL other features to the 8002 A buffered :AR EL headphone monitor jack is conveniently located :AR EL :AR EL on each channel to check sound quality from :AR EL every source. In keeping with 8002 philiosphy. a :AR EL quality 60mm slider attenuator is used on each CAR EL input as well. All inputs (either 12 or 16) are CAR EL based to the 4 nominator channels· 4 track CAR EL recording enthusiats please notel CAR EL CAR EL A major design improvement for these mixers is CAR EL the use of a high-resolution LED 57d87 60d87 CAR EL CAREL bar-graph peak/ average bar-graph VU meters. CAR EL These calibrated (as they indeed are in the 8002) CAR EL meters enable you to know exactly what you are CAR EL sending down to that stack of P.A. amps or CAR EL recorders. CAR EL At last! Massive 12 & 16 Channel Audio Mixers CAR EL CAREL CAR EL CAREL You can purchase mixer components separately or buy the whole 16 in 4 out mixer in one go and save money (see below). The 12 channel unit can be upgraded to 16 channel by simply adding CAR EL 4 x KC-5066 modules. The iront panels for 12 channel mixers are punched out for 16 channel but plastic plugs are supplied for cosmetic reasons. 'CAR EL 'CAR EL 'CAR EL Ordering Information: 'CAR EL Full 16 Channel Kit. This includes 16 input modules. all electronics. connectors. wiring, front panel. all knobs. console chassis and power supply (low noise toroid mains transformer) wooden end 'CAR El pieces etc. 'CAR El Nothing else to buy. 12 Channel Panel Kit. All panel components including input components etc. but 12 input modules supplied 'CAR El 'CAR EL instead of 16. NOTE: Power supply and console chassis extra. Front panel punched for 16 channels. 'CAR EL Cat No. KC-5064 $999 ea 'CAR EL Cat No. KC-5065 Console Chassis/Power Supply. Suitable for either 12 or 16 channel units Ouality3 piece bolt-together 'CAR EL 'CAR EL chassis with power supply which features a toroidal power transformer. Wooden end pieces supplied. 'CAR El Cat No. KC-5070 $239 ea 'CAR El Individual Components 'CAR El 'CAR El Input (Pre amp) board. Similar to 8002 KJ 6503. 'CAR El Cat No. KC 5066 $65 ea 'CAR Eli (16 required for full mixer configuration) We dare you to buy this much mixer for twice the price! 'CAR EL 'CAR Ell Equaliser/Meter Board. This is the sa·me amp board with the high-resolution LED meter board as well. 'CAR El, 14 required for full configuration) 'CAR EU Cat No. KC-5067 $65 88 'CAR Ell Fold back/Effects Board. Similar in operation to the 8002 board KJ 6507. 'CAR Ell GEL BATTERY CHARGER 'CAR Ell Cat No. KC-5068 $39 Ref: Silicon Chip March 1990 'CAR Ell Unmounted Power Supply. Power supply components including toroidal transformer. circuit board and all Will charge any GEL battery from 1.2Ah up to 15Ah. Kit is 'CAR Ell supplied in a short form version so you may purchase the power supply electronics to drive the lull conJiguralion mixer. 'CAR Ell transformer that suits your requirements. Kit includes PCB, 'CAR Ell Cat No. KC-5069 $95 all electronic components, no hardware or transformer 'CAR Ell Specifications: 'CAR Ell supplied. S/N Ratio (with respect to 100mV input and output) 90dB from 20H1 · 20kHz; 93d8 with A weighting 'CAR Ell Optional transformers: for 1.2Ah to 5.5Ah Sensitivity for 1V output 60mV for balanced and unbalanced inputs: 6mV for microphone 'CAR Ell Cat. MM-2008 $16.95 Frequency Response -3dB at 15H1 & 38kH1. -1.5dB at 20H1, -0.8d8 at 20kHz 'CAR Ell Over 5.5Ah to 15Ah 'CAR Ell Distortion 0.015% wi lh respect to 1V in and 3V out at 1kHz 'CAR Ell Cat. MM-2000 $37.95 Equaliser ±12dB 'CAR Ell Peak hold and VU meter; 60dB range with 3dB steps Bargraph Display Kit· Cat. KC-507 1 'CAR Ell 'CAR Ell - «:AR Ell Apart from that similar effects sends capabilities are part of this mixer as well as the 8002 (see 8002 text). The 12 channel and 16 channel mixers are too big to rack mount and rugged chassis mount consoles are available along with attractive wooden ends. $1399 $69 • ' i• i I fo~d Concord 37 (~2T~~~o;~~ Telephone FACSIMILE (02) 744 0767 TOLLFREE (008) 022 888 PARRAMATTA CONCORD HURSTVILLE UNI\..:> JAY\...AH tLt:(.;I HUNl(.;S JAYCAR JA POST .. PACKINO $l0-$24.99 $25 . 49 .99 $50 · 99 .99 s s MAIL ORDER VIA 1r' $ 3.75 $ 4.50 ROAD FREIGHT ANYWHERE $ 6-50 ,uusT1WJA 1,.1oa,1 :AR Ell ~~:!t: :AR ELI :AR EL ------------========::::'...:0:.:_VE::_R:_,:S:,::100~--~$8~00'.::'.....!====S1~3.~50::::::==~ICAR EL CAREL GORE HILL 188 Pacific Hwy (Cnr Bellevue Ave) (02) 439 47~ CAR EL • Mon-Fr, 9 · 5 30 Sat 9 · 4pm CAR EL 117 York St. (02) 267 1614 · 144 Logan Rd (07) 393 0777 . CAR EL Mon-Fri 8.30 • 5 30 Thurs 8.30 pm - Sat 9 • 12 BURANDA OLD Mon-Fri 9 · 5 30 Thurs 8.30 · Sat 9 • 12 'CAR EL 355 Church St (Cnr. Victoria Rd) 102) 683 3377 MELBOURNE-CITY Mon-Fri 9 - 5.30 Thurs 8.30 pm• Sat 9 • 4pm Shop 2. 45 A'Beckett St City (03) 663 2030 Mon-Fri 9 · 5.30 Fri 8.30 · Sat 9 · 12 'CAR EL 115 Parramatta Rd (02) 745 YJ77 • SPRINGVALE VIC 887-889 Springvale Road Mulgrave (03) 547 1022 YCAH E:I Mon-Fri 8.YJ- 5.30. Sat 8.30. 12 Nr Cnr. Dandenong Road Mon-Fri 9 • 5.30 Fri 8.30 - Sat 9 • 2 YCAR El 121 Forest Rd (02) 570 7000 • ADELAIDE S.A. 190 Wright Street (Cnr Selby Street) YCAR El Mon-Fri 9 • 5.30 Thurs 8.30 pm • Sat 9 • 4 YCAR El - I[ SYDNEY· CITY VISA MAIL ORDERS 8 ~,~ ~~a?ra~!~ (02) 747 2022 2137 ~gJ~~~ FOR ORDERS ONLY 1 'AH t::Lt:l, IHUNII..,:) JAT\..,1-\M t:Lt:l. 1nu1"''--"' J,.,,,,, ''--""" CLC\.,I nv,,,.l\,.,,,,:;I :~:= ~t .J,,..,, '"""'"""' C:LL\., ,,,v1•1'-"~ ...,,.., '""'"'11 ... -.. ..... , ,,...,, . ,..,.,.. ..,, • •- "• ---- • YCAA El YCAR ELECTRONICS JA YCAR ELECTRONICS JA YCAR JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JA YCAR El lvcAR ELECTRONICS JA YCAR ELECTRONICS JAYCAR JA YCAR ELECTRO_NICS JAYCAR ELECTRONICS JA YCAR ELECTRONICS JA YCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR El bi:,AQ S:I S:rTOOMIC<:' IAYC"'D r:1 ccror,.,ure ,,vcA n ,,.vr>.0. c.1 cr"I11D..,1lr<: lAYr~ A El CCTDOt,,JICS 14vrAA.EJ .E.CIRQNJ.CS. l..lt.'«'-'LR .FI .ECTRQN.lCS.JAYCAR FLECTRONICSJAYCAR.ELECTRONICSJAY.CAB_EJ AMATEUR RADIO By GARRY CHATT, VK2YBX Single sideband transmission: basic theory & circuits Although it is the most widely used transmission mode on the amateur bands, single sideband (SSB) is perhaps the least understood mode of all. This month's column explains the theory of SSB and shows how it is generated. When a modulating signal is applied to an AM transmitter, four output signals are generated as follows: the original carrier, the original modulating signal, and two sidebands. The two sidebands consist of the sum component, otherwise known as the upper sideband, and the difference component, which is known as the lower side band. For example, let's say that our carrier signal has a frequency fc and that this is modulated by a 2kHz audio signal. The upper sideband will then have a frequency of fc + 2kHz while the lower sideband will be at fc - 2kHz. This is shown graphically in Fig.1. Both the carrier amplitude and frequency are unchanged by the modulation process, while the audio signal is filtered out by the RF output network of the transmitter, leaving the spectral waveforms shown in Fig.1 at the transmitter output. Because all the "intelligence" is contained in the sidebands, the carrier is used only to allow demodulation in the receiver. If the carrier is suppressed at the transmitter, considerable energy can be saved and transmitter efficiency can be vastly improved. The signal can still be 72 SILICON CHIP demodulated at the receiver using a carrier re-insertion technique. Actually, SSB is a derivative of AM modulation. Depending upon which sideband is desired, it can be seen that if the carrier and one sideband is "stripped" from an AM signal (often referred to as a double sideband signal), a single sideband signal remains. It also becomes apparent that this sideband signal, whether upper or lower, occupies far less bandwidth than an AM or "double sideband" signal. In fact, when the correct receiver bandwidth is used to take advantage of an SSB signal, there is an effective improvement of up to 9dB in power over an AM signal having the same peak power. Fig.le shows an SSB signal in which the carrier and lower sideband have been suppressed. (a) le (b) ,___ _.___........___ fe -2kHz le FREQUENCY ___.__ ___ le+2kHz FREQUENCY (e) le+ 2kHz FREQUENCY Balanced modulator Fig.1: the spectral waveforms at the output of an AM transmitter. Fig.l(a) shows the carrier with no modulation while (b) shows the result of single tone sinusoidal modulation. In (c) both the carrier and the lower sideband have been suppressed, leaving only the upper sideband. The most commonly used method of suppressing the carrier signal is to use a balanced modulator. There are several standard types, as shown in Fig. 2. All designs aim to suppress the carrier by 30-60dB, whilst ensuring that the sidebands appear in the output. In all of these designs, there will be no RF output when there is no audio input. When audio is applied, the modulator will become unbalanced (as sum and difference products will be generated), and the sidebands will appear in the output. After nulling out the carrier in the balanced modulator, the DSB FROM CARRIER GENERATOR **GREAT VALUE AND TECHNOLOGY .. BALANCED MODULATOR 4xHPA5082-5826 l: II II II II -. IIII AUDIO INPUT (a) .01i +12vo---------------- CARRIER INPUT vc ~----------"I 3.9k 0.l 3.9k 6 +Vo 511l -Vo ,___-'f MODULATING SIGNAL INPUT 0------<_ _ _ _ _ MC1496, MC1596 2 vs 1k 10k 10k .,. 3 CARRIER NULL (b) +9V ** . 10 PRODUCT OF THE MONTH ... PC FAX SHORT FORM KIT . . . . ONLY $199.00 Featured EA Nov, Dec '89 CONTINUED SAVINGS ON ... AT-4000 SYSTEM 12MHz 512K 101KBO 200W $999.00 PS etc VGA MONITOR 0.31 FOR 800x600 . . ... .... $599.00 EC-F/HOO FOO/HOO CONTROLLER 1:1 . $169.69 GAL PAL PROGRAMMER - 1 only . $350.00 COMPUTER PRODUCTS ... XT1000 MOTHERBOARD V20, 12MHz, Skts 1M RAM . $127.00 AT-4000 MOTHERBOARD 12MHz 80286 AT u/g for XT $299.00 AT-8000 MB 25MHz 80386 inc 0/8M 32-bit . $1320.00 Mem Exp Board ECI VGA-16, CGA, HGA modes Card 800 x 600 x 16 Res . $299.00 AWARD POST TEST CARD . . $802.00 2s+P+G $85; FDC $97.25; 101 KBD $88.43; EC-CGMA $75; CASE & 200W PS $189; XT/AT CLK $49.95 MODEMS ... ECI-FAX CARO FOR XT/AT Aust Made . $399.00 EC-2400S V22 bis External Modem . $399.00 . $299.00 EC-2400P V22 bis Internal Modem DRAM ... 512K-100 Kit 18x256Kx1·10 . . $ 72.00 2M-100 Kit 18x1Mx1-10 .. . .. $280.00 QUALITY DISKETTES ... (Pkt of 10, 100% error free , L/time Gtee) 5¼ ' OSOO $6.29 5¼" OSHO . $14 .40 3½" OSDO . . .. $14.36 3½" DSHO . . $33.00 P&P $8.50 - PRICES INCLUDE SALES TAX. PRICES SUBJECT TD CHANGE WITHOUT NOTICE. 26 Boron St, Sumner Park, Ken Curry Managing Director · Brisbane, Old 407 4. Ph: (07) 376 2955 WELLINGTON NZ: Ph: (04) 85 87 42 Fax: (04) 82 8850 6.Bk - 8 v o - - -......- - - - - - ~ .,. 0------------------- D.DAUNER 15k ELECTRONIC COMPONENTS 470!! OSCILLATOR INJECTION (1V) 2.2k (c) ~ J 15k . CARRIER / . ON S1 .i .,. DSB OUTPUT (0.2V) Fig.2: three balanced modulator designs. Fig.2(a) shows a ring diode modulator, Fig.2(b) uses the Motorola MC1496 balanced modulatordemodulator IC, and Fig.2(c) is based on varicap diodes D1 & D2. All three designs aim to suppress the carrier by 30-60dB. signal can be fed to a bandpass filter, where one of the sidebands can be filtered out. There are several different types of filters that can be used and depending upon the carrier frequency selected, these can be LG, mechanical, or even made from discrete junkbox crystals. However, in practice this is normally done using a crystal filter which will have sufficiently steep "skirts" to attenuate the unwanted sideband. This is all very well in a transmitter operating on a fixed sideband. However, if the transmitter is designed so that the sideband is selectable, then the design must either use two filters, one for each sideband, or the carrier oscillator must be designed to enable it to be WE STOCK A WIDE RANGE OF ELECTRONIC PARTS for • Development • Repair • Radio Amateur • Industrial Electronic • Analog and Digital WHILE STOCKS LAST Quartz in filter 10.9MHz 6kHz BW. $12.50 US Filter capacitor 4µF 3kV. . $15.00 Electromagnetic Airpump for Aquarium . .. . .. . . ... . .. . .. $9.00 Timer Motor 240VAC 6RPH $6.00 Come and see. Showroom: 51 Georges Crescent, Georges Hall, NSW 2198 (Behind Caltex Service Station In Blrdwood Road) Phone 724 6982 TRADING HOURS: Monday to Friday 9.00 a.m. to 4.00 p.m. Saturday from 9.00 a.m. to 12.00 noon. MARCH 1990 73 Fig.4 shows how SSB is generated using the phasing method. Demodulating SSB MIC SPEECH AMPLIFIER LINEAR RF AMPLIFIER FILTER MICO (b) Fig.3: two variations of the filter method of SSB generation. In Fig.3(a), two filters at the output of the balanced modulator are switched to select either the USB or LSB signal while in Fig.3(b) the carrier oscillator is offset by the required amount by selecting one of two crystals. offset by the required amount when the opposite sideband is selected. Fig.3 shows these two selectable sideband schemes. The phasing method Another method of generating a single sideband signal is to use the phasing method. In this scheme, the audio and carrier signals are each fed into 'a 90° phase shift network and applied to balanced modulators. When the outputs of both balanced modulators are combined, one sideband is added or reinforc- ed, while the other sideband is cancelled. For this system to work well, the phase shift and amplitude of both the audio and carrier signals must be very accurate. For this reason, the phasing method became less popular following the introduction of relatively inexpensive crystal filters. The major advantage of the phasing method is that the desired SSB signal can be generated at the operating frequency without using a separate heterodyne oscillator and mixer. The demodulation of an SSB signal requires the reinsertion of a signal at the "carrier" frequency in the receiver. This "carrier" signal is mixed with the incoming sideband signal in a balanced modulator (or demodulator in this case) to provide an audio output signal. In practice, the re-constituted carrier is usually generated by a crystal oscillator. When this is applied to the demodulator (also called a product detector) in conjunction with the incoming sideband signal, demodulation takes place. Fig.5 shows both active and passive product detectors. Active product detectors have the advantage of producing several dB of conversion gain, while passive detectors have the advantage of simplicity and low cost. Typical SSB transceiver A block diagram for a typical HF SSB transceiver is shown in Fig.6. In the transmit mode, signals from the microphone are fed to a balanced modulator where they modulate a carrier signal generated by an offset oscillator to produce a DSB signal (ie, the carrier is suppressed). This DSB signal is then fed to a crystal filter stage with a passband of about 3kHz. Depending on the frequency of the offset oscillator, the filter removes either the upper or lower sideband. The resulting 10.7MHz SSB signal is then amplified and fed to a 2nd mixer stage where it is mixed with a VTO (voltage tuned oscillator) signal. BALANCED MODULATOR SPEECH AMPLIFIER MIC BALANCED MDDULATDII Fig.4: the phasing method of SSB generation. The audio and carrier signals are fed to 90° phase shift networks and the outputs of the balanced modulators combined. This reinforces one sideband and cancels the other. 74 SILICON CHIP 1.Sk RFC 1 + .01 SIG:AL o-ft----'l,-,,.,1,,-11-~ 100k F-o tuuJ!3T .oo,I .,. 10k .o,r (a) BFO INJECTION 01 T2 II SIGNALl',i INPUT JI • Inside a typical SSB transceiver. The large SSB filter can be clearly seen in the centre of the PC board. 2ND MIXER II BFO e (+13dBm) II 1I II II .,. 11 11 II II 11.,. II AUDIO OUTPUT The difference signal produced is then fed to an RF amplifier and applied to the antenna. The receiver is a conventional superheterodyne type with an IF (intermediate frequency) of 10. 7 MHz. As shown in Fig.6, the incoming signal is amplified and fed to an Rx mixer where it is mixed with a local oscillator signal [from the heterodyne mixer) to give a 10.7MHz IF. From there, the signal passes through the noise blanker, SSB amplifier & IF amplifier stages to the SSB detector. HETERODYNE MIXER "f,. . . Tl 0.1-1: (b) Fig.5: an SSB signal is demodulated by mixing it with an injected "carrier" signal in a product detector. Fig.5(a) shows an active product detector while Fig.5(b)is a passive detector. The offset oscillator provides carrier re-insertion at the detector. The USB SW and LSB SW blocks set the frequency of the offset oscillator to give either USB (upper sideband) or LSB (lower sideband) RF AMPLIRER RF AMPLIRER PRE-DRIVER reception as required. Further information on SSB techniques can be obtained from the ARRL Handbook, the Motorola Linear Circuit Databook and the RSGB Handbook. ~ DRIVERS PA LPF METER SSB AMPLIFIER VTO 10.6935MHz CRYSTAL ALTER NOISE BLANKER FREQUENCY COUNTER RX MIXER RX RF AMPLIFIER ATTENUATOR RF IF AMPLIFIER AGC AMPLIFIER SSB DETECTOR RX AUDIO AMPLIFIER DC SUPPLIES AND SWITCH .,. MIC MICROPHONE PREAMPLIRER BALANCED MODULATOR OFFSET OSCILLATOR USB SW LSD SW = + Fig.6: block diagram of a typical HF SSB transceiver. It uses the scheme shown in Fig.3(b) to generate an SSB signal. MARCH 1990 75 Have you seen the ALL NEW ALTRONICS CATALOGUE yet? Packed full of new products at low prices and the products you need fairly often, most at last year's prices or even lower.There is an absolutely HUGE range of kits to take you into the last, and most exciting, decade of this millenium. You can trust ALTRONICS to supplly the most up-to-date products at the lowest prices Australian made whenever possible - and deliver them to you overnight. If you missed our catalogue in February EA phone now TOLL FREE 008 999 007 for a free copy. Labtech Dual Trace 20MHz CRO With Component Tester Why pay $400 or more for a David Clark set? AVIATORS HEADSET WITH OIL FILLED EAR CUSHIONS • High performance, noise attenuating earphoncs. • Noise cancelling microphorx: • Cushioned head pad • Super sturdy • Great perfonnancc • Superb, professional pilot's headset will last a lifetime with reasonable tn:atmcnt. • Includes standard aircraft jacks. C9010 ONLY $189.00 DESCRIPTION: This model is a dual •trace 20MHz Oscilloscope using high brightness CRT. The vertical amplifiers have high scn,;itivity of SmV/Div and tm frequency characteristic response with the smooth roll off exceeding 20MHz. The special circuit is designed so that a single component or components in or out of the actual circuit board can easily be tested. requiring no power to drive the circuit. The display shows component faults, component value, characteristic., and tests components dynamically. FEATURES: • Comp:ment Tester• Wide bandwidth & high sensitivity• Very low power consumption • High sensitivity X ~ Y mode • Z axis (intensity modulation) • Front panel electrical trace rotator• Rgua1ted power supply for greater acr..uracy. Q 0155 LABTECH OUAL TRACE CRO S799.00 2 of O0175 10:1 PROBE KITS 99.90 PR. SAVE $100 THIS MONTH. PAY ONLY $799 THE SET. Resistor Typical component teat status patterns Digital Circuit Capacitor Zener Diode Labtech Test Equipment for Life Audio Frequency Generator In testing audio circuitry it is necessary to have an accurate audio signal source. It e\lCil allows you to te•t 455kHz IF ,tages! Output Attenuator 10Hz -1MHz +/-3% +2Hz Sine/Square Sine:8V RMS Square: 10V P-P -20db, -40db and fine adjust a 1540 Normally $299 This month $249.00 SAVE $SO RF SIGNAL GENERATOR With provision for both Internal and external modulation, this generator Is a winner! SPECIFICATIONS: Frequency Range: 100k -150MHz in 6 ranges RF Output level: lOOmV RMS Accuracy+/· 3% Modulation: Internal (30% depth) - !kHz e External. 50Hz. 20Hz e Crystal locked oscillator a 1550 Normally $299.00 This Month $249.00 Save $50.00 Now available from Altronlcs Dealers ------------, MEGGER METER I I See EA April/May 89 Insulation brcakdown can in electrical wiring and appliances can be determined with this dual range megohm meter. Ideal for checking insulation in transformers, appliances, automotive generators and alternators, house wiring etc. Breakdown can be measured at either 500V or 10OOV depending on the situation. Perfect for work van, toolbox or work bench. I I I I I '-- -Digital - -~2=5!!?.:?~ - - - _J Multimeter with built-in capacitance meter All the normal ranges of current, resistance and voltage PLUS a convenient and simple to use capacitance meter in five range, PLUS transistor tester. Check the features of this top quality digital muttimeler from the Labtech range: • Continuity test • Buzzer sound: less than 200 Ohm• Capacitance: 5 ranges, 200pF h 204pF • Transistor Tester. DC Voltage 0.2, 2.0, 20. 200, 1000V DC Current 200uA, 2mA, 20mA, 200mA, 2A, 10A AC Voltage 0.2. 2, 20, 200, 750V AC Current 200uA, 2mA, 20mA, 200mA, 2A, 10A Resistance 200, 2k, 20k 200k 2M, 20M Display: 3 1/2 digit LCD, 0.5" high with polarity and LO-Bat indication • Over range indication Maximum common mode voltage: SOOV peak Power: 9V alkaline or carbon-zinc battery Dimensions: 170 x 87 x 42mm, Weight: 350grams Specifications: Input impedance: 10M on all ranges Nornmal mode noiae rejection: 46dB at 60Hz (1 k unbalanced) Common mode noiae rejection: 100d8 at 60Hz Overloade protection: 1000V DC or peak on all ranges Response time: less than 1 second. a 1085 USUALLY $139.00 EXTRA SPECIAL P I Get 240V AC Mains Power from your battery with these handy Inverter kit sets 300 WATT Many combinations to choose from: POWERHOUSE 600W INVERTER WITH AUTO INVERTER (Sec EA Dec'87) This inverter has the capacity to produce 600 watts of ma.ins power which will nm a fantastic array of appliances. Ideally suited to running power tools, lighting (including fluros) electric mot<rS and much more. It can be used either u a portable <r a pcnnanent fixture. • Manual c.- Auto Start facilities • Low battery cut-out. START Opcrau:s from 12V Car Battery 1 Auto Start draws power from your battery only when appliance is plugged in and "turned on" ie, battery can be left permanently connect<:d ifn:quircd. • Voltage ' , Regulau:d • Cum,nt Regu!au:d '- , • Cuncnt Overload unit self limits Kit version K 6770 $425.00 Fully built and tested 12V Input K 6774 $525.00 24V Input K 6775 $525.00 Complete Kit K 6750 $279.00 Fully built and tested K 6755 $379.00 100'5 OF USES AT HOME AND AWAY ally exciting news is that all of peskers are available at such• unt price for this month • but be uick • atocka are limited. 15" (375mm) WOOFER Ultra High Power Capacity Polypropylene Bass Drivers Our ALL NEW "Black" polyprop cone Bass Drivers exhibit qu~e astonishing low register reproduction. Power ratings quoted are conservative. Not the cheapest but definitely the BEST VALUE we know of· ANYWHERE. Huge 120 Watts RMS Massive 200 W Max. C3075 12" (300mm) WOOFER Normally $129 Normally $99 NOWONLY$99 YOU SAVE $30 NOWONLY$89 10" WOOFER 60Watt RMS 100W Max. C3065 100Watt RMS 150W Max. C3070 Was $69.00 NOW ONLY $49.00 HUGESAWNGSONSPEAKERS 8" WOOFER 60Watt RMS 100W Max. c 3060 Was $49.95 Now $39.95 SAVE $10.00 61/2" WOOFER/Midrange 30Watt RMS SOW Max. C 3055 WAS $29.95 NOW ONLY $24.00 Passive Infra-Red Pin Point Lite Guard ULTRASONIC CLEANER Floodlight Control 61 /2" Mid Range 30Watt RMS SOW Max. with sealed frame c 3045 Was $27 .50 NOWYOU SAVE AT $22.00 Earn• its cost hunderds of times over in cleaning connectors, PCB's, switches, jewellery, glassea, watches, drafting pena, etc. Awarded the Good Product Design Award for CETDC in 1987 WIii even clean your teeth! How often have you thought there could be a prowler outside your door? Install• LIie Guard & (once armed) any "guest"will be floodlit when detected bythia highly sensitive Infra-Red Detector. Speclflcatlons: • Ralntlght, outdoor, all weather operation• Operation Time: Adjustsblc 120 mins • Sensltlvlly: Adjustsblc UJ • SO, 30 beams• Almable to desired direction with 2 ball joints• Switching Capablllty: 500W max. inundcsoent • Operation Modes: OFF, AlITO, TEST, MANUAL. ON. s 5350 was $135.00 SPECIAL ONLY $99.00 SAVE $36.00 Woo 't 1cratch or damage - UICI ordinary tap water and creat.cs millions of supcr-pcnetratin& bubbles. Hospital tests show that tntruonic cleaning produce, better results aafcr than coo.vcnticmal mcthoda. In Just 3 minutes you will be amazed at the dltrerence! A 0100 TOP VALUE NORMALLY $199.00, ONLY $174.00 THIS MONTH K3300 $195.oo TOP VALUE Plasma Lamp Display Fantastic, pulsating high voltage Plasma discharge continually changes shape and d~ction. Mode selectable to either fingertip control or sound activated, cg from voice or sound system. Provides endless fascination as it siz:t.lcs and arcs. Supplied complete wlth AC Mains Adaptor 3 - 50 Volts at up to 5 Amps ( Ea May' 85) Spees: 1 Output Voltage - 3.50 Volts • Output Current up to 5 Amps (max. 175W) • Floating outputs isolated from ground • Ripple less than 90mV p·p at max. Employs Dual Meters - no swltcliing from one to the other. Normally $199 Save $50 OPTIONS A 0120 10 Turn Output Voltage Control (K 3300 ia normally supplied with standard poL this month only $149 be quick K3301 $29.50 Up to now stmttar tamps sold for $1000 & more Auxiliary+ AND - 12V Output Terminals Desk Mounted Lamp Magnifier Fixed outputs independent of variable main output K3302 $14.50 Audio Purists This Is For You! VIFA 2 W AY 100 WATT WEATHERPROOF SPEAKER Redford and Scan Audio have combined resources to develop this high performance weatherproof speaker system. The heart of the system is the now famous 5" VIFA Woofer/Midrange, computer optimised for use in a 5 litre Bass reflex cabinet. The ferro fluid Dome Tweeter is incorporated with the crossover network as employed woh the SA-50 bookshelf system. The system is fitted with a unique overdrive protection device enabling amplifier input of up to 100 Watts without damage. The combination of the internationally acclaimed VIFA drivers with the rugged Redford extruded aluminium enclosure give an overall performance and appearance that is superior to any competitive weatherproof speaker on the Australian market. Each speaker is supplied complete with mounting brackets. c 0970 Black c 0972 White $199.50 ea $399.oopr 1 GHz FREQUENCY If you have trouble with fine PCB work or component identification but still want both hands free, this is for you. We thoroughly recommend this quality Australian made product. TECHNICAL INFORMATION: lllumlnallon: 22W Pluoresccnt Weight: 8.16kg Lateral Extension: 254mm Vertical Extension: 254mm Fixing: Heavy table hue (grey c:w ivory) with two chrorm plated flexible arms. A 09so Normally $279 This month $229 SAVE $50.00 CouNTER Measuring Mode: Frequency Measurement., CHANNEL A Range: I OHz to I 0MHz direct counter, I 0MHz to 100MHz prescaled by 10 Resolution: Direct counter: 1, 10, lOOHz switch selectable, prcacaled: 10, 100, 10001-lz awitch selectable Gale Time: 0.01S, 0.1S, I.OS, awitch oclectable Accuracy:+/- 1 count+/· time base error x frequency CHANNEL B Range: 100MHz to !GHz Resolullon: IOOHZ to !kHz switch selectable Gale Time: 0.0Z7S, 0.27S, 2.7S switch selectable Period Measurements (Channel A) Range: lOHz to 2.5MHz Resolution: 10-7S, 10-8S, 10-9S switch oclectable Tolallz, Measurement., (Channel A) Range: IOHz to 10MHz Resolution:+/- I count of input Display: 8 digits. 7mm red LED display with decimal point, gate, overflow, kHz, MHZ and uS indication. s.. _;;., 1989 CGlologu, Po1• 62 for faU ,p,cifeolio,u ofthu lop quoW, eOMnJ1r, 110• fll ,,.,,. grslll,r ~Ill,,, for OIi.i ,r,onJI, only. Q 1530 Normally $499.00 This Month Only $399.00 SAVE $100.00 Brilliant Auto Ranging Digital Multimeter 45V 2A Dual Tracking Power Supply Autoranging with Memory Function for relative meeaurementa. Q 1075 Was $99.95 this month $89.95vou SAVE $1 O .oo Specification• DC Voltage Ranges: 5 (200mV. 2V, 20V, 200V, 1000V) Accuracy: 0.5% + 1 Digit Input Impedance: 100M Ohm on 200mV range 10M Ohm on other ranges Overload Protection: 11 OOV DC max. (50 sec) or DC, AC Peak Max Resolution: 100uV AC Voltage Ranges:4 (2V, 20V, 200V, 750V) Accuracy: +/· (0.75% + 0.5 dgr) 40Hz to 500Hz Input Impedance: 10M Ohm Overload Protection: 1100V DC max. (60 sec) or, DC, AC Peak Max Re10lution: 1mV DC C•nelll Accuracy: 20mA- +/· (1% + .5 dgr) 10A • +/· (2% + .5 dgr) 40Hz to 500Hz Overload Protection: 20mA. 0.2A 250V Fuse. 10A- 12A This NEW dual tracking power supply is a must for your workbench . The two rails track exactly woh each other on any voltage and precise voltage is obtained woh the multi-turn rotary control. It also has a clear display and meter movement, a dropout indicator and load ON/OFF swoch . Housed in a medium sized instrument case with a silver anodised and pre-punched and screened front panel. FEATURES: • Housed in a tough "ABS" instrument case ,, •Floating ground • Load swoch K 3375 II $149 PHONEORDER TOLL FREE: AlTR Automatic Charger for NiCads (See EA July '89) Get 100's more recharge cycles from your nicads Its now well known that correctly charging nicad cells greatly extends their service life. Here is a fu lly automatic NiCad battery charger that enables differing charge rates as appropriate for AAA, AA, C, D cells or cells in series up to 9V. Once the battery is charged, the unit automatically switches to trickle charge until you switch it off. K 1650 INSTALLED IN MINUTES. Connects via P 0995 double adapter to telephone line at existing wall socket. Double adapter accepts both telephone and extension bell , which is supplied with a 10 meter lead. NOT SUITABLE FOR COMMANDER PHONE SYSTEMS . P 0996 $29.50 Hot Canaries - The Electronic Canary (SC Feb '90) Get that atmosphere of tranquility that only birds can give. The realism of this project is remarkable. Sounds for all the world like two trilling canaries. • Battery powered $39.so M 9020 (Plug-Pack Extra) $16.95 K 1130 II $25.95 Bel Express 3 Radar Detector Detects X, Kand the new Ka Photo Radar Band. The new Industry standard! Express 3 contains the latest Bel breakthroug h. Image Rejection Technology for KA band Photo Radar detection and twice the X and K band sensitivity of ordinary superhet radar detectors. Fully equipped, Express 3 has no equal. Preprogra mmed Features ■ SAVE $100. NORMALLY $699 A1540 Special introductory price $ 599.00 Bel Express 3 - acclaimed the leader in Canada and USA - now available in Australia from Altronic. ■ ■ ■ Instant On/Pulsed Warning: Encountering radar of this nature results in a warning sequence oonsisting of a series of quick "beeps" (unlike X, K or Ka alerts) followed by the audio alert that corresponds to the type of radar received. Rashid VASS Rejection: Automatic reject ion of signal received from collision wa rn ing systems which operate on the same frequency as police radar (K Band). Automatic K/Ka Band Override: Express 3 instantly alerts to the presence of Kor Ka Band radar when th e FSR mode is engaged. Automatic Test Sequence: Each time power is engaged , Express 3 will sound a single group of X, K, Ka and instant On/PulSed alerts indicating rt is ready to proces s police radar. 4 LTilOnlCl 174 Roe St. Perth W.A. 6000 PHONE TOLL FREE 008 999 007 Perth Metro (09) 328 1599 ALL MAIL ORDERS P.O. Box 8350 Stirling Street Exchange Perth W.A. 6000 AL TRON ICS RESELLERS Chances are there is an Altronics Reseller right near you - check th is list or phone us fo r details of the nearest dealer. Pleue Note: Resellers have to pay t he cost of freight and insurance and therefore the prices charged by individ ual Dealers may vary slightly from this Catalogue• in many cases, however, Dealer prices will still represent a significant cost saving from prices charged by Al tron ics Competitors. Don't forget our Expreat Mall and Phone Order Service- for the coIt of a local call, Bankcard, Vlu or Ma1tercard holder■ can phone order for ■ ame day deIpatch. MORE AL TR ON ICS D EALERS WANTED If you have a Retail Shop, you could increase your income significantly by becoming an Altronics Deal er, Phone Chris Campbell (09) 328 2199 for Details . STANDARD DELIVERY & PACKING CHARGE $5.50 to 1Kg $8 over 1Kg AU STRALIA WIDE - We process your order th e day received and despatch via. Austra lia Post. Allow approx 9 days from day you post o rd er to when you receive goods OVERNIGHT JETSERVICE Up to 3 Kg is $8.00 - 3Kg to 5Kg is $20.00-We process your order the day received and despatch via. Overnight Jet ■ervl ce Courier for delivery next day Country areas please allow add itional 24-48 hours. HEAVY HEAVY SERVICE -All orders of 10Kgs or more mu st t ravel Express Road • Please allow 7 days for delivery. $12.00 to 10Kgs, $15.00 over 10Kgs. INSURANCE -As-with virtually every other Australian supplier, we send goods at consignees risk. Should you require comprehensive insu rance cover against loss or damage please add 1% to order val ue (minim um charge $1). When phone ordering please requ est " Insurance". TOLL FREE PHONE ORDER - Bankcard,Visa, Mastercard Holders can phone order toll free up to 6pm Eastern Standard Time. Remember with our Overnight Jetlervlce we deliver next day . COUNTRY ALBANY BP El e ctr o ni cs ■ 412 681 E SP ERANC E Esperance Com m u ni ca tion s 71 33 4 4 GERALDT O N Bird El ectronic s 641631 KALGOORLIE Todays Electr oni cs ■ 212777 KARRATHA Daves Oscitron ic 854836 PO RT HEADLAND Iva n Tomek Electronics 732531 WYALKATCHEM D & J Pease 811132 NT ALICE SPRINGS Ascom Electronics 52 1500 Farmer Electron ics 522388 DARWIN Ventronics 480030 ACT CANBERRA Bennett Commercial Electroni cs 805359 VICTORIA CITY All Electronic Com po nents 6623506 SUBURBAN CHELTENHAM Talking Electronics 5842386 CROYDEN Truscott El ectronics ■ 7233860 PREST ON Preston Electronics 4840191 COUNTRY BENDIGO KC J o h nso n ■ 411 411 MORWELL Morwell Electron ics 346133 QUEENSLAND CITY Delsound P/ L 8396155 SUBURBAN CAPALABA Kingsway Electronics 3902399 WOODRIDGE David Hall Electro nics 8082777 COUNTRY BUNDABERG Bob El kins Electronics 721785 GLADSTONE Supertronics 7 24459 M A C KAY Phil tron i cs ■ 578855 ROCKHAMPTONA ccess Electron i cs ( East S t.) 221058 TOOWOOMBA Hun t s El e ctronics ■ 329677 TO WNSVfLLE Solex ■ 7724466 MAROOCHYDOREMals Electronics 436119 SA CITY Force Electronic ■ 2125505 SUBUR BAN BR IGHTON Force Electron ics ■ 3770512 CHRISTIES BEACH Force El ect ronics ■ 3823366 ENFIELD Force Electronics ■ 3496340 FINDON Force Electronics ■ 3471188 LO NSDA LE Force E l ectro n ics ■ 326090 1 COU NT RY MT.GA MBIER South East Electronics 250034 WHYALLA Ey r e Electronics ■ 454764 TASMANIA HOBART George Harvey ■ 342233 LAUNCESTON George Harvey ■ 316533 NSW CITY David Reid Electronics ■ 2671385 C ARI NGHAH Hicom Un it ronics 5247878 COUNTRY COFFS HARBOUR Coifs Habour Electro nics 525684GOSFORD Tomorrows Electronics 24 72 46 G RA F TON Eas t Coas t El ect r o ni c 431250 NEWCASTLE Novocastr i an Elect.Supp li es 62 1358 RAYMOND TERRACE Alback Electronics 873419 WINDSOR M & E Electro nics 775935 WOLLONGONG Newtek E l ectro ni cs ■ 27 1620 Vimcom Electronics 284400 WAGGA WAGGA Phillips WA COM.POTER BITS By STEVE PAYOR Digital wave£orm generation This month we will look at some of the finer points of digital signal generation, using the simple 8-bit D-A converter described last month. Armed with a good working knowledge of BASIC, you should have little trouble in getting your PC to generate useful signals up to several kHz. To begin, let's consider the question of software speed. The programming language which the author prefers to use is TURBO BASIC (formerly produced by Borland). This language is easily managed by anyone who is proficient with GWBASIC, and it will run 99% of GWBASIC programs without any changes. A program originally written in GWBASIC will run from 2 to 100 times faster under TURBO BASIC. The difference is that TURBO BASIC is a compiler, whereas GWBASIC is an interpreter. An interpreter processes each line of the program as it comes to it. For example, a line such as "GOTO 500" is scanned character by character until the word "GOTO" has been recognised as a reserved word, then the number "500" is put together by taking the '' 5' ', multiplying by 10, adding a "0", multiplying by 10, and adding the other "0". As if this isn't slow enough, in order to perform the actual GOTO, the interpreter now has to scan through all the line numbers in the program listing to find line 500, if it exists. The next time this statement is encountered, the interpreter has to go through the entire process again. A compiler will initially process a "GOTO 500" in the same way, but having deciphered it, all that will remain in the final machine code is a single JMP instruction, which only takes a few microseconds to execute. Traditionally, compilers have tended to be rather awkward in interactive situations. Before a program can be run, it first has to be compiled, and this used to take some time and lots of keystrokes, whereas an interpreter like GWBASIC only requires you to type RUN (or press the F2 key) and the program is off and running. TURBO BASIC is just as easy to use in this regard. You can go from editing to running a program with two keystrokes, and the only difference you will notice is a delay of around a second or so while the program is being compiled. Machine code This photo shows the completed D-A converter with the filter components added. The filter gives a response that is 13dB down at lOkHz. 80 SILICON CHIP An alternative, and very effective way of speeding up a GWBASIC program is to write the most critical part of the program in machine code. In our case, this is the loop which outputs the bytes to the D-A converter. The machine code for this part only requires simple integer arithmetic. The rest of the program, which contains tricky stuff like floating point SIN calculations, can be left in its original, slow UNFILTERED OUTPUT (1k) CENTRONICS PIN NUMBERS (9) 07 JUMPER 2.7k .01 10•1. 1.,. * 5.6k (8) 06 OUTPUT ADJUST VR1 2k 5.6k (7) 05 22k *470!J (6) 04 * MAY NEED ADJUSTMENT ALL RESISTORS 1% (4) 02 180k (3) 01 o--..JN,Ar--• (19) TO (30) GNO~ running form, because it is only used once during the waveform setup. Another way of getting a faster program is to use a more machineoriented language such as "C". The code produced by the TURBO C compiler is almost as short as handwritten machine code. (We hope to present some C routines in a future issue. At this stage the results appear to be about 2-3 times faster than TURBO BASIC). In summary, the options, in order of increasing speed, are: (1). GWBASIC interpreter (waveforms up to a few hundred Hertz). (2). TURBO BASIC or similar compiler (approx. 10kHz). (3). TURBO C compiler (approx. 20kHz). (4). Any language with a machine code subroutine (Z0kHz plus). (5). Hardware buffer memory for D-A converter (MHz). Turbo Basic Fig.1: the filter circuit consists of an inductor and two capacitors and is simply tacked onto the output of the D-A converter circuit described last month. It gives approximately .06dB ripple from 0-4.5kHz and 13dB of attenuation at lOkHz. For simplicity, we will stick with TURBO BASIC for now. As mentioned last month, we achieved a sample rate of 20k samples/sec on a 4.77MHz PC-XT. This was achieved using the tightest possible loop we could write. The fact that the loop execution time is almost precisely 50µ.s is just a coincidence, but it does make the figures come out nice and round. For example, the maximum waveform frequency we can construct is tokHz. Before we can start producing useful waveforms however, we need to add one more thing to our D-A converter hardware - namely, a low-pass filter. The need for a filter Fig.2: what better way to reveal the filter's frequency response than with a linear frequency sweep, from lkHz to beyond tokHz. Note the aliasing around the lOkHz point. The spectrum folds back on itself beyond this point - a direct consequence of the 20kHz sampling frequency. Sampling theory says that if we have a sampling frequency of 20kHz, then a low-pass 0-tokHz filter is required to reconstruct the desired waveform without distortion. Furthermore, this only applies for a filter with an ideal, infinitely sharp, rectangular cutoff. If you try generating a t0kHz signal, you may wonder why such a sharp cutoff is necessary. There will be exactly two samples per cycle, one up, one down, and the MARCH 1990 81 Fig.3: This is a logarithmic frequency sweep, from 400Hz to 4kHz (just r ight for testing a voice communications channel perhaps?) The sweep time is .05s. Fig.5: a rather short logarithmic frequency sweep, from lkHz to 2kHz in 5ms, ju'st to show how clean the waveform can be. Fig.4: exactly the same waveform as Fig.3, but with the filter out of circuit. What a mess! Fig.6: the same as Fig.5 but without the filter to "reconstruct" the waveform. resultant square wave is easily filtered to a pure sine wave by a filter with a cutoff anywhere below the third harmonic; ie. 30kHz. However, if you try to generate a 9.9kHz signal, the true nature of the problem becomes apparent. Because there are not quite exactly two samples per cycle, the sampling points on the waveform gradually shift until they pa ss through the zero crossings, and then the amplitude begins to rise again. The resulting waveform looks like a double sideband signal, which is exactly what it is. You have actually generated two frequencies, namely 9.9kHz and 10. lkHz. The 10. lkHz signal is an "alias", or beat frequency , caused by the beating of the 9.9kHz signal with the ZOkHz sampling frequency. Wanted: Your Circuit & Design Ideas Have you got a good circuit idea languishing in the ol' brain cells? If so, why not send it in to us and save us from circuit burnout? We'll pay up to $ 50 for a really good circuit . So transfer your circuit to paper and send it to SILICON CHIP, PO Box 139, Collaroy Beach, NSW 2097. 82 SILICON CHIP The only way to convert this heavily modulated signal to a pure sine wave at 9.9kHz is to have a filter which will pass the 9.9kHz component, and completely reject the 10. lkHz component. This is a rather tall order. Filter compromise We chose a simple 3rd order lowpass filter for our demonstration unit, mainly because it only requires one inductor to be wound and the results repres ent a reasonable compromise between performance and complexity. Referring to the circuit diagram, the filter is simply tacked onto the output of last month's D-A converter circuit. If you like, the ex- ' SILICON CHIP LOG/LINEAR FREQUENCY SWEEP GENERATOR DEFINT A-Z DIM WAVE(lOOOO) ' ' ' ' (TURBO BASIC 1.1) All variables are integers unless otherwise stated Array containing output data (sufficient for approx. 1/2 sec of stored waveform, given the sample time listed below) 'Program constants: PORT.A=&H378 ' Parallel port Note: Other possible addresses PORT.C=PORT.A+2 ' addresses for PORT.A are Hex 3BC or Hex 278 PI!=3.141593 SAMPLE.TIME!=50E-6 ' 50fsec (as determined by experiment for this computer, a '4.77 MHz PC-XT, running this program. This will need to ' be changed to accommodate faster or slower systems.) ' Variables defining frequency sweep: ' START.FREQ!=lOOO ' Hz END.FREQ!=lOOOO ' Hz DURATION!=.1 sec Change these three variables to produce the desired sweep range and time N=DURATION!/SAMPLE.TIME! ' Total no. of samples in sweep PHASE!=O 'This section of code fills the output waveform FOR I=O TON 'array with the required frequency sweep (this WAVE(I)=127.5+128*SIN(PHASE!) 'takes a few seconds) FREQ!=START.FREQ!*EXP(I/N*LOG(END.FREQ!/START.FREQ!))' Log sweep, or 'FREQ!=START.FREQ!+I/N*(END.FREQ!-START.FREQ!) 'Linear sweep PHASE!=PHASE!+2*PI!*FREQ!*SAMPLE.TIME! ' (Disable either of the NEXT I 'above statements by ' changing it to a remark) OUT &H21,INP(&H21) OR 1 ' Disable DOS real time clock interrupt WHILE NOT INSTAT OUT PORT.C,O 'Keep repeating the frequency sweep until a key is pressed ' Positive edge of CRO sync pulse '------------------------------------------------------------------------------ FOR I=O TON ' This FOR loop outputs the w~veform to the D-A converter. OUT PORT.A,WAVE(I) ' As you can see, it is about the tightest loop that can be NEXT I 'written in TURBO BASIC - It takes 50fsec. '-----------------------------------------------------------------------------' "Zero" the waveform OUT PORT.A,127 OUT PORT.C,1 WEND ' Negative edge of CRO sync pulse OUT &H21,INP(&H21) AND &HFE ' Restore clock interrupt END Fig.7: this listing is for a sweep generator with programmable sweep time & start & end frequencies isting .0047µF capacitor can be combined with the .OlµF capacitor, but we kept them separate for those occasions when we might want to use the D-A converter without a filter eg, when generating square pulses. The component values chosen give a Chebyshev response with approximately .06dB ripple from O to 4.5kHz, which is the usable frequency range for a flat, clean out- put. The response is 13dB down at lOkHz, which is not quite infinite, resulting in some noticeable aliasing in this region (see Fig.2). However, for a signal at say 4kHz, the nearest alias is at 16kHz, where the filter response is well down. So, for frequencies up to 4kHz at least, the signal quality is perfectly acceptable: as good as any function generator, and second only to a low distortion analog oscillator, such as a thermistor stabilised Wein bridge. Pick a waveform The big advantage that a software driven D-A converter has over other waveform generators is that it can produce any waveform you want. So what should we try our hand at first? The author's first thoughts were along the lines of a tone burst MARCH 1990 83 generator, to specification IHFA-202 1978 (see SILICON CHIP, July 1988}. However, you will have to wait for this one. This month's software solves a more immediate need. For our first demonstration program we present a frequency sweep generator, with programmable start and end frequencies, as well as sweep time. You also have a choice of logarithmic or linear frequency sweep. If you have access to a CRO, this is just the ticket for instant frequency response tests, and incredibly useful for filter alignment, which is why we chose .it first up: to align the D-A's own filter. Looking at the CRO photograph (Fig.3} you will see that the frequency response is quite flat up to 4kHz. (Each horizontal graticule ·division is lkHz, starting at lkHz). Twiddling the inductance adjuster, you will find that the response " droops" slightly if the inductance is too low, or " peaks" if the inductance is a shade too high. Adjusting this filter for a flat response How To Make The Inductor First of all, you will need a suitable ferrite core. We chose a a PCB-mounting RM10 core assembly, with an AL value of 400. Nearly all the ferrite core manufacturers can supply this type and it is very easy to assemble and mount. If you are using a different core type, you will need to know its AL value in order to calculate the number of turns required. The calculation is quite simple: ( 1 ) . Express the desired inductance in nH; eg, 37 .3mH = 37,300,000nH (2). Divide this by the AL value of the core; eg, 37,300,000 + 400 = 93,250 (3). Take the square root; eg, (93,250)½ = 305.4 = the required number of turns (305 and a couldn't be easier! One final note: In order to get a perfectly stable CRO display, we used bit O of PORT.C to output a ANTRIM TOROIDAL TRANSFORMERS QUALITY TOROIDAL POWER TRANSFORMERS, MANUFACTURED IN U.K. NOW AVAILABLE EX-STOCK AT REALISTIC PR ICES. half will be near enough). If the core has an adjuster, find out how much it can increase the inductance and subtract about half this amount before doing the above calculation. For example, the adjuster on our ferrite core had an adjustment range of +20%, so we calculated the number of turns for an inductance of 37 .3mH less 10% = 33.6mH, which came to 290 turns. We used 0.25mm enamelled copper wire, for which there is ample room within the core window. A complete RM10, AL 400 core assembly, including adjuster, coil former and mounting clips is available from Radiospares Components (stock no. 228-258) for $5. 7 4 plus sales tax. TTL level trigger pulse. This is a short, negative-going pulse, the positive edge of which signifies the start of the frequency sweep. ~ General Construction OUTER W INDING INNER WINDING CQ AE INSULA TION TAX PAID PRICES 15VA 30VA 50VA SOVA 120VA 160VA 225VA 300VA 500VA 625VA 10+ 1- 9 32 .80 31.70 36.00 35.00 38.50 37.20 41.75 40.35 44.95 43.50 55.70 52.20 62.00 58.20 72.80 68.25 100.00 93.75 112.00 105.00 Enquiries from resellers and OE Ms welcome. Quantity prices and data sheets available on request. Distributed in Australia by Harbuch Electronics Pty Ltd, 90 George St., HORNSBY, NSW, 2077 Phone (02)476-5854 Fax (02)476-3231 84 SILICON CHIP KITS- SEMICONDUCTORS- ALARMS- COMPONENTS- AUDIO ACCESSORIES- HARDWARE- BOOKS- TOOLS- TEST EQUIPMENT- TV AND VIDEO REPAIR- INVERTERS- S.T.C.- CANNON- ARLEC- KITSSEMICONDUCTORS- ALARMS- COMPONENTS- AUDIO ACCESSORIESHAR DW ARE- BOOKS- TOOLS- TEST EQUIPMENT- TV AND VIDEO REPAIR- INVERTERS- S.T.C.- CANNON- ARLEC- KITSEDM 168 DIGIT AL MULTI METER WAS $169 NOW $139.95 • 3 1/2 Digit, Extra large 17mm LCD • 10 Functions including : DCV, ACV, DCA, ACA and Ohm, Frequency counter 2kHz(1 Hz) to 200kHz. Capacitance 2nF(1 pF res) to20uF. Transistor hFE test. Diode forward voltage test. Audible continuity test. VDC 200mV to t 000V, in 5 ranges 100uV max. res, ± 0.5% VAC 200mV to 750V, in 5 ranges 100uV max. res,+ 0.5% ADC 200uA to 20A, in 5 ranges 0.1uA max. res, ± 1% AAC 200uA to 20A, in 5 ranges 0.1 uA max. res , ± 1.5% Ohm 200ohm to 20Mohm,in 6 ranges, 0.1 ohm max. res + 0.75%. 1 GHZ FREQUENCY COUNTER MEASURING MODE: Frequency Measurements CHANNEL A Range 10Hz to 10MHz direct counter, 10MHz to 100MHz prescaled by 10 Resolution: Direct counter; 1, 10, 100Hz switch selectable prescaled: 10, 100, 1000Hz switch selectable gale time: 0.01s, 0.1s, 1.0s, switch selectable. Accuracy: + t count + time base error x frequency. CHANNEL B Range 100Hz to 1GHz resolution , 100MHz to 1KHz switch selectable gate time: 0.027s, 0.27s, 2.7s, switch selectable. Period Measurements(Channel A) Range: 10Hz to 2.5M Hz Resolution: 10-7s, 10-Bs, 10-9s switch selectable Totalize Measurements:(Channel A) Range: 10Hz to 10MHz Resolution: + 1. Count of input display: 8 digits, 7mm red LED display with decimal point, gate, overflow, KHz, MHz and us indication. 1 WAS.$400 Now$399 WELLER BUTANE SOLDERING IRONS Weller Pyropen WST2 WST2 Pyropen Junior. Mini soldering, and hot air tool with variable temperature control. Small and lightweight. Complete with 0.5mm tapered needle soldering tip and protective cap with pocket clip. NOW $109 FOR HOBBYISTS 2N 3055 Transistors TIP 31 C TIP 32C 1N 4007 Diodes 1000V 1 Amp 1N 5408 Diodes 1000V 3 Amp 80139 Transistors 80140 Transistors MJ2955 Transistors 7805CT Voltage regulator 7905CT Voltage regulator 7812CT Voltage regulator WERE .$2-,56 .$.t,.66 Weller Pyropen WPA2 Self igniting Pyropen kit. Single handed operation with a push button igniter. Fitted with tapered needle \.'\ tip plus hot air nozzle. NOW $1.75 ~~ 65c 65c $.:t--,60 :l-5c 45-c .96c .96c $2-:45 10c 20c 65c 65c $1.75 .95c .95c .95c 65c 65c NOW $169 ~ Weller Pyropen WSTA3 Temperature control led soldering . Lightweight, completely portable. Runs on Butane gas for three hours of operation. Ready to solder in 30 seconds. 65c t-.lOW $169 r.-----------------MAIL ORDER COUPON I Bankcard, Visa and Master card are welcome II ADELAIDE 203 Wright St. Adelaide Ph :(08)212 5505 LONSDALE 5 Somerset Circ. 326 0901 CHRISTIES BEACH 24 Beach Rd. 382 3366 ENFIELD 445 Main Nth . Rd. 349 6340 FINDON 127 Findon Rd. 347 1188 BRIGHTON 500a Brighton Rd. 377 0512 I I I I I I I 7 Day Money back Guarantee. NAME ...... ... ,,, ,...... ,...,,... .,....,.... ,.. ,.. ..,... ... .. ,.,,, ... ... ,,. ,. ,.... ,...... ..... ,.. ..... .. .... . ADDRESS ......... ................ ...... ..... ............ ... .......... ......... ............ ............. ... CHEQUE □ VISA □ B/CARD □ M/CARD □ CARD NUMBER _ _ _ __ _ _ _ _ EXPIRY DATE_ __ ITEM _ _ _ _ _ _ _ _ __ SIGNATURE _ _ _ _ __ ITEM _ _ _ _ _ _ _ _ __ CHEQUE/ORDER ENCLOSED TO VALUE OF $_ __ Delivery charge of $8.00 for packages up to 10kg by mail or up-to 3Kg by overnight Air-bag . Min . order $10 REMOTE CONTROL By BOB YOUNG The controls on a model aircraft This month we will begin to look at how a model aircraft manages to fly. This is necessary if we are to understand the amazingly sophisticated computer encoders used in the new generation of PCM/PPM radio control sets. As stated previously the introduction of the microprocessor into R/C transmitters has revolutionised the model control business. However, this revolution has been so far-reaching that the full implications of the uses and technology involved are almost completely outside the understanding of the average newcomer to R/C modelling. Why do we need such sophisticated encoders and what do they really do anyway? For that matter, how does an aeroplane fly? These are all vital questions to the R/C novice. These questions and many more will form the basis of the next three or four columns. In these columns it will be necessary for me to outline the basis of model aerodynamics and the problems which arise that call for sophisticated computerised solutions. 86 SILICON CHIP And for those dedicated electronics buffs who are scratching their heads over why an electronics magazine should have pages of aerodynamics, the following is an interesting practical application of Bernoulli's Theorem of considerable relevance to the electronics industry. Ever wondered why the solder smoke goes up your nose? Simple! The heat of your body causes the surrounding air to warm up and thus reduce density. This causes the warm air to rise. According to Bernoulli's Theorem, this will create a low pressure region close to your body. Below: the SR-71 Blackbird highaltitude spy plane. As with other modern high-speed aircraft, it could not be flown without a computerised flight control system. Inevitably, smoke from the soldering iron will move into this low pressure region and up the front of the body and some will pass right into your nostrils, aided by the low pressure inside the lungs. Considering that this smoke consists of lead, copper and PVC residues, this is an issue affecting the health of all in the industry. We all live at the bottom of an ocean of air. We breath it, we fly in it. Air is of great interest to us all. For those interested in learning more, read on. The next few columns will be centred upon modern aerobatic model aircraft for two reasons. Firstly, they are probably the most demanding of sophisticated solutions and secondly, I am thoroughly familiar with these problems, having flown competitive aerobatics for many years. This does not mean that other types of model do not have sophisticated needs of their own, merely that for me the explanation is much simplified when describing the modern neutrally stable, centreline aerobatic aircraft. This approach will serve to outline the principles involved. The high point of my aerobatic career came when I competed in PORT WING STARBOARD WING ~ ' RADIAL AIR-COOLED ENGINE LOW CANTILEVER WING TAIL PLANE /FUSELAGE STARBOARD AILERON PORT AILERON \ Fig.1: the basic layout for a typical full-size twin-engine aircraft. The three main components are the wing, fuselage and tail section, the latter two carrying the various control surfaces. the 1971 World Aerobatic Championships in Pennsylvania, USA. It was here that I learned just how badly I flew. Spurred on by that jolt, I went on to become a much better flyer, winning several high level local events, but pressure of business forced me to drop out of competition flying in 1976 and I have not competed since then. The amount of time one must devote to practice to remain competitive is now so great that only the truely dedicated can maintain the standard, yet I still see many of the old names in the contest results. Model aerodynamics Model aircraft aerodynamics and engineering bears only a superficial resemblance to full size aerodynamics and engineering and this is an important point to remember. People coming into the R/C movement from full size avia- tion or those that are just aviation buffs are a real problem to teach. They do, however, have one saving grace: a sound knowledge of aeronautics and airmanship. When they eventually master the subtleties of R/C flying they usually go on to make first class R/C pilots. The big problem they face is that most of them want to build models that look like " real aeroplanes". This is fine when you can fly, but the best flying models are not necessarily the prettiest. In fact, some are downright ugly but they fly well, are cheap and easy to build, and make great trainers for this reason. Scale aircraft are difficult and expensive to build and very demanding to fly - in fact some can be downright mean. The Spitfire has a terrible reputation as a scale model. It is an unfortunate fact of life that scale models do not behave at all like their big brothers. There are three main reasons for this: (1). We do not have "scale" air. This problem is of paramount importance, the ultimate effect being that lifting surfaces whose width is less than 20cm do not work well at all. The main effect of this is that wingtips and tailplanes on models are very inefficient. This leads to scale aircraft being laterally and longitudinally unstable unless some compensation is made to wingtip and tailplane size. This will be explained fully in the discussion on Reynolds numbers. (2). A model aircraft does not carry a pilot. He is firmly planted on the ground and completely out of touch with the model which leads to great difficulties in learning to fly. In fact, the process of learning to fly an R/C model is an extremely subtle one which involves learning to judge speed and propeller loading (climbing or diving) by the sound of the engine. Level flight must be attained even at long distances, at very odd angles and in bad lighting. Finally, and most importantly, the pilot must learn to cope with the apparent reversal of controls when the model changes direction from going away to coming directly towards him. The full size aviator has no previous experience in any of these subtleties. Because of the lack of a pilot though, manouevres generating forces in excess of 10G are quite permissible. This results in vast structural differences between models and full-size aircraft as well. (3). The model aircraft movement has a vastly different set of aims and goals to that of the full size aircraft movement. The most pronounced difference arising from this statement is the question of wing and power loadings. Confused? Fear not, all will be explained in due course. Design compromises To begin, it must be clearly understood that an aircraft is a vehicle whose design is a compromise of hundreds of conflicting factors and which is intended to operate in 3-dimensional space. As MARCH 1990 87 YAW AXIS <p ---ROLL AXIS ~· Fig.2: this diagram shows the three control axes of a model aircraft. The roll axis is controlled by the ailerons, the yaw axis by the rudder, and the pitch axis by the elevator. a result, this vehicle becomes a 3-axis device exhibiting a high level of interaction between all three axes. Here then is reason number one for sophisticated solutions. Carried through to modern high speed aircraft typified by the SR-71 Blackbird - a high speed, high altitude spy and research aircraft - this means that they cannot be flown safely without a computer assisted flight control system. Aircraft components Fig.1 shows the layout of a typical full size twin engine aircraft. The three main components of this aircraft are the wing, fuselage and tail section. Perhaps now would be a good time to have a look at the glossary of terms accompanying this article, so that you'll recognise the various terms as ·they are mentioned. The wing provides the lift and is responsible for supporting the aeroplane and providing roll stabilisation. Setting the two wing halves at a small angle from horizontal provides this roll stabilisation. This angle is termed the "dihederal angle". The fuselage carries the motor, fuel, R/C equipment and any other device that is carried aloft. It also serves as a structural member to locate and hold the wing and tail section. The tail section comprises a horizontal and vertical stabiliser which provide the primary pitch and yaw stability. The wing and tail sections have hinged portions which are used to control the direction of flight by exerting force around the three axes of movement. The three control axes are illustrated in Fig.2. These axes are usually said to act through the centre of gravity but are, in reality, only arbitrary representations. The roll axis The roll axis is controlled by the ailerons which are situated on the trailing edge of the wing. These may take the form of full length strip ailerons or shorter built-in RIGHT All.ERON "UP'' t :::r- _J__ L LEFT AILERON "DOWN" Fig.3: the ailerons are situated on the trailing edge of the wing and travel in opposite directions to each other. If left aileron is down & right aileron is up, the aircraft rolls to the right. 88 SILCON CHIP ailerons at the wing tip. These controls are usually situated on the main control column in a full size aircraft and on the lateral axis of the right hand control stick on a model control Tx. In both cases the movement is from centre neutral to left and right. On the model Tx, neutral is spring loaded. On a full size aircraft, aerodynamic loads provide the centering. The operation of the ailerons is a little tricky and great care must be exercised in setting them up. To turn right, the right aileron must move up and the left aileron must go down (see Fig.3). This increases the lift on the left hand wing and decreases that on the right. The result is a roll to the right. This roll will continue for as long as the aileron deflection is held. Eventually the aircraft will roll through 360°, passing through the inverted position whilst doing so. Learning to turn a model is tricky for this reason as the average beginner forgets that the model will continue to roll unless he takes off the aileron once the correct angle of bank is attained. Before he has time to realise what is happening the novice has his aircraft inverted and is in terrible trouble. The correct sequence for turning is aileron on until the correct angle of bank is attained, . aileron off, elevator up and hold. The elevator is then held until the turn is complete. You then apply elevator off, opposite aileron on, until the wings are level, then aileron off. The correct angles of deflection are dependent upon the airframe control and stability factors and can only be learned by experience. It is very easy to get the ailerons hooked up in the wrong sense. Even the great Bob Young has arrived at the field only to find his ailerons were hooked up in reverse. It only happened once, but that was enough. Fortunately, I found it on the ground but I have seen models crashed because of this error. To emphasise the point, the prototype Avro Tudor II G-AGSU crashed in 1947 due to the ailerons being reassembled in reverse, killing Avro's chief designer Roy Chadwick and-the pilot. Glossary of Terms Mainplane: the wing or primary lifting surface. Wing root: junction of the wing and fuselage. Wing tip: the outer end of each wing. Wing section: the cross section of the wing taken along the chord line; commonly called the aerofoil section. Wing chord: width of the wing from leading edge to trailing edge. Chord line: the straight line through the extreme leading and trailing edge of the wing aerofoil. Dihedral: the angle each wing half is lifted from the horizontal. Aspect ratio: the relationship between wing span and wing cord . Aileron: hinged portion of the wing trailing edge used for control over the roll axis. Flap: hinged portion of the trailing edge used to improve aerofoil shape, to increase the angle of attack and therefore generate more lift. Downthrust: the angle at which the thrustline is offset to the fuselage centreline. Firewall: the bulkhead between the motor compartment and the fuselage proper. Usually used to attach the motor. Longitudinal dihedral: the angle The moral is always check the direction of controls before the first flight of the day, particularly if you have servo reversing switches on your Tx. These switches are very dangerous and need constant attention. I check the operation and direction of the controls before every takeoff. Aerodynamically, the ailerons have a very complex and sometimes peculiar effect and we will examine the sophisticated computer and aerodynamic solutions to these problems shortly. The pitch axis The pitch axis is under control of the elevator or hinged portion of the between the chord line of the wing and the chord line of the tailplane. Angle of incidence: the rigging angle of the lifting surfaces relative to some datum line, usually the fuselage centreline. Undercarriage: the landing gear, usually two main wheels and a tail wheel or skid, or a tricycle, comprising a nosewheel and two mains. May be fixed or retractable. Fin: vertical stabiliser. Rudder: hinged rear portion of the vertical stabiliser and used for control over the yaw axis. Tailplane: the horizontal stabiliser Elevator: the hinged rear section of the horizontal stabiliser; used for control over the pitching axis. Stability: the ability to return to some particular condition of trimmed flight after a disturbance, without any effort on the part of the pilot. Instability: the tendency to diverge farther away from the trimmed position when disturbed. Neutral stability: the ability to maintain the new position after disturbance until disturbed again. Essential for aerobatic aircraft. Centre of gravity: the gravitational balance point of the aircraft. Must be carefully positioned in relation to the aerodynamic centre of pressure of the aircraft. tailplane. Sometimes the entire tailplane is pivoted on a centre axle and this arrangement is termed an "all moving tailplane". This arrangement does have some aerodynamic advantages which are balanced by some mechanical disadvantages. It is not used as often as the conventional hinged elevator arrangement. The entire tailplane also provides the longitudinal stability of the aircraft. The angle between the wing and tailplane chord lines is termed the "longitudinal dihedral". This angle, the tailplane area, wing and tailplane section and centre of gravity location determine the overall longitudinal stability and manoeuvreability of the aircraft. As stated previously, compromise is the name of the game in aircraft design, and the correct balance of the foregoing factors determines how well an aircraft will perform. In the neutrally stable, centreline aerobatic model, the wing and tailplane are rigged at zero-zero incidence, with the thrustline, symmetrical wing and symmetrical tailplane section on the fuselage centreline. The result is an aircraft that will go exactly where you point it - just what the doctor ordered for accurate aerobatics. It will not increase or decrease the angle of climb or dive. It has no natural inbuilt stability. Any such aircraft fitted with a failsafe that neutralises the controls is doomed if control is lost. The elevator control is usually located on the main control column in full size aircraft. In R/C transmitters, elevator is fitted to the fore and aft axis with spring loaded neutral [left hand stick in Mode 1 and the right hand stick in Mode 2). In all cases, pushing forwards applies DOWN elevator and pulling back applies UP. This corresponds to the trailing edge of the elevator going up for UP elevator. The action of the elevators is complex but essentially they alter the direction of the thrust vector and the direction and magnitude of the lift vector. This vector is, in turn, related to engine rpm and aircraft weight. Small elevator deflections will alter the trim from climb to dive. With sufficient thrust and up elevator deflection, the aircraft will complete a loop and will continue to loop for as long as that power setting and control deflection is held. The yaw axis The yaw axis is under control of the rudder, or hinged portion of the vertical stabiliser. This stabiliser provides what may be best described as "weather cock" stability and is used for directional stability and control. The rudder controls on a full size aircraft may be located on the rudder bar or foot pedals on the continued on page 95 MARCH 1990 89 I PRODUCT SHOWCASE I Operating frequency of the transmitter and diversity tuner is just above 200MHz (three frequencies are available) and audio dynamic range is better than lOOdB. This is achieved by using a signal compressor in the transmitter and a corresponding expander in the receiver. Minimum operating range is 50 metres but it can be as much as 200 metres in some circumstances, according to Altronics. In addition to the dual diversity tuner, Altronics has a matching FM wireless microphone, a Shure SM-58 FM wireless microphone, a lavalier type and guitar wireless pickups. For further information, contact Altronics, 17 4 Roe Street, Perth, WA 6000. Phone (09) 328 2199. Wireless microphone system uses dual diversity tuner Wireless microphones and wireless guitar pickups are very popular these days for public speakers, stage performers and bands since they give complete freedom from trailing cords. But any system which relies on a single FM receiver to pick up the signal is liable to have big problems with signal fading and serious distortion as the performer, and thereby the transmitter, moves rapidly around. The acknowledged solution to this problem is to use a dual diversity receiver such as this Redford model from Altronics. It uses two completely separate tuners, IF strips and detectors, both within the same case. Both tuners are set to the same frequency, the output of each tuner is monitored, and the strongest and cleanest signal is selected at any one time. Passive infrared floodlight control More and more people are concerned about security around their homes and businesses and one way to improve the situation is to install a passive infrared controlled floodlight system. This can do double duty as your normal exterior lighting and will switch on automatically as you or anybody else crosses the boundary of your property. This PIR system from Altronics incorporates the infrared sensor and two PAR floodlights (not shown in photo). It is suitable for 90 SILICON CHIP outdoor operation and has an adjustable operation time of 1-20 minutes. It is available for $99 from Altronics Distributors Pty Ltd, 174 Roe Street, Perth, WA 6000. Phone (09) 328 2199. PC rack system for industrial applications Those who wish to use IBM PC XTs, ATs or compatibles in industrial control applications will be interested in this 19-inch rack system from Anitech. Made by Bice-Vero, the Microrack system is 4 units high and 390mm deep and made from anodised aluminium. It accepts BiccVero's IBM backplane as well as 8-slot mini AT or XT motherboards and up to three half-height floppy disc drives. Three separate power supplies are available to suit the user's needs. At the rear of the chassis there are cutouts to suit 4 D-25 sockets, a DIN connector and 1/0 from the expansion boards. At the front, there is provision for two cooling fans, a keyswitch and indicators, as well as the floppy drives. For further information, contact Anitech, 1-5 Carter St, Lidcombe NSW 2141. Phone (02) 648 4088. New Real-Time Telemetry System For Aeronautical Research AM stereo radio kit from DSE At last, it is available. All those people who have been chasing up the kit for the AM Stereo Radio published last year can now get it from Dick Smith Electronics. Featured in the September, October and November 1989 issues of SILICON CHIP, the AM Stereo Radio used quite a number of hard to get precision parts which were essential to obtain its high performance. Finally, Dick Smith Electronics has brought it all together in a high quality kit which is supplied complete with a set of miniature stereo headphones. We checked out the finished unit and it performed right up to specifications - the same easy and precise tuning and wideband stereo sound. The kit is priced at $79.95 and is available from all Dick Smith Electronics stores and resellers. Radio control aeroplanes are not just for fun. They have many applications relating to defence and research into aeronautics. This quarter scale Bellanca Gita Bria is being used for research by Sydney University into variable profile, leading edge laminar aerofoils. As well as being remote controlled, the model carries a complex telemetry system called Aeroling 101, developed by Windsor Communications. This transmits telemetry signals from sensors which include wind and New flat bed printer has improved paper handling One of the big problems with the larger tractor feed printers is that they waste so much paper. You have to discard the first sheet in any print run because of the way the print head has to line up with the top of the sheet. Now there's this new model Prowriter C-610 which is claimed to eliminate the problems with paper handling and wastage. Made by C.Itoh in Japan, the C-610 has a 24-pin print head and is a flat bead design which is claimed to give trouble free handling of cut sheets, fanfold paper and thick papers (up to 0.35mm) like cards, envelopes or an original plus four copies. Auto-loading, auto-parking and auto-tear off are all provided. Fanfold paper can be parked (ie, airspeed, gyroscopic attitude and multiple airframe stress factors. The on-board transmitter and sensors are designed to cope with forces up to 10Gs, and temperatures from - 20° to + 70°C. All sensors are interfaced via an A-to-D converter and the data is transferred at up to 9600 baud. For further information, contact Windsor Communications, 206 George Street, Windsor, NSW 2756. Phone (045) 77 5935. moved back off the platen) with a single command when using cut sheets and these are automatically fed from the front document table and returned there after printing. The auto-tear-off feature operates from the printer's menu. It moves the paper forward to the tear-off point after which it returns it so that the print head lines up with the top of the form, thereby avoiding wastage of the first sheet (or the last sheet, depending on your point of view). The C-610 gives good quality printing at 240 characters per second in draft mode and 80 cps in letter quality mode. IBM graphic character sets are standard, with double height and double-width MARCH 1990 91 TEST EQUIPMENT OSCILLOSCOPES SPEAKERS BOXES SOLDERING IRON ' LOGIC PROBE (LP-2800) ROYEL SOLDERING STATION • Useful for TTL or CMOS has high and low indicator leds and also with pulse memory. • This is a very handy tool for The all solid•state heat sensor and control unit allows the selection of the appropriate soldering tip idling temperature. The very high•powered element (relative to the size of the tool) will replenish heat drained from the tip during each soldering operation and will recover the tip tempreture moments after the tip is lifted. • Zero voltage switching • Zero tip potential • Aux ground connection • For soldering irons• CT6 (3mm Tip), CT7 (5mm Tip) ,, (J) m the hobbyist or serious > "' :n technician for tracing those hard to find faults on logic boards. m .,, (J) 0 :n 011272 ..................$34.95 20MHZ DUAL TRACE OSCILLOSCOPE CRT DISPLAY • 150mm rectangular VERTICAL DEFLECTION • Deflection Factor: 5mV to 20Vi Div on 12 ranges in 1-2-5 step with fine control • Bandwidth DC: DC to 20MHz (-3dB) AC: 10Hz to 20MHz (-3dB) • Operating Modes : CH-A, CH-B, DUAL and ADD (ALT/CHOP L202 only) - Chop Frequency: 200KHz Approx. • Channel Separation: Better than 60dB at 1 KHz 0 ,...,, '" LOGIC PULSER (LP-540H) ~ j? • Can be used directly to inject a signal into logic circuits without removing IC • Compatible with TTL, DTL, RTL HTL, MOS and CMOS 011274 .................. $42.95 !;; SERIES 4000 SPEAKER BOXES FOR AN AMAZING ............ $250 GENERAL TOOLS BATTERIES TIME BASE • Type: Automatic and normal triggered in automatic mode, sweep is obtained without input signal • Sweep Time: 0.2µ Sec lo 0.5 Sec/ Div on 20 ranges in 1-2-5 step with fine control and X-Y • Magnifier: XS at all ranges TRIGGERING • Sensitivity lnt: 1 Div or more Ext: 1Vp-p or more • Source: INT, CH-B, LINE or EXT • Triggering Level: Positive and Negative, continuously variable level ; Pull for Auto • Sync: AC, HF Rej, TV (each+ or-) at TV Sync. TV-H (line) and TV-V (Frame) sync. are switched automatically by SWEEP TIME/Div switch. HORIZONTAL DEFLECTION • Deflection factor: 5mV to 20Vi Div ·on 12 ranges in 1-2•5 step with fine control • Frequency Response: DC to MHz (-3dB) • Max Input Voltage: 300V DC + AC Peak of 600Vp•p • X·Y Operation : X·Y mode is selected by SWEEP TIME/ Div switch • Intensity Modulation Z Axis: TTL Level (3Vp•p-50V) + bright, • dark OTHER SPECIFICATIONS • Weight: 7Kg Approx • Dimensions: 162(H) x 294(W) x 352(0) mm 012105 .................................................................. $695 MICRO CUTTING PLIERS AA SIZE NICAD Great for detailed cutting . These have a stainless steel head and plastic insulated handles. Length: 90mm T12050 .................... $9.95 Nominal Voltage: 1.2V 450mAH S15020 ......... 0NLY $1.50 SURGE PROTECTOR MICRO BENT NOSE PLIERS •• THE BUTTON SPIKE PROTECTOR Simply plug the button into an outlet and ii will protect all equipment plugged into adjacent outlets on the same branch circuit. SPECIFICATIONS: Voltage: 240V Nominal Total Energy Rating: 150 joules Response Time: 10ns Protection Level: 350V peak X10087 .................. $39.95 HALF ROUND NOSE PLIERS 012107...............................................................$1,695 MAIL ORDER& CORRESPONDENCE : P.O. Box 620. CLAYTON 3168 Order Hotline: 008 33 5757 (Toll free. strictly orders only) Inquiries: (03) 543 7877 Telex : AA 151938 Fax: (03) 543 2648 All sales tax exempt orders and wholesale inquiries to: RITRONICS WHOLESALE 56 Renver Road. Clayton. Phone: (03) 543 2166 (3 lines) Fax: (03) 543 2648 ORDER HOTLINE 008 33 5757 LOCAL ORDERS & INQUIRES (03) 543 7877 Plastic insulated handles with stainless steel head. Length: 10cm POSTAGE RATES: T12044 .................... $9.95 CLICK SURGE BUSTER • Input Impedance: 1Mn±2%, 25pF±3% • Bandwidth DC: DC to 1MHz (-3dB) AC: 5Hz to 1MHz (·3dB) (B): 0.2µS-0.5mS/ Div±3% in 1-2·5 steps (X1 only) • Magnified Sweep: 10 times±5%, Max 20ns • Linearity : ±3% or better MELBOURNE : 48 A·seckett St Phone: (03) 663 6151 STR ICTLY O RDERS ONLY HORIZONTAL AMPLIFIER • Operating Modes: X-Y operation CH1·X axis, CH2-Y axis • Sensitivity: 5mV-5Vi Div± 3% in 1·2-5 steps • Sweep Time (A): 0.2µs-0.5S/ Div±3% in 1·2•5 steps (Xl only) Please quote this advertise· ment for the prices listed for this month. SYDNEY: 74 Parramatta Rd. Stanmore 2048 Phone: (02) 519 3134 Fax: (02) 519 3868 (TOLL FREE) 40MHZ READ-OUT OSCILLOSCOPE TIME BASE • Sweep Method: AUTO, NORM, SINGLE ROD IRVING ELECTRONICS BRISBANE : (V.C.R Computer Services) 647 Lutwyche Rd. Lutwyche. Phone : (07) 857 5617 T12040 .................... $9.95 VERTICAL AMPLIFIER (CH1 and CH2 Identical) • Operational Modes: CH1 , CH2, ADD, DUAL, ALT, CHOP • Sensitivity: 5mV•5V/ Div 3% in 1·2·5 steps 1mV•1Vi Div x5% x5MAG • Bandwidth DC: DC to 40MHz (·3dB) AC: 5Hz to 40MHz (·3dB) • Rise Time: Less than 8.7nS :r;1:e· NORTHCOTE: 425 High St. Phone: (03) 489 8866 For delicate or high precision electronic work. Stainless steel head with plastic insulated handles. Length: 10cm CRT DISPLAY • 150mm rectangular T12570 ........ ... ......... .$225 BENT NOSE PLIERS It has a long tip angled at 45", for complicated or delicate work. Stainless steel head with plastic insulated handles. Length: 10cm T12046 .................... $9.95 6 PROTECTED POWER OUTLETS Ideal for protecting personal computers, video equipment, colour TVs, amplifiers, tuners, graphic equalisers, CD players etc SPECIFICATIONS: • Electrical rating: 240V AC, 50Hz, 10A • 3 x Metal Oxide Varistors (MOY) • Maximum clamping Voltage: each MOV: 710 volts at 50 amps • Response time: Less than 25 Nanoseconds. X10086 .................... $69.95 $1 - $9.99 .................... ..... $2.00 $10 - $24.99 ........... ..... ..... $3.00 $25 • $49.99 ................... ..$4.00 $50 - $99.99 ····· ··· ········ ·· ···$5.00 $100 + .............................. $7 .50 The above postage rates are for basic postage only. Road Freight , bulky and frag ile items will be charged at different rates . Errors and omissions excepted. Prices and specifications subject to change. IBM' , PC· XT ' . Ar . are reg1s1cred trademarks ol !nterna1 1onal Busmess Machines ·Apple 1s a r eg istered trad l:' mark Tefl on · 1s a reg ister ed tr adem ark ot Du pont ' Oenontes regisi erecl trademarks ol!he1rrespect1veowncrs. ·--------------· "NEW" AUTOMATIC TELEPHONE ANSWER/ CALL CARD 1 Port installed ( supports 2) EXTRA CHIPS FOR COM 2.. .$35 X18026 ......... ......... $39 · A Sophisticated Voice coil mail system · Auto answering I Dialing 100 voice mail boxes · Password protection · Message mailing · Auto redialing · Beeperless remote control · Toll saver · Call screening · Electronic phone book · Works in background · Menu driven software · Simple and concise operation PRINTER CABLE Parallel interface for centronics printers. 1/0 PLUS CARD Provides a serial port, a parallel port and joystick port, and even a clock /calander with battery backup. NETWORK CARD IBM CARDS R-NET / SINTERFACE NETWORK CARD COLOUR / MONO CARD Fully compatible with SMC, Novell Arenet card Star burst topology through RG-62 AIU coaxial cable · Zero wait at 20MHz or hogher 80386 machine · 2.5 Mbps transmission rate Supports composite RGB & TTL mono monitors · 300 X 200, 600 X 200 & 720 X 348 modes X18007 .. .............. $139 TTL GRAPHICS CAR D Hercules compatible for TTL mono monitors ( 720 x 348) lncudes printer port. X18003 ..... ... .......... $99 X18154 ..... ....... $152.50 512K RAM CARD FOR XT · Upgrade your PC,XT to 640k with this plug in card X18014 .................. $99 POSTCARD DIAGNOSTIC MODULE Pinpointing component problems in IBM' compatible motherboards can take hours. Usually the whole system has to be working to isolate the troubled area. But not so with the new Postcard diagnostic module. So no other cards are necessary to test a bare motherboard. IT NOW ONL V TAKES SECONDS!!! Simple debugging for: Field serice - for on site maintenence or depot work. Manafacturing test• for burn in test flaws and to do quality control. Inspect i onPostcatrd simplifies ingoing and out going test processes on stand. 2 MEG EXPANDED CARD FOR XT X18164 ................ $245 X1 1091 .................. $99 Tower X11105 ..... ........... $250 MULTI 1/0 DISK CONTROLLER CARD This card will controll 2 x double sided, double density drives, and · features a serial port, a parallel port, and a joystick port or games port. It also has a clock calender generator with battery backup. Will control! 2 360k / 720k disk drives. ·XT case X11093 .................. $99 X18071 ................ $350 FLOPPY DRIVE CONTROLLER CAR D Including 2 MIByte RAM X18040 .................. $99 SERIAL/ PARALLEL / GAMES CARD XT, AT compatible. 1 parallel, 1 serial, and 1 joystick port. X18151 .... ...... ... ... $115 · Processor 80386-25 · Cache controller 82385·20 · Speed: 25 MHz or 20 MHz · Memory: 32KB Cache memory (35ns) · 2 M/Byte RAM fitted (70ns) · 2/8 MB plus 32 bit memory card Expansion slots: 1 x 32 bit, 5 x 6 bit, 2 x 8 bit· Intel' Combo Chip set: 82230, 82231 · BIDS: AMI Landmark Test: Up to 43.5 MHz · LED display for speed indication Ability to run OS/2, MS/DOS, XENIX · Real time clock/calendar with battery back up Baby Ar size board X18105 ....... .. ... ..... .$3,000 DISK DRIVES 360K 5 1 4" .. ................. ...... ... ....$175 · 1.2M 5 1 4" CASING X18052 ........... .... . $225 VGA 256K CARD CLOCK CARD X18024 .................. $49 The MIDI DS·401 card is the PC standard MIDI interface that runs most popular PC music programs for sequencing , recording, composing, music printing, patch editing, music instruction and many other applications. · Run all programs designed for the roland MPU·401 architecture .. Socketed EPROM for easy user. · 1/3 length (short) card will fit in any computer accepting standard expansion card , including laptops . Including ··v·· cable, external connector box to transport is unnecessary . Includes softwase. PC, XT, AT, compatible 800 x 600. X18005 .................. $52 MIDI INTERFACE CARD -DS/401 · Babby AT X18072 ... ............. $450 4 PORT SERIAL CARD X18103 ......... ......... $1,232 386 CACHE 25MHZ MOTHERBOARD PC, XT, AT compatible hardware 200M, pan+ windowing. 800 X 600. NEW PRODUCTS 386 MAIN BOARD · Intel 80386 CPU (20 MHz) · Socket for 80387 Math coprocessor · 32 bit Memory BUS system · Built-in speaker attachment Battery backup for CMOS configuration table and real time clock Keyboard controller and attachment · 7 Channel DMA · 16 Level interrupts · 3 Programmable timers · 8 System expansion 1/0 slots: 5 with a 36 pin and a 62 pin expansion slots / 2 with only the 62 pin expansion slot / 1 with two 62 pin expansion slots (32 bit BUS) · Without RAM X18107 .. ....... ... ...... $1,600 I VGA 512K CARD · All ports fitted Can be used with multi- user systems 2 joystick ports. X18019 ................... $29 + X18070 ........ ........ $225 X18160 ................ $425 X18045 ................ $115 GAMES 1/0 CARD Features (DB15) X18048 ................ $849 EGA CARD Fully compatible with Novell NE-1000 Ethernet card · Built in 15 pin D type connector · 1O Mbps transmission rate · Meets the IEEE 802.3 standard X18006 ................ $129 3.5 MEG EXTENDED RAM CARD FOR AT X18056 ................ $275 X19084 ............. ONLY $245 . ______________ ,, E- NET INTERFACE NETWORK CARD · PC, XT, AT compatible Controls up to 4 drives similtamously 360k, 720k, 1.2 M, 1.44 M X18056 ...... ...... ...... $29 Traditional telephone answering machines are obsolete with the release of the NEW Voice Mail Card. Not only can this card turn your computer into a 24 hour personal receptionist , but can answer with different phone messages tor particular callers. Auto switch Hercules, CGA ega ( 640 x 350) 256k ram. FOUR WAY DISK CONTROLLER CARD RS232 CARD TURN YOUR IBM* PC, XT, AT INTO A FULLY FUNCTIONAL ANSWERING MACHINE!!! X18162 ................ $275 SAVE ON ALL IBM CARDS .............................. .. $225 1.44 720K 3 1 2" .. ............................ ..$225 · 20 MEG HD ································$499 · 40 MEG HD ·················· ······· ····· ··$599 VGA card & monitor has disc utilities Upgrade your computer display to the VGA standard with this quality 14-inch multiscan monitor and 16-bit VGA adaptor card from Dick Smith Electronics. The display is compatible with all current video standards such as CGA, EGA, Hercules graphics, MGCA and MDA (for an explanation of these terms, see Jennifer Bonnitcha's column in the July 1989 issue of SILICON CHIP). Maximum resolualso available. With IBM Proprinter and Epson LQ-2500 emulation modes, the C-610 can be used with most popular software on the market. For further information, contact Anitech, 1-5 Carter St, Lidcombe 2141. Phone (02) 748 1711. 20MHz 80386SX motherboard for $1095 If you want to travel on the leading edge of personal computer technology, consider this new 32-bit tion of the display is 800 dots by 600 lines and video signal bandwidth is 35MHz at 3dB, for a really pin-sharp display. The VGA card comes with five 5 ¼ -inch floppies with utilities to select the VGA modes you want and also to configure popular software such as AutoCAD, Autoshade, Lotus 1-2-3 (V.2), Symphony (V.2), Framework (II 80386 motherboard from Electronic Solutions. Featuring relatively few VLSI chips in a state of the art design, the motherboard is loaded with 1 megabyte of RAM as supplied but is expandable up to 2 megabytes onboard. The clock speed is normally 20MHz but is switchable to 8MHz if required. The bus speed is also adjustable to 8MHz (for older AT standard cards) or 12MHz for the newer cards which can cope with faster bus speeds. Page Interleave memory access · I~. lllA\Jl})JIO P1nr. lL1r1[)i. .,.s.,.;. r..~i:.;;: RCS Radio Pty Ltd is the only company which manufactures and sells every PCB f., front panel published in SILICON CHIP, ETI and EA. 651 Forest Road, Bexley, NSW 2207. Phone (02) 587 3491. 94 SILICON CHIP or III), GEM Desktop (2.x or 3.x), Ventura Publisher (1.2 or 2), WordPerfect (4.2 and 5), Wordstar (4 or 5) and MS Windows. Setting up is well explained in the instruction manual. The price? Quite reasonable really, at $299 for the VGA card and $899 for the 14-inch monitor. They are available from all Dick Smith Electronics stores. enables the motherboard to work at zero wait state, even with lOOns RAM. It also caters for extended memory, supports EMS 4.0 and has disc caching via extended memory. The price is a very attractive $1095 including 3-month warranty and full documentation. For further information, contact Electronic Solutions, PO Box 426, Gladesville, NSW 2111. Phone (02) 906 6666 or fax (02) 906 5222. Low cost printer cable for Commodore Amiga Lack of standardisation is the bane of the computer enthusiast and the Centronics printer cable Five-in-one soldering tool kit These butane soldering irons keep getting better and cheaper all the time. This Vulcan 30 model comes with a catalytic flameless burner a nd four separate soldering iron tips plus a number of torch accessories: a pencil flame torch which is useful for brazing, a hot knife which is handy for cutting thermoplastic materials, and a hot blower which is almost essential these days for high temperature shrink sleeving. There is also a wide flame. torch which would be ideal for paint removal or perhaps removing stubborn nuts. All of this is packed into a handy carrying case together with a sponge pad for cleaning the soldering tip and a quantity of 1mm resin cored solder. There is also space inside the carrying case for a butane gas lighter which would be convenient for lighting the torch it is on the left hand lateral stick for the Commodore Amiga. It uses the same DB-25 plug and 36 pin Centronics plug but the wiring is different to that for the IBM PC printer cable. Fortunately, Sheridan Electronics has a printer cable for the Commodore Amiga at the very reasonable price of $6.50. Sheridan's has moved recently by the way, and they're now at 286 Cleveland Street, Surry Hills, NSW 2010. They also plan to open a new store in Blacktown soon, so stay posted. Phone (02) 699 6912 for further information. Remote Control ctd from page 89 cockpit floor or on a steering wheel mounted on the main control column. On both modes in a model Tx, axis with spring loaded neutral and left or right deflections. Operation of the rudder is straightforward with the trailing edge of the rudder moving left for LEFT rudder, when viewed from behind the aircraft. Aerodynamically, the action of the rudder is extremely complex, particularly in aircraft with dihedral, and this will be explained in the control and stability section. Essentially it begins by creating a yaw, which in turn, develops into a roll which in turn develops into a spiral dive. Prolonged application of rudder will result in a crash. In the "good old days", stuck rudders led to the demise of many fine models - usually caused by running out of turns on the elastic band driving the rudder actuator. Sounds quaint, doesn't it'? The three foregoing controls, along with the throttle control, form the primary controls required for a model aircraft. In fact, I prefer to think of an aircraft as a 4-axis device as the throttle is a vital control and is used as much as any of the three primary controls in performing manoeuvres. The throttle is a non-return stick fitted with a friction device or ratchet. On Mode 1 Txs it is on the accessories. Our sample unit came · from David Reid Electronics who have the unit in stock at $59.95. See David Reid's at 127 York Street, Sydney, NSW 2000. right hand fore and aft axis and on Mode 2 Txs it is on the left hand fore and aft axis. ~ ACTIVE SHORT WAVE ANTENNA TECHNIKIT AT4SW (SEE SC JAN '90) COMPLETE KIT $59 BUILT and TESTED $119 (BATTERIES INC) CASE $10 LOOP ANTENNA Q TECHNIKIT PX1 COMPLETE KIT $44 BUILT and TESTED $69 (SEE SC JUNE 89) Improved signal strength & signal quality in a portabl e tunable antenna. PACKING & POSTAGE IN AUSTRALIA INCLUDED IN PRICES QUOTED. WRITE OR RING FOR BROCHURES ORDERS ACCEPTED ANYTI ME PAYMENTS BY BANKCARD. VISA, MASTERCARD, CHEQUE or MONEYORDER TRADE ENQUIRIES WELCOME JILOA PTY LTD (TECHNIKIT DIVISION) P.O. BOX 73, GLENHUNTLY, VIC 3163 Phone (03) 571 6303 M ARCH 1990 95 4 July 197- USA. Happy Independence Day, Dickie! Thank God it's a holiday. I need the rest. Since last I wrote, I've chalked up more air miles than an albatross. We were already short on staff and the boss sacked one of the blokes. He wasn't a bad sort but had a real talent for getting into trouble. Both of us went to that UHF station.ill.Zenith.•,11m,11sed-t~P~ or. made the mistake of asking the chief engineer and a couple of the techs to let me know how he was shaping up. I left him to do a couple of jobs there and went on to Carthage 90 miles away and a generation behind. Anyway, Larry was supposed to be checking out their new production vision mixer and ended up for some reason in the audio booth. Why was he there? God only knows but he managed to bomb an effects tape being edited. The studio supervisor wrote a sharp letter which was supposed to be sent to me but ended up on my boss's desk. He took a dim view of the situation and put Larry on probation. Next, Larry went to a production facility of some religious syndicaium mtfit. Everytnmg went well until he put the final distribution module in, turned on the power and blew the entire mixer. I understand the language was what one would expect in any television facility. Larry said it wasn't his fault and indeed it turned out that the module had a production error which managed to short two power busses - a one-in-a-million chance. So his skin was saved, just. By RICHARD KOPF ers 96 SILICON CHIP Then he went to a small regional station and was having a joke about this automated facility in Zenith which I wrote to you about last. Only problem was, the chief here had been one of the design engineers on that project. He was not amused at having his brainchild r,ubbished and called our boss. Goodbye Larry. It means even more time away from home than ever before. Heather has threatened that since she never sees me she might as well go back to Australia. Maybe it's time for me too, to look for another line of work. I've been thinking a lot about the ~ndustry, both from my own experience and yours. Back home, it's a "she'll be right mate" attitude; here it seems to be a variant of Murphy's Law - there's never time to do it right but always time to do it over. That's similar to what you quoted in your last letter but I saw it on a poster in a shop recently. How to wreck a camera Take the example I saw last month: a fairly decent station in Michigan. A studio camera died one afternoon - rather than get the manual and the CRO, the tech decided to swap modules in the second. He put the camera heads side by side and followed safe procedures in powering down before he swapped. About 20 PCBs later, he still did ~ ~ C ) ~L-E:..'--/ ' :s,="-4 ~ fJ '~ ~M<at>r. qo... t-Af<1<.'-f A, IH~ "RE:UGIOUS OUTFl"roo •. not have a second working camera. Just about then, somebody reminded him it was not long before the evening news. So he stuck all the "good" modules back in the "good" camera - turned it on and got zip. Now, the problem had been a buss fault in the main frame of the crook camera. Every time another module went in, the mainframe zapped it, silently and efficiently. End result: two crook cameras. This station in Carthage is as bad as I've seen anywhere. You could use it as the bad example of all that's wrong with NTSC. It had been a satellite of one of the Zenith stations; they sold it to a local tycoon who ought to be a Texan. He insists on having the biggest building in town, the tallest towers, the longest limousine, etc, etc. Not that he's a bad bloke, but he obviously doesn't watch his own channel. They pick up some network programming from Zenith, off-air. The relative phase is anywhere in 360 degrees; that's when there's enough signal to have colour! The local pictures aren't much better. This is the first station I've ever seen with valve VTRs, fair dinkum. The owner told the chief engineer to order a couple of new machines. Our sales people told the chief there'd be a two month wait before they could be shipped, there were so many back orders. Chiefie conveyed that message but the owner took a dim view of it. Money talks and the owner called the national sales manager. Two top-of-the-line models were delivered three days later. Now, the owner was smart enough to realise that new technology needed some state-ofthe-art training. He told the station manager to send all the techs one by one - to the company tape seminars. What our wealthy entrepreneur forgot was that he also told the station manager that as profits rose, he'd get a piece of the action. This bloke is so inept he only sees cutting costs, not increasing revenue, as the answer. In the past month, he's cheated the staff on their overtime, sold a parcel of land next to the station and taken away the engineering budget. With a shrewd bit of cunning, he chose the oldest and dumbest tech to send to the seminar. When that idiot got back, they asked him how it was. "A big waste of time", the tech said. "I didn't learn nuttin"'. "Well, no sense in wasting any more money sending the rest of the fellas", crowed the station manager. The local dragon One of the blokes who works a studio camera is a university student. When he finished his exams, they asked him to build a new set for the morning talk show. This he did from design to carpentry, to MARCH 1990 97 THE TECHNOLOGY LETTERS - CTD final painting. He turned in his overtime and the accountant - a woman who obviously is in training to become a dragon - said: "No college kid is worth this amount of money". He had to wear it or not have any further income. I saw a funny thing happen right after I arrived here. For some obscure reason, the station tapes a week's episodes of a soap opera off-air from Zenith - and plays it back the following week. They get a B&W film print as a backup. The afternoon tech - who is transmitter staff, loads telecine and tape, and tweaks the studio cameras for local commercials always loads the soapie and the film. The director, who does his own switching, never runs the film. I was back behind a rack of equipment and saw the tech run the soap tape in almost to the end. Then he took the two reels off the machine, went back to the workbench, and planked them down a couple of feet apart. Next, he took a bulk tape eraser, the kind you'd use for audio tape, normally. One quick zap and the remaining program has a nice glitch in the control track. He put the tape away. No one saw this except me. The following week, the program ran fine for 27 minutes, then it broke up, re-locked and so on for the final two minutes. The program manager ran in screaming to go to the backup. The director was in a frenzy, trying to re-cue the film - he was actually crying. The tech on duty needless to say, not the saboteur couldn't do anything with the machine to compensate of course. A couple of days later, the shifts had rotated again and the saboteur was back on afternoon shift. The chief engineer came to him and said: "I noticed the colour telecine is a bit out of registration. See to it promptly". Now the program manager insists all film commercials go to air in colour. They only have one colour telecine, as you might have guessed. The poor bloke'd get his next 98 SILICON CHIP commercial tapes up, flip a test slide up and start to tweak, and the director would insist he be given control of the chain. It looked worse later on than before - not that I blame the tech under the circumstances. It turns out the chief engineer is often away, tending to his own company's affairs. He has a business installing TV antennas, intercoms and such. Two or three blokes work for him doing the actual labour. The power bill Yesterday, things were relatively quiet. About two in the afternoon, the station died. Everyone was running around like chooks. The station manager jumped in his car and started up the laneway for the main road, so he could contact the local power company. A couple of hundred metres along, he saw a linesman. Jumping out of his car, he yelled "I don't know what you're doing, buster, but we just lost all our power!" "Yep", the man called down. "What are you going to do about it?" "Leave it like it is, fella. When you pay your electric bill, I'll reconnect it". To add insult to injury, the business office of the power company insisted that the station manager in person come to them with a cashier's cheque before they'd restore service. It definitely wasn't his week. He came in today and heard some whispering in the hallway. By and by, he came to the realisation some deep, dark secret existed he didn't know about. Finally, the chief engineer admitted the truth. The "saboteur" had tendered a letter of resignation. Not too unusual, at this station. What was different about this one was that it went into intricate detail about the misdeeds of station personnel - and a copy was posted to the owner! The station manager was so distraught, he had to leave. When he drove away, he scraped against a car belonging to one of the news crew. A film cameraman saw it and said so. When the manager returned he was confronted but denied it. As the next part of the story goes, it's total hearsay - but somehow I believe it. The bloke locked himself in his office and was talking on the telephone to some company out in Seattle. Suddenly there was a click and the owner spoke up. "Please, out west, whoever you are, take this idiot off my hands!" Yes, indeed, our hero was trying to find himself a parachute. I heard he'd had eleven jobs in as many years, and lost every one of 'em. The "there's never time" excuse surfaced a couple of days ago, with the aforementioned director. He was trying to cut a furniture commercial. The local talent, one of the co-owners of the furniture store, kept blowing his lines. (Seems like every city I've been to in the US has a local furniture store with an enormous fat bloke trying to be a TV star). The theme for the current hardsell was " Christmas in July" with our fat friend in Santa outfit. After take 42 the fat guy said "Well, I blew all hell outta that$/#$!" Our harried director said he didn't have time to re-cue the tape, so ran on. This cut wasn't perfect but as the commercial went to air in about 10 minutes time, it would have to do. Now, it's shift change time. The bloke going off duty mentions the bad cut in passing; the evening man is too rushed to pay careful attention to the fine details. He runs to the head of the tape, adjusts to the colour bars, zeros the footage counter at the start of commercial video, and winds back for the pre-roll. The tape goes to air in the first commercial break of the afternoon kiddies' program. I guess a lot of tots and mommies had never heard such language, as the station switchboard fairly lit up! The "bad example" director never plans ahead. He was notorious for recording a local spot on new tape, then when he needed a commercial sized reel for it, he'd spool off one of the old spots. If the management had known how much tape stock went out in the trash, they would have croaked! ed again through the glass. The girl's skin tone was perfect both in real life and on camera. Only thing was, her coat - sort of a pale orange - looked completely different, more like a hot pink. The ad bloke asked about this but was not particularly upset. The tech reckoned it was the dye, probably a synthetic, having a different spectral response. The ad person reckoned she looked so good, they could live with it. The first take was perfect, for once. When the poor tech played the tape back, the coat had changed colours and was orange again. I haven't the foggiest notion why it was so and neither did the duty tech. Deep south scam AY YOU'R e:~C..-i"~\C.. BIL-L-, !'L-l.. RE:CONl\lc;.c..,- 1-r" Because of this habit, the blokes made a spoof tape on a "Mission Impossible" theme. We see a shadowy figure walk through the empty studio, into an empty control room, stride up to the VTR and hit the play button. The camera zooms into the monitor and picks up full frame dissolve to film video, a fast montage in really neat style. As the opening ends, we see "Phelps" spooling the tape off into a trash can. As you might have guessed, somehow that bit of satire accidentally went to air one evening. The empty control room is not an exaggeration either. After the late news, they start a local movie; then everyone races outside to hang over the fence, watching the big screen of the movie drive-in close by. Catch a falling snowflake Last winter, they tell me they had a bit of fun with the weather man. Seems he predicted a snowfall one night "so light you could count the flakes". Unfortunately, about midnight, a fair blizzard sprang up, leaving 9 inches on the ground. The next afternoon, two of the techs rummaged around in the junk pile - and built a snowflake counter. Sporting flashing lights, a rotating thingo like a small butterfly net, and sound effects, it was presented, impromptu, to the bloke the following evening on the 6pm news. They say he was at a loss for words. I'm told one of the senior men had a great reputation with the management. Seemed like every time he went on holiday things just fell apart. What they didn't know was that he helped things along - even to the point of having a box of gassy valves in his locker, to slip in the old tape machines just before he left. Not long before I arrived, they lost one of their big local advertisers, a ladies clothing store. The people came back yesterday. Said the other station in town was no better - and here, at least, they know where the coffee machine is. The production manager came in to browbeat the duty tech and warned him not to let anything go wrong. The bloke took extra special care with the GE cameras - colour balance and match was perfect. We were watching the talent in the studio through the soundproofed windows. A foxy model came in wearing some really great gear. The ad agency bloke looked at the colour monitor, did a double take and look- Larry called me this afternoon. He'd managed to get a job in the deeper South. In less than a week, disaster had dogged his heels again. Seems yet another management had built a brand new building and moved the old equipment. One of the incumbent staff was more than a bit hacked and had organised a scam. He'd gotten some balsa wood, aluminium foil and weather balloons. As the motorcade with the mayor and some other city notables wound its way up the hill to the building for the opening ceremony, these ten-foot-high dollar signs rose in the air over the transmitting tower. They glittered nicely in the glare of the spotlights. The top brass burst into the control room where Larry was innocently at work, demanding to know who the culprit was. Larry, of course, hadn't a clue what had happened. They reckoned he must be in on it, if he hadn't actually done it. I think Larry ought to look for another line of work, too. I, for one, am quite weary of the management attitudes in this business. And the thrill of travelling around the country has well and truly worn off. The computer field looks like it might be interesting. From what you've said of the security industry, it looks like another thing to stay away from. Anyhow, I must be off. Must have a look at the job ads. Regards, Colin. ~ MARCH 1990 99 ASK SIUCON CHIP Got a technical problem? Can't understand a piece of jargon or some electronic principle? Drop us a line and we'll answer your question. Write to: Ask Silicon Chip, PO Box 139, Collaroy Beach, NSW 2097. Why does TV set blow protection resistors? I have a GE TV set and it has blown resistor R731 on the circuit I have included with this letter. It is referred to as a protection resistor. This is not the first time it has blown. I need your help with this problem because our town has no TV serviceman. The nearest TV service business is several hundred kilometres away. (J.J., Cunnumulla, Qld). • The fundamental reason why any protection resistor fails is to protect the circuitry it is associated with. In this case, resistor R731 is protecting the 1 ZOV supply and the horizontal output circuitry involving TR60 and the tripler transformer. Evidently there is some fault in the circuit which causes the current to be higher than it should be; hence the resistor cooks. Having said that much, we are Another high energy ignition won't start I have the identical problem with the High Energy Ignition system as experienced by R.K. of Darkan, WA (SILICON CHIP, December 1989, p116). Mine is fitted to a Toyota Lite Ace KMZO, as per the instructions in the article. When cranking, the input voltage from the ballast resistor falls to about 8.5V. When the key is released, the spark immediately returns, as witnessed on a timing light connected to the coil. the points and other associated parts have been checked. I also primarily built the unit for easier starting but the engine will not fire until it has loosened up enough after a few cranks to fire when the voltage returns. Removal of the unit from under 100 SILICON CHIP not in a position to help you further, simply because we are not experienced in TV repairs or with your particular set and even if we were, we would have to be lucky to point out the exact cause of the failure. Continuous recording on the digital voice recorder I appreciated your article on the digital voice board in the December 1989 issue of SILICON CHIP. However, I would like to adapt the circuit to continuously record from my shortwave radio. That way, should I miss a message while I am slightly inattentive, I could press the recorder pause button and hold the last 30 seconds worth of audio output from my radio. I could then press the replay button and replay the 30 seconds worth as many times as are necessary to get the message. After the van is rather major surgery. Can you describe a simple cure that will not involve having the unit on the bench for a week and the van off the road? (D.H., Bathurst, NSW). • Your problem seems to be associated with your ignition wiring. When cranking, the ballast resistor is supposed to be switched out of circuit so that the coil is fed with the full battery voltage. We doubt whether the battery voltage itself is falling to 8.5V when cranking. We suggest that you closely check the wiring to see that it conforms with that in the article. Note that where the circuit says + 12V, it means the 12V supply from the ignition switch, not via the ballast. Only the coil is supplied via the ballast, as in a conventional ignition system. that, I would press the record button and recording would proceed day in and day out until a similar situation arose again. The board would run off a 5V plugpack supply with no back up and all 5V rails would be paralleled together. Would this create any risks and does the board need a start-up routine? The board would be receiving a substantial audio input from the radio extension speaker output or the earphone socket, which is currently driving a small loudspeaker. I guess that no LEDs would be required. If you could suggest the circuit changes necessary to achieve these things particularly the continuous recording and playback from the beginning of a 30 second recorded message - I would be very grateful. I believe that there is an application for this in the shortwave radio world and that there may be scope for a niche market. (F.E., Weston, ACT). • It's quite easy to modify the digital voice board so that it records continuously. All you have to do is connect a lOkn resistor between pin 22 of IC7 (TMS3477) and ground. The digital voice board will then record continuously when the record button is pressed. Pressing the stop button and play buttons will then replay the last recorded message. The unit can be powered continuously by paralleling the + 12V input supply or removing one regulator and paralleling the 5V outputs. We do not recomend using a 5V plugpack unless it is regulated to within 10% of 5V. Also, many components can be deleted from the circuit, including ICl to IC6 and associated components, plus the remaining three memory ICs from ICll to IC13. The CAS (pin 15) of IClO can connect directly to the CASl (pin 12) of IC7 using a short length of insulated wire. Problem with Pools/Lotto Selector I have built the Pools/Lotto Selector described in the May 1989 issue of SILICON CHIP but I am having trouble. It does not select the right numbers. I have checked all solder joints and tracks and everything appears to be OK, and the voltages at the test points are spot on. I have used sockets and even fitted new ICs but to no avail. (A.R., Ingham, Qld). • Unfortunately, your letter is not specific about the nature of the fault with your Pools/Lotto Selector. If you mean that it selects numbers above 36 when Pools mode is selected, then there is something wrong with the wiring of the slide switch or perhaps one section of the switch is open circuit. Alternatively, if it produces more numbers that it should for a given game - eg, selects 7 numbers when only 6 are required - then there is a problem with the wiring of Sl or the two associated 4015 chips, IC6 and IC7, or perhaps with the associated gates in IC5. Judging resistor power ratings I have just finished sorting, categorising and recording some 3000 mixed resistors that I purchased from the UK a couple of years ago. Trouble has arisen with a score or so, and I need your help to identify these. My biggest problem is how does one recognise the wattage of a resistor'? Technology has been reducing the physical dimensions of most electronic components very rapidly over the years. In the precision range, I was flummoxed by the following: markings such as 1 %0.5. Does this mean 10½ % (unlikely), 1 ½ % (my choice) or 1 % down to ½ % '? Two conflicting guides didn't help me in deciding values when the fourth colour band was either silver or gold. Leo Simpson's article on resistors (SILICON CHIP, March 1989) directed one to divide by 0.1 and .01 which produces for a resistor marked brown, white, violet, gold, brown 197/0.1 = Wants parts for AM stereo radio I have been trying to get either a kit nr the vital parts in order to build the 2-Chip AM Stereo tuner, as featured in the September 1989 issue of SILICON CHIP. I want to build it as a substitute unit in my AM/FM tuner, using the existing tuning gang and feeding the output to the AM/FM switch. I want to purchase the PCB (code SC06108891), the main chip (MC1 3024P), the various Tako coils and the Murata SFP450D ceramic filter. The other parts I should be able to get locally. Dick Smith has not got the kit. I am also after a Sony M517252 IC (used in Goko 8mm motorised editor) or data on above. (E.S., Cloverdale, WA). • Kits for the 2-Chip AM Stereo Receiver went on sale in Dick 19700 1 %; or for orange, orange, red, gold, brown 332/0.1 = 33200 1%. My training directs one to multiply which gives 197 x 0.1 = 19.7k0 1 % and 332 x 0.1 = 33.2k0 1 % respectively. Others confusing me are: (1). Orange, white, white, red, brown = 39,900. Is that 39.9k0'? (2). Orange, blue, green, black, brown = 3650. Is that 36.5km (3). Blue, black, yellow, black, brown = 6040. Is that 60.4k0'? I intend to build, some day, either a Wheatstone bridge or an LCR meter but that won't unlock the key to wattages, will it'? My particular delight in your magazine is the cartoonist in the TV serviceman section - not that my knowledge of the idiot box extends further than selecting a channel. (L.A., Cannington, WA). • Unless you know the source or can physically identify the type of resistor, it is almost impossible to say for sure what the resistor wattage rating is. In this case you can only take the practical approach; if a resistor gets hot, replace it with a Smith stores on January 15th (two weeks after your letter was written). You should buy the complete kit, as it will be almost impossible to obtain some of the parts individually (at least initially). While we can understand your desire to build it into your AM/FM tuner, we suggest you first build the tuner as described. Then you have the option of using it as a portable or connecting its headphone outputs directly to the auxiliary inputs of your amplifier. If you are still keen on building it into your tuner, you will at least have the experience of getting the unit going initially - experience that will stand you in good stead when modifying it. We cannot help you with Sony parts. We suggest you contact your local Sony agent or Sony (Australia) Pty Ltd, PO Box 3 77, North Ryde, NSW 2113. Phone {02) 877 6666. larger unit. Wirewounds do not present a problem as they are usually clearly labelled with their rating. Now to those tricky resistor codes. If the fourth colour band of a 5-band resistor is gold, then this means multiply the preceding figures by 0.1 (ie, divide by 10). Thus, for a resistor marked brown, white, violet, gold & brown, the value is 197 x 0.1 = 19.70. Similarly, if the fourth band of a 5-band resistor is silver, then this means that the multiplier is .01 (ie, you divide by 10). A table showing how to decipher 5-band resistors appears on page 12 of Leo Simpson's article on resistors in the March 1989 issue. Take another look at this table - it clearly tells you to multiply by 0.1 and .01 (not divide). Let's take a look at another of your examples: orange, white, white, red & brown. In this case, the red band means that the multiplier is 100, so the value is 399 x 100 = 39.9k0. If the resistor is orange, blue, green, black & brown, then the value is 365 x 1 = 3650 (not 36.5k0). Note that the black MARCH 1990 101 How do you wind inductors? I need your assistance with the design of inductors. I see in a number of magazines they give directions about winding inductors for particular projects. An example might be as follows: "13, 214µH, 61 turns 1mm wire on a 10mm high former R 0.220". How do they come to that conclusion? The reason I would like to learn how to do this is that occasionally I see some projects incorporating inductors but with no winding specifications. The only way I can build these particular projects is to have the inductors professionally made and that's expensive. I suppose it would be cheaper to buy the module complete but half the joy of a hobby is knowing that you did it all yourself. (B.C., Grange, SA). • We quite agree, B.C. There is a formula for winding single layer coils but where several layers are involved, the going gets messy. for a single layer coil, the formula for inductance is approximately: band signifies a multiplier of 1. In any case, we suggest that you check all resistors with a digital multimeter. Some colours can be quite difficult to decipher and a DMM will remove any lingering doubts. As far as resistors marked "1 %0.5" are concerned, they really have us tricked. You appear to have a real mixture of resistors there and it seems as though some may be early metal oxide resistors which had the values printed on them. In this case, the 0.5 designation may refer to a rating of ½ W but we cannot say for sure. Wants heart rate monitor I would like to build a heart rate monitor to assist me while exercising. I can't find a suitable circuit and was wondering whether you 102 SILICON CHIP L = 5a2n2~3a + 9b) where a = diameter of coil (mm) n = number of turns b = length of coil (mm) Most designers would decide on a value of inductance and then do an approximate calculation of the number of turns required on a given size former or bobbin, based on their past experience. Then they would measure the resulting inductance using an inductance tester or Q-meter, and then adjust the number of turns until the required inductance was obtained. In fact, you don't even need an inductance meter to measure inductance. If you have an audio oscillator and an AC millivoltmeter or oscilloscope, you can resonate the coil with a known value of capacitor and then calculate the inductance by using the formula for parallel resonance: F = 1ij27fLC. Alternatively, if you are measuring coils for RF use, you can use a grid dip oscillator to measure the resonance. You can find out more about using a dip oscillator in the RSGB Handbook. would consider this as a project in the future? I think that to be useful it should be portable and give a continuous readout so that it could be worn while cycling or jogging. In the meantime, I would like to have a go at it myself and would appreciate it if you could help me with the following. I can see how a timer circuit using a crystal control could be used to time between successive heartbeats (using a suitable triggering device), giving a readout in say milliseconds. There appear to be numerous circuits around to do this, however I can't find anything to convert this readout to beats per minute. Could you tell me how this could be done or advise where I can locate a suitable circuit? The advantage of a continuous readout is that you can adjust your exercising to maintain a pulse rate to give optimum aerobic results, while keeping the heart within safety limits. (B.D., Caringbah, NSW). • The problem with measuring and displaying heart rate is that the circuitry has to perform a reciprocal calculation for each and every measurement. One way to do this is to take the measured time interval between beats and refer it to a "look up" table in an EPROM so that the correct heart rate can be displayed. This is the method used in a number of commercial heart rate monitors. We don't know of any easier way of doing it. Confusion on PCB code numbers Not long ago, I phoned RCS Radio to see if they had the PCB for the 40-metre HF receiver (code SC06111891, December 1989) and was told that this number was for the FM Radio Intercom published in October 1989. I subsequently went through the magazine and sure enough, they both have the same code number. Could you please tell me which is the correct number for the HF receiver so that I can obtain a board? Also do you know of anyone who makes your PCBs in Victoria? (B.B., Vermont South, Vic). • Our apologies for this mix-up. We've allocated a new code number to the 40-Metre HF Receiver as follows: SC06112891. Your nearest PCB supplier is Electronic Toy Services, 2/111 Glynville Drive, Hackham West, SA 5163. Notes & Errata Alarm-Triggered Telephone Dialler, September 1989: the alarm input polarities are shown transposed on both Fig.2 (page 30) and Fig.3 (page 33). The circuit diagram (Fig .1) is correct. Simple 40-Metre Receiver, December 1989: identical PCB codes were inadvertently allocated to this project and to the FM Radio Intercom For Motorbikes (SILICON CHIP, October & November, 1989). To avoid confusion, a new code has been allocate to the 40-Metre Receiver PC board as follows: SC 06112891. CEN'l Cash in your surplus gear. Advertise it here in Silicon Chip. MEMORY CHIPS CLASSIFIED ADVERTISING COUPON Prices at February 1st, 1990 Speed 12Dns Chip type Advertising rates for this page: Classified ads - $7 .00 for up to 15 words plus 40 cents for each additional word; Display ads (casual rate) - $20 per column centimetre (max. 10cm). Closing date: five weeks prior to month of sale. If you use a PO Box number, you must include your permanent address and phone number for our files . We cannot accept ads submitted without this information . To run your own classified ad, put one word on each of the lines below and send this form with your payment to: Silicon Chip Classifieds, PO Box 139, Collaroy Beach, NSW 2097. SIMMS (MACS) (IBM) SIPPS DIP PLEASE PRINT EACH WORD SEPARATEL V, IN BLOCK LETTERS ZIP 5 4 3 2 9 9 8 9 x x x x 256 1Mb 1 Mb 1 Mb HP PS2 9 x 256 9 x 1Mb 7 8 9 10 11 12 13 14 15 ($7.00) 16 ($7.40) 17 ($7 .80) 18 ($820) 19 ($8.60) 20 ($9.00) 40.00 128.00 122.00 165.00 48.00 132.00 130.00 - 44.00 132.00 52.00 136.00 12.70 13.80 4.10 4.25 2.50 13.40 14.60 4.40 4.60 2.70 18.00 5.00 18.00 - 20.00 3.50 414256 (1Mb) 41256 411000 (1Mb) 4400 (4Mb) 4.00 16.00 2.30 Overnight delivery 150.00 Credit cards welcome DISCOUNTS FOR DEALERS Phone for pricing on 70ns, B0ns, PS2, Compaq, and NTX PELHAM Tel (02) 427 0011 - Fax (02) 428 5460 FIX-A-KIT Name .... $15 PER HOUR LABOUR Street Postcode Suburb/Town Enclosed is my cheque or money order for$ .. Bankcard D Visa Card D MasterCard . or please debit my D Card No - 411000 (1Mb) 414256 (1Mb) 41256 41464 (256) 4164 Sales Tax 20% 6 10Dns 8Dns Prices (excluding lax) L I __L____J__L___L..__L_-'---'-____J_-'---'---_L_- ' ---'-- - '- ' - - - ' NO CHARGE FOR KITS THAT CAN ' T BE REPAIRED 3 MONTHS WARRANTY ON REPAIRS CONSTRUCTION AVAILABLE HYCAL INSTRUMENTS DESIGN, MANUFACTURE, REPAIR OF ELECTRONIC EQUIPMENT (02) 633 5897 Signature ............. ................... .. ...... ... ... .... .......... Card expiry date ...... ./ ...... ../. .... .. . FOR SALE PROJECT PCBs. Talk to the outside world. ETl-1643 PC 1/0 card, PC 1 6ADC 1 6 -channel 8-bit. Both $39.95 each . Rear bracket & DB25 cable $16 . 6502, 6809, Z-80 miniprocessor with 2 x PIA, RAM, ROM, expansion bus $49.95. Intel 8039/48/49 with wire wrap area B&T $199. Digi-125 125W power amplifier PCB $4 .95. P&P $2.00. PC Computers, 36 Regent St, Kensington, SA 5068 . BELT KITS FOR VCRs. Please supply brand & model number & $12 .00 for each kit required. Prompt dispatch assured. James Cotterill, PO Box 44, Farrer, ACT 2607. PCB ETCHING TANKS. Upright style, glass. Suit PCBs to 125 x 150mm, $29.95 kit, $39 .95 assembled. P&P $6 .00. Other sizes on request. 5V 500mA plugpacks $9.95, p&p $2 .50. Kit repair and build service $1 5 per hour or set rate. Phone (08) 382 8919. Electronic Toy Services, 2/111 Glynville Drive, Hackham West, SA 5163. USED EPROMS, 5 MIXED for $6. 00 plus $2.00 p&p. Used 27MHz remote control crystals $1 .00 each plus $1 .50 p&p any quanity. Many other products available. Send SAE for detailed list. Electronic Toy Services, PO Box 491, Noarlunga Centre, SA, 5168. Phone (08) 382 8919. TOSHIBA LCD SCREEN. Originally to suit T1500 desktop. 240 x 180mm, 640 x 200 pixels. Uses 5V supply & TTL drive signals. Suit experimenter. $150. Import Technologies (07) 372 5138. LEADER AUDIO GENERATOR, Model LAG-120A. 1OkHz to 1 MHz, variable attenuator, sine & square wave. As new $269 . Tech RF signal generator, model TE-20D, 120kHz to 500MHz. Good condition, $75. Phone (02) 969 2160, Mosman, NSW. NEW SERVICE - PARTS location and supply. Want just that part of a kit or just a hard to find part? We will find and supply them for you. No search fees. Send SSAE with requirements to Part Search, PO Box 491, Noarlunga Centre, SA 5168. Phone (08) 382 8919 . SATFAX: NOAA, METEOR & GMS weather satellite picture receiving program for IBM XT/AT. Displays in 64 colours. Needs EGA colour monitor & card and "Weather Fax" PC card. $45 plus $3 postage. RADFAX2: HF WEATHER FAX, Morse & RTTY receiving program for IBM XT/AT. Needs CGA, SSS HF, FSK/tone MARCH 1990 103 r~--------------- - -----, FREEPOST SUBSCRIPTION COUPON To: Freepost 25, Silicon Chip Publications, PO Box 139 Collaroy Beach, NSW 2097, Australia. NO POST AGE ST AMP REQUIRED, IN AUSTRALIA. Start in, _ _ _ _ _ _ __ D Renewal D New subscription Name _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ __ (PLEASE PRINT) Street _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ Suburb/town _ _ _ _ _ _ __ _ _ _ _ _ Postcode_ _ __ 1 year (12 issues) D $A42 2 years (24 issues) D $A84 NZ & PNG (airmail) D $A65 Overseas surface mail D $A62 D $A 1 20 D $A130 D $A130 D $A240 Australia Overseas airmail Enclosed is my cheque/money order for $ _ __ _ or please debit my D Visa Card CJ Bankcard Card No D MasterCard .I'---~~~ _,I I'------"--_,_-'-- ] I I '-I___,_____,_____,___, Signature _ _ _ _ _ _ __ _ _ _ _ Card expiry date_ __,_ _ Advertising Index Access Communications ... ...... 3 Allied Capacitors ...... .. ......... . 4 7 Altronics .. .. .. ...... .. .. .... .... 76- 79 Arista .. .. ... ... ...... ... ........ ..... . 27 Board Solutions ..... ..... .... 40 ,41 Dauner Electronics .......... .. .. 73 David Reid Electronics ......... . 33 Dick Smith Electronics ... .. 49-55 Electronic Solutions ........ 18, 19 Elmeasco .. .. .. ...... ... ......... OBC Energy Control ...... .. ........ .. .. 7 3 Force Electronics .............. .. 85 Geoff Wood Electronics ...... .. 29 Harbuch Electronics ...... .. 38,84 Hycal Instruments ............ .. 1 03 Jaycar Electronics .......... 70- 71 Jiloa Pty Ltd .. .. ................. ... 95 Lawson Radio .. .. .. .. .. .. .. .. .. .. . 1 7 PC Marketplace .. .. .. .. .......... IFC Pelham .... ..... ............ ... .. .. . 103 RCS Radio ..... .... .. .. ...... .. .. .. . 94 Resurrection Radio .. .. .. .. .. .. .. 1 7 Rod Irving Electronics ..... 92,93 Sheridan Electronics .......... .. 65 Silicon Chip Binders ....... ..... IBC Tandy Electronics .. .. .......... .. 1 3 L _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ __ _ _ J r~--------------- ---- -- , SILICON CHIP BINDERS Yes 1 Pl ease send me _ _ __ SILICON CHIP binder(s) at $A 11.95 plus $A3 p&p each (NZ p&p $A6). Name _ __ __ _ _ _ _ _ __ __ __ _ __ _ _ __ (PLEASE PRINT ) Street Suburb/town _ _ _ _ _ __ _ _ _ _ _ Postcode _ __ _ __ Enclosed is my cheque/money order for $ _ _ _ _ or please debit my D Bankcard □ Visa Card u MasterCard PC Boards Printed ci rcuit boards for SILICON CHIP projects are made by: • RCS Radio Pty Ltd , 651 Forest Rd , Bexley, NSW 2207. Phone (02) 587 3491 . • Jemal Products, 5 Forge St, Welshpool , WA 6106 . Phone (09) 350 5555. • Marday Services, PO Box 19-189, Avondale, Auckland, NZ. Phone 88 5730. • Electro nic Toy Services, 2/11 1 Glynville Drive, Hackham West, SA 5163. Uses normal or thermal paper. $175. Import Technologies (07) 372 5138. Signature _ _ _ _ __ __ __ __ Card expiry date_ ---''--- L- -------------- --~-----J decoder. Also "RF2HERC" & " RF2EGA" , same as RADFAX2 but suitable for Hercules & EGA cards respectively. $35 plus $3 postage. All programs are on 5.25-inch 360K or 3 .5-inch disc & include full documentation . Only from M. Delahunty, 42 Villiers St, New Farm, Qld 4005 . Phone (07) 358 2785. WOW! DRAM PRICES have dropped . Now is the right time to build your own 104 SILICON CHIP parallel printer buffer. Advertised since January 1985. Featured in AEM in March 1987 and SILICON CHIP in October 1989. Over 2500 units sold . Same kit, just updated. Now 8K-1 M. No obligation . For a free catalog send a 41 c stamp to Don McKenzie, 29 Ellesmere Crescent, Tullamarine 3043 . EPSON P80 PORT ABLE battery rechargeable 80-column printer. Serial interface. Very compact & light. 1.1 kg . TOSHIBA T31 00 CO-PROCESSOR kit. This piggy-back board enables the fitting of a 80287 -8 to the early T3100 . Two types available, solder in & plug in. Solder version $250.00. Plug-in version $375 .00 . Import Technologies (07) 3 7 2 5 138 . LOGIC ANALYSER. Gould Instruments K40 stand alone analyser. Eight nonvolatile memories, 7-inch CRT, 4 x 2K sample memories, 2 x 1 6 -channel , probes up to 100MHz, asynchronous capture . Weighs 7.7kg. $1345.00. Import Technologies (07) 372 5138. Sit.ICON CHIP BINDERS A VAILABLE NOW . * High quality * Holds up to 14 issues * 80mm internal width * Gold printed with SILICON logo on spine and front cover CHIP These beautifully made binders will protect your copies of SILICON CHIP. We are especially pleased with their look and quality. As soon as the first batch came in, everybody on our staff wanted them to store their own personal issues. You will too. How J:o ORDER: Phone (02) 979 5644 Fax (02) 979 6503 Made with a distinctive two tone green high-quality vinyl specially selected for SILICON CHIP, and with heavy board covers, each binder holds a year's issues (the 14 issues of Vol. I or the 12 issues of Vol. 2). They will look really smart on your bookshelf. To order your binders, fill in the coupon on page 112 and send it to SILICON CHIP, PO Box 139, Collaroy Beach, NSW 2097. Alternatively phone (02) 979 5644 and quote your credit card details, or fax your order to (02) 979 6503. Price: $AU.95 plus $A3 each for postage and packing. (NZ postage and packing $A6).