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Hard disc drives: how they work I : - ! SERVICING - HIFI - Phone Dialler For Burglar Alarms Liquid Level Monitor 2-Chip AM Stereo Radio Hifi in a small package ..... ;g "'c. II) z 0 z C .5! -:; .!: j3 :, c. 1ii0 c. -~ ! Electronics l For Everyone l Potentiometers & tri wpoD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR CHIPS ... WOOD FOR C MORE GOODIES FROM WOODIES Popular MJE3055T Miniature PCB In AT0219 . Latching Relays Matsushita Brand. Double Pole. Package ~ Rated to 60W, 125VA. WiH 240Vac and up to 2A Still Rated~ handle switching. 12V coil. Measures at 60V But only 20mm x 10mm x 9 .3mm. 1500V surge rating. Fits Handles 15A NPN standard IC socket. Order DS2E-ML Only $3.00 Nchl ONLY $1.00 each! High Quality BD646PNP C&K Switches Darlington / ·· I Rated 60V ONLY 30c eachl Genuine C&K 7101 Lever Handle SWitch rated at 2A and 250V. 100,000 make and .. ,- . •.. //; ''/ 400V, 35A Bridge 5tv~~r:nt Isolated metal case takes 114" i push-on connec- '.'. tors. Current rating is at 25°C on a 0.8"C/W .heat sink. 1 ~ copies. They're ""' normally $5.50 each this month you can have one for $3.501 $4.50 Nch or $40.00 per hundred Roederstein ERO MKP1841 Metallised Polypropylene Capacitors The popular 0.1µF 2000V version is in stock with 38mm lead spacing. S4.50 •eh or $40.00 per hundred NEW! Chassis Mount Fuseboxes Instead of leaving your fuses out in the open, this strong box takes standard size 0 fuses (32x6.3mm) which are held in the lid and automatically exposed and isolaled from the circuit when the lid is Ufted. Great safety ideal Leads can be inserted through ends or base of the box. Lid is held on by a spring. $2.SO.a IEC Power Cords Australian made 3 pin plug to IEC Socket. A patriotic special at onty $8.251 We also have 3pin IEC plug to 3 pin IEC socket at $11.95 Genuine Veroboard. Toss out the cheap. imitations with their wonky pitch and tracks that won't take solder. This is the real genuine stuff! Plain 102x122mm 163x101mm 201x253mm 457x105mm With Edge 130x96mm Wi,v Wrap 201 x253mm 457x95mm $9.50 $10.30 $33.95 $26.50 $21.80 $22.50 $17.60 Save on Panel ,•.. • Mounted · ·• Fuseholders · 16Amp 250V. Normally $1.85 This month they're $1.00 . Schaffner Mains Filters Limited quantity only of high quality Schaffner mains filters rated at 6Amps built into an IEC chassis inlet. Just what your PC needs and you can save they're down from $16.95 to just $10.00 $33.55 Standard Matrix 115x156mm DIP Layout Sheet ~ ~ cc a ~ 0 a ~ l STATE 3 . - L- I " "'' ,..L, Now stocking ' quality AT&M Kits Voc i,,..-v1 -VF -V3 , }-v, STATE 1 y NAI STATE 1 : BULK CHAllliE STATE 2 : OVER-CHARGE STATE 3 : FLOAT CHARGE CHARGER OUTPUT CUIIIIEHT Battery Charger IC The UC3906 is a battery charger controller for sealed lead acid batteries. Monitors and controls output voltage and current through three separate charge stales - high current bulk charge, controlled over-dlarge and precision float charge or stand-by state. Internal reference tracks lemperature characteristics of lead acid battery. The device stand-by current requirement is only 1.6mA to ensure accurate monitoring of ambient temperature. Separate voltage loop and current limit amplifiers to supply upto 25mA to external pass device. Voltage and current sense comparators sense battery condition and provide logic control to charge state logic. Low tum-on current mode allows for shorted cells. If you use lead acid cells and want them ID last investigate the possibiMlies of the UC3906. It's weH worth $15.90. See Blficle in At last a range of super high quality kits for the professional user. Saves the bother of designing and buildinlJ many of the commonly used arcuit blocks. These kits have been locally developed and come complete with instructions for construction and testing. All components are professional grade and the very latest techniques are used. Ideal for industrial and educational use. A and pi the ATMOS s exam e Abre Opdc Modem Kh uses Siemens diodes, National and TI IC's, pre-formed resistor and diodes for easy loading to the PCB which is fuUy tinned and silk screened. • Uses 1mm plastic fibre • de to 500k8aud up to 25metres • Full duplex _ no clocks • HCMOS VO • Low power < 40mA ._s;_·1ico_n_C_h... ip_J_ul.._y_89_is_sue _ _____. • Single sv operation Circuit is fuUy desaibed with typical waveforms plus assembly and testing with a final TTL compatible sub-miniature outline of applications $75.00 LED housed in a rectangular ($62.50 ex tax) moulding with integral resistor for 5V operation. Designed for KIi Dncription Price edge-mounting on PCBs for ATM01 3 digit Counter 31 .80 fault or status indication. End ATM024 digit Counter 45.60 stackable on 0.1" ATM03 3 1/2 digit DVM 51 .00 grid for bargraphs ATM041Hz nmebase 29.40 etc. Black case ATM05 Fibre Optic Modem 75.00 improves contrast. A7M06 Reciprocal Calculator29.40 63.5(H)x24(W)x ATM0710MHz Timebase 45.60 5.1(D)mm. + sign ATM08V/F- Converter 34.20 on anode.Why pay $2.30 each ATM09 FN converter 34.20 elsewhere when we have them ATM10 Triple Power Supply 51.00 at just SOcenla - less in quantity ATM1110 Minute Controller 45 .60 PCB Mounting LED 8/UfJ Matrix Copper Squsms 160x100mm STATE 2 $25.00 $25.00 .·'· Mono 6.35mm Extension Leads We found these out the back so out they go! 3. 7m long with jack plug one end and socket the other. Shielded for Hi-Fi extension. A bargain at $3.25ea ATM12 6 dig Batch Counter 75 .00 ATM13 IR Proximity Detector29.40 ATM14 FM Transcoder 34.20 ATM15 DC Amp/Attenuator 41.40 ATM1610kV Isolator 65.40 ATM178 AID and 0/A ATM188 bit UART 50.40 ATM19 6 dig Up/On Counter &9 .60 ATM20 IR Transceiver 31.60 GEOFF WOOD ELECTRONICS PTY LTD 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 Telephone: (02) 428 4111 Fax: (02) 428 5198. 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. ,.NOOSE All prices INCLUDE sales tax. Tax exemption certificates accepted if line value exceeds $10.00. BANKCARD, MASTERCARD, VISA, CHEQUES OR CASH CHEERFULLY ACCEPTED - ..... .... --- .._.. ~ -------- .. .. ...... ____,, __. ...... __. _,, _,, _. ---r __,__._._.____,,---.; .....I _____, ---- ~ __. __. __. ~ __. ~ - _.I _ --- --- ____,, .....I _,, _. _,, .....I ____,, _. __. -" ...... ____,, __. __. - -- .....I __ . - - SEPTEMBER 1 989 FEATURES 6 Electronics For Everyone Pt.4: potentiometers & trimpots by Leo Simpson YOU WON'T BELIEVE how good stereo AM radio can sound until you build this nifty little receiver. It's based on the MC13024 IC which is virtually a complete AM stereo radio on a single chip. See page 20. 16 Scopeman Video Microscope by Leo Simpson The easy way to view small objects 88 The Technology Letters by Richard Kopf Fun & games in the security industry 102 The Evolution of Electric Railways by Bryan Maher Pt.23: Swiss tunnels & racks PROJECTS TO BUILD 20 2-Chip Portable AM Stereo Radio by Steve Payor Hifi in a small package 27 Alarm-Triggered Telephone Dialler by Greg Swain Add it to your home burglar alarm system THIS AUTOMATIC TELEPHONE dialler can be added to any home burglar alarm system and will call a pre-determined number if the alarm is triggered. Construction starts on page 48. 52 High Or Low Level Fluid Detector by Peter Gray Low cost circuit has many applications 60 Studio Series 20-Band Stereo Equaliser by Bob Flynn Construction plus troubleshooting details 80 Null Your Amplifier's DC Output To Zero by J. Clarke Simple add-on circuit uses a single IC SPECIAL COLUMNS 12 Vintage Radio by John Hill Valve portables - hard on batteries 40 Serviceman's Log by the TV serviceman It's a long way to trip a "rarery" 72 Amateur Radio by Garry Craft VCR FAULTS CAN be tricky but the serviceman eventually got it all back together again. His battle starts on page 40. Simple DTMF encoder for custom control circuits 75 Computer Bits by Jennifer Bonnitcha A guide to hard disc drives 93 The Way I See It by Neville Williams HDTV: lots of problems at the transmission end DEPARTMENTS 2 Publisher's Letter 3 Mailbag 11 Subscription Page 35 Back Issues 58 Circuit Notebook 96 Product Showcase 108 Ask Silicon Chip 110 Market Centre 111 Notes & Errata YOU CAN USE this simple circuit for detecting high or low fluid levels or for monitoring soil conductivity in greenhouses. Turn to page 52. SEPTEMBER1989 1 SILICON CHIP Publisher & Editor-in-Chief Leo Simpson, 8.Bus. Editor Greg Swain, B.Sc.(Hons.) Technical Staff John Clarke, B.E.(Elec.) Robert Flynn Advenising Manager Paul Buchtmann (02) 982 9553 Regular Contributors Neville Williams, FIREE, VK2XV Bryan Maher, M.E. B.Sc. Jim Yalden, VK2YGY Garry Cratt, VK2YBX Jim Lawler, MTETIA John Hill Jennifer Bonnitcfia, B.A. Photography Bob Donaldson Editorial Advisory Panel Philip Watson, MIREE, VK2ZPW Norman Marks Steve Payor, B.Sc., B.E. SILICON CHIP is publishea 1 2 times a year by Silicon Chip Publications Pty Ltd. All material copyright (c) . No part of the contents of this publication may be reproduced witho1Jt pr,ior written consent of the publisher. Kitset suppliers may n<at>t photostat articles without written permissior,i of the publisher. Typesetting/makeup: Magazine Printers Pty Ltd, Rozelle, NSW 2039. Printing: Macquarie Pul'.llications Pty Ltd, Dubbo, NSW 2836. Distribution: Network Distribution Company. Subscription rates: currently $42 per year ( 1 2 issues) insiae Australia. For overseas rates, refer to the subscription page in this issue. Liability: Devices or eircuits described in SILICON C1,1Ip may be covered by patents. S1L1C©N C_HIP disclaims any liabilit)l for the infringement of sueh patents by the manufacturing or selling of any such equipment. Address all mail to: Silicon Chip Publieations Pty Ltd , PO Box 139, Collaroy Beach , NSW 2097. Phone (02) 982 3935. Fax (02) 982 9553. ISSN 1030-2662 2 SILICON CHIP PUBUSHER'S LE'l.l'E.R. Saving electrical energy is a question of tariffs Just recently an American expert was br ought out to Austr alia to show us how to save electrical energy. He was given a considerable amount of time to air his views on Sydney r adio stations and probably in most other State capital radio stations too. Most of what he said was so trivial as to be nonsense. One memorable example w as his claim that a n incandescent lamp was very wasteful because it was virtually a "short circuit in a vacuum" . That might have seemed plausible with some listeners but most people would be a ware that an incandescent lamp is definitely not a short circuit and neither is it in a vacuum. Incandescent lamps are filled with the inert gas Argon at low pressure. Another one of his erroneous statements was that fluorescent replacements for incandescent la mps are a very new and exciting innovation and should be used wher ever possible to save power in the home. Well, they are hardly new. BC fluorescent lamps such as the Philips SL series have been a round for at least 10 years. But they are quite expensive and the fact that they take at least 10 minutes to reach full brilliance makes them impractical for most home lighting applications. Nor are they practical in industry and offices where the fluorescent tube is king. What the " expert" should ·have emphasised is that we can make much bigger energy savings in domestic heating and cooking by using reverse-cycle air-conditioning and microwave ovens. Many people are doing that anyway, not to save power but for comfort and convenience. Big energy savings can also be provided by the new more energy-efficient r efrigerators. But all that pales into insignifica nce if you consider the energy used for domestic hot water. Solar hot water could give big energy savings here but the present generous tariffs for off-peak hot water presently make solar hot w ater systems an uneconomic proposition. Perhaps it is time those off-peak tariffs were looked at again. If we are serious about conserving coal and the cost of building more power stations, a change to the off-peak tariff and perhaps a subsidy to purchasers of solar hot water systems could make all the difference. Are we that serious about saving coal? I doubt it. Leo Simpson MAILBAG Vintage radios had delayed AGC I have been reading with interest the series on Vintage Radio by John Hill and I must congratulate him on his excellent articles with many practical hints for restorers. However, I noticed an inaccuracy in the July 1989 article regarding his description of the AGC system of a receiver that he has restored. Here Mr Hill is apparently under the impression that the term delayed AGC (or AVC) refers to a time delay. This is in fact, not the case and I can do no better than quote from the Radiotron Designers Handbook, 3rd edition, 1942 (Chapter 19}. The delay in delayed AVC refers to voltage delay, not time delay. A delayed AVC system is one which does not come into operation (ie, it is delayed) until the carrier strength reaches a predetermined level. The result is that no AVC voltage is applied to the grids of the controlled stages until a certain carrier strength is reached. The sudden increase in -volume that Mr Hill noticed is more likely due to the time constant of the AGC system being too high. J. Rickard Heathmont, Vic A missive from alternative NSW I enjoy your magazine though I don't get it every month. The articles on reviewing some solid state devices have been interesting. There was a very comprehensive one in the September 1988 issue on a 150W $35 op amp showing all kinds of applications for it. That was magnificent. Living in the "alternative" part of NSW I'm interested in power electronics, generators, magnets and battery chargers and you have had some articles on these fields (no pun intended). I'd like to see another article on magnets someday, including the neodymium-iron- boron type which have 10 times the resistance to demagnetisation that others do. A place in Wollongong Neomagnets - makes these and uses a 10,000A 1000V pulse to magnetise them. The company uses them for experimental motors for electric vehicles and also sells them. You may like to contact AEVA (Australian Electrical Vehicle Association, Melbourne) for a short article on developments in electric vehicles in recent years. Keep up the good work. R. Stone Coffee Camp, NSW Gel cells are old hat This letter is in regard to the Battery Charger article by Garry Cratt in your July magazine. Garry is obviously an intelligent and handsome young man, however, we must disagree with him on a few points. The term "Gel" or "Gel Cell" is no longer fashionable nor has it been so for several years. The American-Japanese school of thought to which we subscribe is "SLA" (Sealed Lead Acid). The terms "RE" (Recycled Electrolyte) and "Valve Regulated" are also popular in some quarters. The Gel type electrolyte cells are fairly old fashioned and are no longer made by many manufacturers. Starved or absorbed electrolyte systems are most popular at this time. In actual fact, the PS605 shown in your photograph (for which we are most grateful) is actually an absorbed electrolyte battery. This system is used in almost all our units from 500mA.h to 9000A.h, except 12V 30A.h to 60A.h and 80A.h which are in fact Gel type. The charge rate suggested in the article, C/5 to C/10, is more the charge rate for nickel cadmium cells. SLA batteries with their lower internal resistance should be more like C/4. SILICON CHIP, PO Box 139, Collaroy Beach 2097. The writer is a member of the Standards Association Committee that looks at these things and it is approximately this charge rate that is being considered at the moment as an Australian Standard. Ian J. Brown Power-Sonic Corporation 9/260 Wickham Road Moorabbin, Vic Comment: while "sealed lead acid" battery does now seem to be the preferred term, we have used the two terms interchangeably in the article since more readers would be familiar with gel cells. In any case, as you point out, some of your range is of the SLA type while others are gel types. No wonder there is confusion. As far as the charge rate is concerned, Garry Cratt did consult with a number of companies (including yours) and his quoted range of C/5 to C/10 represented the consensus. If C/4 is to be the standard, so much the better. Likes "Electronics for Everyone" articles I now eagerly purchase your magazine each month. As I am a keen model railroader, I initially purchased your magazine to this end. However, I completed a basic electronics course at the local technical college last year and find many other interesting projects in your magazine. I find "Electronics for Everyone" informative and easy enough for other modeller friends of mine to tackle. The articles on "The Evolution of Electric Railways" are very interesting but I look forward to the electronic circuits mostly. Keep up the good work with this excellent publication. It doesn't always have to have railway articles included for me to buy it. They are a bonus. I can always find something of interest between the pages. A. Bierer Port Macquarie, NSW SEPTEMBER 1989 3 PROJECT -~$COMPLETE MI~ FROM $1298 hat's right! Now you can build your own ultra high performance PC/AT, with the exact options you need , and save a fortune into the bargain. The Electronic Solutions Project ATs feature 12MHz and optional 20MHz motherboards for unmatched speed. They are complemented by fast 1: 1 interleave disk controllers and a 42MB 28 msec NEC hard disk drive (optional 20MB). The floppy disk controller supports the full range of formats: 360K 51/4", 1.2MB 5¼" and the new 31/2'' (720K and 1.44MB) formats. For a limited period, we are offering big savings, both on the basic configurations and on the broad range of options shown opposite. If you want the best AT on the market, and you can use a screwdriver, the Electronic Solutions Project ATs are the only choice worth looking at. T 4 1. As Described in 'SILICON CHIP' August 1989 1. Compact "Mini-tower" case and 200W power supply. 2. High quality enhanced AT layout keyboard. 3. Monochrome graphics video card. 4. 12MHz zero wait-state "all-in-one" AT motherboard (20MHz option) . PRICE LIST 12MHz AT PROJECT AT COMPUTERS . . . . . . . . . . . . . . . . . Normal price 12MHz all-in-one motherboard . . . . . . . . . . . . . BabyTowercase . . . . . . . . . . . . . . . . . . . . PowersupplyforBabyTower . . . . . . . . . . . . . . MGACard .. . . . . . . . . . . . . . . . . . . . . . 101-key Keyboard . ... . . ... . . . . . . . . . . 1.2MB Floppy drive . . . . . . . . . . . . . . . . . . . MS-DOS 4.01 . . . . . . . . . . . . . . . . . . . . . Total $549 $149 $145 $115 $115 $199 $159 . . . . . . . Project Price . . . . . . . . . . . . . . . $495 . . . . . . ... .. . . . . $135 . . . . .. .. . . .. . .. $130 . . . ... . . . .. . . ... $99 .. . . . . ... . . . . . . . $99 . . . . . . . . . . . . . . . $195 . . . . . .. . .. . . . . . $145 . . . . . . . . . . . . . . . . . . . . $1,431 . . . . . . . . . $1,298 20MHz AT . . . . . . . . . . . . . . . . . . . . . . Normal price 20MHz AT Motherboard . . . . . . . . . . . . . . . . BabyTowercase . . . . . . . . . . . . . . . . . . .. Power supply for Baby Tower . . . . . ... .. ... . MGACard .. . .. . . . . . . . . . . . . . . . . . . 101 -key Keyboard . . . . . . . . . . . . . . . . ... 1.2MBFloppydrive . . . . . .. . . . . . . . . . . .. HOD/FOO controller card . . . . . . . . . . . . . . . . 1S + 1P card . . . . . . . . . . . . . . . . . . . . . . MS-DOS4.01 $945 $149 $145 $115 $115 $199 $249 $75 . . . . . . . . . . .. . . . . . . . . .. $159 . . . . . . . Project price . . . . . . . . . . . . . . . $899 . . . . . . . . . . . . . . . $135 . . . . . .. . . . . . . . . $130 . . . . . . . . . . ... ... $99 . . . . . . . . . . . . . . . . $99 . . . . . . . . . . . . . . . $195 . . . . . . . . . . . . . . . $225 . . . . . . . . . . . . . . . . $69 . . . . . . . . . . . . . . . $145 Total . . . . . . . . . . . . . . . . . . . . $2,151 . . . . . . . . . $1,996 PROJECT AT OPTIONS 640KRAM 18 x 256K & 18 x 64K chips. (120nS) Normal RRP: $432 Special project price: $395 360K 5.25" FLOPPY DISK MONITORS CAT. DD1157C 1MB RAM 36 X 256KB RAM chips (120nS) Normal RRP: $594 Special project price: $549 Special project price: $175 2MBRAM 18 X 1MB RAM chips (120nS) Normal RRP: $790 Special project price: $750 42MB NEC HARD DISK 28mS CAT. DD3146H 42 Megabyte 3.5 inch hard disk drive. Access time tracK to track 8ms. Average seek time 28ms. • Formatted capacity 42.3 MB • Data transfer rate 625 Kbisec • Power consumption 9.2W • Non-operating shock: 40G 1.44MB 3.5" FLOPPY DISK CAT. DD1137H 14" AMBER or GREEN MONITOR 3.5 inch slimline micro-floppy drive These high reliability drives feature low power consumption and high reliability. Incorporate an autoshutter and head load solenoid to protect media. • Data transfer rate 500 kbits/sec • Power dissipation: 0.015W standby, 1.5 steady state • Seek time: 3ms • Size: 101.6mm x 25.4mm x 130mm, Weight: 0.39kg Special project price: $199 • Size: 41.3mm x 101 .6mm x 146mm Normal RRP : $895 Special project price: $699 EGA CARD CAT. VC1629C TTL Monochrome monitor. The models ACMA (amber) /ACMG (green) are high-resolution TTL monitors, designed to work with the hercules compatible graphics video adaptors. The monitors have 14 inch flat screen, antiglare tubes, making them an excellent choice for both tex1 and graphics. CAT ACMA Normal ARP: $249 Special project price: $199 EGA MONITOR The ACMEGAis a 14" EGA colour monitor. A dot pitch of 0.31 mm and non-glare tinted screen make it ideal for enhanced graphics and applications requiring colour graphics generally. CAT. AC MEGA Normal RAP: $765 Special project price: $645 VGA MONITOR The CAT. ACMVGA. is a 14" VGA colour monitor with a resolution up to 640 x 480 dots. 30MHz bandwidth and .31 mm dot pitch make it suitable for both tex1 and graphics. Analogue drive allows display of up to 256,000 colours. Normal RAP: $875 20MB NEC HARD DISK CAT. DD5126 Special project price: $685 Special project price: $395 This enhanced graphics adaptor is an exclusive design to upgrade the graphics display of the IBM PC/XT. AT and compatibles to a high resolution display. Compatible with the complete expanded IBM Enhanced Graphics Adaptor and providing 256KB standard video memory, it is also fully compatible with the IBM Monochrome Display Adaptor (MDA), Hercules Graphics Adaptor (HGA), and Colour Graphics Adaptor (CGA). HARD DISK DRIVE CARD Special project price: $249 5.25 inch half height hard disk drive. Average seek time65mS. Normal RRP: $595 CAT. DCAH EGA/VGA MULTISYNC MONITOR The Multisync monitor fetaures a 14" colour display which automatically scans all between 15.5-35kHz (horizontal) x 50-70 (vertical) with TTL and analog inputs. It is suitable for CGA, EGA and VGA operation up to 600 x 800 dots. In analog mode it can display an unlimited palette of colours. A tex1 mode switch provides monochrome green or amber displays. CAT. ACMM Normal RAP: $1275 Special project price: $899 VGA CARD The DCAH is a high performance 1:1 interleave hard . disc controller using the latest Western Digital chipset. Automatic optimising circuitry built extracts maximum performance from the hard disk. • Operates at up to 16MHz bus speed for unmatched data transfer rate • Supports MFM encoded ST506/412 interfaced drives • CRC and ECC functions to ensure data integrity • Includes all cabing Normal RAP: $275 CATVC800 This card offers complete register level compatibility with IBM's VGA stamdard. A range of drivers providing resolution up to 800 x 600 pixels for Ventura, Windows, Pagemaker & Autocad are included. Combined with a Multisync or VGA monitor, it provides unmatched resolution and a palette of up to 256,000 colOurs. Facilities include Complete CGAIMDA/EGA compatibility; hardware zoom and smooth panning: 132 column text display for Lotus, WordPerfect etc. Normal RAP: $495 Special project price: $199 Special project price: $475 Box 426 Gladesville 2111, Phone (02) 906 6666, FAX (02) 906 5222. Gosford (043) 24 3405. We accept : Bankcard, Mastercard, & VISA. Mail orders our specially. All prices include sales tax. Note: Products may vary in appearance from those pictured . In all cases they will pertorm to the same or a better standard. • All products carry a 14 day money back guarantee (except software). • All products carry a full 3 month warranty. • All cards come with full documentation ELECTRONl~S FQR RlrnRYO'.NE Potentiometers are widely used in electronic equipment. They are the variable controls you use on amplifiers, tape decks, TV sets and other electronic gear. In effect, they are resistors with a moveable contact. PT.4: POTENTIOMETERS & TRIMPOTS By LEO SIMPSON Broadly speaking, potentiometers come in two types. The most common is the rotary control which is used in the volume, bass, treble and balance controls in your amplifier or car radio and in all other sound equipment. Rotary pots ("pot" is short for potentiometer) are also used for the rotary knobs on power supplies. In fact, these days almost all the rotary controls on electronic equipment are pots. The few exceptions are variable capacitors, as used in some oscillators and the tuning controls on radios. Other places you will find rotary potentiometers are in joysticks as used in electronic games and radio remote controls. Each joystick uses two potentiometers connected so that they rotate through a maximum of 90°. The other type of pot is the linear slider which is commonly used in audio mixers and graphic equalisers. A potentiometer always has at least three connections to its resistance element. There is a connection for each end of the resistance element and one for the moving contact. Fig.1 shows the most commonly used circuit symbol for a potentiometer. As you can see, it is a variation on the zigzag symbol 6 SILICON CHIP for a resistor but with the addition of an arrow to show the moving contact. The moving contact, which is also referred to as the wiper, can move anywhere up and down the resistance element. Fig.2 shows shows another common symbol for a potentiometer and again, this is a variation on the rectangular box symbol for a resistor but with the moving contact shown as an arrow. Most of the rotary potentiometers you come across will be carbon types. Their circular resistance element is made by depositing a carbon mixture onto a thin insulating material which is generally paper based phenolic laminate (similar to printed circuit board material). Some elements may be moulded integrally with the base. Fig.1 shows the most commonly used circuit symbol for a potentiometer while Fig.2 shows a common alternative. The moving contact generally takes the form of a number of springy fingers plated with silver. One of the photos in this article shows the usual construction. Carbon potentiometers can dissipate only a small amount of power, usually less than half a watt. Where the circuit requirement calls for higher power dissipation, a wirewound potentiometer is the answer. As the name suggests, these have a circular wirewound resistance element. Depending on their size, wirewound potentiometers can dissipate a lot of power. One of the units pictured in this article can dissipate about 200 watts. Why are they called potentiometers, anyway? Why not some easier to understand name such as "variable resistor"? Well, pots are variable resistors but the name potentiometer relates to a timehonored voltage measuring technique involving variable resistors and a galvanometer in a bridge circuit. The particular virtue of the potentiometer method of measuring voltage is that no current is drawn from the circuit being measured. In fact, the name "potentiometer" is a coined word made up from "potential" (meaning voltage) This photo shows a collection of typical rotary potentiometers. They are all carbon-track single gang types with the exception of the unit at bottom right which is a dual-gang type. Rotary pots come in a range of values. and "meter" (meaning: to measure). Because variable resistors were (and sometimes still are) used in potentiometer circuits, they became known by the general name potentiometer and the name has stuck, long after the measuring technique has ceased to be relevant. Rheostats OK, so what's a rheostat? This is another olde-worlde term you may occasionally come across and it refers to a variable wirewound resistor which is usually rated for high power dissipation. So when you see the term rheostat, just think "variable high power resistor" and you'll be right. Ganged and concentric pots Pots come in a wide variety of types and it is helpful to be able to put a name to some of the common types when you are shopping for parts. One very common type is the dual ganged pot which is widely used in stereo amplifiers. In effect, a These are linear slider potentiometers. This type of pot is commonly used in audio mixers and graphic equalisers. ganged pot is two pot sections controlled by a single shaft. A stereo amplifier needs a gang- ed pot for its volume control so that when you alter the volume setting in one channel the other channel is SEPTEMBER 1989 7 ~~ L ___ ___ _j FIG.3 Fig.3: the circuit symbol for a dual-ganged pot. The dotted line indicates that the two wipers mo've together. n,r-: Dual-ganged pots are commonly used in stereo amplifiers for the volume, bass, treble and balance controls. In effect, a ganged pot consists of two pot sections controlled by a single shaft. "t: Figs.4 & 5: the common circuit symbols for trimpots. and so dispense with the need for dual ganged pots for each control function. Incidentally, the faders used for balance between right and left and front and back in car sound systems are also variants of potentiometers. Faders used in public address systems are also based on conventional wirewound potentiometers. Loudness taps These two pots have had their dust covers removed to reveal the 'works". The circular resistance element consists of a carbon mixture and is connected to the two outer terminals. The moving contact is connected to the centre terminal and consists of several springy metal fingers. altered by exactly the same amount. Similarly, ganged pots are used for the bass, treble and balance controls in stereo amplifiers. Fig.3 shows shows how a dual ganged pot is shown on a circuit diagram. A dotted line connects the two wipers to show that they move together. Another type of common dual pot is the dual concentric type. These are often used on car radios where front panel space is strictly limited. A dual concentric pot is a combination of two pot elements but each is operated by a separate shaft, both concentric. These pots use knobs that are split. For example, the front portion of the knob might operate the volume while the back 8 SILICON CHIP section operates the tone control. For stereo car radios the concentric pots can actually be dual ganged concentric pots because the volume and tone controls need to use ganged pots. In some stereo amplifiers you may also come across volume controls that are quadruple ganged types. These are used to obtain the lowest possible circuit noise. Another variation you may come across is the triple concentric potentiometer which is used in some of the latest stereo car radios. The relevant control may be used to alter the volume, tone and balance (between left and right or front and back]. In these car radios the three pot sections are used to vary a DC signal to both channels in the radio On some dual gang pots you will find that each pot section has four terminal lugs instead of three. Usually, the extra lug is at about the 40% rotation of the shaft. This provides for the loudness boost circuit in stereo amplifiers. Switchpots As the name suggests, switchpots are a combination of a potentiometer and a switch. They are frequently used as the combination volume control and on/off switch for TV sets and radios. The switch section is mounted on the back of the pot and is switched off when the pot shaft is rotated fully anticlockwise. You may also come across switchpots in which the switch is pushon, push-off or pull-on, push-off. These are preferred by some designers because the switch can be operated without rotating the pot and so there is less wear on the resistance element. On oscilloscopes too, you will find combination switches and pots, usually for the amplifier and sweep controls. These are not conventional switchpots but are combinations of multiwafer switches with a pot section mounted at the back and operated by concentric shafts. Resistance characteristics Talking about resistance characteristics of potentiometers is really opening a "can of worms" since many manufacturers do not use the same coding. Fortunately, you will normally only come across three different resistance characteristics. They are linear, log (short for logarithmic) and antilog. The linear pot is easy enough to understand. The resistance between one of the outside terminals and the moving contact varies in a linear fashion; ie, directly proportional to the shaft rotation. You can check this by setting a linear pot so that the shaft (or knob) is set to exactly half rotation. Then if you measure the resistance between the centre (moving contact) terminal and the outside terminals you should get a result which is close to half the total resistance. Linear pots are often (but not always) designated by an "A" stamped on the case. Some manufacturers use "B" instead of Both the resistance element and the moving contact can be clearly seen in this very large wirewound potentiometer. It can dissipate over 200 watts. "A". Logarithmic pots are normally used for volume controls on audio equipment and on TV sets. What happens with a log pot is that the resistance increases more rapidly for the first half of the shaft rotation and then more gradually for the remainder. This is done to make the volume control seem audibly progressive and to compensate for the more or less logarithmic response of our ears. Log pots are usually designated by a "C" stamped on the case. And as you might expect, an antilog pot is the reverse of a log pot. Combination log and antilog pots ganged to,1Iether are often used as the balance pot in stereo amplifiers. Multiturn pots The normal potentiometer has a rotation range of less than a full cir- Switchpots combine a potentiometer and a switch in the one body. The switch contacts are mounted on the hack of the pot and are opened when the pot shaft is rotated fully anticlockwise. cle; normally it is close to 300°. These are perfectly satisfactory for most applications but where precision setting of a pot is required, designers often specify multiturn potentiometers. Typically, these have 10 turns of rotation from one extreme to the other and allow for very easy adjustment. Trimmers and trimpots Trimmers and trimpots are the same thing. They are miniature versions of potentiometers which are usually adjusted by means of a screwdriver. They are normally set once and then not touched again for the life of the equipment they are in. They are used in a host of applications where once-only or infrequent adjustments are required to set levels, calibrate signals, set quiescent currents or voltages and so on. Trimpots are depicted on circuits as shown in Fig.4. This is a variation on the pot symbol shown in Fig.1 except that the wiper is shown as a slider instead of an arrow. SEPTEMBER 1989 9 As the name suggests, wirewound potentiometers have a circular wirewound resistance element hut the principle is the same as for carbon pots. The advantage of wirewound pots is that they can dissipate more power than carbon types. Another variation is shown in Fig.5 which is based on the rectangular symbol for a resistor. As a further indication that a pot is a trimpot, they will often be labelled on the circuit diagram as RVl, RV2 and so on or perhaps VRl, VR2 etc. Wide variety Trimmers are available in a huge variety of shapes and sizes and resistance elements. As well as the common carbon track and wire wound types there are moulded track and conductive plastic varieties and one you will often come across: cermet. "Cermet" is a contraction of ceramic metallisation and refers to a resistance track which is made with fine metal particles in a glass base fused to a ceramic former. The resulting element can dissipate relatively high power within a small area. The disadvantage is that the wiper wears rapidly so cermet trimpots can not be adjusted very many times before they start to give trouble. Most carbon trimmers look like skeletal versions of pots (ie, no outer case) but there are also sealed or totally enclosed versions 10 SILICON CHIP Trimpots come in a wide variety of shapes, sizes & resistance elements. They are used where once-only or infrequent adjustments are required to set voltage or current levels or to calibrate equipment. which are generally a little more expensive but more reliable in the long run. Trimpots are also available in multiturn versions, usually around 10 or 15 turns , and these have the advantage of easy and very precise adjustment. ~ SUBSCRIBE SUBSCRIBE SUBSCRIBE [! et 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. • • • • • • [j !1 ii !! Police radar: it's not always right t} 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 New subscription D Renewal 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 Australia NZ & PNG (airmail) Detach Coupon and Mail to: FREEPOST 25 SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROY BEACH NSW 2097 *No postage stamp required in Australia. Overseas surface mail Overseas airmail 2 years (24 issues) D $A84 D $A65 D $A62 D $A 120 D $A130 D $A130 D $A240 Enclosed is my cheque/money order for $ _ _ _ or please debit my D Bankcard Card No. I D Visa Card Ii D MasterCard 111111111 I Signature _ _ _ _ _ _ _ _ _ Card expiry date_ _ / __ /_ _ ~ Jio L _______________________ J SEPTEMBER1989 11 VINTAGE RADIO By JOHN HILL Valve portables - hard on batteries Portable radio receivers date right back to the early days of radio. Even then, the idea of being able to listen to radio programs, no matter where you went, had a certain amount of appeal. Portable radio was also another avenue to be exploited in order to sell wireless receivers. Early portables, particularly those from the late 1920s era, were strictly for strong arm types only. The word portable should have been used with inverted commas for these early receivers were only marginally smaller than other radios of the day. A particular advertisement from the late 1920s is a source of great amusement to me if no-one else. The advert shows J3. woman carrying a huge "portable" radio but she is shown only from the waist down. Presumably, the reason for this is not to reveal the pained expression on her face due to the weight and size of the receiver. Either that, or they hired a muscle man for the purpose of the photograph and didn't wish to show him full length. The possibility of getting a hernia while lugging around an early portable was real; so too was the risk of falling out of a tree whilst trying to place an extension aerial in a favourable place so that some form of reception was possible. A frame or loop aerial at ground level was not the best way to pick up a signal at some country picnic ground situated miles from the big city stations. Most valve portables, even late model ones, had some provision for an external aerial. But let's not be too critical. Every new idea must have a starting point somewhere - no matter how absurd it may seem to be some half century or so later. It is marvellous what 50 years of intense development can do! Just how effective those very early portables were is just about anyone's guess these days but some of them must have worked well enough to sustain interest in this type of radio receiver. There have always been portable radios and they held a lot of appeal for those who liked the outdoors. The thought of being able to laze in the sun while listening to the races or the cricket inspired many to buy a portable radio. However, valve portables had a few problems that made them something of a disappointment to many owners. Expensive batteries The big 8-inch speaker used in one particular Healing vaive portable dwarfs the transistor radio shown in the foreground. The cabinet is of leatherette covered timber. 12 SILICON CHIP Although size and weight must have been some disadvantage, the expense of batteries was perhaps the major drawback with valve portables. Unlike transistorised equipment, a valve portable needs two power supplies in the form of "A" and "B" batteries. The "A" battery provides the low tension supply for the valve filaments, while the "B" battery or batteries are used for a high tension supply. "A" and "B" batteries have con- A valve portable is powered from a 1.5V "A" battery (for the valve filaments) and two 45V "B" batteries which provide the high tension supply. Compare their size to the modern 9V transistor battery in the foreground. aspect of their operation is a bit of a humbug - particularly as the batteries are no longer made. There are two choices to make with these old portables: you either collect them or you don't collect them. If you collect them you can either just clean them up and display them or get them going and use them. Using an old valve portable can be a lot of fun. There are few things that attract more attention than a dirty great big old 1940s-style portable radio at a picnic or some other outdoor function. It is not only a great topic of conversation but it can also lead to finding other old radios. It always pays for collectors to advertise their interest and having a working valve portable is one way of doing it. Providing power This photo shows an old Hotpoint portable, together with its batteries. The batteries took up a considerable amount of space inside the cabinet. siderably different life spans and one would expect to replace the "A" battery at more regular intervals than the "B" battery. Buying a full complement of batteries was a costly experience. In fact, valve portables were so expensive to run they often had only a couple of sets of batteries, after which the novelty wore off and the set was put into a cupboard and forgotten. I base that last statement on the fact that there are so many valve portables about which still work OK. The cost (in batteries) to wear out a set of valves would have been phenomenal and in many instances valve portables were simply put away because the average working man really couldn't afford to run one. From a collector's point of view, old portables generally don't hold much interest unless one is enthusiastic enough to specialise in them as an unusual aspect of valve radio. Most collectors will give them a miss because the battery One major problem regarding these old portables has already been mentioned and that is the unavailability of "A" and "B" batteries. Therefore, if one is to use these obsolete portable radios, suitable batteries must be improvised. An "A" battery can be easily made by wiring up half a dozen standard "D" cells. Connecting them together in parallel will produce a battery that will keep the valve filaments glowing for quite some time, especially if the set is used sparingly. The makeshift battery can be wrapped in brown paper, masking tape or placed inside a suitable size cardboard box. Likewise with the "B" battery. A 90 volt battery can be made up using 10 9V transistor batteries. These must be connected together in series and, as before, taped together to keep them tidy and prevent short circuits. If you are really keen, the improvised batteries could be disguised by placing them inside some original battery boxes. The old batteries could be carefully removed from their packaging and replaced with new dry cells, thus dressing up the replacement battery to look like the real thing. Incidentally, the average 4 or 5-valve portable consumes 8-10 milliamps of "B" battery current SEPTEMBER 1989 13 Some receivers have a control knob marked "economy" for this purpose but lower battery consumption means less performance and is therefore only suitable for local station listening. AC-DC sets Most old valve portables were big and heavy, with no attempt made to miniaturise components. This old valve portable used all standard size components. Not all valve portables were for battery operation only; some were of the AC-DC type. These more versatile portables were fitted with a small power transformer, a rectifier valve and/or a metal oxide rectifier to convert the AC voltage from the mains to DC voltages. Now many of these AC-DC sets can be nasty things to play around with for the simple reason that they can have a live chassis when operating on AC power. That means that the chassis can have a 240 volt AC potential and to touch such a chassis under the wrong circumstances could be fatal. Speaking for myself, I consider that I am much too young to die and I am sure that you feel the same way. · So be careful when working on an AC operated portable. They can bite unexpectedly if you are unwary. It is wise to check out the chassis potential with a multimeter set to the AC volts scale. Test between chassis and earth. This simple check could well save your life. The old & the new This spiderweb wound aerial is cqnsiderably different to the ferrite types used in modern-day portable transistor radios. The protruding wire is for an external aerial connection. which is about the same rate of discharge that a 9V transistor battery would receive in normal service. So the improvised 90 volt battery will last a reasonable time and is usable down to around 50-60 volts. Naturally, as the "B" battery voltage drops, so does the performance of the set. On the other hand, the "A" battery consumption on a valve portable is around 250-300 milliamps. For this reason, the "A" batteries require replacement at more frequent intervals. 14 SILICON CHIP Today, as was the case 40 years ago, batteries are expensive and it will cost quite a few dollars to set up any old valve portable to run from battery power. Whether it is a worthwhile exercise or not is entirely up to the individual. Unlike a transistor radio, the volume that a valve radio is operated at has little or no effect on battery consumption. The only way battery life can be extended is to place a small resistor in the filament circuit. This will reduce both "A" and " B" battery consumption. Comparing a valve portable with a modern transistor radio is an interesting exercise for there are so many incredible differences. Let's take a quick look at some of the more obvious ones. The most noticeable difference is size and weight. Almost no attempt was made to make valve portables small and most used stock standard full size radio components. Only in a few instances were there valve portables made that could be described as being small personal portables. Many of the portables from the early post-war period had large wooden ea binets that were covered in leatherette. They still retained the steel chassis type of construction that was typical of the valve era. Although these sets were supposed to be portable, the only thing that made them portable was the 'P11 blems? ... and you don't have our .120page catalogue . .. This metal-cased valve portable from Philips featured a sliding dial shutter that also functioned as the on-off switch. The invention of the transistor made valve portables completely obsolescent. fact that they were cordless and fitted with a carrying handle. Miniaturisation never entered into the equation in those days. Some portables were built with quality of sound in mind and a particular Healing model was actually fitted with an 8-inch (20cm) speaker. Now that's something you're unlikely to see in a modern tranny! Philips made a range of pressed steel portables that had quite a few variations. Some were batteryoperated only, while others were AC-DC models. Some models also had a neon-like tuning indicator which was probably pretty useless anyway. Other models had a sliding shutter that covered the dial when the set was not in use. This cover also activated the on/off switch and the set automatically switched on when the shutter was slid up to uncover the dial. These Philips portable radios also had a large loudspeaker, although not quite in the same class as the previously menti oned Healing. If anything has been truly superseded it would have to be the valve portable. The transistor made it completely obsolete. However, despite the fact that these old portables are pretty useless today, they represent the best the radio industry could offer prior to the solid state era. While these old battery radios have a few problems regarding suitable power supplies, there is no reason why they shouldn't take their place in your vintage radio collection. ~ .,.m•..;. r..1;:.:.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 . At last . .. a TRADE catalogue for the consumer ARISTA ... your one-stop problem solver. Video plugs and sockets .. . Video extension speakers . . . Video flyleads . . . Video RF interference filters . . . Video splitters . . . Indoor antennas . .. Video switching units ... Down converters .. . Video speaker controllers ... Video camera lights . . . Video tape rewinders . . . Video cine adaptors . . . Video head cleaners ... Video splicing kits .. . Video storage cases . . . Video dust covers . . . Video leads . . . Scart plug leads . .. Video dubbing kits .. . Video headphones .. . Video shotgun and wireless microphone systems ... Pre-amplifiers with video inputs . . Video camera stands . .. Just about anything you want. ... Try us ... NOW! Get your catalogue FREE from your local ARISTA dealer or send $2.50 P&H and your return address to: ART~ ELECTRONICS PTY LTD PO BOX 191, LIDCOMBE, NSW 2141 651 Forest Road, Bexley, NSW 2207. Phone (02) 587 3491. SEPTEMBER1989 15 The easy way to view small objects Scopeman large screen video microscope One of the most intriguing instruments we have come across for a while is the Scopeman. It is a medium power microscope which is not viewed directly but via a conventional colour TV receiver. It makes viewing small objects at high magnification as easy as pie. By LEO SIMPSON Getting a close look at an object is not easy, when you think about it. Sure, we have had magnifying glasses and microscopes for several hundred years but these are not necessarily the easiest to use. Say you want to closely inspect a finely tracked printed circuit board for the quality of its platedthrough holes or the solder joints for surface mount components. You really need the magnification of a medium power microscope but putting a large printed circuit board at the focus of a microscope and lighting it properly is not easy at all. Even when you are able to set up a microscope to view a board, only one person at a time can look at the image, squinting through the eyepiece. Wouldn't it be so much The Scopeman is dead easy to use. Just place the camera handpiece directly on the object to be viewed and it comes up in glorious colour on the screen. Note the light from the camera which is via optical fibres. 16 SILICON CHIP easier if you could just bring a miniature video camera right to the object and then view the image on a colour television monitor? Wouldn't it, indeed? That's just what the Scopeman does. Just place its camera head right on the object to be viewed and its image appears at large magnification on the colour screen. For example, take the camera head and place it over a standard metal film resistor which may only be 3.5mm long, with five colour bands which are very hard to decipher. The result is a huge image of a resistor, 17 5 long, with brilliant colour bands which are easy to read. No camera shake You don't have to worry about camera shake or bringing the object into careful focus or the lighting. It's all just so easy. As long as you can place the camera head directly on or over the object to be viewed, it will always be in clear focus, even at the highest magnification. Having tried the Scopeman at our Collaroy, Sydney premises, we were fascinated. We then had no trouble coming up with a long list of applications both within the electronics industry and outside. In fact, while it has obvious applications in the electronics industry, there are many, many more outside it. For example, in the electronics industry, the Scopeman is ideal for printed circuit board inspection, at all stages of manufacture. It can examine the various stages of etching, cleaning, plating through of holes, centring of holes and quality of plating on edge connectors. This shows how dramatic the Scopeman can he. Jean Reynert holds the camera handpiece directly over two resistors on a disc drive. The resistor bodies are actually 3mm long. Magnification on the screen is 50 times. Other lenses give magnifications of 100, 200, 400. On a good quality computer board, the edge connector electrodes look like substantial slabs of gold! In the record pressing industry, the Scopeman can easily examine the surface quality of metal stampers and pressings. It can also examine video heads and drums for wear, as well as capstans, tape guides and the rest of the complex mechanism of a video recorder. Many applications Those are just a few applications in the electronics industry but when you look outside the industry the list gets a great deal longer. For example, in medicine, the Scopeman is a handy tool for diagnosing skin conditions. It has obvious application in pathology, in police forensic work, examining fingerprints, the rifling on bullets, paint damage on vehicles and so on. In horticulture, the Scopeman is a wonderful tool for examining plants and leaves, in detecting plant disease and looking at leaf structure. In geology, the unit is excellent for looking at minerals, fossils, shells and corals. It also has application as a crack detection tool in the automotive and engineering fields, for close examination of antiques, paintings and jewellery and in the fields of printing, entomology (studying insects) and textile manufacture. In fact, it can be used for virtually any application which requires a medium power microscope. Technical details In essence, the Scopeman is not a microscope at all but is a handheld colour video camera with its own internal light source and fitted with a close-up lens. The unit we examined was the Scopeman MS-503 which is a desktop unit about the size of a personal computer. It measures 350mm wide by 120mm high by 350mm deep. On the black front panel it has two knobs which control the light intensity and the selection of optical filters. In between these two selector knobs is a large multipin socket which is a camera ea ble connector. The camera unit is quite small, about 150mm long and with a diameter of 25mm. It has a number of interchangeable lenses which simply screw on and off to change the magnification. The inbuilt light source is a 100 watt halogen lamp with a dichroic SEPTEMBER 1989 17 selected to optimise the image. Besides red, sky blue, blue and green filters, there is one for infrared and one neutral density filter. Automatic or manual white balance is also provided. The internal light source is 3200°K. Magnification factors This untidy mess is actually Leo Simpson's hair, magnified 50 times on the screen. It looks just like monofilament fishing line. mirror. The light from the lamp is passed to the camera head via optical fibres. In this way, the light is aimed exactly at the image which is therefore always amply lit, regardless of the ambient lighting. The camera itself is a ½-inch CCD (charge coupled device) image sensor with approximately 270,000 picture elements. In conjunction with the MS-503 desktop unit, it produces a standard composite PAL video signal which can be displayed on any colour monitor. The recommended monitor size is 34cm. Larger sizes would be good for classroom applications but the 34cm size is best for viewing by the user of the camera head. The camera has an automatic iris which adjusts to give best picture contrast within a second or so of a recognisable image appearing on the screen. Once that has happened, the user can then adjust the brightness of the light source to bring out the wanted highlights in the image. Various filters can then be This is "closed cell" grey foam rubber at 50 times up. On the screen it looks multicoloured, like soap bubbles. 18 SILICON CHIP Four lenses are available giving effective magnifications, assuming a 34cm video screen, of x50, xl00, xZ00 and x400. Interestingly, the lenses themselves do not provide the high magnification; most of it is the natural enlargement between the ½-inch CCD image sensor and the video screen. The four lenses have actual magnifications of xl, xZ, x4 and x8. Each lens has a transparent plastic cap over it and when this is placed directly on the object to be viewed, the image will automatically be in focus . Because the lenses have such low magnifications they also have quite reasonable depth of field, ranging from ± 0.4mm for the x50 magnification to ± .05mm for x400 magnification. It is because of this depth of field and the low lens magnification factors that the Scopeman is such an easy instrument to use - much easier than a conventional microscope. As an additional capability, the Scopeman can be linked to a video recorder so that images ca n be stored for later reference. There is also an optional video still recorder All Japanese watches have a serial number on the dial but you need a Scopeman to read it (50 times mag.). LOOK AT THESE BARGAIN PRICED KITS OUR LATEST UHF REMOTE CONTROL (EA JAN 89 and APRIL 89) • • • High Security , Low Power Consumption . Switch and Indicator Relays. Up to 50 metre range. COMPLETE KITS TRANSMITTER & RECEIVER ONLY $49.90 Extra Transmitter Kits $17.00 ea PASSIVE INFRARED MOVEMENT DETECTOR (EA MAY 89) • • Uses Special Dual Element Pyroelectric Detector. Kit includes two Lenses. SPECIAL BARGAIN PRICE $34.95 Interface Components $7 .95 extra. 16 CHANNEL UHF REMOTE CONTROL (EA NOV 88 and MARCH 89) This is closeweave polyester fabric at 50 times up. All fabrics under this ma gnification show quite wide variations in colour. • Package including Transmitter, Receiver and Four Channel Relay Drive r, plus indicator. SPECIAL $119.00 THE MICROPHONE (EA NOV 86) • • • Professional Qu ality Up. to 1 V RMS Output , Drives any Amplifier , even HI-FI Line inputs. Touch Control. COMPLETE KIT $24.99 MAINS MUZZLER (SC JAN 89) Short Form kit similar to the Mains Muzzler including the Torroid, 3x0 .0 22uF/400V metallised polyester capacitors , 1 M ohm 1 W resistor and a 275V/ 40joule Varistor THE PRICE? ... ONLY $7 .40 That's less than the price of the Varistor! ULTRASONIC MOVEMENT DETECTOR/ALARM • • • • High Qu ality Crystal Controlled Kit. Prewired Transducers. PCB & Componen ts plus ABS Case. Relay Outpu t. COMPLETE KIT $42.95 BANKCARD, MASTERCARD and VISA ACCEPTED WITH PHONE ORDERS. P&P FOR ANY OF THE ABOVE $2.50. OATLEY ELECTRONICS A ballpoint pen under high magnification is fascinating; you can see the ink flowing back round the ball after the pen has been used. using floppy discs which could be very useful when the Scopeman is used in production or analytical laboratories. The cost of this instrument? W ell, as with any specialised optical or electronic instrument it's not cheap but it is still quite MAIL: PO Box 89, Oatley, NSW 2223 SHOP: 5 Lansdowne Pde, Oatley West. PHONE: (02) 579 4985. reasonably priced for its capabilities at around $15,000 plus tax, excluding the cost of the monitor . For further information, contact the distributors, Clarke & Severn Electronics, PO Box 129 , St Leonards, NSW 2065. Phone (02) 437 4199. ~ You can also buy some of our Kits at the following Distributors. Slightly higher prices may apply. NEWCASTLE - NOVOCASTRIAN (049) 62 1358 MELBOURNE - ELECTRONICS WORLD (03) 723 3860 WOLLONGONG - ITEC (042) 26 4044 SEPTEMBER1989 19 ~ ~ ~ 'P. , .II t _, ¼ , &) ri\o Cl{EO TEREO: WIDE-BAND AM STEREO 1- 2-Chip Stereo Radio You won't believe how good stereo AM radio can sound until you build this nifty little Walkman-style receiver. It's based on Motorola's brand new MC13024 IC which is virtually a complete AM stereo radio on a single chip. By STEVE PAYOR AM stereo W alkman-style radios are very thin on the ground in Australia or anywhere else for that matter so this little receiver is a big step forward. As far as most people are concerned, it sounds every bit 20 SILICON CHIP as good as FM stereo, unbelievable though that may seem. It has low distortion, wide bandwidth and wide stereo separation. It is also small and delightfully easy to tune. All you do is rotate the knob to light the LED indicator and then a moment or so later the sound flicks from mono into high and wide stereo. You listen via headphones, just as you do with any other Walkmanstyle receiver. And it is powered from just two penlite cells so batteries won't cost a mint. Best of all, you can build and align it yourself without any need for fancy tools and equipment. When you've got it going, you will have an AM stereo receiver of which you can be justifiably proud. It is hifi in a small package. Let's now discuss how the circuit works. Some of this description may 8 < m a u Cl i ::. , °l Above: virtually all the parts for the AM stereo receiver are mounted on a small PC hoard to give a compact assembly. The MC13024 IC is almost in the centre of the hoard. The completed receiver, shown on the facing page, is delightfully easy to tune and delivers hifi sound. be little foreign to you because it assumes some knowledge of how a superheterodyne radio works. But read on anyhow - you'll learn a lot! How it works The heart of this unique little receiver is a brand new chip [fresh out of the oven, in fact) from Motorola, the originators of the CQU AM compatible AM stereo system used by all AM broadcast stations in Australia. This chip is designated the MC13024 [ICl) and represents a considerable extension of the popular MC13020 AM stereo decoder IC. As well as a C-QUAM decoder, the MC13024 contains a sensitive mixer, a voltage controlled local oscillator [VCLO), an intermediate frequency [IF) amplifier, automatic gain control [AGC) and automatic frequency control [AFC) circuitry, a stereo pilot tone detector, a signal quality detector and a complete AM stereo decoder. By adding a modest number of passive components around the chip and a stereo head- phone driver amplifier, we get a complete AM stereo receiver. Another feature of the MC13024 is that it will operate from a supply voltage as low as 1.8V, with a current consumption of only 5mA. This makes it ideal for battery operation. Fortunately, it is not necessary to fully understand the intricacies of the C-QUAM [Compatible Quadrature Amplitude Modulation) process to use this IC. Superficially at least, the circuit diagram is no more complex than most ordinary integrated circuit AM radios. We will describe those features peculiar to stereo reception as we come to them. Signal & oscillator frequencies The incoming radio signals are picked up by the antenna coil (Ll) which is tuned to resonance at the signal frequency by variable capacitor C3. C3 forms one section of a ganged pair. The other section, C4, tunes local oscillator coil 12. The two sections of the tuning gang are designed so that the oscillator frequency will always be exactly 450kHz higher than the signal frequency. This difference of 450kHz is equal to the intermediate frequency (IF) of the receiver more about this later. Thus, as the signal frequency is varied from 531kHz to 1602kHz [the limits of the Australian broadcast band), the oscillator is tuned from 981kHz to 2052kHz. For this reason, the maximum capacitance of C4 is less than C3 (90pF vs 160pF). Precise tracking of the two frequencies is achieved by careful adjustment of 11, 12 and two small trimmer capacitors which are built into the top of the tuning gang. We have also added two small fixed capacitors across C3 and C4 (4.7pF and 8.2pF respectively) to bring the trimmers to the centre of their adjustment range. The precision of the tuning gang is most important, which is why we have specified the Tako HU-22124 type in preference to more common "no name" varieties. With this gang you can be sure that the frequency calibrations will be within a pointer's width across the entire dial. By the way, this SEPTEMBER1989 21 The only parts not mounted on the PC board are the batteries and the on/off switch. Note that close tolerance components must be used in some sections of the circuit, so be sure to obtain the exact parts specified in the parts list. gang also has two additional sections, marked Cl & C2, which are for FM tuning. These are not used in this circuit. The pre-wound antenna coil (11) is a standard "transistor radio" item, usually supplied wi.t h a short piece of flat ferrite rod. We have specified a much longer (100mm) ferrite rod for superior longdistance reception. The signal from the antenna coil is coupled to the low-impedance RF input (pin 10) of ICl via a small secondary winding. Note that the RF input of the MC13024, as well as the inputs to the pilot filter circuitry, are biased to + 1V DC from an on-chip voltage regulator, the output of which appears at pin 15. The ceramic filter bandwidth determines the upper audio frequency response limit (12kHz) and, unfortunately, the amount of broadband and adjacent channel noise as well. We have found ± 12kHz to be a suitable compromise for reception of local stations. To the hifi enthusiast, an audio bandwidth of 12kHz may seem a bit ordinary but it is not much different from the 15kHz bandwidth broadcast by FM stations. Hearing is believing as far as this aspect is concerned, and we think that you will be amazed at the sound quality this little receiver can achieve (given a good program source). Anyhow, back to the circuit description: ting, the IF output is connected directly to the top of 14, giving a slight amount of damping and widening the - 3dB bandwidth to around ± 9kHz. This is probably the best compromise between noise, sensitivity and audio bandwidth if you are interested in country as well as local radio reception. For city dwellers who are used to the sound of FM radios, the wide setting is the one to go for. This is selected by soldering both the medium and wide pads, which puts an additional lO0kn of damping across 14. This widens the bandwidth to :J;: 12kHz with just a slight loss of sensitivity. Mixer & IF stages IF amplifier & bandwidth selection The output of the IF amplifier is internally connected to an envelope detector, much the same as in a normal AM radio. The amplitude (or envelope) of a C-QUAM AM stereo signal is modulated with the sum of the left and right audio channels, so when the signal is demodulated in an ordinary radio, the signal you get is 1 + R (ie; the monaural sum of the stereo components). This is the key to the compatibility of the C-QUAM system with existing AM radios. When the MC13024 is in monaural mode, the output from the envelope detector (1 + R) is fed through to both audio outputs. The average envelope amplitude is a measure of the signal carrier strength and this voltage is used to adjust the gain of the mixer and IF The signal from the RF input is amplified and "mixed" with the local oscillator signal to produce a difference frequency of 450kHz, which appears at the mixer output (pin 11 ). Coil 13 is broadly resonant at this frequency and transforms the relatively high output impedance of the mixer down to the relatively low input impedance of the ceramic filter. The ceramic filter requires a resistive source impedance of approximately 2kO, so the output of 13 is loaded with a 2.7kO resistor to achieve this. The Murata SFP-450D ceramic filter contains four coupled resonant elements and provides an almost rectangular bandpass characteristic of 450kHz ± 12kHz at the - 6dB points. 22 SILICON CHIP The signal from the ceramic filter is amplified by the IF amplifier, between pins 16 and 19. At the output of the IF amplifier is another 450kHz tuned circuit (14) which can be wired for three different bandwidths: wide, medium or sharp. These a re selected by bridging some tiny solder pads on the underside of the PCB. In the sharp setting, the IF amplifier output is tapped about half-way up the coil, giving minimal damping of the tuned circuit and a very sharp resonance - approximately ± 3kHz at the - 3dB points. If you are interested mainly in interstate reception, where noise is a real problem, use this setting. For the medium selectivity set- Envelope detection & AGC amplifier to maintain a constant output level, regardless of signal strength. Any audio fluctuations are removed by the AGC filter which consists of a large internal resistance at pin 17 and an external 3.3µF capacitor. This sets the AGC time constant. In practice, the ACG voltage swings from slightly above the + 1V reference on weak signals to slightly below on very strong signals. Note, however, that the MC13024 uses a "delayed AGC" system for optimum signal to noise ratio. As the signal strength increases, the IF gain is reduced first, which reduces not only the signal but also the noise from the mixer. Further increases in signal strength then cause the MC13024 to reduce the mixer gain, to prevent overload. The result is that stations which vary by as much as 50dB in signal strength all sound about the same. This also means that it is not practicable to align the tuned circuits "by ear". We have therefore made the AGC voltage available at the edge of the circuit board, so that a multimeter can be used as a tuning indicator during the alignment procedure. In addition, an optional BC549C high-gain transistor (Q1) is used as a current amplifier to drive low impedance (50µA) moving coil multimeters, without disturbing normal operation. :z....,__...,,...1±: 0 O F-,•· + ....... 0 a: w > jjj (.) w a: w ...J ;;; al ~ I· a: 0 c. 0 w a: w ~ ~ ~;: :l!: i~~ ....--------;li <( NZ "' ,-. r--------1,~K ,a!: Phase detection & stereo We have already mentioned that the L + R (ie; mono) information is contained in the amplitude of the CQUAM signal. To complete our stereo signal we also need the L - R information, and this is contained in the phase of the C-QUAM signal. To extract the phase information, the MC13024 IC locks onto the average phase of the incoming signal using a phase locked loop ~§1""''-+-_..,,gMr-.,._-l~HI• -"';;o -·---'-"~!:; "' .,._-... ~-~M----1~~~ > "'+ "' "' c..a! " d > -o ...__ _-'+'-+'-'f'------og <C -----------4------o-w +"' > U.: (PLL). " Fig.1 (right): the heart of the circuit is the MC13024 IC which is virtually a AM stereo tuner on a single chip. Its left & right channel outputs drive a TA7376P stereo headphone amplifier IC. LED 1 provides tuning and stereo indication. SEPTEMBER1989 23 2-CHIP AM STEREO RADIO - CTD First of all, a stable 450kHz reference signal is required for the MC13024's internal phase detector. This is obtained from a 3.6MHz reference oscillator (tuned by 15), which is divided by eight internally to give the required 450kHz reference. The reason for running this oscillator at such a high frequency is to prevent its output signal from interfering with the broadcast signal. Nevertheless, for reception of very weak signals, the MC13024 shuts down the reference oscillator and internal dividers, to minimise " birdies" . In practice, the phase of the IF signal is compared with the phase of the 450kHz reference to derive an error voltage. This error is then fed back to adjust the local oscillator frequency, to bring the IF signal into phase lock with the reference. Two "pull in" speeds are used in the phase locked loop: a fast speed to give rapid lock as soon as a signal is tuned within the capture range, and one 50 times slower for precise fine tuning and low phase distortion. The PLL filter at pin 7 allows the loop to track slow deviations of the signal phase but not the L - R audio fluctuations. The 100 resistor in series with the 22µ,F capacitor damps the response of the loop so that it doesn't overshoot when locking onto a signal. When phase lock has been achieved, the MC13024 turns on the LED connected to pin 3 at half brightness. Full brightness comes a little later when, all being well, the MCl 3024 switches into stereo mode. Automatic frequency control You may well ask just how the local oscillator frequency is shifted when it is already set by the tuned circuit of 12 & C4. The answer lies in the fact that the resonance of the tuned circuit is not infinitely sharp. By advancing or r etarding the phase of the oscillator drive at pin 9, the MC13024 can pull the 24 SILICON CHIP oscillator frequency slightly to eitheT side of the resonant frequency. The 2 70 series damping resistor in the oscillator tuned circuit broadens the resonance and thus sets the locking range of the PLL. The locking range we have chosen is approximately 6kHz, and is fairly constant across the entire tuning range. Having a 6kHz locking range makes precise tuning a breeze, even without any form of vernier reduction drive on the tuning knob. All you have to do is turn the knob until the LED comes on and the MC13024 does the rest. Stereo decoding When the circuit is tuned to a stereo signal and the LED indicates phase lock, any phase fluctuations in the signal will be interpreted by the MC13024 as L - R stereo information. (Note: a full description of how this is done would take several pages. Readers who want all the details can refer to the data sheet for the MC13020 stereo decoder in the Motorola " Linear and Interface Devices " data book). Once the L - R signal is extracted, all that remains is to add and subtract it to the L + R mono signal to get our required stereo outputs. The MC13024 does this gradually, so there is a smooth "blend" from mono to stereo without any nasty pops. The mathematics of this process is shown below. In mono mode, we have: (L + R) + (0) = L + R (L + R) + (0) = L + R In stereo mode, the signals blend to: (L + R) + (L - R) = 21 (L + R) - (L - R) = 2R Note that the total output from both channels is the same in both cases; ie. 2(1 + R). Thus the volume doesn't change during the blend, only the stereo separation. The MC13024 will not switch into stereo mode on just any old signal, however. Valid C-QUAM stereo signals are identified by a low-level 25Hz pilot tone which is added to the L - R information. Don't worry about being able to hear the pilot tone - you can't. In fact the amplitude is so low (4 % modulation or - 28dB) that it takes a fair bit of circuitry to extract it. The output of the L - R demodulator is fed via a high impedance to pin 8 where it is filtered by a .068µ,F capacitor and a lOOkO resistor. This removes most of the audio but the pilot signal is still too small to be recognised at this stage. Bandpass filter To overcome this problem, the low-pass signal is buffered by a x2 amplifier between pins 5 & 4 and is then fed to a high-Q 25Hz bandpass active filter. This effectively extracts the pilot tone (if it exists) from the surrounding low frequency noise. This bandpass filter consists of an internal x-1000 op amp between pins 1 and 24, plus an external multiple feedback network of precision resistors and capacitors. These give the passband filter a gain of 6.5 and a Q of 8.6. Note that the combination of high gain and high Q makes the component values rather critical. For example, a 5 % shift in the capacitor values could cause a 20% drop in pilot tone amplitude. For this reason, 2% capacitors and 1 % resistors have been specified for the feedback network. The output of the 25Hz bandpass filter goes to the MC13024's pilot detector. If the 25Hz signal is present for more than seven consecutive cycles, the MC13024 switches to stereo mode. It takes 300ms to count seven cycles, so you will notice a slight time delay between when you stop tuning and the stereo light coming on. You will also find that the MC13024 switches straight back to mono as soon as you start to turn the tuning knob again. If it didn't, the disturbance to the phase of the signal would be interpreted as a stereo component and the sound would "flutter". The 10µ,F "lock" capacitor on pin 13 determines the sluggishness with which the decoder enters or leaves the stereo mode. Volume control The left and right audio output signals from the MC13024 are filtered by low-pass RC networks before reaching the volume control (VR 1) and again afterwards, to make sure that no IF signal components make it to the audio power amplifier. Even a few millivolts of RF here would find its way back into the front end of the tuner and cause all sorts of whistles and howls. Remember - the antenna is only centimetres away from the power amplifier circuitry. The .068µF coupling capacitors in series with the volume control roll off the low frequency response at 25Hz. There is no stereo balance control on this receiver nor is one really needed, as the channel matching is excellent. This is partly due to the "full-size" volume control pot specified. Maintaining balance at the very bottom end of the volume control is a little tricky though, as the slightest mismatch between the pot wipers will cause one channel to shut off before the other. We overcame this problem by inserting a 3300 resistor at the earthy end of each pot section. This preserves the balance at low volume levels. The minimum volume is just comfortably above the noise floor of the audio amplifier and should be low enough for most applications. If you prefer the minimum volume to be lower still, reduce the 3300 resistors to 2200. Audio amplifier IC2 (TA7376) is a complete stereo headphone amplifier in a 9-pin single in-line package (SIP). The only external components required are a number of bypass and coupling capacitors. The 22µF capacitors on pins 2 and 8 form part of the internal AC and DC negative feedback loops, while the 22µF capacitor on pin 7 is for an internal power supply ripple filter (common to both channels). The amplifier outputs are stabilised against high-frequency oscillation by two RC damping networks (2 .20 in series with O. lµF). As with all high-gain IC audio PARTS LIST 1 PCB , code SC06108891, 59 x 115mm 1 ABS plastic case with plastic I1d, 130 x 68 x 43mm 1 front panel label, 125 x 62mm 1 28mm dia. metal knob 1 22mm dia. metal knob 1 3.5mm PCB-mounting stereo headphone socket (see text) 1 2-cell side-by-side AA battery holder 1 battery snap connector 1 DPDT miniature slide switch (DSE Cat. S-2010, Jaycar Cat. SS-0821 or equivalent) 2 3/8-inch ID plastic P-clips (to fit around ferrite rod) 1 200mm length of light duty hookup wire (red) 1 200mm length of light duty black hookup wire 4 PC pins 1 1 OOkO log dual gang potentiometer Hardware 2 small right angle brackets (for mounting ferrite rod) 3 1/8-inch dia. x 1 /2-inch countersunk machine screws 4 1/8-inch dia. x 3/8-inch round head machine screws 2 M2 x 5mm pan head screws (to fit slide switch) 1 0 1 /8-inch full nuts 11 1 /8-inch flat washers 4 1/8-inch spring washers Parts for tuning dial 1 1 /4-inch dia. x 18.5mm extension shaft for tuning capacitor 1 1 O BA screw for tuning capacitor extension shaft 1 1/ 4-inch ID x 0 .5mm thick Teflon washer 1 29 x 47mm scrap of 1.6mmthick clear Perspex for cursor Parts for battery clamp 2 1 /2-inch long x 1/8-inch tapped spacers 4 1/8-inch dia. x 1/ 4-inch countersunk machine screws 1 82 x 33mm scrap of 1.6mm Perspex or aluminium sheet Semiconductors 1 Motorola MC13024P CQUAM AM stereo receiver (IC1) 1 Toshiba TA7376P stereo audio power amplifier (IC2) 1 BC549C NPN transistor (01) 1 3mm red LED (LED 1) Inductors 1 3/8-inch dia. x 1 00mm ferrite rod pre-wound AM broadcast band antenna coil (L 1 ); eg. from DSE Cat. L-0520 1 broadcast band oscillator coil (L2), Tako A7BRS-T1342AIX 1 450kHz mixer coil (L3), Tako A7NRES-T1341 AYN 1 450kHz IF coil (L4), Tako A7NRES-T1340AYN 1 3.6MHz reference oscillator coil (L5), Tako MF291 ACS-3688VL 1 Murata SFP-450D ceramic filter Capacitors 1 tuning gang, Tako HU-22124-MOOO-O 3 470µF 16VW PC electrolytics 4 22µF 16VW PC electrolytics 2 1OµF 16VW PC electrolytics 1 3.3µF 16VW LL electrolytic 3 0 .1 µF monolithic ceramics, 0.2-inch lead spacing 3 .068µF metallised polyester (greencaps) 2 .04 7 µF 2% polyester or selected 5% greencaps (see text) 6 .01 µF miniature ceramics, 0 .2-inch lead spacing 2 .01 µF metallised polyester 2 .0018µF metallised polyester 2 680pF miniature ceramics, 0 .2-inch lead spacing 1 8 .2pF NPO Philips miniature ceramic plate, 0.1-inch lead spacing 1 4. 7pF NPO Philips miniature ceramic plate , 0.1-inch lead spacing Resistors (0.25W, 5%) 2 1MO, 1 % 1 330k0 , 1 % 1 180k0, 1 % 2 1 OOkO 2 10k0 1 8.2k0 , 1% 1 2.7k0 2 3300 1 270 1 100 2 2 .20 SEPTEMBER 1989 25 This view clearly shows how the ferrite rod antenna is mounted on the PC board using aluminium brackets and plastic "P" clips. The four test points at bottom right are used during the alignment procedure. amplifiers, good high frequency bypassing of the power supply is essential. This is taken care of by a O. lµF ceramic capacitor right next · to the Vcc and GND pins of the TA7376. An additional 470µF electrolytic across the battery helps to extend the usable battery life by supplying the peak current demand on audio transients. On the subject of bypassing, you will notice quite a few .OlµF ceramic capacitors between Vee and ground around the RF circuitry, and also between the + 1V reference and ground. This effectively ties the ground and DC supply rail into an RF groundplane which serves to shield and stabilise the circuit. Although the TA73 76 is really intended for driving headphone loads (around 320 for the higher quality 26 SILICON CHIP types), it also does a pretty good job of driving a pair of 80 loudspeakers, provided they are not the insensitive "compact" variety. The maximum output is around 1V peak-to-peak, which translates into less than 20mW per channel into 80. But don't let this rather low figure put you off - try it and see. With normal headphones, there is sufficient available output to guarantee permanent hearing damage, so be prudent with the volume control. Batteries Both ICs will operate quite happily down to 1.8V but when you notice the stereo light dropping out on loud volume peaks, it is time to replace the batteries. You can expect several weeks of operation, 8 hours per day, from a pair of alkaline penlight cells. In fact, the current drain is low enough to give economical performance from the lesser battery grades. This brings us to an interesting point. The MC13024 and TA7376 both have a current drain of 5mA each and, at normal listening levels, the drain of the TA7376 only increases by a few milliamps or so. However, the tuning indicator LED draws about 5mA when it first turns on and about 20mA when indicating the stereo mode. We thus have a situation where the stereo indicator consumes twice as much battery power as the rest of the radio combined! Well that more or less completes the circuit description. Next month we'll continue with the construction procedure and give the alignment details. ~ Alarm-higgered telephone dialler This automatic telephone dialler can be added to any home burglar alarm system. If someone breaks in and triggers the alarm, the dialler will call a pre-determined number and transmit a beeping tone. By GREG SWAIN Many people have installed burglar alarms in their homes but not too many have bothered to add an automatic telephone dialler to their system. The main reason for this in the past has been the cost automatic telephone diallers can be expensive. Even so, an alarm triggered dialler is a good idea. By dialling a pre-determined number, it can immediately alert the owner or a third party if the alarm is triggered. All the owner has to do is enter in the number to be dialled before leaving the house. The other advantage of a dialler is that you can have a 'silent' alarm; ie, one that doesn't set off a siren. Instead of blasting the neighbourhood, the alarm can be used to dial a neighbour who can then check things out. Most sirens tend to be ignored (or cursed) by neighbours anyway, particularly if a system has been known to false trigger. Of course, use of the dialler doesn't stop you from also having a siren if that's what you want. At least it could be argued that a siren might scare the thief away. OK, so diallers are a good idea but can the cost be brought down to a reasonable level? Recently, the SEPTEMBER1989 27 R&D Department at Dick Smith Electronics decided to take a look at this situation. The result is the 'Alarm Phone Dialler' presented here. To keep costs down, DSE built their dialler around a low-cost pushbutton telephone with an automatic redial facility. This is connected to some fairly simple logic circuitry housed in a separate case to produce a complete alarm triggered dialler for just $79.95. That's about half the cost of the PARTS LIST 1 pushbutton telephone, DSE Cat. F5260-68 1 PC board, code ZA-1430 1 plastic zippy box, 1 50 x 90 x 50mm 3 1 2V SPOT relays 2 momentary contact pushbutton switches 1 battery snap connector 1 3-pin DIN socket & plug 1 2 .5mm DC power socket 1 9V DC plugpack supply 1 9 solder pins 4 9mm spacers 6 4BA x 1 5mm screws 6 4BA nuts 8 4BA washers 1 length of 8-way cable Semiconductors 2 7 4C 1 4 hex inverter (IC 1 , IC3) 1 4011 quad NANO gate (IC2) 2 TIL 126 (or equivalent) optocouplers (IC4 , ICS) 1 BC547 NPN transistor (01) 3 BC557 PNP transistors (02 , 03, 04) 1 red LED (D1) 19 1 N914 diodes D2-D18, D21 , D22 2 1 N4002 diodes (D19 , D20) Capacitors 1 1 5 1 1 00µF 35VW LL electrolytic 33µF 35VW PC electrolytic 1 0µF 25VW PC electrolytic 1µF 250VAC metallised polyester 1 0.33µF metallised polyester 4 .01 µF metallised polyester Resistors (0.25W, 5%) 3 2 1 8 28 1MO 470k0 220k0 100k0 3 18k0 2 10k0 3 1k0 SILICON CHIP commercial units. In practice, the logic circuit is used to take the telephone "off hook" and trigger the automatic redial facility. Well, that's basically how it works but there is quite a bit more to it than that, as we shall see. So, if you are out, you can call home and check whether or not your alarm system has been activated. If there's no answer, it means that everything is OK (either that or your alarm system has been foiled). Main features How it works Most house alarm systems provide a 5-25V DC output when triggered. It is this DC output that is used to trigger the logic circuitry in the dialler. After that, it's quite straightforward. Dialling is achieved by using three relays to make the relevant connections to the telephone. One relay is used as an off-hook switch (ie, it bypasses the normal hook switch in the telephone) while a second relay simulates the action of the redial key. The third relay is used only if the telephone you are using requires a 2-key sequence for last number redial. This usually applies to telephones with multiple memories. On these phones, last number redial is usually achieved by pressing the# key, followed by the Okey. At the same time that dialling takes place, the logic circuit pulses a beeper which is hidden inside the telephone handpiece. This signal is acoustically coupled to the telephone's microphone and can be readily identified by the person answering the called number. A simple delay circuit is also included in the circuit to set the overall call length. This means that the dialler automatically hangs up the phone after a preset time, whether the call has been answered or not. But that's not all the circuit can do. Once it has been triggered and made its initial call, the circuit also automatically answers incoming calls. It does this by monitoring the telephone line for ring voltages. When the ring signal is detected, the telephone is again taken offhook and the beeper activated to warn the caller that the alarm system has been triggered. Then, after a short period of time, it hangs up again. All subsequent calls are then answered in similar manner until the Reset button on the front panel is pressed. Fig.1 shows the circuit of the Alarm Triggered Phone Dialler. The first thing to note is that the telephone line is isolated from the rest of the circuit by IC4 which is a TIL126 optocoupler. This provides about 5kV of isolation between the phone line and the ring detect circuit (IC3a & IC3b). We'll come back to the ring detect circuit later on. Initially, we'll concentrate on the alarm interface circuit and the dialler logic. As previously explained, the dialler is triggered by a 5-25V signal from the alarm. This signal is applied to optocoupler IC5 and turns on the internal transistor connected between pins 5 & 4. This means that pin 5 of IC5 goes low when the alarm is triggered. NAND gates IC2c & IC2d form an RS flipflop. Normally, in the Reset state, pin 10 of IC2c is low while pin 11 of IC2d is high. Similarly, IC2b & IC2a form a second RS flipflop with pin 4 normally low and pin 3 high. Thus, all relays are off and the tone generator circuit (IClb-ICle) is disabled. When the alarm is triggered, pin 8 of IC2c and pin 6 of IC2b are pulled low. This toggles the RS flipflops to the Set condition and sets off a whole train of events. To trace these through, we'll need to look at each of the RS flipflop outputs in turn. Let's start with pin 10 of IC2c. This will now be high and thus transistor Ql turns on and lights the 'Trip' LED (Dl). At the same time, the complementary output at pin 11 will be low. This low is fed to ·one input of a diode OR gate consisting of DB, D9 and Rll. The other input to the OR gate is held high by the output of IC3b, so IC2d's low output has no further effect on the circuit at this stage. That only occurs if the IC2c/IC2d flipflop has been set and a ring voltage is detected. D10 1N914 BUZZER C10 _r--OBZ- 1 .,. 250VAC LNo--1----LINE INPUT 1~i~4 Rlg 100k ---- .,. v+ v+ R20 470k A+ INPUT FROM ALARM S1 TEST v+ Il A- 04 1N914 D14 1N914 .,. 05 1N914 v+ R16 100k RB 100k D20' 1N4002 C4 V+o-----FROM PLUGPACK C11 10 v-°"]_ 25VW! I.,. 10 25VW + + 013 1N914 T B EOC v+ VIEWED FROM BELOW I C6 + 100 35VW .,012 1N914 ALARM TRIGGERED PHONE DIALLER Fig.1: the circuit is triggered by a + 5-25V DC signal at the alarm input. When this happens, RS flipflops IC2a/IC2b & IC2c/IC2d toggle and this pulls in hook switch relay RLYl and momentarily triggers the redial relays (RLY 2 & RLY3). At the same time, the buzzer beeps to warn the called party that the alarm has triggered. If we look now at the other flipflop , pin 4 of ICZb is set high while pin 3 of ICZa is set low. This low on pin 3 does two things. First, it enables the tone generator circuit via D4 and IC1f. Second, it provides forward bias for transistor QZ which turns on and activates the hook switch relay (RLY 1). So immediately the alarm is triggered, the buzzer starts beeping and the telephone is placed on-line. We now have to get the telephone to redial and this process is initiated by the high on pin 4 of ICZb. As soon as pin 4 switches high, C4 (lOµF) begins charging via RB (lOOkn). After about one second, pin 3 of IC3e switches low and pulls the base of transistor Q3 low via C7. This forward biases Q3 which now turns on and pulls in RLYZ. RLYZ's normally open contacts are wired across the redial button (usually labelled #) on the telephone. Thus, when the contacts close, the telephone immediately begins dialling the stored number. At the same time, C7 charges via R16 and, after about one second, removes the forward bias on Q3 to turn RL YZ off again. RL Y3 is used only if two key presses are required for the redial function. R9 and C5 form a delay circuit so that pin 12 of IC1f switSEPTEMBER 1989 29 BUZZER ~~ o I ~~ • B ~ 9V B~BATTERY Dlg 4---"+--+-' HOOK SWITCH -~~ ~ , -~J •,------.,_.,._ _,,,-, '""=~ ,.-.w, ~ ~ lk :!;;;..~ ~O · V+ I 9VOC ...____ PLUGPACK I ...____ Fig.2: here's how to install the parts on the PC board. Note that the two switches (S1 & S2) and the LED (D1) are installed on the copper side of board (see text). Use PC stakes at all external wiring points and don't forget the wire link between RLY2 and D14. A- ...r-.;;;;-,. A+ ~ J , ~ C, ., - 1 ALARM .....-... INPUT I TO - ~ TELEPHONE L~~,_ PLUG 1-.._ "' \ > TO TELEPHONE LINE INPUT 0 POLYESTER CAPACITORS V- FROM PLUGPACK ~/ A+ D D D ~.... ALARM No. 1 1 4 Value IEC 1µF 1µ0 0.33µF 330n 10n .01µF EIA 105K 334K 103K RESISTORS Ii D D D D D D D No. 3 2 1 8 3 2 3 Value 1MO 470k0 220k0 100k0 18k0 10k0 1k0 ches low about 2.2s after the alarm is triggered. This then turns on Q4 and RLY3 for a period of about one second to close the contacts of the second redial key. Note that the different time constants on the inputs to inverters IC3e and IC3f are necessary to ensure correct sequencing of the redial relays. With the values shown, RL Y2 turns on about one second after the telephone is taken off-hook, with RL Y3 turning on a further 1.2 seconds later. Call length OK, so we've taken the telephone off hook and dialled the number. We now have to have some means of automatically terminating the call after a preset time otherwise the called party will not be able to dial out. 30 SILICON CHIP 4-Band Code (5%) brown black green gold yellow violet yellow gold red red yellow gold brown black yellow gold brown grey orange gold brown black orange gold brown black red gold 5-Band Code (1%) brown black black yellow brown yellow violet black orange brown red red black orange brown brown black black orange brown brown grey black red brown brown . black black red brown brown black black brown brown The circuitry to do this is quite simple and consists of RlO, C6 and IC3d. When the alarm triggers, C6 immediately begins charging via RlO. After about 45s, pin 8 of IC3d switches low and, in turn, pulls pin 1 of IC2a low via D18. As a result, the pin 3 output of IC2a switches high again which means that pin 13 of IClf is also pulled high via R14. Q2 and the buzzer both now turn off, thus releasing RLY1 and hanging up the phone. Note that the IC2a/lC2b flipflop does not completely reset until the + 12V from the alarm is turned off. When the alarm does turn off, pin 4 of IC2b immediately switches low again and C4, C5 and C6 discharge via D5, D6 & D7 respectively. Diodes D21 and D22 are there to protect Q3 and Q4 from damaging reverse base-emitter voltage spikes when pins 10 & 12 of IC3 switch high again. Ring detect circuit Although the IC2a/lC2b flipflop is automatically reset in the manner just described, the IC2c/IC2d flipflop remains in the Set condition (ie, pin 10 of IC2c high & pin 11 of IC2d low). It is left this way so that the Trip LED remains alight and so that the circuit can now respond to incoming phone calls. C10, IC4 and Dl 1 form the ring detect circuit. ClO is there to remove the DC component from the phone line while D11 protects the internal LED in IC4 from reverse voltage breakdown. IC4 provides the necessary isolation between the circuit and the phone line as discussed earlier. If a call is now received, the incoming ring signal is fed to optocoupler IC4 via C10 and pulses the internal LED on and off. This in turn pulses the internal transistor connected between pins 5 & 4 of the optocoupler. IC3a's output now delivers a train of positive-going pulses and these rapidly charge C9 (33µ,F) via D10 and R12. After a short delay, pin 4 of IC3b switches low and this low is fed to D9 which forms the other half of the D8/D9 OR gate. Since both inputs to the OR gate are now low, pin 5 of IC3c and pin 2 of IC la are also low. Dl 7 will thus be forward biased which means that both the hook switch relay and the buzzer are activated as before. Thus, when a ring voltage is detected, the telephone is automatically answered and the caller hears a beeping tone from the buzzer. R13 and C9 determine the time that the dialler stays on line after answering a call. When the phone is answered, the ring voltage ceases and pin 2 of IC3a goes low. C9 then discharges via R13 and, after about 33s, pin 4 of IC3b switches high again. Dl 7 is now reverse biased and so the buzzer stops and Q2 turns off to hang up the phone. Note that the circuit will now answer any subsequent calls in exactly the same manner. It will also redial the number if the alarm is retriggered. The dialler can only be fully reset by manually pressing the Reset button (S2). When this is done, pin 13 of IC2d is pulled low via D2 and pin 1 of IC2a is pulled low via D3. Both RS flipflops then revert to the Reset condition (assuming, of course, that there is no + 12V input from the alarm). The Test button (S1) simulates the alarm condition. When pressed, it pulls pin 8 of IC2c and pin 6 of IC2b low via Rl. The circuit then responds exactly as if a + 12V trigger signal had been received at the alarm input (ie, the buzzer sounds, the relays are activated and the dialler hangs up after 45 seconds). The buzzer circuit A simple tone generator circuit consisting of inverters ICl b & IClc is used to drive the piezo buzzer. The PC board is mounted on the lid of the case using 9mm standoffs, machine screws and nuts. Check that the two switches and the LED protrude by the correct amount through the panel before finally securing the PCB. Use cable ties to provide strain relief for the cables. The inverters are wired in a standard 2-gate configuration while R21 and C13 set the frequency of oscillation to about 800Hz. The output signal for the buzzer is taken directly from pin 6 of IClc. The tone generator does not run continuously, however. Instead, it is gated on and off by a second oscillator made up of inverters ICld and ICle. This gating oscillator controls the tone generator via D16. The way in which this works is quite simple: when pin 8 of ICld goes low, D16 is forward biased and this disables the tone generator by holding pin 3 of IClb low. The tone generator then remains off until pin 8 of ICld switches high again. R20 and C12 set the gating oscillator frequency to about 2Hz. In practice, the gating oscillator pulses the tone generator on and off at a 2Hz rate so that the buzzer emits a series of 'beeps'. The gating oscillator is itself enabled via IClf and D15. Normally, pin 12 of IClf is low, D15 is forward biased and pin 11 of ICle is held low. This means that both the gating oscillator and the tone generator will be off and no sound will be emitted from the buzzer. When the dialler is triggered by the alarm (or if it answers a call), pin 13 of IClf is pulled low via D4 or Dl 7 as previously described. Pin 12 of IClf then switches high, reverse biasing D15 and enabling the gating oscillator. Power for the circuit is derived from a 9V DC plugpack supply, with D20 providing reverse polarity protection. This is backed up by a rechargeable 9V nicad battery which supplies power via Dl 9 if the plugpack supply is removed. SEPTEMBER1989 31 This view shows how the two switches and the LED are mounted on the copper side of the PCB. Note that the flat surface on each switch body goes towards the top of the board (see also Fig.2). To gain access inside the telephone, first remove the sticker above the keyboard and undo the two self-tapping screws. The two halves of the case can then be carefully prised apart using a 5-cent piece. Resistor R3 is included so that the battery trickle charges when the plugpack supply is connected. Construction Despite the circuit complexity, this project is easy to build and get going. That's because virtually all the parts are mounted on a single PC board. This board is coded ZA-1430 and is installed in a plastic 32 SILICON CHIP zippy box measuring 150 x 90 x 50mm. Note that this project was developed by Dick Smith Electronics and will be sold by this company as a complete kit of parts. Fig.2 shows the parts layout on the PC board. Begin construction by installing the 10 wire links, then install PC stakes at all the external wiring points. Note particularly the wire link between RL Y2 and D14. The various components can now be installed on the board. The order of assembly is not important although it's a good idea to leave the relays until last. Check your work carefully as you proceed and make sure that all polarised components are correctly oriented. These include the ICs, diodes, transistors and electrolytic capacitors. When installing the transistors, push them down onto the board as far as they will comfortably go before soldering their leads. There's no need to use IC sockets but take care when installing IC2 it facAs in the opposite direction to the other ICs on the board. The two pushbutton switches (S1 & S2) are mounted on the copper side of the board (see photo). Position them so that they are about 2mm proud of the board and use a fine-tipped soldering iron to solder the leads to the pads. The flat surface on each switch body must face towards the top of the board, as shown in Fig.2. The Trip LED (Dl) is also mounted on the copper side of the board. Install the LED so that its top surface is about 12mm above the board, to ensure that it will protrude through the front panel. Don't trim the leads at this stage as you may need to adjust the height of the LED later on. That completes the PC board assembly. It can now be mounted on the back of the pre-punched front panel using the 9mm spacers supplied and secured using 15mm-long machine screws & nuts. Check to ensure that the pushbutton switches and LED protrude by the correct amount through the panel. If not, remove the board and readjust the height of these parts as necessary. Internal wiring The next step is to install the power supply and alarm input sockets. These are mounted on one side of the case (see photo) and must be positioned low down so that they clear the PC board. You will also have to drill holes to accept the 8-way cable supplied with the kit and the telephone cable. Fig.2 shows the internal wiring DSE F-526O/68 TELEPHONE BOTTOM Fig.3: here's how to wire the dialler circuit to the pushbutton telephone. The connections to the redial switch are best made at pins 4 & 16 of ICl on the telephone PCB. The hook switch is mounted on the copper side of the board. TOP GLUE BUZZER TO BOTTOM OF CASE (/) LINE INPUTS I I I JJ details-. Connect up the power input and alarm input sockets, then wire in the battery snap connector. This done, connect the 8-way cable to the hook switch, redial, buzzer and LN terminals (see also Fig.3). The telephone plug and cable is salvaged from the pushbutton telephone and is connected to the LN terminals at a later stage. Connecting the telephone Fig.3 shows how the other end of the 8-way cable is wired to the pushbutton telephone. To do this, we first have to gain access to the innards of the phone. Here's the step-by-step procedure: Step 1: remove the sticker above the keyboard and undo the two selftapping screws. Unclip the two halves of the telephone by prising them apart with a screwdriver or 5-cent piece. Step 2: affix the piezo buzzer to the bottom half of the case using epoxy adhesive. Position the buzzer between the two plastic pillars as shown in the photo. Step 3: remove the telephone cable by unsoldering the leads, then push the PC board towards the loudspeaker until it clears the two plastic clips at the bottom end. Swing the board up to expose the hook switch and connect the 01 and Kl leads from the 8-way cable to the switch terminals. Step 4: re-install the board and connect the 02 lead to pin 16 of ICl. Connect the K2 lead to pin 4 of ICl. Note: these are the redial connections. Step 5: connect the buzzer leads and the line input leads as shown in Fig.3. Step 6: enlarge the cable entry hole in the bottom of the case to take the 8-way cable. Fit a plastic cable tie to provide strain relief, then reassemble the telephone. Step 7: complete construction by TELEPHONE PLUG wiring the telephone cable to the LN terminals of the dialler board (use a plastic cable tie inside the case to provide strain relief). Testing To test the unit, simply connect the plugpack supply and press the Test button. If everything is OK, the Trip LED will light, the buzzer will immediately starting beeping and the hook switch relay (RL Y 1) will pull in. RL Y 2 will then pull in after a second or two and quickly The leads to the hook switch can be passed through a hole in the PCB and soldered to the copper pattern at the points indicated. These points are connected to the hook switch leads via the copper tracks. SEPTEMBER 1989 33 The buzzer should be glued to the bottom of the case between the two plastic pillars using epoxy adhesive. Note that it will be necessary to enlarge the cable entry hole in the case to accept the 8-way cable which runs back to the dialler circuit. release, followed by RLY 3. Now check that the circuit automatically hangs up at the end of the call period (ie, RL Y 1 should release after about 45 seconds). The Trip LED should remain alight until the Reset button is pressed. If the call period is too long, reduce the value of C6 (eg, to 82µ,F or 68µF). The ring detect function can be checked by waiting until the ~nit automatically hangs up (after it has dialled out) and then momentarily shorting pin 1 of IC3 to ground. RLYl should immediately pull in and release after about 33s. should pull in. If RL Yl doesn't pull in, check Q2. If the buzzer doesn't start, check the circuit around ICl. Q3 and Q4 can be checked by shorting pins 10 & 12 of IC3 to ground. Check that the corresponding relays momentarily turn on in each case. The RS flipflops can be checked using your digital multimeter. Apply power, press Reset and check the NAND gate (IC2) outputs. Pins 4 & 10 should be at OV while pins 3 & 11 should be close to + 9V. Now press the Test button. Pins 4 & 10 should now be at + 9V while pins 3 & 11 should now at OV. If this doesn't happen, check the circuit around IC2 for solder bridges. If pin 10 goes high but the Trip LED fails to light, try replacing Ql. The ring detect circuit is easy to troubleshoot. Initially, pins 1 & 4 of IC3 should at + 9V, while pins 2 and 3 should be at OV. If this checks out, short pin 1 of IC3 to ground and check that pin 4 goes to OV. The buzzer should now start and also RLYl should pull in. Finally, be sure to install the alarm phone dialler so that it is out of sight. If the unit is easy to find, it could well be disabled by the thief before it has had a chance to dial out. ~ Troubleshooting If the circuit fails to work as expected, go over the PC board carefully and check the component values. You should also check that all the parts are correctly oriented and that there are no solder bridges or missed solder joints on the copper side of the board. If these checks don't reveal anything, apply power and then short pin 13 of ICl to ground. The buzzer should start beeping and the RL Yl (the hook switch relay) 34 SILICON CHIP Where to buy the kit A complete kit of parts for this project is available from Dick Smith Electronics stores or by mail order from PO Box 321, North Ryde , NSW 2113. Phone (02) 888 2105. The kit comes complete & includes a pre-punched front panel, the pushbutton telephone and a 9V plugpack power supply (but no battery). The price is $79.95 plus postage charges . Quote Cat. K-8300 when ordering. Note : copyright of the PC artwork associated with this project is retained by Dick Smith Electronics. February 1988: 200 Watt Stereo Power Amplifier; Deluxe Car Burglar Alarm; End of File Indicator for Modems. March 1988: Remote Switch for Car Alarms; Telephone Line Grabber; Endless Loop Tape Player. April 1988: Walkaround Throttle for Model Railroads; pH Meter for Swimming Pools ; Slave Flash Trigger; Headphone Amplifier for CD Players. May 1988: Optical Tachometer for Aeromodellers; High Energy Ignition for Cars; Ultrasonic Car Burglar Alarm. June 1988: Stereo Control Preamplifier; Breakerless Ignition For Cars; MegaFast Nicad Battery Charger. July 1988: Fitting a Fuel Cut-Off Solenoid ; Booster for TV & FM Signals; The Disco light Light Show. · August 1988: Remote Chime/Doorbell; High Performance AC Millivoltmeter; Getting the Most Out of Nicad Batteries. September 1988: Hands-Free Speakerphone; Switchmode Charger for 12V Gel Batteries; Vader Voice . October 1988: Stereo FM Transmitter; High Performance FM Antenna; Matchbox Crystal Set. November 1988: 120W PA Amplifier Module ; Poor Man 's Plasma Display; Car Safety Light; How to Quieten the Fan in Your Computer. December 1988: 120W PA Amplifier; Diesel Sound Generator; Car Antenna/Demister Adaptor; SSS Adaptor for Shortwave Receivers . January 1989: Line Filter for Computers; Proximity Detector for Cars; How to Service Car Cassette Players . February 1989: Transistor Beta Tester; Minstrel 2-30 Loudspeaker System ; LED Flasher for Model Railways; Lightning & Electronic Appliances . March 1989: LED Message Board; 32-Band Graphic Equaliser; CD Compressor; Amateur Band FM Receiver. April 1989: Auxiliary Brake Light Flasher; What You Need to Know About Capacitors ; Telephone Bell Monitor/Transmitter; LED Message Board Pt.2 . May 1989: Electronic Pools/Lotto Selector; Synthesised Tom-Tom; Biofeedback Monitor For PCs ; Simple Stub Filter For Suppressing TV Interference. June 1989: Touch-Lamp Dimmer; Passive Loop Antenna For AM Radios ; Universal Temperature Controller; Understanding CRO Probes. July 1989: Exhaust Gas Monitor; Extension for Touch-Lamp Dimmer; Mains Hum Sniffers ; Ultrasonic Car Burglar Alarm. August 1989: Build A Baby Tower AT Computer; Studio Series 20-Band Stereo Equaliser; Garbage Reminder; Introduction to Stepper Motors. Note: November 1987, December 1987 & January 1 988 are now sold out. Use this handy form to order vour back copies ~ , - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - • --7 Please send me a back issue for: □ February 1 988 D March 1988 D July 1988 D August 1 988 □ December 1 988 D January 1 989 D May 1989 □ June 1989 D April 1988 D May 1988 D June 1988 D September 1 988 D February 1989 D October 1988 D March 1989 D November 1 988 D April 1989 D July 1989 D August 1989 Enclosed is my cheque/money order for $. _ _ _ _ _ _ or please debit my D Bankcard D Visa Card D MasterCard Card No l'--- - ' - - ' - - - ' - - - - ' ----'----'---'-- - - ' - - - - - ' -'---'---J.___J.___..L_..J.__J Price: $A5.00 each (includes postage). Overseas orders add $A 1 .00 per issue for postage. Signature _ _ _ _ _ _ _ _ _ _ Card expiry date_!_ _ / _ _ NZ & PNG orders are sent by Name_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ air mail. (PLEASE PRINT) Stree~-----------------------Suburb/town,_ _ _ _ _ _ __ __ _ _ Postcode,____ Detach and mail to: SILICON CHIP PUBLICATIONS PO BOX 139 COLLAROY BEACH NSW 2097 OR FAX: (02) 982 9553 ~-------------------------------------~ SEPTEMBER1989 35 . Two models. ailab\eonceagauED MODEL O'\N SPE tteries or OC voltage 6 • rateS on 4 . AA bared with three chucl<S • volts 1 AMP. 2.9mm. 1 x 2.8 x x o.4 • 1.5mm. 1 . b·ts spanner and tomrnv 11 4mm and three dnOO R'PM and 550 RPM. 11 OimentIons · r. Two s..,,,,,i · 43 x 230mm. I"'~" S~Pf; . 900gm/$cm39.95 rque tT0-2470 1GH SPE~ D MODEL s\lOC 1 .t5AMP. rated from 6 \IOCk 3and 3 drill bits. spann pplied with 3 chuc ~s supplied in loW S. nd d tommY bar \same 30 000 RPM depe ' odell. speed 3500 50-GOOgm. Oirnentions o\tage. Torque 1 UTILUX UX HIG CONNECTORS H POWER AUDIO Another surplus b . ,n black but th uy. Ut1luK now on/ i~rar bought~ ~~1 a quantity Of cKr~:~ thtedese connectors UK have deveio · . a ones and the professional pee/ _this tevolutiona use these at ho~ud10 Industry. But n!connector system for There are two con . you can afford to hne connectors arenftors. one line and on plugged into themse/ ermaphrocfitic. Which e /llne/ type_ The speaker cable pern ves for a line connec _means they can be each for these. ect/y. You would norm r;,on- Fits our jumbo Spees: a Ypay about $10 • Mechanical· of 30 Newtons· cable clamp Withstan Plated. . • Material contacts· a cable pu// out force • Body She//· z' · pper 1ron alloy silve Electrical: Ra~nc alloy die casting eh r LINE CON at 30 Amps continuiou'ome plated. • CatPP-108() NECTOR $2,g,ttO+VmaKimum ~! PANEL CO CatPP-1002 NNECTOR$2.95 $2.50 EXIDE RECHARGEABLE BATTERY MADNESS . . ..... . . EXPENSIVE RECOMBINATION ELECTRODE TYPE Another surplus buy which saves you a fortune. This time we have 12 volt Gel-type batteries. They are high-tech recombination electrolyte batteries (a spin off of the space program) which can be used in any orientation and which do not gas. spill. leak or need top up. We are able to offer these batteries at about l(Z trade price. These are not "cheap· batteries. they are high quality and are made in Japan. PLEASE NOTE. TRADE NOT SUPPLIED. sKV .,,E HEAPS THREE SIZES AVAILABLE 1.9 amp/hour Exide No. RE 12·1.9 ONLY $14.95 Cat. SB-2482 (Trade price $30) ONLY $19.95 Cat. SB-2484 (Trade price $35) 10+ $13.95 ea 2.6 amp/hour Exide No. RE 12·2.6 10+$18.95ea 15 amp/hour Exide No. RE 12-15 10+$95ea ONLY $79 Cat. SB-2490 178mm x 34 x 67 LWH inc connector (1 .9) 134mm x 67 x 67 LWH inc connector (2.6) 181mm x 76 x 167 LWH inc connector (15) Mail order customers in WA and NT please add on extra $2 for 1.9 and 2.6 batteries for extra mai l '~--- / _________ - ----------- IIIIINI STe - Reo """ Thisamp/ifier 0 ::t:~~n(:a:~: supplied With a 1 th ordinary ;peiwn rather than is amplifier;~% 5 watt 0 The amplifier kers. Which effecti mpan,ed With tw uch more usoo With a Dis battery operatedve1y doubles the ; Very ~~':t C::: ~ LIFIER i::::ri;1 :s;:z£~:~:{3:~~::~u~~~n be Indicator s· Pass filter SWitch e/ to monitor out m. one for anyWh . ize 150Lx70D andanon'off _Put.a high ere a low x 25 H " SW,tch · SPECIFICATfON/OWer. battery mm. Idea/ forwa/:th LEO Output Ofleratoo amp/ifie . ans. or Input & Im r 15 requiroo. Band V I WiidthP o !age Gain Input Volta mw ge Cat A/\-D35a $29• 95 * 0.5 Watt 600 h J:er channe/ B h 1 om o ms 20 H2 • 20 Kh2 BdB+;. 1dB ·3dB 250 mv + povfe"':8a~kman only) (wafkman) tput 50 * 3 /N 1 ALARM ln=~r~ ?NOGRAPH Hand held stop Watch ••Clip Stop Watch • Alarm chronograph w . • Whistle fist Watch Features • Ouanz accuracy 1 · II 00 second chron . • Display hours m· 0graph With fat time date and day fl~g mutes. seconds, month, .·:atterm,ya·nd,hour/y Chime function tnc Uded Cat XC-0200 On/y $9.95 COLOUR See catalogue for fullBAR specs Normally $249 ONLY $199 Ust for //y self c le learning mus1 mpo is ed electronics ats or times from 40 to ,ai tchable minute d a Red LEO een audio sou 'PPlierJ With an Vilte use. Ban earphone for e 60 x 106 x 30~ operated. OM.1240 m. bet;'' 9.95 PATTERN GENERATOR Save $50 ~YCAR ELECTF ~YCAR ELECTF ~YCAR ELECTF ~YCAR ELECTF ~YCAR ELECTF WCAR ELECTF \ YCAR ELECTF WCAR ELECTF ~YCAR ELECTF WCAR ELECTF \YCAR ELECTF ~YCAR ELECTli \YCAR ELECTli \YCAR ELECTli \YCAR ELECTli \YCAR ELECTli WCAR ELECTli \YCAR ELECTR \YCAR ELECTR \YCAR ELECTli \YCAR ELECTR \YCAR ELECTli \YCAR ELECTli \YCAR ELECTli \YCAR ELECTli \YCAR ELECTR \YCAR ELECTR \YCAR ELECTR \YCAR ELECTR \YCAR ELECTR \YCAR ELECTR \YCAR ELECTR \YCAR ELECTR \YCAR ELECTR \YCAR ELECTR \YCAR ELECTR \YCAR ELECTR \YCAR ELECTR \YCAR ELECTR \YCAR ELECTR \YCAR ELECTR \YCAR ELECTR \YCAR ELECTR \YCAR ELECTR \YCAR ELECTR Pre-programmed with 12 times* for different cities including Tokyo, Hong Kong, Bangkok, Sydney, London. Paris. 1;, .. · • ... • Cairo, Moscow, Honolulu, Los Angeles. /--Chicago, New York and one spare zone for another city. The times are displayed / immediately after touching the button. k.. .. __ k$JJt, ? t JH!LJ LJ . . 1 . •• J . Also incorporated is a calculator as well as the date and an alarm. Credit card size *Once one time zone is programmed in. the other zones are automatically calculated by the unit. Cat. OM-7210 L.... __ - .... _ LJ!! . . ONLY $19.95 Receives all band 4 and 5 channels through 21 to 69. Ideal for fringe areas. Includes balun for 75 n cable. Max gain 16dB. Cat. LT-31B2 $139 $75 11 Element SAVE $15 ONLY $54.95 Normally $52.50 SAVE $12.55 Cat. CW-2116 ONLY $39.95 8" 60W rms Normally $39.95 SAVE $10 Cat. CW-2114 ONLY $29.95 6" 30Wrms . \YCAR ELECTR EASY TO INSTALL \\ Simply mount above or below your existing VHF aerial and comect to existing cable with a d1plexer Cal LT-3014$12.95 DIGITAL HYGRO-THERMOMETER Measures temperature AND humidity at the same time! This compact battery operated unit has two bright LCD readouts. One for temperature (down to -25°C) and the other for humidity (20 - 95%). Can be used in the car or home/office etc. Cat. 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QM-7220 • ONLY $12.95 l:? __. . $29 95 ~~g;:!m~: ~M...o~ N 1T0- R--M--A- o_N_E_s_s__ 1111111111111111111 ~YCAR ~YCAR ~YCAR ~YCAR AYCAR AYCAR AYCAR AYCAR AYCAR AYCAR AYCAR AYCAR AYCAR AYCAR AYCAR AYCAR AYCAR ELECTR ELECTR ELECTR ELECTR ELECTR ELECTR ELECTR ELECTR ELECTR ELECTR ELECTR ELECTR ELECTR ELECTR ELECTR ELECTR ELECTRC ~~g:: ~~~g~: Another distress stock purchase I This time a quantity of Samsung brand 12' Green composite computer monitors. LIMITED STOCK. BE QUICK GREEN Cat XC-3000 SCREAMER HORN We used to sell this unit years ago for $35. Today, it would cost about double that. Ideal for car alarms and home burglar alarms. It's very loud, the specs say 112dB, but we think it's louder than that. It has a nylon case and the noisemaker is a nylon 4' speaker. It's weatherproof and operates from 6-12 volts. Current drain 2 amps and the frequency is 1200-1500Hz oscillating. Supplied with mounting bracket. Size: 110 x 100mm Cat. LA-5262 LARGE PIEZO SCREAMER ONLY Not unlike our tweety pie, this unit is larger(80 x 105mm) and is housed in a zinc die cast body. This is rare. as most these days are plastic. Sound level is 124d8. Operating voltage 6-12 volts. current drain 350mA. Ideal for car and home burglar alarms. Normally worth about $39. A bargain at $25. Cat. LA-5265 $99.50 SAVE ONLY $25 $50 .L J A T\..f\11 C:.L t:. V I ri. u1 ~ 1v.:> J ttTV.l'\11 c:.Lc.v 1 r,:u1'11v.:> JMtvf'\n c:.L. i:.v I nv , .. ,...,...., Jn I vn1, ......... ...,, , ,...,,.,..,.., ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR Et ECIRONICS JAYCAR El ECTRONICS JAYCAR ELECTRONICS JAYCAR 10+ s11.ts ea GIVEAWAY PRICE· ONLY $25 ea SEE LAST MONTHS ADS FOR FULL SPECIFICATIONS AYCAR ELECTRON11..,;::, AYCAR AYCAR AYCAR AYCAR AYCAR ~•. The baby Agam bands 4 and 5 Includes balun. 8d8 gain. Normally $29.50 •·• > · Cat. CW-2108 Cat. Pl-6472 ~ $39.95 Normally $69.95 '.~;:: ~~~~;: MIDRANGE ELECTR ELECTli ELECTR ELECTR ELECTR .. Cat.lT-3178 ;~g:: ~~~g~: . .W _ H _ I_ T_E_C_O _N_E _ ~YCAR ~YCAR ~YCAR ~YCAR ~YCAR $6.95 per length 10+ $6.50 per/I Suns both bands 4 and 5. Ideal for medium signal reception areas. Includes balun. Max gain 13dB. Cal.LT-3181 Jaycar will purchase your surplus stocks of components and equipment SAVE $$$ ON SPEAKERS POLYPROPYLENE WOOFERS Snap off to any length to make IC sockets. Quality machine pin wire wrap pins 43 Element Tum Your Surplus Stock Into Cash!! CALL GARY JOHNSTON OR BRUCE ROUTLEY (02) 74 7 2022 Wire Wrap Machine Pin IC Socket Strips 91 Element ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR J• , , .... . . . . ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ~~-- • • - · ·· - - • • •• - - • • • ELECTRON ICS 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 ,r< EL ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR EL EL EL EL EL JAYCAR ELcCTRONI CS JAY CAil JAYCAR ELECTRONICS JAYCAR JAYCAR ELECTRONICS JAYCAR JAYCAR ELECTRONICS JAYCAR JAYCAR ELECTRONICS JAYCAR JAYCAR ELECTRONICS JAYCAR EcLCTRONICS JA' ELEC TR ONICS JA ELECTR Ot>IICS JA' ELECTRONICS JA' ELECTRONICS JA ELECTRONICS JA' ONICS JAYCAR ELoClRONtt;:; JAY(;AI( ~Lt.Cl RONI(;:; JAY"-"" ONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR 'ONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR !'ONICS JAYCAR ELECTRONICS JAYCAR ELECT!lONICS JAYCAR !ONICS JAYCAR ELECTRONICS JAYCAR ELECT!lONICS JAYCAR !ONICS JAYCAR ELECTRONICS JAYCAR ELECT!lONICS JAYCAR Cat. QM-1410 DMM's JAYCAR Elf JAYCAR Elf JAYCAR ELE JAYCAR ELE JAYCAR ELE JAYCAR ELE JAYCAR ELE JAYCAR ELE JAYCAR ELE JAYCAR ELE JAYCAR ELE JAYCAR ELE \ JAYCAR E-_E TOUCH LAMP DIMMER KIT 20 ranges Diode checker $59.95 Direct import - one hana cpe ration Frequency cour.ter Capacitance meter Logic Probe 10 amp c.L~ICI HVNI<;:; -'ATWV< t LtlC I t<UNlt;::, JAY<.:At< cL~t; I HONICS JAYCAR ELECTRONICS JAYC ELECTllONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYC ELECTllONICS JAYCAR ELECTR'ONICS JAYCAR ELECTR'ONICS JAYCAR ELECTRONICS JAYC ELECTllONICS JAYCAR ELECTRONICS JAYCAR ELECTR'ONICS JAYCAR ELECTRONICS JAYC ELECTllONICS JAYCAR ELECTR'ONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYC ELECTRONICS JAYCAR ELECTR'ONICS JAYCAR ELECTRONICS JAV""'; ELECTRONICS JAYC t Aet. Silicon Chip June 19ffi \i> Amaze your friends. Replace your normal light switches'-. : . with these. All you see is a plate. To dim simply hold ' your finger on the pla te. To switch simply touch the plate. Works extremely well. Cat. QM-1400 Cat KC-5052 $99.95 REMOTE KIT FOR TOUCH LAMP DIMMER $32.95 . -~ Aet. Silicon Chip July 1989 Add one or more extension uni ts. so you can dim/switch your lights from severa l positions. These can be simply wired in place of 2-way switches. Cat KC-5053 Ni Cad DISCHARGER KIT ~~~;:~~~~~::;;rd all speci*fied compo * nents. Powe * r supp*lied by CatKA-1719 JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR JAYCAR ELE ELE ELE ELE ELE ELE ELE · ;JAR $14.95 SLIDER POT BARGAIN As used in the Equalizer Kits -2801 and ETI 500) Normally $3.SS Cat AP-3912 NOW ONLY $1.25 each •=~ AUTOMATIC CHARGER FOR !~~: ~~ NiCads KIT Cat KA-1718----------:-,-■i JAYCAR ELE ' 11~ ": ,.~ ..... . ·. "' . •~\!'~ , .. . ,. .. ..~ *:~: ,;,~;_ .-'.,:_,.·. .· Aet.EAAugust1989 Combine this automatic discharger with our equally automatic charger kit (KA-1718 $42.50) and rejuvenate your NiCad batteries. It's . h th . ha / h amazing ow they'll respond to e disc rge c arge treatmentyou could add years to the life of yJJJr re-chargeables. Kit includes PCB. JAYCAR JAYCAR JAYCAR ELE ELE ELE ELE ELE ELE ELE ELE ELE _.::::==============:;~=~~~z:::====:::::.- ~~~: ~~: RGBI TO PAL ENCODER/ MODULATOR Aet. EA August 1989 Here's a kit for a low cost AGBI to PAL video encoder and RF modulator, suitable for use with an IBM or compatible computer fitted with a colour graphics adaptor (CGA). By providing a modulated RF signal on a suitable TV chanreJ. it allows a standard colour TV receiver to be used as a colour monitor for games etc. Kit includes PCB. box. and all specified components except those for optional power supply. Cat KA-1720 $39.95 AYCAR YCAR YCAR CAR AR ~- $42 50 -..,_ Aet. EA July 1989 . ■ Th' · · IS kit IS a fully automatic NiCad charger that · · d rea b 'Id o th ba is simpe an c p to ui · nee e tteiy j~J~; ~~~!~~~~e uni t automatically switches to Kit includes PCB. box. panel and all specified -~:,'•.,' .' . ~~ "' 1 1_ '1 ; i.~ 0 .<,- «E) ,_.; ' - ••• ~; ~ ~ ~ J_ • 0 > _ ' ~ - - m H~ i.H. H. ! • • • ~• . JAYCAR ELE JAYCAR ELE JAYCAR ELE JAYCAR ELE JAYCAR ELE ~ JAYCAR ELE JJAAYYC CARAR ELEELE .; =: 0 ~ .~ . - ~~ e •~ •~ N 4.~=su=p=ply=ex=tra=• =====•=~•;=•;=-.~[="'=•;=•;;•;· ;, ; ~•-;•; ';;;--~";·~~-:_•-:_,;__,j JAYCAR ~~~: ELE ~~ ;$=2=7=•=9=5================,-- - -,-·._ 'c. .i_;;:._: ,==~=~=~=~=~=~~=t=s.=PS=~=e= ROBINSON NUGENT HEADERS Another surplus stock pu11:hase. Save a fortune over normal prices. Limited quantities. Be quick. Cat 16 way PP-0952 20 way PP-0953 26 way PP-0954 34 way PP-0955 Each $1.SS $2.20 $2.20 $2.40 10. Sl .65 S2.00 S2.00 S2.20 ~ NEW SPIN IC SOCKET for optocouplers Cat Pl-6509 • 20~ ea 10+ 18~ ea ' . STEREO 1/2 OCTAVE GRAPHIC EQUALISER KIT Aef: Si liconChipAugust1989 Cat KC-5055 This project enables you to equalise your room or disc or other sourte etc.. with great precision. Until recently you had to buy TWO mono equalisers to do this task. The Silicon Chip people have come up with a ~tate-of-the-art design featuring close tolerance capacitors and superior gyrator performance. Headroom is over lOOdB. Distortion? Negligible <()_001 %. With TWO controls per octave you have a precision Hi R instrument that covers 28Hz to 20kHz. 20 sl ider controls per channel with Eq. out for dubbi~ tape. ±12dB per control. 24fN powered. 19" 2 unit rack configuration. The Jaycar kit is complete down to the last nut and screw. $349 • - -mJC'!»<<>.»m.,,c\.tl!IB,...,;=-,A.,.,~s.u:, , . ~ • . ,,~, . -,. --_.- --···......... _.... _,, ~ _-,.,,.,_--:,;:: ....... , ,.,... . .. . - -- . IC SOCKETS 25% OFF Size Cat Norm al Price 8 14 16 1s 20 22 24 28 40 Pl -6500 Pl-6501 Pl-6502 Pl-6503 Pl-6504 Pl-6505 Pl-6500 Pl-6507 Pl-6500 20t 32e Sale Price 1-9 15e 19e 21e 24e 10-99 13.5e 16.5e 19e 21e ; ;j~ , =L i re ~ ' I I[ ~ 48e 36e 33e ~ ~ 38e 38e 7'.Yt 7'.Yt 52c 52e 34e 34e 49e 49e Standard production ~~~e ~:~ts;older tail. all tin plated Phosphor Bronze or Beryllium Copper. • · · , . 1' ' 100+ lle 14e 1se 1Be 27e 28e 28e 38e 38e ~ Jaycarl Find out more by calling in to any Jaycar sto re or call (02) 747 2022 or send JAYCAR ELE• JAYCAR ELE• JAYCAR ELE• us a Fax (02) 744 0767 - or write 1 We w ill send you an aca unt application form by return . It's that simpl e! Cat SEMICONDUCTOR BARGAINS SAVE UP TO 96% 74LS352 74LS109 4528 4538 4419 4076 4028 4024 LM301 ZS-5352 ZS-5109 ZC-4528 ZC-4538 ZC-4419 ZC-4076 ZC-4028 ZC-4024 ZL-3301 Normal Price (ea) S1.50 5 forS1 S1.25 5 for S1 $1.SS 5 for S1 S2.65 5 for Sl $440 5 for Sl $1.20 5 forSl Sl.SS 5 for $1 S1.18 5 for S1 $0.SS 5 for $1 MAIL ORDERS POST & PACKING 11 5 Parramatta Road Concord 2137 P.O . Box 185 Concord2137 HOnlNE (02 747 1888 Te lephone (02) 74 7 2022 FACSIMILE (02) 744 0 767 FOR ORDERS ONLY TOLlFREE (008) 022 888 $lO-S2 . 4 99 $2 _$4 _ 9 99 5 $50- $99_ 99 OVER $100 MAIL ORDER VIA YOUR ff ;~~:~~ ~~~: :~ JAYCAR ELE JAYCAR ELE· Type MINIMUM PURCHASE SS Can be 5 different Sl units or any combinati on of S1 units adding up to $5. JAYCAR ELE JAYCAR ELE JAYCAR ELE Manufacturers! Open an account w ith 5 for $1 HEAD OFFICE • 25e OPEN AN ACCOUNT WITH JAYCAR s 3.75 $ 4 50 · ~~ ROAD FREIGHT ANYWH ERE IN AUSTRALIA $13.50 ~:~~: ~~- ~~g: ~~: JAYCAR ELE• JAYCAR ELE• JAYCAR ELE• ~~~: ~ : JAYCAR ELE• JAYCAR ELE• JAYCAR ELE< JAYCAR ELE1 JAYCAR ELEI JAYCAR ELEI JAYCAR ELEI JAYCAR ELE1 JAYCAR ELEI JAYCAR ELEt JAYCAR ELE• JAYCAR ELEI JAYCAR ELE JAYCAR ELE JAYCAR ELE JAYCAR ELE AYCAR ELE AYCAR ELE AYCAR ELE IAYCAR ELE AYCARELE 'AYCAR ELE }AYCAR ELE }AYCAR ELE IAYCAR ELE IAYCAR ELE 117 York St (02) 'l.67161 4 GORE HILL 188 Pacific Hwy (Cnr. Bellevue Ave) (02) 439 4799IAYCAR Elf Mon-Fri 8.30 - 5.30 Thurs 8.30 pm - Sat 9 - 12 - Mon.fri 9 - 5.30 Sat 9 - 4pm IAYCAR Elf BURANDA QLD 355 Church St (Cnr. Victoria Ad) (02) 683 '3377 144 Logan Ad (07) 393 0777 • PARRAMATTA Mon-Fri 9 - 5.30 Thurs 8.30 pm - Sat 9 - 4pm Mon-Fri 9 - 5.30 Thurs 8.30 - Sat 9 - 12 YCAR Elf MELBOURNE-CITY 115 Parramatta Ad (02) 745 3077 Shop 2. 45 A'Beckett City (03) 663 2030 CONCORD YCARELE Mon-fri B.30-5.ll-SalB.30-12 Mon-Fri 9- 5.30 Fri 8.30- Sat 9 - 12 YCAR ELE VISA SPRINGVALE VIC 121 Forest Ad (02) 570 700) 887-889 Springvale Road Mulgrave (03) 547 1022 HU RSTVILLE JAYCAR ELE Mon-fri 9 5.30 Thurs B.30 pm · Sat 912 Nr Cnr. Dandenong Road Mon-Fri 95.30 Fri 8.30 Sat 9 2 . ._ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ __ _ _ _ _ _ _ _ _. .JAYCAR ELE JAYCAR JAYCAR JAYCAR JAYCAR ELECTRONICS JAYCAR ELECTRONICS jAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR SYDNEY · CITY ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTllONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR St ~~~: ~ ELECTRONICS JAYCAR ELECT!lONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRONCS JAYCAR El f ELECTRONCS JAYCAR ELECTRONICS JAYCAR ELECTllONICS JAYCAR ELECTRONICS JAYCAR ELECTRONCS JAYCAR ELE ELECTRONICS JAYCAR ELECT!lONICS JAYCAR ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTRON CS JAYCAR ELE ELECTRONICS JAYCAR ELECTRONICS JAYCAR ELECTllONICS JAYCAR ELECT!lONICS JAYCAR ELECTRONICS JAYCAR ELE It's a long way to trip a ''rarery'' Sorry about that heading but it was the only way I felt I could sum up this month's main story. The fault was a real "rarery"; so rare as to be possibly unique. And tripping it did involve a long path, mainly through a maze of circuit diagrams and board patterns. The story concerns an AW AThorn video tape recorder, model AV-14. This model first appeared about 4 or 5 years ago and carried a 4-year warranty - a warranty that still covered this particular recorder. According to the owner the machine would usually perform when first switched on, after which it might run for half an hour or more and then shut itself down just as if it had been switched off. And if it was then left in that situation, it could just as suddenly come good. On the other hand, it would also sometimes run indefinitely without any problems at all. When the customer first delivered it and described these symptoms, I set it up while he was there and gave it a trial run. Neither of us was particularly surprised when it worked perfectly; according to the customer, that was exactly what he had expected. Hopefully, a longer run would display the fault. I had no manual for this machine, although I had some for earlier and later models, so I rather hoped that the fault would turn out to be fairly obvious. But it refused to show up. I tested the machine many times over the next few days, running it for long periods under varying temperature conditions, but it wouldn't fail. Finally, I rang the customer, explained the situation, and suggested he take it back until the fault became more predictable. But he said he was about to leave on several weeks' holiday and that I might as well hang on to it and keep trying. 0 ACCOROlt\\G i'O 1'\-\£ OWNE.-1<, ,He: N\OCMINE: WOUL-t) USUAU...'-< P6-RF'ORIV' WHe;N l='"IRS1 SWr,C.HE:O ONooo 40 SILICON CHIP So for the next week or so I did just that, all to no avail. Somewhat discouraged , and facing the pressure of other work, I was forced to push it to one side. Time slipped by and the next thing I knew the customer was on the phone, announcing his return from holidays and enquiring about the recorder. Feeling a bit guilty, I told him I had been unable to fault it so far but suggested that he give me a few more days. He agreed quite readily. So I set it up again, removing the main cover this time in the hope that this might provide access to an appropriate check point if the fault showed up. This didn't help much. The main printed board sits pattern side up above the drum and transport system and lifting it out to get at the component side is quite an involved procedure. So, for the moment, I simply switched the machine on and let it play, as I had already done umpteen times. But this time I was lucky; it ran for about an hour then suddenly shut itself down. So now it was time to lift the board out of the chassis. There are several minor boards at the front of the machine: a board holding the timer controls, one holding the tracking controls, one holding the function buttons, and one holding the on/off and timer switches. These boards are all connected to the main board by flat multi-conductor cables and must be removed from the chassis (by unlocking the pressure tabs) before the main board can be lifted. The same routine applies in order to perform a head and drum cleaning operation. It's a real pain in the neck! Anyway, having lifted the main board I was able to identify some components in the power supply section, where I suspected the fault might be. Then, making sure it was - V +30V C"'79 '""" ; IN-.,C?tX' 1sse2 AE C T OUT iSAl/1.S<at>,® :SAl/750,®,© TV12V } PCB-MAIN (TUNER/VJF) IQ903! 2SC2603<at>.® Lh E9 0907 2SC2603<at> jPOWERI ' !_ _ _ _ __ _ - - - - -- --- - --- -- - ----- - - -- -- ---- - BF BO CTEJ !' PCB.TIMER - - - - ---- - - --- - - - - - -- - -- - - - - - - - - - - - - -- ---- - ' -------~ Fig.1: the circuit of the AWA AV-14 VCR power supply, where the first clue to the fault was observed. It generates no less than four supply rails, two of which failed ( + 12V and + 9V) when the fault occurred. safe to run the recorder in its partially disembowelled state, I switched it on again. Again it came on normally but this time it ran for only about 10 minutes before it failed. In fact, its behaviour became fairly predictable from here on. Voltage checks While it was running normally I made some voltage checks around two transistors and one IC which I had nominated as part of the power supply. I was hoping that when it failed, further voltage checks would provide a clue. Unfortunately, these results were inconclusive, with no drastic changes which might have helped. By now it was obvious that this was not a simple fault which was going to show up in a routine voltage check, particularly without the benefit of a manual. I was going to need all the help I could get. I placed an order for the manual $25 worth, incidentally, but that's cheap as VCR manuals go. The manual arrived quite promptly and I turned immediately to the power supply circuit (on the reverse side of a sheet marked 2/3). It was something of a shock to realise that, whereas I had identified two transistors and one IC, this section contained no less that nine transistors and two ICs. It is reproduced here as Fig.1. The power supply generates no less than four supply rails. Q901 is supplied with - 38.8V at its collector (derived via transformer T971 , diode D901 and filter capacitor C902) and delivers - 30V at its emitter. It did this, even in the fault condition. Similarly, Q902 is supplied with + 45V via diode D905 and filter capacitor C907, and delivers + 30V at its collector. Once again, this value was correct in the fault condition. Which brings us to Q904. This is supplied with + 19V from the bridge rectifier (D908-D911) and is supposed to deliver + 14V at its emitter. And this was the first clue to the fault, because there was no + 14V output in the fault condition. And as I half expected, there was no + 14.4V on the base. Normally, I would have tried to track down the missing base voltage as the next step but I was sidetracked. Q904 is mounted near the edge of the main board and I found that if I exerted pressure on this part of the boa rd, I could sometimes create or cure the fault. This effect was not consistent but it seemed likely that Q904 was faulty. So I pulled it out. It tested OK but that meant very little, so I replaced it. All of which was a furphy; the fault remained. By now, incidentally, the fault was much more in evidence and would usually appear within a few minutes of switch-on. So back to the circuit. The + 14.4V for Q904's base comes from the collector of Q908, the emitter of which is fed from the aforementioned + 19V rail. The + 14.4V rail is also fed to zener SEPTEMBER 1989 41 diode network D917 & D918, which in turn supplies + 12.5V to the base of Q905. The collector of Q905 is fed from the + 19V rail and it delivers + 12V at its emitter. This + 12V rail is fed to the tuner and video IF circuitry and also feeds voltage regulator IC902 which provides a + 9V rail. So absence of the + 14.4V rail shuts down two supply rails: + 12V and + 9V. And if you found all that hard to follow I can assure you that it was even harder to work out in the first place. But the reason for the missing + 14.4V was still a mystery, except that Q908 obviously had to be turned on in order to create it. And equally obviously, Q907 had to be turned on in order to turn on Q908. The base of Q907 is shown as + 0.6V and this voltage was present in the no-fault condition but vanished in the fault condition. Well, we seemed to be making some progress. But it wasn't quite as clear cut as this. When the system failed . the + 0.6V on Q907 didn't simply drop to zero; it dithered its way down and the system continued to function down to around + 0.4V. But at + 0.38V everything collapsed. And in between these two values all sorts of funny things happened to the + 14.4V; it couldn't make up its mind whether to come or go. The next stage down the line was Q906. Unfortunately, there are no voltages given for this stage which meant that I had to go through the routine of measuring them when the system was working and then again when it failed. From this, I established that there was supposed to be + 0.6V on Q906's base but that this also collapsed with the fault. This left only R909 (390k0) and l!>'< NOW ,.,.. w~s o~v,oos w~s 42 -n4~-r "ffi\S NO"r F\. S\N\?l-E. FAUL--,••• SILICON CHIP diode D913 as possible suspects in this area but they were quickly cleared. So the upshot of all this effort was simply to establish that there was nothing wrong with the power supply; it wasn't generating the necessary rail voltages because it wasn't receiving the correct voltage from somewhere else. It was a negative kind of achievement in some ways, although it did mean progress. But little did I realise what kind of a search lay ahead of me. Circuit tracing The first thing to do was to trace the run from the base of Q906. This part of the circuit is on a 6-section foldout sheet portraying, in addition to the power supply, the servo and the mechanism control sections. After getting lost a couple of times, I traced the run from Q906 to pin 20 of the microprocessor, IC5AO, a 64-pin chip at the other end of the sheet. Pin 20 was marked as being at 4.8V and this proved to be correct in the no-fault condition. However, it collapsed in the fault condition so I was still making progress. But where to from here? A faulty microprocessor chip? It could be but I didn't think so and, with 64 pins involved, I didn't want to think so. The alternative was that the microprocessor was not being fed with the correct instruction on its input side. The problem was to identify this circuit. The circuit identifies the pins only by a system of alphanumeric codes and there is no list of these in the manual. I was on my own. I decided on a different approach. Assuming that the missing voltage was an instruction to the power supply to activate the various supply rails, it was most likely to originate at a switch probably the on/off switch. So I decided to take a punt and start at the on/off switch and trace back from there. Does this sound simple? It was anything but. This switch is mounted on one of the sub-boards already mentioned (PCB-SW) and its circuit is on another fold-out sheet marked 3/3. According to this the two active contacts of the on/off switch were connected to pins 6 and 7 of connector F2. And pin 6 was marked "STBY" (standby) and " - 5V". Pin 7 was marked simply "PSW". So was this the voltage that was fed to the microprocessor, to eventually appear as a signal on its pin 20? The minus sign was confusing, because I was looking for a positive voltage. In fact, that sign was a furphy; the voltage was positive and the minus sign on the circuit was simply a draughting error. I began tracing. The mate to F2 was found near the microprocessor, back on sheet 2/3 where I'd started, which looked promising but wasn't. The connection to pin 7 left this board immediately via one of the flat cables (connection 22). After much page shuffling I picked up connection 2 2 again on the back of foldout sheet 1/3, which portrays the timer board. From here it ran to pin 16 of the timer chip, ICBAO, and then the length of this sheet, through another switch (S8A2, RESV) to pin 17 (RES) of the timer chip, ICBAO. So I had two inputs to the timer chip and no idea where the vital signal voltage would reappear. In fact, the circuit involving switch S8A2 turned out to be a red herring and I never did work out its function. I was grasping at straws now. I went over the timer IC diagram and checked each pin designation (there are 64) until I came to pin 36. It was marked "PWV" and "4.9V". Both rang a bell. The 4.9V was close enough to the 5V I was chasing and PWV was the designation of the lead to the base of Q906, where I started. I followed it. It left the timer board at connection 24 and turned up again at connection 24 on the back of sheet 2/3 where I'd started. From here it ran straight to pin 41 of the microprocessor chip, IC5AO. This was the "input" terminal I had been seeking since I had determined that the output, on pin 20, was failing when the whole system failed. So that was the complete path; at least on paper - literally. It was a place to start but that was all. I had PCB-SW [ill[IT) Fig.2: this section of the circuit shows how the control voltage (PSW) is applied to the main board via F7 and then routed away from the board (to the timer board) via cable connection 22. As shown, it is deceptively simple. The physical path is actually much longer and far more complex. identified the major intermedia te points but the physical path between these points still had to be traced out. This turned out to be a most laborious task; so much so that it is virtually impossible to describe it in any way which would do it justice. Suffice it to say that it took a long time. And a major problem was the need to wait for "go" and "no-go" states in order to establish just where the circuit was failing. Voltage checks I decided to start at the switch and the + 5V supplied to it. If the voltage failed at this point I would have to back track to find its origin. If it didn't I would have to trace forward, initially via the points I had already identified. The situation was quickly clarified; the voltage held on both sides of the switch in the no-go state. So far , so good. The next check point was at pin 7 of connector F on the main board. After some waiting for the no-go state, the system was cleared to this point. From here on it was a different story. As already mentioned, this circuit is shown leaving the main board again (reference point 22) without making any other connections. Fig.2 shows the relevant section of the circuit and this indicates a short run into the board and out again. In fact, point 22 is much further away physically than the circuit implies, while the copper pattern connecting it to connector F is much longer again. More importantly, a check at point 22 indicated that the voltage was failing here when the system failed. So the fault was somewhere along this circuitous copper track. But where, and why? I went back to connector F and, using a pair of stainless steel test prods with very sharp points, I began working along the copper track. And here I encountered the pressure sensitive situation that I mentioned earlier. In fact, connector F is not very far away from the various power supply components (Q901-Q909 etc) where I had experienced this before. Now I found that the pressure I was exerting on the prod, to penetrate the protective lacquer, would sometimes change the state from a no-go to a go. But the effect was not consistent and I couldn't make any real sense out of it. All it indicated was that there was a dicey connection somewhere in the vicinity. In an effort to minimise this effect, which seemed to be hindering rather than TETIA TV TIP Sanyo CTP6631 (BOP Chassis) Symptom: No sound or picture. No output from power supply although all fuses are intact. Collector of chopper transistor is likely to be carrying anything up to full bridge output voltage . Warning: discharge the main filter capacitor (C308) before carrying out any tests around the chopper. Cure: R302 (390k0 ½W) open circuit. This resistor supplies bias to the chopper transistor and without bias the chopper can never start up. Note: any attempt to test the chopper transistor in circuit may lead to its destruction if C308 has not been discharged . TETIA 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. SEPTEMBER1989 43 SERVICEMAN'S LOG -CTD helping, I decided to work from the other end of this track, starting at reference point 22, where the cable joined the board. From here I made my way along the track, a few centimetres at a time, and this did seem to avoid the pressure sensitive situation. It all took time of course but eventually I reached a point about one third the way along it, where it runs hard against the extreme edge of the board. In fact, it is one of a group of three tracks between the edge of the board and IC5A2. And here I encountered something which was not indicated on either the circuit or the board diagram; a small polyester capacitor connected between pins 1 and 3 of IC5A2. It was fairly obviously a manufacturer's modification - not that additions like this are all that strange in modern equipment. What was strange was the fact that in addition to being soldered into the circuit - which should have provided more than enough support - it had been laid over on its side, across the three tracks just mentioned, and glued into place. Yes, glued; why I can't imagine, but there it was. More importantly, it quickly became evident that this was where the trouble lay, because the voltage on the track on the other side of this component was normal. Somewhere under that capacitor the copper track was damaged; and damaged so delicately that it was, in effect, a high resistance joint. The cure I took the easy way out and bypassed the faulty section of track with a short length of tinned copper wire, routed over the top of the capacitor. And that fixed it; it was almost an anti-climax after all the sweat and bother of tracking down the fault. Unfortunately, a few questions remain unanswered. Apart from querying why the capacitor was glued in the first place, it is reasonable to ask what caused the track to fail. Was there a defect at that point initially, which was aggravated by whoever mounted the capacitor'? Or, more likely I suspect, did the glue contain some corrosive component which attacked the copper'? If the latter is true, what are the chances of the two remaining tracks surviving'? Since this is all pure speculation I'm afraid that that's a risk that will have to be taken. At least, if I strike more trouble in this machine, I'll know where to look first. So there it is; one of the rarest faults I have ever encountered. And how did I come out of it financially'? Not very well I'm afraid, though it could have been worse. Bar codes Tu~ 4-·9V WA.'S c1--ose:. 6NOO~ -ro 111e: 5V t w~~ Cl-l~~•~G & -PWV w~s '1\-\e: DE.S\GNJ.\-rtOI\\ OF "tl\~ t-eAt> TO ..-Hf; "B~'S~. 44 SILICON CHIP 1: F " O ~ \,. To finish off this month, I have to acknowledge a letter from P. Dunford, of Christchurch, NZ, which appeared in the July 1989 issue, page 5. This was prompted by comments in the April issue concerning VCR digital scanners. I questioned the usefulness of these devices, inasmuch as I had yet to see any programs with bar codes. I now understand that one Sydney newspaper, the Sunday Telegraph, provides this service with its TV guide. Even so, I still have my reservations. As my correspondent points out, some people have difficulty using the scanner but there is a more serious limitation. It's not the fault of the system as such but rather problems caused by incorrect transmission times. Late night programs in particular can be early or late by anything up to 30 minutes, with the indicated running time also sometimes in error. Having been caught myself several times I now straddle such 2 3t .1 20 ,a , __________._ ·_·1_·_·_·_ · _·_·_ _· _·_·_· ~ - - - ~ ~ r t l Fig.3: this diagram shows the physical layout of the relevant circuitry on the main board, simplified for ease of presentation. Connector F is to the lower right and the copper track from its pin 7 runs off to the left, via a couple of bridges, to the extreme left of the board. From there it runs vertically past IC5A2, then turns right and runs along the top of the board to cable point 22. programs with at least 30 minutes at either end, using a 180 tape for a 2-hour program or a 240 tape for anything longer. But there is no way to do this using published bar codes, thus largely negating their value. Mr Dunford also comments on my query as to why some machines now load the tape against the control head immediately the cassette is inserted. In fact, I followed up this point after I had raised the matter and came up with the same explanation that he so clearly set out. I refer you to it. Indexing gimmicks Later I was able to pursue this further at a 2-day National Panasonic seminar in Canberra. A whole range of topics was covered, some of which I may deal with in later notes, but for the moment here are some details on the latest indexing gimmicks (models NVD-38, NVD-48, F-70, H-75 and D-80). The system provides for up to 20 indexing signals to be entered onto a tape while recording. An indexing signal is entered automatically when the record button is pressed, either to start recording or during recording to index a particular segment. When such a tape is re-inserted for replay, it may be run in the normal way by pressing the play button. If the play button is not pressed, it will immediately go into the fast forward mode. Then, as each indexing signal is encountered, it will generate a 1/9 size picturewithin-picture of the following 10-second segment in the top right corner of the screen. If the play button is then pressed during this period, normal play results. If the play button is not pressed, the last frame of the 10-second segment is frozen in the 1/9 area frame and fast forward continues until the next index signal is encountered. This generates another 1/9 area frame below the first one and, at the next signal, a third one below that. A fourth signal replaces the first image, and so on. As each new frame is presented, the index number is also displayed, there being a facility to recall a segment by feeding in this number. A segment can also be recalled be feeding in the elapsed time from the beginning of the tape, assuming this is known. Apart from these indexing facilities, there are several other features, such as a picture-withinpicture facility to enable monitoring of one channel while another is by ing watched, and so on. It's all very clever of course, but I do wonder whether we really need all these facilities, or how many people will use them. Still, the makers say we need them, so I suppose we must. [lEI FIX-A-KIT Kit Repairs - $1 5 per hour. Normal Rate - $35 per hour. No charge for kits that can't be repaired . 3 month Warranty on repairs . Construction - fixed or hourly 1 2 Month Warranty on Manufactured Kits. Custom Designing, Manufacturing, Large or Small Quantitites. HYCAL INSTRUMENTS Design, Manufacture, Repair of Electronic Equipment. (02) 633 5897 Unit 4, 62 Great Western Highway, Parramatta, NSW 2150. Trading hours: 8am to 3pm Monday to Friday. SEPTEMBER1989 45 EASY WAYS TO SECURE YOUR HOME AND CAR! So Easy To Install! Here's a the inexpensive to protect you r car again st theft! A current sensing car alarm that you can easil y install yourself! Features instant boot/bonnet trigger, ignition cut off, battery back up capabi lity and manual override capability. Comes complete with ..... • • • • Transmitter key Boot/bonnet switch Dash warning light Mounting hardware and complete installation instructions. Five zone protection for your home and it can be installed in no time - Withou t Wiring! Simply plug it in , set the code and you've got instant protection . Features instant/delay modes, five zones of protection , built-in speaker and provision for external speaker. Ideal for units, flats or anywhere wiring presents difficulties. Comes with remote control , remote Reed switch, infrared sensor and mains adaptor - it's a complete system! Cat L-5125 s399 Cat L-5069 Priced to clear! Was $129 NowOnlysgg A great addition to your Moss car alarm! The MS701 Ultrasonic Volumetric Sensor is easy to fit to the dashboard or parcel shelf and detects any movement inside the vehicle. It's great for soft tops or cars with a sunroof! Plugs directly into the MS?00/705/ 720 alarm systems. Cat L-5072 Now it's better value than eve r. Th e Moss MS700 keyless car al arm is one of the easiest car alarm to use. Simply turn the ign ition 'off' .. .and the alarm comes 'on '. Features automatic arm ing, bonn et and boot protection hidden valet switch and more. Installation is a breeze. Cat L-5070 Install It Yourself! sgg You won 't have to worry about leaving your home unprotected with this one! It's the best value and quality home security system around and comes with everything you need for truly professional quality security in one carry-home pack. You get a 4 sector control panel , 2 infrared detectors, 2 magnetic reed switches, siren horn and cover, strobe light, internal screamer, plug pack and back-up battery, 100m of cable .. ..everything! Cat L-5150 All For Only sgg 599! 5 ~ ~··"'G l• ~ ...... ~J Instantly arm/alarm before you get into the car! Comes with TWO remote keyswitches that can be attached to you r keyring . • Instant remote arm/ disarm • Indicators fl ash for arm/disarm • Low power usage to prevent battery drain • Easy to fit and comes with window stickers Cat L-5071 _ _ _ _ __ .JJv With Battery Back Up! S720 It's approved by most major insurance companies! Truly profession q uality security for your car. Features key ~~ override, completely immobil izes the ~ ignition , shock sensing, secu rity ci rcui t, battery back up, water and steam resistant ...the list goes on . Comes with TWO remote switches. Cat L-5073 MITH Now s199 The Best Price Around Just The sensation Super Tomcat AM SSB CB mobile at an incredible low price! An outstanding buy with maximum legal power on both AM and SSB, all 40 channels, the extra range and performance SSB offers .... and, with optional power supply, it can even double as a base station! Comes complete with mounting hardware, microphone and full instructions. Cat D-1713 sgg • It's a DRILL • Ifs a SOLDERING IRON • It's a SCREWDRIVER • It's totally PORTABLE • And ifs RECHARGEABLE! This has to be one of the smartest tools for hobbyist, handyman and tradesman alike. Modular components fix to a rechargeable battery pack (handle) and in seconds you can switch from a soldering iron to a drill, from a drill to a reversible srewdriver, etc, etc. . It's easy to handle and the pistol grip action leaves one hand free to make working a breeze! Comes complete with assorted drills, screwdrivers, solder accessories and charger. Check out our great price ... it's the best around. Cat T-5712 This has to be the most comprehensive Databook ever! 3 complete volumes from National Semiconductor. Covers everythingVoltage regulators, operational amps, active filters, analogue switches, audio/radio/video circuits, etc. etc. An absolute must for the library. Cat B-5001 s49ss Pushbutton Channel Selection JustS89 You won't find a better deal! The □ SE 40 AM CB gives you high quality mobile communication without the hefty price tag . Its amazingly compact, beautifully styled and features all 40 AM channels, pushbutton channel tuning and maximum legal power. Comes with Mic and mounting hardware! Cat D-1200 Just what's needed for heavy duty mathematical calculations - and it saves time as well! A maths co-processor can perform high speed and highly accurate arithmetic, logarithmic and trigonometric operations while leaving your microprocessor free to perform other functions. Ideal for working in Auto CAD and most major spreadsheet programs such as Lotus 1-2-3, Symphony, Multiplan, etc, etc. Just plugs into your co-processor socket. For AT's And Compatibles 80287-6 6MHz Co-processor. Cat Z-9106 Limited Stocks! For XT's And Compatibles Over 1200 pages of detailed reference! A fully indexed and cross referenced collection of linear integrated circuit applications using both monolithic and hybrid circuits from National Semiconductor. Cat B-5504 s24ss Robert Witte - 261 pages A comprehensive sourcebook which simpilifies the internal workings of test instruments through easy to understand circuit models and conceptual block diagrams. An excellent supplement to instrument operating manuals. Cat B-4999 s29ss 8087-1 10MHz Cat Z-9107 Limited Stocks! Need More Memory? Building your own computer or extending the memory of your existing system? You'll do it in minutes with these great value DRAM memory chips. They just plug into the motherboard or extension memory card. 256K Chip 41256-12 Was $29.95 A zippy 120NS, 256K x 1Bit chip at a fantastic low price. CatZ-9313 1Mb Chip 51 lOOOp-BO Now $1 995 Here's the way to go for those big memory machines like our AT Mother Board and many other powerful computers fast SONS, 1MB X 1 Bit. Just N.S.W .:• BALLINA: Ballina Electronics81S7022• BOWAAL: F.R.H. Electrical 511881 • BROKEN HILL: Hobbies& Electronics 884098 • CHARLESTOWN: Newtronics 439800 • COFFS HARBOUR: Coffs Harbour Electronics 525184 • DUBBO: Chris's Hi Fi 828711 • FORSTER: Forster Village Electronics 545008 • GLEN INNES: John Som·mertad Electronics 323881 • GRAFTON: Repairs and Spares 421911 • GRIFFITH: Mlatronics 624534 • INVERELL: lnverell Electronics 221821 • LEETON: Leeton Audiotronic 532800 • LISMORE: Decro Electronic Services 214137 • MOREE: Moree Electronics 523458 • MUDGEE: Headware 723895 • ORANGE: Central West Electronics 821491 • NOWRA: Nowra Electronics 210722 • PARKES: Strad Music Centre 823388 • WAGGA WAGGA: Phillips Electronics 218558 VIC: MORWELL: Morwell Electronics 346133 • SHEPPARTON: Phillips Electronics Pty Ltd 219497 • WARRNAMBOOL: Marrtronics 829870 QLD: •BUNDABEAG: Bob Elkin Electronics 721785 • MACKAY: Stevens Electronics 511723 • MARYBOROUGH: Keller Electronics 214559 TAS: DEVONPORT: A.I.Electronics 248322 SAi •LOXTON: G & S Electrical 847495 • MT GAMBIER: Hutchesson's Communication Centre 250400 WA: ALBANY: Micro Electronics 412077 • BUNBURY: Micro Electron ics 218222 • GERALDTON: Batavia Lighting & Electrical 211966 KARRATHA: Daves Oscitronic 854836 399 s499 5 s59ss Best Value in Sight & Sound! New Release! New Release! Ex_pandable FM Wireless Intercom Stereo Cassettte With Auto Reverse Portable Stereo Cassette Perfect for the office, factory or home. Can take up to 6 stations allowing 3 simultaneous (and Private) conversations. There's no wiring , it's mains operated, gives crisp, sharp sound and can also be used as a monitor system. Cat F-1250 Look sgreat, sounds great and has an amazing array of features for the price! The new Digitor stereo cassette with auto reverse and tape direction selector. Fast forward and rewind makes track selection easy, Comes with stereo headphones, belt clip and DC jack. Cat A-4091 New Voice Activated Model! NEW! A bargain price for a stereo cassette with lightweight headphones, belt clip, auto stop and Super Bass Boost - superb, realistic sound! With DC jack so you can save on battery power when you're _ __,_ at home. Cat A-4090 NEW! s499s s299s Two In One! Engineered For Australia! With 10 Memories! Bargain Telephone/ Answering Machine Cordless With Double Adaptor Stylish Two-Tone Phone Built, from the ground up, for Australian conditions this cord less phone offers exceptional value for your money, wall or desk mount capability, plus cordless convenience. Features include maximum range, built-in charger, paging facility, security dialling code (prevents other cordless phones using your line), last number redial, compact design ... the lot! Cat F-7100 A great looking phone with performance to match! Features 10 memories including last number redial! In two-colour finish with large rubber pushbuttons for mistake-proof dialling, pause button, tone/pulse selection, ringer on/ off and much more. Cat F-5505/9 Sensational value and it saves space too! A modern pushbutton phone with all the usual features including selectable tone/pulse dialling, last number redial, etc, etc ... plus a single tape answering machine in one compact unit. Cat F-6140 5 Wireless! It's Incredible! Monitor System Pocket sized LCD Full 'Colour' TV Simply plugs into the mains - so there are no batteries or wiring to worry about. Monitor has adjustable Voice Activated sensitivity and the master can be moved from room to room . .. anywhere you are. Cat F-1400 199 It's the most amazing thing! A full colour TV that you can fit in your pocket. The 2" LCD screen gives a suprisingly clear picture and you get great reception inside and out. Comes with an inbuilt stand so you can get the right viewing angle, has earphone supplied with the TV so you can listen without disturbing those around you. Cat G-5520 329 5 i»XPRESS ORDER BY PHONE - 008 22 6610 (LOCAL CALL FEE) OUTSIDE SYDNEY SYDNEY AND ENQUIRIES - (02) 888 2105 FAX: (02) 805 1986 OR WRITE TO DS XPRESS, PO BOX 321 N/RYDE NSW 2113 ALL MAJOR CREDIT CARDS ACCEPTED. 0/NITE COURIER AVAILABLE. 24 HOUR DESPATCH OF ALL ORDERS Cordless Remote Headphone System Cordless Remote Stereo Headphones - so there's no wires to get tangled in. Just plug the transmitter into your stereo, TV, VCR, radio or whatever and clip the receiver to your belt. There's a volume control on both receiver and transmitter and the unit comes with adaptor plugs, mains adaptor and quality stereo headphones. Cat C-4212 ,J/IIJJ/J//JJIJ//JJ//j/j VOICE ~ /4 lt; · ::J ;;w29 ~~ THE AMAZING Now With The Atari "POWER PACK" ATARI ST Now the world's favourite home entertainment/computer system comes with the astounding ATARI POWER PACK! That's 20 of the most popular software titles, including such all time favourites as 'Double Dragon'. Nearly $1000 worth of software - and it's FREE! . Of course you still get all the superb features of the powerful ATARI ST. High speed, superb sound, amazing power (up to an incredible 1Mb memorY.), standard features that most others call options ... and graphics so good, you wont believe your eyes! PLUS we'll Qive you as an EXTRA BONUS the amazing Partner ST. It's a complete desktop utility with appointment calendar, memo pad, phone list and auto dialler, full function calculator and more! Nearly Just Plug It In! • PLUS EXTRA BONUS - . The ATARI ST plugs straight into your existing TV and comes with mouse, 720K 3 1/2" disk drive, fast 8MHz clock speed, Centronics port, RS-232 port, joystick port, and musical instrument digital interface. $1000 worth of software, Free! Great Range Of Software! BATTLEZONE STAR RAIDERS JOUST MOON PATROL BORODINO GO MOKU CRYSTAL CASTLE DRILLER STAROUAKE CAPTAIN BLOOD SPACE RACER HOSTAGES LOMBARD RALLY MORTVILLE MANOR FLIPPIT G'NIUS EQUATION BUILDER MAGICAL MATH 1 SPELLING BEE MAGICAL ANAGRAM PC DITTO FLASH TIMEWORKS PUBLISHER WORD WRITER DATA MANAGER PARTNER ST Cat X-6120 Cat X-6121 Cat X-6122 Cat X-6123 Cat X-6124 Cat X-6125 Cat X-6126 Cat X-6127 Cat X-6128 Cat X-6130 Cat X-6131 Cat X-6132 Cat X-6133 Cat X-6134 Cat X-6136 Cat X-6137 Cat X-6210 Cat X-6211 Cat X-6215 Cat X-6216 Cat X-6270 Cat X-6275 Cat X-6250 Cat X-6260 Cat X-6261 Cat X-6263 $24.95 $24.95 $24.95 $24.95 $24.95 $24.95 $24.95 $49.95 $49.95 $69.95 $49.95 $69.95 $59.95 $49.95 $29.95 $49.95 $19.95 $19.95 $19.95 $19.95 $169.00 $79.00 $199.00 $99.00 $99.00 $99.00 ATARI 520ST s799 5 1099 With 512K memory and all the incredible ATARI features. Cat X-6000 ATARI 1040ST With an amazing 1Mb memory plus all the ATARI features! Cat X-6005 Colour Monitor A superb colour monitor with high resolution and vivid colours. Gets all your fantastic games and graphics software looking good! With front mounted controls so it's easy to use, and $ inbuilt speaker for sound. . ~-.. 649 Everything To Make Your Computer System Perform! RS-232 Serial L" e s RS-232 Serial Jumper An easy to use tester with 25 pin male and 25 pin female connectors. 18 bright LED's monitor the lines so you 'll know immediately where the problem lies. A great time and headache saver! Cat X-2650 25 pin male and 25 pin female connectors. With jumper pads and wires which allow permanent soldering for RS-232 connections. s1 99s Cat X-3569 sgs5 A great idea! The switch box allows the switching of a common input to any 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 Pin with D825 Connectors. Cat X-3575 36 Pin with Centronics Connectors. Cat X-3576 RS-232 Seria RS-232 ui 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 s399s RS-232 25 Pin o d tor · In-line adaptor with D825 pin female connector one end and DE9 male at the other. Cat X-2661 RS-232 9 Pi to Ad to In-line adaptor with DE9 female connector one end and D825 male at the other. sggs Cat X-2660 S- 32 With Female D825 connectors at each end . Wired for full handshaking . Allows the connection of two corn puters 'back to back'. Cat X-2664 A complete in-line tester/ adaptor which makes complex and time consum ing Serial connections a breeze. Comes with 25 pin male connector at one en d and 25 pin female connector at the other. With jumper pads and wires, as well as 24 in-line switches, for quick selection for any RS-232 configuration. The tester itself has 8 bi -colour LED's which monitor the lines and tell you at a glance when you've got it right. Cat X-2654 s499s A must for when installing expansion cards or changing memory chips. Stray static charges can destroy chips in an instant. With adjustable fastening, coiled ground lead and high value series resistor for added safety. Eliminates the risk! Cat X-2042 sggs A veroboard on an XT compatible expansion card . Complete with interrupt and memory addressing circuits already installed to enable easier construction of more advanced project ideas. With comphrehensive manual. Cat X-2034 5 149 1~~! Flopp IDC Universal A floppy drive data cable which is fitted with both Edge and OIL socket connectors. Facilitates the easy fitting of both 5.25" and 3.5" floppy disk drives. Cat X-2606 Disk Drive Power s199s A great idea! This 'Y' adaptor allows you to connect two disk drives to one power connector. Splits a 4-line Molex male into two females. CatX-2604 _ 0 0 $695 MITH Touch Lamp ................ ~- - p ed Detector ...,., Small in size, simple to construct and it comes at less than half the cost of commercial units! Has 10 metre range and can be used in conjuction with your existing alarm system or with optional interface (Cat K8201) you can use it as the basis for a complete new system for your home, etc. Comes with white filter so it can be used in the daytime (not direct sunlight). This unit can turn your light on and off or dim them just by touching the decorative plate. Unit is intended for dimming incandescent lamps rated from 25 watts up to a total of 300 watts. Cat K-3001 $ Easy to build! 3495 PIR Asdescibed in Silicon Chip June '89 K-8200 Extension For As described in EA May '89 0 0 Do you have a two-way switch in your home and would like them replaced with touch dimmers? We have just the thing for you. An extension touch plate is connected in parallel to the K-3001 main unit, so that you can switch your lights on and off or dim them remotely. This unit can be installed in your vehicle and will detect any carbon monoxide gases which may seep through into the cabin from your vehicles exhaust. Driver will be alerted either by a flashing led or an audible alarm. Cat K-4610 As described in Silicon Chip July '89 Cat K-3002 As described in Silicon Chip July '89 s129s EXCITING NEW KIT SOON TO BE RELEASED! • EXCLUSIVE TO DICK SMITH ELECTRONICS! Sophisticated Security For Your Home Alarm! I Designed by Dick Smith Electronics research and development department! Phone diallers are a great idea but, until now, they've been prohibitively expensive. So here it is! The phone dialler that is not only inexpensive and easy to install but can be fitted to just about any home alarm system with a 5V-25V output (bell/ strobe output). Look what it does .. . All you do is program a telephone number into the Phone and it rings you (and emits a tone) to tell you your alarm has been triggered. If you're away from home (on holidays, etc.), you can phone home and the Alarm Dialler will tell if your alarm has sounded. That means peace of mind no matter where you are. Cat K-8300 As described in Silicon Chip Sept '89 Easily Affordable/ • NSW • Albury 21 8399 • Bankstown Square 707 4888 • Blacktown 671 7722 • Campbeutown (046)27 2199 • Chatswood Chase 411 1955 • ChulJora 642 8922 • Gore Hift 439 5311 • Gosford 25 0235 • Hornsby 477 6633 • Hurstville5808622• Uverpool6009888• Maitland33 7866• Miranda5252 722• Newcaatle611896• NorthRyde 88 3855 •Pamamatta 689 2188 •Penrtth (047)32 3400 •Railway Square 211 3777 •Sydney Ctty 267 9111 ·•Tamworth 66 1711 • Warringah Mall 905 0441 • Wollongong 28 3800 •ACT• Fylhwick 80 4944 •VIC• Ballarat 31 5433 • Bendigo 43 0388 • Box Hill 890 Coburg (03) 383 4455 • Dandenong 794 9377 • East Brighton 2366 • Enendon 379 7444 • Footscray 689 2055 • Frankston 783 9144 • Geelong 43 8804 • Mefboume City 326 6088 • Richmond 428 1614 • Ringwood 879 5338 • Spingvale 547 0522 • QLD • Brisbane City 229 9377 • Buranda 391 6233 • Caims 311 515 • Chermslde 359 6255 • Redbank 288 5599 • Rockhampton 27 9644 • Southport 32 9863 • Toowoomba 38 4300 • Town1ville 72 5722 • Underwood 341 0844 • SA • Adelaide City 592 0699 • ~~ ~~: =::e3jj/g~;.sJ~~j:3~~;4E!i=cf:54i~9f2;~~:'~1!,: ~gg~;s"J~ ;;;~"~':~ 31 0800 •NT• Stuart Park 81 1977 Features • Comes with push button Telephone • Plug Pack included • Battery back-up capability (battery not included) • With pre-punched front panel and case • Fits most alarm systems (with 5-25V output) • Test facility • Trip LED <1: C ALA RM ;:;:-e PHO NE • D IALLE R - ._ . ii "i ~ :.~-. . .: ' --= Low-cost circuit has many applications High or lo-w level fluid detector This simple circuit can detect high or low fluid levels in a tank and trigger a relay output accordingly. It's very easy to build and uses just two low-cost ICs, a relay and a handful of other parts. Design By PETER GRAY There are many applications for a fluid level detector such as the circuit presented here. Some of these applications include monitoring fluid levels in fish tanks, sumps, radiators and washing machines, controlling irrigation systems and pumps, and monitoring soil conductivity in greenhouses. Despite its overall simplicity, this circuit is very reliable. It's based on the LM1830 Fluid Detector IC from National Semiconductor and this feeds an AC signal through a pair of external probes. The circuit can easily be adjusted to detect a wide range of fluids and there's a changeover switch so that you can monitor for either high or low fluid level. The circuit for the fluid level detector is built on a small PC board that should only take a few minutes to assemble. The external switch allows either high or low fluid levels to be monitored. 52 SILICON CHIP Want to detect when the fluid in a tank rises above a preset level? Simple - just set the changeover switch to the HIGH position. If the switch is set to LOW, the circuit will detect when the fluid drops below the preset level. Because the circuit has a relay output, you can easily adapt it to suit your particular application. For example, you might use · the relay to activate an alarm if the fluid level in a tank falls below a certain level. Alternatively, you could use the relay contacts to automatically switch on a pump to top the tank up again. One obvious application is controlling a bilge pump in a boat. In this case, the unit is set so that it switches on the bilge pump when the water reaches a preset level. A small amount of hysteresis is provided by the circuit to prevent "hunting" at the critical level. On the automotive front, this device is suitable for monitoring fluid levels in radiator overflow tanks and in washer bottles. In outback regions particularly, it could save you from the traumas of a blown engine due to coolant loss. An option here is to delete the relay and substitute a piezo buzzer or LED to provide the low fluid level warning. A number of units could also be built to control mist sprays in a greenhouse or plant nursery. By using the probes to monitor soil conductivity, you could automatically switch on the mist sprays when the conductivity dropped below a certain level. An on-board trimpot lets you set the moisture level at which the circuit triggers. is able to turn on the output transistor. In Fig.l, the output transistor drives a small LED but it could also be used to drive a loudspeaker or a low-current relay. OK, that's basically how the chip works but there are one or two more wrinkles. One problem that can arise with the circuit of Fig.1 is that the impedance of the fluid we wish to detect is of a different order of magnitude to the internal reference resistor, RREF· This problem can be solved by coupling the oscillator output to the probe via an external reference resistor, instead of via the internal reference. Fig.2 shows the details. By selecting the value of this external reference resistor, the circuit can be made to work with fluids of virtually any conductivity. A filter capacitor can also be added to pin 9 of the LM1830 to filter the detector output. If this is done, the output transistor will switch on and remain on when the fluid level drops, instead of being pulsed on and off by the oscillator. Fig.3 shows the final circuit of the Fluid Level Sensor. In addition to the LM1830 (ICl), it also uses an LM393 comparator (IC2) and a BC547 transistor (Ql) to drive the relay. The circuitry around ICl is virtually identical to that shown in Fig.2. The .001µ,F capacitor bet- TABLE 1 Conductive Fluids lo1-COnductl11 Aulds City water Sea water All salt solutions All acids All alkaline solutions Household ammonia Water & glycol mixture Wet soil Coffee Distilled water Hydrocarbon fuels and solvents All mineral and vegetable oils Brake fluid Ethyl alcohol Methylated spirits Ethylene glycol Paraffin Dry soil DC blocking capacitor. An AC signal is applied to the probe to prevent plating and corrosion problems, as would occur with a DC source. Note that in Fig.1 we are assuming a metallic container (eg, a metal water tank). This container is simply shown connected to the circuit earth and forms the other probe input. What the circuit does is compare the resistance between the probe and the container with the internal reference RREF· If fluid is present, the probe resistance will be less than RREF and insufficient signal will be fed to the detector to turn on the output transistor. On the other hand, if the probe resistance increases above RREF (ie, if the fluid level drops below the probe level), a strong AC signal is coupled via the detector which then Table 1 lists some of the common conductive fluids which can be detected by the circuit. The nonconductive fluids listed in the table cannot be detected. How it works To understand how the circuit works, we first have to take a look at what goes on inside the LM1830 Fluid Detector. Fig.1 shows the internal workings of this chip. It contains an oscillator (to generate an AC signal for the probes), an internal reference resistor (RREF = 13k0), a detector, a driver stage and an open-collector output transistor. An external capacitor between pins 1 & 7 sets the oscillator frequency. As shown, the oscillator output is made directly available at pin 5 and is also applied to the probe via RREF and an external .05µF •cc •cc '10 O.IOf;,f TIMING CAP ~m " 8.IHl1 1,1 F ~ 12 •cc " LEO 12 •cc TfMIIB CAI'. OSCILLATOR DETECTOR 13 10 FILTER 9 GROUND 11 ':" Fig.1: basic circuit tor detecting low fluid levels. The oscillator generates an AC signal which is applied to the active probe. Fig.2: in this circuit, the oscillator output is coupled to the probe via an external reference resistor (RREF) instead of via the internal reference. By selecting this resistor, the circuit can be made to work with fluids of virtually any conductivity. SEPTEMBER 1989 53 1M' .001 I 1M RL 1 V • c:: : 14 12 PROBE INPUTS 100k TO CONTROLLED CIRCUIT B 11 .,. .i +12V ELJc 1M VIEWED FROM BELOW .,.. FLUID LEVEL SENSOR Fig.3: the final circuit of the fluid level sensor. The output signal from the LM1830 (IC1) is fed to IC2 where it is compared with a ½ Vee reference voltage. IC2 in turn drives Qt and the relay. ween pins 1 & 7 sets the oscillator frequency to about 7kHz, while the 22µF capacitor on pin 9 filters the detector output. Pin 5 is the oscillator output and this is coupled to one of the sensor probes via VRl and a .047µF capacitor. VRl functions as the external reference resistor (ie, the internal reference is not used). A trimpot has been used here so that the circuit can be adjusted to detect virtually any conductive fluid. When fluid is detected by the probes, the oscillator output is shunted to ground and ICla's output (pin 12) is high. Conversely, if the fluid level drops below the probes, the oscillator signal on pin 10 increases and this switches pin 12 low. The output signal on pin 12 is now coupled by DPDT switch S2 to the comparator stage (IC2). S2 simply reverses the voltages on, the comparator inputs to provide the high or low level warning functions. In the low warning mode, pin 12 of ICl is coupled to the inverting input of IC2 via a 100k0 resistor and Sla. At the same time, Slb switches IC2 's non-inverting input (pin 3) to ½ Vee (ie, half supply), as set by a voltage divider consisting of two lMO resistors. PARTS LIST 1 PC board, 82 x 44mm (available from Novocastrian Electronics) 1 DPDT miniature toggle switch 1 1 2V SPOT PC-mounting relay Semiconductors 1 LM1830N fluid sensor (IC1) 1 GL393 or LM393 voltage comparator (IC2) 1 BC54 7 NPN transistor (01) 1 1 N4002 diode (01) Capacitors 1 22µF 16VW PC electrolytic 1 .04 7 µF polyester 1 .001 µF polyester Resistors 3 1MO 1 1 OOkO 1 1 OkO 1 4 .7k0 1 1 OOkO trimpot Where to buy the parts A complete kit of parts for this project is available tram Novocastrian Electronic Supplies Pty Ltd, 24 Broadmeadow Rd (PO Box 87), Broadmeadow, NSW 2292. Telephone (049) 62 1358 or toll free on (008) 02 5942. The kit includes the PC board plus all on-board components but does not include the probes or power supply. The price is $19 .95 plus $3 .00 for postage and packing. Note: copyright of the PCB artwork associated with this project is owned by Novocastrian Electronics Pty Ltd. 54 SILICON CHIP This means that when pin 12 of ICl goes low (ie, the fluid level drops below the probes), pin 2 of IC2 is also pulled low via the 100k0 resistor. Thus, the comparator output is pulled high by the 4.7k0 pullup resistor on pin 1 and Ql turns on to activate the relay. Conversely, in the high warning mode, IC2's inverting input sits at ½ Vee and the non-inverting input now monitors pin 12 of ICl. Normally, the fluid level will be low and so pin 12 of ICl will hold pin 3 of IC2 below the voltage on the inverting input at pin 2. Thus, pin 1 of IC2 will be low and Ql and the relay will be off. Now, when the fluid level rises above the probes, the output transistor inside ICl turns off. Pin 3 of IC2 is now pulled high by the remaining lMO resistor which means that the voltage on the noninverting input is now greater than the voltage on the inverting input. Thus, IC2's output is again pulled high by the 4.7k0 pullup resistor and Ql and the relay turn on as before. Power for the circuit can be derived from any suitable + 12V source; eg, a plugpack supply. Although we have specified a nominal + 12V rail, this can be varied over the range 5-15V with no changes to component values except to the relay coil rating. Construction Fig.4 shows how all the parts are mounted on the PC board. There's nothing tricky here; you can mount the parts in any order you wish Vee OSCILLATOR OUTPUT OSCILLATOR OUTPUT (RREf) OPTIONAL DETECTOR FILTER INPUT CAPACITOR OUTPUT 12 Cl Fig.4: parts layout for the PC board. We used tinned copper wire for our probes but serious applications will require stainless steel probes to minimise corrosion problems. GNO Cl Fig.5: inside the LM1830 fluid detector. The two transistors at left form the oscillator. When the fluid level drops, the oscillator signal is fed to the base of the detector transistor which then pulses the driver and output transistors. RESISTORS No. □ □ □ □ 3 Value 1MO 1 1 1 100k0 10k0 4.7k0 although we suggest that you leave the relay until last. Be sure to install the two ICs and the diode the right way around. Pin 1 of each IC is adjacent to a small dot or notch at one end of the moulded plastic body of the device. The probes for the prototype were nothing fancier than a couple of short lengths of tinned copper wire. These were connected to the PC board using light-duty figure-8 flex. For most applications though, stainless steel probes will be required to minimise corrosion. If you are monitoring the fluid level in a metallic container, the earthed probe input can simply be connected directly to the container as shown in Fig.2. The active probe is then set to the trigger level. Testing To test the unit, set VRl to about mid-range, connect the power supply and introduce the probes to a glass of water. If S1 is set to HIGH, the relay should turn on the moment the probes touch the water and release as soon as they are removed. 4-Band Code brown brown brown yellow black black black violet 5-Band Code green gold yellow gold orange gold red gold brown brown brown yellow Now switch S1 to low - the relay should initially be on with the probes out of the water and then switch off when they contact the water. If the unit fails to work correctly, try adjusting VRl. If VRl is set too low, pin 12 will remain low regardless of the probe resistance, and the relay will remain either on or off (depending on the setting of S1}. Troubleshooting What if it doesn't work? There's not much to go wrong so troubleshooting is easy. First, go over your work carefully and check the parts placement and all the values. Check that the ICs are the right way around, that the resistor values are all correct and that the switch wiring is correct. If this doesn't reveal anything, switch your multimeter to the 20V range and use it to monitor the voltage on pin 12 of ICl. You should get a reading of close to OV with the probes out of the water and a reading of about + 11V with the probes immersed in water. Check black black black violet black black black black yellow brown orange brown red brown brown brown POLYESTER CAPACITORS No. □ 1 □ 1 Value IEC EIA .047µF .001µF 47n 1n 473K 102K the circuitry around ICl if you don't get the correct results here. If ICl checks out, remove the probes from the water and check the voltages on pin 2 of IC2. You should get a reading of a bout + 1V for one position of S1 and + 6V (halfsupply) for the other position of S1. · The same voltages should appear on pin 3 but with the switch positions reversed. If you don't get the correct readings here, the wiring to S 1 is probably incorrect. IC2 can be checked by monitoring its pin 1 output. This should give a reading close to OV for one position of S1 and about + 8.5V for the other. Finally, you can check the operation of Ql by measuring its baseemitter voltage. This should be OV when pin 1 of IC2 is low and about 0.65V when pin 1 switches high. ~ SEPTEMBER1989 55 20MHz DUAL TRACE OSCILLOSCOPE UNDER $400.00??? C1-118A 20MHz 2ch. CRO 12 MONTHS WARRANTY * Frequency range: 10Hz to 20MHz. * Display: CH1, CH2. * Deflection Factor: 5mV steps (up to 10V) * * * INCLUDES 2 * x 1 :1 10:1 PROBES 1, 2, 5 sequence . Pulse Rise Time: 17.5ns. Sweep Rate: 0.05us to 50ms/DIV. 1, 2, 5 sequence. Free-running sweep mode with synchronization from 1 0Hz-20MHz signals and manual setting of the required triggering level. 60 x 80mm screen. s399.9s SPECIAL INTRODUCTION PRICE AVAILABLE LATE SEPTEMBER SALE SALE SALE SALE SALE SALE SALE SALE SALE EDM-166 DIGITAL MULTIMETER * * * * * EDM-168 DIGITAL MULTIMETER * Display: 3.5 digit LCD. * Ranges: AC V, DC V, Ohms, Current (20 amp AC/DC), Diode Test, HFE Test, Display: 3.5 digit LCD. Ranges: AC V, DC V, Ohms, Current (20 amp AC/DC), Diode Test, HFE Test. Audible continuity. Includes probes. 12 months warranty. * * Frequency, Capacitance Audible continuity. Includes probes. 1 2 months warranty. * $102. 75 incl. tax. $88.58 ex. tax. $78.50 incl. tax. $67. 74 ex. tax. SALE SALE SALE SALE SALE SALE SALE SALE SALE * * * QUICK MOUSE MICROSOFT COMPATIBLE NOW $89.95 BE QUICK!!! DB-25 TYPE and CENTRONICS TYPE 2-WAY .. was $59.00 NOW $49.00 Tracking speed: 600mm/sec. Resolution: 200 DPI. Includes driver, test program and mouse pad. was $99.95 COMPUTER DATA SWITCH BOXES 4 WAY .. was $89.00 NOW $79.00 m J . * * ,. COMPUTER FAN * 120mm. Air Flow: 80CFM Speed: 2600 RPM was $28.95 NOW $19.95 DB SERIES COMPUTER CONNECTORS ~ (SOLDER TYPE) ~ *** DB-9 PLUG ALL ONE DB-9 SOCKET PRICE DB-9 BACKSHELL itr DB-15 PLUG $1.00 DB· 1 5 SOCKET h DB-1 5 BACKSHELL eac DB-25 PLUG ~ DB-25 SOCKET .• 1 08-25 BACKSHELL <> ,,,.- ** ** * SALE SALE SALE SALE SALE SALE SALE SALE SALE Business HOU's DAVID REID ELECTRONICS 127 York St. Sydney NSW 2000 Phone: (02) 267 1385 Mon- Fri llusday Sat,.day 8.30 -5.30 8.30 -7.00 9.00 - 1.00 12 volt to 240 volt INVERTERS 600 WATT VERSION 300 WA TT VERSION * Complete kit was $425.00 NOW $399.00 * Fully built was $525.00 NOW $499.00 * Complete kit was $279.00 NOW $269.00 * Fully built was $379.00 NOW $350.00 SALE SALE SALE SALE SALE SALE SALE SALE SALE RACK FRAMES for 19" RACK BOXES RACK MOUNT CABINETS • Standard 19" rack mount 1 2 3 1 2 3 unit unit unit unit unit unit natural. . . .. .... . was $59.95 NOW $49.95 natural . . . . . ... .. . .. .. was $69.95 NOW $59.95 natural. . .. . was $85.00 NOW $75.00 black . . . . . . . . . . . . .. was $59.95 NOW $49.95 black ... .. .. .. . .. . . .. . was $79.95 NOW $69.95 black. . was $89.95 NOW $79.95 4 unit frame 4 unit panels 6 unit frame 6 unit panels 12 unit frame 12 unit panels 18 unit frame 18 unit panels 30 unit frame 30 unit panels 38 unit frame 38 unit panels was $119.00 $49.00 $119.00 $49.00 $135.00 $69.00 $149.00 $89.00 $189.00 $129.00 $249.00 $149.00 NOW $99.00 $39.00 $99.00 $39.00 $110.00 $55.00 $119.00 $75.00 $150.00 $99.00 $199.00 $115.00 SALE SALE SALE SALE SALE SALE SALE SALE SALE TOROIDAL TRANSFORMERS 160 VA MODELS 240 240 240 _240 240 240 240 V/12+12V<at> V/18+18V<at> V/25+25V<at> V/30+30V<at> V/35+35V<at> V/40+40V<at> V/45+45V<at> 160 160 160 160 160 160 160 240 240 240 240 240 240 240 VA was $65.00 VA VA VA VA VA VA NOW $49.99 BI 300 VA MODELS V/12+12V<at> V/18+18V<at> V/25+25V<at> V/30+30V<at> V/35+35V<at> V/40+40V<at> V/45+45V<at> 300 300 300 300 300 300 300 VA VA VA VA VA VA VA was $79.00 NOW $59.99 BI SALE SALE SALE SALE SALE SALE SALE SALE SALE VALVES 6AQ5 . . . $10.50 6V6. . ... . $10.50 6D06 . . . $21.50 6GW8. . .. $9.95 6AU4. . .. $11.50 6B05 ... .. . . $9.95 6L6 .. . ... . $13.50 6CA7 ... . .. $13.25 1 2AX7 . .. . .. $8.45 12AT7 . . . $8.45 PY500 ..... $13.50 PL519 ..... $29.95 MORE VALVES AVAILABLE!!! PLEASE CHECK FOR PRICE AND AVAILABILITY HIGH VOLTAGE ELECTRO CAPS 12" GUITAR SPEAKER * 150 Watts RMS (200 W Max.) * Freq.: fo-5000Hz. * Res. Freq.: 40Hz * SPL: 97 dB/W 1µF <at> 350V . . . $1.50 2 .2µF <at> 450V ..... $1.95 4 .7 µF <at> 450V .... . $2.95 1 OµF <at> 450V ... . .. $3.95 22µF <at> 450V .... .. $4.95 4 7 µF <at> 350V .. .. .. $4.95 47µF<at> 450V . .. .. . $7.95 1 OOµF <at> 350V. . .. $4.95 1 OOµF <at> 450V . . . . $9.95 * Impedance: 8 .0hm. was $160.00 NOW $ 1 35.00 SALE SALE SALE SALE SALE SALE SALE SALE SALE Mail Orders: P.O. Box 0103 Sydney NSW 2000 Fax: (02) 261 8905 II[+ :II P&PRates $5-$25 $26-$50 $51+ $4 $6 $8 VISA 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. Sawtooth/triangle wave£orm generator This interesting circuit generates both sawtooth and triangle waveforms from an external clock signal. In practice, the circuitry is limited to a sawtooth/triangle repetition rate of about 8kHz. The square clock signal is fed to the input of a 4024 7-stage binary ripple counter (IC3) and its outputs are fed to an R-2R ladder via exclusive-OR [XOR) gates IC1 and IC2. The Q6 output of IC3 is fed via switch Sl to either the top of the R-2R divider for sawtooth output or to one input of each of the XOR gates for the triangle output. Because the Q6 output does not go to the top of the R-2R ladder for the triangle function, the triangle output is half the amplitude of the sawtooth. The Digitally-controlled stereo volume control This circuit is based on two 4-bit bidirectional CMOS 4029 counters (IC3 & IC4}. These counters control CMOS switches IC3-IC6 which open or close to vary the amount of feedback resistance around two op amps (IC7a & IC7b). By thus varying the gain of IC7a and IC7b between .01 and 2.55 times, we have an effective stereo volume control. Schmitt trigger inverters IC1d and IC1e provide debouncing for the UP and DOWN momentary action pushbutton switches. These control · the direction of the volume by controlling the UP/DOWN (pin 10) inputs of IC3 & IC4. IC1a and IC1b form a 2-gate CMOS oscillator. Normally, pin 3 of IC1 b is pulled low via D3 and the 10k0 resistor and so the oscillator is disabled. When the UP button is 58 SILICON CHIP --------------------.9V 14 SAWTOOTH 200k 1¾ S1 100k 10/a 100k 04 10/a 5 50k GAIN IC3 4024 03 6 TIME 00 12 1M ':' difference can be made up by the variable gain of op amp IC4. The 50k0 gain control varies IC4's gain from unity to two times. Power can be derived from a 9V battery or plugpack supply. pressed, D3's cathode is pulled high via D2 and clock pulses are gated through to the counters via IC1c. During this time, the UP/DOWN inputs are held low by the output of IC1e and so the counters count down. The Q1-Q4 outputs of IC3 & IC4 are fed to an array of 16 CMOS switches (IC3a-lC6d). There are eight CMOS switches in each channel and each switch is wired in parallel with a resistor ranging in value between 10k0 and 1.28MO. As the counters count down, IC3alC6d are switched so as to increase the overall value of the feedback resistance across each op amp and thus the gain in each channel. IC2 and IC8 form a simple level indicator. The Q2-Q4 outputs of IC4 are inverted by IC2a-IC2c and fed to IC8 which is wired as a binary to octal decoder. Its QO-Q7 outputs drive eight LEDs to produce a 1-of-8 indication of the volume setting. When the DOWN button is pressed, the UP/DOWN input is pulled high and the counters count up. This progressively shorts out the feedback resistors, thus decreasing the volume. Note that the carry out of IC4 is wired back to the carry in of IC3 via inverter IC1f. When IC4 reaches maximum count, its carry out pin goes low and IC1f pulls pin 5 of IC3 high, thus stopping the counter. This prevents the counters from jumping directly from 1111 to 0000; ie, between minimum and maximum volume. As a further precaution, the two counters are each parallel loaded with 1111 (ie, minimum volume) at switch on. Finally, note that some of the resistors in the feedback networks are not standard values and will have to be made up from series and parallel strings. Darren Yates, French's Forest, NSW. ($40) M. Young, Christchurch, NZ. ($25} ~ C,11 (.0 a:, ..... (.0 ::,0 t'l 0:, 3::: t'l -l t'l '"O C/'J 0.11 9V DOS~N, 0.11 ~ 1 ~ql ➔ 33 ~ ..,---,..- RIGHT INPUT + I.,. 33 - 1M • WV. .,. .,. ) +9V r 6 ·1 -=-- I .,. 14 CIN .,. ·: 1 33 RIGHT OUTPUT 10k +9V 5 COUTL 19 BID 11 DE 02 03 04 111 114 12 IC3 4029 112 113 13 J4 J2 J3 U/D 01 11 0 l6 J1 1.28M +9V bs CK 16 12 .01 11oe 6 14 J1 ~2 01 6 ~ 113 J3 J4 19 B/D o-:t33I - LEFT INPUT +9V 02 03 04 11 14 2 IC4 4029 J2 +9V 1M 33! W.+. • .....,. 4~~ .,. 10 3 .,. ") +9V F40 12lc 13J 8 10,A "I * +9V 06 0 04 03 02 4 7 1 15 2 01 14 07 -8- 4~:8 ~ I LEFT OUTPUT ·:r 33 Studio series 20-band stereo equaliser In this second article on our 20-band stereo equaliser we give the construction details and a brief troubleshooting procedure. Three printed boards are used and the two main boards are linked together via removeable multiway cables. By LEO SIMPSON & BOB FLYNN Because this equaliser is housed in a standard 2-unit high 19-inch rack mounting case, it can therefore be mounted in an equipment rack, used in a free-standing mode, or stacked on top of other equipment. Ventilation is not a problem because it consumes very little power (less than 5 watts). While rack-mounting is a feature of the 20-band equaliser, the case design is somewhat simpler than many rack units. The chassis is a basic U-shape made of cadmium plated and passivated steel, while the wrapover lid is made from black Marviplate. The dimensions of the chassis, not including the front panel, are 427mm wide, 80mm high and 197mm from front to back. This gives plenty of room for all the circuitry. 60 SILICON CHIP There is one particular point to be noted about the construction, which was touched upon in the first article. It is very easy to run into problems with earth loops when using an equaliser with other equipment which is earthed. This applies to most big power amplifiers and mixers, especially those intended for semi-professional and professional use. To avoid the earth loop problem, the equaliser circuitry is not connected to chassis or to mains earth. The chassis itself is connected to mains earth, for safety's sake. Since there is no connection between signal earths and chassis, the input and output sockets must be isolated from chassis. Nor must there be any other path from the equaliser circuitry to the chassis. This will automatically be taken care of if you follow the wiring diagrams. Assembly procedure Most of the work in assembling the equaliser is involved with putting the three PC boards together. You can do it in any order but let's look at the slider board first. It measures 370 x 78mm and is coded SC 01107891. This board accommodates only the slider controls and does not have any other components. It connects to the main equaliser board via six multiway cables which are terminated at each end by sockets. Fig.1 shows how the parts are mounted on the board. It is simply a matter of inserting each slider and soldering its three pins to the board pattern. Make sure that each slider is square onto the board and as you solder each one in place, make sure it is parallel with its neighbour. When all 40 sliders are soldered in place, six multipin headers need to be soldered to the board to take the interconnecting cables. You will need two 4-way and four 10-way. headers. The former can be obtained by cutting one 8-way type in half. The multipin headers are ed to the copper side of the slider board, using the short pin side. The long pins take the matching socket plug. With the headers in place, the slider board is complete and can be set aside until you are ready to install it in the case. Main equaliser board The main board accommodates all the equaliser circuitry except for the power supply. It measures 262 x 150mm and is coded SC0l 107891. It has 10 LF347 quad op amp ICs and two LM833 dual low noise op amp !Cs. Fig.2 shows the parts layout for the main board. As mentioned in the first article, you must not substitute the ostensibly equivalent TL07 4s for the LF347s. In this circuit, the LF347 gives lower residual noise and better stability. We suggest that you install all the wire links and resistors first. Note that a lot of the resistors are 1 % tolerance types having five colour bands. To make it easier to select these resistors, we have included a table with the colour codes for all the resistors specified in the circuit. Even though we have given the colour codes, you should still use your multimeter to check the values, to be certain. Next, install the op amps. Note that two rows of LF347 op amps are oriented in the same direction which makes it easier to spot if you've put one in the wrong way. The two LM833s at one end of the board both point in the same direction too. Incidentally, while we used IC Fig.1 (right): this board accommodates all the slider controls. Make sure that each slider is square onto the board and parallel with its neighbour before soldering its leads. The six multipin headers are mounted on the copper side of the PCB. The power supply PCB is mounted as far away from signal circuitry as is possible and has been positioned for minimum noise. Keep all mains wiring neat and tidy and note how the earth lead is connected to a solder lug which is bolted to chassis. The connecting cables between the main board and the potentiometer board are run via multipin headers and matching plugs. The slider board is mounted behind the front panel on 10 18mm-long hollow spacers and secured with screws and nuts. If you can't get 18mm spacers, use 12mm and 6mm spacers instead. RESISTOR COLOUR CODES □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ □ 62 No. Value Tolerance Code 2 6 8 6 6 4 4 2 4 2 4 1MO 11 OkO 1% 1% 1% 1% 1% 1% 1% 1% 1% 1% 1% 1% 1% 1% 1% 1% 5% brown black black yellow brown brown brown black orange brown brown black black orange brown white brown black red brown grey red black red brown violet green black red brown blue grey black red brown blue red black red brown green blue black red brown green brown black red brown green blue black brown brown grey red black black brown violet green black black brown blue green black black brown blue red black black brown yellow violet black black brown orange orange red gold 2 2 12 24 2 1 100k0 91k0 82k0 75k0 68k0 62k0 56k0 51k0 5.6k0 8200 7500 6800 6200 4700 3.3k0 SILICON CHIP sockets for our prototype we don't regard them as necessary for this project. If you do decide to use IC sockets though, make sure you use good quality types (which will cost almost as much as the ICs themselves). Cheap IC sockets are not worth the trouble they can cause. You can now install the multipin headers and then the capacitors. The 8 O. lµF bypass capacitors are miniature monolithic ceramic types, blue in colour. Make sure that all electrolytic capacitors are inserted with the correct polarity. Now for the 5 % tolerance audio filter capacitors for the gyrators. We have specified Wima capacitors, kindly supplied by Adilam Electronics Pty Ltd. These are moulded . metallised polyester and polycarbonate types which are labelled in different ways, according to their RIGHT - - - - - - - - - - - 1 5 ¥ - - + 1 5 Y - - - - - OUTPUT GNO •1 .~F8,•• 2 ~- :6a 1iu ul 220pf 0.47 m~m- E3 228pFA A ~ --rnn-~· ~ GN~ lOOpF(;) (M1{3~= 1~~{3~ ~ GND• 0.47 .~~~- □ .0033LJ _ ~ 680pF I!:::!) .:{TIDe 1••· ••1 SK5a +Q e-[illJ-e .001 □ .oosa □ 1e-cmTI}e .01 □ 0.1 c:::> 0.1 eC» .015LJ .0068□ ~ .0033E!) +0100µF 1ooµFO+ ~ • : •1 .• 0.15□ .022□ 0.22□ -c=- .O~<at>.O~ ... ~ ..[illJ. .068-□ ~ 0.331!:::]i 1 +0220µF 220µFO+ ~ 0.33 □ ~ IE::!)0.22 ~ 1~FLI e-(]!0-_r..;;;;;,__ ~ ~ : ••• 0.11!::!] .0068LJ -iillD-4 ..,~ W"' --o:illJ-e ~ 0-1 «:::e 0.15 0.68 • • MLJ • : •• 0.1i;;---.i ~ • : .022□ 0.1 • 1 E:!) SK3a ..{ill[J-e SK4a 1-0~ 0.22□ <:it --mfili}e 1• e{]fil-4 .osa□ o o 2<at>o·M· --ill.ID◄ MLI 75k 0.33 • 1 8200 8 .O~s-Og : o,33c:--;t ~ o.s8D ..£illiiJ◄ w5 .068LJ ~ 0.47Ll 11 ~ .068LJ ~ O~s~O-~ 0.68□ .0068LJ e{Jfil-e .o&a □ _. 100µF ~ ~ ~i2 I 8100µF .033LJ .047LJ • 0.1 □ oc:» : ~ 1 .022E:!) : •1 1~ 0.1 0.1 This board accommodates all power supply components, including the power transformer, but not most of the bypass capacitors .osa□ .01s □ --mm◄ Power supply board : .oosa.□ 8.oosa□ ~ ..,~ ..ffiDe ~w5 ~ 0. 1 □ value. For values below .0lµF, their values are shown in picofarads but without the "pF" suffix. For example, the value .0068µF is shown as 6800. Similarly, 680pF is shown as 680. Values above .0lµF are designated in microfarads and may be with or without the " µF" suffix. All Wima capacitors are labelled with their tolerance which, in this case, is 5%. As a final step in assembly of the main board, insert the 11 PC pins for connections to the power supply and input and output shielded cables. Carefully inspect your work and then put the board aside. .0331!:::!) .0047LJ --illru-- SK2a ---m<at>J• .01E:!) -ruo-- --c:filJ◄ .0033LJ ~ • I .00¥<at>·0~ .0047LJ 1 e{ill[J-e : .047E!) .01s□ ~ <at> .0022□ ~ .. ~ --mrue-QIO-e w 5 --c:ill:}- .0022f!::!j : .022LJ .:::» 0.1 e:::,, .01s□ .0151!:::::!l e-QK}e{]fil-- .oo1s□ 1~ 0.1 .0015QI ~ SK1a 8 --oru,. w5 ~ .0047LJ 68~ <at>680pFI!::!) ... ~ 8~F .oo 100µFf!\ .0033LJ \_.} ~ 2 w47 Iii ~ 1ooµF .00471!::!) • 4 22opFA A22opF 1 100µFQ+ J: !, • 0• --OK)e l ~--mD-1 - LEFT OUTPUT GND - - - - - - - , 1 22oµFO+ "';:!; 0.33 • MLJ 47i.-=1 220µF . c:.......!! +• 75k • 0.22 7500 !,l~ ~ 1µFLI ~ 0.68 I 0.331!::j) ~ 1 ~ f 1µF □ 0 Fig.2: this is the parts layout for the main equaliser PCB. Make sure that all the resistor colour codes run in the same direction. This makes it easier to check that all values are correct. Similarly, make sure that all ICs are correctly oriented and that the electrolytic capacitors are connected the right way around. which are on the main board. The supply board is coded SC0l 103892 and measures 112 x 74mm. Its component layout is shown in Fig.3. Assembling this board is easy but correct polarity must be observed for all the components: diodes, electrolytic capacitors and the 3-terminal regulators. Note that both regulators face the same way but make SEPTEM BER 1989 63 The mains switch terminals should be shrouded with heatshrink tubing after the leads have been connected, to prevent accidental contact with the mains. Note the shield (at the end of the pen) which stops hum from being induced into the sliders. sure you don't inadvertently swap them over. The transformer is also mounted on this board, using screws, nuts and lockwashers. Terminate the primary and secondary wires and then put the board aside for the moment. You can now turn your attention to the chassis. POWER TRANSFORMER M2855 Chassis assembly We will assume you have complete metalwork for this project and so work on the chassis is basically a matter of installing the completed printed circuit boards and RCA socket panel and running th~ connecting cables between them. The screen printed front panel should not be permanently fitted until all the circuitry has been powered up and checked for correct operation. If you do put the front panei on before all the checking has been done, you are sure to have to do some troubleshooting and this increases the chances of marking or damaging the finish . The slider board is the first to be installed. It is mounted using eight 25mm-long x 3mm countersunk screws fed through 18mm-long hollow spacers and secured with nuts. The 18mm spacers are actually each a combination of a 12mm 64 SILICON CHIP levers protrude by the right amount. Incidentally, although we have not mentioned it previously, these sliders are not fitted with separate knobs - their plastic actuators are used as is. If knobs were used, the spacing between sliders would have to be increased and the whole project would not have fitted inside the specified rack case. With the slider board fitted into place, install the Tape monitor switch (S1} and the bypass switch (S2}. These are both DPDT push on/push off switches with integral mounting brackets. Both are mounted using two 12mm-long threaded pillars. Secure the two pillars to each of the switch brackets using 6mm-long x 3mm roundhead screws. This done, mount the switch bracket and pillar assemblies inside the chassis using countersunk 3mm screws, also 6mm long. Countersunk screws are necessary here, so that the front panel can mount flush against the front of the chassis. Once you have the slider board and the two switches fitted, you might like to check the fit of the front panel on the chassis. Fit it temporarily and check that all the sliders operate without fouling. Any necessary adjustments should be done now, before assembly proceeds further. Fitting the power supply ~ : '---- - A LEOl - • • • ~ ! - ~ I POWER SUPPLY BOARD + -----~ Fig.3: here's how to mount the components on the power supply board. Note that the negative supply input to the regulator uses a lO00µF filter capacitor while the positive supply uses a 2200µF capacitor. and a 6mm spacer. They give the correct spacing for the slider bodies from the rear of the front panel and ensure that the slider The power supply can now be fitted. First fit the power cord, using a cordgrip grommet to secure the cord at the rear of the chassis. The earth wire is terminated at the rear of the chassis using a solder lug secured with a screw, nut and lockwasher. The active and neutral wires are terminated to the power supply board and then figure-8 cable is run to the pushbutton mains switch at the front panel. This figure-8 cable should have 250V AC-rated insulation. Because the mains switch is very close to the slider controls in the left channel, it tends to induce hum and buzz into the lower frequency bands of that channel. To eliminate that problem a small shield is fitted between the mains switch and the G RIGHT ~ ~ LEFT TAPE RECORDER c~~ !:mi H D~ K~~ _Jl-1-~+15V 1c:::::J DV SK6a 1c::::::J SKSa P/B SK3b H SK1a SK2a ~' ~' ~' SK3a ,~ I SK4a ~' 1r::::=J SK6b 11::=J SKSb MAIN BOARD POWER SUPPLY BOARD POTENTIOMETER BOARD A ~ LED K Fig.4: this chassis wiring diagram shows how all the cables are installed. Connect SKla on the main hoard to SKlh on the potentiometer board, SK2a to SK2h and so on. Watch out when hooking up the + 15V, GND and - 15V connections between the power supply PCB and the main PCB - the order on the two hoards is different. SEPTEMBER 1989 65 jo -( ~ :;;;::;:::!::=;;;:;;;=;;:::!::=;;;;;;;:::;::!::::~=~~~ r ~---=-......:--.............- ~ . . - - - ~ -I\....J ~ ~✓ ✓✓ -( r--... " "'° ·w '-' ,n I \.... ,-A/ ;...,,, - '-o'-o r ,u,(./ -,·~ -( ~ ~ °" Fig.5: half-size reproduction of the main printed circuit board. The full size pattern measures 262 x 150mm. 28Hz left channel slider. The shield is retained by the mounting nut of the mains switch. For our prototype we made the shield from PCB copper laminate but we expect that for kits the shield will be made of light gauge steel or aluminium. When the wires are soldered to the switch, a length of heatshrink tubing should be fitted right over the switch to completely shroud it and thereby prevent accidental contact with the 240VAC mains. Alternatively, you can do as we did and fit sleeving over each of the switch terminals. You can fit the power switch temporarily at the front of the chassis so that testing can proceed. Do the same with the LED bezel. Mount the power board as shown in the photos, using four 10mm pillars, screws, nuts and lockwashers. The mounting position shown gave the minimum residual noise. Now apply power and measure the voltages at the supply outputs. They should be close to ± 15V DC. More particularly, the positive rail should be within the range from + 14.4V to + 15.6V. Similarly, the negative rail should be within - 14.4V to - 15.6V. On our prototype, the + 15V rail was + 15.12V while the -15V rail was - 15.31V. 66 SILICON CHIP If the supply rails are not correct, disconnect the power and check out the board for faults. Check also that the LED is working. Now the main board can be checked. You can do this before it is installed; that way, you don't have the hassle of removing the board to do any repairs, should they be necessary. Sit the board on an insulating surface and connect the three supply wires from the power supply board. Do not connect the five multiway cables for the slider board. Now apply power and check that the + 15V is present at pin 8 of IC1 and IC2 and at pin 4 of each LF347 quad op amp. Similarly, check that the - 15V rail is present at pin 4 of IC1 and IC2 and at pin 11 of each LF347. Where to buy the kit Complete kits for this project will be made available by Jaycar Pty Ltd for $349 (Cat. KC-5055). Note that two of the PC patterns are too large to be published full size in the magazine. For those who wish to make their own PC boards, we can supply a set of fullsize positive film transparencies for $20 .00. Alternatively, for those people who have access to enlarging photocopiers, we have published the two larger boards half-size. Next, check the offset voltage of every op amp on the board. That means checking pins 1 and 7 of the LM833 (IC1, IC2) and pins 1, 7, 8 and 14 of the LF347s. The voltage in each case should be within a few millivolts of 0V. If one of the op amp outputs is not at 0V it is likely to be at either + 15V or - 15V due to an open circuit connection on the board. If you get this sort of fault , check your soldering carefully. If all the voltage checks go as they should, you can then install the main board in the chassis. It is mounted using four pillars with screws and nuts. Next, there is the task of making six multiway cables with header plugs . Each connector pin is soldered individually to the rainbow cable and then inserted into the plug. To complete the equaliser, you need to install the RCA socket panel and run the shielded cables. The chassis wiring diagram of Fig.4 shows how to do this. Listening test When everything is complete, you can connect the equaliser into the Tape Monitor loop of your stereo control unit or amplifier with stereo headphones output. With no signal source connected, power up the equaliser and listen to the noise output via the headphones. Noise ro r. o1 0 I I I I N 0) co M 0 .,... .,... 0 (.) 0 0 Cl) 0 ~ Fig.7: full-size reproduction for the power supply PCB. Full size positive film transparencies for all PCBs are available for $20 (see panel). "'"' I i: I ;:? 0 CJ (/) L _J w 1%: <( 0 0.. "' 0 Wt0.. :::> <( 0.. I- l- o => wO I- ::> 0.. I- ::> 0 1%: w C 1%: a::a ii: 0 u w I- w 0.. 1%: t. j 0.. z <( 1- Fig.6: half-size reproduction of the potentiometer PCB. The full size pattern measures 370 x 78mm. levels should be very low and any buzz or hum should be practically non-existent. Finally, check that the noise level increases as you push sliders up and that the noise reduces when sliders are pushed down. If all that checks out, your equaliser is ready for work. ~ ::> w I- z=> _a.. ...JZ 1- 7 ::c (!J ILL ix ...J w r Fig.8: here is a full-size reproduction of the rear panel artwork. SEPTEMBER1989 67 PHONEORDER TOLL FREE ALTRONICS 008 999 007 Look at the really special bargains we've got this month - the wire specials alone will save computer and telephone installers a fortune. And look at the great deal we've got on PCB's - it's a long time since they were this price. Then there're speakers for as low as 99cents! You've waited for it - the fabulous Ultrasonic Cleaner is going for $25.00 Jess this month only. IbyAAMICRON NiCads ~-- . i 1GHz Digital Frequency Meter - / 1 -:===;;;;;;;;;;;;;;;;;;;;;;~ I$3.50 ea, or save a Thermalloy T03 HEATSINK "" 0 0 0) 0) 0) a) 0 0 u, -z 0 0 for as little as 70 cents! fortune by buying I in bulk 10 for $30.00 IPremium grade - good for up to I~oig;~l~:2v sooAh .~ .·.· . .. L ___________ SAVE (SeeSCNov'87Jan'88) I I I I ·---- , $30.00 _J • H 0503 Were $1.S0ea NOW ONLY 80 cents each! 10 up price 70 cents a: ~ Pin Point ULTRASONIC CLEANER Earns its cost hundcrds of tim::s over in cleaning connectors, PCB 's, switches, jewellery, gluse1, watc~s . drafting pen,, etc. <( Awarded the Good Product Design Award for w w CETDC in 1987 water and ~ates milliom of super-penetrating bubbles. HOl!lpital tc1t11how that lntrum.ic cleaning produce, better re11ults safer than conventional mcthocb . ...J ...J 0 -z TOP VALUE AT $199.00, ONLY $174.00 THIS MONTH Ao100 <at> z m m ~ difference! Linear a: Data & ~ AppliCX: cations Set FREE l] l] In )1151 3 minute, you will be amaud at the ~ TOLL 008 999 )> 007 Wcn 't scratch or damage • uses ordinary tap a: u.~- .,, 0 (/) SAVE 0 0 00 $25.00! (0 (0 (0 0 :::c 0 0 -..J ll. Fantastic f • You get Vol1. 1,2, & 3 and the, - Y IWftCU.Tm oeTAIN, latest printing ofNatimal aemiconductar Linear Appiicatiooa. ( Pleue note that the Lira, Applicati0111 can't be aold aeporatcly) 6 1 /2tt p oIypropy}ene t=~;iMJiW?n3Wcfb't!i~\ 30 Watt RMS VoiceCoil25mm only $79.95 the set of 4. $29 .95 Top Value C 3055 4 books normally $24.00 each - $96.00 Value tor (SccE ectronicaAustralia's amazin_g_ new sul>-woofer project Aug/Sep '119 8 Ohm Impedance Fn:quenc~,on.se 0- 3000Hz SOW Max. PHONEORDER TOLL FREE ALTRONICS 008 999 007 PHONEORDER TOLL FREE ALTRONICS 008 999 007 ---- - - - SCOOP PURCHASE! RACK CASES Put your projects on display In a really professional setting FEATURES: • Beautifully crafted to give your equipment a really fir5t class appearance . • Aluminium construction with rcmOYable top and bottan 1meI cover panels. • All dimensions coofonn to the ln1ernational Standard• Subtle Gn:y or Handsome Black finish.• Ventil ated lid• Deluxe finilh front panel• Individual ly cartoned• Supplied in flat pack form· easily assembled in minutes Dimensions: A = Front depth, B = Mounting bolt centres, C = Internal chassis depth, D = 254mm in all cases. Cat.No. ff 0401 ff 0402 H0403 H0411 H0412 H04!3 Finish GREY GREY GREY BLACK BLACK BLACK A 44 88 132 44 88 132 B 34 57 89 34 57 89 C NORMALLY $59.95 38 82 $69.95 $85.00 126 $59.95 38 82 $79.95 126 $89.95 THIS MONTH $55.00 $65.00 $80.00 $55.00 $75.00 $85.00 SAVE $4.95 $4.95 $5.00 $4.95 $4.95 $4.95 0 0 0) 0) 0) GREY FINISH NORMALLY BLACK FINISH THIS MONTH We have just purchased a truckload of blank phenolic PCB board, both single-sided and double-sided. CX) THIS MONTH Typical sizes are 150mm x 400mm to 200mm x 500mm ALL BRAND NEW STOCK Single-sided PCB Sire I 310xl85mm 1-9 $2.00 POWER SUPPLY Sire 2 405xl 70mm $2.00 3 - 50 Volts at up to 5 Amps ( Ea May' 85) Sire 3 5o5 x90mm $1.70 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 switching from one lo the other. 0 0 en -z (.) ~ NORMALLY 44mm H0426 $11.95 $10.95 44mm H0421 SI 1.95 $10.99 H04Z7 88mm $19.95 $21.95 $14.95 H0422 88mm $13.50 H0428 $27.50 132mm $29.95 H0423 132mm $18.95 $17.50 ....__ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ ___, LABORATORY ON BLANK PCB MATERIAL Cal/Ing all PCB Makers BLANK RACK PANELS EXCELLENT VALUE l'- -- -~-~ -- Double-sided PCB 1-9 Sire 505x205mm $3.50 l0up $1.70 $1.70 $I.SO lOup $3.00 TELEPHONE OFF-HOOK INDICATION (See SIiicon Chip Nov '87) K33oo $195.00 TOP VALUE <( 10 Turn Output Voltage Control W W a: $29.50 Auxlllary + AND - 12V Output Terminals K 3302 $14.50 See EA April/May 89 Checks electrical wiring and applianc:e1 for insulation breakdown. Insulation breakdown can be det<nnined by the uoe of !hi, dual ""II" ~gohm m:tcr. Ideally ,uited for checking breakdown in electrical wiring, appliancea transformcn, automotive gcncraton and altcrnaton etc. Bteakdown can be mcuu~ at either SOOV or IOOOV depending on the required 1ituation. w C a: Wo11lJ •"ii ,J.ctrkMUU or t,c#t11ieMUU wori 0 w NII, tool box or worl: IH11cla.. REAL VALUE $79.00 FREQUENCY METER (EA May '88) Flt this Into your toolbox for only $99.001 50MHz in 5 ranges. Featurc1 high input impedance, overflow LED 'indicator, kHz and MHz LED in:iicaton. Use when, 2 or 3 phonca an: connected OD tho ooe line. When ore cxtcmion ii in uc LFD will fluh in each of tho other eXtlOnlliODI. No cx"'"1al supply required · rum off phono line. One module required for each phone. K 1400 $9.95 Get 240V AC Mains Power from your battery with these handy Inverter kit sets 600W Many combinations to chooH from: 300 WATT INVERTER INVERTER WITH AUTO START (See EA Dec'87) Opera,oa &cm 12V Car 11-.y I Auto Start power &om your batmy only w1- applimco is plu...,cI in and "tumod 011" iio, baamy can be lelt pcnnmonlly comecllod ilft>Cluiied. e Voltqc Regulatod • Cllfflmt Regulu,d • Cllltfflt <>-load UDit self limill cnwo This inverter hu tho capacity to produce 600 wan. of maim power which will run a fantutie arny of appl iancc1. Ideally suit<d to running power tools, lighting (including fiuros) eloctrie motors and much more. It can be~ either u a portable or a permanent fixtun: . • Manual or Auto Start facilities • Low battery cut-out. Kit version K 6770 $425.00 Fully bullt and tested 12V Input K 6774 $525.00 24V Input K 6775 $525.00 -en0 0 0 (X) (0 (0 (0 z POWERHOUSE rr- :c 0 z 0 :I: 0. a !:i ....1 MEGGER, METER a: :c )> u. i---------------- ~ C m m m Fixed outputs independent of variable main output ...J :c :c (K 3300 is normally supplied with standard pot. K 3301 0 z m 0 ,, ~ OPTIONS - ""C :::c Complete Kit K 6750 $279.00 100'5 OF USES AT HOME AND AWAY Fully built and tested K 6755 $379.00 PHONEORDER TOLL FREE ALTRONICS 008 999 007 0 0 ...... PHONEORDER TOLL FREE ALTRONICS 008 999 007 ~ . TOP TRANSFORMER BARGAINS! - THE POWER BE WITH YOU Multipurpose 120VA pea This transformer is wound on expensive, grain oriented steel to make it super-effici'ent! And look at the size! Just 110mm x 65mm x 65mm High, wiehgt l.25kgs Primary: 240V Becondary: 12V - JOA, 15V - SA, 24V - SA, 27V - 4.4A, 30V - 4A Multipurpose 60VA Very Versatile ...... 0 0 O') O') O') M 2175 Normally $39.95, 10 This month 1-9 $30.00ea SAVE UP TO )\$14.95 EACH up $25.00each. Output - Two tapped secondarles give: 240V to 3,6,9,12,15,18,21&24Volts at 60V A (60W) Use of rJgh grade silicon steel has enabled surprisingly compact dimensions of 70mm x 70mm x 58mm high. jj;;:_ ~ . -~.J Mini 57mm (2.25 ) ~__,,__,, 200 mW 8 Ohm --with LARGE ferrite magnet from an incredibly low 99cents! C 0610 Normally $2.30 ea but look at this/ 1-9 only $1.25 ea 10 up 99 cents ea Save over 40% M 2165 Normally $26.50 each this month only 00 $22.00 0 SAVE en $4.50 0 z EACH 0 • - RE BARGAINS! Buy t ese by the ROLL and save an amazi 0 a: . ::r· 50% or more! ~ rt <C J:WL. 100% Screened Computer Cable W 0705 4 wire W 0710 6 wire W 0715 9 wire w w 'W••-•M,,,,,_,,,, ...J ...J -----u-su-,,, ~ -•IM NOW S,0.OOp,, "'°~rn ~ . '- • <~ 240V to 15V AC to IOOmA M 9009 Boggins of uses! ~ Reduced to clear at $7.00ea W or $6.00 each 5 or more. z 0 Calling all PA Techs! Telephone Line Isolation Units All Telecom Approved Type 1 • Designed to inlcrfacc paging output of PABX or Ccmrrwidor phone systems to Public Addrco, Amplifier. Coonecu to Aux. input A 0610 $99.00 w ONLY $99 Type l - Provides "Music On Hold" (MOH) to your Commander phme 1ym:m. Program input can be, radio, tape deck, land.line etc. Max. wtput 80<mV P-P, A 0615 $99.00 Type 3 • Similar to type 2 (A 0615) except max. output ii 2.8V P-P/ each A 0620 $99.00 .,, ; m m l> ""'; :c ~ 0 -enz 0 ffi AC Adaptor Bargain! C J: r r ~~~ -----· usually 80cents/M NOW $90.00per 200M usually $2.40cents/M NOW $295.00per 200M a. a :c usually $1.40/M NOW $79.00per 100M usually $1.80/M NOW $90.00per l00M usually $2.30/M NOW $125.00per I00M a: L1. -a 0 z m 0 :c C m :c ::i:: ·"-.... STROBE SIGNAL.LA PS Uses Xenon Strobe tube for High Energy strobe flash al output rate of approx. 1 per MCOnd. Amazing light energy output for the small amount of power used DC input 12V 320mA. Dimensions: 97mm Diam. x 90mm High Save $5.00 each this month! S 5455 Blue S 5450 Red Normally $27.50 this month $22.S0ea Redford Stereo 60 Watt Patio Loudspeake Volume Co 0 g (0 (0 (0 0 0 ...... A2300 No more dashing from the patio to the lounge and back to "Tum it down!" or "Tum it up a bit!" Put this control on your patio and enjoy your patty with your guests. Massive 100 Watt music power capacity. Five volume settings and "OFF". Includes P 8045 mounting block. PHONEORDER TOLL FREE ALTRONICS 008 999 007 PHONEORDER TOLL FREE ALTRONICS 008 999 007 GUARD YOUR HOME! NEW! NEW! NEW! A MULTI SECTOR BURGLAR ALARM ALARM SYSTEM (See EA Man:lv'Ap,il'89) Burglaries an: m the inaeaoo! Doem't it mab: ..,_ to proti,ct your home and its contents? This easy-to-build kit a...cmblcs m asingle PC and INCLUDES 12V 1.2AH inbuilt lead calcium back-up battery. Features include:• Entry and exit delay• Panic alarm input S""'1l Bllnll•n peo/JU - prolecl • Battery bock-up • Line monitoring • Soft alarm Lamp "'lltalc output yoKr pnllU.f.s a,ul c9uip,,uull! • Auxilli.,y relay for e,ar,mal siren etc. • K,:y switch operatiori • Uac, almost KIT WITHOUT SIREN anytyPcof""'""'- start• 110db SPL S 5170 $17.95 K 1910 89 00 ...... features of the more expensive commercial Features:(See EA Jan/Feb'8S or our 1989 Catalogue for full features) Up) Lite Guard K 1900 $149.50 lo O') O') O') ········· models - at a fractiai of the price. Kit (Less Battery Back Infra-Red 0 0 Protect your Home or 81.Ulnen from Intruders with this "State rJl the Art" Burglar Alarm Sysum Over the last few years, House Break-Ins have increased dramatically. The recovery rate of stolen goods is very low. Now more than ever before, it makes extremely good sense to build and install this ingenious Multi-Sector System. This unique Alarm System incorporates the Back Up Battery 12V 1.2AHS5065 $29.95 High Energy Siren with Swivel Bracket 00 0 0 JJ -z (.) How often have you thought there could be a prowler outside your door? Install a Lile Guard & (once armed) any "guest" will be floodltt when detected by this highly sensitive Infra-Red Detector. Sptdllcallons: • Ralntlghl, outdoor, all weather opcr,tion • Operation Time: Adjustable 1-20 Sensitivity: Adjustable W - 50, 30 beams• 0 a: mini• !::i Almable to desired dircctioo with 2 ball joints• Switching Capability: 500W max. incandescent MANUAL,ON. < e Operation ModH: OFF, AUTO, TEST, s 5350 was $135.00 SPECIAL w w 9 00 SAVE $36.00 ~ a: w C a: 0 w z Movement Detector Pulse Count Type Our 1989 model IRD now include, pulse count circuitry with a specific time delay 300mA between pulse sensing. Three pulses of IR radiation an:: required to trigger the detector. Features: Lens - wide angle & narrow angle l 12V DC Powered. S5111 $24.5O 5301 $79 (3) for $180 e BANKCARD e VISA e MASTERCARD e PHONE TOLL FREE 008 999 007 ' e NEXT DAY JETSERVICE DELIVERY Country clients please allow an additional 48-72 hours 4LTilOnlC) 174 Roe St. Perth WA 6000 PHONE TOLL FREE 008 999 007 Perth Metro & After Hour■ (09) 328 1599 ALL MAIL ORDERS P 0. Box 8350 Perth Mail Exchange W.A.6000 AL TRONICS RESELLERS 0 Chances are there 1s an Altronics Reseller right near you · check this 11st or phone us for details of the nearest dealer PleaH Nott: Resellers have to pay the cost of freight and insurance arid therefore the prices charged by tnd1v1dual Dealers may vary slight ly from thts Catalogue - in many cases, however. Dealer pri ces will still represent a sign1t1cant cost saving from prices c harged by Altrorncs Competitors . c. Oon"t forget our E1pre11 Mell end Phone Order Service - for the coot of I local cell, Bankcard. Yiu or M11lercerd holder• can phone order for um• day de1D11teh. Blue Ribbon Dealer■ are highlighted with a ■ These Dealers generally carry a J: Absolutely car spl iuing SPL !20db. Handy B,acket for wall mounting etc. 12V S a: -I -I JJ C m Cl) LL "'C :::c 0 z m 0 comprehensive range of Altronic products & kits or will order any required item for you . Manufacturers, Contractors and Bulk Users Please Contact Our Wholesale Sales Dept. Sydney (NSW Only) ..Colin Fobister (02) 437 4077 Melbc.ume (Vic / Tas Only) Brian Sorensen (03) 811 9967 Perth (WA, SA. OLD, N.T) (09) 328 2199 STANDARO DELIVERY I PACKING CHARGE $4.00 to 1Kg $7 over 1Kg AUSTRALIA WIDE - Wo process your order the day recei ved and despatch via Australia Post . Allow approx 7 days from day you post order to when ycu receive goods $7.00 OVERNIGHT JEYSER,ICE - We process your order the day received and despatch via . Overnight JetNrvlc• Courter tor delivery next day Country areas please allow add1t1onal 24-48 hours . Weight limit 3Kgs (3Kgs covers 95% of Orders) . $10.00 HEAVY HEAVY SERVICE - All orders of 10Kgs or more must travel Express Road - Pl ease allow 7 days tor delivery . INSURANCE - As with v1r1ually every other Australian supplier . we sen,d goods at consignees risk Shou ld you require comprehensive insurance cover against loss or damage please add 1% to order va lue (m1n1mum charge $1) When phone ordering please request " Insurance" TOLL FREE PHONE ORDER - Bankcard.Visa . Maslercard Holders can phone order toll free up to 6pm Eastern Standard T ime . Remember with our Overnight JetNrvlce we deliver next day . COUNTRY ALBANY BP Electron ics ■ 412681 ESPERANCE Esperance Communications 713344 GERALDTON K .B .Eleclronics & Marine 212176 KALGOORLIE Toda ys Electron ics ■ 212777 KARRATHA Daves Oscitronic 854836 MANDURAH Lance Rock Retravision 351246PORT HEADLAND Ivan Tomek Electronics 732531 WYALKATCHEM D & J Pease 811132 NT ALICE SPRINGS Ascom Electronics 521713 Farmer Electronics 522967 ACT CANBERRA Bennett Commercial Electroni cs 805359 Scientronics 548334 VICTORIA CITY All Electronic Components 6623506 SOUTH MELBOURNE Winscott Trading 6995740 SUBURBAN CHELTENHAM Tal ki ng Electronics 5842386 CROYDEN Truscott Electronics ■ 7233860 PRESTON Preston Ele ctro nics 4840191 COUNTRY BENDIGO KC Johnson ■ 411411 MORWELL Morwell Electronics 346133 QUEENSLAND CITY Oelsound P/ L 8396155 SUBURBAN CAPALABA David Hall Electronics 3902399 FORTITUDE VALLEY Economic Electronics 2523762 WOODRIDGE David Hall Electronics 8082777 COUNTRY CAIRNS Electronic World ■ 518555 BUNDABERG Bob Elkins Electronics 72 1785 GLADSTONE Supertronics 724321 MACKAY Phillronics ■ 578855 ROCKHAMPTONAccess Electronics (East St.) 221058Xanthos Electmnics 278952 TOOWOOMBA Hunts Electronics ■ 329677 TOWNSVILLE Solex ■ 722015 SA CITY . 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You can build your own DTMF encoder using just one integrated circuit and a numeric keypad. Dual tone multi-frequency signalling has been with us since the development of the "Touch Tone" dialling system, introduced in the late 1940s by Bell Laboratories in the USA, to replace decadic dialling in telephone systems. Since that time amateurs have adopted the signalling system on an ever increasing basis to control a variety of station operations. While this system is used by many dedicated groups to control amateur repeater operations, remote antenna switching and beacon control, the DTMF system is now gaining momentum in the PSTN (Public Switched Telephone Network), as older decadic telephone ·e xchanges are being withdrawn from service and replaced with " tone" exchanges. Even the latest telephone answering machines use DTMF signalling for remote operation. As an aside, the chances are that your local telephone exchange has tone dialling available. If so, and you have a phone which is capable of tone dialling, then you can have this convenience. It's just a matter of phoning your local Telecom C1 7 i 47 ~16VW voo osc + + ..:c.. 4.5V ..:C.. IN R1 1M C2 33pfl IC1 5089 OUTPUT 8 CJ 33pfl osc OUT vss 6 COL COL 3 2 4 5 ROW ROW ROW ROW 4 3 2 1 11 12 13 14 -:- • 0 C4 10 + - 16 + Table 1 R2 1k ., # DTMF SENDER Fig.1: the circuit uses a standard TCM5089 DTMF encoder chip (IC1), together with a numeric keypad. When a key is pressed, IC1 synthesises and mixes two sinusoidal tones to produce a single dual tone output. 72 SILICON CHIP business office and asking for "tone dialling". They can change it over very quickly and the resulting dialling is much quicker. Decadic dial phones still work so you can have the best of both worlds. Anyway, back to the subject in hand. Many amateur transceivers available on the commercial market incorporate a DTMF "pad" on the microphone, allowing the transmission of these tones for control purposes. However, there are many older transceivers in use that do not have this facility. Would you like it for your transceiver? You can have it. This article describes the construction of a self contained DTMF generator which can be acoustically coupled to any microphone on an amateur transceiver or telephone handset. A standard 12-key DTMF encoder selects one tone from a high group of sinusoidal tones and another from a group of low sinusoidal tones and mixes the two Tone Frequency Row 1 Row 2 Row 3 Row 4 Column Column Column Column 697Hz 77GHz 852Hz 941Hz 1209Hz 1336Hz 1477Hz 1633Hz 1 2 3 4 PARTS LIST 1 TCM5089 DTMF encoder (IC1) 1 3.579545MHz crystal, Jaycar Cat. RQ-5272 1 plastic zippy box, 130 x 67 x 43mm, DSE Cat. H-2853 1 4 AA or AAA cell holder 1 numeric keypad, Altronics Cat. S-5380 or equivalent 1 miniature 80 loudspeaker Capacitors 1 4 7 µF 1 6VW electrolytic 1 1 0µF 16VW electrolytic 2 33pF ceramic Resistors (¼W, 5%) 1 1MO 1 1 kO We simply lashed the circuit up to prove the concept but it could just as easily be built onto a small piece of Veroboard and housed in a plastic zippy box. Fig.2: when a DTMF key is pressed, the selected row and column inputs are pulled low. together to produce a single dual tone output. Table 1 lists the standard tones for 12-key and 16-key DTMF keyboards. How it works Our circuit (Fig.1) uses a standard DTMF encoder chip from Texas Instruments, the TCM5089. This is a CMOS chip designed specifically to operate from a standard NTSC colour burst crystal (3.579545 MHz]. The crystal ensures good frequency stability and highly accurate tones. It also eliminates the need for any frequency adjustment. The TCM5089 synthesises the sine waves and their resulting harmonic distortion is less than - 30dB (3%). When generating a dual tone signal, the encoder generates one column tone and one row tone and adds them for its output. For example, if you press button 8, the two tones generated will be 852Hz (row 3) and 1336Hz (column 2). Table 2 shows the expected row and column frequencies when using a 3.579545MHz crystal, and the variations from the "standard" set of tones. For all practical purposes, these tones are sufficiently ac- 1 680 Parts availability: The TCM5089 is available from VSI Electronics (Aust) Pty Ltd. Phone (02) 439 4655. VSI has offices in every state. DTMF keypads are available from Altronics and Jaycar, as are the 3.579545MHz crystals. Readers may also be interested to know that Motorola have available a DTMF receiver/decoder, the MC145436, which can be used for DTMF control. Details from VSI. curate for our control applications. The tolerance of the crystal should be better than 0.02 % . Unlike the dynamic or scanned inputs commonly encountered in computers, the static row and column inputs of the TCM5089 ensure that no noise is generated. Fig.2 shows how a single key selects two tones. Several of the other inputs to the Table 2 Tone Frequency Deviation from Standard Row 1 Row 2 Row 3 Row 4 Column Column Column Column 701.3Hz 771.4Hz 857.2Hz 935.1 Hz 1215.9Hz 1331.?Hz 1471.9Hz 1645.0Hz +0.62% +0.18% +0.61 % -0.63% +0.57% -0.32% -0.35% +0.73% 1 2 3 4 KEYBOARD REAR VIEW 0 0 Fig.3: this diagram shows the pinouts for the Altronics Cat. S-5380 numeric keypad. SEPTEMBER1989 73 TCM5089 need explanation, as follows: • Single tone enable input: this inhibits the generation of single tones when taken low or left open. If this pin is held high, single tone operation is enabled. • Tone enable output: when held low, this pin causes the output of the encoder to be dis a bled. • Keyboard active output: this output provides for switching of an external receiver, transmitter or other functions. The output is low whenever one or more column inputs are active, and at a high impedance when all column inputs are inactive. The supply voltage may be anywhere between 3V and 10V. As the current drawn during signalling is around 2mA, the device lends itself to battery power and portable operation. Construction Our photo shows the circuit in an experimental lash-up but it would be easy to build it onto a THE VHF FM MONITOR RECEIVER described in the March 1989 issue is now available in kit form from Dick Smith Electronics. The kit is priced at $59.50, comes with full instructions and features a re-designed PCB for improved parts layout. It's available from your nearest Dick Smith Electronics store. piece of Veroboard or matrix board. This could then be housed in a zippy box or mounted inside existing amateur equipment. Our prototype used the standard 12-keypad layout which is most commonly available. Depending on IREECON '89 is The Convention ■ ■ where the present - the future - and beyond come together. IREECON is for EVERYONE within the profession of electronics. the chosen supply voltage, the on/off switch is optional. At 10V DC, the standby current from the unit is less than 200µA. But at 6V or under, the standby current is less than 10µA so no on/off switch is necessary. ~ fflELBOURNE SEPTEMBER 11-15, 1989 An electronics exhibition SHOWCASE not to be surpassed anywhere • • see the very latest equipment from electronic companies in the know, showing a VARIETY of technologies not available at one time under one roof at any other exhibition in Australia. You've seen the rest NOW see the BEST IAEEC®n • CONVERGENCE HIGHLIGHTED • IREECON '89 incorporates a WEALTH OF FIRSTS for both exhibition trade visitors and lecture program delegates. Those FIRSTS listed below -are just the beginning - just take into account the countless FIRSTS on the exhibition floor. A significant AWARD will be given for the best paper presented by a young engineer • • exhibitor product promotion presentations are opeq to everyone FREE of charge • • a technical lecture program which will open a window on the world of the 1990's and beyond . : • 74 • The Institution of Radio and Electronics Engineers Australia \ Commercial Unit 3, 2 New McLean St (PO Box 79) EdgeclitfNSW 2027 (02)327.4822 - Fax (02)327.6770 - Publx AA21822 (Quote User No. SYl35) I/ f • MONDAY, SEPTEMBER 11 SILICON CHIP FRIDAY, SEPTEMBER 15, 1989 • COM.POTER BITS By JENNIFER BONNITCHA A guide to hard disc drives The first law of computing says that software expands to fill the available storage space. Sooner or later, if you've been using a computer with floppy discs, you'll he wondering about the advantages of a hard disc drive. If you use your computer a lot, adding a hard disc to it will he a big step forward. A hard disc drive represents salvation for harassed floppy disc users. When you depend only on floppy discs, you soon find you need an ever increasing number of floppies to store your files. As their number increases, you will have trouble keeping track of them all and storing them for easy access. Wouldn't it be so much nicer to have it "all there" permanently, in the computer? Another important consideration these days is the amount of disc space programs take up. In the good old days you could happily run W ordStar on a single floppy disc machine and store your documents on the same disc. Today, the increased memory requirements of graphics-based programs, so-called "power-users" and lazy programmers has lead to the need for greatly increased storage. Many popular PC programs such as Excel and Ventura just won't work on a floppy disc machine; you must have a hard disc drive. And while many programs can be run on single or dual floppy disc drive machines, the speed advantage of a hard disc drive is quite dramatic. Typically you can expect the hard disc drive to read and Fig.1: this diagram shows the concept of interleaving although a hard disc has many more sectors than suggested here. HARD DISK INTERLEAVING write data at around five to 10 times the speed of a floppy disc drive. As well, you can't beat the convenience of having your word processing, database, spreadsheet, graphics and accounting software all readily at hand without having to boot them up from separate floppies. Just a couple of years ago, you could purchase a staggering 20 megabytes of hard disc storage for "just a few" thousand dollars. Today, the same hard disc with controller is likely to set you back $500 to $600 although most buyers would now tend to go for 40 megabytes, for around $700 or so. And if you shop carefully, 80 megabytes or so can be purchased for around $1200. As you can see, the extra capacity more than justifies the price difference. Hard disc standards The hard disc itself is just a magnetic recording device. What the disc receives, how fast and where it will be placed is determined by DOS (the Disc Operating System) and the controller board. So if you buy a hard disc, you must also have a hard disc controller. The hard disc controller handles the task of formatting the disc for later use, encoding the data it receives and instructing the hard disc where to place the read/write heads. A hard disc drive actually contains several aluminium discs which are coated with particles of ferric oxide which form the magnetic storage. The read/write heads record (write) and replay (read) data to and from the disc in SEPTEMBER1989 75 COMPUTER BITS - CTD much the same way as on an audio cassette deck or a video cassette recorder except that the signal format is different. The read/write head differs considerably for floppy disc drives, high capacity drives and fixed discs. In all cases though, it serves two basic functions: (1). It reads the data stored on the disc dependent on the polarity of the magnetic fields at a given point on the disc. (2). It stores or writes data onto the disc by magnetising the disc surface in one direction or the other (ie, north poles or south poles) for binary ls and 0s. Flying heads Read/write heads ride on a very thin layer of air and so don't normally come into contact with the disc surface. The 10Mb XT fixed disc consists of two 5.25-inch aluminium platters with each of the four sides capable of holding 2.5Mb of data. Both the platters and recording heads are sealed inside a container which includes an air filter to prevent dust particles coming into contact with the highly sensitive surface and recording head mechanisms. The platters are fixed on a spindle which rotates at approximately 3600 RPM. The rapidly spinning sealed disc creates sufficient air flow for the recording heads to "fly" or "float" at around 1.5µm above the platters' surfaces. The PC AT also has two platters and four surfaces but unlike the XT, the AT 20Mb hard disc has six read/write heads. So while the AT's rotational speed of 3573 RPM is not significantly different from the XT's, the AT can access its data at two times the speed of the XT's hard disc. Since the hard disc coating contains finer oxide particles than a floppy disc, information is packed more densely on its surfaces. They MAKE YOUR DREAMS COME TRUE LAPTOPS FROM s1995.oo *INTERNAL BATTERY, EXTERNAL AC ADAPTOR *LIGHT, FAST, 10MHz * COMPACT AND CONVENIENT * SUPER TWIST LCD DISPLAY *64OKB RAM * SERIAL AND PARALLEL PORT REAL TIME CLOCK * LASER PRINTER s2995.oo *6 PAGES PER MINUTE *SERIAL AND PARALLEL (DUAL HOST) * 6 BUil T-IN FONTS * HP LASER JET SERIES II EMULATION * OPTIONAL IBM PROPRINTER EMULATION * 4 ADDITIONAL SOFT FONTS INCLUDED * EXPANDABLE TO 4.5MB COMPUTER CARE KIT s115.oo * 6 CLEANING KITS IN ONE *SUITABLE FOR ALL COMPUTERS FREEPOST NO. 31 ALL PRICES INCLUDE SALES TAX FREE ALL PURPOSE CLEANING KIT WITH HARDWARE PURCHASES 76 SILICON CHIP ESCKAY PRINTERNET PO BOX 2591, NTH PARRAMATTA, 2151 TEL: (02) 891 1282 also spin about 10 times faster than a floppy disc and so a hard disc is able to pack in large amounts of information then access it very quickly. For example, data is stored on the IMB PC's 360Kb floppy disc at 48 tracks per inch while the XT's 10Mb hard disc contains 345 tracks per inch. A mechanism called an actuator finely positions the read/write heads across the disc to locate the required information. Interleaving The disc surface is divided into sectors by a magnetic numbering system. Since the surface of a hard disc moves so rapidly past the read/write heads, most computers can't transfer data to and from the disc fast enough to keep up with consecutively numbered sectors. Sectors are therefore not usually numbered sequentially to allow time for the controller and computer to transfer and process the data being read from the disc. Instead the sectors are interleaved, with the sequence of the sectors called the "interleave factor". For an AT computer, the sectors on the hard disc are often organised with two sectors separating the first and second sectors (1 **2**3 - an interleave of 1 to 3). The slower XT uses an interleave of 1 to 6 (1 *****2*****3). An interleave of 1:1 means data is placed in sequential sectors. If the interleave factor is incorrect, the files aren't transferred to and from the hard disc as fast as possible and the overall performance of the computer is slowed. If the interleave is set too fast, the computer can't process the data as rapidly as it appears under the read/write heads and so must wait for an entire revolution to read the remaining data. On the other hand, if the interleave is too slow, the computer is ready to read the next sector before it appears so time is lost waiting for the sector to appear. Head crash A "head crash" describes the loss of the air layer which brings the heads and the disc surface into contact, usually with disastrous Yet another option in the hard disc field is this completely removeable hard disc drive. Called the Portadisk, it is a standard 40Mb drive which fits into a normal 5¼-inch drive slot. It is available from Electronic Solutions. results. The hard disc surface is very delicate so a head crash can not only wipe out data stored at the particular location where contact is made, it can also tear a hole in the coating although this situation is very rare. Access times Look for information on the data access time when you consider purchasing a hard disc. Anything rated at 50 milliseconds is fairly fast, with 20ms or less very fast; either way, even the slowest hard disc operates much faster than a floppy disc. Installation Installing a hard disc in an existing PC is a relatively simple matter. The hard disc requires the installation of an adapter in one of the system expansion slots of the PC XT system unit. PC users may have to first upgrade their power supply because of the power requirements of the disc, although "low power" hard discs can be installed and used with the original supply included with the PC. You need to check this aspect before you purchase. Other alternatives are the removable hard disc, self-contained drives which fit into a flexible, removable cartridge, and removable hard cartridges. Removable hard discs can be taken out in seconds for transport. Since the platters are rigid, two or more can be packed closely together in one drive to give decent storage capacity. To counter the effects of moving, removable hard discs are typically protected to some extent by shock mounted assemblies. If the computer loses power unexpectedly or you neglect to "park" the read/write heads before turning the power off, the spinning disc no longer provides an air cushion for the heads. The potential for the heads crashing onto the discs increases markedly. To counter this, some makers provide "auto-parking" which may be timeactivated or triggered by the ejection of the hard disc from its receptacle. Flexible cartridges The flexible cartridge is typically enclosed in a plastic case to protect the disc surface. The beauty of this system is its ability to squeeze 20Mb from floppy disc media while remaining small and light - and it provides a storage device which can take a fair amount of rough treatment. However, these benefits don't come cheaply with prices starting at about $1900 for a bottom of the range system. While the system is certainly durable, it is also slow and prone to wear since, like the floppy disc, the read/write heads actually touch the media surface. In an effort to reduce wear, the systems spin anywhere between 600 RPM and 1800 RPM. Although this reduces media wea:r, disc performance is severely limited. Combining the performance of a hard disc with the convenience of removable cartridges seems to be the best of both worlds. The removable hard cartridge separates the read/write mechanism from the disc platter, which rests in its own removable cartridge. However, these systems generally have no provision for auto-parking and the cartridges are more prone to damage if dropped. Since the cartridges are typically equipped with hinged or sliding doors, it is inevitable that dust and debris will ultimately find its way onto the disc surface. Although the presence of debris may not cause severe data loss, expected media life is undoubtedly shortened. So what is the answer? If you can take it out, eventually it will be dropped. Therefore you should choose a heavy duty product and from this angle, the flexible disc seems to be the best choice, particularly if you regularly travel or send information by courier/post. On the other hand, if you want to store a lot of programs and data and be able to access it very quickly at any time, a coventional 40 megabyte hard disc drive is a very hard proposition to beat. 1§;1 Notice to Subscribers Are you about to change your address. Please advise us by the middle of the month to ensure that your new issue arrives at your new address. It helps us if you can send your old address label too. If you have any queries about your subscription call us or write to us at: SILICON CHIP, PO Box 139, Collaroy Beach, NSW 2097. SEPTEMBER 1989 77 IBM PC/XT/AT COMPATIBLE KITS - lll!llHll!!!Uf KIT 1 10MHz Turbo with 1MB RAM and virtual disk software included. XT 10MHz Motherboard $149 XT Case Flip Top $ 99 XT Power Supply 150W $125 AT Style Keyboard $109 1MB RAM $445 Floppy Controller $ 99 Floppy 360k 5 1/4" $179 MGA Card $109 MGA Monitor $199 TOTAL $1533 KIT PRICE $1295 SAVE $238 Assemble a computer to your own specifications using only a screwdriver and pliers. Disk Drive Options • pricing is valid only if purchased with CPU kit 20MB Hard Disk including controller $499 40MB Hard Disk including controller $699 KIT 2 12MHz AT Turbo Kit AT Motherboard AT Case Flip Top 200W Power Supply Keyboard 2MB RAM Floppy Controller 1.2MB Floppy Disk Drive MGA Card MGA Monitor TOTAL KIT PRICE $2199 SAVE $263 Video Options · pricing is only valid if purchased with CPU kit. CGA instead of MGA includes Philips CGA monitor $349 EGA instead of MGA includes EGA monitor $699 $499 $129 $199 $109 $890 $ 99 $229 $109 $199 $2462 llH!!IH!!HHfJUll!UllllrJ! Upgrade to 16MHz NEAT with EMS 4.0 software for only $275 .___ _ _ _ _ _ _ _ · · •·_ ·--_·- __. · MOTHERBOARDS IBM PCtx:T COMPATIBLE TURBO 10MHZ MOTHERBOARD CONTROLLER CARDS 360KBll20KB/1.2MB/1.44MB FLOPPY DISK DRIVE CONTROLLER CARD FOR IBM PCtx:T/AT AND COMPATIBLE COMPUTERS -Allows connection of one or two 360KB, 720KB, 1.2MB or 1.33MB floppy disk drives. Includes cable for two internal disk ~~~l ~ -Expandable to 640K RAM using 4164, 41256 & 41464120ns chips -4.77 or 10MHZ hardware or keyboard selectable operation -Front panel LED indicators supported -Eight expansion bus slots -AMI BOIS ROMs included -8087-1 Math co-processor capability -Performs at an average speed of 100% faster than the original IBM PC/ FLOPPY DISK CONTROLLER CARD FOR IBM PCtx:T AND COMPATIBLE 'S -Run up to four 360KB disk drives -Includes cable for two internal drives -DC37S connector allows for an additional two external drives (external cable not included) -complete with manual $55 MFM H/D DISK CONTROLLER CARDS FOR IBM PCtx:T/AT & COMPATIBLE'S -8 bit MFM hard disk controller card for the 1MB PC/XT and compatible computers. Can be used with many types of hard disk drives. Cables and documentation included. $139 H/D DISK/FLOPPY CONTROLLER FOR IBM PCtx:T AND COMPATIBLE'S • 8 bit floppy and MFM hard disk controller for the IBM PC/XT and compatible computers. It will allow connection of up to two hard disks and two floppy 360, 720KB, 1.2 & 1.44MB drives. Cables are included to allow connection of one hard disk and two floppy disk drives. To connect a second hard disk drive an additional cable will be required. $175 XT -Norton SI rating of 2.0 -Size (12" x 8.5") -Weight (1.75Ibs) HARD DISK/FLOPPY CONTROLLER FOR IBM AT AND COMPATIBLE'S • 16 bit floppy and MFM hard disk controller for the IBM AT and compatible computers. It will allow connection of up to two hard disk drives and any combination of two floppy disk drives. To connect a second hard disk drive an additional cable will be required . $245 MFM HARD DISK CONTROLLER CARD FOR IBM AT AND COMPATIBLE'S • 16 bit MFM hard disk controller for the IBM AT and compatible computers. It can be used with many hard disk drives. Cables are included. $220 IBM PC/XT/AT COMPATIBLE KEYBOARD -101 Key -Enhanced keyboard layout -Tactile touch keyswitches -12 Function keys -lluminated LED indicators for Num Lock, Caps Lock and Scroll Lock -Separate cursor pad -Low profile design -Automatically switches between PC/XT or AT -Manual included -Colour beige -Size (19"w x 8"d x 1.33"h) -Weight (4.6Ibs) $109 84 KEY $99 2MB MEMO RY EXPANSION CARD FOR IBM AT AND COMPATIBLE COMPUTERS -Utilizers (72) 41256-120ns chips for the full memory capacity of 2Mbytes -Offers conventional expanded and extended memory capabilities -Features auto-parity check -EMS compatible driver -RAM disk and print spooler software included -Manual included NO RAM MEMORY CARD PCtx:T for 640K CASES 8088 $99 BABY 8088 $129 BABY 80286 $129 $299 MINI TOWER MAXI TOWER $699 bothwith power supply DISK DRIVES 720k 3.5• 1.44Mb 3.5" BOTH INCLUDE 5.25" mounting 360k 5.25" 1.2Mb 5.25• $199 $225 $179 $225 PROTOTYPE DEVELOPMENT CARD- NEW $245 Basic circuit already built-in. Has 3290 holes· this will save prototypers lots of time and energy. $199 $99 SLOT EXTENSION KIT - NEW ALL PCM CARDS COME WITH A 12 MONTH WARRANTY All other prducts with manufacturers warranty DONT BUY ELSEWHERE CHECK WITH US FIRST FOR DETAILS ON OTHER PRODUCTS PLEASE RING. 1/0 CARDS RS232 HALF CARD FOR IBM PCtx:T AND COMPATIBLE COMPUTER -Fits the difficult to use half card slot or any long slot -RS232 card comes with one ready to go serial port -Expandable to 2 ports by user (parts for expansion not included) -Selectable for COM1 thru COM4 -The user is able to select addresses for ports A and B as well as interrupt requests -Manual included 1/0 CARD FOR PCtx:r W/GMS CLCK 1/0 CARD 2 PORT FOR AT 1/0 CARD FOR AT WITH GAMES MULTI 1/0 CARD WITH MONO GA MULTI 1/0 CARD $55 $125 $65 $125 $229 $149 -Expandable to 1MB RAM using 256K DRAM chips -Expandable to 4MB RAM using 1MB DRAM chips -Expandable to 2.5MB RAM using a combination of 256K and 1MB DRAM chips -8 or 12MHZ hardware or keyboard selectable operation -Front panel LED indicators supported -Six 16-bit and two 8-bit expansion bus slots -AMI BIDS ROMs included -Zero wait state -Selectable RAM chips speed (80 or 100 nanosecond) -80287-8 Math co-processor capability -Norton SI rating of 13.7 -Size (13" c 8.75") -Weight (2.25Ibs) $499 IBM AT COMPATIBLE 200W POWER SUPPLY -Input <at>47 -400Hz (110/240V switchable) -Output +5v <at> 20A, -5V<at> 0.5A,+12v<at> 8A,-12v<at>0.5A -Plug compatible connectors -Built in fanSize (6.5"1 x 5.88"w x 6"h) $199 P/S 150W P/S 150W BABY Compatible with AT and XT. Excellent for test and repair of PC add-on cards $199 NOTE: No RAM on any board unless specified. All prices include tax and are subject to change without notice. SPECIALS FOR THIS MONTH OR WHILE STOCKS LAST 1. NEAT MOTHERBOARD 16MHz - AT compatible and expandable to 8Mb RAM $649 2. 42Mb HARD DISK DRIVE - American manufacture $499 3. VGA MONITOR including VGA card $999 ring for details PERSONAL COMPUTER MARKETPLACE Pty Ltd PHONE (02) 418 6711 FAX (02) 418 6713 Mail Order Address: P.O. Box 1100 Lane Cove NSW 2066 $149 IBM AT COMPATIBLE 12MHZ 80286 MOTHERBOARD FREIGHT CHARGES Include $10 with order for all nonnal items - heavy items, e.g. monitors add $15. 14 day money back guarantee Order by phone (use credit card), by fax or by mail. VISA 88 ---...... This photo shows the Auto-Zero circuit installed in the 120W PA Amplifier. It reduces the offset voltage to less than 100JLV. Null your amplifier's DC output to zero The problem with DC coupled power amplifiers is that they all have a residual DC voltage at the output. If this voltage is too high it can cause problems. This simple circuit can be used to null the DC offset down to 100 microvolts or less. Design by JOHN CLARKE All modern power amplifiers are DC coupled and as a result, they all have a small DC voltage at the output. Typically, this is around ± 20 to ± 30mV but it can be a lot more, depending on how well the input differential pair of transistors is matched and what the amplifier's operating temperature is. If your loudspeakers have a nominal impedance of 80 and the 80 SILICON CHIP amplifier has a DC output voltage of 20 to 30mV then you don't really have a problem. On the other hand, if your amplifier has to drive a 70V or 100V line transformer (as in a PA system) or your loudspeakers contain transformers (such as in electrostatics) that is a problem of an entirely different complexion. Transformers present a real problem to power amplifiers because they have a very low primary DC resistance. This is usually around 100 milliohms (0.10) or less. Now if your amplifier has the typical offset voltage quoted above, around ± 30mV or thereabouts, the DC current through the transformer primary winding will be more than 300 milliamps. Clearly, this is a big problem, not only because it can cause saturation of the transformer (which causes severe distortion) but it can also cause severe heating and perhaps even thermal runaway and ultimate destruction of the amplifier. Our Auto-Zero circuit brings the DC output offset of any amplifier down to a small fraction of a millivolt. It uses a new integrated circuit from National Semiconductor, the LMC669, which has been +50V 0.47 PARTS LIST 2.2k o-=t'•+~Wr....-----11----t LINE TRANSFORMER 22k ..,. -50V 22k 1k 120W PA AMPLIFIER CONFIGURATION Fig.la: basic configuration of the 120W PA Amplifier (December 1988). The power amplifier drives a 100V line transformer. 0.47 <>-=I + 2 2k • LINE TRANSFORMER INPUT -50V 1 PC board, code SC01108891, 69 x 75mm 1 LMC669CCN auto-zero IC (20-pin version) 2 1 5V 1W zener diodes 7 PC pins Capacitors 2 1 0µF 1 6VW PC electrolytic capacitors 3 0.1 µF metallised polyester capacitors 1 .0022µF metallised polyester capacitor Resistors (¼W, 5%) 2 100k!l 2 1 0k!l 1 5.6k!l 1 4.7k!l 2 1.8k!l 5W wirewound 1 330 22k 1k No effect on amplifier performance + 22:r +50V -50V CORRECTING VOLTAGE OUTPUT AMPLIRER SIGNAL GROUND OUTPUT OFFSET INPUT AUTO ZERO MODULE -. -. AMPLIFIER POWER GROUND AUTO ZERO MODULE CONNECTED TO 120W PA AMPLIFIER Fig.lb: how the Auto-Zero module is connected into circuit. It samples the amplifier's output and applies a correction signal back to the input via the 22k0 resistor. designed for just this sort of application. While our circuit may be simple, the LMC669 is not a simple device. It contains a four stage comparator for sampling, a clock and divider circuit, an internal reference voltage and an output amplifier. In effect, the LMC669 can be regarded as a very precise DC operational amplifier with an extremely low DC offset error. When connected in the Auto-Zero circuit, it works to reduce the output offset of the external amplifier by comparing it to an internal reference voltage. When the DC output of the external amplifier swings above or below ground by more than 10µ V (the typical offset of the LMC669's comparator), the Auto-Zero circuit applies a correction signal to the input of the amplifier and so brings it back to zero. The correction process is not immediate but takes place progressively in a large number of ever-decreasing steps as the LMC669 continually samples the amplifier output voltage, generates another smaller correction and so on. Ultimately though, depending on how large the initial offset error voltage is, the LMC669 will settle at a final minimum offset of less than 100µV. While the Auto-Zero effectively nulls out any DC errors in the output of a DC-coupled amplifier, it does not limit the performance in any way. It has no effect on the amplifier's residual noise, frequency response, slew rate, harmonic distortion or any other parameter. The proviso here, of course, is that the Auto-Zero circuit needs to be connected in a particular way, otherwise performance could be prejudiced. Fig.1 shows a typical connection of the Auto-Zero circuit module to a power amplifier such as our 120W power amplifier described in the December 1988 issue of SILICON CHIP. This amplifier was designed to have a particularly low offset voltage but we are using it as an example of how any amplifier could be corrected. The existing 22k!l input bias resistor in the 120W amplifier must be disconnected from the 0V line and connected instead to the correction output of the Auto-Zero module. The only other connections required from the power amplifier are from the amplifier output, the input reference line and the positive and negative supply lines. Fig.2 shows the circuit of the SEPTEMBER 1989 81 *R1 1.Bk 5W 100k P O S I T I V E O - ~ f r l r - - + - - - - - - - - - - -....w.A.-e---. SUPPLY 10 16VW 0.1 + _ AMPLIFIER POWER GROUNO u----------+-----i,-----+-------+----------- AMPLIFIER u---------------~ POWER GROUNO v+ 1 13 15 12 •RESET OUTPUT OFFSET 100k INPUT 0-'YW,~>---.........,..-t (FROM AMPLIFIER 10 + OUTPUT) 16VW 10k CORRECTING --+--'4'A.7~k,+--t--ov8~JtJ/ OUTFe----11...--.is'N.&111,k IN1 IC1 LMC669 IN OUT REF REF 2 6 , - AGND 3 14 0.1 19 9 (TO GROUND END OF NON-INVERTING AMPLIFIER BIAS RESISTOR) 10 AMPLIFIER SIGNAL GROUNO v----------+-------------------------~ 0.1, *SEE TEXT N~~m~EO-..,*'NR\1112- - - - - - _ _ . 1.Bk 5W AUTO ZERO Fig.2: the Auto-Zero circuit is based on National Semiconductor's LMC669 IC. It reduces the output offset of an external amplifier by comparing any offset to an internal reference voltage. A correction signal is then applied to the amplifier's input. The parts for the Auto-Zero circuit are all accommodated on a small PC board. This should fit easily into virtually any amplifier. 82 SILICON CHIP Auto-Zero module itself. The connection from the amplifier output is via a voltage divider consisting of two resistors, lO0kD and lOkD. This divider protects the input of the LMC669 in case a large DC fault appears at the output of the amplifier. A lOµF capacitor filters the signal from the divider so the circuit only responds to DC and frequencies below about 1.8Hz. The resultant slowly varying signal is fed to INl and IN2 (pins 1 and 20) on the LMC669. At the output of the LMC669 is a .0022µF capacitor which smoothes out the voltage steps produced by the circuit. The output is then further filtered by a series 5.6kD resistor and O. lµF capacitor after which it is fed to a voltage divider consisting of a 4. 7kD and 330 resistor. Note that the LMC669 includes three analog signal ground pins (3, 14 & 19) and a separate data ground, pin 18. The analog grounds allow the INl, IN2 and INREF inputs (pins 1, 20 & 2) to have a grounded "guard" electrode incorporated into the printed circuit pattern. The guard electrode helps OUTPUT OFFSET INPUT ____.... ~t~Jf! AMPu:wM~NAL ---1.111 I '""'...::---•AMPLIFIER POWER GROUND CORRECTING VOLTAGE-----41,l OUTPUT NEGATIVE SUPPLY Fig.3: here's how to install the parts on the PC board. Use PC stakes to terminate the external wiring connections and take care with the orientation of polarised components. package for the LMC669. This is denoted as LMC669CCN. As noted previously, we installed the Auto-Zero circuit into the 120W public address amplifier. We made up a couple of small brackets to mount the Auto-Zero board above the amplifier board. After that, the various leads need to be run to the amplifier board and the positive and negative supply capacitors. Connect the offset input to the output of the power amplifier. To connect the correction voltage output from the Auto-Zero board to the power amplifier, the earthy end of the 22k0 resistor at the input of the power amplifier needs to be lifted from the PCB. The resistor is then stood on end and the correction voltage lead soldered to the free end. When all wiring is complete, check it very carefully. The amplifier operation can then be checked, without any load connected. Turn on the power and measure the output voltage at the amplifier with a digital multimeter. The voltage should quickly settle to below ± 0.1 millivolts. ~ D.DAUNER ELECTRONIC COMPONENTS WE STOCK A WIDE RANGE OF ELECTRONIC PARTS Fig.4: this is an actual size reproduction of the PC artwork. • shield the inputs against spurious signals which may cause errors in the circuit operation. The separate grounds also help prevent the noise from the digital switching within the IC reaching the analog ground and thence into the amplifier. Our circuit shows a number of link options (LKl, LK2, LK3 and LK4) which enable the internal clock speed of the LMC669 to be selected. However, links LK 1 and LK2 are the ones to be used, as shown on the PC component overlay diagram of Fig.3. Power for the Auto-Zero circuit is derived from the amplifier supply lines using dropping 1.8k0 5W resistors Rl and R2 and regulating with 15V zener diodes. The 1.8k0 dropping resistors will be suitable for powering the circuit from amplifiers with supply voltages ranging from ± 40V to ± 90V. Construction The Auto-Zero is assembled onto a small printed circuit board measuring 69 x 74mm (code SC 01108891). The main things to watch out for when assembling the board is the polarity of the zener diodes and the electrolytic capacitors, and the orientation of the LMC669. Note that we used the more readily available 20-pin for Development • Repair • Radio Amateur • Industrial Electronic • Analog and Digital WHILE STOCKS LAST * THE FAMOUS TR-DIP METER * (as featured May '89) $98.00 CRO-VALVE 3ACP2A $45.00 * PHILIPS IR-IMAGE CONVERTER VALVE XX1080 $45.00 (For use in infrared sight experiment systems) Come and see. 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This kit includes a 30 watt 240 volt soldering iron, a quality metal stand with sponge, a length of solder and a roll of soldeiwick. Was $29.95 Save $5.00 ONLY $24.95 ~:g; ~:~ NICS NICS NICS NICS JAY JAY JAY JAY PB-8810 PB-8812 PB·8814 PB-8816 PB--8818 PB-8820 172 172 172 224 240 254 13 38 86 180 195 240 100 640 840 1680 2420 3260 $3.75 $10.75 $17.50 $39.95 $57.50 $69.95 1/3 OCTAVE EQUALISER KIT- $239 Cat. KC-5050 ; ,_· • ~--d,8,iQ. ..... ~ ~ - - - • These are high quality 10-way thermoplastic PCB terminal strip. A:; used extensively in the alarm industry. Units are supplied unassembled, i.e. you have to screw the screws in ! These are normally $4.95 Cat HM-3205 RONICS JA\ RONICS JA\ RONICS JA\ RONICS JA\ RONICS JA\ RONICS JA\ . ': - ..·............. ----~-=-~----·----~-. . 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Zener test KA-1699 Bench amp- signal trace KA-1700 Power transistor tester KA-1701 RF detector probe KA-1702 50MHz Dig Freq meter KA-1705 Stroboscopic Tuner KA-1706 Cheap capacitance meter KA-1707 Powermate 2 KA-1708 Supertimer KA-1709 PC-driven Function Gen KA-1710 Beepo Continuity Tester KA-1711 TTL-analog Video Convert KA-1712 PCB Shorts Locator KA-1714 Beat Me Metronome KA-1715 Car Brake Lamp Monitor KA-1716 Auto Tune-up Adaptor KA-1717 Sutmoofer Adaptor KA-1718 Auto NiCad charger KA-1719 NiCad discharger KA-1720 RGBI to PAL encoder KM-3015 Listening post KM-3016 RTTY Encoder KM-3030 Ultrafidelity preamp KM-3040 Dual speed modem KM-3044 6000 Mosfet Module $159.00 $24.95 $19.95 $29.95 $46.50 $19.95 $21.95 $55.00 $39.95 $22.95 $13.50 $79.00 $47.50 $16.95 $119.00 $59.00 $49.95 $19.95 $49.95 $22.95 $29.95 $24.95 $29.95 $29.95 $42.50 $27.95 $39.95 $39.95 $32.50 $359.00 $169.00 $119.00 KM-3046 Super Simple Modem KM-3050 Workhorse amp KM-3056 100W module less MFets KM-3060 Bal Line Driver KM-3061 Microphone preamp KM-3063 Uo satellite decoder KM-3064 Octave EQ mod KM-3065 AS true 232 interface KM-3068 FM minder bug KE-4014 Mixer preamp KE-4023 Signal Spkr protector KE-4029 NiCad battery charger KE-4033 Temperature probe KE-4050 ETl480 50W amp module KE-4052 ETl480 100W amp mod KE-4048 ETl480 power supply KE-4200 5000 power amp KE-4666 RS232 Centronics inter/I KE-4690 ETl342 COi KE-4698 4 sector house alarm KE-4711 Mini FM transmitter KE-4722 RS232 Commodore KE-4724 Parametric equaliser KE-4725 Solder iron temp control KE-4729 Guitar preamp KE-4731 Telephone Intercom KE-4733 Active Crossover KC-5010 Capacitance meter KC-5012 Car radio power supply KC-5013 1GHz Digi Freq meter KC-5015 Telephone ringer KC-5016 Speed control/dimmer $85.00 $35.00 $79.50 $99.50 $36.95 $55.00 $59.95 $27.95 $11.95 $39.50 $22.50 $14.95 $32.95 $27.50 $34.50 $29.50 $499.00 $32.50 $79.50 $29.95 $9.95 $16.95 $23.50 $39.50 $45.00 $49.95 $39.95 $27.95 $28.95 $299.00 $19.95 $18.95 IIIIERE{!_tllltlT""f/0(}tfl/T.f-J,1f/(},1R1111.f 11/E,t/T.f KC-5019 KC-5021 KC-5027 KC-5028 KC-5029 KC-5030 KC-5031 KC-5032 KC-5033 KC-5036 KC-5037 KC-5038 KC-5039 KC-5040 KC-5041 KC-5042 KC-5043 KC-5044 KC-5046 KC-5047 KC-5048 KC-5049 KC-5050 KC-5051 .KC-5052 KC-5053 KC-5054 KC-5055 KJ-6502 KJ-6504 KJ-6505 KJ-6522 KJ-7000 Portasol Professional VIDEO ENHANCER Incorporates a soldering iron, hot knife. blowtroch and hot blow which is ideal for heatshrink tubing. The complete kit contains: CatTS-1425 1 x Portasol Professional heat tool with 2.4mm soldering tip Portasol Gas to suit - 150g 1 x Hot Blow tip See catalogue for full details Cat NA-1020 1 x Blow Torch tip 1 x Hot Knife tip 1 x Cleaning Sponge 1 x Safety Stand 1 x lgnighter Cap Connect between two VCR's to improve the quality of a recording of an original tape. See catalogue for full details. Cat. AV-6521 $79.95 ~ $38.95 $79.50 $49.95 $89.00 $24.95 $49.95 $49.95 $159.50 $229.00 $16.95 $42.50 $12.95 $19.95 $89.00 $34.95 $17.95 $72.50 $29.95 $55.00 $18.95 $16.95 $17.95 $239.00 $49.50 $32.95 $14.95 $24.95 $349.00 $42.50 $595.00 $119.00 $9.95 $19.95 $79.95 Power supply to suit 12V AC Cat MP-3020 $14.95 DELUXE RACK CABINETS These beautifully crafted rack cabinets will give your equipment a real 1st class appearance. All aluminium construction. Removable top and bottom panels. Natural or black finish. All dimensions conform to International standards. Ventilated lid. Deluxe brush finish anodised front panel. Side Elevation: D = 254mm; C= internal chassis height B mounting bolt centres . C Ea Cat Finish A B +5 $65 $62 HB-5411 Natural 44 34 38 $71 $75 HB-5413 Natural 88 57 82 $85 HB-5415 Natural 132 89 126 $90 $62 HB-5410 Black 44 34 38 $65 $80 $85 HB-5412 Black 88 57 82 $95 $90 HB-5414 Black 132 89 126 MIDRANGE& TWEETER LEVEL CONTROL BARGAIN 80 watts handling. See the Jaycar 1989 catalogue for full details. Horizontal mount Cat. AC-1884 Vertical mount Cat. 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OO I..& - ' • -- - 3rd August, 197Australia. Colin, old friend, Your recent missive brought back all the traumas of my entry into the television game. I'm glad you enjoy my tales. Let me tell you, it's easier to talk about it now than it was to live it then. From my diary, 196-: to think I gave up the Bell System for this. Come to think of it, that "security blanket" was one of the reasons I left. I'm too young to be retired. Seems like 10% of the people at Ma Bell do 90% of the work. The majority keep their mouth shut, stay busy doing as little as possible, and get a paycheck every Tuesday. Well, it's a paycheck that put me in this state of mind. The engineering secretary pointed out I was on shiftwork, off on payday and the following day, for the next few weeks. "It would be better to have your cheque posted from head office". Like a fool, I agreed. Come payday, nothing in the mailbox. Next day, the same. On the Saturday afternoon, I arrived at work and asked the supervisor about my pay. He was a model of ignorance and apathy: "I don't know and I don't care". Today, Wednesday, I got the cheque in the mail. I raced to my bank and cashed it, paid the overdue bills and barely got to work on time. Walking through the darkened studio, a voice nearly scared me out of my wits. It was the chief engineer - second time I've seen him since I started. "How dare you cash that cheque?" he demanded. By RICHARD KOPF ers 88 SILICON CHIP "Other than the fact that it was a week old and had my name on it, why shouldn't I?" "We called our bank to stop payment on it", he answered. "And now you make us look like fools". By now I was cheesed off. "If I was independently wealthy and didn't need my pay for the bills each week, I'd be a fool to work here". At that statement, he turned and stomped away. I guess he's not used to rebuttal and expects cringing when he initiates confrontation. Camera work Over the past two weeks, I've been doing camera work on the evening and late news, plus the TV dance party, better known as the fight of the week. I feel pretty good about the results I've been getting. The senior studio man asked how long I'd been doing camera. "Eight days", I replied. "No, before here", he said. When I told him I'd never seen one before here, he was amazed. "Maybe you should give lessons to Rodney". Rod was held up to me as a role model by one of the directors but he appears to be a turkey. Seems like no matter what you do right, you're wrong. Over the past week, I've had several run-ins with one director. On " fight of the week" last time, I found he never checks anything out before going live. We were getting our opening 'ROD W~ l-\E..L'D UP TO N\E AS me:. A ROLE. MODE.L B~r ON~ OF 'D\~C.11)~'S Bu, HE. Af->P~R S 1'0 ~£ A iUR\<..E.'1. shots when I realised the guest rock group had their own style: tuxedos and bare feet. Trying to get an acknowledgment over the intercom is virtually useless. "God" only speaks but does not listen. I'd framed up on two pairs of bare feet and refused to change my shot to the usual "wide shot of the musicians, camera two". Rodney had managed to get camera one blocked off behind some teeny boppers - couldn't grab any kind of opening shot. Now there's one floor manager for two cameras but the times I get help are few and far between. With these TK-42s, you don't need to take up weightlifting they're bigger than a boat anchor and twice as wide. Anyhow, I held my shot until I saw the tally light. Then I zoomed out and framed on a standard shot. The technical director said "great" but The Man still blasted me afterwards. Same director, different show: after three months of talk about the station giving away a Buick Special came the presentation day. Two minutes before air time, I was told to take camera one - Rodney had called in sick again. This day, I had a floor man Butch! After the opening segment, the master of ceremonies had a screaming fit because nothing was organised. During the commercial break, the director, the MC, the audio man and the TD argued about what to do. As no-one could agree and I was closest, the "star " said: "Get that camera out the door and shoot the car coming up the driveway - or it's your job!" Now that was an instruction I could understand. Butch and I pushed the beast across the length of the studio and through the prop room, while someone was getting the roller door up. Well, 180kg of colour camera head on a massive pedestal ain't the easiest thing in the world to stop once it's going. There was only about an inch of difference between the prop room floor and the parking lot. It could have been worse, I guess - it might have been up rather than down. In that case, it probably would have nosed over. Instead, that little dropoff elicited the instruction: "Focus, camera one!" I'd already tried. "Do you want it more blurry or less blurry? I can't find sharp''. So one impressionistic shot went to air; camera two had to cover most of the rest of the show until they got one of the B& W cameras out of the OB van. Well, Colin, old buddy, that was the end of my first TV job. Those 4 ½-inch image orthicons ain't cheap. The chief engineer called me in to say they couldn't afford to have me around anymore. "We need someone with more training", he said. SEPTEMBER 1989 89 THE TECHNOLOGY LETTERS - CTD "You ought to go back to the phone company". I got the last laugh a year later. We'd just finished building the UHF independent in Zenith and that chief called my boss. He made an appointment to see the new facility, to get some ideas and advice for their rebuilding scheme. My boss knew the background and on the arrival of my first chief, told him: "My assistant will show you around. He supervised most of the studio installations and knows more about it than I do. I'm sure Dick can answer any of your questions' '. We ha d a good laugh about it afterwa rds. Jack was the best man I ever worked for . Remind me one day to tell you what happened to him. Looking back on it, Colin, working in television was like a trip to Fantasy Land. After all this time, I still recall the time the director screamed: " Camera one, get a shot of the city councilman". " Who he? " said I. " Behind the woman in the red dress" . As you know, mate, the TK-42 aside from being as broad as an axe handle - has a B&W monitor. Things like that make me wonder about the origin of the phrase "common sense''. The security industry The uncommonness of common sense reveals itself daily in the security industry. My company has just lost a major tender to our arch rival; business is business, I hear you say. Well, part of the specification was for certain ultrasonic detectors that are not proprietary to us, but as near as. This particular job was a government installation. Now, supply officers don't like to be seen to be favouring a particular supplier so they sometimes spread the work around arbitrarily. After the system failed its performance test, my boss was asked to look at the situation ''informally''. The boss was actually reasonably sober the day we visited the building. The thing is, mate, in a multi-head ultrasonic site, the system has to be synchronised, otherwise oscillator drift in one transmitter will be sensed as a phase change in a receiver. And a good phase change says " I am a YOU I--IAV& MVL-Tt-t-tEA.C> UUR~SON\C. S\fE.~ ... 1//1, ~ ~ ?~ f ·· \). ·. •·. (" C:· .. .. ~~~ll ,j ( ,~.. ~ ·. 1 I ~ J, ~~cA~DS UN\Q\JE TO -n\E. St:C.U~\1'-( \N't>Ust'RV .... 90 SILICON C HIP man-sized target. ALARM!" Another lurk about this particular gear is that the manufacturer specifies a certain type of multi-pair cable, only available from one maker [I think they must own a piece of the action). Anyway, the goons hadn't bothered with that factor because of cost. Another case of " she'll be right". Even after the synchronising option was added, the system was still prone to false alarms because of the junk cable they used. If the government can't get a fair go what hope has the home owner? He gets a quote from a big company, whose salesman always happens to mention the problems when dealing with "backyarders". In actuality, Australian Standard 2201 is observed more often in the brea ch - by everyone. I went to one shop which was having problems and found a toy train power supply driving the system. The technicians Aside from shonky equipment, our "professional technicians" are a real hoot. Very often, they are sent out to do a job with no supervision whatsoever - our little apprentice included. Jamie is a weekend "muso" and generally comes to work each Monday morning looking like death warmed over. Several weeks of guidance fell on deaf ears. One day, in a fit of anger, I said I wouldn't draw any more diagrams for him; I'd use musical notation to capture his attention instead. "I can't read music", was his response. Jamie brings to mind my Australian ba shing question: Why Doesn't Anyone Ever Have A Biro? Our technicians on a field call have to get the client's signature on the job sheet. I'll illustrate with a call on a small supermarket. A false alarm the previous night wa s solved by jumpering the offending section in the control panel. " You've still got perimeter protection", explains Jamie. "We, uh, have to order a replacement part from the manufacturer". He fumbles in his toolkit for the paperwork and hands it to the manager. "You got a biro, mate? I can't find mine." Well, the manager doesn't feel like walking back to his office, so he asks the cashier, who yells to the butcher. "I think the fruiterer's got a pencil stub" . Incidentally, I drove by this area a few nights later, on my way to a restaurant. Just out of curiosity, I turned into the car park. Perhaps I could see the cause of the constant false alarms that plagued the market. A grey Land Rover was backed up to the front door. It was dusk. The manager was busy moving boxes out of the shop and into the vehicle. Another fool, Winston, was rabbiting on one day about the unnecessary information in transistor spec sheets. "You can put any voltage you like on a transistor", he asserted. "All you need is the right current limiting resistor in series with the collector". Speaking of transistors, I came across the weirdest circuit of my life in a sensitive government facility. At first, I was sure the alleged input buffer transistor was cactus. My digital meter said so - the $12 multimeter in the company toolkit was useless. The input stage looked like a common emitter circuit. But to my surprise, the "proper" operation was: (1) a remote detector goes into alarm, opening a relay contact; (2) a shunt resistor from base to earth is thereby disconnected, causing (3) the base voltage to rise and (4) the emitter voltage to go up also. The latter effect is natural enough. The end result, however, is hardly what you would expect: the collector voltage also rose, since the transistor was already in saturation. My involvement with this problem started off poorly. One had to be escorted to the control room by a guard. We were caught in a corridor which had to be sealed off for two hours to ensure security for a delivery in an adjacent area. Once we got to the equipment, I found a modular system as I'd been told. What I hadn't expected was that the modules were hard wired (let's save some money on this installation - we don't really need edge connectors). A 24V rail distributed power to every piece of equipment in the system. It had enough capacity to serve as an arc welder and was backed up by the world's biggest emergency battery (and you know how I feel about batteries). I only raised three or four false alarms while disconnecting the module - after the second one, the police stopped checking. The blokes in the control room were awed by the bright blue sparks the earthed Taiwanese soldering iron caused. ,..---------------1 AMATEUR RADIO 1 I Hobbyists communicating world I wide using state-of-the-art I electronics. I I Are you I a radio amateur but not a I I member of the WIA? I Do you know what you are Reverse engineering After I got it out and reverse engineered it to make a drawing, I could analyse the circuit. The resistor values were like nothing you ever saw. When I took the calculations back to the office for an explanation, I was told "For God's sake, drop the whole matter. This buffer circuit was designed by a senior company engineer and accepted by a government bloke in Canberra. It has to be OK!" The company was going into Phase Three at this site. Now, the people who had installed Phase One were long gone. Same with Phase Two. Neither lot had left behind any documentation of problems or variations. You had to find it out the hard way. I guess technical people never write anything down - probably because they can't find a biro. At any rate, I'm involved with Phase Three. Spending most of my time at this one site has provided one benefit: I seldom get to the office or talk to people from there. The state manager did make a PR call to the site one day, however. He called me aside and griped because the work was taking more time than he thought it should. I explained about documenting the work as I proceeded. "We've never needed anything like that in the past. Get on with the engineering - that's what you're paid for!" Sometimes, I wonder about the keeness of men to re-invent the wheel. Every time an on-call technician has to puzzle out a given problem from fundamentals, it takes time. That brings to mind a slogan I recall from the US Navy: "Do it right or do it over". I missing? Do you like using VHF/ UHF repeaters? Enjoy working DX? Want to preserve your bands? Join the WIA - the oldest and most experienced radio society in the world - always at the forefront of radio communications for hobbyists. Receive AMATEUR RADIO, the monthly magazine for members of the WIA, full of news of DX, clubs, satellites, technical articles and lots more. I Other WIA services include: • A wor1d wide QSL card service • Weekly news broadcasts • Classes for all grades of amateur licences • Correspondence lessons available • Meetings, contests, field days • Representation for radio amateurs at Government level I Learn more about the WIA and Amateur Radio Forward this coupon, or write to: WIA EXECUTIVE OFFICE P.O. BOX300 CAULFIELD SOUTH VICTORIA 3162 Registered address: 3/105 Hawthorn Road Caulfield North, 3161 Please send aWIA information package to: NAME: ............................................................ ADDRESS: ..................................................... . ................................... POSTCODE ................ . L.-------------~ E003S1 was my first experience with the "closed shop" syndrome in Australian labour relations. "It's a condition of employment," he told me. "Why wasn't I told when offered the job?" "You know what your boss is like". "Yes, certainly. As I'm doing his work and effectively part of management, how can I be a union man too? If one of the techs came to me with a complaint to solve, I'd have to be for him and against him!" His answer cannot be quoted. Suffice it to say that I joined the union. They (the company) wouldn't pay the dues, either. Emergency services Managers, though, only ever see the short-term side of an installation. "Let's get the work done quickly and go on to something else''. Perhaps they assume that they will have been promoted and moved before the problems occur - and their successor will get to carry the can for any foul-ups. Unfortunately, the long term effect is that clients get jack of being ripped off. I've seen many old and valued cutomers go to the opposition for that reason. It's always interesting in the course of a drubbing to hear the current opinion of what "you are paid for". The job description can change day by day - and sometimes hour by hour. I certainly never anticipated supervising electricians in security installations. Our company runs pretty lean staff-wise and drags in sub-contractors as necessary - all in the guise of saving money. Some additional CCTV cameras were to be installed. Our electrician was given the brief. I was in the control room and had to answer his calls for help. He'd pulled the coaxial cable through but didn't know what to do next. I explained about the different kinds of connectors and told him to look at one of the camera heads. A couple of hours later, he'd returned from the electrical supply shop. Before too long, he was on the 92 SILICON CHIP horn again. "The solder won't stick to the 75-ohm connectors you told me to get". This seemed curious. I was escorted down to view the problem. You would not be surprised to find that he had obtained Belling-Lee aluminium connectors for antenna installations. When I started here, it was as a customer engineer. Hardly any time had passed before I was "acting security manager" because my boss was seldom there. It was not uncommon for him to "go do a quote" and then spend the day drinking with some of his copper mates. The state manager decided that I should take charge even though I was the new boy, since my wide experience gave me the judgment to solve problems. When I use my judgment though, I get told I should have done something else. Skinned knuckles I'd been here four months and was sitting in the boss's chair one day, answering his phone calls. A noise at the doorway caused me to look up. A creature stood there that looked like he had gravel rash on his knuckles. "Youse got to join the union", the ape said. I pushed past him and went into the state manager's office. This My ability to reverse-engineer led to the next fun project, a stateof-the-art emergency services vehicle - fully imported. Except for technical manuals. The company slid in under the deadline for delivery though, so there were no penalties. Some of the control circuits apparently hadn't worked at the factory and the intercom had failed within a fortnight. The latter unit was in a diecast box and looked more appropriate to a Wellington bomber. I was surprised to see that it used discrete components. Having had lots of experience with intercom circuits in television work, I knew that the user always wanted more power. I ripped the germanium transistor circuit out and replaced it with a couple of IC packages in a switchable configuration, singleended or bridge. The first trial was with one IC and the response was that it wasn't loud enough. The internal switch compensated for this and made them happy - my version of applied psychology. On the strength of his expert assistance, the rival company has offered my boss a senior position in another state. He grizzled about losing his long-service leave as he'd only been with this company 14 years. Perhaps when I write next, I will have news to brag about. Regards, Dick. l1fl THE WAY I SEE IT By NEVILLE WILLIAMS High definition TV: lots of problems at the transmission end As a follow-up to his observations in the August issue, we give correspondent Keith Walters an opportunity to list the transmission problems that would arise with the introduction of high definition, wide screen television. He says they would not have occurred to readers unfamiliar with professional TV production technology. Keith Walters (K.W. for short) assumes that our original correspondent W.G. is just such a person: quite familiar with video home movie gear but blissfully ignorant of the complicated equipment and procedures used every day of the week in assembling programs and commercials from a variety of sources. "Through kilometres of high quality 75-ohm coax, countless BNC connectors, Tokyo-by-Night control panels and mixing desks, multiple signal sources have to be synchronised and sub-carrier phases matched to within 2°. Not simple", he says. Most of this equipment, according to K.W., is configured to the TV standard in the particular country ( usually a variant of PAL or NTSC). If another standard was adopted, it would all have to be discarded and production facilities re-equipped and re-cabled at enormous cost. The situation would have little in common with the changeover from monochrome to colour in the 1970s. Most of the old monochrome equipment was nearing the end of its useful life, anyway. It could be replaced progressively with new colour equipment, able to work well in b&w mode until the changeover was actually made. High definition, wide screen television, he says, calls for a "component video" approach to signal processing, already familiar in some applications but having its first public exposure in TV broadcasting in the various MAC formats. The "components" referred to are simply the luminance (Y) signal and two chrominance signals (B-Y and R-Y). Until fairly recently, normal practice has been to encode the three signals into composite video (luminance and a standardised colour sub-carrier) right at the source - the TV camera, special effects generator, &c. All such signal source equipment can be synchronised to a master sync and subcarrier generator. Once this is done, and allowance made for the various lengths of connecting cable, signals can be wiped and splitscreened, and otherwise processed, without further ado. The changing scene TV video production based on composite video was regarded as quite satisfactory up to the late 1970s and still is for most applications. However, the emergence of digital video processing - which bends, folds and otherwise "mucks about" with images - has exposed the limitations of composite video as a production format. At this point, I quote directly from Keith Walters' letter, with some abbreviation to conserve space: "Basically, these gadgets work by breaking up the picture into a half-million or so pixels, and storing them digitally in a high-speed RAM. By varying the manner in which the memory is accessed on playback, the shape of the output image can be manipulated. "You can't do this with composite video because stretching or shrinking would change its sub-carrier frequency. The signal must first be decoded back to its original components - luminance, B-Y and R-Y, commonly referred to as 'YUV'; this, so that the effects machine can handle the components separately and simultaneously. "The problem is that there is no known process whereby composite video can be turned back into YUV components identical to those originally obtained from the camera or whatever. "This statement stands, despite what happens in an ordinary TV set. Usable U and V information is recovered and (with PAL) averaged by the delay lirte over two lines. A 4.43MHz trap extracts most of the colour subcarrier, leaving the high frequency luminance signals reasonably intact. The residual SEPTEMBER1989 93 THE WAY I SEE IT - CTD chroma sidebands are not too intrusive because the subcarrier is specifically chosen for minimum visibility". OK for receivers ... but Overall, says K.W., the components so recovered are OK for direct display on the screen of a TV set, being visually quite pleasing under optimum conditions. But a very real problem arises in a TV production situation if recovered YUV components need to be reencoded on a new subcarrier. As he says: "It is imperative that all traces of the original subcarrier be removed from the Y signal, because even a minute frequency difference between the old and new subcarriers will cause unsightly patterning on the reconstituted chroma signal. " The simplest way to counter the effect is to use a low-pass filter at 3.1MHz, the lower limit of the chroma sidebands. But this also limits the luminance bandwidth. What's more, the roll-off has to be fairly sedate to avoid ringing effects. The upshot is that practical filters are typically flat to 2.5MHz, 3dB down at 3MHz, and rolling quite rapidly above that. "2.5MHz? Where have we heard t?at _before? Yes, anti-patterning filtermg can drag luminance bandwidth back down towards the limits suggested earlier for VHS, Beta or any other helical-scan recorder that uses the 'colour-under ' system". At this point in his letter, K.W. digresses into an explanation of the colour-under recording system and the problems which show up when an incoming composite signal has to be taken apart for recording and playback, then reconstituted to suit the receiver. It is informative but interrupts his main theme. To carry on: "What we really need is something that completely removes the colour subcarrier while leaving the high frequency luminance components intact - something that has not been achieved to date. "Techniques using delay lines or 94 SILICON CHIP digital field stores ('spatial filtering') offer a partial solution. With NTSC, a simple glass delay line can provide good chroma/luminance s_eparation. With PAL, two delay Imes are required, with more complex circuitry, and it doesn't work as well. In both cases it is at the expense of vertical resolution. "The techniques work best on stationary images containing lots of vertical lines, which means that they work better on electronically generated test patterns than they do on real pictures! This is not to say that the process is impractical. By us~ng elaborate digital filtering techmques, quite impressive results can be obtained - at considerable cost. " But the bottom line is that the recovered YUV signals are still never identical to the originals and if they have to go through the sam~ process again, in the course of video production, the deterioration becomes more marked. There's a limit to the number of generations possible". Avoiding compromise Such problems could be avoided s~ys Ke~th Walters, by keeping ali signals m a production facility in component form right up to the end of the process, converting them to composite video at the transmitter. Component signals would be more compatible with digital video effects machines; NTSC " green faces" problems would be elim- Satellite broadcasts: MAC or PAL? "It's not as if satellite links can't handle composite video. You may need a little more power or a slightly larger dish but it's hardly the disaster area some champions of the MAC format would have us believe. "Personally, I reckon that the adoption of the B-MAC system by the ABC had a lot more to do with bureaucratic desire for a fully remote controllable distribution system than any technical consideration". (K.W.) inated; SECAM would become a more practical system; special effects such as chroma-key and electronic captions would benefit in all systems; and NTSC/P AL standards conversion would be facilitated e_ach. becoming virtually indis~ tmghishable fr om the original material. These desirable benefits do not come easily or cheaply. I quote again with some abbreviation: "The preferred approach to operating 'component' is to run three cables everywhere the signal has to go, instead of one as with composite video. However, the length of the three cables has to be closely mat ched and rigidly maintained. " Component vision mixers have only recently become available rend~red pra ctical by the adoption · of highly a ccurate and drift-free signal processing. Slight gain errors which, with composite video would cause negligible contrast change, could produce noticeable colour er rors with component video. " Component video r ecorders have been available for some time notably the Sony Betacam cam~ corders used by news crews. Using two sepa rat e pairs of heads mounted in parallel on the head drum, the luminance and multiplexed chrominance signals are recorded separately on a specially modified Beta cassette run at nine times normal Beta speed". Betacam & Betamax At this point, K.W. digresses to emphasise that Betacam has little else in common with domestic ~etamax VCRs. Similarly, profess10nal C-format video recorders have nothing to do with domestic ':HS-C, despite fr equent implications to the contrary in both instances. C-format uses "one-inch" (25 .4mm) tape and a 152mmdiameter drum rotating at the field rate. It provides for various head options and can cope with a composite signal bandwidth of up to 6MHz. But, to continue with the main theme: " Getting b a ck to component recorders, standard Betacom has a bandwidth of about 4MHz. The new SP (superior performance) using a new metal tape boasts a luminance bandwidth of over 5.5MHz - in my experience a useful response to over 6MHz. On a component input monitor, the picture is incredible". K.W. also mentions the " MII" format, jointly developed in Japan by Matsushita and NHK. Basically similar to SP Beta cam, it offers more features, having been essentially redesigned from scratch as the basis for a full range of TV station equipment, from camcorders to editing facilities. "Finally, many TV stations are looking seriously at S-VHS camcorders [fitted with 3-chip CCD TV cameras) as a low cost format for news gathering, particula rly in hazardous situations. At a round $15,000, they cost about one-sixth of a Betacam set-up. The SIN ratio is not as good but, if they're edited directly onto a higher quality production format, they're adequate for most situations. State of the art "But state of the art in video recording is in the new digital video recorders [D-1 format) made by Sony and BTS [Broadcast Television Systems, a collaboration of Philips and Bosch). "D-1 machines r ec or d components digitally at an industry standard sampling rate known as 4:2:2. They use special large cassette tapes and involve a data rate of 200 megabits per second. "Three principal strategies are used to achieve this seemingly impossible recording rate: • The data stream is multiplexed onto two record hea ds mounted in parallel; • The head drum rotates at three times the field rate; • A special metal particle tape is used, formulated so as to optimise the distinction between ones and zeros. "There is virtually no deterioration between as many generations as one is likely to encounter in a production situation. They guarantee 20; more than enough! "Again, with Quantel ' s new 'Harry' system, about 90 seconds of digital component video can be stored on a combination of hard PAL isn't dead yet! "There's an awful lot of life left in our present TV systems. Over the past 10 years, the SMPTE (Socie'ty of Motion Picture and Television Engineers) has published numerous articles on compatible improvements to current TV systems. Judging by the accompanying photographs, they could otter a substantial improvement over what we have now." (K.W.) discs and RAM - long enough for most commercials. It provides virtually instant access to any frame, which appear on the monitor screen like strips of film, making editing a simple task for nontechnical operators. One Harry and one digital VTR can replace a whole multi-VTR editing suite. To be realistic "Component video has many theoretical advantages but they only add up if a system is component all the way - and that simply isn't practical at the moment. There's too much money tied up in composite equipment, which works well for most present purposes. " Where component systems are introduced, they are usually in the form of component "islands" , essentially isolated from the existing composite chain. Any video that has to be brought in from outside the island has to be decoded from YUV, with a corresponding drop in quality". In an aside, K.W. points to the above as a reason for the lukewarm reception by broadcasters of the various MAC formats. They would be ideal if everything was shot, edited and released in component form. In reality, present program material comes mainly from 1-inch tape which has to be turned back into YUV. As reproduced by a special MAC receiver, the end result may still be pretty good but in most cases, it has to undergo further ·composite encoding/decoding before it appears on domestic receiver screens. The basic point K.W. is seeking to make in all this is that HDTV is not just another extension of present systems. Before addressing the problems of presenting high definition wide screen images in the home, the TV industry must first come up with suitable program material and that, in turn, will involve a n a llcomponent production format. I quote: "Despite all the complexities described above, converting to fully component format might prove to be a mere detail compared to going to full-scale HDTV. As I said right at the start, I don't believe HDTV is anywhere near ready for general release". Summing up K.W. concludes by saying that he was anxious to see HDTV in the Japanese pavilion at Expo '88 , expecting to see real HDTV sets on display, alongside a conventional receiver. What he saw were thr ee HDTV projection screens, shared by slide projectors, viewed from a minimum distance of 3 metres. The cameras on show produced noticeably noisy pictures, even in fairly bright light, which is what one would expect with a 30MHz bandwidth. They're supposed to have solved that problem with a new type of camera tube but the display was scarely indicative of mature technology. As for shooting movies on HDTV instead of film , K.W. sees little advantage in the forseeable future. I quote: "The low-light performance of the best HDTV camera today is laughable compared with relatively cheap and available 400 ASA film. "Admittedly, it's easier to create special effects on video but what is more likely to happen is that footage captured on film will be processed digitally by a special high resolution telecine scanner [straight off the original negative). The effects will be produced by computer and the resulting image transferred in negative form onto film again. Special effects don't have to be done in real time" . There's more but by this time, you've probably had your fill of HDTV. Even the writer admits that the letter is a bit " long-winded" but it certainly seems that the picture he paints is not a HDTV one. ~ SEPTEMBER198 9 95 PRODUCT SHOWCASE I New ICs for DC motor control Five new models in Audiosound loudspeaker range sound range, the 8066A and the 9077, feature an extremely rigid crate-box enclosure which helps them perform very well in the very low frequency region. Audiosound Laboratories have a new range of loudspeakers, all selling below $600 per pair. All are rigorously designed according to Thiele-Small principles and a great deal of work has gone into the optimisation of their crossover networks. After all, it is usually the design of the crossover network which ultimately determines how well a loudspeaker performs. The two top models in the Audio- If you are in the market for speakers now, go and have a listen to Audiosound they are a thoroughly engineered Australian product. They will be on display at this month's Ireecon International show in Melbourne. At other times you can see them at Audiosound Laboratories, 148 Pitt Road, North Curl Curl, NSW 2099. Phone (02) 938 2068. Siemens now has a series of monolithic integrated circuits for the control of DC motors in automotive and industrial applications. They are rated for voltages up to 42 volts and currents up to 4 amps. The ICs are bridge drivers and it is possible to select clockwise or anticlockwise rotation as well as defined acceleration or braking by feeding suitable logic levels to the control inputs. Designated TLE 4202, TLE 4203 and TLE 4204, they are rated at 2 amps, 3 amps and 4 amps respectively and protected against short circuits and over-temperature. For further information, contact Siemens Ltd, 544 Church Street, Richmond, Vic. 3121. Phone (03) 420 7318. New clip on heatsinks for TO-220 transistors New joystick for PC/XTs Now we know that none of you officially play games with your computers but just in case one or two of you might wish to have the occasional game with your kids (nudge, nudge, wink, wink, say no more) here is a joystick that might interest you. It is ruggedly constructed to withstand the rigours of enthusiastic playing (by the kids, of course) and for hastily being whipped off the executive desk and into the drawer. The all important "fire" button (the one at the top of the stick) is great for fingertip control and the stick has trim ad96 SILICON CHIP justments on both axes for cursor centreing with any games software. • It even has spring return to centre the stick when you let it go. For further information, contact Electronic Solutions, PO Box 426, Gladesville, NSW 2111. Phone (02) 906 6666. Some types of flag heatsink can be quite tricky to put on and take off, whether they clip on or attach with a screw. These new clip-on heatsinks are easy to push on and are available in several versions. Type PF750 has integral tags and can be soldered to the PC board. Type PF751 is black anodised and can be anchored to the board by bending the lugs over. PF752 has no tags and is simply clipped on. Thermal resistance of the PF7 50 and PF751 is 20°C/watt while the PF752 is 23°C/watt. Further information is available from Clarke & Severn Electronics, PO Box 129, St Leonards, NSW 2065. Phone (02) 427 4199. Polystyrene capacitors YES Made here in Australia? YES Made Special to Type? YES Where From? New multimeter has lots of facilities Allied Capacitors Australia Allied Capacitors Australia specialises in custom made good quality, high stability polystyrene capacitors. Why design circuitry which requires additional components to achieve a specific capacitance; we can wind exactly the capacitance you need to match your design criteria within the ranges of 10pF to 1µF and up to 10,000VDC. Capacitors are manufactured to 0.25%, 0 .5%, 1.0%, 2.0%, 2.5%, 5%, 10% and 20% and are priced according to tolerance. All capacitors are tested to 2.5 times the rated voltage. • Interested? Call us now on: (02) 938 4690 OR Cut out and post this coupon to ~ 00 ~~~ rl Yes, I-am----------interested in your capacitors. Please post me details of the following values: II ... /... VDC .. . / ... VDC ... / ... VDC ... / ... VDC I Name (Please print) I~ · I ~-~-o_o_~_a_~_._N_._s_.w_._2_1_o_o___ L~~~~~~~~~~~J This new 3 ½ digit multimeter from Jaycar has just about every measurement facility you can think of. As well as the usual AC and DC voltage, current and Ohms ranges, it has a frequency counter with 20kHz and 200kHz ranges, a hpE range for measuring transistor gain, and ranges for capacitance and temperature. The capacitance ranges are 2000pF, 200nF and 201-LF and therefore enable you to measure just about every capacitor you would come across in normal usage apart from electrolytic filter and bypass capacitors. You can measure down to lpF too as the unit has a nulling control to "zero out" residual capacitance of measuring leads. Mind you, while it can measure down to lpF [on the 2000pF range, that is), you still have to think about its overall accuracy which is quoted at ± 2 % of full scale plus 5 digits. So when measuring capacitors which are small with respect to the full scale range value, there can be fairly substantial errors in the reading. We are not saying this to knock the unit since these remarks apply to most multimeters with capacitance ranges. By contrast, the accuracy for all the other measurement modes, except for frequency, is quoted as a percentage of the reading [not full scale) plus a few digits. For frequency measurements, the unit will measure up to 200kHz and it needs a minimum input signal of 30mV RMS. The accuracy for frequency measurements is quoted as ± 2 % + 2kHz + 5 digits for the 200kHz range and ± 2 % + 200Hz + 5 digits on the 20kHz range. We assume that the ± 2 % figure applies to the reading rather than to full scale. An unusual inclusion is the provision of a temperature measurement range and (joy, oh joy) an actual thermocouple with matching connector for the socket on the multimeter. This would be more useful to most enthusiasts if it was made up into a probe [say using a Biro case) but it is a very good inclusion nonetheless. It will enable 'real' temperature measurements such as on heatsinks and transistor cases. The range of permissible temperature measurements is quoted as - 20°C to + 1200°c. Recommended retail price of the new Jaycar multimeter [Cat. (.lM1450) is $169. ----oi>-- '' ' ~ Siliconix has recently released the new DG400 family of silicon gate analog switches which have significantly lower on-resistance SEPTEMBER1989 97 High per£ormance disc controllers Electronic Solutions has just released the Speed-Disk range of hard/floppy disc controllers to complement the latest high speed 80386 and 80286 computers. Using 1:1 interleave (see Jennifer Bonnitcha's column starting page 75 in this issue) and being able to work at 16MHz, they can raise data throughput by over 300%. Using the latest Western Digital 1006 chip set, the controllers are capable of addressing hard discs with up to 16 heads and 2408 cylinders. One or two drives may be connected. The cards are also available with built-in floppy disc controllers and can provide for any (85 ohms) and lower leakage currents than older analog switches. These new ICs also have reduced sensitivity to electrostatic discharge, making them easier to handle in production situations. For further information, contact Anitech, 1-5 Carter St, Lidcombe, NSW 2141. Phone (02) 648 4088. Avtek's 1234 Megamodem is tiny Modems keep on getting smaller, faster and fancier. This model from Avtek runs at 300, 1200, 2400 and 1200/75 baud so it does all the speeds that most users would want. There are no front panel controls, just indicator lights. All functions are selected by the software, so switches are not necessary. There are indicator lights for CD (carrier detect), RD (received data), (SD) send data, HS (high speed), AA (auto answer), OH (on hook) and MR (modem ready). On the back panel 98 SILICON CHIP combination of two drives which may be 360Kb or 1.2Mb 5 ¼-inch or 720Kb or 1.44Mb 3 ½-inch drives. The cards come with full documentation and cabling, a there are American modular sockets for incoming line and a parallel phone plus a 25-pin D socket for the RS-232 cable from your computer. The unit measures just 27mm high, 120mm wide and 165mm deep and weighs all of 250 grams. How small can you get? The Avtek uses the Hayes "AT" command set which basically means that it does everything, including autoanswer and autodial. One of the nice features is that it has an internal speaker so that you can hear when it autodials and establishes contact with the called modem. We have had a sample Avtek 1234 for a couple of months and can report that it works very well. We like it. It costs just $399. For further information, contact Russell Coward at Avtek Data Communications on (02) 888 5333 or toll free (008) 25 2754. 4-way data switch from David Reid A thing of beauty is a joy forever. This simple box with just a 4-position rotary switch on the front may not inspire you to verse but the multipole switch and all the cabling 3-month warranty and 14-day money back guarantee. For further information, contact Electronic Solutions, PO Box 426, Gladesville, NSW 2111. Phone (02) 906 6666. inside is a joy to behold; such neat work. It's a pity to put the lid back on. On the rear panel it has five 25-pin D sockets and these could be used to connect one printer to a number of computers or one computer to a number of peripherals, printers included. David Reid also have a version which accepts 36-pin Centronics sockets. The Data Switch retails for $89 from David Reid Electronics, 127 York Street, Sydney, NSW 2000. Phone (02) 267 1385. PHILIPS FLUKE should be without them! Accessories From the world's leader in Digital Multimeters - Fluke Alarm phone dialler has recorded voice message This alarm dialler can be connected to virtually any home or business burglar alarm and can record a voice message up to 16 seconds; long enough to say "Help, we wuz robbed" in four languages. It will also dial and send that message to up to four phone numbers. Better still it could be used as a security alarm for the aged and infirm - an increasing concern these days. The unit sells for $159 and is available from all Jaycar stores. POWER TRANSFORMED Fluke has an unrivalled range of high quality DMM accessories, all designed to make your life easier and safer. This range includes TL20: Industrial Test Lead Set 80i-Kw: Current/Power probe 1A-1300Adc lA-l000Aac 0.5 kwto 330kw ~ 80T-150u: High accuracy probe that converts your DMMintoa thermometer plus a wide variety of soft and hard carrying A comprehensive range of Australian made safety-designed PCB mount power transformers in 6 power ratings and 7 voltages are now available ex-stock. Mains pins are offset so that the transformer cannot be inserted in the PCB in the incorrect manner. To special order the mains connection can be removed from the PCB and taken to quick disconnect lugs on the top of the transformer. In all sizes from 6Y A up a multiple winding model is available which with the correct 3 terminal regulators will provide +/-1 SY for audio circuits and +SY for CMOS and LSTTL circuits. 6 CONVENIENT SIZES 2.5VA, 4VA, 6VA, 10VA, 15VA, 25VA STANDARD VOLTAGES 2 x 6V, 2 x 7.5V, 2 X 9V, 2 X cases, probes for RF, current, high voltage, temperature and much more. Next time you need a DMM accessory, remember Fluke. No DMM should be without one. Available from: 12V, 2 x 15V, 2 x 20V at 15VA and larger, 32Vct + BV at 6VA and larger .. Data sheets and prices are available direct from the manufacturer. A.C.T.-John Pope Electrical 80 6576, -Aeromotlve Maintenance services 85 2377, - George Brown Group so 4355, N.S.W. -Ames Agency 699 4524, -George Brown & co. 519 5855, -OGE SystemsC049I 69 1625, -W.F. Dixon !0491 69 5177, -Ebson 707 2111, MacelecC0421 29 1455, -Novacastrian Electronic Supply (0491 62 1358, -Obi at 698 4776, -Petro-Ject696 9655, -DavldReld267 1385, N. T.-J. Blackwood &Son 84 4255, -Thew & Mccann 84 4999, OLD. -Aus\ec 277 6055, -Petro-JectC071252 2777, -st. Lucia Electronics 252 7466, - L.E. aoughen 3691277, - Haytech 844 9396, -Thompson Instruments !0701 51 2404, - Nortek corn 79 8600, - Colourvlew Electronics 275 3188, S.A. - Electech 277 1533, - Petro-Ject363 1353, -George Brown Group 352 2222, TAS.-George Harvey Electric 31 6533, -Petro-Ject !0031 44 8400, VIC. - Radio Parts Group 329 7888, -George Brown Group 878 8111, -Electech 482 1577, -Petro-Ject !031419 9377, - Factory controls !0521 78 8222, - Mektronlcs !031 587 3888, W.A. - Atkins Carlyle 4811233, - Dabble Instruments 276 8888, - Petro-Ject 479 1822, HARBUCH ELECTRONICS PTY LTD 90 George St., HORNSBY NSW 2077 Phone (02)476-5854 . SEPTEMBER 1989 99 DISK DRIVES AND CONTROLLERS FROM ELECTRONIC SOLUTIONS XT HARD DISK CONTROLLER CAR NEC 360K 5.25 inch floppy drive. DD1053 .. . . $175.00 Mitsubishi 1.2M DD1157C . . . $199.00 NEC 720K 3.25 INCH DRIVE DD1037A ... $175.00 MITSUBISHI 720K OR 1.2M 3.25 INCH DRIVE DD1137hH ... $199.00 AT/386HARD DISK/FLOPPY DISK CONTROLLER SuitsIBM/PC/AT. Supports up to two hard disks while controlling up to 4 floppy disks. These may be either 2 internal/2 external or 4 internal drives. Floppies may be either 5.25" (360K or 1,2MB) or 3.5" (720K or 1.44MB) DC2340 . . . . $299.00 The MFM encoded Hard Disk controller card for the IBM PC XT compatible machines. It uses the Western Digital Chipset and is compatible with the Western Digital WDXT-GEN2 HDD controller card. Suits almost any XT compatible Mother board with lower cost and higher performance. Controls one or two hard disc drives. Card size is 12.5cm x 10.7cm. DCXH . . . . . $125.00 NEC HARD DISKS hen you want the ultimate in performance and reliabillity, choose from the extensive range of drives from NEC. From 20MB to 600MB. ST506, ESDI, SCSI interfaces all catered for. Match them up with our low cost, high performance controllers, for the best value in Australia. W 20 MB, 5.25", 65mS, ST506, DD5126 . . . . . . . . . $399 42MB, 28mS, ST506 DD3146, 3.5", . . . . . $745 DD3146F, 5.25" $775 110MB, 3.5", 23 ms DD3661 , ESDI . . . . $1 ,395 DD3861, SCSI . . . . $1,495 140MB, 5.25" 18mS DD5655, ESDI . . . . $1 ,895 300MB Full Ht, 5.25", 18Ms DD5662, ESDI . . . . $3,495 DD5682, SCSI . . . . $3,595 600MB Full Ht, 5.25" DD5682, ESDI, . . . . $5,495 DD5882, SCSI . . . . $5,595 HDD Hard disk 16 BIT ETHERNET CARD ESDI HARD DISK CONTROLLER CARD The high speed, low cost interface to the fast new ESDI hard drives. Can be installed to work under MS-DOS 3.2 and Xenix. Jumper settings allow the controller to work with ESDI drives from most manufacturers. Full documentation. DCAEH . . $349.00 DCAEHF* . . . $399.00 The new Speed Disk controllers are among the first low cost controllers to feaature 1:1 sector interleaving, using the latest Western Digital 1006 chip set. This greatly increases performance with the latest high speed drives. 1 or 2 drives are supported. DCAH . $220.00 DCAHF* $249.00 * F= controls FDD Fully compatible with all industry standard networking software and topologies. The IFNE2 card is a full 16 bit Ethernet card with up to 64K RAM buffer (to support multi-packet communications), optional ROM support for diskless workstations, support for NetWare and all Gateway communications products. Cat. IFNE2 .. $449.00 The Amazing "All in One" AT Motherboard ~h~~s ~hi - a compl1;te 12!-1Hz AT (minus video card) built right onto a 'baby-sized" o er ard, only 8.5 . x 13 . Not only do you get superior performance (with all memory and disk running at processor speed), but you save a fortune. Other features include • 12MHz zero-wait-state perfonnance - equivalent to 16MHz on most ATs • DIS<? (dynamic VO speed control) provides superior compatibility with add-on cards • Up to 4MB can be fitted onto the motherboard - no need for memory expansion cards. Uses 256K or 1MB chips. • Two serial ports and one parallel port on-board • On-board floppy drive controller suits both S1/4"and 31,2" drives • "Award" BIOS with built-in setup. 7 channel DMA and 16 level interrupts • Realtime clock and off-board battery backup provided. Universal Wirewrap Card XT/AT/386 compatible CAT IF054 Perfect for the engineer or experimenter, this wirewrap card provides bl,Jffered inputs and outputs to protect your PC. Superb plated through wirewrap area. • Works with all PCs, XT/AT/386 with 4-12MHz busses • Built in data bus, address bus, VO line buffer circuits • DB25 female connector • 4000 hole wire wrap area only $125.00 16 Bit VGA card CATVC800 The 16 bit bus plus RAMBIOS support enable the Electronic Solutions card to run over 2 times faster than old fashioned VGA cards. • The highest level of resolution available on VGA. Up to 1024 x 768 pixels in 16 colours can be obtained by fitting the full 512K of display RAM. High resolution drivers for AutoCAD, Lotus 1-2-3, Framework, GEM Desktop, Ventura, WordPerfect, WordStar, Windows, Aldus Pagemaker. • Text display options include 132 X 25, 132 X 43 and 132 X 60. ....... --:::.-, • IBM VGA compatible at the register level, as well as backwards compatible with EGA, CGA, MDA, MCGA and Hercules. • Full monitor support. Support for analog, digital and multisync monitors. Other cards to this specification cost over $1,000, but for an introductory period, we are selling the card for: only $449.00 • And for an introductory period, the price is $ Australia's lowest price on these brilliant XT motherboards. Now you can boost performance of your PC over 2.5 times without spending a fortune. V20 CPU running at 4.77110MHz, install upto 640K RAM on the motherboard. Size only 8112" x 9 ". But stocks are limited at this price so order early. Note: these boards have NO RAM FITTED. only $149.00 Floppy Controllers that do everything! Dual Adaptor 1.2MB/260K/720K /1.44MB - 3.5", 51/4 11 CAT DC1220 4 way drive adaptor - all formats supported Magic Combo Mono/Colour GraphicsCard CAT DC1240 This high performance floppy controller suits all IBM PC/XT/AT/3 86and compatibles. It can interface upto 4 floppy disk drives configured as2 internal and 2 external or 4 internal drives. Any combination of either 5¼" (360K or 1.2MB) or 3.5" (720K or 1.44MB) can befitted. CAT. VCCOMBO only $130.00 High Performance Mono/Graphics This adaptor is fully compatible with IBM PC/XT/AT/38 6 and compatibles and provides control for: • 1 or 2 drives 545 This card sets new standard for emulation of colour software on monochrome monitors. It runs both 720 x 350 (Hercules text and graphics) and IBM CGA (colour graphics) with superb 16 lev~I grey scale simulation of CGA colou rs. Get the best of both worlds on you TTL monochrome monitor. Supports all mono modes plus zoom and save. Inc. parallel port. Software and full documentation supplied. And the price, for an introdutory period only is: only $129.00 Box 426 Gladesville 2111 Phone (02) 906 6666 Fax (02) 906 5222 • Any combinati of1 .2MB and ·· 360KB (5 1/4") or 720KB/1.44MB 3.5" drives Requires DOS 3.0 or later. Cables for both 5 1/4" and 3.5" are provided. DOS 3.3 or later is required for control of 1.44MB drives. The price has been reduced while current stocks last! only $99.00 f Just released, this card provides Hercules compatible text and graphics at up to 16MHz bus speeds. Perfect for the latest crop of high performance AT and 386 machines. If you are running at slow (8MHz) buss speeds because of a slow graphics card, upgrade now. Includes Parallel port, full documentation. Half slot size. only $115.00 We accept: Bankcard, Mastercard & VISA. mail orders our specialty. All prices include sales tax Note: Products may vary in appearance from those pictured. In all cases they will perform to the same or a better standard. • All products carry a 14 day money back guarantee (software accepted) • All products carry a full 3 month warranty • All cards come with full documentation A MODERN SWISS LOCO on the St Gothard run. The overhead catenary supply is 15kVAC at 16.6Hz but the traction motors are 3-phase, driven by solid state inverters. For a description of this drive system, see the previous episode in this series. THE EVOLUTION OF ELECTRIC RAILWAYS Swiss railways have always been innovative, both in their use of tunnels and electrification and in their electric locomotive technology. They were also among the first to employ rack railways, for use in their mountainous terrain. By BRYAN MAHER For 140 years, Switzerland led the field in hard rock railway tunneling. While other countries were still contemplating railways, Swiss trains were running through long mountain tunnels. Swiss engineers build the world's best railways in terrain which would daunt a mountain goat. Their complex structures allow an electrified main line to gain 100 metres of height in a ground distance of 500 metres, without overly steep gradients. Saint Gothard Tunnel For at least 800 years travellers have crossed the southern Swiss Alps by the Saint Gothard Pass, a 2134m high saddle-back depression in the icy mountains, to reach Italy. The modern steep winding road through the pass leads from Zurich and the Swiss plateau to the Po valley in Italy. To avoid the difficult road many international travellers take the train, burrowing through the mountain via the Saint Gothard railway tunnel. PT.23: SWISS TUNNELS AND RACKS 102 SILICON CHIP 1882 a Locomotive vapeur D 4/4 puissance 950 CV remorque 170-200 t 17 km/h ~ ····•..a-M a 1917 ········... a Locomotive vapeur C 5/6 puissance 1580 CV remorque 335 t 18 km/h ~ a 1920 Locomotive electrique Ce 6/8 puissance 2200 CV remorque 450 I 35 km/h a ,.. 1955 Locomotive electrique Ae 6/6 puissance 6000 CV remorque 650 t 75 km/h ················- a 1975 Locomotive electrique Re 6/6 puissance 10 600 CV remorque 800 t a 80 km/h ·-----. ~~;:;-; < THIS DIAGRAM SHOWS how increasingly powerful locomotives have been able to pull trains at progressively higher speeds on the steep approaches to the St Gothard tunnel over the years. The power designation CV for the various locos refers to Cheval-Vapeur, the metric equivalent to horsepower, equal to 935.5 watts. Tunnel construction First proposed by engineer Gottlieb Koller in 1852, the St Gothard tunnel was initially referred to a 9-state committee formed on 19 August, 1853. Discussions over tunnel construction raged for 20 years. On 6th December, 1871 the company 'Compagnie du Chemin de fer du Saint Gothard' was formed to bore the tunnel and build the railway. Work started in 1872. Conditions were terrible. The continuous uplifting of the Alps causes high temperatures, water rushes and rock splintering deep within the mountain. The difficult tunnel construction caused the illness and death of many workers. Of the 2500 workers employed, mostly Italian, 177 were killed and 400 were hospitalised due to the atrocious working conditions. On 29th February, 1880 the northern and southern working parties met in the middle of the mountain. Where they met, the centrelines of the tunnel bores differed by only 50mm vertically and 330mm transversely; an incredibly good result for the engineering standards of the time. The first run through the tunnel was on Christmas Eve 1881 by a AN INTERNATIONAL EXPRESS train pulled by a 10,400 horsepower Swiss Re 6/6 locomotive negotiates the helical tunnels on the St Gothard route. 0-8-0 steam locomotive weighing 55 tonnes. Full service between the towns of Goschenen at the tunnel's northern portal and Airola at the southern exit commenced the next year. How long would an equivalent railway project take today? Much longer, we suspect. Completing the approach ramps up to the main tunnel are 64 avalanche galleries and smaller tunnels. To gain height in a short distance, seven of them are helixes (or spirals). These complex constructions keep the ruling grade down to 2.8% and protect the track from avalanches and rockslides. Though double track working through the main tunnel was achieved in 1883, the difficult access ramps worked single track until June 1893. The first Zurich-Milan steam SEPTEMBER1989 103 es which are the most powerful single unit locos in the world. These race their BOO-tonne trains up the ramps at 80km/h, then at 125km/h through the tunnel. Of the 713 mainline electric locomotives owned today by CFF, the largest are used on the Saint Gothard section. Modern freight trains of 1600 tonnes use two Re6/6 locos, one at the head and a second about one third of the way down the train length. Trains are marshalled with 470 tonnes of freight wagons between the two locomotives, and 1130 tonnes of wagons following the second loco. With so much power available, Swiss freight trains are scheduled to run at passenger express speeds. Communications THE SWISS HAVE SOME of the most spectacular railways in the world, both for their scenery and their steep gradients. This is the Zermatt to Gornergrat rack railway, with the Matterhorn in the background. The electric supply is 3-phase AC via twin catenary wires which feed divided pantographs. trains weighing 170 tonnes ran at a stately 17km/h up the steep ramps. On the easier grade approaching the 1151-metre high summit in midtunnel, 44km/h was possible. Electrification As far back as 1904 the Swiss were experimenting with a variety of electric locomotives. One AC loco was driven by DC motors supplied by an onboard AC/DC rotary converter. Eventually, the St Gothard tunnel 104 SILICON CHIP was electrified in September 1920 using single phase 7.5kV AC at 16.6Hz. Articulated ''crocodile'' electric locos were tops in those days. Rated at 1.6 megawatts, they could haul 450-tonne trains at 35km/h while ascending the ramps and achieve 75km/h in the tunnel. Today, with the St Gothard system absorbed into the Swiss Federal Railways, CFF, international expresses are pulled by the 120-tonne 7.BMW Re6/6 locomotiv- By 1964 the original telephone system had been replaced by radio telephone and teletype. This maintains communication between ground controllers and drivers of moving trains throughout the tunnel section. Enormous problems are incurred in such radio links. Transmission and reception is difficult in a tunnel anyway and is compounded by the interference generated by the high voltage overhead wiring and the large commutated traction motors. After further upgrading of the radio system in 1981, controllers at Goschenen and Airola can independently identify running trains within the tunnel. In an emergency the ground controller can bring any designated train to a halt without driver response. Results In the first three months of 1882, 27,500 passengers and 3000 tonnes of freight were carried through the tunnel, assuring the project's success. Annual passenger patronage has grown from 250,000 in 1883 to 7,000,000 a century later. Nett freight consigned has increased from 1.5 million tonnes in 1883 to 28 million tonnes in 1980. A 1-day record attained on 25 July, 1979 was 109,950 tonnes. The number of trains passing through the tunnel per day has increased from 20 in June 1882 to 310 JUNGFRAUJOCH, INSIDE THE SUMMIT of a mountain, is the highest railway station in Europe, at 3454 metres above sea level. Note the rack between the rails. Rack and pinion drive is the only way to ensure traction on really steep gradients. ENORMOUS AMOUNTS OF HEAVY freight moves along the mountainous St Gothard route. This train is devoted to heavy trucks. Why can't we have the same system in Australia, for freight between capital cities? today. Sometimes only two minutes separates following trains. At any time up to four trains will be racing through the tunnel. Simplon tunnel The next very large engineering project undertaken in Switzerland was the Simplon tunnel to provide a short route from France and western Switzerland to Italy. The first Simplon tunnel was begun in 1898 and opened for traffic on 25 January, 1906. (This subsequently prompted the building of the ambitious Bern-Lotschberg-Simplon system which was described in the May 1988 issue of SILICON CHIP). At the time it was the world's longest railway tunnel. High above is the freezing mountain pass over which Hannibal marched his troops, elephants and horses in 218 BC. For expediency the 19.8km tunnel was bored single track. The contractors, Brandt and Brandau of Hamburg, Germany added a parallel smaller pilot tunnel for ventilation and spoil transport. Interconnecting the main and pilot tunnels are transverse galleries spaced at 200 metre intervals. The 4000 workers had to endure terrible conditions, not the least being air temperatures of up to 53°C, caused by hot springs. After completion of the Simplon tunnel, traffic problems were compounded by heavy grades on the approach ramps and by the tunnel being single track. With the opening of the Lotschberg tunnel in 1913, more trains came direct from the Swiss capital Bern and western Germany. In effect, the Simplon tunnel became a bottleneck. SEPTEMBER 1989 105 WHILE SWISS LOCOMOTIVES probably would not win prizes for beauty, they are right up among the winners when it comes to sheer power. This 20 year old Re4/4 weighs only 80 tonnes but is rated at 4.7MW (6320hp). It has a top speed of 140km/h. To provide double track running, enlargement of the original parallel pilot tunnel, to be called Simplon II, was begun in 1912. This was interrupted by the 1914-18 war and was not completed until 1923. Electrification was not completed until 1930. Since then, many improvements have been made to the tunnel wiring to allow faster running. Now, trains race through the tunnel at 140km/h, with speeds of 160km/h planned for the near future. Tourist tunnels In Switzerland there are many privately owned and operated railways. These companies cater for the thousands of tourists and ski buffs wanting transport to otherwise very inaccessible places. 106 SILICON CHIP Adjacent to the 4166m high Jungfrau mountain in the Bernese Alps was a centuries-old hospice on the peak of Jungfraujoch. When fire destroyed the ancient building in 1972, the construction of a new modern tourist hotel was hampered by the severe climate. During the day, temperatures vary between + 7°C and - 30°C. In addition, blizzards at 250km/h are common, with 15 metres of snow falling annually. The rebuilding, transport of materials and influx of tourists carried on despite the weather, using the Jungfrau private railway. This unique line has few problems with snow and ice because most of its track is in tunnels inside the Eiger mountain. One of the railway stations halfway up inside that infamous mountain was featured in the movie "The Eiger Sanction". Built in 1910, the Jungfrau line connects with the CFF system at Interlaken, then heads for the high country, to Jungfraujoch, 3454 metres above sea level, the highest railway station in Europe. This station is hewn from solid rock, inside and almost at the summit of Jungfraujoch Mountain. The highest 9.3km of this railway includes 7km of tunnels and the track gradient on the steepest slope is 1 in 4. Rack and pinion drive Since normal wheel adhesion is impossible on such grades, the Jungfrau line uses a rack-andpinion drive. Interestingly, the Jungfraujoch railway is one of the remaining five in the world still using a 3-phase supply. It was built that way right from the start and uses 650V AC at 40Hz. This was the local industrial supply. Twin overhead catenary wires THIS VIEW IS OF another privately run rack railway in the Swiss mountain countryside. How is this train powered, since the pantographs are down? Did they stop for lunch? Note that narrow gauge track and rack drive. and divided pantographs are used to feed the train, with the third phase connection being via the wheels and rails. When trains are negotiating track intersections, one section of the pantograph must not meet the wrong overhead wire for fear of short circuits. Should both pantograph sections touch wrong overhead wires, the train would be instantly reversed. Overhead wiring construction at track points and crossovers must prevent any possibility of such accidents. The designs used to fulfill this condition are truly ingenious. Branches of this line take tourists to Murren, on the western side of Jungfrau mountain. Also served is Grindewalde, near the Wetterhorn and the 4030m high Mount Schreckhorn. Zermatt Gornergrat railway Since 1898 there has been a railway system taking sightseers to the top of Mt Gornergrat in the Pen- nine Alps. It attracts tourists from all over the world, eager for a closeup view of the breathtaking scenery. From the lookout on Mt Gornergrat, at over 4000 metres elevation, visitors have a breathtaking view of the roof of Europe. Only 5.4km to the south is the 4633m high Dufourspitze de Monte Rosa, the highest point in Switzerland. Just 13km to the west is The Matterhorn, 4477m high, regarded by many as the wonder of the world. To the north, a mere 7km distant, are 4203m Mt Rimpfischhorn and 4207m Mt Alphubel. The Zermatt to Mt Gornergrat railway has been continually upgraded and modernised to provide safe and comfortable transport. Hugging the cliffs or bridging the ravines, this 9.35km line ascends the mountain to the terminal station 3089 metres above sea level. Again on grades of 20% or more, adhesion traction is an impossibili- ty and so an ABT type rack-andpinion drive is used. Two-car trainsets are employed, driven by eight motors each rated at 300kW. The overhead supply is again 40Hz 3-phase at 550VAC. On such heavy grades brake design is critical. Dynamic braking is standard and available at all speeds, even during power supply failures. Disk brakes are also provided for emergencies. Passengers come to Brig via the CFF or BLS main lines, then take the narrow gauge train up the Nikolai Valley. Passing close to the 4512m high Mt Weisshorn, the train climbs the foothills to Zermatt where the rack railway is joined. From Zermatt to the top of Gornergrat mountain, the demand is such that on this rack railway trains run every 12 minutes. Acknowledgement The author thanks CFF for information, photos, drawings and permission to publish. ~ SEPTEMBER 1989 107 ASK SWCON 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. Transistor substitute information On page 94 of your July issue you had a request from S.S. (Sandgate, Qld) for you to help find a substitute type number to replace a C1568-R transistor. This is probably the same as a 2SC1568-R. The suffix "R" appears to indicate a difference in the upper limit of hFE; eg, no suffix may indicate a hFE of 70 minimum while the suffix "R" may indicate a hFE of 70 to 140. The characteristics of a 2SC1568 are: Matsushita Device, NPN, Silicon, Vcb 18V, Vee 15V, Veb 5V, le 800mA, Ptot 1 watt in free air at 25°C, hFE 70 minimum, FT 50MHz, TO-126 case. European equivalent: BD375. Other possible substitutes are: 2SD439 (Sanyo), 2SC1173 (Toshiba), 2SD882 (NEC), 2SD667 (Hitachi) and 2SD1189 (Rohm). I feel that by making use of the data I have given on the 2SC1568, many other suitable substitutes could be found in many of the transistor manuals. I hope this information is of some assistance to S.S. (C. H., Cooee, Tas ). • Thanks for that info. It is amazing what you can come up with in a Using the UC3906 to charge 6V batteries I liked the article on the intelligent battery charger in the July 1989 issue. I want to use it to charge 6V batteries. What alterations do I have to make to the circuit to do this? Can I simply scale the critical values? I would also like to see an end-ofcharge indicator so that I know the batteries are fully up to par. (B. B., Macquarie Fields, NSW). • We have had an unprecedented number of calls along these lines. So much so that we have decided to do a follow-up 108 SILICON CHIP half hour of searching through transistor substitute manuals. We certainly did not make the connection between a C-1568-R and a 2SC1568 but now you point it out, it is pretty likely. Where to buy the VHF monitor receiver I was most interested in the articles on the VHF Monitor Receiver in the February and March 1989 issues. I was thinking of using it as an activity in the Scout movement, for construction and fox-hunting. I went to order the principal parts, chip crystal and filters, as none of them are available locally. I intended to make one receiver to evaluate it before ordering 36 or so. The parts shop here that I placed my order with advised me that there would be a $6 surcharge on each item for freight , etc. I understand that $6 is a standard charge so it makes a $3 IC quite expensive. I will now have to pursue other avenues since I am rather peeved by all southern traders placing exorbitant freight charges. I think your magazine is perhaps the best to come along for quite a article explaining how the circuit can be tailored to charge different batteries. The UC3906 also can be the basis of an excellent charger for conventional lead acid batteries and we hope to follow up on that angle too, at a later date. A number of readers have also wondered whether the UC3906 could be used for charging nickel cadmium batteries. The answer to this query is a definite no, mainly because of the way in which the on-charge voltage of nickel cadmium cells actually drops slightly as they become fully charged. while. I have found the articles on electric trains most interesting and I am not a train buff. Perhaps they could be printed as a book. (F. T, Winnellie, NT). • Good news. As pictured on page 74 in the Amateur Radio column in this issue, Dick Smith Electronics have a nice kit of the VHF Monitor Receiver. It is available from all Dick Smith stores and dealers at $59.50 (DSE Cat K-6000). Mains controllers & ignition killers I am writing to get some information on the Automatic Light Controller (June 1988) and the Discolight (July 1988). My problem is that I have built my own light machine using the output of a 4017 chip. I wish to control 240V 100 watt parafloods using your switching network from the Discolight but I am having trouble locating the Neosid 17/73/22 iron dust toroids here in South Australia. Alternatively, I have found that the switching circuit used in the Automatic Light Controller does not use a coil and I would like to know if this circuit is able to control 600 watt loads as well. Also, can you explain what the coil does in the Discolight? I am also building an ignition killer circuit for a friend's car and decided to use the circuit that was used in the Protector Car Burglar Alarm (February, 1988). My problem is that I am not sure how to connect it. In the circuit diagram, you have shown that the negative side of the coil is connected to ground via a set of relay contacts and two series 0.470 5W resistors. Is this correct? According to my calculations, this will result in a current of 12/0.94 = 12.77 A. Wouldn't this blow a fuse? (A.T., Sturt, SA). • The Neosid ring cores you refer to now have the type number Dolby A, B and C: What's the diff ere nee? Many cassette decks these days have Dolby B noise reduction and some have Dolby C. What is the difference between these and is there a Dolby A system? I read somewhere that Dolby is just a system of filtering and it actually removes some of the music as well as the hiss. Is this true? (T. D, Deer Park, Vic). • Dolby noise reduction is not just a filtering system. It is really a compression and expansion system. The first Dolby system was the A301, a professional system that was and still is used in recording studios. What it does is to split the signal being recorded into four frequency bands and then apply compression and expansion to each band. The various bands are provided in the region cif hum and rumble (80Hz and below), mid frequencies 80Hz to 3kHz, mediumhigh frequency (3kHz and above) and high frequencies (above 9kHz). If the signal level in a given band is low, it would normally be down in the noise (ie, hum or hiss) of the recorder. But the Dolby system boosts low 17-732-22 but we don't know of any retail outlet for them in South Australia. They are obtainable from Jaycar though. Their catalog number is LF-1240. The Automatic Light Controller circuit featured in the June 1988 issue is suitable for controlling a 600 watt load, provided the Triac is fitted with a small heatsink. That circuit was not fitted with a mains interference suppression circuit (which the iron dust cores are part of) because it was not intended for switching at a high rate. If you have any sort of circuit which turns lamps on and off rapidly you should have a mains inter£ erence suppression circuit otherwise you will have audible buzzing in nearby radios and audio equipment. signals so that they are above the noise floor. This is the same as saying the signals are compressed. When the signals are played back, an equivalent amount of attenuation is applied to the signal and so any hiss or hum is attenuated by the same amount. By expanding the signal in this way, the original dynamic range is preserved but the residual noise is greatly reduced. So successful was the Dolby A301 that it was a sitter for a simpler version to be applied to the early cassette decks which were hard put to produce a signal to noise ratio of better than - 40dB. The result was Dolby B. It divides the signal up into just two frequency bands, with the split being at 5kHz. Signals below 5kHz are not affected by Dolby B - it just works on the frequencies above 5kHz, as these are the ones that produce tape hiss. So again, low level signals above 5kHz are boosted before recording and then cut when played back. So hiss is greatly reduced. Note that when the signal level for frequencies above 5kHz is high, no compression takes place and the signal goes through recording playback unmodified. As far as your proposed ignition killer is concerned, the two 0.470 5W resistors are connected in parallel with the points by the relay contacts. Therefore, when the points are open, the two resistors are in series with the coil primary. Thus, when the ignition killer is activated, the total current drain is potentially less than when the ignition circuit is operating normally. Higher voltage tranny for Studio 200 power amplifier I have a query regarding the Studio 200 power amplifier described in your magazine in February 1988. I would like to build this amplifier and have on hand a Dolby B gives a maximum of 10dB noise reduction for frequencies above 5kHz and was probably the single most important development in making the compact cassette an acceptable hifi recording medium. Most prerecorded tapes available today have been recorded using the Dolby B process (signified by the double D logo on the cover). For best sound quality, you should play them back with the Dolby switched in on your cassette deck. If your player doesn't have Dolby, as is the case on cheaper players, particularly in cars, a Dolbyised tape will tend to sound shrill. You can partially correct this by using treble cut on your tone control but the real answer is to use a deck with Dolby. Dolby C is a relatively recent upgrading of Dolby B. Dolby C offers more noise reduction than Dolby B, particularly at the higher frequencies. It sounds a lot better but as far as we know, there are no commercial Dolby C cassettes available. Dolby HX, which you may have come across, is not a noise reduction system but a system which allows recording of much higher signal levels at high frequencies. power transformer rated at 40 volts each side of a centre tap at several amps. As I already have this transformer I would very much like to use it and think that I should still be inside the voltage ratings of the transistors. As the output transistors are relatively expensive I would not like to destroy them so could I please have your comments and suggestions in this regard? Thanks for a great magazine. (R. P., Salisbury East, SA). • You can use a transformer rated at 40V per side but there are a number of provisos. First, you have to consider the likely maximum DC voltage of the supply rails. If the mains voltage is 5% high (a fairly common situation which gives continu.ed on page 111 SEPTEMBER 1989 109 Cash in your surplus gear. Advertise it here in Silicon Chip. CLASSIFIED ADVERTISING COUPON Advertising rates for this page: Classified ads - $7 .00 for up to 15 words plus 40 cents tor each additional word ; Display ads (casual rate) - $20 per column centimetre (max. 10cm). Closing date: five weeks prior to month of sale. It 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. PLEASE PRINT EACH WORD SEPARATELY, IN BLOCK LETTERS 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ($7 .00) 16 ($740) 17 ($7 80) 18 ($820) 19 ($8.60) 20 ($9.00) 21 ($9.40) 22 ($980) 23 ($1020) 24 ($10.60) 25 ($11 00) 26 ($1140) 27 ($11.80) 28 ($12.20) 29 ($12 .60) 30 ($1300) Name · ·· · · · ·• •· ·· · Street ··· ··· ·· · ···· ··· ···· · ·· ·· · · ·· · · ·· · · · · · ·· · · ··· · · · ·· · · · · · ·· · · · ·· · · · ·· ••· - Postcode Suburb/Town Enclosed is my cneque or money order for $ ... ... .. .. _____ ______ __ __ _or please debit my Bankcard D Visa Card D MasterCard D Card No i I Signature .. ...... Card expiry date ...... ./ ...... ./ ........ FAX THIS COUPON WITH YOUR CREDIT CARD DETAILS TO (02) 982 9553 FOR SALE SATFAX: WEATHER SATELLITE receiving program for IBM XT/AT. Displays in 64 colours. Needs EGA colour monitor & card , AM demodulator & ADC interface. $45 plus $3 postage . RADFAX2 HF weather fax, Morse & RTTY receiving program for IBM XT/AT. Needs CGA, SSS HF, FSK/tone 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 floppy disc & include full documentation . Only from -Michael Delahunty, 42 110 SILICON CHIP Villiers St, New Farm , Qld 4005 . Phone (07) 358 2785. RADAR INVISIBILITY, locksmithing, surveillance, improvised chemistry, fireworks etc . Books on unusual topics. Send SSAE for catalog to Vector Press, PO Box 434, Brighton, SA 5048. RESISTORS, 1 % METAL film, 0 .6 watt. Finest German quality, 7c each , $6 per hundred, any mixed values . SAE for free sample & data sheet. Also BUX80 $7 , 2N3055 $2 .35, BC547 12c, 2N3019 $1 .20, HEF40508 80c, 1 0nF greencap 20c, 1 00nF monolithic 15c, 220nF 630 volt MEMORY CHIPS D RAM PRICES AT 31st July, 1989 Type 4x2 56 1Mb 1Mb - 256 150ns 120ns 100ns 100ns ?Ons ?Ons 1 OOns 100ns 80ns 9 x100 8 x100 9x80 SuitabiHty Price ex tax XT's AT's 12Mhz NEC 20Mhz Comp Laptop 18 pin $5.90 $6 .20 $6.60 $6 .90 $9 .20 $12 .50 $21.50 $21.50 $23.30 $245.00 $230.00 $280.00 Simm Mac Simm Fast Simm Discounts on large orders Sales Tax add 20% PELHAM Tel (02) 427 0011 Fax (02) 428 5460 TECHNICIANS Secure your future! Develop your communication skills and enhance your employment opportunities . How? Invest in the world famous SMI training kit and you too can join the hundreds of success stories. Telephone (02) 821 1282 today for more details. polycarbonate $2. P&P NSW $2.50, interstate $3.50. Extended Pulse Burn Electronic Ignition: full kit $70, fully built and tested $99 postpaid. Chipspeed Electronics, PO Box 337, Wentworthville, NSW 2145. 1M PRINTER BUFFER KIT. Rev H boards now available. Supports 8K to 1M. $39 kit consists of double sided PCB, EPROM and instructions. Optional additions include 2 x 7 -segment LED front panel display of percentage full, 1 to 99 copies select, 3 polled computer inputs, printer switches, computer switches and serial converter boards. For a free catalog send a 39c stamp to Don McKenzie, 29 Ellesmere Crescent, Tullamarine 3043 . WANTED WANTED TO BUY: infrared image converter valves type XX1080. Contact C. Voarino on (086) 28 2435 anytime. ELECTRONICS FOR EVERYONE KITSETS OR BUil T UP UNITS Advertising Index 7~ information till~d pages detailing over 300 different kitsets and built up units from Australia, USA & England. Includes 14 pages of technical books . Parts location service. Address label printing by the sheet. 33 labels tor $1.50. Send extra large stamped addressed envelope for information. Allied Capacitors .... .. ... ......... 97 Altronics ... .... .. .... .. ....... .. 68-71 Arista Electroniqs ..... ..... .. ... .. 1 5 Dauner Electronics .......... ... . 83 David Reid Electronics .... . 56, 5 7 Dick Smith Electronics .. ... 46-51 Electronics Assembly .. .... ... 111 Electronic Solutions ..... ... .... 4,5 100,101 Elmeasco ..... ... ... ... ..... ... .. OBC Esckay Printernet .. ...... . 76, 11 O Geoff Wood Electronics ....... IFC Harbuch Electronics ............. 99 Hycal Instruments ...... .. ....... . 45 IREE ...... .. ...... ........ .... .... .... 74 Jaycar Electronics ...... .... 36-39 84-87 Oatley Electronics .. ..... .... .... 1 9 PC Marketplace .. .. ... .. .... . 78, 79 Pelham .. ........ ... .. ... ... .. ... ... 111 Philips Test & Measurement .. 98 RCS Radio ........ .. .. ...... .. .... .. 1 5 Rod Irving Electronics .. 112,IBC WIA .. .. ... .......... .. ........ ..... ... 91 ELECTRONICS ASSEMBLY COMPANY (1987) PO Box 21 191, Christchurch, New Zealand. Ask Silicon Chip ctd from page 109 252VAC), the DC supply voltage will be around ± 60 volts or so, depending on the load voltage regulation of the transformer. All the transistors in the power amplifier can withstand these voltages, as can the 8000µF filter capacitors, but the problem is not quite as simple as that. On page 40 of the Feb. 1988 issue we plotted load lines for the MJ15003/4 transistors. These were drawn for a supply voltage of ± 50 volts DC. If the supply goes to ± 60 volts, those load lines have to be redrawn. Having done so, we can state that the transistors' SOAR (ie, safe operating area) curves would be exceeded when a reactive load of 4 ohms is connected. There is definite risk that the output transistors and the driver transistors could be blown. This is a long winded way of saying that you could use the transformer but you would be unwise to connect 40 loudspeakers to the amplifier. Of course, if the transformer had a 250V tap, the problem could be easily solved but these days you don't see many transformers with 250V AC taps. In view of the relatively small power increase that you would get by using the larger transformer we do not think it is worth the risk to the output transistors and we recommend that you use the specified transformer. Where to buy stainless steel screws In the article on the 5-element FM antenna described in the October 1988 issue and in the article on the UHF bowtie array in the THE HOMEBUILT DYNAMO by Alfred T. Forbes ISBN 0-9597749-0-4 Reviewed in S.C. October, 1988. $A85 including air mail post. (Brochure$A5 refundable) Trade enquiries welcome. Todd-Forbes Publishing. PO Box 3919, Auckland 1, New Zealand. January 1988 issue, you strongly recommend the use of stainless steel screws. The only trouble is, I have not been able to obtain them anywhere. Just where do you get them? (M. W., Fairfield, NSW). • You are quite right. Many hardware stores are hopeless when you want to buy something that will last. The best places to go are ship chandlers; ie, boating supply stores. In Sydney and Brisbane, the best ship chandlers are Whitworths and they have a very large range of stainless steel hardware including U-bolts. ' You can phone their Brookvale (Sydney store) on (02) 939 1055 and their Brisbane store on (07) 394 3055. Notes & Errata Studio 200 Stereo Control Unit, June, July 1988: we have had a report of overheating of the output transistors in the headphone driver amplifiers. This is possibly caused by mismatch between diodes Dl and DZ and the transistors Ql and QZ. We therefore recommend that D1 and DZ in both channels be replaced with 1N914s or 1N4148s. Narrowband FM Receiver, February, March 1989: the unused secondary winding of the quad- PC Boards Printed circuit boards for SILICON CHIP projects are made by: • RCS Radio Pty Ltd , 651 Forest Rd, Bexley, NSW 2207. Phone (02) 587 3491 . • Jemal Products, 5 Forge St, Welshpool, WA 6106 . Phone (09) 350 5555. • Marday Services, PO Box 19-189, Avondale , Auckland, NZ. Phone 88 5730. rature coil 12 is shorted out by the underside ground plane of the printed circuit board, as shown in Fig.2 on page 70 of the March issue. This causes a loss of sensitivity. The cure is to remove the coil and then use a small diameter drill to remove the copper away from one of the unused pins of the coil. The coil can then be soldered back into place. Extension For the Touch-Lamp Dimmer, July 1989: the wiring diagram, Fig.2 , on page 33 is incorrect. It shows the Active connection and the Extension connection transposed on the insulated terminal block. This mistake is repeated on the Dimmer extension board shown in Fig.3 on page 35.~ SEPTEMBER 1989 111 9 •. il ' DISK STORAGE UNITS • 80 x 3 1/2" • Lockable C16038 ..................$16.95 "NO BRAND" DISKS • 40 x 31 /2 " . 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Lockable (ALL PRICES PER 10 DISKS) C16025 .................. $14.95 5 1/4" 2S/2D "NO BRAND" DISKS 10+DISKS 100+ DISKS 1,000+ DISKS $6.00 $5.75 $5.50 • 100 x 5 1/4 ""Eclipse" C16042 .................... $9.95 • 100 x 5 1/4 .._ Lockable C16020 .................. $15.95 5 1/4" HIGH DENSITY DISKS (DOUBLE SIDED) 100+ DISKS 10+ DISKS 3 1/2" 2S/2D "NO BRAND" DISKS 386SX 16MHz MOTHERBOARD $21 3 1/2" 2S/HD "NO BRAND" DISKS 10+ DISKS $59 100+ DISKS 1,000+ DISKS $57 $55 Suitable for IBM, PS/2, Macintosh, Atari , etc. DESCRIPTION (ALL PRICES PER BOX OF 10 DISKS) 1-9 BOXES 3 1/2" 1S/2D............... $39.95 3 1/2" 2S/2D ...............$42.95 31 /2" 2S/HD ..............$89.00 51/4" 1S/2D ...............$22.00 5 1/4" 2S/2D ............... $26.00 5 1/4" 2S/4D ...............$75.00 51/4" 2S/HD ..............$41.00 10+ BOXES $37.95 $39.95 $85.00 $21.00 $24.00 $70.00 $39.95 I I I I I L I VERBATIM DATALIFE PLUS Teflon* Coated • Processor: 80386SX•16MHz (0/1 wait state) • Co-processor:80387SX-16 (optional) • CHIPS & TECH NEAT chlpsets • (SMT) Surface Mount Technology for chlpsets & CPU • Supports up to 2MB on board, (Sixteen 44256 and Eight 41256 sockets) • Three 8 BIT slots • Five 16 BIT slots • Memory Expansion Slot • Optional 2-8MB memory card • Supports LOTUS-INTELMICROSOFT (LIM) Expanded Memory Spee. (EMS) version 4.0 • Supports Page Interleave Mode using 100NS DRAM • 8105: AMI or PHOENIX • Turbo Light and Hardware Reset connector • Keyboard or Hardware Reset connector • Power Good Signal on board • Baby size main board II (ALL PRICES PER BOX OF 10 DISKS) I 5 1/4" DS/DD C12522 .......................................$34 5 /14" High Density C12523 .................................$64.95 I I __________ ... : Check these features and our prices. we·re sure you'll agree they're exceptional value for money! • Final assembling and testing in Australia! • Fast TURBO Motherboard • Ar style keyboard • Tested by us for 24 hours prior to delivery! • 8 Slot motherboard • 12 months warranty! • 150W power supply 640K RAM TURBO COMPATIBLE COMPUTER 2 x 360K Disk Drives, Multifunction Card, Colour Graphics, Disk Controller, 1 Serial, Parallel Port (Clock) ............. ....... $1 ,050 WITH 20 M/BYTE HARD DISK: & single 360K Disk Drive ..$1,450 & dual 360K Disk Drives ... $1,600 WITH 40 M/BYTE HARD DISK: & single 360K v.c. H.D...... $1,n5 & dual 360K V.C. H.D .........$1,925 386TOWER PC The 386 Tower PC Is a high performance system that's IBM• Ar compatible. However, the 386 Tower PC gives you 2·5 times the performance. FEATURES: • Intel 80386·16MHz microprocessor • Switchable 16/20 MHz • 2 M/Byte fitted. Total memory expandable up to 16 M/Byte • Up to 2 M/Byte or 8 M/Byte • Option for 80287 & 80387 coprocessor socket • Chips and Technology chip set • AMI Phoenix 386 810S/ • 50 M/Byte hard disk. 42 M/Byte formatted. Fast access • EGA card • 31 /2" drive 1.44 M/Byte X20070 .................. $5,995 TOWER COMPUTER CASING Remount your computer to give it that professional look. • Accepts XT, AT, Baby AT and 386 boards • Horizontal full height hard disk drive mounting • Room for 2 x3 1/2" and 2 x 5 1/4" floppy drives • Full height HDD plus fan mounl • Size: 165(W) x 600(H) x SOO(D) X11105 .....................$250 X18094 .....................$900 286 NEAT MOTHERBOARD r:----------:1 II C16028..................$19.95 $21 $22 $23 • 120 x 51 /4 .. _ Lockable 1,000+ DISKS IBM* XT* 640K RAM TURBO COMPATIBLE COMPUTER • Processor: 80286-12, -16MHz or -20MHz (0/1 wait state) • Co-processor: 80287 (optional) • CHIPS & TECH NEAT chipsets • 1-4MB dual RAM socket • 1-4MB module RAM socket on board • 640KB-384KB memory relocation • Three 8 BIT expansion slots • Five 16 BIT expansion slots • Memory expansion to 8MB • Supports EMS 4.0 • Page Interleave Technology • 8105: AMI or PHOENIX • Hardware and keyboard switchable Clock Speed • LED speed display • Power Good Signal on board • Baby size main board • 16MHz X18090 ..................... $700 • 20MHz X18092 ..................... $895 BABY AT* COMPATIBLE COMPUTER! 2M/B RAM $2,195 • Final assembling and testing in Australia! • 4 M/Byte Maln,Board, 2 M/Byte fitted • Switchable 8110/12 MHz • 1.2 M/Byte Floppy Disk Drive •80286CPU • Colour Graphics Display Card •8Slots • Floppy & Hard Disk Controller • Printer Card and RS232 • Keyboard • 200W Power Supply • Manual • 6 Months Warranty •Size: 360(W) x 175(H) x 405(D)mm With 20 M/Byte Hard Dlsk.$2, 195 With 40 M/Byte V.C. H.D....$2,395 With 80 M/Byte Hard Disk .. CALL REMOVABLE CARTRIDGE HARD DISK Ricoh R260 20 M/Byte Removable Hard Disk Is a subsystem for AT or 386 systems. Extra 20 M/Byte cartridges are available. To enable the end user to build a library that can be safely locked away. Or taken to another site that is using the same sub-system. it·s the ultimate in hard disk back up systems or for transport ability of data. Includes a cartridge X20022 ..................$1,274 Extra 5 1/4" 20 M/Byte cartridge for disk (Ricoh RH5260) X20024 ..................... $220 20MHZ DUAL TRACE OSCILLOSCOPE SHORT TESTER • Instantly shows the open/short position of PCB • It can test whether PCB or solid wire open/short by Buuer 011276 .. . ............... $22.95 CRT DISPLAY • 150mm rectangular VERTICAL DEFLECTION • Deflection Factor: 5mV to 20V/ Div on 12 ranges in 1-2-5 step with fine control • Bandwidth DC: DC to 20MHz (-3d8) AC: 10Hz to 20MHz (-3d8) • Operating Modes: CH-A, CH-8, DUAL and ADD (ALT/CHOP L202 only) • Chop Frequency: 200KHz Approx. • Channel Separation : Better than 60d8 at 1KHz TIME BASE • Type : Automatic and normal triggered in automatic mode, sweep Is obtained without input signal • Sweep Time: 0.2µ Sec to 0.5 Sec/ Div on 20 ranges in 1-2-5 step with line control and X-Y • Magnifier: X5 at all ranges LOGIC PROBE (LP-2800) • Useful for TTL or CMOS has high and low indicator leds and also with pulse memory. • This is a very handy tool for the hobbyist or serious technician for tracing those hard to find faults on logic boards. Q11272 .................. $34.95 TRIGGERING • Sensitivity lnt: 1 Div or more Ext: 1Vp-p or more • Source: INT, CH-8, 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 20V/ Div on 12 ranges in 1-2-5 step with fine control • Frequency Response : DC to MHz (-3d8) • 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(D) mm Q12105 .............. ....... .............................................$695 150W SWITCH MODE POWER SUPPLY FOR IBM* PC/ XT* & COMPATIBLES DC OUTPUT: • +5/ 13A, -5V/ 0.5A • +12V/ 4.5 -12V/0.5A X11O96 ............. ........ $129 180W SWITCH MODE POWER SUPPLY FOR BABY AT* COMPATIBLES X11O98 ..................... $169 200W SWITCH MODE POWER SUPPLY FOR IBM* AT* & COMPATIBLE DC OUTPUT: +5/ 16A, -5V/ 0.5A +12V/5A -12V/ 0.5A X11097 ..................... $199 Y11000 Y11003 Y11005 Y11007 Y11008 Y11009 Y11010 Y11015 Y11018 Y11020 Y11022 Y11023 Y11024 Y11025 Y11026 Y11027 Y11030 Y11033 Y11042 Y11050 Y11055 Y11070 Y11072 Y11080 Y11085 Y11090 1MHz $11 .50 1.8432MHz $7.50 2MHz $6.90 2.3040 MHz $6.50 2.4576 MHz $6.50 2.7648 MHz $4.90 3MHz $4.90 3.57954MHz $3.00 3.93216MHz $4.90 4.00 MHz $4.90 4.19430MHz $3.90 4.33618MHz$4.90 4.44 MHz $4.90 4.75 MHz $4.90 4.9152 MHz $6.90 4.9562 MHz $4.90 5MHz $4.90 5.0688MHz $4.90 6.144 MHz $4.90 8.00 MHz $4.90 8.86723MHz $4.90 12.00 MHz $4.90 14.318 MHz $4.90 16.00 MHz $4.90 18.432 MHz $4.90 20.00 MHz $4.90 -- SUPER BRIGHT LEDS • Red ............... 210146 • Green .... ....... 210147 • Yellow ........... 210148 1-9 10+ $1.00 • 4164-120ns U20832 .................... $5.50 • 4464-1 OOns U20842 .................. $17.85 • 41256-SOns U48262 ..... ............. $18.95 • 41256-100ns U48260 ..................$14.95 • 1MB-100ns U48265 .................. $43.95 12V DC FANS 80 x 80 x 25.4mm 12V DC, 1.7 Watt, 0.14 Amps T12469 .................. $12.95 ...... . 10+ fans only $11.95 each :r :1:e . . . . ROD IRVING ELECTRONICS $0.90 All sales tax exempt orders and wholesale inquiries to: FLASHING LEADS SYDNEY: 74 Parramatta Rd . Stanmore 2048 Phone : (02) 519 3134 Fax: (02) 519 3868 • Red, 5mm 1-10 210159 $1.10 10+ $1.00 QUALITY LEDS Cat. no. 210140 Price Description 3mm Red ........ $O.15 210141 3mm Green .... $O.2O 210143 3mm Yellow .... $O.2O 210145 3mm Orange .. $O.2O 210150 5mm Red ........ $O.1O 210151 5mm Green .... $O.15 210152 5mm Orange .. $O.15 210155 10mm Red ...... $1 .OO 210156 10mm Green .. $1.00 210157 10mm Yellow .$1.00 MELBOURNE: 48 A•Beckett St Phone : (03) 663 6151 NORTHCOTE: 425 High St. Phone : (03) 489 8866 MAIL ORDER& CORRESPONDENCE : P.O . Box 620 , CLAYTON 3168 Order Hotline : 008 33 5757 (Toll free , strictly orders only) Inquiries : (03) 543 7877 Tele x: AA 151938 Fax: (03) 543 2648 RITRONICS WHOLESALE : 56 Renver Road, Clayton. Phone :(03) 543 2166 (3 lines) Fax : (03) 543 2648 ORDER HOTLINE 008 33 5757 ITOLL FREE} 40MHZ READ-OUT OSCILLOSCOPE STRICTLY ORDERS ONLY CRT DISPLAY • 150mm rectangular LOCAL ORDERS & INQUIRES (03) 543 7877 VERTICAL AMPLIFIER (CH1 and CH2 Identical) • Operational Modes : CH1 , CH2, ADD, DUAL, ALT, CHOP • Sensitivity: 5mV-5V/ Dlv 3% in 1-2-5 steps 1mV-1V/ Div x5% x5MAG • Bandwidth DC: DC to 40MHz (·3dB) AC : 5Hz to 40MHz (-3d8) • Rise Time: Less than 8.7nS HORIZONTAL AMPLIFIER b . Rea do u t • Operating Modes: X-Y operation CH1-X axis, CH2-Y axis • Sensitivity: 5mV-5V/ Dlv± 3% In 1-2-5 steps POSTAGE RATES : JUMP WIRE KIT (KS-350) D i s p l ay • Input Impedance: 1Mll±2%, 25pF±3% • Bandwidth DC: DC to 1MHz (-3d8) AC: 5Hz to 1MHz (-3dB) TIME BASE • Sweep Method: AUTO, NORM, SINGLE • Sweep Time (A) : 0.2µs-0.5S/ Dlv±3% in 1-2-5 steps (X1 only) (8): 0.2µ5-0.SmS/ Div±3% in 1-2-5 steps (X1 only) • Magnified Sweep: 10 times±5%, Max 20ns • Linearity: ±3% or better 012107...............................................................$1,695 Contains: 14 kinds of length from 0.1.. to 5" with different colors Q11278 .................. $19.95 CANNON TYPE CONNECTORS AT SPECIAL PRICES!! Cat. no. Description Price P10960 3 pin line male ....... $2.9O P10962 3 pin chassis male$3.25 P10964 3 pin line female . ..... $3.50 P10966 3 pin chassis female$3.75 $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 fragile items will be ch arged at different rates . Errors and omissions excepted. Prices and specifications subject to change . ISM' . PC". XT' . AT" . are registered trademarks 01 Intern ational Business Machine s. 'Apple is a reg istere d trad emark. Tellon ' ,s a reg 1sl ered tra d ema rk ol Du pont ·o enon l es reg is tered lrademarks ol 1heir respective owners.