CANADA'S OWN ELECTRONICS MAGAZINE electronics · 2019-07-17 · CANADA'S OWN ELECTRONICS MAGAZINE...

CANADA'S OWN ELECTRONICS MAGAZINE

electronicsincorporatingAPRIL 1978

Bucket-BrigadeDelay LineDangerousGas AlarmComputerPowerSupply

More PCBNegatives

New SectionETI's X -Ray for theExamination of the EducatedRadio Shack Computer Audiophile

ALPHATUNERSERVICETHE NAME OF QUALITY IN TUNER SERVICING

Service from coast to coast

ATTENTION DEALERS:Hundreds of satisfied customers across the country are utilizing our services because qualityand service is our business.

Quality All tuner repairs are serviced by trained technicians

Fast Service 8 to 24 hour service i3 a must.

One Year Workmanship and parts are warranted for one year from the date ofWarranty delivery

Versatility We rebuild all tuners of any model, or any make, including varactor-electronic, and all foreign makes.

VHF-UHF-VARACTOR TUNERS 13.95 UHF -VHF -COMBO 21.9Major parts and shipping charges at cost. (dealer net).Bring tuners to our Montreal centre or send by mail.

an Electronics8400 St. Lawrence Blvd. - Suite 201, Montreal, Que.

Tel: 514/381-5838

VOL. 2 NO. 4

STEVE BRAIDWOOD electron:es todayAssistant Editor international

GRAHAM WIDEMAN BASc

Marketing Manager and AdvertisingPETER E. PRIEST

Advertising ServicesSHARON WILSON

Advertising RepresentativesJIM O'BRIEN

Eastern Canada JEAN SEGUIN &ASSOCIATES INC., 601 Cote Vertu,

St. Laurent, Quebec H4L 1X8.Telephone (514) 748-6561

Subscriptions DepartmentBEBE LALL

Accounts DepartmentSENGA HARRISON

Layout and AssemblyGAIL ARMBRUST

Contributing Audio EditorWALLACE J. PARSONS

Editorial Director TOM GRAHAM.Published by Electronics Today

International (Canada) Ltd.

EDITORIAL AND ADVERTISINGOFFICES

Unit 6, 25 Overlea Boulevard,Toronto, Ontario, M4H 1 B1Telephone (416) 423-3262

Printed by Livingstone Printing Ltd.

News Stand Distribution Gordon &Gotch, Toronto.

Subscription Rates $12.00 per year,$20.00 for two years. Send to Sub-

scription Dept., ETI Magazine, Unit 6,25 Overlea Blvd., Toronto,

Ontario. M4H 1B1.

ALL ETI PCB PATTERNS ARE COPYRIGHT.NO COMPANY MAY SELL BOARDS TO OUR

DESIGNS WITHOUT OUR PERMISSION.

INTERNATIONAL EDITIONSElectronics Today International

25-27 Oxford St.. London W1 R 1 RF, UK.Editor Halvor Moorshead.

Electronics Today International,Ryrie House. 15 Boundary St.,

Rushcutters Bay, Sydney. Australia.Editor Collyn Rivers.

Electronica Top Internationaal,Postbus 260, Emmen, Holland.

Editor Denis Loos.

Elrad,Kommanditgesellschaft, Bissendorfer

Strasse 8. 3000 Hannover 61. Germany.Editor lido Wittig.

CANADA'S OWN ELECTRONICS MAGAZINE

PROJECTSCOMPUTER POWER SUPPLY 28Eight volts at 7.5 A, plus and minus 16V at 750 mA

BUCKET -BRIGADE AUDIO DELAY LINE 32The latest thing for audio experimenters

GAS ALARM 42Protect your home, your boat, your car, etc

AUDIO TODAYETI's new department for hifi nuts

AUDIO TODAY, LETTERS 12What the hifi nuts have to say

WE REVIEW THE TRS-80 COMPUTER 15Radio Shack's personal computer might be in your home soon

FFTs EXPLAINED 22Isn't it about time you found out what FFTs are?

ETI DATASHEET 39Panasonic MN3001, bucket brigade

BITS, BYTES, & BAUDS 47What's been covered in this six -part course

ETI SOFTSPOT 49Atomic decay game and pseudorandom number generator

TECH TIPS 57Ideas for experimenters

CLUB CALL 61If you're not in 3 electronics clubs already, this is for you

FEEDBACK 63Letters from our readers

THE FUN OF ELECTRONICS 65Just for a laugh

FEATURES

NEWS & INFORMATIONNews Digest 4 ETI Panel Transfers 46Microfile 7 ETI Subscriptions 48ETI Binders 8 ETI Marketplace 54PCB Negatives Centre Insert ETI 741 Circuits 58ETI Circuits 38 ETI Publications 64Canadian Projects Book #1 41 Information 66Next Month's ETI 45 Classified Advertising 66Cover: We didn't really use X-rays., of course, but we gave the machine a very thorough check-up. Seepage 15.

Second Class Mail registration number 3955. Copyright: All material is subject to world-wideReturn postage guaranteed. Post Office returns Copyright protection. All reasonable care isto Unit 6, 25 Overlea Boulevard, Toronto, taken to ensure the accuracy of the information.Ontario, M4H 1131.

ETI CANADA - APRIL 1978 3

1EWS DIGEST

New NCR Retail TerminalsWhat is claimed to be a new generation ofelectronic point -of -sale terminals, whoseperformance can be increased byadding plug-in modules, was announcedrecently by NCR Canada Ltd. Featuresinclude the use of proprietary NVRAM(Non -Volatile Random Access Memory),and the ability to use more than one pro-.cessor. The 2140 can automatically read.

Digital AC VoltsAmps Freq MetersAC Volts, Amps and Frequency can bemonitored with an AC digital panel meterfrom Electro Industries. The LM Series willsimultaneously measure both AC voltswith 1 volt resolution and frequency bet-ween 42 and 99.9 Hz with 0.1 Hz resolu-tion. The indicator utilizes the double LEDdisplay -0.3" high. The VA series is an ACvolt/amps monitor with the same doubleLED display. Amps are displayed up to999.9 amps AC and volts up to 600 volts.The LF series offers a choice of 3 modelsof frequency monitors with a full 4 digitdisplay offering up to 0.01 Hz resolution,using 0.4" high LEDs.

For free detailed technical informationcontact Metermaster, 214 DolomiteDrive, Downsview, Ont. M3J 2P8.

merchandise tags with a scanningdevice or automatically read informationencoded on the magnetic strip of a plasticcard.

Additional modules include: Datacommunications to a computer system atanother location; data consolidation, inwhich one "master" terminal automati-

cally summarizes totals for up to 15 otherunits memory capacity up to 128K bytes;Electronic Funds Transfer transactions,the ability to handle credit -authorizationor debit transactions; and up to threeprinting stations.

Prices for the 2140-2000 begin at$2,950.

RF DataMotorola has a new RF data manual, withcomplete data sheets, practical applica-tion notes, and cross-references. The twopound, 736 page volume describes RFpower transistors with outputs up to 150W, operable in commercial, military, air-craft, marine and ham bands from 1.5MHz to 1 GHz.

Detailed application informationincludes impedance matching networks,mechanical RF construction techniques,biasing, reliability, noise figure and gainoptimization procedures, mounting andheat sinking, as well as discussions ofSSB linearity, broadbanding, and powercombining.

Motorola's RF data manual is availablefor US $3.50 each from US Motoroladistributors.

Rockwell'sBubbleBusinessRockwell International has announced ithas chartered a new organization to con-vert its bubble memory technology into acommercial business, and plans toannounce new product specificationsand prices very soon.

John L. Archer, formerly manager -Applied Magnetics, heads the newenterprise with the title of businessdirector - Bubble Memory Products. Mr.Archer worked at Rockwell's ElectronicsResearch Center where the first operat-ing 1 -megabit bubble memory deviceswere developed and produced in Feb-ruary last year.

4 ETI CANADA - APRIL 1978

Cesco AppointedHEP-MotorolaRepCesco Electronics Ltd, have announcedtheir appointment as the HEP-Motorolastocking representative for Canada.

HEP-Motorola is a line of packagedsemiconductors intended for hobbyistsand as service replacements. The line isaccompanied by cross referenceguides,technical information guides and Hep-notes which provide complete details ofdifferent projects.

HEP-Motorola will be sold to electronicparts distributors through a number ofrepresentatives in different areas ofCanada. Cesco will carry good stocks ofthe line for fast service and delivery.Pricing policy is based on HEP-Motoro-la's own price list. Further information andthe name of the rep in your area may beobtained by writing to Cesco ElectronicsLtd, 4050 Jean Talon St West, Montreal,Que.

HP ProgrammableCalc BooksTen new books designed to provideowners of HP -19C and HP -29C prog-rammable calculators with solutions toproblems in such fields as finance, statis-tics and engineering are available fromHewlett-Packard. The books are $10.95each (plus tax and duty if applicable).

Each HP-19C/29C Solution book pro-vides the user with 12 programs. Foreach there is a summary of the program,a listing of program steps, and an expla-nation of how the results are displayed onthe calculator. The ten books in the "Sol-utions Library" are identified by subject:

1. Surveying. 2. Mathematics. 3. Statis-tics. 4. Finance. 5. Electrical Engineering.6. Navigation. 7. Mechanical Engineer-ing. 8. Civil Engineering. 9. Games. 10.Student Engineering. HP-19C/29C Solu-tion books are available from Hewlett-Packard and selected retail outlets andcollege bookstores.

Errata:Project BookPlease note that in Canadian ProjectsBook Number One, Fifty/One HundredWatt Amplifier, Q6 is incorrectly shown asa 2N4250. It can be replaced by a2N3904.

Video EditorThe BVE-500A broadcast editing consolefrom Sony permits fully automate editingfor a pair of Sony BVU-200A U-Matic vid-eocassette recorders. A major advan-tage of the unit over existing editing con-soles is "bid rex" -two self -return searchdials that operate with picture in both for-ward and reverse modes.

Annual RecordingWorkshopThe third annual summer seminar on thefundamentals of recording will be held atThe Banff Centre, School of Fine Arts,Mon May 29 to Fri, June 2, 1978. StephenF. Temmer, President of Gotham AudioCorporation (New York and Hollywood)will be on hand. The intensive coursefeatures six hours daily of scheduledclass and hands-on recording work. Inaddition, there will be evening discussionsessions probing the philosophy ofrecording and exploring ideas on futuretechnology.

Lending the course greater weight isthe fact that students and faculty of theMusic Division of The Banff School of FineArts will be available for actual recordingsessions.

The fee for the week-long course is$225.00.

Address al queries to Communica-tions, The Banff Centre, Box 1020, Banff,AB, TOL OCO. Registration closes April30, 1978.

Other features include a digital tapetime counter (up to 79mm/59 sec/29frames for both player and recorder),blinking lamp indicators (guide sequ-ence of operation), automatic entry, buttedit, manual edit, automatic "on air"capability, edit preview and review, andentry time shift

LCD PanelMeter PCBIn our February issue we inadvertentlyomitted the PCB pattern we were soproud of. Here it is.

ETI CANADA -APRIL 1978 5

Programmable Control Unit/Learning AidMotorola has announced a 2 -boardIndustrial Control System that combinesa prewired programmable logic control-ler (PLC) with an ancillary Input/OutputSimulator that serves as a systemdevelopment tool and demonstrationunit. Based on the company's recentlyintroduced single -bit microprocessor -the MC14500B Industrial Control Unit(ICU) - Motorola claim this sytem canserve as a learning tool to acquaintdesigners with the power and potential ofa one -bit MPU and, thereafter, as a dedi-cated functional control system. As afunctional system, the I/O Simulator is

replaced by the actual I/O devicesassociated with the working system.

The system has 15 inputs and 16 out-puts, and incorporates a RAM capable ofholding 128 ICU program instructions.The user is able to examine or change thecontents of any memory location and hasthe option of single stepping or runninghis program. Alternatively, a program-

, med PROM may be installed in an availa-ble socket to run the program. Built-inLEDs display the state of the programwithin the system, thereby providing aneasy means for monitoring or troub-leshooting. The system accepts 16

Micro SeminarsE&L Instruments will present four one -day "hands-on" microcomputer semi-nars to product designers attending the25th ASME Design Engineering Show atMcCormick Place, Chicago, Illinois, April17-20, 1978. Design engineers andmechanical engineers will learn how toprogram and interface microcomputersin traditionally mechanical applicationssuch as appliances, tools, process con-trol, automative instrumentation, andconsumer goods.

For seminar registration information,contact Clapp & Poliak Inc, 245 ParkAvenue, New York, New York 10016;telephone: (212) 661-8410.

TDS-M68 MicroThe TDS-M68 microcomputer Trainingand Development System guides the userstep-by-step through the learningprocess (from elementary introductorymaterial to interrupt based sequentialcontrol examples), a lab package thatincludes real world devices (LEDs, relays,small motors, etc.) that are interfaced toand controlled by the computer, plus apractical, applications oriented, textbookcovering programming, interfacing andapplication concepts (including workedout sample application examples). Aninstructor's guide and overhead trans-parencies are also available.

Six general purpose I/O ports (utilizingthe SWTPC bus configuration) accept aline of interface boards that includesparallel and serial I/O ports, a cassetteinterface, an interrupt timer, a calculatormodule, an EPROM programmer, etc.

All items are available separately or asa total package. A descriptive brochureis available upon request from SDSTechnical Devices, 1138 Main St., Win-nipeg, Man., R2W 3F3.

instructions and can be uniquely tailoredto a user's particular requirements.Designed with CMOS technology, itutilizes very little power and operatesfrom a 5 volt power supply.

In the USA the DS14500A IndustrialControl Unit Demonstrator System sellsfor $295.00. This includes the ProcessorBoard, the I/O Simulator Board and anappropriate 40 -conductor ribbon cable.In addition, the Processor Board is avail-able separately under part numberDS14500B, at a cost of $197.00 (unitquantity), for end -use application wherean I/O simulator is not required.


6800 ProgrammingBob Southern's "Programming the 6800Microprocessor" was written to teachprogramming to community college stu-dents. He assumes no previous know-ledge of programming and teaches thefundamentals of assembly language andmachine -code programming of the 6800processor and its peripheral devices.The ACIA and PIA are explored in detail inboth non -interrupt and interrupt modes.The workbook asks the student questionsafter each new piece of information, andthen gives the correct answer.

The book is available ($6.75, prepaid)from The Algonquin College Bookstore,1385 Woodroffe Avenue, Ottawa,Ontario, K2G 1V8.

First 12L,Monolithic 10 -BitA/D ConverterA complete, 10 -bit monolithicanalog/digital converter, which for thefirst time in bipolar technology combineslinear and digital circuitry on a singleintegrated circuit chip, has beendeveloped by Analog Devices Semicon-ductor. The new AD571 is producedusing the integrated -injection logic (I2L)technique which allows very high circuitdensities to be fabricated on a singlechip.

In addition to representing an advancein the application of I2L technology, theAD571 is also the first monolithic A/Dconverter to be laser wafer trimmed.

The AD571 is a successive approxi-mation converter and includes a DAC,voltage reference, clock, comparator,successive approximation register andoutput buffer on a 120 x 150 mil chip. Thedevice executes a complete conversionto 10 -bit accuracy - 1/2 LSB with no mis-sing codes in 25 microseconds.

Contact Tracan Electronics,Downsview, Ont.

microfile

Data Terminal MartThe competitive data terminal market isnow being served by a new style of retailoperation. Data Terminal Mart reducestheir overhead by limiting field sales staff,encouraging the small customer to comein to their sales outlets and save money.Hazeltine, Digital Equipment, TexasInstrument, Tektron, Teletype, Interdate,MI2 and Misco Manufacturing are amongthe lines they handle, of particular interestto computer hobbyists would be DTM's

less expensive lines such as Soroc (aspin off from Lear Siegler) and competi-tively priced Dec -writers.

DTM finds that being located in hotelsin Toronto, Montreal, and Calgary is veryadvantageous to business. In Torontothey are to be found in the Skyline Hotel,and in Montreal at ('Hotel Quatre Saison.

Franchises are also available in Van-couver and Ottawa, interested partiesshould phone Keith Tomlinson at (416)677-0184.

Monitor AndInterface Buses

The new Hewlett-Packard Model 10050AAdaptor and a companion 10051A TestProbe are designed to provide a fast andeasy way to look at activity on the Hewlett-Packard Interface Bus (HP-IB/IEEE-488).Used in combination with the HP Model1602A Logic State Analyzer, theseaccessories let the user monitor busoperation at full operating speeds withoutinterfering with bus operation.

The Hewlett-Packard Model 10050AAdapter costs $43.44 in Canada. TheHewlett-Packard Model 10051A HP-IBTest Probe which includes a 10050A is$230. Duty and Taxes extra whereapplicable.

Programming CoursesThe Computer Mart (Toronto) is organiz-ing a series of Programming classes. Ini-tially, the following courses will be held:

Introduction to Microprocessors (April10), $135.

Programming the 8080 (Mar. 21),$179.

Programming the Z80 (April 11), $179.Introduction to the BASIC Language

(no details available).These courses will be held on week-

day evenings. Each course runs forthree weeks, two lessons each week onTuesday and Thursdays (except Intro-

duction to Microprocessors). Indicateddates are the actual start dates for onecourse. The fees include the necessarytext books, supplies and the cost of'hands on' computer time where applica-ble.

The lecturer for these courses is AndyJohnson -Laird. Andy has fifteen years ofprogramming, systems analysis andteaching experience.

The courses will be held at the HolidayInn at the Don,Valley Parkway and Eglin-ton Avenue. More details from ComputerMart Ltd, 1543 Bayview Ave, Toronto,Ont., M1K 4K4.

Zentronics DataProductsNewly -formed Zentronics Data ProductsDivislon will incorporate the Data Pro-ducts Group of Nedco Ltd. to coordinatethe marketing and distribution of a full lineof data products including those of LearSiegler, Teletype and Extel and the mic-roprocessor systems produced by sev-eral leading manufacturers.

The headquarters of Zentronics DataProducts will be at 99 Norfinch Drive,Downsview, Ontario. Other locationsinclude Montreal and Ottawa, and afourth will open shortly in Vancouver. Formore information call (416) 635-2822.

MicrocomputerExpositionThe International Microcomputer Exposi-tion will be held in the Dallas ConventionCenter, Sept. 29 through Oct. 1. "Co-sponsored by several groups, includingthe American Association of Microp-rocessors, the exposition will be directedtoward all levels of technology." (That'swhat the Press Release says: things havereally advanced when microprocessorsare so smart they can form their ownassociation and hold an expo for all theother technologies. Ed.)

Further details from Beverly Tanner,214-271-9311.

ETI CANADA - APRIL 19787

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Service Depots from coast to coast: Halifax: 902-429-0260 - Quebec City: 418-681-4639 - Montreal:514-342-2043 - Ottawa:613-829-9295 - Toronto, West: 416-781-5201 - Toronto, Central: 416-489-2022 - Toronto, East: 416-438-9822 - Hamilton :416-547-4914 - London: 519-686-9671 - Sudbury: 705-560-4866 - Winnipeg: 204-774-1931 - Regina: 305-543-0466 - Saskatoon:306-244-2299 - Calgary: 403-452-8491 - Vancouver: 604-434-6647.

SerrwlczaarYczServiceBINDERS

In response to many requests from ourreaders we have arranged for binders to bemade so that you can keep ETI's firstCanadian volume together and protectedfrom damage The binders ore covered inattractive leather -look black plastic andare designed to hold twelve issues. The ETIdesign is printed in gold letters on thespine

The binders cost $5.00 each, which includes postage and packaging. Do not send cash - you can pay by cheque. Mastercharge. or ChargesCredit card orders must include your account number, the expiry date. and your signature In all cases allow six weeks for delivery

Send your order to ETI Binders. Unit 6. 25 Overlea Blvd.. Toronto. Ontario M4H 181. Don't forget to include your name and addressOntario residents add 7% PST


ONE GREAT THING about writing acolumn is that the first one is theeasiest. At least, that's what everyonetells me. Seems that you don't haveto write about anything in particular.It doesn't even have to be relevent tothe subject with which it normallydeals. Talk about what a greatmagazine you have, what a nice guythe editor is, and of course, theunusually perceptive readers.

Following along those lines, Imight tell of the day early in January,when Steve asked me how I feltabout doing a regular department onAudio. Being a man of humble mein,all I could say was, "Aw, shucks,fellas" And then I'd start off thiscolumn by telling you how this isyour column, the readers', and whatyou say goes and all that.

But I'm not a humble kind ofperson, I'm arrogant, opinionated,stubborn, argumentive, impatient,and I like the sound of my ownvoice. And this column is not thereaders', it's mine. It's mine toinclude what I deem suitable. But itis for the readers, a means ofexchanging ideas, informationviewpoints, so that I may teach you,you may teach me, and also teacheach other. Anyone who doesn't likewhat appears in these pages isinvited to move on, with no hardfeelings.

This is not to say that I don't care.I do. But even more, I care aboutaudio, and how to use its marvelousmagical technology. Of specialconcern is the need to establishstandards of excellence, and toencourage the application ofrigourous critical standards inexamining new techniques, andequipment, to distinguish real

Audio Today

AudioTodayWally Parsons, ETI's Contributing Audio Editor, introduces thisnew column.

technological achievement from hypeand faddism. You won't find any "geewhiz" reporting in these pages, butyou will find praise for worthwhileand interesting ideas and products.Or acid.

As for "unbiased", forget it; there'sno such thing, and any reporter orcommentator who claims to be iseither a liar or a fool. Or both. Butthe biases will be obvious.

Readers' letters are more thanwelcome, indeed they are the life-blood of such a column. They tell mewhat concerns you, and form thebasis for real dialogue. And youdon't have to agree with me anytime; audio is such a marvellousblend of hard technology, aesthetics,and fashion , with so many built-incontradictions, that you can't castmoulds. Readers should also beadvised that politically I'm a ;eft -wingnationalist with a certain Messiahnistzeal to promote a real Canadianaudio industry. Without it theama:Jurs and hobbyists are justplay-acting. Therefore, I hope to be:ible to devote a great deal of.attention to Canadian developmentsand products

Yes, products, because productreviews will also be part of this

department but not the sort ofreviews you may be accustomed to.For one thing, these kind of testresults are available elsewhere.Rather, more emphasis will be placedon the concepts embodied in newproducts and, in some cases,extended listening and in -useevaluation. This means that productswill receive less than rave reviews,from time to time, but every attemptwill be made to be fair. It's a different

approach, and one which we hopewill be well received by our readers.It is my hope that Canadianadvertisers will quickly realize thevalue of product reviews which arenot only honest, but appear to behonest. Some reviewers seementhusiastic about everything, soeventually the reader believesnothing he reads. I don't want that tohappen here.

Record reviews are out. Obviously,if a recording illustrates someparticular aspect of audio and isrelevent, it will be discussed, butonly on the technical level. Anobvious example would be a direct -to -disc recording, while discussingsuch techniques. My feeling is thatETI's readers are reading thesepages for technical material. If theywant record reviews they will do as Ido, subscribe to publications whichspecialize in that sort of thing. Toomany audio magazines are reallyrecord magazines, and I don't thinkwe need another one. ETI isn'tsupported by tax money, unlikesome music publications, so we haveto make it by writing for our readers.

Letters may or may not bepublished at the discretion of myselfand other staff, unless the writerspecifically requests that they not be,and are subject to editing. Againunless you request that it be with-held, publishing the writer's initialsand home town will be a matter ofdiscretion and common sense (wehope). By the way, if you want apersonal reply, please enclose astamped self-addressed envelope.Answers will be as prompt as ourhectic schedule allows. Anyway, onwith show.


AUDIO HARDWAREBack in the early '50s, a gentleman

named Bachman, having pioneeredwork on the modern magnetic pickup,set about developing an appropriatearm. This was subsequently manufac-tured by Gray Research and Develop-ment Co as their Model 108 and was tobe found in almost every broadcastinstallation up until the '60s. One of itsmost novel features was the use of aunipivot suspension with integral fluiddamping. I was rather proud at the timeof being able to fast -cue with it bythrowing it above the record surfaceand have it gently lower itself right ontothe starting groove. But even moreimportant is the fact that that arm andits damping system was a major factorin the General Electric pickup's finereputation among professionals, butnot with audiophiles. Proper dampingenabled it to deliver its full potential.The technique fell into disuse over theyears, and I suspect that one of thereasons was the inability of manypeople who should have known betterto distinguish between damping andfriction drag.

DAMPINGBut damping has attracted some

attention recently, largely as a result ofrecords cut with excessive modulationlevels and pickups with excessivecompliances. In re -discovering thewheel, engineers have learned what weall knew way back: that pickupcompliance and arm mass combine toproduce resonance, that resonanceproduces a response peak at recordwarp frequencies and makes thesystem sensitive to external shock.Given the realization that a resonancecondition is undesireable, and that anycompliance/mass combination has anatural resonance, but that its effectscan be virtually eliminated by properdamping, it naturally follows that anyundamped arm/pickup combination isimproperly designed. Further, sincepickup and arm form a system, it is notpossible to design one properly inisolation from the other. The fact thatmost pickup manufacturers do notmanufacture arms, and most armmanufacturers do not equip their armswith pickups, therefore, speaks foritself. It is worth noting, then, that oneof the very best pickups in the world,the Decca, really shows its stuff when

used in the (damped) Decca arm, yet isoften disappointing when used in otherways.

DISC TRAKERA few manufacturers are catching

on, though, and are scrambling toredesign their products along morerational lines, but there is still a vastarea, particularly with regard toautomatic, and semi -automatic singleplay turntables where some means ofadding on appropriate damping wouldseem to be in order. One such device ismanufactured by the Discwashergroup under the name of "DiscTraker". It's a little gadget which isattached to the arm and has a partwhich rides on the record surface andanother rigidly fixed to the arm. Thefixed piece fits into the other as apiston and is said to provide pneumaticdamping. In other words, it's what usedto be called a dash pot. There's no wayit will attach to my arm, but reports asto its effectiveness have been mixed.For example, it was tried on a Deccaarm and pickup with results whichcould only be described as terrible, yetwith a Formula 4 arm it turned analready excellent moving coil pickupinto a spectacular performer.

DiscTraker

I must confess to somewhat mixedfeelings on this whole idea. It looksgreat, but . . .1 A 14 -page booklet putout by the manufacturer goes intoconsiderable detail on the subject ofdamping, but the absence of electricalequivalent models results in severalstatements having to be taken onfaith, including some very question-able analogies with automotive shockabsorbers. It deals with other systemsof damping, but dismisses them incavalier fashion without substantiatingits objections. For example, the claimthat oil pivot damping increasessensitivity to external shock runs quitecontrary to experience, especiallybroadcasting studios where it's notunusual for inexpert and/or non-technical help to kick turntableconsoles, stomp the floor andotherwise deliberately or inadvertentlytry to bounce the pickup around. As foraccoustical feedback, I've run controlroom monitors, in the past, at levelswhich would make a disco habitueblanche. But you wouldn't hear theeffect of any of these things at home.

Or the claim that dynamic dampingis very delicate to adjust andunsuitable where the audiophileselects his own arm and pickup. Well, itjust happens that for the past year I've

a) The DiscTraker tone arm damping device.

DiscTraker


Audio Today

been using a dynamic damping systemwhich adjusted so easily, and soeffective that I'm considering lookingfor financing in order to market it.

However, this device does seem tooffer a reasonable alternative to buyinganother, properly designed, arm,especially if you have an integratedarm/turntable. I have serious reser-vations as to its effectiveness indamping most resonances, and I verymuch doubt that it is effective on lateralresonances and the other kind oftorsional, and secondary resonances,including the "collison effect' whichJoseph Grado describes. However, itshould be quite effective in controllingthe wild overloads which result fromrecord warp. These warps tax theelasticity of stylus suspensions, causewild fluctuations in tracking force;drive armatures into non -linearity,overload amplifiers and send woofercones into mad paroxysms of flutter.

I would suggest, however, thatbefore you run out and buy one youread the Disc Traker brochure, thenfind a dealer able to demonstrate it onthe same arm and pickup you now use,preferable with a speaker withextended low end response, butsubject to woofer flutter, and a lowdamping amplifier such as a tube unit.Listen carefully both before and after,and watch the woofer. And bring yourown record. At $45.00 list I think youought to be sure it will work on yourset-up. If it does, it's a good buy. Alsoget a static neutralizer; you'll need it.

THE SME APPROACHA different approach is taken by

SME, with the FD200 add-on unit forthe Model 3009 Mk II, and which is anintegral part of the Mark III. It consistsof a little paddle mounted to the arm,and a trough attached to the base, andfilled with a fluid. The paddle rides inthe trough and the fluid damps armmovement caused by resonances, butdoes not interfere with normalmovement of the arm as it tracksinward. The intriguing thing about thislittle gadget is that it seems to be aprettified version of a techniquepopular with amateurs for many yearsand written up on several occasions.Either they've been reading our mail orwon't let pedigree stand in the way of agood idea. The technique is parti-cularly useful on arms using needle orknife bearings, because, in one fellswoop it bypasses the problem of

limited surface area and fluidmigration. An additional plus which noone seems to have considered, is thatthe device could probably be adaptedto other arms including someautomatic changers. Obviously, theexperimenter is on his own, and it willcost $43.00 to find out.

If you have an SME Mk II it will notupgrade it to a Mk III, which is a newdesign in several respects, but it willcorrect the one serious fault in what isotherwise an excellent arm.

Pickup arm damping is a sufficientlyinvolved subject as to require an articleby itself. As it is I've devoted enoughtime to it tc crowd out Stanton's newstylus configuration which I've beenusing for the past few months, so it willhave to wait.DiscTraker is distributed by H. RoyGray Ltd., 14 Laidlaw Blvd., Markham,Ontario L3P 1W7.SME is distributed by A.C. Simmonds& Sons Ltd., 975 Dillingham Rd.,Pickering, Ontario L1W 3B2.

AUDIO CLUB NEWS

The Toronto Chapter of the AUDIOENGINEERING SOCIETY held itsJanuary meeting at George BrownCollege, and was addressed by LennoxBlizzard, who teaches the acousticscourse at George Brown College.Techniques of measuring variousaccoustical materials were demon-strated. This is an area in which manyaudiophiles are ill-informed, and findinformation hard to come by. TheSociety's membership is open toapplicants on several levels, fromStudent, to Fellow, and with variousdegrees of expertise. Readers in-terested may contact me directly atETI.

If you belong to an audio club or areinterested in forming one, I'd like tohear about it and so would manyothers. Please write to me at ETI.

b) A close-up of the SME FD200 fluid damper.


Audio Today

50/100 Output

Dear ETI:In your Apr/77 issue, I have come across a

problem in the 50/100 Amp. In theschematic on page 26, it shows only oneoutput. I am not sure where the other outputshould be connected to, directly to the input(the lower lead) or to OV. Please help me.

Also, when are you going to publish plansfor a suitable pre -amp for this amp. I

presume that the pre -amp will have volumecontrol, loudness control, high and lowfilters and bass and treble controls. I hopethis is possible.

M.W. Winnipeg

The amp is really a bridge circuit in whicheach power supply and each output deviceforms one of the legs, the output beingtaken between the two power supplyjunctions and the output devices junction.Strictly speaking, it doesn't matter which ofthe four junctions is grounded, or even ifnone is grounded. In this circuit, though,the "OV" point may be connected toground, thus allowing the return side of thespeaker to be grounded. In addition, sinceany preamp is likely to have a groundedreturn, the "Input Comm." terminal shouldalso be grounded, preferably at the inputterminal itself. A word of caution: since thisproject does not include chassis, etc., watchyour grounding system carefully to avoidinstability. Especially avoid stringingchassis grounds any old places whichhappen to be convenient. In general, keepinputs and outputs well apart, and be readyto experiment. And DO follow the setupalignment carefully.

A pre -amp project is a good idea, onewhich I'm considering tackling myself,sometime this year. Several good ideasappear in ETI Circuits No. 1 which youmight find useful. In addition, our firstCanadian Projects Book contains details ofaudio modules ( plus the 50/100W Amp forthose who missed it) which may becombined to suit your desires.

Tube Tale

Dear Sirs:I have purchased lately some old tube

amps. They are brand names, and I amabout to rebuild and use them.

Even after using them for hours, they.sound O.K., though the highs are not crispand they are boomy at the low end.

The tubes passed the test. There is noaudible hum or distortion. I tested out thepower amp with a 1000Hz signal andobserved the wave form at the speakerterminals (on both channels) on the scope.The lower part is a bit smaller and thinnerthan the upper one. What does it mean? I did

some research, and learned that the newtube amps are built of low noise tubes, metalfilm resistors and polyester and silveredmica capacitors.

The amps I own utilized 10-20% resistorsand capacitors. If I change them to theabove quality what results can I get?

Are there any low -noise 12AX7 s and61305s on the market?

Since the output transformers arerelatively small, by changing them withbigger and slightly more powerful qualitytransformers, would the overall per-formance be better?

I would appreciate all the advice I can get.

Mr. C.J., Toronto

I mentioned in an article in ETI ("V-FETSFor Everyone", Oct/77) that only a

perfectionist, masochist, or a nut like mewould get involved with tube amplifiers.Nice to know I have company. Welcome tothe club.

To begin with, any comments I mightmake are limited by the fact that you supplyno circuits, or make and model number, so Imust speculate on the circuitry used. It'sdifficult to comment on the sound qualitywithout knowing something about yourspeakers and other equipment. My owntube amps have a bright, clean, detailedhigh end, but not the rough edge oftencalled crisp. As for the boom, this is really afault of the speakers. Most speakers soldtoday exhibit poor impedance/frequencycharacteristics, the most noticeable faultbeing a pronounced impedance rise at thebass resonant frequency. Since efficiencyrises at resonance, output also rises (See"Equalization", ETI March 78). Also sincethis corresponds to a condition of poordamping, there is a lot of hangover,resulting in a boomy sound. Most designersget away with this by counting on the highdamping factor of transistor amplifiers toeliminate the peak and the hangover. Thismay be bad design but it is the way thingsare done. Generally tube amplifiers willexhibit damping factors of less than 20, asagainst upto 1000 fora big super -amp. Also,high effective damping factors are difficultto achieve with low power designs. Becauseof the phase compensating circuits usedeven the full damping may not be availableat very low frequencies because thefeedback rolls off from as high a point as 100Hz. Your first instinct, then, would seem atfirst to be a good one: improve the lowfrequency response wtih a large trans-former. While you're at it replace thecoupling capacitors with larger value units.This will give better low frequency responseand damping. It will probably also cause theamplifier to break into violent oscillation. Atboth audio extremes. Chances are this is afairly simple circuit with two pentode outputtubes driven by a paraphase phase splitter,and RC coupling. Such a circuit has adifferent number of phase shifts on each

half of the circuit, making stability aproblem. There is obviously no room here todeal with this aspect properly, and in factI'm in the process of preparing an article onfeedback and I hope to cover tube circuitsand their special problems. But as you cansee, unless you have a lot of knowledge offeedback circuits you're asking for trouble ifyou play with it, especially if themanufacturer played some fancy tricks withphase margin.

I wouldn't pay much attention to the tubetests. The best test here is to substitute newtubes and see what happens. Use Europeanor U.S. tubes wherever possible, notJapanese. The low noise version of the12AX7 is a 12AX7A/7025, and its Europeancounterpart (very quiet) is the ECC83. The6.9Q5 is a beam power tube and would nothave a low noise equivalent. However if youdon't mind paying a premium price youmight try 7199A, an industrial tube availablefrom such places as Electro-Sonic, Saynor,etc.

As for your proposed changes in resistorsand capacitors, I don't know about you, butif I did it, along with the premium tubes, themost likely result would be a letter from mybank, specifically the guy who doesn't likeoverdrawn accounts. In a well -designed,sophisticated circuit they can make all thefancy circuitry meaningful, especially whendealing with direct -coupled circuits, cross -coupled phase splitters, differentialamplifiers and push-pull drivers, andbalanced primaries. Otherwise it isn'tworth it.

Theasymmetry of amplitude and shape inthe scope trace you sent suggest high levelsof odd and even harmonic distortion and I'msurprised you can't hear it. I hope this helps.

His Master's VoiceSir:

In ETI Nov/77 issue, an article by WallyParsons (The First Century) made mentionof a poster of Nipper, and the machine hemade famous.

I was wondering if you could suggestwhere I could get one of these posters (incolour if possible), for my music room.

Thank you.R.G.H., Calgary, Alta.

I didn't check at the time of the show, but aclose look at my original colour slidessuggest that this was not a new poster butan early copy of the original. In any caseRCA informs me that they have not madeposters generally available.

However, if you would write to thefollowing address they might be able tohelp: Public Relations, RCA Ltd., 21001 N.Service Rd., Trans Canada Highway, Ste.Anne de Bellevue, P.Q.

Also, the inside liner of "The Worst ofJefferson Airplane" (RCA LSP 4459) has alarge reproduction.


Audio Today Letters

And, if all else fails, I have severalphotographs of a large stuffed "Snoopy" infront of one of my 6 -foot high TransmissionLines. Looks pretty happy, too.

Organ KeyboardsDear Sirs.

I enjoy your publication very much. I hopeyou can help me. I am interested in buildingan electronic piano or organ. Do you know ifthere are any companies in Canada whocarry keyboards or plans, or kits for theseprojects? I have ordered plans fromEngland (Maplin), however I would verymuch like to spend my money in Canada.

Thank you.

Ralph Sperry, 11112-134 Ave., EdmontonAlta. T5E 1 K4P.S. Besides Heathkit

Amateur organ building is almost a sub-culture in itself, and the or,ly person I knowwho is involved in it could not come up witha single Canadian manufacturer. If therewere any recently, they may have followedthe Prime Minister's advice and left thecountry.

One U.S. source is: Devtronix OrganProducts, 5872 Amapola Dr., San Jose, CA95129.

There are organ building clubs inexistence, and contacting one of themmight help. Keep your eyes on our ClubNews section; as soon as we hear from sucha group it will be included.

I am publishing your address so that anyreaders who wish to help may contact you.

This would also be a good time to remindpotential advertisers that Mr. Sperry isundoubtedly not the only organ buff amongETI readers.

Spring QuestDear ETI:

I am interested in reverb and echo units. Iwas wondering if you will be putting anyprojects related to these areas in any of yourfuture issues. What I am looking for is amethod of producing reverb or echo effects.A circuit with component values could begreatly used.

A few companies have advertised springswhich, when a signal is passed throughthem, produce a reverb effect. However, thesprings seem to be in short supply as all myefforts to obtain one have been un-successful. The suppliers have either nothad the springs in stock or they have beendiscontinued. If you might possibly be ableto refer me to a supplier who might havethese springs in stock I would greatlyappreciate it.

D.A., Stettler, Alta

Every supplier I know informs me that.they are unavailable. Conjecture is that no

one is making them any more. This strikesme as a likely explanation. The springreverb system has usually been a method ofaccomplishing on the cheap what wouldordinarily cost thousands of dollars instudio equipment (At CBC in the early daysof television we saved even more by usingexisting facilities - one of the ladies'washrooms. Sometimes got some interes-ting sound effects too!). The first one I everbuilt was plagued by the production ofgong -like tones due to poor control ofresonance damping. but even after solvingthese problems, it's not a satisfactorytechnique unless you spend thousands ofdollars in refining it as AKG did with theirunit.

The preferred approach today is tointroduce delay digitally using a BucketBrigade Device (BBD). A project using thistechnique is 'o be found in this issue.

Another approach is the Madsen tube, along hollow tube, coiled up and carefullydamped, with an input transducer at oneend, and a pickup critically located along itslength. If taping early Toscanini 78's is yourforte, you might like this, but it's tricky.

AUDIOTODAY

Audio Today is ETI's newregular section dealing withnews and views on topicsranging from loudspeakerdesign to audio circuits, fromauditory perception to con-certhall acoustics, frommicrophone techniques todesigning domestic listeningrooms.

If you want to express yourviews or report on news writeto Audio Today, ETI Mag-azine, Unit Six, 25 OverleaBlvd, Toronto, Ont. M4H 1 B1.

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Radio Shack TRS-80In the February 1978 issue of ETI we reviewed Commodore's PET system,and we were quite impressed. Radio Shack's TRS 80 aims at a similarmarket. Mark Czerwinski and Graham Wideman investigate.


WE ARE STILL not quite sure whosemachine was "pre -hinted" first but theway we heard it, Radio Shack'spreliminary announcement about theTRS 80 followed very closely the firstwords from Commodore on their PET.Is one machine a reaction to the other,or did both companies see the samemarket area opening up indepen-dently? We don't know. One thing isclear however, the two products arevastly different.

THE MARKETThere must be alot of people whocould be made interested in homecomputing so long as no tinkering wasinvolved. In addition, they are lookingfor convenience of operation, payinglittle attention to what is inside the box,but rather are concerned with what itcan do.

What then are the characteristics of amachine that will fulfil their needs? Itwould need to be elementary to puttogether, include keyboard and videomonitor, have built in easy -to -useprogramming language (such asBASIC) and the facility for long termstorage of programs. It would alsoneed to be inexpensive.

Both the PET and TRS 80 aredesigned on these lines, and it isparticularly the built in BASIC that setsthem apart from most other homecomputing systems.

WHAT YOU GET WITHTHE TRS 80

You can buy the package in thevarious separate units, or as acomplete system. Let's suppose youbuy the whole lot - what does itinclude? Out of the big box comes themain keyboard unit which contains the"brains" of the machine. Next there's aRadio Shack cassette recorder forstoring data and programs over a longperiod. The biggest unit is the 12"video monitor included in the system.To complete the system there's aseparate power supply to run theelectronics.

In addition a comprehensive instruc-tion manual, cassettes, and cablescome with the set.

THE FIRST RUNInitial set-up is quite easy - simply

put all four units on the same table,grab the cables and plug them alltogether. Three five -pin DIN plugs go

Removal of cover exposes sloping PCBs.

in the back of the keyboard, and theycan be interchanged - but this doesnot appear to cause much damage.The sockets are labelled so this shouldavoid trouble. Plugging into thecassette recorder is less obvious sincetwo of the plugs can be interchanged,with no labelling other than beingdifferent colours. Finally, you will haveto run out and buy an "octopus"adapter, since there are three powercords to plug in.

This sounds like a total of manycables running all about. It is.

Now you're ready to go, so on withthe two power switches. Your friendsare all standing around some eager toplay with your new toy, some skepticalof computers, as the screen springs tolife with a "READY". Now what? Ifyou're a neophyte programmer you aregoing to have to reach for theprogramming manual.

We had very mixed feelings aboutthis 233 page book. It is written in avery friendly, "let's get to know yourcomputer" style as it takes the readerexcruciatingly slowly through everynook and cranny of BASIC LEVEL 1.

The manual assumes you knownothing of computers or mathematics- which could get somewhatfrustrating.

If you do have some experience youcould probably skip straight to 232 -"Summary of Level 1 BASIC," and notmiss too much. Refer to the contents tofind any section you're not clear on,such as graphics etc.

Tape I/O Video PowerOutput

Cassette ......Section

Video .... ................. ...Section

Overview of the main computer board.


Radio Shack TRS-80

In fact, what you'll most likely wantto do is discover that CLOAD is themagic word for loading one of thecassette programs included with theset - such as Black Jack orBackgammon. Having thus won overyour friends you can sit back andlearn BASIC later.

Let's take a look at the hardware andsoftware in more detail.

HARDWARELooking at the total system, there are

advantages and disadvantages tohaving four separate units. The main"pro" is the flexibility of being able tomove the keyboard, video monitor andcassette recorder to suit yourconvenience. On the other hand,having such a multitude of cables andunits lying about is a nuisance. A farnicer approach, in our opinion, wouldhave been to combine the cassettedeck and power supply in the keyboardbox, reducing the packages to two. Wesuspect that the lack of integration wasdue to a rush effort in getting the TRS80 on to the market, an impressionsupported by various other details.

PowerSupply

5 x 2102's forscreen memory

KEYBOARD UNITThe keyboard itself is typical of that

used with most hobby computers,fairly reasonable quality and opera-tion. Also contained in this case is themain computer board. On this boardare found a Z80 processor, 4K of ROM(BASIC Interpreter etc., see "SOFT-WARE"), 4K of dynamic RAM (the Z80does automatic refresh), and inter-faces for keyboard, cassette and videomonitor. On board regulation of thepower supply is used.

We don't feel that this system wouldbe much fun for hardware enthusiasts.It's difficult to manage when takenapart, the keyboard and main boardare attached by an easy to break

flexible cable with no plug. No I/Oports are on board, which rules outsimple add-ons, such as switching

PowerTransistor

723 VoltageRegulator

4K BytesROM, contains (may be replaced

by Level II)BASIC Level I

8 x 4K DynamicRAMS

devices on and off, hooking up aspeaker, and other popular experi-ments and applications. The backconnector brings out the address, dataand control buses. Thus a separate boxwith interface adapter could be added.Also on this connector are thekeyboard lines, which would pre-sumably facilitate adding morekey Doards (possible numeric pad) inparallel with the existing one. Thekeyooard interface is done not with aPeripheral Interface chip as might beexpected, but with ordinary buffersand latches, a cheap but less flexiblesystem.

To summarize, this product does notappear to be aimed at the serioushardware person. Add-ons are dif-ficult, although Radio Shack is comingout with an I/O unit. In addition, an S-100 interface is in the works, accordingto Radio Shack literature. The TRS-80must then be best suited to softwaretype, keyboard plus video (and later ona printer) applications. The suggestedretail price of the keyboard and gutsunit plus power supply is $575.95Canadian. The system includingcassette and monitor is available for$879.95.

BusConnector

(may bereplaced by16K RAMs)

Reset"Switch

Z80 MPU


Radio Shack TRS-80

Opening the flap on the back of the keyboardprovides access to the expansion connector andreset button.

CASSETTE STORAGEData may be recorded on cassettes

by means of the built in cassetteinterface which converts the data to aseries of audio tones. Thus, anyreasonable quality cassette recorderwill do the trick. In fact, even our $15special managed the task, if a littleunreliably. The cassette itself shouldalso be fairly good since any tape"drop -outs" mean lost data. RadioShack plans to introduce high qualityfive minute -per -side cassettes for thispurpose.

The particular recorder recom-mended for this system, the CTR-41 isone of Radio Shacks better models at$69.95. Cables from the keyboardconnect to the "AUX" input, "EAR"output, and also the remote on/offjack. Thus, when recording or playingcassettes, the operator (you) pushesthe desired keys on the recorder andthe TRS-80 switches the recorder onand off at appropriate times. You alsoneed to set the volume level whenplaying back tapes. When recording, adummy plastic plug must be stuck inthe MIC jack to deactivate the built-incondenser microphone. Altogether abit messy, but it works.

VIDEO DISPLAYDescribed as "designed especially

for the TRS-80" this monitor displaysthe 16 lines of 64 characters, or 128 by48 dot graphics, with reasonablequality on a 12 inch CRT . . . at$299.95!

Opening up the box to discover whatyou get at that price - inside there'sthe equivalent of a portable TV set,minus tuner, IF, sound section andspeaker. The circuitry is AC -DC, whichis very inexpensive to produce, butrequires some kind of isolationbetween the monitor circuitry and thevideo output from the keyboard. Toachieve this, an opto isolator circuit isincluded.

Should you happen to be part of the99% of the population who like to savemoney - here's how. First, wemeasured the video output signal, it's afairly popular arrangement with OV forsync level, 0.6V for black and 2V forwhite, into 75 ohms. Then you can referto our January 78 issue to see how tomodify your TV to accept video signalinput.

Alternatively, you could get hold ofan RF modulator (less than $20) anduse your TV without any modifications.

Finally, take a look at our pictures tosee what you're getting inside that$299.95 monitor.

POWER SUPPLYA Radio Shack brochure describes

this unit as follows: "Important to anycomputer is a reliable source of pureDC power. This regulated supplyconverts standard 120VAC housecurrent into the stable direct currentrequired." This appears beside apicture of the TRS 80 system with eachunit labelled, including the PowerSupply.

In actual fact, the Power Supply unitoutput is 17V AC. (Regulation is doneon the main board) This kind of

Here's the "Non-Maskable Hardware MicrophoneInterrupt Unit"

NMHMIU shown in place.

4:arsh. It*The upright board pictured here is theopto-isolator module, (Isolator in themini -DIP)

We thought point-to-point wiring was out of date,but point -to -mid-air? This hanging resistorconnects to the CRT in the $299.95 video monitor.

Another example of sloppy construction in thevideo monitor, tie strip off at an angle and onlyrivetted at one end. We hope the monitorinternals will be cleaned up a bit.


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misleading advertising serves only toconfuse the public and increase theirdistrust of electronics and probablydoesn't do Radio Shack any goodeither.

FUTURE HARDWAREThe first expansion of a TRS 80 that

is possible is the replacement of the 4KRAM chips with 16K chips ($399.95)(no kidding, it's that easy) andreplacement of the 4K ROM, with theLevel II BASIC kit contained in 12KROM ($159.95 - see "LEVEL II"). Wehave advanced details on a variety ofother add-ons as well.

The key to further expansion is the"Expansion Interface" unit, whichcomes in its own TRS-80 style plasticbox designed to sit under thekeyboard. At $399.95 this unit enablesyou to add more additional RAM (16 or32K), dual cassettes, four mini floppydisks and a line printer. It includes aclock, and space for an extra PCB. Andguess what, it has a separate powersupply, but it has a slot in the back inwhich to place the power supply, andalso the original TRS-80 power supply.The interface requires BASIC Level II.

The Mini Disk unit stores up to 96Kbytes, comes with operating system,and for $799.95 gives you an accesstime for any single byte of less than halfa second.

Two printers are to be available. The"Line Printer" is a modified Centronicsdot matrix impact printer capable of upto 110 characters per second and 80 or132 characters per line, at $1,899.95.Level II and the interface box arerequired. On the other hand a "ScreenPrinter" can be obtained for $899.95,which according to Radio Shackliterature will at the touch of a buttonreproduce your screen (includinggraphics) on 51/2" electrostatic paper ata rate of 2,200 characters per second!

SOFTWAREAs a home computer system, the

TRS 80 is probably the least hardwareoriented. There are two points whichsupport his thinking: you can't get atthe internal hardware without voidingthe warranty and there is no hardwareinterface capability other than to thedisplay and the cassette recorder.

So how would you go aboutevaluating a relatively complexproduct like this? Probably in the sameway as you'd evaluate another type ofproduct which enjoys a high profile atRadio Shack Stores: a home stereosystem.

In choosing a computer system, thepotential customer will be influencedby what he sees (ie: packaging) and bywhat he can be led to believe about it(by advertising, by friends, by usingthe system, and even by readingelectronics magazines). That cus-tomer's attention will be focused on thekeyboard and display not on theinternals. It won't matter to him that aZ-80 incorporates efficient machinelanguage instructions for data search-ing and moving or that it's a

microprocessor that can run at a 2MHzclock rate. He will be more interested inwhat it can do as opposed to how itdoes it (he's buying capability, fun andperhaps even status, not speed).

A LOOK AT WHAT YOU GETON THE SOFT SIDE

The TRS 80 comes with "RadioShack Level 1 BASIC" in 4K ROM.Level I claims to support "stancardBASIC statements". But whosestandard? It seems to be Radio Shack'ssince some important capabilities aremissing (for example: exponentiationand array dimensioning). All calcula-tions are performed in floating pointwith 5 or 6 decimal place accuracy.Twenty-six numeric variables areavailable (A to Z) along with onenumeric array variable. Two 16 -

character string variables can also beused. Actually, these are moreproperly called "string things", sincethey cannot be compared, manipjla-ted, indexed or used in any but themost mundane ways. You can inputand output using them, but that's allfolks.

Cassettes can be used to handleprograms (CSAVE and CLOADcommands) or data (PRINT # andINPUT # statements). Since whatever

you have in memory will be wiped out ifyou cut off the power (intentionally orotherwise), having a cassette recorderto store your information permanentlyis invaluable. And it makes entering ofother people's programs (such as theBackgammon and Blackjack gamessupplied by Radio Shack) especiallyconvenient.

Speaking of which, the Backgammongame makes extensive use of the TRS80's rather limited graphics capability:there are virtually no special graphicscharacters - you've got to constructwhatever image you have in mind byturning on some points on the display(48 points vertically by 128 pointshorizontal). This can be tedious. Mindyou, in the low cost home computersystem field this is not unusual. Tocompensate you can write sub-programs which draw vertical andhorizontal lines, draw patterns, fillthem in etc.

YOU AND YOUR PROGRAMImmediately after powering up your

display and keyboard, the followingwill appear:

READYAt this point you can:1) do simple calculator type computa-tions (immediate execution)2) bring in a program from tape.3) type NEW and enter a program

Program statements are precededby line numbers to distinguish themfrom immediate execution statements,and keep them in order. A LISTcommand is available to display theprogram. Unfortunately the cursorcontrol keys cannot be used to edit thisdisplay, so if you want to change a linein a program, you must retype theentire line.

1 1 f. TEXT MIME IRS -38 WKS LIKE THIS. EMI MtnIS A FIVE EY SEVER DU HATRIX. THE COMTE SET LOX

LIKE THIS:

-; I Ialt$W vafmr

SIM INS OF SIXTY40UR MORS ME AVAILABLE._

This is the TRS-80 character set,


Radio Shack TRS-80

11

11

11

11

1=R011 DICE, 2-4EDRAW BOARD, 3=HEM ENV_

II

11

II

It

11

II

23 22 21 28 19 18 17 16

2 3 4 5 6 7 8 9

15 14 13

18 11 12

Here's the TRS-80 version of Backgammon.

WITH A BIT OFPLAYING ABOUT WEDISCOVERED THESE BIGLETTERS, ABOUT TWICEREGULAR SIZE.

We did it again wonder where those bigletters came from?

Output which would otherwisestream by while your program isexecuting can be frozen by depressingany key. Unfortunately, if you interruptthe program itself, you cannot modifythe variables it is using and then returnto the point of interruption. So youronly alternative is to rerun the programand in many cases, that's a nuisance.

As for error messages, they areconfined to: WHAT? HOW? or SORRY(along with an indication of where theproblem is). These terse messages arenot unexpected when you considerthat the interpreter was written to fitinto 4K of ROM. In a tradeoff ofreadability against the amount ofprogram code you can fit into thestandard 4K of RAM, Level I has a

"shorthand dialect". For example:G.=GO TO, N.= NEXT, and P. = PRINT.However, REA. seems to be ashortform of dubious value for READ(probably done for consistency).

MAKE IT FITThe overriding philosophy control-

ling the design of this interpreterseems to have been "make it fit". It'shard to believe that a 4K interpreter isanything but "stripped down" afteryou've used this one. Radio Shack hasdropped a few hints about releasing aLevel II BASIC. Until then it is unfair tocompare this software package with,say, the 14K monitor/interpreter thatcomes in Commodore's PET. They'rejust not in the same leagues.

At the same time, it is somewhatunrealistic (no pun intended) for RadioShack to claim, as they have in theirsales literature, that "applications ofthe TRS 80 are limited only by theimagination and ability to writeprograms". Try something quiteunimaginative like sorting a list ofnames. Good luck! You'll need it.

LEVEL IISketchy details are available on

Level II BASIC, an interpreter writtenby Microsoft. From the list ofstatements and functions to beavailable, it appears that this version ofBASIC is at least as powerful as PET'sincluding many editing features. In factwe would go so far as to say that LevelII is the most significant upgrade forthe TRS-80. We wonder how logical itis to sell a home computer with such alimited BASIC and then offer theupgrade as an option. Will this turnpeople off computing, or will most ofthem jump for BASIC II anyway? At thetime of writing it was expected thatLevel II would be available after March'78.

OVERALL IMPRESSIONFirstly, we were not nearly so

impressed with this machine as withthe PET, and for the same price rangewe should have been. Lack ofhardware access, and software whichis primitive, combined to make it a lessattractive product to anybody witheven a little experience in home (or forthat matter any) computers.

In our opinion, to have a satisfactorycomputing machine, one needs the"optional" Level II BASIC. The cost ofthis system would then be $1,039.90($879.95 for TRS-80 plus monitor andcassette recorder plus $159.95 forLevel II). This machine would comparevery favourably on a softwareapplication basis with the 4K PET. Butyou still don't have any hardwareinterface capability, something whichups the system cost to $1,439.85.

The end result is that if you're in themarket for a machine like this youshould look very carefully at what youneed and what you can get for themoney.

Any guesses on where we'll be withsysTems like these 20 years from now?Buy yours now - in 20 years they'll becollectors' items.

ETI CANADA -- APRIL 197821

Fast FourierTransformsYou may have heard of Fourier Analysis, but more often than notexplanations of what this is all about are drowned in mathematics.E.J. Hughson describes how it's done electronically.

MUCH OF ELECTRONICS is con-cerned with the processing of signalsof some sort or another. It is onlynatural then, that a lot of effort hasgone into analysing these signals. Onone hand one must know certain basicthings about the signals in order to beable to build useful circuits. On theother hand, investigating signalproperties with no particular applica-tions in mind, has led to various usefulresults that later helped to simplify,improve or introduce new circuitdesigns. The field of study concerningsignals is known, naturally enough, as"Signal Analysis".

In order to go deeply into some of thetheory in this field, some pretty heavymath must be employed. However, it isquite easy to understand the majorityof the material intuitively, and besides,that's a much more entertainingapproach.

THINK OF A SIGNAL . .

How do most of us think of signals?Probably "signals" conjures up imagesof a scope with a waveform on it. Let'suse this waveform as an example -suppose it's a 1KHz triangle wave.What characteristics does this wave-form have? It is a voltage (say) varyingup and down periodically, thus it hasan "instantaneous amplitude" at eachinstant in time. This is what we see onthe scope, an amplitude versus timegraph. We can also say that thewaveform has a characteristic we callfrequency. Most of us use the termfrequency to mean the basic frequencyof repetition of the entire waveform.Why this distinction? Here's where atheoretical concept must be justaccepted if we're not to get sub-merged in abstraction.

FOURIER ANALYSISIt is convenient to think of a sine

wave as the "purest" waveform, anduse this kind of wave as a basis forstudy of other waveforms. It has beenfound possible to make any other kindof waveform from a combination (sum)of sinusoidal waves of variousfrequencies and amplitudes. This isanalogous to being able to combinethe three basic colours of light, green,red, blue to form other colours.

In fact we have cheated a little bit, weshould correct the above to say thatany kind of waveform can be madefrom combinations of sine and cosinewaves of various frequencies andamplitudes, a cosine wave beingsimply a sine wave but one quarterwave ahead.

Ok, so what? The next step is tointroduce a graph of amplitude versusfrequency. Figure 2 is an example inwhich we plot the "frequency content"of a sine wave of amplitude 1 andfrequency 1KHz. There is only onepoint on the graph, because as we saidbefore, a sine wave is considered to be"pure" or only one frequency.

So how about our triangle wave?What does its frequency content looklike? Figure 3 shows that the frequencycontent is quite complex.

The graph shows that there is a largecontent of the fundamental frequency,with decreasing content of odd orderharmonics.

The process of converting the "time"waveform to the "frequency" graph iscalled the Fourier Transform. Thereverse process is called the InverseFourier Transform.

In the case of a repetitive waveform(such as the triangle wave) the FourierTransform yields a frequency contentgraph which has non -zero points only

Fig. 1. Scope trace showing triangle wave

1kHzFrequency

Fig. 2. Amplitude vs. frequency plot of 1 KHz sinewave

1-

a)

Tn.

E

1kHz 3kHz 5kHz 7kHzFrequency

Fig. 3. Amplitude vs. frequency plot for trianglewave.


Fast Fourier Transforms

at multiples of the fundamentalfrequency. Thus, a series of numbersmay be used rather than a graph torepresent this information. For thetriangle wave, the series is:.81 x (1kHz sine) -.09 x (3kHz sine) +.032 x (5kHz sine) - .017 x (7kHz sine) +

.

Fora 1KHz, +1V square wave the seriesis:1.27x (1kHz sine)+.424 x (3KHz sine)+ .255 x (5 KHz sine) +

On the other hand, you are no doubtalready familiar with frequency plots ofnoise, and particularly audioequipment response curves, which arenothing more than the frequencycontent graphs of the output with "allfrequencies" fed in. (Fig. 4.) Note thatthe frequency plots in this example arecontinuous rather than just the oddpoint here and there.

Input Noise

: . . : . ........ .. . . . . . .

Frequency

Output Spectrum

Frequency

Fig. 4. Noisy amplitude vs. frequency spectra

DOING ITA picture of actually doing the

transform is shown in Fig. 5. The"transformer" could be a person with apiece of paper working out the graphor more usefully a machine doing thework. Suppose a computer was used todo the task on an input waveform, howwould it do it?

AUTOMATICTRANSFORM

If an analog waveform is sampled atregular intervals, we get what is calleda discrete time series - discrete

because it is a series of separate pointsand time series because we havesomething changing with time. Figure6 shows a sampled sine wave displayedon an oscilloscope.

If we were to measure the level ofeach of the points we would get aseries of numbers. If we do thiselectronically using analog -to -digitalconversion we get a series of digitalnumbers representing the discretetime series. OK so far? It is this set ofdigital samples which a FourierTransform (or "Discrete" FT in thiscase) takes and turns into informationdirectly showing the frequency orharmonic content of all signals whichmake up the original time series. Thetechnique shows any componentsfrom DC to half the samplingfrequency. is not possible to obtainany frequencies higher than this sinceit would contradict a fundamental ruleconcerning sampled waveforms,established by Nyquist.)

ADDING NEWFREQUENCIES ANDFILTERING

If the output numbers undergo aninverse DFT we get a series of numbersoutputted represent the originalwaveform.

By taking a waveform and analysingit using a DFT, then performing aninverse DFT on the output we canarrive back at the original waveform. Afilter can be made by performing aninverse DFT only on those numbersrepresenting the frequencies whichare required.

a:

E

Time

Similarly, by adding numbers torepresent new frequencies beforeperforming an inverse transform extrafrequencies will be present in theoutput time series (and after digital -analog conversion, in the outputwaveform).

The DFT does not work on analog orcontinuous information: only on a setof numbers representing theinstantaneous values of a portion of awaveform. The result is a set of num-bers corresponding to the frequencycontent of the waveform. Not only doesDFT give us each frequency present inthe original waveform, it also gives therelative phase and amplitude of eachfrequency component.

By performing a power calculationon the output frequencies a powerspectrum may be obtained. Of coursethe more numbers or samples whichare input to the DFT, the moreinformation is available at the output.However, for a fixed set of numbersinputted, a fixed set of numbers isoutputted.

INTERPRETING THENUMBERS ON THEOUTPUT

To illustrate how outputted numbersare interpreted consider a DFTperformed on a portion of a time seriescontaining 1000 samples. The 1000numbers inputted will have variousarithmetic operations performed onthem and 1000 numbers (known asfrequency cells) will be outputted. Ofthese 1000 cells only the first 500,

FourierTransformer

Fig. 5. The transform process

Fig. 6. Analog sine wave sampled at intervals


representing the frequency range, willhave any real meaning.

For example, suppose all inputnumbers representing samples froman analog -to -digital converter are thesame. (This would mean that a DCvoltage would have had to have beenapplied to the converter.) Of the 1000numbers obtained by the forwardtransform, only the first would have avalue other than zero, since this firstnumber is reserved for the DC contentof the input series and all the energy ofthe input is in form of DC. (See Fig 7a)

Suppose now the output of ananalog -to -digital converter is beingsampled at 1000 samples/sec, alsosuppose a sine wave of 1 Hz is appliedto the input of the converter. Onethousand numerical samples or onesecond's worth of data is collected. Ifthese 1000 numbers are used as theinput of a Fourier Transform, then ofthe 500 numbers output, the first willhave zero value (DC) but the second,reserved for frequency of 1 Hz, willhave maximum value (Fig 7b). Allothers will have zero value also.

If the frequency of the sine waveinputted to the converter is nowincreased to 2 Hz, and the 1000samples at 1000/sec are collected, theFourier Transform processor outputwill consist of zeroes in all 500numbers except the third correspon-ding to 2 Hz (Fig 7c). The outputnumbers, are the cells, cell 0 to cell 499in this case being reserved forfrequencies of 0 (DC) to 499 Hz.Figure 7 gives a graphic representationof these inputs and outputs. (NB, sincethe output cells are numbered startingfrom zero so also are the inputsamples, for clarity.)

CELL NUMBER ANDFREQUENCY

The example given above assumes asampling frequency of one thousandper second so that with a 1000 pointtransformer the cell numbersautomatically correspond to thefrequencies they represent in the inputtime series. It is of course, not alwayspractical to have the samplingfrequency tied to the number ofsamples in the DFT as rigorously asthis. But it is a very simple matterobtain the actual frequency to which acell output corresponds. This isobtained by the following relationship:Frequency correspondingto Cell Number (1st cell = 0)

= Cell No. x Sampling FrequencyNo. of points in FFT

The outputs depicted by Figure 7 areof course idealized. In practice slighterrors will occur due to the finitenumber of bits used in the arithmetic ofthe calculation.

As so far discussed, the DiscreteFourier Transform both forward andreverse has been put in terms ofnumbers which are inputted, thecalculation process and numbersoutputted. The calculation process isvery involved and tedious but could becarried out by a computer or even ahand calculator (if you had the timeand patience). To perform a 1000 pointtransform, it would require over 2million discrete calculations, tediousindeed!

FAST TRANSFORMThe Fast Fourier Transform tech-

nique is able to reduce the calculationsof a similar size transform to about22,000 which is a significant reductionin the number of calculations andhence the amount of computer time.(Still a little much for the averagepocket calculator, however!) Soalthough digital computers can beused to obtain the results of FFTsunder the control of a program, theamount of time needed to load thesamples into the machine, to accessand compute the data and to output theresults makes even a general purposedigital computer an impractical signalanalyser.

-o

aE

-0

E

a)V

E

0 Time 999

1000 Input Samples to a DFT

4991

1000 Input samples to DFT

0 249 11

it

499Lti

1000 Input samples to DFT

999

1999

For this reason, analysers usinghardware capable of only performingFFTs are a far more practicalproposition. Such analysers arecapable of taking an analog wave forminput performing analog -to -digitalconversions on it, sampling accord-ingly, loading the desired number ofsamples into a dedicated FFTcalculator and presenting the results tosome display for presentation. See Fig.8.

The instruments using FFT anal-ysers usually come complete withaccumulators and memories so thatfrequency spectra may be integratedand compared to each other. Integra-ting (or summing) the results ofcontinuously computed FFTs oversome period of time has the effect ofshowing up signals buried in noise. Nomatter how deeply the signal is buriedthe cell or cells which the signaloccupies will eventually build up overall the other cells where the noise willbe randomly distributed. This tech-nique is now used, for example, insubmarine detection where the noisefrom the vessel is discriminated overthe sea noise by continuous integra-tion of FFT results.

Figure 9 illustrates a sampled waveform consisting of 2 sine waves ofequal amplitude and the displayedresults of an FFT performed on a set ofnumerical samples taken from the timeseries. The display has its own

Fig. 7a. Transforming a DC voltage

a)

aE

0 499 999Output cells of DFT Irrelevant numbers

Fig. 7b. Transformation of 1Hz sine wave.

aE

a)

E

arearbararraokbarboa.

1 499 999Output cells of DFT Irrelevant numbers

Fig. 7c. 2Hz sine wave sample

2 499 999Output Cells of DFT Irrelevant Numbers



Input amplifiersand attenuators Convertor

FFTCalculator

A

SamplingControl

fi

MemoriesAccumulatorsData -Manipulations

Display.ntupro

Front Panel Controls

Fig. 8. Typical FFT Analyser basic functions

amplitude graduations and the twolines represent the energy in the cellscorresponding to the frequencies ofthe 2 sine waves. (Note no other linesappear as all other cell values are zero).The display is produced by continu-ously outputting the cell numbers fromthe FFT result to a digital -to -analogconverter and including the amplitudegraduations.

THE MATHEMATICSThis article is not the place to

consider the in depth mathematicaltheory necessary to fully understandthe processes which form part of theFourier transform. Numerous books

Displayed FFT output with two cells only present,corresponding to the series input. Note lines aresame height and the second twice as far from zerofrequency as the first.

ora

II

i

A1 a a

Ia

11

Original sampled times series - two sine waveswith one twice the frequency of the other, bothsame aplitude.

Fig. 9. Actual inputs and output of a FFTprocessor

and technical articles now exist on thesubject. However the basic operationand its adaptability to digital hardwareis quite easily understood.

One major constraint on an FFTprocessor is that the number ofsamples inputted to it cannot be variedcompletely. With most processors, thenumber of samples in fact have to be apower of 2, e.g., 32 or 64 or 256 or 1024.The more samples taken then thelarger the range of frequencies whichcan be determined or alternatively thenarrower the band width betweencells. However, the calculation processtakes longer. In practice sample blocksof 512, 1024, 2048 are amongst themost commonly chosen as these offera compromise between frequencyrange and computation time.

Essentially in the case of a ForwardTransform the samples from the time

Input samples S1 S2

Intermediate resultsStage 1.

Intermediate resultsStage 2.

series are loaded into a buffer andcombinations of samples are addedand subtracted from each other,multiplied by trigonometrical valuesusually looked up from a Read OnlyMemory. This process is repeatedusing different combinations ofsamples and trigonometrical values.The number of processing stages isrelated to the number of samples, eg, if2048 samples were inputted, then 11processing stages are needed.(21"--2048). If 512 samples wereinputted, then 9 stages are required,etc. This is illustrated in outline by Fig.10.

The advantage over the old 'conven-tional' method of computation is thatwith the conventional method thenumber of stages of calculation equalsthe number of samples. In a 512 pointtransform the process would be 512/9or approximately fifty-five timesshorter by using an FFT. In acontinuous process where FFTs arebeing continuously computed, obvi-ously a very real saving is made interms of result presentation.

As mentioned earlier the FFTprocessing idea lends itself very easilyto a dedicated machine and the idea ofpipeline processing is used in most ofthese. Pipeline processing is usedwhere a number of calculations inseries are performed and where anunacceptably long delay results for the

Fig. 10. FFT Processing stages for 512 pointtransform

S511 S512

I I

Processiing stage 1

Processing stage 2.

Processing stage 3

EOutput cells 1 2

Processing stage 9.

Frequency spectrum data Irrelevant data forfor FFT normal purposes.



computing of an answer before thenext inputs are applied. Figure 11shows an arrangement where this islikely to happen.

In this example an adder precedes amultiplier followed by another adder.With no pipelining, no further inputscan be supplied until enough time isallowed for the results of previousinput numbers to be stored away.However with a pipeline processor,(Fig. 12) latches are included instrategic places allowing sets ofnumbers to follow each other asthough they were coming down a pipe.Thus after the first set of results havetrickled through the latches, a much

Inputs

A >

C >

Adder

faster throughput of numbers willresult.

This type of arrangement is verysuitable in FFT processors since alarge throughput of samples withmuch number crunching takes place.

PRESENT & FUTURE FFTANALYSERS

Essentially an FFT processor (whichis the heart of modern spectrumanalysers, voice print identifiers, etc)usually consist of a memory whichstores the samples and intermediateresults and a processor whichcomputes intermediate results. Thetotal samples are stored internally in

Multiplier Adder

Inputs

A -41

C-->D ->

Latch

Adder

Result> - (A+B)C+D

Output

Fig. 11. A no-pipelining example. Note that a newset of inputs cannot be applied until the old inputshave trickled right through two adders and amultiplier.

Fig. 12. Pipelining arrangement, here new inputscan be applied after only one adder's delay. Atterinitial trickle -through processing speed is muchbetter.

clock

LatchMultiplier

the memory and when the FFT processbegins, the samples are taken in pairs,arithmetically operated on to formintermediate results and stored readyfor the next level of processing. Twomemories are sometimes used wheresamples and results are alternatelyread from one memory through thepipeline processor into the othermemory, where they are ready for thenext level of processing. Thistechnique saves still more time incomputing FFTs. See Figure 13.

This article has only touched ontothe now very broad field of FFTprocessing technology. The approachlends itself easily to band shifting,frequency zoom effects and otherfeatures made relatively easy with adigital system.

Until the 1970s few people knew ofFourier Transforms. At best the termwould evoke a feeling of somethingobscure, very mathematical andhaving few, if any practical applica-tions. But in recent years a whole newworld of applications has beenunleashed.

FFT techniques are today used for avariety of applications including

Latch

Memory A

x

a -

Ea)

Memory B

a)xa)

Read/WriteControl.

FFTPipelineProcessor

Fig. 13. FFT processor with 2memories for faster processingof intermediate results. MemoryA and memory B alternateloading and unloading roles.Input and output paths are notshown for clarity.

OutputResult =(A+B)C+D

Adder

extraction of signals buried deep innoise, sonar processing, spectrumanalysis of complex waveforms, voiceprint analysis and the digital synthesisof music. Research is finding still moreuses, such as in the oral synthesizinginterface of talking computers. Someday you may be able to phone acomputer and hold an intelligentconversation with it, obtaining suchthings as account balances, travelreservations, etc, with tonal expres-sions no different from those of ahelpful person!

With the advent of bubble memoriesand the ever decreasing size butincreasing complexity of microcircuits, it appears that the FFTprocessing field will expand to a pointwhere it will soon be a part of every daylife, a truly big step forward from just 10years ago when the technique was noteven heard of.


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ETI 478i

ETI Project

Microcomputer PowerSupply

This supply has been specifically designed to power S100 (Altair and IMSAItype) computer systems. You can modify it to suit your applications.

A LTAI R/IMSAI TYPE microcomputerswhich use the Altair, or S100, bus useseparate cards for the CPU, memory,I/O and special functions. These 250 x130 mm (approx.) cards each have on-board regulators to reduce cost by notrequiring expensive high current regu-lation and b) avoid the damage whichwould be caused by catastrophic fail-ure of such a regulator. With the on-board regulator scheme, if a regulatorfails, damage is limited to one board.

S100 cards require three supplyvoltages; 8 V which provides the 5 Vsupply, +16 V which is regulated to 12 Vto supply some MOS and linear IC's and-16 V for a -12 V supply to accomo-date MOS substrate bias and op -amps.Although early Altairs had problemswith an 8 V 8 A supply, the powerconsumption of memory has droppedconsiderably since then, and the 28 Asupply of the IMSAI may be viewed asa slight over -reaction.

If the 16 V secondaries are notloaded, this supply can give up to 10 Aat 7 V, though the transformer must beadequately ventilated - this is sailingrather close to the wind. We have useda pre -regulator to avoid problems withthe output voltage rising too high onlight loads. A side benefit of the SCRregulator is the provision of a 120 Hzsync pulse which can be used as a RealTime Clock.

SPECIFICATIONS

Nominal outputs

Actual output voltages@ full load, 120 V input

Regulation+8V output, 0 - 7.5 A+16 V output, 0 - 750 mA-16 V output, 0 - 750 mA

Ripple voltage@ full load +8 V

+16 V-16 V

+8 V@ 7.5A+16 V @ 750 mA-16 V @ 750 mA

+7.5 V+15.3 V-16.2 V

100 mV1.5 V1.5 V

0.7 Vp-p1.0V p -p1.0 V p - p

DESIGN FEATURESWe initially had the transformer design-ed to give the required output voltageat full load but the moment we removedthe load we knew that either a pre -regulator was needed or a much largertransformer to keep the voltage betweenthe limits. Cost ruled out the largertransformer so that left the regulator.

We first designed a series regulatorbut due to the additional losses involved(a total of about 20 watts at 10A out-put) this was ruled out. The SCR(silicon controlled rectifier) regulatorwas chosen as it has very little extrapower loss compared to a straight recti-fied supply. As high regulation is not

28ETI CANADA - APRIL 1978

Microcomputer Power Supply

asJ., SO

41cEITIOOit (4)Alat

(1)85 °C

Fig. 1. Here's howthe PSU looks, withthe board mountedon the big capacitor.

needed we used a simple circuit withoutthe usual choke associated with thistype of regulator. Even so the output ismaintained to approximately 1/2 voltover the load range.

CONSTRUCTIONMount all the components except thetransformer onto the printed circuitboard. Due to the size of the main filtercapacitor, the PC board is mounteddirectly to it. The capacitor is thenbolted to the chassis by its clamp. Whenmounting the capacitor ensure that thetracks on the PC board are clean ortinned, preferably use the star type lockwashers between the board and thecapacitor.

The SCRs must have heatsinks fitted,the ones shown are the minimumrecommended. Alternatively a separateheatsink could be used. Remember thatthe currents are fairly high(peak curr-ents around 40A in SCRs) and thecables used should be an appropiatesize.

If the unit is to be used continuouslyat full load in an enclosure adequateventilation must be provided.

BV

CALIERATIONVERTICAR 200 mV / div.HORIZONTAL.. 2 ms /div.

Fig. 2a. Rfdple voltage on 8 volt output at7.5 amps.

CALIBRATIONJERTICAL 2 Vichy.HORIZON-AL.. 2 ms / div.

Fig. 2b. Sync pulse output.

5.9 V

CALIERATIONVERTICAB .. 200 mV / div.HORIZONTAL.. 2 ms / div.

Fig. 2c. Waveform on the base of Q2.

CALIBRATIONVERTICAL 2 V Idly.HORIZONTAL.. 2 ms /

Fg. 2d. Waveform on the base of 03.


ETI Project

Fig. 3. Printed circuit layout. Full size 130 x 100 mm.

Fig. 4. Component overlay of the power supply. Note thatcapacitor C3 is bolted onto the copper side of the board.

SYNC

ov

640°3

R3 -1:=2,-R 4 -(=)-

CR73A9 "4=3-ZD1D7 -II} /

AS-CD-et+47N 031,111fry

R6

R5 "4"-:-.}e13 -b

+8V-16V ---41+16V

+1

C2

D5

D6

C3

RESISTORS all 5%unless otherwise markedR1,2 220R3 100R4 470R5,6 10kR7 2k2R8 22kR9,10 10k

POTENTIOMETERRV1 500 trim

CAPACITORSC1, 2 4700µ35V electroC3 68000u (or more) 16V

Philips or Mallory etcC4 10u 25V electro

SEMICONDUCTORS01 T I P30C02, 3 2N3904ZDI 5.1V Zener 300mWDI -D4 1N5404D5,6 1N4004D7 1N914SCR1,2 20A SCR

MISCELLANEOUSPC board ETI 635

TRANSFORMERFor 8V supply - 18Vct @ 5AFor 16V supply - 30Vct @ 1AHammond Mfg supplies suitable types

Cl

gate

cathode

SCR1

cathode

gate

15V -d

9 v --

CT

9 V-,

15V,.

TO TRANSFORMERSECONDARY

SC R2


Microcomputer Power Supply

D1

15 VvJ

Ti 120V/18Vct

12 120V/30Vct (1 1AD2

C15 V ,I..'_____.)

-HOW IT WORKSThe ± 16 volt supplies are simply fullwaverectified and filtered, this giving adequateregulation and ripple rejection. The 8Vsupply however needs regulation. With thisthe normal rectifier diodes are replaced bySCRs (silicon controlled rectifiers) wherethe turn on point can be varied. Thecontrol of the SCRs is as follows.

Transistor Q3 is used to synchronisethe triggering of the SCRs to the linefrequency. It is normally biased "off'by the negative voltage generated by D5and D6. However when the voltageapproaches zero this transistor turns onfor about 3ms. During this period capa-citor C4 is discharged to about 5.6 voltsand then it is allowed to charge up againvia R7. The voltage rises only about IVbefore it is again discharged by Q1.

This generates a sawtooth waveformat 120 Hz rate, transistor Q2 comparesthe voltage to that on RV1 which is prop-ortional to the output voltage. Thecomparator transistor, Q2, controls theSCRs via Q1. Because the referencewaveform is a sawtooth, as the outputvoltage falls the firing angle of the SCRmoves forward in the cycle until theSCRs are on permanently and control isthen lost. This point occurs at about 10Ain this unit.

Due to the lack of a choke which isnormally employed in this type of regu-lator, the relative fast charging of C3causes the unit to move into a type ofhalfwave rectified output under light loads.The ripple still remains well within the1Vp.p. limit specified.

8

25

28

144700

68000p

0 16V

TIP30C

MATERIAL: 16G AL.PAINT IT BLACK

BEND UP 90°

6.5mm DIA. HOLE

19.5V )

2N3904

R72k2

MAA

45 59

MATERIAL: 16G AL.PAINT IT BLACK

BEND UP 90°

45 59 90

Fig. 6 Details of the heatsinks used onSCR 1 and SCR 2. Heatsinks of similar orlarger area may be used if required.

..8) 7V

08228

1010k

Q32N3904

b

NOTES:SCR1, 2 16-30A 100V01-04 IN5404D5-D7 IN4004VOLTAGE READINGSTAKEN ON NO LOAD.

0 1 6 V

0 +8V

0 SYNC

26V

0 OV

Fig. 5. The circuit diagram of the power supply.

SPECIAL!4K DYNAMIC RAMS

TMS 4030Access time 300ns

$2.00each

CMOS - .20$ eachCD4001 CD4007CD4015 CD4044 CD4021

LINEAR ICMC14589 Dual op ap .50STL080JFET input op amp .754MOC1001 OPTO coupler .50¢PA301 Audio amp 13W RMS$15.00 2 modules and board

ACTIVE SURPLUS ANNEX345 QUEEN ST. WEST

Telephone (416)368-7936

WE BUY AND SELL ANYTHING


ETI Project

Bucket BrigadeAudio Delay Line

This audio delay line uses the latest in IC technology, the 'Bucket Brigade'to give a simple unit suitable for various effects. However this is a projectfor the experimenter as full details for any particular use are not given.

ANYONE WHO has been in an anechoicchamber will appreciate the need forsome reverberation. In music the use ofartifical reverberation or echo cancompensate for a 'dead' room or createa new effect. Up until recentlyreverberation was normally obtained bymechanical means such as a spring orplate which is vibrated or excited by anelectrical signal; a pickup elsewhere onthe plate or spring receives the delayedsignal. Due to the nature of resonancesin springs, multiple echos occur givingthe effect of reverberation.

A single echo is obtainable by using atape loop, recording the signal on onehead and playing back through a second.

The distance between the heads and thetape speed determines the delay. Echocan also be obtained accoustically by along tunnel with a microphone andspeaker.

When the price of digital ICs startedto come down a number of digital delaylines were developed. These used anA-D (analogue to digital) converter, along shift register and finally a D-Aconverter. To accomodate the widedynamic range required very good, fastA-D, D-A converters along with alarge shift register. Even with the lowprice of ICs these units still cost around$500.00 or so (this is the main reasonwe have not published one as a project).

A number of years ago several ICmanufactures started playing with a'digital' delay line which works bystoring an analogue voltage on acapacitor and then transferring thisvoltage to another and then successivecapacitor. This is accomplished byswitching FETs on and off under digitalcontrol. The circuit became known as abucket brigade and this name has stuck.

The IC we have chosen is theMN3001 which is a dual 512 stepdevice. Brief specifications of otherdevices we know about are givenbelow.


Bucket Brigade Audio Delay Line

USES OF BBDVariable or fixed delay of analog signalsReverberationEchoTremolo, vibrato, flanging or chorus

effectsVoice control of tape recordersTime compression of telephone

conversationsVoice scrambling

CONSTRUCTIONAs we are describing no mechanicalarrangement our description of con-struction is limited to the assemblyof the PC board. It is recommendedthat a socket be used for the BBD IC asit is an expensive MOS device. Theinputs are protected but it should behandled with care. The same care shouldbe taken with the CMOS IC but as asocket costs more than the IC it is hardto recommend it!

The interconnection between the pcboards depends on the effect needed.

The mixer, filter board ETI 4508.

SPECIFICATIONSMaximum input < 3% distorticn

Delay time internal oscillator

Frequency response

Distortion 1V in 1 kHz

Signal to noise re 2V inputCo

Supply current (A) + 5V- 15V

(B) + 5V-15V

2.0V RMS

6 - 30ms

see graph

0.3%

67dB

6 mA9 mA6mA6 mA

The bucket brigade board ETI 450A.

4/V___Ohdtv-33Alci+USki-e

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.1.

The

circ

uit d

iagr

am o

f the

buc

ket b

rigad

e bo

ard

( E

TI 4

50A

1.

The

buc

ket b

riga

de d

evic

e -i

s an

ana

logu

ede

lay

line

whi

ch s

ampl

esth

e in

put

wav

efor

m a

t an

inst

ant

intim

e an

dst

ores

this

vol

tage

on

a ca

paci

tor.

As

we

need

mor

e th

an ju

st o

ne p

oint

on

the

wav

efor

m w

e sa

mpl

e th

e in

put a

t lea

st2

times

fas

ter

than

the

high

est f

requ

ency

requ

ired

. A s

ingl

e ca

paci

tor

cann

ot s

tore

mor

e th

an o

ne v

olta

ge a

t one

tim

e an

dso

a s

erie

s of

cap

acito

rs is

use

d. B

efor

eth

e se

cond

sam

ple

is ta

ken

the

ener

gy in

the

rust

cap

acito

r is

tran

sfer

red

to th

ese

cond

cap

acito

r th

us f

reei

ng th

e ru

st to

sam

ple

the

inpu

t aga

in. T

hen

befo

re th

eth

ird

sam

ple

the

ener

gy in

the

seco

ndca

paci

tor

is tr

ansf

erre

d to

the

thir

d. T

hefi

rst i

nto

the

seco

nd a

nd th

e fi

rst a

gain

sam

ples

the

inpu

t.T

his

proc

ess

cont

inue

son

eac

hsa

mpl

e w

ithth

een

ergy

inea

chca

paci

tor

bein

gtr

ansf

erre

d to

the

next

. Eve

ntua

lly w

eru

n ou

t of

capa

cito

rs a

nd th

is th

enbe

com

es th

e ou

tput

. The

num

ber

ofca

paci

tors

,or

stag

es, a

nd th

e sa

mpl

e(c

lock

) fr

eque

ncy

dete

rmin

e th

e tim

e it

take

s an

inpu

t sam

ple

to a

ppea

r at

the

outp

ut.

HO

W IT

WO

RK

SIn

the

devi

ce w

e ha

ve u

sed

ther

e ar

e51

2 st

ages

in e

ach

of tw

o id

entic

al a

ndin

depe

nden

tse

ctio

ns.

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inte

rnal

circ

uit d

iagr

am o

f th

e in

itial

par

t and

of

the

outp

ut s

tage

is s

how

n be

low

(th

ere

are

over

100

0 ca

paci

tors

and

200

0 FE

Ts

in th

e IC

!)T

he tr

ansf

er o

f en

ergy

is d

one

usin

gFE

Ts

whi

ch a

re c

ontr

olle

d by

the

two

cloc

klin

es C

P1 a

nd C

P2. T

hese

are

com

plem

enta

rysq

uare

wav

esi

gnal

s.U

sing

a40

kH

z cl

ock

the

inpu

tis

sam

pled

eve

ry 2

5ps

then

'rem

embe

red'

and

tran

sfer

edev

ery

25µs

. On

the

outp

ut, f

rom

sta

ge 5

09 o

n, th

e si

gnal

isdi

vide

d in

to tw

o pa

ths,

one

hav

ing

anex

tra

stag

e. T

his

is n

eede

d as

the

sign

alon

the

outp

ut is

onl

y th

ere

for

half

tilt

25µs

per

iod.

By

addi

ng th

ese

two

out -

ofph

ase

outp

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aco

ntin

uous

outp

ure

sults

.A

ll of

this

tran

sfer

ring

of

ener

gy d

oe:

how

ever

was

te e

nerg

y an

d th

e ou

tput

isof

a lo

wer

am

plitu

de th

an th

e in

put.

Inth

e M

N30

01 it

is a

bout

8.5

dB lo

wer

. To

incr

ease

the

dela

y it

is n

orm

al to

con

nect

two

sect

ions

(or

mor

e if

nee

ded)

inse

ries

. How

ever

the

outp

ut h

as th

en

5 50

OU

TP

UT

A

0

10k O

UT

PU

T

twic

e th

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nd e

ven

with

an

inte

r-m

edia

te a

mpl

ifie

r th

is r

esul

ts in

a lo

wer

sign

al to

noi

se r

atio

.A

sec

ond

met

hod

of o

btai

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a la

rge

dela

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to r

un th

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o se

ctio

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para

llel

with

each

sam

plin

gon

alte

rnat

e ha

lf c

ycle

s of

the

cloc

k w

ave-

form

givi

ngef

fect

ivel

y tw

o sa

mpl

ing

peri

ods

per

cloc

k pu

lse.

Thi

s al

low

s th

ecl

ock

freq

uenc

y to

be

halv

ed f

or th

esa

me

freq

uenc

y re

spon

se g

ivin

g tw

ice

the

dela

y w

ith o

nly

one

atte

nuat

ion

loss

.H

owev

er a

s yo

u ne

ver

get a

nyth

ing

for

noth

ing

the

low

erin

gof

the

cloc

kfr

eque

ncy

incr

ease

s th

e lo

w f

requ

ency

ener

gy c

onte

nt o

f th

e no

ise,

mak

ing

the

filte

r do

mor

e w

ork.

Get

ting

back

to th

e ci

rcui

t dia

gram

we

see

that

the

inpu

t sig

nal i

s co

uple

d to

the

inpu

t of

both

hal

ves

of th

e B

BD

with

dc b

iasi

ng b

eing

pro

vide

d by

RV

1. I

C2

isus

ed a

s an

osc

illat

or w

ith f

requ

ency

adju

stab

le f

rom

abo

ut 2

0 kH

z to

90k

Hz

givi

ng d

elay

s of

5-2

5 m

s pe

r se

ctio

n. T

heou

tput

of

1C2/

3 is

inve

rted

by

IC2/

4 gi

ving

the

two

com

plem

enta

ry c

lock

s re

quir

ed b

yth

e B

BD

. The

out

puts

of

the

BB

D a

rem

ixed

with

RV

3 be

ing

used

to r

emov

e th

e

cloc

k fr

eque

ncy

befo

re th

e 6

pole

filt

erIC

2 -

IC4

rem

oves

all

the

othe

r ha

shge

nera

ted

by th

e cl

ocki

ng. T

he f

irst

two

sect

ions

of

this

filte

r ha

ve u

nity

gai

nw

hile

the

thir

d st

age

has

a ga

in o

f 8.

5 dB

to c

ompe

nsat

e fo

r th

e lo

ss in

the

BB

D.

The

se g

ains

are

of

cour

se b

elow

the

cut

off

poin

t!T

he s

econ

d bo

ard

used

is s

impl

y a

mix

er a

nd 4

pol

e fi

lter

whi

ch c

an b

eus

ed to

geth

er o

r in

sep

arat

e pa

rts

of th

eun

it. D

ue to

the

sam

plin

g do

ne b

y th

eB

BD

, the

fre

quen

cy o

f an

inpu

t sig

nal

mus

t not

exc

eed

half

the

cloc

k fr

eque

ncy

othe

rwis

e it

will

app

ear

at th

e ou

tput

at

som

e ot

her

freq

uenc

y lo

wer

than

the

cloc

k fr

eque

ncy.

Thi

s ef

fect

is s

imila

r to

mod

ulat

ion

whe

retw

osi

gnal

sar

em

ultip

lied

toge

ther

and

pro

duce

com

pon-

ents

at t

he s

um a

nd d

iffe

renc

e fr

eque

ncie

s.In

this

cas

e, (

if th

e in

put s

igna

l exc

eeds

hal

fth

e cl

ock

freq

uenc

y) th

e sq

uare

wav

e cl

ock

tend

s to

mul

tiply

with

the

inpu

t sig

nal.

The

sum

and

dif

fere

nce

freq

uenc

ies

wou

ld th

enfa

ll at

qui

te o

bjec

tiona

l fre

quen

cies

in th

eau

dio

rang

e. F

or th

is r

easo

n th

e 4

pole

filte

r is

use

d be

fore

the

BB

D.

:

ETI PCB NegativesHERE WE present negatives for Feb,March and April issues. (We will try tosqueeze in the Hammerthrow pcbsnext time). These negs can be usedwith presensitized boards (eg. Injec-toral). Typical exposure times under aNo. 2 photoflood bulb with reflector atten inches we expect to be around 20minutes. Use test strip to make testexposures to find optimum exposurefor your setup. Full details were givenin Jan 78 ETI.

1'-t r(ii-opS

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. 3. T

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eque

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of t

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ters

. The

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rall

resp

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is a

ppro

xim

atel

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m o

f the

se tw

o fil

ters

pro

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freq

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3000

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Fig

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/

H10

100k

100

F IL

TE

RIN

PU

T

+7

1..0

H12

126

C10

3n9

-1 I R

13 12k

C11

680p 3 2

C14 2

IC3

301A

C15

4

7 o)

017

1M

R16

C16

loof

t1/

10

0C CD co I. C Ike

Oa

(D

ILT

ER

OU

TP

UT

1.14

CD

ETI Project

+5V

OV

R7 C.) C7C" --)C1

""C.-t"' -4 0 n -(=:.-c9. c, v i 8

C10C), C=)C84:Z} C12

8Nt.)CC

C11 ..(""--'a>.

-15VRV2

4.=> C16

OUTPUTca

G6 .!) (1) 8

c 1R17+C

7

rirV-211OUTPUT A

C14

Fig. 6. The component overlay of the bucket brigade board.

C70°5100+

N M `CI'cc cr

rMIXER6-1INPUTS ft

b

C13

R6 cv C11,7 0 cio

2c=)881:111101)(1c

A co C14CC CC

-C15

R5 0 G1306

> > >Lc) 0 in I-

CC

wI---D-20

Fig. 7. The component overlay of the mixer - filter board.

ADJUSTMENTRV1 is used to set the bias voltage. If anoscilloscope is available look at theoutput of the board while feeding in asine wave signal. Adjust RV1 to allowthe maximum input signal withoutclipping. RV2 adjusts the delay whileRV4 sets the output level to com-pensate for differences in the loss of

c0+ R 16

R 17

w

LL -

G16

CC ,wI- -

the BBD sections. RV3 is used toremove the clock frequency from theoutput. If an oscilloscope is availablelook at the wiper of RV3 and adjust togive the smoothest output. Theswitching transients at this point arevery high but these are removed by thefilter.

RESISTORS all W 5% unless otherwiseR1 47k markedR2 10kR3 100kR4 12kR5 820RR6 4k7R7-R10 . . 100kR11,12. . . 12kR13 100kR14 5k6R15 3k9R16 15kR17 10k

POTENTIOMETERSRV1 50k trimRV2 25k trimRV3 5k trimRV4 25k trim

CAPACITORSC1,2 100n polyesterC3,4 10012 25V electroC5 1µ0 25V electroC6 1 n0 polyesterC7 680p ceramicC8 39p ceramicC9 33p ceramicC10 2n2 polyesterC11 1n0 polyesterC12 33p ceramicC13 1Oµ 25V electroC14 6n8 polyesterC15 1n0 polyesterC16 33p ceramicC17 114 25V electro

SEMICONDUCTORSIC1 MN3001IC2 4011 ( CMOS )1C3-105 . . . 301A

MISCELLANEOUSPC board ETI 450A

Kits are available for these fromLivingstone Electronics and Dominion Radio.See their ads elsewhere in this issue.

PARTS LIST

RESISTORS all 1/4W 5% unless otherwiseR1-R6. . 100kR7 100RR8 1MR9-R11 . 100kR12-R15 . 12kR16 100RR17 1M

CAPACITORSC1,2 100n polyesterC3,4 10012 25V electroC5 10 25V electroC6 10µ 25V electroC7 33p ceramicC8,9 1µ0 25V electroC10 3n9 polyesterC11 680p ceramicC12 33p ceramicC13 2n2 polyesterC14 1n0 polyesterC15 33p ceramicC16 1/20 25V electro

SEMICONDUCTORSIC1-1C3 . . . 301 A

MISCELLANEOUSPC board ETI 450B

marked


- Bucket Brigade Audio Delay Line

INPUT -

0 MIXER

ETI 4608

OUTPUT

0

FILTER

ETI 4508DELAY 1ETI 450A

OUT B

OUT A

DELAY 2ETI 450A

OUT B

OLT A

LHr- - - - - - -10LIT BDELAY 3 I

ETI 450A IOL TI-- -1

TO EXTRA STAGESIF REQUIRED

10k

Ov

Fig. 8. The interconnection for reverberation.

INPUTFILTER'6 4508

DELAYETI 450A

OUT A

Fig. 9. Connections for a single echo. With a shortdelay this becomes a phaser.

REVERBERATIONIf the audio signal is fed via a mixer intothe delay line and its output fed backinto the mixer we have a feedbacksystem which will repeat a single soundmany times. This is reverberation. Ifseveral different delays are used theeffect will seem more natural. With allfeedback systems if the sum of all thedelayed outputs exceeds the originalsound uncontrolled oscillations willresult. This is similar to howl -round inPA work and careful adjustment is

MIXERN ETI 4508

UUT PUT

0

needed if long reverberation times arerequired.

ECHOThis is similar to reverberation exceptthe delayed signal is not fed back to itsown input. A single echo only results(from a single delay) and it can be ofany amplitude in relation to the originalsignal.

PHASING (FLANGING)By varying the delay times and bymixing in the right proportions totalcancellation of some frequencies cancccur. Now if the clock frequency ismade variable a phasing or flangingeffect occurs. A variable clock can bemade by replacing potentiometer RV2by an LDR and illuminating it with abulb the brilliance of which is

controlled (try a 555 timer). We mustleave details of this to the individualconstructor.


®AKTRON'S

New C BSound Saddle

let's you hear

What you'vebeen missing

Oaktron Industries puts your CB radio inthe SB Sound Saddle to give you reception younever before thought possible. The speciallymade, built-in 3" x 5" voice communicationspeaker virtually eliminates unwanted high andlow frequency interference - then directsthe sound to you, not to the floor.

Oaktron's CB Sound Saddle is fully adjus-table to almost any transmission hump. Even

if it is not permanently attached, it's designedto ride out any kind of trip with ease, yet isfully portable if you want to remove entireunit.

CB Sound Saddle includes all hardwareneeded, takes 4-6 minutes for custom assembly.No tools needed. Your choise of grilles; BlackEnamel, Walnut Woodgrain or Chrome Plated.All American made for dependability's sake.

Meet a wholenew conceptin CB soundand convenience.1. Powerful 3" x 5"voice communicationspeaker aims clear,crisp sound directly atyou.

2. Puts your CB radiocontrols within easyreach.

3. Custom -fits com-pletely secure on mostany transmission hump.

4. Permanent or porta-ble installation

2056 SOUTH SERVICE RD. TRANS CANADA HWY. - DORVAL, QUE. H9P 2N4 - PHONE: (514) 683-6993

m"(sprRr--..---`ALARMSBasic AlarmPhoto Intruder AlarmIntruder AlarrnPhoto Electric RelayLow Temperature,Lights outTemperature SensorCoolant levelWater LevelElectronic LockCar Battery WatchdogSimple Car AlarmSimple Lock

lir AMPLIFIERS &PREAMPLIFIERSHigh Input ImpedanceHigh Impedance BufferLow Output ImpedanceHigh Input ImpedanceLow Frequency ExtenderVirtual Earth PreampIC Tape Head PreampSimple Stereo Tape Player2 5 Watt20 Watt Slave10 WattLoudspeaker MicrophoneVoltage Controlled AmpWide Band AmplifierVideo Power AmpBroadband Amp

z

gx

imsILI

SIGNAL PROCESSORSFuzz BoxGuitar FuzzFuzz BoxWaa WaaDisco AutofadeSimple AutofadeInformation TransferOptical Pulse ConditionerTV Sound PickoffCracklefree PotentiometerVoltage to FrequencySine to Square WavePrecision AC to DCVoltage ProcessorUniversal MeterDouble PrecisionFast Half WaveSimple ChopperNoise Rejecting SCR TriggerPhase Shifter

SIGNAL GENERATORSSimpleVariable Duty cycleFast EdgeFETImproved MultivibratorVariable Duty cycleStable R CCheap (CMOS)Simple TTL XTALUncritical XTALPulseZero CrossingSimple Pulse

Needle PulseStable Linear SawtoothZenerNoisePinkSimple RelaxationTriangle with independent slopeExponentialWiderange MultivibratorMultiple WaveformLinear SweepStep FrequencyBeeper7400 SirenSimple SirenShip SirenTwo ToneToy SirenKojak, StartrekSound EffectsSound Effects

FILTERS

BandpassLow & High PassRejection NotchBandpassCartridge E0 8<f:tumbleHum StopperTape Hiss ReductionSimple Crossover

DIGITALThermometerHeads or TailsBinary CalculatorVoltmeterSeven Segment to DecimalDieRandom BinaryCMOS DieMultiplexer HintsLearning MemoryCMOS Clock

POWER SUPPLIESConstantTemperature StableConstantVoltage ControlledPrecision Voltage DividerDual PolaritySimple BalancedVoltage DividerLow RegulatedShort Circuit ProtectedSimple TTL SupplyZN414 SupplyStable ReferenceTransformerless lnvertorDC to DC ACVoltage MultiplierAutomobile ConvertorShaver AdaptorDC -DCHigh Voltage From BatteryVariable + ve or -ve outputSimple12V from Battery ChargerBucket RegulatorAdjusting Zener Voltage

Variable ZenerZener Boosting of RegulatorsHigh PowerElectronic FuseBetter FuseRegulator & FuseFas' ActingSCR CrowbarVoltage PolarityNI CAD DischargeCurrent Limiting

TESTDiode CheckerGO NO GO Diode TesterZener CheckGO,NO GO Transistor TesterQuick JFET TestCurrent Gain TesterBasic Transistor TesterSimple Transistor -SCRSCR TesterCrystal CheckCrystal CheckerGood -Bad Battery TesterBattery TesterOp -Amp TesterOp -Amp CheckerCheap Logic Probefiudible TTL ProbeAudible Slow PulsesLogic ProbeLogic AnalyserI and 0 Display ProbeSimple High ImpedanceVoltmeterAudioiRF TracerThermocouple ThermometerMetering Stabilised suppliesSimple Frequency Meter

TIMERS & DELAYS

Low Standby Drain741 TimerSelf Triggering TimerPulse TimerPulse DelayVoltage Controlled MonostableSequential RelaysDoor Chime Delay

SWITCHING

Touch Triggered BistableTouch Sensitive SwitchElectronic SwitchSound Operated 2 WaySPST Switch Flip FlopTwo Signals on one Wire

INDICATORS

Line -o -Light3 Step LevelLight LevelBargraph DisplayFuse FailureBlown FuseBack Up LampDC Lamp Failure

FM Tuner StationCurrent FlowDisco Cue

FLASHERS

Dancing LightsLow Frequency StrobeFlasherUltra Simple

POWER CONTROL

LDR Mains ControlFloodlamp ControlZero Crossing SyncTrain ControllerLow Differential ThermostatSimple Temperature ControlFull Wave SCR Control

AUTOMOBILE

Brake Lamp FailureCourtesy Light DelaySimple Hazard LightLight Extender & ReminderFour Way FlasherHeadlamp DipperWiper DelaySuppressed Zero VoltmeterRev Counter TachometerAuxiliary Battery

DETECTORS &COMPARATORS

Peak Detect & HoldWindow DetectorPeak ProgramPositive PeakReaction Comparator

RADIO FREQUENCY

Crystal Marker100 kHz MarkerRF VoltmeterRF DetectorLED RF IndicatorRF Amplifier ProtectionFET-RadioOp -Amp Radio

MISCELLANEA

Phase Locked LoopTouch DoorbellPhase Lock ControlAudio MixerVirtual Earth MixerPlop EliminatorLoudspeaker ProtectionDigital Capacitance ProbeDigital Tape Recorder AdaptorBreakdown Diode SubstitutionDual Function ChargerDual Mode Amp

Capacitor SubstitutionElectronic CapacitorSpeeding Up DarlingtonsShutter SaverThyristor SensitivitySound Operated FlashStrength TesterLogic Noise Immunity

TIPSIdentifying 74 SeriesSupply PinsSoldering IC'sTinning With Solder WickPCB StencilsFront Panel FinishDIL DrillingFluorescent StartingAvoiding Insulated Heat SinksTTL Mains InterfaceBoost Your MainsHigh Resistance on Low MetersHigh Voltage ElectrolyticsTransistor IdentificationTemplate & Heat Sink forPower TransistorsTransistor SocketSolder Flow ProblemsOdd Resistor ValuesResistors in parallelCMOS OIL HandlingIdentifying Surplus ICSExtending Battery LifeBattery SnapsPower Supply or BatteryBattery CheckingMuck RemoverTransformers in reverseLoudspeaker Checkingimproving UJT LinearitySignal TracerCrystal EarpiecesCheap VaricapsZener Lifts Capacitor Rating

DATA

741 Op -Amp DataBC 107-109 DataBC 177-179 DataCMOS 8 TTL Data2N3055 DataMJ2955 DataBipolar Data TablesBipolar FETs RectifiersDiodes Pinouts Zener Misc

AN IDEAS BOOKFOREXPERIMENTS

SEND $5.00To ETI Circuits,ETI Magazine,Unit Six, 25 OverleaBlvd., Toronto,Ontario. M4H 1B1


ETI Data Sheet

Panasonic MN3001THE MN3001 is the heart of our BBD experimenter's boards featured in this issue.

Each device contains two 512 -stageBBDs with independent input, outputand clock terminals. A pair of outputterminals is provided in each BBD forcancellation of the clock componentsuperimposed on the output signals.

P -channel silicon gate technology isused to fabricate the BBDs from chainsof tetrode type MOS transistors andstorage capacitors. The MN3001 is

packaged in the standard 14 -lead DI Lplastic package.

TYPICAL CHARACTERISTICS (1a = 25°C)

1.0

0.9

0.8

0.7

0.6

0.5

0.4

0.3

V00 - Vcrt.- -15VV00- -14VVie,. .5Vfcr 40 kHzfin 1 kHz

0 5 (00m) 10

E

-5

1010 1.5 20 25 30Input Sign& Lvel Vin (Vrms)

Fig. 2. Voltage transfer characteristic&

CP2 (A)

OUT 1 (A) 04

OUT2 (A) ®4

Fig. 1. Block diagram.

Nr 0

CP1 (A)®

V00Cu)

BBD (A)

512

Stages

OPERATING CONDITIONS (Ta = 25°C)

0IN (A)

CP2 (B)

VOG

BBD (B)

512

Stages

-PO OUT1 (B)

-PC) OUT2 (B)

e-C) GN D

CP1 (8)

Item Symbol Conditions Typ. Unit

Drain Supply Voltage vcjo - 15 V

Gate Supply Voltage v - 14 V

Back gate Bias Voltage Ves VCPH = 0- -1V + 5 I V

Clock Voltage "H" VCPH vas =+4-- 6V 0 .1V

Clock Voltage "L" VcpL - 15 V

1 The MN3001 can be used at VBB = 0 V, if VcpH is f ixed at -3V.

ELECTRICAL CHARACTERISTICS (Ta = 25*C, VDD=VcpL=-15V,Vcc=-14V,VBB= +5V. RL=100

Item Symbol Conditions Min. Typ. Max. Unit

Clock Input Capacitance Ccp 350 pF

Clock Frequency fcp 10 800 kHz

Signal Delay Time tD 0.32 25.6 msec

Clock Pulse Width 2 tcpw 0.5T 3

Clock Rise Time 2 tPr 0.05T

Clock Fall Time 2CPt 0.05T

Input Signal Frequency fin fcp = 40 kHz 3d8 down 0 0.3fcp kHz

Input Signal Swing Vin 2.5% Distortion 2 Vrms

Output Signal Attenuation fcp = 40 kHz, fin = 1 kHz 8.5 11 d8

Output Distortion Dtot fCP = 40 kHz, fin = 1 kHzVin = 2 V rms

2.5 %

Noise Level VNfcp = 100 kHzWeighted by-A'curve

0.25 mVrms

Signal to Noise Ratio S/N eVoltaOutputgMax.70vs. Noise Voltage d8


Panasonic MN3001 Bucket Brigade

10

5

0

VD,. \rm. -15VV00 . -14VVu- 5Vfa- 40 kHz1,n. 1 kHz

100 .Jd8rn/10 1S

input Signal Laval2.0 25

V,n (Vrrns)

Fig. 3. Distortion characteristics.

010

-15

0.45

0.40-6

VDD - -15V, VDD Vcat. 1VVag EiVVIII 0.78 Vrms atm/

2 15

Ica . 40 kHzfin . 1kHz

E 0.35 7

EO

0.30 -8 0

LL

0.3 tapO

-9

to 0.25-10

-113.0 -9 -11 -13 -15 -17 -19 -21

Clock Voltage Vctii, (V)

Fig. 4. Cut-off frequency.

VD0 Vm. -15VVoD. -14V. Vag. +5VVin . 0.78 - 1.94 Vrrns

(0 - 8 d8m1

,-1.....

CS PO 16

.5.1

P.14...

10 30 50 100 300 500 1K 3K 5K 10Kinput Frequency tin (11z)

Fig. 6. Frequency response.

30K 50K 100K 300K

Fig. 8. Compensation of DC level shift due to clock frequency change usingtwo BBDs.

V.. +5VV" -I4V

+ 0-198

tv

C

tyF

-( 2[3

5

p --L6 9

7 8

4 DO -15VC

-{ 1 14 ) - + OOKII 100Kil13]12 )-

4 11]

10

MN3001)

8

C

8

ulyia a,

ttpCC

O

CPICP2

CC OV

Audio Input

Voo- -15V, V00. Viz's +1VV.. +5VVin . 0.78 Vrms (0 d8rn)to, - 40 kHzfen 1 kHz

-9 -11 -13 -15 -17 -19Clock Voltage "L" VD., (V)

Fig. 5. Output voltage swing.

Clock Amplitude -16V

-21

VDD -15V

Delayed Output

Fig. 7. Basic circuit with clock component cancellation(single channel).

VB. +5VV20 -14V

-C -10 a

tY

C 8

.-Vb in .3 7 Si

LL

C

-c

-v-[1 14]2 13]3 12ii]-

to)-6 9

7 8

(MN3001)

C

VD, -I 5V

CY

C

1µF

OVCP1CP2


Fig. 9. Extension of bandwidth nearly twice using two BBDs.Effective sampling rate becomes twice clock frequency.



Canadian Projects Book Number Onegives you twenty-five projects from issues

of ETI sold in Canada.

The Best Of ETIFor Only $3.00!This book is a must for all Canadian electronics enthusiasts.Weshow youhow to

make your own digital voltmeter, and an injector -tracer for your test -bench.Then you can set about building our induction balance metal locator -this is the Cadillac of metal locators, a big

improvement on the usual BFO types. And when you are out searching for treasure you can relax in the assurancethat our burglar alarm project is watching over your home (to make sure no-one steals your valuable CanadianProjects Book).

While you are building our electronic version of the Mastermind game you can keep your kids/parents/roommatesoccupied with your homebuilt reaction tester and double dicegames. If the excitement gets too much you can relaxwith our biofeedback GSR (Galvanic Skin Response) meter (and if you want to do more experiments withbiofeedback you can build our heart -rate monitor).

Another project for the experimenter is our sound -activated photographic flash trigger. With this device you canphotograph a bullet leaving the barrel of a gun, or a balloon bursting, etc.

In addition to the projects mentioned above we have designs for fifteen audio projects. Eight of these can beconnected together to make the mixer and power-amp sections of a discotheque sound system. For the musician wehave plans for a fuzz box and for a phaser; for the beginner in electronic music we have our clever twenty-five noteelectronic organ which uses a touch -sensitive keyboard etched into half of the single PCB (and we include variable-depth tremolo, volume control, and two voices).

For the hi-fi enthusiast we have do-it-yourself instructions on how to build a simple LED indicator to tell you whenyou are overloading your amplifier. If you aren't getting the bass response yoJ would like from your speakers youcan build up a little gadget to put that right. If you are more adventurous with your sound system you will beinterested in our audio limiter. This project can be used to protect your group's amplifiers from distorting when high-level signals are produced, it can be used to compress the dynamic range of a signal for recording or addressingpublic meetings, or it can be used as a voltage -controlled volume control for remote or automatic adjustment.

There's got to be something in this book for all ETI readers. Allthe projects have been reworked since they were first publishedto update them with any information we might have receivedabout availability of components, improvements, etc.

All for the amazingly low price ofthree dollars.

To order Canadian Projects Book Number One send$3.00 per copy (no extra to cover postage) to CanadianProjects Book, ETI Magazine, Unit Six, 25 Overlea Blvd,

Toronto, Ontario, M4H 1B1.ETI CANADA - APRIL 1978 41

ETI Project

Gas AlarmThis versatile alarm prevents the engine being started or electricalequipment used if there is a build up of gasoline vapour or gas thus protectingyour boat against fire.

GASOLINE VAPOUR, closed spaceand electrical sparks are not ideal com-panions. Many a boat has beendestroyed when the owner hasswitched on the ignition withoutrealising there had been a fuel leakand that the vapour content in theengine compartment is at a dangerouslevel. Unfortunately the circumstancesalso lead to injury and loss of life.Therefore any system which canprevent this is of great value.

This unit is designed to meet thisrequirement and uses a semiconductorgas detector (TGS cell) to monitor theatmosphere in the engine compartmentand either prevent the engine beingstarted or shut it down if a high vapourconcentration occurs during operation.

CONSTRUCTIONThis is relatively easy if the printedcircuit board is used and the wiringdiagrams are followed. Some precautionsshould be taken if the unit is to be usedin a boat to prevent corrosion. The rearside of the board should be coated witha cellulose spray (dope, nail polish, etc.)and the box, while having to be near thecontrol panel, should be shielded fromdirect spray. Although we have used aseparate box the unit can be mountedbehind the control panel if desired.

A small heatsink (about 25 mm squarealuminium) should be bolted on to IC1to keep it cool.

The relay we used can handle up to6 A current but if higher currents arerequired it can be replaced with any12 V relay providing its coil resistanceis over 100 ohms.

Obviously the sensor must bemounted in the engine compartmentand while it must be in free air it mustalso be protected against mechanicaldamage.

SAFE

otv

FAIL

eti 583

GAS 11101111On

42 ETI CANADA -APRIL 1978

Gas Alarm

'coCC,

CC 0

N0LLJ

CC

e-s.A.AA/-4

N.

z - c7-0

r

1.0 000CC

-Yv- CC

-44---43 OUTPUTRLI

0

z

U0

UM

of

vWv

..CtCr, J>

Cr)Z Z ZCNI

lf)aN-000

07

CI 0

Fig. 1. The circuit diagram of the alarm.

0

HOW IT WORKSThis project is designed primarily tomonitor the concentration of volatile gasesinside the bilge of gas-engined boats.The circuit provides an electrical cutoutwhich prevents the engine from beingstarted if fumes are present and also willremove all electrical power if fumes becomepresent at any time.

The unit acts as a master switch anddue to its warm up requirements, a twominute delay occurs on switch on. Twoindicator lights indicate either "safe" or"fail" condition and in the initial warm upperiod both lights are on. The initial timingis performed by Cl and IC2. With themain switch off there is +12 V across ClWhen it is switched on the capacitor isallowed to discharge through RI. IC2compares the voltage on Cl with that onpin 3 (about 3 V). During this period theoutput of IC2 will be about +2 V.

ICI is a 5 V regulator and supplies thepower for the heater of the sensor. Thesensor's resistance element is in series withRV1 and this voltage is compared to thevoltage set by R4/R5.

The transistor Ql gives a fail safeoperation and if the sensor is not con-nected this transistor will be off giving+5 V on pin 2 of IC3. Resistor R8 ensuresthat the voltage on pin 2 will always beslightly less than +5 V.

If vapour is present the sensor resistancewill be low and the output of IC3 will behigh. During the first two minutes thediodes DI and D2 prevent the feedbackloop (R11) operating. After two minutesif the output goes high the reference volt-age on pin 3 of IC3 will go above 5 V andtherefore the IC will latch in that position.

The relay is operated by Q4 and for itto close the output of IC3 must be low(no vapour) and also the output of IC2must be high (more than two minutesafter switch on). If the unit does switchoff, or prevents initial switch on, it mustbe switched off and then on again (afterclearing the fumes) and the two minutedelay operates again.

INSTALLATION ANDADJUSTMENTThe sensor should be mounted in aposition where vapour may be expectedand should be mechanically protectedagainst damage. The connection to thesensor should be via a 4 core cable (onlong runs use a shielded cable) and theconnection of the sensor is shown inFig. 3. Note that it is symmetrical in lay-out and also the fact that it will fit intoa standard 7 pin miniature tube socket.

The only adjustment is the sensitivitycontrol and this is set by bringing asmall container of gasoline near thesensor and ensuring it operates. Theadjustment should be as sensitive aspossible without giving falseoperation.


ETI Project

+12VINPUT

COMMON

OUTPUT

TERMINALSTRIP

LFig. 2. Component overlayand wiring diagram.

R SRESISTORS all 12W 5% unless statedR1 3M9 otherwiseR2 1MR3 6k8R4 47kR5 100k

R6 12kR7 33kR8 100kR9 15kR10 8k2

R11 100kR12 8k2R13 5k6R14 -R16 1k8

POTENTIOMETERSRV1 100k trim

CAPACITORSC1 2211 16V tantalumC2 330n polyesterC3 10µ 16V electroC4 loop 25V electroSEMICONDUCTORSIC1 7805 regulatorIC2,3 301 or 741

Q1 2N390402-05 2N3638A, 2N2905

D1,D2 1N914

MISCELLANEOUSGas Sensor: Figaro 812 or 813PC Board ETI 583LP1,2 Indicator lamps 12V

100 mA max.SW1 single pole toggleRL1 12V relay 280SL coil single

poleMetal box to suit

The individual gas sensors and completekits of parts are available from LivingstoneElectronics, see their ad in this issue.

RL1

TERMINALSTRIP

44 ETI CANADA -APRIL 1978

Gas Alarm

60

2 0 0 50

3 40

0

Underneath view.Note that pins 1 and 3 are internallyconnected as are pins 4 and 6.

Fig. 3. Connections of the sensor.

Fig. 4. Printed circuit layout.Full size 52 x 92 mm.

WHAT TOLOOK FOR

IN MAY'S ETIAudio Feedback

EliminatorBy raising the signal from a microphone by 5Hz before it

is fed to the PA system you can eliminate audio feedback inmany cases. This project can also be modified for specialeffects (with variable frequency offset).

Add -On FM TunerThis PCB tuner can be added to a stereo amplifier or can

be mounted in its own box. Then you can add up to threemeters, a couple of switches, a rotary or slider tuning pot,etc., to your own custom -design.

White -Line FollowerMount this project in a suitable model car and it will follow

a white line drawn on the ground.

Tools in CanadaTools aren't boring. Read about the new developments in

this field and see how you can save yourself a lot of time infuture. We look at what's on the market and who's selling it.

MAKE SUREYOU DON'T

MISS IT!These articles are in an advanced state of preparation, but in order tokeep you up-to-date with the fast -changing world of electronics we mayhave to change our plans at the last minute.


NEW ETI KITSFINALLY -we now have available COMPLETECOMPONENT KITS for current projects everymonth! Our kits include all components and misc.hardware as well as etched, drilled and plated pcboards with component layouts.

ETI 450 BUCKET BRIGADE KITComplete kit both boards 55.00

Bucket Brigade board kit 450A 40.00

Mixer- Filter board kit 4508 15,00

MN3001 IC & Socket 2500

ETI 583 GAS SENSOR ALARM KITComplete kit (Specify Sensor type) 40,00

Plain metal box for above 3.00

Sensor & Socket (Specify type) 10.00

TGS812 suitable for Carbon Monoxide &TGS813 for gas vapours

Prices are postpaid-Ont.Res.add pst.- no C. 0.0's

Send $1 for catalog - refundable with first order

/ ivingstoneElectronicsSUITE 201- 801 YORK MILLS RD.DON MILLS, ONTARIO M3B 1X7

Rapilipe *PANELTRANSFERS/-

1

T

H

et!

Rub -down panelmarkings

New from ETI

A really high quality systemfor finishing off your pro-jects. The sheets include amass of letterir g and controlscales for both rotary andlinear pots.

The lettering is trans-ferred simply by laying on tothe panel and rubbing down- it's strong and permanent.

The markings are on two

nol

sheets (a full-sized one cut inhalf for easy postage) andcontain sufficient letteringfor dozens of projects.Send $3.50 (including post-age) to ETI PANEL TRANS-FERS, Unit Six, 25 OverleaBlvd., Toronto, Ontario. M4H1B1.0ntario Residents add 7°0PST.

SPEC FOR SPEC

LEADER DELIVERS THE BEST PRICES AVAILABLEmom.

t t

If you haven't already comparedLEADEF'S wide range of functional

oscilloscopes, do so! The prices, specsand warranty are better than what youare probably looking for. Probes and

accessories included.

h... I

LEADER TEST INSTRUMENTS F-191 omnitronix ltd.2056 SOUTH SERVICE RD.TRANSTRANS CANADA HWY

"PUT US TO THE TEST." WRITE FOR OUR DETAILED CATALOG. DORVAL, QUE. H9P 2N4PHONE: (514) 683-6993

BITS, BYTES and BAUDSA review of Bill Johnson's six -part introduction to personal computing concepts.

IN THE SEPTEMBER 1977 issue BillJohnson started a six -part series tointroduce the computer hobby toreaders who previously knew nothingabout computers. The series putstogether all the main concepts ofpersonal computing and enables thereader to construct a mental picture ofhow a computer works (and what allthe common buzz -words mean)without needing to have any contactwith the computers themselves. Withthis simple model stored in his cerebralmemory the reader can tackle articlesand sales literature written for theexperienced computerist. The basicmodel will help the newcomer identifyand file new information without anymental block.

To refresh the memories of readerswho have followed the series (and toprompt you into going back over areasthat were perhaps a bit hazy on firstreading) and to guide any new ETIreaders we will now briefly go over themain headings in the various sections.

Bits, Bytes and Bauds No 1 (Sept 77)looked at the state of data transmissionbefore microcomputers were devel-oped. This area is the nearest thathobbyists got to computers in the daysbefore IC logic. From the start of theseries Bill assumes the reader has noknowledge of digital electronics. Thisfirst part mentions the Baudot andASCII codes, the asynchronoustransmission of serial data and the useof the parity bit.

The microcomputer is introduced inthe second part of the series (Nov 77),

with a look at how a piece of data canbe stored in a memory. Briefly thearithmetic of binary numbers isexamined. (But what's single precisionarithmetic, as opposed to doubleprecision? Maybe you'd better dig outyour Nov ETI and make sure you've gotit straight.)

In the December issue Bill pulls backfrom the memory and looks at theroads of access - the address bus andthe data bus. So you should know whatis a synchronous bus, and what is anasynchronous type. Also in thissection the problem of communicationwith peripherals is introduced - whathappens when the peripheral com-municates much slower than thecomputer?

A further look at I/O techniquesfollows in part 4 (Jan 78). Here you canlearn about interrupts and the cleverway the computer uses the stack andthe stack pointer during an interrupt.Pushing and popping the stack, theindex register, maskable and non-maskable interrupts, priority setting,vector addresses, polling by theinterrupt service routine, directmemory access. . . all these fearsome -sounding concepts are really verysimple, aren't they?

Previously memory was an abstractplace where data could be stored. Inpart 5 (Feb 78) Bill looks at whatmemory is like in practice. His wordson ROM, paper tape, cassettes andfloppy disks, are as easy to assimilateas the stuff on the back of a cornflakespacket. The need for leader preample

and checksum is clear to everyone.Bill's final part (March 78) puts

together a complete system and talksabout the software ingredients - texteditor, assembler, etc. The readerlearns about the levels of language atwh.ch the programmer can communi-cate with the machine. Do you knowwhether you'd prefer a compiler -typeor an interpreter -type high levellanguage?

The course finishes without lookingat specific components in thecomputer. You have a program, youhave various forms of memory and youhave peripherals. To know more abouthow the computer executes theprogram, how it actually drivesperipherals, or how the program iswritten the reader canelsewhere. Much can be learned aboutspecific microcomputer ICs by readingMicrobiography in ETI (8008 and 8080in Oct 77, 8085 and Z80 in Nov 77, 6800and 6500 in Dec 77, 1802 in Jan 78, 2650in Mar 78, and more to come). Readingthe reviews of the PET (Feb 78) and theTRS 80 (this issue) personal com-puters will help the newcomer toappreciate the relative importance ofhatdware and software facilities.

Bits, Bytes and Bauds is completedbut this doesn't mean ETI will moveaway from computer articles. On thecontrary we intend to lead our readersfrom the beginner's stage further intopersonal computing as the hobbydevelops in Canada.

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ETI Soffspot

Pseudorandom NumberGeneratorThis month we have two more programs submitted by P. Cornes for the SinclairProgrammable calculator.

Object - To generate a random number of any requiredlength up to eight digits in such a way that eachdigit can take any value from K to L.OR generate single random numbers with valuesfrom K to L.OR play an ESP game such that the player hasthe opportunity of entering a single digit numberbefore the calculator generates a random num-ber, both digits being displayed at the end of therun for comparison and statistical purposes.

SLOT MACHINE

Use execution 1 with K = 1 and L = 4 and score winsaccording to the following table.

Display Win111 10222 10333 10444 10221 5331 5441 511- 4

2With thepay -out.

RACE

values of win shown, the program gives a 95%

Use execution 2 with K = 1 and L = number of players(say four). Run the program and each time a number comesup enter a one in the table shown, in the next emptysquare down, underneath the number displayed. Thefirst player to fill the column below his number is thewinner.

BATTLE

Use execution 3 with K = 0 and L = 5. Each player takesit in turn to enter his own number (one to five) and runthe program. When the display appears subtract the smallerdigit from the larger and then add the larger digit to thisanswer. The player with the highest number at the endof the round wins the round. The first player to win fiverounds wins the game.

EXECUTIONExecution 1 -

Any number between 0 and1/A v/Sto4v/A 7/got° /0 /0/c/ce/RUN/random digit/ if you require a two digitrandom number then press RUN again and asecond random digit will be displayed alongsidethe first, a three digit random number, pressRUN a third time etc ....When you have a random number of the requiredlength and w sh to generate another numberpress the clear button followed by RUN/random-digit/ etc....

Execution 2 -Any number between 0 and1/A7`/Sto/a v/A oto/0/6/c/ce/RUN/random number/R UN/random number/RUN/random number/ etc ....

Execution 3 -Any number between 0 and1/Av/Sto /A v/a. v/goto/0/0/c/ce/Your guess/RUN/random number and your guessYour guess/RUN/random number and your guessYour guess/RUN/random number and your guess

With the program as it stands the variables take the follow-ing values:-

K = 1L = 6

Obviously with these values the program can be used tosimulate the throwing of dice with executions 1 or 2.

When you come to change the variables you should do itin the following way:-Executions 1 and 3

Choose a value for K from 0 to 8 (integer).Choose a value for L from K to 9.Replace line 9 and 10 with the value of L -K.Replace lines 29 to 31 with the value of K - 1

(including sign).Run as per execution instructions.

Execution 2Choose a value K from 0 to 9 (integer).Choose a value L between K and 99 (integer).Replace lines 9 and 10 with L - K.Replace lines 29 to 31 with K - 1 (includingsign).

Run as per execution instructions.With a moments thought you will see that there are one

hundred and one uses for this program, a few of these aregiven above.


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Engineering Technicians andEngineering Technologists are meetingthe unique and growing demands of theCanadian Electronics Industry forcollege -trained professionals.Engineering Technicians andTechnologists are not journeymen andneither are they professional Engineers(P. Engs.); they are known asApplication Engineers. They combinemany of the journeyman's practicalskills with those obtained throughextensive training in the scientificprinciples of electronics enabling themto design and develope sophisticatedcircuits. In effect, they are the supportforce of the university-trainedprofessional engineer.

Granted, there are many situationswhere the Engineering Technologist andTechnician share the responsibilities ofthe graduate engineer.

Usually the training program for anEngineering Technician requires twoyears, full-time at a Community Collegeand for an Engineering Technologist,three years full-time.

Through CREI home study programsyou can attain equivalent depth oftraining plus the opportunity ofspecializing in your choice of the majorfields in electronics.

The McGraw-Hill Center forContinuing Education, TorontoOntario, of which CREI is a division hasthe facilities and the expertise to provideelectronics training for entry into allprofessional levels in Canada, fromjourneyman to Engineering Technician,Engineering Technologist and, throughcertain accredited United StatesColleges and Universities, to theBaccalaureate degree.

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This Lab Program helps youunderstand advanced electronics. It alsogives you practical experience in manyother important areas of electronics, asin prototype construction, breadboard-ing, test and measurement procedures,

:)() ETI CANADA - APRIL 1978

Career Training at Home

circuit operation and behavior,characteristics of electronic componentsand how to apply integrated circuits.

Only CREI offers the unique LabProgram. It is a complete college Laband, we believe better than you will findin most colleges. The "Lab" is one of thefactors that makes CREI traininginteresting and effective. And theprofessional equipment in this programbecomes yours to keep and usethroughout your professional careerafter you complete the training.

Engineering DegreeCREI offers you special arrangementsfor earning credit for engineeringdegrees at certain accredited UnitedStates colleges and universities as part ofyour home study training program. Animportant advantage in thesearrangements is that you can continueyour full time job while "going tocollege" with CREI. This also means youcan apply your CREI training in yourwork and get practical experience toqualify for career advancement.

Wide Program ChoiceCREI gives you a choice ofspecialization in 14 areas of electronics.You can select exactly the area ofelectronics best for your career field.You can specialize in such areas ascomputer electronics, communicationsengineering, microwave, CATV,television (broadcast) engineering andmany other areas of modern electronics.

Free BookIn the brief space here, there isn't room togive you all of the facts about CREIcollege -level, home study programs inelectronics. So we invite you to send forour free catalog (if you are qualified totake a CREI program). The catalog hasover 80, fully illustrated pages describingyour opportunities in advancedelectronics and details of CREI homestudy programs.

QualificationsYou may be eligible to take a CREIcollegelevel program in electronics if youare a high school graduate (orequivalent) and have previous trainingor experience in electronics. Programarrangements are available dependingupon whether you have extensive orminimum experience in electronics.

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74 '41


Pseudorandom Number Generator

FLOW CHART

V

/ Enter RandomizingLFac or

Sto e R

Enter A 0 or yourguess

Calculate randomnumber from 0 to IL -K)

T R ((L -K) 97)

D= -T

Is D positive

Yes No

Set new R value

P.O

Round up T

T = T.D

Shift T up to rangebetween K and L

B (K-1)

Figure out display byshifting over guess orprevious digit(s) and

adding new digit

A = 10 A B

Output A

D1

PROGRAM00

3 01

020 03

04

6 05Rc1 5 06

073 08

0 0 095 5 10

A 11

9 9 127 7 13

14FINDS NEXT Sto 2 15RANDOM NUMBER 16

17

3 18

19

20

V A 21

GIN 2223

7 7 24A 25

MEx 26

27Rcl 28

293 30

0 0 31

326 33

DISPLAYS 34RANDOM NUMBER Stop 0 35

The program above runs on the SinclairCambridge Programmable.

A: Last guess or number

B: Random digit from K to L

D: Temporary storage

K: Bottom limit

L: Top limit

R: Randomizing factor

T: Temporary storage forrandom number from0 to (L -K).

1 2 3 4

START

FINISH

Above: the score sheet for thebattle game and left are the listingand flow chart for the overall game.

SOFTSPOT is ETI's programmablecalculator software department. Weknow there are many of you who havegone to a lot of effort to write routinesfor your machines - how aboutsharing the fun. Send us a copy of yourpet program, preferably with flowchart. To make things interesting wewill restrict our choices to only thoseprograms making use of loops orconditionals.

All programs we publish will be paidfor.Mail to: ETI Softspot

Unit 6, 25 Overlea Blvd.,TORONTO, OntarioM4H 1B1

Don't forget to mention what kind ofcalculator you use - and we'd also beinterested to know where you boughtit.

FLOW CHART SYMBOLS

/OInformation Output

Data to be Input

Branch

V0

Operations

Program Entry Point

End


Atomic Decay GameObject - To simulate the decay of M grams of a radioactivematerial with a half-life of H seconds in such a way that: -

1. The player has the opportunity of guessing how muchof the material (plus or minus T grams) is left aftereach second.

2. The player is given indications of right and wrong (hitand miss) guesses.

3. A running total of the player's score is displayed aftereach guess.

EXECUTION1/0/0/Av/sto/ArAv/goto/0/0/0/RUN/ score (0) /Your guess/RUN/Hit-Miss/RUN/ score/Your guess/RUN/Hit-Miss/RUN/score/ etc ...

With the program listing and execution sequences giventhe variables take the following value:-

M = 100 grams. H = 10 seconds. T = 1 gram.

Should you wish to change the variables (When you getused to playing the game) then:To change M Put the new value in place of the 100

at the beginning of the executionsequence.Change lines 21 and 22 in the programto your new value (any 2 key -strokenumber between .1 and 99)

- This variable is the most difficult of thethree to change as it requires calculationof a new F.

To change T -

To change H

N.B.

F = exp(- 693/H)

If the answer is less than one, thenreplace lines 08 to 10 with the threemost significant digits after the decimalpoint. If the answer is greater than onethen replace lines 07 to 10 with thefour most significant key -strokes.e.g. If answer is 0.9330114 then put933 into lines 08 to 10.The only way the answer to thissequence can be greater than one isif your value for D is -ve in which caseyou are no longer working with a

radioactive decay curve but with anexponential growth curve.

See next page for program.

D= Difference between newmass and guess

F= Decay Factor

G= Guess

H= Half Life

M= Initial Mass

S= Score Total of Hits

T= Tolerance on guess

FLOW CHART

Enter Initial Mass

Store M

Start score at zero

S=0

ETI Softspot

Display Score

Enter Guess

Store G

Calculate new mass

M= F=M

Calculate deviationfrom guess and take

absolute value

D = J (M -G),

Is deviation less thantolerance allowed,

DT

Calculate new score

S.S. Display

Display:Hit = 1

Miss = 0


ETI MARKET PLACEWe will allow you up to twenty-five words to advertise items you want to buy or sell, or to publicise meetings of clubs, etc.Advertising will be accepted at our discretion - we will not accept commercial or any form of company advertising.For more insertions mail in again.

Please send in your advertisement on the back of apostcard or empty sealed envelope.

WANTED APRIL/77 ISSUE OF E.T.I. OR REPRINT OF COMPLETE ARTICLECONCERNING 50/100W AMP IN SAME ISSUE. W. MARKIN., P.O.B. 153,

ERRINGTON, B.C. VoR 1VO.

FOR SALE COLLECTORS SPECIAL! AMERICAN BOSCH MODEL 61CB VINTAGEFLOOR CONSOLE RADIO. WORKING CONDITION. $100.00 OR OFFERS. G.R.YAWORSKI, 14 CLIFTON CRESCENT, LONDON OR (519) 681-0154 EVENINGS.

WANTED I WANT TO BUY THE E.T.I. APRIL 1977 ISSUE. WRITE ME IF YOU HAVETHIS RARE ISSUE. BRUNO DORAIS, 524 ST. CLEMENT, BEAUMARNOIS, QUE. J6N2A7.

FOR SALE 2 NEW MARANTZ 250 WATT OUTPUT METERS WITH BOARDS -$80.2250W AMPLIFIER BOARDS R.S. PARTS, RCA INSTRUCTIONS, HEAT SINKS -BEST OFFER. CALL ONTREAL WK -DAYS MORN. (514) 325-1836, BORIS.

FOR SALE SILICON RECTIFIERS 500 M.A. 500 P.I.V. 13¢ EACH, ELECTROLYTICCAPACITORS 12 UF 60V 146 EACH, 325 UF 5 VOLT 126 EACH. DOUG BRYAN, 29DORCHESTER DR., BRAMALEA, ONT. L6T 3C8.

PERSONAL AD CLEANING OUT ELECTRONIC WORKSHOP! MANY PARTS NEWAND USED FOR SALE. SEND FOR LIST. D.W. BRYAN, 29 DORCHESTER DR.,BRAMALEA, ONT L6T 3C8.LOOKING FOR ANY INFO OR MOD ON XTORS RECEIVER VHF NO. R962/ARR-5ZALSO DIAGS ON MULTI PLEXING LED OR GAS DIS & H ON BURROUGHS, 12DIGITREADOUT NO. BR13451 OR 16 DIGIT PANAFLEX BURROUGH NO. 16401 (KR85). IF BURROUGHS CAN DO IT E.T.I. READERS CAN. J.J. BOURE, 454 NOTREDAME AVE., ST. LAMBERT, Pa J4P 2K4.

FOR SALE 1 ONLY 604-B 16 OHM 15 IN. DUPLEX SPEAKER WITH ORIGINALCROSSOVER - COLLECTOR'S ITEM. BEST OFFER. DONATO C., 10451 ROME AV.,MONTREAL -N, QUEBEC H1H 4N8. PROMPT RESPONSE.

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WANTED DEMANDE LIVRES ET PERIODIQUES MECANIQUE ELECTRONIQUEPHOTO ENVOYEZ LISTE & PRIX. WANTED BOOKS AND MAGAZINES MECHANICELECTRONIC PHOTO. SEND LIST & PRICES. LACHAPELLE, 3924 MENTANA,MONTREAL, QUE. H2L 3R8.

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Atomic Decay GamePROGRAM

0001

SCORE DISPLAYED Stop 02A 03

MEx 040506

CALCULATES NEXT A 07

VALUE OF DECAY 9 08CURVE 3 3 09

3

101

9 A 12

MEIg 13

Re) 1:16

FINAL VALUE COMPARES GUESS 7

OF BRACKETS WITH VALUE 18

ADDED TO CALCULATEDTOTAL PLUS OR MINUS 3 20PUNNING C GRAMS 0 21

SCORE 2223

A 24

UN 25CALCULATES 3 3 26

HIT/MISS FIGURE 27

1 HIT 28

0 MISS 29

303 31

3233

HIT/MISS DISPLAY Stop 346 35

The program above runs on the Sinclair CambridgeProgrammable.

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tech -tipsBATTERY OPERATED VCOR. Zaman.

BY USING the LM3900N quad -op -

amp, a simple portable batteryoperated VCO can be made verycheaply. Al forms a integrator, theramp rate depending on the voltage Viand capacitor C. This ramp is fed to aSchmidt trigger which switches atabout 5.8V, making Al ramp down,generating a triangular wave of about0.85 V.

The Schmidt trigger feeds a tran-sistor switch and an emitter follower.

The triangular wave is then fed toA3 which acts as an inverting amp-lifier, and the output is fed to A4which is an exponential integrator setat a pseudo -ground of 4.5 V. The biasand gain pots must be adjusted togive the best sine waveform.

MARK SFACERATIO

V, 0 5V--152_, .AXAt 1

0-0 500k

1E1

100k100k

Al

101

w10k

Tech -Tips is an ideas forum and is not aimed at the beginner.ETI is prepared tc consider circuits or ideas submitted by

readers for this page. All items used will be paid for. Draw-ings should be as clear as possible and the text should prefer-ably be typed. Circuits must not be subject to copyright.Items for corsideration should be sent to ETI TECH -TIPS,Electronics Today International, Unit 6, 25 Overlea Blvd.,Toronto, Ontario, M4H 1B1.

-/V/\F-0100k

range of about 1 :100. Capacitor C+0.5 <-+ 15 .0 V, giving a frequency can be any value from 1 On< --->47 n and

Vi can be any positive voltage from

NOVEL LOUDSPEAKERCOUPLING CIRCUITP. Mills.

In most amplifier designs the speaker is fed by a high value capacitor toprovide DC blocking, but this may result in a heavy switch -on surge, as thecapacitor charges up.

An alternative approach, which is worthy of experiment, is shown in thediagram below. Here the ground side of the speaker is connected to thejunction of two equal high value capacitors (1000 uF is typical), across thesupply.

The amplifier output voltage will be at Vs/2, and so will the voltageacross C1 (if C1 and C2 are equal); so as the supply voltage builds up, the DCvoltage across the speaker will remain zero, eliminating the switch -on surge.The circuit is shown with the LM380,but could be applied to any amplifiercircuit, providing that theDCvoltageat the output s half the supply voltage.

IC1 IS LM 330

LS18R

INPUT

+18V

C21000u

Cl10000

OV

0

the outputs have a low distortion up toabout 20 kHz.

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58

ETI Tech Tips

CHANNEL SPLITTER FORRADIO CONTROL

G. Bathe.

This circuit is designed to replace theelectromechanical reed units used as

channel-splitters in radio controlledmodels.

The circuit is based on the MC 1310Pintegrated circuit, a chip that is prim-arily a stereo decoder for use in stereoradio tuners. When used as a stereo de-coder, the MC 1310P automaticallyswitches itself from the mono modeto the stereo mode whenever its inputcontains the 19 kHz subcarrier of a

stereo multiplex signal at a sufficientlyhigh level (16 mV), and switches backto the mono mode when the 19 kHzsubcarrier ceases to be present. Pin 6of the integrated circuit drives a stereoindicator lamp to give a visual indicationof whether the circuit is operating in thestereo or mono mode.

It is this lamp driver facility of theMC 1310P that makes it an ideal chipto use as a channel-splitter. When usedas a channel-splitter the circuit is nottuned to the 19 kHz of the stereodecoder but to the audio frequency thatthe circuit is required to detect, and thelamp driver output from pin 6 is used todrive a power transistor controlling amotor or other device.

The output from the detector of aradio receiver is amplified by the2N3904 and then fed into a series ofMC 1030P channel-splitters (connectedin parallel) each tuned to a differentaudio frequency.

The audio frequency to which thechannel-splitter responds is determinedby the tuning circuit R1, VR1 and C1,and is given by the formula: -

f= 1

27T C1 (R1 + RV1)Hz

The value of C1 is chosen to givethe required tuning range for the presetRV1. For example, if C1 is 10,000 pF,then the tuning range is approximately750 Hz to 1,000 Hz.

The output is a switched current out-put between Pin 6 of the chip and thepositive supply rail. This current shouldnot exceed 35 mA and so a 470 ohm re-sistor is inserted in the output connect-ion from Pin 6 as short circuit protect-ion. If a voltage output is required thena resistor can be connected from Pin 6to the positive supply and the voltageoutput taken from Pin 6.

L1

0

TO OTHER MC1310P CIRCUI `STUNE 0 TO DIFFERENT AUDIO

REOLENCIES

566

INPUT I HoMDE TEC TOR 01H c RECEIVE

211

417

all

2N3904

250u

100u

411 4708 OUTPUT

CURRENT

4 13

3 4 1 6

MC 1310P

12 11 8

16

250n

AUDIOTUNINI1RV1sk

500.

1-11-1250n

SO.

0.12V

MOTOR

PNPPOWER -TRANSISTOR

110

The MC 1310P is triggered when theinput to Pin 2 contains its tuned fre-quency at a level greater than 16 mV.It can be triggered by noise if the noiselevel is greater than 16 mV. Some radiocontrol transmitters tend to transmitnoise when they are not transmitting a

CMOS RADIOJ. P. Macaulay

The circuit shown is of a simple AMreceiver based on the 4011 CMOS IC.

The four gates in this package areused as linear amplifiers by connectingtheir inputs together and applyingnegative feedback.

Ll, 80 turns of 22 SWG enamelledwire close wound on a 3/8" diameterferrite rod, is the pickup coil. This istuned by the 500p trimmer and theresulting tank circuit referred to ground .at RF by C1.

The high input impedance, that ofIC1/1, 'seen' by the tank circuit ensuresthat little damping occurs, and thus the

0

tone, and if this is the case the trans-mitter should be modified to preventnoise being transmitted. This couldbe done by making the transmittertransmit an extra unused tone when-ever it is not transmitting one of theused audio tones.

receiver is highly selective. The outputof IC11/1 is an amplified RF signal andis passed to IC1/2 for detection.

The unwanted RF appearing at theoutput of the detector is removed bythe km/pass filter formed by R4 and C2.

The audio signal is then fed to anamplFier formed by IC1/3 and IC1/4.

The circuit's current consumption isabout 10 mA when operated from a 9 Vsupply.

Ncte that the IC used must be a 4011AE and not the 4011B whose

input protection network will preventit from operating in the linear mode.

C2 D1=1N9141508 IC1=4011AE

R84M7


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The Ontario DXAssociationODXA Headquarters, 1202 York Mills,No. 1910, Don Mills, M3A 1Y2.Alms and Objectives: The Ontario DXAssociation, ODXA, is a body of Ontarioradio listeners which seeks to unify lis-teners in this province and assist them togrow in and enjoy the hobby more. This isdone by means of a monthly bulletin,entitled "DX Ontario", personal contact atlocal and province -wide meetings andother means of communication amongstthe members. The ODXA is also com-mited to promote the hobby to the publicand assistance and information is pro-vided to those expressing an interest.

The idea to form the ODXA originatedin the summer of 1974 and a three-manorganizing committee then undertook tobring the club into reality. By February of1975 our first bulletin was off the press.The club has continued to grow at asteady rate since that time and "DXOntario" has been published monthlyever since.Newsletter: "DX Ontario" presentlyaverages 40 to 45 pages per month anddeals primarily with listening to themedium and short wave bands. There arecolumns of loggings and verifications aswell as news and schedules. We alsohave a monthly column discussing theprogramming heard on shortwave. Othercolumns include articles on stations,equipment, DX programs, and Englishbroadcasts audible in Ontario.Meetings: In the Toronto area membersof the ODXA may attend a meeting heldon the first Monday of each month, at 7:30pm at the Downsview Public Library(Keele and Wilson). Often there aremeetings held on Saturdays at the homesof members. And there are one or twoweekend -long get-togethers held eachyear. All of these meetings are publicizedin advance in "DX Ontario". Any listeneris welcome to attend, and information onupcoming meetings may be obtainedfrom ODXA Headquarters.Directors: The ODXA is operated by themembership. An elected three-manBoard of Directors directs club opera-tions, supervising other such staff as

Club CallPublisher, Managing Editor, Treasurer,Membership Secretary and Publicity andAwards Committees. Approximately teneditors are on staff to edit the columns forthe bulletin.Membership: Membership in the ODXAis restricted to residents of Ontario.Annual dues are $11.00 (special rate of$8.00 for full-time students). Membersreceive a certificate, personal identifier(number), 12 issues of "DX Ontario" andare entitled to participate in all club elec-tions and activities. Members areencouraged to make contributions to thebulletin, such as their loggings, reports ofverifications received, etc.

If you would like to inquire about joiningthe ODXA, write to: ODXA MembershipSecretary 18 Riverview Road Lindsay,Ontario K9V 1B1.

The Canadian ComputerCorrespondence Clubfor Hobbyist ComputerUsers5768 Davies Ave. Cote St. Luc, Montreal,Quebec, H4W 2R4.Aims and Objectives: We at CCCC are acomputer mail correspondence clubformed to aid the hobbyist in program-ming in the most common hobbyist lan-guage, BASIC. We are non-profit andrequest that all new members enclosestamped, self-addressed envelopes or atleast enclose an extra postage stampwhen writing to us, so that we may keepexpenses down.Membership: Any person wanting tojoin, whether this person has access to orowns a BASIC computer, or not, will beaccepted. Bimonthly (and maybe evenmonthly, depending on the number ofmembers) newsletters will be sent out. Inthese letters, we will include informationabout the club, answers to members'problems, and interesting programs thatmembers have sent in.

Contributions in the way of programswill be greatly appreciated. If a memberhas a program that has a bug in it, wewould be glad to offer any assistance.Executive Members: We, the executivemembers of CCCC, are experienced

;programmers in BASIC and we would liketo hear and correspond with other com-puter enthusiats. We feel that we haveenough experience to solve or help solvealmost any problem.

I am presently the Chairman and theChief Public Relations Officer of CCCC,and I hope to be able to have many ETIreaders as members. There is no presentcharge for membership. Interested par -

should send a SASE (self-addressed,stamped envelope) to the club address.

M. Salonin

Club HelpI am working with students at our smallschool in Elphinstone (pop. 215), grades7-12. There are a few students interestedin electronics and lately we decided toget together weekly at noon. That's howECEC (Elphinstone Collegiate Elec-tronics Club) got together.

We started by dismantling TVs andother old equipment for parts, and by fix-ing minor ailments in electronic equip-ment.

Is there anyone who can suggest howwe might obtain electronic componentsand appropriate projects for beginners inelectronics with a very limited budget?The club would also be interested inhearing, from anyone who started outusing salvaged components, what canbe done with them in terms of buildingprojects.

E.M. Shemeliuk, ECEC, Box 157,Elphinstone, Man. ROJ ONO.

Previously ListedClubsTRACE: Computer Club, Toronto. See p7Jan 78 ETI.CSWLI: SWL Club, Thunder Bay. See p7Mar 78 ETI.TRAC: Amateur Radio Club, Thornhill.See p7 Mar 78 ETI.

Club CallSend information about any clubs notmentioned on this page to ETI Club Call,ETI Magazine, Unit 6, 25 Overlea Blvd.,Toronto, Ontario, M4H 1 B1.


DIODES/ZENERS SOCKETS/BRIDGES TRANSISTORS, LEDS, etc.1N914 100v 10mA .05 8 -pin pcb .25 ww .45 2N2222A NPN 12N2222 Plastic .10)1N40051N4007

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.25 ww

.25 ww.40.40

2N2907A2N39062N3904

PNPPNP (Plastic)NPN (Plastic)

1N4148 75v 10mA .05 18 -pin pcb .25 ww .75 2N3054 NPN1N753A 6.2v z .25 22 -pin pcb .45 ww 1.25 2N3055 NPN 15A 60v1N758A 10v z .25 24 -pin pcb .35 ww 1.10 T1P125 PNP Darlington

LED Green, Red, Clear, Yellow1N759A 12v z .25 28 -pin pcb .35 ww 1.45 D.L.747 7 seg 5/8" High corn -anode1N4733 5.1v z .25 40 -pin pcb .50 ww 1.25 XAN72 7 seg corn -anode (Red)1N52431N5244B1N5245B

13v14v15v

z

z

z

.25

.25

.25

Molex pins .01

2 Amp BridgeTo -3 Sockets

100 -pry

.45

1.20

MAN71MAN3610MAN82AMAN74A

7 seg com-anode (Red)7 seg corn -anode (Orange)7 seg corn -anode (Yellow)7 seg corn -cathode (Red)

25 Amp Bridge 200 -pry 1.95 FND359 7 seg corn -cathode (Red)

C MOS4000 .154001 .154002 .204004 3.954006 .954007 .354008 .954009 .454010 .454011 .204012 .204013 .404014 .954015 .904016 .354017 1.104018 1.104019 .504020 .854021 1.004022 .854023 .254024 .754025 .304026 1.954027 .504028 .954030 .354033 1.504034 2.454035 1.254040 1.354041 .694042 .954043 .954044 .954046 1.754049 .454050 .454066 .954069 .404071 .354081 .704082 .45

MC 14409 14.50MC 14419 4.85

- T T L -

.15

.15

.10

.10

.35

.50

.35

.151.951.251.251.251.251.501.25

7400 .15 7473 .25 74176 1.25 74H72 .45 74S1337401 .15 7474 .30 74180 .75 74H101 .75 74S1407402 .20 7475 .35 74181 2.25 74H103 .75 74S1517403 .20 7476 .40 74182 .95 74H106 .95 74S1537404 .15 7480 .55 74190 1.75 74S1577405 .25 7481 .75 74191 1.05 74 LOO .25 74S1587406 .35 7483 .95 74192 .75 74L02 .25 74S1947407 .55 7485 .75 74193 .85 74 LO3 .30 74S257 (812317408 .25 7486 .25 74194 1.25 74 LO4 .307409 .15 7489 1.35 74195 .95 74L10 .30 74 LSOO7410 .10 7490 .55 74196 1.25 74 L20 .35 74 LS017411 .25 7491 .95 74197 1.25 74L30 .45 74 LS027412 .30 7492 .95 74198 2.35 74 L47 1.95 74 LSO47413 .35 7493 .35 74221 1.00 74L51 .45 74 LSO57414 1.10 7494 .75 74367 .85 74L55 .65 74 LSO87416 .25 7495 .60 74L72 .45 74LS097417 .40 7496 .80 75108A .35 74L73 .40 74 LS107420 .15 74100 1.15 75110 .35 74L74 .45 74 LS117426 .30 74107 .35 75491 .50 74L75 .55 74 LS207427 .45 74121 .35 75492 .50 74L93 .55 74 LS217430 .15 74122 .55 74L123 .85 74 LS227432 .30 74123 .55 74H00 .15 74 LS327437 .30 74125 .45 74H01 .25 74S00 .35 74 L$377438 .35 74126 .35 74H04 .20 74S02 .35 74 LS407440 .25 74132 1.35 74H05 .20 74S03 .30 74 LS427441 1.15 74141 .90 74H08 .35 74SO4 .30 74 LS517442 .45 74150 .85 74H10 .35 74S05 .35 74 LS747443 .65 74151 .65 74H11 .35 74S08 .35 74 LS867444 .45 74153 .75 74H15 .45 74S10 .35 74 LS907445 .65 74154 .95 74H20 .30 74S11 .35 74 LS937446 .95 74156 .95 74H21 .25 74S20 .35 74 LS1077447 .95 74157 .65 74H22 .40 74S40 .20 74 LS1237448 .65 74161 .85 74H30 .20 74S50 .20 74 LS1517450 .25 74163 .85 74H40 .25 74S51 .25 74 LS1537451 .25 74164 .60 74H50 .25 74S64 .20 74LS1577453 .20 74165 1.50 74H51 .25 74S74 .35 74 LS1647454 .25 74166 1.35 74H52 .15 74S112 .60 74 LS3677460 .40 74175 .80 74H53J .25 74S114 .65 74 LS3687470 .45 74H55 .20 74C047472 .40 74C151

9000 SERIES9301 .85 95H031.109309 .35 9601 .459322 .75 9602 .45

MICRO'S, RAMS,CPU'S, ETC.

74S188 3.001702A 4.50MM5314 3.00MM5316 3.502102-1 1.452102L-1 1.75TR1602B 4.50TMS 4044-45N L 14.508080AD 12.008T13 1.508T23 1.508T24 2.008T97 1.002107B-4, A 4.002708 11.50

MCT2 .95 LIN EARS, REGULATORS, etc.8038 3.95 LM320T5 1.65 LM340K15 1.25LM201 .75 LM320T12 1.65 LM340K 18 1.25LM301 .45 LM320T15 1.65 LM340K24 .95LM308 (Mini) .95 LM324N .95 78L05 .75LM309H .65 LM339 .95 78L12 .75LM309K (34oK-s 185 7805 (340T5) .95 78L15 .75LM310 1.15 LM340T12 1.00 78M05 .75LM311D (mint) .75 LM340T15 1.00 LM 373 2.95LM318 (mini) .95 LM340T18 1.00 LM380 (8-14 PIN) .95LM 320K 5(78o5)1.65 LM340T24 .95 LM709 (8,14 PI N).25LM320K 12 1.65 LM340K 12 1.65 LM711 .45

INTEGRATED CIRCUITS UNLIMITED7889 Clairemont Mesa Blvd., San Diego, CA 92111 U.S.A.

No MinimumAll prices in U.S. dollars. Please add postage to cover method ofshipping. Orders over $100 (U.S.) will be shipped air no charge.

Payment should be submitted with order in U.S. dollars.All IC's Prime/Guaranteed. All orders shipped same day received.

.40

.55

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.35

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1.10.50.65.65.95.95.85

1.00.95

1.20.85

1.90.75.75.25

2.25

LM723 .50LM725N 2.50LM 739 1.50LM 741 (8-141.25LM747 1.10LM 1307 1.25LM1458 .95LM3900 .50LM75451 .65NE555 .50NE556 .95NE565 .95NE566 1.75NE567 1.35

SPECIALDISCOUNTS

Total Order Deduct$35 - $99 5%

$100 - $300 10%$301 - $1000 15%

$1000 - Up 20%

Phone (714) 278-4394 BarclayCard / Access / American Express / BankAmericard / Visa / MasterCharge

FEEDBACKPCBs AND VEROBOXES

I want to make the ETI Option Clock:where can I obtain the PCB and at whatprice?

Also, who is the distributor for theVerobox, and is it possible to obtainone catalogue?

N.M., Thetford Mines

ETI PCBs are advertised in themagazine (there is at least onecompany who supplies them for allprojects). The distributors for Veroboxare Electronic Packaging Systems POBox 481, McAdoo Park, Hwy 38,Kingston, Ont K7L 4W5. Cataloguesare available from this company.

4

You Can Write, Draw or AdvertiseAnything You Like in This

ANSpace, for Only

..:::::.

FOR MORE DETAILS CALL

Peter Priest416 423 3262

COVERS & CODES

In your "Feedback" column of Aug 77 acouple of readers were bitching aboutyour June 77 cover - can one judge abook by its cover? If an individual isfamiliar with your publication onemight expect that individual to concernhimself not only with the cover, butalso the contents. I'm wondering if thesame individuals wrote back thefollowing month regarding your July77 cover, claiming subliminal signifi-cance of the young lady and/or thebeverage. Some people can find faultwith anything! I'm sure you'd becriticized by someone if your nextissue appeared with no picturewhatsoever on the cover (lack of

imagination).Allow me to commend you on your

adoption of the International Standardof component notation and units in anattept 'o eliminate errors. It obviouslyworks well for resistance andcapacitance values (4k7, 5p6, etc.) sowhy not other measurements as well?eg, 6V3 for 6.3V, 1A5 for 1.5A, etc.

Back to covers again - your May 77cover was absolutely stunning! With abit of cropping, I think it would make anexcellent conversation -piece to frameand proudly display on the wall of myshop.

T.McD., Hyde Pk., Ont.

eve Stec tronic.1 AH L2 GH R Y

WESTERN CANADA'S ELECTRONIC CENTRETTL

7400 $ .24 7474 $ .427402 $ .24 7475 $ .647404 $ .24 7476 $ .487406 $ 32 7485 $1.357408 $ .28 7486 $ .427410 $ .24 7490 $ .637411 $ .26 7491 $ .907413 $ .54 7492 $ .607414 $ .98 7493 $ .607416 $ .33 74121 $ .457417 $ .33 74123 $ .697420 $ .25 74125 $ .537427 $ .40 74145 $1.197430 $ 24 74150 $1.957432 $ .33 74154 $1.507440 $ .24 74161 $1.147441 $1.19 74163 $1.307442 $ .69 74177 $1.097447 $ .98 74191 $1.607448 $1.15 74192 $1.147450 $ .25 74193 $1.147451 $ .25 74194 $1.14

7473 $ .42 74196 $1.60

RESISTORS1/4 & 1/2 watt . . .04 ea. or

$3.00 per 100YOUR CHOICE FOR MIXED VALUES

CMOS4000 $ .28 4020 $1.47 4052 $1.404001 $ .28 4023 $ .28 4066 $ .984002 $ .28 4024 $1.16 4071 $ .384007 $ .28 4025 $ .28 4072 $ .384011 $ .28 4027 $ .57 4081 $ .384012 $ .28 4046 $2.30 4082 $ .384013 $ .61 4049 $ .61 4511 $1.894017 $1.30 4050 $ .61 4518 $1.404018 $1.30 4051 $1.40 4528 $1.53

DIODES ZENER DIODES

1N914(4148) $ .09 1N746to 1N759 $ .17

1 N4001 $ 09 1N47281N4002 09 to 1N4752 $ .231 N4003 .10 1N47531 N4004 .10 to 1N4764 $ .331 N4005 .11 1 N 52211N4006 .11 to 1N5257 21

Send cheque or Money OrderDO NOT SEND CASH

LINEARLM301ANLM308NLM311HLM324NLM376NLM555NLM556NLM709CNLM723CHLM733CNLM739CNLM741CNLM1458NLM3900N

$ .53$1.33$1.32$1.33$1.60$ .64$1.18$ .49$ .75$1.46$1.66$ 47$ .78$ .92

I.C. SOCKETSlow profile

8 pin14 pin16 pin18 pin22 pin24 pin28 pin40 pin

2529293948556492

TRANSISTORS2N2222 $ .252N3055 $1.002N3819 $ .332N5525 $ .402N6027 $ .472N6028 $ .47TIP29A $ .55TIP30A $ .65

Further Prices Available Upon RequestOrders under $25 add $1 Post. & Handling

Minimum Order $5.00 Please - Prices Subject To Change Without Notice


ETIPublications

Canadian Projects Book No. 1 $3.00Top projects from the early issues of ETI's Canadian edition, plus some of the projectsfromtheUK edition's issues whichwere distributed in Canada in 1976. All projects use parts available in Canada. Those projects from UK edition have beencompletely re -worked in Canada for Canadian constructors. Includes a series of modular disco projects, plus games,biofeedback, metal locator, etc.

Circuits No. 1 $5.00A brand new concept from the house of ETI. More than 100 pages packed with a wide range of experimenters circuits.Based on the 'Tech Tips' section carried in the overseas editions of ET, Circuits 1 is the first of a series of specials -produced for the enthusiasts who know what they want, but not where to get it! Circuits 1 will also act as a catalyst forfurther development of ideas, ideal for the experimenter. The collection of more than 200 circuits is complemented by acomprehensive index, making searches for a particular circuit quick and simple. Also, similar circuits can be comparedeasily, due to the logical layout and grouping used throughout. Last and by no means least, Circuits 1 has no distractingadvertisements in the main section!

Top Projects No. 3 $2.50Twenty-eight projects from the UK edition of ETI. Includes Twenty -Five Watt Hifi Amp, FM Tuner, Line Amp, DualBeam Scope Adapter, Impedance Meter, DVM, Ignition Timing Light, Colour Organ, Radar Intruder Alarm, ElectronicIgnition, Fluorescent Light Dimmer, Drill Speed Controller, etc.

Top Projects No. 4 $2.50Now available in Canada, this book contains 27 projects reprinted from the UK edition of ETI. Includes WaaWaa, HifiAmp, Car Alarm, Audio Millivoltmeter, Pushbutton Dimmer, Expander -Compressor, Dual Tracking Power Supply,Photo Timer, Car Amp, Touch Switch, Exposure Meter, etc.

Electronics it's easy Volume 1 $3.50*The best introductory series to electronics ever published in a magazine. Volume three completing the series, will beavailable in a few months. Volume One introduces electronics to the beginner by going through the systems approach,basic concepts, meters and measurements, frequency and wavelengths, electronics and communication, capacitanceand inductance, capacitive and inductive reactance, resistance, capacitance and inductance in combination, detectionand amplification, elements of transistor amplifiers, emitter followers and DC amplifiers, and basic operationalamplifiers.

Electronics it's easy Volume 2 $3.50*Volume Two introduces the sources of power, simple power supplies, how regulated power supplies work, genera;purpose supplies, generating signal waveforms, generating non -sinusoidal waveforms, all about electronic filters,more about filters, introducing digital systems, the algebra of logic, integrated circuit forms of logic functions, digitalsub -systems, counters and shift registers.

V.,64600600000)* ..N.Matalterefee.,,,w

$6.00 For Both*

Send your order, with payment (not cash), to ETI PUBLICATIONS,

Please specify which publications you require,and print your name and address clearly.

Electronics Today InternationalUnit Six

25 Overlea BoulevardToronto, Ontario

M4H 1B1


16 re

GE 16F

THAT NEW ANTENNA I DESIGNEDIS SOMETHING ELSE, I JUST GOTA RECEPTION REPORT FROMALPHA-CENTAURII

YES SIR, FRED, THIS IS A QUALITY PRODUCTYOU'VE GOT HERE: THE BREAKDOWN VOLTAGELISTED IN THE MANUAL IS DEAD -ON.

GE/6 E

I SHALL BE CERTAIN TO GIVE YOUR CALCULATOR AN A+,JONES. YOU, HOWEVER, WILL BE RECEIVING AN F.

The

FunofElect-ronics

I BELIEVE WE'RE IN TROUBLE, SIR: THE LATESTRESEARCH FIGURES SHOW THAT IT TAKES 10MONTHS TO DEVELOP A NEW PRODUCT. ANDONLY 6 MONTHS FOR THAT PRODUCT TOBECOME OBSOLETE.

MUM

Et6 Ge

616Eg'

WHAT'S THE MATTER, HAVEN'T YOUEVER SEEN A VACUUM TUBE BEFORE?


INFORMATION

COMPONENT NOTATIONS AND UNITSWe normally specify components using the recentlyagreed International Standard. Many readers will be un-familiar with this but it's simple, less likely to lead to errorand will be used by everyone sooner or later. ETI hasopted for sooner!

Firstly decimal points are dropped and substituted withthe multiplier, thus 4.7uF is written 4u7. Capacitors alsouse the multiplier nano (one nanofarad is 1000pF). Thus0.1uF is 100n, 5600pF is 5n6. Other examples are 5.6pF

5p6, 0.5pF == Op5.Resistors are treated similarly: 1.8M ohms is 1M8,

56k ohms is 56k, 4.7k ohms is 4k7, 100 ohms is 100R,5.6 ohms is 5R6.

BACK ISSUESPrevious issues of ETI-Canada are available direct fromour office for $2.00 each. Please specify issue by themonth, not by the features you require.

EDITORIAL QUERIESWritten queries can only be answered when accompaniedby a self-addressed, stamped envelope, and the reply cantake up to three weeks. These must relate to recentarticles and not involve ETI staff in any research. Markyour letter ETI Query.

MA 1002 AC Clock Mod $14.95, +TR &SWS $19.95MA 1003 12 VDC Car Clock mod +3SWS $24.95Strong Stn Wagon Tailgate Mtr 12VDC

$ 4.95IC SOCKETS 8-25d, 14-25d, 16-30d, 24-25d

40-$ 1.00FM -1 FM wireless Mike Kit 100 FT Range

$ 2.95FM -2 Ditto with 1 Trans Mike Preamp

$ 4.95MG -1 Mag Stereo Preamp Kit High Sens

$ 5.95MG -2 Mag Stereo Preamp & Control Kit

$14.95CPO -1 Code OSC Kit . . $2.95, Brass Key

$ 3.95LO -1 Light Organ Kit 200 W per chan (3)

$12.9514V -5.5A Trans . . $5.95, 100V -25ABridge $ 3.5012VCT-500MA . . . $1.50, 25V-200MA

$ 1.5016VCT-300MA + 21V200MA . . $1.50,50VCT-200MA . . . . . . ...... $ 1.5053VCT-2A . . . $4.95, 2200 UFD-35C .

50d .. 10/ $ 4.00Heavy Duty Line Cords 2 Wire. 50d, 3Wire 1354!

C.O.D., Chargex, Mastercharge, Collectall OK

Send for our FREE 1978 CatalogueARKON ELECTRONICS LTD.,

91 QUEEN ST.E., TORONTO, ONT.M5C 1S1

(416) 868-1315

NON-FUNCTIONING PROJECTSWe cannot solve the problems faced by individual readersbuilding our projects unless they are concerning inter-pretation of our articles. When we know of aly error weshall print a correction as soon as possible at the end ofNews DigeSt. Any useful addenda to a project will besimilarly dealt with. We cannot advise readers on modifi-cations to our projects.

COMPONENT STORESETI is available for resale by component stores. We canoffer a good discount and quite a big bonus, the chancesare customers buying the magazine will come back to youto buy their components.

PRICESAll prices quoted in the editorial of ETI are in Canadiandollars, except where stated. Advertisers in U.S. may giveU.S. dollar prices. Where we only know an overseas price,e.g. in U.K. pounds, we convert approximately to Cana-dian dollars, erring on the conservative side, where possi-ble.

COMPONENT SUPPLYWe do not supply components for our projects and areunable to supply advanced information on componentsused in any projects. However to enable readers to obtainprinted circuit boards without undue delay we will besupplying retailers and manufacturers with certain p.c.board designs. Any company interested in receiving suchdesigns should write to us on their headed note paperrequesting details.

CLASSIFIED

J & J ELECTRONICS LTD.,P.O Box 1437 E,Winnipeg, Manitoba R3C 2Z4Semiconductor SpecialistsDo you get our bargain flyers? Send$1.00 to receive the current literatureand specials and to be placed on themailing list for the future publications.

SUPERSTRIPThe Quality Full -Size Breadboard

ONLY

$1995

840 NICKEL -SILVER TIE POINTS6% in. x 2% in. (165mm x 57mm)

B.C. add 7% tax. Handling 65c/orderFor rush delivery, send M.O. to:Wolverton Enterprises, 5, S. HytheAvenue, Burnaby, B.C. V5B 3H6.

AUDIO KITS BUILD YOUR OWN AND SAVE20+20W Stereo Amp. with

Tone and Power Supply30+30WStereo Power Amplifier40+40W Semi -Assembled Stereo

132:88Power Amp. $38.00

50+50W Stereo I.C. Drive POW. Amp. $47.00AUDIOVISION SERVICE

P.O. BOX 955, STN. B. WILLOWDALE, ONT.M2K 2T6

AMPLIFIER KITS,ELECTRONIC PARTS

New, expanded FREE '78 catalog,new lower competitive prices.

50W/50W complete stereo kits $155.0060W low TID pow module $38.00100W low TID pow module $70.00Class -A 60W pow module $130.00Stereo low TID pre -amp $95.00Stereo Active tone -control $40.00MJ802/MJ4502 5MHz 200W $8.50/Pr.2N3055/MJ2955 2MHz 100W $3.00/Pr.1N4148 .05, 1N4003 .10, 2N5088 . 25LM -741 .30, LM -1310 1.50, LM -555 .557400N .22, 7404N .22, 7490 .60Resistor .05, capacitor .10, etc.Post. & pack. add 100/0, Que.Res. add8% S.T.

COMPUTRONICSP.O. BOX 531, STAT. "H"

MONTREAL, QUEBEC H3G 1R0


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