BUYER'S GUIDE TO DIGITAL MULTIMETERS ^ All you need to know i before you buy your next DMM I ^ _ MAY 1992 Gimmes. STEREO ??ERVICE Let MIDI control more than musical instruments with our MIDI LIGHT CONTROLLER Easy-to-Build DIGITAL ALTIMETER is a fun project! Build a DEVELOPMENT SYSTEM for the 1802 microprocessor Build a simple SOLID-STATE REUY j and control the world with digital circuits! 59933 - S-DIGir 53151 W 75a456HRR5165rin93 D5 11 \m S3 4B We Only Skimped OnThe Price. Introducing The Ruke Series 10 — From $69.- Actual size: Easy to carry, easy to use. Newf V Chek'": For fast accurate checks on power sources and suppJEes. set your meter on V Ctiek— and let it do the rest. V Chek will deternnine continuity/ohms; if vollage Is present, it wilt autom^iicBffy change modes to measure Au or DC volts, whichever ts detected. For most iniiial troubleshooting checks, here's the only setting you need to make. Fluke quality: Made in the USA by Fluke, with the same rugged reliabillly that's made us the world leadsr in digital multimeters. Counl on hard -v.ro rking high performance — and a two-year v/arranty to back it up. Large, easy-Jo-read display: 40DD count digital readout. Audltile Conlinuity: To perform fast conHnutty checks, just listen for the beep; no need to watch the display. F(uliilt) New! Min/Ma)( record w^lh relative time stamp and Continuity Capture'": Makes intermittent problems easier to find. Records highs and Jows— and ' lime stamps ' v/hen they occurred. In continuity mode, opens or shorts as brief as 250 MS are captured and displayed. Capacitance: Autoranging from .001 uF to 9999 pF. No need to cafiy a dedicated capacitance meter. For high perlormance at Fluke's Id west price, get your lands on Ihe new Series 10. Stop by your local Fluke distributor and feel v;hat a pov/erful difference the right muitimeler makes — at the right price, For a free product brochure or the name of your nearest distributor, cal El -800-87- FLUKE. 4Q0D CQuntdl^iUl display 1.5% tasiCdc voJts accuracy 2S^i basic acvDtls 1.5% basic onir^ accuracy Fast conttritiity Oiods Test Sltep Uq^h Two-yiar warranty Fluke 11 S7&.93- V CJieit^^ C^p^citanc«. 001 t3 9999iiF 4OQ0 count digrial O S's, basic ie> table pJarn or infc*Tn«tKjfi r^HatinQ lo n«wtwOfthf pn?n ^UO^O'ELECTn0^flCS may nftji» txa of ba CQv«f«d hy US. patenti. RADfO-ELEQTRONICS ditclaim^ arty lj«btlitf For IKa K5tfingtffi*nt $ych patents by ih* m^lufig, i^^trtg, or tilling of Airy luch aq^W^^ne^t or cincuttry, mnd liiggesls thai a^yi»i« irit«i¥lt*d in mch projectx cansuH a pdtvfit attoifwy. RAD^O-EUCmONfCS. BSSN 0033-7362) Aph\ ^992 PWMi*h»d monmy by Gem*b#cfc Publie*(ion». Inc , WB Bi-Cowfity Boul«v3Jii. F^vmingdala, MV S^cond-CUu pQitAg* ptid mi Fannin^l«. NY and adtitiCHur mailing elfic«s Second- Clan maul rrQitrrai^Dn No flt2S1662BO. authonied atTortjnio. Canadii One^ye^r ^ut^$cHpbon rots IT S A and pos9««mion$ S17 97. Canadj S25 65 [mcfudes G S T Can^Jdn Coodi and 5«rvi^ccs Jitx fWgfsiraiion No Rl2SI&£780). all other counifios $26 47. All tubt^ripbon order's payjible rri U,S A tund% only, via Jmterriatiorual poaUl money order qi check drawn on a U SA bank. Single copiei Sa &S 1992 by G«m3J3«ck PtiblicAtiDni, Itjc. AJI righu rtMfved Prinled in U S A POSTMASTEfti Ptea» und addraia changts to BAOlO ELECTHONICS. Subscnpljon EJapl,. Bo> BouMer. CO A ttamped »eH -a4dfeu«l envelope mutt accam|iBny all tubmittvd manuscripts and/or artwork or pholographa if their rvtum is deijrqd s^^uld Ihtry be rviectad. We disclaim any respontibillity lor the kiss or dJimage of nWMiuifripts pnd/or irtwodt or photographs while in our poss«ssjcn or otherwise. HaqoCwmh&dk UBB^\^7^ rounder Lsrry Stockier, EHF. GET. edilor^n- chief and ptibfishef EOfTORlAL OEPARTMENT Brian C. Fenton, editor Neil Sclatar, as»oci«te editor Tflrt Sc^duto, difti^nt editor Jeffrfiy K* Kattzmcin eomputor editor Robert GrosiblnK, circuits editor Lorry KteJn, audio editor David Lachenbruch contrit>gtlng editor Don LancMivtor contributing editor Katiiy Terenxii editorial assistant ART DEPARTMENT Arndr* Duxant, art director |fija« Lee, illustretor Ru«s«JI C* TrueE»i>ffi, illustrator PRODUCTION OEPARTMENT Ruby M. Yee- production director Karttn S* Brown HiidvtrtrStntg production MareeUa Amoro Ao prDduction assistant John tegorfo editorial production CmCULATION DEPARTMENT Jacqueline P. Cheese boro cir^ufatiorii director Wendy Atanko drcutntion aitatyiit Thareea Lombardo circulation assistant Mlqhele TorHlto, reprint bookstore Typogrnptiy by Mate* Graphics Cover photo by Diversified Photo Services Radlo-Electronicfe is indexed In AppHttd Sci&nct* S Tecbnoiogy Index. end Readers Gtjide io Periodha! Utst- Microfilm & Microfiche editions are avatlabfe. Contact circulation depart* ment for detaiis . Adveriiatng Sales Offices listed on page Radio- ElectronjJi Within budget. Mthout compromise. >0 Get more of what you vmnt in a 6^k digit DMM for just $995. nie HP S440 1 A gives you more performance than any other DMM for the price. More resolutioa Belter accuracy. The hi^est read- ing speed. Fastest throu^put And \^1clest AC banchv^dth» It tias mor^ standard features. Uke HP IB, R&232 and built-in SCPI commands for more system flexibitity. Pli»s ten extended func* tions including continuity* diode test, limit test, reading hold, dB and nuU lo give you greater flexibility on the bendi. Wluii more could you want? The HP ;M401A also comes with a d-year warranty, standard. O For more information , or same- day shipment from ilP DIRECT, call 1800-152-4844". Ask for Ext TB26. And we'll send you a data sheet HP S44()1A Digital Multimeter DC Accuracy (1 yoBf) 0.0035% AC Accuracy (t year) 0i)6% Maximum Input IDOaVdc Reading spaed iDDiVsec ResDlution m nV, 10 nA, 100^ -In Canada caU }-m^^m^,lk^m There is a better way. HEWLETT PACKARD ancLE iio OH free (hforuatioh carii WHAT'S NEWS A review of the latest happenings in electronics. High-power semiconductor laser A series of refiable. 150-mW laser diodes that oscillate at wavelengths between 800 and 870 nanometers has been developed at Sanyo Elec- tric Company's Semiconductor Re- search Center in Allendale, N J. The high-powered lasers are expected to enhance pnDcessing speeds in erasable optical-disc memories and image-processing equipment and to be used in satellite communication. In addition, they can be used as pumping sources for blue laser-light generation when they are used with a second harmonic generation CSHG) device. Blue spectrum lasers with suffi- cient power are critical to informa- tion-intensive applications as long- playing, high-definition, moving-im- age video storage as well as for full- color image processing. An SHG device doubles the frequency of an infrared-spectrum laser when the light from the laser passes through a special crystal in the device, halving the wavelength of the beam and moving it from infrared to visible blue on the color spectrum. A blue lasers beam illuminates about 25% of the area on a receptor surface — quadrupling the recording density on a laser disc and significantly im- proving resolution in laser image- prDcessing applications. The Sanyo development overcomes previous OSCILLATING AT WAVELENGTHS be- tween SOO and 870 nm, Sanyo's high- power lasers will have applications in optical-disc memories, satelllle commu- nications, and blue-laser light genera- tion. obstacles to blue-laser light genera- tion by providing a high output power to compensate for the power loss inherent in the SHG process. The 860-nm lasSng wavelength can be produced for phase-matching conditions at room temperature using a typical SHG device. The laser diodes are fabricated using a relatively uncomplicated two-step, liqutd-phase epitaxy pro- cess. Adjustments made to layer thickness, lasing cavity length, and the crystalline active layer insure re- liable high-power output and sup- press temperature rise, which helps prevent degradation or catastrophic damage. Stable continuous wave operation at 150 mW has been con- firmed for more than 5000 hours at room temperature, and for over 2000 hours at 50"C. PIN pho- todiodes for monitoring light-output are built into the assembly. Three models operating at 800. 830, and 860 nm will initially be pro- duced, with volume production ex- pected by mid -1992. Safer gold elect roplatirtg nnethod A process allowing intricate gold electroplating on microelectronic devices, developed by Researchers at Sandia National Laboratories (Al- buquerque. NM)p uses a plating so- lution that is safer than the conven- tional cyanide-based solutions. While gold has many properties that make it attractive for use in manufacturing microelectronics- high corrosion resistance, high con- ductivity, high melting point, and ability to form good electrical con- tacts — standard gold-plating solu- tions can release large amounts of poisonous cyanide gas if the solu- tion becomes too acidic. The cyanide-based solutions are so dan- gerous that the EPA has classified them as "acutely hazardous;" therefore, they require special safe- ty precautions. Sandia has applied a gold sulfite solution, which was developed in the 1970 s and has been used since then for protective coverings but not for circuitry, to form precise gold patterns for semiconductor de- vices. The method has been suc- cessfully used to plate extremely fine lines on substrates. Sandia re- searchers have also used the sulfite solution, which contains no cyanide and is not dangerous, to make mini- ature gold bridges that form crossovers on gallium arsenide sub- strates. The crossovers allow con- ductors to cross on the surface of the IC without touching or shorting out adjacent conductors. Tests have shown the plating efficiency to be close to 100% in such applica- tions, and the plated gold s density approached that of pure gold. Transmission-line impedance measurement Beckman Industrial has been awarded a patent for developing a time-domain reflectometry CTDR) technique for the accurate mea- surement of transmission line im- pedance. The technique has been incorporated in the company's model TMT-1 transmission media tester, which is used to test and certify IAN and telecom physical layer cabling systems. TDR could be described as "ca- ble radar" — an electrical pulse is sent along the U\N under test and cable faults (impedance changes) reflect some of the energy back to the TDR where an associated pro- cessor plots it in a display or graph as a waveform. Traditional TDR techniques are plagued by "cable dribble-up ' or impedance rise, where the fundamental impedance of the cable under test appears to increase along the length of the ca- ble, Beckman "s measurement tech- nique correctly measures the impedance along the entire length of cables under test. R-E Ylni Can Always Spot Die iteHNiGUN Who DOESNl Use ItKTRONm If you're sending technicians and FSEs into the field with equipment other than Tektronix, \ don't be surprised to discover Sonne unusual tools in their service kits. Signal feres, for instance. On the other hand, portable test gear (iom Tek gets technicians to the root of the problem long before the problem gets to them. Everything from oscilloscopes and spectmm analyzers to handheld DMMs. As a result, your customers will be back on their feet (\ happy for that Not to mention a whole lot nicer to in whatll seem like no time at all. Ttiei'll be woik with. For your employees' sake, ^ in iDudi with a Tektronix representative tocby. Or keep an ej^e peeled for signs of distress. TALK TO TIK/1-8DD-426-2200 wm-mw Copintric TttUnam Tektronix /ifesl and Measurement ORCLE 1»4 OM Ff^EE tNFQRUATlON CARD VIDEO NEWS WhaVs new in the fast-changing video industry. DAVID LACHENBRUCH • Multimedia* That singfe word seems to be the hottest topic in both the television and the comput- er worids today. With the develop- ment of digital video and bandwidth compression, the computer and the TV set are coming increasingly close together, and there are many forecasts that the two will eventually merge. Bets are even being placed as to which will be the survivor Of course, that is a ridiculous question, reminiscent of the days when people talked about the com- puter-controlled home, in which a central computer operated the washing machine, refrigerator. Stove, dishwasher furnace, and ev- erything else. As we ali know, that never happened because micro- prtxessors* or nfiini-computers^ be- came so cheap that they could be incorporated into the appliances themselves. Since computers and television sets are used in different nDoms of the house, the speculation as to which will sun/ive reflects a misun- derstanding of the potential of dig* itaf technology. We would hope that the computer and the TV set will speak the same language so that their software can be intermixed and combined, but it's ridiculous to think we will attach a keyboard to our W set of the future to write a nasty letter to the fiber-optic com- pany for overbilling us , while the rest of the family is deprived of watching their favorite sitcom- By the same token, who will want to sit at the 12* inch computer monitor to watch the Olympics? Certainly not anyone who has the option of a 100- inch wall-screen (which, incidentally has no value in word pnocessing), • TV^Computer Compati- bility, Capitalizing on the hope that the TV set and the computer will be able to speak with one another with- out too much translation is Thom- son Consumer Electronics {RCA and GE brands in the United States). Thomson says that all of its efforts in advanced TV will be focused on standardization with computer multimedia. Thomson re- cently won the contract to supply the digital-compression system and consumer receiving boxes and an- tennas for Hughes Communica- tions' 100-channel high-power di- nsct-lo-home DirecTV satellite sys- tem, due to start in 1994. Thomson is also participating in a proposed digital HDTV system with Philips. NBC. Sarnoff Research Center, and Compression Labs, Their HDTV system and Thomsons sat- ellite transmission signal use a stan- dard based on the Motion Picture Experts Group (MPEG) digital-com- pression formula for full-motion vid- eo on a CD-ROM disc. Thomson calls its system "MPEG+ + be- cause it has much higher resolution than the current MPEG standard. Actually, the MPEG + + system is one of 32 different proposals for a movie-quality digital-compression system being considered for the ti- tle of MPEG 2" standard. Thomson notes that it expects the MPEG H- + system DirecTV to be directly compatible with multi- media systems, computers, video recording systems of the future, and all other encoded digital-com- pression media. They don't say what will happen if MPEG doesn't choose MPEG + + for MPEG 2, • How Far Off? Although we're hearing optimistic forecasts that the multimedia age is upon us, one ma- jor Japanese manufacturer doesn't see it that way. Toshiba, which, with C. Itch and Company paid $1 billion for part of Time Warner s TV-related business, says its preparing For the multimedia age, but doesn*t agree that it s just around the corner Rather than go off chasing a non- existent standard, they prefer to wait for the industry to set a stan- dard. Says Kojo Hase, senior man- ager of Toshiba Media and Commu- nications Group, " Our dmam is a ftve-inch disc with 120 minutes re- cording and playback time, erasable and with high*definition quality A higher density disc and the next MPEG standard for full-motion [movie quality! video will provide this. But the standards negotiations are only beginning, and there are 32 contenders. There cannot be a stan- dard until 1995/' Asked about CD-I. now on the market and hailed by its principle sponsor. Philips, as a success, Hase said. "We do not think that CD-I is fully interactive. The fact that there are only around 50 titles sug- gests that the tooling is wrong, that the platform is not sufficiently flexi- ble. We are studying very carefully and asking what is the right materi- al. Certainly not encyclopedias. We need something sparkling that makes people say I must have it ," • Small Camcorders Domi« nate. Last year, 60% of all camcor- ders sold in the U.S. were "compacts" — that is, 8mm or VHS- C. That is an increase from just over half in 1990 and only 37% in 1989. The figures are supplied by the Elec- tronic Industries Association CEIA). which doesn't break down the com- pacts by format, but a good esti- mate is that 8mm won by a large margin, comprising 63% of all com- pacts and 43% of total camcorder sales, compared to 32% full-size VHS and 25% VHS-C. • Ghostbusting Winner. As we go to press, the National Associa- tion of Broadcasters has declared a winner in its field tests of TV ghost- canceNng systems CRadio-Elec- tronics, April 1992). It is the sys- tem developed by Philips- All five of the proposed systems require that the TV station transmit a pilot signal during the vertical blanking intenal. and therefore FCC appnDval is re- quired. Action on a standard system is expected as early as June. R-E Mini] Our Name says quality, service and dependability - Our customers agree! ''The best pa rt of the Optoelecironics LCD counters are their extreme seJisUiuity, their brilliant LCD readout that can he seen even in bright sunlight and the rugged construction allowing them to get banged around^ but still continue to operate smack dab on frequency... Yours is the only counter which reliably gives us (at Radio School) an instant frequency readout with its rock-steady LCD digits featuring incredible IHz resolution." Gordon West Optoelectronics has satisfied its customers for over 18 years - See for yourself what countless others have already discovered! FACTORY DIRECT ORDER LINE 1-800-327-5912 (305)771-2050- FAX(305)771 -2052 seal NE 14lh Avonuo * Fart Laudardalo, FL 33334 5% Shipplna Handlirrg, j Maximum SlO) U.3- ^ Canada. IS*;^ outsfde continenral U.S.A. In Ftojida add S% sates tax. Visa and MasterCard accoptod. '"I was encouraged by one of my readers words of wisdom f and bought the Model 2300. Your service was superb! After testing this unit I persojially feel that all serious radio enthusia^^ts should own an Optoelectronics Frequency Finder'' Ron Bruckman Radio Monitors Newsletter Of Maryland Madet a030 3000 2S10 2G00HA 221 OA 2300 Function Freq, Period Ratio, interval Freq, Period Raiio.lneeeval Frequency FfOquQ-ncy Frequency Frequency ^ange 10Hz- 3 0GHz tOHz- 3,0GHz IIWHZ' 3.0GH? 10H2- 3.0GH2 iQHz- 2.4GHI Display 10 Dki'l LCD wtFuFKKion Annundatdir^ 10 Dig»| LCD w/Fynction Annuficiatars 10 Digil LCD lOOigi! LCD lODogil LCD B Digit LED 8 Opgit LED RF Signal Strength Indicator Adjuslabb Bargraph 16 Segment AdjUstabFe Oargrapii 16 SsgmcHil Adjustable Bargraph Hold SwitchYes Yes Yes Yes No Yes Price $57S. $375. S325. S22S. Si 79. S«f44rv4y: -d to lOrnV typCAJ. Trr* BAie: ± l.ppm. i^ppn »d>ards to test circuits • art audio amp checker for iroubfeshooting radios and TV • and more. Hundreds of (llustratiorrs guide you through each process 300 pp, 336fitus. m75N S27.95 MICROWAVE OVEN REPAIR'-'2ND ED, Save yourself countless dollars in repair ti4tts with this fi3c4t manual by your side. You get dear, step^* step instructions, deiaiied ilJu^xa* tfons, and photographs to help you easily accompiish repairs yourself. You'll discover specific solutions for more than 200 common microwave oven malfuncf or^s 363 pp 3B3 "34S7H S29.9S SECRETS OF RF CIRCUIT DESIGN Design and build your own radio frequency amplifiers, preselectors, signal generators, inductor coils, antennas* microwave circuits, and other devices. You also got eitpert- menls that help you ojcplpre such problems as electromagnetic i n terf e re nee - 4 T 5 pp, , / 75 iUus. #371 OH $32,95 THE NEW STEREO SOUNDBOOK Discover the future science of 3D sound with this step-by-step guide to sound perception, recording, and repraduclton. Optimize your stereo equipment and listening environ* ment by using the iatest sound quaiity and Spaced microphone techniques, 304 pp., 251 itiuB. #37e9H, $29.95 CUSTOMIZE YOUR PHONE: 15 Electronic Projects THE TALKING TELEPHONE —And 14 Other Custom Telephone Projects Bui id pleasant-soundtng ringers, a late-night telephone guard, hold buttons, LEO dial displays, offurse, youll Ix^ able to .select from Pomona's mmplete fitmily of SMD and IC test acces^sories includini; IC clip kiLs and PGA adipters. You cm also chotm' fi-om 18 EIAJ QR* test adiptcr mtxlels. Pomona lest accessorieij are the bgiail choice. We're Making Technology Easter To Live With. Pomona,:^ Oill. I'AX or wriU' itjcj^iy for your fftv (.cjpy of Pumoriii's full-t olor Suifaa* Muftnt & iC T&si AcCfiiSiiries brochure. ITT Pomona Tliu \\ orkl JjTjdtT ][i Test Aatssoricft IMO E. Hinth Street, P.O. Box 2767 Pomona. CA 91769, ^71 4} 469^2900 FAX {714) 629^3317. I .1 g. 9" m 3 3 17 CIRCLE 101 QH FREE INFORMATION CARD UJ 6 Learn to troubleshoot and service today's computer systems as you build a 386sx/20 MHz mini tower computer! Train the NRI way — and leam to service toduy^s computers as you build your own 386sx computer systemj now with 1 meg RAM^ 40 meg IDE hard drivcy and exciting new diagnostic hardware and software! Jobs for computer service technicians will almost double in the next 10 years according to Department of Labor statistics, making computer service one of the top growth fields in the nation. Now you can cash in on this exciting opportunity — either as a fiill-time industry technician or in a money-making computer service business of your own — once you've mastered electronics and computers the NRI way. NRFs practical combination of "reason- why theory and hands-on building skills starts you with the funda- mentals of electro nicSj then guides you through more sophisticated circuitry all the way up to the latest ad- vances in computer technology. Train with and keep a powerftd 386sx/20 MHz computer system plus popular Microsoft^' Works software! Only NRI gives you hands-on training with the finest example of state-of-the-art technology: the powerful new West Coast 386sx/20 MHz mini tower computer. As you assemble this 1 meg RAM, 32-bit CPU computer from the keyboard up, you actually see for yourself how each section of your computer works. You assemble and test your computer's "intelligent" keyboard, install the power supply and 1.2 meg^ high- density floppy disk drive, then interface the high-resolu- tion monitor. Your hands-on training continues as you install a powerful new 40 meg IDE hard disk drive — now included in your course to dramatically increase the data storage capacity of your computer wliile giving you lightning-quick data access. NEW! 386SX/20MHZ Mini Tower Computer Plus you now go on to work with teday^s most popular integrated software package, Microsoft Works, learning to use its word processing, spreadsheet, data- base, and communications utilities for your own personal and professional applications. But that^s not all. Qiiirklect Only NRI gives you hands-on training with the remarkable plug- in diagnoHiic card and QuickTeck tti agnostic software from Vltra-X— professional^ sta te-of- th e-art dlagnosiic tools that make computer troub leshooHng fast and uccu- rate* 10 Your NRl computer training includes all this: • NRFs unique Diacovery Lab^ for circuit desi^ and testing * Hamhheld digital multimeter with ^alk-you-through^ instnictionn on audio casaette * Digital logic probe that lets you viaually examine computer circuits • The new Went Cousi 38fjHxl20 MHz computer system^ featuring a high-speed H0386sx CPV\ 1 meg RAM, 10 J -key intelligent^ keyb(xirii^ L2 meg high-density floppy drive^ and high-resolution monitor • 40 meg IDE hara drive • MS-DOS, GW-BASIC, and Micro$oft Works software • K-A.C^J?, plug-in diagnostic card and QuickTech menu- driven dit^gnoBtic sofhLeare * Reference manuals with guidelines and schematics printer ports, serial communicatiorLs ports, video display memory » nopp3^ drives, and hard disk dri%'es. OnJ}* NRl gives you such Gonfidence-building', real- world experience. Only NRl gives you both the knowledge and the professional tools to succeed as today's in-demand computer service technician. No experience needed NRl builds it in NRl training gives you practical, hands-on experience that makes you uniquely prepared to take advan- tage of today*s opportunities in computer service. You learn at your own convenience in your own home. No classroom pressures, no night school, no need to quit your present job until you're ready to make your move. NRl starts you with the basics, building on that foundation step by step until you have the knowledge and skills you need for success. And all throughout your training you've got the full support of your pei^nal NRl instructor and the entire NRl technical staff, always ready to answer your questions and help you achieve your training goals* FREE catalog tells more. Send today! Send today for NRrs big, free catalog that describes every aspect of NRFs innovative computer training, as well as hands-on training in other growing high-tech career fields. If the coupon is missing^ write to: NRl School of Electronics, McGraw-Hill Continuing Education Center, 4401 Connecticut Avenue, NW, Washington, DC 20008, tBM li ft regutfml Irademark of InUfmttionAl Biipinrc* Mftdiinei C^orp. H.A,C,E.R- and QijickT*th ttiT TH'ifipitl'rwi tradflmflrk." of Ultrci X, liic NOW! Traming now includes Ultra-X diagnostic hardware and software for quick, accurate troublesliooting! Now you train with and keep the latest in diagnostic hardware and software: the extraordinai^' Rj\,C.E.R, plug-in diagnostic card and QuickTech diagnostic software, both from Ultra-X. Using these state-fjf-t lie- art tools, you learn to quickly identify and service virtually NEW! 386SX 1. SEND TODAY FOR FREE CATALOG McGniw-Hill Coiiiliiiuing Education Center , -1401 Cblem. If you find that it doesn^t work, the best advice I can give you is to con- tact the modem manufacturBr and let them come up with an answer Cail waiting is a common seivtce and you can be sure that youVe not the only one who's had this prob- lem. If that fails, you'll just have to spring for a second phone line or drop call waiting — ^whichever meth- od you prefer. Your phone company should have a way to disable call waiting temporarily as well. R-E ClfiCLE 123 ON FREE INFORMATION CARD 48 HOUR SHIPPING ELENCO & HITACHI PRODUCTS ^:°%S.%n AT DISCOUNT PRICES 1-800-292-7711 Hitachi RSO Series (Portable Real-time Digital S to rag a OscfUoscoptjs) VC'6023 - 20MHz. 20MS^S ^ VC'6024 ' 50MHz. EOMS/S VC'6025 - 50MHz, ZOMS/S VC^6045 ' 100MHz, 40MS/S VC'6145 - 100MHz. 100MS/S_ RSO'S Irom Hitachi teaSure modo memory, smDOthing, io1erpol[3tion, pretnggenng ^ S1.695 S1,995 $2,195 S2.995 S4.495 averaging, Sfsve SPECIAL BUY V-212 - 20MH2 Scope $425 measurojTisntS- These scopos onable more accuratiJ. simpJief observation of complex waveforms, in addjJion lo such functions as tiarcJcopy vsa a plotter interjace and waveform transfer via the RS 232C interface. Enjoy the contort of ariaiog and (ho po^er to digjlaJ. 25MHz Elenco Oscilioscope Hitachi Portable Scopes DC to 50MHz, 2'Chann&h DC offset fyiic* lion. Alternate mognifier function V-525 - CRT Readout, Cursor Meas, S995 ■ Deta^ed Sweep $975 ■ Basic Model SB75 ■ 40MHz $775 S695 S625 V-523 V-522 V-422 V.223 V-222 20MH2 delayed sweep _ 20MHz deluxe. $349 S-1325 ♦ Dual Trace « i mV Sensitivity • 6" CRT • X-Y Operation * TV Sync (2) ix/i6x Probes incfuded PRICE BREAKTHRUi 20MHz Digital Storage Oscilloscope * Anaiog/Disptal Scope * 2K VfOT6 p©r Chan nel m emory D S203 - 1 0MS/s sa mpJing rat« $ 7 9 5 ■ Siate-ol-ari: l^noJogy * IncliK^ proo«£ HITACHI COMPACT SERIES SCOPES Ttiis Mrios proryidfls many n«w functiions stich as CRT RQOdo^, CurMritieasurements t V-1 Oas/1 065A/665A). Frg- Quency Qr, ^V-lOBS}. Swa^ptum^ AutOiangfng, Delayjjd Svfe6U ar^ Tnpper Lock, using a B-incn CRT.Yoli cJon'l tee I tfte oompaclnwi in terms Of performance arid opera^O.i, 60MHz, Duaf Trace $1,149 V-665A - 60MH2, DT. w/cursor Si. 345 V-1060 - 100MHz, Dual Trace $1,395 V-1065A- 100MHz. DT. w/cufsor . $1,649 V-10S5 - laOMHz, CT. w/cursor $1,995 V'llOOA- 100MHz, Quad Trace S2,195 V'1150 ' 150MHz. Quad Trace 52,695 Elenco 40MHz Dual Trace iGoodto J4gg S-1340 - * High luminance 6" CRT • imV Sensitivity 1 1 0KV Acceteration Voltage ir ♦^-'1? • 17ns Rise Time »X'YOperatfon Jncludes (2) 1x, 10x Probes 50MHz AN scopes Include probes, &dio mattes, operators manual and 3 year {2 yrs for Eknco scopes) worFd wido warranty orv parts & labor. Many accessories available for all Hrtachi scopes. Call or writo for complete specif kratbns on these and many other fine oscilfoscopes. ] x, l Ox Scope Probes: P- 1 65MHz $ 1 9. 95, P-2 1 OOMHz $26.95 B + K TEST EQUIPMENT All Models Avoiloble Call for special price Digttal Capacitance Meter / awB CM*1S5aB $58.95 9 Ranges ,1p(-20,000urd .5% basic accy. Zero conlrol yff Cast? Big r Display Dtgital LCR Meter LC-tBOl $125 Mea^uro^: CoiJs l uH-20aH _ --''^ Caps .lpl*200uf l^l^'Se Res.D1-20M Big r Display Multimeter wltti CopocHonce & TronsJslof Testei $55 CM-150DB Reads Voits, Ohms Current. Capacitors, Transistors and Diodes / with case FLUKE MULTIMETERS AS Models AvGltoble Fluke 70-11 S65 Fluke 77-11 $145 Fluke 79-11 S169 Fluke 87 S239 Coll for spectoi price Quad Power Supply XP-sao i$59.95 12V ^ TA ^5V @ .5A FuEty regulated and ^tvit\ cfrcuct prof«cte(^ GF-fl016 Function Generator with Freq. Countef $249 'Sine. S<^uafe. Tnangle Pulse, Ramp, .2 lo 2tAHz Ffoq Coumer,1 - 10MHz Int/^Kl opersdijon I QF^aata without Freq, Meter $ 1 79 Learn to Butid and Program Computers with this Kit Includes: All Parts, Ass-embly and Lessori Manual htodel MM*8000 $129.00 Siarjng from scratch jfou bukld a cooiplcie system. Our h%crO'kt3£tcT trainor lo^es you to Wftte "nlo RAh%^. ROMs and ain a 60fiS micfopfooesso/', which uses similar machino Language as IBM PC. WE WILL NOT BE UNDERSOLD! UPS Shipptng: 4S States 5% ($3 Min$10 Max) Stitpping IL Res.. 7.5% tax FAX: 706-520-0085 Digital Triple Power Supply XP-765 J $269 P ^^^^^ **'lir 0-20V@ lA 5V@5A Fully regulated, Stion circuit protecied with 2 limrt control. 3 separate supplies XP-EBD wHh Analog feelers S1S5 Function Generalor BEOK #9600 $28,95 Provides sine, iri^gle; square wave Irom 1 H; to iMNi AU or fU capability Wtde Band Signal Generators RF Freq lOOMSOMHz AM Modula^ tiofiol 1KKz Variable RF otrtpyt SG-gSOa wf Digital Dtspliy & 1 50 MHz bu I Et-ln Counter $249 AM/FM Transistor Radio Kit wltti Training Course MOfiel AM/FM 108 $26,95 14Trar^istors * S DiCHjes Uakes a great sclioal proj«c1 True eMS4172 Digit Multimeter M>7000 $135 .0^% DC Accuracy .1% Hesistanco wiih Freq. Ccurvter and Deluxe Ca$e CoJor Convergence Generator $79.95 * KJt$59j5 Rnest tn the i^idostry 10 rocksteady panams RF a Vid&D output High Current Power Supply XP^O $295 Dtgimi VoU/Amp Meters FuEly regulatBd, 0'1Z2VAC @ 2A, 0- 40VAC@ 10AorO-30VDC@ lOA. Rjlly STANDARD AMATEUR RADIOS Kow available - Ttie worlds finest arriateur radias. Unsurpassed quality^ and features make STAt^DARP the worids most popular line oi amateur radms. Mini Deluxe HTs: C163A2 meter C468A490MHr Twin Band HTs C22dA 2M/220MHZ C528A2M/440MHZ Twin Band Mobile C56Q8DA 2M/440MHZ CALL CALL CALL We also have many accessaries for these radios and mast t^eath radios. Call lor details. C & S SALES INC. 1245 Ro.se\mo(L DeorHi-UI, IL 60015 tHOOl 293-771 1 1 70S) 541-0710 E 15 Day Money Back Guarantee 2 Year Warranty price-, subject change WRITE FOR FREE CATALOG CIRCLE lot ON FREE INFOBMATIOK CARD NEW PRODUCTS Use the Free information Card for more detalis on these products. VIDEO FRAME GRABBER. You can take a video image and incorporate it in a vari- ety of word-processing and desktop publishing applica- tions— creating a custom- ized letterhead including your photograph, for exam- ple—using MacroHard's Video Frame Crabber package. With the help of a VCR or camcorder, the Video Frame Grabber will digitize a video signal, which you can then modily to suit yourneeds and save it in any of five different for- mats for export to various third-party software. The images can be scaled to size and positioned any- where in your document, and formats for popular programs fnciuding Micro- soft Patnt and Windows PBrush. Corel Draw. Ven- tura Publisher and Aldus ORCLE 16 ON FREE INFORMATION CARD PageMaker are pravided. The package, which con- sists of the Video Frame Grabber board, a 5y4-inch floppy disk, and a manual, allows you to capture real- time video at up to two frames per second. Pause and freeze modes are avail- able for viewing and modi- fying the image. The package features scalable printing, user-defined mar- gins, auto-exposure com- pensation, and anti-altasing filtering for lower noise and less snow. The Video Frame Grab- ber, which carries a one- year warranty, has a sug- gested retail price of $149.95.— MacroHard, 755 Tatum Street, Wood- bury. NJ 08096-3431; Phone: 609-853-4680; Fax: 609-853-0677. RF DETECTOR/FREQUENCY COUNTERS. Two new pocket'Sized counters from Startek each feature a 2-inch, 10-segment LED signal-strength bar graph that functions indepen- dently of the digital fre- quency counter. The bar graph, which can be used to locate or adjust an RF ^ signal, will indicate the nela- ^ tive strength of an input sig- ^ na! at any frequency from g- 500 kHz to 3.5 GHz. The g user can switch between ^ dot-graph and bar-graph [J] operation, and the sen- .9 sitivity is adjustable. ^ The frequency-counter function has a range of 1 MHz to 1.5 GHz on the model /5-eGandl MHz to 24 3,2 GHz on the model 35- CIRCLE T7 0N FREE INFORMATION CARD BG. Other than the fre- quency bandwidth, the only difference between the two models is that the 35 BG is more sensitive above 500 MHz. Both counters have a display-hold switch with in- dicator and three switch- selectable gate times. Res- olution is 1 kHz at 0.25 sec- ond, 100 Hz at 2.5 seconds, and 10 Hz at 25 seconds, over the entire range. The display consists of eight red LED digits. A 1- PPM TCXO time base is standard, and there are provisions for an optionaf, ultra -high- stability TCXO. With the Ni-Cd battery pack fully charged, the counter will operate for 3-5 hours. An AC adaptor/ charger is standard. Models 15-BG and 35- BG bar-graph/frequency counters cost $220 and $265. respectively— Star- tek International Inc.. 398 NE 38th Street, Fort Lauderdale, FL 33334; Phone: 305-561-221 or 80-638-8050 for orders only; Fax: 305-561 -91 33. ANALOG/DIGITAL STORAGE SCOPES, A series of 100- and 2OO-MH2 analog/dig- ital oscilloscopes from Fluke and Philips combines analog familiarity and digital performance. It offers true four-channel operation as well as models with 2 + 2 input-channel configura- tions. Additional features include direct-access con- trols, closed-case calibra- tion, serial interface for printer/plotter, full pro- grammability, automatic pass/fail testing, signal math and analysis, signal averaging, and peak-detect mode for HDTV tri-level sync. A touch-hold-and- measure feature is used for initiating measurements from a probe- mounted but- ton. The units have a wide range of applications in ra- dio/TV, medical elec- tronics, and the new 1100- line resolution video. The four Fluke/Philips oscilloscopes— PM 3382. PM 3384, PM 3392, and PM 3394— can each be considered two scopes (n one, with the easy opera- tion and realtime 100- or 200-MHz bandwidth of an analog scope, and digital sampling rates of 200 mil- lion samples per second. According to Fluke, the analog portion is not redun- dant: there continue to be many applications that de- mand the "live" signal rep- resentation and infinite resolution of analog instm- ments. Switching between analog and digital opera- tion is simple. The units have full digital capture and signal analysis capabilities, providing powerful storage and measurenr>ent ca- CIRCLE 18 ON FREE INFORMATION CARD pabilities on demand, In^ stant nesults are obtained by selecting the required function and channel from a set of built-in. fully auto- mated voltage and timing measurement functions. Triggering modes in- clude logic state and pat- tem triggering, and glitch triggering. In addition to pre- and post-trigger signal display, the scopes have event delay and time-after- event delay. Models PM 3384 CI 00 MHz) and PM 3394 (200 MHz) offer true four-chan- nel operation, which pro- vides full sensitivity with complete attenuation ranges on each channel. The 100-MHz PM 3382 and the 200'MHz PM 3392 offer 2-^2 channel opera- tion, a configuration that provides a cost-effective alternative to four fully fea^ tured inputs. Models PM 3382, PM 3384, PM 3392, and PM 3394 have list prices of $4490, $5490. $5990. and $6490. respectively.— John Fluke Mfg, Co., Inc., P.O. Box 9090. Everett, WA 98 206; Phone: 800-44-FLUKE, SELF-TUNING TEST RE- CEIVER, For testing the nnodulation quality of mobile voice transmitters and verifying the accuracy of audio signalling tones such as DTMF and CTCSS, Optoelectronics R'lO communications test receiver is a quick, easy, and inexpensive alternative to costly modulation meters. The unit can auto- matically accommodate the enormous difference ratio between an unknown carrier of up to TOGO MHz and a modulating frequen- cy as low as 50 Hz, without any manual tuning. The R-W automatically determines and locks onto whatever carrier signal is the strongest within a 100- foot range. Once the signal is locked in. the de- modulates whatever FM audio is present on the car- rier and outputs that audio to an Internal power ampli- fier/speaker and the BNC output jack. For DTMF and CTCSS testing, the audio output is evaluated on a fne- quency counter or os- cilloscope. For counter- surveillance operations, the R'Ws dennodulated au- dio can be nnonitored to de- termine if a surreptitious transmitter is in the area. CIRQE 19 ON FREE INFORMATION CARD The test receiver fea- tures two operating modes; a squelch ca- pability that serves as a sensitivity control: audio gain, power, and low- bat- tery indicators; and a rear connector that provides output to external frequen* cy counters and other in- struments. Power is sup- plied by an internal Q^volt battery. Options include a rechargeable battery pack and a telescoping whip an- tenna with swivel base. The R-^0 test communi- cations receiver costs $359 —Optoelectronics Inc., 5821 NE 14th Avenue, Fort Lauderdale, FL 33334; Phone: 800-327-5912 or 305-771 2050: Fax: 305^771-2052. MULTI-PURPOSE INTER- FERENCE FILTER. Ace Communications MPIF-1 receiver filter eliminates a variety of unwanted sig- nals. The compact (3 x 2 x iy2-inch) external filter eliminates most of the sources of interference common in broad banded receivers. Unwanted sig- nals are filtered from the 54-108 MHz, 174-220 MHz, and 512-806 MHz ranges, as well as the range above 869 MHz. A switchable notch will also eliminate interference on the 150-153 MHz range, which is a common source of interference in naany areas. The use of BNC connectors makes the fil- ter quite versatile; the MPIF't can even be used on handheld receivers. The MPfF-1 multi-pur- pose interference filter has CIRCLE 20 ON FREE INFORMATION CARD a suggested retail price of $59. — Ace Communica- tions, Monitor Division, 10707 East 106th Street. Fishers, IN 46038; Phone; 817-842-7115: Fax: 317-849-8794. POWER SUPPLIES, The "smart" front panels on the 15 instruments in Hewlett- Packard's new line of DC PUSHBUnON TECHNOLOGY AT PRICES THAT WONT PUSH YOU OVER / THE EDGE • Environmentally Engineered Formulations • Chemicals For All Your Repair/Production Needs • Quality Products Since 1965 Ca// Today for More Information Manufacturers Reps Wanted WE DARE YOU TO COMPARE' RITEl 1545 5THJNOUSTRJAL COURT BAY SHOHEh N E W f OfK 1 ItQi Yesterday's Vaiues, Tomonow^s Technology CIRCLE mOH FREE IhEFOReiAATION CARD i m m m m CIRCLE 21 ON FREE INFORMATION CARD power supplies help pro- vide fast, flexible, and pre- cise oulput control . With outputs ranging from 200 to 2000 watts, the HP 6000 series power sup- plies provide a variety of choices for benchtop or systenri applications that do not require HP-IB control of the power supply The series consists of five power supplies (which vary by voltage ratings) in each of three power ranges: 200, 500. and 2000 watts. All models have low out- put noise, extensive load- protection features, and the "smart" front panel. The peak-to-peak ripple and noise spans fnDm a low of 3 mV p'p on the low- power, low-voltage models to a high of just 16 mV on the 2-kW. 120*volt model. Overcurrent, overvoltage. and over-temperature pro* tection are provided for the device under test and for the power supply. Those features protect the device under test by disabling the output voltage of the power supply when potentially dangerous conditions oc* cur. "Smart" front-panel controls provide three methods for setting the output voltage and curnent. A numenc-entry keypad al- lows the user to set the voltage quickly and pre- cisely while up/down but- tons and rotary pulse generators permit the user to quickly and conveniently change the voltage and cur- rent settings in small incre- menls For repetitive benchtop tests, up to five states or sets of power- supply settings can be stored and recalled for easy sequencing among states. Front-panel con- trols also allow the user to calibrate the power supply. In addition, the output volt- age can be contrDlfed via an external voltage signal, allowing for computer con- trol or analog modulation. List prices for the HP 6500 series of power sup- plies range from $1650 to $1750 for the 200 watt models, $2100 to $2300 for the SOO-watt models, and $3650 to $3800 for the 2000-watt models — Hewlett-Packard Company. Inquiries^ 19210 Pruneridge Avenue. Cupertino. CA 95014; Phone: 800-752-0900. HAND-HELD DIGITAL MUL- TIMETERS. Aimed squarely the field service technician. Fieldpieces digital multi- meter models HB75 and HB77 are professional- grade instruments that are durable and easy to use in the field. They include a built-in logic probe and a variable-pitch tone. The tones pilch varies propor- tionally from high to low with high to low readings. In the field, that feature has two primary uses. First, in- termittents can easily be found by listening for dis- continuities in the tone while wiggling suspect connections. Second, one **odd" test point in a series CIRCU 22 ON FREE INFORMATION CARD of test points that are near< ly the same can be found without waiting for the meter to display a number; instead, the technician can quickly scan the test points and "hear" the one that is different. Both models have a built- in logic probe that re- sponds up to 20 MHz. "Hi" and "lo" are indicated both in the display (with up/ down arrows) and by a beeper with two different tones. Both DMMs also have a built-in capacitance meter that measures ca- pacitors up to 200 fiF in the circuit using the test leads. Model HB77 measures the tme-RMS value of AC voltages and currents. Cur- rent ranges go from a low of 200 \lA to 20 A. Be- cause the meter is manual ranging, the voltage burden (the voltage acn^ss the de- vice when cunenl is flow- ing through it) is low— 0.25 volts for the 200-^jlA range. Both heavy*duty meters feature a drop -resistant housing. 0-ring seals to protect against con- taminants, MOVs to pro- tect against transients, and full 600-V fusing on all cur- rent jacks. They come with a tilt stand and a hanger on the back, test leads, and fuses and batteries in* stalled. Both DMM's have 24 ranges in AC and DC volts, AC and DC amps, and ohms, and both include a high-voltage indicator that warns the user when touching anything over 28 volts. A single rotary dial, with the "menu" of func- tions printed around it. makes the meters easy to understand and use. The models HB75 and HB77 digital multimeters have suggested list prices of $139 and $179. respec- tively— Fieldpiece Instru- ments, inc., 8322B Artesia Blvd.. Buena Park, CA 90621 : Phone: 714*992-1239; Fax: 714-992-1239. 2.7-GHz SYNTHESIZED SIG- NAL GENERATOR. De- signed for use in research and development, man- ufacturing, and servicing electronic products. Lead- er's model 3221 syn- thesized signal generator CfRCLE 23 ON FREE tNFORMATlON CAJID offers high-stability and high-purity outputs to 2.7 GHz. Its extensive modula- tion capabilities include seven modes with 14 simul- taneous combination mod- ulation modes — pulse, log- ic. DC-FM, and internal or extemal AM and FM. RF- output level engineering units are selectable be- tween dBm and dBfx with 0.1 -dB resolution. Three convenient presets are in- cluded for commonly used RF-output levels. One hun- dred preset memories al- low storage and recall of all front-panel setting condi- tions- RF output on/of con- trol and 50-watt reverse power- protect ion reset are accomplished with a single key. A continuous, variable RF-output mode allows ±5-dB variation in 0.1-dB increments for squelch ad- justments. Edit functions for frequency output level, and modulation make it easy to change operating parameters. Other stan- dard features include GPIB and a GaAs FET pulse modulator The model 322^ syn- thesized signal generator costs $12,300.— Leader Instruments Corporation, 380 Oser Avenue. Haup* pauge. NY 11788: Phone: 800^645^51 04 or 516-231-6900. R-E REMOTE CONTROL A-B SWITCH-lets you hook up your cable box by remote control, when needed. Itien unhook it just as easily! Restores TV. VCR features. Or. replace any A-B switch with this superb quality remote version. Bright LED indicators, JUST S35, INCLUDES SHIPPING. Visa, MC. or check. (CO D. $5 extra) Fast delivery, 30 day money back. STAR CIRCUITS, RO, Box 94917, Las Vegas, Nevada 89193 1-SOO- 5 35-7827. CABLE TV CONVERTERS AND DE^ SCRAMBLERS SB-3 $73,00 TRI-BI $95.00 MLD-$79.00 M35B $69,00 DR2-DIC $149m Special combos available. We shrp COD. Quantity discounts. Call for pricing on other products. Dealers wanted. FREE CATA- LOG. We stand behind our products where others fail. One year warranty ACE PROD- UCTS. RO, Box S82, Saco, ME 04072 1 (300)234-0726. CIRCLE 7S ON FREE INFORMATrON CARD FREE CATALOG! ELECTRONIC TOOLS & TEST EQUiPMENT— Jensen's new Master Catalog, available free, presents major brand name electronics tools, tool kits, and test in- struments, plus unique, hard-to-find products for assembly and repair and custom field ser- vice kits available only from Jensen. All fully described and illustrated. Enjoy free technical support and rapid, post-paid delivery any- where in the Continental USA. JENSEN TOOLS, INC., 7815 S. 46tti SI, Phoenix, AZ 85044, Phone: 802-968-6231 ^ FAX 1-600-366-9662. CIRCLE 115 ON FREE INFORMATJON CARD TWO TRANSMITTERS IN ONE! 5 MINUTE ASSEMBLY! MONEYBACK GUARANTEE! New Law Enforcement grade device on a single chip is the most sensitive, powerful, stable room transmitter you can buy. Uses any 3V'12V battery. Or attach to telephone line to monitor all telephone conversations over 1 mtle away without batteries! lOOmW output! 80-130MHZ. Receive on any FM radio or wideband scanner. VT'75 micrctransmitter S49.95 + 1,50 Sm. VISA, MC, MQ. COD's add S4.00. DECO INDUSTRIES, Box 607, Bedford Hills, NY 10507. 1-800-759-5553. CIRCLE 127 ON FREE INFORMATION CARD CREATE INTELLIGENT PROJECTS WITH THE VERSATILE Z8 PROGRAMMABLE MICROCOMPUTER. This powerful comput- er was designed for flexibility and can be used for various electronic projects. I/O Intensive. Up to 20MH^ operation. Download programs or njn EPROM code. Special hardware fea- tures included. Prices from $125.00. Battery- backed RAM, X-assembter, and other options available. CALL FOR FREE BROCHURE. MJS DESIGNS, INC., 1438 W, Broadway Rd., Suite B185. Tempe, AZ 65282. (602) 966-6618, CIRCLE 181 ON FREE INFORMATION CARD CALL NOW AND RESERVE YOUR SPACE • 6 X rate $940.00 per each insertion. • Fast reader service cycfe. • Short lead time for the placement of ads, • We typeset and layout the ad at no additional charge. Call 516-293-3000 to reserve space. Ask for Arfine Fishman, Limited number of pages available. Mail materials to: mint-ADS, RADIO-ELECTRONICS, 500^ B Bi'Gounty Blvd.. Farm ingd ale, NY 11735. FAXi 516-293-3115 APPLIANCE REPAIR HANDBOOKS-13 volumes by service experts; easy-to- understand diagrams, illustrations. For major appfiances (air conditioners, refrigerators. wasiierSt dryers, microwaves, etc.), elec. housewares, personaf-care appliances. Basics of solid state, setting up shop, test instruments. S2.65 to S5.90 each. Free brochure, APPLIANCE SERVICE, PO Box 789, Lombard, IL 60148. 1^(312) 932-9550- CIRCLE 84 ON FREE INFORMATION CARD TUNABLE 50dB NOTCH FILTERS— for TV. Can be tuned precisely to required f requency. Model aSH'Ch's 2-3 (50-66 Mhz) Model 46FM'Ch's 4-6 plus FM {66-108 Mhz) Mode! 713-Chs 7-13 (174^216 Mhz) ModeH417-Ch"s 14-17 (120-144 Mhz) Mode] 1822-Ch s 18-22 (144-174 Mhz) $30 each, includes shipping. Visa, MC. or check. (CO D, S5 extra). Fast delivery, 30 day money back. Quantity prices to S16. STAR CIRCUITS, RO. Box 94917, Las Vegas, Nevada 89193 1-600-535-7827, I JO !^ DO m m o o n 27 NEW LIT Use The Free Information Card for fast response. RADIO FREQUENCY INTER- FERENCE: How to Find it and Fix it; book edited by Ed Hare, KA1CV, and Robert Schetgen, KU7G; Ttie Amer- ican Radio Relay League; 225 Main Street, New- ingtofi, CT 06111; S15 JO plus $3M shipping and liandiing (S4M for UPS). If you Ve ever experi- enced black bars flashing across your TV picture in a rhythmic pattern, a garage door opening or closing by itself, a buzz that drowns out AM stations, a touch- controiled iamp with a mind CIRCLE 40 ON FREE INFORMATION CARD of its own, or anonymous conversations that inter- rupt music on your stereo you Ve experienced radio- frequency or electromag- netic interference (RFI/ EM IX This 256-page book not only explains the me- chanics of RFI/EMI, but also provides practical ^ cures for the problem. ^ Opening chapters offer ^ general information on how tn to find the interacting "1 equipment, locate help, and resolve conflicts. Sub- sequent chapters discuss g RFI/EMI problems and pro- ^ vide cures for specific elec- tronic systems, including transmitters, televisions, telephones, amateur-radio 26 equipment, stereos and other audio gear power lines and electrical devices, computers, and auto- mobiles. The chapteron fil- ter performance explains how to select a filter and provides test results and performance tables for dozens of low-pass, high- pass, power-line, and mis- cellaneous filters. In addi- tion, the book also explains RFI/EMI regulations and standards, and provides a copy of the ARRL EMI/RFI report form, which can be used to file official EMI/RFi complaints. SECRET SIGNALS: The Eu- ronumbers Mystery; by Simon Mason. Tiare Pub- lications, RD. Box 493, Lake Geneva, Wl 53147; Ptione: 414-248-4845; $9.95 plus $2.00 shipping and han- dling ($3.00 outside the U.S.). If you've ever tuned to the frequencies outside the shortwave and ham bands to the regions allotted to "fixed" stations, you might have heard broadcasts consisting of a single voice reading out long lists of numbers in four- or five dig- it groups. While explana- tions for those mysterious broadcasts have ranged from commodity prices to Secret Signals M.HriM:AjiihK> CIRCLE 39 ON FREE INFORMATION CARD lottery numbers, the most likely explanation is that they are coded messages sent to espionage agents. The end of the Cold War hasn't ended the transmis- sion of coded numbers; they're still being sent, day and night, over all the shortwave-radio bands. This book, written by a man who has studied the Euro- pean numbers stations for years and has monitored thousands of transmis- sions in the process, is an indispensable tool for tracking those stations from North America, It in- cludes numerous traffic ex- cerpts, identifiers, sched- ules, and clues turned up by hearing mistakes in transmissions. Descrip- tions of transmissions from "Bulgarian Betty." 'Papa November," The Russian Man," "Swedish Rhap- sody,"' and 'The Lin- colnshire Poacher" are included, as is a complete frequency log with more than 300 entries that are listed by frequency and contain notes on formats and schedules. THE HARD DRIVE ENCYCLO- PEDIA: The Guide to PC- Compatible Hard Drives; tiy Adrian Alting-Mees. Anna- books, 12145 Alta Carmel Court, Suite 250-262, San Diego, CA 92128; Phone: 800-462-1042 or 619-271-9526; Fax: 619*592-0061; S89.00. Consisting of more than 600 pages in a three-ring binder and a companion diskette of utilities, this book provides a complete reference on PC-compati- ble hard-disk drives. The CIRCLE 37 ON FREE ^N FORMATION CARD book includes sections on ST-506. ESDI, SCSI, and IDE specifications, as well as a section covering five other interfaces. Other sections cover the physical and electrical charac- teristics of hard drives, log- ical encoding schemes, and file formats. Sections covering controller param- eters, hard-disk drives, and manufacturers include ex- tensive lists of related infor- mation. Another section lists the BIOS hard-drive tables for many popular BIOS s, and explains how to use the utilities on the companion disk to see the drive- type tables in your own BIOS, Wore than 1600 hard-drive model numbers are listed by manufacturer, so that if you have to install a drive but don't have a spec sheet, you can locate the important parameters in the included tables. 1992 ELECTRONIC TEST AC- CESSORIES CATALOG; from ITT Pomona, 1500 East Ninth Street, RO, Box 2767, Pomona, CA 91769-2767; Phone: 714-469-2900; Fax: 714-629-3317; free. Specially featured in this 140-page catalog are an expanded line of oscillo- scope-probe kits and two CIRCLE 36 ON FREE INFORMATION CARD new lines of test probes and clips for miniature and heavy-duty applications. Also featured are accesso- ries designed to make test- ing SMT devices and high- density leaded compo- nents easier end more re- liable. New products in- clude new IC clip kits, coax/BNC universal adapt- er kits, digital multimeter test-lead kits, cable and patch accessories, and jumper kits. ITT Pomona s popular selection of jum- pers and cables, boxes, piugs and jacks, con- nectors, adapters, single- point test clips, and static contiol devices are also de- scribed. An easy-to-use in- dex is provided to help readers quickly locate spe- cific products. LENO LASER HANDBOOK: Featuring CD, CDV, and CD- ROIVI Technology; by John 0. Lenk. McGraw-Hill, Inc., Professional Book Group, 11 West 19th Street, New York, NY 10011; Tel. 1-800-2- MCGRAW; 339.95. This new addition to McGraw-HiUs Consumer Electronics Series is a practical reference book filled with the information needed to troubleshoot to^ day's laserbased products. 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OJC grabt^wri Clips to poriablt>'!i rod an- tenna. 2341 wtre eiemerit stores on pcrCkOt'Si;^ reel. f27F.(-t3y4 . . . B.95 (2) Dial Cord Repair Kit. Radio Shack excEusivel Includti^ liix toet of hsgh^ strengtl-i dial co?d anu tension springs if27*\-^^S (3) 3" Brushless 12VDC Fan. Exclusive' BrushlesJS design arrd DC operation maku it a greai chOEce tor coclinQ r^iotsi]^ tquipmeni and circuits ihat are sensftEve to hum ot noise. 27 CPK^ airfjQw. ftS7Z^2^3 14, 9S (4) UL- Recognized Power Traasformcr. Exclusive! 120VAC primary Corner lapped secondary provides 12VAC Eit 1.2A. ^273-1352 .... 5.99 0) Double 'Shielded, 4 Conduc- tor Cable. For data or audio. The besti 30 tt. ^276-777 7.95 (2) Colled Mike Cable. Replace CB, ham, marine radio cords, 4 con- ductors. 5 ft, #278-358 2.99 (1} 1N9I4/4148 Switching Diodes. Popular silicon type. Raied 75 PIV. #276 1122 Pkg. of 10/99C (2) 1N34 Germanium Diodes. Hard-to-find signal diodes. 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Bench/portable DMM 'S have seized the high ground where empha- sis is on accuracy, resolution and automated test* ing. Bench top DMM's are in use for electronic equipment testing, service, and calibration In both shop and field. They are also filling important roles in design departments, scientific labs, and as components In industrial data acquisition and automated test systems, lb be classed as a DMM. a meter is usually ex- pected to be able to make the five basic electrical measurements: DC and AC volts, DC and AC cur- rent* and resistance. However, the term DMM now covers a wide range of instruments from the low- cost handheld, battery-powered units costing less than $100 to the AC line-powered bench/portable units whose base list prices can range from $200 to nearly $2700. Bench top DMMjs are distinguished from hand- helds by their rectangular eases and front- face displays and controls. Their long depth dimen- sions give them stability on a bench or other flat surface. Most are equipped with tilt bails to raise their front faces for easier user reading. Despite those differences* there is considerable overlap In features between high-end handheld and low-end bench top DMMs, In fact, some bench- type meters are little more than repackaged handhelds, and they cannot be distinguished by looking only at specifications. All handheld DM Ms are por table » but bench top DMMs are also portable, and those that are bat- tery- powered can be used conveniently in the field. Many bench DMM s have ilquld-cr>^stal displays, typical of todays handhelds» but most of the high- end models have vacuum -fluorescent or LED dis- plays that afford better viewing In subdued light. These displays can be used because the bench top units have less restricted power budgets than the handhelds. I 31 to gi o m a 8 3 31 How they work Figure 1 is a simplified func- tional block diagram of a DMM, In practice, both AC and DC voltage measurements are made by one circuit, and both AC and DC currents are mea- sured by another. Typically there is a separate resistance measuring circuit. The latest DMM s, both hand- held and bench, include either a microcontroller (microcomput- er-on-a-chip) or microprocessor for various control and self- check functions, A micro- processing function block has been omitted from the sim- plified diagram^ but it would typicEdly be located between the analog-to-digital (A/D) convert- er and the display. The microprocessor or micro- controller provides control sig- nals for the true root-mean- square (RMS) voltage and cur- rent converter if the DMM has one. Bench meters are more likely to have this feature than handhelds; thus it is not ex- clusive to either one. However, provision for interfacing with systems is an exclusive bench DMM feature. Bench DMM manufacturers have used a number of different schemes to convert analog in- put signals into a digital read- out. Among them are voltage- to- frequency» successive approx- imation, reciprocating re- mainden and dual*slope inte- gration conversion. However, the most popular scheme in use today is some form of dual -slope integration. Figure 2 is a simplified block diagram of a dual-slope inte- grating DMM. Instead of con- verting voltage to frequency as is done in other methods, it is converted to time. The timing sequence for this technique is shown in Fig. 3. Switch SI con- nects the unknown input volt- age to the integrator consisting of input resistor Rl and an oper- ational amplifier with capacitor CI in its feedback loop. Switch SI remains in that po- sition for the integration period. During this time, CI is charged at a rate determined by Rl, At the end of the integration period. CI has a charge that is proportional to the input volt- age. The op-amp causes the voltage across CI to build lin- early so the charging rate is gov- erned by the current through resistor Rl. In the second phase of dual- slope operation, control logic switches SI to connect a refer- ence voltage to Rl and the input of the integrator. The reference polarity is always opposite to that of the unknown input volt- age. TWo references are used — one negative and the other DISPUV FIG, 2— SIMPLIFIED BLOCK DIAGRAM of a dual-slope mtegratir^g DMM. Switch S1 connects the unknown voltage to the integrator for the first half of the cycle, and the reference voltage for the second half. The time to d ischarge capacitor CI Is converted to a digital readout. I c 9 m g '-a CONSTANT'CURREHT SOURCE DCV DCMA OHMS ANALOG/DIGITAL CONVERTER DECADE COUHTER DISPLAY + / 1 U l_l u 32 FtG. WBLOCK DlAGflAM of a basic digital multtmeter. Q |3|yfDER ^^^^^^^^ ^^^^^ SWITCHES r- 1 R1 |:r2 R3 200niV,2V DC ■^'x^ — ^ AC 20V.2O0V 1000V R4 TRUE RMS CONVERTER Jl.^^ I -4- I ^ COM PIQ, 4— SIMPLIFIED DIAGRAM of a typical voltage-measurement clrculL R1 R2 TRUE RMS . CONVERTER ;T|| R5 COMo— FIG. 5— SIMPLIFIED DIAGRAM of a typical current-measurement circuit. INTEGRATIOH | p— PERIOD ^ *1 S1 CONNECTED TO Si CONNECTEO TO UNKNOWN INPUT REFERENCE VOLTAGE FIG. 3— DUAL-SLOPE INTEGRATION measuring sequence. The slope angle deper^ds on the magnitude of the un- known input voltage and the time to dis- charge to zero Is a function of that value. positive. At the beginning of the second phase, the output from the clock is gated. Capacitor CI is then discharged linearly by the reference voltage, and the dock is stopped when 01 is dls- charged through zero. If the unknown input voltage is doubled, 01 charges up twice as fast. Since a constant refer- ence voltage is applied to dis- charge the capacitor, the dis- charge rate will be constant. This means that the time to dis- charge 01 is doubled if the un- known input is doubled, as showTL in Fig. 3. The accuracy of the dual-slope technique de- pends primarily on its reference voltages. This method is favored because errors introduced dur- ing charging are canceled dur- ing discharge. Some benchtop DMM A/D converters can now take 1000 readings per second. Hewlett-Packards HP 34401A DMM can, for example, makes up to 50 range/function changes per second. Figure 4 is a simplified di- agram of a typical DMM circuit for measuring both AC and DC voltage. Many different proprie- tary circuits are used for true RMS AO and DC voltage con- version. As can be seen, the out- put of the truie RMS converter goes to the A/D converter. Both AC and DO current can be measured with the circuit shown in simplified form in Fig. 5. Again, the range switch block represents either manual or au- tomatic range functions. Fuse Fl can represent two fuses in series, one rated for low current values, and the other rated for high current values. Those pro- tect the meter against acciden- tal damage and the user from shock. The true I^S converter functions in both the voltage and cLirrent measurement cir- cuits and, as in the voltage cir- cuit, the output goes to the A/D converter. Several different resistance measuring circuits can be found in today *s crop of bench DMM's. The most popular are the constant-current source and voltage-ratio techniques. The constant-current source supplies current to the un- known resistance value. The DMM then measures the voltage drop across the unknown. In the voltage ratio-method, shown in simplified form In Fig, 6. there is a voltage source and an internal divider consisting of a reference resistor (R]^i.-jr) and the unknown value (Rx)- The value of Vj^x *s obtained from the lower op-amp. Figure 7 illustrates a conven- tional 2-wire ohms converter found in most bench DMMs. It is based on a DC constant-cur- rent source. Figure 8 is a sim- plified schematic of a four-wire ohms converter that will elimi- nate measurement errors intro- duced by lead resistance in precision DMM's, Alternate or optional battery power enhances the bench/por- table meters portability and im- proves its isolation from the AC line for certain critical measure- ments. It also ensures the safety of the user when making cer- tain kinds of high-voltage and current measurements. Most low-cost, battery-powered bench DMM's use multiple "0" or **D" cells, or 9-volt transistor batteries, typically disposable alkaline. However, the battery power sources of the h Igher per- formance meters are typically multiple rechargeable nickel- cadmium (Ni-Od) cells or sealed j; Radio-Electronics, May 1992 TABLE 1— BENCHTOP DIGITAL MULTIMETER CHARACTERISTICS BASIC FEATURES DC VOLTS AC VOLTS AC & DC AMPS DHMS SPECIAL FEATURES a in O a u C3 ra m ra "o S ° K _ fe ^ a 00 ra E CO u CJ «c CD c» ra "5 ra ^ £ ^ D V> Q> DC K ra E £ cu ;a Frequency Range, kHz o CC M E a Q_ o. E <: K ra £ E a o vt Ol ra oT ra ]w 'w K ra £ Auto/Manual Ranging e> E 03 to ra £ 01 Ll_ O (£} GC E CD ■D ca Offset/Relative Reference m jg "D < .E o CJ K £ _ OJ ■D _o o CJ ra ID >K m CO o Manufacturer Model No. UViUU 200,000 LCD 0.0035 450 0.1 0.35 450 1.0 ' • 50 1.0 2.0 1,0 20 • * 1 — * — ■ — ■ — 232fST) (B/AC)(DM)(TM} 595 B & K 2000 LED OJ 1200 100 0.5 IQOO 100 — 40 OJ 20 100 20 ■ — : • — • — 295 2000 LCD 0.5 1000 100 1.0 1000 100 — 500 0.1 20 100 20 — • — • — (B/AC)(CA) 195 2833 4:^ 20.000 LCD 0.05 1000 10 0.5 1000 10 « 50 0.01 20 10 20 ■ * — • — (B.^AG){OH) 356 --■ ■ DBCkniBni 3^ 2000 LCD 0.1 1500 100 0.6 lOOO too ' — 10 0.1 10; too 20 . • — * 259 2000 LCD OJ 1500 100 0.6 100 100 * 40 o.t 10 too 20 — • ■ — • • — 329 Daetron MMiUUA 20.000 LCD 0.2 500 10 2.0 500 1000 0.06 1000 2 1.0 20 ■ ■ ft • 232(0P) (BG)(M)(PH) 450 Fluke 37 3200 LCD 0.1 1000 100 0.5 1000 100 — 30 0.1 10 100 32 m — • • {BG)(CO)(DH) 269 45 5 100,000 FL 0.02 1000 1.0 0.2 750 1,0 • 100 OJ 10 1 300 t • * * ■ • 232(STM88(0P) (OH) 635 2000 LCD OJ 1000 100 0.5 750 too * 50 0.1 10 too 20 • iCO) 379 801 26 3:4 2000 LCD 0.1 1000 100 0.5 750 100 * 50 0.1 2 1 20 • — " iCO) 389 4i4 20,000 LCD 1 003 1000 10 0.5 750 10 • 50 0.01 2 10 20 • — — • ■ — (CO) 479 5^ 200.000 FL Q.005 1000 1.0 0.16 tooo t.o (OP) 100 to 2 1 10 4SS{0P) 875 Dd4£A 200.000 FL 0.003 1000 o.t o.oe tooo 0.1 m too 1.0 2 OJ 20 488{OP) 1095 Goldstar DM7241 20,000 LCD 0.05 1000 10 0.5 750 10 — 50 0.1 10 10 20 — — * — (OH} 229 Kewtett' Packard 34401 A 1,200.000 FL 0.0035 10OO 0.1 0.06 750 0.1 300 0.01 3 0.1 120 232, 488(ST) (M)(DM)(PH) 995 346a A/B 300,000 LCD 0.018 300 10 0.26 300 1.0 ■ 300 1.0 3 1.0 30 — — — — — (B/AC) 1095 3478A ^A 300,000 LCD 0.006 300 1 1.0 : 0.20 300 1.0 • 300 1,0 3 0.1 30 — — — 488(ST) — 1295 Keithley 175A 20.000 LCD 0,03 1000 10 0.5 750 10 • 100 0.01 10 10 200 — — • 488(OP) (B/AC)(OP) 495 196 3.029.990 LED 0.003 300 0.01 0.15 300 1.0 • 100 0.001 3 0.1 300 — • — * — 488(ST) — 1495 197A 219,999 LCD 0.01 1000 1.0 , 0.35 750 1.0 * 100 Q.001 10 1.0 220 • — * 488(0P) (B/ACJ(OP) 659 199 302.999 LED O.OOB 300 1.0 0.15 300 1.0 100 0.0 1 3i 1.0 300 • 488(ST) 1045 20001 21.000,000 FL 0.0007 1100 0.01 0.03 750 0.1 2000 .00001 2 0.001 1000 • * • 48a(ST) {CF){TM) 2695 Kenwood DL712 3i^ 20D0 LCD 0.1 1100 100 0.75 850 1000 0.5 0.1 10 100 20 (B/AC) 249 Leader 856 m 20,000 LED 0.05 10OO 10 1.0 750 100 100 10 3 to 30 232or488(OP} (BG) 800 Prfilek HC-797 32.000 LCD 0.04 1000 10 0,4 750 10 30 OJ 10 10 30 • * * 232(ST) (BG)(CF)(M) 350 Simpson 460-6 20.000 LCD 0.07 1000 10 1.5 750 10 100 OJ 10 10 20 * « {BG)(B/AC) 500 461-2R 2,000 LED 0.10 1000 100 0.5 750 100 SO 0.1 2 100 20 (B) 300 464-4 2,000 LED 0.10 1000 100 1 1,0 750 100 100 0,1 to too 20 • 360 467-2 2,000 LCD 0,10 1000 100 0.5 750 100 5 OJ 2 100 20 • (8G)(PH) 1 420 K ^ A/0 BUFFER COKFteURAIlON) FIG, 6— SfMPUFlEO DIAGRAM of a typical DMM voltage ratio msi stance- measure- ment circuit lead-acid batteries. Manufac- turers offer power options: 117 or 220 volts, 50 to 60-Hz line, and/or batteries. Some bench DMM's have been designed for dual use as pK3rta- ble or rack-mounted instru- ments. Raclc mounting is used in systems applications. The purcliaser can specify the case style desired. Available bench DMM's If you examine Table K Digital Multimeter Characteristics » in- cluded here you will see 3-1/2- digit bench/portable DMMs list priced below S200, and higher performance instruments priced for more than S2600 — a price spread of better than an order of magnitude. Those prices include only the bare nec- essities such as basic test leads, power cord, and manuals. Most DMM accessories such as probes and carrying cases are extra expense items. The basic electrical measure- ment functions in bench DMMs are usually supplemented with special features, many of wliich are can also found in the hand- helds. The most common exam- ples are diode test and audible continuity As stated earlier, bench models are more likely to include true RMS AC voltage and current measurement than handhelds, and system com- patibilit>^ is an exclusive feature with the bench models. Many bench DMMs can also display such math functions as min/ max hold, and provide readouts in dB and dBm. With their focus on accurate measurement, many DMM s have only a few of the special features found in handhelds. TO A/D DOhfVERTER : UNKNOWN DC COfiSlANfTi ill SOURCE Rg. 7— SIMPLE 2-WlHE ohms ccnverter. HI \UPUX TO DC iNPUT AMPLiFIER UNKNOWN Ml -O- i DC CONSTANT- CURRENT SOURCE LOW LOW mpuT ^ LEAD RESISTANCE FIG. 8— SIMPLIFIED 4-WIRE ohms con- verter for ellmioa ting lead resistance er^ rors. Current is supplied by a separate current source. The line separating the features of handhelds from those of bench top DMM's is fuzzy, at least in the $200 to $300 price price range. Features such as peak hold, sleep mode, and ca- pacitance measurement are more likely to be found on the handhelds. But it's worth keeping in mind that, generally speaking, you get what you pay for in bench/portable DMMs. Prices have been raised on many of the models that have been on the market for ten years or more. However, there is general agree- ment that you can get more for your DMM dollar today than ever before. This is due. in part, to the ongoing transfer of ad- vanced A/D converter IC's and microprocessor devices to in- strumentation, and Intense worldwide competition. Experts agree that the most critical parameter In benchtop DMM s land the one you should look at first) Is DC voltage ac- curacy. It can be stated in a number or ways: (% of read- ing + number of least signifi- cant digits). ± [% of reading + % of range), ± [ % of reading + number of counts), and even parts per million (ppm) of read- ing as ± {ppm of readlng + ppm of range). Regardless of the form used, it will be given at a spec- ified ambient temperature » usu- ally between 18^C and 28^C. with relative humidity up to 90%. Accuracy ratings might be given for periods of one year stx months, 90 days, or even 24 hours, lb cut through all this complexity, most inanufac- Ixirers give short forms of their accuracy specification known as basic DC-voltage accuracy. That is what we used in our characteristics table. After you have checked out basic DC-voltage accuracy, you should study the specifications and literature to be sure that the meter you are considering Is a quality product built ruggedly enough to meet your needs and Includes all of tlie accepted user safety and instrunienl protec- tion features for that class of product. Next you might want to examine the basic AC-voltage accuracy rating. A 5-1/2- or 4-1/2-dlglt DMM can be expected to offer higher accuracy and resolution than a 3- 1/2-diglt DMM. and this should be kept in mind during your search. The 1/2 In Lhe spec- ification of the DMM display re- fers to the use of the digit I in the most significant digit (MSD) position. The full scale on a 4- 1/2 digit display, for example, is 9999. but the additional digit 1 permits the displav to show a value that is 100% higher (19999) in what is known as the 100% overrange condition. There is a close but not abso- lute correlation between the number of display digits and counts. For example a 3-1/2- dig- it DMM might have 2000 or even 3200 counts, a 4-1/2-digit meter typically has 20.000 counts, but it could hav^e more, A 5-digit DMM will have 100,000 counts, but a 5-1/2-dig- it meter would be expected to have a count of at least 200,000, Rather than try to define such confusing designations as a 4-3/4 -digit DMM, it is a lot easi- er to look for the display count Uiat we have listed In our selec- tion table. As you move upscale in bench DMMs. prices rise accordingly. Therefore, it becomes even more important to pay atten- tion to the reputation of the manufacturer, and Inquire about any guarantees or war- ranties being offered. Not sur- prisingly, even some reputable manufacturers who are willing to offer 3-year warranties on their handheld and low-cost bench DMM s are reluctant to of- fer more than a one-year war- ranty on their most sophisti- cated bench models. However, one-year warranties can usually be extended for a fee. We suggest that you carefully read and com- pare specifications, literature, and any available evaluations of products before you buy any bench DMM. In searching for the bene fa DMM best suited to your needs, you should consider the value of such features as autoranglng vs. manual ranging, Autorang- lng automatically determines the proper range and polarity for the DMM to display a mea- surement with the best resolu- tion. Manual ranging allows you to override the autoranglng function and make manual se- ANALOGIC S DP 100, BECKMAN INDUSTRIAL'S MODEL S&O lections. While some DMM's have both, many high-perfor- mance DMMs do not include autoranglng. This is acceptable because those instruments will be used in controlled environ- ments where the ranges of un- known signals are generally known. Measurement capabilities In addition to basic DC-v^olt- age accuracy you will want to know the maximum DC voltage that can be measured without a plug-In probe, and maximum DC-voliage resolution, Basic DC-voltage accuracy will range from 0.1% in 3-1/2-digit (2000 count) meters to 0.003 % in 5-1/2-digit (200,000 count) meters. A rating of 1000 volts maximum DC voltage is com- monplace in modern bench DMM s; it will be obtained at the high end of as many as five ranges, typically 200 mV, 2 V, 20 V. 200 V, and lOOOV. Maximum DC-voltage resolution should typically b^ a value of 100 micro- volts or less. The AC-voltage specifications also include basic accuracy maxitnum resolution, and max- imum (RMS) value without the use of a probe. Frequency range l!i hertz over which AC mea- surements are valid is another variable included under AC volts. Basic AC-voltage accuracy Is typically a fraction of the DMMs DC-voltage accuracy; in some cases it is as much as an order of magnitude less. Maximum AC resolution, also measured in microvolts, typ- ically matches the values for DC volts. Maximum voltages for bench DMMs are typically be- tween 750 and 1000 volts AC RMS. Expect five AC voltage ranges comparable to the DC voltage ranges. The ability to measure true RMS volt age "is a popular feature for bench DMMs; most bench DMMs ei- ther otTer this feature or make provision for it as an option. Maximum ratings for AC and DC current in amperes that can be measured without a probe are also importan t for the bench DMM usen Don't be surprised to find that handhelds have higher maximum current ratings than high-performance bench meters to protect against the unknown conditions encoun- tered in making current mea- surements in the field. They could be only 2 amperes. How- ever, you can expect the bench meter to have better current res- olution — 0,1 microampere or better Maximum resistance values that can be read on a bench DMM are typically 20 megohms or belter but they could be as FLUKE'S DUAL-DISPLAY MODEL 45 high as 300 megohms. How- even maximum resistance reso- lution could be 1 milliohm or less in the high-end models. The diode tests and con- ductance measurement func- tions are less popular in high- performance DMM's. Special features Beyond the capability for measuring the five basic elec- trical parameters and doing di- ode tests, many DMM functions are considered to be speciaL In general » with the exception of system compatibility, none are exclusive to bench DMMs. Because of their normally controlled working environ- ments, accuracy and resolution outrank versatility in the selec- tion of a bench DMM. It has been found that specialized temperature, frequency, and even capacitance measuring in- struments are preferred over i» 1 GOLDSTAR'S MODEL DM-7241 those functions in DMMs used in labs or shops. Manufacturers will, however, include these functions if they find a demand for them. But if you don't need them you could be paying a lot for a feature with lower perfor- mance than is obtainable in a specialized instrument. By contrast, the handhelds follow the Swiss Army knife phi- losophy of stuffing as many "tools" as is practical in a single package. Battery conser\^ation and protection against personal shock and destruction of the DMM are, as you might expect, more important characteristics in handhelds. True RMS voltage and cur- rent: This feature provides accurate measurement of non- sinusoidal waveforms such as square waves, pulses, or the outputs of silicon-controlled rectifiers. This function, either standard or optional, is widely found in bench DMM's» but less often found in handhelds. You can be sure that any DMM with the true RMS measurement fea- ture will cost more than a com- parable meter without that feature. System compatibility: Some bench DMM's offer an El A RS-232C and/or IEEE-488 in- terface as either standard or op- tional features. The RS-232C interface allows data to be inter- faced to any serial printer or computer. The data can be filed, manipulated, printed, or trans- mitted by modem. Internal DMM circuits format the mea- surement data transmission. Host computer software per- mits remote operation of all in- strument functions. IEEE-488 (also known as the general purpose information bus or GPIBK is a parallel inter- face bus that consists of eight bidirectional data lines and eight signal grounds (three wires for handshakes between equipment* and five wires for management). Some DMMs permit both RS-232C and GPIB interfaces. Although RS-232C interfaces are becoming more popular because of the pro- liferation of personal computers in laboratories, the IEEE-488 HEWLnrPACKARD S MOOEL 344aiA KEITHLEY'S MODEL 2001 bus is si ill widely used in indus- trial data acquisition systems. Decibel (dB) and dBM read- out: DMMs with this function measure and display the dB gain or loss of amplifiers, filters or attenuators- The dBm read- out is referenced to 1 milliwatt and 600 ohms. Offset/relative reference: This function stores the input in memory as a zero "reference". Any subsequent input is auto- matically compared to the refer- ence in memory, and the display shows the difference ( ± ) be- tween these two values- It is also a handy feature for nulling out test lead resistance or measur- ing the dB gain for the stages of an audio amplifier. Relative ref- erence works in all functions and ranges, and is a feature found on high-end handhelds and low-end benchtops. Frequency or period: Some DMM's can also measure fre- quency or its reciprocal period. Bench-type DMM*s are likely to have frequency responses in the megahertz range, especially if they have six or more readout digits. Some DM Ms now have AC voltage input ranges as high as 15 MHz and AC current input to 1 MHz. These can be trans- lated into period. You will want to know accuracy, sensitivity, maximum input, and trigger level for these measurements. Temperature measurement: Some bench DMM's have the ca- pability for measuring tempera- tures with one or more standard thermocouples or a resistance temperature detector [RTDJ. Here again, the specified ac- curacy and resolution will be important in your decision if you want this feature in your multimeter Continuity beeper and diode test: Continuity, diode and transistor checks can be made quickly on DMMs with this fea- ture without looking at the dis- play. A continuous tone indi- cates continuity, while a beep signals a forward-biased diode or transistor The beeper is easi- ly heard in a noisy industrial environment. Analogic Corp. 8 Centental Drive P^abody, MA 01960 (508) 977-3000 CIRCLE 301 ON FFI6E INFORMATION CARD Beckman Industriai Corp, Instrumentation Products Div, 3833 Ruffin Road San Diego,, CA 92123-1898 (619) 495-3200 CIRCLE 302 ON FREE INFORMATION CARD B&K Precision 6470 W. Corlland St. Chicago, IL 60635 (312) 889-1448 CIRCLE 303 ON FREE INFOBMAtrON CARD Daetron 935 The Queen sway, Box 641 Toronto, Ont. Canada M8Z-5Y9 (416) 676-1600 CIRCLE 304 ON FREE INFORMATION CARD John Fluke Mfg, Co. Box 9090, MS 250E Everett, WA 98206 (800) 443-5853 {800-44 -FLUKE) CIRCLE 305 ON FREE INFORMATJON CARD Min/max bold: DMM's with this feature store the highest and lowest readings, permitting you to monitor a signal for sec- onds» or even days. Collected average values during the period arc calculated and dis- played, and when the recording period ends, you can examine the readings at your con- venience. Overloads or manual stop/starts wont erase memory until you give the command. Min/max recording is possible when measuring AC and DC voltage or current, and resis- e&K PRECISION S MODEL 2833 tance. This feature is also found on some handheld meters. Analog Bar Graph: The ana- log bar graph Is a segmented analog needle simulator. It per- forms the same role as a VOM needle, while eliminating the mechanical/inertial distortion BENCHTOP DMM SOURCES Goldstar Precision 13013 E. 166 St. Cerrilpos, CA 90701 (213) 404-0101 CIRCLE 306 ON FREE INFORMATION CARD Hewlett-Packard Company 19310 Pruneridge Ave- Cupertino, CA 95014 (800) 752-0900 CIRCLE 307 ON FREE INFORM ATION CARD Keith ley Instruments, Inc, 28775 Aurora Road Cleveland. OH (216) 44139 (216) 248^0400 CIRCLE 30B ONFRliE INFORMATION CARD Kenwood USA Corp, 2201 E, Dominguez Si. Long Beach, CA 90810 (213) 639-4200 CIRCLE m ON FREE INFORMATION CARD Leader Instruments Corp. 380 Oser Ave. Hauppauge, NY 11788 (516) 231-6900 (800) 645-5104 CIRCLE 310 ON FREE INFORMATION CARD inherent in a needle's move- ment. This feature is not widely available in bench DMMb. Sleep mode: This feature au- tomatically shuts off power if you forget or if no measure- ments are taken for a specified length of time, say 60 minutes. This conserves battery life. It is found in some battery-powered bench meters. Peak hold: This feature is useful for recording transients as low as 1 millisecond, es- pecially from intermittent power lines or connections. This mode can also be used to measure the plus and minus peak values of sine waves up to about 450 Hz. It permits easy measurement of both peak line voltage and line current in power supplies and electrical equipment. However, it is rarely found on bench DMM's. Data hold: This feature is known by different proprietary names such as "touch hold" or "probe hold." It allows you to keep your eyes on the probes and on the circuit under test. The DMM's microcomputer de- termines when the input signal is steady alerts you with a beep, and then captures and holds the measurement on the display until you are ready to view it. It Prema Precision Electronics Inc. 4650 Arrow Highway Building Montclair CA 91763 (714) 621-7292 CIRCLE 311 ON FREE INFORMATION CARD Protek Inc, RO. BoK 59 Norwood, NJ 07648 (20t) 767-7242 CIRCLE 312 ON FRgE INFORMATION CARD Simpson Electric Co, 853 Dundee Ave. Elgin, IL 60120 (708)697-2260 CIRCLE 313 ON FREE INFORMATION CARP TripJett Corp. One Triplet! Drive Bluffton, OH 45817 (419) 358-5015 CIRCLE 314 ON FR£E INFORMATION CARD Yokogawa Corp.- America 2 Dart Road Newnan, GA 30265 (404) 253*7000 CIRCLE 315 ON FREE INFORMATION CARD automatically updates with each new measurement. Reading spec sheets Manufacturers' specification sheets can be quite confusing because they do not follow a uni- form format. They can be es- pecially intimidating for the first time DMM buyer trying to decipher the baffling termi- nolog)'^. The wise buyer should understand such terms as CMR, NMR, and RMS. average, and peak AC readout. Definitions of some of the commonly used terms in DMM specificastions sheets will be helpful to you. Remember that the manufacturers are trying to attract your attention to their instrument's more glamorous features which may or may not be something you need. So bro- chures do not necessarily rank the qualities that are of most importance to you in any logical order. The burden for interpret- ing these specifications falls on you, the prospective buyer and user. But this also holds for a lot of other purchases such as ap- pliances, automobiles or home- entertainment products. Noise is an especially severe problem in DMMs due to their high accuracy, resolution, and sensitivity. DMMs used in sys- tems are more susceptible to noise than those used just in isolated measurement applica- tions. Long signal leads and coupling between adjacent sig- nal leads compound the prob- lem in systems. Noise can be defined by its ori- gin relative to signal mput lines on the DMM. Normal-mode noise enters with the signal and is superimposed on it. Com- mon-mode noise is common to both the high and low signal in- puts. Common mode noise be- comes normal-mode noise when it fiows into the DMM's signal inputs. Normal-mode noise ori- ginates from power-line pickup, electromagnetic fields or even from within the device being measured. Noise can be sin- usoidal, spikes or white noise. There are two techniques used to reduce normal-mode noise: integration and filtering. Inte- LEADER S MODEL BBS SIMPSON S MODEL 460-6 TRIPLETT'S MODEL 4800 gration stretches the measure- ment out over a fixed period of time during which amplitude variations are averaged out. If the integration period includes a sufficient number of periodic noise cycles, the noise will be averaged out. Filtering slows down the con- version process or measure- ment speed so it is used judiciously Integration does a better job of rejecting line-re- lated noise, and filtering is bet- ter for broadband noise. Common-mode rej e c t i o n (CMR) is a measure of the change in output voltage when both inputs are changed by equal amounts of AC and/or DC voltage. It is the measure of an instrument's ability to cancel undesirable signals entering the measurement circuit be- tween the input and ground. A reasonable value for CMR in a bench DMM is 100 volts DC or peak AC from any earth input. Normal-mode rejection (NMR) is a logarithmic measure of at- tenuation of normal-mode noise components at specified frequencies in dB, For an ampli- fier used in instrumentation, the normal-mode signal is the actual difference signal being measured. This signal often has noise associated with it. DC voltage uncertainty = Kppm of reading) x (measured value) -i- (ppm of range) x (range used) 1/1, 000, 000, Percent uncertainty = (ppm uncertainty)/10.000. AC voltage uncertainty = 1% of reading) x measured value) -f (% of range) x (range used)]/100. Crest factor (CF) expresses the waveform's peak value ratio to that of its RMS value. Crest factors in true RMS meters ac- tually specify their dynamic ranges. Self-test: DMM's with a micro- processor-controlled seif-test feature usually run through this routine when they are turned on and the results show up on the display as segments that appear as rapidly as four times per second. Self-check capability Is ex- tremely important for the as- surance of accuracy and con- tinued calibration to laboratory or international standards. Nev- ertheless, all DMM's, even those with this feature should be re- calibrated at least once a year for maximum accuracy and re- liability. Imput impedance is the com- bined AC and DC resistance at the input of the DMM. An input impedance of 10 megohms or better virtually eliminates mea- surement errors caused by load- ing in most circuits. The outstanding charac- teristics of bench-type DMM*s have been highlighted primarily ^ on a basis of published specifi- ^ cations and unusual features. g In an evaluation section that fol- N lows we have selected a cross- ^ section of available benchtop %^ DMMs and discussed some of m their outstanding features. All a of the bench multimeters dis- § cussed in this article are capa- g ble of making the five basic elec- trical measurements: AC and DC voltage, AC and DC current and current. 39 Selected reviews Analogic offers the DPI 00. with a 5-1/2-digit LCD display capable of measuring voltage current and resistance. It is also a frequency counter capable of measuring up to 25 MHz as well as an RTD temperature meter. The portable DPIOO is powered from both built-in rechargeable batteries and the AC line. It of- fers ±0,003% basic DC-voltage accuracy. 0, 1-microvolt sen- sitivity and the ability to mea- sure true RMS AC voltage and current, and 2- or 4-wire resis- tance. The DPM Includes RS-232C compatibility or op- tional lEEE-488.2 converter. B&K Precision offers three bench DMM's all capable of making the live basic measure- ments—AG and DC voltage and current, and resistance. The model 2831A is a 3-1/2-digit meter with a LED display that also offers continuity checking and diode test. It has a Oa% basic DC-voltage accuracy rat- ing. The model 2833 with a 4-1/2-digit LCD display, features true RMS voltage and current measurement. It has basic 0.05% DC-voltage accuracy. Other features include audible continuity check, diode test, data hold. dBm readout, and frequency measuring. The B&K model 2832, with a 3-1/2 digit LCD display, mea- sures capacitance. lt*s basic DC- voltage accuracy is stated at 0.5%, Other features include audible continuity check and diode test. This DMM can be powered from the AC line or six "C* cells. Beckman Industrial Corp. of- fers two 3-1/2-digit bench/ por- table DMMs with LCD displays, the models 350 and 360 B. Both are packaged in similar cases with a front-panel rotary func- tion switch, and both have basic 0.1% basic DC-voltage ac- curacy and 22'megohm input impedance. In addition to the five measurement functions, the meters provide audible con- tinuity checking and diode test- ing. The model 360 offers true RMS AC voltage and current measurement as well as temper- ature measurement with a type K thermocouple. Both meters are powered by six "D" cells and are built for field use. John Fluke Mfg. Co. offers a family of seven bench/portable DMM^s with 3-1/2 to 5-1/2-dlgit displays. Some also offer diode test and others measure con- ductance. There is, however, considerable variation in the special features offered. The 3-1/2-digit model 37 has a basic DC*voltage accuracy of 0.1% and the 5-digit model 45 has a basic DC-voltage accuracy of 0.02%, The model 45 has a dual vacuum-fluorescent display and it can measure frequency and display dB and dBm. It also has the m in/max hold feature. Fluke is also offering two 5-1/2-digit models in the 8800 series, the 8840A and 8842A. The 8840A offers 0.005% basic DC-voltage accuracy, while the 8842 A has 0.003%, Both fea- ture optional true RMS AC volt- age and the ability to measure frequency to 100 kHz. Goldstar Electronics offers the DM-7241 with a 4-1/2-digit LCD display. It has a basic DC- voltage accuracy of 0.05% and a resistance range to 20 megohms. Hewlett-Packard offers four bench top DMM's. The HP34401A has a 6-1/2'digit vac- uum-fluorescent display and features true RMS AC voltage and current measurement. Re- sistance is measured in ohms with 2- and 4- wire circuits. In addition, the model 34401A measures frequency, period, and continuity^ and can do di- ode tests and DC: DC ratios, DC- voltage accuracy is given as 0.0035% while AC-voltage ac- curacy is 0.06%, The meters bandwidth is 3 Hz to 300 kHz. Its math functions include null, min/max average, dB and dBm readout, and limit test. Both the IEEE-488.2 and RS^232C inter- faces are standard. Keithley Instruments offers five bench/portable DMMs. The model 2001 has a 7-1/2- digit dis- play and a rated basic DC-volt- age accuracy of 0,0007%. Basic AC-voltage accuracy is given as 0.03%, and bandwidth is 1 Hz to 2 MHz. The 2001 can mea- sure resistance values from 1 micro-ohm to 1 gigohm. It takes 2000 readings per second with 4-1/2-digit resolution, 300-500 with 5-1/2-digit resolution, and between 45 and 200 with 6-1/2- dlgit resolutton. The 2001s standard mea- surement functions include AC crest factor, frequency from 1 Hz to 15 MHz, true RMS, and peak and average AC. It also makes DC in-circult current measure- ments, and offers simultaneous displays. Options include a ten- channel scanner. GPIB (lEEE-488.2) output is stan- dard. Kenwood USA Corp. offers the model DL-712 that has both manual and autoranging. Other standard features of the DMM include diode test, data hold, and continuity checking. Leader Instruments' model 856 has a 4-I/2-digit LED dis- play which inciudes a bar graph. Equipped with auto- ranging, it measures true RMS and frequency. The 856 also does diode test and continuity checks, displays dB and dBm, and makes data comparisons. Its basic DC-voltage accuracy is 0,05%, Simpson Electric offers four 4-1/2* and 34/2-digit benchtop DMM's. They all feature true RMS AC measurement. The 4-1/2-digit 460-6 offers Ni-Cd battery/AC^line operation and 0.07% DC volts accuracy. The 467-2, a 34/2-digit DMM, has peak hold. TOpIett Corp. offers the model 4800, a 4-1/2-digil benchtop DMM with true f^MS readout Its features include data memo- ry, peak hold* dBm readout, au- toranging, temperature mea- surement, and diode test. Yokogawa offers the 5-1/2-dig- it models 7551/7552 and the 6-1/2-digit models 7561/7562. They are rated for basic DC- vollage accuracies of 0.005% and 0.003%. respectively. These DMM*s can be calibrated with external signals. The 7552 and 7562 offer RMS AC measure- ment, while the 7551 offers AC mean measurement. The 7552, howeven offers both frequency measurement and a 20-ampere range. The RS-232C or lEEE-488 interfaces are stan- dard on all these models, R-E MOST SMA1.L BANDS USUALLY HAVE ^feuch a hard time paying for travel and instruments that their shows must forgo any type of sophisticated lighting. The lights provided by the clubs and bars where they play do little to showcase a bands talent. With the MIDI (Musical Instrument Digital Interface) light control- ler presented here, that can all end- A simple microprocessor with a handful of components can transform their act into a full fledged '^concert/' Every* thing that is needed to syn- chronize lights and music already comes out of the MIDI port of MIDI keyboards. This cir- cuit will make use of that infor- mation and enhance the show. MIDI is a communications protocol originally created for interfacing syntliesizers and other electronic devices, li has evolved into a communications standard that is used in all phases of audio and video pro- Our MIDI fight controller can turn an ordinary musical performance into a concert! duction, MIDI allows devices to talk to each other with different types of control and data values. The values can be either channei.. system, ri£A1.-tjiviEh or SYSTEM exclusive mcssagcs* MIDI communication is achieved through multi-byte messages, each consisting of one STATUS byte foUowed by one or two DATA bytes, f-ieal-time and exclusive messages are excep- tions to that rule. Two types of data bytes are sent over the MIDI cable, status and data. Status bytes are eight- bit binary numbers in which the most-significant bit is set to "L" A status byte sets the func- tion of the data by tes that follow it, and a new status byte is re- quired for each new action. The MIDI specification also outlines RUNNING status. That defines the action for all data bytes that ^ follow a status byte> until a new ^ status byte is sent. That way 5 more information can flow down the cable. Data bytes are J eight-bil binary numbers in %- wiiich the most-significant bit m issetto**0/" " ^ The MIDI light controller pre- | sen ted iiere reacts to note oh, g NOTE OFF. START. STOR and continue status bytes. The data bytes are used to determine which light to control and how 41 10 11 12 13 14 DO D1 UHZ11 D3, ADDRESS OA ^^^^^^ D5 D6 D7 B2^ 5K E3 1 + 5V 0 1 2 3 4 5 6 7 KEYPAD iC5 74C9Z2 D DE DA DEawc OSC INTO ADDRESS (20001 13 12 C4 lO^F C5 4r FIG. 1— SCHEMATIC OF THE MAIN PROCESSOR BOARD, The MIDI signal is fed In through an optocoupfer (IC&) to the microcontroller (Id)- to respond to different condi- tions on the MIDL It can operate on any of the 16 MID! channels, and will respond to note infor- mation from octaves 1—8. The MIDI Hght controller is user- configured. You have control over whether the lights will iatch, toggle » or stay off in reac- tion to note information- on the MIDI by setting the output type keyboard selection. When a stop command is re- ceived (stop, start, and CONTINUE commands syn- chronize all elements of a MIDI system), the lights can either all go off, all go on, or light selec- tively, depending on the user's STOP DEFINE parameters. That is useful for creating a ''scene*' be- tween songs and during breaks on stage. The control octave determines which range of notes will be used to control the lights. The operating channel is set by selecting channel define. The message change channel # will be displayed on line L Line 2 will toggle between "1" (chan- nels 1-8) and "2" (channels 9-16). You must select ^T" or ^^2" for the desired range of chan- nels (1-8 or 9—16) and select the desired channel. The lights are controlled by note information on the MIDI. They can respond to actual notes of a song or notes that are placed in the sequence specifi- cally for the light controlleL To use existing notes, you would select the channel and octave from the sequence, and enter them on the keyboard. If the lights are to be controlled by a separate track, you would enter the note information for each light, keeping all notes m one octave. Timing and syn- chronization is provided by a se- quencer (A sequencer is any instrument that can store and read back MIDI dataj The light controller will also work directly from a keyboard without the aid of a sequencer by connecting a keyboard's MIDI output to the jack on the light con t roller. As you play the keyboards the appropriate lights will illuminate. The circuit Figure 1 shows a schematic of the main processor board. The MIDI signal is fed in through IC8, an HP 6N138 optocoupler. Any optocoupler can be used as long as it has a rise time of less than 2 microseconds, and can turn on with less than 5 mA. The MIDI signal has the follow- ing operating specifications: 3K25-kHz baud rate, asynchronous* 1 start bit, 8 data bits, and 1 stop bit, with a period of 320 microseconds per serial byte. The signal is well suited to the serial portion of the Intel 80C32 microcontroller (ICl) that has built-in transmit and receive serial ports, 128 bytes of internal RAM, two inter- rupt lines (each with program- mable priority), and external memory addressing capability up to 64K. The CMOS version of the 8032 was used because of Its higher speed and lower power consumption. The output of optocoupler ICS enters the serial receive port (pin 10) of microcontroller ICl. Software in the 27C64 EPROM (ICS) controls port setup and baud-rate selection. At power up, a small reset circuit (R3, D2, and C3) initializes the micro- controller. An oscillator is made up of a 12-MHz crystal (XTALl) INCHES . COMPONENT SIDE FOIL PATTERN for the light controiler BVi INCHES SOLDER-SIDE FOIL PATTERN for the light controller and two 30 pF capacitors (CI and C2). The address and data buses of the microcontroller are multi- plexed, lb remove the low-order address information, a 74LS373 8-bit latch is used. The 74LS373 is strobed with the ALE (address latch ElMAFiUi) signal from the microcontrollen and address data is removed. The 27C64 EPROM (IC3) is used to store program data. The EPROM is enabled by the micro* controller's psen (program STORE enable) line. The keyboard and LCD cir- cuits both require an address signal to interact with the data bus, A 74LS138 (IC4) is used to generate a signal when certain addresses are reached (lOOOh, 2000h, 4000h. 6000h,.,), The keyboard is mapped at external address 200 Oh. The keys are scanned by the 74C922 key- board controller chip, IC5. All keyboard action, including de- bouncing, is handled by ICS. The scan rate is controlled by C4, and debouncing by 05. The LCD is mapped at exter- nal address 8000h. An Opt rex LTN211 two-line LCD module is used to display current channel and mode information. Also, user-definable selections are displayed there. Function data is written to the module at ad- dress 80D0h. and display data is written at 8200h. Address selec- tion and read/write functions are established by IC6, a 74LS00. Contrast of the LCD is altered by R21. Output from the microcontroller is on port 1, pins 1-8. A resistor network, R30, is used to pulLup output lines. The lines drive the Triac and LED sections. Figure 2 shows the high- power outpul section of the light controller. Eight identical drivers are used to control the output channels. An output from ICl is passed through a 1N914 diode and a 120-ohm re- sistor that drives an MOC3010 Triac-driver optocoupler. Out- put from the optocoupler is sent to a high-power Triac. The cir- cuit is designed with 6-amp Tri- acs, which are fused at 5 amps for added protection. The 120- volt AC input to the Triacs must 0^ AO OUTLETS FIG. 2— HIGH-POWER OUTPUT SECTION. An oytput from the microcontroller is passed through a 1N^4 diode, a 120^hin resistor, an MOC301O Trtac-driver op- toco u pier and finally to a high-power Triac. be connected to a circuit that can handle the current. Power consumed by the light control- ler at 120 volts AC with aU eight channels operating at full power is 4400 watts — that's almost 40 ampsf Most household wiring is 15 or 20 amps per circuit break- en so the AC input should be separated into multiple circuits to control that much power Figure 3 is the LED display section. It's used to indicate which output channel is active. It also helps you set up MIDI se- quences without having to hook up any external lights, A clean 5-volt DC power source is required for the light controller The author used a self-contained 5-volt supply that includes a built-in trans- former, rectifier and regulator The supply accepts a 120-volt AC input and outputs 5- volts DC. You can use a similar sup- ply if you like, although they are 10 m S02 FROM ?2 -O+SV 13 15 17 10 olB 20 r 1A1 1A2 1A3 1A4 ™ IC7 2A2 74L5244 2A4 1Y1 1Y2 1V3 1Y4 2Y1 2Y2 2Y3 2Y4 18 16 -^VA 12Q12-120£1 R24 i2oa B26 12011 R25 120Q R2B t2GQ R27 R29 i2oa LED2 LED3 LED4 0 0 LED5 LH06 LE07 LEDe 0 0 0^ FIG. 3— LED DISPLAY SECTION. These LED^s will indicate which output channel Is active without having to set up the full-power lights. more expensive. Otherwise any 5'volt supply will do. Software Software for the light control- ler is interrupt-driven. Upon re- ception of MIDI data, an interrupt is generated. The soft- ware jumps to the interrupt routine for the serial port. First the interrupt is cleared, then the byte is placed in the receive buffer. As more data comes in, it is buffered. The iteyboard also generates an interrupt any time AM resistors are Vi-watt, 5%, unless otherwise noted. Rl , R4— 220 ohms R2— 280 ohms R3--1 0,000 ohms R5, R6, R8, RIO, R12, R15, R17, R19, R22-R29— 120 ohms R7, Rg. R11 , R13, Rt4, R16, R18, R20— 180 ohms R2 1—5000 ohms, poten Ho meter R30— 1Kx8 SIP resistor Capacitors CI, C2— 30 pF, mica C3— "10 jjlR 16 volts, electrolytic C4— 10 tantalum CS— 1 jxF, tantalum Semiconductors IC1— 80C32 microcontroller IC2— 74LS373 8-b3t latch IC3— 27C64 EPROM IC4™741S138 3"to-8 demultiplexer tG5— 74C922 16 -key keypad encoder IC6—74LSG0 quad NAND gate IC7—74LS244 octal buffer/line driver ICS— 6N138 optoGoupler IC9-JC16— MOC3010 optoisolator D1-D1C^1N914 diode TR1-TR8— any 6-amp Triac in aTO-220 case LED1-LED9 — Chassis-mount light- emitting diode, any color Other components XTAL1—12-MH; crystal F1-F8 — 5- amp fast- bio fuse PI, P2— 10-pin header strip SOI, S02— 10-pin header socket J1«™5-pin DIN socket Misceilaneous: inverter {for use with LCD backplane, see text), 5-volt power supply {see text), project case, grounded AC tinecord, 8 grounded AC outlets, wire, solder, etc. I^ote: The following items are avail- able from Audio Visual Imagery, P.O, BOX 332, Randolph, MA 02368: • PC board— S35.00 • Programmed 27C64 EPROM— $10.00 A diskette with the sample fifes wiN be included with any order. Please add $1 .50 S&H to any order, ^fl A res- idents must add 5% sales tax. a key is pressed. As in the serial section, first the interrupt is cleared. The main monitor loop of the program simply tests to see if data is in the receive buffer or the keyboard flag is high. If data is in the buffer, the byte is checked for a high MSB indicat- ing a status byte- If it is a status byte, the status register is up- dated. The status will then re- main until a new status byte is received. Tlie program then continues the main monitor loop. If the byte is data, it is ex- amined to determine the action to be taken. Depending on the current user-set mode of the controller, a light will be turned on, a light will pulse, or nothing will happen. If the data turns out to be bad, it is flushed. After examining the data and acting upon it, the main monitor loop is resumed. When the key Oag is high, the data in the temporary liuffer is exam- ined. The action desired is stored in the appropriate regis- ter. The main monitor loop is then resumed. All user-defined actions are entered on the key- board. As options are entered, the LCD displays the choices available. The option being de- fined is displayed on the top line, and the selections are cy- cled through. Press the key for the desired action. If more infor- mation is needed for the chosen item, it will be presented on the LCD. The source code for the EPROM and some sample files to run on a sequencer are avail- able on the RE-BBS as a self- unarchiving zip file called MLC1.EXE. A programmed EPROM is available from the source mentioned in the Parts List. Construction The PC board for the light controller can be made using the foil patterns weVe provided, or it can be purchased from the source mentioned in the Parts List. A parts-placement di- agram is shown in Fig. 4, Notice the row of pads to the left of the PI header that divides the board down the center; the board can be cut there if you want to re- motely locate the power section of the board and then run low- voltage wiring between tiie two sections. If you are going to cut the board in two, do it before stuff- ing it, as it will be easier. Install the components according to Fig, 4, and check your work as you go. The pads marked "INV'* on the board are for a voltage Inverter (see parts list), if used. It that generates the proper volt- ages for the backlight on the LCD if the LCD you use has one. If it does have a backlight, and you wish to use it, install the inverter and connect the LCD's backlight terminals to the pads marked "BL" on the board. Any kind of case will do for tilts project, as long as every- thing Ots inside — keep in mind the power supply you will use and be sure to leave room for it. If you use a metal enclosure be FIG. 4— PARTS-PLACEMENT DIAGRAM. The PC board can be cut down the row of pads to the left of the PI header If yau want to run low-voltage wiring between the two sections. sure to ground it to the AC safe- ty ground as shown in Fig. 2, and also properly ground all eight AC outlets. As a reminder, the light con- troller can output about 5 amps per channel, and any wire com- mon to all eight outputs must carry about 40 amps. The con- trollers internal AC wiring must therefore be chosen accordingly. Also, if your house wiring is rated 15 or 20 amps per circuit breaker, the AC input to the controller should be separated into at least two circuits. Figure 5 shows the current version of the PC board. Ibating To test the light controller, simply adjust R21 to the middle of its range, and appiyaclean 5- volt DC power source to the cir- cuit. A message will appear on the LCD. Adjust R21 tor the best-looking display. Plug a MIDI cable into the Mun in jack (JI) on the light controller The other end should be placed in the OUTPUT jack of a sequencer or the THRU jack of a svnthesizer. (If you're not using a sequencer, connect it to the output jack of the keyboard.) At power up, the light controller is on MIDI chan- nel 1. Make sure your MIDI equipment is sending notes out on channel 1, As notes are sent, LEDl will light, indicating that data is being sent over the MIDI. As notes are received and exam- ined, the appropriate LED(s) will light (as long as the notes are In the control octave of the light controller). If the circuit does not work, check the supply voltage. Make sureXTALl is oscillating. Check for a I -microsecond reset pulse on pin 9 of ICl at power up. If the reset circuit does not pro- duce a pulse, the circuit will not start up. At power up. the eight LED's should light and then ex- tinguish. If that does not hap- pen and tlie clock and reset circuits are working, check the wiring of the LED's and the Dri- ac section. If nothing happens still, the problem is with the mi- crocontroller. Check the wiring of the ADDRESS and data bus. The circuit will function with- out the keyboard and LCD sec- tions. If the circuit seems to be working (responding to MIDI notes* turning on LEDs) but the keyboard and/or LCD do not respond, check the wiring of IC4 and IC6. Check for read and WRITE (rd and wr) signals from ICl, pins 17 and 18 respectively Along with source code and HEX data for the EPROM, sam- ple songs are provided in the zip file on the RE-BBS. (The sample flies are also included with any order from the source men- FIG. 5— THE CURRENT VERSION of the PC boardi shown here with all parts in- stalled. tioned in the Parts ListJ Three samples are provided in both *.WRK and MVtID formats that will help you get started. The songs were set up using a Roland MT-32, Cakewalk 3.0, and our MIDI Light Controller The MIDI Light Controller and knowledge of your sequencer's operation will provide you — and your audience — witli a great looking show r-e SOLID STRTe RCLRV Why buy expensive^ commercially made solid-state relays when you can make your own solid-state relays at a fraction of the price? SOLID-STATE RELAYS MAKE IT A Cinch to connect digital logic to the nasty world of 115 volts (or more). These handy little de- vices make it possible for a bat- tery-operated supply to turn on 100-watt light bulbs. lO-^horse power motors, a lawn sprin- kling system, or almost any- thing else you can imagine. Solid-state relays, or SSR's, usually consist of an op- toisolator and a TViac, which is used as an AC switch. There are many SSR variations such as those using reed relays m place of the optoisolator, and those using SCR's instead of Tk-iacs, but most consist of less than a dozen parts. Solid-state relays can provide isolation from 2 to 7. 5 kilovolts and can drive tens of amps. They're usually offered in a plas- tic-fiited cube with a heat sink on the bottom and screws for attaching the four wires — nothing could be simpler. There are three common com- plaints with SSR's: First is the cost — twenty dollars apiece is about average. Second is the fact that they can't be repaired. When SSR's go bad, the fix could usually be a two-dollar IViac. but you can't get inside the plas- tic potting compound to repair it. Third is the fact that most SSRs made in large quantities are usually rated at about 10 amps. Who wants to pay for a ten-amp relay when all he needs RODNEY A. KREUTER is a two-amp relay? Besides, the larger the TViac, the larger the leakage currents. There is hope for readers of Radio-Electronics, however. Using all new parts, the solid- state relay presented in this ar- ticle can be built for less than eight dollars. An added bonus is that it can be repaired if any- thing goes wrong. Operation The basic operation of a solid- state relay is much like a switch that is controlled by an input voltage or current. That is illus- trated in Fig. L Keep in mind that this switch can only be used for AC voltages because it wiU "latch up" on DC. (A TViac will turn off only when the cur- rent drops to zero.) Our SSR circuit is shown in Fig. 2. Diode Dl provides pro- tection in case you connect the input backward. Resistor Rl limits the input current. If you would like to use an SSR that requires a large input voltage (to increase the noise immunity) you can make Rl a large value. If you make Rl 470 ohms, the re- lay will need about 12 volts to turn on. The power rating of Rl is a function of the maximum Input voltage. For inputs up to 10 volts, a 1-watt resistor is needed. The voltage across Ql's collec- tor-emitter junction is almost constant (with a minimum in- put of three volts) at 1.75 volts (typical LED voltage) plus 0.7 volts (typical V^j^), or 2,45 volts. The voltage across Rl will there- fore be the input voltage minus about 2.5 volts. The minimum input voltage needed to turn on the SSR is a function of the minimum LED current (the LED inside ICl) and RL The minimum for the MOC3010 is 15 milliamps. That works out to an input voltage of about 4 volts using the compo- nents shown. You can reduce the minimum voltage needed by decreasing Rl or by using an op- toisolator that requires less LED current. Since the LED needs about 1.75 volts across it before it begins to emit light, operation below three volts isn't practical. The maximum cur- rent through the LED is set by resistor R2. When the voltage across R2 reaches about 0,65 volts, Ql be- gins to conduct, shunting cur- rent from the LED. The result is a that, although the current through Rl rises as the input g voltage rises, the current ^ through the LED stops increas- ? ing at about 15 milliamps. The minimum LED current, there- Q] fore, is not the minimum cur- | rent you can pass through the | LED: rather it is the minimum SJ LED current that will operate the Triac. Probably the most misun- derstood aspect of solid-state re- 47 LOAD IMI AC SOURCET SOLID STATE RELAY FIG. 1-A SOLID-STATE RELAY is much like a switch that is controlled by an in- put voltage or current. POSITIVE INPUT you can use a transistor to pro- vide a current sinlt as shown in Fig. 5. Zero-voltage switching Some of the newer SSRs pro- vide zero-voltage or zero-cross- ing switching, in normal opera- Q1 2N3904 FUSE RZ 43Q MTt R5 OK BLACK IH0T1 AC PLUG ItSVAQ '(SAFETY GROUND) TR1 NEGATiVE INPUT 1 LOAD WHITE I (AC DAILY) (NEUTRAU FIG. 2— SSR CIRCUIT. Diode D1 protects the unit if yoy connect the input backward, and R1 limits the input current. lays is that the input require- ment is really current, not voltage. That means that the driving circuit must be able to supply the current necessary to operate the LED in the SSR. In the example shown, the current is about 15 milliamps. The cur- rent can come from a current source as in Fig. 3 or a current sink as In Fig. 4> Most circuits can sink more current than they can source. For example, TTL can source only one milli- amp or so, but it can sink 10 to 15 milliamps. If you must use a logic family that can*t source or sink much current, such as the output of most computer ports. tion the trigger side of the relay is totally asynchronous to the AC side. That means that a trig- ger could occur during any part of the AC sine wave. If the trig- SOLID I LOAD STATE I RELAY I zmm FIG. 5— IF YOUR CIRCUIT can t source or sink much current, use a transistor as a current sink. DRIVE ClRCUlTl CURRENT +0 — INPUT -O — gcr occurs near a peak (90 or 270 degrees), a large current will How into the load almost in- stantly. That creates a lot of RFl (radio frequency interference) and also is very hard on the fila- ment of ordinary light bulbs. In order to prevent that, zero- crossing SSR*s accept the trig- ger at any time but delay turn- ing on the AC load until the next time the AC voltage, passes through zero volts. Safety Building an SSR requires putting 110 volts on a printed circuit board. From an electrical point of view, that can be per- fectly safe. However, its proba- bly a good idea to cover all printed circuit runs on the 110- volt side of the PC board with silicone sealer Also, try to use only isolated TViacs (where the case is electrically isolated from the Tk^iac), and ground the heat sink to the AC safety wire (green, or earth ground}. Choosing a Triac There are three basic require- ments when choosing the out- put Trlac. First is to make sure that it will handle the voltage required* The minimum for a 115-volt AC line requires a 200- volt Triac. A 220- volt line re- quires a 400'Volt Triac, Re- member that those are the minimum so, for a few cents more, it pays to use the next highest voltage rating. The next requirement is cur- rent. A 6-amp 'Driac will handle 6 amps only if it is properly heat u & J o 51 _ a e ^^g^ COMMOH a m 1 1 FIG. 3— THE INPUT REQUfREMEhfT of an SSR is current. Here the driving cir- cuit is shown as a current source. GROUND LOAD AC PLUG HOT MEATSmKO -- fUSE T0220 mCKA6El' O ' DRIVE ICURREHT CIRCUIT SOUD STATE FtELAY LOAD MAIN TERMINAL 1 FIG. 4— THE DRIVING CIBCUiT is shown here as a current sink. l^GATE MAIN TERMINAL 2 FIG. 6— PARTS-PLACEM ENT DIAGRAM. You must heatsink the Triac and connect the heatsink to earth ground, even if you're using an isolated Triac. PARTS LIST All resistors are Vi-watt, 5%, un- less otherwfse noted. R1— 100 ohms, 1-watt {see text) R2 — 43 ohms (see text) R3— 180 ohms R4— 2200 ohms R5— 10,000 ohms Capacitors CI— 0.01 \if, 500 volts, ceramic Semrconductors 101— Motorola MOC3010 Triac-out- put optolsolalor (or MOC3011 for zero-crossing switching, see text) D1— 1N4002 diode (or any 1-amp, 100-volt or greater diode) Q1— 2N3904 NPN transistor FIG. 7— THE AUTHOR'S PROTOTYPE. The board is shown here without a heat^ sink on the TrJac^ although one should definitely be used. sinked. As a word of warnings motors draw a lot more current on start-up than they do during normal operation, sometimes as much as ten times more. The third requirement is the gate current. The Motorola MOC3010 optoisoiator will pro- vide about 100 milliamps of drive current for the output TViac. That should be adequate TR1— Teccor Q4006L4 Trlac (or equivalent see text) Note: The following items are available from Q-Sal, PC Box 110, Boaisburg, PA 16827: • A printed circuit board for two solid-state relays, can be cut in two or left together (part number SSR-PCB)— $8.00 postpaid • A complete kit minus heat sinks for two solid-state relays (sorry, sold in multiples of two only, part number SSR-KIT) — $18.00 postpaid SSR FOIL PATTER ^{ shown actual size. for any Ttiac you can find in a TO-220 package. Although not a strict require- ment, an isolated Tk'iac is a good safety precaution. Isolated Trh acs provide electrical isolation from the electrical connections TABLE 1— TYPICAL TRIAC-OUTPUT OPTOISOLATORS Motorola Blocking LED Current Maximum R2 Zero Crossing AC Line Type Voltage (mA) (ohms) Switching Voltage MOC3009 250 30 22 No 115 MOC3010 250 15 43 No 115 MOC3011 250 10 68 Ho 116 MOC3012 250 5 130 No 115 MOC3020 400 30 22 No 220 MOG3021 400 15 43 No 220 MOG3022 400 10 68 No 220 MOC3023 400 5 130 No 220 MOC3030 250 30 22 Yes 115 MOC3031 250 15 43 Yes 115 MOC3032 250 10 68 Yes 115 1 MOC3040 400 30 22 Yes 220 k MOC3041 400 15 43 Yes 220 to the case. Early TVlacs were not normally Isolated, That meant that you had to use mica washers and thermal grease. Thermal grease is still a good idea, but the mica washer isn't required for isolated Triacs. If you den t know whether or not your Triac is isolated, simply measure the resistance from each lead to the case. An iso- lated IViac will measure open on all three leads. Warning: The Radio Shack 400-volt, 6-amp Triac (part number 276-1000) will work well in this circuit, but il is not isolated. You must use a TO-220 mica washer and thermal grease if you plan to use that device. Construction For a simple SSR. an op- toisoiator such as the Motorola MOC3010 will be sufficient. For a zero-crossing SSR, an MOC3031 will do. Many compa- nies make optoisolators. Make sure yours has a Ti-iac output and that the pinouts are com- patible with your design. Tdhlt I shows some typical ^IViac-out- put optoisoiator specifications. Although the SSR can cer- tainly be built without a printed circuit board, using the foil pat- tern weVe provided will make building it a simple task. You can also buy a pre-made PC board from the source men- tioned in the parts list. Figure 6 shows the parts-placement di- agram. The only precaution, other than the one about work- ing with 110 volts, is to heatsink the Tibiae. If you leave the leads on the Tibiae long, it should be a simple matter to find some heat sink to attach to the Ti-lac. Just remember to connect the heat- sink to an earth ground. Even if you're using an isolated Triac, the earth ground is still neces- sary. Otherwise you should buy your solid-state relays from a re- liable company^ — don*t build them yourself. Figure 7 shows the author's completed pro- totype. Remember that SSR's can switch only an AC line. TVying to switch a DC line will result in a relay that closes but never opens. R-E ANTHONY J, CARISTI IF YOU ENJOY HIKING OR DRIVING through mountainous coun- tr>' — but without knowing how far above sea level you are— this project will be of interest. Its a simple, easy- tO'bu lid, compact electronic altimeter that pro- vides altitude readings from zero to 1999 feel with a resolu- tion of 1 foot. The device has a 3'/i-dlgit LCD readout and Is powered by a common 9-volt battery. The altimeters small size and light weight allows it to be easily carried wherever you travel. The modest power drain of the cir- euH ensures many hours of op- eration on a single 9-volt battery. If desired* the instru- ment can also be powered by the 12-voU electrical system of any vehicle. The electronic altimeter is a pneumatically operated device that responds to absolute at- mospheric air pressure. It oper- ates on the same principle as the aneroid altimeters found in every aircraft. Absolute atmospheric pres- sure is a mathematically defina- ble parameter that varies inver- sely with altitude- At sea level the pressure is 14.7 pounds per square inch, and decreases as altitude increases. The heart of the altimeter is a high-quality solid-state abso- lute-pressure sensor that is sen- sitive enough to detect changes In altitude as small as one foot. The surrounding circuitry am- plifies the analog voltage output of the sensor, and converts it to digital form to drive the display. The sensor The pressure sensor was de- oi veloped by Motorola Semicon- ^ ductor Products. Inc. Phoenix. ^ AZ, It-s designed to respond to & absolute atmospheric pressure, I which is defined as pressure ^ measured with respect to a per- CD feet vacuum (zero pounds per :g square inch absolute, or 0 (g PSIA). Over the alti meter *s range of interest. 0 to 1999 feet, the absolute atmospheric pressure varies from 14,696 PSIA to 50 13.67 PSLA (which corresponds to 29.92 to 27.82 inches of mer- cury, respectively). Inside the sensor is a mono- lithic silicon plezoresistor that is ion-implanted on a thin sil- icon diaphragm. The pressure sensor contains two chambers separated by the silicon di- aphragm. One of the sensors chambers is exposed to at- mospheric pressure by means of an external port. The other chamber is evacuated to as per- fect a vacuum as possible, and sealed. That way the diaphragm of the sensor is under constant stress in accordance with the difference between atmospheric pressure on one side, and an es- sentially "perfect" vacuum on the other The mechanical stress placed on the diaphragm (and the piezoelectric resistor) causes the sensor to generate an output voltage that is propor- tional to the applied pressure as seen by the open port of the sol- id-state sensor. to 1999 feet)* the sensor's out- put voltage will change only about 1.4 millivolts. A differential amplifier com- posed of three sections of an LM324N quad op-amp (ICl), provides voltage amplification of the sensor output. The gain of the amplifier can be adjusted by potentiometer R3 to allow for the normal tolerance difference between different sensors. The DC voltage level at pin 8 of IC 1 is set to 2.5 volts when the al- timeter is at xero altitude (sea level}. At 1999 feet, the amplifier output falls to about 2.4 volts. The DC voltage from the dif- ferential amplifier (ICll drives an ICL7106CPL analog-to-dig- Ital (A/D) converter (1C3). That chip, which is used in many commercial DMMs. converts the differential voltage from ICl to digital form and drives the sy^-digit liquid crystal display (DSPl). An external reference voltage, generated by R14— R17, a. digital MLtimeter Add new dimensions to your next trip to tiie mountains witli our pocltet-sized electronic altimeter. Refer to the schematic of the altimeter circuit shown in Fig. I. The plezoresistor within the sensor (IC4) is connected be- tween pins 1 and 3, and Is driv- en by the 5*volt power supply in the circuit. The taps on the re- sistor, connected transversely across the element, are brought ou t to pins 2 and 4 of the sensor Under normal conditions in which atmospheric pressure causes a stress on the piezo- electric resistor, the sensor dif- ferential output voltage Is a finite but very small value — about 20 millivolts. Over the range of interest for climbers (0 provides the proper conversion factor between the analog input voltage and the desired digital display in feet. As described earlier, the out- put voltage of the amplifier sec- tion is set to 2,5 volts by R3 when the altimeter is at sea level. That voltage Is fed to the negative analog input of 1C3 (pin 30). Since the altimeter must read zero at sea level the positive input of IC3 (pin 31) must see a constant 2,5-volts. That way the differential input voltage between the positive and negative inputs will be zero, and the display will read 000 as desired. As the elevation of the altimeter increases, the voltage fed to pin 30 decreases while the voltage at pin 31 remains con- stant. As a result, the net dif- ference in voltage is detected by IC3 and converted into an in- creasing digital display readout of altitude. There is one other factor that must be taken into considera- tion in a pneumatically sensing altimeterof this type. Changing weather conditions cause changes in barometric pressure from the standard value of 14.7 PS! (or 29.92 inches of mercury at sea level). As with any al- timeter that reacts to absolute air pressure, the effect of chang- ing barometric pressure must be canceled out. In this project the effect of barometric pressure is canceled out by means of baro set potentiometer Rll which can be adjusted for about 2.4 to 2.6 volts at Us wiper Therefore, Rll must be set so that the voltage at pin 14 of ICl-d causes the dis- play to indicate the correct known altitude at any reference location. Once that is done» the altimeter is calibrated for the current barometric reading — but changing weather condi- tions can change the readings significantly. You will probably have to recalibrate the altimeter before each use, or simply set it to zero and use it to measure a relative altitude. Power for the altimeter comes from a 9-volt battery or from a vehicles 12-vaU electrical sys- tem. Either source Is fed to an AN78L05 fixed 5 -volt regulator (1C2). The a!timeter*s modest current drain of about 6V2 mlllamperes allows many hours of operation from a 9-volt bat- tery When 12 volts is used as the power source, a resistor and di- ode are used to isolate the al- timeter circuit from any elec- trical transients. Construction The altimeter Is built using two single-sided PC boards — one analog and one digital. The two PC boards can be made using the foil patterns we've provided, or they can be purchased from the source mentioned in the Parts List. Point-to-point wiring can also be used. Parts-placement di- agrams for the analog and dig- ital boards are shown in Figs. 2 and 3, respectively You should use sockets for the two DIP ICs, but because of the limited space in the prototype's enclosure* only low-profile sock- ets would fit* Do not Install the ICs in the sockets until in- structed to do so. Note that the altimeter's accuracy will suffer if metal-film resistors, where specified, are not used. Also FIG. 1~THE PRESSURE SENSOR (IC4] has an analog output that is converted to digital form by 1C3 and then displayed on the LCD, note that R20 and Dl (shov^Ti on the analog board In Fig. 2) are to be installed only If you wish to power the unit from a vehicles 12'Volt source. The pressure sensor should be handled with care. Its leads must be bent at right angles so that the sensor lies flat on the analog board. Use two long- nose pliers when bending the leads — one to prevent stress on the lead where it enters the plas- tic body and the other to bend it. Before forming the leads, lo* cate pin 1 of the sensor; its iden- tified by a notch cut into the lead. Then you'll be able to form the leads in the correct direc- tion. Mounting hardware for the sensor is optional because the leads will hold it in place. No pneumatic connection to the sensor's pressure port is re- quired, except calibration. The LCD module can also be mounted in a socket if you like: you can make one for it by cut- ling a 40-pin DIP socket in half lengthwise. To keep the al- timeter as compact as possible* the LCD module is mounted on the copper side of the digital board, after all of the compo- nents are installed on the com- ponent side. (You can install a socket for the LCD now, but don't install the LCD just yet.) Mounting the LCD on the cop- per side allows the digital board to be mounted on the cover of the enelosure. -OPnONALfSCt TEXT) FtG. 2— PARTS-PLACEMENT DIAGRAM tor the analog board. Note the components that are optional for 12-volt use. Also note the four connections that must tie made to the digital board (see Fig. 3). Obtain a clip for the 9-volt battery* or salvage a connector taken from an exhausted bat- tery. Be sure to observe proper polarity on the battery con- nector. Power switch SI and po- tentiometer Rll should be installed on the side of the en- closure, easily accessible to the user If you are dealing with lim- ited space (a small enclosure), use a miniature toggle or slide switch for SL Once Rll is set. its best if it can not be acciden- tally changed during the use of the altimeter. Therefore, Rll should be a screwdriver-ad- justed part. IfmountingRll is a problem, the resistor can be ep- oxled in place next to the power switch, A multltum potentiom- eter will make it easier to cali- brate the unit. A number of jumper wires, la- belled JU1^U20, are required on the component side of the digital board to complete the cir- cuit. You must solder a jumper wire between each pair of pads^Ul to JUl, JU2 to JU2. and so on. Use #24 or #26 insu- lated stranded wire. Examine both boards carefully for bad solder joints, shorts, and im- properly installed components before continuing. Final assembly When both boards are com- pleted, power, ground, and the two differential output wires from ICl-c and ICl-d must be connected between the analog and digital boards, as indicated in Figs. 2 and 3. Use insulated stranded wire for those connec- tions and be sure to allow suffi- cient length to permit proper mounting in the enclosure. In the prototype, the boards are placed one above the other 12-volt power If you want the option of powering the altimeter from a vehicles 12-voU source, R20 and Dl must be installed on the analog board. To allow opera- tion from either the 9-volt bat- ieiy or l2-volt source, a mini- ature jack can be installed in the enclosure to allow connection to the vehicle's electrical system and stiU allow portable use. Be sure to observe proper polarity when wiring the altimeter for 12-volt operation. You can make a power cable by putting a mini plug on one end and. most like- ly, an automotive cigarette light- er plug on the other. Just be sure to plug the cable into the altimeter first, to avoid having a live male connector completely exposed. The altimeter can be wired for 12-voIt power exclusively* or as a combination 9- and'l2-volt unit. Follow the wiring di- agrams in Figs. 4 and 5 for the selected power-source option. Give the project one final visual inspection before continuing with the checkout. Figure 6 shows the authors prototype. Electrical checkout Bclbre proceeding, make sure the ICs are not in the sockets. You 11 need an accurate DC volt- meter with an input resistance of at least 1 megohm to perform the checkout. Use a fresh 9-volt alkaline bat- tery or a well-regulated DC power supply to power the cir- cuit. If the power supply has current-limiting capability, set the limit to 10 milliamps to pro- tect the project in the event of a malfunction. (The normal cur- rent drawn by the circuit is about 6^2 millamperes.) Set the supply for 9- or 12''Volts output, as applicable. First, check voltage regulator 1C2, Apply power to the circuit and measure its output voltage. Anything between 4.75 and 5.25 volts is good. In case of trouble here, check the orienta- tion of CI and IC2. and the po- larity of the power supply. Measure the terminal voltage of the battery or supply while it is powering the circuit to be sure it is delivering at least 7 volts to the regulator Disconnect power and measure the resistance be- tween the 5-voit line and ground to be sure there is no short cir- cuit. As a last resort, try a new regulator. Check the analog circuit next. Insert ICl into its socket, and apply power to the circuit. Measure the voltage at pin 8 of ICl: adjust R3 for a reading of 2.5 volts. Measure the voltage at pin 14 of ICl while rotating po- tentiometer Rll over its range. Make sure the range of adjust- ment is about 2.4 to 2.6 volts. If you don't see the correct volt- ages, check the wiring and com- ponents associated with ICl. Check the pressure sensor for correct orientation. Tly chang- ing ICl as a last resort. Disconnect power from the circuit and insert IC3 into its socket. Place the readout in its socket on the solder side of the ANALOG posrrtvE Imm ANALOG BOARD P\m OF (DSPi MourjTS on solder sidei ANALOG riEGATTVE FBOM ANALOG FROM ANALOG BOAFIO * 117 I JIIID JU9 m JU12 JUI3 * * 3?^ JU17 JDTB * iiiii* JU20 jUlO JUB I I -J *JU4 RQ. 3— FARTS-PLACEMENT DIAGRAM for tfie digital board. Note that the LCD mod- ule mounts on the solder side of the board after all other com pone nts are Installed and the board is tested (see text for details). Also note the twenty pairs of pads labelled You must solder a jumper wire between each pair of pads; for example, JUl to JUl, JU2 to JU2. and so on. AAV3H FIG, 6— HERE'S THE AUTHOR'S PROTOTYPE, Notice the four wims that connect the analog and digital boards together. R2Q iC2 78L05 \n OUT ' GND I V J, ^ ■-□JNPUT FIG. 4— WIRE THE ALTIMETER as shown her© for 1 2- volt power ex- clusively. FIG. 5— THE ALTIMETER IS SHOWN wired for both 9- and 12-vort operation. digital board in accordance with Figs. 3 and 7, if you didn't use a socket for the display, po- sition it so that its terminals are flush with the component side of the board tind solder With the LCD Installed, set R15 to mid position, apply power and adjust Rll over its range. The display should indi- cate some number that can be varied via RU between approxi- mately - 1000 and + 1000. If the display is completely blank, check the orientation of the LCD module and IC3 to be sure I hat they have not been placed backwards in Ihe circuit. If available, an oscilloscope can be used to verify the presence of the backplane signal generated by IC3 at pin 1 of the readout. A normal indication at pin 1 is a 5* volt peak-to-peak square wave with a period of about 140 mi- croseconds. If the readout displays digits but the numbers do not ascend and descend with adjustment of RIL the fault is most likely with the components or wiring of ICS. Clieck all parts to be sure they have the correct value. The reference network composed of R14-R17 can be checked by re- moving IC3 from its socket and measuring the voltage between pins 35 and 36 of the socket while adjusting R15 over its range. Normal indication is 15 to 35 mlllivolls with pin 36 posliiv^e with respect to pin 35. Operation of IC3 can be cliecked by removing ICl from its socket and temporarily shorting pins 8 and 14 of ICl socket. That causes the dif- ferential input voltage fed to the A/D chip to be zero, and the dis- play should read 000. Once the display is operating properly, operation of the al- timeter can be verified before linal calibration. Set R15 to mid position and adjust Rll for a display of about 20 or 30 feet* Physically move the altimeter higher and lower to observe the change in altitude reading. Hold the project horizontally or vertically as you make this test: a change from one orientation to the other can cause the read- out to vary 3 or 4 feet, due to gravitational force on the ex- tremely sensitive solid-state pressure sensor You should be able to detect and resolve 1 or 2 feet of vertical displacement. It is normal for the display to fluctuate 1 or 2 digits. Additionally it should be noted that the altimeter is a pressure-sensitive device and will respond to any variation in barometric pressure, in which a change in pressure of only 0.001 inch of mercury at sea level will All resistors are V4-watt, 5%, un- less otherwise noted. m, R4-R9— 100,000 ohms, 1% metal film R2— 2210 ohms. t% metal film R3 — 5000 ohms, cemiet PC-mount potenlio meter RIO. R12— 107,000 ohms, 1% met- al film R11— 10.000 ohms, PC-moynl po- tentiometer, screwdriver adjust R13— 100,000 ohms R14, R1 7— 249.000, 1% metal film R15—2000 ohms, cermet PC- mount potentiometer R16— 1500 ohms, 1% metai film R18— 1 megohm R1 9—47,000 ohms R20— 330 ohms (optional for 12- volt operation) Capacitors CI— 10 (j-F. 25 volts, axiaf elec- trolyttc C2 — 0.1 p.R 50 volts, ceramic disc C3— 10 25 volts, radial elec- trolytic C4. C7— 0-47 fiF. 50 volts, metal I nim C5 — 100 pR 50 volts, ceramic disc C6 — 0.01 fiF, 50 volts, ceramic disc C&— 0.22 ^F, 50 volts, metal film Semiconductors IC1— LM324N quad op-amp IC2— AN78L05 5-volt regulator IC3— ICL7106CPL A'D converter (Intersil) IC4— MPX2101AP semiconductor nnnnnnnnnnnnnnnnnnn J I t^uuuuuyuyuuuyyuuuuiju FIG. 7--THE LCD MODULE has a mark- ing similar to that on an [Q, indicating where pin 1 is. Note that the module mounts on the solder side of the digital board, so l>e careful where pin 1 goes. cause a change of I foot in the altitude reading. Even though the resolution of the instrument is 1 foot, the al- timeter will not have either the accuracy or stability to indicate altitude that accurately pressure sensor, 15 RSI absolute (Motorola) D1— 1N4004 silicon diode (optional for12-voit operation) DSP1— 3!^digit LCD module (Di- giKey LCD002) Other components J1 — Miniature jack (optional for 12- volt operation— also requires matching plug] SI— SPOT minature slide or toggle switch B1— 9-volt transistor battery, al- kaline or heavy duty Miscellaneous: 9-pad/dlsplay unit as shown in Fig. 11. Mount the ICs without sockets, as there is not enough clearance to use them. However, mount each display using half a socket un- dcr the rear row of pins only. Doing so angles the display about 20 degrees for better view- ing. The pull-doWTi resistors for the kev switches must be Vh- watt units to fit the 0.3-lnch mounting centers. The six-conductor telephone cord connects directly to the foil side of the board, as shown in Fig. 12: secure the cord with a nylon wire WTap. The other end of the cord has a modular plug that fits into Jl on the main board. The color codes in phone cords and connectors seem to vary, so we haven't provided spe- cific details. It doesn't matter which color you use for which signal: just make sure that youYe consistent at both ends of the cable. Figure 13 shows the completed keypad/display board. EPROM board assembly Assemble the EPROM board as shown in Fig. 14, Mount a six-pin female connector { Jl) on the solder side of the board- it will mate with P4 on the main board, and serves to hold the EPROM board in place. The completed EPROM board is shown in Fig. 15- When mounted properly, the EPROM board rides about V2' above the EPROM that is being pro- grammed (see Fig. 16). hi front of this connector are two solder pads used to connect the EPROM programming voltage. Connect the ground side (gnd) only if the programming voltage doesn't have a common ground with the main board. In case you want to install HAM in IC20, remove the EPROM circuit; otheru^ise every CO LJ O CO Ul o < a o 0 « o o 0 • • • # o 9 ^ c o ^ Op o e o ^1 col ^^^^^^ O 0 0 • : f o ft o « o a ^ a B|i D Q B 0 9 1 6(0 B B 0 S 0 B B S ' n [ \ o a 0 B a B B b 0 B q B a B e B a B q a s 0 « • \\ \ofo \ I ] i\o\o 'J a ,0 o • 0 o 2" t J 00/0 • j» o e 0 f r J: i y : c CO CO o o o CO z 0. X COMPONENT SIDE OF THE KEYPAD/DISPLAY BOARD. LISTING t-WEX DUMP OF OPERATING SYSTEM (OOOCMWFF) T 1 (X AA FB 00 33 F8 09 A3 D3 F8 FE 62 FB FF A2 E2 00 B4 F8 60 A4 F8 00 B5 F8 70 A5 F8 00 B8 F8 Oii ?! Ao ■a A 3A E3 62 00 62 01 E2 08 69 FB FF 3A 3D Do CQ OV FA CA FO C2 02 24 30 52 CO 04 Al F8 OD 52 F8 05 A? F8 00 52 7B 61 08 22 27 87 3A 45 *1A FF FF FF FF FF FF FF FF FF FF CO EO 00 D3 UUDU a 4 fS □o ^3 yj B6 33 A 6 46 63 46 A3 3Q 5F D3 0070 96 S3 86 A3 E2 12 72 A6 FO a6 30 6F FF FF FF FF 0080 21 7D 13 19 40 89 81 3D 01 OD 05 CI A3 51 S3 87 0090 D3 7B 7A 7B 7A 7B 7A 7B 7A 76 7A 76 7A 7B 7A 7B Art h A 7X 30 90 99 66 89 A5 05 FF D4 00 CE 46 68 46 AB cobo 46 B9 46 A9 46 A7 46 32 C3 E9 OS 28 73 27 87 3A ODCO BA 30 CA 48 59 19 27 87 3A C3 D4 00 EE D5 S7 73 AAr\A 52 §0 60 60 02 A7 22 02 B7 22 22 22 69 73 99 OOEO 73 8A 73 9A 73 88 73 98 73 87 73 97 73 D5 60 42 OOFO B7 42 A7 42 B6 42 AB 42 BA 42 AA 42 S9 42 A9 60 0100 50 60 87 73 97 73 22 42 B7 02 A7 DS 87 73 97 73 QUO 88 73 98 73 F8 00 38 F8 91 A8 FS 02 B7 A7 27 97 At '^A 3A IE F3 00 S2 62 22 F8 01 52 62 22 08 69 FB FF 0130 3A 22 OB 69 FB FF 3A 22 D8 69 FB FF FA OF 3A 22 0140 F8 10 B7 27 97 3A 43 FB 00 AA F8 00 52 62 22 FS 0150 01 52 62 22 08 69 FB FF 3A 78 FB 08 AA D8 69 FB 01 60 FF 3A 7B Dfl h9 FB FF FA OF 32 47 F9 80 AA 60 72 0170 B8 72 A9 72 B7 FO a7 D5 f6 33 6E lA 30 78 FF FF 0180 88 73 98 52 F8 FF B8 F8 FO AS FS 05 58 18 FS DF 0190 58 IB 99 F6 F6 F6 F6 6A D4 02 09 9A 58 18 99 BA 01 AO D4 02 09 9A 58 18 89 F5 F6 F6 F6 BA □4 02 09 9A OlBO 5S 18 89 BA 04 02 09 9A FF 01 58 IS 09 F6 F6 F6 01 CO F6 BA D4 02 09 9A 58 18 09 6A 04 02 09 9A 58 09 OlDO BA 72 B6 FO A8 D5 87 73 es 73 96 73 89 73 99 73 OlEO E6 72 B9 72 A9 E2 F8 00 68 FS 91 A8 F8 00 52 62 nil cA Ft} A£ 06 A7 E9 76 61 D8 27 87 3A FS E2 60 72 B9 T5 Ay I'* /A DO Bo 72 A8 FO A7 D5 88 73 9B 52 FB 00 B8 ro OA AB 9A FA OF 32 10 FF 01 18 30 16 OS BA 72 B8 FO A6 D5 F8 00 B9 A9 D4 01 SO 04 01 D6 FF FO LI4 A1 SA 52 FE 33 4A F8 04 A7 89 FE A9 99 7E A"?itA ay 4./ O ( dA 3U 89 Fl A9 30 28 SA F6 33 5C F6 33 3U rO & A AU A Z4 D4 00 A3 D4 01 80 09 73 D4 01 AA r r r z flil u% UJL nr^ UC fiA £5A FE 33 86 F8 FF 68 F8 F7 0270 m 02 FE FE FE FE 52 8A Fl 52 08 28 58 IS 02 22 0280 BA 134 02 09 9A 58 30 5E 8A F6 33 94 F6 33 9A F6 >jj "in Z4 A^ uz oy AO uy F3 3A 59 19 38 29 30 59 FF 02A0 FB 02 D 1 CQ Al F8 FF B8 FS FA AS EB 49 73 49 02E0 / t A B/ dZ 2F 2F 2A 8A 30 41 OF A9 2F OF B9 IF D4 ri'^ ra 80 D4 01 D6 FF F2 30 34 8A F6 33 98 F5 33 98 0360 F6 33 66 CO 00 □9 D4 01 OC BA FE 33 89 FB 04 A7 0370 89 FE A9 99 7E S9 27 87 3A 70 8A 52 89 Fl A9 D4 03SO 01 80 04 01 D6 FF F2 30 66 SA F6 3B 93 89 5F 2F AT Q A QA 5F IF 97 AA 30 3B FF FB 03 61 F8 9F Al Dl F8 ft A IF A/ ^ A z / O / 3A A2 40 BF 40 AF 40 BE 40 AE 40 03 BO BD 40 AD 40 BC 40 AC 40 BB 40 AB 40 6A 40 AA 40 03 CO B9 40 A9 40 68 40 A8 40 67 40 A7 40 B6 40 A6 40 03DD B5 40 A 5 40 B4 40 A4 40 B3 40 A3 40 62 40 A2 40 03E0 7A CE C4 7B 40 F6 22 22 CO 02 CO FF FP FF 46 BB 03F0 46 A6 16 E6 F5 A7 26 9B 75 16 16 B7 17 FB 00 60 04 00 AD AC EB 97 3A 09 87 32 13 BC F4 AC C7 ID C4 27 0410 IB 30 03 ec A9 80 69 D4 01 80 F8 FF BE F8 FO AE 0420 9D F6 F6 F6 F6 BA D4 02 09 9A 5E IE 90 6A D4 02 0430 09 9A 5E D4 01 D6 FF FO US 46 BB 46 AB 16 E6 F5 0440 A9 26 9B 75 B9 19 16 16 46 BC 46 AC 99 3A 52 89 0450 32 6A OB SC D4 01 BO D4 01 06 FF FO EC 08 F3 3A 0460 ee IB XC 29 30 4C 9C B9 BC A9 04 01 80 04 01 06 0470 FF FO D5 46 B7 46 A7 27 17 27 87 C4 C4 3A 77 97 0430 27 17 27 C4 C4 3A 77 D5 D4 04 39 04 86 04 AO FF 0490 00 D4 01 OC CO 02 24 FF D4 03 EE 00 00 00 00 30 04A0 09 7B FB 40 B7 57 FS BO B7 07 7A F8 CO B7 57 34 04Sa Al F8 FE B2 A2 12 E2 69 22 6A 22 66 22 6C 22 6D 04C0 22 6E 22 7B 7A 6F 67 66 65 64 63 62 61 22 3D B7 04D0 FB 00 BS FB 91 A8 E3 7B 62 01 62 00 61 55 DS E2 04E0 3E D6 F8 00 B8 FB 91 AS £3 62 00 62 01 E2 DB 69 04 FO 22 FB 00 52 62 7B 61 22 DS 3F E8 FF FF FF FF FF -m INCHES- SOIOER SIDE OF THE KEYPAD/DISPLAY BOARD, Otto aootttt _ _ 9 mm m B B a D e a B B a a 6 B B 8 # mm mm • ••• -3 INCHES- COMPONENT SIDE OF THE EPROM BOARD. SOLDER SIDE OF THE EPROM BOARa COMPONENT SIDE OF THE MAIN PC BOARD. access to that location will incur a 50-ms delay. After assembling each board » check all work, and correct any mistakes. Then apply power and hold down the 0 key ffall is well, all segments and decimal points of the display should light up. If they do not, remove power and check all connec- tions again. Electronic construction is complete^ now you can mount the boards in their proper chas- sis locations. Operation Boot up normally; Ihe display should read "A-OObO/* The "A^' indicates Address Select mode; the zeros indicate the current address. Actually, the monitor pro- gram has four modes r Address Select, Memor>^ Monlton Run* and Debug. PARTS LIST— MAIN BOARD All resistors are V4-watt, 5%, unless otherwise noted R1, R11. R12— 1000 ohms R2— 150.000 ohms ft9— 30,000 ohms RIO— 22 megohms R13"R24^5t,000 ohms. 14 watr Capdcttors CI— 1 p.f. 35 volts, tantaliim C2. C3— 20 pF, ceramic C4— 10 ^iR 25 volts, tantafum C5, C6 — 0.1 ^iR mini ceramic Semiconductors (CI— 74HC238 340^8 line decoder IC2-IC13— 74HC373 octal D fatch IC14— 74HC138 3-to-8 line decoder IC15--74HC373 octal D latch IC16— 74HCa6 quad 2-input XOR gate IC17-74HC299 8-bit shift register ICt8— 1802 microprocessor IC19— 6264 static RAM IC20— see text 1C21— see text IC22— 2764 EPROM (with operating system) IC23^556 dual lH0f-4 decoder Ottier components XTAL1— 2.010 MHi cryslaJ PI -P4— wire-wrap pins, 0.025" sc^uare X 0.75' Jt — 6-oondyctor telephone jack PARTS LIST— KEYPAD/DISPLAY BOARD All resistors are Vi-watt, 5%, unless otherwise noted B1-R20— 51,000 ohms. Ve-watt R21-R6B— 330 ohms R69— 100.000 ohms Semiconductors lC1-fC6— 74HC164 8-bit shift res _._ fC7— 74HC0O quad 2H'nput NAND gate IC8™IC1 0—4021 8-bit shift register Other components DS1-0S3— dual 7>'segment LED dis- play, 0.5", common anode S1-S20— SPST, normally open, push- button, PC mount When the display shows the monitor is in the Address Select mode. Any time the oper- ating system is in coniroL pressing F4 returns you to Ad- dress Select mode. To enter a new address* just press the corresponding keys. The digits you enter scroll from right to left; if you make a mis- take, simply enter new digits until you see correct address displayed. After entering the desired ad- dress, you have three choices > with corresponding keys: PARTS LIST— EPROM BOARD All resistors are Vi*waU, B%, unless otherwise noled R1. R4— 22 megohms R2-^7.000 ohms R3— 100,000 ohms Capacitors Ct-0.001 ^iF, Mylar C2— 100 pF. ceramic C3— Q.OOI nF. Mylar C4-0.02 ;iF, 5%, Mylar C5™0.1 \i.f, ceramfc Semiconductors IC1— 74HC02 quad 2-mpul NOR gate IC2— 555 limer D1— 1N4148 diode Q1, 02— 2N4124 NPN Iranstslor MisceHaneous: Chassis & hardware, power supply, telephone cord & con- nectors- terminal block, toggle swUch, push tjutton switch. solderJess bread* boarding connectors, PC txjards. Note: The following Items are avail- able from Dage Scienlific, 6124 Bald- win St,, Valley Springs, CA 95252 (209) 772-2076: • KU Including everything but power supply (Model MC-a)— $195 • Surplus power supply ( i 12, + 5» -5)— S11 • Operating system In EPROM— $10 • Set of 3 PC boards and manual— S35 Please add SS shipping It handling per order. California residents add applicable sales tax. Monitor (Fl), Run (F2). and De- bug (F3). Monitor mode allows you to examine and modify memory contents on a bytc-by-byte basis, Run mode lets I lie CPU execute the program at the cur- rent address. Debuj^ mode in- serts a breakpoint at the currenl address. To enter Monitor mode, tj^pe the desired address and press Fl. That address and its eon- tents will appear For example. OOOCFF indicates a hex- adecimal value of FF at address OOOOh, In this mode, the function keys lake on new meanin#*s, Fl stores the currently displayed value into the currently dis- played address and moves on to the next address. F2 displays the next address. F3 displays the previous address* Tb change the cu rrenlly dis- played value, use the hex keys lo roll new digits into posi lions 5 and 6. If you make a rnislake, simply enter new digits until SOLDER SIDE OF THE MAIN PC BOARD. the correct value appears. Mem- ory contents will not be altered until you press Fl. When you do press FK the currently dis- played value will be stored at the displayed address, and I lie next address will be displayed. If the value can not be stored into memory the address counter will not increment, [Us possible to program values one byte at a time into an EPROM using that procedure, but there's a better way. as discussed below.) And remember: Press F4 at any time to return to Address Select mode. After storing a program in memory you can execute it using the Run command. Start- ing l^rom Address Select mode, enter the desired starting ad- dress and press F2. The monitor program then trans- fers control to your program. If your program hangs, press the P3 COMPONENT SIDE TOP pm 1-r 9-17 19-27 29-37 39-47 49-57 59-67 $9-77 79-87 59-97 99-107 109-17 119-27 J3 SER. FUG n OUT n OUT #4 OUT OLIT #6 OUT ft our #A \h #B K m #0 IN m #F IN iOT 2-S fO-19 20-28 30-38 40- 4S 50-5S ao-aa 90-98 100-08 110-lB EF2 EF1 EF4 EF3 SERIAL IN QCLK SERIAL OUT INTER- RUPT SERIAL I/O ANO FLAGS DAJA. ^ ': } ( - 1 D3 06 ■ D7 ; ■ ■ t^.- i 02 D4 OB TYPICAL OIHPUT PORT LATCH m Dt L!Lj 1 m 02 04 1 06 TYPICAL INPUT PORT FIG. 9— PLUG P3 CONNECTIONS. The 128 pfns of P3 consist or one group of S pins (for serial 1/0^ EF flags, 0 clock, and Interrupt) and 12 groups of 10 ptns each. Tfiose 12 groups break down Into six Input ports and six output ports, each with plnouts as shown. FIO. 10— THE COMPLETED MAIN BOARD. Sockets stiould be used in all IC positions, and are required for IC20 (itie EFRQM burner slot) and IC22 (the EPROM that contains the operating system). SI 0 St6 F S14 0 I © S20 * # F4 r: 1 S3 2 3 C : sigs" F3 S5 S6 5 S12 siee F2 S3 S9 9 S11 A f R1 S17 F1 -R32- -Ft37- -R61- 053 FIG. II^KEY PAD/DISPLAY PC BOARD. Mount all parts as shown here. If you use our case, don't use IC sockets except under the rear row of display pins. FIG. T2— PHONE CABLE connections. Solder the wires directly to the foil side of the board, reset switch to regain monitor controL In case your program doesnl work the first time, you can use Debug mode to track down problems. Use Address Select mode to select a likely address for troubleshooting and press F3. You'll return to Address Se- lect mode. Now enter the desir- ed starting address and press F2. Later when the CPU hits the breakpoint address. It will start executing a special debug pro- gram that allows you to view the CPUs internal registers, and to verify that what you Intended to happen is indeed happening. You can set only one break point at a time: you cannot breakpoint addresses in ROM. When your program reaches the breakpoint, it will halt and dis- play the current address. You are now In the Debug mode. In Debug mode, the display appears the same as in Monitor mode, Howeven as you press the hex keys the display wiU show the internal register number (in positions 1—4) and the value in FIG. 1^-COMPLETED KEYPAD/DISplay board. Mount each display using half a socket under the rear row of pins only, to provide better viewing. FIG. 14— EPROM PC BOARD, Mount all parts eiEcept J1 ort the component side of the boards mount Jl on the foil side. FIG. 15— THE COMPLETED EPROM board, A sIx-pIn female connector (J1) on the solder side mates with P4 on the main board. that register (in positions 5-6). The debug program uses regi- sters 0 and L which have been resented for DMA and interrupt. Pressing hex key 0 displays the contents of the D register in po* sitions 1 & 2, the X register in position 3, and the P register in position 4. Pressing hex key 1 displays Q in position 2 (set= I, reset =0) and DF in position 4* While in debug mode, register contents can be altered by first selecting a register pair and then pressing function key F3. Change the value by rolling new digits in from right to left. When the correct value appears* press Fl: otherwise press F3 to back out without changing the cur- rent register Registers D, X, R Q, and DF can also be modified by selecting liex keys 0 and 1 as described above, Tb exit debug mode and continue execution, press F2. Of course you can press F4 to return to Address Select mode. The debug breakpoint alters program memory by replacing three bytes at the selected ad- dress. When the user program reaches the breakpoint address, the debug program takes over and restores the original three bytes to the proper locations. However, if the user program never reaches the breakpoint, those three bytes will never be restored. In that case you must restore them either by con- tinuing execution at the break- point, or by reentering the bytes manually using Monitor mode, if you continue at the break- BG. 16— THE EPROM BOARD mounts on the maJn board and rides about W above the EPROM that Is being programmed. TABLE 1-«WE imUTY ADDRESSES AddiBss Memorv Contents FF03 Start address (hi) FF04 Start address do) FF05 End address (hi) FF06 End address (loj FF07 Destination address (Nl FF08 Destination address Ho) point, the debug program will restore the three bytes and im- mediately jump into Debug mode. As usual, you can modify registers, continue execution, or return to Address Select mode. EPROM programming With the EPROM program- ming board connected to J4 and the proper programming volt- age available, ilip the EPROM switch to on, and you are ready to program the EPROM mounted at 1C20. All that is re- quired to program a location is to "write ■ to it. As mentioned earlier, you can do this byte at a time using the Monitor mode. However, due to the error-prone nature of that procedure, the author recommends a more au- tomated procedure. The preferred method is to en- ter your program in RAM and then transfer it to EPROM with the operating system's built-in "move" utility, which in fact will move a block of data anywhere in memory, not just to EPROM. Start the utility by running at 0488. Doing so transfers the move utility itself to RAM start- ing at FFOO. Now enter the start, end, and destination addresses as shown in Tlible L Double -check your values to ensure that they are correct, and then run at FFOO. The dis- play will show the remaining number of bytes to be trans- ferred. It will be changing rapidly, but will at least give some idea about how things are progressing. In case data can- not be transferred correctly, the program will terminate and the display will show the address that didn't change. That about wraps things up. 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Stop throwing away those used Polaroid batteries — use them in your electronic experiments instead! MARC SPIWAK DID VOU BVKR NOTICE HOW I'OI^I*- Old cameras never need bat- teries? That's because every pack of film you buy contains a brand-new Polaroid Polaputse battery to power the cameras motor and flash. Some people might consider that a modern convenience: Ever\^ change of film also replaces the battery* The worry of dead batteries is over once and for all — or Is it? While these flat 6-volt cells cer- tainly make instant-picture tak- ing as convenient as possible, they can be harsh on our en- vironment* or at least our land- fills* To add insult to injur>'. the Polapulse battery that you throw out with your old film pack is still in pretty good shape. FIG. 1— THE BATTERY JIG lets you recy- cle "old" Polapulse batteries. Most people, however, would have no use whatsoever for these used but still perfectly good batteries. The batteries, which can be accessed only by breaking open the film holder don't fit into any standard bat- tery holder But readers of this magazine should certainly be able to find hundreds of uses for these "recycled" 6-volt cells* Using tlie Polapulse. To get at the battery, all you have to do is crack open the plastic film holder — after the film is finished, of course. Just be careful of the metal leaf- springs sharp edges. You'll find the batter>^ itself mounted on a piece of cardboard with its two contacts exposed on one side. Holding the battery with the contacts nearest to the top, positive is on the right. You can removT the battery from the cardboard mount if you'd like to work with a smaller overall package. The one problem with using the batteries is that its hard to make reliable electrical contact with the battei^'s positive and negative terminals. Its virtually Impossible— as well as unsafe — to solder to the terminals. That s where our handy battery jig comes in.lt allows you to use a Polaputse battery for whatever the need may be, and pop in a new one when it s dead The jig is fashioned from two pieces of perforated con- struction board, four screws and spacers, and some contact springs from a sacrificed AA-cell holder. TXvo of the springs make electrical contact with the bat- tery, and a third spring helps to liold the battery in place- Mini- hook leads are soldered to the contact springs, and small nylon screws hold the springs to the fixture. FIG. 2— THE BATTERY JIG uses two pieces of perforated construction board, screws, spacers, and springs from an AA-celt holder. Nylon screws hold the contact springs to the fixture. You can, of course, use al- ligator clips or other connectors that better suit your needs. And you may wish to modify the me- chanical constructiori as well. In any case, do ti^^ to get the most use possible from these batteries before they are thrown away r-e anCLE 190 ON FREE INFORMATION CARD WORKING V/ITH LED DISPLAY DRIVERS Learn all about 7-segment display decoder/drivers in our continuing coverage of optoelectronic IC^s. RAY M, MARSTON "HUtJDREDS" DECADE COUNTER -RESET "TEiNS" DECADE COUWTER DECODER/ DRIVER ^'UNITS'' DECADE COUNTER DECODERS DRIVER DECODER' DRrvER ^^ j^^TQ^ ^ INPUT Gisn 5 1 I I I 1±1 COUNTER RESET TIMEBASE > GENERATOR WAVEFORMS BG. 1— SIMPLE DIGITAL f requency- meter dmult. m OUR LAST INSTALLMENT WE looked closely at theory and practical applications of the LM3914-series of LED bar- graph driver IC's and concluded with 7'Segment display sys- tems. In this article, well exam- ine 7-segment display driving techniques in detail, con- centrating on decoder/driver de- vices and circuitry. Display latching In the last article we Intro- duced 7*segment displays and simple BCD-to-7-segment de- coder/driver IC s that can be used to activate those displays. Figu re 1 shows how three sets of those ICs can be used with a trio of decade counters to make a simple digital-readout "fre- quenc>^" meter In the figure, the amplified external frequency signal is fed to the input of the series*connected counters with one pin of a 2-input and gate. The other input is derived from a timebase generator When the timebase Input sig- nal is low, the AND gate IsofH and there is no input to the coun- ters. When the timebase gate signal switches high» a brief itEstcT pulse is fed to all three counters, setting them all to zero. Simultaneously the input gate turns on and remains on for one second. During that time the input-frequency pulses are summed by the coun- ters. At the end of the one-sec- ond period, the gate turns off as the timebase gate signal goes low again. Tliai ends the count and enables the display mod- ules so that they give a steady reading of the total pulse count, and therefore the frequency. The whole process repeats itself again one second later when the timebase gate signal goes high. The simple system illustrated has one major drawback: The display blurs during the count- ing period, becoming stable and readable only when each count is complete and the input gate Is off. Figure 2 shows a circuit for frequency meters designed to overcome display blurring. In the circuit, a 4-bit data latch is wired between the output of each counter and the input of its decoder/driver IC* When the timebase gate sig- nal goes high, a reset pulse is fed to all counters, setting them to zero. Simultaneously, the in- put gale Is turned on» and the counters start to sum the input signal pulses- The count con- tinues for one second while the 4-bit latches prevent the coun- ter output from reaching the display drivers. As a result* the display remains stable during that interval. At the end of the period a brief latch enable pulse is fed to all latches* The Instantaneous binary- coded decimal (BCD) outputs of ^ each counter are then latched ^ into memory^ and also fed to the g display via the decoder/driver ^ ICs. That steadies the reading m of the display to give a total % pulse count, which cor re- 0! sponds to the input signal fre- a quency A few moments later, | the sequence repeats itself with S the counters resetting and then counting the input frequency pulses for one second, and so on. 6S 4-BIT LATCH h -RESH HUriDREDS" DECADE COUflTEft iins- DECAOE CCUNTEH DECADE COUPJTER ■a BIT LATCH h LE 4'BIT LATCH OECODEFV DECODER/ DECODER/ DRIVER DRIVER DRIVER 'aTOg ' aTOg 1 FIG, 2— IMPROVED DIGITAL frequency-meter circuit Thecircull in Fig. 2 generates a stable display that Is updated once per second. In actual cir- cuits, the count periods shown tn Figs. 1 and 2 can be set at any decade multiple or submuitiple of one seconds provided the dis* play is suitably scaled. Many commercial dccodcr/driver IC's are available with built-in 4-bit data latches. Multiplexing You can sec in Figs, 1 and 2 that at least 21 connections must be made between the IC circuit ry and the 7-segment dis- plays of a 3-dlgil readout. Sim- ilarly, at least 70 connections must be made for a 10-digit dis- play. The number of IC-to-dis- play connections can be signifi- cantly reduced with a technique known as mullipicxing. Figures 3 and 4 illustrate muUiplexing. Figure 3 shows how each digit of a 3-dlgit common-cathode LED display is individually acti- vated with only 10 external con- nections. In the display circuit- ry, all "a" segments are con- nected together, as are all other sets of segments ('*b'" to '*g"). Thus only seven external "a" to "g" connections arc made to the display, regardless of the number of digits used. However, no 7-segment display Is illumi- nated by signals on the segment wires unless the display Is en- abled by tying its common ter- minal to ground. In Fig. 3, enabling is achieved by activat- ing switching transistors Ql, Q2, and 93 with suitable exter- nal signals. However, this scheme calls for an additional connecting wire for each display module. Figure 3 also shows how three different sets of segment data can be selected with switch Sl- a, and each of the three display modules can be selected with switch Sl-b and 92. or QS. SI -a and Sl-b are ganged to- gether to form a two-pole rotary^ -ELfCTROmCS- 1«- Sl-a MUUIPtEXEfl SWITCH -vw- + V switch which provides the mul- tiplexing. These switch ele- ments represent a fast-acting electronic switch capable of cyc- ling the contacts through posi- tions 1, 2, and 3 fast enough for flicker- free multiplexing. The operat ing sequence of the circuit shown in Fig. 3 will be discussed here. Assume ini- tially thai the contacts of SI -a and Sl-b are in position I so tiial Sl-a selects segment data of display module 1 (L^l* and Sl'b activates display module 1 with Ql. Module 1 will then show an illuminated number "3." Moments later the switch contacts move to position 2. se- lecting segment data 2 (2,^) and illuminating module 2 witli Q2. Module 2 will then be il- luminated to show the number "2." Moments after that, the switch contacts move to posi- tion 3, causing module 3 to show the number "7," Thus only one digit is ever on at any one time. In practical displays, the se- quence is repeated fast enough so that you do not see the dis- play segments being turned on and off. Your eyes persistence of vision makes it look as if the three digits are all lit up to- gether. The multiplexing fre- quency must be about 1 kHz. Figure 4 shows a more real- istic arrangement for multi- plexing a 3-digil frequency meter, the multiplexer (MUX) Is located between the outputs of the three BCD data latches and the input of a display-driving BCD-to-7-segment decoder/ -OISPLJS^- 2 1 COM Ql FIG. 3^MULT1PLEXING METHOD for a 3Kiigit common-calhode LED display. HUrJOREOS' COUMTER COUNTER 4-6IT LATCH -oflESET 4-011 LATCH J INPUT 4 BIT LATCH LE J MULTIPLEXER (MUX) RESET « LATCH EflABLE ' (LE) TiMEBASE DECODER' DRIVER MUX SEGMENT DATA /I 5 1 MUX COMTBOl SIGNAIS FIG, 4— PRACTJCAL MULTIPLEXING of a 3Hdigil f roquency meter. driver IC. The scheme shown has two major advantages: Only one decoder/driver IC is needed (regardless of the number of readout digils)» and Us multi- plexer includes only five ganged 3-way sequencing switches* One of those switches is for con- trol data, and four are for BCD- segment data. That arrange- ment saves three ganged 3-way switches, as compared with the eight needed in Fig. 3. Commercial large-scale inte- grated (LSI) IC's now available can perform all of the coLmting* latching, multiplexing, decod- ing, timing, and display-driving functions in Fig. 4, A device of this complexity is typically packaged in a dual- in-line pack- age (DIP) with only 20 pins. Those pins provide for all neces- sarj" connections to the power supply, display modules, and in- puts. Therefore, a complete 4- digit counter can be built with a dedicated IC in a circuit such as that shoum in Fig. 5. Another example of an LSI IC in a display circuit is the S^z-digit digital voltmeter (DVM) chip shown in Fig. 6. RippLe blanking Unless there is automatic suppression of the two un- wanted leading zeros, the 4-dig- it circuit in Fig, 5 will give an 4-V INPUT 0 MUX SEGMflfr nm 1 MUX' CONTRDL DATA FIG. 5— 4-DIGIT COUNTER CIRCUIT based on an LSI chip. FIG. fr-3-1/2-DIGIT VOLTMETER based on an LSI chip. actual reading of 0027 if it is used to measure a coLint of 27, Similarly, if the 3V2-digil circuit of Fig, 6 measures OA volt, it will display 0, 100 vol t unless the two unwanted trailing zeros are automatically suppressed. In practical circuits, auto- matic blanking of leading or trailing zeros can be performed with a ripple-blanking tech- nique, as shown in Figs. 7 and 8. Each decoder/driver IC (with a BCD input and 7-segment output) is provided with a RIPPLK- BLANKING INPUV (hHI) and scripple-blanking output (rbo) pins. Assuming those pins arc ac- tive-high, if the HBi terminal is held low (logic 0}, the 7-segment outputs of the IC are enabled, but the RBO terminal is disabled (held low). If the rbi terminal is biased high (logic 1). the 7*seg- ment outputs become disabled in the presence of a BCD 0000 input, and the rbo output goes high under the same condition. The Ruo terminal, therefore, is normally low and goes high only if a BCD 0000 input is present at the same time the rbi terminal is high. Figure 7 shows the ripple- blanking technique for leading- zero suppression in a 4-digit display with a reading of 207. The RBI input of the thousands or most significant digit (MSD) decoder/driver is tied high, so the readout is automatically blanked in the presence of a zero when the rbo terminal is high. Consequently, the rbi pin of the hLindreds IC is high, the readout shows 2, and the rbo terminal is low. Tlie rui Input of the tens unit is low. so the read- out shows 0 and its rbo output is low. The units readout shows the least significant digit {LSD], which does not require zero suppression. Its rbi pin is grounded and the readout shows 7- The display therefore gives a total reading of 207. 5 In the leading-zero suppres- ^ sion circuit. Fig. 7. the ripple- S blanking feedback is applied ^ backwards from the MSD to the 5 LSD, Figure 8 shows how trail- %■ ing-zero suppression is accom- m pi i shed by reversing the dlrec- o tion of feedback from the LSD to § the MSD. Therefore, when an ^ input of LI volts is fed to that circuit, the LSD is blanked, be- cause its BCD input is 0000 and its rbi input is high. The rbo 67 i c g m Q IMPinS mOM DECADE COUHTERS f\ DECODER' DRIVER RBI HBO ??f ? DECODER/ DRIVER IC* RBt RBO DECODER DRtVE^^ ic- RBI RBO mi DECODER' DRIVER IC" RBI RBO 'SEETEXT 1 THOUSAMDS |MSD» HUN&REDS TEMS UNITS FIG, 7— RIPPLE-SLANKIHG for leading-zero suppresston in a 4*dtgil counter. BCD TllPirrS FROM DECAO€ COWmiS ? ? T y DECODER' DRIVER IC* RBO RBI LLLl DECOOEa' ORiVER IC ROD RBI mi DECODERS DRIVER IC- RBO RBI mi 1 DECODER/ DRIVER IC- RBO RBI ■fV *S£ET£XT DECIMAi POINT O UNITS (USD} TENS HUmiflEDS TKOUSAHDS asD) 1 FIG. 3 — RIPPLE-BLANKING for trai ling-zero suppression of the last two digits of a 3-r^^-digit DVM readout terminal is high under that con- dition. so the hundredths digit is also bianited In the presence of a 0000 BCD Input. Most decoder/driver iC's have KIPPLE-BLANKINC; INPUT and Ei[PPLE'BLANKING OUTPUT pinS, Usually these pins are active- low. If a decoder/driver IC does not include integral ripple- blanking logic, it can usually be obtained by adding external log- ic circuitry similar lo that shown in Fig, 9. The hbo pin is connected to the hi-\nk[ng input pin of the decode r/driver IC. Fig- ure 9 shows an active-high cir- cuit in which the output of Ihc 4-input NOR gale goes high only with a 0000 BCD Input. The [ -^nitilf m^- f /itiiiJi MfluH'.- Wt' t •Jn '■htm If HI htm Ut e,p^i% ti\ Gel In Now - S. I f ,H iifiH I itik*t t ItMn if f i jI j »i < * -in tMrn $hS A M 1 1< x re used between each output- drive segment and the input segment of the display. Resistor Rx sets the operating segment current of the display in those examples, and Ry sets the base current of the transistor. The 451 IB can also drive 7- segment liquid-crystal displays (LCD) with an external square- wave PHASE signal and a set of XOR gates similar to those of Fig. 12. In practical circuits, how- even It is better to use a 4543B IC for that speciiic application. The 4543B Is a 7- segment CMOS decoder/driver with an integral 4-bit data latch, it was designed for driving LCDs, but it can also drive most other 7- tie 4543B VPHASE GND 1 SEGMENT DRIVE OUTPUT COMMON CATHODE FIG. 1&— DRIVING A common-cathode LED lamp or display segment wilh a 4543B. 1 CLK 2 OUI CI c 01 ^^^^ t> 14 2 13 3 i 12 11 4 0,1 OlfT e 10 5 CARRY OUT a RESET f GNO 0 ts 9 15 6 8 7 SEGMINT OUTPUTS SEE TEXT FIO. 19 — DRIVING A gas-discharge tube or display segment with a 4543B. + V 4543B 'GWO PHASE aUORESCEMT TUOl SEGMENT DRiVI OUTPUT 6 -V RG, 20— DRIVING A fluorescent tube or display segment a 4S43B. segment displays* The 4543B has three Input control pins: latch ijisahlk (ld), PHASE, and blanking {ulIl In nor- mal use* the latch disaiile pin Ra 21— PINOUT ot the 4026B decade counter wKtr 7-segment outpuls. is biased high and the bijvnking pin is tied low. The state of the PHASE pin depends on the dis- play that is belnf^ driven. For driving LCD displays, a square wave (approximately 50 Hz, swinging fully between tlie ground and V^.,J must be ap- plied to the i^HASiv pin. The i^HASE pin must be grounded for driving common -cathode LEDs and it must be tied to logic-high for driving any common-anode displays. The display can be blanked at any time simply by driving the BLANKING pin to thc logic-high state. When the i-atch disable pin is in its normal high state, BCD Inputs are decoded and fed 15 JO HUNDREDS DECADE RESET CI GND CARRY OUT 40268 CLK D/E 15 'TtNS' CATHODE ■+V RESET P QUO CARRY OtJT 402ftB CLK D/E CLOCK , •UNITS' 16 COMMON CAmODE INPUT RG. 22— CASCADING TWO 40268 decade counters. CLK CI R9I Rao CARRY OUT RESfT GND 15 SEGMENT OUTPUTS FIG, 23— PINOUT for the 40335 decade counter wJth 7-segment outputs and rip- ple blanking. directly to the 7-scgrnent output pins of the IC. When the latch DISABLE pin Is pulled low, the BCD Input signals present at the moment of transition are latched into memor>' and fed (in decoded form] to the 7-segment outputs while latch display remains low. Figure 17 shows a method for using the 4543B to drive an LCD. and Figs. 18-20 show how that circQll can be modified to drive other 7-segment displays. .TO HUKDREDS DECADE RESET Ct CAHftV OUT 4Q33B LT GI^D CLK RBI 15 14 TENS' 16 COMMON CATHODE RESET CAFRV OIH a b Gl 40331 c d U e GNO CLK 0 RBI CLOCK INPUT ' "UfllTS-* 16 COMMON CATHODE + V FtG. 24— CASCADING TWO 4 03 38 decade counters without zero suppression. NO COMPLICATED ELECTRONICS. NO EXPENSIVE INSTRUMENTS: Home study course shows you how to make good money in VCR repair. An amazing tact: you can do more Uian (our out of five VCR repairs with ordinary tools and basic fix- it proce- dures. Our home study pro- gram shows you how Learn all of the systems, mechanisms, and parts of almost all brands of VCRs. With no expensive instru- ments. JVo complicated elec- tronics. Ab fancy workshop. The step-by-step texts and close personal attention from your instructor make learning easy Texts, course materials, and tool kit are sent to your home. Graduate ready to make up to $50.00 or more per hour in your own spare- time or full- time business. Send today lor your free career booklet. Or call 800-223-4542 Name , , AcJdress City_ , , State , 2ip . The School of VCR Repair 2245 Perimeter Park, DepLVF342 ,.\tianta, Georgia 30341 The value of in Fig. 18 must be chosen to limit the output drive current to below 10 mA per segment (individual LED lamp). If higher drive currents are needed, use a bufTer transistor between the output of the 4543B and the input of the dis- play segment. Figure 21 shows the pinout of the 4026B, a complete decade counter with integral decoder/ driver circuilry It can drive a 7- segment common-cathode LED display directly. The segment output currents are internally limited to about 5 mA with a 10- volt supply or 10 mA with a 15- volt supply Therefore, the dis- play can be connected directly to the output of the !C without ex- ternal current-limiting re- sistors. The 4026B does not Include a data latch and is not capable of ripple blanking. As shown in the Fig. 21. the 4026B has four input conlrol pins and three auxiliary output pins. The input pins are desig- nated: CLOCK (CLK}. clock rNHlFJ* IT (c[), RESET (reset), and DISPLAY/ ENAiiLE (d/e). The IC has a Schmitt trigger on its clock (clk) input line, and clock sig- continued on page 93 Let's Phase the Music: More comments on papers from the 91st AES convention LARRY KLEIN Acoustic phase, and its au- dibility, has been a subject of controversy ever since Hermann von Helmholtz addressed :he subject in the late 1800 s. Yet. despite all we've learned about Hearing since Helmholtz, and the current availability of sophisticated new research tools, the controversy ingers on. The argument is not. as Dne might Ihink. simply an abstract, if sometimes heated, debate among philosophical psycho* acousticians. It has real-world con- sequences for the way audio signals should be recorded an audio equip- ment should be designed. IVe been aware ever since I built my first Wilfiamson amplifier in the early 1950"s that signal phase shift was a significant audio parameter^ — at least in power amplifiers. In its early incarnations, the Williamson suffered from marginal instability because the 20-dB negative feed- back loop sometimes shifted positive at the frequency extremes. That frequently resulted in pulsing woofers at one end of the spectrum and RF oscillation at the other But aside from such obvious instability disturbances. I've never felt that lin- ear phase shift posed a severe threat to fidelity. In the early 1980s, many speaker manufacturers decided that the conventional two or three drivers in- stalled on the single vertical front panel of a system resulted in acous- tic phase shifts caused by the dif- ferent path lengths to the listeners ears of the woofer and tweeter sig- nals. That was usually "solved" by stepping a cabinet s front panel so that the woofer was several inches forward of the tweeter. Aside from generating new opportunities for advertising copy writers (and some expensive pot-bellied speakers), the arrangement s audible advan- tages were elusive — at least to my ears. And, in any case, it seems to me that on a purely theoretical basis such "time alignment" would only hold when a listeners ears were also aligned exactly on axis with the acoustic center of the two Cor more) drivers. I once saw/heard a speaker- phase demonstration using a two- way system with a movable tweeter A square wave was fed to the sys- tem and the speaker's output tNTERCHANNEL SPEAKER PHASE Most of us first encountered *'phase" as an audio phenomenon when we were told to make sure that the right and left speakers of our stereo system were connected in proper poiarity. That meant that when presented with, say, a positive audio pulse from both amplifier channels, the cones of both woofers would move simulta- neously in the same direction, ff the speakers were wired incon^ectly the cones would move in opposite di- rections, and bass performance would suffer. In addition, the 180- degree phase differences in the high frequencies would confuse the ear*s localization system, disturbing the stereo sound-stage image and imparting a vague "phasiness" to the reproduced sound. In general, speaker polarity/phase, if correct in the original installation, remains so unless the connections are changed. ^^gii^i^, R-E picked up by microphone and dis- played on an oscilloscope. As the tweeter installed on top of the sys- tem was slowly shuttled back and forth over a five-inch distance, the square wave would visibly distort and then restore itself as its high- and low-frequency harmonic com- ponents shifted in and out of phase. I stood in front of the display for several minutes, really trying to hear the waveform distortion that was cleariy evident on the scope screen. Following in the tradition of Hen' von Helmholtz. I never did hear any effect. All of this is background for the latest phase controversy beauti- fully delineated in the following Au- dio Engineering Society CAES) preprint. Observations on the Au- dibility of Acoustic Polarity [Greiner and Melton C3170 To understand what is meant by absolute polarity, it helps to use a simple musical example, such as the sound of a kickdrum. The impact on the drum head produces an air compression that moves outward and is picked up by a recording mi- crophone. Ultimately, it is re* produced by a forward-moving speaker cone as an air compres- sion. However anyone who deals with electronics knows that the orig- inal electrical signal frcrm the micro* phone has had its polanty flipped probably dozens of times by the re- cording and reproduction elec- tronics before it reaches the speaker In fact, there's a 50-50 chance that the initial kickdrum im- pact is being reproduced by a speaker cone that is pulling at the air rather than pushing it. In other words, what reaches our ears is an air rarefaction, although the original was a compression. It follows that our eardrums are also being pulled rather than pushed. Does it make a difference? That's what Greiner and Melton set out to explicate in their paper The audibility^-or inaudibility — of absolute inversion is a recent ele- ment in the ongoing discussion. Un- like other phase shift phenomena discussed eariier polarity inversion does not change the shape of a transient signal nor shift the phase relationship among its component elements. However, as the authors state, it does present to the ear a fundamentally different signal. A major part of the authors re- search effort involved extensive, carefully controlled listening tests to determine the types of signals I most sensitive to polarity rnversion. (t seems self evident that highly asymmetrical signals were most likely to be audibly changed by tnver- sion. For example, note the trom- bone waveform shown in Fig. L In general, it could be said that acoustic polarity inversion is clearly audible in some circumstances (par- ticularly with test signals), although most of the time with real-world mu- sic it is not. It seems that even when waveforms have clear asymmetries as in Fig. 1 — and not all of them do — other effects inherent in the com- plex nature of most musical tones tend to mask the identifying charac- teristics of the inversion. The authors conclude that "while polahty inversion is not easily heard with nomial complex musical pro- gram material, as our large-scale lis- tening tests showed, it is audible in many select and simplified musical settings. Thus it would seem sensi- ble to keep track of polarity and to play the signal back with the correct polarity to assure the most accurate q j\jr he TIME Fig. 1. Trombone waveform. In gener- al, reed instrunients show the great- est asymmetry. reproduction of the original wave- form." No one can argue with the above as an ideal goal, but exactly how is it likely to be realized? Assuming that (1) we have a recording with all the instruments recorded in phase, that (2) our three-way speaker doesn't have its mid-range connected in in- verted polarity to flatten the sys- tem's frequency response Ca no longer common practice), and that C3) anyone in authority cared enough to manufacture discs and tapes with all their polarity ducks in Cable TV Article Parts We stock the exact Parts & PC Board for an article published in Radio Electronics Magazine on building a Snooper Stopper* Snooper Stopper Kit S19-95 InciLTdas Ul ir>fl ongtnal Parts & Elched^ DnItBd Sik^crwfled PC Boanl. Snooper Stopper S39.00 This IE an ^ssambKid and Tdctiid lixad frequency 106.SMh2. Snooper Stepper for rnosn JerrDld sv^ems. Protect yourself from descrambter detection and stop the Bullet wEth one of our Snooper Stoppers* Macrovision.^now you see it^ now you don't* Macrovision Kit S29«CI0 Includes ol] \n& onginal Pan$& Eicned, Drill SUk^craen^d PC Board, QnginaJty PuMsnod \n Radio Electronics Magazjns. Call Toll Free 1-800-B86'8699 Visa, MasterCard or COD Northeast Electronics^ Inc. PO Box 3310 Attieboro, Ma. 02761 74 CIRCLE 103 ON FREE INFORMATION CARD ►^CABLE Tn DESCRAMBLERS WE'LL BEAT ANY PRICE! CALL TOLL-FREE 1-800-284-8432 • JERROLD • TOCOM • ZENITH • • OAK • PIONEER • HAMLIN • 'SCIENTIFIC ATLANTA > 24 HOUR SHIPMEHTSl QUANTn^Y DISCOUNTSl MONEY BACK GUARANTEE! FREE CATALOG a INFORMATION MasiefX&r^ • American fjpn*si • Visit • C.O*D. imi js^^o MoocL m^m of i R-E PHASE INSENSITIVITY It is well known that loudspeaker cone travel is sefdom equally linear in both its outward and inward ex- cursion. In other words, the speaker cone's push on the air may not be exactly equal to its pull, even when driven by a low-distortion, highly symmetrical sinewave. It seems probable to me that most human ears are also asymmetrical in their responses to the compressions and rarefactions of an impinging acous- tic waveform and therefore generate harmonic distortions. Whether any individual listeners degree of hear- ing asymmetry correlates with their sensitivity to absolute phase is an , open question. I noted with interest i that Greiner and Melton suggest at ^ one point that a distorting sound system may increase the audibility of polarity inversion. I know for a fact that I've always been comparatively insensitive to phase. For example, in the early days of quadrophonics 1 was eval- uating a four-channel synthesizer that attempted to generate artificial rear channels by tapping off the front channel, 'wobbulating" it at a 25-H2 rate, and feeding it to a pair of rear speakers. The four-channel I e ff ect 1 f 0 r bette r 0 r wo rse , was b afe- ^ ly perceptible to my ears. A friend dropped in unexpectedly while I was doing my listening and greeted me With, '*Hi Larry {three-second pause) your rear speakers are out of phase." I sat alongside hi m on the couch between the wobbulated i rear speakers and for the life of me ^ couldn't hear what he had detected instantly— and claimed was giving him a headache! ' I also know that some listeners are incredibly sensitive to very smail percentages of tape flutter^ a phase-shift phenomenon, but the numbers have to get pretty bad be- fore I hear it. In case you are won- dering, my overall acuity and sensitivity were (by test) pretty good in those days, so my phase insen- sitivity was, in effect, an independent : variable, I wonder what the normal distribution of phase sensilivity is, and whether ignoring it may not skew the lesulls of psychoacoustic stud- ies of phase, R-E COMPUTER CONNECTIONS The personal digital assistant. JEFF HDLTZMAN adget lovers lake heed: Per- sonal Digital Assistants (PDAs) will be the fastest- growing segment of the computer business within two years — maybe by the end of this year. What is a Personal Digital Assistant? It's a pa- perback-size computer thai bridges the gap between calculator-like or- ganizers on the one hand, and hefty notebooks on the other In so doing, the PDA hopes to provide both power and ease of use, but without the size, weight, and battery-life and -weight constraints of a notebook PC. Numerous technologies are com- ing together to make this category a reality. Low-voltage CPU's, system controllers, video controllers, and DRAM's from Intel. Cyrix. AMD. Western Digital, and others prom- ise to drastically lower power con- sumption. The chips run at 3.3 voltSn and could motB than double battery life, from 3.5 to 8.0 full hours. Emer- ging standards for credit -card sized memory modules seem to be taking hold. Hard-disk drives continue to shrink. Integral Peripherals has introduced 20- and 40-megabyte drives in 3-ounce packages that measures'" x 3". and that consume 500 mW of power during operation and IS mW in the "sleep" mode. IBM. Conner. Seagate, and others will ship similar drives fater this year Look for two basic appnDaches to the PDA. One. promulgated by PC vendors, amounts to a miniature DOS machine with a QWERTY key- board that allows touch typing. It has a full 80 x 25 C640 x 200. CGA-level graphics) non-backlit LCD screen. The other promul- gated by consumer electronics companies (e.g.. Sony), consists of a proprietary device using a stylus input in place of a keyboard. The DOS version may well con- form to a spec developed by Phoe- nix Technologies, called the Com- panion PC CCPC). A CPC will be based on an 8086-level computer- on-a-chip developed by Chips & Technologies (see the January 1 992 issue of this column for more infor- mation). PCMCIA memory cards. Phoenix BIOS and power manage- ment software, and special battery technology developed by DuracelL As for software. Microsoft has deliv- ered a ROMabte version of DOS 5.0» and promises to do the same for Windows 3.t. Lotus might sup* ply a suite of applications, including a task switcher, although Microsoft Works could very well provide steep competition. Tantalizing views of the other cat- egory have been revealed by Sony And there are persistent rumors that Apple and Sony are working together to put a Mac-style inter- face on this new breed. Sony has released one such device in Japan, but apparently has no plans to mar- 1— DYCAM*5 MODEL 1 digitat cam- era stores 32 shots, each with a resolu- tion of 376 > 240 X 256gray levels. Kfsa harbinger of the future for PC-based dig^ ital Imaging. ket it hene. Electrical power usage remains a major issue with portable comput- ers of all configurations. In the ROMable versions of DOS 5,0 and Windows 3.1, Microsoft has intro- duced an Advanced Power Manage- ment CAPM) Application Program- ming Interface CAPl), co-developed with Intel and Phoenix, that provides the system with information about which peripherals are not being used, so it can remove and thereby conserve power Several battery manufacturers have introduced flat, wide batteries that provide both a better fit with today s sleek designs » and more power For example. Por- table Energy Products has a battery that measures 2.6" x 3.9" x 0.3" and produces two volts at three amps. One interesting device is the ■'Commuter Computer" intnDduced by Memorex at the January Con- sumer Electronics Show CCES). The device weighs 1.3 pounds, lists for $599. and includes a word pro- cessor, scheduler, notepad, theDR- DOS 5.0 operating system, carry- ing case, power adapter, and ca- bles: an external 1.44 megabyte floppy drive is available forS299. Multimedia update Here s an imaginative use of muU timedia: The Virtual Press Con- ference. Redgate Communications of Vero Beach Florida plans to outfit ^ more than 100 movers and shakers "Z. of the computer industry with 1,2- ^ meter satellite dishes. TVs. VCR's. x fax machines, and dedicated phone S lines, at a cost of about $2 million. ^ Redgate wilt then broadcast to them ^ hour-long interactive press con- § f eren ces . du rin g wh i ch they can ask i questions, receive printed materials by fax. and record the whole thing on VHS tape. The viewers wilf pay nothing for the service; Redgate in- 75 SELECT 5 BOOKS for only (values to $157.75) g o T3 Membership Benefits • Big Savings. In addition to this inlroductory offer, you keep saving sub si an U ally with members* prices oi up to 50% off the publishers* prices. • Bonus Books. Starting immediaiety. you will be eligible (or our Bonus Book Plan, wilh savings o( up to 80% off publishers* prices. * Otub News Biilletlns. 1 S times per year you will receive the Book CJub News, describing all the current selections — mains, alternates, extras— plus bonus offers and special sales, with scores of titles to choose (rom. • Automatic Order. If you want the Main Selection, do nothing and it wif! be sonl to you aulomaticaK ly, !f you prefer another selection, or no book at aJI. simp- ly indicate your chcf may resign any time ttiereafter. A shipping/handling charge and sales tax wil^ be added to aM orders. Name Address City ^ Stale . ,Zip. _ Phone Ssgnaturo , . , ^ V»lMl iw ntm mflrnlwi only, Fon^n appjicantt will remvf ipKMU txttanng : 120 pix- els, running at 15 frames per sec- ond. That's obviously no competi- tion for broadcast-quality video CBQV): Apple hopes that the stan- dard will evofve to accommodate more powerful hardware that can support BQV. Apple has announced a Quick- Time "player"' that will allow PC- based Windows users to experi- ence QuickTime movies. (Corel Systems, of CorelDraw fame, wrote the File -format transialorJ In addi- tion. Mtcnosoft has announced sup- port for QuickTime: add-ins for the Mac versions of Excel and Word will allow end-users to build simple movies within the respective ap- plications. You could use this tech- nology to combine a series of spreadsheets into an animated demonstration of how sales are pn3iected to grow. In response, IBM quickly demon- strated technology with twice the resolution and the same frame rate. Naturally it runs under OS/2 2.0. One demo showed how advanced features of OS/2 allowed several program processes to control sepa- rate halves of a duet in sync. Product watch The Dycam Digita! Still Camera Model 1 rs the first of a new breed of all-electronic snapshot takers. The Dycam is an easy-to-use, light- weight, hand-held camera that al- lows you to take as many as 32 pictures, then upload them to your PC or Mac for bit-map editing or desktop publishing, (Logitech mar- kets a neariy identical version under its own nameJ Despite flawed installation in- structions, getting the Dycam going IS easy Attach a base mount to the main unit and plug in a waSl-mount charger. When the LED starts blink- ing^ the battery is fully charged. Then its just point, shoot, and up- load the images to your PC via an RS-232 port. The Dycam comes with control software for both PC and Mac; I tested the PC version, which actu- ally comes with both Windows and DOS versions. 1 found the Windows version unstable, due to frequent UAE s CUnexplainable, uninten- tional, unwanted Application Er- rors); consequently 1 worked mostly with the DOS version. The DOS-based software works pretty weiL The main screen con- sists of a series of "thumbnails." miniature versions of each image- To view an enlarged version, use the arrow keys to highlight the desired image, press Enter, and the soft- ware downloads, decompresses, and displays the complete image; the whole process lakes about 10 seconds per shot, depending on system speed. Documentation is both clear and brief and it includes both Mac and PC instructions in one booklet: the software includes on-line help in the form of brief summaries of key- stroke options. The camera can operate in two modes, regular and tripod. Unfor- tunately to switch modes you must download different software to the camera, a process that takes about 45 seconds. In regular mode, you just point and shoot: the camera determines shutter speed and whether to use the flash. Tripod mode allows you to set the shutter speed manually from 1 to 640 milli- seconds. Shutter bugs would prob- ably prefer to set shutter speed in familiar inverse time units Ct/f. e.g., 1/60. 1/30. etcl There's no way to attach a standard remote shutter re- lease, but you can take a picture from the keyboard CAlt-T). The software allows you to save images to disk in a variety of for- mats', including EPS. TIFF. PCX, a proprietary Dycam format, and others. The software provides some ability to adjust image contrast and brightness, but for optimal results you'll want to use a third-party tool Ce.g.» PhotoShop). When the cam- era is full, you will have to clear it out (Alt;C) to make room for more, and you cannot selectively delete pic- tures from memory. Although the camera maintains a time/date clock, you cannot include a time/ date stamp as part of the image. When I first learned of the Dycam. I thought it would be an ideal way to develop product and screen shots for the magazine. Un* fortunately* that will not be feasible. The problem is not limitations with the software, but the optics. The lens system provides image quality comparable to a $20 instant cam- era — but the Dycam lists for almost $1000. The CCD provides a total resolution of 376 x 240 pixels, which is less than found in a TV, It compensates by providing 256 lev- els of gray which definitely helps, because the eye responds better to variation in tone and color than lo absolute resolution. Even the best shots, however, come out grainy. Shots of people generally fane bet- ter than inanimate objects. Add-on lenses are available, in* eluding wide-angle, telephoto, and macro (close-up). Other accesso- ries include an adapter for 12-volt auto operation. Despite its limitations, the Dycam opens a world of pos- sibilities for users who don't need publication quality. For example, a real estate agent could publish house shots to give prospective oil- ents some idea of layout. Schools could create classroom newslet- ters. Dycam is to be commended for being first to market with an all-elec- tronic digital camera. An impiwed optic system, faster software, and more reliable Windows operation would make it a must-have item for professional desktop publishers. Keep your eye on this one. If you*fe interested, contact Dycam, Inc.. 9588 Topanga Canyon Blvd.. Chatsworth, CA 91311 C818) 998-8008. News bits Slate Corporation is a technology leader in the fledgling Pen-comput- ing market. Two officers of the com- pany, Dan Brickliti and Bob Frankston, designed the first spreadsheet for personal comput- ers, VisiCalc. The dynamic duo is at it again, with a pen-based spreadsheet called At-Hand. At- Hand reads and writes 1-2-3 and Excel files, and runs under the Pen- Roint operating system, it s sched- uied to ship in the second quarter After several false starts with por- table and notebook PC's, the new IBM is trying a new tack. Big Blue just bought a 6% chunk of the French company. Groupe Bull, which owns Zenith Data Systems. The deal provides the rights for IBM to sell ZDS fHirtables, and will give Groupe Bull access to IBM's RISC technology The deal also provides for swapping micro- pn3cessor technology; one report indicates that GB will join IBM. Ap- ple, and Motorola in developing the PowerPC, part of last summer's ac- cord between IBM and Apple. Worried about Japanese en- croachment 'on American markets? Maybe it's time to start learning how to deal with them on their own terms — literally A company called BayWare (415-949^3190) has intro- duced a Windows-based program that the company claims can teach the essence of Japanese in four to eight weeks, by studying only an hour per day Power Japanese was developed using my favorite multimedia authoring system. Tool- Book* and it includes an audio out- put device that connects to a standard parallel port. The device, which is housed in the connector shell, contains an 8-bit D/A convert- er and it can drive headphones or an audio amplifier Software includes 2000 files of native Japanese speech, animated writing se- quences, and a set of progressive lessons. The company plans to re- lease versions in French. Spanish, German, and advanced Japanese. Big-bucks consumer-oriented ad- vertising is becoming the rule in the PC business. You've probably seen Intel's flashy "Vacancy" ads on ca- ble. Now Microsoft is gearing up for a $30 million Windows pro^ motion, including $8 million for TV spots alone. 1992 is going to be remembered in the PC industry as the year the battle for graphical op- erating environments became really down and dirty. R-E Ovor 750,0110 readers of earlier EHlltioIlS of The Forrest Mims Engineer's Notebook agroo — nobody knows pmdicnl IC applicationH liko Farrtjsl Mims! This nowly- rovisod Gdilion contauis huntlriids of provon, tosjled circuits — lianti- drawn by Forresl — using today's most popular linear^ TTL, and CMOS ICs. Forrest gives you full dam for each do vice and circuit — pin numl)ers, logic tables* supply voltages, and signal vvaveforms— so you can quickly duplicate each circuit. There's also practical in- formation on construction nielli' ods, troubleshooting* and inter- facing different IC families. If you work with ICs you gotta get this book! Only St 4 ^95 at bookMtonsordlifctnmk: parts fifahrt. Or ofidifT dkcct from m^Jpxtt Add S3 shipping {S4 to CanQdn. SS ffhewhcrv}. CA pteasf add saJcs tait. VS. i'umf.% fttrh p/fxiJtt.*. 7128 Mtranur Rcud Stiite ISL San U'le^o, VA QZIZI mtmmmmm UJ o Your Ticket To SUCClilSS Over 2B,000 lechr^icians havu gained admit- tanco worldwide} as certified nrofassionals^ Let your tickot start openifig doors for vou. ISCET offers Journeyman certification m Consunrtor ElGctrontcs, IndoMrial, McdicaJ, Communications, Radar. Compuier and Video. For more information, contact the; tniernational Sociaty of Certified Etsctro- nici Technleians, 2708 West Berry Street. Fort Worth, TX 76109; iBl7\ 921-9101. Name Addre*i_ City State jSend matartal about ISCET and becommg certified. _Send one "Study Guide for the Associate Levei GET Test.' En- ctosed is $10 (inc. postage^ CIRCLE 10a ON FRiE mFanMATlON CARD 81 DRAWING BOARD One step backward to automotive regulators and two steps forward to our oscilloscope. ROBERT GROSSBLATT I 8 S I LU 6 m tr 82 Just when I thought we had driven in the final nail on the whole business of auto- motive charging systems. I got a fetter with some stuff in it that I have to pass on . Even though we spent all our time talking about alternator- based systems, there a lot of mail from people who had gener- ators. The voltage regulators we de- signed were specifically aimed at alternators but a regulator is stilt a regulator is still a regulator and. if you give it some thought, the one we designed can be used with a generator as well. The most important factor in modifying the design is to realize that regulators for generator have to handle much larger amounts of cur- rent and because of that, our exist- ing circuit can*t drive the generator directfy. The standard way to do deal with this is to use relays and that's exactly what was done by Craig Shippee. a reader from Bridgewater Massachusetts who sent his design to me in the mail. His circuit, shown in Fig. 1, does several interesting things. First, the basic design is the one we did for an alternator with a pulled-up field Cone aide of the alternators field wind- ings are hard wired to the positive side of the battery) but the gener- ator is set up with a grounded field Cone side of the field hard wired to ground). The other interesting part of the design is that it uses only one DPDT relay instead of the two or three relays found in standard gen- erator regulators. Craig's circuit is a classic exam- pie of what happens when need comes up against ingenuity and ex- perimentation. He said that he couldn't give me the exact specifi- cations on the relay he used be* cause he salvaged an old 30-amp light relay from a dead truck. The relay opens when the regulator doesn't want it to charge the bat* lery, and the 40-amp diode makes sure there s no backflow of current from the battery to the generator. If you're going to use the prcuit* make sure the relay is rated high enough to handle the maximum out- put current of the generator and tweak the 500-ohm potentiometer to get the cut-in point that's best for your system. Craig is using the clr- ^3 Ci £5 ^C2 ./moos iic P-3 cuit on a tractor but there s no rea* son why it can't be used with any generator-based automotive elec- trical system. FIG. 1— A REGUU^TOR FOR A GENERATOR has to handle a lot o1 cyrmnt, so a relay must be used. RG 2— TO EXPAND THE VERTICAL dis- ptay to twenty elements well have to add a second LM3914 to the circuit. The 3914's were designed to be easiiy cas- caded. O TM/CG£R o — 1C8 T7 07 I3_ IN PB 01 Oh 05 Pf P3 PI CO IF —y^ — iZ_ 1 ■ 1 IC4 4017 — e>-»-o — GROUND iCiA — IDl ' 0/ 10* 9 9 1 A a C i> laa AM: B *j- fy ^ rV- ;3 M ^ c i> EN JCZB « 4) £ Li- Ail—, U tz is RG, 3^0MPLETE SCOPE SCMEMATtC 50 FAR. All we have to add Is an input amp and a pad arrangement to pre scale the Input voltages* on 6 ts 84 Some good thinking went into the modification and. in the words of Jimmy Hatio, a "Tip of the Hat" to Craig Shippee for a good job, a great fetter, and taking the time to pass it on. Let me hear some more from you. But back to the scope. The next step we have to take is to expand the vertical display to the full twenty elements we specified in the design criteria. Since we'ne using an LM3914 as the LED driver we'll have to add a second chip to the circuit. The 39V4's were de- signed with that in mind, so it doesn't take much though to string two tor more) of them together The circuit fordoing that is shown in Fig- 2. While the actual wiring is simple, there are a few points that should be made a bit clearer I'll also mention here that all of that informa- tion Cand a lot more) can be gotten from the 391 4"s data sheet. One of the most important things when you're designing circuits is to be absolutely familiar with the compo- PLUGViniTO THE WEATHER! The WS-t(i indstiiiim roof-mp inmof plugs direct ly into thi' PC Gme Port. Ii sends you tmmedbte measurements of your local 1^ eat her paucrn » . U i nd ^peed , direction and gusi v^lut^ djia are continuously dlspbyed. Outside tempeniure. 2-1 hour extmnts and w I nd ch i U values art optionaj . Months of information can be storifd for vieninj;. pbtitng and analysis. To plug into the weather, caO the order line: 1-800 992*81t0 ^ WeatherPort (9l6)l?4-aiOO CtRCLE 186 ON FI^EE INFORMATION CARD nents on the board. It's okay to dis* cover things by accident but onty if you then take the time to figure out what happened and why. You can't control what you don't understand. ThefB are four ways the 3914 can be set to operate: single-chip dot. single-chip bar. cascaded dot. and cascaded bar. In order for the 3914 to reliably know what mode to work in Cdot or bar) when two or more chips are cascaded for an expanded display, its internal mode-select am- plifier has to watch Ihe stale of three pins: MODE SELECT (pin 9>. V (pin 3), and the cathode of LED9 on pin 1 1 . That last piece of information — the state of pin 11 — is critical only when you're doing an expanded dot display. Remember that having a dot display means you want to have only one out of twenty LED s on at any one time. The 3914 controlling LED11— LED20 has to know for sure when one of the earlier LED s is being lit. Tlie circuit in Fig. 2 has the MODE CONTROL pin of the first 3914 connected to the first LED output (pin 1) of the second 3914. That's because when the input sig- nal is driving one of the second bank of LEDs (12-20). there will always be some voltage at pin 1 . It may not be enough to light the LED but it will be enough to turn off the LED s in the first 3914. As a result of that, the last LED on the first 391 4 will always be turned off when any of the LED s on the second 3914 are being lit. The same sort of reasoning ap- plies to what keeps the second 3914 from lighting an LED when the input voltage to the whole circuit is in the range of the first 3914. In that case, however the control for the second 3914 is being provided by the voltage on pin !1, In order for the circuit to be as linear as possible and have each of the LED s indicate equal increments in input voltage* you have to be care- ful about the reference voltage for each chip. The iC has an internal reference- voltage generator and» even though it can be configured to provide different voltages, we're using it in the plain vanilla mode to generate a L2-volt reference. On the second IC in the chain, we have to set the neferBnce voltage a bit higher. Remember that the first 3914 has to respond to input signals from 0 to 1 .2 volts while the second 3914 has to respond to input signals in the range of L2 to 2.4 volts. That sounds more difficult than it really is. Ail we have to do is use the voltage at the top end of the com- parator chain in the first 391 4 as the low voltage for the bottom end of the second 3914, By doing that, the absolute working -voltage range for the second 3914 will be 1.2 volts higher than the first one. or 1.2 to 2.4 volts. This isn't quite the end of the sto- ry because we have to give some thought to LED current as well. The drive current for the LED's is deter- mined by the voltage from the 4- V rail on one side and the IC's refer- ence voltage on the other side. There's a ratio of about ten4o-one between the current for each of the LEDs and the current drawn fram the reference voltage at pin 7. Since the second 3914 is working with a reference voltage twice as high as the first 3914. we have to adjust the ^^lue of the resistor on the second 3914, A simple application of Ohm s law tells us that if we have twice the voltage but want the same amount of current, we have to double the value of the resistor Since we used about IK on the first 3914, we have to use a 2K resistor on the second one. Before we turn av^y from the 3914, let me repeat that while it's a relatively simple chip to use, there's more going on inside it than you imagine. The only way you'll ever be able to get a good handle on using it is to work your way through the in- formation in the data sheet. The way to do that is to call or write the folks at National Semiconductor (2900 Semiconductor Drive. Santa Clara, CA 95052-8090, 408-721 -5000) and ask for the data sheet. The complete schematic for the scope so far is shown in Fig. 3. Just about the only thing we have to add to it is an input amp and a pad ar- rangement to prescale the input voltages. The time has also come for us to deal with some of the me* chanical problems in the scope- mainly the wiring of the display. While it's certainly not impossible to hand wire four hundred LED s. it's a lot easier to use a commercially available mulli-LED module, R-E BUYER'S MART FOR SALE LAND General mobllo radios. CB's, scannerSp radar detectors, auto alarms^ marine trans^ ceiv^rs catalog 52,00, RAYS. Box 14862HE, Ft, Worth, TX 76117-08a2. CABLE TV conveitefs: Jerro4d, Oak. 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Mtnimum; 15 words. 1 2 3 4 S 6 7 8 9 10 IT 12 13 14 15 (S46 50) t7(S52.70) 18 fS55.eO) 19 ($58.90) 20 (562.00) 21 t565-t0) 22 (S6B.20} 23 (S7 1.30) 24 (S74,40) 25 (577.50) 28 (580.60) 27 (S83.70t 28 (SS6,80) 29 (S39.90) 30 (S93 00) 31 (S96J0) 32 {S99.20) 33 (SI 02.30) 34 (SI 05.40) 35 i$l06.50) V^^cccpl Maslf^rCard and Visa for payrrtent of orders. If you wish to use your credit card to pay lor your ad fill in ttie loiiowing addiiiona] informaiion (Sorry, no telephory} ofdsrs can ba acc^ted,): Card Nymber Eirpiratjon Dale Please Pnm Name S^gnaiurt IF you USE A BOX NLTMBER YOU «UST INCLUDE YOUR PERMANENT ADDRESS AND PHONE NUMBER FOR OUR RLES. ADS SUBMnTED WITHOUT THtS UIFORMATIOIJ WILL NOT S£ ACCEPTED. CUkSSIFiED COMMERCUIL RATE: {lor hmis or indmduilft oltoniia oonwiercial products or $wvioes) S3 to pef pr^^^ ir^ charge iot zip code) . MINIMUII tS WORDS. 5% dsooont lor iamt ad tn e ^(r^ di^ouni for same ad m 12 issu&s w!th4n «^ ye^; «f prapaid. HON-COiaiEilCIAL RATE: jiof iri M cor Acrd EXPANDED TYPE AD: ti.70 (wr wOf d prepaid. Entifleadin botolace. S5 eo p*jt Atjrd TINT SCREEN BEHIND ENTIRE EXPANDED TYPE AD; S5 90 per word TINT SCREEN BEHIND ENTIRE EXPANDCD TYPE AD PLUS ALL BOLD FACE AOS^ 90 per word DISPLAY ADSi r . 2-.-S4m00:2- ■ 2'r-S8?000 3 ^ — S 1230 00 Gene/31 information: iFrequer^cy r^l:l!,'1> .ind pmp-iyrricnt oscouiis arc avaiF,ibie ALL COPY SUBJECT TO PUBLISHERS APPROVAL, ADVERTISEMENTS USING HO, BOX ADDRESS WILL NOT BE ACCEPTED UNTIL ADVERTTSER SUPPLIES PUBLISHER WITH PERMANENT ADDRESS AND PHONE NUMBER. Copy to be n majMlfacdjrtn§ Contact cur sales depanmeni for iitormation and quotes CAPrTAL CtRCUrrS, 1214 Capitot. Addisor. IL 60101. (708) 628^715. ¥sx: (708) 628-8278. Modem (708) 628-9282- CLOCK, 1-32MH2 vanabte squaro wravo gener- ator. Request specs, price. TROLEX* 1292 Meams Fid.. Wtennimter, PA 18974. Qualitv Micmwave TV Antennas WHELESS CUll tFTS MMDS - Amasttf TV • 36-Cft*wm«l Ooh Syslerri $124 95 • (teief#C*wHfr*r/*ti - . ^ iml^^ fmilPS-TEiai E11CTR0KIC5 LIFETDUE 1602) <52 DQ DeOil all phant ofilmj OSCILLOSCOPE 50 MHz. Hewlett Packard, sol* td siaie calibrated, manual S290.00 1 (800) 835-6335 X-15&. CABLE TV EquipmenL Most type available. Special: Oak M35B S39 95- fslo catatog. COD or- ders orxly 1 (800) B22-99SS. FIBER optics kits, Exponmeniers S24 50, Oata]tnk wPCB $36 25. HILL ELECTRONICS, Bot 47103. PhoentK. AZ 85068-7t03 IMPOSSIBLE cabfe systems New user pfogram* mab^e umis aushofue anv oi aR featums of Ph oneeror JerroJd descramblers- TAKE CONTROL, 1 {600) 968-4041. TUBES, new, to 90% off, SASE. KIRBY, 298 Wtest Carmel Dnvw. Carmel. IN 46032 CB RADIO OWNERS! We spedalize \n a wide vanety of lechr^ic^l information, parts and services lor CB radios 10-Meter and FM conversion Jiils, repair books, pfans, high-performance accessofies. Thousands of satisfied customers since 1976! Catafog S2. CBCIMTERNATIONAL \ P.O. BOX 3I500RE, PHOENIX, AZ 85046 i I to a? o o 3 85 A Monumental Selection TestlMeasurenimt and Prototype Equipment Jdineco S<»ld«rl«is Breodboards suiiiblr for nunr kinds of prpionTiing ind ciraiit design. Larger models fcatuica hc3VT*dui:)" duminum backing wnn voliagc and groufidinj; p*>i(s. Pan 3^ Dim. Contact Bmding P*Tt Dim- CaJiuct Bindltie JE21 5,25*1125 400 n $4.95 JE2S 6,500 1 4.25 LfifiO 3 $17-95 JE23 fi.50i2.l25 0 6.95 JE26 6.87^x 5,75 2.390 4 22.95 JE24 ft.SO* 3.125 1,360 I 12.95 j£27 7,250x7,50 3.220 4 31.95 51 -Piece Electronic Teel Kit Tools Included in Kit 10' mciiu ring tape 5.25" needle nose pliers Udtt^* compantnu box (y long twcocrs 8 jjicce bcx kej- wTeneh set 7 brusb ind scraper Digital MuJti meter U£i]jt>' knife with actra blade 6 picee precision sawdriver set 7 floe point probe Round needle file 6 Slotted & A Phillips scrrwdtivers 7" slotted probe Flat needle fde 4.3" di:igDnii cutting pliers 5.25" Bent needle nose pltcrs Soldering stind Rosin core Mulder 3.25' Flat tioic plietj 30 Watt soldering iron 5.5' Stainless steel sdsson Desokknng pump 6" ailttnalHe wrcndi Carripitig cue MS5a5 $119.95 JAMECO EIBCITOIC COMPONENTS COMPUTER PRODUCTS 24 Hour Toll-Frce Order 1 lotltnc 1.800«831«4a42 N«rtien«il oihI ittfel DaiiilM»oks C3 Ple^ rder i» Mail Key! ndieei ardcfing 400026 NatJdiul itrncral rutpoic lineal l>cvkei Diubc»k..l9,95 400039 Nauoiul Logic DjtabwL... 19.95 400O15 Nanotii) Dai» Acqukiiion Unear Dciriccv DataWk.J 1,95 400104 N a [ io n J t .S pccia I Pii rposc IJncjr Devkes l)aiaWk..l J ,95 400044 National US/SHTL Daiabook 14.95 230845 Inicl Niemury Dat3book...24.95 270645 Intel tmbcddcd Controllcf Procmon Djtabook ........24*95 AMimnd [hitahafks at^dabi^ Metex Digitol MuMmeten • Handheld, high accuracy • AC/ DC vokage, AC/DC current, reistance> diwfcs, continuity, timisistor KFli {otcept M3900) • Manual ranging w/ovcrload proleaion • Comes with probes, batteries, case and manual M34i50&M4«Saon]>-: • Abo measures frequency' and capacioincc M3BO0 35 D%it Mtiltimrtcr ,».«,S39.95 M3610 3 5 D%if Muliimttcf S59.95 M1900 5.5 Dipt Mdi indiTiclirt>*dl ***^*„_J59.95 M365O 3,5 l>igrt Mukbtictcr nr/FrcqucTKy 144650 4.5 1^;^ w/Tit^tKooi' 6c CifuoLanor U Daia Hold .599-95 M46W J fliiiec e IC Test Qip Series * Test Oips are designed for lemporaTy connections to Dll* package component,^ ■ Heavy-duty ip ring lt>adcd hinge provides positive contact JTC16 JTC20 JTC24 JTC28 JTC40 E(E)PIIOM 1 Sock«l 10K-1M*9 • Built-in Normal. Intelligent l&ll, and Quick- pulse algorithms • XP6000A needed for operation • Software included XP6001 ..$119-95 XP60O0A Adapter Cml S29.95 IG^pin {ki a J4 & 16-pin ICs) $5*95 20^pin (for 18 U 20-pin IQ) 6.95 24-pm 7*95 2Ji-pin 8*95 40.p(n 11.95 UVP EI»ROM Eraser • Erase* all EmOM's • E™s 1 chip in 15 minutes and 8 diip* in 21 min - m ima^xvr. 6800 DE4 »„» SS9.9 Ei*IIOMs - for yeur pregrammlng needs T\SS2516 ,-S4^5 TMS2552A 6.95 T\1S2564 , 5.95 TMS2716 5.95 f ri CT Pan No - JEikf Fin N^J1 „S3,75 ^3*75 1702A 270« 2716 2716*1 27C16.. .«J.95 .4.75 f*«mp*3*39 «..«3.75 .„„4.25 2732 .4.95 2732A-20 4.49 2732A-25 3*49 2732A^5 , 2.95 27C32 .4,75 2764*20.,, ,3.95 2764-25,^ 2764A'20 2764A-25 -«3.19 27C64-I5 3.95 27C64-25... 3.25 271280TP ..2.49 27128^20 .,.,7*95 27128^25.*. .*.*7*75 27I2SA-15.*... 4.95 27128A-20 4.49 27128A-25 3.75 27Cn8^l5,.*„*.,*,5.75 27C128 25 7*95 272560TP 3.75 27256-15.*. .*.*5.49 27256-20 2715G^25 4.4 27C256-15 5.9 27C256-20 «...4.9 27C256-25.. 4.2 275I20TP..,. 4.9 27512-20 .,.,.,,6*7 27512-25 * 5.9 27C512-15..... 6.7 27C5I2-20 6.4' 27C5 12.25,. 5*9' 27C0I0-15 9.9' 27C020-15,., 17*9^ 27C020-20, 15*9^ 68766-35...* ..4.9^ ' Partial Listing * Over 4000 Electronic and Computer Components in Stock! ORCLf 114 ON FREE INf OeitATK>N CAftD It Competitive Prices Computer Upgrade Products and Electronic Components Upgrade your existing computer system! Jameco will help you upgrade easily and economically. Fujitsy lOl-Key Enhanced Keyboard Jameco 803865X Motherboard • Baby motherboard {8. 5"xl 3") • Ztro or one wait siaie operation ' Supports up tu 16MB ofRAM • Iniei 80387SX/t:ompatib[c maih coprocessor socket vVMIBIOS ; • Stx Ifj-bir anti two 8-bit espruion bus slots • One-year Warranty $299.95 lanteco IBM Comporible Power Supplies ll.LJ an* 1030; Output: +5V @ ISA, -5V @ hI2V@ 5,5A, -12V@0.5A 1 50 Watt lO/220Vswitchable Bui kin fan Jne-year Warrant)' JE1036: • Output: +5V @ 20A, -5V 0.5A tl2V@8A.-l2V@0.5A ^ • 200 Watt • 1 10/2 20V swirchablc • Built-in fan • Size: 6.5"'Lx5.88"Wx6 'H • One-year Warrant)" 1030 1 50 Wan PC/XT Power Supply .$69-95 :i 036 200 Ware AT Power Supply.,„.,»,.» ..-.$89.95 ^V/'^ avrnkhk^ 0) This ktyboard features 12 funcuon k(ty%, separate cursor and nun i t rie ktys • [BM PC/XT/AT and corapatibfe tompuiers • AL5tomaiicallj^ swiiciies between XT or AT • LED Indicators for Nurti L^ock Caps Lock, and Scroll Lock • Tactile Feedback •Manualincludcd* One-year Wa r ran ty * - FKM700 J79.9S Toshiba 1.44MB 3.5" Internal Floppy Diik Drive • IBM PC/XT/AT and compatible • Compatible with DOS vctsioiis 3.3 or higher • Includes all necessary insiilbiion hardware • 1.44MB formatted high density mode • 720KB formatted low density mode ' $iz£: rHx4''Wx5.9''D(aau3l drive size) • One-year Manufaeiurcr's Warranty 356KU $99.95 Many more Upgrade Products available! Intesraied Circuits* LSOO. $.25 $.15 LS02 as AS \JS04 «,.25 AS LS08»„»».»»»™. .29 A9 LS14. 39 .29 1530 a.5 AS LS32 25 .15 LS74 29 .19 LS76,, „ 39 .29 LS86 .25 -15 LSI 12 .35 .25 LS123 39 .29 -LSI 38 39 ,29 LS175 39 .29 LS193 ..^ .59 .49 LSIU „ 69 .59 LS245 « .69 .59 bLS373 .69 .59 :LS374„..,.„„.....„„ .69 .59 Linear iCs* jtNo. 1-9 la* L0S2CP X59 $.49 V1317T 65 ,55 vf324N 35 -29 v^336Z 1,05 .95 \1339N 39 35 E555V.. ......29 -25 U556N 49 .39 U723CN 49 .39 Vi74lCN 29 .25 Vil458N. .......35 .29 V11488N 45 .39 M1489N .45 .39 LN2003A .69 .59 M3914N 1,95 1.75 E5532 _M9 1.09 f05T „ ,45 -41 312T 45 ,41 ' QiH fhr s cQmplkte ibting of fQ Memory Part No. Fptijcdon Eocs 41256^120 256KDIP n0m.....SI.79 4 1 ISS-i 50 2%K Dl V 1 50m .....A .69 5nCWK)P'80 LMBDIP SOn „5.99 5 1 1 000 P- 1 0 i Si B DI P 1 OO ni 5.49 i 1 2%A9A- 1 0 256K 5 IPr 1 OOns 1 8,95 41256A9B^ 2>fKS!MM BOns 20,95 4210OOA9A-8O LMBSIPP 80ns..».54.95 4210OOA9B-8O 1 MB SIMM 80ns ....54,95 Miscellaneous Components* Potentiometers Values a^iilaUe (inseii ohms into space maiked 500fi, IK, 5K. lOK. 20K, SOK. ICKIK. IMEG 43PXX 3/4 Wart, 1 5 Turn ..... $.99 63PXX l/2Watr> 1 Turn 89 Itansistofs And Diodes PN2222 S.12 1N751 S.15 PN2907 .12 C106B1 .65 1N4004 .10 2N4401 .15 2N2222A .25 lN4l4S ,07 1N4735 .25 2N3055 .69 2N3904 .12 1N270 .25 Switches JMT123 SmTOn-On (Toggle) SI. 15 206-8 SPST. K^-pin {D^D .,. 1 ,09 MPC121 SPOT On-OfF-On {Toggle) 1.19 MS 102 SPST. Mcmcntacy (Pmh-BuETon) .39 ^Addin&nal £ompontnts avaiLihle Pan No. Connectors Description DB25P DB25S Da25H DB25MH XC209R XC556G XC556R XC556Y Male, 2 5 -pin Female, 25-pin Hood Metal Hood S.65 .75 .39 1,35 LEOs XL (Red) $.14 Tl 3M, (Green) .16 Tl 3/4, (Red) .12 Tl 3/4, (Yellow) ,16 IC Sockets 8LP $.10 8WW $.49 14LP 14WW ,69 I6LP .n 16WW .79 24LP .19 24WW 1.15 28LP .22 28WW 1.39 40LP .28 40WW 1,89 Call or Write for a FREE 90-P^e 1992 Catalog! 24-Hour Toll-Free Order Hotline •4242 530.00 Minimum Ord^r Mention MailKi^ 2 1*800*831 J AIVIECO ELECTBOWIC COMPONENTS COMPUTER PRODUCTS 1355 Shorcway Road Belmont, CA 94002 CARttuffnoi p3aic add .ippjidblc uld tu I^WSS Sliipping-lundlingind Term): Prkti iL]:b|t£[ id ckingf weibolu notice. krmi subjeci td i^iiiabLtiTy Afuj p>riof ule. Complete list of itriTuiwir wiTce$ « ivaiUbk upon rn|un(. © i992jdme€o 5/92 FAX: l*800»237-6948(fw.tk) FAX; 4 1 5-592*25035intc,«.i»«4!3 BBS Support: 415*637*9025 Tccfinicii! Support: 1 "SOO-SJ I '0084 SeniccDirca'":l-800'83l'aO2O The following scrvicei arc available thmugh 4 15'592'8097 from 7AM - 5PM P.S.Tj • International Sales * Customer Service * Credit Depanmeni ■ All Other Enquiries CIRCLE 114 OK FREE IN FORMATION CARD 6 o: 88 WIRELESS CABLE RECEIVERS 1.9 TO 2.1 GHz 30 CH PA>"1 AEOLIC DtSH SYSTI U Si 73 30 CH ROD AN I E HUk SVStEW 30 CM CRYSTAL CONTflOtlED SrSTtM S294 95 SLTN MICROWAVE INT'L. WC, mO SI M m PKQ t AJ. ftSO^T m OTHER EIKE 1602f ?50.12^5 V(MO PRODUCTS DUAJJTlTlfEtlSCDyHTi TV. notch fillers, phone recording equipment, bro- chure S1.00. MICRO THinc. Box 63/6025. Mar- gate, FL 33053. (305) 752-9202. CIRCUIT Boards — Connplete printed circuit fab- ricaiion from single sided to production multi- layers. Twenty-four hour turnaround availatsle, CfRCUIT CEMTER. PO Box 12B, Addison. IL 60101. (708) 543-0671 ■ OUR monlhty pictLrre flyer lists quality surplus parts at low prices. Send today for yours, STAR- IRON I OS, Box 683, McMinnviJle, OR 97128. CAHI,K l\ i>KSHtAi\lIUJ:kS BEST BUYS BEST SERVICE nULLET PROOF W TESTED WANT TO BUY; TOCOM, SA eSB^l,DPV72ia Mutt ba reasonable prlcn. CaEI fa Your VrtitileMl* Catalog cr Swid SI .CO TO; ElaclronEctt'v 2.730 S0JJ3rd Dealer! Wanltyd I 800-835-2330 CL*n6 OmahM, N'l^ 6EI44 OESCRAMBLERS cable TV converters, lowest prices, guaranteed, best quality, all types avail- able, CNC CONCEPTS, IMC, Box 34503. Min- neapoEis. MN 55434; 1 (800) 535-1 fl43. OESCRAMBLERS |#EX192 All major brands carried *JERROLD, *TOCOM, *ZENITH *GENERAL INSTRUMENTS ^SCIENTIFIC ATLANTA, *OAK *I!AMLIN, *EAGLE, *PIONEER 7th Year in business. Thank You Member of Omalja Chamber of Commerce 1 Year warranty on new equipmcnl 30 Day money back guarajilce Orders shipped from stock within 24 hours CALL TODAY FOR A FREE CATALOG 1-800-624-1150 111 CO.D. % > 875 so. 72nd St JERROLD, Tocom and Zenith ''tear chJps. Fully activates ufiit. SSO.OO. Cabte de^ scramblers from £40.00, Orders 1 {800) 452-7090. InfOfmation (310) 367-0081. AFFORDABLE Diode lasers! Our small laser head (1.4" x 1.8") snaps right on top of a 9V battery. Includes drive electronics, colltmat* Ing lens, & adjustable output power Visible *?i:670nm: 3mW (TOLDSZOO) $79.95, or 5mW (TOLD9211) $99.95. Detailed plans only — $9.95. SECURICOM, PO Box 5227, Chatswofth, CA 91313-5227. S/H $3.75 (818} 710-0110. ^ ^-tf PRESENTING ^-tf**" CABLE TV OESCRAMBLERS ♦ ♦★-♦f-lr STARRJNG ^^*^-it JERROW, HAMUN, OAK AND OTHffi FAMOUS MANUF^CTUlRFIfS • fJMcST WARRAMTV PROGRAM AV^IL/^^EiLE • IjOWEST ftETAfL; wholesale PHJCES FN US. • ORDER5 5HEFPED f fiOM STCtCK WITHIN 24 HRS • Au. majoj? credit c^ds accepted FORAILINFOJTMATION !-800'34S-S927 ' PACIFIC CABLE CO.. INC. 7325V? Reseda Blvd., Dept. 2114 Reseda, CA 91335 80C52-Ba5ic microcontroHer board. Basic inter- preter, 32K RAM, 16K Eprom, Eprom programmerp RS232, expansion connector. Bare board with FTianual. schematics S22.95. 80C 52- Basic micro- processor chip $25. 95. Assembled and tested SI 24 .95. PROLOG IC DESIGNS, PO Box 19026. Baltimore, MP 21204. PHOTOFACT folders under #1400 $5.00. Others S7,00. Postpaid, LOEB, 414 Chestnut Lane^ Easl Meadow, NY 11554. (516) 481-4380. SPEAKER repair. AH makes — models. Stereo & professional. Kits available. Befoamlng $13.00, ATLANTA AUQIO LABS. 1 (BOO) 568-6971. ENGINEERS G software and harcJware, PC/ MSDOS. Circuit design and drawing, PCB layout, FFT analysis, Mathematics. Circuit analysis, etc. Data acquisition, generation, I/O RGB's, etc. Call or write for free catalog. (614) 491-0832. BSOFT SOFTWARE, INC, 444 Colton Rd,. Columbus, OH 43207. REWlOTe CONTROt! K^YCBAIN Comptcte wmijnl-Uan^niEtlef and +5 vdc RF fcceivef. Fully a^scrrtbltjd ir>oluding p[anft' fo build your owrr auio sJami:: QuaFiCdly dt^cQunts avf^Nsble:; Add $ ^ shipping VISJTECT JNC, Box 141 £S. Frcm&nt, Ca. (510) 651-1425 Fax (510) 651-8454 $24.95^ PLANS AND Kits FASCINATING electronic devicesf Dazersi leasers? FM AM 'phone transmittersf Detectors! Kits, assembled J Catalog S2.00. QUANTUM RE- SEARCH, 16645-113 Avenue, Edmonton. AB. T5M 2X2. HOBBY/broadcasling/HAM/CB/surveillance transmiHers, amplifiers, cable TV. science, bugs, other great projects! Catalog Si .00 PANAXfS, Boic 130-F5. Paradise. CA 95967. PCB and schematic CAD. S195 00 JBM EGACGA Multilayer, rubberband. autovia, NC drill, laser, ciol matrix, plotter, library. Gerber, AUTOSCENE, 10565 Bluebird St., Minneapolis, MN S5433. (612) 757-8584 free demo dtsk. REMOVE LEAD VOCALS Call or write fat free info (513} 444-2276 Build ttsis kit which removes lead vocals liQm standard stereo fecords, CD's, tapes or FM broadiasls. Sing along with the background mumc. Use with any home component ste-reo. Additional k^t adds reverb to your voEca, then mines it with music. Pre-aGsemblod' boards avalEable. Weeder Technotogio?; 14773 Lind- seyRcf.; Mt Qrab, Ohio 45154. y DESCRAMBLER kits. Complete cable kit $44.95. Complete salellite kit $49.95. Add $5 .00 shipping. Free brochure. No New York sales. SUMMIT RE, Box 489, Bronx, NY 10465. SURVEILLANCE transmitter kits tune from €5 to 305 MHz. Mains powered duplex, telephone, room, combination lelephone.'room. Calaloq with Popular Communicattons, Popular Elec- tronics and Radio-Electronics book nsviews of ""Electronic Eavesdropping Equipment De- sign," $2.00, SHEFFIELD ELECTRONICS, PO Box 377785-0, Chicago, IL 60637-7785. DESCRAMBLINQ. New secret manual. Build your own descramblers for cabio and subscrip- tion TV. In SI ructions, schematics for SS AVI, gated sync, Sinowave. (HBO, Cinomax, Showtime. UHF, Adult) 512,95, $2.00 postage. CABLETftONtCS, Box 30502 R, Bethesda, MD 20824. ANTIQUE RADIO CLASSIFIEI Free Sample! Antique Radio's — j ^^t--,i Largest Circulation Monthly, [Sl©J] Articles, Ads & Classifieds. 6-Month Trial: $15. 1-Yr: S27 ($40-1 st C?ass; A.R.C., P.O. Bo% e02-L9, Carlisle. MA 01741^ ANTI-THEFT Alarm, self contained, loud, com- monly available parts, install in TV, VCR, comput- er, etc. Plans and instructions, S4.50. TECH- NtCAL SPECIALTIES, PO Box 7216. Rfverside. CA 92513. EASY 10 build lethal gas alarm. CO propane natu- ral S8.00. ROM, Box 2481. Hazel ton, PA 18201. ETCH PCB's yourself, no chemicals, easy, cheap, lull instructions. S2.00, SASE, NiCKN AP, PO Box 593, HowelL NJ 07731. TESLJV coil design program for IBM PC! Fan- tastic, graphic, menu driven. Coils any size! S24.95. W.C.N.* 32B3 Belvodona, Riverside, OA 92507. CABLE TV J7A -800-582-1114: Olf^CLE 53 ON FREE mFOHMATlON CARD FREE CATALOG GUARANTEED BEST PfllCES • IMMEDIATE SHtPPJNG ^^ M.K- ELECTRONICSbssi IliE^a 6362 Pines BJvt and rear paf^Gl$ baling rrmdo frorr^ filumjnum f^ar oasier, custom filting, Tho front punel Js 1/9" thick. Tlioso cabinuttj hav« b4- Do:iros for the pan-ttme hobbyist. sVucent or engineer SBS30 <:olor coof Dimensions Order # Price Output Voc/ Amps Watts (HxDxW in.) Weight KCT030FJ1 5.95 *5Viained in easy-tChurKferstand la/^uage w#i plenty of dmv/ings. dEagrams and pto^os. V/e sfioi^v you ho^' to traubtehoot and rep^sr videocassstte recorders and TV seis. flow to harnfle fwuse calls and sttop repairs for almost any make of television or VCR. Tools are included v^h your course so you can get ^hgntfs-ort" practice as yQU foilow your lessorts step by step. Send for free facts about the exciting opportunities in TVA/CR flepair and find oirt hov; you can start TOking nncwiey sn tf ir$ g reat career, MAI L COUPON TODAY ! K33 School of TV/VCFI Repair, Dept. Aumis 925 Oak Street, Scranton. PA 18515 Please serm tu!l inlorrrtaiion ana Dofor brtjcfiure on t\mi I can learn TV,iVCfi Repair at home in my spare !5me. I ixntfef- I stand ttjere is no oWcaiJori and w saltan wU ^-^srt me I Him - Affe I ctfr/suit. _Apl- *_ S/VTELLITE TV FREE catalog — Lowest prices worldwide, SKV« VISION. 1012 Fromier. Fergus Falls, hAU 56537, 1 {BOO} 334*6455, See full page ad the Shopper secttpn, VIOEOCIPHER II. descramblmg manual. Sche^ matics, video, and audio. Explains DES. Eprom, CloneMaster^ 3 Musketeer, Pay-per-view (HBO. Cinemax, Stiowlime. Adult, etc.) Si 6.95. S2.G0 posrage. ScherrfaUcs for Videocypher Plus, S20.00. Schematics for VEdeocypEier 032, $15.00. Collection of sothvaro to cop/ and alter Eprom codes. S25.00, CABLETRONICS, Box 30502R, Berhesda. MD 20624. Cable TV Descrambler Kits Universal Kit $55.00 includes All parts ana PC Board. Hot inotudea is in« AC adapior or encJosure. Tri-Mode Kit S39.00 inciuaes att pans PC Board and AC Aaapior f^ot SB-3 Kil...».. , S29.00 tncludes all parts. PC Board and AC Aaapidr. No' inolud&d r£ the enclosyre. Universal Tutorial..-., $9.95 Includes an in depi hi study of ine tecnonoloQy u%&g and has iroubiasnooimg hmis. Tri-Mode Tutorial..., •.„.$9.95 includes a gate^ by gaie study of tne circuit and na$ trou&ia^rtooimg hints. Snooper Stopper S39.00 Protficr youmH from OBscrimPier deiecMon ana stop tne *Du]iar Call Toll Free 1-800-258-1134 Visa, MasterCard & COD h/T & G Eleetronics, Inc. 301 Westminister Street Providence, Rl. 02903 DIGITAL SATELLiTE imaging syslen^, Becaive pFCturos from outer space of plarei earih! Works with any IBt^ compatible computer. Systems as fow as 5499 00. Call or write now for free details: Moonbeam) Satetlite. 339 Neighborhood Rd. Mastfc Beach. NY 11951. {516) 261 2669. (516 281-8250-fax. CABLE TV DESCRAMBLER LiQUIDATIONI FREE CATALOGI Hamlin Combos S44, Oak M35B S60 (min, 5), elc. 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VOLT. 1-34 25-99 100+ TOSHIBA 3 mW as mA 2,5 V 129.99 123.49 111.14 TOSHIBA 3iTiW B$ ittA 2.av 49.99 47.93 43.19 LS3201 TOSHIBA S70nm S mW BO mA 2.4 V 59.99 56.99 51.29 LS92n TOSHIBA 670nm 5 mW SO rn A 2,3 V 69.99 66.49 59,84 TOSHIBA 670nm 10 mW as mA 2.4 V 109.99 104.49 94.04 LS320O KEC 670fim a mW B5 mA 2.2 V 59.99 se.99 51.29 LS022 SHARP 7eOnm S raw es mA 1.7SV 19.99 16.99 17,09 PHILLIPS 82Dnm 10 mW &a mA 2.2 V 10.99 10.44 9.40 WAO II PROGRAMMABLE ROBOTIC KIT • Power Source -3 AAbatiOfic^ [no£ ircSL^ded) DESCRIPTION MV961 WAO if PfOsr^mmaft/^ BoboUc Kit WIIAP intoffaci^ Kj! Fcr Appie n. ifB. ih The pofi mechanisnni in- cluifod With I he robot allows it to draw. In acFdltlOfi drawing straight linos, it can also accu- rateiy draw circles, and even draw out words and short phrased, WAO It comes with 12Q X 4 toils HAM and 2K ROM, and is programmed directly via thfl keypad attached lo it. With ils buiit-in connector port, WAO II is ready [ocorT5miun.tcate with your computer, With the optional interface klL you can connect WAO II to an Apple W, lie, orlt>compuler. Editing gnd trans'enng of any movement progfam. as v^/ell as saving ar^d loading a program can be performed: by the mterfaoe Kit, The !iil includes software, cable, card, and instructions. The programming language is BASIC. 10-34 25+ 79.99 39 99 75.99 37.99 6B39 34.19 • The total dosign wor3< station - including exparrded instru mental! on, breadboard and power supply. • Ideal lor analog, digital and micro- processor circLfitS • S logic probe circuits ■ Function generator wi I h continuously variabte si^e, square, triangle wave forms, pJus TTL pufso& • TripEo power Supply Oilers (ixod 5 VDC supply plus 2 variabEe outputs - ^^5 - IS VDCand-S- tSVDC « 8 TTL compatible LED indicators, switches • Pulsers • Potentiometers t Audio experimentation speaker • Mustipl^ tgaiures in ono ccmptelo test instrument saves hundreds ol dollars needed for inOivi^Jual unit$ • Uniimileullon operated^ op en -co I lector output pulsers. each with : normal ty- opon, 1 normaily-cfosed output. Each output car> sirik up to 250 mA • Potentiometers t-IK ,110K , all leads avEsilable and uncommitted ■ BNC connectors 2 BNG connectors pin available and uncommtttod shell connected to ground 0 25 W. 8 Q • Br^^d boarding area 2520 uncommitted tie points « Dimensions 1 1.5 ' Jong x 15" wide x 6 5" high • Input 3 wire AC line inpul { 117 V. fiO Hi typtcal) • Wslghl 7 lbs PBS m 239.99 1D-24 2S+ 2^4 .99 IDC BENCH ASSEMBLY PRESS The Pflr,ftvi!i.& PV£0^ ton mar^ual IDC tench jjistrnbl^ pfBfl tl 4 aigoed. pfJKlica! irriTai- laMon t(k9l dmgn'i'd lor loyn volum'9, Itrfnl nation □) vsnous IDC connectorb on tiAi fibtoan cable • A$4«Fnbiy !34H & standard piatan induced • e«s& plate &. pifittn my b« rolatdd 90' fs-r Friaxd'TU'ri ^&rfa(ill1^ « Gaao plates £ cultm^ acces- sone» nrfi quiciily ch,an{]tid wllhotil any tools ^ouutckJ * AifWltional accMiforKsj below # SilO-10"Wxe.7S-Dnr H * Weignt - 5 Stba. COLLIMATING A tow powfif co'limflficfl- pof» eoniain- if>g a MOVPE gfcvfti ga-n GaAIAs liser Tr^ts pOllirnalSr pem tleliver^a majcHtiij rrt C^it outpol jxjwcr of 2.5 mW st AM nm Trie O^jeratiTig vo^ta^e 0\ ?.J-2.5v (S Sil'iSOmA is desigrvod Tor lowor pff^or ^ppiicaiicna inch data r&tTicvar. lelemetry, akgnme^it. e!c. The nor^ hermetic fitafnh&sa atWH case ts specifically designed for easy aJifln- ttv^nt in an optica) r^ad or wrjlc Bystcim, and consjsl^ o5 & lens and a laser dicKte. Trjfl lenis systenrs colHmalea the flivorg- mg las^r Eighl .1& mred-. Thu wavd^ont quality Is iliffractioni hmltiMl. The houslrtg is circular a*id piecision manutactuTwl measuring 1 1 .0 mm irntiflm&t^r aitd 2-7.0 rtim long. Data sheet inclutlENl. As wiin all special buy iSenns. qruantity is limited to stock on hartd LASER DIODE MODULE TT* LOM ifslegrated as- aemtjly j;Onsi55irvg qI a las^r diOde. corhmaling opdcs and (framt}iy conjjsis oi a bi^cii AnodUdd I turn mum i^arrai inai acti ■» t. hMl iinh. and a olast Im with i focfll point of? ,5 fflim. l>«iQn«l l& H ■fandard ^mm liser di-odes, tt|l« as«*mb4y wilE hi all th« fliwve J«Mr ciodj;*. Simply place diodfl m \he tuns assym- itiy. fldjuit ttmm to dfrSff'Pd Tocu-j incn Ml with Aani:!«ivt>. STOCK * MSCntPTlON LSLEHS Col imstiitg Lent Aissm.biy 24 99 DUAL MODE LASER POINTER r^Tflw slimline laser pointer is only vr in diarrvetef !i 6V*" iong and WOifllB under ? oz . 6^0 hfT @ loss than 1 friVii prodLici?* a e mm beam. 2 switches. One tor conTinuoiB mwfe. ajitJ one for p^Il34^ moclo jred dot thasH^es rapldlY^ ^ AAA batlori^^ proviite hours of use 1 ywr WTBiranEy 13 1&24 as* LDW1 3&-2 2 ffl tv iasor D;ode WDdu/a- I LPM1 ^ m 1^ idser D/ocre Vodu/fr 179.99 170.99 153.69 109.99 180.49 1S3.44 1 99.99 1S9.9& 170.99 209.99 199.49 179.54 He-Ne TUBES iJtr3^iWftfe£a«rrPOfn(esf 199 99 ie9.Ef9 170 99 23 74 21 37 ROBOTIC ARM KIT New. testfiiJ 632nrr» He-lsle laser lubes rartgmg rrom .&mV/ to 3mV*r ioui choice). Perteel tor hobbyists for hoiioe prD|.6cts. Because o( ttw variety WD puiffrtasfl. WB oartnot gyarflntw ipecitic outpi^la wiJi tje swUUaie al itmc ol ofder A![ urtits ar« n««r. leslfid. artd guara^i^ed to function et msnutacture^s speaticalioM. POWER SUPPLY « Oulpul -Svi^STSA M?v@1iA STOCK ft PRICE PSIOOa £10.93 RoSkUS were once confine^d lOSCScniC* IfCton movies. Today, wntttwr Ifwy ns Eogelher complex producls. rottotia are hcid^ng t^r way mio more ar^l mor« rnduslfri^. 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FEDERAL EXPRESS SHJPPtNG AVAtLABLE » OPEN MON-FR^ 9:00 AM ^ 6;00 PM, SAT lOiOO AM - iiDO PM POT • CA RESfPEKTS ADD B' SALES TAX * CALL FOR QUANTITY DISCOUNTS • CALLFORFREE CATALOG (FOR 1ST CLASS DELIVERY Ofl CATALOGS DELIVERED OUTSIDE THE U.S. ~ SEND %2M} • WE CARRY A COMPLETE LIME OF ELECTRONIC COMPONENTS *N0 SHIPPING CHARGES ON PflE-FAID ORDERS DELIVERED IN THE CONTINENTAL U.S. CIRCLE 17G ON FREE INFORMATION CARD FREE CATALOG! 1-800-648-7938 JERROLD HAMLIN OAK ETC CABLE TV C0tjrt^0sjg Se/Hce ■ DifCOUni PiiC6$ ' Fust Shipping nLLELECTROniCSCORP. Mail Ord^^r Eleclronic Paris And Supplies P.O. Box 567 • Van Nays, CA 91408 INFRARED Remote A.C. SWITCH This infjarod rtimQle cOntTOl device te;s yo\j turn oru'cfl tamps, appliances oi other 120 Vac do^o$5 \3&\p.g Stn IR rransmiti&r simiLaf to ih^ one on your TV or VCR. Ofighal'^ dastgned for use with a hydromassage unfi, these tfansmsSfirs arid receivers will apparantly c^id^e mostA.C. devices with 2 prong non-polarif&d pFi;g&. Nol reoornmended fof usa with heaters-. R^yiffts ^ 9 vofi battery {noE induded^. catjk RC-1 2 lor Jt7,00 Electroluminescent BACKLIGHTS At ia^tl A iow cost etacirolLimmesceni glow sirip and inverter, Th&sa bia/id new units wero designed lo bacl^^ light small LCD TVs made by the CHi^en Watch conpany. The Invortof circuli changes 3 or 6 Vdc la approximately lOO Vac, the voltage rt^qulred lo lighuhe glowstrip. Luminesoent surface area Is 1,7* X 2,25", The El rip is a salmon csslor Iji (i£ elf atato. and glows white when energised. The cErcuii board is 3.2^ X r. Glow strip and circuitry can im removed eastly from plastb heesing. ideal for special lighiing elfecis and backiighting. Two models available: Ciilzenj* 91TA opefates on 3 Vdc CAT# Cctf zen# 92TA operates on 3 6 VtJc C AT# OLU - W LARGE QUANTITY AVAILABLE 10 lor »32.00 * 100 Iw J27S.OO SUPER SMALL Surface Mount Green LED Surlace mouni LED ctiip. _-^v Ctear when off. qj een when fs. Very 1 iny - whole u nil Is 0, 1 1 5' "^sc:^^ X 0,055" X 0.06' IhicH. 1mm (0.04') lens diameter. Gold-plaEed rrxjuniing surfaces for superior cooductiv^y, CAT«SMLED-2 lOOtorSia.CX) -tOOOforSUO.OC S,RS.T. Pushbutton SMK Manufaciurtng 0,47" square bJack pushbutton, SPST nonmaSy opan.4 p.c. phs lor n)3unling. tdeaEfor tow current sw^chEng applicatiorra. TOLL FREB ORDER LINES 1-800-826-5432 TERMS: Minimum orcktf S J O.OO.Sh'f ping istrtd h^irxUmg including AK", Hi, PR Qr CAn^d^i mustp^i/ tuH shfiptng. AS orders, dafflfoiwi tn CAilFORNIA musr incSocfs srat& SAisstax (71/4%, 7 J/2%, 7$/4%, B 1M %} .Ouannrtoa UmH&d. NO C.O.D. Piice^ subjdc! to cbartga w/qut norico Call or Write For Our FREE 64 Page Catalog (Outside The U.S.A. Send $2.00 Posrage) ALL ELECTRONiCS CORP. P.O. Box 567 ' V3n Nuys, CA • 9UQB DESCRAMBLERS MAKE CONNECnON NU-TBK EUECmONI CABLE IV EQUIPMENT ORDER TOLL FREE 1-800-228-7404 DON'T FORGET TO ASK ABOITT GL'J? FREE CATALOG WITH BUYING GUIDE FRIENDLY. PROFESSIONAL SERVICE 30 DAY MONEY BACK GUARANTY BEST PRICE - BEST SERVICE m i i&i s [aoDj m\m\mimM NU-tEK skhrowcs I «07 005. 294 mm TDCAS 787&? FREE CATALOG ► CABLE T.V. BOXES - ALL TYPES ^ • LOW PRICES - DEALER PRICES • CABLE TV DESCRAMBLERS ^CONVERTERS' and ACCESSORIES. SAVE MONEY. DON'TRENT! PANASONIC, JERROLD, OAK, PIONEER. SCIENTIFIC ATLANTA AND MORE LOWEST PRICES, FREE CATALOG. CABLE READY COMPANY (800)234-1006 CABLE TV DESCRAMBLERS I CABLE KINGDOM! *JEROLD* *OAK* *HAMLIN* *ZENITH* ^PIONEER* ^SCIENTIFIC ATLANTA* IN STOCK 6 MONTH WARRANTY! WE SHIP COD 1 AeSOLTLEY LOWEST WHOLESALE/RETAIL PRICES 1 l#;**ac**FREEl CAT At-OQj^c****:** J -P. VIDEO 1470 OLD COUNTRY RD SUITE 315 PLAINVIEW, NY 11803 NO N,Y, SALES CALL NOW! 1 (800) 950-9145 l"J=WH:f:^rj|:]M:ki • Special Deafer Prices! • Compare our Law R&tail Prices} • Guaranteed Prices & Warrmties! • Orders Shipped immedfatety! REPUBLIC UBLE PRODUCTS. INC, 13 4080 Paradise Rd. #15, DaptR£S92 3 Las Vegas. NV 89109 For aif otlmr inrprmaiion (702) 362^9026 EDUCATION & INSTRUCTION F.C.C. CommerdaJ General RadSotelefihonQ li- cense. EEectfonics home study. Fast, mejcpen- Sive! "Free'' details, COMMAND. 0-176, Box 2824, San Francisco, CA 94126. ELECTRONIC engineering. 8 volumos com- plete. SI 09. 95. No prior kno-iwledge required. Free Brochure. BANNER TECHNICAL BOOKS, 1203 Grant Avenue, Rockford. IL 61103. MAKE a thing,,, make a living... Study Industrial Desagn Technology and bring your ideas to life. Learn to problem -sot ve, sketch, render and de- sign. Develop models, create prosthetic appEi- ances. Build your future in movie and theater special effects, toy and product, exhibit, transpor- tation, furniture/fixture, architectural and amuse- ment environmental design at The Art Institutes of Pittsburgh, Fhlladelphta, Fort Lauderdale, Seattle or The Colorado Instttute of Art. For information write 526 Penn Avenue. Dept. 61, Pittsburgh, PA 15222. Cr call 1 i}4^'41S9 Ext 72 jCfl^PlB Stipplif, D*(* ML I ' Jt^lm 79S7 HIghtDwer Tfall J^^T UtZionU^OA 30098 l^K Unfr f404i4a3-24SS Ext T2 ^-^m CIRCLE 107 ON FREE INFORMATION CARD DISPLAY DRIVERS continued from page 72 TO 7-SEGMEHT COMMON-CmfODE LEO'S nals do not have to be pre- shaped. The counter is reset by driving the reset pin high. The CLOCK iNHierr pin must be grounded to allow normal counting. When clock iNHierr is high, the counters are inhib- ited. The display Is blanked when the display enable pin is grounded. The three auxiliary output pins of the 4026B are desig- nated PISPLAY/ENABLE OUT (D/E out), carry out (carry out), and 2 OUT (2 our). The displays ENABLE OUT Signal Is a slightly delayed copy of the dispi^y/en- ABLE input signal. The carry OUT signal is a symmetrical square wave whose frequency is one-tenth of the clock input fre- quency, and is used when cas- cading 4026B counters. The 2 OUT pin goes low only on a count of two. Fig. 22 shows the circuit connections for cascading stages. l> JL JL Jt -THOOSAiaS' 4033B RBI aeo 'HUHOREOS" RBI RBO TENS' 4033B RBI RBO 1 "UNITS' 4033B RBI RBO FIG, 25 — MODIFICATION of Rg. 24 circuit to obtain automattc leading-zero suppres- sion. Figure 23 shows the pinout pattern of the 4033B. a modi- Jied version of the 4026B. The DISPLAY ENABLE and DISPLAY EM- ABLE OUT pins of the 4026B have been eliminated and replaced by HIPPLE'BLANKING INPUT (HUI) and RIPPLE-BLANKING OUTPUT (HHo). Figure 24 shows the wiring scheme for two 4033B's in nor- mal use. The reset, clock inhib- rr, and lamp test pins are all grounded, and the ripple-bijvnk- ING input pin is positive. That configuration does not blank leading or trailing zeros. If cascaded 4033Bb are to give automatic leading-zero sup- pression, the circuit in Fig. 24 must be modified as shown in Fig. 25 to provide ripple-blank- ing. In Fig. 25, the rbi pin of the most significant digit (MSD) is grounded, and its rho pin is connected to the Riii pin of the next least-significant stage. That pattern is repeated on all except the LSD» which does not require zero suppression. If trailing- zero suppression is re- quired, the direction of ripple- blanking feedback must be re- versed. The RBI pin of the LSD is grounded and Us hbo pin is wired to the rbi pin of the next least-significant stage, R-E MCM ELECTRONICS Opens the door to over 17,000 products! Come on in and see for yourself! MCM is a broadline distributor of electronic replacement parts sucti as: semiconductors, connectors, audio/video accessories, test equipmenl, hardware, chemicals, tools and lots more. With 17,000 items stocked and ready for delivery, MCM atso opens \he door to great service. Our latest catalog features an expanded line of diodes and rectifiers; as well as reduced prices on select video heads. Call today for your free MCM Electronics Catalog. TOLL-FREE 1-800-543-4330 or Fax 1-513-434-6959 MCM ELECTRONICS 650 CONGRESS PARK DR, CENTERVILUE, OH 45459-4072 A PREMIER Company SOURCE NO. RE-76 CIRCLE 87 ON FflE£ INFORMATION CARD THE ELECTRONIC GOLDMINE Si 9 Q- 94 m km in a/ atsk^ MACHO random (ar>'*rii flflyi ROLLING Dies KIT ■rid *rf VJT njTti^ tjf ynu C6412 $14« nm CALUEK Ktr C4 S66 $4 » FIASfUNC STOP SIQH KIT H [STOP C64S8 INFRARED DET^CTOA V.fvi *f !fl5lr>(] 3X1 WJ^lXTi v\ C6441 v;e .vccd MC Vaa -ind Money O^teis S£KD OfiDEflS T& The EfectriMK Gateiww PHOfJE ORDERS (602) 451 7454 FAX OBDEfiS (6023 451 9^5 . CIRCLE 179 ON FREE INFORMATION CARD CABLE TV DESCRAMBLERS THE MOST ADVANCED TECHNOLOGY IN GABLE EQUIPMENT: • BASE BAND • JEnROLD • PIONEER • TDCOM • HAMLIN • ZENITH • SCIENTIFIC ATLANTA • OAK For out of this world prices call WORLDWIDE CABLE 1 800-772-3233 FREE CATALOG AVAILABLE 7491 C-5 FEDERAL HWY . SUflE 142 BOCA RATON. FL 33487 MC/ OX) / VISA SALES ADVERTISING INDEX RADIO-ELECTRONICS does not assume any responsibility for errors that may appear in the index below. Free Information Number Page 108 AMC Salts 81 75 \ce i'nducts 27 107 All Eiecln>nics 92 171 A mt' ricii n Rel i ance Inc 14 84 AppHiince Service 27 — Business JNFOLINE 22 109 C fit S Sales .23 — CIE 8 1^ Cable Warehouse 74 54 Cfieinrronics ...29 — Command Productions. . . 7{> 127 Di!ctJ Indujilries 27 178 t:asylcch .89 179 Eleclninic (goldmine .94 — KIcctninics Book Club ..... 15, 7ft 121 Fluke ManufacturinE . . , CV2 187 Global SpedaUies 13 — Grantham College. ........... 69 180 Hewlett Packard 3 — tlii^hText Publications, Inc 81 — ISCET ....81 114 Jameco ... ,86 104 Jan Crystals , 16 115 Jensen To(jls 27 192 M&G Electronics 9Q 87 MCM Electronics 93 53 Ml> Electronics 88 181 MJS Design 27 — NHl Sclmols. .18 193 Northeast Electronics , . 74 183 Optoelectronics 7 101 Pomona Etectronics 17 191 Rite-Ofr ... 25 — Science Probe CV3 — Star Circuits . , 27 92,194 Teklnmix 5, CV4 123 Test Probes 22 182 The School of VCR Repair 72 Free Information Number Page 176 Unicorn .91 190 y.S. Cahte 64 184,185 Viejo l^jblications , . 16, 70 186 Wcalherport. .........84 195 World wide Cable. 94 189 Zentek Corp 64 ADVERTISING SALES OFFICE Gernsback Publications, Inc* 50O'B Bi County Blvd. Fnrmingdnle. NY 11735 1 (5163 293 3000 Presidenlr Larry Sleekier For Adverttstng ONLY 516 293-3000 Fax 1 516 293 3115 Larry Stockier publishor Chrifltlna Estrada assistant to the Rresident Artine Fishman odvertising director Denise Haven adverttsing assistant Kelly McQuado credit manager Subscriber Customer Service l-Q0O'2Q 8 0652 Order Entry for New Subscribers 1-e00-99&'7l39 7:00 AM . 6:00 PM M-F MST SALES OFFICES EAST/SOUTHEAST Stanley Levitan, Eastern Sales Manager ad io- Electronics 1 Overlook Ave. Great Neck. NY 11021 1.516-487^9357. 1-51 6-293-3000 Fax 1-516-487^402 MlDWESTH'exas/Arkansas/Okla. Ralph Bergen^ Midwest Sales Manager R ad jo- Electronics One Northfield Plaza. Suite 300 Northfietd, IL 60093-1214 1-708-446^1444 FaJt 1-708-559-0562 PACIFIC COAST/Meuntatn States iUIarvin Green, Pacific Sales Manager Radio-Eleclfontcs SA30 Van Nuys Blvd. Suite 316 Van Nuys. OA 91401 1-8ia-9Q6-20O1 Fax 1.810-966-2009 RE Shoipper Joe She re. National Representative P.O. Box 169 Idyllwild. CA 92549 1-714-659 9743 Fa* 1-714-659-2469 CIRCLE 195 ON F^EE INFORMATION CARD Science PROBE! — the only magazine devoted entirely to Amateur Scientists! If you are fascinated by sci- ence in ail its many forms . - . if you can't stay away from a microscope, tele- scope, calipers, or test tube — we in- vite you to share the wonders in every issue of Science PROBE! You will join a community of Amateur and Student Scientists who enthusiastically seek scientific knowledge or follow scientific pursuits for their own sakes and not merely as a profession. Obtain your next issue of Science PROBE! by visiting a quality News- stand, Convenience Store, or Super- market or by reserving your personal copy through the mail by completing the coupon below. From your very first issue of Science PROBE! you will be involved in a world of scientific facts, experiments, and studies pursued by amateur scientists who are university students, investors, academicians, engineers, or office workers, salesmen, farmers—whose quest is to probe into the mysteries of science and reveal them to atL Plan to become a Science PROBE! reader! Welcome to. . . ENCE The /Amateur Scientist's Journal Ennbark on an irresistible new journey into the realm of mystery^ challenge, and exploration! The perfect magazine for the budding scientist, the serious amateur, the professional who would like to relax, and those who simply want to gaze at the stars. Articles to appear in upcoming issues of Science PROBE! are: How an Amateur Mapped the Milky Way Make your own Seismometer Operate a Solar-powered Weather Station Grow Crystals Automatically Experiment with a Saltwater Aquarium How to Keep a Science Notebook If you're fascinated by science in all its many forms, if you are compelled to experiment and explore, then Science PROBE! is your kind of magazine! Science PROBE! 500-B Hi'Countv Boulevard Farmiiij^^dale, NY 11735 7RE25 Please forward my copy of Science PROBE! as soon as it comes o(Tthe press, I am enclosinft $3,50-U,S. A. ($4.2:J-Canada-includes G S T.) plus $1.00 for shipping and handling. B^^Uer still, please enroll me as a subscriber and send the next four f4) quarterly issues of Science Probe* I am enclosing $9,95- U.S.A. (Canada: $16.00— includes G.S/n [1 Next Issue Only □ Next Four Issues (1 Year) Offers valid in the U S, A, and Canada only. No foreign orders. Name ^ Address . City -State . All Orders payable in U,S,A. 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