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PRACTICA DECEMBE

ROBOTICS - MICROS - ELECTRONICS - INTERFACIAFG

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POWIRTRAN cybernetics lidPORTWAY INDUSTRIAL ESTATE, ANDOVER, HANTS SP10 3PE

ELECTRONICSVOLUME 20 No. 12 DECEMBER 1984

CONSTRUCTIONAL PROJECTS

CAR COMPUTER-Part 1 by S. H. Cousins BSc PhD and P. D. Wilson BEng . . 10Ignorance is an expensive bliss where motoring is concernedRING MODULATOR by John M. H. Becker

. . 23Part Two: Music Modulation-The effectsNICAD CHARGER by M. Tooley BA and D. Whitfield MA MSc CEng MIEE

. . 38Fully automatic charger with 24 charge rate optionsAUDIO NOISE GENERATOR by Tom Gaskell BA(l-ions) CEng MIEE .. 48Produces "white" and "pink" noise for testing audio systemsNEPTUNE AND MENTOR ROBOTS by Richard Becker and Tim Orr 52Part Four: The electro-mechanics and control electronics for Mentor

GENERAL FEATURESSEQUENTIAL LOGIC TECHNIQUES by M. Tooley BA and D. Whitfield MA MSc CEng MIEE . . 16Part Three: Latches, registers and countersVERNON TRENT AT LARGE 44SEMICONDUCTOR CIRCUITS by Tom Gaskell BA(Hons) CEng MIEE 46Digital Noise Source (MM5837N)

NEWS AND COMMENTEDITORIAL 7

NEWS AND MARKET PLACE 8Including Countdown and Points ArisingINDUSTRY NOTEBOOK by Nexus 14News and views on the electronics industryS PAC EWATC H by Dr. Patrick Moore O.B.E. . . . . . . 36Glorious Past --Bright Future; The Sun; Think Tank; The Sky This MonthPRINTED CIRCUIT BOARD SERVICE 37A new service for readersSPECIAL OFFER-PE QUASAR STEREO CASSETTE KIT 45INDEX FOR VOLUME 20 59Complete index for PE 1984

BUYER'S GUIDESOLDERING INSTRUMENTSWe look at a wide range of soldering equipment

OUR JANUARY 1985 ISSUE WILL BE ON SALE FRIDAY, DECEMBER 7th, 1984(for details of contents see page 50)

. . 30

© IPC Magazines Limited 1984. Copyright in all drawings, photographs and articles published in PRACTICALELECTRONICS is fully protected, and reproduction or imitations in whole or part are expressly forbidden. All reasonableprecautions are taken by PRACTICAL ELECTRONICS to ensure that the advice and data given to readers are reliable. Wecannot, however, guarantee it, and we cannot accept legal responsibility for it. Prices quoted are those current as we goto press.

Practical Electronics December 1984

WATFORD ELECTRONICS TRANSISTORS

33, CARDIFF ROAD, VVATFORD, HERTS 40D1 8ED, ENGLAND AC127/8 35AC141/1 35

EIC30813 15BC327/8 15

BFX79/84 135BFX84 35BFX85/86 3 5BFX87/88 28

TIP30C 37TIP31A 38TIP31C 45TIP324 43T1P32C 45T1P33A 70TIP33C 75TIP344 85TIP34C 105TIP35A 120T1P35C 130TIP364 130TIP36C 140TIP41A 50TIP4113 52TIP414 55TIP428 58011170 70010121 73110141 120011142 120TIP147 1201112955 701113055 7001543 5071544 45TIS884 50TI590 30TIS91/93 32VK 1010 99V510KM 70V5464F 951156641 110V6/884F 120VN89AF 120ZTX107/8 12ZTX109 12ZTX212 28ZTX300 13ZTX301/2 18Z7X303 2527X304 1727X320/26 30ZTX500/1 14ZTX502/3 18ZTX504 25ZT)(531 25ZTX550 2575696 3015697 2324398 4075699 48257064 252N708 25

25914/5 3225918 402N930 20251131/2 401N1303/4/5251307 702N1613 302N1671B 150252160 3282522194/204/214/224 252523694 18252646 452N2846 80252904A/05A/064/074 26252976G 10753053 25253054 55253055 50253442 140253615 1992N3663 20253702/3 10253704/5 10253706/7 10253706/9 10253710 10253771 1792N3777 196253773 210753819 35253820 60153821'3 602N3866 90253903/4 162N3906/5 15254037 60254058 15254061/2 15254264 30254286 25254289 25754400 25254427 80254859 782N5135 30255138 25255172 262N5180 45255191 752N5194 80255305 24155457 30

255458/9 3 0255485 36255777 45256027 32256109 60256290 70254636 250254671 250254715 75250495/6 852501061 2502501096 852$01162 45

31252501172.

2501306 1002501307 1502501449 9525C1679 1902501678 1402501923 652501945 2902501953 902501957 902SC1969 1852502028 852502029 2002502078 1702502091 852SC2166 1652502314 852502335 2002502465 1262502547 402502612 20025D234 752S 645 90206288 22525J83 2252SJ85 22535128 11535140 11540251 15040311 13040313 1 3040361/62 7040408 7640412 9040467 13040468 8540594 10540595 11040603 11040673 7040871/2 90

Tel. Watford (0923) 40588. Telex: 8956095 WAELECORDERS NORMALLY DESPATCHED BY RETURN OF POST

ALL DEVICES BRAND NEW. FULL SPEC. AND FULLY GUARANTEED. SEND CASH. P.O.' OR CHEQUEWITH ORDER. GOVERNMENT AND EDUCATIONAL INSTITUTIONS OFFICIAL ORDERS ACCEPTED(ACCESS ORDERS BY TELEPHONE 092 3-502 341. TRADE AND EXPORT INQUIRY WELCOME. P A PADD 70p TO ALLCASH ORDERS. OVERSEAS POSTAGE AT COST. PRICES SUBJECT TO CHANGE.

Export orders no VAT. U.K. customers please odd 15,4 VAT to total cost incl. p&p.VATWe stock thousands more items. It pays to visit us. We are sit d behind WatfordFootball G round Open Monday to Saturday, 9.00 arnto 6.00pm.Ampla FREE Car parking.

POLYESTER RADIAL LEAD CAPACITORS: 250V; 100, 200, 15n 22n, 27n Bp; 33n. 47n, 68n, 100n 86; 150n,220n 10p; 330n, 470n 15p; 680n 19p; 1 µ 23p; I t.t5 40p; 2 p2 46p.

AC176 35AC187/8 35AC188 35AD142 120AD149 79AD161/2 42AF118 95AF139 40AF239 558C107/8 1 2

BC10713 14BC1088 14BC108C 14BC109 1 2B01098 14

BC337/8 158C441 348C461 34BC477/8 40BC516/7 40BC547/8 12BC549C 15BC556/7 15BC558/9 15BCY41/47 30BCY10 TBBCY71/2 20BCY72 2 5BCY78 308D131/2 65

8FY50/51 30BFY52 30BFY53 35BFY55 35BFV56 35BFY64 40BFY90 80BRY39 50BSX20 308SX29 45BSY26 3 5BSY95 35BU105 180BU205 190130206 200

ELECTROLYTIC CAPACITORS Values in uFl 500V: 107AF 52p; 47 78p; 63V: 0 47. 1 0. 1 5. 2 2, 3 3. 8p; 4 79p; 10 10P; 15 21 12p; 33 16p; 47 12p; 68 16p; 100 19p; 220 26p; 1000 70p; 2200 99p; 50V: 68 20p; 100176; 220 24p; 40V: 6 8 15p; 21 9p; 33 12p; 330, 470 32p; 1000 45p; 2200 90p; 25V: 4 7. 10, 22, 47 86;100 11p; 150 12p; 220 156; 330 22p; 470 25p; 680, 1000 34p; 1500 42p; 2200 130p; 3300 76p; 470092p; 16V: 2 5. 40 8p; 47. 68 100 9p; 12512p; 22013p; 33016p; 470 20p; 680 34p; 100027p; 150031p;2200 36p; 4700 79p.

BC109C 1 4BC114/5 30BC117/8 2 5BC140 388C142/3 386C147/8 12801478 15

BD133 60BD135 4513 4060138/9D138/9

4080140 40BD158 88130245 65

BU208 200MJ2955 90MJE340 54MJE371 100MJE2955 99MJE3055 70MPF102 40

TAG -END TYPE: 64V: 4700 245p; 3300 198p: 2200139p; 13011: 3300 154p; 2200 110p; 40V: 4700 160p; 25V:4700 98p; 10.000 320p; 15,000 3450

POTENTIOMETERS: Carbon Track025W Log & Linear Values.5000, 1K & 26 ILIN ONLY) Single 35..

BC148C 10BC149 12BC149C 15BC153/4 30

130434 70B06954 15080696A 15081115 45

MPF103/4 30MPF105 30MPS405 30MPS406 25

TANTALUM BEAD CAPACITORS:35V: 01m, 0 22 0 33 156 0 47, 0 68, 1 0 1 5 168 2 2. 3 3 18p 4 7.6822p 1028p 113V: 22.3 a 1116 4 7.6 8, 10 18p 1536p 22

5101-2MII single gang .,8,...-

5101-2M0 single gang D/P switch 1311--pv

5101-2M11 dual gang stereo 990-

130157/8 14130159 111301674 14

131154/8 30Et 167 358E173 35

905408 30905412 32905455 30

6 100 75p.36p 33,47 506 100 956 220 100p 1011: 15,22 26p 33,4750 SLIDER POTENTIOMETERS

025W log and linear values 60mm track

BC168C 12BC169C 12BC171/2 12

BF177 3581178 358F179 40

MPS456 30MP5470 40MPSUO2 58

SILVER MICA (pf I SIEMENS mulitlayer miniature5611500611 Single gang 50P BC173 15

8C177/8 16131194/5 12ElF1913/9 18

MPSUO5 60MPSUO6 607. 3 3, 4 7, 6 8, 8 2, 10, 12, 18,

22, 27. 33, 39,47, 50. 56, 68, 7582 85, 100, 120, 150 180 1130.120 250. 270, 330, 360, 390,

capacitors.250V: mill, 1n5, 2n2, 3n3 407,6n8, 8n2,.10n. 15n, 22n 7p; 18n,27n, 33n. 47n 86; 39n, 56n, 68n

PRESET POTENTIOMETERS0 1W 50112 2M Mint Vert & Hon: Bp025W 22011497 Vert & Hon, 12p

80179/131 2080181 30BC182/3 10BC184 10

131200 3061274 40BF244A 28BF244B 29

MPSU52 65905055 60MPSU56 600023 170470 600 800 & 820pF 210

1000, 1200, 1800 30p each3300, 4700 60p each

9p, 100nF 11p.100V. 100n. 120n, 10p; 150n11p; 270n 13p; 330n 18p; 470n23p;680n30p;lpF346;2A2506.

RESISTORS Hi -stab, Mini , 5%Carbon.

RANGE Val.1 -% 1.-''' '0 25W 202 4 M7 024 3p in

BC182L 10BC183L 108C1841 108C186 7 28

E11245 50812568 508F257/8 3281259 40

0028/36 2200041/42 750070 400072 50

CERAMIC Capacitors: 50VRange 1pF to 6800pF 4p; 10415n, 33n, 47nF 5p; 100nF/30V 7p.

POLYSTYRENE Caps:10pF to 14 13p1 n5 to 12nF 10p

-

0540 2112 - 4 M7 E12 3p ic-P

1W 2112 - 10M E12 6p 61% Metal Film 5111-1M E24 89 6p

BC212/3 1 2130212 10BC213L 12130214 10

8E394131451

4 040

13E494/5 4013E594/5 30

0075/76 5 50076 500081/82 500083/84 70

RESISTORS S.LL Package: 7 Commoned, 10011. 6800. 16, 7K2. 467, 10K. 476, 1006 24p8 Commoned. (9 pins) 15011, 18011, 27011, 33011, 1K. 2K2. 41(7, 61(8 106. 22K, 47K, 10015 20p

8C214 12BC237 8 15BC307B 15

BER39/40 25BFR41/75 25BFR80/131 25

TIP294 32TIP29C 38TIP304 35

LINEAR IC's SA83271 485SA84209 595SG3402 295SL490 350SL924 00SL6270 150S5760135 350SN76033 350S576488 525SP0256AL 825147120 140TA7130 125TA7204 150TA7205 90747222 150TA7310 00144900 39514.4671 296149661 190TAA700 275TA0100 159T1341205 70189540 27571345500 33018A641 290184661 190TBA800 80TBA810S 95TBA820 80TBA9200 200106-900 350TCA270 350TC42804 220TCA-94° 175,T,CA95°,,,,, 00''''''' 180TDA10013 310TDA1010 235TDA1022 499TDA1024 1151091034 350TDA1054 00TDA1490 3507042002 3257042003 2501DA2004 300TDA2006 3307042020 3207042030 190TD80791 420TI-°61CP 4011°6201 8 5

,T1-264,,,C,N98

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u -s"." 761107405 150TL081CP 351108201 607103300 757108400 120TLO91CP 8011170 50T14300 9011-507 11011509 110UA2240 1200478540 230044170 180UA4180 180ULN2003 901/1-812004 90UL N2283 100ULN2803 190UPC556 00UPC575 275UPC1025H 375UPCI 156H 295UPC1181 00UPC1182 425UPC1366 195X82206 375X02707 400082211 575)32216 875082266 3802N414 80ZN419CE 180ZN423E 130ZN424E 130ZN425E .8 345

ZN426E-8 200254270-8 82025428E 450ZN429E-8 24525459 615ZN1034E 200ZN1040E 696ZNA234E 925

8214 4958216 2008224 3508226 3508228 2708243 6608250 £118253 7608255 9508256A £158257A 7008259 £78271 POA8272 £258279 7508282 4508283 4508284 5508288 £118748 £5587264 998127 1508131 35087955 9087975 909364AP 5509602 220AM261531C 125AM/61532A 125AM261.533 150AM7910 £3040.3-1015 300405-1013 300AY 5-1350 386AY -5-3603 750C04724 150C0M8017 275COM81 16 700DM8131 275DP8303 45000830485 350DS3647 00DS3691N 595DS8820 110DS8830 198058831 1251358832 25064[5668008815170 495093 80019365 E36101691 £15FD1771 £15101791 £22101793 £23101795 £28101797 £28HD26501 75HM6845 755196402 35015580605 1250MC1488 100MC1489 1009014411 875MC14412 725MC3242 590MC34,46 250MC3447P 315MC34136 175MC3487 175M63886 -2M £7MM5280D 895MM5303 835MM5307 1275M5153874 475MM58174 87580-3-25131 70090.3 25130 6505445050 875SFF963E4E 800SP0256412 495TCM3101J £1379527163 7251954047 100TMS416415 395TMS4416-2 5957954500 £12TMS4 532-3 350TMS5100 600TMS6011 500IM59914 895

TMS9927 £14TMS9928 £20TMS9929 E16TMS99/30 E20TMS9995 £12ULN2003 75UPD7002 725UPD7007 725WD1691 £14WD1770 £19.95WD2143 850280CPU 2 5 300280,ACPU4M375Z8OACTC 3352800 E1)Z800ART 496Z80ADART 820ZBOADMA 925Z8ODMA 795Z800 1 0 325Z1304P10 350180510.1 850Z804510 900Z804510 2 £9/8007CPU 00

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74196 14074197 12074198 24574199 25074221 12074246 13074247 13574248 17574249 17574251 10074159 10074265 8074173 21074276 15074278 18074279 10074283 12074284 35074285 35074290 12074293 10074297 175742% 20074351 21074365 9074366 9074367 9074368 9074376 17574390 12074393 14574490 150

LS83 751585 100LS136 40LS90 55LS91 100LS92 65LS93 601S95 80LS96 100LS107 50LS109 55LS112 55LS113 45LS114 45LS122 75LS123 120LS124 100LS125 56LS126 65LS132 75LS133 50LS135 28LS136 45LS138 70LS139 70LS145 120LS147 155LS148 150LS151 75LS153 75LS154 200LS155 75LS156 75[5157 70L5158 60LS160 751S161 7515162 75LS163 85LS164 95LS165 13015166 196L5168 140LS169 90L5170 175L5173 11015174 10040106LS175 80L5181 21015183 200L5190 10010191 7515192 100LS193 10015194 8015195 8015196 10015197 10015221 100LS240 100L5241 100LS242 100LS243 100LS4 100[524524

20015247 115L5248 115LS249 115LS251 80L5253 80L5256 17515257 75LS258 so1S259 1301S260 80LS261 19015266 60L5273 14015275 380L5279 75LS280 195LS283 951.5290 85LS292 850LS293 901S294 9991S295 140152% 110LS299 240LS320 230

L5322 360LS323 360LS324 ISOLS325 150LS326 290LS327 290L5347 130LS348 200LS352 12515353 125LS355 220LS356 220L5351 180[0365 60LS366 50LS367 75LS368 50LS373 110L5374 140LS375 80LS377 145LS378 120LS379 150L5380 310L5382 310LS384 457LS385 330LS386 5015390 90LS393 120LS395 135LS396 300153% 195[5399 150[5445 1251.5447 8015465 ISO[5467 120LS490 160LS 540 145LS541 145[5624 150LS629 150L5640 200LS641 20015645 200

90[5669 90LS670 190[5673 890L5674 00LS682 250

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555 CMOS 106702 757090 8 pin 35710 48741 16747C 14 pin 7074808 pin 30753 8 pin 185810 15994111fj 375ACC0808 885AY -1-1320 22590-1-5050 99AY -1.5051 16090-1-6720 210AY -3-1270 730AY -3-8910 390AY -3-8912 600A1,513174 630CA3011 130CA3012 175C83314 275CA3018 86CA3019 90CA3020 210CA3023 210CA3028A 130CA3035 255CA3036 270CA3043 275CA3045CA3046 7008.3048 220C83059 32504.3375 213CA3013DE 75CA3081CA3885 160043086 800430891 20004309040 375CA3123 185CA3130 90083140 50CA3160 95043161E 199CA3162 525083189 275CA3240 1104141366 176HA1388 235ICL7106 690ICL7107 975ICL761 I 99ICL7660 24.8ICI RAWL: 3606:1.8211 3501097205 1160)CM7207 4751CM7215 105010972164 £22ICM72174 7501097224 785ICM7240 300ICM7555 105IC547556 1501A3350 250LA40311 340LA4032 295LA4400 350LA4422 320107170 3001C7130 320LC7137 350LF347 15011351 70LF353 90LF355 95LF356 99LF357 11011398 4951M10 325LM3014 351M307 45151308 9519311 6519318 150LM319 195

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N914N916N4001/1N4003N4004/5144006/7144148N5401115404NI3406N5408S445921

64/100V6A/400V6A/800V

405065

BRIDGERECTIFIERSpiestir dS..14/50V 1814/100V14/400V14/600V24/50V74/200V2A/400V24/600V6A/100V6A/600V104/200V104/600V254/200V254/600VBY164VM18

2025343040486583

125215298240395

5650

2ENERSRange 7V7 to39V 400mW

8p eachRange 3V3 to33V 1 3W

15p each

OPTOLEDS price includes Clips

TIL209 Red 3mm 10TIL211 Green 3mm 14T0212 Yellow 14T1L220 2" Red 120 Tel, Grn, Amber 14Rectangular LEDs withtwo pad clip R, G & V 45Rectangl StackableLEDS 18Triangular LEDs R&G 1807 Flashing LED Red 5602' Eli colour LEDsRed/Green 100Green/Yellow 8002' Tr! colour LEDsRed/Green/Yellow 8502' Red High Bright 59High Bright Green orYellow 100LD271 Infra Red (emit/ 48T1L32 Inha Red (emit) 52SFI-1205 (detector) 118711.78 (detector) 55TIL38 50TIL81 82 T1L100 90

0.5" LCDDISPLAYS3) digit 4954 digit 5306 drip! 625

OPTO8P025 250BPVV21 320BPX65 3201074 1450074 275ILCT6 Darlrngto,Isolator 135TIL111 70OCP71 120ORP12 782N5777 504N33 135Po diode 720SchmittReceiver 716

VARICAPSMVAM2 16584107 30BB1058 4088106 40

7 Segment DisplaysT1321 5"CAn 140T1L322 5" C th 140DL704 3" C Cth 125DL707 3' C Anod 125END357 or 500 1303 Green C A 140 1 3" Red or Green 150Bargraph 10 sag Red 275Bargraph NSM3914 500

OPTOSWITCHReflectiveTIL139 225Slotted similarto RS 186

VOLTAGE REGULATORS14 701213 Plastic Casing

ve -ve5V 7805 46p 7905

12V 78'2 45p 793615V 7815 45p 791218V 7818 45p 791524V 7824 46p 7918100mA T092 Plastic Casing

5V 78L05 30p 791056V 78162 30pBV 78181 30p

I /V 78111 30p15V 78115 30p

55p56p55p55p55p

50p

79112 50p791.15 50p

1CL7660 248 LM31 7K781105 5V/5A 560 LM317P78H17 12V/54 640 LM323K/8NG 5 to LM337T 24V 5A 599 LM7237961G 2.25V to 18462513-14V 54 685 RC4194

LM309K 120 RC4195

25099

5001753075

375160

DILSOCKETS ..

r -r pit Op 25p14 pro 10p 35p16 pin 10p 42p18 Din 16p 52p20 pm 20p 60p21 pin 22p 65p24 pm 25p 70p28 pm 28p 80p40 pin 30p 99p

ZIF DIL SOCKET24 way 575p28 way 695p40 way 845p

SPECTRUM32K UPGRADE

Upgrade your 16K Spectrum to full48K with our RAM Upgrade Kit. Verysimple to fit. Fitting instructionssupplied. ONLY £22

SCR'sThyristors08A -100V 3254/300V 3854/400V 4054/600V 4884/300V 6084/600V 96124/100V 78124/400V 95114/800V 188BT106 150BT116 180C106D 38TIC44 24T1C45 29TIC47 357145061 387144444 130

MACST2

TRIACS34/100V 4834/400V 5634/800V 8584/100V 6084/400V 6984/800V 115124/100V 78124/400V 82124/800V 135164/100V 10316A/4005 105164/8005 220254/400V 185254/800V 295754/100(0

480304/400V 525728000 125

FERRIC CHLORIDEstais 1lb

195p 50P P&P

DALO ETCH RESISTPen plus spare tip 100p

ALUM.BOXES4.2167 1004.21x21 103404021' 12050407 1055x21kIr 905021x21' 1305k4k ir 995x4x2r 12060407 1206.4.3" 1507x5x3" ISO80603- 2101004103" 240100703" 275120503 260110807 296

SWITCHESSLIDE 250VIA DPDT 1414 DPDT C OFF 15t4 DP nn on on 40

PUSH BUTTONSpring loadedLatching orMomentary 6ASPDT c/over 150DPDT crave, 200

MINIATURENon LockingPush to make 15pPush break 25p

TOGGLE 2A 250VSPST 35DPDT 484 pole Ire, otl 54

SUB -MINTOGGLE 2 sawSP changeover 84SPST on off 58SPDT c/off 85SPOT Biased 105DPDT 6 tags 80DPDT C/OFF 88DPDT onion/on 185DPDT Biased 1454 -pole 2 way 220

DIL PLUGS (Headers)Pons Solder IDC14 38p 95p15 42p 100p24 88p 138p78 185p 290p

195p 218p

RIBBON CABLEIpoce per foot)

Ways Grey Colourr 15p 28p

16 25p 40p20 30p 50p26 40p 65p34 60p 85p40 70p 90p

1013p 135p

IDC CONNECTORS ,Speed block typedPCB Male Femalewith latch Header Car,

2 rows Strt Angle Socket Corr, .

Pins Pr,10 way 90p 99p 85p 120p16 way 130p 150p 110p 195p20 way 145p 166p 125p 240p26 way 175p 200p 150p 320p34 way 205p 236p 169p 340p40 way 220p 250p 190p 420p50 way 235p 270p 200p 470p

EUROCONNECTORSGold flashed contactsDIN 41612 2.32 wayDIN 41612 23 .32 wayDIN 41612 3 32 way

FEMALE MALESOCKETS PLUGSStd Angle Stn Angie275p 2.20p 285p295p 240p 300p360p 385p 260p 395p

COPPER CLAD BOARDSFibre Single- DoubleGlass sided sided

100p 125p6" 12" 175p 225p

SRBP9 5 .8 5

110p

ROTARY: (Adjustable Stop Typo)1 pole/2 to 12 way. 2p/2 to 6 way, 3 pole/2 to 4 way. 4 pole/2 to 3 way 48p

ROTARY: Mains 250V AC, 4 Amp 64p

SOLDERCONPINS

75p25 370p

VEROSOARDS 01"Clad Plain

21.31" 95 -21.5' 110 -31031" 110

125 96p31 x17" 420 276p41,18" 590 -Pkt of 100 pins 55pSpot Face Cutter 150pPer. Insertion Tool 185p

'VCE Board'DIP' BoardVero Strip

PROTO-DECsVeroblockS DecEurobreadboardBimboard 1Superstrrp SS2

180395144

480395590695£13

DIP SWITCHES: ISPST r 4 way 65p,6 way 80p; 8 way 87p; 10 way 100p,I SPOT 4 0, 190p.

AMPHENOL CONNECTORSIDC Solder

24 way IEEE 475p 470p36 way Centonix 525p 475p14 way Female 490p 450p

'D' CONNECTORS.Pins 9 15 25

way Wir/ way

MALESolder 80p 110p 160pAngle 150p 210p 250pStrad 170p 160p 220p

FEMALESolder 105p 160p 200pAngle 165p 215p 290pSnail 1 75p 200p 300p

COVERS 80p 75p 75p

37way

240p355p310p

338p440p420p

90p

IDC way Ply 385p, St 450p

ASTEC UHF MODULATORS6MHz Standa,8MHz Widebel,'

375p550p

VERO WIRING PEN and Spool 380pSpare Wire iSpooll 75p; Combs 6p eaWilt. VV1,10,,Iflq Slakes 100 250p

ANTE X Soldering IronsC15W 535p Spare bitsG517W 545p Elements018W 550p Iron stand0015W 560p Heat Shunt

90p280p180p

35p

SILSocketsUI20 way66p31 way95p

1 18 wry2 .22 way2 +23 way1r. 25 way2.28 way2.3C way2.36 way2 040 way2.43 wav7.75 way

TRANSFORMERS imams Prim 220240V13. t 62 100014, 9-09V 75014.

12 0 12V 15014, 150. 15V 75rnA 98p6VA: 1x6V 54, /x9V 4A. 2x12V-0 34,215V 25A 250p12VA: 1x4V5-1 34, 2k6V 1 2A, 7,12V 54.,I5V 44 345p I35p P&p)

24VA: 6V-1 54 6V-1 54. 9V-1 2A 9V 1 2A1 2V1A 12V 14, 15- 84 15- 84. 10V 6A20V 6A 385p i6Op p&p)SOVA: 1 6V-44, 2 9V2 54. 2 12V-24 2 15V' 54. 2 20V-1 2A, 1. 250-24. 2 30V-0 84

520p 160p p&p100VA: 2 171744. 2 15V 3A. 1 20V 5A2 30V -15A. 2 40V 125A, 2 50V to

965p 1609 P&P

215p

28553

JUMPER LEADS Ribbon Cable AssemblyDIE Plug iHeaders1Singly Ended Lead 74 long

EDGE

17'

ORS Length 14pin 16pin 74 pin 40 pro

210p

175p

74" 1459 165p 240p 328pDouble Ended Leads

24"36'

6"

210p 235p 345p 540p230p 250p 375p 595p

185p 205p 300p 465p198p 215p 315p 490p

310p360p IDC FEMALE RECEPTACLE Jumper Leads 36380p 20pin 76, 34prn 4

450p 1 end 160p 200p 260p 300p650p 2 ,,(1., 2909 370p 480p 525p

COMPUTER CORNER EPSON RX80 Printer £229

EPSON RX80 F/T Printer £245

EPSON FX80 Printer £318 EPSON FX100 Printer £435

SEIKOSHA GP100A £125

KAGA/TAXAN KP810 Printer £235

KAGA/TAXAN KP910 Printer £435

QUEN-DATA DPW1120 Daisywheel £175

BROTHER HR15 Daisywheel Printer £339

Centronics PRINTER CABLE for all the aboveprinters to interface with the BBC Micro £7

KAGA - RGB 12 inch medium resolution colourmonitors £195

ZENITH 12" Hi-RES, Green Monitor 40/80column select switch, value for money. £75

MICROVITEC 14" colour monitor. RGB input.Lead incl. £173

MICROVITEC 1451 Hi-res 14" Monitor incl.Lead £295

TEX EPROM ERASER. Erases up to 32 ICs in15-30 min £30

Spare UV lamp bulbs £8

C12 COMPUTER Grade BASF Cassettes inLibrary Cases 36p

81" or 91" Fan fold paper (1000 sheets) £711500

Teleprinter Rotl (no VAT) £4

MANY MORE PRINTERS, MONITORS, INTERFACES,AVAILABLE. CALL IN AT OUR SHOP FOR DEMON-STRATION OR WRITE IN FOR OUR DESCRIPTIVE

LEAFLET.

(P&P on some of the above items is extra)Call in at our shop for demonstration of any of theabove items. Be satisfied before you buy.

Plastic LibraryDISC STORAGE

CASESHolds ten 5;" Diskettes £2

DISC ALBUMSAttractively finished in beigeleather -vinyl, these convenient-ly store up to 20 discs. Each disccan easily be seen through theclear view pockets.

ONLY £4.25

5;" Disc DriveHEAD CLEANING KIT

£14

SPECTRUMCENTRONICS/RS232PRINTER INTERFACE

* It was the first!It is still the best!

* Centronics and BI-DIRECTIONALRS -232 with full hand -shaking

* Obeys SPECTRUM LUST andLPRINT.

* Split -Speed Operation for RS -232.(Use it to communicate withthe BBC MICRO or OTHERPERIPHERALS)

* Interface 1, Interface 2 & Microdrivecompatible.

* Configuration program createscustomised M/C driver to suit yourprinter

* HI-RES screen cumps in 2 sizesOn EPSON, SEIKOSHA.STAR. SHINWA. MANNESMANTALLY, NEC, RITEMAN, KAGA.etc. This is a STANDARDFEATURE! Not an extra.

* Compatible with TASWORD TWOand most professional programs.

Price: £29.95 (Carr.Celtronics Cable £8

CRYSTALS32 768KHz 100100KHz20CIKH,455KHz1MHz1 008M1 28MHz1 5MHz1 6MHz1 8MHz1 8432M2 OMHz24576M2 5MHz2 56750M31768M3 57954M3 6864M40MHz4 032MH:4 194304104 433619M4 608MH:4 80MHz5 OMHz5 185MH:5 24288M60MHz6 144MHz6 5536MHz7 OMHz7 168MHz7 68MHz8 OMHz8 08333518 867237M9 00MHz9 375MI010 until:10 5MHz10 7MHz10 24MHz12 OMHz12 528MHz14 318185114 74565114 765MHz15 OMHz16 OMHz18 OMHz18432M19 968MHz20 OMHz/4 OMHz24 930MHz29 695M dr26 670MHz27 125MHz27 145M27 648MHz38 66667M48 OMHz55 5MHz100MHz116 OMEtz145 8MEtz

545370370275275450420595545250225200225220150

98300150290200100200200160300390140150200150250200150

17:200350175250150200175300170175250240220180150150265170325ISO325295190300240240400295300225

BBC MICROCOMPUTERSPECIAL OFFER THIS MONTH ONLY £315We stock the full range of BBC Micro peripherals, Hard-ware & Software like, Disc Drives (Top quality Cumana &Mitsubishi), D skettes, Printers, Printer Paper, InterfaceCable, Dust Covers, Cassette Recorder & Cassettes, Mon-itors, Connectors (Ready made Cables, Plugs & Sockets),Plotter (Graphic Tablet) EPROM Programmer, LightpenKit, Jcysticks, Sideways ROM Board, EPROM Eraser,Machinecode ROM, The highly sophisticated Watford's16K BEEB DFS, WORDWISE, BEEBCALC, Software (Edu-cational Application & Games), BOOKS, etc. etc. Pleasesend SAE for our descriptive leaflet.

DISC DRIVES FOR BBC MICRO CS100 - TEAC Cased with own Power Sup-

ply, S/S, 40 track, 51", 100K £129 CD200 - TEAC Twin Cased with own PSU,

S/S, 40 track, 51", 200K £265 CS200 - TEAC Single Cased with own PSU,

S/S, 80 track, 51", 200K £175 CD400 - TEAC Twin Cased with own PSU,

S/S, 80 track, 51,", 400K £349 MITSUBISHI 51," Slim line Disc Drives double

sited, double density, track density 96 TPI,track to track access time 3msec.

SINGLE MITSUBISHI Slim line - Cased withown

nIPSU, DS/DD, 1 Megabytes (400K with

EC £199 TWIN MITSUBISHI Slim line - Cased with

own) PSU, DS/DD, 2 Megabytes (800K with£395

511" Disketies (Life Time Warranty) 10 3M Diskettes S/S D/D £14 10 3M Diskettes D/S D/D £24

Many more types available.F lease send SAE for our detailed leaflet.

N. B Carriage is extra on drives.

WATFORD ELECTRONICSTel. (0923) 40588 Telex. 895609

Cirkit stock all thecomponents, accessoriesand tools and the kitsyou're looking for.

Designed andselected to offer the bestpossible standards at thebest possible price.

Cirkit's always wellstocked.

As soon as newproducts are available,Cirkit has them.

When it comes to kits,Cirkit's got the lot. At theprice you want to pay.

Just send for ourcatalogue or visit one ofour three outlets at:200 North Service Road,Brentwood, Essex. CM14 4SG;53 Burrfields Road,Portsmouth, Hampshire. P035EB; Park Lane, Broxbourne,Hertfordshire. EN10 7NQ.

Please add 15% VAT to all advertisedprices and 60p post and packing.Minimum order value please.We reserve the right to vary prices inaccordance with market fluctuation.

///- Niir eor 1Y

p (4) I;r7d

Cirkit Making itCkKsCIRKIT ELECTRONICS TOOL KITContains: 15W Soldering Iron 2 sparebits, heat shunt, solder, pliers, cutters,and screwdriver 40-00007 15.56

AUDIO FUNCTION GENERATORVersatile waveform generator withsine, triangular and square wave outputs.On board mains PSU 41-01302 27.00STEREO 40W AMPLIFIERSingle board 40W per channel stereoamplifier 41-01301 38.00

STEREO VU METER5 LED per channel stereo VU meter foruse with stereo amplifiers 41-01401 11.50

5W AUDIO AMPA very compact audio output stage for usein a wide range of equipment 41-0140.3 4.60

UNIVERSAL AMPA universal audio pre -amp with again of 10

MONO REVERBERATION UNITSingle channel, spring line reverb unit to add echoeffects to tape recording etc. 41-01602 10.00

TONE GENERATOR AND DETECTORVery low distortion tone generator and sign aldetector for circuit fault finding10MHz DFM 41-01603 10.45

8 Digit LED digital frequency meterand period measurement 41-01500 54.10

50MHz PRESCALERExtend the range of the 10MHz DFMto 50MHz 41-01501 8.55

1-5MHz PRE AMPLow frequency pre -amp and waveformshaper for the 10MHz DFM 41-01502 5.13

1-30V I mA-2A PSUAdjustable 1-30V Power supply with pre-setablecurrent limit from I mA-2A 41-01600 37.46

To: Cirkit Holdings PLC, Park Lane, Broxbourne, Hertfordshire. ENIO 7NQ.I enclose 85p. Please send me your latest catalogue and 3 x SI discount vouchers!If you have any enquiries please telephone us on Hoddesdon (0992) 444111.

41-01604 6.45

Name

Centronics

Address

Area of Special Interest

PE1 2

Telephone

CirkitBigger Stock. Better Service.

/if

1 43*444114

5-12V IA PSUAdjustable PSU from 5-12V with currentprotection, I amp max output 41-01504 6.45

I -30V I .5A PSU1-30 volt adjustable PSU with protectedoutput up to 1.5 Amps 41-01402 10.45

3 DIGIT LED DVMDVM to read up to 99.9 volts or configured as anammeter to read up to 9.99 amps 41-01403 17.00

INFRA RED LINKSingle channel IR Linkwith relay outputTEMPERATURE SENSORThermistor based temperature sensorwith relay output 41-01303 6.20

LOCOMOTIVE SOUND GENERATORRealistic steam sound and whistle formodel railways 41-01304 920

LAMP DIMMERControl lamps and drill speed 41-01305 5.70

WATER LEVEL ALARMAlarm to indicate high water level orflooding 41-01601 2.70

3 NOTE CHIMEDoorbell chime with adjustabletones 41-01503 7.00

2M PRE AMPMiniature low -noise MOSFET pre -ampfor the 2m amateur band 41-01307 3.91

2M CONVERTERLow noise 144MHz-28MHz amateurband converter 41-01306 17.35

2M POWER AMP20W - 10dB gain - power amplifier for the2m band. Automatic TX switch over, RXpre -amp, robust construction 41-01404 32.87

70cIn PRE AMPLow noise, miniature pre -amp for the70cm amateur band 41-01506 4.78

70cm CONVERTER70cm to 144MHz low noise converterfeaturing pre -aligned helical filter,schottky diode mixer and low noisetransistors 41-01405 21.50

70cm PAIOW Power amp to boost the output ofhandheld and portable 70cmtransceivers 41-01505 33.82

CRYSTAL CALIBRATORCrystal reference calibrator for alignmentof receivers, outputs at 4, 2, 1MHZ,100, 50 AND 10KHz 41-00801 4.32

CB NOISE SQUELCHImproves to mute performance of themajority of CB rigs 41-01605 5.40

CENTRONICS INTERFACEConnect your personal computer tothe outside world via the Centronicsprinter output 41-01406 22.50

p &IF

10MIlz DFM

41-01300 9.60

a or // // 4. r

/16f AP

and better.Nicad Batteries & ChargersHigh quality nickel cadmium rechargeablebatteries. Equivalent in size with popular DryCell sizes e.g. HP7 (AA), HP11 (C), and HP2 (D).Minimum life 600 (300 PP3 size) fullcharge/discharge cycles. Batteries must becharged from a constant current source only.All batteries are supplied only with a residualcharge and should be charged before used.

DATA & PRICESTypeAAC

D

PP3

V(nom) Capacity Stock No. 1-9

12V 500mAH 01-12004 0.8012V 12AH 01-12024 2.3512V 12AH 01-12044 2.008.4V 110mAH ()I-84054 3.70

10-490.741.992.003.50

CH/4/50To recharge up to 4 AA size NiCads.Size; 112 x 71 x 37mm 01-00409 4.95

CH1/22To charge PP3 type NiCads.Size; 70 x 50 x 32mm 01-00159 4.30

CH8/RX

Will recharge AA, C, D and PP3 size cells with auto-matic voltage selection. Will recharge followingcombinations: 4xD, 4xAA, 4xC, 2xPP3, 2xD + 2xC,2xD + 2)(AA. 2xD + 1xPP3, 2xC + 2icAA, 2xC +1xPP3, 2xAA + 1xPP3. Charge rate: IlmA for PP3,45mA for AA size, 120mA for C and D size, for 16hrs. Power: 240V 50Hz. Output Voltage: 2.9V for AA,C and D size, 11.0V for PP3 size. Weight: 0.475kg.Size: 199 x 109 x 55mm.

01-02204 9.45

HT320High quality, high specification meter at areasonable price. In addition to the usual ranges,facilities are provided for measuring transistorparameters such as Iced and Hfe.Meter movement fully protected against overloads.3 -colour mirrored scale in robust case. Suppliedcomplete with comprehensive instructions, testleads, transistor test leads and batteries (2 x HP -7,1 x PP3).DC Volts: 0.1V, 0.5V, 2.5V, 10V, 50V, 250V, lkV(20kON). AC Volts: 10V, 50V, 250V, I kV (18kf icV).DC current: 50µA, 2.5mA, 25mA, 250mA.Resistance: 2k, 20k, 2M, 20Mz. AF Output: -10dB to+22dB for 10VAC (OdB/0.775V, soon). Leakage(Iceo)15µA, 15mA, 150mA. Hle: 0-1000 (Lc/Tb).Weight: 410gms. 56-83201 14.00

/

RF Generator LSG17A stable wide -range generator for the hobbyist,service technician schools, colleges, etc.Frequency range: A/100kHz-3001cHz, B/300kHz to1MHz (Harmonics 96-450MHz) C/1MHz-3.5MHz,D/3.0MHz-11MHz, E/10MHz-35MHz,F 32MHz-150MHz. Accuracy: k1.5%. Output greaterthan 100mV (no load). Ext. xtal osc for 1 to 15MHzcrytal. Power required: AC100, 115 or 230V 3VA.Size & Weight: 150(H) x 238(W) x 130(D)mm, 2.5Kgapprox.

56-90017 115.00

WNW*At

4.1*fp loggIAS

Linear ICs Stock No. PriceLF35I Bi-FET op amp 61-03510 0.49

LF353 Dual version of LF351 61-03530 0.81

LM380N 1W AF power amp 61-00380 1.45

LM381 Stereo pre -amp IC 61-00381 3.27

NE.544 14 pin D.L servo driver IC 61-00544 1.80

NE555N Multi -purpose low

cost finer 61-05550 0.21

uA741CN DIL low cost op -amp 61-07411 0.42

TDA1062 RF ocillator and mixersystem for 1-200MHz 61-01962

TDA1083 Portable radio AM/FMaudio in one IC 61-01983 1.95

HA1388 18W PA from I4V 61-01388 2.75

MC1496P Double balanced mixer/modulator 61-01496 125

TDA2002 8W into 2 ohmspower amp 61-02002 1.25

ULN2283 1W max 3- I 2V

power amp 61-02283 1.00

CA3089 FM IF anp, detector,mute, AFC, AGC system 61-03089 2.84

CA3130E BIMOS op amp 61-31300 0.80

CA3140E BIMOS rersion of 741 61-31400 0.46

MC3359 Low cuirent dual conver-sion NI3FM IF and des 61-03859 2.95

LM3900 Quad norton amp 61-39000 120

LM3909N 8 -pin DIL LED flasher 61-39090 0.68

KB4412 Two ba anced mixers IF amp

with A:1C for AMSSB 61-04412 1.95

ICM7555 Low power CMOS versionof 55 timer 61-75550 0.98

HA11225 Low nose FM IF 61-11225 1.45

HA12017 83dB S/N phono preamp

0.00144 THD 61-12017 0.80

MC14412 300 baud MODEM controller(Euro/US specs) 61-14412 6.85

lir

1.95

Selected LinesPB2720 80dB Piezo Buzzer 43-27201 05510M15A :0.7 Filter 20-10152 2.10I OMO8AA :0.695 Filter 20-11152 3.49FC I 77 LCD Freq. Meter 39-17700 20.00CM161 Min LCD Clock 40-80161 825BBC to Centronics Cable 03-10019 725Dragon to Centronics Connect Cable 03-10017 725C12 Computer Cassete Tape 21-00012 0.558 x 03" IC socket 28-00800 0.1214 x 03" SC socket 28-14000 0.1316 x 03" socket 28-16000 0.136V KUIT-A Relay 46-80000 0.489V KUIT-A Relay 46-80001 0.48I2V KUTT-A Relay 46-80002 0.48CXI20P COAX Relay 46-90120 11.96CX520D COAX Relay 46-90520 26.98CX540D COAX Relay (BNC) 46-90540 26.98

BooksBeginners aide to Amateur Radio 02-11262 4.50Beginners Guide to Electronics 02-04134 4.50Active Filter Cookbook 02-21168 12.70CMOS Cookbook 02-21398 11.85TTL Cookbook 02-10358 11.00Design of Active Filters 02-21539 10.15Design of Op -amp Circuits with

experiments 02-21537 9.30Effectively Using the Oscilloscope 02-21794 9.30The ZX Spectrum 02-00100 5.95Practical Design of Digital Circuits 02-11831 10.45Electronic Projects for HomeSecurity 02-05351 3.80

Electronic Telephone Projects 02-21618 7.6055 Timer Applications Sourcebook 02-21538 6.40Television Engineers Pocket Book

7th Ed 02-21313 8.50Electronics Pocket Book 02-21309 75099 Practical Electronic Projects 02-21635 5.90More Electronic Projects in the

Home 02-21307 3.80The Radio Amateurs Question and

Answer Reference Manual 02-02157 5.95Basic Programming on the BBCMicrocomputer 02-06640 5.95

Using Microprocessors andMicrocomputers:The 6800 Family 02-98728 11.05

Z-80 Microcomputer DesignProjects 02-21682 12.70

Z8000 Microprocessor:A Design Handbook 02-37345 16.10

68000: Principles andProgramming 02-21853 12.70

8085A Cookbook 02-21697 1355Handbook of Electronic TablesFormulas 02-21532 11.00

Popular Circuits: ReadyReference 02-04585 13.95

Semiconductor Data Book11th Edition 02-04797 9.00

r

ELECTRONIC SIRENKIT

Produces an extremely loud piercing sweptfrequency tone from a 9 15V supply Enableinput for easy connection to alarm circuitsIncludes 5in Horn Speaker

E7.90

Mkd SkeetAs above, but with a small speaker (insteadof horn speaker) for internal use E4.30

SECURITY PRODUCTS

Protect your homeand property andsave by buildingyour own burglaralarm system

Stair Mat 23 . 7 in 1950 1201 E7.70Floor Mat 29 161111950 1251 E2 60Tamper .proof connecting block(950 1101 E0.30Door/Window Contacts. Flushmounting 4 wire, Magnet switchPer Pair 1950 1401 £1.05Window Tape 0 5" wide 50m1950 1451 E2.50Window Tape TerminationsPer pair 1950 150) 10.36Key operated Switch 1 5A 250VSP5I Heavy chrome metal(3501281 14 50Passive Infra -Red DetectorDetects intruder's body heat Range10 metres 12V DC, no & n'c contactSize 4 . 2 . 2 ins 1950 1351 E45.00Alarm Control Unit. 4 input circuits 2instant and 2 delayed Adjustable entry,exit and alarm times Built and tested Fullinstructions supplied Size 180 13030mm Supply 12V DC1950 1601 126.00Ultrasonic Burglar Alarm. Self-containedmains or battery powered unit completewith horn and AC adaptor

(45.00r p&p 12 208W Horn Speaker. 5 5 ins 8 ohm idealfor sirens. etc 2 5m lead and 3 5mm jackplug 1403148i E6 15

IR GARAGE DOORCONTROLLER KIT

For controlling motorised garage doorsand switchinggarage and drivelights on off up toa range of 40 f t

Lots of applecations likecontrolling lightsand TVs.etc. in the home Ideal for aged or disabled persons. this coded kit comprises ofa mains powered infra red receiver with anormally open relay output plus twolatched transistor outputs. batterypowered transmitter and opto isolatedsolid state mains switch

X1(103XK105 Extra transmitters 110.50

PANTEC KITS

TOP QUALITY . . . TOP SERVICEBOTTOM PRICES!

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P142 FM Micro Transmitter 17 50PI143 Stabilised Power Supply £13.70PN5 2 lOw Stereo Amplifier 114.50PN8 2 40w Stereo Amplifier 12496P1117 Pushbutton Stereo Preamp £12.80PNEI Tone & Volume Control 113.60PI1111 3w FM Transmitter 111 95P1813 Single Channel FM

Transmitter 1980PN14 Receiver for above 115 50

Tit

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DOOR/0111Zgimummk

3 -NOTE DOORCHIMEBasomed on SAB0600

IC the kit includesallcponents, loudspeaker.

PCB. predrilled box (95 . 71 , 35mm1instructions

Requires a 9V batteryand full

andpushswitch. IDEALPROJECT FORGINNERS.

BE -Order as XK 102E5. 50

DIGITAL MULTIMETER19 ranges including dc current to10A resistance to 20M, ac & dcvolts and npn pnp transistor gain

Full overload protection Comeswith test leads, battery and

case Size 175 93 42mm14052041 132.00

STOCKING FILLERS All full spec branded devices

PACK 111 650 Resistors 47 ohm to 10Mohm - 10 per value 14.00PACK (2) 40 x 16V Electrolytic Capacitors 100F to 10000E 13.25PACK 131 60 Polyester Capacitors 0.01 to 1,,F,250V - 5 per value 15.55PACK 141 45 Sub -miniature Presets 100 ohm to 1 Mohm - 5 per value 12.90PACK 15) 30 Low Profile IC Sockets 8. 14. and 16 pin - 10 of each 12.40PACK 161 25 Red LEDs 15mm dial 11.50

These kits are designed to enable infrared remote control to be incorporated intovirtually any application from switchingcar locks or alarms to controlling Hi Fr orTV The application will determine theinterface circuitry between the receiverand the controlled device General in.structions and applications are suppliedThe kits are coded and provide a highdecree of security and noise immunityMK 18 Transmitter Kit for use withMK 11/MK 12 receivers Requires PP3 battery Size 8. 2 13crns Range approx.60 ft 16.130Keyboards for MK 18MK9 4 -way for use with MK 12 El .90MK 10 16 -way for use with MK 12 E5.40MK 13 11 way for use with MK 11 E4.35MK 11 Receiver Kit - mains poweredProvides 10 latched plus 3 analogue outputs ideal for controlling audio amplifiers.TV or lighting where control of lightbrightness is required E13.50MK14 AC Power Controller Kit for(phase) controlling AC loads from MK 11analogue outputs. eg lamp dimming

15 20

MK19 Stereo Amplifier Controller Kitfor remote control of bass, treble andvolume (or balance) by MK II Includes a one of10decoder remote channel or input selection.May be connected between the pre amp andpower amp of almost any audio system.

E10.70

MK12 Receiver Kit mains poweredwith 16 latched or momentary outputsLatched version is for applications requiring one output on at a time. eg TVchannel selection Momentary type givesan output only during transmission Linesmay be latched as requiredSize 9 4. 2crns E 1 3 50

MK 15 Dual Latched Solid State Relay --

for switching mains loads such as lamps.TVs, etc. from the outputs of the MK 12Imomentaryl 15 items may be switchedindependently using 8 MK 15s Triacs Inotsuppliedl switch at mains zero to reduceinterference 14.50

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CT 6000K

XK 114. Relay Kit for CT 6000includes PCB. connectors andone relay Will accept up to 4relays 3A 240V c'o contacts

701 115 Additional Relays

ELECTRONIC LOCK KITWith hundreds of uses indoors, garages.car anti theft devices, electronic equip-ment, etc Only the correct easilychanged four digit code will open iti Requires a 5-15V DC supply Output750mA Fits into standard electrical wallboxComplete kit lexcept front panel)XK101 E11.50Electric Lock Mechanism for use withexisting door locks and the above kiti Requires relay.) 12V AC/DC coil1701 1501 E14.95

HOME LIGHTING KITSThese kits aredesigned toreplace a standard wall switchto control up to300w of lighting

TDR300K Remote ControlledLight Dimmer 114 95

MK6 Transmitter forabove (4 50

TD 300K Touch Dimmer 17 75

TS300K Touch Switch 17 75

TDE/K 2 -way extensionfor above kits £2 50

10300K Rotary controlledLight Dimmer 13 95

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DL 1000K This value -for -money 4 waychaser features bi-directional sequenceand dimming. lkW per channel E15.95DLZ 1000K A lower cost uni directionalversion of the above. Zero switching toreduce interference. E13.95Optional opto input allowing audio 'beatlight response IDLA/1/ 70p013000K 3 -channel sound to light kitfeatures zero voltage switching, automatic level control and built-in microphone lkW per channel E12.95

OTHER KITS

CT1000K Clock Tinier E14.90CT1000KB Clock /Timer . Box E17.40XK126 DVMi Thermometer 115 .50MK1 Thermostat £4.60MK2 Solid State Relay 12.60MK4 Temperature Control E6.50MK5 Mains Timer E6.50MK6 Infra Red Transmitter (4.50MK7 Infra Red Receiver E10.50All kits include PCBs, components andassembly instructionsFor further details send S A.E.

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poNWEILGRKGE


PE VOLUME 20 No. 12 DECEMBER 1984

IN CAR ELECTRONICSELECTRONICS in motor cars has

provided PE with many interestingfeatures and projects over the years.Back in 1965 we were publishing caralarms, instruments and parking lightsas projects. Interestingly one newsitem at that time reported the first carto car 'phone call across the Atlantic.The call was made on July 5 1965from a car in London using a

Radiophone made by Pye to a taxi cabin Montreal also using Pye equipment.This event followed the official openingof the London Radiophone servicewhich covered an area of about 30miles around London.

Electronics has moved on in the lasttwenty years and of course so haveour projects. In December '81 wepublished our first car computer whichbroke new ground in this area and isstill an unsurpassed design. Now weare pleased to publish another, totallydifferent car computer design, a designbased on a computer model of the car'sperformance, consumption etc. Thisnew design is not as complex as the PE

Car Computer of 1981 but provides allthe basic information without the needto fix a fuel sensor and is consequentlyan inexpensive item to build. Webelieve this design again breaks newground in its mode of operation.

BUYER'S GUIDESBuyer's guides, as regular readers

may have noticed, are becoming quitea part of PE. It seems that the informa-tion we provide is of great value tohobbyists and those involved in theelectronics industry and education. Wehave now covered quite a wide fieldwith our guides and are planningfurther subjects for next yea?.

Soldering equipment is well coveredin this issue and, while we make noclaim that the guide is complete, it willgive readers a good basis or which tobuild a Hs*: of required equipment. Nodoubt mary readers will find new com-panies and products which they werenot aware of before. If you make an en-quiry about any product we describe(especially those detailed in our buyer'sguides) would you please mention PE

as the source of the original informa-tion. This applies equally to educationalestablishments and industry or trainingdepartments etc., as such feedback tothe suppliers assists us to give goodcoverage in future guides.

INDEXAs usual this issue of PE carries the

index for the year. If you find an articleyou would like to read our backnumbers department may be able toassist-see below. Alternatively a locallibrary, particularly a technical one orone attached to a school or collegeetc., might carry copies.

In extreme cases we can supply aphotostat of the article from theeditorial office but we do have tocharge 75p for each article or part of aseries.

Editor Mike Kenward

Secretary Pauline Mitchell

Assistant EditorsDave Barrington (Production)David Shortland (Technical)

Technical EditorMike Abbott

Projects EditorDavid Brunskill

Technical Sub -EditorsRichard BarronBrian Butler

Art Editor Jack PountneyAssistant Art Editor

Keith WoodruffSenior Tech. Illustrator

John PickeringTech. Illustrator

Isabelle Greenaway

Advertisement Manager David Tilleard 01-261 6676Secretary Christine Pocknell 01-261 6676Advertisement Sales Executive Richard Willett 01-261 6819Classified Supervisor Barbara Blake 01-261 5897Ad. Make-up/Copy Brian Lamb 01-261 6601

Technical and editorial queries and letters(see note below) to:Practical Electronics Editorial,Westover House,West Quay Road, Poole,Dorset BH15 1JG

Phone: Editorial Poole 671191We regret that lengthy technicalenquiries cannot be answeredrive, the telephone

Que-ies and letters concerningadvertisements to:Practical Electronics Advertisements,King's Reach Tower,Stamford Street, London SE1 9LSTelex: 915748 MAGDIV-G

Letters and QueriesWe are unable to offer any advice on theuse or purchase of commercial equipmentor the incorporation or modification ofdesigns published in PE. All letters requiringa reply should be accompanied by a stam-ped, self addressed envelope, or addressedenvelope and international reply coupons,and each letter should relate to onepublished project only.

Components and p.c.b.s are usuallyavailable from advertisers; where we antici-pate difficulties a source will be suggested.

Back Numbers and BindersCopies of most of our recen- issues areavailable from: Post Sales Department(Practical electronics), IPC Magazines Ltd.,Lavington House, 25 Lavington Street,London SE1 OPF, at £1 each including In-land/Overseas p&p. Please state month aridyear of issue required.

Binders for PE are available from thesame address as back numbers at £5.50each to UK or overseas addresses, includ-ing postage, packing and VAT where ap-propriate. State year and volume required.

SubscriptionsCopies of Practical Electronics are availableby post, inland for £13, overseas for £14per 12 issues, from: Practical Electronics,Subscription Department, IPC MagazinesLtd. Room 2816, King's Reach Tower,Stamford Street, London SE 1 9LS.Cheques, postal orders and internationalmoney orders should be made payable toIPC Magazines Limited. Payment forsubscriptions can also be made using acredit card.


Items mentioned are availablethrough normal retail outlets,unless otherwise specified.Prices correct at time of goingto press.

1111A/Ple

4.1,. NNW &PO

Mains' utilities lopWOMEN?Monitoring

SystemA new remote -monitoring system, designed forload -management of electricity, gas and water sup-plies, is presently undergoing trials in London andMilton Keynes. The Thorn/EM I system MainsborneTelecontrol uses the electricity mains to carry bi-directional coded data between the central controland the consumer combining far more cost effec-tive tariff structures with remote meter reading.

The purpose of the trials is to establishthe long term levels of reliability of the uni-que spread spectrum bi-directional signall-ing system over the low voltage mains, asystem adopted to overcome excessivenoise problems. A spread spectrum signalessentially provides a continuous frequencyover the band and is highly resistant tonarrow band interference. It is also capableof signalling through a high noise level en-vironment such as the mains and ad-ditionally provides high security.

The consumer is provided with a

microprocessor controlled home unit andcommunications module. These carry out anumber of tasks including accumulatingsignal pulses from electricity, gas and watermeters; tariff switching; calculating actualand estimated costs incurred by the con-sumer; operating 80 amp and 25 amp con-tactors for space and water heating controland also for detecting any tampering withthe meters. The communications modulecontains a clock/calendar synchronised tothat of the central controller which ishoused in the local C.E.G.B. transformerchamber. Non-volatile RAM storage of 1Kbyte permits a one day store of incremental

meter readings for each utility.The central controller can communicate

via the mains with up to 1,024 addresses.There is 500K bytes of non-volatile bubblememory capable of storing three days of 48half-hourly meter readings from all threeutilities as well as storing data re-transmission upstream to Load Manage-ment Control or downstream to home units.

The customer display (pictured) has a 10digit, alpha numeric, vacuum fluorescentdisplay with 19 touch sensitive keys. Aseries of control and data display functionsare available to the customer such as dis-play of meter reading including multi -tariffmetering; display of units consumed andcost so far since last bill; display of es-timated cost of next bill; display of waterand space heating on/off times; when not inuse for any other reason the display showsthe time.

Two other communication systems arepresently being tested in the UK forremote -monitoring and load management;one uses an idle line facility on the standardtelephone network, the other uses radiosignals transmitted in the 200kHz band bythe BBC.

Leisuretronics, the broadbased electronics show

which was to be held at the Royal Hor-ticultural Hall in London from November 8thto the I I th, has had to be cancelled by theshow's organisers Trident International.

Despite the fact that the show was beingsponsored by ten leading magazines. PE in-cluded, it did not receive the necessary back-ing from the electronics industry and theOrganisers felt it would not be possible to go

NOV. SHOWCANCELLEDahead with the show under these conditions.

Mr. Gordon Johns, Managing Director ofTrident International, said "We are very dis-appointed. It was obvious from the reaction ofthe public that there is a very real demand fora show that reflects all aspects of the leisureindustry but because of general market condi-tions many companies were unwilling to givethe show their support."

Trident do hope however to stage the showas soon as market conditions improve.

Women in London will have the oppor-tunity to train for top engineering jobs innew technology thanks to £350,000 ingrants from the Greater London EnterpriseBoard, the Greater London Training Boardand the European Commission.

The grants are in recognition of the workbeing done by the GLEB-sponsored LondonNew Technology Network (LNTN) based inCamden and will finance training coursesfor women to be supervisors and trainers inmicro -electronic engineering.

Enter MSXThe long awaited MSX computer range isfinally finding its way into the UK shops.MSX is a standard system adopted by 15multinational electronics companies, mainlybased in Japan. The standard is based on theZ80 processor, a TI video display chip and aGeneral Instruments sound generator chip; allMSX machines and their peripherals aretotally compatible. It is undoubtedly the hopeof the conglomerate that their standard willeventually dominate the home -computermarket.

Mitsubishi, Toshiba, Sony, Sanyo, JVC,Hitachi and Canon recently held a jointlaunch for their machines which all costaround the same-between £279 and £300.The software has been written by theAmerican company Microsoft, it is a versionof Basic. Around 75 general interest softwarepackages are currently available. All themachines have a similar appearance and eachpossesses 64K bytes of user RAM with aseparate I6K bytes of video RAM; the Basicis stored in a 32K byte ROM.

Peripherals available will include 3+ infloppy discs, printers, data cassette recorders,joysticks, touchpads, tracker balls and com-munications adaptors. Mitsubishi are the onlycompany to launch two machines, the cheaperversion (pictured) is a 32K byte model MLF48 costing £249.

8 Practical Electronics December 1984

MARCH= imamWATFORD'S Computer Briefly...MODEM 84 look alikesThe Watford Modem 84 is a direct connectunit for use with BBC micros; it is a fullyBritish Telecom approved device and isprobably the cheapest way to connect toPrestel. The unit is supplied with or withouta software ROM.

Having a full duplex capability thesystem can send and receive data at thesame time. Only 1K byte of memory is usedby the system for preparing mailboxes andsystem operation. User passwords can beoptionally programmed into the ROM giv-ing automatic log -on whilst still allowingyou to change the personal passwords fromthe keyboard. The system has many specialfeatures. Modem 84 costs £97 includingthe software ROM. The two can be boughtseparately, Modem 84 alone £74, softwarealone £23. All prices include VAT and p&p.For further details and full specificationcontact: Watford Electronics, 33/35 CardiffRoad, Watford, Herts, WD1 8ED. (092340588).

Systema has introduced a mini deskcalculator together with an LCD clockboth styled like modern computer ter-minals.

The DC2 computer -calculator has afull working keyboard with memory,percentage and square root functions.Its eight digit display is fitted into theVDU cabinet. Overall measurementsare 80 75 47mm.

The time and date are displayedalternately on the VDU of the CC1computer -clock and its time keeping isaccurate to within two seconds a day.Overall measurements are 52 4541mm.

Both items are fitted with long lifebatteries. Prices are £6.95 for the DC2computer -calculator and £3.68 for theCC1 computer -clock, inc VAT and P &P. From, Systems (UK) Ltd., 72/74South Street, Reading, Berks. RG141G. (0734 586429).

Cons!ructors please note: as part of a 'movingsale' the Midwich Computer Co. Ltd. is

featuring many BBC products and compatibleperipherals at low prices. Examples include a100k, 40 track disc drive for £99.95, and theUchida daisy wheel printer for £227.65.Prices exc VAT. All offers are while stockslast. New address: Gilray Road, Diss, Norfolk1P22 3EU. (0379 4131). The Mitsubishi Electric Corporation hasdeve.'oped a method of access control thatrecognises personnel by their palm prints.Empioyees' palms are photographed andentered into a Charge Coupled Device(GCE) camera recognition system. Accessto restricted areas is gained as the prospec-tive entrant keys in a personal code andsimultaneously presses his palm on arecognition plate; a positive palm printcheck coupled with the correct code num-ber permits entry.

POINTSARISING . . .

PARALLEL/SERIAL CONVERTERSeptember '84The +ve connection of C2 should be connected to +5V and not to TR2 as printedSee page 18. Fig. 3 (circuit diagram).

Please check dates before setting out, as we cannot guarantee the ac-curacy of the information presented below. Note: some exhibitions maybe trade only. If you are organising any electrical/electronics, 7adio orscientific event, big or small, we shall be glad to include it here. Addressdetails to Mike Abbott.

Leisuretronics Cancelled (see report, far left.)Compec Nov. I3-16. Earl's Court. K2P.c.b. Manufacture & UV Box Construction (meeting) Nov. 17. Elec-tronic Organ Constructors Society. Y4Systems Security Nov. 19-20. Barbican Cntr., London. EComputers In The City Nov. 20-22. Barbican, London. 0Data Security Nov. 20-22. Barbican, London. 0Business & Data Processing Nov. 20-24. Kelvin Hall, Glasgow. MNorthern Computer Fair Nov. 22-24. Belle Vue, Manchester. K2Northern Energy Manager Nov. 27-28. Lancashire County CricketClub, Old Trafford, Manchester. W3Transducer Tempcon Nov. 27-29. Harrogate Exhibition Centre,Yorkshire. T

Electronic Displays Nov. 28-30. Kensington Ex. Cntr., London. D4Electron & BBC Micro User Dec. 6-9. New Horticultural Hall, Lon-don. LAmusement Trades International Dec. 18-Jan. 14 '85. Olympia. ESYour Computer Xmas Fair Dec. 30-Jan. 2 '85. Olympia. K2International Light Show Jan. 14-28 '85. Olympia. E6British Toy & Hobby Fair Jan. 18-Feb. 2 '85. Olympia. D6

D4D6EES

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Network 0280 815226g' 01-701 7127Evan Steadman ir 0799 26699f 01-228 41072' 058 84 658Reed Exhibitions, Surrey Ho., I Throwley Way, Sutton, SurreyDatabase ( 061-456 8383Montbuild (01-486 1951Online ( 01-868 4466Trident Exhibitions ( 0822 4671Cahners 0483 38085MCM 01-231 1481Percy Vickery f 0202 423863

Practical Electronics December 1984 9

TRIP Mt

DIST FUEL

CAR COMPUTER

MPG COST

IONE0

SET

Lir %I J. I 1 I

CAR COMPUTERS.H.COUSINS BSc PhD P.D.WILSON BEng PART ONE

HOW MUCH DOES IT REALLY COST TO USE YOUR CAR?

ONDON, 3eneva, Frankfurt, Paris . . . hardly a motor showgoes by without a major car manufacturer introducing a

new top-cn-tie-range car fitted with either a trip computeror a digital -n.p g. readout integrated into the instrumentpanel. Nov* here is an opportunity to bring your car righ: upto date with one of the new generation of car computers.These devises are designed primarily to add interest to yourmotoring, bu-. they can save you money as well.

There is plenty of money to be saved. The averagemotorist drives 9000 miles eau] year, which given a typical30m.p.g. mearis consuming 300 gallons per annum), costing£540 at £' .E.0 a gallon. Next year petrol is likely tc go above£2 a gallon ir only to keep pace with inflation and the weakpound. But tnis is only half the story because, at a rule ofthumb, for every pound spent on petrol another pouni isspent in total on oil, tyres, maintenance costs and cardepreciation iue to additional miles on the clock.

The Out-icer car computer has been developec after thefirst wave of car computer novelties, and we are able to buildon their experience. We have concentrated on achieving ahigh standard of design so that the Outrider will De simpleand safe tc use whilst driving, easy to fit to the car and easyto refit if you change cars. But most important of a I we havedeveloped a -ugh quality digital m.p.g. readout which isstable under continuous driving conditions, sucl- as on amotorway, ),et is also responsive to acceleration, andresponsive too, when easing or the accelerator pedal. t isnot necessary to fit sensors to the accelerator incidentally!

When the car is stationary otter features of the computercan be access d. For example, the computer will predict thegallons of kiel required for a trip and the trip cost tefore b(0.1travel. To do -his simply enter onto the computer the dis-tance you exjpect to travel and view the appropr ate ftnc-bons. Precisely how data is entered is dealt with later, but itis worth ncting at this stage that, as a safety measure, cat.3can only to entered into the computer when the ca- isstationary.

Another important computer feature is the calculation oflong term average m.p.g. which orovides the information /ourequire to decide whether the car needs servicing.

CAR SHARINGDisplaying the trip cost can be an incentive for car shar-

ing. Not only do you become fully aware of the cost of cartravel, which may encourage you to share, but so do yourpassengers)

The Outrider automatically displays the cost of the trip(petrol cost plus a mileage charge) when you switch off theignition. This is shown for ten seconds before the computerswitches off the display.

BUSINESS TRAVELMany of us have to record our mileage in order to reclaim

expenses from our employers. The trip distance key is in-valuable for this as we can easily underestimate the truelength of trips when claiming expenses. Self-employed peo-ple and company managers may also benefit from knowingthe cost of car operation for particular business trips.

CAR OPERATING COSTSSo how should we evaluate the cost of travelling by car,

and at what value should the mileage charge within thecomputer be set? To work out the cost of operating your carfill-in Balance Sheet 1.

The most obvious cost of motoring is fuel cost and if themileage charge is set to zero then just the fuel cost of a tripwill be displayed by the COST key.


However, each time you drive you incur additional costs.When you have estimated these and set the mileage chargeto cover these costs then the trip cost displayed by the COSTkey will be the sum of the fuel cost and the extra costs thatyou incur having driven the distance of your trip. If you hadstayed at home this is the total amount that you would havesaved. If you use the trip cost prediction facility you wouldhave an 'estimate of the trip cost that you could directly com-pare to the rail fare or a telephone call. Setting the mileagecharge to cover these additional costs is the most usefulsetting for household owned cars.

Business users, the self employed and car sharers mayhowever want to add the fixed car costs into the figure, notjust those additional costs which are incurred at the time ofdriving.

MAIN BOARDThe heart of the circuit is a Motorola 6803 single chip

microcomputer. This chip contains the processor, 128 bytesof RAM, a programmable timer and 13 input/output lines.The program for the microcomputer resides in a 2K byteEPROM. A 74LS373 is used to latch the low order addresslines from the 8 bit multiplexed address/data bus. Timing in-formation is derived from the 3.579545 MHz crystal. Thispart is commonly available as it is used in colour t.v. sets.

KEYBOARD AND DISPLAYEach of the four I.e.d. digits and the function indicator

I.e.d.s are controlled by a transistor driven from one of fiveoutput lines of the 6803. Rapid scanning of the digits syn-chronising with the data to switch segments on or off, whichis held in the 74LS374 latch, gives the impression of alldigits being on simultaneously but with great economy inwiring and components.

The 7 -segment I.e.d.s were selected for both their ap-pearance and their high brightness. The latter is particularlyimportant for car instruments which must be readable in alllight conditions

The five digit lines are also used to scan the five inputkeys, which have a common line of input to the processor.The processor detects a key press when this line goes high.

The Outrider contains calibration and trip informationwhich must not be lost when the ignition is switched off 64bytes of the 6803 memory can be retained even when theprocessor is turned off, through the Vcc standby pin. This pinis connected directly to the 5V regulator which is in turnconnected directly to the 12V car battery. The power to therest of the circuit is switched by a transistor which is turnedon either by the ignition line or an output line from the 6803.This enables the 6803 to hold the power on to enter adefined power down sequence and to display trip cost infor-mation for a 10 second period after ignition is turned off.

TRANSDUCERThis is a high inductance coil mounted as close as possi-

ble to the rotating magnet found in all conventionalspeedometers. Normally it is sufficient to place the coil tightup against the back of the speedometer case and mountedat right angles to the axis of the drive cable. Exceptionally itis necessary to drill through the speedometer side or backand locate the transducer internally.

Each time a pole of the speedometer magnet passes thesensor coil a voltage is induced which is then converted to adigital signal by a Schmitt trigger on the main circuit board.A twisted pair connects the sensor coil to the main board toremove any electrical noise problems coming from the car'signition circuit.

BALANCE SHEET 1

Annual costOilTyresServicingMaintenance £

(brakes, exhaust, etc)Half the annual depreciation

Mileage charge in pence is given th,

100 x Aannual mileage

Total, A =

pence

p

BALANCE SHEET 2

Fixed costsAnnual Vehicle TaxInsuranceFinance chargesHalf annual depreciation £Other, e.g. AA/RAC membership £

Mileage charge in pence covering All non petrol costs is given by

100 x (A+B)annual mileage =

Total, B =

pence

Just for interest sake are can now calculate the cost of a years fuel, this is giver, be'

annual mileagex price per gallon = £average MPG

Your CIP coats you en total for a whole year

A+ +C=

=C

A computer model eliminates theneed for a fuel flow meter

INPUTS

'DISTANCE SF NSOR KEYBOARD \

cIFIRFIRRIMPP

01-111 El

TIMERSIGNAL CONDITIONINGELECTRONIC NOTEBOOKLOGIC

OUTPUTS

8 8 8 8

COMPUTAT ION

Fig. 1.1. Block diagramLPE5S91

THE COMPUTER OUTPUTSThe keys display these functions

Keys FunctionsDIST Distance travelled on tripFUEL Fuel used on tripMPG Instantaneous m.p.g. (above 20m.p.h.)

Trip average m.p.g. (below 20m.p.h.)COST Trip cost in £.pSET Display brightness

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HOW THE COMPUTER WORKSThe overall configuration of the computer is shown in

Fig. 1.2. Distance travelled is detected by a sensor coil locatedbehind the speedometer. Fuel consumption information isfed into the computer via the computer keyboard. This isdone by entering into the computer's electronic notebookthe amount, in pounds and pence, spent when fuel ispurchased. The computer then displays the price of a gallonof petrol the previous time it was bought to check that this isstill the current price. The amount spent on fuel purchase isthen divided by the price of a gallon of petrol to give thevolume of petrol purchased. The volume of fuel purchased isnot displayed but is retained in the computer and ultimatelydivided by the total distance travelled when the user re-quests a calculation of long term average m.p.g. Thiscalculation is best made when the tank is completely filledand gives a highly accurate result. Long term average m.p.g.may be displayed at any time by pressing the MPG key whenthe computer is in calibration mode.

The distance sensor controls the dynamic behaviour of thecomputer outputs in conjunction with the crystal oscillatorwhich provides a time source. Together the distance andtime inputs are used to determine distance travelled, coldstarts, vehicle speed, vehicle acceleration and vehicle brak-ing. These factors are used in the computer model to deter-mine instantaneous m.p.g. using the long term averagem.p.g. to calibrate the model itself. Readers will recognisethis kinetic method of calculating instantaneous m.p.g. asbeing very similar to the approach taken in the standard EECdriving cycle for new cars. Here m.p.g.s are given accordingto the speed at which they are driven (56m.p.h. and75m.p.h.) and for an urban driving cycle involving accelera-tion and braking.

There are advantages to this kinetic method of determin-ing instantaneous m.p.g. Flow meters in the fuel line can beinaccurate or expensive and there is always a slight ad-ditional risk of a petrol leak if a meter is introduced into thefuel line. Fuel flows reflect the characteristics of the car-burettor float chamber as well as driver behaviour and thecombination can be confusing to the driver particularly dur-ing continuous, e.g. motorway driving. By contrast thekinetic method can give a high quality signal to the driver.

Trip m.p.g. is the average of the instantaneous values overthe period since the trip data were reset to zero. Fuel con-sumed on trip and trip cost are also calculated from the tripaverage m.p.g. figure. In the latter case the cost of fuel usedand distance times the mileage charge are also used todetermine the total trip cost. Users determine an appropriatecharge per mile to reflect an average of all non -petrol costsor those costs less the truly fixed costs (tax, insurance, etc..

Provided that the power supply to the computer is main-tained, all trip and calibration data are retained when thecomputer display is off and the car is not in use.

THE M.P.G. READOUTThere has been considerable debate about whether a

digital or analogue readout is best for car instrumentation ingeneral and for the m.p.g. display in particular. Our display(Fig. 1.2) is something of a hybrid using three of the 7 -segment I.e.d.s to display digital m.p.g. while the fourth I.e.d.is effectively an analogue display summarising how the caris being driven. This horizontal bar can be usefully positionedat the edge of the driver's vision when the driver is at thewheel and looking straight ahead.

DATA ENTRYAlways begin data entry by pressing the SET key (for two

seconds until SET is displayed and the light above the SET

key flashes slowly). Next choose the function key that youwish to tell the computer about, e.g. COST. Now any numberbetween 00.00 and 99.99 can be entered as follows. Eachof the four left-hand keys rolls a separate digit on the display."Roll -up" your desired number (the price of a gallon ofpetrol, say 1.75 in this case) then press the SET key tofinish.

This is the sequence keys you will press to enter dataSET FUNCTION NUMBER SET(2 secs)

Remember the car must be stationary and the SET keypressed for two seconds.

Data entries are as follows for each function key:

SET DIST 0000 SET- Resets all trip data to zero, e.g.fuel used on trip, distancetravelled on trip and cost oftrip

SET DIST NUMBER SET- Predicts the fuel required andcost of a trip a NUMBERmiles long

SET FUEL NUMBER SET Enter the amount spent onfuel each time you buy petrol.The NUMBER is the total costof fuel which you have justpurchased. The computer alsoneeds to know the cost pergallon of the fuel and to helphere the computer automatic-ally goes over to the costfunction and displays the costper gallon last used. Changeif necessary. Press SET toreturn to normal computeroperation.

SET MPG tF.00 SET- Calculates your averagem.p.g. over the last 6 to 10gallons'. tF stands for "tankFraction". Enter here theposition of the needle on yourpetrol gauge. If it is readinghalf full enter tF50; if it is aquarter full enter tF25 etc. Tomake a completely accurateresult fill the tank and enterfuel purchases in the usualway (above) then the tF99should be entered. Afterpressing SET, average m.p.g.will be displayed. Press SETto return to normal computeroperation.

SET COST NUMBER SET Enter here the cost of a gallon'Equal to the volume of your petrol tank, see calibrationsection.

The Outrider car computer is available from: Mark SpaceEnterprises, 11 Church Green Rd., Bletchley, Milton KeynesMK3 6BJ. The complete kit costs £59.95 inclusive ofcarriage and VAT. A kit comprising those parts not generallyavailable, i.e. case, label, 5 x front panel switches, p.c.b.s, 4x 7-seg. displays, coil, programmed ROM is available for£29.95-most useful for the constructor with a well en-dowed spares box!

When ordering, please specify the make and model of thevehicle if known.

NEXT MONTH: Construction, installation and setting up.


INDUSTRY

NINON

Breezy BusinessEconomic predictions are notoriously un-

reliable. The experts are often provedwrong, not by failure to correctly analyseand marshal data from which to fashion aconclusion, but by unforeseen events. Pitythe poor economist whose job is to predictin an unpredictable world.

Energy demand and resource forecastingshould have a much better record if onlybecause it is a narrower field. But it hasbeen no more reliable. In the 1950s wewere all worrying that the world wouldsoon run out of oil. In the 1960s there wasan enormous surplus. In the 1970s theprice explosion forced us to think aboutalternative sources as well as renewingfears that oil would soon run out. Today,nearing the mid -80s, we have another glutof oil not to mention more coal in theground than has ever been mined, naturalgas in abundance and an increasingcapacity in atomic energy.

Of course nobody in the 1950s imaginedthat in the 1980s the family car wouldtravel 50 miles to the gallon instead of 30,or that all -solid-state TVs would consumeonly 30 percent of the energy of theirvalved predecessors, or that double glazingand loft insulation would cut domesticheating demand by 10 percent.

Abundance of supply plus more efficientusage has eased our fears and almost, butnot quite, extinguished popular enthusiasmfor the alternative energy sources so keenlydebated in the late 70s. Whatever hap-pened to tidal power, wind power and solarenergy?

Wind power, I am happy to report, isalive and well. The Wind Energy Group, aconsortium of GEC Energy Systems, BritishAerospace and Taylor Woodrow Construc-tion, has identifed a world market for windturbine generators estimated to be in tensof thousands of installations.

The demonstration model is now underconstruction on a hill at Ilfracombe, Devon,and should be operational by the end of theyear. It has a three -bladed rotor 25m indiameter and will generate up to 250kW,The project is financially aided by the EECand by the Department of Trade and In-dustry. Naturally, the control system is elec-tronic and one of the more interestingfeatures is that microprocessor technologyis employed for remote control over atelephone link from WEG's offices in Green -ford, Middlesex, together with feedback ofoperating data for analysis.

The windmills of the 80s and 90s willhelp conserve oil resources but that is notthe main sales message. The real truthbehind WEG's optimistic sales forecast isthat by clever engineering wind energy isnow price -competitive with conventionaldiesel generated electricity in small com-munities.

TurnaboutConventional wisdom has it that the re-

quirements of national defence and, in par-ticular, a fighting war, is the forcing groundfor truly innovative developments. The mostnotable example is radar which made enor-mous progress during World War 2 anddidn't come into civil use on any scale untilafter the conflict.

An offshoot of radar was microwavetechnology which, again, only surfaced forcivil communications use after the war. To-day we still hear stories that defence R & Doperates on the very frontiers of knowledgeand with large budgets, especially in theUnited States, there is still an element oftruth in such assertions.

But curiously, the most revolutionary in-novations of all time, the integrated circuitand later the microprocessor, had theirorigins in the civil market and were adoptedonly with some reluctance by the military.

The first simple i.c.s were the brain-children of Jack Kilby of Texas Instrumentsand Bob Noyes of Fairchild Semiconductorin 1958 and 1959. Acceptance by the in-dustry was painfully slow until ten yearslater Intel was formed (in 1968) as aspecialist i.c. company with its first producta 64 -bit solid state memory.

In 1969 a Japanese company, Busicom,asked Intel to help produce a set of i.c.s fora projected range of high performancecalculators. Busicom's ideas were verygood but in the opinion of Intel's projectengineer, Dr Marcian E. Hoff Jr, they couldbe made more cost-effective by adopting asystems approach using a general purposecentral processor and using peripheralmemory chips to achieve the calculatorfunctions.

Hoff had previously worked on the PDP-8 computer at Digital Equipment and wassystems -trained. He also foresaw many ap-plications other than calculators where aCPU could be of value. This was the begin-ning of the MPU as we know it today andwhat brought Intel to its present impressivestatus in the industry.

Hoff's ideas came to the open market inNovember 1971 with the 4004 CPU chip

followed by the 8008, the first of the 8 -bitchips and a succession of more powerfuldevices. By 1975 the new innovation wasgaining ground with Intel and its com-petitors shipping 1 million chips.

Five years later the annual shipmentshad topped 50 million. Ironically, Busicomwho had started the bandwagon rollingwent out of business. Note, too, that cross-fertilisation of TI and Fairchild's originalwork plus Digital Equipment system ex-perience plus market demand (Busicom)combined with Intel's own expertise togenerate something entirely new.

The military are not entirely to blame fortardiness in adopting the new technology.They were apprehensive over reliability inview of earlier experience with transistorswhich were sensitive to breakdown throughpower line surges and spikes. Additionallythere were storage and other militaryspecifications to be met. Many of today'soperational devices for the military demandMil Spec qualification in both productionand testing but in non -operational orsheltered environments good commercialquality is good enough.

We see this also in certain items ofequipment. Naval minesweepers and patrolvessels, for example, frequently use goodcommercial quality radio equipmentoriginally designed for the trawler market.Financial constraints even led to the idea ofVTOL Harriers and helicopters operatingfrom converted merchant ships instead ofconventional aircraft carriers which are verymuch more expensive.

There are many areas of course wheremilitary R & D is essential and money wellspent. But it is good to see that manyproducts pioneered in the civil field for civilapplication are no longer sneered at by themilitary establishment.

Self -HelpOne of the Government objectives has

been to encourage self-reliance as being farmore virtuous than outright dependenceon the nanny -state. Cut -backs in centralfunding have forced many organisations toseek internal economies and, in somecases, to search for alternative sources ofrevenue.

University R & D is a case in point. It hasbeen traditional for research departmentsto take out patents and enjoy the benefitsof royalties but there are now signs thatour academics are becoming far morebusiness -minded. They are actually formingseparate companies to sell their services.Thus we see Salford's Industrial Centre,Unisheff Ventures owned by SheffieldUniversity and Unived Technology set up byEdinburgh University.

There are others and the trend is likely tocontinue. As private companies they canraise their own funds in the commercialmarket and even conceivably go beyond R& D and consultancy work through tomanufacture and marketing, either in-dependently or in joint ventures with ex-isting companies.

How refreshing to see people rising to achallenge instead of indulging in perpetualself-pity.


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Sequential LogicTechniques ye 0

M.TOOLEY BA and D.WHITFIELD MA MSc C Eng MIEE

VVE have already made some use ofa simple data latch configured

around the four D -type bistable stagesof a 7475. Data latches are ideal forthe temporary storage of data andseveral enhanced devices have ap-peared. One such device, the 74175, isa quad edge -triggered bistable whichcan be used both as a conventionalparallel type latch having separate datainput and output lines from eachbistable, and as a serial type shiftregister where data is fed from onebistable stage to the next.

The 74175 is housed in a 16 -pind.i.l. package, the pin connections ofwhich are shown in Fig. 3.1. The inter-nal logic of the device is shown in Fig.3.2. A common clock input is appliedto each of the bistable stages and datapresent on the D inputs is transferredto the Q outputs on the positive -goingedge of the clock pulse. It should benoted that clock triggering occurs at a

+5V 03 63 03 02 02 02 CLOCK

LEAK 00 00 00 DI 01 01 OV

LPES446

Fig. 3.1. Pin connections for the 74175

4Trzik(1)

CLOCK 00(9) (13)

DI

particular voltage level present at theclock input and is not directly related tothe transition time of the positive -going pulse. A common master resetinput is also provided which, whentaken low, asynchronously clears all ofthe Q outputs.

74175 4 -BIT PARALLEL DATALATCH

We shall start our investigation ofthe 74175 by showing how it can beused as a 4 -bit parallel data latch in thearrangement shown in Fig. 3.3. Thefour incoming data lines are connectedto the four D inputs whilst the four out -

+5V

16

'54' 1s'04'03 03

10.03.

DATAD2 02

DATAINPUTS OUTPUTS

DI 0

74175_51

DO 00

LOGIC 1 CLEAR

CLOCK CLOCK

1PE54661 OV

Fig. 3.3. A 4 -bit parallel data latchusing the 74175

-MCP

rCP

Pr(11) (10)

41 01

CP

RD

(6) (7)

02 02

Fig. 3.2. Internal logic of the 74175

03(4)

.11=11.1.

CP

(3) (2)43 03

put lines are derived from the four Qoutputs. The latch enable signal is ap-plied to the clock input whereas theclear signal is applied to the masterreset pin.

The 74175 should be inserted intosocket C of the Logic Tutor ensuring, asusual, that pin 1 aligns with C1. Thefollowing connections should be made:

Cl to logic 1C2 to D1C4 to S1C5 to S2C7 to D2C8 to OVC9 to clockC10 to D3C12 to S3C13 to S4C15 to D4C16 to +5V

(active low clear)(D1 shows state of 00)(data input, DO)(data input, D1)(D2 shows state of Q1)(common)(latch enable)(D3 shows state of 02)(data input, D2)(data input, D3)(D4 shows state of 03)(supply)

Adjust S1 to S4 to produce logic 0on all input lines. Check the state of theoutput lines (Q0 to 03) by examiningthe state of D1 to D4 and verify thatthese all go to logic 0 (and stay at logic0) after the first rising clock edge. Nowwait until the clock goes low anddepress S4 so that logic 1 appears onthis input. The corresponding output(indicated by D4) should remain atlogic 0 until the clock next goes high,at which point the output shouldchange to logic 1.

Readers should experiment withvarious combinations of data input ob-tained by appropriate adjustment of S1to S4. It should be noted that, in allcases, data is only latched on a positvegoing clock edge (i.e. as the clock I.e.d.becomes illuminated). Furthermore, af-ter the clock transition has occurred,the 74175 ignores any further changeson its data inputs until the next risingclock edge arrives. In practice, thismeans that input data MUST remainstable for the duration of the risinglatch enable input signal since this isthe only time at which the input data isvalid.


The clear input may now be testedby first loading data into the latch, dis-connecting the link from C1 to +5V(the input pin of the 74175 remains atlogic 1 during this process) and thenconnecting the link from C1 to logic 0.All four outputs should then im-mediately go to logic 0 and no furtherdata will be latched until the clear inputis returned to logic 1 (or left to floathigh again).

A SIMPLE LOGIC ANALYSERHere is an example of the use of

the data latch. One of the primary func-tions of a logic analyser is that of "cap-turing" transient data present in a

microprocessor based system and"freezing" it so that it can be displayedand examined at leisure.

The point at which data is capturedis defined by a "trigger event". Thisusually takes the form of a particular

DATA BUSINPUT

CONTROLBUS

SERIAL DATAINPUT

DO -D3

SEQUENTIAL LOGICset of logic states present on the con-trol bus. When this pre-set bit patternoccurs, data is latched into the memoryof the logic analyser, decoded and dis-played in binary or hexadecimal form.

A very simple form of logic analyseris shown in Fig. 3.4. Two 4 -bit datalatches are used to capture the lowernibble (present on data lines DO to D3)and the upper nibble (present on datalines D4 to 07). The clock and clearlines of all eight bistable stages arecommon: the clock being driven fromthe trigger event decoding logic (whichis arranged to produce a 0 to 1 transi-tion when the trigger event occurswhilst the clear line is connected to apush-button 'reset' switch.

Whilst this simple arrangement isonly capable of capturing a single byte(i.e. the eight data bits present on thebus) at a time, most logic analysersprovide a memory of 1K bytes (or

4 -BITDATALATCH

LEAST SIGNIFICANT NIBBLE

.11.11=101,

CLOCK

CLOCK

04-D7

11,

CLOCK. [(PEI60341

0 Ci

CK

CLEAR

DECODER DISPLAY

CLEAR

4 -BITDATALATCH

I MOST SIGNIFICANT NIBBLE)

TRIGGEREVENTLOGIC

DECODER D ,P A

Fig. 3.4. A simple logic analyser

,111111111, .111=11r

CK

rCA

0

`,10

CA

OV

RESET

SERIAL DATAOUTPUT

Fig. 3.5. A 4 -bit SISO shift register using D -type bistables

SERIALDATAINPUT

more) and, in addition, will offer thefacility to capture data both before andafter the pre -determined trigger event.

SHIFT REGISTERSShift registers essentially provide a

form of serial memory (as opposed tothe parallel form of data latch whichwe looked at last month) in which datacan be synchronously clocked from onestage to the next. In a simple shiftregister made from D -type bistablesthis means that the Q output of the firststage must be taken to the D input ofthe next stage, and so on. A register ofthis type is shown in Fig. 3.5 and isknown as a serial-input/serial-output(SISO) shift register.

Instead of using D -type bistable ele-ments in the SISO shift register wecould, of course, use J -K bistables. Theequivalent of Fig. 3.5 using J -Kbistables is shown in Fig. 3.6. Both ofthese arrangements use four cascadedbistable elements, thus four clockpulses will be needed in order to shiftdata right through the shift register.

At this point it is probablyworthwhile making a clear distinctionbetween the SISO shift register andthe simple binary counter. In the for-mer case, the clock line is common toevery bistable element whereas, in thelatter, the Q output from the first stagefeeds the clock input of the next stage,and so on.

On its own, the SISO type of shiftregister is only capable of providing adelay equivalent to the length of theshift register in clock pulses. Hence an8 -stage SISO shift register will, for ex-ample, impose a delay of eight clockpulses between serial data entering theregister and that leaving it.

Other types of shift register do,however, have a seemingly endlessvariety of applications arguably themost important of which involves theconversion of serial data to paralleldata and vice versa. In such cases thebasic SISO register arrangement mustbe modified so that parallel data access(input and/or output) is possible. One

C

1=11111111, ,11111.

4111C

K

411111.11111116

CK

K 0

SERIALDATA

OUTPUT

CLOCK

IPEmi.A]

Fig. 3.6. A 4 -bit SISO shift register using J -K bistables


obvious possibility is that of makingeach Q output of the SISO shiftregister available. Such an arrange-ment is shown in the serial-input/parallel-output (SIPO) register ofFig. 3.7. Here serial data is syn-chronously clocked into the registerand, after the requisite number of clockpulses (four in this particular case), theregister is completely loaded and thedata is then available in parallel formfrom the four Q outputs.

Another possibility is that of parallelloading the data into a shift register us-ing the PRESET and PRECLEAR inputsof the bistable elements. Data maythen be shifted out in serial form. Suchan arrangement is known as a parallel-input/serial-output (PISO) shiftregister, a simplified form of which isshown in Fig. 3.8. The data on theparallel inputs should not, of course, beallowed to affect the state of thebistable elements during the shifting

SERIAL DATAINPUT

Cr

CLUCK or

E 16050

SEQUENTIAL LOGICprocess and hence the PISO shiftregister must have additional logic tocontrol the parallel loading of data.Most, if not all, PISO shift registersalso provide a serial data input andthus can be also used for serial -to -parallel data conversion.

A further refinement is that ofproviding both parallel data input andparallel data output from the shiftregister. Such an arrangement isshown in Fig. 3.9 and is known asa parallel-input/parallel-output (PIPO)shift register. This arrangement, whichis sometimes also referred to as a

"universal shift register", is very similarto that of the PISO, the only differencebeing the addition of data output linesderived from the Q outputs of eachbistable stage.

We shall begin our practical in-vestigation of shift registers showinghow a simple SIPO arrangement canbe built using the four D -type bistables

PARALLEL DATA OUTPUT

Fig. 3.7. A 4 -bit SIPO shift register using D -type bistables

SERIALDATAINPUT

PRESET

r PREP. EAR

O

PRESET

0

PRE Clf A

PRESET

0

PRECL EAR

1PPP,

0

c.

VPARALLEL DATA INPUT

Fig. 3.8. A 4 -bit PISO shift register using D -type bistables

SERIALDATA

INPU'

of a 74175 quad data latch. The74175 was introduced last month andhence we will not repeat the pin -out orinternal logic schematic of the device.

SIPO SHIFT REGISTER USINGTHE 74175

The circuit diagram of a simple SIPOshift register based on the 74175 isshown in Fig. 3.10. It should be notedthat the clock input (pin -9) is commonto each D -type bistable. The active -lowclear input is taken to logic 1 and theserial data input (derived from pushbutton Si) is taken to the D input ofthe first bistable stage. The four I.e.d.indicators of the Logic Tutor are usedto monitor the state of the Q outputs.With the 74175 in socket C (and withpin -1 aligned with C1), make thefollowing connections on the LogicTutor:-CI to logic 1 (active low clear)C2 to D1

PARALLEL DATA OUTPUT

LPRESET PRESET

0

CLOCK

Ct

PRECLEAP

VPARALLEL DATA INPUT

Fig. 3.9. A 4 -bit PIPO shift register using D -type bistables

+5%, DI

16

02 D3 04

51 0 D 01-aD OJSERIAL DATA

INPUT CK CK CK CH

CLEAR CLEAR CLEAR CLEARO -8--rCLOCK

Ov

LOGIC 1

PE 61:41

Fig. 3.10. A SIPO shift register based on a 74175 quad data latch


SEQUENTIAL LOGICC4 to S1 (data input)C5 to C2C7 to D2C8 to OV (common)C9 to clockC10 to D3C12 to C7C13 to D10C15 to D4C16 to +5V (supply)

Outputs (indicated by D1 to D4) ofthe shift register should initially all bezero. With S1 providing a logic 0 datainput, the outputs should remain atzero as the logic 0 is effectively shiftedinto the register during subsequentclock cycles. Now wait for the clock togo low and then depress Si. Nothingshould happen until the clock next goeshigh, at which point D1 will becomeilluminated indicating that the logic 1

has been loaded into the first stage ofthe shift register. Now release Si toproduce a logic 0 input. On the nextrising clock edge D2 should becomeilluminated and D1 should become ex-tinguished. This shows that the logic 1has now shifted into the next stage ofthe shift register whilst the subsequentlogic 0 input has moved to replace theinitial logic 1 output of the first stage.The subsequent movement of the logic1 should be observed as it shifts rightthrough the register. Operation shouldconform to the timing diagram shownin Fig. 3.11.

(SI DEPRESSED]

CLOCK

DI

D2

D3

04

1PE141141

1 1_Fig. 3.11. Timing diagram for the shiftregister of Fig. 3.10

It should be noted that, had we stop-ped the clock after four complete clockcycles, we would have producedparallel output data on the four Q out-put lines that was equivalent to theserial data input (i.e. 1000).

It is now suggested that readersrepeat the foregoing exercise holdingSi down for the first four clock cycles.A logic 1 will then be seen to load intothe register, apparently filling the

register from left to right. After thefourth clock cycle, S1 should then bereleased and the register will empty asthe logic 1's are successively replacedwith logic O's. After observing thisprocess for one or two further periodsof four clock cycles, readers should bereasonably familiar with the operationof this simple form of 4 -bit SIPO shiftregister.

It should be noted that the outputsof the 74175 shift register can besimultaneously set to logic 0 by takingthe active -low clear input to logic 0.Readers may wish to confirm that thisis so.

CLOCK

+5V

14

K

CLEAR

01

OV

01

CK

L AR

counter using a 74175 is shown in Fig.3.12, the Q output of the last stage isfed back to the D input of the firststage. Since all four Q outputs start atzero, a logic 1 is fed to the D input andthe first stage changes state as soon asthe clock input goes high. The registerthus first fills with logic 1's but, whenthe fifth clock pulse arrives the logic .0present on the Q output of the fourthstage is transferred into the first stageand hence the register then begins tofill with logic 0's. The timing diagramfor the four stage walking ring counteris shown in Fig. 3.13.

To convert the arrangement used in

02 03 04

17

010 13 j

:K CK

CLEAR CLEAR

LOGIC 1

(P(1110741

Fig. 3.12. A 4 -bit walking ring counter based on a 74175 quad data latch

CLOCK

DI J

D1

03

04

(pEmoGi

Fig. 3.13. Timing diagram for thewalking ring counter of Fig. 3.12

THE WALKING RING COUNTERWe shall now digress slightly from

our main theme of shift registers totake a look at an interesting applicationof the SIPO shift register. If the com-plementary output from the last stageof a shift register is fed back to the in-put of the first stage, we can produce acounter which has twice as manystates in its counting sequence as thereare stages in the shift register. Such anarrangement is known as a "walkingring counter" or "Johnson counter". Inthis type of counter, as compared witha conventional binary counter, only onestage changes state at a time.

A practical four stage walking ring

Fig. 3.10 to that in Fig. 3.12 it is onlynecessary to disconnect the link fromC4 to S1 and reconnect C4 to C14.When power is applied the register willsuccessively fill with 1's and then 0's,taking eight clock cycles for the com-plete sequence.

THE 74195The 74195 is a versatile 4 -bit

parallel access PIPO shift register. Thedevice is useful in a wide variety ofshifting, counting and storage applica-tions. The 74195 is particularly suitedto high speed serial -to -parallel andparallel -to -serial data conversion. Thedevice is housed in a 16 -pin d.i.l.package, the pin connections of whichare shown in Fig. 3.14. The internallogic of the device is shown in Fig.3.15.

The 74195 has two distinct modesof operation: shift right and parallelload. These modes are selected bymeans of a SHIFT LOAD input. In theshift mode the SHIFT LOAD control in-put is taken to logic 1 and serial dataenters the first bistable via the J and Kinputs when the SHIFT/LOAD input isat logic 1. Data is then shifted throughthe register one bit (in the direction QO


SEQUENTIAL LOGICCLEAR +5V

OV

(P116150)

03

CLOCK

SHIFT/LOAO

Fig. 3.14. Pin connections for the74195

SHIFT/LOAD

SERIAL DATA INPUTFROM SI

C.LEAK INPUTFROM S3

SHIFT /LOAD INPUTFROM 54

(11E16110j

DATA OUTPUTSA

( \01 02 03 04

151 11 13i 12i

0 a, cn 01

CLEAR

S11 I FT/1.0.60

DO

7 4 1 9 5

DI

CLOCK

Di 03

+5v

16

LOGIC I

DATA INPUTS

Ov

Fig. 3.16. Parallel 4 -bit PI PO shift register using the 74195

CLOCK (CiDo

CLEAR (I' *0

(PEIII 60)

Q1 Q2 03) following eachlow -to -high clock transition.

In the parallel load mode theSHIFT/LOAD control input is taken tologic 0 and data on the four paralleldata inputs (DO to D3) is transferred tothe respective bistable outputs (QO to03) at the next low -to -high clock tran-sition.

Shift left operation (Q3 Q2 -> Q1-> Q0) can also be achieved by tyingthe On outputs to the Dn__ -1 inputs (i.e.03 to D2, Q2 to D1, Q1 to DO) andholding the SHIFT/LOAD control inputat logic 0.

It should be noted that all paralleland serial data transfers are syn-chronous and occur after each positive

--011I> C P

5 0

Fig. 3.15. Internal logic of the 74195

clock edge is received. Furthermore, byvirtue of the edge triggered charac-teristic, there is no restriction on theactivity on the J, K, D and SHIFT/LOADinputs other than that associated withset-up and release.

The 74195 also has an active lowclear input which sets all Q outputs lowindependent of any other input condi-tion. It should be noted that, since theclear and clock inputs are internallygated, to avoid false clocking a low -to -high transition on the clear inputshould only be permitted during theperiod for which the clock is low.

The 74195 should be inserted intosocket B of the Logic Tutor ensuring, asusual, that pin -1 aligns with B1. The

RD

-OS> CP

(13

02

following connectionsmade:-B1 to S3B2 to B3B3 to S1B4 to logic 1B5 to logic 0B6 to logic 1B7 to logic 088 to OVB9 to S4610 to clock612 to D4613 to D3614 to D2615 to D1B16 to +5V(A total of 15 links)

CLOCK

03

should then be

(active low clear)

(serial data input)(parallel data input DO)(parallel data input D1)(parallel data input D2)(parallel data input D3)(common)(shift/load control)(clock input)(D4 shows state of Q3)(D3 shows state of 02)(D2 shows state of Q1)(D1 shows state of 00)(supply)


SEQUENTIAL LOGIC

LOGIC

LCLEAR INPUTFROM 53

9

LOGIC 0

Qo

7 4 1 9 5

SN I F T, rats

00

a, 03

Di

eI

CLOCK

SERIAL DATA INPUTFROM SI to EleiiG)

Fig. 3.17. Arrangement used to permit left shifting of the 74195 (SIPO model)

The Logic Tutor arrangement con-forms to the circuit shown in Fig. 3.16.The shift register should be tested byfirst adjusting S3 to produce a logic 0input on the clear line. All I.e.d. in-dicators should immediately becomeextinguished as all the Q outputs golow. Note also that Si and S4 have noeffect whilst the clear line is held low.Now adjust S4 to produce a logic 1 onthe SHIFT/LOAD input and thenoperate S3 to generate a logic 1 on theclear line. The register will now com-mence loading from the serial inputbut, since S1 is producing logic 0,there will be no change in any of the Qoutputs and the I.e.d. indicators willremain extinguished.

Now wait for the clock to go low (D9extinguished) and depress Si. Thisplaces a logic 1 on the serial input.Notice how, as the clock next goeshigh, this logic 1 is transferred into thefirst stage of the shift register and D1becomes illuminated as the firstbistable changes state and QO goeshigh. Now release 51 and notice how alogic 0 loads into the first stage on thenext rising clock edge whilst theprevious logic 0 is transferred into thenext stage. Readers may now like toexperiment with serial loading of theshift register, inputting data manuallyby means of 51.

Readers should also confirm that S3can be used to clear the register on thenext rising clock transition after S3 hasbeen set to produce a logic 0.

The parallel load mode can be selec-ted by adjusting S4 to produce a logic0 input, checking first that the clear in-put is at logic 1. On the next risingclock transition the data (1010) thathas been hard -wired on the data inputswill be transferred to the Q outputs.The data remains static as long as the

SHIFT/ECAD control input is held lowbut as soon as S4 is set to produce alogic 1 normal shift right operation isrestored.

SHIFT LEFT OPERATIONIn order to obtain shift left operation,

the 74195 should be left in socket Band the links re -arranged as follows: -

B1 (active low clear)B2B3B4B5B6B7 (serial data input)B8 (common)B9 to logic 0B 10 to clock (clock input)B12 to D4 (D4 shows state of 03)B13 to D3 (D3 shows state of Q2)B14 to D2 (D2 shows state of Q1)B15 to D1 I D1 shows state of Q0/B16 to +5V (supply)

to S3to B3to logic 1to B14to B13to B12to Sito OV

(A total of 15 links)

This arrangement conforms to thecircuit diagram shown in Fig. 3.17.Serial data can be fed into the registerby means of 51 and cleared by meansof S3 (a logic 0 being required to clearthe register). Now wait for the clock togo low and then press Si to generate alogic 1. D4 will become illuminatedwhen the next rising clock edge occursand data will then be subsequentlytransferred from Q3 to Q2 (D4 to D3)on the next rising clock edge, and soon. To clear the register S3 should beadjusted for logic 0 and all 0 outputswill then go low regardless of the stateof the clock.

NEXT MONTH: Pseudo randomnumbers and universal shiftregisters

leactatori thepacks

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ALARM CONTR I LUNITCA 1250

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PE MONO -STEREO ECHO-REVERB (SEP84) 200ms echo, lengthyreverb, multi -tracking kit as published BLK box. SET 118 £55.66

PANEL CONTROLLED SUPERKITSBASS BOOST. Increases volume of lower octavesBLOW BOX. Voice operated VCF & VCA for fascinating effectsCHORUS UNIT. A solo voice or instrument sounds like more,COMPRESSOR. Limos & levels maximum signal strengthDIGITAL TO ANALOGUE 8 -bit binary to Lin & Log voltageENVELOPE SHAPER. Note triggered ADSR unit with VCAEQUALISER. Variable combinations of Low. Mid, Top & NotchEQUALISER: 10 Channels fully variableFADER: Voice operated with 5 response controlsFILTER: For voice bandwidth enhancement over backgroundRANGER: Fascinating music effects plus phasingFREQUENCY CHANGER Tunable note & waveform modifierFREQUENCY DOUBLER. Gurtar octave raiser & tone changerFREQUENCY GENERATOR Muhrwaveforrn. 0 41-0-470KHzFUNKY-WOBULO Modulates a singing voiceRIE: Smooth distortion, retains attack & decayGUITAR OVERDRIVE Heavy fun with selectable qualitiesGUITAR SUSTAIN: Extends note decay time, with noise gateGUITAR TO SYNTH INTERFACE: With voltage & trig outputsHAND CLAPPER: Auto & manual variable clap effectsHEADPHONE AMP: 2 watts into phones or speaker. vanableHUM CUT: Tunable marts hum cut NterJABBERVOX: Voice disguiser with reverb & tremoloMETRONOME: Wrth audio output & visual beat & downbeatMIC PRE -AMP: Venable again 8 switched tone responseMIXERS: Several in catalogueMOCK STEREO Splits mono signal into stereo simulationMULTIPROCESSOR- Rog, Rvb, Faze, Fun, Wah, Trem, SibMULTIWAVEFORM V03: Log voltage to frequency, switchableMUSIC MODULO. B variable tremolo & weh guitar effectsMUSICAL CALL SIGN. Programmed call sign generatorNOISE GATE Reduces tape & system noisePHASER ISIMPLEI Auto & manual rate & depth controlsREVERB: (SIMPLE) Mono/stereo, variable depth & delayRHYTHM GENERATOR: Computer driven, 9 drum effectsRHYTHM GENERATOR. 15 pre-programmed rhythms. 9 effects

CODE STD BOX BLK BOXSET 1398 (146 f1146SET 214 £2431 12133SET 162 131.40 £3490SET 133 £1016 £1316SET 176 r/396 126.96SET 174 07.15 f20.65SET 217 f2233 12513SET 134 f37.83 f41.113SET 167 £1421 f1721SET 142 £973 £1221SET 153 f72.74 0124SET 172 0446 07.96SET 913 E9.110 f12/0SET 128 119.04 E/254SET 149 £12.40 £15.40SET 91 E10.57 £1357SET 56 119.73SET 222 f22/1 f25.31SET 173 /3217 0637SET 197 f2269 f25.69SET 156M £1293 f15.53SET 141 £1126 0426SET 150 ED14 f37.34SET 143 113.81 E1621SET 147 £7.13 f 10 13

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PHONOSONICS, DEPT PE4D, 8 FINUCANE DRIVE, ORPINGTON, KENT, BR5 4ED.Tel: Orpington 37821 (STD 0689, London 66), Mon -Fri 10-7.


RING MODULATORJOHN M.H.BECHER PART 2

AT this point it is worthwhile looking at some oscillogramsof simple waveform combinations, produced with the

unit described in Part 1. Table 1 shows a schematic repre-sentation of the control settings used.

Fig. 57 54 56 55 53 52 VR1 VR5 VR4 VR6 51

3a ii i ix -.- X \ / x -.-

313 ii i i X - X Nib I x \3c ii t i X - X \ \ X if4 i i 1ji X ...- X \ \ X -..-

5ct i 3 i X X \X \X X X

5b i i i X X \X \X X X

Sc 3 i X X \X \X x x

5d ii i X X \X \X X X

6a it i i X .....- X \ / X -*-

61) it i i X -..- X \ / X \6c it ti X ....-- X \ \ X fe

6d if i i x fx \ / X -.-

6e i t i x -...-- X / / x -.-6f it ii x -...- x / / x \6g it $ i X ....- X / / X ,,,

6h if i i x fx / /X -...-

61 i t ii X - X \ / X

6j if i i X ...- X \ / X \6k it ti X .....- X \ / X ,1

61 itiiX_ .....- X \ / X -...

7° i t i x X\X X X X X

7b i f i X x \ x X X x x

7c i f i x x \ X X X X X

7d i l 3 x x N.,,x x x x x

Pi (MOP.' Table 1. Switch settings

WAVEFORM OSCILLOGRAMSIn Fig. 3, a triangle wave of 3kHz is being used as the

carrier signal going to one input, though its actualwaveshape is irrelevant at this moment. This is beingmodulated by a second waveform, on the other input, at amuch lower frequency of about 1 50Hz. The two frequenciesshown are widely diverse for illustrative convenience but asimilar principle applies to other spacings. The modulatingwaveform is shown in the upper trace, and the compositeoutput in the lower, with the higher frequency inside the'bubble' envelope. It will be immediately apparent that theunit in the mode selected has doubled the frequency of the

sine and triangle modulators to 300Hz. Although the rampmodulator appears not to be doubled, close examination ofthe scope reveals that each diamond 'bubble' is in fact two,with a very fast change at the centre, coinciding with theramp trailing edge. The effect of modulating by square waveis not shown as the edges are too fast to produce a readilyvisible effect, though it can just be discerned audibly. Whatis not apparent in the oscillogram is that the carrier withinthe 'bubble' now consists of 3kHz-300Hz = 2700Hz, and3kHz + 300Hz = 3300Hz and on the oscilloscope the carrierin the alternate 'bubbles' is seen to be phase shifted by180°, with a slight vibrato on its edges. Although the full har-monic content of the product signal is not seen in the oscillo-grams, the differentials can be heard clearly through anamplifier. Using two signal generators with one supplying afixed frequency, the other is slowly swept across the audiospectrum. When the sweep frequency is rising but below thefixed one, two notes are heard at the output, one rising, theother falling. Close to frequency equality the lower notebecomes progressively deeper until at the balance point thelow frequency is totally cancelled and only a doubling of thefundamental is heard. As the sweep progresses upwards sotwo frequencies are again heard, but each rising, one moreslowly than the other. The very low frequency heard near thebalance point is clearly shown in Fig. 4. The high frequencywithin the shape is at twice the original. This then is the sumof the two, and the difference. The frequency doubling canalso be verified without a scope by taking both the finalsignal and one of the originals into a mixer and alternatingthe pan control between both, whereupon the octave dif-ferential will be heard. The same can be repeated when alow frequency note modulates a high frequency one. If thehigh frequency is out of audio range, the low frequencymodulator will be heard to be one octave lower than thebass content of the output.

FREQUENCY COUBLINGFig. 5 shows the effect of deliberately feeding the same

signal in to both the modulating and carrier inputs. Fromthese photos it will be clear that frequency doubling occurswith each of the four different, original waveforms, but alsothat the output does not have the shape of the original. Inthe photographs of the ramp and squarewaves, both originalwaveforms have been intentionally slightly distorted so thatthe very fast intermediate peaks are more clearly seen. In allcases the frequency doubled waveform takes on a much

23Practical Electronics December 1984

MUSIC PROJECTspikier shape, even for the sine wave. Indeed in other fre-quency doubling methods known to the author, a similardegree of sharpening is experienced. Any frequency doubledsignal is thus bound to be a harsher note one octave higher,especially so with the ramp, and from an audio position, fre-quency doubling of a square wave will only produce objec-tionable clicks as the mark -space ratio is so wide. Doublingstill takes on a harsher sound when introducing a time delay,which produces a phase shift, to one of two identical signals.(Interesting sounds are produced though, if the completering modulator is preceded or followed by echo, or reverbunits). The doubling effectiveness is also subject to the com-plexity of the original signal. For simple monotonic frequen-cies, the effect is quite usable. However, if used when thesignal is complex, like trying to double the pitch of a chord orof multiple instruments, the effect is cacophony. Speech tootakes on extremely odd noises if octave raising in a ringmodulator is attempted. For true frequency doubling withwaveform retention, much more complex equipment isneeded.

and interesting effects. When using a low frequency simplewaveform with a higher frequency source such as speech ormusic, tremolo can be given to the music, and speech can bemade to sound robot-like. In creating Dalek voices, one ofthe essentials is to modulate the voice at a low frequency,though other factors are involved in the production of theauthentic Dalek sound. Tremolo and vibrato modulation areboth effects that when used with discretion can greatlyenhance the interest of many sounds.

For music the speed of modulation is at its most satisfyingif the rate is in the region of 6.5Hz. In an analysis someyears ago of the modulation given by violin players andopera singers, there was remarkable consistency between allof them, modulating their pitch within about 1 cycle of6.5Hz. The author is involved in many types of effects unitsand finds that when testing rhythmic sources the mostsatisfying, and eventually the most hypnotic rates, are thosewithin this same range. It is an interesting speculation thatthere might be a correlation between this frequency and thebrain wave frequencies associated with Alpha and Theta

Fig. 3b. Triangle modulator Fig. 3c. Rising -ramp modulatorFig. 3a. Sine -wave modulator

Fig. 3 (above). Triangle wave 3kHz, used as the carrier. The upper trace is the modulating waveform and thelower, the composite output

- i

-4111

Fig. 4 (above). High frequencymodulator, with modulatingcarrier at almost same frequencyshowing effective slow -beat fre-quency

Fig. 5 (right). Effects of using thesame signal in both modulatiand carrier inputs

1111111pl -10*111

AAALAALIII1111111011111/MplIA

ISIAIlliallAllailialFig. 5a. Sine -wave Fig. 5b. Triangle -wave

1..1.111"11° Minirlit1111.11111111.

Fig. 5d. Square -waveFig. Sc. Rising ramp -wave

TRACKED RING MODULATINGAnother option available is to use the inputs with two ac-

curately controlled waveforms of different frequencies. Themost usual source of these is two oscillators of a syn-thesiser, with the frequencies tracking identically, and exac-tly spaced so that the correct harmonic relationship is thesame throughout the range. The complex chording structureis then simpler to achieve. Referring back to the frequencyexample earlier, 'G' at 396Hz is 1.5 times the frequency of'C' at 264Hz. Similar relationships between two originalsignals will produce other equivalent composites, though notnecessarily of a concordant nature.

FIXED CARRIERIt is not necessary for the carrier frequency to be shifting

in sympathy with the modulator and in many cases it is bet-ter to keep the carrier static for the production of some weird

rhythms. Theta rhythms are those with a frequency of about4Hz to 7Hz, and which appear to be connected with mood.Alpha rhythms occur between 8Hz and 12Hz and occurmost often in relaxed meditation. It is possibly no coin-cidence that the most satisfying tremolo and vibrato rates liebetween the two.

Proper vibrato cannot be readily produced by a ringmodulator as it involves true frequency shifting without ad-ditional tone generation, but tremolo with a trace of vibratois easily obtained through low frequency amplitude modula-tion around 6.5Hz. Voice modulation for Dalek-type produc-tion lies in the range of about 15Hz to 30Hz. At frequencieslower than this the modulation tends to be lost amongst theconsonant peaks of speech as the vowels are usually muchshorter than in singing. As the modulation rate increasesbetween 400Hz and 1 kHz so a metallic quality is acquiredby the voice, becoming more pronounced but less intelligible


as the carrier goes beyond 1 kHz. If music is modulated witha fixed carrier in tl higher frequency ranges extremely un-canny effects are produced. This is particularly true ofcarriers between 3kHz and 6kHz, when music can take onpn almost nightmarish quality. When working on theprototype, the author found that 10 or 15 minutes of this up-per frequency modulation was all that was tolerable at onetime. Using low frequency ramps and squarewaves tomodulate complex higher frequency sounds usually results inobjectionable clicks. However, these clicks can be made useof if the carrier is a single high frequency or white noisesource. With the former 'pinging' sounds can be producedand with the white noise, a variety of steam engine effectscan be created. Using a white noise generator in conjunctionwith an external pulse source can also produce sounds akinto gun shots.

Fig. 6 shows the effect of VR5 in the d.c. control mode atthree settings when a high frequency intermodulates with a

low frequency. As will be seen some quite distinctivewaveform shapes appear, all of which have their own uniqueeffect upon the final output quality. When bypassing the ALCcontrol a 180° phase change occurs and the rampwaveform changes to the opposite slope introducing a fifthset of variations. Full modulation in the d.c. mode is inten-tionally inhibited as the ,ncreased level required would in-herently raise the carrier breakthrough level. Full carriermodulation is of course provided when S4 is in the a.c.mode. When switching between both modes, the nature ofthe circuitry produces a cross -fade effect between them.This is due to the relative d.c. levels applied to C21 changing,at a rate determined by the biasing resistors and provides asmooth changeover. A similar effect is produced when S7 isswitched in and out. Fig. 7 shows the effect of using thesame signal as both modulator and carrier in the d.c. mode.Frequency doubling still occurs but with a changed am-plitude relationship.

Fig. 6. Various effects in the d.c. control mode with a high frequency intermodulating with a low frequency

111,1111111rati_____i_

1P411111141111

Fig. 6c. Rising ramp -wave

1

Ibild11111111111111Fig. 6a. Sine-wave Fig. 6b. Triangle -wave

-11111111'11411111111111111111Fig. 6f. Triangle -waveFig. 6e. Sine

._

-waveFig. 6d. Square -wave

116**WIFig. 6g. Falling ramp -wave

IMIIIIIIIIIM_ l

Fig. 6h. Square

1 1

-wave

aillitillihdFig. 6i. Sine -wave

i

Fig. 6k. Rising ramp -wave11116AllifilidallAt

Fig. 6j. Triangle -wave111111- ' MI I

Fig. 61. Square -wave

Fig. 7c. Rising ramp -waveFig. 7a. Sine -wave Fig. 7b. Triangle -wave

Fig. 7. Effects of using the same signal for modulator and carrier in the d.c. mode


ASSEMBLYThe p.c.b. layout is shown in Fig. 8

and the wiring diagram in Fig. 10. It iseasiest to assemble the printed circuitboard in order of component size, leav-ing the insertion of i.c.s into theirsockets until last. The short wire linkson the p.c.b. can be shaped fromresistor offcut leads. It also helps withsubsequent checking if the compo-nents are mounted with their identitiesreadily visible. Diodes, electrolyticcapacitors and i.c.s must only be inser-ted the correct way round as shown. Atthe very least the circuit will not workproperly if this is ignored, at worstcomponents could suffer extinction.Wiring to the controls must be tackledneatly and methodically to avoid theunit looking like a pig's nest! Make theconnections between the panel com-ponents first, then wire up to the p.c.b.,keeping all wires coming round theedges of the p.c.b.-coming over itmakes it messy. They should bereasonably short, but long enough toenable the p.c.b. to be turned over fortrack side examination. Try to get itright first time as the box space is tightand it is tricky to manoeuvre the p.c.b.between the various panel parts. Tick-ing off components and wires as theyare connected minimises errors, asdoes closely studying solder joints witha magnifying glass. These should lookround and shiny, covering all round thesolder pad on the p.c.b. If they lookdull, crazed or daylight can be seenthrough them, then they are not goodjoints. Neither is one that has the solderspread across adjacent tracks. Theauthor sometimes sees home assem-bled projects returned for servicing,and in practically all cases the onlyreason for malfunction is that improperattention has been given to soldering.It is very rare for modern componentsto be the cause of any misbehaviour.

SETTING UPAlignment of the three presets is

quite straightforward and nospecialised equipment is needed. First,VR1 min, VR2 and 3 fully right, VR4midway, VR5 min, VR6 max, VR7midway, S1 position 1 (sinewave), S2position 1 (internal VCO), S3 up (gateoff), S4 off (d.c. coupled), S5 up (slowVCO), S6 up (ALC bypass), S7 up (R -mod override). If a signal generator isnot available it is preferable to use apre-recorded speech or music trackfrom a cassette recorder or similar dur-ing testing. Plug this in to the high in-put jack socket, and the output jacksocket into the main amplifier. Checkthat the cassette signal reaches theamplifier, if necessary increasing VR 1

Fig. 8. The p.c.b. layout of the Ring Modulator

Fig. 9. The component layout of the Ring Modulator

17 18 19 20

01R41

CIO

LEENC

U 0 0 0 U

MEM

EMIR1 HIP

C15 -4

0R2

MIERILEM

4-

TT

10 11 12

IEMI R

C9 4.4 R 37 HO

C 11IP-{ R 313

I1H R20 1-0

1 I 1

9

Co

3

Ai cu ('a

111-t

+

C 2R3 4 I-40 _

044 R 3 3 1... II .4 , :2 1_. ."IR2F...r, C 13 4/ .4 ' ''1. voec F..oo$.4,2 0


r-

L

52:- 1 INT VCO2 DOUBLING3 EXTERNAL4 INT & EX T

FRONT PANEL

22 26

r-L ,---1-1--f-77=. =

boS7 a S4

V14 20 21 23

SOLDEREDTO POTBODY

5

- ---1

10 6 11 12 9

Fig. 10. Wiring diagram of the Ring Modulator

to a suitable level without distortion. Switch on S7 and asimilar output level should remain. Switch on S4 to a.c.mode whereupon the sound should diminish. Slowly adjustVR3 around its midway point until the minimum level isheard. Bringing up VR5 to maximum, a slow modulation ofthe sound should be heard. Varying VR4 the modulation ratewill change. Switching on S5 the rate will increase dramati-cally, and the quality of the audio output change with it. Re-move audio source from the input leaving only the carriersignal. Switch S1 through its four settings and note thatchanges in carrier quality are evident. The carrier level willalso change with the settings of S 1 . With S6 switched on toALC mode the variations will be less pronounced and on anamplifier VU meter, the levels will appear practically the same.Maximise VR5 and carefully adjust VR2 around its midwaypoint until carrier breakthrough is as low as possible. Againapply audio source from cassette. Switching on S7, carriermodulation will cease leaving only the original sound. Nowalign VR7 adjusting it around its midway point until minimumwaveform distortion is heard at higher amplitudes. If no dif-ference is noticeable, leave midway and ignore, though thecorrect setting will be obvious on an oscilloscope if a trianglewaveform from a signal generator is used. Finally againremove the cassette, switch off S7, set VR5 max, VR4 andS5 set for maximum frequency. Increase amplifier volumeuntil carrier breakthrough is audible. Switching on S3 thenoise gate should come into operation and close down theoutput, eliminating all but the very smallest trace of crosstalkwithin IC4. Experiment with all the controls and switcheswith various types of speech and music inputs until familiarwith the operation of the unit. If making minute adjustmentsto VR2 and VR3 allow the unit to be switched on first for afew minutes in case of a slight temperature sensitivity,although this was not apparent in the author's model.

The basic functions of a ring modulator have been covered

OUT ot; ,,Jr.

16 25

04 Si

15

51:- 1 SINE2 TRIANGLE3 RAMP4 SQUARE

III MCC $N tO lo N.

Photographs illustrating the internal and externalassembly of the complete unit

in the introduction. The use of the unit is otherwise subjectonly to the imagination of the user. It will soon becomefamiliar knowledge which settings are best for which type ofinput, whether for trains or tremolo, musical effects, or formodifying speech for robot and Dalek type vocalisations. *


TERMS OF BUSINESS

* All prices exclude V A T and carnage Please add Goods incorrectly ordered cannot be accepted forcarriage to order total before adding V A T replacement without our prior agreement Due to

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Printers, Monitors. Disc drives. etc. £4.50 * We will issue a full immediate refund, if requested.

Strictly cash with order or credit card (Access or VISA) for out of stock itemsonly * All items carry full manufacturers warrantyDelivery is normally from stock but please allow up a A VAT receipt will be supplied with all order,to 28 days

* Prices quoted are correct at the time of going to

HI TECH COMPONENTS,

Any query or complaint regarding an order should press but we reserve the right to effect changesbe made in writing within 7 days of receipt of the without prior noticeorder No telephone queries will be entertained

6502 8086 MEMORIES - EPROM 75173N 144 F.D. CONTROLLERS FAIRCHILD 74HC251N 1.03 741522 0.25 4033 2.40 4078 025FAMILY FAMILY 75174 2 82 74HC253N 1.03 7415221 1 08 4034 1.00 4081 0406502 3.506502A 4 956520 2.25

8086 29.508088-2 22.508216 0.75

.2` 32 30065 4 952532-450ns 3 95

2564,,,.399.2s 6 95"-1.-43..,0.8675,75

1 %

75182 0507518375t88

0.50

FD17718FD1791FD1791-02

35.0030.0015.5011-00

FAST74100K 0.60741048C 0.60741088C 0.65

74HC257N 1.037414(266N 0.9274HC2736 2.2174HC276 0.60

741.5240741524174152427415243

1.401.401.361.36

4035 0.544040 0.654041 0.364042 0.76

4082408540864093

0.250.660.400.326520A 2.45 82374-5 23.50

.3,n271,6-4.,50ns 3 3.27163 RAIL 75189 FD1 793 18.40 741109PC 0.65 74HC280N 3.26 74L5244 1.40 4043 064 4099 0.506522 340 82515 7.50 74 0.22 FD1793-02 11,00 74111PC 0.52 741-4( 32 040 74L5245 1.95 4044 0.62 4502 0.8665224 4 45

6532 5.458253 5 7.508255A 5 7.00

,95`....,'-',...3,r,_.'"s''3,"".-"'s 4 452764.200m

7754545571P

75453/3p 0220.29

FDI 795 25.0021.00

74F138PC 0.52741138PC 1.26

74HC 3736 2 40z4HC3741-12 40

74152487415249

1.161.16

4045 2.004046 0.77

45074508

0.470966532A 5.95

6551 5 958259A 6.608272 35.00

7 9577,64-7,,,,,,,.513"S 5 15

754548P754686 0 22 "1691WD2143

14.0012.00

741139PC 1.26741151 1.26

74H(393N 1 787411(4002 0.64

74L52517415253

0.780.78

4047 aso4048 0.40

45104511

0.680.6982844 9.50

80(86 46.654 IV I. 4' .3,n4. 6 4.75

27C84 -250^s 1°9575491N

031754926 0.41 DATA CONVERTERS741153 1.26741157 1.30

74HC4017 1.167411(4020 1 46

74L525774L5258

0.780.78

4049 0.504050 0.49

45124514

0.401.766800

FAMILY

80(88 46.6582(52 15.68

27C64- 300ns 450,1n

"`",27128.25°in ''43.1015 3.50AS 3-1270 43.40

26425E 8ZN4251-8

3.768.00

741158 1.17741161 2.34

74H(4024 1 207411(4040 1 46

7415259741526

1.770.30

4051 0 524052 048

45154516

1840 6882(54 19.04 27128. 300ns 16 00 AS 3-8910 6.40 2N426E-8 110 74F164 1.68 74H14060 1 46 7415261 2.60 4053 0.66 4518 0.4082(554212.98 AY -5 3600 084 ZN427E -8 6.68 74F175 1.82 74HC40 IS 064 7415266 0.35 4054 1.30 45t9 0.25t"800 `-'n' B2(594 1522 MEMORIES RAM

DP8304 4.50 ZN4271-8 12.50 741181 3.90 74HC42N 090 741527 0.25 4055 072 4520 0.96,rn.,0802 ,'. 82(82 6.26 4116 150ns 1 28 L203 0.99 ZN428E-8 5.10 741189 5.10 74H(4511 2 51 7415273 1.35 4060 0.68 4521 1.324w..." f".,`: 82C844 8.94 4116 200ns 1 20 11398 3.80 ZN4281-8 9.70 741190 3.20 74HC4514 3 76 7415279 0.77 4063 0.60 4522 0.84"''' ' " 82(88 16 80 4164-150ns 4 45 LM301AN 030 Z64298-8 1.60 74F191 3.20 74FIC4538 2 36 741528 0.25 4066 0.50 4526 0.526809P 6 25 4416.200ns 4.70 1M308AN 0.94 ZN4320-10 20.79 741194 1.68 74HC4543 3.04 7415283 1.00 4068 0.25 4527 0.526810 1 70Z80 4532-200ns 2 45 1M308N 0.56 Z6432E-10 1300 74120PC 0.52 741-K51N 0.64 7415290 0.86 4069 040 4528 0.486821 1 70 4564-1SOns 4.45 LM311N 0.60 Z6433(1-10 25.00 741240 3.16 74HC533N 240 7415293 0.86 4070 0.40 4532 0686840 3 70

62A5 6 45

FAMILY 8118.100ns 1 95 LM317MT 0.80 ZN434 0.98 741241 2.42 74HC534N 2 40 741530 0.25 4071 0.40 4541 0.826850 1 70 780.4(Pu 2.99 81256 15Ons 25 00 3M3171 1 06 ZN435 4.38 741243 2.80 7411(5896 1 72 741532 0.25 4072 0.40 4543 0606862 3 75 Z8OACTC 2.99 13416-200ns 6.00 LM319N 3.30 ZN436E 1.26 741244 2.96 74HCS8N 064 741533 0.30 4073 0.40 4553 2406875 4 9568800 4 30

Z8OADMA 7.952804810 2 99

8416-LP-200ns 6.408417-200ns 6 00

LM324N 0.50115/1337T 1.20

ZN440ZN441

550046.80

741245 6.08741251 1.26

74HC595N 1 8474HC597N 1 72

74153657415366

0.550.55

4075 0.464076 0.48

45554556

0.48044

68809 9 95 2804510-0 7.95 8417.1P 200ns 640 1M339 0.48 ZN447 280 741253 1.26 74HC 73N 084 7415367 0.55 4077 0.40 4585 04868810 1 88 2804510 1 7.95

MEMORIES RAM1M339N 0A8 I64486 6.66 741257 1.26 74HC 74N 084 7415368 0.55Z804510-7 7 95 - LM348N 0.64 ZN4481 12A8 741258 1.34 74HC75N 0 92 741537 0.25 CRYSTALS6868804021 63 6070

7.808CPU 5 95 *ZERO POWER ZKXB LM3SOT 3 12 ZN449 2.72 741280 1.74 741-4C 76N 064 7415373 1.50 411 18 1MHz 4 5068850 158 ZBOBCTC 55'9 CMOS* LM358N 0.60 ZNA1 341 22.50 741283 1.74 741-4(856 2.02 7415374 1.50 Al 24 1 008MHz 400681354 7.95 Z806P10 5.95 LM3900 0.68 Z64.7341 940 74132PC 0.52 746(866 080 7415375 0.75 Al 1 34 1 8432MHz 3.5078013510-0 9.95/808510.1 9.95Z8013510-2 9.95280510 0 6.00Z80510-1 600

MK48Z02B-15Ons 00MK413202B-200ns 24 00MK48/0213-250ns 23.00

BIPOLAR PROMS

LM393N 0.481M725CN 3.00741CP 0.161M747CN 0.601.44748CN 0.30

VOLTAGE REF.ZN404IN423

0.500.98

1.26761353 1.26741373 3.1674F374 3.1674F 379 1.83

74600046 0 80

Try_0.25

741501 0.25

741537774153787415370

'7415387415386

1.501.221.500.250.50

416A 2 4576MHz4120814MHZ

411432A 6MH7

A04 8MHz

4169A 3 6864MHz

2001 251.701.252.00280510.2 600 18P185030N 1 54 41(1413P 0.80 ZN458 0.92 741381 6.62

741502 025 7415390 1.10 A1734 9 8304MHz 2.75TBP1854030 1 38 MC1416 0.80 IN4584 0.92 74F 382 4.22 25 7415393 1.10 4181A 19 6608MH7 2.506805 FAMILY41(1468052P 12.6041(146818P 7 20MC146823P 610

18P245106 2 06TBP2454IN 6 68713P24581N 5 501E112454 10N 1 40

MC14411 10.10MC14412 14 20MC1458CPI 0 35M(14951 6.30

ZN458BZNREF 025ZNREF 040ZNREF 050

1.121.901.901.90

74f 398 3.16741399 2.70741521 2.76741533 3.16

741504 0 25741508 0.251741509 0.25

741540741542741547

741548

0 250.851.00

1°°

DIL SKTS TIN. icor

MC68705KT3 75.00 TBP245441N 4 40 MC1496P 0.70 ZNREF 062 1.90 741534 3.16741510 0 25 741549 11)° 07070802 8 PIN 0.07 0.05

MC68705R31 40 00 1BP28122N 3 10 MC1723P 0.40 /6811 100 3.05 741537 6.02 .,,, '-'1')" 741551 0.25 07071402 14 PIN 0.09 0.07

MC68705U31 38.00 TEIP281422N 4 147882851261119 00

MC32424 6.30M(3302P

0-48

741538 4.384.38 ' --

74LS11 0.25 741554741555

0.250.25

07071602 16 PIN 0.0907071802 18 PIN 0.15

0.07010

TBP28542N 4 so m(33404' 2.36BUFFERS

741648C 0.52 7415112 0.547415670 2.30 07072002 20 PiN 019 01468000 FAMILY

MC 6800%10 3. '-'.TBP213546N 4 SOTBP28S86N 500

MC3357P 100.

MC 3423P1. 0.81

81L596131L597

1.101.10

0.5874,86,,, 0.777415113 0 427415114 0.44

741573741574

0.300.35

07072202 22 PIN 0.2107072402 24 PiN 0.24

0 150.16MC680001.8 50.00 TBP285442N 4 so MC3441AP 210 811598 110 741512 025 741575 0.50 07072802 28 PIN 0.26 0.17MC680081.8 45-00

MC6823018 195018P285446N 450 MC3446AP 2.90

MC3447P 4.30812648128

1 101 10

HIGH 7415122 0.757415123 0.95 741576 0.35

000.74325

07074002 40 PiN 0.29 0.18n4(6845118 67.00

TBP285.86N 862AM27513PVC 3.74 MC34484 3 '79 13128A 1 10 SPEED 7415124 2.30 DMC68901P 75.00

TI 9900 FAMILYTM59901 9S 4 50

44427519PC 1 92AM275191DC 15.00AM27525DC 15.00AM275290C 6 46

M(3470P 644MC3480 7.76M(3487 110

665551 0 25

8195819748198

1 101.101.10

CMOS

141-8.00N 0A2746CO26 0.4274HCO3N 0.64

7415125 0.497415126 0.49741513 0.467415132 0.737415136 0.46

741565

741590741591

1.16

0.661.30

06060802 8 PIN

06061602 16 PIN06061802 18 PIN

0.160.200 210 22TmS9902 4 50 AM27535DC 22 00 NE556CP 0 65 OPTOISOLATORS0.2874HC04N 0.44 7415138 0 77 741592 0.66 06062002 20 PINTMS9918 35 00 R0325131 9 40

4625 0.75 74HC08N 0.42 7415139 0.77 741593 0.66 06062202 22 PIN 0.32TMS9927 n.60TM59928 13.00

MEMORIES E2 PROM 8032513-U 9400 44TL010-(P060628024626

4633 33

0.750.90

74HC I07 N 0.7874HC109N 0.50

741514 0 8074L5145 1.23

741595 0 77 06062402 24 PIN28 PiN

0.420.46T4459929 13.00

TMS9937 6.70TM59980 17.20TMS9995 13,70

X2804AP 300nsr 14 9542804417,350ns 13.45x2804.413-450ns 12.75X2816AP 300ns 29.95

TL061-CLP 0 2811062-(P 0 4711064-CN 0 95

1.066-C1 0.28UHF MODULATORSuM1111 7.95

741K ION 0.64746(1 t2N 0.8674HC113N 0.86

7415148 1 50741515 0 251415151 1 10

cmos.

4000 Series4000 0 25

06064002 40 PIN

DIL SKTS W/WRAP

0.66

x28164P350ns 25.00 1.071-CP 0.28 UM 121+ 3.45 746(1 326 1.28 7415153 1 10 4001 052 TURNED PINx2816AR 45Ons 22.50 11072-CP 0.56 74HCI37N 1.81 7415155 0 77 4002 0.25 9090802 8 pirsi 0.36T1074-04 110 VOLTAGE REG.

74HC138N 1.20 7415156 0.77 4006 0.90 9091402 14 PIN 0.75LINEAR/INT. DEV. TL081-CP 0.29 7413C139N 0.78 7415157 0 62 4007 0.25 9091607 16 PIN 0864702 8.90HCI- 55564-5 10.66

71084-. 02T1084 -C6 1.0211091-C1 039

780578121815

0.750.750.75

741K1516 1.1674HC153N 0.90746C1576 1.02

7415158 0 627415160 0.807415161 080

400840094010

0.920 250.25

9091802 18 PIN

9092002 20 PIN9092202 22 PIN

0.%1 081 18(Speech Synthesis) 11092-C1 0.72 78H055C 7.50 741-1(1586 1.02 74L5162 0.80 4011 0.30 9092402 24 PIN 1 28AM7910DC 3488 T1094 -(N 1.30 78H12A5C 8.95 746C1606 0.90 7415163 0.80 4012 0.25 9097802 28 116 1 50AM7911EK 34-88 11.487-CP 0.59 78H0A5( 9.95 74H(161N 0.90 7415164 1.10 4013 0.45 9094007 40 PIN 1 7025152518P( 3.60 T1489 -(P 0.59 78105 0.30 746(1626 1.51 7415165 1.30 4014 050

25152521PC 3.28 1L494-CN 1.99 78112 0.30 74HC163N 1.51 7415166 1.95 4015 06525152538P( 2.72 11496-CP 0.59 78115 0.30 74HC164N 0.95 7415173 1.13 4016 0.46 ZIF SOCKETS

Hi -Tech 251525398(261531 PC

2.722.62

261532K 2 62

71507-00

7;;4,44Z°1 -.EE

1.226.087.40

78540DM78540PC7905

7.503.00095

74HC1656 2.2474HC173N 1.3574H(174N 0.80

7415174 1.307415175 0.967415181 2.09

401 740184019

0 630.460 39

08082402 24 PIN08082802 28 PIN08084002 40 PIN

5 706.90825components 6402 6 40 /6451 -KIT 29.95 7912 0,95 74HC175N 0.78 7415190 0.98 4020 0 45

75107BN 0 69 7915 0.95 74H(194N 1.28 7415191 0 75 4021 0.5675110AN 0 86 1M3094 0.95 74H(195N 1.28 7415192 1 10 4022 0 420ea75150P75I54N

0 861 05

75159 2 307516046 2 60

1M317416323K1M338K

7.454.954.50

74HC20N 0.4074HC237N 1.80746(2406 1.3874HC241N 1.34

74L5193 1.1074L5194 0 787415195 0 787415196 1 10

4023402440254026

0.340.660 250 74

0379 413175161AN 2.8275162AN75172NG

4 0874HC242N 2.2474HC243N 2.2474H(244N 132

7415197 1 10741520 .

741521 0.25

402740284031

0 520 340.93

26Practical Electronics December 1984

componenGILRAY ROAD, DISS, NORFOLK. TEL: 0379 4131

INSULATION DISPLACEMENTCONNECTOR SYSTEMHEADERS SHROUDED OPEN

90' 90"

10 way14 way16 way20 way26 way34 way40 way50 way60 way

0.861 221.341 361.702.042.282.703.20

0.650.830.921.131.401.782.072.543 02

OPEN -STRAIGHT

PINS0.470.590.650.770.951.191.371.671 96

CABLE ASSEMBLIES

IDC JUMPERSSINGLE ENDED36" cable IDC socket10 way 1.7214 way 2.0716 way 2.2220 way 3.1426 way 3.7534 way 3.9840 way 4.2350 way 5.3660 way 6.36

DIP JUMPERS

Single Ended- 14' cable

lapin 1.7316 pin 1.9024 pin 2.7340 pin 3 96

Double Ended6' cable 1 riable 18'cable

14 2.74 2.84 2.9416 3.03 3.14 3.2524 4.18 4.36 4.5540 5.89 6.18 647

iOCKETS0 way4 way6 way'0 way16 way14 way10 way

way30 way

CARDEDGE10 way?0 way26 way34 way10 way(0 way(0 way

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Cassette recorder cables:ON109 7 pin DIN to open endCON110 7 pin DIN to 2 x 3 5mm + 1 x 2 5mm 1/plug:ON111 7 pin DIN to 5 pin DIN + 2 5mm I/plugCON118 5 pin DIN to 2 x 3 5mm 1/plugsCON117 5 pin DIN to 2 x 3 5mm + 1 x 2 5mrn 1/plug

BBCBBCBBCSpectrum/ZXDragon

1.252.502.502.50250

Parallel printer cablesCON130 36 way plug to 36 way plug (2M)CON131 36 way plug to 36 way plug (5M)CON1 32 36 way plug to 36 way socket (2M)CON133 36 way plug to 36 way socket (SM)CON144 36 way plug to 25 way male D type (2M)CON145 36 way plug to 25 way male 0 type (5M)CON134 36 way plug to 25 way male D type (2M)CON135 36 way plug to 25 way Male D type (5M)CON142 36 way plug to 20 way DC socket (2M)r.ON139 36 way plug to 26 way IDC socket (2M)LON140 36 way plug to 26 way IOC socket (SM)CON 141 36 way plug to 34 way card edge (2M)CON143 36 way plug to 34 way IDC socket (2M)

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CON106 25 way male 0 type to 5 pin DINCON128 'Universal' RS232 cable (pins 1 8. 20 connected

and 201umpered as required) 2MCON164 'Universal' RS232 cable as above but 5MCON120 25 way male to male 1, 25 connected (2M)CON121 25 way male to male 1-25 connected (5M)CON122 25 way male to male 1-25 connected (10M)CON123 25 way male to male 1-25 connected (30M):ON124 25 way male to female 1.25 connected (2M)CON125 25 way male to female 1-25 connected (5M)C014126 25 way male to female 1 25 connected (10M):ON127 25 way male to female 1 25 connected (30M)ZON129 25 way male to 9 way male:ON162 25 way male to 9 way male:014163 25 way male to 5 pin DIN

BBC

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DISC DRIVES WITHOUT POWER SUPPLYBBC30 Single 100k TEC 40 track single sided E99.95BBC31S Single 100k TEC (expandable to dual) 40 track (115 00BBC310 Dual (2 x 100k) TEC 40 hack single sided (225.00BBC 34 Single 400k TEC 80 track double sided (174.00BBC 34S Single 400k TEC (expandable to dual) 40/80 track switchable

double sided (194.00BBC345W Single 400k TEC 40/80 track switchable double sided (184 00BBC 34D Dual (2 x 400k) TEC 40/80 track switchable double sided (310 00BBC 345/80 Single 400k TEC (expandable to dual) 80 track double sided E184 00BBC 340/80 Dual (2 x 400k) TEC 80 track double sided E300 00

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MONITORS9MON 9 inch green screen high resolution NEC high quality monitor (1250012MON 12 inch green screen high resolution NEC high quality monitor E135.001431 Microvitec 14' RGB colour monitor (175.001441 Microvite< 14' RGB colour monitor high resolution (410.001451 MIcrovitec 14' RGB colour monitor medium resolution (295.001431/AP/MS Microvite( 1431 PAL & RGB inputs and sound facility £225.00

BBC COMPATIBLE SOFTWARESBB03 View Rom (45 0058804 View Printer Driver (750AES20 Fileserver Level 1 40 track E80 50AES21 F deserver Level 2 80 track E202.00SNB08 Acornsoh Invoicing program (1600SNEt09 Acornsoh Mailing System program (1600SNBIO Acornsoh Accounts Receivable program (16.00SNB11 Acornsoh Stock Control program (1600SNB12 Acornsoh Order Proceising program (1600SNB13 Acornsoh Acounts Payable program (16.00SNB14 Acornsoft Purchasing program E16 00SNLO1 Forth - 40 track (15.00SNLO2 Lisp - 40 track (1500SNLO4 Microtext - 40 track (47 50

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11 x9 1 pan plain listing paper (2.000)11x9 2 pan loco) plain listing paper (1,0001I 1 x9 3 part (otc) plain listing paper (700)11x 14 1 pan ruled listing paper (2.000)11x 14 2 pan (nor) ruled listing paper (1.000)11 x 14 2 part (off ) ruled listing paper (1.000)12 x9; 1 part plain living paper with side perfs (2,000)Brother HR1 ribbonDiablo Hytype II Muitistrike film ribbonDiablo Hytype II fabri. ribbonEpson MX80, RX130.1X80, fabric ribbonMannesmann Tally MT80 film ribbonUchida DWX 305 multistnke film ribbonBrother HRS ribbonBrother HR1 S multistrike ribbonBrother HR25 multisoke ribbonBrother daisy wheelsUchida/Ourne daisywheels3 x 1 7/16 Labels - 1 wide (12,000)3 1 7/16 Labels - 1 wide (2.000)2 1 7/16 Labels - 3 wide (1/10")(2.0001

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SOLDERING is one area of electronics where many con-structors seem to give little thought to either the equip-

ment they use or the methods they adopt. This often causesdamage to components and p.c.b. tracks and can result inmany unnecessary hours of fault finding once the project hasbeen assembled. These problems can be easily overcome byusing a suitable soldering iron and following the few simplerules set out below.

The basic requirement of a soldered joint is to provide anelectrically conductive path with a secondary considerationbeing the mechanical strength of the joint.

Before soldering it is essential that the surfaces to besoldered are clean and free from any dirt or grease. If solderis to be applied to any heat -sensitive components then asuitably sized heat -shunt should be used. These are normallyin the form of specially designed tweezers, although manypeople prefer to use a small pair of pliers.

The most important part of the soldering iron is the 'tip' or'bit'. This is the part of the iron which stores the heat readyfor passing onto the joint. The size of the bit and the powerrating of the iron will determine the amount of heat that issupplied by the iron to the work and also the rate at whichthe work can be carried out.

the entire joint. The solder should be removed first and thenthe iron. After the joint has cooled it should then be checked.Remember, to ensure a good joint, never blow or move asoldered joint before it has set!

A good joint should have a smooth, shiny appearance withno pitting, spikey or dull parts; and should of course bemechanically sound.

It doesn't take long to realise that when you are solderingyou always seem to need an extra pair of hands to holdeither the work or the component. If you are working on ap.c.b. then it is best to use a p.c.b. holder which will allowyou easy access to both sides of the board and hold it steadywhilst you are soldering.

Before you start soldering ensure that all the componentsyou require are laid out in the order in which they are to besoldered. An ideal method of storing components prior tosoldering is to use a polystyrene block; note though thatMOS components should be kept in their packages until youare ready to solder them into place.

You should also ensure you have plenty of light over yourworkplace and that you have a comfortable sitting position.

Always replace your iron in its holder when you havefinished with it. Never leave an iron on your workbench.

SOWEUfFGBUYER'S GUIDE

If the temperature of the bit is incorrect it can lead to anumber of problems. Too low a temperature can result in theinsufficient activation of the flux, poor solder flow andtherefore dry joints. If a joint is dry it will exhibit a highresistance which can be very difficult to trace. It should benoted that the majority of dry joints will only become dryafter a period of time.

When the temperature setting is too high the flux will bevaporised, causing the solder to oxidise, resulting in poorquality joints and perhaps damage to any heat -sensitivecomponents.

Soldering iron bits are usually made from copper toprovide the maximum heat transfer at low cost. Because thecopper soon becomes eroded many bits are coated witheither nickel or chromium on their non -soldering surfaces toprevent oxidising whilst the tip can be coated with iron to in-crease its operating life.

The surface of the bit should be clean and free from anypits, burrs or indentations. To enable the smooth flow of heatfrom the surface of the bit to the joint a small amount ofsolder is placed on the bit prior to soldering each joint, this iscalled 'tinning'. After each soldering operation the bit shouldbe cleaned with either a damp cloth or sponge and re -tinnedif another joint is to be made.

When making a soldered joint the pre -tinned bit of theiron should be held against the joint and the flux -coredsolder applied; the solder should flow immediately covering

When choosing a soldering iron for your particular needsyou must take into account all the applications for which itwill be used. Soldering irons come in a variety of wattages,bit sizes and operating voltages. Some irons come as part ofa soldering station and include a holder, sponge tray and atemperature adjustment to set the operating temperature ofthe bit.

In this buyer's guide we have tried to show the wide rangeof soldering irons currently available and have also includedsome of the soldering aids that can be used.

The prices shown include VAT but not post and packingexcept where stated.

PLEASE NOTEWe would like to point out that readersbuying from the guide are not protectedby the Mail Order Protection Schemeunless the company concerned haveadvertised the product in a displayadvertisement in this issue.

The guide is designed as an aid to thepurchaser and makes no recommenda-tions.


SINSTRUMENTBUYER'S GUIDE

The Oryx M3 iron is rated at 17 watts and has a normal operating temperature of 380degrees centigrade. It is supplied complete with a replaceable push -on tip and storagehook. The M3 is available in 12V, 1101/ and 210/240V versions with the 12V modelfitted with a cigar -lighter plug for car repair work. Priced at f6.85 it is available fromGreenwood Electronics, Portman Road, Reading, Berks (0734 595844.

The Litesold EC50 has an electronic temperature control which canbe easily adjusted via an aperture in the handle. The temperaturecan be adjusted between 280 and 400 degrees centigrade. The bitsare iron coated copper for long life and are retained by circlips toprevent sticking. The 50 watt iron is priced at £28.00 and isavailable from Light Soldering Developments Limited. SpencerPlace, 97/99 Gloucester Road, Croydon ;01-689 0574.

loc LC18Litesold is a high efficiency

iron suitablefor general

electronicassernbly

and servicingwork. It can be either

mains or

low VOttagepowered

and takesa wide range

of bits. The12 is

similar tothe LC18

but is rated at 12 watts 310 is mainlyintended

for smallerwork. The

LAis priced

at 725and the

LC18 is

priced at C7.31. Light SolderingDeveloprrients

Ltd. e 01689

0574

The Weller WM12D weighs just 7 ounces and is thesmallest iron in their range. It is rated at 12 wattsand develops a tip temperature of 425 degrees cen-tigrade. There is a choice of three tips which can beeasily interchanged. The WM12D which is priced at£6.58 is also available in kit form together with twospare tips, a pair of tweezers and a supply of resincored solder. Cooper Tools Limited, Sedling RoadWear, Washington, Tyne & Wear (091 416 6062.

'''"'w14"1"lies6oinx-evieffeThe new portable butane powered soldering iron from Oryx is only slightly bigger than afelt-tip pen. There is no flame during use, the chemical energy of the gas is converted intoheat by means of a catalytic converter in the bit. The iron delivers the equivalent of 60watts with the tip temperature being variable between 250 and 450 degrees centigrade.The iron will run for 60 minutes on its gas supply. The Oryx Portasol is available fromGreenwood Electronics and is priced at £1 7.25. (0734 595844.

The totallyself-contained Drys

HSR1 requiresno external air

or vacuumsupply lines. It consists of five units:

the TC84 tem-

peraturecontrolled iron, the SR84 vacuum solder

removing iron,

p.s.u. and two magneticbase safety

stands for the irons. The

TC84 is fittedwith a fume extractor

which can be switched from

the TC84 to the SR84 asrequired. The

workstation is priced at

£570.00. Greenwood Electronics0734 595844.


S JDEf22.AGINSTRUMENTBUYER'S GUIDE

The LitesoId ETC-4/FXc soldering station has a built in fume ex-tractor (see inset), and fully variable electronic temperature controlwith digital readout. The 40 watt iron uses a thermocouple sensor,is "spike" and "r.f.i." free, and also free of static and leakage. Price£299 + p&p from Light Soldering Developments Ltd., SpencerPlace, 97/99 Gloucester Rd., Croydon. Surrey CRO 2DN.( 01-689 0574.

P.c.b.'track Repair

Kit includesMaster

frameswith tracks,

fingers,pads, elbows

and flatpackpads, eyelets

and funneletsplus

the settingtools. lneudes

epoxy,flux, cleaner,

spatulas,abrasive

sticks,tweezers,

clamps

and knives. Am economyversion

is also

available.Price, standard

045-90.Economy

E. OK Industries

UK Ltd., DuttonLane,

Eastleigh,Hants

$O5 4AA.0103

619841.

The TCSU-Dis a 60 -wattsoldering stationwith an elec-tronic temperature controlrange of ambient to 495 deg.C. The iron itself works on24V stepped down frommains to safety and isolation.Price £8081 from Amex(Electronics)

Ltd.,Mayflower House, Plymouth,Devon. f 0752 667377.

214-8 desolderingiron is a

Thelightweight

tool

combiningheating

and suction.The suction

chamber

is easilyremoved

for cleaning.Available

/5 or

23011. Pricef 19-19

from OK industries.

Adcole 101 electroniccontrolled

soldering iron is productionorien-

tated. Featuresr.f.i. free temperature

control, zeroleakage, open cir-

cuit tailsafe protection,l.e.d. temp. indicator, and

lockable, temp. dial

1120-420 deg.Cl Viler wound to prevent

magnetic effects.price

E7840 l+ £6 carriage)from Adcole Products

Ltd., Adcola

House,Gauden Rd., London

SW4 60-1. C 01-622 0291.

32

SA -8 series industrial grade soldering irons, available in 371deg. C (SA -8-15) and 427 deg. C (SA -8-20), heat -up in twominutes using ceramic elements. They may be used withstatic -sensitive components without earthing. Tips arecorrosion resistant. Available in 115 and 230V versions.Price £21.50, from OK Industries.


_DE122A07-1INSTRUMENTBUYER'S GUIDE

it

LitesoIdSOS Soldering

includesthe

ctioof bits,

18 s.v4.g.fluxed

solder,

desolclerbraid.

p.v.c.wallet.

Price

setsn

DevelopMerits.

The Weller 51-25 25 watt iron, along with the Weller SI-1 5, SI-40and WH 1/2 hobby kits are claimed to be the only soldering relatedproducts on the market entitled to display the BEAB seal of approvalfor safety. Price £7.80 from Coopers Tools Ltd., Sedling Rd.,Wear, Washington, Tyne & Wear NE38 9BZ. ; 091 416 6062.

with

1..C1818 ifitabliteieroontbaleocnsgotalosan

dolingtweezers

Oryx ISO -TIP series irons are cordless (rechargeable) forcomplete mains isolation. The iron automatically rechargesitself when placed in its base, and has a built in spotlight.The 50 watt iron can solder 100 joints between charges. Tiptemperature is 370°C. Also takes a drill attachment. Pricef41 from Greenwood Electronics, Portman Road,Reading. Berks RG3 1NE. r 0734 595844.

Solon-Electrex 325 is a 25 watt mains 'instant' heat soldering ironof maximum temperature 380 deg. C. It uses C25 tip or TP30. Pricef 10.79 from GEC -Henley.


Solon-Electrex DS400 Station supplied with TC24 Iron (50 watt)is thermostatically controlled from 150-400 deg. C (1% precision)with digital readout. The iron takes the 'Duratyp' range of bits. Pricef 138.69 from GEC -Henley, Gravesend. Kent DAll 90A.; 0474 64466.

AdeminMode!

75 miniatureiro i

available in 2401/or 1.2V

12 atts).

One of the smallestirons

in the vionr1;ar1takes

a rangeof bits from

1.2rnrn

to 4.7rnm.Price

(iron) £5.97,(spring

stand) £5.1/from Light Soldering

SurreyCRO

2D N. f 01-6890574.

Developments

Ltd., SpencerPlace,

97/99G/oucester

Road,Croydon.

guiam-imormt == r_ii11110.111101%

- ..

33

ST4 ---------7417721T,T137T17;3072-4- mange 65°C to 470°C

-To suit all irons. or 12 volts. Accuracy 2%.spongetray Aar

GLORIOUS PAST-BRIGHTFUTURE

A rather sad note has been struck. The Car-negie Institute of Washington, which operatesthe observatory on Mount Wilson in Califor-nia, has announced that during 1985 the great100 -inch Hooker reflector there will be"mothballed", and support for the two famoussolar tower telescopes, the 150 -foot and the60 -foot, will be gradually withdrawn. Theother large instrument, the 60 -inch reflector,will remain in service, but, as one commen-tator has said, the decision "sounds the death -knell" for Mount Wilson as a leadingastronomical institution.

The trouble is due to the continued spreadof the city of Los Angeles, which has becomenot only larger, but also brighter and morepolluted. From the city, the summit of MountWilson can be clearly seen, and from the topof the mountain the sky is not nearly so darkas it was in 1917, when the 100 -inch reflectorcame into operation. This means that manybranches of research can no longer be carriedout there.

The 100 -inch has a glorious history. Whenit was completed, it was not only the world'slargest telescope, but it was in a class of itsown, and it remained so until 1948, when itwas surpassed by the Palomar 200 -inch.

Using the Mount Wilson reflector in the1920s, Edwin Hubble proved that the objectsthen called "spiral nebulae" were in fact in-dependent galaxies, far beyond the limits of

our own Milky Way system. Hubble achievedthis by studying the behaviour of certainvariable stars inside the spirals. Thesevariables, known as Cepheids, "give away"their real luminosities-and hence theirdistances-by the way in which they brightenand fade. In Hubble's day, only the 100 -inchwas powerful enough to be used in studyingthem.

The telescope itself is as good today as itever was, but by modern standards it is old-fashioned, and there is no thought of moving itto a better site. So its story may be coming toa close, even though it is still capable of carry-ing out really valuable research. At any rate,its place in history is assured, and mercifullythere has been no suggestion as yet that it willbe dismantled, so that hope remains.

Two major telescopes are being plannedelsewhere: one in Hiroshima in Japan, and theother to be set up at the observatory on LaPalma, in the Canary Islands, where theI.N.T. or Isaac Newton Telescope is now infull operation. (While I was there, a fewmonths ago, we used the I.N.T. to obtain acolour video picture of the Ring Nebula inLyra-the first time that this had beenachieved for an object beyond the SolarSystem.) The projected new telescope is a 100 -inch reflector, and will be a joint venture byNorway, Sweden, Denmark and Finland. Theoptics will be made at Turku in Finland.

Halley's Comet is now under regular obser-vation, and continues to brighten slowly as itdraws in toward the Sun, but it will not comewithin the range of average -sized telescopesuntil the middle of next year. Unfortunately,this is a poor return, and the comet will be notnearly so conspicuous as it was in 1910 or in1835, though with luck it will be easily visiblewith the naked eye towards the end of 1985.

THE SUNOn 22-23 November there will be a total

eclipse of the Sun. The path of totality beginsin the Molucca Islands and then crosses NewGuinea, passing north of New Zealand andending in the South Pacific. The maximumlength of totality is exactly two minutes.

The partial phase will be seen from thePhilippines, parts of Australia and NewZealand, and also from part of Antarctica, butof course the eclipse will be invisible fromEurope, as it occurs during European night.

The next total eclipse to be seen fromanywhere in Britain will be that of 11 August1999, when the track of totality will crossCornwall.

Despite Skylab and other space -stations,total solar eclipses are still of tremendous im-portance, because it is only when the Sun iscompletely covered by the Moon that ground -based observers can see the corona in its fullglory. At this month's eclipse the corona willbe of the "minimum" type, because the Sun isnow approaching the lowest point of its 11 -year cycle of activity. There have already beenseveral spotless periods this year, when thesolar disc has been entirely blank.

The solar cycle is not perfectly regular, andthe usually quoted figure of 11 years betweensuccessive maxima is only an average.Moreover, it may well be that we know lessabout the Sun than we used to believe. Eventhe cycle may not be permanent; there is ex-cellent evidence that between 1645 and 1715there were almost no sunspots at all-a periodnow generally known as the MaunderMinimum, since attention was first drawn to itby the British astronomer E. W. Maunder(and, independently, by Sparer in Germany).

SPACE MINEVery important studies are being carried

out from what is undoubtedly one of thestrangest observatories in the world. It issituated a mile below ground, at HomestakeMine in South Dakota. This is the country ofthe gunslingers; little more than a century agoit was the home of colourful characters suchas Calamity Jane, Wild Bill Hickok and"Doc" Holliday.

It is also a gold -mining area. Today thegunslingers have gone, but the gold is stillthere, and Homestake Mine is the largest inthe whole of the United States. The solar ob-servatory has been set up in a special cham-ber, or rather pair of chambers, hollowed -outspecially for the purpose.

The Sun is radiating by nuclear transforma-tions taking place near its core. Basically,hydrogen nuclei are combining to form nucleiof helium, with release of energy and loss ofmass. (The mass -loss amounts to 4,000,000tons per second, though by solar standardsthis is not very much, and there is no reason tosuppose that the Sun will change dramatically

THE SKY THIS MONTHThis is not a particularly good month from the view-

point of planetary enthusiasts. Mercury, Venus, Marsand Jupiter are all technically evening objects, butMercury is well south of the celestial equator and isbadly placed from Britain, even when at its greatesteastern elongation on 25 November.

Mars and Jupiter are also in the southernhemisphere of the sky, and set not long after the Sun;moreover Mars is now so far away that its magnitudehas faded to 0.8, about the same as that of Aldebaran,and even large telescopes will show little upon itsdisc. Saturn is in conjunction with the Sun on Novem-ber 11, and is therefore out of view altogether.

It may be worth noting that Ceres, the largest and

first -discovered of the minor planets or asteroids,comes to opposition on November 10. It is in Taurus,near the stars Xi end Omicron Tauri, but its magnitudeis only 6.9, so that it is too faint to be seen with thenaked eye. Binoculars will show it, though of course itlooks exactly like a star. Its diameter is rather over 620miles, and it is mt.ch the most massive member of theasteroid swarm.

Plans for asteroid probes are now being made, andshould be put into practice by the mid -1990s, but itseems likely that the first target will be not Ceres, butVesta-the brightest member of the group-which issmaller than Ceres, but considerably closer -in to theSun.


for at least 5,000 million years in the future.)Theorists also calculate that there should bethe emission of neutrinos, which are particleswith no electrical charge and virtually nomass -so that they are extremely hard todetect, since they can pass through the Sunand also through the Earth without beingchecked.

The only way to catch them is by makingthem interact with atoms of chlorine. If aneutrino hits a chlorine atom, the result will bean atom of Argon -37, which is radioactive andis therefore comparatively easy to track down.

THINK TANKIn Homestake Mine, Dr. Ray Davies and

his colleagues have set up a large tank con-taining 100,000 gallons of perchloroethylene,which contains a great deal of chlorine and isnothing more nor less than cleaning fluid! Theprocedure is to leave the tank for a period ofaround eight weeks, and then carry out tests

to see how many atoms of Argon -37 havebeen produced.

Since there will not be more than about adozen of them, and the whole tank containsabout a thousand million million million atomsof various kinds, the tests are far fromstraightforward. But for the radioactivequalities of Argon -37, there would be no hopeat all.

Why "go underground"? The answer issimple. Cosmic rays from space will affect thechlorine in exactly the same way as neutrinos.But cosmic rays cannot penetrate a mile ofsolid rock -at least, not easily; a few can getthrough, but these can be allowed for. This iswhy Homestake is so suitable for this par-ticular experiment.

The solar observatory has now been in ac-tion ever since the 1960s, and the results havebeen startling. Apparently the Sun is sendingout only about a quarter as many neutrinos asin theory it ought to do. Unless there is

something wrong with the experiment, which

seems unlikely, or else there is a defect in ourtheories -or even the possibility that at thepresent epoch the Sun is behaving abnormally.

Neutrino emission is very sensitive to tem-perature. It has been calculated that the tem-perature at the core of the Sun is about15,500,000 degrees Centigrade. If we reducethis by a million degrees, the neutrino resultsfall neatly into place, but such a fall incalculated temperature would raise othertheoretical problems. Is it possible thatneutrinos are more complicated than we think,so that they could break up or becomemodified during their 93,000.000 -mile journeyfrom the Sun to the Earth?

As yet we do not know. The Homestakeresults seem reliable enough, and are con-firmed by a similar experiment being carriedout in the Soviet Union. So we must do somere -thinking, and it is not surprising that solarphysicists are placing great importance on thebehaviour of a tank of cleaning fluid deep in aSouth Dakota gold -mine.

PRACTICAL ELECTRONICSPRINTED CIRCUIT BOARD SERVICE

Printed circuit boards for certain PE constructional projects are nowavailable from the PE PCB Service, see list. They are fully drilledand roller tinned. All prices include VAT and postage and packing.Add f1 per board for overseas airmail. Remittances should he sentto: PE PCB Service, Practical Electronics Editorial Offices,Westover House, West Quay Road, Poole, Dorset BH151JG. Cheques should be crossed and made payable to IPCMagazines Ltd.

Please note that when ordering it is important to give projectorder code and the quantity. Please print name and address inBlock Caps. Do not send any other correspondence with your order.

Readers are advised to check with prices appearing in thecurrent issue before ordering.

NOTE: Please allow 28 days for delivery. We can onlysupply boards listed here or in the November issue.

PROJECT TITLE OrderCode

Cost

SEPT '81Horologicum 109-01 £3.16

109-02 £3.11109-03 £2.97

Analogue Frequency Meter 109-04 £2.87Ignition System 109-05 £2.47

109-06 £2.28APRIL '82

Med. Resolution Equaliser (UK 101) 204-01 £1.73Enlarger Timer 204-02 £4.02

AUG '82Automatic Photographer 208-01 f 1.94Home Alarm 208-02 £3.21

SEPT '82Waveform Digitiser 209-01 £8.24

FEB '83Radio Booster 302-02 £1.80

MAR '83Into the Real World 303-01 £3.99Accessory PSU 303-02 £1.3541 Digit Frequency Meter 303-03 £3.69

APRIL '83Phaser 304-01 f3.41

JUNE '83Program Conditioner 306-01 £2.30

PROJECT TITLE OrderCode

Cost

SEPT '83Guitar Active Tone Control 309-01 £2.27Ground Communication System 309-02 £2.13

309-03 £2.31DEC '83

Expanding the Vic 20 312-01 £5.18MAR '84

Spectrum Autosav a 403-01 £1.83APRIL '84

Microstepper 404-01 £10.74MAY '84

Sustain Unit 405-02 £2.82Audio Signal Generator 405-03 £4.28

405-04 £2.51JUNE '84

Cross Hatch Generator 406-01 £3.52JULY '84

Simple Logic Generator 407-01 £7.73EPROM Duplicator 407-02 £3.74Alarm System 407-03 f3.19Oscilloscope Calibrator 407-04 £4.23

AUG '84Comm. 64 RS232C Interface 408-01 £3.02Field Measurement 408-02 £3.19

408-03 £2.76Digital Dice 408-04 £4.23Simple Logic Analyser 408-05 £2.93Alarm System 408-06 £4.24

408-07 £3.14408-08 £3.23

SEPT '84Parallel to Serial Converter 409-01 £2.92Through the Mains Controller 409-02 £2.88

409-03 £2.71OCT '84

Logic Probe 410-01 £1.90NOV '84

Computer DFM Adaptor 411-01 £2.76DEC 'Ed

Ni-Cad Charger 412-01 £2.40


4

37

NICKEL CADMIUM WoBATTERIES MICHAEL TOOLEY BA

DAVID WHITFIELD MA MSc CEng MIEE

UNLIKE their lead acid counterparts, nickel cadmium cellsrequire a constant current rather than a constant voltage

charging source. Furthermore, comparable sintered andmass plate cells have different charge rate requirements andthis must also be taken into account.

The maximum indefinite charge rate for a sintered cell isusually taken as C/8, i.e. for a lAh battery the maximum in-definite charging current is 125mA. Cells may, however, becharged at higher rates provided care is taken to avoidovercharging which can permanently damage the cells. Themaximum charge rate for a sintered cell is usually assumedto be 10C but, before attempting to 'fast -charge' a nickelcadmium cell of any variety, it is essential to ensure that the

HOURS

MIN

20

10

6

4

3

2

1

40302

to

64

3

2

C/10 C/2 C SC 10C

CHARGE RATE

Fig. 1. Charge time versus charge rate for nickel cad-mium cells

cell is initially fully discharged. Using the same lAh battery,for example, a 2C charge would be achieved by charging at2A for 30 minutes.

The relationship between charge period and charge ratefor nickel cadmium cells is illustrated in Fig. 1. To ensure along cell life and a maximum number of charge/dischargecycles, charge rates in excess of C should be avoided if at allpossible. Mass plate cells cannot, by virture of their con-struction, be charged at the high rates associated with sin-tered cells. The maximum charge rate for such cells isusually C/10 for 14 hours whilst the maximum indefinitecharging current is often no more than C/100. Hence, for a110mAh PP3 battery, the recommended charging current is11mA for a period of 14 hours. Furthermore, if this type ofbattery is to be left on -charge indefinitely, the chargingcurrent should not be allowed to exceed 11mA. Table 1

shows the recommended charge rate for a number ofpopular nickel cadmium batteries.

Battery typeMax. indefinite

charging current(mA)

AAA 20AA 66

C 250D 500

PP3 1-1PP9 100

Table 1. Maximum indefinite charge rates for variousnickel cadmium batteries

We shall now describe a simple automatic charger whichprovides a total of 24 different charge rate options.

Mud CHARGERThe easiest method of obtaining a reliable constant

current source involves nothing more than a d.c. supply, onetransistor and just three other components. Fig. 2 shows atypical family of output (collector) characteristics for a tran-sistor operated in common emitter mode. It should be notedthat, for a fixed value of base current, the collector currentremains substantially constant and is reasonably indepen-dent of the value of collector -emitter voltage. Hence, if thebattery to be charged is connected as the load in the collec-tor circuit, and the base voltage held constant, the batterywill receive a reasonably constant current charge. A typicalcircuit is shown in Fig. 3. The base voltage is stabilised bymeans of the Zener diode, D, and the base current is deter-mined by the value of emitter resistor, RE. Since the collectorcurrent is equal to the base current multiplied by the value ofcommon emitter current gain for the transistor concerned,the charging current can be set by appropriate choice of RE.


COLLECTOR CURRENTIcImA)

[PE23041

IB CONSTANT

COLLECTOR -EMITTER VOLTAGEVCE (VI

Fig. 2. Typical output characteristics for a transistorconnected in common emitter mode

Another simple constant current charging source is shownin Fig. 4. Here a conventional monolithic three -terminalregulator is connected in what, at first sight, may appear tobe a strange arrangement. The normal regulator output is, infact, developed across Rs and since this voltage remainssubstantially constant, the current flowing through it willalso be constant. The output current is given by:-

5lo =- + I where I Pe, 5mARs

The value of Rs can be varied so that different charge ratescan be catered for, as shown in Table 2.

With the two previous circuits, the charge rates may beeasily selected by changing just one component. In practice,different charge rates can be obtained either by switchingresistors or by incorporating a variable resistor into the cir-cuit. There is, however, one problem; it is all too easy to con-nect the charger to a battery, switch 'on', and then forget it!Whilst this may be of little consequence when charge ratesof C/10 are concerned, serious damage may be done if a fastcharge rate is selected and thus, ideally, a charger should in-corporate a facility which will discontinue the charge after apre -determined time interval has elapsed. Hence, if separatecontrols for charging current and charging time are provided,a wide variety of charge rates can be accommodated to suitalmost any type of cell which may be encountered. Further-more, the user can rest assured that no harm will be done ifthe unit is left connected for an indefinite period!

AN AUTOMATIC CHARGERThe complete circuit of the automatic charger is shown in

Fig. 5. A conventional mains transformer, T1, and bridge rec-tifier, REC1, provides an unregulated supply rail of approx-imately 17V. A programmable timer, IC1, is used to provideaccurate monostable timing periods which are derived froma timebase and eight -stage binary counter. The two fun-damental timing components are C2 and R2 and only thelast four divider outputs are employed. A miniature normally -open push-button switch, S4, is used to initialise the timingsequence whilst a similar switch, S3, is used to re -set thetimer, aborting the current timing period and discontinuingthe charge.

The time period is selected by a rotary switch, S1, and thevoltage at this point goes low for the duration of the timingperiod removing the bias from TR 1 and switching the tran-sistor 'off'. In this condition, R5, D1 and D2 supply bias forthe constant current source, TR2. At the end of themonostable period the base voltage of TR1 rises and TR 1conducts. In this condition, D1 no longer achieves its Zenervoltage and no base current is supplied to TR2. The output

HOME PROJECT

IPE24141

VS

UNREGULATEDD.C. SUPPLY

OV

BATTERY1 ON -CHARGE

TR

RE

Fig. 3. A simple charger using a transistor connectedas a constant current source

'VS

UNREGULATEDD.C. SUPPLY

LOEr2r1 Dv 0

RS

BATTERYON -CHARGE

Fig. 4. Simple charger using a monolithic three -terminal voltage regulator

Rs(ohm) 1W)

Charge current(mA)

820 0.5 11

470 0.5 15330 0-5 20220 0-5 2882 0.5 6656 1 10022 2.5 25010 4 500

Table 2. Relationship between R, and charge currentfor the circuit of Fig. 4

current, which is selected by means of rotary switch S2, thusfalls to zero and remains in this state until another chargingperiod is initialised by the user.

CONSTRUCTIONThe majority of the components for the automatic charger

are mounted on a single sided p.c.b. measuring approx-imately 53 x 104mm, the design of which is shown in Fig.6. The corresponding component layout is shown in Fig. 7.The recommended sequence for mounting components is:terminal pins, d.i.l. socket, resistors, diodes, transistor, bridgerectifier, and capacitors.

The underside of the completed p.c.b. should be carefullychecked for solder bridges and dry joints whilst the compo-nent side should be examined paying particular attention tothe placement and orientation of the polarised components.The remainder of the components, excluding the mainstransformer, fuseholder. and mains connector, are all moun-ted on the aluminium front panel. The wiring of the frontpanel should follow the layout given in Fig. 8 and connec-


COMPONENTS .

ResistorsR1

R2R3R4R5

47k R8,R9 506 (2 off)2M2 R10 10100 R11 1510k R12 1

1k R13 22kR6 56 R14 1k

R7 202Al to R5, R13 and R14 are IW 5% carbonR6 to R12 are 1W 10% carbon

CapacitorsClC2C3

1000µ 1 6V p.c. electrolytic22011 16V p.c. electrolytic100n polyester

SemiconductorsDI BZY88 C4V7 ZenerD2D3,D4D5TR1TR2IC1REC1

Green 0.2in I.e.d.IN4148 (2 off)Red 0.2in I.e.d.BC108TIP32A224050V 1 A p.c. mounting bridge rectifier

MiscellaneousTi 6VA mains transformer with 2 x 6V or 1 x 12V

secondary winding rated at 500mA16 -pin d.i.l. socket 10220 heatsink (see text)Si 3P 4W rotary switch (1 pole only used)S2 2P 6W rotary switch (1 pole only used)S3 normally -open miniature push-button switchS4 normally -open miniature push-button switchS5 DPST mains switchPCB Plastic case (West Hyde)Push -on knobs (2 off) Terminal pins (20 off)

F S1 2501nA S5

IMAINS ONI

SK1

240V

MAINSN

-

17C

HE 1

I RESETI

1

53

'SET'

S4

tions to the p.c.b. may be most conveniently made usingshort lengths of ribbon cable.

Where less than six series connected cells (or a battery ofequivalent voltage) is to be charged at currents of 100mA, ormore, the series transistor, TR2, MUST be mounted on aheatsink. This should be a T0220 variety of 10.5°C/W, orbetter. The front panel should be labelled as shown in thephotograph.

INITIAL TESTSWhen all wiring is complete, a final check should be made

before inserting ICI into the d.i.l. socket (taking care to ob-serve the correct crientation). The mains supply should thenbe connected and the charger switched 'on'. The red I.e.d.,D5, should immecEately become illuminated whilst the greenI.e.d., D2, should remain extinguished. At this point it isworth checking the positive supply rail voltage which ap-pears at pin 16 of IC1. This should be 17V +1.5V. If this isnot the case, connections to the mains switch, fuse, andtransformer should be carefully checked.

The charge period switch, Si, should then be switched togive the shortest time (3.5 hours) whilst the charge currentswitch, S2, should be switched to the lowest current setting(12-5mA). S4 should now be momentarily pressed at whichpoint the green I.e.d., D2, should become illuminated. Nowmomentarily depress S3 to reset the charger. As S3 isreleased, D2 should become extinguished. This set/resetprocedure should be repeated a few times until the user isfamiliar with its operation. If no charge is apparent, readers

R2 R14

2142 1

C2

220k

LS

IC12240

17

1/2

C3

100n

l'7H 144'

51

28FIR

R9

250mA

TIME

RIC

S2

7

D3 04

01 011N4148 1N4148

TR1

BC108

MD1 14B 2Y88C4V7

83 RS

ISO 1k

R11

12 SrnA

'CURRENT

TR2

Fig. 5. Complete circuit diagram of the automatic charger

5,3

4(1 Practical Electronics December 1984

Fig. 6. P.c.b. design

k

PC 2.141

53 54 eCOMMON '0

51 (AMR ).4*-

SI (7HR) Nk 0SI 114 NR ).1I-0

51(21MR .4

susELEcToR) 4 '

54 ®

53 S -0Ds Atio0F.2..._®

DS CATHOOE.5/11,.. fTR1%513, FRON T PANEC' ,.4 5 5 1.0 MO

02 CATTOOE..* 40-41121- illVLi-.DI A NCIOE-0.® 04 03

b

512 .01 c 004 5'2 C TR2

,111 12VacROM

T1 SEC

R7 `1111

s26Re.e.-2-14 56 14

Fig. 8. Front panel wiring

O

(.14 2441

Fig. 7. P.c.b. component layout

Asa c. MAINS FROM Fl

mac MAINS TO T1


Test pointVoltage

Reset SetIC 1 pin -16

c

TR 1 {e

b

cTR2 ( b

e

Output (Sk2)

17.017.014.013.4

016.817.0

0

17.017.0

1.08.8

16.616.016.716.6

All voltages measured with a 20kohm/Vmultimeter

Table 3. Test voltages

should refer to the test voltages provided in Table 3. If thesupply voltage is correct but neither I.e.d. is illuminated, it isworth checking the polarity of D2 and D5.

Having confirmed that the set/reset switching isfunctional, the next stage is to check the charge time. Sinceit would be somewhat tedious to wait for even the shortestcharge period (approx. 3.5 hours) it is more expedient to em-ploy one of the unused shorter time periods available fromthe programmable timer, IC1. The shortest of these isavailable at pin 1 and readers should refer to the test circuitof Fig. 9a. The time period for a 'high' output should bemeasured using the following procedure: -1. Connect the test circuit using either a voltmeter or

digital timer. The voltmeter should be switched tothe 20V, 25V or 30V range whilst the timer shouldbe adjusted to 'start' on a positive edge and 'stop'on a negative edge.

2. Depress S4. The voltage at pin -1 should be low'for several minutes and then it will go 'high'. At thispoint timing should commence (using a stopwatchor the digital timer).

3. After approximately 13 minutes the voltage shouldgo low' again. At this point timing should stop.

The time period at pin -1 is 1/16 of the nominal 3.5 hourperiod. However, due to component tolerances (particularlythat associated with C2), the time period will seldom beexact. Where a precise time interval is desired, R2 may be

10k

ICI2240

17V

..... ...N.

START STOP

TIMER I 4790S 11..----...)I

1

OV

Fig. 9a. Arrangement for testing the charge time

IkExisd)

I SK2

I SK30

4 .1 AA CELLS(APPX.SVS TOTAL)

Fig. 9b. Arrangement for testing the charge current

2M 2

(ADJ. CHARGE TIME )

201.)

I PE 31bij

17V

Fig. 10. Circuit modification for precise time period ad-justment

replaced with a 2M2 pre-set resistor in series with a 1Mfixed resistor, as shown in Fig. 10. The pre-set resistor isthen adjusted for a pin -1 high output time of approximately790 seconds.

Finally, the charge current should be checked. This is ac-complished using a typical battery pack consisting of fourseries connected AA cells and measuring the currentdelivered with the charger 'set'. The required circuit arrange-ment is shown in Fig. 9b. The charge current on each rangeof S2 should be measured and this should be within approx-imately 10% of that marked. If this is not the case, minor ad -

Charge Time(hours)

3.5 7 14 28

4.C

23

1e-a

U

12.5 30 60 90(PP3)

180(AAA)

33

,

80 160(AAA)

320 640

45 110(PP3)

220 440(AA)

880

66 160(AAA)

320 640 1280(PP9)

100 250 500(AA)

1000(PP9)

2000(C)

250 612 1200(PP9)

2400(C)

4800(D)

(Note: Battery capacity is shown in mAh)

Table 4. Recommended charge rates for the automaticcharger

justment to the appropriate resistor (R7 to 1311) may bemade simply by connecting larger resistance values inparallel and trimming for the exact current desired.

This completes the initial tests and the automatic chargeris now ready for use. Table 4 provides a guide as to thecharge rate obtained with various combinations of S1 andS2. Recommended rates for charging various common typesof nickel cadmium battery are also shown. Note that onlycells of similar type should be charged at any time and theyshould ALWAYS be connected in series. Users should equipthemselves with a range of battery holders to suit the cellscurrently in use. Such holders are readily available from mostelectronic component suppliers.

Finally, care should be taken to ensure correct polarity ofcells connected to the charger. Failure to observe thisprecaution may result in damage to both the cells them-selves and to the charger!


Heathkit IT'S A PLEASURE TO BUILDBring the enjoyment back into your hobbywith a kit from Heathkit. The beautifullyillustrated documentation and step-by-step instructions make building a Heathkita relaxing, absorbing pleasure! Choosefrom their huge range of fascinating kitsand self -instruction electronics andcomputing courses.The Heathkit range includes the ultimatein amateur radio kits, computerisedweather stations, a highly soph-isticated robot, a 16 -bit comp-uter kit and a range ofhome (or classroom)learning courses. Thesestate-of-the-art courseshave easy -to -under-stand texts andillustrations,divided into sect-ions so that you canprogress at yourown pace, whilstthe hands-on exper-iments ensure long-term retention of thematerial covered.

You'll find Heathkits available for Amateur RadioGear Car Test Equipment Kits For The Home Self-Instraction Courses Computer Kits TestInstrument Kits Kits For Weather Measurements.

All the mos: popular kits and educational productsare fully detailed in the 1984 Maplin catalogue (seeoutside back cover of this magazine for details) or

for the full list of Heathkit products send 50p forthe Heathkit International Cataloguecomplete with a UK price list of allTeems.

You'll be proud to say,"I built it myself!"

All Heathkit products available inthe UK from:

Maplin ElectronicSupplies Ltd.P.O. Box 3, Rayleigh,Essex, SS6 8LR.Tel: (0702) 552911.(For shop addresses see back cover. )

TOROIDALSThe toroidal transformer is now accepted as the standard inindustry, overtaking the obsolete laminated type. Industry hasbeen quick to recognise the advantages toroidals offer in size,weight, lower radiated field and, thank to I.L.P., PRICE.Our large standard range is complemented by our SPECIALDESIGN section which can offer a prototype service within 14DAYS together with a short lead time on quantity orders whichcan be programmed to your requirements with no price penalty.

STEEL DISHEDWASHER

OUTERINSULATION

SECONDARYWINDING

INSULATION

PRIMARYWINDING

CORE

END CAPS

1

NEOPRENEWASHERS

15 VA62 x Hrem 035Kg

Regulation 19%SERIES SECONDARY RMS

No. Volts Carnes0+010 6+6 1.250.011 9+9 0.830.012 12+12 0.630x013 15+15 0.500x014 18+18 0.420.015 22+22 0.340x016 25+25 0.300.017 30+30 0.25(encased in ABS plastic)

30 VA70 x 30mm 0.45Kg

Regulation 18%1 x010 6+6 2.501 x011 9+9 1.661.012 12+12 1.251.013 15+15 1.001 x014 18+18 0.831+015 22+22 0.681 x016 25+25 0.601.017 30+30 0.50

50 VA80 x 35mm 0.9Kg

Regulation 13%2.010 6+6 4.162 x0112 x0122x0132 x0142 x0152 x0162x0172 x0282 x0292x030

9+9 2.7712+12 2.0815+15 1.6618+18 1.3822+22 1.3325+25 1.0030+30 0.83

110 0.45220 0.22240 0.20

80 VA90 x 30mm 1Kg

Regulation 12%3 x010 6+6 6.643.011 9+9 444

12+1215+1518+1822+2225+2530+30

110220240

3 x0123 x0133 x0143 x0153 .0163 x0173 x 0283x0293.030

3.332.662.221.811.601.330.720.360.33

120 VA90 x 40rrim 12Kg

Regulation 11%4x010 6+6 10.004.011 9+9 6.664.012 12+12 5.004x013 15+15 4.004.014 18+18 3.334x015 22+22 2.724x016 25+25 2.404.017 30+30 2.004.018 35+35 1.714.028 110 1.094.029 220 0.544.030 240 0.50

160 VA110 x 40mm 1.8Kg

Regulation 8%5.0115.0125.0135.0145.0155.0165.0175.0185.0265.0285.0295.030

9+912+1215+1518+1822+2225+2530+3035+3540+40

110220240

6.665.334.443.633.202.662.282.001.450.720.66

225 VA110 x 45mm 22Kg

Regulat on 7%6x012 12+12 9.386.013 15+15 7.506.014 18+18 6.256x015 22+22 5.116.016 25+25 4.506.017 30+30 3.756.018 35+35 3.216x026 40+40 2.816x025 45+45 2.506.033 50+50 2.256x028 110 2.046x029 22D 1.026.030 240 0.93

300 VA110 x 50mm 2.6Kg

Regulation 6%

Prices including P&P and VATVA Size E VA Size E

15 0 6.98 160 5 12.0930 1 7.87 225 6 15.2750 2 9.05 7 174180 3 10.10 500 8 24.39

120 4 10.97 625 9 29.94For 110V primary insert "0" in place of "X" in type number.For 220V primary (Europe) inert "1" in place of "X" in type number.For 240V primary (UK) insert "2" in place of "X" in type number.IMPORTANT: Regulation - All voltages quoted are FULL LOAD.Please add regulation figure to secondary voltage to obtain off load voltage.

7.013 15+15 10.007.014 18+18 8.337.015 22+22 6.827.016 25+25 6.007.017 30+30 5.007x018 35+35 4.287x026 40+40 3.757 x025 45+45 3.337.033 50+50 3.007.028 11) 2.727 x029 220 1.367x030 240 1.25

500 VA40 x 60m -n

Regulation 4%,016 25+25 10.00. 017 30+30 8.33+ 018 35+35 7.14.026 40+40 6.25.025 45+45 5.55.033 50+50 5.00

4Kg

x042 55+55 4.54x028 110 4.54.029 220 2.27x030 240 2.08

625 VA140 x 75m -n 5Kg

Regulation 4%9.017 30+30 10.419.018 35+35 8.929.026 40+40 7.819.025 45+45 6.949.033 50+50 6.259.042 55+55 5.689.028 110 5.689+029 220 2.849.030 240 2.60

Why a Torpid? Smaller size & weight to meetmodern 'slimline' requirements. Low electrically induced noisedemanded by compactequipment. High efficiency enablingconservtive rating whilstmaintaining size advantages. Lower operating temperature.

Why ILP? Ex -stock delivery for smallquantities. Gold service available. 21 daysmanufacture for urgentdeliveries.

5 year no quibble guarantee.Realistic delivery for volume

orders. No price penalty for call offorders.

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Post to: ILP Electronics Ltd., Dept. 2Graham Bell House, Roper Close,Canterbury, Kent. CT2 7EPTel: (0227) 54778 Telex: 965780

ELECTRONICS LTD.

"VERNON a11111111111111111111111111

1.'s views and opinions are entirely his own and not necessarily those of PE

HERE'S A QUESTION: just how manycompanies in the components business,

do you think, started out as a display ofvalves in the side window of a butcher's shop?I know of only one. That's the firm of A. F.Bulgin-a household name in the industryfor more than half a century.

The founder was one Arthur Bulgin whosefather was a respected purveyor of high -quality meats to the gentry (this was thegrand title, or something similar, that gracedhis letterheads). And although he wasprobably disappointed that his son showed noinclination to follow the tradition of victuall-ing the well-to-do, he gave the lad every en-couragement in a venture which was, on theface of it, somewhat dicey. So the side win-dow was donated willingly, if, I suspect, withnot a little trepidation. What the squire andother distinguished beef-champers thoughtabout it is not recorded.

Arthur justified his father's confidencewhen he set up a business proper in April1923. This was at a time when the BritishBroadcasting Company had just launched thefirst public radio service in the UK and thefuture was rich in golden opportunity.

"The first product . . .

was a light -emittingescutcheon"

411111111P AN

Long before he went in for manufacturing,Arthur traded as a distributor-he wastotally dedicated to this method of marketing.His family claims-and who shall blamethem-that he was one of the first to operatein this now firmly established branch of thecomponent sector.

The first product to come out of Bulgin'smodest stable was described as a light -emitting escutcheon. Or, to put it more sim-ply, a signal window. It was set in the cabinetof a radio receiver and a quick ganderthrough it told you if your valves were aliveand well. A comforting glow meant you werein business. An inky blackness spelt trouble.

By 1948 --and we're having to skip a bit ofhistory here-Bulgin had become a limitedcompany employing 250 people and turningout what the Americans call panel hardware:passives, switches, connectors, fuses, fuse -

holders, signal lamps, clips and so on. And inspite of a considerable broadening of therange over the years, such "nuts and bolts"remain the firm's bread and butter.

Arthur's four brothers emulated theirfather's farsighted support of his meat -shyson and one -by -one they came into thebusiness, leading it on to bigger and betterthings and consolidating the high reputationit continues to enjoy.

Today the family tide runs even morestrongly. Ronnie Bulgin, son of the founder,is chairman and MD of what has become agroup rather than a single company. Hiscousin Robert is his deputy. Ronnie's sonRichard (25) bowler -hatted his way throughthe Stock Exchange for three years beforejoining the fold in 1980 and is now involvedin selling and marketing with a new Bulginventure-of which more anon. Robert's sonClifford (23) is equally active on the produc-tion side. And I'm told there is a reserve stockof other little Bulgins-too young yet to getin on the family act-watching out for theircues.

I met Ronnie and Robert the other day.Ronnie is shrewd and softly -spoken. Robert isa burly, jovial extrovert. That's understand-able. Before joining the firm he was in ad-vertising for a spell. It's the group's goodfortune that he eventually decided to mendhis ways. Between them, the cousins house alot of ability and a treasury of enthusiasm.

"Let's tell you about our exciting newoperation," said Ronnie. "Some months agowe consolidated Ambit International, SolentComponent Supplies, Broxlea and ProjexDistribution-which represent Bulgin's dis-tribution and custom manufacturingactivities-into a single company calledCirkit. It's the first stage of a major develop-ment programme.

"Cirkit, far from taking a 'me too' stancein the distributor ranks by stocking all andsundry, is going for the specialist route. It isbuilding an inventory of essential popularcomponents from the top manufacturers withan emphasis on exclusivity. Among the linesfor which it is sole stockist are Alp's (theworld's largest manufacturer of electro-mechanical devices) and Toko (tops in woundcomponents). Additionally, we're appointeddistributors in the South of England forCooper ToolsAVeller, brand leaders in solder-ing and desoldering equipment. And we'renot stopping there. We plan to secure otherimportant franchises, with the accent onhigh -volume components and hightechnology, in such key areas as telecoms,defence, control and computers."

Cirkit is also stepping up its operations inthe home -user and hobbyist market, throughboth mail order and across -the -counter out-lets. New kits coming on to the market in-clude, in the 'expert' category, a 20W,144MHz linear power amplifier for boostingthe output of hand-held and transportabletransceivers, but also, in the 'enthusiast'bracket, a universal audio function generatorwith on -board mains I'SU.

The aspiring 'student' class is not forgotteneither. Kits in this area range from a univer-sal temperature sensor which can be used as afrost warning, deep freeze alarm, greenhousetemperature alarm, etc., to a locomotive

sound- generator with whistle-a boon and ablessing for the rabid thwarted railwaymanwho has turned his attic into a miniatureClapham Junction.

While Ronnie and Robert Bulgin keep awatchful eye on Cirkit as non -executive mem-bers of the board, they have mustered a wholenew team to steer the company on its adven-turous path. Spearheading the team is ChiefExecutive Christopher Sawyer, a born leaderwho has achieved a particularly successfultrack record with such giants as BMW,Smedleys and the Ross Group. Alongside himis Financial Director, Ronald McKellar CA,who like Sawyer is in his late 30's and hasan equally impressive business background.

Chairman of Cirkit is Alistair McDonald,who brings not only a wealth of experience intop-level financial -type appointments, butalso, I suggest, an odour of sanctity. He spentmany years with the Church Commissioners,juggling, as investment secretary, with assetsin excess of £1,000 million. Another stalwartis ex -sailor Ken Hollingsworth. He came intoelectronic component distribution in 1963and has become rich in the knowledge of thegame. Then there's Jonathan Burchell, whois master -minding the introduction of Cirkit'snew range of kits. Richard Bulgin (ConsumerServices) and Clifford Bulgin (Manufactur-ing Services) represent the third generation ofthe founding family.

"We have tried," said Ronnie Bulgin, "tobring a real breath of fresh air into thebusiness of electronic component distribution.This is typified by the appointment of AlistairMcDonald, who, in spite of coming into thissector for the first time, is generating enor-mous enthusiasm.

"When you think about it, this kind of con-solidation of several distribution companiesinto one is plain commercial common sense.Promoting each of them individually, withtheir own advertising and catalogues, as wellas premises, is not only hideously expensive,but inefficient."

There's one point the Bulgins underline inbold capitals: In spite of its expansion in thedistribution area, it remains firmly in thebusiness of manufacturing, with a mainfactory at Barking (Essex) and a satellite atBroxbourne (Herts). In fact, in the currentyear the ratio will be 40 per cent distributionto 60 per cent production, turning out compo-nents for internationally -known customerswith products ranging, as Robert Bulgin said,from toasters to telecoms, robots to oil rigs.

With an eye, no doubt, on future man-power needs, Cirkit has put £100,000 into anelectronics award scheme for young people atschools and colleges. They must make anddesign an electronic device with a viable ap-plication in everyday life-for business orleisure. Any design taken up will attractroyalities and, what's more, the company willhelp with patenting.

Arthur Bulgin would, I'm sure, bedelighted to see what that valve display,cheek -by -jowl with the lamb chops, has led toin the space of one man's lifetime. But wouldhe, like me, have some doubts about thatname Cirkit? It's certainly ingenious. But,because I've that sort of mind, I can't for thelife of me resist adding 'and see'.

And I'm sure we shall.


SPECHL OFFER!QUASAR

ECK

12995INCLUDING VAT 5 CASE PLUS £215 P and P

In April 1982 PE, in conjunction with RT-VC,published the PE Quasar Stereo Cassette Deck design.The design provides some outstanding features, in-cluding variable recording bias and a gate noise reduc-tion system. As a result of this successful design weare now pleased to be able to offer kits to PE readersat this exclusive price. The kits, including a wrap roundsimulated wood finish case, will be accompanied witha reprint of the PE articles which fully describe theunit and its construction.

The offer is for a limited period only and a couponshould be sent to the address shown. The specifica-tion of the made-up unit is given below:

SPECIFICATIONCase size 285 x 260 x 90mm approx.Mechanism with automatic stop and tape counter with resetbutton.Tape Speed: 4.76cm/sec. (1i in/sec.).Wow & Flutter: Typically 0.1%.Drive Motor: 12V d.c. with electrical governor.Play Torque: 40-75g/cm (DYNAMIC).Rewind & Fast Forward Torque: 60-140g/cm (STATIC).Rewind & Forward Time: Less than 100 sec. for C60 tapes.Bias/Erase Oscillator: Externally variable, frequency90-100kHz.Output: (Adjustable) Up to 1 volt r.m.s.Mic. Sensitivity: 1 mV @ 47k.DIN Sensitivity: 30mV @ 47k.Frequency Response; 30Hz-12.5kHz (-3dB).Signal to Noise Ratio.

Noise reduction OFF -50dBNoise reduction H.F. -56dBNoise reduction FLAT -70dB

Cross Talk: Typically -50dB.

To: RT-VC, 21 B High St., Acton, London W3 6NG

Please send me

One deck kit costs £29.95 plus £2.75 p&p (£32.70)

I enclose PO/Cheque No Value

Name

Address

Kit's

Please allow 28 days for deliveryOFFER CLOSES FRIDAY DECEMBER 14 1984

Name

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Access 'phone orders 01-992 8430To: RT-VC, 21 B High Street, Acton, London W3 6NG

L -J


EMT IOM GAME Um' CM MIII

DIGITAL NOISE SOURCE (MM5837N)

AT first sight it might seem a little odd thatsomeone should produce a special i.c. to

generate noise. After all, noise is somethingthat we usually strive to get rid of inelectronics! Indeed, there are very few areas ofthe business where noise doesn't regularlycause problems. Video noise results in thefamiliar 'snow' on pictures, digital noise(especially when carried along power supplytracks) can cause spurious changes in logicstates, corrupting data or even causing seriousmalfunction of equipment. Audio engineersface a continuous battle against noise inmicrophone amplifiers, record deck pickupcartridge pre -amps, and most of all in

cassette and reel-to-reel tape recorders,where noise reduction systems such as Dolbyor dbx are often used specifically to try toovercome limitations of the medium.

So why should anybody actually want toproduce noise? One reason is connected withthe sort of problems that have just beendescribed. In order to test out designs of noisereduction equipment, and to test the ability ofcircuits to reject noise or remain unaffected byit, we need to have a reliable source of noise,probably at a relatively high level initially sothat it can be reduced and controlled toproduce exactly the effect that we require.Noise is, by definition, a random or semi -random type of signal, and the veryunpredictability of it can prove useful ingenerating random numbers in digital systems,or random voltages in analogue systems.Many digital communication links are testedwith digital noise sources to simulate a widerange of signal types. Analogue noise hasapplications in sound synthesis, forming thebasis for many types of sound or sound effect.It's used in speech synthesis to model thehissing sounds made by the human mouth andvocal tract, and it's also used extensively inaudio systems to allow the precise adjustmentof tone controls or graphic equalisers whenoptimising the response of a sound system inany given room or building.

{Vdd

E Vgg

I NOT CONNECTED

I NOT CONNECTED

OUTPUT E m NOT CONNECTED

VE SUPPLY IVssl NOT CONNECTED

-VE SUPPLIES

MM 5837N

Fig. 1. Pinout and specification

GENERATING NOISEWe've already considered the fact that

noise is a random type of signal. It contains nosteady frequency components at all which arediscernible; in fact, a perfect broadband noisesignal can be considered to simultaneouslycontain all possible frequencies from d.c. up toinfinity, the net result of which is a wavepat-tern in which no repetitive waveforms or tonescan be distinguished. This is the type of signalproduced by natural phenomena within allnormal semiconductor materials, albeit at anextremely low level. In very high gain am-plifiers this noise is amplified along with thesignal, resulting in unwanted background'hiss'.

One technique for generating noise uses ex-actly this effect, and is shown in Fig. 2. TR1 isconnected as a reverse biased diode with itscollector open circuit. The tiny noise currentgenerated by this is amplified, first by TR2then by the op -amp IC I. This technique issimple, and usually works fairly well, althoughdifferent types of transistor used for TR I cangive different types of noise, i.e. noise signals

with different amplitudes at different parts ofthe spectrum; a lack of low frequency compo-nents in the noise, an excess of mid -band com-ponents, or similar. A more consistent perfor-mance can be obtained by using a specialnoise generating Zener diode, such as the Z5.1,with a suitable high gain amplifier configura-tion, although these tend to be quite expensive.There can also be problems with mains humand interference, or instability, caused by thevery high gains of the circuitry involved, socare must be taken with the design and con-struction of this type of system.

A DIGITAL NOISE SOURCEAn alternative way of generating noise uses

an 'artificial', rather than an amplified naturaleffect, and this is the basis for the i.c. featuredthis month, the MM5837N from NationalSemiconductor. It's a digital technique using aclocked shift register with multiple feedbackpaths. Fig. 3 shows the block diagram of thei.c. An internal high frequency clock oscillatoris used to continuously clock a 17 bit shiftregister. The shift register acts as a 17 bit 'first

Characteristic NotesMinimum

ValueTypically

MaximumValue

Units

Vdd supply voltage

Vgg supply voltage

With respect to +ve supplypin, V (pin 4).(absolute maxima)

Vs, -25

Vs, -33

Vs, -14

Vs, -27

Vs, +0.3

Vs, +0.3

V

V

+ve supply Vssfor normal operation

Vdd and Vgg connectedto OV +89* +14 +25 V

Temperature range 0 +70 °C

For all following spec's, Vs, = OV, Vdd = -14V,Vgg = -27V

Quiescent current,Vdd (pin 1)

Quiescent current,Vgg (pin 2)

No output load 3 8

7

mA

mA

Half power point 24 56 kHz

Cycle time 11 2.4 s

Output voltages:

LOGIC 1LOGIC 0LOGIC 0

'pin 3 loaded with 20k to Vss)and 20k to Vdd

Vg, = Vdd, i.e. -14V

Vs, -15Vdd

Vdd

VVdd + 1 5Vdd +3.5

V

V

V

= data not available from manufacturer- this was measured on prototype circuit.


A A I/P

VE SUPPLY 6 TO 15V

741C, AAPIWKOR SIMILAR

VE SUPPLY I-6 TO 15V 1

Fig. 2. Analogue noise generator

BIT14 0/17

17 BITSHIFT REGISTER

CLOCK

CLOCK

OSCILLATOR

DATA 0/P(BIT 17)

LPINS 5.6.7.8 NOT CONNECTED I -lee 34M1

Vss I VE I SUPPLY

Vss TO RESTOF CIRCUITRY

Vdd TO RESTI OF CIRCUITRY

V 4 V dSUPPLY SUPPLY,

NORMALLY OV

Fig. 3. Block diagram

in first out' storage device. Any data bit pre-sent at its input when the clock is pulsed willemerge at the data output pin exactly 17 clockcycles later. In this respect, the action of theshift register can be likened to pushingcoloured balls into a length of tubing one byone; they emerge at the other end, one by one,a fixed time later, in exactly the same orderthat they were pushed in. If the output of theregister is connected back to its data input,whatever pattern of logic l's and 0's is presentwithin the register at that time will be 'rotated'continuously round the register withoutchanging.

If we look at other points within the shiftregister, such as the 14th bit rather than theoutput (the 17th bit), we see the state that theinput was at 14 clock cycles earlier, ratherthan 17 cycles earlier as would be the casewhen looking at the output. If the 14th and17th bits are combined together with somelogic gating, such as an exclusive -OR gate, wecan feed a rather oddly derived signal back tothe data input of the shift register. Themathematics of the resultant effect are verycomplex, but the practical end result is analmost purely random digital signal, known asa 'pseudo -random' signal. In fact, it's notperfectly random; it does have a pattern whichrepeats, but only every 1.1 to 2.4 seconds,which only affects very low frequency applica-tions of the noise source. Various differentlengths of shift register, and various combina-tions of output bits in multiple feedback paths

3

NOISE OUTPUT

...V

could be used, but the arrangement employedby the MM5837N is quite satisfactory formost applications.

OUTPUTS FROM THE I.C.The i.c. is fabricated using PMOS

technology, hence the unusual approach ofcalling the positive supply Vss, and thenegative supply Vdd. A third, optional supplyVgg can be biased somewhat more negativelythan Vdd if required, which will slightly im-prove the output drive voltage available fromthe MOSFET output buffer stage connectedto pin 3. The manufacturer's specifications arebased on using the i.c. in a positive eartharrangement, with OV connected to pin 4,-I4V connected to pin 1, and -27V connec-ted to pin 2. This would cause considerableheadaches in most potential applications, so itis quite acceptable to simply connect pin 4 tothe positive supply rail (+8.9 to +25V) andconnect both pins I and 2 to OV. This will givean acceptable output voltage swing for mostpurposes. Note that the lower voltage limitgiven in the specification, Fig. 1, is derivedfrom experimentation on the prototype ap-plications circuit, not by the i.c. manufac-turers. who don't give a lower limit figure. Asthe voltage drops to around this figure, thenoise spectrum becomes somewhat irregular,and below this voltage fixed frequency tonesstart to become discernible within the noise.

The clock oscillator is completely self-contained, so no external timing components

are needed. This is a high frequency oscillator,and it totally defines the maximum high fre-quency limit of the output noise spectrum. The'half power' (i.e. the -3dB) point is specifiedas between 24 and 56kHz, inferring that theclock frequency must be around 100kHz ormore.

NOISE COLOURThe spectral content of a noise signal is

referred to as its colour. There are actuallymany colours of noise: red, blue, etc., but thetwo types most commonly used are white andpink.

White noise is characterised by havingequal energy per constant bandwidth in thespectrum. For example, the energy content inthe region between 1kHz and 2kHz will be thesame as that between 2kHz and 3kHz,because in each case the bandwidth is 1kHz.The energy content will rise by 3dB per oc-tave, however, with an octave being defined asa doubling of frequency, so the energy con-tained in the region 2kHz to 4kHz will be 3dBhigher than that in the region 1kHz to 2kHz.The converse is true for pink noise, which hasan equal energy level per octave, i.e. a 3dBloss in amplitude per constant bandwidth. Forexample, the energy content in the region2kHz to 4kHz will be 3dB LOWER than thatin the region 1kHz to 2kHz. Put very simply,white noise is a very hissy sound with high fre-quency content, whereas pink noise is a duller'wooshing' low frequency content sound.

For audio use, especially in the setting up ofgraphic equalisers and sound systems, the useof pink noise is widespread. Graphicequalisers are usually calibrated in octaves,with each control cutting or boosting theaudio signal in a narrow octave wide, or evenone third of an octave wide band. Using pinknoise ensures that the mean signal amplitudewil. be the same in each band of the equaliser,allowing the spectral response of the system tobe tailored precisely.

CONVERTING WHITE NOISE TOPINK

The MM5837N produces only white noise,so to obtain a pink noise signal we must in-clude filtering to roll off the amplitude at therate of 3dB per octave. Unfortunately, even asimple resistor/capacitor network has a 6dB

YE SUPPLY I TYPICALLY 151/ I

IPE3SM1

Fig. 4. Simple pink noise generator


per octave slope, and most active filters aredesigned for 12, 18, or more dB's per octave.The easy solution is to cascade severalresistor/capacitor networks together, each setto different turnover frequencies in such a waythat they combine to produce an overall slopeof only 3dB per octave. National Semiconduc-tor's recommended network to do this for theMM5837N is shown in Fig. 4. Note that theoutput of this circuit has a fairly small am-plitude for the actual noise signal (only aboutIV peak -to -peak) but this rides on a d.c. level

of just over half the supply rail voltage, and asa result will normally need a series decouplingcapacitor prior to feeding into any other cir-cuitry.

APPLICATIONSThe i.c. can be used either as a purely

digital noise source, or with suitable filteringor amplification as an analogue noise source.Consider using the i.c. output to feed into aCMOS serial in/parallel out register's data in-put, then clock that register with a regular

slow clock pulse. The output from the registerwill be a pseudo -random digital number. If fedinto a digital to analogue converter, this wouldproduce a regularly changing randomanalogue voltage, ideal for use in experimentalsound or music synthesis. Other potential usesfor a noise generator have already been dis-cussed, but perhaps the most obvious is thebasis for this month's applications project.

The MM5837N can be obtained fromAlpha Electronics, 66 Wilbury Way, Hitchin,Herts, SG4 OTT.

AUDIO NOISE GENERATORTHE circuit diagram for a useful audio

noise generator is shown in Fig. 5. Itcan produce either white or pink noise, andhas a variable level control to adjust outputamplitude. The output is electronically bal-anced, making it ideal for feeding into bal-anced inputs to audio equipment, although itcan equally well be used with unbalancedsystems.

One of the attractions of the MM5837N isthat it is very compact, replacing severallarger i.c.s with an 8 -pin d.i.l. package. Thecircuit, and its Veroboard layout, have beendesigned to take advantage of the small size ofthe device, and the result is a very smallassembly, ideal for building into a hand-heldcase. R1, R4, R5, R6, R7, R8, C2, C3, C4,and C5 form the passive network whichderives pink noise from the i.c. output. Themore difficult to obtain values in Fig. 4 havebeen replaced by different quantities of othervalues of component to make it easier to buildwith full accuracy. The pink noise is amplifiedup to a reasonably high level by IC2a, then fedto the selector switch SI. The white noise feed

to SI comes from the output of IC 1,decoupled by C 1, attenuated and biased to OVby R3, and with a high frequency roll -offprovided by R2 and C7 to help reduce highfrequency components in the waveformcaused by the sharp edges of the digital outputof IC I.

9V TO .24V

IC2d buffers the output of the level controlVR1, and feeds into the two halves of thebalanced output, IC2b and IC2c. These areconnected to give EXACTLY the same gain,one with signal inversion, and the otherwithout. The two outputs are thus sym-metrical, i.e. mirror images, about 0 volts. This

CI

10p

25V

Pv!

R2

10k

=MI1, 3,3

SC R6

2k7 270

R5 R7

1

270 27

02 C 3

P 36611

R9

22k

C7min

R8

1k

C4 C5

POLY -j1110 1 T00n T70nT3n

OV

R3

27k

C8

100n

C61=1

2517 2

R1I

330k

MC3403P

R13

12k

WHITE

PINK

CIO

-1-6tj0

TAN T

(NOISE)

CII

VR1 1Q°'100kLOG

(LEVEL)

MC 3403P

IC2d

R15PI6

10k 1%

mc4403P

IC2c

R18 014

10k 160p

C16 25V

47p

017

47p

R 17 C15

CF100p25V

10k 1%

HALF RAIL)

R10 R12 R14

22k 467 560k

C9

T2u 25V

Fig. 5. The Audio Noise Generator

L12mim

TCOn Di SC

IC/b

MC14:3P R19

10k

OR

GNI)0

R20

10k

0U

PU


+95 10+245

OS

C4 CAN BE MACEUPOF TWO CAP-ACITORS INPARALLEL

[PE ISM]

Fig. 6. Veroboard layout

can directly drive into balanced inputs ofaudio equipment, while for conventional un-balanced systems, either output, positive ornegative, can be used, with the common OV orground connected as the return. C I6 and C 17roll off the response of the amplifiers at highfrequencies to keep them stable, and R I8

S1(FINN)VR1 WIPER

VR1

helps to match the response of IC2c as closelyas possible to that of IC2b. Ideally, the valuesof R16 and R 17 should be within 0.1% ofeach other, although the actual value itself isnot as critical. Practically, 1% is adequate formost systems, and even 5% resistors can beused if non -critical uses are anticipated.

BIAS POINT

Components R9, R 10, and C6 provide ahalf -rail bias point for the op -amps, C 12 andC13 decouple the supply, C 14 and C15decouple the outputs to block d.c. from the op -amps, and RI9 and R20 bias the outputs toOV. The output impedance is very low indeed,so if a 600 ohm output impedance is required,then a pair of 300 ohm resistors, againmatched to within 0.1% or I% of each other,should be added in series with the +ve and-ve outputs. The relative amplitudes of pinkand white noise can be adjusted by varying thegain of lC2a (change RI2 or RI3) or the at-tenuation of the white noise source (changeR3), although care must be taken to avoidclipping of the waveform, which could bechecked for on an oscilloscope. Many quadop -amp packages could be used for IC2, butsome do not work well on low supply voltagesin the voltage follower mode. The MC3403Pdoes work well under these conditions,although if supplies of 18V or more (or +/-9V) are used the TL074 offers better high fre-quency performance, and is to be preferred.

The noise generator can be used for testingnoise rejection or reduction systems, forsetting up graphic equalisers or roomequalisers, or even for generating special ef-fects. Its compactness is largely due to thediminutive MM5837N, and shows a typicaluse for this digital noise source i.c.

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va.ikOnf-,

LASERS ANDHOLOGRAMS

RADAR ALARM

You probably benefit from the use ofHolograms and LASERs every day. Now youcan find out what they are, how they workand what they are used for.

Part two of the Radar Security Alarm (Part 1 wasin the October '84 issue) will include a newtransmitter design and give full construction andsetting -up details of the complete system. Makesure your home is protected.

PRACTICAL

ELECTRONICSROBOTICS - MICROS - ELECTRONICS - INTERFACING

JANUARY 1985 ISSUE ON SALE FRIDAY, DECEMBER 7

al Practical Electronics December 1984

ELBAR SALEAll products new with money back guaranteesIn Car Equipment:7 Stage Graphic Equaliser 19.50Door Speakers (per pair) L9.50Wedge Speaker (per pair) L4.10

Professional Audio (Literatureavailable on request)100 Watt Compression Drivers L65.00100 Watt Tweeters L50.0012" 60 Watt Bass Units L26.00HD 30 Watt Tweeters L7.0015" 100 Watt Bass Units LIO 1 .00

Opto ElectronicsRed LEDs LOA 0

Green LEDs C0.25Orange LEDs £0.25

7 Segment DisplaysLED 0.3" L0.90LED 06- LI .40LED 1.0" L2.00Filament 9mm. high brightness ... L1 .50Filament I 8mm, high brightness LI.70

Back PanelFuse Holder L0.105 pin Din Sockets £0.352 pin Din Sockets L13.03

Push button Micro Switches L0.50

Panel Mounting Pots25K/25K dual log CO 30

100K/ 100K dual linear CO 3047K single linear CO 15

Hi-Fi Systems - Seoum(all reviewed)Tuner LW/MW,FM £25.0030 Watt Amplifier L29.0020 Watt Amplifier L42.00High Velocity Headphones LI 1.00

Hi-Fi Speakers:Minimax II (per pair) L59.90BB 1312 (per pair) L39.00

(2 way)DB 1206 (per pair) £49.00

(Many more items - send for list' 7447 Driver Decoder £0.80 (3 way)Sub Woofer Special "Practical

Components: Tantalum Capacitors Electronics- Design £69.00Green Clock Displays L1.50 Panel Meters Dry type 8 asstd values between 2.2 MFD Kit as above L40.90Clock Driver Chips L1 .25 Centre zero 100uA L1.60 & 47 MFD 0.90 the lot P&P i 5pTransformer for above £0.45 Level Meter 100uA . L1.50 Min 4 pcs. one value L0.15 each P&P 15p LCD Dot Matrix Panels:PC Board L0.20 VU Meter 100uA L1.50 x16 I x 40

Cermet Trimmers 2x 16 2 x 4

Mounting Hardware for LED Capacitors All values £0.60 each. P&P 15p 2 x 24

Modern professional system for mounting Ceramics 0.01 50 for L 1.00

digital indicators. Includes sockets and Full range of Mica Types available Trimmer Capacitors Computer Products:attractive front hazel with polarized screen.From 2 to 8 digits. Switches Min. Toggle Mill 5 pieces L0.10 each. P&P 15p Graphics/Colour Graphics

CPU/Mernary Boards

Price for 0.3" & 0.5" LEDS (3.50 plus 50pper digit over 2 digits.Price for 0.6" and I" Reds (4.50 plus 60p

I pole. 2 way2 pole. 2 way3 pole. 2 way

L0.62(0.73L1.10

Trimmer Carbon Pots5 pcs asserted values L0.25. P&P 15p

Printers/Bar Code ReadersMonitors - send for full data and prices

per digit over 2 digits.Front Bazel only l/2 price P&P 50

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Digital Clock ModuleNeeds on y single power supply L7.00

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ELECTROVAMYour

SPECIALISTSIMMERS

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II


RICHARD B. H. BECKER - SYSTEM DESIGN AND MECHANICAL ENGINEERING.

TIM ORR - COMPUTER INTERFACE AND CONTROL ELECTRONICS.

!IC% 1110T40I 11MI\IIM I I I Alh

=MI.m. ,

TI

IIIS SERIES is concerned in part four with the control elec-tronics and mechanical construction of the MENTOR robot.

Like the NEPTUNEs, MENTOR interfaces directly to any oneof three popular home computers and provides the facility forcontrol either from the keyboard, or by making use of the"learning arm".

PRINCIPLES OF OPERATIONMENTOR is a 6 -axis servo controlled electric robot (Fig.

4.1). Whilst the NEPTUNEs are designed for industrial use,MENTOR is primarily intended for educational purposes but ascan be seen from the specification (Table 1) it too has therepeatability for many commercial applications, where the loadis light. Each of the axes is powered by a small d.c. servo motorwith integral gearbox with a large reduction ratio.

Axis 0 is the centre column which rotates in a nylon bearingin the top plate of the base of the robot and is powered by themotor through an additional pair of gears (Fig. 4.2). The radial

PART FOUR

position of the column is sensed by a conductive polymer poten-tiometer fitted to the underside of it. The column is hollow toenable the cables to pass down it to the computer interfaceboard.

Axis I is the lower section of the arm which rotates about anaxle fitted to the centre column (Fig. 4.3). Again a pair of gearsis used to transfer torque from the motor to the axle and a poten-tiometer provides the feedback information. The axle is hollowfor the cables to pass through it.

Axis 2, the fore arm is driven in the same manner as axis 1. Alarge piece of steel at the back end of the lower arm sectioncounterbalances the weight of this section of the arm making therobot's position stable when there is no power applied to it;

AXIS 0 (centre column)

AXIS 1 (shoulder)

AXIS 2 (elbow)

AXIS 3* (left wrist axle)AXIS 4* (right wrist axle)WRIST PITCHWRIST ROTATIONAXIS 5 (gripper)

REPEATABILITYLIFTING CAPACITYREACH (from axis 1 axle

centre)BASE DIMENSIONS

Table 1. MENTOR SPECIFICATION

Angular movement 210°.Axle centre 170mm abovetop of base.Angular movement 180°.Arm length between axlecentres 165mm.Angular movement 230°.Arm length between axlecentres 150mm.Angular movement 320°.Angular movement 320°.Angular movement 140°.Angular movement 320°.Jaw opening 30mm. Jawpressure 10 newton. Distancefrom end of jaws and axis 3and 4 axles 105mm.2mm.300gm.420mm.

Overall width 320mm.Overall depth 270mm.Overall height 189mm.

CONTROL SYSTEM All axes servo controlled withservoing performed by thecontrol electronics.Position defined by 8 data bitsgiving angular resolutionof 0.4%.

COMPUTER INTERFACE Parallel. Robot addressed asif part of computer memory.Connects to expansion port(1MHz bus on BBCI.

SOFTWARE Accepts commands in BASICor machine code.

SOFTWARE PROVIDED Extensive package of BASICprograms including directcontrol from computerkeyboard, control bysimulator, sequence storing,replay, sequence editing,sequence storage on disc ortape, multi -speed control andgraphical illustration of robotdynamics.

*AXIS 3, 4 movements are combined to provide wrist pitchand wrist rotation.


ROBOTICS PROJECT

WRISTELEvAT1ON

140° WRISTRCTATION

: 0°

Fig. 4.1. Exploded view of the complete MENTOR system

therefore the drive motor does not have to be continuously on tokeep the arm in position. There are also counterbalance weightson the fore arm to balance out the wrist motors.

To

Transformer

ac POWERINPUT

Axes 3 and 4 are the wrist drive motors. The movements arecombined to provide wrist elevation and wrist rotation by meansof a set of bevel gears. When axes 3 and 4 advance together the

Axis drive systems: Fig. 4.2, above, shows the system usedto drive axis 0. Fig. 4.3, opposite, shows the drive system foraxis 1. See also Fig. 4.1, and the text

LOWER ARM

701 GEAR

POTENTIOMETERMOUNTING PLATE

POTENTIOMETER

IBM!,

301 GEAR -/SET SCREWS

500 :1GEARBOX

NYLONBUSHES

SPINDLE

MOTOR

NUT

111111111116

CENTRECOLUMN


wrist rises. When the axes move in equal and opposite directionsthe elevation remains constant but the wrist rotates, as shown inFigs. 4.4 and 4.5.

Axis 5 is the gripper which is also servo controlled. To keepdown the weight at the front end of the fore arm the drive motorfor this is fitted to the lower arm with the power applied to thejaws via a flexible cable consisting of a nylon -coated multi-

strand steel wire inside a spiral wound PVC -coated conduit. Thisis similar to the brake cable of a bicycle. Torsion springs openthe jaws when tension is released on the cable. Being servo con-trolled it is possible to program different degrees of jaw closure.If the programmed position is for a gap between the jaws of lessthan the size of the object to be handled then the grip will dependon how much further the servo system is trying to move thejaws.

THE MENTOR CONTROL SYSTEMThe MENTOR, like the NEPTUNE, can be connected to one

of three popular computers, the Commodore VIC20, the Sin-clair ZX Spectrum and the BBC. When the computer sends therobot new data it responds by moving to a position where thefeedback information from the potentiometers exactly matchesthe information from a DAC (digital -to -analog converter) con-trolled by the computer. This process is called servoing. Each ofthe 6 axes of movement can be defined with 8 -bit (1 part in 256or 0.4%) resolution.

ROBOT CONTROLTo move each of the axes the computer sends (WRITEs) 6

bytes of data to the robot, one to each axis. The servoing is per-formed by dedicated hardware on the computer interface boardof the robot. In a typical movement of the robot, the computer

POTENTIOMETERMOUNTINGBRACKETS

POTENTIOMETERS

AXIS 3MOTOR

7511GEARBOX

NUTS

GEARS

121GEARS

ALUMNUMBLOCK

FOREARM

(ECIaTtl

JAWS

STEEL CABLE

TORSION SPRINGSSET

SC FEW BUSHES

BEVELGEARS

`CONDUITOF CABLE

AXIS 4MOTOR

751GEARBOX

Fig. 4.4. Wrist and gripper drive system

AXIS 4

AXIS3 AX1S4 E

0

0 +1 +

-1 0

-1 0

+1 0

+1 0 + ++1 -1 0 +1

+1 +1 +1 0

Fig. 4.5. Wrist operation showing effect of one -bit changeon axes 3 and 4

sends 6 new bytes of data to the robot. The computer is thenwriting to what it "thinks" is just another area of its memory.The interface board then stores these 6 bytes of information andconverts them to 6 position control voltages. The analog elec-tronics on the interface board then compares these voltages withthe feedback voltages. The difference between these two voltagesis delivered to high power operational amplifiers which drive themotors in the direction which reduces the difference to zero. Thisis the servoing process.

FEEDBACKThe computer is not involved in the servoing, it is merely

generating data and relying on the robot to follow the instruc-tions correctly. However the computer can perform a READ ofany or all of the 6 feedback voltages and can thus be aware of allthe movements of the arm. This process can be used to delaysending the next set of co-ordinates until the previous set of co-ordinates have been reached or for varying the speed of therobot during playback of a sequence. It is also easy to produce agraphical display of the movements and observe the effect ofvarying loads and of alterations to the components determiningthe characteristics of the servo system.

The computer can also READ the position of the simulator,which is a small hand operated model of the robot which can beplugged into the learn axis input CN400. The computer READSthe position of the simulator and then WRITES this data intothe robot. The arm follows the real-time motion of the simulator.The movements are stored in the memory of the computer andcan be transferred to tape or disc for later use.

COMPUTER INTERFACESAll three computers make available various signals for exter-

nal use. See Fig. 4.6. These include the data bus DO to D7, someof the lower address lines, READ and WRITE signals, thesystem clock and on the VIC20 and BBC a memory blockdecode. The BBC and VIC20 both use the 6502 microprocessor,so have relatively similar decoding electronics. The Spectrumuses a Z80. This together with some unusual practices in theSpectrum design makes interfacing somewhat different.

All the data and address lines are hard wired together so iftwo computers were simultaneously connected a bus clashwould occur. However there is no reason why two or morerobots should not De daisy -chained together either to performthe same task or completely different tasks if a different addressis used. For example, using a BBC Computer one robot could beaddressed with the link -selected "FRED" decode (FC 00-FC FF)whilst the other is addressed with the link -selected "JIM" decode(FE00-FEFF). All three interfaces generate a VALID WRITEsignal. The Spectrum WRITES to the block 0000-1FFF whichis where the ROM resides and as ROMs are not normally writ-ten to no conflict occurs. The other computers WRITE to non-existent areas of RAM. IC302 is a multiplexer which selectswhich interface will generate the READ and WRITE signals.The Spectrum interface generates two READ signals (ZXRD63and ZXRD95). These are not passed through the multiplexerbut are used later on in the electronics to perform directREADs.

The MENTOR simulator (learning arm)


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WRITINGData is sent to the robot as 6 bytes, each with a different ad-

dress. See Fig. 4.7. Six latches are used to store this data (IC104,107, 109, 112, 114, 117). These are individually clocked with theaddress decodes from IC102, which is driven by the lowest threeaddress lines. A typical WRITE is as follows. In one computerinstruction cycle, the data is set up on the data bus, a VALIDWRITE signal is generated and the LSBs of the address bus areset to the correct axis address. When the VALID WRITE signalgoes high the data is written into the latch corresponding to thataxis. The other axes are then written to similarly. The data heldin the latches is converted into position control voltages by theDACs (1C105, 108, 110, 113, 115, 118). All the data passes

COMPONENT REFERENCESIC100 -116TRIO° -101C100 -137R100 -125CN100

/A +0°YANA_ 01/DID

D7

06

05

04

D3

02

DI

DO

I.B A

B A

B A

B IC100 "7415245

B A

B A

B A

DIR

DIR: 11 7. READ FROM FEEDBACK A....13 413L = WRITE TO ROBOT

R118+5V),

27k C12410,u

A

R119

10k1A

POWER PINOUT

AA

DIR( FROM 1C401)

SAO

BA1

BA2

BA3+5V-ILt

VALID W

EOCL

EOCF

DEVICE PINS +5V OVD +15V -15V

7415244 20 20 10 - -741 5245 20 20 10 - -741 5374 20 20 10 - -7415136 16 16 B - -RC45513 6 - - 6 4

A

B

TO

T1

G2A 1C102 "74LS136

GI

G2BY5

Y6

Y7

+15V

R121100

TR100BC182L

through IC100 which is a 74LS245 bus transceiver. When theDIRection signal is low, data passes from B to A (WRITEmode). When the D1R signal is high, data passes in the otherdirection from A to B (READ mode).

READINGThere are two ADCs in the system, IC400 and 402 as shown

in Fig. 4.8. These are 8 -bit devices with integral 8 -way analogmultiplexers and integral 3 -bit address latches. IC400 is used tolook at the feedback voltages VF139) to VFB5 and the otherlooks at the learn axis (simulator) signals VLO to VL5. The in-put voltages to the analog multiplexer must not exceed the ADC

2 MSBBD7 0B07

66B06 0BD6

BD5 0BUS

sBD4 1C104 °804

BD3741.6374 II

B03IS 10

B02 BD217 11

BD1 BDIIf

BDO BOO D 0

WCKO

WCK1

CE Oo

13 WCK2

WCK3

VICK4

10 WCKS

9 WCK6

7 ViCK7

10V REF

A

-ISV

-1011 REF

TR101BC212L

8124100

DEIC2121BCIB2L

D

07

D6

DS

D4 IC105D3 DACM°

10

D2

+10V REF

VREF+ R1°.-0\r".,s R101 5"

VREF-

GRID 2

31 VLcC102

'.!ADO COMP+50 VEE

e?"1C106b . 107, 1013

BOO

VCC

13 3(On

0100 C101T 100n 100n

8103 - 105

°IP -1IC109,110,1110

Bt20

R106 -106

R102

Ski C103

100n

IC1

RC4558

)080

C104 _107 OP1

0106-111 1.)0P2

131?7[---1 IC1119,112,113 R109 - Ill C112-115 H DP3

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Br --I-IC114, 115,116a R112 -114 C116 -119 H DP4

131)04

BI:f7

1C1160, 117, 118 R115 - 117 C120 - 123 OP5

800 J

CN100/1 +59)

CN100/2 01f0

C11100/3 +15V )

CN100/4 OVA )

CN100/5 -15V )

CN100/6 +12V

CN100/7 OVM )

CN100/6 -129)

C135 0127-130,T41371;134

11 0136 1 C131T0,047 T 100n

10137 1 C132TO/u47 T 100n

) +5V

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+I5V

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Fig. 4.7. The electronics concerned with a "Write" operation

R125

ADDRESS READ WRITE

X X 0 0 WCKO - DPOX X 0 1 WCK1 - DPIX X 0 2 W012 - DP2X X 0 3 WCK3 - DP30004 WCK4 - OP4X X 0 5 WCK5 - OF'S

0906 WO% - RE*0007 WCK7 -grX X 1 0 0rEX X 1 1 15EY

x 0 1 2 EtIFCT

X x 1 3

*D7 06 06 Di D3 D2 DI DO CONTROL BYTEX ,C13 A X C 13 A ILE

L-1-/FB LEARN


supply rails. To prevent this from occurring diode and transistorclamps are used wherever higher voltages could possibly arise.

A READ is performed as follows. The axis channel is selectedby writing a 3 -bit code (13130,1,2, and BD4,5,6) into the ADCs.The ALE (Address Latch Enable) signal latches these codesinto the ADC internal registers. These codes select the multi-plexer position. A start conversion signal is then generated. TheADC takes about 100 microseconds to perform the conversion.A test can be made for the end of conversion (EOC). Bygenerating the =In signal both EOCs can be tested as both

1P6133341 C400

BD7 N58

1306

1305 ,<

BD4 <

BD3

(BD1

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OEF(

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47n13 * 51P400

Vcc REF

ISB

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158

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I C400ADC0809

FEEDBACKADC

REF 61405

to 51P401- 1147 54c S1P402

1 6 0 --"NC252 SIPNE -WORK

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1144 VFB4

VFB3

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25

22

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081.<

10 17

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21

20

19

14

COMPONENT REFERENCES

1C400-406, 1C306TR 400 - 405D400 - 413C400 - 411R400 -4185IP400 - 40208400 - 405CI4400

+5V

MSB

0

LSEI

E

SC CK EOCALE

A

IC402ADC0809

LEARNADC

B

INS

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23

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(BOO

2-NCNC

252 SIPNETWORK

I 5 .LO\A/k

INO

Vcc VREF VREF 0140

<8131

(802

ADCs convert at the same time. A high indicates end of conver-sion (see IC101). When the conversion is complete then one orboth of the ADCs can be READ. The ADCs have tri-state out-puts which are enabled by the OEF and OEL signals (activehigh). The READ is then performed by generating a VALIDREAD signal and an address code to select one of the twoADCs. This enables the tri-state output of the selected ADC andalso generates a DIR signal which sends data out from the inter-face board onto the computer's data bus. The computer can thenREAD the axis data.NEXT MONTH: MENTOR construction

BAO

BA1

BA2 L

BA3

+5V 441.

VALIDR-.15

A

B

C

G2A

GI

GOB

IC406 y37415138

READ "DECODER

YO

Y1

Y7

POWER PIN OUTS

+-5,11C4Old, IC3060

+5V

IC40547n

REF DEVICE PINS +5V OVG +15V OVA -15V

10400 ADC0809 26 11 13 - 13

741504 14 14 7 - - -IC402 ADC0809 26 11 13 - 13 -IC403 RC4558 8 - - 8 3.5 4

10404 RC4558 8 - - 8 3,5 4

10405 RC4558 8 - - 8 3,5 4

IC406 7415138 16 16 8 - - -1C306 741511 14 - 7 - - -

+3V6

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R404- R406 --1.)VL4 014400/7

13404,405 104035 VR404_____ _I

FTR402 -0406.407 1C404 a 1/11403

1-7IR403 0439 R410 - R412

0408,409

r TR404 C410 R413 -15415

' 0410,411 1C405 a VR401- - __J

C 4 0

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11

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-10V 04400/9110

-10V REF

) OV CN400/112

A

+10V

VR405105

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%A

C406 R407 -8409 1)%,L3 CN400/6

CN400/5

1C40413 _VR402_

CN400/4

LTR405

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IC4054 VR400J IN

Fig. 4.8. Analog -to -digital conversion for a "Read" operation


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Accuracy: d.c. ranges and fl 2% a.c. 3% (of f.s.d.)39 ranges: d.c. V 100mV, 1 OV, 3 OV, 10V, 30V, 100V, 300V, 1000V.

d.c. 150µA, 10014A, 30012A, 1.0p,mA, 3mA, 10mA, 30mA,100mA, 1A, 10Aa.c. V 10, 30V, 100V, 300V, 1000V;a.c. I 3mA, 10mA, 30mA, 100mA, 1.0A, 10A.fl 0-5.0kt1, 0-50kfl, 0-500kf1, 5M11, 50M11.dB from -10 to +61 in 5 ranges.

Dimensions: 105 x 130 x 40mm.These special offers is a wonderful opportunity to acquire anessential piece of test gear with a saving of nearly £20.00.

(complete with carrying case,leads and instructions) ONLY £33.50

PRICES Our prices include VAT and postage and goods are normallydespatched by return.

For details of these and the many other instruments in the Alcon range,including multimeters, components measuring, automotive and elec-tronic instruments, please write or telephone:

ALMONInstruments Ltd.19 MULBERRY WALK LONDON SW3 602 TEL 01-352 1897 TELEX 918867

58

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Please allow 7 days for deliveryAll brand-new Components. All valves are new and boxed

80303 1.181BC327 INII

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113224 NI

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Telephone. 01-9042093 & 904 1115,8Telex: 932885 Sunmit

INDEXJANUARY 1984 TO DECEMBER 1984

VOLUME 20CONSTRUCTIONAL PROJECTS

Alarm, Anti -Theft Mar 24Alarm, Baby May 43Alarm, Low Water Level Aug 58Alarm, Radar Security Oct 30Alarm System by G.E. Lumley July 48, Aug 60Analyser, Simple Logic July 14, Aug 50Anti -Theft Alarm by M. Tooley BA and D Whitfield

MA MSc CEng MIEE Mar 24Audio Noise Generator by Tom Gaske// BA(Hons)

CEng MIEE Dec 48Audio Signal Generator by Stephen Ibbs May 30Autosave, Spectrum Mar 14

Baby Alarm by Tom Gaske// BA(Hons) May 43

Calibrator, Oscilloscope July 56Camera Trigger, Ultrasonic Jan 26Car Computer by S.H. Cousins and P.D. Wilson Dec 10Car Interior Light Delay Switch by N.J. Chaffey April 36Clock Timer by T.J. Johnson Feb 24Combination Lock by Tom Gasket/ BA(Hons)

CEng MIEE Nov 26Commodore 64 RS232C Interface by R.A. Penfold Aug 12Computer, Car Dec 10Computer DFM Adaptor by R.A. Penfold Nov 49Computer Terminal by Ray Stuart Feb 16, Mar 28Continuity Checker by Chris Lare June 52Controller, Temperature Feb 50Controller, Through -the -Mains Sept 40Converter, Parallel to Serial Sept 17Cross Hatch Generator by R.A. Penfold June 48

DFM Adaptor, Computer Nov 49Digital Dice by P. Leah Aug 30Dissolve, Slide July 30Duplicator, EPROM July 20

Echo & Reverb, Mono/Stereo Sept 10EPROM Duplicator by Prof. K. Padmanabhan

PhD MIEE and S. Ananthi July 20Expanding the VIC 20 by Sam Withey Jan 36, Mar 36,

April 46, May 36

f -Stop Enlarger Timer by Tom Gaske// BA(Hons)AM/EE July 28

Field Measurements by T.P Manning Aug 22Filter Shift Phaser by John H. Becker Oct 10Frequency Oscillator, Spot June 60Generator, Audio Signal May 30Generator, Cross Hatch June 48Generator, Heads & Tails April 42Generator, Logic Signal May 23

Heads and Tails Generator by M. Tooley, BA andD. Whitfield MA MSc CEng MIEE April 42

Hyperchaser by P. Newbury June 24

Interface, Commodore 64 RS232C Aug 12

Light Delay Switch, Car Interior April 36Lock, Combination Nov 26Lock, Opto Oct 56Logic Probe, Pulse Direction Oct 52Logic Signal Generator by M. Tooley BA and

D. Whitfield MA MSc CEng MIEE May 23Low Water Levet Alarm by Tom Gaske// BA(Hons)

AMIEE

Mastermind Timer by J.D. Parkinson BScMeasurements, FieldMeter, Plant Watering April 39Microstepper by L.G. Parkin BA April 18Modulator, Ring Nov 10, Dec 23Mono/Stereo Echo & Reverb by John M.H. Becker.. Sept 10

Neptune Robots by Richard Becker and Tim Orr .... Sept 32,Oct 28, Nov 28, Dec 52

Opto-Lock by Tom Gasket/ BA(Hons) CEng MIEE Oct 56Oscilloscope Calibrator by M. Tooley BA and

D. Whitfield MA MSc CEng MIEE July 56

Parallel to Serial Converter by R.A. Penfold Sept 17Phaser, Filter Shift Oct 10Plant Watering Meter by Tom Gaske// BA(Hons) April 39PSU, Simple May 60Pulse Direction Logic Probe by S.A.Withey Oct 52

Aug 58

Aug 18Aug 22

Radar Security Alarm OctRegulator, Voltage and Current SeptRing Modulator by John H. Becker Nov 10, DecRobots, Neptune Sept 32, Oct 28, Nov 28, Dec

30542352

Simple Logic Analyser by Chris Atkins July 14, Aug 50S mple PSU by Stephen /bbs May 60Simple Speech by P. Creighton Jan 55Slide Dissolve by Peter F. We//s July 30Spectrum Autosave by R.A. Penfold Mar 14Spot Frequency Oscillator by Tom Gaskel/ BA(Hons)

AMIEE June 60Stardesk by Peter Newbury Jan 16, Feb 32Sub Woofer by Cliff Hardcastle July 24Sustain Unit by R.A. Penfold May 26System, Alarm

Temperature Controller by T.J. JohnsonTerminal, Computer Feb 16, Mar 28Through -the -Mains Controller by RA. Penfold Sept 40Timer, Clock Feb 24Timer, f -Stop Enlarger July 28Timer, Mastermind Aug 18

Ultrasonic Camera Trigger by RA. Penfold Jan 26Unit, Sustain May 26

VIC 20, Expanding the Jan 36, Mar 36, April 46, May 36Voltage and Current Regulator by Tom Gaske//

BA(Hons) CEng MIEE Sept 54

Woofer, Sub July 24

July 48, Aug 60Feb 50


GENERAL FEATURESCompact Disc by Chris Kelly Jan 30Disc Drives Explained by M. Tooley BA and

D. Whitfield MA MSc CEng MIEE Sept 22, Oct 20,Nov 40

Fibre Optics by D. Stewart July 42

Hands on the QL by Dr. A.A. Berk July 34INGENUITY UNLIMITED April 25, 31, 41, May 63,

June 34, Aug 44, Oct 58A Simple VCO by A.Flind Aug 48Audible Reversing Alarm byJ. McPherson ....June 34Audio to Logic Interface by P. Thompson Aug 48Automatic Bilge Pump by G.W. Co/es Oct 58Flood Alarm by Dr. C.J.D. Catto Aug 44Foolproof Switch Bank by G. Durant April 41

Infra -Red Shop Doorbell by A.R.W. Hall Aug 46Internal Resistance Meter.by R.P. Dudley Aug 47Intruder Alarm by P.E. Mackrel/ May 63

Joystick for Dragon 32/64 by T.M. Gooding ...Aug 45

Low Cost Keyless Lock by S.A. Brown Aug 49Low Power Voltage Regulator by A. Flind Aug 45Micropower Regulator by B. Hunter Oct 58Monostable Frequency Divider

by P. Thompson April 25

Power Supply Fast Shut Off by G.V. Whitney ..Aug 46

Scalectrix Motor Control by A. Cook June 34Venetian Blind Intruder Alarm by G.E. Lumley .Aug 49Voltage Controlled Amplitude by A. Flind Aug 44

35 I.e.d. Tacho by I. Benton April 31

INMOS by Tom Nall March 50Introduction to Digital Electronics by M. Tooley BA

and D. Whitfield MA MSc CEng MIEE Jan 46, Feb 60,March 54, April 62, May 52, June 38

Micro Bus ....Feb 67, March 61, April 35, May 58, June 56,Aug 26, Sept 57, Oct 29

Microprofessor Review by M. Tooley BA April 58Monitors for Home Computers by M. Tooley BA and

D. Whitfield MA MSc CEng MIEE Feb 44, March 47Multimeters-Buyer's Guide May 14

Nickel Cadmium Batteries by M. Tooley BA andD. Whitfield MA MSc CEng MIEE Nov 17, Dec 38

Radio Astronomy by Frank W. Hyde Aug 35

SEMICONDUCTOR CIRCUITS by Tom GaskellBA(Honsi CEng MIEE Jan 60, Feb 28, March 18,

April 38, May 42, June 58, July 26, Aug 57, Sept 52,Oct 54, Nov 24, Dec 46

Stereo Signal Processor (TDA 3810) Jan 60LED Bargraph Drivers (UB ..B Series) Feb 28Tachometers (LM 2917N-8 and LM 2917N)

March 18Window Discriminator (TCA 965) April 38Gain Controlled Preamplifier (SL6270C) May 42Touch Tuners (SAS 580 and SAS 590) June 58Programmable Timer (ICM 7240) July 26Fluid Detector (LM 1830N) Aug 57Voltage and Current Regulator IL 200C) Sept 52Encoder/Decoder (MM 53200N) Oct 54Pushbutton Locks (LS 7228 and LS 7229) Nov 24Digital Noise Source (MM5837N) Dec 46

Sequential Logic Techniques by M. Tooley BA andD. Whitfield MA MSc CEng MIEE Oct 16, Nov 53,

Dec 15Soldering Instrument -Buyer's Guide Dec 30Spot Pricing by T.W. Berrie June 35

Technology Update: SO SMD's May 48Test Instruments -Buyer's Guide June 14Transputer by R.W. Coles April 26

Vernon Trent at Large ...Jan 34, Feb 56, March 23, April 32,May 35, June 47, July 41, Aug 54, Sept 56, Oct 51,

Dec 44

NEWS AND COMMENTBAZAAR Jan 59, Feb 21, 40, 68, March 16, 20, 44, 62,

April 53, 60, May 41, 50, 57, June 44, 51, July 29, 59,Aug 41, 65, Sept 50, Oct 50, Nov 45

BOOK REVIEWS Aug 67

EDITORIAL Jan13, Feb 13, March 11, April 15, May 11,June 11, July 9, Aug 7, Sept 7, Oct 7, Nov 7, Dec 7

INDUSTRY NOTEBOOK by Nexus Jan 24, Feb 22,March 17, April 54, May 45, June 23, July 33, Aug 29,

Sept 31, Oct 36, Nov 23, Dec 28

LEADING EDGE by Barry Fox Aug 43, Sept 46

NEWS AND MARKET PLACE ....Jan 14, Feb 14, March 12,April 16, May 12, June 12, July 10, Aug 8, Sept 8, Oct 8,

Nov 8, Dec 8

PATENTS REVIEW Feb 43, April 44, May 47, July 38

PRINTED CIRCUIT BOARD SERVICE Nov 37, Dec 37

READOUT Jan 62, March 34, 62, Oct 46

SPACEWATCH by Frank W. Hyde Jan 45, Feb 59,March 35, April 57, June 33

SPACEWATCH by Dr. Patrick Moore OBE . Aug 40, Sept 49,Oct 49, Nov 38, Dec 36

STRICTLY INSTRUMENTAL by K. Lenton-Smith Aug 66

SPECIAL SUPPLEMENTSMicro -File by Ray Coles Filesheel 16 NSI6032 June

Filesheet 17 Z800 JulyFilesheet 13 Z8 JanFilesheet 14 8073 MarchFilesheet 15 NSC800 May Robotics by Tom Ivall Nov


ORIC AND SINCLAIR COMPUTERS

Oric 1 computer 48K £95 (E92) £102.Oric Atmos computer 48K E171 ([158)£168. Oric Colour Printer £134 (£123)£140. Oric disc drive £304 (f278) 1298.New Sinclair OL Computer £406 (£385)£410. Sinclair Spectrum 48K (with 6 freeprograms while Sinclair 's offer lasts)£131 (E131) £143. Microdrive £51 ([50)£60. RS232 interface 1 £51 (E50) £60.Limited period special offer:- Microdrive

Interfce 1 A- 4 Blank cartridges E102(£100) £120. Blank microdrive cartridgesEa (ES) £9. Interface 2 [20.45 (£20) £24.32K memory upgrade kit for 16K Spec-trum (Issue 2 and 3 only) E31 (£28) MO.Fuller Master Unit for the spectrum in-cluding speech synthesizer, sound syn-thesizer, amplifier and (oystick port t36(£56) E62. Fuller FDS full sized keyboardfor the spectrum with proper space bar£52 (£52) £62. Spectrum printer inter-faces with cables:- Centronics £51 (E47)E52, RS232 E35 (£33) £38. ZX printer hasbeen replaced by the Alphacom 32 £71(£67) fn. 5 printer rolls (State whetherSinclair or Alphacoml £13 (£16) f21.2X81 computer £45 (£44) £54. 16K rampacks for ZX81 128 (£25) MO.COMMODORE COMPUTERSCommodore 64 1204 (£184)E204. Vic 20£104 £97) E117. Vic 20 starter pack £150(£143) £173. Convertor to allow mostordinary mono cassette recorders to beused with the Vic 20 and the Commo-dore 64: £9.78 (f9) Ell. Bargain pack-age:- cassette convertor r- compatiblecassette recorder [37 (E38) £44. Com-modore cassette recorder E43 (£44) SO.Printer interfaces for Vic 20 and theCommodore 64:- £45 (£41) E46. RS232£45 (E41) E46. Disc drive £233 (f209)£234. 1520 Printer/Plotter £165 (£149)£159. 1525 Printer £235 (£220) £245.

SWANLEY ELECTRONICSThe Computer Export Specialists

Dept PE, 32 Goldsel Rd., Swanky, Kent BR8 812, England.Please allow 7 days for delivery.

Tel: Swanky (0322) 64851. Official orders we/come. UK prices are shown first andinclude post and VAT The second price in brackets is for export customers inEurope and includes insured airmail postage. The third price is for exportcustomers outside Europe /including Australia etc) and includes insured airmail

postage

1526 Printer £350 (E330) £360. Light pen£29 (E29) £33, Vic 20 Accessories. -Super expander high res cartridge £33(£29) £34, Programmers aid cartridge1E33 (E29) £34, Extra memory ram packs8K £19 ([17) 120. 3K E6 (f7) £9.

ACORN COMPUTERSElectron £203 (£209) £229. Electrcn -

stick and printer interface E61 (£62) £69.BBC Model B £404 (6357) [387. BBCLight Pen [29 (£29) £13. 14' Colourmonitor £228 (1299) £319. (endadouble density disk interface system

(f125) £135 Disc drives 5.25" 40track:- single £200 (E1841 £204, dual£356 (E3251 E355.

PRINTERS

Brother HR5 £185 4E171) £190. ShinwaCT) CP80 £225 (U18) £248. CannonPVV1080A E332 ([299) £329. EpsonRX80 £277 (E251) 1282. Epson RX80F/T£314 (£286) 016. Epson FX80 £399(£358) £388. Combined matrix printersand electric typewriters- Brother EP22£173 (E166) £186. Brother EP44 £258(E235) £260. Smith Corona TP1 Daisywheel printer £252 (1225) £255. MCP40Oric colour printer/plotter £134 (£123)£140. Interfaces to run the above print-ers from Vic and the Commodore 64 E45(E41) £46, We can supply interfaces torun the above printers from Shan com-puters £58 (£52) £55.

'TORUS"Computer -controlled Robot built around the gear-box described below Complete kit of parts inc PCB,program livings for BBC )other micros soon/244.85. 20W ribbon cable Imin 3m recommended

5m better- 21.30/m SAE for illustrated leaflet.

The unit has 2 3V motors, linked by a magneticclutch, thus enabling turning of the vehicle, and agearbox contained within the black ABS housing,reducing the final drive speed to approx 50rpmData is supplied with the unit showing variousoptions on driving the motors etc 2595. Suitablewheels also available 79mm dia plastic wet bluetyre, drilled to push -fit on spindle 2 for 21.30)limited qtyl 3' dia aluminium disc 3mm thickdrilled to push -fit on spindle 2 for 58p.

FIBRE OPTICSScoop purcrtase of single and twin cable For usewith visible light or infra red Core lmm dia, overall1 25mm dia. Single 50p/m; 20m coil £530. Twin90p/m; 20m coil 211.00.

MINIATURE RELAYSPCB mounting. DPCO size 20 15 15rtmnAvailable in 3, 9 or 115 El each.

1W AMPLIFIER2914 Audio amp panel 95 65mm with T3A820

chip. Gives 1W output with 9V supply,Switch and vol control Just connect banand speaker Full details supplied. Only21.50; 10 for [12; 25 for f25; 100 for f7111.

Z915 Stereo version of above 115 r 65mm reetur.ing 2 TBA820M and dual vol control23.50; 10 for £30; 25 for 265; 100 for2209

AM TUNER PANELZ916 For use with mono amp above Neat panel

60 45mm Only [1.60; 10 for [121:11).

NI -CAD CHARGER SCOOP!!Ever -Ready model CH4, this charger will take up to4 AA c or D cells plus 2 PP3 if required Smart twotone grey case 212 97 60mm Only 27.95.

1984/5 CATALOGUE84 page A4 size - Bigger. Brighter, Better - morecomponents than ever before' With each copythere's discount vouchers. Bargain List. WholesaleDiscount List. Bulk Buyers List, Order Form andReply Paid Envelope All for just 21.030I1 WinterSupplement due out November - Send large SAEfor your free copy

These digital multnneter cases are moulded in highimpact black plastic and are offered at an extremelyattractive price to clear stocksDP2010 110 Y 80 20mm, this too has cut -oursfor range switches and terminals, with a smartaluminium fascia marked with ranges etc. Batteryaccessible by removable cover on back. 75p.DP100 Same size as above, but this was for use asa digital thermometer, so there's only a single9mm 0 hole in the front panel. 75p.

NICAD CHARGER PANEL177 114mm PCB with one massive Verta Deac57 50mm 0 rated 7 2V 1003rnAH and anothersmaller Deac 32 35mm 0 rated 3.6V 600mA Theprice of these NI -cad stacks new is over E20 Alsoon the panel is a mains input charger transformerwith two separate secondaries wired via bridgerectifiers, smoothing capacitors and a relay to theoutput tags The panel weighs lkgm. All this forjust 2900.Official orders welcome - minimum invoice charge210. No min on CWOOur shop has enomous slid ofcomponents and is over from Int Minimum Access9-530 Mon-Sar Come and 50. US" older am

GREENWELD443C Millbrook Road Southampton501 OHX 764107031 772501/783740ALL PRICES INCLUDE VAT JUST ADO 60p PuP

PRACTICAL INTERFACE CIRCUITSFOR MICROS

by G. Loveday Price: £8.50RADIO AND TELEVISION SERVICING 1983-84MODELSby R.N. Wainwright Price £24.00

UNDERSTANDING SOLID STATE ELECTRONICSby Texas Ins. Price E4.50

ESSENTIAL ELECTRONICS AN A TO Z GUIDEby G Loveday Price: £7.00

OPERATIONAL AMPLIFIER EXPERIMENTALMANUALby G.B. Clayton Price: £7.30

TELEVISION PRINCIPLES & PRACTICECOLOUR & MONOCHROMEby J.S. ZARACH Price: £7.60

SERVICING DIGITAL CIRCUITS IN TVRECEIVERSby R. Fisher Price: £14.60

VLSI TECHNOLOGYby Sze Price: £10.95

ENGINEERING APPROACH TO DIGITAL DESIGNby W.I. Fletcher Price: E17.50

DIGITAL TECHNIQUES & SYSTEMSby D.C.Green Price: E6.75

PRICES INCLUDE POSTAGE & PACKING *

THE MODERNBOOK CO.BRITAIN'S LARGEST STOCKIST

of British and American Technical Books

19-21 PRAED STREETLONDON W2 1 NP

Phone 01-402 9176 Closed Saturday 1 p

Please allow 14 days for reply or delivery.

ADVANCEDTELECOMMUNICATIONSCareers with extensive scope at CheltenhamJoin the Government Communications Headquarters, one of the world's foremost centres forR & D and production in voice/data communications ranging from HF to satellite - and theirsecurity. Some of GCHQ's facilities are unique and there is substantial emphasis on creativesolutions for solving complex communications pro Dlems using state-of-the-art techniquesincluding computer/microprocessor applications. Current opportunities are for:Telecommunication Technical OfficersTwo levels of entry providing ..wo salary scales: £6262 - £8580 & £8420 - £9522Minimum qualifications are -EC/SCOTEC in Electronics/Telecommunications or a similardiscipli le or C & G Part II Telecommunications Technicians Certificate or Part I plus Maths B,Telecommunication Principles B and either Radio L ne Transmission B or Computers B orequivalent: ONC in Electrical, Electronics or Telecommunications Engineering or a CIE Part I

Pass, or formal approved Service technical training. Additionally, at least 4 years' (lower level)or seven years' (higher level) appropriate experience is essential in either radio communica-tions or radar, data, computer or similar electronic systems.At the c)wer entry level first line techinical/supervisory control of technicians involves "hands-on" participation and may involve individual work of a highly technical nature. The higher levelinvolves application of technical knowledge and experience to work planning includingimplementation of medium to large scale projects.Radio Technicians - £5489 - £7818To provide all aspects of technical support. Promot on prospects are good and linked withactive encouragement to acquire further skills and experience. Minimum qualifications are aTEC Certificate in Telecommunications or equivalent plus 2 or more years' practicalexperience.Cheltenham, a handsome Regency town, is finely -endowed with cultural, sports and otherfacilities which are equally available in nearby Gloucester. Close to some of Britain's mostmagnificent countryside, the area also offers reasonaoly-priced housing. Relocation assistancemay be available.For further information and your application form, please telephone:Cheltenham (0242) 32912/3 or write to:

Recruitment Office, Government Con-munications Headquarters,Oakley, Priors Road, Cheltenham,

Gloucestershire, GL52 5AJ.


When replying to Classified Adver-tisements please ensure:(A) That you have clearly stated your

requirements.(B) That you have enclosed the right

remittance.(C) That your name and address is

written in block capitals, and(DI That your letter is correctly addres-

sed to the advertiser.This will assist advertisers in proces-sing and despatching orders with theminimum of delay.

RECEIVERS AND COMPONENTS

BOURNEMOUTW BOSCOMBE. Electronic components special-ists for 33 years. FORRESTERS (NATIONAL RADIOSUPPLIES), Late Holdenhurst Road. Now at 36, AshleyRoad, Boscombe. Tel. 302204. Closed Weds.

FIFTY 74 SERIES Les on panel £2.20. Assorted components£5.00/£6.50 7Ihs or 10Ibs post paid. J. W. BLANSHARD. 2Barnfield Crescent. Sale, Cheshire M33 1N1.

RESISTOR PACKSFOR ALL PROJECTS

1 watt carbon film resistors 5% 1 ohm to 10ME24 series. Packs of 10 each value (1690resistors) E10.00. Your choice of quantities/values 125 for E1.00. VAT and Post Free.

GORDON HALLETT20 Bull Lane, Malden Newton,Dorchester, Dorset DT2 OBQ.

BARGAIN BUMPER BOXOF BITS

Contains: working calculator, working watchmodule, Various I.C's, transistors, display tubes,PCBs, diodes batteries, gears, switches etc., etc.,etc. All useful items. Would cost much, much moreif bought separately. ONLY £15 (inc. VAT and P&P)Send cheque/P.O. to:

Barbara Page, Spares Dept., Decimo Ltd4-18 Chobham St., Luton LU1 3BS

SMALL ADSThe prepaid rate for classified advertisements is 36pence per word (minimum 12 words), boit number 60pextra. Semi -display setting f12 00 per single columncentimetre (minimum 2.5 cms). All cheques, postalorders etc., to be made payable to Practical Electronicsand crossed "Lloyds Banks Ltd". Treasury notes shouldalways be sent registered post. Advertisements,together with remittance, should be sent to theClassified Advertisement Dept., Practical Electronics,Room 2612, IPC Magazines Limited, King's ReachTower, Stamford St., London, SE1 9LS. (Telephone01-261 5846).

NOTICE TOREADERSWhilst prices of goods shownin classified advertisements arecorrect at the time of closingfor press, readers are advised tocheck with the advertiser tocheck both prices andavailability of goods beforeordering front non -currentissues of the magazine.

TURN YOUR SURPLUS capacitors, transistors, etc into sash.Contact COLES HARDING & CO., 103 South 13 -ink.

Wishech, Cambs. Tel. 0945 584188. Immediate settlement,

FREE! Parcel of components worth £10. Send only 80p post-age! D. HORSI.EY, 113 Clare Road, Braintree. Essex.

BRAND NEW COMPONENTS BY RETURNElectrolytic Capacitors 15V, 25V, 50V.047, 10, 22. 47 & 10 Mfds 5p22 & 47-6p. 100-7p. 150V -8p1 220-8p. 150V- 10p470-11p. 140V -16p1, 1000/15V -15p. 1000/25V 25p1000/40V -35p. 4700V/25V-70p.Subminiature bead Tantalum electrolytic*.01. 022. 047, 10 @ 35V, 47 @ 6 3V - 14p.2 2/35V. 4 7/25V -15p. 10/25V. 15/16V-200.22/16V, 33/10V, 47/6V, 68/3V & 100/3V-329.15/25V, 22/25V, 47/10V -35p. 47/16V -80o.Subminiature Ceramic Caps. E12 Series 100V.2% 10 p1 to 47 pf.-3p. 56 pl to 330 pf.-49.10% 390 p1 to 4700 pf -4o.Vertical Mounting Ceramic Pieta Caps. 50V.F12 22 pf. to 1000 p1. E6 1500 p1 to 47000 pf .- 20.Polystyrene E12 Series 63V. Horizontal Mntig.10 pf to 820 pf.-3p. 1000 pf to 10.1300 p1 -4P.Miniature Polyester 250V Vert. Mtg. Ed Series.01 to 068 -Op. 1.-5p. 15. 22-6p. 33. 47-10p.68 - 12p. 10 - 15p. 15 - 22p. 2.2 - 24p.Mylar (Poly I Flint 100V. Vertical Mounting.001, 0022. 0047-3p. 01. 022- 4p. 04, 05. 0 1-5p.High Stability Miniature Film Resistors 5%.

E24 Series 0.518 - 10M0. - 1p.IW El2 Series 1R0 to 10M0. - lip.1W El2 Series lOR to 10M0 - Op.AN metal film E12 Series 10RIMO 5% - 2p. 1%-E24 - 3p.1N4148 -2p. 1344002-4p. 1 N4006 -6p. 1N4007 -7pBC107/8/9-12p. 13C147/13/9, BC157/8/9. 13E195 & 7-10p.8 Pin i c's. 741 Op. amp -/8p. 555 Timer -24p.Dd Holders 8 pin -Op. 14 pin -12p. 16 pin -14p.LED's. 3 & 5mm Red -10p. Green & 14p.Grommets for 3mm.-lip. Grommets for 5mm-2p.20mm G.B.Fuses 15, 25, 5. 1. 2. 3 & 5A -5p.20mrn Anti Surge 100mA to 5 OA-- Bp.20mm. Foseholders P.0 or Chassis Mtg - Bp.Battery Snaps Ipairs1 PP3-6p. PPS- 12c.400mW Zener diodes E24 series 2V7 to 33V iip.

Prices VAT inclusive Post 20p (Free over f5.00I.THE C.R. SUPPLY CO.

127, Chesterfield Rd., Sheffield S8 ORN.

SERVICE SHEETS

BELL'S TELEVISION SERVICES for service sheets on Radio, TV,etc. £1.50 plus SAL. Colour TV Service Manuals on request.SAE with enquiries to B.T.S.. 190 Kings Road, Harrogate, N.Yorkshire, Tel (0423) 55885.

BOOKS AND PUBLICATIONS

Rill SIZE, top quality service sheets £2.50 + Lti.a.c. CTV/Music Centres £3.50 + I.s.a.e. Repair data almost any namedTV -Video £10.50 inc. circuits. L.s.a.e. brings any quote freemagazine/price lists. T1SPE, 76 Churches, Larkhall, Lanark-shire. 0698 883334.

HOME SECURITY

SECURITYAlarm Systems

FREE COMPREHENSIVE CATALOGUE(

LOWEST DISCOUNT PRICES HIGHEST QUALITY EQUIPMENT FREE DIY DESIGN GUIDE FULLY ILLUSTRATED MICROCHIP CIRCUITRY QUICK DESPATCH SERVICE FULL INSTRUCTIONS

SEND SAE OR PHONE

C-TEC SECURITY, Dept PW60 Market St, Wigan WN1 1HX.Telephone 10942) 42444

isz.Ozo$ 40s.1, R'

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cp04sz`s(** .t,.; _,,,.0°44,cf<ico

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ORDER FORM PLEASE WRITE IN BLOCK CAPITALSPlease insert the advertisement below in the next available issue of Practical Electronics for

insertions. I enclose Cheque/P.O. for C(Cheques and Postal Orders should be crossed Lloyds Bank Ltd. and made payable to Practical Electronics)

NAME

ADDRESS

Company registered in England. Registered No

PRACTICAL ELECTRONICSClassified Advertisement Dept. Room 2612,King's Reach Tower, Stamford Street,London SE1 9LS. Telephone 01-261 5846Rate:36p per word, minimum 12 words. Box No. 80p extra

53626 Registered Office: King's Reach Tower, Stamford Street, London SE1 9LS. 12/84


SOFTWARE

CIS COMPUTER CASSETTES, 3 for £1.10, 6 for £2.10, 15 for £5.C.M. ELECTRONICS, 28 Heage Road, Ripley, Derby.(0773-48932). C. MURF1N.

6809 CPU CARDPowerful Add-on to Your Home Computer

Quality, plated through PCB with full assemblyinstructions. Full RS232 Serial Interface (up to 19,200Baud). Data storage to cassette (via external CUTSinterface). Versatile Parallel Interface for control ap-plications, or keyboard and printer. Operation at1MHz or 2MHz. 2K/8K Static Ram with 2K/8KEPROM, or alternatively, 4K/16K EPROM (2 sockets).Communication via serial link to your home comput-er. Software available: Monitor, Disassembler, Edi-tor/Assembler. FORTH Programming Language.Coming soon: Floppy Disk Interface, EPROM pro-

grammer and others.Prices plus VAT: PCB only £29,95; with monitorE39.95; Monitor Disassembler E14.95; Upgrade£5; Mono Dis Editor/Assembler 04.95; Up-

grade £20; FORTH £34.95.

SOLASCAN MICRO -SYSTEMS LIMITED91 Bryanston Road, Bitterne, Southampton SO2 7AL.

Telephone (0703) 436224.

INVENTORSThink of something new?

Write it down! -American industry offers potentialroyalties for your innovations and newproducts. We offer free confidentialdisclosure registration and initialconsultation in London regarding youridea's potential value. Write withoutdelay for your free informationpackage.

American Inventors Corporation82, Broad Street, Dept PT

Westfield, Massachusetts 01086United States of America.

A fee based marketing company.

FOR SALE

OSCILLOSCOPES Minicomputer £120. Printers RS232£70, Golfball £120; paper. U.V. lamps. Call now! Sinclare01-316 1779.

WANTED

WANTEDREWARDS OFFERED FOR CAPTURE

NATIONAL SEMI CONDUCTOR

MM57109MR. PRICE 052789 2061

MISCELLANEOUS

CABINET FITTINGSFretcloths. Coverings. Handles. Castors.Flight Case Locks & Parts. Jacks. XLRs.Bulgins, Reverb Trays, P & N mic Stands.ASS Glassfibre Horns.CELESTION POWERSpeakers.

Send30p30p cheque/

PO for illustratedcatalogue Adam Hall (PE Supplies),

Unit G. Carlton Court, Grainger Road,Southend-on-Sea.

MISCELLANEOUS - CONT.

ELECTRONIC ORGAN KEYBOARDS and other parts being dearedout as special offer. ELVINS ELECTRONIC MUSICALINSTRUMENTS, 40a Dalston Lane, London E8. Tel.01-986 8455.

CLEARING LABORATORY: scopes, generators, P.S.U's. bridges.analyser.. meters. recorders, etc. 0403-76236.

NEW AND SURPLUS components and equipment now in stock.Also amateur F.M. and T.V. aerials, and a complete range ofburglar alarm equipment. Write or phone for price list:SPECTRUM RADIO & ELECTRONICS LTD, 36 SlaterStreet. Liverpool 1.) 4BX. 051 709 4628.

NEW TYPE TELECOM EXTENSION Telephone Sockets £4.25P&P 50p. P. MORTIMER. 3 Furlong Gardens. Trowbridge.Wdtshire.

BURGLAR ALARM EQUIPMENT. Ring Bradford (0274) 308920for our Catalogue or call at our large showrooms oppositeOdsal Stadium.

SPEAKERS FROM 30p, Capacitors from 2p, Cassette Motors60p. S.A.E. for lists. Rochdale 50540. BRUTEC, 17 HealdClose. Rochdale, Lancs. OL12 7W.

HEATHKIT. U.K. spares and service centre. CEDARELECTRONICS. Unit 12, Station Drive, Bredon, Tewkes-bury. Glos. Tel. (0684) 73127.

AERIAL AMPLIFIER, Improve weak televisioi reception.Requires 9v battery. £5.75. ESSA, 20, St. Lekes Avenue.Ilford, Essex.

SUPERB INSTRUMENT CASES ho BazeUi. manufactured fromPVC faced steel. Vast range. Competitive prices start at a low£1.50. Punching facilities at very competitive prices. -BAZELLI (Dept 23), St Wilfreds, Foundry Lane. Halton.Lancaster LA2 6LT.

RUN YOUR 9 VOLT CIRCUITS FROM ASINGLE NICKEL -CADMIUM CELL

with a Verkon miniature p.c.b.-mounteddc/dc converter, the reliable alternative toexpensive batteries. Learn of the full technicaland economic benefits by sending s.a.e. fordata sheet to:

J. BILES ENGINEERING120 Castle Lane, Solihull, West Midlands 892 8RN

THE SCIENTIFIC WIRE COMPANY811 Forest R3ad. London E17. Telephone 81.531 1568

ENAMELLED COPPER WIRESWG 1 lb 8 oz 4 oz 2 oz8 to 34 3.63 2.09 1.10 0.88

35 to 39 3.82 2.31 1.27 0.9340 to 43 6.00 320 2.25 1.6144 to 47 8.67 5.80 3.49 2.7548 '5.96 9.58 6.38 3.69

SILVER PLATED COPPER WIRE14 to 30 9.09 5.20 2.93 1.97

TINNED COPPER WIRE14 to 30 3.97 2.41 139 0.94FluxcoreSolder 5.90 3.25 1.82 0.94

Prices include P&P VAT. Orders under 7:2 add 20p.SAE for list of copper and resistance wire.

Dealer enquiries welcome.

To Advertise inthis space

RingMANDI

01-261 5846

- ...-* BAKER itGROUP P.A. DISCO 0 0 0 0 ....AMPLIFIERS post 12150 wan Output. 4 input Mixer pre amp illustrated150 wan Output. Slave 500 my Input 3 Speaker Outputs150.150 wart Stereo. 300 wan Mono Slave 500 my150 wan PA Vocal, 8 inputs. High/Low Mixer Echo100 watt Valve Model. 4 inputs. 5 Outputs Heavy duty60 watt V sloe Model 4 inputs. Low imp and ION line60 watt Mobile 240s AC and 12v DC 4-8.16 ohm -100yBAKER LOUDSPEAKERSType Model Size WattsPA./Disco/Group DG50/10 10 50Midrange Mid 100/10 10 100WEI Major 12in 30Hi -F1 Superb 12in 30P.A./Disco/Group DG45 12in 45Hi-Fo Woofer 12in 80Ho.Fo Audotorourn 15in 60PA./Disco/Group DG75 12in 75P A./Disco/Group DG100 I2on 100P.A 'Disco/Group DG100/15 15in 100

_.

..-- ' i..

£99£80

Inputs E125Socket E129

(125output £69

lone E89

Post 12 eachOhms Price8/16 £18.008 E25 004/8/16 E16.008/16 £26 004/8/16 E16008 £25.008/16 E37.004/8/16 £20.008/16 £26.008/16 E35.00

DISCO CONSOLE Twin Decks, mixer pre amp £145. Carr EIOCOMPLETE DISCO 150 watt E360; 300 wan £430. Carr 130.

DISCO MIXER. 240V, 4 stereo channels. 2 magnetic, 2 ceramic/tape. 1 niono mic channel, twin v.0 metere headphone monitoroutlet. shier controls. panel or desk mounting, grained aluminiumfacia Tap output facility. £49. Post El.DELUXE STEREO DISCO MIXER/EQUALISER as above plusLED. VU displays 5 band graphic equaliser. left/right fader,switchabie inputs for phone/line, mike/lineHeadphone Monitor, Mike Talkover Switch Ell a._ PP 12As above with 7 Band Graphic £128.P A CAEINETS lempN) Single 12 E30. Double 12 E38 cart E10WITH SPEAKERS 60W 127. 75W 152; 90W £73, 150W £82.HORNBOX ES 200 Watt E30, 300 Watt E35. Post 14

OUTDOOR WATERPROOF HORNS 8 ohms 25 wan £20. 30 wattE23 40 watt E29. 200 plus 100 volt line 638. Post E2MOTOROLA PIE20 ELECTRONIC HORN TWEETER, 3ito square f5100 watts No crossover required 48.I6 ohm 7i .3ion £10

CROSSOVERS. TWO-WAY 3003 c/s 30 wan 0 MO watt E43 way 950 cps/3110 cps 40 watt rating 14, 60 wan (6. 100 watt EIOLOUDSPEAKER BARGAINS Please enquire many otners in stock4 ohm, Sin 7 .4on (2.50: 66n, 8.5n 0 flon 0 SO. Egon 20W (7 SO8 ohm. 26n Sr £2; 5,3n. 6 yolon 7 -lin. 9n f2.50: 64,,, 20W ft 50,B Sin Ci; en £4.50; 10in (5: iin C6. flin 25W £6.50.IS ohm. Zion, 36n. 5.3n 6 .4tn 12.50. 66n IOW 11. ear E4 I5n £725 ohm, 3n (2; 5.3n. 6 .4n. 7. tin 12.50 120 ohm, Sin de IIMake Model Sue Watts4110AX WOOFER Sin 25GOODMANS HIFAX 71.4;in 100

GOODMANS HB WOOFER 6n 60VVHARFECALE WOOFER Bin 30CELESTION DISCO/Group lOon 50

GOOOMAIS HPG/GROUP 1 lin 120

GOOGMANS HPD/OISCO 12m 120

GOODMANS HP/BASS 15in 250GOODMAYS HPO/BASS 1810 233

hms Price PostE1050 CI(30 E2

61350 II69 50 0

/16 01 C2

15 129 50 0/15 (29.50 E2

(72 PIIN E4

RCS SOUND TO LIGHT CONTROLLER KITPrinted .drcuit. Cabinet 3 channels 1.000 watts each Will operatefrom Ho-Fi or Disco £19. Post El.Ready Built Deluxe 4 Channel 4,000 watt with chaser speedprogramme controls E69. Post C2MAINS TRANSFORMERS Price Post250-0-250V 8OrnA. 3.5A 6.3V £7.00 E2350-0.350V 25OrnA 6.3V 6A CT £1200 Shrouded 114 00 17250V 60rnA 6.3V 2A £4.75 11220V 25mA. 6V 1 Amp £3.00 220V 45mA 6V 2 Amp £4.00 ItLow voltage tapped outputs available1 amp E. 8, 10, 12. 16. 16 20. 24, 30, 36. 4a 46 60 E6.00 12ditto 2 amp E10.50 3 amp £1260 5 amp £16.00 12LOW VOLTAGE MAINS TRANSFORMERS £5.50 each post paid9V. 3.A. 12V, 3A, 16V, 2A, 20V. 1A, 300, 11A, 30V, 5A 17-P17V,2A, 35V. 2A. 20-40-60V, IA, 12-0-12V, 2A. 20.0-20V, 14. 25-0-25V.2A

E11.50 post 50p MINI -MULTI TESTERDeluxe pocket sire precision mov.ng coilinstrument. lmpedence - Capacity 4000op v Battery included 11 instant rangesmeasure DC volts 5, 75, 250. 500. AC volts10. 50, 500, 1000 DC amps 0-250µ3. 0-250ma Resistance 0 to 600K ohmsDe -luxe Range Doubler Meter, 50,000o.p.v. 7 . 5 7in Resistance 0,20 meg in5 ranges Current 50,A to 10A Volts 0.25/1000y DC, 10v/1000v AC £21.00 post Et

PANEL METERS E5.50 post 50p50.A. 130µA. 500,A, 1mA 5mA. 100mA. 500mA 1 amp, 2 amp. 5amp. 25 volt. VU 21.2 11 Stereo VU 31 v i Ion.EQUIPMENT CASES. Black Vinyl Covered Top4 21 . 2;on E2.50; 6 4 11in. E3.60, 8 5 o 2m 1400;11 6 3on 15.50;111 6 Sin. 19.00; 15 8 . din £1200.ALI ANGLE BRACKET 6 1 Tin. 30p.ALUMINIUM PANELS 18 s.w.g. 12 . 12in 11.80; 14 . 9in £1.75;6 4in 55p, 12 gin E1.30; 10 Tin. 96p; 8 6in 90p; 14 x 3m.72p, 12 5in 90p; 16 101n. £2.10; 16 * Bin. E1.30.ALUMINIUM BOXES. MANY OTHER SIZES IN STOCK.4 2j 2.r. 11.20; 3 2 lin. El: 6 * 4 v 2in. £1.90: 8 * 6 * 3on (3.00; 12 . 5 < 3m 13.60; 6 4 . 3on. E2.20; 10 7 x 3mE3.60. 7 5 . 30. 0.90; 12 8 31n. £4.30.HIGH VOLTAGE ELECTROLYTICS 32 -32 .32/450V E1.5020/500v 75p B -8/500V . Et 32 .32/500V E232/350v 45p 8 16/450V 75p 220/400V E232/500v 95p 16.16/350V 75p 16.32-32/500V £2

SINGLE PLAY DECKS. Post E2Make Model Cartridge PriceBSA P207 Ceramic E20GARRARD 6200 Ceramic E22BSA P182 Ceramic £26BSR P232 Magnetic £28BSR P200 Magnetic 1134AUTO( HANGER BSR Ceramic E20

DECCA TEAK VENEERED PLINTHSuperior finish with space and panel for small amplofier.Board at for BSA or Garrard 183on 141m. 4m E5Black/chrome facia trim Post ElTINTED PLASTIC COVERS for Decks, Music Centres, etc. Post II17 12i 3iin E6 141 x 121 x 26n. E5221 13; 3m E5 161 x 13 x 4in. if711 - 14, 21on £5 141 v 131 v 21in. E514; 13 3,..; ES 21 132 44,r1 E5

E5 301 131 3.,r E5

RADIO COMPONENT SPECIALISTS

Dept 3, 337, WHITEHORSE ROAD, CROYDONSURREY, U.K. Tel: 01-684 1665

IACCESS) Post 65p Minimum Callers Welcome !VISA)Lists 32p Same day despatch Closed Wed


THE NEWCLEF CMS

The FULLY programmable digitalsynthesiser that you can AFFORDTHE NEW CLEF COMPUTER MUSICSYSTEM is so user programmable thatyou need a BBC Micro to run it! 32harmonically programmable oscilla-tors. 32 programmable envelopes. 5

octave touch sensitive keyboard, up to4 OSC/ENVS per note. Real time se-quencing. Massive potential for futuresoftware. Complete system (withoutBBC Micro) £475 built. Phone or writefor details. Modular systems alsoavailable.

MASTER RHYTHMPROGRAMMABLE DRUMS

AsPublishedin PE

Twenty -Four Rhythm programmableDrum Machine with twelve instruments.Eight sections are extended to 24/32measures for two bar programming.Sequence operation and instrument toneadjust. COMPLETE KIT £79STRING ENSEMBLE E198.50ROTOR -CHORUS 08.00

SQUARE FRONT KEYBOARDS88 NOTE E60 49 NOTE £2973 NOTE ESO 30 NOTE £19KEVSWITCH ITEMS ALSO AVAILABLE

88/72 NOTE PIANOSSPECIALISTS SINCE 1972

Using Patentec electronic technique to giveadvanced simulation of Piano Key Inertia.

COMPONEN- KITSincluding Keyboard

88 NOTE £26672 NOTE E234The above ma,, also bepurchased in four parts.

DOMESTIC NITSInc Cabinet, PA.. & Splu.

88 NOTE PHONE72 NOTE £398

STAGE MCDELinc. Cabinet & Stand

72 NOTE PHONE

ALL PRICES INC /AT. CARR & TELEPHONE ADVICE.

SAE. for full Specs & MANF. PRICES. VISA -ACCESS -AMERICAN EXPRESS Competitive quotes can be

given for export, Allow 3-14 days for normal despatch.

BAND -BOXPROGRAMMABLE BACKING TRIO

As Published in P.E.THREE PIECE BACKING BANDGenerates the sounds of three in-strumentalists to back SoloistsDRUMS + BASS + KEYBOARDSOver 3,000 chord changes 160scores) on 132 different chords - 16chord sounds. Master Rhythm alsorequired.FULL KIT E265

CLEF PRODUCTS (ELECTRONICS) LIMIIFED(Dept P.E.) 44A BRAMHALL LANE SOUTH BRAMHALL

STOCKPORT CHESHIRE SK7 1AH TEL 061-439 3297

P.E. HYPERCHASERI4CHANNELPSEUDOINTELLIGENT

LIGHT UNIT* 16 Programmes * Manual Rash Buttons

"* Manual/Auto Programme * Strobe Outputs* Individual Dimming * Sound To Light

Not just a light unit but a sophisticated & comprehensive effects unit A full kitof parts including P C B Face. Case etc Repnnt of article on request

PRICE INCLUDING P&P £84.95

P.E. STAR DESK8 + 4 CHANNEL LIGHT MIXING DESK*8 Channel Twin Preset Mixer * Strobe Outputs*4 Independent Channels * 4/8 Channel Sequences*8 Programmes * Manual Rash Buttons*IKW Output/Channel (can be boosted to 2KW/Chl* Timed Cruseade *Soft/Hard Sequence

A truly magnificent unit ideal for clubs, groups, drama, etc A full kit of partsInc PCB. Face. Case, etc Repnnt of article on request. PRICE INCLUDING P&P

BENSHAM RECORDING LTD327 Whitehorse Road. Croydon, Surrey CR0 2HS

9 am -S pm. Mon -Sat.Please allow 14 days for delivery

£209

arm

* * * STEPPER MOTORS * * *For robotics, turtles and X/Y Plotters

Type 1035/014. Low Current Model * 48 steps/rev (1 deg steps )* W1 300 Grms Price f13.50 incP/P & VATType MR23.(Higher Resolution) * 200 steps per rev 112 deg steps. I * Wt 600 Grins Price DUOInc. P/P & VATRS 8 stage Darlington * Drives 2 (035's from the User Port Price f225 inc P/P & VAT.SA1027. I.C. Single Pulsed input determines speed. Second input determines direction Suitable fordirect Drive of one In 1HR23 requires additional Power Transistors) Price E6.50 inc. P/P & VAT.Book, DIY Robotics & Sensors with the BBC MICRO 0.95 Inc P/P (Commodore 64 versionsame price INOTE. Motor prices vary with foreign exchange rates. If ordering after 1 12.84, please telephonefirst

Telephoned ACCESS & VISA orders welcome.

We cannot help with advice on projects, but a Pnce Ust of the RS components mentioned in theabove books, plus limited Stepper Motor data is available free. BUT will be sent ONLY ON RECEIPTOF AN A4 SELF ADDRESSED ENVELOPE, STAMPED WITH 24p

CARDIGAN ELECTRONICSChancery Lane, Cardigan, Dyfed, Wales. Tel: (0239) 614483

Shop Hours Mon -Sat, 10 to 5 Closed all day Wednesday

Goods normally by return post allow 14 days delivery if not in stock

I

IIAddress

FREE CAREER BOOKLETTrain for success, for abetter job, better pay

Enjoy all the advantages of an ICSDiploma Course, training you ready for anew, higher paid, more exciting career.

Learn in your own home, in your owntime, at your own pace, through ICS homestudy, used by over 8 million already!

Look at the wide range of opportunitiesawaiting you. Whatever your interest orskill, there's an ICS Diploma Coursethere for you to use.

Send for your FREE CAREER BOOKLETtoda -at no cost or obligation at all.

TICK THE FREE BOOKLET YOU WANTAND POST TODAY

ELECTRONICS ElENGINEERING LJ

:ELECTRICAL ElENGINEERING LJ

TVEtAUDIOSERVICING ElRUNNING YOUR El 1OWN BUSINESS L-1 I

Name

I ICS ICSDept EDSC4Division or Nat,Oha, ,,, 160 Stewarts Road. CP Or 622 991'tail hours,L...1t,On (Or DO, at,c, London Oral 4U.I.

III

I

INDEX TO ADVERTISERSAC/DC EleCtronicsA.D.E.Alcon InstrumentsAmerican Inventive Corp.AntexBensham RecorcingsBiles J. Ltd.B.N R E SCardigan Electronics

21

6258633564634964

Cirkrt Holdings 4 & 5Clef Products 64Computonics 62

C.R. Supply Co. 62Cybernetic Applications 58

Driftwood Ltd. 62

Elbar 51

Electrovalue 51

G.0 H Q 61Grandata 58Greenweld 61

Hall. Adam. Supplies 63Hallett. Gordon 62ICS Intertext 64ILP Electronics 43

Maplin Supplies 43 & Cover 4HI Tech Components 28 & 29Modern Book Co. 61

Phonosonics 22Powertran Cover 2Proteus Cover 3R.C.S. 63Riscomp 22

Scientific Wire Co. 63Solar Scan Microsystems 63Sparkrite 51

Swanley Electronics 61

Tandy 15T.K. Electronics 6

Watford Electronics 2 & 3Weighpack Ltd. 63

Published on approximately the 7th of each month by IPC Magazines Limited, Westover House, West Quay Road. Prxile, Dorset BH15 LIG. Printed in England by Chapel River Press, Andover.Hants. sole Agents for Australia and New Zealand - Gordon and Gotch (Asia) Ltd.; South Africa - Central News Agency Ltd. Subscriptions INLAND £13 andOVERSEAS f 14 payable to IPCMagazines Ltd.. "Practical Electronics" Subscription Department, Room 2816, King's Reach Tower. Stamford Street, London SE I 9LS. PRACTICAL ELECTRONICS is sold subject to thefollowing conditions, namely that it shall not, without the written consent of the Publishers first having been given, be lent, resold, hired out or otherwise disposed of by way of Trade at more thanthe recommended selling price shown on the cover, and that it shall not he lent, resold, hired out or otherwise disposed of in a mutilatedcondition or in any unauthorised cover by way of Trade oraffixed to or as part of any publication or advertising, literary or pictorial matter whatsoever.

FANTASYADVENTURE GAME"THE TOWER OFTERROR"

rigilDREDS OF NEW LINESfr

The amazing Maplin Catalogue is here again!The new edition is packed with hundreds andhundreds of new electronic components tc bringyou right up to date with all the latestdevelopments. As all home constructors agree(and a good many professionals too) the MaplinCatalogue is the one essential piece of equipmentthey really need. And now with all our prices onthe page the Maplin Catalogue is better value /than ever.

On Sale From 10th November 1984.

Pick up a copy as soon as it's published at anybranch of W.H. Smith or in one of our shops. Theprice is still just £1.35, or £1.75 by post from ourRayleigh address (quote CAO2C).

E

L

Post this coupon now for your copy of the 1985 catalogue.Price £1.35 + 40p post and packing. If you live outside the U.K.send £2.40 or 11 International Reply Coupons.I enclose £1.75.

Name

Address

PE''

1

mapunELECTRONIC SUPPLIES LTO

Maplin Electronic Supplies Ltd. Mail Order: P.O. Box 3, Raleigh, Essex SS6 8LR.Tel. Southend (07021552911. Shops ot:159-161 King Street, Hammersmith,London W6. Tel: 01-748 0926. 8 Oxford Roac, Manchester. Tel: 061-2360281.Lynton Square, Perry Barr, Birmingham Tel: 021-356 7:92.282-284 London Rood, Westcliff-on-Sea, Essex. Tel: 07C2-554000.46-48 Bevois Valley Road, Southampton. Tel: 0703-25831. All shops closed all day Monday.

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