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4EKTORELECTRON/CAS

CONTENTSNovember 1993Volume 19Number 216ISSN 0268/4519

We regret that 'Telephone -controlled switch' has had to

be carried over to next month.

In next month's issue

More than 50 construction

projects including:Medium power MOSFET

amplifierAF r.m.s. voltmeter

Photographic workshoplights

Choosing componentvalues for LC resonant

circuitsSCART switching box

and others for your

continued interest

Front cover

Integrating an EPROM

emulator into a microcon-

troller system give.s

and reduces costs. It also

makes the 800535 -Lased

processor board shown here

and described on pages

30-33 a splendid tool fOr

application software

developers.

Copyright ©1993 Elektuur

CONSUMER PRESS

The solution to the Prize Electronic Crossword by Matrix(September 1993) and winners of the prizes are on page 22.

; 4 s

34 PROJECT: Output amplifier with AF band-pass filterDesign by T. Giesberts

24 PROJECT: Precision clock for PCsDesign by B. Zschocke

30 PROJECT: 535 card with EPROM emulator- Part IDesign by B. Zschocke

40 COURSE: Figuring it out- Part 10: PowerBy Owen Bishop

55 The analogue subsystem-Part 3 (final)By Joseph J. Carr

2 9 , ;

PROJECT: Electronic loadDesign by M. Marquart

10 PROJECT: VHF/UHF television tuner- Part 2Design by W. Sevenheck

60 DX TelevisionBy Keith Hamer and Garry Smith

18 PROJECT: Digital hygrometerDesign by A. Rietjens

46 PROJECT: Power MOSFET testerDesign by T. Giesberts

62 PROJECT: Fuzzy logic multimeter - Part 3 (final)Design by H. Scholten

Buyers' guide 74Index of advertisers 74Readers' services 70-71Terms of Business 72

Electronic load - page 5

Digital hygrometer - page 18

Output amplifier with AF band-passfilter - page 34

VHF/UHF television tunerpage 10

Elektor Electronics is published monthly, except in August, by Elektor Electronics (Publishing), P.O. Box 1414, Dorchester, Dorset DT2 8YH, England. The magazine isavailable from newsagents, bookshops, and electronics retail outlets, or on subscription at an annual ( 1994) post paid price of £2700 in the United Kingdom; air speeded: £34.00in Europe; £43.00 in Africa, the Middle East and South America; £45.00 in Australia, New Zealand and the Far East; and $57.00 in the USAand Canada. Second Class Postagepaid at Rahway N.J. Postmaster: Please send address corrections to Elektor Electronics, do Mercury Airfreight International Ltd Inc., 2323 Randolph Avenue, Avenel, NewJersey, N.J. 07001.

ELEKTOR ELECTRONICS NOVEMBER 1993

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REF: EK, HARDING WAY, ST.IVES, HUNTINGDON, CAMBS, ENGLAND, PE17 4WR.Telephone: 0480 461778 (7 lines) Fax: 0480 494042International: +44 -480-461778, Fax:+44-480-494042 ACCESS, AMEX, MASTERCARD, VISA Welcome.


Design by M. Marquart

For testing a power supply, afairly large resistive load,

preferably variable, is needed.Moreover, testing of the

dynamic performance of thesupply makes it essential thatthis load can be switched on

and off rapidly. The loaddescribed in this article hasbeen kept relatively simple,yet it can dissipate 130 W for

brief periods and may beswitched on and off at a

repetition rate that can be setbetween 10 Hz and 100 kHz.

\

ELECTRONIC LOADFOR TESTING POWER SUPPLIES

load for testing a power supply mustraw a steady current, that is, be-

have as a pure resistor, and enable theuser to check the performance of the supplyin rapidly changing circumstances. Thislast requirement means that a circuit isneeded to switch the load on and off anumber of times per second. How manytimes depends on the type of test: a fewtimes per second shows the performanceof the buffer capacitors, but it is also im-portant to know how the supply behavesat an on -off rate of a few thousand timesper second. An ideal power supply pro-vides a constant voltage across any load(however variable), which shows up as asmooth trace on an oscilloscope. Sincesuch units do not exist, the aim of the de-signer is to keep the output voltage assmooth as possible in widely varying cir-cumstances. This means that the rippleon the output voltage of the power supplymust be minimized. This may be testedby switching the load on and off rapidly.

Circuit descriptionThese requirements can be met by a powertransistor or FET, which functions as avariable load, and a rectangular -wavegenerator, which switches the transistoron and off at a variable rate. In the pre-sent circuit (Fig. 1), a FET TYPE BUZ384(T1) and a Type 555 timer (IC1) are used.The 12 V supply voltage is obtained from

a mains adaptor. Diode D1 is the 'supplyon' indicator. The current through thisLED is determined by R1. Capacitor C1provides smoothing and buffering of thesupply line.

Timer IC1 functions as an astable mul-tivibrator because of the feedback be-tween its pins 2 and 6. Pin 7 is linked in-ternally to the collector of a switchingtransistor. Pin 6 is connected internallyto a comparator that reacts to voltages of1/3 and 2/3 the level of the supply voltage,

One of capacitors C2 -C6 (dependingon the position of switch S2) is chargedvia R3 and D3. When the potential on thecapacitor has reached a value of 2/3 U,the comparator drives the switching tran-sistor connected to pin 7 into conduction.This results in the discharging of the rel-evant capacitor via R2 and D2. When thevoltage across the capacitor has droppedto 1/3 Uss, the comparator switches off thetranstor linked to pin 7 and the capaci-tor is charged anew. Diodes D2 and D3

12V S1

100p 25

C2

7010o25V

A6

C3 5 ICo

25V 25VTOOTOn

7CMin

100n

K1

° S2bD4 - -

1N4148

11 12 04

P1

10k

39

Ti

DS

BUZ384411N5408

7

K2

K3

0R6 R8

4

GND

930088 - 11

Fig. 1. Circuit diagram of the electronic load.


6 POWER SUPPLIES AND BATTERY CHARGERS

PARTS LISTResistorsRl = 470 52R2, R3 = 82012R4=390R5 = 1 Id2R6= 0.1 a 10 WR7 = 100 kOR8= 11.3 k0, 1%Pt = 10 kO potentiometer, linearP2 = 4 7 k12 potentiometer, linear

Capacitors:C1, C2 = 100 p.F, 25 V, radialC3 10 µ F, 25 V, radialC4= 1µF, 25 V, radialC5, C7= 100 nFC6 = 10 nF

Semiconductors:D1 = LED, 3 mmD2 -D4 1N4148D5 = see textTl = BUZ384

Integrated circuits:ICI = 555

MiscellaneousSi = single -pole on -off switchS2 = 2 -pole. 6 -position rotary switchKi-K3 = 13NC socket for PCB mounting2 off spade terminal (male and

female) for PCB mountingHeat sink for Ti (SK85*, 75 mm high)Enclosure 80x200x132 mm (HxWxD)

Dau (Ulf) Ltd, 7075 Barnham Road,Bamham, West Sussex P022 OESTelephone (0243) 553031

ensure that the duty factor of the charg-ing/discharging process is 1:1. Five dif-ferent capacitors, and thus five differentfrequencies (10 Hz, 100 Hz, 1 kHz, 10 kHz,and 100 kHz), may be selected with S2.

The square -wave output signal of IC 1,available at pin 3, is applied via D4 andS2b to potentiometers Pi and P2, whichset the gate voltage for T1 (coarse and finerespectively). The magnitude of the gatevoltage determines how hard the tran-sistor conducts and thus the value of theresistive load that the FET presents to thepower supply on test. The higher the drainvoltage, the lower the drain -source trans-fer resistance of the FET and the harderthe transistor conducts.

The drain and source of T1 are con-nected to the power supply on test viaspade terminals Ix in and GND.

The BUZ384 is a so-called FREDFET,which is typified by a very fast integratedinverse diode that prevents the devicebeing damaged by negative voltages acrossthe drain -source junction. It can handlecurrents of up to 10.5 A and has a min-imum drain -source transfer resistance,RDs(on), of 0.6 SI Diode D5 needs to be usedonly if a FET without an integrated pro -

Fig. 2. Printed -circuit board for the electronic load (not available ready made).

tection diode is used.The source of T1 is linked to the GND

terminal via a 0.1 0, 10 W resistor, R6.The potential drop acros this resistor isa measure of the current through the FET(100 mV A -l); it may be measured at K3.

The output voltage of the power supplyon test is measured with the aid of po-tential divider R7-Rg at K2 (100 mV V-1).

The pulses applied to the FET are alsoavailable at K1 via R5 and may be used todrive the trigger input of an oscilloscope.

Switch S2 is shown in the calibrationposition in which T1 is on continuouslybecause Pi is linked directly (via S2b) tothe positive supply line. In this position,the current the load draws from the powersupply on test is measured at K3 and setto the wanted value with Pi and P2. Afterthis has been done,the dynamic perfor-mance of the supply on test may be checkedby setting S2 to the other positions.

ConstructionAlthough a ready-made PCB is not avail-

able, it is recommended to build the elec-tronic load on a board made according toFig. 2. The design of the board allows thepotentiometers and the rotary switch tobe mounted on it. It is best to start withfitting the smaller components, followedby the solder pins, the spade terminals,the potentiometers and the rotary switch.

Mount the FET on a heat sink, whichmust be fitted at the back of the board.The position must be such that the bent -forward terminals of the FET protrudethrough the relevant holes on the board.

Fit the PCB to the heat sink on shortspacers that leave enough space betweenthe board and the heat sink for access tothe transistor terminals for soldering themto the board.

Fit the resulting assembly in an en-closure as specified in the parts list insuch a way that the spindles of the po-tentiometers and the rotary switch pro-trude through the front panel far enoughto enable knobs to be fitted to them. Notethat the heat sink must be insulated fromthe enclosure since the drain of the FET


is connected internally to the housing.Finally, wire up the controls and sock-

ets: the supply on -off switch, the LED, two(car -type) spade terminals for connect-ing the power supply on test (use heavy-duty wire), and the three coaxial socketsfor the measurement outputs (K1 -K3). Thecoaxial sockets are best wired with screenedcable since fairly high frequencies mayoccur.

Fit a suitable socket at the rear of theenclosure for the mains adaptor plug. Theadaptor need not be able to provide highcurrents: 50 mA is sufficient. DO NOT TAKE

THE SUPPLY VOLTAGE FROM THE POWER SUPPLY

ON TEST!

Using the electronic loadAn oscilloscope is indispensable for view-ing the waveforms. The simplest test isinspecting the waveform of the outputvoltage when the load is being switchedon and off. To do this, connect the signalat K3 to Channel 1 of the oscilloscope, sothat the scope is triggered by the square -wave switching signal (it is also possibleto trigger the scope by the signal at K1).Connect Channel 2 to K2 or to the out-puts of the power supply on test. Connecta multimeter, set to 2 V d.c., to K3. Set P1to zero before switching on the powersupply on test. Then switch on the supplyto the load and the power unit on test.Adjust the output of the power unit to,say, half the maximum permissible value,set the frequency switch on the load tothe calibration position and adjust Pi andP2 so that a current flows which the uniton test can provide comfortably, say, 1 Aor 5 A. Do not leave the load in the cali-bration position for too long to avoid theFET getting too hot. Then, switch to the

N

Fig. 3. The prototype of the electronic load with the cover removed.

various frequencies in turn and observeat each of them how the output voltagevoltage and current behave. Dependingon the output impedance of the powerunit, the output voltage will drop slightlywhen the load is connected. If there areirregularities in the output voltage andcurrent around the switching points, thispoints to the fact that the power unit isnot able to cope satisfactorily with changesin the load. This may become particularlypronounced at high frequencies, becausethe control electronics then cannot fol-low the switching rate.

It is also possibe to use the x -y settingof the oscilloscope (K2 signal drives y andK3 signal drives x). The oscilloscope tracewill look like an hysteresis curve: the closerit is to a straight line (ideal case) the bet-ter the power unit is.

The maximum current that the FETcanhandle continuously is 10 A. Moreover,the rating of 130 W on the front panel ap-plies to peak currents, not to average cur-rents. This should be borne in mind es-pecially during calibration.

END

°COARSE

ED

ix ADJUST

FINE

x IN

GND

Fig. 4. Suggested front panel for the electronic load (true scale).


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7440374 0.387480375 0.51

74E10377 0.5174E10386 0.197450390 0.367450393 0.417446423 0.647400521 0.647400533 0.647400534 0.60

0.697440541 0.5674E10563 0.5974E10564 0 597460573 0.6474605730 0.687450574 0.6474E10589 1.107450590 0.8074E10592 0.807450593 1.127480595 0.847480897 0.7974110620 1.097400623 1.097440633 1.0974110640 0.897440643 0.8974E0645 0.9474110646 1.197440648 1.197440651 0997440652 0.99744 658 3.024HC

7440659 3.027440664 3.027440665 3.027440670 0.747440677 2.557440678 3.98

2.58'7440682 2.8474E10684 3.847440688 0.797440690 1.097450891 1.09745 0692 1.16744 0693 1.167450696 POA744 0697 1.06744 0698 1.0674110699 1.0674504002 0.24741104015 0.72741104016 0.43741104017 0.30

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74504049 0.3774504050 0.3674804051 01474804052 07474804051 068741104053A 07474E104060 0.32741104061 1.7074804066 0.3174H04066A 0.38745 04072 0.30741104075 0.25741-04078 0.3174804094 0.4974404316 0.8874404351 0.8974404511 0.5574404614 1 19

74404515 1.1974404516 0.5474404520 0.5974404538 0.7474904543 0.5574407001 05874007002 06874007032 0 68

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74407274 1 3474407292 0 77242234745040102 0.84748040103 0 84748040105 1 40

741101165 05274407166 0.52744CTI 73 0.5274401174 0.52741-1C1175 0.5274401181 2.4874401182 0.96744C1190 0.6474407191 0.6474407192 0.6474401193 0.6474401194 0.7674E101195 0.78741101221 0.9874E101237 0.94741101238 0.5174801240 0.44744 01241 0.44745 01242 0.7674E101243 0.6474001244 0.4474E101246 0.4474401251 0.5874001253 0.3474401257 0.4874001258 0.4874401259 0.7874407273 0.6874401-280 0.9874401-283 0.96741-101299 1.64740 01354 0.86]4507356 0.85748 01365 0.5474801366 0.5474801367 0.54741101368 0.5474401373 0.4474801374 0.447 01377 0.8474001390 166741101393 0.6874001394 098740CT521A 1.1074001533 0.68748CT534 0.6474001540 0.64748107541 0.6474001563 0.6674501564 0.6674401573 0.6474001574 5.6474507513 1.2874001640 0.9074607643 0.9074601645 0.7574507646 1.2874001648 1.2874401551 1.1074407652 POA74407670 1.1074401673 1.10741101688 1.10740014002 0.26740014015 0.76744014016 0.52744074017 0.88740014020 0.74744014024 0.68744074040 0.70744014046 2.1074E1014051 0.84744074052 0.84744014053 0.84744074060 0.84744014066 0.66744014067 3.327411074075 0.38744074094 0.8432744014316 0.687411074351 1.04744014510 1.04744014511 0.94740014514 1.64740014515 1.88744014516 1.08744014520 0.90744074538 1.02740077007 0.26744077046 2.807440140102 1.647440140103 1 487440140104 1 827440140105 1 40-

74F SERIES

74100 0.2874F02 0.2874804 0.2874606 0.7474F07 0.7474F08 0.28

74F10 0.2874F11 0.2874F13 0.6274614 0.4174F20 0.2874627 0.2874F30 0.2874F32 0.28740024574p37 0.41740025174638 0.4474840 0.6674651 0.4474864 0.3274674 0.3074685 2.3674F86 0.4174F109 0.4274F112 0.7274AC54174F113 1.1224,1474Ft 25 674F12674613224,130 0.00

746139 0.5274F145 0.90746151 0 52248183 0.62

746157 5.5474FI 58 a54748160 1.2874F160/1 1.2974F161 1.2874F162 1.28746163 1.28746164 1.28746166 4.3274F168 3.40746169 3.4074F174 0.7674F175 0.76748181 3.38748182 122748189 4.36748190 P9274F191 .92

74619274F193 2.92740221746194 1.3174024074619574F219 4.3874F224 1.92746240 0.62746241 0.6274F244 0.62746245 0.72746251 0.6274F251A 0.66746253 0.62746257 0.627482570 0.6674F258 0.62746259 3.7274826074F269 8.2874F273 220748280 062748283 0 78748299 3 36746323 4.48748350 1.50746352 0.64746353 1.1474F365

74F386 1.30746367 138746368 1.30748373 0.6274F374 0.6274F378 1.56746381 3.68748385 11.18746395 3.2874F399 0.9874F412 5.0274F413 19.66748432 4.48746521 1.2074F524 7.2674F533 2074F534 .2074F537 .6074853E1 .6074F539 .6074F540 .78748541 .76748593 4.92740175746544 4.9748546 3.36746547 6.0474F563746564 2.24746573 1.60748574 1.60

78F579748004

874F621 3.52743274748623 3.98740280748646 5.35000074F64674F8713 10.607 F821 3.984746823 3.9874F1325 3.98746827 3.98746828 4 48746841 448'4,44746846 4 307461242 2417461243 2 41

74F1244 2.12

7440109 0.61

7440138 0.68

744C139 0.65

74AC151 0.68

74,10153 0.6574AC157 0.657400158 0.6574AC163 0.727400169 1.71

7400174 0.6574AC175 0.8074A6191 1.12

7400240 0.88

7400241 0.8874A0244 0.88

1.100.60

7400253 0.6074.40258 0.6074A0273 1.10

7400299 2.067400373 0.887400374 0.887400377 0.8474AC540 0.98

0.98

74A6573 1.2674A6646 3.8674A6648 3.86

74C SERIES

74000 0.58

74002 0.567400874010 0.

74014 0.

74620 0.98LIA78GU1C7403074032 0.6874042 0.9874048 1.9874073 1.1574074 0.6874076 1.15

74085 75274090 1.2574093 2.1074695 1.50740150 6.10740151 4.16740154 198740157 2.48740164 1.52740165 1.23

1.542.08

740244 2.08740373 2.08740374 2.06740901 0.86740902 0.88740903 1.52730906 0.86740907 1.52

740908 2.80740911 14.42740912 8.30740914 1.16

740915 2.74740922 4.35740923 4.35740925 9.30740926 9.30740929 930

78L05ACZ 0.2878L12 0 28781_12A 0.2878L12ACZ 0.3078_15 0.28781.24 0.28781_56 1.1078805 0.32781405A 0.36786112 0.32

781Al2A 0.367(1413A 0.6578M15 0.3278505 0.4878S12 0.4878515 0.557905 IN7905A 0327905FA D.60

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DIODES

192986R8 18.20183881 2.54183997A 5.55164001 0.04164002 01341N4003 0.041N4006 0.041N4007 0.04154148 3.03154149 106194150 0.08154446 0.06194728A1547350 0.241947366 0.24194740A 0.241947430 0.241547444 0.2411.147568 0.241952268 0.091552328 0.0911152348 0.091553375 0.48195349E1 0.481653528 0.481953578 0.4811153658 0.48111536681 0.4811453709 0.481653809 5.48155401 11

1554021562876 1.551 N825 1.801118254 1.34q480ras9.'9°7115827 1.40155252 0.20NMA0509s9V50)32-2800 0.885082.2810 1.40

5082-2835 0.4485119 0.6085144 0.72AAZI 5 0.58AAZ17 0.58AAZ18 0.488AV10 0.08BAV45 4.98800082 0.0685.0113 0.0886204 0.3285212 2.48884058 0.2203809 0.6087179 0.42137260.200 3.58B5261-200 3.98B7728-100 0.99BYV32-50 1.60CV8805 0.8005160 0.40MV1404 15.90MV209 1.200A200 0.100A202 0.2020000000A47 0.140590 0.14P6KE36A 0.88P6KE476 0.88REC53A 0.402702.7V 0 06

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7 55 to 2705Price 4013 each


3 3V to 2GOVPrice 42p each

ZENER DIODESSTUD MOUNT

20 WATT7 5V to 75VPrice 04.94 ea

BADGERECTIFIERS

0.9A/200VDIL 0.383.0N200V SIL 0576/V1 00V SIL 1 60378200V S1L 1.9635A100V Sqr 2.98KBP0I 002 1.64KBPC3502 2.98WOOS- 18050V0.32VVO2G- 1.5A 0.402W02 0.402KBB1OR/SIL 0.662KBB208ISIL 07058001500/So 0.3588001500SIL 06001036008/60A POA

CRYSTALS

HC49( 5018/U)

.11 843200 1602.000000 1 662 457600 1 49

2713000 D983.579545 1.10

1.02

4000000 1024 096000 1.104 194304 1.104 433619 1.104.608000 1.104.915200 1205000000/5 1025 068800 I 10

5242860 1205 884200 1.806000000 1.02

6144000 1.026400000 184

6."'6°° L217 .372800 0.788 ooa0008.867230 1.349.830400 1.2010.00000 110

1069500 12011. 11012000001397500 2.4014 00000 1641431818/S 0851474560/S 10

14.74560 10

15 00000/5 10

16 00000 .0216.00000/S .201043200/S .101966080/5 .202000000/S .6022.11840/5 .6824.0000015 .82

27 - -- - .203000000/5 6.99

00000/5- IRO4030000/S 1.685 8 Series

HC33/U

0.204800 8235.307200 6.991 000000 3.951 843200 3.712.000000 4.652 097152 3.712.457600 1 922.500000 1.92

3000500 225

EIC49/U44

1 66,52,45 1,6066800 2257.86 1.498.00 1.14

00000 22511.05920 2.40

1.141400000 2.2516. 1.14

2400000 190

UM -1

8. 2 258.192000 2.021000000 2.2511.00000 2.2512.28800 2.6615.00000 2.2517 73447 2.8018.0 2.5020.00000 2.2521.00000 2252400000 2.80

CRYSTALS MISC.

HC43,71.000000 6.99

MINI GYUNDER

0.032788 0'88

WATCH0.032768 082

24, 32. 40 & 50MHZPrice 23.40 ea.

... ---------------------- -8pin DIL

Sealed MetalPackage

HCMOS Output

13.2r1,1ri sq

Pins spaced atcorners of 8pinDILFreq.- MHz3.6864.4.8.10,12.16.20.24.32.40 8 50Pricer E4.20 each

TTL Output14pin DIL Layout

Sealed Metal4pin Pkg

Freq =MHz1MHz £8.90 es

4.4.9152.6.29.830410.12.16121E432. 19.660820. 24. 25 8. 30MHzPrice: £3.52 ea.

30. 32. 32.768,31.33. 40 8 50MHz

Price' £4.45 ea.

ProgrammableCrystal

Oscillators

EXO-3C SERIESSpin DIL Plastic

PackageFreq.- MHz12. 14.31818. 16.

6616...384.19.66°8 8`31-4,Price: ''''."- ea.

16pin DIL PlasticPackage

Pro rammable forg

97 DISFrecluencY

SPG8640AN0.005 to 13008-18

seca64oBN0.0063 to 1MHz

5868540060.064 to 768kHz

SPG86501390.00053 to 100k1lz

Price: £ 9'25 00'

440256A2-10 6.95440256-8 5 00511000-85 8.4545148416AP-15 4.60HM48416AP-20 4.2543530256LS-80 1.8043530464LS-80 3 95411351100585 8.45KM4402564210 6.95M53/14464P.15 4.60m1541165-54 2.80MK45645-15 1.00NM03764N-15 1 60UPD41464C-12 4.20UP041464C.15 4.200130416C-2 3.40UPD416C-3 3 65UPC/4460-1 2 60

STATIC RAM

2I14 -3L 3 406264LP-10 2.4062641.6-12 2.4062255LP-12 4.9562256LP-10 4.9500461165E3 5.30ODM6117AE3 5.85181M1-6116.5 4.38FIM3-6116-5 3.60FIM6116LP2 2.60Eim6116LP-3 2.605136117LP-3 675E1462256LP10 7.935 61 62 64 01.6.12 3.95HM6264ASP-20 3.95Hm6267P-35 5.07HM628128LP-80

19 55E1M66204L.12 15.80KM62256ALP10 4.60LE151641310L 2.406211401.-2 3.40P2114AL-4 340PCD5101P 130UPD43256AGU1OL

8.33660432560-12 5.600104364075 4.70

UVPROMS

270128-25 295270645-15 2.74270256-15 3.95270256-25 3.95027256 4

HM2701010.20 9.8011827010244010

16.631-11127064FP-201 3.401-1111276640-15 4.204527064G-20 4.20564625326 4.50181 44827128G-25 4.554 54827640 3.804Y6264LP-10 2.40M2716-1F1 3.5045L2732K 4.40M5L2764K 3.3046427664-20/21V

490.464270128-30 4.20MB4270256-30 5.10W02702560-25

4.956610270640-25 3.68185251311_45 4.58TMS27128.31_25 4.60TM02716.1L-45 4.60U180272560210 5.60UPD2732021V 4.95UP02702560-15 5.802802705120-15 6.96660270640-25 4.95

EEPROMS

41280256-150028.50

412805425 9.80A128064-15 10.95KM280256-20 25.84K4280266-1 5 27.50K428064-25 9.20X281600 5.10X2816AP-25 5.1032864AP-35 12.20

MISC. MEMORIES

6341-1J 4.58AM 148-45DC 1442

AM275281PC 358DT7130LA-100P

10.431DT7132LA-10019

11 194B13414E 4.954C44027A03 2.80582012555 2.494825153N 5.80582918145 6.098406504J9 3.40661093065 1.45P51010-1 3.90TBPIEISCI3ON 1.7478624S10N 290TBP24SA1011 3.151055018 3.50TC5504AP2 3.4070551561.-15 4.20105517AP-2 4 2070556561.-15 3.60TMS401400L 3.40

TEL 081-471 9338 TLX 929709 VICOM G FAX 081-552 0946

DIGITAL INTEGRATED CIRCUIT SPECIALIST

4000 SERIES 45128 0.30 401387 036 74163 0.80 28741.5174024

7411642 0.82

4000B 0.124000UB 0.144001A 0.1240016 0.124001UB 0.1440028 0.1240068 0.30400730 0.144008B 0.3140094E 0.18400968 0.2240108 0.2240118 0.144011 UB 0.144012AE 0124012B 0.1440135 3.174014B 0.3040150 3.3040168 0.1840178 2.2640189 0.28

45138 2.6045145 0.727411054045155 0.7245168 0.3045178 0.92451813 0.274519B 0.2845208 02845218 0.6045228 07245268 0.4045278 0.3845288 0.4045298 0.44453013 1 4845318 0.8845328 0.4448340 IR45368 0.9845388 0.4445398 0.6245418 0.324543B 0.44

401587 067401513T 034401751 06240185T 0.62402057 0.764021BT 0.52402387 0.254024131 0.61

4025137 0.254027137 0.364028E11 0.454029131 0.79404061 0.65404201 0.59404687 1.13404761 0.85404961 0.854050131 3 384051131 0.67405287 078

0 86406087 0674068BT 0 47

74164 0.5674165 0.9874166 0.6674174 0.657417574184 2.9574185 1.1074152 0.7274193 1.0374221 1.4274259 2.4574266 0.9074273 2.4074276 2.407427974283 0.8874LS22474298 2.6074365 0.4474367 0.6674393 2.0574403 PTA74423 POA

741.5175 0

74LS181 1.4074LS182741318374L5189A 1.8874LS190 0.30701.5191 0.38741.5192 0.38741.5193 0.387475194 0.38741.61940 0.44741.51950 0.42741_5196 0.427413197 04074LS221 0.38

24.50741.5240 0.32741_0241 0.3274136707413242 0.32741.5243 0.3274LS244 0.327413245 0.32741_5247 0.34

74LS542-1 2.4874LS643 0.84741.0543u 2.48741.5644 0.647413644-1 2.487473645 0.667415645-1 1.287415646 .7 62741.5647 6.687415648 6.8874.3649 6.68741.55516.306.9474136527413653 5.5874LS854 5.5874LS668 0.837413869 0.56

0.6828 46741.5673 .

741.5 674 17.6067474LS682 2.82783680 2.85741.5684 3.85

40198 0.20 45448 1.62 4068131 025 74LS SERIES 7413248 0.38 74E5685 2.82340204E 0.2940208 0.3040218 0.3140225 0.3240238 0.144023UB 0.1740240E 0.2140248 0.2140258 0.1440268 0.3840278 0.1840289 0.2840298 0.274030B 0.1840318 0.80

45478 17845498 POA45518 1.3645538 1.8245548 4.62455513 0.3245568 0.3845578 1.8845588 1.6845609 11645618 1.3445628 396456611 1.6045688 3.9845698 234

40690131 0254070131 0 28407157 025407587 0.254077611 0.28407887 0.2540131611 0.254093BT 0.36409481 076450881 1.64451087 0.81

9511 BT 1 084512131 0.52451831 1.76451687 0.81

741_500 0.12741.503 0.12741.502 0.12741.503 0.12741304 0.12741305 0.12741306 0.39741.507 039741.508 0.12741.509 0.12741.510 0.12741.511 0.1274LS12 0.12741.51 3 0.16

7413249 0.68741.5251 0.227413253 0.347413256 0.50741.5257 0.247413257A 0.347413258 0.247413258A 0.327413259 0.48741.5260 0.207413266 0.20783273 0.32741.5275 6.107413279 0.25741.5280 0.86

743696 3 64.

741.5687 2.42743688 1.88743689 2.4574E5693 4.907413697 15.847413716 6.587413718 6.587413724 124741.5748 1.15741.5794 8.86741.5795 2.347405796 23474LS797 234741_0848 320

40328 0.54 4572UB am 451 8BT 0.94452081 0.94

74LSI 4 0.1874LS15 0.12

7413283 0.4474L5290 0.24

74HC SERIES4033B 0.5440348 1.1040358 030

1.9840368040378 D.9840389 5.6040399 2.4840408 0.294041B 0.324042B 0.2240438 0.284044B 0.3040458 0.7240468 0.324047E1 0.27

4573P POA458013 6E30

45810 2.96

45820 1.6845838 0.6645846 34445855 0.384597CP 44045988 4.404599B 3.4247208 POA4720V POP47238 POA47248 POA4731VP 720

452191 0.86452251 0.904528131 0.704534130 3.4245313131 0.8445418T 0.844543E17 0.82455581 0.70455681 0.84458557 0.76401065T 0.4240244BT 1 0840373B1 1 82

74LS20 0.1474LS21 0.14741_522 0.14741324 0.33741326 0.1474LS27 0.1474LS28 0.14741_530 0.14741331 .

74LS32 0.1374LS33 0.13741.537 0.14741_0313 0.13741.540 0.13

74E0292 18.357474LS29410293 0.24

741.5295 0.58741.52950 0.6474LS298 0.637413299 1.187413321 S.627470322 1.5874LS322A 1.6474L5323 1 64741.5347 1.40741_0348 1 187413352 0.84

748000 0 13748002 0 1318.35

74E1003 0.13e n1vs9Do' --- -" 8 -ar.Hza rta n,

. - - -- -a748605 0.14744C08 0.17748040207411010 0.19744011 0.137407411014 0.24748741-10144 2745020 0.1874804046745621 0.19744027 0.19

DC to DCConConverters.

10K 0E-0344 560

3W5R 15-15 27 501PL 5.010 23.40

1 Watt DC/DC58 Input -OutputDILby8 SIL

NMA0505e5V

N MA°512872VNMA0515e15V

Pric"7'96ee'

DC/WC Convertersby Computer

Products661623 24 60PM671 26.70PN1172 26.70661903 44 00PM951 46 50

40488 0.3240496 0.20

4737VP 17 304738VP 17 50

74 SERIESOIL

741.542 0.23741.544 1.62

741.5353 0.887413363 1.38

7411030 0.19744032 1 9

4049UB 0.2040508 0.2040518 0.254052B 0.2540538 0.2540549 0.5240558 0.4840566 0.3840595 2.964060E1 0.3040638 0.2840666 0.2240678 1.4240688 0.144069UB 0.1640708 0.164071B 0.1840725 0.1540739 0.1640758 0.164078840778 0.164078B 5.164081B D.1340828 0.1640858 2.324086B 0.294089B 0.5440938 0.1440948 .304095B 0.5440965 0.8540978 1.2040988 0.3140996 0.384104P 0.784106B 0.5841608 0.654161E1 .6641638 0.9841745 0.9841758 0.884194E1 1.104409P 8.504410P 12.654411/8 16.6044128 POA4412FL POA441257 ADA4416P POA4419P POA442968 5.604433P 15.854443P 2904447P 9.784468P 9.754469P 24.104489P 12.85449019 3.904490L 9204495P 4324497P 10.4544990 4 BO45008 14.964501UB 0.27

47514/D30 204752VP31 7147531/P P004754VP POA40085 02440097 0.4540098 0.4840100 1.1440101 0.7640102 0.9240103 0.6840105 0.6440106 0.3040107 0.2740108 POA40109 0.5040110 0.604011440116 9.6040117 1.6640147 0.954016040161 464016240163 .464017440175 0.3640181 POA4019240193 2

40194 POA4019540240 1.3640244 1.3640246 1.3640257 1.3240373 1.1040374 1 1045000P POA45026 3.4045027 4.6145028 34545040 7.4445041 7.8845100 1.6345106 5.4045109 3.0845138 1.4845145 92545146 10.4445151 15.0045152 16.5045156 13.5045157 110645158 11.9445159 18.9045406 2.1045407 4.9845411 POA45414 10.5545428 POA45433 POA45440 12 7545441 POA45453 POA

7400 0 207402 0.207403 0 207404 0.257405 0.257406 0 307406A 0.337407 0.307407A 0.327408 0.237410 0 157412 0.407413 0.277414 0.287416 0.33

7 0.3074200.207425 0.157426 0.2074270.1874300.227 0.277 7 0.24

7 0.387 0.487442 0.387445 0.707446 0.847447 0.84

7447A74517454 0.407470 0.277472 0.187473 0.237474 0.357475 0.257478 0.237480 0.797483 0.607485 0.287486 0.267490 0.397490A 0.727491 1.607492 0.427492A 0.707493 0.5474930 0.817495A 0.6974104 0.4274107 0.3074110 4.1674116 3 1074115 39574119 1.9874121 04674123 0.3274125 0.3774126 0.547412874132 0.5174150 1.3674151 0.42

74L047 0.42741_048 0.4674LS49 0.6274LS51 0.1274LS54 0.12741.555 0.3074LS73 0.17741.0735 0.24741.574 0.16741.5790 0.1874LS75 0.20741376 0.2274LS76A 0.2474LS77 0.4274LS78 0.22741.583 0.30741383A 0.3474LS85 0.34741.586 0.20741.590 0.2474LS91 0.50741.092 0.32741_093 0.24741395 0.3874LS913 0.4874LS107 0.2374LS107A 0.2874LS109 0.2074LS1095 0.2674LS112 0.20741.51125 0.2674LS113 0.2074LS113A 0.26741.5114 0.2274L51145 0.26741.5122 0.3074LS123 0.3074LS125 0.2174LSI 25A 0.28741.5126 0.2874LS126A 0.2874LS132 0.2074LS133 0.1874LSI 36 0.2274LS137 0.6274LS138 0.2474LS1 39 0.26741.5145 0.54741.5147 0.867413146 0.70741_5151 0.247413183 0.2474LS154 0.70741.5155 0.24741_5156 0.24741.5157 0.22741.5158 0.24741.5160 0.3274LS160A 0.3674LS161 0.3274L0161A 0.3674LS162 0.3274LS162A 0.3674LS163 0.32741.51630 0.36

74L5364 1.38741_5366 0.2174LS365A 0.2674LS366 0.287413366A 0.327413367 0.2174LS367A 0.3074LS388 0.28741.53650 1.327413373 0.3274E0374 0.3274LS375 0.327413377 0.367413378 0.627413379 0.867445381A 3.057413385 2 22741_0386 0 4874L5390 0.30741.0393 0.347413395 0.3674LS395A 0.667415396 1 6B741.5398 1.227470399 0.62741_5423 1.827413445 1.8874LS450 53074LS461 4.4574LS461A 5.407415465 3.627413467 3327413468 3.827413469 5.6274LS469A 6.7074L04919 0.907413491A 5.98741.5502 2.6074LS540 0.93741_5541 0.767413546 4.4374L5548 4.187413549 4.1874LS5613 1.62741.5569 1.1474LS573 1.34741.5574 1.34741.5590 4.537413591 6.58741.5592 5.2874LS593 8.25741.5595 3.78741.5597 4.64741.5604 4.4674LS605 4.46741_3606 4.4674LS610 9.9574LS611 11.94741.5612 6.6874LS620 1.3874LS621 1.7674LS622 1.6674LS623 1.287413624 2.10741.5625 2.28

740042 0.2974H051 079744058 0.287as4r, n os - - - ---748074 023744075 0.27744076 0.27744077 0.34745085 0.32744086 0.247446107 0.267440109 0.247440112 0.277440113 0.277440123 0.347400125 0.317400126 0.327400131 0.357400132 0.277400133 0.317400137 0 44741-16138 0 327440139 0.217440141 0.4174E10147 0.41327660074110148 0.377440151 0.317440153 0.317440154 0.897440155 0.4724.10167 0.33

7460158 0.3274E10150 0.4374E10161 0387400162 0.430.347400163 0.4374E10164 0.387480165 0.557440166 0.597456173 0.517440174 0.327440170 0.327440181 1.307440182 0.407440190 0.457440191 0.487406192 0.527400193 0.407400194 0.457400195 0.327400221 0.417440237 0.4974E10238 0.507446240 0.447400241 0.4474110242 0.547400243 0.597446244 0.437466245 0.44741-1C251 0.24

7'1462" 0'357446257 0.3274110258 0.4974110259 0.447446266 0.32

745 SERIES

74000 04474002 0 4474503 0.5174504 0.4274508 0.4274509 0.4874510 0.9874511 0.4874520 0.4874532 0.7874540 0.2574551 0.3674564 0.3674074 0.9874088 1.12745112 1.013

745124 2.42745132 0.98740133 0.73745134 1.95745138 0.88745139 0.88745140 0.78745153 1.26745157 1.72746163 2.80745174 0.92

1.35740182 3.29740189 2.14740195 2.40745240 1.00740241 1.12745244 1.77745257 1.22745258 1.22740260 0.70740273 2.44

2.420.96

740253 1.90745374 2.18740394 2.10740412 2.10745436 2.82745431 2.62745472 2.32745734 2 62

RESISTORS

METAL FILM0.25W 1%

024 Series108 to 18 3p eachN.B Min Qty. OrderMig 500s Per value

METAL FILMPRECISION

0.25 WATT 0.1%E96 Series1009 to 255KPrice: 00.94 each

HIGH PRECISIONNON -INDUCTIVEWIRE WOUND

0.15 WATT 0.1%

Te inp.Coeff.3pqmlORSOR.100R.250R,10K.100KPrice: £3.85 each

HIGH PRECISIONNON -INDUCTIVEWIRE WOUND

0.33 WATT 0.1%

Ternp.Coeff.3ppm1R,513.10R2OR,50RP116e: 03.60 each

1008120R. 250R,500R,1K. 2K, 5K,10K,20KPrice: E3.10 each

74110 SERIESSURFACE

MOUNT

744000M 0.21741-1CO2M 021744003M 0.211074H004M 0.217400004 0.2112000007400081A 0.21740010M 0.2174HC14M

2740020M 0. 1

30M 0.217,1,H,,C..,,,,,' --- 0.21741-10745 0.27

m 0.29' 4HC75740085WM 0.65744C /36M am74HC1 23AM 0.42744C125M 0.46746620

7474501313M 5.34H01328 0.42

7400139M 134741-10154WM 0.48745015761 0.3474E10161M 0.42741-10164M 0.4674810165M 0.57741-10173M 0.447480174M 0.38744 0221410 ass74110245/WM 01574 40244WM 0.5574802454W 0.6178008AP745025161 0 84

7440259M 0.69

74HC273WM 0557440367WM 0.5374110373WM 0.55744C374WM 057

74HC39°M 057 57

744039361 0.53,..666,,,,------ 07674110541WM 0.76744C573WM 1 09

74HC574VVM 0847440688VVM 0.84744040171A 044

74004"OM 0 44

74507 SERIES

7480100 0.227480102 0 2274110103 0.2274E10104 0.2274E10108 0.22741-10110 0.2274110111 0.2274E10114 0.267440120 0.2674E10121 0.257310127 0.22741-101-30 0.22708m 2 0.2274110142 0.46

'367457480,4 0.26748017574,0180 0.60740 0186 0.36748 019,

744 11107 0.40741-1071 09 0.4274E101112 0.4274417123 0.6474407125 0.5674001126 0.5674407132 0.5074401137 0.5274Hunae au744013 39 0.4574401147 0.54741-101151 0.5274407153 0.44741101154 1.1874001157 0.4474E10115B 0.4474501160 0.5674501161 0.5674507162 0.5874801 163 0 5674401164 0 52

VOLTAGEREGULATORS CAPACITORS

SURFACE MOUNT1.15

7805 0.2878054 0 327805FA 0.457806 0.287808 02873097812 0.28p7812A 0.3278120TC 0327815 0287818 5287 824 am713L05 0 2471305A 0 2878L054CLP 0 40

mitiiilityct('1137116., ,,, -,Case Size: 1318I ..,,,,,.286,n,

11171. 2271, 3.1p8 47oE1 i. ,p, 72,, 3.9,7,IMO, lissipl/ 2215493.10p1 47010E1001022imira. 3.1144121

Price: 15p cieh

47, mpl. 111011011,1pr, i gip. ,,,,,

MEMORIES

DYNAMIC RAM

4164-10 I 204164-12 1.004164-15 11041256-8 1S041266-10 1.5041256-12 1.4041464-12 4.4541464-10 4 459464-10 2.80414256A-70 3.90

CRYSTALOSC. MODULES74HC SERIES

744000 049744002 0.49

742,,_60g4 0.4974711-09 0.4974501074AC11 0.49745014 0.49740620 0.49740032 0.49745074 0.49

8pin DILPlastic k g

711 Output4 Pins spaced atcorners ot M5801

Req.= MHz4 4 9152 8 10

i -

12. 15 6 20Price C2.98 ea

4502B 0.3445038 0304504B 1.37

4000 Serie.SurfaceMount

74151A 0.6274154 1.56

74155 0.78

74LS164 0.2874LS1135 0.4874LS166 0.52

74LS626 2.187413627 2.337413628 2.18

7446273 0.417446279 0.3474116280 030

4505B 3 4045068 07245088 0.7245108 0264511B 0 32

4001 BT 0 25400261 02540118T 02540112810 25401281 0 25

74157 0.4374158 0.9874159 3.2074160 047741614 I 60

74LS168 0.5874LS169 0.52741.51 70 0.6674L5173 0.3074[51735 0 42

74LS629 0.937413631 42.207413640 0347440641 0.86741_5641-1 1.28

7440283 0.3874110298 0.497400299 1.047440323 107

74HC"4 "7



EP610PC-35 POA001-0165-5 10.96712146818AP 4.20H03-6402-9 8.16803-6440-9 B.89

H83-6495-9 B.89

8044883 9.52HD46505SP 9.85HD46802P 5.50HD6321P 4.2000634857032 32.509D63803XP 11.95#068000-8 11.5980684557 692

SAB80C32P 595 TIL100SAB8155-P 382 TIL111SAB8259AP 3 59 TI

SA882C54.2.P 4.12 11L11756882855A -2-P 4.80 TIL119SC80C451con6413.60 T1L311SCN2661bc1528 3.35 TLP504ASCN2661ccn28 3.35 TLP521PAL16R4-15CN 298 7060173TL16C552FN 12.58 TOTX173TMP7002NL.2 497TMP80515AP-2 598TMS3477NL 6.68TMS3700NSB 8.78 3630BM/BB

49620/1313

1 980.60

L113 0.800.851.209.651.58

-4GB 4.204964.96

CL7621DCPA 1.98

CL7622 POACL7650CPD 4.48

L765000PD 5.64CL7652BCPD 824CL7652CPD 8.24CL7660CPA 1.40

CL7660SCPA 3.80CL7662CPA 3.80CL7663BCJA 678CL7663BCPA 5.10CL7664CPA 7.95CL7665ACPA 4.98

L7673CPA 1 268.73

LM343H 8.80LM346N 386LM348DP 040LM348N 2.40LM350T 6.65LM351N 2.60LM358N 0.32LM359N 4.68LM3608 772LM361 M/SMD 640LM363H-100 16.50LM36904 3.82

LM3699RC 3.70LM380N 1.20LM381AN 7.88

NE5530N 382NE5532AN 1 58

NE5532N 0808E5534AN 1.80NE555N 0.20NE556/SMD 0.70NE556N 0.38NE558N 228NE564N 3.42NE565N 2.94NE567N 065NE568N 385NE570N 4E0NE57113 3.405E5896 425

TL071 CP 048TL072ACP 184TL072CN 0.50TL072CP 0.50TL074ACN 285TL074CN 084TL081CP 0.34

TL082CP 136TL084CN 0.48TL27L2CD/SMD 1.40TL4974C6 3.14TL507CP 4.03TL77024CP 2.04TL77054CP 2.04TL7705CP 2.04

ULN2001AN 0.44ULN2002A 044ULN2003AN 0.44ULN2004AN 140ULN2024A 1.40

ULN2032A 140ULN2803AN 0.89UM5100 POAUM5101 3.60XR2211CP POAXTR1106PY1112/11ZN1445 P

ZN414ZZN415E 1.84

75452 0.28754528 04875453 564

538 0.647 0.6475454B 0.9875462 0.9875463 1.10

75468 3.8075489 1.3075470 POA75471 1.6875472 1.4875473 1.4875474 2.25

2N4401 0 18284403 0 18284921 1.40

285401 0.132N5415 0.72

2N5449 0.88285459 0.52285485 0482N5876 1.32

286034 0.72288037 0.72286050 3.12286051 3.492116054 2.202416056 1 94

MICROPROCESSOR& SUPPORT ICs

100114DEC 740100141 DG 98063217 4.2063485CP32/sm 19.9563603XP 10.076502 2.946502A 666- -85207 4.40

4.406522LINEAR65225655165516

4 ;,0

& MISCS.

3 40POA

6500272 ,. 6,5"- HD68452P 5.608068821/54.29

TMS3702ANS 875TMS3835ANS 7.55 555.T1MER 0.20

L8052ACPDL8068AJD 9.65 LM3852-1.2 2.20 NE592/SMD 1 80 TL77094CP 2.04 ZN423 2.20 75477 2.10 286057 224

8500273 6.98813-7159.5 20 98 TMS77C01NL 10.74 6341-13 POA L8069CCS0 3.75 LM385Z.2.5 2.20 NE592N 1.40 TL7770-SC 3.82 ZN425E-8 4.46 75491 0.68 286058 268

65010272 7.0065C22P2

66 H13-71594-5 23 40 TMS9900NL 24.40L8069DCS0741-OPAMP 0.

ADOPO7CN 2.14L8069DCZR2.86 LM3866-1/SMD 1.65

LM386N-1 1.40NE592N14 0.92NE602AN 2.98

1L783C0C 3.06TLC2201CP 3.06

ZN426E-8 3.88Z5428E-8 518

75685176 2.8875AL5192 2.88

286109 0.78266125 2.88

65C51 E-13 5-3

1358516.2 4-.3-8-

680007-10/12 POA

HM10422 14 30

082C81311 17.06M6402AIPL 7 09M64021PL 3.73

TMS9901NL 14.113

TMS9902ANL 15 94L8211CPATMS9914ANL 23.10TMS9928ANL 740

AD52OJN POAAD524 21.605341/1 18.24CM71701PG

2.852.28

L8212CPA 1.107.66

LM386N-3 1.80LM386N-4 2.60LM387AN 590

NE602N 2.25NE60446 7.205E61256 2.87

TLC2202CP 3.06TLC2274CN 2.85TLC251CP 2.54

ZN4298.8 232ZN449E 476

75ALS193J 3.2275C1154 2.8875C1406 2.73

256388 0.98256517 0.34286519 0.34

75107 1.02

75107A 1 021 80

75108A751088 2.08751098 2.46

680007-18 POA68000P.8 4.95680087-8 POA6801015-12 POA75108, 0,6802PAD581KC5N5MD7.856803AP

A-99-6805E3E

44640317L POAMS2600/15 4.40NS8250N 7.80N582508-13 7.80M5M82C51AP 4 20M5M82C54P-6 5 40MAB8031AH12P 4 56

TM5999535L 6985IJA9636ACP 1 96UA96375M7209IPA1.96UA9638CP 1 98069639CP 1.98

UM6845B 4.95CM7212AMIPLPOAUM9151CM72131PU

0052739706AD548JNA0578111AD581JH 6.96

5058550 24.60A059208 14.88

M720741PD 680M72071PD 6 80

3.75CM7211AMIPL 4 02

M7211M1PL 4023.204 58

LM388N-1 4.25LM389N 3.40LM3900N 1.60LM3909N 2.84LM3914N 4.40LM393N 0.30LM393P 0.30

181M45560 1.20NJM45566 1.20NJM4558DX 1.20NJM4558S 1.20

OP070.1 3.6001107CN 0.95OPO7CP 0.95

TLC2652815 4.46TLC2654CPTLC271CPTLC272CPTLC274CNTLC339CNTLC372CP2S41096R

750185 3.98750.39 1.207501894 1.3275C189A0 1.3275LBC176 2.60

2146668 1 40

2N896 0262N17013A 0.482041015 0.102541048/0 0.142S410489 0.14

0746810P68217 1.52

6840P6844P 17'

5 98MCI 0103P 1.98

MCI 0115L 3.21

UM9151-3 POAUPB82313 PO4UPB8282C 4.98UPB828440 4.98

60594A0 10.566059540 6.65AD648JN751143.40

AD75"N

CM7216A1J1 18.05CM72 t 7A1P1 7 20CM721713131 10.42

CM72171J1 10.42

LM394CN 5.98LM3999Z 2.76LM399H 7.85LM4250J 11.82

OPO7EP 3.10OPI 1 GP 5.85011177FP 3.71

OP27GP 2.89

TLC551CP 1682541100TLC555CP 0.65T4C5513CN 1.14

TLC7524CN 186

751106 1.36

75113 3.02

75115

MAB8035HL-BP

2622194 0

0522541102 2.102541104 2.102S41111 1 18

6845P 4.886845577512168600P 7.02686097 7.6268621P 3'684407 6

68650P ,688097

;',I,

68821P 1.9;, .5

68640P -77

MC10115P 1 98

MC146805E2P 9.18MC68000P12/16 POAMC68010P1 0/12 POAMC6802P 2.47MC6809P 6.78MC6821P 1.80

MC6840P 5.05MC6844P 18.40MC6845P 7.38

UPB8286C 4.98UPD70108C-10 9.10UPD70108C-8 6.95UPD70116C-10 12.90CM7218EULUPD701180-8 9.20CM72241PLUPC/71055C 43UPC/72016C 11.68CM7226BIPLUPD7201CUPD765ACUPD765AC

AD711JN2N2222AD717.IN 3-607245.11(60741KN 3.69282369A60752366282484617175372975140AD7537LN PO2142905A075421(8 I.A075433CWE607578662129074

1

CM721BAIJI 6.85M721BAIPI 6 85

CM7218DIJI 6 8514 767.77

CM7226A13L 26.1225.04

CM72491DM POACM75551BA 2.40CM75551PA 0.64

LM555C6 0.28LM565CN 7.48LA/1710CH 2.60LM723CH 2.80LM723CN 0.70LM733CN 2.65LM741CJ-14 2.20LM741CN 0.45LM747CH 2.40LM747CN 0.90

OP42FZ 7.44OP77GP 2.07OPO7C6 0 95PM7548HP 14.04RC4136N 0.90RC4193N POA8741949 2.85RC4207GN 1.92

RC4558 0.9011845587 0.60

TLE206ICP 2.20TLE2062CP 3.40TLE2064CN 145TLE2161CP 2.42TMS3477NL 5.96TPIC2408NE 7.140.78TPIC28021(V 8.40TPIC6259N 3.28TP1C6273N 3.28TPIC65956 3.28

75116751220.24P092N236975136751380.32

2.6528213947515075150M

7515275154

0.282N2222A 0

0.20

0.29252905A 0.32242907 0.27

0.30

2541115 0.802641145 0.802SA1283N 87025612648 2.811

25412656 2.762S41283 0.242041295 2.782561302 3.742S41399 0.782S41482 0.78

4'968080AAD844613MC6850P 3.3525.35 UPD780C-1 CM7556IPD 1 30 LM78GCP 2.40 REFOI CP 2.10 TSC426CPA 75154M 262923 0.30 2SA1515 0.78

808561428086 3.469086.2 3.90800286-12/pg4 48.50800288-8/plcc 24.40608856 4'9.5

MC68705R3PMC68400P 7.02MC68409P 7.62MC8314P 6.60MCM6810P 3.00MCM686.10P 5 35

UPC/808399C 8.42M6403IPLUPD8155HD2.10UPD8251AFCUPD8253C-23.90UPD8253C-5 3.324.69

ADC0804LCN 4.2575155ADC0820CCN 22.40L272263053ADC0834CCN 7

ADC11104LCOVM 12.10L6,93,ADC84KG-10 12.68ADC908HP 16.424.92

10.80

72M 2.10

L.2,76

LM79GCP 240LM833N 282LS28548 2.40LS288B 3.60LS7210 4.40

REFO1HP 2.98REFO2CP 2.30REFO3GP 2.30REF25ZS25604

TSC5000PETSC7106CPL 6.81TSC7116CPL 5.25TSC7126CPL 5.35TSC7860CPA 1.40111096B

75157751590.767390°75161475162A

282243 0.78

0.32

293055293441 1.20

263553 0.982N3684 1E8

2541516 3.72204156 1.40204235 1.60256485 1 80256545 078

808855.2 5.9,8118.5CH 7 6093C464

AL -5,-938468 4.4093L3402 7.08AM26LS2588P 2186M25L52589P 2.686M2602PC 2.30

MM53200N 140MM58167BN 10.64MM58174AN 14.80MM58274CN 9.18MSM5832RS 3.39MSM80835RS 4.90MSM80C391SMD6.45MSM80C856 3.95

UPD8286C POAUPD874140 12.52

UPD8749HC 13.98V20.10MHz 10

V20-8MHzV30 -I OMHz

V30-8MHz 9.20V61C3OP 7.80

ADDACEION 19.7475172NGADC2014KN 4.86AD01907CN 1.6064001500AY -3-1270 3.60AY -5-1013 3.201.6041/-5-1 0134 5.24AY -5-1250 POA751789T

L4805CV 2.20L487 3.15L4960 3 15L7028 2.94LA8250 POAL,635,3 POALA6510 P06,..665,0 POA

LT1006GN8 2.72LT1010CT 4.58LT1028CN8 7.32L41032C6 4.70LT1070CT 9.14LT1083CP 8.82L41086CT 2.90LTC1052 7.97

54410270441043PSAA3049P 9.92S8A5025D 7.65SAA6002A 10.80SAS560S 3.40SED2000FVA 9.80SEC2301ADC 8.78

620668 2.64IC5.50U2400130

06646 3.95U42240PC 1.400.783470901, 0.8.6

1_14709PC 0.85LIA71514C 4.500.700.3

3.68263702751737517475174NG 3.682N3725751752.162.6075176°0.38751768

0 10283704 10

263706 010

2537892163819293866293904

SOCKETSLOW PROFILE

No Pin Gold Tin Goldof spacTurn aldr sldrPins -ing Pin Tail Tail

0.3 18p 6p 18p18p 6p 18p

AM26LS31 DC 2MSM80C056-2 5.98 VC0106/46 8.60

4Y -5 -3600 -PRO 9.96LG7132 2.30 LTC485CN8 2.16 SFC2741DC 0.18 1.14723CP

U4733CJ 2.96 75177 2143905 14 0.3 31p 8p 31pAM26LS31PC 1'

AM275191ADC 10.26

MSM80088 7.60MSM81C55 4.60MSM82C51A 3.58

Z0800110PSC 16.90Z0868112PS0 3.20Z180-MPU POA

666109139BA6208 1.40

LC7522 POALC7555 POALD111ACJ POA

LTC490 4.40M52186L POAM5220 POA

SG3524N 4.60517680CJ 1.92SL1452 6.75

L14741MP 0.80U4741TC 0.280.37517875162 2.60283958

263906 16 0.3 33p 109 33p39p I1p 39p

-0442]5281 PC 6.25AM296480C 12.36

MSM82C53-2 3.98 Z8001B.CPU 111 6 CA3046 051CA3046(SMD) 0 8926405LF135080 1820 M5238L POA SL2364C 3.97 LA-148CP 0.36

0.52

7518375188

2640372.

20 0.3 45p 12p 45522 D.3 54p 14p

644296500 6.38MSM82C53-5 3.58MSM82C54-2 4.20

Z80113008VSC 8.252806 -CPU 1.25 863054 094

LF311H 10.80LF3478 1.10

M5298P POAM70681 1.25

S431178 POASL486DP 2.98

U4748TC3677000610 POA 75189 264062 0.3 54p 14p

AM2966PC 3.98AM298280C 3.346446850L 9.82

MSM82859A-2 3.98MSM82C84A 3.30MSM82C846-2 3.60

ZBOA.GTC 1.98

2805-062/1 3.15Z804 -DMA 3.95

CA3059CA3078AT 242CA30792941242

LF35IN 0.130

LF353N 0.42LF355N 0.70

MAX1232CNG POAMAX1232CPA 3.57MAX1259CPE PO4

SL490B 2.51

SL560CDP 3.00SL6270C 3.30UCN51101/8

114798TC 18038658004 2.40

2.60

75189A 0.8575361 2.8475365

264091 0.78264123 0.10

0.20

24 0.6 54p 14p28 2.6 60p 16p32 0.6 65p 22p

AM8238PC 5

6449050000AM9050CPC 4

MSM82C88 12.60N808286 -10E1 24.50N800206.12/0 29.54

280A -P10 1.29

Z804-00/0 3.40Z800 -CPU 1.52

C63080EC63081 o0.64063089 E

LF356N 1.40LF357BN 4.98LF357M/SMD 4.98

MAX162ACNG POAMAX232ACPE 4.84MAX232CPE 2.80

SL67000DP 5.47307429819SN5281CN POA0N55451BJG P06

2.00UDN29824 2.00UDN6118A 1.65

7342767°45°90.3275451 028

264125 0282N41262842216 2.96

40 0.6 70p 22p49 08 65p64 0.75260p

AM9102070 2.82880L286-BC2/8136.20 Z808-CTC 3.00 0630944E LF357N 1.05 MAX232EWE 3.80 00C12 0.20 8083501M POA 754515 048 2N4236 3.72 64 0.9 260p

AM911430M6M9551 PC

.

AM96L02PC 3

57-5-8138 64'

AY -5-81364308 6.4C11641SMD 4.98

582355 3.68N8264N 3.88N82012646 3_25

N82S1B1F 10.04NS16450N 468

ZBOB-DART 5.80LF398NZ8013

ZOOSPIO 2 20ZEIOSSIO 450

3.48CA30964ECA3096CE 2.67

CA3597E 2E 0

CA9199E P06CA313OBT 19 20863130E 1 10

2.75

LF412CN 1.21

LF441CN 0.75LF442CN 0.99

MAX232N 2.80MAX280CPA 5.94MAX452CPA 5.38MAX627CPA 2.98MAX660CPA 5.72

SP18481DG 5.53SP4534 P06SP4740DPSP86290P 3.44SP8680DP 4.96

MOTHER BOARDSProcessor BusIntel804867.2-66

PERSONAL

Ch p BIOSSe

SA SS AM

COMPUTER -

Cache ExpendRAM Memory256K 32MB

HARDWARE& SOFTWARE

Expansion BoardSize PirceSlots in rnm E p

641161,1x8bit 245 x 220 499.00TELECOM & SPECIAFUNCTION ICsC82314

NS16550AFN 12.60CA31404E 1.34

LF444CN 240 MAX690ACPA 158POA

447215P804867/X2.86 SA AU AM 256K 32MB 5/06191.28bit 220 x 220 490.00

C8253'

CABOCEI5B 5.98CD82C85 1628048600.33CD/328869-5 9.74

NSC800N-1 10 80P8032AH 429P0051611 11.207805248/Basic 23..

88(MGA3/0

6200890-018 370707W52020 5.25733W00123 5.25AMA1503GXB 868

8631406 0 60863146E863180E

9-991.25

C63240E

LH0002CN 10.80LH0032CG 33.60LM101AH 5.65LM1OCN 9.24LM1118 174

MAX694CPAMAX697CPE POAMAX7219CNG 7.15MAX8211CPA 2.28MAX901BCPE POA

T67251315

TA7368PTA -7658P PO4478005AP P4482004H 0

8048600-508048600-50

80486DX-33

SA 5 S AMA AU AM

SA SS AMA AU AM

256K 32MB 6x1664.1x8bit 245 x 220 450.002560 32MB 541664208511 220 220 444.00256K 32MB 641024148W 245 220 349.002561( 32MB 51649 //bit 220 x 220 325.00

CG80C286-12 4E5080808288-16 65.00COM8136 8.45

P80854-2 5.985.98"2"

136/81505 110CLA25106/PLCC 5.95GA0500-131DB 3.20

CA3240E1 21-.9146

CA324ECA3280E

2601 68

LM13600N 140LM13700N 232

MC1377P 4.93MC1413P 0 74

TA8410K 2.80TA8449P POA

0048650-2580386DX-4080386SX-33

SA 55 AMSA SS AMSA SIS AM

126K 32MB 6x161/1.148bit 245 220 220.0084K 18MB W6641480/I 220 220 128.00OK 16MB 651664158M 220 x 220 79.00

COW CI 7 B.

8882854CRT -8004.001C08205 192

89999 4.80P80C311311 4.54P80C8BAL-2 1

781558/2 8.

88185 18.10LMKS-49256/PLCC 5.92 , .. , ,k9.3 '9540. r .66MK5175N 3.00OC.147.7 2.40

0632806E 594CA3280E 3.4206555CE 0.20CA7410E 0 18

LM139114 3.60MC14411P,139j 6.60LM1458N 0.45UM1496N 2.95

I ODIN 7.92

11.313

MC14416L 17.60MC14495P 482MCI 45406P 2.10MCI 455P 0.40

TA8659AN POA4448614 POATEI51200 0.60TBA2406 POATBA570 POA

80486052-66 VESA SIS AM8048600.50 VESA 015 AM-8048605.33 VESA S S AMAll Mother Boards are supplied

256K 32MB 7418901.232(VESA) 260 x 220 510.002580 32MB 7164732932(VESA) 260 x 22D 470.00258K 32MB 7r16iAl1,0732(VESAi 260 x 220 349.00

with Zero K bytes of RAM. Add 228 per MegaByte of RAM.D3232 86080352303

P8205 2.008 4.35 055503-1(D POA LM1881N 3.60 MC1455P1 0.60 TBA820MT POA CONNER HARD DISK DRIVES MICROPROCESSORS08088 5.48PP34C108

PB212 2880 00792513 POA LM1889N 7.40 MC1458P 0.32 TBA920 POA CP-30104E 120MB 19msec 3.5' LP £189.00 80286-16MHz INTEL 085.00

D8086-2 8

08202A PP8226 2.

P82614 3.90604704 3.50OMV18BP5 7.98

016983 906DAC0800LCN 4.10

LM1894N 4.16LM21911 15.75

MC1488L 2.40MCI 488P 0.58

TBA9E10 POATC9106BP POA

8730174E 170MB 19msec 3.5' LP 1219.00 8038600-40MHz AMC 075.00

CP-30344 343MB 13MISee 3.5' LP E575.00 80486SX-25MHz INTEL C125.0008254-2 6OMV18C

P8253,k

6.66 DAC0832LCN 10.67 LM239N 3.90 MC14896 0.80 TC43354 P06 8048605-33MH8 INTEL 5275.00D8204A

P8255N5OMV1BC11 765 DACO88P 2.60 LM2901N 1.16 MC1489AL TCA965 pow QUANTUM HARD DISK DRIVE 80486DX-50MHz INTEL E375.00

08286 6P8259

OMV18CW1 7.85 DAC08015 3.64 LM2903N 0.85 MC1489AN 0.80 TCM1520AP 198 ELS-170 170MB 17msec 3 5"LP £170.00 804860X2-66MHz INTEL E350.000828284-12 9.80

P82594OMV25C 8.42 DAC1008LCN 10.73 LM2904N 0.85 MC1489L 2.20 TCM1531P POA FLOPPY DISK DRIVES

082828441P8274

OMV62AW1 6.90 DAC1222LCN 20.40 LM291-76-14 6.10 MC1489P 0.48 TCM1705AN POA TEAC FD-235HF 1.44MB 3.5' 035.00 CO -PROCESSORSD82C288-10

P8279-539:98 S4534-AMI 4.20 00201413K 3. 83 LM2917N.8 5.80 MC1498/4 2.20 TCM3105/4 897 TEAC FD-55GFR 1.2MB 5.25' £39.00 80287-8 INTEL E40.00

0828280.12 11.85P6282 2.

56336931 2.95 0G211 138 LM2940C415 2.73 MC1558L 3.32 TCM5087N 2.40 TEAC FD -505 INTEL £48.008828288-8 9.36

78266 3:311

SAA5025D 5.40 00508603 5.95 2.10 M81648P 2.40 TCM509,13/4 2_40 MITSUMI 0359T3 1.44MB 3.5" £35.00 80287 -XL INTEL E65.00287481-1

P132C54SCM66115P 3.40 00508081LM2940CT53.25 LM2984CT 7.50 MCI 658P 12.70 TDA1083 2.60 MITSUMI 0509V3 1.2MB 5.20' C32.00 803137DX33MHz INTEL £65.00

DM960114 2.45DP8228NDP82386 6. 6SIMMP82054-2 4.80

PALL OLBCN 1.90PALI 2H6CN 1.90

SGS7P050 4.55SP1450B 376ULA1R13029E1 180

051488N00DS14C88M/SMD I 65

DS14C88N 1.65

LM301AN 0.36Lm307, 0.84LM308N 1.10

4401709071 120M81723CP 1.20M81741CP 045

70610856 2.9640410850 3.80T061151 1.10

MITSUBISHI MF355C/258MG 1.44MB 3.5" E29.00 MEMORIESMITSUBISHI MF504C1318MP 1.2MB 5.25' E35.00

I Mx9x9 01-11P7Ons 028.00CANON MID5601-V13 3.5'3.5.25' E9/00

07830488 2

DP831118 6.54PAL16R4BCN 2.17

ULA2ORK008E159.72XR.T5683 3 60

001488946 1 658512017 1 44

LM31011 2.98 MC3242AP 754 TD611700 2.80 SIMM 1Mx9x3 CHiP7Ons £29.00

FLOPPY DISKS SIMM 4Mx9x9 CHIP7Ons £107.00051221

,- " .

PAL2OLI0CNS 4.35PAL2OXEICNS 332

ZNA2L029J-BS 3.80 HA13426 11.96LM311N 0.30LM31111-14 2.15

MC3301P 0.88MC3302P 0.60

TDA1515A 4.98

4041521A 4.37 MANUF. 3.5"41.44M13 5.25"/1.2MB SIMM 4Mx9x3 CHIP7Ons £107.00051231-20 4.44 PALC16180-25C0

ZNPCM1J-BS 8.95 #4177231 1° LM312H 8.95 MC3340P 1.60 TDAI 576 2.95 TDK C 10.65 E 7.45 SIMM 256Kx9 CHIP 8Ons £10.00

0512326 10 OPTO H075189P POA LM317AT 2.60 MC3357P 3.20 1051578A 3.60 SONY 010.10 07.65

0534888 3.20PALC20L8Z-45COS ELECTRONICS HEF4754V 22.20 LM3170 0.52 MC3403P 1.40 TDA2595 3.32 FUJI £10.10 07.65 SOFTWARE

DS3487N 3205.17

811-0201-5 160 LM317T-505 0.52 MC3446AP 6.75 TDA304BN 1.85 MITSUBISHI E 10.70 E 7.00 MICROSOFT ORIGINAL4825 0.60DS34C8814 4.80

DS34C87N 48. PALC22V10H-3505LM318NH11.5086-5 11.21

1311-549-5 POA2.80

LM319N 1.60MC3479P 792MC3523U 5.80

TDA3505 POA71943810 POA

UNBRANDED 7 6 50 E 4.5D MS DOS 5 £40.00

Price per Box of 10 Disks MS DOS 5ANINDOWS 3.1 882.000126 0.60DS363I N 3.33

PC08584P 4/433 0.46 F111-574AKD-5 42.50MSLM32OLZ-12 0.34 MC4024P 12 78 705440 806 GRAPHIC CARDS DOS 6 P 0A.053632N 2.

PCF8568P 8. 4/438 0.56 613-0201-5 3.20 LM324AN 3.68 MC42 0 84 41144510 3.38 TRIDENT TO/GA 8900 Trident 1MB SVGA E41.0013036336 3'

PCF85138T 8 66139 160 H13-05094-5 715 4324, 1.20 MCT61 1 18 1044583 3.38 TRIDENT TVGA 8900CL New Trident 1MB SVGA E44.00 IMPORTANT2.810S3634679036

0536918 A5- -

PCF8570P 7.85LM324NPCF8573P 6.72706038CNY17-3 0.64

1113-201-5 3.20HIIL1

0.35

LM325N 9.40MF1OCCN 8.95ML924 4.90

TDA4660 POATDA7010T P06 CIRRUS LOGIC XYJ(X 1MB SVGA 05200

TSENG LAB ET -4000 1MB SVGA momAll prices quoted are

Excluding V.A.T.DS38626 7.38CNY21N095000-32-12 97.50 PCF8574P

PCF8574T

P06DF08 0.40

HS574-AK 18.20CL7104-16CPL26.08

LM3301N 2.60LM3342 1.80

MM53013/4 5 76MM531056 4.98

TDA7052 2.52T068702 E22

METHEUS Premier 1280 Ni New Premier S3 E299.00METHEUS Premier 1M TSENG LABS ET4000 E240.00 Postage & Packing

208640NDS8820ANDS8832/4 2.68DS8836N 2 44

PCF8591P 9 35

R6502AP 5 79

R6520P 4 40

HCPL-2200 5.98HCPL.2231HCPL-2602 5.68HCPL-2830 388

L7107COH/PLCC520

L7109CPL 9.85L7118CPL 5.25

LM335Z 216LM336Z-2.5 1.28

LM336Z-5.0 1 20

MM80C956 1.44MP7570JD POAMUX24E0 a6o

7E61045 POA7E61080 4.201E65820 POA

KEYBOARD & MICEMITSUMI KPO-E99YC 102 UK KeyBOard Regular Size £20.00MITSUMI KPO-E996C 102 UK KeyBoard: Space Saver E2000

Charge of 03.001sapplicable to all goodsunder the heading of'Personal

0088379 2-40

008133814 2'40EF68034-1P 3 -BO

.0-53,EF6803P -'--EF6821 P 1.30EF68809P 3.18EF68821P 1.44

86522 4.40R6522AP 5.80

R65802P2 5.8486580273 E90R65CO2P4 8.95R65C102P2 6.85R65821182 5.94

HCPL-2730 3.45HCPL-2731 3.20HCPL-4200 5.98LE/74 1.44IL01 1808074 2.25

19074 2.25

L7117CPL 5.25L7126CP1 5.35L7135CPI 832L7136CPL 6.551_7137CPL 6.98L7606CJN 12.24L76110CP6 1 32

L6633,1 15

LM339AN 1.10L6,3395, 0.24LM340AT12 168Lon34oT-5 a3oLM340T12 0 30LM340T15 0 30

MUX24FP 9.60MV500DP 3 05MV601DP 316MV8870DP 5 52NE5020N 10 84NE5278 3.71

NE532N 0 60

TIPC2801KV 8.40TL026CP 1.84TL062Chl 0.48TL062CP 0 48TL064CD 0.90TL06409 0 48TL06411)/SMD 2 10

BTC 7849R 102 UK KeyBoard. Regular Size £24.00MS1 SYSTEM MOUSE 3 Button Serial E10.00/0 CARDS,0 2S/1P/1G wth cables 01000IDE 280/2FD w1th cables E10 00DE 2HD/2FD/25/1P/IGI512kB with cables £15000099/512k CACHE Controller, 2MB RAM. Max 8.5MB 889.00

ComputerHardware & Software'.

Postage & Packing willbe charged at cost for

all destinations outsidethe United Kingdom.

R6582282 4.80 LM340T5 aoo NE536H 4.90 TL071ACP 1.84 DE992 5MB CACHE Controller, 2.5448 RAM. Max 8 5449 0125 00

PLEASE SEE PREVIOUS ISSUES FOR OTHER ITEMS & FEB/MAR 1992 ISSUES FOR LEDs,DISPLAYS & RELAYS.

VIEWCOM ELECTRONICS PLEASE ADD 95p P & P and then 17.5% VAT. OFFICIAL ORDERS from Govt. & Educational Establish-ments are accepted. VAT at 17.5% is chrageable to all orders received from EC Member Countries unless

77 UPPERTON ROAD WEST VAT Number is quoted. OVERSEAS orders, postage AIR/SURFACE will be charged at cost. VAT is not

PLAISTOW, LONDON E13 9LT applicable for EXPORT orders from Non -EC Member Countries. Stock items by return of post.N.B. All prices are subject to change without notice & stock availability.

PLEASE PHONE/WRITE FOR ITEMS NOT LISTED Retail Shop: 139, New City Road, Plaistow, London El 3 9PX


10

VHF/UHF TELEVISION TUNER(PART 2 FINAL)

This second and final part of the article deals with theconstruction and mechanical finishing of the TV tuner. Also,we tell you how to operate and program the tuner via the built-in menu.

Design by W. Sevenheck

The tuner is built on four printed cir-cuit boards, which are supplied as twopairs. Figure 7 shows the artwork ofthe single -sided processor board andthe keyboard, while the artwork for thedouble -sided, through -plated mainboard and supply board is given inFig. 8. Although populating these fourprinted circuit boards should notcause problems to the experiencedconstructor, there are a few simplerules to observe.

Processor boardStart by separating the keyboard andthe processor boards. This is easythanks to the fraised seam betweenthe two sections. There are no fewerthan nine screw holes in the keyboardsection. If you can make do with six,cut off the 'empty' part at the left-handside of the small board. Next, mountthe five press -keys and the two LEDs.The position of the LEDs is best deter-mined by looking at the layout of thetuner's front panel. The last part fittedon to the keyboard PCB is the single -in -line 4 -way PCB header.

On the processor board, it is recom-mended to fit a 40 -pin IC socket for the8751 microcontroller. The polarity ofboxheaders K i , K2 and K3 is clearlymarked on the component mountingplan. After fitting jumper JP1, the tworesistor arrays may be soldered on to

the board. Fitting the remainder of theparts is straightforward, and requiresno further comment. The terminals ofthe LED on the processor board arebent such that the LED protrudes fromthe front panel. The function of thisLED is to acknowledge reception of avalid (RC5) infra -red command signal.

The processor board and the key-board are interconnected via sevenwires. This connection is not madeuntil all boards are installed in the 14 -inch rack enclosure. The same goes forthe LC display connection, which onlyrequires a short length of flatcable.

Main board

Separate the main board and the sup-ply board along the fraised seam be-tween them. Alternatively, if yourenclosure has sufficient space, leavethe board whole. Note, however, that afew wires are required to connect themain board to the supply board, irre-spective of whether these are sepa-rated or not. Voltage regulators IC5and IC6 are fitted with TO -220 styleheat -sinks, which can be bolted on tothe main board. To prevent strain onthe solder joints caused by heating,align each regulator on to the heat -sink, and secure the two before sol-dering the terminals.

Pay attention to the polarity of theSAW filters, Fl i and F12, before mount-ing these components. The polarity isindicated by a dot on the componentoverlay.

Having fitted all parts on to theboards, it is time to concentrate on the

MAIN SPECIFICATIONS

TV bands:

TV channels:TV standards:Presets:Sound:Remote control:Display:Outputs:Input:Menu language:

VHF -1, VHF -3 and UHF47 MHz to 170 MHz170 MHz to 450 MHz450 MHz to 860 MHz2 through 120 (incl. Hyperband)PAL, NTSC, SECAM100mono, analogue stereo, analogue two -languageRC5 compatible2 -line alphanumerical LCDCVBS, audio left and right (cinch sockets)coax, 7552English or German


VHF/UHF TELEVISION TUNER -2 1111

screening. Cut 1.5 to 2 -cm high stripsof tin-plate sheet or thin brass, andbend these as indicated by the dashedlines on the PCB overlay. The screen-ing is essential, and helps to keep mu-tual interference between sub -circuitsto a minimum. The SAW filters mustbe completely surrounded by screens,for which separate pieces of sheetmetal must be bent.

To prevent interference in the audiodemodulator section, the video outputsignal produced by the IF section iscarried to cinch socket K2 via a lengthof screened cable. The cable ends aresoldered to the points marked with an

arrow (w) and a ground symbol (nearR28 and K2 respectively). In this way,the video signal can go safely acrossthe analogue sound stage.

Check the type numbers of the ce-ramic filters and the Toko inductors tomake sure that these parts go to theright PCB positions. An error is easilymade at this stage because these partslook almost identical. The connectingpins of the Philips tuner module, Xi,are soldered directly to the relevantsolder spots. The two large metal tabsat the sides of the metal box are sol-dered to the ground plane at the com-ponent side of the board. For this

Fig. 7. The first PCB combination contains the processor board and the keyboard. These twoboards are easily separated using the seam between them.

operation you may need a high -powersoldering iron. The rest of the parts onthe main board should not cause prob-lems. The polarity of the boxheader,Ki, is indicated by the componentoverlay printed on the ready-madePCB.

The holes in positions D i and D2 onthe main board are used for wires thatconnect to LEDs D2 and D3 respec-tively on the keyboard via connectorK4. This connection is best made by alength of 4 -wire flatcable fitted with anIDC socket at the side of K4 on the key-board PCB.

The parts list gives alternative types

PROCESSOR BOARD

Resistors:1 1500 R1

1 8kC12 R21 4517 R31 471d1 R41 39052 R51 101Q 8 -way SIL array R61 4kS17 8 -way SIL array R7

1 100 R81 6528 5W R91 10k52 preset H P1

Capacitors:1 41.1.F7 63 V C1

2 10pf 63 V C2;C122 22pF C3;C44 100nF ceramic C5;C7;C10:C131 220nF C61 3nF3 C82 47nF ceramic C9;0111 470µF 25 V C14

Semiconductors:1 LED, high efficiency 3mm 012 LED, high efficiency 3mm D2;D31 87C51H (supplied ready -

programmed, order code7141, see page 70) ICI

1 PCF8582A (PhilipsSemiconductors)1 IC2

1 74HCTOO IC31 SFH505A (Siemens)2 IC41 7805 IC5

Miscellaneous:1 Jumper JP11 Boxheader 14 -way K1

1 Boxheader 16 -way K21 Boxheader 10 -way K31 SIL-header 4 -way K45 Digitast press -key

(w=12mm) 1 S1 -S51 Quartz crystal 10 MHz X1

1 LCD module with backlight,2x16 characters, e.g., LM086ALN

1 Printed circuit board 930064-1 (seepage 70)


RADIO AND TELEVISION

Fig. 8. Artwork of the double -sided and through -plated main board and supply board combination (track layouts shown at 70% of true size).


VHF/UHF TELEVISION TUNER -2 rnfor inductors X2 through X5. The re-placements for X4 and X5 are pin -com-patible. Those for X2 and X3, however,have pins 4 and 6 soldered in the holesfor pins 1 and 3.

If Xs can not be obtained, it may bereplaced by a 270-S2 resistor connectedbetween the input and the output.

Problems may occur regardingavailability of the Siemens SAW filters.In the original design, the Types

OFWG9250 and OFWG1963 are used.Unfortunately these devices are notSiemens 'preferred products', whichmeans that series of these filters areonly manufactured to customer or-ders, after which they are available forsome time. Consequently, it may takea while before they are available againwhen they are out of stock at the timean order is placed. The upshot is thatnew batches of non -preferred products

are not made until there is sufficientdemand. Fortunately, both filters maybe replaced by near equivalents thatare better available: the OFWG9250may be replaced by the OFWG9253,and the OFWG1963, by theOFWG1962. These near equivalentsgave entirely satisfactory operationwhen compared with the types origi-nally designed into the circuit.Equivalent types for the UK CCIR-I TV

RECEIVER BOARD

Resistors:

" k

6 47nF ceramic C16;C41-C44;C56

2 47gF 25V radial C17;C35

Miscellaneous:1 Boxheader 14 -way K1

3 PCB -mount cinch socket K2 -K4

2 5600 R1,R2 10 100nF ceramic C19,C21;C29, 1 2 -way PCB terminal

1 5100 R3 031;C33;C36; block, pitch 7.5mm K5

1 47052 R4 C37;C39;C48; 1 TV tuner module

3 4427 R5;R6;R8 C54 UV816PLL (Philips

1 2422 R7 2 330nF C24;C52 Components)1 X1

2 39052 119;1410 1 lOnF C27 1 SFE5.74 (Stettner-Murata) X6

2 1MQ R11;R12 1 1gF C28 1 SFE5 5 (Stettner-Murata) X7

1 5426 R13 2 100gF 10V radial C30;C40 1 TPS5.5MB (Stettner-Murata) X8

4 47Q R14 -R17 1 220LiF 10V radial C32 1 Quartz crystal 10 MHz X9

2 22k12 R18,R22 1 220tiF 25V radial 038 1 OFWG9250 (Siemens) FL1

2 202 R19;R20 1 470LLF 40V C45 1 OFVVG1963 (Siemens) FL2

1 6428 R21 1 220gF 40V C46 2 Heatsink for IC5 and 106.

1 1422 R23 1 i000g 35V C49 1 Mains transformer 15V/15VA

1 1542 R24 1 470nF 050 (not on PCB)

3 1W R25;R33;R37 1 1000µF 16V C53 1 Mains socket with integral fuseholder

1 22052 R26 1 Enclosure Type ET32/04

1 1052 R27 Inductors: (21 cm deep) (ESM)

1 680 R28 1 4gH7 L1 1 Printed circuit board 930064-2 (see

1 15052 R29 1 15gH L2 page 70)

2 224211% R30;R31 2 113CNS-K1272HM-81091

2 1000 R32;R39 or 07202-342 1 X2;X3 Printed circuit boards 930064-1 and -2,

1 1200 R38 2 199KCAS-A359HM-81088 and a programmed 87C51H are available

1 506 5W R40 or 199KCS-A877-2C 1 X4;X5 as a package under order code 930064

2 8200 R34; R36 (see page 70). The programmed 87C51H

1 1425 R35 Semiconductors: is also available separately under order

1 542 preset H P1 1 B80C1500 B1 code 7141 (see page 70).

2542 preset H P2 Dl;D2 = 02;D3 on keyboard PCB2 1N4001 D3;D4 Component changes for PAL TV system I

Capacitors: 1 ZTK33 D5 used in the UK (sound carrier at

3 4gF7 63V radial C1;C20;C22 4 BC547B T1 -T4 6.0 MHz):

2 1 nF C2;C3 1 BF256B T5 FL1: QFWG9253 (Siemens)

1 100nF 04 1 TDA3857 (Philips FL2: OFWJ1952 (Siemens)

3 2gF2 63V radial C5;C6;C25 Semiconductors)1 1C1 X7: SFE6.0 (Stettner-Murata)

1 lOnF ceramic C7 1 TDA8415 (Philips X8: TPS6.0MB (Stettner-Murata)

2 22LIF 25V radial C8;C34 Semiconductors)1 IC2

5 10gF 63V radial C9;C10;C47; 1 TDA3842 (Philips 1 C -I Electronics, P 0. Box 22089, 6360

C51;C55 Semiconductors)1 IC3 AB Nuth, Holland. Fax: (+31) 45 241877.

3 47nF C11;C12;C26 1 LM339 IC4 2 Electrovalue, see advert on page 53

2 2LLF2 C13;C14 1 7812 IC5

3 220riF C15;C18;C23 1 7805 106

Fig. 9. Front panel layout (shown reduced to 50%).


14 RADIO AND TELEVISION

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standard (vision -sound spacing6.0 MHz) are also given in the partslist.

That completes the construction ofthe printed circuit boards, leaving youwith mechanical work on the enclo-sure, mounting the boards into thecase, and, of course, adjustment of theTV tuner.

Mechanical work andwiringThe TV tuner is built into a matt black13 -inch rack type case from ESMFrance (type number ET32/04). A sug-gestion for the front panel layout andlettering is shown in Fig. 9. Thearrangement of the four boards insidethe case is evident from last month'sfront cover photograph.

Five holes have to be drilled in therear panel: three for the audio andvideo outputs, one for the tuner's RFinput (antenna socket), and a muchlarger one for the mains socket withintegral fuseholder. The LCD and thefive press -keys require two slots to be


VHF/UHF TELEVISION TUNER -2 Elcut in the front panel. Further, youneed to drill three holes for the LED in-dicators, and one for the IR receiver,while a rectangular clearance is cut toaccommodate the mains on/off switch.

Once all four boards, the mainstransformer and the parts on the frontand rear panels have been mounted,you are ready to start working on thewiring - see Fig. 10. All mains carry-ing wires and terminals should beproperly insulated, and the case mustbe connected to the mains earth. Runa thorough check on the wiring beforeyou apply power.

Test and adjustmentConnect the coax input of the TV tunerto your antenna system. Apply power.If the LCD backlight does not work, ac-tuate it by fitting jumper JP1. Start byturning the AGC preset (P2) to the cen-tre of its travel. Next, connect a volt-meter between pin 8 of the TDA3842(IC3) and ground. Turn off the AFC viathe keyboard, and tune to a known TVstation in the UHF band. Do not usethe 'search' function to find a station.Instead, enter the channel number di-rectly. Be sure to tune to a strong(local') station which transmits on astandard channel number. This warn-ing applies to those of you who con-nect the tuner to a cable network,where channel numbers such as 46+and 66- are used to indicate positiveor negative 1 -MHz offsets from theCCIR standard frequencies. Do not se-lect a station transmitting on a `+' orchannel. Next, connect a video monitoror TV set to the tuner's video output.Use a plastic trimming tool to adjustthe core in the IF filter, X5, for a volt-meter reading between 2.4 V and2.6 V, which indicates resonance at38.9 MHz exactly. This is essential forthe 'search' function and the AFC. Ifthe picture on the monitor is noisy, theAGC adjustment must be correctedwith the aid of preset P2. The operationof the AGC may be verified by tuning toanother station, and checking if the re-ceived picture is all right again. If so,you may disconnect the voltmeter.

Next, adjust the sound receiver.Start with the IF section of the soundcircuit. Be sure to tune to a stereo ortwo -language broadcast. Connect anoscilloscope to pin 15 of the TDA3857(IC 1). Adjust the 38.9 -MHz filter untilthe 5.5 -MHz and 5.74 -MHz IF signalsare in phase. If this is difficult to seeon the scope screen, it is also possibleto adjust the filter for the highest sig-nal level measured at pins 13 and 17.

Next, adjust filters X2 and X3.Connect the scope to pin 5 of ICI, andadjust X2 for the highest possible sig-nal level. Similarly, connect the scopeto IC i pin 9, and peak X3. At this

point, the LEDs and the display shouldindicate reception of a stereo or two -language broadcast. Reception of astereo broadcast is indicated by bothLEDs lighting, while only one LEDlights (depending on the selectedchannel) if the broadcast has two -lan-guage sound.

Finally, optimize the channel sepa-ration by adjusting Pi for best results.In practice, good results are obtainedwith this preset set to the centre of itstravel.

OperationThe use of a microcontroller allows alltuner functions to be selected and con-trolled with the aid of only five presskeys on the front panel. The press keyshave the following functions:

Key 1:Key 2:Key 3:Key 4:Key 5:

Main menuKey 1:Key 2:Key 3:Key 4:

Key 5:Display shows: program number; AFCand mono/stereo or two -language.

menu selectionmenu -dependentmenu -dependentmenu -dependentstore

menu selectionprogramme number +1programme number +10mono/stereo or channel1/2 switchno function

Channel menuKey 1: menu selectionKey 2: channel number +1Key 3: channel number +10Key 4: no functionKey 5: store channel number

with previously selectedprogramme number

Display shows: channel and pro-gramme numbers; lower line: fre-quency.

Search menuKey 1: menu selectionKey 2: frequency +62.5 KHzKey 3: frequency -62.5 KHzKey 4: search start/stopKey 5: store channel number

with any shift (62.5 kHzresolution)

Display shows: 'searching' flashes onstart of search, programme and chan-nel numbers; lower line: frequency.

Language menuKey 1: menu selectionKey 2: switch on AFCKey 3: switch off AFCKey 4: select between English

and GermanKey 5: store settingDisplay shows: language selection andAFC on/off.

General user informationPressing the 'store' key while in thesearch menu, channel menu or lan-guage menu automatically takes youback to the main menu. The audio out-put is muted during searching until astation is encountered. The searchfunction has two speeds; it starts athigh speed until a station is found,and then switches to low speed. If thereceived signal is too weak, or not froma TV station, the tuner switches tohigh speed searching again.

If you tune to a TV station from themain menu, the selection is automati-cally stored after 12 seconds. The sta-tion is immediately available themoment the TV tuner is switched onagain.

The AFC is only active in the mainmenu, provided it has been enabled inthe language menu. The frequencyrange of the AFC is ±375 kHz, and itstuning effect is visible on the LC dis-play: a '>. indicates a tuning frequencyabove the standard frequency; a '<' atuning frequency below the standardfrequency. A is shown if the tunedfrequency is in accordance with theCCIR channel raster. The AFC actionis delayed a few seconds after a pro-gramme number is selected.

One hundred presets (0-99) areavailable for television channels be-tween CCIR E2 and 120, which in-cludes the so-called S channels,S I -S20, and the channels in the hy-perband, H1 -H21.

Finally, the tuner responds to thefollowing commands received via theRC5 infra -red receiver: programmenumber up/down, sound on/off,stereo/mono, channel 1 or 2, numbers0 through 9, 1 or 2 -digit input, andswitching between the last two se-lected programmes.


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LLOYD RESEARCH LTD7H/7aAntsB.rs000k3 9LFanHe,Warsash, Nr Southampton,

Tel: 0489 574040 fora device list

and published by ELEKTORLECTRONICS (Publishing)

Editor/publisher. Lea SeymourTechnical Editor: J. Buitmg

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ux Advertising Office.3 Crescent TerraceCHELTENHAM GI 50 3PETelephone: (0242) 510 760Fax: (0242) 226 626

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0 0

v v

18

DIGITALHYGROMETER

Design by A. Rietjens

e temperature of the human body ismaintained at about 36.9 °C (98.4 °F),

whatever the temperature of the sur-roundings and the nature of the thermalinsulation with which it is clad. Heat iscontinually generated by the chemical ac-tions which occur in the body, and thismust be dissipated as fast as it is pro-duced if the temperature is to remainsteady. This dissipation is achieved largelyby the evaporation from moist internalsurfaces of water which is exhaled, andby evaporation of perspiration from theskin. If the evaporation is too rapid, aswehn one sits in a draught, a sense ofchill and discomfort is felt. If the evapo-ration is not rapid enough, as in a smallinadequately ventilated room, the evenmore acute discomfort of stuffiness is pro-duced. This has little to do with the ac-tual temperature or with the accumula-tion of carbon dioxide, for it is experi-enced in the open air at all temperatures

Our personal comfort is deter-mined not so much by theambient temperature as by

the relative humidity of the airsurrounding us.

in moist climates. It is because the air isso near saturation that the necessaryevaporation from the body is reducedbelow the comfort level. The factor thatdetermines personal comfort is not howmuch water vapour the air contains, buthow much more there is room for at thattemperature; in other words, how far the

air is from being saturated with watervapour.

The moisture content relative to thatof saturated air, expressed as a percent-age and called the relative humidity(r.h.), is thus the really important quan-tity that controls the evaporation of waterfrom a surface. Relative humidity can bedetermined by an hygrometer. There arevarious types of this instrument, of whicha modern one, based on digital electron-ics, is described in this article.

Relative humidity sensorThe r.h. sensor used in the present de-sign is an element whose capacitancechanges with humidity. It consists of anair permeable housing that contains anon-conductive foil, which is sensitive tohumidity, with a thin layer of gold at bothsides. The gold layers form the electrodesand the foil the dielectric of a capacitor.

JF

oscillator

sensorC(r)

IF

MMV integrator

offset

uo.)

(0)

A/o -converter .ZZ7

EPROMwith

linearizationtable

bufferlikely

comparator change

117Lilo

++ 930104 - 12

Fig. 1. Block schematic diagram of the digital hygrometer.

The dielectric constant of the foil, andthus the capacitance, changes with vary-ing relative humidity-see Fig. 2.

The capacitance is used to vary the fre-quency of an oscillator, here based on theHCT version of a Type 4060 lc.

There are two problems that need tobe solved. The first is that the change incapacitance is not linearly proportionalto the relative humidity. This is solved bythe use of a linearization table containedin an EPROM. The second is the large pro-duction spread of the sensors, which isreflected in Fig. 2 by the three curves.This is solved by the use of a capacitancefactor instead of the absolute capacitanceof the sensor. The calculations con -elat-ing the dielectric constant, relative hu-

100

1 90

-852 80

70

60

50

40

30

20

10

090

Clete Otyp

100 110 120 130 140 150 160 170

C(pF)

900124-10-12

Fig. 2. Capacitance of the sensor as afunction of relative humidity.


DIGITAL HYGROMETER 19

33p

C2

1MHz33p

R1

10

T

IC1

CTR14

G

RCX

RX

X

CT=0

CT7

9

13

C34

74HCT4060

3

15

2

5V

0R3

2

6

2

:100n

to

1-11

HUMIDITYSENSOR

DISC)

IC2

THRTLC OUT555

TRCV

5

C4

40.210n

R18

C10

5V 22 2 16V

114 R17

E

R15C

6

22n 116V

I C17

:1130n

20

C7

MMN100n

P1

10052

9V

7

P2

25k

R16

VI+

VREF 1C4

DBO

DB1

DB2

DB3

DB4

DB6R19 ADC0804

101.-r718 CLKR

C9 C11ME Me

T1000 .7150p

IC9

DB5CLK

INTR

AGND WR

CS y RD

10

DO 9

8

D2 7

D3 6

D4 5

05 4

D6 3

D7 25

24

3

6

5V

0712

IC8a

28 27

VPP ® PGMAO

2

3

5

A6

A7

A8

A9

A10

AllAl2

A13

IC3DO

D1

02

EPROM D3D4

27C64D6

D

:100n

11

12

R4

22052

3

R12

2k2

1

IC8b 5V

T1R13

2k2

BC557B BC557B

LD1

10

9

3 8 LD2 3

CA CA

b T7 01

22052c1122052 d

22052 e

22052 f O 018 220521 g dp

22052

22 114 20

R116

HD1105

10

9

2

T2

CA CA

o1109 dp

6

HD1105

IC8c 5V

9

1172017 D1

16 D2 /"N D215 D3/.."\ D314 D4/..N D413 D5/..N D512 DSPN D611 D7 1 D7

3

IC8d

3

1 4

R S

IC7a

J:r - C

OR21

U02 44

5 144

2

3

4

5

6

7

8

9

IC574HCT574

10> v 19

18

5V

D4 10

D5 12

17

16

5

D6

D7 1

14

13 1

12

10

IC8f

2

5V® 13 7,-,

5V

OR20

1

1N4148

:100n

IC8e

117-IL

C12

EN

2

0

3

2

P

COMP

IC6

O

74HCT85

P<0

> P>o

5V

IC7 = 74HCT74IC8 = 74HCT04

C15 ;Idl IC5 IC6

6 14

D3 ++

D2 = green

D3 = red

C19 U C20

IC8 mom100n n 100n

930104 - 11

Fig. 3. Circuit diagram of the digital hygrometer.

CALCULATION OF VARIOUS PARAMETERS

In these calculations:e is the dielectric constant of the sensor

foil (F in -1).

Cr= erAld

Kr = 100 (Cr - Co) / Cr

[Eq. 1)

[Eq. 2]

er = ad / Abfr

Substituting Eq. 5 into Eq. 3:

[Eq. 5]

A is the surface area of the electrodes (mm2).C is the capacitance of the sensor (F).d is the thickness of the foil (mm).

Substituting Eq. 1 into Eq. 2: Kr. 100(1 -frIfo) 114. 6)

Kis the capacitance factor (%). Kr =100 (er - 80)/ er [Eq. 3] from which:f is the oscillator frequency (lis)a, b are oscillator constantsr is relative humidity (%).

fr a / bCT [Eq. 4] fo = fr/(1 -KS 100) [Eq. 7]

Uav(r) is the average input voltage (offsetdeducted) into the A-1) converter (V).

Substituting Eq. 1 into Eq. 4: Uav(r) ce [1 / (1 -Kr / 100)] -1 [Eq. 8]


20 TEST & MEASUREMENT

midity, capacitance factor, and oscillatorfrequency are given on the preceding page.

The design

The block schematic of the design is shownin Fig. 1. A crystal -controlled oscillatorprovides a stable frequency that is usedto drive a monostable multivibrator (MMv).

The length of the pulses produced by themultivibrator is determined by the ca-pacitance of the r.h. sensor.

An integrator (a simple RC network)transforms these pulses into a direct volt-age, the level of which is a measure of thehumidity of the air. An offset is deductedto compensate for a relative humidity of0%. The resulting direct voltage is thusan accurate measure of the relative hu-midity. This direct voltage is applied toan analogue -to -digital (A -D) converter.

The data produced by the converterare used to address an EPROM that con-tains a linearization table. The EPROM cor-

Fig. 4. Printed -circuit board for the digita hygrometer.

relates the measured voltage with a par-ticular relative humidity.

The EPROM drives two seven -segmentdisplays, that is, the data stored in thememory determine which segments shouldlight when a particular direct voltage isinput.

The output of the A -D converter is alsoapplied to a buffer and comparator whichcompare the previous data with the pre-sent ones to determine whether the rel-ative humidity is rising or falling. This is

PARTS LIST

Resistors.= 10 MD

R2, R19 = 10 linR3, R25 = 1 MD

R4-Rl1 = 220 SZ

RI2, R13= 2.2 ItR14 = 390

R15, R16= 39 k12

R17= 10012

R18=100k1R21=47052PI = 100 II presetP3 = 25 IES-2 preset

Capacitors:C1, C2= 33 PFCs Is 1 nFC4= lOnFC5 = humidity sensor, Philips Type HIC6, C7, C9, C12. C14 -C20 = 100 nFCa = 22 16 V, radialGlp = 2.2µF. 16 V, radial

= 150 pFCis is 100 µF, 25 V, radial

Semiconductors:Di = 1N4148D2 = LED, greenDs = LED, redT1, Ts sss BC5i57B

Integrated circuits:ICI = 74HCT4060IC2 = TLC5551C3 = programmed 27C64 (6301 -p. 70)

1C4 = ADC0804IC5 = 74HCT574106 = 74HCT85IC7 = 74HCT74

ICs = 74HCTO4

10a I. 7805

Miscellaneous:X1= crystal. 1 MHzLD1, LD2 = 7 -segment LED display, comet

anode, Type FiD1105 = orange)EnclosurePCB with programmed EPROM, No. 930104


DIGITAL HYGROMETER EN

program test;

uses dos,crt;

vari:integer;j,l,k:integer;g: file of byte;result: real;

constdisplay:array[0..9] of byte =($c0,$f9,$a4,$b0,$99,

$92,$82,$f8,$80,$90);vallist:array[0..16] of byte = ( 0, 15, 31, 47, 63, 79, 95,111,127,

143,159,175,191,207,223,239,255);humidity:array[0..16] of byte =( 0, 13, 23, 32, 40, 48, 55, 61, 67,

73, 78, 82, 86, 90, 94, 97,100);

beginclrscr;assign (g,'humidity.dat');rewrite (g);for i:=0 to 15 do (next curve part)

beginfor j:=0 to 15 do {linearise curve part)

beginresult:=j*(humidity[i+1]-humidity[i])/(vallist[i+1]-vallist[i]);result:=result+humidity[i];1:= (round (int (result/10)) ) mod 10;k:= round ((frac (result/10) *10) );

if k=10 thenbegink:=0;1:=1+1;

end;if (1=10) and (k=0) thenbegin1:=9;k:=9;

end;writewritewritewriteend;

writeln;end;close(g);

end. 930104-13

( 1 ) ;

(k," );(g,display[k]);(g,display[1]);

{Open the desired filename)

Fig. 5. Pascal listing for computing the content of the EPROM.

indicated by two LEDs.

The circuitThe oscillator, ICI, the Itc-r version of the4060, generates a frequency of 1 MHz,which is divided by 256 and this signal,available at pin 14, is applied to the trig-ger input of monostable multivibrator IC2,a cmos version of the well-known 555.Differentiating network R2 -C3 makes thetrigger pulses short to ensure that thetrigger level of a 555 is high again beforethe mono time has elapsed.

Humidity sensor C5 determines thewidth of the output pulses from the mmv.The output of the mmv is integrated byR18 -C10, whereupon the direct voltageacross C10 is converted into a digital valueby eight -bit A -D converter IC4. The refer-ence voltage of the converter is set withP1, while P2 provides the offset voltage

Preset P2 is part of potential dividerR15 -P2 -R16, which, via additional smooth-ing network R17 -C8, is connected to thesupply voltage.

Network R19 -C11 is required by the in-ternal clock used in the conversion.

Resistor R20, capacitor C12 and diode

D1 ensure that the converter starts promptlywhen the supply voltage is switched on.

When the supply is switched on, pin 3is held low briefly to allow C12 to be chargedvia R20. Diode D1 prevents C12 short-cir-cuiting the pulses at output pin 5, whichare linked to pin 3, and which provide theclock for buffer IC5. The link between pins3 and 5 sets the converter in its free -run-ning mode. As soon as a conversion hasbeen completed, pin 5 signals to pin 3that new data may be output.

The data provided by IC4 are appliedas addresses to EPROM IC3 and to bufferIC5. The data outputs of the EPROM driveLED displays LD1 and LD2.

The EPROM contains data that deter-mine which segments must be poweredto indicate the r.h. value associated withthose data. The EPROM thus serves as adata -to -seven -segment converter and cor-rects the non -linearity of the sensor.

Since the content of the EPROM is onlyeight bits wide, which allows storage ofthe data for one display only, the displaysare multiplexed by IC8a, IC8b, T1 and T2.The clock required for this is provided byICI (pin 1). This clock is also applied topin 10 of IC3, so that when an interchange

of displays takes place, there is also achange of address. Thus, for every num-ber on the display, two addresses are re-quired in IC3. The EPROM is available readyprogrammed (see page 70), but may alsobe programmed with the aid of the Pascalprogram in Fig. 4.

Circuit IC5 is supplied with a clockwhen new data appear at the output ofthe A -D converter. Immediately afterwards,these data are stored in IC5. ComparatorIC6 checks whether the new data on thefour highest lines are greater or smallerthan the previous data. Its P inputs(pins 10 12. 13, and 15) are thereforelinked to the four highest data lines ofIC4. while its Q outputs (pins 1, 9, 11 and14) are coupled to latch IC5. Pins 5 and7 are connected to two inputs of IC5, sothat the status of these outputs is alsostored in the latch.

At the instant new data appear at theoutputs of the converter, they are appliedimmediately to the P inputs of IC6. Thiscircuit then compares the value with thatof the previous data which at that mo-ment are still stored in IC5. Depending onthe result, either pin 5 or pin 7 of IC6 goeshigh and this level is applied to pin 2 orpin 3, as the case may be, of IC5.

Pins 18 and 19 of IC5 are linked to in-verters IC8d and ICs respectively. The in-verters control the set and reset inputsof bistable IC7a.

Since the signals from the comparatorare applied via the buffer, they control thebistable synchronously with the newdata. This ensures that the bistable doesnot give wrong readings owing to transitvalues on the D4 -D7 lines.

The bistable controls a green and a redLED. These diodes indicate whether therelative humidity tends to rise (green) orto fall (red). It also ensures that when twosuccessive data trains are identical, theLED that was lit at the previously detectedchange in r.h. remains on.

The power supply for the hygrometeris provided by a 9 V mains adaptor via aType 7805 voltage regulator. The adap-tor should be capable of providing a cur-rent of 300 IDA.

ConstructionThe hygrometer is most conveniently builton the printed -circuit board in Fig. 4(available ready made - see p. 70). Con-struction is straightforward by followingthe layout of the board. The tcs may bemounted in suitable sockets, as may thedisplays to elevate them slightly abovethe other components. The LEDs shouldbe at the same height as the displays: thismakes viewing them rather more conve-nient.

Regulator IC9 does not need a heat sinkand it may be screwed directly on to theboard.

After everything has been soldered, theboard can be mounted in a suitable en-closure. It is, of course, important to use


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Solution to thePrize Electronic Crossword

by Matrix(September 1993)

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23 Ashore27 ECT28 mA

Stephen ScottR.M. SmithG.W. SprayD. Westbury

All winners have been advised person -Winners of the construction kits, sup- ally.plied by Maplin Electronics - see backcover - are:

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either a transparent case or one with anappropriate window through which thedisplays and LEDS can be viewed.

The sensor should be fitted on or nearthe enclosure and linked via two shortlengths of flexible wire to the C5 connec-tions at the left-hand side of the PCB.

Finally, connect the output of the mainsadaptor to the + and 0 terminals on thePCB, preferably via a plug and socket onthe enclosure.

CalibrationA calibrated hygrometer and multimeterare required for the calibration. Removethe lid of the enclosure and switch on thesupply to the digital hygrometer. Wait afew minutes to give the unit time to ad-just to the ambient humidity. Check thereading of the calibrated hygrometer. Findthis value in Table 1 and note the asso-ciated rating of K. Enter this rating intothe formula for calculating the offset volt-age:

Uoffset = (1 - K / 100) Urh,

where Urh is the value of the direct volt-age at pin 6 of IC4. Connect the multi -

meter to pin 7 of IC4 and adjust P2 till themeter reads the calculated value of theoffset voltage. Finally, adjust P1 till the

display reads the same value of relativehumidity as the calibrated hygrometer.

END

R.H. (%) K (%) R.H. (%) K (%) R.H. (%) K (%) R.H. (%) K (%)

10 2.135 31 6.693 52 11.962 73 17.75811 2.349 32 6.926 53 12.228 74 18.03912 2.562 33 7.161 54 12.496 75 18.32113 2.775 34 7.398 55 12.765 76 18.60414 2.988 35 7.638 56 13.035 77 18.88915 3.201 36 7.879 57 13.307 78 19.17716 3.414 37 8.123 58 13.580 79 19.46917 3.626 38 8.368 59 13.854 80 19.76718 3.839 39 8.616 60 14.130 81 20.07019 4.052 40 8.865 61 14.406 82 20.38020 4.265 41 9.116 62 14.683 83 20.70021 4.478 42 9.368 63 14.961 84 21.02922 4.693 43 9.622 64 15.240 85 21.36823 4.908 44 9.877 65 15.519 86 21.71924 5.125 45 10.133 66 15.799 87 22.08225 5.343 46 10.390 67 16.079 88 22.45726 5.563 47 10.649 68 16.359 89 22.84327 5.785 48 10.909 69 16.639 90 23.23828 6.008 49 11.171 70 16.918 91 23.64329 6.234 50 11.433 71 17.198 92 24.05730 6.463 51 11.697 72 17.478 93 24.482

Table 1. Correlation between relative humidity and capacitance factor K.


Ap

6.00 LI

4A.uC 0

OSCILLOSCOPE LIVE CHOP Page 0.0046.6 V

AC4u. 0

2.00 1 4.0 psec 33.3

0.00 (Nr.10.0

20.0

Psec

nee26.6

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0.2

msec

msec13.3

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-8.001.0

2.0

msec

msec0.00

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t1,00(psec) 12,00 10.0 msec

CH2 S20.0

50.0

msec

msecFREEZE ONE SHOT MODE 1 CHI SET

TIME/DIU TIME-MAG. TIME-OUT HYSTERESIS SLOPE 0.1 sec CH 10.2 sec

PRINT COMMENT READ DISK WRITE DISK ( DEVIC I

AP " I I "

Connect the HANDYPROBE to the parallel printer portof the PC and start the software Measuring can becarried out at once The HANDYPROBE does not needan external power supply Some technical parameters0 5-400 V softwareselect input range,one input channel,8 bits resolution(overall accuracy 2%),A complete softwareprogram consisting ofa digitalstorage oscilloscope,spectrum analyzer,voltmeter and atransient recorderis providedThe HANDYPROBE iseminently suitable forservicing andeducational purposes

The TP5008 is an interface cardthat provides an analogueoutput in addition to two inputchannels This output incombination with the twoinputs may be used for thesetting up of a completecontrol loop The outputmay also be used as afunction generatorThe TP5008 has aresolution of 8 bitsand a sampling rateof 200,000 samples/sec (200 kHz) The input range may be set to 0.5-20 Vfull-scale deflection The output range covers 1.25-2.5 V.The TP5008 is fitted with BNC connectors and isdelivered complete with a user manual and softwareSeparately available are 1 1-1 10 probesand 1 100 oscilloscope probes

TiePie engineering manufactures a completerange of computer -controlled measuring instrumentsConnecting these units to a PC (MS DOS 3 0 or higher)results in a number of compre-hensive test instruments - oscilloscope;

- voltmeter;- spectrum analyzer;- frequency meter;- transient recorder.

All measured data can be storedon disk or run off for documentation Because of themany trigger possibilities, a variety of signals can bemeasured, while the powerful software enables amultitude of measurements to be carried out in astraightforward manner Application areas includeservice, medical research, automatic test systems,research and development, and education

I

I II

The HANDYSCOPE is connected to the parallel printerport This makes it possible to carry out measurementswith a laptop or notebook PC Because of its highresolution (12 bits), the HANDYSCOPE is a very accurateinstrument The measuring rate is 100,000 samples/secEither of the two channels can be set independentlyover a range of 0 5-20 V (with a 1 10 probe up to 200 V)The advanced software enables many measurements tobe carried out Two probes (switchable 1 1-1 10) areprovided The HANDYSCOPE is constructed as a smalltable model with two BNC connectorsThe length ofthe cablelinking thePC and the

Ais 18 m,HANDYSCOPE

which can beextendedto 3 8 m

I 11

The TP208 is an interface cardwith a measuring speed of2x20 Megasamples/sec(8 bits) Phenomena shorterthan one millionth of asecond can still bemeasured wellThe completely digitizedtriggering ensures verystable triggering withmany triggerpossibilitiesThe TP208 has aninput range of5 mV/div to 20 V/div in 12 steps and an auto calibrationfunction Since both channels may be sampledsimultaneously, phase differences can be measuredvery accurately Even single phenomena can bemeasured since each channel has a32 KByte memory Comprehensivesoftware is provided

A I

Interested? Then write or fax for a FREE demo diskette to

INSTRUTEK (UK)28 Stephenson RoadIndustrial EstateSt Ives, Cambs PE17 4WJEngland

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Telephone (04801460028Fax (0480)461 654

24

PRECISION CLOCK FOR PCsBuild this small add-on unit and put an end to the (often gross)inaccuracy of the real-time clock that ticks in your PC.Complete with a software driver, the precision clocksynchronizes your PC to DCF77, a time standard transmitteroperating in the long -wave band

Design by B. Zschocke

many PC owners, it is amazingand frustrating to note that even

the cheapest quartz -controlled littlealarm clock bought in a high -streetshop has a far better accuracy thanthe real-time clock in, say, a state -of -the art 486 -based PC. Although manyPC users will notice the clock inaccu-racy only twice a year (on changingfrom summer time to winter time andvice versa), there are also cases whenlarge time errors on a PC have disas-trous consequences. For instance, ona small network, where one programsuch as Turbo Pascal is shared, andthe MAKE option is used from time totime to produce code (MAKE automati-cally compiles the latest version of the

program). In this situation, it can hap-pen that the latest version of the soft-ware is overwritten by an olderversion, because the associated timeinformation is incorrect. It may alsohappen that a back-up program savesdata which is outdated, while the lat-est version is 'forgotten' - all becauseof an inaccurate system clock.

The inaccuracy of a PC clock mayhave several causes: supply voltagedips and surges when the computer isswitched on and off; large temperaturevariations in the case; or ageing effectsof the quartz crystal. Furthermore,most PC clocks lack an adjustmentpoint, so that one is totally dependenton the accuracy of a cheap crystal.

Atoms for the right time

The radio -controlled clock describedhere enables a PC to always 'know' theright time. The time information re-ceived from the DCF77 transmitter inMainflingen, Germany, is decoded andsubsequently applied to the PC via theRS232 serial port. This is done to savespace and energy required for an addi-tional PC insertion card. Further, thecurrent drain of the DCF77 receivermodule and the associated interface isso small that an additional power sup-ply is not needed. Before discussingthe hardware, however, let us have alook at the source and structure of thetime information picked up by the re-ceiver.

DCF77 is a 50 -kW transmitter oper-ating at 77.5 kHz from Mainflingen,near Frankfurt in Germany. The sta-tion is operated by the Physikalisch-Technische Bundesanstalt, and has arange between 1,500 and 2,500 km.The time information transmitted byDCF77 is derived from a caesiumatomic clock which is claimed to beamong the most accurate in the world.

As with nearly every clock, an oscil-latory movement is used as the refer-ence. However, in contrast with, say, apendulum clock where the length ofthe pendulum is a measure of 'time', ora quartz clock, in which the self -reso-nance of a crystal is used as the refer-ence, an atomic clock is based on thefact that atomic energy levels are asso-ciated with certain frequencies. To un-derstand this relation, a littleknowledge of atomic physics is re-quired.

Depending on their energy, atomscan take on different states. This phe-nomenon may be compared to a fuelgauge in a car: a high reading indi-cates a high energy, a low reading, alow energy. To change the meter read-ing from low to high, you have to fuelup, i.e., energy has to be added.Likewise, the state of atoms can bechanged by adding energy. However, itis only possible to go from a low stateto a high state by adding an exactamount of energy. Adding less or moreenergy than the critical amount willnot change the atom's state from lowto high. Because of this phenomenon,it is possible to generate an ultra -exactfrequency by using radiation to add adefined amount of energy to the atom.

In the atomic clock, an amount ofcaesium is vaporized at a temperatureof 100 °C. Caesium is a metal with alow melting temperature of 30 °C. Inthe first stage of the clock, atoms with


PRECISION CLCOK FOR PCs 111

a low' and `high' energy state are sepa-rated. The low' level atoms arrive in aresonator in which they are exposed toradiation from a signal source operat-ing at a nominal frequency of9.192631770 GHz. The radiation en-ergy is transferred to the atoms, whichchange to the `high' energy level. Afterbeing moved through the resonator,the atoms are collected and separatedagain.

The fewer low level' atoms remainin the resonator, the more accuratethe resonator works. This enables acontrol system to adjust the resonatorfrequency for a minimum number ofatoms that remain at the `low' energylevel. The resonator frequency so ob-tained forms the reference for the timeinformation transmitted by DCF77.The estimated accuracy of the caesiumreference is one second in 300,000years.

DCF77 time informationIn order to transmit the complete timeinformation, a protocol has beendrawn up that enables the exact timeand date to be contained in a periodictransmission which lasts 59 seconds.A complete time code is transmittedevery minute, as illustrated in Fig. 1.The transmitter frequency is 77.5 kHz,which is derived from the caesium res-onator. This has the advantage of al-lowing the transmitter frequency to beused as a reference, since its accuracyequals that of the timebase of the clock(phase errors may, of course, stilloccur in the path from the transmitterto the receiver). The transmit fre-quency used lies in the long -waveband, which means that only theground wave is usable for transmis-sion. Reflections of radio signals atthis wavelength are insignificant, sopropagation is by one 'path' only, theground wave. Consequently, receptionof long -wave signals is virtually con-stant around the clock. In practice,DCF77 reliably covers most ofContinental Europe, the South ofScandinavia, and the larger part of theUK and Ireland.

The coding systemThe coding system used on DCF77 wasdeveloped at a time when microproces-sors were virtually unknown. Hence, asimple coding system with BCD (bi-nary coded decimal) was chosen, al-lowing `ordinary' TTL components tobe used for decoding the time informa-tion. Each code word consists of59 bits (bit 0 through 58). One bit istransmitted every second. A logic oneis transmitted as a pulse with a lengthof 200 ms, and a logic zero, as a pulseof 100 ms. During the pulse time, the

miscellaneousapplications

10

month 84

4

day of 2

week 1

208

4

day ofmonth

Fig. 1. Schematic organization of the time/date information transmitted by the DCF77 timestandard transmitter.

transmitter carrier is reduced to 25%(amplitude modulation). The ampli-tude reduction takes place at the startof a second. Since there are 60 sec-onds to the minute, and only 59 bitsare transmitted, the missing 60th bitis used to mark the start of the timecode. The function of each of the59 bits contained in the time code isgiven in Table 1.

Three times an hour, during the19th, 39th and 59th minute, the sta-tion ident, DCF77, is transmitted inmorse. Each letter or number is trans-mitted between two second signs byswitching the transmitter modulationdepth between 100% and 85% at a rateof 250 Hz. This identification is auto-matically transmitted without inter-rupting the time code.

The ideaToday, a wide range of ready-madeDCF77 receivers/clocks is available atreasonable prices. In most cases, suchunits are identified as 'radio -con-trolled' clocks. The receiver section insuch a clock usually supplies the dig-ital time code as 100 -ms and 200 -mspulses. The best known receiver IC isthe U2775B, developed by TelefunkenAG for use in Junghans clocks. Apartfrom a ferrite rod antenna, this IC re-quires only a couple of external partsto make a sensitive and reliable DCF77

receiver. The U2775B is capable of op-erating at a low supply voltage of be-tween 1.2 V and 3.4 V, and has acurrent drain of only 0.5 mA.

There are also ready-made receivermodules based on the U2775B.Unfortunately, these usually supplyoutput pulses with a length of 160 msand 60 ms because about 40 ms is re-quired for reliable decoding of the timeinformation.

The designer's aim was to find asimple way of using a DCF77 receivermodule with 'shortened' output pulsesto decode the time information withthe aid of a PC. This has been achievedby turning the pulses into charactersconveyed to the PC via a serial link op-erating at a low bit rate. In this sys-tem, the binary code 000011111 (OFH)represents a 60 -ms pulse, and0000000001 (00H), a 160 -ms pulse.The leading 0 in the code is the startbit, and the trailing 1 is the stop bit.The advantage of this approach is thatthe software is relieved from pulse de-coding, which is taken over by the ser-ial interface. Furthermore, theinterface ensures that an interrupt isgenerated only once a second. At sucha slow interrupt rate, the PC is hardlyslowed down. The functions that re-main for the software are limited tofinding the start of the time code, de-coding the actual information, andconveying the decoded time to the op -


26 COMPUTERS AND MICROPROCESSORS

[)0

0

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R2

BF245B

D3

3

2

'Cl C2 D2= Xr.X70070p 1N4148

16V

BF245B

G D

BC547B

C3ROD

IC1

7

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TL071

1N4148C4I= X D4

MOM100p 1N414825V

RTS

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1N4148.

2x1N4148

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SG04

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135

1N4148

D10DTR

14 04

BC547B

R4

930058 - 11932001 11 - 11

Fig. 2. Circuit diagram of the interface between the PC and the DCF77 receiver module.

erating system installed on the PC.

The serial interfaceThe circuit diagram of the serial inter-face between the DCF77 receiver mod-ule and the PC's RS232 port is given inFig. 2. The interface is powered via theRTS and TxD lines. Capacitor C4 ischarged via diode D3 to the level of the

Resistors:1 4071 1kfl51 22kil1 1000

Capacitors:2 100nF1 10µF/16V radial2 100uF/25V radial

Semiconductors:1 LED 3mm green8 1N41481 LED 3mm red1 BF245B1 BC547B1 TL071

R1

R2R3R4

C1,C3C2C4,C5

D1

D2 -D9010T1

T2IC1

Miscellaneous:1 9 -way sub -D socket K1

RTS line, which is between +7 V and+12 V. At the same time, capacitor C5is charged to the TxD line level, whichis between -7 V and -12 V. Diodes D4and D5 protect the circuit againstdamage caused by an incorrectly ini-tialized RS232 port. The voltages builtup across the capacitors form the sym-metrical supply voltages for opampIC i. The opamp gives the digital time

1 DCF77 receiver module: Conrad1.2order code 190969-66.

1 DCF77 ferrite antenna. Conrad1,2order code 535630-66

1 Plastic enclosure 60x50x30 mm;e.g., type E406 (Bopla)2

1 Printed circuit board 930058 plussoftware 1871 (see page 70)

The control software for this project isalso available separately: order code1871 (see page 70).

1 Conrad Electronic Nederland BV, P.O.Box 12, 7500 AA Enschede, Holland.Tel (+31) 53 282000. Fax (+31) 53283075,

2 C -I Electronics, P.O. Box 22089,6360 AB Nuth, Holland. Fax: (+31) 45241877.

code applied to its +input a level thatenables it to be recognized as a serialsignal by the PC's RS232 port.

Generating a suitable supply volt-age for the DCF77 receiver module is alittle more complex. Here, a greenLED, D1, is used to stabilize the mod-ule's supply voltage. A stable voltage ofabout 1.8 V is obtained at a small cur-rent already.

Extensive decoupling is necessaryin the interface, because cross -inter-ference occurs easily between ana-logue and digital sub -circuits. Inparticular, every care has been takento prevent the digital sections upset-ting the operation of the sensitive ana-logue receiver. A very effectivedecoupling device is the high internalresistance formed by T1 -R2, a currentsource inserted in the positive supplyto the receiver module. Together withcapacitors C i and C2, this currentsource forms a filter that affords a veryhigh degree of decoupling of the re-ceiver's power supply lines. The combi-nation D2 -R1 is also connected to themodule power supply, and provides areference voltage of 0.6 V at the -inputof the opamp. This is necessary to en-able the opamp to recognize the highand low levels supplied by the receivermodule.

The last part of the interface is the

Fig. 3. Track layout and component mounting plan of the printed circuit board designedfor the receiver -to -PC interface.


Bit Meaning Function

0-14 Miscellaneous applications / as required.

15 Antenna bit. 0 = normal antenna; 1 = spare antenna.16 Al 1: change to summer or winter time in next hour.17 Z1 Time zone 1: 1 = summer time; 0 = winter time.18 Z2 Time zone 2.19 A2 1: switching second follows.

20 Always 1; start marker for time/date transmission.21 1 Minutes bit, value 122 2 Minutes bit; value 2.23 4 Minutes bit; value 4.24 8 Minutes bit; value 8.25 10 Minutes bit, value 10.26 20 Minutes bit; value 20.27 40 Minutes bit, value 40.28 P1 Parity bit for all bits transmitted so far (complement

to give an even number).

29 1 Hours bit; value 1.30 2 Hours bit; value 2.31 4 Hours bit; value 4.32 8 Hours bit; value 8.33 10 Hours bit; value 10.34 20 Hours bit; value 20.35 P2 Parity bit for all bits transmitted so far

36 1 Day of month bit, value 1.37 2 Day of month bit, value 2.38 4 Day of month bit, value 4.39 8 Day of month bit, value 8.40 10 Day of month bit, value 10.41 20 Day of month bit, value 20.

42 1 Day of week bit; value 1.43 2 Day of week bit; value 2.44 4 Day of week bit, value 4.

45 1 Month of year bit; value 1.46 2 Month of year bit; value 247 4 Month of year bit; value 4.48 8 Month of year bit; value 8.49 10 Month of year bit; value 10.

50 1 Year bit; value 1,51 2 Year bit; value 2.52 4 Year bit; value 453 8 Year bit; value 8.54 10 Year bit; value 10.55 20 Year bit; value 20.56 40 Year bit; value 40.57 80 Year bit; value 8058 P3 Parity bit for all bits transmitted so far.

Table 1. Meaning of all bits contained in the time information signal.

circuit around transistor T2, whichdrives an LED, D io, to signal receptionof time pulses received from DCF77. A6-mA current source, T2 -R4 -Ds -D9, isused to cope with the wide range of

voltages that can occur on an RS -232interface. In this way, the LED alwayslights at a constant intensity, whilebeing supplied via the DTR line.Consequently, the opamp and receiver

PRECISION CLCOK FOR PCs ElEl

supplies are not loaded by the LED.

ConstructionThe compact printed circuit board de-signed for the interface is shown inFig. 3. Construction is simple. First fitthe passive components, then the ac-tive components. You may want to fitcapacitors C4 and C5 last because theyare fairly tall, and complicate the fit-ting of the parts around them.

The DCF77 receiver module men-tioned in the parts list is connected tothe interface via four wires, for whichsolder pins are provided. The positivesupply voltage is connected to the sol-der point marked '+' on the receivermodule, while the ground wire goes tothe point marked The module hastwo further connections. The pointmarked with an outgoing arrow is thesignal output, which is connected tothe signal input on the interface board.The last connection is marked with an`input' arrow. This input is used to ac-tuate the module, and must be con-nected to its positive supply. At theinput side of the receiver module, con-nect the ready-made ferrite rod an-tenna to the indicated points on theprinted circuit board. If the receivermodule is fitted into an enclosure, twopoints should be observed. First, theenclosure may not be a metal typesince that would make reception of theDCF77 signals on the ferrite rod an-tenna impossible. Second, to reduceinterference to an absolute minimum,the receiver module must be fitted at areasonable distance from the interface.

An alternative to the receiver mod-ule mentioned in the parts list is aready-made DCF77 clock which con-tains an U277513. If you happen tohave such a clock, open it to see if itcontains this IC. If so, proceed as fol-lows: IC pin 14 is the signal output,pin 1 is ground. A power supply con-nection is not required, since the clockis usually battery -operated. Pin 13must be connected permanently to theclock's supply voltage, and any otherconnection to it must be broken.Usually, the processor in the clockswitches the receiver IC off after a cer-tain period. This is done to save power.However, even if the U2775B is perma-nently on, the clock will run for morethan a year on a fresh penlight battery.A suitable clock is, for instance, ELV'skit number 4434 (also available ready-made; order code 4435). For more in-formation, contact ELV, Postfach1000, D-2950 Leer, Germany.Telephone: (+49) 491 600888, Fax:(+49) 491 7016.

The connection between the inter-face board and the RS232 port on thePC is best made in 4 -core screenedcable. The screening of the cable is


28 COMPUTERS AND MICROPROCESSORS


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CABLES CAPACITORS

used for the ground (SG) connection.For best results it is recommended

to install the receiver module or theclock at a distance of at least 4 m fromthe PC or the monitor. This helps tokeep interference caused by stray radi-ation to a minimum. LED D to is conve-niently used to find a suitable locationfor the receiver module. Reception isall right when the LED flashes at a reg-ular rate.

SoftwareThe control software for the precisionclock is a so-called device driver, calledDCFCLOCK.SYS, which is supplied ondisk through our Readers Services(order code 1871). It must be installedafter the mouse driver in the CON-FIG.SYS file. Consequently, it is not al-lowed to call the mouse driver in theAUTOEXEC.BAT file. Any other orderof initialization is only allowed if it iscertain that the mouse driver, whilelooking for the mouse, does not affectthe port to which the clock interface isconnected. It should be noted that thesoftware does not run on PC -XT com-puters.

The driver initialization command hasthe following options:

P = nThis sets the RS232 port the receiveris connected to. Valid numbers for nare 1 to 4; the default is 2. By default,the driver assumes the following inter-rupt lines for the ports:

COM I : IRQ4

I.

VIDEO HEADS_

SPEAK ERS

I I 11II I. A I

COM2: IRQ3COM3: IRQ5COM4: IRQ7

ak

I=nThis is used to change the interruptline assignment from the default value.Valid numbers for n are 0 to 15. If youwant to set the port and interrupt line,this parameter must be given after P =n. Owing to missing hardware, IRQ 8-15 could not be tested.

S = nIf n = 1, the driver will adjust the real-time clock in your PC -AT after everycorrectly received time informationpacket. Setting n to 0 will disable thisfunction. The default is n = 1.

B = nThis sets the SIO's divisor rate andthus the baudrate. You only needthis option if the pulse widths suppliedby your receiver deviate considerablyfrom the standard (60/160ms). Thedefault is 2500, which equals 46 baud.

D = nGenerally, the driver checks whetheranother program or driver alreadyuses the COM port in interrupt -drivenmode. If so, an error report is pro-duced. This test may be disabled bysetting n to 1. The default is 0, i.e., runthe test.

W = nIf n = 1, the driver will erase the COMport's I/O -address from the BIOS datasegment. This is necessary if you arerunning MS -Windows, which resets all

CONNECTORS SEMICONDUCTORS

411 oss S II: I: A

Nsw r1=-

ports at startup and would otherwiseturn the receiver's power off. Clearingthe address makes the port invisiblefor Windows, and the clock continuesto work. The default is n = 0.

T = nThis allows the driver to be used in atime zone different from that of theDCF77 transmitter, for instance, inthe UK, where GMT = CET minus onehour during most of the year.Whenever a correct packet is received,this value will be added to, or sub-tracted from, the 'hours' information.Parameter n may be negative or posi-tive.

Practical useStart your PC without the precisionclock connected. Call up the time anddate. If the clock is fast, you may havea small problem to fix - see below.Next, with the driver included in theCONFIG.SYS file, and the receivermodule fitted in a suitable position,the PC may be started again. Fromthen on, the clock in the PC ticks atatomic precision. Do take care, how-ever, if the original PC clock used to be`fast', i.e., running well ahead of thecorrect time. Once the precision clockhas taken over from a `fast' clock, newfiles suddenly have older date/time in-formation than the original ones. It is,therefore, better to wait with savingnew files until the precision clock hasgained on the `old' time. From then on,old and new files can not be swappedany more by accident.


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305 Circuits demonstrates the practical aspects of electronicsthrough projects that can he built at home, in a small workshop,or in the physics or science department of schools and colleges.There are projects for everyone, covering Audio & Hi-fi; Computers& Microprocessors; Music and Electrophonics; Radio, Televisionand Communications; and Test and Measurement.ISBN 0 905705 36 X Price £14.95*

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30

535 CARD WITH EPROM EMULATOR(PART 1)

Integrating an EPROM emulator into a microcontroller systemgives flexibility while reducing cost. It also makes the 800535based processor board described here a splendid tool forapplication software developers.

Design by B. C. Zschocke

ALTHOUGH microcontroller boardsre generally inexpensive and easy

to build, the cost of ancillary equip-ment to get a microcontroller to actu-ally do something useful may well beon the high side for many enthusiasts.Assuming that you wish to developyour target program in a time -efficientway, i.e., forget about programmingEPROMs bit -by -bit and byte -by -byte(which was nothing unusual about tenyears ago), a minimal configurationconsists of the following 'tools':

- a PC running an assembler capa-ble of producing machine code forthe relevant microcontroller;

- an emulator to enable target codeto be tested in the controller sys-tem;

- an EPROM programmer to burnthe final version of the programinto EPROM.

The above equipment represents aconsiderable investment. Fortunately,

it is possible to cut down on the bill.An EPROM programmer is not re-quired if your activities are restrictedto experiments only. Similarly, the em-ulator may be struck off the list if youhave the time to burn a new EPROMafter every modification made to thetarget program. However, developingsoftware without these two tools istime consuming. After all, we do nottap our writings into clay tablets anymore!

Considering that most computerhobbyists will have a PC, and that themain interest will be experimentingwith a microcontroller, it is fair to saythat the emulator is the most impor-tant tool. Ideally, an EPROM program-mer is not called for until the code isdebugged and ready to be installedpermanently on a controller system(for example, a so-called turnkey sys-tem). The good news for all of you withtight budgets is that (1) the present800535 controller system has an on-

board EPROM emulator, and (2) thesystem can be built without theEPROM emulator if you do not requirethis function.

One controller, twofunctionsFigure 1 shows a detailed block dia-gram of the system. In fact, the draw-ing is so detailed that it enables theoperation of the entire system to be de-scribed in great detail. The blockmarked 'GAL' (generic array logic) hasa crucial function because it containsthe entire address decoding for thememory ICs, as well as the controllogic that allows the system function tobe switched from controller to emula-tor and vice versa. This means that thecontroller can execute instructionscontained in the program memory orin the emulator memory. Actually, in-structions in the emulator memoryserve to copy a program downloadedfrom the PC into the program memory.

On close examination, the systemdrawn in Fig. 1 looks very much like astandard configuration for controllersin the MCS51 family (of which theSAB80C535 is a member, although itis not manufactured by Intel). Such astandard configuration consists of thecontroller itself, an address latch, adata memory and a program memory.The program memory contains thecode which is executed by the con-troller. The GAL allows a number ofcomponents to be 'moved around' inthe system. If the GAL switches thecontroller to 'run' mode, the circuitworks as a standard configuration de-scribed above, with the emulator mem-ory and Centronics interface switchedoff. If the 'emulator' function is se-lected (again, via the GAL), the datamemory is 'made invisible', and itsfunction is assumed by the programmemory, while the program memory isthen formed by the emulator memory.This causes the microcontroller to runthe program contained in the emulatormemory. This program ensures thatdata (i.e., a target program) receivedvia the Centronics interface is copiedinto the data memory (which is formedby the program memory).

It will be clear that the GAL has akey function in the circuit. Actually,the control of the GAL is based on asingle signal: the strobe signal receivedvia the Centronics interface. Before itarrives at the GAL, the strobe pulse is


535 BOARD WITH EPROM EMULATOR - 1 Ell

controller800535

LI

5V

JP6E0R0

JP5

LJ

0.

IR

ADO...AD7\\\\\\\ADO...AD7

ALaddress

latch

OE

(////////A6...A15

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CSRAM

OE

DO...D7

datamemory

RAM

WE

CS

OE

W

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AO..A14'mom=

AO...A14

/////// ///////////

Al,All...A15

TRES

RD

WR

PSEN

EPROM

5V

I-ACK

POWON

I-STB

GAL

0

CSROM

DO.. D7

programmemory

RAM(EPROM)

WE

CS

OE

AO...A14

AO...A14

///////P/////////

ADO...AD7

I -BUSY

CSPROM

PSEN

1

//

emulatormemory

ROM

A7

EN1

EN2

AO...A6

DO..D7

-77

ENLCD

/////P///////AO...A6 ///

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CSPROM

ENLCD

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POWON

0 =I I-STBlOps

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> ACK

STRB41011,

=111,930103 - 12

Fig. 1. This block diagram is detailed enough for a comprehensive functional description of the 535 controller system.

stretched to about 10 is. This is doneto make sure that it can be used alsoas a reset pulse for the GAL.Incidentally, the reset pulse is onlysupplied when the system is still in`run' mode, and the strobe pulse indi-cates that the first byte of a new pro-gram has been sent. Next, theprocessor is supplied with a resetpulse, and the BUSY line is takenhigh. From then on, the GAL ensuresthat the controller uses the programmemory as data memory, while allow-ing the controller to address the emu-lator program contained in theemulator memory. The reset causesthe program to be run from address0000H. The emulator program ensuresthat the received data is stored in theprogram memory. To enable the soft-ware to detect that data is held ready,the BUSY signal is tied to the most sig-nificant address bit of the emulatormemory. In this way, the system is ca-pable of switching between two pro-gram halves which are identical withthe exception of one byte. Also, the

address data memory program memory address

0000

7FFF

data memory (U3)address 0000to 7FFF

program memory(U4) address 0000to 7FFF

0000

7FFF

8000 data latch (U8)read-only

800187FF

data latchmirrors

8800880188028803

LCD moduleinstruction writedata writeinstruction readdata read

88048FFF

9000BFFF

LCD modulemirrors

free for memory -mapped I/O

C000

FFFF

program memory {U4)address 4000 to7FFF

program memory(U4) address 0000to 7FFF

FFFF

Table 1. Memory map of the 535 board (all addresses in hexadecimal).


COMPUTERS AND MICROPROCESSORS

0 0 0 0 0

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Fig. 2. Circuit diagram of the 535 board with EPROM emulator.

processor is not interrupted while exe-cuting a program, irrespective of theinstant BUSY goes high. By the way,BUSY can only go high if the processoris not looking into the emulator mem-ory. The only change is that the pro-gram uses the one byte to detect that anew byte is available in the data latch,and ready for storing away. On com-pleting this action, the emulator pro-gram supplies an acknowledge pulsevia output P4.0. This pulse causes theBUSY line to be taken low again, and

the computer supplying the data to beflagged that the next byte may be sent.

Once the emulator program is run-ning, the controller no longer needs tobe reset on a strobe pulse. It is suffi-cient at this point for the GAL to re-spond by taking the BUSY line high.The program does the rest.

When all data has been received,the GAL has to ensure that the circuitis returned to 'run' mode. For this pur-pose, the program records how long istook since the last byte arrived. After

one second, the program initializes thecontroller (`soft' reset), and jumps to8000H to signal the change to 'run'mode.

The jump to 800011 is explained asfollows. The program memory has asize of 32 kByte, and can be addressedwith 15 of the 16 address bits. The16th address bit. A15, is used in thecircuit to select (address) the program,rather than for address decoding(which also goes for the GAL).Consequently, a jump to 800011 is the


535 BOARD WITH EPROM EMULATOR - 1 Elsame as a jump to 000011 (the addressat which the controller starts after areset). The only difference is that A15goes logic high at address 8000H. Thisis detected by the GAL, which re-sponds by switching the system to'run' mode, when the data memory isenabled again, and the program mem-ory serves to hold the program again.The upshot is that the controller startsexecuting the instruction at address0000H in the program memory, exactlyone second after receipt of the last bytetransmitted by the PC.

The memory map of the 535 boardis determined by the structure of theaddress decoder contained in the GAL- see Table 1. In contrast with theprogram memory, the 16th address bitis decoded for the data memory. Thisprevents the 32-kByte large RAM fromappearing two times in the memorymap.

The second piece of data memory(also 32 kByte) contains a number ofthings. To begin with, there is the ad-dress of the data latch which serves todirect data into the system. Since itsaddress decoding is limited to linesA14 and A15, the latch appears at anumber of locations in the memorymap. Next, memory space is reservedfor an LC display, which is an optionalextension of the 535 board. An exam-ple of an LCD that may be connectedstraight away is the Hitachi LM093LN,which was described in Ref. 1. TheLCD also has a number of 'mirror' ad-dresses in the memory. The nexthigher memory block has a size of11 kByte, and may be used for extraI/O or RAM.

The highest part of the data memoryhas a size of 16 kByte, and offers anumber of interesting applications.For instance, the upper half of the pro-gram memory (4000H to 7FFFH) maybe used as data memory. In this way,it becomes possible to place data (de-fault settings, look -up tables, etc.) intothe program memory. This feature willbe particularly valued in non -experi-mental systems, where such data is'read-only' because it is contained inEPROM. It also allows a system with-out an external data memory to be setup, in which internal registers areused to store temporary data, whilethe fixed data are found in the pro-gram memory via addresses C000H toFFFFH.

Since the resetting of the controlleris also used to switch between 'run'and 'emulator' mode, it is not possibleto connect the controller's reset inputto a press -key. The same goes for theusual RC network to furnish a power -on reset pulse. To ensure proper tim-ing and co-ordination, both resetsignals are routed via the GAL. Thisensures that the circuit is automati-

PROGRAM MEMORY(READ ONLY)

PSEN

DATA MEMORY(READ/WRITE)

FFH:

00

INTERNAL

RD WR

MCS51 MEMORY STRUCTURE

The Siemens SAB80C535 is a member of the MCS51 family of microcontrollers.Originally designed by Intel, the core and memory structure of all MCS51 familymembers is basically identical. The devices differ mainly in regard of theperipheral circuitry that has been added to the core.An MCS51 controller has two types of memory: program memory and datamemory. The controller can only read the program memory Is writing is notnecessary because this area is usually ROM, PROM or EPROM. Some devices inthe MCS51 family have an on -board mask -programmable ROM, or an EPROM.The presence of external memory is signalled with the aid of the EA (externalaccess) pin, so that the controller 'knows' that the program memory is (partly)internal or (entirely) external.The data memory always has an internal part, which also contains the so-calledSFRs (special function registers). SFRs are addresses which are used to controlthe controller's peripheral circuits (I/O ports, timers, etc.). A part of this internalmemory is 'hidden' behind a number of normally accessible addresses. The datacontained in these indirect registers are accessible only by swapping them withdata in directly accessible registers.Independently of the internal data memory and the program memory, thecontroller is capable of addressing an extra amount of 64_kBytes of externaldata memory. This is achieved with the aid of separate instructions and addresslines. This external data memory is usually RAM.If the controller is not equipped with external memory, it is possible to use thedata and address pins normally used for this purpose as an I/O port.Since the controller can only read data from the data memory, it is oftenrequired to use a special initialization routine to put data in the data memory.This 'quirk' of the MCS51 processor is particularly annoying if fixed data isinvolved. A solution often adopted to solve this problem is to make a piece ofthe program memory visible as data memory to the controller. This is also doneon the 535 board described in this article.

cally switched to 'emulator' modewhen the supply voltage is switchedon. Pressing the reset key gives a to-tally different response from the GAL.The controller is also reset, but thistime it starts executing the applicationprogram or the emulator programagain.

Before turning to the circuit dia-gram, a word about using I/O bit P4.0

and the Centronics input in your ownapplications. Bit P4.0 consists of anopen -drain output (with an internalpull-up resistor) which is connected inparallel with an input. This allows thebit to be used as an I/O port for yourapplication, despite it being used as anoutput in 'emulator' mode. J

Continued next month


34

OUTPUT AMPLIFIER WITHA.F. BAND-PASS FILTER

Design by T. Giesberts

The circuit consists of three parts: a1 steep -skirted speech filter, an inte-

grated amplifier, and a power supply. Theamplifier can provide an output of up to1.2 W and may thus be used as an audiostage in home -constructed receivers.

The diagram of the circuit is shown inFig. 1. Its sensitivity can be adjusted withpotentiometer P1. This potentiometer makesit possible for large signals, such as thoseat a headphone output socket, or the socketfora second loudspeaker, to be used. Thisenables the circuit to be used with a re-ceiver without having to modify this (con-venient in case of a type -approved unit, whichcannot be tampered with for legal rea-sons). The signal at the wiper of P1 is ap-plied to filter ICIa-IC lb and to switch S1.

Depending on the setting of P1, the sig-nal is passed filtered or unfiltered to vol-

ume control P2 and the amplifier. The fil-ter consists of a low-pass section, IC la,and a high-pass section, ICib. Together theseform a third -order band-pass filter withcut-off points at 740 Hz and 2.1 kHz. This

Amateur listeners and DX-ersoften have to contend withstrongly distorted speech

signals. The intelligibility ofsuch signals can be improved

appreciably by the circuitpresented in this article.

means that the bandwidth of the filter isnarrower than that of a telephone signal,so that much interference is suppressed.However,a small part of the speech signalis also suppressed, so that it may becomedifficult to recognize a familiar voice. The

frequency characteristics of the circuitwith the filter actuated and with it disabledare shown in Fig. 3.

The d.c. operating point of the two fil-ter opamps is set by RI and R5. The + inputof ICib is set to half the supply voltage. Sincethis opamp has unity amplification, the+ input of IC la is also at half the supply volt-age. The two resistors are decoupled by C4,so that filter elements R1 and R3 are con-nected to ground, as they should be.

The amplifier comprises a single IC (IC2)that contains a bridge amplifier completewith several protection circuits and a de -bouncing circuit. Strictly speaking, itneeds no external components, but in thepresent circuit some have been added. Atthe input, two anti -parallel connecteddiodes, D3 and D4, ensure that the inputsignal is limited. This is necessary, be-cause the sensitivity of the amplifier, andthus of the filter which, as already stated,has unity gain, for full drive is120-150 mVpp.

At the output, which is normally con-nected directly to a loudspeaker, provi-sion is made for a headphone. This is con-nected to only one of the output terminals.Since both terminals carry half the supplyvoltage, a coupling capacitor, C12, becomesnecessary (this is not needed with theloudspeaker which is connected to bothterminals). R11 ensures that C12 is charged

R2

--11---111-1122n 22n 22n

R1

6V

OD1

6

1C1b5

C4

71763V

R4

R5

0

R3D2 2x

X1N4148

6V'

76 R7

SI

B

39n

88

ED MI EMI

C5

72n

3

C7MIM

Tn2

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P

5k

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220n

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2

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C11=MI

:00n

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71n7

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L J

GND

OUT

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5

8

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47p25V

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0E

TDA7052ale

6V

R11

0

O "-V

mL, A352

Ls1

6VIC1 = TLC272

810 6V'

100110V

IC1

930071 - 11

Fig. 1. Circuit diagram of the amplifier and integral active band-pass filter.


OUTPUT AMPLIFIER WITH A.F. BAND-PASS FILTER El

Fig. 2. General view of the completed printed -circuit board.

and discharged, even when neither a loud-speaker nor headphones are connected.Although the headphone socket, J1, is astereo type, both earpieces carry the samesignal.

It is possible to supply the unit from bat-teries, but these have a limited life, ofcourse. If batteries are used, IC3, B1 andassociated components may be omitted.It is, however, in many cases better to usea mains adaptor. This should be capableof providing 7.5 V a. c. or 10 V d.c. and acurrent of up to 1 A. Commercial adaptorsnormally have an output of 15 V and may

5.0000L vel(dB)

0.0

I I fI

4li1 -I 7

-5.000

-10.00I lil

III\ ,

-15.00 /Ili,-20.00

.25.00I

\-1,

f

-30.00

-35.00

)

-40.00

-45.00 ir HI\10k 20k50 100 1k

Requencey (Hz)

Fig. 3. Frequency characteristics of the amplifier withthe filter ac-tuated and with the filter disabled.

be used with the filter and amplifier. ThePCB (Fig. 4) has provision for a home -constructed mains adaptor; if batteriesare used, this section of the board may becut off.

Socket J1, switch S1 and potentiome-ter P2 may be mounted on the board, butthey may also be connected to the boardvia lengths of insulated circuit wire. END

Fig. 4. Printed -circuit board for the amplifier and integral active a.f. band-pass filter.

PARTS LIST

Resistor*:Ri =6.19 1%R2= 1.91 kit, 1%R3=61.9 la 1%R4, R5= 22 kQR6 -R8 = 10.0 kfi. 1%Re =5600Ri0=47 flR1 1 = 3.9 kgP1= 10 MI preset potmeterP2 = 5 Ica (4.7 kfl) potmeter. log

Capacitors:C1 --C3 = 22 riFC4 = 4.7µF, 63 V, radialC5= 12 nFC5 = 39 nF07 = 1.2C8 = 220 nFCg = 4.7 nFC10 = 10011F, 10 V; radialC11, C14= 100 TIFC12 =47µF, 25 V, radialC13= 10 p.F, 25 V, radialC13= 1000µF, 16 V, radialCw-Cig = 47 nil', ceramic

Sezakenductors:D1 -D4 = 1N4148B1= B80C1500 bridge rectifier

Integrated circuits:ICI =1"I.C.272102 1DA7052IC3 = 7806

Miseellsneous:S1= change -over switchJ1 = stereo audio socket. 6.3 mm. with

integral switch1S1= loudspeaker. S II 1WHeat sink for IC3 (about 17 It VifrPCB No. 930071 (see page 701


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40

FIGURING IT OUTPART 10 - POWER

By Owen Bishop

This series is intended to help you with the quantitative aspects of electronic design:predicting currents, voltage, waveforms, and other aspects of the behaviour of circuits.

Our aim is to provide more than just a collection of rule -of -thumb formulas.We will explain the underlying electronic theory and, whenever

appropriate, render some insights into the mathematics involved.

In all our analyses of networksand circuits, we have been con-

cerned with currents and poten-tial differences, but have neverconsidered their joint effect,power. Given a circuit elementwith a pd U across it and a cur-rent I flowing through it, the in-stantaneous power, Pi, is theproduct of U and I:

Pi = UL [Eq. 64]

Instantaneous power is measuredin watts. It is the rate of conver-sion from one form to another ata given instant of time. In thecase of resistance, electrical en-ergy is being converted into heatenergy. In a capacitor beingcharged, energy is being used tobuild up a charge on the platesagainst the opposition of the chargealready existing there. In termsof energy, the watt (W) is equiv-alent to the expenditure of en-ergy at the rate of 1 joule (J) persecond:

1 W = 1 J sec -1.

With a resistor or resistive el-ement, we also have the rela-tionships U = IR and I = U IR.Substituting these in Eq. 64, weobtain two more equations for in-stantaneous power:

Pi = /2R,

and

Pi= U2/R.

[Eq. 65]

[Eq. 66]

As an example of the applicationof these equations, let us analysea purely resistive network witha steady voltage applied to it. Insuch conditions, instantaneouspower is constant. Figure 84 isan example of a purely resistivenetwork that may be analysed

30 212

12

Fig. 84.

by the method of mesh analysisdescribed in Part 3. First, we writeout the equations for the threemeshes:

8/1 - 4/2 - /3 = 2;

-4/1 + 6/2 = -4;-/1 + 8/3 = 4.

These are solved as three simul-taneous equations, aided if pos-sible by a scientific calculator orthe computer program for de-terminants (Part 4). The resultsare:

= -0.032 A;

930010 - X - 84

/2 = -0.688 A;

I3= 0.496 A.

Figure 85 shows the currents ineach branch of the network, com-bining the currents for two mesheswhere an element is part of twomeshes. We use Eq. 65 to calcu-late the power being dissipatedin each resistor:

This adds up to a total resistorpower of 4.672 W, that is, the re-sistors are converting electricalenergy into thermal energy atthe rate of 4.672 J s-1. Note thatthe direction in which the cur-rent is flowing through the re-sistor makes no difference to theamount of energy being converted.

It follows from the Principleof Conservation of Energy thatno energy is created or lost dur-ing this process. The energy iscoming from the power sourcessupplying this network. The totalenergy supplied must equal thetotal energy converted to heat.This is a good check on the cor-rectness of the current and powercalculations. We calculate the en-ergy being converted from chem-ical form (if it is a battery) or frommechanical form (if it is a gen-erator) by the 4 V source. UseEq. 64:

Pi 4x1.184 = 4.736 W.

This is more than the energy3 Q: P = 0.0322x3 = 0.003 W; being dissipated by the resistors!2 Q: P = 0.6882x2 = 0.947 W; But let us look at the 2 V source.4 Q: P = 0.6562x4 = 1.721 W; The energy being converted there1 Q: P = 0.5282x1 = 0.279 W; is:7 Q: P = 0.4962x7 = 1.722 W.

Fig. 85.

930010 - X - 85

P1 = 2x-0.032 = -0.064 W.

Here the direction of the currentdoes matter. The calculationsshowed that that /1 is negative,so that it flows anticlockwisearound mesh 1 (Fig. 84), that is,against the polarity of the 2 Vsource. The current is supplyingpower to the source. If the sourcewere a rechargeable cell, the cur-rent would be charging it. Thisfact makes the power equationsbalance correctly:

Ptht = 4.672 + 0.064 = 4.736 Wand

Ps4 = 4.736 W,


FIGURING IT OUT 10 41

Fig. 86.

The current through the resistorhas the same frequency and is inphase with the voltage:

I = UIR = (10 sin (00/4= 2.5 sin tot.

The instantaneous power is, asbefore, the product of the pd andthe current:

Pi = U/ = 10 sin catx2.5 sin cot= 25 sin2 oat. [Eq. 67]

We make use of the trigonomet-ric identity:

cos 20 1 -2 sin2 0,

where Ptot is the total power sup-plied to the resistors and the 2 Vsource, and Ps4 is the power sup-plied by the 4 V source.

In general, the total powersupplied must equal the totalpower absorbed. From a practi-cal point of view, it is interestingto note that the power dissipa-tion varies widely between re-sistors. Calculations of this kindpoint to the components that needto be highly power rated.

AC powerA sinusoidal voltage, U= 10 sin at,is applied across a 4 Q resistor.

UNI/A A

P/W

20-

10 -

Fig. 87

which gives:

sin2 8 = (1- cos 20)/ 2.

Substituting this in Eq. 67:

P1= 25x(1 - cos 2a)t)/ 2= 12.5 - 12.5 cos 2a)t.

[Eq. 68]

Figure 86 shows the graphs forU, I and Pi plotted on the samescale; U and I are in phase, os-cillating about zero. The graphfor Pi oscillates about 12.5 W. Thislevel is the average or appar-ent power, S, since the curve issymmetrical about the line

930010 - X - 87

P= 12.5, as indicated by the shadedareas in Fig. 86. Note that theinstantaneous power oscillateswith a frequency which is twicethat of U and I. Current and volt-age are both positive togetherfrom cot = 0 to TC and also from 71

to 27c. Thus, S is always positive.This is another way of saying thatthe direction in which the cur-rent flows through the resistormakes no difference to the amountof power dissipated.

Another way of calculating av-erage power is

S = Ulmsxl

In this example,

Urms = 10N2,/rim = 2.5/\12, andS = (10x2.5)/N2x \i2) = 25/2

= 12.5.

This is the same result as ob-tained by the earlier calculation.

Capacitive circuitIf the same sinusoidal voltage isapplied across a capacitor, thecurrent is also sinusoidal an d ofthe same frequency, but leads thevoltage by 90° (see Parts 2 and 5).We say that I = I° sin(a)t+ 90°).Or we can consider the currentcurve is a cosine curve and thatI = I° cos cot, which is trigono-metrically the same thing. Thevalue I0, that is, the amplitudeof the current curve, is deter-mined by the reactance of the ca-pacitor:

I0 = = UocoC.

In this example, U0 = 10 V, andlet us assume that C = 1000 [IFand o) = 400. This makes I, = 4,and I = 4 cos cot. The curves forU and I are plotted in Fig. 87.

The instantaneous power is,as before, the product of U and

P1= 10 sin cot x 4 cos cot=40 sin catx cos cot.

Once again, we make use of atrigonometrical identity:

sin 20 = 2 sin cos 0.

The power equation then becomes

P1= (40 sin 2(4)/2= 20 sin 2o.t.

This equation is also plotted inFig. 87: the cxurve has ampli-tude 20 and frequency twice thatof U and I. In general, the am-plitude may be calculated with


42 GENERAL INTEREST

930010 - X - 88a

the equation:

Pi = Urmsx/,,xsin 2cot= U, /)/( \i2x.\12)]x sin 2cot

= 1/2 Uo /0 sin 2cot.

One point to notice in Fig. 87 isthat the power curve is sym-metrical about the x-axis. In otherwords, average power is zero.Instantaneous power is zero wheneither U or /is zero. Power is pos-itive and energy is being trans-ferred to the capacitor when bothUand/ are ofthe same sign. Workis being done against the repul-sive force due to the charge al-ready present: the charge on thecapacitor is increasing. Power isnegative and energy is being trans-ferred from the capacitor to thecircuit when U and I are of op-posite sign. The charge of the ca-pacitor is decreasing.

Example. A pd of U= 3 sin 4000tis applied across a 221.1F capaci-tor. What is the instantaneouspower when t = 1 ms? From theequation, we identify the valuesof U, = 3 and w = 4000 (the fre-quency is 637 Hz). Calculate Io:

/0 = U0 / Xc = U, / ok'= 3 / (4000 x 22 x 10-6)= 34.09 A.

Thus, the current equation is:

I = 34.09 cos 4000t.

Instantaneous power is:

Pi =1/2 x3 x 34.09 x sin(2x4000t)= 51.14 sin 8000t.

When t = 1 ms,Pi= 51.14 sin 8= 50.6 W.

Inductive circuitSimilar behaviour is shown by

UR =3.714L 68.2°

41=1.857L 68.2°

= 68.2°

Fig. 88.

an inductor, except that beingthe dual (Part 5) of a capacitor,some of the properties are in-verted. Following the same linesof argument, if the applied pd isas before:

U = U, sin wt.

Current lags the voltage:

I = -Is cos cot.


P, = -UI sin 2cot= -1/2 Urms /rms sin at

The instantaneous power os-cillates at twice the frequency,and average power is zero. Sincethe power curve is a negative sinecurve, it is the inverse ofthe powercurve of Fig. 87. Energy is beingstored when U and I are of op-popsite sign (power positive) andis returned to the circuit when Uand / are of the same sign (powernegative).

Example. A pd U = 4 sin 5000tis applied across a 1541 induc-tor. What is the instantaneouspower when t = 1 ms? From theequation, we identify the valuesof U0 = 4 and co= 5000. Calculate

10 = U0 I = U0 I al,= 4 / (5000 x 15 x 10-6)= 53.33 A.

Thus, the current equation is:

I = -53.33 cos 5000t.


Pi= -112 x 4 x 53.33 x sin (2x5000)t= -106.7 sin 10 000t.

When t = 1 ms,Pi = -106.7 sin 10 = 58.0 W.

Uc =9.285 ;

930010 - X - 88b

We have been preoccupied withsinusoidal signals, but voltage orcurrent may vary in other ways.The voltage may be a ramp, forexample, U = 3t. If such a volt-age is applied to an inductor, thecurrent may be calculated fromEq. 28 (Part 5).

Assuming there is no initialcurrent:

7= 1/Lf Udt= 3 t2/ 2L.

If L has the value 0.5 H, thenI = 3 t 2. At any instant,

Pi = U/ = 3t x 3 t2 = 9 t3.

Conversely, we can calculatepower when we are given the ap-plied current. For instance, giventhat the current through a 0.1 Hinductor is / = 4e2t, we use Eq. 26to calculate that

U = LdIldt = 8Le2t = 0.8e2t,and

P = UI = 0.8e2t x 4e2t = 3.2e4t.

The power after 0.5 s is 3.2e2= 23.6 W.

Calculations such as these as-sume that the network is in asteady state, by which we meanthat the function for U or / is con-tinuous, not piecewise. If thereare abrupt changes in U or I, areactive impedance, as might beexpected from its name, reactsto cushion or even to oppose thechange. In passing from one steadystate to another there is a tran-sient period. The analysis of whathappens in such brief periods isa fascinating one which we shallleave until a later issue.

Mixed impedanceThe examples above apply only


to networks that are purely ca-pacitive or purely inductive, sothat the voltage and current are90° out of phase. If the phase angleis other than this, a different sit-uation arises. Consider the ex-ample of Fig. 88. The appliedvoltage and the impedance of thecapacitor are expressed as com-plex numbers (see Parts 8 and9). The total impedance,

Z = 2 - j5 = 5.385 Z-68.2° Q

in polar form. From this, we cal-culate I, which is the same forboth components:

I=U I Z= 10 Z0° / 5.385 Z-68.2°= 1.857 /68.2° A.

Now look at the power developedin the individual impedances.For this we need to know the pdsacross them:

UR = RI = 2 x1.857 /68.2°= 3.714 /68.2° V.

= XcI = -j5/= 5 /-90° x 1.857 /68.2°= 9.285 Z-21.8° V.

The phasor diagram in Fig. 88shows the relationship betweenthese quantities. Current in thenetwork is in phase with the pdacross the resistor. It is 90° outof phase with the pd across thecapacitor.

As far as the capacitor is con-cerned, the voltage -current re-lationship is the same as inFig. 87, in which we saw thatthe average power is zero. Duringa whole number of cycles, thecapacitor neither absorbs norsupplies energy.

For the resistor, the power maybe calculated as in Eq. 64.

In a phasor diagram, all pha-sors must have the same angu-lar frequency. Since power hasdouble the angular frequency, wecannot show it in Fig. 88, nei-ther can we calculate it by vec-tor multiplication. However, sincewe are concerned with only twovectors, I and UR, which have thesame direction, ordinary scalarmultiplication is applicable. Wedo not use the moduli of the com-plex numbers directly, since theseequal the amplitudes of the cur-rent and voltage. For a.c. powercalculations, we need to use r.m.s.values as noted above:

Urnis = mod UR / '\12= 3.714 / Ai2 = 2.626 V.

FIGURING IT OUT 10 43

Irms = mod I 1 Ai2=1.857 / 12 = 1.313 A.

From Eq. 64:

P = 2.626 x 1.313 = 3.45 W.

This is the true (or active) powerdissipated in the network.

There is another way of look-ing at the power calculation.Knowing U, we can calculate Iand the phase angle cp. Then:

P = S cos cp,

where P is the active power, Sthe apparent power (Urmslrms),and cos co the power factor. IfU and / are in phase, as in a purelyresistive network, co = 0° andcos co= 1. The whole of the ap-parent power, S, is dissipatedin the network. If U and I are90° out of phase, as in purely ca-pacitive or inductive circuits,cp = 90° and cos co = 0, and noneof the power is dissipated in thenetwork.

With mixed networks, whenU and I are neither wholly inphase nor wholly out of phase,the power factor tells us whatproportion of S is being dissi-pated. We call the dissipated por-tion the active power, P, andthe non -dissipated portion thereactive power, Q.

The apparent power is not ex-pressed in watts, as there maybe no or little actual conversionof energy, but in volt-amperes(VA). With reactive power, some-times known as the wattlesscomponent, there is no con-version of energy; it is expressedin volt-ampere reactive (VAr).

Power factorWe shall now see how to calcu-late the power factor of a circuitas in Fig. 89. If you have a cir-cuit with impedances marked inohms, henrys and farads, thefirst step is to calculate the com-

930010 - X - 89

Fig. 89.

plex impedances for the givenfrequency. These impedances havealready been marked in the di-agram. Next, we calculate thetotal impedance, Z, summing forthe two branches and then usingthe standard formula for im-pedances in parallel.

Z= (10+j3)(5 -j12)(10+ j3)+(5- j12)

86-j10515- j9

135.7/-50.68°17.49L-30.964°

=7.758Z-19.716° [52]

Now we calculate the current/=U/Z

=10Z0°/7.758Z-19.716°

=1.289/-19.716 ° [A]

The angle between the voltagephasor and the current phasoris 19.719°. The power factor, pf,is the cosine of the angle:

pf = cos 19.716 = 0.941.

Another way of arriving at thesame result is to proceed as fol-lows. After calculating Z as be-fore, convert it to rectangularform:

Z = 7.758 Z-19.716°=7.303 -j2.617. [52]

The real part of Z is the resis-tive part of the total impedance:

R = 7.303 Q.

Having found / as above, we ig-nore the argument (the phaseangle) and take only the modu-lus, since current and pd are inphase for resistive elements. Usingthis, we calculate the true powerfrom Eq. 65:

P = I2R = 1.2892 x 7.303= 12.134 W.

The ratio between the true powerand the apparent power givesthe power factor:

pf=P/S= 12.134 / (10 x 1.289)= 0.941.

TO BE CONTINUED

Test yourself1. Calculate the power dissipated

in each resistor of Fig. 84 ifthe two voltage sources areinterchanged. Confirm that

the total power dissipatedequals the total power sup-plied.

2. What is the average powerdissipated by a 552 resistorconnected across a sourceU = 20 sin cot?

3. A voltage U = 4 sin 2000t isapplied across a 100 µF ca-pacitor. What is (a) the in-stantaneous power whent = 5 ms, and (b) the averagepower?

4. A voltage U= 2.5 sin 3000t isapplied across a 100 mH in-ductor. What is the instan-taneous power when t= 1.5 ms?

5. A 40 Q resistor and a 100 mHinductor are connected in se-ries across a voltage sourceU= 5 sin 2000t. Calculate theactive power (i.e., that dissi-pated in the resistor).

6 Given the circuit of Fig. 89,calculate the power factor whenthe frequency is doubled.

Answers toTest yourself (Part 9)

1. Product is (22+j7). Conversiongives: 3.606 /56.31° x 6.403Z-38.66° = 23.089 /17.65°= 22 + j7.

2. Quotient is (-1 + j2). Conver-sion gives: 8.062 /60.255° di-vided by 3.606 Z-56.310°= 2.236 /116.565° = -1 + j2.

3. /1 = 3.444 -j0.415; /2 = 3.112- j0.830; /3 = 0.332 + j1.245.

4. /2 = 18.570 /21.801°. The cur-rent through the resistor isI1- /2 clockwise. Its value is-3.448 + j8.6204 or 9.2845Z111.803°. The conversion atthe last step may give the angleas -68.197°, but the negativesign of the real part of the rec-tangular form shows the re-sultant to be in the 2nd quad-rant..

5. Without load: 0.37 Z-68.3°.With load: 0.356 Z-63.6°.

To be published in November 1993

305 Circuits demonstrates the practical aspects of elec-tronics through projects that can be built at home, in asmall workshop, or in the physics or science depart-ment of schools and colleges. There are projects for every-one, coveringAudio & Hi-fi; Computers & Microprocessors:Music and Electrophonics; Radio, Television andCommunications; and Test and Measurement.ISBN 0 905705 36 X Price £14.95*

SMT Projects by Owen Bishop. This book describesthe special features of Surface Mount Technology andhow to work with Surface Mount Devices on the work-bench. It includes over 20 constructional projects, allof which have many useful applications in and aroundthe home and workshop. The projects are selected anddesigned to take advantage of the distinctive featuresof SMT. They introduce the beginner to SMT in a prac-tical 'hands-on' way without requiring expensive spe-cial equipment.The book is for those who want to know more aboutsurface mount devices and to gain practical experi-ence of handling them.ISBN 0 905705 35 1 Price £9.95*

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Elektor Electronics (Publishing), PO Box 1414, Dorchester,Dorset, England, DT2 8Th.



SURVEILLANCEPROFESSIONAL ()mum KITS

Whether your requirement for surveillance equipment is amateur, professional or you are just fascinated by this unique area ofelectronics SUMA DESIGNS has a kit to fit the bill. We have been designing electronic surveillance equipment for over 12 yearsand you can be sure that all of our kits are very well tried, tested and proven and come complete with full instructions, circuitdiagrams, assembly details and all high quality components including fibreglass PCB. Unless otherwise stated all transmittersare tuneable and can be received on an ordinary VHF FM radio. Note that certain products are for Overseas use only.

UTX Ultra -miniature Room TransmitterSmallest room transmitter kit in the word! Incredible 10mm x 20mm including mic.3-12V operation. 500m range £16.45

MTX Micro -miniature Room TransmitterBest-selling micro -miniature Room TransmitterJust 17mm x 17mm including mic. 3-12V operation. 1000m range £13.45

STX High-performance Room TransmitterHi performance transmitter with a buffered output stage for greater stability and range.Measures 22mm x 22mm including mic. 6-12V operation, 1500m range £15.45

VT500 High -power Room TransmitterPowerful 250mW output providing excellent range and performance. Size 20mm x40mm. 9-12V operation. 3000m range £16.45

VXT Voice Activated TransmitterTriggers only when sounds are detected. Very low standby current. Variable sensitivityand delay with LED indicator. Size 20mm x 67mm. 9V operation. 1000m range £19.45

1111X400 Mains Powered Room TransmitterConnects directly to 240V AC supply for long-term monitoring. Size 30mm x 35mm.500m range £19.45

SCRX Subcarrier Scrambled Room Transmitter

Scrambled output from this transmitter cannot be monitored without the SCDM decoderconnected to the receiver. Size 20mm x 67mm. 9V operation. 1000m range £22.95SCLX Subcarrier Telephone TransmitterConnects to telephone line anywhere, requires no batteries. Output scrambled sorequires SCDM connected to receiver. Size 32mm x 37mm. 1000m range £23.95

SCDM Subcarrier Decoder Unit for SCRXConnects to receiver earphone socket and provides decoded audio output toheadphones. Size 32mm x 70mm. 9-12V operation £22.95

ATR2 Micro Size Telephone Recording InterfaceConnects between telephone line (anywhere) and cassette recorder. Switches tapeautomatically as phone is used. All conversations recorded. Size 16mm x 32mm.Powered from line £13.45

*** Specials ***01.TX/OUIX Radio C111111111 Switch

Remote control anything around your home or garden, outside lights, alarms, pagingsystem etc. System consists of a small VHF transmitter with digital encoder and receiverunit with decoder and relay output, momentary or alternate, 8 -way dil switches on bothboards set your own unique security code. TX size 45mm x 45mm. RX size 35mm x90mm. Both 9V operation. Range up to 200m.Complete System (2 kits) £50.95Individual Transmitter DLTX £19.95Individual Receiver DLRX £37.95

IMX-1 Micro BroadcasterNot technically a surveillance device but a great idea! Connects to the headphone outputof your Hi -R, tape or CD and transmits Hi-Fi quality to a nearby radio. Listen to yourfavourite music anywhere around the house, garden, in the bath or in the garage andyou don't have to put up with the DJ's choice and boring waffle. Size 27mm x 60mm.9V operation. 250m range £20.95

A

UTLX Ultra -miniature Telephone TransmitterSmallest telephone transmitter kit available. Incredible size of 10mm x 20mm!Connects to line (anywhere) and switches on and off with phone use.All conversation transmitted. Powered from line. 500m range £15.95

TLX700 Micro -miniature Telephone TransmitterBest-selling telephone transmitter. Being 20mm x 20mm it is easier to assemble thanUTLX. Connects to line (anywhere) and switches on and off with phone use. Allconversations transmitted. Powered from line. 1000m range £13.45

STLX High-performance Telephone TransmitterHigh performance transmitter with buffered output stage providing excellent stabilityand performance. Connects to line (anywhere) and switches on and off with phone use.All conversations transmitted. Powered from line. Size 22mm x 22mm.1500m range £16.45

TKX900 Signalling/Tracking TransmitterTransmits a continous stream of audio pulses with variable tone and rate. Ideal forsignalling or tracking purposes. High power output giving range up to 3000m. Size25mm x 63mm. 9V operation £22.95

CD400 Pocket Bug Detector/LocatorLED and piezo bleeper pulse slowly, rate of pulse and pitch of tome increase as youapproach signal. Gain control allows pinpointing of source. Size 45mm x 54mm. 9Voperation £30.95

CD600 Professional Bug Detector/LocatorMulticolour readout of signal strength with variable rate bleeper and variable sensitivityused to detect and locate hidden transmitters. Switch to AUDIO CONFORM mode todistinguish between localised bug transmission and normal legitimate signals such aspagers, cellular, taxis etc. Size 70mm x 100mm. 9V operation £50.95

QTX180 Crystal Controlled Room TransmitterNarrow band FM transmitter for the ultimate in privacy. Operates on 180 MHz andrequires the use of a scanner receiver or our QRX180 kit (see catlogue). Size 20mm x67mm. 9V operation. 1000m range £40.95

QU(180 Crystal Cointrolled Telephone TransmitterAs per QTX180 but connects to telephone line to monitor both sides of conversations.20mm x 67mm. 9V operation. 1000m range £40.95

QSX180 Line Powered Crystal Controlled Phone TransmitterAs per QLX180 but draws power requirements from line. No batteries required. Size32mm x 37mm. Range 500m £35.95

QRX180 Crystal Controlled FM ReceiverFor monitoring any of the '0' range transmitters. High sensitivity unit. All RF sectionsupplied as a pre -built and aligned module ready to connect on board so no difficultysetting up. Outpt to headphones. 60mm x 75mm. 9V operation £60.95

A build-up service is available on all our kits if required.UK customers please send cheques, POs or registered cash. Please add£1.50 per order for P&P. Goods despatched ASAP allowing for chequeclearance. Overseas customers send sterling bank draft and add £5.00 perorder for shipment. Credit card orders welcomed on 0827 714476.

OUR LATEST CATALOGUE CONTAINING MANY MORE NEWSURVEILLANCE KITS NOW AVAILABLE. SEND TWO FIRSTCLASS STAMPS OR OVERSEAS SEND TWO IRCS.

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8051 TOOLSICL51 £225

Low cost entry level In -Circuit -Emulator for the 8031/51.Operates at 11Mhz 28k bytes of program memory, includesmany features to aid program development but uses some

resources of the target 8051.

ICE51+ £495Advanced emulator for the 8031/51. Operation selectable upto 16MHz, 64k bytes of program memory, uses none of the

target (8051) resources.

8051 "C" COMPILER £125Micro/C51 is an integer 'C' like compiler for the MCS51family. Easily customised for any MCS51 family variant.

High level language debugger available (05)

8051 BOOK £49.95A very good text on the 8051 architecture, programming andapplication. The book is supplied with free (un-supported)

IBM/PC based assembler and simulator.

Other tools available prices exclude VAT and delivery

ACCESS

Micro AMPS Limited66 SMITHBROOK KILNS,

CRANLEIGH,SURREY GU6 8JJ, UK

Tel: +44(0)483 268999Fax: +44(0)483 268397

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MICRO -CONTROLLER DEVELOPMENT SYSTEMS8748/9 Series and 8751 Series

KARE 48 8748/9 System. Recommended for beginners.Includes Single Board Computer. Using 8749 OTP Micro with built-in Monitor/Downloaderprog . Allows downloading of assembled progs to non-volatile 2K memory. Edit individualbytes and examine memory. Switch to external memory to run loaded program. Comes com-plete with Shareware Editor,Assembler and Comms package, RS232 inter -connect lead.AllIC's socketed. In fact all you need , is an IBM compatible PC and a 5v power supply. Softwareavailable on 3.5 or 5.25. Please note no charge is made for software, and will require registra-tion for continued use L76.00 inc.

KARE 51 8751 SystemAs above, but using 8751 OTP Micro with Monitor/Downloader program L89.00 inc68HC11 Dev Kit available soon.Replacement OTP Micros with Downloader/Monitor available, should you have an accident.(Strictly replacement only). Programming service available for 8748/9 and 8751 ring for details.

Recommended LiteratureIntels Embedded Controller & Microprocessor Handbook.Includes details of 48 & 51 series micro's 2 vols L24.00 plus L4 p&pIntels Embedded Control Applications HandbookUseful information on applications and soft and hardware techniques £24.00 plus L4 p&p68HCI 1 Manual

Fully describes structure and operation. Covers all HC II family of devices ...L 10.00 plus f2 p&p

PC EPROM PROGRAMMERInternal Card for PC, XT, AT, 386, 486 or Compatible - £165 inc

* AffordableEasy to instal, just plug in.

* Programs E(E)proms and flash memory* Supports 2716 through 27C2001 EPROMS.

Reads, programs, verifies and saves to disk.Accepts Intel hex, Motorola S, and binary format.

* Requires 8 -bit bus slot of MS-DOS PC with 512K ram.* Supplied with software and 60 page handbook* I year warranty* MICRO ADAPTORS AVAILABLE - 05.00

STAND-ALONE PROGRAMMERS also available.Call us today for further information and DEMO DISK

KARE ELECTRONICS32 Pear Tree Avenue, Ditton, Aylesford,

Kent. ME20 6EB. Tel: 0732 844633

ELECTRONIC SURVEILLANCE KITSS.C.S. are experts in the field of surveillance & counter -surveillance equipment.We have the largest range and unbeatable prices, not to mention are fast andefficient mail order service. All our products are tried and tested and come withan unconditional guarantee. Below is just asmall selection of our products.

5 MILE BROADCASTING TRANSMITTER KIT £29.00TRACKING TRANSMITTER KIT £1 7.00MINIATURE ROOM TRANSMITTER KIT £1 2.00MINIATURE TELEPHONE TRANSMITTER KIT £12.00BUG AND TELEPHONE DETECTOR KITS FROM £13.00CRYSTAL CONTROL ROOM TRANSMITTER KIT £35.00CRYSTAL CONTROL TELEPHONE TRANSMITTER £29.00REMOTE CONTROL TRANSMITTER & RECEIVER KITS £38.00

ER

JUST TELEPHONE, WRITE OR CALL IN FOR A FREECOPY OF OUR LATEST CATALOGUE.

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46

POWERMOSFETTESTER

Design by T. Giesberts

rrThe output signal of power amplifiers1 is usually provided by two transistors

that each take care of one half of the sig-nal. To ensure that these halves are pro-cessed in an identical manner - and thatthe d.c. operating point is stable - it is es-sential that the performance of the twodevices is as near -identical as possible.This can be quite a problem, particularlyin the case of a complementary outputstage, because the designer needs to takeinto account not only the spread of theparameters, but also the differences en-suing from the dissimilar design and man-ufacture of n -p -n and p -n -p or n- and p -channel transistors.

MOSFET output transistorsshould be as near -identical as

possible, irrespective ofwhether they are

complementary pairs orconnected in parallel. The

tester described here enablesyou to check that they are.

An additional reason for matching mos-FET devices for use in power stages, is thatin these amplifiers output transistors areoften connected in parallel so that theamplifier can provide a higher current. Ifsuch transistors are very dissimilar, thecurrent will be divided unequally betweenthem. The transistor drawing the high-est current will get hotter, which will ac-centuate the inequality, and the transis-tor will draw even more current. Soon itwill be destroyed, so that the remainingtransistors have to handle a higher cur-rent: this normally quickly leads to theirdestruction also.

The only way of minimizing the in-equalities between two transistors is tofind a matching pair from among many.This matching is best done in circum-stances that are identical, or nearly so,to those in normal operation. Therefore,the present tester can provide drain cur-rents of up to 13 A (peak).

What needs to be tested?The most important parameter that should

be equal in two output transistors is thetransfer function. In MOSFETS that is therelationship between the gate -source volt-age, UGS, and the drain current, ID. Tomake that relation visible on an oscillo-scope, a circuit is used in the tester whoseprinciple is shown in Fig. 1. To enablen -channel as well as p -channel FET5 tobe tested, there are two complementaryversions of the circuit. The circuit is dri-ven by a direct voltage superimposed ona triangular voltage; it is designed to en-sure that the current through the FET is

directly proportional to this voltage. Thistask is carried out by the differential ampli-fier formed by the two transistors. Becauseof the feedback through the FET on test,the differential amplifier keeps the po-tential drop across RD equal to the drivevoltage. Since only the FET can providethe current required to do so, it followsthat ID is directly proportional to the dropacross RD and thus to the drive voltage.To make the relationship between ID andUGS visible on an oscilloscope, use is madeof the property that during the leading

Fig. 1. The principle of the power MOSFET tester.


POWER MOSFET TESTER 47

lx

FET 2

o

Test -circuitN -Channel

FET 1

00

X

H_FL

0FET 3

X

0FET 4

Test -circuitP -Channel

x

TRIG.

i

i

930107-13

Fig. 2. Block schematic diagram of the power MOSFET tester.

triggerout

triangularwaveformgenerator

draincurrent

you'UGS

N-FET

1 2

P-FET

3 4vao* *6,46

J

1 1 1 1 1111 1111 1111

A1111 1111 1111 1111

444

EXT 2.00 V DC_J L_

ydiv = 2 Vxdiv = 2 ms

930107_14

Fig. 3. A number of important signals in the power MOSFET tester.

edge of the triangular voltage, the draincurrent is directly proportional to the time.It suffices, therefore, to trigger the scopeat the onset of the leading edge and to ad-just the time base so that a sweep of theoscilloscope lasts exactly as long as theedge. This means that the drain currentis portrayed on the x-axis of the oscillo-scope. The gate -source voltage is depictedby connecting it to the y-axis. The oscil-loscope then shows a clear UGS - ID char-acteristic.

However, to make comparisons, thecurves of at least two FETs must be dis-played at the same time. The present de-sign enables the simultaneous testing oftwo n-FETS; two p-FETs; an n-FET and a p-FET; or two n-FETS and two p-FETs. Thelatter possibility is particularly useful dur-ing the design of a complementary out-put stage with parallel connected outputtransistors. To display four curves, it isnot enough to build four test circuits, be-cause in one of them UGS must be mea-sured with respect to ground and in an-other with respect to the positive supplyrail. A similar problem occurs with thedrive voltage of the test circuit.

Figure 2 shows the basic design of thetester. The tester is driven by a generatorthat provides rectangular as well as tri-angular waveforms. The rectangular sig-nal controls an electronic switch whichswitches the four FETs in turn ON for 1 msand OFF for 99 ms. Since the devices areon for only 1/10o of the time, they may betested without a heat sink, even whenthey draw an average current of 10 A(13 A peak).

The operational amplifiers buffer thevarious signals and two of them performthe vital task of converting potentials thatare referred to earth to voltages that arereferred to the positive supply line andvice versa.

The electronic switches at the outputsarrange in the first instance that the out-put signals of two test circuits are appliedto one oscilloscope input. In conjunctionwith a potentiometer, they also optimizethe images of the curves: this is essentialin view of the shape of these signals - seethe bottom curve in Fig. 3. The shape ofthe pulses is the required UGS - ID char-acteristic. Note the near -triangular apexes.

When the switches are closed, the op-erational amplifiers determine the out-put voltage (since they are ideal currentsources). When they are open (i.e, noneof the FETS is being measured), the po-tentiometer determines the output volt-age. The potentiometer is used to shiftthe voltage level upwards during the mea-surements lulls until it is level with theapexes of UGS. It is clear that in Fig. 3(bottom curve) the potentiometer had notbeen adjusted properly (yet). In this way,a steady voltage with a ripple superim-posed on it is obtained. With the oscillo-scope input set to AC, the ripple may beinspected in detail by increasing the sen-sitivity of the input amplifier.



This means that the time base of theoscilloscope must be set with some care.To display the four signals as in Fig. 3,it was set to 2 ms/div, which is a conve-nient setting for checking whether the

FETs have been connected correctly andwhether everything functions properly.However, for a detailed comparison of theFET5, the time base should be set (withthe VAR control) to slightly more than

0.1 ms/div. If the oscilloscope is triggeredby the TRIG output (set oscilloscope to nor-mal trigger), it will display the four UGS - IDcharacteristics as shown on the intro-ductory photograph. Any differences be -

Fig. 4. Circuit diagram of the power MOSFET tester.


POWER MOSFET TESTER 49

tween the FETS are then clearly visible.

The circuitThe rectangular -triangular waveform gen-erator is formed by Schmitt trigger IC laand integrator IC lb.

The rectangular signal clocks counterIC3. This circuit serves as an electronicswitch to switch the FETs on and off. Aftereach FET has been switched, monostablemultivibrator IC4a is triggered via pin 12of the counter. The mmv then disables IC3for 90 ms, so that the FETs can cool off.To obviate unnecessary loading of theFETS, they are driven only when mea-surements are being carried out. Thishappens when S1 is closed. When thisswitch is open, IC3 is reset, so that thereis no drive to the FETs. However, this doesnot mean that there is no voltage at theirpins: a short-circuit between a drain anda source may still be disastrous.

Circuit IC3 has more positions thanthe electronic switch in Fig. 2; there arealso more of these switches. This is be-cause, after testing, the gate of each FET

must be linked briefly to the source todischarge the gate -source capacitance.This ensures that the FET switches offfaster. During the ensuing pause, the os-cilloscope gets ready for the next mea-surement. If the two switches at each gateare open, a 1 MQ resistor connects thegate to the source, so that the FET is switchedoff.

The test circuits, T1 -T2 and T4 -T5, arepowered by electrolytic capacitors C9 andC 10. Since these capacitors are isolatedfrom the regulated supply line by R13, thetest circuits can draw a current of up to13 A from them, but the voltage regula-tor and transformer need not provide sucha high current (the peak current throughthem is a few amperes). However, the av-erage current is not more than 400 mA.Thus, the advantage of R13 is that thepower supply rating can be kept relativelylow. A disadvantage is, however, that thesupply voltage has quite a ripple. This isinconvenient, because in the case of n -chan-nel FETS the drive voltage must be referredto the supply line, whereas in the case ofp -channel FETS the gate voltage must be

referred to ground. These slight problemsare nullified by operational amplifiers.

The drive voltage for the n -channel testcircuit is provided by IC2a. It is unortho-dox, but essential to keep the d.c. com-ponent on C8 constant, to provide the in-verted alternating output voltage with adifferent d.c. offset. Without this arrange-ment, the ripple on the voltage across C9and C10 would cause the charging anddischarge currents to distort the trian-gular drive voltage. This would lead to dis-torted characteristics on the oscilloscope.

In the p -channel test circuit, the gatevoltage is converted from being referredto the supply line to being referred toground. Here again, an operational ampli-fier, ICga, is used; this obtains its d.c. op-erating point from C9 and Ciovia R52 andR53. Diode D5 raises the operating pointslightly to ensure that the amplifier workscorrectly in varying circumstances.

Several components, T3, R30, R31 andP4, have been added to the circuit aroundoperational amplifier IC9b to provide thegate voltage of n -channel FETS with thesame offset as that provided by D5 in the

K5

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CC CC

0CC

B1 01 R57 10

0

C23

C4C

T6 1C10C22

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00'-00.

R13

P5 C3

cov

R2

R1 7

C1700110 C1900110 C18

01:44

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56

D9 55

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03

R 5

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0 R R 117/ME 5

1- 5R47

R

R

R 8

R 0

MCI:1R

C25 0-I R49 29 O24P1

JP 1

R28

16

0

D G

Qti

930107

Fig. 5. The double -sided, through -plated printed -circuit board for the power MOSFET tester (track side on next page).



case of p -channel FETS. Preset P4 is ad-justed so that the outputs of IC9a and IC9bhave identical offsets.

The drain current through the FETS isdetermined by the drain resistance andthe drive voltage. The drain resistance isselected by switch S2 from R19 -R26 andR39 -R46 as relevant.

The d.c. component of the drive volt-age is derived from diodes D 1 and D2.

The gate -source voltage is set to 1.5 Vby P2 and P3, as the case may be.

Without the triangular voltage (that is,with the wiper of Pi at the junction C5 -C6),the following values of ID may be set withS2: 10 A, 7 A, 4 A, 2 A, 1 A, and 500 mA.The position of S2 must not be alteredwhile S 1 is being pressed to avoid seri-ously reducing the life of that switch.

When the peak value of the triangularvoltage is set to 0.5 V (with P1), the draincurrent varies by ±33% with respect tothe set operating point. It is possible toset Pi to any value between 0 and that atwhich the circuit is saturated to make,respectively, only a small portion or alarge part of the UGS - /D characteristic

visible on the oscilloscope.The rating of the power supply is rel-

atively low. Although the test circuits candraw a current of up to 13 A, the mainssupply has ample time (90 ms or almostfive mains periods) to recharge the ca-pacitors from which that current is drawn.Nevertheless, the transformer can pro-vide currents of up to 1.7 A, while the reg-ulator has been enhanced by the addi-tion of power transistor T6.

Diode D161functions as on -off indicator.Diodes DI , D2 and D10 are low -current

types. This is not essential in the case ofD10 but the other two must be, since theyfunction as voltage references.

ConstructionThe power MOSFET tester is intended tobe built on the PCB illustrated in Fig. 5.The tracks of the test circuit that carryhigh currents are as short as possible andrun, wherever feasible, on both sides ofthe board.

To keep the wiring of the drain resistorsand S2 short, these components are mounted

on a small board which must be cut offthe main board. This small board mustbe fitted at right angles to the main boardjust behind terminals K i-K4. The twoboards are interconnected by a right-angleprint header. The diameter of the headerpins and the paralleling of several of thesepins ensure that, even at currents of 13 A,the voltage drop across the connectionsis tiny. For mechanical robustness, thetwo boards should be fixed together withthe aid of small angle pieces.

When the board is built into an en-closure, it is advisable to order the se-quence of connecting the FETS. Owing tothe short connections, connectors K1 -K4are not put in correct order on the board.This can be confusing when the oscillo-scope is set to check whether a FET hasbeen connected properly. On the oscillo-scope, the curve at the extreme left is thatof the signal at K1; that at the extremeright results from the signal at K4. Mistakesmay be avoided by giving the connectionson the enclosure the same position as thecurves on the oscilloscope screen.

Short-circuits are avoided by the use

Fig. 5b. Copper side of the printed -circuit board for the power MOSFET tester. Component layout on previous page.


POWER MOSFET TESTER

of well -insulated clips for attaching to thetransistor pins. Further protection is ob-tained by inserting a fuse in each drainconnection (fit the fuseholder on the frontpanel of the enclosure). Use a fast fuserated at 0.5 A, although the current throughthe FETs may reach 13 A. That currentflows for such a short time that even afast fuse will not blow.

The electronics following the gate con-nection may be protected by inserting a680 SI resistor in the gate line.

Since, owing to the large currents, thecircuit is sensitive to any voltage dropover the source line, it is advisable to runthe connecting wires through the frontpanel of the enclosure and to connectthem direct to to K1 -K4. These wires shouldhave a cross-sectional area of 2.5 mm2.

CalibrationConnect the wiper of P1 to the junctionC5 -C6 and that of P5 to ground. Close Si,whereupon the signal at the TRIG outputshould look like that in Fig. 3. If the firstpulse is shorter than the next, the periodof the triangular -rectangular generatoris not entirely in accord with the monotime of IC4a. This results in an extra clockpulse in IC3, which causes the first trig-ger pulse to be too short. In most casesthis can be remedied by soldering a 1 MQ

Power stows?*It is typical of power mosywnsthat the drain current runsthrough the chip more or lessvertically as shown in the di-agram. In effect, this showstwo paralleled FETs (a rght-hand and a left-hand). Forclarity's sake, only the areaaround the gat is shown, butthe drawing should really beextended quite a bit to bothsides. The drain and sourceterminals, situated in thoseimaginary extensions, are fairlystout so that the chip can drawfairly high currents.

If the chip consisted of per-fectly doped silicon, the draincurrent, ID, would split equallyover the two Kis. But evenwith less perfect material, Inwill divide fairly evenly. In the

SOURCE 0 GATE

polysiliconSiO2

N.

P. P.

substrate

metal

construction of power FETs,use is made of this propertyby paralleling not two, buthun dreds of small FETs Withthe structure in the diagram,

resistor across R34. If not, use 1 MS1 pre-set and turn this slightly past the posi-tion where the pulse has the correct width.

Connect the oscilloscope across R17:DO NOT USE channel 2 or an external trig-ger input. Press S1 and adjust P2 until thepeak value of the two pulses measured is

PARTS LISTResistors:

R1, R28, R29, R48, R49 = 1 MCIR2= 10052R3= 100R4-126, R17, R30, R33, R37 = 100 ItS2R7= 330 Id/R8= 82 IcaREr-R12 = 10.0 kS1, 1%R13 = 1 Q, 5 WR14= 1.5R15. R35 = 560R16, R36, R54 = 10 k.(1R18, R36. = 330 52

R19, R3g = 0.27 0, 5 WR20, R40 = 0.33 0, 5 WR21, R22, R41, R42 = 0.12 Q, 5 W

R23, R43 =0.15 i/, 5 WR24, R44 =0.39 O. 5 WR25, R45 = 0.82 II, 5 WR26, R48 = 1.551, 5 WR27, R47 = 6.8 MI

R31 = 560 ki2R32, R56 = 3.3 Id/Rs4 = 270R50 -R53 = 100 kfl, 1%R55 = 5.6R57 = 2.7 kitR58 = 3.3 lP1 = 10 k52 preset potentiometerP2. P3 = 1 Id/ preset potentiometerP4 = 250 Id/ preset potentiometerP5 = linear 5 k52 potentiometer

Capacitors:

Ci, C2, C14 -C20 = 100 nF

C3 = 220µF. 16 V, radialC4 XI 10 rIF

C5 = 100 pF, 16 V. radialC6, C8, C12 = BFC7= 33 pFCg, C10, C23 =4700µF, 35 V, radialC11 = 330 nFC13 = 8.2 pFC21 = 22 p.F. 40 V. radialC22 = 470 nFC24. C25 = 150 pF

Semiconductors:D1, D2, D10 = 3 mm LED, red. low ID3, D4 = zener diode 10 V, 400 mWD5 = BAT85D6 --Dg = 1N4148Bi = S13605 (600 V. 6 A)

, T2 = BC557B (pair)T3 = BC560CT4, T5 = BC547B (pair)T6 = BD244C

Integrated circuits:ICI, IC2, IC9 = CA3260IC3 = 4017IC4 = 4538IC5-1C5 = TLC4066IC10 = 7812

Miscellaneous:JP1-JP16 = 4 -way right-angle header

= 3 -way terminal block5 mm pitch

R5 = 2 -way terminal block, 5 mm pitchSI = press -to -make push buttonswitchS2 = 2 -pole, 6 -position, rotary switch

for PCB mountingPCB No. 930107 (see p. 70)

drain 920083-13

this is fairly simple: repeatthe same structure and linkIt to the previous one, not onlyto the left and the right, butalso in depth.

1.5 V.Connect the oscilloscope across R37.

Press S1 and adjust P3 until the peak valueof the pulses measured is 1.5 V.

Connect the oscilloscope across theSCOPE output of the tester. Press SI, where-upon four pulses are available (these looklike the trigger signal). Adjust P4 until thefirst two pulses are as high as the othertwo, or until the voltage across R30 is equalto that across D5.

Finally, adjust P1 until the peak valueof the triangular signal at its wiper is 1 Vpp.

Oscilloscope settings

Trigger:ExternD.C.Leading edgeNormal (No auto trigger)

Time base:Four consecutive measurements:

1 ms/divFour simultaneous measurements:

slightly more than 0.1 ms/div

y -channel:A.C.No offsetSensitivity as high as possible

(depending on FET and chosendrain current).

Power MOSFET tester:Si: start measurement52: /D 0 0.5 1 2 4 7 10AP5: vertical position of characteristics

on screen of oscilloscope(replaces offset setting ofoscilloscope)

END



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THE ANALOGUE SUBSYSTEMPART 3 (FINAL)

BUILD A UNIV :RSAL MULTI-GiiIN

Amplifiers are used to boost weak electrical signals to higherlevels. For example, a voltage amplifier will boost a weakvoltage signal to a higher voltage level so that it can bedisplayed on a meter, viewed on a cathode ray oscilloscope(CRO), written on a paper chart recorder, or processed by ananalogue -to -digital converter for input to a computer.

By Joseph J. Carr

Although many experimenters will usetheir computers for data collection today,it is nonetheless true that it is still an`analogue' world. Thus, one will still finda large number of applications for ananalogue voltage amplifier. In this arti-cle you will find described a design ideafor such an amplifier. This universalmulti -gain laboratory amplifier(UMGLA) can be used for boosting theoutput signals from assorted sensors, bi-ological signals, and a host of other sig-nals found in scientific and electronicinstrumentation.

But first, before looking at the ampli-fier, let us review some basic amplifierterminology so that everyone is on a levelplaying field. If you already know quite abit about electronics, this material willbe somewhat simplified. It will, however,serve as a good review, so you are invitedto either read through it or skip ahead asyou please.

Figure 20 shows the symbol for a basicamplifier. The symbol most commonlyused is a triangle on its side. The inputconnections are along the vertical line on

Fig. 20. Basic amplifier symbol andconnections.

-0GUE AMPLIFIER

the left side, while the output connectionis always at the opposite apex.Sometimes there are several inputs, butmore of that shortly. Because both inputsignal voltage (U) and output signalvoltage (U0) are referred to the samecommon (sometimes called ground evenwhen not connected to actual earth) con-nection, this type of amplifier is said tobe single -ended; i.e., both input andoutput connections are single terminals.Another name for this particular ampli-fier configuration is unbalanced.

The amplification of an amplifier isa measure of how much it will boost theinput signal. The symbol A is usuallyused to represent amplification. Becausethe amplifier project in this article, andindeed the most commonly used type, is avoltage amplifier, the symbol is modi-fied with a subscript v to denote voltageamplification: Av. A current amplifiermay have its amplification symbolized byA. There are other forms of amplifica-tion, but they are beyond the scope ofthis article. In all forms of amplifier, in-deed in all forms of electronic circuitwhere there are inputs and outputs, theamplification is defined as the ratio ofoutput to input. In the context of thevoltage amplifier, therefore, the amplifi-cation is the ratio of the output voltage(U0) and the input voltage (U) that pro-duced it:

A, = U0 / U (1)

Consider a quick example. If a voltageamplifier produces a 1 -volt output signalwhen a 2 -millivolt (0.002 volt) input sig-nal is impressed, the amplification is

(1 V) / (0.002 V) = 500.

The amplification term is dimensionless,

and merely refers to the scaler by whichthe input signal is increased at the out-put.

The relationship between input volt-age, output voltage and amplification isfound from:

Uo = U, Av

Typical amplifications for amplifiersused in the laboratory are:

CLASSIFICATION VOLTAGEAMPLIFICATION

Low amplification 10 to 50Medium amplification 50 to 500High amplification >500

Fig. 21. a) Non -inverting amplifier, b)inverting amplifier.

Amplification can have either of two po-larities (Fig. 21), which is seen by com-paring the input and output signals. If apositive going input signal produces apositive going output signal (Fig. 21a),and vice versa, then the amplification ispositive (+Av). As you can see from thewaveforms in Fig. 21a, the output signalis not inverted with respect to the inputsignal. Such an output signal is said tobe in phase with the input signal, andthe amplifier is said to be non -invert-ing. If the output signal is inverted withrespect to the input signal (Fig. 21b), i.e.,a positive going input signal produces anegative going output signal, the amplifi-cation is negative (-Av) and the amplifier


56 GENERAL INTEREST

a

of

USIG

bat

C

d

e

Time (s)

UsIG

930014 - III - 13a

-I. Time (s)

Time

930014 - Ill - 136

930014 - III - 13r1

Fig. 22. a) d.c. signal, b) quasi -static signal,c) periodic sine wave signal, d) varying d.c.signal, e) a.c. signal with d.c. component.

is said to be inverting. The negativesign is used in math calculations of am-plifiers, and indicates the phase reversalof the output with respect to the inputsignals.

The nature of the input signal issometimes important to the design of theamplifier used to process it. For example,some signals are unchanging direct cur-rent voltages (Fig.22a), or very slowlyvarying voltages (Fig. 22b) that changeonly a small amount over a very long

time. In other cases, the signal might bea periodic voltage such as a sine wave(Fig. 22c), square wave, triangle wave,sawtooth wave, pulse wave or other waveshape. Note in Fig. 22c that the signal issymmetrical around zero volts. One halfof this bipolar signal is represented bypositive voltage, while the other half ofthe signal is represented by negativevoltage. One complete cycle consists of asingle positive and single negative excur-sion, with an average value (taken to-gether) of zero. An implication of thistype of signal is that the amplifier thatservices it must be capable of operatingover both negative and positive voltages,both at the input and at the output. Stillother signals might be exponentially de-caying peaks (Fig. 22d), either symmetri-cal about zero or all of one polarity (asshown).

Figures 22d and 22e illustrate one ofthe little problems found on real signals.Note that these signals are symmetricalaround some line other than zero. If thisline, representing a voltage, were de-pressed to zero, the sine wave signal ofFig. 22e would resemble Fig. 22c. Thisoffset form of signal is said to have a di-rect current (d.c.) component. In otherwords, it can be thought of as a time -varying waveform (Fig. 22d) or periodicwaveform (Fig. 22e) riding on a d.c. com-ponent, U, .

In some cases, the d.c. component is adesired part of the overall signal, andtherefore must be accommodated in anyamplifier handling the signal. In othercases, the d.c. component is merely anoffset on the desired signal, and shouldbe suppressed. In some cases, the d.c.component is so severe that it is manytimes higher than the variations repre-senting the desired signal. A good exam-ple is the electrocardiograph (ECG)signal. The ECG is a low value bipolarsignal with a peak of about one millivolt(0.001 volt). When metallic electrodes(e.g. silver -silver chloride, Ag-AgCl) areattached to skin, which is electrolytic innature, a tiny natural 'battery' is formedbetween the skin and electrode. This so-called half -cell potential can be as highas 2.5 V, although around 1 V is typicalfor the types of electrode normally usedin ECG recording. In this, the desired0.001-V ECG waveform is riding on top ofa 1-V d.c. half -cell potential, so would becompletely obscured.

The amplifier input circuit is some-times modified in order to deal with vari-ous input signals. An amplifier inputthat is unmodified, that is, will recognizeall components of the input signal includ-ing the d.c. offset component, is said to bedirect coupled (d.c.). If an amplifierinput circuit is modified to block the d.c.component and only passes the alternat-ing current portion, it is said to be a.c.coupled. The a.c. coupled amplifierwould pass the sine wave in Fig. 22e, butnot the d.c. offset U,. The most usual

Fig. 23. A.c.-coupling strips off the d.ccomponent.

form of circuit for suppressing unwantedd.c. components is the capacitor inputshown in Fig. 23. The signal voltage, Um,is the algebraic sum of the actual signal(U,,g) and the d.c. offset (U). In this typeof circuit, the capacitor (C) is connectedin series with the signal source voltagesand the amplifier input terminal. Insome amplifiers, there is also a resistor(R) connected between the amplifierinput and ground. This resistor is used toprevent the capacitor from being erro-neously charged by the d.c. offset voltageand spurious currents from the amplifierinput (a fact of life in real amplifiers, un-fortunately).

The type of amplifier in Fig. 20 is saidto be single -ended because only one con-nection is made to the amplifier inputand output sides; such amplifiers are un-balanced with respect to ground. In sci-entific and electronic instrumentationthe single -ended amplifier may be eitherinappropriate (perhaps because the sig-nals are not single -ended), or inadvisable(e.g., because of certain interferences). Insuch cases, a balanced input amplifieris needed. Such amplifiers are called dif-ferential amplifiers because they pro-duce an output signal that is the productof the amplifier amplification and thedifference between two input signals.

Figure 24 shows a typical differentialamplifier. It has two inputs, labelled (-)and (+). The negative input is an invert-ing input (-IN), while the positive inputis a non -inverting input (+IN). Both in-puts provide the same amount of voltage

Fig. 24. D.c. differential amplifier with inputsignals.


THE ANALOGUE SUBSYSTEM - 3 laamplification, but of opposite polarity.Thus, if the exact same voltage, withexact same polarity, is applied to both-IN and +IN, then the resultant outputis zero. In the circuit shown in Fig. 24,the output voltage is the difference be-tween the two input voltages, U1 and U2:

U0 = Ud(U2-U1)

-e Ud is the differential voltagea. lification, and U1 and U2 are sin-g -l' nded input voltages.

a voltage signal is applied equally toJoth inputs (U3 in Fig. 24), it is called acommon mode voltage. This voltagetends to be suppressed because of thereciprocal action of the two inputs. Thesuppression is not complete, but is verygood (100,000:1 and 1,000,000:1 are com-mon). The ratio of the differential ampli-fication to the common modeamplification is a measure of this sup-pression, and is called the commonmode rejection ratio (CMRR).

Real amplifiers are not ideal, al-though with modern integrated circuitamplifiers the departures from 'ideal-ness' are very small. Although a com-plete discussion of practical amplifiers isbeyond the scope of this article, there areat least two aspects that must be consid-ered: output resistance (Ro) and inputresistance (R,) - these are sometimescalled 'impedances' rather than resis-tances, so read output impedance (Z0)and input impedance (Z,). Figure 25

Fig. 25.amplifier.

Equivalent circuit for a voltage

shows these resistances modelled as dis-crete resistors in the output and inputcircuits. In order to faithfully reproducesignals, the amplifier needs to be de-signed to maximize input resistance, andminimize output resistance. Ideally,

and R.-M. In real amplifiers, theinput resistance will be 106 Q up to1012 Q depending on design and quality,and output resistance will be 1 to 100 Q,with 25 Q being quite common.

What kind of amplifier forthe laboratory?The amplifier for the laboratory needs tohave certain characteristics. Although adiscussion of 'why?' for some of the se-lected parameters can be a bit involved,there are some guidelines. For example,for maximum diversity, a lab amplifiershould be a differential input type. In

cases where single ended amplifiers areneeded, it is only necessary to ground theunwanted input. For example, to makean inverting single -ended amplifier, sim-ply ground the non -inverting input anduse the inverting input. Similarly, tomake a non -inverting amplifier all youneed to do is ground the inverting input.Thus, the differential amplifier will serveas a differential amplifier, an invertingamplifier and a non -inverting amplifier.The laboratory amplifier should also havea single -ended output so that it is compat-ible with the usual types of display andrecording devices (meters, oscilloscopes,paper recorders, A -D converters, etc), inorder to process a wide variety of signals,but a.c. coupled and d.c. coupled inputsshould be available.

A laboratory amplifierdesignThe circuit for the UMGLA is shown inFig. 26. The heart of this circuit is theBurr -Brown INA-110 integrated circuitinstrumentation amplifier (ICI). This de-vice is designed for a wide variety of in-strumentation applications, of which thelaboratory amplifier is a good represen-tative example. It has a very high imped-ance, differential input stage, and asingle -ended output. It uses a minimumof components, and the amplification isprogrammable. The INA-110 comes in a16 -pin integrated circuit dual in linepackage (DIP).

-IN J1

F-)C1

2207

+ IN J2

0'0227

S2: A = x 10B = x 100

C = x 200

D = x 500

S1a

S1: A = DC

B = GND

C=AC

(H)

R12 R1312V

O

(N)

C3

1/16V

IC2 = CA3240; LM1458

S2GAIN SELECT

A 0-Bp ckc

(R) (0)12 1613

(P)

INA-110

7 14 A

I 1=A15 4 5

4=1R1la R2

1

100k 00k

C4

1:6V

11

7P1

0

12V

O

J4

(J,K,L)

3

12V RIO

R5

10kGAIN 0

POWERON/OFF

S3

(D)

POWER8 -Pin DIN

(B)

POSITIONR9 All 12V

(C)

R3

DI

red

10k

R8

R7

C5

100n

C6

(A) 100n

IC2

930014 - III - 17

7

(M)

12V

12V

J3

Fig. 26. Circuit diagram of the lab amplifier.


58 GENERAL INTEREST


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Table 1

Voltage gain connect togetherpins

x10x100x200x500

3,3,

3,

3,

13

12

16

11

The INA-110 provides an amplifica-tion of x10, x100, x200 or x500, depend-ing on the programming performed onpins 3, 11, 12, 13, and 16, according tothe scheme in Table 1. To obtain any ofthe four specified voltage gains you onlyneed to short together pin 3 and the indi-cated pin that corresponds to the desiredgain. In Fig. 26, the gain is selected by asingle -pole, four -position (SP4P) switch.The pole of the switch is connected topin 3 of the INA-110, while the program-ming pins are connected to the four selec-table positions (labelled A, B, C and D inFig. 26).

The input pins of the INA-110 arepin 1 (-IN) and pin 2 (+IN). A two -pole,three -position (2P3P) input switch isused to either ground these inputs, con-nect them directly to the input connec-tors (Jl/J2), or provide a.c. coupling bypassing the signal through a pair of 0.22-µF capacitors (Cl and C2). A pair ofmatched 10 -Me resistors (R12 and R13)are connected between the inputs of theINA-110 and ground. These resistorsshould be matched to exhibit the sameresistance from a collection of 10 Me, 5%tolerance I/4 watt, metal film resistors.Alternatively, if you have them avail-able, use a pair of 1% (or better) precisionresistors and skip the matching task.

The second stage in the circuit ofFig. 26 is a post amplifier made with a

dual operational amplifier (1C2). Thesedevices contain two operational ampli-fiers (IC2A and IC2B) inside a single 8 -pinDIP package. Use either the low-costLM1458 device, or the somewhat pricier(but still reasonable), CA3240.

The first stage of the post amplifier,IC2A, is connected as an inverting ampli-fier with a gain that is adjustable fromzero to one. The gain in these circuits isthe ratio of the feedback resistor to theinput resistor, or in the case of IC2A theratio R5/R4. Resistor R4 is a 10-ke fixedresistor, while R5 is a 10-ke potentiome-ter. Thus, the voltage gain of IC2A is zerowhen R5 is set to minimum (zero ohms),and the gain is one when R5 is set tomaximum (10 ke).

The second stage serves to provide aposition control (R9), as well as servingas an output 'buffer' to isolate the ampli-fier from the outside world. The gain ofIC2B is one (R7/R6), and is fixed. The out-put of IC2B is routed to the output con-nector, J3.

The position control (R9) is connectedas a d.c. offset control to IC2B. It providesa voltage that is seen at the output as ad.c. offset to the output baseline. Whenthe voltage at the wiper of R9 (point 'C')is zero, the output offset voltage of theamplifier is zero. When the signal isviewed on an oscilloscope or paper chartrecorder, the effect of R9 is to set the po-sition of the 'zero' baseline of the com-bined signal + offset. Potentiometers R4and R5 are mounted on the front panel ofthe amplifier so that they can be ad-justed by the user.

The power supply for this amplifier isderived from outside of the circuit. Apower connector (J4), which in this caseis an 8 -pin DIN audio -style connector, isprovided. The required voltages are±12 V. These voltages can be supplied ei-ther from an a.c. powered electronicpower supply, or from a set of batteries.

Fig. 27. Output display circuit.

A power switch (S3 in Fig. 26) turnsthe amplifier on and off. The switch canbe any single pole -single throw (SPST),panel mounted, toggle switch, but it ismore likely that you will, like I did, findit easier to obtain a double pole -doublethrow (DPDT) switch. Either can be used(ignore the extra connections on theDPDT version).

The output of the laboratory amplifiercan be monitored on an oscilloscope,strip -chart paper recorder, analogue -to -digital converter (for input to a com-puter), or an analogue meter. If youprefer, a digital multimeter can be usedto indicate output voltage values in staticcases (e.g. the output of some sensors).Alternatively, use an analogue meter(Fig. 27). A single pole double throw(SPDT) switch is connected to a 1-0-1milliampere, zero -centre, analoguemeter. The other terminals of the switchare connected to a pair of resistors thatdetermine the sensitivity, making this atwo -range instrument. Analogue meters,incidentally, are best for nulling typemeasurements, as in when a Wheatstonebridge is used to measure certain scien-tific parameters.



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60

DX TELEVI I N

A two -monthly column by Keith Hamer and Garry Smith

JUNEand July 1993 proved to be an

action -packed period for sporadic -Ereception between 48 and 70 MHz. Therewere many days of intense all -day activ-ity, with countries in the South andSouth -East of Europe received virtuallydaily in some parts of the UK. Many ofthe openings were already in progressbefore 0600 UTC, and with many coun-tries screening a breakfast TV pro-gramme, very early monitoring wasessential if you wanted to see test cards.Compared with previous seasons, 'ex-otics' were less evident. Nevertheless,there were reports of transatlantic DX onchannel E2, and the Middle East(Jordan) on June 9th.

Test card changesNorway: Stephen Michie (Bristol) ad-vises that the Norwegian PM5534 testcard (with the date, time, transmitteridentification and PTT message) isshown only before 1015 UTC. Just beforethis time, the transmitter name disap-pears, and the PM5534 switches to textpages with programme schedules. Theschedules are also shown after close-down.

Austria: Stephen Michie has also com-mented that ORF-1 shows text pages be-fore the station opens at 0700 UTC.There has been no sign of the PM5544test card so far this season.

Slovenia: TV Slovenia shows mainlytext pages during the day. The PM5544test card is very rarely shown after0600 UTC.

Spain: Tony Mancini (Belper) has iden-tified TVE-1 Spain relaying 'Euro TV'news. The 'Euro TV' logo is shown in thecorner of the screen, which is causingconfusion among some DX-ers.

Mystery signalsReaders have written in with several`mystery' signals which they would likeidentifying. If you can help, please writeto the address given at the end of this ar-ticle.

1. Adverts introduced by the letters'EPP' have been seen on channel E3.This abbreviation has been used to in-troduce advertisements for many

years in former Yugoslavia.2. The identification PTC-G1 (or PTC-61)

appears to come from TVB-1 (Beograd).`PTC' is the abbreviation for 'RadioTelevision Serbia' in Cyrillic.

3. Several sightings of a '2' corner logo onchannel E3.

4. Various colour bars, line sawtooth andchessboard test patterns have beenseen on channel R2.

5. `NTA' corner logo on channel E3.6. There is a mystery surrounding the

possibility of a second Portuguese sta-tion operating on channel E2 when asecond station was received in Europeearly in the season. The only oneknown to be currently operating isMuro with an ERP of 40 kW.

Recently the RTP FuBK test pattern wasnoted in Derby, around mid -morning, su-perimposed in the background of a strongSpanish TVE-1 transmission. Althoughdifficult to read, there seemed to be a '2'after the `LISB' part of the identification.Since then, Chris Howles (Erdington)has returned from the Algarve inPortugal, and confirms that the RTP-2FuBK is shown during the morning,while the 1st Network is on programmes.The local RTP-2 transmissions in theAlgarve were on channel E5. Normally,the second network is confined to UHF.On June 8th, a transmitter announce-ment caption was shown by RTP at1830 UTC with mention of various chan-nels, but unfortunately it seemed in-significant at the time.

Reception reportsIan Johnson (Bromsgrove) reports an 'ex-citing' sporadic -E season for TV and 6 -metre reception. The highlights include a6 -metre transatlantic opening toVirginia, North America, at 1827 UTC onJune 11th, when he contacted stationW4DR using 35 W (100 W ERP) intoFM17. K1TO1 and WA1OUB were alsoheard. The 6 -metre band also opened upto Maine, North America, very briefly at1920 UTC on June 25th.

David Glenday (Arbroath) recalls11 days of tropospheric reception duringthe first half of June. Conditions subse-quently remained flat until the 28th. A`first' was NRK TV2 on channel E37 withthe `TV Norge' PM5534 test card seenaround 0000 UTC on the 29th/30th June.The signal is thought to have originatedfrom a 1 -kW outlet in Stavanger on the

Fig. 1. The new Norwegian test pattern withdate and stylized `NRK' at the top. The testpattern was received by Bob Brooks (SouthWirral) on channel E3 from the Hemnestransmitter.

west coast of Norway.Sporadic -E reception during the pe-

riod brought in lots of Spanish stations.On June 21st, strong signals from Russiawere received in colour. The signals wereclean enough to decode Teletext; theRussian 1st programme has a pageheader called 'TELEINF'. David feelsthat the Moscow services have becometoo commercialized. There is an endlessstream of adverts for Schweppes, Twix,various brands of shampoo, Kodak film,Sony electronic goods, Hewlett-Packardcomputers and even Cadbury's Fruit 'n'Nut chocolate!

Peter Chalkley (Luton) receivedAlbania for the first time from the 100 -kW Tirana transmitter on channel IC at82.25 MHz. This reception confirms thatthe transmitter is still operating on thischannel even though it is no longer listedin the EBU Station Listings. The 1993edition lists many Band -I relays whichhave recently been commissioned, butunfortunately these are only low -power,so only time will tell whether these canbe received in the UK. The Tirana trans-mitter has 'officially' moved to UHF.

Peter has also monitored the FM radioband during intense openings. He hasnoted several Spanish and Portuguesestations.

Barry Bowman (Manchester) has alsotaken advantage of the high m.u.f's, andDX-ed at FM. Catches on July 28th in-cluded Spain (Cadena FM) at 88.15 MHz,the Canary Islands (Onda Zero Musica)at 87.70 MHz, Portugal (various stationsfrom 106.00 to 106.90 MHz) and Moroccoat 87.55 MHz. Other openings producedItalian and Croatian FM stations.

Chris Howles (Erdington) has com-mented that RTE -1 signals from Eire onchannel B (Gort) were in evidence sev-eral times during his recent two -weeks'holiday in Portugal. Other sporadic -Esignals included Spain, Belgium, theNetherlands, Germany, Tunisia andMorocco. The latter signal originatedfrom the Layounne transmitter(channel E4), which is located almost op-posite the Canary Islands. TVE-1 trans-


DX TELEVISION 61

missions on channel E3 were present atthe time, possibly from the Izafia trans-mitter on Tenerife. Various MoroccanBand -III stations were present all thetime in the Algarve, despite the distanceof more than 200 km. Chris has com-mented that the Moroccan second net-work at UHF is encrypted.

Log for JuneSporadic -E activity was evident everyday except June 2nd and 6th. The mostintense and prolonged openings are de-tailed below.

09.06.93: Finland on channel E4;Portugal E2 and E3, Spain E2, E3 andE4; Hungary R1; Unidentified signalsfrom the CIS on R1, R2, R3 and R4; ItalyIA and IB; Serbia E3; Croatia E4; IcelandE3 and E4; unidentified transatlanticsignal on A2; Jordan E3; Germany E3;Albania IC; Corsica L2.

10.06.93: Czech Republic on R1; Italy IAand IB; Norway E2 and E3; Sweden E2,E3 and E4 (test card and programmes);Portugal E3; Spain E2, E3 and E4;Denmark E3; Albania IC; SwitzerlandE2 and E3; Austria E2a; Croatia E4;Hungary R1 and R4.

11.06.93: Unidentified transmissionsfrom the CIS on R2; Germany E2; ItalyIA, IB and IC; Moldova R2 and R3;Rumania R2 and R3; Estonia R2;Denmark E3; Croatia E4; Slovakia R2;Czech Republic R1; Sweden E2; E3 andE4; Austria E2a; Spain E2; Slovenia E3.

12.06.93 Czech Republic on R1 and R2;Slovenia E3; Hungary R1 and R2;Rumania E3; Austria E4; Germany E2,E3 and E4; Switzerland E2 and E3; ItalyIA and IB; unidentified CIS on R1 andR2; Spain E2, E3 and E4; Norway E2, E3and E4; Poland R2; Ukraine R1.

Log for JulyLong-distance reception occurred dailyexcept for July 3rd and 4th. The high-lights were as follows:

08.07.93: Slovenia E3; Serbia E3;Croatia E4; Denmark E3 and E4;Sweden E2, E3 and E4; Finland E3 andE4; Norway E2, E3 (Hemnes) and E4(Kongsberg); Italy IA and IB; Corsica L2and L3; Czech Republic R2; Rumania R3;Albania IC; Iceland E4; Germany E2, E3and E4; Switzerland E2; Hungary R2;Poland R2 and R3; Estonia R2; AustriaE2a and E4; Spain E2 and E3; unidenti-fied CIS R1; R2, R3 and R4.

16.07.93: Spain E2, E3 and E4; Italy IAand IB; Corsica L2; Czech Republic R1;Germany E2; Hungary R1, R2 and R4;Rumania R3; Austria E2a and E4;Slovenia E3; Serbia E3; Croatia E4;

Fig. 2. Rumanian 1st network logo receivedon channel R2 by Bob Brooks.

Denmark E3 and E4; Poland R3; EstoniaR4; Moldova R1 and R3; Albania IC.

Reception reports and logs kindly sup-plied by Barry Bowman, Simon Hamer,Peter Chalkley, Bob Brooks, StephenMichie, Ian Johnson and David Glenday.

Service informationGermany: The FuBK currently used bythe ARD now carries the identification`ARD1 - FFTM' with a digital clock in thelower part of the test pattern. A continu-ous announcement advises the viewer ofwhich network they are watching.Regional variations (for example NDR-1)now appear only infrequently. MDR -3have virtually abandoned the FuBK,which has been replaced by a full -screencaption advertising the MDR Sputnikradio channel.

Before the start of the breakfast mag-azine programme, ARD and ZDF show a`live' picture of either Cologne (ARD) orBerlin (ZDF) with the latest news head-lines running across the bottom of thescreen. The main part of the screen usu-ally features a `tauten Morgen aus Koln'or `Guten Morgen aus Berlin' message.

Bayern -3 are filling spare time beforetheir programmes start by screening`weather panoramas', i.e., pictures fromvarious locations in Bavaria, giving de-tailed local weather information.

SFB in Berlin is filling the spare timebetween closedown and the start of pro-grammes by giving viewers an uneditedtrain driver's view of some of Berlin'surban railway routes. Up to 20% of view-ers remain tuned in to the railway show!

West -3 is now on Astra 1C viatransponder 39. BRF-3 (Bavaria) is ontransponder 45. Since August 27th,MDR -3, SWF-3 and ZDF have beenbroadcasting via Astra; ARD-1 will even-tually replace Eins Plus on transponder19. S-3 in Baden-Wuttemberg is also con-sidering such a move.

Moldova: The new channel R3 transmit-ter located at Straseni is 50 kW TRP pro-viding an ERP of 800 kW!

Netherlands: Various channels have

been assigned for regional public broad-casting with ERPs ranging from 1 kW to1,000 kW.

Russia: The Finnish television companyOy Mainostelevisio Ab (MTV) has boughta minority share of the commercially -owned TV company called RegionalTelevision (RTV), which is operating inSt. Petersburg. RTV started transmis-sions in the St. Petersburg area in June,and broadcasts Monday to Friday from1800-2300 local time.

Moscow on channel R3 has its ownlocal Teletext service called `MOSTEXT'.TELEINF via the OK -1 network has ex-tended its pages, but still does not showthe correct date - only a flashing day inItalian!

Lithuania: The low -power channel R11transmitter in Vilnius is back on the air,relaying the German SAT -1 channel.TV26 (on channel R26 in Vilnius) is nolonger operational.

Rytu R28 (Lietuvos TV, which wasoriginally a state-owned enterprise) hasbeen re -opened by the private TV com-pany Baltijos Televizija. Their own pro-grammes are screened several times perweek, but at other times the transmitterrelays TP-1 programmes from Poland asbefore.

The former CT -1 network has re-sumed a full-time relay of OK -1 fromMoscow. The LTV -2 programmes fromKaunas, which used to share this chan-nel, have ceased.

The former CT -2 network now carriesa selection of satellite material from var-ious sources, including Super Channel,Discovery and Pro -7, plus selected relaysof Russian TV (TKR) such as the Vestinews and programmes of the new privateTV company TELE-3. The government isopposed to the new private company andwants to close it down.

Australia: Channels in the upper part ofBand III are to be moved up by 1 MHz tobring them in line with CCIR 'E' frequen-cies, as used in Europe. This will alsoallow the introduction of two newAustralian allocations - channels 9aand 12 at 203.25 MHz and 224.25 MHzrespectively.

This month's Service Information waskindly supplied by Gosta van der Lindenand the BDXC, Netherlands; ReflexionClub, Germany; Pertti Salonen, Finland;Roger Bunney, UK; Thomas PahIke,Germany; Bernd Trutenau, Lithuania,Lt. Col. Rana Roy, India.

Please send any news about DX -TV inyour part of the world to: Keith Hamer, 7Epping Close, Derby DE3 4HR, England.


62

FUZZY LOGIC MULTIMETER(PART 3 FINAL)

Fuzzy logic is not fuzzy at all,but a scientifically based wayof getting electrical equipmentto adapt to us, humans,instead of the other wayaround. This articleintroduces the Fuzzy ControlOne software package for PCsand compatibles, and inaddition gives you hands-onexperience in using thissoftware by describing anintelligent heating systembased on the PC DMM carddiscussed in the previous twoinstalments.

Design by H. Scholten

The core of the hardware required forthe experimental fuzzy logic controlsystem described here is the 'Fuzzylogic DMM' described in the previoustwo instalments of this article. To beable to control a mains -operated load,the DMM needs to be complementedwith a proportional phase angle con-trol circuit, which is described here.You also need the Fuzzy Control Onesoftware, in particular, the digital mul-timeter software, which already con-tains a number of control routinesspecially written for the present exam-ple. Strictly speaking, the DMM hard-ware and the associated software aresufficient to set up an elementary con-trol system. This is because the soft-ware contains a driver that makes useof the digital outputs on the multime-ter board.

We decided to offer you something alittle more elaborate than a controlsystem based on a simple 8 -bit paralleloutput. The fuzzy logic application ex-ample described here comprises phaseangle control of the mains voltage, i.e.,a regulation system that enables thepower fed to mains -operated loadssuch as motors, heating elements andlamps, to be accurately adjusted. Just

for the purpose of demonstration, acontrol system is made that keeps thetemperature in a cardboard box con-stant at a certain value. An ordinary75 -watt bulb is used as the heating el-ement. Admittedly, such a tempera-ture control can be built with muchsimpler means, but the lamp in thebox is just as good an example as themore esoteric (and often spectacular)applications conceived to demonstratethe power of fuzzy logic. A fuzzy logic`starter' can not be simple enough, andshould concentrate on setting up alimited, yet intelligent, control system.Once the basics of fuzzy logic havebeen mastered, you are, of course, freeto make your own applications as com-plex as you desire. How? By writingyour own system control specifica-tions!

Computer -driven phaseangle controlProportional phase angle control is themost commonly used method of con-trolling the amount of power fed to amains -operated device. The best knownapplication of phase angle control isprobably the ubiquitous dimmer.

The block diagram of the computer -controlled `dimmer' is given in Fig. 9.The heart of the circuit is a Type 8253programmable interval timer (PIT).Apart from a computer interface, thisIC from Intel contains three counters,which are programmed to function asmonostable multivibrators (MMVs) inthe present application. The length(duration) of the pulses supplied bythe MMVs is determined by the com-puter. These pulses are synchronizedto the mains frequency with the aid ofa zero crossing detector.

Apart from the computer, a clockgenerator also determines the length ofthe counter output pulses. The clockfrequency is 102,400 Hz, which meansthat there are 1,024 clock pulses tocover each half period of the mainsvoltage (assuming a mains frequencyof 50 Hz). Essentially, the task of thecomputer is limited to telling the coun-ters the length of the output pulses ex-pressed in clock pulses. In otherwords, each half cycle of the mains canbe divided into 1,024 phases, giving aresolution of 180°/1,024=0.176°.

Before looking at the timing dia-gram to discover how the various sig-nals are combined in the first two AND


FUZZY LOGIC MULTIMETER -3 63

gates, we first discuss the function ofthe three counters in the PIT.Counter 1 and counter 2 determine thephase angle at which the triacswitches on the mains voltage for out-put 1 and output 2, respectively.Counter 0 serves to determine thephase angle after which the triac is nolonger supplied with firing pulses. Thisis particularly useful when controllinginductive loads, since it prevents thetriac being triggered again after thezero crossing of the current (when thetriac is switched off).

The timing diagram inset in Fig. 9illustrates the operation of the PITcounters involved in the control of out-put 1 (counter 0 and counter 1). Thecounters are triggered on the zerocrossing of the mains voltage, whentheir outputs go low. Since the outputof counter 0 is inverted before it ar-rives at the AND gate, it enables thegate, and so indicates that the timeavailable for triggering the triac is notover yet. However, counter 1 does notenable the AND gate yet, since the in-stant at which the triac is to be fired,is not reached yet. As soon as the out-put of counter 1 goes high, the ANDgate is enabled, and clock pulses areallowed to reach the triac. The use of apulse train to fire the triac has two ad-vantages. First, it ensures reliable trig-gering (should the first pulse fail to firethe triac, there is always a second, athird, etc.); and, second, the gate isnot constantly driven, which reducesthe amount of power it has to dissi-pate.

Four piecesThe circuit diagram, Fig. 10, is subdi-vided into four sections, which corre-spond to the four printed circuitboards that make up the completecontrol system. Considering the totalnumber of components, some of youmay find the use of four boards extrav-agant. Note, however, that the (sub)circuits form part of the 'MicroSystem'developed by the author (see Part 2),and have to be relocatable because ofthe system's modular structure.

The PIT board contains relativelyfew components. The main circuit, ICI,contains the interface and the coun-ters shown in the block diagram inFig. 9. Circuits IC2 and IC3 are notshown in the block diagram, and forman extension of the interface betweenIC 1 and the MicroSystem bus. Addressdecoder IC3 and register address linesR2, R3 and R4 enable up to eight PITboards to be located at a single cardaddress. In this system, jumper JP1 al-lows you to define the register addressof the card. If the jumper is mountedin position 'K' (default), IC3 is disabled,and the PIT card is addressed with the

zero crossing

counter 0

counter 1

clock

out

A

920049 - HI - 11

240VAC

Fig. 9. Block diagram of the experimental heating control system based on fuzzy logic.

aid of the card selection signal only.The PIT card also contains its ownpower supply, and that for the propor-tional phase angle control board. The12-V supply voltage on theMicroSystem bus is reduced to 5 V byregulator IC4.

The phase angle control is accom-modated on a separate board, onwhich the PIT counter and clock gener-ator signals are combined to producethe firing pulses for the triac in themains switching circuit. This boardcontains rather more electronics thansuggested by the block diagram. Oneof the 'extras' is bistable IC3a, whichprovides the power -on reset. Thebistable is reset when the supply volt-age is switched on (or when the twocontacts of terminal block KS1 are in-terconnected). Gates ICic, ICia andIC1b are then disabled, so that themains switching circuit receives nodrive signal. Setting the bistable en-ables the gates. This happens auto-matically as soon as the phase anglecontrol is taken into use.

Another extra sub -circuit is a shiftregister based on IC2a and I2b. Thisserves to delay the PIT counter 0 out-put signal by two clock periods (20 p.$).The delay prevents glitches whichcould cause early triggering of thetriac.

The clock signal on the board issupplied by a clock generator, ICs. Thetwo AND gates shown in the block dia-gram correspond roughly to IC la andIC2a, although actually ICid belongs to

this function also. The gates combinethe inverted counter -0 output signalwith the clock signal. Next, the com-bined signal is applied to ICia and IC ib(via ICic) where it is combined againwith the output signal of counter 1 andcounter 2 respectively. The output sig-nal produced by the AND gates is sub-sequently sent to a darlingtontransistor which serves as a driverstage.

The sub -circuit marked mainsswitch is controlled by the output sig-nal supplied by the phase angle con-trol. Ready-made electronic relays are,unfortunately, not suitable here, be-cause they usually switch on the zerocrossing, and not at the phase angle(instant) determined by the phaseangle control. The mains switch drawnin the circuit diagram is nothing spe-cial: an optocoupler drives a triacwhich switches the load. Further, theswitch is surrounded by the usual de -coupling and noise -suppressing com-ponents.

The zero -crossing detector is also aconventional circuit, and for the mostpart contained in IC1. Resistor Ri andcapacitor C i provide the series reac-tance ahead of the supply circuit con-tained in IC1, while C2 is the buffercapacitor associated with that supply.The mains voltage is applied to the de-tector input via resistor R2. The detec-tor output is connected to anoptocoupler via R3. The optocouplerensures that the signal is passed tothe phase control in a safe manner.


64 TEST AND MEASUREMENT

Four boardsI- 1

As already mentioned, the completecontrol consists of four boards (apartfrom the DMM board). The artwork ofthe boards is given in Figs. 11, 12, 13and 15. Construction is entirelystraightforward with the exception of asmall modification on the PIT board. Inthe original design, IC4 was a 78L05,which, unfortunately, proved unableto source enough current, and had tobe replaced by a 7805. To enable the7805 to be fitted on to the board, itscentral pin has to be bent backwards alittle. Mount the 7805 such that itsmetal tab is at the side of the boardedge.

The triac can make do without aheat -sink if the load current remainsbelow 1 A or so. If higher load currentsare expected (up to 4 A), the device isbest fitted with a small heat -sink (ther-mal resistance approx. 17 K W-1). Ifnecessary, the voltage regulators mayalso be fitted with such heat -sinks.

Interwiring the boards is not a prob-lem because the connections areclearly indicated in the circuit dia-gram.

The enclosure of the PIT board hassufficient space to accommodate thephase angle control also. The DMMboard (discussed in the previous twoinstalments) is fitted into a similar en-closure. The mains switching boardand the zero -crossing detector are fit-ted into a mains plug-in case with amoulded mains plug (see Fig. 17 andintroductory photograph).

Let's get fuzzyThe introductory photograph with thisinstalment shows the example applica-tion of the Fuzzy Control One software,developed to get you started. The ex-ample is a temperature control. Not anovel application, this, but it has, inprinciple, everything associated with a`real' process control.

In addition to the hardware de-scribed here, you need the 'fuzzy logicDMM' board, a 75 -watt bulb with asocket, a thermometer and an LM35temperature sensor. The size of thecardboard box used for the prototypecontrol was 30x30x10 cm. A perspexwindow is made in the box to allow thelamp intensity and the temperature tobe viewed from the outside. Using thefuzzy logic control, the 75 -watt bulbwas capable of heating this little 'oven'to over 50 °C.

Connecting the LM35 is simple. The

Fig. 11. Artwork for the single -sided PITboard. `Aansluiting' = connection; 'adres-keuze' = address setting; `kaart keuze' = cardselection.

DO

D1

D2

D3

D4

D5

D6

D7

RD

ST

WR

RO

R1

R2

R3

R4

+12V

+12V

OV

OV

PIT-board

I K1

0O

24

O25

O26

O27

O28

2900

23 8

R2 R3

7

6

5

4

3

0

IC2a5

2

7

O

2

4

5 >1 6

00

10IC2b

23

0O0

2

20

3

4

O

OO

O

000

O

0

OO

5V

6

5n

th

JP215

16 o-.170

° 0 0-- 319 0- 420

21

22 0-card selection

31

DX0

1

II

2

IC3 3

74HCT138 4

5

fi

7

3

4

.5

RD

WR

AO

CLKO

OUTO

IC1 GO

8253

CS

CLK

OUT

CLK2

OUT2

9 13

K2

10

5

13

5

7

6 3

21

JP1

j11_0

11_0

0405

N? --0 6

NL-0 0-41 7

IC4

C1

TOP

7805+

5V

5V

IC2 = 74HCT32

2

C3

700n

KS1

Fig. 10. Combined circuit diagram of the PIT board, the phase angle control, the mains switch and

r-+ 5 U 0 U

KS1

C40

L_

CI

AANSLUI TI NGR2

R3 101

I Cl

PI T 8253

3334

26

ADRES-KEUZE * 4))K0123'4567

7 HEADER 0

KAART KEUZECP---gaa

MI KROBUSCONNECTOR



r rI Phase angle control

I ICJ = 74HCT08I IC2 = 74HCT74

I K1 IC3 = 74HCT74- IC4 = 74HCT14

00

3

2

0

5

4

2

L

5

3

5V

8

D

if

IC1b

-R1

5V

O

R4

R5

10011

T2

BC517

IC2a

>cF,

91

,110

D IC2b

ff >C

V

5V

KS5I

0

KS4I

O

I Mains switch

KS1

0

113

11

RESET

5V

9

IC1 d13

2

OQ 0IC1IC2IC3IC4

IC5

5V

BAT85

R3 D1

IKS1

2

C4

C3

56p

IC4a

111

R7

R6 5V

BM 0

IC5

CTRI4

1G- CX10

RX

X1 = 3.2768MHz

mim

the zero -crossing detector.

CT4RCX

4

5

8

9

11

12

13

7

4

6

14

13

15

3_

74HCT4060

Cl 0

R3

RI

H.

2

OPI3020

N4148

3k3

Cl11=

47n

R2

TrilA2

Al

TIC206D

MOV2

50V -

C3

700n

R4

100n

Ll

10...100p H

Fl

C2

4AT

MOV

250V

KS2

0

Lal

KS3]-0

L

r

I Zero -crossing detector

KS2 5

L

R3

18011

OPT01

4

TIL127

IC1

_1- RPD

NC3

4

5

6

8

0

HYS

PR

L

OR

RX

NC

PW

VZ

BR

V

V

TB

Cl R116

15 100n R210

470k11

9

14

TDA1023

3

12

a,,1L_4:::::::

17u0

.71

c-)

cono

E

c-)

00CK

(-7

rn

1

_J

C2

16V

MOV

250V

1

KS1

J

OMPONENTSLIS

PIT BOARD

Resistors:3 10KO

Capacitors:1 10µF 16V radial3 100nFC2: not fitted

Semiconductors:1 82531 74HCT32

1 74HCT1381 7805

Miscellaneous:I 34 -way header, angled

1

pins, with side latches26 -way boxheader

1 2 -way PCB terminal block,pitch 5mm18 -way 2 -row pin header

216 -way 2 -row pin headerjumper

F11;RZR3

C1

C3;C4;C5

IC1IC2IC3IC4

1(1

K2

KS1



COMPONENTS LIST

ZERO CROSSING DETECTOR BOARD

Resistors:1 39052

1 47052

1 lson1 siov S1OK250

R1

R2R3MOV1

Capacitors:1 10onF 630VDC C11 220µF 16V C2

Semiconductors:1 TDA10231 T1L127

IC1

OPTO1

Miscellaneous:2 2 -way PCB terminal

block, pitch 5mm KS1;KS2

COMPONENTS LIST

MAINS SWITCHING BOARD

Resistors:1 390521 10k52

1 31(n31 10052 1W2 SIOV S10K250

Capacitors:1 47nF2 100nF

R1

R2R3R4MOV1;MOV2

C1

C2;C3

Semiconductors:1 1N41481 TIC206D1 OPI3020 or MOC3020

Dl;D2TR1OPTO1

Miscellaneous:1 10-100pH 4A toroid choke L1

1 Fuse 4A slow plus PCBmount holder Fl

3 2 -way PCB terminal block,pitch 5mm KS1;KS2;KS3

supply voltage is taken from connectorK1 on the DMM board. Pin 1 has +5 V,and pin 2, ground. A third wire con-nects the temperature output signalsupplied by the LM35 to the U, inputon the DMM board. For your reference,Fig. 16 shows the pin connections ofthe LM35.

Setting up the program is illus-trated (and summarized at the sametime) in the series of photographs inFig. 14. Following the instructions in

Fig. 12. Artwork for the single -sided zero -crossing detector board.

74) 0\1

"6 -10 I 0(c)a5 Iffici.o2onLcs bp112 4513 SM0116

0

KS

(c)aS irlickoaonkc6 bpaz .1513 SPA0116 Nf

Fig. 13. Artwork for the single -sided mains switching board.

the captions with the screen pho-tographs should produce a workingcontrol system. This control is basedon the knowledge rules and the fuzzyset definitions provided by the demobatch on the Fuzzy Control One disk(order code 1721; see page 70). A dis-cussion of these parameters is unfor-tunately beyond the scope of thisarticle, since it would take up toomany pages of this magazine. This iswhere the 40 -odd pages of help textssupplied with the program come in(these pages can be printed to producea kind of manual). Once you have thetemperature control up and running,

you have a solid basis for further ex-periments. A couple of tips are inorder, though.

Tip 1. The file containing the fuzzydata does not define legible (i.e., mean-ingful) names for the various inputand output groups ('fuzzy sets'). Thegroup names are simply 1 through 7.Once the temperature control works,assigning legible names to the groupsis easy using the 'input division' and'output division' windows. This makesstudying the knowledge rules mucheasier.



rM

Fig. 14a. Start the program with DVM.BAT. Set the meter to the 4-V range. Leave it on for a couple of minutes while keeping theLM35 at a constant temperature. Go to the Multimeter Settingsmenu. Enter the temperature (in degrees celsius) in the 'calibrate'window. return to the multimeter screen, and leave the multimeter.This takes you back to the program's main menu.

Flit 4>%/ //>'Xiz

Fig. 14b. Click on the menu option 'hardware', and select 'set har-ware'. Select channel 1 as the input channel, and define the multi -meter card address (default: 0). Click in the white area behind'input type', and select the DMM card as the input device. The as-sociated window then appears. Turn off auto -ranging, and selectthe 4-V range. If necessary, correct the other entries in the win-dows. Copy the DMM calibration to the control settings. Return tothe previous menu.

I. 4

k

1.`" ' - \\N NZ,N,W s;Pkdv. *alit

\\N

'Fig. 14c. If necessary, set the output channel to 1. Set the card ad-dress to 1024 (assuming that the PIT card has the default setting).It is possible to enter the card number (1) or the real address rela-tive to the base address (standard: 1024). Select 'phase control'from the options under 'output type' and, if necessary, enter thevalues shown in the above window. Return to the main menu, andsave the file containing the hardware settings. save this file underthe name CONTROL.FZH.

;Mel trr h

a baxari

'I Its**, 14

Ilmipmt Aat.

1

..ilu i.1

FA

Fig. 14d. Load the control file DEMO1.FZK via the Files option inthe main menu. DEM01.FZK contains the fuzzy data on the controlsystem. These data require only minor changes in the input andoutput descriptions. Via the main menu, you enter the above menuafter passing through 'knowledge', 'input division' and 'channeldata'. Enter the data shown above.

Tip 2. Looking at the output division,you will notice that the direct outputvalue of the heating is spread over aninterval ranging from -100 to 100. Thismay strike you as unusual, if not odd,for a phase angle control which is ca-pable of regulating from 0 to maximumonly. The interval limits can be ex-plained as follows: we are looking atthe output of a proportional control, ofwhich the output signal equals theproduct: (error x amplification). Sincethe error can be positive or negative,and the amplification is a constant,

the output signal of the proportionalcontrol may be positive or negativealso. In the case of our example, thismeans that the interval -100 to 100corresponds to 'reduce lamp intensityas far as possible' (maximum lamp in-tensity reduction), or 'increase lampintensity as far as possible' (maximumlamp intensity increase). Note, how-ever, that this does not imply that thehardware has to process negative drivevalues. This is because of the knowl-edge rules, which have an effect simi-lar to that of integrating and

differentiating regulators, ensuring asum value with a range between 0 andmaximum under normal circum-stances. Although the sum may benegative or greater than the maximumin the rare case of extreme circum-stances arising, the effective result is'clipped' to nought or maximum.

There is one situation in which it isnot advisable to program the directoutput value division around zero:when you wish to create a proportionalcontrol based on knowledge rules ofthe type 'IF error THEN output' only.



tow

'11P'

i 411111 111 1111111ii 11114

low,. !wow t nor or

Irropr

In,

h1 011

11011

11111 IM

101111 6

Fig. 14e. Back again in the main menu, you arrive in the abovewindow via the selections 'control', 'output division' and 'channeldata'. Copy the data shown above. Return to the main menu, andsave the settings as CONTROL.FZK.

Fig. 14f. Finally, set the process characteristic. The above windowis reached from the main menu by selecting 'process' and then`define process characteristic'. The window is quite crowded,however, only the data in the upper section, and the ones in thefirst column, matter. The temperature you wish to set in the box isentered as the target value (see mouse arrow). Back in the mainmenu, save the process file under the name CONTROL.FZP.

Ur. 11 *auk tit* en 14 k frioi

'es Li

Fig. 14g. Before arriving in the above window, also save the 'op-eration' file as CONTROL.FZS for the sake of completeness. Next,to arrive in the above window, select (from the main menu) 'files'and 'make start batch'. if a file is missing from the list, or has a dif-ferent name, you have forgotten to save it under the name 'CON-TROL'. If necessary, correct this before proceeding. Click on theYES button, and select the desired 'start with' option. Click on the`change (F6)' button, and enter the name of the start batch (for ex-ample, CONTROL.BAT). Finally, click on the button 'save all'.

In this case, set up a direct output val-ues distribution with a range of zero tomaximum.

Tip 3. If you create a fuzzy division onan input and an output channel, youcan not locate the start of one group atthe same value as the end of the nextlower group. The software refuses toaccept this division because it is anoverlap of more than two groups. Theproblem may be solved by assigning agroup start value that is just higherthan the end value of the previousgroup.

Tip 4. Doubts can be raised aboutcalling the proposed temperature con-

trol 'intelligent', because it strives tokeep the temperature in the box con-stant. Many processes require a muchmore dynamic behaviour. Fortunately,that is not a problem because the pro-gram allows you to define increasingand decreasing target values using thewindows available for the process defi-nition. Alternatively, the process maybe subdivided into different steps (upto three), for instance; first increasetemperature, then keep it constant for10 minutes after desired temperatureis reached, then lower temperature ina controlled manner.

Tip 5. Try your hand at making adimmer. If you succeed in achieving

this (it should not be too difficult), andyou have fine-tuned the results, it isfair to claim that you have a reason-able 'command' of the program as wellas of fuzzy logic in general. A poten-tiometer of, say, 1 la -2 may act as aninput control. The input is divided intotwo groups, 'resistance at minimum'and 'resistance at maximum'. The out-put is divided into 'lamp on' and 'lampoff. Next, you need the following twoknowledge rules:

IF resistance minimum THEN lamp off:IF resistance maximum THEN lamp on.

The 'dead zone' of the control pot inthe low -resistance part of its span may



soluoacnoim see 1(3)snows 38 1-008-Jil CI t eudiaoR

Fig. 15. Artwork for the single -sided phase control board.

COMPONENTS LIST

PROP. PHASE CONTROL BOARD

Resistors:3 10k52 R1;R2;R32 10052 R4;R51 470Q R61 2k02 R71 4M127 R8

Capacitors:1 10),LF 10V radial C1

1 56pF C21 47pF 031 22pF trimmer C41 100nF 05

Semiconductors:1 BAT85 D1

2 BC517 T1;T21 74HCT08 101

2 74HCT74 IC2;1C31 74HCT14 IC41 74HCT4060 IC5

Miscellaneous:1 3.2768MHz crystal XTAL11 26 -way boxheader K1

5 2 -way PCB terminal block,pitch 5mm KS1-KS5

be eliminated by moving the two out-put groups upwards.

Tip 6. The bulb appears to light un-steadily; it even appears to flash from

LM35

e 011114111-

920049 - III - 13

Fig. 16. LM35 temperature sensor connections.

time to time. This is normal, however,and no cause for alarm. To make thecontrol as reliable as possible, the PITis initialized over and over again. This,in turn, may cause the triac to be trig-gered too early by a glitch, or too late.Although this imperfection is visiblewhen using a bulb, it has no effect onthe control proper.

Fig. 17. The PIT board and the phase control board fit in an Eurocard size plastic enclosure.The mains switching board and the zero -crossing board may be mounted into mains adaptorcases with a moulded mains plug/socket.


70

READERS SERVICESExcept in the USA and Canada, all orders, except forsubscriptions and past issues (for which see below),must be sent BY POST to our Dorchester office usingthe appropriate form opposite. Please note that wecan not deal with PERSONAL CALLERS, as no stockis carried at the editorial and administrative office.Readers in the USA and Canada should send orders,except for subscriptions (for which see below), to OldColony Sound Lab, Peterborough, whose full addressis given on the order form opposite. All US$ prices arepostpaid to customers in the fifty states except forbooks. Please add $2.00 for the first book and 750 foreach additional book ordered. Canadians please addUS$4.50 for the first book, and 750 for each additionalone. Canadians may expect Canadian duty chargeson shipments of any items except books.All other customers must add postage and packingcharges for orders up to £25.00 as follows: UK andEire £1.95; surface mail outside UK £2.45; Europe(airmail) £2.95; outside Europe (airmail) £3.70. For or-ders over £25.00, but not exceeding £100.00, thesep&p charges should be doubled. For orders over£100.00 in value, p&p charges will be advised.

SUBSCRIPTIONS & PAST ISSUESSubscriptions and past issues, if available, should beordered from Worldwide Subscription Service Ltd,Unit 4, Gibbs Reed Farm, Pashley Road, TICE-HURST TN5 7HE, England. For subscriptions, usethe order form on the opposite page. Prices of past is-sues (except July/August and December), includingpostage for single copies, are £2.70 (UK and Eire);£3.00 (surface mail outside UK); £3.20 (air mailEurope); £3.95 (airmail outside Europe). Prices of pastJuly/August and December issues, including postagefor single copies, are £3.75 (UK); £4.00 (surface mailoutside UK); £4.25 (airmail Europe); and £5.00 (air-mail outside Europe).

PAST ARTICLESPhotocopies of articles from January 1978 onwardscan be provided, postage paid, at £1.95 (UK and Eire),£2.10 (surface mail outside UK), £2.45 (airmailEurope), or £2.70 (airmail outside Europe). In case anarticle is split into instalments, these prices are applic-able per instalment. Photocopies may be orderedfrom our editorial and administrative offices.

COMPONENTS

Components for projects appearing in Elektor Elec-tronics are usually available from appropriate advertis-ers in this magazine. If difficulties in the supply ofcomponents are envisaged, a source will normally beadvised in the article. It should be noted that thesource(s) given is (are) not exclusive - other suppli-ers may also be able to help.

BOOKS

For book availability, see advertisement on page 59.

SHELF BOXElektor Electronics shelf box £2.95 $6.00

FRONT PANELSPROJECT

Timecode interfaceDigital functiongenerator

4 -Megabyte printerbufferFM tuner4MB printer buffer cardLC meterGuitar tunerNICAM decoder12VDC to 240VACinverter

Audio DACDig. audio/visual system

1.2 GHz multifunctionfrequency meterU2400B NiCd batterycharger

No. Price Price(£) (US$)

910055-F 8.80 17.60

910077-F 10.60 21.20

910110-F 11.45 22.90920005-F 13.20 26.40920009-F 8.25 16.50920012-F 11.45 22.90920033-F 8.80 17.60920035-F 8.25 16.50

920038-F 16.15 32.30920063-F 10.00 20.00

920022-F1 10.00 20.00920022-F2 19.40 38.80920022-F3 28.80 57.60

920095-F 13.80 27.60

920098-F 8.75 17.50

PROJECT No. Price Price(£) (US$)

Workbench PSU 930033-FInexpensive phase meter 930046-FMIDI channel monitor 930059Ah meter w. digital readout 930068Autoranging frequencyreadoutElectronic load

930034930088

17.00 34.0017.25 34.50Not availableNot available

Not availableNot available

EPROMS / PALS / MICROCONTROLLERSAmiga mouse/joystickswitch (1 x GAL 16V8) 6001 8.25 16.504 -Megabyte printer buffer(1 x 2764) 6041 15.30 30.608751 emulatorincl. system disk (MSDOS) 6051 29.40 58.80Connect 4 (1 x 27C64) 6081 15.30 30.60EMON51 (8051 assemblercourse) (1 x 27256 +disk 1661) 6061 20.00 40.00EMON51 (8051 assemblercourse) (1 x 27256 +disk 1681) 6091 20.00 40.00Multi -purpose Z80 card:FM tuner (1 x 27C256) 6101 20.00 40.00Multi -purpose Z80 card:GAL set (2 x GAL 16V8) 6111 11.15 22.30Multi -purpose Z80 card:BIOS (1 x EPROM 27128) 6121 15.30 30.601.2 GHz multifunctionfrequency meter(1 x 27C256) 6141 11.45 22.90Digital audio/visual system(1 x 27C256) 6171 10.30 20.60TV test pattern generator(1 x 27256) 6151 13.00 26.00DiAV system. Package:1 x 27512; 2 x GAL; 1 xfloppy disk (MSDOS) 6181 30.50 61.00PAL test pattern generator(1 x GAL 20V8-25) 6211 9.40 18.60Watt-hour meter (1 x 27256) 6241 10.00 20.00Four fold DAC (1 x GAL) 6251 10.75 21.50Multipurpose display decoder(1 x 2764) 6261 11.50 23.00Relative humidity meter(1 x 2764) 6301 14.50 29.008751 programmer (1 x 8751) 7061 46.40 92.80Microcontroller NiCd charger(1 x ST62E15) 7071 10.00 20.00Maxi micro clock (clock) 7081 11.50 23.00Maxi micro clock (darkroom timer) 7091 11.50 23.00Maxi micro Clock (cooking timer) 7101 11.50 23.00Mini micro clock (clock) 7111 11.50 23.00Mini micro clock (darkroom timer) 7121 11.50 23.00Mini micro clock (cooking timer) 7131 11.50 23.00VHF/UHF TV tuner(1 x 87C51) 7141 25.75 51.50

DISKETTES

Plotter driver (D. Sijtsma) 1541 11.15 22.30I/O interface for Atari 1571 7.65 15.30Tek/Intel file converter 1581 7.65 15.30B/W video digitizer 1591 11.15 22.30Timecode interface 1611 7.65 15.30RTC for Atari ST 1621 7.65 15.3024 -bit colour extensionfor video digitizer 1631 11.15 22.30PC controlled weatherstation - 3 (supersedesdisks 1551 and 1561) 1641 7.65 15.308051/8032 Assembler course(IBM version) 1661 7.65 15.308051/8032 Assemblercourse (Atari version) (3.5") 1681 7.65 15.30AD232 converter 1691 7.65 15.30GAL programmer (3 disks;upgrade: June 1993) 1701 11.15 22.30Multi -purpose Z80 card 1711 7.65 15.30Fuzzy Control One 1721 7.75 15.50Pascal library for MMC 1751 9.70 19.40Speech/sound memory 1771 7.65 15.30PC -aided transistor tester 1781 7.50 15.00IR receiver and DTMF decoderfor 80C32 SBC 1791 9 00 18.00I2C opto/relay card 1821 7 65 15.30Video digitizer for PCs 1831 14 50 29.00GAL programmer for Amiga 1841 11.00 22.00

PROJECT No. Price Price(£) (US$)

I2C alphanumerical display 1851 8.50 17.00Philips preamplifier 1861 8.50 17.00GAL programmer (excl. OpalJr. disks) 1881 10.75 21.50Precision clock for PCs 1871 8.50 17.00X2404 -to -8751 interfacing 1891 8.50 17.00

PRINTED CIRCUIT BOARDS

Printed circuit boards whose number is followed by a+ sign are only available in combination with the as-sociated software item, and can not be supplied sepa-rately. The indicated price includes the software.

MAY 1993FM stereo signal generator 920155 23.00 46.00VHF/UHF receiver 926001 19.00 38.00Philips preamplifier 930003 7.50 15.00Workbench PSU 930033 21.50 43.00

920075-1 4.70 9.40

JUNE 1993Spectrum VU meter 920151 13.00 26.00GAL programmer upgrade 930060 4.50 9.00Digital frequency readoutfor VHF/UHF receiver 926001-2 11.50 23.00Inexpensive phase meter- main board 930046 9.00 18.00- meter board 920018 4.75 9.50

JULY/AUGUST 1993Active 3 -way loudspeakersystem 930016 21.50 43.00Maxi micro clock 930020 15.50 31.00Four -fold DAC for PCs 930040 Kolter ElectronicSMD soldering station 930065 9.50 19.00VHF -low converter 926087 15.50 31.00I2C bus fuse (5 on 1 PCB) 934016 8.00 16.00Voice operated recording 934039 6.00 12.00General transformer PCB 934004 6.50 13.00Plant humidity monitor 934031 4.50 9.00Plant humidity monitor (suppiy) 934032 4.00 8.00

SEPTEMBER 1993Fuzzy logic multimeter - 1 920049-2 20.00 40.00Linear temperature gauge 920150 7.05 14.10Digital output for CD players 920171 Not availablePC -aided transistor tester 920144 9.75 19.50Harmonic enhancer 930025 13.50 27.00I2C alphanumerical displayincl. disk (1851) 930044+ 14.25 28.50

Mini micro clock 930055 7.50 15.00950-1750 MHz converter UPBS-1 1.95 3.90

OCTOBER 1993Stereo mixer UPBS-1 1.95 3.90MIDI channel monitor 930059 14.00 28.00Ah meter with digital display 930068 14.00 28.00Autoranging frequencyreadout 930034 12.50 25.00ROM -gate switchover forAtari ST 930005 30.25 60.50Microntroller-driven NiCdbattery charger (incl.programmed ST62E15) 920162+ 25.50 51.00Fuzzy logic multimeter - 2incl. disk (1721) 920049-1+ 23.75 47.50

NOVEMBER 1993Fuzzy logic multimeter - 3(four boards)

Precision clock for PCsincl. disk (1871)

VHF/UHF TV tunerboards -1 and -2, andµC 87C51 (7141)

Output amplifier with AFbandpass filterElectronic loadRelative humidity meterincl. EPROM (6301)

Power MOSFET tester

920049 Not available

930058+ 12.25 24.50

930064+ 57.25114.50

930071 6.75 13.50930088 Not available

930104+ 28.00 56.00930107 32.50 65.00

IA list of all PCBs, software products and front panels available through the Readers Services ispublished in the March, June, September and December issues of Elektor Electronics. ELEKTOR ELECTRONICS NOVEMBER 1993

xr

11-93Send this order form to *Elektor Electronics (Publishing)P.O. Box 1414Dorchester DT2 8YHENGLAND

*USA and Canada residents only: use $ prices,and send order form to:Old Colony Sound Lab,P.O. Box 243, Peterborough, NH 03458.Tel. (603) 924-6371, 924-6526Fax: (603) 924-9467

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J


TERMS OF BUSINESSHOW TO PAYUnless you have an approved credit accountwith us, all orders must be accompanied bythe full payment, including postage and pack-ing charges as stated on page 70, section 1.

Payment may he made by cheque drawnon a London clearing bank (but see para. 4below), postal order, VISA, ACCESS, MAS-TERCARD or EUROCARD (when paying bycredit card, the order must go to the card-holder's address). Do not send cash throughthe mail. Cheques and postal orders should becrossed and made payable to 'Elektor Electronics(Publishing)'.

Payment may also be made by direct trans-fer from a private or business Giro account toour Giro Account No. 34 152 3801 by com-pleting and sending to the National Giro Centre,in a National Giro postage paid envelope, aNational Giro transfer/deposit form. Do not sendGiro transfers direct to us, as this will delay yourorder.

If you live outside the UK, payment mayalso be made by Bankers' sterling draft drawnon a London clearing hank, Eurocheque madeout in pounds sterling (with holder's guaran-tee card number written on the hack), or US orCanadian dollar cheque, but such cheques, ac-cepted at the exchange rate prevailing at thetime your order is received, must be increasedby the equivalent of 15.00 to cover our bankers'negotiating Ice.

If you pay by Bankers' sterling draft, makeclear to the issuing hank that your full nameand address MUST he communicated to theLondon clearing bank.

Our bankers are National WestminsterBank PLC, 100 High Street, BRENTFORD

r

TW8 8AY, England. Our account number is4285 0134.

DELIVERYAlthough every effort will be made to dispatchyour order within 2-3 weeks from receipt of yourinstructions, we can not guarantee this time scalefor all orders.

RETURNSFaulty goods or goods sent in error may be re-turned for replacement or correction, but notbefore obtaining our consent. All goods re-turned should be packed securely in a paddedbag or box, enclosing a covering letter statingthe dispatch note number. If the goods are re-turned because of a mistake on our part, wewill refund the return postage. Goods returnedfor refund must he in resaleable condition andwill he subject to a 10% handling charge witha minimum charge of £2.50.

DAMAGED GOODSClaims for damaged goods must be received atour Dorchester office within 10 days (UK); 14days (Europe) or 21 days (all other countries)from the date on our "Recorded Delivery" slip.

CANCELLED ORDERSAll cancelled orders will be subject to a 10%handling charge with a minimum charge of£2.50.

PATENTSPatent protection may exist in respect of circuits,devices, components, and soon, described in ourbooks or magazines. Elektor Electronics (Publishing)do not accept responsibility or liability for fail -

ing to identify such patent or other protection.

COPYRIGHTAll drawings, photographs, articles, printed -cir-cuit boards, EPROMS, and cassettes published inour hooks or magazines (other than in third -partyadvertisements) are copyright and may not bereproduced or transmitted in any form or byany means, including photocopying and record-ing, in whole or in part, without the prior per-mission of Elektor Electronics (Publishing) inwriting. Such written permission must also beobtained before any part of these publicationsis stored in a retrieval system of any nature.

Nothwithstanding the above, printed -circuitboards may be produced for private and personaluse without prior permission.

LIMITATION OF LIABILITYElektor Electronics (Publishing) shall not beliable in contract, tort, or otherwise, for anyloss or damage suffered by the purchaser what-soever or howsoever arising out of, or in con-nexion with, the supply of goods or services byElektor Electronics (Publishing) other than tosupply goods as described or, at the option ofElektor Electronics (Publishing), to refund thepurchaser any money paid in respect of thegoods.

LAWAny question relating to the supply of goodsand services by Elektor Electronics (Publishing)shall be determined in all respects by the lawsof England.

April 1993

Annual subscription rates (1994)

United Kingdom £27.00Rest of the world (surface mail) £33.00AIRMAILEurope & Eire £34.00USA & Canada $57.00Middle East & North Africa £43.00Central & southern Africa £43.00Central & South America £43.00Australia & New Zealand £45.00Far East & South Pacific regions £45.00

Payment may be made by cheque in sterling drawnon a London clearing bank (but see below), postalorder, VISA, ACCESS, MASTERCARD or EUROCARD (in whichcase the subscription must be sent to the cardholder's ad-dress) or by direct transfer to our Giro Account no. 34152 3801. Do not send cash through the mail. Chequesand postal orders should be made payable to `ElektorElectronics Publishing'. Giro transfers should be made bycompleting and sending the appropriate transfer/depositform to the National Giro Centre (UK) or to your nationalGiro Centre.

If you live outside the United Kingdom, payment mayalso be made by Bankers' sterling draft drawn on a Londonclearing bank or Eurocheque. Eurocheques should bemade out in pounds sterling and have the holder's guaranteecard number written on the back.

US dollar cheques. Subscribers in the USA and Canada

only may pay in $US cheques.

The standard subscription order period is twelve months.If a permanent change of address during your subscrip-tion period means that copies have to be dispatched by amore expensive service, no extra charge will be made.Similarly, no refund will be made, nor expiry date extended,if a change of address allows the use of a cheaper service.

Student applications, which qualify for a 10% (ten percent) reduction in current rates, must be supported by ev-idence of studentship signed by the head of the college,school or university faculty.

Please note that new subscriptions take about four weeksfrom receipt of order to become effective.

Cancelled subscriptions will be subject to a charge of25% (twenty-five per cent) of the full subscription price or£7.50, whichever is the higher, plus the cost of any issuesalready dispatched. Subscriptions cannot be cancelled afterthey have run for six months or more.

Our bankers are National Westminster Bank PLC, SortingCode 60-03-23, 100 High Street, Brentford TW8 8AY,England. Our account number is 4285 0134.

June 1993

L J



Surplus alwayswanted for cash! THE ORIGINAL SURPLUS WONDERLAND. Surplus always

wanted for cash!

LOW COST PC SPECIALISTS - ALL EXPANDABLE - ALL PC COMPATIBLE8088 XT - PC99

)

Illelkowikaudipa

OrrgaTi 256k RAM - expandable

to 640k 4.7 Mhz speed 360k 5-1/4" floppy 2 serial & 1 parallel ports MS-DOS 4.01

Factory burnt -in Standard 84 key

keyboard 12" green screen

included In good used condition

Optional FITTED extras: 640K RAM £39. 12" CGA colourmonitor with card £39. 2nd 5-1/4" 360K floppy £29.95. 20mbyte M FM hard drive £99.

oniy£99.00(F)

FLOPPY DISK DRIVES51/4 " from £22.95 - 31/2" from £21.95!

Massive purchases of standard 51/4" and 31/2" drives enables usto present prime product at industry beating low prices! All units(unless stated) are removed from often brand new equipmentand are fully tested, aligned and shipped to you with a 90 day

286 AT - PC286

640k RAM expandable 2 serial & 1 parallelwith standard SIMMS ports

12 Mhz Landmark speed MS-DOS 4.01 20 meg hard disk Co -processor socket 1.2 meg 5-1/4" floppy Enhanced 102 key 1.4 meg 3-1/2" floppy keyboard

Clock & calendar with EGA driver on board batteryback up

BRAND NEW AND BOXED!

oniyE249.00 (F)

/The Philips 9CM073 is suggested for the PC286 and theCM8873 for the PC386. Either may use the SVGA MTS 9600if a suitable card is installed We can fit this at a cost of £49 00

\tor the PC286 and £39.00 for the PC386

POWER SUPPLIESPower One SPL200-5200P 200 watt (250 w peak) Semi openframe giving +5v 35a, -5v 1 5a +12v 4a (8a peak), -12v 1 5a,+24v (6a peak). All outputs fully regulated with over voltageprotection on the +5v output. AC input selectable for 110/240vac. Dimsl 3" x 5" x 2.5". Fully guaranteed RFE. £85.00 (B)

guarantee and operate from standard voltages and are of stand- Power One SPL130. 130 watts. Selectable for 12v (4A) or 24 vand size. All are IBM-PC compatible (if 3t2" supported). (2A). 5v @ 20A. ± 12v (d 1.5A. Switch mode. New. £59.95)B)3.5" Panasonic JU363/4 720K or equivalent £29.95(B) Astec AC -8151 40 watts. Switch mode. +5v @ 2.5a. +12v @3.5" Mitsubishi MF355C-L. 1.4 Meg. Laptops only' £29.95(8) 2a. -12v CO 0.1a. 6-1/4" x 4" x 1-3/4".New £22.95)B)3.5" Mitsubishi MF355C-D. 1.4 Meg. Non laptop £29.95)B) Greendale 19ABOE 60 watts switch mode.+5v @ 6a,+12v @5.25" EXTRA SPECIAL BRAND NEW Mitsubishi MF501B 15,+15v © 1a. RFE and fully tested.11 x 20 x5.5cms. £24.95)C)

360K. Absolutely standard fits most computers £22.95(B) Conver AC130. 130 watt hi -grade VDE spec.Switch mode.+5v* Data cable included in price. (4) 15a, -5v © 1a,±12v @ 6a.27 x 12.5 x 6.5cms.New. £49.95)C)

Shugart 800/801 SS refurbished & tested £175.00)E) Boshert 13090.Switch mode.ldeal for drives & system. +5v© 6a, burns) 90 day guarantee. 15" x 14" x 12". Only £139)E)Shugart 851 double sided refurbished & tested £275.00)E) +12v @ 2.5a, -12v (0 0.5a, -5v @ 0.5a. £29.95)B) Philips 9CM073 similar (not identical) to above for EGA/CGAMitsubishi M2894-63 double sided switchable Farnell G6/40A. Switch mode. 5v 4 40a.Encased £95.00)C) PC and compats. 640 x 350 resolution. With Text switch with

hard or soft sectors- BRAND NEW £250.00)E) Farnell G24/5S. As above but 24v © 5a. £65.00)C) amber or green screen selection. 14" x 12" x 13-1/2" £99(E)Dual 8" drives with 2 mbyte capacity housed in a smart case KME 10" high definition colour monitors. Nicewith built in power supply! Ideal as exterior drives! £499.00)F) tight 0.28" dot pitch for superb clarity andEnd of line purchase scoop! Brand new NEC D2246 8" 85 modern styling. Operates from any 15.625 khzmegabyte of hard disk storage! Full CPU control and industry sync RGB video source, with RGB analog andstandard SMD interface. Ultra hi speed transfer and access time WIN Et00 composite sync such as Atari, Commodoreleaves the good old ST506 interface standing. In mint condition Amiga, Acorn Archimedes & BBC. Measuresand comes complete with manual. Onl £299(E) only 13.5" x 12" x 11". Also works as quality Tv with our HUB

BBC Model B type computer on a board. A major purchase Telebox. Good used condition. 90 day guarantee. Only..£125 (E)allows us to offer you the PROFESSIONAL version of the BBC £145 (E)KME as above for PC EGA standard

Brand new Centronic 14" monitor for IBM PC and compatiblescomputer at a parts only price. Used as a front end graphicssystem on large networked systems the architecture of the BBC at a lower than ever price! Completely CGA equivalent. Hi-res

Mitsubishi 0.42 dot pitch giving 669 x 507 pixels. Big 28 Mhzboard has so many similarities to the regular BBC model B that bandwidth. A super monitor in attractive style moulded case.Fullwe are sure that with a bit of experimentation and ingenuity many 90 day guarantee. Only

. £129 (E)useful applications will be found for this board!! It is supplied NEC CGA 12" IBM-PC compatible. Highcomplete with a connector panel which brings all the I/O to 'D' quality ex -equipment fully tested with a 90and BNC type connectors - all you have to do is provide +5 and day guarantee. In an attractive two tone± 12 v DC. The APM consists of a single PCB with most major ribbed grey plastic case measuring 15"L xic's socketed. The ic's are too numerous to list but include a 13"W x 12"H. The front cosmetic bezel has6502, RAM and an SAA5050 teletext chip. Three 27128 been removed for contractual ktt. ,...EPROMS contain the custom operating system on which we reasons. Only.......... E69 (E)have no data, On application of DC power the system boots and 20" 22" and 26" AV SPECIALSprovides diagnostic information on the video output. On board Superbly made 'UK manufacture. PIL all solid state colourDIP switches and jumpers select the ECONET address and monitors, complete with composite video & sound inputs. Attrac-enable the four extra EPROM sockets for user software. Appx. tive teak style case. Perfect for Schools,Shops,Disco, Clubs.dims: main board 13" x 10". I/O board 14" x 3". Supplied tested In EXCELLENT little used condition with full 90 day guarantee.with circuit diagram, data and competition entry form. 20"....£135 22"....£155 26"....£185 (F)

386 AT - PC386J-0.13)0386%

......................

2 meg RAM expandedby slots

20 Mhz with 32k cache.Expandable to 64k

40 meg hard disk 1.2 meg 5-1/4" floppy VGA card installed

AnitiRE^:7

2 serial & 1 parallelports

MS-DOS 4.01 Co -processor socket Enhanced 102 keyboard Kwik Disk Accelerator

Software - FREEBRAND NEW AND BOXED!

Only E425.00F,MONITORS

THE AMAZING TELEBOX!Converts your colour monitor into a

QUALITY COLOUR TV!!

TV SOUND& VIDEOTUNER!

The TELEBOX consists of an attractive fully cased mainspowered unit, containing all electronics ready to plug into a hostof video monitors made by manufacturers such asMICROVITEC, ATARI, SANYO, SONY, COMMODORE,PHILIPS, TATUNG, AMSTRAD and many more. The compositevideo output will also plug directly into most video recorders,allowing reception of TV channels not normally receivable onmost television receivers (TELEBOX MB). Push button controlson the front panel allow reception of 8 fully tuneable 'off air' UHFcolour television or video channels. TELEBOX MB covers vir-tually all television frequencies VHF and UHF including theHYPERBAND as used by most cable TV operators. Compositeand RGB video outputs are located on the rear panel for directconnection to most makes of monitor. For complete compatibility- even for monitors without sound - an integral 4 watt audio

Trio 0-18 vdc bench PSU. 30 amps. Newamplifier and low level Hi Fi audio output are provided asFujitsu M3041 600 LPM band printerstandard. £32.95 DEC LS/02 CPU boardTelebox ST for composite video input monitorsRhode & Schwarz SBUF TV test transmitterTelebox STL as ST but with integral speaker £36.50 25-1000mhz. Complete with SBTF2 Modulator £6500Telebox MB as ST with Multiband tuner VHF -UHF -Cable. Calcomp 1036 large drum 3 pen plotter £ 650

& hyperband For overseas PAL versions state Thurlby LA 160B logic I £ 3755.5 or 6mhz sound specification. £69.95 1.5kw 115v 60hz power source £ 950

Telebox RGB for analogue RGB monitors (15khz) £69.95 Anton Pillar 400 Hz 3 phase frequency converter 75Kw POAShipping code on all Teleboxes is (B) Newton Derby 400 Hz 70 Kw converter

RGB Telebox also suitable for IBM multisync monitors with RGB Nikon PL -2 Projection lens meter/scopeanalog and composite sync. Overseas versions VHF & UHF call. Sekonic SD 150H 18 channel Hybrid recorder

SECAM / NTSC not available. HP 7580A Al 8 pen high speed drum plotter £1850Kenwood DA -3501 CD tester, laser pickup simulator £ 350

BBC Model B APM Board£100 CASH FOR THE

MOST NOVELDEMONSTRATABLE

APPLICATION!

Only E29.95 or 2 for £53 (B)SPECIAL INTEREST

No Break Uninterruptable PSU's

14" Forefront Model MTS-9600 SVGAmultisync with resolution of 1024 x 768.0.28pitch. "Text" switch for word processing etc.Overscan switch included. Ideal for the PC-

st 386 or PC -286 with SVGA card added. Also`4.' compatibe with BBC, Amiga, Atari (including

the monochrome high resolution mode), Ar-chimedes etc. In good used condition (possible minor screenburns). 90 day guarantee. 15" x 14" x 12". Only £159(E)

14" Philips Model CM8873 VGA multisyncwith 640 x 480 resolution. CGA, EGA orVGA, digital/analog, switch selectable.Sound with volume control. There is also aspecial "Text" switch for word processing,spreadsheets and the like. Compatible withIBM PC's, Amiga, Atari (excluding themonochrome high resolution mode), BBC,

Archimedes etc. Good used condition (possible minor screen

CALL FOR PRICING ON NTSC VERSIONS!Superb Quality 6 foot 40u

19" Rack CabinetsMassive Reductions

Virtually New, Ultra Smart!Less Than Half Price!

Top quality 19" rack cabinets made in UKby Optima Enclosures Ltd. Units featuredesigner, smoked acrylic lockable frontdoor, full height lockable half louvered backdoor and removable side panels. Fully ad-justable internal fixing struts, ready

punched for any configuration of equipment mounting plus readymounted integral 12 way 13 amp socket switched mains distribu-

Brand new and boxed 230 volts uninterruptable power supplies Lion strip make these racks some of the most versatile we havefrom Densei. Model MUK 0565-AUAF is 0.5 kva and MUD Microline 183. NLQ 17x17 dot matrix. Full width. £139 (D) ever sold. Racks may be stacked side by side and therefore1085-AHBH is 1 kva. Both have sealed lead acid batteries. MUK Hyundai HDP-920. NLO 24x18 dot matrix full width. £149 (0) require only two side panels or stand singly. Overall dimensionsare internal, MUD has them in a matching case. Times from Oume LetterPro 20 daisy. Qume QS -3 interface. £39.95 (D) are 77-1/2"H x 32-1/2"D x 22"W. Order as:interrupt are 5 and 15 minutes respectively. Complete with full Centronics 152-2 9 x 7 dot matrix. Full width. £149 (D) Rack 1 Complete with removable side panels £275.00 (G)operation manuals MUK £249 (F) MUD £525 (G) Centronics 159-4 9 x 7 dot matrix.Serial. 9-1/2" width £ 99 (D) Rack 2 Less side panels £145.00 (G)

1992 Winter Issue of Display News now available - send large SAE - POCKED with bargaInsi :See

01811°

I 9 le . I I.. .I ..

.

-ELECTROIYIC5-

0

0

BRAND NEW PRINTERS

. .

£ 470£2950£ 150

POA£750

£2000

9 . .

1I.

s

III

4 0

All prices for UK Mainland. UK customers add 17.5% VAT to TOTAL order amount. Minimum order £10. PO orders from Goyernment,Uniyersities,Schools 8 Local Autho 'tieswelcome -minimum account order £30. Carriage charges (A)=£2.00. (A1).£3.75. (B)=E5.50. (C)=£13.50. (D)=211.50. (E)=-£14.30 (F)=£18.00 (G)=Call Scotland surcharge: call.All goods supplied subject to our standard Conditions of Sale and unless otherwise stated guaranteed for 90 days. All guarantees on a retum to base basis. Rights reserved tochange prices 8 specifications without prior notice. Orders subject to stock. Quotations willingly given for higher quantities than those stated. Bulk surplus always wanted forcash.


F L COLOUR GAME TO ELECTRONIC PRODUCTS

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BS 5750Part 2 1987

Level B:Duality Assurance

RS12750

Over 700 colour packed pages with hundredsof brand New Products at Super Low Prices,

on sale now, only £2.95.Aval a rom all branc es , se ecte ranc es o

RSIVESSLL in Scotland ONLY, and Maplin stores nationwide.The Maplin Electronics 1994 Catalogue - UNIQUELY DIFFERENT!

Africa customers please contact MAPLIN (SOUTH AFRICA)Tel: (024) 5 I -5 I 24

THE BEST LOW COST PROGRAMMERSDESIGNED & MANUFACTURED IN THE UK

0 AS

FOR MORE DETAILS, DEVICE LIST AND DEMO DISK CALL NOW ON

ICE TECHNOLOGY LTD, UNIT 4, PENISTONE COURT, STATION BUILDINGS, PENISTONE, S. YORKS, S30 6HG, UK.

SPEEDMASTER 1000SPEEDMASTER 1000E

UNIVERSAL PROGRAMMERNI Superfast PC based programmerII Programmes; EPROMS UP TO 8M BIT,

FLASH EPROMS, EEPROMS, BPROMS,NVRAMs, MICROs (8748/51),PALs, GALs, EPLDs, PEELS,MACHS, MAPLs, MAX

Plugs directly intoO cipp

parallel port 1000E Version has ROM/RAM

emulator built in: 128k(1 Mbit) standard,optional 512K (4Mbit)

MICROMASTER 1000MICROMASTER 1000E

UNIVERSAL PROGRAMMERIII Programmes: EPROMS UP TO 8M BIT.

FLASH EPROMS, EEPROMS,BPROMS, NVRAMs, PALs,GALs, EPLDs, PEELs,MACHs, MAPLs, MAX etc.

PLUS over 80 different Microsincluding 8748/51, 68HC705, 68HC711,PICs, Z86, TMS320, TMS370 etc DIPsWITHOUT ADAPTORS ORPERSONALITY MODULES!

Package adaptors available.II 1000E Version has ROM/

RAM emulator built in:128K (1Mbit) standard,optional 512K (4 Mbit)

SPEEDMASTER 8000GANG/SET PROGRAMMER

8 way, Pc or stand alone Super -fast programming times,

manufacturer recommendedalgorithms

32 pin devices as standardII Support for 8748,51,

TMS370, PIC Micros and40 pins.

WHY BUY AN INFERIOR IMPORTED PROGRAMMER WHEN YOU CAN HAVE A MANUFACTURERAPPROVED UNIVERSAL PROGRAMMER/EMULATOR DIRECT FROM ICE TECHNOLOGY!

[i We offer the best range of low-cost programmers available, now including our uniqueUNIVERSAL PROGRAMMERS WITH BUILT IN EMULATORS

E Unrivalled device support, for example the Micromaster 1000 programmes PICS, Z86, 87C705, 68HC705,TMS370, 77C82 ETC WITHOUT ADAPTORS, as well as the full range of Eproms, PLDs etc supported byall our universal programmers.

E Approved by National. Semiconductor for their full range of PALs, GALs, and MAPLs - other programmersclaiming approval are often only approved for EPROMs - a much less exacting specification!

El All our programmers and programme/emulators work off the standard parallel port with any IBMcompatible PC, even laptops

O Unbeaten programming times: Programme a 27256 in just 5 SECONDS including download and verify.[i] Easy upgrade path between Models. 0 0 Y

0s -

o.

74

ELEKTOR ELECTRONICS is available from, among others:CRICKLEWOOD

ELECTRONICS LIMITED40 Cricklewood Broadway,

London NW2 3ETTelephone 081 450 0995

Fax 081 208 1441

L.P. HANNEYYour electronic componentspecialist for Avon, Wilts &

Somerset.77 Lower Bristol Road, Bath,

Avon, Telephone 0225424811

AAGE NIELSEN1 Sortedam DosseringenDK-2200 Copenhagen,

Denmark,Telephone 01 39 30 10

Fax 031 39 05 02

TABACCARIA BRITANICAPraca do Duque da

Terceira 191107 Lisboa, PortugalTelephone 932 4752

MK KNJIGARNASlovenska 29

LjubljanaSlovenia

Telephone 061 150 196

THE ELECTRONIC SHOPElectronic components, test

equipment, telephoneaccessories, computer

accessories, microphones,disco lighting, speakers, turntables, mixers, meters, stylus.

29 Hanging Ditch,Manchester M4 3ES,

Telephone 061 834 1185

HELMHOLT ELEKTRONIKFarvevej 2

DK-7600 Struer, DenmarkTelephone 97 85 26 11

D.P. HOBBS (NORWICH)LTD

Electronic componentspecialists. Amateur radio

equipment.13 St. Benedict Street,

Norwich NR2 4PE,Telephone 0603 615786

RCE ELECTRONICCENTRE

Boulevarden 34DK-9000 Aalborg, Denmark

Telephone 98 16 07 10

TECHNICAL BOOKS &MAGAZINES

289-299 Swanston StreetMelbourne, Australia 3000

Telephone 663 3951MANCOMP

240 Platt LaneManchester M14 7BS

EnglandTelephone 061 224 1888

ELEY ELECTRONICS100-104 Beatrice Road

Leicester LE3 9FFTelephone (0533) 515 944

VEJLE RC ELEKTRONIKSdr Brogade 42

P 0 Box 332DK-7100 Vejle, DenmarkTelephone 75 83 25 33

INEL Co.P.O. Box 1397

JL. Hariang Banga No. 3Bandung 40116

IndonesiaGREENWELD27 Park Road

Southampton SO1 3TBEngland

Telephone (0703) 236 363Fax (0703) 236 307

OMNI ELECTRONICSStock a wide range of

electronic components.174 Dalkeith Road,

Edinburgh EH16 5DX,Telephone 031 667 2611

BEBEK ELECTRONICSHirsimetsantie 26

SF -15200 Lahti 11Finland

Telephone (18) 33 99 46

ADVERTISING INElektor Electronics

The closing date for copy is five weeks beforepublication date (four weeks for camera-ready copy).Colour advertisements should be submitted on film

separations. Elektor Electronics is published on the thirdThursday of the month preceding cover date.

Elektor Electronics (Publishing) will not be liable forany loss caused by the failure of any advertisement toappear for any reason, and they do not accept liability

for printers' errors, although every care is taken to avoidmistakes.

Copy instructions, artwork and all correspondencepertaining to advertisements should be addressed to

Elektor Electronics (Publishing)Advertisement Office

3 Crescent TerraceCHELTENHAM GL50 3PE

EnglandTelephone (0242) 510 760

FAX (0242) 226 626

INDEX OF ADVERTISERS

AutonaBadger BoardsBaylin PublicationsB K ElectronicsBull ElectricalCirkit DistributionCricklewood ElectronicsDisplay ElectronicsElectroValueElektor ElectronicsHCT ElectronicsICE TechnologyInstrutek (UK)J P DistributionKare ElectronicsLabcenter ElectronicsLloyd ResearchMacro Cross AssemblersMaplin Electronic SuppliesMicrogemMicroAmpsNumber One Systems LtdPico Technology LtdPOWERwareRoline Systems LtdSCSStewart of ReadingSuma DesignsThose EngineersTsien (UK) LtdUltimate TechnologyViewcom ElectronicsWhite House SystemsZE Systems

5958371752292873535959

Inside back cover235345381659

Back cover2945

43653394529443754

Inside front cover8, 9

5837


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