f ; 6C107/8/9 BC547/8/9 BCS67/8/9 BC516/517 BC2 12/3/4 IN4001/2/3 IN4004/6 . . 1M007 74 SERIES TTL • / , // X' ;■ •.-•is* • . • v Elektor November 1978 — 3 22 Newfand Street /k^rfer mg Northants. Technical enquires ring Kett 520910 sales & order enquires 83922. Shop open Monday to Saturday 9.30 to 6.00 p.m. Early closing Thursday. Answer phone order service after 6.00 p.m 83922 Back lUtfW of E «ktor & fcleklof finwrti normety *r»> *b*« from *tock Outntxy and trade enqu«n«* welcomed lor all component* Quantity and trade enquires welcomed for all components. A Member Firm of tne Bnket Developments (Holdings) Group EXPERIMENTING WITH SC MP BUILD YOUR OWN MICROPROCESSOR DEVELOPMENT SYSTEM The current Elektor senes leads to the construction of a hexadecimal seven segment microcomputer with a cassette interface. Further development is planned, to produce a private computor system with visual display unit, cassette based programmes and an extended memory capacity. To enable you to reduce your costs we are preparing a kit order list for each part of the ser es to enable you to order |ust those parts you need and not to duplicate com- ponents you already have. Please send SAE for lists or phone Kettering 520910 for further details about_thejgnei_ . . J Announce new low*' price* on many product* end a wide 'ang> ol money laving bulk offer*. Sand SAE for full ust. All components FULL SPEC- e&p/io 76(1/10 75p/10 180/10 76p/10 4ap/io 56p/10 7 Op/ 10 1N4148 Rod LEO 0.2 Rad LEO 1 25 Ve»ow/Green 0.2 Vei>ow/Green 126 0L707 LM741 op amp 6 pm OIL LM555 1 < 1 1» SS?8 *8 IL 74 opto i»oleto> 3*10 IRL60 infrared led LO 241 tnfr* rod transmitter 140 2N6777 photo derlmgion ' M ORP12 light dependent remtor 00 Wire ended neon • • -20 LEO red o.2" 16 LEO md 0.128" 12 LEO green: yellow; deer 0.1" 22 LEO yean, yellow; 0.126“ OISCOUNT Mai' order customer* deduct 10% on order* over C20.00 VAT add high rate to ’item*, standard rate io other* POST 6 PACKING 50 p on order* under C7.60. Otherw le free Oversea* pleaie add freight coin and •tate turfece or Air. DELIVERY AH order* p«oc*»»*d on dev of receipt, All good* offered subject to availability end our con- dition* of tale PAYMENT. Ce»h. cheoue o» postal order witn order Accen. Me»ter«h*rge. Bank Amencere v-*a o» Barclay- card number by phone or letter for order* over C2 O'fioai order* from Government bodes, accepted, but minimum invoice charge €2 60, GUARANTEE. All devflr WJB usa^ot SifiQ UP *0 JJV «tev»On<(> k> OP and In this issue, several 'Santatronics' circuits are described: little projects that should prove suitable as Christmas gifts. November may seem rather soon for this, but the idea is to allow time for neat construction and 'gift -wrapping'! As to the cover, 'Santatronics' is associated both with electronics and with 'Dashing through the snow' . . . contents selektor UK-16 cackling egg-timer 11-02 ASCII keyboard 11-06 Tag! 11-12 This strenuous game can now be played without physical effort. joysticks — G. Wiinsch 11-16 Joystick -type controls are becoming as popular in the elec- tronic game field as they have always been for remote control of model aircraft and boats. Provided the appearance isn't considered too important, it is quite feasable to construct a joystick control that will be quite suitable for most appli- cations. digiscope — E. Muller 11-17 For examining pulse trains in digital circuits oscilloscope is an invaluable aid. However, oscilloscopes are expensive, and furthermore the analogue display capability of a conventional 'scope is rarely required in digital circuits. The Tigiscope offers a low-cost alternative. ring the bell and win a prize 1 1-22 extending the TV scope 11-25 As explained last month, a normal TV set can be used as an oscilloscope. A simple converter for this purpose was des- scribed in detail: the 'TV scope-basic version'. In an introduc- tory article it was explained that this basic version could be extended. Before discussing the details of the extension circuits, a fuller explanation of the underlying principles is in order. 15 duty-cycles at the turn of a switch 11-30 hello, all you folks back home! 11-31 Instead of gathering around the fire as in the 'good old days', we tend to gather around the telephone. The circuit described will pick up the telephone conversation and reproduce it via a loudspeaker, so that several people can listen in. applikator 11-34 R.P.M. and dwell meter using a TCA 965. SC/MP 'Mastermind' tm programme 11-35 F. Schuldt Pit your wits against the computer with the aid of the 'Mastermind' TM programme, which is designed to run on the Elektor SC/MP system. pocket bagatelle 11-38 There are many electronic versions of popular games which can be played without recourse to a TV set. One of the more simple (but not necessarily easy!) games, which is ideally suited as a small Christmas present, is 'bagatelle'. market 11-41 advertiser's index UK-28 COMING SOON In response to readers queries, the additional circuits required to extend the range of the electronic piano (Elektor, September 1978 ) to eight octaves (!) will be described next month. 11-02 — elektor november 1978 cackling egg-timer cackling egg-timer Boiling eggs is one of the more delicate of culinary occupations, especially since the ideal consistency of a boiled egg can be the subject of quite heated discussions: the hard-boiled spurn soft hearts, and the difference is a matter of minutes. It is not surprising, therefore, that some fertile brain in the distant past came up with that highly practical invention: the egg-timer. Of recent years, electronics engineers have devoted a surprising amount of their time, ingenuity and eggspertise into the quest for an electronic version, and circuits are published at regular intervals. However, to the best of our knowledge, the circuit presented here is the first to cackle loudly when the timing period has elapsed! Figure 1. Block diagram of the cackling egg- timer. The section enclosed in dotted lines is the 'cackle generator’. Figure 2. Output waveforms from the three oscillators in the cackle generator. Figure 3. The complete circuit. The upper portion is the timer; the lower section is the cackle generator. Electronics is invading the most unlikely fields. After several experiments, with sometimes highly comical results, a member of the Elektor design team has even succeeded in imitating the sound of a self-satisfied hen — using a single CMOS IC. A simple timer, consisting of two further ICs, completes the novel egg-timer. The block diagram is shown in figure 1 . The timer section is fairly conventional. A decade counter receives pulses from a clock generator. Since the period time of the clock generator is 1 minute, the decade counter effectively counts min- utes. The counter is started by pressing the ‘reset’ button. When the time selected by the multi-position switch has elapsed, two things happen: the clock generator is blocked, stopping the count, and the electronic switch (S) is closed. This switch applies power to the second part of the circuit, enclosed in dotted lines: the ‘cackle circuit’ that imitates the smugly complacement hen. This circuit consists of three square- wave generators, two of which are volt- age-controlled (the VCOs). The three generators are labelled accord- ing to the frequency they produce: ‘L’ for low, ‘M’ for mid-range and ‘H’ for high frequency — relatively, of course. The audio signal is derived from the third VCO (‘H’). The other VCO, ‘M’, provides the basic modulation required for the ‘bock-bock-bock’ effect. The first generator adds two further effects: the repetition rate of the cackling and the duration of each cycle. These two effects, combined, also determine the number of clucks-per-cycle. If one considers the characteristic 1 9985 1 11-04 — elektor november 1978 cackling egg-timer Parts list Resistors: R1 = 100 k R2 = 680 k R3.R16 = 10 k R4,R6,R18 = 220 k R5,R7 . . . R12 = 1 M R13 = 2M2 R14.R15 = 820 k R17 = 220 n PI = 100 k, preset P2 = 220 k, preset Capacitors: Cl = 10 n C2 = 100 m/10 V C3 = 1m5 C4 = 470 m/10 V C5 = 1 80 n C6,C7 = 470 m/6 V C8,C9 = 1 m CIO = 1 n C11 = 22 n Cl 2 = 10m/10 V Semiconductors: D1 . . . D4.D6 = DUS D5 = DUG T1 ,T2 = BC 107, BC 547 or equ IC1 = CD 4093 IC2 = CD4017 IC3 = CD 4049 Miscellaneous: LS - 8 S2/200 mW loudspeaker 51 = single-deck 1 1-way switch 52 = pushbutton, single-pole make cackling produced by domestic fowl after laying an egg, it will be apparent that three or four normal ‘bock’s are followed by one emphasised and long- drawn-out ‘BO-O-O-O-CK’ with pro- gressively rising frequency. In the cackle circuit, this effect is obtained by feeding the output from the ‘L’ generator through an RC-network to the ‘H’ gener- ator. The delicate interplay of these three generators provides a surprisingly realistic imitation of a proud mother hen. Figure 2 illustrates the signals at various points in the cackle generator. The circuit The complete circuit is shown in figure 3. The upper half of the circuit is the timer section; the rest is the cackle generator. The clock generator for the timer consists of gates N1 . . . N3, with the associated components. It produces an asymmetric square-wave, with a period time (set by P2) of 1 minute. This oscil- lator can only produce an output signal when the output of N4 is at logic ‘1’, i.e. when the input to N4 is logic ‘O’. Assuming that the counter, IC2, is initially reset, it will count the clock pulses and its outputs will swing to logic ‘1’ in turn. When the output selec- ted by SI is reached, the input to N4 will therefore become logic M \ stopping the oscillator. The count is stopped and, simultaneously, T1 is turned on. This transistor is the ‘electronic switch’, S, shown in figure 1 : it applies power to IC3 in the cackle generator, causing the hen to give voice. The lower half of the circuit, the cackle generator, may appear rather confusing cackling egg-timer elektor november 1978 — 1 1-05 Figure 4. Printed circuit board and com- ponent layout for the cackling egg-timer (EPS 9985). Figure 5. When it comes to 'Santatronics', the gift-wrapping is almost as important as the contents. The demonstration model shown here is perhaps somewhat large for normal domestic use, but it may help to stimulate the imagination. at first sight. Reference to the block diagram may help to clarify matters. The free-running generator ‘L’ consists of N5 and N6; the ‘M’ and ‘H’ VCOs are similar circuits using N7/N8 and N9/N10, respectively. A diode, D2, is included in the ‘L’ gen- erator to obtain an asymmetrical output signal. This signal is fed, via C9 and R7, to the ‘M’ VCO. The output from the ‘M’ VCO now contains most of the information required for the ‘bock-bock- bock-bo-o-o-ock’ effect. As illustrated in figure 2, the number and length of the ‘bock’s, the breathing space and the (rising) frequency shift are all deter- mined, with one exception: the modu- lation for the final, long-drawn-out ‘b-o-o-o-ck’. This signal is derived from the output of the ‘L’ generator via an RC network consisting of RIO, R 1 1 , R12, C6, C7 and three diodes. Capaci- tors C6 and C7 and diodes D3 and D4 together are basically equivalent to a bipolar electrolytic. D5 limits the negative swing of the voltage across R 1 1 . The outputs from the ‘M’ generator and from the RC network are summed and applied to the ‘H’ generator, which produces the actual audio signal. A single-transistor buffer stage, T2, drives the loudspeaker. The desired volume can be set with PI . Construction The electronics involved in the egg-timer can be mounted on the printed circuit board shown in figure 4. The supply voltage (9 V) and the low current consumption make the circuit suitable for battery operation. If a mains supply a used, due care must be taken to re- liably insulate the complete unit: it will be used in decidedly damp surroundings, quite possibly beside the kitchen sink! There are only two adjustments. As mentioned earlier, PI sets the desired volume. P2 is used to calibrate the timer. The easiest way to do this is to set SI to position ‘1’ and adjust P2 until the timing interval (i.e. the time between pressing the reset button and the first squawk) is exactly one minute. The switch positions will then correspond to timing intervals in minutes. There is, of course, no reason why P2 should not be set to give a different timing interval. For instance, if the initial period is set at Vh minutes, the switch positions will correspond to multiples of this time. Position 2 will be 3 minutes, position 3 will correspond to 4 x h minutes, and so on. Position 9 would then be 9 x 1 14 = 1 3Vz minutes — ideal for ‘bullet’-lovers. No matter what the setting of P2, position 0 will always correspond to 0 minutes: the hen will give voice as soon as the reset button is operated. This option is included mainly for demonstration purposes. As with most ‘Santatronics’ circuits, the ‘gift’ value is greatly enhanced by the wrapping. Since this is an ideal challenge to individual creativity, no constructional details for a case will be given here. Just a suggestion: a novel idea would be to shape it like an egg or, of course, a hen. Perhaps some further inspiration can be gained from figureS: our demonstration model, which has been one of the center-pieces at otherwise serious exhibitions! M 11-06 — elektor november 1978 ASC II keyboard The most common method of communicating with a microcomputer is via an alphanumeric keyboard. The keyboard assembly described here is principally intended for use with the 'Elekterminal', which will be described next month, however the standard design ensures that it can also be employed with other data terminals. As its name suggests, an alphanumeric keyboard is one which contains both alphabetic characters and (decimal) numerals as well as the usual punctu- ation marks. Obviously, for the com- puter and data terminal to be able to ‘understand’ one another, they have to speak the same language, and to this end, several standard formats have been devised, which allocate a particular binary code to each alphanumeric character. The most popular and widely- used format is the American Standard Code for Information Interchange, usually referred to by its acronym, ASCII. This is an 8-bit code, in which the most significant bit (MSB) is used as a parity bit for error detection. Since 7 binary digits can be arranged in 128 different combinations, it is clear that a considerable number of the 7-bit codes are left over once all the decimal digits, alphabetic characters and punctuation symbols have been catered for. In the ASCII format the remaining codes are assigned control functions. A complete listing of the ASCII character set, with an explanation of the control characters, is shown in table 1 . Keyboard circuit Although, in principle, it would be la OUTPUT OUTPUT ASC II keyboard elektor november 1978 -11-07 AY-5-2376 Top View ©Xx c • 1 40 D Frequency Control A Frequency Control B C 2 39 3X0 Frequency Control C C 3 38 3X1 Shift Input C 4 37 3X2 Control Input C 5 36 3X3 Parity Invert Input C 6 35 □ X4 Keyboard Matrix Parity Output C 7 34 3X5 Outputs Data Output B8 C 8 33 3X6 Data Output B7 C 9 32 3X7 Data Output B6 C 10 31 3Y0 Data Output B5 C 11 30 □ Y1 Data Output B4 C 12 29 3Y2 Data Output B3 C 13 28 3Y3 Data Output B2 C 14 27 3Y4 Data Output B 1 C 15 26 JY5 Keyboard Matrix Strobe Output C 16 25 3Y6 Inputs 3 Y7 ^ v gndC 17 24 O V GG C 18 23 3Y8 Strobe Control Input C 19 22 3Y9 Data & Strobe Invert Input C 20 21 3Y10 9965 - 1b Figure 1. Pin configuration and block diagram of the AY-5-2376 amount to a circuit diagram of the keyboard. Figure 2. This figure illustrates which el- ements of the matrix are occupied by keys. YO Y1 Y2 Y3 Y4 Y5 Y6 Y7 Y8 Y9 Y10 parts list to figures 1 , 3 and 4 Resistors: R1 = 100 k R2 = 680 k Capacitors: Cl = 4n7 C2 = 56 p Semiconductors: IC1 = AY-5-2376 (General Instru ments) Miscellaneous: 62 keyboard switches: TKC type MM9 — 2 We have been informed that the TKC switches are to be supplied in the UK by the following companies (see advertisement section for further details): Astec Europe Ltd., Windsor De Boer Electronics, Eindhoven Marshall's Ltd., London Figure 3. Track pattern of the keyboard p.c.b. (EPS 9965). Figure 4. Component overlay of the keyboard p.c.b. Note that the copper layout and component overlay are reproduced here at 90% of actual size. ASC II keyboard elektor november 1978 — 1 1-09 possible to design a keyboard which had a separate key for each of the 128 characters, it would obviously be not only extremely expensive, but rather unwieldy. Thus, as is the case with typewriters, each key is normally assigned a double (or triple) function, with a shift key to determine which of the codes which correspond to a par- ticular key is in fact generated. The key closures are converted into ASCII code by means of an encoder IC; this is basically little more than a ROM in which the complete ASCII code is stored, and which is addressed by the keyboard. There are several IC encoders currently available, the one used here is the AY-5-2376 from General Instru- ments. Pin-out details and internal block diagram of the IC - which constitutes virtually the entire circuit diagram of the keyboard — are shown in figure 1 . In order to keep the wiring of the keyboard as simple as possible, the keys are arranged in a matrix as shown in figure 2. For reasons which will become clear, not every point in the matrix requires a key. In addition to those keys in the matrix, several additional keys are shown in figure 1 , namely a break key, two page keys, a reset key, a shift key and a control key. The break- and page keys are intended for the Elekterminal (to be described next month), whilst the reset key is optional. The shift- and control keys are used to select the different functions of each key in the keyboard matrix. This is illustrated in table 2, which lists the characters obtained when the ‘N’ (normal), ‘S’ (shift) and ‘C’ (control) keys are de- pressed. As can be seen, a large number of characters occur more than once in the table, which is the reason why not all the points in the matrix need be occupied by keys. A number of ASCII characters are assigned non-standard functions in the Elekterminal. These are listed in table 3, along with an explanation of their new function. If the keyboard is used with other data terminals, then the characters can, of course, retain their original significance. All mechanical switches are prone to a certain amount of contact bounce. In order to eliminate the effects of this the IC contains a delay network which can be controlled externally. The length of delay is determined by the time con- stant Rl/Cl . Via wire links a, b, c and d, pins 6 and 20 of the IC can be connected either to a ‘0’ or ‘1* voltage level. In the latter case, the data outputs, strobe-output and parity output are inverted. In normal use these pins are grounded, i.e. only links c and b are made. Construction In order to facilitate construction of the keyboard a printed circuit board was designed, which is intended to accomo- 11-10 — elektor november 1978 ASC II keyboard Table 1. Character Binary Bit 7 to Bit 0 Hexadecimal Character Binary Bit 7 to Bit 0 Hexadecimal NUL 00000000 00 @ 01000000 40 SOH 00000001 01 A 01000001 41 STX 00000010 02 B 01000010 42 ETX 0000001 1 03 C 01000011 43 EOT 00000100 04 D 01000100 44 ENQ 00000101 05 E 01000101 45 ACK 00000110 06 F 01000110 46 BEL 000001 1 1 07 G 01000111 47 BS 00001000 08 H 01001000 48 HT 00001001 09 1 01001001 49 LF 00001010 0A J 01001010 4A VT 00001011 0B K 01001011 4B FF 00001100 oc L 01001100 4C CR 00001101 0D M 01001101 4D SO 00001110 0E N 01001110 4E SI 00001 1 1 1 OF O 01001111 4F DLE 00010000 10 P 01010000 50 DC1 00010001 11 Q 01010001 51 DC2 00010010 12 R 01010010 52 DC3 00010011 13 S 01010011 53 DC4 00010100 14 T 01010100 54 NAK 00010101 15 U 01010101 55 SYN 00010110 16 V 01010110 56 ETB 00010111 17 w 01010111 57 CAN 00011000 18 X 01011000 58 EM 00011001 19 Y 01011001 59 SUB 00011010 1 A z 01011010 5A ESC 00011011 IB [ 01011011 5B FS 00011100 1C \ 01011100 5C GS 00011101 ID ] 01011101 5D RS 00011110 IE A 01011110 5E US 00011111 IF — 01011111 5F SP 00100000 20 • 01100000 60 t 00100001 21 a 01100001 61 " 00100010 22 b 01100010 62 # 00100011 23 c 01100011 63 $ 00100100 24 d 01100100 64 % 00100101 25 e 01100101 65 & 00100110 26 f 01100110 66 ' 00100111 27 9 01100111 67 ( 00101000 28 h 01101000 68 ) 00101001 29 i 01101001 69 * 00101010 2A j 01101010 6A + 00101011 2B k 01101011 6B 00101100 2C 1 01101100 6C - 00101101 2D m 01101101 6D 00101110 2E n 01101110 6E / 00101111 2F o 01101111 6F 0 00110000 30 P 01110000 70 1 00110001 31 q 01110001 71 2 00110010 32 r 01110010 72 3 00110011 33 s 01110011 73 4 00110100 34 t 01110100 74 5 00110101 35 u 01110101 75 6 00110110 36 V 01110110 76 7 00110111 37 w 01110111 77 8 00111000 38 X 01111000 78 9 00111001 39 y 01111001 79 00111010 3A z 01111010 7A ; 00111011 3B { 01111011 7B < 00111100 3C 1 01111100 7C = 00111101 3D } 01111101 7D > 00111110 3E 01111110 7E 7 00111111 3F DEL 01111111 7F NUL — null, or all zeros SOH — start of heading STX — start of text ETX — end of text EOT — end of transmission ENQ — enquiry ACK — acknowledge BEL — bell BS — backspace HT — horizontal tabulation LF — line feed VT — vertical tabulation FF - form feed CR — carriage return SO — shift out SI — shift in DLE — data link escape DC1 — device control 1 DC2 — device control 2 DC3 — device control 3 DC4 — device control 4 NAK - negative acknowledge SYN — synchronous Idle ETB — end of transmission block CAN — cancel EM — end of medium SUB — substitute ESC — escape FS — file separator GS — group separator RS — record separator US — unit separator SP — space DEL — delete Table 1. This table lists the complete ASCII character set, along with the corresponding binary and hexadecimal values for each character. Table 2. This table illustrates the relationship between the keyboard matrix and the corre- sponding set of characters. It is apparent that, since several characters appear more than once, a key is not required for every element of the matrix. Table 3. A number of ASCII characters are assigned non-standard functions in the Elekterminal. This table indicates which characters are involved and also their new significance. Figure 5. Keyboard layout. ASC II keyboard elektor november 1978 — 11-11 Table 2. C: control S: shift V 0 V 1 V 2 V 3 V 4 V 5 y 6 V7 V 8 y 9 y 10 N: normal C NUL SOH STX ETX EOT ENQ ACK BEL DC1 DLE SI x 0 S NUL SOH STX ETX EOT ENQ ACK BEL DC1 @ 4- N NUL SOH STX ETX EOT ENQ ACK BEL DC1 P 0 c DLE VT FF SO CR NAK SYN ETB CAN EM SUB x 1 s DLE [ \ t 1 NAK SYN ETB CAN EM SUB N DLE K L N M NAK SYN ETB CAN EM SUB C FS GS RS US SP US x 2 s = FS GS RS US < > SP , 4— N — FS GS RS US < > SP • 4- C DLE US BS ESC GS CR LF x 3 s • P DEL ’ BS { } CR LF N 0 P 4- BS 1 1 CR LF c CR SO STX SYN ETX CAN SUB x 4 s + ? > < M N B V C X z N / • . m n b V c X Z c FF VT LF BS BEL ACK EOT DC3 SOH FF ESC x 5 s L K J H G F D S A FF ESC N 1 k i h 9 f d s a FF ESC C SI HT NAK EM DC4 DC2 ENQ ETB DC1 HT VT X 6 s 0 1 U Y T R E W Q HT VT N O i u V t r e w q HT VT c RS FS x 7 s ) < ' & % $ = •• ! ESC 1 N 9 8 7 6 5 4 3 2 1 t \ Table 3. CTL + L = FF (FORM FEED) = home cursor + page clear CTL + J = LF (LINE FEED) = LF + cursor 4 CTL + 1 = HT (HORIZONTAL TAB) = cursor -► CTL + K = VT (VERTICAL TAB) = cursor t CTL + M = CR (CARRIAGE RETURN) = CR = erasure to end of line CTL + H = BS (BACKSPACE) = cursor *- CTL + \ = FS (FILE SEPARATOR) = home cursor SFT + T = ESC (ESCAPE) = scroll up CTL + Z = erasure of current line date all the necessary hardware (i.e. including the keys). Figures 3 and 4 show the copper track pattern and component overlay respectively. The board layout is designed to take TKC type MM9 keyboard switches. The keyboard layout is illustrated in figure 5 . A certain amount of care should be used when mounting the keys. Since they are only held in place by their terminal pins one must be careful to ensure that the keys are correctly positioned, otherwise there is the danger that the key tops may touch one another and a key will remain depressed after being hit. The best solution is to mount the keys row by row, using a jig or template to hold the keys in place. The connections between the keyboard and receiver section of the terminal are best made using ribbon cable, via which the keyboard can simultaneously be provided with the necessary supply voltages of +5 and 1 2 V. The current consumption of both supplies is a maximum of 10 mA. H L 11-12 — elektor november 1978 One of the simpler games known to man is 'Tag'. Variations of the game were probably played by cave-men. There are very few rules: it is simply a question of one person being 'him' or 'it', and running around trying to 'catch' or 'tag' the other player(s). What the game lacks in sophistication, it makes up for in sheer physical strenuousness. In its basic form it is not really a parlour game, either; the risk of toppling tables, falling flowers and the cat in the curtains is more than most parents are prepared to take. Since the main characteristics of the coming months are snow, sleet and Santa Claus, a safe, indoor version of the game should prove welcome. Figure 1. Block diagram of Tag. As the two players operate their control potentiometers, the course of the game is apparent from a fascinating variety of optical and acoustical indicators. Figure 2. The complete circuit. Instead of running like mad, the two players of the electronic version of tag merely twist the knob of a poten- tiometer madly to and fro. The rules are as simple as in the original game: player ‘A’ attempts to manipulate his knob in such a way that the pointer of a multimeter moves out of a small area around mid -scale; player ‘B’ does his utmost with his knob to keep the pointer within the area. In other words, player ‘A’ tries to ‘run away’, and player ‘B’ tries to catch him. If ‘B’ is successful, in that he succeeds in tracking ‘A’ for a sufficient length of time, a LED lights to indicate that ‘B’ has ‘caught’ his opponent. To increase the effect, sound effects are included: the player controls also sweep two oscillators up and down. The outputs from these oscillators can be fed to the two channels of a stereo amplifier, producing penetrating wails that sweep up and down through the audio range. The block diagram (figure 1) illustrates the basic principles involved. The control potentiometers ‘A’ and ‘B’ provide voltages ua and ug. The differ- ence voltage ug — ua is determined, and added to half the supply voltage Ub- The result is a voltage um which swings to and fro around VHJb, depending on the values of ua and ug. This voltage is displayed on the mul- timeter. Obviously, if the two poten- tiometers are in the same position the difference voltage ug — ua will be zero, and the meter will read mid-scale (assuming that full-scale corresponds to the full supply voltage). If player ‘A’ now ‘runs away’, turning his knob in such a way that ua decreases, the pointer will move to the right. Player ‘B’, seeing this, counters by twisting his knob in the same direction, causing the pointer to swing back toward mid-scale. A further optical indication is provided by means of two LEDs. The voltage um is fed to a ‘window comparator’. This part of the circuit is discussed in detail elsewhere in this issue (see ‘Pocket Bagatelle’). For the present appli- cation it is sufficient to know that the Tag! Tag! a strenuous game can be played without physical effort output voltage uc from the window comparator is logic zero as long as the input voltage um remains within the voltage ‘window’, and becomes logic ‘one’ as soon as um is outside the ‘window’. In other words, since the voltage window is a small range around half supply voltage, uc is logic zero as long as the pointer reads approximately mid-scale, and becomes logic 1 if the pointer moves out of this area. As soon as this happens, a LED lights (‘escaped’). If player ‘A’ succeeds in catching ‘B’ again, the LED will extinguish. If ‘A’ can now ‘hold on to’ player ‘B’ for a sufficient length of time (determined by an RC-network) a different LED will light: ‘Gotcha!’ The two VCO’s are driven direct from the player control voltages, ua and ug. If the outputs from these oscillators are fed to the two channels of a stereo amplifier, an audible indication is obtained of the positions of the two controls. If ‘A’ has caught ‘B’ — in other words, if the control voltages are equal — the tones produced by the two VCO’s will also be (almost) the same. The circuit Having understood the basic principles, the circuit itself (figure 2) is fairly straightforward. PI and P2 are the player controls. The voltages at the wipers can be varied between approxi- mately 3 V and 9 V. The two voltages are fed to the differential amplifier Al. Half the supply voltage (ViUb) is avail- able at the R7/R8 junction, and this reference voltage is also fed in at this point. The output from Al is the voltage um, also shown in the block diagram. The pointer instrument is connected to this point. Two options are available, a built- in milliameter or a normal multimeter, as will be discussed later. The same volt- age is also fed to the window compara- tor, consisting of A2 and A3. The width of the window can be set with P3 (‘handicap’). Obviously, a wide window makes it easier to catch the opponent, 11-14 — elektor november 1978 Tag! nnnftOQO, .annooaa o ooooot j m ouooodo D OOOOO 6666 6666 6 Parts list Resistors: R1,R2= 1k2 R3 . . . R6= 100 k R7,R8,R9 = 4k7 RIO = 5k6 R11,R13= 330 O R12 = 470 k R14 = 47 k R15= 22 k R1 6 = see text PI ,P2 = 4k7 (5 k) linear potentiometer P3= 22 k (25 k) linear potentiometer P4 = 4k 7 (5 k) preset potentiometer P5 = 47 k (50 k) preset potentiometer P6.P7 = 100 k preset potentiometer Capacitors: Cl = 10 m/1 6 V C2.C3 = 4n7 C4 = 470 m/1 6 V Semiconductors: D1 ... DIO = DUS D11,D12= LED T1 . . . T4 = TUN IC1.IC2 = CD401 1 ICJ = LM 324 Miscellaneous: SI = pushbutton, single-pole, make M = meter, see text *f.s.d. U b = 12 V U b = 10 V 50 pA 220 k 220 k 100mA 120 k 100 k 300 mA 39 k 33 k 500 mA 22 k 22 k 1 mA 12k 10k 3 mA 3k9 3k 3 5 mA 2k2 2k2 and vice versa. The two diodes D1 and D2 are the (wired) OR gate shown in the block diagram. The voltage at the junction of these diodes (u£) is ‘high’ when the voltage um is outside the ‘window’, causing Dll to light: ‘escaped’. As long as uc remains high, capacitor Cl will be charged. If uf: becomes ‘low’ (‘B’ has caught ‘A’), Cl discharges slowly through R 1 1 , R 1 2 and Dll. When the voltage on Cl falls below the voltage set by P4, the output of A4 swings high and D12 lights — Tag! The time that ‘B’ must ‘hang on to A’ depends on the setting of P4, and can be anything up to a few seconds. The remainder of the circuit consists of the two VCOs. These circuits may be familiar by now: the modified ‘simple CMOS squarewave generator’ described in the Summer Circuits issue is also used in ‘Ring the bell and win a prize’, described elsewhere in this issue. For the first VCO, T1 and T2 are a current mirror and diodes D3 . . . D6 are a bridge circuit. Together, these com- ponents are a kind of current-controlled impedance. Since the current mirror is fed through a series resistor, R14, the net result is a voltage-controlled impedance. This impedance is incorpor- ated in a conventional CMOS oscillator circuit in such a way that voltage variations at the input (R14) cause changes in the output frequency. In other words, the complete circuit is a Voltage Controlled Oscillator, or VCO. Tag! elektor november 1978 — 11-15 79007 Figure 3. Printed circuit board and com- ponent layout (EPS 79007). Figure 4. The only really important thing about the case is that it should be strong enough! The controls could also be mounted in the main case, but this usually proves awkward unless one of the players happens to be left-handed. The output level from this oscillator can be set with P6. The second VCO is basically identical, with one minor exception: preset potentiometer P5 is included, so that the ‘tracking’ of the two oscillators can be adjusted. Construction A printed circuit board design and corresponding component layout are shown in figure 3. Although only four NAND gates are used in the circuit, use of a single quad NAND gate IC proved unsatisfactory: the two oscillators tended to ‘bite each other’. For this reason, two IC’s are used, one for each VCO. As far as the meter M is concerned, there is a wide range of options. Micro- or milliameters with any sensitivity between 50 /aA and 5 mA f.s.d. can be used. In this case, the value of the series resistor R16 is chosen so that the meter reads full scale when the full supply voltage is connected across the series- connection of meter and resistor. The value of the resistor should be approxi- mately: U b R >6=iT- 2 T (kn) > tf.s.d. where Ub is in volts and If.s.d. (the full-scale sensitivity of the meter) is in milliamps. In the interest of saving the batteries in thousands of pocket calcu- lators around the world, the Table lists values for R 1 6 for several common full- scale sensitivities and for two supply voltages. The nearest standard value has been chosen in each case — the meter doesn’t have to be a precision instrument! If a multimeter is available there is no real need to invest in a new meter for this circuit — unless, of course, one is afraid to let that expensive item fall into the hands off one’s offspring. If a mul- timeter is to be used, R16 can be replaced by a 1 k resistor — just in case of accidental shorts — and the supply voltage is chosen equal to a suitable volt- age range on the meter (10 V f.s.d., for instance). It is advisable to mount this type of circuit in a sturdy case. The players are liable to get highly excited! Figure 4 is just one possible suggestion. In this case, the two controls are mounted separately and connected to the main unit by means of a standard three-core (mains) cable. H 1 1-16 — elektor november 1978 joysticks joysticks (G. Wiinsch) Joystick-type controls are becoming as popular in the electronic game field as they have always been for remote control of model aircraft and boats. One of the major drawbacks of this type of control is, however, the expense - they usually cost rather more than two normal potentiometers! Provided the appearance isn’t con- sidered too important, it is quite feasable to construct a joystick control that will be quite suitable for most applications. The two sketches illustrate the construc- tion of a simple and a more sophisti- cated version. In the simple version shown in figure 1 , the two potentiometer spindles are joined at right-angles. This can, of course, be done in several ways; using a block of brass or plastic with holes drilled in it, as shown, is probably as good as any. One of the potentiometers is mounted on a stand; the other is fastened to a control lever. The more sophisticated version, shown in figure 2, works on the same basic principle: two normal potentiometers joined at right-angles. However, in this case two springs are included to return the control lever to neutral. The con- struction is, understandably, more com- plicated. One of the potentiometers is mounted on a base-plate. A metal (or plastic) right-angle is mounted on the spindle. A spring is looped round the potentiometer spindle, with its open ends resting against a bolt. A longer bolt, mounted on the right-angle, engages the spring in such a way that the spring acts to centre the right-angle — and, with it, the poten- tiometer. Two further bolts, mounted on the base-plate, serve as end stops (the height of sophistication!). The second potentiometer is mounted on the second flange of the right-angle. The control lever is mounted on its spindle, with a similar spring-and-bolts con- struction to centre it. M elektor november 1978 - 11-17 digi scope For examining pulse trains in digital circuits an oscilloscope is an invaluable aid. However, oscilloscopes are expensive, and furthermore the analogue display capability of a conventional 'scope is rarely required in digital circuits, since only two voltage states, corresponding to logic 0 and 1, are encountered. The Digiscope offers a low-cost alternative to the conventional oscilloscope for digital work, and displays digital pulse trains on two rows of light-emitting diodes. E. Muller The principle of the Digiscope is illus- trated in figure 1 . The digital waveform to be displayed is sampled at a number of points and the value of the waveform at the instant of each sample (logic 0 or 1) is stored in a number of latches (flip-flops). The Q and Q outputs of the latches are connected to two rows of LEDs, the upper row indicating logic 1 and the lower row indicating logic 0. The pattern displayed by the two rows of LEDs will thus correspond to the digital waveform. This is shown in figure 1 , where a digital waveform is shown together with the corresponding display on the Digiscope. Any number of samples can be taken, and obviously the greater the number of samples per cycle of the waveform the more accurate will be the resulting display. However, the cost factor must be considered, since each sample requires a flip-flop and two LEDs, and a reasonable compromise of 16 flip-flops and 32 LEDs was adopted. Block diagram Figure 2 shows the block diagram of the Digiscope. The memory consists of 16 D flip-flops. A ‘timebase’ consisting of a clock oscillator, 4-bit counter and l-of-16 decoder ‘scans’ the memory, i.e. takes the clock input of each flip-flop high in turn. The input signal is connec- ted to the D inputs of all the flip-flops, so that if the input is high when the clock input of a particular flip-flop is activated then the Q output of that flip- flop will go high. Conversely, if the input signal is low then the output of the flip-flop will remain low. The scanning of the memory by the time- base is analogous to the spot sweeping across the screen of a conventional oscilloscope, hence the term ‘timebase’ is used for this function. Like the timebase of a conventional oscilloscope, the timebase of the Digiscope has coarse and fine speed controls. Fine speed control is effected by varying the frequency of the clock generator between 100 kHz and 500 kHz, whilst coarse speed control is effected by preceding the 4-bit counter by a variable frequency divider, whose division ratio can be varied from 1 to 1000 in steps of 1,2, 5, 10, 20 . . . etc., just like a conventional oscilloscope. The timebase speed range is from 4 /as per LED i.e. 64 /as for a single scan of the complete display, to 20 ms per LED, i.e. 320 ms to scan the display. Trigger circuit In addition to a timebase with a wide speed range it is also important to have a reliable trigger circuit. When the digiscope is used to display repetitive pulse trains the trigger circuit ensures that each timebase sweep starts at the same point in successive pulse trains. If the timebase were not synchronised to the display in this manner then the display would appear to run in one direction or the other depending on the relative speeds of the timebase and the input signal. In addition to being triggered by the input signal the time- base may also be triggered by an external signal or allowed to free run. Complete circuit In order to keep the circuit as simple and cheap as possible it was decided to base the design on the 74-series TTL logic family, since this logic family is readily obtainable, inexpensive, can operate at high speeds and is capable of supplying sufficient current to drive LEDs directly. The full circuit diagram of the Digiscope is given in figure 3. It should be noted that as it stands in figure 3, the Digiscope operates only with TTL logic. However, with the addition of one 4050 CMOS IC, being used as a level converter interface, it can be used with CMOS. The 4050 should be powered by the 5 V supply in the Digiscope, this will allow CMOS 11-18 - elektor november 1978 circuits with a suplly voltage of up tc about 15 V to be tested. Since there are 6 buffer amps in one 4050, it can also be used for level conversion of the ‘clock input’, and ‘trig, input’. Since the 4050 can only drive 2 TTL loads, it is advisable to connect 2 of the buffer amps in the 4050 parallel, since the input loading of the Digiscope is 3. The display memory consists of 1 6 D flip-flops contained in 8 7474 dual D flip-flop packages, IC1 1 to IC18. Since the D inputs of these flip-flops present a total of 16 TTL loads and a normal TTL output can drive only 10 TTL Figure 1. This diagram illustrates the principle of the Digiscope. Figure 2. Block diagram of the Digiscope. Figure 3. Complete circuit of the Digiscope. Resistors R29a, b, c and d can, of course, be replaced by a single resistor (R29) as on the p.c. board. Table 1. Listing of the timebase ranges for each position of the timebase switch. loads it is necessary to drive the D inputs of FF7 to FF22 in two groups of 8. This is done by a pair of EXOR gates, which buffer the input signal and pro- vide a choice of normal or inverted display depending on the position of S9. The memory is scanned by a 74154 binary to l-of-16 decoder, IC10, which is driven by the four-bit counter, IC7. The remainder of the timebase circuit comprises the clock generator (which consists of two monostable multi- vibrators, MMV3 and MMV4, cross- coupled to form an astable multivibrator with good frequency stability) and the variable frequency divider consisting of 51 : triggering int./ext. 52 : triggering pos./neg. S3ab : trigger hold off 54 : single/norm 55 : pushbutton single sweep 56 : clock input invert/norm 57 : clock divider 58 : free run/norm 1= triggering) 59 : data input norm/invert B40C1000 ooooaoo] e .nnnnnnnnnnnnj touuuuuuuouuu 'tj ouuuuoo 1 O O OOOOOU 11-20 — elektor november 1978 digiscope C13 oH ho 1C 19 dig i scope elektor november 1978 — 1 1-21 parts list to figures 3, 4 and 5 Resistors: R1 = 1 M R2,R4,R9,R1 0,R1 1 = 1 k R3,R5,R7,R8 = 4k7 R6.R28 . . . R35 = 2k2 R12 . . . R27 = 270 SI R36 . . . R39 = 1 SI P1,P2 = 47 k Capacitors: Cl = lOn C2,C3 = 390 p C4,C9 ... Cl 3 = 1 00 n C5,CG = 470 p C7 = 1000 m/10 V C8 = 330 n Semiconductors: IC1 ,IC3 = 741 23 IC2.IC1 1 . . . IC18 = 7474 IC4,IC5,IC6 = 7490 IC7 = 74193 IC8,IC9 = 7473 IC10 = 74154 IC19 = 7805 IC20 = 7486 D1 . . . D32 = LED 81 = B 40 C 1000 (40 V/1 A bridge rectifier) Miscellaneous: SI ,S2,S4,S6,S8, S9 = switch SPDT S3 = switch DPDT S7 = switch single pole 1 1 (1 2-)-way transformer at least 9 V/1 A counters IC4 to IC6 and flip-flops FF3 to FF6. The ranges covered by the time- base switch are listed in table 1. An external clock signal may also be fed in via EXOR gate N3 in normal or inverted form. The trigger circuit comprises mono- stables IC1 and flip-flops IC2, and offers a variety of triggering modes. SI offers a choice of internal or external trig- gering, whilst S2 selects between normal and inverted trigger signal. By switching S4 to the single-shot mode the timebase can be triggered manually by pressing S5. S3 can be used to switch to ‘hold- off’, in which mode the trigger pulse can be delayed for a variable period. Finally, the trigger circuit can be inhibited and the timebase allowed to run continu- ously by switching S8 to the ‘free-run’ position. Figure 4. Printed circuit board and com- ponent layout for the Digiscope, excluding the display section (EPS 9926-1). Figure 5. Printed circuit board and com- ponent layout for the display section of the Digiscope (EPS 9926-2). Power supply The Digiscope requires a stabilised 5 V power supply. The circuit of a suitable supply consisting of a transformer, bridge rectifier, reservoir capacitor and an IC regulator is also shown in figure 3. Construction The complete circuit of the Digiscope is mounted on two printed circuit boards. The p.c. board whose layout is shown in figure 4 accommodates all the logic circuits and the power supply, with the exception of the mains trans- former, whilst the display is mounted on the board whose layout is given in figure 5. This should be connected to the main board using a 33-core ribbon cable or something similar. H 11-22 — elektor november 1978 ring the bell and win a prize One of the favourite attractions at fair-grounds has always been some variation of 'bash-the-block-with- a-mallet'. Originally, this was a purely mechanical device, although of recent years technology has advanced to the stage where no self-respecting fair-ground attraction is complete without a dazzling display of flashing lights. However, electronics have now progressed to the point where a portable version is possible — suitable for desk-top use. In olden times, the strongest men in the village used to demonstrate their prowess by walloping an innocent wooden peg with a heavy mallet. Through a more-or- less intricate system of sturdy levers, this resulted in the launching of a metal ball towards the heavens; the mightier the wallop, the higher it rose. Real muscle-men could deliver a suf- ficiently hard blow to send the ball right up to the top of the structure, where it would hit a bell with an almighty clang. This won them a prize and, more importantly, the esteem of all those who witnessed the feat. Nowadays, of course, the battle for superiority is more likely to be fought out indoors - specifically, at parties and business meetings. The desk-top model described in this article should therefore fulfil a major need. Operated as it is by fist-power instead of by means of a blunt instrument, it can also prove useful as an ideal ’fury-indicator’ for managers. In fact, every executive should have one. the bell and a prize! The circuit Before even starting to design the circuit, a suitable force sensor must be found. This should not only be suf- ficiently sturdy; it should also be reasonably cheap and readily available. The solution chosen may be somewhat inelegant, but it has proved highly satisfactory in practice. The sensor consists of a piece of con- ductive foam plastic, of the type cur- rently in use for packing CMOS IC’s. The specific resistance of this foam drops dramatically when the foam is compressed — this is not particularly surprising, in view of the fact that the carbon particles in the foam become more tightly packed as the volume decreases. Remember the carbon mike? The mechanical construction is shown in figure 1 . The foam is placed between two metal plates (with wires attached) and this ’sandwich’ is placed in a suit- able wooden holder. A two-piece wooden block serves to spread the force connecting wires wooden blocks wooden holder 79006 1 metal plates or laminate board conducting foam of the blow evenly over the upper metal plate. For most ordinary mortals, with the possible exception of karate experts, it is advisable to glue some softer material over the upper surface of the target area — hitting a solid wooden block with the bare hand, hard, is not everybody’s idea of fun! Having settled the details of the sensor, it can now be reduced to a small rec- tangle marked R x and included in the circuit shown in figure 2. The sensor, R x , and R1 together form a potential divider. A sudden change in the resist- ance R x causes a sudden jump in the voltage at the R X /R1 junction. This voltage ‘spike’ is passed through Cl to the input of opamp A1 . The gain of this amplifier stage can be preset by means of PI, to suit the characteristics of the sensor and the (expected) strength of the potential customers. The output from A1 (a positive-going spike) is passed to a peak detector and to a trigger circuit. The peak detector consists of D1 and C3. The highest voltage level appearing at the output of A1 as a result of a blow on the sensor is ‘stored’ in C3. This voltage is buffered by the super-emitter- follower T1/T2 and is available as the output voltage Up. It can be used to drive a pointer instrument (e.g. an AVOmeter) or a LED voltmeter, as will be described later. The trigger circuit consists of A2, R4 . . . R7 and P2. The trigger threshold (and thus the strength of the blow required to ‘score’) can be set with P2. The output from A2 is fed, via T3, to a set/reset (RS) flip-flop consisting of N1 and N2. This flip-flop controls the ‘ding’ generator, A3/A4, which is derived from the ‘electronic gong’ (see the ‘Summer Circuits’ 1978 issue, circuit no. 13). The output can be fed, via P4, to a power amplifier; if a suitably ‘hefty’ amplifier and loudspeaker are used, a very grati- fying ‘bong’ will be produced. To further enhance the audible effect, a VCO (voltage controlled oscillator) is also included. The peak output voltage, Up, is fed via R 1 1 to C4. C4 will there- fore charge up slowly to Up, causing the VCO (T4,T5,N3,N4 and the associ- ated diodes, resistor and capacitor) to produce a slowly-rising wail. However, the VCO can only operate if the Figure 1. The sensor consists basically of conducting foam, sandwiched between two metal plates and mounted in a wooden box. Copper laminate board can, of course, be used instead of the metal plates. Figure 2. Complete circuit for 'Ring the bell and win a prize'. Figure 3. A suitable 12 V power supply. 11-24 — elektor november 1978 ring the bell and win a prize Parts list Resistors: R1,R4,R10,R21,R22 = 10 k R2,R8,R12,R13,R14,R15, R23 = 100 k R3 = 33 k R5.R6 = 2k2 R7 = 220 k R9 = 220 n R1 1 ,R17,R18 = 1 k R16 = 180 k R19.R20 = 1 5 k PI ,P3,P4 = 100 k preset poten- tiometer P2 = 10 k linear potentiometer Capacitors: Cl ,C6,C8 = 100 n C2,C5 = 4n7 C3 = 1p5/15 V C4 = 1 00 m/1 5 V C7.C9 = 220 n Semiconductors: T1 . . . T5 = IC3 = CA 3086 D1 . . . D7 = DUS N1 . . . N4 = IC1 = CD4011 A1 . . . A4 = IC2 = LM 324 Miscellaneous: SI = pushbutton, single-pole, make R x = conducting foam plastic, approximately 3" square (7x7 cm). RS flip-flop N1/N2 has been triggered. The circuit can be reset by means of SI : C3 is rapidly discharged and the RS flip-flop is reset. Final notes The most sensational effect can be obtained by using a LED voltmeter to indicate the U p output level. A suitable circuit is the ‘UAA 180 LED voltmeter’ described in Elektor 33, January 1978, p. 1-20. Both the circuit described here and the LED voltmeter will operate on a simple 1 2 V supply like the one shown in fig- ure 3. extending the TV -scope elektor november 1978 — 11-25 extending the TV-scope As explained last month, a normal TV set can be used as an oscilloscope. A simple converter for this purpose was described in detail: the TV scope - basic version'. In an introductory article it was explained that this basic version could be extended, thereby eliminating its two major weaknesses: limited usefulness at high frequencies and lack of triggering facilities. Before discussing the details of the extension circuits, a fuller explanation of the underlying principles is in order. The basic version of the TV scope, described last month, can be used to display low-frequency signals on the screen of a domestic TV receiver. This is achieved by sampling the input signal and using each sample to determine the position of a white spot on one line of the final picture. Sync pulses are added to complete the video signal, and an (optional) VHF/UHF modulator is included. The exact details of the circuits were described last month; for the discussion of the extension circuits it is sufficient to consider the basic version as a ‘black box’ with a low- frequency input and a video (or VHF/UHF) output. The only important technical details for the present are the sampling rate (TV line frequency, i.e. approximately 15 kHz), the fixed time- base frequency (TV frame frequency, i.e. 50 Hz, corresponding to 20 ms) and the lack of triggering facilities. To extend the capabilities of the TV scope, the first priority is to get away from the fixed timebase frequency. Basically, what is required is a timebase expander, that is, a circuit that will ‘slow down’ a signal to any desired ‘speed’. The signal goes in at one end, at high frequency, and comes out at the other with its frequency reduced to a manageable value. In a way, a tape recorder with several tape speeds is equivalent to a timebase expander. If a signal is recorded at, say, 1 5"/s and then played back at 7V2"/s, the frequency of the output signal will be half that of the original. This corresponds to ‘timebase expansion’. Timebase expansion can also be achieved by purely electronic means. In the extended version of the TV scope, the (by now familiar) bucket-brigade mem- ory is used. The principle is simple: feed the signal into a bucket-brigade memory using a suitable (input) clock frequency and then retrieve it from the memory using a lower clock frequency. Figure 1 illustrates this. The originaJ signal is shown at ‘a’. It is assumed that the fre- quency is too high for the basic version of the TV scope to handle comfortably, so timebase expansion is required: the signal must be ‘stretched’ along the time axis. To this end, it is first read into the bucket-brigade memory. As explained in last month’s article ‘Analogue reverber- ation unit’, this process involves sam- pling the input signal. In figure 1, the (sampling) clock pulses are shown at ‘b’ and the sampled signal, as stored in the memory, is signal ‘c’. The latter signal consists of a succession of discrete voltages, and these can now be read out of memory using a lower clock rate (signal ‘d’). The output signal (‘e’) is a similar succession of discrete steps, with one major difference: the steps are longer. Suitable filtering of this signal results in the final output signal ‘f’. As can be seen, this signal has the same ‘shape’ as the original signal (‘a’), but it has been ‘stretched’ over a longer period of time. This figure illustrates the function of the extension circuit for the TV scope. Relatively high-frequency signals are read into a bucket-brigade memory, using a suitably high clock frequency, and then read out using a low clock frequency. The two clock frequencies are chosen such that the ‘stretched’ output signal can be clearly displayed on the basic version of the TV scope, in spite of its fixed 20 ms timebase. A block diagram for the extended version of the TV scope was included last month in the introductory article, and it is repeated here (figure 2). The operating principle should, by now, be fairly clear. As explained earlier, two bucket-brigade memories are used (per channel). These are used alternately: as one is storing the input signal, the contents of the other are being read out and displayed on the screen. This additional complication is necessary if the display is to remain uninterrupted: if only one memory were available, the different clock frequency during the read-in cycle would make the display useless during that period. A slight simplification of this block diagram is possible: the selector switch at the input to the two memories can be omitted. When a memory is being used as ‘display memory’, i.e. when it is being 11-26 — elektor november 1978 extending the TV -scope read out, any new signal entered into it will remain unused — it will be lost during the following read-in cycle. In the more detailed block diagram shown in figure 3, this input selector switch is omitted. Figure 3 is the ‘final’ block diagram of the extended version of the TV scope. The shaded portions are the extension circuits, which will be described in greater detail next month; the remainder is the basic version of the TV scope, as described last month. Some of the sections are shown in dotted lines, and these are only re- quired for the two-channel version of the TV scope — i.e. if two signals are to be displayed on the screen simul- taneously. If a single-channel version is sufficient, these portions may be omitted. The basic structure should be fairly clear by now. Y\ is the input amplifier for (one channel of) the TV scope; the circuit details were discussed last month. The output signal u ya is fed direct to the inputs of two analogue shift registers (bucket brigade mem- ories), A1 and A2. At any given mo- ment, one of these shift registers oper- ates as ‘input memory’ and the other as ‘display memory’. The ‘input memory’ samples and stores the input signal, u ya (as noted earlier, the same signal is also stored in the ‘display memory’, but it is lost during the next read-in cycle). The clock frequency for the read-in cycle - i.e. the sampling frequency - deter- mines the ultimate ‘timebase expansion’. ^00 TV SCOPE, BASIC VERSION 1 1 Y- 1 1 amplifier L. voltage-to-time converter video section EXTENSION *[ ^ clock M: n or i f _r | L rz «s 15 kHz approx. i Figure 1. The basic principle of 'timebase expansion'. The original signal, 'a', is sampled ('b' and 'c'), slowed down t'd' and 'e') and retrieved I'f'l. The result is a 'stretched' replica of the original input. Figure 2. A simple block diagram of the extended version of the TV scope. Figure 3. A more detailed block diagram. The portions shown shaded-in are the extension circuits, the remainder is the basic version of the TV scope as described last month. This diagram shows the complete two-channel version; the sections shown in dotted lines are not required for a single-channel TV scope. extending the TV -scope elektor november 1978 — 11-27 This signal is generated by the ‘input timebase’ — the latter being basically equivalent to the timebase in a normal oscilloscope: the input clock frequency determines the time scale along the X-axis in the final display. The phrase ‘input timebase’ is used to distinguish this circuit from the existing timebase in the basic version of the TV scope (the circuit that provides the clock- and sync pulses required for the actual display). As the input signal is being sampled and stored in the input memory, the infor- mation stored in the other memory during the previous cycle is displayed on the screen. To this end, the display memory receives its clock signal, uij ne , from the (output) timebase. The fre- quency of this clock signal can be either equal to or half of the fixed sampling rate of the basic version of the TV — approximately 15 kHz or 7.5 kHz. The output from the display memory, selected by S a , is fed to a low-pass filter in order to retrieve the original wave- shape (see figure 1 , e and f). This signal is then processed by the circuits already described in the basic version of the TV scope and displayed on the screen of the television receiver. When the display cycle is completed, the electronic switches S a , S c , Sd (and Sb) are oper- ated; the input memory becomes display memory and vice versa. Obviously, the circuits for the second channel (shown in dotted lines in figure 3) operate in exactly the same way. Control signals Even if the basic principle of the TV scope may by now seem fairly straight- forward, getting it to work reliably in practice is another matter and some fairly intricate control circuitry is required. Two different clock signals are required for the memories: 256 pulses at the desired sampling frequency during the input cycle, followed by 256 pulses at TV line frequency (or half that) during the display cycle. More- over, the two clock pulse trains (01 and 02) must be fed to the memories at the correct point in the input and display cycles. Since the memories are used alternately as input and display memory, and since the changeover occurs at the end of each cycle as determined by the u rese t pulses from the (output) timebase, the two clock signals must obviously be linked in some way to the u rese t pulses. This is illustrated in figure 4. As can be seen, a further signal u m is generated, which changes state at every u rese t pulse. This signal determines which of the memories is to operate as input memory and which is to operate as display memory: it controls the elec- tronic switches S a . . . Sd in figure 3. The beginning of each display cycle is determined by the signal u x . This signal goes ‘high’ shortly after each reset pulse, the delay between u rese t and u x deter- mining the position of the actual display along the time-axis (‘X-position’). The beginning of the input clock pulse train is determined in a similar way by pulses generated by the trigger circuit, so that a stable picture can be obtained. Each pulse train, both for 01 and for 02, consists of 256 pulses. The fre- quency of the output clock pulses is normally equal to TV line frequency; the input clock frequency is higher, and is determined by the desired time scale in the final display. The frequency of the u rese f pulses corresponds to TV frame frequency (50 Hz). All the electronics involved in the memory circuits, including the control circuits that produce the signals shown in figure 4, are mounted on a single printed circuit board — the ‘memory board’. This board can be linked into the basic version of the TV scope described last month, resulting in the ‘extended version’. Controls and facilities The various facilities offered by the extended version of the TV scope can be assessed from the front panel con- trols. The prototype front panel is shown in figure 5. Most of the controls are direct equivalents of their counter- parts on a ‘normal’ oscilloscope: The on/off switch, labelled ‘power’, requires little explanation. Above it, there are two ‘intensity’ controls. ‘Signal intensity’ sets the brightness for the displayed signal; ‘grid intensity’ does the same for the calibration graticule. 11-28 — elektor november 1978 extending the TV -scope Two time-base controls set the scale of the X-axis in the display. A multi- position switch (‘time/div’) is used to select a basic period-per-division be- tween 40 /as and 2 ms; fine control of this setting is provided by a poten- tiometer. A two-way switch, ‘x-magni- tude’, is also included. With this switch in position be 1 ’ and with the fine control turned fully clockwise (‘cal’), the time per division corresponds to the value selected by the main time/div switch. When the ‘x-magnitude’ switch is set in position ‘x 2’, the signal being displayed is ‘stretched’ along the X-axis: the time per division is halved. The potentiometer marked ‘x pos’ (X pos- ition) sets the position of the displayed signal along the X-axis. The switch ‘trigger/free run’ is also common to most ’scopes. In the ‘trigger’ position, the display is synchronised to an incoming signal. Exactly which incoming signal is used for this is selected by the switch marked ‘trigger source’: channel A or channel B (‘Y a ’ or ‘Yb’, respectively), or an external trigger source connected to the socket below the trigger controls. This external trigger input is either AC- or DC-coupled, depending on the setting of the switch beside the input socket. The signal level at which triggering occurs is set by the ‘trigger level’ control; the fact that the TV scope is actually being Figure 4. Some of the control signals required for the memory section. 01 is the clock signal for memory A1 (and B1 in a two-channel version); 02 is the clock for A2 (and B2). Each clock pulse train consists of 256 pulses. The input clock frequency is higher than the display clock, in order to obtain the necessary timebase expansion. Figure 5. The (prototype) front panel for the extended version of the TV scope gives a good idea of the facilities offered. triggered is signified by a green LED, ‘trig’d’. Two signals can be displayed simul- taneously on the TV scope: Y a and Yb. In some cases it will be useful to display them as two distinctly separate signals, side-by-side on the screen; at other times, it is more useful to have them overlapping so that minor differences can be evaluated — for instance, when comparing the input and output of an amplifier which is being driven to the verge of clipping. On the TV scope, the position of the two signals on the screen can be continuously varied between completely separate and exactly over- lapping, by means of the control marked ‘trace distance’. In essence, this control is a kind of synchronised Y-position control that affects both channels to an equal amount but in opposite direc- tions. The sensitivity of the TV scope is set by the controls marked Volts/ div’. On both input sections, the upper control is a multi-position switch and the lower is a fine control potentiometer. A switch next to the input socket offers a choice between AC and DC coupling. The Y-position control, as one would expect, sets the position of the trace along the Y-axis. The circuit details, constructional hints and calibration procedure will be explained in detail next month. W 11-30 — elektor november 1978 15 duty-cycles at the turn of a switch 15 duty-cycles at the turn of a switch 1 ^100n "ST ici &ie IC2 08 -O j- yiy 3... 15 V 10mA 214 3 30 Si OJ 1 ' 1 2 3 4 5 6 7 8 9 0 dock RESET IC2 4017 carry out J U L O^T_TL_r c* f 100 n 7 Hz . . 200 Hz 10 n 70 Hz . . 2 kHz 1 n 700 Hz . . 20 kHz 100 p 7 kHz . . 200 kHz N1 ... N4 = IC1 =4011 Only two CMOS-ICs are used in the generator described here, but in spite of its simplicity it offers a selection of 1 5 precisely determined duty-cycles without any need for calibration. It is a useful item of test gear, especially for calibrating other instruments that are designed to measure duty-cycles in one form or another — dwell meters, for instance. The outputs of a divide-by-ten counter, the CD 4017, are connected to an 8-position switch. One of the outputs is selected and fed back to the reset input of the IC. The result is a divider stage that can be set at any division ratio between 2 and 9. If the output is taken from the ‘O’ output of the divider, both the frequency and the duty-cycle of the input frequency will be ‘divided’ by the preset ratio. Furthermore, the duty-cycle of the output signal will be independent of the input frequency: it is determined only by the setting of the selector switch. To complete the unit, a clock generator is included (N1 ... N3). The ‘clock’ fre- quency is determined by the value of the capacitor, C, and by the setting of the 1 M potentiometer. The Table lists frequency ranges for a few capacitor values. The duty-cycle at the output (pin 3 of IC2) is equal to the division ratio times 100%. For instance, if output ‘5’ (pin 1) of IC2 is selected, the division ratio is 1 :5 and the duty-cycle is Figure 1. Only two IC's are required for this little generator. The Table lists frequency ranges for a few capacitor values. Figure 2. The duty-cycle at the output is determined by the division ratio. No calibration required! As can be derived from figure 2, eight duty-cycles between 50% and 1 1.1% can be selected. N4 inverts the output signal, providing eight duty-cycles varying from 50% up to 88.9%. Since 50% is 50% no matter which way you look at it, the total number of duty-cycles available is fifteen. The amplitude of the output signal is equal to the supply voltage, i.e. anywhere between 3 and 1 5 volts. M hello, all you folks back home! elektor november 1978 — 1 1-31 hello, all you folks hack home! Modern technology has produced fast transport and centralised industry. A somewhat less desirable side-effect is that close relations have tended to become distant relations. Instead of gathering around the fire as in the 'good old days', we tend to gather around the telephone. This means of communication suffers, however, from one major flaw: Ma Bell never intended it as a vital link between whole families. The system itself and all the legal restrictions involved with it are geared to private conversations between two individuals. The solution to the problem? A loudspeaking telephone. Kigure 1. Block diagram of the telephone booster. The signal is picked up by a coil, since a direct connection into the telephone lines is not permitted. The booster itself consists of two sections, one mounted as close as possible to the phone and the other — much larger — section placed in any con- venient spot. The circuit described here will pick up the telephone conversation and repro- duce it via a loudspeaker, so that several people can listen in. This is only possible, of course, if the electrical signals from the telephone are first picked up in some way. Since the Post Office, understandably, does not like people tampering with their wiring, some kind of indirect coupling is required. The most common method is to use a so-called telephone pick-up coil. This operates on a very simple principle: in every telephone there is a transformer which is wound and wired in a cunning way in order to route the incoming signal from the telephone line to the earpiece, and at the same time feed the microphone signal onto the line. In effect, it forms a kind of splitter for audio signals, with good coupling from line to earpiece and from microphone to line, but with poor coupling between the microphone and earpiece to avoid acoustic feedback. All transformers have a stray field, and this one is no exception. If a suitable coil is placed in this field, it will ‘pick up’ the audio signals. Logically enough, a device of this kind is called a pick-up coil. The electrical signal delivered by the coil is extremely small, so that a lot of gain is required in the following amplifier stages. As shown in the block diagram (figure 1), the amplifier described here consists of two sections. The first section has a gain of 180 (45 dB). It can be connected via almost any length of single-core screened cable to the second section, which has a gain of up to 50 (34 dB). This second stage drives the loudspeaker. The advantage of cutting the circuit in two is that the first stage can be mounted quite near to the pick-up coil, mini- mising the amount of hum and inter- ference picked up by the connecting wires. The bulk of the circuit, including loudspeaker and power supply, can be mounted at any suitable remote pos- ition. Up to 50 m (160 ft) of screened cable can be used between the two stations more than enough for any practical application we can imagine. The first section has no power supply of its own: it is powered from the main section via the connecting cable. The circuit The complete circuit is shown in figure 2: figure 2a is the first stage, which is mounted near the pick-up coil; figures 2b and 2c are the second stage and the power supply, respectively. The pick-up coil, LI, is a normal minia- ture choke and the value is not particu- larly critical. It is sometimes possible to obtain coils designed specifically for this purpose, mounted in a plastic capsule with a suction cup at one end. LI and Cl together form a resonant circuit, but this is so heavily damped by R 1 and the input impedance of T1 that the res- onant peak is hardly noticeable — the main effect is to limit the bandwidth to a useful value. The first stage would be a two-transistor elektor november 1978 — 1 1-33 hallo, all you folks back homel Parts list Resistors: R1 = 22 k R2.R3.R9 = 47 k R4.R13 = 10n R5.R1 2.R14 » 470 n R6.R7 = 1k8 R8 = 27 k RIO = 33 k R11 = 15 k R15 = 1 kn R16.R17 = 2U2 R18 = 1 k R19 = 100 k PI = 10 k log. Capacitors: Cl = 470 p C2.C6 = 2p2/10 V C3 = 680 p C4 = 1 00 m/ 4 V C5 = 100 p/10 V C7 = 270 n C8 = 82 n C9 = 22 n CIO, Cl 2 = 220 p/IOV C11 = 10 n C13= 2200 p/16 V C14 = 1 p/10 V Semiconductors: T1 ,T2,T3 •= BC 109C, BC 549C or equ. T4 = BC 177B, BC577B or equ. T5= BC 140, 2N2219 T6 = BC 160, 2N2905 D1,D2= 1N4148 D3 . . . D6 = 1N4001 D7 = LED Miscellaneous: LI = miniature choke. 47 ... 1 00 mH , see text LS = 8 n/200 mW loudspeaker Tr = 9 . . . 1 2 V/1 50 mA mains transformer SI = DPDT mains switch amplifier with a gain of 180, if T2 had a lk8 collector resistor. Following the connecting cable, this resistor can indeed be located: R6 in figure 2b. This little trick, which was also used in the Preco, saves one wire: the same cable is used to feed the audio signal from the first section to the second and to supply power from the second section to the first. The output of the first section is basically a current source and can be loaded by a relatively low impedance, permitting the use of a fairly long cable. The second section is a ‘bare-bones’ design: only four transistors and a handful of other components are used in this little power amplifier. There is no quiescent current adjustment — that would be an unnecessary luxury for this application. On the other hand, no quiescent current at all would be the other extreme — the maximum gain would be lower. PI is the volume control. A tape output is also provided, although it should be noted that — strictly speaking — the other party should be notified if the conversation is to be recorded. The power supply (figure 2c) is straight- forward. The only ‘luxury’ there is the LED, D7. Construction and use Printed circuit board designs for the two sections are shown in figure 3 . The main (figure 3 b) contains both the second section and the power supply. It is perhaps interesting to note that this board can also be used on its own as a low-cost, low-fi ‘power’ amplifier, pro- vided R6, R7 and C5 are omitted. For that matter, the complete unit can also be used as a ‘low-fi’ public address installation . . . Note that T5 and T6 should be provided with cooling fins or clips. There’s no harm in them running ‘warm’, but they’re not supposed to get ‘hot’. The two sections can each be mounted in their own case (even a tobacco tin will do for the first stage!) and connec- ted by means of the desired length of cable. The pick-up coil should be connected to the first stage by the shortest possible length of twin-core screened cable: the two ends of the coil are connected to the two cores and the screening is connected to supply com- mon. The best position for the pick-up coil can be found by trial and error. When the handset is lifted off the hook, a dialling tone is obtained (if no dialling tone is heard, complain to the Post Office, not us) and the pick-up coil can now be moved, twisted and turned all over the telephone ( not the handset) until this tone is reproduced at maxi- mum strength by the loudspeaker. Note that both the position of the coil and the direction in which it is pointing will influence the ‘reception’. Once the best position and location have been found, the coil can be fixed in position. M Figure 2. The complete circuit. Figure 2a is the first section, which is connected by means of single-core screened cable to the second section, shown in figure 2b. The power supply, figure 2c, can also be mounted in the main station. Figure 3. The two p.c. boards required. The larger of the two (figure 3al, EPS 9987 - 1. is for the main station including power supply; the second is for the first section of the circuit (EPS 9987 - 2). 11-34 — elektor november 1978 applikator R.P.M. and dwell meter using a window discriminator, the TCA 965. This interesting circuit appeared as 'Circuit of the day' in the Siemens Components Report no. 2/78. The circuit is easy to construct and calibrate, it will operate over a wide range of supply voltages (8 ... 20 V), and it is quite accurate. It is also ideally suitable for use in cars, since it is insensitive to temperature variations over a wide range and has high noise immunity. Figure 1 shows the complete circuit, using a 1 mA instrument (a modification for more ro- bust 10 mA instruments will be discussed later). With the switch in position 1 the circuit operates as a rev. counter. The input (CB) is connected to the contact breaker; R2, D3 and C2 provide protection against high voltage transients. When the contact breaker opens, the voltage at the input rises; as soon as the voltage at pin 6 exceeds the trigger voltage at pin 8 (i.e. 3 V, derived from the reference output, pin 5), the open-collector output at pin 13 is turned on for a period set by R3 and C5. During this set period, current therefore flows through the 1 mA instrument. This current is made virtually independent of supply voltage fluctuations by the simple expedient of deriving it from a second refer- ence output, pin 10. The mechanical inertia of the meter is sufficient to integrate the current pulses, resulting in the desired RPM indication. With the switch in position 2, the circuit operates as a dwell meter. Basically, it merely 'cleans up' the pulses from the contact breaker: as long as the latter is closed, current flows through the meter. As before, the inertia of the meter itself is sufficient to average-out the pulses — producing the desired reading. The choice of component values shown is such that the same scale can be used for both measurements. In switch position 1, full scale corresponds to 8000 RPM. In position 2 (dwell), the meter will read full scale for an 80% duty-cycle (contact closed for 80% of the time). It is common practice in automobile elec- tronics to use heavily-damped and relatively insensitive instruments with a 270° scale. For instruments of this type, the circuit modifi- cations shown in figure 2 are required. D5 and D6 compensate the relatively large tempera- ture coefficient of the instrument, and D7 protects the 1C from reverse-voltage spikes caused by the quite considerable inductance of the coil. Using this circuit, meters with a sensitivity of up to 10 mA f.s.d. can be employed. Calibration With the switch in position 2, apply a positive square-wave with an amplitude of 5 V and an 80% duty-cycle to the 'CB' input; adjust PI until the meter reads full-scale (80%). If one does not have access to either an oscilloscope or an accurately calibrated pulse generator, the generator described elsewhere in this issue ('15 duty-cycles at the turn of a switch') will prove useful. Alternatively, one can resort to a normal, symmetrical square-wave and adjust PI until the meter reads 50%. For the RPM measurement (switch in pos- ition 1), calibration is not really necessary. If 5% tolerance components are used for C5 and R3, the reading will be sufficiently accurate for most practical purposes. The correct value of R3 depends on the number of cylinders (c) and the 'number of strokes’ (s), as follows: R 3 = — x 40 (kn). c To give a few examples: for a four-cylinder four-stroke engine, R3 would be 40 k (use 39 k); for a 6 cylinder 4-stroke the correct value is 27 k. Of course, if a pulse generator and a frequency counter are available, exact calibration is possible. R3 is replaced by a suitable preset potentiometer (50 k will be correct in most cases), and a square-wave of sufficient ampli- tude is applied to the CB input. The fre- quency is determined by the number of cylinders and 'strokes’, as follows: f = -x266 Hz. s At this frequency, the preset is adjusted until the meter reads full scale (8000 RPM). Note that this calibration must be carried out after the dwell scale has been correctly calibrated! Final notes Installing the unit in the car should not present any real problems. The positive supply line is connected to the 1 2 V supply in the car at some (fused) point after the ignition switch — the connection for a car radio or cigarette lighter is usually a good point — and the 'supply common’ connection is taken to the bodywork of the car at some convenient point near the meter (Note that the circuit is not intended for use in cars with positive ground!). Finally, the CB input is connected to the lead between the ignition coil and the contact breaker. To avoid excessive interference problems, it is advisable to run the lead to the CB input as close to the metalwork of the car as possible for the whole of its length — keeping away from ‘hot spots' of course! Better still, screened cable can be used, with the screen connected (at one end only!) to the bodywork of the car. u Under the heading Applikator, recently introduced components and novel applications are described. The data and circuits given are based on information received from the manufacturer and/or distributors concerned. Normally, they will not have been checked, built or tested by Elektor. SC/MP 'Mastermind' ™ programing elektor november 1978 11-35 SC/MP ’Mastermind’ ™ programme Pit your wits against the computer with the aid of the following 'Mastermind' ™ programme, which is designed to run on the Elektor SC/MP system. COMPARE me = machine code pc - player's code F. Schuldt :o moare^S^ with other digits Sl"iC| = PC k )^ Figure 1. This flow-diagram should help to clarify the operation of the 'compare' rou- tine. decrement counter 3 RESULT 11-36 — elektor november 1978 SC/MP 'Mastermind' TM programme Table 1 0C00 C46D ENTER: LDI 60 0C5D AA0B ILD B (2) 0C02 C906 ST 6(1) 0C5F E410 XRI 10 0C04 C479 LDI 79 0C61 9C18 JNZ KEY 0C06 C905 ST 5(1) 0C63 C0E6 LD(XX) 0C08 C478 LDI 78 0C65 CA0B ST B(2) 0C0A C904 ST 4(1) 0C0C C400 LDI 00 0C67 AA0C ILD C(2) 0C0E C903 ST 3(1) 0C69 E41 0 XRI 10 0C1 0 C902 ST 2(1) 0C6B 9C0E JNZ KEY 0C12 C901 ST 1(1) 0C6D C0DC LD(XX) 0C14 C440 LDI 40 0C6F CA0C ST C(2) 0C16 C900 ST 0(1) 0C18 C471 LDI 71 0C71 AA0D ILD D (2) 0C1 A C9FF ST— 1(1) 0C73 E410 XRI 10 0C75 9C04 JNZ KEY 0C1C C455 XP3 (PUSH) - 1 0C77 C0D2 LD(XX) 0C1E 33C4 0C79 CA0D ST D(2) 0C20 0037 0C22 3F XPPC 3 0C7B Cl 08 KEY: LD 8(1 ) 0C7D 94 D4 JP LOOP 0C23 C207 LD 7(2) 0C25 C901 ST 1(1) 0C7F C400 LDI 00 0C27 C209 LD 9(2) 0C81 CA0E ST E(2) 0C29 C820 ST(XX) 0C83 C43E NEXT: LDI L(GETHEX)— 1 0C2B 8FFF DLY FF 0C85 CA1D ST 1DI2) 0C2D 8FFF DLY FF 0C87 C455 XP3(PUSH)— 1 0C2F C480 START: LDI 80 0C89 33C4 0C31 C906 ST 6(1) 0C8B 0037 0C33 C905 ST 5(1) 0C35 C900 ST 0(1) 0C8D 02 CCL 0C37 C9FF ST— 1 (1 ) 0C8E C401 LDI 01 0C39 C439 LDI 39 0C90 EA0E DAD E (2) 0C3B C904 ST 4(1) 0C92 CA0E ST E (2) 0C3D C43F LDI 3F 0C3F C903 ST 3(1) 0C94 3F XPPC 3 0C41 C45E LDI 5E 0C43 C902 ST 2(1) 0C95 C400 LDI 00 0C45 C479 LDI 79 0C97 CA0F ST F (2) 0C47 C901 ST 1(1) 0C99 CA10 ST 10(2) 0C49 C4XX LDI XX 0C4B CA0A ST A(2) 0C9B 903A JMP COMP 0C4D CA0B ST B<2) 0C9D 9090 JS: JMP START 0C4F CA0C ST C(2) 0C51 CA0D ST D(2) 0C9F C41F OUT: XP3ITAB)— 1 0CA1 33C4 0C53 AA0A LOOP: ILD A(2) 0CA3 0137 0C55 E410 XRI 10 0CA5 C20E LD E (2) 0C57 9C22 JNZ KEY 0CA7 D40F ANI 0F 0C59 C0F0 LD(XX) 0CA9 01 XAE 0C5B CA0A ST A(2) 0CAA C380 LD— 1 28(3) 0CAC C9FF ST-1(1) Most readers will be familiar with one or other variation of the game ‘Mastermind’™, in which a secret code of colours, letters or numbers has to be ‘broken’ by an opponent in the mini- mum number of moves. In the fol- lowing programme, which can be run on a SC/MP with ‘Elbug’ monitor software, the player has to guess a random sequence of four numbers which are generated by juP. The full listing of the ‘Mastermind’™ programme is given in table 1 . When the programme has been loaded and started (by hitting the RUN-key), the text ‘set — F’ should appear on the dis- plays. The player can then select the desired difficulty level by pressing one of the keys from 4 to F. This determines which hexadecimal digits the pP can use to make up the code which the player has to break. If, for example, the key ‘9’ is pressed, then the code ‘word’ may consist of a combination of any four digits between 9 and F (i.e. 9, A, B, C, D, E, or F). Once the desired data key has been pressed, the displays will show the text ‘code’, indicating that the player can begin to guess the four-digit number selected by the computer. This is done by entering four (legal) numbers from the data keys, these are registered on the displays. The pP now compares these numbers with the secret code and indicates the result as follows: the number of digits in the player’s guess which are contained in the computer’s secret code, but which are in the wrong position , is registered on the extreme right-hand display, whilst the number of digits which occupy the correct position is indicated on the extreme left-hand dut- iable 1. The complete listing for the Waster mind’ TM programme. SC/MP 'Mastermind' TM programme elektor november 1978 — 11-37 Table 1, cont. 0CAE C20E LD E (2) 0D03 C501 LD @+1 (1 ) 0CB0 1C1C SR 0D05 01 XAE 0CB2 1C1C SR 0CB4 01 XAE 0D06 C1F8 LD— 8(1 ) 0CB5 C380 LD— 1 28(3) 0D08 9809 JZ §5 0CB7 C900 ST 0(1) 0D0A 40 §4: LDE 0CB9 C479 LDI 79 0D0B E701 XOR @+1(3) 0CBB C906 ST 6(1) 0D0D 9C16 JNZ §6 0CBD C437 LDI 37 0CBF C905 ST 5(1) 0D0F AA1 0 ILD 10(2) 0CC1 C45E LDI 5E 0D1 1 CBFF ST-1 (3) 0CC3 C904 ST 4(1) 0CC5 C400 LDI 00 0D13 BA00 §5: DLD 0(2) 0CC7 C901 ST 1(1) 0D15 9814 JZ RESLT 0CC9 C902 ST 2(1) 0CCB C903 ST 3(1) 0D1 7 C1F8 LD— 8(1 ) 0D19 C9FC ST -4(1) 0CCD Cl 08 WAIT: LD 8(1 ) 0CCF 94FC JP WAIT 0D1B 31 XPAL 1 0CD1 8FFF DLY FF 0D1C 0140 STE 0CD3 90C8 JMP JS 0D1E 33 XPAL 3 0D1F 40 LDE 0CD5 90AC JN: JMP NEXT 0D20 31 XPAL 1 0D21 C7FA LD @-6(3) 0CD7 C4E7 COMP: XP3(STKBSE)+7 0CD9 33C4 0D23 90 DA JMP §3 0CDB 0F37 0D25 BA01 §6: DLD 1(2) 0D27 98EA JZ §5 0CDD C404 LDI 04 0D29 90DF JMP §4 0CDF CA00 ST 0(2) 0D2B C401 RESLT : XP1 (DISPL1+1 0CE1 C7FF §1: LD @ — 1 (3) 0D2D 31 C4 0CE3 E307 XOR 7(3) 0D2F 0735 0CE5 9C08 JNZ §2 0D31 C41F XP3ITAB)— 1 0CE7 CB00 ST 0(3) 0D33 33C4 0CE9 AA0F ILD F (2) 0D35 0137 0CEB E404 XRI 04 0CED 98 B0 JZ OUT 0D37 C20F LD F (2) 0D39 01 XAE 0CEF BA00 §2: DLD 0(2) 0D3A C380 LD— 128(3) 0CF 1 9CEE JNZ §1 0D3C C906 ST 6(1) 0CF3 C701 LD @+1 (3) 0D3E C210 LD 10(2) 0CF5 C4EA XP1 (STKBSEl+A 0D40 01 XAE 0CF7 31 C4 0D41 C380 LD— 1 28(3) 0CF9 0F35 0D43 C9FF ST— 1(1) 0CFB C404 LDI 04 0D45 908E JMP JN 0CFD CA00 ST 0(2) 0CFF C403 §3: LDI 03 0D01 CA01 ST 1 (2) play. On the basis of this information, the player then enters a second number, whereupon the jtP will respond in a similar fashion, indicating how many digits are correct and how many are in the right place etc. This continues until the player finally guesses the secret code, at which point the text ‘End XX’ will appear on the displays, the number XX indicating how many attempts the player took to guess correctly. The game can be restarted by pressing one of the data keys. If the difficulty level is to be modified, the game must be restarted with the ‘Run’ key. Compare routine As already mentioned, the ‘Master- mind’ TM programme can only be run on a system with ‘Elbug’ monitor soft- ware. This is because the programme utilises several Elbug sub-routines so as to save memory space. A complete explanation of the pro- gramme would be too lengthy, however it is worthwhile taking at look at the most interesting section, namely the compare routine, the flow diagram of which is shown in figure 1. The first part of this routine compares each digit of the computer code with the corre- sponding digit of the player’s guess. If one or more of the comparisons are positive, then that digit is noted as being both correct and in the right position (if all four comparisons prove positive, then the player’s guess is obviously cor- rect, and the programme exits from the routine). The digits which were not marked as correct are next compared, one at a time, with the remaining digits of the computer’s code. If any of these comparisons proves positive, the corre- sponding digit is noted as being correct, but not in the proper position. When all the comparisons are complete, the final result is displayed via the Elbug rou- tines. Along with those programmes pre- viously published (‘reaction timer’ and ‘digital clock’), and a number of pro- grammes which are still to appear, ‘Mastermind’™ wil! also be available on the disc to be produced by the Elektor Software Service (see the article on this subject in Elektor 38, June 1978). TM We acknowledge the fact that ‘Mastermind’ is a registered trade mark of Invicta Plastics Ltd., Oadby , Leicester. H 11-38 — elektor november 1978 pocket bagatelle pocket bagatelle An electronic version of the age-old dexterity game. Many traditional games, which have been passed on unchanged from generation to generation, can now be simulated electronically (see, e.g. 'Marbles' in Elektor 21, January 77). In particular, 'video' games, which utilise the screen of a TV set to represent the field of play, have achieved enormous popularity in recent years, and with the advent of more and more complex 'games chips', this trend shows little sign of slowing down. However there are still many electronic versions of popular games which can be played without recourse to a TV set. One of the more simple (but not necessarily easy!) games, which is ideally suited as a small Christmas present, is 'bagatelle'. There are several variations of the game ‘bagatelle’; the one described here belongs to the species of manual dex- terity games which are designed to test a steady hand, strong nerves and infinite patience. The original and simplest version of the game consists of a round flat container with a transparent top, inside which a small ball rolls around. The object of the game is to manoeuvre the ball into a shallow hole set into the bottom of the container. However, since the ball is very small and light, and both it and the surface over which it rolls are extremely smooth and have a very low coefficient of friction, it is extraordi- narily difficult to control the direction in which the ball will move, or indeed to hold it steady at any one point. Further- more, the hole itself is quite shallow, and very little is needed to make the ball jump back out. This fact is particularly annoying if one has a more complicated version of the game with two or more balls to be manoeuvred into two or more holes. It is quite amazing how many times one can manipulate one ball into its hole and be just on the point of succeeding with the second, when the first ball suddenly pops back out. Grown men have been seen to weep with frustration! With Christmas not too far away, the following circuit for an electronic version of this tantalising game may help to solve that perennial problem of choosing presents — especially as far as younger relatives are concerned. pocket bagatelle elektor november 1978 — 11-39 The game is played as follows: a single ‘ball’, whose position is indicated by four LEDs, has to be manoeuvred into a central ‘hole’ represented by a LED of a different colour. The arrangement of the LEDs is shown in figure 1. The ‘ball’, which in fact does not physically exist, can be ‘rolled’ in two directions: north- south and east-west. The four LEDs, one at each of the compass points, indicate whether the ball is to the north, south, east or west of the ‘hole’. The position of the ball is controlled by two potentiometers, one for each direction. When the ball has been successfully manoeuvred into the ‘hole’, the central LED lights up and the other four LEDs are all extinguished. The degree of diffi- culty of the game, as it were the ‘size of the hole’, can be varied by means of a third, ‘handicap’ potentiometer. The circuit The electronics of the game are revealed in the circuit diagram of figure 2. The circuit basically consists of the two window comparators formed by A1/A2 and A3/A4. To help explain how this type of circuit works, the basic circuit diagram of a window comparator is shown in figure 3. As can be seen, the circuit has a single input signal, uj, and two output signals, U! and u 2 . Op-amps A1 and A2 are connected as compara- tors, i.e. due to the absence of feedback, their outputs are always in one of two states: either high or low. When the voltage at the non-inverting (+) input of a comparator is greater than that at the inverting (— ) input, the output voltage of the device swings up to + supply. However if the voltage on the inverting input is greater than that at the non- inverting input, then the output of the comparator swings down to — supply, in this case, to ground. One of the inputs of each comparator shown in figure 3 is connected to a con- stant reference voltage. These reference Figure 1. The board of the 'pocket bagatelle' contains five LEDs. The middle (green) LED lights up when the player succeeds in rolling the ball into the hole. The other four (red) LEDs indicate the position of the bail relative to the hole. Figure 2. The complete circuit diagram of the pocket bagatelle, which is based on two window comparators. Figure 3. The basic circuit of a window com- parator. Figure 4. This figure shows how the two output voltages of the comparators, u, and u, , vary with the input voltage, Uj. voltages, Ua and Ub, are derived from an attenuator network, consisting of Rl, R2 and P. Depending upon the value of the input voltage, uj, one of three possible situations can occur: a. Uj is greater than U a , in which case Ui will be high and u 2 low. b. u; is smaller than Ub, in which case u 2 will be high and U] low. c. uj lies between U a and Ub, in which case both Ui and u 2 will be low. When this occurs, the input voltage, u(, can be said to lie ‘inside the window’. The height of the window can be varied by means of poten- tiometer P. These three situations are illustrated by the diagram of figure 4, which shows how the outputs of the two op-amps react to a rising input voltage. Two such window comparators are employed in the circuit of the pocket bagatelle. The input of each is derived via a potentiometer, these being PI and P3 respectively. PI controls the vertical position of the ball, whilst P3 varies the horizontal position. Each of the outputs of the two window comparators drives an LED; it is clear from figure 4 that each output voltage goes high when the input voltage of the window comparator lies on that ‘side’ of the window. With two window comparators, whose input voltages represent the horizontal and vertical position of the ‘ball’ (and whose windows intersect) it is obvious that the logic state of the comparator outputs, and hence the on/off state of the corre- sponding LEDs, tell us whether or not the ‘ball’ has ‘rolled’ to a given side of the ‘hole’. If all four ‘pointer’ LEDs are extinguished, the centre LED will come on indicating that the player has suc- ceeded and the ball has been ma- noeuvred into the hole. The LEDs are driven directly by the outputs of the comparators; the current through the LEDs is limited by a series resistor. The voltage across this resistor is also used to turn on Tl. This transistor will remain conducting as long as one of the LEDs D1 . . . D4 is lit. If all four LEDs are extinguished, however, Tl will turn off, causing T2 to turn on, and the green central LED, D5, to light up. The dimensions of the window, and hence the difficulty level of the game, can be varied by means of stereo poten- tiometer P2ab. 11-40 — elektor november 1978 pocket bagatelle Figure 5. The printed circuit board for the pocket bagatelle. The potentiometers are deliberately not mounted on the board. Figure 6. One of the many possible designs for housing the circuit of the pocket bagatelle in a suitable case. The playing possibilities and the physical construction of the bagatelle are improved by incorporating a joystick in place of the two control potentiometers PI and P3. Construction The circuit of the pocket bagatelle can be constructed on the printed circuit board shown in figure 5. The potentio- meters are deliberately mounted ‘off- board’. This keeps down the size and cost of the board and allows the con- structor a free hand in the choice of controls and type of case. With games such as these, especially if they are intended as gifts, an attractive exterior is just as important as the electronics. Although the physical construction of the game is, as already mentioned, left to the ingenuity of the individual, figure 6 provides an example of a possible approach. Regarding the controls, there is one point worth mentioning: one can, of course, use conventional rotary- or slider potentio- meters for PI and P3. However, if one is willing to go to the extra expense (or trouble of making it oneself), the enjoyment of the game can be consider- ably enhanced by using a joystick to replace these two potentiometers. Using a joystick prevents one from adjusting just one of the potentiometers to the correct position (until the corresponding LEDs are extinguished), and then homing in with the second potentio- meter. Like it or not, both potentio- meters are operated simultaneously in a joystick. What is more, as figure 6 shows, a more interesting case design also becomes possible. A means of constructing a joystick from two conventional rotary potentiometers is discussed elsewhere in this issue. For those readers who do use potentio- meters (whether in a home-made joystick or not), it should be noted that the values of PI and P3 are anything but critical and if needed, could lie any- where between 1 k and 1 M. It is also of little importance if PI and P3 have dif- ferent, even widely different values. M Parts list Resistors: R1.R2.R5 . . . R8, R1 1 , R12.R13 = 10 k R3,R4,R9,R10,R14 = 1 k PI ,P3 = 47 k (50 k) lin potentiometer P2ab = 1 k lin stereo potentiometer Semiconductors: IC1 = LM 324 T1 ,T2 = TUN D1 . . . D4 = LED red D5 = LED green market elektor november 1978 — 1 1-41 Subminiature Tantalum capacitors A new series of Kemet subminia- ture axial-leaded tantalum capacitors in a high precision epoxy moulding has been launched by Union Carbide UK Limited Electronics Division. Designated the T 322 series, it is designed for high speed automatic insertion applications as the four case sizes correspond to standard resistor and diode sizes. These capacitors offer an extremely high volumetric el'ficcncy and include among their applications decoupling, blocking, bypassing and filtering in computers, data processing, communications and other electronic equipment. Electrical ratings extend from 68 uF/6 V through 4.7 mF/ 50 V. Tlte temperature range spans -5S°C to +85°C (or to +125°C with voltage derating). The T 322 series replaces the T 320 series of epoxy moulded tantalums and metal-cased types. Prices for the new series are significantly lower than for the larger T 320 series, and compare favourably with the standard T 310 axial-moulded type. Union Carbide UK Limited, Electronics Division, Hilton Road, Aycliffe Industrial Estate, Nr. Darlington, Co Durham DL5 DL6 (919 M) 4 Digit multimeter Known as the Digimer 10, this new portable instrument from Iskra Limited also enables a.c. measurements to be taken at frequencies from 20 Hz up to 50 kHz. The digits are readable over a horizontal angle of 150° , and a vertical angle of 90°. Other outstanding features of the Digimer 10 include: 17 ranges, an accuracy of ± 0.05%, ± 1 digit; automatic polarity indication; a selection of optional shunts for measuring higher currents; and rechargeable nickel-cadmium batteries that power the mul- timeter for eight hours between charging operations. In addition, the Digimer 10 can be used while connected to an optional battery charger, except when measuring parameters involving voltages above 1000 volts. Carefully designed to maximise ease of use, the Digimer 10 has a 7-segment LED display. The figures are 7.62 mm high, and the display is angled for optimum readability when used on a flat surface. Only two controls provide instant range switching to any one of the 17 ranges. A built-in over-ranging trip circuit allows safe operation on all ranges up to 50% above full-scale deflection value. The unit features integral automatic drift compen- sation and overload protection. Voltage ranges (a.c. and d.c.) have a high degree of resolution, which is given in brackets after each full-scale deflection: 200 mV (0.1 mV), 2 V (1 mV), 20 V (10 mV), 200 V (100 mV), and 2000 V (1 V). Current ranges (a.c. and d.c.) and their resolutions are: 20 uA (10 nA), 200 mA (100 nA), 2 mA (1 uA), 20 mA (10 mA), 200 mA (100 mA), and 2 A (1 mA). Resistance readings extend from 0.1 ohm to 20 megohms in six ranges. Under over-ranging conditions, each range is increased by 50%. All d.c. and resistance measure- ments have a sampling time of approximately 300 milliseconds. And the unit is designed to operate at any temperature from 0 to 55°C. Iskra Limited, Redlands, Coulsdon, Surrey CR3 2HT. (929 M) Compact bridges Designed for the user who demands an economical product without sacrificing quality, reliability and electrical performance. International Rectifier announce the introduc- tion of a range of small single phase bridge rectifiers. Coded 1 KAB, the series has current rating of 1.2 A into a resistive load, and 1.0 A if the load is capacitive. Correct mounting orientation is ensured by the use of a 9.5 x 9.5 x 8.0 mm polarised package, which is particularly useful when checking load identi- fication on densly populated PCB assemblies. The leads are on a standard 2.54 mm grid. The range is equivalent to the B . . C1000 series of DIN bridges and may also be used as superior replacements for the B . . C500 and B . . C800 devices. The 1 KAB is offered over the voltage range 100 to 1000 V Vrrm. The product data sheet gives useful application infor- mation and a cross reference to the DIN types, as well as full details of the device specification. I l Typical applications would be in general purpose power supplies, auxiliary supplies in power equip- ment, low current battery chargers, communications systems and the entertainment industry. International Rectifier Co., (G.B.J Ltd., Hurst Green, Oxted, Surrey. (923 M) Circuit testing in the open Testing circuits while your equip- ment is in operation is at best difficult and at worst impossible. To ease the problem Vero Electronics Limited have introduced two Eurocard compatible extender boards to complement the Vero Eurocard System 4. They are 100 mm wide x 263 mm long - one carries 64/64-way plug and socket to DIN 41612, the other a 64/96-way plug and socket. Included in the kit with each board are 20 terminals that can be assembled into pre-drilled holes in the board for test points. Both boards are manufactured from Epoxy Glass. Vero Electronics Limited, Industrial Estate, Chandler’s Ford, Eastleigh, Hampshire. S05 3ZR. 913 M) New hyreg module Wcstcode Semiconductors of Chippenham announce a new addition to their popular range of Hyreg module units. Called the IPT 1/250-25, a single- phase basic ac regulator module, it has been developed to control loads of up to 6.25 kW from a mains supply and features a 10 mSec surge rating of over 210 amperes. The high overcurrcnt and I 1 1 ratings make this unit especially attractive for the control of loads with heavy starting currents such as stage lighting, motors or transformers. This module employs a ceramic substrate bonded to an isolated base plate and the whole is potted to provide a rugged module fully protected against a wide range of environmental conditions. Westcode Semiconductors, Chippenham, Wilts. 903 M 11-42 — elektor november 1978 LiLiiiiii' LCD multimeters Two low cost LCD multimeters have been added to the existing range of N.L.S. DMM’s. The LM 300 has a 3 digit high contrast display powered by 3 AA size cells which can be either zinc- carbon or the optional nickel cadmium with an external mains adaptor. The 21 ranges cover AC and DC volts in 1-10-100-1 KV and AC DC current in 1-10-100-1000 raA ranges. Resistance is measured in 5 range; from 1 Kohm to 10 Mohm. All ranges are fully protected and will withstand up to 1 Kv DC or AC peak on any voltage range. The LM 350 is similar to the LM 300 but with a 354 digit scale and 100% coverage. Case size is only 1.9”x2.7”x4.0”. Price £ 74.00 (+ V.A.T.) for the LM 300 and £ 87.00 (+ V.A.T.) for the LM 350. Lawtronics limited 139 High Street, Edenbridge, Kent TN8 5 AX. (833 M> Etch resist dry transfers The Belgium company of Alfac *.••**• „t5§» .*•, O ?* # * *..• boo ; •V*v ; are now marketing in England a range of about 100 different electro Symbols which will enable amateurs and industrial users to make up P.C.B.’s much more quickly, easily and accuately. Alfac etch resist electro symbols can be transferred directly on to copper clad boards for making ‘one-off’ P.C.B.’s, or they can be used on drafting film to make electronic circuit diagrams. They are made in a range of component sizes, and they give exact and correct spacings for intergrated circuits and transistors. Alfac transfers need no special fixing, since the double action adhesive prevents the symbols moving when they are laid down. The quality of the special ink which is used by Alfac eliminates any cracking, and a very professional finish can be achieved. They are economical in price and are available in handy blister packs which are ideal for storage. Further details may be obtained from the Alfac sole agents in the U.K. Pel l tech Ltd., Alfac Electro Division, 6 Church Green Witney Nr. Oxford, England. (839 M) VSWR bridge This VSWR Bridge has been specifically designed for use with transmitters capable of producing > y \ \ • -* asM A - -*'* ,J|® ■W 1 ih 1 1 - i ^ Zh ^ $ ? b, „a c5 & ■* A high power outputs. Unlike many of the other VSWR Bridges on the market, this particular piece of equipment will handle the high power without giving misleading results. This so often occurs due to high sensitivity in order to read low power levels. When at high power levels the diodes which detect the sampled portion of R.F. energy become saturated and can no longer be relied upon to give a true reading. With this problem in mind, the sensitivity of the instrument has been deliberately reduced. The heart of the instrument is a double sided glass fibre printed circuit board with a printed stripline of a characteristic impedance of 50 ohms. The forward and reflected power measurement is accomplished by means of a loosely coupled printed line with diodes at each end and a high quality carbon film ’’cermet” trimmer, to enable the instrument to be calibrated precisely, fixed at the centre point. Connection to the 50 ohm stripline is by means of ”N” type flange connectors with low inductance grounding of the body to the ground plane of the double sided printed circuit board. The measurement of the voltage standing wave ratio is directly calibrated on a moving coil meter mounted on the front panel of the instrument, along with a sensitivity control to set full scale deflection on the forw ard range. A miniature rocker switch switches between the forward and reflected detectors. Specification: Impedance Sensitivity Input/Output Connectors Maximum Power Levels Hi-power VHF V-FETs A new range of vertical-geometry V-channel field-effect transistors, available in the UK from Walmore Semiconductors, can handle continuous-wave output powers of up to 100 W at frequencies of 175 MHz. The devices, manufactured by Communications Transistor Corporation, draw negligible d.c. input gate current, making biasing and modulation much simpler, and are much more rugged than comparable bipolar devices. The new range of V-FET products, intended for r.f. amplifier applications, includes — 50 ohms — 5 Watts @432 MHZ 10 Watts 144 MHZ — 'N' type UG 58/ U — 500 Watts @432 MHZ 1 ,000 Watts @ 144 MHZ Polar Electronic Developments Ltd., Domville Road, Liverpool LI 3 4 AT England. (831 Ml tluee devices - the BF 25-35, BF50-35 and BF100-35 - designed to handle 25, 50 and 1 00 W of continuous-wave power, respectively. All the transistors arc characterised for operation at either 80 or 175 MHz. The ease of biasing and modulation, plus the ruggedness of the devices, are important features of the V-FET devices. The problems of thermal runaway or breakdown, sometimes encountered with bipolar transistors do not occur, and hence the devices are more tolerant of load mismatch. The third-order distortion of the V-FET devices is similar to that of bipolar products, while the square-law-type characteristics of the V-FET technology gives a higher-order distortion figure 5 -10 dB lower than that for comparable bipolar devices. Noise performance is also improved because the V-FET is a majority-carrier device. The vertical V-channel structure allows a very narrow diffusion to take place, which leads to a good frequency response. Interconnection of a large vertical area of tightly defined gates also allows the higher power levels to be achieved. Maximum gain of the V-FET rf power transistors is 10 dB at 175 MHz. Breakdown voltage from source to drain is more than 65 V, and the source-to-gate breakdown voltage is more than 25 V. Typical ’on’ resistance is less than 1 fl measured at a 10 A drain current for the 100 W transistor. Walmore Semiconductors, 11-15, Betterton Street, Drury Lane, London, WC2H9BS England. ^ M) market elektor november 1978 — 11-43 —UHtllA’. Smaller capacitor A new range of aluminium electrolytic capacitors available from Gould Electronic Components Division is available in cylindrical aluminium cases with axial wires for easy mounting. Designated Sccorel 85, the new capacitors range in size from 6.5 mm diameter and 15 mm long up to 25 mm dia- meter and are designed to fill an important need for high- performance capacitors in smaller size ranges. The Sccorel 85 Series is a professional-grade range using a similar standard of construction and the same advanced electrolyte as the established Gould Prosec and Indel ranges. Eight sizes arc available, with capacitance values ranging from 1 /uF to 22 000 juF and voltages from 6.3 V to 350 Vd.c. Allied ranges with very low' equivalent series resistance, designed for use at the high frequencies encountered in switch- mode power supplies, arc the Secorel 032 and FRS Series. The 032 range is available with working voltages from 6.3 V to 100 V d.c. and capacitances from 6.8 /aF to 1000 /jF, and offers the same capacitance/voltage per can -ize as the Secorel 85. The FRS range provides even lower equivalent series resistance, but at some sacrifice of capacitance/ voltage per volume. Operating temperature range of Gould Sccorel capacitors is -55°C to +85°C, capacitance tolerance is -10%, +50%, and shelf life is 3 years. Because of their low eakage current and good stability, muld Secorel capacitors can be jsed in time-constant, timing, iifferentiation and integration nrcuits in addition to the usual roupling, decoupling and smoothing applications. Zould Electronic Components Division, •hosymedre, Hexham, Civvy d. (914 M) Midget power reed relay Despite measuring only 25 mm :':gby 8 mm wide, the Erg PM 21 midget reed relay can switch up to 20 W, both a.c. and d.c. Coil power required is only 70 mW. This 1 Form A (n.o.) s.p.s.t. component has a switching rate of 1000 Hz. Initial contact resistance is 5 0 mfi max. and insulation resistance 10 12 fi. Off-the-shelf 10 W versions of the Erg PM 21 reed relay have contacts rated at 200 V 0.5 A (1A carry), with initial contact resistance of 200 mn and insulation resistance 10 8 n. Insulation resistance between reed and coil (for both versions of the PM 21) is 10 10 a min. at 500 V d.c. min., while dielectric strength between reed and coil is 500 V r.m.s. min. The relays are completely encapsulated with leadout pins set on a standard O.lin. pitch for p.c.b. mounting. All relays incorporate internal magnetic screens. These minimise interaction from adjacent relays to only 10% of the ’’just operate” voltage when a relay is mounted between two similar relays with O.lin. spacing. Weight of the PM 21 is just 3 gm. It is available in coil voltages of 5, 12 and 24 V and the relays will work satisfactorily with a ± 10% voltage variation. Vacuum-encapsulation in epoxy resin with glassloaded shells and headers gives reliable protection even in unfavourable environments. The PM 2 1 relays arc designed to conform to the requirements of draft BS 95 12. Special versions of the PM 21 are available to order. Price of the relay is around £ 1 dependent upon quantity. Erg Industrial Corporation Limited, Luton Road, Dunstable, Bedfordshire LU5 4LJ. (922 Ml Complementary transistors Eight new' PNP and NPN transistors with 80 V collector- emitter voltages, 5 A continuous collector currents and operating frequencies to 70 MHz, provide high-performance in power amplifier and switching circuits. Developed by Solid State Devices, Inc., the 2N5002, 2N5005, 2N5151 and 2N5153 PNP transistors have 100 V collector- base voltages, 2 A continuous base currents and emitter-base voltages of 5.5 V. The 2N5003 and 2N5 1 5 1 have static forward- current transfer ratios of — - ; — 30 minimum to 90 maximum @5 V Vce and 2 J A I C . The 2N5003 and 2N5153 have a transfer ratio of 70 minimum and 200 maximum with the same drive conditions. Typical turn-on time is 0.5 mscc while turn-off time is 1.3 *isec. The NPN devices, 2N5002, 2N5004 , 2N5 1 5 2 and 2N5 1 54 , have similar electrical ratings permitting their use in comp- lementary-pair circuits. For broad safe-operating areas, the devices have a 15 m Joule reverse-energy rating. The 2N5002 to 2N5005 devices, packaged in the TO-59 case, have a continuous dissipation of 50 W @50°C case temperature. The 2N5151 to 2N5154 in T039 packages are rated at 10 W @ 50°C case temperature. Solid State Devices, Inc., 14830 Valley View Avenue, La Mirada, California 90638 USA. 905 M Static invertor A new static invertor from Bandenburg Ltd., the Model 060-02, is specifically designed as a prime power source for the Hawker Siddeley HS748 aircraft, and is ideal for retro- spective fitting in place of the conventional rotary invertor. The 060-02 meets BS 3G100 specifi- cations on shock, vibration and humidity, and is supplied with a mounting tray designed to fit the HS748. Because the 060-02 static invertor is a purely electronic device with no moving parts, it avoids the problems of wear and mainten- ance which traditionally occur with electromechanical invertors. The invertor provides a 3-phase output of 1 500 V A total rating from a nominal 28 V d.c. supply; each output is rated at 500 VA at 115 V, 400 Hz and phase-shifted by 120°. Output voltage and frequency are maintained constant over a wide range of input voltages, loads and environmental conditions, and the unit maintains a balanced output voltage even where there is a high degree of load imbalance. The 060-02 is of rugged design to ensure trouble-free operation under the conditions of shock and vibration normally encountered in civil aircraft, and cooling by natural convection. The output voltage on each phase is maintained at 1 15 V + 1.5 V r.m.s. over the normal input voltage range, and the output frequency is 400 Hz i 4 Hz over the full operating temperature range of -35° C to +55°C at ground level, or -20°C to +45°C at altitudes of up to 15.2 km. The total harmonic content of the output does not exceed 5% with a 1500 W resistive load for normal input voltages. Brandenburg Ltd. has approval from the Civil Aviation Authority under the Air Navigation Order for the supply of equipment used in civil aircraft. Brandenburg Limited, High Voltage Division, 939 London Road, Thornton Heath, Surrey, CR4 6JE. (911 Ml 11-44 — elektor november 1978 market Transparent epoxy elastomer Eccogel 1265 is a two part epoxy resin which will cure at room temperature to a clear tough, but flexible solid. Eccogel 1265 bonds well to most substrates and is therefore useful as a flexible interface between dissimilar materials. Typical of this type of application is the bonding of safety screens to cathode ray tubes. Cured Eccogel 1 265 is sufficiently flexible that a '/»” square, 1 2” long rod can be tied in a knot, and this allows the material to be used for the encapsulation of pressure sensitive devices, or delicate components such as fluorescent tubes. When first mixed Eccogel 1265 has a very low viscosity and will readily impregnate components and will also produce bubble free castings. The cured material may be cut open and faulty components removed. Repair is effected by refilling the cavity with fresh material. Eccogel 1 265 also exhibits excellent vibration damping properties. The photograph shows how a circuit module encapsulated with Eccogel 1 265 is cut with a knife, repaired and resealed with Eccogel 1265. Emerson & Cuming (U.K.) Ltd, Colville Rd., Acton, London W3. 904 M First schizophrenic CMOS 1C A unique pair of CMOS ’’Display Controller” IC’s, the MM74C911 and MM74C912,have been developed by National Semiconductor. These devices exhibit the unusual characteristic of appearing as memory to the input devices, while convincing the display that they are drivers. The device inputs believe they are memory. They may be addressed as RAM via address buffers — the MM74C91 1 has two address lines and eight data lines (accepting 7-segment plus decimal point information) whilst the MM74C912 has three address lines and five data lines (accepting BCD plus decimal point information). The outputs, however, are convinced they are drivers - and to prove it they are multiplexed to drive 4-digit (MM74C91 1) or 6-digit (MM74C91 2) LED or gas discharge 7-scgment displays. The segment outputs will drive up to 100 mA each. This is achieved using a buffered guard bank CMOS process in which the segment outputs make use of a parasitic NPN emitter follower bipolar transistor structure inherent in the CMOS process and an N-channel sink transistor. Digit outputs drive the digit transistors directly. The key to these devices’ split personality is their ‘Central nervous system’: - MM74C91 2 accepts the BCD information into one of six 5-bit latches. The latch outputs are scanned by an internal oscillator, decoded to 7-segment format by a 16 x 7 Read Only Memory (ROM), and fed to NPN segment drivers. Segment outputs can be TRI-ST ATED - especially useful for display blanking in a standby power mode. MM74C911 operates similarly, except that the 8-bit input data after latching is fed directly to the segment drivers, without further decoding. This device is capable of digit and segment expansion. For example, two 74C91 l’s can be cascaded to drive a 1 6-segment alphanumeric display. Chip size is 1 30 x 1 30 mil, and both devices come in 24 pin DIL packages. Applications include micro- processor display buffers, clock systems, silent hospital paging systems, personalised message receivers and pin-ball machines. National Semiconductor Ltd., 301 Harpur Centre, Horne Lane, Bedford, MK40 1TR. (908 M) 1.7 dB noise at 4 GHz A new packaged microwave GAAS FET with the lowest guaranteed noise figure at 4 GHz in the industry and superior gain characteristics has been introduced by Hewlett-Packard. The new HFET-1102 Low Noise Transistor has a guaranteed 1.7 dB maximum noise figure at 4 GHz and a useful range from 1 to 12 GHz. This low noise per- formance makes the HFET-1102 ideal for use in critical first stage microwave receiver/amplifier applications in land and satellite communications, radar, avionics and ECM. In addition to its quiet per- formance, the HFET-1 102 has a high minimum associated small signal gain of 11.0 dB at 4 GHz, which should minimize distortion even at the moderate power levels at which the device can be operated. The new transistor is packaged in the hermetically sealed HP AC-1 00 A for rugged, reliable performance in demanding applications. Price of the HFET-1 102 is £104.40 each for 1 to 9 units; £91 .87 each for 10 to 24 units; and £83.52 each for 25 to 49 units. Delivery is from stock. Hewlett-Packard Limited, King Street Lane, Winnersh, Wokingham, Berkshire. RG11 5AR 901 M Optical shaft encoder A new medium-resolution optical shaft encoder specifically developed for the industrial and instrument markets, has been introduced by the Ferranti Industrial Components Group, Dalkeith. Known as the Ferranti Model 24 ST encoder, it has a stainless steel shaft carried on ballbearings and a stainless steel protective can. It is mechanically robust and well protected. In addition, a tough optical plastic disc is used in preference to glass, for increased resistance to shock. A powerful output drive stage gives a high degree of immunity to noise and a unique low-level operation LED circuit provides an extended life expectancy compared with conventional units. The counting range extends between 200 and 635 lines per revolution. Dual outputs in quadrature and a once per revolution marker pulse, all at 5 volt logic levels, are offered as standard. Operation at up to 10,000 r.p.m. is specified for normal life application. The Ferranti Model 24 ST encoder is a medium-resolution unit that provides all-round mechanical and electrical reliability. Industrial Products Department, Ferranti Limited, Thorny hank Trading Estate, Dalkeith, Midlothian, EH22 2NG. (915 M) Alphanumeric printer The Printina CSC is a 24-column alphanumeric printer. However, by adjustment of an internal trimmer, characters may be compressed until 32 columns be printed on a single line. The CSC accepts bit parallel character serial inputs coded according to 6 bits ASCII, or to 4 bits BCD if only numbers arc used. Fastest print rate is 1.2 lincs/second at 5.2 power supply (the unit will operate from 5 V ± S% or 6-8 V d.c.). Write time is approximately 400 ms. Life is estimated at 10 6 lines without service. The printer uses standard rolls of metallised electro-sensitive paper. A roll 25 metres long allows 5,000 lines to be printed. Paper flow is downwards. The paper roll is stored internally and a new roll can be fitted easily in a matter of seconds. One of the most rugged printers available, the CSC can withstand the most severe environmental conditions. Price of the Printina CSC is only £195 (25+) and it is also available without case as a single p.c.b. printer for O.E.M. applications. Housed in a cabinet measuring 54 x 192 x 130 mm, the printer weighs only 1 kg. Seltek Instruments Limited, Hoddesdon Road, Stanstead Abotts, Herts SGI 2 8EJ. (910 M) market elektor november 1978 — 11-45 LUlLlILH 7 . Multi-purpose DIL package The new Erg DILpack 14 is a low- profile multi-purpose DIL packaging component. Basically a precision-moulded 14-pin DIL skeleton package, it offers a choice of two tiglit-fit, snap-on covers giving a 5.7 mm or 8.9 mm height profile, and can house numerous components. Because of the close tolerance and tight fit of the covers, components may be encapsulated easily. The Erg DILpack plugs directly into any standard 0.1 in. hole spacing; either a DIL socket or directly onto a p.c.b. for flow soldering. The two rows of 7 , linked terminals may be individually disconnected using only wire cutters, and can be linked and/or cross-linked with direct soldered connection wires. This feature allows the DILpack to be used for preparing programme addresses. ■USt *tr Hybrid circuits and/or passive net- works may be built inside and fully protected from environmental hazards. Using ribbon or regular 14-way cable with an Erg DILpack at each end provides a simple and inexpensive means of reliable board-to-board coupling. Moulded in glass reinforced nylon, these packaging components can be used in the temperature range -55°C to +100“C. Both con- nections and pins arc hard gold plated. Delivery is ex stock. Price 25p each (100 rate). Erg Industrial Corporation Limited, Luton Road, Dunstable, Beds LU5 4LJ. (916 Ml Variable geometry power transformers Parmeko Ltd have developed a range of toroidal power trans- • Turners based on a variable reometry concept. This allows ■ iriations in dimensions for Transformers of a given rating to St them within confined spaces and thereby overcome one of the najor problems facing users of Electronic circuits. Recent developments in ‘micromin’ electronics now- demand smaller inductive components for a given electrical rating. Designers faced with this ‘quart into a pint pot’ problem will be helped considerably by the introduction of the Parmeko 5500 series of toroidal power transformers. Compared to conventional laminated transformers of a similar rating, transformers of toroidal construction typically save about 45% of the volume and can reduce the height even more significantly. The variable geometry concept takes these space savings a stage further. It allows the shape to be changed in three ways: by altering the ratio of height to diameter; by selecting a small core with the winding space fully utilised; or by using a larger core with only part of the winding space utilised. The 5500 series covers a power range at 50 Hz of up to 1 KVA, and within the overall range there is a selection of standard toroidal power transformers to cover popular applications with shorter lead times. Parmeko Limited, Percy Road, Leicester LE2 8FT (924 M) SI 00 Universal Micro- processor/Microcomputer prototyping board Following the increasing use of the SI 00 board size and bussing system in microcomputers (e.g. Attair 8800, IMSAI 8080) and microprocessor applications, Vero Electronics Limited announce the release of a universal SI 00 bus-compatible prototyping board. This board is designed for the manufacture or breadboarding of microprocessor. memory or interface assemblies, and will, without modification, mount directly into any equipment using the SI 00 bus system. The layout of the Vero SI 00 prototyping board has been optimised for maximum flexibility in use and as a memory board will hold up to fifty-two 16-way DIP’s (equivalent to 6K of memory) or in more general use, thirty-six 16-way plus eight 24-way plus two 40-way packages, making it ideal for microcomputer expansion and general digital and analogue circuits. The board has an SI 00 edge connector configuration (i.e. 100 gold-plated contact fingers on 3,175 mm/0.125 inch pitch) and is fully pierced with 1 ,02 mm/0.040 inch diameter holes on a 2.54 mm/0.1 inch matrix. Provision is made for mounting up to four standard TO-220 plastic package regulators together with heatsinks for on board regulation, and the voltage plane is capable of being divided to provide up to four separate positive or negative supply rails. The component side of the board carries a ground plane which can be used for terminations or screening and the wiring side carries both voltage and ground planes, thus providing for up to five planes. The board is intended primarily for interconnection by wire wrap methods, although connections can be made directly from wire wrap pins to the ground and voltage planes by use of the Vero ‘Z’ links. Alternatively the board can be used for soldered connections by using the Verowire pen which wraps a solder through insulated wire around the pins of solder spill DIP sockets. A wide range of compatible standard accessories such as DIP sockets, pins, headers, ribbon cables etc., is available enabling the Vero S100 prototyping board to cope with virtually any micro- processor or microcomputer circuit requirement. Vero Electronics Limited, Industrial Estate, Chandler’s Ford Eastleigh, Hampshire 505 3ZR. (917 M) 3-Rail power supply A thrcc-rail Eurocard power supply announced by Lascar Electronics is claimed to be suitable for most circuits where digital and linear devices arc mixed. They may also find application as micro-processor power supplies. The supply features one output of 5 V 1000 mA, and dual tracking outputs adjustable between ±5 V with a maximum of 100 mA per rail. The 5 V and twin-rail supplies are isolated from each other and feature short-circuit, over-temperature and fold-back over-current protection. Input voltages 220 V a.c. or 240 V a.c. The supply is fitted w ith terminal blocks on the input and outputs, and is assembled on a PCB measuring 160 x 100 mm, with a maximum height of 47 mm. Lascar Electronics Limited, P. O. Box 12, Module House. Billericay, Essex CM 1 2 9QA. 902 M Crystal Oscillators Verospeed, the Vero Group’s rapid despatch service, now have two DIP Packaged Crystal Oscillators included in their range of general electronic components. Both are TTL compatible. One has normal and complementary outputs at 1.0 and 2.0 MHz and the other has a single 10 MHz output. Priced at £ 9.36 and £ 1 1.96 respectively they are both becoming widely accepted in the electronics industry. Verospeed Barton Park Industrial Estate, Eastleigh, Hampshire, S05 ERR England (855 M) 11-46 — elektor november 1978 market Top access case 12 variations are currently available of a new version of the best selling ‘D’ Series instrument case from Vero Electronics Limited. It features quick and easy access to the top of the case by removing 2 screws which release the top panel - ideal for microprocessor applications or chassis-mounted equipment, where immediate access is required. Multiple front panel fixing, anti- slip feet and four optional colour finishes are further features of the range. Vero Electronics Limited, Industrial Estate, Chandler’s Ford, Eastleigh. Hampshire, S05 3ZR. (912 M) Miniature 6 A rectifiers A new line of miniature 6 ampere ion-implanted rectifiers, from Solid State Devices, Inc., block up to 100 V and have a recovery time over two times faster than conventional devices. Designated the HSR-2-52 series, the devices have a typical reverse-recovery time of 15 nanoseconds with a maximum recovery time of 20 nsec. Maximum forward volt- age drop, at 100°C junction temperature, is 825 millivolts; maximum reverse-leakage current is 20 microamperes. By comparison, conventional high- speed rectifiers have a typical reverse-recovery time between 30 nsec and 50 nsec with forward drops of about 1 V. Typical reverse-leakage current is approxi- mately the same as the HSR-2-52. Thought to be the smallest in their current and voltage range, the HSR-2-52 series devices measure only 0.15 inches high by 0.25 inches in diameter. The key to their high-power dissipation is packaging assembly. The die is eutectically bonded to a modified TO-18 transistor case which, along with one lead, serves as a high-current anode. The two other leads are ultrasonically bonded to the cathode with dual 10 mil wire. Manufactured using SSDI’s patented EPION'R ion-implanted process, the devices are radiation hardened. This occurs because their low carrier lifetime permits operation at higher switching frequencies with lower forward- voltage drops. In addition, the small (70 mil square) device geometrically contributes to radiation tolerance. There are seven devices in the HSR-2-52 series with maximum peak- repetitive reverse voltages from 20 V to 100 V; maximum root-mean-square voltages arc 15 V to 70 V. For all devices, average one-half wave rectified current is 6 A, with nonrepetitive surges to 125 A. Operating tem- perature range is -55°C to +175°C. Solid State Devices, Inc., 14830 Valley View Avenue, La Mirada, CA 90638 USA. (906 M) A match for any switch! A ‘rogue* matchstick lines up with a collection of tiny reed switches — ranging from 0.47 in. to 2.070 inches in length (1 1.6 mm- 52.5 mm) - that can perform over one hundred electronic operations per second. Made by a leading British company, the reed switch is a glass-encapsulated device in which the moving parts are cantilevered blades known as ‘reeds’. These reeds are made of ferromagnetic material and are arranged so that their ends overlap, normally with a small air gap between them. The switch is operated by supplying an external magnetic field, which causes the blades to be attracted together to make contact. The simplicity of operation and the sealed environment in which they work gives the switches a long life - up to 100 million operations - and a very high degree of reliability. Reed switches are initially found in areas where high speed and miniaturisation are significant factors. Telecommunications and data processing are two examples. They can also be found in power system controls, office machinery, anti-theft devices and vending and amusement machines. Astralux Dynamics Ltd., Brightlingsea, Colchester, Essex, CO? OSW, England. (907 M) Neat cases A case for micro-processors, data terminals, calculators, etc. has been produced in four sizes by West Hyde. This range of four cases has been designed by R. Fran Sutton, M.S.I.A, N.R.D. The features include the correct angle of the keyboard and data display, the space to take Eurocards or double Eurocards, power supplies, etc., the connec- tions to remain hidden; and a second steeper slope for displays or meters. Produced in leather-grain black and tan or all leather-grain shiny black A.B.S., the cases are ex -stock and the prices include feet. Prices from E 3.90 for one off for the smallest size, with big quantity discounts. West Hyde Developments Ltd. , Unit 9, Park St. Ind. Est., Aylesbury, Bucks. HP20 IET. (928 M Largest UK printed circuit board Close co-operation between Stone Platt Crawley, and Circaprint Ltd., has resulted in a much faster and more efficient assembly operation of their Motorway Signalling Units manufactured at Crawley. The printed circuit board measures 22" x 26" and has 5,200 drilled holes, it carries 520 diodes, 137 lamp holders, and there are 1,600 soldered joints made in one flow solder pass. The printed circuit board is made exactly to a high specification, however, owing to its large size a special jig has been developed by Stone Platt, to ensure perfect flatness when it passes over the solder wave, resulting in less than a half per cent of dry joints. Circaprint supply conventional and Plated Through Hole printed circuit boards to numerous leading British Companies for application ranging from Brain Scanners to Automatic Telephone Exchanges. Circaprint Ltd., Foster Street, Maidstone, Kent. (920 M) Elektor November 1978— 17 advertisement From Science of Cambridge: the new MK 14, Simplest, most advanced, most flexible .ii, microcomputer - in kit form. 5 V regulator PROM -51 2 bytes Power rails and input/output edge connector Extra RAM (optional) ■RAM I/O device (optional) 8-digit, 7-segment_ LED display PROM- 512 bytes ■Extra RAM (optional) Display and keyboard CPU interface circuitry. MK 14 including optional RAM I/O and Extra RAM. Edge connector for external keyboard with up to 32 keys Designed for fast, easy assembly The MK 14 can be assembled by anyone with a fine-tip soldering iron and a few hours’ spare time, using the illustrated step-by-step instructions provided. How to get your MK 14 Getting your MK 14 kit is easy. Just fill in the coupon below, and post it to us today, with a cheque or PO made payable to Science of Cambridge. And, of course, it comes to you with a comprehensive guarantee. If for any reason, you’re not completely satisfied with your MK 14, return it to us within 14 days for a full cash refund. SPECIFICATIONS •Hexadecimal keyboard# 8-digit, 7-segmcni L.EI) display# 8 x 512 PROM, containing monitor program and interface instructions •256 bytes of RAM • 4 MHz crystal • 5 V regulator# Single 8 V power supply* Space available for extra 256-bvte RAM and 16 port I/O# Edge connector access to all data lines and I/O ports Free Manual Every MK 14 kit includes a Manual which deals with procedures from soldering techniques to interfacing with complex external equipment. It includes 20 sample programs including math routines square root, etc), digital alarm clock, single-step, music box, mastermind and moon landing games, self-replication, general purpose sequencing, etc. The MK 14 is a complete microcomputer with a keyboard, a display, 8 x 512-byte pre- programmed PROMs, and a 256-byte RAM programmable through the keyboard. As such the MK 14 can handle dozens of user-written programs through the hexadecimal keyboard. Yet in kit form, the MK 14 costs only £39.95 (4- £3.20 VAT, and p&p . More memory— and peripherals! Optional extras include: 1 . Extra RAM -256 bytes. 2. 16-line RAM I/O device (allowed for on the PCB) giving further 128 bytes of RAM. 3. Low-cost cassette interface module- which means you can use ordinary tape cassettes/ recorder for storage of data and programs. 4. Revised monitor, to get the most from the cassette interface module. It consists of 2 replacement PROMs, pre-programmed with sub-routines for the interface, offset calculations and single step, and single- operation data entry. 5. PROM programmer and blank PROMs to set up your own pre-programmed dedicated applications. All are available now to owners of MK 14. A valuable tool— and a training aid As a computer, it handles operations of all types-from complex games to digital alarm clock functioning, from basic maths to a pulse delay chain. Programs are in the Manual, together with instructions for creating vour own genuinely valuable programs. And, of course, it’s a superb education and training aid - providing an ideal introduction to computer technology. Science of Cambridge Ltd, 6 Kings Parade, Cambridge, Cambs., CB2 1SN. Telephone: Cambridge (0223) 311488 To: Science of Cambridge Ltd, 6 Kings Parade, Cambridge, Cambs., CB2 1SN. Please send me the following, plus details of other peripherals: CD MK 14 Standard Microcomputer Kit 0 £43.55 (inc 40p p&p. □ Extra RAM " £3.88 (inc p&p.) □ RAM I/Odcviec « £8.42 fine p&p.) I enclose cheque/money order/PO for £ (indicate total amount.) Name Address (please print). Science of Cambridge Allow 21 days lor delivery advertisement Elektor November 1978 — 27 Now, from the breadboard specialists even better boards! Since the appearance of the first breadboards back in the '40's, we've really been going places. (The U.K., for one.) So we now have an exceptional range of prototyping products which are outstanding in their simplicity, versatility and reliability. Just see. (And for prices and specs., eyes left!) X Experimentor Series Low-cost, interlocking, solderless breadboard the world's first for 0 and 0.6 in. pitch DIPs. v4 -• 3 The Protoboard Series. Solderless breadboards with built-in 10% regulated 5Vd.c. 1 A power supply; 2,250 solderless tie points; and capacity for DIPs of 14 to 40 pins. Quick Test Series. Low-cost, snap-locking solderless circuit boards for fast design with discrete components. Mate Test Instruments. DM-1 power supply, 5V to 15Vd.c. at 600mA; DM-2 function generator for sine, square and triangle wave generation; DM-3 R/C bridge giving 1 0 ohm to 1 0 megohm, lOpF to I.Opf; DM-4 pulse generator with 0.5 Hz to 5MHz frequency and 100ns to 1 sec pulse widths. IIC Test Clips. .Ultra-low cost 1C *14, 16,24 and 40 pin versions. And, much more too logic monitors, probes, frequency counters and test equipment to ensure the best, fastest results from your design. I I Take a look at our low, low prices and quality specs., and get aboard! (Or if its data you're after, pick up the phone or drop us a line.) For the best, from the specialists in breadboards. Continental Specialties Corporation (U.K.) Ltd., Unitl, Shire Hill Industrial Estate, Dept. 2H Saffron Walden, Essex. CBN 3AQ Telephone (0799) 21682 Telex 817477 Reg. in London; 1303780. VATNo:224 807471. T rade Mark applied for © CSC (UK) Ltd. 1977 Dealer enquiries welcome. Please supply. OOATMMATN. SMOMU.THS OOtPOtUTKXI Name Address My Access/American Express/Barclaycard no. is My cheque/postal order No :tl ★ ★ 1400 1«# 74109 SOp 7401 14# 741 IB •Op 7407 >4# 74120 9«P 7403 !4p 74121 75# 7404 14*, 74122 ♦Op 7405 14# 74123 60p 7406 40p 74125 50p 7407 40p 74126 SOp 7408 20p 74178 75p 7409 20p 74130 '30# 7410 15*. 74131 lOOp 7411 /Op 74132 65p 7417 to# 74135 '00# 7413 30p 74136 •Op 7414 SOp 74137 lOOp 7416 30p 74138 1 25p 7417 TOp 74141 60p 7420 ISp 74147 ?70p 7421 30p 74143 77 Op 7422 TOp 74144 7/0# 7473 TSp 74145 T5p 7425 25p 74147 230# 7476 ?5p 7414B 160# 7427 26p 74150 1 TOp 7428 40p 74151 65p 7430 15p 74153 65# 7432 » P 74154 'TOp 7433 40p 74155 7 Op 7437 75# 74156 /Op 7438 75 p 74157 70p 7440 15# 74160 90p 7441 65p 74161 •Op 7447 65p 7416? •Op 7443 1 10p 74163 •Op 7444 HOP 74164 l?5# 7445 BOp 74165 1 75p 7446 95p 74167 375p 744 7 75p 741 70 TOOp 7448 70p 74173 1 SOp 7450 15p 741 74 lOOp 7451 ISp 74175 25p 7453 15# 741 76 100# 7454 15# 74177 lOOp 7480 15p 741 78 140p 7470 30p 741 79 1*Op 74/2 25# 74 1 8f lOOp 7473 Kip 74181 ?OOp 7474 JOp 7410? /5p 7475 JOp 74184 150p 7476 JOp 74 IBS 150p 7480 45# 74 188 J50p 7401 95# 74 189 3SOp 74B2 BOp 74190 1 40# 7483 *5# 74191 140p 7484 90p 7419? 120# '485 lOOp 74193 l?Oc '486 JOp 74194 lOOp 7489 ?50p 74195 75p 7490 35# 74196 100# 7491 75# 74197 lOOp 749? 45# 74198 '65# 7493 40p 74 199 185# 7494 90# 74293 lOOp 7496 60# 74LSOO 25# 1496 70p 74S1I? lOOp 74100 74104 74105 74107 96p *0p •Op JOp 12Sp 7805 781? 7815 7818 140p 140# 140p '♦Op 74166 125# 7410 7412 7420 7430 7432 744? 7474 7476 7463 7493 7496 74107 74121 741 S3 74161 10 tor 10 to. 10 tor 10 tor 10 to. 10 tor 10 tor 10 to. 10 lor 10 tor 10 »0r 10 tor 10 tor 10 tor 10 lor CMOS TTL OFFERS 7 00# 250# 4 50# 2 00# 250# 4 00p • OOp 4000 4001 4002 4006 4007 4009 4011 4012 4013 4015 4016 40p 4017 90p 4018 90p 4020 lOOp 402? 4023 4024 4025 16p 4026 160p 4027 SOp 4028 90p 4029 110p 4030 S6p 4032 96p 4035 120p 14# 14# 14# 14# 16p 4043 4046 4047 4048 4049 4050 4054 4055 4056 4060 4066 4069 4070 4071 4072 4077 4061 4062 4510 4518 4520 4628 250# ISO# loop 55# 120p 20# 25# 1«P 120p MURATA ULTRASONIC TRANSDUCER MA40LIR/S £2.50 Each £4.00 Pair SPECIAL OFFER TOOOuF 35V 40p 100 tor £30.00 LINEAR 450p 890p WOp AY3 8500 AY3 8710 AY3 8760 CA3060 CA3066 CA3004 CA3066 C A 3086 CA3088 C A 3089 CA3090 AO CA3130 CA3I40 CA3123I LM2I1H LM300 T 05 LM301 AN IM304 LM307N . M 306 T05 lM308 O'L imjo9* LM310 T05 LM31' T05 LM317K LM324 LM348N IM360N LM382N LM391 IM555 LM709C IM710 705 lM 7 1 0 Oil LM723 705 LM 723 0*1 IM733 LM 74 1 LM 748 LM1303N LM 1 458 LM3080 LM3900N MC' 31 OP MCU12P MC1314P MC131SP Ml 747CP MMS314 MM5316 NE529* NE555 NE556 225# 200p 250# 2«Op 325# 150p 200p 110p 25# 45p 155p lOOp 150p 28p NE5428 SL917B 5N76003N SN76013N 5N78013N0 SN 76023N Sh760?3hO SN76033N SN76727N SN76228N SN76660N • A A 300 TAA350 1AA550 T A AS 70 TAA661B T AA 700 T AA 790 T A0 100 t AD1 10 TBA1 70S T3A120T TBA480O T0A52OO TBA5300 TBA54C T BA 5400 T0A55OO TBA560C T0A64I Al? 7BA700 TBA7?0 TBA720Q IBA 7500 T8A80C TBA810 T8A820 TBA920C 'BA990 7CA270O TCA270S TCA760 7QA2020 XR320 XR7706 XB2207 XR7708 XR2216 X R256 7 XR4136 XR420? XR42I2 XR4739 ZN414 50p 220p 160p 1 30p •Op l?5p 200p 250# 215# 230# 250a 135# 335p 250p 200p 250p 250p 225p 110p 110p lOOp JOOp 280p 250p 325p 750p 675a 450p 650p •50p 2SOp 150p i50a POWER SUPPLY CAPS 35a 50p 220C 16 7200 40 2200 63 2200 100 3300 30 3300 63 4700 40 4700 25 4700 63 120a 470070 1 35p 0000 10 lOOp 0000 25 ISOp »p 15000 15 65# 22000 25 50p 150p 50p 150p 200p ENQUIRES f OR any OTHER Ty#|S ELEC CAPACITORS 047 25 i 16 t 25 1 50 2 2 25 2 2 35 3 3 25 4 7 10 4 7 16 4 7 25 4 7 50 6 8 25 10 10 10 16 10 25 10 50 22 6V3 22 10 22 16 27 25 2? 35 2? 50 33 «V3 33 16 33 25 33 40 33 50 7p 7# 7p 7p 7# 7p 7p 7p 7p 7p 7p Ip 7p 7p 7p 7# 7p 7# 7p 7# •p 7p •a •a •a 47 10 47 16 47 25 47 35 47 50 100 10 100 16 100 25 100 50 100 63 220 16 220 25 720 50 330 25 330 35 330 50 4 70 10 470 75 470 35 470 50 1000 16 >000 75 1000 35 1000 40 <000 63 1 200 63 7200 10 15a 12p 14p 22 » 17# 1®P 20# 1*P 2*P 22p POLY CAPS 1000 Pf 5p 0 1 uF 6p 2200 5P 0 22 uF 7# 3300 5p 0 33 uF »P 4700 5p 047 uF 12# 6800 5p 10 uF TOP 001 uF 5p 7 7 uF 25p 0 02? uF 5# 4 7 uF 35# 0 033 uF 5# 6 8 uF 40p 0047 uF 5# TANT. BEADS Oil /36V 0 15/36V 0 22, 35V 0 33/36 V 0.4 7/10V 0.4 7/36V 0 66. 36 V 1 00/10V 1 00 35V 1.5/36V 2. 2/26 V 2 2/35 V 3.3/ 16V 4 7/16V 4.7/2SV 4 7 736V 6 8'6V3 68'3SV 1 0/35V 22/ 15V 33/16 47/3V 47/UV 100/3V 14p 14p 14p 14p 14p 14p LATE EXTRAS 400uF 96H90 LF 356 LF357 TDA1008 TDA1034 P.O.A p.o.a. p.o.a R.O. A. TRANSISTORS AA113 AA?1 7 AC12I AC 126 ACl ?7 AC127 01 AC 128 AC 151 AC153 AC153K AC 154 AC187 AC 188 AC y 1 7 AC Y 19 AC y TO AC y ?? ACV40 ACV4I ACY4? AO I 30 AD143 AO U9 20p 20# 25# 30# 20 p 20# 50p 50a I50p 150a BC1 7? BC1/7 BC178 HC IB? BCI871 BCIB3 BC183L BC1B4 BCl»4i BC ’96 BC704 BC205 BC207 •C21? HC?1?L BC7I3 BC2131 BC214 BC714L BC237 BC237B BC 768 H( 794 15# 15p iOp 12a IOp 1 2p iop i2a 20p 12 a 12p i2a iia 12 a 12p 15a 15a IBo iop 16a BDX3? BOX47 BOY 10 BE Mb BE 170 BE 121 BE 123 BE 175 BH 2/ BE 13/ BE 154 BE 160 BE 161 BE 173 BE 17B BE 179 BE ISO BE 181 HE 1B7 BE 183 HE 1B4 BE 186 BE 194 200a 50p 100a 20a 50p 45p 20p 26a 75a 30a 30a 30p 25a 20p 7Sp 10 a 40# 0(300 25p Bf 195 10# AD16? «op BL30I 25p ef 196 10# AOI6' ?MP 90# 8(303 JOp af 19/ 10# AF 1 14 25# 81. 30 7 ISp Hf 190 ?5p At 115 75# Hr 308 ISp Bf <99 75# Af 1 16 75# 8C3I7 17p 8» 700 JOp AH 1 7 75# HC318 12# Hf ??4 TO# AM IB 80# 8C373 30# Hf 775 ?1>P Af 1 78 «5p 8(378 18# Hf 741 16# AF 139 J5p 8C337 70# HF ?44H 3Sp Af 239 45c 81.338 18# Hf 755 25# Af ?79 60# HC348 TOp Bf 75 7 25# AUHO 180p BC46I 3Sp Bf 758 25# HA 1 14 12# 8CS16 SO# Hf 759 25# HA1 ?' 12# 8C517 SOp Hf?7l 25# 8A154 12# BC54 7 17# Hf ?/4 JO# 8 A 1 5 7 is# 8C54/0 13p Bf 374 30c HA1 73 15p BC548 12# Hf 336 35# HAX 1J s# BC 5481. 14# Hf 337 35# 0**19 s# 8C5498 13# HF367 20p BAA?' TOp BCS491 14# Hf 394 35# 88105 J5p BC55? 13# Hf 45« SO# rri in 35o 8C5S/B. IS# Hf 594 50# BC107 10p BCY34 •0# Hf 596 SOp BC 106 10p 8C Y38 100# 0/59/ so# 8C108C 15# BCY42 25# Bf R40 JOp BC109 10p BCY43 25# 0f RBO JOp BC109C 15# BCY58 18# Bf *58 TOp BCI13 12# BCY59 75# Hf A6C 25p BCH4 15# BC Y 70 IS# Hf A 88 JOp BC115 ISp 8CY7I 20# Bf *89 JOp BC1 16 ISp BC y 7? IS# 0f W91 JOp BC 117 lie BD11S 4S# Bf X?9 25p BCi 18 12# BD171 85# Bf *34 25p BCI 19 25# BD131 35# Bf X 38 75p BC 1 75 16# BD13? 35# Bf X44 35p BCi 258 TO# BD133 45# Bf X48 45p BCi 76 70# BD135 35# Bf Xfli lOOp 80 34 ISp BDI36 35# Bf X85 30p 80 36 ■6# BD137 40# Bf X87 ?Sp 8037 15p BD139 40# Bf *88 25p BC 1 38 30# BD140 40# Bf Y 10 JOp 80 40 30b BD 144 160# Bf Y18 100# 8041 30# BD181 100# Bf YI9 lOOp 804? 30# BD18? 100# Bf YSO TOp 8043 30p BD'88 130# Bf Y5I 20c 8047 10# BD707 70# Bf YS2 20p 00 48 10p BD720 65# Bf Y53 25# BC»48C 14# B077? 65# Bf •90 1 25p 0049 iop BD733 SOp BRIO! 35# BC1S3 16P BD738 50# B R v 39 35# BC ’ 54 l«P BD242 60# BRY56 35# BClS? 10p BD757 SO# B5X70 20p 8058 10p 8D263 65# BSY40 25p BCi 59 10p 8060 ' •Op BSY95 TOp BC167A !2p B0608 •Op BT100A •Op 0068 14# 00609 •Op BUI 35 TOOp BO 69 is# BD6’0 SO# BUI 33 190# 80 71 12# BD679 75# 8U708 2 TOp B 0680 75# By 100 T5p Bvi?6 15c BY 17/ BV164 BV133 By 164 BYX94 Cl 1 70 Cl 1 64 MOO 1701 E204 t 300 1310 1 470 E470 MJE340 ME>SA05 MPSA06 MPSA56 TIP29 1IP29A TIP79C TlE»30 TIP30A TIP30B 7IP30C 7lP3t 1IP31A IIP318 TIP3IC 1 IP37 7IP33 IIP34 IIP35 7IP35C. f |P4 1 A 1IP41B TIP4IC T|P4?A MP47B TIP42C TIP2955 IIP3055 TIS90 TIS91 IN9'« 1N3754 IN400I IN400? IN4003 IN40O4 IN 4005 IN 4006 IN4007 IN4148 7N456A 2N979 7N930 ?N1»? 7NI303 2NI305 2N1306 7N1306 2N1711 7N2719A 7N74B3 2N2906 2N2907 2N3053 2N3054 2N3065 7N3702 7N3703 2N3704 7N3705 7N3706 2N3706 2N3715 2N3819 2 N 3866 7 N 3904 2N6027 2S0234 7N5777 56a 25p 42p 50p 30a 32a 32a 47p «9p 75p 55a 58p 65a 5ta 65a 70p 115a 225a 250p 70a 75a •5a •Op 70a 50a 75a 75a 5a 70a 5a 5p 5a 5a 5a ?Op 70a 25p 30a 30p 3«a 50p 72a 75a JOp 16a 70p TOp 50p SOp up 1 2 p 12 a I2p 12 p 12p 300p 25a •6a i5a 50p 50p * 1N4148 DIODES BY ITT TEXAS U30 lor £1.50. Please note these are full spec devices Texas TIS 88A V H F F E T 10 lor £2.30 100 lor £20 00 555 TIMER 10 tor £2 50 741 OP- Amp W 10 for £2 00 , MULLARD MODULES LP115? lOOp LP1153 4 OOp LP1 165 400p LP1166 4 OOp LP 1168 400p LP1 169 400p LP1173 400p LP 1181 400p LP1400 400p EP9000 280p EP9001 28Tp EP9002 2 BOp d POTENTIOMETERS IK UN 5K LIN 10K LIN 25K LIN 50K LIN 100K LtN 750K LIN 500K LIN 1 M LIN 7M LIN All SK LOG I OK LOG 75K LOG 50K LOG 100K LOG 750K LOG 500K LOG 1 M LOG 2M LOG •t 30p EkIi GANGED POTS All al SOp Each SK . 5K LIN or LOG I OK • 10K UN or LOG 75K ♦ 25K UN or LOG 50K . SOK LIN or LOG 100K • I00K UN or LOG 750K . 7SOK LIN or LOG 500K • SOOK LIN or LOG 1 M > IM LIN or LOG 2M ♦ ?M LIN or LOG ★ ★ LIMITED OFFER BC237 100 for €5.00 ELEKTORNAOO AMPLIFIER KIT. All part* £12.00 P.C. Board £2.96 PoM*r Supply parts P.O.A. OIL SOCKETS • PIN 13a 14 PIN 16 PIN 28 pin 14# 15a % GHz COUNTER Twtm base and control board parti .... £22.44 P.C. Board extra £7.86 Counter and Oiaplay board parti £31.76 P.C. Board extra £8.96 L.F. Input board parti £4.01 P.C. Board extra £1.40 H.F. Input board £1X26 P.C. Board extra £1.30 Pr«ce o* Total kit leu mechanical parti . £81.86 A.. P.C. Boardiextra £19.60 Total Pricai £101.36 MK50398N A Six Decade Counter /Decoder as used >n Elektor issue 38 £8.25 High quality Trimmer Caps Mm Max 2.5pF-6pF All one 3.5pF-13pF price 20p 7 0pF-35pF . 10pF-60pF W FERRITE BE AOS 6 MM long OD 3MM ID 1MM 3p each 100 for £2.00 Paper 0.5uF 400V AC C*>* Ideal for Car ignition Systems etc. 50p each Assorted Japanese I.F. Transformers 20 for £1.25 ENAMEL COVEREO COPPER WIRE 40p 16 SWG 40p 18 SWG 45p SOp 22 SWG &0p 24 SWG SOp 50p 28 SWG SSp 30 SWG SSp SOp 34 SWG SOp 36 SWG 65p 70p 40 SWG 70p 42 SWG BOp ROTARY SWITCHES BY LORLIN 1 POLE 12 WAY 2 POLE 6 WAY 3 POLE 4 WAY 4 POLE 3 WAY All at 40p Each OPTO ELECTRONIC CORNER SPECIAL SCOOP OFFER 0 125 or 0 2 inch RED LEDS 16# each. 10 for £1.00, 100 for £7.60, 1000 for £60.00. 0.125 or 0.2" YeHow and Green LEDS 16#. 10 for £1.40 100 for £1X00 HP 508 2 - 7750 16 Op each OL747 Seven Segment Common Anode Displays. Character Height 0.6" £2.00 each FND6O0 Seven Segment Common Cathode Displays. Character Height 0.5" £1.30 each. 4 for £5.00 2N5777 Photo Carlmgton SOp each. ORP12 Japanese 76# each. Muliard £1.25 aach. DECODER BOARD CONTAINING 18 x 74156 2 x 74155 2 x 7409 1 x 74180 1 x 74150 1 x TIP3? 2 x 60 WAY EDGE CONNECTORS Few only left of this unreap unrepeatable bargain £3.50 aach. • • • • • XTAL MIC Inserts 75p each 5" Scopetubes SE&J I for calkers onlyl £15.00 each Bit* Reiector ceils 50- 100KHZ “••“l • •• • 1 MHz CRYSTALS CXOO Push to Make Switches 20 p each Chokes 10uM 35p aach IOOuH 65p aach Futaba 5LT02 Non Multiplexed 4 Digit Phosphor Diode Display With A M /P M /Colon £5 (X) PRE SET POTS lOOmtv non/' Vertical 50 H IM Ohm 8# Each MULLARDPOT CORES LA3 100-500KHZ 75p LA4 1O30KH? 100# LA5 3D100KH2 LAI 3 200p B2Y88 ZENER DIOOES 400m wr OV7 33V 10# Eacf BRIOGE RECTIFIERS 1 AMP 50V 1 AMP 100 V 1 AMP 200V 1 AMP 400V 1 AMP 600V 1 AMP 1 000 V 7 AMP 50V 2 AMP 100V 2 AMP 200V 30# 30# R.C.A TRIACS 400V 8 AMP £1 20 400V 15 AMP £1.50 MICRO BLOCK 2102 250 Nano Sec Static RAM H024 x 1 BIT) £2.20 aach 4 for £8 40 8 for £16.00 -fa 2102 450 Nano Sec Static RAM 11024 x 1 BIT) £1.00 aach vt_ 2112 450 Nano-Sec Static RAM 1256 x 4 BIT) £2.95 aach 4 for £11.60 a 8 for £22.80 M 2513 Character Generator. Upper Case £7.00 aach t? 2513 Character Generator lower case £7,00 each -ft MM5204 E Rom , £8.00 each 'yf 8212 8 Bit m/out . Port £3 00 each "ft 8080 an MPU(CPU) £12.00 aach . 8831 Tri State Line** Driver £2 00 each 8833 Tri State Trans T ransceiver £2.00 each 8835 Tri State T ransceiver £2. 00 each AYS- 1013 U/ART £6.00 T. POWELL 306 ST PAULS ROAD HIGHBURY CORNER LONDON N1 01-226 1489 BARCIAYCARD SHOP HOURS MON - FRI9 - 5.30 PM SAT 9 -4.30 PM OVERSEAS AGENTS. BUYERS, ETC. ALWAYS WELCOME 1 MINUTE WALK FROM HIGHBURY CORNER TUBE ALL PRICES INCLUDE POST AND VAT