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,;, = ~ :;, -...."-~'ii ~::.m::~"-~~ 0 • 13.79• ' Test yourself on the Reaction Trainer Improve your skill at your favourite sport by practising on this Reaction Trainer. It can be used to improve eye-to-hand response & coordination, or it can be used as a fun toy at parties or at school. By JOHN CLARKE The Reaction Trainer is our version of a device shown recently on the TV show "Beyond 2000". It was touted as one of a number of electronic training aids for testing and improving eyeto-hand response for sportsmen and women. Our version consists of 10 LEDs plus 10 pairs of associated touch plates scattered over a large board, together with a 4-digit counter which indicates time up to 99.99 seconds. Touching the START plates resets the counter and then a LED lights at random. The counter starts counting from the time the LED lights to when the plates associated with that LED are touched. The counter then stops until another LED lights at random. The player continues to respond to illuminated LEDs until the FINISH LED lights and the game is over. Since the LEDs light at random , there is no way of anticipating which LED will come on next and so the game is unpredictable, even for those who have become familiar with it. An extra level of unpredictability has also been added in that the next LED in the sequence does not necessarily illuminate immediately after the previous LED has extinguished. This keeps the player searching for a LED on the board until it lights. Of course, the reaction time counter does not increment until a LED is lit. The score on the counter indicates the total time taken to respond to all the illuminated LEDs. The total number of LEDs to be illuminated is set by MARCH 1993 57 a DIP switch; you can select an 8, 16, 32 or 64 LED sequence. I Circuit details The circuit comprises a 1-in-10 LED driver, a random sequence generator, a test length counter and a reaction time counter - see Fig. i. ICl is a decade counter and 1-of-10 decoder. It is clocked by IC2b, a Schmitt trigger oscillator connected to run at 10kHz. Provided the CE input (pin 13) of ICl is low, it is clocked and each of its 10 outputs goes high for 0. lms every lms. The 10 outputs ofICl drive transistars Ql-QlO via lOkQ base resistors. These transistors in turn drive their respective LEDs (LED 1 - LED 10). However, even though ICl may be counting rapidly and driving the transistor bases, none of the LEDs is allowed to turn on until transistor Ql 1 switches on. This transistor remains off while ICl is counting and turns on only when ICl stops. ICl is stopped at random to make one of the LEDs come on by pulling pin 13 high. This pin is driven by pin 1 of flipflop IC5b. This flipflop also controls Ql 1 so its operation is central to the whole circuit. We will come back to IC5b later. ,, \"w\'\ ~ 0 0 ; H•· ~ a. 0 "' "' ~ ... < 0 I• "' ~ ... < C> "' 0 ~ ... < "'0 "' "' ~ ... < I• .... "' ~ ... I• < ~ ~ ... < Touch plates Each LED has a pair of touch plates associated with it. One touch plate connects to the collector of the driving transistor (Ql-Ql0) while the other touch plate of the pair is commoned with all the other touch plate pairs and connected to the pin 1 input of Schmitt NAND gate IC2c. A 2.2MQ resistor normally holds this input high and so the output at pin 3 is normally low. If you place your fingers across a set of touch plates associated with a lit LED, your (relatively) low skin resistance and the conducting transistor cause pin 1 of IC2c to be pulled I 0 I• .,, "' 0 ~ "' ... < 0 I• "' "' ~ I· < < I• < ... ~ ::: I• ~ Fig.1: the circuit uses 1-of-10 decoder ICl to drive 10 LEDS & 10 touch plates via Qi-QlO. These LEDS come on at random, as controlled by a pseudo random sequence generator based on IC3, IC4a & IC4b. IC7 & IC8 record the elapsed time for a complete game & display this on 7-segment LED readouts. 58 SILI CON CHIP -0~ .., .,., w 0 0 ::!'. ~"' "'°' Q~ a: g"' 0 ....... ~ 0 H•· 0 0 ~ ~ I• i:0 1:,1 co w .... co ::i: :i:, (") s:: > 0.1 7 7 +5V r 5V 8 IC3 4015 7 DA RB 7 6 B 03B 11 8 IC4a 4030 7 15 DB VIEWED FROM BELOW EOc RANDOM PULSE GENERATOR 14 +5V 10 O4A 1 CKB 9 CKA RA 11 TEST LENGTH COUNTER 7 8 5 4 64 10 IC6 3 CK 4040 16 2 32 R 16 2 I GO ~ 11 7 7 ~K 12 3 +5V 01 1N4148 7 +5V 7 1 7 1 IC7 7555 8 .047+ REACTION TRAINER 4 +5V 12 5 6 18 13 CK LE OS R 9 IC8 74C926 7 DISP1 4xHDSP5303 15 17 g f 4 2 •3 d 1 C 16 b a D 11 C 10 B 6 9-12V INPUT 013 BC336 7 3,6 7x68D 02-D5 4x1N4004 B 014 BC338 3,8 5 DP B 015 BC338 +5V 68D DI_SP2 DISP3 7 3,8 ~ f1:-,b 7 7 • 100 5x0.1 16VWi 3,8 d 6 c 4 7 I ' b ·/=I!: I g 10 • DISP4 I OUT ' B 016 BC338 I_I 1=1 ,_,. 1=1 ,_,. ,_,. 9 START +5V +5V RESISTOR COLOUR CODE o No. Value 4-Band Code {1%) 5-Band Code {1%) 0 1 0 1 2.2MO 1MO 150k0 100k0 47k0 210k0 1800 680 red red green brown brown black green brown brown green yellow brown brown black·yellow brown yellow violet orange brown brown black orange brown brown grey brown brown blue grey black brown red red black yellow brown brown black black yellow brown brown green black orange brown brown black black orange brown yellow violet black red brown brown black black red brown brown grey black black brown blue grey black gold brown 0 1 0 2 0 ' 0 0 2 0 8 Below: take care to ensure that the decimal points on the 7-segment LED displays are oriented towards bottom right when installing the displays in their sockets. A small heatsink is sandwiched between the 3-terminal regulator & the PC board for cooling. low. IC2c drives the reset pin of IC5b. Hence, when IC5b 's Q output goes high, it stops IC1 and allows a LED to light. When you touch the appropriate pair of touch plates, IC2c then resets IC5b which allows IC1 to start counting again and so no LEDs are alight. At least, no LEDs are alight until IC5b is toggled and changes state again. IC5b is toggled by flipflop IC5a and the associated "pseudo random sequence generator" which we will now discuss. Random sequence generator The pseudo random sequence generator consists of a clock (IC2a), a shift register (IC3) and two XOR gates (IC4a & IC4b). IC2a is a Schmitt trigger oscillator with its frequency set by trimpot VR1. The oscillator output at pin 10 clocks the two inputs of shift register IC3. IC3 is wired as a single 8-bit shift register by connecting the fourth output (Q4A) of the first stage to the Data input (DB) of the second stage. The Data input of the first stage (DA) connects to the output of XOR gate IC4b. XOR (exclusive OR) gates only have a high output when the two inputs are different. In other words, the output is low when both inputs are high or both inputs are low. It is high otherwise. IC4a acts as an inverter for pin 11 of IC3, so the only XOR gate we are really concerned with is IC4b. This produces a low output to DA (pin 7 of IC3) whenever pin 6 ofIC4b and Q4B (pin 2) ofIC3 are different. The result is a series of low and high outputs at Q4B with a sequence that continually varies between the limits of one high output per eight clock pulses to seven high outputs per eight clock pulses. This is called a "pseudo random sequence". The output of IC3 is fed to IC5a, a D-flipflop which divides the Q4B output by two. Its output at pin 13 is in turn fed to flipflop IC5b which has its 60 SILICON CHIP Fig.2: install the parts on the PC board & complete the external wiring as shown here. Take care to ensure that the correct part is used at each location & don't forget the four wire links that run beneath the 7-segment LED displays. Note particularly that Qt 1 is a BC328, while Qt-QlO are all BC338s. 1 0 2 LE02 LEOS LE04 LEOS LEOS LE07 LEOS LE09 LED10 START TOUCH PLATES 0 - - - - - - - - , ---- SHIELDED CABLE TO TOUCH PLATES 2-10 (DAISY CHAIN CONNECTION) data input (pin 5) tied to the positive supply rail. On the first positive clock input, its Q output at pin 1 goes high and the Q-bar output at pin 2 goes low. As noted previously, the Q output of IC5b connects to the clock enable (CE, pin 13) of ICl and prevents it from clocking when it is high. At the same time, the Q-bar output is low POWER SOCKET and this turns on transistor Ql 1 so that one LED is lit. As soon as IC5b is reset by ICZc, ICl begins to count again and it continues to do so until IC5b is again clocked by MARCH 1993 61 (REG1). The 5V output from the regulator is decoupled with a lO0µF capacitor. Construction This rear panel view shows how the commoned touch plates terminals are daisychained together using shielded cable. The LED anodes are daisychained in similar fashion using hook-up wire & connected back to the PC board . . IC5a. Normally, IC1 has time to run through all its outputs several times before it is stopped again by IC5b. Test length counter IC6 is the test length counter. This counts the number of times the clock enable (CE) pin of IC1 goes low and this controls the number of times a random LED is displayed. The 8, 16, 32 & 64 outputs ofIC6 are selected by DIP switch DIP1. When the selected output goes high, it resets IC5a, thus preventing further clocking of IC5b. At the same time, the high output drives transistor Q12 which drives the FINISH indicator (LED 11). This leaves the circuit with the Q output of IC5b low and Q-bar high. IC1 is thus stopped, transistor Ql 1 is off and no LEDs are lit. This state will remain until IC6 is reset by pressing the START touch plates. These control Schmitt NAND gate IC2d which is connected as an inverter. A 1MQ resistor normally holds the pin 13 input of IC2d high. When the start plates are touched, pin 13 is pulled low and IC2d's output goes high. This resets IC6 and so the selected output goes low to release the reset on IC5a. Diode Dl now holds the reset on IC5b high so that the LEDs are kept off until the START touch plates are released and flipflop IC5b is clocked by IC5a. The reaction time counter consists 62 SILICON CHIP of IC7, IC8 and four 7-segment LED displays. IC7 is a CMOS 555 counter which is set up to produce a 100Hz signal from its pin 3 output, provided the reset input at pin 4 is high. When pin 4 is low, no oscillation occurs. As well as all its other functions, IC5b controls the reset pin of IC7. So when pin 1 of IC5b is high, IC1 will have a LED lit and IC7 will oscillate to clock IC8. IC8 is a 4-digit counter and display driver. The 7-segment LED displays show time in seconds; eg, 23.45 seconds. And guess what! When the game is to be started again, IC8 is reset by IC5b, via diode DL So IC5b is the hub of all the circuit operations. Let's recap on the circuit operation. IC1 is clocked by IC2b but it can't count while its CE pin is high and nor can any LED be displayed until Ql 1 turns on. Both are controlled by IC5b which in turn is clocked by IC5a and the pseudo random sequence generator. This ensures that the LEDs turn on randomly for 8, 16, 32 or 64 times, depending on the setting of switch DIP1. IC7 and IC8 record the duration of the game and everything starts anew when the START touch plates are touched. Power for the circuit is derived from a 9-12V AC or DC plugpack. Its output voltage is rectified by diodes D2-D5, filtered by a lO00µF capacitor and applied to the input of a 5V regulator Most of the circuitry for the Reaction Trainer is mounted on a PC board measuring 143 x 194mm (code 08312921) - see Fig.2. We mounted the PC board and the remaining components on a sheet of white Perspex measuring 670 x 450 x 2.5mm. This Perspex sheet was supported on a timber frame made from 25 x 25mm Ogee moulding. The touch plates were made from self-adhesive aluminium strips (the kind used to make front-panel labels), but you could also use suitable pieces of thin aluminium sheet and affix them using contact adhesive. A cutout was made in the top right-hand corner of the white Perspex sheet to allow the LED displays to be seen and this was fitted with a red Perspex viewing window. Naturally, you can make the game board as large or as small as you wish, depending on the size of the Perspex offcut you can obtain from your local plastics retail outlet. Nor do you have to use Perspex. You could use a sheet of plywood, Laminex or virtually any insulating material. Begin construction by checking the PC board for shorted and open circuit tracks. Shorted tracks can be corrected by scraping between them with a sharp hobby knife, while open circuit tracks can be repaired with a short length a tinned copper wire and solder. Once the PC board pattern has been checked, you can install all the PC stakes and links. Don't forget to install the links that sit under the dis. plays. This done, install the resistors, DIP switch, trimpot VR1, the diodes and ICs, making sure that each is inserted correctly. The capacitors can be installed next. Note that the electrolytic capacitors should be laid flat on the PC board to provide sufficient clearance between them and the Perspex panel. The transistors can then be inserted, noting that Ql 1 is a BC328 while the others are BC338s. The regulator is mounted with its leads bent at rightangles, so that its metal tab can be bolted to the PC board. It should be fitted with a small U-shaped heatsink made from scrap aluminium - see photo. PARTS LIST 1 PC board, code 08312921, 143 x 194mm 1 front-panel label, 178 x 237mm (available from RCS Radio) 1 500mA 9-12V AC or DC . ·plugpack 1 sheet of white Perspex, 670 x · 450 x 2.5mm 1. piece of red transparent Perspex, 207 x 67 x 2.5mm 1 15 x 30 x 1.6mm aluminium panel.for heatsink 1 ~mm screw & nut for heatsink 22solder lugs 10 5mm LED bezels 26 3mm x 10mm screws & nuts 14 countersunk wood screws 4 12mm tapped brass spacers 4·4mm x 6mm screws 1 SPOT toggle switch 1 4-Way DIP switch 1 panel mount DC socket 2 2.5mm screws & nuts to suit socket 1 1.5-metre length of shielded cable 1 1-metre length of 10-way Finally, the displays are mounted on Molex strips to raise them above the PC board. First, cut the Molex strip into 10 5-way lengths, then insert and solder them into the board. This done , snap off the shorting strip on the top of the pins before inserting the displays into the resulting Molex sockets. LED 11 is inserted so that it is at the same height above the PC board as the displays. Initial testing For the initial testing, you will need to temporarily solder each of the LEDs (1-10) to the PC pins at the bottom of the PC board. Set the DIP switch for a sequence of eight and apply power. Check that the digital displays light up. If they do not, switch offimmediately and check that all the parts on the board are correctly located and oriented. If all is well, the display should be counting up and one of the 10 LEDs (LED 1 - LED 10) should be alight. If you now momentarily touch the START PC stakes (A & B) with your fingers, the display should reset to 00.00, after which it should begin rainbow cable 1 700mm length of 0.8mm tinned copper wire 17 PC stakes J 40-way Molex socket strip (for mounting !.,ED displays) 1 1Mn miniature horizontal trimpot (VR1) (01-010, 012-016) 1 BC328 PNP transistor (011) 1 1N914, 1N4148 diode (D1) 4 1N4004 1A rectifier diodes (D2-D5) 4 HDSP5303 common cathode red LED displays 11 5mm red LEDs Semiconductors 1 4017 decade counter & decoder (IC1) 1 4093 quad 2-input Schmitt NANO gate (IC2) 1 4015 dual 4-bit shift register (IC3) 1 4030, 4070 quad 2-input XOR gate (IC4) 1 4013 dual D-flipflop (IC5) 1 4040 binary counter (IC6) 1 ICM7555, LMC555 CMOS timer Capacitors 1 1OOOµF 16VW PC electrolytic 1 1OOµF 16VW PC electrolytic 7 0.1 µF 63VW MKT polyester 1 .047µF 63VW MKT polyester 1 .01 µF 63VW MKT polyester 1 .001 µF 63VW MKT polyester 2 220pF ceramic (IC7) 1 74C926 4-bit counter & display driver (IC8) 1 7805 3-terminal 5V regulator (REG1) 15 BC338 NPN transistors counting again and another LED should light. If you now touch PC stakes C & D, that LED should extinguish, the display should momentarily stop and another (or the same LED) should light up. Trim pot VR1 sets the speed at which the next LED comes on after the previous LED has been extinguished. If this time is too short, the LEDs will appear to come on instantaneously and that removes some of the difficulty from the game. Note that the outputs of IC1 are not in sequence. This was done to simplify the PC board layout. Since we want randomly lit LEDs, the order is not important. You should be able to continue your test until the FINISH LED lights; ie, after eight LEDs have been lit. Note that one or more LEDs may light more than once in a particular sequence. Completing the assembly You are now ready to complete the construction and so we will outline how we put ours together. The first step is to cut out the top right-hand corner of the white Perspex Resistors (0.5W, 1%) 1 2.2MQ 1 47kQ 1 1MQ 1210kQ 1 150kQ 2 180Q 2 100kQ 8 68Q Miscellaneous Contact adhesive, PVA glue, masking tape sheet so that the red transparent piece can be fitted. We assembled the timber frame with PVA glue and affixed the Perspex to it with contact adhesive. Countersunk screws through the Perspex and the frame can be used for added strength and to further support the red Perspex window. You will need to drill holes in the Perspex for the 10 LEDs, the power switch, the input socket, the four mounting pillars for the PC board and the touch plate contact screws. You will also need a cutout to provide access to the DIP switch. The positions for two of the pillars for the PC board, the DIP switch cut-out, the power switch and socket are shown on the front panel label and this can be fitted and used as a drilling template. The top two mounting positions for the PC board are found by placing the board against the Perspex and marking out the locations. When marking out the hole locations for the LEDs, try to position them so that they are randomly placed. Keep in mind that there needs to be sufficient room for two touch plates around each LED and be careful that MARCH 1993 63 ... N N CJ' .... SI C) ~ A ' I0 I you don't encroach on the space needed for the two START touch plates which are mounted below the front panel label. It's best to drill small pilot holes for the LEDs first and then ream them to size so that the LED bezels are a tight fit. It's also necessary to drill each touch plate to accept a machine screw. This is then used to secure a solder lug on the underside of the Perspex to 64 SILICON CHIP terminate the leads from the PC board. The power switch and power socket can now be mounted and the wiring completed as shown in Fig.2. Note that a separate lead is run from the PC board to the cathode (K) of each LED via a touch plate terminal. The LED anodes are commoned and connected to the PC board adjacent to Ql 1. The other touch plate terminals are commoned to the centre conductor of a shielded cable to prevent noise pickup. The START touch plates are connected via a single length of shielded cable. With all the wiring complete, you should test the circuit operation again to ensure that everything is operating correctly. Note that you may need to clean the touch plates periodically with methylated spirits to ensure reliable operation. SC