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Items relevant to "Test Yourself On The Reaction Trainer":
Articles in this series:
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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.
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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
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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
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RESISTOR COLOUR CODE
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No.
Value
4-Band Code {1%)
5-Band Code {1%)
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100k0
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brown grey brown brown
blue grey black brown
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brown black black yellow brown
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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
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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
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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.
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