Download Reaction Timer

14
Reaction Timer
The circuit below can be used to test a person’s reaction time to a precision
of ±0·01 seconds. The time is indicated by a series of seven leds showing the
output of a binary counter (4060). The two D type flip-flops are in a 4013.
The led shown on the circuit diagram is the “stimulus”. Switch S1 starts the
timer and illuminates the stimulus led. Switch S2 stops the timer.
7805
+9v
10k
100k
1k
Q
D
cl
S2
cl
Q
rst
100n
-
S1
set
rst
Q
11
1M
1M
Q
D
10
9
1n5
100k
12
15
13
14
6
4
5
7
to leds
1k
-
1
To calibrate the timer
1.
Remove the 4013 from its holder; this allows the oscillator in the 4060 to
run continuously.
2.
Connect the battery and then connect an oscilloscope across the first led
(that is, the led which is connected to pin 7 of the 4060).
3.
Adjust the variable resistor to produce an oscillation of time period 10ms.
© David Hoult 2001
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