Elenco Electronics EP-130, Manual

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This is a control circuit that produces short pulses.
When you close the key, the LED display shows 1
for an instant and then goes off, even if you keep
pressing the key.
You can make up a game with this circuit. Display a
number or letter on the LED, and have the players
tell you what number is on the display. You can have
different numbers or letters displayed by the LED by
changing the wiring of the LED. Connect the
appropriate terminals to form letters or numbers to
terminal 71 (in place of terminals 21 and 23). The
connections for the number 3 would be: 17-21-22-
23-20-71.
You might want to try different values of capacitors
and see their effects, but don’t use a capacitor value
higher than 10
μ
F or the transistor might be
damaged by excessive current.
Notes:
EXPERIMENT #14: RAPID LED DISPLAY SWITCHING (PERSISTENCE OF VISION TEST)
Wiring Sequence:
o
21-23-71
o
25-124-137
o
40-73
o
41-72
o
82-83-42-119
o
74-81-111
o
84-112-138
o
121-122
Schematic