Elenco Basic Electronic Experiments - Manual (Page 59)

59
EXPERIMENT #42: ONE-SHOT
Do you know what this circuit will do? Connect everything, then press the switch and release it. The LED is on for a few
seconds and then goes out. What effect do you think changing the value of the variable resistor will have? Try it. The higher
the resistance the longer the LED stays on.
This circuit is a variation of the astable multivibrator and is called a one-shot multivibrator, because the LED comes on once
each time the switch is pressed. The 33k
Ω, variable resistor, and 100μF control how long the LED is on. This circuit can
be used as a timer. You might use a circuit like this with your microwave oven. You press the switch to turn the oven on
and have a knob (the variable resistor) to adjust how long the oven stays on; it then shuts off automatically.
+9V
3.3k
Ω
100
μ
F
33k
Ω
1k
Ω
10k Ω