Elenco 130-in-1 Electronics Playground - Manual (Page 99)

-99-
The LED circuits in experiments 78 and 79
(“Operational Amplifier Blinking LED” and “LED
Flasher”) each use one LED, but the circuit in this
project uses two LEDs that take turns lighting. Slide
the switch to position B and assemble the circuit.
Then, turn the power on by sliding the switch to
position A and wait for a few seconds. The LEDs light
and turn off in rotation.
The operational amplifier works as an astable
multivibrator. When the output is low, LED 2 lights;
when it is high, LED 1 lights.
You can alter the speed of the blinking by using
different values for R and C. See how the speed of
the pulses alters when you alter the value of R to
220k
Ω
k k .
Notes:
EXPERIMENT #80: DOUBLE LED BLINKER
Schematic
Wiring Sequence:
31-36-67-90-94
33-70-135
34-63-132
93-68-113
81-89-69
82-114-124-119
121-134
122-131