Elenco 130-in-1 Electronics Playground - Manual (Page 115)

-115-
VCO? What’s that? VCO stands for voltage
controlled oscillator, and as the name implies, this
oscillator changes its oscillation frequency according
to the voltage applied to the circuit. The circuit
creates two different output signals that have
triangular and square waves.
When you finish the wiring sequence, slide the switch
to position A to turn on the power. Turn the control
slowly while you listen to the sound from the
earphone. The sound becomes lower when you turn
the control clockwise.
Turning the control changes the voltage at terminal
27, which changes the 0.01
μF capacitor’s charging
and discharging times, which changes the oscillator
frequency. The output signal from the first operational
amplifier is a triangular wave signal is at terminal 67,
and is applied to terminal 65 of the second amplifier.
The second amplifier acts as a comparator, and
produces a square wave signal at terminal 64.
Notes:
EXPERIMENT #96: VCO
Wiring Sequence:
79-63-26-131
27-87-89
46-91
47-76
86-92-109-64
65-78
66-80-83-85
67-102-77
68-90-101-75
69-88-81
84-70-134
121-135
122-132
124-119-28-48-94-82-14-EARPHONE
110-93-13-EARPHONE
Schematic