Elenco Basic Electronic Experiments - Manual (Page 49)

49
EXPERIMENT #33: ELECTRONIC RAIN
Connect the circuit and press the switch. You hear a sound like raindrops. The variable resistor (VR) knob controls the
rain, turn it to the right to make a drizzle and turn to the left to make the rain come pouring down. If you find it inconvenient
to turn the VR knob while pressing the switch then just connect a wire across the switch.
Do you know how this circuit works? Remember that as you lower the oscillator’s resistance the frequency increases, and
obviously the VR controls the resistance. What would happen if you replaced the 10k
Ω resistor with the 100kΩ? Try it.
The rain is now very slow, and it sounds more like a leaky faucet than raindrops.
You can experiment with changing other component values if you like.
+9V
S
P
10k Ω
10 μF
100
μ
F
+
-
-
+