Falling Bomb Sound
Électronique / Electronic
Here's another siren that can changes its pitch. The siren we built in our last project Hand-Operated Sweep Oscillator changes pitch from low to high, but this one changes its pitch from high to low and finally stops making any sound. When it stops, press the key and the siren sound will start again.
Set the switch to position OFF and assemble the circuit. When you complete the wiring, slide the switch to position ON to turn on the power, and you hear a high-pitched siren sound that becomes progressively lower. Press the key to start the sound again.
Like the siren in our last project, this siren uses IC 1 as a buffer and IC 2 as an astable multivibrator. The capacitor C1 and the resistor R1 change the pitch of the siren sound.
The pitch changes slowly when you increase the values of C1 and R1, and it changes quickly when you decrease their values. Use the 3.3μF capacitor for C1 and notice how the pitch changes.