Siren/Alarm Sound Generator (555)

Circuit Diagram

How to Build It

1. Wire the 555 in an astable configuration, with resistor and capacitor values chosen for an audible frequency (a few hundred Hz).
2. Connect the output (pin 3) through a coupling capacitor to a piezo buzzer or small speaker.
3. Add a second 555 (or a potentiometer) connected to the first's control pin (pin 5) to vary the frequency over time and create the 'siren' effect.
4. Power with 9V and listen — you should hear a continuous or warbling tone depending on the configuration.
5. Adjust the resistor values to change the base pitch.

Bill of Materials