Rain Alarm

This circuit consumes no current until moisture is detected on the rain plate.

Police Siren

                    The Police Siren circuit uses two 555's to produce an up-down wailing sound. The first 555 is wired as a low-frequency oscillator to control the VOLTAGE CONTROL pin 5 of the second 555. The voltage shift on pin 5 causes the frequency of the second oscillator to rise and fall.

Hee-Haw Siren

Build the circuit and listen. Change the resistors and capacitors to get all sorts of different results.

Music Box

          This circuit produces 10 different tones and by selecting suitable values to change the voltage on pin 5, the result can be quite pleasing. Note: the two unused outputs of the 4017 produce a tone equal to that produced by the 555 when pin 5 has no external control voltage.

Machine Gun

This circuit produces a sound very similar to a machine gun: