Police Siren using IC 555 Circuit Schematic Diagram

This circuit will produce sound similar to police siren using astable multivibrator mode of IC timer 555. This circuit is controlled by 2 timer ICs and 2 resistor variables. First IC timer will produce 1 Hz frequency which will increase and decrease periodically. The second IC timer serves as periodic ON/OFF switch. VR1 has a function to control the speed of the rhythm, and VR2 control the frequency of the siren. Here is the schematic :

Police Siren using IC 555 Circuit Schematic

Police Siren using IC 555 Circuit Diagram

Estimated price : $2

Component list :

R1=R2=2k2 ohm
Variable resistor VR1 : 4k7 ohm
Variable resistor VR2 : 100k ohm
Capacitor C1-C2 : 0.01 uF
Capacitor C3 : 0.1 uF
Polar capacitor C4 : 47 uF/15V
Polar capacitor C5 : 1 uF/15 V
Timer IC : NE555
Speaker : 8 ohm, o.5 W
ON/OFF Switch
5-15 V power supply

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