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Police siren sound effect circuit

Police Siren Sound Effect Circuit

Electronic Siren Circuit Diagram

We are going to make a Police Siren Circuit using two 555 timer IC. The circuit will produce an up-down wailing sound from the speaker. In this circuit there are two 555 timer ic is used.

Both 555 ic is connected as astable multivibrator/oscillator.  In an Astable mode, it delivers a continuous sequence of pulses on its output Pin No. 3, the capacitor C1 charges and discharges continuously.

Circuit diagram

Police siren sound effect circuit

The first 555 is wired as a low-frequency astable oscillator. IC2 is wired as Fast astable Oscillator and output of first ic from pin 3 is connected to shift the signal with control voltage pin 5 of the second 555. Whose frequency is modulated depending on the varying voltage from the IC U1. The voltage shift on pin 5 makes the frequency of the second oscillator to rise and fall. 

The frequency range of the siren can vary with changing the value of R2 and R4 resistor with a potentiometer variable resistor.

The circuit can be made with one NE556 ic at the place of two separate 555.  556 has a dual 555 timer. Output sound can be Amplified for high pitch by using any audio amplifier to make a loud sounds.

This circuit can be assembled on any general-purpose PCB/Vero board  

Components

555 timer IC – 2
68K Resistor – 1
1K Resistor – 1
10K Resistor – 3
10uf Capacitor – 2
o.1u (104)capacitor – 2
Speaker – 1

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