Simple Siren Circuit


Posted on Feb 6, 2014

This circuit generates a tone that sounds very similar to a siren. The generator part of the circuit is made of the combination of PNP and NPN transistors. Toghether, the two transistors build up a free runing multivibrator. If the C2 capacitor was connected to the positive line of the power supply, it would have worked as a constant frequency osc


Simple Siren Circuit
Click here to download the full size of the above Circuit.

illator. However, we dont want a constant frequency oscillator. We want a siren. So to generate an up and down going signal tone, the resistor R2 is fed from an RC circuit. When the switch S1 is pressed, the capacitor C1 charges via R1 slowly until it reaches the maximum voltage level of 4 volts. This increasing voltage results to a decreasing time constant at the R2/C2 junction. This furthermore results to an increasing frequency of the multivibrator. After the switch S1 is released, the capacitor C1 discharges slowly resulting to a decreasing frequency cycle. Through the combination of the two time constants a sawtooth waveform is generated.




Leave Comment

characters left:

Related Circuits

  • New Circuits

    .

     


    Popular Circuits

    60Hz pulse generator
    smoke detector alarm schematic re46c140
    phono and line preamp
    Modular Headphone Amplifier
    Phase Locked Loop (PLL) Oscillator Circuit 860 MHz
    Automatic Lamp Dimmer Circuit
    Pulse Reading Logic Probe
    Controlling the Air Muscle actuators
    Battery Charger Regulator
    PCM1794A audio DAC
    Cat toys electronic circuit
    Discrete components sound and light control stairs delay switch circuit 5
    Class AB output circuit diode coupling



    Top