Siren Generator Circuit Using UM3561 Ic With Bc 547 Transistor

by prem saini26 in Circuits > Electronics

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Siren Generator Circuit Using UM3561 Ic With Bc 547 Transistor

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This is a simple yet very useful siren sound generator circuit built using the UM3561 IC, a BC547 transistor, a few resistors, and a buzzer. The circuit operates on a 3V DC battery and can generate police siren-like sounds. It’s widely used in toys, alarms, and learning projects.

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Supplies

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UM3561 IC

  1. Known as a "Multi-Sound Siren IC".
  2. It is capable of generating multiple siren tones.
  3. A 220KΩ resistor is connected between Pin 7 and Pin 8 to set the oscillation frequency.

BC547 NPN Transistor

  1. The output from UM3561 is very weak and cannot directly drive a buzzer.
  2. Therefore, the output pin (Pin 3) is connected to the base of the BC547 transistor via a 100Ω resistor.
  3. The transistor amplifies the signal and drives the buzzer with enough current.

Buzzer (or Small Speaker)

  1. The buzzer is connected between the battery and the transistor’s collector.
  2. When the transistor conducts, the buzzer produces loud sound based on the IC’s output.

3V DC Battery

  1. The circuit is low-power and works perfectly with a 3V supply (two AA cells).
  2. When the circuit is powered ON, the UM3561 IC generates siren tones internally.
  3. These audio signals are passed through the 100Ω resistor to the transistor’s base.
  4. The BC547 transistor amplifies the signal and makes it strong enough to drive the buzzer.
  5. The buzzer finally produces loud police siren-like sound.



Used in toys (police car sound, fire truck sound, etc.).

In security alarms and warning systems.

As a learning project for beginners in electronics.

For experiments and hobby electronics.

This siren generator circuit is low-cost, simple, and very effective. With just a handful of components, you can build your own police siren sound system. Since it works on only 3V, it is perfect for battery-powered