Simple Beeper circuit

Here is a simple beeper circuit  which can be used in a scooter or vehicle as a sidelight indicator , or any other application that requires simple beep sound.

This circuit has only one disadvantage, i.e. , we cannot control the beeping rate. But the audio tone being produced can be changed by changing the value of the feedback capacitor C1 of the relaxation oscillator circuit.

The oscillator’s frequency is nearly about 1 kHz and the value for producing this frequency is a C1 disc capacitor.

 The heart of the circuit is a blinking LED. When the unit is connected to the battery of 4.5V, LED1 glows and the transistor SL100 starts conducting. The oscillator get activated thus producing an audio tone.

This oscillator consists opf transistor T2 and T3 i.e. AC128 and AC127. This transistor forms a DC amplifier where feedback is provided through c1. Resistor R1 prevents excess current flow that can damage the LED.

beeper circuit


Resistors (all ¼-watt, ± 5% Carbon)

R1 = 10 Ω

R2 = 4.7 KΩ


C1 = 0.22 µF


D1 = 1N4002

T1 = SL100

T2 = AC128

T3 = AC127


LS1 = 8 Ω speaker


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