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.

PARTS LIST

Resistors (all ¼-watt, ± 5% Carbon)

R₁ = 10 Ω

R₂ = 4.7 KΩ

Capacitor

C₁ = 0.22 µF

Semiconductors

D₁ = 1N4002

T₁ = SL100

T₂ = AC128

T₃ = AC127

Miscellaneous

LS₁ = 8 Ω speaker

LED₁