Variable LED flasher

This is single IC LM3909 variable LED flasher circuit, and it needs only 1.5 volts for operation, we can vary the speed of flasher by varying variable resistor R2.

IC LM3909

The LM3909 is a monolithic oscillator specifically designed to flash Light Emitting Diodes. By using the timing capacitor for voltage boost, it delivers pulses of 2 or more volts to the LED while operating on a supply of 1.5V or less. The circuit is inherently self-starting, and requires addition of only a battery and capacitor to function as an LED flasher.

Circuit Diagram

Variable LED flasher

Components List

S.No Name Quantity
1. IC LM 3909 1
2. Battery 1
3. LED green 1
4. Capacitor 350uF/10V 1
5. Resistor 100 Ω
Resistor 2.2K Ω
Variable Resistor 2.5K Ω
2
1
1




2 thoughts on “Variable LED flasher

  1. thank you for this circuit. I have had 2 of these ICs over 30 yrs but didn`t know what to do with them.

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