LED Flasher Circuit Using LM339

Last Updated on March 16, 2024

Simple LED Flasher Circuit designed by using LM339 IC From Texas Instruments. This Circuit contain Quad Differential Comparator and this circuit operate with 12V DC supply. Generally this LED flasher circuit are used in toys for flashing light or siren effects.

The LED Flasher circuit makes use of this amazing components to turn it flash ON and OFF . Thai circuit employs a voltage source, capacitor, resistor, IC, and LED. This circuit requires voltage supplies varying from 6 Volts to 12 Volts.

Circuit Diagram


1U1BLM 3391
4D1, D2Green, Red LED 5mm2

Construction and Working

Here the IC LM 339 act as a comparator , input is fed to the two input terminal (Inverting input terminal and Non-Inverting input terminal) and it produce a single output potential at the voltage potential. The device consists of two input terminals in which the reference input signal is fed to one terminal and the actual value of the signal if fed to another terminal. Then an output signal is generated at the output terminal based on the difference between the two input signal fed the two input terminal. This generated output signal is either (0) low or (1) high.

In this circuit pin 6 or inverting terminal of comparator connected with 12V throughR5 resistor and balanced to connect through C1 capacitor. The non-inverting terminal is connected the resistor R1 to supply voltage then connect between the R2 and R3 resistor. The two LEDs are connected to output pin of comparator in the reverse polarity which means the positive pulse will derive one LED and the negative pulse will drive the other LED.

As the 12V is connected to the circuit the LEDs will glow as the positive and the negative pulses are provided to the LEDs and the duration of ON and OFF pulses are decided by the value of timing resistor and the capacitor charging time. Therefore the LED continues to operate in a loop until the circuit power is cut-off.

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