LED or Lamp Flasher

Minimum parts counting

Designed for 3V battery operation

Circuit diagram

LED or Lamp Flasher-Circuit diagram


  • R1 33K 1/4W Resistor
  • R2,R3 47R 1/4W Resistors
  • C1 10µF 25V Electrolytic Capacitor
  • D1,(D2 LED(s) (Any type and color)
  • Q1 BC560 45V 100mA PNP Transistor
  • Q2 BC337 45V 800mA NPN Transistor


  • Power supply can vary from 2 to 4.5V.
  • Add D2 to obtain two LED alternate blinking.
  • D1's on-time is shorter than off-time. The opposite regarding D2.
  • You can also use D2 only, shorting D1.
  • Don't change resistors' values.
  • Flashing frequency can be varied changing C1 value from 2.2µF to 100µF and higher.
  • This circuit is very efficient when driving a 3.2V lamp. In this case omit the LEDs and R3, connecting the lamp at Q2's collector and to positive supply, further reducing parts counting.
author: RED Free Circuit Designs
circuit from http://www.redcircuits.com/