LED or Lamp Flasher

Minimum parts counting

Designed for 3V battery operation

Led Flasher


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.

Title: LED or Lamp Flasher
electronic circuit
Source: www.redcircuits.com
Published on: 2005-02-03
Reads: 1108
Print version: Print version

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