LED or Lamp Flasher

Posted in LED, on 2015-08-21

Circuit diagram:

LED or Lamp Flasher


  • R1________1M 1/4W Resistor
  • R2______100R 1/4W Resistor
  • R3_______22R 1/4W Resistor
  • C1________1µF 63V Electrolytic, Multilayer Ceramic or Polyester Capacitor
  • D1_______LED Any type and color
  • Q1____2N3906 40V 200mA PNP Transistor
  • Q2____2N3904 40V 200mA NPN Transistor
  • SW1_____SPST Switch
  • B1________3V (Two 1.5V AA or AAA cells wired in series, etc.)


  • Flashing frequency can be varied by changing R1 value in the 1M - 4M7 range.
  • This circuit is very efficient when driving a small 3.2V incandescent lamp. In this case omit the LED and R3, connecting the bulb across Q2 Collector and positive supply, further reducing parts counting.
  • Maximum current drawing of the bulb type used should not exceed 100mA.
  • In order to facilitate oscillation when a bulb is driven, R2 value should be lowered to 82R or 68R.

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