How to build Car-Bulb Flasher

September 26, 2010 - category: Automotive light


This astonishingly simple circuit allows one or two powerful 12V 21W car bulbs to be driven in flashing mode by means of a power MosFet. Devices of this kind are particularly suited for road, traffic and yard alerts and in all cases where mains supply are not available but a powerful flashing light are yet necessary.

Circuit Diagram:

Circuit Diagram:


  • R1 = 6.8K
  • R2 = 220K
  • R3 = 22K
  • C1 = 100uF-25V
  • C2 = 10u-25V
  • D1 = 1N4002
  • Q1 = BC557
  • Q2 = IRF530
  • LP1 = 12V-21W Car Filament Bulb (See Notes)
  • SW1 = SPST Switch (3 Amp minimum)


  • Flashing frequency can be varied within a limited range by changing C1 value.
  • As high dc currents are involved, please use suitably sized cables for battery and bulb(s) connections.

circuit from http://www.extremecircuits.net/2009/07/car-bulb-flasher.html

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