Learning Electronics

Learning Electronics

Learn to build electronic circuits

Car-Bulb Flasher

Suitable for alerting purpose, Drives 12v Car bulbs

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:

Large View


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.
Source: Red Free Circuit Design