Led or Lamp Flasher Circuit

Ideal to operate 3 to 24V DC existing on-circuit lamps

This circuit was designed to provide that continuous light lamps already wired into a circuit, become flashing. Simply insert the circuit between existing lamp and negative supply. Especially suited for car or panel pilot lights, this device can drive lamps up to 10W.

Circuit diagram:

Led or Lamp Flasher Circuit Diagram

Parts:

R1 = 6.8K
R2 = 270K
R3 = 220K
D1 = 1N4002
C1 = 220uF-25V
C2 = 10uF-25V
Q1 = BC557
Q2 = BD139
B1 = Any type in the range 3-24V
B1 = Suited to the lamp adopted
LP1 = Filament Lamp 10W-3V to 24V
SW1 = On-Off Switch

Notes:

Break lamp to negative supply connection, and then insert the circuit between existing lamp connection and negative supply (respecting polarities!).
C1 value can be varied from 100 to 1000µF or higher, in order to change flashing frequency.
Although rather oversized, this circuit can also drive any LED, providing a suitable resistor is fitted in series with the light emitting device.
The resistor should lie in the 47R to 2K2 range, depending on supply voltage.

Source: Red Free Circuit Design