Two-wire Lamp Flasher

Posted in LED & Light, Misc, on 2015-07-01

Circuit diagram:

Two-wire Lamp Flasher

Parts:

  • R1______________6K8 1/4W Resistor
  • R2____________270K 1/4W Resistor
  • R3_____________22K 1/4W Resistor
  • C1____________220µF 25V Electrolytic Capacitor
  • C2_____________10µF 25V Electrolytic Capacitor
  • D1___________1N4002 100V 1A Diode
  • Q1____________BC557 45V 100mA PNP Transistor
  • Q2____________BD139 80V 1.5A NPN Transistor
  • LP1___________Existing filament Lamp: any type in the range 3-24V 10W max.
  • SW1___________Existing On-Off switch
  • B1____________Existing V DC source: any type in the range 3-24V suited to the lamp adopted

Device purpose:

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.

Notes:

  • Break lamp(s) to negative supply connection(s), then insert the circuit between existing lamp(s) connection(s) 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.

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