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
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.
- 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.