Circuit diagram:
Parts:
R1________1M 1/4W Resistor R2______100R 1/4W Resistor R3_______22R 1/4W Resistor C1________1µF 63V Electrolytic, Multilayer Ceramic or Polyester Capacitor D1_______LED Any type and color Q1____2N3906 40V 200mA PNP Transistor Q2____2N3904 40V 200mA NPN Transistor SW1_____SPST Switch B1________3V (Two 1.5V AA or AAA cells wired in series, etc.)
Notes:
- Flashing frequency can be varied by changing R1 value in the 1M - 4M7 range.
- This circuit is very efficient when driving a small 3.2V incandescent lamp. In this case omit the LED and R3, connecting the bulb across Q2 Collector and positive supply, further reducing parts counting.
- Maximum current drawing of the bulb type used should not exceed 100mA.
- In order to facilitate oscillation when a bulb is driven, R2 value should be lowered to 82R or 68R.
