Flashing frequency can be varied by changing R1 value in the 1M to 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.
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.
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