Minimum parts counting
Designed for 3V battery operation
Circuit diagram
Parts:
- R1 33K 1/4W Resistor
- R2,R3 47R 1/4W Resistors
- C1 10µF 25V Electrolytic Capacitor
- D1,(D2 LED(s) (Any type and color)
- Q1 BC560 45V 100mA PNP Transistor
- Q2 BC337 45V 800mA NPN Transistor
- Power supply can vary from 2 to 4.5V.
- Add D2 to obtain two LED alternate blinking.
- D1's on-time is shorter than off-time. The opposite regarding D2.
- You can also use D2 only, shorting D1.
- Don't change resistors' values.
- Flashing frequency can be varied changing C1 value from 2.2µF to 100µF and higher.
- This circuit is very efficient when driving a 3.2V lamp. In this case omit the LEDs and R3, connecting the lamp at Q2's collector and to positive supply, further reducing parts counting.