Here is a simple circuit that can be used to pulse an LED or a low power filament lamp. The effect is such that the LED lights up from OFF state gradually and then dims gradually. Such a circuit is very useful in decoration purposes.
The circuit is nothing but a triangular wave generator based on dual opamp IC LM 358.The two opamps inside the IC is used for the purpose. The transistor Q1 BC337 is used to drive the load (LED or lamp).The resistor R4 and capacitor C1 are the timing components of the circuit. Here the values of R4 & C1 are so chosen that the timing is around 5S.
- Assemble the circuit on a good quality PCB or common board.
- The circuit can be powered from three 1.5V cells in series (4.5V) or a 5V DC regulated power supply
- By using a 5M POT in place of R4, you can vary the time period of the circuit.
- You can use a 3.2 V /200mA bulb instead of the LED.If bulb is used R6 can be omitted.