I would like to share a circuit design from the Internet, which can continuously or intermittently change the brightness of LED lights.

 Components: Resistors, capacitors, diodes, MOS tubes and push switches are used here.

Circuit working status

When the circuit is powered on, hold down the left switch and the LED will gradually brighten until it reaches the maximum brightness. Then you can press the right switch and the light will go out immediately.

However, if the switch on the left is not pressed continuously but is pressed intermittently, you will see that the LED lights up once when pressed.

How does this work? Let's analyze this circuit.

Continuous Change

It mainly uses a capacitor charging circuit. When the circuit is powered on and the left switch is pressed, the current will charge the capacitor through R1, R2 and the button switch. This process is not completed in an instant.

As the voltage across the capacitor increases, the gate voltage of the MOS tube also increases.

When the gate voltage is higher than the pinch-off voltage of the MOS tube, current begins to flow between DS and the LED begins to brighten.

As the gate voltage of the MOS tube increases, the current between DS increases, and the LED gradually becomes brighter.

But when the right switch is pressed, the capacitor will discharge.

The discharge circuit passes through resistor R4. Since the previous charging circuit passes through R1 and R2, the resistance value is large, so the charging process will be slower.

That is to say, the discharge speed is only a matter of a moment, and the change in LED brightness can be clearly seen during the discharge time.

 Intermittent changes

Press the switch on the left intermittently. Press it once to charge the capacitor, which will increase the gate voltage a little, change the current between DS, and make the LED brighter.

The speed can be designed by yourself.

As long as the resistance value of R1 or R2 is changed, the charging circuit will change, the charging speed of the capacitor will change, and the brightness of the LED lamp will also change quickly.

That’s how this circuit works, thanks for reading!

Some of the above pictures and information are from the Internet