LDR Photoresistor for Making Automatic Street Light

LDR Photoresistor for Making Automatic Street Light

If the room gets dark, and the light bulb automatically turns on and eliminates the darkness, Isn't that cool? And you can even use it as an emergency lighting system.

Ⅰ. How to use the LDR photoresistor to turn on or off the LED light?

LDR (Light Dependent Resistor) is a special type of resistor. When the light is dark, only a lower voltage (high resistance) is allowed to flow, and when the light is strong, a higher voltage is allowed to pass through it (low resistance).

The parts required to construct this night light circuit are as follows:

  • Mosfet irfz44n or similar;

  • 18650 battery power;

  • LDR photoresistor;

  • 22k/270k (if the circuit is intended to be used internally without exposure to direct sunlight).

Simple, cheap components can be found online, and this mini-project can be adapted to 220V operation.

An important element of this circuit is a voltage divider composed of a resistor and LDR, and a resistor.

Then, you need to make a simple circuit diagram of the night light. You can observe the voltage divider. The voltage divider controls the mosfet by providing more voltage to over 3V at night and light up the LED light; during the day, the voltage is less than 2V and the mosfet is turned off. And turn off the LED lights. It is possible to use regular transistors to modify the mosfet, but since the mosfet is different from the transistor, there will be some power consumption.

Ⅱ. The application of LDR photoresistor

1. Automatic street lights;

2. Detect day or night;

3. Automatic headlight dimmer;

4. Position sensor;

5. Used as obstacle detector together with LED;

6. Automatic bedroom lights;

7. Automatic rear-view mirror.

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