Introduction: How to Make Simple Automatic Night Light Circuit Using LDR

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Hi there fiends today i will show you how to make a simple automatic night light circuit using an LDR (Light depending resistor) and a mosfet so follow along and in the next steps, you will find the automatic night light circuit diagram as well as the electronic components needed for building this simple and useful circuit.

Step 1: Automatic Night Light Circuit and the LDR

When we say automatic night light circuit we may think about the nightlight street illumination system that automatically turns on at night and they turn off in the daytime.All this automation process is possible with an electronic circuit that has a sensor that detects the sun intensity.We will replicate this process but very simple with the help of a light depending resistor that has the specs when is light it can have 500-2000 ohms, and when is dark 100Kohms.

Step 2: Simplified Night Light Circuit

A photoresistor (or light-dependent resistor, LDR, or photo-conductive cell) is a light-controlled variable resistor. The resistance of a photoresistor decreases with increasing incident light intensity; in other words, it exhibits photoconductivity.
A photoresistor can be applied in light-sensitive detector circuits, and light-activated and dark-activated switching circuits.

A photoresistor is made of a high resistance semiconductor. In the dark, a photoresistor can have a resistance as high as several megohms (MΩ), while in the light, a photoresistor can have a resistance as low as a few hundred ohms. If incident light on a photoresistor exceeds a certain frequency, photons absorbed by the semiconductor give bound electrons enough energy to jump into the conduction band. The resulting free electrons (and their hole partners) conduct electricity, thereby lowering resistance. The resistance range and sensitivity of a photoresistor can substantially differ among dissimilar devices. Moreover, unique photoresistors may react substantially differently to photons within certain wavelength bands.

Step 3: Automatic Night Light Mini Project

The parts necessary for building this night light circuit are as follows:

- A mosfet irfz44n or similar

-Battery source 18650

-LDR (photoresistor)

-22k / 270k if this circuit is meant to be used inside not exposed to direct sunlight

Simple, cheap components that can be found online and this mini project can be adapted to run 220v light bulb but maybe in a future tutorial.

An important element of this circuit is a voltage divider composed of the resistor and the LDR also a resistor

Step 4: Automatic Night Light Circuit Diagram

Here you have the circuit diagram of a simple night light on the left side you can observe the voltage divider that will control the mosfet by providing more than 3v on night making the led to light,and less than 2v when is daytime turning the mosfet off and closing the led light the mosfet can be changed with a regular transistor but because the mosfet is different than a transistor we will gain some power consumption.

Thanks for your time if you want to see the video representation of this Automatic night light circuit

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