LM393 IC-based Automatic Night Light Circuit

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Hello friends! Welcome back to ElectroDuino. This blog is base on the LM393 IC-based Automatic Night Light Circuit. Here we will discuss project Introduction to Automatic Night Light Circuit, Block diagram, Component Required, Component Description, Circuit Design, Circuit Wiring, Working principle and output Result

Introduction

LM393 IC-based Automatic Night Light Circuit is a very simple project which can automatically control Light on/off by detecting light and dark. In this project mainly consists of an LM393 Comparator IC and an LDR. The LDR detects light and dark and the LM393 processes the LDR data and provide output. The circuit works like this, when LDR detects dark then it turns on the light and when LDR detects light then it turns off the light.

Automatic Night Light Circuit Block diagram

Automatic Night Light Circuit Block diagram
Automatic Night Light Circuit Block diagram

Component Required

Components Name Quantity
LM393 Comparator IC1
LDR (Light Dependent Resistor) or Photoresistor1
10K Potentiometer1
33KΩ Resistor1
330Ω Resistor1
LED1
5v Power Supply1
Connecting wireAs required in the circuit diagram

 

Tools Required

Tools NameQuantity
Soldering Iron1
Soldering wire1
Soldering flux1
Soldering stand1
Multimeter1
Desoldering pump1
Wirecutter1

Component Description

LM393 Comparator IC

The LM393 integrated circuit (IC) is a dual differential comparator, it consists of two inbuilt operational amplifiers. Each comparator accepts 2 inputs for comparison. The comparator compares these two input voltages and measure which input voltage is the larger, then it provides output. These ICs can perform different tasks using a single power supply. Also, it can be work perfectly by the split power supply sources.

LM358 IC Pin Configuration, pinout, Pin Diagram
LM358 IC Pin Configuration, pinout

LDR (Light Dependent Resistor)

The LDR or Light Dependent Resistor is a variable resistor. It is also known as a photoresistor. These LDR, Light Dependent Resistor, or Photoresistor works on the principle of “Photo Conductivity”. The LDR resistance is change depends on the light intensity falls on the LDR surface.  When light falls on the surface of the LDR then the resistance of the LDR decreases and increases the conductance of the element. When no light falls on the surface of the LDR then the resistance of the LDR is high and decreases the conductance of the element.

LDR or Light Dependent Resistor & Symbol
LDR or Light Dependent Resistor & Symbol

Circuit Design of LM393 IC-based Automatic Night Light Circuit

LM393 IC-based Automatic Night Light Circuit Diagram Schematic
LM393 IC-based Automatic Night Light Circuit Diagram Schematic

Circuit Wiring

The LM393 IC Vcc pin is connected to the positive terminal of 5v power supply and the IC GND pin is connected to the negative terminal of 5v power supply.

The LDR one terminal is connected to the positive terminal of 5v power supply through the 33k resistor and another terminal is connected to the negative terminal of 5v power supply. This makes a voltage divider circuit. The junction point of the LDR and the resistor is connected to Inverting 1 input (pin 2) of IC.

The Potentiometer one pin is connected to the positive terminal of 5v power supply and another pin is connected to the negative terminal of 5v power supply. The potentiometer output pin is connected to the Non-Inverting 1 input(Pin3) of the IC.

The LED positive terminal is connected to the positive terminal of the 5v power supply through the 330-ohm resistor and the negative terminal is connected to the Output 1 (Pin 1) of the IC.

Working of LM393 IC-based Automatic Night Light Circuit

First of all, we need to calibrate the Non-Inverting 1 input voltage by rotating the Potentiometer and set a referral voltage at Non-Inverting 1 input. Potentiometer calibrates like this, during light conditions the LED is off and the LED is on during dark conditions.

Then the lm393 comparator IC compares this reference voltage with the voltage produced from the voltage divider between the LDR or photoresistor and the 33KΩ resistor.

When light falls on the photoresistor surface, its resistance decrease below 30KΩ. So, most of the voltage gets allocated to the 33KΩ resistor and a small voltage goes across the LDR. So, the voltage divider produces a small voltage. Then, this small voltage goes to the Inverting 1 input (pin 2) of IC, which is less than the reference voltage. So, the IC output 1 is High, it means the output voltage is equal to the positive supply voltage (5v Vcc), and there is no current flow across the load because there is no potential difference. So the LED is turned OFF.

LM393 IC-based Automatic Night Light Circuit Working off mode
LM393 IC-based Automatic Night Light Circuit Working OFF mode

When no light falls on the photoresistor surface, it has very high resistance. So, most of the voltage gets allocated to the LDR. So, the voltage divider produces a High voltage. Then, this High voltage goes to the Inverting 1 input (pin 2) of IC, which is greater than the reference voltage. So, the IC output 1 is Low, it means the output voltage is equal to the Ground of supply voltage (0v Vcc), and the current flow across the load from positive supply to groud because there is a potential difference. So the LED is turned ON.

LM393 IC-based Automatic Night Light Circuit Working on mode
LM393 IC-based Automatic Night Light Circuit Working ON mode

Output Result

When LDR detects dark then it turns on the LED and when LDR detects light then it turns off the LED.

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