220V Automatic switch with LDR
Aim of this project
The main aim of the circuit is To construct a night lamp which switches on automatically when darkness comes in the evening and switch off automatically as sun rise in the morning.
Introduction
Some times we want to light some places where we can not switch on and off light manually. For these places we can not remain on the light every time , so we want to to switch the light automatically in darkness and switch off the light in brightness automatically
In this article we are going to make a street light circuit that automatically switches ON when the night falls and turns OFF when the sun rises. so we have to use some logic to do that because we don’t want to do this manually.
So in this circuit we are going to uses a Light Dependent Resistor as a sensor to sense the light. In the day time due to light the resistance of LDR will be very low. So the voltage drop be high.This keeps the TRIAC (BT136) on off stage. BT136 is a TRIAC that is used to control the main power 110/220V directly. The bulb will remain OFF.
As night falls the resistance of LDR increases and it turn on the TRIAC points M1 and M2. When M1 and M2 of TRIAC joints the current the bulb Turns on. ( TRIAC is a component that is use to control the light directly 110/220 volts AC main power)
Change in the circuit
you can also make it with out DIAC (db3). I will work without DB3 perfectly.
WARNING
The circuit works on 110220v AC Directly and if you are not accustomed to working with mains voltage or do not have experience in working with 220v AC Mains Voltage please stay away from this project while it is connected with Main power.
Components used in this Circuit
- TRIAC BT134/BT136/BT139
- Resistor 220k 1/4 watts
- LDR
LDR
LDR is a Sensor device that sensitivity depends upon the intensity of light falling on it. As the the light falling on LDR increases the LDR resistance decreases and as the strength of the light falls on LDR is decreased, its resistance increases.
The resistance of LDR is in the range of mega ohms In the time of darkness and when there is no light, , while in the presence of light or in brightness in decrease by few hundred ohms.
Resistor
It is a passive component having two terminals that is used to manage the current flow in the circuit. A current that flows through a resistor is directly proportional to the voltage that appears across the resistor.
There are two types of Resistors
- Fix Resistor: Its value is fixed
- Variable resistor: Its value can be changed with the movement of its nob.