An Electric device working in Solar light.

This project is based on the topic that reduce the loss of electricity. By this project we can work the device at the presence of solar light. In order to save our electrical energy we introduce an electrical device which works in the presence of any light.

Objective :-

Work an electric device in solar light


Now a days the usage of electricity is gradually increasing. In order to save our electrical energy we introduce an electrical device which works in the presence of any light.

The circuit may be used to automatically switch on an any electrical device using any light. Here we are using solar light as a transmitting unit and the motor( motor of any electrical device such as fan, water motor,etc)as a receiving unit.


The circuit has two stages :Transmitting unit and receiving unit. here the transmitting unit is the solar light and the receiving unit is the motor.the circuit may be used to work automatically in the presence of light.


* I C
* Transistor
* Resistor
* Capacitor
* Diode
* Relay(switch)


* High sensitivity
* Low cost
* simple construction
* Easy to install and maintain
* Less power consuming
* Require less space
* Reliable


It is a device which works in the presence of a light. when the light signal is passed through LDR the resistance decreases and the current start to flow through the circuit. The main advantage of this circuit is - It is low cost, simple construction and less power consuming.

There are two signals generated during the process. They are the input signal and the out put signal. The inputs signal is light signal and the output signal depends on the the electrical device used. Here input signal and output signals are same. One of the most basic components of this device is the transistor. The materials of the components used for an amplifier must be able to conduct electric current in a varying manner. That is why the transistor is often used.

Working of NPN transistor in this device

N-type semiconductor carries and P-type semiconductor carry holes. In an NPN transistor, the p_type semiconductor will kept in between two N-type semiconductor.

From the left the first N-type semiconductor is called the emitter. The middle P-type semiconductor is called the Collector. The output circuit which is supposed to drive the motor or glow the light. It is connected between this collectors and the emitter ends. The output circuit will be connected between the emitter and the base terminals.

The N-type electrons and the P-type holes that to get attracted,But the number of free electrons is way higher than the number of holes. As a result of these combination depletion holes will be created at the boundaries of the N-type and the P-type. this will conduct the semiconductors to switch back to its insulating state.


Where the light signal reaches in LDR, the resistance of LDR decreases due to the movement of electrons and holes then the voltage reaches in base.

The transistor act as a switch in between collector and emitter. The transistor used is NPN transistor. We can adjust the preset on the basis of the availability of light. If we want a large power light we can turn the preset on left or we want to work the device on any light we can turn it to right. so the device will work on the day light easily.

The circuit is simple and low cost . It is a device which works on the presence of sunlight or solar light.


When the light signal is passed through the LDR, the device start to be glowing.We can work any device easily and also by avoiding the electric loss.


The project provides the work of an electrical device using ordinary light. The light is user friendly and highly reliable. This project has the advantages of saving the electricity since the light is a naturally occurring one. Here we use the solar light for the purpose.

When a light with any frequency is passed through LDR the LED light will glow.


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