ADVANCEMENTS BY LDRin Electronics

Prepared by : Bhavin K. Vekariya B.Sc.(IC)

Shree M. & N. Virani science college

Reaccredited at the level “A” (CGPA = 3.28) by NAAC, “STAR college Department status” by MST-DBT 

A “College with Potential for Excellence-CPE (phase –||) by UGCAccredited at the level G-AAA “A-1”

Level by KCG Government of Gujarat.Rajkot 360 005

AIM ⟹ the aim of this project is Automatic light power

saving system with LDR, this to save the power. We want to save the power Automatically instead of doing manual. So it is to easy to make cost effective. Control

ABSTRACT ⟹ We need to save and conserve the energy because the

most of the energy sources we depend on, like coal and natural gas can’t be replaced. once we use them up, ⟹they are gone forever. Saving power is very important, instead of using the power in unnecessary times it should be switched off. Over here we avoiding the problem by ⟹having an automatic system which turns ON & OFF the light at given time or when the ambient light falls below the specific intensity. This purpose is attained by the ⟹LDR(Light Dependent Resistor). LDR is useful ⟹especially in light/dark sensor circuits. Because of this ⟹we can get many advantages.

INTRODUCTION ⟹ We need to save the energy for the purpose of the

saving energy and for the saving of money. In any city ⟹“street light” is the one of the major power consuming factors. Most of the time we see the street lights ON ⟹even after the sunrise thus wasting of lot of the energy. ⟹Automatic street light control system by LDR is simple yet powerful concept, which uses the transistors as a switch. ⟹By using this system manual work is 100% removed. It ⟹is automatically switches the lights ON when there is vehicle goes. This is done by sensor called LDR. Which ⟹senses the light actually like our eyes. It automatically ⟹switches the lights OFF, whenever there is not any vehicles light.

PRINCIPLE ⟹ Here the principle of the project is, overall system

is controlled by the light, when the sensor got any light the street light will be made ON and when the sensor not founds any light the street light will made OFF. It clearly demonstrate the working of the transistors in saturation region and cut-off region.

What is LDR ⟹ LDR or Light Dependent Resistor, are very useful

especially in light/dark sensor circuits. Normally the ⟹resistance of the LDR is very high, sometimes as high as 1000000 ohms, but when they are illuminated with light resistance drops dramatically. It is made up by ⟹cadmium sulphide (Cds). In a LDR the electrons are ⟹exited by photons as well as by temperature. The dark ⟹resistance is not therefore infinite at normal temperature.

Generally the resistance does not increase ⟹immediately to its dark value. So it takes some times ⟹of the order of 100 k ohm/second. In general LDR is ⟹sensitive, inexpensive and readily available device.

STRUCTURE AND SYMBOL OF LDR

PARTS LIST ⟹ Transistor

NPN BC 548 (2X) ⟹ Resistance

1k ohm100 ohms

⟹ LED ⟹ LDR ⟹ Battery and Battery

clip ⟹ Circuit Board

Circuit diagram

CIRCUIT OPERATION ⟹ When the light is falls on the LDR, its resistance

is very high, so most of the voltage is dropped across it, hence the first transistor is conducts which making its collector potential near ground potential. ⟹ There fore second transistor does not conduct so the circuit is in OFF state. ⟹ Now when the light falls on the LDR, resistance becomes low therefore the first transistor can not conduct, hence its collector potential rises near to the supply voltage which cause the second transistor and the circuit in ON state.

USES AND APPLICATION ⟹ LDR’s have low cost and simple structure. They

are often used as light sensors. ⟹ They are used when there is a need to detect absences or presences of light like in a camera light meter. ⟹ Used in street lamps, alarm clock, burglar alarm circuits, light intensity meters, for counting the packages moving on a conveyor belt, In security systems, Light intensity control for street lights,Lightning switch from sunset to sunrise, smoke detector etc.

Thank You

“The real problem is not whether machines think but whether men

do”