Under the SupervisionOf

Md. Ashraful Islam Jewel

Lecturer, Department of CSE  

Submittedby

Md. Mahfuzur Rahman 201130496

Dept. of Computer Science and EngineeringAsian University of Bangladesh

Reducing the wastage of power

Reducing physical efforts

Improve the system in our daily life

simple and powerful device, which uses

Transistor (BC547 NPN)

switches ON lights (LED) when the light (i.e.

day light) decreases

switches OFF lights when light falls on LDR

Transistor BC547

LDR (Light Dependence Resistor)

Resistor

LED

Transistor BC547:

has an emitter terminal, a base terminal

and a collector terminal

current flowing from the base to the

emitter controls the collector current

LDR

an electronic component whose resistance

decreases with increasing incident light intensity

used in a potential divider setup with a second

regular resistor

Resistor

resist the flow of current across the resistor device

adjustable resistors are refers to as potentiometers

Light falls on LDR, it shows its minimum

resistance and voltage drops across LDR

less than VBE of Transistor Q1.

So, no current will go from the collector to

the emitter and transistor remains turn off.

No light falls on LDR, it shows its maximum

resistance and voltage drops across LDR

greater than VBE of Transistor Q1.

Now the transistor enters into ON state and

at the output side Ic current will flow

through the LED. So, the LED is ON

Energy savings

Low cost

Safety and Security

Reducing physical efforts

It has a limitation of power

Light turns on when shadow falls on LDR

LED is a low voltage device

By using same concept we can modify this

project for commercial use

It is possible to make the project

appropriate for high voltage of power

Question ?