Under the SupervisionOf

Md. Ashraful Islam JewelLecturer, Department of CSE

  Submitted

byMd. 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 resistorResistor 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 ?