Reducing the wastage of power Reducing physical efforts Improve the system in our daily life 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.

1. Under the Supervision
Of
Md. Ashraful Islam Jewel
Lecturer, Department of CSE
Submitted
by
Md. Mahfuzur Rahman 201130496
Dept. of Computer Science and Engineering
Asian University of Bangladesh

2.  Reducing the wastage of power
 Reducing physical efforts
 Improve the system in our daily life

3.  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

4.  Transistor BC547
 LDR (Light Dependence Resistor)
 Resistor
 LED

5. 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

6. 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

8.  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.

9.  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

10.  Energy savings
 Low cost
 Safety and Security
 Reducing physical efforts

11.  It has a limitation of power
 Light turns on when shadow falls on LDR
 LED is a low voltage device

12.  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

13. Question ?