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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.
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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 ?