Automatic
street light is an electronics based project which is useful for Final
semester students of Electronics dept, even it can be implemented
practically in urban and rural areas where manual switching of street
light is not possible or inefficient as it consumes power when not
turned of in the daylight.
Introduction
This
project can be implemented in Household too. If you don't know all the
electronics and circuit stuffs then u need not. Go to an electronics
technician and tell them to build the circuit shown below and the whole
procedure how to make it stated in this article. .
It automatically switches ON lights when the sunlight goes below the visible
region of our eyes. It automatically switches OFF lights under illumination by
sunlight.
How does it work
This
circuit works in 9V DC. If you have AC supply connect it to a AC-DC
converter available on electronics store. The brain of the circuit is a
sensor called LDR or Light Dependent Resistor which senses light. The
resistance of the device goes high in dark and reduces in light. This
principle is applied in Automatic Street Light project.
Block Diagram & Circuit Diagram
This is the schematics --------
Short Description of the LDR
LDR is the heart of the circuit. It is a kind of light sensor. The
commercial photoconductive materials include cadmium sulphide (CdS), cadmium
selenide (CdSe), Lead sulfide (PbS) and Indium
antimonide (InSb) etc., There is large change in the resistance of a cadmium
selenide cell with changes in ambient temperature, but the resistance of
cadmium sulphide remains relatively stable. It is made by photoconductive material. Light sensitive material is arranged in the form of a long strip,
zig-zagged across a disc shaped base with protective sides. For additional
protection, a glass or plastic cover may be included.
Parts List
S.No.
|
Component
|
Nos
|
Used
|
1
|
1K Resistor
|
2
|
To offer resistance
|
2
|
10K Resistor
|
1
|
To offer resistance
|
3
|
LDR 10 mm
|
1
|
Photoconductor
|
4
|
SL100 Transistor
|
1
|
Amplifier and switch
|
5
|
BC 107 Transistor
|
1
|
Amplifier and switch
|
6
|
Relay HRS 4H-12V 1C/O
|
1
|
Switch
|
7
|
SPDT ON\OFF Switch
|
1
|
Switch
|
8
|
Fuse
|
1
|
Provides protection
|
Detailed Working Procedure
The
circuit uses an LDR to sense the light .When there is light the resistance of
LDR will be low. So the voltage drop across POT R2 will be high. This keeps the
transistor Q1 ON. The collector of Q1(BC107) is coupled to base of Q2(SL100).
So Q2 will be OFF and so do the relay. The bulb will remain OFF.
When
night falls the resistance of LDR increases to make the voltage across the POT
R2 to decrease below 0.6V.This makes transistor Q1 OFF which in turn makes Q2
ON. The relay will be energized and the bulb will glow.
Uses of this project
By employing this circuit, energy consumption can
be reduced considerably as the light switches ON or OFF automatically in
appropriate time. Moreover, errors which occur due to manual operation also can
be eliminated completely. The Automatic
street light controller unit fabrication is
cost-effective with good sensitivity and high reproducibility. Moreover, the
construction of the circuit is also simple so that it can be done easily as it
involves locally available components. The circuit is designed in such a way
that the extent of darkness at which the light has to switch ON or OFF also can
be tailored whenever it is needed. It can be used for other purposes like
garden lighting, balcony lighting etc.
Conclusion
Implementation in
solar cell -
The above circuit can be powered from a battery, which can
be charged during day time by harvesting
the solar energy through a solar cell .
Implementation in Sun Tie
Converter-
The solar energy harvested from sunlight
can be stored, inverted from DC voltage to AC voltage using sun tie converter.
The AC voltage can be stepped up and given to the electric grid.
This project
is very cheap and easy to build. You don't need any hard work for building this
circuit and it is also very useful for the developing countries which needs
consuming more power day by day, using this we can reduce power wastage. If
this project is used in bulk then we must have lowered the energy wastage by
means of implementing this circuit as a step towards green earth.