Saturday, 8 September 2012

Automatic Street Light For Energy Conservation

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.


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 

1K Resistor
To offer resistance
10K Resistor
To offer resistance
LDR 10 mm
SL100 Transistor
Amplifier and switch
BC 107 Transistor
Amplifier and switch
Relay HRS 4H-12V 1C/O
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.


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.


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