Introduction-

Automatic Street Light Control System is a simple and powerful concept, which uses transistor as a switch to switch ON and OFF the street light automatically. By using this system manual works are removed. 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. This is done by a sensor called Light Dependant Resistor (LDR) which senses the light actually like our eyes.

                     By using this system energy consumption is also reduced because now-a-days the manually operated street lights are not switched off properly even the sunlight comes and also not switched on earlier before sunset. In sunny and rainy days, ON time and OFF time differ significantly which is one of the major disadvantage of using timer circuits or manual operation.

 This project exploits the working of a transistor in saturation region and cut-off region to switch ON and switch OFF the lights at appropriate time with the help of an electromagnetically operated switch.

                    Automatic Streetlight needs no manual operation of switching ON and OFF. The system itself detects whether there is need for light or not. When darkness rises to a certain value then automatically streetlight is switched ON and when there is other source of light, the street light gets OFF.

This is the concept of Automatic Street light it does so by using a light dependent resistor called LDR which senses the light just as our eyes senses the light.

Because of this concept only energy consumption also reduces to a considerable level because the manually operated street lights are not switched off properly and lead to the energy consumption.

This project operates the transistors in cut-off and saturation regions which causes the on off of the switches and at appropriate timing.

Working & Principal –

Before we go to the working and principal of the Automatic Street light we first go through the circuit diagram of the Autmatic Street light using LDR.This is as follows-

The working is as follows The transistors are basically arranged such that they both complement each other oppositely, meaning when the left hand side transistor conducts, the right hand side transistor switches OFF and vice versa.

The left hand side transistor T1 is rigged as a voltage comparator using a resistive network. The resistor at the upper arm is the LDR and the lower arm resistor is the preset which is used to set the threshold values or levels.  T2 is arranged as an inverter, and inverts the response received from T1.

Initially, assuming the light level is less, the LDR sustains a high resistance level across it, which does not allow enough current to reach the base of the transistor T1. This allows the potential level at the collector to saturate T2 and consequently the relay remains activated in this condition.

When the light level increases and becomes sufficiently large on the LDR, its resistance level falls, this allows more current to pass through it which eventually reaches the base of T1.

The transistor T1 conducts, pulling its collector potential to ground. This inhibits the conduction of the transistor T2, switching OFF its collector load relay and the connected lamp.

The power supply is a standard transformer, bridge, capacitor network, which supplies a clean DC to the circuit for executing the proposed actions.

The circuit uses a Light Dependent Resistor (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.

Components required – Solder Wire,

Soldering Wire,

LED bulbs,

Two Transistors BC 548

Two resistors of 100 ohms

LDR.

Circuit Diagram-

A

Synopsis

On

AUTOMATIC STREET LIGHT

Submitted in partial fulfilment for the degree of

Bachelor of Technology

In

Electronics and Communication Engineering

SUBMITTED BY

Submitted To

A.B.E.S Engineering College, Ghaziabad

G.B Technical University

August 2013-14