Automatic Street Light Controller Circuit Using LDR And 555 Timer IC

We are living in the world where everything goes to be automatic from your washing machine to your ceiling fan. Street lights are one of those examples of the automatic world. Automatic street light are those light which needs no manual operation to gets turn ON and turn OFF. Did you ever try to make such kind of street lights that gets turn ON and turns OFF automatically? In this article, we are going to make automatic street light using LDR and 555 timer IC.

List of Components  

1. 555 Timer IC
2. LDR
3. LED
4. Potentiometer
5. Resistor 1* 1k ohm 
6. Resistor 1* 220 ohm
7. 9V Battery
8. Printed Circuit Board(PCB) Or BreadBoard 

Circuit Diagram

A very simple circuit diagram of automatic street light is given below. 

Automatic Street Light Controller Circuit

Principle and Working of Automatic Street Light Controller

555 Timer IC is the main part of the circuit that works as a comparator. All the working of this circuit depends on the working of the 555 timers Ic.To know more about 555 times IC read this article Working of 555 Timer IC. In this circuit pin, 3 produce output which has just two states high and low. Output goes to high when  trigger pin  is at a lower level than the 1/3rd level of the power supply voltage and output goes low when trigger pin 2 is at above then 1/3rd  of the power supply voltage. In this circuit pin, 4,6 and 8 are connected to the power supply. Here we use LDR to detect the presence of light which is formed a potential divider circuit with the help of 1k ohms resistor. LDR is a special type of resistor whose value depends on the light. Read this article to know How LDR Works. The output of this divider circuit is given to trigger pin of the 555 timer IC. 

In this circuit, we use a simple LED to know how the whole circuit works. You can also connect as much led as you want by using the transistor or you can connect a Relay to control high voltage electrical bulbs. 

You must use caution while connecting Relay to this circuit because its may be danger and as different bulb have different wattage.

Video Demonstration of Automatic Street Light Controller