Automatic light using 555 timer

Automatic light using 555 timer

Introduction

 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.

Circuit diagram (automatic light using 555 timer)

Components required

1. IC NE555.                             

2. LDR.                                      

3. variable resistor 100k.      

4. capacitor 47uf/16v.            

5. Lamp 6v.                              

6.supply 9v.                             

7.pcb board.                            

Working

   When light falls on LDR it's resistance decreases, which results

In increase of the voltage at pin 2 of the ic 555. IC 555 has got inbuilt comparator which compares between the input voltage from pin 2 and 1/3rd of the power supply voltage. When input falls below 1/3rd then output is set to high. Otherwise it is set to low. During daytime when the sunlight falls on the LDR it's resistance decreases, which results in low in output. So during daytime the street light will be off state due to brightness. As a result input voltage rises. So we obtain no positive voltage at output of pin 3 to drive relay or LED, besides poor light condition where we get output to energise. But during night time, when darkness rises to a certain level,the resistance of LDR increases which results in decrease of voltage at pin 2of the ic. In this case, input falls below 1/3rd of power supply voltage and the sensor circuit gets activated and switches LED ON.