Traffic light(using NE555)

Traffic signals are used to control the traffic on the road, so to avoid accidents and jams. Working of this project is not anyway different from traffic indicators we noticed on the roads. We construct this circuit with the help of well-known IC i.e. NE555. Control signal in this circuit is mainly three LED i.e. red, green and yellow.

This circuit is low cost circuit as it used minimum amount of components. Also assembling of the circuit is too easy to do.

Basic building block of this circuit is IC NE555 and LEDs along with capacitors and resistors as supporting components.LED1 (red in colour) has identical amount of on and off time. Just before the stop of LED1, LED2 (yellow in colour) glows for a very short period of time after that LED3 will glow. IC2 gets the power from the IC1, this brightens the LED3 (green in colour).And as soon as IC2 alter the state LED3 switch off and LED 1 starts blink.

This circuit needs 12V of supply to work. While the second IC (IC2) gets 2V less supply than the actual given.

IC1 as well as IC2 both are connected like a oscillator which will work in the astable mode. Till the time both IC get supply they will oscillate for all that duration of time. But IC2 will not get power for all the time. As soon as the power is given IC1 turns on but C1 is not charged which in turns output at pin 3 at high. As a consequence of it LED1 will not blink. But this output will send to IC2 and IC2 turns on.

LED3 will start brighten as its gets high voltage from the IC2 pin3.And capacitor C2 charged by the 2/3 of the applied voltage due to which IC2 changes its state and LED3 stops glowing. And LED1 starts glowing as C2 begins to discharge but C1 begin charging by the help of R1 and pin3 of IC1 reaches to low state. LED2 will glow just before LED3 glow. Capacitor C2 is used in the circuit so that LED2 will remain glow for short duration only.

Underground secret for the long cycle-time of IC1 is R1 while IC2 short cycle is due to R3.