TRAFFIC LIGHT CONTROLLER

Components Required
Integrated Circuit
IC-1 (555)
IC-2 (CD4017)
Resistors
R1 (10K)
VR1 (100K)
Capacitor
C1 (100mfd/ 16V)
Diode
D1-D9 (IN4007)
Transistor
T1 (BC148)
T2 (BC148)
T3 (BC148)
Miscellaneous
Three LED(RED,ORANGE,GREEN)
Battery (9V DC)
Flexible wires
Soldering rod etc..

Principle and Working:-
This circuit is self explanatory by its name, and can be used to control traffic in public places, or to demonstrate traffic rules in traffic-parks.
IC2, which is heart of the circuit, is a decade counter. In this counter for every pulse fed to pin-14, potential keeps shifting from D1 to D9 in cyclic order.
IC1 is used as a pulse generator and generates pulses in regular configurable intervals. These intervals can be changed by varying VR1.
The circuit is designed in such a way that out of nine pulses, RED LED remains glow for 4 pulses, ORANGE LED for 1 pulse and GREEN LED for remaining 4 pulses. Since D1-D4 provide current to T1, T1 is on whenever there is potential on any diode D1 to D4, which keeps red LED glow. Similarly other diodes are responsible for orange and green led glow.