power supply

You can use 5v - 12v DC power supply depending on your project or use 9v general purpose battery, its easily available.

4 way traffc control system  uses 8051 microcontroller ( AT89C52) , 7-segments and LED’s for indication. The LED’s which was used as lights was connected to the Microcontroller by means of common Anode configuration. In this configuration the Microcontroller PCB was used to sink the current from the LED to its ports. That means logic 0 signal in the Microcontroller switches the LED ON and logic 1 signal switches the LED off. Here we are using 6 MHz crystal for the 8051 Microcontroller operation and you can use upto 12MHz crystal with this controller.