Working principle of tragffic light control system using 8051 With circuit and block diagram

working principle of traffic light controller using 8051

Traffic lights were first invented in the year 1868 at London’s House of Commons where traffic light signals were placed at intersections of George and Bridge Street. Later the traffic lights were developed in the year 1914 by an American Traffic Signal Company, which fixed green and red lights at corners of the 105th street and Euclid Avenue in Cleveland, Ohio. During this period traffic lights were controlled either by timing or by switching manually.

Traffic lights are also named as stoplights, road traffic lamps, traffic signals, stop-and-go lights which are signaling devices placed at road crossings, everyday pedestrian crossings and other locations to control competing flows of traffic. Traffic lights have been fixed allover the world in many cities. Traffic light control assigns a right way to the road users by using lights in normal colors (red – amber/yellow – green).Traffic light control system uses a worldwide color code (a specific color order to enable color recognition for those who are color blind).



In China, there were unsuccessful efforts to change the importance of “red” to “go” during the Cultural Revolution. Typically traffic lights consist of three types of colored lights such as red, orange and green. In a typical cycle, turning on of a green light allows traffic to continue in the way indicated. Similarly,lighting of the amber/orange light for a short time of transition represents a signal to prepare to stop, and the Illumination of the red signal disallows any traffic from going on.

So far we have given the introduction about traffic signals, and therefore a control system is necessary to control these lights in a specific manner. This traffic light control system can be achieved by using a microcontroller to make simple and low-cost system.

Traffic Light Controller using Microcontroller
The main objective of this traffic light controller is to provide sophisticated control and coordination to confirm that traffic moves as smoothly and safely as possible. This project makes use of LED lights for indication purpose and a microcontroller is used for auto changing of signal at specified range of time interval. LED lights gets automatically turns on and off by making corresponding port pin of the microcontroller “HIGH”.

Working of the Traffic Light Controller

In the above circuit diagram of traffic light controller,a seven-segment display is used as a counter display, and three LEDs are used for the purpose of traffic light control. An 8051 Microcontroller is the brain of this whole project and is used to initiate the traffic signal at the intersections on road. This circuit diagram makes use of a crystal oscillator for generating frequency clock pulses. The LEDs are interfaced to the Port zero of the microcontroller and are powered with 5v power supply. Seven-segment display is connected to the port2 pins of the 8051 microcontroller with a common anode configuration.

The LEDs get automatically switched on and off by making the corresponding port pins of the microcontroller high, based on the 8051 microcontroller and its programming done by using KEIL software. At a particular period of time, only the green light holds ON and the other lights remains OFF, and after sometime, the changeover traffic light control from green to red takes place by making the succeeding change for glowing of yellow LED. This process continues as a cycle and the timing for changing the LEDs can be displayed with the use of a seven-segment LED display in this project.

This traffic light control system can be further enhanced in such a way to control the traffic signals automatically based on the traffic density on roads with the help of IR sensor modules with automatic turnoff if there are no vehicles on either side of the road which leads to power consumption.

TRAFFIC LIGHT CONTROL

Traffic lights, which may also be known as stoplights, traffic lamps, traffic signals, signal lights, robots or semaphore, are signaling devices positioned at road intersections, pedestrian crossings and other locations to control competing flows of traffic.

INTERFACING TRAFFIC LIGHT WITH 8051

The Traffic light controller section consists of 12 Nos. point LEDS are arranged by 4Lanes in PS/8051 Trainer kit. Each lane has Go (Green), Listen (Yellow) and Stop (Red) LED is being placed.

ABOUT THE COLORS OF TRAFFIC LIGHT CONTROL

Traffic lights alternate the right of way of road users by displaying lights of a standard color (red, yellow/amber, and green), using a universal color code (and a precise sequence to enable comprehension by those who are color blind).
In the typical sequence of colored lights:

Illumination of the green light allows traffic to proceed in the direction denoted,Illumination of the yellow/amber light denoting, if safe to do so, prepare to stop short of the intersection, andIllumination of the red signal prohibits any traffic from proceeding. Usually, the red light contains some orange in its hue, and the green light contains some blue, for the benefit of people with red-green color blindness, and "green" lights in many areas are in fact blue lenses on a yellow light (which together appear green).