Abstract:
This project is introducing the application of the PLC nowadays. PLC is a black-white relay
controller of logic foundation using Ladder Diagram and Mnemonic codes, with the 3C technology
(Computer, Control and Communication) unifies. Programmable Logic Control is important because
all production processes go through a fixed repetitive sequence of operations. A PLC is used to control,
time and regulate the sequence. In this project, PLC was used to design a Four-Junction traffic light.
Sensor was used to sense and give priority to emergency vehicles through any junction. The sensor
will sense the emergency vehicles and give a signal to PLC to turn on green light for that way. All the
red light will turn on for a while when it change from junction to junction as a safety factor. The traffic
light will be function follow the sequence from junction to other junction starting from green, yellow
and red. Photodiode was used as a sensor. The Radio Frequency receiver will be mounting at the
signboard 100 meter from the traffic light. The Radio Frequency receiver will turn on when it sense the
emergency vehicles. PLC will receive the signal from the Radio Frequency transmitter from the
emergency vehicles and will turn on green light at that junction. It means, the traffic light will give
priority to emergency vehicles cross the junction. Furthermore, the other junctions turn to red
