Three way Traffic Light Control using PLC

Design ladder logic for Three way traffic light control system using Programmable Logic Controller PLC programming.

The traffic light is one of the classic examples in PLC ladder logic.

We can take three directions (North, South, west, and east) with three outputs (Green, Red, and Yellow) lamp as output.

You can build your own concept for making logic for this example or follow the below given conditions for the traffic light.

Three way Traffic Light Control using PLC

Following tabular column is the sample logic for the three-way traffic light,

Traffic light control Sequence

Write the ladder logic for this 3-way traffic light control using the above sequence.

Inputs and Outputs

Inputs and Outputs in PLC Traffic Light

Three way Traffic Light Control

Three way Traffic Light Control using PLC
PLC Programming examples traffic light
PLC ladder diagram for traffic light control

PLC Program Description:

RUNG 000

Latching rung to operate the system through Master Start and Stop PB. 2.

RUNG 001 and RUNG 0002

Starting the timer to turn on first output West Green so east and west should be in red.

The Comparators in Parallel rung are used to turn off East red after 15 sec.

Timer T4:2 timing bit in parallel contact used to turn on East red again in 5th and 6Th Step. (Refer Above Tabular column for clarification)

RUNG 0003

Turning on North Red up to 3rd step using T4:0 and T4:1’s timer timing bit and comparator blocks.

Rung 0004

Turn on East yellow for 5 sec using comparator blocks.(Step 2nd) 5.

Rung 0005-0006-0007-0008-0009-0010

The same procedures followed to turn on further outputs. ( Refer the above Tabular column for the sequence of operation)

RUNG 0011

Reset coil is turned on using T4:2 ‘s done bit to restart the cycle from beginning

Program runs continuously until STOP PB is pressed.

Also Read: 4-way Traffic Light Control

Author: Hema

Training Course: Allen Bradley PLC Course

Related Articles


Your email address will not be published.

  1. Hi! I am a Plc program beginner. Can you send me a simple 2 way traffic signal with 6 output.
    Thank you..