# Traffic Light Control using PLC Ladder Logic Programming

Design ladder logic for 4 way-traffic light control system

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

We can take four directions (North, South, west, and east) with three output lamps (Green, Red, and Yellow).

You can build your own concept for making logic for this example.

Follow below tabular column – Logic for the four way traffic light

## Logic Explanation

#### Network 1

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

#### Network 2

Starting the timer to turn on output East Green, North-South-West is in red. Parallel circuits are added to turn ON/OFF the output in up next sequence.

#### Network 3

Turning on North Yellow and East Yellow. Parallel circuits are added to turn ON/OFF the output in up next sequence.

#### Network 4

Turn on East Red and North Green.

#### Network 5, 6, and 7

Same procedures followed to turn on further outputs.( Refer Tabular column for sequence of operation)

#### Network 8

Timer 7 (T7) done bit is used to restart the cycle from beginning

Program runs continuously until STOP PB is pressed

Time delay of 5s has given using timers which will make each cycle with 5s delay.

Author: Hema

Training Course: Siemens PLC Training

## Three way Traffic Light Control using PLC

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

## Overview of Memory Section

The memory refers to the section of the PLC where data and instructions are stored (either temporarily or semi-permanently).

## Basic PLC Instructions

Symbolic representations of contacts and coils are the basic symbols of any ladder logic instructions set used in the PLC programming.

## Timers and Counters

Timers and counters are PLC internal instructions that provide the same functions as timing relays and counters.

## Two Floor Elevator PLC Program

PLC program to execute an elevator system in a two-floor apartment using Allen Bradley PLC ladder logic programming.

#### Responses

1. This illustration was very helpful. From it, I also learned that there is more than one way to obtain a desired result.
Thank you so much

2. This is great, thank you.

3. I learned the logic and from it I am being able to design a different logic.
It is helpful and I am so excited, therefore I cannot wait to gladly take another lesson and become a programmer.
Thanks.

4. I have a doubt in Network 2 and 8.
After the Timer T7 in Network 8 runs for 5 seconds, won’t the N/C contact of T7 in Network 2 become open ? If it opens how will output coil Q0.0 and Q0.1 will get energized? Thus, how reset action will occur ?
Kindly clarify my doubt.

5. 1) I have doubt in n/w 2 Q0.1(North-red) line..we have connected parallel Ncc T0 with T3. in this prob, shount’t be OCC T7 along with NCC T4 ,instead of T3 (as Northen red will be red after T4 and remains till T7 )??
2) in same n/w , Q0.2(west-red), you have connected Ncc T2 parallel with Occ T5,, shoun’t it be occ T6 in series with Ncc T7,,instead of occ T5???
I have these doubts….I hope u have understood what i’m tryinbg to sya
I be waiting for doubt clearification. Thank you

6. it was clear explanation and am so excited .thank you very much

7. sir,
Logic Explanation should be immediate after network no.

8. Hi I’m new this course please explain detials me