PLC Ladder Logic Design: Control 3 Motors with Toggle Switch

PLC ladder logic design to control 3 motors with toggle switch and explain the program using the video & article.

Note: This example ladder logic is for education purposes and for practicing PLC programming.

Control 3 Motors with Toggle Switch

Problem Statement:

Design a PLC ladder logic for the following application.

We are using one toggle switch to control 3 Motors.

When the Start Button is ON,

The First Stage Motor runs for 10 seconds, then stops.

After a 5-second delay, the Second Stage Motor runs for 20 seconds and then the Third Stage Motor will run for 15 seconds.

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This video explains the given PLC problem statement with a detailed solution.

Inputs and Outputs

Digital Inputs:

Start Button: I0.0

Digital Outputs:

Motor 1: Q0.0

Motor 2: Q0.1

Motor 3: Q0.2

PLC Ladder Logic Design

Program Description

We have used Normally Open Contact for the Start Button(I0.0).

In Rung 0:

1. Normally Open Contact is used for the Start Button (I0.0) to Turn ON the output  Motor 1 (Q0.0).
2. TP timer is used to Turn ON the output Motor 1 (Q0.0) for a limited time.

In Rung 1:

1. Normally Open Contact is used for the Start Button (I0.0) to Turn ON the output Motor 2 (Q0.1).
2. TON timer is used to delay the turning ON time of the output Motor 2 (Q0.1) for some time.
3. TP timer is used to Turn ON the output Motor 2(Q0.1) for a limited time.

In Rung 2:

1. Normally Open Contact is used for the Start Button (I0.0) to Turn ON the output Motor 3 (Q0.2).
2. TON timer is used to delay the turning ON time of the output Motor 3 (Q0.2) for some time.
3. TP timer is used to Turn ON the output Motor 3 (Q0.2) for a limited time.

Simulated Logic

Now we will simulate our program and see the test cases.

Rung 0:

When the Start Button (I0.0) is turned ON, the signal will flow through the Start Button as Normally Open Contact is used for the Start Button (I0.0).

The output Motor 1 (Q0.0) turns ON for 10 seconds because Timer Function Block type TP is used to turn ON the output Motor 1 (Q0.0) for a limited time and the time is set to 10 seconds. After 10 seconds, the output Motor 1 (Q0.0) will turn OFF.

Rung 1:

When the Start Button is turned ON, Motor2 (Q0.1) will turn ON after 15 seconds ( i.e after 5 seconds when Motor 1 gets turned OFF) because Timer Function Block type TON is used to delay the turning ON time of the output Motor 2 (Q0.1) and the time is set to 15 seconds.

The output Motor 2 (Q0.1) will remain ON only for 20 seconds as we have used Timer Function Block type TP to turn ON the output Motor 2 (Q0.1) only for a limited time and the time is set to 20 seconds. So after 20 seconds, the output Motor 2 (Q0.1) will turn OFF.

Rung 2:

When the Start Button is turned ON, Motor 3 (Q0.2) will turn ON after 35 seconds ( i.e immediately when Motor 2 gets turned OFF) because Timer Function Block type TON is used to delay the turning ON time of the output Motor 3 (Q0.2) and the time is set to 35 seconds.

The output Motor 3 (Q0.2) will remain ON only for 15 seconds as we have used Timer Function Block type TP to turn ON the output Motor 3 (Q0.2) only for a limited time and the time is set to 15 seconds. So after 15 seconds, the output Motor 3 (Q0.2) will turn OFF.

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