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