PLC Ladder Logic Example based on Set Coil and Reset Coil

Step-by-step guide to plc ladder logic with set coil and reset coil example presented in this educational blog.

Please note: The logic diagram example is designed for educational use for students and engineering graduates to learn PLC fundamentals.

Set Coil and Reset Coil Example

Problem Statement

Design a PLC ladder logic for the following application.

We are using two toggle switches to control two motors.

If Switch 1 is ON, then Motor I and Motor II will be ON.

If Switch 1 is OFF, then Motor I and Motor II will be still ON.

If Switch 2 is ON, then Motor I and Motor II will be Off.

PLC Ladder Logic

Learn this PLC programming example with the below video.

IOs List

Digital Inputs:

The list of inputs given below.

Switch 1: I0.0

Switch 2: I0.1

Digital Outputs:

The list of outputs given below.

Motor 1: Q0.0

Motor 2: Q0.1

PLC Example using Set and Reset Coils

Program Description

• We used EcoStruxure Machine Expert software for PLC programming.
• In the above program, we have used Normally Open Contact for Switch 1 (I0.0) and Switch 2 (I0.1).
• Set and Reset Coils are used for both Motor 1 (Q0.0) and Motor 2 (Q0.1).
• For Motor 1 and Motor 2 to be ON, switch 1 should be ON.
• We have used set coils in Rung0 for the outputs, Motor 1 and Motor 2.
• Motor 1 and Motor 2 will remain ON when the input Switch 1 changes its state from true to false.
• In Rung 1, we have used Reset Coils for the outputs.
• When the Input Switch 2 gets ON, the reset coils will turn OFF the outputs.

Result

Let’s see the program result with different input simulations.

When Switch 1 is ON

Switch 1, in the true state, will allow the signal to flow through it and Motor 1, and Motor 2 will get ON.

When Switch 1 is OFF

Motor 1 And Motor will remain ON when Switch 1 is turned OFF as Set Coils are used for these two Motors. The set coils will remain ON even when the input is changed to false.

When Switch 2 is ON

When Switch 2 is turned ON, Motor 1 and Motor 2 will TURN OFF as Reset Coils are used for Motor 1 and Motor 2 in Rung1.

The reset coils, once activated, will turn OFF the outputs. And it will keep it OFF even when the input is turned OFF.

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