Playground Swing Logic Exercise Program in PLC

In Playground Swing Logic, a timer should count down from 30 seconds when a child starts Swinging. An Alarm activates after time is up.

Contents

Note: This PLC program was created for the persons to learn the PLC basics.

Playground Swing Logic

Problem Statement

Design a PLC ladder logic for the following application.

We are using one toggle switch and one Push Button to control the Alarm.

When a child starts Swinging, a timer should count down from 30 seconds. An Alarm should sound when the time is up.

A Reset Button will start the countdown again.

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This video explains swing example programming using ladder logic.

Inputs and Outputs

Digital Inputs:

Start Button: I0.0

Reset Button: I0.1

Digital Outputs:

Alarm: Q0.0

Program in PLC

Explanation

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

We have used Normally Closed Contact for the Reset Button (I0.1).

In Rung 0:

Normally Open Contact is used for the Start Button (I0.0) to Turn ON the output Alarm (Q0.0)
Timer TON is used to delay the turning ON time of the output Alarm (Q0.0) for some time.
Normally Closed Contact is used for Reset Button (I0.1) to turn OFF the output Alarm (Q0.0) and restart the timer.

When the Start Button (I0.0) is turned ON or (child starts swinging), the output Alarm (Q0.0) will turn ON after 30 seconds as Timer Function Block TON is used to delay the turning ON time of the output Alarm (Q0.0). The time is set to 30 seconds.

In a false state, Normally Closed Contact used for the Reset Button (I0.1) passes the signal to turn ON the output Alarm (Q0.0). After 30 seconds, the output Alarm (Q0.0) will turn ON.

When Reset Button (I0.1) is pressed and released, the output Alarm (Q0.0) will turn OFF because When the Reset Button (I0.1) is pressed, Normally Closed Contact used for Reset Button (I0.0) will be in True state and does not allow the signal to pass through it and the output Alarm (Q0.0) will turn OFF.

When the Reset Button is released (I0.1), Normally Closed Contact used for the Reset Button (I0.0) will be in a false state and allow the signal to pass through it. Then, the timer again starts in the Timer Function Block type TON. The time is set to 30 seconds. After 30 seconds, the output Alarm (Q0.0) will turn ON again.

Simulation Results

Now we simulate our PLC program and discuss the results.

When the Start Button is turned ON (Child Starts Swinging)

The time is set to 30 seconds.

In a false state, Normally Closed Contact used for the Reset Button (I0.1) passes the signal to turn ON the output Alarm (Q0.0).

After 30 seconds, the output Alarm (Q0.0) will turn ON.

When the Reset Button is Pressed and Released

When the Reset Button (I0.1) is pressed and released, the output Alarm (Q0.0) will turn OFF because When the Reset Button (I0.1) is pressed.

Normally Closed Contact used for the Reset Button (I0.0) will be in a True state and does not allow the signal to pass through it and the output Alarm (Q0.0) will turn OFF.

When the Reset Button is released (I0.1), Normally Closed Contact used for the Reset Button (I0.0) will be in a false state and allow the signal to pass through it.

Then, the timer again starts in the Timer Function Block type TON. The time is set to 30 seconds. After 30 seconds, the output Alarm (Q0.0) will turn ON again.