Smart Automation Solutions: PLC Logic for Stairway Lighting

Implement smart home automation solutions using PLC logic for stairway lighting control with the help of sensors.

Disclaimer: This PLC programming example is for educational purposes only and is provided to study the ladder logic with simple applications.

Stairway Lighting

Problem Statement:

Design a PLC ladder logic for the following application.

We are using three sensors to control 3 Lights. There is one sensor in each place, there are three places so we need 3 sensors. The sensor will detect if there is any presence of a person in the respective place.

The Light on each step (or place) of the stair should remain ON for 10 seconds after the last detected movement.

Home Automation Solutions

This video helps you to implement smart automation for your home application using sensors and lights.

Inputs and Outputs

Digital Inputs:

Sensor 1: I0.0

Sensor 2: I0.1

Sensor 3: I0.2

Digital Outputs:

Light 1: Q0.0

Light 2: Q0.1

Light 3: Q0.2

PLC Logic

Program Description

We have used Normally Open Contact for Sensor 1(I0.0), Sensor 2 (I0.1), and Sensor 3 (I0.2).

In Rung 0:

1. Normally Open Contact is used for Sensor 1 (I0.0) to Turn ON the output  Light 1 (Q0.0).
2. Timer TOF is used to delay the turn-OFF time of the output Light 1 (Q0.0) for some time.

In Rung 1:

1. Normally Open Contact is used for Sensor 2 (I0.1) to Turn ON the output  Light 2 (Q0.1).
2. Timer TOF is used to delay the turn-OFF time of the output Light 2 (Q0.1) for some time.

In Rung 2:

1. Normally Open Contact is used for Sensor 3 (I0.2) to Turn ON the output  Light 3 (Q0.2).
2. Timer TOF is used to delay the turn-OFF time of the output Light 3 (Q0.2) for some time.

PLC Code Testing

Let’s test our PLC code with the simulation of different input statuses. We may show only the required part of the logic or rung instead of the complete program. We recommend you watch the above video for full details.

Rung 0:

When Sensor 1 (I0.0) gets activated, the output Light 1 (Q0.0) will turn ON as Normally Open Contact is used for Sensor 1 (I0.0) and the signal will flow through it.

When Sensor 1 (I0.0) turns OFF, the output Light 1 (Q0.0) remains ON but for a limited time because Timer Function Block type TOF is used to delay the turning OFF time of the output Light 1 (Q0.0) and time is set to 10 seconds.

After 10 seconds, the output Light 1 (Q0.0) will turn OFF.

Rung 1:

The output Light 2 (Q0.1) will turn ON, when sensor 2 (I0.1) gets activated.

When Sensor 2 (I0.1) turns OFF, the output Light 2 (Q0.1) remains ON but for a limited time because Timer Function Block type TOF is used to delay the turning OFF time of the output Light 2 (Q0.1) and time is set to 10 seconds.

After 10 seconds, the output Light 2 (Q0.1) will turn OFF.

Rung 2:

When Sensor 3 (I0.2) gets activated, the output Light 3 (Q0.2) will turn ON as Normally Open Contact is used for Sensor 3 (I0.2) and the signal will flow through it.

When Sensor 3 (I0.2) turns OFF, the output Light 3 (Q0.2) remains ON but for a limited time because Timer Function Block type TOF is used to delay the turning OFF time of the output Light 3 (Q0.2) and time is set to 10 seconds.

After 10 seconds, the output Light 3 (Q0.2) will turn OFF.

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