PLC Ladder Logic Example – Automatic Lamp Control using PLC

In this article, we are going to discuss another PLC ladder logic example of an automatic lamp control system in a large storage facility. The conventional method to turn ON and OFF lamps in a large storage facility is to press buttons manually.

This is a time-consuming task and also consumes more electrical energy than required resulting in increased energy bills. To overcome this problem, a solution is required to minimize the usage of electricity as per requirement.

In this example, we are going to see how to draw a ladder logic diagram for an automatic lamp control system in the warehouse using PLC. One should note that these are the basic examples of PLC ladder logic examples for PLC ladder logic practices.

Automatic Lamp Control System

In this example, we are going to see an automated system for automatic lamp control using PLC.

Problem Statement

Draw a ladder logic diagram for an automatic lamp control system with the help of an interlock system.

Let us consider that there are 3 sections in a warehouse. When a person enters the warehouse, the lamp of the respective section will turn on and other lamps will stay turned off at the same moment.

For example, if a person enters the warehouse, first of all, the system will turn on. Then if that person enters section 1, the lamp of section 1 will turn on and lamps of sections 2 and 3 will remain off. The same logic should be carried out for sections 2 and 3.

If the person enters section 2, the lamp of section 2 will turn on and the lamps of sections 1 and 3 will remain off. If the person enters section 3, the lamp of section 3 will turn on and the lamps of sections 1 and 2 will remain off.

List of Input and Output Tags

In this example, we have used object detecting sensors at the entry points of the warehouse and each section. Hence, there are 4 sensors indicating 4 inputs, memory is used to turn on the system at the entry of the warehouse, and 3 output lamps in all 3 sections.

Inputs are denoted by the letter I, memory is denoted by the letter M and output is denoted by the letter Q. All sensors are normally open (N.O) type.

Automatic Lamp Control system Ladder Logic Diagram

In this example, we have used Siemens S7-1200 PLC and Siemens TIA portal for programming a ladder logic diagram. The PLC we selected has a work memory of 100 kb, 24 V DC power supply with 24V DC 14 digital inputs, 10 digital outputs, and 2 analog inputs on board.

Network 1

Network 1 shows the system’s start and stop function. Two sensors are installed at the entry and exit of the warehouse.

When a person enters the warehouse, the sensor at entry will turn on I0.0 starting the lamping system of the warehouse. Output is stored in a memory M0.0 and is latched to the input.

Network 2

Network 2 shows the behavior of section 1. All inputs are connected in series along with output. Section 1 sensor is normally open (N.O) and section 2 and section 3 sensors are kept normally closed (N.C).

When a person enters section 1, the sensor senses the presence of the person and turns on the lamp. If that person moves to either section 2 or section 3 N.C contact will become N.O and will turn off the lamp of section 1.

Network 3

Network 3 shows the behavior of section 2. All inputs are connected in series along with output. Section 2 sensor is normally open (N.O) and section 1 and section 3 sensors are kept normally closed (N.C).

When a person enters section 2, the sensor senses the presence of the person and turns on the lamp. If that person moves to either section 1 or section 3 N.C contact will become N.O and will turn off the lamp of section 2.

Network 4

Network 4 shows the behavior of section 3. All inputs are connected in series along with output. Section 3 sensor is normally open (N.O) and section 1 and section 2 sensors are kept normally closed (N.C).

When a person enters section 3, the sensor senses the presence of the person and turns on the lamp. If that person moves to either section 1 or section 2 N.C contact will become N.O and will turn off the lamp of section 3.

The last 3 networks can be combined to form a single network that shows the automatic lamp control of the warehouse. The ladder logic diagram of the same is shown in the figure below.

Download automatic lamp control of the warehouse plc program, plc programming examples, and solutions pdf.