PLC Systems: Frequently Asked Questions

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PLC Systems: Frequently Asked Questions

29 January 2019
 Categories: , Blog

PLC stands for Programmable Logic Controller, and it is an industrial digital computer that has been adapted to control manufacturing processes. Here are some answered questions about programmable logic controllers.

Overview

PLCs have a wide range of uses. They can start from small modular devices with tens of I/Os to large modular devices with thousands of I/Os. When digital computers were available, they found application in industrial processes. One of the main traits of PLCs is reliability. Automated processes require precise response times, and PLCs can easily comply with these requirements by even milliseconds.

What Is The Working Principle Of Programmable Logic Controller Systems?

A PLC system takes input information such as temperature, pressure, volume and flow and turns it into output signals to regulate the ongoing manufacturing process. Every PLC is composed of three main parts: the CPU module, the power supply module and one or several I/O modules.

A CPU Module is composed of a central processor and its memory. This module is responsible for processing all the data from the inputs and turning them into appropriate outputs.

A power supply module is a module that provides the required power to the whole PLC system by converting the alternating current into direct current.

The I/O modules or input and output modules are modules that serve as sensors and actuators to the system. They sense the various parameters mentioned before. The I/O modules can be either digital or analog.

Which Programming Language Is Used For Programmable Logic Controller Systems?

The most commonly used programming language for PLC systems is ladder logic. Ladder logic represents a program by a graphical diagram based on circuit diagrams of hardware that rely on logic. Like a ladder, it represents the various steps of the process. In the case of PLCs, the steps are as follows:

  1. The operating system starts cycling and monitors the time.
  2. The CPU reads all the data from the input module and checks their status.
  3. The CPU begins executing the user or application that is written in ladder logic.
  4. The CPU performs an internal diagnosis.
  5. According to the input data and the program results, the CPU writes the data into the output to make all the necessary changes.
  6. This process continues in cycles as long as the PLC is in run mode.

Where Are Programmable Logic Controller Systems Used?

PLCs are used in all the industries that include automated process and building systems, such as the glass industry, the paper industry, cement manufacturing and cable manufacturing. There are also more common uses such as in washing machines, traffic signals and elevators.

Contact an electrician to learn more about PLC control systems.