PLCs: Its Definition, Design, And Tasks

If you have previously heard of the terms PLC or Modicon Quantum, and you want to know more information about such things, we advise you to read the following article. 

A short definition of the PLC

This system is a device that performs a task according to the program it receives. In other words, PLC is a type of computer that runs a specific program. With the advent of PLCs, the equipment and components used to control industrial processes and production lines changed, and solid-state contactor and hardware relay circuits gradually gave way to programmable logic controllers.

What is PLC (an in-depth definition)

PLC is the abbreviation for Programmable Logic Controller. PLC is designed for reliable operation in tough industrial environments like extreme temperatures, humid areas, dry or dusty environments. We use PLCs to automate industrial procedures such as the assembly line of a production factory, ore processing plant, or wastewater treatment plant.

PLCs share several features with a home PC or laptop. Both have power supplies, CPUs, inputs and outputs (I / O), memory, and operating software (although it is a different operating software).

The biggest difference is that a PLC can do discrete and continuous operations that a personal computer cannot do. Also, PLC is much more suitable for the industrial field. A PLC can be thought of as a strong digital computer that manages the electromechanical operations of an industrial environment.

PLCs play a major role in automation by forming part of a larger SCADA system. A PLC can be programmed based on the operational requirements of the procedure. And because of the changing nature of production, there will be a need for re-planning in the manufacturing industry. To bypass this issue PLC-based control systems were founded.  

If you are willing to learn more about programming PLCs, you should watch the different PLC training courses found online. Such courses will help you start working in the field of control engineering.

A quick overview of PLC  

  • PLC is an industrial computer with no mouse, keyboard, or regular monitor.
  • Because it is an industrial computer, a logical program has been developed to control the procedure in the public computer.
  • The program is then transmitted to PLC through a wire. This program is saved in PLC memory.
  • A logic program is created by a programming language called a ladder logic, statement list, or function block diagram.
  • The program is made so that people with a knowledge of electricity or precision instruments can easily work with it. 
  • A programmable logic controller is made of many terminal inputs and outputs.
  • A PLC employs the input terminals to watch the status of switches and sensors, and according to this status commands the output devices through the output terminals.

The PLC design 

These are the important components of a PLC system:

  • Central processing unit
  • Processor
  • Memory
  • Power supply
  • Input / output module
  • Communication protocol
  • Programming device

How does PLC work?

The operation of a programmable logic controller can easily be understood as a cyclic scanning method called the scanning cycle.

A PLC scanning process involves the following steps:

  • The operating system starts cycling and time monitoring.
  • The CPU starts reading data from the input module and checks the status of all inputs.
  • The CPU starts the user or application written in RelayHolder logic or any other PLC programming language.
  • Next, the CPU performs all internal detection and communication tasks.
  • Based on the program’s results, it writes the data in the output module, to update all the outputs.
  • This process continues as long as the PLC is running.

For additional information about PLC, you can visit the MRO Electric official website. 


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