PROGRAMMABLE LOGIC CONTROLLER

 WHAT IS PLC ? PROGRAMMABLE LOGIC CONTROLLER

 Are you an engineer by training?

Have you studied or earned a degree in the engineering fields of instrumentation and control, electrical, electronics, or electronics and communication?

So then, you might find information about the Programmable Logic Controller interesting. You may be wondering things like, "What is PLC explain?". What is PLC and how does it function? Why is PLC used? What does it mean? What varieties of PLC are there? What make up the PLC's primary parts? You will then find all of the answers to the questions above in this post.

The PLC is essential in today's industrial era for managing the intricate control system. Compared to outdated electromechanical relay systems, PLC has many benefits. In layman's terms, we may state that PLC provides an easy way to change the intricate workings of a control system without significantly altering the control wiring.
What is a PLC or a programmable logic controller? How does it function? Why is it so crucial?

PLC : 

A programmable logic controller (PLC) is an industrial digital computer that has been ruggedized and tailored for the control of manufacturing processes or any activity that necessitates high-reliability control, simplicity of programming, and process fault identification.

An industrial computer called a PLC excludes a mouse, keyboard, and monitor.
Given that it is an industrial computer, the general computer has created a logical programme to control the process.
Then cables are used to transfer this software to the PLC. The PLC memory houses this programme.
A programming language known as Ladder logic, Statement List, or Functional block diagram is used to create the logical programme.
Those with electrical or instrumentation expertise can quickly grasp a programme because of the manner it has been written.
Many inputs and outputs are seen on a programmable logic controller.
A PLC uses input terminals to monitor the status of switches and sensors, and based on that status, it sends commands to the output devices via output terminals.

PLC ARCHITECTURE : 

            

The PLC system's fundamental architecture is depicted in the above diagram. The PLC system's key elements are as follows:

                             ⇨  Central Processing unit

                             ⇨  Processor

                             ⇨  Memory

                             ⇨  Power Supply

                             ⇨  Input/Output Module

                             ⇨  Communication Protocol

                             ⇨   Programming Device

PLC PROGRAMMING LANGUAGE : 

       The program is prepared using a language which is called programming language. This is the list of PLC PROGRAMMING LANGUAGE:

• Ladder Diagram(LD)

• Instruction List(IL)

• Structured Text(ST)

• Function Block Diagram(FBD)

• Sequential Function Charts(SFC)

Out of all these languages, Ladder Diagram(LD) is widely used in the Automation industry because of its easy understanding.

 TYPES OF PLC : 

        There are mainly two types of PLC in terms of physical hardware:

• Compact PLC or Fixed PLC
• Modular PLC

COMPACT PLC OR FIXED PLC : 

       Each module is contained within its own casing. The number of input/output modules in this form of PLC is fixed.In a single case, the Processor, power supply, and communication card are all contained. You can see an example of a stationary or compact plc in the image below.

 MODULE PLC : 

This kind of PLC is implied by the name to have a variety of modules. Just simply adding modules, inputs and outputs modules can be readily increased.

It is also known as a rack mounted PLC because all of the modules are mounted in a rack. The modular type PLC is depicted in the image   . 

ADVANTAGES :

        Relays are used to control the process prior to the introduction of PLC. Even when troubleshooting, this relay control panel requires a lot of work to discover the issue because there are many cables, and it takes too long to figure it out. It also requires routine maintenance and uses a lot of power.

      PLC control systems have some benefits over relay control systems.Easy to install and maintain PLC system (There are fewer wires in this system as compared to the Relay control system).

The logic is simple to programme and alter both online and offline (Luckily, there is no need to change in wiring of the PLC system during modification of a process).      

 DISADVANTAGES :

      PLCs have restrictions when operating in high-temperature, vibrating environments.
     High Start-Up Cost (PLC is not considered necessary when applied to industrial systems that do not need to change the wiring)

APPLICATIONS : 

   PLCs are widely used in almost all types of industries because of their rugged nature, flexibility, and reliability.