Types and Parts of a PLC  What are they and how do they work? ▷ 2020

If we have ever been curious to know how industries make, for example, a car in such an exact way through robotic mechanisms, we are one step away from answering these questions.

The programmable automaton device is in charge of performing these tasks, since it is used in all factories for assembly and other tasks that have to be repetitive and exact in the shortest possible time.

Thanks to these advanced technology equipment, today we can enjoy many objects and elements that we use daily. We are going to show you what a PLC is, what its functions are and the different types that exist. In addition, we will reveal all the internal components that a programmable automaton has.

What is a PLC and what is this type of device used for?

What is a PLC and what is this type of device used for

A programmable logic control is an electronic device or computer that is used in factories for the assembly line, with which the inputs and outputs are established in real time in order to carry out the industrial processes automatically.

Its design is designed to withstand extreme noise as well as vibration and shocks. It is designed to work at high temperatures and its operating program can be stored in batteries in memories that are not volatile.

Its name comes from the acronym for “Programmable Logic Controller” or PLC, it is also known as a programmable automaton.

What are the main advantages and disadvantages of a programmable controller?

What are the main advantages and disadvantages of a programmable automaton

As we said before, a programmable automaton is used to carry out continuous processes in a factory, according to specific orders in a given time.

Like any programmable computer, it has its advantages and disadvantages that we detail below:


Among the advantages of scheduled manufacturing we can highlight the following:

  • It allows work to be carried out according to previously stipulated standards without any deviation.
  • It is possible to perform the tasks in a time that can be quantified, thus generating a budget planning in time and costs with great precision.
  • It allows direct labor savings, since these teams can carry out the work of several operators.
  • Changing a process is relatively easy and the results are immediate as the PLC instantly gets used to it once programmed.
  • According to its small size, it allows generating a suitable infrastructure without being a concern for industrial engineers in the place where they will have to be installed.
  • Being robust they can withstand temperatures and wear that a person or operator could not do.


There are also disadvantages of this device which we mention below:

  • Specialized labor is needed to handle it, as well as the assembly or replacement of certain parts.
  • It can stop an entire manufacturing process if it breaks and there is no backup of it.
  • High initial investment, although it is true that the investment payback time is short, but it is often cheaper to hire operators than to acquire all the PLCs that are needed at the beginning of a manufacturing process.

Types of PLCs How are programmable logic controllers classified?

How Programmable Logic Controllers Are Classified

We can classify programmable automatons according to their type, they are:


When the CPU, the power supply, the interface boards and the modules that serve to input and output information exist in the same compartment.


It is a variation of the previous type but the CPU is separate from the communications processor. The main characteristic is that it has many inputs and outputs for the automation of manufacturing processes.

Rack mountable

As its name indicates, the different internal components are not in a compartment, but rather they are presented in a rack, where the interface boards and others, for example, the CPU and the power supply, enter a plant.

Operator panel

This type of programmable automaton is related, in addition the compartment provides us with a panel so that an operator can control the functions directly from the PLC and not remotely.

Industrial computer

This type of programmable automaton refers to when there are two classes or two modules that are separated, one of which can be in a CPU and the other directly in an assembly line, or how they are found through hardware and the other installed in a software.


This type of PLC is a more versatile version since its form is a card that can be used in different functions and can transmit the controls and orders that the different manufacturing components have to do.


This PLC is actually a virtual automaton since it is installed in a CPU and from there all the functions that it performs are controlled. It is one of the most modern types that exist today.

Red Band

When you need to work speed, we have to have programmable robots that can perform their tasks adapted to this type of speed, that is, they have to provide the possibility of monitoring at lower frequencies.

Narrow band

PLC is not intended for industry, as it performs tasks with minimal frequencies and can perform jobs with much smaller or lower performance than industrial ones.

List of the main parts of every programmable logic controller (PLC)

We will show you the main parts that a programmable logic controller has, which we will detail below:

Power supply

It is the element by which the electrical voltage is obtained continuously, according to the specifications that a PLC has to provide the CPU with correct operation.

Central processing unit

The Central Processing Unit is the part that directs the entire system, it is the one that reads the instructions and executes them, consulting the status of inputs and outputs according to the precise specifications given by the user.

Input module

These interfaces are dedicated to connecting the CPU with the electronic cards and other devices that exist around it. Thanks to these electronic equipment, it is possible to exchange data in order to control all the machines that are dedicated to the manufacturing and assembly process.

Output module

They are in charge of taking from the CPU to the outside all the indications and the control results that it carried out in the Central Processing Unit. Thanks to this part of the PLC we can obtain the corrections and put them into practice in a real way.

Memory module

As their name indicates, they are electronic devices that connect to the CPU and their purpose is to store the information or data that is produced in the PLC.

Programming terminal

The programming terminal is the means by which the instructions that are constantly generated when the user controls what is programmed are entered. Thanks to this component, all the operations that a PLC can do can be corrected and reprogrammed.


They are those input elements that allow a connection between the user and the CPU, through which different information is entered. An example of this can be the hard drive, keyboard, mouse, and so on.

If you have any questions, leave them in the comments, we will answer you as soon as possible, and it will also be of great help to more members of the community. Thank you! 😉

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