What are the main types and parts of a PLC and how do they work?

by Kelvin
Internet Paso a Paso

If we have ever been curious to know how industries make to manufacture, 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 responsible for performing these tasks, since he himself is used in all factories for assembly and other tasks that have to be repetitive and accurate in the shortest possible time.


Thanks to these advanced technology equipment, today we can enjoy many objects and elements that we use every day. 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 for?

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

Its design is designed to withstand extreme noise as well as vibration and shock. It is designed to work in high temperatures and its operating program can be stored in batteries in non-volatile memories.

His name is due to the acronym of «Programmable Logic Controller» or PLC, it is also known as programmable automaton.

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

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, which are detailed below:


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

  • It allows to carry out work according to previously stipulated standards without any deviation.
  • It is possible to carry out the tasks in a time that can be quantified, thus generating a budget planning in time and costs with great precision.
  • It allows the saving of direct labor, since these teams can carry out the work of several operators.
  • Changing a process is relatively simple and the results are immediate since the PLC gets used instantly once programmed.
  • According to its small size, it allows generating an appropriate infrastructure without being a concern for industrial engineers, instead of 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.
  • You 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 recovery time of the investment is short but many times it is cheaper to hire operators than to acquire all the PLCs that are needed at the beginning of a manufacturing process.

PLC types 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 used 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 feature is that it has many inputs and outputs for the automation of manufacturing processes.

Rack mount

As the name implies, the different internal components are not in a compartment, but instead 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

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This type of programmable automaton, refers when there are two classes or two modules that are separated, which one can be in a CPU and the other directly in an assembly line, or how they are found through a 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 on a CPU and hence all the functions performed by it 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 controllers that can perform their tasks adapted to these types of speeds, that is, they have to provide the possibility of monitoring at lower frequencies.

Narrow band

PLC is not intended for the industry, since it performs tasks with minimum frequencies and can perform jobs with a much smaller or lower performance than industrial.

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

We will show you the main parts that have a programmable logic controller 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 proper operation.

Central processing unit

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

Ticket Module

These interfaces are dedicated to connecting the CPU with 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 responsible for carrying all the indications and control results that were carried out in the Central Processing Unit from the CPU. Thanks to this part of the PLC we can obtain the corrections and put them in a real way to practice.

Memory module

As the name implies, 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 generated constantly are entered when the user controls what has been programmed. Thanks to this component, you can correct and reprogram all the operations that a PLC can do.


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 disk, the keyboard, the 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 surely be of great help to more members of the community. Thank you! ????

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