Programmable Logic Controller (introduction)

Once we have studied the sensors and actuators it is time to dedicate time to understand the function of the controllers, previously we began describing pneumatic controllers and from this point we will focus on the study of electronic controllers, specifically we are going to study the one of greater use that is the Programmable Logical Controller, from now on PLC.

The fields in which a PLC system can be applied are practically innumerable. These control systems are mainly intended for the functions of "process control", where they ensure that each step or phase of the process is carried out in the correct chronological and synchronized order that was previously established.
A PLC system is based on a specific type of computer, designed for work environments where its primary mission is the control of industrial processes, which can be constituted by various types of machinery, robots, assembly lines

In many occasions a PLC may have a keyboard as a data input element, but the programmable logic control will only respond to its control actions with the information provided by its sensors. On the other hand, the programmable logic control can be monitored in detail of the control activities carried out during its operation, by means of a monitor or printer. Depending on the real situation to which an answer has to be given, the internal configuration of the PLC can have a high or low degree of complexity, regardless of the degree of complexity of the application.

A PLC consists of the following essential components:

Hardware: These are all the electronic components that make up the control system, its main task being to activate or deactivate the controls by means of which all the series of power elements connected to it are manipulated, all this according to a specific logical sequence. The most important element of the hardware is the microprocessor or microcontroller.

Software: It is the intangible part that does not have a physical part, since it is the programs that determine the way to operate the control system, or in other words, the instructions that represent the generation of the controls that govern the electronic part. The programs are stored in a memory, which can be accessed for the execution of the instructions. When both the order and the instructions that make up the program are modified, the execution sequence of the control system is invariably altered, even if this modification does not imply a change in the hardware.

Sensors: They are those devices that interpret the physical variables found in the environment, convert them to electrical signals and finally communicate them to the PLC, this information represents the state of the process being controlled.

Actuators: In order to be able to modify the physical variables that are important within a process, the power elements known as actuators are used.

Programmer: It is the means through which the instructions of the software are ordered that later will be memorized in the PLC. At present, through the mediation of a personal computer, this process can be carried out, in addition to the fact that in most cases it also serves to check the programs of the control system.

This concludes another installment that I leave for you with much affection hoping that I can be of use to you and sincerely thanking you for the time you have taken to read my article.

All images used in this article are my own, photographs taken during my professional work. I allow the use of these images as long as they are mentioned to me in the article and the source is cited.

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