PLC system (programmable logic control) is an advanced and smart approach in the IT world.


PLC stands for the programmable logic controller. PLC system is also famous as a programmable controller. It is a digital computer used at the industrial level. These systems are suitable for manufacturing processes. For instance; assembly lines, robotic devices, etc. it is capable of completing such activities that demand procedure default analysis, high reliability and efficiency, and convenient programming.


PLC system comes in a wide range. May it be a small and brief modular device of inputs and outputs in 10 or may it be a large and expansive modular device of inputs and outputs in 1000. The type described later can be gridded with other PLC systems.

Types of PLCs:

There are two primitive types of PLC system:

  • Compact PLC
  • Modular PLC

Composition and formation:

It is a technical controller based on a microprocessor. Its memory is programmable. Thus it is used to program guidance and various other functions. A PLC system consists of the following major parts with their chief functions:

  • A CPU (central processing unit)

Its part is to decipher and interpret the input received, operate the control program as saved in memory, and then transfers the output signals.

  • Power supply unit

Its main purpose is to convert AC voltage to DC voltage.

  • Memory unit

As the name states, this unit stores data from inputs received. Furthermore, the information about the programs to be executed is saved here.

  • Interface

Two types of interfaces are present.

  • An input/output interface used to control the reception and sending of data.
  • A communication interface used to transmit and seize data from a remote PLC system.


Modernized PLCs are programmed in a number of ways. From generally structured programs to specialized dialects. Currently, the PLC system complies with basically 2 textual  programming languages stating:

  • Structured text
  • Instruction list

Moreover, they adhere to 3 graphical programming languages stating:

  • Ladder diagram
  • Functional block diagram
  • Sequential functional charts


  • The basic functions performed by a PLC system are as following:
  • They imitate the programs of electromechanical relays.
  • It processes the binary input signals into processing techniques output.
  • It plants continuous and uninterrupted monitoring of different modules of a system.


  • The features which make the PLC system more attractive and unique includes
  • They can tolerate relentless conditions like dust, humidity, hotness, and coldness, etc.
  • They display a PLC system with an extensive input/output connection to sensors.
  • They afford to accept input from most simple types to most complex ones. For instance; limit switches to machine vision systems.
  • They provide a variety of outputs comprising; electric motors, hydraulic cylinders, analog outputs, etc.