How Does a PLC work?

A PLC or Programmable Logic Controller is a special type of computer that is commonly used in the industrial sector. It is used for controlling industrial manufacturing processes. These computers can automatically control a specific process, machine functions, sometimes even an entire production line. PLCs are made to be very durable and can run almost constantly, unlike home computers.

Different Types of PLC

There are three different types of PLCs in terms of size.

Compact PLC

The simpler type of the three is a compact PLC. It contains all the basic system components within a single housing. These PLCs typically include ports for input and output connections, and the processor running the software program. Typically, compact PLCs are connected straight to the device that is being controlled.

Modular PLC

A modular PLC includes several distinct components that can be combined to create a custom controller. A base module typically includes key features such as regulation of electrical energy, a computer processor, and input links. Additional components may be added to this key device as required.

Depending on the size of the program memory and the number of I/O features, modular PLCs can be further divided into small, medium and large PLCs.

Small PLC is a tiny PLC intended to be positioned next to the machinery to be controlled.

Commercially, medium-sized PLCs are mostly used. There are many plug-in units that are installed on this system.

Large PLCs are used in complicated system control tasks. They have a higher memory capacity, I/O ports, programming languages, and communication modules as opposed to small and medium PLCs.

Rack PLC

Rack PLC is similar to the modular PLC but it is implemented differently. In rack PLC each module is kept separate. All additional modules are linked via a network and the modules are kept in organized racks. It allows building bigger installations without becoming overly cluttered and complex. On the rack PLC, the modules can be separated and reinstalled as necessary.

How PLC Works

 The PLC gets information from connected sensors or input devices. Then it processes the data and sends outputs based on parameters that are pre-programmed.

A PLC can track and record runtime information such as machine efficiency or working temperature, begins and stops procedures automatically. It can also generate warnings when a device fails. PLCs are a versatile and reliable option that can be adapted to nearly any implementation.

There are a few main characteristics that distinguish PLCs from industrial PCs, microcontrollers and other alternatives for industrial control devices.


The PLC’s CPU processes program data, but it connects to the rest of the machinery through the input and output modules. These I/O modules provide the CPU with data and trigger particular outcomes. I/O can either be digital or analog. Sensors, buttons, and meters are some of the input devices. Relays, lamps, valves, and engines are some of the output devices. In order to get the right configuration, users can mix a couple of I/O of a PLC.


A PLC may also need to communicate with other types of systems. PLCs provide a variety of ports and communication procedures to guarantee the PLC is able to interact with these other devices.


Users need an HMI or Human Machine Interface to communicate with the PLC in real-time. These user interfaces can be simple screens with keypads or big touch screens. They allow users to check and submit real-time data to the PLC.

Final Verdict

PLC is the major key to technological development. Nobody will question nowadays the significance of a PLC system. It is the one system that keeps everything running efficiently and quickly. Without the PLC system, we simply could not achieve this stage of development.

  Modified On Sep-12-2019 03:25:05 AM

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