Today, Programmable Logic Controllers are used for virtually all industrial automation and control applications, so in this edition, we decided to look into the basics of how PLCs work.

Your new logical assistant - The PLC

A PLC contains a programmable microprocessor that is programmed using a specialized computer language. Typically, the program for the automated process is written on a computer and is then downloaded onto the programmable logic controller directly through a cable connection. The program is stored in the programmable logic controller in non-volatile memory. Where ever there is a need to control devices the PLC provides a flexible way to connecting components together. Below are five basic areas where PLCs are mostly used.

PLCs are used for automation of electromechanical processes: Today, the automation of many electromechanical processes, such as the movement of  machinery on an HVAC systems or assembly lines, amusement rides control, traffic light control, automated door control are done through the use of programmable logic controllers (PLCs). PLCs are manufactured to be reliable and withstand harsh environments — making them perfect for industrial manufacturing.


PLCs function better in networked environments: While the PLCs is not a new technology, its functionality has evolved to include networking, relay control and advanced data-handling capabilities. The first programmable controllers were small, with a limited ability to send and receive signals at a reasonable response speed, which today has been cut down to mere milliseconds. The first PLCs also lacked standardized communication protocols, which made PLC-to-PLC control difficult. Eventually, PLCs became programmable with personal computer software, and PLC communication became more and more standardized as it has grown into an integral part of a variety of manufacturing processes, with capabilities equivalent to those of computers. Today a single PLC is able to handle hundreds of inputs and outputs. They can also be expanded if the base model doesn’t have sufficient I/O. Once programmed, a PLC is triggered by specific stimuli to produce a desired sequence of operations at specified times.

Any Application that requires customized controls needs a PLC: A PLC is a customizable control solution that can be tailored to almost any application, whether it’s dictating the movements of a CNC machine or managing the shutdown response to an emergency stop on a production line. The PLC will remain one of the most important industrial manufacturing automation advances of all time.

PLCs reduce rewiring

In the manufacturing and Oil & Gas industries, where a series of industrial processes need to be controlled automatically, there is a need for a process controller. The PLC evolved out of a need to replace racks of relays controller in ladder form. The relay were not particularly reliable, were difficult to rewire, and were difficult to diagnose. PLC made the constant rewiring of control panels for every new production model obsolete.


Some questions you should ask before ordering your next PLC

  • Will there be frequent control logic changes, flexibility and rapid modifications? Some industries believe they will never need to change a design but  then  ideas and objectives and goals are subject to change and so  some modifications on your programs  will be required. Wouldn’t it be better to do that in software (PLC) than in hardware (Relay)?
  • Is there a need for future growth?
    A PLC can easily accept a new module in a slot or get an expansion base.
  • Is there a need for high reliability?
    PLCs are seen as more robust over individual components.
  • Is downtime a concern?
    Any change or troubleshooting on a relay system means the system might have to go offline. Changes in a PLC can often be made online with no downtime.

At GIL Automations, we offer boot camp and detailed training courses on PLCs. These and more are embedded in our GIT A1 (Introductory part) and GIT A2 (Programming and Operation of PLC) training. We train across multiple PLC platforms e.g. Allen Bradley, Siemens, GE Fanuc, Omron, Mitsubishi, ABB etc.

The training is structured to cover all the basic knowledge needed to become a skilled automation engineer. Therefore the only perquisite for one to be a part of this training is a basic science and engineering knowledge, new recruit engineers, technicians, supervisors, managers and subject matter professionals.

At the end of the training you will be able to understand the concept of industrial process control using PLC, be able to program a different type of PLC using different software. You can learn more about our training courses at or send an email to


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