Understanding Programmable Logic Controller and Its Workings

Programmable Logic Controller, more popularly known as PLC, is a digital computer without a mouse or a keyboard, or a monitor. Programmable Logic Controller (PLC) focuses on automating different electro-mechanical processes taking place in various industries. It has specially designed and implemented controllers with a well-programmed microprocessor that are immune to extremely high and low temperatures, humidity, dust, etc.

Just like any usual program, the coding is programmed on a computer. From here, it is transferred to the PLC using a cable. After downloading the programs, these are loaded and stored in the PLC. To make sure the programs do not vanish at the time of power cut or switch off, it uses non-volatile memory storage.

It is programmed using a programming language called Ladder Logic. It is already known that it is an industrial computer. To program it, a programming language had to be designed so that the electricians and electrical engineers in an industry could easily understand and feel comfortable enough to code in it.

A Programmable Logic Controller consists of various input and output terminals. Using the input terminals, it interprets the logical states from switches and sensors. There are two logical states, also known as high (or 1) and low (or 0). The output from the output terminals is used as a signal for various devices, providing them on/off controls. The electrical engineers understand the ladder logic diagrams, and so it was the inspiration behind the programming language used to program it.

The most common areas of use are washing machines, elevators, and also traffic signals.

How does a PLC work?

A programmable Logic Controller is a small computer that automatically controls various processes and components in an industrial system. For the sake of comparison, let’s take a manual process; as an example, thinks of PLC as a brain controlling a finger on a trigger of an applicator. The brain sends a signal to the finger directing it to pull the finger when something is dispensed, and when the brain wants to stop, it sends another signal. Like most of the brains, it can multitask, and it’s lightning-fast. Just like that, it can control many input and output signals like directing a paint line to change colors, so all the widgets being painted go from one color to another.

It communicates the CPU status of the field devices as well as acts as a tool to control. The programming device is a computer loaded with programming software that will allow a user to create and make changes in the PLC software. The memory provides storage media for the PLC program as well as for other data.


  • Easily programmable
  • Well, shielded to outlast harsh situations
  • Input and output interface available where thousands of input and output can be controlled through a single PLC
  • Highly reliable
  • Easy to maintain

Required skills

PLC professionals are experts in concepts, electrical designs. They are also knowledgeable about fabrication and circuit board layout.

Also, they entail meeting global standards in providing solutions to companies. This ensures making tasks easier by correct relaying of messages and the required team coordination.

Why should we use PLC?

The most common use of it is in washing machines, controlling traffic signals, elevators, etc. Also, we cannot neglect the use of PLCs in industries to monitor and control building systems and production processes.

Why do we need PLC, and What can you do with PLC?

It is needed to automate machines in the industry to reduce human errors, thus minimizing the human errors that might occur in the process. Consider a situation where a human handling a system missed to switch the motor on. Imagine the delay it might cause in operation to begin. The simple solution to solve this is by automating the motor using PLC. So, the basic and most important use of it is in the automation of machines.

Who is the Right Audience for learning PLC Technologies?

The one-step solution to learning is various available courses online. It is also the best economical and easy way; however, the challenge in learning PLC online is you might learn the names and functioning of software and hardware parts of PLC, the ladder logic diagrams creation or configuring the various modules, but just the theoretical knowledge is not enough. To be successful, one needs to have hands-on experience. The one with an interest and background in logic diagrams and controls can start with the PLC programming tool. An elaborate program for an application is not at all an easy task to create. It would help if you had a lot of practice and hands-on to do so. To excel in this, one can begin from a small machine building company to gain insight and full-fledged skills and experience of the job.

Scope and how this technology will help you in career growth?

As we all know that every industry is moving on to automating its processes and tools, the demand for the programmer is rapidly increasing. Industrial sectors in India like food and beverages, manufacturing industry, oil and gas industry, transport, process industries, etc., are also stepping into Industrial Automation. Technologies like AI, IOT are merging with OT or operational technologies, which include PLC, SCADA, DCS.

Because programmable logic controllers remove the human element from monitoring complex industrial machinery, the skills to program them are in high demand. A PLC programming education from Tata Steel Digie-Shala is essential for industrial designers and vital for entrepreneurs in other fields where automation is advantageous. The course on PLC from Tata Steel Digie-Shala teaches you how to program with a focus on ladder logic, which is the most popular PLC programming language. The goal is to teach you everything you need to know to make a PLC do what you want it to do. 

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