How to Use a Programmable Logic Controller

DATE: Feb, 2   COMMENTS: 0   AUTHOR: Allan Azarola

Whether you work in manufacturing, traffic control, automotive, or another industry where machinery and automated equipment reign supreme, it’s likely you’re familiar with programmable logic controllers or PLCs. 

These intelligent devices are critical for the smooth operation of automated machinery—but how exactly do they work, and how can you use one correctly? Industrial parts can be extremely complex. Find out in this article.  

What is a programmable logic controller?

Programmable logic controllers are a type of computer designed to control the automation of industrial processes. The name programmable logic controller stems from the device’s ability to execute complex logical sequences of programmed instructions.

PLCs are popular within manufacturing and other industrial settings for controlling machinery and equipment such as conveyors, cranes, and ovens. You’ll also find them in civil applications such as controlling traffic lights and elevators.

Basic PLC functions and applications

To function, PLCs follow preprogrammed instructions presented as a sequence of steps, called a program. The program is stored in the PLC’s memory, allowing it to carry out automated operations in a given sequence.

PLCs play a vital role across a range of applications, including:

  • Batch processing in the cement, food, paper, and chemical industries,
  • Water tank quenching in the aerospace industry,
  • Washing machine, elevator, and traffic signal control,
  • Burner management systems (i.e. flame safety checks, valve switching for fuel changeover, etc.)
  • Screen washing and register control systems in the printing industry,
  • Escalator and safety control system operation in the travel industry,
  • Many more.

PLCs use several helpful features and functions to perform their duties within these applications, such as timers, counters, and sequential control. Its robust construction allows for reliable control and ease of programming even under harsh industrial conditions.

Using a PLC effectively

To understand how to effectively use a programmable logic controller, you’ll first need to learn about its parts. The three modules a standard PLC comprises are:

  • Input/output modules, which connect the actuators and sensors to the PLC, allowing it to detect parameters such as flow, temperature, and pressure,
  • Power supply module, which receives AC power and converts it into DC for the other modules to use,
  • CPU module, which performs the processing and data computations necessary to run the device.

Programming a PLC typically requires specialised programming software or a programming device. You can write instructions in one of five standard programming languages, which are:

  • Instruction List,
  • Ladder Logic,
  • Structured Text,
  • Function Block Diagram,
  • Sequential Function Chart.

Ladder Logic is the most common language for programming PLCs. In Ladder Logic, programmers use symbols representing shift registers, counters, mathematical applications, and opening and closing relays to tell the PLC what to do. Its visual layout makes it easier to program and read than other languages.

The future of PLCs

With the rise of cloud computing, robotic integration, and intelligent automation, PLCs will continue to play a central role across industries. As technology changes, PLCs must adapt, using artificial intelligence and communication with the Industrial Internet of Things (IIoT) to continue serving businesses around the globe.

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