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What is PLC and Discover Why It’s Essential for Efficient Automation

By Telstar Inc |

Read any report on the future of plant-based operations and the manufacturing industry, and there’s only one consensus: Automation is set to disrupt almost every area and process, including equipment communications, maintenance and repairs, and production.

The only area in manufacturing that seems to be immune to the automation takeover so far is the Programmable Logic Controller, or PLCs. There’s a reason why the global market for PLCs stands at $16 billion a year, growing annually at 9.2%. Their robust design, low costs, and simplicity in the face of complex integrations make them a fundamental component in manufacturing.

Without PLCs, many businesses wouldn’t be able to support the implementation of new control technology. For now, PLCs continue to remain integral to the digital transformation Industry 4.0 promises to make.

What is PLC Designed To Do?

PLC stands for “programmable logic controller,” and is both an amalgamation of units and a theoretical model used to control input and output modules. PLCs must include four essential components to be a full system:

  • A CPU module: This is the central processor and the memory required to store information and execute tasks. All data computations and processing occurs here through receiving inputs and producing outputs.
  • A power supply: All modules of the PLC rely on the power supply. PLCs are designed to receive AC power and convert to DC power.
  • A programming device: PLCs call for programming software that introduces the control logic to the system. Users can then create, transfer, and make changes, ad-hoc, within the PLC software.
  • Input/Output modules: These units are the meat and potatoes of the PLC system. The input and output modules collect data from sensors and actuators, feed it into the PLC system, and then produce readable information. These modules can either be digital or analog.

The question “What is PLC?” unveils the essence of its innovation: The fact that this unit or system is programmable is a significant improvement from previous controls for processing tasks. It’s also the source of a PLCs competitive edge: Technicians don’t have to change the hard wiring when switching between tasks or applications. Instead, they can simply re-program the unit.

what is PLC Diagram

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PLCs include a processor that executes the control action based on the data provided by input and output modules. The control logic that governs the PLC system is developed first and only then is it transferred to the PLC system.

The easiest way to visualize a PLC is to imagine a computer with a microprocessor but no keyboard, mouse, or monitor. Its wide-ranging and industrial use often means that this physically robust system is built to withstand very harsh environments.

Functional features of a PLC can include timers and counters, measurement devices, and sensors used to sense parameters like vibration, pressure, temperature, and flow. Though some industries have unique tasks and applications, PLCs, in general, perform the following functions:

  • Relay-switching
  • Counting, calculation, and comparison of analog values
  • Modification of control logic in the shortest time
  • Rapid response to changes in process parameters (and responses can be programmed)
  • Improvement of overall control system reliability (requires human intervention), when monitored over time
  • Troubleshooting with increasing simplicity and effectiveness over time
  • Integrates seamlessly with HMI (human-machine interface) computers

When constructed correctly, companies can harness PLCs and use them in a wide variety of applications, across several industries. You may not know it, but the most mundane, everyday pieces of technology we’ve come to rely on use PLCs to operate correctly. Civil applications as diverse as bakeries, washing machines, elevators, and even traffic signals call on PLC control and data collection to modulate tasks.

Why Do Manufacturing Businesses Use PLC?

In 2019 (and beyond), PLCs will continue to make their presence felt because of their inherent simplicity and flexibility. They’re powerful enough to adapt to multiple environments and tasks, but simple enough that even technicians with no prior programming or scripting knowledge can quickly learn them.

There are specific features of PLCs that make them the preferred choice for industries that rely on these systems. Oil & Gas, water utility companies, food and beverage manufacturing, and public works use are just a few examples of industries that depend on the opportunities that PLCs present.

1) PLCs Are Easy to Program

When someone touts the flexibility of a PLC system as its benefit, they’re speaking of how these systems can be programmed by individuals with even the most perfunctory levels of knowledge.

This means they’re as easy for a technician to work with as a consumer. You can also extend a PLC system by programming it to follow a set of instructions if certain conditions are true.

With such a wide range of uses across industries, the workers within each company will have their own skillset. When using a PLC, the ease of programming control logic into the system means that you don’t need someone proficient in the nuances of computer languages to re-write programs when a task or application changes.

2) PLCs Can Offer A Unified Programming Environment

PLCs are the preferred method of controlling, measuring, and carrying out tasks in complex manufacturing and industrial applications because they play nicely with other systems. PLCs work well with PCs, PACs (programmable automation controllers), motion control devices, and HMIs.

To be effective, however, the unified environment needs to be well-planned, and it shouldn’t be too difficult for a user to operate. However, PLCs situated within a larger programming environment allow users with a basic level of knowledge to access multiple functions that communicate with each other, feeding each other data, and carrying out complex tasks.

3) PLCs Collect Robust Data

The number of inputs you set on a PLC system is up to the user. This means that there is no limit to the number of data sources, nor the amount of data streaming in. Measuring devices, sensors, and motion controls can pick up on several parameters, so it’s up to the user to delineate how this data is collected and how the output displays.

4) What is PLCs Use For Predictive Maintenance

Since PLCs are being equipped with greater memory and processing capacities today, they can be programmed to perform complex and heavy-duty tasks. One such task is predictive maintenance. The power of predictive maintenance, especially at the onset of Industry 4.0, cannot be overstated.

In a connected factory, which is one of the features of the fourth Industrial Revolution, one piece of equipment may connect with and be responsible for the operation of several other processes. Predictive maintenance, then, can significantly increase efficiency and make downtime a less frequent and less catastrophic event.

Predictive maintenance starts with preventative maintenance. If particular equipment reaches a pre-programmed threshold, a sensor goes off that tells the technician that the equipment needs maintenance or replacement. Enough of these reports are then collected as data points themselves to communicate to the system about which factors predict wear and tear or an impending issue. PLCs would interact with a SCADA to display maintenance schedules or allow the flexible configuration of new maintenance rules.


As manufacturing and plant-based, industrial businesses navigate the digital transformation, the question “What is PLC?” becomes increasingly relevant. Programmable Logic Controllers (PLCs) are proving their worth now more than ever. Their fundamental ease and simplicity, amidst growing complexity, make them a flexible and familiar solution for modern automation challenges.

Working professionals prefer the PLC system when using other IoT applications or in tandem with controls systems like SCADA. As a logic control system, PLCs are well-suited to Industry 4.0’s tendencies to demand data prediction, error state prediction, finding correlations between two or more independent streams of PLC data, and system optimization.

The critical position and role that PLCs occupies also requires it to be fully functional at all times. There are best practices that manufacturing and factory-based businesses can call on to ensure these central components are always running smoothly.

Contact Telstar Instruments, California’s only state-certified instrumentation and controls integrator, to learn more about how cost-effective and timely automation services can ensure your PLC continues to remain the linchpin of your operations.