what is a programmable logic controller

What Is a Programmable Logic Controller?

February 15, 2023 - Emily Newton

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As factories and other industrial environments become increasingly automated, programmable logic controllers (PLC) remain a critical part of productivity and expected performance. But what is a programmable logic controller, and why do people use them? Keep reading to find out. 

What Is a Programmable Logic Controller?

A programmable logic controller is a small, specialized computer that receives inputs and can send operating instructions to complementing machines as outputs. Put simply, the PLC controls industrial equipment via its internal programming. 

The information coming into the PLC can come from human inputs, such as when people flip switches or press buttons. However, the programmable logic controller can also accept details from automatically captured data and process it to operate machines. 

The first PLCs became available in the 1960s. They replaced the relay-based control systems many industrial facilities had at the time. However, people operated those manually, so PLCs represented a major improvement. 

What Advantages Does a Programmable Logic Controller Provide?

A programmable logic controller is one of the simpler industrial controllers now available. However, many decision-makers still prefer them. For starters, these options are cost-effective and reliable, often running for years before requiring replacement. 

Moreover, PLCs use programming languages that are more straightforward than what some other industrial controllers need. That can make them accessible for people to program and troubleshoot, even if those individuals don’t have industrial control backgrounds. 

Many manufacturing leaders or others interested in using PLCs for automation appreciate how they’ve been available for decades. That history can make them more trustworthy for people who want assurance the technology they invest in is highly likely to perform as expected. 

Another advantage is that it’s highly probable a person can find a programmable logic controller to suit their budget. People at many smaller businesses prioritize purchasing the least expensive, most basic ones first. Then, they can scale up and graduate to more expensive models as their budgets allow. 

Despite their affordability, most PLCs are versatile enough to control a wide variety of processes for the businesses using them. Some people even say the PLC set the stage for what we now know as the Industrial Internet of Things (IIoT) because they’ve played such an important role in automation. PLCs are solid-state devices, which means they have no moving parts. Thus, they’re extremely reliable and well-suited for the often-demanding conditions of many industrial facilities. 

What’s the Market Outlook for Programmable Logic Controllers?

PLCs have been on the market for decades but still represent a product category with growth potential. One market research firm recently provided an outlook from 2022-2026. The analysts expect a 3.51% compound annual growth rate over the study period. If that happens, it will represent a $2.70 billion market worth increase. 

Another interesting takeaway was that 33% of the expected growth will come from the Asia-Pacific market, with Japan and China emerging as key drivers. Moreover, the growth associated with the Asia-Pacific region will happen more quickly than in Europe, the Middle East, Africa and North America. That said, the United States will be another nation vital to the sector’s growth during the studied period. 

The analysts also clarified that another emerging trend is people’s increasing demand for micro and miniaturized PLCs. Those work the same way as a traditional programmable logic controller but feature a smaller package size. Additionally, these tinier PLCs are typically even more affordable than their standard counterparts. As a case in point, one company released one with a 17.5-millimeter body, offering a pocket-sized option. 

It’s too soon to say what the long-term future holds for PLCs. Some people advocate switching out a programmable logic controller for an embedded system directly on the machine in question. The conventional approach is to have PLCs housed outside of but close to the equipment they control. In such cases, cables usually provide the connections from the PLCs to the machines. However, unitary PLCs are now among the most popular. They attach directly to the respective equipment. 

Does a Programmable Logic Controller Pose a Cybersecurity Risk?

Since programmable logic controllers directly affect essential equipment and other company assets, cybercriminals have historically targeted them. One of the most well-known cases was the Stuxnet worm, now widely accepted as developed by United States and Israeli intelligence. The main goal was to disable the centrifuges that were a vital part of the Iranian nuclear program. People in the information security community identified Stuxnet in 2010, though work on it probably began several years earlier. 

The Stuxnet worm checked for the presence of certain kinds of PLCs. When it found them, the worm changed the PLCs programming to make the centrifuges operate incorrectly. However, the worm sent a message to the PLC that everything was working as expected. That made it hard for people to diagnose the problem or even know an issue existed. 

More recently, the Department of Energy (DOE), the Cybersecurity and Infrastructure Security Agency (CISA), the National Security Agency (NSA) and the Federal Bureau of Investigation (FBI) issued a joint cybersecurity advisory in 2022. It alerted people that hackers had deployed custom-built tools to target PLCs once adversaries gained access to operational technology networks.  Then, hackers could elevate their privileges and disrupt how PLCs work throughout an organization. 

Then, in October 2022, cybersecurity researchers published findings of vulnerabilities in some PLCs that could let malicious parties launch large-scale attacks. More specifically, the flaws would enable attackers to obtain the cryptographic keys normally secured inside a programmable logic controller. They could then bypass four access-level protections in the system and cause irreparable damage to the PLC. 

These instances should not discourage decision-makers from exploring how they might use programmable logic controllers in their organizations. However, people should take proactive steps to minimize and mitigate potential attacks. That could entail setting up port monitoring, deploying system-wide anti-malware protection and segmenting networks into zones. 

The Programmable Logic Controller Is the Foundation for Automation 

While it’s true that an automated system needs more than a programmable logic controller to run, this small component has played a significant role in helping move industrial automation forward. Many company leaders still select it as their industrial controller of choice, which will likely remain so for the foreseeable future.

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Emily Newton

Emily Newton is a technology and industrial journalist and the Editor in Chief of Revolutionized. She manages the sites publishing schedule, SEO optimization and content strategy. Emily enjoys writing and researching articles about how technology is changing every industry. When she isn't working, Emily enjoys playing video games or curling up with a good book.

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