Programmable Logic Controller (PLC)

A programmable logic controller is a type of tiny computer that can receive data through its inputs and send operating instructions through its outputs. Fundamentally, a PLC’s job is to control a system’s functions using the internal logic programmed into it. Businesses around the world use PLCs to automate their most important processes. 

A PLC takes in inputs, whether from automated data capture points or from human input points such as switches or buttons. Based on its programming, the PLC then decides whether or not to change the output. A PLC’s outputs can control a huge variety of equipment, including motors, solenoid valves, lights, switchgear, safety shut-offs and many others. 
The physical location of PLCs can vary widely from one system to another. Usually, however, PLCs are located in the general vicinity of the systems they operate, and they’re typically protected by a surface mount electrical box. Skip to the end if you’re interested in seeing the electrical junction boxes that help protect PLCs. 
PLCs largely replaced the manual relay-based control systems that were common in older industrial facilities. Relay systems are complex and prone to failure and, in the 1960s, the inventor Richard Morley introduced the first PLCs as an alternative. Manufacturers quickly realized the potential of PLCs and began integrating them into their work processes.
Today, PLCs are still a fundamental element of many industrial control systems. In fact, they’re still the most used industrial control technology worldwide. The ability to work with PLCs is a required skill for many different professions, from the engineers designing the system to the electrical technicians maintaining it.
Advantages of Using PLCs

PLCs have been a standard element of industrial machinery design for many decades. What advantages do PLCs offer that make them such a popular choice?
PLCs are fairly intuitive to program. Their programming languages are simple in comparison to other industrial control systems, which makes PLCs great for businesses that want to minimize complexity and costs. 
PLCs are a mature technology with years of testing and analysis backing them up. It’s easy to find robust research about many different PLC types and comprehensive tutorials for programming and integrating them. 
PLCs are available at a wide range of price points, including many extremely affordable basic models that small businesses and startups often use.
PLCs are extremely versatile, and most PLC models are suitable for controlling a wide variety of processes and systems. 
PLCs are completely solid-state devices, which means they have no moving parts. That makes them exceptionally reliable and more able to survive the challenging conditions present in many industrial facilities.
PLCs have relatively few components, which makes them easier to troubleshoot and helps reduce maintenance downtime. 
PLCs are efficient and don’t consume very much electrical power. This helps conserve energy and may simplify wiring considerations.