A Programmable Logic Controller (PLC) is an industrial computer control system that continuously monitors the state of input devices and makes decisions based on a custom program to control the state of output devices. PLCs are used to control and monitor industrial equipment based on custom programming. They are modular and can be customized with additional backplanes and functional modules to fit different types of industrial applications. PLCs are essential hardware components in SCADA and HMI systems, which enable users to view data from the manufacturing floor and provide user interfaces for control and monitoring. PLCs can communicate, monitor, and control complex automated processes such as conveyors, temperature control, robot cells, and many other industrial machines. The functionality of the PLC has evolved over the years to include sequential relay control, motion control, process control, distributed control systems, and networking. PLCs use built-in ports, such as USB, Ethernet, RS-232, RS-485, or RS-422 to communicate with external devices (sensors, actuators) and systems (programming software, SCADA, HMI) . The operation of a PLC is broken down into three stages: inputs, program execution, and outputs. PLCs take in inputs from automated data capture points or from human input points such as switches or buttons, and based on their programming, they decide whether or not to change the output. The outputs of a PLC can control a wide variety of equipment, including motors, solenoid valves, lights, switchgear, safety shut-offs, and many others.
PLCs are important in the world of automation because they are useful tools for repeatable processes, and they have no mechanical parts, making them more reliable than the mechanical technologies they have replaced. They are known for their ability to operate continuously without maintenance and have had a great impact on digitizing many industries, particularly manufacturing. Almost any production line, machine function, or process can be greatly enhanced using this type of control system. The ability to change and replicate the operation or process while collecting and communicating vital information is another advantage of a PLC system.
