A Programmable Logic Controller (PLC) is an industrial computer that has been ruggedized and adapted for the control of manufacturing processes, such as assembly lines, machines, robotic devices, or any activity that requires automation. PLCs are used to automate a specific process, machine function, or even an entire production line. They receive information from connected sensors or input devices, process the data, and trigger outputs based on pre-programmed parameters. PLCs are modular, meaning that you can mix and match the types of input and output devices to best suit your application. The functionality of the PLC has evolved over the years to include sequential relay control, motion control, process control, distributed control systems, and networking.
PLC programs are typically written in a programming device, which can take the form of a desktop console, special software on a personal computer, or a handheld programming device. Then, the program is downloaded to the PLC directly or over a network. It is stored either in non-volatile flash memory or battery-backed-up RAM. Depending on the inputs and outputs, a PLC can monitor and record run-time data such as machine productivity or operating temperature, automatically start and stop processes, generate alarms if a machine malfunctions, and more.
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.
