Programmable Logic Controller
A programmable logic controller (PLC) is a rugged industrial computer that controls and automates manufacturing processes. It continuously reads sensors and other input devices, runs programmed logic, and switches output devices such as motors, valves, and conveyors, providing reliable, real-time control on the factory floor.
A PLC runs in a repeating scan cycle: read all inputs, execute the control program, update all outputs, and start again, often many times per second. Programs are commonly written in ladder logic or other standard industrial languages, and PLCs are built to withstand heat, dust, vibration, and electrical noise.
For example, a PLC on a bottling line reads a photo-eye that detects each bottle, starts the filler at the right moment, and stops the conveyor if a jam sensor trips. A vision AI system can send a reject signal to the PLC, which then triggers the arm that removes a defective item.
A PLC differs from a general-purpose PC because it is designed for deterministic, real-time control in harsh environments. It also differs from a SCADA or HMI system, which supervises and displays what PLCs are doing rather than controlling the machine directly.