A Programmable Logic Controller (PLC) is a specialized industrial computer designed to automate and control machines and processes efficiently. Built to withstand harsh environments, including exposure to dust, heat, and moisture, PLCs ensure reliable performance in demanding industrial settings. They operate by receiving input signals from devices such as sensors, processing these signals through programmed instructions, and directing output devices like motors, actuators, or lights to perform specific actions. This capability allows industries to optimize operations, enhance precision, and improve overall productivity.

PLCs are available in two primary forms: fixed and modular. Fixed PLCs, which have a set number of inputs and outputs, are compact and economical, making them well-suited for smaller, standalone systems where future scalability is unnecessary. Modular PLCs, however, provide enhanced flexibility by allowing the addition or replacement of modules as requirements evolve. Although modular PLCs come with a higher initial investment, their ability to isolate faults and perform targeted repairs without disrupting the entire system makes them essential for larger, more complex applications.

PLCs function in a continuous cycle of input scanning, program execution, and output activation, ensuring real-time control of processes. Their versatility lies in their ability to handle both digital (on/off) and analog (variable) signals, enabling them to support a wide range of industrial tasks. While technologies such as Programmable Automation Controllers (PACs) offer advanced computing capabilities, PLCs remain fundamental to industrial automation due to their reliability, scalability, and cost efficiency.