Programmable logic controller

A programmable logic controller (PLC) is an industrial computer that monitors inputs and controls outputs to automate machines and processes. It is designed for reliable operation in demanding industrial environments.

PLC scan cycle: The repeated sequence in which a PLC reads inputs, executes its program, and updates outputs. This cycle explains how a PLC converts changing sensor states into timed control actions.
Industrial automation: The use of control systems and technology to operate industrial processes with reduced human intervention. PLCs are widely used as local controllers within automated production systems.
Bedford Associates: An engineering company that developed the Modicon 084, an early programmable controller. The company created the controller proposed to replace complex automotive relay systems.
Microcontroller: A compact integrated computer containing a processor, memory, and input/output peripherals on one chip. A microcontroller can control equipment, but typically lacks a PLC's industrial packaging and ecosystem.
Industrial control system: A system of hardware and software that monitors or controls industrial processes and equipment. PLCs are core components in many industrial control systems.
Ladder logic: A graphical programming language that represents control logic with relay-like contacts and coils. Its rungs express the Boolean conditions PLCs evaluate during each scan.
Programmable logic controller in manufacturing: The use of PLCs to sequence and coordinate equipment on manufacturing lines. Assembly and packaging machines rely on PLC logic to coordinate sensors, motors, and actuators.
Dick Morley: An American engineer widely associated with the development of the first Modicon programmable controller. Morley led the engineering work behind the Modicon 084.
Industrial PC: A computer built or adapted to operate reliably in industrial environments. Industrial PCs offer flexible computing, while PLCs specialize in deterministic control and rugged deployment.
Programmable logic controller security: The practices and technologies used to protect PLCs from unauthorized access and disruption. Networked PLCs expose control functions to cyber threats that can affect physical operations.

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