How does a PLC typically operate during a scan cycle?

A PLC (Programmable Logic Controller) operates during a scan cycle through a specific process that involves three primary steps: reading the status of inputs, evaluating control logic, and updating outputs.

First, the PLC reads the status of all input devices, such as sensors and switches, to gather real-time data about the system's conditions. This step is crucial as it ensures the control logic is based on the most current information available.

Next, the PLC evaluates its control logic based on the input status. This logic typically consists of instructions programmed by the user and defines how the PLC should respond to various input conditions. It is during this step that the PLC processes tasks, performs calculations, and makes decisions regarding the appropriate actions to take.

Finally, after evaluating the control logic, the PLC updates its outputs accordingly. This includes sending signals to actuators, motors, and other output devices to effect changes in the system based on the processed input data and control logic results.

This sequential operation is vital for ensuring that the PLC functions effectively in a control system, enabling automation and precise control of processes in various applications.