A Programmable Logic Controller (PLC) is a microprocessor-based control system used in industrial environments to sense, activate, and control equipment. PLCs operate in one of two modes: program mode, where a user's program is downloaded to the PLC memory, and run mode, where the program executes in a continuous scan-based cycle of reading inputs, executing the program, and updating outputs. PLCs use digital and analog inputs and outputs to interface with sensors and actuators in industrial control applications.

3. Hardware components of a PLC

4. Memory structure of a PLC

6. Wiring Diagram

8. Connecting DC Proximity Switches