Programmable logic controllers (PLCs) are the cornerstone of modern industrial automation, providing a robust and flexible platform for controlling machinery and processes. In a nutshell, PLCs are industrial digital computers adapted for controlling manufacturing processes such as assembly lines, robotic devices, or any activity that requires high reliability, ease of programming, and process fault diagnosis. PLCs were developed in the late 1960s to replace the complex relay and timer systems in use at the time. Richard Morley is often credited with inventing the first PLC, the Modicon, in 1968. Since then, the technology has evolved, and PLCs have become essential components in numerous application areas, including machine control, building automation, predictive maintenance, data logging, remote monitoring, and security.
A PLC consists of several key components:
- Processor (CPU): This controls all the PLC’s activities. It processes the data from input modules and sends signals to output modules.
- Input/output modules (I/O): The PLC can interact with the outside world. Inputs receive data from sensors and human-machine interfaces (HMIs), while outputs send signals to actuators and other devices.
- Memory: This stores the user’s program and other information needed for the process.
- Communication ports: These enable communication between the PLC and other devices, such as computers, other PLCs, and network systems.
- Power supply: This provides the necessary power to run the PLC and its I/O modules.
