In a Mitsubishi PLC system, I/O modules (Input/Output modules) play a key role in connecting the CPU with real-world field devices like sensors, switches, motors, and valves. These modules act as an interface between the PLC and external devices, allowing the controller to receive and send signals for automation processes. Simply put, input modules receive signals from field devices such as pushbuttons, proximity sensors, and limit switches, and convert them into a form that the PLC CPU can understand. On the other hand, output modules take commands from the CPU and convert them into electrical signals that can operate actuators, relays, solenoids, or indicator lamps. The I/O module also provides electrical isolation between the high-voltage field equipment and the sensitive PLC processor, which helps in protecting the system from electrical noise or surges.
There are different types of Mitsubishi PLC I/O modules based on signal type and application. Digital I/O modules handle discrete signals, such as ON/OFF or HIGH/LOW states, used for basic control tasks. Analog I/O modules process continuous signals like 4–20 mA current or 0–10 V voltage, commonly used in sensors measuring temperature, pressure, or flow. Mitsubishi also offers combined I/O modules, which include both input and output points in one unit to save panel space. One major advantage of Mitsubishi modular I/O design is flexibility — users can add, remove, or upgrade I/O modules as needed for specific automation systems. In advanced series like MELSEC iQ-F and MELSEC iQ-R, I/O modules feature diagnostic functions that monitor signal quality, detect wiring errors, and simplify maintenance. Overall, I/O modules in Mitsubishi PLC systems act as the communication bridge between hardware and control logic, ensuring reliable, safe, and efficient operation in any industrial automation setup.