Industrial Remote Input/Output Systems:
In industrial automation, input/output (I/O) refers to the connectivity that lets control systems interact with physical equipment. “Input” is the data flowing from a field device to the controller for processing, while “output” are the commands from the controller to perform actions. An I/O module manages these communications, acting as a bridge between the controller and the devices.
There are two primary types of I/O: local and remote. When it comes to industrial settings, the latter is the more common. This article aims to help you gain a better understanding of the basics of industrial remote I/O.
What Is Remote I/O
Also known as distributed I/O, remote I/O is a system where an I/O module and multiple field devices operate in a decentralized location far away from a main controller, often because the harsh industrial environment may damage the controller. More often than not, this controller is a programmable logic controller (PLC), but can also be a DCS, RTU or industrial PC.
Sensors or other field input devices are connected to the remote I/O module, sharing information such as temperature, pressure, vibration, chemical properties, light intensity, and flow rates. These data signals are transmitted back to the I/O module and the PLC. Once processed by the PLC, output data is transmitted to valves, motors and other final actuators, essentially telling them what to do in response to the input data. Signals are sent on high-speed twisted pair wires and fiber optics using Ethernet/IP, Modbus TCP, Profibus or other transmission protocols. To enable communication between remote I/O modules and the PLC, an adapter module is installed in the local PLC rack that serves as the gateway between the PLC’s backplane/protocol and the remote I/O network.
Benefits of Remote I/O
Remote I/O has been the industry standard for 20+ years for very good reasons. Here are the real, practical advantages of using industrial remote I/O systems instead of traditional centralized home-run wiring:
- Lower wiring costs: Remote I/O systems substantially reduce the amount of wiring that needs to be run. Instead of running hundreds of individual wires from field devices back to the central PLC cabinet, a single network cable is run from the PLC to the I/O modules, alon g with running short local wires from the field devices to nearby I/O modules. To expand, the company simply adds another I/O module and plugs it into the existing network. Plus, a faulty module can be hot-swapped in minutes without rewiring dozens of field cables.
- Diverse Configuration Options: Due to the flexibility that a remote I/O setup provides, a greater variety of hardware configurations can be created. For instance, I/O can be mounted directly on the machine, eliminating local junction boxes entirely. Different topologies are also possible depending on the factory’s layout.
- Facilitating Communication in Harsh Environments: In many industrial plants, a PLC can’t be deployed close to field devices due to harsh environmental conditions. In instances of extreme temperatures, strong vibration, or moisture, the PLC must be installed in a safe space—often in or near a control room—while the I/O system is located near the instrumentation.
- Integrated diagnostics: Diagnostics are built-in down to the channel level meaning that issues like wire breaks, short circuits, and under/over voltage is reported into PLC tags or HMI. Instead of spending hours using a multimeter, technicians identify issues quickly.
Potential Disadvantages of Remote I/O
While remote I/O systems offer noteworthy benefits, they also pose a few disadvantages that you should be aware of compared to traditional point-to-point wiring. Drawbacks include:
- Vulnerability: All of the signals being communicated in a remote I/O system rely on a single point of communication between the PLC and the remote I/O portion of the hardware. If this point becomes interrupted or lost, all of the data being received could get lost. In addition, you would likely also lose the ability to control the hardware. To minimize this risk, it is important to implement redundant communication channels within a remote I/O system.
- Hidden costs: While remote I/O systems save a considerable amount of money by reducing wiring needs, certain hidden costs can emerge if you aren’t careful. For example, users should know that when implementing remote I/O in a system, they will need to configure all of the additional I/O modules. This can take a considerable amount of time in a large system when even one module in the system is changed.
- Cybersecurity risks: If not appropriately segmented by VLANs or firewalls, IP-based remote I/O (EtherNet/IP, PROFINET, OPC UA) exposes the control system to the plant network and potentially to external attacks.
- Latency: EtherCAT, PROFINET IRT, Sercos III and other real-time industrial Ethernet protocols are very fast; however, standard Ethernet-based remote I/O like EtherNet/IP or Modbus TCP can introduce jitter and non-deterministic scan times that are problematic for fast motion control or safety applications.
Ethernet Switches in Remote I/O
Managed Ethernet switches play a critical and often under-appreciated role in remote I/O systems, especially when the remote I/O is based on protocols like EtherCAT, PROFINET IRT, EtherNet/IP, SERCOS III, and Modbus TCP. Without switches, remote I/O systems can be slow, unreliable, or impossible to build over longer distances.
Antaira Ethernet switches provide remote I/O systems with traffic segmentation and bandwidth management, QoS, IGMP snooping, diagnostics, security and redundancy.
Antaira switches are the high-speed, reliable “highway” carrying the real-time I/O data packets between the PLC and the remote I/O modules. Many Antaira switches also deliver IEEE-compliant Power over Ethernet (PoE) technology, combining data and power transmission through a single Ethernet cable to streamline installation, reduce infrastructure costs, and simplify ongoing network maintenance.
Antaira is an industry leader in Ethernet switches and industrial networking devices. To learn more, visit www.antaira.com.
