Adding Ethernet for I/O: Pros, Cons and Crucial Things to Know for Industrial Automation Design

PROS of Ethernet for I/O

Networked I/O, using Ethernet, has provided improved better performance, flexible topology and simpler configuration as well as a range of other advantages.

1. Faster Processing – Ethernet I/O makes it possible to run real-time updates in less than a millisecond. The higher processing speeds create efficiencies in data collection and analysis, a crucial building block for data-heavy industrial automation.
2. Standardized open communications protocols for industrial automation design – Ethernet is used in combination with open-source, standard protocols, such as EtherCAT, Profinet, EtherNet/IP, Powerlink and others. And all of them can easily interface into many devices, such as drives, encoders and industrial controls on the I/O network. As fieldbuses have become more open and dependent upon known physical technologies like Ethernet, I/O network update rates have increased to the point where they can keep pace with real-time events in the control system.
3. Less Copper — Lower Costs – Previous IEEE networking required significant amounts of copper wiring for industrial devices. But today, connecting I/O devices to the controller requires only the I/O network connection, control power and, in the case of high-energy devices, three-phase power. This eliminates ground loops and messes of copper wire. Instead, one standard cable connects the controller to the industrial operating system, which can be located far from its controller and be distributed.
4. Protection from Platform Obsolescence – Because Ethernet is available for virtually every hardware platform in existence, it’s not tied to any one manufacturer or even class of equipment. It will continue to work for the foreseeable future, providing a future-proofed investment in connectivity, which also has the benefit of bolstering long-term security.
5. Reliability – Ethernet I/O works reliably in harsh environments, like those in solar power plants, oil & gas refineries, railways, wind power plants and even marine facilities. Odds are, industrial automation design using Ethernet I/O will meet that demanding needs of your production environment.
6. Common, certified standards and wide vendor support – Industrial Ethernet uses the transport and control protocols from traditional Ethernet and the media access and signaling technologies found in off-the-shelf Ethernet interface cards. It’s a robust, certifiable standard that allows great flexibility in equipment use while ensuring devices are certified, tested and approved by EtherNet/IP test labs to ensure their quality and consistency. The core of EtherNet/IP is the Control and Information Protocol (CIP) used in ControlNet, DeviceNet, and CompoNet. This standard organizes networked devices as a collection of objects, defining access, object behavior and extensions. This provides access to a massive range of devices using a common mechanism, and because it’s such a widely used standard, — every industry uses Ethernet — there’s extensive vendor support for nearly any type of I/O device.
7. Simple, Fast Setup – Ethernet provides producers more options, whether it’s safety, fieldbus, less programming or web servers. It allows plants to move between protocols or implement a fieldbus for the first time in simple, plug-in fashion. Many products are self-configuring, as they automatically recognize the master protocol.
8. Other Benefits – Some additional minor benefits of industrial automation design with Ethernet for I/O include: Single (or pair for high-availability) interconnect for networking and storage I/O; Power reduction, more efficient cooling and floor space use and a more sustainable plant environment; Server performance improvements, maximizing PCI and mezzanine slots; Better scaling of I/O capacity to handle high-performance and clustered application needs.

Cons of adding Ethernet for I/O

Now that we’ve extensively covered the benefits of Ethernet I/O, we’ll discuss some of the biggest drawbacks:

• Bandwidth Limitations – Ethernet I/O has limited bandwidth. Many PLCs can only move packet sizes of around 500 bytes, which can be a significant hurdle at times, potentially slowing down operations.
• Processing Gets Eaten Up by TCP/IP Layers – EtherNet/IP is an application layer protocol that’s transferred inside of a TCP/IP Packet. That means significant processor bandwidth goes to the processing of the TCP/IP layers, again slowing down performance.
• No Information Modeling – With Ethernet, there’s no true information modeling. You can create objects with attributes but can’t link objects together into any sort of hierarchy. This can create some challenges in real-world implementations of industrial automation design.
• Equipment Variation – There is limited functionality to Ethernet with certain controllers, so you still need to be careful about selecting the best equipment.
• Overpowered – In many cases, Ethernet is best used for discrete control applications. It can work in process control, scenarios but it can be an over-powered solution that unnecessarily eats up too much budget. In some cases, more practical, less costly solutions exist.
• Diagnostics – Generic diagnostics aren’t built into all Ethernet devices. Each device may need to have its own custom diagnostics designed and implemented, which can take up significant time.

Comparison of Ethernet to Other Technologies

Crucial Things to Know

When transitioning to Ethernet I/O, it’s critical to assess a wide range of features to get the right sort of Ethernet. Consider the following Ethernet IOS architectures:

• Ethernet Per Module Systems
• Module Carrier Systems
• Star Cluster Systems

Essential Features

Aside from its architecture, every Ethernet IOS has important functional features that must be evaluated. Every industrial IOS must provide some level of support for the following common functions:

• Power monitoring
• Power distribution
• Interlock support
• Environmental Protection