Ethernet down to device-level

Industrial Ethernet-based solutions are now established and gaining popularity for plant networking. Ethernet is preferred by many engineers for automation applications for the simple reason that it allows device manufactures to add previously impossible features. These features make working with Ethernet-based devices easy and convenient while providing plant personnel tools they need to incre...

06/01/2007


Industrial Ethernet-based solutions are now established and gaining popularity for plant networking. Ethernet is preferred by many engineers for automation applications for the simple reason that it allows device manufactures to add previously impossible features. These features make working with Ethernet-based devices easy and convenient while providing plant personnel tools they need to increase overall machine uptime and availability:

  • Integrated web servers simplify diagnostics and configuration,

  • Fault notifications can be sent via e-mail,

  • Easy data routing to a PLC and,

  • Monitor applications on a PC.

With these advantages, it’s no wonder that Ethernet solutions are used increasingly to replace networks like Profibus, DeviceNet and others. However, the farther a user goes down to the lowest networking levels, Ethernet’s capabilities begin to run out, and another solution must come into play.

Match network with function

While Ethernet is well suited for top-level architecture, it is not practical for device networking, particularly where devices have simple functionality such as discrete sensors and actuators. This is important to know since users may not currently be able to purchase many devices with a connection to Ethernet, and must therefore use traditional networking solutions to avoid the problems associated with discrete hard-wired I/O. AS-Interface is particularly well suited for this use for a number of practical reasons:

  • AS-Interface is a low level solution designed and optimized for efficient transmission of sensor and actuator data. I/O nodes are small and inexpensive, allowing solution providers to develop highly distributed I/O systems, minimizing total cable cost.

  • AS-Interface provides standard 24 Vdc power to individual devices, which is still not practical via Ethernet. This eliminates the need for supplying power to devices individually.

  • Configuration and troubleshooting functions of AS-Interface minimizes installation and commissioning time.

  • By connecting simple devices like sensors and actuators to AS-Interface, the time and engineering effort invested in low level I/O structures is protected. Going from one network (e.g. DeviceNet) to another (e.g. Profibus) is effortless. In addition, the performance of upper level networks is significantly improved, with increases in efficiency of approximately 10x when AS-Interface is used to consolidate I/O.

  • AS-interface is the only truly independent solution with regard to other networks, since it was not developed by a specific PLC manufacturer.

  • AS-Interface is the only network where technological modifications are not dictated or dominated by a single company. As a consequence, backplane scanner cards for all major PLCs are available with gateways to virtually any industrial network.

  • AS-Interface does not compete with or attempt to replace any traditional upper level networks. Instead, it enables users to utilize networks to their full potential, by increasing data transmission efficiency, and addressing installation shortcomings like topology limitations, inflexible I/O distribution, and high cost of physical media including cable, taps and terminators. Complex devices (RFID systems, drives, HMIs, etc.) are still good candidates for these upper level networks.

  • AS-Interface enables users to network safety devices at up to Category 4, while still transmitting standard, non-safe data over the same network.

Simplify upper-level choice

With AS-Interface at the I/O level, selecting the correct upper-level network for an application becomes much simpler and safer. Since these networks are heavily influenced by system vendors, selecting the PLC for an application effectively selects the network. While most PLC manufacturers support an Ethernet solution, this doesn’t mean they are compatible. The reason is that Ethernet by itself does not fully define a communication procedure.

Users must get used to talking about the specific Ethernet protocol they use. For instance, Modbus/TCP and EtherNet/IP are both Ethernet-based protocols, but incompatible. While both use standard Ethernet frames and employ TCP for data transport, they do not share a common application layer and cannot exchange information. Some manufacturers address this dilemma at the PLC level by designing devices that simultaneously implement several Ethernet protocols. One such device is IDENT Control from Pepperl+Fuchs, an RFID system that supports four different Ethernet protocols: Modbus/TCP, EtherNet/IP, PROFNET and serial stream over TCP/IP.

While selecting a network for complex devices is primarily driven by the PLC platform, using AS-Interface at the I/O level is the right choice in any context. Its flexible gateway approach completely shields the user from any changes that occur at the I/O level, and allows engineered solutions, including control drawings, to be reused as new networks and network protocols become available. AS-Interface combined with Ethernet may very well be the winning combination for the future.



Author Information

Helge Hornis, Ph.D, is intelligent systems manager, Pepperl+Fuchs. Reach her at sales@us.pepperl-fuchs.com .


PLC networking platforms

Most PLC manufacturers prefer one traditional device-level network, and an Ethernet protocol. This complicates life for device manufacturers since they have to support multiple platforms. Ethernet-enabled devices are less complicated, since one can operate with multiple protocols. AS-Interface gateways communicate with all these networks and many more:

Rockwell Automation (A-B): DeviceNet; EtherNet/IP

Siemens: Profibus; Profinet

Schneider: ModBus; Modbus/TCP

Mitsubishi: CC-Link; (no preferred Ethernet protocol)



No comments
The Engineers' Choice Awards highlight some of the best new control, instrumentation and automation products as chosen by...
Each year, a panel of Control Engineering editors and industry expert judges select the System Integrator of the Year Award winners.
Control Engineering Leaders Under 40 identifies and gives recognition to young engineers who...
Learn more about methods used to ensure that the integration between the safety system and the process control...
Adding industrial toughness and reliability to Ethernet eGuide
Technological advances like multiple-in-multiple-out (MIMO) transmitting and receiving
Big plans for small nuclear reactors: Simpler, safer control designs; Smarter manufacturing; Industrial cloud; Mobile HMI; Controls convergence
Virtualization advice: 4 ways splitting servers can help manufacturing; Efficient motion controls; Fill the brain drain; Learn from the HART Plant of the Year
Two sides to process safety: Combining human and technical factors in your program; Preparing HMI graphics for migrations; Mechatronics and safety; Engineers' Choice Awards
The Ask Control Engineering blog covers all aspects of automation, including motors, drives, sensors, motion control, machine control, and embedded systems.
Join this ongoing discussion of machine guarding topics, including solutions assessments, regulatory compliance, gap analysis...
News and comments from Control Engineering process industries editor, Peter Welander.
IMS Research, recently acquired by IHS Inc., is a leading independent supplier of market research and consultancy to the global electronics industry.
This is a blog from the trenches – written by engineers who are implementing and upgrading control systems every day across every industry.
Anthony Baker is a fictitious aggregation of experts from Callisto Integration, providing manufacturing consulting and systems integration.
Integrator Guide

Integrator Guide

Search the online Automation Integrator Guide
 

Create New Listing

Visit the System Integrators page to view past winners of Control Engineering's System Integrator of the Year Award and learn how to enter the competition. You will also find more information on system integrators and Control System Integrators Association.

Case Study Database

Case Study Database

Get more exposure for your case study by uploading it to the Control Engineering case study database, where end-users can identify relevant solutions and explore what the experts are doing to effectively implement a variety of technology and productivity related projects.

These case studies provide examples of how knowledgeable solution providers have used technology, processes and people to create effective and successful implementations in real-world situations. Case studies can be completed by filling out a simple online form where you can outline the project title, abstract, and full story in 1500 words or less; upload photos, videos and a logo.

Click here to visit the Case Study Database and upload your case study.