# Wireless Ethernet and Modbus/Ethernet

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#### Jody Gallant CET

We are planning on building a high speed wireless ethernet system in our local area. We currently build and service the control stations in the City (small city) and would like to make it so these stations can be on the same backbone. Is it possible, with a Sixnet RS-232/Ethernet converter, or something similar to reliably put all the stations onto the network? They are all Modbus RTU at this point and the master stations use a variety of communications types. (ie from Dialup to leased lines) Any thoughts? Ideas? Thanks Jody Gallant CET

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#### K3MPJ

I know that Data-Linc offers advanced radio modem technologies for both Modbus and ethernet (Modbus/TCP/IP). They have been a leader in the industry for a long time, and their products are very cost effective.

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#### Richard Theron

Hi Jody How many wireless stations (nodes) would you be putting on the network? Are all the RS-232 devices Modbus RTU? What wireless system would you be thinking of? I presume that the master station is Modbus RTU as well. I have done a similar application before using UHF with 10 nodes and four RS-232 devices on each node. Worked very well. Regards Richard Theron FieldServer Technologies 1991 Tarob Court, Milpitas, CA, 95035, USA Phone: 408-262 2299 ex 125 Fax: 408-262 9042 www.fieldserver.com

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#### Paul Horvath

hi jody,

it sounds like you have a solid plan in place to justify the installation of a wireless high speed (10 mbs) network. Your potential customers for sharing the backbone may demand more of your system than you can provide however.

we have used data-linc products, but as fas as i know, they haven't offered a proven TCP/IP wireless connection yet. Most of there devices a simply a copper replacement medium and do not adhere to any IEEE standards.

i have come across two systems that work well.

The first is Grayhills EZ-Com IP Router. This is and industrial modem, however, it is only 2 Meg throughput and it does not comply with IEEE 802.11 or IEEE 802.11.B. It is capabale of going 30 miles using the appropriate antennaes and 60 miles (claimed) using a repeater.

The second is by BreezeCom as distributed by Black Box. This is an IEEE 802.11 (hopping, not dispersed, more important that you hop since you may have "customers") device and can go 30 miles with approriate antennaes and amplifiers. however, the throughput is 3 Mbps but you can overlap the cells to achieve 15Mbps throughput. This device is less expensive than the data links and we are currently using it in industrial applications. The device also provides load sharing so you can "promise" your customers reliable connections.

As far as using Modbus RTU over TCP/IP, there is a published protocol for "wrapping" modbus/TCP and a RTU packet. This is an industry standard and is published for public information.

i think someone had already mentioned putting a pc local which would perform your RTU conversion to OPC. This also is a solid solution. Once you have a number of OPC Servers installed talking to all of your RTUs, it is quite simple to develop and HMI for paramter downloading. Entivity and Iconics are two products that have fairly nice libraries for HMi development. Iconics Genesis is based on OPC so the intergration is completely seemless. I believe Entivity is also but, i have not had enough interaction with it to give it high mark.

If you have any questions, please feel free to give me a call 734-975-8108.

Thanks, I hope this helps

Sincerely,
Paul Horvath
Sr. Integration Engineer
Schnedier Automation
[email protected]

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