Wireless Ethernet

B

Thread Starter

Bronson, Robert

Does any one have experience using wireless ethernet for data transfer using DH+, modbus or OPC?

I am considering a 4.3 km wireless ethernet segment between a field office and compressor station. An A-B SLC 505 would be installed at the
compressor. I'm thinking it should be possible to integrate critical data back to RS-View or similar at the field office over wireless ethernet.

At the unattended compressor station there are a number of displays for the compressor control and station control. Rather than duplicate these back at the field office, I would like to bring these back over the wireless ethernet using either PC Anywhere, webclient or terminal server technologies.

If the "box" that gets installed at the compressor station has OPC server capability, I may consider integrating the critical data to the field office HMI using OPC (if it has client capability). I would like to also bring condition based monitoring data back to our data historian (Honeywell PHD) OPC client data collector. (I am trying to avoid bringing non-critical data into the control system HMI just so it can be shuffled on to the data historian.)

One of the advantages of getting wireless ethernet to the compressor station is that maintenance personnel can connect to our maintenance system and the data historian. (Citrix and HTML based so fairly low bandwidth requirements) I also see that we should be able to use the ethernet connection for remote maintenance.

Any comments on this strategy are appreciated. Again, anyone with real world wireless ethernet experience please speak up.
 
H

Hullsiek, William

Weather has a big effect on some forms of wireless Ethernet. Talk the vendors about which frequency spectrum they are using. Some frequencies do not work very well when you have dense fog. You also need to look at frequencies in use around the site (Radar by airports, or cell towers), because they can interfere. For example, my wireless LAN at home (Proxim), will occasionally re-transmit packets when my
next door neighbor uses his Gigahertz phone. But this often transparent to the application, Ethernet and TCP/IP will re-establish the connection. I recently replace my wireless connection with a Cat-5, and then put a wireless to Ethernet bridge. If you have the right-of-way for copper (or having existing copper from the
bad old days), you can use copper pairs with a xDSL / Ethernet bridge. Ethernet on one side, DSL on the copper, and then Ethernet out the other.
Look at Pairgain's technology. This often beats using RS-423 and is cheaper than installing fiber or the wireless. From a topology perspective, you have two alternatives a bridge or a router.
A bridge (in practice) just links two remote LANs; generally with no single-port of failure. A router will detect an downed link, and find the next lowest cost route for the connection. So a router can have a wireless connection and a dial-up connection. (Degrade to a dial-up if the wireless becomes unavailable). Cost is generally the deciding factor.
- Bill Hullsiek
- Software Engineer
 
F

Félix Blanco

Bob,

wireless ethernet is a good solution for short range systems (around 50 km).
I am working with a Ethernet wireless network (Airotnet http://www.tribecaexpress.com/aironet.htm) and it giving to us a good performance. We have 24 oil well cluster locations with AB plc's (5/40)with
a ethernet side card and a 2.4 GHz wireless bridge (Aironet BR-2000).

Bob, you do not need any "box". Remeber your slc or plc is a network node itself (data client or server). RSlinx gives you anything you need (dde,
opc, etc.) in order to spread the information through the supervisory network level (the RSlinx server it is a gateway).

regards,
Félix Blanco
 
A few people have asked me to comment on this subject.
Wireless Ethernet has been available for more than 3 years. There are several forms that it may take:
1) LAN bridge - there are commercial products which bridge between two Ethernet segments using full duplex radio, typically microwave, or infrared links. These have been used for many years to link buildings across a public way (road). They are inexpensive, reliable, and dumb. They typically cover distances of 100 meters, but can be extended with directional high
gain antennas.
2) Wireless LAN (IEEE802.11) - actually does not specify the network protocol at all, but is used almost exclusively with Ethernet. This is only
part of the Physical Layer or PHY, and is called the "air interface." There is an "Access Point" (AP) device connected to a LAN. The best APs act as a Layer 2 switch to isolate the wireless devices from the LAN. The wireless devices may roam anywhere within radio reach of the AP, typically about 100 meters. Being radio, there are some "dead spot" problems, but these
networks are reported to work well. Speeds are either 1 or 2 Mbps or a new not-yet-standard 11 Mbps. If the remotes are not mobile, directional high gain antennas can be used to reach several kilometers. Roaming is a problem with wireless LANs, only because LAN software expects to log you off when you roam out of range of an AP. Then, when you show up at another AP, you
must log in again.
3) Bluetooth (IEEE802.15) - not yet a standard, but the specification is completed and we expect to see a flood of products this year. Reaches about 10 meters. Devices learn about other Bluetooth devices and may join into a local "piconet". Expected to be used with Ethernet protocol, but this is another "air interface" that knows nothing about the network protocol.
Bluetooth solves one of the problems of the wireless LAN - roaming is expected; as you move between piconets, you join them and later become
disconnected.
4) VoIP (Voice over Internet Protocol, IP) - I mention this because it is not straight computer stuff, and products are already available. The
technology is IEEE802.11 wireless LAN using Ethernet and TCP/IP. The data is voice converted to digital messaging and packed into IP. We expect this to boom and perhaps become the largest segment of wireless LAN terminals. VoIP will be the force to merge the voice and data networks.

ARC sees a surge in the use of wireless over the next 5 years as costs come down. In manufacturing, the wireless PDT (Portable Data Terminal) will change how we do shipping, receiving, warehousing, and the rest of the
supply chain. The biggest change, however, will be in how we think about and use the telephone system, which is why I mentioned VoIP.

Dick Caro
==============================================
Richard H. Caro, Vice President
ARC Advisory Group
3 Allied Drive
Dedham, MA USA
Tel: +1.781.471.1123
Fax: +1.781.471.1023
E-mail: [email protected]
Web site: http://www.arcweb.com
 
Rob:

We have implemented several projects, for both internal and external clients, using Allen Bradley TCP/IP and MODBUS TCP/IP, over Ethernet and the Internet. The wireless ethernet component covered distances up to 20 km, on one hop. One client allowed us to through their firewall, access their LAN, and then access the PLC at their site. Trouble shooting and monitoring was
immediate, effective and efficient. Security was at the firewall, the client only allowed the Allen Bradley protocol through.

Other clients have used a physical connection as the security. A person had to be on site to make the connection.

We have used spread spectrum radios to extend plant LANs, up to 60 km (4 hops). Data and graphics were shared at 4 locations.

One thing to consider is the criticality of the data being communicated and the impact that a communications slow down or loss would mean on your operation.

Regards
Ken Sim, P. Eng.
The opinions expressed are my own and not necessarily those of Kenonic
Controls Ltd.
 
J

Jeremy Pollard

Used Aironet RF bridges to communicate with 31 PLC's and Unix box, along with VB apps etc. Reasonable speed and dont use spanning tree protocol:) Alternate supplier is Telxon. Breezecom has similar devices.

Cheers from:

Jeremy Pollard, CET
[email protected]
On The Web - http://www.tsuonline.com
PLCopen North America - [email protected] www.PLCopen.org
the Training Factory, Inc.
Programmable Controller Support Systems
The Software User Newsletter ONLINE
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8 Vine Crescent, Barrie, Ontario L4N 2B3
705.739.7155 Fax 705.739.7157
 
B

Bronson, Robert

Thank you to all that have responded to my original posting. Certainly looks like wireless ethernet should be considered as a telecom
infrastructure for oil & gas.

As part of my investigation I went looking for simple HMIs that could serve up displays for remote viewing over ethernet. I didn't have to look too far. CIMREX have an operator terminal that supports activeX displays on Internet Explorer. The WAN connection allows for remote maintenance and file transfer as well as display. There is also the potential to connect
operator displays on a local LAN.

I would be interested to know if other operator terminals are going this direction.
 
J

Jamil, Babar

Several HMI packages (e.g. Wonderware's InTouch) can display graphics on Internet Explorer.

Talking via wireless Ethernet and displaying graphics on Internet Explorer are two different features. Talking via wireless Ethernet is a function of I/O driver and displaying graphics via Internet Explorer is a function of the MMI software itself.

I/O driver is relativlier easy to modify and work with wireless Ethernet protocol. I would assume that most drivers written for Ethernet would talk
Wireless Ethernet too.
 
R

Robert Bronson

Two recent replies to my posting regarding remote display of operator panels have referred to packages such as Wonderware and FxView. My view of operator displays is simpler than this. Products such as QuickPanel and CIMREX don't have a real-time database that must be maintained. It is these simple HMI products that I would like to see serve up displays over ethernet.
 
G

Gillingham Household

Advantech Automation in Cincinnati has a CE based OI Terminal with a "Pocket WebHMI" embedded. It is designed for specifically these type of
applications, doesn't have the database support issue and is priced right!

CG
 
Robert;

I have two solutions I've been using for some time.

First, PCSoft ( http://www.pcsoftintl.com/ ) produces a product called Wizcon which enables users with java enabled browsers to view their process accross the internet or LAN with no additional software.

Second, I use a product called VNC, produced by ATT in the UK ( http://www.uk.research.att.com/) which provides remote access via numerous
means... and it's FREE !!!

Give them both a visit.
You may find your answer at either place.

Regards
Mark Hill
[email protected]
 
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