I need a multi-port Modbus to MB+ Bridge!

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Thread Starter

Ric Peterson

I have an application with 20 to 30 modbus devices that I would like to get onto a modbus plus network. I realize that Modicon makes their BM-85 with 4 modbus ports, but I'm looking for something with more than 4 ports. Does anyone know of such a device? Thanks, Ric
 
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Sivakumar Sankar

> I have an application with 20 to 30 modbus devices that I would like to get onto a modbus plus network. I realize that Modicon makes their BM-85 with 4 modbus ports, but I'm looking for something with more than 4 ports. Does anyone know of such a device? > Hi Ric, We are an embedded systems company in Chennai, India offering custom solutions for Industrial automation applications. We do lot of special development. I am enclosing some of the solutions we have developed. Our web site is under construction, so please contact me for more information. Sivakumar Sankar Inventa Micro Technologies, Inc 90 Waverly Dr, # W301 Frderick, MD 21702 [email protected]
 
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Greg Goodman

i don't know of a bridge with more than 4 ports. but why do you need more than 4 ports? you could put all 20 or 30 of your devices on a single port, (configured as a network port) with different node addresses for each device.
 
You have not indicated whether the modbus devices are masters or slaves. If they are all slaves then they can be connected on an RS-485 multidrop network and run into a single BM-85 port configured in "Network" mode. Make sure each device has a unique address. Also watch the "Link Timeout" setting in the BM-85; the default value is 60 seconds! Polls to nonresponding slaves can literally lock up the network waiting for the error timeout period. Ian Milne
 
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Jerry Miille

>I have an application with 20 to 30 modbus devices that I would like to >get onto a modbus plus network---- Can the modbus devices be connected by a multidrop network (RS485)? If so, you can use a modbus data concentrator such as our Omnii-Comm product or program the BM up to collect data from all the devices. Jerry Miille Miille Applied Research Co., Inc. Houston, Texas 713/472-6272 [email protected] http://www.miille.com
 
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Ric Peterson

This is a reply to both above responses. I need more than four ports for exacly the reasons stated above. My devices are slaves, and I certainly could multidrop the thing, but the poll time for the devices would be quite slow, in addition to that one device could lock up the network due to timeouts. Ideally to maximize my throughput it would be great to interface each device separately onto a high speed network. Initially I was thinking MBP coming into my SCADA system, but have reconsidered. Because I have a GE 90-30 PLC it would be great to bring them in direclty to the PLC on Ethernet or Genius. Any thoughts on this? -Ric [email protected]
 
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Brian Kukulski

I know you said 20-30 Modbus ports, but FYI a company called "Calta" manufactures a 3 port to 1 port Modbus device they call an arbitrator. This device has 3 serial Modbus ports in; 1 Modbus port out. This allows three master devices all talking thru 1 Modbus port to the PLC. This device is about $650.00 CAD. I asked why "Modicon" wouldn't call them a Modconnect partner and the reply was that it would take away from the wonderfully expensive Bridge Mux market. See them at www.calta.com. BTW they also sell a Modbus to AB converter. Clever guys
 
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Carlos Araya Mackenney

Yes, you can connect up to 32 MODBUS devices in a RS485 net. Remember, each MODBUS device had an address from 1 to 254 and you must set a different address for each device in the same 485 net. Carlos Araya Mackenney [[email protected]] Automation Manager - PLC International S.A. Phone (562) 269.8727 - Fax (562) 269.8728 Santiago, Chile www.plci-ge.com <http://www.plci-ge.com>
 
Check out Novatech-LLC.com. They have an Orion 16 that supports 16 protocols (one of which is ModBus Plus) and up to 20 ports.
 
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Thank you for all your responses! I knew there were some options out there, just tracking them down is the problem. This forum has definitely been a help for me. Regards, Ric
 
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