Control.com - Nerds in Control

Hi,

This installation consists of 3 Modbus RTU RS485 slaves on the same bus at a remote site. Each could be configured with its own modem for access from a PC master, but is there a way to accomplish the same thing with a single modem for all three slaves. For example, could a Modbus master can be installed on same bus as slaves acting as master for those slaves, but appearing like a slave with more registers to the remote PC master. Any products or resources on this appreciated.

Sven

What exactly are you trying to do.. For example.. Connect 3 slave (Remote) through modem to PC (Master).. If that's the case then I don't see why not as long as the modem can handle data through-put.. (Speed etc..)

Vance Newman

>What exactly are you trying to do..

Hi Vance. Trying to do exactly what the two suggested products below accomplish. Thanks for the reply.

Sven

Hi,

I think that there are a number of options that you have to choose from. I would use a gateway like:

http://www.hms.se/support/support.asp?PID=317&Product Type=Anybus Communicator

The gateway is a modbus slave on one side and modbus master on the other. With it, you would connect one modem to the Modbus slave side of the gateway, using RS232 and then connect the 3 modbus slaves to the masters side of the gateway, using RS485.

If you have any technical questions regarding the gateway, let me know.

Patrick L
support [at] hms.se

Hi Patrick,

Thanks for the reply. Your product too does what we needed, but as I just said in reply (should read all replies first) to Jerry we've decided to go with Modbus RTU to TCP device.

Sven

We have two products that can be used for this application. The Omnii-Comm:
http://www.miille.com/din266-p00.pdf
works as you describe by polling the 3 slaves and building a data base with the concentrated data from all 3. The master can then read this data remotely via the modem connection. This product is also available with an Ethernet port.

The Multii-Port:
http://www.miille.com/din366-10p.pdf
passes the incoming modbus message from the remote modem through to the slave network. The ports are all selectable for RS232 or RS485 operation on both models. Our contact information is on the data sheet if you have further questions.

Jerry Miille

Hi Jerry. Your product does exactly what we needed, but we've now decided to make connection via Internet and are therefore going to use a Modbus RTU to Modbus TCP gateway. Thanks for answering and I've archived your product literature should decide to stay in the serial world.

Appreciatively,

Sven

Hi Sven.

There are of course many gateways out there that could accomplish your task. Our offering is either the ETH-200 (if you need RS232 and/or RS-485 to Modbus TCP conversion), or the ETH-1000 (if you just need RS-485 to Modbus TCP conversion).

http://iccdesigns.com/Merchant2/merchant.mv?Screen =PROD&Store_Code=ICC&Product_Code=eth1000

http://iccdesign s.com/Merchant2/merchant.mv?Screen=PROD&Store_Code=ICC&Product_Co de=10570

Regards,
Darrin Hansen
ICC