I am looking to integrate inexpensive, reliable Modbus RTU on existing RS-485 network. It would be able to take up to 20 Discrete Inputs which could be easily mapped into its memory map to be pooled by Modbus master.

Unit will be used to collect number of discrete inputs in vascinity and map them into memory map so they can be easily pooled via Modbus communication. RTU unit should be able to communicate with No parity, 19200 baud speed on daisy chain RS-485 network. I welcome any suggestions.

Thanks

 

I use SCADAPack RPUs by Control Microsystems quite often and they are cheap (as controllers go) and they are built entirely on the MODBUS protocol. You can get various versions of the SCADAPack that come with a variety of discreet and analog inputs/outputs built into the main unit, plus expansion units are available. They aren't your typical PLC and the ladder logic programmer is pretty basic, but they are robust and get the job done for the price. They come standard w/ RS-485 and RS-232, plus available Ethernet. They should be able to do the job. Hope that helps. If you do choose to go with those I'll be happy to give you any further help.

Cheers

 

Sounds like you want a Schneider Twido controller. It supports Modbus RTU as standard and comes with 16, 20, 24, 40 I/O and most are expandable. look on http://wwww.telemecanique.com

You can download twido software from internet. Just go to google search for 'twidosoft download'
Play with software before purchase hardware.
Standard baud rate is 19,200 no parity.

 

Take a look at the RAIL I/O (RIO) Products manufactured by Open Control Solutions. http://www.opencontrolsolutions.com. The RIO-128 offers 40-DI, 40-DO, 40-AI and 8-AO for only $895.

Regards,
Dave Walker

 

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