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Walks

Connecting multiple RS-232 devices to the same PLC

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Does anyone have any experience with sending multiple RS-232 devices to the same PLC? My current set up has 2 RS-232 devices sending raw ASCII data to a 2-port Comtrol DeviceMaster EIP-2202 where it is then sent  to the PLC via Ethernet/IP. The problem is that now I need to add three more RS-232 devices. Without buying more DeviceMasters, is there a way of adding the 3 extra devices to where the data from each device can be read separately?

I know RS-232 is 1 to 1, but is it at all reliable to use a multiplexer? I've looked into and I think it MIGHT work, but I'm a little nervous about adding the extra complexity.

Another option I was looking into was to somehow convert multiple RS-232 connections to a single RS-485, which from my understanding can support multiple command and listening devices and I would need to be able to address each different device. My comtrl supports RS-232/422/485.

Thanks for any help!

Edited by Walks

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What sort of devices are the ASCII devices ?    Do they have any sort of handshaking (Xon/Xoff, or RTS/CTS) that could prevent them from transmitting at the same time ?

In some applications a "code activated switch" would be appropriate.    B&B Electronics (now owned by Advantech) makes a neat device they call a "buffered smart switch" that allows you to add a prefix or even do some polling, so you could tell each port's data apart.

http://www.bb-elec.com/Learning-Center/All-White-Papers/Serial/Automatic-Serial-Data-Collection.aspx

 

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