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Posted: 2022-04-10 12:13 AM
Scadapack RS485 comm issues
I am having issues communicating to a valve on an RS485 network. There are a total of 10 valves and the RS485 is daisy chained starting from the PLC to the first valve, and onwards to the last valve. The issue is I can see all of the valves utilizing modscan, except the first one the PLC is daisy chained to. I am not sure if there are termination resistors wired. Is there any reason I cannot see the first valve in the daisy chain but all others?
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Posted: 2022-04-11 10:37 AM
Hi Kevin,
Attached is an old document I sometimes refer to when dealing with an RS-485 issue. Please dig into that and check all the various issues discussed. One other item to consider is "What's different about that first valve?" Maybe different firmware, maybe a different switch setting, maybe a poor terminal connection, could be any of many different things...
Joel
Remote Operations Specialist
Schneider Electric
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Posted: 2022-04-11 10:37 AM
Hi Kevin,
Attached is an old document I sometimes refer to when dealing with an RS-485 issue. Please dig into that and check all the various issues discussed. One other item to consider is "What's different about that first valve?" Maybe different firmware, maybe a different switch setting, maybe a poor terminal connection, could be any of many different things...
Joel
Remote Operations Specialist
Schneider Electric
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Posted: 2024-10-23 06:54 PM
i used to get same issue as well.
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