PLC Communication Issues
PLC Communication Issues
(OP)
I am a former military electrician gone manufacturing. I'm looking for a little help with PLC serial networks. We are using IDEC PLCs in a daisy chain serial network linked to a main control PC running KEPServerEx. My issue is that as the day goes on, the PLCs "fall off" the network. KEPServer gives me a "channel not responding" alarm and that PLC goes off line, the others drop off one by one over time. Reseting the PC brings the network back up, but there has got to be a better way. Thanks for any help you can give.
--Alex
--Alex





RE: PLC Communication Issues
What's the distance?
What cabling are you using?
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RE: PLC Communication Issues
RE: PLC Communication Issues
--Alex
RE: PLC Communication Issues
RE: PLC Communication Issues
I suggest you "google" these words:
rs485 four wire termination biasing
You will find several good application and troubleshooting notes on the topic. The biasing is where I would look first, as I don't think your distances are enough to worry much about termination.
I must warn you, I could be pointing you in the wrong direction here, as I do not have particular experience with your hardware. But it is certainly something to look at!
If you have a scope, you may be able to view the lines and see what they are doing. The curse is that the added capacitance will sometimes "fix" the problem. Until you quit looking! Grrr. Thanks, Mr Heisenberg :p
Good luck!
RE: PLC Communication Issues
--Alex
RE: PLC Communication Issues
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RE: PLC Communication Issues
Also in the KEPServer increase the Pulling time (Look under the topic).
Iam not sure how much data you are pulling and at what speeds but I often find people over taxing thir systems.
RE: PLC Communication Issues
--Alex
RE: PLC Communication Issues
I would check into the bus termination of the network. If left unterminated, wierd things can happen.