I/O not responding then I/O Ok message appearing automatically

asim_rana

Member
Join Date
May 2005
Posts
50
We are using 9 contrologix chassis communicating on control net.We are facing a problem that when we open RSlinx or RSlogix 5k & go online some cards of two nodes show abnormal behaviour.The status of cards become Faluted & aftrer some time we get a message I/O not responding & after some time these cards become OK & I/O s also become Ok.we had run Rsnetworx agin but every thing seems to be fine in Rsnetworx(keeper is valid to all nodes).Is it possibe that controlnet cable has got damaged due to which this problem is coming?how we can verify that there is no problem with cable,any test? If cable had some problem is there any connector through which we can reconect this damage portion of cable
 
Just looking for more info, are the cards actually faulted, or are you simply referring to the I/O indicator in your RSLogix screen? As far as the cable test goes, you should be able to find a printout from AB website and ohm the cable to make sure it's good. We have done this many times. Also, is there ever a problem when you're not connected with a computer?
 
I will keep this very simple to help with the language.

The ControlNet cable MUST be installed using all the correct cable and connectors. The cable MUST be the correct grade of low loss, quad-shielded RG6 coax, and the correct node droppers MUST be used.

All the BNC connections MUST be done to the highest standard using the correct crimper tool that has the correct tool for the quad shield coax.

All of the rules for length and number of nodes MUST be correct.
 
Thanks 4 ur response.I just want to tell u in more detail

Above mentioned system has been running good since last two years almost.No this problem came out.
LED status on cards
Initially solid green
after some time flashing green

after some time flashing red then again solid green
so this behaviour is transmitted to RSlogix 5k screen.After some time all I/Os become ok.Then yellow mark apper on some I/Os then automatically to OK.
Would you please give some more details about cable testing ?
 
You can detect a bad crimp on the bnc connector. Use an ohmmeter to test the resistence between coax and the shield. If you detect a short between the 2 you need to cut it off and recrimp.
 
Inspect the entire length of the cables for damage where the shield may be getting grounded. I have found cables in trays that had been damaged and you would not suspect them to be damaged there.

You can remove the cable from both ends and then verify with your digital meter at least 2 meg ohms of resistance between the shield and center conductor. Inspect the crimp on the shield to make sure there is NO corrosion.
 
You can have bad cables that look perfect on the outside. We have, in the past, used a TDR (time domain reflectometer) to find bruises in our coaxial cables. The hardware is expensive, but can tell you exactly where any problems are in the cable.

I would start with the status counters in the 1756-CNB. They may tell you more about the location of the problem.
 

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