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DeviceNet Communication with PLC

Hello All,

We are looking at communicating with a CompactLogix PLC through an Allen-Bradley 1769-SDN Scanner Module. We have been able to establish the communication with the PLC and are able to pass along data both ways, but are now having some communication issues with some devices on the DeviceNet network. We have had a few devices (Powerflex drive and some E3 overloads) give a fault status due to a communication problem. The Powerflex Drive is giving a Port 5 Fault and the E3 Overloads are giving that the communication status is bad. It requires us to cycle power on the buckets (and disconnect the DeviceNet cable to cycle power to the E3’s), and then we are able to restart the motors. This problem initially started when we first connected the PLC and it went away when we disconnected the PLC, which leads me to believe that our problem stems from the addition of the PLC on the Network. 

• I am wondering if we are having issues with overloading the DeviceNet card. I see that there is a limit of somewhere around 60 devices which we are nowhere near, but is there a way to check whether we are overloading the network? The PLC that we added is passing a fair amount of data currently, and we could cut this back if needed.

• We had this problem initially and simply disconnected the PLC from the Network and our issues went away. Does this mean there is some sort of issue with the physical wire, or should we primarily be looking at the overall network?

I am just beginning to troubleshoot fully, as we did not have the communication established until last week. Any help, or other suggestions, would be greatly appreciated.

Regards

SLemasters

• 15 Jun 2015 2:36 PM
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3 Replies

• Bill Thackston

  

  • 15 Jun 2015 3:10 PM

  It sounds as though you are on the right track. I've seen issues like this on other systems when the new device is polling too rapidly. It's using up bandwidth and causing other nodes to time out. It's been a really long time since I set up a VIM, but you should be able to adjust the polling rate, either as a card setting, or by setting the scan rate for the control modules with the dataset references.

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• Tinh Phan

  

  • 15 Jun 2015 3:33 PM

  In reply to Bill Thackston:

  I do agreed with Bill. DeviceNet poll for device packages but if the E3 packages are getting lost for a number of poll, it will timeout the device and causes the device goes to fault state. If this solution still don't work, look at your topology. You should be able to push the reset button and re-establish communication without disconnecting the device from the network. I would suggest that you check your terminator or other issue with the topology if that don't work. I used to use the DeviceNet detective to give me a quick indication of all my DeviceNet network. Turn off the PLC communication and connect the DeviceNet detective to see how your DeviceNet communication doing.

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• SLemasters

  

  • 15 Jun 2015 4:30 PM

  In reply to Bill Thackston:

  Thanks for the reply.
  
  The only thing that makes me question whether it is the overloading on the network is that we initially had the PLC connected, but with no signals configured. We were seeing this issue even then, but I attributed this to the fact that we had not fully established the communication. Would we see this bandwidth issue if there was no signals configured?
  
  Also, at this time, we did not have any control modules configured. Does the control module scan rate actually effect the polling of the device?
  
  Regards,

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