11 posts in this topic

Hi,

I have a problem with Omron PLC and Beckhoff IO. The IO just disconnects in a few minutes and comes back! I received different errors: Link off error, Illegal slave disconnection, process data reception timeout. When I also check "Display Diagnosis/Statistics information" I see errors on all ports A and B of all nodes.  I have called and talked to both Beckhoff and Omron. 

I have two NX1 and one NJ101 to test. And I have three EP2318-0001. I have the same problem with all the PLCs and EP boxes. It does not matter if I have one, two, or three nodes.

I have tried different revisions of the EP2xxx from the XML file, different settings for the slave, different task periods, and the error still is persisting.

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I've never used that exact module but have you tried a different EtherCAT(Ethernet) cable? I've seen similar errors on systems with cabling issues.

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Yes I did. Different etherCAT cables and different Power cables. 

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I haven't used Beckhoff IO. But on one of my projects I did have an Omron EtherCAT coupler with IO cards that was exhibiting similar behaviour. It ended up being a fault Ethercat Hub (Omron Junction Slave) that was downstream of the Ethercat Coupler (Network topology was CPU to Coupler to Hub to VSD's). Not sure if you have any of these in your network, but if so, see if you can remove them to test if you still have the same problem.

To be honest, tech support didn't know why my setup was exhibiting that behaviour. I only removed the hub because I was at the stage of removing parts of the network so that I could find the problem area.

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There is no extra device in the network. The plc is connected directly to node 1 and node 1 to node 2 and so on.

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Sure sounds like an issue with cabling, such as grounding or electrical noise.  There's no other devices on the network like an Ethernet switch or PC right?  EtherCAT uses Ethernet cables, but not Ethernet devices.  Make sure you are using shielded Ethernet cables, though I can admit I have use 10m unshielded cables without an error.

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The thing is that I have the issue while I am connecting with a plc to IO on my desk. When I saw this issue in the machine I made a small set up with only two IO and one PLC. Nothing more, No switch and no middle device. Still I have same issue. I have ordered some prefabricated cables to just test them. 

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8 hours ago, Hadi.B said:

The thing is that I have the issue while I am connecting with a plc to IO on my desk. When I saw this issue in the machine I made a small set up with only two IO and one PLC. Nothing more, No switch and no middle device. Still I have same issue. I have ordered some prefabricated cables to just test them. 

There are some reported issues with other EP modules over EtherCAT but the EP2318 is reported as working. What is the firmware on your PLC?

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I want to appreciate all suggestions made to solve the issue we had. Beckhoff representative was here to check our system with Beckhoff PLC and he saw the same issues we had. 

We did a few tests on the EtherCAT communication. In all tests, the connections were good and correct and they were checked several times.

Test 1: PLC and two IO with a normal 4 wire cable for EtherCAT network
        Result: IO could not connect at all to the EtherCAT network. 
 
Test2: PLC  and two IO with the current cable that we have (the brand is Lapp) for the EtherCAT network
        Result: Around 10 frame loss in a few hundred thousand frames (Normally frame loss can be neglected by the master) plus a complete disconnection normally around 4 to 5 minutes
 
Test 3: We did test 2 with another cable (same brand and same model). 
       Result: same as test 2
 
Test 3: PLC and four IOs and cables from Beckhoff for the EtherCAT network:
      Result: a few frame losses (which is neglectable) in one million frames and no disconnection.
 
Test 4: In Test 3, all frame losses happened only in one node so we changed its cable. And now, after sending 10 million frames there is not even one frame loss, this is great.
 
I have ordered prefabricated cables from Beckhoff in Germany that I think can solve our issue. 
The big lesson we learned after weeks of working on this and engaging Omron and Beckhoff's supports in it, is that the cables in communication are very important. Checking the cable connection only by multimeter will not be enough (We had a very good cable with good shielding and also expensive EtherCAT connectors from Beckhoff) and the best always is using prefabricated cables. 

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Out of curiosity, were the LAPP cables prefabricated or where they custom made cables using LAPP branded CAT6?

On a different note, thanks for posting the end result :-)

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No they were not prefabricated. They were CAT6e I think. Actually, all cables (both LAPP and Beckhoff) and connectors we were using were good and expensive. Also the connections we checked several time by multimeter. But they did not work properly and finally, prefabricated cables worked. I exactly do not know what happened there. Maybe the impedance changes at the connecting point.

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