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Splash

Rack Faulting

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Have the system described in the attachment, basicilly a CPU 416 talking to 5 racks via Profibus and ET200M. Problem they're having is a couple of the racks are dropping and faulting and they're having to reset to whole system to get everything back up. It also may take 2 or 3 trys to bring it back up, and they're having to do this a couple times a week. Have checked and tighten all connections on all the cabling and wiring and have not been able to notice any out of the ordinary. Any ideas or other test to perform? C__Program_Files_Siemens_Step7_.pdf Edited by Splash

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Hi Splash. That is a lot of HMI panels, and I guess that they share the same Profibus network as the ET200M stations you mention. Are the MMI-A and MMI-C1 maybe really connected to the same Profibus network ? Are there possibly other stations on the network that is not included in the STEP7 project ? The reason I ask is that it is critically important with Profibus that all stations are accounted for when the bus parameters are calculated, which STEP7 do for you automatically. When you have a fault you absolutely MUST investigate the hardware diagnostics (select the PLC, end then go to "PLC" .. "Hardware diagnostics". Post here what you uncover. For really difficult cases, you may have to have a profibus analyser or a diagnostic repeater. Totally unrelated to your question: I would never put so many panels on the same Profibus network as the i/o racks. The i/o racks are handicapped by the multimaster operation with so many HMI panels. My guess is that the profibus cycle time for the i/o can be reduced by a factor 10-20 (!) by splitting the i/o and HMI on two separate networks. Your S7 CPU has two Profibus capable ports. Use them to configure two networks.

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Thanks for the reply Jesper. I think the Profibus network is pretty much like the Step7 project shows but i will double check. I'll try and get a drawing of how the profibus is actually wired. Theres actually a repeater where there used to be a display. They took the display out and coiled up the repeater in the ceiling. Again thanks for the help.

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Think we may have found the problem, possible loose profibus connection. Went take one of the profibus cables off the connector and one wire pop out real easily, reterminated all the cables and so far no problems. Edited by Splash

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