IDC32 Module Intermittently Losing Communication

We recently replaced the control panel on a machine, but kept the software basically the same. The only change was moving the I/O tags to fit the new SNAP-PAC module layout. Part of this change was moving points from an old IDC-16 module to an IDC32 module.

We’re having an issue where every few hours the IDC32 module seemingly drops its communication with the R1 controller, causing all inputs that are ON to register as OFF for anywhere from 200 ms to 1 second. Every time this happens, the “times discovered” for the module in PAC Manager increments by 1.

We’ve tried the following to remedy the issue:

  1. Deleted old tags on the IDC32 module, and re-entered the tags
  2. Checked rack voltage (5.12 V)
  3. Updated I/O coprocessor firmware to 3.0
  4. Installed new IDC32 module

We’re still having the issue. All other modules on the rack appear to be working properly.

Has anyone seen this issue before, and do you have any recommendations on troubleshooting?


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This probably isn’t your issue, but I just recently had a module that would occasionally disconnect from vibration and then reconnect. A couple of points would get disabled from loss of communication. We have remedied this, but I thought I would toss it out there as a possibility.

Are the modules screwed down?

We had issues with higher point count modules losing electrical contact from the rack over time as the weight of the wires/cables would cause the module to gradually sag on the rack. Opto training way back when told us that screws were unnecessary unless you are installing on an ice breaker - we found this not to be true in practice - especially when mounting racks in a vertical orientation. I always have the screws installed now.

If the module is mechanically secure, then I would relocate it to another spot on the rack to rule out a bad port on the rack.

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I had an analog output module that reported as digital inputs in pacManager. All other modules reported correctly. I changed to a different 5 volt supply and the issue went away. If the 5 volt supply measures 5.12 with a meter, it may not be so during the failure. If there is no way to monitor it with a scope triggering on a failure, change the supply and see if anything changes.