We are using a third-party weight controller that communicates via CAN, connected through an X20IF1041-1 card.
There are two interface cards in use. On the first card, 10 CAN devices (nodes 1–10) are connected. Occasionally, communication between nodes 3 to 10 is lost and does not recover even after a power cycle. Strangely, after 2–3 hours, the communication resumes on its own.
I checked the logger but found no relevant entries. Could someone explain what might be causing this issue?
Do you have a CAN reader device (something like this for example)? I think it would be helpful to plug a reader in downstream and see if you can catch what happens when the communication drops. I’m wondering if you still see traffic from those nodes, and if those messages contain any error information. Unfortunately if the messages aren’t making it to the PLC, the PLC won’t be able to know what’s happening.
One possibility is that the devices themselves have stopped communicating (e.g., due to a power failure). Another is that there’s an issue with the wiring such that they are communicating, but that communication isn’t reaching the PLC. I think it’s also possible for the CAN bus to be flooded with messages if too many devices try to talk at once, but I’m not sure why that would happen intermittently and I would expect a power cycle to have some effect, at least temporarily.
