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Under review

Watchdog Fault on MC41 when almost exceeding DOUT-HS Current (4A)

Kai Rasporich 5 months ago in Master modules / MC4x updated by Gustav Widén (System support) 5 months ago 2

I'm hoping someone might be able to chime in if they have seen something similar before.

I'm driving two contactors (they close at different times) off the MC41. The contactors at peak draw 3.9A for about 75ms. When the contactors close, a very short time later, the MC41 enters a critical fault. The flashing lights (4R, 1Y, 12Y, 3Y, 1Y, 2Y) seems to indicate there is a 'watchdog' fault. Looking at my CPU/RAM usage and cycle usage, we are not even using 1% capacity. Is it possible this overcurrent condition could trigger this particular fault?

As well, I can't seem to find any information on what the 12Y is supposed to mean? "R4:1 n:3:1:2" which would be the "n" in the manual. What would the 12th part of the software mean?

I should also note that contactors have built in coil-suppression so I don't think it is a transient spike.

Under review


Over-current on a DOUT will just give status overload. But with current of < 4.2 A you are below the over current threshold. 


If the supply to the MC41 is the limiting factor, for example with a weak DC power supply in a bench setup, you may also be seeing a module restart when activating a load. 

But I assume this is in the actual machine installation? 


An interesting test could be to see if it really related to the DOUT draw could be to leave the large loads switched via the contractors disconnected. 

What SW version is this MC41 running?

The meaning of "n" in R4:1 n:3:1:2 can differ between software versions.