dkonigsberg
commented
4 months ago It should be noted that there's a good chance that the current approach is perfectly fine. Its just that there is so much conflicting guidance out there that it always creates doubt, so this ticket was created simply to track that doubt.
The main board's grounding strategy is currently somewhat naive, as it uses DC ground for everything (including TVS diodes) and then directly bonds the DC circuit ground plane to the chassis through the mounting holes.
There is a lot of confusing and conflicting advice out there as to how to correctly handle this. It is often suggested to connect TVS diodes to the chassis ground. Then some suggest connecting DC ground to the chassis in one place near I/O ports. Some suggest doing this, but then connecting the rest of the mounting holes through high voltage capacitors. Furthermore, some suggest that when the chassis is actually connected to mains earth, then don't connect DC ground to the chassis except maybe at the power supply, and maybe connect all the mounting holes through capacitors. Like always, the real answer is some form of "it depends" where the specific scenario in question is never directly covered.
As some of the improvements in power filtering that will result from #56 are likely to couple some amount of noise to mains earth, dealing with this correctly is going to become a little more important.
So for the next revision, the current proposal is to do the following:
And finally, all of this can be changed or thrown out if more useful advice is actually provided.