Hi Leo,
There are a few questions left dangling in this post and I’d like to backtrack to one to close out. My proposed method for providing the Nano with a regulated and isolated supply, with a sufficient load rating to cover the requirement was to connect the 12V to a LM7805 to regulate the supply, then to a Hi-Link 1D0505 (5V output) to provide isolation and connect to the 5V pin. In post#9 you indicated this is not possible: “Can't have a 12>5volt linear regulator and a 5volt switching regulator in series.”
I’ve just received the Hi-Link 1D0505 I ordered and tried this out with an LM7805 and it seems to work OK.
An alternative is to use a Hi-Link 1D1212 (12V output) on its own connected to Vin, which is regulated, but as I already indicated the load rating for 1D1205 is marginal.
Can you explain your concerns and maybe suggest the best way to protect the Nano from any interference through the supply?
Michael.