Hi
Pretty much all wall-wards are class II, but does this imply that the outputs are floating? Our could, say, the negative output be connected to the neutral of mains?
There seems to be another symbol for "insulated transformer", but those that I've measured seem to be insulated, symbol or not.
thanks
if the wall-wart has a ground pin, it is not isolated, as a rule. If it does not have a ground pin, then it is isolated, as a rule.
You can check for isolation on a DC wall-wart by checking continuity between the negative polarity and ground, as I understand it.
I am not a font of authority on this, though, so I welcome corrections if I'm wrong.
As known, the Schuko style socket common in the EU does not enforce polarization. Accordingly either plug pin can be randomly live or neutral. A class II gizmo cannot rely on either pin being L or N every time. So isolated secondary rules.
Yes, they're normally isolated, although the SMPS units tend to be more leaky as they have Y1 capacitors connected between the DC side and mains.
Thank you all!
Very nice argumentation Kremmen. I totally missed that conclusion. Mine all have europlugs, which aren't polarized.
Why would they put a capacitor between mains and the dc out?
I'm planning the super trival wall-wart, dc-dc regulator, and pot "bench supply". Seems it will be isolated :-)