What to do with these transformers? Build an isolation transformer, of course. Of course, your dumpster transformer might be a little different than the one shown in the post (and the video, below).

A transformer provides electrical isolation and impedance matching, and, in the application we’re considering here, translates voltages between primary and secondary circuits.

As a variable transformer, often referred to as a variac, it lets [Lajt] select how much voltage is passed through to the output side.