Note the use of a standard extension cord. I figure if something breaks or needs testing I can simply unplug it and take it to the "lab" etc.
Currently plugged in is the +48VDC PSU that drives the left power "sockets" in the back. They go through a small fusebox to protect both plus and minus. The right section will be connecting to Arduino's Vin and (ideally) +12VDC power gained from the connected Arduino PSU.
Left: Closeup of the fusebox. 8A fuses for the left +48V and 8A for the +12V on the right. I'm using red vs blue cables so it's easy to select the correct voltage. (Note: The right fuses need to be replaced with weaker ones, since the current PSU only gives 3.5A)
Right: Closeup of the on/off button that controls the main power. This probably needs some t.l.c in the future as the soldering is really sloppy. Hopefully it's correct to have the ground connected at all times...