This takes most of the load off the Arduino Pro Mini’s teeny SMD regulator by knocking the +12 V ATX supply down to +7 V:
It’s on the heatsink beyond the ATX connector at the right edge of the board:
It also provides a (more) stable voltage for the current sense amp than you can reasonably expect directly from the ATX power supply:
Not much to it: the thing Just Works…
The Smell of Molten Projects in the Morning 