Windy City -" What powers your DC power supplies?" - I have a board at my control panel with with open frame transformers with the outputs fused - again, all rip outs and no cost. You can also use wall warts provided you use the proper size. Its really a shame the amount of transformers I throw away.
Mike - Its really very simple - you have a board/power supply that converts AC voltage into DC so you can run your DC devices. You feed it AC from your transformer and you have a DC output. I just put a few on a board with different voltage power supplies.