Revision 2 notes:

Power utilization (whole board):
    * Full brightness LEDs (rainbow pattern): ~1210mA (~13.9mA per LED)
    * Default brightness LEDs (rainbow pattern): ~360mA (~1.79mA per LED)
    * Hall effect sensors: ~235mA (~3.36mA per sensor)
    * 74HC4067 multiplexers use less than 80µA so they're negligible.
    * IRM-H6XXT/TR2 (and similar) IR sensor uses ~1.2mA.

Things to investigate:
    * Running a magnet across the rotary encoder caused the keyboard to hang...  Why?
