There was a thread a while ago (can't find it right now) where the OP had a sensor powered from the IOREF pin. I know that Arduino's not a power supply, and that even the 5V pin has limitations, but can the IOREF pin be used for anything other than a reference?
Could it for example, be used as the 5V on a pot, just as a convenience when the 5V pin is otherwise engaged?
The IOREF pin is connected directly to the 5V pin, so yes, just keep current draw in mind, 5V regulator load, circuit board trace size, etc. There's also a 5V source on the ICSP socket, pin 2.
I think the thread was about the Aref pin, not the IOREF pin.
The Aref pin should not be used to power things, but it can be used to connect an external reference to, if... Aref is set to external in setup.
The IOREF pin is AFAIK connected to the MCU supply, for a shield to know it's plugged onto a 3.3volt board or 5volt board.
So the IOREF pin on an Uno/Mega is connected to the 5volt pin, and on a Due it's connected to the 3.3volt pin.
Leo..
For future reference: Arduino_Uno_Rev3-schematic.pdf. See the connector labeled 'POWER'.