Where can I find the electrical specs for the Domino board?
Stuff like output pin high level current, 5 v and 3.3v power supply output current, etc.
FEZ Domino is based on USBizi Chip set.
http://www.ghielectronics.com/product/116
For such advanced information you need to consult USBizi User Manual and LPC2388 datasheet.
But to answer your question, the IOs are 3.3 volts. but they are 5 volts tolerant when used as input ports.
I would also like to know how much current the board will draw by itself and how much is available from the Voltage regulators. So I know how big a supply to use to power the board and will be able to calculate when I will need an additional supply for the shields and accessories.
How much does the board draw?
http://www.tinyclr.com/compare/
How much does the regulator provide?
800mA but keep in mind heat dissipation
To add to what Gus said, if you are trying to power something where you actually need to think about how much current the FEZ will provide, you probably need to go with a separate power supply.
good point chris
Yes and always make sure you do not blow up your IO’s because of drawing too much power.
You might want to add a transistor or even a relay in this case.