DC power for USB Arduino

Forum 2005-2010 (read only) General Frequently-Asked Questions
6

I have a couple of new power related questions:

  1. When powering the board with USB, what voltage and mA come out of the pins? what about the power pins, the 5V and 9V are these usable?

  2. What are the specs when powering from a DC adaptor? eg. 9V 500mA?

  3. I have read somewhere that powering devices, sensor / actuators from the board is not the best way to work because microchips like the ATMEGA8 don't like power fluctuations. Is this true?

I'm probably asking pretty silly questions, but my electrical knowledge is very limited atm so any help would be appreciated.