I want to power my project with a wall adapter when it's done. I know the UNO can take an input of 7-12v but does the board regulate that? I eventually want to run my project off just the atmega328p. Does it require a specific voltage or can it do 7-12V too? Or do I need 5v specifically for the standalone chip?
Yes, it does regulate, there are voltage regulators on the board.
Chip require:
16 MHz +4.5 - +5.5 V range. .
8 MHz +2.7 - +5.5 V range.
You can use your own power supply, but be careful, don't overdrive + 5.5V
Switching PS for most mobile phones in this area of voltage.
Or just get a 5V adapter
http://www.mpja.com/prodinfo.asp?number=18520+PS
and a panel mount connector
http://www.mpja.com/prodinfo.asp?number=18549+PL
Bring the 5v in to the VCC/5V pin.
if you're building the Uno in.
Which seems a waste - after development is done, plop in a promini or a standalone or whatever suits your needs.
The Arduino has an input voltage of 7-12V.
The ATmega328 is not an Arduino, and has an entire datasheet dedicated to its operation.
powering till 12VDC is ok for the board ,However with 328p minimum 2.7VDC is needed to activate it in the internal oscillator mode if you want to activate it on LOW power than 2.7VDC then you can use the ATmega168A-PU(takes a minimum 1.7VDC) a cheap substitute but yes only when you code can fix in it.
Just FYI, my short article on powering an arduino:
For standalones, you can read the article from NYU:
Liudr,
Why no mention of powering direct from a clean 5v source(such as a 5v regulated wllwart) into the VCC or +5V pin?
I don't go thru the regulator for any of my projects. The 4A regulator I linked to may be overkill, but it sure puts out clean power.