Ok so for my setup in Tempest SXR I plan on having a separate adapter so the Arduino will be powered on when the computer is off (unless I can figure something else out - I'll get into that later). If I have the 5v socket hooked up and the USB (I'll need the USB hooked up for a bit once it's first installed to adjust the coding) will it automatically switch to the best power source or will it fry something?
Also, can I build a circuit that will take 5v from the PSU and store it in a capacitor so the arduino will have 4 or 5 seconds of power after the computer is off so I don't have to keep it plugged into a separate power source all the time? I need it to stay on after the computer shuts off so that it will close the louvers. If I just power it off the PSU, the same 5v line controls the loop in the code, so it'll power down before it has time to shut the louvers. But when I power it on it'll work just fine.
So after typing all this, I think I'd like to go the capacitor route and just supply 5v to the arduino for 5 seconds or so after the computer is off. Can anyone suggest how I might do this or point me in the right direction?