A quick question. If I have my Arduino connected to a computer with a USB cable and also connect a 9v DC supply to the Arduino at the same time, what happens exactly? Will the Arduino draw its power from the external supply or the USB cable? Furthermore, will attaching an external supply interfere with the Serial Communication along the USB connection between the Arduino and the Computer?
I need that Serial Connection, but don`t want to draw power from the computer along the USB.....more than needed for the Serial communication I mean.
I am running (and receiving) a number of multiplexers and relays from the digital and analog ports and am thinking the safest way to deliver the steady power for all the outputs is from external power. It is connected to a mac mini that is getting rather hot and must stay on for an extended period of time during the installation. I want to tax the mac mini as little as possible...
Any suggestions, and information regarding how the external power supply and the USB will interact would be greatly appreciated.