I am wondering, If Having the USB and Vin on Nano board connected at the sametime, if it can harm anything?? I read it should NOT! SO anyone know?? It should choose between the Higher of the Voltage Inputs, right??? What if you upload a sketch then too?? Does it harm it then????
Note the Schottky diode that prevents power flow from +5V back to the USB port, so the USB will not be concerned. Note also that the FT232 chip is powered from the +5V, not the USB port side of the Schottky, so it will always be operative even when there is no USB power (and it also provides a minor 3.3V supply).
The only real concern with multiple power sources, has been that sudden connection of a live 5V supply to the “Vcc” port of some Arduinox can harm the regulator as it charges the Vin reservoir capacitor, however the Nano does not have such a capacitor, so this is not a problem in any case.
OK THANK YOU very much!