uno powersupply and usb

is it safe to have the power supply running the arduino uno AND the usb cable plugged in? just curious. thank you.

grendle:
is it safe to have the power supply running the arduino uno AND the usb cable plugged in? just curious. thank you.

Yes, you can have both USB connector plugged into a PC and an external DC voltage source connected to the Uno's external DC connector at the same time. If both connectors have power then the Uno's internal auto-voltage selector will utilize the external voltage source to power the board.

Lefty

thank you my friend