arduino pro : usb + external power supply


I have just bought an arduino pro with external usb connector. It works fine with the power supplied by the usb connector. I need now to have more power. I wants to add an external DC Power (9V for example). Can I connect both the power supply and usb connector to control the board ? Do I need to disconnect the power supply before connection usb ?

Best regards,


There are usually jumpers that control if the board is being power by the USB or an external power supply. If you choose external then it should be connected before plugging it into the USB.

on my board there is only ext or battery ...

Wierd i have EXT or USB... Anyway EXT is external (so battery or adaptor)... When i use my arduino on a finisched product i use a 9V battery with a 7805 voltage regulator (brings power down to 5v). Works fine :slight_smile:

I'm putting together finishing touches on a project with the Arduino pro and an external 9V power supply. I'd like to be able to connect the USB cable after I've soldered the power supply connection in and do software uploads. Will that damage the board (5V + 9V > 12V) or is the power select module smart enough to power off one source, but not both?

It's the 16Mhz/5V version, btw.