USB Serial connection and external power

Hi there,

I am a new user. I have had my arduino for a couple of weeks now and I have completed some of the tutorials. Everything good so far. Lately I have been experimenting with motor control and H-bridges.
I have the Duemillenova with automatic power selection (no jumper).
When I use the Vin pin (7.2V) can I still connect the USB cable to monitor serial data and upload code? If I upload code the motors are being powered through USB and that is probably not good.
Currently I’ll upload the code and then quickly unplug the USB cable and switch to my external power. But I would like to see the serial data to debug code on external power.
I have not found anything on the net that speaks to that question. I have not tried it because I don’t want to blow anything.


You ca. Use your usb serial safely with external power attached.

Great and thanks for the quick reply.

Thanks for asking the question, helped me out too!