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It took me about 4 hours to desolder an Arduino Nano I fried and solder on the new one. I'm not exactly sure how but I shorted it somehow while trying to install the nano onto my robot. I could smell a fait burning and the nano no longer powered on or allowed me to upload code via USB.

When I put the second nano on, before properly insulating exposed wire, I fried it again!! This time I actually saw a little smoke and quickly unplugged it. The nano no longer responds to the USB, but...

I have this nano also being powered by an Arduino Uno. When I turned on the battery connected to the Uno, the Nano turned on and everything was working fine!! I was pretty relieved after a short spout of depression! I plugged in the USB to the Nano and I was able to upload code... only with the nano being powered from the Uno. If I turn off the battery to the Uno the Nano doesn't work with USB.

I have no idea what happened exactly and I'm not sure what fried on my Nano but I sure am glad I have this work around instead of replacing the Nano again!

Does anyone know why it's doing this? What did I see smoking? Is it repairable?

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Judging by your list of observations:

  • Cannot power through USB
  • Can power from external source
  • Can program through USB

it is most likely that the power feed from the USB to the +5V rail has been interrupted. There is only one component in that link - the diode D1 (an MBR0520). That is rated at an absolute maximum constant forward current of 0.5A and most USB ports these days are capable of providing far more than that. A short circuit on the +5V to ground would draw considerably more current than that diode can handle and the Magic Smoke™ would escape.

The diode is on the underside of the Micro and close examination may show a small crack in the surface of it. That is if it's still there. I have used a similar PIC32 based board with 0.5A rated diodes on it, and a short of the power rail when powered from USB caused the diode to completely vaporise (at least I could find no trace of it afterwards).

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  • Can program through USB only while powered from external source*
    – Michael Rader
    Jun 23, 2015 at 11:01
  • @MichaelRader The ability to program the board and the ability to provide power to the board (either while programming or at other times) are two separate things. The issue here is not with programming, since programming works - the issue here is with providing power, which is a prerequisite to programming, not part of the act of programming.
    – Majenko
    Jun 23, 2015 at 11:03
  • Yes I understand, however it is part of the act of programming if it must have power to program. But anyway, thanks!
    – Michael Rader
    Jun 23, 2015 at 11:04

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