I have an arduino micro that works fine off USB. I need to power it from an external 12V power supply. When I connect the 12V supply to the adjacent VIN and GND pins, the arduino will not power up. When I measure the power at VIN, it's 12V. When I measure power at the 5V pin, it's also 12V. If I disconnect the external power and go back to USB, it powers up.

Blown regulator?

  • 4
    Or unconnected ground? Otherwise I can't imagine 12V on 5V without blowing MCU.
    – KIIV
    Commented Jul 28, 2017 at 21:39

1 Answer 1


In comparing this with another Arduino Micro, it appears that the regulator is malfunctioning.

  • Is this actually an Arduino product, or some unspecified knock-off? Commented May 6, 2018 at 16:38
  • Actual Arduino. I certainly won't rule out that I fried it at some earlier point, but it's clear that the regulator is not working.
    – plinth
    Commented May 8, 2018 at 14:16
  • It may blow the entire board. Feeding 12V into the regulated 5V line would likely damage the CPU and various other subsystems.
    – Duncan C
    Commented Apr 25, 2020 at 21:45

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.