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 Jul 28 '17 at 21:39

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

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  • Is this actually an Arduino product, or some unspecified knock-off? – Chris Stratton May 6 '18 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 May 8 '18 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 Apr 25 at 21:45

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