I have a genuine (purchased from Adafruit) Arduino Leonardo that I have had for 2 years and I have not had any issues with. However, I have always noticed that it seems to be running suspiciously hot for a low power microcontroller, sometimes even too hot to comfortably touch. I measured the temperature today with an infrared thermometer at 121 degrees Fahrenheit (~49C). Based on observations by feeling the board, the 32U4 seems to be what is getting hot and everything else is cool to the touch. This happens when it is powered over USB as well as through the power jack. The chip gets hot even when nothing is connected to the I/O or power pins. The board is entirely working and does not appear visibly damaged. I am a bit worried about this as I may use this board in a project where it will be inside in enclosure and running for long periods of time. Any ideas why this is happening and if this normal?

  • Mine is getting hot as well. A genuine Leonardo too. I'm using Ethernet Shield and an RFM69HCW radio.
    – A.W.
    Aug 14, 2017 at 18:44
  • I think I solved mine, I was using 12v supply, I changed it to another one using 7v. It's normal now.
    – A.W.
    Aug 14, 2017 at 19:10

1 Answer 1


My Leonardo, which I leave on all the time, is not hot. The CPU chip feels at room temperature as far as I can tell. If you were powering something from it, maybe you are drawing too much current. If it gets hot just sitting there doing nothing, and with nothing connected, something is wrong.

Maybe you damaged it in the past? Maybe hooked up some LEDs without current-limiting resistors? If not, it sounds like a faulty device to me.

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