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I have two Arduino Uno R3 boards and both of them now seem to have an issue. There's a micro sized 8 Pin chip near the dc power port. This seems to get incredibly hot (i managed to get a blister from touching it) and the "L" Led seems to stay dimly lit even when the reset button is pressed.

The Arduino Uno was working fine during operation and only started giving me this problem recently, i cant seem to find any visible short or loose terminal on the board.

I can see that the reset function is being used as my LCD does reset. Would anyone have a reason for this mysterious issue?

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    This chip seems to be the dual op-amp labeled LMV358IDGKR in the Uno R3 schematic.
    – Edgar Bonet
    Commented Feb 12, 2016 at 9:30
  • How are you powering the Arduino when this condition occurs?
    – uint128_t
    Commented Feb 12, 2016 at 15:19
  • I had something similar before because I tried to attach a fan to it. Are there any short circuits or something that would take a huge amount of power?
    – Matthew
    Commented Feb 12, 2016 at 18:37
  • post a picture of your UNO board
    – Chetan Bhargava
    Commented Feb 12, 2016 at 21:44

1 Answer 1

Reset to default
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There are two issues here:

  • The "L" LED lighting. On the R3 Uno this is driven by an op-amp and if pin 13 is "floating" the op-amp may, or may not, turn the LED on. So this is normal.

  • The 8-pin chip near the power plug getting very hot. This is definitely not normal. You must be consuming a lot of current to do that. You could try measuring it. A Uno running an "empty" sketch should be consuming around 50 mA. Note that this chip is the op-amp mentioned in my first point. Possibly you have damaged it. Did you connect an LED (or motor) or similar to pin D13? If so, what current-limiting precautions did you take?

  • Try running an empty sketch (or the Blink sketch) with no hardware connected to the board, to see if it still happens.

  • Try measuring the power consumption, if possible, with a meter measuring the input through the 5V pin, if you have a 5V power supply you could use for this.

  • Are these genuine boards, or cheap clones from eBay?

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    – Nick Gammon ♦
    Commented Mar 14, 2016 at 0:51

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