I have did something stupid.. I connected 10K Ohm potentiometer at its maximum value PARALLEL with a LED. The positive long leg of the led to arduino 5v and the negative leg to the GND. After giving arduino 5v from USB Mobile Charger ( Output: 5V , 1A ) I smelt a burn and quickly removed the charger from the outlet. I waited a few hours and connected the arduino ( without any components ) to the charger again. and the arduino worked. I then connected it to the PC and uploaded the blink sketch of the on-board led and it worked ! Then I uploaded a sktech for blinking led on other pins and it worked also !

My question is: 1) What is damaged on the board ? The smell is near the regulator but I'm not sure if it's from the regulator itself or just a component near it.

2) Can it be safe to still using the arduino board on USB Power or Battery Power without any problems ?

  • 1
    One can only speculate, especially with regard to the current condition, but it's likely that either F1 was activating or T1 was getting hot. Excessive current consumption can be a result from past damage, however it is also quite possible that the reset behavior you see with a 9v battery has nothing to do with this incident, and everything to do with the fact that 9v batteries are very weak and a poor choice for powering an Arduino. Jul 17, 2017 at 15:07
  • I think it probably did not damage any components, and the smell probably came from the plastic that started to burn because of the high current, but for sure if you left a little more, something could have been damaged. To be sure only by testing component one by one. Jul 17, 2017 at 15:09
  • @ChrisStratton I didn't understand what F1 and T1 are ? I don't use batteries for powering my arduino but just wanted to test the external power. You may be right about the 9v battery, but what about the burn smell ?
    – Youssef13
    Jul 17, 2017 at 16:57
  • @AndrewPaes What plastic part do you mean ? on the board ? I don't know how can I test component. I don't even have voltmeter and such measuring tools. :( But the smell is from the regulator or just something near it. I can't determine.
    – Youssef13
    Jul 17, 2017 at 16:59
  • Could it be that the reverse polarity diode failed closed with high resistance?
    – Avamander
    Jul 17, 2017 at 20:09

1 Answer 1


That burn is likely the smell of the potentiometer, not the arduino. I would check the arduino with a multimeter set to resistance to make sure that the Vin trace resistance is nominal.

  • No. the smell isn't from the potentiometer. the smell was from the LED and the board itself. I can smell it when I get near to the regulator but not sure if it's from the regulator itself or something near it.
    – Youssef13
    Jul 17, 2017 at 17:00
  • @Youssef13 what voltage are you feeding the arduino?
    – tuskiomi
    Jul 17, 2017 at 17:01
  • I used a mobile charger that outputs [ 5V - 1A ] into the USB port ( the same port is used to connect arduino to PC for programming ) If that has nothing to do with the regulator then the smell is just near it. It's away from the microcontroller the the pins
    – Youssef13
    Jul 17, 2017 at 17:03
  • @Youssef13 do you have a multimeter?
    – tuskiomi
    Jul 17, 2017 at 18:35
  • Unfortunately, I don't have one :(
    – Youssef13
    Jul 17, 2017 at 19:10

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