So I've recently been playing with my first Arduino, until it, for some weird reason, stopped working.

What I did:

I had it attached to a breadboard. When I say attached, I mean it was supplying power to the breadboard. I was messing around with a motor, which wasn't performing very well when using the standard 5v output the Arduino supplies. So, I decided to buy some batteries - 10 AA batteries, to be precise. As I connected my battery back to the other side of my breadboard (there are two power input rows on my breadboard - one on the left and one on the right. (I thought) the Arduino was supplying power to the left input), I had completely forgotten that I had the two power input rows linked together with jumper wires. So I had the Arduino powering both the left and the right side rows of the breadboard. So all of a sudden, when I linked the battery pack to the right side row of my breadboard, my Arduino turned on. I was puzzled. When I finally realized the two power input rows were linked, I slapped myself.

Now, my Arduino turns on, but the code I had on it is no longer executed. And usually, when I turn the Arduino on, the "L" LED blinks twice. Now, it just turns on and stays on. The power outputs still work, as I still have power flowing through my breadboard. The reset button does nothing.

The Arduino IDE also no longer detects my board. Infact, my whole computer doesn't even detect it.

I know it was really stupid of me to supply 14+ volts to it, but I didn't do it intentionally. And, the only reason I used 10 AA batteries was because that's the amount my (only) battery pack required.

Bad news?

What do you guys think? Am I screwed? Is it fried?

  • \$\begingroup\$ WHERE did you plug in the 14v? To the VIN pins? To the 5v or 3.3v pins? \$\endgroup\$
    – Passerby
    May 4, 2013 at 23:50
  • \$\begingroup\$ The breadboard was attached to the 5v pin and the ground pin on the Arduino. That is the only way the two were connected. No digital or analogue pins were attached. \$\endgroup\$
    – user11047
    May 5, 2013 at 10:10
  • \$\begingroup\$ I did something similar only I have some spare chips and arduinos. After I got smoke I tossed a bootloader on a blank chip and. .. nothing led just sits there on. Hooked up pin 13 and gnd to an led, loaded the blink sketch on the chip and the external LED blinks. The on board led no longer blinks and is always on, but everything else seems okay. \$\endgroup\$
    – user50218
    Jul 27, 2014 at 21:08
  • \$\begingroup\$ I think you mean 15v. \$\endgroup\$
    – Wyatt Ward
    Jul 27, 2014 at 22:08
  • \$\begingroup\$ If you have arrived to this present thread, you should look into arduino.stackexchange.com . It's the stack dedicated to Arduino. \$\endgroup\$ Jul 27, 2014 at 23:16

3 Answers 3


The reality is that you most likely did fry it. We can think about it this way: you supplied much more voltage to it than it was designed to handle, and now it doesn't respond to your computer. What other possibility is there?

The question now is: what exactly did you fry? One thing that could very well be toasted is the ATmega328 chip. Whether you are in luck or not depends largely on whether you have an UNO with the SMD chip or the DIP ATmega328. If it is the former, and the chip is dead then you'll need to get a new Uno, unless you have advanced soldering equipment. If it is the latter you can buy a new ATmega328PU and replace it in your Uno, however, even in this case the solution isn't necessarily easy.

The problem is that you'll need to get a bootloader onto your new ATmega328PU, and without an Arduino or an ISP programmer this isn't easy to do. Fortunately, ATmega328PU with bootloaders already on them are sold on ebay for just a few more dollars than the bare ATmega328PU which runs about $3-$4.

It could also be the case that other (non-MCU) components are damaged either instead of, or (worse) in addition to the MCU: the USB interface chip, voltage regulators, or any of the many passive components that are directly connected to the +5 rail. The trouble is that even with a multimeter it may be difficult to assess the damage. For my money, the best option is to buy a new Uno and move on, however, if you are interested in a (potentially complicated) project, at least the schematics are available. So you would want to look at the schematic drawing and test at least every component that is connected to +5 and ground. Then you might want to test every component connected to those components, in case the blown out component shorted out something else. In the end you might have to test everything.

The alternative strategy would be to assume the best, and look, and maybe try to smell the damage, and replace one or two components that look suspect, and then pray for the best.

  • \$\begingroup\$ Right! So I've just ordered another Atmega - let's hope it does the trick. Thanks for your input! \$\endgroup\$
    – user11047
    May 4, 2013 at 21:00
  • \$\begingroup\$ But did you get one with the bootloader already on it? If not, you'll have to hack together an ISP programmer, which isn't that difficult, but something that will need to be done. \$\endgroup\$ May 4, 2013 at 21:02
  • \$\begingroup\$ I got this one: ebay.co.uk/itm/… = it does say that it already comes with the Arduino bootloader xD \$\endgroup\$
    – user11047
    May 4, 2013 at 21:03
  • \$\begingroup\$ Ok, good. I do worry that the USB intf might also dead, but lets hope that you are in luck! \$\endgroup\$ May 4, 2013 at 21:05
  • 1
    \$\begingroup\$ If the computer doesn't recognize the Arduino, the USB interface chip is probably dead aswell. Of course you can program Arduino using a USB-serial cable instead (or replace the chip). Just try and see how far you come, it is the best way to learn stuff. \$\endgroup\$
    – jippie
    May 5, 2013 at 9:49

Since you placed 14 (15? 10 * 1.5V Alkaline AA) volts on the 5v rail, you have possibly (Considering the Uno Rev3) damanged both ATMegas, a few capacitors, and two leds. The ATMegas both have a maximum voltage of 6 Volts on any pin, except the Reset pin, which has a maximum of 13 Volts. The capacitors are common ceramics, with no specific part number mentioned. They might be 6.3V, 10V or 16V maximum, so in 2 out of 3 cases, they would be fried.

There is also the possibility that the usb fuse has blown, you might want to check that with a continuity meter.

If neither the code already on the arduino is running, and it is not recognized by the computer, most likely, both ATMegas are dead.


You really should have only used 4 AA batteries - a USB connection provides 5V, and the voltage regulator works with 9V, but the fewer volts supplied, the fewer watts dissipated and the lower the heat. 6 volts is close enough to 5 and lower than 9, and would use fewer batteries.

Also, I think that it is most likely the little ATmega16u2/u3 is bad - that would be the small little un-socketed chip that interacts with the USB. It's possible both the 16u3 and the 328p are both bad, but the 328p is replaceable and the 16u3 isn't. If your computer doesn't detect it, it is definitely the 16u2/u3. The best thing to do now is to get another and not make that mistake again. get a new battery pack, (or do what I did and make one out of popsicle sticks, wire, solder, and electrical tape :) but that's dangerous.)