Photos and Screenshots: https://i.sstatic.net/NazA6.jpg

By the way, I used a screenshot that was originally from this post: Have I bricked my Arduino Uno? Problems with uploading to board

Hey guys,

I was trying to wire two TEC1-12706 Peltier plates to my breadboard, and I saw that using the USB connection for power was not enough for both plates. So, I found a 19v--3.9A DC/AC adapter/computer charger and plugged it in to my Uno via the Power Jack port. The Peltier plates were not wired to the board when I plugged it in and everything looked fine, all the normal LEDs on the UNO lit up, etc. Then, I wired a peltier plate to my breadboard. As soon as I did, a part exploded, and grey smoke come out of the "L" light area. I unplugged it immediately. The next day, I plugged the adapter back into the Power Jack port and a screenshot is attached of some observations I made by touching the board. Photos of my Uno are also attached. As you can see, the "Slightly less hot but still burning part" is pretty much destroyed. The "L" light will not light up and as of right now I can't upload any code to it. Might be an unrelated issue so I will continue troubleshooting that, but it is still another observation. The test LED I wired is lit up, so I guess the board can still kinda function? I'm high school student and obviously a complete beginner. Will continue to do research on this. I really want to know what happened. Please help? Thanks everyone.

  • 1
    Certainly you've blown your 3.3V regulator - probably by blowing the 5V regulator and pumping 19V straight into the 5V section of the board. It's toast.
    – Majenko
    Feb 5, 2021 at 23:02

1 Answer 1


You did a pretty good job of nuking your board. Gratz.

Basically what has happened: you connected 19V to the input of the 5V regulator (rated at 800mA max) and connected a 12V 50W device to the output.

I have no idea what a peltier will do when under powered, but at 12V it's going to want about 4A. That's 20x more than the 5V regulator can provide (also exacerbated by the massive amount of heat needed to be dissipated to drop 14V) - so it went pop.

In going pop it short circuited. That meant that 19V (or just short of) ended up going into the rest of your Arduino. The 3.3V regulator didn't like that (the bit that looks toasted), and neither will any of the rest of the components on the board.

In short: probably almost every component on the board has been nuked.

The moral of this story: don't connect high powered 12V devices direct to the Arduino. Things like peltier devices need their own dedicated power supply which can be controlled (as you would a motor or relay) through a power MOSFET.

  • Thanks so much man! This makes alot of sense. You think there's any way of salvaging the board? Appreciate your response.
    – czhang07
    Feb 6, 2021 at 0:23
  • There is no financial benefit to trying to fix it. The only benefit would be that you know how to fix it. If you fancy learning about component level diagnostics and testing then this could be a fun project. If you just want a working Arduino as cheap and easily as you can, then buy a new one.
    – Majenko
    Feb 6, 2021 at 0:29
  • Definately will be a Spring Break project for me when I'm finished school. Again, thanks man!
    – czhang07
    Feb 6, 2021 at 2:15
  • Quick question- if the regulator can supply 800mA and the peltier needed 4A, wouldn't the peltier just been underpowered and nothing happens?
    – czhang07
    Feb 6, 2021 at 6:58
  • Not with 19v going into the regulator. Yes it would be under powered for a while, until the regulator melted...
    – Majenko
    Feb 6, 2021 at 8:37

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