Arduino heating up

Hey everyone,

I'm pretty new to Arduino, so I apologize in advance if there's a really simple answer out there that I wasn't able to find. :slight_smile:

I've been using my Arduino mainly to test LED's and other small components, so I've kept it plugged into my laptop without any issues until now. Recently, I built a project using a receipt printer (Hello Printer), so it was necessary to plug the Arduino (connected to an ethernet shield and the printer) into a wall socket. Almost immediately, both boards began to heat up to the point where it hurt to touch. I unplugged it as quickly as I could, and there didn't appear to be any damage. My first thought was that I was using the wrong adapter, so I checked and confirmed that it is a 9v AC-DC adapter. My next thought was that the printer was using too much power, so I unplugged it and tested a simple LED blink program. That made the Arduino and the ethernet shield heat up as well. Finally, I tried the LED blink program in a different socket, only to have the same results. I am aware that it's normal for the board to heat up slightly, but this seems a little extreme.

What should I do? I'm all out of things to try.

Thanks in advance!

Have you tested it without the ethernet shield attached?

Yes. I've the blink program with and without the ethernet shield.

If the '328 chip gets hot all by itself, (nothing else attached) that's usually a good indication you have an output pin or several.
Only a matter of time until it fails.
Get another chip before your current one dies.

Or is something else getting hot?

same when using usb power?

Power source doesn't matter. If the ATMega chip gets hot, that's usually a good indication you have an output pin or several are damaged.

The Ethernet shield will get hot. It will also cause the Arduino's on-board regulator to get hot when powered through an external adapter. The chips tolerate more heat than your finger tolerates. So "hot to the touch" isn't necessarily a good measure of "too hot."

As CrossRoads points out, if nothing is attached and the ATmega328 gets hot, then it is damaged.