Arduino Nano Every gets VERY hot.

I bought 60 Arduino Nano Every boards from Arduino a few months ago. A couple of days ago one of them started smoking from the Atmel Atmega4809 chip. I contacted Arduino and they still have not responded. Today the same thing happened with another board. I contacted them again and am waiting for a response but do not think i will get it. The arduino was being powered by an external voltage regulator with 12v input and 4.95 output. I connected the USB cable for connection with the Serial Monitor. When i removed the cable the Arduino started smoking. I turned off all power to the Arduino. The board now would not take new code, does not work based on the code that was on the board and gets hot if i connect power of any kind. Today, the same thing happened without the smoke. I cut a usb cable and measured the voltage from my PC and it is at 5.05v. I actually burned my finger from a brief touch of the board and had to keep it on ice for 10 minutes. What is causing this?

Where did you power the nano with the 4.95 volts ? And was anything else connected to it ?

The power was at the 5vpin and gnd. Nothing connected just some 4.3k pulldown resistors. Btw i came to an agreement with arduino, they are going to replace them. You dont need to reply.

Hi, My name is Greg and I am Every smoker as well.

Here is what I did.

Powered the Every with Vin at 10V, 20V etc.

Plugged in usb, plugged out usb a couple of times. Or maybe the power supply with USB plugged. Then bing overcurrent protection on the 10V vin.

After a few attempts of resuscitation, I realized the board was smoked.

Did it a second time with another board. Same issue.

Here is what happened IMO:

My power supply is floating and it makes a real clean 10V, with high impedance.

THEN my raspberry (which I use to program) is connected to a standard raspberry usb wall plug. Floating as well.

(make a guess make a guess).

The USB potential and my lab power supply are both floating, not on the same potential. When I measure on VAC, I get like 80 to 110V (basically half mains). High impedance, but WAAAAY too much. My theory is that USB and external supply at the same time may kill the board.

At minimum you need to measure the voltages before connecting usb & external.

Let me know your thoughts... G

With my board an external voltage regulator was conncted to the 5v pin. When i disconnected the usb cable it started smoking. I contacted arduino and they replaced the 2 boards that failed.

The 5V pin is an output so you mustn't connect a 5V source there. Furthermore minimum voltage at the VIN pin for Every is 7V. Powering the board with both VIN and USB cable is one ot the quality checks in the manufacturing plants and you can safely do it

Actually the arduino can handle getting power from the 5v pin but only if it is stable 5v with the correct current capability.

Historically, you can power Arduinos via the 5v pin, as long as Vin was floating. The nano every has a new voltage regulator, and it’s looking like we don’t quite understand its limitations.

And that is what i did. If you dont mind, i would like to close this thread. It happened a long time ago and the arduinos were replaced.