Nano Every USB + 12V VIN burn out during sketch upload

I had a nano power regulator blow out when I tried uploading a sketch while I was supplying 12V to the VIN pin and had the USB plugged in at the same time. I realized I had two normally open reed sensors wired to ports D18 and D19 (respectively the SDA and SDL ports) as pull-up resistor inputs. Before I plugged in 12V to VIN and just was powering my set-up via USB things worked fine. That is to say my sensors did their job and a light wired through D2 went on to indicated when either sensor was active. Then when I tested my set-up with 12V to the VIN alone I noticed my lights were going on when the sensors should have been open. I plugged in the USB and tried uploading a correction to the sketch, the upload process wasn't working and before I could do anything I started smelling hot electronics. After some time and investigation I realized I didn't have my sensors wired to proper input pins. I rewired my circuit with a new NANO Every and everything works fine under 12V power.

Here's the thing I'm scared to upload a sketch or even plugin the USB while 12V power is being supplied via VIN. Should I be? Did I only have a problem because I uploaded a sketch while I had the SDA and SDL ports coded as pull-up resistors? Is it best practice to just cut-off any unregulated power to the board when uploading a sketch in general?

-RG

Why are you using 12V? Get a 5V supply.
I use these in a lot of projects when 12V is not used elsewhere in the project.

I'm using 12v because I'm also controlling a stepper motor and using the available power from the supply and don't want more wires than necessary. Also, the NANO doesn't have 5V plug-in for that wall wart, are you suggesting plugging it into the +5V pin? I need that to power another board for RS485/MODBUS communication, without having to split up more wiring.

-RG

The Nano Every has a nice little switching regulator module that SHOULD do a lot better than previous efforts.
But it seems to have some failure modes that aren’t well understood yet :frowning:

It just seems to me that this is the key:

ryangrg:
After some time and investigation I realized I didn't have my sensors wired to proper input pins. I rewired my circuit with a new NANO Every and everything works fine under 12V power.

Maybe the switches weren't open and were shorting something out on the board. "Best practice" is to double check all wiring before applying any power.