Hi,
I have been working on an altimeter using a BMP 388 pressure sensor that logs data to a micro SD card. However I have encountered problems with my arduino microcontroller frying. I have fried two Arduino Nano 33 iot boards and have been unable to pinpoint the problem. The arduino's LEDs are still on but the port doesn't show up and I am unable to reset the board. My arduinos have broken when testing them on a 9 volt battery but after checking with multimeter I cannot see how I fried the board. I attached some pictures of my circuit and was wondering if anyone has any insight to why my boards are frying. Being a novice at soldering I was wondering if my bad technique could be to blame but take a look and tell me what you think, any suggestions would be welcome. Thanks!
Please provide a schematic diagram of your wiring. A design or wiring error can just as easily to be the cause, as a "soldering error".
Very hard to say , but try to wire with short lengths of wire and use more colours - keeping say black for 0v , red for 5v etc . Makes things much easier to check and avoids errors .
Have you taken the nanos off the board to check them ?
“9v” batteries do not last 5mins and may make you think there is a problem.
Avoid twisting wires together , it’s possible a bad connection here could damage your Nano ( eg if it loses supply voltage , but there is still voltage on another pin.
Not great but this is easier to fault find :
The wire being used is too large, not appropriate.
Use solid 30 AWG wire wrap wire.
Also, the solder looks suspicious 
Do you use liquid soldering flux ?
Here 28AWG (16 strands) is being used.
The most likely things to kill an Arduino are excessive voltage or static discharge.
Usually static discharge comes from your body... You walk across carpet (or something like that) and a charge builds-up on your body and when you touch something metal and you get a spark. But, you can damage electronics with a lower voltage that doesn't create a spark and that you don't see or feel. ...The chip just dies "for no reason" after you touch the circuitry
Shorting the voltage regulator output or an output pin can also burn-out a chip, but usually the components will survive and work once the short is removed.
Hi,
Do you know how I can avoid static discharge and tell if that is the problem I have been having?
Thanks
Hi,
I don't have a schematic for my design but I followed Adafruit's tutorials for wiring the sensors and micro SD card slot. The BMP 388 uses an SPI connection and I attach the 9 volt battery directly to ground to VIN. Before I connected the battery everything was working fine, and now the USB port is not showing up.
Sure, but you can make one now.
One of the failure modes of the voltage regulators is shorting Vin to Vout.
Spec sheet says Vin 3-5V dc ........ 
adafruit-bmp388.pdf (2.7 MB)
Hi,
Are you using "Lead Free Solder"
Are you using header sockets to plug the 33 into?
If so, then check your connections with power OFF, BEFORE fitting the 33 with a DMM.
Then power the project up BEFORE fitting the 33, check your power supply pins.
When your are happy with the results, THEN turn OFF the power and plug the 33 in!
Using a circuit diagram, you should be able to see what your DMM readings should be BEFORE applying power.
Tom... 
And figuring it out from that menagerie sounds like a recipe for a headache! 
Hi,
Well now is the time to have one, so it can help you troubleshoot.
In fact reverse engineering your project might find your problem.
Tom.....
PS. Check all close joints for any shorting.
I have Kicad, should I use that to make schematic?
Hi,
I am using "Lead Free Solder" as well as header sockets to plug the nano into. I don't know what a DMM is but I will definitely try what you suggested in the future!
If you are comfortable with it, sure. Otherwise just make a pen drawing, take a photo and post that.
Digital Multi Meter
Right,that's a start.
Now join up which conductor goes where.
Show power supply and type.