Hello
I've recently experienced a magic smoke episode that I'm not able to explain myself. Hopefully somebody else can help!
I was using DJI guidance system. Which is a board that does on-board image depth calculations and spits out the images via USB.
I was also using Beagle Bone Black(single board computer).
The DJI guidance system requires external power in the 12-24V range, which I provided with a 4cell LiPo battery.
The Beagle Bone can be powered with a mini-USB (5V 2A recommended).
When the Beagle Bone was powered from my laptop USB, while I've had the DJI guidance system connected to the 4cell LiPo, as well as with a USB to the Beagle Bone with no problems whatsoever (communication between those two working and everything).
Then I've powered the Beagle Bone with a variable power supply, which also has a 5V 1A USB output "for phone/camera charging". The Beagle Bone still worked just fine - however, when I've connected the DJI guidance system (which was already connected to the 4cell LiPo) to Beagle Bone (trough the USB, for communication purposes) a lot of smoke came out of thee DJI system. In the process the 5V usb cable from Beagle Bone to the DJI system also got very hot.
After the episode both boards were appeared to be not working. My initial investigation shows that the micro usb power input on the Beagle Bone was burned (the plastic inside the socket). Opening the DJI systems shows an obviously blown diode, but nothing else.
My own theories:
Some kind of ground/earth loop short
None of the equipment was every earthed (not the computer with everything working, none the 5V power supply)
The 5V power supply failing
This seems to be the most plausible option for me. Maybe I drew too close to the 1A max of the output, which cause it to over-voltage the 5V output? Or maybe short it? Is that even something that happens?
My next steps are to hook up the power supplies 5V output to different resistive loads (20mA -> 1A), and look at the output with a scope.
I hope somebody can help me with this detective work! Maybe I'm missing something?