Sorry for the necromancy, but I thougth this was a better option than starting yet another thread on this.
I have and Arduino Leonardo¹ that controls a LEGO robot crane arm I built.
I need sufficient power for the LEGO motors. It’s not that much power actually, but more than the Arduino can supply.
I power the arduino trough an exteral adapter rated 12V 1.5A. The crane runs a demo program at the moment, and will operate with a limited AI once I can get the LEGO light sensor installed in a way that works with the rotating claw.
I want to be able to read data from, and write instructions to the Arduino using the USB interface (virtual serial interface).
However when I connected both external power supply and USB, I started to smell the characteristic smell of a frying PCB, and I quickly disconnected the power, before anything was permanently damaged.
Is there a safe way to connect an Arduino Leonardo to a USB interface without frying the board?
I doubt my laptop is connected to ground, since the anodised aluminium parts feel slightly electrified, and there are capacitive touch buttons above the keyboard.
The arduino is definitely not connected to ground, since the adapter has a non-grounded plug.
I am a software engineer that recently started dabbling in electrical engineering, so I am limited in my understanding of these things, and I thought it would be safer to ask, than to risk fry the board.
¹ Actually it is a BE² Board³
² Borderless Electronics (borderlesselectronics.org)
³ Which is built from the same Open Source hardware specification as the Arduino Leonardo, to ensure the specifications are identical.