People here seem to get worked-up about 9V smoke alarm batteries to power a UNO.
Not so the folks at MIT Fast-forward to about 13:50
The Arduino is powered by the laptop via USB.
The 9 V battery has a single wire connected to the near terminal.
Appears the MIT folks are smarter than you thought.
This topic was automatically closed 180 days after the last reply. New replies are no longer allowed.