If I wanted to make a USB desk fan from a spare CPU fan (input: 12V, 0.15A), could I just solder a resistor to the positive lead of the USB wire? I plan on getting an adjustable voltage booster, but I was curious if this was possible. I think I would need a 13 ohm resistor for USB 3.0.
usually fans have a min start voltage. u can try if your fan starts at 5v and if the resulting RPM is ok for you, just solder it without any resistor on USB
I actually tried that and it moved a little, then stopped.