I am interested in the same topic. Since my background is not in electrical engineering, I need a little more explanation than a diagram. In my instance, I want to control 2 fans synchronously (http://www.delta-fan.com/Download/Spec/ ... DE-F00.pdf
). These are 4pin PWM fans from a server. For testing, I am using a Pi3B+ attached to a breadboard with an external power source (PC power supply) for the fans. In the final configuration, I will be using a PiZeroW for a controller and the same external power supply. It would be nice to power the Pi from the external source as well since there is a 3.3v rail but that is a different topic.