Accessing the RPM sensor on a pc fan

This one is almost too simple, but it might come in handy. It turns out that Pabst fans (and probably several others) already have the circuitry for RPM monitoring. Pop it apart allow pcb access and add your own RPM sensor lead to the PC board. Not all fans will have it, but it’s a safe bet that it’ll have an RPM sensor instead of a rotor lock indicator on the common PC board component.