I'm actually not using it with a fan, I just said that to make explinations as simple as possible haha, but it didnt go that way.
What I want to do is have it control underglow led strips under my longboard.
I have made underglow under my longboard before with 12v led strips,
but i thought it would be cool to add a little extra.
What I want to do is have the tachometer pointed at the ground and vaguely detect the speed I am going and change the colour of the lights accordingly.