I will agree that the fan does not serve ..
Obviously the fan laser cooling will connect to the main power as Leo60 said in the tutorial.
According to the images in fact thought that the negative take him to the ramps because common … but … correct me if I’m wrong … if the power of the laser (12v) I take the ramps from the town is the same so you do not need the second wire TTL-
I’m wrong? 🙂