my Melzi board has a fan connector on it for an additional cooling fan. How can i use it? Can i just connect it directly to my 12v fan because i dont see a flyback diode in the schematics?
Basically you can connect a fan, but be aware that if you use a laptop power supply adapter then the voltage is most probably 19 V. Larger fans (e.g. 80 mm) will probably resist, but small ones (e.g. 40 mm) may die rapidly. Don't bother about diodes