Optional Bed Fan wiring

Hi,

i decided to install an optional Bed Fan to speed up the cool down period after the finished print. On the linked Site in nopheads post [www.hydraraptor.blogspot.de] is described, that the +12v and GND wires should be connected to the pins on the board. But the description is for sanguinololu. It looks like the VCC pin on the Melzi pin terminal only supports +5V.

So i took a look and noticed, that there is the unused +12V screw terminal for the extruder fan. Would it be a good idea to connect the Mosfet for the bed fan to the +12V screw terminal for the extruder fan and the GND wire to the pin terminal or could this cause any interferences? Or should i conect it to the +12V and GND inputs for Melzi? I rather wouldn`t do that because the wires on the input terminals are already a tight fit.

What would you suggest is the best way to wire the bed fan?

The fan control signal and ground come from the Melzi 10-way expansion header (pin 6 and pin 10 respectively to use P28 for control).

+12V can be taken from the unused FAN+ screw terminal on the Melzi and this connects to the fan red wire. The fan black wire will connect to the MOSFET Drain pin.

Note that the MOSFET switches the ground end of the fan not the +12V end.

Consult the Melzi circuit schematic if you have any doubts about this and be very careful to check your wiring is correct. A damaged Melzi is expensive to replace.

Regards,
Neil Darlow

Edited 1 time(s). Last edit at 10/21/2013 07:31AM by neildarlow.

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Printing with Mendel90 from fedora 25 using Cura, FreeCAD, MeshLab, OpenSCAD, Skeinforge and Slic3r tools.