Adding the bed fan

UnlikelyBarley

Adding the bed fan
February 14, 2015 01:19PM

Registered: 9 years ago
Posts: 6

Has anyone added the optional bed fan the the Mendel90? I have got hold of an appropriate fan, but have no idea how I might be able to connect it to the Melzi board. I'm aware that the Melzi has a single fan output, which is occupied by the extruder fan. I saw that nophead once did a hack on a Sanguinololu board to take an extra fan, is this also possible on the Melzi?

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QuackingPlums

Re: Adding the bed fan
February 14, 2015 02:07PM

Registered: 11 years ago
Posts: 369

Quite a few of us do I think, though we use a variety of different methods. I wire mine up to my Panelolu2 break-out board, which exposes FET switched headers for two additional devices - I use one for my bed fan and the other for 12V gantry LEDs. This is not the only way, but was convenient for me because I already had my Panelolu2.

There's a photo of mine on Thingiverse with my fan cowl for directing the airflow down onto the base of my printed objects here: http://www.thingiverse.com/thing:646973

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nophead

Re: Adding the bed fan
February 14, 2015 02:07PM

Admin
Registered: 17 years ago
Posts: 7,879

Yes very similar but a different expansion connector pin out.

Connect the source to the bottom outside pin of the expansion connector and the gate to the next but one pin above it. I.e. 0.2" away, which matches the pitch of the MOSFET. If it has a middle pin remove it and take the FAN- from the drain tab. Connect the FAN+ to the unused +12V terminal on the Melzi fan connector.

Turn it on with M42 P28 S255 and off with M42 P28 S0.

[www.hydraraptor.blogspot.com]

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Ralph.Hilton

Re: Adding the bed fan
February 19, 2015 06:24AM

Registered: 10 years ago
Posts: 439

I connected mine to the main +12 volt supply via a switch with a red LED to show when it is on. I only use it sometimes so a purely hardware solution seemed best for me.
If I am printing several things in succession I find it faster to swap the glass.

Edited 2 time(s). Last edit at 02/19/2015 06:26AM by Ralph.Hilton.

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D4RK1

Re: Adding the bed fan
March 21, 2015 10:06AM

Registered: 9 years ago
Posts: 73

Hi,

I also added the bed fan to my mendel90 and it works nicely, but every time I switch on the printer, the bed fan is started with it. Can I change that? And if yes, how?

I used the method described above for the sanguinolulo (and nopheads comments to apply it to the melzi)

Jens

*Edit* I just switched the printer off and on and the fan wasn´t running this time... weird

Edited 3 time(s). Last edit at 03/21/2015 12:54PM by D4RK1.

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Rich K.

Re: Adding the bed fan
March 21, 2015 10:51AM

Registered: 9 years ago
Posts: 254

Anybody have a photo or photos showing how to hook the bed fan up to an output on the Panelolu2 breakout board on the Melzi? Been wanting to do this for a while, but photos help me a lot more than simply describing it...

Edited 1 time(s). Last edit at 03/21/2015 10:57AM by Rich K..

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nophead

Re: Adding the bed fan
March 21, 2015 02:51PM

Admin
Registered: 17 years ago
Posts: 7,879

@D4RK1,
You probably need a gate pull down resistor between the G and S pins. Anything between say 10K and 100K would be fine to keep the MOSFET off before the pin is defined to be an output.

@Rich K,
The red wire bottom left is FAN+, the black wire on the P2 FAN-. M42 P28 S255 to turn it on, S0 for off.

P2_fan.JPG

[www.hydraraptor.blogspot.com]

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Rich K.

Re: Adding the bed fan
March 21, 2015 05:02PM

Registered: 9 years ago
Posts: 254

Thanks again, Nop! Will I also need a gate pull-down resistor?

Also, what controls the length of time it is on?

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nophead

Re: Adding the bed fan
March 21, 2015 07:43PM

Admin
Registered: 17 years ago
Posts: 7,879

The P2 adaptor already has a gate pull down IIRC.

It stays on until you turn it off. You can put a G4 dwell command in between the on and the off to keep it on for a specified fixed time.

With the later version of Marlin that Neil distributes you can wait for the bed to cool down to a specified temperature with M190 Rxx.

E.g.

M104 S0             ; turn off extruder
M140 S0             ; bed off
G1 E-1 F1200        ; extra retract
G1 X-100 Y100 F9000 ; y-carriage to the back
M106                ; carriage fan on
M42 P28 S255        ; bed fan on
G1 Z200 X-100 F9000 ; go to top
M190 R30            ; wait for bed to cool to 30c
M107                ; carriage fan off
M42 P28 S0          ; bed fan off
M140 S0             ; bed off
G1 Y-100            ; bed to front
M84 X Y E           ; disable motors

For older versions of Marlin replace the M190 with G4 P300000 to wait 5 minutes.

[www.hydraraptor.blogspot.com]

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Rich K.

Re: Adding the bed fan
March 21, 2015 10:17PM

Registered: 9 years ago
Posts: 254

Got it working! smiling smiley

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