Need help: how to control cooling fan by the 12V-aux pin

Dear All,

I recently tried to use the 12v-aux pin to directly connect a cooling fan (please see attached picture for the pin that I used), since D8, D9, D10 have been used for extruder 0&1, heat bed. But I found that I'm unable to control the fan on/off by sending M106 S0 or M107 command in Pronterface. The fan is always on. The firmware I used is Marlin, I set the motherboard to 34 (RAMPS 1.3 / 1.4 (Power outputs: Extruder0, Extruder1, Bed)), and all else setting is default setting.

Can anyone help me to figure out if the 12V-Aux pin is able to control the cooling fan, and if yes, how should I do to make it work? Any suggestion is greatly appreciated. Thank you!

No, that's unswitched power. If you want to control a print cooling fan you will need to add a mosfet to a spare digital pin (the servo connector is ideal, pins 11, 6, 5, 4) and configure the firmware to use it.

Thank you for the answer. I get confused by the website here [makerdev.com]
saying that using that pin to control cooling fan.

That's exactly the sort of thing you need - it's the mosfets to connect to the servo pins and control the fans. It needs a source of 12v power for the fans, so they chose to take that from the 12v aux connector.

Thank you so much! Now I understand.

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JamesK
No, that's unswitched power. If you want to control a print cooling fan you will need to add a mosfet to a spare digital pin (the servo connector is ideal, pins 11, 6, 5, 4) and configure the firmware to use it.

Will D9 work for print cooling with out any changes to the firmware? I'm currently using D9 for extruded fan (extruder auto fan on pin 9).
It's nice to have the extruder fan go off automatically when not needed, but I'm willing to bare the noise if I can get automatic cooling for the print.

One solution that gets both automated is leave the extruder fan as is and use this simple mosfet circuit to run a cooling fan for the print.
[www.instructables.com]

This guide uses a different board so I'm unsure how to connect it and what lines do I have to change in firmware.

Quote
Backdraft
Will D9 work for print cooling with out any changes to the firmware? I'm currently using D9 for extruded fan (extruder auto fan on pin 9).
It's nice to have the extruder fan go off automatically when not needed, but I'm willing to bare the noise if I can get automatic cooling for the print.

One solution that gets both automated is leave the extruder fan as is and use this simple mosfet circuit to run a cooling fan for the print.
[www.instructables.com]

This guide uses a different board so I'm unsure how to connect it and what lines do I have to change in firmware.

I think D9 is the 'normal' connection for the part cooling fan for ramps with a single extruder, but if you've redefined it to use it as the cold end auto-fan switch then you would have to change the firmware back again. Fans don't take a lot of current (at least not the ones we're using for print cooling), so it's easy enough to get suitable mosfets to drive them. I put four mosfets on a scrap of stripboard and connected them to the servo connector: [forums.reprap.org]

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JamesK

Quote
Backdraft
Will D9 work for print cooling with out any changes to the firmware? I'm currently using D9 for extruded fan (extruder auto fan on pin 9).
It's nice to have the extruder fan go off automatically when not needed, but I'm willing to bare the noise if I can get automatic cooling for the print.

One solution that gets both automated is leave the extruder fan as is and use this simple mosfet circuit to run a cooling fan for the print.
[www.instructables.com]

This guide uses a different board so I'm unsure how to connect it and what lines do I have to change in firmware.

I think D9 is the 'normal' connection for the part cooling fan for ramps with a single extruder, but if you've redefined it to use it as the cold end auto-fan switch then you would have to change the firmware back again. Fans don't take a lot of current (at least not the ones we're using for print cooling), so it's easy enough to get suitable mosfets to drive them. I put four mosfets on a scrap of stripboard and connected them to the servo connector: [forums.reprap.org]

Ok thanks for the info.

Can you tell me (or point to a guide) how the pins need to be configured in the firmware if I were to use a mosfet to drive a print fan? I've been scrolling the pins.h, but it gets confusing with all the different boards. I'm new at this and don't want to blow up anything.

I use repetier firmware and it's as easy as selecting Digital pin 11 (or 4 or whatever) from a drop down list in the online config tool, in the extruder section, field "extruder cooling pin". I don't remember if Marlin has the same function or not.

Edited 1 time(s). Last edit at 03/27/2016 12:50PM by JamesK.

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JamesK
I use repetier firmware and it's as easy as selecting Digital pin 11 (or 4 or whatever) from a drop down list in the online config tool, in the extruder section, field "extruder cooling pin". I don't remember if Marlin has the same function or not.

Ok I'll try to figure it it out. I'm more familiar with Repetier, but I'll stick with Marlin since I'm a noob and don't want to start experimenting just yet.