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Fan only runs at full speed on Marlin

Posted by Wisar

Wisar

Fan only runs at full speed on Marlin
April 21, 2014 02:32AM

Registered: 10 years ago
Posts: 82

I have a Prusa I3 that I am driving with Marlin. I have a cooling fan mounted on the extruder assembly but am unable to get it to run at other than full speed. I use slic3r to generate G-code and can see the M106 S99 command but it is being ignored. At the console I can get the fan to run but only if I exclude the S99 (speed) part of the command. Without the speed component the Marlin code defaults to full speed (PWM 255). Any ideas?

Regards

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waitaki

Re: Fan only runs at full speed on Marlin
April 21, 2014 06:29AM

Registered: 11 years ago
Posts: 1,592

Where is the fan wired to?

_______________________________________
Waitaki 3D Printer

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Wisar

Re: Fan only runs at full speed on Marlin
April 21, 2014 07:20AM

Registered: 10 years ago
Posts: 82

Doop! Crucial missing data. D9 on a RAMPS 1.4 board...is that just a 12V supply? How should it be wired?

Thanks

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Dust

Re: Fan only runs at full speed on Marlin
April 21, 2014 09:03AM

Admin
Registered: 13 years ago
Posts: 7,001

d9 is PWM capable

unfortunately not all fans are able to be PWM....

But some just require full on to start then you can reduce it after

try a m106 s255 then a m106 s128. see if it will do that

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Wisar

Re: Fan only runs at full speed on Marlin
April 21, 2014 01:52PM

Registered: 10 years ago
Posts: 82

Starting at full speed then issuing a second command for a slower speed results in the fan turning itself off! I have another fan that I will try ...or...I will try hooking up the fan that I want to use to another motor driver and see if it plays with PWM. In the meantime I am printing a fan duct to try and force the air flow where I want it and vent some of the 'extra' to where it does not matter.

Cheers,
Wisar

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Dust

Re: Fan only runs at full speed on Marlin
April 22, 2014 02:07AM

Admin
Registered: 13 years ago
Posts: 7,001

Some people have had good success with putting a small capacitor across the fan terminals, mentioned [forums.reprap.org]

also [blog.arcol.hu]

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Wisar

Re: Fan only runs at full speed on Marlin
April 22, 2014 02:37AM

Registered: 10 years ago
Posts: 82

Thanks Dust, will try that as soon as a couple prints of PLA stuff finish. Running the fan at 100% works for PLA but I need more control for ABS to keep the bed from cooling to the unstick point! Will post a result when I have one.

Cheers,
Wisar

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Wisar

Re: Fan only runs at full speed on Marlin
April 23, 2014 02:10AM

Registered: 10 years ago
Posts: 82

Capacitor did the trick. Seems to require an electrolytic capacitor of a reasonably low capacitance. E.g. 47uf worked but at a 1000uf the fan ran but at full tilt (without the capacitor it would not run at all unless asked to run at full). Did not seem to care about the voltage specification? In any case the fan now responds to the PWM speed command.

Thanks for the help,
Wisar

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Apex86

Re: Fan only runs at full speed on Marlin
July 27, 2015 12:51AM

Registered: 11 years ago
Posts: 3

Wisar, can you explain what you were trying to say about the different capacitor sizes?

Thanks!