I recently ordered and received a new part cooling fan (50mm) from Makergear.
I have an older 12V/19V machine and I received a fan with a 12V label, as I requested.
However, when I try to use the fan, I get zero fan speed until I'm above a command of about 250, then I get full fan speed.
I must be missing something obvious here, any thoughts?
New 50 mm cooling fan has no modulation
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- Posts: 34
- Joined: Mon Apr 14, 2014 4:09 am
Re: New 50 mm cooling fan has no modulation
Mount,
Some brands of fans are not very tolerant of PWM speed control. These little fans have electronics in them to control commutation (reversing polarity of the magnetic field) --- that's how brushless DC fans work without brushes... On some, the electronics are happy to receive pulsed DC --- some are happy IF the pulsed DC is at or below certain frequencies --- and some are not tolerant of it at all.
The firmware on the M2s from the 12V/19V era (mine was a late one, received April 2013, a few months before the switch to all-24V) is set up with a fairly high PWM frequency -- somewhere above 20 kHz, so it won't be audible (to humans, anyway). I have seen some fans that won't run on that with a setting of less than about 220 / 255.
The newer Marlin firmware source code has a #define macro that lets you select a configuration for slower PWM --- about 400 Hz. I've found that every fan I've tried with 400 Hz PWM works fine and can be speed controlled down to about 25% (64/255). I actually got an Arduino and a motor shield to test this and was merrily collecting data when my cheapie laser tachometer stopped working. Got a new laser tach, but haven't had any time lately to test fans, or print for that matter...
By the way, with the PWM at 400 Hz, none of the little 40mm and 50mm fans I tested really "buzzed" audibly at all. The sound of the fan was pretty much the same -- all you hear is the impeller pushing air, no power supply noise at all.
Long story short: there's a firmware solution for better fan speed control. I'm not on my printing PC right now to find where I got it, but searching this forum for "PWM" and "Marlin" should get you the articles where we discussed this and a link to the firmware (probably at github).
Dale
Some brands of fans are not very tolerant of PWM speed control. These little fans have electronics in them to control commutation (reversing polarity of the magnetic field) --- that's how brushless DC fans work without brushes... On some, the electronics are happy to receive pulsed DC --- some are happy IF the pulsed DC is at or below certain frequencies --- and some are not tolerant of it at all.
The firmware on the M2s from the 12V/19V era (mine was a late one, received April 2013, a few months before the switch to all-24V) is set up with a fairly high PWM frequency -- somewhere above 20 kHz, so it won't be audible (to humans, anyway). I have seen some fans that won't run on that with a setting of less than about 220 / 255.
The newer Marlin firmware source code has a #define macro that lets you select a configuration for slower PWM --- about 400 Hz. I've found that every fan I've tried with 400 Hz PWM works fine and can be speed controlled down to about 25% (64/255). I actually got an Arduino and a motor shield to test this and was merrily collecting data when my cheapie laser tachometer stopped working. Got a new laser tach, but haven't had any time lately to test fans, or print for that matter...
By the way, with the PWM at 400 Hz, none of the little 40mm and 50mm fans I tested really "buzzed" audibly at all. The sound of the fan was pretty much the same -- all you hear is the impeller pushing air, no power supply noise at all.
Long story short: there's a firmware solution for better fan speed control. I'm not on my printing PC right now to find where I got it, but searching this forum for "PWM" and "Marlin" should get you the articles where we discussed this and a link to the firmware (probably at github).
Dale