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Electronics => Projects, Designs, and Technical Stuff => Topic started by: daywalkerdha on March 27, 2013, 05:01:20 pm

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Post by: daywalkerdha on March 27, 2013, 05:01:20 pm
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Title: Re: Brushless DC Fan Speed Controller via PWM
Post by: SeanB on March 27, 2013, 06:37:18 pm
Just use 4 wire PC cooling fans, which are quite happy to run off 12V but have both a tacho output and a PWM input for speed control. Also available in a few sizes.
Title: Re: Brushless DC Fan Speed Controller via PWM
Post by: SeanB on March 27, 2013, 07:16:51 pm
Depends on the fan, use around 100Hz and it will probably do for most of them, and most will go to either a very low speed or off if you have the PWM low.
Title: Re: Brushless DC Fan Speed Controller via PWM
Post by: baoshi on March 28, 2013, 01:28:12 am
Hi daywalkerdha,

I made this a while ago. Since I do not have 12v rail I used a boost converter, controlled by a PWM. Output is 7-12V driving a Sunon 0.7W fan.

Bob
Title: Re: Brushless DC Fan Speed Controller via PWM
Post by: NiHaoMike on March 28, 2013, 08:41:10 pm
Quote from: daywalkerdha on March 27, 2013, 11:44:39 pm
Found this Pdf (http://www.formfactors.org/developer%5Cspecs%5CREV1_2_Public.pdf) which describes the/a spec for a 4 pin fan. If i can find a cheap fan somewhere around here, I'll do some tests.

But I really like the 60x60x10 Sunon MagLev fans and would prefer to use them. They aren't available with 4pin connectors. So if anybody can help improve my circuit, that would still help.
Some fluid dynamic bearings dislike low speed operation and wear out very quickly. I presume MagLevs might have the same problem. (Ball bearings should be fine.)
Title: Re: Brushless DC Fan Speed Controller via PWM
Post by: NiHaoMike on March 28, 2013, 10:19:13 pm
Quote from: daywalkerdha on March 28, 2013, 08:51:40 pm
In this datasheet (http://www.produktinfo.conrad.com/datenblaetter/175000-199999/183728-da-01-en-LUEFTER_DR_MAGLEV_12V_MB60101V1_0000_A99.pdf) it says that the fan supports operation from 4.5-13.8VDC
Quote
. DO NOT use power or ground PWM to control the fan speed. If the fan speed needs
to be adjusted, please contact Sunon to customize the product design for your
application.
I suggest a buck converter to derive a variable rail voltage. It can even be an open loop control.
Title: Re: Brushless DC Fan Speed Controller via PWM
Post by: smashedProton on March 29, 2013, 07:28:27 pm
I think that it looks good!  I didnt know that photodarlington transistors existed!  Your circuit looks nice, but you may run into a problem where one fan reaches a higher rpm than the other due to different resistances.  That problem will only get worse.  You could, however, create a second channel running off the same opamp with a different FET.  Maybe even use the sense pin on the brushless motor.