PWM fan controller

Discussion in 'General Electronics Chat' started by arthur92710, Feb 26, 2008.

  1. arthur92710

    Thread Starter Active Member

    Jun 25, 2007
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    I need to be able to adjust the speed of my fans in the computer. I hear that PWM is an efficient way to adjust the speed of the fans. I need to adjust the speed of 4 fans. Is this a good circuit? Also is there a way to lower the number of components?
    [​IMG]
     
  2. SgtWookie

    Expert

    Jul 17, 2007
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  3. DC_Kid

    Distinguished Member

    Feb 25, 2008
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    9 components? not bad.
    http://www.allaboutcircuits.com/vol_6/chpt_6/9.html

    i think you need to choose the frequency carefully. i know for heavy inductor fans (automotive cooling fans) we drive them around 30Hz. pc fans may like to be driven at 100Hz, etc. experiment and see.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    If you look at the link to my simple PWM circuit, you would see that it has only six components not including the load, and all except for the power MOSFET are quite basic components.
     
  5. hgmjr

    Moderator

    Jan 28, 2005
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    Arthur, are your fans brushless motors? I think that many small fans such as those used in computers are brushless.

    If they are brushless, I don't know if PWM will work as well as a variable DC drive such as an one based in LM317.

    Sgtwookie, is that your understanding?

    hgmjr
     
  6. DC_Kid

    Distinguished Member

    Feb 25, 2008
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    the 9 had transistor driver in the count...

    6 or 9, does it really matter, still a low count of parts....
     
  7. arthur92710

    Thread Starter Active Member

    Jun 25, 2007
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    Yes they are brushless.
     
  8. SgtWookie

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    Jul 17, 2007
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    Actually, I'm not sure offhand. :confused:

    National's datasheet for the LM317 has a couple of switched-mode supply schematics. Those would be more efficient than simply using an LM317 by itself - but actually, a DC-DC converter would be more efficient than that.

    OTOH, one could always build a comparator circuit to control a MOSFET to keep the voltage across a cap in an approximate range. A stripped-down switching power supply, if you will.
     
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