PWM Trouble with PC Fan

Discussion in 'General Electronics Chat' started by tony48, Mar 1, 2014.

  1. tony48

    Thread Starter New Member

    Jun 11, 2013
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    Hello,

    I'm trying to use a PWM controller to control a 12v PC fan. When I wire it up, it controls the fan as expected but there is a loud squealing noise coming from the fan that changes pitch when I change the fan speed. Can anyone help me understand why this is happening and hopefully fix it?

    Here's the PWM unit I have:
    http://www.amazon.com/LEDwholesalers...1&keywords=Pwm

    Thanks very much!
     
  2. shteii01

    AAC Fanatic!

    Feb 19, 2010
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    The blade might be unbalanced. When the speed changes, the blade wobbles and hits the fan frame.
     
  3. spinnaker

    AAC Fanatic!

    Oct 29, 2009
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    Bad bearing in the fan? Can you take the fan apart and get to the bearings? Perhaps a bit of lubricant will get rid of the squeal for a while.
     
  4. tony48

    Thread Starter New Member

    Jun 11, 2013
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    The sound is not present when I run the fan without the pwm circuit. It is a distinctly electrical squealing sound
     
  5. BillB3857

    Senior Member

    Feb 28, 2009
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    The base frequency of your PWM circuit may be in resonance with the fan producing the sound. Can you change the base frequency to something higher or lower?
     
  6. tony48

    Thread Starter New Member

    Jun 11, 2013
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    I'm kind of inexperienced and not sure how to do this
     
  7. tony48

    Thread Starter New Member

    Jun 11, 2013
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  8. #12

    Expert

    Nov 30, 2010
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    That's not a chip. It's a completed module. If you're going to change the frequency, you're going to have to dig inside the box and find out how it's made.
     
  9. THE_RB

    AAC Fanatic!

    Feb 11, 2008
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    12v PC fans only use about 50mA to 100mA, you can fix this by putting a resistor between the module and the fan. And a large cap (1000uF) across the fan wires. A resistor of 10 ohms should do it.

    An inductor can work better than the resistor but is harder to find and can cause other issues.
     
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