How would you make a rheostat to support 2-3 Delta 120x38mm TFB1212GHE fans?

Discussion in 'Electronics' started by BurntToast, Mar 2, 2005.

  1. BurntToast

    BurntToast 2[H]4U

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    Can anyone give me any ideas? I would rather build my own that to purchase one, but even if I did want to purchase one I doubt that there would be a bay bus on the market to support these fans. I guess that it would also be recommended to get an ATX2.0 PSU and to dedicate one rail to all of the fans and accessories.

    Specs:
    120x120x38mm
    220.01 CFM @ 4600 RPM
    65.0 dBA
    29.40 watts
    2.45 amps
    Maximum Air Pressure 26.44 mm H²O
    12v DC


    I want to control these fans so that I can sleep at night. Then when I go to a LAN I can crank them up and have the noise drown them out.

    I won't be using these fans just yet, I will be waiting until I do my next upgrade. And I hope that will be to a dual core AMD. Then I will buy a PCP&C 510w or Zippy/Emacs 600wPSU or what ever is on the market at the time. I wouldn't trust my current PSU with these suckers. I need a new one as it is :p

    Thanks!
     
  2. BurntToast

    BurntToast 2[H]4U

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  3. xonik

    xonik [H]ardForum Junkie

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  4. BurntToast

    BurntToast 2[H]4U

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    So that would work with a unit that draws a constant 7.35amps, yet uses 15amps when warming up?

    Also, I am a utter n00b at electronics. Would you happen to have a photo of the top and bottom of the unit for me to take reference. As well as a part sheet?

    I'm that n00b.

    Thanks
     
  5. xonik

    xonik [H]ardForum Junkie

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    Oh, I didn't see the "one rail" requirement. Back to the drawing board...
     
  6. joecool234

    joecool234 Limp Gawd

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    Off topic, but you should add some wings to your case...it'll have no problems taking off!!!
     
  7. cpemma

    cpemma Limp Gawd

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    For those fans, a PWM design is best. Linear controllers, like the MIC29032 design, will need a massive heat sink; with 30W fans at 6V, the heat produced from each is around 7.5W.

    Several here to pick from, the IRF530 MOSFET shown will handle 14A, but a BUZ71 or IRF640 instead will cover 18A.
     
  8. mattg2k4

    mattg2k4 Gawd

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    65 decibels? That is freaking loud!

    If you don't mind using multiple rails and don't need full adjustability, a 12v/7v/off controller would be extremely simple.

    PWM is much better than any solution which dissipates power as heat because you'd be dissipating many watts of heat. It is fairly simple to use 2 555 timer chips or one 556 dual timer chip, a few resistors and capacitors, and a potentiometer to drive a mosfet for PWM, but a dedicated chip would probably be simpler.

    The gist of the 555 timer circuit is the first chip is run astable at your switching frequency (probably 20khz or higher so it's inaudible), and it triggers the second one which is wired monostable, and by adjusting how long the second one stays on you can drive a mosfet at varying duty cycles. I know I've seen a guide online, if I figure out where that was I'll post it.
     
  9. cpemma

    cpemma Limp Gawd

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    This kit's documentation download gives a 556+mosfet circuit and some tips.
     
  10. joecool234

    joecool234 Limp Gawd

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    I just remembered that way back in the day a forum member, er...god, uller posted some very useful info about PWM control of fans.

    http://casemods.pointofnoreturn.org/pwm/

    A little peak should provide you with most of the basics for a PWM fan controller.