Electronics Fan control by parallell port

Discussion in 'Modding' started by thrust, 3 Feb 2003.

  1. thrust

    thrust What's a Dremel?

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    Hi!

    I want to be able to control the speed of the fans (CPU and GFX), since i rarely do anything that uses the full power of the CPU and the graphics card, i thougt of building a software controlled fan control.

    I don't know so much about electronics, but my goal is to at least turn the fans on and off with the parallell port, or if possible to have some kind of speed selection. First i was thinking of using some opto-swithces, but i believe that these can't handle the "high" current that the fans need. Anyone have a better idea?(The construction should not be too expensive)


    Thanks in advice,

    Oskar
     
    thrust, 3 Feb 2003
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  2. linear

    linear Minimodder

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    Welcome to the boards.

    You have definitely got the right idea.

    Regular old transistors would make good switches in this application. Something like a TIP31A would be inexpensive (< 1 Euro) and can handle a 3A current.

    However, I'd be really really nervous about software failure causeing the premature death of these critical components. If you want to control lighting, go right ahead, but having the CPU fan controlled by software that depends on the CPU to run, that's not a good design.
     
    linear, 3 Feb 2003
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  3. thrust

    thrust What's a Dremel?

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    Thanks for the reply,

    I've been trying to investigate the possibilites, the goal is to control the speed individually of four 12 volt fans through the parallell port.

    It's getting more and more advanced, my plans so far is this (no schematics yet)

    LPT -> OptoSwitches -> Quad-Serial D/A converter -> Amplifcation? -> Four Fans

    I havent found any serial D/A converter with four "channels" that (as I understande the specs) can handle more than 50mA, so i need some kind of current amplification. Am I right, and what would be the best solution, using transistors or OP-amplifiers?


    Thanks in advance,

    Oskar
     
    thrust, 14 Feb 2003
    #3
  4. cpemma

    cpemma Ecky thump

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    Have a look at the DiscoLitez pages, they have several schemes for switching lamps on that may well be adaptable.

    Speed control by software gets a bit harder, if you've got the right chipset something like Speedfan (google) may work for you, or this lad is doing it with a PIC. :geek:

    linears TIP31A may do, but it's only low gain (10@1A) so may suck too many mA out of your DAC if you give it any work to do. A more modest 2N2222A should run a single small fan, or the old favourite TIP122 darlington will run a case-full.
     
    cpemma, 14 Feb 2003
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  5. thrust

    thrust What's a Dremel?

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    Thanks for the replies. I've been trying to develop something on my own, and because my electronics knowledge suck i haven't succeeded... yet.

    Im trying to control a MAX534 (8Bit quad-serial D/A converter) via the parallel port.

    The problem is that i don't know if my hookup are wrong or if i have misunderstood SPI. (The hookup is most probably incorrect, since i dont understand everything in the datasheets)

    [​IMG]

    I am trying to measure the voltage over the resistor, but so far nothing.

    Should Analog and Digital GND be connected to eachother?

    Oh. And one question about SPI... Can it "time-out", or can i send data at a really slow speed?


    Any help would be appreciated

    /Oskar
     
    thrust, 4 Mar 2003
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