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Thread: Fan voltage drop to 7v via resistor

  1. #1

    Fan voltage drop to 7v via resistor

    Here's the scenario: a friend has 2 x 120mm fans attached to the regular 12v molex connector, but he wants those fans to run@7v . He doesn't need more control than that (no switches, no rheostats pls), so which resistor should he use? Here are the fans' specs: DC 12v, 0.28A, 3.36w

    Before some1 asks, i've tested the fans with 7v feed, they do fine.

    thx for the help.

  2. #2
    The Main Man Dewayne's Avatar
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    Fan voltage drop to 7v via resistor

    Easy...take the 5 VDC power to one lead of the fans and then take the 12 VDC to the other lead.
    What this does is give you voltage difference between the 2 above voltages....12-5=7

    This will give you the 7VDC needed.

    I used this same principles to get multi voltages for my test PSU...

    http://modders-inc.com/how-to-story--4.html

    and a 12VDC/7VDC switch.


    This ONLY works with DC VOLTAGE!

  3. #3

    Fan voltage drop to 7v via resistor

    Yeah, i've used the 7v trick for single fans, wasn't sure if the power drawn from 2 x 120mm fans would be too much for it. I'll give it a try maybe tonite on my (250w i think) test psu

    btw, any chance we could have something like the old LED calculator? was very useful modding tool

  4. #4
    The Main Man Dewayne's Avatar
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    Fan voltage drop to 7v via resistor

    Look to your left under Content and you will see Tools :-)

  5. #5

    Fan voltage drop to 7v via resistor

    Look to your left under Content and you will see Tools :-)
    You guys rock!!!

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