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5V DC to 12V DC Is this posable ?

Discussion in 'General Electronics Discussion' started by Bradhome10, Jun 27, 2011.

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  1. Bradhome10

    Bradhome10

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    0
    Jun 27, 2011
    hello,

    I have installed 2 fans onto my Xbox and now i need a way to power them. I have hard-wired 1 fan in my last xbox and did not like how it wired up. So this time i would like to wire it up to a USB so i can easly plug and unplug them if nessaserry. All i know is that the USB is 5V DC and i am useing a standard 12V PC fan. So how do i come about doing this ? How can i transform 5V to 12V ? I can not change the incomeing power or the outputting power but i am willing to have a small box next to my xbox whitch will contain resistors capasitors switch ETC ETC if needed. If you need any more info to help me pleas just ask.

    All help apresiated.

    Regards
    Bradhome10
     
  2. daddles

    daddles

    443
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    Jun 10, 2011
    You can find DC-to-DC converters that can do the job. But first you have to find out whether the USB connector can provide enough power. IIRC, the typical spec is around 50 mA at 5 volts, although with a wall-wart-powered USB bus, I think you can get up to 200 mA. You don't say what power or current the fans require.

    I suspect it will be cheaper and simpler if you just go buy a 12 volt wall wart to power your fans. I usually go to the local thrift stores, as they often have boxes of wall warts for 50 cents or a dollar apiece.
     
  3. Bradhome10

    Bradhome10

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    Jun 27, 2011
    ok, so if i got a 12V wall wart how would i wire it up to the fan ?
     
  4. TBennettcc

    TBennettcc

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    Dec 4, 2010
    What is the current rating on the fans? USB power is rated 500 mA MAX at 5 volts. This gives (amps * volts = watts, 0.5 A * 5 V =) 2.5 watts. If your fans are rated above 200 mA current draw, you're going to need an external power supply. If you want to build one yourself, you're looking at a transformer and rectifier, minimum. You might look around for an extra 12v DC wall wart with an amperage rating that can handle both fans (and then some).

    Edit: Whoops. Guess daddles got to you before I did.
     
  5. davenn

    davenn Moderator

    13,798
    1,939
    Sep 5, 2009
    and of course thats 500mA at 5V its only going to be ~250mA @12V
    and what else is that original 500mA of the USB being used for.

    5V PC fans are readily available use one of them instead of the 12V one, and available at under 100mA :)
    saves all the hassles of building a buck converter cct.

    cheers
    Dave
     
  6. Resqueline

    Resqueline

    2,848
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    Jul 31, 2009
    Or simply just use the 12V fans directly at 5V (most will start & run) for a gentle quiet breeze. It doesn't take much of a flow to cool equipment appreciably.
     
  7. TBennettcc

    TBennettcc

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    Dec 4, 2010
    I've pulled 12V DC fans out of Dell computers that pull over 1500 mA... Best to check the ratings on that fan if you're going to straight-up plug it into USB...
     
  8. Bradhome10

    Bradhome10

    3
    0
    Jun 27, 2011
    The USB are for xbox wired controlers, So all i need to do it get a fan that is under sed Miliamps and sed voltage then just wire them up. When wireing them up do i need to just wire in the Live and nutral or do i need to some how wire up all the wires (some fans have more than two wires as you know)
     
  9. TBennettcc

    TBennettcc

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    Dec 4, 2010
    First of all, live and neutral denotes mains AC current, like you would typically find in a wall outlet. Please don't plug one of these fans straight into the wall.

    You would be wiring the +5V and 0V (i.e., ground) of the USB connector to your fan. You could try touching the leads to a 9V battery (just for a short amount of time) to help you figure out which lead is which.

    Yes, as long as the voltage rating of the fan is +5VDC, and the current rating is under 500 mA, you should be fine. Keep in mind, your current limit might be lower if those USB ports are connected to anything else that needs that power.
     
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