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Thread: Before i do something stupid. . .

  1. #1

    Before i do something stupid. . .

    If i cross two 12v lines on a power supply will i get double the volts and amps, just double the volts, or nothing at all?
    Or will the power supply burnout or blow up?

  2. #2
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    Before i do something stupid. . .

    If you have a multiple rail power supply (for example http://www.newegg.com/Product/Product.aspx?Item=N82E16817182067 )
    Avoid doing it if at all possible, unless you can be sure that the load will be split either perfectly evenly, or in a 100% consistent manner.
    If you need to pull 30amps and your device decides to pull 24 amps out of one rail while only drawing 6 on the other -- your powersupply (at best) will shut itself down in protection mode, (at worst) physically explode/light on fire and possibly eletrically fry your components).

    If you have a single rail power supply (for example http://www.newegg.com/Product/Product.aspx?Item=N82E16817139006 ) thats rated to power your load (the example can drive 60 amps on the +12v rail) then all that connecting multiple wires together does is provide an easier path to the device from the power supply. (less likely that the wires will melt) In reality, anything you connect to a +12v computer rail will have no chance at melting the wires, so its rather pointless.



    From a PURELY THEORETICAL standpoint, you would get the sum the amps, with no change in the voltage.

  3. #3

    Before i do something stupid. . .

    Ok that makes a little more sense. It seems that my electronics classes are starting to slip away I should start using them more Thanks for the info funisfun

  4. #4
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    Before i do something stupid. . .

    heh -- no problem.. Its all fresh in my brain. I'm a double E (electrical engineering) undergrad at the moment.

  5. #5
    The Main Man Dewayne's Avatar
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    Before i do something stupid. . .

    Kind of out of curiosity, what are you trying to do?

  6. #6

    Before i do something stupid. . .

    Using an old AT power supply for my electronics hobby. Just got curious as to what would happen if i crossed two lines

    Was also wondering how you get 7 volts out of one? I've read about it before but couldn't quite figure it out.

  7. #7
    Master Modder Tazz's Avatar
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    Before i do something stupid. . .

    Using a 12V+(positive) and a 5V+(negative) line will give you 7V+.

    I guess I should have reworded my post..... LOL thanks fusinfun.

  8. #8
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    Before i do something stupid. . .

    If you use the +12v on positive side of your device (lets say a fan in this case) and the +5v on the negative side of the fan, you get a net of 7 volts. This is great for running LEDs and other lower current supplies, but as your power supply isn't really designed for "negative amps" on the +5v rail -- I have seen many people recommend avoiding this technique if at all possible.

    for the negative amps concept think about hooking a fire hydrant to your home faucet with a suitable connector and then turning them both on... The firehose is going to push water OUT of your house (unless you have some really special plumbing) possibly bursting pipes along the way. NOT something you'd want to try though... I suggest the same with your power supply. (unless you got it for free or otherwise don't care about it)

  9. #9

    Before i do something stupid. . .

    i would not mess around with my power supply if I were you. Good way to get a shock. Or to fry your components. In addition Never Skimp on a quality brand named Power supply.

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