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How to get to 12 volts?

  1. Oct 27, 2011 #1
    I just got a new external hard drive that wants 12 volts at 1.5 amps. it comes with a wall wart, but I'd rather find some other method to power it to keep it more portable friendly. (only need 1 outlet to power the drive and laptop)
    I've got several options, but i don't think most of these work easily...
    I've got some open USB ports (i know those have a 5 volt output, so i don't think that works)
    firewire (looks like 4 pin, which i don't think supplies power)
    esata (i don't think that carries power either)
    now the ones that i think may get somewhere...
    there's an expresscard slot, ethernet, and phone line port.
    as another possibility, the power supply for this laptop outputs 19 volts at 6.32 amps.

    any help in a way to build something for this, a place to buy one, or to just say it won't work, or it's just a bad idea, that would be appreciated.
  2. jcsd
  3. Oct 27, 2011 #2
  4. Oct 27, 2011 #3
    Sell the external drive and buy another that's powered by the USB.
  5. Oct 27, 2011 #4


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    Just for kicks, I tried to see what it would take in terms of AA batteries and I came up with 27 batteries and 3 diodes to get 1.3 hours of operation. Not very useful.
  6. Oct 27, 2011 #5

    jim hardy

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    is this a large drive?
    i see those little USB flash thingies are up to 64 gb now , isn't that plenty?

    but i am getting old - in my day memory was magnetic and one meg was huge.
  7. Oct 27, 2011 #6


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    eh!? How did you figure that one out!?

    Firstly, it won't pull 1.5A all the time, that is the rating for peak loads during operation. You can set your computer to power down the hard drive if unused for 60s, or whatever, if it doesn't do it itself.

    Even if it did pull 1.5A continuously, 10 2000mAh rechargeable batteries will last you an hour, poss a little longer (that is 2Ah = 2A for an hour).

    Diodes? Why?

    ...so the answer speaks for itself, as already mentioned: Don't try doing electronics! Just get a USB-self-powered drive!
  8. Oct 27, 2011 #7
    One option is to use a 12-volt lead-acid gel-cell, which can be bought at most electronics suppliers (not Radio Shack) or places like Battery Works. However, you will have to devise a reliable method to charge that battery as well.
    It's bulky, but one of those Jump It units can work, and is a self-contained portable gel-cell battery and charger. The bulky battery cables and clamps may be awkward, but removable. http://www.associatedcontent.com/article/205180/product_review_prestone_jump_it_portable.html [Broken]
    Last edited by a moderator: May 5, 2017
  9. Oct 27, 2011 #8


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    That gave me a good chuckle. In my day, memory was little iron donuts and 16 KILObytes was huge. 1 meg did not exist.
  10. Oct 27, 2011 #9
    Oh yeah, well in MY day we had little 3 inch plastic "floppy" discs that weren't very floppy at all!

    Power strip is probably the simplest option, especially compared to the battery suggested above and the necessary charging equipment.
  11. Oct 27, 2011 #10


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    3" floppies!!! Luxury tech!!

    "You don't know how lucky you were!!"

    So... who remembers when 'memory' was a 1" wide strip of blue paper with 7 rows of holes across it.

    Huh! And you guys think you had it primitive!!

  12. Oct 27, 2011 #11

    jim hardy

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    """So... who remembers when 'memory' was a 1" wide strip of blue paper with 7 rows of holes across it."""

    and after a while you learn to read the seven bit ASCII holes in the tape directly as text...;

    and you can fix a corrupted binary file with scotch tape and a pocket knife;

    ahhh yes, i remember it well - a ASR33 is forever!! (wish i'd kept mine)

    sounds like you might also remember 12AU7 flip-flop logic ..

    :) :) :)
  13. Oct 27, 2011 #12


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    Actually, it was just before my time. I remember my Father coming back from some night classes he was taking, with these rolls of computer tape. I'm from the 'M68000' generation - 'solid state' RAM you could 'DIY' with, and programmes you could store on a cassette tape.
  14. Oct 27, 2011 #13


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  15. Nov 26, 2011 #14
    hiiiiiiiiiiii dear , i want build 12vdc voltage regulator supply but i do not deside what rating of transformer diode capactior if input 230v ac and load 20ohms
  16. Nov 27, 2011 #15


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    Hi Vead,

    I gave you answers in the other forum :)

    And by the way dont hijack other people's threads its rude
    Always start your own one :)

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