Designing a step-up USB output that's iPad capable

Discussion in 'iPad' started by troop231, May 1, 2010.

  1. troop231 macrumors 603

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    #1
    I'm pretty good with electronic components, and was wondering if anybody would even want to use one? Instead of using one or two usb y adapters (2 or 4 ports) Why not just make a circuit to boost the current that's plug n play? Chime in here.
     
  2. troop231 thread starter macrumors 603

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  3. miles01110 macrumors Core

    miles01110

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    #3
    Not sure why anyone would bother rigging up some hack when there's too many things that could go wrong. Plug it into the wall.
     
  4. troop231 thread starter macrumors 603

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    #4
    Not really. Resistors would prevent such problems.
     
  5. miles01110 macrumors Core

    miles01110

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    #5
    Famous last words. I didn't ask explicitly before, but why would this be worth the trouble and/or the risk in the first place? You could end up frying your iPad, your computer, and yourself.
     
  6. troop231 thread starter macrumors 603

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    #6
    No, the voltages are too low to harm you, and certain components would prevent the iPad or computer from becoming toast, and this would be a niche market for people wanting to sell an inline charging cable.
     
  7. 3goldens macrumors 68000

    3goldens

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    #7
    And I am supposing you are going to try and
    Use this for externalmdevices like a hard drive?
    Would you be designing the software that would enable you to detect the hard drive and its files once you've created your new accessory for the iPad?
     
  8. troop231 thread starter macrumors 603

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    #8
    No this has nothing to do with that. I'm talking about charging the iPad via any computer usb port and not just a high powered one.
     
  9. danpass macrumors 68020

    danpass

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    #9
    Are you talking about combining the output of USB ports?

    Like two (for example) that are next to each other, as on a laptop?

    Hence creating a 1.0A output into one cable? 4 ports for 2.0A into one cable? etc



    Personally if I have my iPad with me I won't have something else (besides my iPhone).
     
  10. troop231 thread starter macrumors 603

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    #10
    Yes that is one way to do it, I think alot of people actually overlook using Y usb adapters.
     
  11. Torq macrumors regular

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    Jun 8, 2009
    #11
    Because the circuit that boosts the current from a single USB port could only do it at the expense of yielding lower voltage.

    Assuming a perfectly efficient implementation (not possible), a 5v 500ma USB port could power a circuit that offered 1000ma at 2.5v. 2.5v is not enough to charge Lithium chemistry batteries.
     
  12. troop231 thread starter macrumors 603

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    #12
    You can step up voltage with a DC-DC converter though.
     
  13. Torq macrumors regular

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    Jun 8, 2009
    #13
    You can, but at the cost of available current. So you'd be right back where you started (actually worse off due to conversion losses).

    If the available power is 2.5w (5v @ 500ma) then any circuit you build can only deliver a total power level of 2.5w. Anything else is creating energy out of nothing!
     
  14. troop231 thread starter macrumors 603

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    #14
    How about an inductive (wireless) iPad accessory? :D
     
  15. Torq macrumors regular

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    #15
    You could build such a thing, but it would require a coil on the outside of the iPad's case and the PSU for your charging pad (the device that creates the oscillating field that induces current in in the recieving coil) would need to be significantly larger than the little 10w adapter the iPad ships with.

    And of course that charging pad would need to be wired to AC.

    You could, technically, even build this so it worked without the iPad being placed on anything, but you'd be looking at many kilowatts of input power to get a range of more than a few feet.
     
  16. troop231 thread starter macrumors 603

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    #16
    Let's collaborate.
     
  17. ikdo macrumors newbie

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    #17
    I wonder if the 12v (output) charger (for the firewire ipod) can charge the iPad? I have the Alpine iPod controller which also has the 12V output.

    ikdo
     
  18. Torq macrumors regular

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    Jun 8, 2009
    #18
    There are already shipping products in this area, be they inductive or contact-based pads. They don't sell; principally because the inductive coil you need on the device to be charged isn't built-in.

    Look at the main picture on the first page of www.powermat.com ...

    You have a Kindle that you're charging "wirelessly" ... buy plugging it in to a different charger ... which then gets it's power wirelessly. What's the point of that?

    Now if the Kindle (or iPad) had the charging loop built-in it would be different, but it doesn't. This is a classic chicken/egg problem. There is no inductive charging standard, so no one (well, almost no one) is putting such loops in their products. So everyone offering the charging pads has to come up with adapters (that need cables to connect to the devices to be charged) or dongles.

    If I have to plug in a dongle or an adapter or in the case of one iPhone solution use a special case, why not just plug it in to its original charger?
     
  19. Torq macrumors regular

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    #19
    It won't work natively (it won't even work with any iPod that was built after Apple dropped FireWire syncing support).

    There IS more than enough power available on a full IEEE 1394a specification port to do the job though (45w ... the supplied iPad charger is 10w). You'd need to fashion a voltage conversion circuit (current limiting is already present in the iPad's internal charging circuit) and then integrate an authentication chip, to make it work.

    I'd be surprised if there weren't FireWire to USB charging adapters for the iPod, and if they defer current limiting it the iPod (as they should), they'd work on then iPad too.
     
  20. flynz4 macrumors 68040

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    Portland, OR
    #20
    I know this probably sounds rude, but would I suggest that you re-take your freshman engineering courses. Everything will soon become really clear.

    /Jim
     

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