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Thread: Powered USB hubs

  1. #21
    Maximum Bitrate DJiK's Avatar
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    I agree with Rawson, you'd be safer not doing the 7V trick just yet.
    Instead, check your hubs again and be sure the voltage is not 5V, because it should be.
    Then see if the '8V' one works off a 5V home adapter. If it does, just use 5V... If you feel safe, do the same thing on the '3V' one.
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  2. #22
    FLAC W3bMa5t3r's Avatar
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    Yeah, I'm gonna have to jump on the band wagon and discourage using the -5vdc method. I would either use the +5v or see about a voltage dropping circuit.

  3. #23
    FLAC W3bMa5t3r's Avatar
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    Just found this sweet page. Reduces the math/thinking you have to do. lol.

    Just adjust the slider values to where you get the voltage you want. You'll then have the circuit/voltage you need/want. :-)
    >-GO HERE-<

  4. #24
    Constant Bitrate RawsonDR's Avatar
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    Quote Originally Posted by W3bMa5t3r
    Just found this sweet page. Reduces the math/thinking you have to do. lol.

    Just adjust the slider values to where you get the voltage you want. You'll then have the circuit/voltage you need/want. :-)
    >-GO HERE-<
    I'm not sure that will work unless one of those two resistors is actually the USB hub you intend to use - and I'm not sure if the hub's resistance would stay constant or how that works. If you hooked up your hub, lets say, in parallel with R2 after configuring your resistors, the hub would provide another path for current and lower the equivilent resistance across R2, changing your voltage value.

    An 8v regulator might be more reliable if you can find one suitable.

  5. #25
    FLAC W3bMa5t3r's Avatar
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    Quote Originally Posted by RawsonDR
    I'm not sure that will work unless one of those two resistors is actually the USB hub you intend to use - and I'm not sure if the hub's resistance would stay constant or how that works. If you hooked up your hub, lets say, in parallel with R2 after configuring your resistors, the hub would provide another path for current and lower the equivilent resistance across R2, changing your voltage value.

    An 8v regulator might be more reliable if you can find one suitable.
    Yeah I was talking to another guy about this. This will work for low current apps, but for things like hubs that can draw up to 2.5A, the resistors (if the don't burn up) would produce alot of heat... so much for that idea. The only problem is all the voltage regulators I've seen, the +6vdc, +3vdc, and I think I saw a +7vdc, their Amp rating is usually ~1A or less. So that still leaves the hubs, etc without a decent power source (providing the right voltage/Amp rating). Unless you just buy a small low current DC-DC power adapter like at powerstream.com. Just a thought. :-\

  6. #26
    Constant Bitrate RawsonDR's Avatar
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    I found this. The 8.0V version, LD1585CV80, looks good, but I can't find any place to buy it in low quantities. They carry the adjustable version though if you can figure out how to bias it for 8V.

  7. #27
    FLAC W3bMa5t3r's Avatar
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    Quote Originally Posted by RawsonDR
    I found this. The 8.0V version, LD1585CV80, looks good, but I can't find any place to buy it in low quantities. They carry the adjustable version though if you can figure out how to bias it for 8V.
    Holy Crap!! min order 1000!! haha... that's only $810 + shipping. I'm sure a group purchase would cover this I'll look around some more too and see if we can't find them (or something similar) elsewhere.

  8. #28
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    Or...

    Why not just go buy a hub you know is 5v and save yourself all the trouble?

  9. #29
    FLAC W3bMa5t3r's Avatar
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    Quote Originally Posted by Kaspin
    Or...

    Why not just go buy a hub you know is 5v and save yourself all the trouble?
    The thread starter is good to go as far as I can tell, his was a 5vdc hub, just had to splice into a molex. The second guy has an 8vdc and a 3vdc hub. While I agree that buying two new hubs would work, if he wants to spend the extra money for two new hubs (they are relatively cheap... but the parts for this circuit would be just a few bucks), this is also applicable to other external devices that some may have. Personally I have one (usb capture) that's gonna need 6.5vdc... fwiw

    You can always underpower something (probably won't work 100% as it's supposed to, if at all) or overpower it (eventually burn out components), but supplying the desired voltage/current level is preferred and if it only costs a few bucks... that's what I'm going for...

  10. #30
    Constant Bitrate RawsonDR's Avatar
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    Quote Originally Posted by W3bMa5t3r
    Holy Crap!! min order 1000!! haha... that's only $810 + shipping. I'm sure a group purchase would cover this I'll look around some more too and see if we can't find them (or something similar) elsewhere.
    I'm not sure what "standard package" refers to but I don't think it's the min order.... they list prices for quantities of 1 ($1.80) and let you add one to your cart. If you do a general search for LD1585 you'll see that the Min Qty is 1.

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