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Thread: Powering USB Hub

  1. #1
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    Powering USB Hub

    I got a USB hub that takes 5v dc. I was wondering if I could cut off the AC plug and power inverter and just wire the hub into my cars 12v along with a resistor. I think I would only need a couple ohm resistor.

    Do you guys think it will work or does it something else to power it?

    edit: I've searched around and it seems like all the solutions people are using arent really what im looking for. I think it should be as easy as wiring in a resistor to limit voltage. Plus a resistor only costs about 35 cents.

  2. #2
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    I power my hub off the 5v rail from the psu. Powering it the way youre suggesting isnt ideal since the voltage in an automotive electrical system is not necessecarily constant. This will most likely lead to a shortened life of the hub and possible the other peripherals it powers.

  3. #3
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    I used one of these off the ignition wire before and it worked well:
    http://www.parts-express.com/pe/show...artnumber=7805

  4. #4
    Variable Bitrate 84RegalRider's Avatar
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    yea at least go with the regulator, tho i think you need a heatsink to get the full 1A out.
    Core duo
    1tb harddrive
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    still installing...

  5. #5
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    if you have a spare cell phone car charger available you can use that, just open it up and wire the lead you cut of the ac brick to the existing cable

  6. #6
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    Quote Originally Posted by koolmoedee View Post
    if you have a spare cell phone car charger available you can use that, just open it up and wire the lead you cut of the ac brick to the existing cable
    Thanks, great idea.

  7. #7
    Constant Bitrate
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    Do not just use a resistor, you have no way of controlling the voltage drop over it since this depends of the current cunsumption (ohm's law: U = I * R). And since the currenct cunsumption will vary a lot for a USB hub, there's no way to get a constant voltage supply with just a resistor.

    At least use a 7805 voltage regulator circuit with a couple of capacitors and a heatsink, or what's even easier is to just connect GND and a +5V output from your CarPuter power supply. This will also use less energy than a 7805 voltage regulator or other series regulators, because PC power supplies are switch mode converters which are much more energy efficient than series regulators.
    Besdides this, connecting it to you PC power supply will also turn off the hub when the PC turns off. If you just connct a simple 7805 circuit, the hub will consume power even when the PC is turned off.

    Edit: There's already another topic discussing what you are asking for.
    Read here: http://www.mp3car.com/vbulletin/powe...g-usb-hub.html
    The best option if you do not wish to use a 5V output from your PC power supply is to use a point of load 5V DC-DC switch mde converter like this one: http://store.mp3car.com/Automotive_P..._p/pwr-022.htm
    Or use a cheap cigarette lighter 5V USB charger like this: http://www.dealextreme.com/details.dx/sku.688
    You can take the cigarette lighter USB charger apart and add 12V and 5V wires to make it a more permanent installation than just plugging it in your cigarette lighter plug. Read here how to do this: High Current USB

  8. #8
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    Feb 2008
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    Wow thanks for all the input guys. Alot of great ideas. If the weather here would ever clear up I'm going to rip the car apart and wire in the hub.

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