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Thread: How to power a USB hub

  1. #1
    Variable Bitrate
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    How to power a USB hub

    I've been looking around for a powered USB hub, and they aren't hard to find, but they all seem to come with AC adapters. How do I hook this up using DC current?

    I haven't found one yet that comes with a cigarette lighter attachment that I can hack up... also my computer is in the trunk and the hub will need to be in the center console where the USB ports are, so a Molex powered hub will not work. Unless I can run a Molex powered USB hub from the trunk, with one cable, where I then split inside the glovebox using a non-powered hub. Will it still work?

  2. #2
    Fusion Brain Creator 2k1Toaster's Avatar
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    Look on the transformer (the big black brick thing usually with the wall prongs on it) and you should see ~110AC/??DC where ?? is the voltage it convertts to. Get one that has a brick with a 12v or 5v output. Usually they are 5v because that is an electronics standard somewhat.

    I see no reason why you can't run a molex from the trunk to the glovebox. Just use 2 wires and tap into the 5v/12v and a ground so you don't need the entire molex saving you half the space.

    And running a nonpowered HUB off a powered HUB will achieve nothing but extra ports. The limitation is not within the HUB, it is within USB standards. 250mA total per USB, so if you take 250 from the mobo and split it and split it then you need to add some voltage to keep it at 250, instead of continually splitting it. Then when you get a powered HUB, it will give 250 out for each of its ports. Split off of that, and you again have lower voltage.
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  3. #3
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    Ok so you're saying I need to take a look on the transformer and find the voltage, and find one that matches my power source...I get that...but then what?

    How do I physically connect the DC power (which is literally just a couple stripped wires) to the USB hub? Do I have to cut off the end of the transformer that plugs into the hub and attach that to my power and ground wires?

    Also I understand what you're saying about splitting a split signal...I guess I just didn't think that one through lol

  4. #4
    Variable Bitrate
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    Yes, cut the power wires in roughly half - so you can reconnect the brick if possible. You'll need to figure out which lead needs to be positive and which one needs to be ground, but you can do that with it plugged in and test the tip and the shield of the lead. There's also a symbol that indicates if the lead is positive tip or negative tip, but I've always found it simplete to just test it with a multimeter. Then figure out which wire corresponds to the tip and wire everything appropriately. There's a very good reason a power supply puts out 5v, take advantage of it!

  5. #5
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    Thats what i did. I have 1 molex conntector split to reg power connetors. 1 for 12v rail and the other for 5v rail. The screen and sirius run from teh 12v and the sound and usb hub run from the 5v rail.

  6. #6
    Fusion Brain Creator 2k1Toaster's Avatar
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    Fusion Brain Version 6 Released!
    1.9in x 2.9in -- 47mm x 73mm
    30 Digital Outputs -- Directly drive a relay
    15 Analogue Inputs -- Read sensors like temperature, light, distance, acceleration, and more
    Buy now in the MP3Car.com Store

  7. #7
    Variable Bitrate
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    Well I have a 12v connector with a few LEDs hooked to it available that is very near my console already, so i don't need to cut up my molex connectors and extend them.

    I'll just go test the voltage with a multimeter and buy a hub that takes the same input.

    Thanks for the information Toaster and peecee!

  8. #8
    FLAC W3bMa5t3r's Avatar
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    I know it's a moot point here, but I'm bored and I've been up since 4am and working till 6pm.. lol but I think the actually power standard per USB port is 500mA, not 250. If devices require more than 500mA or are powering additional devices down the line, USB standards require they provide their own power (granted that isn't always followed).

    anywho... Cheers

  9. #9
    Low Bitrate
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    I just bought one of these:

    http://www.radioshack.com/product/in...tId=2498117&cp


    It takes up two USB ports on your PC - one for regular USB and the other provides power. They're on sale right now for $9.99 through Jan 6, 2007.

  10. #10
    Newbie tooby's Avatar
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    you should do what i did
    cut a hole in the wall of your car, somewhere kinda low, but not too low, mount an outlet, run some hidden cables around, hook up like a 400 watt power converter to your battery, and run a nice hidden switch in line with that, so in the future when ever you have the ac/dc problems, you wont have any problems, or ever need any converters for anything again, cause you'll just plug em into the outlet, flip the switch, and be ready to go
    VIA EPIA-EN12000EG - 512 MB DDR2 533 - M2-ATX - 60GB HD - VoomPC enclosure

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