How to power a USB hub

spoonraker · 12-28-2006, 04:44 AM

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?

2k1Toaster · 12-28-2006, 05:22 AM

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.

spoonraker · 12-28-2006, 06:11 AM

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

peecee · 12-28-2006, 10:26 AM

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!

psptibby · 12-28-2006, 10:39 AM

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.

2k1Toaster · 12-28-2006, 05:08 PM

spoonraker · 12-29-2006, 07:13 AM

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!

W3bMa5t3r · 12-29-2006, 07:28 AM

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

timeshifter · 12-30-2006, 02:12 PM

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.

tooby · 12-30-2006, 02:41 PM

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

v1per · 12-30-2006, 04:31 PM

I think the whole point of wiring the hub into the computer's PSU (not to mention getting a DC-DC PSU in the first place) is to avoid AC-DC inverters. If you can cut a wire, solder another one on to it and connect it to the PSU then why buy a $40 power inverter?

gsd_racing · 12-30-2006, 10:02 PM

Most hubs are 5v DC, since thats what the posts put out.....Just buy a cigarette lighter adapter which puts out 5v DC and splice it onto the hub. Then wire it to your battery and you're all set!

Shameless plug for where I work: (Radioshack) We sell the adapters with one plug free to put on the end, so you can use the adapter for more than one thing....now you can keep your AC adapter whole, and just splice or even use a cigarette lighter 12v DC to power this one

peecee · 12-30-2006, 11:29 PM

Except for those people who

1) Don't have a cigarette lighter or
2) Have a cigarette lighter that is hot all the time.

I like the fact that my computer accessories are only powered from my computer psu and only powered when the pc is on.

Curiosity · 12-31-2006, 12:00 AM

I use something like this:
http://cgi.ebay.com/LUCENT-5V-10A-DC...QQcmdZViewItem
They are very efficient and usually work at lower than rated voltages and take very few support components.

spoonraker · 12-31-2006, 12:50 PM

Well, at the moment I do not have access to a cigarette lighter.

I think the simplest solution was buying a HUB that has the same input voltage as my available pwr/gnd source (which I believe is 12v), and cutting off the AC adapter so that I can put the end on those lines.