# DC powered USB hub



## naiku

Apologies for how long winded this may get... 

I have this USB hub set up in my car, and am using a DCDC-USB to provide power. 

The usb hub has an FDD connector on the back of it, that can be used to make it a powered hub. I picked up an ATX to Molex that is plugged into the DCDC-USB, then a molex to FDD that plugged into the back of the USB hub. However, when I turn the ignition on, the hub does not power on. I checked with a multimeter at the end of the molex and I get 5.02v (DCDC-USB is set to output 5v). At this point there is only the yellow and black wires, when connecting the FDD connector, I now have the yellow, red and pair of black wires. 

Is this because when using the FDD input, that I need both the 5v and the 12v to be connected? Where as at the moment I am only supplying the 5v? If that is true, can I tap into a switched 12v source and splice that into the 12v intput of the FDD on the back of the hub? And, should I add a fuse to that 12v source?

For now I am soldered on a female USB port, and use that to the barrel connector on the hub. But, I would prefer to use the FDD connector if possible.

Thanks.


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## minbari

usb has no use for 12v, so i cant imagine what it is used for. why not just the barrel connector?


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## naiku

minbari said:


> usb has no use for 12v, so i cant imagine what it is used for.


That's what kind of confuses me as well, if I look at the pin out on an FDD connector it has 5v, 12v and the 2 grounds. Maybe I just need to switch the pins around, as I think that I currently have (had) the 5v on the yellow wire, which the FDD connector is expecting to be 12v. Perhaps if I switch them around it may work?

1 +5VDC Red +5 VDC 
2 COM Black Ground 
3 COM Black Ground - I have this connected
4 +12VDC Yellow +12 VDC - And this connected, but with 5v and not 12v



minbari said:


> why not just the barrel connector?


The reason I don't want to use the barrel connector, it's a poor connection. It feels very loose on the hub, and I don't want it to fall out behind the glovebox somewhere while driving.


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## minbari

naiku said:


> That's what kind of confuses me as well, if I look at the pin out on an FDD connector it has 5v, 12v and the 2 grounds. Maybe I just need to switch the pins around, as I think that I currently have (had) the 5v on the yellow wire, which the FDD connector is expecting to be 12v. Perhaps if I switch them around it may work?
> 
> 1 +5VDC Red +5 VDC
> 2 COM Black Ground
> 3 COM Black Ground - I have this connected
> 4 +12VDC Yellow +12 VDC - And this connected, but with 5v and not 12v


ah, yes, if you have it backwards, it wont work, 

if I had to guess, the 12v wire goes no-where internally.

plug it into your Pc and see if it comes on.


> The reason I don't want to use the barrel connector, it's a poor connection. It feels very loose on the hub, and I don't want it to fall out behind the glovebox somewhere while driving.


wireties!


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## naiku

minbari said:


> wireties!


This may be the route I take, especially as I currently have everything working well. There are 2 x outputs on the DCDC-USB, I just soldered a female USB port onto each pair, one provides power to the USB hub, the other charges the Nexus.

The need to work on something wants to try getting the FDD connector working though!!


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## minbari

I know the feeling............stuff like that just bugs me till I fix it


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