Increasing available USB current


4 posts
by jbuehl » Fri Jun 22, 2012 12:03 am
I'm trying to come up with a way to increase the current available to a USB device so that I can run a wireless adapter without the need for a separate powered USB hub that is physically as big as the Raspberry Pi and needs another power supply. This is the only way I could get an Asus USB-N10 adapter to work. Maybe there's another adapter that uses less current, but most of the posts I have read seem to indicate that most of them will have the same problem.

My goal here is to come up with a prototype for a compact wireless camera by combining the RPi with a USB camera and wi-fi dongle. I'm envisioning mounting the camera on a daughter board. I started by removing the composite video, audio, and ethernet connectors from the RPi because I'm not using them and they will be in the way of the daughter board.

I began playing around with some ideas, but I'm not satisfied with what I have come up with. I modified a cheap Aluratek un-powered hub by disconnecting the +5 lead in its cable from its circuit board. Then I connected the +5 and ground leads from a cut off USB cable to the hub, and also to the +5 and ground pins of the GPIO header on the RPi. Now I can power everything from a single supply, which is an iPhone power adapter that delivers 1A.
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I guess I should put a fuse in line with the +5 supply since I am now bypassing the one on the RPi. I'm not clear if the fuse protects the board or the power supply. For now I'm just living dangerously.

I don't really need the extra USB ports that the hub provides so I'm thinking of removing the USB connector from the RPi and running wires directly from it to the daughter board. I'm assuming that since they will be only about 1 cm long there shouldn't be any signal issues. The camera can be directly wired to the board, but the wireless adapter probably will need to plug into a USB socket on the board. The same piece of metal that forms the USB plug housing on it also functions as the heat sink and also possibly something related to the antenna, so I don't want to mess with it. I had to order USB sockets as I couldn't find any locally.

Any comments or suggestions are welcome.
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by Gert van Loo » Fri Jun 22, 2012 6:41 am
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by jbuehl » Fri Jun 22, 2012 2:16 pm
Thanks. I'll move over there.
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by AndrewS » Fri Jun 22, 2012 2:29 pm
jbuehl wrote:I started by removing the composite video, audio, and ethernet connectors from the RPi
photo.JPG

Impressive Raspberry-butchery ;)
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