USB hub as power supply

Crackle
Posts: 1
Joined: Tue Jan 22, 2013 9:55 pm

USB hub as power supply

Postby Crackle » Tue Jan 22, 2013 10:44 pm

Can I use a powered USB hub as the power supply for the mk808B that is hosting it? This way I would only need one power brick in the wall but can plug in several external harddrives as external storage.

I think the answer depends on the current draw on the mk808b, and possibly also how the hub works, but am asking for some advice.

If the current draw of the mk808b is less than 100mA then I could make a non-data USB cable (i.e. a usb cable with the data lines cut) and use that as the connection from the hub to the power connection on the mk808b, then use a normal cable as the connection from the mk808b to the USB host device connection. This should work as without a data line the hub will assume the mk808b is a low power device and only supply 100mA or less. What's the current draw of the mk808b?

If the mk808b is a high power device then it needs to request more current from the hub. I'm not sure how this works and I don't think having the mk808b as the client device requesting more power from itself as the host device is a good idea. Obviously this power would actually be supplied from the powered USB hub, however I don't know if the requesting process (enumeration) would cause problems, and I don't know if the host device would know about the enumeration process, or if this would be entirely handled by the hub (it's a Belkin F4U022v hub if that's any help).

If the power in USB port on the mk808b is only electrically (i.e. not electronically) connected to the rest of the device it might enumerate anyway, completely separately to the operation of the rest of the device, in which case it may be fine to simply plug in. This might be true and why the power USB plug is not used for connecting the mk808b as a client device?

Has anyone tried powering their mk808b from a USB hub that it is the host of? and/or does anyone know enough about electronics to tell me if this is a good idea?

Jerryo100
Posts: 13
Joined: Mon Feb 11, 2013 11:04 am

Re: USB hub as power supply

Postby Jerryo100 » Tue Feb 12, 2013 10:19 am

Unless you can find one of those usb hubs that has one port that can handle 2000ma for charging purposes, I wouldn't advise using one to power your MK808b. It comes with a 2000ma wall wort for a reason. I've read several posts in forums of people having major problems trying to power theirs with the usb port on their TV or USB hub. I picked up a cheap surge protector with a switch at Walmart for $7.00 and plug the MK808b, powered USB hub, and my hard drives PS into it and it works great. One switch turns everything on and then when I'm done I use a Rebooter app to softpower off the MK808b then one switch turns everything off.


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