From: Manuel Dejonghe <manuel_at_dejonghe.de>
Date: Fri, 27 Jan 2006 00:57:20 +0100

On 1/26/06, Holden Bonwit <hbonwit04_at_yahoo.com> wrote:
> I also am wondering about making a USB to Power plug. I looked a while back and the charging wall wart gives 12volts, but I'm not sure what current the unit charges at. The USB standard coming out of a computer has 12volts, I believe. I'm not sure what the current limit is. I'd like to not fry the computer :)


Hi Holden,

the usb has 5V, so it's just what you need for your iriver.
The problem is, as you already pointed out, the current.

Following to the specs, a device can take up to 500mA, but only after
having requested and granted from the usb-host-chip.
Before having requested and granted, a chip may take up to 20 or 50 mA.

You can easliy test it, if you got the chance to plug your iriver to
the keyboard of a macintosh. I've seen it several times that the macOs
will tell you that there is not enough power anymore.

That clearly means that all those devices that pretty certainly do not
have a controller on it, do take more power than allowed.
Where some host controllers have power in abundance or are limiting
the current, others may not, and damage hardware.

regards, lImbus
Received on 2006-01-27