| Jack Erbes 2007-05-31, 10:33 am |
| Larry G wrote:
<snip>
> let's say for the sake of argument.. that someone plugs a USB hub into
> their computer and that hub does not have a separate power supply and
> then they proceed to plug in a bunch of devices that draw power....
> what happens? what is at risk for damage? Does the hub get fried.. or
> the devices or the UBS port on the computer? ...
The whole USB is pretty well thought out:
http://en.wikipedia.org/wiki/USB
even the power management is spelled out clearly:
http://en.wikipedia.org/wiki/USB#Power
But then the people that buy the stuff get involved. If you overload
the 5V side a PC's power supply it will normally bring the whole
shooting match to screeching halt. And, if you are lucky, replacing the
power supply will get it all back up again. If you open the power
supply up you'll find a fuse or two but they are usually either soldered
in or are surface mount components on PCBs and not easily replaced at
the consumer level.
> The
> bonus question: what tells the consumer.. when buying a computer-
> powered USB hub to NOT overload it?
The bits and pieces that are sold with a USB sticker or logo on them are
made by people that have paid money to use the logo. And they've agreed
to play by the USB rules and maybe even have had to submit their stuff
for testing before it can be sold.
So when you buy that kind of stuff and plug it in, with the power
management scheme and the coordinating of the details via various bits
and pieces of electronics, it is unlikely that damage will occur.
But over to the west a little bit there are a lot of people that are
more interested in making money than they are in complying with the
rules. They make their own USB connectors, put them into, onto, or
together with just about anything that they might be able to sell. On
much of that stuff there is little or no regard for compliance with the
USB.org "rules".
There are no USB police that I know of. The fact that sales will fall
off quickly if you make something that does not work at all or not very
well, makes the market police itself a little bit. But otherwise, it
boils down to most of us learning things the hard way.
I don't like that consumers have to pay the price for what our trade
agreements with China have brought us to. Our politicians have sold us
down the river again as near as I can tell.
But China's having recently sentenced the head of their FDA-like agency
to death for being crooked is a step in the right direction as far as I
am concerned:
http://tinyurl.com/37tf75
People's pets have been dying because of some pet food component from
China. And our politicians want me to believe that there is no danger
to us humans from the Chinese made stuff that is going into our food?
Jack
trying to prevent
Jack
--
Jack Erbes in Ellsworth, Maine, USA - jackerbes at adelphia dot net
(also receiving email at jacker at midmaine.com)
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