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The Monday 2008-01-07 at 12:52 +0100, jdd wrote:
Carlos E. R. a écrit :
Rather a problem of badly designed usb hub. The hub should detect the pc
bus is down (no power) and power down itself, too, or go to standby,
remove the voltage from the usb line.
there is absolutely no intelligence in an usb ub :-), and the power is so low
(I think 1A / 5V) than even a mechanical switch is not possible
That's no excuse :-p , a transistor or two would do the trick.
The hack for you would be to use a main switch for all appliances, and
switch it off, instead of swathing off the bus, the printer, the scanner,
etc, etc.
it's what I do, but even if I don't switch the appliance on the laptop runs
and the ub also, but only for a short time :-)
for the desktop computer I use a monitored appliance, but I don't know if
this will work for a laptop (power used is much smaller)
It would be possible to design one. The device only needs to monitor the
presence of power in the usb power line coming from the laptop, and 1mA
would be enough to trigger the base of a transistor that would in turn
power up the device. It could even be designed around an optocoupler/triac
to power up the AC side of the device.
You just pay an engineer, and he'll do appropriate wonders :-)
- --
Cheers,
Carlos E. R.
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