[kwlug-disc] WAS: USB hard drive mount / Electrical

Bob Jonkman bjonkman at sobac.com
Thu Jan 21 14:28:34 EST 2010

The ground and voltage pins on a USB connector are slightly longer than 
the data pins, so that as you insert the USB connector into the 
computer's socket, stable voltage is available before the data pins 
connect.  So, it's supposed to be completely hot-pluggable.  Similar to 
a computer that powers up, but only activates its circuitry when the 
power supply's "power good" line indicates everything is ready to go.

--Bob (who just read Andrew Kohlsmith's treatise on USB 
hot-pluggability, and is reconsidering the whole idea of posting this 

Charles M wrote:
>> So it's the order.  Turn on, plug in, no go.  Plug in, turn on, works.
> Glenn's question reminded me of one of my own. While USB drives are
> suppose to be plug and play, it seems to me a bad idea to be putting
> anything in the USB port that already has electricity going to it.
> It's almost like pulling memory out without unplugging the system
> unit, it may not appear to hurt the system, but the system still has
> electricity running through it, and damage could be done...
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