[iyonix-support] Re: Dead Iyonix
- From: Alan Adams <alan@xxxxxxxxxxxxxxxx>
- To: iyonix-support@xxxxxxxxxxxxx
- Date: Sun, 13 Mar 2011 12:05:11 GMT
In message <4D7C0285.7020103@xxxxxxxxxxxx>
"David J. Ruck" <druck@xxxxxxxxxxxx> wrote:
> On 11/03/2011 11:41, Grahame Parish wrote:
>> In message<4D7A0763.4000303@xxxxxxxxxxxx>
>> "David J. Ruck"<druck@xxxxxxxxxxxx> wrote:
>>
>>> On 11/03/2011 11:09, Grahame Parish wrote:
>>>> Last night I attached a self-powered native formatted external hard
>>>> drive to a USB port and it froze the machine - this is not usually a
>>>> problem.
>>
>>> It may well have been. Self powered drives can draw too much current
>>> from the Iyonix's USB ports.
>>
>> Probably not the best term to use - by self-powered I mean that it has
>> its own power, not dependent on USB power.
> Sorry, miss interpreted that.
> However, some badly designed devices can still attempt to power
> themselves from the USB port if their external power supply isn't on. So
> you have to take care to always turn the PSU on before connecting the USB.
> At work we had 16 USB smart card readers connected via 2 10 port hubs,
> all working correctly for some time, then I noticed someone had
> unplugged the mains cable powering both hubs, so both the hubs and
> readers were getting all the juice from the PC's USB port. Luckily we
> only use one reader at a time, so it didn't blow anything.
I think, remembering an earlier message, that this particular drive
feeds power OUT of its USB connector when powered from its external
source. That sounds like seriously sloppy design - it is very sinmple
to connect the two sources together - but in this case means that the
5 volt obtained from the PS2 port of one computer is connected
directly to the 5 volt obtained from the Iyonix.
The 5 volt supply from a USB port is meant to be current limited, but
usually is direct from the main power rail of the computer.
If I am right in my recollection this could have a serious effect on
the Iyonix, the other computer, or both.
--
Alan Adams, from Northamptonshire
alan@xxxxxxxxxxxxxxxx
http://www.nckc.org.uk/
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