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2011-05-20
, 23:22
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Posts: 1,258 |
Thanked: 672 times |
Joined on Mar 2009
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#172
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Lots of PCs lack adequate overcurrent protection...
I've seen one form where there's common overcurrent protection for several ports, so all ports go dead once protection kicks in.
Worst case is weak protection that works more like a fuse, permanently killing the port (but saving the PC)
The ideal is of course per-port resettable overcurrent protection, which notifies the OS on overcurrent condition.
I have a powered USB hub myself that gives about 700mA to my N900. However, everything else connected to it dims...
Last edited by shadowjk; 2011-05-20 at 23:36.
I've seen one form where there's common overcurrent protection for several ports, so all ports go dead once protection kicks in.
Worst case is weak protection that works more like a fuse, permanently killing the port (but saving the PC)
The ideal is of course per-port resettable overcurrent protection, which notifies the OS on overcurrent condition.
I have a powered USB hub myself that gives about 700mA to my N900. However, everything else connected to it dims...
Last edited by shadowjk; 2011-05-20 at 23:36.
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2011-05-21
, 07:42
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Posts: 284 |
Thanked: 320 times |
Joined on May 2010
@ Peterborough, UK
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#173
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That's exactly what happened to my previous laptop - all of the ports suddenly died, presumably because of a combination of 1 and 2. Not pretty.
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2011-05-22
, 00:41
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Posts: 5,028 |
Thanked: 8,613 times |
Joined on Mar 2011
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#174
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Thanks for the info... Fortunately, i got one with smart protection - otherwise i would screw it many years ago, when tried to check max port current with multimeter A measurement (which obviously made overcurrent prot. to go berseker - don't ask, it was one of most stupid ideas i had during my hardware modifications learning phase...). Fortunately, Os just shouted at me to get out with that, and disabled port until driver restart. Really good to know that there are fuse-based solutions still circulating...
By the way, out of curiosity - why everything else connected to that 700 mA port "dims"? Shouldn't peripheral things drain only as much as they need from port current "pool", so they don't care if port can provide 700 mA or 7A?
Last edited by Estel; 2011-05-22 at 00:43.
By the way, out of curiosity - why everything else connected to that 700 mA port "dims"? Shouldn't peripheral things drain only as much as they need from port current "pool", so they don't care if port can provide 700 mA or 7A?
Last edited by Estel; 2011-05-22 at 00:43.
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2011-05-22
, 15:28
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Posts: 1,258 |
Thanked: 672 times |
Joined on Mar 2009
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#175
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The charger chip in N900 happily operates at, for example, 4.5V input. The Hub's powersupply was unable to provide sufficient current, so voltage sagged to below 5V.
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2011-05-23
, 20:25
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Posts: 219 |
Thanked: 80 times |
Joined on Mar 2011
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#176
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Looks like changing those values messes up pc suite file browsing + mass storage mode for windows
Of course all of this is unless there is some bug in overcurrent protection, that I'm not aware of (which got high chances to be the case), so use at Your own risk.
Thanks for great scripts, shadowjediknight!