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From: Mark F on 27 Apr 2010 12:49 I'm looking for a USB cable that supplies power "downstream" and doesn't send power upstream. I have seen many powered hubs that supply downstream and don't specify if they are isolated from the upstream power or in parallel to it. I need a cable with power since I can't get support for many devices if I connect through a hub; I don't want to draw power from upstream since I have already had 6 motherboard ports on several machines stop working and I want to eliminate high current load as a possible cause of the problem.
From: Rod Speed on 27 Apr 2010 15:06 Mark F wrote: > I'm looking for a USB cable that supplies power > "downstream" and doesn't send power upstream. > I have seen many powered hubs that supply downstream and don't > specify if they are isolated from the upstream power or in parallel to it. It isnt practical to parallel, so you can be confident they dont do that. > I need a cable with power since I can't get support for many > devices if I connect through a hub; I don't want to draw power > from upstream since I have already had 6 motherboard ports > on several machines stop working and I want to eliminate high > current load as a possible cause of the problem. Any decent powered hub will work fine.
From: Arno on 28 Apr 2010 09:05 Mark F <mark53916(a)gmail.com> wrote: > I'm looking for a USB cable that supplies power "downstream" > and doesn't send power upstream. > I have seen many powered hubs that supply downstream and don't > specify if they are isolated from the upstream power or in parallel > to it. The external power supply in a hib is allways arranged so that if connected, it is insulated in upstream direction. If it was not, a) it would probably not work well and b) it could well damage the USB port the hub is connected to. Don't worry about this. > I need a cable with power since I can't get support for many > devices if I connect through a hub; I don't want to draw > power from upstream since I have already had 6 motherboard ports > on several machines stop working and I want to eliminate high > current load as a possible cause of the problem. Well, you do not get this in cable form as basically nobody needs it. You can roll one yourself by cutting the 5V line and attaching a regulated (!) 5V PSU on the device side. However if your device kills ports, then you are doing something seriously wrong. Maybe look into that? Arno -- Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email: arno(a)wagner.name GnuPG: ID: 1E25338F FP: 0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F ---- Cuddly UI's are the manifestation of wishful thinking. -- Dylan Evans
From: Mark F on 30 Apr 2010 08:46 On 28 Apr 2010 13:05:37 GMT, Arno <me(a)privacy.net> wrote: > Mark F <mark53916(a)gmail.com> wrote: > > I'm looking for a USB cable that supplies power "downstream" > > and doesn't send power upstream. > > > I have seen many powered hubs that supply downstream and don't > > specify if they are isolated from the upstream power or in parallel > > to it. > > The external power supply in a hib is allways arranged so that > if connected, it is insulated in upstream direction. If it > was not, a) it would probably not work well and b) it could > well damage the USB port the hub is connected to. Cannot use a hub. (I don't know what thing about hubs might make things go wrong, but whenever a device that had been working with a hub stops working and I have to call support, the first thing I am told to do is remove the hub and connect directly to a USB port. [There may be things that don't work with hubs for actual protocol reasons or that would require driver changes to work with a hub, but even when I have used the device through the hub in the past I am told I have to remove the hub before I can get support.]) > > Don't worry about this. > > > I need a cable with power since I can't get support for many > > devices if I connect through a hub; I don't want to draw > > power from upstream since I have already had 6 motherboard ports > > on several machines stop working and I want to eliminate high > > current load as a possible cause of the problem. > > Well, you do not get this in cable form as basically nobody needs > it. You can roll one yourself by cutting the 5V line and > attaching a regulated (!) 5V PSU on the device side. > > However if your device kills ports, then you are doing something > seriously wrong. Maybe look into that? > > Arno
From: Arno on 30 Apr 2010 13:13
Mark F <mark53916(a)gmail.com> wrote: > On 28 Apr 2010 13:05:37 GMT, Arno <me(a)privacy.net> wrote: >> Mark F <mark53916(a)gmail.com> wrote: >> > I'm looking for a USB cable that supplies power "downstream" >> > and doesn't send power upstream. >> >> > I have seen many powered hubs that supply downstream and don't >> > specify if they are isolated from the upstream power or in parallel >> > to it. >> >> The external power supply in a hib is allways arranged so that >> if connected, it is insulated in upstream direction. If it >> was not, a) it would probably not work well and b) it could >> well damage the USB port the hub is connected to. > Cannot use a hub. (I don't know what thing about hubs might > make things go wrong, but whenever a device that had been > working with a hub stops working and I have to call support, the > first thing I am told to do is remove the hub and connect directly > to a USB port. [There may be things that don't work with hubs > for actual protocol reasons or that would require driver changes > to work with a hub, but even when I have used the device through > the hub in the past I am told I have to remove the hub before I can > get support.]) I think this is several issues. First, there are substandard hubs out there with bad signal quality and protocol errors. Second is that the MS USB stack is pretty brittle compared to the alternatives. Combinations that fail for Windows only give the occasional error log entry under Linux. (Nothing new here, monopolies are always bad for quality...) Arno -- Arno Wagner, Dr. sc. techn., Dipl. Inform., CISSP -- Email: arno(a)wagner.name GnuPG: ID: 1E25338F FP: 0C30 5782 9D93 F785 E79C 0296 797F 6B50 1E25 338F ---- Cuddly UI's are the manifestation of wishful thinking. -- Dylan Evans |