USB connections; power; settings

[dmcnab]

Hi loungers....I have a hardware question.I am using a SONY Vaio computer, XP fully patched. I have a docking station. The computer has 2 USB ports and the docking station has 3 USB ports. Upto now, I have just been using the ports in any manner that was convenient, but I suspect that there is a preferred way to use these ports.

I like to use SKYPE and so I have a webcam connected to a USB port; I also use a wireless mouse and I have a small (9") second monitor from DoubleSight that runs by connecting it to a USB port (this powers it and provides the video feed).

I bought a USB hub that does not require it's own power source.......how do I figure out which of the available USB ports (2 on the computer, 3 on the docking station) will provide the best power? Is there a recommended way to use USB ports (eg: should I always hook up a webcam or a 2nd monitor to the computer, or can I use the dcoking station ports?).....is there a difference b/w using a port that is on the computer versus using one that is on the docking station? Do I 'weaken' the effectiveness of these ports if I use more than one, or more than two etc etc...?

Anything you can tell me to educate me about the best way to use USB ports and maximize their effectiveness would be great.....thank you.

[Paul T]

USB ports don't care how you use then except when it comes to power. You cannot plug a device that needs power into a non-powered hub, either plug it into the PC or get a powered hub.
Note: if you move a USB device from one port to another it will attempt to re-install.

cheers, Paul

[dmcnab]

...hmm...ok...thank you...so I gather that I should plug the 2dn monitor into the computer (it works when plugged into the docking station, but sometimes Skype freezes or hangs)...and maybe plug the camera into the docking station (or computer) and leave other non-powered devised (like the wireless mouse) in the docking station??

[Paul T]

Depends on how you use the devices. Things you use with the docking station should be plugged into the DS.

Maybe it's just Skype being bad?

cheers, Paul

[CLiNT]

Laptops typicaly are not very potent when it comes to powering usb devices. You'll hit a limit at some point
with usb devices that require power. The best alternative is to get the device with it's own power cord or get a
usb hub that has it's own power cord to plug in.

[dmcnab]

OK...thanks guys....I now have a better understanding of USB connecitons and will probably get a powered hub...that seems to be then consensus...thanks again....over and out.

[scaisson]

Here are the specifications on USB on EACH connector:
1. Voltage = 5Vdc, from either USB input or self powered.
2. Current = 500mA max. See note below.

The current is short circuit protected, up to a sloppy 500mA limit (typically). That means you may get up to 600mA before it limits. That's why some old USB hard drives may work or may not work on a USB connector. Sometimes, switch to another USB connector may magically work. New portable hard drives require less current to spin up to start working. They almost always work even on a passive hub.

For a passive USB hub, the only source of power is from the USB connector linked to the single USB connector of the PC. That means the entire hub is powered by a single USB connector from the PC. That is, 500mA max.

Depending on the number of devices plugged into the hub, and the devices themselves, the current limit maybe reached easily. Memory card usually uses up to 500mA. So a single memory card, such as SD card, would consume all the available current by itself. On the other hand, some large physical devices have its own power. It does not draw any current from the hub. This includes physically large USB hard drives (3.5-inch type), as an example.

Sometimes, long USB cable may create too much voltage drop. I had experience that a long USB extension to a SD card adapter did not work. Removed the long cable and it worked fine.

In a nut shell, advise to use powered USB hub.