USB hub

[Skunkworks]

I recently bought a USB hub. It did come with a power adapter, but I have noticed that it works just fine (for now...) without plugging in the power supply.

I suppose that the hub gets the power from the computer, or from some other connected hardware?

Question is: Is there a risk of damaging the hub or whats connected to it by not using the power supply?

/skunks

[BayAreaLondoner]

You shouldn't damage anything, but certain devices that you plug into it may require that you use the external power supply. Sometimes the only warning you will get is that one or more of the devices won't work properly.
If you go into the Control Panel System menu and take a look at the Hardware, you'll see a device like "General Purpose USB Hub". Opening up its properties and looking at the Power tab will give you some information about what it is capable of supplying and what each device is using.

[GeneralElectric]

BAL is absolutely right, the maximum power available from your PC for the WHOLE USB chain is 500mA per USB port.

My USB scanner takes up to 500 mA when in use so if I had an unpowered hub with my scanner, then connected some other bits and pieces, I would expect some strange behaviour if I used them all at the same time.

You're probably OK if you've only got a printer connected as that won't take power from the USB, only its AC input. Once you start adding things like scanners that draw all their power from the USB supply, you'll need to power up the hub to ensure reliable operation.

You are unlikely to damage anything by unplugging the power to the USB hub while it's on, but some devices (like digital cameras) really hate you doing that when they're transferring data. Put it this way - it's not highly recommended!

Hope this helps.