Windows 7: Checking USB Device Power Usage

Did you know that there's preset limit on the available amount of power on a USB bus? If you have several USB devices plugged into your computer's USB ports, you need to be aware there is only a small amount power available for them.  Most computers have multiple what are known 'USB root hubs', and each hub can  deliver a maximum of 500 milliamps of power to attached devices. If the energy demands of the connected USB devices exceeds that limit, the USB bus can shutdown.

To check power draw of the USB devices connected to your computer:

• In the Start menu search field, type: Device Manager and press the Enter key
• In the Device Manager window, expand the node Universal Serial Bus controllers
• Double-click on one of the USB Root Hub entries.
• Click the Power tab. 

This tab displays a listing of attached USB devices, how much power they use and how much is available.  If you have more USB devices then you have available ports or power.  Consider buying a power USB hub that uses energy from the wall socket and not your computer's motherboard.