I have a number of Flip boards running off their own wall wart style power supplies (which also powers sensors, etc). The problem occurs when I hook these Flips to a USB hub and then into a laptop to receive telemetry from them. The Flip modules receive power from the usb hub even when the laptop is turn off and when the Flip wall wart power supplies are turned off. So the Flip never turn off unless I remove the USB cables or remove power from the hub. Can the ability of the Flip to run off the USB cable power be disabled?