so I read that an ac/dc adaptor should be 9 to 12 volts. I found a way to power the arduino using the USB cable by using the plug from the kindle charger. it is rated at 4.9V and 0.85 amps. I know that it is a 5 volt system, so can I run it this way using this cable. In other words, am I hurting my board by using the USB but connected to the wall adaptor from the kindle?