I am embarrassed to ask such a noob question.
I am getting started with an Uno R3 and a box of sensors from eBay. I managed to make a bluetooth transceiver work with an LED. Yay.
Now I want to add another sensor into the mix. I believe the other sensor takes 5V. How do I know how much power I have available by this (USB-powered) Uno?
I don't have documentation on most of my sensors, should the power consumption normally be printed on the sensor/dongle? Does the fact that the Uno can be powered by a 9V battery mean that its max power output is 9V?