Sensors with external power supply

Other Hardware General Electronics
10

If you want to draw close to the 450mA limit (the Uno uses ~50mA itself) from the 5volt pin, then

  1. Use a 5volt cellphone charger plugged into the USB socket.

  2. Use a ~7.5volt regulated supply on the DC socket.

9volt on the DC socket is not going to work, unless for a short while, because of the thermal limits of the 5volt regulator of the Uno.
Leo..