Which sensor for a wheel


This is my first project with Arduino. I need to attach a small cardboard wheel to Arduino (10 cm) and receive signal every time the cardboard moves. The wheel can move only in one way. A potentiometer could be a good choice but I need a unlimited rpm. Which sensor I have to use?

Thank you very much, Daniele

Hi, Daniele.
Sorry, but your request is not that clear to me…
Do you want to attach a piece of cardboard to a 10 cm wheel? Or is the wheel made of cardboard? 10 cm is the diameter? What do you attach to Arduino?
And you want to measure the change of state (from stop to movement, and from movement to stop), or the rotational speed?