Using an analog microamperimeter this circuit has a phototransistor adapted to the wheel as a sensor. The circuit is from American documentation from the 1980s, but the components are common today.
We have dozens of similar projects in articles and circuits on this site. This is from Radio...
This circuit with an unusual configuration was found in the January 1974 issue of Radio...
This interesting circuit from 1967 documentation uses three series lamps to regulate the voltage...