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.
The components of this circuit are not common today, as it was obtained in the Linear Applications...
Suggested by General Electric documentation from 1968, this circuit activates a relay after 60...
This basic amplifier circuit that can be powered by voltages from 6 to 24 V has the output...