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.
This circuit uses a voltage comparator and can produce signals up to 20 MHz. The resistors R are...
This system makes use of incandescent lamps only and uses a SCR with a full wave bridge for powers...
Frequencies from 1 to 10 MHz can be obtained with a small adjustment of the variable in a narrow...