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 Audio System circuit was found in 1965 documentation. It is a 50 ohm line circuit with 22 dB...
This circuit is from an Electronics Now, American magazine from December 1992. The magazine no...
This circuit allows to increase the output power of a 741 as an amplifier. The circuit is from a...