Found in a 90s Popular Electronics, this sensor operates by infrared reflection. The components are modern, and the phototransistor can be of almost any type.
This circuit was obtained in a 1982 English magazine. This circuit can be used both as a simple...
This sensor triggers an oscillator emitting sound when a magnet is approached by a reed switch....
Suggested by Burr Brown in 1969 documentation, this circuit makes use of an integrated component...