We found this circuit in the September 1971 issue of Radio Electronics magazine. The sensor is an LDR and R1 adjusts the sensitivity. A relay with the appropriate voltage can be used instead of a buzzer.
The circuit shown consists of a bilateral constant current source with an operational one that...
The sound of this experimental musical instrument is produced by the movement of the hand in front...
We found this circuit in a Japanese 1968’s documentation. The circuit makes use of transistors from...