Found in a 90s Radio Electronics, this circuit uses a ceramic capacitor (C1) as a sensor. The operational amplifier is a double 741 of the time.
I found this circuit in a 1992 Electronics Experimenter Handbook. The circuit can be easily...
This egg timer has been found in an English magazine that no longer exists in 1982. The...
This comparator application circuit was obtained from the June 1986 Radio Electronics magazine. The...