This circuit is from an old Popular Electronics, but it can be easily implemented nowadays, even adapted to act as a shield. The circuit has the frequency given by C1 and adjusted in R1.
The presented logical configuration uses one comparator of the four existing in an LM139 or...
This zero-crossing circuit was found in the 1989 Radio Electronics Experimenter. The Triac must be...
This transformerless low-current power supply circuit was found in the August 1998 issue of...