This simple rain, leak or moisture detector circuit appears in other places on this site with slight variations. This was obtained in an English documentation from the 70s.
Originally this circuit was indicated to be used in a garage door control, but it can be modified for...
This conventional oscillator with the 741 can be precisely adjusted to produce a 400 Hz signal. The...
This current-limited circuit was found in a Popular Electronics from the 90's. ...