The sensor of this circuit found in Popular Electronics can be formed by a piece of fabric between two bare wire screens. When wet, the fabric will pass the current between the screens, triggering the alarm.
Originally suggested by Popular Electronics to control Christmas lights, this circuit can...
We found this easy start circuit in Electronics Now magazine from December 1993. The frequency is...
This circuit was obtained from an English magazine from 1977. The magazine no longer exists, but...