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.
This circuit is suggested by National Semiconductor and has an excellent gain, for a photodiode as a...
With the circuit shown, when the brightness of one lamp decreases, that of the other increases. There is...
We found this circuit in an Intersil documentation. Temperature sensors are special components of the time,...