Humidity detector circuit
This humidity detector circuit diagram is very simple and uses few components and can be used for activation of an electronic devices when the detector senses a certain humidity.
The sensor is constructed from two pieces of copper placed at a short distance of each other. when the electrical resistance of copper conductors drops below a certain value, Schmit trigger built using transistors T1 and T2 switch. Bistable multi-vibrator is flip through C1, so that at point B there is a low voltage (relay triggers).
Relay is activated when the resistor R6 is connected to point B but the point A.
The circuit has a low and requires a 5 volt DC power supply.