This humidity sensor indicates the different levels of conduction of the sensors through an LED bar. The circuit is from Popular Electronics and must be powered by cells or battery.
Equivalent operational amplifiers can be used in this circuit of the 1990 Linear Databook,...
This circuit was suggested by General Electric in a 1965 documentation. The circuit can be...
This conventional circuit uses the 4017 to control incandescent lamps or LEDs, according to...