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.
This circuit was found in a NASA documentation from the 1980s. The components used are of the time...
This circuit, found in a 1994 documentation, uses 20 A 2N5448 triacs or equivalent and should be...
This circuit using a SIDAC as a relaxation oscillator was found in the ON Semiconductor manual for...