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.
In the figure we have the way to control a triac with a low current and low voltage switch,...
This trigger circuit was found in old European documentation, but it can be implemented with...
May 2017 - The new ROHM SFR series anti-sulfur resistors can now be obtained from Mouser...