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.
The transistors of this old circuit from the 60s can be the BC548, in a current version. The...
This electronic soldering gun circuit was found in the December 1998 Electronics Now magazine. The article...
This circuit was found in an American documentation from the 90's. What it does is provide at the...