This circuit was found in Radio Electronics from the 90s. The sensor is an oscillator whose frequency depends on humidity, an uncommon component nowadays.
We found this circuit in an American publication from the 90s. The transistors must be provided with...
The critical components of this project from a 1978 publication are the transformers, which can be...
September 2017 - Mouser Electronics already has the AP431S adjustable regulator from Diodes...