This circuit uses a heated filament as a sensor. With the air current it changes resistance, and the circuit detects it. The circuit is from a 1969 EEE.
When the sensor X1 is opened, the relay is energized. When waiting, the current drained is very...
This circuit can also use other series operational amplifiers such as MC33172, MC33174, MC35171,...
This circuit was originally designed to power the CB18698's MSX interface, but it is suitable for...