Using the CA3140 integrated circuit, this switch was found in the June 1986 Radio Electronics magazine. Sensitivity adjustment is made at the trimpot in series with the sensor.
We found this circuit in an English documentation from 1979. It shows how you use a 100 uA...
This circuit was found in an EDN from the 90s. For the components indicated, the frequency is 10 kHz....
This is a very interesting automation that can be adapted for other types of applications. In...