This circuit was found in a 90's EDN. The circuit provides two 15 V outputs and one 5 V output from the 12V voltage of a car battery. The components are from that time.
By LED flashes you can get an idea of the degree of moisture in the soil. The sensors are wires...
This capacitive switch or approximation relay was found in a 1980s US publication. Power should...
Found in an Electronic Design of 1964, this circuit operates with control voltages from 0 to 12 V...