Schematic Reference

This sensor switch circuit diagram is designed using CMOS components. This sensor switch circuit has nine channels and consist of only three integrated circuits and some resistors. Due to high input impedance, 74HC147 allows to use of 4.7 M resistors to create a logic level "high" to sensor inputs. When one sensor is touched, the resulting low resistance to ground circuit causes IC1 to read a logical level L.

9 Channels Sensor Switch Circuit Diagram
If several sensors are touched simultaneously, priority encoder delivers 4-bit code corresponding to the sensor with the highest number.