9 channels sensor switch circuit
This 9 channels sensor switch circuit diagram is designed using CMOS components.
This 9 channels sensor switch circuit 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.
If several sensors are touched simultaneously, priority encoder delivers 4-bit code corresponding to the sensor with the highest number.