As you can see in the schematic all three TC74 sensors have their SDA and SCL pins connected in series to pin A4 and A5 on the Arduino board. ... 1001010 which converts into decimal 72, 73 and 74 ...

The microcontroller-based concept was chosen because I wanted to scale the sensor system later to suit other applications. Here is the diagram of my Arduino infrared close proximity sensor. As you can ...