I recently had to build an infrared close proximity sensor that could tell if something was ... IRED1 is modulated by connecting its anode (A) to ~38kHz signal yielded by D9 of the Arduino Uno (TP1) ...

The digital signal output to be detected (usually marked as DO in the module) is applied to D2 input of the Arduino. Analog output (marked as AO) from the module is not used here. Sensor-head of the ...