The part list consists of one Arduino, two resistors, and one IR emitter. That’s right, an emitter. When an LED (IR or otherwise) is reverse biased it can act as a light sensor.

In my case I have used only 3 x 330Ω resistors, 3 leds and a TSOP4838 IR receiver module. You must check the datasheet before use the IR module to see which pins connect to the power supply and which ...