LED (Light Emitting Diode)

Light emitting diode, or better known as LED (Light-Emitting Diode) is a semiconductor that emits light given forward voltage. LED consists of two legs of the anode and cathode. The amount of power that exists between the poles of the LED anode and cathode determines the intensity of infrared light is generated.
      Light LED (Light Emitting Diode) function to emit light to the receiver (receiver) phototransistor, help detect objects placed objects in the middle between the transmitter (transmitter) and receiver (receiver), which will be received by the phototransistor, because the presence of these LED light intensity of light to be received by the phototransistor will depend on the placement of objects objects.

LED is in principle the same as the diode, ie when there is current flowing from the anode to the cathode leg then the LED will light. And to determine which leg is the leg length of the anode (positive) while the cathode is the short leg (negative).