Infrared light-emitting diode is a kind of diode that can emit infrared rays, usually used in remote control and other occasions. Commonly used infrared light-emitting diodes are similar in appearance to light-emitting diode LEDs and emit infrared light. The tube voltage drop is about 1.4v, and the working current is generally less than 20mA. In order to adapt to different working voltages, a current-limiting resistor is often connected in the loop.

　　 Infrared light-emitting diodes are made of materials with high infrared radiation efficiency (commonly used gallium arsenide GaAs) to make a PN junction, and a forward bias is applied to inject current into the PN junction to excite infrared light. The spectral power distribution is the center wavelength of 830~950nm, and the half-peak bandwidth is about 40nm. Its advantage is that there is no red storm, (using 940~950nm wavelength infrared tube) or only weak red storm (red storm is visible red light) and prolongs the service life.

　　 Light is an electromagnetic wave, and its wavelength range is from a few nanometers (1nm=10-9m) to about 1 millimeter (mm). What the human eye can see is only part of it. We call it visible light. The wavelength range of visible light is 380nm~780nm. The wavelength of visible light is divided into red, orange, yellow, green, blue, blue, and violet from long to short. The wavelength is shorter than violet light. It is called ultraviolet light, and the wavelength longer than red light is called infrared light.

　　 There are two ways to receive infrared light-emitting diodes, one is the direct type, and the other is the reflection type. Direct type means that the luminous tube and the receiving tube are relatively placed at the two ends of the transmitter and the controlled object, with a certain distance between the middle; the reflective type means that the luminous tube and the receiving tube are arranged side by side, usually the receiving tube is always without light, only in the infrared emitted by the luminous tube When the light meets the reflector, the receiving tube will only work after receiving the reflected infrared light.