Light emitting diode as light source in some photoelectric control device, used as a signal display device in many electronic equipments. The tube core which made by LED strip, composed of 7 segment semiconductor digital tube 7 strip, each digital tube can display 0 ~ 9 ten number. When it is in the positive state of the work (i.e. ends with forward voltage), the current flows from the LED anode cathode, semiconductor crystal emitted from the ultraviolet to the infrared light of different colors, light and the strength of the current;

The core part of the light emitting diode chip is composed of P type semiconductor and N type semiconductor, between the P type semiconductor and N type semiconductor has a transition layer, called the PN junction; its basic structure is a piece of electroluminescent semiconducting materials luminescence, placed on a wire rack, and then sealed all round with epoxy resin, to protect the internal core role, so the seismic performance of LED well.

In some semiconductor materials of PN junction, the injected minority carrier carrier and the majority of the extra time will be the form of light energy to release, thus the electric energy can be directly converted into light energy. PN junction reverse voltage, a few hard carrier injection, it is not luminous. The use of injection electroluminescent diodes is produced by the principle of light emitting diodes, commonly known as LED.