LED (Light Emitting Diode) is a new type of light source developed and produced. It has the advantages of low power consumption (current is only 10~20mA), high brightness (light intensity can reach tens of thousands of mcd), small volume (minimum diameter can reach 3mm), light weight (a light emitting diode weighs only a few tenths of a gram), long life (average life of 100000 hours), etc. Now it has gradually replaced incandescent lamps and low voltage halogen tungsten lamps to produce road traffic signal lamps.