Light-emitting diodes in the production, the use of different materials, then you can make different colors of light. LED light colors: red light, yellow light, green light, infrared light and so on. The shape of light-emitting diodes are: round, rectangle, triangle, square, combination of shape, special shape and so on. Common application circuit of four light-emitting diode, drive circuit that is DC, AC drive circuit, pulse drive circuit, color LED driver circuit. When using the LED for indicating circuit, current limiting resistor should be connected in series, the size of the resistor should be based on the use of different voltage and LED operating current required to choose. Light-emitting diode drop is generally 1.5 ~ 2.0 V, the operating current generally take 10 ~ 20 mA appropriate.
Classification of LED light-emitting diode