Using LEDs, LCDs and GLCDs in Microcontroller Projects

5.2 LED Colours

Early LEDs were available only in low intensity red colour. Today, with the use of different inorganic semiconductor materials, visible LEDs are available in red, orange, yellow, blue, green, violet, purple and white. In addition, non-visible infrared and ultraviolet LEDs are also available for specific applications.

Table 5.1 gives a list of the available LEDs with their emitted wavelengths, typical forward voltage drops and the typical materials used in their construction.

Table 5.1 LED colours.

The white LED is constructed either by using three primary colour LEDs, red, green and blue and mixing them to obtain white light (called RGB based white LEDs); or alternatively, by converting the monochromatic blue light into white by using a phosphor material (called phosphor based white LEDs).

The technical specifications of some LED types are given in Table 5.2. The LED selection for an applications depends on the following factors:

• size;
• shape;
• colour of emitted light (wavelength);
• colour of the case;
• brightness of the light;
• viewing angle.