Another type of displays is liquid crystal (LCDs) that are used in similar applications where LEDs are used.The applications of LCDs are display of numeric and alphanumeric characters in segmental and dot matrix displays.
Liquid crystal have been called "the fourth state of matter"(after solids ,liquid and gases) because they have certain crystal properties normally found in solid,yet flow like liquids. Unlike LEDs and other electroluminescent devices,LCDs do not generated light energy,but simply alter or control existing light to make selected areas appear bright or dark.
The liquid crystal display has the distinct advantage of having a low power consumption than the LED.It is typically of the order of microwatts for the display in comparison to the some order of milliwatts for LEDs. Low power consumption requirement has made it compatible with MOS integrated logic circuit.Its other advantages are its low cost and good constrast. The main drawbacks of LCDs are additional requirement of light source,a limited temperature range of operation(between 0 and 60°C),low reliability,short operating life,poor visibility in low ambient lighting,slow speed and the need for an ac drive.
There are two basic ways in which liquid crystals are used for controlling properties of light and thereby change its appearance.
Accordingly,there are two types of LED displays-dynamic scattering display and field-effect display.
When dynamic scattering display is energized,the molecules of energized area of the display become turbulent and scatter light in all directions.Consequently,the activated areas take on a frosted glass appearance resulting in a silver display.Of course, the unenergized areas remain translucent.
Liquid crystal have been called "the fourth state of matter"(after solids ,liquid and gases) because they have certain crystal properties normally found in solid,yet flow like liquids. Unlike LEDs and other electroluminescent devices,LCDs do not generated light energy,but simply alter or control existing light to make selected areas appear bright or dark.
The liquid crystal display has the distinct advantage of having a low power consumption than the LED.It is typically of the order of microwatts for the display in comparison to the some order of milliwatts for LEDs. Low power consumption requirement has made it compatible with MOS integrated logic circuit.Its other advantages are its low cost and good constrast. The main drawbacks of LCDs are additional requirement of light source,a limited temperature range of operation(between 0 and 60°C),low reliability,short operating life,poor visibility in low ambient lighting,slow speed and the need for an ac drive.
There are two basic ways in which liquid crystals are used for controlling properties of light and thereby change its appearance.
Accordingly,there are two types of LED displays-dynamic scattering display and field-effect display.
When dynamic scattering display is energized,the molecules of energized area of the display become turbulent and scatter light in all directions.Consequently,the activated areas take on a frosted glass appearance resulting in a silver display.Of course, the unenergized areas remain translucent.
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