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LED is short for Light Emitting Diode. It is a small solid state electronic device with what is known as a PN junction. When an electrical current is applied to the LED, electrons flowing through the PN junction experience transitions in energy level, emitting radiant energy. The frequency of this radiant energy (the colour of the emitted light) is determined by the crystal structure of the semiconductor material and the elements comprising it. Some semiconductor junctions with special chemical combinations emit radiant energy within the spectrum of visible light. Simply put, these junctions glow when electrical current is applied. At present, red, green, amber, yellow, blue and white LED colours are available.
LEDs have a life expectancy of 100,000 hours. Their reliability and long life shows that there is no need to change bulbs and virtually no maintenance is required for the life time of the equipment. Power consumption is also significantly lower than incandescent lamps.
LEDs are often packaged into very compact modules for displaying meaningful information.
| The common module types: |
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| 1. |
a versatile dot matrix which can be controlled to display graphical images, text and numbers. The smaller the dot size and pit size gets, the more dots are needed in a given display area, with a corresponding better resolution of the characters that can be formed on the modules. Dot size can be as small as 1.8 mm to as large as 10 mm.
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| 2. |
seven segments for representing numbers from 0 to 9
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| 3. |
sixteen segments for showing letters and numbers
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