What is LED ?

LED itself is pretty old invention. Abbreviation LED means Light Emitting Diode and first mark about light emitting crystal was from 1907. 20 years later was also invented first LED, until this time all items was not constructed, but simply discovered. After this was whole thing "put on hold" because there wasn't any practical use duo to extremely low light output.In 1962 Nick Holonyak Jr. succeeded to make specimen which was powerful enough to justify their existence. Later he became "father of LED" and a year later he was sure, there will be time, when LED become superior compare to Edison bulb. It is pretty clear that price about $200 per piece was too high and nobody was interested of this strange thing with price like this. But "gin was out of the bottle" and in 1970 the price was about 5 cent.If so far only red LEDs could be made, then in 1972 yellow, green and blue were finally released. But still got a long time until the year 1993 could be prepared by a blue LED that will light the real power of their own.
At the moment LED is major light source and in some places (Australia, EU) tungsten is even forbidden doe to low light output compared to LED. In the case of filament, visible light receives about 4% of energy, while LED can achieve an average of 12%. But lighting efficiency is something else entirely. While lamps with up to 100W filaments were about 17 lumen per watt, newer LEDs already have almost 300 lm / W.

The size of the LED is determined by the dimensions of the housing. Because very small LEDs are currently in use, they are mounted on a surface and the housing is called an SMD (surface mounted device). The number after it indicates the size of the part. For example, the SMD5050 part has a surface mount and side dimensions of 5 × 5 mm. Many other electronic components have similar markings. It also sets its own limits, as very small details are sensitive to any physical force. Electric shock also occurs at relatively low voltages and sets limits on applications.