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Beneath the sign’s skin are 18 million Light Emitting Diodes4 (LEDs), attached to minicircuits called pixels. Within each pixel are eight small light-emitting diodes; two blue in the middle with two green and a red on one side and two red and a green on the other (LED Cluster). The flickering lights that they produce are translated by the human brain as true colours and images. The density of the pixels allows for bright and vivid colours that can be viewed easily in direct sunlight. The LEDs are also less prone to damage from temperature change or blowouts than light bulbs, and are supposed to last 100 times longer — a total of 100,000 hours.

Fig. 18 LED clusters [Source: Electronix Express]

Many people think of large-format displays in terms of the year the NASDAQ sign went up. This outdoor installation demonstrated that besides size, another factor important to ubiquitous display is its ruggedness. A display that can be left out in the rain opens a very different realm for imagination.


KPN Telecom building

However, the NASDAQ sign has no interactive features; it actually provides a passive one way visual communication. It displays only advertisements and stock information. On the other hand, during the same period, that is 2000, Renzo Piano completed the headquarters of KPN Telecom Corporation in Rotterdam. The building is located at the end of the Erasmus Bridge, which is an icon for the city of Rotterdam. It is a relatively tall tower in the Netherlands since most of the country does not have high rises. The

Fig. 19 KPN Telecom Building, Rotterdam [source:http://www.galinsky.com/buildings /kpntelecom/]

4 A light-emitting diode (LED) is a semiconductor device that emits incoherent narrow-spectrum light when electrically biased in the forward

direction. This effect is a form of electroluminescence. The color of the emitted light depends on the chemical composition of the semiconducting material used, and can be near-ultraviolet, visible or infrared. Nick Holonyak Jr. (born 1928) of the University of Illinois at Urbana-Champaign developed the first practical visible-spectrum LED in 1962. [source; http://en.wikipedia.org/wiki/LED]

Physical Computing:

Using Everyday Objects as Communication tools


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