Outdoor LEDs 1

[Paddymagee]

Hi,

I note with intrest the number of petrol stations changing over to LED pricing displays.
What intrests me is the excellent readability of the displays, not only can you see them from 200m+ but they are viwable at narrow angles (until you are almost side on to the sign)

Does anyone know what sort of LED is used in these signs?
I have designed a sports display using electro-mechanical digits but I would prefer to use LEDs if I can find one bright enough with a good view angle.

From what I have seen so far the higher the mcd (brightness) the lower the view angle. Whats the best compromise between the two for an outdoor display?
Also whats the best colour to use? Most of the pricing displays are red but I would prefer to use amber, yellow or white.

All ideas and suggestions are welcome.
Thanks in advance.

 

[MacGyverS2000]

Color: That will depend on your application. Blue may be easier to see during the night, whereas green may be more visible during the day. White gives you full-color rendition capabilities with colored filters (if RGB LEDs are used, not the typical blue LED with yellow phosphour). Red is often used because those LEDs are the cheapest (the red technology is the most mature of the colors).

Angle: For a particular process/LED type, there is only 'X' amount of photons emitted. You can either have those photons emitted over a large angle (and therefore look more dim but uniform), or over a small angle (and look quite bright from straight on, but almost non-existant from the sides). Once you have selected the proper viewing angle, you simply need to find an LED that is powerful to give you your desired output at that angle (read, lots of searching).

Manufacturers: There are a number of manufacturers making LEDs, but only a handful make reliable, high-brightness versions. Lamina Ceramics is one, with their COB (chip-on-board) LEDs. Philips is another, with their Luxeons. Without external optics, these units have viewing angles of 120-180 degrees.

Backlighting Types: In some situations, you can light the board directly from behind with the LEDs. In others (e.g., thin boards), you must sidelight the boards and use a light spreader.


Dan - Owner

http://www.Hi-TecDesigns.com