White LED's

["Paul Watkin" <paul_watkin@xxxxxxx>]

Hi,

Not sure if anyone has already posted these URL's so forgive me if
reposting, there have been a lot of questions from people about using the
LED's in arrays, below are url's for two different approaches  (i.e. one
diy
and the other buy it in finished!)

http://radiolocation.tripod.com/LEDdimmer/LEDlampDimmer.html

http://www.hdssystems.com/Subassemblies.htm

If you wish to buy 5mm LED's alone then I really would strongly advise you
head in the direction of Nichia, they are recognised as being the leaders
in
this field and have quality products. Also you can buy online via their
website, or locally in Europe I think they rep via Germany, pricing  1off
@$5, 100 @ $2.05, 500 @ $1.85,  1K @$1.35 , 5K @ $1.00 (from website) for
6.4cd (shipping $25).

When you purchase the devices try to get them supplied binned for
Intensity,
Colour/wavelength, Vf otherwise you may wel have some interesting colour
affects accross an array, some suppliers do this as a matter of course
others don't, i.e. all the devices in one packaging increment (bag or reel)
are from the same repsective bins

Before people get too carried away thinking about 6 LED's replacing a 40W
bulb it is worth pointing out that these things are point sources of light,
in the case of some of the high power devices the viewing angle will be as
low as 10 to 20 degrees. In order to get nice friendly even illumination at
close range you may need to look at secondary lensing etc.

Another company to take a look at from an ideas perspective is Lumileds (
http://www.lumileds.com/ ) , they
are part owned by Philips Lighting and
their charter is to replace the filament bulb in a number of applications,
have a look at there application showcase section, for instance
http://www.lumileds.com/pdfs/AS03.PDF
, unfortunately there webiste aint up
to much

If you aren't limited on the ammount of current to throw at the problem
(700ma to 1000mA) then one product that might be of interest is the Luxeon
5
Watt emitter (http://lumileds.com/pdfs/DS34.PDF
) , will also act as heating
for the room!! in order to get the heat out of the device the die sits on a
copper heatsink. These won't be cheap, and im not sure who you would deal
with in Europe but could find out if anyone was interested.

I am not affiliated with Nichia in any way but know there products from a
competitive perspective, I work for the other shareholder in LumiLed!

just my thoughts

Paul