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Re: [APD] LEDs once more



This is from my brother who works for Colorkinetics...now a division of
Philips...........http://www.colorkinetics.com/..

TerryBarber.................................................................
............................................................................
.

"Cree XR-E Spectral Dist" is the wavelength distribution for one of the
white LEDs we use (full datasheet at
http://www.cree.com/products/pdf/XLamp7090XR-E.pdf)

compared to

"Ushio Aqualite Spectral Dist" for a specialty lamp from a company I've
actually talked with about aquarium/marine applications. (full datasheet at
http://www.ushio.com/files/specs/Aqualite.pdf)

If you look at the 10,000K lamp vs the 5,000-10,000K LED, the distribution
is fairly similar - the lamps primary peak at about 420nm vs the LEDs 450nm,
but both with some "yellow" around 550nm.

Colored LEDs (simpler and cheaper than white LEDs) are very monochromatic,
such as the royal blue XR-E which is centered at 450nm, but has no ouput at
other wavelengths. (Interesting note - the technology of ceramic/metal
halide lamps can produce single color light too. The MGM Grand hotel in Las
Vegas is lit by CMH lamps that output only green light)

The primary problem with LEDs for aquarium lighting (and we've looked at it
with some potential partners) is the cost. The 150W Aqualite lamp produces
7000 lumens (lumen is a measurement of raw light output from a source) for
about $65, but you'd need 70 or so white LEDs (and even more blue LEDs) to
get the same light output at a cost of $150 or more.

So, technologically LEDs could be used for aquarium applications needing a
very specific spectral distribution (likely with a mix of white and blue
LEDs), but this hasn't proven to be financially viable.
----- Original Message ----- 
From: "Jerry Baker" <jerry at bakerweb_biz>
To: "aquatic plants digest" <aquatic-plants at actwin_com>
Sent: Friday, December 07, 2007 12:54 PM
Subject: Re: [APD] LEDs once more


Erik Åslund wrote:
> The "white" LED's give very little light of
> wavelengths that plants can use effectively.

I don't know either way. I haven't seen a spectral distribution for
these LEDs.

As far as I know, plants can use any visible light fairly effectively,
but they absorb reds and blues more efficiently on account of their
green color being due to the fact that chlorophyll reflects green light.
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