# led wavelength



## ragdolltwoone (Jul 7, 2011)

i am a total noob about LEDs so may sound like a dumb question and even then the question i am asking may not make any sense

looking at the XP-G datasheet for the warm white the XP-G wavelength at 450nm peaks at 70% while the 620nm peaks at 100% does that mean every XP-G warm white led will produce those wavelength specification?

because as soon as i look at the XP-G binning datasheet chromaticity regions for warm white, lets say i pick 7C1, which is in the 3000K region, will it alter the peak percentage of the 450nm and 620nm curve?

is there any relationship between the chromaticity regions and wavelength?

thanks for your help


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## B0wz3r (Jul 7, 2011)

ragdolltwoone said:


> i am a total noob about LEDs so may sound like a dumb question and even then the question i am asking may not make any sense
> 
> looking at the XP-G datasheet for the warm white the XP-G wavelength at 450nm peaks at 70% while the 620nm peaks at 100% does that mean every XP-G warm white led will produce those wavelength specification?
> 
> ...


 
Yes. Chroma is determined by wavelength and the constituent wavelength components in any light source. A wavelength of 620 is in the red-orange region of the spectrum, so will produce a warm tinted color temperature.


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## ragdolltwoone (Jul 9, 2011)

so if i pick a XP-G warm white of a binning in the 3000K region will i still have a wavelength peak in the 450nm at 70% (page 4 in the XP-G pdf)

i ask this because i wish to try hydrophonics and have read 620nm and 450nm are the key wavelength for photosynthesis and want to ensure whichever XP-G warm white binning i get the wavelength will not be altered.


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## Norm (Jul 9, 2011)

Moved to LED Forum - Norm


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## wrf (Jul 9, 2011)

ragdolltwoone said:


> [...]does that mean every XP-G warm white led will produce those wavelength specification?[...]


 
Exactly? No, it does not mean that.



ragdolltwoone said:


> [...]want to ensure whichever XP-G warm white binning i get the wavelength will not be altered.


 
Realistically, if the spectral distribution did not vary between LEDs, there would not be the variations in tint. The chart you are referencing does not accommodate variations in manufacturing nor operating parameters nor lifespan. It does not list upper/lower boundaries, it does not give +/- % accuracy, etc.

See also this post by Harold_B regarding the variations due to viewing axis.


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## Harold_B (Jul 10, 2011)

I think you might be disappointed with the results of an XP-G based grow light. Even though the distribution of energy over the spectrum looks close to what you desire you need a lot more energy from a narrower band of wavelengths. You would be better off to look at large arrays of red and separate arrays of deep blue and then turn them on / off with the appropriate growth cycle. They can be mixed in the same enclosure or on the same PCB and made switchable but ifthe plant doesn't need a particular spectrum during the cycle it is wasted energy.


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## qwertyydude (Jul 10, 2011)

For the money for grow lights I'd go high pressure sodium. You'll get about the same energy efficiency but it'll be cheaper and easier to construct. Once you get to driving these high powered led's strong enough for grow lighting you simply lose efficiency. I tried sprouting some tomatoes with an XM-L wired to a power supply driven at 2.5 amps and after it grew a couple inches I found it was almost insufficient light to keep it growing healthy.

A typical 100 watt HPS light is 9500 lumens and is nearly at the perfect wavelength for plants. To get that many lumens from the most economical and energy efficient led, the Cree XM-L you're looking at at least 10 XM-L led's plus the driver and construction costs. This doesn't even take into account the large hit you'll take because the led's emit a lot of green light.


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## LED-grower (Jan 22, 2013)

qwertyydude said:


> For the money for grow lights I'd go high pressure sodium. You'll get about the same energy efficiency but it'll be cheaper and easier to construct. Once you get to driving these high powered led's strong enough for grow lighting you simply lose efficiency. I tried sprouting some tomatoes with an XM-L wired to a power supply driven at 2.5 amps and after it grew a couple inches I found it was almost insufficient light to keep it growing healthy.
> 
> A typical 100 watt HPS light is 9500 lumens and is nearly at the perfect wavelength for plants. To get that many lumens from the most economical and energy efficient led, the Cree XM-L you're looking at at least 10 XM-L led's plus the driver and construction costs. This doesn't even take into account the large hit you'll take because the led's emit a lot of green light.



Sorry, but I think that was full of misinformation.

HPS won't give same energy efficiency as LED's, not even close. For growing LED lights can be tuned exactly as wanted to fit to specific peaks in chlorophyll curves a & b. HPS, at first radiates most of its energy as IR (heat). And then there is lot's of green to yellow wavelengths included - like you said that LED's do. Almost like you would have read "why LED's are better than HPS" summary, and then turned everything vice versa.



Strong enough? LED's are "stronger" than HPS. Longer lifecycle.
Efficiency? They are more efficient than HPS for the reasons I already told.
LED lights are more expensive, you are right about that. Even if making them by self, like I am.
"..large hit you'll take because the led's emit a lot of green light" - LED lights don't emit green unless you add green LED's to them. LED components have typically very narrow spectrum compared to other light types.
HPS light is 9500 lumens and is nearly at the perfect wavelength for plants. NOT true. Only small parts of the spectrum fits in the peaks in the chlorophyll curves. HPS have too much green and yellow and they radiate lots of heat.


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