Building LED lights from facts, no theories

[knna]

Knna, to the best of your knowledge what would be the wavelengths that would most efficiently and productively enhance marijuana growth? I was hoping you had tossed a few out.

Hello, physicsnole, welcome to this thread (and welcome back to the board).

I preferred to not go that way in this thread because this issue has been well addressed on your perfect led grow light thread. I agree with conclusions there.

If any, i would like to point out two things:

-Red part of the spectrum, from 625 to 685nm must be at least 50% of all PAR watts used. And preferably close to 70%. Using 640 or 660nm leds makes little differences. Ideally, both would be used, but only one works fine. Although all the red of 660nm obliges to use higher amounts of blue and far red.

All the rest of the spectrum may share the remaining 25-50% of the PAR watts, with special weight of blue, preferably about 440-450nm, which need to be at least 10% of the PAR watts and preferably 15-20%. More than 30% of blue often harm more than help.

Green and yellow need to be at least 10% and preferably 15% (but how much of this range is optimal is what im working now, and share between green and yellow).

Out the PAR range, some far red, preferably peaked about 720-725nm, is required. Along most of the time, on small amounts. On flowering induction, it need to be higher, in order to shorten it. Ideally, far red must be independent adjustable in order to control plants morphology and phenotype expression.

Im not sold on the benefits of UVB (and im against UVA), but im thinking on carry some experiment with it right now. Obviously, i dont have any idea if it worth or at what amounts.

But we still need to learn a lot of how enhance MJ growth by far red manipulation, and the best way of doing it.

-Selection of wavelengths used are more dependent of the efficiency of the leds at each wl than to the peak wavelength:

For example, 660nm peaked leds produce about 5-10% more than 640nm peaked leds when using same amount of photons. But 640nm leds currently emits at least 50% (up to more twice) more photons per watt burned the 660nm. So currently 660nm are clearly not profitable.

This situation may change on the future, as in fact max radiometric efficiency of AlInGaP leds happen on those peaked about 654nm (almost none Al used on the chip composition). But manufacturers choose to do 633nm red leds, that still with lower radiometric efficiency, gives more lm per watt burned.

But its probable than on a near future industry need longer wl red leds for color compensation on white leds so they will be available for us. So i experiment too with 660nm leds, but only for in case they are profitable on the future. Currently, they are not, with efficiencies below 20% (21% the ledEngin ones), while there are 635nm leds with efficiencies well over 30% (50% more energy emitted as light per watt burned).

So we must differentiate between the perfect led grow light and the perfect led grow light available (or possible to build) at a given moment.

Doing this distinction was what move me to open this thread.

gioiapura, welcome to the thread, too.

I think you are right on track. I just can to cheer up on your project and ask you to share your progress.

I had to order 400Kg (about 890lb) of heatsinks of anodized aluminium. It exceed my needs, so probably ill sell it at ebay, together with the excess of current adjustable LED drivers (100-270VAC input, 50VAC output, 100-900mA current range) i had to order. Ill had them on about two months. But if i sell them ill link them here.

Im thinking on ordering a reel of the new Edixeon 740nm leds too, and for sure ill have excess of them if i finally do it.

knna Reviewed by knna on 12-04-2008. Building LED lights from facts, no theories I was going to post this at the Perfect LED Grow Light thread, but as some of what im going to post was posted 2 years ago on the stickied thread about LEDs and people still continue developing lights from wrong ideas, i think a thread about this topic is largelly needed. The main problem is related to efficacy of spectrums. When the firsts LED experiments at Overgrow, we work on the hypothesis that blue and red light are more effective. It was an appealing hypothesis that promises large Rating: 5