I have started this thread to help prosper discussion of different aspects of LED lighting. Wavelengths, ratios of light, vegging, flowering, pulsed light, IR, UV-B, china panels vs high power LED's, ect. I hope this thread and all its participants can determine the "perfect" LED array before my first grow (set for Fall '08).

Thanks to SnSsteath and his LED test grow, which has shown exceptional results for LED lighting, I DO believe LED's work, however there is plenty of room for improvement...the main reason for this thread...

I cant figure out why I cant select the underline, font, quote, picture, ect. buttons on the top of the reply box!!! I need to post pictures and shit! This is bothering me....any help..

Anyways until I get that question answered I will proceed without them..

Wavelengths:
Blue- 425nm 470nm
Red- 660nm, 640nm

These are the basic wavelengths that will be used, as they are the most essential to growing.

Another interesting topic on photosynthesis is caroteniods:
http://www.iupac.org/publications/pa.../6301x0123.pdf

Carotenoids are responsible for some amount of the plant's total photosynthesis reactions, so the best wavelength for these pigments are approx 450-480nm.

So so far we have 425nm, 450nm, 470nm, 640nm, and 660nm.

Green light is not used by the plant (hence the reason plants are green since they reflect it) so supplying the plant with green light seems useless....

Yellow and orange light may be used by other pigments...some information on that would be nice....

Blue light is primarily responsible for vegetative leaf growth. Red light, when combined with blue light, encourages flowering.

Colorado State University Master Gardener - Plant Growth Factors: Light

From this information I think having a majority blue LED light for vegetation is the best idea, then switching to red for flowering. In SnSstealth's grow, he is using 3 procyon 100's, which have a majority red light and yet his vegetive growth is amazing, so maybe some experimentation with blue lights for vegging is necessary...

Now for the type of LED's to be used....

Many people discourage the use of "china panels" as they are thought to not provide enough light. Take for example this 5mm LED
http://ledshoppe.com/Product/led/LE1001.htm
This red LED creates 8000mcd at a 10deg angle. candela (millicandela) to lumen conversion wizard
This in turns calculates to .191lm. So 500 of these LED's would produce about 191lm. On the other hand, a single 5W LED like this:
High Power LED Set of 10 ProLight 5W Red 192 lumen - eBay (item 160035237495 end time Mar-20-08 03:36:22 PDT)
creates approx 190lm. So you can replace 500 5mm LED's with 1 5W LED. So I think the most efficient way to create LED grow lights would be to use 5W LED's.

5mm- 2.38 lm/W
5W- 38.4 lm/W
So obviously 5W LED's are WAY more efficient than 5mm LED's

Thanks to Opie for helping creating this ratio:

UV: 310 5%
Blue: 412,440,470 20%
Green: 499 5%
Yellow: 566 2%
Amber: 613 3%
Red: 645,660 60%
Far Red: 730 5%

I think this is an ideal ratio for flowering-minus the green (unless research proves green should be used). Some of you may wonder why the 730nm far red?

Flower with shorter Nights

There are another pair of pigments involved in things here - phytochrome-R and Phytochrome-FR. Phyto-R is most sensitive at 660nm Red, while phyto-FR is most sensitive at about 730nm Far-Red, hence the R and FR naming (IE, JUST 735nm and very near wavelengths, but nothing under 710nm or so). With 735nm far-red/near-infrared emitters available then it's possible to flower cannabis with 15 hours 'daylight'. How? Why? Well, the plant senses that critical 12-hours-darkness that triggers flowering in cannabis because a critical amount of phytochrome-FR has slowly, naturally, reverted to phytochrome-R during the dark cycle. But during the 'day' 660nm red light converts the phyto-R into phyto-FR, while far-red 735nm light more slowly converts the phyto-FR back to phyto-R. So we run all lights for 15 hours, then run nothing but 735nm for another two hours and finally 7 hours darkness.- artificially driving much of the phyto-FR back to phyto-R without waiting 12 hours for the natural reversion- so you can actually flower with shorter nights.

That's 30% more light per day reaching the plant, the result is that we can pump 25%-30% more energy into the plant each day - that means 25%-30% more growth - during the flowering cycle. Pushing even longer is probably possible, with sufficient intensity of 735nm alone during some portion of the 'dark' cycle. Several experiments have already documented this effect.

I feel so lonely on this thread!!!

Here is a page on pulsing LED's:
https://mywebspace.wisc.edu/tsharkey...ght%201995.pdf


Quote:
so instead of long slow electricity usage you get super spikes every 200ms? wouldnt that strain the hell out of your equip?

Exactly right SnS. You overdrive the LED's for a shorter period of time. The LED's are fine with this, as long as they are pulsed for the correct duration so they dont burn out (Most LED sompanies give pulse time and rate for overdriving LED's). The paper proves that with 100us pulses, photosynthesis remains 100% of that with constant light. Were not trying to trick the plants by "flickering" the lights, merely providing increased amount of light over a shorter amount of time by overdriving them for 100us pulses.

Quote:
but is turning on/off so many times going to hurt the leds?

LED's can turn on in 200ns. There is no harm done to the LED's by pulsing them, it actually increases life expectancy (if overdriven than life expectancy stays same).

Opie- Photosynthesis only happens so fast(but still very fast)...its not like the more light you give it the more it will grow(there is a linear relationship between amount of light provided and plant growth, up to a point). Plants require certain amount of photons per unit time to attain cellular reactions for light cycle, sugar creation, ect.

this is from the paper:
Much of the light used for photosynthesis by leaves within canopies is from sunflecks (Pfitsch and Pearcy 1989; Pearcy 1990). These sunflecks range from milliseconds to minutes in duration and their photon flux densities can be as bright as full sunlight.

So plants undergo photosynthesis naturally with these "pulses" of light.

Also from the paper:

We measured photosynthesis under light/dark times of 15/135, 7.5/142.5 and 1.5/148.5 us which required instantaneous pulse PFD of 500, 1000, and 5000 pmol mp2 s-', respectively, to achieve an intcgrated PFD of 50 pmol m-2 s ' .

Basically this confirms what you guessed Opie, that there is still the same amount of light reaching the plant by pulsing the lights at a greater power.

The photosynthetic apparatus integrates the pulsed light and uses it as effeciently as continuous light

Thus saying pulsed light for photosynthesis is just as effecient at continuous light.

So say we have 200 5W LED's (as my plans are). By pulsing them at a 10% duty cycle, the actual power used y the LED's is only 100W compared to the original 100W. However we are providing the LED's with more power (from 1000mA to approx 2500mA), so the power used would be approx 1/5 of the original, saving 800W of energy. The plants still received the required amount of photons for photosynthesis, but with way greater effeciency by pulsing the LED's.

Of course I do not take every word of this paper and assume it is true, I am merely showing how pulsing LED's could be used for greater effeciency. I created a simple 555 timer circuit and hooked up 7 LED's to it and pulsed them at the required specifications (100us on, 900us off, 5kHz), and recorded the power consumtion, and indeed there was an increase in effeciency (by that I mean less watts used by the LED's). The effeciency does not come from giving the plant less light, but form giving the LED's a smaller total energy consumption. Hope Im was able to clear some thing up without confusing anymore people.

Look at the top left of pg 265 of that site....nice graph showing increased photosynthesis with increased photon density (amount of light in the pulse).

Ive done a bit of research myself. Ive found that 65/35 is a very good ratio. High on the blue for veg, high on the red for bloom.

Narrow field of view leds are not the best to use unless plans are made to have the full array quite close to the plant material.

I use leds from the 5mm series only at this point to avoid the heat issues with both the leds and the plants with the higher wattage devices.

Tests run with an IR thermometer on any of my 5mm series leds only shows a max high of 95f and that is taken right on top of the led. Air temps even an inch away drop to ambient temps.

I havent really looked but where is it you are getting high wattage leds with a 660nm output ?

My brief looks at the 1, 3 or 5w leds only come up with a max red in the 620nm ish range.....

aint led's really good way to make your crop grow as fast as fingernails with low yields?

Rascal....I have not yet found a 660nm 5W LED. I do believe however within the next 4 months they will be available. With the heat issue...you are right about the 5mm LED's. I originally planned to use 5mm because of the low heat, but switched to 5W after I changed the size of my grow. Thanks for the ratio info...I read it somewhere but could not remember the site...so your info sounds like a go to me.

post #50....time to celebrate....

phys, thanks for thinking out loud. I was about to start a similar thread, but I think I'll just watch this one, and maybe contribute if I feel I can. Rep for you.

Still not sure about the green. It seems you have been scrubbing the web about as much as I have, so I don't know why you haven't run across things that indicate we need a complete spectrum, including a little green. Green is not completely reflected away from the plants. It is the only color that can penetrate the canopy well, and some of that is absorbed, some passes to the grow medium surface and bounces back, and then is absorbed, and yes some bounces back and passes right back through the canopy again. It is definitely not the most important and most used color, but I'm still not convinced we should leave it out.

If price were no problem I would use all 5W or 10W LED's. Right now however, I can get more light with smaller LEDs for less money.

Hydrorascel brings up a good point. Nobody ever talks about the distance of the lights. There is a huge difference where they should be placed depending on what kind of intensity angle the LEDs have. SnS's are like what, nearly 3 feet away? I don't understand how this can be efficient when the intensity degrades with distance so rapidly. Wouldn't it be more efficient to have the light close to the plant? Like with fluoros?

Why not white? White is generally much more bright. There are whites that spike in many different colors, including red and blue, just like fluoros.

I wish people would stop saying that, for example a 660 red emits one color only. Wrong people. EVERY LED has a spectrum, not just one color.

Phys, keep spewing. I'll keep regurgitating.

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We don't know for sure yet, but the theory is that if we throw enough of the proper light at a plant, it will yield around the same as HID, while at the same time using less power and producing much less heat, which nearly eliminates the need for venting.

And in the near future... better yield?

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Oh yeah, pulsing.

hmmm,

hmmm,

hmmm?

hmmm.

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LedEngin, Inc.

This site has some very good LEDs some even 10w, 15w in multiple wavelengths for one LED also.

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Yeah, I smoke weed. . . Why? Well I just say to myself... What would Jesus do?

CFL Grow, just harvested check it out

Carotenoids and chlorophyll b absorb some of the energy in the green wavelength.

found that at PHOTOSYNTHESIS


and also found this

It is important to remember that leaves often absorb more than half the green wavelengths and use them in photosynthesis. It is a widespread misconception that leaves reflect all green light. That misconception is based on looking at a chlorophyll So
absorption spectrum (see second website cited), which is obtained by extracting chlorophyll into an organic solvent, such as acetone, and measuring its absorption in a spectrophotometer at wavelengths between 400 and 700 nanometers. The chlorophyll absorption spectrum does show that chlorophyll in a test tube absorbs only about 2 to 3% of the green light. However, that is very artificial because a leaf is highly . structured. Salisbury and Ross (1985) note that in the intact leaf, a green photon may not initially be absorbed by a particular chlorophyll molecule but it is reflected and then gets another chance to be absorbed, and perhaps another, and another, etc.

here Re: Why photosynthesis pigment of plant is green and not black?


Opie-wow you are right...we need green light as well. Luckily, green 5W LED's are MUCH cheaper than red or blue 5W LED's, so suppling alot of green light would help immensly. As for white light...I find it a good idea to supply the plants with white light. White light may not be the most EFFICIENT color for photosynthesis, however we could use some white light to compensate for some of the "lost" lumens compared to sunlight, for example.

Whats your opinion? Good, bad? I find it an excellent idea, but would very much like to test before actually implementing in my grow.

Paht- thanks for the LED link. Looks very interesting. Might be what I was looking for. Their 10W LED's look very nice..Might buy a couple of those and test. Will definitely e-mail and get prices for everybody.

Ya Opie the LED's can handle multiple times their rated max current as long as it is very brief (100us, thats 100x10^-6 s). And since the LED's and a turn-on time of 200ns (200x10^-9 s), it is possible for the LED's to handle short, high energy pulses.

Here is an example on one LED:

Pulse forward current conditions: Pulse Width ≤ 10msec and Duty Cycle ≤ 10%.

found on page 5 from here: http://ledengin.com/products/15wLZ/LZ4-00G115.pdf

Oh and that 15W LED produces 777 lumen at 1500mA pulsed at the above conditions. I think this could be very helpful for mj plants....thats alot of light that will eventually be absorbed by the plant.

The very very very near future. I think with green, yellow, and amber wavelengths are the missing link for LED growing. These missing colors are really the only difference between the MH and HPS spectrums and the LED spectrum (but the MH and HPS are much more inefficient in their spectrum). And with the added amount of light from higher powered LED's (3W, 5W, ect.) and the additional wavelengths (490-560nm, 560-590nm), LED's will prove to be the alpha-male of grow lights. I am very excited and my money is really burning a hole in my pocket.

Can someone explain LED pricing to me?

From some of the links, it looks like a 5w is 192 lumens and is $25?

so to have, lets say just 10,000 lumens... enough for 1 or 2 plants, you would have to buy 52 of these 5 watt lights to reach 10,000 lumens, at a cost of $1300. 52 lights at 5 watts each = 260 watts.

Is that right?

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peace, ahimsa

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White is a produced light by leds. It is NOT a full mix of all spectrums.. hence.. totally useless for plants.

I looked at Elgin's spec sheet. For their red, 100% output at 750ma. Higher I levels dont do that much for output as by cranking up the I level to a full Amp.. the output only goes up about 20%.

Unfortunately 5x the power input to an led does not equate to 5x the lumen or mcd output. About 99%+ of all leds flatten off their output by the time 2x the power level is achieved. IOW... a 5mm, 20ma unit maxes out at 40ma and you only get about 125 to 150% output meaning that even pulsed its very seldom worth the effort....

One bin level gets to 645nm+.. but still no 660nm