Grow light information Arena here!

beholderOctober 27, 2006

Any of you feel free to place cool information on plant-light physics and artificial-light gardening here. I will post some cool stuff information and discussions I have seen here. I will have to find out how to place photos and here. Unfortunately no PDF's of OCR magazine scan's though. It's exciting! So lets discuss! Later! - Shawn

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How much later? ;)

    Bookmark   November 14, 2006 at 9:09AM
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Apparently he/she is sifting through the volumes of information available to decide what belongs here :0)

    Bookmark   November 14, 2006 at 9:56AM
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"spectrometer" post has more than the law allows.

    Bookmark   November 19, 2006 at 5:53PM
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Sorry for the delay, I have been busy attending to a failed hard drive, potting up some new passion vine cuttings, setting up some temp. grow lights, and getting over some SAD, if you like. Right now I am still getting all of my software reinstalled on my PC, including the OCR stuff! Currently nursing my cuttings under 4- 4' 32W Daylight tubes all under and on Emergency blankets and heating pads. So far so good. I am saving up for an 8 - 52W T5 light fixture though, but I will have to wait till after the holiday spending. I will get some pics up here of my happenings soon with some tidbits on lighting. Cheers! - too bad they don't allow a person to edit their own comments here. Jeez...I may have deleted this post after I got busy again.

    Bookmark   November 21, 2006 at 3:09AM
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I'm running some hydro-aero experiments with LED lighting. Have a look at if you are interested

    Bookmark   December 10, 2006 at 8:20PM
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habman(5B CND)

Great stuff ledaero!!

your plants look very healthy.
It would be great if you could grow some plants but with a diffrent ligth source to compare the growth diffrence.

Keep us posted on the progress.

Maybe just lower resolution of the pics on the web site they take a long time to load.

    Bookmark   December 11, 2006 at 3:53PM
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ralleia(z5 Omaha, NE)


You sound almost as obsessive-compulsive as I am. I've got four 40W cool whites running to help with my SAD and my tomato seedlings. Are the daylight bulbs more expensive than cool white? If so, you might save a few bucks toward that T5 luminaire by using cool whites for general plant growth--according to an article I read from U of Alaska's Extension service they're as good or better than the more expensive specialty fluorescents for plant growth (

The only caveat might be during the flowering and fruiting stage, when the red spectrum will be more important.

ledaero -- Cool setup! I've been researching LEDs for plant growth, but haven't taken the plunge yet because their lumen efficacy isn't yet enough to justify their high initial cost. The good news (for us plant fanatics, at least!) is that red is most efficient. Here's a re-hash of something I posted on the lighting forum:

Red LEDs were best at 55 lumens per watt (lpw)
White LEDs were 25-29 lpw
Blue was weakest at 10 lpw

For reference, lumen efficacy of other common lamp types are:

standard incandescents : 5 - 18 lpw
tungsten halogen: 15 - 25 lpw
low-wattage compact fluorescent : 20 - 55 lpw
high-wattage compact fluorescent : 50 - 80 lpw
linear fluorescent : 65 - 95 lpw
metal halide : 40- 60 lpw (and 65-80% lumen depreciation)
sodium : 100 lpw (and 10% lumen depreciation)

LEDs have been doubling in lumen efficacy every 18-24 months, while the price has been decreasing by 20% per year. By about 2010 white LEDs should bust the 200 lpw mark, while the price will have dropped exponentially as well.

Lumen depreciation data is sketchy for LEDs due to their relative newness. I did find an article on Compound that showed reds to be most stable, with white faring worst. Again, good news for us plant fanatics.

    Bookmark   December 11, 2006 at 7:07PM
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shrubs_n_bulbs(z8/9 UK)

Retail LEDs are now widely avaialble offering 30-40 lpw, about half that of the best fluorescent tubes and easily double that of the best halogen and incandescent bulbs. And I think the lumen maintenance is significantly better now than on those graphs. The more expensive white LEDs are now offering 50% lumen maintenance at 20,000 hours, although you seem to get what you pay for. LED lifetimes and lumen maintenance improves dramatically when they are slightly "under-driven" within their design operating range. Unfortunately many of the cheaper devices simply make claims like 100,000 hour lifetimes without mentioning that the poor LED will be barely visible by that time :)

    Bookmark   December 11, 2006 at 7:39PM
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shrubs_n_bulbs(z8/9 UK)

Could you not find 670m LEDs? I know they exist but are not widely used in lighting intended for humans because they look dim to our eyes. One of the potential advantages of LEDs is the ability to generate light only in the wavelengths where photosynthesis is most efficient, without the disadvantages of decreased efficiency and life shown by the fluorescent phosphors that operate near 670nm.

    Bookmark   December 11, 2006 at 7:42PM
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ralleia(z5 Omaha, NE)

I'm aware of the difference between the human luminous efficiency function curve and the plant PAR curve, though I need to do much more research. The red Luxeons produce light at about 625 nm, and according to one site I read this is absorbed by plants only slightly less effectively than the optimal 670 nm, while being far more effecient than the LEDs used to produce the longer 670 nm-range wavelengths. ( As mentioned before, the red Luxeons convert at an efficacy of 55 lpw, less efficient than a tube fluorescent.

If the electricity costs and lamp longevity were the only factors, then I would definately go for the LEDs. The problem is in the initial cost. The cheapest cost I've found so far is $129.95 for the red Luxeon line putting out 450 lumens of 625 nm light. That initial dollar figure alone puts a damper on things, though I would still buy it if the mathematics proved out.

I'm missing a good, useable PAR graph and the relative intensity of a cool white fluorescent at 625-670 nm. Could you point me to either of these?

    Bookmark   December 11, 2006 at 8:50PM
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ralleia(z5 Omaha, NE)

Woops, found an even more interesting alternative--the Nemalux 24" 16 LED general purpose lighting fixture--16 1 watt Luxeon Star LEDs in any combination. Sounds like I good way to sneak in 1 blue LED for every several red ones.

They're $194 for a red array for a 120 degree beam angle or $274 for either 45, 30, or 10 degree beam angle lens. I suppose the 120 degree beam angle comes from the lambertian emitter Radeon star, and the other "beam angle lens" option is a lens that fits over the fixture??? If so, I'm not sure if I like that.

    Bookmark   December 11, 2006 at 9:58PM
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I did recently change the resolution of the photos way down to speed things up. I totally didn't think about this when I first loaded up the site as it's on my local machine and was fast for me...doh!

I did find some 660NM and 670NM LEDs. 2500MCD 20 degree viewing angle is the highest MCD rating I could find. $35 for a hundred. A little pricey compared to the traffic lights ($25 for 420 630NM same MCD). I also read that plants use 630 about as good as 670NM, so trying what I have first.

I'm finding trying to compare Fluorescent, MH, HPS intensities, lumens, etc, to LEDs to come up with the magic formula is basically futile and So much conflicting data which is why I'm just running the trial and error method. More fun than crunching numbers and arguing intensities. Regular lighting is inefficient. You don't get much 'plant useable' spectrum from conventional lighting once you throw away the heat and all the green ,yellow, orange spectrum that supposedly plants do not use. Luminosity is also a measurement of human brightness.

You have to be careful also and not go by Wattage ratings. For example, I have some 670NM Red Leds, 2500 MCD rated. Voltage drop is 1.9V current = 30 MA. I also have some 630NM Red Leds, 70,000MCD rated. Voltage drop 1.9V, current = 30MA. So, if I made a bulb out of each using the SAME number of LEDS, both would consume the same wattage. However, as you can see, the MCD output would be a heck of a lot higher on the 630s. This confuses most folks as they are used to purchasing conventional lights in Watts.

The correct (and possibly only) way to do this would be to have a good spectrometer and measure different NM ratings at different distances on MH. HPS, Fluorescent, etc. Then see how the LEDs compare and what it takes to get them equivalent in the NM ranges that count for the plants. Then you'd know. Unfortunately, new Corvettes are cheaper than good spectrometers. If someone wants to donate one to me let me know :)

Right now I don't see any signs of my plants starving for light, just the opposite in fact. I think I'm seeing pretty good growth rates. The larger Tomatoes and Pepper plants you see on my site were started for about 30 days under a New Wave T5 four bulb fluorescent. Once they reached about 8-10 inches in height, they started looking really bad with the lower leaves dying off and blossom drop. Then I recieved the first of the Red Traffic lights and just hung them up there and a day or two later, I saw the plants come back to life. I shut off the T5 and the plants looked like it didn't matter. They stayed looking healthy under just Red LED. This is when my Tomato blossoms stopped dropping and fruits set. I actually have quite a few Tomato fruits now just waiting to get ripe. So, I do know that the LEDs are already better than a four tube T5. I don't know about the rates and yields, but I know 470NM and 630NM in the MCD range I am giving them sustain plant life.

Unfortunately, I do not have HPS or MH lighting nor enough space at home to do a side-by-side test. I would love to do this someday. Take a proven MH/HPS system with same grow box, seeds, nutrients and have an LED parallel version. Try and make the LED version as good or better.

What actually started me on this was trying to get a comfortable living atmosphere with the plants in the same room. Of course I realize that if you have dedicated growing huts, basements, and closets, that really bright lights don't matter. I'm living in the same room as mine (I work as a computer programmer at home and the plants are in my office). When I had the T5 going it was giving me headaches.

I also like the way LEDs are cheap on the electric bill and they put out no heat. I also notice I hardly have to add water anymore and I have no dried up leaves/damage no matter how close I put the lights.

I'm not claiming that LEDs can run entire farms like conventional lighting and/or the sun, but I'm not dismissing it yet either. However, I do feel LEDs work on small scale stuff like mine. Also I don't feel they are high cost on a small scale. I figure on my tomato box, I would need 250Watts of MH and/or HPS. The leds I have on this box cost much less than a conventional light, plus lower electric. Two Red lights and four blues I have on this box = 44 Watts power use = $80

Luxeons and Prolights look very promising as you can get these pretty powerful. They were little pricey for me to start experimenting with and need heatsinks and possibly collomators.

I do not recommend overdriving LEDS. As shrubs and bulbs says, it WILL severely shorten the life of the LED. Overdriving can and will affect the NM range output also. One thing I did not add is that the traffic lights have tight government specifications they must be built from. This is a good thing.

Bottom line - this is why I chose to go the way I did - get plants growing and play around with the LEDS and see if I can get them to work. The cucumber grow on my site will be attempted 100% LED with no other lighting (I even have the sun blocked out from coming in the windows and my room window faces north anyway, so no sunlight to cheat with. The challenge will be to also keep the nutrients, temperature, everything else right to give the lights the test. Heck...I know people that can't grow anything under the best of lighting conditions.

    Bookmark   December 11, 2006 at 10:44PM
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ralleia(z5 Omaha, NE)

Found an interesting resource. DAYS of reading about plants and lighting are available below!

Here is a link that might be useful: International Lighting in Controlled Environments Workshop

    Bookmark   December 11, 2006 at 10:50PM
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ralleia(z5 Omaha, NE)


I can probably help out with the mathematical number cruching of lighting comparisons. I used to be a computer programmer as well (BS in CS from WPI in '92), and am now studying architectural engineering. I currently in an engineering lighting class and will probably select lighting as my specialty. The units and conversions for lighting are very frustrating, partly due to the lack of creativity in naming the fundamental units. Get this--the five fundamental terms (and their units) are:

luminous flux (lm)
luminous intensity (cd)
illuminance (lux aka lm/m^2)
luminous exitance (lm/m^2)
luminance (cd/m^2 aka nits)

Can you see the source of the confusion? They're all different, but they all sound the same. Maybe it's job security, like the IRS.

So the conversions are a challenge to figure out, but definately calcuable.

Incidentally, we've got an entire lighting lab at our school with access to some advanced (and expensive) equipment, so I might be able to get some data from the lab there. All the various types of light sources are already installed in the room. I have yet to drive the room controls, though!

    Bookmark   December 11, 2006 at 11:02PM
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shrubs_n_bulbs(z8/9 UK)

Unfortunately I think I detect a fair amount of wishful thinking here.

As an example, the claims that "red Luxeons produce light at about 625 nm, and according to one site I read this is absorbed by plants only slightly less effectively than the optimal 670 nm" and "red Luxeons convert at an efficacy of 55 lpw, less efficient than a tube fluorescent" and "if the electricity costs and lamp longevity were the only factors, then I would definately go for the LEDs" can't all be true at the same time.

It is clear that LEDs (on the market today) don't emit more light per watt than fluorescents, therefore they need an advantage somewhere else if they are to be more cost-effective in electricity use. This advantage is generally claimed to be by producing light at a wavelength that is used more effectively by the plants. That wavelength needs to be near 670nm, it cannot be at 625nm which is effectively where fluorescents have their red peak. Either plants work much better at 670nm than at 625nm or LEDs are not cost effective. Also consider the plant-aquarium type fluorescents which produce light at the supposedly best wavelengths, they are less efficient (in lumens) than other fluorescents but still more efficient than LEDs. Once a benefit can be demonstrated in terms of efficiency per watt, then we can start thinking about total lifecycle cost factoring in the high upfront costs. Note also Luxeons own figures on lumen depreciation which show 50% loss at around 20,000 hours, much much worse than fluorescents. The usable life of a Luxeon as a plant light is currently about the 10,000 hours you get before it starts to lose light.

There is also mention that 670nm LEDs are less efficient. Quite possibly they are but don't compare figures in lumens because they are close to meaningless at these wavelengths. If lumens are all you have then I can convert that to actual photon flux if you know the relevant wavelengths. One lumen at 670nm represents about ten times as much light (photons, the light the plants care about) as 1 lumen at 620nm! That's why 670nm LEDs look dim to us.

And the last related myth that I'd like to stomp all over yet again is the idea that "LEDs are cheap on the electric bill and they put out no heat". LEDs are cheap on the electricity bill and put out little heat (certainly they do put out some heat, actually a higher proportion of the input power than fluorescents do) because they are low power. Again, a lower power LED can only be as effective as a high power light source if it puts out more light pre watt (which it doesn't) or the plants use the LED light more effectively (we can hope, but probably not with the 625nm LEDs). A third possibility is that more of the light is actually reaching the plants, since LEDs naturally emit almost all their light in a narrow cone. However if this is the only advantage, buy yourself a decent reflector. Plants dropping their lower leaves may be an important sign here that the light levels are too low at the bottom of the plant while adequate (or too high!) at the top of the plant.

On PAR curves. PAR is not a curve. PAR is a count of photons emitted between (usually) 400nm and 700nm. There is no weighting for how effectively different wavelengths may be used by the plants. Note that PAR is not measure by lumens, see the discussion before. What you really want is a photosynthesis action spectrum. Search google for them, there are loads published, they are all different depending on which plant you look at, but all have same basic shape with peaks near 670nm and 420nm and a dip in between. Ignore the ones for sea creatures! And also ignore chlorophyll absorption spectrums, they are not relevant although plant light sellers love them because they kake it look like you need special lighting.

    Bookmark   December 12, 2006 at 11:11AM
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ralleia(z5 Omaha, NE)


Could you explain how the following statements can't all be true at the same time? I strive to be accurate in what I say or write. I am making no "claims." I only state research findings, and if it isn't a research finding I attribute where I found a statement, implying that the credibility of the statement is based on the source, not on my own findings.
"red Luxeons produce light at about 625 nm," (wavelenght statement and fact)
"according to one site I read this is absorbed by plants only slightly less effectively than the optimal 670 nm" (wavelength and attributed to another person)
"red Luxeons convert at an efficacy of 55 lpw, less efficient than a tube fluorescent" (power efficacy and calculated)
"if the electricity costs and lamp longevity were the only factors, then I would definately go for the LEDs" (money and time)

And Luxeon actually states that their products will deliver "an average 70% lumens at 50,000 hours" according to p. 16 of the March 2006 "Luxeon Emmitter" technical datasheet DS25. ( What is the date of your 50% lumen depreciation at 20K hours data?

I think all this stuff can be quantified, but it will take a long research trail. There should be no problem in making a statement that "a 670 nm LED has lower lumen efficacy than a 625 nm Luxeon" LED IF it is factual (and it will probably vary depending on the manufacture). It's just a data point along the way, not a conclusive statement of superiority in producing plant growth.

As far as the myth that LEDs are cheap on the electric bill, just keep pointing people back to basic lumen efficacy data. LEDs are now cheaper in electric usage than standard incandescents, but more expensive in electricity usage than fluorescent shop lights and HPS lamps. If current trend continue, people will be able to state that as fact though, since LEDs should push over 200 lpw by 2010, exceeding even HPS by a healthy margin.

Thank you for the pointers on PAR v. the absorption spectrum. I'll read up on it and on the effects of the 670 nm wavelength, particularly compared to other near, commonly-available wavelengths. I need to figure out something soon, because my tomato plants are a month away from the flowering/fruiting stage. We're also getting a garden window installed in the office soon, and will need some compact low-heat supplemental lighting there.

    Bookmark   December 12, 2006 at 1:01PM
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ralleia(z5 Omaha, NE)

Experiments compared the performance and productivity of spinach (Spinacia oleracea L. cv. Noric IV), radish (Raphanus sativus L. cv. Cherry Belle), and lettuce (Lactuca sativa L. cv. Waldmann's Green) grown under conventional broad-spectrum lighting sources (high-pressure sodium and cool-white fluorescent lamps) versus LED arrays at certain red wavelengths (660, 670, 680, 690, nm central wavelength) supplemented with blue LEDs (470 nm central wavelength).

Source for high power LEDs in wavelengths of 660 nm, 670 nm, 680 nm, 690 nm, etc. Haven't figured out lumen efficacy or price yet--datasheets available require lots of conversions.

    Bookmark   December 12, 2006 at 2:30PM
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This is exactly why I'm doing what I'm doing...trying it instead of arguing about it. I'm not saying either of you are wrong or right.

Also, the most important thing I'm seeing now is my tomatoes have set and I have 1/8" to 1" diameter cherry tomato fruits. My peppers are blossoming, and my cucumbers are growing at what I think is a good rate (getting fourth true leaves).

So, I don't have stats on yield rates, efficiencies, etc for comparisons of LED vs HPS, etc, but my LED lights are sustaining three vegetable varieties of growth right now. Maybe not the best, but that could be due to other factors like am I running correct nutrients and are my homemade Aeroponic machine efficient?

BTW - two of my RED LED Traffic lights have 50,000 hours on them already and they are still lit and doing what I said above, so they already have lasted years....

Now - technically the amount of light a plant needs is the number of photons reaching the Stomata at certain wavelengths. Red photons have less energy than Blue. This is why lots of red and a few blue are needed as blue contains more energy for the plant to use. The plant has to collect more low energy Red for the light needed for further chemical reaction. Stomata need minimum numbers of blue thru red photons at various NM ranges. It's the number of photons the light can generate, NOT the lumens, watts, heat, whatever. It's ludicrous to try and compare LEDS with Fluorescent, HID, etc, by using the measurements that are used for Fluorescents, HID, etc.

Until we can count the number of photons a light puts out and how they match the plant's needs we won't know.

Here's a little mathmatical snippet of what I am talking about:

Light has a wavelength and a frequency. Light can also be thought of as a stream of particles, photons, or quanta. Units can be expressed in moles per square meter per second (mol m2 sÂ1), where "moles" refers to the number of photons (1 mol of light = 6.02 Ã 1023 photons, Avogadro's number). This measure is called photon irradiance.

Quanta and energy units can be interconverted, provided that the wavelength of the light is known. The energy of a photon is related to its wavelength as follows:

where c is the speed of light (3 à 108 m sÂ1), h is Planck's constant (6.63 à 10Â34 J s), and λ is the wavelength of light, usually expressed in nm (1 nm = 10Â9 m). We can solve for the hλ part of the equation, and we obtain 1,988 à 10-16, and write this equation as:

where λ is expressed in nanometers. From this equation we can see that a photon at 400 nm, which is in the blue region of the spectrum, has twice the energy of a photon at 800 nm, from the infrared region of the spectrum. A photon of 400 nm light contains 4.97 à 10Â19 J. On the other hand, the 800 nm photon contains 2.48 à 10-19 J. Stated differently, the higher the wavelength of a photon, the lower its energy, as indicated by the larger denominator in the equation.

Now, suppose we have 3 µmol of 400 nm light falling on 1 m2 every second, or a photon irradiance of 3 µmol mÂ2 sÂ1. This quantity is approximately the amount of blue light at 400 nm that strikes the surface of Earth on a sunny day. If we want to convert photon irradiance to energy irradiance, we must first convert micromoles to moles (1 µmol = 10Â6 mol): (3 µmol mÂ2 sÂ1) à (10Â6 mol µmolÂ1) = 3 à 10Â6 mol mÂ2 sÂ1 of photons, or quanta. Calculating the number of quanta from Avogadro's number gives: (3 à 10Â6 mol quanta mÂ2 sÂ1) à (6.02 à 1023 quanta molÂ1) = 1.8 à 1018 quanta mÂ2 sÂ1. As we already calculated, each photon, or quantum, of 400 nm light contains 4.97 à 10Â19 J . Thus (4.97 à 10Â19 J quantumÂ1) à (1.8 à 1018 quanta mÂ2 sÂ1) = 0.9 J sÂ1 mÂ2. Since 1 J sÂ1 = 1 W, we have an irradiance of 0.9 W mÂ2.

    Bookmark   December 12, 2006 at 8:20PM
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ralleia(z5 Omaha, NE)

I'm not interested in arguing--I just desire open, factual and neutral discussion of research. I want to take the plunge and experiment with some LEDs as well, but since money is a finite resource and since lamp life of LEDs is 50,000 - 100,000 hours (longer than my first marriage!) I want to be thorough in my research before committing.

Thank you for analysis breaking things down to the photon level. I've printed it so I can chew on it for a while--we didn't go through that type of analysis in the first lighting class.

But now, back to studying for that unpleasant acoustics exam...

    Bookmark   December 12, 2006 at 11:13PM
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For me, when I get away from the Lumens, watts, and other 'Brightness' measuring paradigms it makes more sense. I'm attempting to get down to what the plant needs (according to the light-CO2-chemical process). What I'm understanding is the need to get the right number of photons at the right wavelengths to the open stomata. I'm building another light bulb that is almost done that I'm putting 660NM, 405NM, 585NM, and 615NM LEDS into. I will shine this on only one of my four cucumber plants. They will get equal 470/630 and this one plant will get the additional NMs above. I will be setting this up in a couple days. I'll take photos and add them to the website cucumber grow pages. It'll be interesting to see if there is a significant difference.

Also - one of the things to watch out for in this research is the date of these LED -> Photon -> Stomata -> Co2 -> chlorophyll articles. Most of them will say something like LED technology needs to improve for LEDS to be feasible. Then you look at the dates of these articles and they are 1992-1996. Leds have come a long way since most of these studies were done. The data is valid, the remarks about LED power and how many they needed for testing are not anymore. I believe even though I do not have a spectroradiameter (measures photon density at specific wavelengths) that my LEDS I'm using put out WAY more photons in 470 and 630NM than a whole bunch of them fluorescents and for electric bill considerations (what watts are only useful for measuring) I'm at 20 watts (15 Watts Red and 5.5 watts Blue) 'possibly' equivalent to what a 200-250 watt MH or HPS can do. I do know they are out-performing a 96 Watt T5 New Wave 4 tube fluorescent.

    Bookmark   December 13, 2006 at 12:41AM
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shrubs_n_bulbs(z8/9 UK)

I don't know if this is what you have, but TransLEDS claim 70% lumen maintenance at 100,000 hours on their website.

The Luxeons have obviously moved on another step from when I last looked, 70% at 50,000 hours puts them firmly ahead of the best fluorescents which offer 95% lumen maintenance to about 28,000 hours (less if switched frequently) but then tend give up completely.

Thanks for the NASA link which shows the same results as many other experiments but has a particularly nice breakdown of the photon fluxes at various wavelengths which makes it very relevant to this discussion. To summarise, cool white fluorescents and HPS lighting were compared to LEDs at 660nm, 670nm, 680nm, and 690nm (each combined with a small number of blue LEDs at 470nm since plants won't grow healthily without it). All providing the same PAR output, that's the same total number of photons. The photon fluxes in the 600nm-700nm range were similar for all the LEDs, about half as much for the HPS, and about half again for the fluorescents. Blue photo fluxes at 400nm-500nm were similar for all the LEDs and the HPS, and about double for the fluorescent. The rest of the PAR photons were in the green-yellow range at 500nm-600nm. In addition, the HPS lamp produced a significant amount of non-PAR radiation in the infra-red and near UV, which is one of the reasons it makes plants stretch.

Total photosynthetic activity was highest for the 680nm LEDs at about 50% higher than the fluorescents and HPS. Total plant yield by weight was highest for the 690nm and HPS lights, about 50% more than for the fluorescents. The apparent inconsistency appears to be explained by the HPS lighting causing the plants to stretch. A similar effect seems to occur for the 690nm LEDs which would otherwise be expected to be beyond the ideal wavelength for photosynthesis.

So this is the same essential result that has been shown in other experiments: monochromatic light near the red photosynthetic peak produces growth as good, or arguably 50% better, than "white" light sources. If you can't duplicate this, more or less, then you need to examine your comparison light source because you're doing something very very wrong. This part of the data is not something that changes over time, monochromatic light in 1990 is exactly the same as monochromatic light today and it will never be any different.

So now the only question is what power levels are needed to get the same photon flux from an LED as from a fluorescent or HID lamp. This is the hard part to track because LED efficiencies are improving every year. In photon terms, the best LEDs available at retail today are approximately 50%-75% as efficient as the best fluorescent lighting (PAR photon flux), and about half as efficient as HPS. That means that plant growth per watt of electricity should be in the same ballpark, possibly a bit more than fluorescent and a bit less than HPS. Talk of 20W LEDs being equivalent to 96W of fluorescent light are hard to swallow, and comparison to 200W HID is simply a joke. I know folk who know what they're doing and have tried to use LEDs to replace this sort of level of lighting and it was pretty pathetic. Sorry, but until people stop trying to make out LEDs as some kind of magic device that will produce more output than you give it input then people like me will continue to argue with you.

    Bookmark   December 13, 2006 at 12:23PM
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shrubs_n_bulbs(z8/9 UK)

Red photons have less energy than Blue. This is why lots of red and a few blue are needed as blue contains more energy for the plant to use. The plant has to collect more low energy Red for the light needed for further chemical reaction.

Sorry, but this is garbage. You need to go and read some more about photosynthesis. One blue photon produces the same chemical end result as one red photon. The excess energy is lost as heat while being transferred to the ultimate photosynthetic receptors.

And there is no necessity for plants to collect lots of red photons and a few blue photons in order to photosynthesis, certainly no need to balance the energy inputs from the two as you imply. A plant can photosynthesise quite happily with just red photons. Or just blue photons for that matter. Red photons are used as the primary monochromatic light source because they can be produced more efficiently and because of some physiological processes in plants which are regulated by the ratio of red:far red light. Basically without a strong element of red light the plants etiolate badly and fall over.

The reason blue photons are needed at all is to regulate the size, shape, and orientation of the leaves and the chloroplasts within them (and other physiological processes important to longterm health such as inbuilt pesticides and pigments like tannins). Without any blue photons, plants fail to orient properly to the light, fail to organise their chloroplasts efficiently, and as a result cannot photosynthesise well. With higher levels of blue light than the 5%-10% used in these experiments, plants start to produce more compact leaves and also produce other pigments which absorb light without transferring it for photosynthesis. These effects may be desirable in ornamental plants (and medicinal plants) but simply reduce yield in leafy crop plants.

    Bookmark   December 13, 2006 at 12:37PM
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Let's just say we agree to disagree. We'll see how my plants do. I don't know where you get that I claim 20 LEDS will do it. I never said that. I have 420 LEDS in my red bulb and 62 LEDS each for total 124 in the Blue.

For you to say 'garbage' is in my opinion rash unless you of course are the main Biological authority. There are more conflicting Biological studies on Photosynthesis as there are about lights. By the way, there is more than just Photosynthesis going on. It's not an exact science and pegged down last I heard. Kinda like brain surgery, still room for experimentation and results not quite figured out yet.

You keep on saying LEDS are not as efficient as Fluorescents. Once again, I disagree as you are missing the obvious - try throwing away all yellow, green, amber frequencies that MAY not be necessary and try again. I may be wrong, but I see better results from my plants when I shut off the 96 watt T5 (which had two brand new 6500K and two 3000K tubes) and put up a 15 watt Red led and (2) 2.75 watt Blue LED bulbs. I got fruit set instead of blossom drop and the plants came back to life...something worked there I think

Like I say, I'm trying it and posting the photos and results and to the best of my ability trying to get it to work. Time will tell. If I'm wrong you'll see it. If I get some good results you'll see it. If it doesn't work, you'll have more proof to add to what you are saying.

see the ongoing results on

    Bookmark   December 13, 2006 at 4:20PM
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ralleia(z5 Omaha, NE)


Thank you for summarizing the NASA report. It helped me to finally understand what the tables and results meant. It would have been nice if they also tested the red wavelength that is commonly available.
I checked out prices on that Roithner Laser site that sells LEDs in a wide range of wavelengths (including 660-700 nm) and have temporarily retreated with my tail between my legs. Ack!

So instead I sent Philips/Luxeon a pouting email inquiring about future availability of Luxeon emitters with a peak wavelength of ~680 nm. When the giants make it, it will be more affordable. LEDs in the mainstream (human lighting) market is already on the verge of affordibility. They'll get to the plant market sooner or later.

In the meantime, I hope my 50" luminaires for my 4' CWFs fit nicely in the new 55" wide garden window. Maybe by the time I exhaust my stockpile of fluorescents, LEDs will have made another leap forward. In the meantime, I'll keep reading.

Neat--Luxeon already replied:

Good day Mrs. Thompson,

Thank your for emailing Future Lighting Solutions, your LUXEON® solutions enabler. We are pleased to address your inquiry.

Thank you for the information regarding plant photosynthesis. Presently our highest transmitted wavelength is 645 nm; as per AB 21. I have also heard that there needs to be a bluish wavelength as well to aid in agricultural growth? If you know this to be a fact, I would like to receive a reply.

We will be equally pleased to address any future product, power, optical, or thermal inquiries that you might have.


Paolo Patafie
Technical Solutions Specialist
Future Lighting Solutions
Future Electronics Inc.

    Bookmark   December 13, 2006 at 5:10PM
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Okay, here is a little side note on T5 HO tubes, There may be something to ponder here for many. The real issue is getting more light within a greater range of distance. I am hoping to get a nice 8 - T5 unit for the holiday gift extravaganza so I am really getting back into the subject. I am currently using 4 - T8 32W day tubes to grown cuttings.
Happy growing! - Bhldr

    Bookmark   December 14, 2006 at 9:03PM
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I am sure that if phosphors "make" the light then LED's will make there stand eventually. Let's hope it is a better world for all of us when the time comes and better plant lighting technology is made readily available. For now I am pretty optimistic about HO T5 technology. There are a lot more choices in customizing the tube fixture with a variety of T5 bulbs. I imagine the Aquarium-Reef community has played the largest role in getting out this technology. After all, much of life did begin in Salt-water. I am glad to see so much positive information getting out to the general public via internet forums such as this. When I was growing ten years ago under lights I could only have imagined this. How far we have come and where we can go! Exciting indeed! Happy growing! Cool forum -

    Bookmark   December 14, 2006 at 11:35PM
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Text-book Info. on plant physiology explaining in simple terms photosynthesis, spectrum, etc. Can be entertaining too! ;)

    Bookmark   December 14, 2006 at 11:54PM
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A note on Phillips lumiled luxeon site.

    Bookmark   December 14, 2006 at 11:58PM
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ralleia(z5 Omaha, NE)

I assume that'll be with the program start ballast? How far away from the plants are you trying to get? Even if you managed to get double the lumens there's still that irritating inverse square law of illuminance to deal with. That dratted exponential curve wins every time!

Other than the raw lumen output (and resulting design flexibility), the issues described in paper regarding T8 ballasts can be remedied by proper selection of a T8 ballast. One can just as easily select an improper T5HO ballast.

I think you should really try to get the photometric report on whatever ballast/lamp combination you're considering before you buy it. A sample of such data is in the link below. From the right photometric report you can get the data to do a detailed comparative analysis between what you have now and what you're considering purchasing. A new "solution" may not do as much for you as you think.

    Bookmark   December 15, 2006 at 12:21AM
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ralleia(z5 Omaha, NE)

I forgot to whine about my lighting engineering final scheduled for 12 hours from now. The prof is terrific--so dedicated to helping the students learn, so organized and pragmatic. I wish all my profs had the same characteristics.

    Bookmark   December 15, 2006 at 12:33AM
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Colors and Spectral Characteristics of Various Fluorescent Lamps.

    Bookmark   December 15, 2006 at 12:43AM
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Broad and General plant grow light overview.

    Bookmark   December 15, 2006 at 1:30AM
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    Bookmark   December 15, 2006 at 1:43AM
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    Bookmark   December 15, 2006 at 2:23AM
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habman(5B CND)

Great info beholder.
nlites site does not appear to be selling these products online.
Where can I buy these lights?
The "Bio Tropic 25000K" purple T5 are exactly what I'm looking for.
I need it !!!!!

    Bookmark   December 15, 2006 at 9:44AM
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Yeah, about the "Purple light" post. I am not so sure the nlite is a place where a person would do business. I think they could be pot promoters since I only see the CF 'nurturelight' discussed on "pot" growing sites. I have yet to find any credible company that sells the BioTropic and Nurturelight. It sounds and looks very interesting though doesn't it? That NASA stuff too, hmmm... All interesting stuff but is it in the wrong hands here? I was thinking the "purple" light spectra was similar to what 'ledaero' is experiencing with the red and blue LED's. Interesting...Be safe when you explore!

    Bookmark   December 15, 2006 at 2:35PM
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Thanks for all the information. The purple light seems very interesting, but I also read your posts and I'm now wondering if it's even true. Please let me know what you find out.

Actually, I'm hoping that there is some evidence it may be true. I have some 405 NM LEDs that purple/blue. I may hook them up and add them to my 470NM Blue and see if it makes a difference. I also see they are claiming increase in the Red and Blue and less green. I'd like to see onre of these purple bulbs.

    Bookmark   December 15, 2006 at 9:20PM
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habman(5B CND)

Here's a link from a guy who is using the purple CFL.
Looks like he also has purple tube t12.
Scroll down to "Step four: Flowering"
Nurturelite Fluorescent purple 125w

So yes in europe they do have the purple CFL just not sure about the purple T5.

    Bookmark   December 16, 2006 at 1:45AM
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It has been a while since I have had time to visit this forum. I have been extremely busy trying to compensate for some of the "downs" in lifes "ups and downs". I have seen this PURple Light site before. It seems a bit purple heavy to me. Score another one for marketing.

I looked at their page showing the spectrum for the "Bio Tropic 25000K" purple light:
Ignoring a bit of stretching on their graphic, it looks EXACTLY like the spectrum of the Sylvania GRO-LUX Standard lamp, as shown on page 10 of the PDF literature from Sylvania titled "Spectral Power Distributions of SYLVANIA Fluorescent Lamps", or "faq0041-0800.pdf". The link to the PDF had appeared here many times before, but can be seen on:
Or, as a search interestingly showed:
on the nurturelite site itself.

The 25000K figure being significantly touted by PURple, really is not useable information, even though it may be a correct number. Everyone should look up a good definition of the word "metamer" to see how Correlated Color Temperature, or "K", can be so nebulous, conferring no real information about the precise wavelength content. I think Sylvania never even bothered to publish any CCT data on their GRO-LUX Standard.

The phosphors used to create the PURple spectrum are standard, the BLUE phosphor especially. The RED phosphors (actually 2 of them) are rarely used. The one at 626nm (Strontium magnesium phosphate) is often used as the coating on "coated" HID lamps. The taller one at 658nm (Magnesium Fluoro-germanate) seems to be only used on a few lesser-known plant/aquarium lamps.

I was lucky enough to have Jeff Waymouth, from Sylvania, to look up the design information for the GRO-LUX Standard. That lamp was developed by his father, John Waymouth, and a Greek photobiologist, Christos Mpelkas, many decades ago. If you want to read what he, and other lighting experts said, then go to:
and enter "zink" in the "Search this group" box. There will be a GRO-LUX discussion somewhere on the list.

I have found that takes a LOT of time to try and compose a really good and informative dialogue here, if I want to convey technical stuff correctly. I would like to try to return an correct a couple of errors (but not many hah!) that I did make in the past here (particularly a list of wavelengths where I noted UV far into the visible colors I meant to use HG for mercury).

On a few visits I noticed shrubs_n_bulbs had really been getting into disseminating information at every turn. Good job shrubs! It takes a lot of composing time to get your info right, which I havent had time for lately.


    Bookmark   December 16, 2006 at 2:17PM
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ralleia(z5 Omaha, NE)

The following is a portion of the text from an interesting patent (US #6921182) on LEDs for plant growth. I don't know if they're right or wrong, but it's food for though in trying to find home in on an effective wavelength for plant growth at an affordable cost:
660 nanometers (nm) is the wavelength that drives the engine of the photosynthetic process. The 680 nm wavelength is perhaps closer to the peak absorption wavelength of one of the two chlorophylls found in higher plants. However, at 680 nm you miss completely the absorption curve of the second chlorophyll, and furthermore the output curve of a 680 nm LED has a fair amount of light output above 700 nm, which is known to cause unwanted morphological changes to plants. LEDs of 680 nm output are also rare in the marketplace, making them relatively expensive. Our choice of a 660 nm first wavelength component is a compromise wavelength commonly used in plant growing research, which supplies energy to both types of chlorophyll without emitting enough light above 700 nm to adversely affect plant growth.

The 620 nm LEDs used in the aforesaid Ignatius et al. patents, are meant to provide the light energy for photosynthesis, but a look at the absorption spectrum for the two chlorophylls shows that this wavelength falls almost entirely outside the absorption curve for chlorophyll.

Our research showed better results using LEDs of 660 nm and 612 nm rather than the wavelengths of 620 nm and 680 nm. Beneficially, LEDs of 660 nm are also readily available in the market, and are very inexpensive.

    Bookmark   December 18, 2006 at 4:02PM
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ralleia(z5 Omaha, NE)

A very interesting article on pepper physiology as a result of growth under different spectrums of light: Metal Halide, and three different LED mixes. I'm afraid I don't understand the botanical science well enough to really understand.

Pepper plants (Capsicum annuum L. cv., Hungarian Wax) were grown under metal halide (MH) lamps or lightemitting
diode (LED) arrays with different spectra to determine the effects of light quality on plant anatomy of leaves
and stems. One LED (660) array supplied 99% red light at 660 nm (25 nm band-width at half-peak height) and 1%
far-red light between 700±800 nm. A second LED (660)735) array supplied 83% red light at 660 nm and 17% farred
light at 735 nm (25 nm band-width at half-peak height). A third LED (660)blue) array supplied 98% red light
at 660 nm, 1%blue light between 350±550 nm, and 1%far-red light between 700±800 nm. Control plants were grown
under broad-spectrum metal halide lamps. Plants were grown at a mean photon ¯ux (300±800 nm) of 330 lmol m−# s−"
under a 12 h day-night photoperiod. Signi®cant anatomical changes in stem and leaf morphologies were observed in
plants grown under the LED arrays compared to plants grown under the broad-spectrum MH lamp. Cross-sectional
areas of pepper stems, thickness of secondary xylem, numbers of intraxylary phloem bundles in the periphery of stem pith tissues, leaf thickness, numbers of chloroplasts per palisade mesophyll cell, and thickness of palisade and spongy mesophyll tissues were greatest in peppers grown under MH lamps, intermediate in plants grown under the 660)blue LED array, and lowest in peppers grown under the 660 or 660)735 LED arrays. Most anatomical features of pepper
stems and leaves were similar among plants grown under 660 or 660)735 LED arrays. The effects of spectral quality
on anatomical changes in stem and leaf tissues of peppers generally were correlated to the amount of blue light present in the primary light source.

    Bookmark   December 18, 2006 at 4:24PM
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ralleia(z5 Omaha, NE)

Sounds rather hokey, but if there's any truth to it, the "synergy" might help drive down the price.

Two sources--I haven't obtained technical specs from either yet:

    Bookmark   December 18, 2006 at 4:45PM
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ralleia(z5 Omaha, NE)

It looks like the latter source is based on the SunLED XLZR12WF ( with an output of 4000 mcd and a 20 degree beam angle. Put 672 of these together and you get a whopping 257 lumens according to my calc's. UGH.

    Bookmark   December 18, 2006 at 5:13PM
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Nice article on the Peppers! Good find on the website too! I did post an outside note on the purple light in the general light forum, you can see if there is any other info. there. I did get some emails back from a few person's who offered to sell me some "Purple" lights and one also named a manufacture. It still seems that quality control is lacking though. I really don't want to buy from a source that has not been around or can be vouched for. I really prefer to buy from the larger manufacturer's as they seem to have the best quality of light bulbs. So, even if the Purple lights are there I would prob. still buy the standard high quality bulbs.

    Bookmark   December 19, 2006 at 7:14PM
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I really wonder about my post here. I cannot say I made it with a clear conscience.
Here is the story behind this post. I had just had an exciting day visiting a previously unknown Hydro Supply store locally. The owner gave me 14 Hydroponic supply magazines and catalog's and I was elated to know the world again.
Sadly I did not know it was all childish hubor (once again :() and what information the magazines had was a mix mash of adverts and slanted reviews.
I really knew nothing whatsoever to do with the specifics of lighting! In fact I was rather clueless. How absurd you might say, you would be correct.
So, I hope some confusion can be cleared and we can get on with our lives!
I really wish they would put a after post edit capability on this forum! I would have corrected the error's of my naive hubor long ago! ;)
- I am only too human in an inhumain world. But that is no one's/things fault "per say". ;) Feel free to Laugh, cry, or vomit...

    Bookmark   December 21, 2006 at 3:21AM
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I seem to be getting good vegetative growth using the 630 NM Red and 470 NM blue. The more blue I give it the better for foliage it seems. I did an experiment on my peppers. I had them just under the red for a couple weeks and they were surviving, but not much action. Once I turned the Blue on directly, they took off on another veg spurt and got real bushy and started blossoming again. I have some young cucumbers doing pretty well also in the early stages.

Although 660NM seems it might be the best from the research articles, they are available, but not that cheap and not that powerful (at least what i can find). The best price I found was $35 for hundred at 2500MCD, 20 degree viewing angle.

The real challenge I feel right now with the LEDs is the blossom/fruit set stage. I was able to get a couple dozen Tiny Tim tomatoes to set, but that's not very many for one plant. I cannot get a pepper blossom to set yet. The peppers I am trying are miniature chocolate bells.

Another problem I have is I'm a rookie on Hydroponics and Aeroponics anyway. So, basically I can't be guaranteed that I'm doing everything else right yet! It's very likely that I could have problems even under the real SUN!!!

    Bookmark   December 21, 2006 at 10:29AM
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shrubs_n_bulbs(z8/9 UK)

Although 660NM seems it might be the best from the research articles, they are available, but not that cheap and not that powerful (at least what i can find). The best price I found was $35 for hundred at 2500MCD, 20 degree viewing angle.

You can't easily compare LEDs at far red wavelengths using MCD. 2500MCD at 660nm is equivalent to over 10,000MCD at 630nm. Those LEDs are probably better than you think! At 670nm, you have to double the MCDs again, and again at 680nm and again at 690nm (very roughly) to compare in terms of photon fluxes. Actually I'd be surprised if you find a 690nm LED which will show you MCD output becdause it is so meaningless, probably they'll just quote a radiant output in mW. You also have to check the viewing angle, half the angle means a quarter of the light. I've seen 625nm LEDs at 30,000MCD (2.2V/50mA) but only an 8 degree viewing angle, probably giving less total light than your 10,000MCD version.

    Bookmark   December 21, 2006 at 11:29AM
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ralleia(z5 Omaha, NE)

Hey ledaero,

Part of your issue with the peppers might be that they're bells. Somewhere on one of these forums I read that they're more difficult to get to set fruit indoors. You might try a non-bell variety, like a Cubanelle. If you send me an email with your address I'll mail you some seeds of cubanelle to try, along with whatever other non-bells are in my freezer downstairs. I think those thin chili pepper types would be even better, but I have no seeds of those types because they're too hot for me.

    Bookmark   December 21, 2006 at 1:20PM
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ralleia(z5 Omaha, NE)

SunLED has 660 nm LEDs that according to one of the sellers of assembled arrays has very reasonable prices. It's a ~4000 mcd LED with 20 degree beam angle with 20mA.

The seller stated that it has independently tested at the following optical outputs:

20mA = 5.2 mW
25mA = 6.4 mW
30mA = 7.8 mW

I signed up for SunLEDs catalog for some educational reading, but haven't received a reply yet. The link is available below. Perhaps they may have other further red LEDs as well, which shrubs_n_bulbs says will be more effective for plants. (up to the cutoff somewhere around 700nm).

BTW Shrubs_n_bulbs, I just wanted to thank you for all the insightful input that you provide this forum. Your posts are always valuable reading and show your experience and knowledge in plant growth lighting. Don't ever go away!

    Bookmark   December 21, 2006 at 6:58PM
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Thanks all for the helpful information.

Shrubs_n_bulbs - do you have some links on some details of calculating the photon flux or is there a formula to get photon flux using wavelength, viewing angle and MCD or how can I do it best?

Ralleia - thanks for the pepper tip and the SunLed link. Maybe I picked too hard of a challenge for my lack of experience...I'll email you thanks!

    Bookmark   December 22, 2006 at 3:35AM
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shrubs_n_bulbs(z8/9 UK)

This table gives the relation between radiant power and lumens at different wavelengths. Note that lighting lumens are photopic, although you will occasionally see comparisons made using scotopic lumens. You will see the value of 683 lumens/W at the wavelength of 555nm, this is the definition of a lumen and also the theoretical maximum efficiency of a light source at that wavelength. White light must include a spread of wavelengths (or at least three wavelengths such as RGB) which the eye doesn't perceive as well, so the maxiumum theoretical efficiency of a white light source is less than 400 lumens/W.

The conversion to photon fluxes is simply to multiply by the wavelength, longer wavelength means more photons per watt of radiant power. If you want an actual number of photons then you have to multiply the power in watts by the wavelength in metres (nm / 10^9), then divide by 6.626 x 10^-34 (planck constant), divide by 3 x 10^8 (speed of light). You'll get an absolutely huge number of photons/sec, divide by 6 x 10^17 to get micromoles/s. Cutting out the middleman, radiant power in W, times wavelength in nm, times 4, gives micromoles/s.

Converting candela (or milli-candela) to lumens exactly for a directional light source such as an LED is almost impossible. The mcd value is a peak value at the centre of the beam and you can only make a very rough estimate of the brightness over the whole viewing angle. Similarly, comparisons between the total light output of LEDs with different viewing angles is very approximate. The solid angle calculations are a bit of a pain, but this calculator will give you some reasonable numbers.

    Bookmark   December 23, 2006 at 7:54PM
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Thanks much for the info and links!

    Bookmark   December 23, 2006 at 9:24PM
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I fould that the best way to find out information about led grow lights is from the companies that commercially produce they. of course as many of you have found out they don't exactly give out their trade secrets to just anyone but there is one place where any smart company must will tell every detail of their product to and that is the united states patent office. if you try to search for "led grow lights" at the patent search web site you will come up empty handed. so if you want the really good stuff you have to find a product that someone alrady has a patent for. I accomplished this through putting the products name and "patent number" in as a search query and would you know it there it was, so then all you need to do is go back to the patent search page put in that number and your good to go. the best thing about Patents is that inorder to be granted one you must give grave detailed descriptions and grahics as to why and how the company changed there product design so that most likely it worked better the another one. give it a try you'll be amazed.

    Bookmark   January 20, 2007 at 9:49PM
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Is it safe to use metal hallide bulbs without a lens? If not, is the danger from fire or mercury? Thanks

    Bookmark   February 2, 2007 at 3:35PM
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watergal(z6/7 Westminster, MD)

It is safer to use a lens. This protects the bulb from bumps or stray water droplets that could cause it to explode. If the bulb cracks, it puts out UV radiation that is very bad for your eyes; if the bulb breaks, you get hot flying glass shards, which is just plain bad all around! A lens helps protect you from both. I would not run mine without a lens - in fact, I paid more for a fixture that could use a glass shield; many of the cheaper ones can't.

    Bookmark   February 2, 2007 at 6:10PM
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shrubs_n_bulbs(z8/9 UK)

The "lens" is for protection from intense UV, semi-molten bits of flying glass, and I suppose mercury vapour, not to mention several hundred watts of exposed electrical arc. It should be considered essential for metal halide bulbs unless they are "O" (for open) rated, since metal halide bulbs frequently fail explosively. O-rated bulbs are becoming more common and have a built-in envelope that keeps the UV, hot glass, and mercury contained if the inner bulb fails, also circuitry to shut down the arc quickly in the event of failure.

Bulbs that require a separate glass shield are marked as "E" or "S". The bulb sockets are subtly different with the intention that bulbs are not used in a socket where they wouldn't be safe, but it is often possible to remove the shield from protected lamps if you have a death wish.

    Bookmark   February 2, 2007 at 7:12PM
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Thank you both very much, especially shrubs n bulbs for the tip about O-rated bulbs.

    Bookmark   February 2, 2007 at 11:20PM
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ralleia(z5 Omaha, NE)

Hey ledaero,

Just wanted to let you know (for the purposes of your pepper experiment) that 2/2 (two out of two) North Star and 1/2 Cubanelles pepper plants have set fruit. They're all grown under close fluorescent light, mostly bright whites. The plants seem somewhat dwarfed under the conditions--they only got about 1 foot tall and started popping out flowers. I thought that my outdoor plants got a bit taller last year before flowering, but I could be wrong.

The fruits might be similarly small, but they're still growing.

I have yet to get a single ripe tomato off all the indoor tomato plants. I have a couple dozen growing green fruits, but none have started to change color.

All the plants were started approximately 1 November.

    Bookmark   February 7, 2007 at 4:57PM
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I've been heads down working on my LED lights and have got great results! I built a really powerful RED LED light at 630NM and have the bell peppers blossoming like popcorn and at least 3-4 dozen small pepper fruits have set on the two plants. A couple of the chocolate bells have gone green to brown and soon will be Red and ripe. I now have excellent veg/grow blue lights figured out and now I think the blooming is there too. If you want to check out these results see HTTP:// where I have photos of all the above. It's been a long haul, but things are really looking up on the LED side. What are most promising as far as growth rate are the 3 watt High power LEDS in a collimator and lens that really put out the FC. They cost a whopping $15 dollars each and look like they are providing enough light for one plant (cucumber right now). Thanks everyone for the info provided on this forum, it really helped a lot.

    Bookmark   February 7, 2007 at 11:21PM
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shrubs_n_bulbs(z8/9 UK)

Wow, you've gone at this big time!

You really need to convert those lux readings to photon fluxes. Do the blues look brighter to the naked eye? Hard to compare I know, but that's what the lux readings say. Lux (=foot-candles x 10) can be pretty misleading for monochromatic light in the blue and red ranges. Conversion rate (no units, just relative levels for comparison) at 470nm is 1/62 and at 630nm is 1/180, which suggests the blue LEDs are putting out a LOT more photons than the reds. But even slight variations in the wavelength can make a big difference. For 460nm the factor is 1/95 and at 640nm it is 1/120. Those PlasmaLEDs look to be way more efficient than the GroovyGrows.

Your burnout was almost certainly due to heatsinking problems. Might be inherent in the bulb, might be that it needs mounting a certain way.

    Bookmark   February 8, 2007 at 1:05PM
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Many reasons why LEDs burn, insufficeint heat sink is one. The others:

1. Manufacturer intentionally overdriving the LEDs.
2. The design does not have a good electronic driver circuit to limit current and voltage.
3. the LEDs are plug into the same outlet circuit with other heavy inductive load appliances such as refrigerator, air conditioners.
4. Thunder storm inducted surge in you household electric system.


    Bookmark   February 8, 2007 at 5:17PM
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Thanks Shrubs and bulbs -

I'm only using the meter to compare 'like' bulbs right now. For example, I'm not comparing a 470 to a 630, just comparing all 470s against each other. The 3 watt plasmaLEDS are pretty cool, great quality, and they work darn good.

The ones that burnt out were from BESTHONGKONG - real crap is waht they sell and #2 reason from Darch is their problem

I have not had a PLASMALED, Groovygrow or traffic light ever burn out or fail in any way yet.

    Bookmark   February 9, 2007 at 10:17AM
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ralleia(z5 Omaha, NE)


Thanks for the synopsis on besthongkong. I looked into their stuff following a lead from an LED enthusiast but stopped researching them after finding some gross incongruencies in their advertised numbers. Happy to know that the source can be ruled out for future research...

Hey, I've been getting lots of little red 'maters for the past couple weeks with excellent flavor off the Red Robins! They're not as quite as good as my summer Black from Tula 'maters, but they're packed with flavor when compared to the supermarket tomaoes this time of year. The biggest trick is resisting the urge to pick them underripe--the full flavor develops when they're truly red. I'm pleased to find that they *DO* still develop that flavor when grown indoors.

The biggest North Star pepper fruit is now over 2" long. I don't plan on harvesting any of them until I see a hint of color change so I know that they've achieved full size.

I'll try to post some photos today...

    Bookmark   February 27, 2007 at 5:26PM
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I'm happy you did not buy any besthongkong. The few I bought all burnt out. Worse yet, they don't even have the decency to answer my emails to their support.

The prices are coming down on the Luxeon stars to about 3.00 apiece for the 3 watters. Then optic lenses are only a couple of bucks. So, I'm thinking of putting some of those together for some blue lights. The High power Reds at 625 NM seem too low range though. I seeem to have luck at 630NM. I know it's close, but 625 NM seems to do nothing.

Congrats on the tomatoes. Isn't it nice to have a vine ripened tomato in the winter!

I know what you mean about the temptation to pick too soon. My mini chocolate bells get green, then brown, then red-brown. They are good eating at all colors, but they are really the best at the red-brown stage, but waiting is hard! They continue to blossom and set still, so I'm finding I have quite a continual supply of them coming out for quite a while now.

My tomatoes are doing okay and are about 7-8 inches high now. Two are Red Grapes which seem to be growing really well and one is Tiny Tim that seems a little stunted. I am trying a new machine, new nutrients, and new lights on them so I have so many factors to figure out to get right.

    Bookmark   March 2, 2007 at 11:44PM
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Wow! Too much info here. My head is about to explode.

Any of you debaters want to summarize what was discussed?

A graph? KISS

    Bookmark   March 4, 2007 at 10:05AM
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ralleia(z5 Omaha, NE)


Since "Tiny Tim" is a dwarf variety, the "stunted" appearance that you're describing may be just normal for the variety. All my Red Robins (another dwarf variety) were stouter with smaller leaves than the standard tomato varieties.

I've harvested a couple of the peppers off the Cubanelles and the north stars. They're incredibly crisp and a bit more pungent than I would expect for sweet peppers, but oh, so fresh!

Last week my new 6' wide garden window was installed, so I'm temporarily running without any supplemental light. In the fall I'll once again have to revisit the LED v. fluorescent v. HID supplemental light choice. By that time we may have new selections.

For eating, I found "Tiny Tim" to be worse than flavorless. Red Robin is ok, but lately I've found the tomatoes I've picked off my indoor plants to be watery and weak-flavored. My toddler has started rejecting them, so the plants are soon bound for the compost. The "Gardener's Delight" indeterminates have started producing just a few small but delectably-flavored fruits. The "Orange Pixie" plants, though they produced well outdoor, were a big disappointment for indoor winter growing.

Next winter I plan to grow strictly indeterminates on sturdy indoor trellises, along with a few pepper plants for fresh eating. I'll try Gardener's Delight, Pink Pink Pong, Yellow Pear, and Tommy Toe. I've now got over 12' of south-facing windows and will set up supplemental light again.

    Bookmark   March 20, 2007 at 4:27PM
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Anyone had any experience with these lamps?

I think they may also be the same as these:
If the link is broken you can find it by doing a Google search for "new leaf 7 Watt High Power LED Grow Light"

They claim to have six 660nm (red) LEDs and one 455nm (blue) LED. Each 1 Watt LEDs.
I ordered some from Quasar and opened one unit up. All the LEDs are in series and the total current is just above 300mA.
BTW the quality and consistency of manufacturing is what you'd expect from mainland China:
1. The cast aluminum body has thin sections where the casting is not great and light shines right thought the back of the lamp in a couple of places.
2. During assembly someone used inconsistant length screws holding the lamp together.
3. The packaging is so bad that some of the lamps I received could not be screwed into a lamp socket as the screw thread was crushed.
4. One of the lamps had a faulty inverter which was overdriving the LEDs (680mA instead of 300ma for the others)
5. The LED lenses are not glass, just plastic and are claimed to have a 30 degree pattern, which is a little too tight, looks like they'd be best to go for 40-60 degree lenses for illuminating a reasonable sized plant.
6. The LEDs are soldered to a printed circuit board and white thermal compound has been put under the LEDs to help with the thermal transfer. However I cannot be sure that the printed circuit board is thermally conductive, it might be, as it is a funny black color, perhaps not regular fiberglass... or maybe just a dark solder mask to throw me off the trail... But in any case application of the thermal compound is inconsistant - some of the lamps had little or no thermal compound under the LEDs, so no doubt those ones will run hotter and have substantially reduced life. The printed circuit board is held in place against the cast aluminum by the force of the lenses pressing down on the LEDs when the cover is screwed in place. The underside of the printed circuit board is generously smeared with thermal compound.

The red light is very bright, and seems too bright for 660nm light, I suspect these are not actually 660nm LEDs but perhaps regular ~624nm ones. What I read on Internet was that because 660nm is getting close to the edge of human color perception, an equivalent light intensity to regular red (624nm) will seem a lot dimmer.

Apart from roithner-laser's C11A1-660-30 (no doubt very expensive) I am unable to find any manufacturer anywhere claiming to have 1W 660nm LEDs which look remotely similar, which also makes me suspicious.
Opening the grow lamps up, I closely inspected the LEDs and found they are a white body LED, flat on the bottom, with flat gold connections emerging from each end. They have a small rectangular pressing in one of the leads to recognize the positive side. They look pretty similar to these ones:
I contacted Hebei (the Chinese manufacturer) and they told me they do not have a 1W 660nm LED, only 624nm, and they said they know of no other manufacturer that does have them.
Also the blue lamps listed on Hebei's web site are described as Royal Blue 460nm (not 455nm) so if the manufacturer of these grow lamps is using Hebei LEDs then I am dubious about their claim of the light wavelengths.

I am tempted to have the wavelength of the light tested to confirm the manufacturer's claim.

Has anyone seen these lamps?

    Bookmark   May 8, 2008 at 10:16AM
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You guys are getting too carried away with wavelengths - now repeat after me: there is no magic optimum wavelength for photosynthesis. Because of billions of years of evolution, plants have adapted themselves to use (now pay attention here): all wavelengths just about equally well. The only additional use that LED's have is in (pay attention again) - photomorphogenesis. Google is your friend here, look this up and all will be confirmed on the internets. If you wish to manipulate the phytochrome red pigment between Ph fr and Ph r, then go buy yourself some 730 nm leds, these are useful in industrial growing of cannabis, and no, I am not high on pot, I have not been high for over 2 years since LEO shut me down, but I still know a lot about growing. Blue light is useful ONLY because it is required to synthesize chlorophyll, but you don't really need very much. Now click on the link and observe the glory of 5 billion years of evolution, all in one nice graph. Now just find out how to optimize the greatest number of photons per watt, and you will be in business!!!

    Bookmark   May 8, 2008 at 8:32PM
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(Shrubs) "You need to go and read some more about
photosynthesis. One blue photon produces the same chemical
end result as one red photon."

(Lermer) I hate to interrupt Shrubs' heroic refutation of
LED claims (shockingly I find myself generally agreeing
with him on this), but each photon carries an energy that
is described by Planck's equation:

Q = hc/wavelength in meters
where Q is the photon energy (joules), h is Planck's
constant (6.623 x 10 to the minus 35 J s), c is the speed
of light, over wavelength in meters. Figure 2.1, chapter 2
of Light Measurement Handbook (1998), shows a direct
linear relationship between wavelength in meters
(spectrum) and photonic energy. The more toward UV, the
more energy; the more toward infra-red, the less energy
per photon.

From "Photosynthesis" (1987), fourth edition, by D.O. Hall
and K. K. Rao, chapter one, page 6:

"The energy of a single quantum of light or photon is the
product of the frequency of light and Planck's constant,
i.e., E = hv. Since frequency is inversely related to
wavelength, it follows that photons of short wave length
are more energetic than photons of longer wavelength, ie,
at one end of the spectrum photons of blue light are more
energetic than those of red light at the other end."

(Lermer) For any given pulse of light, the blue light is
slightly ahead of the red light. So, the blue acts like a
spearhead, penetrating the leaf and carrying the rest of
the spectrum with it. That does not mean, blue light by
itself is more efficient for plant growth; but it has
specialized functions.

    Bookmark   May 8, 2008 at 10:42PM
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This is the context of the exchange between "Shrubs" and
another poster:

"Red photons have less energy than Blue. This is why lots
of red and a few blue are needed as blue contains more
energy for the plant to use. The plant has to collect more
low energy Red for the light needed for further chemical

(Shrubs) Sorry, but this is garbage. You need to go and
read some more about photosynthesis. One blue photon
produces the same chemical end result as one red photon.
The excess energy is lost as heat while being transferred
to the ultimate photosynthetic receptors.

(Lermer) I also disagree with the top post, but Shrubs'
refutation is misleading. Blue spectrum does have more
energy than red spectrum. But the reason plants need red
more than blue, is that they have evolved under a forest
canopy and red penetrates the canopy better than blue.
Because red bends better. So it is the most efficient
single spectrum. Blue is the most important single
spectrum, due to it's specialized functions.

One blue photon does not result in the same chemical
reaction as one red photon. Each portion of the spectrum
results in a different chemical reaction. Lack of a
specific spectrum is compensated for by chemical processes
(at a loss to efficiency).

    Bookmark   May 8, 2008 at 11:00PM
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jkirk3279(Z5 SW MI)

"Because of billions of years of evolution, plants have adapted themselves to use (now pay attention here): all wavelengths just about equally well."

That's completely wrong, of course.

Let's try a thought experiment:

Suppose chlorophyl was 'magic' and could in fact absorb all wavelengths of light perfectly.

Then foliage would be black in sunlight, wouldn't it? No light would bounce off, so no reflected light would reach your retina and you'd experience the color of the leaves as "black".

But in normal sunlight, foliage appears GREEN.

Now, as it happens the foliage under my LED Red/Blue arrays DOES show up as a very dark greenish black -- the effect is to make the leaves look like they're made of very hairy black leather.

Which suggests to ME, that the chlorophyl in the leaves is in fact absorbing the LED light pretty well. Only a fraction of the light is reflected.

(Place a white index card next to the leaves, and it reflects purple light back at you. The light reflects off the paper, but not off the leaves. So it's being absorbed.)

But turn on the fluorescents, and suddenly the plants are bright green and healthy looking.

Now, with these results, we should ask ourselves WHY the blue and the red LED light is absorbed better than, say, green and yellow light.

Well, imagine this: light absorption is an electro-mechanical process. Light shines on chlorophyl and the molecule is excited.

The energy thus captured is used to drive chemical reactions.

To perfectly absorb sunlight, you'd need a molecule specifically tailored to each frequency of sunlight, and of course that's not the case.

Instead there are a few variants of the chlorophyl molecule, a, b, c1, c2, and d.

Between them they manage to capture some frequencies of blue and red light pretty well.

There are some alternate dye molecules that can store excess energy for very brief periods, in other frequencies. You see those dye colors in the Fall when the leaves change colors.

But still, there's a wide frequency range that chlorophyl can't capture, and since that range is centered on the color green, that's why foliage looks green.

Suddenly, I wonder if someday a bright chemist could synthesize a brand new form of chlorophyl that improves light capture efficiency in the green frequency band.

Add that new molecule to a plant's genome and maybe you could achieve food plants that could survive in shade or during shorter growing seasons.

It's an interesting idea, but of course plants can't deal with bright sunlight as it is. They have mechanisms to deflect bright sunlight and discharge excess energy before the excess causes the cellular mechanisms to oxidize to death.

    Bookmark   May 22, 2008 at 12:48AM
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Ultimately I think led's can grow a plant, but I think a full spectrum is probably best. Go with a hortilux HPS blue or Ceramic Metal Halide HPS retro.

    Bookmark   May 28, 2008 at 2:54PM
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you are wrong as well: light is a biochemical process its a (photochemical process to be exact)and under no circumstances a fact there is nothing either electric or mechanic about photosynthesis (REDOX yes but not electric). furthermore the colorful "dyes" as you call them are called pigments and they come in all sorts of colors (absorbing in different NM ranges from chlorophyll). pigments are NOT monochromatic they absorb a short range of wavelengths so you would not need one for each wavelength.
In fall the green chlorophyll pigments are broken down, the green color vanishes, which makes the secondary pigment (red-yellow) visible.
as far as i know geneticists (not chemists) are working on a) optimizing chlorophyll absorption and b)adding secondary pigments to plants for hi-yield biomass production.
im currently working on an algae project and this forum was very helpful. however i wonder what led efficiencies are right now compared with when this tread started.
im not very good with numbers so a "quick and dirty" formula for converting mcd and opening angle to photonic flux ( mumol photons/(m2-s) would be greatly apppreciated.

    Bookmark   November 7, 2008 at 7:03PM
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