The three most widely used kinds of grow lights seem to be HID, fluorescent, and LED. The strong point of LED as a grow light is that it can selectively emit the colors most efficiently used by a plant. A big problem with LEDs is that the quantity of light they emit is limited, and so its very expensive to build a big enough LED lamp to be useful as a primary grow light.

The HID, (MH, HPS), emmission spectrum is a little less well tailored to a plant's needs than the LED, but HID lights more than make up for that disadvantage by emiting a far greater quantity of light than a reasonably priced LED or a fluorescent grow lamp can. HID lights also penetrate deeper into foliage than fluorescents or leds can. HID light's disadvantage is that it creates lots of potentially damaging heat which usually has to be sucked away with a fan.

Fluorescents are nice because they burn cool enough, (like LEDs), to be able to burn very close to the tops of the plants without damage, and the bluish spectrum of some of the phosphor coatings is very good for vegetative growth. But they lack the red light plants need for flowering, and their light penetrates foliage less than HID light would. So far so good?

But why is it that HID light penetrates better? Is it because light from an HID light has more energy? A photon is a photon, isn't it? Why should an hid's photon penetrate better than any other light source's photon?

I also wonder why cold cathode, (CC), lamps aren't more popular as grow lights. CC tubes come in a very wide variety of colors, including saturated reds and blues, and can be hand bent to conform to any shape, and can be quite bright. CC lamps also burn cool like fluorescents. I'd think cold cathode grow lamps would be cheaper and better than LED lamps, and be at least as good as T5 fluorescent lamps are, and in certain grow schemes, maybe even better than HID. Yet nobody seems to talk about them. Is there some disadvantage to cold cathode lamps I haven't considered?

Thanks!

Best question of the year so far! Answers on a postcard please. And if anybody gets this right by the time I come back tomorrow, I'll eat my hat. Or a pork pie, whatever I find in the fridge! Hint: the answer is already on this forum.

Some of your assumptions about the pros and cons of lighting are understandable since they are repeated ad nauseum all over the internet, but some of them are wrong. Blue wavelengths are in no way preferable for vegetative growth or any other kind of growth. There is a sort of cult about blue light, almost entirely created by pot growers who desire it to increase alkaloid production in their cannabis plants. For 99% of plants a normal person would wish to grow, blue light is only require as a small portion of the output to maintain a good plant shape, and is easily obtained from almost any lighting source (HPS may contain too little blue). Red light from about 630nm-680nm is the main range which is valuable to plants and tends to be lacking in lighting since it is not very useful to humans. Plants grow OK without it but specialist plant lighting (LEDs, fluorescents, or ceramic metal halides) attempt to provide it in order to get an extra advantage in growth. Light at around 580nm has certainly been shown to be the most efficient for plant total growth, but in practice even the specialist fluorescent and HID plant lights contain too low a proportion of the best wavelengths to make a huge difference over other light sources. LEDs can provide exactly the most efficient wavelengths and their actual effectiveness as plant lights can potentially exceed what their basic light output would suggest.

The mantra of red for flowering and blue for growth is a complete oversimplification of the situation. It just happens that the spectrum of a metal halide produces compact growth while the less blue spectrum of an HPS lamp is less suitable for vegetative growth of many plants because it causes etiolation, but the very high efficiency makes it very suitable during flowering and fruiting stages. You should not assume from this situation that blue light produces more growth or that red light produces less growth but forces flowering. HPS lights actually produce more growth in most plants than metal halides of the same power, but the growth may be paler, taller, and thinner, therefore less attractive and possibly less able to support later stages of growth.

As for heat output, you are being confused by a number of different assumptions. First, you get more or less the same amount of heat from any lamp which generates the same amount of light, doesn't matter whether it is fluorescent or HID. LEDs (commercially available in 2007) actually generate more heat at the same level of light output because they are less efficient. LEDs tend to have extremely low power and extremely low light output, hence extremely low heat output. Fluorescents tend to have moderate light output, per tube, and so only moderate heat output. HID lamps, for plants, tend to have very high light outputs and hence very high heat outputs. Do not be deceived, 400W of fluorescent lights put out just as much heat as a 400W metal halide. The fluorescent will spread that heat over perhaps a 4'x2' array of tubes, so quite cool to touch, while the metal halide will be only a few inches long and so extremely hot to touch, but the total heat output is the same. In addition, HID bulbs radiate a higher proportion of their heat than fluorescents which can affect the plants. a 400W array of LEDs would generate even more heat but it would be even larger than the array of fluorescents. The LED array would also be cool to touch since it must incorporate cooling fins or fans to extract the heat or the LEDs will die very quickly.

The reason that cold cathode lighting is not used for plants is really very simple, it isn't efficient enough. The advantages that it has in terms of long life, colour control, and continuous architectural lighting are simply irrelevant to a plant light, therefore there is no reason to prefer it over a fluorescent tube which puts out more light. They are also expensive and hard to find.

However lumens is not a good measurement for plant growth, because it is biased toward the center part of the spectrum. Sunlight has a color rendering index (CRI) of 100, with all the colors between 400-700nm represented. Also important is the UV-a and UV-b bands between 280-400nm. Lacking a direct measure of photosynthetically active radiation (PAR), look for a combination of high output (as measured in total lumens, or lumens per watt) and full spectrum (as measured by CRI).

HPS has a high total output, but low (only 22) CRI. Standard Metal Halide has a moderately high output, and moderately good CRI of 70. Ceramic Metal Halide (CMH) has a moderately high output, and a full spectrum (between 85 and 95 CRI, depending on brand).

The higher quantity of light produced by HID (either HPS, MH, PSMH or CMH) does concentrate the light. This helps the intensity, and if you also move the light (with a track or spinner) you get good distribution over a larger area. The movement of the light constantly changes the light angles, resulting in fewer shadows on the leaf surface. The radiant heat is effectively reduced by dispersion, so the leafs are not heat-stressed. The total amount of heat produced would be less (with full-spectrum and spinning) mainly because fewer watts are needed.

Light energy from a point source disperses spherically at the inverse square law. Light energy from an infinite line source disperses cylindrically at ½ inverse square law. See:
http://www.physicsforums.com/archive/index.php/t-14843.html

A 4' fluorescent tube is a line source, and light from it spreads out at a rate more like an infinite line source than like a point source. In both cases, light intensity decreases with distance. The light is not destroyed, but is spread out over a larger area. As you add more and more fluorescent tubes, their "footprints" overlap to maintain intensity for a certain distance, except for the edges. Even with a large number of fluorescent tubes, you don't get the high intensity of HID.

The point source of the HID light can be spread out by a light mover, so with HID you both the high intensity and good distribution of light. With CMH (type of HID) you get both good intensity and excellent spectrum.

Full-spectrum LEDs are not commercially available, to my knowledge, at this time. You could go with 70% red LEDs and 30% blue LEDs, and get OK results. However plants have evolved under full spectrum sunlight for millions of years. Every part of the spectrum, from 280-700nm, has specific functions. If parts of the spectrum were missing, the plant could compensate, but that would reduce the efficiency for plant growth.

The biggest problem with LEDs is that most people can't afford to get enough to grow over a large area.

(Lermer) Cannabis does not produce alkaloids. You're thinking of poppy. Blue light does not increase phenolic compounds; that is done by UV-b (about 280-320nm). Blue is about 420nm (no pun intended).The flavor in licorice is from phenolic compounds (that are increased by UV-b light).

Many, many studies have been done, showing that blue spectrum light induces growth hormones, and red light produces flowering hormones. Blue has other functions, like rooting and prevention of stem elongation. Red (peaking at 670nm) is the most efficient monochromatic spectrum (for plant growth). See: McCree.Other studies show the specific functions of each spectrum band, from 280-700nm.

Plants have evolved for millions of years under full spectrum sunlight reaching the earth surface. Plants can compensate for an incomplete spectrum, but that reduces efficiency of plant growth.

You want three main things from a light:
1. full spectrum
2. high output, efficiently produced
3. good distribution of light, over a large area and with multiple angles.

Regarding the question of color, I have a spectral energy distribution graph of a cold cathode tube that I wish you would take a look at if you have time. It's at http://www.tecnolux.com/images/stories/RgbyDir/226.pdf. The same site gives spectra graphs for other colors and triphosphor whites. Also, take a look at neon gas in clear CC tube, at http://www.tecnolux.com/images/stories/ColorClearDir/ne.pdf.
I wonder if any of those look to you like they might make good grow lights. Electrical efficiency, I think they are about 80% as efficient, (lumen/watt), as T5 fluorescents.

Hair splitting here: everything you said, plus a tiny tiny tiny energy lost thru air if the light system generates RFI. This energy will not be converted into heat in the immediate area.

dcarch

In any case, with a good reflector, well placed light sources, reflective grow area, shadowing is not very important. Don't forget, plants have this natural ability to seek out light. There is no need to spin lights or moving tracks. If you must, every couple of weeks, move the plants around will do fine.

dcarch

Your understanding of CRI seems to stretch only far enough to understand that the product you are pushing, Ceramic Metal Halides, have high CRI and that you need reasons why this is a good thing. I remember from only a couple of weeks ago that you denied that Ceramic Metal Halides had especially high CRI values, but have now looked at the data and realised they do. CRI is a poor measure of how useful a light is to plants. The highest CRI available from a light source, other than the sun which is arbitrarily defined as 100, is incandescent lighting, yet incandescent lighting is the worst form of plant light. Clearly CRI is not significant for plants. Plants grow excellently with just a light from just a few wavelengths. CRI, like lumens, is actually biased towards spectrums with high quantities of green light. Very wide smooth spectrums with little green, such as a GroLux Wide Spectrum, are rated with low CRIs. Very spiky spectrums with lots of green, such as a standard cool white triphosphor, get relatively high CRI values. Old technology metal halides had very poor CRI values and yet were still preferred as plant lights over technology with much better CRI. Ignore CRI, get lots of light, very simple. References to millions of year's evolution under the sun are really pretty desperate stuff. If the sun is only way to grow plants, then get some big mirrors and stop mucking about with lights. Artificial lights work great. It is worth remembering in this context that triphosphor fluorescents, a fundamentally spiky light source based on combining narrow red, green, and blue emissions into white light, exceed the CRI of ceramic metal halides at every turn and specialist versions achieve CRIs of 98. Basic triphosphor fluorescents have a CRI around 85 and I have observed no difference between the two types as plant lights, other than cost.

Cannabis has no alkaloids? You probably think you're a genius for being the one person on the plant that realises THC isn't an alkaloid? True, but cannabis still contains alkaloids. As you may or may not be aware, chemically pure THC does not give the same "experience" as mariujana, there is a lot more in there. Still, I was referring loosely to all the psychoactive substances and I should have described it better.

Now for the real techno-babble lies:
Light energy from an infinite line source disperses cylindrically at ½ inverse square law.
LOL. You lifted that quote directly. Unfortunately the person stating it was wrong. Light from an infinite line source decreases inversely with distance. Light from a point source decreases with the inverse square of the distance. There is no such thing as a "½ inverse square law". Light from a line source decreases more slowly than light from a point source? Hold that thought ;)

The higher quantity of light produced by HID (either HPS, MH, PSMH or CMH) does concentrate the light. This helps the intensity, and if you also move the light (with a track or spinner) you get good distribution over a larger area.
Do you have any idea how stupid that sounds? You want high intensity, then you want to spread it out with a track or spinner? Light spreads itself out, save yourself the effort.

The movement of the light constantly changes the light angles, resulting in fewer shadows on the leaf surface
So plants have evolved for millions of years under an intense point source, the sun, and yet they need a spinner to avoid shadows? Give me a break, plants are extremely good at avoiding shading the lower leaves, not something you have to worry about.

Full-spectrum LEDs are not commercially available
No commercial light source except for incandescents is a full spectrum source. They all work by producing emissions at specific wavelengths, often several emissions at different wavelengths, and often broadened by doppler shifting or energy state broadening. Spectral charts produced by light manufacturers often use unfortunate scales or averaging to hide the height of the spikes, but the spikes are always there. The basic LED is also a single wavelength emission source. So-called white light LEDs use a phosphor to absorb and re-emit this light in a broad band. Such LEDs have the least spiky spectrum of any main commercial light but current technology produces a broad hump peaking to the blue side of green and is not very pleasing to humans, nor is it ideal for plants. Lastly, these white light LEDs are less efficient than those operating at single wavelengths and so not yet suitable for use as plant lights. At the moment, LED sellers are marketing on the basis of producing very narrow wavelength output at precisely the most effective part of the spectrum, the exact opposite of what sellers of broader spectrum light sources claim. One group is very wrong, probably both, because they can;t both be the perfect plant light.

Penetration is simply a macho word to describe the relative intensity of light at the base of a plant compared to the intensity at the top of the plant. It is a function of two things only!

First is the degree of collimation of the light emitted. This is another way of describing how much or little the light spreads out as it travels away from the lamp. The worst case is a point source, where the intensity decreases as the square of the distance travelled. The best case is something like a laser or hypothetical perfect searchlight, where the light intensity does not decrease at all with distance. Light sources may actually be focused so that they become more intense at some distance from the source but these are unlikely to be found in plant lights, and in any case the light always diverges again after passing through the focus.

Second is the relative distances of the bottom of the plant and the top of the plant from the light source. This, combined with the degree of collimation, defines the difference in intensity between the top of the plant and the bottom. Note that nothing else matters. The power of the light source is irrelevant, and the size and shape of the light source is only important in the effect it has on the collimation of the emitted light.

A perfectly collimated light source will have the same intensity at the top and bottom of the plant, but in other cases the bottom will have a lower intensity because it is further away. Reflectors are important! As an example in the case of the inverse square situation, if the bottom of the plant is twice as far away from the light as the top of the plant (say one foot away from the top of a one foot tall plant), then the intensity will only be a quarter. This is not a particularly good result, but most light sources will do much better than the inverse square law. A typical good plant light will produce light which decreases more or less as the inverse of distance. Here, the plant above would have half the intensity at the bottom, not too bad.

We can improve things in two ways. One is to improve the collimation, by providing reflectors and baffles to get the light onto the plant no matter how far away it is. We can never achieve perfect collimation, some light will be lost by scattering or simply by absorption at each reflection. Perfect collimation is also not desirable because we usually want the ability to spread the light less or more by lowering or raising it.

We can also improve penetration by increasing the distance of the light from the top of the plant. In the case of out one foot tall plant, if the light source is moved to three feet away, then the intensity at the bottom will be three quarters of the intensity at the top, very good indeed. Mount the light even further away and the penetration is even better. Note that intensity at both the top and the bottom will be lower but they will be more similar

This last finding is critical to out understanding of why HID lamps are preferred for tall plants. HID lamps are necessarily mounted at some distance from the top of a plant and fluorescents often mounted very close to the top of the plants. In these typical situations, penetration of the fluorescent light is very poor and penetration of the HID lamp is good or excellent. This has NOTHING to do with the power of the two light sources. An example to show this would be to compare a 25W metal halide mounted at the same distance as a 250 metal halide, with comparable reflectors. The little lamp produces the same penetration, but only a tenth of the light at both the top and bottom of the plant. Use ten of them and you have exactly the same intensity and penetration from a low power light as from a high power light.

To fully understand how you can achieve good penetration with fluorescents, or for that matter, bad penetration with HID lamps, consider why the two different light sources are typically used the way they are.

HID lights are small hot light sources which radiate a good amount of infra-red. They MUST be mounted at some distance from the plants to avoid damage. Because of this they necessarily have to be used with a decent reflector or the overall intensity at the distant plants would be too low. So HIDs necessarily have well collimated light used at a distance from the top of the plants, perfect for good penetration. Additionally HID lamps are available as very high power sources with very high total light output, increasing the ease of use at distance from the plants.

Fluorescents are distributed light sources, relatively cool to the touch. They CAN be used close to the plant and so they often are. Fluorescent fittings are often simple batons, reflectors, or diffusers designed to illuminate a whole room, not a small area directly below the light. Consider the fittings in this attractive system. You can actually see the fluorescent tubes from the side, a considerable proportion of the light will obviously be sent straight out sideways nowhere near the plants. In such a system, the cheapest solution to the poor collimation is to place the tubes very close to the plants, but that produces very poor penetration. If the light is one inch from a one foot tall plant then the intensity at the bottom of the plant is less than a tenth of the intensity at the top, awful. If a fluorescent tube is used with a decent reflector just like an HID lamp, and used at a distance from the plants just like an HID lamp, then penetration will be just as good as an HID lamp. Note that a single fluorescent tube is more comparable to the little 25W metal halide and one of them a couple of feet from a plant would produce quite a low intensity, so you would need an array of perhaps ten tubes to match a single 400W metal halide.

There are few few minor detail comments on this. I have ignored shading of the bottom leaves by the top leaves. Plants are designed to use a distant point source and to deal with shading all on their own, so I don't worry about it. A distributed light source necessarily has better collimation of its light output than a point source. In the situations we are considering, with reflectors and at some distance from the light source, this is not a very important difference. Also, "reflector" in this context covers a whole range of devices which function to get light from a source onto plants at some distance from the source. These devices include specular curved "focussing" reflectors around the light, specular flat non-focussing reflectors, matt or irregular surfaced reflectors near the light, and reflective surfaces far from the light. In the case of the simple baton in the picture, the light escaping from the sides could be used by having a reflector close around the tube or by using a reflective wall around the whole growing area. Reflective walls around the whole growing area have the advantage that light which misses the plants on the first try will always be reflected back again and again until it contacts a leaf (or is absorbed by the reflector). Most lighting systems get half or less of the light onto the plants, even using expensive curved reflectors. This is the first place to look to improve your growing.

(Shrubs) "Additionally HID lamps are available as very high power sources with very high total light output, increasing the ease of use at distance from the plants."

(Shrubs) "In these typical situations, penetration of the fluorescent light is very poor and penetration of the HID lamp is good or excellent. This has NOTHING to do with the power of the two light sources."

(Lermer) What I mean by good "penetration" is the ability of a bulb to deliver at least 1000 foot candles to the bottom leaves, without exceeding 5500fc to the top leaves. What should be obvious, is that if the bulb starts out at a high light intensity, it will be more likely to produce more light intensity at the bottom leaves than a low intensity bulb. Of course a reflector can add to the intensity and help penetration. Having a point source instead of a line source also increases light intensity, and combining several line sources can also increase penetration (because of overlapping light footprints).

(Shrubs) "Ceramic Metal Halides, have high CRI and that you need reasons why this is a good thing. I remember from only a couple of weeks ago that you denied that Ceramic Metal Halides had especially high CRI values, but have now looked at the data and realised they do."

(Lermer) I have been aware of the high CRI of Ceramic Metal Halides since a Philips engineer called me to tell me, shortly after CMH was developed (many years ago). I never denied that CMH has a high CRI.

(Shrubs) "The highest CRI available from a light source, other than the sun which is arbitrarily defined as 100, is incandescent lighting, yet incandescent lighting is the worst form of plant light. Clearly CRI is not significant for plants."

(Lermer) I didn't say that CRI is the ONLY factor to consider. The ideal measurement would be the amount of photosynthetically active radiation (PAR) per watt, but manufacturers do not generally give this data. To get a rough approximation of PAR, consider both lumens and CRI.
Ideally you want an even distribution of light between 400-700nm, with a slight bump in the red at 650-675nm, (and in some cases, also some in the 280-400nm range).

(Shrubs) "CRI, like lumens, is actually biased towards spectrums with high quantities of green light."

(Lermer) If that were true, incandescent would be biased toward green light. In reality they are biased toward the red and infra-red. Often other high CRI bulbs happen to have a spike in the green, but CRI is a measurement of color rendering not of green spikes. That is why CRI by itself isn't a good measure. See:

http://en.wikipedia.org/wiki/Color_rendering_index
"Although an objective measure, the CRI has been criticised in recent years as it does not always correlate well with subjective color-rendering quality for real scenes, particularly for modern light sources with spikey emission spectra (e.g. fluorescent lights or white LEDs)."

(Shrubs) "Cannabis has no alkaloids? You probably think you're a genius for being the one person on the plant that realises THC isn't an alkaloid? True, but cannabis still contains alkaloids. As you may or may not be aware, chemically pure THC does not give the same "experience" as mariujana, there is a lot more in there. Still, I was referring loosely to all the psychoactive substances and I should have described it better."

(Lermer) I'm not aware of any alkaloids in cannabis. Besides the THC, CBD and CBN are also important. All are phenolic compounds, none are alkaloids. "Phenolic compounds" does not equal "psychoactive substances", unless you consider licorice to be psychoactive.

(Shrubs) "Light from an infinite line source decreases inversely with distance. Light from a point source decreases with the inverse square of the distance."

(Lermer) Yes. I appreciate the verbal explanation, albeit lifted directly from the same link. I'm not a math major. My point is, light from fluorescents also disperses with distance, though not as much as from a point source.

(Shrubs) "Do you have any idea how stupid that sounds? You want high intensity, then you want to spread it out with a track or spinner? Light spreads itself out, save yourself the effort."

(Lermer) I guess that the millions of growers who are using light movers are all wrong, and you, Shrubs, like a Howard Roarke hero, know better than them. Wait, that's my line. Actually, I don't like the idea of moving lights, and for years I resisted them. I was persuaded by reality.

Observe leaf surfaces from a single line or point of light. You will see shadows, because some leaves will shade others. Add a second line or point of light. You will see fewer shadows. Now move the light, and see how light and shade alternate on the leaf surface.

Now take the same plants, and place them outside in the sunlight. Because the sun appears to move across the sky, rising in the east and setting in the west, the light moves and therefore compensates for shadowing.

(Shrubs) "At the moment, LED sellers are marketing on the basis of producing very narrow wavelength output at precisely the most effective part of the spectrum, the exact opposite of what sellers of broader spectrum light sources claim. One group is very wrong, probably both, because they can;t both be the perfect plant light."

(Lermer) Actually, both are right. CRI isn't the only factor, red and blue are the most important but the other spectrums are also important. You need a balance between full spectrum and high output/efficient delivery. So if you have both red (70%) and blue (30%) LEDs you can get OK results, certainly better than a high CRI light like incandescent. But if full spectrum can be achieved efficiently, with even distribution between 400-700nm (with a slight bump in the red), that is the best.

Great stuff guys! I've joined because the 'feel' of the discourse is good; bright minds not bashful with ideas and opinions!

Now slowly back on topic . . .
For Shrubs - I actually knew the answer to the 'penetration' pop quiz, but didn't answer thinking you might not have enjoyed eating hats or pork pies. Glad that’s not the case. Over the years I've learned to enjoy the taste of hats myself, particularly the fruity ones.

I hadn’t seriously considered indoor growing until coming across this post and others made since '06 on this forum, particularly since nobody I know has REAL practical experience and I have no faith whatsoever in the hype out there.

I do however have a 'perfect' spot in my home for use of a T5 8-bulb 4 foot fixture based on what I have read here. One of our downstairs bathrooms has a bit of an alcove (formerly a bathtub space) with a front-loading washer and dryer. Above the machines is an unused area about 54" wide, 26" deep, and 36" tall from machine tops to the ceiling. When I remodeled and plumbed, I used cement board on walls and covered with the white plastic sheeting commonly used at car washes - totally impervious to water and water vapor.
Everything is there - electric service, water taps, a drain, and even natural gas! The original iron tub was left in place with a platform constructed over it, so the washer atop the platform has a large reserve drain space. This was to insure any future drain blockage would not immediately flood the teak floor I labored so hard on. I read all kinds of conflicting junk about the various fluorescent bulbs on offer as being 'best' for growing and blooming, alone or in different combinations. For instance, one recent claim is that a T8 'narrow spectrum' grow bulb is still the best fluorescent to use. Pure science aside for a moment - I prefer to leave that at work, what has been the experience here in using the different T5 and T8 bulbs? By that I mean actual growth outcomes? I'm interested in using the little grow space to experiment with exotic fruiting plants and bloomers that would normally grow at lower latitudes or in different environments than naturally are available here. Some just need a bit of help to improve their chances of good health outside part of the year like my pineapples and bromeliads. Others, well that’s where the fun of experimenting lies!
T5’s seem to be the best for me since more light is generated from a smaller fixture, but if there is a reasonable argument in favor of T8’s where plant growth is concerned, I’m all ears. Cost of the bulbs is not a big issue for me as I’ll be servicing only one 8-bulb fixture, not one hundred fixtures. Besides, compared to my boat and car projects, gardening indoors will be like an all-expenses-paid vacation!

I Hope it’s ok to join in here rather than starting another thread. I’m hoping my questions and your answers may focus or illuminate . . sorry :)) . . . some of the issues above for other readers with similar goals as mine.

By the way, Happy holidays to all of you! Thanks for giving me thoughts and ideas for a new and fun project!

Phil

dcarch

http://www.sunlightsupply.com/products.cfm?sid=F5AB8624E0815D55343A4C9F81546180&c=55&sw=1

Also, I'm wondering if Sunlight Supply actually manufactures these lamps, or if they only mark-up and market the fixtures?

- Break -

Ok, I did have a few moments to web search commercial fluorescents while traveling up the coast yesterday. All I could find down that avenue in a T6 setup was a sea of 6-bulb HO fixtures, no 8-bulb lamps. And all those had their ballasts mounted conventionally atop the reflector making them nearly twice as tall and more bulky. None were aluminum. None offered a choice of bulbs, and most had reflectors that didn't seem as well designed as the purpose-built grow/aquarium fixtures. Prices for the generic commercial fixtures were cheaper of course, but surprisingly by only $50-$80 dollars.
After I've been freed from the yoke of Christmas responsibility I'll call a few commercial lighting suppliers here in the Orange County / Los Angeles area and let you guys know what I find.
In the mean time, if anyone knows who might offer the best price on the TEK lamp described above – or its generic cousin , please chime in. If all else fails that'll probably be the way I go.

Thanks again guys, may your bulbs all burst this season -
not your lamps! . . . I mean you gladdies :)))

Phil

In terms of the lighting technology, every single T5 system is almost identical, same electronic ballasts and same triphosphor light output. If you look really hard you can now find a few tubes with different spectrums. The efficiency of the T5HO tubes is no better than a good quality T8 or T12 but they put out a lot of light from a small tube. Feel free to source the ballasts and tubes from anywhere you want.

The area to be careful with is the reflectors. Commercial reflectors simply aren't designed for lighting plants. But to be honest, even the reflectors on the lamps at your link don't look so fabulous to me, despite being made from German aluminium (is the periodic table somehow different in Europe?) and having a trade-marked name :) A good reflector has the tubes recessed inside it and not sticking out spraying light all over the place. A good fluorescent reflector system casts a distinct illuminated patch below it and doesn't light up the whole room. You might want to make your own.

Frankly, I didn't pay too much attention to the 'numbers', assuming bulbs and ballasts were off-the-shelf. I was more interested in packaging size and the reflector's suitability.

I was just hoping someone could impart practical experience looking over the TEK lights IN THE FLESH, or one of their generic cousins if they exist.

Short of this, a source referral to the desirable components either by name or location would be very useful.

( EX: I like 'XYZ' brand reflector available from, or manufactured by 'XYZ' company, simply because . . . . )

I build boats and racecars, so I'm less geared to sourcing and building custom light fixtures. For me it's not the act of building the fixture that gives me pause, but the inevitable time, trials, and errors associated with sourcing, choosing, and matching the various parts to make the whole perform as envisioned, without practical referrals from those that had been the route, learned what is very good, and who know where to get the components to duplicate their experience. Otherwise, I need to get something plug-n-play. And if something plug-n-play under consideration is substandard or flawed in ways that can be addressed, what is a competing product that is better? Who manufactures it? Where is a good place to buy it?

PS - Don't worry about me falling prey to any lamp vendor's sales hype . . if I took it all as gospel, I wouldn’t be here pestering you guys for answers. In the boat and racecar world I've heard it all and while some issues are subjective, nearly all are slaves to the bottom line and the timeclock. So my selective and intuitive listening has become a performance art.

Thanks again,
Phil

Has anyone grown marijuana under HID and CFL, and have some tangible results? Or flowered orchids? Or grown tomatoes? Or kept a coleus? Or managed to get a Cheiridopsis to flower during an English winter (shrubs, that one's for you :-)?

a confused, x

Side by side trials are much more difficult than it might appear. The various lighting types cannot be fitted with the same reflectors, cannot be persuaded to light the same area, or provide the same collimation of the light, and it is hard to maintain the same temperature levels at the plant. It is hard enough even to provide an equivalent level of light, whether measured by input power or output light. Hence you get different results with different plants at different times.

Results from full-fledged published side-by-side trials, not done by me, show some variation but also consistent trends. Plant yield, measured by the weight of the plants and any crop from the plants from a given input power, is consistently highest with HPS lights, followed by metal halides and fluorescent lighting. The two papers I could find that included LPS lights obtained the highest yields from the LPS but commented on the extreme etiolation and poor colour of the plants. Studies have shown that comparable yields to HPS can be obtained using mainly LEDs at around 670nm, using LEDs of an efficiency not widely or cheaply available yet but its only a matter of time. There is certainly room for more study, much of the research was done decades ago using lighting technology far inferior to stuff you can pick up today at Home Depot.

It is simpler to compare different spectrums from the same technology. Again, it is hard to know if you are comparing a results from a different spectrum or from a different light output level, but if it is coming from the same input power, in the same reflector, then at least you can choose which bulb is best. My own testing is that triphosphor warm white colours do not provide as much growth as cool white and daylight colours, but there is no noticeable difference between cool white (4100K) and daylight (6500K). Wide spectrum, high CRI, fluorescents were a major non-no, I presume because of their overall lower light output.

FWIW, I have some tropical hibiscus that are under fluorescent lights right now just to sustain them through the winter, and some are forming new flower buds even with temps not higher than 55F.

I'll let you guys know in a few days what I figure out.

Best to all,
Phil

Shrubs - very, very interesting stuff, particularly your actual experiences with the flowering genus you mentioned. Also it is totally understandable the point you make about the difficulty of fairly comparing the competing technologies. And wouldn't it be nice if a real LED solution was available . . and cost effective. LED's sure have offered improvements in transportation lighting. My boat's nav lights, courtesy lights, and locker lighting are all LED. They work beautifully and consume far less energy. This is a big deal when passagmaking.

xerophyte_nyc - Maybe you should make some hibiscus tea to see if those flowers look and smell nice, but taste awful compared to their outdoor cousins :)))) Thanks for the sharing your experiences - very . . (wince) . . illuminating!

Phil

dcarch

Next to think about, is the use of Solatubes through the ceiling to supplement artificial growing with natural light. I wonder what is lost from the naturally available spectrum when these are used? These devices use no glass, and seem to collect and intensify visible sunlight. I'm wondering about loss though because there seems to be little heat transmitted through them. . reduction of IR? I have never run across a discussion of these devices in the context of indoor gardening. Solatubes aren't cheap, but their cost can often be justified as an element of home improvement, not just an indoor growing tool.

Here are a few interesting general references to UV light and bulbs I had found at the time -

http://www.americanairandwater.com/uv-facts/uv-light.htm

http://members.misty.com/don/uvbulb.html

Reading the above got me to wondering if a modified surplus tanning booth might make an awesome grow 'chamber' with the right combination of bulbs. There are probably more tanning booths here in 'sunny' Southern California than anywhere that actually might need them, so there's bound to be surplus equipment available.

Dcarch - interesting about the insects. If we could only find a way to use invisible UV emissions to detect a lamp marketer's BS . . I'm just sayin'.

Phil

In simple terms, plants don't need UV to grow. UV is harmful to plants. However, it does stimulate certain response in plants, including the production of chemicals which are quite prized although also illegal, UV also stimulates certain pigments as well as things like stronger spine growth in cacti.

A tanning lamp would be the right sort of UV to use. Do not use the UV-C germicidal. If you add any UV to your light setup, do it very carefully. The plants must be given time to adapt or they will be damaged. Just the same as if you took a plant out of your kitchen and stuck it in the garden, it would burn and maybe die.

I think either the mites are unable to penetrate the polymer coating with their "mouths", or somehow the polymer coats the mites themselves and suffocates them.

Also, I think photoperiodicity is species specific. Some plants have no problems growing with 24-7 light, others will weaken.

x

Photoperiodicity is different from whether a plant will grow well under 24/7 light. Photoperiodicity is a response to the length of the dark period which controls seasonal events like flowering and dormancy. Certain plants will simply not grow well under continuous light, typically succulents which only open their stomata when it is dark, but also some other plants.

Well if it wasn't for shrubs I would not have even bothered.

Shrubs ... you know what you are talking about ... or at least you know a lot more then I do about growing. However.

I build LED Growing Systems for a living and I have yet to find Red Led's that are of the wavelengths you are talking about. Red led's are typically 630nm ... not 680 or 690 ... if they were they would outstrip all other growing methods tomorow. Unfortunatelly commercially available blues are also slightly off the required wavelength. They are 470nm and plants want 430nm.

As to the cost of Led growing systems I will pull my own chain here as I am about to release on eBay an all white panel ... watch for it ... made in Canada as well.

Here are as I see them the challenges to using Leds.

1. Density ... how many leds can you AFFORD to fit on a panel.

2. Size and type of Led .. is a 5mm twice as bright as a 10mm and if so... does it matter? Is brightnest what we really want?

3. You need to analyze the absorption sprectrum VS the emmision spectrum of the plant in question. Somebody in this thread said that plants like UV light because the bugs see it. What they are describing is the emmision spectrum of that plant and the ability of the bug to see it.

4. ONLY leds can produce basically monochomatic light and can therefore be programmed...what I mean by this is that I can build a timer circuit that would turn on 730nm and 830nm Infrared light for a few minutes just before the end of the daily photoperiod. Why on earth would you want to do that... as you are no doubt scratching your head about now.

For the answer to this point please research the Emerson Effect and co related studies.

As for the comment that you made that many studies have been done using 690nm light...where are they...I have been reaserching this subject for a long time and I have not seen a single one...that is probably because they don't make them.

Again the main and posibly only challenges about led lighting are capital costs and what I call the blue red shift

LED available
red 630nm
blue 470 nm

Plant wants
red 660 at daytime
680nm , 730, and a tiny , very tiny 830nm shot in the dark so to speak
blue 430

As to Efficiency ... another word misused in this thread.

First of all a Watt is a Watt whether it is produced by 220v or 110v ac or DC voltage. Therefore efficiency is a matter of watts in vs watts out and it is that simple for most calculations.

If you want to improve efficiency ... look to your power supply not the light as you have no control over that.

Having said that this makes leds very attractive from a power consumption point of view as they ... or at least mine ... are designed using Level IV Efficiency rated supplys.

Look at the rating on MH or HPS supply or use a meter to figure it out .. no shocks please.

So the claim that leds will reduce your power bill by 90% is true. I calculate 96% actually. But now you have a new problem ... beleive it or not the room is too cold and dry. I use the excess heat from my computer room to heat the grow room. Ratio is one AMD chip to ten plants or one Intel to three plants (Intel runs cooler).

Also if you increase the density to pot growing needs you need to double up. But after the first electrical bill your already that much closer to electrical independance. Which is after all the holy grail of growing.

All in all we need people out there trying leds to see what the combination of colors and photoperiods can do for us...there are just far, far too many for any one person to figure this out.

As a matter of fact I would love any assistance I can get on the absorption spetrum of plants, the photoperiods required, etc... So

WATCH FOR MY WEB SITE ON LED GROWING SYSTEMS IN THE NEXT WEEK...I will return and supply the link to this club in a couple of days...don't expect miracles as it will be brand new and I have no help...yet!

shrubs I would very much like your help.

I'm not sure what your issue with sourcing LEDs at the correct wavelength. 660nm is very readily available as a component LED. Manufactured products at this wavelength are rare because it looks so dim. 670nm are also available, this is right at the chlorophyll absorption peak. Beyond that, you are like to find 680nm and 690 nm lumped in with the IR LEDs since they are almost invisible to human eyes.

Anybody selling LED plant lights operating at 630nm is a conman and anyone buying them is a fool. If you want light at 630nm then buy a fluorescent. You can actually get fluorescents that use only the red triphosphor if you really want to load it on at that wavelength. Use an LED light if you want your light right at that 660/670nm wavelength.

First, I am glad that different people try different things, that’s what progress is all about. So don’t take any of my comments here as being negative.

1. Manufacturers will be unlikely to gear-up to produce LEDs with spectrums specifically for plant growth because it is more profitable for them to use their capacities to produce LEDs for other applications.

2. It is my own believe that plants grow better with a whole range of light spectrums. LEDs is monochromatic. Vitamins are important to human health, but I don’t think you will do well just eating vitamin pills.

3. "Density ... how many leds can you AFFORD to fit on a panel",
Not only that, heat kills LEDs quickly. When you pack LEDs, heat evacuation becomes a major issue.

4. "Size and type of Led .. is a 5mm twice as bright as a 10mm and if so... does it matter? Is brightnest what we really want?"
Absolutely!

5. LEDs have built-in lenses, that severely limits your options in light distribution design. It’s very difficult to use reflectors for LED arrays.

6. "ONLY leds can produce basically monochromatic light and can therefore be programmed...what I mean by this is that I can build a timer circuit that would turn on 730nm and 830nm Infrared light for a few minutes ".
You can turn any lights on/off, not just LEDs.

7. "First of all a Watt is a Watt whether it is produced by 220v or 110v ac or DC voltage. Therefore efficiency is a matter of watts in vs watts out and it is that simple for most calculations. "
Not sure what’s your point. In lighting, efficiency is watts vs foot-candles.

8. "Having said that this makes leds very attractive from a power consumption point of view as they ... or at least mine ... are designed using Level IV Efficiency rated supplys."
Again, I am not sure what’s your point. You can have a 100% efficient power supply and still useless if your light source is only 50% efficient.

9. "believe it or not the room is too cold and dry. I use the excess heat from my computer room to heat the grow room."
I don’t quite understand. A computer uses less than a 100 watts of power. 100w x 3.4 = 3,400 btu/hr, even you add other devices there is still not enough to heat any room (in the summer may be).

10. "Also if you increase the density to pot growing needs you need to double up."
If you are talking about pot as in containers, again, you need as much foot-candles of all spectrums as possible. If you are talking about pot as in cannabis, yes, they will try anything, spin lights, moving lights, LED lights, they have plenty of money to burn.

dcarch

Maaaan, that is one EXPENSIVE grow light.

But of course if it could efficiently grow Thai house-girls I might write the check :)))

Phil

To Shrubs

Yes they do make them and they are not usually from China either. But I misspoke before...it wasn't the leds...it was the reports I wanted...where are they...please provide links. I want to read all I can and find the proper wavelength of leds.

I disagree with your second point however due to the radiation pattern of red leds...they do have components in the proper wavelengths but like MH and HPS you have to turn up the other wavelengths in order to get the ones you really want. But buy a fluorescent...that is a bit harsh.

How about a comprimise..could not one supplement the other in order to acheive the conditions of nature.

I would like your help for the obvious knowledge you have with growing. I guess questions in this forum would be enough but I was hoping to get you to try advanced techniques like Infrared. I can make all Led panels...using any led. I thought you might start a site like greenpinelane. Interested?

I considered well your point about raising lights vs lowering them and you are absolutely right and the sun proves it. By the time the rays get to the earth their power is even thru out the plant worlds short height of 100 meters or so as in the jungle and that also explains the shadow problem that other fellow thought he had but didn't.

To dcarch

you are in left field for most of your 1 thru 10 points.I won't hit them one by one that would take too long.

First of all I MANUFACTURE LED PANELS I am not buying them. I have only made a few dozen so far as I am a startup and as far as them being hot...what planet are you on...they do not get hot AT ALL the resistors do! Not the leds themselves. If you are refering to High Power Leds then diferent story.. I am refering to standard 20ma Leds which is all you need. you don't need the new 1W or 10W leds for plants you can even get away with 5mm spaced at a half inch.. my own panel has 300 leds spaced very close and there is no heat whatsoever...none at all. The room is hotter.

You have answered some of my questions tho. Bright is allways better you say. Well how bright should I make the Infrared considering I can't see it! As far as a light switch goes well you can stand their with a watch and turn on the IR at the end of the night and you can stand there and turn the knob that simulates the falling sun but I would rather put all that in a circuit to do the job for me.

As for efficiency. As allways people comming from the visible light world keep thinking of things like lumens per watt and such things. Therefore your argument about foot-candles goes out the door and we talk instead about micro einsteins. Either way your argument is irrelevant because it has no place in the monochromatic world, which after all is a plants world. So you are absolutely wrong about a plant requiring the full spectrum of light. If that were true then plants would all be black..or would they all be white. Either way they would not be green. This is very simple. Furthermore...why is NASA using leds on the space station and on the mission to Mars if they don't work?

The next time you write a novel do some research, you are wrong on 90% of your points. The only one you had right was brighter is better.

I do in fact use the excess heat from my computer ROOM run thru a bathroom fan to heat and fan my plants and it works! I'm looking at it right now. If I could upload a picture I would. But I really said it a a joke ...you know...I didn't think anyone would take me seriously on that point. Call it a test.

Leds have built in lenses.. my god I hope so!!!! However light distribution is not what I want...I want the ability to concentrate the light in an area not throw it all over the room so again leds win!

Efficiency is not watts vs foot candles in an led world. It is the efficiecy of the power supply that matters. I don't manufacture the led's, I just use them, so I can't waste my time worrying about whether they are as efficient as other lights. hell they are all inefficient for that matter. What I care about is the power bill for the plant I get. that's all. Who cares about the rest of the power equation. You can't change it!

Light source only 50%...???? what the...

You are so wrong on that last point it is not even funny...do your reasearch on the four types of chlorophyll ( a thru d ... yes there are more then two types) and their ABSORPTION SPECTRUM with respect to the plant you are growing and then see if you have a new view point

I have been assembling quite a few LED devices for various applications using different types of LEDs. It is my experience that 5mm LEDs do generate significant amount of heat, if driven to their rated power. With higher power LEDs (Cree, Luxeon, K2, Rebel, etc.) They will not last more than a few seconds if not properly heat sinked. Obviously, by definition, resistors turn power into heat, that’s where system inefficiency becomes unavoidable. I was hoping that you would be using electronic regulated driver power supply to get better efficiency as well as better reliability. If all you are doing is running LEDs in series with resistors after DC rectifiers, then LED’s intolerance to voltage spikes becomes an issue.

"Well how bright should I make the Infrared considering I can't see it!"
It is of course very silly for me to tell you this, as it sounds like you know so much already. But here it is, I use my digital camera’s viewer to view infrared from my IR LEDs.

"As far as a light switch goes well you can stand their with a watch and turn on the IR at the end of the night and you can stand there and turn the knob that simulates the falling sun but I would rather put all that in a circuit to do the job for me. "
I humbly apologize. I didn’t know you have such mastery of digital circuit design. I recently have built, in such clumsy way and with such difficulty, a working solid-state light timer which has adjustable dimming on/dimming off (sunrise/sunset) controls. Unfortunately it is at this point for incandescent lights only, as I am still having difficult figuring out how to dim LEDs gradually. Perhaps you can help.

"As for efficiency. As allways people comming from the visible light world keep thinking of things like lumens per watt and such things. Therefore your argument about foot-candles goes out the door "
I am too old to understand new concepts. If I pay for watts, I want to know how many foot-candles or lumens I am getting back.

"So you are absolutely wrong about a plant requiring the full spectrum of light. If that were true then plants would all be black.."
I know a few black friends, may be they can explain to me better.

"The next time you write a novel do some research, you are wrong on 90% of your points. The only one you had right was brighter is better. "
Thank you for your complement that I am 10% right.

"Leds have built in lenses.. my god I hope so!!!! However light distribution is not what I want...I want the ability to concentrate the light in an area not throw it all over the room so again leds win! "
So with say a 20 degree typical beam spread for LED lens, I should be able to keep my one tomato plant happy, NO?

"so I can't waste my time worrying about whether they are as efficient as other lights. -------- Who cares about the rest of the power equation-----"
Yeah! right on! Don’t worry, be happy, life is too short.

"You are so wrong on that last point it is not even funny..."
I have been told many a times I don’t have a good sense of humor.

dcarch

And your responses to me in particular show that you are refusing to accept the basic laws of the universe. I repeat again and perhaps you will read it this time: if an LED light outputs the same wavelengths that a fluorescent light outputs (eg. 630nm and 420nm) then you should throw it away and use the fluorescent because it produces more light (in 2007/8 with commercially available LEDs) for a given input power. No attempt to bootstrap up a perpetual motion machine with IR flashes are going to change that. Until available LEDs roughly double their output efficiency, they can only be effective as plant lights by doing something that other technology cannot. At present this appears to be producing light predominantly near 670nm which no other light can do.

A sunrise/sunset dimmer will need very smooth full range (100% to 0%)dimming for about 45 minutes. I did it using zener controlled charging circuit to charge a capcitor and disipate the current over an adjustable resistor (temperature compensated). This circuit is then used to control the gate of the power portion of the circuit to a 500w halogen light.

BTW, this type of dimmer is useful for people who are into birds, and other pets, not for plants.

dcarch

Here are my comebacks...which is all you guys seem to want to do..argue that is...how about trying to cooperate in order to acheive a goal. Or do you all just want to be right?

dcarch

You have no clue dude...use constant current or regulated 5volt supllies..use Toshiba 16 channel LED driver..one resitor and a 555 timer and voila a circuit that can dim from 40% to 110% of relative illumanance, (no flicker?????)
be contrlloed in any way I see fit and DOES NOT GET HOT AT ALL >>> NO RESISTORS.

There are many ways to connect Leds not just the standard. Again do your research which I know you have not done because you just rattled off an answer to me without taking the time to check any of my research...but your so smart.

Well dcarch I won't bother responding to a guy who doesn't take the time to read!

shrubs...go buy a flourescent bulb ... you also have no clue as your answers show..and I thought you were smart.

And if you think that a flourescent can compare to leds then you need to buy a spetral analyzer dude cause you are way wrong.

Anyway guys go ahead and argue with me since that's all that's going on here anyway and I will come back in a few days and show you where the real work is getting done...not this farce of a dicussion group!

I will even tell you where my site is so you can and buy real led grow lights!!

"You have no clue dude...use constant current or regulated 5volt supllies..use Toshiba 16 channel LED driver..one resitor and a 555 timer and voila a circuit that can dim from 40% to 110% -------------,"

Thanks again for the education, as I said, I am too old and cannot remember how to use this IC timer 555, which was made 36 years ago and long discontinued. But now that you have reminded me, I will have to go to some antique shop to find one. I am very interested to be able to dim LEDs from 40% to 110% even all I need is to dim from 100% down to 0%.

"There are many ways to connect Leds not just the standard.----------"
That I am sure you have found a great way to connect them. Because 300 LEDs x 2 connections = 600 soldering connections, the fume from the soldering flux can reconnect quite a few of your brain cells in the wrong way.

"I will even tell you where my site is so you can and buy real led grow lights!! "
Yes, that would be nice. Do me a big favor; put me down for 10 of those panels before other pot growers empty out you stock.

BTW, I like the name you gave me,

dcarch, aka no-clue-duke

Anyway, I'm off too. I'm fed up arguing with idiots who are only interested in promoting their own products and have no interest in giving sensible advice to people or on actually learning what on earth they are doing. I really really hate people who decide what they are going to believe first, then hunt around for facts to support it and ignore anything that doesn't match their pre-conceived notions.

Sorry to anyone who wanted some impartial advice, I'll be hanging out somewhere that isn't populated by spammers. Here's a couple of places you might find me, not specifically lighting related, just for people who like to grow plants if you can believe that ;)

The Garden Forums
Cacti Guide

Come on dude...what is your problem. 555 timers are not obsolete..they work. I too have been using them for about 30 years so I don't see your point about an antique shop..but I do see that you had nothing to say about the Toshiba led drivers which you didn't know about.

And yes it is a lot of work if you solder by hand ... but they make things like high speed pickers and wave solder machines for these purposes so again you have no point!

Personally I make grow lights. I don't care if you grow pot or petunias. I make electronic products and if you want to buy I won't discriminate against you because of your obvious hang up on pot growers. I'm Canadian and we really don't care about YOUR pot laws! Or your prejudices!

As for dimming led from 40% to 110% RTFM, go to Toshiba you idiot and read for once instead of opening your yap!

Shrubs I could care less about promoting MY PRODUCT I AM INTERESTED IN MAKING THE BEST LED PANEL I CAN FOR YOU GROWERS!

I don't grow anything, I need input from growers to know what blue/red/infrared ratio they want. As a matter of fact I intend on doing something for growers that no other led manufacturer would do. I have a downloadable program that allows you to design your own led panel and send me the plans and I will put it in my casing system.

I wanted your help in that, but you like the rest of these fools have an attitude problem...I am only trying to build the best panel posible and save money for my friends...I DON'T NEED THE MONEY I'M DOING THIS BECAUSE I WANT TO!

My friends asked me to do this...I have a bunch of pot head programmer friends and they wanted cheap lights...so here I am ...I have spent $5000 so far just setting up a small shop and I'll end up spending about $25,000 when I'm done...but like I said ...money is not the issue for me.

I want good lights to save people electrical bill money ... that's all. So I could care less if you or anyone else buys one. I already have the ones I was asked to build sold!

So how did you get from Australia to Canada?

dcarch

Australia ???? where did that come from ???? I don't get it.

My question is do plants require UV light or can they grow without they also have limited winter sunlight.

Fluorescents are ok you could use the new T-5 fixtures which give off the same light as a 400 w mh, OR you could use HID lights, But I want to conserve on energy so I am using LEDs.

LEDs are expensive , but you could build a grow light for next to nothing if you know what your doing. I bought 100 LEDs at $0.66 each thats $70 , Less expensive then a High output Fluorescent, or an HID, it took me about 2 hours to build. I am an electrician by trade so I know my way around lights.

A HID looses about 20% of its light in the first year and then keeps loosing light over time. A HID produces a lot of heat which is also a waist of energy.

A Fluorescent Light uses less energy and heat, but contains mercury. It also looses light after awhile.

Both systems create particle dust from the heat they produce kinda like your computer or TV and that also reduces light which you can clean the fixtures up and gain more light about 25% more.

Also both of these systems require much maintenance , changing bulbs, ballasts, lamp holders which could result in high overall costs over time.

LEDs on the other hand are the new oddity. We use lots of LEDs in the buildings we work in and I am getting more and more familiar with them. They use hardly any energy and they are evolving every day.

You may have to change a ballast over time with them but they outlast HID and fluorescent by light years, no pun intended,lol! bulbs can last up to 50,000 hours or more and they don't create unwanted heat.

We should all consider using lower energy systems anyway, incandescents and HID's are being phased out soon and we should start conserving energy anyway!

I have an old armoire that is about 40 inches wide, 28 inches deep and 64 inches tall. Inside is a 105 watt, 5000K CFL bulb, along with two hydro chambers. One is a 5-gallon bucket, another a 22-gallon Sterlite tub. The tub has two cucumbers in it, the bucket two Green Sausage tomatoes. The light runs about 14 hours per day.

The cukes are flowering and setting fruit and the tomato is growing nicely, but isn't quite old enough to flower just yet.

I also have a chamber I built to germinate tomato and pepper seeds in. It also uses the 105 watt CFL lamps, spaced 30 inches apart. When I measure the lux at 15" from the middle of the bulb, at 10 inches below it, I get 7,000 lux.

The bulbs cost $25 each, much cheaper than LEDs. I love the latter, especially the higher-powered ones, but they are too expensive at this point if one wants to cover a large area.

Just my 2¢ worth.

Mike

Lermer here. Shrubs is wrong here. Blue does stimulate growth hormones, and also reduces stem elongation and enhances rooting. Blue does not increase potency of pot, although UV-B does. Pot has no alkaloids at all.

Generally the original poster is correct, however he overlooks Ceramic Metal Halide. Ideally you want both full spectrum and high intensity. However there is a trade-off between these two factors. Generally the best trade-off is Ceramic Metal Halide. The Philips CMH is 4K, better suited to veg stage; the GE CMH is 3K (and higher output), better suited to bloom stage.

Right now Southern California Edison is subsidizing the cost of a plain jane looking four foot fluorescent light fixtures so they sell for $1.99 each.

Purchase cost isn't the only consideration. Power is generally a bigger cost than upfront costs. Think about drawing 450W for a HID on an 18/6 day/night cycle year-round -- that's 3,000kWh, or $325 a year at average electricity rates. That's no chump change. :P

so I decided to try some 225 mixed LED's for some seedlings as I have read about some success with this 14 watt setup, unfortunately the results were less than spectacular, albeit the plants did grow, and did not stretch I still got 2x the growth from the Fluoro in half the time. I cannot comment to the scientific explanation, but It appears that 14 watt LED over 1sq foot is not enough power to really drive growth,

Well, obviously ;) LEDs are nice, but they're not magical. The sun on a clear day puts down about 93 watts per square foot (times the sine of the angle to the sun -- if it's straight overhead, times 1.0). Even if your LEDs were 100% efficient, which they're not (for blue, probably a quantum efficiency in the 40%s) that'd still be 15% of the energy of sun shining directly overhead. In practice, factoring into account inefficiencies and light straying from where you intended to illuminate, you're probably getting under 5% of the light of the sun. Now, you get to pick your ideal frequencies, which is good (the graph at the bottom is what you want to look at). But that isn't nearly enough of a boost to compensate for how little light you're putting out.

If you want to drive growth, you don't need to double your light; you should at least 4x it. And be sure to minimize any stray light that you can :) Also, as the plants get bigger, penetration will become an issue. LEDs are effectively point light sources; there's nearly no penumbra. The more reflections you can get and the deeper the LEDs are into the canopy (and the more they move, if that's an option), the better your results will be. I'm about to try an experiment with dangling LED christmas lights through my planters to see how they like that.

I am finding that the LED's radiate so little heat to the plants that the leaves are staying moist and attracting mold. This is becoming a big problem.

What attracted me to LED's was the fact that my 1000 watt HID gave 520 watts to unwanted heat. Then in the 480 watts of actual light going to the plants, the plants only needed some blue and lots of red, they didn't need to have the yellow and green etc. But I was paying my bulb to provide it. By using some blue and lots of red LED's I am only using 180 watts of LED's to replace the 1,000 watts that went to my HID system.

I have found that tomatoes have lots of short internodel length when supplemented with extra red, most everyone I ask says it is blue light that would do this. My banana's can be made to stay under 7 feet tall using 3 15 watt 470nm bulbs on for 12 hours per day. Sometimes it is difficult for me to provide enough light for my pineapples and I get pineapples with out a crown. I have 24 pineapples under 3 35 watt panels [red 660nm] and they are all thriving. They are bigger than pineapples imported from Mexico and sweeter than anything from Hawaii.

LED lights are really working for me.