Building LED lights from facts, no theories

I was going to post this at the Perfect LED Grow Light thread, but as some of what im going to post was posted 2 years ago on the stickied thread about LEDs and people still continue developing lights from wrong ideas, i think a thread about this topic is largelly needed.

The main problem is related to efficacy of spectrums.

When the firsts LED experiments at Overgrow, we work on the hypothesis that blue and red light are more effective. It was an appealing hypothesis that promises large electric savings. But unfortunatelly, it has proven wrong :mad:

Now we know both by theoretical research and practice that only red and blue spectrums arnt more effective than complete spectrums, but less.

LED grow light sellers obviously not want to notice it, so they may claim efficacies of their lights 8 or 10X higher than HPS. But thats simply false, and any grower that have checked it got dissapointed.

Does it mean that we cant develop LED lights with higher perfomance than HID? No, we can still develop LED lights with better spectrums, by reducing (not elimitating) cyan, green and yellow light and adding it on the red side of the spectrum. This result on a enhanced photosynthetic efficacy, but its small, from 5 to 15% of enhanced efficacy of same amount of photons.

So any further electric saving from using LEDs must come from other factors: better light distribution and increased energy efficiency.

Better light distribution

HID lights, specially HPSs, are very energy efficients (emit a lot of photons per watt burned) and have good spectrums for growing plants, but have a mayor drawback: they run very hot, so they must work at some distance of plants. This mean all the light of the grow comes for a single point of light, and it creates a very uneven light distribution along the grow. Both horizontally (plants below the bulb have way higher irradiances than the edges) and vertically (bottom of plants gets insufficient light while top of plants are exposed to excess light).

This uneven distribution strongly drops photosynthetic efficacy, because as higher is the irradiance, the lower the photosyntesis rate (per photon). But you must expose the top of the plants to such high irradiances if you want the light reaches some into the canopy.

LEDs dont have this problem. They are solid (no risk of breaking them) and run cool enough to be in contact with plants without problems. So they may be distributed along the grow, both horizontally and vertically (sides and between plants) in a way plants gets the optimun irradiances (those at photosynthetic efficacy is higher) along all their height.

This increases photosynthetic efficacy strongly. When NASA scientistist thought on this, and changed half of the light from top to side and intracanopy (IC) lighting, the yield enhancement was of 35%.

Using LEDs on IC lighting not only enhances productivity, but allows to grow taller plants indoor than any previous type of lighting: the equivalent strategy with HIDs has been vertical growing, wich avoid optical losses at reflectors and achieves more even lighting. We all know how vertical setups increases productivity compared to top reflectorized HIDs. But LEDs allows to do it at any scale, still on very small grows, and control of light delivered at each part of the plant may be controlled accurately, in order to get the max.

Increased energy efficiency

Any enhancement on efficacy may be related to an amount of photons. A better spectrum or a better distribution enhancement is applied to the baseline of PAR photons.

So the first and by far most important factor to determine the growing efficacy is the energy efficiency of the light: how much PAR watts it deliver per each watt burned.

But this factor is almost ignored on most LED grow lights development threads ive read, while is the most critical parameter.

For example, the difference on photosynthetic efficacy from a 635nm peaked led to a 660nm peaked led is around 5%. But most 660nm leds are 50% less energy efficients. Independent of the wavelenght efficacy, using 660nm leds is a bad choice (except if they have same energy efficiency than 635nm, but find me such one and i invite you to dinner :D).

In order to compete with large HIDs with energy efficiencies about 36-38% is to use leds at least 30% efficients (an that if the HID is reflectorized). A bit less if the HID has a glass barrier.

But if you use LEDs with energy efficiencies below 25%, and most LEDs on sale are so, there is no way they may offer electric savings (same yield with less watts).

Forgot to analyze this critical factor had led to many dissapointing LED grows. So please, do it yourself a favour and think on the efficiency of the LEDs before buying them.

Happy growing
knna

Other esential parameter is often forgot when designing a LED array: what current we are going to use to run them.

Light emision of a led is directly linked to the current flowing across it. But any led emits at the higher efficiency as lower the current, and it drops as current increases.

Depending to the thermal design, there is a point when increasing further the current dont achive any increase of light. Increasing current from it raises strongly the electrical consuption without any increase of light emited. This is extreme, but what happen very often is using currents so high that efficiency is very low. As i explained on the last post, enough energy efficiency is key in order to achive electric savings.

So current used (or range of current used) may be carefully considered.

Some examples (thermal resistance solder point to ambient temp supposed to be 10 K/W, for a very good mounting with heatsink):

Cree XR-E coolwhite Q4 (luminous bin, 100-107lm@350mA): 28.5%@350mA, 22%@700mA

Cree XR-C red (R3:625-630nm dom wavelenght), bin M (39.8-51.7 lm@350): 29%@350mA, 25%@500mA, 20%@700mA

Cree XR-E Royal Blue, bin group 14 (350-425mW@350mA): 33%@350mA, 29%@500mA, 26%@700mA

Luxeon K2 red, bin S (typ 60lm@350mA): 26%@350mA, 23%@700mA

Luxeon K2 coolwhite, 200lm min group: 26%@350mA, 21%@700mA, 19%@1A, 13%@1.5A.

(Note: there is more unaccuracy on Luxeon products, as i have not digitalized their SPDs at operating conditions).

A LED cost the same independent of at what current you use it. So if you run 2 leds at 350mA instead of one at 1A, you get almost same light but using just a little more than half watts, but it initially cost you double.

But check that except for the Royal Blue, at 700mA or over all those leds that are state of the art currently gives efficiencies too low to be able to save watts against a large HID.

The Procyon, for example, probably use those red leds and lower bins of the whites (i believe P4). If they run them at 350mA (0.8 and 1.2W for red and whites/blues, respectively), and use double of leds, it may offer a good perfomance. Far for sustituting a 600W HID, but maybe able to get close to a 250w. But by driving them at 700mA to reduce costs, the perfomance is too low.

At the end, buyers only think on: "120watt for xx dollars, wow, its nice". If instead of watts, they say how many micromols of photons it deliver, we could compare perfomance. But they dont say anything about it, or how many PAR watts it emit. The only honest LED grow lights manufacturer who says the emission of the lamp is what makes the TI Smartlamp. And unfortunatelly its output (265uE if i remember well, similar to a reflectorized 250w HPS) is too low to do it cost effective.

Always there is a trade off between initial costs and efficiency. Always. So choose carefully the current or current range for your setup, in the way its the best compromise between both ends for your situation.

procyon doesn't use any white leds dude

Quote:

---

Originally Posted by justdirt

procyon doesn't use any white leds dude

---

Yep, you are right. I wanted to mean blues (white leds are mostly a blue led covered with phosphors: bins of both are tightly linked, as the white always has about 20-25 lower efficiency than the correspondent blue due the Stokes effect).

And BTW, it should carry white leds. It probably enhances its perfomance. Although most people using it ends adding CFLs to give the white light it doesnt emit.

Wow, finally someone on the forums that has a grasp of the situation with LEDs.

Here's my some of the first of many questions?

1. While HPS is more efficient the LEDS, how much of that disadvantage can LEDS make up by being closer? I have been building arrays that use no lenses, 140 to 160 degree view angle and trying to get them placed about an inch above the top of the plant. I think the closest you can get with HPS is about 6 inch for a 400 watter and 8 inch for a 600 watter. And that is with air cooled hoods and a light mover.
My personal thinking is 100 watts LED is equiv to about 60 HPS at this time.
I have yet to see a documented LED grow of more then .3 gram/watt/month and the grower has so far been unable to repeat that performance.

2. I am undecided on getting better efficiency by running about mid-range on current and allowing better area coverage with more LEDs. Or running them rascals as close to max ma as possible, spending more $$$ on cooling in order to get better penetration. Any thoughts?

3. What is your thinking in light ratios? Mine has been approx 3 to 1 red/blue with a little white light for insurance. However, I really want to experiment with a heavier blue ratio. I am close to the point where I think I can use LEDS in a vegging set-up where it will be able to outperform both CFL and HPS.

4. For some reason, LED in combo with CFL seems to produce the best results. Any thoughts?


I am currently building a test fixture where I can start experimenting with different set-ups. I will post a pic tomorrow of current progress.

So I might be better off running discrete royal, blue, cyan instead a cool whites of equal wattage ....because I won't have to take an efficiency hit from the phosphor coating ?

Quote:

---

Wow, finally someone on the forums that has a grasp of the situation with LEDs.

---

After OG's fall i registered here. I posted some about lighting, but at that time this board becames very unconfortable, and i get very little feedback. So i went to other boards. Now things seems to go smoother here, and ive read good threads about LED on this board, so im here again. :rasta:

Quote:

---

1. While HPS is more efficient the LEDS, how much of that disadvantage can LEDS make up by being closer? I have been building arrays that use no lenses, 140 to 160 degree view angle and trying to get them placed about an inch above the top of the plant. I think the closest you can get with HPS is about 6 inch for a 400 watter and 8 inch for a 600 watter. And that is with air cooled hoods and a light mover.
My personal thinking is 100 watts LED is equiv to about 60 HPS at this time.

---

Mant people had a bad understanding of the "square law" and its meaning. It refers to how fast irradiance drops with distance. But its due to a given amount of photons are dispersed on a exponentially increasing volume of space as distance increases. When you distribute small points of light along the grow, you deliver the light exactly where its needed, so you can keep irradiances at leaves surfaces very even, as you dont need the light of each LED cover a large volume.

But light from a top HID dont dissapear magically with distance :wtf: irradiance goes dropping from very high figures on top to very low on bottom and edges, but its not due to less photons avalaible, but to almost same photons diluting on a larger volume as distance increases.

Of course there is optical losses as the light must travel larger distances. Dust in air absorb some photons (more as dirtier the environment), aswell as light bouncing on walls let part of the light at them. And it obviously happen more as more far is the light source (and the reflector footprint match less the plants area).

So distance affect light efficacy by two ways: less total photons avalaible and suboptimal photons densities at leaves.

How much less photons are avalaible depends of a lot of factors: how well the reflector footprint matches the grow area, how much reflective are walls, how clean is the air, if there is a glass barrier between the bulb and plants, how much reflective is the light's hood...so its impossible to generalize those losses. It depends of each setup. A well designed LED setup almost eliminate these losses, and it allows to use less total photons than a HID to get same results.

How many less photons? Little difference if you compare with a vertical HID setup surrounded by plants. For top reflectorized HIDs, optical losses at reflector are 20-25% of the total amount of photons emited by the bulb. With a glass barrier (cooltubes and such), its a minimun of 35% of the light emited. These are the minimun less photons we may use on a LED setup to get similar yield. As i noted before, there are other optical losses, but it varies strongly between setups. For a well designed HID setup (reflective walls, ventilated and filtered (clean) area, reflector footprint mtaching the shape of grow area) they exist but are small, so we may ignore it for doing estimations.

On the other hand, what have a large enhancement of light productivity (yield/uE of photons) is keeping irrandiance at leaves on the optimun range. For a whole grow room, the only data i have about this is the 35% enhancement from the NASA study. We must calculate it for cannabis, but until we do it, we may use this figure (with a grain of salt ;) ).

So, answering directly your question the fact of using the LEDs closer reduces slighty the light losses, although keep irradiances at optimal levels. We may suppose initially an enhancement of 35% on photons efficacy. It means we can get same yield using about 75% of the total photons emited by a top HID.

(Important math's note: we are talking of enhancement of photons efficacy, so we may apply it to the baseline of amount of photons. If we use 75% of photons with 35% enhanced efficacy it result of a total efficacy of 75%+(35% of 75%=0.35*0.75=26%)=101%. )

If the enhancement on cannabis is of 25%, we must use 80% of photons (to get same results than a top HID).

Having this reference in mind, we need know to know how many photons emit a HID avalaible to plants. It depend of the setup, so the amount of uE to be delivered by the LEDs in order to get same yield depends of with what setup you compare it. For example, a generic 600w HPS emits 1000uE (per second) (good ones as Grolux, Hortilux, Plantastar, Green Power or Sunmaster may reach up to 1100uE):

-Verticaly unreflectorized . Very little enhancement, especially if plants are kept short (usually with this type of setup), so we must use near same amount of photons delivered (1000uE).

-Top lighting with reflector. Optical losses at reflector are 20% (very good ones), 25% on average (dirty or low quality reflectors may have way higher losses). It mean about 750-800uE. If we suppose a 35% of enhancement for optimum irradiances, we need 550-600uE of leds.

-Sealed (glass barrier) top lighting. Average losses of 35% on clean setups. So just 650uE avalaible. We will need about 475-500uE to get similar yield.

Take in mind HID are less efficients at smaller wattages. So its easier (less watts of leds for each watt of HID) to get similar yields as smaller is the grow.

Quote:

---

I have yet to see a documented LED grow of more then .3 gram/watt/month and the grower has so far been unable to repeat that performance

---

Yep, current perfomance LED commercial units are producing about 0.2 g/W per month. But this parameter is very important to decide when comercial units are cost effective, but of little usefulness on the actual stage of development. g/mol of photons is a way more meangliful and useful parameter, due LEDs are improving very fast, and for a given amount of uE you need now 100W of leds, but one year later only 60W. At it depends too of how hard (efficiently) you are running those leds. As i noted on my last post, it affect strongly to their efficiency (uE/W).

When we determine production in terms of g/mol of photons we can extrapolate that data to watts required of any LED with known emission, so we could estimate the amount of watts to install to get a given yield target.

I dont know how many times ive claimed that we may use LEDs with accurately known emission on our experiments so we could get universal conclusions that can be extrapolated. BTW, Ive been little sucesfull. So im running now a group buy of components of known emission with about 20 growers that are going to do logs with them, using differents styles of growing (soil, hydro, scrog, LST, sog...) so we can get conclusions fast of the amount of light required to grow cannabis and get similar yields than with HID, fluos, etc.

Quote:

---

2. I am undecided on getting better efficiency by running about mid-range on current and allowing better area coverage with more LEDs. Or running them rascals as close to max ma as possible, spending more $$$ on cooling in order to get better penetration. Any thoughts?

---

Thats a very personal decision. You must find the best compromise between initial cost and efficiency: more leds at lower current means higher initial cost but lower efficiency.

On the actual LED's state of art, they just may be cost effective on very small grow spaces. So i suggest to build an experimental LED setup very small and use them at very good efficiency figures. The size of such grow determined for your budget.

I try to avoid as much as possible active cooling. Of course its doable, but a failure of fans may result on permanent damage or strongly reduced life of LEDs. I prefer to rely on passive cooling and LED distributed sparingly along the grow so power concentration is low (thus easy to cool down): lower cost on fans, less electric consuption, increased efficiency.

At least, i suggest to follow this way for side and IC modules. If you want max power on top, modules on top may be actively cooled. Indeed, PC's socket heat dissipators are one of the cheapest options as heatsinks, and they comes with fans. You can conect the fans or not, depending on the density of leds you install and current used. Those bulky heatsinks arnt a problem on top, butthey are on IC lighting. As on IC we need lower power densities, often passive cooling are a better choice.

You dont need any penetration ability if you use the LEDs between plants, so you always may place LEDs very close to plants and using wide emission angles.

Relying on light penetration is a limitation of HIDs, not an advantage. We are so used to work that way that we not realize how bad its it: produce uneven light distributions (reduced productivity), and light passing though leaves increase strongly its wavelenght, resulting of a strongly far red lighting on bottom plants that produces fuffly buds.

Quote:

---

3. What is your thinking in light ratios? Mine has been approx 3 to 1 red/blue with a little white light for insurance. However, I really want to experiment with a heavier blue ratio. I am close to the point where I think I can use LEDS in a vegging set-up where it will be able to outperform both CFL and HPS.

---

Check the Inada curve. It shows the amount of photosynthesis promoted for 1W of light of each wavelenght (2nm bands) (isolated, each waveband at a time; study performed on sunlight grown plants):

(i was to post here the attachment, but i dont know how to do it; anyway, its on the bottom of the post, open it).

The curve 1 is the average response of 27 herb plants (curve 2 are for trees). Note how the minimun photosynthetic response is about 465nm, the emission range of blue leds! Still lower than of green light.

Blue light is added because plants need it, not because increased photosynthetic efficacy (at least, at no CO2 limited irradiances). Cannabis is a little demanding plants in term of light quality: it needs very little (if any at all) blue to be able to grow (opposite to most plants). But blue light has some "colateral" effect that advice to use it: first, the lack of blue light strongly increases internodal distance, so you need to add some blue if you want the compact plants we seek for indoor. But just 30-40uE per sq meter are enough for this, while we rarely use less the 500uE/sq meter of average radiances. So we need less than 10% photons of blue, often just about 6% of total radiance in order to keep plants short and compact. As blue photons carry way more energy than red ones (in direct correspondence to its wavelenght: a 450nm photon carry 650/450 more energy than a 650nm photon), if we talk about PAR watts instead of number of photons (uE), then that 6% correspond to about 10% of total PAR watts. This are minimum requeriments.

But blue photons have another collateral effect that may advice to use higher amounts of it, and its especially important on LED grows due the high percentage of red photons: blue photons promote the opening of stomatas, while red photons promote the opposite (maximum effect peaked at 450 and 660nm, respectivelly). It affects the transition point between the light limited part of the photosynthetic response curve to the CO2 limited part of the curve.

So the higher the irradiances used, the higher the percentage of blue you need to add. Thats why blue enhanced HPS bulbs (or MHs) tend to work better as higher the w/sq ft used, while it offer little enhancement of gardens using low light densities

So if you keep irradiances low to medium (up to 250-300 uE/m2), you wont need to add more blue. But we often use higher irradiances in order to get fat colas, and then the internal (leaves) concentration of CO2 becomes very important to get good photosynthetic efficacies. So in that situation, if you are growing with LEDs and you want to keep light's productivity high, you need either supplement with CO2 or add more blue light so plants are able to keep CO2 internal concentration higher.

On a side note, the ratio of Blue, Green and Red (simplified ranges for B:400-500nm, G:500-600nmn, R:600-700nm) must be refered to the amount of uE or PAR watts, not to the number of leds or watts installed, as leds of different colors and running currents have different efficiencies.

Quote:

---

4. For some reason, LED in combo with CFL seems to produce the best results. Any thoughts?

---

Thats due commercial units using just blue and red have spectral lackings that results on reduced perfomance. By adding white light, the perfomance of all photons are improved.

Apart of it, people are using to little photons per sq ft because they are wrong about LEDs perfomance. They strongly overstate it so they end installing too little watts. By adding CFLs, they complete the spectrum and add some more photons.

(Will you expect a good yield using a 100w HPS on 1 sq meter? LEDs arnt different, if you dont give enough photons you cant expect good yields)

Quote:

---

Originally Posted by redline

So I might be better off running discrete royal, blue, cyan instead a cool whites of equal wattage ....because I won't have to take an efficiency hit from the phosphor coating ?

---

The problem is yellow and green leds have low efficiencies. As we require very little of it, aswell of cyan, the most profitable way of adding them is with white leds. Coolwhite leds have a huge peak around 450nm and then a continous spectrum peaking on yellow but that go beyond 700nm. So they complement very well with red leds, as gives the rest of wavelenghts and still some far red, wich its needed too. Coolwhite leds often have about 21% less efficiency than comparable Royal blues due to the change to longer wavelenghts at phosphors. But although it lower in that figure the energy efficiency, most of that drop happen on wavelengh conversion of photons, so they emits a very similar amount of photons than the Royal Blue inside it.

But today currently there is a way of giving that white light with a similar spectrum by using fluorescent tubes, at least from top ligting, wich is way cheaper. Using a Reflex tube with electronic ballast you get still higher energy efficiencies than a reflectorized HPS, and more than with white leds.

White leds emiting 150 lm/w are expected to be released in about 2 years (they are already developed in labs). By that time LEDs wont have alternative. But currently is reasonable to cut initial cost by giving the white light with fluorescent tubes or still with CFLs (for experimental purposes it dont mind if its slighty less efficient).

As red leds are cheaper, using a conventional white light and red leds is a cheap way to have good productivities on small gardens without investing huge money. And splitting the investment: now red leds and in two years, white ones.

There are Royal Blue LEDs very efficients, so they may be used together with white leds or white light in order to obtain the desired spectrum.

A very interesting page about optimal light spectrums for plants is this article: OPTIMIZATION OF LAMP SPECTRUM FOR VEGETABLE GROWTH.

We need to perform similar experiments with cannabis, but im working with the optimum RGB distribution of tomatoes as starting point (10-20%:15-20%:60-75%; B:G:R).

As coolwhite leds (aswell as daylight floros, with similar CCT ratings (6400K)) emits a bit more on the green than in the blue, but balanced, just adding to them red leds result on very well balanced spectrums.

For example, this is the result of 3 reds and 1 coolwhite all running at 350mA (CREES XR, white color WF (5700-6400K) and red R3 (625-630nm dominant), luminous bins Q4 and M):

[attachment=o206256]

It have a B:G:R distribution of 11:14:75% (R/B=7) wich seems pretty well balanced for flowering at medium-low irradiances.

The nice thing about leds is they are easily current adjustable, so we can modify the RGB distribution to adapt a given setup to different stages (veg, early bloom, late bloom) by modifying the current feed to each color. For example, with the same mix, if we put the white at 700mA but keep reds at 350mA, the spectrum is 14:19:67%.

Running all at 700mA results on 9.5:13.5:77% (both efficiencies and spectrum varies with current and temperature).

Options including Royal Blue are possible, especially when thinking on vegging lights, or using high irradiances along flowering. A mix 4R3+CW+RB result on this:

[attachment=o206257]

With a distribution of 29.5:9.5:61%.

Or, for example, 8R3+3CW+RB:

[attachment=o206258]

With a distribution of 22/14/64%.

Just a few samples of the spectrum you may create using red and white or red, white and blue.

Well, this thread isnt been sucessfull. My only purpose when i started it was to help poeple wanting to develop thrier own LED lights.

I noticed there was here some people who want to do it the right way, and thats why i posted some info. Im lighting designer (meaning i work on it every day), i talk often with LED companies distributors and still sometimes with developers. I have a first hand experience in this field and i ve been researching from years ago about LED grow lights.

So i thought (wrong) i could help guiding others by giving them the tools and basic knowledge aswell as informing them of ways that has been proven wrong.

I use same nick on all boards, anybody may do a search and check that. For me is very sad that some "smart" people took the early research a group of growers did at the Overgrow boards and use it to do LED grow lights that simply dont work because they are based on biased premises and wrong research.

But its still sadder than people trust on obvious biased and false info from LED sellers that are mostly marketing hype than on people who provides the scientific facts and the tools to check them by yourself.

But i realized its not my problem. If people want to waste their money is their problem, not mine. Ive already posted on the net the info needed to avoid it. I cant do more than that.

From now on, i give up giving free reliable info about LED products. Im going to concentrate on earn money. Ill develop my lamps based on what i learned on the MJ boards: people prefer a reasonable and appealing lie than a hard truth.

It has been a nice social experiment, from what i learned a lot of the right way of marketing. Product quality dont matter on the industry for stoners. I already knew it for nutes products, but i thought that the strong impact of light efficacy should be evident. It isnt. People prefer to believe what they want to believe, still when real world clearly clearly points up its wrong. Selective blindness is the strongest power on the MJ boards.

BTW, this way i dont waste my time trying to write understable enough on a lenguage that isnt mine.

bitter much?

It is better to appear stupid than to open one's mouth and remove all doubt. --Mark Twain

f*uck :/ knna, I'm sorry. actually I think it's not that way you wrote - think some ppl found it too clever and/or need some time to 'metabolize' the infos. me personally just have no time at the moment and temporarily stopped writing in all threads.
I know it's bitter and I feel bitter often when trying to talk about leds with ppl I know. esp marketers cause a frustration
and I do appreciate your work! and the par energy calculator was smth that impressed me
anyway, while thankful for the thread, my focus is not on the photosynthesis rate but on the photoreceptors driving specific responses, esp. flowering. I promised much to the ppl in the other thread long ago and still play with the papers, but want to gather as much I can and present it fully, then I reveal another and another and it goes deeper, dont know when to stop at certain level to systematize and present it, so I read read and don't write,
plz don't take it personally at least me is interested and appreciating! also have to admit I really learned from you. If you expect polemics, for the moment I say imo photosynthesis rates are much less important than ppl think, as leds usually do good veg and little buds. and in the photoreceptors realm there are many things already and widely not considered theories, and web is rich in it. secondly, that is rather a question than a polemic: do you have any prove that plant needs only a certain amount of blue and not a proportion to total light? not talking about pores or stomatas opening and stetch blocking, but 'bout all other responses?
ps. nice to see an European here!

Hey, Glutek, im glad my Bulb Analyzer tool is useful for you.

Im too interested on qualitative and no quantitative effects of light quality. But the problem is this topic is way more specie dependent than light productivity. And effect are very often not linear, but modulated, and it mean lots of experimentation to be able to get any valid conclusion. Very similar experiments have different results

For example, about blue requeriments for healthy growing, it strongly depends of the plant specie considered. There are some than requires a relatively high percentage of blue light, and there is some than not require blue at all, as wheat.

About cannabis, there is little scientific data about. Most i know is for my personal experience, and is very difficult any not controlled experience proves anything. We know that cannabis requires little blue because it has been grown sucessfully using HPSs emiting very little of it. I want to try to grow cannabis only under red light and see what happens. I really suspect that cannabis not strictly require blue to grow healthy. Ive read of cannabis grown under LPS lamps, so under a absolute lack of blue, sucessfully. But ive never seen it.

What ive noticed is cannabis is a little demanding specie in terms of light quality. It thrive under almost any type of light, and its basically a photon's whore as wheat. At to what point it need a given amount of each waveband, i still dont know, but for sure is little.

Of course, not requiring not mean cannabis wont benefit for using more complete spectrums.

Hello Kanna!
Tell me please if I have understood you right: you can find out most energy efficient led for a given wave length and assemble the prototype?

Quote:

---

Originally Posted by cture

Hello Kanna!
Tell me please if I have understood you right: you can find out most energy efficient led for a given wave length and assemble the prototype?

---

Not exactly. I can calculate accurately the efficiency of a given led, as anybody else interested on doing it.

And according to it, choose the better models for each given wavelengh you wish to use. Or if not precise wavelengh tuning required, i can say what model avalaible should give you better results for plant lighting.

LEDs wavelenght is a consecuence of chip molecular structure and composition. Manufacturers choose to produce chips wich emit the most usable wavelenght for many different applications and at what thay can get the best photometric output.

In the practice, it mean we can use blue and white leds very well, because their spectrums and peak wavelenghts are well suited to be used with plants. But on the red side, we have a problem. The highest photometric perfomance (lm) is produced with AlInGap chips emitting around 632-633 nm. At that peak wavelenght, the compromise between radiometric efficiency and photometric conversion is max, so manufacturers arnt really interested on producing other red wavelenghts in high power chips.

That mean that is very difficult to obtain chips emiting on longer wavelenghts, specially close to 660nm, wich would be the better for us. There is no a technical problem to do them, its just lack of interest of LED chips manufacturers. Indeed, AlInGap chips emiting at 650nm have the highest radiometric efficiency, that is what interest us.

But that wavelenght have only one main application (ours), and our demand is not enough to any manufaturer makes a production line of it.

So unfortunatelly, we cant get red leds of those wavelenghts at a cost effective price. We have avalaible a narrow range of wavelenghts between to choose what we prefer.

What i can do is helping in that task, by calculating of how many photons per burned watt emits each LED, so you can choose if using a 660nm peaked led emitting 1 uE/w or a 635nm LED emiting 1.3 uE/w, for example.

This should change on some years. Currently, all LED manufacturers are concentrated on developing high efficients white leds, and especially, warm white leds. This mean all the reseach funds are dedicated to InGan chips. Along the last 5 years, InGan (blue, green, white) leds have strongly improved its permomance (about 3x), while red leds are almost sttoped in their development.

But when the 150 lm/w has been reached on commercial LEDs (about 2 years, 3-4 for warm whites), then the competition is going to translate to improve the light quality. And this requires high efficiency red leds emiting on longer wavelenghts for color compensation. After years sttoped, now some companies are adquiring machines for AlInGap leds, preparing that time. Then we should have very high efficiency 650nm red leds easily avalaible.

But currently, its almost impossible to get them. The longer you can get on high power and efficiencies high enough are 640-645nm peaked red leds. And getting them is a headache (im already had spent last month discussing with distributors about it).

That is great that you are doing this. Cause at the moment I had carried out biological research on the wave lengths and PAR wattage required (I just can't really convert enrgy of light in to photon flux). Apparently we do need leds higher than 640, especially wee must have 680nm and 700nm as theese wave lengths affect photosythetic rate and photomorphogenesis of the plant.
So these are the wave lengths I have discovered are preferable to have.

420
430
440
450
460

620
630
640
650
660
670
680
700

720 (optional)
We need to maintain approximately the same light energy power output on each wavelength.
Total light energy power should be around 350 Watts per meter sq (500 PAR (photosynthetic active radiation) watts for eqatorial sun).
Also you may have a look at my link in signature. There you may find spectras for chlorophyll a and b and carotenoids.

You must notice that led arnt lasers (wich emits on very narrow wavebands), and emits along a relatively long waveband:

[attachment=o206959]

The nm rating of a led refers only to where it put more energy, but it still emits light of a lot more wavelenghts. So you dont need to use so much differents wavelenghts close to the next. For example, a Royal Blue led is going to cover very well the from 440 to 460nm. And still decently 10nm more at each side.

So you can simplify that distribution of leds. For the blue range, with two different colors, Violet and Royal Blue (but Violets on the 425-430nm range arnt very efficients, compared to those peaked 20nm shorter). And for the red, with a typical red peaked at 625nm and a deed red peaked at 670nm.

Most of the peak nm you mention are rare to find. If you still want to use so many different SPDs of each color, for fine researching on the propierties of each one, you will need to buy them at a very specialized company, as Roithner Laser. They have all, but you will need a good budget to afford it.

Quote:

---

We need to maintain approximately the same light energy power output on each wavelength.
Total light energy power should be around 350 Watts per meter sq (500 PAR (photosynthetic active radiation) watts for eqatorial sun).
Also you may have a look at my link in signature. There you may find spectras for chlorophyll a and b and carotenoids.

---

Dont guide too much by absortion spectra of photosynthetic pigments. One thing is their absortion in lab and other very different how they perform on live plants.

Photosynthetic response dont follow at all the pattern of chlorophills absortion. Many LED experiments have failed to be guided by chlorophills absortion instead by photosynthetic response, that are very differnt.

On the other hand, controling accuratelly the energy emission of such narrow wavebands is very complex. You are going to need a science rocket equipment to do that.

If you want to check reactions to very narrow wavebands, then probably laser diodes are a better choice than LEDs.

350W/m2 of irradiance is pretty high. Its about 1500uE/m2. Think that max irradiances at noon at 40ºN rarely goes over 1800uE/m2. And the daily average is way lower. You are going to need to use CO2 supplementation in order to use those average irradiances sucessfully.

What if we go another way: you could provide me with spectrum graphs of light emitted by leds you find that are most efficient and I will pick the needed.

Or another one.
Match the spectrum to
420-490 30%
490-620 10%
620-700 60%
What kind of soft do you use to build spectra graphs, may I have a link?

Jackpot!!!
I'm subscribed, totally!
keep the precious info comin, there are people lime me reading in silence:D

I'm a total n00b in regards to LED lighting n generally lighting, but I'm learning and since i probably wont own a place of my own for another 2 years, i may as well start the grow operation when there are some improvements made with a ton of education that i will accumulate till then;)

Quote:

---

Originally Posted by cture

Or another one.
Match the spectrum to
420-490 30%
490-620 10%
620-700 60%
What kind of soft do you use to build spectra graphs, may I have a link?

---

Check the 4R3+CW+RB on post #8. It has almost the same distribution, except on the red range where it only reach up to 670nm. In order to get a less concentrated output on the red range and increase its bandwith up to 700nm (it should cover slighty after it) you can use 2R3 and 2 650-660nm peaked red leds, as the LedEngin ones. They are less efficients than the M bin of red Crees, but no so much you cant use them if you want to cover the longer part of the red range.

You should be aware than when choosing LEDs, you need to consider carefully not only models/brands, but bins of each one. Usally LEDs are binned according three parameters: luminoux flux, color and Vf (forward voltage).

For same model, often there are 3-4 color bins that cover the range. For example, red Crees are avalaible on R2 (620-625nm dominant wavelenght), R3 (625-630nm) and R4 (630-635nm) color bins, although they give up serving the R4 on the high power models (its only avalaible for the medium power XL4550 currently). There are aswell 3 color bin for the Royal Blues and more than 20 for coolwhite.

Luminosity bins determines LEDs efficiency. For same color bin, there are different light fluxes avalaible. As for same SPD, higher photometric flux (lm) means higher energy efficiency, and often top bin is more than double than bottom bin, almost any LED model have a very wide range of efficiencies.

We always should try to get top bins, but they are more expensive and not always avalaible.

Cree is currently the better manufacturer for InGan leds (Royal blue, Blue and white). They are a step forward the competence. They are serving currently up the bin group 15 for Royal Blues (>450mW@350mA) and up to bin Q5 on coolwhites (107-114lm@350mA) for the XR-E model.

There are some other manufacturers that are using the Cree EZBright1000 chip on their models, as Seoul Semiconductor, Edixeon and Kingbright. They are a cheaper alternative, but construction quality is often far from Cree ones. Osram has been licenced the EZBright too but its still unavalaible.

For the red side, Cree does good LEDs, but difference is smaller than for InGans. Indeed, Osram does more efficient red leds, but unfortunatelly Osram not allow to select a single bin as Cree or Lumileds.

So when selecting what LED model to use, its impossible to generalize: best choice would depend on what you can get on your situation, involving how many LEDs are you going to buy, where you live, if your distributor allows to select concrete bins, etc.

Although prices for manufacturers is very competitive and there is little differences, when an individual look for a given model/bin, differences may be very large.

So one thing is the ideal LEDs to use, and other what you can actually obtain, and price.

So it would be better to have a general idea of what models are valid for us, seek for them and select the best avalaible for you.

In the USA and Canada, for example, ordering from Future Electronics (official distributor of Lumileds) allows you to select individual bins and get decent prices still buying low quantities. They arnt the best LEDs avalaible, but probably they have the best price/perfomance for a northamerican.

And the other good source is Digikey, that distributes Osram at very competitive prices in NorthAmerica. Not bin selection allowed, but excelent average price/perfomance. For example, the red Argus (Golden Dragon with lenses, from 20º to 160º beam angles) is 1.64$ buying 200.

So i suggest you first look for what leds (models/bins) you have avalaible, and then select the best choice between them. I can help you on the selection, but i dont think it would be worthwhile to list the best model/bins possible if you cant access them.

I built those spectrums using OppenOffice (its a free suite equivalent (but better, IMHO) than MS Office. But ive uploaded the Bulb Analizer tool on Excel format too. Ive liked it on the Perfect LED grow light thread. I uploaded too the sheet for the Cree some post later, aswell as how to calculate the true radiometric output.

In order to build the spectra, ive used the Output percentual wavelenght column of the sheet. By multiplying it by the true radiometric output of the LED you get the normalized SPD so you can sum different LEDs SPDs and build spectra of any combination.

hi
first I have to mention that i didn't manage to read all the news on 'perfect grow' so forgive me if I ask/say smth that's not new..

knna, could you please gimmie a hint where should I buy small numbers of LEDs in EU? do you live here actually, I noticed you removed Spanish flag from the profile?

btw, I wouldn't say cannabis is little demanding about light quality (otherwise we could grow under MV ie.), better to say it's just resistant as a weed and grows quite good under different conditions. just a better word.
wheat is a monocot so not a best comparison. still good, as most important photoreceptors are so old origined that are found ubiquitus, and crys are found in likely all animals, including mammals, as humans, for sure
I'd rather say cannabis will benefit from more complex spectrums. but in this topic I mostly wanted to ask for a hint at the moment, dont really know if I want to talk about quality here. thanx a lot in advance:)

another question.. do you think(have you experimented) that in vivo it doesn't make a critical difference to have equal quantity of photons at, say, 10 or 20 nm away from 660 and other peaks? as we know from mcree and inada it doesn't affect photosynthesis rates much, but what about the overall effect?photomorphogenesis, plant architecture?

third..what's more efficient for FR, blacklight incands or blacklight fluos?

third..what's more efficient for FR, blacklight incands or blacklight fluos?

if possible, please, can you also include the data about where to order FR diodes too? for some reason I'd like to include them in project

Quote:

---

Originally Posted by glutek

hi
first I have to mention that i didn't manage to read all the news on 'perfect grow' so forgive me if I ask/say smth that's not new..

knna, could you please gimmie a hint where should I buy small numbers of LEDs in EU? do you live here actually, I noticed you removed Spanish flag from the profile?

---

In EU there is little good choices for getting LED directly from distributor on small quantities. Just LED shops, that charges large margin profits and often not inform about bin being on sale. LED tech, LED1, dotlight...

For little leds, i use dealextreme. Its from honk kong, but they send you the items (less than 100â?¬) without any problem. Competitive prices with free shipping. But they are more especialized on top end white leds, although sometimes they have some decents of colors.

Im currently doing a group buy of leds and constant current drivers (from mains). At manufacturer's price, top bins (SSC P4 red 635nm [email protected], Crees Royal blue (group 15) and white (Q4-Q5)). 1.94, 3.3 and 2.4â?¬ respectively. CC drivers less than 10â?¬. If you are interested, send me a PM.

Quote:

---

Originally Posted by glutek

btw, I wouldn't say cannabis is little demanding about light quality (otherwise we could grow under MV ie.), better to say it's just resistant as a weed and grows quite good under different conditions. just a better word.

---

When i say is little demanding, its on the sense it requires little (if any) of any given wavelenght. Its a different thing if it performs better using certain spectral distributions.

Cannabis had been grown under MV lights. They were displaced by HPS and MH (that are enhanced MV bulbs, BTW) due mostly the superior energy efficiency. More photons per watt=more yield per watt.

Spectrally, MH are superior to HPSs, but we already know that except very special conditions, at equal wattages HPSs produce more, just because they emit more photons per watt. Some people choose to use MHs at a cost of lower yield because they prefer the quality, but cannabis production is mostly determined by photons absorbed by plants (given there is no other limitant factors, that shouldnt on a well designed grow room).

The main parameter to know perfomance growing cannabis of a given bulb is how much photons per watt burned it emits. And HPS rule here. Until this year it has been impossible to get same photons per watt using LEDs, and spectral advantage only compensate partially that.

Quote:

---

Originally Posted by glutek

wheat is a monocot so not a best comparison. still good, as most important photoreceptors are so old origined that are found ubiquitus, and crys are found in likely all animals, including mammals, as humans, for sure
I'd rather say cannabis will benefit from more complex spectrums. but in this topic I mostly wanted to ask for a hint at the moment, dont really know if I want to talk about quality here. thanx a lot in advance:)

---

Yep, i know wheat and cannabis are very different. I just use it as example of a very well known plant that is almost light quality insensitive.

Quote:

---

Originally Posted by glutek

another question.. do you think(have you experimented) that in vivo it doesn't make a critical difference to have equal quantity of photons at, say, 10 or 20 nm away from 660 and other peaks? as we know from mcree and inada it doesn't affect photosynthesis rates much, but what about the overall effect?photomorphogenesis, plant architecture?

---

Yes, i have experienced that. I think is good to use both 645 and 660nm red light in order to avoid electron flow imparements between Photosystems I and II that may reduce quantum yield. But it happens mainly at high irradiances. When using medium-low irradiances (below 500 uE/m2), there is little difference on using 660 or 635nm.

For that reason, i choose to distribute the light evenly (to avoid high puntual irradiances) and use LEDs that emits the most photons possible per watt burned. Currently, 635nm ones. Its sad that most radiometricaly efficients AlInGaP leds emits at 654nm, which is almost perfect for us (maximum quantum yield (10.3 photons per O2) recorded was using a 657nm peaked led) but manufacturers dont do it (i dont know if LedEngin uses AlInGaP chips, but i doubt it, as effciencies are about 21-22% and its possible to get over 40% with known technologies. Maybe its just a patents issue).

Photomorphogenesis is mostly driven by blue light (cryptochromes) and red/far red relationship (phytochromes). From 620 to 700nm is red light, so there is little difference on using a peak 20nm ahead. Practical differences are negligible.

Quote:

---

third..what's more efficient for FR, blacklight incands or blacklight fluos?

---

By far, an incandescent. And you dont need a blacklight one. You can use it, but it use high K to get some UV emission, and it results on a way reduced FR emission. I think people uses incand blacklight to avoid getting a filter, due they emit very little on the visible range. But im not sure at all that they filter all visible light.

A filtered standard incand is the cheaper and more efficient way of adding FR.

FR leds arnt very efficient, but decent enough. And for experiments with 1-2 small plants, you would need little. I believe LEDEngin has released 740nm leds recently. Roithner-laser has them too.

thanks again. I'm good at light in physiology but not a specialist on light sources. And electron flow imparements was smth I didn't thought about before;) I know what sensors drive photomorphogenesis, and wanted to confirm what I thought, that in vivo they react quite good also to somewhat shifted wavelenghts, thn for your opinion. Anyway, imo, of course, photons quantity are very important, but quality counts indirectly via driving morphogenesis. So better to say cannabis is not 'almost insensitive', it probably just less sensitive/needs higher ratio of red to green and blue than more shade loving plants. But it's only the issue of formulating words for what you of course already know:), otherwise you would propose pure red, while proposing some blue and green to treat stretching, stomatal and other responses:)
Well, a propos green light, I guess it could be possible to reduce GL if adding FR, becuse leaves probably would grow larger and thinner under FR supplementation.
Nice you want to help with buying..but I can't send you a PM;)

It seems there is no PM service at this board. So i give you the link to the group buy: http://www.cannabiscafe.net/foros/sh...d.php?t=125174

Im knnabinoide there. Its a spanish forum, but it has a english users subforum (used little, BTW).

knna,

Sorry I've been away for a few months, or I would have chimmed in sooner.

First, thank you so much for your thread here and postings on the other LED thread. I've spent days catching up on my reading here, and I have gotten a whole lot of good info from your postings, plus a bunch of confirmations to things I've seen and done.

I started experimenting about 2 years ago, and in the last year just said screw it, let me apply the technology NOW; build some DIY stuff and also try what's out there: I bought two Procyons last year and two SmartLamps this past August.

Last year I had a failed experiment for a bloom bulb set-up, a combo of red Cree's and (another mfg) whites. What I found was the actual spectograph of the white sucked, it was a bunch different then the mfgs graph. The blue die used was way to the left of ideal blue and the coating (phosphor ?) responce really lacked any red. Oh, it's light output was white...to the human eye, but lacked blue and red for a plant. The real dissapointment was, I had solved other physical problems (I was growing in a rotating garden and needed 360 degree light output, not LEDs strong point!) using an octagon aluminium piece mounting the LEDs inside the glass tube used for HPS.

I stripped the white LED PCBs from the alum octagon (don't ever use heat sink epoxy- gease and mechanical fasteners are better) and replaced them with 2' T5s driven to VHO, 40watts a tube. 8 times 40w gives 320watts of T5 and 8 strips of 2 watt red Cree for 160 watts, the resulting 480watt hy-bred exceeds my wildest expectations. It out grows a 600watt HPS by a good amount. IMHO LED/T5 together is better then either on its own.

I'm just about to build a 4 light 4' T5 VHO (340watts) to supplement a TI SmartLamp (300watts) to get enough "umph" to cover a 4'x4' aero/fog grow tray. We'll see how well it does soon.

I have some questions for you, hope you'll be around awhile. There have been so many good LED experimenters on these boards, both DIY like physicsnole, redline, veggi and others and the guys willing to take the plunge and buy then document thier grow experiences, led by the likes of snsstealth and now others. While some here just want to do pure LED, I think many will start to embrace the hy-bred concept, untill we can get ideal LEDs manufactured.

veggi,

Sorry to hear you've been ill.
Hope things get better for you....that's what I keep hoping for myself.

Hey, oldmac, thanks for sttoping by here.

I cant agree more whit your post. Ive used CFLs (twin T5s) plus red leds on my main cab. Until now, its been by far the best compromise of price/perfomance. It avoid any spectral lacking and its an excelent way of growing SOG or SCROG style.

But last CREE whites are pretty efficients, and their spectra is decent, similar to halophosphor fluorescents. With some far red emision too. With efficiencies over 90 lm/w at 350mA they offer more light per watt burned than any fluorescent. But price is still higher for just an small perfomance enhancement. But at least its possible to use them together with reds and blues (or just reds).

I wonder why you mounted the octagon inside the cooltube. I think it would be better to mount the exhaust directly to the octagon and aircool it form inside (if the diameter is large enough, add some aluminium sheets inside to improve cooling perfomance) and remove the glass which is blocking at least 10% of the light.

What color temperature T5s did you use?

Also, I thought overdriving to be less efficient power wise (watts/lumen), is it not?

Quote:

---

Originally Posted by RackitMan

What color temperature T5s did you use?

Also, I thought overdriving to be less efficient power wise (watts/lumen), is it not?

---

Hey RackitMan,

I used full spectrum, tri-poshphor T5s, mostly because I was gun shy of "warm whites" from my LED experiment. I wanted to make sure I covered the blue side of things to off set the red Cree's. The light set I'm building right now is going to use 4'- 2,700K T5s, sold or made by Sunblaster. Finally a T5 with less then 3000K! (They also make a 2' T5 and for CFL fans a 200watt CFL in 2,700K.) The TI SmartLamp seems to have a more balanced (?) light spectrum output, so I'm pushing the "warm" side for flowering with the T5 2,700K bulbs.

A T5 at HO levels has about 95-100 lumens/watt at VHO levels abt 115-117 lumens/watt or more. Almost twice the lumens for 65-75% (depending on size) additional power input....Id say it's more efficient. Also takes fewer bulbs to cover an area, I can use 4 VHO driven tubes to cover the area of 8 HO.

Quote:

---

Originally Posted by knna

It avoid any spectral lacking and its an excelent way of growing SOG or SCROG style.

I wonder why you mounted the octagon inside the cooltube. I think it would be better to mount the exhaust directly to the octagon and aircool it form inside (if the diameter is large enough, add some aluminium sheets inside to improve cooling perfomance) and remove the glass which is blocking at least 10% of the light.

---

I came to the conclusion mnay years ago that for indoor growing, single cola plants (many of them) less then 2' was the way to go, 18" or so is ideal.

As for using the cooltube, it was just a matter of necessity....to protect the LED PCBs and T5s from dripping nutrient and water. Plus it is easier to clean a glass 6" tube then 8 individual T5 tubes not to mention the 8- 20" metal PCBs. I clean the glass at least once a day!

It sounds sexy to say I grow in a rotating garden, but it is the most labor intensive system invented by man so far, and it is not a "clean" operation. Only thing worst I can think of is being a dirt farmer. BUT it has had one advantage... more then twice the growing output with the same amount of light input.

The question I have for you kanna is can you quantify light output in terms of micromoles of photon energy for T5s? I have to admit I didn't know a micromole from a gopher until I read some scientific papers posted by physicnole; but it seemed to make the most sence when talking about plant growth. I saw you mention that a 250HPS had about 100 micromoles, that would put SmartLamp at 310 claim well within a possible 600w HPS.

I like how the SmartLamp preforms; in a grape vine propagation experiment, it covers and grows equal to a 600HPS, but with a high light level loving plant like MJ..."a photon whore" (I love that) it suffers what most "brick design" hi power LEDs suffer from, coverage area. Bring the light close enough to take advantage of its higher output, (and you can because there is no heat) and the area covered is just too small. Raise the light to get a wider footprint and suffer with not enough "umph" for those photon whores.

I just happened to luck into my first T5/LED hy-bred light. Its results and what I'm hearing from others, seem to confirm that currently it's the way to go. When I first started with LEDs, I was comming from the "I'm going to save at least 50% of my electric bill". I even got hung up with trying to compare grows to a 600w HPS, but frankly now even if I use the same amount of electric power, if the results in both weight and quality are superior, that is what counts. My new hy-bred uses about 640watts of light, so I hope it can compare favoribly to a 600watt HPS. If not I really am going backwards here.

Did you overdrive your T5s (how did you do it?) or did you purchase them overdriven?

Also saw an older fluorescent light spectrograph, though I imagine it has not changed very much. Very interesting is that the warm white actually has more blue than the cool white. What makes the cool white look bluer is more green and yellow. This is backward to almost everything posted here, but check it out for yourself. (Link is currently not working for me: www.weedfarmer.com/cannabis/lights.php ) The cool white has much more red light.

Quote:

---

Originally Posted by oldmac

I came to the conclusion mnay years ago that for indoor growing, single cola plants (many of them) less then 2' was the way to go, 18" or so is ideal.

---

Fully agree. I grow SOG style, 15-20" tall plants at harvest time. Floros and LEDs (without narrow optics) don go further than that.

I prefer to grow two stacked tables (one over the other) of 15" plants than one with 30" ones. Higher bud to total dry matter ratio with shorter plants, apart of the reduced (almost none) veg time.

Anyway, the arrays im designing now are intended to be used into canopy so im going to try to grow taller plants that produces good buds along all the height.

Quote:

---

Originally Posted by oldmac

As for using the cooltube, it was just a matter of necessity....to protect the LED PCBs and T5s from dripping nutrient and water. Plus it is easier to clean a glass 6" tube then 8 individual T5 tubes not to mention the 8- 20" metal PCBs. I clean the glass at least once a day!

It sounds sexy to say I grow in a rotating garden, but it is the most labor intensive system invented by man so far, and it is not a "clean" operation. Only thing worst I can think of is being a dirt farmer. BUT it has had one advantage... more then twice the growing output with the same amount of light input.

---

Yep, in that sense vertical grows works better, although the problem with them is to get an even nutrient distribution for plants at different heights.

Quote:

---

Originally Posted by oldmac

The question I have for you kanna is can you quantify light output in terms of micromoles of photon energy for T5s? I have to admit I didn't know a micromole from a gopher until I read some scientific papers posted by physicnole; but it seemed to make the most sence when talking about plant growth.

---

Yes, i can do it. You can do it aswell. Ive uploaded the spreadsheet to do it easily. The spreadsheet uploaded on The Garden's Cure already have floros SPD's from phillips digitalized.

54w T5 HO have about 27.5% energy efficiency working at 35ºC, for about 76 uE in PAR (~1.29 uE/watt, already counting ballast losses). It drops to 24% and 66 uE when running at 25ºC.

Losses at reflector are about 25%. So 76*0,75=57 uE avalaible for plants. Close to 1 uE/W.

Clearly uE (micromols of photons per second, abreviated) is the relevant figure when talking about plant's lighting. Any calculation or stimation must be based on it.

Quote:

---

Originally Posted by oldmac

I saw you mention that a 250HPS had about 100 micromoles, that would put SmartLamp at 310 claim well within a possible 600w HPS.

---

I said that if the Procyon uses the top bins for CREE it may emit more than 200 uE so it should compete with a 250W HPS. If it uses normal bins, it likely gets half way to do it.

A good 250w HPS gives about 385 uE. If working with reflector, its about 290 uE avalaible for plants. Pretty close to Smarlamp output, which should outperform slighty it (the other smartlamp model states 265 uE, and that should be on par with the 250w HPS). Slighty improved photons absorbance from the LEDs spectra (near 10% based on NASA experiments) and similar average quantum yield (photosynthesis for photon absorbed).

Quote:

---

Originally Posted by oldmac

I like how the SmartLamp preforms; in a grape vine propagation experiment, it covers and grows equal to a 600HPS, but with a high light level loving plant like MJ..."a photon whore" (I love that) it suffers what most "brick design" hi power LEDs suffer from, coverage area. Bring the light close enough to take advantage of its higher output, (and you can because there is no heat) and the area covered is just too small. Raise the light to get a wider footprint and suffer with not enough "umph" for those photon whores.

---

The critical factor is to give the adecuate light density (uE/m2).

Most HPS grows range from 500 uE/m2 (at 400w/m2, or roughly 35 w/sqft) to 1000 uE/m2 (70 w/sqft). Its clearly more than required, as those high light densities are provided by means of achieving enough photosynthesis on lower areas. Probably 300-400 uE/m2 are enough if growing short plants. And when growing taller plants, adding LED lighting to lower areas directly instead than from top seems the way to use way lower average light densities than those used by HPS grows without losing much yield but increasing strongly productivity (g/W).

Quote:

---

Originally Posted by oldmac

I just happened to luck into my first T5/LED hy-bred light. Its results and what I'm hearing from others, seem to confirm that currently it's the way to go. When I first started with LEDs, I was comming from the "I'm going to save at least 50% of my electric bill". I even got hung up with trying to compare grows to a 600w HPS, but frankly now even if I use the same amount of electric power, if the results in both weight and quality are superior, that is what counts. My new hy-bred uses about 640watts of light, so I hope it can compare favoribly to a 600watt HPS. If not I really am going backwards here.

---

You have choosed a really ambitius target. 600w HPS are the kings about uE emission per watt burned. And they have a very decent spectra for cannabis. Perhaps easy to beat, but for little. Quantum yield for well tuned LED lamps should be slighty higher, but not much more of 10%.

So to beat a unreflectorized 600w HPS is really difficult today. Its way easier to beat a reflectorized one, wich cost a 25% of the light, and easier too if it has a glass barrier, which blocks an aditional 10% of light. You need to give at least 80% of the photons the HPS emits to be able to compete with it.

With current LEDs efficiency, you need to use top bins runned at 350mA max to be able to achieve it.

I think current state of art of LED are still insufficient to compete with 600w on circular gardens. Its possible to beat it by little, but at way higher cost, impossible to take back for electric savings.

Currently i think LEDs are good to give supplementary lighting to low areas of HPS grows and for very small grows. Large wattage HPS are still unbeatable on price/perfomance, IMO.

Today CREE has reported a lab result of 161 lm/W of a white high power LED. Surely it will take about two years to see it commercially avalaible, but at those LEDs efficiencies beat large HPS is going to be much easier.

Quote:

---

Originally Posted by RackitMan

Did you overdrive your T5s (how did you do it?) or did you purchase them overdriven?

Also saw an older fluorescent light spectrograph, though I imagine it has not changed very much. Very interesting is that the warm white actually has more blue than the cool white. What makes the cool white look bluer is more green and yellow. This is backward to almost everything posted here, but check it out for yourself. (Link is currently not working for me: www.weedfarmer.com/cannabis/lights.php ) The cool white has much more red light.

---

I used before and I'm using now a fluorescent ballast made by IceCap inc. They are capable of driving T12, T8, T5 to VHO levels and can be used to power up non-ballast cfls like TT-105s.
As a matter of fact, this time I bought one of their T5 "retro kits" that comes with the ballast, end caps (water proof ends), stand offs, reflectors and wiring harness. I'll be building a frame out of aluminum channel, that will also hold the Ti SmartLamp.

I failed to mention before that the only downside is bulb life is shorten.

I think the trade off is good. For me the biggest up side is the ability to light a 4'x4' tray, with a square light footprint. And hopefully get an added bonus from the LEDs.

Overdriving shorten tubes life strongly. Up to 1/10. And it reduces energy efficiency too, although little (about 15%).

I think is better (and especially, cheaper in the long run) to put twice the tubes than to run them twice the power. If you do it because space limitations, go to Reflex tubes. You can mount them almost touching themselves because they have an internal reflector with a 160º window. If there is no space for that, yep, overdrive is the solution, but its an expensive practice on the long run.

I wouldnt advice to do it except as the last option.

RackitMan, you are right on the money. Coolwhites (~4000-4500K) often are the tone which emits more between 500 and 600nm, the range in what we are less interested. Ive always used fluorescents to grow and i avoid 840. I use 865, 830 and 827.

But daylight tubes (typically 6000-6500K) emits about 40% of light on blue (simplifying the 400-500nm range) while warm whites less than 20%.

knna,

I was trying to digest some of your earlier post.

As to my use of 4-4' T5 VHO, it is not the cheapest way out, but gave me a few pluses, like a square light footprint to match my 4'x4' trays and still have room for the Ti SmartLamp mounted in the middle. Something that 8 tubes would make difficult. As to shortened tube life, everything I've read indicates about 50% less usefull life. The 2700K T5 tubes are $9 each, I can afford to change them periodically.

Actually, from a cost standpoint, I would have done better with 2- 200watt 2700K CFLs ($71/ea) and a cheap bright star fixture ($35/ea)....but felt the light coverage better using 4' tubes.

I currently use regular 4' T5s over my ez-cloner set-up, actually two (2) 120s cloners side by side. I currently have a 5 bulb set up that I may increase to 7. I have one 4' in the middle, without reflector that is a super actinic bulb. Talk about blue output....it's all blue. The other 4 tubes are 6500K. I use the single actinic tube for the first 3-5 days, untill the stems sprout, then they get the rest of the light.

In my old set-up for the rotating garden, I clone with Rockwool plugs lit by 5mm LEDs mixed 3 to 1 blues to reds, about 30 watts worth.
My transplants from plugs to 4" delta blocks happens on a 2'x8' shelf that uses HGL DIY 14watt 5mm boards.....16 of them. For the last year and a half the little 5mm LEDs have done their thing...remarkably well. All of this prior to hi-power LEDs, but they actually worked.