Building LED lights from facts, no theories

[knna]

I was going to post this at the Perfect LED Grow Light (http://boards.cannabis.com/indoor-lighting/150174-perfect-led-grow-light.html) 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

[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.

[justdirt]

procyon doesn't use any white leds dude

[knna]

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.

[redline]

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.

[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 ?

[knna]

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:


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.


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.


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.


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.


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)

[knna]

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 (http://biology.mcgill.ca/Phytotron/LightWkshp1994/1.4%20Prikupets/Prikupets%20text.htm).

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.

[knna]

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.

[justdirt]

bitter much?

[knna]

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

[glutek]

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!

[knna]

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.

[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?

[knna]

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).

[cture]

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.

[knna]

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.

[knna]

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.

[cture]

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.

[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?

[flyingimam]

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;)

[knna]

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 (http://boards.cannabis.com/indoor-lighting/150174-perfect-led-grow-light-59.html). 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.

[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?

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?

[glutek]

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

[glutek]

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

[knna]

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.


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.


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.


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.

[knna]

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.

[glutek]

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;)

[knna]

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/showthread.php?t=125174

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

[oldmac]

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.

[oldmac]

veggi,

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

[knna]

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.

[RackitMan]

What color temperature T5s did you use?

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

[oldmac]

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.

[oldmac]

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.

[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.

[knna]

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.


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.


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.



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).



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).


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.

[oldmac]

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.

[knna]

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%.

[oldmac]

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.

[oldmac]

This is something I mentioned before on another LED thread, maybe you have some thoughts about.....

I would like to see a multi color high power (10watts?) LED, (LedEngin?)
that would have instead of Red Amber Green Blue two Reds, one 660 one 627, one Blue and a forth color (cyan?) all together in one LED.

A complete grow light in one 10w LED.

I know that a lot of gains have been made with high power whites, just because that's what is marketable. Horticulture is just a small niche market, especially in comparisons to general lighting needs. Somehow we need to do better then just get trickle down technology.

[RackitMan]

Looks like there may very well be a new(er) player: induction fluorescents. The watt/lumen outperforms the best T5s and lamp life is 5 to 10 times as long. My big concern is they are very likely way too expensive for the hobbyist. Perhaps in a few years this technology will become the default and prices will drop accordingly. I requested a quote.

I have no affiliation, but here is their ad copy:

Everlast Induction Lighting

Unmatched 100,000 hour rated bulb life!
Replace Metal Halides 1-for-1
Reduces energy costs up to 60%
Lowest lifetime cost of any light source
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6/10 Zero Maintenance Conditioned Spaces Warranty
Excellent Lumen Maintenance, 70% for 10 yrs
Universal voltage standard 120/208/220/277
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Operates 800° cooler than HID sources
Balanced 5000 kelvin 90+ CRI output
Low temperature starts to (-30c)
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Profiled heavy-duty extruded aluminum housing and crystal clear tempered glass lens. Features an anodized aluminum reflector and gas-tight silicon rubber seal made for wet locations. Ideal for retail, manufacturing, outdoors, wet or dusty locations. Flexible mounting brackets allow for this fixture to be suspended or wall mounted with angled adjustment. Available in 100, 150, 200, and 400 watt versions. 100 watt emergency ballasted for power outages is also available.

[redline]

OldMac,
Here are a couple of pics of what I am working currently on, whenever I can find the time. It is an anti-brick design. I have moderately high hopes for it but I am really having difficulty finding time to work on it.
The metal work is very labor intensive. My next step is to make the control panel.

[knna]

Redline,

what material have you used on those heatsinks? Are they of extruded anodized aluminium? What size are they? How much watts of LED are you going to install on each?

I too think that brick design is the worst possible way of doing LED grow lamps.

Right now i ordered a batch of extruded heatsink bars (13.4cm wide, about 5 1/2") to do LED modules that may be placed either on top, using an frame like yours, or hanged between plants.

RackitMan, induction fluorescents was released at the beggining of the decade. It was a very promisory technology, but manufacturers had been unable to offer it at competitive prices. And they have a reliability problem with the induction units: while the bulb itself may last very long (60-100Kh), the inductor units often fail between 25-30Kh. So it nevers gets a decent share on sales, and prices continues high. And with 150 lm/w LED expected on 1-2 years, nobody is going to invest more on induction fluorescents development.

[oldmac]

RackitMan,

Yeah I saw those induction tubes a few years back. I discounted thier use because they where only available in the same light range as MH, not really good for blooming. And a good producing bloom bulb is what we need to get to, we already know that in terms of dgrees Kelvin we would like a color temp of about 2,500 for MJ, that is why I was excited about finding 2,700K T5 tubes finally. ( Instead of the usual 3,000K)

Damn knna, I'm pissed at you! You have gotten me reading spec charts and science papers again, and going crazy in my head how to build a perfect LED light to meet my coming needs. Really fell back into the too much "theory" and too much thinking. But late yesterday I got some aluminum channel to build with, and started to layout my T5s when it struck me.

I need to produce LED strips of about 4', using Red only. Maybe a combo of Cree and some 660 from somewhere else. Each 4' strip could be made of aluminum extrusion, with a heatsink profile. My current design for the T5s is 4 tubes at VHO, all I really need to do is sanwhich them with 5 strips of LED, hopefully about 100watts per strip, depending on the ability to cool them.

That just made me think that I wish I had the two Ti SmartBars instead of the SmartLamp. The bars would fit the design of using 4' T5s better and would have a few more watts of LED. Oh well, let me see what I get with what I've got.

I actually have a 600 digi ballast and bulb, and was going to use it over one of my 4x4 trays and use the LED /now to be hy-bred over the other. Try to get direct comparisons. I think tho, because of some recent money set backs I'm going to have to wait a bit to build some more LED based lights.

Right now me and my partner (I'm slowly passing the baton to someone younger then I) are setting up a "quick and dirty" grow set-up in our new location in order to regroup some money losses, so that we have the money to finish off my dream grow set-up room(s). Plenty of room to work and grow, and systems that produce. He is a frustrated dirt farmer, does hydro to waste in pots of soilless mix. Setting up and 8'x9' room, with 48 sq' of grow space and 2- 1000w and 1- 600w HPS (was mine). Once he's underway, I'll set up a table to hold my 2- 4x4 aero/fog grow trays and get started with at least 1 LED/Ti SmartLamp hy-bred.

Oh, in running designs in my head, I thought about the Reflex tubes you mentioned. I think it could be good to do away with reflectors for the T5s in a LED strip design hy-bred....it could give more space to the heatsink aluminum. I googled them and can't find anything about them. Could you steer me to more info on them. Thnx knna. I'm not really pissed at you BTW, you just got me thinkin' and thinkin' about some of this stuff again.

[oldmac]

OldMac,
Here are a couple of pics of what I am working currently on, whenever I can find the time. It is an anti-brick design. I have moderately high hopes for it but I am really having difficulty finding time to work on it.
The metal work is very labor intensive. My next step is to make the control panel.

Redline,

I reallly like that design, each brick being height adjustable and angle adjustable. Seems it could be the answer to grow taller plants with LEDs.

When I built my LED strips last year, the Red Cree's had a Vf of 2.7v and all where within a tenth of that. So a string of 10 made an easy descion to use 28v power supply. I remember you worked with some LedEngin 660nm reds, do you recall what they actually measured? and how consistent where they?
I'm thinking, just build bigger strips (48" vs 24") with more power, and a mix of reds.

[redline]

I cannot remember exact number. But every single one of them was within .1 volt of the min (some were even outside of specs) I had designed for "typical" and had to end up squeezing in an extra LED.
I was a little dissapointed, since this would indicate they were a low bin unit, and will place you low on the watts/current curve.
I really haven't had a chance to do a decent comparison test on the 660nms.

[veggii]

hey mac thx i'm still very sick and things are looking very bad, have you seen these t5 bulbs they are the fullest spectrum i've seen
a color index 96cri !! very curious too see how well they would grow plants
BlueMaxââ??¢ Full Spectrum Fluorescent Lights (http://www.bluemaxlighting.com/full_spectrum_fluorescent_bulbs_38_ctg.htm)

there about $11 ea or they were ,anyhow gotta go good luck

oh and 2700k hell yea!!



..

[oldmac]

Veggi;

The T5's I used for the 2' hy-bred set-up where full spectrum blubs with a very high CRI also, don't remember exactly what it was now.

I do remember they where made by Hagen and cost 19.99 per bulb (and I needed 8!)

I'm going to replace them soon with the 2700K, and see how it effects things.

I was originally hoping to end my indoor and greenhouse grow after this year, and move everything to the new location. It's very difficult to harvest the 8x16 greenhouse because of the odor, trying to dry and cure that much material. Could not let my kids or grandkids or anyone else for that matter, near my house for a few weeks. This year I only got to harvest some top colas from some of the seed mothers, then everything got stolen from the greenhouse one night. Most of the money I live on....gone. Worst part they poisined my outside dog to get to the greenhouse. Major hurt comming to three of the town's crack-heads who did this.

Anyway, my small indoor op keeps putting out enough MJ for me and all of the patients I take care of. And a couple of fast and dirty grows and me and my partner can recoup some money and build my dream indoor set up, hopefully before I pass on.

[redline]

Veggi... Sad to hear you are not doing well, hope you get better soon.

KNNA.. Each module will be about 15 watts. 12 modules total. No 660nms in the small modules, but I will be adding 2 strips 2.3 feet longstrips that will be 660nm. I will toss them in about a month before harvest.
My goal is to stay under average of 40 watt per square foot.

My primary goal is to replace a 500 watt CFL array that is used for Vegging only. If I can save 300 watts during the 6 week veg cycle, that will be a huge savings since they are running 18 hours a day.

To be honest I don't have high hopes of replacing my HPS during flowering. I am running about 50 watts per square foot for my HPS. So I will be comparing it against 40 watts per square foot LED. I think that is the best we can possibly hope for. I think the claims about 150 watt LED replacing 300 watt HPS are grossly optimistic. I have yet to see LED compete on a watt to watt basis against HPS. If I can get 40 watts LED to compete against 50 watts HPS during flowering, I will be overjoyed.

Heat sinks are extruded aluminum. I buy them from a guy on EBay who cuts larger slabs into any sizes you want. Very convenient and cheapest source I have found. I am going to try and run ducted area cooling over the top of the heat sinks, but have drilled holes to mount fans on top of each one if need be. Fans are little power hogs.

OldMac, Regarding your Red strips: Has anyone come out with a 660nm besides LED engin? Check out Luxeon K2s or the IIIs as opposed to Cree's.
They have a much wider bandwith and do a pretty fair job of delivering photon juice at 660nm. The Crees have a razor sharp bandwith around 620nm. I haven't had a chance to compare efficiencies, but imagine they are both very close.

In the past the LUXs have also been cheaper and available in better BINS. I have not worked with Crees, but from what I have read, the bare emitters are not supposed to be hand soldered. Given a choice, I will always work with an emitter instead of a star to eliminate an extra thermal barrier and save a few bucks.

I am now working on cutting the front panel to accomodate panel meters and switches. I also have to finish up two power strips with Cinch Jones plugs. The metal working is what really bogs me down, since I am working with basic tools. Lots of drilling, grinding, filing, tapping, cutting, blood,swearing etc.

[knna]

Oldmac, ive been searching too for the Reflex tubes in the US and it seems Phillips dont sell them there. But there are other brands which does them, as Hagen, the same of the tubes you are using. They sell an actinic tube for marine acuariums with a 160º window. Ive seen it on acuaria webs for around 20$.

Unfortunatelly it seems that Reflex tubes are hard to find in the US.

Im sad to know what happened you and your greenhouse. I gave up growing outdoors after being robbed two years straight. All the worst karma for those sons of a bitch :mad:

Be aware, its very probably they will try to do it again next year.

Coming back to LEDs, i think is still too soon to replace large HPS bulbs. probably on about 2-3 years its going to be doable, but currently the extra cost is difficult to recover by electric savings. Spectral tunning, micro grows and suplementary lighting for lower areas seems the areas where currently LEDs may be halpul and cost effective.

Veggi, take care. All the best.

I dont see any advantage on using full spectrum bulbs. MJ likes a lot of red light, at least 60% of total. Full spectrum bulbs emits too much green, IMHO.

Redline, i was trying to calculate the thermal resistance of your heatsinks. 15w on each seems correct, although maybe some less ( about 10) would work better, specially if you are going to run your LEDs at 700mA. Are they about 10*10cm and 2 cm thick (4*4", 1")?

I try too to avoid as much as possible the use of fans. Given the large surface area we have avalaible on a grow room, i think using passive cooling is easier and more efficient, as far as heat dissipating surface is well calculated.

I have a spectrografic chart of a red Cree XL lamp running at 700mA. Peak wavelenght is at 642-643nm. Half intensity at 630 and 651nm. Not ideal, but good enough. Emiting spectrum of red leds shifts noticiably with the increasing temperature. Datasheets spectrums must be taken as orientative. Spectrum emited on operating conditions is always longer.

Although not designed for hand soldering, its possible to do it with Cree Xlamps. Ive done it several times without problems. Some leds have been soldered and desoldered some times and are still working fine. The problem is you need to do it on the top sides, where there is very little space avalaible. I solder the electric contacts directly on the side of the led, where there is no problem if there is too much tin (no shorts with the metalic ring of the center).

I use to put a piece of Kapton tape below the electric contacts, and solder the side of the led to the wire over the tape. Kapton tape do well up to 300ºC. Ive tried to put the solder tip on the tape directly for more than 10 seconds without damaging it

[attachment=o209743]

[redline]

KNNA,
I am right at the 9 square inches/watt for heat sinks that Luxeon recommends for passive cooling. In practice, I have found that the figure is cutting it a little too close. I am working on ducting a concentrated flow of air across the tops of the heat sinks. Hope that does the trick.

Any reason to go with the Crees over the Luxeon IIIs or K2s?

[knna]

Wit 9 sq inches per watt, you get a thermal resistance about 20 K/W. Plus the thermal resistance of the LED package itself and any aditional dielectric layer (a thin film of thermal adhesive is 0-9-1.3 K/W), it put the thermal resistance of the system near 30K/W. Although its enough to keep decent efficiencies, it may result on unaceptable LEDs duration when running LEDs hard:

At 700mA, a blue leds draws about 3.5V or more. Still at 3.5V, its 2.45W. At 30 K/W, it result on a increase on junction temps of 73.5ºC. So with ambient temps around 25ºC, the LED chip is going to work near 100ºC. Its good for many applications, but on ours, with many hours on a day, that result on shortened life. Not dramatically shortened as if Tj were 150ºC, but shortened.

Most manufacturers only "guarantee" (based on extrapolating short term measurements by stadistical analisis) a lm mantenience of 70% at 50Kh when Tj is kept at or below 80ºC. For the typical depreciation curves, its about 35Kh for 80% of initial output, which mostly is the criteria for horticultural lamps replacement (while human barely notice a drop below 30% on light intensity, for plants it means at least 30% less production, that is usually inaceptable).

For Tj over 80ºC, lm degradation is exponential with the increased temperature. So Tj about 100ºC are aceptable for many applications, where 25Kh until reaching an emission 30% lower of initial is aceptable. But for ours, if you want to recover initial higher investment by electrical bills savings, we want a lm manteinance of 80% at 30Kh minimun, and for that is a must to keep Tj closer as possible to 80ºC. It requires a thermal resistance from chip's junction to ambient temp of 22 K/W.

So when using 9 sq inches per watt instaled of heatsink dissipating surface, if you run your LEDs at 700mA you get a somewhat reduced expected useful life of the array.

Probably the use of airflow on the heatsink will help reducing further those 20 K/W of the same heatsink on open air. So probably with it, you are going to be able to expect 30Kh of useful life. But i would choose to run LED slighty below 700mA to guarantee it (about 600mA). Aditionally, it enhances LED's efficiency.

When running the LEDs at 350mA, that heatsink is more than enough, without the need of forced airflow.


Any reason to go with the Crees over the Luxeon IIIs or K2s?

About blues and whites, way better energy efficiency. Currently Cree is doing much better blue leds than Luxeon (as better as double light output per watt).

For red leds, benefit isnt so clear. I prefer the Crees over the Luxeons because the reduced Vf. But differnce on efficiency, although still better for the Crees, is small, and the easy avalaibility of Luxeons and price (when buying small amounts and not full reels) often does the Luxeons a good alternative.

One think you must take into account when using Luxeons and controling voltage, and not current, is their tendency to reduce Vf for same current after some hundred (or less) hours of operation. It mean that you design the system initially to run, for example, at 600mA, but after 200h, its running at 750mA.

Curently, im going to try the Seoul SemiConductor P4 red leds. If specs are correct, they are way more efficients than both Cree and Luxeons (always talking about top bins avalaible: M for K2 and S for Lux and SSC).

[redline]

Appreciate the advice. I am an electronics hobbyist and don't work in the field, so I can always use some good help.
I bought a bunch of P4s, blue and cool white really cheap, so I am stuck with them. I was planning on using them with red K2s, but will probably need to buy some more reds. I might try the Crees and see if I can get a comparison.

Regarding Cree Vs Luxeon: Isn't a higher VF better? Since you will be running a higher wattage at same current.

I try to be pretty conservative on the current. Don't like to run at more then 60% of max.

I do a couple weeks of break-in during array building process.

The array I am building will have several panel current meters, so I can monitor overall current plus each string.

What are your thoughts on where to operate on current curve? What do you think is the sweet spot where you are trading off efficiency for better penetration? I am setting my rig up so I can play around different current settings and see what produces best yield/watt.

It wouldn't surprise me if we have to run these guys as close to max as possible and use aggressive cooling.

I think with LEDs we are going to have to start tailoring the grow to fit the light. We need to start thinking a little more 3D about productive growth area then we do with HPS. Maximizing available light in the Z axis is the real limiting issue with LEDs. You probably only have a couple of inches of decent penentration with LEDS. If you can somehow increase that to 4 or 5 inches you should be able to double yield in the same square footage.

I am currently playing with growing horizontal /flat plants, trying to keep the canopy depth within 6 inches.

[redline]

My crude method for heat management:
I look for hotest spot on array with IR thermometer and make sure it is not more then 10 degree F above ambient temp after it has been running for a few hours. Max ambient temp is 80 degrees.

I know there are some pretty good ways of estimating junc temp with basic equipment. I just haven't got around to doing it.

I would like to set my test array up so I can continously monitor temp of each array. Any ideas?

[knna]

Regarding Cree Vs Luxeon: Isn't a higher VF better? Since you will be running a higher wattage at same current.

With LED, light output is determined by current, not wattage. Any curve of light output is given vs the current level, independent of the Vf associated to that current.

So for a givent current, a given light output. As higher the Vf, higher the consumption, for the same light output: lower efficiency (more watts burned for same light output). This analysis is valid when comparing different Vf bins of same model.

When comparing different LEDs, obviously they havent the same light output at a given current level, so its necessary to compare energy efficiencies of both. But in general, for leds having similar light output at a given current, the lower the Vf, the more efficient. As manufacturers always report light output at a given current (350mA for 1W leds and 700 mA for 3W), when you compare them, the lower the Vf, the better. As higher Vf increases the wattage burned but not the light emission.

We need to forget using wattage to estimate light output of LEDs, because the wide differences between brands and models, and still between different bins of the same LED (both of flux output and Vf).

That way has worked pretty well with HID lights, because efficiencies of them are very, very similar. Saying "i have 50w of HPS per sq ft" gives a very good indication of the light used, because HPSs have near constant energy efficiencies (400-1000W).

But it dont happen with LEDs. 10w of a given LED may gives 1.5 PAR watts while others (or same with way superior bins) may give perfectly 3 PAR watts (double light for same watts burned). So watts burned dont say nothing about light emited when working with LEDs. At least, currently.


I try to be pretty conservative on the current. Don't like to run at more then 60% of max.

I think its the right way: easier to cool. more efficients, more light points. But its more expensive (more drivers or components and heatsinks, more leds for same light).


The array I am building will have several panel current meters, so I can monitor overall current plus each string.

I agree with that way. Its the only way to take conclusions of how the array works better.

I think current adjustable systems are almost a must. Way more versatility, specially if each color has its own control. Once you do a constant current driver, doing it supporting current limit adjusting is as simple as adding a variable resistor to the current sense circuit.


What are your thoughts on where to operate on current curve? What do you think is the sweet spot where you are trading off efficiency for better penetration? I am setting my rig up so I can play around different current settings and see what produces best yield/watt.

For the increased efficiency, the lower the better.

From cost/performance perspective, it depends of each LED model. On most cases, below 600mA. I think 400-500mA is a good compromise on most cases. Some top LEDs support higher currents keeping decent efficiencies, but currently they are little. I believe in just 1-2 years LEDs released are going to support 700mA very well. But not yet.


It wouldn't surprise me if we have to run these guys as close to max as possible and use aggressive cooling.

If you find that you need more light, you can only do that or add more LEDs. Anyway, id dont think we are going to use our experimental arrays for many years, so running them hard is doable.


I think with LEDs we are going to have to start tailoring the grow to fit the light. We need to start thinking a little more 3D about productive growth area then we do with HPS. Maximizing available light in the Z axis is the real limiting issue with LEDs. You probably only have a couple of inches of decent penentration with LEDS. If you can somehow increase that to 4 or 5 inches you should be able to double yield in the same square footage.

I am currently playing with growing horizontal /flat plants, trying to keep the canopy depth within 6 inches.

Fully agree. I noticed this many time ago. Thats why im insisting about the need of use side and/or intracanopy lighting. That of only grow SCROG. As i dont like SCROG at all (just personal preference), i tend to seek for ways of allowing the grow of tall plants with LEDs. And BTW, increase the light's productivity.


My crude method for heat management:
I look for hotest spot on array with IR thermometer and make sure it is not more then 10 degree F above ambient temp after it has been running for a few hours. Max ambient temp is 80 degrees.

I know there are some pretty good ways of estimating junc temp with basic equipment. I just haven't got around to doing it.

Measure temp at solder point or just next to the led base when heatsink temp is stabilized.

You must know the thermal resistance of the LED package you are using. Its a figure on K/W (or ºC/W, its the same) that says how many ºC junction temp raises for each watt burned by the led. Multiply it (add 1 before if there is a thermal adhesive layer) by watts drawn by the LED (If*Vf, current multiplied by voltage (A*V=W)).

Add the result to the base temp and you get a close approximation of the junction temp.

More accurate measurements implies using very short light pulses (microseconds) and compare Vf of them to Vf on continous operating condition. But this requires to know accurately how much drops Vf for each ºC more, and manufacturer's data often is not precise enough.

I would like to set my test array up so I can continously monitor temp of each array. Any ideas?

Using a thermocouple attached to each heatsink, always on the same position (preferably, the center). But if all arrays uses same LEDs, same power and same heatsink, differences shouldnt be large enough to justify measuring each one, IMHO. But doing it together with current control is going to give very valuable info. :thumbsup:

[physicsnole]

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

[physicsnole]

Also Knna, here is a program that simulates LED junction temperatures, max temps, whatever. Very useful. Future Lighting Solutions | Making LED Lighting Solutions Simple (http://www.futurelightingsolutions.com/qled/)

[gioiapura]

hey knna first of all thank you to share your experiences with us...i really need some facts to start in the right way my first DIY Led array.

Like you, english isn't my first language so please don't look at the form but the meaning!
I'm working with commercial 90w led arrays(R/B 8:1) like UFOs and i've already made some grow tests mixing Leds with HPS and CLFs with some good results.
I'm a "perfect led light" thread follower since physicsnole(thanks god) put the first post so after a while i decided to do my perfect led array but i already know how difficult is to make a efficient led light...and finally my techincal skills are really poor in assembly an array by myself...lukily a friend works in this field and can do it for me.
From what i've seen regular commercial arrays like procyon and ufos are good for veggi but lack in potency and spectrum in the flowering stage.
My ideal light is a "bloomer"... something to add to the 2 90w red/blue led grow lights in my room when i turn the light 12/12!

Yesterday...after a long waiting i received the Ledengin Leds and 4 35v 1050 mA drivers:

LLZ1-10R105 LEDENGIN 5W RED ON MCPCB PZ 2
LLZ1-10UA05 LEDENGIN UV ON 5W MCPCB PZ 1
LLZ1-10WW05 WARM WHITE 5W MCPCB PZ 8
LLZ1-10B205 BLUE ON 5W MCPCB PZ 3
USLEDLPC351050ALIMENTATORE LPC-35-1050 PZ 4
LLZ1-10R205 DEEP RED 5W MCPCB PZ 8

I still waiting for the 2 5w 720nm Leds that should be here in a week but i need a good projet! The glutec's antibrick idea is nice IMO but hard to move.

I've got a mover and i'd like to move this array between the 2 90w Grow Lights but now i'm thinking about at the heatsink.
I've got 20 cpu coolers with fans and i'd like to keep colors divided to play with spectrum at different blooming stages!

Any help is gold for me at this moment!

[knna]

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

gioiapura, welcome to the thread, too.

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

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

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

[Weezard]

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

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



That's a lot of good intel, Knna!
Mahalo!:thumbsup:

Hmmm, "50VAC output":confused::D
If you meant DC, I could sure use a few if the price is right.:cool:
Please give us a "heads-up" when you e-bay them.

Sorry to be so scarce lately. Been re-searching this Martian method.
(Also reading up on Dogz "Martin" method.:rolleyes:)
Thanks for the rep, Dog.
I'd also kill for an uncle like that.:thumbsup:


You guys are all way over my head, but some of it is slowly sinking in.
I'll just keep quietly readin' and :weedpoke: for a while.

No worry, if/when I have any new info to offer, I'll come back out of lurker mode with fingers blazing.:)

Aloha nui.

Weezard

[Dogznova]

Right on Weeez. This tread is great.... Thanks Knna for your time..:clap:

[gioiapura]

knna.....i wll start my own thread to avoid pollute yours...thanks for the big help!

[knna]

Hmmm, "50VAC output"
If you meant DC, I could sure use a few if the price is right.
Please give us a "heads-up" when you e-bay them.

You are right, Weezard, it was a typo. Its 50VDC output actually.

So they work directly from mains AC and power up an array up to 50VDC. 82% efficiency slightly below half load, close to 90% when near full load. Ive done more efficient drivers myself, but those are very versatile, due the wide range of operation both on voltage (6-50VDC) and on current (100-900mA). They are CE certified. Current adjustment is done with a screwdriver.

I dont know the price yet, but they are way cheaper than any similar driver ive ever found. When i pay duties and taxes ill know accurately how much they cost, but i believe i will be able to sell them below 30$ each.

The reason to order 400Kg is its the minimum order requeriment Ive been able to find for extruded aluminum. But as its been hard to find LED heatsinks large enough to build illumination arrays, i think i wont have problems selling the excess. Ill get them on 6m bars, so ill cut them at any desired length (they are 13.4cm wide and 2cm deep with 15 dissipating fins).

[Weezard]

You are right, Weezard, it was a typo. Its 50VDC output actually.

So they work directly from mains AC and power up an array up to 50VDC. 82% efficiency slightly below half load, close to 90% when near full load. Ive done more efficient drivers myself, but those are very versatile, due the wide range of operation both on voltage (6-50VDC) and on current (100-900mA). They are CE certified. Current adjustment is done with a screwdriver.

I dont know the price yet, but they are way cheaper than any similar driver ive ever found. When i pay duties and taxes ill know accurately how much they cost, but i believe i will be able to sell them below 30$ each.

The reason to order 400Kg is its the minimum order requeriment Ive been able to find for extruded aluminum. But as its been hard to find LED heatsinks large enough to build illumination arrays, i think i wont have problems selling the excess. Ill get them on 6m bars, so ill cut them at any desired length (they are 13.4cm wide and 2cm deep with 15 dissipating fins).

Aloha Knna.

So, you have heatsink to burn, variable CCs that go to 50V at 1+amps, and deep understanding of PAR.:cool:

Hmmm, an enviable position!:)

I gotta wonder what's stopping you from fabricating a few 100+ Watt gro-lights and flogging them on e-bay instead of, or along with, the parts?
There are thousands of folks out here that can't construct a paper pinwheel without needing stitches:D.
Or, that have the skills to build, but not the knowledge.
Or, are just too darn busy/lazy.
Heck, I'm so lazy, I'd buy a few from ya.:rastasmoke:
Food for thought?

Mahalo
Weeze

[knna]

Very good suggestion, Weezard. Ill think on that. I thought of only selling the exceeding components, but why not selling finished modules as well?

Anyway, it would be just some ones. Im waiting to have built and tested some arrays, and know accurately how they works and to how many watts of HID equal. 6 months, i believe.

But my idea is to order them when they are cost effective against HID and produce them at large quantities (so unitary costs keep low), not building them myself. With current labor costs, its cheaper to order them.

But next Tuesday i have a date on a mounting electronics company which is near bankrupt, and ill see if i can get some industrial equipment for cheap. With a reflow owen and a pick and place machine, i should be able to do many modules a day myself. I let my job to work in this project, so indeed im plenty of free time.

Yep, you gave me food for thought :thumbsup:

[Revanche21]

I'll leave it to you experts to make a tutorial :)

[redline]

KNNA, Thanks for the info. I was able to comprehend about 80% of it.
This will give me an opportunity to educate myself trying to understand the other 20%.

Another question: I bought some LED drivers, 24 volt, 180 watt, voltage regulated.
Why are the larger wattage LED drivers all voltage regulated? instead of current regulated like the small drivers?
Is the voltage regulation tight enough that you don't have to worry about excessive current swings. Or is it expected that you use secondary current regulation, like a resistor or a reg chip in each string?

I am currently using a resistor in each string since it is cheap and simple. I could make some small reg circuits if need be, but am lazy. I burn them in for a couple hundred hours, then I customize the resistance on each string to get desired current.

[knna]

Another question: I bought some LED drivers, 24 volt, 180 watt, voltage regulated.
Why are the larger wattage LED drivers all voltage regulated? instead of current regulated like the small drivers?

There are some CC high wattage drivers out there, but they are very, very expensive. Ive seen up to 400w ones. They are similar to HID electronic ballast. Often they comes together with a DMX unit, as mostly this equipment is used on discos and such, using RGB leds.

I dont know exactly the reason of almost nobody doing these type of devices. Although as the voltage increases the driver design becomes more complex and the components used are more expensive, any manufacturer should be able to do it without mayor problems. At least, if they dont seek for very high efficiencies.

I believe that manufacturers thinks that any that want to do arrays of high wattage have the knowledge to do a dedicated driver for the application with higher efficiency than any generic one, thus demand for high wattage generic CC drivers is not enough for mass production.

Along the last year, most manufacturers of power ICs have been releasing components designed specifically for high power LED arrays. They have integrated the current sense circuit and the FET with comparators, so often only needs an external capacitor, inductance and a resistance to complete the basic CC circuit. So a basic CC circuit is now easy to do yourself. Tuning it to take care of the LEDs (avoid transient spikes) and work with the higher efficiencies is more complicated, thought.


[quote=redline]Is the voltage regulation tight enough that you don't have to worry about excessive current swings. Or is it expected that you use secondary current regulation, like a resistor or a reg chip in each string?

I am currently using a resistor in each string since it is cheap and simple. I could make some small reg circuits if need be, but am lazy. I burn them in for a couple hundred hours, then I customize the resistance on each string to get desired current.

If you use a voltage regulation, you always need a secondary current regulation. But a resistance on each array is enough.

This secondary control is needed because the negative coefficient of electric resistance vs temperature of LEDs: Vf associated to a given If drops when chip temperature increases. Thus, if you drive the array controlling just the voltage, as the chips heat, for the same Vf, there is more If (current) flowing. As the relationship between Vf and If is exponential, little changes on Vf lead to huge changes of If.

As the resistor drops more voltage as higher is the current, it filter this effect and strongly minimize the current swing: as chips heats, for same Vf, If increases. But when If increases, the resistor drops more voltage, thus there is less voltage available for the leds, thus If increase is controlled.

So although not ideal (the ideal is to limit the current, not the voltage), a tight voltage supply with a resistor on each string works fine enough. And its by far the easiest way, and currently, the cheaper way, of driving high wattage arrays.

The problem of this way of driving leds is its inefficiency: the resistor burns power and rest efficiency to the circuit. Additionally, as LED's chips heats, their efficiency drops. By this effect is partially compensated by the fact of the reduced Vf at a given current (because power burned is Vf*If and light emitted only depends of If). When using resistors, you lose the efficiency gain by the dropping Vf, because what you do is burn those volts at the resistor: all the theoretical gain is wasted.

So as higher the resistance of the resistor used, higher filtering effect (lower If swing) but more power losses.

And when you add the loses of the PS converting AC to DC to the losses on the resistors, you may get perfectly an overall efficiency of the driver design at 70%, meaning that each watt used by the LEDs needs 1.4W. Way larger than any HID or floro ballast, which are about 10% (1.1W for 1W of bulbs consumption) and still less. And that way is difficult to get true electric savings.

So for experimenting arrays, constant voltage PS and resistor are easy and cheap, but expensive on the long run.

The better the thermal path of you arrays, the smaller resistances you may use and you will have lower power losses. When using a good thermal setup and using not high currents (Tj raises very fast with the increased current), it allow you to use resistances with way lower power losses (because less ohms). But obviously this will require the sum of the LEDs Vf is very close to the voltage supplied to the array, and that is not always possible.

In this scenario, if the sum of Vf is just a bit over the supplied voltage, maybe you could use the array without resistances at all. You wont have any control over current, but you can do a try an measure the current after temps are stabilized and if it falls on a good range, run it that way (the disadvantage of no using any resistor, or still small ones is in case one led fail and open: the increased current on the array may fry all it)

[knna]

A way of eliminating the need of resistors is using a linear voltage regulator on each string, on CC mode (with a sensing circuit with a small resistance).

Linear regulators are problematic when they must reduce many volts. But when they only need to reduce voltage on some tenths of a volt, they work pretty well. And they are cheap. And that way you are controlling directly current of the array. Way better than the resistors way (although still worse than a switching CC driver, way easier to do)

[redline]

I got a bunch of LM317s kicking around, but wasn't planning on using them.
I figured resistors would do the job as long as I will willing to do a 200 hour array break-in and readjust resistance if needed. I am also going to have a couple of panel current meters monitoring 6 arrays each. I am also going to have a couple more meters where I can spot check current to individual arrays.

Does an electronic regulator have about the same power loss as a resistor?

Also, I figured using 24 volt power supply is better then using a lower voltage since any power supply voltage variation is distributed across a larger number of LEDs.

I was trying to find info on how large arrays are set up in the sign industry, but could find very little on the web.

I don't know how to calculate thermal efficiency (yet), so I have another question. I figured mounting bare emitters directly to the heat sink is preferable to stars, since you eliminate an extra thermal barrier. But you need to use an adhesive instead of a grease which cuts down a bit on thermal efficiency. Any thoughts on best way to go...stars or emitters?



I am getting ready to start constructing the individual modules. I will run the design specs by you for criticism before I start inhaling solder fumes.

I am going with 10 to 12 watt arrays. so will be running around .5 amp. I am going to try and keep the resistor around the .5v to 1.5v drop range. Do you think this will provide adequate secondary regulation? I hate to see it eating up more then 10% of the power.

[knna]

I got a bunch of LM317s kicking around, but wasn't planning on using them.
I figured resistors would do the job as long as I will willing to do a 200 hour array break-in and readjust resistance if needed. I am also going to have a couple of panel current meters monitoring 6 arrays each. I am also going to have a couple more meters where I can spot check current to individual arrays.

Does an electronic regulator have about the same power loss as a resistor?

No, it has lower losses. But it depends of how much voltage it need to adjust. If its little, the power loss is kept small. The closer the voltage of the array to 24V (supplied by th PS), the less volts drop.

You will notice it for how much hot get the LM317 (if i remember well LM317 have a max current rating of 0.5A, so you could use them).


Also, I figured using 24 volt power supply is better then using a lower voltage since any power supply voltage variation is distributed across a larger number of LEDs.

Yep, but the issue here is not variation on the PS, but different current flowing for same voltage with the changing chips temperature. So the larger the array power, the larger the variation:

say Tj is about 80ºC, for example. The K2 drops between 2 a 4 mV for each ºC over 25ºC. So 80-25=55ºC of increase on Tj lead to 165mV less (at 350mA, average of -3mV/K). The more LEDs in the array, the higher voltage drop along the array, so you need an higher resistance resistor to compensate for it, but lower than the sum of two resistors if you split the string in two series, each one with its own resistor (so better a 24V PS than a 12V one)

In this example, with 165mV less the associated increase in current is about 250mA. If you dont compensate that with the resistor, the array will work at 750mA (in the practice, still higher, because at 750mA and only 0.165V less, the power being burn is over 20% (near 25%) higher than initially, and that lead to the chips getting still hotter, and so on.

So you need a resistor that when all leds on the array drops 165mV, as current increases it increases the voltage dissipation as closer to that figure as possible. For example, if the string is 8 leds long, 8*165mV=1.32V. At 500mA, it implies 2.64 ohms. Power dissipated by the resistor would be 0.5A*1.32V=0.66W.


But obviously, you will determine the value of the resistor according to how much difference of voltage are between that supplied and the string requirements at the target current. In this case, its going to be similar, as you say its going to be about 1 and 1.5V, so its going to be very similar of that calculated before (about 2.5 Ohm, which drops 1.25V at 0.5A).

So if you use a 2.5Ohms resistor to regulate the current at 0.5A, then as chips heats, current across the circuit raises. But each 0.05A of increased current does the resistor drops 0.05A*2.5 Ohm=0.125V more. At a increase of 250mA, it would drops 625mV more. In the first example, we calculated a drop in each led of 165mV, so the resistor would compensate fully a string 5 leds long.

In order to calculate it accurately, you need to estimate the raise of Tj. Thermal resistance of your setup is about 20 K/W, eyeballing. Maybe 25 K/W. At 0.5A, blue K2 draws 3.51V (average, you should measure it for your batch), that may drop to 3.35 after 200h. Its 3.51V*0.5 A=1.575W, for 25K/W, increase of Tj= 39K. So at -3mV/K, you may expect a max drop of voltage at each led of 117mV. In 24V, you may fit 6 blue leds (at 3.51V each), up to 7 (at 3.35V). So you get a max drop in a blue string of 117*7=819mV.

Ive done this calculations so may may know how to do it.

But the right way to do them is by first calculating the number of LEDs on each string. To do it accurately, you should measure the voltage drop of your leds at you current target. Ill use the average Vf from the K2's datasheet: 3.51V for blues and 3.22V for reds (at 0.5A).

The PS gives 24V. So in each string fits 6 blues or 7 reds, and rest 2.94V (blues) and 1.46V (red) to dissipate with the resistor. At 0.5A, then you need to use a resistor of 2.94V/0.5A=5.88 Ohms (remember, R=V/I) for blues and 1.46/0.5=2.92 Ohms for red strings.

In order to compensate for the voltage drop due to the increased temperature, always choose the closer value of resistance over the calculated figure. That way, you set the current in cold below the current target, so as leds gets hotter, the final value is close with your actual target.

For the average figures of Vf of the K2, it would be a 6 ohm resistor for blue strings and a 3 Ohm for the red strings.

Would this minimize the current swing? Lets go to calculate it, although with the calc done in the example, i know the answer is yes.

At 25 K/W (estimated thermal resistance junction to ambient temp), blues may increase Tj up to 39K, as seen before. At -3mV/K, its 117mV less. For 6 leds in the string, its 702mV. How much the resistor will let increase the current before compensate it? As I=V/R, I=0.7V/6 ohms=0.117A, about 100mA.

As the setting for cold LEDs were regulated below 0.5A, final current on operating conditions is going to be lower than 600mA. Likely, about 550mA.

The problem of this design is that a 6 ohm resistor is going to dissipate about 550mA and 3.3V, or 1.8W wasted for each string.

Notice that the excess voltage on operating conditions for that Vf figure is pretty close to the Vf of another blue led. If the Vf of your leds is exactly that, then you could use a string of 7 blue leds connected directly at the 24VDC PS without any resistor and get a current very close to 500mA. As far as the PS is solid giving the 24V, it should work perfectly. But in order to do it you need the Vf of your leds were exactly that (and likely, it wont :(, but who knows?).

Measure accurately the Vf of your leds is a must if you are going to control them by voltage.



I was trying to find info on how large arrays are set up in the sign industry, but could find very little on the web.

They mostly use strings of 3 leds with a resistor on a 12V PS, and prefer to forget about reliability of the system. Mainly because they rarely use LEDs over 200mW, in which thermal effect is way less important than when using high power leds.


I don't know how to calculate thermal efficiency (yet), so I have another question. I figured mounting bare emitters directly to the heat sink is preferable to stars, since you eliminate an extra thermal barrier. But you need to use an adhesive instead of a grease which cuts down a bit on thermal efficiency. Any thoughts on best way to go...stars or emitters?

If you keep the thermal adhesive layer thin enough (by applying some pressure during the curing process), the thermal resistance added is kept below 1.5 K/W, and very often, below 1K/W. Of course, a good thermal adhesive makes a difference. The Arctic Silver is common and very good.

If possible, better the emitters. Mounting is more complicated, but it worth the thermal enhancement.

The problem of many stars is they are of poor quality. Thick layers of dielectric, poor soldering jobs, bad adhesives. Very often they penalize thermal path. With good ones, there is little difference with the emitter glued on the heatsink directly.

But if you know to mount directly the emitters, its cheaper and better.

[redline]

Knna,
I have an idea that I have also been working on in order to get more growth in Z-plane. This would also help if you are wanting to grow taller plants.

I have a design for a vertical plug-in module that drops down below the top of the canopy. The problem is with cooling. Heat sinks block too much light, plus they are dissipating heat onto the plants.
My design low profile water cooled module, where I am mounting emitters right onto a piece of U bent copper tubing about 6 inch long. I have only built one and it seems to do okay. I don't know how ganging up mulitple units will work.

Another issue is that you would have to reduce top lighting in order to keep within your watts/sq. ft. parameter. So the question that needs to be answered is "where will a watt of LED power need to be positioned to get the best results?" On the top?, On the side? or a combo?
I hate to introduce more complexity into the array if it is not beneficial

[Weezard]

Aloha Knna,

Beeg mahalo fo' all dem fish.:)

Just a quick FYI.
The LM317 maxes at 1.5 Amps.
And they need about a 2.5V drop.
Not all that bad for 24 -36V strings.
So, 2.5W wasted as heat. and only half of it is regulator heat.
(1.25V X 1 amp in sense resistor)
Got some running @ 50 C. :cool: @ 1 amp with a 2" sq 1/2" high finned 'sink, no fan.
That help, R. L.?

ciao
Weeze

[AfricanAlien]

A basic high-power led circuit???

Say i have a 24V DC @ 1 amp power supply
6.84V @ 700ma 5W high-power LED (3 led's in total)
high-power constant-current source input 6v-24v @ 700ma

If i connected the three LED's in series with the constant-current source and connect it to the power source, would this work?

Ignoring the thermal issues, just need to know if my understand of LED array is correct using high-power LEDs

[Weezard]

A basic high-power led circuit???

Say i have a 24V DC @ 1 amp power supply
6.84V @ 700ma 5W high-power LED (3 led's in total)
high-power constant-current source input 6v-24v @ 700ma

If i connected the three LED's in series with the constant-current source and connect it to the power source, would this work?

Ignoring the thermal issues, just need to know if my understand of LED array is correct using high-power LEDs

Yes.:cool:

Weezard

[redline]

Weez,
So you are saying that I will most likely loose more energy in a LM317 then I would with a sense resistor?
I haven't had the time to really study linear regs, so I am very weak on this subject.
But it just seems to me if you are dropping 2.5 to 4 volts (LM317 instead of 1.5 volts (resistor) at equal currents you are going to dissipate more power.
Of course the trade off is you are giving up better current regulation.

Knna/Weez- If I go with resistors and 24v VR driver, do I need to be concerned about start up transients damaging LEDs?

[redline]

I mount directly and use Artic Alumina. Is the silver a better way to go?

I didn't use pressure since I was worried about shorting out the pad. I did try to minimize layer thickness.
Now it seems I would be better off using pressure and if it shorts, just tear it up and mount another one. I will custom make some kind of fixture that applies weight to the LED

[Weezard]

Weez,
So you are saying that I will most likely lose more energy in a LM317 than I would with a sense resistor?

Little bit.

I haven't had the time to really study linear regs, so I am very weak on this subject.

Not that much to know really. Take you about 15 minutes to learn all you need for practical application.

But it just seems to me if you are dropping 2.5 to 4 volts (LM317 instead of 1.5 volts (resistor) at equal currents you are going to dissipate more power.

That is correct.
Don't matter how you do it. V x A = W

Of course the trade off is you are giving up better current regulation.

Exactly!
I don't stress over a Watt or 3.
And a dropping resistor will happily pass-on a voltage spike!:)
The LEDs may not be quite so happy to receive it.:(

Knna/Weez- If I go with resistors and 24v VR driver, do I need to be concerned about start up transients damaging LEDs?

In a word? Yes.
Not to mention shut-down spikes, lightening strikes and plain old everyday "gotcha" spikes.
Of course that does depend on the VR supply used, how heavily you load it, and what you feed it.
I'd just rather Pay the piper daily when considering the cost, time and effort of LED replacement.

With voltage controlled devices, I use VR.
With current driven devices ,CC is the best way to go for full control, consistency, and longevity. IMO.

I'd really like to see your multi-source lighting scheme in operation.
It sounds like a good idea.

Aloha,
Weeze

[knna]

Much time since i worked with LM317. But for what i remember, although specs usually advice to let 3V for the possible drop in the regulator, when you measure it often is around 1.5V. You know, there is wide tolerances and manufacturers obviously give safe margins of operation.

Anyway, i think the better current regulation worth using the LM317. Resistors arnt adequate to drive high power leds. Doable, but seeing the maths on my last post, is easy to understand why current control is advisable. 10%, and still 20% of variation on the current target is not a problem. But with resistors the variation may go way far from that.

I dont think transients are a practical problem. Although any manufacturers recommend to avoid them, there are many systems working without compensating them and work fine. So its preferable, and life test are done avoiding them, so its difficult to know if not compensating them shorten leds life. But on large strings i dont think its a mayor problem. But i dont know for sure, i use smooth regulators.

The Alumina and the Silver works pretty similar. In the practice, no difference. Any of them have low heat transmission compared to a metal. The key with them is to keep layer thin if you want it dont penalize heat transfer too much. I like the Crees because the electrically isolated bottom slug, as it allows to forget concerns about derivations if the adhesive layer not cover fully the slug.

I like to apply the adhesive directly to the slug, ensuring all is covered and then place it and apply some pressure with the hand (i use a nut to avoid pressing the dome). I let the adhesive cure enough to keep LED in place and then i put a book over the module (a nut over each led) for all the night. Using anodized aluminum is a secondary way of avoiding electrical derivations (the aluminum oxide layer is not electrically conductive).

You can try too to add kapton tape to the conductive slug. It works very well isolating. But then the problem is to glue the led itself to the board. But i think it would be possible to add adhesive (and not requiring to use thermal conductive one) on the perimeter of the base.

I think the main reason of many people to use stars is ensuring that there is no problems with conductive bottom slugs (and beware with that, ive found stars which indeed have the bottom electrically connected)

AfricanAlien, it will work perfectly as far as the constant current device is able to give 3*6.84V=20.5V @700mA. From 24V input, it should, still if its a linear regulator. But be ensure about that.


I have an idea that I have also been working on in order to get more growth in Z-plane. This would also help if you are wanting to grow taller plants.

I have a design for a vertical plug-in module that drops down below the top of the canopy. The problem is with cooling. Heat sinks block too much light, plus they are dissipating heat onto the plants.
My design low profile water cooled module, where I am mounting emitters right onto a piece of U bent copper tubing about 6 inch long. I have only built one and it seems to do okay. I don't know how ganging up mulitple units will work.

Heat from a heatsink shouldnt be any problem for plants. All thermal issues of LED arrays are about themselves perfomance and duration, not about plants. If you design well the system, the heatsink shouldnt be over 40ºC. A max, you should feel it slightly warm at the touch. That temp wont be any problem for plants (its similar to T12 fluorescents walls temperature).

Heatsinks on side walls shouldnt block any large amount of light either. But intracanopy, light losses may be noticeable, i agree with that.

I think there are two ways to fighting it. By using low power densities arrays intracanopy, able to be mounted on flat heatsinks, flat white painted (i use a highly reflective DIY mix, by adding barite to latex paint).

Or by mounting the leds on tubes (preferably, at least with some flat area, or directly squared) and aircooling them.

NASA intracanopy modules used this last option: each module has its own driver on a edge with a fan sucking thought a tube where LEDs are mounted.


Another issue is that you would have to reduce top lighting in order to keep within your watts/sq. ft. parameter. So the question that needs to be answered is "where will a watt of LED power need to be positioned to get the best results?" On the top?, On the side? or a combo?

Yep, this question is very important. I believe nobody along the Mj forums has studied this topic. And not only about LED lighting, but for any type of side lighting.

On the group buy im doing on a local forum, most people is going to use side and/or intracanopy lighting (mostly, side because cabs are small, mostly microgrow areas).

The initial rule of thumb we are using to size LED modules is to use 300uE/m2 from top and 180uE/m2 for lower areas. We think that each module should cover one cubic feet.

So we put 27uE for each upper cubic feet, so the distance covered for each LED module is about 1ft. And 16 uE on each bottom cubic feet.

But as the system is modular, at any moment each grower may change the configuration and put more or less power to up or sides.

We expect that we may learn the best power distributions from this experience, as there are 20 growers participating.

The initial rule of thumb has been extracted from the light distribution of a 400W HPS in 1 sq meter (about 11 sqft) for plants 75cm tall (2 1/2 ft). But translating some more light to bottom areas than the HPS does, and less directly on top (about 25%), so keeping light density way more even, and just about 60% higher on the top of the plants than on the bottom.

I hope that the experience of 20 growers using different styles of growing allows us to learn fast the best way of distributing light along the 3 dimensions of a grow.

[redline]

I have decided to reduce module wattage to under 10 watts down from 13 to 15, driving at 350ma (max.400ma) I will have to add 4 more modules to compensate.
This will give me better top coverage, longer LED life and easier to regulate with a resistor. Of course I give up some brightness that would help with penetration.

My LED selection is based on what I have on hand, instead of what is truely optimal.
Each module will have
4 red K2s, R (second) bin.
1 k2 royal blue, Q (top) bin
1 SSC cool white, top bin
1 SSC blue, top bin.
Resistor to drop 1 to 2 volt.
I plan on using this for vegging to replace a 350 watt CFL array.
I will be playing around trying to flower. I will be adding a couple additional 2.5 foot long strips of red and far red LED during the budding period only.

I don't have high hopes for the budding and don't think it will replace HPS, but I would really like to trash the vegging CFLs and save a couple hundred watts if possible.
Do you guys think the LED color selection is close to optimal for vegging? I might be able to squeeze an extra red LED in, if real Vf's are lower then spec sheet.
I would like to start wiring LED modules this week.

[redline]

Once I get things going and have unit in operation, I will probably replace resistors with regulator. I will look for one with a lower drop out voltage. With LM317s they use a much power as an LED. I hate to give up that much wasted power.

I did decide not to initially go with fans on top of each module, but instead will be blowing air across the tops of the heat sinks. Fins will be aligned in direction of air flow.

[billyjojimbob11]

It looks like warm white and farred are providing the mechanics that are needed in early and efficient flowering within cannabis and most likely many short day flowering plants.

2 Warm white (3000k) led with red x6 630 and red 660 x 10 and farred 730 x1, blue 455 x1, blue 470 x1 with 25deg lenses on the reds and 40deg lenses on the blue are giving the results that all are after. If I could only find a good 440nm blue to replace the 455!
If cree would make a 660 and 440 :-(.

The lenses are making a huge difference. even though you loose roughly 12-15% of the lux, the luminous intensity is focused much more efficiently with little or no light scatter. :thumbsup:

I have not been able to try results of near UV {400-425nm}
Thats next. W00T!

Billyjo :pimp:

[Weezard]

It looks like warm white and farred are providing the mechanics that are needed in early and efficient flowering within cannabis and most likely many short day flowering plants.

2 Warm white (3000k) led with red x6 630 and red 660 x 10 and farred 730 x1, blue 455 x1, blue 470 x1 with 25deg lenses on the reds and 40deg lenses on the blue are giving the results that all are after. If I could only find a good 440nm blue to replace the 455!
If cree would make a 660 and 440 :-(.

The lenses are making a huge difference. even though you lose roughly 12-15% of the lux, the luminous intensity is focused much more efficiently with little or no light scatter. :thumbsup:

I have not been able to try results of near UV {400-425nm}
Thats next. W00T!

Billyjo :pimp:
:postgood:


Aloha BJJB

I'm sold on lenses.
They give me penetration I wanted,
and the lensed 5 watters are outperforming the un-lensed w/reflectors almost 2:1
IMO, 160 degree/lambertian is a waste of watts.

ciao,
Weezard

[Crunchypants]

Weezard, I'm planning to homebrew a version of your 4+1 x 15w. light. :thumbsup:Looks like the Ledengin LED's have a 90-110 degree beam, though. Would you recommend additional optics or did the 15's work okay for you unmodified?

Also, MPJA has a 28v. / 5.5A power supply (the 24v. is out of stock for awhile). I was thinking getting one to power 2 parallel legs of (2) 15w. 660's, with an LM317 on each leg. Am I just making extra work for myself by not running a 24v. supply into a single LM317 and parallelling (4) 660's off the 317? Seemed like a bit of current to push through a single 317, but I don't really know.

I would like to underdrive the LED's slightly, and have some extra headroom in the build. Thanks!

[Weezard]

Weezard, I'm planning to homebrew a version of your 4+1 x 15w. light. :thumbsup:Looks like the Ledengin LED's have a 90-110 degree beam, though. Would you recommend additional optics or did the 15's work okay for you unmodified?

Mine are mounted in a deep aluminum cake pan which serves as a reflector.
Didn't find lenses for the ledengins but the 5Watt leds that I lensed are clearly better than the same configuration without the lenses.
Would call it proof if the red leds were identical.
The lensed set is 660nm., the un-lensed are 625nm.
Perhaps the difference in efficiency compensates.
Ah dunno.
I just ordered more lenses.
Will install them on the 625nm lamp and start taking pictures
of the progress.
If you find, say, 40 degree lenses that fit the 15W ledengin lens, please drop me a line.

Also, MPJA has a 28v. / 5.5A power supply (the 24v. is out of stock for awhile). I was thinking getting one to power 2 parallel legs of (2) 15w. 660's, with an LM317 on each leg. Am I just making extra work for myself by not running a 24v. supply into a single LM317 and parallelling (4) 660's off the 317? Seemed like a bit of current to push through a single 317, but I don't really know.

LM317 has a absolute maximum of 1.5A!
You might want to use an LM138 - 338 instead.

Driving an approximately. 12V led from a 28V supply will work well if you run the 2 parallel sets in series.
That will give you 4V headroom but would have to pass 2.1A.
That would require a pass transistor, etc.

So the LM138 series with a max of 5A. would probably serve better for ease of design.
Google the LM138 series for a quick and easy schematic.

The problem then is the blue led which uses closer to 15V, for peak efficiency.
I use 2 separate supplies because dissapating "excess" energy just rubs me the wrong way
My next ledengin lamp will have 2 Blues.
The goal here is to waste as little power as possible in the regulator.

I would like to underdrive the LED's slightly, and have some extra headroom in the build. Thanks!

Good idea!
I limit mine and use a thermal switch in series with the fan to keep everything under 50C.
Better Photons:Watts = less waste heat to deal with as well.

Easy lamp to build and it will work for flowering.
Mine covers app. 2 sq ft. and takes 2 or 3 weeks longer, start to finish, than HPS.
But the quality?
Wicked good!:stoned:

Let me know if I can help.

Aloha,
Weezard

[Crunchypants]

Google the LM138 series for a quick and easy schematic.


Okay, glad I asked.


The problem then is the blue led which uses closer to 15V, for peak efficiency.
I use 2 separate supplies because dissapating "excess" energy just rubs me the wrong way
My next ledengin lamp will have 2 Blues.
The goal here is to waste as little power as possible in the regulator.


Yes, I think I've read everything you've offered on this board (and Steve F.'s as well) and had already planned using a 19.5v Dell PS for the blue(s) as you have mentioned. I am still deciding whether to add a second blue to my plan, or a warm white instead. I realize the white is a crippled blue, so to speak, but I might like the WW just so I can view my hobby better. Not so sure I need all the blue 2 x 15w. would provide. I have a Procyon and although it is probably the best thought-out compromise of ratios for overall use, it's a bit blue-heavy for mid-late flowering, IMO. (Works great as for transition into 12/12 from veg, though.)

Anyway, thanks. I have read a lot of posts, and of the many knowledgable folks contributing on this subject your explanations are by far the clearest to me.

[billyjojimbob11]

Yes, the lenses are far more efficient than without IMO. Also, the light is culminated which, from what I understand, makes absorbing the photons more efficient. I think lenses will be an absolute must when building a highly efficient array, unless the emitters use a very narrow angle already.

[nodestar]

I've been researching LED's for a couple of weeks now. Reading everything I can on the subject mostly from this forum but from others as well. This thread is the most comprehensive on the subject of what LED's (and their various qualities) to use and how to use them. Really good stuff.

But what I haven't been able to find is a clear picture of exactly how to build a proper, efficient, and effective LED lamp or strip or board or square. Whatever you would call it.

What I'm talking about is some instructions on how to put together your own LED grow light from parts easily available on the internet or your local Hardware/Electronics store. But I'm not asking for a beginner guide such as.

"Hook up a 12v power supply to your LED's with this resistor."

I want something that will actually work and work well.

If I had the option of requesting such a guide I would ask that it contain the following:

A guide where you actually build or explain how you would build a decent size array of high powered LED's such as the Cree LED's that would function in the real world of a grow room.

A brief explanation on Power Supplies and why you are using this particular Power Supply and which ones work best for LED's and why.( I realize this may depend on your setup and how large or small it is. But answering the question for the array you are building and then giving a small tidbit on what might work for smaller or larger LED's arrays would be helpful to everyone whatever kind of LED grow light they are trying to adapt to their current setup.)

An brief explanation on LED drivers and how to apply them to your LED grow light.

How to pulse LED's using cheap and easy to program micro chips such as the Picaxe Micro Controllers ( PICAXE (http://www.rev-ed.co.uk/picaxe/) ).

The best way to limit current without using a bunch of resistors that burn power and create heat. I've heard allot of technical names thrown around such as "transistors" and many others. And many good explanations and threads are out there on what these things are but not so many on how to apply them to your LED grow light.

How to put the Power Supplies, LED Drivers, and Micro Controllers all together to do advanced techniques such as the "Martian Method". Whereby you might have a string of Far Red LED's continue to pulse for a predetermined amount of time into your Dark Period or Lights out Period of your grow.

Touching on things such as Pulse Width and Variable Frequency(for different types of LED's)

How to string LED's together and a brief explanation on stringing LED's In Series and Parallel and how doing this affects the final results as well as the voltage/amperage/wattage/current and the pros and cons of each.

What to mount your LED's to. And how to string them together.( As in the actual material for connecting them.)

How to apply proper cooling methods such as mounting your LED's to cooling fins.

And anything else that would come up in the building of an LED grow light.


I realize that many of these questions have been answered before, some even in this thread but none of them have been put together in an easy to understand practical format that even beginners can start to grasp.


Now I'm not asking for everything to be handed to me on a silver platter.
I've personally started my quest for building a LED grow light by picking up some cheap LED's, a power supply and I even ordered a Picaxe micro controller to start playing around with. And I have no dout I might eventually figure it all out. But that will take quite some time and many people won't make it through the journey, choosing instead to give up on LED's and stick with HPS/MH or buying LED Lights such as the UFO or Pyrcon. Never being able to realize the benefits of building your own custom arrays and spectrum's in a way that fits your own grow room and style.

I believe even a small guide to building a basic LED grow lamp that covers all the material above would improve the communities understanding of LED's and bring LED's down to a level that everyone could get involved with. What could spring from this is more people using LED's and more and better styles and techniques being developed. With a large enough community behind building their own LED's group buys could be organized such as those going on at the Spanish forum that Knna is apart of. Making top notch LED's such as Cree more affordable for everyone. Even those looking into smaller projects.

If this is beyond the scope and discussion of this thread then I ask that someone create a new thread dedicated to showing people how to build LED's and answering questions they may have along the way.

Thanks for reading.

[Weezard]

" I ask that someone create a new thread dedicated to showing people how to build LED's and answering questions they may have along the way."

Aloha Nodestar

You might want to look at;
"Calling out to Weezard for led advice"
In the indoor lighting forum.
Sounds like it's just what you are looking for.:cool:

If not, tell us why.
We aim to please.
Regards,
Weeze

[nodestar]

Thank you for the reply Weezard. I've actually already read through that thread. And it is very informative. But it shares problems that almost all threads on the subject share. The information is to spread out(not huge but still problematic for beginners) and it's to complicated for beginners. For instance.


A sense resisror is so called because it hooks to the sense input of a regulator.

Here's how the LM317 CCR circuit works;

The lm317 is designed to be a variable voltage regulator
and it "wants to see" 1.25Vdc between the output pin and the ADJ/Sense pin. before it will begin regulating anything.
We take advantage of those facts for our current regulator.
We tie a restor to the output pin and draw the current to our load through that resistor.
If we run a wire from the load side of the resistor to the adjust pin, that pin will sense the voltage drop across the resistor.
So, ohm's law.
If we want a 1 ampere current limit, we use a resistor value that will drop 1.25V at 1 amp.
Once the adjust pin senses 1.25v.it regulates voltage to keep that voltage drop, and thus the current, constant.
1 A. X 1.25 V. = 1.25 W.
While a 2 watt resistor would suffice, a 5 or 10 watt resistor will run cooler and thus regulate tighter.
I had some 10 Watt, 1 ohm power resistors laying around so I thermal glued them to the heatsink.
Overkill? Perhaps,. But overkill is a good thing in this case .
Gives me about 1.2A. which is exactly what I wanted.
Seems to be the sweet spot in photons per watt.

What is this R2 you speak of?
The current limit configuration only requires one resistor.

And then you end with.


It's very simple.


Hehe. It probably is very simple in the context of building an LED Grow Light. But separated from allot of other facts and all out on it's own it's complicated to the beginner. Or at least it's complicated to me. I didn't understand most of it and what I did understand was just stand alone information. I don't know how to apply it properly.

That's why I think a full guide would be very helpful. I will reread that thread and try and digest some more information. Thank you for bringing it back up.

I will tread lightly on posting to much more about this subject in this thread unless you guys want to steer the discussion in that direction.

Thanks for the help.

[Weezard]

But, your point is well taken.
"That's why I think a full guide would be very helpful. I will reread that thread and try and digest some more information. Thank you for bringing it back up."
Reading it over, I have to agree.
Guess we were having too much fun.;):stoned:

I was talking directly to DH by request.

He's got skills and knows electronics so we were able to shortcut a lot of the basics.
Never occured to me that we were probably confusing some folks.

OK, I'm about to construct a new light.
Soon as I have my excrement gathered, I'll try to get organized and just do a straightforward fabrication.

Plenty of pictures.
No techie talk, :( unless asked.
Insert tab A into slot B sort of thing.
That what you're looking for?

Wait a minute, who am I kiddin'?:wtf:
There's no way I'm gonna suddenly get "organized".
That thread is about as lucid as I get.:jointsmile: Sorry.

Perhaps Dreadedhermie will volunteer to translate.
Or, re-render my ramblings into a more readable style.:)

We now return this thread to it's rightful owners.
Aloha,
Weeze

[DreadedHermie]

That thread is about as lucid as I get. Sorry.

Perhaps Dreadedhermie will volunteer to translate.
Or, re-render my ramblings into a more readable style.


I'll help however I can. :thumbsup:

I can't promise to keep a straight face any better than Weezard, though. :D

[McCheez]

Hey guys I've been researching this topic from an amateur's perspective.

I like all the info on this site it is amazing what a bunch of stoners can come up with when there's money to be made ;)

In regards to the color spectrum, specifically UVA vs UVB requirements, Click Here (http://ncr101.montana.edu/Light1994Conf/3_3_Hashimoto/Hashimoto%20text.htm)

I am very interested in Knna's quoted spectrum requirements. They do not appear to match the standard photosynthetic action spectrum. Any info on specific requirements for herb? Perfect led grow light thread was mentioned but I can't seem to find it...

Knna: can you tell me the exact LEDs you'd recommend currently given your spectrum suggestions? Price is not much of an object on initial purchase, but I want maximum efficiency.

Hurray! My first post!:rastasmoke:

[Weezard]

"Hurray! My first post!:rastasmoke: "

And a darn good one too!:D

Welcome.
Weeze

[McCheez]

Hey not to beat a dead horse, but why is the McCree spectrum different than this one? I searched for photosynthetic action spectrum. This is also the spectrum from my photosynthesis book. Kinda important when selecting LEDs...

[knna]

The spectrum action curve you have posted, and that you may find on most botanic books, is just a sum of the absortion of the different pigments present in the higher green plants.

But it notably differ from what is observed actually on live plants, that uses green way better than that, along with other differences.

There is some things that explain that difference:

-Pigments arnt distributed homogeneously along leaves, but stratified.

-They arnt present of the same relation, and almost never at the 1:1:1 (Chl a: Chl b: carotenoids) that is used to obtain the action curve. It varies with the tipe of light, for plant specie, light intensity that they receive on the long term...

-And the most important: absortion of lab's extracted pigment on solution is very different to absortion of those same pigment in vivo. The process is still very unkown, but the fact is same pigment molecule may absorb the better light of a given wavelenght depending of its orientation (into the leave) and depending to the protein its binded. For example, the central Chlorofill a molecules on the Photosynthetic Reaction Center have a max of 680nm (Photosystem II) and 700nm (Photosystem I), while its the same molecule. Max absorbance from 650 to 720nm of the same molecule has been reported.

So the action spectrum curve you posted is a virtual creation, from unrealistic lab's extractions, while McCree and Inada curves were obtained measuring the photosynthetic response of in vivo plants.

[McCheez]

Ok, so I've been researching action spectra and quantum yields of in vivo photosynthesis. I can't seem to find exactly what I'm searching for:

Is there a spectrum which indicates the maximum amount of each wavelength which can be absorbed in vivo?? Also I need to know the relative lumens/einsteins/intensity or whatever per meter squared so I have a rough idea not only of the appropriate spectrum to construct, but the irradiance necessary for each bit of plant...

I'm also capable of searching for academic papers if you've got any citations.

After this, I will find the most efficient LEDs in the proper amounts and wavelengths. Any choice picks?:angelsmiley:

[knna]

Good luck in the search, Im on it since 4 years ago.

There are many studies about it, but with limitations. The most known are those written by McCree and Inada, along the 70 and 80's of past century. You can fin the same curves for individual specias and strains of commercial crops in agronomic studies. Differences with the averaged curves are small, anyway.

But these studies all have three main limitations:

-They are measurements of usually sun growth plants performed under not saturating photosynthesis irradiances. Efficacy of each wavelenght has proven to be dependent of the irradiance level, specially on the long term, after plant's acclimatation.

-Plants adapt their photosynthetic systems to both the intensity (irradiance) and light's quality they receive, in order to do the best with it.

-All studies concentrate on the effect of isolated wavelenghts. But its different when plants receive all wavelenght at a time. There are sinergies between wavebands that modulate the response. The most known is the Emerson Effect, that is universal (related to the electron flow between photosystems), but there are many unkown ones that are specie especific. Each plant specie have somewhat different liking in their light's quality preferences.

Photosynthetic response is something that is not fixed at all. If there is something remarkable about plants is their adaptation ability in the way to use resources. And light is their main resource.

[McCheez]

:thumbsup:Thanks for all the help Knna, you really know what you're talking about!

I've downloaded all the McCree and Inada journal articles I could find. Here's what I learned:

Enhancement (Wavelength modulations such as the Emerson Effect) seems to only be about 7% different from the action spectrum.

McCree has some great data in the 1971 paper, "Action Spectrum, Absorptance and Quantum Yield of Photosynthesis in Crop Plants". On Page 206 species #13 is a tomato plant. From this you can see the quantum yield of 16 key wavelengths in vivo.

Also, according to McCree's article in Plant Physiology vol. 49(5) pg 704, the difference in photosynthesis between the action spectra taken from the sum of each individual wavelength and that of the white light combination was within +/- 7%.
I find this close enough, especially if the emmerson effect is accounted for. I believe this will be my starting point.

Now, the question of photosynthesis saturation must be explored. What are the maximums? I understand that this is a sliding scale, because of the variables of temperature, humidity, nutrients, soil moisture, and CO2 content in the air. What conditions are ideal here? Temp? CO2? Humidity? Given these ideal parameters, I can begin running experiments.:cool:

[knna]

You can find details of photosynthetic perfomance of cannabis at varying irradiance, temperature and CO2 levels in the study "Photosynthetic response of Cannabis sativa L. to variations in photosynthetic photon flux densities, temperature and CO2 conditions", by Suman Chandra, Hemant Lata, Ikhlas A. Khan and Mahmoud A. Elsohly. Its a very complete study, again with the limitation of studying responses on the short term, and not on after long term acclimatation.

The study reveals that cannabis can handle very efficiently up to 500-600 uE/m2 at ambient CO2, with optimal day temperature near 30ºC (but strongly dropping over it!), and the best range being 25-30ºC. There is no clear photoinhibition point, with photosynthesis still increasing (although little) at 1500 uE/m2 (not at low temps), so that point at optimal temps and ambient CO2 is over that figure

You must take into account than that 7% of margin error refers to white lights sources, broad band ones with limits on the saturation of a given waveband.

On the LED growing research, we are working with relative narrow wavebands strongly saturated, in the look for the highest photosynthesis but accomplishing the most positive sinergies, trying to achieve way highest photosynthetic efficacies than a white light can do.

We are actually getting very nice enhancements on the spectral efficacy (yield/mol of photons PAR) using this approach when refered to white light sources, of near 200%. So its possible to go way ahead. Its not exactly photosynthetic response, but how carbon efficiently fixation is used, that is related to more factors. But the difference is so huge that sure that a significant part is achieved by enhanced photosynthetic response.

A group of grower are performing experiments with standarized measurements in order to find the optimal spectrums (different according to irradiance used?) for cannabis. If you want to join us, you are welcome. Stadistical analysis of experiments may strongly fasten the research, so sharing our results benefits all.

[McCheez]

I was thinking about and experiment for photosynthetic spectral analysis for a given plant. Since some of the wavelengths are codependent, you could not just examine them one by one. You would need to have all of them on at once, and reduce the amount of just one until the O2 output of the plant decreased. Then you would know you'd gone below the max. If you had the right equipment, this would be extremely simple. Though, you'd need an O2 meter to quantify photosynthesis, and you'd need exact amounts of light for every wavelength running simultaneously.

Do you have 200 lasers we could calibrate? :D



Maybe trial and error would be a better way to go...

[knna]

Hmmmm...but its a very good idea, at the end. Equipment that measures instant O2 flux from a leave is not so expensive....

It would be needed to use a dark period of 30min between each light quality, but using large steps, like 20% for each waveband, we may identify the bext mixes in a rough way and then work in fine tuning it.

Using the same irradiances of differnt SPD needs some work, but its doable. A single testing array with 1 or 2 LEDs of each color and current adjustement for each color is all we need.

I think its a very good idea. At least in order to identify the best photosynthetic respones. Long term (whole grow under a given quality and irradiance) would be still needed to study which matter at the end, the carbon fixation, morphology traits, to understand the final relation between light and yield. But it would be experimenting in far narrower settings.

[McCheez]

So, what's that gizmo that instantly measures O2 flux called? :wtf:

[knna]

CID Bio-Science, Inc.: Portable Photosynthesis, Plant Canopy, Root and Leaf Measurement and Analysis: CI-340 (http://www.cid-inc.com/ci-340.php)

Qubit Systems: Photosynthesis and Transpiration (http://www.qubitsystems.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=QS&Category_Code=PSB-01)

[McCheez]

:wtf: Only $4,000... Maybe I can barrow one. I'll see if my university has one. Might have to test tomatoes instead. that could be as close as I can get. Think it's similar? Would tomato results be remotely useful?

[ForgetClassC]

I wish I understood this.......:( I wanna build my own LED so badly:D

[mrmarbles]

Let me start off by saying... I appreciate the interesting reading and feel free to remove or bash this post at will, it's probably deserving.

By comparison, this question will be elementary at best, maybe even ridiculous, but since I know nothing about LED's I'm just gonna throw this out there.

Has anyone ever heard of, or is it even possible to use a large flat panel t.v. to grow marijuana? With the new LED and/or Laser t.v.'s I was just curious as to whether or not it's even possible. Is there similar technology involved that may potentially crossover?

I realize the cost, both initially and while in operation, would be impractical, among any number of other things, I just thought it would be interesting to try. I assume the major problem would be, that I'm confusing color with spectrum or lumens.? Hell, I don't know, you're the smart ones.

Anyone got $10,000 they can loan me for a test.

Peace

[knna]

Let me start off by saying... I appreciate the interesting reading and feel free to remove or bash this post at will, it's probably deserving.

By comparison, this question will be elementary at best, maybe even ridiculous, but since I know nothing about LED's I'm just gonna throw this out there.

Has anyone ever heard of, or is it even possible to use a large flat panel t.v. to grow marijuana? With the new LED and/or Laser t.v.'s I was just curious as to whether or not it's even possible. Is there similar technology involved that may potentially crossover?

I realize the cost, both initially and while in operation, would be impractical, among any number of other things, I just thought it would be interesting to try. I assume the major problem would be, that I'm confusing color with spectrum or lumens.? Hell, I don't know, you're the smart ones.

Anyone got $10,000 they can loan me for a test.

Peace

There are LEDs designed to be viewed, and LEDs designed to give light.

Of course those designed to be viewed gives light too, but its way less than required for plant's growing. Plants requires a lot of light, and the only practical way to give it with LEDs is using high power ones.

Think that HID growers uses in 1 sq meter (11 sq ft) what streetlights uses for 50X times that area. That is a lot of light.

[ForgetClassC]

I was walking next to a po-po car the other day and was thinking that its lights would be awesome to grow with. The new LED ones are the 7mm(i think, they are def big) and they are bright as balls, I bet you could get some sort of harvst from using popo lights. Just another thought triggered by the post above.

[McCheez]

hmmm... red and blue... Cop lights might work...

Let's get some Maui Wowie and try it. We could call it Hawaii 5-0!!!:rastasmoke:

[Bubbleblower]

A group of grower are performing experiments with standarized measurements in order to find the optimal spectrums (different according to irradiance used?) for cannabis. If you want to join us, you are welcome. Stadistical analysis of experiments may strongly fasten the research, so sharing our results benefits all.

Hey knna, I'd like to join you and may be I can interest others also.

I only heard the clock tick and don't know what time it is ;), but I have some ideas on how measurements should be taken and better spectrums can be found that I would like to discuss.

[knna]

Hi, Bubbleblower ,

glad to find people interested.

Light measurement is the most complicated part without expensive equipment. What I do is calculate how many micromols of photons equals to a given number of lm for a given spectrum. I obtain the spectrum of LEDs used using an spectroscope, a camera and some sofware.

Having the amount of uE emitted, at least we can know the average light density in the grow. In order to obtain irradiance data, I use the same procedure than to calculate the absolute uE, so it leads to have a correction factor between uE and lux (measured with a light meter). Only problem is only works for each separated spectrum, so I need to do a measurement for each color used and then add up all them. I use a grid to build a irradiance map for a given distance from lamps.

Consuption of LEDs alone and full system is measured using a voltmeter and amperimeter.

About yields, I suggest to record as many info as possible. Both fresh and dry weight, and unprocessed yield and manicured one. I suggested to weight all the plant weigth (without roots) is fresh, later manicure and weight stems and manicure's rest (better if separately). After drying, report the bud's dry weight and stems and manicure's rest dry weight. I know its too much work weighting, but I think its necessary to eliminate the large differences induced by how each grower process its yield. With such data for each grower, at least for one time, it would be possible to normalize weight reports in a meanglifull way.

Im really interested on any suggestion on how to standarize measurements.

[Bubbleblower]

Im really interested on any suggestion on how to standarize measurements.

I know so little that I have many.

To find better spectrums and PPFD levels of course we need photons per nm.
Some use SPD's to convert and others spectrometers to measure the irradiance and they get a -normalized- spectrum, the amount of photons per nm and total irradiance per m2 or so.

But one bulb could give its energy per cm2 on 10 times more surface than another so the sweetspot should be taken into account..
Also the normalized spectrum would be very inaccurate, because different wavelengths loose their energy in a different pace. That effect is big.
So spectrums change depending on the distance from the bulb and we are not really giving the spectrum we think or the amount of photons.

May be we can use 3-dimensional top down measurements and normalize the spectrum once more for every wavelength/distance from the bulb.
That will give a better indication of the real amount of photons and give us like an average spectrum.
We could take measurements with 10cm increments horizontal and vertical.

[knna]

Yeah, thats why I say to calculate both the "theoretical" average irradiance, meaning the absolute photon emission divided by the surface area of the grow (footage) and or/ volume area.

And aditionaly take measurements using a standard light meter (a 20-30$ one) and convert it to photons/m2 using an Excel sheet. This is a true, actual measurement of the light reaching leaves (the main measurement is taken at top of canopy level).

There is no differential absortion of different wavelenghts in air (when talking about 1, 2 or 3 meters as most, and mostly distance is way below 1m). Another thing is how light quality changes below canopy due the differential transmision of leaves, but I always claim to use undercanopy lighting as the most efficient one, that apart of it, largely avoids this problem. So irradiance measurement using LEDs is usefull both at top canopy and undercanopy.

It would be nice people has spectrometer or spectrorradiometers, but I wouldnt expect it. Its necessary to find ways of measurent that any grower interested may do it if he has the will, having a limited equiptment, as a standard light meter. My purpose is to build a database of the spectrums of LEDs most used, so all people has to do is measure with a light meter and then convert lux or fc into uE/m2.

[Bubbleblower]

Yeah, thats why I say to calculate both the "theoretical" average irradiance, meaning the absolute photon emission divided by the surface area of the grow (footage) and or/ volume area
And aditionaly take measurements using a standard light meter (a 20-30$ one) and convert it to photons/m2 using an Excel sheet. This is a true, actual measurement of the light reaching leaves .

That should give very interesting -and surprising- results.


There is no differential absortion of different wavelenghts in air (when talking about 1, 2 or 3 meters as most, and mostly distance is way below 1m). .

May be I put it wrong. I noticed for example a much bigger difference in mW/m2 output relative to distance (below 1 meter) in UVB as in longer wavelengths. Also I saw this graph on page 7 (http://www.vsl.nl/files/The_LED_Facts.pdf) which is very interesting.



Another thing is how light quality changes below canopy due the differential transmision of leaves, but I always claim to use undercanopy lighting as the most efficient one, that apart of it, largely avoids this problem.

I like the idea of intra/under canopy lighting a lot, it was next on my list.
Since no more than 15% (?) of the light penetrates through the canopy this should boost yield per m2 (I obviously like m3 better:)) and only little light is needed to get significant results.



Its necessary to find ways of measurent that any grower interested may do it if he has the will, having a limited equiptment, as a standard light meter.

Lux at certain distances from the bulb, both horizontal and vertical would be easy. I think many people are willing to take these measurements if they understand why that is important and how these data will be used. Everybody -on forums like these- should know where they can find and send this information.
We should get them with the program.
I will ask in a few forums that have thousands of growreports and do many tests.

Let me go further down my list.
Just check this pic and you understand the potential implications for cannabis.

[knna]

May be I put it wrong. I noticed for example a much bigger difference in mW/m2 output relative to distance (below 1 meter) in UVB as in longer wavelengths. Also I saw this graph on page 7 which is very interesting.

Very useful article, thanks.

But that graph refers to how angle of viewing affect the spectrum. And its not related to how light transmit, but to the LED source itself. This difference is caused in white LEDs by how the phosphor layer is added. LED manufacturers had improved it strongly on the last years, but is imperfect yet.

Standard LEDs dont emit almost any UV, and less specifically UVB.


I like the idea of intra/under canopy lighting a lot, it was next on my list.
Since no more than 15% (?) of the light penetrates through the canopy this should boost yield per m2 (I obviously like m3 better) and only little light is needed to get significant results.

Purdue University is working hard on this, and in general all researchers involved on the development of grow areas for NASA missions.

Planophills plant's species strongly benefit for intracanopy lighting. Average improvement in yield is being 35% for the same amount of light used, but some species has increased it by 100%, doubling yield with same amount of light.

Percentages of IC lighting generally varies from 25 to 50% of the total light.

Due undercanopy areas are mostly underlit, and many times severely underlit, very little light (compared to the amounts of light used overcanopy) transform lower leaves from sinks to sources of energy and resources. Bottom leaves arnt discarted, as happen when there is only top lighting, due the arey are a ballast for the plant. This mean undercanopy lighting achieve a way better use of plants resources and allows to use optimal irradiances for all the leaves of the plant, strongly improving photosynthetic efficacy.

We are getting excelent bottom buds using very low irradiances undercanopy, below half of used overcanopy (on uE/cubic feet basis).

I believe Ive linked it before, but check here (http://www.gardenscure.com/420/lighting/117933-bulb-analyzer-tool-actualized.html#post1132481) the Excel spreadsheet

[Bubbleblower]

Very useful article, thanks.

But that graph refers to how angle of viewing affect the spectrum. And its not related to how light transmit, but to the LED source itself.

Unfortunately there is a lot I don't understand correctly, also because I got much disinformation. May be I did something wrong, I compared a light-distance chart of 5 HPS bulbs with measurements of UV output from 8 other lamps.
uW/m2 was -relatively- lost faster than foot-candles. The graph seemed to confirm what I read in all the why plants are green articles.


Standard LEDs dont emit almost any UV, and less specifically UVB.

For my UVB I use Philips medical grade UVB broadband (http://www.prismaecat.lighting.philips.com/FredhopperPDFWebServiceInter/docts/3dd577cf-4b02-49b7-86ce-d3990bd0a871/TL_40W_12_RS_SLV.pdf). It seems somehow the most "extreme" wavelengths within extended PAR are most important to the plant.


Planophills plant's species strongly benefit for intracanopy lighting. Average improvement in yield is being 35% for the same amount of light used, but some species has increased it by 100%, doubling yield with same amount of light. Percentages of IC lighting generally varies from 25 to 50% of the total light.
Due undercanopy areas are mostly underlit, and many times severely underlit, very little light (compared to the amounts of light used overcanopy) transform lower leaves from sinks to sources of energy and resources. Bottom leaves arnt discarted, as happen when there is only top lighting, due the arey are a ballast for the plant. This mean undercanopy lighting achieve a way better use of plants resources and allows to use optimal irradiances for all the leaves of the plant, strongly improving photosynthetic efficacy.

We are getting excelent bottom buds using very low irradiances undercanopy, below half of used overcanopy (on uE/cubic feet basis).

Great. So what I need for my room is at least 8 rings of about 25 watt of leds in the correct combination.
It is for 1.4m2 where I have 2 induction -electrodeless- lamps of 300 watt* plus the 2 x 40 watt UVB (and 2 x 50 watt HPS but only as signaling light).
My idea is also to "finish" my spectrum with red leds most of all.



I believe Ive linked it before, but check here (http://www.gardenscure.com/420/lighting/117933-bulb-analyzer-tool-actualized.html#post1132481) the Excel spreadsheet

Darn, homework :thumbsup:

* Here is a testreport of the 6500K version of it with an accurate SPD. I should still get this for my 2700K.

[Bubbleblower]

I believe Ive linked it before, but check here (http://www.gardenscure.com/420/lighting/117933-bulb-analyzer-tool-actualized.html#post1132481) the Excel spreadsheet

Mmm, I still don't get the privilege to access that page, do you have it somewhere else?

[oldmac]

Hey Bubbleblower,

Just saw the spectrum graph you got there, I would like to point out to you to be very carefull, it may or maynot be accurate. The chinese have a tendency to lift spectrum graphs from american companies, and thier diodes don't actually meet those graphs.

The first large DIY LED light I built was going to be based on reds and white LEDs, since the whites (I had looked at) had plenty of blue spike (driving the phosphor) and then covered green, yellow and some orange/red. When finished the light sucked, it lacked the needed blue. I took a white diode sent it to someone to spectrographed it's output was a lot different. The blue spike was there but way to the left missing the needed wavelenght. The rest never reached orange/red. After looking around I found an identical spectorgraph, like the one they sent me, for a luxeon white. I have not trusted the chinese since, I thought they would saved me money but in the long run a costly lesson.

[knna]

BB, I dont know how old is the version, but you can find it here (http://www.cannabiscafe.net/foros/showthread.php?t=103423). Its my local forum (spanish). But I believe you can download the sheet without being registered there. Not sure actually. I uploaded it to Rapidshare some ago, but I lost the URL.

On the same forum, there is a subforum dedicated to LED growing with many journals, if you are interested (at least on pics, if you dont understand spanish).

That tone /12 of Phillips is the best UVB Ive seen, but unfortunatelly I dont find it here. Its listed on Phillips website, but no any distributor carry it :(

Thank you for that test report, its very complete. I think its pretty accurate, due it seems to have being performed using a good spectrorradiometer, as it not only states photometric values on a very complete way, but radiometric ones.

Not all days I have the possibility of checking the accuracy of my sheet, so I digitalized that induction lamp SPD and introduced the measured lm output of the report , 23881.5lm.

The sheet reported 81,940 Watts of output 380-780nm, while the report says 80894. Its less than 1.3% of error, which I think is excelent when data comes from a graph.

That spectrum contain 14.1 uE (PAR) on each 1000lm (or lux). So you can know the irradiance from it just multiplying by 14.1 the reading of your lightmeter (in lux) and dividing by 1000.

Now you just need to do the same with your LED's spectrum.

[Bubbleblower]

That tone /12 of Phillips is the best UVB Ive seen, but unfortunatelly I dont find it here. Its listed on Phillips website, but no any distributor carry it :(

You can order them here (http://www.spezilamp.de/lampen-fuer-medizin-lichttherapie-c-210_213.html?language=en&sort=2a&osCsid=4h3dtrmm653bpct0fur1v6ipc3). Shipping to Spain is â?¬ 17,44.
Here is a normalized spectrum of the lamp compared with 4 other UV sources.
UVB-leds (http://www.roithner-laser.com/LED_UV_SEOUL.htm) are still VERY expensive unfortunately.