Are LEDs Misunderstood?

[secondtry]

The other topic I would like to discuss is the average PPFD to use on a grow.

Based on same studies, secondtry and me think different. He thinks 1500 uE/m2 is optimal, as MJ continues increasing photosynthesis up to that. Indeed, MJ does well close to 30ºC up to 2000uE.

I don't suggest that high, over ~1,600 PPFD causes "photoinhibition", and lower intercellular Co2. That high irradiance (i.e., 2000 PPFD) will cause the plant to have "midday depression" and low stomatal conductance. I suggest at least 1,000 PPFD, and ideally 1,300-1,500 PPFD, but not over 1,500 PPFD according to the four studies on cannabis I was able to find.

also If a grower is looking for max production (g/m2) of a given grow area, I agree this would be the optimal, specially if there is CO2 enrichment.

Me too, up to about 1,500 PPFD.

On the opposite, me, as a grower, Im more interested on the productivity of the light (g/W). As irradiance increases over 400uE/m2 or so, light productivity starts to drops.

What do you mean by "productivity"? Do you mean by energy, i.e., 400 PPFD is a lower electric bill? If so I agree, but I for one want the biggest yield, not the best energy use efficiency; I don't mind spending an extra $50 a month on electric bill for great increased yield, Pn, WUE (Water Use Efficiency), etc.

Notice that average PPFD is a concept very different to actual PPFD. While PPFD is a measured figure only valid for the conditions and situation of the point where the measurement were performed, average PPFD is calculated by dividing the PPF by the area to be grown.

PPFD is measured by the meter^2 per second, net PPFD is the total PPFD over a day, which is called the "daily light integral" (DLI). That is why one can offer high PPFD (e.g., > 1,000 PPFD) and still keep the DLI low enough to prevent photoinhibition by using an hour of dark, or simply dimming the lamp for a bit. However, if one keep PPFD around 1,300 all day the DLI will not cause photoinhibition and the associated ills like midday depression, etc.

Here is dietoring for find the Its just a reference for configuring setups, to know how much light we need to install depending on our priorities. In general, growers looking the best light productivity uses about half light that growers looking for max production of grow area, for any type of light.

I agree, those who want to spend less on the monthly electric bill will use lower PPFD while also lowering their yield. But a grower who wants max yield and doesn’t care about the electric bill will use at least >1,000 PPFD all day for a high DLI.

For example, HPS growers looking for max light productivity uses about 40-50W/ sq ft, and growers looking for max total production uses 75-100W/ sq ft. For reference, that means than on a 10 sq ft area ( al ittle less than 1 sq meter), a grower using a 400W HPS looking for max light productivity is aiming an average PPFD of 500uE/m2, while one looking for max production uses a 600W (825uE/m2) up to a 1000W (1300 uE/m2).

I’m curious where you got hose PPFD figures, are they just examples or are the from a quantum sensor? I only ask because they look accurate and I have yet to find studies or data showing the PPFD of HID lamps over 400w.

But saying that averages irradiances of 500uE don’t yield is simply false.

I didn’t' say that, all I ever wrote was ideal Pn and yield comes from high irradiance, I always agreed lower irradiance can grow plants, but it won't grow ideal cannabis plants.

Many people uses that irradiances using HIDs. Taking into account than well designed LED lamps offer better spectral productivity (P/mol photons or g/mol photons) and distribute light way more homogeneously (PPFD measured along the grow have way lower differences that those measured on any HID grow), 500uE/m2 is an excellent average. Indeed, I know many people using 300-400uE/m2 in average with excellent results (getting over 2g/W).

I agree that "productive" (i.e., electric bill) is better with lower irradiance; and I also agree LED arrays offer a more homogenous irradiant footprint, but that footprint is small. To insure HID offers very high homogenous irradiance footprint I use a light mover; that makes HID irradiance footprint very high in terms of homogeneity; that and an HID grower needs to buy the best reflector they can. I plan to design my own reflector, which is the best way as one can design it around a specific lamp which will greatly limit "re-strike" of photons and max the PPFD and homogeneity of the irradiance footprint.

Notice than an average 500 uE/m2 may obtain PPFD in excess of 1000uE/m2 on the upper canopy below the lamp. Way higher when using single point light sources (HID), that need to keep at some distance of canopy to avoid light bleaching due excessive irradiance, that means PPFD over 2500uE/m2.

I don’t' quite understand what you are wrote above. How can 500 PPFD (umol/m^2/s) equal 1,000 PPFD? Do you mean the "incident PPFD" (aka "PPFD-I") of the "whole canopy"? If so HID with high green photons is best (like Hortilux Blue) because green photons best penetrate into the lower canopy bouncing off of leafs until they are absorbed. For example, I will use the Hortilux Blue 1000w HID with a PPFD of at least 1,000 which will offer VERY high lower canopy PPFD due to the green photons, and the PPFD-I will also be very high. You can find PPFD-I by finding the leaf angle and total leaf mass/density. Using PPFD-I is like 3-D while using PPFD is like using 2-D. Here is a great paper on this topic: http://www.plant.uoguelph.ca/courses/pbio-3110/documents/Lec11.pdf


Thanks for the good talk!

 

[secondtry]

Oh yea knna,

You used to write about an hour of dark to replenish active rubisco (RuBP), but that doesn't help turn inactive RuBP into active RuBP; to make active RuBP we need lots of "rubisco activase". To keep RuBP activase high we need to keep temp below ~89'F and CO2 must stay below about 1,200 ppm; high CO2 levels lower RuBP activase and thus lowers the conversion of inactive RuBP into active RuBP which in turn lower the Pn and Pnnet (daily net rate of photosynthesis). I remember you wrote you were not sure if the hour of dark helped RuBP and it doesn’t. I thought you might like to know that. I for one use your suggestion of an hour of dark to lower the DLI (daily light integral) which makes sure my plants will not have "midday depression" so Pn stays very high all day

Ideal Co2 ppm for cannabis (and most all other hihger plants) is ~700-1,000 ppm.

In that other thread I linked to I offer lots on info on RuBP and how to control it, also lots of info on VPD (Vapor Pressure Deficit) which is very critical to growing plants with high Pn and in high CO2 environments.

HTH and I am very happy to see you here!!!

 

[FreezerBoy]

Share personal info at your peril. Better yet, just say NO! We like to think we're brothers in arms but the truth is we're strangers. Do you want your personal safety in the hands of strangers?

 

[Cali_Boss]

ive read this whole thread and found that it wasnt helpful at all. can someone with experience comparing LED lighting to HID chime in with some information?

secondtry, i understand that you know a lot about how these lights work, but until you can show me some grows you've done with LED compared to your HID your creaming your pants over, then i dont find it very credible. data is far different than experimental results.

theres this thread: https://www.icmag.com/ic/showthread.php?p=3204389#post3204389

which sounds great, but results arent done yet. has anyone else done any similar experiments?

i think the battle here is whether HID or LED increase yield, which seems to me to be neck and neck from the LED grows ive researched vs HID grows. but does anyone have any information on how it smokes? different light waves as well as penetration affect buds differently. flowers take in numerous different types of chlorophil (spelling?) and these affect the buds. from what i read LED does great with indica strains, how does it fare with Sativa or Hybrid strains. i know Sativa's react positively to CFL whereas Indica perfer other methods. these are the kinds of questions we should be answering...

i cannot use HID with my set up so im determining if i want to do an all CFL/blue compact grow or add an expensive LED light in there with it. would it be worth it for my hybrid and autoflowering (Sour 60) strains?

how does LED (red/flowering type light) compare with:
1. resin production
2. vegetation stage
3. compactness of buds
4. look/size of buds
5. taste/high of buds

and can you guys stop bickering? its dumb and youre making yourselves look like immature idiots. can we just grow some buds?

 

[Cali_Boss]

this is new technology so i understand that there is limited information on it and some people dont like these new technologies. but an unbias and informational approach would be helpful. thanks guys

 

[MeanBean]

ive read this whole thread and found that it wasn't helpful at all. can someone with experience comparing LED lighting to HID chime in with some information?

secondtry, i understand that you know a lot about how these lights work, but until you can show me some grows you've done with LED compared to your HID your creaming your pants over, then i don't find it very credible. data is far different than experimental results.

Sorry Bro Some are just just hear to proclaim thier data, and let us led users know what they think.

Thanks, I will keep you updated I won't post the results here

According to Secondtry, to get some of HIS real information you must log off this forum and go to his... What was the Dot com again?? just put a link in your sig..

 

[MeanBean]

Because I don't agree with you does not mean I have anything against science.

Please don't compare your collage of "data" with science in general and bounce it off my statement.

I know what you think, still you got nothing for me to see. I downloaded the "data" necessary to build a "time machine", just didn't build it yet.

BUT shame on you if you don't believe me, I have the data!

p.s. your not just lacking pics my friend

 

[FreezerBoy]

And another one bites the dust.

If you want to understand LEDs and what they can and cannot do, look to those with experience and avoid those with none.

Those with hands on experience include: Sleepy, Hazy, Verdant Green, Blazeoneup and others.

Those with NO experience include secondtry. You'll note there's no link. That's because secondtry has no experience with LEDs. He's never used them and only plans to in an agenda driven weighted test to prove they don't work on his own site where he'll brook no debate.

The choice is yours.

 

[JJScorpio]

What I find odd is now that you guys/gals see that knna and I apparently agree on everything, except PPF vs PPFD, I would think everything I have been writing about would now be fully accepted...but it's not! ...

Now do you see why this thread got closed?

I could give a rats ass what you or anyone else has to say that has never used these lights. For every study you find saying one thing, I'll find one saying something else. So for the time being, I for one am going to pay attention to the ones that have used both LED and HID lights.

Stop ruining the threads talking your mumbo jumbo. If you have used LED's and HID's then post the pics and give your results. If you haven't then please do everyone a favor and stop trying to force your beliefs based on nothing but scientific articles down everyone's throats. It does nothing but ruin good threads.

I'm going to reopen this thread.

 

[habeeb]

maybe you should just rent a spectroradiometer, and do some testing. I found a couple sites and the quote was $100 a week so...

I would rent one, but I'm sure I don't know how to run one / connect it to a PC.. I would buy one, but I'm just not willing to spend that type of money for something I know nothing about.

I think what people are getting at is, you can only talk so long. And I guess if you can't get a spectroradiometer yet, wait till you do and post some info we can all use.

I am very interested to see what you guys that know about led say about the units out. I think it will also push the sellers to conform to selling units that are best geared to plants, and not for money.. as stated, look around in even just renting one for a week so you can prove everyone what you know.

 

[ak-51]

data is far different than experimental results.

!? I don't think that statement makes sense. Experiments yield usable data, data comes from experiments. I'm not sure where else I would get reliable data. Controlled, scientific experiments and real-world hands-on experience are not mutually exclusive. Data can be culled from both, just in different ways. I would not discount all of the five-thousand charts and tests that secondtry cites, I would only question their practical application to our specific situation. Let me add... that I do not disagree with the rest of your post...

I don't think there is such a thing on earth as a non-power limited environment. Virtually all electrical components from extension cords to outlets to circuit breakers have a rated power limit. Non-power limited is the same as saying unlimited power, so unless you get your electricity (and unlimited amounts of it) 100% free then I think this is incredibly misleading and an unfair basis for comparison. Following this point to its logical end I must contend that there is ultimately a trade off between power cost and the product quality and quantity. If HPS produced 10% more but the operating cost was 95% more would it be worth it? No, unless you are living in a non-power limited environment, which I already stated doesn't exist.

I currently run one 318w LED fixture. I previously had a 400w HPS. Don't ask me too much about how they compare, I probably can't give you the answer that you deserve for two reasons: 1. I am a noob 2. There were substantial variables other than the light. The only thing I can tell you is that they SEEM to be AT LEAST equal on a watt-for-watt basis, I don't think I was handicapped by moving from the 400w HPS to the 318w LED. I know this is not what LED manufacturers advertise, I don't care. I would just go ahead and ignore any "600w equivalent" or "1000w equivalent" statements, I have seen no scientific basis for such statements so I just ignore them. While keeping my inexperience in mind I am inclined to say that if you expect the 318w that I have to replace a 1000w HPS you will probably be disappointed.

If I were living in a non-power limited environment I would probably still be running HPS. I would have by now upgraded to either 600 or 1000 watt HPS systems, I would have stuck another AC unit in the room here, and I would have a robust ventilation/exhaust system. The reason that this isn't happening is that I do actually have to pay for my electricity, outlets are only rated to handle a certain load, 2 AC's for one room would look strange, and my breakers are so weak it's as if a gentle summer breeze would trip them.

Different people have different situations, if I lived in an area that was perpetually cold then HPS would be more attractive to me since in the winter my old 400w simply kept the room warm. I think the biggest thing to think about when addressing any advantage that LED may pose for you is heat mitigation. The reduced size is another major plus for any micro-growers.

 

[habeeb]

I just looked on ebay, UFO's in there 7 generation? ( quad band ) for $144 shipped.

seems like a good deal to me. it has 70 red, 10 orange, 10 blue, and 10 white, bridgelux blue and whites used..

I'm not sure of a cheaper led light out there right now. also not sure on quality..

 

[knna]

Do you see that PPFD is a relative measurement? It depends of a lot of things that arnt lamp related.

Each time you report PPFD for caracterizing of a lamp, you must note at what distance is was recorded, at what angle respect the lamp, how reflective are walls, how clean is the air....Its a no sense. Are you going to take 300 measurements for each plane to be analyzed? 300 measurements at 10cm, 300 at 20cm, and so on. And still if you do that, it wouldn't offer significant information about the lamp, but only of how you are using it.

I try with an analogy. If we were trying to say what car engine is better, what do you think that would be better: horsepower that its able to give, or a measurement of the speed of the car?

You are saying the speed of the car. People who knows of cars (not me) will say you that speed depend of a lot of things more than the engine. Aerodinamics of the car, and specially, transmision relation, among many other factors

You, as a driver, should use the transmision to control how the power that gives the engine translates to speed. You, as a grower, must control the height over plants you put the lamp to control the PPFD from the PPF that it emits. A Ferrari on second gear
may be slower than my citroen on 5th, and that dont mean engine of my car is better. Potentially, Ferrari one is able of much more.

Continuing with the analogy, growers are interested on the total photons (PPF) that a lamp is able to emit as drivers are interestd on the horsepower of the car. And in both cases, we are interested on the cost and manteinance, putting special attention to the consuption (in relation to perfomance). We look at PPF/Watts consumed as drivers look at HP/gal of gas.

For sure, drivers want to know what speed may reach the car, as we want to know how much a lamp may yield. But max speed depends on the road you drive (strain), the gear used (distance to plants and other factors of light distribution) and in general, of your driving skills. A driver with a car potentially slower may win a race against another driver with faster car, just because the first drive better.

How to translate the best a given PPF to local PPFDs is a matter of how you use a lamp, not a caracteristic of the lamp itself.

Saying this, good measurements (notice the plural) of PPFD should help a lot grower to use their lamp the best way possible. But definitively, PPFD as a parameter for caracterizing a lamps is a no sense.

PPFD is a measurement of the number of photons falling on a given unit area (that of the sensor used). If we want to know what a lamp can do, we want to know the total number of photons that it emits. Then depending of the grow area, we will put the lamp the best to get good PPFDs. You can decide if you want the total photons emitted spread on a larger or smaller area. The larger the area being lit, the lower the PPFD, because same amount of photons spreads along a larger area, thats all.

And please dont answer saying that PPFD is not homogeneous and that some areas will get more photons than other areas. It not invalidate the reasoning and BTW, one of the best (if not the main) advantages of LEDs is the possibility of getting the lower differences in PPFD from any amount of PPF. Huge differences in irradiance obtained from the massive amount of photons emitted is probably the main drawback of HID lamps (and the reason behind vertical grows get better yields per watt).

When we are designing a grow room, we use the average PPFD (PPF/surface area) in order to decide how much light to install. Its not a physical figure, but virtual, just a tool for growers.

About the productivity at different PPFDs. Curves plotting Photosynthesis-PPFD are typically formed by two parts. The first one, lineal or almost lineal that represent the called "light limited" part of the curve, and the second, that is a curve that progressively lose inclination until gets flat and finally decreases (since the photoinhibition point), called the "CO2 limited" part of the curve.

Cannabis curve is very typical in this sense. Thus, over the point of max slope of the curve, happening at about 400-500uE/m2 any upper irradiance is subjected to the decreasing productivity law: each aditional uE produces each time less increase on P, until its 0. The consecuence is you can increase total photosynthesis increasing irradiance (up a point), but P/uE is each time lower,meaning you are using light less efficiently.

This is the curve plotted on the article "Photosynthetic response of Cannabis sativa L. to variations in photosynthetic photon flux densities, temperature and CO2 conditions", where Ive painted how should be the curve if it were not CO2 limited and the light wasted:

On that graph you can see productivity of light decreases with ioncreasing irrradiance, thus if you look for max productivity of the light (g/uE), you should use as lower irradiance as possible in order to achieve effective budding. When I advice to use an average PPFD of 500uE/m2, its because I tested many strains and I noticed its enough. On the LED lab thread I linked some grows using lower average irradiances yet with excelent results. Check this one for reference: http://www.cannabiscafe.net/foros/showthread.php?t=143647&highlight=Lupanar BTW, MrX is a very experienced grower that is getting double yield per watt using LEDs than when he use HIDs (which still use). He was initially very skeptic about LEDs. There is another journal of him of a grow of same genetic under a 600W HPS.

My spectroradiometer is the Jaz, from ocean Optics too. I took it with fiber optic with cosine corrected probe. Im waiting the calibrating lamp for absolute irradiance measurements.

About my sheet to analyze lamps, I believe is the best you can get when you havent the equipment needed to do accurate measurements. Of course its as reliable as the data entered. Its obvious that it cant be too accurate when data are extracted from a graph. But surprisingly, I checked its results with manufacturers published data and margin error is mostly below 5%, although its not a guarantee, just a data for the small number of lamps that Ive been able to check.

If you refer the lack of accuracy not due the source data, but for how the sheet calculates, please tell me exactly where I can improve it.

 

[knna]

ive read this whole thread and found that it wasnt helpful at all. can someone with experience comparing LED lighting to HID chime in with some information?

secondtry, i understand that you know a lot about how these lights work, but until you can show me some grows you've done with LED compared to your HID your creaming your pants over, then i dont find it very credible. data is far different than experimental results.

theres this thread: https://www.icmag.com/ic/showthread.php?p=3204389#post3204389

which sounds great, but results arent done yet. has anyone else done any similar experiments?

i think the battle here is whether HID or LED increase yield, which seems to me to be neck and neck from the LED grows ive researched vs HID grows. but does anyone have any information on how it smokes? different light waves as well as penetration affect buds differently. flowers take in numerous different types of chlorophil (spelling?) and these affect the buds. from what i read LED does great with indica strains, how does it fare with Sativa or Hybrid strains. i know Sativa's react positively to CFL whereas Indica perfer other methods. these are the kinds of questions we should be answering...

i cannot use HID with my set up so im determining if i want to do an all CFL/blue compact grow or add an expensive LED light in there with it. would it be worth it for my hybrid and autoflowering (Sour 60) strains?

how does LED (red/flowering type light) compare with:
1. resin production
2. vegetation stage
3. compactness of buds
4. look/size of buds
5. taste/high of buds

and can you guys stop bickering? its dumb and youre making yourselves look like immature idiots. can we just grow some buds?

It would be unfair to generalize reaction to "LED" lighting, as there is many different spectrum emitted by LED lamps. On of the advantages of LED is you can build near a custom spectrum. But as actually nobody knows whats the best spectrum to grow cannabis, each lamp uses a different one.

For example, blue and red alone mixes proven to work fine for some strains, but others have huge problems to bud with it. Adding a little of white (or yellow) fixed the problem for most strains, but still some (typically very sativas) have problems. When we added some more white, no any strain gave the problem again.

Most grower that are using a lamp guided by me are using spectrums with 10-20% blue (400-500nm), 10-20% green-yellow (500-600nm) and 60-75% red (600-700nm). With respect to those spectrum, I can tell you that:

-1. resin production. At least as good as with HID. Generally, same strains under LEDs are more resinous.

2. vegetation stage. (We are using less red and more blue for this stage). Clearly better than any other type of lighting avalaible.We are getting excelent results using 1/3 of the watts used for other types of lighting. Growth is healthy and fast. Due we need less watts on veg, thus LED setups for veg are relatively cheap, currently I dont advice anyone to use anything else for vegging. A friend replaced his 400W HM for 120Wof LEDs and he is getting better results (faster growth and more branching,meaning more cuts) , apart of forget his severe temperature problems. When low growth rate is required, some guys are using so little power that is near ridiculous.

3. compactness of buds. It strongly depends of how much light you use (for a given genetic). Those using high irradiances are getting very compact buds,still more than they get with HID. In general, its similar or slightly less compact when growing with LEDs.

4. look/size of buds. Excelent, nothing to envy to any other lighting.again, its strongly dependent of the light density used (same as with HID, its not the same to use 35W/sq ft than 120W/sq ft).

5. taste/high of buds. Excelent, but some people notice differences, but without a trend of better/worse. Simply different, some people prefers it, some not. You will have to try for yourself

 

[dunkybones]

In response to the post's initial question, "Are LED's misunderstood?", and in light (no pun intended) of how this thread evolved, I would say it is decidedly so - LED's are misunderstood.

Don't believe all the hype, but don't believe all the slander either. Led's are a workable grow light, that come with their own sets of strengths and limitations. Will they bring down the same bank as a 1000w HPS? Prolly not. Are they complete garbage better suited to the tail lights of a Toyota? Certainly not.

I'd like to see an LED specific forum on this site, just like there is for coco. Let the LED growers show their stuff, and help each other out

 

[PetFlora]

I just looked on ebay, UFO's in there 7 generation? ( quad band ) for $144 shipped.

seems like a good deal to me. it has 70 red, 10 orange, 10 blue, and 10 white, bridgelux blue and whites used..

I'm not sure of a cheaper led light out there right now. also not sure on quality..

I purchased my UFO 90 from a US company ($370). One of the transformers blew- they replaced it. One also blew in the replacement- they replaced it. I doubt you would get that kind of support on E-Bay.

BUYER BEWARE

I have seen others on IC mention bad transformers, too. It seems there are a lot of either undersized or underspeced transformers being used in LED lights.

 

[Babbabud]

MrWags has documented a lot of good grows here on ICmag ... He gave his back ... thats enough for me

 

[renz]

Wow i get a job and am gone for a week and you guys 10 page thread about LEDs all over again...

Someone mentioned transformer in the UFO... anyway does anyone have information on current regulation methods in popular LED arrays?

For all this talk about HID power vs LED power, no one mentions drive methods on these things. I'm still not convinced some of these things just aren't off the shelf china contract manufacturer jobs with unregulated supplies and resistor current limiting.

Also, I'm as interested in LED vs LED grows with different spectrum as much as I am LED vs HID.

It might take a few years, but LED efficiency *will* continue to get better and people will learn more about optimum spectrum for different growth effects.

As far as the LEDs dont penetrate canopies argument...

Well, yeah duh, most people are using arrays with little LED emitters to use cheap cooling solutions and still get efficiency. Those little LEDs just don't go far. They are making multiple emitter LEDs -- if you wanted custom spectrum from a single point with ridiculous intensity, it not a problem, the technology is already sitting there. You just have to be willing to pay for a real cooling solution. High efficiency passive heatsinks are expensive.

 

[asde²]

But as actually nobody knows whats the best spectrum to grow cannabis

if you had checked my old account posts.. 200-340nm and 680-800nm ratios are unknown. 340-420 and 630-680nm is unsure but the main idea is very stable - im still after the old calculations because there came no new factors yet but in the end only practical tests can show! and me, nor anyone else without extreme buget can test it yet but having real numbers not just "use white" is a good start

 

[habeeb]

I purchased my UFO 90 from a US company ($370). One of the transformers blew- they replaced it. One also blew in the replacement- they replaced it. I doubt you would get that kind of support on E-Bay.

BUYER BEWARE

I have seen others on IC mention bad transformers, too. It seems there are a lot of either undersized or underspeced transformers being used in LED lights.

thanks for that info...

I guess I'm just gonna have to wait longer