Math behind

Rahz

Well-Known Member
Note that he incorrectly claims to have measured lumen and "µMoles" when in fact he measured lux and PPFD (µmol/s/m2)
That's what I was pointing out. There should be a formula based on the radiance pattern in the datasheets but it was happenstance that he measured at 19" as he admits. Without such a formula you would need to know the expected value to find the right height to take a measurement that would mimic the luminous flux/PPF.
 

Rahz

Well-Known Member
Good.

The LER is the calculated lm/W which you would get at 100% efficiency for that SPD. We can use this to get the efficiency percentage from the actual lm/W figure. For instance, 63lm/W would only be 63 / 209.2 = 30% efficient.
This is where he seems to be missing the difference between QER and output efficiency. A light source with a QER of 4.65 for instance at 30% efficient would provide an output of 1.395 umol/j.
 

NoFucks2Give

Well-Known Member
Learn to USE THE CORRECT SYMBOLS AND UNITS!
Why is it when I say µMole without the m²/s you jump down my throat. Yet no one uses the units after lm? Do anyone ever say lm/m² ? Or lm/m²/sr ? or lm / sr? No they don't they just say lm or lumen.

Oh!! Wait a second. That may be our failure to communicate. I never use moles/s. I never use moles/m². I only use µMole/m²/s.

I am only concerned about the photons the reach the leaf. Moles/s only is the amount of energy at the light source, not direction, and not area.

And when I'm referring to lumens I only mean lm/m²/sr as in luminance not luminous flux. Or maybe lm/m² as in Illuminance.

Luminance and Radiance are the only measurements that tells me how many photons are reaching the leaves at a specific distance and angle. That's PPFD. Nothing else matters when it comes to grow lights.

At the University when someone says µMole it is known that they mean µmol/m²/s, it just assumed everyone knows that.

When they ask me to build some 150 µMole fixtures for a grow chamber, I know they mean µmol/m²/s, but we all just say µMole. Like WTF else would it mean?

So what it comes down to is I cannot use your spreadsheet. What I need is, given this LED or this fixture, what current do use and how many LEDs do I need to get this many µMoles over a specific area. Moles/s? I couldn't use that for anything.

And I apologize for the 7.55 lm, I did not see that until you repeated it.

but what I meant by 1 µMole @ 660nm = 7.55 lm was 1 µmol/m²/s @ 660nm = 7.55 lm/m²/sr
 

Rahz

Well-Known Member
This isn't the first time this issue has came up, wanting to take direct spot measurements to quantify PPF. The benefit of using manufacturer data is that there is (hopefully) a level playing field, which can be validated using sphere measurements. Although the results aren't direct indicators of what is hitting the canopy they don't rely on meters being calibrated properly or other variables (height) that can be manipulated to someone's advantage. All other things being equal (optics) the radiometric efficiency and QER values are good numbers for comparing one source to another. They don't tell you exactly how much light will reach the canopy but they do tell you how much light will hit the canopy relative to another light source. They provide accurate output figures which would be further modified with efficiency figures for the optics being used.

As mentioned, it's possible to derive a formula based on the radiation pattern in the datasheets that should provide an absolute value with a spot measurement taken from any height directly under the source. That's the direction I would look if that's what you're trying to get at. How accurate a single formula would be across different sources would depend on how closely the radiations patterns matched.
 

CobKits

Well-Known Member
cob to cob radiation patterns are pretty similar. i can provide a lot of spot measurement that nofucks can comapre with datasheets to hopefully arrive at an empirical constant

the prob being that damn temp bug. cobs are almost never operated at the same temps used in the datasheets
 

NoFucks2Give

Well-Known Member
See this paper
Thanks. Did you make that screen shot? I have the same software and use it everyday. I never noticed it had that capability.

What is you do? You sound like you know what you're talking about.
This is a common misconception
Well I guess it's a common misconception because that is what is being taught.
Plant Physiology and Development is a well respected textbook. And expensive.
You saw their action curve here: http://6e.plantphys.net/topic07.01.html
http://6e.plantphys.net/topic07.01.html
When I said that about the reflected green it was not something I pulled out of my ass or read at some grow light vendor site.

What do you think of this (highlighted text)? Most green is not absorbed and reflected back in our eyes? I believed them.
greenLightAction.jpg
 

wietefras

Well-Known Member
Look at the McCree absorptance chart:

https://support.heliospectra.com/portal/helpcenter/articles/which-regions-of-the-electromagnetic-spectrum-do-plants-use-to-drive-photosynthesis

Indeed only 70% of green light is taken up by the plants. So the quoted text is technically correct.

Although the chart looks at the chlorophyll absorption and that's a completely different story. In reality it's not that bad. It's 70% and not 0%.

If you see the McCree action spectrum or RQE chart then it's clear that the plants also actually use the wavelengths which are not used by chlorophyll. That's because there are many more pigments than only chlorophyll and those also contribute to photosynthesis.

So yes, plants will look green because they reflect that color more than others, but green light is not completely useless as that text seems to suggest either.
 

NoFucks2Give

Well-Known Member
They don't tell you exactly how much light will reach the canopy but they do tell you how much light will hit the canopy relative to another light source. They provide accurate output figures which would be further modified with efficiency figures for the optics being used.
I digitize the radiation pattern characteristics, and use the angles to calculate the radiance over a specific area for multiple LEDs at their respective angles.

First I calculate each view angle and flatten out the numbers from the sphere to flat earth.
Then I simulate multiple heights and distances between LEDs to find the ideal height and spacing that will give me maximum uniformity. With no 10% loss to optics.

And what I was wanting to do is add the radiance so I know how many LEDs to use to get the desired radiance.
I buy a lot of LEDs to test them and add the measurements to my library. I was thinking this spreadsheet could save me from buying the LEDs and use the digitized numbers instead.

So all I want is what hits the canopy. I need just one number, the quantum radiance at 0°.

The spreadsheet is very impressive. I know what went into it. And how difficult it to get the information necessary to put it all together.

compareViewAngles.jpg


anglesMultiple.jpg
 

wietefras

Well-Known Member
Why is it when I say µMole without the m²/s you jump down my throat. Yet no one uses the units after lm? Do anyone ever say lm/m² ? Or lm/m²/sr ? or lm / sr? No they don't they just say lm or lumen.
Yes, because there is no need to put something behind lm when you are referring to lumen. Or lm/W if you are talking about luminous efficacy and indeed people do add the W for that.

You could say lm/m2, but most people use lux or lx. The other strings of symbols are outdated or irrelevant too and never used. So why would anyone use those if there are better options?

Unless you want to make a certain calculation more obvious. Like when I wrote J/s instead of W to show that you will lose the s or J in a calculation

Oh!! Wait a second. That may be our failure to communicate. I never use moles/s. I never use moles/m². I only use µMole/m²/s.
No, you say µMoles. Which is simply wrong. Then you get confused yourself about whether it's PPFD or PPF. When you measure lux on your spectrometer you call it lumen. When you measure PPFD you call it µMoles and subsequently confuse it for PPF etc etc.

It's not just a matter of typo, but of constant sloppiness and it's completely confusing even to yourself. Let alone us. We really have to guess what you mean. Rahz is still confused thinking alesh just happened to arrive at the correct number by chance, all because you used incorrect units and symbols.

At the University when someone says µMole it is known that they mean µmol/m²/s, it just assumed everyone knows that.
Absolutely and completely false. I actually went to university and they will kick you in the nuts if you make these mistakes. Especially if you make them on purpose.

Read any research paper and they will meticulously use the correct units and symbols everywhere.

Perhaps in some mom and pop greenhouse they try to act all cool and shorten the units, but then they would just use PPFD instead. Besides that's in speech. Not written text.
 

NoFucks2Give

Well-Known Member
it's clear that the plants also actually use the wavelengths which are not used by chlorophyll.
The textbook basically says that all wavelengths that are absorbed are equal. So the green that gets absorbed is used the same as red. The blue is used the same but it has to burn off the excess energy. And red emits some energy as florescence. in the high 600's

absorptionAndEmmisionSpectra.jpg
 

Rahz

Well-Known Member
Here are a couple absorption profiles. Green slightly less but still a high absorption rate. Absorbed by other photo receptors or converted to heat which is why there's a variance between the absorption rate and the photosynthetic rate.

Fig Sch 2.jpg
Rahz is still confused thinking alesh just happened to arrive at the correct number by chance, all because you used incorrect units and symbols.
I'm not confused, you misunderstand me. The spot measurement is what I was referring to and it just happened to be in the ballpark. That's why I said the result was happenstance, not that Alesh's numbers are correct by chance.
 

nfhiggs

Well-Known Member
What do you think of this (highlighted text)? Most green is not absorbed and reflected back in our eyes? I believed them
It wouldn't be the first text book to get something wrong. It is more correct to say that "more green light is reflected back" rather than "most".

I can't take credit for the screenshot - I found that here. SAG is very knowledgeable on the subject (of plant science), and pokes holes in more than one plant myth.

I am an electronics tech by profession - going on 35 years now.
 

NoFucks2Give

Well-Known Member
Absolutely and completely false.
When I said everyone knows what is meant by µMole that is in conversation. Like Dr. Coluhoun asked me for five 150 µMole fixtures he did not ask me for five 150 µMole per meter squared per seconds. When I write, I write in conversational mode as if I were talking. Now I understand why you were kicking me in the balls, shit runs down hill. And on the spectometer lux is express in lumens/m². So I just say lumens. I'm not that formal. And getting old is not easy. What my mind is telling my fingers to type does not work as well as it used to. Sometimes my fingers type a completely different word than what I am trying to type. On average I make 3 typos per sentence.
 
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NoFucks2Give

Well-Known Member
Guess you meant lux and µmol/s/m^2. Doesn't matter for the conversion, though.
I'm sorry, whenever I say µMole I mean µmol/m²/s. I type conversationally and casually. Lumens to me is lm/m²/sr, and lux is also lm/m²/sr, even though I know it is wrong. I use lux to mean luminous also. Same with everybody I work with when µMole is said it's assumed to be µmol/m²/s because we have no use for any µMoles other than those that reach the leaf. My mistake was thinking you guys were on the same page. And didn not know you guys were expecting me to be as accurate with the units as if I were writing a research paper. I did not realize the confusion it would cause.

I now almost understand what you are doing. I still cannot account for your 209.2 lm/W when Bridgelux specifies 63 lm/W.

Overall I am very impressed with your spreadsheet. I am not easily impressed. I remember what a bitch it was to get from photon energy to luminance the first time. I was on my own and had no one to ask any questions. I doubt there are very many people on the planet that know how to do what you did. I certainly couldn't find a one of them when I needed them.
 

alesh

Well-Known Member
I'm sorry, whenever I say µMole I mean µmol/m²/s. I type conversationally and casually. Lumens to me is lm/m²/sr, and lux is also lm/m²/sr, even though I know it is wrong. I use lux to mean luminous also. Same with everybody I work with when µMole is said it's assumed to be µmol/m²/s because we have no use for any µMoles other than those that reach the leaf. My mistake was thinking you guys were on the same page. And didn not know you guys were expecting me to be as accurate with the units as if I were writing a research paper. I did not realize the confusion it would cause.
This is understandable but it's important to use correct units. Both µmol/s and µmol/s/m^2 are widely used there, same goes for lm vs lx. Keep the units correct and it will make understanding much easier.
I now almost understand what you are doing. I still cannot account for your 209.2 lm/W when Bridgelux specifies 63 lm/W.
They don't measure the same quality. Guess you probably know that not all of electric power a LED consumes is converted to radiation (light).
BL publishes the COB's luminous efficacy at given conditions (current, voltage, temperature) - number of lumens per number of dissipated (electric) watts.
What I calculated is luminous efficacy of radiaton (LER). It's actually a quality of a spectrum. It is number of lumens per watt of radiation. It is used to convert luminous flux to radiant power. Then QER is used to convert radiant power to photon flux. The same process could be used to convert illuminance to irradiance and then to (photosynthetic) photon flux density.

LER and QER could be combined but I like to be able to calculate heat a LED produces for which radiant power is needed.

Sorry about .00836. Of course it is 10^-3/(N_a * h * c).
 

NoFucks2Give

Well-Known Member
It is used to convert luminous flux to radiant power.
A lot of the guys watching my posts yesterday thought I was saying your stuff does not work. I was confused because my formulas worked and my equivalent of your QER already worked. What I did not understand is you were going for Flux not PPFD. That's why our conversion factors did not march.

I was called sloppy and that's why my shit doesn't work. But my stuff worked, your stuff worked but the conversion numbers did not match. Not even close.

My revere engineering of the spreadsheet may have appeared that I was crazy, but any one that first meets me thinks I'm weird but interesting. Then they realize I'm just different and refer to me as a genius. Those that get to know me well understand I am crazy.

The rambling of my post is exactly how I think. I wrote everything that popped into my head and I wrote my exact thoughts.
I drank a 12 pack of Bud while I was reverse engineering the spreadsheet. It took many hours. I hate trying to figure out others code. I can duplicate in much faster by writing it from scratch. And in this case I already had the formulas. I just did not know what you were doing with them.

It is used to convert luminous flux to radiant power.
This is what confused me about cell F4. It cancels out B2 in row E formula. That makes no sense. That's why I stopped there.

You did not need to convert luminous flux to radiant. The sum of B2 is radiant. Column B2 is like the spectra of a 1 Watt LED where the spectra is expressed in radiometric Watts. You only needed to convert column B from radiometric to luminous.

When I posted asking this thread to help me and show me the math a couple of guys said it was explained in the first few posts of this thread. But it really was not explained the description was too vague. It was some formulas I recognized from Wikipedia. I did not understand that at first. When I write open source I explain a little bit about the coding. But I was impressed because not many people understand how to go from the energy of a photon to luminous flux. It is not simple until after you've done it the first time.

Sorry about .00836. Of course it is 10^-3/(N_a * h * c).
It's actually 1/cNa, no h

That's okay if you read my post, I did not remember what it was either. The post is the only reason I was able to tell you as I went back to my original formulas to find where it came from. I never documented my work because I could remember everything. Well those days are long gone.

Now what happened last night was funny. I am still using Win XP. I turned of updates in 2006 and do not use antivirus because the antivirus cure was worse than the disease. So there is a lot of stuff on my hard drive.

I saved your math spreadsheet in a folder called protons. Last night I went to review your spreadsheet and there were a couple other spreadsheets in that folder.

There is this guy David Wyble. I call him a colored guy. Not that I know his race. In the early 2000s he was very active in the CIE chromaticity x y z stuff. I call those guys colored. David was a student at University California San Diego and published some spreadsheets as open source. They would do things like take some spectra and calculate the CRI.

Ten years later in 2010 he published BlackBody.xls on Wikipedia as open source.

Untitled.jpg



First thing I notice is the style of the formula there is like the ones you posted.
The constants are in almost the same place as yours
The formula that I called big and ugly that should be replaced in your spreadsheet, almost the same formula is in this spreadsheet.

I thought the was a cool story that a spreadsheet from way back ended up in the same folder with yours and they are almost identical in both programming and layout style.

I digitize the the view angle radiation pattern for a couple of my apps. I just enter the percentage the values on the graph at 10° intervals and my code fills in the other 9 degrees in between. Those parts of the slope are so linear it simple to do it that way.

I was looking at the SPD graphs wondering how I would digitize them.

It must be difficult to digitize when there are multiple CCT curves plotted on the same graph.

My idea was to do a web app where you upload the SPD and it gets displayed on the screen.
You click on 400nm 100% and 700nm 0% to identify the corners of the graph.
Then you click on a some points on the curved parts of the curve and then I can generate the the efficiency numbers from those points. I just need to know where the curves curve and in which direction. Then I can fill in everything in the linear portions between the x y coordinates that were clicked. If you are interested.

Well at least now you guys have all the detail of how the spreadsheet works if you can follow the way my mind works in my ramblings. It may not appear so at first but I kinda know what I am doing.

And those that criticized me and made fun of me, that's okay, I understand. And really, I don't give a fuck what anyone else thinks and I've got no fucks to give.
 

alesh

Well-Known Member
This is what confused me about cell F4. It cancels out B2 in row E formula. That makes no sense. That's why I stopped there.

You did not need to convert luminous flux to radiant. The sum of B2 is radiant. Column B2 is like the spectra of a 1 Watt LED where the spectra is expressed in radiometric Watts. You only needed to convert column B from radiometric to luminous.

When I posted asking this thread to help me and show me the math a couple of guys said it was explained in the first few posts of this thread. But it really was not explained the description was too vague. It was some formulas I recognized from Wikipedia. I did not understand that at first. When I write open source I explain a little bit about the coding. But I was impressed because not many people understand how to go from the energy of a photon to luminous flux. It is not simple until after you've done it the first time.
I don't think I can agree there. The idea behind this is to able for us to convert photometric units from data sheets (lumens) to quantum units (µmol/s) used in botanics.
F4 doesn't cancel the B column in the E column calculation as it's sum - sum is represented by integral in the original formula. You definitely need all 3 columns (B&D,E).

It's actually 1/cNa, no h
It's not. It is 10^-3/(N_a * h * c). I'm completely sure. You can try it in the spreadsheet easily.

Interesting coincidence with the other spreadsheet. I've never seen it before, though. I guess it's just a most straightforward way of translating the formulas to excel.

Graph digitizing software is there already. Two of the apps are in fact discussed in this thread alone. I've switched from DigitizeIt to (opensource) Engauge Digitizer as per @Mathay 's recommendation.
 
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