Anyone have an Apogee AGP-MQ-500 quantum meter?

[fanleaf]

Actually, according to the inverse square law, intensity should drop to 1/4 at twice the distance. Readings, however, are proof of circumstances in this particular setup.

What I was referring to is the linear relationship of power to intensity. If you double the power, umols at the same distance should be double. And no, I didn't account for driver loss or the change in emitter efficiency as current drops, and it wouldn't be a linear line, no. The 3590s are FAR more efficient at 350ma than 2100ma.

ha ha. Gotcha, my bad. The funny thing is now that I have this great tool I have a lot more work to do now to try to optimize my area. This is gonna take some playing with.

 

[fanleaf]

Actually, according to the inverse square law, intensity should drop to 1/4 at twice the distance. Readings, however, are proof of circumstances in this particular setup.

Yea, these are sure not dropping to 1/4 intensity at twice the distance. Not even close says the Apogee. That's interesting

 

[Graytail]

I remember reading elsewhere that the 90 degree? reflectors tend to blend optimally at 12" centers and 24" distance. There might be a focus/overlap effect in your setup. I wonder if those numbers work for 8" centers = 16" optimal blend?

 

[Icemud]

Yea, these are sure not dropping to 1/4 intensity at twice the distance. Not even close says the Apogee. That's interesting

This is because LED's do not follow the inverse square law exactly. The do behave in a similar manner, as light particles disperse the more distance they get from the source but not in the format that Inverse Square law applies.

LED's don't directly apply to the inverse square law because the inverse square law only applies to a point source of light, emitting in ALL DIRECTIONS, like a star in space would, or similar to a old filament (edison) style light bulb which is what Inverse Square Law by definition applies to. Since LED's not only partially reflect the light but also focus it, this adds complication to the ISL.

Since with LED's/COBs the light is only shining in 1 direction, and projected in a narrow/wide beam, the process of focusing the light rivals the inverse square law since the light is not shining in all directions.

For example, take a flashlight with a zoom lens. Inverse square law would say that the zooming lense wouldn't matter, and that the beam would be the same intensity whether zoomed to spot, or zoomed out to floodlight. We know this isn't true because the more focused the beam, the further the intensity carries and the wider the zoom, the faster the intensity drops off (or rather disperses).

Now if you completely removed the flashlight lens, where the lightbulb were able to emit in all directions, then the inverse square law would apply for the most part. (minus the loss at the base of the light) as the dispersing photons would equally emit from the point source, without reflection, collemating (parallel light beams) or manipulated in an angled beam.

 

[TorturedSoul]

Interesting. I knew that there was some debate about the optimum light levels for cannabis, but I didn't realize that current thinking placed the optimum (in regards to the previous suggestions) at such a low figure. Would you know what PPM of CO₂ was meant when they mentioned an optimum with supplementation? I think I used to shoot for around 800 PPM, but it has been so long that I'm not sure. I used to hear/read that ambient outdoor CO₂ level was around 300 PPM, but last year I read it was now closer to 400 PPM thanks to the human race f*cking up the planet. And I've always understood that the CO₂ level in side people's homes might be a little above ambient (assuming doors/windows are kept closed) due to the people and pets living there. I do not remember what kind of average a person might find inside, though.

Regarding LEDs and the inverse square law: I found that interesting, too. It makes sense, lol, I just never thought about it. It might not be a factor with COBs (and probably isn't), but with monochrome/mono-color LEDs, might the particular wavelength of the LED also play a part? I've read that certain wavelengths travel farther/better/something than others. <SCRATCHES HEAD> Or... maybe that was under water, IDK. Hi, I'm TorturedSoul, and I'm burnt .

 

[Icemud]

Thank you very very much. I understand what you are saying. I do have a question though. Looking at my numbers and the back and forth between me and Graytail you an see where when I'm running the lights only 10" above canopy at .82amps I'm getting a ppfd of 1000 at 12 inches which will be a ppfd of 500-550 at 24 inches down from the top of the lights but only 12 inches down into the canopy my best bet is to raise the lights more from the canopy and increase power a bit. Lets say for example if I were to move the lights up 16 inches from canopy and tune the lights to provide a ppfd of say 1100 at the canopy top which will then still have roughly a ppfd of 550-600 16 inches down from the top of the canopy? If I understand right it will increase yield for 2 reasons. #1 because I'm simply using more wattage but also because I'm getting better ppfd further down the canopy?

Hey Fanleaf,

Its a great question, however its one that I can not comfortably promote an answer for that I deem accurate. I've tried to find information on intracanopy lighting PPFD, and almost all sources that mention DLI, PPFD or anything relating are taking measurements at the top of the canopy level but make no mention of PPFD under the canopy.

Because the LED beam angle and pattern of dispersion wouldn't change if you raised the current and output, the ratio of measurement A at 12" to measurement B at 24" would be the same I believe. What I am not sure though is if it actually would promote better penetration or be virtually the same. A couple things come to mind, and I don't know the right answer...

Since the ratio of photon dispersion would be the same between A and B, lets say you raise the levels from 1000 at A and 500 at B to 1400 at A and 700 at B. Well at 12", 1400 would be too intense, therefore you would have to raise the light a couple inches, which then also would raise the point B a couple inches as well. So for example lets say you needed to raise the light from 12" to 16" to get point A back around 1000 umol... so if you raised point A by 4", then point B would also raise 4" so you would be getting 700umol at 20", and still would only be around 500umol at 24". I don't think you would gain much penetration due to the change in intensity.

HOWEVER, due to you raising the lights, and having multiple point sources of light, by raising the vertical height of the light, this will allow for the light point sources to cast angled light acrossed your canopy, reducing shadowing and possibly increasing penetration to the lower leaves.

Just as if you were to take a flashlight, and hold your finger close to the lens.. the shadow of your finger would be huge... shading a large area of the wall. Now if you were to move your finger away from the lens, the shadow would be much much smaller on the wall, therefore more light is reaching the wall.

So in that case, you may actually get more penetration. But not because of the increased intensity, and more due to reduced shadow size, and also the ability for more cross lighting (angled light from COBs not directly above).


Like I originally mentioned, I don't really have an accurate answer for your question that I have confidence in and have not found solid evidence of truth, however many things I have read hinting at this being true, so take it with a grain of salt.

I wish I have more information on intercanopy PPFD requirements but I have not found it yet... I mean even the most intense source of light we know, the sun, which is so intense that PPFD measured at 1' or 10' isn't going to hardly change, still only a fraction of this sunlight gets into the canopy of a plant.. how much... ?? not sure... but I would say probably about 10-25% at best. (mostly green and Far Red light) as blue and red get easily absorbed and aren't reflected much at all.

 

[Icemud]

Interesting. I knew that there was some debate about the optimum light levels for cannabis, but I didn't realize that current thinking placed the optimum (in regards to the previous suggestions) at such a low figure. Would you know what PPM of CO₂ was meant when they mentioned an optimum with supplementation? I think I used to shoot for around 800 PPM, but it has been so long that I'm not sure. I used to hear/read that ambient outdoor CO₂ level was around 300 PPM, but last year I read it was now closer to 400 PPM thanks to the human race f*cking up the planet. And I've always understood that the CO₂ level in side people's homes might be a little above ambient (assuming doors/windows are kept closed) due to the people and pets living there. I do not remember what kind of average a person might find inside, though.

Regarding LEDs and the inverse square law: I found that interesting, too. It makes sense, lol, I just never thought about it. It might not be a factor with COBs (and probably isn't), but with monochrome/mono-color LEDs, might the particular wavelength of the LED also play a part? I've read that certain wavelengths travel farther/better/something than others. <SCRATCHES HEAD> Or... maybe that was under water, IDK. Hi, I'm TorturedSoul, and I'm burnt .

Here is the summary of the Abstract.

Effect of different photosynthetic photon flux densities (0, 500, 1000, 1500 and 2000 μmol m(-2)s(-1)), temperatures (20, 25, 30, 35 and 40 °C) and CO2 concentrations (250, 350, 450, 550, 650 and 750 μmol mol(-1)) on gas and water vapour exchange characteristics of Cannabis sativa L. were studied to determine the suitable and efficient environmental conditions for its indoor mass cultivation for pharmaceutical uses. The rate of photosynthesis (PN) and water use efficiency (WUE) of Cannabis sativa increased with photosynthetic photon flux densities (PPFD) at the lower temperatures (20-25 °C). At 30 °C, PN and WUE increased only up to 1500 μmol m(-2)s(-1) PPFD and decreased at higher light levels. The maximum rate of photosynthesis (PN max) was observed at 30 °C and under 1500 μmol m(-2)s(-1) PPFD. The rate of transpiration (E) responded positively to increased PPFD and temperature up to the highest levels tested (2000 μmol m(-2)s(-1) and 40 °C). Similar to E, leaf stomatal conductance (gs) also increased with PPFD irrespective of temperature. However, gs increased with temperature up to 30 °C only. Temperature above 30 °C had an adverse effect on gs in this species. Overall, high temperature and high PPFD showed an adverse effect on PN and WUE. A continuous decrease in intercellular CO2 concentration (Ci) and therefore, in the ratio of intercellular CO2 to ambient CO2 concentration (Ci/Ca) was observed with the increase in temperature and PPFD. However, the decrease was less pronounced at light intensities above 1500 μmol m(-2)s(-1). In view of these results, temperature and light optima for photosynthesis was concluded to be at 25-30 °C and ∼1500 μmol m(-2)s(-1) respectively. Furthermore, plants were also exposed to different concentrations of CO2 (250, 350, 450, 550, 650 and 750 μmol mol(-1)) under optimum PPFD and temperature conditions to assess their photosynthetic response. Rate of photosynthesis, WUE and Ci decreased by 50 %, 53 % and 10 % respectively, and Ci/Ca, E and gs increased by 25 %, 7 % and 3 % respectively when measurements were made at 250 μmol mol-1 as compared to ambient CO2 (350 μmol mol(-1)) level. Elevated CO2 concentration (750 μmol mol(-1)) suppressed E and gs ∼ 29% and 42% respectively, and stimulated PN, WUE and Ci by 50 %, 111 % and 115 % respectively as compared to ambient CO2 concentration. The study reveals that this species can be efficiently cultivated in the range of 25 to 30 °C and ∼1500 μmol m(-2)s(-1) PPFD. Furthermore, higher PN, WUE and nearly constant Ci/Ca ratio under elevated CO2 concentrations in C. sativa, reflects its potential for better survival, growth and productivity in drier and CO2 rich environment.

 

[TorturedSoul]

Thanks, Icemud!

 

[Stage]

This a great thread Fan!
Icemud and Graytail are some pretty knowledgeable cats.
I'm learning and eating popcorn.
Carry on..

 

[fanleaf]

Well, I built and installed yet another Cree panel today. Now in this 4.5'X4' area im running 25 Cree's. Thats 1.38 cobs psf if I remember right. Im running all of the panels at 1amp right now. I also put my 2 seedling under them a few days ago. The seedlings are autos and sitting in 12/12 light because of the flowering cheese plant. I still think the autos are getting plenty of light as far as DLI goes. They are sitting at a ppfd of 725 and loving it.

Sent from my VS980 4G using 420 Magazine Mobile App

 

[Graytail]

It's a beautiful thing, Fanleaf.

 

[Icemud]

Well, I built and installed yet another Cree panel today. Now in this 4.5'X4' area im running 25 Cree's. Thats 1.38 cobs psf if I remember right. Im running all of the panels at 1amp right now. I also put my 2 seedling under them a few days ago. The seedlings are autos and sitting in 12/12 light because of the flowering cheese plant. I still think the autos are getting plenty of light as far as DLI goes. They are sitting at a ppfd of 725 and loving it.

Sent from my VS980 4G using 420 Magazine Mobile App

Bravo!!!! that is one beautiful LED setup you have going on! very nice!

 

[Stage]

Why couldn't you be my neighbor? Awesome cob DIY bro.

 

[fanleaf]

Why couldn't you be my neighbor? Awesome cob DIY bro.

Haha Stage. The real funny thing is that to one side of my house I have a neighbor that bought that house a year ago and did some major remodeling and he grows. I think he grows on a bigger scale than I do just because of the work I see going on over there. Not to mention the 12 inch exhaust I see that wasn't hidden as well as he thought. To the other side of my are a few smokers but they don't grow that I know of.
Both neighbors I haven't spoken to yet. One of these days when I catch the 1 that grows I'm just gonna come out with something funny as hell about weed to break the ice. I'm sure he knows I grow because I don't hide it to well when I go out on the back porch and toke up even if they are in their back yard lol. I'm sure they have seen me by now. I've done it on purpose just to give him a clue that I'm good with what he's doing.

 

[Stage]

What about the house behind yours? Available?.

 

[fanleaf]

What about the house behind yours? Available?.

lol
Sure is actually. Shoot man, right now I'm just sitting here not knowing what to do. Plants are sleeping, light projects are done for now, not tired so I'm just in limbo. I keep contemplating on buying a 8x8x7 tent just so I can build more lights and grow more plants.
I was just looking pretty hard at the Mars Hydro 8x8 tent but it don't look like it has any type of flaps to cover the zippers and stuff so that scares me about light leaks. IDK, maybe I should go hit up SmokeSara and see.

 

[TorturedSoul]

lol
Sure is actually. Shoot man, right now I'm just sitting here not knowing what to do. Plants are sleeping, light projects are done for now, not tired so I'm just in limbo. I keep contemplating on buying a 8x8x7 tent just so I can build more lights and grow more plants.

Lol. Someone once asked me if cannabis was addictive. I replied, "No - but growing it can be."

 

[triggz2k15]

Lol. Someone once asked me if cannabis was addictive. I replied, "No - but growing[/i] it can be."

Hahaaaaaaa literally made me lol dude

Thankyou lol that's the best post iv seen all day!



Sent from my SM-A300FU using 420 Magazine Mobile App

 

[fanleaf]

Ok
So, I just got a 8X8 tent on the way and have a huge order in on my next cob light.

Goint for a SUPERPANEL!!! Gonna be 42X yes 42, you read that right Cree CXB3590's ran by Meanwell 320W 1400 milliamp dimmable drivers. These will run at very low current and at a high rate of plant growth I hope lol.

 

[Stage]

Damn Fan. You are the man.
Where's the popcorn?!
Question for us mere mortals...do you have a budget? .