(μmol/s)/(PPFD) with respect to Hang height

ChiefRunningPhist

ChiefRunningPhist

Well-Known Member
PSUAGRO. said:
Sooooooo when are you coming out with your light chief? Blux eb gen 3 on the short list?
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Before the turn of the century for sure. Lol maybe end of summer. I've a new idea I'm trying to implement as of a couple weeks ago and it's changing the design a bit so its taking a bit longer but should be more streamlined and cheaper if manageable. I've a woking Wi-Fi dimming cct and the MCL, and the intended chip selection has almost been finalized so just trying to track down 1 or 2 more WVs and I'm ready for printing and population. Haven't added FLIR or other sensor suite yet though, and mainly been working on power distribution. Strictly focusing on light atm and once that's legit I'll turn to the sensor suite. I think FLIR will be easier, but the integration of the junction box controlled by sensor suite into the light itself will be made in stages. I'd like to have the sensors on the lights, but initially I'm just going to make the junction box + sensor suite independent of the light. Ill never finish if I keep changing and trying to add everything into the first light, so I think I just want to make a legit light (probably still try to have FLIR) and then the upgrade will be expanding the light network to include the junction box, but at a later time in an effort to see what control systems have been developed in the meantime to possibly use, as well as to split up the entire process into more manageable bites. @Overcomplicatotron has urged me into a CPU type of organization like a raspi but I'm trying to only use individual esp's, though as I progress into the design of the sensor suite I realize a CPU seems like the practical way forward. I'm learning everything from scratch so theres just a ton that I didn't even know that I didn't know lol, so its coming along but not yet as "X-men" as I had originally envisioned, though working on it lol :bigjoint:
 
wietefras

wietefras

Well-Known Member
ChiefRunningPhist said:
I'm assuming his 2/3 rule works because most of the chips are radiated at 120°.
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Yes, like I said that's for 115/120 degree beam angle. Of course when the beam angle is narrower the light needs to hang higher for adequate uniformity and when the beam angle is wider the light can be lower.

That's how I explained in an earlier post that I mixed four 150 degree far red leds with nine 115 degree COBs. That way they can work at the same height and still cover the entire area uniformly.

I'll just repeat the quote if you missed it:
wietefras said:
It's easier if you have a bigger beam angle. For instance a 150 degree beam angle spreads the light over 4 times the area compared to a 115 angle led. That's how I combined 4 Osram FR leds with 9 COBs. 4 light points would normally need to hang higher than 9 (for uniformity), but due to the bigger beam angle of the 4 they can then hang at the same distance for similar uniformity.
...
For COBs and single light points you can go with 2/3 of the maximum distance between them. For example if you have 4 light points (with 115 degree beam) angle in a 4x4 then the light points would be 24" apart and the needed hanging height would be 24" * 2 /3 = 16". You really don't need to calculate ISL or anything. It simply just scales up with the size of the tent since the beam angle is the same.
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To be complete, for 90 degree beam angle you need to be at about 1 to 1 height to distance. For 150 degree about 1/4. That would give similar distribution to 2/3 with a 115 degree beam angle.

ChiefRunningPhist said:
I also question just how significant a 2/3 ratio really would be.
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It's of course not a fixed number, it's a compromise between uniformity of light distribution and loss of light on the walls (or in aisle ways etc). The lower you go, the more light you have left (less wall losses), but the bigger the difference is between hot spots and dark area's. The higher you go, the more light you waste on the walls, but the uniformity will be better (slightly).

As I explained in post 52, if you don't care that much for uniformity at the edges of the grow then you can get away with using a hanging height calculated by 1/2 of the led to led distance. See the second image that I posted of a simulation of that in #52.

Distribution_2x2_15cm_50%.png


ps I'll just ignore the ISL loon. Unfortunately there is always one.
 
eatled

eatled

Active Member
ChiefRunningPhist said:
Trying to asses real world correlation between PPFD, μmol/s, hang height, and fixture design.
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This is the whole premise to my grow lighting experiments.
What is the optimum height and intensity at each stage of growth?
ISL is the key.
Here I am comparing intensity vs height. I do this with tomato seeds because I go through about 100 seeds per week in my experiments.
This is a comparison between Bridgelux Vesta 2700K 90 CRI running at 350 mA and 700 mA and at 12" and 24".


IMG_0290-035.jpg
 
ANC

ANC

Well-Known Member
My pet peeve is Mars using PEAK PPFD values to market their shitty lights.
It is an utterly useless stat that just gets a value from dead center under the light. Probably no more than 1sq foot of canopy gets anywhere near half of that value.
 
ChiefRunningPhist

ChiefRunningPhist

Well-Known Member
DLI is just what the average intensity is multipled by the duration.

Daily Light Integral

So if you have 700μmol/s average output, and you ran for 12hrs a day you'd have a DLI of:

60secs/min
×
60min/hr
×
12hr/day
=
43,200 seconds in 12hrs

700μmol/s × 43,200s
=
30,240,000μmol/day; or 30.24mol/day; or DLI of 30.24mol

EDIT:
If you used the sensor you could make a simple program in arduino that would record the sensor reading every second and keep a running tally for you. If you had a green house with varying light intensity and you had a specific DLI that you were trying to hit, then undestanding that the DLI is the same thing as μmol/s, just over an entire day, you could work back to find what the per second intensity you're trying to hit, or the μmol/s, then whatever your sensor is lacking in target μmol/s (PPFD) would make your program increase intensity of supplemental lighting till the correct target PPFD were measured by the sensor, so the program would interpret what the sensor was reading and distribute more or less power to supplemental lighting accordingly to hit your target DLI.

When lights don't vary in intensity:
DLI(μmol) = (PPFD) × (#hrs light is on) × (3,600)
 
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ANC

ANC

Well-Known Member
What I take away it is basically a calculation based on many measurements throughout the day. Not a measurement per se.

I just realise I should add the qualifier that it is not for a static environment, like a tent with a light. In which case the umol/s x seconds would be the answer...
 
ChiefRunningPhist

ChiefRunningPhist

Well-Known Member
InTheValley said:
Just my

DLI can be measured?

you being funny,lol..?

I think DLI needs can be measured thru the stalk thickness. thicker the stalk, more light is needed.
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I just got what you were trying to say. You were talking more about how to determine what the correct DLI should be. Idk that one lol
 
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