Sputnick and Europa design an environmental chamber

[Europa]

About two months ago Sput left home to begin his journey through engineering school. Soon thereafter, when sanitizing his room, I (a.k.a. dad) found a bag with a number of pot seeds. Thinking it would be fun to see them sprout I germinated them and then of course, they sprouted, so I had to transplant them (in various ways) and… so began the first grow. That was the origin of our grow fever but, it didn’t end there. Sputnick decided this would be a good way for us to keep in touch and have some fun at the same time (scientists and engineers do have some strange ideas about fun). Both our schedules are cramped so this is going to take some quite a bit of effort to complete. Wish us luck!


This (with the administrators’ permission of course) will be the means of communicating our research and design ideas between us and with the greater grow community. If you have any suggestions, directions, links, experiences, whatever you would like, please take the time to post.

And so, I started with a paper by Tazawa that Ozgrowa cited. After re-reading it I believe that it is an excellent reference although there are unexplained assumptions and biases, errors, omissions, and perhaps transliteration problems within the text and tables. Here are some of my initial conclusions and recommendations:

http://ss.jircas.affrc.go.jp/engpage...wa/tazawa1.htm

http://ss.jircas.affrc.go.jp/engpage...a2/tazawa2.htm

A) The paper was written with commercial interests (costs) foremost. Because our project is for fun, not-for-profit, I suggest we ignore power consumption à photo conversion efficiencies unless there are other significant reasons to reevaluate (e.g. excess heat production).

B) A key aspect of the lighting is the PPFD (photosynthetic photon flux density, conv. 16.8 umol/m-m-s-klux for daylight). Color rendition HPS and grow-Flo’s produce more PPFD’s/lux than sunlight because UV, green, and IR are not PAR. Other lamps can be used (if desired) for better color balance. Forget the quantum sensor, we ain’t got one.

C) Plants adapt to total PPFD by producing more or less chlorophyll, within the same plant.

D) Different morphological changes occur as a result of the ratio of blue/red and red/far-red light. Depending on species, the color and duration of light exposure can affect flower formation.

E) There is a saturation point at which greater PPFD no longer increases the rate of photosynthesis. The saturation point varies widely between species. WE MUST HAVE AN ESTIMATE FOR MJ.

F) “Composite Lighting” part 1 - fig 10 looks really good but isn’t explained. WHAT IS IT?

G) Part 2 fig 1, what is “CIE photopic curve”, maybe sensitivity of human eye?

H) Defines “light quality” as closeness of agreement of source R/B ratio to photosynthesis action spectum (PAS). For lack of any other justification, I agree and will assume it implies growth (mass) rate. Error: optimum R/B for PAS is 1.9 not 2.71. Doesn’t describe “effective” growth.

I) MH is only lamp that solo can produce good quality growth (ed. without stretching).

J) The title and contents of Part 2 table 6 don’t agree with each other or text.

K) HPSL…lead to optimum conditions for growth (ed. growth here means increase in height).

L) The mean PAS matches very closely the absorption spectrum of chlorophyll (duh).

Based on this data we should be able to configure the chamber with a set of light sources that blend to produce the appropriate spectral balance (PAS) and flux PPFD.

[Europa]

Here is a transmittance spectrum of a water mash of an upper male leaf. It compares well with Tazawa's PAS except at low wavelenths which could be scattering and non-PAS absorption. I also scanned an intact leaf; Tmax @540, Tmin @685, and was opaque below 500nm.

[sputnick]

Heh. cool... any idea where we could get some accurate graphs of spectrum vs intensity of various light sources? what next? how about a plan of action. or a list of questions to answer.

[Europa]

Accurate graphs, no. But I did download spectra for HPS, MH, warm-HPS, Warm-MH and cool-MH. AFter expanding and printing them I measure the emission at 10nm intervals (only HPS and MH so far). I ran the numbers and this is how it turns out:

For every lumen of HPS we need 2.6 lumen MH. This gives an R/B of 1.85, R/FR of 6.8, and an PAS efficiency of 54% (MH PAS efficiency sux). I'm going to run the HPS with cool-MH next and see if the numbers are any better.

[Europa]

After much discussion with sput we've decided to go with 400watts MH and 100watts HPS. That'll give us r/b=1.8 and r/fr=7, and 51,000 lum. We are thinking of running at 50klux so this gives us a square meter to work with. Now, how many plants in a square meter?

[Europa]

Sput,
What do ya say we make that a 150W HPS? The 100 watter is a bit weak on the lumens.

[plainsman1963]

Ok, give me a brief rundown on why you made the decision to go with more mh than hps?

For every lumen of HPS we need 2.6 lumen MH

So why not go with hps alone, or the expanded spectrum hps?

Not second guessing you two at all, just trying to understand the process. Speaking from depths of ignorance here.
I am still reading the two tazawa reports, I think I will have to reread those many times before I get it all.

Good growing,
Plains

Edit: "How many plants in a sq. meter?" Oh, and what's a meter? 3.2 feet or somewhere? Without doing a sog grow or something like that you figure a sq. ft. per plant...Math...conversions...losing super powers...

[Europa]

Plainsman,
Tazawa implies that quality light matches the photosynthetic action spectrum (PAS). To get “perfect” light then we’d need to match luminant flux at every wavelength. Due to the ability of mixing phosphors, fluorescents are better than any other discharge lamps at matching PAS, if you pack them so they touch you can get about 50klux. But 1sq meter would require ~30 bulbs. So forget flo’s.

I was unable to find the saturation point of MJ so I’m guessing it’s 50klux. Since I couldn’t find enough valid data to make integrating spectra worth while, I printed and measured the emission spectra of several HID sources at 10nm intervals; HPS, MH, cool-MH, warm-MH, warm-HPS. I fit a 6th order curve to the PAS and multiplied it by the normalized spectra then summed the results. This gave me a measure of “quality”; perfection has a value of 1.00. Tazawa also indicated that plant stretching was induced by high (red/blue) ratios, and low (red/far red) ratios. The PAS has a r/b of 1.9 and r/fr of 6.6.

Quality; r/b; r/fr
HPS = 0.70; 3.1; 4.8
MH = 0.64; 1.5; 9.1
cMH = 0.61; 0.7; 6.6
wMH = 0.69; 2.0; 15.3
wHPS = 0.72; 5.6; 5.1


I suppose you could solve the equations for three parameters simultaneously using all five lamps but, yikes, I don’t want to use a combination of all five lamps, so I solved @r/b=1.9 using only two types at a time. This gave me all the r/b=1.9, combinations. All resulting qualities were between 0.65 and 0.67, not much difference, so I chose the combo that gave the r/fr closest to 6.6. This was 2.0 lum MH per l.0 lum HPS yielding r/fr=7. (NOTE: 2.6 was a calculation error).

Oh, you said brief, sorry.

1sq-ft per plant, I was thinking 3sf/plant! Oh yea, good luck with the Tazawa reports!

[plainsman1963]

so I chose the combo that gave the r/fr closest to 6.6. This was 2.0 lum MH per l.0 lum HPS yielding r/fr=7.

Ok, with ya now.

I was thinking 3sf/plant!

Then you might be able to call them trees!
They would be real nice trees though.

Experiment on,
Plains

[sputnick]

I should have posted these a couple days ago but been busy.

400 watt metal halide ballast $41.93
150 watt hps ballast $43.76
mogul sockets are listed on that site at $12 apiece but i am going to see if i can get them at a local electrical supply for cheaper

Still not entirely certain on specifically where or whose bulbs we are getting. but they will be phillips or sylvania regular bulbs. no special tuned bulbs. i figure on them being $20-30

Light cost exc reflector (which i will bend out of aluminum) is about $150. not a bad price for 550 watts of two different hid types. back to the web for bulbs... stay tuned for schematic drawings in mspaint woohoo!