Pulsed Lighting = more efficiency?

[puffenuff]

I would love to have attended the presentation that accompanied that slide deck. I particularly was interested in the last slide about diffused light. It makes sense and makes me wonder about the diffused lenses popular in the aquarium sector, perhaps rapid led is wise to keep diffused lenses on the onyx panels.

 

[Doer]

I would love to have attended the presentation that accompanied that slide deck. I particularly was interested in the last slide about diffused light. It makes sense and makes me wonder about the diffused lenses popular in the aquarium sector, perhaps rapid led is wise to keep diffused lenses on the onyx panels.

Diffusion for me comes from mylar panels and side lights. All light is diffuse, compared to laser.

I coat my grow area in mylar bubble warp and foil covered foam panels, to bounce as much light around as possible. Penetration here is different from "penetration of the canopy." That has to do with the transmission of some of the light straight thru the leaves into the next lower leaves and so on.

With diffusion we bounce light under there.

I remember a Mythbusters where they were trying to light an Egyptian Tomb with mirrors, per the myth. Surprisingly impossible.

But when the substituted brass polished surfaces that could not even return a reflection of your face, they were able to channel sunshine all the way into the tomb.

 

[heckler73]

All this makes sense somehow on a quantum level.
The question is about how to make an experiment?

That gentleman's experiment I ref'd in the OP has a perfectly good circuit from which to test. I can easily plug my Arduino across the 1 Ohm resistor (using a Megaohm bleeder or whatever to get logic-level voltages) and plot what happens, just like him. At the same time, I can monitor lumens (as per my BH1750 thread).
Bam...experiment engaged! Although...I need a higher voltage source for that particular circuit (my PS only pushes ~25VDC @ 2A max)
Or if need be, I can go super-nerd and set something up at the Uni in a lab. Who knows, maybe there's a grant proposal in there?

And it occurs to me that you don't have to flash all the lights so you never get to no light.

That is true, but saturation "burn" is still a potential issue (which I have managed to observe in my Multichip lab) although, probably not that serious if using 1-10% Duty Cycles, which is the point, anyway.

You could flash as a supplement to see about results of adding intense flashing to get higher molar flux without ruining COBs, wasting juice, or depriving/overdriving the factories to distraction.

That sounds like a 2nd tier experiment. I'm still in proof of concept stage on the technology. How far can the photons be pushed? Can maximum Entropy be achieved?
Based on the reading I did last night, there seems to be a "hole" (hyuck hyuck) in the research of this phenomenon. Never mind the conflicting results which are akin to the climate change wars--albeit, devoid of the emotion .

And iac, on a quantum level I wonder what continuity has to do with it anyway? It could be rather instant. One photon=one event of synthesis. It may not matter about the photon before the event, or after. A Quanta, as they say.

What continuity are you referring to, exactly?

Meanwhile...
Here's another blast from the past which may benefit some lurkers' "dislocated/interstitial cognitive lattice structures". Check out the near-end where he fires up what (unintentionally) was probably the first LED !
IT'S ALIIIIIIIIiiiVE !!!

PS My copy of the following should be here next week.

If there is a biblio elettronico , that is probably "it". I can't wait to see how it's changed in the 25+ years since the 2nd Ed. The only things I know ATM are the removal of the "BASIC prog. lang" section and the addition of shitloads of oscilloscope plots.

 

[churchhaze]

Until they put out a third release... (that book you mentioned will have you designing james bond era inventions.. lol)

Although to be frank, a book on designing electronics should come after a book on analyzing circuits. This book is written in ancient Egyptian.

(damn.. i guess they're up to 7th edition now!! lol.. I bought 4th edition in school. textbooks these days seem like a racket)

 

[churchhaze]

Wait, did 3rd edition just get released?? In that case, the 3rd edition could be a good replacement or supplment to sedra... if you ever manage to read through the entire book (good luck...).

 

[_MrBelvedere_]

If it is more efficient in electric consumption... wouldn't it be less efficient photosynthesis/yield wise? Wouldn't it be better to determine what the minimum light required is for a certain plant?

(over simplified)
For example clone plant x four times.

Grow plant 1 under 600 watts

Grow plant 2 under 500 watts

Grow plant 3 under 400 watts

Grow plant 4 under 300 watts

Let's say the yield on plant 1 and 2 is nearly the same, plant 3 and 4 are substantially less...

So now we know just using 500 watts is sufficient for max yield, so drive the LEDs with that?

Has anyone studied pulsing and yield?

The main point is draw-efficency-wise ultimately we care about yield, not par?

Thx

 

[heckler73]

Wait, did 3rd edition just get released?? In that case, the 3rd edition could be a good replacement or supplment to sedra... if you ever manage to read through the entire book (good luck...).

I pre-ordered in February If I lived a little more into the boonies, I could have it delivered by Amazon Drone !
That would've been an awesome "unboxing" vid.

 

[Doer]

The only experiment I would design involves a test bed of lighting and plants. I think Heck is working on the should he build a test bed, level.

The quantum event is the kick off of the photosynthesis cascade. I saw it somewhere... oh yeah...nope. SDS posted it a few days ago.

So, the question I have is about the process of that chain of events that begin with a photon strike of a certain energy on a certain type of molecule.

Is that one photon enough to produce one molecule of sucrose or whatever is the first result that is stored and transported? Or are there more photons involved elsewhere in the molecular process.

In other words does a flash of dark disrupt photosynthesis at that level? And if so, can it be predicted in the biology?

Real science mystery.
--------------------------------------------------------------------
Based on the reading I did last night, there seems to be a "hole" (hyuck hyuck) in the research of this phenomenon. Never mind the conflicting results which are akin to the climate change wars--albeit, devoid of the emotion

 

[_MrBelvedere_]

Also wouldn't a slow pulse up/down/up/down be easier on the equipment and just as efficient?

Thanks

 

[_MrBelvedere_]

Any thoughts or comment @heckler73 @churchhaze

 

[churchhaze]

1 pound.

 

[heckler73]

Well well well...t'ree 'oles in de ground...
--Newfie saying

I finished reading,
Efficiency of photosynthesis in continuous and pulsed light emitting diode irradiation
--Tennessen et al. 1995

Mind opening, for sure.



I believe that demonstrates two important elements; total mols (i.e. saturation), and capacitance in photosynthesis.
I just checked that calc in the figure. Technically, at 200μs there are ~6x the photons...but ignoring those factors of magnitude, 1e17 photons = ~1 μmol m^-2 seems to be an implied upper bound per pulse, at least as far as tomato leaves blasted with red freqs. can be compared. Much in the way high-level injection has its limits in semiconductors. That creates an interesting parameter to work with, meaning it may not be necessary to pulse with triple-rated currents, since there is a functional threshold of photons per square-meter! However, the question of upper-bounds in continuous PFD, crops up in the back of my mind... If 5000 μmols/m².s for 200 μs is the pulse peak, at what level does that translate into continuous time? I wonder if Tennessen's work was followed up with blue and green? What are their pulse limits? I need to see if he did any follow-up. His more recent works seem to be on a different path altogether...too bad.


It's all about the doping, man...

 

[heckler73]

Also wouldn't a slow pulse up/down/up/down be easier on the equipment and just as efficient?

Thanks

I don't know if this answers your query directly, but it caused a cartoon to start developing in my head while contemplating what you said.


I recall reading (somewhere) that "smooth" transitions (or ripple, sine, etc) would be ineffective. It seems counter-intuitive in the face of Tennessen's work. However, I can't find the quote directly, so it's only hearsay ATM

I don't know what you mean by efficiency in this case. The electronics (semiconductors especially) have a "built-in" smoothing function that responds to temperature. There is no "perfect pulse" as far as the LED response unless we start dipping them in liquid nitrogen. In fact, that's what I am banking on in order for this to work in the first place I suppose if I use an electrolytic cap in the circuit, it might take some abuse.

 

[guod]

LEDs grow; Pulsed lighting with LEDs
September 2004

"However, from literature the hypothesis was made that photosynthesis and thus the growth of plants under pulsed light can only approach, but never exceed photosynthesis and thus growth under continuous light with the same daily light integral under identical environmental conditions.

To test this hypothesis an experiment was set-up where Lemna plants where grown in the same environment, 21 °C, 60% RH and a photoperiod of 16 hours, with the same daily light integral, 11.52 mol m-2 day-1, but different light sources providing this daily light integral. One treatment consisted of fluorescent tubes, which provided a light intensity of 200 µmol m-2 s-1, another treatment that consisted of 24 LEDs spread out over 300 cm2 that provided light over an area of 500 cm2 , this treatment also had a light intensity of 200 µmol m-2 s-1. The last treatment provided light in pulses and consisted of 48 LEDs spread out over 300 cm2 to light an area of 500 cm2 , where the ‘on’- signal was 400 µmol m-2 s-1 and the ‘off’-signal was 0 µmol m-2 s-1. With these light sources six experiments were set-up, where the frequency of the pulsed light ranged from 0.012 Hz till 120 Hz, with a difference of a factor ten between the experiments. These frequencies also were used to name the experiments in some graphs. The results of these experiments where not as expected, in that different effects occurred over the range of frequencies. At 1.28 Hz the area growth rate of the plants was higher than that of the control treatment, and there also was a higher leaf area ratio (LAR). However, at 0.012 and 0.12 Hz a higher relative area growth rate is combined with a lower LAR. At 12 and 120 Hz the relative area growth rate is equal to the control treatment, at 12 Hz the LAR is also equal, but at 120 Hz the LAR is much lower. The final conclusion reached from these data is that it is possible to grow plants under pulsed red LEDs, however some morphological features of the plants change, furthermore most of the time it is not beneficial to grow plants under the pulsed light, certainly not below a frequency of 1 Hz."

 

[alesh]

LEDs grow; Pulsed lighting with LEDs
September 2004

"However, from literature the hypothesis was made that photosynthesis and thus the growth of plants under pulsed light can only approach, but never exceed photosynthesis and thus growth under continuous light with the same daily light integral under identical environmental conditions.
To test this hypothesis an experiment was set-up where Lemna plants where grown in the same environment, 21 °C, 60% RH and a photoperiod of 16 hours, with the same daily light integral, 11.52 mol m-2 day-1, but different light sources providing this daily light integral. One treatment consisted of fluorescent tubes, which provided a light intensity of 200 µmol m-2 s-1, another treatment that consisted of 24 LEDs spread out over 300 cm2 that provided light over an area of 500 cm2 , this treatment also had a light intensity of 200 µmol m-2 s-1. The last treatment provided light in pulses and consisted of 48 LEDs spread out over 300 cm2 to light an area of 500 cm2 , where the ‘on’- signal was 400 µmol m-2 s-1 and the ‘off’-signal was 0 µmol m-2 s-1. With these light sources six experiments were set-up, where the frequency of the pulsed light ranged from 0.012 Hz till 120 Hz, with a difference of a factor ten between the experiments. These frequencies also were used to name the experiments in some graphs. The results of these experiments where not as expected, in that different effects occurred over the range of frequencies. At 1.28 Hz the area growth rate of the plants was higher than that of the control treatment, and there also was a higher leaf area ratio (LAR). However, at 0.012 and 0.12 Hz a higher relative area growth rate is combined with a lower LAR. At 12 and 120 Hz the relative area growth rate is equal to the control treatment, at 12 Hz the LAR is also equal, but at 120 Hz the LAR is much lower. The final conclusion reached from these data is that it is possible to grow plants under pulsed red LEDs, however some morphological features of the plants change, furthermore most of the time it is not beneficial to grow plants under the pulsed light, certainly not below a frequency of 1 Hz."

Interesting, but at 50% duty cycle and 120 Hz frequency, the length of the pulse is 4.17 ms - at least 40 times longer than suggested <100 µs.

 

[heckler73]

Interesting, but at 50% duty cycle and 120 Hz frequency, the length of the pulse is 4.17 ms - at least 40 times longer than suggested <100 µs.

It needs to be kept in perspective against Tennessen et al. 1995, though, which was a different analysis, and a different plant (WTF is lemna ? Oh...it's a duckweed?)
It's a pretty funny thesis...the authour "doesn't know why" a photodiode would still register "5 umols" in darkness.

From pg. 15 of the thesis where Tennessen et al. (1995) is acknowledged:

A different approach in studying intermittent light was adopted by Tennessen et al. (1995).
They used LEDs to study the effect of light pulses (µs to ms) on photosynthesis of intact tomato
leaves. The light response of photosynthesis was measured in continuous light and compared with
the same total photon flux but given in pulses that only lasted 1% of the time. They found that
photosynthetic output was similar during light pulses and continuous light (50 µmol m-2 s-1)
treatments. However when light/dark pulses where lengthened to 2 ms of light and 198 ms of
dark, net photosynthesis was reduced to half that measured in continuous light. Their conclusion
was that plants use intermittent light (in kHz frequencies) only as good as they use continuous
light. Emerson and Arnold (1932) found that at 25 °C, a dark period of 40 ms was “adequate for
the complete removal of the material remaining at the end of each light flash.” The same reason
can be used to explain why the light/dark pulses lengthened to 2 ms of light and 198 ms dark
reduced the net photosynthesis as observed by Tennessen et al. (1995) (Jao and Fang, 2004),
because the dark period in this experiment was too long compared to the light period.

 

[_MrBelvedere_]

Thank you, great stuff

 

[_MrBelvedere_]

LEDs grow; Pulsed lighting with LEDs
September 2004

"However, from literature the hypothesis was made that photosynthesis and thus the growth of plants under pulsed light can only approach, but never exceed photosynthesis and thus growth under continuous light with the same daily light integral under identical environmental conditions.
To test this hypothesis an experiment was set-up where Lemna plants where grown in the same environment, 21 °C, 60% RH and a photoperiod of 16 hours, with the same daily light integral, 11.52 mol m-2 day-1, but different light sources providing this daily light integral. One treatment consisted of fluorescent tubes, which provided a light intensity of 200 µmol m-2 s-1, another treatment that consisted of 24 LEDs spread out over 300 cm2 that provided light over an area of 500 cm2 , this treatment also had a light intensity of 200 µmol m-2 s-1. The last treatment provided light in pulses and consisted of 48 LEDs spread out over 300 cm2 to light an area of 500 cm2 , where the ‘on’- signal was 400 µmol m-2 s-1 and the ‘off’-signal was 0 µmol m-2 s-1. With these light sources six experiments were set-up, where the frequency of the pulsed light ranged from 0.012 Hz till 120 Hz, with a difference of a factor ten between the experiments. These frequencies also were used to name the experiments in some graphs. The results of these experiments where not as expected, in that different effects occurred over the range of frequencies. At 1.28 Hz the area growth rate of the plants was higher than that of the control treatment, and there also was a higher leaf area ratio (LAR). However, at 0.012 and 0.12 Hz a higher relative area growth rate is combined with a lower LAR. At 12 and 120 Hz the relative area growth rate is equal to the control treatment, at 12 Hz the LAR is also equal, but at 120 Hz the LAR is much lower. The final conclusion reached from these data is that it is possible to grow plants under pulsed red LEDs, however some morphological features of the plants change, furthermore most of the time it is not beneficial to grow plants under the pulsed light, certainly not below a frequency of 1 Hz."

What I meant is that the original theory of pulsed lighting was to improve efficiency because most humans cannot readily notice the FAST pulsing. And probably plants cannot notice the fast pulsing either- but whether it degrades yield is unknown. And also it is unknown if fast pulsing affects the led equipment MTBF.

My point is that dimming instead of pulsing may be as effective in plants and increase the MTBF. Since humans are not looking at grow lights all day... continuous repeated SLOW bright to dim bright to dim bright to dim during the photoperiod may increase efficiency also. When I say dim I don't mean dark.

It is finding the sweet spot of light usage to yield that will result in efficiency gains.

 

[heckler73]

Check out this patent from 2001. It uses music to pulse the lights which is supposed to make the plants grow better.
That's some out-of-the-box thinking...the refrigerator box, that is.
I'm not saying it's crazy, but "loosely founded" could be an appropriate euphemism.

http://www.google.ca/patents/US8074397

Hmmm...it appears to be from a group of Japanese technophiles. That almost makes sense, then. But where are the tentacles? HOLY SHIT!!! They claim double growth rates in their "experimental findings" ?!?!

Yup....must be the tentacles.

 

[_MrBelvedere_]

bump @heckler73 did you do any experiments?