A " must read all x10 times " for all LED growers & DIYers ....

djwimbo

djwimbo

Well-Known Member
Thanks for the link, 63 pages is more time/attention than I can give this morning. I'll read it all hopefully this weekend.
 
stardustsailor

stardustsailor

Well-Known Member
Ok .....


In Summary ( set as a trap...make few to read the whole thing ... ) :

Reasearch was done at


AALTO UNIVERSITY

SCHOOL OF ELECTRICAL ENGINEERING

Department of Electronics

Lighting Unit


Not in a Botany / Biology school .
So paper is 'missing ' / 'lacking ' lots on that "chapters " ....
Keep that in mind .
But finally plants ,do "talk " ,for themselves ....

Humans perceive light in different way than plants.

The human eye has the strongest
response to light in the green/yellow part of the s
pectrum. Plants respond better to their
growth with blue and red light, as shown in Figure
3.4. Chlorophyll does not absorb

light in the green region of the spectrum, since it
is reflected [34]. For this reason, the
chlorophyll and plants are green.
Click to expand...
So .It starts mentioning the importance of two basic wls range ( peaking at 450 nm & 670 nm ) ,
for plants and that this is the most " efficient " ...

In Figure 3.4, the absorption of light by chlorophyll
is at a maximum at two points on
the graph roughly in 430 and 660 nm. The rate of ph
otosynthesis at the different
wavelengths of visible light likewise shows two pea
ks which roughly correspond to the
absorption peaks of chlorophyll [34]. Plants do not
depend only on chlorophyll, but also
have other pigments which absorb light of other wav
elengths. The rest of the
wavelength values, to know how to affect plant grow
th, are shown in Table 3.1
Click to expand...

Only ,a bit later ,to mention ,that " yeah..Indeed it's been swown that plants do grow better in full spectrum ,rather than just B & R leds ..."

37


Previous studies have demonstrated that the mixture
between blue and red light is the
most effective for the crop growth. This combinatio
n has been examined in many areas
of photobiological research, including photosynthes
is and chlorophyll synthesis,
obtaining good quality in the vegetables growth [41
].
The third color analyzed is
green light
. Normally, the role of green color consists in the

regulation of vegetative development, photoperiodic
flowering, stem growth
modulation, and stomatal opening [41]. This spectra
l region also affects chlorophyll and
carotenoid synthesis, improving the color of leaves
[42]. Furthermore, effects produced
in plants by green light are completely opposite of
effects with red and blue lights.
However, blue and red lights are sometimes mixed wi
th green light to enrich the
development and plant growth.
Click to expand...



The horticultural lighting is quite difficult to id

entify the best combination for plants,
since there are different valid mixtures. According
to the vegetable or plant used will be
better to utilize one kind of color combination or
another one. Thus, this combination is
capable of providing the best growth and developmen
t for them. This blend consists of
merging blue and red color, and some other color ca
n be also added to enrich and
accelerate the plant growth.
On the other hand, LEDs also present problems when
are utilized for general lighting.
People need to sense well-being in their work envir
onment or in any other situation.
This light quality is mainly measured through color
rendering index (CRI). This factor

will be used in the next sections to measure and ac
quire a correct light for people and to
avoid an uncomfortable lighting.
Click to expand...



Ok ..
And starts to analyse different monochromatic led combinations ( Blue-Green -Yellow -Red -IR ) ,sometimes with Cool White ,phosphor conversion leds ....And " giving away " the " right combos " of them ..

Colors, such as amber, blue, cool white, cyan, gree

n (524 nm), green (532 nm), infrared,
red (630 nm), red (670 nm), warm white, and yellow,
are acquired in the lab-room.
Microsoft

Office Excel 2010
software and a special application developed to Ex
cel are
used to combine these colors, acquiring the best po
ssible CRI value to provide a notable
lighting for people. This application allows playin
g with colors and knowing what

percentages used are for each combination.
Click to expand...


4.4 Conclusions
Analyzed all cases, it is possible to obtain some c
omments about them. Firstly, all these
measurements are simulations; therefore, these resu
lts are nearby reality. The results
simulated are not exact, because there are always s
ome errors that are obviated in these
simulations.
Attending to results obtained, there is no differen
ce between if the combination has
been acquired through fixed percentage or variable
percentage. Namely, good-quality
lighting is obtained in both cases for horticultura
l lighting and general lighting.
The best mixture for plants is blue and red color;
since, this blend generates a rapid
growth and provides appropriate properties for the

plant development and
photosynthetic aspects. All these plant characteris

tics can be improved when some

different colors are mixed with red and blue color.

According to the colors added for

plants, their attributes can enhance their quality

for some aspects or other.
52


All results show notable color rendering index valu
es, since these values are comprised
from 85 to 94, supplying fine light for general lig
hting. However, CCT values are very
variable because cool white and warm white are acqu
ired for different combinations.
Warm white or cool white can be indistinctively uti
lized in many applications, but
depending on planned application will be more inter
esting to use cool white or warm
white.
Finally, it is possible to procure a notable lighti
ng for people through horticultural
lighting. These light sources are very simple to ob
tain in simulations; nevertheless, it is
sometimes possible to find little problems when the
se lights or combinations are
executed for real cases.
Click to expand...
More or less ,all combinations do have same growth efficiencies ....
 
stardustsailor

stardustsailor

Well-Known Member
And here come the led growing "school " of White & Red ....

Using different monochromatic leds ,to build a real-life " full spectrum " led grow panel has quite a lot of "obstacles " :

-Spectrum blending .

-Extreme power of blue dies .

-Low efficiencies of Green ,Cyan,Yellow and Amber leds .

-Driving issues of so many diffferent led chips .

-Power blending .

-Design difficulties due to different led contact pads ,emission angles , R th , etc ...


White & red school is more "simplistic " ....

Choosing high efficiency pc white leds and 'enhancing' them -usually- with red monochromatic leds .
Yes there are conversion losses ,but Green ,Cyan,Yellow and Amber leds have low efficiencies,also ....
( Although there are some advancement ,specially in green dies ..) ....

And light spectral blending ,is by far superior ....


Ok ....

In fact W& R school is ...a "masked " B&R school ....

"Put a phosphor over the blue leds to supply the rest 'colors',also and "drop " some of blue raw power at same time ,while keeping the reds ... "
...

That's what's all about in the W& R school ...

And trust me,with all these new white leds and the improvements around them , things at that school ,start to get really interesting ...


P.S. : mj is not a green leafy shrub ..Blue and Red leds are enough to grow her ,but will never reach to her 'best' ....
 
PetFlora

PetFlora

Well-Known Member
A " must read all x10 times " for all LED growers & DIYers ....

I felt there was very little actual personal experience from which to draw his conclusions, which pretty much mimic (plagiarize) other findings
 
stardustsailor

stardustsailor

Well-Known Member
PetFlora said:
A " must read all x10 times " for all LED growers & DIYers ....

I felt there was very little actual personal experience from which to draw his conclusions, which pretty much mimic (plagiarize) other findings
Click to expand...
That 's not the main reason that makes this pdf so important ....

I has lots of useful GENERAL information about leds and their application in horticulture ....

And in not that scientific-heavy language ....
 
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