COB LEDs - Is Too Much Light Counter-Productive or Just Wasted Energy??
- Thread starter newguy41410
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wietefras
Well-Known Member
Leaf temperature is usually between 2 and 4C lower than the ambient temperature. Depends on the amount of air movement over the leaves too though.
Chart below shows 6 days (with "nights") where the yellow line is the ambient air temperature and the green line the leaf temp. Orange is the VPD.
This was with the exhaust fan at the same level all the time. So temperature was not altered by a temperature controlled fan. It's only depending on intake temperature and humidity, plus what the plants do to cool themselves of course
Chart below shows 6 days (with "nights") where the yellow line is the ambient air temperature and the green line the leaf temp. Orange is the VPD.
This was with the exhaust fan at the same level all the time. So temperature was not altered by a temperature controlled fan. It's only depending on intake temperature and humidity, plus what the plants do to cool themselves of course
Gquebed
Well-Known Member
So why do so many HID guys say the spot is 75f? They say thats how they get bud density, but... I was always around 77-81f with HID.
So anyway 85+ with COB.
Does lights off temp matter much? Usually drops to 63ish in my basement. So it'd be a 20 deg temp differential....
Photon Flinger
Well-Known Member
Lower temps are actually better as they allow the leaf to absorb more light along with the additional heat created by that additional light.
For example, the sweet range is 20-35c, strain dependent of course. Say your ambient is 25c, the spot temperature on the leaf might be 27 for 400umoles, 28 for 600umoles, 29 for 700umoles,.....34c at 1800umoles.
I have been able to hit leaves with 3500-3800umoles to no ill effects but the temps were kept low (max 25c) and I didn't see any improvement in yield from the 1000-1200umoles range. This was tested over winter when I could keep the ambient temp low enough.
What is true is that plants have an easier time with longer wavelengths. Blues carry a lot of excess energy that is converted to heat through the various processes.
wietefras
Well-Known Member
It depends on a lot of factors unfortunately. Airflow is probably the biggest influence on the temperature difference. When there is a lot of airflow, the leaves cool more and the difference in temperature gets bigger.
The chart above is with COBs and minimal airflow.
This chart below under HPS where I was struggling to get the temperature and humidity in the tent under control:
I even installed a humidifier next to the tent which causes the high intake humidity and still it's bone dry inside the tent.
Anyway, that's really the max difference I tend to get between plant temperature and ambient.
@CobKits , Lol, thanks. See my signature for some Arduino prototype sensors. Even an "advanced" logging system in a cardboard box
The PT sensor is probably the easiest to make really.
Photon Flinger
Well-Known Member
Low humidity + low temps allow you to use more light.
My water usage is also down for some reason as well. Once the lights go out, it jumps from 30-45% up to 55% within 15 minutes and the wonderful smell of plants napping permeates the area.
My water usage is also down for some reason as well. Once the lights go out, it jumps from 30-45% up to 55% within 15 minutes and the wonderful smell of plants napping permeates the area.
CobKits
Well-Known Member
smds and cobs would be identical to your plants if same spectrum and delivering same intensity at canopy level
OLD MOTHER SATIVA
Well-Known Member
about the no mould thing..
i think the biggest thing is air movement..i never get lower than 60% RH
i think the biggest thing is air movement..i never get lower than 60% RH
stardustsailor
Well-Known Member
1 ) At 1500 μmol/sec/m^2 , Ta = 30°C and Atm.CO2 = 400 ppm the photosynthetic rate of
Cannabis Sativa species is peaking . To take advantage of more light ,the other two factors ( Ta / CO2 )
need to be adjusted accordingly .
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3550641/
2) Photosynthesis functions like ...LEDs(but over a certain threshold = ~ 30 μmol/sec/m^2 ),
meaning :
- Lower light power available = low Photosynthetic rates =higher photosynthetic efficiency (thus higher yield efficiency ,but low overall yield per plant and/or grow area surface )
+ Higher light power available =higher photosynthetic rates= lower photosynthetic efficiency
(thus lower yield efficiency ,but higher yields per plant/ grow area surface )
3 ) Overdoing it with light power can and may have serious adverse effects.
It's called "photoinhibition "- for some people around here that they claim that this is a myth.
The photosystem II is stopping producing the photocomplex protein D1 which activates
the PSII.As a result is the canceling of chlorophyll biosynthesis at the PS II (thus the initial symptoms look like "bleaching" )
and if the source of the problem is not removed then the plants eventually will wither and die prematurely.
Basic wikipedia knowledge : Photoinhibition is light-induced reduction in the photosynthetic capacity of a plant, alga, or cyanobacterium. Photosystem II (PSII) is more sensitive to light than the rest of the photosynthetic machinery, and most researchers define the term as light-induced damage to PSII. In living organisms, photoinhibited PSII centres are continuously repaired via degradation and synthesis of the D1 protein of the photosynthetic reaction center of PSII. Photoinhibition is also used in a wider sense, as dynamic photoinhibition, to describe all reactions that decrease the efficiency of photosynthesis when plants are exposed to light.
https://en.wikipedia.org/wiki/Photoinhibition
And while photoinhibition is a direct result of too many blue light photons (high energy quanta),
the direct adverse effects of too many red light photons (low energy quanta ) is called "light saturation" .
"Above the light saturation point, the light-dependent reactions are producing more ATP and NADPH than can be used by the light-independent reactions for CO2 fixation. "
That excess energy ends up dissipated via non-photochemical quenching ways,into
internal heat and fluorescence.Too much (red ) light and you're frying the plants .
http://w3.marietta.edu/~spilatrs/biol103/photolab/saturati.html
https://link.springer.com/chapter/10.1007/978-3-319-16730-5_11#page-1
Cheers
P.S. :
Haven't we been through all these stuff some years ago ?
How come they are still matters of question and research ?
They should 've been "basic knowledge " of mj growers by now ...
Cannabis Sativa species is peaking . To take advantage of more light ,the other two factors ( Ta / CO2 )
need to be adjusted accordingly .
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3550641/
2) Photosynthesis functions like ...LEDs(but over a certain threshold = ~ 30 μmol/sec/m^2 ),
meaning :
- Lower light power available = low Photosynthetic rates =higher photosynthetic efficiency (thus higher yield efficiency ,but low overall yield per plant and/or grow area surface )
+ Higher light power available =higher photosynthetic rates= lower photosynthetic efficiency
(thus lower yield efficiency ,but higher yields per plant/ grow area surface )
3 ) Overdoing it with light power can and may have serious adverse effects.
It's called "photoinhibition "- for some people around here that they claim that this is a myth.
The photosystem II is stopping producing the photocomplex protein D1 which activates
the PSII.As a result is the canceling of chlorophyll biosynthesis at the PS II (thus the initial symptoms look like "bleaching" )
and if the source of the problem is not removed then the plants eventually will wither and die prematurely.
Basic wikipedia knowledge : Photoinhibition is light-induced reduction in the photosynthetic capacity of a plant, alga, or cyanobacterium. Photosystem II (PSII) is more sensitive to light than the rest of the photosynthetic machinery, and most researchers define the term as light-induced damage to PSII. In living organisms, photoinhibited PSII centres are continuously repaired via degradation and synthesis of the D1 protein of the photosynthetic reaction center of PSII. Photoinhibition is also used in a wider sense, as dynamic photoinhibition, to describe all reactions that decrease the efficiency of photosynthesis when plants are exposed to light.
https://en.wikipedia.org/wiki/Photoinhibition
And while photoinhibition is a direct result of too many blue light photons (high energy quanta),
the direct adverse effects of too many red light photons (low energy quanta ) is called "light saturation" .
"Above the light saturation point, the light-dependent reactions are producing more ATP and NADPH than can be used by the light-independent reactions for CO2 fixation. "
That excess energy ends up dissipated via non-photochemical quenching ways,into
internal heat and fluorescence.Too much (red ) light and you're frying the plants .
http://w3.marietta.edu/~spilatrs/biol103/photolab/saturati.html
https://link.springer.com/chapter/10.1007/978-3-319-16730-5_11#page-1
Cheers
P.S. :
Haven't we been through all these stuff some years ago ?
How come they are still matters of question and research ?
They should 've been "basic knowledge " of mj growers by now ...
Photon Flinger
Well-Known Member
Photo-inhibition is also indicative of too high temperatures. When photons hit a leaf the energy is used for photosynthesis and converted to heat. IF the plant can't manage the heat, you get bad things.
Reduce the temperature and increasing airflow allow more light to be used.
Reduce the temperature and increasing airflow allow more light to be used.
Hybridway
Well-Known Member
Vented Hps runs around 7-10• hotter on the canopy then the rooms temp. W/ fans.
My LEDs are actually 1• cooler then the room at the canopy w/ fans.
I feel the ir does more then raise leaf temp for the plants/buds.
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Photon Flinger
Well-Known Member
My aluminum sheets run 2-10c above ambient.
newguy41410
Well-Known Member
my heatsinks stay around 37°-40° usually. Nothing wrong with that right?