UV supplementation - use the sun?

Hadez411

Hadez411

Well-Known Member
Hi all,

Been reading about adding 5% of your total light as UV-B during the end of flower to boost THC.

I'd like to try to achieve this by bringing a plant or two outside for 1 hour a day, perhaps in the evening since the colour spectrum is more red then.

Anyone done this?
 
M

mr. childs

Well-Known Member
Hadez411 said:
Hi all,

Been reading about adding 5% of your total light as UV-B during the end of flower to boost THC.

I'd like to try to achieve this by bringing a plant or two outside for 1 hour a day, perhaps in the evening since the colour spectrum is more red then.

Anyone done this?
Click to expand...
kinda dangerous bringing them in & out. there is a uvb thread on here that will help you immensely. you could just buy a uvb bulb & separate timer if the funds dedicated to this hobby allow.
 
Hadez411

Hadez411

Well-Known Member
Renfro said:
Well there is no better light source for your plants than the sun. So why not just give them all the time outside that you can?
Click to expand...
The weather is rainy/windy as hell this time of year. Some frosts too. It's barely the same temp as my grow room during the peak hours of the day. I wouldn't want them to become fully sun dependant if I couldn't put them out for a few days at a time. Also that may be too much light stress, wind and temp swings. Next year I'm going to have a window into my grow room for optional sun supplementation.
 
ChiefRunningPhist

ChiefRunningPhist

Well-Known Member
Hadez411 said:
Hi all,

Been reading about adding 5% of your total light as UV-B during the end of flower to boost THC.

I'd like to try to achieve this by bringing a plant or two outside for 1 hour a day, perhaps in the evening since the colour spectrum is more red then.

Anyone done this?
Click to expand...
If you're going for UVB bring them out during the day when the sun is most directly over head for an hr or so.

You can see how the suns position effects the intensity observed at the surface...
Screenshot_2019-04-24-21-42-50~2.png
 
ChiefRunningPhist

ChiefRunningPhist

Well-Known Member
Hadez411 said:
I definitely will. I'm looking further into when the best time is and trying to crunch some figures on how much of my plants DLI will be UV-B with an hour of exposure at noon.
Click to expand...
Go by UV index.

UV index weights the total emmision from 280nm - 319nm at 99% weight and the rest (320nm-400nm) at less than 1%. So UVI is most influenced by UVB.

A UVI of 10.0 means there is 250mW/m2 of erythemally weighted emissions. 250mW is the figure they got when they added up all the emissions from 280nm-319nm and weighted each individual WV at 1-99% with 280nm being 100% and 319nm being 1%, and then added up all the 320nm-400nm emissions and weighted each individual WV with a max weighting of less than 1%, equating 320nm to the highest weighted nm in that range (320-400) but at less than 1%, and then equating 400nm to the lowest weight% at 0%. The total between all the weighted sums is 250mW erythemal or a 10.0 UVI day. They use an arbitrary 25mW/m2 to divide the total erythemally weighted emissions by, to give a nice easy fugue to use. So 250mW/m2 ÷ 25mW/m2 is 10, or a UVI of 10.0.


EDIT:
2 hrs under a 10.0 UVI equals...

1mW = 0.001W
1mJ = 0.001J
W = J/s
mW = mJ/s
hr = 3600s


10.0 UVI × 25mW/m2
=
250mW/m2 erythemally weighted emissions

Then..

[(250mW)·(2hrs)] × {[(mJ/s)·(1/mW)] × (0.001J/1mJ) × (3,600sec/1hr)}
=
(250)·(2)·(0.001)·(3,600)·mW·hr·mJ·sec·J
________________________________________
(1)·mW·hr·mJ·sec
=
1,800J


{...} conversion factor for future calcs...
(3,600)·(0.001)·mJ·sec·J
________________________
(1)·mJ·sec·mW·hr
=
3.6J/(mW·hr)


In a nutshell...
Multiply any UVI by 25mW/m2, then by the duration of hrs exposed, and then finally by a conversion factor of 3.6 to calculate total erythemal doseage in J per m2, or use a conversion factor of 0.0036 to calculate total erythemal doseage in kJ per m2.

(10.0)UVI × (25)mW/m2 × (2)hrs × (3.6)
=
1,800J/m2

Or...

(10.0)UVI × (25)mW/m2 × (2)hrs × (0.0036)
=
1.8kJ/m2 total dose
 
Last edited:
Hadez411

Hadez411

Well-Known Member
ChiefRunningPhist said:
Go by UV index.

UV index weights the total emmision from 280nm - 319nm at 99% weight and the rest (320nm-400nm) at less than 1%. So UVI is most influenced by UVB.

A UVI of 10.0 means there is 250mW/m2 of erythemally weighted emissions. 250mW is the figure they got when they added up all the emissions from 280nm-319nm and weighted each individual WV at 1-99% with 280nm being 100% and 319nm being 1%, and then added up all the 320nm-400nm emissions and weighted each individual WV with a max weighting of less than 1%, equating 320nm to the highest weighted nm in that range (320-400) but at less than 1%, and then equating 400nm to the lowest weight% at 0%. The total between all the weighted sums is 250mW erythemal or a 10.0 UVI day. They use an arbitrary 25mW/m2 to divide the total erythemally weighted emissions by, to give a nice easy fugue to use. So 250mW/m2 ÷ 25mW/m2 is 10, or a UVI of 10.0.


EDIT:
2 hrs under a 10.0 UVI equals...

1mW = 0.001W
1mJ = 0.001J
W = J/s
mW = mJ/s
hr = 3600s


10.0 UVI × 25mW/m2
=
250mW/m2 erythemally weighted emissions

Then..

[(250mW)·(2hrs)] × {[(mJ/s)·(1/mW)] × (0.001J/1mJ) × (3,600sec/1hr)}
=
(250)·(2)·(0.001)·(3,600)·mW·hr·mJ·sec·J
________________________________________
(1)·mW·hr·mJ·sec
=
1,800J


{...} conversion factor for future calcs...
(3,600)·(0.001)·mJ·sec·J
________________________
(1)·mJ·sec·mW·hr
=
3.6J/(mW·hr)


In a nutshell...
Multiply any UVI by 25mW/m2, then by the duration of hrs exposed, and then finally by a conversion factor of 3.6 to calculate total erythemal doseage in J per m2, or use a conversion factor of 0.0036 to calculate total erythemal doseage in kJ per m2.

(10.0)UVI × (25)mW/m2 × (2)hrs × (3.6)
=
1,800J/m2

Or...

(10.0)UVI × (25)mW/m2 × (2)hrs × (0.0036)
=
1.8kJ/m2 total dose
Click to expand...
<3 tvym this community is gold.
 
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