Yet another UV thread

[canadian1969]

According to this uva spectrum reduces photosynthesis. So, clearly, if we are going to add uva to these experiments, they shouldn't be on for very long. I'm looking at uva like the initiator of UVB. Any reason to slow down photosynthesis before exposure to UVB? Maybe actually, maybe not.

http://www.fondriest.com/environmental-measurements/parameters/weather/photosynthetically-active-radiation/

I have yet to sort through all the material I have encountered on the subject, but so far it seems life form dependent. Some algae showed reduced or even ceased photosynthesis when exposed to certain wavelengths, others increased function, the papers are out there you can read them, but thats algae , not cannabis.

I feel you can have UVA/B in your grow all the time, but you have to get the balance and intensity right, so there is a choice, high intensity tanning or low intensity integration with your existing light. It doesn't seem to be at all required during veg (confirmation?) and some recommend only using it in the last 2 weeks of flower so as not to interfere with growth presumably.

There are so many experiments to be done

 

[Johnnycannaseed1]

I think here is what is really happening from a power level in a 4x4

0.3 W/m2 (total UV irradiance at ground level on a hot clear August 1st Florida day at 1pm roflmao)
1.49 m2 (tent)
0.3 * 1.49 = 0.447 W

So you only have to throw half a watt across a 4x4 tent to simulate UVA in the solar spectrum (UVB being inconsequential as its such a small amount that a few diodes is fine). So you will have to figure out your square footage and the efficiency of each diode, annnnnd take into account height from canopy annnnnd diode distribution/coverage.

I guess where you want to be is some equal division of the energy across 310-390nm , could be 3 or 7 or more wavelengths, but the power output is of the most concern. The more wavelengths the better of course. But still we are only talking 447 mW total (as replicating the Sun).

I guess there will be a part two to this thread, lol.

Nice Thread Canadian in light (excuse the pun lol) of what anarchist said with regards to his measurements and the readings he obtained with his meter do you think that maybe your figures are possibly on the low side?...

Tbh I was surprised at how high the reading was at 300mW/cm2 @ 400nm but it has been measured so I cannot argue with that, therefore I am thinking an increase by a factor of 100 might be more in line with environmental effects what do you think?

My final thought is you should probably consider Daily light Integral of UVA in respect to Cannabis and factor that into your final analysis... From what I have read UVA/UVB seems to be of particularly high value, especially toward the end (last 3-2 weeks) of flowering because UVA/B invokes a defence response within the plant, which helps it to produce more Jasmonates and increase trichome.production.

Forgot to add too much UV particularly UVB will destroy DNA so I think your ratio of 95%-5% UVA-UVB is probably about right. The destructiveness of UVB seems to be in line with the defence response (trichomes) the plant will produce in order to protect itself, hence the increase in production when UV levels are optimally high.

 

[iHearAll]

I think here is what is really happening from a power level in a 4x4

0.3 W/m2 (total UV irradiance at ground level on a hot clear August 1st Florida day at 1pm roflmao)
1.49 m2 (tent)
0.3 * 1.49 = 0.447 W

So you only have to throw half a watt across a 4x4 tent to simulate UVA in the solar spectrum (UVB being inconsequential as its such a small amount that a few diodes is fine). So you will have to figure out your square footage and the efficiency of each diode, annnnnd take into account height from canopy annnnnd diode distribution/coverage.

I guess where you want to be is some equal division of the energy across 310-390nm , could be 3 or 7 or more wavelengths, but the power output is of the most concern. The more wavelengths the better of course. But still we are only talking 447 mW total (as replicating the Sun).

I guess there will be a part two to this thread, lol.

But with only 4mW radiant power from the led sources we would need a hundred of these? They don't say if its per watt or if its total average. Ill touch back soon when I figure this out.

 

[canadian1969]

But with only 4mW radiant power from the led sources we would need a hundred of these? They don't say if its per watt or if its total average. Ill touch back soon when I figure this out.

Note that the diode efficiency goes up rapidly above 350nm
this was interesting http://www.koppglass.com/blog/current-state-of-uv-led-technology/

 

[iHearAll]

Note that the diode efficiency goes up rapidly above 350nm
this was interesting http://www.koppglass.com/blog/current-state-of-uv-led-technology/

Oh right, so its .44 w-.5w total emission of the general UV spectrum, forgot. Ill pick up some of the digikey uvb diodes I guess. Alibaba distributors touched back and they want 46$ a diode. Clearly the 1$ price tag is a marketing trap. I hate that site a much. For 46$ at digikey I can get four of them mounted and at my door in a week.
https://www.digikey.com/product-detail/en/rayvio-corporation/RVXE-280-SB-071004/1807-1003-ND/7363758

 

[canadian1969]

I would go with the 310's actually, I am still going to try and use my 280s but you get better performance from the Rayvio 310nm. Yes and apparently a little UVB goes a long way so if the average UVA diode efficiency is 15% and the total power required is .4 watts then you would get 0.15 watts per 1 watt diode. So you would need something like 3 x 1 watts diodes right?

3 watts @ 15% eff = .450 watts
I think thats right

I think I have bought way too much wattage actually. Gonna build it into a separate rail and let it run on its own timer for a tested 10, 20 , 30 min a day till I get the right amount.

 

[iHearAll]

http://www.highpowerleddiode.com/sell-2324807-310nm-uv-led-smd3535-light-emitting-diode-plant-growing-lamp.html

The rayvio 310nm are 60$ a piece. The ones linked are 2w plant light diodes for 20$ a piece. Im trying to score data and a three piece price estimate after shipping.

 

[iHearAll]

I would go with the 310's actually, I am still going to try and use my 280s but you get better performance from the Rayvio 310nm. Yes and apparently a little UVB goes a long way so if the average UVA diode efficiency is 15% and the total power required is .4 watts then you would get 0.15 watts per 1 watt diode. So you would need something like 3 x 1 watts diodes right?

3 watts @ 15% eff = .450 watts
I think thats right

I think I have bought way too much wattage actually. Gonna build it into a separate rail and let it run on its own timer for a tested 10, 20 , 30 min a day till I get the right amount.

Sounds smart. You can get real close with a separate bar.

 

[canadian1969]

http://www.highpowerleddiode.com/sell-2324807-310nm-uv-led-smd3535-light-emitting-diode-plant-growing-lamp.html

The rayvio 310nm are 60$ a piece. The ones linked are 2w plant light diodes for 20$ a piece. Im trying to score data and a three piece price estimate after shipping.

My bad, I thought they were the same price. All I am saying though is that the power drop off below 310 is so significant that you probably dont need to go down to 280, where a good 310-320 diode would probably suffice. In theory they should be more efficient and cheaper. In theory.

 

[iHearAll]

My bad, I thought they were the same price. All I am saying though is that the power drop off below 310 is so significant that you probably dont need to go down to 280, where a good 310-320 diode would probably suffice. In theory they should be more efficient and cheaper. In theory.

Yea totally agree

 

[Abiqua]

In vitro dried leaf analysis was the "general consensus". I have seen exactly one study, thanks @CobKits........
How many studies do I need to post showing UV-b either as inconsequential or an inhibitor....it really takes just a Google Scholar search to find a decent article and then READ the bibliography.......

@Growmaus5 might attest to more UVA......but they themselves might want more qualitative samples before making any solid declarations....

Terpene content could be modulated with more 660 and 4k....ala @greengenes....

I still like deep red from white and some added blues to stimulate "far blue".....I think there is hope in that direction, in vivo.

 

[Abiqua]

Another thing wavelengths throughout the day...vary considerably....an average is good, but its not a mimic....

 

[iHearAll]

Another thing wavelengths throughout the day...vary considerably....an average is good, but its not a mimic....

It's about as entertaining as a good aquarium though

 

[canadian1969]

Another thing wavelengths throughout the day...vary considerably....an average is good, but its not a mimic....

I think you mean that the intensity changes through the day, wavelengths are always the same, the sun cannot change its colour and the sun puts out all wavelengths 100% of the time. The refraction of sunlight through our atmosphere makes it seem like it though.

 

[canadian1969]

Someone convert 400uW/cm2 to W/m2 for me before my brain melts.

 

[Johnnycannaseed1]

Someone convert 400uW/cm2 to W/m2 for me before my brain melts.

400 Microwatt to Milliwatt is 0.4Mw

0,4Mw/cm2 = 4W/m2

 

[Devildenis69]

I think you mean that the intensity changes through the day, wavelengths are always the same, the sun cannot change its colour and the sun puts out all wavelengths 100% of the time. The refraction of sunlight through our atmosphere makes it seem like it though.

First of all I would like to thank you for all findings you are sharing, I started few researches about uv, but it got messy and I dropped it along the way ...
Just about the sun not changing its 'color', I believe you are wrong, I don't have any sources to support my claim, but I am pretty sure I read that the most UV and 640-680 is emitted during noon, while most blue and FR is emitted during sunrise and sunfall.
I widh you best luck with your findings

edit: not actually the sun changing its spectrum, but the light flux having different energetic 'drifts' while travelling until our leafs.

 

[iHearAll]

I was quoted:
- 6$ a piece for 1.2mW radiance 310nm diodes. 20mA 5-7v.
Model th-uv310t1wa-3535

-30$ a piece for 9.5mW radiance 310nm diodes. 200mA 5-7v.
th-uv310t1wa-6363

Free pcb star mounting service.
Unfortunately they want 31$ for shipping.
I'm on the fence here and I think the way to go is to have a separate hanging uvb light the i can max effectiveness with daily repositioning. The 6363 model is the best bang for your buck but is point source and I think these leds will have a pretty great drop off in efficiency with distance, similar to the fluorescent bulb.

Probably won't purchase anything until the tech is better and more cost effective. Anyone interested in links to this supplier just pm me.

 

[canadian1969]

I guess they would be in a sphere talking those readings eh?

 

[Abiqua]

I think you mean that the intensity changes through the day, wavelengths are always the same, the sun cannot change its colour and the sun puts out all wavelengths 100% of the time. The refraction of sunlight through our atmosphere makes it seem like it though.

umm no....https://science.nasa.gov/science-news/science-at-nasa/2003/17jan_solcon

there are a host of factors from albedo to humidity.....the sun is never static...in intensity and wavelength....