Thank you, thank , thank you. Says a lot about a person when they’ll help out a stranger. You went above and beyond, thank you for taking the time to pay attention to a greenhorn like myself. Your calculations are stellar. Thank you again.Ya, 30W/ft2 - 35W/ft2 for mid to high efficiency LED (2.35μmol/J - 2.7μmol/J), I'm not sure if you were asking for confirmation or not.
1m2 = 10.764ft2
1W = 1J/s
Lets say your LED pushes ~2.5μmol/J.
2.5μmol/J × (10.76ft2/m2) × [(30J/s)/ft2]
=
807μmol/s·m2
If your fixture is 2.1μmol/J, and your target PPFD is 850μmol/s·m2 then...
(850μmol/s·m2) = (2.1μmols/J) × (10.764ft2/m2) × [(θJ/s)/ft2]
(850μmol/s·m2) ÷ (22.604μmol·ft2/J·m2)
=
[(θJ/s)/ft2]
θJ/s = 37.6W
Walls ect will absorb some of the photons emitted, and if the spread or throw of your trajectory is greater than 1ft2, then youll have to add more wattage to achieve whatever per ft2 intensity you desire.
After further review of your light I'd estimate an efficiency of ~1.5μmol/J. The luminous efficacy of emission of a typical 5000k 80CRI SPD is somewhere around 310lm/W (max lumens per watt, or 100% efficiency). The datasheet linked shows a CRI of 67, so its luminous efficacy of emission is probably closer to 300lm/W (less diverse SPD, SPD is more clumped around base pump of ~450nm which is less observable to the human eye than a higher CRI SPD). The data sheet shows 98lm/W as the highest performing model in the 5000K category. A typical radiometric efficacy of the emission of a 5000K SPD is ~4.55μmol/J, perhaps a bit less considering lower CRI than the one I'm modeling after (a 80 CRI, max μmol/J or 100% efficiency).
View attachment 4471295
(98lm/W) ÷ (~300lm/W)
=
0.326 electrically efficient
0.326 × (~4.5μmol/J)
=
1.47μmol/J
So...
(416W) × (1.47μmol/J)
=
611.5μmol/s
You'd want to divide the surface area that the throw of your light creates by ~610μmol/s to calculate your canopy PPFD, at least concerning the street light. Lets say you hang it to the point that your throw is 4ft2.
(610μmol/s) ÷ (4ft2)
=
152.88μmol/s·ft2
10.764ft2 = 1m2 so...
(152.88μmol/s·ft2) × (10.76ft2/m2)
=
1644.98; 1,645μmol/s·m2; 1,645PPFD
That's quite a bit of blue light and not a very diverse SPD without supplementing with your clamp-on's. I'd recommend hanging the street light so that it provides a throw of ~12ft2 (548PPFD) and then add some 3000K 90CRI bulbs for the clamp-on's (enough for 300 - 350PPFD more, for a total of 850 - 900PPFD).
You can estimate your clamp ons in the same manner but use 340lm/W as the luminous efficacy of emission for a 3000k 90CRI bulb, and 4.8μmol/J as the radiometric efficacy of a 3000K 90CRI emmision. They won't be exact figures but will give you an idea of the wattage per bulb you'd want to buy/use, how many of them, and how high to hang in order to blend your ratio to your desired level.
Also you can buy a cheap light meter to estimate intensity or PPFD from. They are sensative to a limited spectra so they'll measure certain SPDs with more intensity than others and are not exact but they can give a, "this spot is brighter than this spot" type of indication. The measurements may resemble true intensity, or they may not, it just depends on the SPD of emission and the spectral response of the instrument. Price will likely scale with accuracy.
EDIT:
The calcs are averages, so you'll still have greater intensity directly under than at the edges, so if you're not reflecting the side emmisions back in you may want to further increase your hang height to account. If you're good with trig you can calculate an estimate based off the beam angle found on the data sheets, sometimes they're listed as radiance, or in units of output power per steradians per m2.
LED help
- Thread starter Texsun
- Start date
Thank you, thank , thank you. Says a lot about a person when they’ll help out a stranger. You went above and beyond, thank you for taking the time to pay attention to a greenhorn like myself. Your calculations are stellar. Thank you again.
Well spoken. Thank you.
Rocket Soul
Well-Known Member
340 for luminous efficay rating on the 3000k 90cri?? Ive never calculated it myself but ive seen people quote 260-280.
Anyways lovely writeup, how goes your light?
Airwalker16
Well-Known Member
Ya I was wondering about that too...
ChiefRunningPhist
Well-Known Member
@Texsun, @Rocket Soul, @Airwalker16
Yes you guys are correct. Apologies! Its quite a bit lower than 340lm/W! I was referencing a CRI80 and just estimated a small difference.. Smh. CRI90 3000K efficiency metrics of the LM301B emission look closer to ~300lm/W for luminous efficacy & for photonic efficacy, 4.94μmol/J
Attached are the .pdf's which can be zoomed in for a clearer pic ect, but here's a few screenshots for quick reference...
LM301B CRI80...
LM301B CRI90...
As far as the light, I think I've finally gotten over the hurdle of achieving good PFC in the PS. Hopefully have something soon. Will be working on it tonight (I've been getting sidetracked too much!).
Yes you guys are correct. Apologies! Its quite a bit lower than 340lm/W! I was referencing a CRI80 and just estimated a small difference.. Smh. CRI90 3000K efficiency metrics of the LM301B emission look closer to ~300lm/W for luminous efficacy & for photonic efficacy, 4.94μmol/J
Attached are the .pdf's which can be zoomed in for a clearer pic ect, but here's a few screenshots for quick reference...
LM301B CRI80...
LM301B CRI90...
As far as the light, I think I've finally gotten over the hurdle of achieving good PFC in the PS. Hopefully have something soon. Will be working on it tonight (I've been getting sidetracked too much!).
Have some brand new T8, 4’ fixtures.
Nice graphs. Are they proprietary or is this software I can find/download?
You guys have some badass info.
Quick question.
Let’s say you add a reflective Mylar film (smooth or raised hexagonal domes, it matters, I know), but for simplicity reasons, not having a light meter, how do you value the adjustment factor if light height and footprint are ideal? Also, has anyone ever played around with different wall coverings to soak up any negative spectrums?
ChiefRunningPhist
Well-Known Member
Its just an excel file I built to calculate the relevant metrics per SPD. And thanks 
Walls, even reflective, will absorb some light. The process of calculating I posted earlier accounts for total photon emmision, so if you're containing all your photons in an area by using reflective barriers, then you should only diminish your intensity by ~5 -10% (guess) depending on how absorptive your barrier is and how many photons hit your barrier (how high you hang).
Walls, even reflective, will absorb some light. The process of calculating I posted earlier accounts for total photon emmision, so if you're containing all your photons in an area by using reflective barriers, then you should only diminish your intensity by ~5 -10% (guess) depending on how absorptive your barrier is and how many photons hit your barrier (how high you hang).
hybridway2
Amare Shill
Nice Toosh!
Airwalker16
Well-Known Member
White is the best reflective surface we've come up with. Unless in a tent, then the reflective material in them works just fine.
I experimented with an automotive windshield sun reflector. It was used, came out of my vehicle, to my knowledge it didn’t have anything toxic spilt on it. 24 hour experiment. Eighteen light, six dark. Lights on at six am, off at midnight. Visor was placed around plant, not touching, but in an order to reflect as much light as possible at the ninth hour of daylight. At the fourteenth hour, plant looks good, saturated with light. At the fifteenth hour, everything changed. Top growth was drooping, mature fan leaves turning almost a silver metallic color, top fan leaves clawing. Removed reflector, plant sat over night, and almost twenty four hours later, seems to be back to original state. Added twenty five ounces of straight tap water. Previously only r.o. bottle. All other parameters were held constant. Any ideas?
Airwalker16
Well-Known Member
Lol, that was your plant going to sleep man. Normally your lights are off so you don't notice or see it as much. But they're going to go to sleep whether it's dark in time or not.
Airwalker16
Well-Known Member
It's your plant sleeping, man. No question about it. Take a peek at your plant in the middle of its dark cycle. You'll be surprised to see it droopy and looking like its about to die. Hahana
What’s up guys? In my absence I’ve been a little busy. Acquired a new light from work, new freebie that a wind storm blew down. I have a new problem, any help will be reciprocated in electrical/automation help. Scratch my back, I’ll scratch yours. I need ventilation help. I can come up with a dozen ways that might work, or we could all sit around and watch a monkey fuck a football. I need to know what works. Will an in-line 4”-6” fan with carbon filter clean air/circulate the same air? View picks
Attachments
P.S. The bottom will be wrapped and the top joist will be covered with same material. Hope all is well