How high to hang LED light
- Thread starter mngrower
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Give a few details about your grow. We can help you with a more accurate setting.
I'm currently running 80% on autos in mid flower. They didn't like 100% so I backed it down. Currently they like the sweet spot of 20in canopy to light distance. @VIVOSUN vsf6450
But then I have some early veg photo plants loving 100% at 18in on @ViparSpectra ks2500
I try to watch the response from the plants, to gauge the light. I don't use a meter. I have one, it just don't see the light of day!! Bwahahhahahahahah
There is so much variation in manufacturers, electronics, etc with lights
Alot of specs are bs
Nunyabiz
Well-Known Member
I would get a cheap LUX meter.
Then you'll know exactly where to hang it.
Edit: doh, already got a PAR meter, missed seeing that somehow
Then you'll know exactly where to hang it.
Edit: doh, already got a PAR meter, missed seeing that somehow
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- #5
I have a 5x5 tent,to Dwc buckets,running mars fc 8000 currently at 25 percent,3 weeks into veg. Light about 12 inches,I just lowered it this am
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- #6
Nunyabiz
Well-Known Member
Personally I use the Lux to PPFD calculator as it seems to be a bit more accurate.
And in veg I usually shoot for about 600 PPFD and in flower try to average around 1000 PPFD.
Convert Lux to PPFD - Online Calculator | Waveform Lighting
Online calculator to convert illuminance (lux) to PPFD (micromoles per second per meter squared).
www.waveformlighting.com
Delps8
Well-Known Member
The OP has said that he as a PAR meter. If it's a PhotoBio or any of the inexpensive meters that use the same sensor, he'll have to adjust his readings because the sensor in that meter cannot read light with a wavelength > 660nm and, looking at this page, that model does generate an appreciable amount of light in that higher range.
Other than that, 0.017 is pretty high, based on the data that I've been able to gather and on the testing that I've done. Using a higher factor will result in a lower actually PPFD so he can always turn it up but 0.015 to 0.016 might get him closer to the 10 ring from the outset.
I run autos, so I don't know if this applies to photos but using my PAR meter (Photone app on iPhone), my babies like about PAR 350 as seedlings, then I raise up to about PAR 1,000 as they grow, then start dropping PAR down as they start flower until reaching about 350, which they seem to like all the way through to the end. To me, the height above canopy is more about light footprint than strength of the lite so I use a combination of distance and dimming. The ladies in the photo are 6 weeks old. Trichomes are forming. Checked PAR this morning and it's about 425. I think they have about 6 weeks to go.
Delps8
Well-Known Member
Big flippin' thumbs up on this! Those are excellent numbers.I run autos, so I don't know if this applies to photos but using my PAR meter (Photone app on iPhone), my babies like about PAR 350 as seedlings, then I raise up to about PAR 1,000 as they grow, then start dropping PAR down as they start flower until reaching about 350, which they seem to like all the way through to the end. To me, the height above canopy is more about light footprint than strength of the lite so I use a combination of distance and dimming. The ladies in the photo are 6 weeks old. Trichomes are forming. Checked PAR this morning and it's about 425. I think they have about 6 weeks to go.
A few thoughts…
"To me, the height above canopy is more about light footprint than strength of the lite so I use a combination of distance and dimming."
Great way to describe it. I'm going to steal your idea.
I'm no fan of Photone but, if you're getting numbers that are supported by your plants, rock on. If the goal is to get plants to the light saturation point (800-1000µmols in a non-CO2-enhanced environment), almost anything will get you in the ballpark but it's up to the grower to "adjust fire" from there.
If your plants are able to handle 1000 µmols, that indicates that you have a very good grow environment. I used the graphic below (from a Bugbee video) to get things squared away in my tent.
What throws me is, given that you've got a grow environment that supports plants at high levels of light, why are you reducing the amount of food that you're giving them? All research into cannabis demonstrates that plant and crop yield and quality increase as light levels increase, as long as light is the only limiting factor. The one study that quantifies it best includes the data from which I've draw up the following table.
For more info, the title of the paper in the header.
As Bugbee talks about, and which Chandra et al demonstrate, the rate of net photosynthesis starts to roll off > 500µmols, even in a CO2 enhanced environment, but that does not mean that growth and quality diminish at the same rate. That's counterintuitive, of course, and the fact that growth in cannabis appears to be "inelastic", to borrow a phrase from economics, was what spurred the researchers in the FiPS paper.
It's great that you "turn it up to 1000" but reducing PPFD in flower…not this fella!
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- #12
I have a Lux Meter. Never use it though. I just hang my light as high as possible & turn it up till my leaves are praying.
Once the leaves are pointing upward I know I'm good enough. Of course I waste more electricity that way since I'm running my light at a minimum of 70%. You save more by lowering your light & dimming it down. But you still only need to watch your leaves to see if they are praying, twisting or pointing downward. Find the sweet spot where they are praying & you're good.
Once the leaves are pointing upward I know I'm good enough. Of course I waste more electricity that way since I'm running my light at a minimum of 70%. You save more by lowering your light & dimming it down. But you still only need to watch your leaves to see if they are praying, twisting or pointing downward. Find the sweet spot where they are praying & you're good.
Delps8
Well-Known Member
Check the Mars website for recommendations for a non-CO2 environment. If you find a recommendation, follow it.
I just checked their site and I see detailed info only for grows that are using CO2. My thinking is to step through the thought process and get to an answer that will get in the ballpark and then let you fine tune it.
The second picture in the scrollable list of pictures at the top of this page is their PPFD map shows that PPFD is ≈ 1550µmols at 12". If you're at 14", that reduces PFD to about 1400µmols. At 25% power you're getting about 1400*25= 350µmols or perhaps 140*.2=280. With Photone reading 250, that seems to be reading low which means that you would be giving more light than expected for a given PPFD reading from Photone so tired lightly.
This link shows more info re PPFD. I'd take that data because it's a third party and it give info re. ePar which means it's including a broader range of wavelengths. If you scroll about half way down the page, you'll see that there are readings at 12" . Good stuff!
Check out the settings for 75% power - further down the page, on the left. That's showing 1000µmols and a beautiful uniform light spread. Check out the ratio between the full power at 100% for ePar (about 1375) and the PPFD for 75% power and the PPFD guesstimate is pretty close. Hmm, check the power draw values vs the dimmer % - that's where things seem to go off track.
Back to PPFD. 1000µmols is a lot of light. I've run a couple of grows at 950µmols (20 hours lights on) and one of the colas bent a little bit so I backed it down to the high 800's and left it there for the rest of the grow. I add that as background info when you decide what light level you want for your plants.
My plants are at day 29 above ground and are at 685µmols on a 21/3 schedule for a DLI of 52. I've been at that light level for two days because I thought I had a Mg def. That turned out to not be the case so I'll be ramping up to about 750 today. I've posted my light levels below. If you're at 25% power//250'ish µmols, you might want to use my schedule as a guide but look to increase more quickly. I'm growing Chemdog photos and they were at 250 on day 10. If you want to stay with the Photone app, I'd say bump to 350 for a day or two and then add 100µmols per day until you hit about 750. At that point, I think you're actually going to be giving your plants about 900µmols. That's in the range for light saturation which, if you hit it, you'll see leaves doing "photo avoidance" - tacoing or canoeing, or rotating around the axis of the petiole. If you see those symptoms, drop your PPFD by 100µmols and those part of the plant that have reacted to the light levels will turn back to their normal orientation very quickly (for a plant), say within 30 minutes to an hour. I work out of my home office which means I can monitor things pretty closely. My practice is to bump up light levels and check the plants every hour or two over the course of the day. After a day or two of "good to go", I'll bump it up again.
True dat. Unless you can spend a lot of money ($500+ U.S.) to get a super-great meter, just "listen" to your plants. They'll tell you what they need - "praying" leaves or leaves pointing down as if they need water but don't, flower hairs curling down (Owe! Too bright!), those kinds of things. I've had to adapt to what I have; I grow in the corner of a store room that's a pretty constant 68 degrees F and 50% humidity. 80 degrees F and 80% humidity would be much better, but it is what is is and I smoke happy. One of the most important things is to KEEP NOTES! Jot down your thoughts. Take pictures and so on.
Delps8
Well-Known Member
68° - brr. Makes me shiver thinking about it!
Agree completely about keeping notes. I take pictures pretty frequently and I keep a journal in Excel that I update almost every day. By the end of a grow, it's about 1200 lines of text.
What I like about having a meter is that it allows you to get to a value right away. Without a meter, it's a bit of a WAG though the manufacturer's guide lines do help (stay away from the offered without evidence recommendations from Migro and growlightmeter.com, though).
Great way to put it!
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- #17
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- #18
Delps8
Well-Known Member
You raised it 16" before or after?
313 PPFD on the canopy should be fine. If my quick math is correct, your Photone is reading low so your plants are actually getting 350-400µmols. Based on who good they look, they will take that in stride. If you're watering right and temps and RH are good, they should do just fine all the way to normal light saturation of 800-1000µmols.
Some of the leaves on the plant to the right are turned downward. It doesn't look to be anything untoward. Do you think that's a problem?
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- #20
This light is driving me nuts,lol. I raised to 16 inches then turned up the dimmer to get that reading. The whole plant was not going down,just a couple. This grow is Dwc,75 degrees,48 percent rh