LUX, Wattage & Distance Analysis: 6x CREE CXB3590 Array

[Emilya Green]

This is a graph that I compiled tonight based on extensive measurements of my new COB array. I have tested the LUX hitting the table at 30", 24" 18" and 12" and I have tested it at 10w intervals from 15-245w per side, which equates to 5-81w per COB chip.
The colored sections of the chart show the optimum LUX levels for 3 stages of growth.

I have built this LED COB light array but still have not had a chance to see it in action. The wattages that are shown here are for 3 COB chips in series, so the total array is running twice the current shown in the graph. It occurred to me after my last LED experience that I had better use some good science to determine what the proper distances and wattages should be. I am glad that I did this, or I am sure that I would have been burning up some plants, not realizing how powerful this light can be!

This 6 COB array is designed to be run very efficiently. Since the CRI 90 light from this COB closely resembles the spectrum used to figure LUX, we can use some known numbers from the HID world to figure out where we are at. I have a $30 FC/LUX meter that does a pretty good job of measuring this light. We know that clones and seedlings need between 5000-7000 LUX for optimum growth. We know that in Veg the plants can take a lot more light and depending on how big they are, 15k-50K LUX is appropriate for optimum growth. In flower we can hit them with even more light, and 45K-65K LUX will do just fine. Some plants can stand up to 75K LUX in flower, but you are in risky territory of bleaching up here, and generally anything over 85K would be lethal.

Checking these numbers with what I can now produce in my tent, at 12", it can be seen that this light can definitely be lethal. It looks to be proven by this graph, that around 16" or so, the efficiency of this light is crazy and I should be able to achieve superior growth with far less electricity than ever before, begging to be used in a SCROG situation. Max growth in Veg would be at around 145w per side and in bloom around 190w. The graph also proves that as far as 24" above the canopy, very useable amounts of light are being produced, if that much vertical depth of field is needed. My biggest problem will be making sure that I don't produce too much light.

Now I have a much better idea what I will be dealing with. It will soon be time to test these numbers in the grow room.

 

[Barney86]

Oh wow, that s really made my day mate. I'm still using caveman leds from a time when I didn't even think they had electricity and they still measure 70k at the canopy. No competition for the cob but still better than I thought lol.

 

[Old Salt]

Congratulations Emilya, This is a very good, informative write up. I can hear some complaining "But that's not PAR." To them I say you do what you can. Meters for PAR are expensive, and there are other things I need more than that.

Are you going to map out the coverage under the light at various distances to determine how even the coverage is? Depending on the array's design, you may find a 'sweet spot' where you get a very even coverage. I suspect this will be where the light is at the same distance from the canopy as the COBs are from each other.

 

[Emilya Green]

Congratulations Emilya, This is a very good, informative write up. I can hear some complaining "But that's not PAR." To them I say you do what you can. Meters for PAR are expensive, and there are other things I need more than that.

Are you going to map out the coverage under the light at various distances to determine how even the coverage is? Depending on the array's design, you may find a 'sweet spot' where you get a very even coverage. I suspect this will be where the light is at the same distance from the canopy as the COBs are from each other.

Thank you @Old Salt! I don't think we yet understand what correct PAR actually is, so I would never invest in an expensive meter to measure such a thing. Many tests show that full spectrum light (imitating the sun) is the best for plants overall, and even though we think we understand various responses to specific spectra, such as the Chlorophyll A and B points, I don't think that we human beings yet understand the full picture.
This being said, I am mostly comfortable equating the output of these COBs to LUX, but there are some notable distinctions between this light and HID light based on the characteristics of the efficiency of the emitters. It can be seen on my chart that the inverse square law is not working right... that more usable light actually hits the table at twice the distance as the formula predicts. Odd isn't it? This is the proof that LED light is more focused than incandescent, and also shows the efficiency added by using focusing reflectors along with the COBS. I suspect that this light is a bit stronger than the same LUX of HID light, and I am going to be very cautious when approaching the upper usable boundaries.
It is also interesting that you bring up looking to see how wide the coverage of each light is and at what distances you can see additions to the LUX because of surrounding lights, and being able to map out high and low areas along the table relative to the position and height of the light. At first I was going to shut down all but one light and map out its coverage area at these heights. This would bring into the discussion whether I was using wide or narrow angle reflectors or any reflectors at all. It really could get complicated, depending on if both banks of lights were on at the same intensity or even at all, how much light hits a certain spot on the table.
As I was setting up to do the measurements for the graph presented above, I made a significant observation. As I adjusted the left side to a target wattage, I watched the LUX meter as I dialed up the right side. Sure enough, light coming from adjacent lights was adding to the LUX at my test point. Knowing that even with reflectors directing most of the energy down, enough came from the sides to make a difference.
Now you would think that knowing that there are hotspots and dark spots (relatively) at various points on the table, that you would want to know where they are. Does this matter to the plants which will be existing across various hot and dark spots during their time? I think the answer is no. The plants are going to use an average of the LUX hitting all of its points, and if one leaf or another is getting a little more or less than its neighbors, the plants will adjust. Besides that, I move and rotate my plants all the time, or in the case of a stationary SCROG operation, there is simply so much active surface area, that it really doesn't matter much. If I am ever going to be so close down on a plant that side interaction isn't much of a factor, that plant is going to be in the center of the beam anyway.
With these thoughts in mind, measuring hot and dark spots at the various heights was not attempted.

 

[Barney86]

Oh wow, @Emilya you understand what inverse square law means. And also understand that it doesnt really apply to us. THANK YOU!!!!
I've had to back out of a few threads on here because of people quoting that law then baffling people with science and I'm just sat here like...
"Yeah mate quote all the science you want I don't care, you're still wrong. Those LEDs don't work like that."
But can't post it as all I have is working experience and science says I'm wrong.
I've had it a few time now and it's led people astray. Mostly with guys thinking they can cover enormous spaces with inferior wattage. Because a+B2-3 to the 6th power /zc49 says it's enough to do it at 7ft from the canopy.
Science means nothing in this game if you've never tried to apply it.
Love what youre doing though and I'm gonna have to tag you next time I see someone misquoting the law.
I've still no idea what it is or what it means but I know when people are wrong about it lol X

 

[Emilya Green]

Hey! @fanleaf, I don't want you to miss this!

 

[fanleaf]

Hey! @fanleaf, I don't want you to miss this!

Oh, I wouldn't miss this! I've been waiting for a new thread from ya.
It's funny you mentioned inverse square law. I realized that didnt work here when I built my 42 Cree Cob array and as soon as I did my par testing at different heights I realized in ratio of height I had more par, deeper down than I would expect to see by quite a bit. I've argued with many here about how with par readings of 1150 at canopy I still see over 900 two and a half feet down the plant. "But LED cant do that".....Oh yes, yes it can.
BTW, with the layout of your chips and reflectors (which I would always have on) your chips should blend very well at 12-14" so you could run it there and use less juice and you should see very, very even numbers at 14-16".
16" should be about the sweet spot for mid flower on running on high. If you ever add a few extra chips, that may.....will change.

The nice thing about being able to run that close is the par/lux wont have a fast drop off rate (breaks inverse square law ), and plenty will hit down low.
Seems 16" on high should be great on full blast or 12-14" turned down just a tad.
It is several of the things you mentioned in your original post as to why I give quality Cobs an edge over other light types. Look at what you are seeing running 1 chip per every 1.33sqft of space. Now imagine a 1:1 ratio! Once you are at 1:1 that's where it's just magical IMO.
Anyways, this is gonna be neat! When does the grow start?

And have you compared the chart above with your other LED lights? I know it wont be the same because of the spectrum difference but it may give an idea of the difference.

 

[fanleaf]

Nevermind, I see in your journal it's going to be a bit before a grow starts. I'll be waiting.

 

[Emilya Green]

I have done some more lab tests with my new light array and have some interesting results. It is clear now what Timber is talking about with the more even coverage claim without reflectors, but this comes with a 50% predicted loss of total LUX. It takes 66% more electricity to produce the same amount of light at a point on the table without a reflector, but you get more even coverage. Equalizing out the power, you get the following charts, with and without the reflectors.

Raising the lights to 24" increases the footprint in an interesting way too... compare the 50% Max Lux distance from center with this next chart and the 16" distance charts.

These measurements were taken with one single COB active, and the total LUX able to be achieved was significantly less than when the other 5 lights were lit. Clearly, looking at the energy patterns of these lights, they are additive at any single point on the table. It can be seen that by using higher wattage and no reflectors, a very even light canopy could be achieved, at the sacrifice of maximum LUX. With the spacing between my lights, at 16" height I can achieve 80% of full light for a full 11" diameter from the center of the light and fully half the light from the COB next to it will also hit that space. It makes sense that super even coverage can be had without the reflectors and that with this setup I could achieve a usable but not overly impressive LUX across the entire room while in veg, but in bloom the light needs increase and the reflectors are going to be necessary. This narrows the 80% diameter to 6 1/2 inches with the 50% points at a 12 1/2 inch diameter and with up to 30% of the neighboring light adding to the LUX.

 

[fanleaf]

Still thinking of adding maybe 2 of the 5000k chips? Perhaps 2 without reflectors at all. Lux numbers would be off the charts adding those. They would be additive to the rest of the room but adding a blue peak to the spectrum would have a HUGE impact on the lux levels you see. Red photons carry energy great and I think LUX per LUX do more. If you had all 5000k chips instead of the 3000k your lux numbers would be higher however I think a more even spectrum peaking in red like yours does more for us. Adding a few chips in the 5000k would give a bit more blue but increase LUX numbers by a huge margin. I'm riding in a car right now so I hope that all came out the way it was in my head. I'll read what I wrote when I get back home lol. Car sick looking at my phone.

 

[Emilya Green]

Still thinking of adding maybe 2 of the 5000k chips? Perhaps 2 without reflectors at all. Lux numbers would be off the charts adding those. They would be additive to the rest of the room but adding a blue peak to the spectrum would have a HUGE impact on the lux levels you see. Red photons carry energy great and I think LUX per LUX do more. If you had all 5000k chips instead of the 3000k your lux numbers would be higher however I think a more even spectrum peaking in red like yours does more for us. Adding a few chips in the 5000k would give a bit more blue but increase LUX numbers by a huge margin. I'm riding in a car right now so I hope that all came out the way it was in my head. I'll read what I wrote when I get back home lol. Car sick looking at my phone.

yes, definitely planning to add 2 5000k chips without reflectors, at least for veg, but I am thinking that running those at a lower wattage during bloom just to even out the spectrum, would also be a good thing. There has got to be a point where the blue disappears and the output becomes CRI 100.
Don't text and drive! TTY when you get home.

 

[fanleaf]

yes, definitely planning to add 2 5000k chips without reflectors, at least for veg, but I am thinking that running those at a lower wattage during bloom just to even out the spectrum, would also be a good thing. There has got to be a point where the blue disappears and the output becomes CRI 100.
Don't text and drive! TTY when you get home.

That's exactly how I have tuned my room to work best for me. I am running 16 of the 3000k and 9 of the 5000k and in bloom I run the 3000k at 40w each and the 5000k at 40w each. Not sure what that ratio would be off the top of my head. I guess 16•40= 640 and 9•40=360 so it's a 1.8:1w ratio for me in bloom.

 

[SQl2kGuy]

This is a graph that I compiled tonight based on extensive measurements of my new COB array. I have tested the LUX hitting the table at 30", 24" 18" and 12" and I have tested it at 10w intervals from 15-245w per side, which equates to 5-81w per COB chip.
The colored sections of the chart show the optimum LUX levels for 3 stages of growth.

I have built this LED COB light array but still have not had a chance to see it in action. The wattages that are shown here are for 3 COB chips in series, so the total array is running twice the current shown in the graph. It occurred to me after my last LED experience that I had better use some good science to determine what the proper distances and wattages should be. I am glad that I did this, or I am sure that I would have been burning up some plants, not realizing how powerful this light can be!

This 6 COB array is designed to be run very efficiently. Since the CRI 90 light from this COB closely resembles the spectrum used to figure LUX, we can use some known numbers from the HID world to figure out where we are at. I have a $30 FC/LUX meter that does a pretty good job of measuring this light. We know that clones and seedlings need between 5000-7000 LUX for optimum growth. We know that in Veg the plants can take a lot more light and depending on how big they are, 15k-50K LUX is appropriate for optimum growth. In flower we can hit them with even more light, and 45K-65K LUX will do just fine. Some plants can stand up to 75K LUX in flower, but you are in risky territory of bleaching up here, and generally anything over 85K would be lethal.

Checking these numbers with what I can now produce in my tent, at 12", it can be seen that this light can definitely be lethal. It looks to be proven by this graph, that around 16" or so, the efficiency of this light is crazy and I should be able to achieve superior growth with far less electricity than ever before, begging to be used in a SCROG situation. Max growth in Veg would be at around 145w per side and in bloom around 190w. The graph also proves that as far as 24" above the canopy, very useable amounts of light are being produced, if that much vertical depth of field is needed. My biggest problem will be making sure that I don't produce too much light.

Now I have a much better idea what I will be dealing with. It will soon be time to test these numbers in the grow room.

I love this post and all the science you bring to the forum.

At this point in my research, I have covered soil, nutrients, water and pH to my satisfaction ... and would now like to return to my lights and my environment. That is, I would like to measure the lux at various heights ... and also measure CO2, temperature/relative humidity a bit closer so I can dial in VPD.

I have been using these values as guidelines since June 11, 2019:

HOW MUCH LIGHT DO YOUR CANNABIS PLANTS REQUIRE?

• Clones and seedlings: 5,000–7,000 lux
• Vegetative growth: 15,000–50,000 lux
• Flowering: 45,000–65,000 lux
• Maximum recommended amount of light: 75,000 lux

HOW MUCH PAR/PPFD DO YOUR CANNABIS PLANTS REQUIRE?

Between 200-400 PPFD: This is great for seedlings, clones, and mother plants.
Between 400-600 PPFD: This is great for early to late stage vegging cycles.
Between 600-900 PPFD: This is great for the flowering, fruiting, or budding stage of plants.

X6 1800W LED Full Spectrum Grow Light

... And based on the light data, I have been trying to keep my light about 53 cm (21") above canopy.


*************************************************************


I saw you mention the meter and saw these two available on Amazon ...

Dr. Meter

Holdpeak​

Do you have any feedback for me before I purchase one?

I was thinking the 0.1 to 200, 000 LUX meter ...

 

[Emilya Green]

I think you can go with a much better spectrum and probably a better deal by going with one of our true full spectrum dealers and sponsors to this forum or building your own light. The light spectrum of that light would not be acceptable to me... it is far from true full spectrum and you will be dissatisfied with it because it is going to look very pink. The light meters were plentiful on the big stores websites and I just picked one that sounded good. You have to establish a standard somewhere... and I think I spent just north of $30.

 

[Old Salt]

X6 1800W LED Full Spectrum Grow Light

This is the light I started with for a 2' X 4' tent, only I had the dimmable version. The coverage was not very good. I had four plants in the tent. The two closest to the center of the light produced 40% more than the two at the outer edges. I put this down to the concentrated area that the COBs are in.

You are better off with a light that has its emitters covering more of the tent's footprint. I built an eight COB fixture, with the COBs on a 12" (30cm) grid. My wife won a Mars Hydro TSL-2000. Both of these outperform the X6, at the same power levels. The coverage is more even throughout the tent, and the light is far more natural.

 

[Old Salt]

@SQl2kGuy a light meter (Lux/ft cd) dies not work well at all with the X6. For that you'll need a quantum or PAR meter.

For lights that are 3000°K - 5000°K, par can be estimated as Lux/67.

 

[Remystemple]

Have you used the light yet? I just saw this thread now and crazy how much testing you did, it's awesome! are you looking to ever build the 1 cob / square foot rig?

 

[Old Salt]

Have you used the light yet? I just saw this thread now and crazy how much testing you did, it's awesome! are you looking to ever build the 1 cob / square foot rig?

If you are asking me, then yes I did. It has been used for the last two weeks of veg, and now is at 12/12 for the flip. Links are in my signature block.

 

[Emilya Green]

Have you used the light yet? I just saw this thread now and crazy how much testing you did, it's awesome! are you looking to ever build the 1 cob / square foot rig?

And I am using my light for the first time as well, documented in my current journal.

 

[SQl2kGuy]

I think you can go with a much better spectrum and probably a better deal by going with one of our true full spectrum dealers and sponsors to this forum or building your own light. The light spectrum of that light would not be acceptable to me... it is far from true full spectrum and you will be dissatisfied with it because it is going to look very pink. The light meters were plentiful on the big stores websites and I just picked one that sounded good. You have to establish a standard somewhere... and I think I spent just north of $30.

Thanks for the feedback @Emilya and helping to point me in the right direction.

I will start researching full-spectrum lights this week ... and I will check for the pink color ... I hadn't really noticed that.

Unfortunately, I am committed to these lights for a while ... unless my friend's kids buy them from us as a starter pack.

With the lower quality spectrum, should I expect a lower yield maybe?

Which part of the spectrum will affect the blooming of the buds?

Got it, ... I'll shop around at the big box stores for a reasonably priced meter that measures over 50, 000 LUX.