My glass lenses arrived early.. now this is happening [3DCOB] 70watt

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This is my 3d printed LED COB grow light, dimmable, operating range is 30-35 volts at 2 amps. It runs dirt cheap but high quality chinese full spectrum COBs and uses recycled computer heatsink+fans.
I just received these also dirt cheap 60deg glass lens and collimators, I am looking forward to trying these lenses out as right now the lights sit only a few inches above my plants for my desired ultra high intensity.


Ignore the fact only 2/4 of the screws are installed, I installed the others as it was pissing me off :p
Also please excuse the bad first layer, these are just prototypes printed ultra fast
3dcob.png
 
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Olive Drab Green said:
What do you think? Lenses or reflectors?
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So far I am leaning toward lenses with collimators. The problem I was having with the bare COBs was that too much light intensity was lost to poor angles. I just tested these 60 degree lenses and it nearly tripled the light intensity in the same spot. Went from 40-45k lux to 120k lux, so now I am able to raise the light significantly to increase the useful light coverage area. I still have to test for hot spots, but good, even decent glass seems to be the way to go! It really does a good job at directing the light down to where it needs to be.

If i'm being 100% honest though I would go with many smaller (possibly lensed) LED cobs, like I think it would be better to go with 40 5 watt chips over say four 50 watt LED cobs. I think the reason mose cheapo chinese LED array systems like Mars work so well because their light coverage across the whole canopy is so good because of the multiple sources. This reduces hard shadows and really lets the light penetrate deep into the canopy
 
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CobKits said:
so what material did you print that with and how thermally conductive is it?
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All of the frames except this one is ABS plastic, this one is PLA plastic (experimenting, as the lights run cooler than expected)
Inside the frame is a large heatsink+fan combination that handles all of the thermal transfer, the case is actually an insulator, so not ideal :p But the actively cooled computer heatsinks more than make up for this.

Not ideal yes ... but cheap!!
 
Olive Drab Green

Olive Drab Green

Well-Known Member
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All of the frames except this one is ABS plastic, this one is PLA plastic (experimenting, as the lights run cooler than expected)
Inside the frame is a large heatsink+fan combination that handles all of the thermal transfer, the case is actually an insulator, so not ideal :p But the actively cooled computer heatsinks more than make up for this.

Not ideal yes ... but cheap!!
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I use Vero29C 7th Gens and CXB3590s with Angelina reflectors. Never had a single problem with intensity. I was just asking his opinion.
 
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Olive Drab Green said:
I use Vero29C 7th Gens and CXB3590s with Angelina reflectors. Never had a single problem with intensity. I was just asking his opinion.
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I would be so happy to have some Veros or Crees, unfortunately I only have these pretty much untested, unbranded, previously unseen (at least to me), LED cobs by an unnamed chinese factory that cost $4.20 each. If I had a proper name brand COB and PAR meter the results would probably show the chinese cobs have lower efficiency. The spectrum is a pretty crazy full spectrum pink though. I am suspicious they may even have UV in them. I wish I could measure the spectrum.
 
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CobKits said:
ill send you some real cobs if you teach me how to use my lulzbot lol
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hehe printing is the easy part, since your printer does not have automatic bed leveling (i think), it will be a little bit of a bitch to get a good first layer. This really is the hardest part of 3d printing. I have an automatic bed leveling probe so I cheat a bit :p.

If you can spare the time I suggest you research the following topics on youtube: Bed Leveling, Infill, Retraction, and like a 3d printing 101 type video.\
For software use Cura, it's just the easiest and free, and it is very advanced. You just need to add your printer as a "Custom FDM Printer" and you're pretty much ready to download something and hit print.

Them lulzbots are some nice kits out of the box, once you get it going you shouldn't need to mess with it too much.
The hard part for me is learning how to use Autodesk Fusion 360 to model my parts to print. It's really not too bad to learn, and best of all it's free for hobbyists and students!
 
wietefras

wietefras

Well-Known Member
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I just tested these 60 degree lenses and it nearly tripled the light intensity in the same spot. Went from 40-45k lux to 120k lux, so now I am able to raise the light significantly to increase the useful light coverage area.
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These lenses are focusing the light in a circle which is a third of the diameter of the bare COB. Which means the surface of the lit up area is reduced to one ninth. So you should really be measuring an intensity that's 9 times higher than without the lens. Although that will depend on where you measure. Which means you should not measure a single spot but a lot of them and average out the measurements.

I also don't understand why you would put lenses on the COBs to focus the light in much a smaller area and then you need hang it higher to "increase coverage". Isn't that just a giant detour?
 
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wietefras said:
These lenses are focusing the light in a circle which is a third of the diameter of the bare COB. Which means the surface of the lit up area is reduced to one ninth. So you should really be measuring an intensity that's 9 times higher than without the lens. Although that will depend on where you measure. Which means you should not measure a single spot but a lot of them and average out the measurements.

I also don't understand why you would put lenses on the COBs to focus the light in much a smaller area and then you need hang it higher to "increase coverage". Isn't that just a giant detour?
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I seem to be losing a lot of light at angles high angles, enough to where the coverage at my desired intensity is about 1 square foot per COB at just a few inches. It's possible I didn't measure a nine times increase because I am just using a camera phone app. I am hoping I will be able to focus much the light lost at angles above 60 degrees. In my preliminary, barbaric testing it seems to be doing the trick, but I am still printing the last of the hanging parts to install this new black light and really test its coverage. I'm hoping I can get 60000+ lux focused in a 1.5 square foot area. We'll see how it goes. I am only using a smartphone app and phone's my built in light meter as the light meter so the measurements could all be garbage anyway.


All I know without the lenses if I increase the distance of the light by just a couple inches the intensity drops by ~25%+ it's dramatic
 
nfhiggs

nfhiggs

Well-Known Member
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So far I am leaning toward lenses with collimators. The problem I was having with the bare COBs was that too much light intensity was lost to poor angles. I just tested these 60 degree lenses and it nearly tripled the light intensity in the same spot. Went from 40-45k lux to 120k lux, so now I am able to raise the light significantly to increase the useful light coverage area. I still have to test for hot spots, but good, even decent glass seems to be the way to go! It really does a good job at directing the light down to where it needs to be.

If i'm being 100% honest though I would go with many smaller (possibly lensed) LED cobs, like I think it would be better to go with 40 5 watt chips over say four 50 watt LED cobs. I think the reason mose cheapo chinese LED array systems like Mars work so well because their light coverage across the whole canopy is so good because of the multiple sources. This reduces hard shadows and really lets the light penetrate deep into the canopy
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Strips are where it's at bro.
https://imgur.com/hCdwUsZ
880 individual LED total, running at 320W in 2x4 space:
https://imgur.com/nQz38Ji
 
Randomblame

Randomblame

Well-Known Member
Such lenses are deceptive. They seem to work, but in reality you'll lose light. Forget values of 98% transmittance, in fact you lose more than 10% with the poor reflector and the lens above. And do not forget that you usually use a tent and much of the light emitted from the side either reflects off the wall or benefits other plants.
If you use multiple COBs, overlapping will compensate that what you call "losses". To get to 60.000lx, you only need to reduce the distance. Over 100klx would lead to bleaching in the long run and such hotspots should actually be avoided.
If you take a look around and read a few COB-light threads, you'll find that most people use bare COB's and refrain from reflectors and lenses.
 
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Hmmm, thank you all for sharing your knowledge! I think I will stick to bare cobs for now as you all make valid points, and my tent walls are indeed reflective. I don't seem to have any problem with plant growth and node density using my bare COBs a few inches from the canopy. Perhaps I will do a solo cup from seed experiment in the future running both with and without lenses.
 
Olive Drab Green

Olive Drab Green

Well-Known Member
Dave455 said:
do you find much reflector loss of light ?
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I don’t have a PAR spectrometer because I’m not rich, but I don’t think so? My plants are actually really tightly noded, and I almost thought I stunted them in yhe beginning, because the nodes were stacked less than a quarter inch directly on top of each other.
 
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