You’ll be very happy with that setup @MadScientist.
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Thanks Mr. B. Can’t wait to have it here…
First person that got cobs instead of vipars😂 goodjob bro! You wont be disapointed. Unlike the people that bought the viparsXD where are they at again?XD
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I’m right here…haha and I have no complaints about them. They were cheap, and work wonderfully for clones and veg.
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Yes but were not talking growing millions of clones to sell. We want big fat juicy terp filled nuggets of crystally goodnessXD
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I wanted to share with you all my DIY COB light I built. The light is based on four CXB3590s. These diodes are 3000K and run at 36 volts. The 3500Ks are more efficient, but I wanted more red in my spectrum. These are attached to a 30 inch piece of 5.886 inch extruded aluminum heatsink from heatsinkusa. Active cooling is provided by four Noctua 140mm fans. Finally, the COBs will be powered by a HLG 240H C1750B Meanwell driver. This driver is dimmable and will run the COBs up to 1750 milliamps. With four COBs at 1750 mA, that’s about 250 watts. I took a bunch of pictures of the build. Enjoy!
First layout the COB holders. And punch the centers for easier drilling.
Next mark holes for wiring and hanging. I’m short a D-ring, so I’ll have to pick one up.
Next I drilled the holes for hanging and the COB holders. Tappping these is turning out to be a bitch. I broke two taps before getting the hang of it.
I sanded the heatsink where the COBS will go and whipped it down real well with alcohol.
Next step is to mount the COBS. Take the COB holder and flip it over. The chip clicks in place, make sure the positive signs match up. Add a thin layer of thermal compound, then attach the holders firmly to the heatsink.
Next I wired them up in series, so negative from the previous COB goes to positive of the next COB and so on. I put a power cord on the driver and hooked up the positive and negative wires to the COBS.
A quick bench test confirms that the lights are wired correctly. I’m still seeing spots.
Next I hooked up the fans and ran the wires for the remote driver. The fans are simply connected by shoving the rubber feet between the heatsink fins. They may be overkill, but they sure are silent!
Finally I mounted the driver in the electronics section. That little box on top is the 12v power supply for the fans.
Here is the light all complete with plants ready to transplant.
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Very well done! Thank you for the step by step tutorial. 
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Nice clean design @ReikoX. For those yet to take the plunge, that there is a 400w HPS-killer, delivering the same lumens at 30% less electricity and 30% less heat. Even light spread across the canopy, no degradation in light output for, say, the first 40,000 hours of use vs.1000 hours on an HPS bulb.
I like that you use the heatsink as the main structural component of the lamp. Two of those fans would have been plenty for the job - I’ve found even the slightest air movement across the sink provides significant heat mitigation over passive cooling.
I like to use these DC voltage step-down units on my fans, $1 on Ebay, and 1 inch sized. I just glue them onto the side of the fan housing.
-b420
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There you have it the HPS killer, i almost order my lamps with this chip (runs @ 1750k), but i wasn’t sure so ended up buying the regular 3500k ones…
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3500k would be much more efficiant anyways:) that cob is only for people that think the light from the sun turns super yellow around harvest time. Personally ive never seen the sun go soo yellow that i cant take picturesXD
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Agreed @lotus710. 3500K is the sweet spot I think for a universal veg-bloom COB. HPS bulbs are 2700K, 1750K is too far down the red spectrum and lumen/watt takes a big hit.
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what Ive read and some experienced, in the mommy room it grows maybe a bit better than under 5000K , but 3500K was also super , but 90CRI is better, so its also probably more universal. just my two cents
good luck
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How would 90 cri be better when thats layers of stuff put on the light to change the color? Technically a 70 cri would be better then a 90 cri because you get more light.
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It’s a dance between efficiency and spectrum. Photons are photons in the grand scheme of things.
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Ive read what people experienced in compare to 5000k in mums room and mean than its overall better to have that even for mumms (you can flower by them autos). 3500k is also very feer buds and grow of course
And what have written with one man in firma testing, 1750k is not so good as it seems, same results with 2700 if i remember his words correctly
just from my searching ive found as best 3000k 90cri as best for whatewer you want, and thats why ive made it 
But yes, for flowering there was a very known compare 80 with 90 cri and nothing about 70. About 70cri i have no data. Do you have xperiences? Theory doesnt interest me so much 
there is tons of theory sometimes
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It’s really difficult to decipher the spectrum charts in the datasheets when
it comes to 4000K spectrum because of the peaks in BOTH blue and red
ends of the chart.
As you move UP in CRI it puts out less light, but 90CRI “are supposed to”
speed up flowering. Read something about higher CRI closer to natural solar
but have NEVER seen a chart showing say 3000K 70-80-90 CRI in one graph.
Current story - EB strips 4000k were at 30 inches above plant while sexing.
Past runs under 3000 & 35000 the plants would stretch to 12-14 inches in
the time to show sex. This time only reached 8 inches, but the underscape
was pushing hard against the undersides of the fans to get out.
Have a second group ready to sex (different and unknown strains) and since
the heat is mostly over will turn on 3000K & 3500K 80CRI spots to see if it
influences the growth. I’ve moved the EBs down to the same height that is
used for the Veros in the past. For the last month of flower will turn on the
90CRI (with or without the 80CRI) and give it a shot for late flower.
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Wow! That’s some heady shit man. I’m grateful for you really smart guys that can cipher this shit out. I’m gonna smoke a fat one now and marvel at your genius! One Love.
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lumens are not what we want, but 80cri have more in that case (3500K).after month under my diy i see 90cri flowers better faster imo . should be best as you have written - first month 80cri and second month 90cri ,-)
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