DIY LED with COBs - small medium and large grows

  • Thread starter SupraSPL
  • Start date
  • Tagged users None


Hey guys a lot of you know me from RIU or ICMag but for the LED growers here that have not seen it, here is the recipe for building DIY LED very cheaply. Why build a DIY lamp? You can get up to 49% efficiency if you can find the top bins and run them soft (700mA). You can get 36% efficiency with the mid bin running hard (1400mA). The best commercial LEDs (Area 51, Apache, Onyx) are in the low 30s. Another advantage is the ability to have remote drivers to keep that heat out of your grow space and away from the LED heatsinks.

Everything has changed since COBs became available to us. It is much easier to build a lamp and it turns out that 3000K works just fine on its own, better than HPS even.

For the simplest build the best COBS to use are the Cree CXA3070 and Vero 29. The CXA 3000K has 14% blue and the Vero 3000K 8-10%. They are available on Digikey or if you need a bulk order you can save $ on Arrow.

As far as drivers go, 1.4A is a good compromise between cost and efficiency. They are available on eBay for $13, 90% efficient and power factor corrected. You can use Mean Well LPC-60-1400 but it is lower efficiency and not power factor corrected. If you want to run at 1050mA you can use Mean Well LPC-60-1050. The one I tested was 88% efficient.

For heatsinks, CPU coolers work great for small grows. The 92mm Arctic 11 Plus is a favorite because it can be found for $10 and uses a fluid dynamic bearing fan, lots of cooling power and not too loud. Amazon and Newegg sometimes offer them for $10. Currently outletPC has them for $10 with reasonable shipping cost.

If you are building a medium or large lamp, I recommend HeatsinkUSA 5.88" profile. A 12" length is good for (2) COBs and a 24" length is good for (4) COBs. You can cool it with a single 140mm fan to make a super efficient cooling combo. I recommend the Prolimatech 140mm $11 from Amazon. It is quiet even at 13V and moves a lot of air.


The Vero is solder free but the Cree requires a COB holder and to go solder free. Both methods require drilling and tapping the heatsink. I don't mind the soldering so rather than drilling, I mount the COB with Prolimatech PK3 thermal paste and then use kapton to tape the COB in place so it cannot slide sideways. The paste makes a very strong vacuum when you press the COB onto the heatsink. It will not come off from gravity or heat. If you try to pry it off it will break. You have to twist it and then slide it sideways to get it off.

Small build:

Medium build:

Large build:
Last edited:


For wiring I recommend 18 gauge stranded alarm wire. It is cheap on eBay and makes the install much cleaner. You can use this to remove your drivers outside of the tent which also get the AC power out of your grow space (except maybe your circulation fan).

For the connections I use bare .25" crimp slide connectors. I get them from elecdirect but there are lots of parts stores selling them. The slide connectors make a very secure connection with no "flicker" which is very important for LED circuits. Also they force you to use the correct polarity. They make it easy to swap out drivers or swap out LED modules. They make it easy to bug in with your multimeter if necessary. You can use them to make splitters to power multiple fans. Then I heat shrink them for color coding and insulation, also available from elecdirect.


If you really want to build a nice custom lamp, heatsink preparation comes into play. This is especially important if you are running the COB hard. The thing to realize is that aluminum extruded heatsinks are not flat. Cree recommends flattening them and then sanding to 1000 grit US before installing your COB. Aluminum dust is hazardous in my opinion so please wet sand outdoors and wear a mask. The wet/dry sandpaper seems to work much better than dry sandpaper on aluminum.



An evenings work:


I am using about 25W per sq ft but if you think you can keep up with the feeding and watering you can as much as double that intensity

TGA - Ace of Spades (3 buckets = 160 g dry)
IMG_0049a Ace of Spades.jpg

Dinafem - Blue Widow
IMG_0058a Blue Widow.jpg

Reserva Privada - Kandy Kush
IMG_0116a KK.JPG

HSO - Green Crack + HSO - Bubbba Kush + Cali Connection - Purple Chem

HSO - Desert Diesel
IMG_0123b DSD.jpg

IMG_0132a EM1.JPG

Cali Connection - Purple Chem
Last edited:


This guy is the one of if not the top diy guru's there is. He is so generous with help and openness of his idea's. It's literally is the top efficiency of any lighting. Which translates to output. 1.9µmols/w...or for guys stuck on lumens, around 150-160+lm/w...all while in a perfect flowering(and general growth) spectrum for cannabis.

I am building a system pretty much all based on his work and his guidance. It's in the works as we type. Super pumped for it to be completed.

Bringing top quality LED's to the masses.
Thank you as always.


THNX guys. KNNA got me started way back on Gardenscure and he gave away very valuable info for free, even buying reels of top bin LEDs and sourcing dimmable drivers and shipping them all over the world to help LED DIYers. Now we have a great team of growers testing and sourcing equipment and helping each other out. It is amazing what you can achieve with COBs as far as reducing heat/humidity and improving quality not to mention electrical efficiency.

You could build a very small lamp to test it out and then scale it up as large as you want if you like the results

3000K CXA3070 or Vero 29 $40 Digikey
1.4A driver $13 eBay
heatsink/fan - $10 PCOutlet
fan power supply high efficiency - $6eBay
total $68 for 52W dissipation

Of course that does not take into account the costs of all the misc stuff you might not have on hand, soldering iron, kapton tape, thermal paste, slide connectors, heatshrink tubing, zinc chain etc. But it could be even cheaper if you already have a CPU cooler laying around and you could use any old wall wort to power the fan.
Last edited:


One thing KNNA always pointed out is that what LED does best is vegging. During veg you are dealing with a shorter canopy and you can get very rapid growth with very few watts. I use 2-5W/sq ft to veg but I am in no hurry. You could use 10W/ sq ft to veg rapidly.

Since we are dealing with a shorter canopy and less power, COBs might not be the best option for vegging. One of my favorites is the Cree XML-2 4500K. If you run them at 350mA they dissipate 1W each if you run them at 700mA 2W and at 1050mA 3W. There are 88% efficient 300mA drivers available for $3 on eBay and they can run up to 30 LEDs each. You can get one of the most efficient neutral white LEDs in the world (u2 4C bin) for $4.50 mounted on an aluminum star at Fasttech. Another good option is the 5000K Vero 10s which are only $5 on Digikey.


Nice thread,Never really been an LED guy but this is interesting.


Yes that sounds about right.

Was lucky enough to get my hands on some of the biggest the CXA3590. These are the top bin 5000K (150W) COBs. I installed them on Arctic CPU coolers 92mm fan. The $3 driver on the left runs at 250mA. The COB puts out of 200 lumens/W at that current. The drtiver on the right is adjustable from 100mA to 650mA. At 650mA it dissipates about 50W.
Top Bottom