DIY LED with COBs - small medium and large grows

[DGP]

Interesting thread, thanks so much for posting all of the data and experience!

I was designing chip on board systems 7 years ago for industrial applications (up to 6 KW systems... thats true power not equivalent to arc/plasma or HID) and I often wondered when this technology was going to hit the cannabis and grow light market. In past years the COB substrates were typically very expensive being they were surface mounted and wire bonded to Alumina Nitride or synthetic diamond. The systems we worked on that were in the KW range used chilled water as coolant. Water cooled systems although somewhat of a hassle might be great for big grows cause you extract almost all the heat out of the room via the chiller. I have also wondered when someone would do a big grow with water cooling or water pumped through fan assisted radiators that are outside the room. wouldn't be cheap but in the long run could save a lot in AC and the power bill for a big setup.

We used Cree and Samsung and I really believe they are some of the best but since I left the industry I suppose others have come along with good LED's as well. They had the highest efficiency and the top bin stuff was really tolerant of running at temperatures above recommended Tj (junction temps).

I want to build a system because so many of the commercial offerings seem shady (no pun intended) being made in China with little accurate data on the real CRI or brightness. I have lived and worked in Asia and have seen the lack of reliable data and the out and out lies on specification sheets or components used.

So, I see it costs about the same or slightly more to build one but the difference seems to be in the end you actually know what you have.

Thanks Again for the thread!

DP

 

[CBDfutute4]

Just watched YT video on HLGs new veg light kit for $99. Pretty damn cool

I have the next one up. 185 bux, 135 or 150 w

Just setting it up n tossing it in with a 600hps. I've got a vented hood so I'm not going to melt it. Plus I'm putting a 80mm fan for some active cooling.

 

[Dawn Patrol]

I want to build a system because so many of the commercial offerings seem shady (no pun intended) being made in China with little accurate data on the real CRI or brightness. I have lived and worked in Asia and have seen the lack of reliable data and the out and out lies on specification sheets or components used.

So, I see it costs about the same or slightly more to build one but the difference seems to be in the end you actually know what you have.

Thanks Again for the thread!

DP

Do it, you won't regret it especially since you already know what you're doing! The only downside I've experienced is that just like building a PC, as soon as you're done there's something better coming along.

 

[CBDfutute4]

Do it, you won't regret it especially since you already know what you're doing! The only downside I've experienced is that just like building a PC, as soon as you're done there's something better coming along.

I would agree

All my led research in the last year has kept me finding new companies using different tech.

I still think the cobs, especially the newest ones n the Samsung strip 561 are as good as your going to get

It was mentioned before, its more if u get stuff of quality. The old cob 3070 n now vero/Crees are all great, but u just want to make sure your buying stuff as advertised. Idk what comes out of some of the Asian countries but we do have a few, good, solid rep led companies in the us.

They mostly just sell out all the time cuz ppl know quality. The good n bad gets out over the net n forums like this.

 

[DGP]

I want to build a light for a small 2x4 tent to see how it goes before I build a larger system for my 4x5 room. Any suggestions for which led and driver? Would like to build something I can scale up later.

Thanks,

Dp

 

[Dunge]

My problem is not exactly a DIY, but fixing 3 piece of crap LEDs is not likely to be done by anybody other than myself.

The COBs started burning out in a few weeks, but after 19 months, only four of the original 15 COBs still worked.
Fans and power modules are still good but:

These things are toast.
Note that they are all wired red to negative.
Can this be the cause of the failure?
They look cooked.
Does this indicate that the thermal design is a fail?

I can't find any identification markings on the COB.
Is it worth replacing all 15, or is the thermal fail a design flaw that will just cook the replacements?

Any help is appreciated.
Thanks

 

[Toaster79]

My problem is not exactly a DIY, but fixing 3 piece of crap LEDs is not likely to be done by anybody other than myself.
View attachment 764548
The COBs started burning out in a few weeks, but after 19 months, only four of the original 15 COBs still worked.
Fans and power modules are still good but:
View attachment 764549
These things are toast.
Note that they are all wired red to negative.
Can this be the cause of the failure?
They look cooked.
Does this indicate that the thermal design is a fail?

I can't find any identification markings on the COB.
Is it worth replacing all 15, or is the thermal fail a design flaw that will just cook the replacements?

Any help is appreciated.
Thanks

What are these "COBs" attached to? Is there a big chunk of a heatsink in there or just that thin metal sheet? Any kind of thermal pad or paste between the emitter and the mounting surface? Drivers are working properly? Can you rewire a driver from a toasted COB to a functional one and measure the voltage and current? Do the same prior to rewiring? What does it say on those drivers voltage and current wise?

 

[Dunge]

What are these "COBs" attached to? Is there a big chunk of a heatsink in there or just that thin metal sheet? Any kind of thermal pad or paste between the emittee and the mounting surface? Drivers are working properly? Can you rewire a driver from a toasted COB to a functional one and mesure the voltage and current? So tje same prior to rewiring? What does it say on those drivers voltage and current wise?

I unplugged the driver from a broken lamp and plugged it into the working lamp.
They all worked, so the drivers are all still good.
There is a smear of thermal paste under each COB base to an aluminum mounting plate. The fans blow on this plate.
Is the reverse wiring an allowed configuration?
These are my drivers.

Thanks

 

[Toaster79]

I unplugged the driver from a broken lamp and plugged it into the working lamp.
They all worked, so the drivers are all still good.
There is a smear of thermal paste under each COB base to an aluminum mounting plate. The fans blow on this plate.
Is the reverse wiring an allowed configuration?
These are my drivers.
View attachment 764552
View attachment 764553
Thanks

The aluminum plate, how thick is it approximately? 3/16 or so? Just a plate, no ribs on the inside? The white paint, is it also beneath those cobs?

Drivers are 27-36V, 1.5A, so you could easily hook a 3590, vero7 or citizen 1818 instead of that chinese trash.But first get the thermal path and heat dissipation in check.

 

[Dunge]

The aluminum plate, how thick is it approximately? 3/16 or so? Just a plate, no ribs on the inside? The white paint, is it also beneath those cobs?

Drivers are 27-36V, 1.5A, so you could easily hook a 3590, vero7 or citizen 1818 instead of that chinese trash.But first get the thermal path and heat dissipation in check.

Thanks.
And the reverse wiring.
Any thoughts on that?

 

[Toaster79]

Thanks.
And the reverse wiring.
Any thoughts on that?

If they were wired reverse, they would have never worked.

I would really appreciate if you answered the questions about the heatsink. You can get those running on a budget until those drivers die if you do it right. And get better spectrum and efficiency while you're at it.

 

[Dunge]

If they were wired reverse, they would have never worked.

I will grind off the paint under the COB and put fresh thermal paste on.
May try to find heat sinks that I can add to the plate.

This is what I found on disassembly.

 

[Itsagas69]

Heres Cutter Au. Website

Cheers mate appreciated

 

[Cob scribble]

U c

My problem is not exactly a DIY, but fixing 3 piece of crap LEDs is not likely to be done by anybody other than myself.
View attachment 764548
The COBs started burning out in a few weeks, but after 19 months, only four of the original 15 COBs still worked.
Fans and power modules are still good but:
View attachment 764549
These things are toast.
Note that they are all wired red to negative.
Can this be the cause of the failure?
They look cooked.
Does this indicate that the thermal design is a fail?

I can't find any identification markings on the COB.
Is it worth replacing all 15, or is the thermal fail a design flaw that will just cook the replacements?

Any help is appreciated.
Thanks

U call dad for sure put some butter on that toast

 

[DGP]

Just finished my first light build. I am using 3 of the luminous LX22 90 CRI 3000K 50V (150W) chips with a copper slug and aluminum fin type CPU cooler.



I ran them last night a 50% power (70W per COB) which is about where I want them and the heat sinks seemed very cool for the first few hours but later in the night after being on 8 hours or so they were quite warm (could touch them but only for few seconds or less). I used the best performing Shinitsu thermal grease on the market. The light assembly is in a 2X4X6 veg tent. Maybe they would cool better in my much larger flower room but what is amazing is it only added a few degrees to the tent where an HPS lamp cooks it without cover glass on the lamp and isolated air coming in and out of the hood.

How hot should my heat sinks be if they are doing their job correctly? Anyone know?

I am about to set up some thermo-couples and maybe even bury one under the chip in a tiny notch so I can calculate the approx. temperature of the LED junctions. Also, I will put a spot of thermal paint on the top of the heat-sinks (emissivity correcting paint) and do some IR scans to see the exact surface temp of the heat sinks.

BTW the lights seem very bright and the color seems really natural.....

Thanks,

DP

 

[DGP]

In my 2X4X5 grow tent I took some data. The Luminous 150W LEDs at 75 watts (3 COBS) are running well and I think the temperatures are reasonable (the hot spot is under 95 F and a delta over ambient of about 25 F). The heat sinks are some surplus copper slug base assemblies with folded fins. I also have some of the Arctic pro heat sinks with 80mm impinged fans that are what LEDgardener.com recommends. My plan is to see which heat sink performs the best. The Arctic ones are $13 and the surplus ones are $2 and as you all know it really adds up when building an array to fill even a small 4X4 space.

The most critical thing I noticed in the tent application is the thermal problem of having a hot air bubble form in the top of the tent that chokes off cooling of the heat sinks. Adding more ventilation (and keeping the air stirred up) in the upper part of the tent seems to have solved this. My initial run had a issue with the LEDs trying to go into thermal runaway even though the ambient temperature in the tent was generally normal (say in the middle or lower part of the tent).

The plan is to run one 3 COB (12" spacing) bar in the veg tent and 12-16 COBs in the 4X4 flower room (3 or 4 sets of 4 on a bar).

Attached is an Excel chart.

Here is what I am using:
-Meanwell HLG-240-54B 50V Constant current/constant voltage 200w with dimmer
-Luminous CXM22 Gen3 90 CRI 50V LED's capable of 150w running at 75w wired in parallel
-BJB holders
-14 gage solid copper insulated wire
-3 copper heat sinks with folded fins
-3 60mm 12V 1.6 amp fams
-3 Angelina reflectors
Aluminum angle stock tying the COBs together along the edges of the heatsinks

Cost for the 3 COB bar was about $177.

DP

 

[DGP]

Pictures:
-3 COB light bar
-Arctic 11 plus fan/heatsink
-Grow tent setup
-

 

[sixstring]

View attachment 766224 View attachment 766225 View attachment 766226 Pictures:
-3 COB light bar
-Arctic 11 plus fan/heatsink
-Grow tent setup
-

You shouldn't have any heat issues with those heatsinks,not so sure about the cheap sinks.i run some cree 3590 at 75w each on a 140mm x 70mm with 10mm base thickness and they are right about at the border of needing fans.they run about 120 to 130f depending on a few variable like wind speeds and temps in the room.

 

[DGP]

You shouldn't have any heat issues with those heatsinks,not so sure about the cheap sinks.i run some cree 3590 at 75w each on a 140mm x 70mm with 10mm base thickness and they are right about at the border of needing fans.they run about 120 to 130f depending on a few variable like wind speeds and temps in the room.

Yeah, the surplus heat sinks worked but not quite as well as the Arctic 11 plus. So, that is what I am going with. Already ordered a bunch more from NewEgg who happens to be selling them for $7.61 right now so with shipping they are under $10.

I didn't even take formal data on the Arctic 11's because the hottest spot on them never went much above 85F and only about 15F over ambient. The surplus ones were about 25F over ambient.

I completed testing yesterday of the first fixture I built and it is already running some rooted clones in the veg tent.

It seems Cree has always been the gold standard for the industry but I really wonder if these 90 CRI Luminous parts aren't just as good. They seem to be readily available stateside (without having to wonder about what you get from China) and are only $19 for the 50V/150W version.

DP

 

[sixstring]

Yeah, the surplus heat sinks worked but not quite as well as the Arctic 11 plus. So, that is what I am going with. Already ordered a bunch more from NewEgg who happens to be selling them for $7.61 right now so with shipping they are under $10.

I didn't even take formal data on the Arctic 11's because the hottest spot on them never went much above 85F and only about 15F over ambient. The surplus ones were about 25F over ambient.

I completed testing yesterday of the first fixture I built and it is already running some rooted clones in the veg tent.

It seems Cree has always been the gold standard for the industry but I really wonder if these 90 CRI Luminous parts aren't just as good. They seem to be readily available stateside (without having to wonder about what you get from China) and are only $19 for the 50V/150W version.

DP

Yeah the lumi chips are a great value and that guy cobkits has tried very hard to get us cheaper cobs at an equal quality. Tell ole Bobby I said hi when ya order. Also if anyone wants cheap cree Jerry at King bright has them down to about 30 bucks per cob now