It's tax refund time how much LED light can $1k buy

Those are on centers or from edge to edge from heatsinks?

If you don’t mind me asking, what ways are you gonna be changing them? I had my four in a square at 15” from cob centers. When I was transitioning them to bar, had to tighten them up to about 12” so would fit in space. That seemed that it would be a little better at lower power.

It’s from the centers. I am actually going to kick the whole side rails further out so they will be about 19-20" from the center rail then tilt them so they face the center (10-15°). My 3000k 90cri are on the outside rails 4000k 80 cri is in the center. By doing this, I will get better side lighting and focus more light towards the center as well without wasting so much light.

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I use SOG because My plants are staggered in height due to different start times I found SOG works best for me so far @Myfriendis410


Do you find the 4000k helps or should I just consider getting all 3000k COBs?

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I think if you use the 90cri 3000k is good.

@Daddy has them mixed, we can ask him.

@skgrower and @dbrn32 I think the mixed actually works better. You are covering the whole spectrum very well and the plants want for nothing. Lots of blue all the way to far reds. They veg really fast and impressive flowers. I would build this same exact light again.


Do you think I can make use of some of the heatsinks I have to build this light. I have found that they are ok with one 50 watt cob and a fan blowing on them.

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I find that interesting. The 4000k doesn’t provide anything that the 3000k doesn’t. It’s just more intensity in blue wavelengths. Mixing the two evenly pretty much gives you a 3500k color temp. More of either one just leans toward which one there’s more of. Provided they are blended equally anyway. In your case, a spectrometer would probably measure out around a 3200k color temp. There’s not enough difference between 3000k and 3500k that I’ve seen to justify doing it. Especially since most of the distributors will offer quantity discount at 10 pieces.

About halfway through typing that I realized I’m doing the same damn thing lol. But the intent is much different. My light is not a dedicated flower light. It was picked the way it was to primarily veg under the 4000k qb, and then dim that out and ramp up the 3000k cobs for flowering. The led placement on my light is also a lot tighter and they’re lower powered.

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If you’re gonna go with 50 watt cobs should be fine as long as you’re sure they’ll cool to needed level.

I’m running the test fixture with the driverless COBs over my autos and they run pretty cool. I don’t mind buying something else if I have to. I just happen to have 20 of those heatsinks. I will get what is needed to build a good light. @dbrn32

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Thermal path is pretty much thermal path, and if it’s good with those at 50 watts it should certainly be good with a more efficient led.

My comment above was more along the lines of, as long as you’re confident enough to put s bunch of $20 or more dollar leds on them, I’m good with it.

I’ll be monitoring them with temp probes, so I won’t let any expensive COBs get cooked. I guess it’s time to start looking at what to get and who to get it from. I’ve been following your DIY thread, but there are quite a few to buy from so I’m not sure where to start @dbrn32

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You have 20 of those heatsinks?

If you’re not buying heatsinks you can do something like @Bogleg with those $9 citi 1212’s. You can run 5 on an hlg-185h-c1050a at 40 watts each. Would be extra protection on the cooling. 3 drivers worth of that would probably be fine.

For about $20 per cob you can jump up to a luminous com-22. Would be more efficient like the bigger citi, the vero 29, or the cree cxb3590.

Any of those will be fine. If you’re not buying heatsink and we’re looking at 50 watts per cob, you’re gonna come in way under your budget either way.

But I think doing something around 3-4 200 watt bars would be your ticket. You can have separate dimming on each, and the flexibility to move them around as needed.

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Dryer Thermostat

This thermostat offers excellent thermal protection for about $7. You mount it on one of your heat sinks and wire ALL the lights’ power through the thermostat’s big terminals. If the heat gets too high, it cuts the light power until it cools off. Then it cycles on again. It’s for a clothes dryer so the power handling is like 15 amps and 240 VAC: Plenty high enough for a big grow chamber’s lights. The nice thing is that it cycles back on, so it does not cut off your lights totally and screw up the photoperiod. (Toss out the little thermal fuse,)

My exhaust duct actually fell off and it saved my COBs twice so far. Don’t trust duct tape alone! Screw those ducts together, then duct tape just to prevent leaks.

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@dbrn32 I would really like separate dimmers. I also agree about the multiple bars concept. My biggest concern is that I start plants 3-4 weeks apart to keep it perpetual, so there’s a foot difference in some of them. I’m wondering if I need to build light bars similar to the light setup I have.

Or will the lights be so much better than the Chinese ones that I could build one big one to cover 25 sq ft. And keep it at least 18" away.

Thanks @1BigFella. I was thinking about that when I was working on the dryer last summer. I was wondering if I could get one around 150°, then I forgot all about it. I think thermal protection is a good idea.

Well, they’ll be way better than Chinese panels we have access to on amazon. But you’ll probably still find that having them on separate fixtures will be a lot easier to use. Especially if you’re putting plants into the space in different waves.

I think you’d probably be most ideal with three bars of 5 cobs, or four bars of 4 cobs. Either way will give you a lot of flexibility.

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With 20 of those heatsinks, I can go to 1kw. So we know I need 20 COBs at~$20. 5 drivers capable of driving 200w. Would it be better to spend the money for bigger drivers than needed
To get a little better efficiency. Or not worth it.
Sounds like I’m way under budget using my heatsinks. Around $500 dollars so far @dbrn32

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I forgot to ask yesterday. Can you post a picture of yours or steer me to one of your threads that has a pic? I’m thinking I’ve seen it and liked it, but it could have been someone else @Daddy

That’s more light than you need. 12 50 watt cobs is pretty much where it’s at for a 4x4. I was giving benefit of doubt for the extra 4 square feet saying 15 or 16 lol.

Even at that you’re at or exceeding “cats ass” type lighting system. So I would say hang there and at least run a grow or two. If you want more after, then address it. But I don’t think you will.

Besides cobs and drivers you’ll need cob holders, thermal material, wiring, and frame. But you’re in the ballpark.