Lol. Kids. I know about those. Back at work, and I’ll be climbing under a building next. I’ll check this measurements before I leave today. The power supply says 5.4A
@dbrn32
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On paper that’s enough to run 10 fans. I don’t know if that will play out to best scenario, but no more than two power supplies at max. You’ll be good.
Free is great, but typically PC power supplies put out a lot of current at 5 volts or recently 3 volts, and not much at 12 volts. I think some of them won’t even work if you only draw current on the 12 volt circuit because all the fancy switching is for the 3 volt circuit.
But that’s wonderful if you can get free heat sinks with fans. They usually cost more than the COB. And those little whisper fans usually take 4-6 watts, so you might want to use them because they make the heat sink about 4 times as effective.
You can usually get them to work with a jumper. Have done a couple of them and never had a problem. The seen one the went molex to molex on one of those pc fan controllers too. Was pretty sweet! I didn’t source the parts or inspect closely for mods either. So I’m not really sure what it takes. But guy was jamming 8 fans on 4 channels with what appeared to be full speed control.
Yeah, the jumper in the main molex is a given. Or you can just find the two wires and splice them together. But I meant even if you do that they might not work. Most will but I’ve seen some that won’t.
On another topic: Does anybody make high power red COBs? Like 50 watts or above.
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I can believe that. It’s hard to say anything is certain in the electronics world. Just when you think something can’t be feasibly done, out comes your answer.
By red cobs, what are you looking for, like a specific 660nm cob? Or something that has almost all red wavelengths? @1BigFella
@dbrn32 so the solid aluminum part measures 1.5” wide. But the cooling fins all the way across are 3.5” inches. There’s a “step out” that I might have to machine off with a grinder. Unless you think it would work just fine. Guess who scored more heatsinks after a search in another building??
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looks great 1.5” is like 38mm, I think you’re good. The cob is much smaller, but these have built in holder. Unlike the cree where you had to purchase a separate holder.
I think doing something with the vero 18 is going to be a good choice, gen 7 or se. the se is same as gen 7 but comes with poke in connector like your cree’s with ideal holder.
Give them some research and see what you think. It shouldn’t be difficult to find them in use as grow light. I personally have only used the bigger 29 model, but they’re just a smaller version of the same thing. If you like what you see, we can start narrowing down a model number and looking for drivers.
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@dbrn32 We can also spend a little extra on LED’s. If there’s one that would fit better on there. I have a few heat sinks that are very large, and I know a Cree would fit. I grabbed 4 power supplies just in case. Haha. After I disassemble the other PC’s, I’ll see what other heat sinks I can get from those as well. We may be adding even more LED’s than just the veg tent. I would love to add some to the flower tent if I have the heat sinks for it. I just can let a free thing go to waste.
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Well those vero 18’s are about the perfect size, and they perform very well. Better than a lot of the comparable stuff from Cree. They just happen to be cheaper. So it’s not really like making a concession at all.
Bridgelux runs the test data on them between like 20 and 40 Watts, and they come in 3 different voltage configs helps with driver fitting.
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Here’s what I’m thinking… we’ll look for a driver fitment at around 30ish Watts per cob. I think those sinks will cool effectively there. But just in case they are a little iffy, we’ll make sure to go with a dimming driver. That way if for whatever reason they ever got warm, you can dim.
Like I said, I think there’s enough heatsink there that it won’t matter. But can’t be certain without knowing exactly how much surface area there is and what ambient conditions are. But I would build them out like that and see first, and only add the fans if absolutely needed. Even dimmed 10 would be enough to veg at nearly one cob per square foot.
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Yes, I want a 660 nm COB, if they exist. I already found the 2.5 watt Cree LEDs for $3 at RapidLED (and for $2 each on ebay and they claim the are the most luminous bin). I could run a series string of 65 of the LEDs with my DIY driver to get some red if I want to flower. That would be 162.5 watts of LEDs, since I would run them at full power. (1 amp) According to the datasheet, they hardly degrade on efficiency if you run them at full power. The blue or green LEDs do have a bad fall-off when you run them near full power. (Isn’t chemistry interesting?)
I could use the Cree LEDs, but I don’t look forward to mounting and soldering 65 LEDs. If somebody made 660 nm COBs, they would be easier to use. But just finding the LEDs with useful peak is terrific. All I saw before tonight had a peak where chlorophyll doesn’t.
BTW: A lot of Intel processors are 60 or 70 watts, so those cpu heat sinks might handle that if you put the fan on them.
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As far as cobs go, I found stuff like these. But I’m not sure if that’s the performance you’re looking for?
If you’re looking for hard performance data without as much work, something like this may be a better option.
Which Cree diodes were you looking at, the xp-e photo red he? It does pretty good at higher current but keep in mind they are binned at 25c.
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Yeah, those are them: XP-E photo red. I read the data sheet pretty carefully and it looks like the photo red are not very affected by current and heat. In the chart, they ran them up to 1 amp and the output looks just like a straight line. I would use enough heat sink to keep them pretty cool anyway.
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Copy that. I just wanted to point out that you have to watch Cree with their data sheets. Well, most of the companies really. They give you that chart at 25c, which is only really feasible with liquid cooling or in an ice box or something. Then a few pages above they’ll show you the drop off with temperature.
Also, if you go that route make sure to get the high efficiency model labeled with the “he”. It looks quite a bit better than the original released photo red. I have a handful of them mounted on heatsink usa 2.079 extrusion, but I haven’t wired them up yet.
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Do you remember what size screws you used to mount the stars? I’m pretty sure you did not buy surface mount bare LEDs and reflow solder them!
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I didn’t. 20mm stars that I mounted with arctic thermal epoxy. I still have a few unmounted, I can take a look tomorrow and see what seems to line up. I would guess 4mm or so with a flat washer. I’ve read people using small self tapping screws as well.
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I do have some surface mount leds and empty stars though. I was planning on giving a little home reflow a try. I have big aspirations of eventually trying it with my own pcb’s. Found a pretty good deal on them via alibaba a while back. Thought maybe I could give it a try on some small inexpensive stuff and see how it goes.
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That’s actually a better idea. I’ll have to buy some thermal epoxy. I was not looking forward to tapping 390 holes. Tapping is a bitch, and invariable you break off a tap every 20 or so holes. Did you know about the alum trick? You can dissolve broken taps or steel screws in aluminum by soaking it for a few days in saturated alum solution. Did not hurt the aluminum at all.
That’s cool if you can get a reflow setup working. Those Cree LEDs are only $1.20 each but you have to buy a reel of 1000 at Digikey. You could make your own XP-E strips and sell them. Photo Red for people with 5000 K lights, Blue for people with 3000 K. Pair them up with the right Mean Well driver and voila: The perfect supplemental light.
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