This a side view of the light in action:
This is a view from underneath with the light off. Notice the copper blocks under the COBs. Those are heat spreaders.
Thanks for sharing the pics!
The copper blocks are used to tie the cobs to the sinks and frame then?
Just for heat transfer. Copper is almost twice as good at it than aluminum. The COBs have about one square inch of heat transfer surface and the copper effectively doubles that over screwing the COB directly to the aluminum heatsink. The COBs are screwed into the copper, the copper is screwed into the heatsink but has almost a six square inch area. Both sides of the copper have heat transfer grease.
That copper can be expensive. You have to hunt around to find it near scrap copper prices. New retail 1/4 inch copper sheet is 10 times as expensive as scrap.
I’m familiar with the copper and using it. I was always told that in that kind of application you typically don’t see the increased thermal performance to justify the cost. What you gain from the copper, you typically lose from having an additional joint. Thoughts on that? I suppose with modern transfer material that may not apply anymore, if it was ever true.
I haven’t yet experienced any issues with thermal transfer. But I’m also paying decent cash for what I believe are top notch heatsinks and sizing them well within their capabilities. I suppose surface quality, flatness, and good application of a decent transfer compound all play into that some as well.
It’s probably overkill but the COBs do put out more light the cooler you can get them. I’m sure just using a 1 inch square block of copper would lose transfer capability due to the joints, but my copper-to-aluminum joint is six times bigger. I think this is the way you get the near equivalent to a full copper heatsink. It spreads the heat over more area of the aluminum heatsink. Since they were sold as scrap, the copper only cost me about $4 per block. I notice some highend heatsinks online use copper heat spreaders with an aluminum body and fins.
What made a huge difference though, was to put a little 8 inch fan on the end of the fixture blowing air down the heatsinks. The heatsink without the transistor was hot and the one with was just about too hot to touch after I let it equilibrate with a fan blowing in my grow chamber. But when I put the little fan right on it, both heatsinks are barely warm. I am definitely going to enclose them in ducts and suck exhaust air through the ducts.
@1BigFella another though for efficiency, if you’re any good at soldering, you could possibly solder the copper to aluminum connection for better heat transfer. But it sounds like it’s doing ok the way it is. I was just suggesting another way to efficiently transfer heat.
Technically you wouldn’t want a copper heatsink, as aluminum displaces heat better. I will agree that copper will receive heat better though. Perhaps the larger surface area offsets the increased thermal resistance of the joint, that’s really above my ability to test lol. But it would make sense.
Depending on the manufacturer, you typically get test data at 25c and 85c for tc and tj. Some you’ll see a 50c, which is probably closer to a real world application. Maintaining case temp of 25c may be realistic in a freezer lol, and The 85c is usually a sign of undersized heatsinks for application. Depending on the led, you should be able to measure temps and see about where you fall on charts. If you so choose to know anyway.
As far as adding fans, they definitely help with cooling. But you can’t necessarily say the light will be more efficient. Cooling the heatsink will not result in a linear reduction in led temp. If you calculating lumens per watt, the only fair way to do it would be to include the power draw of the fans. That’s why I try to build without them.
Assuming you’re buying heatsinks anyway, then fans, and components to run fans, it’s probably not much if any cheaper than just buying properly sized heatsinks isn’t it? Now if you had some heatsinsks, fans, and most of other stuff needed lying around, you can absolutely make it work. You just eat the extra power consumed to make something out of what you have.
That’s a thought, but mounting isn’t usually the issue. The thermal conductivity of the materials used, surface cleanliness, and flatness is usually the biggest concern. Provided the two surfaces are tight, I’m not sure how much soldering would increase. Probably some, as the the surface contact would increase a little as @1BigFella stated. I’m just not sure if it’s enough to be noticeable and justify doing the work.
I concur, although I did mention a slight amount of an efficiency boost. I personally would do just as you stated, properly sized aluminum heat sinks would do just fine. Additional fans, only reduce the efficiency just because it’s somethhing else using electric. Now, adding fans to a properly sized heatsink, may or may not increase longevity. These are just my opinions, and thoughts. With my limited experience. They may or may not reflect actual real world results. @dbrn32
I think the longevity on most of them look like a pretty straight line until you start surpassing the 85-105c range. Then there’s a significant drop off in life expectancy. So unless you’re running at or above those numbers, I wouldn’t be adding to the power draw on account of them lasting longer. But that’s just me.
Otherwise, this is just a place for us to throw different ideas around, ask questions, or whatever. I don’t see any issue at all with saving some cash or finding cheaper ways. There’s just almost always down sides that come with it.
Couldn’t agree with you more @dbrn32 creativity and kind suggestions are where it’s at. Random question, what size in diameter are those vero 29’s you run? Local grower here left his DIY cob set up somewhere I could see it. Didn’t feel comfortable with pictures, but they looked about 1-1.5 inch across. Not very big. I was just trying to guess what kind of COB they may be. I may try to sneak some pics sometimes soon before they go up…
Vero29s are 2 inches across. The heatsink contact area is a 1 1/4 inch square. The light emitting surface is a 1 3/16 inch circle. Just buying the proper solder is very expensive: You can’t solder aluminum with regular solder. Plus you can’t solder the COB to the copper and that joint is the heat transfer bottleneck here. The COB is made out of plastic and the manufacturers info tells you not to burn it just soldering on the wires.
As for buying and operating the fan, I have an exhaust fan that would just take air from the top of the chamber and vent it outside. I’m just going to duct all the air into that fan through the heatsinks. No additional cost to run it, and the only expense is some flexible drier duct from home depot.
You can have great heatsinks and still overheat the COBs if the top of your chamber is 120 degrees! You need to remove the heat somehow. The cooler your heatsink runs the better it transfers heat from the COBs.
They’re only 30 to 40 watts per fixture typically. Most of the 300w and 600w LEDs have 2 running at max 500 mA or so each. Looks like the easiest way to get rid of heat. I’ve been running 2 x 4" and 4 x 40mm fans on this 200watt driverless cob test fixture I’m running. I tried turning them off and the light ran fine, but the room temp rose 2° in a few minutes.
It may be the easiest way to remove heat. But it’s way easier not to have to remove it at all. The amazon lights run the fans because they use some of the least efficient mono’s available and very small heatsinks. Just because it has fan doesn’t mean it will run any cooler. My strips are running tc temps of 38c and they’re not even mounted to heatsinks, just 1.5” aluminum bar stock without any fans. It’s just par Watts vs heat watts.
I’ll use your example of a 300 watt led. Let’s say it’s actually 300 Watts from wall. It has a cheap driver we’ll say is 80% efficient, deduct 60 watts. If your estimate is correct we’ll deduct another 40 watts for fan and power supply efficiency. Now we’re left with 200 watts from wall. Being generous we’ll call the epileds 35% efficient. That’s 70 par watts for your 300 from wall. Making the lamp essentially something like 23% efficient. Isn’t that a little ridiculous? Taking away the fans will boost the fixture efficiency up to almost 35%.
The vero’s Are sized by their light emitting surface diameter I’m pretty sure. Vero 29= 29mm, vero 18=18mm and so on. There may be some subtle differences in overall diameter from the se models to non poke in models, but I believe @1BigFella is right at around 2”.
If it was vero 29 se it would look just like these
5 Pcs Silver Tone Aluminium Radiator Heatsink Heat Sink 100x25x10mm
Too small, unless you blow air over them. That makes them about four times better. You can figure out how many square inches of aluminum a heat sink has and Vero has a document all about figuring out how many square inches you need. I think I needed about 300 square inches per COB, but I only run them at about 82 watts for efficiency. If you run them with more power you would need more.
"believe @1BigFella is right at around 2”: I have a bunch of them sitting right next to me. I measured one.
I think those are about 70 square inches going from the dimensions.
I suppose you’re right, but who isn’t exhausting their grow from the top? I’m not sure what you have in mind, but that flexible duct kills cfm pretty quickly. That may or may not be a problem depending on how your things are sized. The pin sinks benefit some just from drawing of warm air passed them. Probably another benefit that you don’t see with traditional extruded sinks. But if it works, it works right. I think it just goes back to overall cost not being too much different by the time it’s all said and done. The $18-20 up front for something that’s sized properly, pre drilled and tapped, and proven to work doesn’t end up being all that expensive.
The current light I’m working on will run quite a bit cooler than the vero’s, and I never had a problem with the vero’s. I’ve had sink temps pushing 120 plenty of times, but as long as exhaust is running ambient even at the ceiling never gets that high. Pulling 70ish air from the bottom constantly will do that with the pin sinks.