Confused about heatsinks

So I'm making my first COB light, and I'm getting 4 CLU048-1212 80 CRI Gen 6 and a HLG-120-C700A for the driver, now, the problem I come to is heat sinks, I was looking watching the growmau5 DIY LEDs and he did go over how many square inches I'd need for a passive to work with what I am getting, however my problem is, how exactly do I find out how many square inches a heatsink is from heatsinkusa.com, I'm new to this kind of stuff and trying to make a nice soft running light.

Use this:

https://www.dropbox.com/s/2s0xo583lw10m29/CitiCalculator.jar?dl=0

Kkesu said:

So I'm making my first COB light, and I'm getting 4 CLU048-1212 80 CRI Gen 6 and a HLG-120-C700A for the driver, now, the problem I come to is heat sinks, I was looking watching the growmau5 DIY LEDs and he did go over how many square inches I'd need for a passive to work with what I am getting, however my problem is, how exactly do I find out how many square inches a heatsink is from heatsinkusa.com, I'm new to this kind of stuff and trying to make a nice soft running light.

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Those are some pretty old vids now. If you look at the newer ones he's using pin-fin sinks like pretty much everyone else They cool a bit better and are lighter, and usually make for a bit cheaper build. The smaller pinfins will work great for that size cob driven softly like that, and there tons of threads with this style of build onsite for you to check out (pinfins mounted to an aluminum frame)

Good luck with your build

DrBlaze said:

Those are some pretty old vids now. If you look at the newer ones he's using pin-fin sinks like pretty much everyone else They cool a bit better and are lighter, and usually make for a bit cheaper build. The smaller pinfins will work great for that size cob driven softly like that, and there tons of threads with this style of build onsite for you to check out (pinfins mounted to an aluminum frame)

Good luck with your build

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Yeah, saw the thing he did back in march too for some newer stuff, I thought Pin was just much more expensive but I'll have to look into those, the frame would be cheap and easy to make.

https://cobkits.com/product/120-mm-passive-pin-fin-heatsink/

16.65 with RIU discount and holes are pre-tapped, also no need to buy any fans.

Kkesu said:

So I'm making my first COB light, and I'm getting 4 CLU048-1212 80 CRI Gen 6 and a HLG-120-C700A for the driver, now, the problem I come to is heat sinks, I was looking watching the growmau5 DIY LEDs and he did go over how many square inches I'd need for a passive to work with what I am getting, however my problem is, how exactly do I find out how many square inches a heatsink is from heatsinkusa.com, I'm new to this kind of stuff and trying to make a nice soft running light.

Click to expand...

Go with pinfin heatsinks cobkits.com has as hit load of them

Kkesu said:

Yeah, saw the thing he did back in march too for some newer stuff, I thought Pin was just much more expensive but I'll have to look into those, the frame would be cheap and easy to make.

Click to expand...

Go WITH the Force Luke...get the pin fin heatsinks.

pins are what most peopel use

only reason youd use extrusions is if youre a masochist into drilling and tapping or you have a design that uses an absurd amount of low-cost discrete chips at low current

The main thing pin fin brings is reduced weight. They are expensive but once you add in a fan cost is similar as @DrBlaze mentioned. The cooling isn't generally as good as it would be using fans with the 40sq/cm per heat watt rule but fans on some pin fin models can be added to get the lower air cooled temps and still benefit from reduced weight. Also it's worth it to over size the sinks. If you can get a few lumens per watt more by bumping up the sink size for 5-10 dollars each it would be worth it over the long run.

Rahz said:

40sq/cm per heat watt rule

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Can you elaborate?

Confused about heatsinks?

They're for keeping your dirty dishes warm, OBVIOUSLY.

I'm here to help!

canadian1969 said:

Can you elaborate?

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40 sq/cm of surface area per heat watt with fan, 120 sq/cm of surface area per heat watt without fan.

I never tried running passive with that formula on extruded designs but it generally provides a 10-15 degree rise over ambient with fans. I've done some testing with common pin fin solutions and observed case temps reach 54C fairly quickly (limit of my thermal probe) so the point of equilibrium somewhere between there and 85C and not comfortable to touch. Would be interesting if someone ran the numbers on a couple pin fin designs and see how it comes up.

75C isn't going to be comfortable to touch but also within manufacturer specs, so it shouldn't decrease lifespan below the warranty... but getting temps down is still worthwhile because there are photons to be had between 85 and 40C and that's what we're ultimately paying for.