COB Talk

How about a thread just for chatting about COBs, drivers, mounting solutions. A place where people can ask questions, post COB porn and share ideas. Others behind us can read a thread just about COBs and get a lot of info in a single source.

I'll throw up a first question, what do you think of extruded heatsinks vs pin heatsinks?

Seems like everyone lately is moving towards passive cooling pin heat sinks. I think the pin heatsinks are amazing just need a better way to mount them than L aluminum.

Pin heat sinks offer more surface area using less material.
Since we are basically paying for aluminum by weight, less material should be more cost effective.
There are some pretty cheap sources for pin heat sinks direct from china, depending on the wattage you are looking to dissipate.

I imagine some brackets for simple mounting are in the works, if not already available.

cdgmoney250 said:

Pin heat sinks offer more surface area using less material.
Since we are basically paying for aluminum by weight, less material should be more cost effective.

Click to expand...

Pin sinks biggest advantage over a radial heat sink is that they remain at peak efficiency when used at an angle, but star/radial heatsinks offer the same weight and cooling advantages, and don't cost as much. Having just shopped for way too long on a build, radial heat sinks are less expensive to buy for similar thermal resistances, probably because they are easier to manufacture, but thats just a guess.

Here's two I was going between before ordering for my build. The first will look familiar if you have seen the Cutter/Growmau5 kits, $17 at CDI: https://www.cdiweb.com/ProductDetail/LPF11180ZHEB--mechatronix/573584/

The second is a radial comes in under $10: https://led.cdiweb.com/ProductDetail/MODULEDXTRA9980C-MechaTronix/574062/

The radial is 573g vs 567g, and cools a tiny bit better at 1.02 vs 1.07 C/W. Definitely a little heavier, but nothing like an extruded heatsinkusa, and a lot cheaper to buy.

Pin heat sink would be great for side lighting or angles like Growmau5 is working on.

Edited to fix weights after re-reading datasheets.

cdgmoney250 said:

Pin heat sinks offer more surface area using less material.
Since we are basically paying for aluminum by weight, less material should be more cost effective.
There are some pretty cheap sources for pin heat sinks direct from china, depending on the wattage you are looking to dissipate.

I imagine some brackets for simple mounting are in the works, if not already available.

Click to expand...

not to mention that after smacking your head on the corner of one of these a few times,the pin heat sinks sounds like an awesome option.

JorgeGonzales said:

Pin sinks biggest advantage over a radial heat sink is that they remain at peak efficiency when used at an angle, but star/radial heatsinks offer the same weight and cooling advantages, and don't cost as much. Having just shopped for way too long on a build, radial heat sinks are less expensive to buy for similar thermal resistances, probably because they are easier to manufacture, but thats just a guess.

Click to expand...

Should have shopped a little harder... These are pretty darn cheap and can be drilled/tapped for specific applications.

http://m.alibaba.com/product/60434341998/LED-Pin-Fin-Heatsink-with-Diameter.html?spm=a2706.7835515.1998998356.3.JQHgXw

Cheaper than most other options I have found, that have similar thermal resistance.

Also, if there is any air movement in your grow room, the sink with the largest surface area 'typically' has the best cooling ability.

Edit:
This is especially true of pin heat sinks because of the design to allow free flowing air from all directions, as opposed to the air having to be channeled in a certain direction or pattern.

cdgmoney250 said:

Should have shopped a little harder... These are pretty darn cheap and can be drilled/tapped for specific applications.

http://m.alibaba.com/product/60434341998/LED-Pin-Fin-Heatsink-with-Diameter.html?spm=a2706.7835515.1998998356.3.JQHgXw

Cheaper than most other options I have found, that have similar thermal resistance.

Click to expand...

I found them as cheap as $3 to $4 each per 100 ordered on Alibaba if ya look around for the AL forger (no color clear )
but shipping & payment then importing seems a pain

cdgmoney250 said:

Should have shopped a little harder... These are pretty darn cheap and can be drilled/tapped for specific applications.

http://m.alibaba.com/product/60434341998/LED-Pin-Fin-Heatsink-with-Diameter.html?spm=a2706.7835515.1998998356.3.JQHgXw

Cheaper than most other options I have found, that have similar thermal resistance.

Click to expand...

Except for $9.50 mine are already drilled, shipped from the US along with the rest of my order for $8, and will be here in 2 days.

Drilling heatsinks is something I dont enjoy, and I own a drill press.

And ironically, in the comparison I linked to above the pin has less surface area than a radial heatsink, but I think you are right that it uses that area more smartly because it works from all sides.

JorgeGonzales said:

Except for $9.50 mine are already drilled, shipped from the US along with the rest of my order for $8, and will be here in 2 days.

Drilling heatsinks is something I dont enjoy, and I own a drill press.

Click to expand...

I was implying that they can be ordered to spec for whatever LED or chip holder that you want.
Meaning pre-drilled.
You can even have a thermal grease pre-applied.
If you are in a hurry, then do what you gotta do. But for many of us that are trying to build these lights as cost effective as possible, paying $17 per heat sink (pin fin) is cost prohibitive. Especially when you can get basically the same heat sink with competing performance for about 25% of that cost. One of the members here used their site and had fast service and cheap shipping.
That floats my boat.

JorgeGonzales said:

And ironically, in the comparison I linked to above the pin has less surface area than a radial heatsink, but I think you are right that it uses that area more smartly because it works from all sides.

Click to expand...

cdgmoney250 said:

... the sink with the largest surface area **typically** has the best cooling ability.

Click to expand...

Because I like to be technologically disruptive, I thought I'd pop in here and ask why people think passive setups are so great? Is it because you're saving a few watts on a fan?

Because I think passive approaches are hurting efficiency; before going further, let's first remember that COB LED chips perform BETTER the cooler they are. Cree even provides charts, and the best example I can think of is the sexy CXB3590. Cree says it produces (CD bin) 12,000 lumens at their test wattage at 85C. They also say the very same chip produces 13,237 lumens at the test temperature of 25C/77F. That's a full TEN PERCENT BETTER. In other words, free lunch, as long as you maintain your chip temperatures.

The cooler you can get your Tj, the more light the chip makes. It's that simple. So why go on a quixotic quest to eliminate fans that are directly helping your light output?!

Why aren't people running big fans to help maximize airflow? The strategy MAKES MORE LIGHT PER WATT, perhaps as much as a bin jump!

Thoughts?

@ttystikk I completely agree with you, but I chose passive out of laziness. It's less to wire, and is one less thing to break. I didn't want to wire up and babysit 8 little cpu fans, or rig up a method to cut power if one dies.

But active is definitely lighter, cooler and more efficient. Just arguably not as elegant, and a little more fragile.

cdgmoney250 said:

I was implying that they can be ordered to spec for whatever LED or chip holder that you want.
Meaning pre-drilled.
You can even have a thermal grease pre-applied.
If you are in a hurry, then do what you gotta do. But for many of us that are trying to build these lights as cost effective as possible, paying $17 per heat sink (pin fin) is cost prohibitive. Especially when you can get basically the same heat sink with competing performance for about 25% of that cost. One of the members here used their site and had fast service and cheap shipping.
That floats my boat.

Click to expand...

If you ask for a quote on a radial heat sink with the same thermal resistance, it will be cheaper vs a pin heat sink at hzangteng too. I used the CDI heat sink as an example because it's the same one being used in the Growmau5 kit.

Actually, here is a quote from the exact heat sink you linked to: "Under vertical position the thermal results are comparable with our star shaped led coolers, but once tilting the lighting fixture over an angle of more than 50 degrees these pin fin led heat sinks keep their optimal performance."

Which is exactly what I said originally. I'm not really sure what the problem is. Extruded is cheaper than forged, and they literally perform the same if you are running them horizontally. Nothing to argue about, except the $3 I might have wasted ordering from the US. That's plenty arguable but who cares.

JorgeGonzales said:

@ttystikk I completely agree with you, but I chose passive out of laziness. It's less to wire, and is one less thing to break. I didn't want to wire up and babysit 8 little cpu fans, or rig up a method to cut power if one dies.

But active is definitely lighter, cooler and more efficient. Just arguably not as elegant, and a little more fragile.

Click to expand...

I see no reason why it has to be so finicky; one good fan and some intelligent ducting (at least per bar) would do just fine, be easier to wire up, save on parts and juice and come much closer to that elusive 'elegant' solution.

Besides, you can always add fans. Now you'll have a good excuse!

ghetto rigged cob's working to advantage...super tight ropes rather than metal triangle hangers for easily adjusted light angles...chain link for easy hight adjustment .... a perfect blend of top shelf technology and ghetto macgyver ingenuity..

I'm all about the McGuyver action!

haha just you wait until i switch to vert...i'll be hanging this shit with something crazy..get me an avocado, an ice pick, and my snorkel... ive browsed through your thread and love the idea of vert.. seems pretty obvious for maxing out square footage. just sort of stuck in the cycle of learning one good method and moving on to a better one the next year. though lately id rather focus on the medicine over yield and avoid the profiteering aspect... my town is plagued with an incompetent police chief who would rather spend time combating inevitable legal marijuana than tackling the real problem of pharmaceutical drug abuse.. better force myself to digress before i go on a ramble rant lol...

ttystikk said:

Because I like to be technologically disruptive, I thought I'd pop in here and ask why people think passive setups are so great? Is it because you're saving a few watts on a fan?

Because I think passive approaches are hurting efficiency; before going further, let's first remember that COB LED chips perform BETTER the cooler they are. Cree even provides charts, and the best example I can think of is the sexy CXB3590. Cree says it produces (CD bin) 12,000 lumens at their test wattage at 85C. They also say the very same chip produces 13,237 lumens at the test temperature of 25C/77F. That's a full TEN PERCENT BETTER. In other words, free lunch, as long as you maintain your chip temperatures.

The cooler you can get your Tj, the more light the chip makes. It's that simple. So why go on a quixotic quest to eliminate fans that are directly helping your light output?!

Why aren't people running big fans to help maximize airflow? The strategy MAKES MORE LIGHT PER WATT, perhaps as much as a bin jump!

Thoughts?

Click to expand...

Exactly what I'd discovered by spending hours playing the Product Characterization Tool (PCT).

I had built my bars for passive, but upon testing one over 6 hours I found my heat sink temp. getting up to 47c and slightly above with an ambient temp. of 24c.

I too would have loved to run these bars passive but given my entire reasoning for building my own was to get the best efficiency possible and so I built some add on fans that run @1300 RPM and are virtually silent. (Have to put my ear up next to them to hear the fan at all). The end result being that my heat sink temps. @ the same ambient temps are now a mere 28.5c directly behind the cob after 6 hours running. From my calculations over the 4 bars I've built that works out to be 16-20K lumens output.

I was afraid it would destroy my good looking bars but find them pleasing to look at with the fans.


PS. Need to tidy up the fan wiring and will before I hang them.
And they are truly heavy the heat sinks weigh in @10KG each.



And as an aside I also cool my drivers with fans as they also suffer losses from high temps.

JorgeGonzales said:

If you ask for a quote on a radial heat sink with the same thermal resistance, it will be cheaper vs a pin heat sink at hzangteng too. I used the CDI heat sink as an example because it's the same one being used in the Growmau5 kit.

Actually, here is a quote from the exact heat sink you linked to: "Under vertical position the thermal results are comparable with our star shaped led coolers, but once tilting the lighting fixture over an angle of more than 50 degrees these pin fin led heat sinks keep their optimal performance."

Which is exactly what I said originally. I'm not really sure what the problem is. Extruded is cheaper than forged, and they literally perform the same if you are running them horizontally. Nothing to argue about, except the $3 I might have wasted ordering from the US. That's plenty arguable but who cares.

Click to expand...

Pins.. Radial.. Who gives a shit??
My whole point is that any body ordering more than a few of these might be better suited ordering China direct to save 50% or more than compared to "other" options.
Sounds like we agree right?
Not trying to argue or get in a pissing match.

ttystikk said:

Because I like to be technologically disruptive, I thought I'd pop in here and ask why people think passive setups are so great? Is it because you're saving a few watts on a fan?

Because I think passive approaches are hurting efficiency; before going further, let's first remember that COB LED chips perform BETTER the cooler they are. Cree even provides charts, and the best example I can think of is the sexy CXB3590. Cree says it produces (CD bin) 12,000 lumens at their test wattage at 85C. They also say the very same chip produces 13,237 lumens at the test temperature of 25C/77F. That's a full TEN PERCENT BETTER. In other words, free lunch, as long as you maintain your chip temperatures.

The cooler you can get your Tj, the more light the chip makes. It's that simple. So why go on a quixotic quest to eliminate fans that are directly helping your light output?!

Why aren't people running big fans to help maximize airflow? The strategy MAKES MORE LIGHT PER WATT, perhaps as much as a bin jump!

Thoughts?

Click to expand...

I built both my veg and flower lights actively cooled with Vero/CXA running @ 1.4 A. Not only were the fans a pain in the ass to wire up, but it added to the parts list and build expense. And I've since had to dim my lights since they are so bright, basically eliminating the need for a 100w heat sink.

Going forward I will be running passive sinks that are pre-drilled for my application, and probably be running the chips at 1.05A while still dimmable. This will make the build come together sooo much quicker and cheaper too.
I'll sacrifice some lumens for convenience. The amount seems neglible to me.