Heatsinks for DIY LED lamps

researching · Oct 13, 2016

Randomblame said:
Hey researching,

why so expensive?
Simple take 2mm thick aluminum C-channels with 20x 40x 20mm(|____|), 3' length, that's ~1200cm² : 110cm² is enough for 10,9w of heat. 110cm² are required for 1w passive and 40cm² for an active cooling design.

I've 2 channels in parallel each with 20w of red, deepred and near IR Osram SSL's running on a HLG-60H-C350B and the channels never go above 40-50°C depending on ambient temps(20-30°C). ΔT=20°C means 20°C over ambient! Not bad for so cheap...
Another benefit: if you choose the inner side to mount the LED's, sides of the channels acts like a reflector.

The first one is very inexpensive. It is only $.16 an inch . If that will work that is what I would like to get. Is that profile adequate?

Randomblame · Oct 13, 2016

researching said:
The first one is very inexpensive. It is only $.16 an inch . If that will work that is what I would like to get. Is that profile adequate?

Okay, then..
Calculate the total surface area of the heatsinks in cm², then divide the result by 110 and you have an inkling of how much watts of heat it can dissipate passively

researching · Oct 13, 2016

Randomblame said:
Okay, then..
Calculate the total surface area of the heatsinks in cm², then divide the result by 110 and you have an inkling of how much watts of heat it can dissipate passively

Here is my calculation for the first one. Does this seem correct? 1064cm2

Randomblame · Oct 15, 2016

researching said:
Here is my calculation for the first one. Does this seem correct? 1064cm2

Hi again!
If you have calculated 2x the mounting area(front and backside) + 2x area of the outsided fins(both sides) + 10x inner fin area(because there are 6 fins - already calculated outsides), it will be correct.
In this case the heat sink is good for about 9,7w heat. 10w of heat would also okay because there is always a bit air movement.

Randomblame · Oct 15, 2016

Okay, it's saturday morning here, drinking coffee and only turn my thumbs, Lol ...

Outgoing, the dimensions are given in inches, the small heat sink should be about 76cm long, 2.54cm wide and 1.2cm high, floor plate about 0.25cm thick.
This results in about 1295cm² for the small and 3025cm² for the larger one.(LxWxH: 76x 4,6x 3,175cm, floorplate 0,75cm)
Divided by 110cm²...
Thus, the small is good for 11.8w of heat and the large one for 27.5w.
The small one would be enough, but would be fully occupied (unless you choose the new XP-E HighEffiency photored's then you have room for 12).
The big one still has more room, if you want to upgrade later!

researching · Oct 15, 2016

Randomblame said:
Okay, it's saturday morning here, drinking coffee and only turn my thumbs, Lol ...

Outgoing, the dimensions are given in inches, the small heat sink should be about 76cm long, 2.54cm wide and 1.2cm high, floor plate about 0.25cm thick.
This results in about 1295cm² for the small and 3025cm² for the larger one.(LxWxH: 76x 4,6x 3,175cm, floorplate 0,75cm)
Divided by 110cm²...
Thus, the small is good for 11.8w of heat and the large one for 27.5w.
The small one would be enough, but would be fully occupied (unless you choose the new XP-E HighEffiency photored's then you have room for 12).
The big one still has more room, if you want to upgrade later!

Thank you for the reply. Not to sound ignorant, but for confirmation, you mentioned the smaller profile will dissipate 10w approx of heat. I am not up to speed on all the calculations for dissipation. I am intending on 10 3w leds driven by a 20w 650ma driver. The smaller profile is adequate for that correct? I may even use less led's if need be because the price difference is so significant between the sinks.

Randomblame · Oct 16, 2016

researching said:
Thank you for the reply. Not to sound ignorant, but for confirmation, you mentioned the smaller profile will dissipate 10w approx of heat. I am not up to speed on all the calculations for dissipation. I am intending on 10 3w leds driven by a 20w 650ma driver. The smaller profile is adequate for that correct? I may even use less led's if need be because the price difference is so significant between the sinks.

The smaller one should cover your needs.
There is also always a bit of airflow inside your room which have a big impact on cooling performance and if you not choose crappy 25% eff. Epiled deepreds it should stay cool to the touch.
The better the LED's the cooler stay your heatsink.
Osram has released their horticulture SSL120 t3t4 bins and Cree has released a new XP-E series called HE-high effiency last week, both are more as 50% efficient @350mA, maybe 45-48% @650mA.
And what is best, both are already available from different sources!

XP-E HE from here:
http://www.ledsupply.com/leds/cree-xlamp-xpe-high-power-led-star

Osram SSL120 here:
https://www.led-tech.de/en/High-Pow...d-on-Star--Horticulture--LT-2693_206_207.html

researching · Oct 16, 2016

Randomblame said:
The smaller one should cover your needs.
There is also always a bit of airflow inside your room which have a big impact on cooling performance and if you not choose crappy 25% eff. Epiled deepreds it should stay cool to the touch.
The better the LED's the cooler stay your heatsink.
Osram has released their horticulture SSL120 t3t4 bins and Cree has released a new XP-E series called HE-high effiency last week, both are more as 50% efficient @350mA, maybe 45-48% @650mA.
And what is best, both are already available from different sources!

XP-E HE from here:
http://www.ledsupply.com/leds/cree-xlamp-xpe-high-power-led-star

Osram SSL120 here:
https://www.led-tech.de/en/High-Pow...d-on-Star--Horticulture--LT-2693_206_207.html

Thanks for all your help. It is very much appreciated! :bigjoint:

Randomblame · Oct 16, 2016

researching said:
Thanks for all your help. It is very much appreciated!

Let us know how it works is more than enough ..
Always happy to help ... the most I've learned here from the pros...

bobbuck · Nov 20, 2016

So I just found a bag of these while waking the dog. they're 12" long 5" Wide base plus 3" (the thing on the side) and 1/2" thick. the top side of the main base is serrated maybe 1/16 -1/32 tall fins. wondering how I can use these as COB heatsinks. Not Sure how the thickness would come in to play when trying to calculate. any input on what people think would be awesome. thanks

bassman999 · Nov 20, 2016

bobbuck said:
So I just found a bag of these while waking the dog. they're 12" long 5" Wide base plus 3" (the thing on the side) and 1/2" thick. the top side of the main base is serrated maybe 1/16 -1/32 tall fins. wondering how I can use these as COB heatsinks. Not Sure how the thickness would come in to play when trying to calculate. any input on what people think would be awesome. thanks

Is the back side smooth for the cobs?

bobbuck · Nov 20, 2016

bassman999 said:
Is the back side smooth for the cobs?

Yeah it is smooth.

bassman999 · Nov 20, 2016

bobbuck said:
Yeah it is smooth.

Not a lot of fin height to catch air, but it has a thick plate.

bassman999 · Nov 20, 2016

Non scientific opinion...I think with a slow speed fan or 2 on top it could easily cool 100 watts

bobbuck · Nov 20, 2016

bassman999 said:
Not a lot of fin height to catch air, but it has a thick plate.

I found a backpack and duffel bag full of these and other smaller ones. I'd like try to do something with them

bassman999 · Nov 20, 2016

bobbuck said:
I found a backpack and duffel bag full of these and other smaller ones. I'd like try to do something with them

I found a local mom and pop store called Blue Collar Supply. They have heatsinks in 8x8 with fins.
I run a pair of cobs underdriven to 25-35 (depending on dimming) watts each on them passively with an intake fan blowing over them sorta from the top of tent. They never get over 95*F

CatSpeaker · Nov 20, 2016

I used a .524 inch plate of aluminum 9" x 24"and a .745 plate, 3.75" x 24.75", used heat sink epoxy to attached a bunch of cpu heat sinks and fans.
I've built 4 variations of these using a mix of 3070s and 3590s and They work.
My next is this 9 pound beast of .245 copper, 2.5 inches by 24.75 inches.

Free is good.
Let those creative juices flow.

Randomblame · Nov 21, 2016

bobbuck said:
I found a backpack and duffel bag full of these and other smaller ones. I'd like try to do something with them

Hey Bobbuck!
Take them to the scrap yard! You get money for it and scrap yards are a good place to find better suited heatsinks than this! Found 8 of these 9,84" x 7,87" x 1,57"(250x 200x 40mm) bad boys and got them for only 35 bucks.

Randomblame · Nov 21, 2016

These lights have I made for a friend of mine!
Two

72v CXB's @ 1050mA, dimmable, with daisy chain, 150w, four he already has!

Maine_Coast · Nov 21, 2016

Randomblame said:
These lights have I made for a friend of mine!
TwoView attachment 3835985 View attachment 3835986 View attachment 3835987 72v CXB's @ 1050mA, dimmable, with daisy chain, 150w, four he already has!

Spectacular! Super job using junk yard heatsinks to make DIY lights. Well done :clap:

Heatsinks for DIY LED lamps

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