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> Heatsink For 100w Led
serein
Posted: January 23, 2012 11:01 pm
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Hi everyone I am new here and was wondering if anyone could help me in finding a good heatsink for the 100w LED

thanks
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telomere
Posted: January 24, 2012 12:59 am
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CPU heatsinks designed for high-power CPUs work well. Look for those meant for overclocking, they usually have a lower thermal resistance than the stock units. All-copper units made for servers are especially well-suited.

At those power levels, you either have to go forced-air, or get really exotic if you want to stay passive.

user posted image


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Geek
Posted: January 24, 2012 01:13 am
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blink.gif

Shiny.... copper.... heatsinks... WAAAAAAAAAAANT!

laugh.gif

As for the heatsinks for the LED, just scavenge.... sinks from old stereos, the CPU ones mentioned above.... no need to get too fancy as it'll dissipate at worst 40W as heat.

Cheers!


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telomere
Posted: January 24, 2012 01:20 am
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QUOTE (Geek @ January 23, 2012 05:13 pm)
As for the heatsinks for the LED, just scavenge.... sinks from old stereos, the CPU ones mentioned above.... no need to get too fancy as it'll dissipate at worst 40W as heat.

40W heat from a 100W LED... so 60% efficient?

Whatever LEDs you're using, buy them all up. You'll make billions. wink.gif

The highest-efficiency LEDs that I know of (130-150 lumens/watt) only convert about 25-30% of the energy to light... and those 100W modules are probably only about 50 lumens/watt real-world. Even Cree's big units barely manage 100 lumens/watt when you're talking 10 watt units, and somewhat less for their 45-watt units. The cheap ones coming out of China aren't in the same league.

Put another way, incandescents are only about 2-3% efficient in converting electricity to light, and the best LEDs are in the ballpark of 10x more efficient when you compare lumens per watt. Especially once their efficiency drops 15-20% from theoretical, because real-world die temps aren't 25C. laugh.gif


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Geek
Posted: January 24, 2012 02:18 am
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Digikey had a learning module on these recently... as power goes up, efficiency tanks, right. I have this backwards.... those little things are close to 50% efficient blush.gif

Cheers!


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Sch3mat1c
Posted: January 24, 2012 02:37 am
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When you include operating temp and lifetime, they sadly aren't all that much better than CFL (*good* CFL, if such even exists..). Part of that is simply due to the phosphor, which is essentially common to both technologies, and which cannot physically be improved in efficiency the way it works (one blue photon in, one yellowish photon out = ~60% efficient). The other part is the die, which has efficiency limitations due to the semiconductor (not every electron makes a photon, though it's not bad on those terms), and not every photon can find its way out of the die (internal reflection is a big problem!). Likewise, fluorescents are limited by how many emissions an electron is able to produce for a given applied voltage, which depends on... all sorts of things inside the tube.

Tim


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serein
Posted: January 24, 2012 04:55 pm
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Thanks everyone for your suggestions

Will this be okay for the 100w LED ?

http://tinypic.com/r/ael7xi/5



Thanks
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telomere
Posted: January 24, 2012 05:28 pm
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QUOTE (serein @ January 24, 2012 08:55 am)
Thanks everyone for your suggestions

Will this be okay for the 100w LED ?

http://tinypic.com/r/ael7xi/5



Thanks

With a fan, I would think that it would be more than sufficient.


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Particle
Posted: January 24, 2012 08:10 pm
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You might do well to use passive 1U or 2U heatsinks for high end computer CPUs as previously mentioned. They're relatively inexpensive.

Here's a Supermicro 1U G34 heatsink for instance ($22):
http://www.provantage.com/supermicro-snk-p0042p~7SUP921L.htm

Or the 2U version for $24:
http://www.provantage.com/supermicro-snk-p0043p~7SUP91XJ.htm

These things, when combined with modest airflow, are meant to cool chips that can produce up to 140 watts of heat.

As far as thermal compounds go, I recommend Prolimatech PK-1 if you're going to have a great mating (excellent pressure & uniformity, smooth surfaces) or Shin-Etsu X23-7783D if your contact is going to be somewhat less than ideal. Both are affordable if you don't need to trowel it on your device. heh
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serein
Posted: January 24, 2012 08:48 pm
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Wow thanks for detailed info and the links of the heatsinks.
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tekwiz
Posted: January 24, 2012 10:36 pm
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QUOTE (serein @ January 24, 2012 07:55 am)
Thanks everyone for your suggestions

Will this be okay for the 100w LED ?

http://tinypic.com/r/ael7xi/5



Thanks

Yes, that should be sufficient. As long as you keep the surface of the emitting area of the LED under 120C, you should have no problems. This temperature can be measured with one of those cheap IR temperature guns. Measure immediately after power is removed from the LED, within 2 seconds.
Beware, however, as a failure of any one of the heatpipes in that heatsink will quickly result in LED failure, unless a temperature monitoring circuit is employed to shut down the power if things get too hot.

This is my first 100W LED unit. The heatsink is ~30mm thick & has a high fin density. A fan is absolutely necessary. This keeps the surface temp to ~85 in 25 ambient tempature.
user posted image

Those copper heatsinks that Telomere posted are not big enough on their own. Even the largest isn't quite big enough, requiring the use of two with a heat spreader block.
I am using 3 of them to support 2 of those leds. This is the setup, including linear power supply:

user posted image

The underside, with the LEDs mounted to the aluminum heat spreader block:
user posted image

Now, this setup is designed for high ambient temps, so the heatsinking is ~30% bigger then necessary. It now has close to 2000 hours on it & still working like new.
I always plan on enough heatsinking to carry the full input power to the LED, because the cooler you keep them, the longer they last. If you don't mind a 50% loss in lifespan, you can run up to 150W through each, with corresponding increase in output.


BTW: Telomere, are those heatsinks the ones I have, or is that another batch?


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tekwiz
Posted: January 24, 2012 10:49 pm
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QUOTE (Sch3mat1c @ January 23, 2012 05:37 pm)
When you include operating temp and lifetime, they sadly aren't all that much better than CFL (*good* CFL, if such even exists..). Part of that is simply due to the phosphor, which is essentially common to both technologies, and which cannot physically be improved in efficiency the way it works (one blue photon in, one yellowish photon out = ~60% efficient). The other part is the die, which has efficiency limitations due to the semiconductor (not every electron makes a photon, though it's not bad on those terms), and not every photon can find its way out of the die (internal reflection is a big problem!). Likewise, fluorescents are limited by how many emissions an electron is able to produce for a given applied voltage, which depends on... all sorts of things inside the tube.

Tim

Where do you find *good* CFLs? The best I've been able to find is 50 lumens per watt, well under the 65-80 per watt of those LEDs. With the higher effeciencies of the newer Cree single chip hi power LEDs, only HID can compare.
Counting everything, I'm presently using 21 high powered CFLs to light my shop & equipment. I'd love to find some that offer higher output for the same power. Then I wouldn't have to use so many...I'm using 32W CFLs in groups of 3 or 4 to get enough light.


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For to you, kings & armies are things mighty & enduring.
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telomere
Posted: January 25, 2012 01:33 am
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I don't know if they are the best, but there are a few brands of cfls here in the 65-70 watt range, and they are under $20 each.... They are big, but A few of those can really light up a room. A BIG room.


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serein
Posted: January 25, 2012 08:42 pm
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Thanks and thats a nice setup for the LED'S
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Cearl
Posted: January 25, 2012 08:48 pm
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i'm curious i read this and still have no idea what this is for or about ^^ i'm new to this kind of stuff can someone explain it to me? smile.gif it seems very interesting
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tekwiz
Posted: January 25, 2012 08:51 pm
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QUOTE (serein @ January 25, 2012 11:42 am)
Thanks and thats a nice setup for the LED'S

Like I mentioned, my heatsinking is a bit more than necessary because of high ambient temps. Those particular LEDs are part of an experiment in indoor plant growing.
The unusual part about my setup is that I am using a linear power supply without regulation. The power supply is based on a custom autotransformer, that I built by reworking a microwave oven transformer. It's quite efficient & also very, very reliable. I originally started with one of those 100W LED driver boards, but it didn't even last 3 months. mad.gif


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For to you, kings & armies are things mighty & enduring.
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serein
Posted: February 02, 2012 08:31 pm
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Hey everyone

Found these from a chinese seller

They look awesome which one would be best suited for the 100W LED ?


http://i42.tinypic.com/r9r5aq.jpg

http://i42.tinypic.com/s61tli.jpg

http://i39.tinypic.com/20gnvpk.jpg







This post has been edited by serein on February 02, 2012 08:33 pm
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tekwiz
Posted: February 03, 2012 09:40 pm
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It's hard to say if any of them are big enough, as the pictures give little clue to the overall size of them. The middle picture link is dead.
However, guessing based on the pictures, I'd say that either one would be good, but you must use a fan. In fact, the first one may be too big, but again, I can't say without knowing the actual size.
Your heatsink must be able to dissipate 75W of heat.


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atom
Posted: February 03, 2012 09:50 pm
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If you can get hold of the degrees C/watt numbers for the heatsink, the maths is dead easy. Just multiply that number by the number of watts being dissipated, and you have the temperature rise. Add this to the (maximum) air temperature in which it will be operating, then you have the (approximate) maximum temperature it will reach. As long as this is a reasonable safety margin below the maximum temperature of the LED, then you should be okay.
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telomere
Posted: February 03, 2012 10:09 pm
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QUOTE (atom @ February 03, 2012 01:50 pm)
If you can get hold of the degrees C/watt numbers for the heatsink, the maths is dead easy. Just multiply that number by the number of watts being dissipated,

Don't forget to take into account the thermal resistance from the die to the case of the LED, and a little bit for the imperfect junction as well.


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tekwiz
Posted: February 03, 2012 10:12 pm
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QUOTE (telomere @ February 03, 2012 01:09 pm)
QUOTE (atom @ February 03, 2012 01:50 pm)
If you can get hold of the degrees C/watt numbers for the heatsink, the maths is dead easy. Just multiply that number by the number of watts being dissipated,

Don't forget to take into account the thermal resistance from the die to the case of the LED, and a little bit for the imperfect junction as well.

And a little more to account for the hot spot that results if the base of the heatsink is too thin. Anything under 12mm thick requires derating. wink.gif


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For to you, kings & armies are things mighty & enduring.
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Fortuna favet fortibus.
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serein
Posted: February 07, 2012 08:36 pm
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Thanks everyone for your suggestions

Found another heat sink and I guess this would be better than the previous ones

As the supplier said that it will be able to cool down till 300W


http://www.alibaba.com/product-s/476498917...l_heatsink.html


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telomere
Posted: February 07, 2012 08:43 pm
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QUOTE (serein @ February 07, 2012 12:36 pm)
Thanks everyone for your suggestions

Found another heat sink and I guess this would be better than the previous ones

As the supplier said that it will be able to cool down till 300W


http://www.alibaba.com/product-s/476498917...l_heatsink.html

Your link doesn't work.

Be careful with specs that you see on Alibaba. That may be 300W if you can allow 150C rise, and with massive airflow. laugh.gif

One of my in-laws imports large quantities of stuff from Chinese manufacturers, and Alibaba is one of the sites that she uses. She's told me that it is quite common for things to be... not quite as described, if you get my drift.


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AwesomeMatt
Posted: February 07, 2012 10:33 pm
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QUOTE
Be careful with specs that you see on Alibaba.


I don't quite get it. Are we the consumers supposed to be Ali Baba, stealing the treasure from the 40 thieves of the world and butchering them, or are they Ali Baba and the consumers are the thieves who attempt to thwart Ali Bab's attempts to steal their gold and end up getting executed by his future daughter in law?

Or are we not supposed to know anything about Arabian Nights?
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telomere
Posted: February 08, 2012 12:40 am
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QUOTE (AwesomeMatt @ February 07, 2012 02:33 pm)

I don't quite get it.


Uh... it's the site that he linked to.


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