Can this cool a 10w led? - Page 1
Forum section: electronics / projects

author: kalel
author_rank: Frequent Contributor
timestamp: May 16, 2017, 07:27:27 pm
content: I don't know if links are allowed or not (may appear like a promotion), so here is a screenshot of the web page instead.I'm wondering whether or not these "GPU heatsink coolers" can cool down a 10W LED.10W LEDs are really cheap from china ($0.2-0.4 shipped) but proper heat sinks can be quite expensive in comparison, I'm just looking for the absolutely cheapest option that will do, even if not for very long durations.Of course, considering that the fan is on to give it the best chance (12v fan 12v led is not a bad combination).Does anyone have any experience with these and some opinions?Thanks.

author: sokoloff
author_rank: Super Contributor
timestamp: May 16, 2017, 08:01:27 pm
content: Heatsinks are rated with a nominal degrees-per-Watt or "how many degrees above ambient will the part run for every Watt of power dissipated in the heatsink?"From that, determine the temperature rise (delta-T) for 10W of output, and the max ambient temperature you want to support and then look up whether your LED is rated for that. That's the steady-state rating. Transient temperature rise (from a 5-10 second operation) will be less, but it's good practice to size the heatsink to the steady-state (worst-case).The short answer is "probably".

author: kalel
author_rank: Frequent Contributor
timestamp: May 16, 2017, 08:12:37 pm
content: Hi there and thanks for your response!CPU heatsinks usually have at least a TDP stat to consider (even these cheap chinese ones, if you believe the rating of course), but this one doesn't come with any thermal information on the product description page, and it costs about $1.8~2 depending on the seller and website.The only information I could find is about the fan:"Voltage: DC 12VRated Current: 0.10A"and the dimensions (of the entire thing):"Dimension: 55*55*13mm/2.17*2.17*0.51inch (Approx.)"I think I'm just looking for a guesstimate rather than a certain answer of course.Edit: To be clear, I don't mean for any extreme operating conditions of course. Home use.

author: grumpydoc
author_rank: Super Contributor
timestamp: May 16, 2017, 09:15:04 pm
content: Quote from: kalel on May 16, 2017, 08:12:37 pmIt's frustrating that none of the sellers of this sort of heatsink quote a figure for thermal resistance. In fact it is astounding how many heatsinks are listed even on "reputable" suppliers' sites without that all-important figureI'd guesstimate 1-5oC/W unforced, up (or down) to half that with a fan, maybe a bit better depending on air flow. Dissipating 10W you could be anywhere from OK to scorching.Suck it and see seems the best advice, if you can comfortably keep your finger on the heatsink with the LED powered up it should be just fine.

author: sleemanj
author_rank: Super Contributor
timestamp: May 16, 2017, 09:25:44 pm
content: Quote from: kalel on May 16, 2017, 07:27:27 pmI seem to recal Julian Ilet used those fans with 10w ok. I would expect it to be fine.

author: james_s
author_rank: Super Contributor
timestamp: May 16, 2017, 10:55:05 pm
content: Speaking from seat of the pants experience, that heatsink will probably be suitable with any reasonable amount of fan cooling.

author: DaJMasta
author_rank: Super Contributor
timestamp: May 17, 2017, 01:03:43 am
content: I agree that it will probably be sufficient, but it's difficult to say for sure. If you're inside of a housing or near other parts or something that will also decrease efficacy, so even if open air with the fan on will be sufficient, that's no guarantee for every environment. It's also worth noting that the max temp spec on the LEDs may not be high either, and even if the heatsink can get rid of the heat, if the temperature it equalizes at is still too high for a lower-spec LED die, you'll be out of luck soon enough.The way to be sure, as with many of these cheap things off ebay or what have you, is to try it. The specs, when available, aren't even necessarily accurate in a lot of cases, so even if you've got full specs for everything.... maybe your fan RPM is 20% low, or maybe your LED actually only uses 6W. A highly efficient 10W LED will also produce less heat than a less efficient one (more of those 10W will be turned into light), so there can be some variance in heating requirements there, too. There's even a chance that under-driving the LED only a little bit makes a comfortable margin with this fan whereas it's at its limits or longevity of the LED is considerably less.If you're cooling a bunch of lights though, and they don't have to be individually mounted, maybe consider something like aluminum channel strips. Not as much surface area as a standard heatsink, but it's easy to just force air along it and you can mount several LEDs in a row with only a few mounting holes.

author: Audioguru
author_rank: Super Contributor
timestamp: May 17, 2017, 02:52:56 am
content: This cheap Chinese heatsink has no important thermal spec's maybe because it has too much rice in the metal?How will you mount the LED to the heatsink?Does the LED have built-in current regulation or must you add a current regulator?

author: james_s
author_rank: Super Contributor
timestamp: May 17, 2017, 02:59:04 am
content: Most of those power LEDs have a metal base with a pair of screw holes. They all require an external driver to supply the constant current.

author: BravoV
author_rank: Super Contributor
timestamp: May 17, 2017, 03:15:02 am
content: If its just one off project, just use this kind of old used Intel cpu heatsink.Probably you can get it really cheap or even free, and it will be far better than your choice there.Just an example :

author: sleemanj
author_rank: Super Contributor
timestamp: May 17, 2017, 03:50:46 am
content: Quote from: BravoV on May 17, 2017, 03:15:02 amHeatsinks of that size will handle the 10W (but not too much more) without fan.

author: james_s
author_rank: Super Contributor
timestamp: May 17, 2017, 05:28:25 am
content: With the fan, one of those CPU heatsinks should be good for at least 100W.

author: tszaboo
author_rank: Super Contributor
timestamp: May 17, 2017, 10:18:54 am
content: Quote from: sleemanj on May 17, 2017, 03:50:46 amWhat? have you seen a 10W commertial light bulb that plugs into the mains? It has much less surface area. You dont need to run the LED that as low temperature as a CPU.

author: sleemanj
author_rank: Super Contributor
timestamp: May 17, 2017, 11:16:26 am
content: Quote from: NANDBlog on May 17, 2017, 10:18:54 amBut they also are designed for and mounted suitable for convective cooling and good coupling of the LED package to heatsink, something that an active CPU heatsink does not because it was not designed for that.I prefer to run (unknown specification "high power") leds at about 70 - 80 C measured at the tab, probably some would run at 100 C or maybe even more, but cooler is better.Right now I have exactly the CPU heatsink pictured, without fan, and a 10W led on it (with thermally conductive tape) being driven at 10W give or take half a bee's dick. Currently 74C at the tab, with ambient 20C, heatsink at the fin is 38 and rising. I expect it to equalise out at about 74-75 but time will tell.I don't have any 20W leds and can't fit two 10W on it unfortunately.

author: sleemanj
author_rank: Super Contributor
timestamp: May 17, 2017, 11:27:11 am
content: Top left volts bottom left amps, middle temperature at led tab (K type thermocouple), right ambient (K type thermocouple). Excuse the usual chaos.

author: sleemanj
author_rank: Super Contributor
timestamp: May 17, 2017, 11:51:22 am
content: 30 minutes in and it's 88 degrees at the tab and 50 at the heatsink interface (copper slug).

author: ebclr
author_rank: Super Contributor
timestamp: May 17, 2017, 11:55:25 am
content: https://pt.aliexpress.com/item/Aluminium-Heat-sink-Heatsink-for-12V-20W-Led-Energy-Saving-Lamp-NEW/2019773125.html?spm=2114.02010208.3.34.qZfzxc&ws_ab_test=searchweb0_0,searchweb201602_2_10152_10065_10151_10068_10136_10157_10137_10060_10138_10155_10062_10156_10154_10056_10055_10054_10059_100032_100033_100031_10099_5150019_10103_10102_10096_10147_10052_10053_10050_10107_10142_10051_10173_10084_10083_10119_10080_10082_5180020_10081_10110_10111_10112_10113_10114_10181_10183_10182_10185_10032_10078_10079_10077_10073_5160018_10123_10120-10120,searchweb201603_4,ppcSwitch_5&btsid=6206b82a-cc07-42b1-9833-bc0fa148b106&algo_expid=405c5c12-bdcd-4d06-8895-8d123a984020-4&algo_pvid=405c5c12-bdcd-4d06-8895-8d123a984020

author: tszaboo
author_rank: Super Contributor
timestamp: May 17, 2017, 12:15:15 pm
content: OK, I should take into account that these are chinese LEDs, probably they dont like constant 125 degrees junction temperature, like brand LEDs. You are probably right.

author: sleemanj
author_rank: Super Contributor
timestamp: May 17, 2017, 12:29:48 pm
content: For sake of completeness, 1 hour in, 90 degrees C at the tab, I think it's about stabilised at that, 51C at the heatsink slug, ambient still 20C.For me, that's hot enough for long term, if I drilled, tapped and and screwed the led to the heatsink with thermal paste interface the thermal resistance would certainly be lower, but that's too much hassle.

author: Fungus
author_rank: Super Contributor
timestamp: May 17, 2017, 02:07:12 pm
content: With a fan they should be fine.I'd be more worried about the "10W" LEDs really being 10W LEDs. I might plan to run them at 6-7W, just in case.

author: perieanuo
author_rank: Frequent Contributor
timestamp: May 17, 2017, 02:34:57 pm
content: YesEnvoyé de mon iPad en utilisant Tapatalk

author: kalel
author_rank: Frequent Contributor
timestamp: May 17, 2017, 04:02:13 pm
content: I just want to thank everyone for their answers. I really didn't expect this many.