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Thread: Repurposing CPU coolers for indoor LED lighting.

  1. #1

    Default Repurposing CPU coolers for indoor LED lighting.

    I recently built another PC, and as Intel insists on including a stock CPU cooler (heatsink + fan), I now have a second CPU cooler that's going unused. I'd rather they not go to waste, I was thinking about instead using them for LED indoor lighting. I would love to replace my CFL lamp with something more efficient, and hopefully dimmable as well.

    The coolers are made for 95W and 77W TDP CPUs, and are essentially identical except for some minor differences in the fin design. Each features a copper insert at the base, 28mm in diameter, which is then shrouded in radiating aluminum fins. I've uploaded an image of the two coolers (top of one and bottom of the other, fans are identical).

    A few things are holding me back before I order, so I came here seeking advice. They are:
    1. How should I attach the LEDs to the heatsinks? Obviously they'll have thermal grease between the emitter's base and the copper core of the heatsink, but I'm afraid that that won't be enough to hold it on securely, especially once it gets hot. Perhaps some wire between the fins to tie it down? I don't want to use anything too permanent.
    2. Will I need active cooling, or can I get away with passive? I currently have a 13W and 26W CFL in my lamp, and though I typically only use the 13W, it's nice to have them both on in some occasions. From my quick googling, it looks like 13W CFLs output around 800 lumens, and the 26W is roughly double with 1600 lumens. So, to get the same output with 2 LEDs, I'd need ~1200 lumens/LED, but I'll take anything close to that (+/- 300 lumens/LED). Will the heatsinks alone be enough for cooling LEDs with that output or will I need to plan on running the fans as well?
    3. Which LEDs in particular, or perhaps more importantly, where to get them? I've browsed around DealExtreme for some time now, but it appears most of their LEDs are a cool white (I definitely prefer a warmer white, i.e. 3500-5000K), and those that are warmer don't have very high output.
    4. What to drive the LEDs with? I'm in the US, with 120VAC mains. Ideally I'd like adjustable output (voltage, not PWM) to dim the LEDs, and if I need to drive the fans as well, I'd also need a second (ideally adjustable) output as well. Any commercial products I should look at (including fixed voltage options)? Of course, whatever I drive it with will have to be fairly efficient, or else I'd have to put the regulator on the heatsink instead of the LED .


    I'll be sure to update this thread once the build is underway, but right now I just need to figure out what to order.

  2. #2
    Flashaholic
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    Default Re: Repurposing CPU coolers for indoor LED lighting.

    This may be an opportunity to look at the Cree MT-G or MPL with a Tyco holder. The holder needs three small holes drilled into the heatsink but secures the LED to the heatsink with no solder. You can also buy reflectors from Ledil that match the LED and fit into the Tyco connector. This will prevent custom circuitboard design and reduce the cost of the custom build.

    The heatsink you have should work passively but always test before committing to the total build.

    As for power, try an off the shelf Meanwell power supply.

    All these parts can be purchased from places like Digikey, Mouser, Newark. Good Luck.

  3. #3
    Retired Administrator Norm's Avatar
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    Default Re: Repurposing CPU coolers for indoor LED lighting.

    I think at all costs you want to try and cool passively, I for one don't want to listen to computer fans in my living room, it's bad enough in the office.

    Norm

  4. #4
    Flashaholic* The_Driver's Avatar
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    Default Re: Repurposing CPU coolers for indoor LED lighting.

    The 95W rating of those coolers is the absolute mxaimum. Normally when a cpu is idling (most of the time) is produces muuuch less heat. At 95% the fan will be blowing full power (another 6W). You can calculate though how much heat you can produce without using fans with this heatsink. The sorface area of the fins is very important for this.

    Regarding the mounting options:
    The best thing you can do is solder an emitter directly onto the copper core, but this is difficult and requires a custom pcb. A more realistic method is using emitters on stars and screwing those done (with set screws or better even torx screws) and arctic silver in between. For optimum efficiency you could use 3 or even 7 XM-Ls. You could also use one of the big bridgelux leds, which are made for this kind of thing.
    If you want "quality" light use an led with a high cri rating (90 or more) and no less than 3000K. These leds wont be nearly as efficient as cool white ones though.

  5. #5

    Default Re: Repurposing CPU coolers for indoor LED lighting.

    CPU heatsinks, unless you happen to be using one of the huge old fashioned ones that used to run with P3s are designed for active cooling only. You can run them without a fan, but because of their thin fins they are very inefficient and moving heat away from the central plate and they'll over heat quickly. 10watts is about the limit I'll use with a solid copper CPU sink with no fan.

    Most of the newer fans are pretty darn quiet, and below audibility if mounted on a bookshelf or something. If they are still too loud use a 6volt walwart to drive them.

    I use standard Epoxy to mount LEDs. Bolting the led to the heat sink is the most efficient way, but I don't have a machine shop. It's the width of the gap that matters most, and in this respect fancy thermal adhesives are rip off.

    Inventronics drivers have the easiest built in dimming, but are more expensive than Mean Wells. Dimmable bucks are the easiest to use, but require a fixed voltage supply. Many easy ways to do dimming.

  6. #6

    Default Re: Repurposing CPU coolers for indoor LED lighting.

    I believe that Total Power Dissipation ratings for CPU heatsinks are based on the far more robust thermal margins of CPU's along with the already-stated assumption of forced-air cooling.

    I know that if you spend more than the minimum on a heatsink/fan combo, you tend to get a fan that will run for many years continuously without trouble ... dust accumulation and blockage will be your main problems.
    I apologize that this letter is so long; I did not have time to write a short letter

  7. #7

    Default Re: Repurposing CPU coolers for indoor LED lighting.

    Quote Originally Posted by Norm View Post
    I think at all costs you want to try and cool passively, I for one don't want to listen to computer fans in my living room, it's bad enough in the office.
    The room these will be going in already has a PC in it, and if I'm in the room, chances are it'll be on. If you undervolt the fans they can be quite quiet.
    Quote Originally Posted by The_Driver View Post
    The 95W rating of those coolers is the absolute mxaimum. Normally when a cpu is idling (most of the time) is produces muuuch less heat. At 95% the fan will be blowing full power (another 6W). You can calculate though how much heat you can produce without using fans with this heatsink. The sorface area of the fins is very important for this.
    This is true, but the other half of it is they actually produce more than the TDP under constant load. This is due to how Intel (and AMD as well in recent times) defines TDP--it's not an absolute maximum, just what they expect to see when running "real" applications (Intel's words, not mine!).
    Quote Originally Posted by The_Driver View Post
    Regarding the mounting options: ...A more realistic method is using emitters on stars and screwing those done (with set screws or better even torx screws) and arctic silver in between. For optimum efficiency you could use 3 or even 7 XM-Ls. You could also use one of the big bridgelux leds, which are made for this kind of thing. If you want "quality" light use an led with a high cri rating (90 or more) and no less than 3000K. These leds wont be nearly as efficient as cool white ones though.
    Well, I don't need really high CRI, but I definitely don't like cool lights. I put up with cool LEDs in my flashlights as there efficiency is paramount, but for indoor lighting I'm willing to sacrifice some efficiency for a more ideal color temperature. Good idea on the mounting!
    Quote Originally Posted by blasterman View Post
    I use standard Epoxy to mount LEDs. Bolting the led to the heat sink is the most efficient way, but I don't have a machine shop. It's the width of the gap that matters most, and in this respect fancy thermal adhesives are rip off.
    I think I'll stick with the paste that's already on it, and just bolt it down well. I'd rather avoid epoxy as I'd like something easily removable.
    Quote Originally Posted by blasterman View Post
    Inventronics drivers have the easiest built in dimming, but are more expensive than Mean Wells. Dimmable bucks are the easiest to use, but require a fixed voltage supply. Many easy ways to do dimming.
    Ah, thanks. I was considering building my own, but my knowledge of AC to DC conversion is lacking (most of the stuff I do is just DC->DC LDO, etc.). If I can buy a good supply, and just slap a pot on it for dimming, that will more than suffice.

  8. #8
    Thread Killer Illum's Avatar
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    Default Re: Repurposing CPU coolers for indoor LED lighting.

    Given the nature of fixed lighting, passively cooled will see neglect in cleaning over time and become a "sediment tank" for the dust that floats around in the air in the house. So forced cooling is a good thing, but reliability is drastically reduced compared to that of passive cooling. If the fan fails the heatsink is no different than a block of aluminum with little or no air circulation in between. A heatsink with large spacing between fins coupled with a low rpm 120mm box fan I think noise will not be a significant issue.

  9. #9

    Default Re: Repurposing CPU coolers for indoor LED lighting.

    As a computer repair tech I've seen some of the newer radial heatsinks are definitely under-sized but with the fan having an open frame and actually an airfoil design (on the latest Intel's at least) they would be rather ideal for cooling. I wouldn't run an LED at the 65 or 90w TDP spec, but 15-30w of LED's with a 6-10v powered fan turning slowly would last years and probably throw out a ton of light. If you wanted to get really creative, the fans now have PWM drive pin, one could create a PWM signal for dimming the led's and feed an inverse signal (because no PWM signal = fan runs wide open) simultaneously to the fan, more light = more fan.

  10. #10

    Default Re: Repurposing CPU coolers for indoor LED lighting.

    Check out http://www.quietpc.com/products/cpucoolers/nof-icepipe coolers they cool 95 watt TDP processors passively. I think they were designed for LED lights in the first place. They're a bit pricey though.

  11. #11
    Flashaholic*
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    Default Re: Repurposing CPU coolers for indoor LED lighting.

    Passive CPU coolers aren't really passive. Many rely on case airflow from other means. The computer power supply and computer case fans usually draw air through the computers case, and there is some airflow turbulence from graphics cards too. There is no point in spending $100 on a fancy passive CPU cooler when all you need to do is find the biggest free-$10 cpu cooler and remove the fan. Surface fin area and thermal mass are what you want.

    Other so-called passively cooled LED lights are used by the ATV, bicycle, bike, snowmobile, boating....crowd. Many of these small and high powered 12v LED lights have minimal thermal mass and fin area, but do work fine as long as there is some 'external windchill'. They also heat-sink to whatever they attach to.

    The issue with indoor lighting is that the bulb needs to be pretty and/or enclosed. You can't suffocate the heat sink. If you do, it'll overheat. You might be forced to use an under driven fan. Another option is the hidden heat sink... like a 3-4ft aluminum bar-stock tucked into the rafters or wall with a thermal connection/pipe to your LED's heat sink.

    You'll need to drill/tap the heat sink so that you can mount LED star board to it. A little thermal paste should be used.
    Another option is to use a thermal adhesive.

    Smaller LEDs are mounted on star boards. LED output is great. But, sometimes it is difficult to put the light where you want it. You'll need lens, reflectors, diffusers,..... to move that LED light around some. The lens and LED will determine if you'll get a flashlight-like spotlight on the wall, or if you'll get a good 360 degree flood.

    I've used CPU coolers. Simple divide by 10 will give you a good starting point for a passive LED light cooler. A 100w sized CPU cooler should give you excellent passive cooling for a 10w LED. Invest in an IR temperature gun for timed temperature measurements.

    A 10w LED, the the CREE XM-L could give you the 1000 lumen. You'll take a 10-20% hit when you toss in the lens/diffusers...depending on the beam that you're looking for.
    Plenty of LEDs to choose from depending on the light type, budget, skill ability, driver chosen..... If its interior lighting, I'd even skip some of the higher output LEDs for something with a tad less efficacy/efficiency in order to improve CRI. Bridgelux is another good choice.

    It would also be good to read into this forum for several pages. Many have experimented and have built lights.
    http://www.candlepowerforums.com/vb/...ghting-Threads

  12. #12

    Default Re: Repurposing CPU coolers for indoor LED lighting.

    I have a better idea on this theme if you want to go passive. Google older coolers designed for Pentium 3's and 4's. For instance, some of the passive heats-sinks Dell used for their P3 and P4 towers were stupidly huge, and if you were to buy the equivelant performing heatsink from Mouser or Newark today you'd pay $30-40. Some of the older Dell sinks also had thick, pin type radiators -vs- the thin metal fins we see on today's coolers. The former are far superior for passive cooling.

    At one job I was at the older PC tech I was working with was saving all heat sinks from junk PC and had a large box filled with these passive coolers, and they were all the legacy bigger ones. His theory being the aluminum at some point would be worth a lot of money.

  13. #13

    Default Re: Repurposing CPU coolers for indoor LED lighting.

    I used blastermans advice on the recycled PC sinks. I went to all the local PC repair shops, most had a box full of various sinks. 5-10 bucks usually, I found 4 all copper, heavy slug sinks. Cant use them passive, but Im runnin about 125 watts to a bridgelux with active cooling. Im a total novice in the electronics compared to most of yo guys, but this DIY lighting is addictive.



    Your image is too large and has been replaced with a link.
    See Rule #3 If you post an image in your post, please downsize the image to no larger than 800 x 800 pixels. - Thanks Norm
    Last edited by Lon; 07-02-2012 at 06:01 PM.

  14. #14
    Flashaholic* The_Driver's Avatar
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    Default Re: Repurposing CPU coolers for indoor LED lighting.

    Quote Originally Posted by Lon View Post
    http://i225.photobucket.com/albums/dd77/L-trainphoto/IMG_5838-1.jpg
    Thats a bad*** picture
    Last edited by Norm; 07-02-2012 at 02:27 PM.

  15. #15

    Default Re: Repurposing CPU coolers for indoor LED lighting.

    If you remove the shades, you only need only one of the lights!

  16. #16
    Flashaholic* eebowler's Avatar
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    Default Re: Repurposing CPU coolers for indoor LED lighting.

    DUDE I WANT BEAMSHOTS!! Wrt passive vs active cooling, the fan has three wires, I'm not good with electronics but doesn't this mean that a simple +ve and -ve connection wouldn't work?
    When was the last time you washed your feet?

  17. #17

    Default Re: Repurposing CPU coolers for indoor LED lighting.

    I call that pic "say Ello ta ma little freindS".
    I have 4 of those mounted to my boat for fishin. 2 front, in pic, and 1 on each side. These are designed to flood light wide and down at the water. Im not sure what your asking about the fan anf the + - VE.


    Your images are too large and have been replaced with links
    See Rule #3 If you post an image in your post, please downsize the image to no larger than 800 x 800 pixels. - Thanks Norm
    Last edited by Lon; 07-02-2012 at 06:01 PM.

  18. #18
    Flashaholic* eebowler's Avatar
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    Default Re: Repurposing CPU coolers for indoor LED lighting.

    @ the pics!! The three wires/fan statement was aimed at the original poster.
    When was the last time you washed your feet?

  19. #19

    Default Re: Repurposing CPU coolers for indoor LED lighting.

    Thanks man.
    As a reread, Id say blasters right from my experience, the CPU sinks are good for 10w, maybe 20w with one of the warm white 3000ish K arrays. Bridgelux has a nice selection of CCT in their lineups, I also found these mounting brackets(term?) from Molex for the RS series Bridgelux, nice little spring contacts fit right over the chip, and give you quick stab wire connection, very easy to use. I kinda rednecked mine and just used screws screwed into the fins, frame, or whereever I could predrill a hole. Mine need to be bulletproof for the beating they take trailering the boat and in rough waters.
    Last edited by Lon; 06-30-2012 at 04:52 PM.

  20. #20

    Default Re: Repurposing CPU coolers for indoor LED lighting.

    Ya know, I hear all the time from the flashlight freaks that you can't use Bridgelux in portable lighting because they 'have no throw'.

    Eh, what's that again :-)

  21. #21

    Default Re: Repurposing CPU coolers for indoor LED lighting.

    Quote Originally Posted by blasterman View Post
    Ya know, I hear all the time from the flashlight freaks that you can't use Bridgelux in portable lighting because they 'have no throw'.

    Eh, what's that again :-)
    A badly overrated concept for most flashlight usage, where you're interested in making out detail within a few meters.

    The increasing voltage requirements for the newer arrays is what's going to keep Bridgelux out of flashlights.
    I apologize that this letter is so long; I did not have time to write a short letter

  22. #22

    Default Re: Repurposing CPU coolers for indoor LED lighting.

    Id look into this array http://bridgelux.com/products/ledarray_es.html

    Id use the 6th one down for color I think. And Im sure theres a puck or some driver, getting 120vac input drivers has many choices compared to DC to DC drivers for some reason I know not.
    I have several sinks like the OP posted, seems some have much thicker copper slugs in the base some are only 1/8" and the ones in the pic are 1/2" thick with copper fins instead of Alum.
    I would think the thicker the better. So Id check that.

  23. #23

    Default Re: Repurposing CPU coolers for indoor LED lighting.

    The increasing voltage requirements for the newer arrays is what's going to keep Bridgelux out of flashlights.
    That's pretty much the case with the newer Bridgelux. Obivously they've commited fully to interiour lighting with their arrays increasingly wired for series / voltage optimization -vs- current / parallel. Obviously 12volt and lower environments are dominated by XP-G or XM-L configurations which are also more eficient.

    The advantage with Bridgelux is (1) Utter simplicity - Only one array to solder and troubleshoot. (2) The medium and wide angle optic options, notably the Ledil Brooke series are about as smooth as it gets.

    Obviously tyhe first thing that comes to mind with 12volt circuits and higher voltage lighting needs are inverters and such. However, Boost - Buck drivers are clearly within the realm of possibility here. I just don't work with them much even though I have a few LuxDrives hanging around. I'll have to test and see if my 350mA BoostBuck can drive a 20volt Bridgelux with a high current, 12volt Mean Well fixed supply.

  24. #24

    Default Re: Repurposing CPU coolers for indoor LED lighting.

    Quote Originally Posted by blasterman View Post
    That's pretty much the case with the newer Bridgelux. Obivously they've commited fully to interiour lighting with their arrays increasingly wired for series / voltage optimization -vs- current / parallel. Obviously 12volt and lower environments are dominated by XP-G or XM-L configurations which are also more eficient.

    The advantage with Bridgelux is (1) Utter simplicity - Only one array to solder and troubleshoot. (2) The medium and wide angle optic options, notably the Ledil Brooke series are about as smooth as it gets.

    Obviously tyhe first thing that comes to mind with 12volt circuits and higher voltage lighting needs are inverters and such. However, Boost - Buck drivers are clearly within the realm of possibility here. I just don't work with them much even though I have a few LuxDrives hanging around. I'll have to test and see if my 350mA BoostBuck can drive a 20volt Bridgelux with a high current, 12volt Mean Well fixed supply.
    It took me a very long time to realize this, but once you look at sources other than the likes of LED Supply selling turnkey/packaged drivers targeted at hobbyists such as LuxDrive for happy happy money, there's quite the array of nearly-as-finished products from the likes of meanwell that are marginally more expensive than rolling your own with the benefits of superior engineering and likely better efficiency.
    I apologize that this letter is so long; I did not have time to write a short letter

  25. #25

    Default Re: Repurposing CPU coolers for indoor LED lighting.

    LuxDrive, in my experience doesn't exactly build the best Buck drivers. Mean Well's LDD series have much better specs, efficiency levels, are PWM dimmable and have a better rep. For fixed DC/DC drivers I get the cheap ones from Satistronics for about $1.25, and they last forever. For boost though you are limited to DIY, flashlight drivers, or Boost Bucks.

  26. #26

    Default Re: Repurposing CPU coolers for indoor LED lighting.

    Just a follow-up, but I had no problems driving a 500mA / 20volt Bridgelux with a LuxDrive 4015 / 350mA Boost-Puck from a 12volt supply. This is good news for directly boosting a 12volt battery supply to Bridgelux levels without having to resort to inverters. Would it work with a 30volt (or higher) Bridgelux? Not sure. The 4015 is limited to 1.5amps input, and this might not be possible.

    The bad news is this is a bit of a waste. The Bridgelux can certainly be driven harder than 350mA, and ideally you'd want to push them around 700mA as long as you had good heat sinking. I'm sure there are Boost-Bucks out there capable of doing this (and likely cheaper than LuxDrive), but I'm just not familiar with them.

    What you would do then is power a CPU cooler with the 12volt supply used to power the Boost-Buck, and then run one of the bigger 20-30volt Bridgelux off the Boost. Small, absurdly simple package - HID light levels at 120 lumens per watt.

  27. #27

    Default Re: Repurposing CPU coolers for indoor LED lighting.

    Quote Originally Posted by blasterman View Post
    Just a follow-up, but I had no problems driving a 500mA / 20volt Bridgelux with a LuxDrive 4015 / 350mA Boost-Puck from a 12volt supply. This is good news for directly boosting a 12volt battery supply to Bridgelux levels without having to resort to inverters. Would it work with a 30volt (or higher) Bridgelux? Not sure. The 4015 is limited to 1.5amps input, and this might not be possible.

    The bad news is this is a bit of a waste. The Bridgelux can certainly be driven harder than 350mA, and ideally you'd want to push them around 700mA as long as you had good heat sinking. I'm sure there are Boost-Bucks out there capable of doing this (and likely cheaper than LuxDrive), but I'm just not familiar with them.

    What you would do then is power a CPU cooler with the 12volt supply used to power the Boost-Buck, and then run one of the bigger 20-30volt Bridgelux off the Boost. Small, absurdly simple package - HID light levels at 120 lumens per watt.
    The meanwell LPC-35-700 can feed from 110v, run up to 48v and supply constant current of 700mah. You can run two Bridgelux in series.

  28. #28

    Default Re: Repurposing CPU coolers for indoor LED lighting.

    How are you going to power the LPC from DC?

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