How good is a CPU heatsink for use with an LS?

Simple question here: Should a CPU heatsink (486DX2/50 or DX4/100) be able to handle the heat from a 1W LS being driven at or slightly above ratings? The star boards are going to be mounted to the heatsinks with thermal pads which claim a thermal resistance of 0.05DegC/W, can probably arange a fan to fit to the heatsink if required.

This is for bench or fixed use, rather than in a flashlight, to the heatsink isn't going to be in an enclosed space or anything (Most likely on top of my wardrobe).

Heatsinks to be used are here: One already has a red/orange LS fitted (The one that has wires coming out of it), was being run earlier (at ~200mA), and I wanted to be safe.

In my humble opinion that should be plenty of heatsinking. 1 watters don't produce that much heat. I'm sure one of the resident experts should be around to give you a professional opinion.

i use bx chip coolers without trouble.
even near an amp. 486 coolers are overkill imho.

that should be more than adaquate for a 1watter /ubbthreads/images/graemlins/smile.gif

ripping the emitter off of the star will provide increased thermal transfer.

Good to hear it. I might remove the emmitters from the stars at some point, but I'll probably leave that until I know what I'm going to do with these...and when I find the post I remember that said the easiest way to do that.

The short answer: like Roth said. /ubbthreads/images/graemlins/grin.gif

The longer answer: If you take a look at this page and find the 486DX4-100, it lists "Maximum Power Dissipation" of 4.29 watts. Therefore, that heatsink should do for a few emitters, and certainly should be fine for a single 1-watter! /ubbthreads/images/graemlins/thumbsup.gif

The one caveat would be that most CPU heatsinks are designed to have some airflow over them. Given the extreme overspec in this case, that might not be necessary, but it couldn't hurt, either. Keep the heatsink in an open area with fins facing either upright or sideways (NOT down), or position it so a little air passes through the fins. You could use a computer fan for this purpose; this Panaflo fan is super quiet and can be run with as little as 5V and maybe lower, at which point it will still provide a decent amount of air and be effectively silent. (It only pulls about 65mA, too!) For $5 this would be good insurance, though in your case you might not really need it.

Good luck to you!

This is from an old post with a REALLY small fan cooling an LS/O:

THREAD HERE

I've got a red/orange on a CPU sink that I've been torturing mercilessly and the sucker won't die... /ubbthreads/images/graemlins/eek.gif

Here I'm testing at a "friendly" 3V.. /ubbthreads/images/graemlins/grin.gif

As inefficient as it might be, I would love to see just how much I could overdrive a Luxeon if attached to a Peltier with a massive CPU heatsink/fan combo on the other side. /ubbthreads/images/graemlins/smile.gif

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Entropy said:
As inefficient as it might be, I would love to see just how much I could overdrive a Luxeon if attached to a Peltier with a massive CPU heatsink/fan combo on the other side. /ubbthreads/images/graemlins/smile.gif

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You are one sick dude, Entropy. /ubbthreads/images/graemlins/grin.gif But given that the best CPU heatsink-fan combos can sink perhaps 100W of heat and the Peltier will improve performance further, it's gonna be veeerrrry interesting. /ubbthreads/images/graemlins/mad.gif Strangely, your biggest worry would likely be the Peltier making things too COLD, resulting in condensation or even, of all things, ice! /ubbthreads/images/graemlins/rolleyes.gif

too bad you would exceed the wirebond limit before you got there.about 2.3 a is about it.color shifts and out she goes if you dont shut it off fast.

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milkyspit said:
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Entropy said:
As inefficient as it might be, I would love to see just how much I could overdrive a Luxeon if attached to a Peltier with a massive CPU heatsink/fan combo on the other side. /ubbthreads/images/graemlins/smile.gif

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You are one sick dude, Entropy. /ubbthreads/images/graemlins/grin.gif But given that the best CPU heatsink-fan combos can sink perhaps 100W of heat and the Peltier will improve performance further, it's gonna be veeerrrry interesting. /ubbthreads/images/graemlins/mad.gif Strangely, your biggest worry would likely be the Peltier making things too COLD, resulting in condensation or even, of all things, ice! /ubbthreads/images/graemlins/rolleyes.gif


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Yeah. Which is why (like the overclockers) I'd have to use foam insulation in some areas to prevent condensation.

The limitation would most likely be the thermal resistance of the die and Luxeon slug, not the HSF's ability to dissipate heat. In which case the only thing that matters is making the slug as cold as possible.

Stacked Peltiers... hmm... /ubbthreads/images/graemlins/smile.gif

Okay, you've already gone this far, why not finish the job, eh? /ubbthreads/images/graemlins/wink.gif Remove the emitter from the star circuit board if necessary, mount it using Arctic Silver heatsink grease to a large block of aluminum, epoxy it fast using thermal epoxy, and run two long wires from it. Next, carefully coat everything with a thin layer of a clear, waterproof glue, or perhaps even silicone caulk (if it's clear enough). Next, fill a large bucket with water that is circulated and kept at exactly 33 degrees Fahrenheit; I'll leave exactly how to do that part as an exercise for the reader. /ubbthreads/images/graemlins/grin.gif Finally, submerge the emitter and aluminum block, and wait for the block to reach 33 degrees. Then fire away! /ubbthreads/images/graemlins/mad.gif

Let us know how you do, including plenty of photos. /ubbthreads/images/graemlins/grin.gif /ubbthreads/images/graemlins/grin.gif

Why only 33 degrees? Why not submerge the emitter, then let the water freeze? The ice will absorb a huge amount of heat in changing phase from solid to liquid again.... You could forego the waterproofing if you used a block of CO2 dry ice instead. Although the CO2 vapor might interfere with your beam pattern. Also if you used distilled water, you wouldn't need any waterproofing either since pure water is an insulator.

A Peltier will get the temperature *well* below 33 degrees.

There isn't much heat to be removed as compared to a CPU dissipating 50-60W, BUT when trying to push the Luxeon to its limits, the thermal resistance of the junction (Degrees celsius per watt) means that you want to have the back of the slug as cold as is possible. With two Peltiers stacked one should be able to achieve some extreme negative temperatures. /ubbthreads/images/graemlins/smile.gif

Liquid N2 cooling would also be fun to experiment with. /ubbthreads/images/graemlins/smile.gif