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Low Cost Heat Sink Tests

Cyparagon

Well-known member
This is always a compromise: in theory you can passively heatsink anything you like, but the solution would have to be extremely large.
I've got a big problem with the word anything, here. For instance, you can make a copper block a mile cubed, and I can still melt part of it nearly instantly with a standard welding torch. I can think of countless other examples where active cooling is just required by physics.

Although the thermal resistance of standard heat sink materials is very low, there are limits. Pumping water or air to the source increases these limits substantially.

dont kill me..

paul1598419

Well-known member
That is one tiny fan, Len. Like I said, it was not possible to ascertain its size without something of known size in the photo.

Cyparagon

Well-known member
it was not possible to ascertain its size without something of known size in the photo.
That got me thinking. Since I'm bored and I need algebra/geometry exercise... Is that not a standard 12mm hole? I checked the pixel widths in paint:

41/12=148/x
if 41 pixels is 12mm, then 148 pixels is ~43mm. Assuming the standoffs are straight, 162 pixels in the foreground is also ~43mm. 40mm is the closest standard size to this estimate, but It really doesn't look like 30mm.

41/x=148/30
If that actually is a 30mm fan, then I would estimate the hole size at 8mm, which seems goofy.

Exactly what dimension are you measuring to get 30mm, Mr. lifetime?

Benm

Well-known member
I've got a big problem with the word anything, here. For instance, you can make a copper block a mile cubed, and I can still melt part of it nearly instantly with a standard welding torch. I can think of countless other examples where active cooling is just required by physics.
You could indeed since thermal conductivity is limited. But i would like to point out that you could still melt a hole in a cube of copper with fans blazing at it at 500 mph and fins engraved all around that cube, and that wouldn't make it that much more difficult to do.

The issue is that with electronics design you often work from a realistic situation - you put laser x into a module y into a heatsink z, and then add up all thermal resistance of that to see if it's feasible under continuous operations.

Practically you can perfectly well weld a railing onto a ship without heating the entire thing to melting temperature, but those are not continuous conditions. If you had your cubic mile of copper and wanted a section of that to remain molten indefinitely, it would require a fair amount of power input to to so.

RedCowboy

Well-known member
It's 20mm wide is it not ? 4/5 of an inch........well at 25.4mm per inch slightly less, still my ballpark speculation was close, not close enough to pre fabricate a mounting but as far as judging between huge/large/med/small/very small 30mm or 20mm is what I would call very small.

hakzaw1

Well-known member
Using crtl -

I made the pic 'full' size the blue label is ~13mm the fan frame is ~17mm.
I will locate the fan soon and re-measure..
@ paul you do realize I left out anything that would give away the size including the teensy heat sink (raspberry pi).

JETLASERS tried hard to active cool a PL-E--and gave up,
IIRC the fan and TEC used too much power..or the hot side of the TEC did more harm than 'help' they sent me a host pre- machined with air 'slots'.
Dont think they tried w/ a pure copper heatsink though. its been a while and I have slept since then...I got the fans in that size to use with the modded PL-E host(s) I sent a second one w/ fan and more to P-man--afaik he has not worked on his (either) :-(
Could be a great host for the '1500mW' 405 --w/ fan only...but pure copper heat sink..hmmm

paul1598419

Well-known member
Unless you can move a lot of air around the heat sink and the sink has a large surface area, it is likely that actively cooling handheld hosts is too difficult and will remain a lab laser option. I can't imagine that tiny 17 mm fan moving much air especially in a restricted host that makes the free movement of air near impossible. Using a TEC in addition to a fan adds waste heat to your host that will also need to be removed. There really is no free lunch here.

RedCowboy

Well-known member
Unless you can move a lot of air around the heat sink and the sink has a large surface area, it is likely that actively cooling handheld hosts is too difficult and will remain a lab laser option. I can't imagine that tiny 17 mm fan moving much air especially in a restricted host that makes the free movement of air near impossible. Using a TEC in addition to a fan adds waste heat to your host that will also need to be removed. There really is no free lunch here.
Not really a shirt pocket size build, not with a multi watt diode, but for a Maglite size build it's possible, here's Barnett getting some stability it seems the fan gets the output to tick back up rather than the usual trickle down we see. >

paul1598419

Well-known member
That is more like a lab laser host than one that would fit a handheld unit. You would need to leave the back end open so the fan could push air through the heat sink. Don't really see a viable way to do this. Someone here took a lab laser and put it on the end of a battery tube. It looked awful and the fan was blocked from having free access to the air behind it. I think a regular lab host that could be had on ebay might work as well, if not better, and for less money.