Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers



Laser Pointer Store

Low Cost Heat Sink Tests

paul1598419

Well-known member
Joined
Sep 20, 2013
Messages
13,856
Likes
1,994
Points
113
I used the ones you said did the worst to build some fan cooled 532nm DPSS lasers in aluminum cases about five years or so, ago. They were screwed down to the aluminum enclosure with Arctic Alumina Thermal adhesive and had unlimited run times at 200 mW. I couldn't use a heat sink that didn't contact well with the enclosures, so these worked out pretty well. considering they had 1 watt pump diodes in them.
 

BobDiaz

Active member
Joined
Mar 4, 2014
Messages
137
Likes
32
Points
28
""
The AixiZ came out to be #2 in my tests.

There was one thing that pissed me off. the AixiZ came with an M3 set screw that was too short. After I screwed it in all the way, the screw would not reach the laser. What the heck? """

Sorry about that.. if you want the correct ones I will make that happen..AixiZ must have a thousand different items. and ,any sizes of screws. I saw the same thing when I checked mine -- it is too short.

BUT am very happy with the testing.. but getting 'pissed off' is a stretch.. did you get a free one?
I assure you this was an accident ... and that is 'what the heck' is...
TY for the work you did...len
Maybe "Pissed Off" was too strong a term and I should have said, "unhappy". AixiZ doesn't need to send me anything, I went to the local electronics store and picked up some M3x10 and M3x16 screws. The M3x10 are the correct size, but it's always nice to have the larger ones just in case.

One nice thing about the AixiZ heat-sink, it fits on the same PCB where I build my power supply for it. This will make for a nice clean build that is all in one. I plan on writing up how to build this for my students. Every semester I get one or two students who like my lasers so much that they want to build their own.

Did I get a free one? I'm not sure, I forgot how many I ordered. I did receive 4 of them, but I just don't remember if I ordered 2, 3 or 4.

EDIT ADDITION:

Several people have suggested I add a small fan to help cool it down. This is a future test to see how well it works. Past tests with fans show that they do a great job of keeping things cooler.
 

hakzaw1

Well-known member
Joined
Apr 2, 2009
Messages
9,355
Likes
1,430
Points
113
Bump Double post
want posters in this thread to see some pics.
Do you think this fan would work well? TOO big?
yeah but it is quiet.....VERY QUIET

pic refuses to load..resized twice..

WAIT WHAT?? omg== I thought I uploaded both pics...

.. FAN 038.jpg
 

Attachments

Last edited:

BobDiaz

Active member
Joined
Mar 4, 2014
Messages
137
Likes
32
Points
28
My guess is there are a lot of other low cost heat sinks out there. Are there any favorites that anyone has?
 

paul1598419

Well-known member
Joined
Sep 20, 2013
Messages
13,856
Likes
1,994
Points
113
It looks like it might be 40 mm along the side of the fan. It must be quite fast as my 5 VDC fans are 130 mA and this one is 400 mA.
 

paul1598419

Well-known member
Joined
Sep 20, 2013
Messages
13,856
Likes
1,994
Points
113
It's not possible to know what size the fan is since there is nothing of common size in the photo next to it. I could be any size really. I happen to have some fans that are 4 cm along one side that are 5 VDC, so that was the reason for my guess.
 

RedCowboy

Well-known member
LPF Site Supporter
Joined
Jul 10, 2015
Messages
7,026
Likes
1,761
Points
113
It's not possible to know what size the fan is since there is nothing of common size in the photo next to it. I could be any size really. I happen to have some fans that are 4 cm along one side that are 5 VDC, so that was the reason for my guess.
Actually there's the wires, the print, the bolt holes, the blade design and dimensions....also the power specs. granted it could be a non typical design although it looks to be a compact size, I would speculate 30mm across as a rough guess.

----EDIT----

I found the part number elsewhere and it appears to be a 20mm fan, that's not bad and should be strong going by the power spec.

https://www.eio.com/sunon-kde0501pdb3-8v.html

hakzawfan1.JPG
 
Last edited:

GSS

Well-known member
Joined
Apr 28, 2015
Messages
3,653
Likes
1,469
Points
113
UPDATE:
View attachment 62184
I tested the AixiZ heat-sink and there were some surprises. First this is the smallest and the lightest of the heat-sinks and I expected it to be the worst, BUT surprise, it did far better than expected. The other two small heat-sinks could run for only around 5 minutes before hitting the limit of 89F. (15F below the limit of the diode.) The AixiZ ran for 7 minutes before hitting this limit. I can only assume that the larger fins results in greater surface area for cooling. The AixiZ came out to be #2 in my tests.

There was one thing that pissed me off. the AixiZ came with an M3 set screw that was too short. After I screwed it in all the way, the screw would not reach the laser. What the heck? Now I have to go to the store and purchase longer screws, not cool. At $3.95/each they should have paid the fraction of a cent extra for a longer screw. I had to use a 1/4" 40 tripod screw to hold the laser in place.

View attachment 62185
This one performed the best of the group. I ran it for 15 minutes and ended up at 87F with 2F to go before the limit. This was the most costly of the small heat-sinks, but so worth it if you have to keep the heat away from the laser module. This one was #1 for my tests.

View attachment 62186
This gold heat-sink didn't do too bad. I could run for a little over 5 minutes before I reached the limit. This was #3 in my tests. It's only around $4.50 for each. Still for the money, get the AixiZ and save 50 cents.

View attachment 62187
This did the worst in my tests, but could last 5 minutes before reaching my 89F limit. At $3.50 each, the price is reasonable and one could mount it to a metal plate, a metal block, or another heat-sink for additional cooling. This was #4 in my tests.


The one from ebay may take a while to arrive: SK12 Bearing Linear Rail Shaft Support
https://www.ebay.com/itm/113307812293
So I have no idea how well or badly it will do, but because it clamps around the laser, rather than a set screw, I think it may have some strong points for selecting. AT $1.60 each, it may be worth it to use two of them.
Hak, i'm thinking the 3rd down gold plated sink might just do alot better with your fan. It looks purposely manufactured for the air flow over it and below through a tunnel. I wouldn't mind seeing a comparison this way..
 

RedCowboy

Well-known member
LPF Site Supporter
Joined
Jul 10, 2015
Messages
7,026
Likes
1,761
Points
113
Just stating the obvious here:

Forced air over fins wins out over convection in most cases where the volume of material is close to the same, actually more material only acts as a heat reservoir that saturates in short order ( minutes ) with our favorite LD's.

It's the surface area that's the heat vehicle hence the value of fins and forced air multiplies the cooling. I have built some massive heat sinks with no active cooling and they will saturate in a short time, this is why the projectors that we harvest from us fins and fans. :)
 

Benm

Well-known member
Joined
Aug 16, 2007
Messages
8,086
Likes
688
Points
113
It's the surface area that's the heat vehicle hence the value of fins and forced air multiplies the cooling. I have built some massive heat sinks with no active cooling and they will saturate in a short time, this is why the projectors that we harvest from us fins and fans. :)
This is always a compromise: in theory you can passively heatsink anything you like, but the solution would have to be extremely large. Computers generally use fans to get rid of the heat, though it is possible to do so without any fans in some cases. A laptop would not be that portable if it had a shoebox-sized heatsking sticking out of it, and neither would a laser pointer.

Considering that you have 2 options: limit duty cycle, or actively cool with a fan.

With a beamer you cannot really limit the duty cycle (wel'll watch this movie, 1 minute on, 2 minutes off?!) so putting in active cooling is the best solution. For a laser pointer this can vary - perhaps it's only intended to be ever used in short bursts and there is no need for more heatsinking or active cooling.

Personally i see this as a design flaw unless you do something about it. On high power compact flashlights with high "turbo" mode setting this is often addressed: You can run the LED to the max until something overheats and the circuitry just dials down the current to prevent damage. Most laser diode drivers lack such a mechanism and will overheat when in continious operation without adequate heatsinking.
 




Top