Extending the duty cycle on a 1150 mw 445 nm laser via cooling methods

My laser is awesome, but one of the problems is how quickly it overheats. It's slightly annoying having to manually cycle it every 45 seconds, and that means that I can't set it down to play with the beam at a distance.

Has anybody found any methods of drawing heat away from the heatsink in an already constructed handheld? Or alternatively any simple ways to automatically go through a duty cycle?

I was brainstorming and came up with placing the tip of the pointer in a makeshift heatsink and maybe using a fan to make up for the inefficiency of the cooling. However, I'm not sure if the case of my host is conductive enough to draw away enough heat for it to be plausible.

we would need pics.
but there is about to be some fan cooled 445nm laser hitting the market very soon.
i am making them personally.
once we have a picture of it we can tell you more
(expensive but cheap way would be to used canned air it comes out super cold. but it would only work for so long...)

Only play with it inside a deep freeze. You can find them at any fast food restaurant. They all have freezers that stay at -20 Fahrenheit.

Problem solved. Your welcome & yes, I know i'm a genius!

Are you saying your diode is overheating or you want to find a way to put a heatsink on your driver? The most common problems with a 445 is the driver overheating not the diode if you have it in a halfway decent heatsink.

DTR said:

Are you saying your diode is overheating or you want to find a way to put a heatsink on your driver? The most common problems with a 445 is the driver overheating not the diode if you have it in a halfway decent heatsink.

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Do the micro drives heat up as well? I may have to find a way for the driver to be heat sinked by the hosts as well when i make my 445.

I know the lm317 drivers get really hot, and never noticed much heat with the flex drives. I have not ever used a micro boost yet.....

Mohrenberg said:

Do the micro drives heat up as well?

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If you max it out it will overheat. The host of yours that I built was set to 1A ran for over a minute without overheating. It all depends on what current you want to be driving it.

ah okay.
I've got to stock up on aluminum bar stock tomorrow...but MAYBE i'll get to order my micro drive too depending on how much the aluminum costs.

I've got my diode, module, lens, and trustfire 18650 ready...Just need the driver and then i can machine a custom host for it.

Uhm ..... just indicatively, you can try to made host and heatsink with anticorodal alloy, instead pure aluminium (it's an alloy used normally for sailships, cars or bikes parts, is almost corrosion-proof and have a strenght and density that is greater than aluminium) ..... or copper, but this cause some working problem (machinists knows that work with copper it's a damn pain you-know-where ) .....

Also, increasing the surface in all the possible ways helps a lot (fins and caves and "waved" surfaces), ofcourse without forgot the needed thickness for transfer the heat to the fins (there's no reason in doing lots of thin fins, if the remaining metal cannot transfer enough heat to them ).

And as last resource, fans (but is difficult to add a fan to an already-made host, or also just to a custom small one)

Make water proof host
put laser in fishless tank
add ice cubes as needed
profit

In actuality that wouldn't work well because of the glass, but with a water proof host you could do something like wrap it in a sub zero gel pack like what is used for drink coolers etc... If the laser isn't water proof though condensation could get inside. Not sure about possible condensation inside around the battery. Maybe put some silica gel in there?

Nearly all of the heatsinks I've ever seen for custom built lasers are not really heatsinks. They're heatdumps. A true heatsink will transfer it's heat to the air by means of thin fins.

The best you can do is to minimize medium junctions. If the heat has to be dissipated from the diode -> Aixiz module -> aluminum heatsink -> LED Flashlight host -> air, the thermal conductivity is reduced. Even a tiny air gap will insulate the heatsink from the air. I try to only use solid aluminum, direct press hosts, for my builds, but even still my 445 diode get warm pretty quick.

-Tony

Xplorer877 said:

Nearly all of the heatsinks I've ever seen for custom built lasers are not really heatsinks. They're heatdumps. A true heatsink will transfer it's heat to the air by means of thin fins.

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You're absolutely right about that: most designes for handhelds i've seen here consist of a metal rod the inner diameter of the flashlight, with an aixiz-sized hole in the middle. For continous operation you rely entirely on the surface area of the flashlight to get rid of the heat.

This often works fine for the 1 watt or so dissipated by the typical red diode, but these high powered 445's use about 5 watts. To get continous operation you'd need a big housing that acts as a heatsink, like the RPL or Hercules green lasers.

Heatsink IS the correct term. Heat flows from source (diode) to the sink(whatever you have the diode in) so it's still a source-sink. Therefor, heatsink. It's no different than a current sink or an RF sink (antenna dummy load)

And these behave exactly like your finned heatsinks as well. They still dissipate their heat to the surrounding envoironment. They're just not as efficient at it since they don't have a large surface area, which is what the purpose of fins are. To increase the radiating surface area.

Yeah I know, technically speaking they're still heatsinks. I'm just making the point that they aren't very efficient at radiating heat off into the air. Once they get saturated with heat you really just have to let them cool down. In other words they absorb heat from the diode faster that they radiate it off, at least at ideal operating temps that is true.

-Tony

Xplorer877 said:

Yeah I know, technically speaking they're still heatsinks. I'm just making the point that they aren't very efficient at radiating heat off into the air. Once they get saturated with heat you really just have to let them cool down. In other words they absorb heat from the diode faster that they radiate it off, at least at ideal operating temps that is true.

-Tony

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Couldn't agree more.

What's the point in adding an, or using the term "heat-sink" if you're going to wrap it in an insulating sleeve like air, steel, wood, or another material of lower thermal conductivity?

You see lots of designs here that seem contradictory, like a great material for a heat-sink, that's clamped to the module, or a good material + large volume that only exposes less than 10% of itself to the air, because the rest is sleeved in steel, plastic, or wood!!

There's a problem with these designs as they mislead the user as to how hot their diode is actually getting, whilst insulating it and making it worse at the same time.

This link to another thread demonstrates how to properly apply a heat-sink...

... http://laserpointerforums.com/f48/ive-finally-made-complete-host-52636.html

As already mentioned though, you could achieve similar performance if you ensured that from the surface of the LD can to the outside air there were minimal interruptions or junctions the heat has to conduct across by press-fitting everything, using thermal paste, and reducing the thermal conductivity difference between the materials used as much as possible.

Most hosts I see people use are aluminum and the heatsinks are usually threaded in or press fit. Since the aluminum is in contact with the diode heatsink, the whole host becomes a heatsink.

The only examples I can think of off the top of my head that fit what your talking about is dieselmarine's wooden pepper shaker build, and whoever it was that put a 405 diode in a happy meal toy.

That host you pointed out, while neat and well done, is actually extremely overkill for what thermal mass/transfer is actually needed. While it's impossible to have too much heatsinking, the point of diminishing returns is reached far earlier than I believe you think it is. Which when designing and machining a host.. usually means more work for little gain.

After all, we're talking about <5W of thermal power here, at least in 99% of the portables. It's not like these are little nuclear reactors.

I have a bunch of cheap 50mW 532nm 18650 pointers. The modules are pressed into a maybe 15mm thick aluminum donut, which is threaded into the aluminum host. When I first got some of these, being the sort of person who can't leave anything alone, the first thing I did was tear one apart. Well, I destroyed that one heh, but the second one I did some tests to see well the donut actually worked. What I found was that after leaving the thing on for an hour, the module itself was only 19F higher than ambient.. By my calculations the diode was putting out a little over 2W of heat going by optical power output, Vf, and current draw.

Needless to say the arrangement was working far better than I figured it would, cooling wise, so I left it alone and the only thing I do to these is add IR filters now.

My point is, I myself would trust a similar arrangement with pretty much anything lower than 200mW 532nm modules, and 500mW 405nm and 445nm diodes... which still encompasses the vast majority of DIY builds.


And BTW.. High thermal mass like that host you pointed out has an achilles heel as well. While lots of thermal mass makes it slow to heat.. It also makes it equally slow to cool off.