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heatsinking a 2W laser - impact on duty cycle?

ryckmans

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Hello all,
Just got a 2W 445nM diode here:
2W Copper 445nm M140 Blue Laser Module w x Drive 405 G 2 Glass Lens | eBay
it works a treat, but gets hot quickly. The seller says "90 seconds on 30 seconds off with proper heatsinking". If I had a big enough heatsink (maybe even a water cooled one) - could I increase the "on" duty? It has a driver included (1.8A X-Drvie bucking laser driver).
I'd like to do engraving with this, and I need longer duty cycle...

many thanks
Thomas
 

ARG

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:eek: I hope you didn't run the module without a heatsink, it's not good for the diode to be that hot.

How long do you need it to be on for?
 

ryckmans

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Thanks ARG - it has a small heatsink: the housing of the driver. I did not let it get hotter than 45C (100F). I would need to keep it "on" for 10 mins or so
any ideas? Many thanks!
Thomas
 

ARG

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Do you need it to be portable? (Is the work you're engraving moving or is the laser moving?)
 

Distillate

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I would guess that for a 10 minute duty cycle you would need quite a large heat sink. MrCrouse, Eudamonium, or jayrob are some of the members here who could make a custom heatsink for you.
 

ryckmans

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Hello there,

I would like to do engraving - the laser will not move as it will be above a XY moving table, so it is okay to be a bit heavy.
The eBay quote for this laser is "2W in light output"; the heat output I would guesstimate (I over estimated here for safety) at around 4V (voltage drop) * 2 amps (delivered by the driver) = 8 watts - 2watts of light -> I need to dissipate at least 6 watts - let's design for 8 watts.
I turned a brass bar (I know it's not the best conductor) to end up with a cylinder that is 5 cm (2 inches) long, D= 2.5 cm (0.8 inch) with a 12mm hole inside (0.5 inch) to fit the diode. Weight is 130g (1/3 of a pound).
This does get warm (not hot) to the touch in about 3 mins - I probably need a better heatsink.
My seller says I also need to heatsink the IC on the driver (which is included) - this sounds more difficult as it is a very small unit. Any ideas?
What I could do is pre-reduce the current I feed to the driver to 2amps - then the driver will have less work to do? Is this a good option?
many thanks

Thomas
 

TheDukeAnumber1

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Reducing the current through the driver will save heat in the IC and diode. The data sheet for the Nichia 9mm 445nm doide which is similar to the M140 445nm lists the max operating case temperature to be 50°C (122°F), letting the sink get warm is ok, just shoot to be below that temperature. You can sink the driver using some arctic alumina epoxy and maybe one of these-
Amazon.com: Cosmos ® 8 PCS Copper VGA RAM Cooling Heatsinks cooler + Cosmos Cable Tie: Electronics
-or a comparable sink. I've taken the X-drive and completely covered it with arctic alumina epoxy before and saw no negative effects on operation. For your diode I think a sink with fins and a fan would be best.
 

ryckmans

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Thanks Duke,
I ordered some PC heatsink + fan, should be enough...
I was surprised - when only the LM317 circuit is powered by a laptop charger, it draws 2.2 amps. If I then plug the laser driver and laser, it draws 1.4 amps (the driver is designed to deliver 1.8 amps to the laser) - I thought these laptop chargers I use were very stiff, with low current drop when a load is present.
This would explain why the driver does not get hot - the current is already limited. I would now be scared to run this laser at 0.4 amps higher!

cheers

Thomas
 




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