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Does a cooled laser run longer?

MojoLA

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I'm currently using a garden variety 5mw green pointer to fuel my lumia wheel show (and by "show" I mean I project it on my living room wall/ceiling all night long). To keep it running ive had to use rubber bands to keep the "on" button depresed and even though I have no idea what the duty cycle is, with a 5mw I'm not really worried about generating enough heat to fry it.

Speaking of which, it does get warm after being on for so long, so, just to be on the safe side, I have a small desk fan I keep aimed at the laser and wheel motor.

The thing is, I could SWEAR the batteries in the pointer last longer when I keep it fan-cooled as opposed to just letting the heat dissipate naturally.

Is this my imagination, or is there some science that flat out says "of course a cooled unit will drain power more slowly (or) batteries drain more slowly in a cooler enviroment."

Would love to know the truth behind this.
 

millirad

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Inside your battery a chemical-electrical reaction is taking place to provide current flow. Temperature increases will speed the reaction taking place within the battery. Therefore it stands to reason that the opposite will occur if the temperature is reduced.
 

Benm

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Its certainly possible that the batteries performance is degraded by elevated temperature. I dont know what batteries you are using or what the current draw is though.
 
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Are there pictures of your creation anywhere? I'm really interested in seeing this thing.
 

MojoLA

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Ha ha trust me my lumia wheel "rig" is about as ghetto as it gets... but it works.

I actually took some video last night to share with the group, as soon as I get a chance to process and upload it i'll let ya know.
 
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Thanks! I think something like that would look cool in my dorm. You should see people's faces when I've got a couple front mirrors set up and I'm playing with beams. XD They think I'm a mad scientist.
 

Benm

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Its fairly odd - from NiMH's you would expect better performance with rising temperature (within reasonable limits). Perhaps the laser draws more current at high temperature though - the only way to figure that out is to measure the current draw with and without the fan.
 

MojoLA

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Well like I said, I'm not sure, I haven't measured anything, which is why I was curious what the science behind it was.

Either way, one thing is certain - keeping electronics at a lower operating temperature is always a good thing!
 

Benm

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Hmm.. thats a rush conclusion without doing the science involved ;)

In general it holds true, but batteries can be a notable exception, with many chemistries showing improved performance in at least some aspects with higher temperature. Chemical reactions kill most electronics over time, but batteries are one of the few things that depend on chemical reactions, and therefor can benefit from heat.
 

MojoLA

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Ah but batteries don't run themselves - you have to put the batteries IN something, and those somethings (like lasers) I would say ALWAYS benefit from cooler operating temperatures.

So maybe the batteries themselves enjoy high temps, but the things they power do not.
 
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Ah but batteries don't run themselves - you have to put the batteries IN something, and those somethings (like lasers) I would say ALWAYS benefit from cooler operating temperatures.

So maybe the batteries themselves enjoy high temps, but the things they power do not.

DPSS lasers are very dependent on temperature, sometimes it helps them to be a little warm, and sometimes it helps to be a little cold. It can vary a lot from laser to laser, even if they are manufactured to be exactly the same. Diode lasers however, are not nearly as temperature dependent. I've had red laser diodes run at -100F and they seem to operate fine... I have not tried violet diodes yet, so I can't comment on them atm.

--Hydro15
 
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If the laser diodes is running in an APC configuration with a photodiode, then it will likely draw less current at the same power, since higher temperature increases the current necessary to achieve a given power.

But there are a lot of variables built into a system such as that.
 




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