TECs/Peltiers with Mitsubishi 635 Diodes worth having?

[Humphry]

I have bought a simple TEC temp controller for my sextuple Mitsubishi knife edge array, but does a TEC help substantially with output/lifetime of the mistubishi diodes? Planters seems confident it does, maybe he will chime in.
It's throwing so much heat into my baseplate and my "un-TECced" 445nm knife edge array is ending up warmer than I would like.. (bad planning I know)

Still worth doing?

[steve-o]

Running the 445s hotter may raise them to 450-455nm (while reducing the mttf tho) .. :/ .. not really a noticable difference in wavelength to the eyeballz in my experiments tho ..
What kind of a simple TEC setup do you have ?
It probly does do some good to keep those mitsus cool I would think.

[Humphry]

Digital on/off relay based, so it stays within -+2 deg of the set temp, works well for me
Ok so you think let the 445s get a bit hotter and go for the TEC! I wonder if the brightness would be noticeable when cooled.

Running the 445s hotter may raise them to 450-455nm (while reducing the mttf tho) .. :/ .. not really a noticable difference in wavelength to the eyeballz in my experiments tho ..
What kind of a simple TEC setup do you have ?
It probly does do some good to keep those mitsus cool I would think.

[steve-o]

I wouldn't let the 445s get over 50C .. I think 60C is their upper limit iirc. Cooling the red mitsus will keep their wavelength below 640 and stay bright and happy. Yeah some others need to chime in as I am not a tec/ temperature expert with these diodes. Which mitsu red diodes are you using? Do you have a link to the relay controlled tec setup? Sounds like what I've been looking for .

[Humphry]

20$ system or sale on O-like's site, but I see here they can be bought all over ebay!

[buffo]

John Murphy (Polishedball) had a Mitsubishi P73 running at 930 mw after optics at SELEM last year. He said the only way to get that much power out of the diode reliably was to cool it well below ambient with a big TEC. I think he had it running slightly below 10 degrees C.

Also, he used a heat-pipe arrangement to move the heat out from under the TEC and up to a vertical riser, where he had a big fan and heat-sink mounted. That kept the heat from being dumped onto the baseplate, which may have otherwise affected the alignment of everything.

He said he built a 6-diode red based on this same concept. While I've never seen that rig in person, he said it was making 5.6 watts after optics, and he used a similar arrangement for heat management on that build.

Bottom line: Mitsubishi diodes run better when they're cold.

Adam

[Humphry]

Okay thanks, I am definitely getting the feeling that cooling makes a difference.

Does anyone know HOW MUCH of a difference it makes to the 300mw version? I am sitting here with two different thickness baseplates and very indecisive.

[robvdv]

Also, he used a heat-pipe arrangement to move the heat out from under the TEC and up to a vertical riser, where he had a big fan and heat-sink mounted. That kept the heat from being dumped onto the baseplate, which may have otherwise affected the alignment of everything.

This is similar to what I'm doing except I'm running it on the other side of the base plate. Alignment isn't so critical for me. I'll show you when you come around today.

[planters]

From my testing the most is gained in the first 20 -30 degrees C. The increase is approx. 1%/1degree. The wavelength shift is about 0.2 to 0.25nm/degree. After this it seems to settle in at 1%/2degree C and 0.2nm /degree all the way down without any known limit. I also run my G71's @ -5C for these benefits. You can not see the wavelength shift, but the power noticeably increases. The lens, both Dave's 2mm and the Optima 4mm, does not shift focus with this modest cooling.

I had the same problem with the heating of the base plate until I just went ahead and installed a closed circuit water heat exchanger. This is overwhelmingly effective.