Mitsubishi P73

[planters]

I promise, I'll try to get the video up tonight.
No controller is needed because the benefit of cooling occurs within the safe operating current range of the diode ( when it is run at ambient). The extra output is just that, extra. The color balance might suffer a little, but I think that's obsessive. A few % change in red output as the temperature changes a few degrees is not going to make a frost white into blood red. In any case, passive cooling with just a heat sink and a fan will suffer the same power variations, but only at a lower PO set point.

My older son and I have successfully run CPU's down to -45C with 1700W of TEC and as long as you avoid condensation and overzealous clamping pressure these devices are pretty forgiving.

[polishedball]

I promise, I'll try to get the video up tonight.
No controller is needed because the benefit of cooling occurs within the safe operating current range of the diode ( when it is run at ambient). The extra output is just that, extra. The color balance might suffer a little, but I think that's obsessive. A few % change in red output as the temperature changes a few degrees is not going to make a frost white into blood red. In any case, passive cooling with just a heat sink and a fan will suffer the same power variations, but only at a lower PO set point.

My older son and I have successfully run CPU's down to -45C with 1700W of TEC and as long as you avoid condensation and overzealous clamping pressure these devices are pretty forgiving.

What if you are over driving them outside of normal operating range? not trying to argue, just trying to understand.

[planters]

With the diodes we are almost always driving them beyond the normal maximum specified current. This is probably shortening their life, but it is hard to say, with little experience,how much. Operating them below their design operating temperature may also be affecting their life, but, here I would speculate that cooling, at least some cooling, will probably increase their life expectancy. Extreme cooling will probably be bad, but just like upping the current some testing will have to be done... LN2? In any case the practical real world limit on how cold a portable projector based diode can be run is not very cold and so I personally think the risk is low.

[steve-o]

In my work, we pump LN2 into environmental test chambers , and I can say for a fact that in dealing with sub-zero temperatures (below 0C or 32F ) especially from -40 to -90C, any leaks to the outside world will suck all the moisture right out of that warmer ambient air and deposit it all over everything that you don't want it on, drenching it completely and thoroughly. But, if you're dealing with electronics (CPUs) at -45 degrees, then you already know that . Just sayin' for everyone's benefit. (Having learned it the hard way myself :]

[planters]

You are absolutely right. The biggest bane of low temperature work is not so much the insulation. Unless you're completely reckless, moderately low temperatures can be reached with ease and the insulation just reduces the power requirements and the powers we're discussing here are modest to begin with. But, water water everywhere; if you target a hermetic seal ie. you could pull a low vacuum on the chamber then you are more than good enough. As a comparison, consider a home freezer that also runs in the -20C range. If you do not open the door when the temperature is down then the soft rubber gasket around the edge does a decent job and this is 24/7 not a few hours a week.

[steve-o]

Ok, well with that resolved, I'll briefly change topics. I did a short torture test on the P73 yesterday: Start- 12:53pm, End- 2:17pm. Duration= 1 hr 24 min. I=929mA, output at start= 649mW, output at end= 648mW. No significant heat generation noted. Ambient room air temp approx 22C (73F). No mode hopping, no beam profile changes noted.