Cheapest way to make a cooling chamber?

I need minus 20 minimum

Klaus Kragelund wrote in news:67201209-a594- snipped-for-privacy@googlegroups.com:

"A household freezer" is usually a pretty big box and they are not cheap and they are usually a horizontal footprint. They go down to about 10 degreef F below zero F. and are full of humidity.

A thermal chamber, OTOH, is a precision controlled device and costs many hundreds more, but can be a benchtop small cavity solution that can go down to like 150 F below zero in some cases.

Lowest I saw my Kenmore 25cuft freezers at was -18*F. I don't know if you could get a smart refrigerant guy to mix a cocktail of refrigerants to get you down to say -25*F. I had 12 freezers all with separate thermometers. The stock built in thermostat minimum setting was -10*F, but the internal temperature went lower than the -10*F thermostat setting.

Mikek

I had a smaller product to test. I got a Styrofoam cooler, a small computer fan, and bought dry ice (solid CO2). Got down to about -35F, if I recall correctly.

Just a thought.

how much power will it dissipate?

much lower. I've once saw beautiful ice crystals forming in bubbles when pouring almost syrup-like vodka from the freezer!

Do you just need to check if your stuff works or do some more measurements ? You might put your thing in a box with fan and heating element+thermisto inside the fridge to create a bit more controlled environment. Then just run the freezer at almost maximum setting and control the temperature with the heater.

And get some cheap used freezer - don't use the one you use to store all the good stuff!

Usually I've been able to do cold testing by just putting stuff out from the window, but this winter has been very warm and mostly above zero.

Mikko OH2HVJ wrote in news: snipped-for-privacy@mspro.home:

Damned Russkies! :-)

Maximum power dissipation is about 5W

I will be running hot, meaning powered and will have various probes attached to monitor important nodes

Cheers

Klaus

Klaus Kragelund wrote in news: snipped-for-privacy@googlegroups.com:

Then you need a 3 or 4 inch hole saw to open a hole in the chamber which you then fill with a foam plug. That allows the wiring to be passed through without compromising the chamber temp stability. It does not need to be 4", but that size allows one to pass one's hand through as well.

As to the running hot thing, I would place the UUT in unpowered and let it settle to the cold temp for at least ten minutes, then do your live tests and hot running observations. Maybe more than ten minutes to settle in. If you also had an oven, you could do full bore thermal shock tests too. Super cold board into super hot environment, and back again.

Back in the thru hole solder days, that would expose bad solder joints, etc. Not so much any more.

Something like this could cool down to 1 degree, better than nothing:

Down to minus 20 for just 150 USD

I got a cheap Peltier heater/refrigerator from Amazon, just the size for a few beers. It only has two temps, but effectively sweeps if you switch. Handy for temp testing small boards or saving/curing epoxy or keeping cokes cold for engineering Rum and Coke requirements.

You can assemble a box of styrofoam boards, and put a little liquid nitrogen in, to get a good range of low temperatures. A chest freezer will HOLD a low temperature, and probably is resell-able after the project is done. Or, you can find a local outfit that has environment chambers, and pay 'em to do the test (that gets you some extras, like humidity control). Most costly, you can become such a local outfit...

I have used mine to recover data from an IBM Deathstar(R) SCSI disk.

I have seen pics of a ham from OH who concentrated alcohol in the deep freezer from wine by fractional freezing. I have tested the procedure :-), but didn't dare to try that oily red liquid.

I have not seen any snow this "winter". OK, a hint that melted immediately when it hit the ground, and the phenomenon lasted 3 minutes.

Around here, this time of year you might do your testing outside at night w ith a temperature controlled heater. Maybe not this week. It's supposed t

What's your climate like?

Never mind

g out any heat? That would make a big difference. If the tests are short including a lot of thermally dense material can act like a buffer. But if it needs to run continuously I expect you will need a pretty high capacity compressor in a small box?

This guy reaches -7, with a concept that has room for improvement