Electronics > Projects, Designs, and Technical Stuff
Poor man's Thermal Chamber, meat packing box II
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jbb:
It’s counterintuitive, but I have heard from a couple of sources that you may gain a bit of delta T by reducing the drive current. Have you tried it?

This is apparently because pushing more current through causes lots more loss in the Peltier (ie I squared R losses) which may overwhelm the heatsink.
joeqsmith:
Watching the temperature of the two heatsinks, I can hold it right on the edge where it would start to run away.   It doesn't seem to gain me much running it there vs 10Watts lower.  A much larger heatsink on the ambient air side may help as I could push a lot more current through the peltiers. 

It will hold -10C with the UT181A installed, powered up with its backlight on, during the summer.     
https://youtu.be/NogCSiIKQq0
joeqsmith:
I used a tunnel made from paper and held the blower with some wood blocks when I tested the UT181A.  Bent up some parts for it tonight. 

joeqsmith:
My home lab is sitting around 80F which is fairly warm.   I thought I would just let the box sit as see how low it will go.   It's really struggling to do much of anything.    It made it to -12.8 and I decided to push another 5A or so through it.  Gained about 0.2 was all before the heatsink could not keep up.   I shut it down and the temperature rises fairly quickly.  I imagine most of this is the heat transfer through the peltiers.

I would guess that tripple the power with the 2-stages has gained me about 10C lower.    Not to mention is that 120 Watt space heater is doing a fine job heating the lab even more.    Much larger ambient side sink would help.  More insulation... 
   
branadic:
I bought one of those Happy Reptile / Herp Nursery II boxes used as a poor man's thermal chamber for my experiments on voltage references and can recommend them as a cheap ready to go solution. As Dave showed in his video #101 I drilled a 40mm hole into the wall and glued come water pipe fitting to it. Furthermore I installed Smartec SMT172 temperature sensors in TO18 package to one wall together with a SMTAS04USBmini.

https://www.smartec-sensors.com/cms/pages/products/temperature-sensors.php

Attached is a profile with additional cooling packs. As can be seen temperatures below 5° are possible this way.

-branadic-

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