On 2/11/2013 2:41 PM, Pavel314 wrote:
I'm building a portable cold frame; it's a 2x2 frame about 1.5 feet
high, 4 feet long, and 3 feet deep. Sides and top will be covered
with double thick polycarbonate sheeting left over from building the
greenhouse a few years back. My wife's idea is to put it out in the
garden and start some seeds under it to get a jump on the growing
season. Garden places sell things like this but want a fortune for
them.

The problem is that on a very sunny day, it can get hot enough inside
there to cook and kill the growing vegetables. I can put in a small,
manually operated vent, but would like to have something automatic,
that opens when it gets too hot and closes when it gets cold again.
I've googled around but can't find what I need. I'm looking for
something about 2 inches square that I can mount though a wall of the
construction.

The people on this group have such a wide range of experience that
it's possible that someone can give me a link to these devices, if
they exist. Thanks for any help you can give.

Paul


Perhaps the bimetallic choke coil from an old carburetor is sensitive
enough for your purposes. Here's a couple of links that may help with
your project. ^_^

http://www.crestmfg.com/

http://incubatorproject.wikispot.org/Bimetallic_Coils

TDD