Good day!
I'm building simple digital thermometer based on common Dallas DS18B20 sensor with parasitic power. I want to put it outdoors, it can became very cold in my location (about -25 C) and very hot (about +45 C). Is it safe to just solder two wires and throw sensor outdoors? Will it survive or I need some case for it and\or some special wire?
Thanks in advance!
I've got one outside, hanging out of the window (via a CD rom audio cable to plug it into) but I encapsulated it in a white diffused plastic 135 film canister, with self-amalgamating tape to cover the slot I cut in the lid to get the cable through. It needs a certain amount of weatherproofing, but the position mine is in can get sun shining on it (on those odd days) and that gives rise to over-reading.
I previously used an older version of the DS1820 outdoors, and found that it absorbed moisture and lost its accuracy over time. To get around this problem, I took a small piece of plastic tubing from a hardware store, just large enough to hold the sensor (with the wires coming out one side) and epoxied the sensor inside. I have had this outside for several years now and it is still accurate. The disadvantage is that it takes a bit longer to respond to temperature changes. Supposedly the newer versions of the DS1820 are not as sensitive to moisture, but I think protecting it is not a bad idea if it might get wet. I don't believe the temperature extremes you mention should require special consideration.
Thank you all, now I got some ideas how to protect this sensor with details from local hardware store :)
To avoid heating from Solar Radiation, you need to build what is known as a Stevenson Shield.
http://en.wikipedia.org/wiki/Stevenson_screen
It is an enclosure that allows heated air to EXIT whatever container is protecting the sensor from the elements. See examples... you should be able to com up with a waterproof solution without too much trouble.
That's interesting. I'd always assumed those were beehives.
You're right — case in point. This morning my outside one was indicating -2°, which is true, everything was below freezing and frosty. Now the sun's out for a few minutes, and it is apparently +15.5° out according to that sensor, so probably no need for a coat! Except that everything is in fact still covered in frost.
Thanks for the tip, if I build one my neighbours for sure will be thinking about bees :)