@Dimitrios commented the other day on my Funky+DHT22 post that my readings seem to have a lot of 99.9% relative humidity readouts and suggested that it may be due to the black box that I enclosed the project. I do have some holes drilled, but probably not enough to get decent air circulation:
I compared my readings to Weather Underground data that I also collect and they seem to be relatively close, yet don’t hit the 99.9% RH mark that often:
Dimitrios suggested to send me a 3D-printed Stevenson screen to try out (Thanks!). I got it today, quickly inserted the Funky+DHT22+AAA battery, and in the process took a battery measurement. It measures 1.35V, pretty amazing since I inserted that battery on Sept. 15th 2012. It will work down to 0.8V, so I guess it will be around for a year at least. Some pictures of the setup:
The screen was printed in natural PLA and then painted white to increase reflectivity.
One of the M3 support screws is cut longer, to serve as the RFM12B
antenna for the 868MHz band.
Pretty cool 🙂
Thanks again, Dimitrios!
p.s. freeCAD design files for the screen are available: stevenson_screen_v2
Hey Martin, it’s so nice to see it in service!!
In the meanwhile my own larger Stevenson screen got some water inside, on the electronics, during a heavy rainfall. Although it’s hard to know for sure, I think the reason is splashing coming from the supporting concrete parapet under the screen, because I tested the top section afterwards and I found it still watertight. So it is best if the screen is mounted on top of a longish PVC tube or something, to avoid splashing during a rainfall. Also, some protection of the electronics, like a plastic bag, but not of the DHT22, would be useful.
Hopefully the Stevenson screen+Funky+DHT22 will be in service for a long-long time!
Cheers!
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what things are required to make stevenson screen?