As part of this project, I inquired into the wolrd of sensor enclosures, and I cite Debashis (OpenGreenEnergy) here: «The ideal enclosure for keeping the weather sensors is the Stevenson Screen. A Stevenson screen is an enclosure for weather sensors against rain and direct heat radiation from outside sources, while still allowing air to circulate freely around them.»

Upon searching through the web, I found several designs of such enclosures, however, all seemed to be excessively bulky and costly to print, as well as quite tricky to assemble or modify reliably. Thus, I decided to develop my own version of such enclosure, with the aim of making it highly modular, easy to assemble or modify, and most importantly, resource-efficient.

I mainly based my design on the aesthetics of Glen’s enclosure, but about half the size in al dimensions, which translates roughly to 1/8th the volume of plastic, or even less, as I made the wall thickness of the flanges effectively as thin as possible while remaining strong and durable (around 1.5mm). I found that even the hollow level modules are surprisingly stiff and rigid mostly due to ther geometry. The 3D modelling was done in SolidWorks and all pieces are optimized to print cleanly without support material.

On my first implementation, I created several stackable hollow modules, plus a slated top module, which all press fitted together and, of course, I couldn’t resist adding a small solar panel atop the enclosure and set the whole thing outside. The inside mounting board features spring loaded locks to hold it in place and is just the right size to fit a breadboard with a bit of air surrounding it.

All the pieces MUST be printed in PETG filament, as PLA will inevitably soften and deform under the sun, plus it is much less resistant. For printing PETG I have found it is essential to print with a 0.6mm nozzle (or wider), in order to both prevent clogging and significantly reduce print time. The settings for all pieces must be 2 perimeters, 0.2 — 0.3mm layers and 4 top and bottom solid layers. This will effectively make all pieces fully solid, as they are designed to work as an active surface structue.

This first version however, had several flaws, begining with the flimsyness of the assembly, but mainly around the whole thing getting excessively warm in the sun and therefore not being very useful as a reference for the greenhouse. So for the second iteration I decided to make a more sturdy and adaptable enclosure, and implement the whole station inside the greenhouse with an external panel. Also, the whole assembly system had to be replaced with some sort of threaded fastener system, hopefully all 3D printable. So for the second version I set out to fix all these issues.

The CAD file for the original enclosure is available on this step in case you are interested in viewing them.

Leave a Reply