Level Up In A Connected World Using 3D Printing

One of many extra­or­di­nary aspects of being alive in 2023 is access to resources. In this case, it was access both to a 3D print­er (a Prusa Mk3S+ I assem­bled from the kit) and find­ing design tal­ent to get max­i­mum val­ue of the print­er. Before we get there though, let’s start at the beginning.

Some­time in Decem­ber of 2022 I’d ordered a soil mois­ture sen­sor from Mak­er­Fabs, an out­fit out of Shen­zen Chi­na set up to pro­duce open source hardware.

I thought it’d be a fun project, I knew that many oth­ers had already done it, and that while there might be fid­dly bits, it was a well trod­den path. I was most­ly right, and helped by a bunch of tech savvy peo­ple in a chan­nel on the GK Dis­cord serv­er, I end­ed up writ­ing a post on how to get this LoRa sen­sor onto Heli­um’s LoRaWAN net­work.

The one thing that bugged me was the enclo­sure it came with. It had 2 areas for improvement. 

First, it did­n’t real­ly pro­tect from mois­ture get­ting in. The case is a 2‑piece design with a few vents in the side for airflow. 

Dirk (our GK engi­neer) had put a cou­ple of ’em in the ground a few weeks before me and was see­ing mois­ture inside of the case. The seams aren’t water­tight, and the vents don’t pro­tect at all from water com­ing in from the side. Now, the board and the parts on it are cov­ered (as I under­stand it) with a pro­tec­tive film, but the twin AA bat­ter­ies are open to the world.

Sec­ond, it is a roy­al pain in the ass to open and close. It ships with 2 x M2x8 bolts and nuts. The bolts are just bare­ly long enough to get through both sides of the case, and the way the case is set up makes it real­ly fid­dly to actu­al­ly thread the nut on. It’s not impos­si­ble, just an unnec­es­sary obsta­cle. I tried replac­ing the 8mm ver­sions with 12mm long bolts, and that was slight­ly eas­i­er, but still, not what I wanted.

Obvi­ous­ly once you’ve got the sen­sor up and run­ning you don’t real­ly care about open­ing up the case, but there was just some­thing about not hav­ing a well designed case that trig­gered the thought, “I can improve this.” So I did.

I start­ed by think­ing about what I want­ed: A case that I could open up eas­i­ly with min­i­mal tools, one that pro­tect­ed the bat­ter­ies from mois­ture while giv­ing the actu­al sen­sor (an AHT10) plen­ty of air­flow, and some­thing I could print at home on the Prusa. The mate­r­i­al had to be some­thing that could with­stand being out­side and exposed to the ele­ments, so I set­tled on ASA fil­a­ment. ASA is a UV-resis­tant form of ABS, a durable plastic. 

I thought a mush­room shape would work well, so I sat down and sketched out a first draft.

As you’ll see, this isn’t what we end­ed up with, but it’s close. The les­son here is to start. Your idea does­n’t have to be per­fect, you’ve just got to get it out of your head and into some medi­um you can share.

Now, while I have a 3D print­er, I am not by a long shot a 3D design­er. Here’s where the rad part of being alive in 2023 comes in: Design­ers (and experts of all types) are get­ting eas­i­er and eas­i­er to find. I turned to Upwork to find mine. I wrote up a cre­ative brief of what I want­ed, added in a few para­me­ters, and post­ed it.

I added in a few “sift­ing” ques­tions to help me sort through all the appli­ca­tions faster. I’ve found writ­ing your own ques­tions on Upwork is real­ly help­ful to quick­ly elim­i­nate can­di­dates who are unlike­ly to be a fit.

Then I sat back and watched a bunch of sub­mis­sions come in. Some of ’em read the brief and respond­ed cogent­ly, many were just copy/paste bull­shit, and one in par­tic­u­lar was from a fel­low named George Z. We mes­saged back and forth a few times, he sug­gest­ed we jump on a Zoom call (done through Upwork, which was pret­ty slick), and we talked about it for 15 min­utes. I decid­ed he was a rea­son­able bet, we agreed on a price per hour and he start­ed work.

I took some time to sil­hou­ette out the sen­sor and take a bunch of mea­sure­ments with my dig­i­tal calipers. I’d real­ly want­ed to buy a 3D scan­ner, but George let me know all we real­ly need­ed were pre­cise mea­sure­ments; that tem­pered my prof­li­gate tool buy­ing habits. 

With that sent over, it was time to let George do his thing. When I saw his first pro­posed design I was reas­sured I’d made the right choice and this would be a super fun con­trac­tor to work with. He did what an excel­lent design­er does, which is to take the clients idea and improve it in ways the client had­n’t thought to ask.

The soil sen­sor slides into a pro­tec­tive cov­er and is secured with one of the pro­vid­ed screws. The cap is screwed on with a quar­ter turn lock­ing mech­a­nism (the raised dome in the pic­ture on the right). Sim­ple, durable, plen­ty of air­flow, rea­son­ably easy access (still have a screw at the bot­tom to secure the board to the print­ed cover.

I print­ed up the first mod­els in PETG; the col­or I had on hand was pur­ple. PETG is cheap­er than ASA and eas­i­er to print with. It was super excit­ing to see the first print commence!

Now, noth­ing goes from zero to hero with just one step, and along the way we had a few mishaps; failed prints, fit­tings that were a bit too loose or tight, and minor mod­i­fi­ca­tions. It took us, oh, 8 print attempts (maybe a few more) to get to a spot we were both hap­py with. Some of those were my fault as a begin­ner 3D print­er, and some of those are a result of the nec­es­sary obsta­cles on the path to improvement.

The note­wor­thy mod­i­fi­ca­tions were shrink­ing the cap, mak­ing a small chan­nel at the bot­tom for the screw instead of hav­ing it be just a hole, mov­ing and slight­ly the shrink­ing the main air flow open­ing oppo­site the sen­sor, and clos­ing off the the cap top on the bat­tery side to pro­tect the bat­ter­ies as much as we could.

Work­ing with George on this end­ed up being real­ly engag­ing and fun as we went back and forth with ideas. When we end­ed up with a design we were both psy­ched with, I put in a final request for the Meteo Sci­en­tif­ic logo (MS is the sen­sor busi­ness arm of GK) to be added to the print, and we did our first run in white ASA.

If you’d like to see these devices actu­al­ly in use, I shared a video over on YouTube about how they’re get­ting deployed.

So, that’s it, from ini­tial prob­lem iden­ti­fi­ca­tion to solu­tion find­ing, incre­men­tal improve­ments, and a fin­ished prod­uct. The whole thing cost about $500 in design work from George, which seems super rea­son­able to me for the qual­i­ty and out­come we got. I’ve made the print file freely avail­able over on Print­a­bles, so if you’d like to print this out for your V3 sen­sor you’re wel­come to do so. 

All the print set­tings are con­tained in that file, so if you’ve got a Prusa or access to one it should be a straigh­for­ward job to have your own hous­ing up and run­ning in no time. If you’d like to hire George to do work for you, check him out on Upwork here (you’ll need an Upwork account).

Hope­ful­ly this inspires you to lean in a lit­tle to the next prob­lem you’re pre­sent­ed with and see if you can use the pow­er of our con­nect­ed world to solve your prob­lem and share that solu­tion with others. 

Rock on!

Nik @ Gris­tle King


One response to “Level Up In A Connected World Using 3D Printing”

  1. Mark Roberts Avatar
    Mark Roberts

    This is an awe­some pack­age for the soil mois­ture sen­sor. Print­ed like a dream import­ing the step file into Prusaslicer and using their gener­ic PETG profile.

    BTW, ref­er­enc­ing your oth­er arti­cles on using this sen­sor on Heli­um Con­sole and in Chirp­stack… the github point­ed to has a new order for the mea­sure­ments so the decoder in Chirp­stack needs to be reworked.


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