Mini Parasite

[chucknorris101]

My use case for bparasites is to have them buried in the soil - given the size of most pots around the house, this necessitates a smaller form factor, and eliminates need for photo sensing.

After modifying the gerbers and having them made up, Ive finally been able to test them and confirm they work. Right now it seems sensitive enough with the smaller loop to still work well

See size comparison

The request/my repo has two new folders for the mini gerber and csvs for use.

Calibration i found worked best with air and wet potting soil - I have worked with dry potting soil as a baseline but the %'s get thrown off - i also have some calibration references for cactus mix if people are interested - the cal equations modified in adc.h for potting soil are: const double dry = 59.66 x + 331; const double wet = 34.44 x + 173;

these are in mini-adc.c, would just rename the file or put these equations in adc.c for the mini config

My waterproofing process is dipped oil poly over the capacitance area, with adhesive heatshrink over the electronic bits. Dont love the heatshrink as modifying in the future makes it difficult to remove, so open to ideas there

[rbaron]

@chucknorris101 that looks adorable! Thanks for the PR. I'm specially looking forward to see the long term results of the coating you did. Which brand/type of oil poly did you use?

As for the PR, I suggest we keep such variants in their own working, consistent branches. Otherwise if we keep working on the software and hardware of the main variant, it will stop working. I took the liberty of changing the base branch to 1.2.0-mini.

I would also like to ask you to:

• Also include the .pcbnew file, otherwise we have no way to iterate on the design/regenerate the gerbers
• Substitute the gerbers in place (so users don't see two sets of gerbers, which may be confusing)
• Update the adc.c in place (I don't think the code will build as is in this PR)

In general with this branch-variant approach, you can substitute all the files you need or modify them in place. I think it's less confusing and more future-proof.

[chucknorris101]

Thanks! That makes sense, and ill get on the updates you suggest tonight.

Yea - in my setup i have different adc's and just rename them and re-make as needed depending on my use case for the specific parasite (i have different calibrations for the large, cactus, etc), but for this purpose ill make just one adc for consistency now that it has its own branch.

As far as poly, this may get a bit lengthy, i feel like ive posted my trials before but not sure....

Ill post all below but the TLDR is Varathane Oil Based Poly, just one dip up to the bottom battery terminal and then hang. The critical item is cure time. The coating is dry/handleable within a few hours, but it actually isn't waterproof for ~30 days similar to latex paint or other coatings.

I had several options laying around and attempted oil poly, water poly, liquid rubber (flexseal), and a 'triple thick' oil poly.

The water poly (dip) was a complete disaster - likely as i didnt allow full cure as mentioned above, with water being the method of dispersion of the coating, it immediately became a water sponge :). Could work if allowed to cure properly/lengthily

The Liquid Rubber, if optimizing for durability and timeline to use - flawless! Drawback, much lower sensitivity due to thickness of coating - though a better 'process' than dipping (maybe the spray they sell?) could lead to better results for long term stability than any poly. the durability might have been due to the default thickness, but may be worth investigating.

Triple thick oil poly was about equivalent to the oil referenced above in the TLDR.

In all oil poly cases i continued to have some ingress or increasing moisture with coatings until the coating was 'cured' then it levelled off.

The liquid rubber i may come back to for replacement of the heatshrink im using over the battery area. I think it will have enough durability without the PITA of removing thick heatshrink for battery replace or reprogram, depending. Either needing to recalibrate the sensor for the thickness or may just oil the sensor and rubber the circuitry

[rbaron]

Hey @chucknorris101, we've had a couple of PRs with different/specialized hardware, and I'm leaning towards keeping them in separate repos. Otherwise maintenance quickly gets tricky. I hope that's okay. Thanks!