Weatherproofing Moteino's

[jarrods]

PlastiDip also works great and provides abrasion resistance.

Just remember that any time you are going to try to seal a PCB that you need to heat the board to at least 195 degrees for a minute or 2 and then let it cool to the max temp of the coating your using. If you do not then you will likely get corrosion from trapped water.

Also it is a good idea to clean the board with Acetone first (q-tip not a dunk) to make sure you don't have any flux or other gunk left on the board.

[WhiteHare]

FWIW, I did a bit more searching and found that Scotch makes a moisture sealant rubber mastic tape that self seals and is readily available (even my local Home Depot carries it):  http://www.amazon.com/3M-Scotch-Moisture-Sealing-Electrical/dp/B001B1AP3O  At least for one-offs, it looks to be a lot easier, cheaper, and faster than potting compounds.  Indeed, I'm hoping that for basic moisture proofing of a Moteino before slipping it inside something like an outdoor motion detector, it may be sufficient.  Anyone here have experience with it?

I tried out this material, and although I did find a use for it elsewhere, I don't think it's the best choice for this application.  Though doubtless it will perform better than regular electrical tape, it does retain some degree of surface stickiness that's kind of annoying.

[EdM]

I've been using heat shrink tubing to form little "bags" around my sensor assemblies, and then filling them with Loctite e-30cl.

https://edwardmallon.wordpress.com/2015/03/01/using-ds18b20-sensors-to-make-a-diy-thermistor-string-pt-1-the-build/

The process is a bit gooey, but once the ends are sealed off, applying more heat tightens up the tube forming a tension structure that makes the final shape very smooth. These have been standing up very well to long term underwater deployments.

(and these cheap dispenser guns work ok:
http://www.ebay.com/itm/221750881004?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT  )

[WhiteHare]

Very nice!  I'm guessing that part of the reason you selected Loctite e-30cl was for its low viscosity, so that it would fully encase the wiring without air bubble cavities?  Looks like it may cost around $11 per 1.69 fluid ounce double syringe.  Does that sound about right, or have you found a source that sells it for a lot less?

Great website you have, by the way.   

[EdM]

Sounds about right. I usually buy the epoxy from Zoro tools online, and I use clear large diameter poly heat shrink tubing so that I can see if bubbles are trapped before sealing the far end. Sometimes you have to knead the bubbles away from the wiring. E30-CL is a good viscosity for this, but after you (gently!) tighten up the outer sheath, the heat forces the e30 to cure much faster - often hardening within an hour where it would normally take more than a day to do so.

 I usually have lots of cables passing out of both ends but if you don't you could probably seal the ends with small zip ties (perhaps around a small diameter cork?)

Also these are the cheapest mixer nozzles I've found that work OK:
http://www.ebay.com/itm/300933122565?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
(don't buy shorter ones as they don't mix well enough)

Thanks on the site.  My philosophy is that if I can't find something with google, then it's probably worth adding to the blog.  But since I am just learning it as I go along, there's probably allot there to make someone who actually knows what they are doing, cringe.

[WhiteHare]

Closing the loop: I've tried out the liquid electrical tape, and I'm not a fan of it.  The biggest problem is that when applied, it can bridge voids, but as it dries it gets sucked down into those voids and often leaves openings when it does so.  That necessitates another pass to correct, and sometimes those passes need yet another pass to finally correct.  That, in combination with a long dry time (typically overnight), tallies to a rather lengthy process, unless maybe what you're sealing is a perfectly flat, smooth surface.   About the only positive feature, should you ever need it, is that the rubbery surface that it becomes when it dries is, in some sense, removable without residual presence if you peel it off.

[WhiteHare]

PC Clear epoxy may be a winner:
+ It's relatively cheap ($3.51 for one ounce, including Amazon Prime delivery: http://www.amazon.com/PC-Products-PC-Clear-Adhesive-Syringe/dp/B008DZ19WC/ref=sr_1_1?ie=UTF8&qid=1456094399&sr=8-1&keywords=pc+clear#customerReviews ). 
+ The packaging says not only is it waterproof, it's "impermeable".
+ The packaging says it doesn't shrink
+ The PC Products website says it's non-conductive
+ It claims that it's clear not only in liquid form before curing, but also after it has cured
+ The PC Products website says its nontoxic after curing.
+ It has a 4 minute pot life.
+ It is cured enough within 1 hour that it can be put into service.
+ It comes in a 2-part syringe for easy dispensing. 

[Edit: I've ordered one to kick the tires.  Meanwhile, the liquid electrical tape that I previously applied (above) to a solar garden light's electronics has performed extremely well.  After about a month outdoors, I'm not seeing any of the performance degradation that I had witnessed in the same electronics on a prior occasion when they were unprotected for a month outdoors.  It's still performing "good as new," so to speak.      I'm hoping that the epoxy will perform just as well, but after just one application instead of the multi-pass application I had to do with the liquid electrical tape. ]

[Felix]

WhiteHare, nice, thanks for the update and for your experiments they are surely valuable to those looking to put their nodes outdoors or in the ground/water etc.

[WhiteHare]

You're welcome.   

I tried the PC Clear, and I think it would be a good choice for weatherproof potting of a Moteino that's in a container.  For just coating electronics, though, rather than potting them, it's a bit too runny.  It's viscosity is similar to honey.  Also, mixing it in a cup and then pouring it wastes a lot: it's difficult to get it fast enough to where you want it within the time allowed, and a lot sticks to the mixing cup and never leaves it.

So, for those reasons, I'm next going to try their more viscous epoxy, called "SuperEpoxy," which costs about the same and has a longer pot life (15 minutes), but which unfortunately is only  translucent  rather than clear.

Either way, I can already see how gunning it through a mixing nozzle would be preferable: thorough mixing, and you can more easily apply it right where you want it.

By the way, I am curious as to whether hot glue can be used to good effect, as it is definitely cheap.  The most common kind is thermoplastic and waterproof, but I've also read that it can chemically react with the plasticizer used in wire  insulation, causing the waterproofing to fail.  That said, there are different kinds of hot glue, and maybe not all of them are like that.

[Felix]

WhiteHare,
I don't think I mentioned this before, but I like your inquisitive nature and attention to detail, even for such simple things as glue and epoxy. It makes for some really deep and meaty discussions that are sure to be welcome for those that are tech savvy.

Regarding hot glue ... i just tried that on a connector yesterday. I wanted it to be clear so I can see the internal wires colors. While that was mostly achieved, it was a pretty mess in the end and although I didn't do it for weather proofing purposes, I can't help but not want to have to do that again. I'm not that skilled with the hot glue gun and I just created a mess of spider web like hot-glue threads all over my bench and hands and clothes. Messy but... it could have it's niche app for weatherproofing.

[WhiteHare]

The "super epoxy" worked well in the sense that it stayed exactly where I put it.  At the thickness I was applying it, however, it was much more opaque than translucent.

I also tried the hot glue, and I have to say I like it a lot.  Like the "super epoxy," it stays where I put it.  Dispensing is precise, because it comes out of a hot glue gun, which can be had for $1.  It also rapidly sets and can be put in service within minutes.  Plus, the glue sticks are very cheap (an order of magnitude lower cost than an equivalent volume of epoxy).   Plus, non-toxic, and no mixing issues.  So, I did some test units and put them outside to see how well the encapsulated electronics will weather.  I used some cheap solar lights that I know are prone to rapid corrosion as the test units, so it should flag a moisture penetration problem if one exists.  It will be easy to monitor, because the light won't come on at night or will dim if it fails.  Therefore, how well it performs remains to be seen, but I suspect it will be good enough for above ground, especially if used inside the shell of another container.  Well, time will tell....  I may look into polyurethane hot glue sticks, because those should be thoroughly waterproof if it turns out the cheap glue sticks just aren't good enough.

Yeah, there is spider webbing from the glue sticks, but I found it to be only a minor nuisance.  Also on the negative side, at the thickness I'm using it, it's much more opaque than translucent.  Furthermore, because of possible shrinkage, I don't think I would trust it for an underground (earth contact) installation.  For that, I think I would go with what EdM is using, since it seems that he has proven that particular epoxy really works well even when continually submerged in water.  The PC Clear might work, but its in-use performance is more of an unknown (at least to me), and it might take years for a bad choice to reveal itself as such.

Anyhow, I'm still open to alternate ideas, and I hope others will share whatever they have found works well for them.

[WhiteHare]

I'm  noticing that encapsulating lithium batteries may be unwise.  That's because many (all?) lithium batteries include venting as one of the safety mechanisms.  However, until now I didn't realize it's true also for primary cells like Energier Ultimate Lithium Batteries.  According to its safety sheet: "Mechanical Containment: If potting or sealing the battery in an airtight or watertight container is required, consult your Energizer Battery Manufacturing, Inc. representative for precautionary suggestions. Do not obstruct safety release vents on batteries. Encapsulation of batteries will not allow cell venting and can cause high pressure rupture."  http://data.energizer.com/PDFs/lithiumirondisulfide_psds.pdf

So, if potting is inadvisable, just how is it that you're supposed to use such batteries outdoors and still avoid their corrosion?  Up until now, I thought they were a great choice for outdoor use, because of their ability to function at freezing temperatures.

[executivul]

All my outdoor units until now have been in small boxes with gaskets, used for food storing, or at least normally found in food hypermarkets (kaufland, lidl).

Just use the smallest one able to hold what you need since large temperature variances make the air inside expand and contract quite a bit. I can find 10/5/3cm (4"/2"/1.5") in my country for a few pence.
Use a bit of silicone oil on the gasket if you want to be able to open it again or sanitary silicone for a lifetime seal.
The wire hole if one needs it is filled with sanitary silicone as hotglue has a tendency to loose adhesion after a while, and placed on the bottom if the unit is not fully submerged.

[MrGlasspoole]

Hm, the question was weatherproofing but it looks like it turned more into 20,000 Leagues Under the Sea 

I mean there are millions of commercial products for outside usage that are not sealed or maybe just a coat of plastic spray.
Maybe tapplastics.com or Smooth-On has something (Smooth-Cast 300).

What about CorrosionX? You can run motors under water:

There is this spray where they sprayed a 230v hair dryer and did take a shower with him - can't remember the name.

[perky]

Conformal coating might be the answer, but I wonder how the radio modules themselves behave when coated. Does it make the module non-compliant for FCC and CE marking? I think you can get conformal coating specifically for RF stuff though.
Mark.