Author Topic: Weatherproofing Moteino's  (Read 8513 times)

LazyGlen

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Weatherproofing Moteino's
« on: December 19, 2013, 09:45:44 AM »
A couple of my pending projects may require sealing up the Moteino. I've seen some suggestions for small enclosures including Felix using hardware store screw boxes and packing tape.

I have recently discovered Polycaprolactone, which is a "low" melting point, bio-degradable and re-useable plastic which is great fun to play with. Available on your neighborhood intertubes under a variety of names (Instamorph, Shapelock, Polymorph...). I think this would be perfect to 'pot' a Moteino with, for electrical insulation purposes, securing wires or weatherproofing. It becomes putty-like at around 60oC and can be formed by hand until it cools and hardens. It does sometimes stick to other surfaces (like a rolling pin if you are making a sheet), I have not tried it against IC's or PCB material yet to see if it sticks to that. I'm thinking that it might even be removable once you decide that you want your Moteino back. Drop the whole thing into a pan of hot water, wait a bit, and peel off the Polycaprolactone to access the Mote'. Perhaps putting a layer of plastic wrap (or a condom) on the Moteino first would make removal easier.

It may also be useful for making programming jigs a little less fragile.

I'm not yet ready to seal up any projects, but thought I would put this out there for anyone who is.

I will update when I get to this point in my project(s).

Felix

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Re: Weatherproofing Moteino's
« Reply #1 on: December 19, 2013, 02:22:25 PM »
Thanks!
Is it somewhat like sugru?

FWIW you can make something similar to sugru using silicone and starch: http://www.instructables.com/id/How-To-Make-Your-Own-Sugru-Substitute/

kolumkilli

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Re: Weatherproofing Moteino's
« Reply #2 on: December 19, 2013, 06:30:22 PM »
I have been using the Shapelock branded version for years, and I agree, it is pretty great.
It's not like a silicone-based product, when it hardens up it feels more like HDPE or Nylon 6,6.

I've even used it for Moteino enclosures as well!  But I've had limited success with certain applications, mostly for the following reasons:

1) when warm, it flows, so while you can shape it, unless you are using a mold, it continues to deform and you cannot get repeatable dimensions.

2) its flexibility changes with thickness as you are molding it, so you really have to adjust for thin parts cooling off faster than thicker parts.

3) it traps air in bubbles if you knead it and capture some air.  That in itself is not so bad, but if you heat it in water, it will also trap a lot of moisture in similar bubbles.  I would not want to put that next to electronic components (or not directly - if you seal things in plastic first, that may work just fine).

4) because of the above, I do not use water to heat the substance.  It goes from a white color to a near-clear color when it crosses its glass transition temperature, but you do not get any further visual clue about the temperature until it begins to boil, and that occurs at a much much higher temperature.  Heating it in water creates a maximum temperature at 100C so at worst you get scalded, but not using water so as not to trap water is very dangerous.  It can get above 200C very easily, with no visual cue.  And when you grab it, it instantly adheres to your skin, and has a very high heat capacity as well, so burns you and continues to burn you and you cannot remove it except by sacrificing some other fingers.   Even if you have a handy source of cold water, all this will do is harden the outer shell, while the inner part that is adhered to you continues to burn you.

The "stickiness" of the substance seems to be parametric to temperature.  I mean that against ICs and PCBs, but also against glass, and stainless steel, and of course, human skin. 

As you might be able to surmise, #4 above happened to me.  It was because I lost track of the time elapsed while heating.   Stupid of me, I know.  It just got hotter and hotter, with no visual cue.  It was supposed to be just a bit warm... The result was not pretty.  I still don't use water to heat the substance, but now I always check it with a non-contact infrared thermometer, you can get for $10 or $15.  Even if you do use hot or boiling water, you will find that when it is uncomfortably hot but able to be handled, it will be much stickier than when closer to its transition temperature.  I recommend checking the temperature no matter what you are doing.

The stickiness does change after adhesion as well - so while it will stick to glass strongly when really hot, as soon as it cools it can be peeled right off.  That makes it less useful for things where you want to partially embed something in it, that doesn't have a mechanical shape that prevents slippage, especially if under load.

I'd be concerned about the polymer flowing around and under the components if applied directly, and then when/if you remove, it might cause sideways forces that exceed the trace to fiberglass adhesion force, tearing off the components.

Don't get me wrong, the stuff is great, and I have used it over and over for a lot of things where tight final dimensions are not critical.  And you can sand it down after, if you need to adjust more precisely.  I love the stuff.  But be careful!

Please post if you come up with an excellent technique!  I've clearly already disqualified myself...

LazyGlen

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Re: Weatherproofing Moteino's
« Reply #3 on: December 19, 2013, 11:21:01 PM »
Yeah, what he said!

Well part of it anyway.

It is hard, rather that soft and rubbery, they claim you can machine it, but I had a hard time getting clean cuts or drilled holes. I may have been trying to work it before it was fully cooled.

I don't see you making motionmote cases out of this stuff. Unless you are a highly skilled sculptor, it's going to look like a 2nd graders fathers day present.  I did get good results pressing it into a mold, and better results when it was closer to cool than hot.

I did notice that at relatively higher temperatures it stuck to other surfaces more. I used water to heat it, and found that some extra care and kneading was necessary to eliminate water and air bubbles.

I did not have the experience of super-heated stick to your hands ouchiness, and will attempt to ensure that it does not happen! My 13 year old daughter loves the stuff, so we use the water bath method.

Instamorph actually sells on their web site a pasta roller that they suggest for making sheets of uniform thickness. I used a rolling pin and bamboo skewers. The way I envision using it would be to roll out a sheet a little more than double the size of a Moteino, poking the antenna wire through and then folding the sheet over the Moteino, pinching the edges closed. (Then cursing when I realize that THIS was the one that I had programmed, the one in the Instamorph only has the node sketch loaded. How does wireless programming work?) Some method for supplying power would also need to pass through the plastic, either wires soldered in or a connector of some sort.

You can "weld" it together by heating it locally and applying pressure, or adding heated material to the joint.

So many things to try, so little time.
LazyGlen

WhiteHare

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Re: Weatherproofing Moteino's
« Reply #4 on: December 14, 2015, 06:30:26 PM »
Thanks for the posts.  I had never heard of ShapeLock or the other materials before.  Are they non-shrink?  i.e. as it cools, it's not gonna crush or warp whatever is inside it?

Before reading this thread, I was thinking of either using some kind of epoxy (which would probably be expensive?) to fully encapsulate outdoor electronics.  However, maybe plastidip would do the job?  It's not terribly expensive, considering you'd only need a skin of it over whatever it is that you want to encapsulate.

Another idea I've read about is to use a PVC pipe and glueweld PVC caps onto both ends, resulting in what should be a sealed, waterproof enclosure.

What else have folks here tried?
« Last Edit: December 15, 2015, 01:07:12 PM by WhiteHare »

Felix

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Re: Weatherproofing Moteino's
« Reply #5 on: December 15, 2015, 12:36:38 PM »
I've used Spraon Clear Electrical Lacquer Sealer EL2000
It's specifically for sealing electronic circuits from moisture and dust. Several coats need to be applied depending how sealed the product has to be.

WhiteHare

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Re: Weatherproofing Moteino's
« Reply #6 on: December 15, 2015, 02:41:53 PM »
Good suggestion!

I just ordered some liquid electrical tape (for some reason, bright green was markedly cheaper: http://www.amazon.com/gp/product/B005FB1VX4?psc=1&redirect=true&ref_=ox_sc_act_image_1&smid=ATVPDKIKX0DER).  The marketing materials describe it as waterproof. 

However, as proven by tyvek, waterproof does not equal vaporproof, and the tech sheet says it does have some small permeability.  I don't know how small is small enough (i.e. what would be a good spec?), so I'm going to do a crude test by applying this green stuff over the electronics inside the enclosures of some cheap solar LED garden lights that my wife recently purchased and which have been rapidly dying one by one from corrosion after just a couple months.  If it manages to halt that debacle in its tracks, then for above-ground use maybe it's good enough, at least where I live.

Epoxy potting material for electronics is probably pretty good, but there's a bewildering array of them, and it's not immediately obvious which ones would be the best choice or the best value for money. For instance, Amazon sells some by 3M, but it costs $17 for a mere 1.7 fluid ounces (http://www.amazon.com/3M-Scotch-Weld-Epoxy-Potting-Compound/dp/B000X5G6O6/ref=sr_1_1?ie=UTF8&qid=1450205932&sr=8-1&keywords=potting+compound).  On the one hand, it seems like a lot for a little, but on the other hand, if it completely protects  a couple  $30 Moteino's  located outdoors from death by corrosion, maybe i't's a smart purchase.  I don't know what the answer is, so anyone and everyone feel free to share your thoughts and ideas.
« Last Edit: December 15, 2015, 02:45:06 PM by WhiteHare »

TomWS

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Re: Weatherproofing Moteino's
« Reply #7 on: December 15, 2015, 03:08:15 PM »
I've used Epifanes Spar Varnish (it works well on bright work  ;)  but I don't have enough 'mileage' on my test to draw any conclusions.  Give me another 5 years and I'll let you know.  :)

Tom
Update: Corrected spelling of Epifanes.
« Last Edit: December 15, 2015, 06:29:54 PM by TomWS »

joelucid

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Re: Weatherproofing Moteino's
« Reply #8 on: December 15, 2015, 03:55:00 PM »
I built a lake thermometer this spring and potted the electronics in epoxy. Worked well so far / but it's only been one season.




Joe

syrinxtech

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Re: Weatherproofing Moteino's
« Reply #9 on: December 15, 2015, 04:21:06 PM »
That's awesome joe.....you could even add a flag to the lid like the divers use so you wouldn't run over it with a boat.


WhiteHare

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Re: Weatherproofing Moteino's
« Reply #10 on: December 16, 2015, 12:46:55 PM »
I built a lake thermometer this spring and potted the electronics in epoxy. Worked well so far / but it's only been one season.


Joe

@joelucid What type of epoxy?

P.S.  Nice photos by the way!  Thank you for posting them.
« Last Edit: December 16, 2015, 12:55:10 PM by WhiteHare »

jra

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Re: Weatherproofing Moteino's
« Reply #11 on: December 16, 2015, 01:41:28 PM »
@joelucid like Tom said you might want to apply a coat of spar varnish over the epoxy, especially if it is going to sit in the sun all season.  Epoxy degrades under UV, see http://www.oneoceankayaks.com/Epoxtest.htm for a non-scientific test.  I suspect it won't make a real difference for your application as it looks like your epoxy layer is way thicker than anything I have ever applied to a kayak.

joelucid

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Re: Weatherproofing Moteino's
« Reply #12 on: December 16, 2015, 02:24:27 PM »
It's just so pretty, right?  :) :) :)

Made from my youngest daughter's lunch box ... A man changes when living with 3 girls over extended periods of time.

syrinxtech

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Re: Weatherproofing Moteino's
« Reply #13 on: December 16, 2015, 02:45:00 PM »
You're preaching to the choir joe....I have 5 sisters.

WhiteHare

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Re: Weatherproofing Moteino's
« Reply #14 on: December 17, 2015, 12:05:05 AM »
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?


« Last Edit: December 17, 2015, 12:24:43 AM by WhiteHare »