Waterproofing can be subdivided into many different grades according to the international protection rating system. The second digit of a code (ex: the 8 in IP Rating IP68) lets you know a device, connector, housing, button, etc's water resistance. These range from dripping water directly onto the device from overhead to taking it deep under the sea for prolonged periods of time.
One way to waterproof something is to put in an an o-ring sealed housing. The material and its thickness that you use for the housing will determine the depth rating assuming a proper matching o-ring design. With an o-ring seal the o-ring and all mating surfaces must be very clean because a grain of sand could cause your seal to fail. The groove that the o-ring sits in also needs an "o-ring grade" very smooth surface finish or it won't seal properly.
A second alternative is to use a
gasket sealed housing as is found in many waterproof consumer digital cameras. The benefit of this technique is that gaskets are relatively easy to manufacture yourself because you can cut them on a laser or mold them.
Important: before lasering any rubber to make a gasket look at the chemical composition and avoid anything with flourine, chlorine, or other corrisive and toxic chemicals. The picture below shows a
laser cut silicone rubber gasket for an antenna connector on a weather resistant relay station for an acoustic positioning system. After lasering the silicone rubber you will see a thin layer of crispy material around all of the cuts. This material will rub off and yield a nice clean surface.
A third alternative is to "dip" the circuit board and all exposed electronics of the item you would like to make weather resistant in waterproofing epoxy to give it a conformal coating. There are materials that you can spray on as well that will give the same thin water resistant coating.
A fourth alternative is to make an epoxy
mold or find some kind of plastic tube/box, place your item in the box/mold, and fill it with a marine grade epoxy(
potting). Alternatively, if you want a hard clear plastic outer shell (so you can protect your solar panels), you can machine something out of
polycarbonate. With this kind of technique it is important to minimize the amount of bubbles by degassing the epoxy in a vacuum. If your item isn't going to be subjected to high pressures (such as at 2,000m deep), then the bubbles don't matter as much and they'll just be a cosmetic issue. The image below shows this technique used to fill a polycarbonate shell for a solar powered remote releasable instrument carrier for marine mammal research. The nice thing about using polycarbonate is that although the machined part may not have a clear surface the epoxy will fill the imperfections in it and make it optically clear so you don't have to buff the surface or get a perfect finish before filling it with epoxy. Ideally the surface should be rough with lots of imperfections so that the epoxy will bond better.
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