The first step in constructing an autonomous buoy is to design a suitable-rugged enclosure for the electronics. This enclosure should be easily replicated by anyone anywhere at a low cost point. Here are three possibilities:
A 500ml Coke bottle cut in half to add the electronics. The bottle would then be resealed with 3D-printed brackets and some silicone. This would enable anyone to construct the enclosure with access to a 3D-printer and a bottle of coke. Below is a photo of the attempt. It was found that sealing the 3D-printed parts to the bottle proved difficult and did not prove to be rugged enough.
A plastic honey-jar available from a nearby factory. These jars come in very cheap and are already equipped with a screw-able lid. However, these jars may not be available as a standard across the world and was immediately discarded.
Image from http://www.plic.co.za/
The final design which has been chosen for the project is a PVC pipe sealed ends. PVC is available everywhere in standard sizes and Perspex can easily be obtained. In this design a PVC pipe is sandwiched between Perspex using 4 threaded rods. This enclosure proved to be extremely rugged and 100 percent waterproof.
This was simply a waterproof test model. The final model would have rounded Perspex ends which will be manufactured on a CNC machine. The only problem with this design is the effort needed to open the container by unscrewing 4 bolts. This will affect the design of the electronics. Wireless charging and over the air programming will need to be implemented to make the design practical.
The bill of materials is as follows:
4 x Threaded rods (M6 Length: 230mm)
1 x PVC pipe (Diameter: 50mm Thickness: 2.5mm Length: 200mm)
2 x Rubber washers
2 x Perspex ends
12 x nuts and washers (M6)
Silicon sealant to seal washers to PVC