Waterproofing floating arduino

Projects General Guidance
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I will have a tiny IMU, which is 0.75in by 0.30in, floating at sea to measure the waves. I, therefore, need to waterproof it and need it to be as light as possible. The IMU will be connected to a logger that resides in a waterproof box.

I was thinking of putting the IMU in a freezer bag cut to fit the board, sealing the bag by melting the plastic around it, and then maybe using some silicone to seal the opening made for the cable going from the IMU to the logger.

Do you have any comments on this idea, or maybe another suggestion of how I can waterproof the board and keep it as light as possible?

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Pot it in expanding foam?

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Freezer bags might be semi permeable ( Osmosis and all that ) .

You need to buy a IZpx7 type enclosure , anything home made is bound to leak in the sea .

Getting wires in and out is also a difficulty .

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How often do you need to access it? A piece of 1-1.5" pvc pipe with an endcap on one end and a threaded plug with sealant tape on the other would work. The downside is that it is somewhat difficult to access.

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5

Fill the waterproof box with food-safe oil.

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You could also use a survival capsule like this for example. And paulpaulson's idea of filling it with food safe oil is a good idea. Dielectric grease or petroleum jelly are good options too.

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Thank you! I will try out both and see what works best.

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If you use an aluminum capsule, make sure you don't have any pins touching the aluminum, even if it is anodized.

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I don't know the best solution but I do know that polyethylene is permeable to water vapour, so no good to use in the way you suggest.

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Sorry, I was a bit brief. I think I'll try out the pipe solution you suggested, as well as lining the inside of the pipe or bag with food-safe oil, as paulpaulson mentioned. The aluminium capsule might be a bit heavy for my project.

12

Don't forget about UV. Many materials will slowly deteriorate when exposed to UV

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13

Your biggest hurdle would be condensation.

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Why light as possible? Anything in the water that will float will follow the waves! If you do not have it weighted so it maintains an upright position at all times, you will NOT get the up-down motion of the wave, but a rolling action plus the up-down.

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If possible, I always used two layer of protection.

I used many enclosures in wet conditions and even those specified as IP68 would let moisture in over time. Sometimes expansion and contraction would be enough to let moisture in. Some industrial enclosures have valves fitted to overcome that.

It's attention to detail. Every bit, cable glands, screws etc. all have to be right.

I would add a desiccant, silica gel, as well and if it's a two piece enclosure, tape the joint as well. A waterproof gaffer tape or aluminium tapes work well.

As others have suggested, look elsewhere for items like plastic waste pipe and fittings. You can get soil pipe up to 150-mm with endcaps as well. Take care with gluing. I have used gas grade PTFE plumbing tape on it's own to successfully seal pipes with the advantage you can take them apart. Certainly good for full immersion.

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Have you considered potting epoxy?

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From the minute you pot it, you find you need to change something.... .that is my experience.

I would suggest a piece of PVC pipe, sealed at one end and with a screw lid with gasket at the other.

I did this for a Nano running an ultrasonic sensor on my pond and it lasted years.
I mounted the electronics on a frame in the middle of the tube, and then I covered it all in a thin film of Dielectric Grease. You could use Vaseline, but it's not quite as good.

I also had a small drain hole at the bottom of the tube for any condensation to escape, but you won't be doing that.
Maybe some silica packs, but they will quickly become saturated.

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