I'm working on an ROV project as a senior design project and am nearing completion of it. The current plan house all of the electronics (arduino, motor drivers, telemetry) in a polycarbonate box filled with tech grade mineral oil. The mineral oil does two things for us: (1) equalizes ambient (external) and internal pressures
(2) protects electronics from humidity/moisture. By equalizing pressures we can easily keep water out.
Anyone see any issues with submerging electronics of this nature in mineral oil? Max depth the ROV will achiever is 30' so capacitors should be fine as far as pressures go.
I can't comment, except to say this might not be the best place to ask. Someone here might have experience, sure, but you might never get a definitive answer. My advice would be to track down some of the specialist oil manufacturers- like (eg) the guys who make transformer oil maybe- and ask them. You may find they have a product exactly spec'd for what you want to do.
Alternatively, how about potting the whole thing?... of course that's a rather permanent way of doing things and makes upgrading parts impossible.
The oil will work without problems.
If complete PCs can be placed in it, the Arduino can be placed in it for sure.
How much is 30' in meters ? It that 30 inch (=76 cm) or 30 feet (= 9 meters) or 30 yard (= 27 meters) ?
The X-tals contain air. But 1 or 2 meters should be no problem.
The newer Arduino boards use mini X-tals. They should be able to withstand more pressure.
Going up very fast will put mechanical stress on the larger capacitors. I have no idea what that will do in the long term.
9 meter water pressure = 1 bar = 15 psi
That is something to be noted. It might damage some components.
The capacitors are completely filled (with no air inside), so perhaps they are not a problem after all.