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I have an idea for an automated small toyish submarine. Can I use the Arduino for this? Does it behave well under the ocean surface? I think I'll need some kind of casing with silicone around it, and a small propeller that will push it forward. What's the best suited Arduino for this project? It will need to be remote controlled.

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    \$\begingroup\$ If the casing you select is rigid and air-tight, then pressure upon the Arduino would not be an issue, right? \$\endgroup\$ – JohnB Apr 10 '13 at 7:45
  • \$\begingroup\$ There you go, i did not think of that. Maybe there are other things to watch out when building underwater arduino-powered machines? \$\endgroup\$ – bogen Apr 10 '13 at 7:55
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    \$\begingroup\$ @John Unless specially constructed for extreme pressures, even a rigid and air-tight enclosure would suffer increased atmospheric pressure inside - this is why diving bells for instance are constructed with specific designs, including a double hull for greater depths. Pressure-sealed enclosures are not trivial to make. \$\endgroup\$ – Anindo Ghosh Apr 10 '13 at 8:07
  • \$\begingroup\$ Question related to: How to water-protect my Arduino? \$\endgroup\$ – Tomáš Zato - Reinstate Monica Apr 10 '13 at 13:54
  • \$\begingroup\$ Yep, I've had my arduino dataloggers under water for almost a year now: edwardmallon.wordpress.com While I have not released the full build plans for the housing yet (coming in 2015), it's not hard to see how it goes together. Really just a bunch of plumbing parts from the hardware store, much like the DIY rov crowd are using. \$\endgroup\$ – Ed Mallon Jan 5 '15 at 20:15
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There is at least one project in progress to create a dive computer using an Arduino. What the question describes is considerably less ambitious.

Hence, yes, it is feasible to use a suitably enclosed Arduino for such a toy submarine.

The challenges will be:

  • Watertight casing, yet which can be opened when needed: Silicone caulking will probably not survive under pressure and with salt water. Silicone gaskets on a torque-bolted enclosure will work though.
  • Interaction without having to open the case every time: If inputs are needed at all, innovative approaches such as hall switches need to be considered. See this answer for ideas.
  • Access ports: If programming or power connections need to reach the Arduino without taking it out of the case, pressure- and water-sealed cable ports will be needed in the enclosure. This is best avoided if at all possible.
    • Consider wireless programming such as through a ZigBee shield, to reduce the number of times the enclosure needs to be opened, and the number of access ports needed.
    • Charging batteries will be an issue, wireless charging is still in its infancy - this may require opening the enclosure anyway.
  • Pressure: Depending on the depths being considered, the pressure the enclosure can stand will become a concern. For "toy submarine" depths, this should be a non-issue.
  • Humidity and salt: No matter how carefully the system is designed, oxide formation and leakage currents due to humidity + saline deposition will be an issue at some point.
    • To add one additional level of protection, consider DIY or professional conformal coating on the Arduino, just in case the enclosure some day springs a leak or suffers condensation internally.
    • Also consider using a Ruggeduino or similar ruggedized board, for just that extra bit of survivability.

Many Arduino enthusiasts would be very keen to know how this project progresses, so do keep us posted.

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    \$\begingroup\$ Thanks for this great answer! It's a perfect model on how to write a good answer in the beta phase of the Arduino SE. \$\endgroup\$ – bogen Apr 10 '13 at 8:01
  • \$\begingroup\$ Depending on the size of the vessel you might want to consider an active bilge system as well, with a void bilge area underneath the vessel's sensitive components, a pump and a water detector. But if there's enough head for pumping, it can be difficult keeping the vessel in trim given the possibility of sloshing, so something like a sump would be in order, and you'd need a pump strong enough to counteract the static head. You can't use baffles because you'd get unpredictable trim. Only really an issue for a larger vessel. But this isn't really electronics at this point. :-) \$\endgroup\$ – Dan Sheppard Jan 5 '15 at 20:24

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