Have you stress-tested your Tupperware, Greg? (I ask because I had a box develop a crack down one side this week – possibly because of repeated trips to and from the freezer.)

I’m excited to see the progress of this but am concerned with the Tupperware as well. Have you considered using a Pelican case? They’re waterproof with built in pressure valves, and they take a huge beating – I love the one I use for my eReader. Pelican can also make custom cases for projects such as this – just a suggestion – http://www.pelicancases.com/micro-cases-s/12.htm

Tupperware is indeed a good point, I am also curious or I must have missed it about the flip over capabilities. What if the boat lands up side down (big waves and such)

This looks great.

No idea on the electronics and stuff, but looking at the shape of the boat it might be worthwhile sticking a big heavy weight at the bottom for ballast. Unless I’m wrong spreading the batteries around will make it less stable and more prone to tipping over
Effectively, give it a Keel – http://en.wikipedia.org/wiki/Keel

I guess you’ll want some kind of battery voltage monitor, to give you a chance to cleanly shut down the RPi when you’re running low on power? The last thing you want is an unexpected shutdown causing a corrupted SDcard in the middle of the ocean! :)
And then (somehow) turn on the RPi again once the batteries have recharged enough to a specific level.

be careful the sea is dangerous ;)
http://www.youtube.com/watch?v=vb11rZgfihc

What about tracking and telemetry? Add a GPS receiver and a satelite uplink to the FunCube or other suitable spacecraft for relay to ground tracking stations?

NottingHack! Awesome it’s been ages since I’ve gotten along to one of those and now seems like the perfect excuse :)

Tupperware is NOT UV stabilized. Also consider using desiccant packs and\or vapor phase corrosion inhibitors inside to mitigate any moisture issues. Additionally, In a salt water water environment 316 or 316L stainless steel is the only way to go.

Will you be recording anything?

Photographic evidence, GPS location, humidity, temperature, amount of sunlight, amount of rain? It’d spend a long time on see, a long time to log interesting data no matter where it ends up!

Curious why you’ve chosen a brushed motor when the brushless ones available these days are generally so much more efficient? I would have thought you’d want to harness every ounce of power you can. Also – will you be swapping out the linear regulators on the Pi for switching ones? That should halve the Pi’s comsumption.

I recommend an onboard Taser as a Kraken repellent. If that seems too extreme, as a “warning shot” an arm could pop up holding a jar of cocktail sauce to warn him of his impending fate should he get too close.

Otherwise, this seems like a way cool project! Looking forward to updates as it progresses :-)

Amazing work. However, please consider Loch Ness for your pocv or prototype. Let’s be realistic and scientific here; there is no kraken, but you might find Nessie!

I know what’s really going on here…hacking from international waters!!

Pretty awesome idea but it needs a better design–maybe a buoyant torpedo shape or something. The standard boat-like shape will be capsized within a few hours or days at most. The torpedo will just keep going no matter what.

Next will be Pi in the Sky, a robotic aircraft!

I’d avoid an ESC altogether and use a relay – ESC’s use power themselves and I would imagine basic on/off control of the motor will be sufficient – the only thing and ESC brings to the table is the ability to have variable speed.

This will reduce your costs and also remove a fail point – ESCs can over heat easily and die at the hint of moisture….

If it were me I’d use a brushless motor (they can e had for pennies off ebay) and a basic brushless driver circuit – just for on and off again.

The thing is, with a brushed motor, you run a very real chance of the brushes wearing out mid-voyage. in fact, it’s a certainty if you plan to have the boat out for any real length of time.

Good luck. I did something like this in 1990 for my engineering degree (z80 compatible, programmed in Modula-2/assembler) but mine was controlled from a computer ashore (steer 270, speed 3). And GPS and solar panels didn’t exist – but it had a flux-gate compass and so knew which way to go and it could tell me where it was pointing, the temperature and battery voltage. Best bit was making a kitchen rudder for it (waterproof tube, inside a tube, inside a tube stuck to the fibreglass hull).

I think the interesting bit for you is to make sure that you have some way of making it leak water quicker than it gets in the hull and before it destroys the batteries!

Except for the publicity it gives the Pi, I cannot understand why a DuinoMite-Mini would not be used as this little computer in this project, as it is built for industrial applications, uses less power, and thus would have a better chance of finishing the trip. I only encountered the DuinoMite computers when looking for information on the Pi, received several the day after ordering, and had a project up and running in about 3 hours from first opening the box.

Interesting news article, this is radio controlled, but could be a pi robot.

http://news.bbc.co.uk/1/hi/programmes/click_online/9728920.stm

One thing definitely worth looking at is using a design that avoids the need for any moving hull penetrations like a properllor shaft.
Right now, there will be a small-but-steady leakage up the propellor shaft. While it won’t matter on a lake because it’s not going to spend more than a few days in the water, the real thing is probably going to spend many weeks on the Atlantic.
For example, a catamaran design with the motor between the hulls – the challenge there is to make it self-righting, but that’s not insurmountable.
– It’s much easier to make a completely watertight enclosure than to try to bail out a ‘nearly’ watertight one, and you’ll never make a completely watertight enclosure if it’s got any moving parts going through the hull.

One interesting possibility is a “wet” brushless motor – brushless motors don’t need any connections to the rotor, so you can build one with the rotor “in” the water but the rest of the motor completely watertight – for example, by flooding the coils with a suitable sealant.
The bearings would be “wet”, which is a challenge (limits the choice of materials) but still easier than trying to seal a propellor shaft.

Anyone interested in putting a Pi in an autonomous boat might also be interested in competing in the Microtransat Challenge (http://www.microtransat.org). This is a transatlantic race between autonomous sailing (wind powered) robots. We are having a series of little races between these boats in Cardiff in September, if anyone is interested have a look at http://www.microtransat.org/wrsc2012. Most of the current boats use Linux based computers of one form or another or Arduino’s, so I see no reason why a Raspberry Pi wouldn’t make a good controller.

Might I suggest that the Fish Pi folks contact Roz Savage, the british woman who has rowed across the atlantic and pacific ocean on how to protect and insulate the electronics since she has probably among the most experience in this kind of thing.
I followed her exploits on Twit.tv over the years and salt and corrossion are very, very big problems in these endeavours.

Best of luck you crazy bastards!!!

Given the limited power available, wouldn’t it be better to keep to a single voltage on board? Then you can have more capacity in the same number of cells.

I’m almost certain the RPi will run on 3.3v. The ARM certainly does, and the supply from the Micro USB connector goes almost immediately into a 3.3v regulator on the board. The 5v does get passed onto the USB ports, but I don’t think anything crucial requires a 5v source. You might have to bypass the regulator though, I don’t know if it’s an LDO or if it will take a chunk out of your 3.3v on the way past.

Excellent project. Will be following progress with great interest. I was shocked when I saw the Tupperware box though. Will you need to incorporate a heat exchanger? Could get warm in that box. The use of a closed cell foam to fill any voids could help make it “unsinkable”

NiMH batteries rarely get as many charge/discharge cycles as you’d want, and the amount of electronics to charge them properly makes them cost prohibitive. You actually have to monitor current rates, cell temperatures, and be prepared to shut off individual cells as they go bad, because one will inevitably fail quicker than the rest. Just relying on a basic charging algorithm that monitors voltage, as most commerical chargers do, turn the cells to soup in less than 100 cycles. NiCd is more robust and cheaper, if less environmentally friendly. Lithium Polymer might be something to look at as well.

I would definitely consider a LiPo battery rather than NiMH. The power density is far greater, as is the available capacity. You could consider running the moter only at night, using the daylight hours to charge the battery. Self-righting is easy to achieve, which will endure that your PV cell is always in daylight. I echo all the comments on brushless v brushed motors. You will save weight, in addition to the increased reliability and efficency. I would have a word with your local model boat club – they will have already met and overcome many of the challenges you are about to face.

A great project – I wish you much luck!