Possible Hardware for Future Model

I am thinking of having the next size model be about twice this one (so about 8 times the displacement).   If it is 8 feet long it could hold 2 of the 100 watt panels by the same people that make the 50 watt panel used in the first size or 4 of the 50 watt.  Either way the total for solar would be about 8 lbs.

I would like to have 4 motors, one on each float, so that if one breaks we can keep going.    With 200 watts it would even be able to pull a kayak.  This means testing can be riding in a kayak that is pulled along by the robot.  Should be fun.

In this larger model I would put the batteries down inside the floats.  This lowers the center of gravity and also makes for a high rotational inertia as the weight is then widely spaced.  With 8 times the weight capacity we could use more and larger batteries and so make it through the night.

The first version just uses relays so the motor is either on or off.   With an electronic speed controller (ESC) we could use whatever power level we wanted.  There is a board called IOIO which can talk to an Android phone and an ESC.   There are other boards to go from bluetooth to ESC.   There are some ESCs that can talk bluetooth.

There is an underwater T100 thruster by Blue Robotics who is also making an autonomous solar robot boat.   You can get these with ESC built into the thruster.   These can go up to 140 watts but at about 12 watts it seems to give about 1 lbs thrust.  So 4 of these could be very nice.    We would normally run all 4 thrusters at low power but if one goes out then we run the other one on that side at higher power.

The BlueESC is the T100 model with the builtin ESC.  This also has the ability to be controlled with I2C, which is a protocol where one controller talks over  a bus to several devices.   With this a Bluetooth to I2C board could be an easy way to go.  However, a bus is not so good as far as keeping independent failure modes.  Saltwater getting into the wires by one thruster could disable all the thrusters.

For good independent failure modes I like having 4 different 50 watt solar panels going to the 4 different floats.  Inside the foam for each float there could be a charge controller, battery, bluetooth relay, and motor.   So the phone would be talking bluetooth seperately to each corner of the boat.   Could have a diode protected power line from each of the 4 batteries going to the power adaptor for the phone.   The diode would make sure that a short in one battery could not drain power from the others.

Could even have a backup phone that only took over if the first phone stopped working.

There are phones starting to come out with Ubuntu on them.  This Ubuntu phone has compass and GPS for $192 US.   This would let us write fast native code.    It could be interesting for a future model. 

I think having a 3D printed part to connect the drive shaft and the motor and help mount the motor would be good.   With shapeways anyone could just get one printed even if they did not have their own printer. 

Voltage Sensor

I would like to be able to have the robot go on multi-day trips.   But for this it really needs to know how much power it has.  I would like a small bluetooth voltage sensor.  Seeed used to make one for $39 but it seems it is discontinued.  There is a $120 Mooshimeter by moosh.im that could work.

Field Testing Navigation

We adjusted for magnetic north, and it now points very well. We had to use two phones together.   The phone with a compass does not have GPS and the phone with GPS does not have a compass. We followed the arrows as we went around the field.

Autopilot Demo

In the video below I demo the manual mode and switching to autopilot.
The arrows point the direction we want to go.
If were pointed about the right direction both propellers spin.
If were pointed too far left or right then only one propeller will spin.

Testing the motor and propeller

We hooked our 12 volt battery to the motor and propeller.

We then put it in a 5 gallon bucket of water, and it had enough power to get the both of us wet.
The shaft for the propeller was too wobbly, it needs something to stabilize it.

Future Data Options

Our current phone can use data roaming near many of the islands in the Caribbean.  So we could send the boat to other islands where it will still be able to communicate with us.   At some point we will do this and have it send back status updates and pictures of the island.

Data Roaming is rather expensive with our regular phone service so this Skyroam service is interesting.  It gives you lots of data for only $10/day.  However, it does not seem to cover the Caribbean yet.

Longer term we want to have some sort of satellite link so we could send the boat even further than the Caribbean and still keep in contact with it.

Elon Musk and Richard Branson are both working on cheap satellite Internet services.  However, these seem to be 5+ years out.

There is an Iridium Go that is a satellite link that makes a wifi hotspot  Today the data rate is slow but Iridium will be upgrading to Iridium Next soon and this device will work with the new faster service.   With this our Android phone could send us data while crossing the Atlantic without us having to change any of our code.   The slow data rate would even be ok, we just would not be sending many pictures.    The Iridium Go device gets power from a USB port so that is easy for us.    At the moment this is our first choice for communications when we are ready to send the boat far from land.   It seems Iridium next has been delayed till 2017+.

 Globalstar has data service for $40/month for 9000 seconds and there is a Globalstar hotspot device for $158.   Not sure how much data this really is but something made it seem like 9000 bytes.

Orbcomm has a data service and devices.   Seems to be flat monthly rate but can't find products on Amazon or other easy retail location so far.

Some Spot Connect but seems only one way and costly.

Quadmaran vs Sailboat

In the videos below both the quadmaran and the sailboat are each about 10 lbs.  In real boats the cost is roughly proportional to the weight of the boat.  So in some sense this is a fair comparison.  However, the sailboat gets stability from moving through the water and from the wind against the sail and in this test it does not get those. 

We are interested in slow moving solar powered boats and just want to show that the sailboat shape is not ideal design for our purpose.  The 4 floats on the quadmaran are widely spaced and the sailboat is much smaller with much of the floatation in the center.    So the sailboat rocks much more in this slow no wind against the sail test.   Note that the quadmaran has a lot more area for solar panels as well.

These videos are slowed down by a factor of 4 which would be right if these are models of boats 16 times larger.  So imagine the 4 foot quadmaran model is 64 feet long and 32 feet wide.

The wind for this scale is hurricane force, the waves on this scale are large for the Caribbean.    

Testing chase kayak

Teryn with paddle and Corey and Amoni in kayak

We will use the kayak to chase the robot boat around in case it has any trouble.  We had not used it in awhile so wanted to check that it was still OK.   This is Sandy Hill Bay and just 5 minutes from our house.  There are calmer bays so this will probably not be our first test location but it will probably be our most common test location.

Teryn and Ethan

Big enough bay for some good robot boat testing