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November 2015
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Seabot and science hack day Dublin 2015

Many thanks to all of the organizers and contributors to science hack day Dublin.

It was fascinating to see what a roomful of fun and talented scientists can accomplish over a weekend. The event and collaboration helped me bring seabot from a concept towards reality. Here are some details and goals of seabot:


Seabot is a marine platform for electronic hacking. It was inspired by Cesar Herada’s Protei, James Gosling’s liquid robotics and 600 million year old prior art by Portuguese Man of War polyp colonies.

P. physalis. Photograph by A. E. Migotto, Center of Marine Biology, University of Sao Paulo, Brazil.

P. physalis. Photograph by A. E. Migotto, Center of Marine Biology, University of Sao Paulo, Brazil.

The original plan was to begin with a data gathering buoy and progress to a moving platform. But with access to UCD’s 3d printer, the help of Mohamed and Eoin, we were able to create a sailing platform along with a 3d printed propeller for those rare days when Irish wind falls below 100kph.

We began with a multihull because it gave us a wide, stable platform with the least amount of plastic and hours on the 3D printer. The model we used was a bottle boat created by Richard Albritton on Thingiverse. Because it used ordinary 500ml soft-drink bottles as pontoons, it used even less plastic.

Richard Albritton’s bottle boat.

I had the code to make the ATiny85 blink the light at the ambient temperature. Unfortunately the source code was on an encrypted partition of a crashed laptop but when it is available, I’ll provide a link here. (which is easier, cracking Symantec’s drive encryption or decompiling the bytecode inside the Atiny?)

When we tried floating the temperature-flashing buoy in UCD’s lake,  the swans thought we were trying to feed them. This reminded me that some of the kids in Cesar Herada’s educational project suggested a shark-shaped seabot to scare fish away.

Greg was our navigator. He worked on software for reading a GPS so the Seabot knew where it was. Paul worked on hacking the remote control for an RC toy to run the motor or turn the sailboat’s rudder. We’re already beyond our original goal of a data buoy but perfecting a robotic motorsailer will take some time and sea trials.

I used an Arduino Nano to program a cheap (~1 Euro) Atiny85 processor. The processor has an internal thermister and I dual purposed a red LED as a photodetector and temperature blinker. (1 blink per degree C)

I also intended to PWM modulate red and blue LEDs, red means temperature rising, blue means temperature falling. Imagine Toro Nagashi style floating lanterns where the temperature of the water is reflected in the color of the lantern.

But we didn’t have time to make the navigation system work and the last thing we need is more plastic in our already polluted seas. If we can’t make the seabot boomerang back to us, how can we find the seabot? This is where RF comes in. I had a 433Mhz transmitter which Greg found uses a very simple protocol. Toggling the ATAD line toggles the transmitter.
If the seabot can’t come to us, we must go to the seabot. I had some experience with software designed radio, particularly gqrx and Eoin had contributed code patches to cubicSDR. Paul happened to have his HF yagi antenna with him so we decided that this would be how we would track down the seabot. As a bonus, I connected the RF ATAD pin to the Atiny’s temperature controlled PWM pin.

A little RF direction finding, a 17.3 cm antenna inside a soda pop bottle and a 3d-printed hull. We’re in business.  Thanks to all!


Comment from Paul Morrison
Time November 17, 2015 at 10:24 pm

Interesting project ! Do you have any overview diags or schematics ?

Comment from bnitz
Time November 17, 2015 at 10:40 pm

Nothing beyond what’s here right now but I do plan to link to the source code and I can add the schematic to this very simple circuit.

Thanks for the suggestion!