Let's Make Robots!


Measure water depths in lakes
Bilde.jpg881.9 KB
MarkII_LOG_microSD.zip2.73 KB
MarkII_NAV_microSD.zip5.11 KB
DELFTship_linesplan.pdf159.55 KB
Mark_II_versjon_1a_mod.zip9.02 KB

This is Mark II of the Whirligig project http://letsmakerobots.com/node/16995 code name SEA RENDERING (it’s not actually a code name, just an anagram for my name :-) )

The purpose of this robot is to have it log water depths along a predefined set of waypoints. It stores its data on memory sticks or on SD cards. The estimated runtime is about 24 hours and with a top speed of 3km/h it will travel roughly 72km. With a log entry for every 10m this would give us over 700 depth measurements   with full GPS reference.

Most of the control system has been moved from the original Whirligig to save cost and time.

The hull was designed in the free version of DELFTship http://www.delftship.net/ and built this winter. With the split mould I can produce a second hull in matter of days.

The original plan was two hulls working in pairs as a catamaran with a solar panel on top. This can still be done but two robots working independently we can cover a larger lake on shorter time.

Some images from the hull build

Adding fiberglass to one half of the mould

Mould completed

The first casting

Here are some pictures from the complete robot


Polymorph beddings for the batteries

Control system

Some electronics in the lid

The waypoints are entered using my adaptation of the Ardupilot tool. A great application that lets you interactively add waypoints to your list. This list is then copied onto the SD card and the robot is ready to run.

I run this routing 3 times and this is a GPS visualization of the log. The green markers are the waypoints.
(one of the log files are attached)

My brother (a professor at the University of Oslo) that will be using this robot, then run these 3 logs in something called  "Thin plate spline" http://en.wikipedia.org/wiki/Thin_plate_spline to see if the depths we logged made sense. And this is what he came up with.

All in all this project seems very promising.

Update 28/6-2010

After having had some problems with the VDIP1 USB interface I decided to go for the microSD shield from Sprakfun http://www.sparkfun.com/commerce/product_info.php?products_id=9802 .
Now the whole thing looks much cleaner and is probably more robust.



Update 11/7-2010

This weekend my brother and I went to the lake ‘Riskedalsvatnet’ to do a full scale test. The full waypoint routing had 337 waypoints and a total length of 18,1km.

The traveling speed of the boat is about 3km/h so the mission should have been completed in about 6 hours. As this was the first full scale test and we had some uncertainties on where the shore line actually where, we decided to split the trip into 3.
This is the first segment of the mission.

This is how the boat run

And this is an Dr.Depth rendering of the depths we got.

After all segments where completed this map was generated in Dr.Depth

A full size map in b/w is attached


UPDATE 14/7-2010

Added the Arduino sketch if anyone want to have a look.

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You’re probably right in that the transducer gives you surface speed as it has a small impeller that gives you the speed in normal NMEA sentences. And as you say the speed is of no importance to us. It’s fun to know when regarding mission calculations but for the logging part it’s of no value.
When it comes to the cable plug, there is no plug with the system. It’s only bare wires so I cut the cable and added a 3-pin polarized plug of my own. I do believe it’s a regular TTL UART (that make sense as the supplied voltage is 5-24V), -but check the signal before you fire your microcontroller.
The way I did it was to hang the transducer in a bucket of water and checked the signal on a scope. You hear a faint clicking as the transducer fires. If the signal is within the TTL UART range, hook it up and decode the NMEA.

This is badass, great job! :D

In reference to the VDIP1 Module.. that's a fun one to play with. lol I had alot of problems myself, had to use someone elses code to be able to use it reliably.  I know it's all good and long done by now but for future reference :D



Bottom link is the .pde files.   This is just a "demo"  so the data being copied is the "supposed sensors" you should have hooked up. :D    Bit late but hey.. better late than never, some how? :)

Even if the boat is working good now I still want to make it better so I ordered a FEZ Domino from Sparkfun http://www.sparkfun.com/commerce/product_info.php?products_id=9797
I’m accustom to the Microsoft visual studio and the .NET framework so this can be exiting.
Arduino is fine for things not involving string manipulation or file IO, so I'm looking forward to write real managed code in C# and a proper file system.

A few years ago I wanted to set up a robot boat or sub with a camera mounted underneath. I have recently moved into my own apartment in China with a view of the river. Reading about your good work is making me think about re-starting my old project.

Looking at how clear the water is in your photo it would be nice if you could set up a camera under the boat. If those PIR motion detectors work underwater then you might be able to set it up to only take a photo when it detects motion.



It might be hard to get them completely sealed. Water would end their usefulness.

What about a clear plexiglas set into the bottom of the boat? That would be easier to seal, and set sensors at enough of an angle that the sensors see through it without reflection ruining your other readings.


ADDED: Now that you have added more about the build, I can see you have the leakage problem taken care of. So disregard my earlier thoughts.

In fact, the boat construction looks great !


this is outragious stuff!, im supprised the military aint contacted you for this kind of GPS locomotion :P

Very good build, awsome design im pretty sure you have got allot more insperation where that came from to make the next node even more exciting :D, cant wait to see it :P

Simple and effective design, cool work man... I love it. By the way my ABE its under redisign...

One question-  How long last the battery:_?



The batteries are rated at 12Ah and with the two in parallel I should have 24Ah on board. With the motor and all systems running it pulls about 1.5A, and that should give us about 16 hours of running time. As these are not deep cycle batteries I would not run them for more then 10 hours.

Hi Geir, what kind of motor and propsize do you use? 1.5A seems little to me, is it running at top speed with 3km/u? And the batteries 12ah in such a small package?

The motor I’m using is a cheap eBay motor 12V and 1000RPM.
These are not brushless racing RC motors but geared high torque motors.
It actually draws less then 1A but the other equipment also draws some current.

The propeller is a 70mm. Can’t remember the pitch or the maker, but it’s a standard RC boat propeller.
And these are the batteries http://www.biltema.no/no/Bil---MC/Elektrisk/Batteri/Blybatterier/ number 80412.
So it all adds up :-)

I took it out for a run this evening and it had an average speed of 3,3km/h with a top speed of 3,64km/h