I have started a little aquatic vehicle project that will be used to do depth mapping of the various ponds, lakes, and canals where I live in southern Florida. The mapping will allow the owners to determine their silt levels and silting rates.
My RSV is based on a similar RSV, only smaller, that appeared in the July/August 2010 issue of Robot Magazine and can be seen here: eTrac RSV
I chose to use fiberglass pontoons for a .60 size R/C plane and can be seen here:
The pontoons are manufactured by Great Planes and can be found at Tower Hobbies.
For propulsion I was originally going to build a couple of small outboard electric motors using Johnson-Mayfair 750GPM bait pump cartridges and 50mm Robbe three bladed propellers.
The housing for the bait pump cartridges was going to take a little bit of machining and the jaws in my Tag lathe still needed to be machined to allow me to chuck up plastic pipe couplers that are bigger than 1" in diameter.
Since I like Traxxas products, I found that the geared propulsion system for the discontinued Villain R/C racing boat might fill the bill as there are quite a few of the legacy Villain parts to be had on eBay for cheap:-).
So I downloaded the Villain exploded hull and drive train views and the parts list and proceeded to buy what I needed to put together two of the Villain geared propulsion drive trains.
At this time, while searching for Villain parts on Amazon, I found one last Villain built hull for sale and proceeded to order it so that I can build up a competition autonomous boat for competitions like the Sparkfun AVC only on the reservoir.
I began the installation of the Villain drive trains by cutting two sections out of the right pontoon just aft of the wire connecting bridge mounting points. I reinforced the sides and ribs of the pontoon, where I removed the fiberglass glass sections, with thin strips of poplar wood.
The toughest part of mounting the drive train was spotting the hole for the stuffing tube in the pontoon stern plate and getting clearance for the motor under one of the pontoon ribs. Pictures of the installation are below:
550 motor_reduction gears_and stuffing tube
Stuffing tube exit on stern plate
The propeller drive shaft is attached to a universal joint that is coupled to a short propeller shaft that is supported by an outdrive housing that is attached to a hinged trim support that allows the pitch of the propeller to be varied up and down vertically. I plan to epoxy the motor mount to the bottom of the hull once I have installed the rest of the propulsion hardware beyond the stern plate.
Right and Left Pontoons with Bridge
More build details and pictures to come.
Regards,
TCIII ArduBoat Developer
Replies
wire from the Intelliducer I get no data. I get data only with TXA
and SoftwareSerial set for inverted signal. But the data is not
intelligibile, I can see from time to time SDDBT or SDDPT and the
measure of depth but together with a bunch of nonintelligibile
characters.
TJC, what are the voltage levels from the intelliducer? 0-5V?
Thanks man!
Rafael
@Rafael,
Yes, they are 0-5vdc on the serial output lines.
Regards,
TCIII AVD
Hi All,
I thought that I would put up a couple of pictures of my completed, except for the paint, Pontoon RSV.
I have yet to put the RSV through it paces as it has either been too windy or rainy here in Southern Florida to run it on my Association's mini lake.
Regards,
TCIII AVD
Hi Tom. Nice clean setup. I am wondering if a transom mount depth sounder would have been easier to mount than the thru hull version. Not saying you would mount it on your transom but just building a housing/ bracket for it. Blue Robotics is getting ready to ship the next batch of thrusters so hopefully I will be in the water soon. Again, looks clean.
Regards,
David R. Boulanger
@David,
Unfortunately the Garmin Intelliducer NMEA 0183 is no longer available in the transom mount configuration. They only make the NMEA 2000 in the transom mount configuration so I had to go with the NMEA 0183 through hull configuration.
Regards,
TCIII AVD
Hi Thomas,
Don't forget to measure the speed of sound in the water as well as the elevation of the water when you do your survey for silting. This is very important! If the Garmin unit allows you to enter a speed of sound, you can do it by doing a bar check. Put a flat plate of Al under the transducer at a fixed depth. Take the reading and calculate speed of sound. If no data can be entered, the sounder is probably using 1500 m/sec as the speed of sound. (i.e. overestimating the depth). You will have to take the speed of sound you measured and recalculate all the depths to be accurate vertically. For the water level you can mount a ruler on a fixed structure. If there is tide you would have to read at least every 15 minutes. If not the read the level at the beginning and end of the survey and correct you data set for the water level. If you do this each time you survey, the data will be comparable.
Also, from an operational point, make sure that all the air bublles on the face of the transducer are removed by wiping with dish detergent on a rag.
Airmar (www.airmartechnology.com) makes similar units and I believe they still have a transom mount available.
Regards,
Ken McMillan
@Ken,
Nice information, much appreciated.
We have run the depth finder in a swimming pool with known depths and so far the transducer has be accurate to within ~0.1 foot consistently.
The RSV will only be operated in small lakes, large ponds, and channels.
Regards,
TCIII AVD
Hello Thomas,
The speed of sound effect is not as noticeable in a swimming pool. I used to teach my hydrography students the art of hydrography (it was a winter course) but we couldn't do any practical work due to the hard water in the lakes. (ice) As a result of this, I used the university's Olympic size swimming pool with a rubber boat powered by a trolling motor. We had speed of sound velocimeters as well as bar checks, and all gave us a speed of sound in the chlorinated water of 1495 m/sec. Since this is quite close to 1500 m/sec there is little difference in the readings when corrected for speed of sound. The difference in 10 feet of water would be 0.03 feet.
All this means is that the speed of sound in the pool is very close to that used by the manufacturer as default. In some tailings ponds the speed of sound was greater than 1600 m/sec.
Regards,
Ken McMillan
Hi All,
I had planned to test the GPS/Depth Finder data logging capabilities of the GPS/Data Logger Shield on Monday, but did not make it to the Association swimming pool until today. Though I did spend Monday adjusting the Depth Finder Transducer suspension height such that when there is a full load of batteries onboard the RSV, the bottom of the Transducer Housing is approximately one to one and a half inches below the surface of the water.
Besides recording the GPS position and bottom depth on the micro SD card, I transmitted the GPS/Depth Finder NMEA 0183 sentences over my Xbee 900MHz Pro telemetry link to my laptop so I could view the data real time.
Once I started receiving good GPS and depth data over the telemetry link, I had the wife push the RSV from the middle of the pool (~3.6 ft depth) to the deeper end of the pool (~5.0 ft) depth.
In the attached data log file you can see the depth change from 3.6 ft to 5.0 ft as the RSV was pushed to the deeper end of the pool. The GPS data changed also, but only fractionally as the RSV was only moved about 10 ft from the starting position to the deeper end of the pool.
The next step will be to try the UnderSee Explorer app while manually driving the RSV around the pool with the R/C transmitter. If I get a good contour display from the UnderSee Explorer app, I will then try a manually controlled run in the Association mini lake. If that is successful, I will try and use the MP to set up a grid mission over the mini lake and see what results I can get.
I am also attaching the Arduino code for the Arduino Duemilanove 328 board and GPS/Data Logger Shield that I used to capture, record, and transmit the GPS and Depth Finder NMEA 0183 sentences.
Regards,
TCIII AVD
DATALOG.TXT
GPS_Depth_Finder_Sketch_v5.ino
-
1
-
2
-
3
-
4
-
5
of 13 Next