Shrimp hatcheries
da...@untiredwithloving.org
I am looking for a practical robot to use to manage the shorelined
shrimp hatcheries in Red Sea. They are basically shallow very large
pounds (10 hectars). I would like to make feeders and underwater
photographers and many other such ideas.
It would be ideal if I could build them or assemble them myself.
Thanx and I love your projects and the kids look so smart :)
--DARA
Christiaan Adams
Welcome to Perch Chat!
Sounds like the SeaPerch ROVs might be pretty close to what you need. All the instructions for building them are available under the "Building SeaPerch" section of the website. If you want to discuss your specific needs (depth, distance, power, cameras, payload, etc.), I would be happy to give suggestions for design and customization of your SeaPerch.
We would be very excited to see what you do with them, as would many of the teachers who build them with their classes, so do send us photos or stories when you have them!!
Best of luck,
-Christiaan
==================================================
Christiaan Adams
Research Engineer & GIS Specialist
Massachusetts Institute of Technology
MIT Sea Grant College Program
office: 617-253-9311
lab: 617-253-0511
cell: 617-803-9413
ada...@mit.edu
AUV Lab: http://auvlab.mit.edu
Ctr. for Coastal Resources: http://massbay.mit.edu
==================================================
da...@untiredwithloving.org
Perhaps next week I will post photos from the site.
The pools are simple rectangular sand dugouts about 2 meters high.
Generally the water is calm but occaisionally there may slight vexation
and the bottoms may be disturbed.
I will take permission to post some of the field data next week though.
I need to know:
1. Can the robot be sent to the middle of a very large pond, say in
relatively calm weather with slight waves on the water?
2. Right now there are tiny boats the workers take to examine the pond
and lower the feed-place, I would like to see if the robot could have
an attachment i.e a sq neter wide feeding plate and lower it to feed
the shrimp?
3. Do you know what chemical sensors I can add to your robot? Can I get
the data wirelessly? I know I can but which simple techs can I slap
together that you know works in the water!
4. I need simple cameras, no big deals just to get snap-shots, possibly
video. Can I get a real-time feed from under the water?
5. Can the robot stay in the water indefinitely i.e. I leave it there
on the surface since to pull it in and out may be cumbersome.
I am an engineer so feel free to throw techs at me.
Thanx a lot
--DARA
Christiaan Adams
Two meters deep is no problem for a SeaPerch... we run them upto upto
12-15m deep. As far as getting out to the "middle of a very large
pond"... that depends how large. The limitation on depth and distance
is mostly due to power loss in the tether cable. With the standard
(ethernet) cable that we use for the tethers, we've found that having
over 12-15m (40-50ft) of cable starts to cause significant power loss,
resulting in rather poor motor performance. In the past we've built
larger robots to run off of 24, 36 or 48 volt systems, using several
bundled ethernet calbes for the tether. You could also find a larger
gauge cable to use as a tether.
So yes, getting a robot 12-15 meters out into your ponds should be
quite easy. Waves shouldn't effect it, since even at the surface it
sits completely submerged. Underwater, you won't notice the effect,
unless there are really big surges.
I'm not sure what you're refering to with the feeding plate... a photo
would help give an idea. But a few potential problems come to mind.
First, how much does it weigh? The standard SeaPerch is not designed
to carry much weight, and this sounds pretty heavy... it would take a
wider frame and more floatation to hold it in place. Does the plate
have to be held above the water on it's way to the middle of the pond??
If so, you would probalby need a robot much larger than the standard
SeaPerch to support it. And once it does lower the feeding plate, I
assume it gets lighter quickly, as the food is eaten? If there it a
large change in weight, then the robot's bouyancy would be thrown off,
causing it to rise (unless you install a bouyancy compensation
system... getting complicated quickly).
As for chemical sensors... any sensor that you can waterproof and get
to run on it's own can be strapped on board a SeaPerch. We regularly
use some of the little dataloggers available from a company called
"Onset Computer". These include temperature, light, etc. Other kinds
of chemical sensors get complicated quickly (we haven't found
simple-easy to use, water-proof versions yet), but if you have
something that can run on it's own and is waterproof, the SeaPerch can
carry it. As for getting the data back, you have a few options.
First, you can record the data onboard, and download it later, like
with the dataloggers. The second option is to use the extra 2
conductors in the tether wire to run a signal back (or add extra tether
cables to send/recieve data). The third option would be wireless...
now, radio waves don't travel through water well, but if you're only
going 2 meters deep, you MIGHT be able to get away with it... if not,
you could consider putting the antenna on a float that is connected to
the robot, but again, that gets complex really quickly.
Cameras are no problem. In fact, we do video on SeaPeches all the
time. The video is actually easier than a still camera, since it
simply provides a constant video feed down the cable (the cameras we
use come with about 30m of cable attached), and doesn't require any
signal to trigger the shutter. They even have LEDs built in to provide
some illumination. We use cameras that cost about $150 to $200 each,
strap right onto the SeaPerch, and whose cable gets tied alongside the
robot tether. On the other end of the cable are two plugs, one for 12v
power, one with a BNC or RCA jack for the video out to a monitor or TV.
The 30m cable is fine for the normal SeaPerches, but would have to be
extended for a larger robot with a longer tether. If you're
interested, it's also easy to put a simple microphone on-board.
About longevity... the standard SeaPerch is not designed to stay in the
water indefinitely. It's motors would start to leak, and it's metal
parts (most importantly the motor shafts) would start to rust. I
assume you're working in salt water? If so, you definitly want to
rinse them after every use. In fact, I wouldn't want to leave any
cameras or sensors in salt water indefinitely, unless they are
specifically designed for that, since it's a really harsh environment
for metals.
It sounds like a SeaPerch might be a good platform for occasional
inspections, sampling and video monitoring. It was designed to be
simple and as cheap as possible, so it works well for class projects
and such, but it does have numerous limitations. That said, once you
build one, you'll see how flexible and upgradable it is... you can
change anything you want! If you want to carry multiple instruments,
stay out indefinitley, travel more than 12m from shore, etc., then you
could build something like our "Advanced SeaPerch", which runs on 24v,
has much more powerful motors, motors potted in oil in stead of in wax,
which makes for much more durable waterproofing, and other imrovements.
To build it on your own, you'ld need some machine tools available.
Other ideas come to mind that might be more appropriate if you have one
or two specific tasks that you want to perform. for example, a tower
installed in the middle of the pond might be able to host
remote-controlled instruments that could perform some of your functions
more effectively. A radio controlled boat might also be a good option
for some of these things.
Alright, let me know what you think. This sounds like a really neat
project!
Cheers,
-Christiaan
da...@untiredwithloving.org
1. I spoke to the General Manager of the project in two locations in
Red Sea and he was excited to know that such techonology exists and he
offered a workshop to make the final robot suitable for our use.
2. He and the GM a very large shrimp farm will allow us to use their
facilities for tests.
3. I will get there to take photos and meet the two GMs for ideas
4. I will take pictures of the feeding plate. I can think of many ways
to remedy the issue
5. I will be in Toronto aroun 15th and would try to come to see you, I
will confirm before hand. If I can get there ontime I guess you can
teach me how to build one :)
I will be meeting these people in comging days to collect photos and
ideas, I will get back to you.
Thank you so much.
--DARA