PiSub... Raspberry Pi Submarine...

[Bigcat123]

Hello all...

I am currently brainstorming a few projects for my Raspbery Pi... Ideally I would like to do something that has not been done before.

What about a Raspberry Pi powered submarine?!

Does anyone have any ideas about any potential problems?

I would like to make the sub remote controlled... However how would I do this? Does anyone know what wireless transmissions work underwater? Radio? Wifi? What? Not sure that thu actually function underwater though... Your thoughts?

Thanks!

[raspberrypiguy1]

Interesting... You've given me an idea!

The Raspberry Pi Guy

[aTao]

Radio underwater is a bit like electricity down a soggy string... not much cop really. I believe that ultra low frequency is the way to go. However sound underwater is fantastic, you probably want to consider an ultrasonic transmission.

[joan]

http://www.raspberrypi.org/phpBB3/viewt ... 99#p378199

[aTao]

http://www.raspberrypi.org/phpBB3/viewt ... 99#p378199

Not a submersible, in fact it has ~1/5th the density of water, guess you could tie a brick to it..... but then WiFi wouldnt reach it.

[keal]

BigKat,

I have had a similar idea for quite some time, but never had the time/resources to play too much with it. In my experience it is better to get a functioning prototype of the hardware on a tether first. Things I ran into I really didn't expect. I.E. I decided to use 6 in thin wall pvc from Lowes. I cut a 1 ft section of it to test buoyancy and I filled the pipe all the way up with water while capped and it still floats too much!.

To speak to your specific wireless connection issue, I have seen guys on the internet use a small tether to a floating antenna to achieve wireless for further distances in shallower areas. Also, if you look on youtube for RC Submarines conventional 2.4ghz radios seem to be able to reach the sub. Allowing their operators smooth control almost all the way down to the bottom of the diving end of public pools. That being said, how far do you want to go?

My concept is that I want a sub with several cameras. At least one dome one on the front and one on a track sliding forward and back the whole length of the sub looking through a clear floor. I believe that using exhaust vent pipe (brazed and sealed) will give me the weight I need to avoid rocketing back to the surface. If that goes well I am going to try working on the electronics and com. systems. Most likely it'll be a simple pipe with ballasts, pressure sensor and Pi controller only. Communications will be USB Wireless adapter > Ad Hoc networking being broadcasted from my laptop. I'll calibrate the pressure sensor to be able to read depth ( Pressure of water doesnt change, just the weight experienced due to depth) and have a RPI read depth, ping my laptop and log both results. At that point let a little bit more water in the ballasts and repeat .

Using the previously mentioned method you will be able to have a log and find out what your range(at what depth does packet loss start occurring) is. Regardless of equations, experience, or even dumb luck you don't know what is going to happen until after you do it. Here are a few things I would worry about enough to test and get data on what actually happens with your specific sub.

Test different types of material, if your radio is in the hull, different materials bounce RF signals differently.
Is the water clear? After a rain storm it may leave water not so clear, potentially adding interference. Or maybe pond scum?
See how solid objects slightly in the way affect communications. If your at a local park with a pond, does the wooden pier your diving around make a huge difference?

If you are trying to push what you can do, just for the sake of doing it documentation is key. Record / Write as much info as you can to later look back on. I never noticed it until my sister pointed it out, but we can't hear trains passing through our town normally. When it storms or is very cloudy we can hear it at the same place we previously couldnt. When the clouds are there and low the sound actually bounces off them, then the ground, then back again making the sound carry a lot further. My point in this example is that routine/regular things may affect any experiment. So try to get as much info to be able to re-create it as possible. Dont overlook anything.

Sorry for the rambles
Hope it helps

-Keal

[ModifiedPi]

Standard 6/8 channel Tx & Rx seem to be widely used with most R/C Subs (http://www.sub-driver.com), although I'd personally go for a tethered ROV using a cat 5 network cable. Lot of money to lose if a ballast servo sticks & sends everything to Davey Jones' Locker

Loads of info here:

http://openrov.com/
http://eccesociety.co.uk/?page_id=143
http://www.rc-sub.com/resources/index.php5 (see links at bottom of page)
http://www.vabiz.com/d&e/
http://homebuiltrovs.com/
http://seaperch.mit.edu/
http://coconutpi.wordpress.com/
http://spectrum.ieee.org/geek-life/hand ... rsea-robot
http://forum.arduino.cc/index.php/topic,6584.0.html
http://forum.arduino.cc/index.php?PHPSE ... c=174524.0

[Mr.Dave]

Radio underwater is a bit like electricity down a soggy string... not much cop really. I believe that ultra low frequency is the way to go. However sound underwater is fantastic, you probably want to consider an ultrasonic transmission.

An antenna inside of a raised periscope could be a solution to the wifi under water issue

[Ravenous]

Bigcat, maybe you could get started by having a go at an underwater camera first. On a pole and powered by a long wire, which would probably save a lot of work and money on motors, propellors, battery packs etc.

It's a lot less money than the full-on sub and it would give you a chance to get into the electronics and waterproofing, etc. first. You might be able to make a little money or fame on the side by recovering people's lost keys, mobiles, etc (well I was kidding about the money and fame, but it'd be a fun toy anyway )

[aTao]

Radio underwater is a bit like electricity down a soggy string... not much cop really. I believe that ultra low frequency is the way to go. However sound underwater is fantastic, you probably want to consider an ultrasonic transmission.

An antenna inside of a raised periscope could be a solution to the wifi under water issue

Yup, but it looks like I was wrong about underwater radio, perhaps thats only relevant to hundreds of feet down.

[aTao]

although I'd personally go for a tethered ROV using a cat 5 network cable. Lot of money to lose if a ballast servo sticks & sends everything to Davey Jones' Locker

it is most likely that any sub will require ballast weights, these could/ should be attached by a timer released mechanism, 2 hours after setting it will drop, or at least have a few more chances of dropping enough weight to make the expensive part float.

[dbwilliams]

Simple electromagnet setup would be ideal for your ballasting system. If you lost power for any reason your ROV would surface. Another possibility is to maintain positive bouyancy and dynamically maintain depth, though this would be inefficient.

I don't think the PVC pipe would be a good pressure vessel for anything very deep, but it would be a start for early testing. The person that suggested the remote camera on a stick is on the right track. I'd test things incrementally, such as "camera on stick" then cat 5 tether then to wireless and perhaps autonomous.

I think this would be a cool project and maybe I can convince my wife to let me try it.

[Kane]

You could fill the interrior of the sub filled with mineral oil to get over the pressure aspect.