Let's Make Robots!

ROV submarine

I playing with the idea of building a ROV.

A ROV is a Remotely Operated underwater Vehicle.

I plan to start simple, with a webcam connected to a computer, and 3 motors with propellers controlled by switches, all of it strapped to a frame of sealed plastic tubes. Something close to this instructable

But the robot geek in me wont stop there! I want to build:

A moisture sensor (to warn if the electronics compartment has sprung a leak) 

A gripper (pretty obvious huh? anybody know any simple design that uses a motor, not servo?)

a compass (any good ideas on how?)

PMW controll of the thrusters (done with a microcontroller I guess)

Pan/tilt of the camera.

It seems like controll by umbilical cable is the only option. There is RC submarines on the market, but I cant find out what kind of reception radio signals get under water. Doesn't all the Hollywood movie-subs have to go to surface to get in radio contact? And as a technical breakdown is very likey, a line to pull it back up to the surface isn't that bad an idea anyway.

Does any of you have any suggestions, what kind of technotrickery can I add to impress? maybe a pressure sensor for depth?

Would a picaxe 28X1 onboard and a picaxe 28X1 on shore be able to communicate using one cable for serial communication? -Would that be sufficient to give 3-4 sensor inputs one way and motor/servo controll the other way? 

I think I'd need to be able to controll 4 motors and two servoes (pluss any extra you come up with).

 

I'm sorry for the messy post, writing and thinking at the same time isn't really my expertise. Actually, according to my wife thinking in general isn't... Here's a few other links I've been browsing while writing this post

http://www.homebuiltrovs.com/

http://www.rov.net/ 

 http://www.rcgroups.com/forums/showthread.php?t=1068847 

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You can have your antenna attached to a small buoy which, of course, remains out of water and makes communication easier. As far as i know real submarines do have to emerge to transmit radio communications...or well, this in ww2!

You can use one cable for serial communication on a 28x1, but i suggest you take a look at the serial upgrades that the 28x2 has, maybe they could come in handy. You could use an interrupt to monitor the serial pin while the same MCU takes care of servos and motors. 

As for the compass...there are for sure electronic compasses, i've seen them once. 

But the coolest thing i can think of is making the device that regulates his depth. What comes into mind at a first glance is:

-using a pressure sensor to determine depth

-use a solenoid valve to let water in

-use a pump to send it out (don't know where you could get one of those though) 

I was considering building one of these, in thinking about it, you really need to consider a lot of things.

Depth, type of materials, control methods, distance, weight distribution, pump thrust or motor thrust. Emergency procedures in case of flooding(mosture sensors are a must, as well as materials that can obsorb water). Of course there are a ton more things, but just some examples...

oh...and a pool to test it out in  :D

I bought a book on it as well that goes into simple construction and design. I'll see if I can find it and post the title. 

 

Never thought about a project like this, but living at a lake makes me think as well....

I googl-ed bing-ed around and found this: http://www.submarineboat.com/building_bob.htm. Makes a fascinating read. You might find some good suggestions there.

Take care
Ycd

Well this video and that one should interest you...
impressive stuff, I particularly liked the san diego ibotics stingray....great design!

• Water sensor? Check this out. You could add some sponges and silica gel capsules to help keep moisture away from your electronics. Silica gel sachets are easy enough to get, just go to a shoe store and take them out of all the boxes =D
• Long-wave radio has much better water penetration, which is why modern subs use it, but getting the transmission equipment will be a pain. If you're not planning on going all that deep, the buoy idea gets my vote.
• Underwater pressure has a very nice linear relation to depth, making calculations very very easy. I recently bought some of these little pressure sensors for a project at work, they were extremely easy to use since they've got a little amplifier built in which produces a nice, convenient linear voltage output. You can probably find even cheaper sensors that will still be more than accurate enough for your ROV.

Good luck!

Another source of inspiration here :

Build your own underwater ROV for £250. 

 

this is the book I ended up buying a few years back.

I wasn't sure how well a compass would work underwater, but it seems it might after googling a little. Something about "dive compass". One thing to remember is to read the compass when it is level. To find "level" an accellerometer  or gyro or both in an IMU is needed. Sparkfun has some various electronic compasses, plain as well as those already tilt compensated.

I might try a few underwater tests with a cheaper model before getting an expensive one. Anything, a metal bar nearby, running motors can through off readings.

I have been thinking about a swimming pool based bot as well. One idea for navigation I had is to place navigation beacons around the pool. So rather than rely on a compass, the bot would locate 2 or more of the nav beacons and determine position relative to those.

Of course this means the bot is dependent on an external system, but since I just have the one swimming pool, that'll work for me.