Underwater HD video taking. now i just need a robot crab to stick it on :P

[blackbeard]

so i've been thinking of making an underwater robot of some sort to explore my lake. i bought an olympus stylus tough 3000 so i could get some underwater footage and here was one of the videos i took by sticking the thing underwater for 10 minutes

mashersmasher's underwater filming volume 1

so what are some approaches to underwater robotics that people have done in the past? right now i'm thinking of something allong the lines of a netbook motherboard controlled tracked robot to crawl allong the bottom. i'm thinking of having an ethernet cable going to the netbook and using skype from my boat to view info from the web cam. i've read about the use software to control robots through wifi which i imagine would also work through an ethernet cable. my stylus tough cam would go allong side a web cam and would film independantly while the web cam is used for stearing. this is all brainstorming at this point though so shoot some ideas (inexpensive ones if possible ).

[propertyco]

I'd reccomend using a tether incase it gets stuck, cause it looks like you've got some serious vegitation!

[voyager2]

looks like the fish are a bit nosy

[blackbeard]

looks like the fish are a bit nosy

they all want to take alook at the new big red shiny fish

[macdad-]

I'd reccomend using a tether incase it gets stuck, cause it looks like you've got some serious vegitation!

I'll second that, you should have the ethernet cable in a tubing. Flexible electrical conduit tubing is first thing that comes to mind(You can grab about 200 Ft. of it for about $50-60). Another thing is Vinyl tubing(Which is somewhat cheaper), but I would recommend the conduit tubing as it is much more rugged. Both should easily fit the ethernet cable into the tubing. But remember the maximum cable length to get a good signal on ethernet is ~300Ft.

Keep that in mind, if you want to extend the range of the explorer.

[parallax]

Underwater is an incredibly challenging environment to try and build robots for- I have participated in the Marine Advanced Technology Education ROV competition for the past two years; here are a few quick things I have learned to keep in mind:

*Most commercial "waterproof" servos are really just water resistant, and have no depth rating. Actuating your robot at depth will be difficult, as many common waterproofing techniques for servos have some negative consequences. A walking robot can be done, but there are reasons we don't see them wandering the ocean floor right now... mud and actuation 

*Professional waterproof connectors (for cables and electronics) are a lifesaver, and will save you a lot of frustration in the long run.

*Once you are set with a final design for an electrical component, "potting" it by encasing it in a layer of epoxy (the two part kind you use on bar tops actually works great) will ensure that it is entirely waterproof/shockproof at the expense of not being able to make modifications to it.

*Bilge pumps make great underwater motors. Usually you can cut away most of the housing and the impeller; this gives you a waterproof DC motor ready to go. I recommend SeaSense 1100GPH as a good compromise between price and power. I can dig up the specs on it if you want.

*Macdad and propertyco are totally right about the tether. Being able to fish out your robot is a must. Not to mention most wireless signals degrade incredible quickly under water so that isn't an option. 

*There are a few people on this forum that are experienced on this subject. If you have questions, try JonHylands, Admin, or madsci1016. They all do work with underwater robots on a regular basis, and may be able to offer expert advice.

BTW I love the video! 
   

[macdad-]

*Bilge pumps make great underwater motors. Usually you can cut away most of the housing and the impeller; this gives you a waterproof DC motor ready to go. I recommend SeaSense 1100GPH as a good compromise between price and power. I can dig up the specs on it if you want.   

Don't those operate on the same principal as JetSkis?

[parallax]

I don't know a lot about the specifics of JetSkis but from what I understand they do work on the same principle. They both essentially do the same thing: move water via use of an impeller and "flow channels." The jet ski uses this flow of water to propel the craft, while the flow of water itself is the point of the bilge pump; emptying water from the bilge of a ship.

For the purpose of an underwater vehicle, you can use the bilge pump as is by leaving the impeller intact. I have found that removing the impeller allows you to use a variety of marine propellers; this means that you can tune the output of the thruster to be exactly where you want it to be.

[propertyco]

...line loss on a 300 ft cat5 would be what?

[madsci1016]

Don't those operate on the same principal as JetSkis?

Not really.





Jet pumps don't change the water flow direction much, and can handle large flow rates. They are more like just a propeller in casing. Bilge pumps are centrifugal pumps that slosh the water around in a circle till it finds it way to the discharge port.

[parallax]

Don't those operate on the same principal as JetSkis?

Not really.

..............

Jet pumps don't change the water flow direction much, and can handle large flow rates. They are more like just a propeller in casing. Bilge pumps are centrifugal pumps that slosh the water around in a circle till it finds it way to the discharge port.

I stand corrected!  I told you he was one of the experts on this! 

@propertyco: In terms of line loss over CAT5:
http://www.netkrom.com/voltage_loss_over_cat5_calculator.html