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Topic: ROV motor (Read 2 times) previous topic - next topic

John_Ryan

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Good source for motors: rechargeable power drills. Small ones can be had for 5-10 euro. They even come with NiCd cells and a charger. I bought some and they have a 3:1 gearbax, wich seems ideal for most boat propellors. They're not waterproof, evidently.

I am building a land prototype first, wich will be wireless. Underwater, you can forget about wireless comms, I think. Hance, GPS will probably not function, unless you are really close to the surface.

Sure, underwater modems exist, but they only offer a few hundred bits/sec...

I really hope someone here will prove me wrong about underwater comms, tho  :-)


I read this at Faludi's blog

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Here's a quick primer on how to program an Arduino over a wireless connection.

Now, we can put an Arduino on the ceiling, underwater, up a tree, stuffed in a turkey or what have you and still be able to change and improve its behavior. In fact, by adding an XPort or WiPort to the XBee, we can extend the connection over the Internet, and program anything from pretty much anywhere.


It's worth checking out first though I can't be sure he was joking or serious.



moolc0ol

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For a sub, a ballast system would be needed, and if I were lucky enough to be working on such a project, I'd also need to be working on a solution.

I dont think that if i make a traditional ROV that i would even need a ballast. If the ROV has some weights on the bottem and the foam on the top and i work it a bit then i can achieve neutral buoyancy and have some more balance. and if there is a prop on the top or bottem that would make it go up and down. The lack of PWM with relays is a problem with me however. being able to pivot motors for steering in an ROV would be difficult and impractical.  Lets say there are 2 motors on the back and one is put in reverse and the other forward. the turning radius would be nil. it would also make it easy to control with  a hacked old joystick. and make a pc interface easy.
would i be able to make a pseudo pwm? where say if i wanted to half the speed then it would kill the motors every seccond half seccond? its obviously not the most efficent way to do it but is there any other way to pwm it? these guys must of done it http://binarybridge.k3.mah.se/

John_Ryan

For sure. I'd love to see a more efficient way of doing it too. A common problem is that sometimes devices requires a larger voltage than the board delivers. Plus you don't want the options narrowed because of those limitations. Since relays are cheap as are the 595's, until there's a better option, that would be my immediate choice.

You could pulse the motor to manage speed, which is actually quite ingenious when you think about it. I don't think pulsing would be inefficient either.

An object of neutral buoyancy also wouldn't need to conform to any particular shape. You could use a ping pong ball, for example,  attached to shaft attached to two rotary encoders to determine the objects tilt for staying flat in the water, and using thrusters for making corrections. The ROV could be the shaped like a ball, hypothetically.    

Once I'm over my current back log of work, and other projects I'm working on, I'd definitely like to put all that to the test.

moolc0ol

I have a sub question about this. i didnt want to start a new thread. I appologise for the crude terms because im kind of new to electronics. but if there is an electrically powered switch (relay) what about an electrically powered resistor. that could ajust how much power goes to the motor. that would make the motor ajustable.

moolc0ol

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For sure. I'd love to see a more efficient way of doing it too. A common problem is that sometimes devices requires a larger voltage than the board delivers. Plus you don't want the options narrowed because of those limitations. Since relays are cheap as are the 595's, until there's a better option, that would be my immediate choice.

You could pulse the motor to manage speed, which is actually quite ingenious when you think about it. I don't think pulsing would be inefficient either.

An object of neutral buoyancy also wouldn't need to conform to any particular shape. You could use a ping pong ball, for example,  attached to shaft attached to two rotary encoders to determine the objects tilt for staying flat in the water, and using thrusters for making corrections. The ROV could be the shaped like a ball, hypothetically.    

Once I'm over my current back log of work, and other projects I'm working on, I'd definitely like to put all that to the test.



hey,
i saw there was a reply to my thread just before i posted the last one. heh heh. i guess this is going to result in a double post. srry. but wouldnt a crude PWM in a mechanical relay make it vibrate and kill the battery? thats why i said it would be inefficient. I dont think ill need a 595 because i only need 3 motors. would going 595less not let me do the reversing polarity trick to reverse the motors? I thaught about the neutral buoyancy, it would definitely be ideal but it will work fine for my purposes for the time being.
The roll compensation idea would work but that would over complicate it. but if i use a neutral buoyancy rig with weights on the botem and foam at the top than it would also prevent roll. As for the wired/wireless situation, i think im going wired for the time being. i think cat5 cable is cheap. i dont know if it will carry video, definitely not if its analog. i have no idea what im going to with the camera. even though im going wired id like to keep the arduino, batteries etc underwater. it should make any future updates to wireless slightly less painless.

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