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Hey. I'm new to the boards and to this forum. im not sure if this is the proper board, if not feel free to move. I have an arduino NG and i love it. i successfully made a KAP rig and it is sweet. I recently saw this video
http://www.engadget.com/2007/09/04/build-your-own-underwater-rov-for-250/
I am looking to do something similar with arduino. In would definitely characterize myself as leaning more in software then hardware so i have one question about the hardware that would go into an arduino ROV. Specifically my question is what kind of motor would i be able to use underwater or modify to use underwater thats powerful enough to do what the one in the video does. And i want to control it with the arduino. How would i do this? Obviously the output from the actual device is not enough to power a hefty motor. Would i use a transistor for this? if so would it still work with the analog out's on the arduino so i can control speed?
thx

modified**
oh, and what kind of battery would i use to do this? and would i have to have separate batteries for the motors and the arduino? and how would i go about a camera?
« Last Edit: September 07, 2007, 07:52:13 pm by moolc0ol » Logged

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hey weird timing. I was looking at a larger version of that design a few wees back, it looked like it had got itself stuck in a lake amongst some lake-gunk. One thing I'd like to build is an autonomous ROV using gps to chart its way around the shorelines. I think I'd prefer a more efficient design like a tube or classic sub shape, that way less power would be needed for propulsion as these ROV designs don't look very hydrodynamic. You could use relays for switching, I just bought 50 x 5v for 12 bucks off ebay so they're not expensive.  Any of the LED examples will power a 5v relay, you just need to hop the 220ohm resistor(s). I've seen a design using a battery powered toothbrush, I pulled one apart the other day and the motors pack quite a punch, and they're already water proof.  The larger motors they've got attached to that thing I wouldn't know what they're called, Curvetech Thrusters? They look expensive. Anyway, all very doo'able with Arduino, and then some  smiley
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hey weird timing. I was looking at a larger version of that design a few wees back, it looked like it had got itself stuck in a lake amongst some lake-gunk. One thing I'd like to build is an autonomous ROV using gps to chart its way around the shorelines. I think I'd prefer a more efficient design like a tube or classic sub shape, that way less power would be needed for propulsion as these ROV designs don't look very hydrodynamic. You could use relays for switching, I just bought 50 x 5v for 12 bucks off ebay so they're not expensive.  Any of the LED examples will power a 5v relay, you just need to hop the 220ohm resistor(s). I've seen a design using a battery powered toothbrush, I pulled one apart the other day and the motors pack quite a punch, and they're already water proof.  The larger motors they've got attached to that thing I wouldn't know what they're called, Curvetech Thrusters? They look expensive. Anyway, all very doo'able with Arduino, and then some  smiley
GPS would be neat but expensive. and would it work well underwater? I was thinking of putting things in like pressure sensors that set off a land alarm if it gets too deep and meb if i find another arduino/other microcontroller a computer interface. Could i make it wireless with xbee? or would it not work well underwater? I like the sub style idea but  that has some problems like that i dont have a submarine shaped shell. and i would then also have to figure out a water ballast system. The tube shape may work though, a large piece of pvc pipe with the electronics inside would definitly work but then roll in the water is an issue. They all have advantages and disadvantages including the clasic design. I love the idea of having the relays. so with a 5v relay 5v activates the switch but does it matter how much current goes through the switch after activated? and what about the analog output so i can control the speed of the motors how would a relay deal with that? Do you think toothbrush motors could really do it? with a camera, sensors, stuff to waterproof all the electronics etc.. i was looking at inexpensive electric screwdrivers I saw another ROV with small bilge pumps. i have no idea for batteries yet. and if i if i go wireless with xbee how to handle the camera.
thx for the help
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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  :-)
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I think if variable speed is an issue, then you'll be needing another solution, and not one that springs to my mind.

I had envisaged the motors would be turned on to initiate thrust, and when that's been achieved, they'd be turned off. Using two relays, forward and reverse wouldn't be a problem, and using daisy chains of 74HC595 shift registers, 8 relays each, you can control any number of relays, which incidentally, have a UL/C-UL rating of 10A 28VDC / 12A 125VAC.

You can hack this code ( http://www.arduino.cc/en/Tutorial/ShiftOut ) for controlling the relays, substituting the LED's and bypassing the 220ohm resistors.

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.

Attached to large enough propeller, I think the tooth brush motors would be perfect, they aren't expensive either so you could use a few for thrusting in different directions. Electric screwdrivers would also do the job.

Your battery options are wide open if your using relays, XBee "apparently" works underwater (properly sealed). Maybe Arduino BT could function underwater, if I had one, I'd throw it in a bath tub to test it for you unfortunately I don't, so perhaps someone else might volunteer.

Here's an interesting link with more info on XBee:-

http://blog.faludi.com/category/networking/

The Arduino, I recently discovered, fits nicely inside the old audio cassette boxes, with room for batteries. You'd need to check if there's room for an XBee, fortunately, that also won't cost much to determine.

For water-proofing, silicone sealant doesn't cost much. Though, a few months back I starting working with thermo-plastics (Easycast) which allow you to sculpt a clay model, make silicone (Ultrasil) molds, and fabricate any shape you can imagine in plastic.  So, building a custom water-proof enclosure would be a matter of adapting something that's already water-proof, or, you could build one specific to your requirements.  

Cameras and control, unfortunately I haven't reached that chapter yet either  ;D
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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

Quote
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.


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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/
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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.
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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.
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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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yip, lots of theory to test  ;D

If you have another plan for reversing polarity, then for sure go with that.

I'll take a crack at building something autonomous, with tooth brush motors, with relays, with gps, with XBee. Worst case scenario, it doesn't work, but I like a challenge when I've got the time smiley
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yip, lots of theory to test  ;D

If you have another plan for reversing polarity, then for sure go with that.

I'll take a crack at building something autonomous, with tooth brush motors, with relays, with gps, with XBee. Worst case scenario, it doesn't work, but I like a challenge when I've got the time smiley


heh heh, yeah. I like the relay way.  arduino has got pletny of analog outputs. im going to hold off on gps and xbee. expencive stuff. but yes. i should probably start with something smaller scale like this http://www.rgu.ac.uk/eng/robotics/page.cfm?pge=8192
PS. does that ajustable resistor thing from afew post back egsist?
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heh heh, yeah. I like the relay way.  arduino has got pletny of analog outputs. im going to hold off on gps and xbee. expencive stuff. but yes. i should probably start with something smaller scale like this http://www.rgu.ac.uk/eng/robotics/page.cfm?pge=8192
PS. does that ajustable resistor thing from afew post back egsist?

Perfect, but lost me re: resistor?


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heh heh, yeah. I like the relay way.  arduino has got pletny of analog outputs. im going to hold off on gps and xbee. expencive stuff. but yes. i should probably start with something smaller scale like this http://www.rgu.ac.uk/eng/robotics/page.cfm?pge=8192
PS. does that ajustable resistor thing from afew post back egsist?

Perfect, but lost me re: resistor?



From a previous accidental double post
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.
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I cee, yip that would work, use one for max and another for half - I still like the pulse idea though, I'll be trying that one with trusty tooth brush smiley
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