Questions for a ROV (tethered sub)

[jibeling]

OK I am new here. I am going to describe what I want and hopefully get direction on what to buy. So here goes.

I want to build a ROV (Remote operated vehicle). I've been reading some posts and websites but here is a list of requirements:
Ideally would be fully remote, worried about crash and burn though. Thoughts lean to a serial cable hookup.
Depth 100' Not sure how well remote controls work underwater.
Camera
3-4 motors, 2 for forward/reverse/turning and 1 for up and down. Note these need forwards and reverse capability. max current ~2-3amps
multiple i/o  for sensors maybe grippers
I was thinking using a joystick with pots for movement

I can program but I am not wonderful by any means, so programming needs to be beginner to intermediate
I am not an electrical engineer, mechanical actually, so no homemade circuits please. remember KISS.
The camera should be good for low light/contrast. I will have lights on it, but you know how things go.

So the questions I have is:
Control method? ethernet serial radio freq? if it has a cable that is OK. Gives a retrieval method using a cord along side.
Control circuit? Circuit with a processor? H-bridge setup for motors? Remember not an EE so most would need to be off the shelf, or easy to build
Programming? language software, code links.

[airman00]

dunno if you saw this yet

http://www.popsci.com/diy/article/2006-08/homemade-spy-sub

[Admin]

This might help you some:
http://www.huv.com/uSeeker/index.html


I'm building a robot fish, and I can tell you the #1 hardest problem you will face is water proofing. I noticed it wasn't even in your list

Oh and remote control works, but the range is really bad. Like 10's of feet tops. Lower frequencies travel farther in water - and don't even bother with anything above 700MHz (that cuts out most transmitters on the market).

I am not an electrical engineer, mechanical actually, so no homemade circuits please.

I'm a mechanical engineer too . . . but personally I think you should learn circuitry as I feel its made me a much much better engineer as a whole.

[ceruleanplains]

I'm also really interested in cloning the ROV airman00 linked too. 

An ROV will likely need a GUI - much like the Rollette's project (see airman00's post).  They provide the software at that site, but it's specific to that ROV project and source code isn't provided (I also asked the programmer). 

C# or Visual Basic seem to be the primary options for a GUI.  There's a few books out there for automation of processes over serial connections via Visual Basic that I've found and used in the past.

For my project, I'm prototyping my interface using a ground based robot first and going to try and experiment with the Parallax Boe-bot connected via 'tether' and compiled using the Microsoft Robotics Studio.  I'll also try to control it with a joystick.  Later I'll drop the TTL and go wirelessly via bluetooth.  I'm chosing this approach to reduce risk - both by keeping it out of the water and to make sure the control algorithms work. 

Then I'll prototype an ethernet connection on an AVR board probably and try again with adding the video controls, lighting controls, sensor monitoring, etc.

If you use prop screws instead of the bilge pumps, you may be able to test the motor control out of the water depending on the thermal range of the components. 

The tether itself should be also tied off to another location before the laptop! If something bad happens with your control software and the ROV takes off and stretches out the cable you could not only lose your ROV but your laptop too!  So I'll also build an anchor post with this in mind... 

Project starts in May!

[jibeling]

I have the waterproofing down pat. Motors are good to 100+ feet with no leaks. CNC is awesome. I also have the rest figured out for waterproofing, ie wires, push pull etc. Seals are rated for 3000 psi. So I am reading a ton and trying to get enough info and knowledge to ask somewhat decent questions. So questions I have is this.
1. H bridge motor controllers run off Digital IO correct? I will need a minimum of 3 h bridges to control mine.
2. I am looking at using a laptop to connect to the ROV via serial or ethernet. Any suggestions which one?
3. Seeming how this is my first setup I am looking at the following Robot Controller. How does this compare with what I am trying to do? 3+ h bridges, 1 pressure transducer, 1 temp sensor, 1 servo. Might be overkill but then I have room to expand and play.
http://www.roboticsconnection.com/p-16-serializer-net-robot-controller.aspx

PS If anyone needs Solidworks cad work done, let me know. I have 2007 on my comp.

[ceruleanplains]

Actually, I really don't think that serializer will work.  It's wireless - so I'm sort of confused at your intent there.

I'm planning on using ethernet because of the bandwidth. 

I was looking at getting Solidworks for this summer's build myself.  I was inspired by the Admin's tutorials to look into it more.  I miss my AutoCAD license for windows 98... that was no longer supported by XP.  But having since used Solidworks for design, definately better program for 3D (at least at that time).

[jibeling]

Is there a controller that you would recommend? I am all ears. That has been an issue for me is figuring out which one will work for me. I saw the serializer site said it can be connected in several different ways. Look at the pics on the page. It said it is able to be connected bluetooth as an option. I had already thought of the laptop/anchor scenario, it would rather suck. lol. I will be using propellers, not bilge pumps. I never liked the bilge pump idea. SolidWorks and Pro/E are sooo much better than AutoCad. I know AutoCad has made some strides into the 3d realm but still is a 2d tool in the engineering world. Very nice for electrical schematics however.

[ceruleanplains]

If you're planning on having the serializer you mentioned on the sub - then I don't think it would work.  Bluetooth under any amount of water is not going to work.  It's a higher frequency RF channel that penetrates poorly through water.  I am considering that anything that I put in that bot is going to be considered expendable, so the throwaway cost has got to be reasonable and that board is not that reasonable to me - especially for a prototype design with moderate risk.  A swimming pool isn't as high of a risk but a river or ocean is a very high risk.

Seperately there's all sorts of weird things that can happen underwater and having a method to ground the sub from a electrostatic discharge is a good idea, which may be some grounding through the ethernet cable to the anchor. I liked Jason Rollet's approach of the tethered ethernet cable actually since the data rate can be pretty high for video transmission.  You have to build your own proto board, but that's not that big of a deal especially since he beautifully provides the specs on the site. 

I honestly intend to try and mimic a lot of his work with a few exceptions like enlarging the PVC diameter from 2" to 4" over more of the body to allow for maintainance room and assembly.  My hands are too big to play in those tight areas.  I also plan on jacking up the maximum power on the lights and using LEDs to reduce heat and power consumption as well as building a custom heat-pipe system for heat transfer to the water.  I do plan on using the bilge pumps for my initial design.  My friend has a sailboat and we can pawn them off to others if we want to convert propulsion systems.  Mainly I haven't found cheaper alternatives.  For increased control authority, you can add jet vanes to the piping and eliminate the individualization of 1 pump per exit nozzle.   You can also add some pressure regulator feedback and solenoid gates to pulse the thrust.  And also Rolette mentions the obvious you can reduce the exit area to increase the exhaust velocity.  I also plan to vary the design by having a specialized payload module that can be 'easily' changed out.  This is for experiments of various types including new cameras, sensors, etc. to be added on a future revision that I'd want to test out.

[jibeling]

Bluetooth will not work but a RS-232 cable will work. They have a serial plug to hook directly to it. Pretty sweet. I was talking with the President of the company a bunch. It will work quite well for what I am doing.

[ceruleanplains]

or you could build your own for $20.  : )