Low cost educational ROV

[oceanrov31]

Hi,

I have been working a low cost arduino based ROV and wanted to share my progress with the community. The ROV topside consists of a laptop running a GUI using
microsoft visual c# and a USB to serial UART converter/circuit that interfaces with the tether, a USB gamepad controller with joystick provides control as well as the GUI. The tether is a duplex plastic fiber optic cable running in center of a nylon braided rope strain relief member. Subsea the ROV uses an arduino Mega 2560 to do all the processing and control. The thrusters are low cost brushed dc motors in film can housings with 3d printed parts for the o-ring adapter, propeller and duct. The ROV frame is just PVC pipe and some packing foam for buoyancy. There is a video camera using Arducam that sends 5-10 fps video depending on the resolution also can take high res stills. Has LED lighting, compass, depth gauge, battery voltage and current and sonar altimeter. A 24vdc Li-ion battery pack is planned to run the electronics subsea so there is no need power conductors in the tether. Still need to make a subsea housing from acrylic + endcaps. The ROV is meant a to be used as an educational exhibit for youth/adults.

https://www.dropbox.com/s/p87y1srn2iodw ... c.jpg?dl=0

[Oldsirhippy]

Thanks for posting your ROV design.

Your Design is impressive and am intrigued to hear more on the fibre optic system you used. What I have seen from other posts is that the Tx and Rx for fibre optic cables are expensive and can be cumbersome for smaller ROVs - how did you get around these issues?

You have populated your ROV with many of the features that I aim to have in mine too Gives me hope that I am on the right track.

The only concern I have is regarding depth that can be achieved, the float foam (is it polystyrene?) used looks like the type that may well crush with pressure.

It's great to see someone using C#, I too have settled on that for my GUI having done the rounds of various other s/w and found them wanting. Would you post pour code so that we may learn what you did and adapt it for our own ROVs? It would be great to see it, the picture you posted looks good.

When do you plan to have it submerged and will you be posting a first dive video?

Well done

[oceanrov31]

thanks for the compliment.

The fiber optic cable is a duplex plastic type i got from Fiberfin, it is a double jacked type cost about $1.60 a meter i think, i could not find it on their site but i think http://www.fiberfin.com/index.php/produ ... cable.html about $1.20/meter
would work fine, maybe better since mine is slightly negative in water with the braided nylon rope, the other would probably be a bit positive buoyant which is i understand preferable. The cable is easy to use. fiberfin also sells a cheap tool for clean cutting the plastic fiber and jacket or you could just use a new razor blade. I did not need to polish the fiber either just cut and put into the tx/rx module. If you do want to polish for super finish i found that auto part store plastic head lamp polishing kit works great and has more supply of stuff( solution and sand paper) than the fiber polishing kit sold.

I am using only 10meters to start but could probably go up 30 to meters maybe more, no problem from what i can tell from the attenuation loss of the cable and the strength of the tx/rx diodes,have not tested at 30 meter but that is just my feeling.

As for cumbersome cable. The actual cable is very light compared to copper and with the nylon rope jacket is still quite flexible and light, so does not seem to be a problem. How do you mean cumbersome in what way?

Topside i am using an adafruit usb to gpio/uart converter pcb http://www.adafruit.com/product/2264, to convert USB to a UART RX/TX serial data stream. there are plenty of these modules out there but this is the only one i have tested running a 1Mbit/S speed baud rate that i use, any higher and i get alot of errors. and even at these speeds it may have be introducing errors as i still get some but am not sure of the source. I use a simple checksum technique for all up/down control/telemetry data that keeps things running smooth. The video is not error checked with checksum but have an exception handler in the gui so i won't crash the app. Subsea the arduino UART rx/tx hookup is simple matter.

Also tx/rx circuit has a simple inverter circuit both topside and subsea as the rx signals need to be inverted. be happy to share that if needed.

The actual tx/rx parts are about 5-10 dollars a piece and have max data rates of 10Mbits/sec i think, about $30 for the set of four. I can dig up the actual part numbers and source if you'd like.

I will probably have some kind of potted fiber to electrical converter subsea so i dont have to use a optical connector bulkhead on the electronics housing, though that is still a option as fiberfin sells optical bulkhead connectors but they are not a perfect fit for the application.

The ROV was intended to goto 10-15 ft depth to start maybe 25-50 ft eventually so maybe the foam is ok but i can always get a different type or cast some stronger.
Blue Robotics sells a buoyancy foam that would work but i did not want to buy i yet.

I would be happy to share the code, although you may not be happy trying to read it in its current uncommented messy state. But for sure if i have time i can clean it up an comment it out. I am still working on it now, it has a few bugs around the issue of selecting video resolution and still shots and not all features are fully coded.

Later this month i will be giving a demo at the local marine science education center, the ROV has been submerged in a aquarium without the electronics bottle so far and it handles nice. just has wires running to the thruster motor driver pcbs. I'm not sure when it will be complete as i work on it when i can and am busy with other stuff but will surely post a first dive video or pic when i get there.

[Oldsirhippy]

Thanks oceanrov31 for your reply.

The cumbersome comment I made was for the encoder/decoder boxes to the optical fibre, not the cable - sorry for the confusion.

Which tx/rx modules did you use? Are they also from Fiberfin?
The actual tx/rx parts are about 5-10 dollars a piece and have max data rates of 10Mbits/sec i think, about $30 for the set of four. I can dig up the actual part numbers and source if you'd like.
Thanks - it would be interesting to see how you did the encoder/decoder to the fibres.
Overall it looks like you have a good working low cost solution for an optical fibre cabling system up to 30-50m.

As I am a noob with C# - anything that helps me get going would be a bonus, even if not commented. I program in C, assembler and Arduino C++ so can figure out what you have done. I tend to program at a low level as I am mostly into hardware electronics, rather than high level software development.

I look forward to seeing a video of your demo - hope it all goes well.

[oceanrov31]

hi,

the parts i used for fiber tx/rx are http://www.digikey.com/product-search/e ... s=fb142-nd
and http://www.digikey.com/product-detail/e ... ND/3461614

also used a cd4011 quad nand gate configured as an inverter on the Rx outputs since the Rx signal was inverted by the photodiode reciever circuit.
i use cd 4011 cause thats what i had in my parts bin. The Tx and Rx then go to the arduino and adafruit UART Rx/Tx pins and you've got the fiber link.

I am also pretty novice at C#, took a C course years ago but forgot most of it so learned most of visual c# from others examples and youtube videos.
the difficult parts were for the digital video most that is modified from the ArduCam manufacturers code and joystick gamepad controller for which i use slimDX.
will post code for subsea and pc when i get a little time in the near future. I am using visual studio 2013, what are you using?, i can create a template so you can have the code and the all the GUI graphics elements included, if i remember you just put that into a template folder for for visual studio and it should run.

[oceanrov31]

hi Oldsirhippy,
here is the code for the ROVGUI and the rov. ROVGUI is written for visual c# in visual studio 2013, and the ROV code is for arduino mega 2560.
i'd be happy to answer any question about it or the specific components i'm using i.e. compass, depth gauge etc. mind you this is working code
and a bit messy, but it should give the basic idea., You will need slimdx installed on your pc as well as a usb gamepad joystick controller, i use a logitech model.

[Oldsirhippy]

@oceanrov31 Many thanks for the code, brilliant - I'll have a study of it. I am looking forward to seeing your interface to the arduino and also the camera.

[oceanrov31]

short video demo of rov at local marine science workshop