DIY ROV
Months ago I decided I was going to build my own underwater remotely-operated vehicle. I got sidetracked by a kitchen remodel, but since it is now complete I will have some free time to start working on my vehicle. There are some decent videos out there where others have done the same thing, some are wildly complicated and others are basically built from items out of a scrap bin. I am hoping to land somewhere in the middle.
During the bit of research I have performed, I discovered companies selling very high-end parts, the likes of which you would find on a highly funded/sponsored deep sea expedition or a government project. I didn't find a whole lot of middle ground really, either you DIY or you dump a ton of money into it.
My plan is to use PVC for my hull. I had thought about constructing it similar to the Russian Typhoon-class submarine, with two pressure hulls within an outer hull. That would allow the electrics to reside in dry compartments while I use the void space for ballast. I even found RC submarine ballast systems on eBay which would allow me to take on water and dump it remotely so I could trim it out on the fly.
The general opinion, I have discovered so far, is to make it neutrally buoyant. As much as I would like to add that ballast tank system I may need to just keep it simple for my first attempt. Tethers also seem to be an issue, adding too much weight when they get to a certain length and if you do not take steps to make them buoyant. I thought pool noodles, but learned from someone else that they become water logged and are a bad choice. Then there is power, the trend I noticed is keeping it onboard in the form of a battery pack, but I would like to keep it ashore and just add a wire to the tether so I can not have power to worry about.
So far I have an Arduino board, some old laptops, and some rivers to explore. If we had a makerspace or hackerspace nearby I would be all set. I did search, and the closest is an hour away, which is disappointing since I know I am not the only person into ridiculous projects/hobbies around here! Anyone on here into things like this?
I love things like this! The added challenge of doing it underwater seems really fun. I could see myself setting up pumps and ballasts and all sorts of fun stuff.
As for the tether, I'm not sure how I'd feel about running power lines to the thing. I'd be worried about snagging on something and possibly shorting out, exploding the lithium battery you have with you on shore. Then if the motors on board require any significant amount of power, you'll need to run thicker gauge wires, which are less flexible, more expensive, and heavier. Plus if they're especially long, you'll have to deal with the resistance of the wires, causing a voltage drop by the time it gets to the sub. The batteries would also work as ballast, so I can see why people would put them in the sub.
What sort of hardware are you looking at using? If you'd like a recommendation, I've been playing with ESP32 boards lately and they're incredibly capable. They have wifi, bluetooth, BLE, dual core processors clocked at like 200mhz, 4MB flash, all sorts of I2C, SPI, PWM ports, 3 hardware serial ports, all kinds of shit. They're basically more powerful than the first PC I owned, but they cost ten bucks. Pairing them with a OV7670 I2C camera is really popular, and the chips have plenty of power to stream video over wifi or similar.
I had thought I was brilliant, that I would make this thing work with WiFi and Bluetooth so I could reduce or even eliminate some wiring on the tether. Nope! Won't transmit through water, not far enough anyways to be useful from what I have read on the subject so far.
Voltage drop was a concern, but I don't plan to have a 1,000' tether. I am looking at maybe 250' to start. Hollow-core nylon line seems to be the best choice for something at this scale, you can pass the wiring within the line itself which acts as an abrasion shield as well as keeps it all in a tidy package. I was looking at keeping the battery ashore because I know I will be fighting the current quite often, so battery life will be a concern. I may look into having multiple batteries, some for the lighting, others for the "brain", and the rest for propulsion.
Funny you mention the ESP32 boards, I ruined an F-3188 board several months ago trying to solder it to a breakout board. I am thinking about grabbing the ESP32 to give that project another go since it has some nice large pins to work with! At the moment I have an Ardunio Uno board, and have a schematic that someone else came up with to use a PS3 controller to operate the vehicle with the same board. If I keep all my batteries onboard, then I am sure I could use some Cat5 or Cat6 cable within my tether since there would be no real load. Tough part would be finding stranded Cat5/6 instead of solid core.
I decided a garden hose reel would be perfect to wrap the tether around, it would pay out easily enough and I can reel it in just as easily. Not to mention, it has wheels and a handle so transporting it would be easier than lugging around a coil of line. If it works out, and I enjoy it enough, I may move on to building something better like a wagon where everything is more permanently installed and make it more self-contained. I figure by the end of summer I could probably prowl around boat launches and docks to find a fair number of fishing poles and tackle sitting on the bottom forgotten. If nothing else I can at least watch how the fish behave, like my own nature documentary.
Hmm, yeah, water just loves to absorb radio waves. Maybe another option would be to put the antenna on a buoy of some sort. But then you also have more latency to deal with, which if you're going to be fighting currents might be a problem. If you're taking the thing into a river, you'll probably want very responsive controls.
It does seem really appealing to lose the tether though. I'm still sketched out by the idea of running such long power cables. The motors they're using in the youtube video you've posted below are rated for 18A each. Let's say you're using two, and only running them at half power. That's still 18A, so you'll probably want at least 6AWG, if not 4. You're going to want high-strand-count silicone sheathed RC wires for flexibility, edit:
so if you cut corners (the water will cool the cable) you're looking at $3.50/m for 8AWG, so you're going to be paying out the nose, and ending up with substantial voltage drop. The spool will also weigh like 30lbs, which is a bit inconvenient to carry.Edit: Err, nope. You don't actually want to rely on the water to cool the cables, unless you submerge the payout spool as well. The coiled wire is going to get pretty hot being all coiled and sheathed.
Also, don't trust my wire rating abilities. I really don't know what I'm talking about. I googled "wire size calculator" and all the ones I could find were targeting a max 5% voltage drop over 250 feet. So, if you stick an extra lithium cell on, you can probably get away with much smaller wire.
I will probably go with a battery pack, if I can find a spot welder cheap enough I might even build my own battery pack so it can have a custom fit into the hull. If i lived near the Gulf coast I would be trying to pick the brains of the people who operate/maintain ROVs out on the oil wells! I wanted to lose the tether so I could not worry about getting tangled, but I now think having it is a great way to ensure I don't lose the thing!
When I used to live in the Caribbean I often thought about making an ROV, but never did. I do play with all kinds of R/C aircraft though. When I was thinking about an ROV I considered using an old large Ikelite underwater camera case for the hull. The ones for outdated cameras are pretty useless and cheap, and I happened to have one laying around. They are square and not very fluid dynamic, but with a tether you are not thinking about speed. I was definitely thinking tether, for power and the feed from the go pro I would put in it.
In any case, good luck and keep us updated!
I am planning to use the ducted fans from RC aircraft for my propulsion. There is a guy on YouTube who has tested them underwater and they produce some great thrust even in water. This guy has taken it pretty far in the testing department! He has some good videos if you are interested.
Cool channel, thanks! Hmm, I was thinking saltwater so I was planning on putting the motors in the case, and using some sort of bushing and bearing around the shafts. But I honestly never got too far down the road of design.
If you watch the video you can see that he is testing in saltwater, and even having them exposed they still function properly. You would want to flush them with freshwater after use, and their life would be shortened, but they are inexpensive enough to not really be worried about that bit. I'm going to be in freshwater, so I am even less concerned. Some guys I have seen are using bilge pumps for propulsion instead of RC motors.
Oh, wow. So check these guys out: https://www.bluerobotics.com/store/
They have thruster pods for relatively cheap, and all kinds of other interesting parts for an ROV, including the hull.
They are in my bookmarks, I planned to get my acrylic dome from them since I have no way to make one, but thanks for sharing! I had played with RC quad-copters for a while but they can get expensive fast and if you lose it then it's just gone. With this being on a tether I figure it's going to be extra difficult to lose it!
Dude that sounds like such a sweet summer project. I wish I could offer you input, but my knowledge of technical stuff lacks depth. I haven't looked into any submersible designs so it's pretty much all over my head. I tend to dive in head first when it comes to practical fabrication and assembly though.
Okay maybe that was laying it on a little thick. I'm running out of underwater puns though.
Are you gonna do any progress pics? I love that kinda stuff. And I think it can be a really useful way of getting feedback and suggestions as it progresses because it makes it easier to see the details of how the concepts are executed and what potential design issues might arise.
Once I get going I will be taking some photos, try to document progress. It's all over my head as well! I've flown some RC quads but this is all uncharted territory for me!