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NÃ¸kken - Underwater Exploration Vehicle

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uzzors2k

Thu May 27 2010, 01:06PM

Registered Member #95 Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308

NÃ¸kken - Underwater Exploration Vehicle

As some of you may remember, I've been working on an ROV since Christmas. Progress has been slow, but steady, and now just two weeks before I hoped to have it finished I have yet to test it in water! What have the last five months been spent on?

January/February/March: Idle shopping on ebay and browsing various DIY ROV websites. A good month was spent programming an ATmega8 and VisualBasic program which could communicate with one-another. The end result is a control board with camera feed, PWM light control, forward/reverse of three motors, battery level monitor, temperature sensor and a leak detector. All communications to the surface are sent through a 4-wire cable (cat-5 paralleled at each end) and received by any PC with two USB ports and appropriate drivers. Camera feed is received using a 20$ EasyCap device, while the serial commands to the ATmega8 are sent over RS-485 thanks to an FTDI chip. Most of the project time was spent creating this interface, despite it not seeming like a big job initially.

Camera feed is provided by a small PCB type composite video camera, 30$ at Sparkfun. It's excellent at adjusting to various light levels, and works best in near darkness, which suits the ROV well. Lighting is provided by two 10W LEDs, though I will probably only run them at 20% duty, where they seem to give more than enough light for the camera. Power is supplied by a 8Ah 12V SLA battery.

April: The fun is beginning! PCBs were made for the electronics and soldered up, and the tether assembly was made. I had seen the "HomebuiltROVs" guy had made a slip-ring reel for his tether, and I thought something like that would be vastly more practical than throwing cable overboard and reeling it again by hand. Having waterskiied for some summers now, I knew that this would only result in headaches when it came time to untangle the mess, especially if the ROV couldn't be disconnected from the tether. A decent amount of woodworking went into the tether reel, and with two coats of varnish it should hold up to salt water splashes. The slip ring is a professional unit purchased on ebay, well worth the money. The electronics housing is simply an ice-cream container. Thrust is provided by four 360gph bilge pumps. I've modified them to use propellers, using some modified RC components (also from ebay).

May: Finally the actual ROV construction started. The circuit boards were put in tubs and submerged in hot wax, rendering them pretty much water tight in the event of a leak. The camera PCB was simply covered in RTV silicone, so it can withstand splashes at least. I was worried about wax seeping in on the camera sensor, otherwise I would have submerged it too.

I found a neat PVC coupler with an O-ring sealed lid at the hardware store, which solved several problems. I could now use a battery with twice the capacity, and not have to worry about maintenance. An old pop-bottle crate was used as a foundation, and after some cutting I had mounted the PVC pipe, bilge pumps and LEDs by using some zip-ties. Hull penetrations were done using some water-block nipples from an old water cooling setup, and lots of RTV silicone.

1274965030 95 FT0 8rov Electronics Housed

Well, thats enough writing for now, I have to get better at starting project threads earlier. What remains is to test the ROV in my bathtub to see if it leaks and how buoyant it is.

uzzors2k

Sat Aug 21 2010, 02:46PM

Registered Member #95 Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308

Alright, long time no see. Since my last post I've taken the ROV out for a few tests, in both a nearby lake and the ocean. I haven't been able to make the ROV entirely watertight yet, and as the main chamber filled with water the ROV would begin to tip backwards. To counter this, I sealed an ABS pipe full of air and suspended the ROV beneath it, while placing weights on the bottom of the ROV. This keeps it stable even as the hull takes on water.

With that the ROV was finally ready for a proper test. In the ocean! All in all, it was out for about 30 minutes, but because of the camera angle (straight forward), there is only a few minutes of interesting footage. None the less, it's enough to make me eager to improve the ROV further, and hopefully take it much deeper. In the video below the ROV was driving near the surface down to about 3 meters at the most. At that depth a few centimeters of water had already collected in the hull. Upon inspecting the hull later I've found a fracture, so the PVC drainage pipe is definitely not pressure rated. The major problems so far have been water leaking into the hull, water leaking into the tether connector, seaweed jamming the propellers and the tether itself sinking. The poorly chosen camera angle was a real bummer too.

See the video here:

I plan on fixing these problems soon, and I've already dismantled the ROV. The plan is to seal all of the electronics, camera and wire connections in wax, that way leaving no empty space for water to leak into. I'm also looking at some IP68 rated connectors for the tether. I'm not sure whether I should leave the battery on board or not at the moment. Keeping it on land would remove the need for an openable, watertight container, which would vastly simplify waterproofing. On the other hand, I would need a new tether, and heavy currents flowing beside the camera feed might introduce too much noise.

I just noticed I haven't explained the name yet. NÃ¸kken is a supernatural being that lives in small inland waters and is a shapeshifter. It tries to trick people into drowning, often by changing shape into a horse, which when mounted would charge into a lake and take you to the bottom with it. I've never liked water, and a certain illustration by Theodor Kittelsen came to mind when I saw the LEDs glowing.

Jiffycoil

Sat Aug 21 2010, 03:17PM

Registered Member #2524 Joined: Wed Dec 09 2009, 06:29AM
Location: Johns Island, South Carolina
Posts: 23

Well done on the ROV. I love the video and music.

Reaching

Sat Aug 21 2010, 05:32PM

Registered Member #76 Joined: Thu Feb 09 2006, 10:04AM
Location: Hemer, Germany
Posts: 458

In the video you see some fish, a lion's mane jellyfish and my uncle

.. hrhr and my uncle, a terrifying deep water beast^^

well done.. never seen anything like this done with so few $..

Hon1nbo

Sat Aug 21 2010, 09:58PM

Registered Member #902 Joined: Sun Jul 15 2007, 08:17PM
Location: Pacific Northwest USA
Posts: 1042

great job on the sub!

now I need to renovate mine lol

-Jimmy

uzzors2k

Fri Aug 27 2010, 02:23PM

Registered Member #95 Joined: Thu Feb 09 2006, 04:57PM
Location: Norway
Posts: 1308

Thanks for the replies!

Adam Munich

Fri Aug 27 2010, 03:00PM

Registered Member #2893 Joined: Tue Jun 01 2010, 09:25PM
Location: Cali-forn. i. a.
Posts: 2242

You should also figure out a way to steady the camera. Putting it in a gimbal along with a gyroscope could work nicely. A real gyro (spinning disk kind). A lead disk on a hard drive motor could work nicely. If you need any more cable, I'm your guy! I have 400 feet of the 6 wire stuff.

Torchwood

Sat Aug 28 2010, 12:13PM

Registered Member #2668 Joined: Sun Jan 31 2010, 12:11PM
Location: South Australia
Posts: 18

Very cool project!

It would be great for finding the snags at your favourite fishing spot so you can map where they are and avoid them, you could even find where the fish like to go.

Maybe you could use it to tow a line to the perfect spot and release it then move the ROV out of the way and wait for the fish to come back.

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