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Exploring the Hobby of Building your own ROV - Imagine, Create, Inspire.
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 Post subject: Skagen ROV
PostPosted: Jul 23rd, 2017, 4:18 pm 
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Joined: Jul 22nd, 2017, 12:11 pm
Posts: 5
Hi!
This is an ROV project I've been working on for a while (in between browsing this forum!) it's main purpose is just to have a look around Skagen harbor in Denmark, so it's only intended to go down to about 5-10M (next versions will hopefully do more).
File comment: Top view of ROV
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File comment: front face of the ROV
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File comment: Isometric view of the robot
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File comment: Back View
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As you can see it has lasercut plexiglass side panels where the bilge pumps are mounted, and a hull in the middle where all the electronics are stored. The ROV has 4 bilge pumps, with the two vertical ones for up/down movement and the other two for forward/backwards and turning. The two vertical ones is probably overkill, but I couldn't find a way to position them with an imbalance of weight. All the green and black parts are 3d printed, so those are the parts that hold the motors and the hull in place. There are 10mm stainless steel rods that connect the whole thing together, I chose to do it like this so it could be modified easily.

I designed the whole ROV in Onshape, an online CAD software that I would really recommend
File comment: Onshape CAD screenshot, ROV in early planning stage
ROV2isometrictrans.png
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The hull is made of PVC and has end caps, which I'll show soon enough when they are ready and watertight, the whole robots runs off a 11.1 V battery inside, this battery provides power to an arduino uno inside the hull which controls all the bilge pumps through motor controllers. The arduino "talks" to a PyBoard on the surface through 9600 Baud serial and a 30M cable containing the 3 wires need for serial, I choose the board as it allows you to program in Python which I'm much more familiar with then C.
File comment: This is the controller for the ROV it's 3d printed, the PyBoard is clearly visible on the top, the two joysticks control movement and the switch lights.
controller.png
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Live video is provided to the surface through a USB webcam in the robot, this USB signal is passed through a 30M Ethernet cable and converted back to USB on the surface, there is no power increase or anything, you just plug it in and amazingly it works!

Since I've been building this for a while I don't have any build photos, the entire system was tested just before Easter where I wired everything up, and was going to waterproof it so it would be ready for the sea, but I decided to redo the wiring and add a grabber, which I'm working on now. The ROV is at the moment very heavy so I also need to figure out how to stick some floats on it, which is just one of many things to be done!

Please give feedback! I haven't tried it in water yet, what are your thoughts?

-MantFish <><


Attachments:
File comment: Closeup view of the 3D printed hull holders
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File comment: Closeup view of 3D printed bilge pumps motor holders
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 Post subject: Re: Skagen ROV
PostPosted: Jul 24th, 2017, 12:39 am 
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Joined: Oct 17th, 2013, 5:21 am
Posts: 32
Location: Germany
I love the simplicity of your design but it also provides everything you need. Also the idea of using a lot of 3D-printed parts. I did the same in my ROV.
Hopefully the PVC pipes can hold the pressure. They dare not made for pressure from outside.

Keep on. It looks very promising.


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 Post subject: Re: Skagen ROV
PostPosted: Jul 25th, 2017, 2:24 pm 
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Joined: Jul 22nd, 2017, 12:11 pm
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Thanks ArduRov!

Yes, I hadn't thought about that but you're probably right, what I think I might do to counteract the outside pressure is 3D print something along the lines of this:
insidebit.png
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It will sit inside the hull and hopefully the 3D printed parts will support the pressure...? It will also serve as the "tray" to mount the electronics on. But I have no idea if this is a good solution. Any thoughts?

I've also made progress with the grabber, I bought a "waterproof" servo motor off aliexpress, I have no idea how waterproof it really is but it cost around 9 euros, and free shipping, so it's not the biggest loss if it breaks. I designed (with fusion 360) and 3D printed a sort of frame for the servo motor and the arm that doesn't move to sit in, and an arm that moves on top of servo motor. Everything's held in place with some M3 screws and nuts and here's a video of it in action! In the video the PyBoard is getting the value of the resistance of the potentiometer (the x axis one in this case) in the joystick, and depending if it's higher or lower then a certain value, i.e not in the middle, it sends the character 'U' or 'D' to the arduino which then movies the servo clockwise/anticlockwise respectively by 5 degrees.


And some photos
servograbber2.jpg
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servograbber1.jpg
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The idea is for an 8mm rod to go through the hole on the servomotors frame, and nuts to secure it in place and then I'll 3D print some parts to go attach the 8mm rod to the bottom of the ROV once I find a place where it doesn't obscure the footage too much but where you can still see what it's supposed to be grabbing! The grabber is actually surprisingly strong, and can easily carry a large screwdriver.

-Mantfish <><


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 Post subject: Re: Skagen ROV
PostPosted: Jul 26th, 2017, 3:47 am 
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Joined: Nov 28th, 2011, 11:24 am
Posts: 121
Looking good Mantfish.
I think you'll be fine with the pipe down to 30m no problem. water pressure is only 43psi at that depth.
3D printing seems like a great way to prototype things, I'm still machining stuff out on the lathe so it takes a bit more work.
Are you planning on ducting the props?
I'm not familiar with 3D printing but can you vary the density of the plastic so you could print floats?


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 Post subject: Re: Skagen ROV
PostPosted: Jul 26th, 2017, 4:36 am 
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Joined: Jul 22nd, 2017, 12:11 pm
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bigbadbob wrote:
Looking good Mantfish.
I think you'll be fine with the pipe down to 30m no problem. water pressure is only 43psi at that depth.
3D printing seems like a great way to prototype things, I'm still machining stuff out on the lathe so it takes a bit more work.
Are you planning on ducting the props?
I'm not familiar with 3D printing but can you vary the density of the plastic so you could print floats?


Thanks bigbadbob, And that's a relief that I won't have to worry about that! I have to agree with the fact 3D printing is great for prototypes, I think the problem with making 3D printed floats is that although you can easily vary how much plastic is inside the part (the infill) if your outside layers print badly (as they do!) Or the pressure manages to force water inside, then you're in trouble as the density will change. I think Steve filled his 3D printed parts with buoyancy fill, here: http://www.homebuiltrovs.com/rovforum/viewtopic.php?f=18&t=1668&start=30 and that is probably the way to go, but thanks for the idea! Maybe this way I can make some really nice streamlined floats!

And as for the ducting of the props, I'm not sure, since my ROV is intended for a big harbor I thought it would unnecessary to, because I thought it was mostly for preventing tangles when I designed and printed the parts that hold the motors, but now I'm not sure, does it make a big difference?

-MantFish <><


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 Post subject: Re: Skagen ROV
PostPosted: Jul 26th, 2017, 11:02 am 
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Joined: Nov 28th, 2011, 11:24 am
Posts: 121
To duct the props properly to maximise thrust you need props designed for ducting, the ones with square tips to the blades,
but I would guard your props because even seaweed or debris floating in the harbour can foul your props.
And if you ever hit a jellyfish.... well you can imagine the mess. hahahaha...


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 Post subject: Re: Skagen ROV
PostPosted: Aug 10th, 2017, 3:52 pm 
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Joined: Jul 22nd, 2017, 12:11 pm
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bigbadbob wrote:
To duct the props properly to maximise thrust you need props designed for ducting, the ones with square tips to the bladtes,
but I would guard your props because even seaweed or debris floating in the harbour can foul your props.
And if you ever hit a jellyfish.... well you can imagine the mess. hahahaha...


Yes, ducting the props is probably a good idea, although I don't think I'll do this right now as the motor "holders" are already in place and replacing them would be a lot of work, and right now I really want to get this thing in the sea!

Since the previous post I've been working hard on the inside of the ROV
IMG_20170803_204643.jpg
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So far it looks like this, the led ring is a 12V LED car headlight circle, which is really bright and was very cheap, underneath it is the webcam. These are mounted on two 8mm steel rods that run from a circular base to the end, the idea is that all the electronics are mounted on these, and these rods are glued onto the back piece of the ROV which can be removed, so as maintenance and recharging the battery is easier!

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Here's a top and side view of the inside, the big green circuit board on the top is one of the motor controllers, underneath it is a voltage regulator and the Arduino, underneath it is the battery. Up front the second motor controller and a relay for the LED ring and the master on/off switch. This switch also means that I don't have to unplug the battery every time I want to recharge it, as all I have to do is turn off the switch and connect the charging station to the female port that I soldered on the side of the switch that the battery is soldered on to. I did this as in my experience you need to exert considerable force to disconnect the battery and it's port, and I didn't want to risk destroying the solder joins. The rather long USB wire of the webcam that has to be converted to Ethernet is wrapped around the battery and the entire thing does fit inside the hull, although it is tight!

Everything is working as it should and I'll soon post more!

-MantFish <><


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 Post subject: Re: Skagen ROV
PostPosted: Aug 12th, 2017, 4:25 pm 
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Joined: Nov 28th, 2011, 11:24 am
Posts: 121
Nice work there Mantfish.
I like the way you've mounted the electronics on a removable chassis.
Nice to be able to remove it all in a oner for access.
Looking forward to seeing it swim. :-)


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 Post subject: Re: Skagen ROV
PostPosted: Sep 12th, 2017, 3:29 pm 
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Joined: Jul 22nd, 2017, 12:11 pm
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It's finally gone into the bath (and had a paint job)! Here's a video of it, everything is working well, I need to change some things though, the LED ring at the moment over saturates the webcam's image. I also need to come up with a nice solution to how to secure the float, as the float in the video isn't the final one, and how to store the bilge pump wires. So once again advice is appreciated!


Waterproofing surprisingly hard, I did what Steve suggests on his page with epoxying and so far it is working well, for around the acrylic in the front I used silicon.

Don't hesitate to ask for details!
-MantFish <><


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