Underwater ROV

391,997

863

212

Published

Introduction: Underwater ROV

This instructable will show you the process of building a fully functional ROV capable of 60ft or more. I built this ROV with the help of my dad and several other people who have built ROVs before. This was a long project that took al summer and part of the beginning of the school year.

Step 1: Design

In order to keep the ROV stable in the water, you need a design that is weighted on the bottom and has floats on the top.

The first ROV was built by Steve of Homebuilt ROVs. His website has numerous ROV designs as well as links to other ROV websites. He also incorporates several How To instructions in his site. I found this site to be invaluable in building my ROV, and would recommend it to anyone interested in building their own

The second ROV was built be Jason Rollette at Rollette.com His design is a little different but still very effective.

For my ROV I decided on a large center tube with two smaller tube located on either side, slightly underneath the center tube.

Step 2: Frame

Here is the beginning of the frame I am building for the ROV. I cut plexiglas windows and sanded them to fit inside the pipe. This is Schedule 40 ABS pipe, commonly used for sewage. When joining this pipe, make sure you use solvent glue that is specifically made for gluing ABS. Normal PVC cement will not work or create a poor bond that could leak. I am also using a marine sealant to seal the plexiglas and prevent water from coming in. On the back end, I am using screw plugs in case i need to access the batteries or electronics again. I will need to wrap the threads in teflon tape to make it water tight.

After some testing, I found that the screw plugs leak, so I switched over to rubber end caps that have a band clamp to secure them.

Step 3: Thrusters

One of the most important features of an ROV is movement. I found that most people use marine bilge pumps as a means of thrust. BIlge pumps have many advantages. They are meant to be submerged, they are fairly powerful and they are easy to add to an existing ROV. Most use them in their current configuration, but I opted to use propellers to increase thrust. I followed the instructions at Homebuilt ROVs. In the How To sections, he has instructions on converting a bilge pump to use a prop. The propellers came from Harbor Models, they have a good selection of plastic and some nice brass props, with many different sizes.

I used 4 Rule 1100 GPH bilge Pumps, 2 for forward, backward and turning, and 2 for up and down.

Step 1: Cut off all of the white housing of the bilge pump, but be careful not to cut into the red motor housing

Step 2: Use a screwdriver to pry off the impeller, the blue thing to expose the motor shaft.

Step 3: I use a prop adapter for an airplane to attach the propeller to the shaft. It has a set screw, and I just tightened the nut against the threaded hub on the prop to lock it in position. I had to re-thread the prop adapter because it was a little too big. As a extra precaution, i used thread locker to seal the assembly together.

Since the threads did not line up, I was forced to re-tap the prop adapter. Although it seemed straightforward, it took considerable time to do it correctly.

Step 4: Navigation

To determine which direction the ROV is facing, I used an electronic compass. This is a Dinsmore 1490 electronic compass. I got it from Zargos Robotics. I used this schematic to create a visual representation of the direction. One note: This compass has no North. You just select a direction as north, and then all the rest will line up. It is also very sensitive to tilt, a few degrees and it gets screwed up. It senses changes in Earth's magnetic field, so make sure you place it far enough away from magnets, like the ones in the motors. If you need more info about the compass, check this site out

In the picture, the four wires in the silver casing will go to the surface and interface with the computer to show me which direction I am facing. I am writing a program that will rotate an image of the robot to show direction. However, this might take a while so for now I might just use the LEDs

For a tilt compensated compass, check out this one at Sparkfun. It is definitely top of the line, but also carries a huge price tag

EDIT:  I removed this because of its inability to maintain a steady heading.  This is most likely due to the tilt that the compass couldn't handle, along with the magnieting interference.

Step 5: Camera

Obviously you need a camera to be able to see what is going on, right? There are several different ways to go when getting a camera. If you're planning on going pretty deep, then a black and white infared camera would be a good bet. For shallower water, color works just as well, plus it shows more detail (ie. color?). If you really want a good picture, then go with a dedicated underwater camera. These cost quite a bit more, but you don't need to worry about an enclosure, and they often switch to night vision automatically with built in IR illumination when there is not enough light.

I went with a 30$ color camera from Spark Fun. It has an RCA output that I will attach to my computer. Here it is attached to a mount ready to be installed.

The PC card connects to the camera via RCA, and also came with a program to view and capture the video feed

Step 6: Lights

I needed some lights that are fairly bright and also efficient. LEDs are exactly that, and I found some at Spark Fun Electronics. I used two 3 watt LEDs, and to be honest, they are blinding. They do get a bit toasty, so be sure to use a heat sink to prolong the life of the LED. Spark Fun sells an aluminum breakout board that has solder spots for wire and also acts as a heat sink. They have different LED colors too.

I attached the LEDs to a stand I made out of an L bracket to hold the in the center of the viewport. to make it easier to change, I bolted them to a aluminum strip so that they an be adjusted or replaced

The pictures do not show how bright these things really are. After looking for a second at one, I had spots in my vision

Step 7: Control: ROV Side

This is probably the most difficult part of the entire building process. I have seen numerous different approaches to controlling the ROV. Jason Rollette used a microcontroller, which is really the best way to go. He has full analog control of all motors, and at the data is transmitted up a Cat 5e Ethernet cable. However, unless you have the means to print out a circuit board and program a microcontroller, this is not the easiest to assemble. Jason has a diagram of the circuit and the PCB on his site here

Alternatively you could use relays to switch the motors on and off. this is not as good as full range control, but it is much simpler and straightforward. At Homebuilt ROVs, Steve used relays to control the Seafox, and he has a good guide to assembling any number of relay controlled motors.

This is one of the 4 speed controllers I am using for the thruster control

Step 8: Power

I decided to carry batteries in my ROV to make it more independent and reduce the number of cables going to the surface. This is one of two 12 volt 2.5 amp hour batteries I bought from Battery Mart. I have already wired it up to a Deans Ultra connector so it can be easily removed if it is needed. Due to the amp draw of the thrusters, I might need to incorporate a charging circuit to keep the batteries topped off. They will be carried in the two side tubes, and add much needed weight to the ROV

Step 9: Control: Surface

Now we enter the difficult realm of piloting. The two people I talked to use a laptop to control their ROV, using a keypad or joystick to move the ROV around. This is great because all you need is the ROV, the control cable, and your laptop.

I wanted full analog control with out using a microcontroller, so I decided on ESCs, Electronic Speed Controllers. These should be familiar to everyone who has a model plane or car. I needed reversing speed controllers, and stumbled across some at Bane Bots. They are plugged into the Reciever inside the ROV, and the antenna is attached to one of the Cat 5 wires. From there I used my Hitec Remote control with the appropriate crystal and frequency.

The light are controlled by a switch that is operated by a servo. The compass has yet to be set up, but I think I might just use a bunch of LEDs instead of trying to interface it with my laptop.

EDIT: I have since upgraded my control system using an Arduino microcontroller and a servo controller.  I will post my results a soon as I finish sea trials.

Step 10: Tether

To connect the ROV to the controller, I am using 100 feet of Cat 5e Ethernet cable. It has 8 wires, which fit in with my plans nicely. I might add a second cable if I have more features I need to run, but for now it looks good.

This is plenum rated Cat 5, meaning that it can be pulled through walls using a fishtape. The covering is tightly shrunk and has a thin nylon cord inside that helps distribute the load over the entire cable. This makes it more durable and reduces that chance that I damage the cable from load stress.

I will need to add floats to the cable because it will probably sink due to its weight.

The connector I used is a Bulgin Buccaneer Ethernet connector. It makes it easier to transport the ROV by separating the cable and the robot. Bulgin tests their connector thoroughly, and this is supposedly rated to 30ft for 2 weeks and 200ft for a few days. As I am planning on going no more that 100, this is well within the limits.

Step 11: Testing

The first time the ROV saw water, I tested it in my uncle's pool. As was expected, the ROV was too buoyant. I have since added lead weights I purchased at a hunting store to add weight to the skids. Lead shot would have been preferable because it is finer and easier to use, but it is really expensive. The lead also allows me to adjust the ballast with a reasonable degree of precision in the event that I need to change the weight on the spot. The total required ballast was about 8 lbs, quite a load. The next test will be in another pool, and then its hopefully into a lake! If you plan on using this in salt water, it would not be a bad idea to rinse it off afterward to keep corrosion down.

I will try to post some videos in the near future to show how this thing works in the water

Share

    Recommendations

    • Microcontroller Contest

      Microcontroller Contest
    • Woodworking Contest

      Woodworking Contest
    • Make it Move Contest

      Make it Move Contest
    user

    We have a be nice policy.
    Please be positive and constructive.

    Tips

    2 Questions

    Hi, can you please tell me the dimensions of this design?? Thanks in advance

    Where or how can I order 3 motors like yours ?

    212 Comments

    How much current drawn by the bilge pump motor when propeller is connected?

    Further to comments on IR underwater:

    Yes the absorption of light increases rapidly toward the longer wave-lengths. However, many aquatic animals use IR, e.g. goldfish. This must have an evolutionary advantage, nature tends not to waste energy in non-working systems. It is probably only useful at very short range, but the difference between being 'blind' or having some sight is massive and resolution is probably not too important at a few inches.

    It's about horses for courses. Suck it and see!

    Fun build by the way, hope it stays water-tight. ;)

    Good work ! I wonder,how much money did you spend to make this? I'm considering to build something similar to this as a mechanical engineering undergraduation project.

    Rollette.com seems to be dead now, I was able to come across a pdf with some info, including a parts list.

    http://downloads.deusm.com/designnews/852-click_here.pdf?force=true

    Hello!

    Great Work!

    I am interested in building an underwater communications system (not a ROV, it's for an underwater sensor which will send signals to surface).

    One question, which is the cost of the Ethernet cable for underwater communications and what it's your experience with daily use?

    user

    Hi!

    I'm planning to build my own ROV and the camera bit is confusing me a lot! How do you get a live feed from the camera? Did you connect it to an Arduino?

    possibly, it might work. there are some likely downsides to this method. 1)the craft would be much slower and have an exponentially slower reaction time to commands such as forward/backward/left/right 2)water would barely do anything to propel the craft in any direction due to its very low viscosity so you would have to have a lot of pumps 3)since the pumps suck in water that surrounds it, if you have the craft in a particulates polluted water, it is likely that they would ofton get cloged

    How did u control your ROV?

    U said that Fm transmitter and receiver is used for this purpose. But radio waves cannot propagate through water. So, can u tell me how did it work

    Thanks & Regards

    1 reply

    You can just plug in very long cables(the tether that he uses is essentially an internet cable) 1 for power if you do not want to use a battery and one for controlling it, also, it says "Control: surface"

    if you are put this robot anywhere but in a swimming pool, i would HIGHLY suggest putting a sheet of wire mesh all around it of and on the motors to protect this from what ever it might encounter like weeds and get entangled with you therefore losing the robot

    Hey SpaceShipOne,

    how are you?

    I am from Sultanate of Oman. I am doing my graduation project about the RC submarine and I need to download the PDF but, I can't because I already have free registers. So, if it is possible can you send it to my e-mail? or just tell me about the main parts of the submarine, Please.

    Best wishes,

    Ibrahim

    This might be of interest to you, but deadline is this Friday!

    CInvetors Coral 02.PNG

    If you set the boyancy in a pool, and then move to salt water it will need to be adjusted again for the salt water.

    You could use an air compressor and an electronic valve to let in water and another to let in Air to a ballast tank but it would add another 30 + dollars in airhose and valves

    1 reply

    As long as it's a non compressible hull then you don't really need controllable ballast tanks. Once you set it to neutral buoyancy then it'll stay at neutral buoyancy and require very little power to move it up or down. As neutral is hard to get I would opt for slightly positive or negative depending on one or two things. If you want to predominately look at things on the bottom then I would opt for very slightly positive buoyancy. This is so the thrusters don't throw up all the crap on the bottom and ruin your view. As long as the tether is strong enough to retrieve the ROV with if you get a fault then no problems with slightly negative either. If very near neutral then the power needed to stay put or move up and down is minimal so IMO not worth the effort and complexity of controllable ballast..

    If you need to alter ballast due to picking something up or dropping it off then you could use a bladder in the weighted section of the ROV. That is put a balloon in a chamber at a little bit of pressure (greater than the dive pressure) then use a water pump to put water in to the chamber . As long as the water pump is higher pressure than the balloon then water will enter the chamber and the ROV sink. As the pressure equals the balloon pressure it will then be static and if less then the water will be forced back out. As long as the pump can deliver the pressure then as the balloon collapses the pressure needed to put more water in will increase. So a speed controller on a centrifugal pump with a bladder chamber will give you buoyancy control. Whilst this will work it would require constant power on the motor so if you need if for long period then valves could be used but again more complexity...