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Aug 30, 2016, 07:53 PM
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Build Log

Underwater ROV Build from Household Parts


As a disclaimer... this is a work in progress... yeah there might be mistakes,, but if you have a question let me know...

So I sunk my rc boat in a local reservoir in 5 minutes of its maiden (next time I won't put in an over-sized ESC and motor)...that is when I decided to build an underwater ROV to find it. This blog will be dedicated to my build so if others want to duplicate it or get ideas to learn from my mistakes. It took me about a week to assembly the entire ROV, but I have been tweaking the design for the last year.

To keep the ROV cheap I decided to use old recycled parts from past projects and home building project I already had. Having a background in RC and FPV really helped out the process.
After extensive research and gathering what i thought might work I found these two videos/blogs to guide my design.

http://www.instructables.com/id/Unde...-ROV/?ALLSTEPS

Micro DIY ROV Overview. Home Built Submarine Drone. My first narration, be gentle! (7 min 46 sec)


I also found the OpenROV community that has turn key units or kits (http://www.openrov.com/) and blue robotics (http://www.bluerobotics.com/). They both have amazing products with really good assembly instructions and support, but they cost a lot! I am cheap so I stuck with a recycled parts ROV. Currently, I have dove down to 80 feet in freshwater and plan over 100 feet in the near future in the ocean...

Biggest lesson I learned- Remember to keep everything as simple as possible (KISS). Add nothing extra you do not absolutely need in the beginning. I made the mistake of adding lots of extra gadgets on the ROV (Grabber, HUD, ground station relay, quick disconnects, etc). It took all of my time to get them working and detracted from the fun. Adding on extra gadgets after the ROV is functioning makes the experience so much better and cuts out the initial frustration!

Break down of assembly steps-
*Frame construction
*Tether/parachord/motor wires gluing
*Electronics installation
*Front viewing port and FPV gear

Step #1- Determining the size of the ROV and layout. I knew that I wanted to salvage things from the bottom of the lake like fishing poles, etc. So I made the ROV large enough to handle the extra weight (about 32 inches long). This did cut down on the portability of the ROV. I also knew that I needed positively buoyant materials on the top of the ROV and weight on the bottom to keep the ROV stable. The goal is to get the ROV neurally buoyant. (Some like a slightly positively buoyant ROV to keep the ROV from landing on the bottom of a lake and then having to power up to stir up sediment)
Frame Parts:
4" schedule 80 PVC (Main Hull)
1.5" schedule 80 PVC (Frame)
8x 1.5" T-connectors (Frame)
8x 1.5" 90* connectors (Frame)
2x 4" PVC rubber endcaps with 2x 4" hose clampsfor each end cap
PVC Glue

The 4" PVC hull was cut to 32" length (This will house all of the electronics/fpv camera). The 4" end caps were then installed using two 4" hose clamps each. Then I constructed the 1.5" PVC frame by constructing the vertical rectangular frames first then the base. I eyeballed the size of the 1.5" frame by making sure I had enough room to put on the 4" rubber caps on the hull. If the frame is too long it is really hard to install the 4" rubber caps on the hull. I did not glue anything together till the 1.5" frame fit together easily. This took some shortening the 1.5" pipe in certain areas. The frame should fit snugly around the hull so that it will hold the hull firmly, but you can still slide the hull out with some force. When everything fit I made sure to glue all pieces so that they did not leak. A decent amount of pressure was applied to the joints by hand for at least 30 seconds while each glue joint dried.

The Frame is Complete!

***If I were to do this again I would have cut the 4" hole in half and installed a t-connector. This would have allowed me to add a cap on the open end of the t-connector and glue the tether and motor wires (according to http://www.homebuiltrovs.com/howtosealingwireexits.html ). I sometimes get a very small leak from my tether line when it flexes too much when moving. I added Marine Goop and that has fixed the issue, but would have been a permanent solution with the t-connector.*** Not sure if it will slide into the 1.5" frame though... might have to assemble and glue the 1.5" frame with the hull installed...
Last edited by TheDonski; Sep 20, 2016 at 09:52 PM.
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Aug 30, 2016, 08:42 PM
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Step #2- Electronics (I come from an RC background so I didn't want to mess with programming a seperate board to control the ROV. I just wanted to use my radio and keep it RC so it is simple)- If you want to program a board www.openrov.com has amazing guides on how to build a rov with a beaglebone board or bluerobotics has good documentation too. The boards you flash have more capabilities than what a simple RC system has, but it has the potential to be more complicated.

I decided to continue to be simple and cheap so I bought 125' of Cat5 cable for $9.99 shipped on ebay. Cat5 is basic internet cable that I will use for my tether since UHF/VHF radio waves cannot penetrate the water very deep (couple of feet is what I have read- some low mHz systems have been able to go a little deeper, but I don't have one and I want to go a lot deeper). The problem with Cat5 is that it is not rated for pulling a ROV to the surface so I attached para-chord rope with it that has a 500 lb pulling capacity (Found at local camping store). I carefully zip-tied the para-chord rope to the Cat5 cable about every 3 feet making sure I didn't pinch the cable and gave the Cat5 a small amount of slack when zip-tieing so that I only pulled the para-chord and did not strain the Cat5 cable. You can also buy Cat5e for a higher price which is rated for pulling the wire in house installations through walls. Might be strong enough for a ROV, but I have not tried it. Others have complained that it is too stiff of a wire and causes the ROV to not be able to move freely. I have had zero issues with my Cat5 and parachord. I just have to be careful when I wind up the cable so that I do not pinch it. Next I tested the wire to make sure I did not break continuity of the wire with a multi-meter. I then drilled out a hole large enough for my tether to fit in top of the 4" hull. (The hole was drilled about 1/3 back on the hull) This placed the tether in the back portion of the hull so it was not in the way of the camera. I waited to glue the tether since I still had the motor wires to glue in the same hole too.
The DT700 brushless motors I chose to install on the ROV were cheap and were from my first quadcopter I built many years ago. They have way more power than what I needed, but were very tough.
Link to the DT700 motors: https://www.hobbyking.com/hobbyking/s...ner_700kv.html
Then I needed ESCs to control the power sent to the motors. You needed ESCs that have a forward and reverse.
Link to the boat waterproof escs I used:
https://www.hobbyking.com/hobbyking/s...C_3A_UBEC.html

I then connected the tether to esc's servo wires. (Signal wire each to a new wire on the Cat5 cable. All gnd servo wires were connected together to one Cat5 wire-Common Ground. The red 5v servo wires were not connected to Cat5 since you don't need power back up the tether. It will have its own power at the ground station).

I then placed the 4 ESCs (one for each motor) in the 4" hull near the hole that was drilled earlier. I soldered on longer wire extensions that would be long enough to reach the motors on the 1.5 inch support frame on the side of the ROV. Make sure that each set of three wires from the ESC are the same lengths. You can get de-sync issues causing the brushless motor to not work correctly if the ESC wires to the motors are not the same length for each individual ESC. Next I used marine epoxy after stripping the wires using this guide to allow the hull to be water tight. http://www.homebuiltrovs.com/howtosealingwireexits.html (Worth reading through the entire "how to" section for different ideas)

Here is the best epoxy I have found for the tether:
https://www.bluerobotics.com/store/t...-marine-epoxy/

Just remember that this epoxy is not flexible so I also covered the marine epoxy in marine goop to allow the silicone wires and tether to flex some. Gluing in the tether and motor wires can be tricky. Using a syringe (https://www.bluerobotics.com/store/t...otting-kit-r1/) to get into the gaps can be very helpful. After I let the glue dry, I tested the ROV in the bathtub to check for more leaks. (Bubbles) It took two coats my first time...
Next you can separately solder all of the positive wires of the ESCs together and the Negatives together seperatly and attach the battery connector. This will power all of the escs and motors from a single 3s 4000 mah lipo battery. (See lipo safety- http://www.hobbico.com/ama-lipo-warning.html)

Battery I am using from old projects:
https://www.hobbyking.com/hobbyking/s...Lipo_Pack.html

Now I connected the RC receiver to the other end of the tether so I could control the escs/motors on the ROV (You will need to power the receiver with another battery since no power goes up the tether to the ground station). I used FrSky for quadcopters so I bought a 6 channel version of that. I also made sure to make sure that if I pulled the tether that I was only putting strain on the parachord and not the Cat5 cable. (Tie the parachord onto the top of the ROV frame)
Last edited by TheDonski; Sep 05, 2016 at 01:12 AM.
Aug 30, 2016, 10:44 PM
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Now I was getting close to being done...
To be able to see out of the ROV with a camera to steer the ROV I needed to cut a circular hole in one of the rubber PVC end caps with a dremel. The hole needed to be about an inch smaller in diameter than the rubber cap. To get a clean cut in rubber I used a cutoff disk on the dremel and lubricated the rubber with dish soap. I then bought a small sheet of Lexan (I think 1/8 inch thick) and cut that with the same dremel tool to fit snugly inside of the rubber cap. I then glued the lexan inside of the rubber cap (not on the outside of the cap) to make a viewing port hole. When pressing in the rubber cap to the PVC hull it helps hold the lexan in place. Marine goop or I heard that Poly Zap Ca will work to bond lexan to rubber. I then installed the cap again and checked for leaks in my bathtub.
I then installed the FPV camera inside the hull to look though the port using a round plastic salsa dish that was about 4" in diameter by gluing the camera to the bottom of the dish with a hot glue gun. Shoving the dish into the hull was tight enough to hold the camera in place, but you can still move it to get the angle you need later. I used the Runcam Skyplus http://shop.runcam.com/runcam-skyplus/ as my FPV cam. I had it laying around from an old project. It has really good low light abilities if you turn on WDR (Wide Dynamic Range) using the controller it comes with. To connect the camera I soldered the red (power) directly to the red (power) battery lead and black (ground) from the camera to the black (ground) battery lead. Same battery lead the escs are soldered to. I like the camera because it can also handle the main lipo voltage you are running the ROV off of. No extra BECs are needed. Then the signal wire from the camera gets soldered to an open wire on the tether.
On the other end of the tether I connected the signal wire from a monitor. Now you can see what the ROV sees if you plug in the main lipo battery to the ROV.
Last edited by TheDonski; Sep 10, 2016 at 11:40 AM.
Aug 30, 2016, 10:58 PM
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I then mounted the motors on the ROV. Here is a video of what the ROV looks like in operation to see where the motors are mounted:
First ROV test in bathtub. (0 min 40 sec)

I used zipties to mount all motors with 3D printed mounts I made in tinkercad (I included the stl files if you have a 3d printer). If you don't have a 3D printer you could easily make them out of wood or plastic. you just need to mount the motors to the 1.5" pvc tubes.
2 motors face up and 2 motors face forward. This allows for up and down, forward and back, and left and right turning movements. This is a point and shoot ROVer. No strafing....
The goal is to have the motors be as straight of the ROV as possible. You can fine tune them later after a dive, but get them as close as possible. I 3D printed the props too (Included a 3d print file link: http://www.thingiverse.com/thing:338127 ). You can also buy these props if you don't have a 3D printer: Graupner 2308.65 (You will need 4 props)
Aug 30, 2016, 11:05 PM
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Then next part takes some guessing and checking. I setup my radio to run the up and down thrusters on the throttle stick. Then I mixed the forward thrusters to go forward above mid elevator and backwards below mid elevator stick. To turn the ROV I mixed the Aileron stick to move the motors in opposite directions. I played around till I figured it out. The last thing that needs to be done is attaching weights to the bottom of the ROV to achieve neutral buoyancy. I used old lag bolts and metal concrete form spikes I has laying around. I zip tied them on and added more weight each time till I got the ROV to sit level and at neutral buoyancy. Also I used regular spray paint so I could see it easily...
As you can see from the movie above I added lots of attachments. It made for some serious headaches. I would recommend that you get your ROV ready and working first before you add anything that is not vital to the ROV operation. (GoPro's are great in their waterproof case ziptied to the top of the ROV) Amazing footage!!! My latest project is attaching a 360* camera to the top of the ROV to look around in HD...

Things I have added to the ROV:
Waterproof servo grabber
Scuba depth guage
Scuba Flashlights (500 lumens each): https://www.amazon.com/Esky-lumen-Su.../dp/B00OSW3R8I
360* camera in a waterproof housing with a 3d printed nylon mount that I can change out a GoPro 3 HD Camera in waterproof housing if I want.
Heads up display overlay on the video with an old full Naze32 board connected to a micro minimosd (Compass, heading, battery voltage, timer)
FPV ground station relay for and multiple monitors/goggle displays
Tether reel
Gasket to the front view port to attach plexiglas: https://www.bluerobotics.com/store/w...lange-seal-r3/ and https://www.bluerobotics.com/store/w...-p-end-cap-r1/
Last edited by TheDonski; Sep 10, 2016 at 11:38 AM.
Aug 30, 2016, 11:17 PM
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If you are interested in my dives I post them on my youtube channel:
https://www.youtube.com/user/rsokors

Or have questions about any of the steps let me know...
Last edited by TheDonski; Sep 04, 2016 at 05:29 PM.
Sep 07, 2016, 07:54 PM
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Quote:
Originally Posted by TheDonski
Then next part takes some guessing and checking. I setup my radio to run the up and down thrusters on the throttle stick. Then I mixed the forward thrusters to go forward above mid elevator and backwards below mid elevator stick. To turn the ROV I mixed the Aileron stick to move the motors in opposite directions. I played around till I figured it out. The last thing that needs to be done is attaching weights to the bottom of the ROV to achieve neutral buoyancy. I used old lag bolts and metal concrete form spikes I has laying around. I zip tied them on and added more weight each time till I got the ROV to sit level and at neutral buoyancy. Also I used regular spray paint so I could see it easily...
As you can see from the movie above I added lots of attachments. It made for some serious headaches. I would recommend that you get your ROV ready and working first before you add anything that is not vital to the ROV operation. (GoPro's are great in their waterproof case ziptied to the top of the ROV) Amazing footage!!! My latest project is attaching a 360* camera to the top of the ROV to look around in HD...

Things I have added to the ROV:
Waterproof servo grabber
Scuba depth guage
Scuba Flashlights (500 lumens each): https://www.amazon.com/Esky-lumen-Su.../dp/B00OSW3R8I
360* camera in a waterproof housing with a 3d printed nylon mount that I can change out a GoPro 3 HD Camera in waterproof housing if I want.
Heads up display overlay on the video with an old full Naze32 board connected to a micro minimosd (Compass, heading, battery voltage, timer)
FPV ground station relay for and multiple monitors/goggle displays
Tether reel
Gasket to the front view port to attach plexiglas: https://www.bluerobotics.com/store/w...lange-seal-r3/ and https://www.bluerobotics.com/store/w...-p-end-cap-r1/

I'm a ROV supervising pilot and work in the Gulf of Mexcio on an oil rig. Interesting build. Best of luck.
Sep 07, 2016, 08:18 PM
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Quote:
Originally Posted by Play2win70
I'm a ROV supervising pilot and work in the Gulf of Mexcio on an oil rig. Interesting build. Best of luck.
Thanks for the supporting words. If you have any suggestions since you do this for a living that would be great!


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