RC transmitter and receiver for DIY submarine (control+video feed)

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  • laukejas
    Ensign
    • Oct 2021
    • 4

    RC transmitter and receiver for DIY submarine (control+video feed)

    Hi,

    I'm just getting into RC submarine hobby. I am designing a RC submarine for lake bottom exploration. I plan to go as deep as 10 meters, and as far as 100 meters. I am looking for a transmitter/receiver pair that would allow me to send controls to the submarine from the controller, and receive video feed from the submarine to the controller or laptop.

    Most of the transmitters/receivers and controllers I find operate in 2.4 Ghz, which is very bad for water penetration. Ideally I want something like 40 Mhz or even lower (there are no legal regulations in my country regarding RC submarine frequencies), assuming such low frequency can be used to transmit live video feed.

    I live in Lithuania, so most of the options available to USA folks are not available to me, or are expensive as hell to ship. I am looking for something that could be bought on Aliexpress/Ebay, preferably under $200 for the whole setup (excluding the camera, if it can be plugged in separately).

    Are there any options for this, or will I have to build my own transmitter/receiver and controller? If so, any similar projects or tutorials? Would really appreciate someone putting me on the right direction. Thanks!
  • RCSubGuy
    Welcome to my underwater realm!
    • Aug 2009
    • 1768

    #2
    Not to bash you, but I get this sort of question all the time.

    "I want to drive my yet to be built submarine that I have no experience with a mile away and a hundred feet deep through salt water while carry a 10kg payload and traveling at 15 knots, all while videoing everything it sees and relaying to me in real time. Oh, and I have a budget of $75. Please send me all details immediately."

    I hate to sound harsh, but a few minutes of research here would net you dozens of threads on radio limitations. What you're asking for is, frankly, not feasible, or at least not the video aspect. You may get away with running a ton of wattage through a custom built radio to get control at those depths and distances (assuming pure fresh water environments), but there is no way you'll get anything but a couple of frames per second of video, if that. The data rate is just too high for video of any kind.

    Again, my apologies if I overused my trademark sarcasm ( my flight home just got delayed 1.5hrs and I'm just on this side of irritated at the moment). I certainly don't want to dissuade you from trying. I'd love for you to prove me wrong.

    Bob

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    • laukejas
      Ensign
      • Oct 2021
      • 4

      #3
      Hi RCSubGuy , and thank you for your criticism. My apologies. I have done some research, but apparently not enough. I thought that I could get away with video if I stick to low frequency radio.

      With that in mind, what alternatives would you suggest for getting video feed? If radio is not feasible, could sonar modems be utilized, or is the bitrate too low for that?

      Failing that, what else? Cable would be the last resort, but if I were to go with a cable, what kind of video camera and what kind of cable would I need to transmit video over 100m of cable without severe power loses due to cable resistance? Theoretically I could power the sub itself via that cable (which would solve the power requirement issue, as I wouldn't have to use batteries), but I suppose I would have to use thick cables and high voltage to avoid power losses as well over such large distances, which doesn't bode well for a small sub. Any advice?

      Comment

      • laukejas
        Ensign
        • Oct 2021
        • 4

        #4
        I did some research. Apparently I could go with optic fiber cable (ethernet), and have a rasberry pi on the sub that would transfer video and receive control commands through that cable, while the cable would also supply power. Problem is, at 100m length, such cable would weigh around 20kg - there is no way in hell that the sub would be able to tow that. Is there a more lightweight alternative?

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        • RCSubGuy
          Welcome to my underwater realm!
          • Aug 2009
          • 1768

          #5
          I agree that cable is what you're going to be relegated to using. The cable can be made to be neutrally buoyant using floats spaced evenly apart, but the actual towing out to the full distance is something that can't be helped. The issue is not with the control methodology, but the mission you've elected to tackle. That said, I have to think a solution exists and commercial ROV manufacturers surely have mission capabilities of that scope (if not greater).

          I'd start with looking at ROV manufacturers and seeing what they are doing for control lines.

          Comment

          • SubDude
            Captain
            • Dec 2019
            • 803

            #6
            I have a Qysea Fifish V6S that uses fiber optical cable. All controls and video are fed through it. It comes with 100m of cable on a spool. The video is 4K. As Bob said, you might consider something like it. Honestly it is one of the coolest things I own.

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            One end of the cable...

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            • laukejas
              Ensign
              • Oct 2021
              • 4

              #7
              Originally posted by RCJetDude
              I have a Qysea Fifish V6S that uses fiber optical cable. All controls and video are fed through it. It comes with 100m of cable on a spool. The video is 4K. As Bob said, you might consider something like it. Honestly it is one of the coolest things I own.
              Thank you for these pics! I was considering fiber optic cable (hopefully it can transmit data both directions at once, since I need video feed going one way, and controls the other way), but the issue was that I could not find any fiber optic data converters that could fit into my sub. Most of these converters are large boxes (10x10x5cm at the smallest) with a fiber optic port and a LAN port, like this one. That ROV you have in your pics looks small enough that I'm pretty sure it doesn't have a converter as large as that. It must be using some compact version of a similar converter. Do you have any idea where I can get something like that?

              Comment

              • jphatton
                Lieutenant
                • Jan 2021
                • 84

                #8
                There are a number of sites and forums which cover the construction and operation of Remotely Operated Vehicles (ROV's) which might be of interest.

                For simple ROV's there are Seamate family of ROV's which were developed to support education activities, some information and component kits can be found on their webpage;

                SeaMATE was founded via funds from the National Science Foundation. SeaMATE provides student interns with workplace experience with underwater robotics products while supporting the MATE ROV Competition community and STEM education initiatives around the globe. Visit educate.materovcompetition.org for more resources!


                This family of ROV's are based on PVC pipe fittings for structure, using boat bilge pump motors to drive thrusters as these generally are designed to withstand immersion and pressure of a few meters water depth. For the tether they are often using speaker wire or similar.

                The Underwater Robotics book listed on their site is quite good, covering all aspects of DIY ROV design and practical construction along with theory. Also I think there are some Seamate build logs online.

                More advanced open source ROV's are often based on the Ardusub code and system, using a Pixhawk autopilot for thruster control coupled with a Raspberry PI to provide the communication link, camera and other functions. The Ardusub site can be found here, ;



                For the tether typically a neutrally buoyant twisted wire pair is used for an ethernet connection, with two interface boxes at either end to convert the signal. I think that for short tethers up to a few 10's meters length water resistant ethernet cable (eg. used for buried cables) has also been used, although water ingress is an issue.

                Bluerobotics uses the Ardsub code in their BlueRov and also sells many the components, including the tether and interface. They also have a forum which has a lot of useful information and some build logs.

                https://bluerobotics.com/

                https://discuss.bluerobotics.com/

                Comment

                • SubDude
                  Captain
                  • Dec 2019
                  • 803

                  #9
                  Originally posted by laukejas

                  Thank you for these pics! I was considering fiber optic cable (hopefully it can transmit data both directions at once, since I need video feed going one way, and controls the other way), but the issue was that I could not find any fiber optic data converters that could fit into my sub. Most of these converters are large boxes (10x10x5cm at the smallest) with a fiber optic port and a LAN port, like this one. That ROV you have in your pics looks small enough that I'm pretty sure it doesn't have a converter as large as that. It must be using some compact version of a similar converter. Do you have any idea where I can get something like that?
                  I got mine from a place called Urban Drones out of Florida which is more of a retailer and probably know little about the technical side of them. They sell all kinds of ROV's. A bit pricey but it was turn key and it performs great. The fiber optic cable handles all of the data signals coming and going with ease. I do not know what they use for converters. Here is a short video of me chasing my sons Thunder Tiger Neptune around the pool.

                  Comment

                  • rwtdiver
                    Vice Admiral
                    • Feb 2019
                    • 1770

                    #10
                    Originally posted by RCJetDude

                    I got mine from a place called Urban Drones out of Florida which is more of a retailer and probably know little about the technical side of them. They sell all kinds of ROV's. A bit pricey but it was turn key and it performs great. The fiber optic cable handles all of the data signals coming and going with ease. I do not know what they use for converters. Here is a short video of me chasing my sons Thunder Tiger Neptune around the pool.

                    Steve,

                    I have a couple of questions for you about Nathen's Neptune!? I am going to assume that he is using the ACE Sea Commander T6M Transmitter!? What battery pack are you using for the TX? Also, are you using the 12 volt lead acid battery for the submarine itself?

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                    Thanks for the information Steve!

                    Rob
                    "Firemen can stand the heat"

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                    • SubDude
                      Captain
                      • Dec 2019
                      • 803

                      #11
                      As far as I know it has an SLA battery in the sub and he is using the Ace RC Sea Commander radio which has a rechargeable NiCad battery in it. I have never had to open it up yet.

                      Comment

                      • rwtdiver
                        Vice Admiral
                        • Feb 2019
                        • 1770

                        #12
                        Originally posted by RCJetDude
                        As far as I know it has an SLA battery in the sub and he is using the Ace RC Sea Commander radio which has a rechargeable NiCad battery in it. I have never had to open it up yet.
                        Thanks for getting back to me Steve! I am going to stay with the original batteries on mine as well! I am going to replace them both, they are not holding a charge at all 5 to 8 min run time on the TX and about 20 to 30 min run time on the lead acid on board battery!!

                        Rob
                        "Firemen can stand the heat"

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