Cable type for drop cam

Hi all,
I am planning a submersible build. I want to use an off the shelf camera, two BR thrusters, and two BR lights. The camera will require cat5e. I am looking for a cable type that can accommodate cat5e plus the controls for the lights and the thrusters.

The tentative plan is the following: the underwater housing will have the battery, the camera, the board, the drivers, and an extender transmitter balun [ for USB from camera to cat5e]. Up top, the other transmitter balun will accept the cat5e, and output USB which would go into a laptop.

It’s just a tethered cylinder with a hi def camera that uses thrusters to rotate about 350 or so degrees.


If you use BR concept with Fathom X you only need one pair, use BR Slim tether.
If you want your own ethernet solution, use BR regular 4 pair tether.

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Hi @jim_p, welcome to the forum :slight_smile:

One option here would be to order a custom cable (from a cable manufacturer) with different wires for the different purposes. A more common approach would be to use ethernet communication along a tether, which then goes through something like an Ethernet Switch, which splits out relevant signal to the camera(s) and the other peripherals (likely via some form of onboard computer like a Raspberry Pi).

Depending on your tether requirements, it may be helpful to use something like our Fathom X boards, which allow an ethernet signal to be transmitted over a single pair of wires (like our Fathom Slim), instead of the four pairs in a cat-5e cable (like our Fathom Tether), as @Boko suggested.

I’m not sure how your camera stream is encoded, but if you already have a Raspberry Pi (or similar) onboard then you can potentially use that to pass the video stream on to the tether connection. A Raspberry Pi has GPIO pins that can be used for sending PWM signals, so it should be possible to use that to control the thrusters and lights (with some code) :slight_smile:

Ok Thank you. So if I use the Fathom X boards and the Fathom slim tether, I would be running the camera on one pair of wires out of a total of four pairs. That leaves three pairs for the thrusters and the lights.

In this scenario, I would need a board and drivers for the light and thrusters and then the fathom x boards to run the signal from the camera to the surface?

Is there a resource that you are aware of to get a better sense of how to put all of these pieces together? For me, the housing is the easy part. It’s the electronics that I have to figure out.

No, the Fathom Slim has only a single twisted pair inside. If you’re using a USB camera that has a H264-encoded output option then it should easily be able to be streamed via the Raspberry Pi. It should also be possible to control some lights and thrusters via the Raspberry Pi, although it would require some custom code to get working.

Hopefully this diagram is clarifying:

A few notes:

  • the specific Raspberry Pi pins to connect the lights and motors to will depend on the controlling code
  • the thrusters and lights would actually be outside the enclosure
  • the battery may be in the same enclosure as the electronics, or in a separate one
  • while our camera would be inside the enclosure, a depth-rated waterproof camera may be outside the enclosure
  • if you wanted to use one or more IP cameras, an Ethernet Switch would go between the Fathom-X and the Raspberry Pi, and the IP camera(s) would connect to that instead of the Raspberry Pi’s USB port(s)

This comment may also be relevant/useful to refer to for understanding the software requirements :slight_smile:

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Thank you Eliot. Would the quality of the signal to the computer degrade over a certain distance? Part of the motivation for this project is to get really good video quality. That’s the reason I didn’t want the camera looking out of a dome, or from inside of an acrylic cylinder. (These would have been much easier I think, because I could just rotate the camera inside, without having to rotate the entire sub.)

Video quality will not change over distance.
But you will have a maximum distance where you can keep the bandwith.
For full HD (1920x1080) there is no problem to at least 300 meters.

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It’s a digital signal, so it’s not any issues that are caused will be due to lost/corrupted packets, from electrical noise or insufficient bandwidth. Effectively, any frames that get through will have the same quality regardless of distance (which is what @Boko was referring to), but if the tether gets too long there might be some missed or damaged frames.

I don’t believe you mentioned that earlier - does that imply you’re using a flat window, or is your camera external and has a waterproof lens? If it’s the former, you may be interested in this: