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Tethered Underwater Camera


(Nikos Maurommatis) #1

Hi everybody,

I would like to build a tethered camera for one of my friends who is a driver. He needs to carry a camera with him with live hd at the surface to a monitor or a laptop. I am thinking of using a) Fathom-E Interface Board Set, b) a Raspberry pi zero, c) a Raspberry Pi camera, d) some meters of Fathom Slim ROV Tether and e) a 2’’ Watertight Enclosure.

But I don’t know what I have to have at surface so as to have live hd picture on a laptop. Have anybody any idea? Is it right/possible the above idea? Is there any other idea?

Nikos


#2

Sounds like a difficult way to build a tethered camera, why don´t he buy something like this: http://www.fishsens.com/fishsens-sondecam-hd-underwater-camera.htm


#3

@ Nikos Maurommatis, if you’re still interested in building one yourself, here’s a good recipe:

For the submersible side you will need:

  1. BR enclosure with the appropriate end caps and penetrator.
  2. An HD camera with an HD-SDI output.
  3. A SeeEyes HD to EX-SDI transmitter (can send EX-SDI over 150m of UTP and come in Tx/Rx pairs). Approx US$100.00 for the pair.
  4. A 4S LiPo battery.
  5. A Pololu 12v Voltage Regulator board S18V20F12 (for the cam and transceiver). US$14.95.

For this system you can use the BR tether with the single UTP.

On the topside you will need:

  1. Laptop with USB 3 port.
  2. SeeEyes EX to HD-SDI receiver (the other half of the pair above).
  3. Magewell USB Capture SDI Gen 2.. Approx US$299.00
  4. Magewell USB Capture software. Free.
  5. A 12V power source for the SeeEyes receiver.

Apart from a few minor details, this is pretty much the system I’m building into my new ROV. I’ve got the entire video system running on the bench and the quality is absolutely crystal.

The real issue here is which camera you decide to use but I would avoid using one of those generic $50 board cameras. Spend some money and get something like a Sony Exmor Starvis (superb low light performance) with a decent lens on the front.

You could use a PoE system but the 8-UTP tether and PoE regulators are probably going to make it a lot more expensive.

SROV.


(Nikos Maurommatis) #4

@Mikxie, thank you but I think I need more than 50 meters cable.

@Sarawak_ROV, very analytic and helpful answer! I would like to ask you a) why do I need the “Magewell USB Capture SDI Gen 2.3”? I can.t understand what exacly do this little machine…If I don’t need to use a laptop I think I don’t need it, is that right? b) can you send me any specific link for the Sony camera? Thank you in advanced!!!


#5

Nikos, when the EX-SDI signal comes up the tether, it arrives at the SeeEyes receiver and is converted into HD-SDI on a coax cable. I do not know of any laptop that will accept coax HD-SDI so you will need some way to import the video, this is where the Magewell USB Capture device comes in.

In fact, not only will it import the the video, it also comprises an off-platform graphics processor so all the video processing is done at no expense to your laptop’s internal hardware. Furthermore, the accompanying software will display the video and record it at the same time. Magewell also have a very capable SDK for importing video into any custom app that you may want to write (useful for those who write their own ROV pilot software). And the Magewell hardware will integrate with just about any video software you can name. Phew!

Your choice of camera depends on the conditions in which you will use it, and whether your diver will be using dive lights. I suggested the Sony Starvis modules on the assumption that the camera vessel would not be fitted with lights but there are many, many other options. The best way to find one is start Googling, the criteria you need to watch out for are:

  1. HD (1080p, 30fps)
  2. HD-SDI output (preferably through a MMX coax connector)
  3. 12VDC supply voltage.

Often this will mean trawling through pages like this and downloading the datasheets. It’s time consuming but worth the effort when you find the right camera for your application.

SROV.


(Nikos Maurommatis) #6

@Sarawak_ROV thank you for your post! I have found this little module

https://www.bhphotovideo.com/c/product/1247784-REG/blackmagic_design_convcmic_sh_micro_converter_sdi_to.html

which is very cheap and very reliable (one friend of mine is using it for a long time with no problem).

At the same time I managed to find this manufacturer of camera boards with amazing features:

https://hupuu.com/category/camera-board

Nikos


#7

Hi Nikos,

Sorry for the late reply. The converter looks fine provided you use the SeeEyes transceivers to get the video signal topside, it also supports re-clocking so it should accept pretty much any HD-SDI signal format. The downside is that you may not be able to record the video without additional hardware (this is why I chose the Magewell unit) but this will depend on the laptop spec - most of them use the HDMI port for output only. This means that you can only feed the signal from the converter straight into a monitor but you will need to find a way of recording the parallel HD-SDI output.

The camera boards also look good but remember you will need an HD-SDI output so better to start from here.. Please note that you can’t use the EX-SDI outputs from these boards; they are designed to use with coax cable and will not be compatible with the tether’s twisted pair (another reason for the SeeEyes transceivers!).

The only other advice is to get a decent lens for the camera board, avoid wide-angle lenses which will give you a lot of peripheral distortion due to the refraction of the acrylic end cap on the camera housing. This will depend on whether you choose a flat or domed end cap but it’s worth experimenting to get the right combination, adjusting the distance from the camera lens to the end cap will make a lot of difference.

Best of luck and tell us how you get on.

SROV