TetherCam Build


#1

I have put together a tether camera, so that you can get a third person perspective of the rov. It could be useful for discovering what you are stuck on or seeing how sea life is reacting to the rov.

It works great in the air, but once the ribbon cable goes into the water, the signal dies, or on occasion, the picture has lots of interference then dies. Once the whole cable is in the water though it is over.

I thought perhaps there was some sort of interference from the water, but that does not seem to make any sense. Perhaps it is lack of interference between the conductors that the cable relies on for a clear signal? Any one have any ideas? Pictures below of the build for interest sake and so you have an idea what the ‘H E double hockey sticks’ i am talking about. :smiley:

The first few pictures are from the test run. I did take pictures of potting the the actual tether cam body. It is a Raspberry pi with the excess ports snipped off.

Oh ya, I added external lights too.


RPi-Cam-Web-Interface
Tether disconnect
Second Camera suggestions
#2

Darcy, that’s just fantastic. I;m using a pi for my CTD and was thinking of throwing a camera on it as well. As for the cable in water, do you mean the camera cable or the tether? it’s not that clear…


#3

Ah, sorry. I mean the camera’s ribbon cable. It is 2 m long which is great, and works well normally (though not so well when it is rolled up…)


#4

Yeah there may be some impedance issues and what not. Its thin, and I’m not sure about sheilding…looks pretty minimal. More to come…


#5

I just ordered this:


It lets you use hdmi in place of a ribbon cable. HDMI is shielded, so I am hoping this will solve the issue. :smile:


#6

Hi @Darcy_Paulin

Just noticed

Have you added a Hub / Switch / Router to send more data up the tether?

If so can you pass on a couple more details on how you did this and how you have found it work

Scott


#7

@Scott_W It is a switch. D-link go-sw-5e. It is really small!
I plug the raspberry pi, the baby and the homeplug into it. Then I have a router topside to assign ip addresses.
It is powered by 5v so I run it from the openrov board. I potted extra wires out of my endcap and used them to attach ethernet and power to the raspberry pi.

I have had zero problems with it.


Deep ROV Implications
#8

Thanks @Darcy_Paulin

I had been wondering how doable that would be (and now you have shown it works well)

@Stretch maybe something like this could also be useful to you for your Panoptix build


#9

Hello Darcy,

you external lights are Looking very interresting . Do you have some more pictures of it or a Short explanation how you have builded them ?

Dominique


#10

@Darcy_Paulin and @Scott_W,

Now that I’ve had some time to think about that work with the switch, I’ve been thinking about other things we could add with an Ethernet expansion.

In addition to possible Panoptix tests (we’ll have to see how to tap into it from the surface), most mechanically scanning sonars like the Imagenex 852 use RS-485 communications, and they make RS-485 to Ethernet converters.

Another thought is to connect a spare Arduino with Ethernet shield and use it as a servo expansion (I’m thinking a 6 axis arm here, Niskin bottle, etc) You may have to use two computers because you can’t keep two internet tabs open at the same time, but it might be worth looking into and wouldn’t require any additions to the tether. It would also require an additional enclosure. It would free up the OpenROV controller board to now only handle video, thrusters, lights and all the AUX functions could be moved off. I should probably dive into Arduino programming now.

I’m sure others have some Ethernet based modules that could be mounted.


#11

Yep it’s had me thinking as well (and wasting a lot of time looking all sort of cool applications)

Thinking more and more about a localised mapping bolt on (SfM with maybe structured light scanning)

mmmmm

Maybe a thought for the Trident as well as localised 100mm WiFi


#12

Hi @Darcy_Paulin

I am starting to put together a concept “equipment list” for something fairly similar (and thanks for the trail blazing)

How did you go with the ribbon to HDMI converter?

Would you suggest this is the way to go? Was the RFI issue only when the ribbon was rolled up?

What would you do the same / or differently?

Scott


#13

@Scott_W
The short ribbon cable seems to be fine. The long one goes nuts under water though. The hdmi converter works but it is an added expense and component. The long ribbon cable would probably work if it had a little more insulation. Rolling up the ribbon cable is also an issue though, you are right.

if the ribbons are short, they might work fine. I suspect if they were potted in resin they would work too, but at that point the hdmi converter starts to look good again. :D.

Depending on where you plan to place them you can pick:
Short ribbon (like the one that comes with the camera)
HDMI converter
Potting the ribbon.
or maybe try putting duct tape along the ribbon. :). that just occurred to me.heh. And it might actually be why the short ribbon worked when it did, as a portion of it was covered by duct tape…


#14

Thanks :+1: @Darcy_Paulin

I might start with the ribbon, as at a guess, it will be a while till I full on marinise the system (Ideally I like the round cable over the flat ribbon for porting it through pressure components - But I also like your potting of the electronics)

Scott