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 Post subject: Making the Tether
PostPosted: Jul 31st, 2017, 7:57 pm 
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Joined: Jul 31st, 2017, 7:42 am
Posts: 2
Hey,

For school I am making a ROV, and was hoping to get some advice on the tether. I'm using a Ethernet cable to connect two RPi together for my camera, and will have another Cat5 cable to control my motors, lights, etc. i will also have power cables as my battery is on the surface. I would like to have the tether approx 15m if possible. What im wondering, is there a way to keep there 3 cables together, something like braided hollow rope? also would it be possible to disconnect at the remote and ROV for easy transportation?

Thanks
Darq


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 Post subject: Re: Making the Tether
PostPosted: Aug 1st, 2017, 5:24 pm 
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Joined: Nov 28th, 2011, 11:24 am
Posts: 121
Hi Darq.
I use polyester braid to keep my tether wires together, it's not bouyant but is easy to use.
http://www.ebay.co.uk/bhp/braided-cable-sleeving

It comes in various sizes and you need to allow plenty of length as it gets shorter when you bunch it up to get it over the cables.
2 x cat5 + power cores is quite a chunky cable though, it wouldn't flex much and you'd need a big ROV to drag it around.
If you can reduce the number of cores by using the r.Pi's to control your thrusters you could do away with one of the cat 5's.
Hope that helps.
BBB.


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 Post subject: Re: Making the Tether
PostPosted: Aug 2nd, 2017, 7:41 am 
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Joined: Jul 31st, 2017, 7:42 am
Posts: 2
Hey BBB

Thanks for the link (polyester braid), i think that might work nicely, besides being unable to float.

I didn't think of that (chunky cables), and it does makes sense to use the RPi in the sub to control the thrusters if possible. thanks for the idea.

Darq


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 Post subject: Re: Making the Tether
PostPosted: Aug 2nd, 2017, 11:42 am 
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Joined: Nov 28th, 2011, 11:24 am
Posts: 121
Good luck with it Darq.
Another tip is to use separate power cores for your thrusters and electronics supply, ie: 2 thick ones for thruster power and two thinner ones for electronics power.
This keeps the volt drop at the bottom end caused by the motor current from affecting your electronics.
You can supply them from the same battery topside but don't connect thruster+ to electronics+ or Thruster- to electronics- at the sub end.

I have a total of 6 wires in my umbilical and it still ends up about 10mm diameter.

1-thruster+.
2-thruster-.
3-elex+.
4-elex-/video gnd.
5-comms.
6-video coax core.
And a 4mm tube for pneumatic gripper.

BBB.


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