Hi all,
I am building a tethered submersible. It has a camera, a servo to pan the camera, and an LED. I need to extend the USB cables a couple hundred feet for camera and servo control. Is USB over fiber with transmitters the best way to extend the distance of the cables?
Thanks,
Jim

 

It is a possible way to go, but we have no idea what your criteria for best might be. Can you elaborate?

 

USB will not run that distance , so yes you need a solution,
"problem" with sub stuff is , apart from the obvious water,

cable weight ( does it float or sink )
thickness

Currents underwater, can drag a cable, the thicker the cable the more drag
if the cable floats or sinks, the "sub" has to cope with this,

All in all quiet a drag.

Fibre is great, but has strong dislike of water, even damp damages glass fibres,
it is also very susceptible to stress ( snaps if pulled or if bent to tight )
so the fibre needs a dammed good sheaf on it , which adds weigh / size .

Then you have to decide how to encode the signal, is it going to be bi directional on one fibre, or two fibers
then how do you get power down to the sub ?

whats your experience ?

 

I like the optical fibre way but never used it.
For several years I used a USB to CAT5 adapters at bot ends and ran a few hundred feet of CAT5 as tether with no problems. Perhaps I still have the adapters behind the spider webs.
Impermeabilization is always mandatory no matter what you end using.

 

Thanks for your reply. I have considered the cable weight and drag issues. Although not the fragility of USB fiber. The idea was to keep it as simple as possible. The camera runs off its battery, as does the servo to pan. That way, I figured, I run two wires and the cable. Of course every solution presents another problem. (Like battery heat...) This one is designed to sit on the ocean floor or just hang. I'm using ocean floor loosely. Think shallow.

I am a mechanical engineering student. But I'm older and I worked as a metal fabricator and I have a shop and a lathe. I'm not so concerned about the housing.

With the electrical side my thinking was well, they use USB so maybe I can extend USB.

Do you think cat5 would fare better? I found an UHD 4K extender kit.

Thanks again!

 

I like the optical fibre way but never used it.
For several years I used a USB to CAT5 adapters at bot ends and ran a few hundred feet of CAT5 as tether with no problems. Perhaps I still have the adapters behind the spider webs.
Impermeabilization is always mandatory no matter what you end using.

What did you sheath the cables with?

 

USB will not run that distance , so yes you need a solution,
"problem" with sub stuff is , apart from the obvious water,

cable weight ( does it float or sink )
thickness

Currents underwater, can drag a cable, the thicker the cable the more drag
if the cable floats or sinks, the "sub" has to cope with this,

All in all quiet a drag.

Fibre is great, but has strong dislike of water, even damp damages glass fibres,
it is also very susceptible to stress ( snaps if pulled or if bent to tight )
so the fibre needs a dammed good sheaf on it , which adds weigh / size .

Then you have to decide how to encode the signal, is it going to be bi directional on one fibre, or two fibers
then how do you get power down to the sub ?

whats your experience ?

Thanks for your reply. I have considered the cable weight and drag issues. Although not the fragility of USB fiber. The idea was to keep it as simple as possible. The camera runs off its battery, as does the servo to pan. That way, I figured, I run two wires and the cable. Of course every solution presents another problem. (Like battery heat...) This one is designed to sit on the ocean floor or just hang. I'm using ocean floor loosely. Think shallow.

I am a mechanical engineering student. But I'm older and I worked as a metal fabricator and I have a shop and a lathe. I'm not so concerned about the housing.

With the electrical side my thinking was well, they use USB so maybe I can extend USB.

Do you think cat5 would fare better? I found an UHD 4K extender kit.

Thanks again!

 

If you have a camera, I assume you have lights also ?
and you say you have no propellers / motors, so yo are using the cable to lift the thing as well ?

Can you give us an idea of what depth you want to go to, what length of tether, and what you actually want to send up / down the tether ? what type of water, salt / fresh , is it moving ?

Suggest you look at a few of the off the shelf ROV's
they all seem to have cables that can be purchased separately ( as they tend to break they need to be replaceable )
may be re purpose one of them, or at the minimum, see what they do,

I've only had experience in the big boy stuff, dipping sonar and such like.
so I might over designing this , hence why I want to know a bit more,
But I do know the salt water environment is a horrible one for low voltage electronics,
to the point that all connectors need to have a cap that can be affixed so that the pins / sockets are never accessible ,
even when the cable is un plugged, water absorbers and water proof box's for every thing are the order of the day,
I've seen a cable that was water proof, be unplugged on a deck, and put in a water proof box without a dryer pack in there and no end cap placed on, A week later when cable was taken out of box, the plugs had to be replaced as they had corroded.

at 100 quid a plug and a few hours work, not fun,

 

If you have a camera, I assume you have lights also ?
and you say you have no propellers / motors, so yo are using the cable to lift the thing as well ?

Can you give us an idea of what depth you want to go to, what length of tether, and what you actually want to send up / down the tether ? what type of water, salt / fresh , is it moving ?

Suggest you look at a few of the off the shelf ROV's
they all seem to have cables that can be purchased separately ( as they tend to break they need to be replaceable )
may be re purpose one of them, or at the minimum, see what they do,

I've only had experience in the big boy stuff, dipping sonar and such like.
so I might over designing this , hence why I want to know a bit more,
But I do know the salt water environment is a horrible one for low voltage electronics,
to the point that all connectors need to have a cap that can be affixed so that the pins / sockets are never accessible ,
even when the cable is un plugged, water absorbers and water proof box's for every thing are the order of the day,
I've seen a cable that was water proof, be unplugged on a deck, and put in a water proof box without a dryer pack in there and no end cap placed on, A week later when cable was taken out of box, the plugs had to be replaced as they had corroded.

at 100 quid a plug and a few hours work, not fun,

It's basically a camera and a light in an acrylic tube with machined aluminum end caps. It doesn't move around. There are no propellers. There's a support cable and the wires for the camera and servo. If I can get to a depth of 30 meters and see what the camera sees on a laptop it will be an enormous success. Imagine a water tight lantern with a camera in it that can pan L and R. I will definitely look at some of the off the shelf ROVs that is good advice, thanks.

 

Don’t forget to consider the resistance of 2 x 30m of cat5/24guage wire. Twice, because you’re going down and back. Depending on the current drawn by the light and camera, there may be a significant voltage drop over 30m of cable. Perhaps enough to cause issues with the camera.

 

It is a possible way to go, but we have no idea what your criteria for best might be. Can you elaborate?

I need to connect a camera to a laptop over a distance of about 30 meters. I have no criteria for best. I guess I'm asking what my options are.

 

Don’t forget to consider the resistance of 2 x 30m of cat5/24guage wire. Twice, because you’re going down and back. Depending on the current drawn by the light and camera, there may be a significant voltage drop over 30m of cable. Perhaps enough to cause issues with the camera.

I'm planning to use batteries. I'm already worried about condensation.

 

I need to connect a camera to a laptop over a distance of about 30 meters. I have no criteria for best. I guess I'm asking what my options are.

In that case, anything that works and is affordable is de facto the best solution. It could also be the case that if you have large amounts of time to research the matter then you might find one that is more to your liking. It is an optimization problem that does not have a unique solution.

 

What did you sheath the cables with?

Adapters inside PVC capped pipes filled with silicone, normal CAT5.