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Topic: Cable for submarine robot (Read 5568 times) previous topic - next topic

giacomomarelli

I'm building a submarine robot that has to go in non-salty water( a lake) and I will control it with a cable. I'd like it to go at least 100 meters deep. The cable will have 7 wires, 2 for the power (24vDC and ground), 3 wires for the serial comunication between the arduino ouside the water that prints the commands and the arduino in the robot that reads them (pin 1 and 0 + ground), and  2 wires  for the usb comunication beetween an HD web cam and a Pc outside the water.

Serial comunication cables can reach 50 meters and to reach more than a hundred you need some ICs like a couple of max483. The real problem is with the web cam signal, I need to see what's happening in real time and to see it on a screen. Usb cable can't reach more than 5 meters... What happens If the cable is more than that? Is there any solution?

What if I convert the signal from the web cam from usb to serial, send it on the cable as a serial signal an then convert it back to usb, so that a computer can connect to it?

Sorry for the grammar.

SurferTim

Have you considered ethernet instead? An onboard router would allow a much faster connection for the cameras. 100 meters is about the limit of a normal ethernet cable connection.

MichaelMeissner

Have you considered converting the communication to ethernet?  There you could use off the shelf solutions like switched hubs or repeaters which can deal with error correction and resending.  You might also check out fiber optic transmissions, though I suspect you find more off the shelf solutions if you convert it to tcp/ip packets rather than plain signal wires.

giacomomarelli

But how do I go from web cam to ethernet? I found this on amazon http://www.amazon.com/SANOXY-over-Extension-Cable-Adapter/dp/B003BDMK3S/ref=sr_1_1?s=electronics&ie=UTF8&qid=1344427592&sr=1-1&keywords=ethernet+webcam, can I use someting like that? What if I use a 300 ft ( nearly 100 meters) CAT 5 cable instead of only 150 ft?

SurferTim

Maybe you should use an IP camera that has a CAT5 cable connection. Do a Google search for "ethernet camera". That route is a bit more expensive tho. Here is a start:
http://www.vivotek.com/

I don't think you will get a usb cable to go 100 meters with a usb webcam (like Logitech webcams).

MichaelMeissner


But how do I go from web cam to ethernet? I found this on amazon http://www.amazon.com/SANOXY-over-Extension-Cable-Adapter/dp/B003BDMK3S/ref=sr_1_1?s=electronics&ie=UTF8&qid=1344427592&sr=1-1&keywords=ethernet+webcam, can I use someting like that? What if I use a 300 ft ( nearly 100 meters) CAT 5 cable instead of only 150 ft?

It might work, but it might not.  I suspect such devices need the cable to themselves, so you would need to run 2 cables, one for the web cam, and one for the arduino.

I would go for a web cam that knows ethernet and use that, rather than trying to convert USB to ethernet.

What ethernet/tcpip adds is putting everything into a packet that is check-summed.  If the packet is malformed, the sender has to resend the packet.  If you are doing straight wires, you have to essentially recreate this checking and resending, or possibly have some communication glitches.

pito

http://www.selinc.com/SEL-2800/?v=2

gr0p3r

hi,
a bloke at work had a similar problem. he used usb web cams for a security system. not underwater, but still had the problem of usb <5m. he got some cheep generic eBay USB to Ethernet converters. they worked a treat. but then you would have the problem of having more wires. they cant be run through a switch.
it has to be    cam --- usb-eth --------cable------eth-usb ---- computer.
you would have to work out if any of the wires are not being used in the ethrnet cable to pipe you serial down.

otherwise, the suggestion of a Ethernet camera would work, though they are more expensive and heavier.

gr0p3r

How about a lansheild for the arduino and ethernet camera(s)? plug it all into a simple switch and then you can send what you like up one ethernet cable.

Riva

Quote
Serial comunication cables can reach 50 meters and to reach more than a hundred you need some ICs like a couple of max483. The real problem is with the web cam signal, I need to see what's happening in real time and to see it on a screen. Usb cable can't reach more than 5 meters... What happens If the cable is more than that? Is there any solution?

Use RS422 instead of RS232. Something like the MAX485 or MAX491 chip depending on if you need half/full duplex comms. For full duplex though you will need 5 wires instead of 3.

SurferTim

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otherwise, the suggestion of a Ethernet camera would work, though they are more expensive and heavier.

Heavy is good for a submersible. Less ballast required to submerge it. And considering the pressure at 300 feet (just short of 150 psi), the cost should be more to build the submersible hull with a non-leaking viewport and connectors. Just a thought...

gr0p3r


considering the pressure at 300 feet (just short of 150 psi), the cost should be more to build the submersible hull with a non-leaking viewport and connectors. Just a thought...

true...
not on topic of cable, but out of interest, have you already got that part sorted giacomomarelli? can you post a pic, it would be cool to see.

giacomomarelli

Thanks for the answers, I think I  will try the usb to ethernet converter and buy two ethernet cables on ebay (100 meters long each). One for the usb and one for power and serial.
If it works I'll tell you,but I think it won't be before september-october.

To gr0p3r & surferTim: I haven't got any pictures yet, I'm running the project with four friends of mine and one of them is sorting out the mecanical point of view. The structure will be a steel tube (170 mm diam, 480 mm long), motor and propeller at the back and web cam at the front. No static immersion, only dynamic through propeller job. Another friend an I are doing the electronic part.
It will go in lake Como (italy).

To Riva: how do I chose to use a RS422? When I connect two arduino with pin 1, pin0 and ground is it using RS232? I'm not really practical of these things..

Thank you!


Riva

Quote
how do I chose to use a RS422? When I connect two arduino with pin 1, pin0 and ground is it using RS232? I'm not really practical of these things..

You will need an external chip like the MAX485 or MAX491 http://www.maxim-ic.com/datasheet/index.mvp/id/1111 to do RS422. Connect to a couple of pins on the UNO and use software serial or on the Mega use one of the other serial ports. It may even work using TX/RX pins on UNO but I have not tried this (Only used RS422 on PIC chip)

zoomkat

I'd put a small ethernet hub or router in the sub and connect the IP cam and arduino with ethernet shield to it.
Google forum search: Use Google Advanced Search and use Http://forum.arduino.cc/index in the "site or domain:" box.

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