Homebuilt ROVs Forum

I did not think about waterproofing. I know I will have to find a way to waterproof the electrical side of the transceiver. But can water get in and mess with the transmission on the optic side?

Hi rovdude. Thanks for posting your findings. Good to read that the supplier said TTL was OK. Would have been interesting to hear the response to Ethernet use. After thinking about this a bit more I'm pretty sure that you will need at the very minimum some sort of zero-crossing detection and interfacing circuitry between the Ethernet cable and the FO transmitter.

If you can put up with a bit more bulk than the transceiver alone, then we come back to complete media converters, where all this work is done for you. I've seen them for $100 (each end, Western retailers). Single, bi-directional fibre converters cost a bit more.

Having said that, if one were keen enough, then building a custom link 2-way data and one-way video (not IP) would be possible, plus save you the need for IP camera, Ethernet Arduinos and an Ethernet switch. Basically a similar thing to the off-the-shelf CCTV gear KenL was looking at.

ROVER3D mentioned that water didn't affect his connections. As long as the water is clean, this is not suprising. I've read elsewhere that a grease or gel is used.

There are FO transceivers that do specifically ethernet, all circuitry for media conversion included. I have not completely read through the spec sheets for those, but they are basically the same as for TTL, just different pinouts. Again that's definitely something I have to check with one of the techs.

Digikey has such a huge catalog, they have basically every model each company makes. With the companies that Digikey use, they basically make a "series" of products that do exactly the same thing, just slightly different application. One example I found is a honeywell pressure sensor I bought through them, they had a series of sensors with 20 different ranges, and each had the option of absolute, gauge, or differential. It's the same with a lot of the transceivers they sell.

A non-IP camera would also probably be ideal, but I'm still working with processing, and I found a library for IP. I would prefer to use a USB camera because it's less hassle and guess, so I definitely will be looking into the Media converter for that.

For Arduino, something I noticed is none of the non-linux boards (they now have one or two, but look painful to program) is none of them have the memory or processing power to work with good quality images, so my camera is going to be a separate system.

That said, I will be using two separate fiber optics "systems" though, whether they are both just transceivers or if one is a transceiver and one is a media converter. Making a custom 2-way data and one-way camera feed sounds like a lot of guess work, and if it didn't work off the bat I would be worried I would never get it to work

Again, would be good if the tech support can give you some confirmation on the direct connection of cat5 Ethernet to the transceiver .

Getting off-topic perhaps.....I'm currently playing with Processing but not for video. Was planning on using my IP camera and it's normal browser interface (IE) in a window alongside the Processing GUI I have written. Thanks for pointing out the new Arduino. The Yun? I haven't checked this out much - giving the ROV mechanicals, wiring/plugs/ and tether priority - but would be interested to see if a camera module could be used with good results. Would allow a simplified connection to fibre-optic - just the one IP device, so no need for the Ethernet switch or USB adaption, not to mention multiple fibres.....

Apparently many IP cameras use Linux operating system and a similar-sounding chip to the Yun. I don't know anything about linux myself, but wonder whether or not a cheap IP camera's code could be modified to provide, in addition of course to video, the simple functions "our" Arduino Unos do, such as control, depth and bearing, . Control, monitoring and video for less than $40, and again a simpler Ethernet/fibre optic connection.

Just to throw another Arduino into the mix, I think my next bottom side board will be a Multiwii pro board. It has all the sensors on board and no end of inputs and outputs all for $40 or less.
Of course you would add your own sketch to it.

Gidday Ken. I tried to find a circuit diagram of the Pro to find out if the SPI was used for anything. The SPI is what the Ethernet shield connects to in a "conventional" Arduino. The sensors all use I2C, so I'm guessing that the SPI is free.
I reckon that board would be good on it's own if a cheap fibre CCTV converter could be found to do the video and data comms.

A bit more digging around re connecting to fibre transceiver modules. The inputs and out puts of the transceivers i have looked at are internally capacitively coupled, meaning that they will not pass DC , which pretty much rules out serial as used by the Arduino's UART, or serial pins. The voltage levels do however look like they are compatible with what comes out (and in) the end of a cat5 Ethernet cable. I'm considering a direct connection to the Wizz chip (bypassing the Ethernet shield's connector and magnetics (transformers)). To answer the question whether any of this would work, I nearly clicked the buy button on a couple of transceivers. Difficulty in sourcing the cable termination tools stopped me, as did my total lack of experience with FO termination, and near total lack of termination knowledge. There's also going to be more time involved in fiddling around, unfortunately conflicting with other life commitments for now.....

Reliable water- and pressure-proofing is do-able I believe, but another challenge

Hey guys,

I've been on hiatus from my ROV project for a while, but did any of you find a solution for full-duplex converters with video as well? Ideally I am looking for one that can support up to four cameras, but can start with one or two. Although I think the money upfront for the right one is a better option. I've seen plenty of converters that do this online, like ebay, but they are not full duplex. They are simply controllers for security camera systems...for use with PTZ systems.

I have put several calls into companies because I don't fully understand the technical details in their descriptions, but they never get back to me. I finally found a company local to me, MN, that I might be able to make some headway...will let everyone know when I do.

Just checking to see if anyone has found a solution that works for them.

Thx!

Hi MNDeepROV. I reached much the same conclusion as you did. Contacted one company (Asian, cannot remember their name though), but they either didn't understand their own specs and/or figured that I wasn't going to be buying several hundred units at a time.

Anyway, I'm more interested in Ethernet over Fibre rather than the composite video/RS232 converters. Alot more choice in transceivers, but means that one is committed to IP cameras, Ethernet connections at each end and a PC running custom control software.

Whatever path is taken, the fibre and termination issues remain the same.

I myself was wondering whether Ken or rovdude had been making any progress with the fibre stuff. Would be good to see this thread moving again.

Ross

Hey rossrov,

Ok, been meaning to post this info for a week or so now. I finally found a potential solution for the fiber TX/RX with full-duplex, and audio. I've found a couple actually. One very expensive setup, and one seemingly affordable solution, just the wrong size for me but wanted to pass the info along for everyone.

My ultimate goal:
4 Video Channels (ambitious I know but really hope to get forward/reverse/up/down views without much switching)
1 One-way Audio Channel (alarms and general interest)
RS485 Full Duplex communication (four conductors)
Cost - affordable (I didn't really have an idea of what they would cost so I was "hoping" for under $300.

Expensive Options:
After much explanation to three less-than-techie sales reps, I got one local distributor to offer up a solution that may have almost fit my parameters, but missed the mark on the price by a long shot.

Description from Marketing material:

"The ComNet™ FVT/FVR412(M)(S)1 Series transmits four channels of video utilizing
state of the art digital encoding and decoding for high-quality video transmission,
along with two channels of bi-directional data and one bi-directional contact
closure over one single mode or multimode optical fiber. ...

http://www.comnet.net/comnet-products/v ... 12ms1.html

Cost: Total = $2,250. ($1,125/ea. for the TX and for the RX separately). HA!...I think not. Not sure what they were smokin'. Perhaps they can be found for cheaper, but it still doesn't hit the mark without the audio channel, and I didn't even bother to look at the dimensions or power requirements.

NOTE: The company offered up another multiplexer just for the audio which was an additional $500 for both the TX and the RX together. Not ideal for many reasons...


Reasonable Option:
I saw a post on this forum (somewhere) where someone bought a device off of ebay but it didn't have what was needed to make it full duplex. I also had seen a couple of those types of units on ebay and they all lacked my specs, especially the four-wire full duplex comms for RS485.

So, I started contacting a few of the overseas companies and got one positive response. Actually, whomever was on the other end had pretty good english and we were able to communicate pretty well. The persons name was Queenie...and that just made it that much more interesting. Other companies did respond, but they could not modify their units as Queenie was offering.

Anyway, check the link below:
http://www.ebay.com/itm/1CH-Data-Digita ... TM:US:1123

The ebay seller is "safer-guard"

Cost: $270 - $320 (with mods)....much more reasonable.

It shows as sold now but you can still see the specs. I'm sure others units are available.

Basically, this specific model can be modified (upgraded) to RS485 four-wire full duplex for just an additional $25. It has everything else I wanted. 4CH Video, 1 CH Audio, multimode fiber (also an add-on..I think it was $25 as well).

Unfortunately, I am using a 5.5 inch I.D. tube for my main ROV hull. This unit is too big, and they couldn't give me spec on the circuit board inside, but I think it's just a touch too large.

They also have 2CH and 1CH video that are smaller units and can also be converted as above. I think those units would go for under $200. However, if I am going to "pony up" (that means "pay" for some of our international members) for a fiber optic multiplexer unit, and deal with a whole new tether, etc., then I certainly want it to have the flexibility for growth.

After finally finding a solution for fIber, I've weighed the pro's and con's and since I already have my cat5e wire bought and the tether in the works, I may just stick with that for now and take a serious look/attempt at what I can do with IP cameras...I think they only use four wires actually, and I've got four spare in my tether! (or another converter of sorts perhaps).

You're right though Ross, it seems there are a lot more options for ethernet to fiber converters. More research to do. For right now I'll have to stick to 2 constant video channels with video baluns and switch different feeds inside the ROV via relays or get the IP cameras to work in my current cat5e tether. Time to focus in on the rest of my design and leave the upgrades for later I guess. I'll be monitoring this one if anyone has any Q's or if a better solution pops up in the near future!