Power and network connection to the ROV

[fryslan76]

Hi Ross,

Sorry not a great electronics guy. And you only need the chip and some small parts around it actually (datasheet is not freely available). So maybe somebody can design that, sell them as breakout boards.
For the use of coax cable, these are not very flexible and thin. So you might get drag issues again then. Strength wise they are nice to use, I think.

Found somebody who got a board similar as mine working with only removing the capacitor and adding 12V there so I am going to try that first, somewhere this or next week first. Before I really break it apart.

Kind regards

[olegodo]

Found somebody who got a board similar as mine working with only removing the capacitor and adding 12V there so I am going to try that first, somewhere this or next week first. Before I really break it apart.

This is exactly what I did. Then just use the two contact points intended for the 230v AC to connect my tether.

I have it powered with a usb to 12v (mine runs at 12v) converter on the topside and a voltage regulator that will power the on at the bottom side. It converts anything from 9-24v down/up to 12v if I remember correctly.

[fryslan76]

Found somebody who got a board similar as mine working with only removing the capacitor and adding 12V there so I am going to try that first, somewhere this or next week first. Before I really break it apart.

This is exactly what I did. Then just use the two contact points intended for the 230v AC to connect my tether.

I have it powered with a usb to 12v (mine runs at 12v) converter on the topside and a voltage regulator that will power the on at the bottom side. It converts anything from 9-24v down/up to 12v if I remember correctly.

Could you post a few photos of your boards and maybe identify the main chips on it. That would help other readers to replicate your solution and mine to if it works

[olegodo]

Sure I can!

I also gutted a 15m cat5 cable today. took out all the pairs and soldered them together end to end making a 60m test tether of 24awg wire. Connected and testes and still got a good 100mbit connection
I am typing this through this connection now actually.

[fryslan76]

Hi Olegodo,

Thanks for the photos. Your board uses the same chip as mine the AR7420. During my search for information I came across a few hack messages and the antenna function of the cable which made it an easy hack. Looking at your first picture and the gap, I have to agree. Not that I worry about it with a ROV.

Regards,

Fryslan

[rossrov]

fryslan76: Good idea about the breakout board. Just thinking about my earlier suggestion of ready-to-go tether solution, there would be compliance issues and the manufacturer would have to have CE certification, probably making things more expensive. The board would get around this, leaving the end user to complete the product very easily. From what I've read, the frequencies used fall across the HF or shortwave radio band. The potential for RF interference exists, with possible legal consequences.
I think that coax cable like RG58 is worthy of consideration. It is 5mm diameter, coax has strength, as you say, and I think quite flexible enough. RG6 TV antenna cable, solid inner conductor is not as flexible. Solid dielectric rather than foam would be needed for depth.

olegodo: That 20mm gap certainly opens up some possibilities. I've considered capacitive and inductive coupling for rotary joints, and inductive coupling for power transmission to thrusters, but not as a tether connection. One could eliminate data cable penetrations and messy connectors - especially useful for modular type ROVs with separate camera etc housings. Two biggish copper pads with a thin wire soldered to each going through small holes in the housing, then cover the pads with a thin layer of epoxy. Similar thing for the tether or interconnecting cable. How many HomePlugs can be used in a network? Inductive coupling using small broadband transformers could be better than capacitive but no way as simple.

[fryslan76]

Hi Ross,

The coax you are referring to is much thinner than I am used to. Which is indeed more TV cable. So that thinner coax migth work.
In general the easy route would be that each user who succesful demoblishes a unit and gets the network working should post a picture and a desciption of the components on the board. That way other users can buy units and follow there lead.

So here is my succes picture:

Left pc is using the powerline network

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The left pc is using the powerline network. I ran a speedtest over it and that was running the same speed as on a direct connection.

details

20140708_221554_klein.jpg (507.75 KiB) Viewed 6110 times

Oke the details, I removed the capasitor and injected 12V there. That is all.

Regards,

Fryslan

[rossrov]

Wow Fryslan - very simple - thanks for photos. Now for what cable to use? Because I want to use coaxial cable (various reasons, plus I have about 100 metres or so of RG58 in the shed), I am looking at using an Ethernet over Coax adapter pair, hoping that that they use the same OFDM technology as Ethernet over Powerline. The logic is that they are already matched to 75 ohm impedance coaxial cable, whereas I do not know what cable impedance the HomePlugs are best suited to.
The TV cable you were thinking of is probably lower loss used for distribution to multiple dwellings in the one building. The cable I was referring to is what runs from TV antenna to TV set(s) in the one dwelling. I did some quick research on best prices (Australia) of each type. From memory, approximately:
RG58, 50 ohm impedance, not the ideal 75 ohm, but thinner slightly $60 for a 100m roll
RG59 $60 for 100m roll
Cat5, multistrand conductors, $50 per 100m roll
Speaker cable about half those prices for 100m roll
I was seriously looking at fibre-optic and would like to again one day but for now EoP/EoC would be much easier to work with, cheaper for shorter tethers and (hopefully) connects the same as fibre (Ethernet) so can be easily replaced by a fibre tether system for lower drag, longer tether and greater bandwidth should the project require.

[fryslan76]

Hi Ross,

I am going to use some strands of UTP or telephone wire to begin with, I have miles of that stuff at home. Coax is in the Netherlands very sturdy and I don't have it at home

This was indeed much easier then I thougth, I was also reading about the fiber options, maybe for the next ROV. I found these powerline adapters which have three lan ports on each side in a low budget store (Aldi). Which made breaking it down a bit easier on the wallet.
I hope to start some testing during the weekend or next week to see how it works with the arduino and a PI at the same connection.

Kind regards,

Fryslan

[fryslan76]

Oke I can around to some testing this evening. Had some troubles with soldering the power connections to the boards. Not my best work and never will be my strong part.

So I have my laptop now connected through two strands from a UTP cable about 1.5meter long. And have my raspberry PI connected together with the laptop and did a test run with ping about 5 minutes without a single packetloss. From my laptop I have a ssh connection with X forward running also and it forwards my USB camera without a problem, same framerate as before. Even watching RV Seekers youtube movies about his great build at 420P was no problem.

Just for the fun some pictures:
screen cap from usb camera connected to PI.

screencap usb camera

Image.jpg (18.49 KiB) Viewed 6055 times

The floor without the camera present.

the floor

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the table with laptop and one unit powered through a lipo.

the table.

20140731_212839.jpg (678.23 KiB) Viewed 6055 times

oke now the next part of the project.