On openrov.com an nice conversation is going on, regarding sending power down the line and still maintaining an 100Mbit link over two wires.
http://openrov.com/forum/topics/teardow ... 3#comments
Power and network connection to the ROV
Re: Power and network connection to the ROV
Since i recently ran into some cheaper powerline units with as a bonus 3 lan ports per adapter. So no problems with an IP Camera, Rapsberry PI and an Arduino with Netshield on board of the ROV.
I had to break it
oke first I did a check if the units where working and that test was succesful.
So here are the insides:
The two red circles are the location of the powersocket. The print is up side down to show its guts.
The blue circles are the connectors for 250V (Europe) to the main board.
The yellow square is the hart of the operation the Atheros AR7420 chipset.
The same unit in more detail, the purple line looks like the divider between high voltage 250 and the lower voltage stuff.
Above the red bar are markings about the board model: PI699E2.8P51A rev 1.0 the first bit is a common find on google, seems the board is rebranded a lot.
Anybody knows for certain which voltage is used by the AR chipset? I hope it is 5V that would be rather nice since I have a 5V powersource here.
I had to break it
oke first I did a check if the units where working and that test was succesful.So here are the insides:
- Insides with powerstuff
- 20140628_212010_markings_small.jpg (673.59 KiB) Viewed 9247 times
The blue circles are the connectors for 250V (Europe) to the main board.
The yellow square is the hart of the operation the Atheros AR7420 chipset.
- detailed view
- 20140628_212049_markings_small.jpg (623.35 KiB) Viewed 9247 times
Above the red bar are markings about the board model: PI699E2.8P51A rev 1.0 the first bit is a common find on google, seems the board is rebranded a lot.
Anybody knows for certain which voltage is used by the AR chipset? I hope it is 5V that would be rather nice since I have a 5V powersource here.
Re: Power and network connection to the ROV
Oke managed to pry it a bit more appart. And measured the voltage across the capicator I exepect I need to replace with my own accu. It is 11.8 Volt was hoping for something easy like 5V or 3.3V 
- back side
- 20140630_212747_small.jpg (734.6 KiB) Viewed 9215 times
Re: Power and network connection to the ROV
Hello fryslan76. Not having visited the other forum more than a few times, I had not seen that thread before. There was a university or school ROV blog which described using Ethernet over power line, and I was tempted to post a link to it but for safety reasons did not. Clearly here though you are separating the communications components from the 240 or other mains voltage and wanting to use extra-low voltage
Once you have gotten the ELV system working on the bench, a good initial test would be to see what length of cable can be utilized in water before communications drop out. A very quick flick through the other forum's thread did not see any mention of testing. I have used cat5 and Ethernet but have not tested to more than a few metres of cable in water and for the same reasons I suspect that the water will have a detrimental effect on the distance capability. What you are doing may prove better than plain cat5 Ethernet. Your thread got me wondering what carrier frequencies were used by the "plugs" so I did some (more) Googling and found this site that says the frequencies used go from about 2 to 30MHz http://www.powerguru.org/the-next-big-thing-part-2/
Please keep us posted!
Ross
Once you have gotten the ELV system working on the bench, a good initial test would be to see what length of cable can be utilized in water before communications drop out. A very quick flick through the other forum's thread did not see any mention of testing. I have used cat5 and Ethernet but have not tested to more than a few metres of cable in water and for the same reasons I suspect that the water will have a detrimental effect on the distance capability. What you are doing may prove better than plain cat5 Ethernet. Your thread got me wondering what carrier frequencies were used by the "plugs" so I did some (more) Googling and found this site that says the frequencies used go from about 2 to 30MHz http://www.powerguru.org/the-next-big-thing-part-2/
Please keep us posted!
Ross
Re: Power and network connection to the ROV
Hi Ross,
In the posts there is a guy who tested it over 500 feet with 22 awg wire. Openrov has fully switched to this for thether, some people are even working on charging/ powering the ROV from the surface.
Regards,
Sjoerd
In the posts there is a guy who tested it over 500 feet with 22 awg wire. Openrov has fully switched to this for thether, some people are even working on charging/ powering the ROV from the surface.
Regards,
Sjoerd
Re: Power and network connection to the ROV
This is correct. Tests have shown that you can use a longer tether using this solution then normal cat5 network.
Also, you only need two leads instead of the cat5's 8, witch makes for a much lighter and more manageable tether.
I am using this myself, but have only tested it on my bench so far. with 100m cable (one twisted pair from cat5) I got a rock stable 100mbits both ways. I suspect this will decrease as the the tether gets longer, but not much is needed for both signal and video anyways.
Also, I believe they also tested running DC voltage down the tether. and this also works. making it possible to send 48V down the tether for trickle charging or backup/emergency power.
Also, you only need two leads instead of the cat5's 8, witch makes for a much lighter and more manageable tether.
I am using this myself, but have only tested it on my bench so far. with 100m cable (one twisted pair from cat5) I got a rock stable 100mbits both ways. I suspect this will decrease as the the tether gets longer, but not much is needed for both signal and video anyways.
Also, I believe they also tested running DC voltage down the tether. and this also works. making it possible to send 48V down the tether for trickle charging or backup/emergency power.
Re: Power and network connection to the ROV
Question from a Noob... what would the down sides be from just using the 120/240 V AC down the tether be? You could power everything with a small inverter topside and use a small AC/AD transformer in the ROV to bring down to whatever voltage you needed. The voltage drop would be substantially lower with 120/240 over a large distance and you could potentially run the entire ROV off of two 12 AWG wires. I may be missing something but that is why I ask you guys.
Thanks!
Thanks!
Re: Power and network connection to the ROV
Long story short: Risk of getting electrocuted..
If done right, all proper steps taken and done right. It would work and be safe. The danger is when people without enough knowledge, care or the right equipment try this and stuff starts to get dangerous quite quickly.
If done right, all proper steps taken and done right. It would work and be safe. The danger is when people without enough knowledge, care or the right equipment try this and stuff starts to get dangerous quite quickly.
Re: Power and network connection to the ROV
Thanks for the quick reply, I'm not too worried about the risks... like you said if done properly it should be safe. The added factor of water always complicates things but AC current carries much lower risks than DC anyway (anything under 30V DC isn't going to do much though). I work at a commercial electrical contractor and we are often dealing with service voltages over 13KVA. I'm an not the most knowledgeable person where I work but I know enough (to get myself in trouble, LOL). Well I'm a long way off with my project from needing this but I was following this topic since it popped up a few days ago and was curios what draw backs there were in using 120V I hadn't thought of.olegodo wrote:Long story short: Risk of getting electrocuted..
If done right, all proper steps taken and done right. It would work and be safe. The danger is when people without enough knowledge, care or the right equipment try this and stuff starts to get dangerous quite quickly.
Cheers
Re: Power and network connection to the ROV
That's great you guys! Maybe there is a sales opportunity for someone who can modify HomePlug pairs into a pairs of user friendly (ie safe, powered from ROV and topside batteries) easy to connect units just for ROV use? Even after many years around electronics and mains-powered gear I am still very cautious when there is 240 volts on a circuit board millimetres from my fingers holding onto the meter or scope probe 
. Pre-modded plugs would let the less electronics-experienced among us get on and concentrate on the other ROV bits. Battery in the ROV, and a roll of cheap speaker cable and there's your tether solved. That length quoted would certainly do for most of us. Coax cable worth considering too - bulk amounts from TV antenna suppliers alot cheaper than by-the-metre retail.
I linked to the SCINI project mentioned in the OpenROV thread some time ago but that was with regard to the ROV shape and thruster configuration - never looked at SCINI's tether
Taking things a dreamy step further, a while back I considered how a single insulated wire might be used for communications, with two carrier frequencies, one for video and data up, and another for control data down. Thinking of the signal loss over distance, impedance issues, the cable reel etc, I went no further. The Windowed OFDM used in the plugs would overcome some of those issues, perhaps allowing use of a plastic coated stainless-steel fishing trace as comms medium and strength member combined.
. Pre-modded plugs would let the less electronics-experienced among us get on and concentrate on the other ROV bits. Battery in the ROV, and a roll of cheap speaker cable and there's your tether solved. That length quoted would certainly do for most of us. Coax cable worth considering too - bulk amounts from TV antenna suppliers alot cheaper than by-the-metre retail.I linked to the SCINI project mentioned in the OpenROV thread some time ago but that was with regard to the ROV shape and thruster configuration - never looked at SCINI's tether
Taking things a dreamy step further, a while back I considered how a single insulated wire might be used for communications, with two carrier frequencies, one for video and data up, and another for control data down. Thinking of the signal loss over distance, impedance issues, the cable reel etc, I went no further. The Windowed OFDM used in the plugs would overcome some of those issues, perhaps allowing use of a plastic coated stainless-steel fishing trace as comms medium and strength member combined.