Teardown of a HomePlug Adapter


#101

Thanks Walt! They are $20 instant off + free shipping if you have Amex.


#102

Hi Stefan, Thanks for the post, we have been having the same problem as you, but you seem to have answered half of it!

Would you be able to tell me the procedure you followed to modify the board for the topside adapter?

Many Thanks

Matt


#103

Hi Walt, thanks for all your work on this awesome project. My application requires a topside power supply and so I would like to adapt power over tether (POT). From what I gather from your homeplug teardown and the 5V DC signal sent down the tether to turn on the ROV, it seems the homeplug communication can work on top of a DC voltage. I would like to use 48V or less. I do not need the ESC circuitry. From what I see I will need to do this:

Topside:1. Remove R1 & R2 at the topside board

2. Connect my power supply topside

3. Anything else?

At Controller:

1. Connect power to aux power-in (through buck converter or straight is voltage compatible)

2. Increase R3 as needed based on the LTV-8141S voltage limits?

3. Can the LM25011 handle <48VDC? (assuming I don't use a buck converter before the controller)

Have I missed anything or am I really off base?

Thanks, Newbie Rob


#104

Hi Rob:

While you have the basic steps right, I'd first measure the resistance of the tether you're proposing to use, and see what the voltage drop across it is going to be when you draw the required power. I think you're definitely going to need a buck converter in the ROV, and it will likely need a maximum-power-point tracker to keep from overdrawing power from the tether.

The Controller board is not designed to handle anything greater than about 17V (a 4S lithium cell configuration). If you want to feed it anything more you'll have to verify the various circuits yourself.

-W


#105

Thanks for the input. I looked around for a bucking converter with MPPT with no luck. I may just beast it if my tether is beefy enough. I don't care too much about power consumption at this point. If you know of any off the shelf modules please let me know. I can only think of Traco, Vicor, and Mini-Box right now.


#107

Hi Stefan,

I just got a pair of tplinks just like what you have in your pics here.
I am just getting ready to tear it down, but I wanted to pause and ask you for any suggestions on these particular pair of adapters.

I need to join these pair of adapters on 24VDC over twisted pair cable, I believe it is ~ 24 AWG gauge (I may be off a bit).
Any caps, resistors, inductors I need to add?? I am not an expert in electronics so any suggestions is appreciated.

Thanks in advance.
Inti


#108

@olegodo With regard to the TP-Link TL-PA411 - I am about to setup these for use on a tether. I wanted to ask about your experience after the initial testing you did. Any problems driving a longer tether ? Did you have to remove any components once you started to apply Voltage to the Tether ? Thanks !
Mark


#109

I would stay within 300ft or just under 100 meters.
I used a 200V 1uF cap on the positive terminal of the tether.
I have tested with DC voltages up to 48Volts, no issues.

I had to supply a 3.3V on the board. However there is a way to feed the board with a combination of a step down power supply micro board and a ferrite core. You need to be careful on the selection of the ferrite core.
FYI
You can still form a bridge with 3.3V and a ‘dead’ wire.
This is really cool when things breakdown, you still have a link!!


#110

Hi, I am new to openRov, I am highly interrested in powering the rov through the tethering cable.
Where a you now? does anybody have tried and succeeded in powering his rov from the surface?


#111

Hi:

The 2.X series of ROVs does not currently support power over the tether, though we have played with this feature in the lab, and there’s no reason why one couldn’t modify their ROV to do this. We don’t support this feature out-of-the box because it adds a surprising amount of complexity and cost to the system, and as of yet there hasn’t been enough demand for such a feature. With the current batteries the ROV will operate for about two hours on a charge, which is plenty for most applications.

The current plan for Trident is for it to support power over the tether.

If you choose to modify your OpenROV to take power over the tether, please post your results here for us all to see!

-Walt


#112

Does anyone know the limitations on how much wire the signal will work through? I’m trying to rewire a commercial ROV and use OpenROV controls. We have a really nice 1500 foot tether. Anyone know if the Tenda would work through that much wire?


#113

The bandwidth over the tether starts to taper off once you have about 100m of tether out. We haven’t done a good job of quantifying this yet, since the ROVs we sell are only rated to 100m. But we need to get a handle on it as we progress to deeper diving units.

The farthest we’ve ever run a homeplug link is about 320m, and the connection was noticeably slower at that point. There’s no way I can predict whether it would be good enough for your application, especially since I don’t know what kind of wire is in your 1500’ (~450m) tether. The best thing I can say is hook it up and try it out. Note that when the tether is all reeled up you will get a deceptively high connect speed, since there is coupling between the loops of tether in the reel. The only way to find the true connect speed is to have it all reeled out.

Also note that there is a utility on the DVD that is included with the homeplug adapters, and this will tell you the speed at which the physical layer of the homeplug connection is running. The actual throughput is something less, but using this utility will at least give you a way to map out how the data rate drops as a function of unreeled tether.

We’d love to hear more about the commercial ROV you’re rebuilding. If you’re open to it, please post some photos and a story here on the forum.

-W


#114

Hello Mr Holm

a great job all the stuff you exposed on powerline over copper pair
if you want to go 1000m and even more coax cable is a better choice.
also very easy to do is power over coax in order to inject 48v one side
If you need working sample easy to use contact Xingtera.com they have ready to use product based on G.hn chipset ( similar to powerline but ITU standard)
but you can also use coax cable on Tenda and buy power coax injector for 2$ an extract other side
that standard technology used in TV cable distribution.
but it probaby better to use 60V AC on coax on long distance … used in Cable TV and Docsis industry
By the way I learn a lot reading your post and it gave me some ideas


#115

Hello

OFDM over copper like adsl vdsl2 have a reach of 1000m but high frequencies are to much attenuated and speed drops.

I suggest to use coax cable even they poorest is many times better than copper
1000m link over coax is not a problem

have a look coax adapter with remote power used in video surveillance business.
I suggest to have a look www.xingtera.com


#116

Oh man, this is awesome info… really it is!
i appreciate your whole effort to compile custom power adapter article with detailed info.
Cheers to that!
#Brain


#117

Is there any specific information on which of the six power header pins for the Tenda P200 V2 require to be used to power it? I can’t get mine to power up when applying power when it is separate from the it’s supplied mains power, even although I know they are still working.


#118

@b11,
According to Sheet 2 of the 2.8 Controller Board Schematic, the Tenda P200 V2 is supplied 3.3vdc, by U5, from J18-5 on the Controller Board. If you can match the correct Tenda P200 V2 pin to the J18-5 connector socket then you will have identified the power pin.
Also, you must provide a dc return path (gnd) to the Tenda P200 V2 and that gnd is on J18-1 on the Controller Board.
Regards,
TCIII AVD


#119

@b11:

Here’s an old forum post you can use for pictorial guidance- see the topside photos at the bottom of the post. The controller board schematic is a good place to start, but unfortunately trying to figure out the correct orientation of header blocks based upon schematic pin numbers tough chore.

-W


#120

@Walt_Holm, Hi Walt, I read your posts and I found very useful for my project (not related to openrov).
Hoping you can help me, here my question.

I need to inject 24VAC into the tether line.
Should I add some components (in one or both the TENDA V2 units)?

Thank you very much
Regards


#121

@Walt_Holm et al.

Network loss due to draw from thrusters… Can anyone advice? Thanks :slight_smile:

I’m mentoring a team of high school students competing for their third year as an underwater ROV team. We are trying to eliminate our network cable and so we got the Tenda pair and two interface boards from the OpenROV store and are able to stream IP cams to a surface laptop over a 100ft 12 gauge +ve/GND tether which powers the ROV with 12V and 20-25A. We pulled the resisters on the interface boards on both ends so that powering of the tether line is isolated from the powering of the Tendas, as instructed by the OpenROV support team. We are using Blue Robotics T100 thrusters with their Basic ESCs. These can pull up to 11.5A each. We use algorithms to make sure we don’t fully power more than 2 at once.

The problem is that when we power on a single thruster (even gradually) there is occasionally some temporary network packet loss (over 1-2s) - noticeable video frame drop/lag, and increased ping time. We haven’t yet hooked up the Raspberry PI controller. The indicator lights on the Tendas stay on.

As an A/B test, we connected a network cable straight from the laptop to the IP camera, while still powering the cameras over the tether, and this eliminated the issue, therefore the issue is definitely related to the network going over the tether in some way.

I assume the current draw or the power pulsing from the ESCs is throwing off the Tendas.

Is there a way to buffer this power draw and/or prevent the power pulsing of the ESCs to the thruster coils from affecting the Tenda connection?

Note that we are not allowed in the competition to use any on-board batteries, or voltage up-converters, but capacitors and voltage regulators are allowed.

Thanks for any help.

Colin