Teardown of a HomePlug Adapter


$86.25NZD (~$73USD) inc 15% tax without shopping around - http://www.pbtech.co.nz/index.php?z=p&p=NETTEN0202&name=TENDA-P200Kit-200Mbps-Powerline-Adapter-Up-to-200M

So a bit more expensive but we're kinda used to that down here if we want things quickly.


Here's what looks to be a pre-packaged solution for the USB 3.3V regulator. Cheaper than trying to build it yourself. They don't list board dimensions, but from holding a ruler up to the screen it appears to be 1.1" x 0.5". I think this would fit nicely in the original Medialink case.


I've never ordered anything from these guys before. Anybody have any experience with them?



The main board on my pair is version 1.0, vs your V1.1. The only difference is a change in supplier of the RJ45 socket, everything else appears identical. There's 13 weeks difference between our units according to the date codes.

Time to connect everything over my full tether length and see how stable it is when the motors are running.


Hi Mike:

So both my power supply boards say 1241 on them. Is that what you're figuring is the date code (year/week)? My plastic housings have little date markers molded into them as well, showing month 12 of 2012. Given how fresh that would make the hardware, it's interesting that Amazon has these on sale. I hope they're not about to be discontinued!

So after posting above about this being a generic product for all markets, I had a head-slapping moment when I realized why the AC power supply prongs are connected via wires, rather than being soldered directly to the circuit board which would be cheaper. The use of wires allows for several different power prong arrangements to use the same circuit board. Duh!

Let us know how your tether experiments turn out. We're going to be doing the same tests here at OpenROV headquarters on Saturday, hopefully including some in-water tests.

My units came with some software utilities on a CD, that supposedly show connection speed. I don't know whether it updates in real-time, so that we can see the effect of motors running and such. I'm going to try to play with the software a bit between now and Saturday.




I grabbed a few different sizes of twisted pair wire (in 100m lengths) from the surplus electronics store today so we can experiment with that during the build day. Believe it or not, the store didn't have an Ethernet crimper, so we may need to improvise on how to make a really short patch cable.

Does anyone out there who's coming to the build day have the tools put ends on Cat-5?



My powersupply boards are marked 1228. My housings are marked August 2012.

It's quite a new chipset (BCM60321), and a few of the bigger name manufactures (Netgear, D-Link, Cisco Linksys) have announced products using it in the last 5 months so I have no fear that we won't be able to source these soon.

Broadcom says in their marketing "entire PLC modem design size of 51mm x 38mm is possible" so take that as a challenge to manufactures to keep these units small.

I was wondering if there's a firmware difference between v1.0 and v1.1. The small chip on the back is a 3MB eeprom for the firmware. I'll get mine powered up and try out the software and see what it can tell me.

Sounds like some productive Saturday work on the horizon. Hopefully I can get mine in the test tank tomorrow to.

- Mike


So in preparation for Saturday's build day, I decided to put a right angle power connector on the ROV side adapter. Changing out these pins is a bit trickier than changing the ones for the tether, with more risk of killing your adapter.

So here's a look at the ROV-side adapter when I last left it:

The tether connection has right angle pins, but the power connection is over the three ragged cut pins that originally went between the adapter power supply and this board.

To desolder the existing pins, I first used a hobby X-acto knife to cut the pins apart, so that they could be desoldered one at a time:

To desolder the individual pins, first apply a little flux to the pin. This helps to conduct heat into the joint from the tip of the iron:

If you haven't got soldering flux, you can actually apply a little blob of new solder. The flux in the fresh solder is what you're really after.

These pins connect to the power and ground planes of the board, and even though they have thermal reliefs, they conduct heat away far faster than the pins for the tether connection. Use the highest temperature you have on the iron- I had problems using a 700 degreeF tip on my soldering station, until I remembered that I had an 800 degreeF tip tucked away in the drawer. Heat each pin, and when the solder has melted, grab the pin from the underside with a needle-nose plier and wiggle it free.

After that, use some solderwick to clean up the pads, and then clean off all the flux residue with a swab and some alcohol. Insert the right-angle header, then add some flux again. This will allow you to solder the joint with minimal amounts of solder, avoiding solder bridges.

Here's the completed unit:

So now all of the cables stream to the sides:

If testing goes well this Saturday, my next project will be to get one of those USB 3.3V supplies mentioned above, and package the complete top-side unit back into the original MediaLink case. Stay tuned!



If not, I have a couple of 1' patch cords that we can coil up I suppose.



I just connected up everything on my pair and tested it. It worked, same as Walt found. But I couldn't resist putting some power on the tether too, so I added 14v DC via a 56R resistor to the tether. This resulted in no change to the reported connection speed.

Top side: USB power to LM3940 3.3v regulator with a caps - should have one on the input side too but I didn't have one handy.

ROV end: Powered straight from the 3.3v on J1 of the cape.

Covered the back of the HomePlug board with kapton tape, it nests perfectly inside the cape.

Tether: 50m tether from the kit, with two joins in it.

Here's what the config util shows for the connection:


Mike- great report! May I ask, where did you get that short, bare-wire patch cable that links the Homeplug adapter to the Beaglebone? Do those have to be hand built or is there a place that sells them like that?




I built that - I have a RJ45 crimping tool, from my data comms days, and used just the two needed pairs to keep it flexible. If you want a bunch I can send them up, it'll just take about 1.5 weeks to get there. Just message me the address and how many.


Thanks, Mike, for the offer, but I think we'll get a crimper and start building patch cables like that here in house- something makes me think we may need a few hundred of them in the near future...

Our test was a complete success.

I'm happy to report that not only did the taken-apart Medialink MHP-EA20 board effectively communicate across a two wire tether, it did so at a speed consistently faster then 100mpbs across more then 100m of copper that was only 30AWG!

The implications of this are tremendous:

We can now virtually neglect buoyancy and drag issues related to the tether

We can relay much higher bandwidth data

We can communicate over longer distances

Tether can be acquired, replaced, or repaired quickly and easily without heavy regard to wire or junction quality

It is possible to pay tether this thin out from the ROV (instead of from the surface) to prevent fouling in hazardous areas

Multiple ROVs can be connected through the same two wires

We can send power down the tether which (depending on tether wire gauge) may be sufficient to power the ROV indefinitely

And the list goes on..

In essence, this system allows us to achieve performance and capabilities that are similar to (and even better then in some ways) fiber-optic ROV communications equipment that costs tens of thousands of dollars - all with two $20 pieces of electronics that can be bought over the counter, and some wire that would be barely good enough for a telephone.

I think this is just the beginning of some amazing things that will emerge from this capability.



That's awesome!

This week I plan to try powering the electronics over the tether and leave the batteries just for the motors. I need to think about DC vs AC, and balancing voltage vs current to minimise loss while staying safe and within the range of the BB and cape regulators, or putting another switch mode regulator in front of the BB.

But first I have to work out why one coil of my port motor is intermittent - teething problems are fun....


Nice job on the packaging Mike. I love the RJ-45 patch cord. I suspect by the end of Monday there's going to be a RJ45 crimp tool at OpenROV HQ.

The ROV we were using during yesterday's build day had a bigger camera module, so we had to put the adapter on the back side of the electonics module. A tiny ethernet cable would have really helped to package it all together.

Your macro photography is gorgeous. Out of curiosity, what kind of camera and flash arrangement do you have?

So as Eric related above, we ran a test and got full connection speed over 100 meters of 30AWG twisted-pair. Eric's pretty excited about this because that's likely the thinnest possible tether you can use- the stuff's pretty near invisible. I was actually more interested in a second test we ran, where we got full connection speed over 100 meters of 22AWG teflon-insulated twisted-pair. The teflon insulation is really thin, so the wire ends up being smaller than you would assume, and this tether weighed only half of what 100m of the current Belden tether did. But most importantly, the resistance of the tether was only 5 ohms per side, or 10 ohms total. If we try to limit ourselves to 40 volts on the tether for safety purposes, this cable could deliver 40 watts to the ROV out at 100 meters- and all of our battery life issues would disappear.



Camera is a Fujifilm HS30exr, shot in sunlight (it's summer here). No flash or tripod.

That 22AWG wire sounds pretty interesting, do you know who it's made by? I'm going to start thinking about a topside power supply, something that can run my netbook and send power to the ROV. I wan't thinking of going over 30V as I have two 14v hardcase Lipos that I was going to use.


I spent the last couple of nights packaging up the top-side Homeplug adapter into its original case. By now this thread is no longer a teardown of the adapter, but more along the lines of "how to switch your tether over to HomePlug". But I didn't feel like starting a new thread right now.

So at Jameco I found some very small terminal blocks, on 8.25mm centers:

A little work with a Dremel tool cut it down from 6 to 4 positions. Drill some matching holes in the adapter case:

And some plastic glue mounts the thing:

You could get by with a 2 position block, since the wires for topside power can be put in the same screw terminals as the tether. But I liked the idea of splitting them out separately, so you can work on one without disturbing the connection of the other.

On the HomePlug electronics board, remove the header pins for the power and tether inputs, and install some wire pigtails:

You should probably test the thing now before you mount it into the case.

I glued the electronics board directly onto the lid of the original case. I wanted a flexible glue, due to the way the RJ-45 connector is going to slide into the case. Silicone caulk/glue is good, but it needs to be acid-free or you can end up with corrosion issues (the vinegar you smell when the silicon cures is acetic acid). GE Silicone II is claimed to be acid-free:

Apply some big dollops of silicone to the inside of the lid, making sure you stay clear of the LED windows. Set the electronics board onto the lid, and then re-assemble the case so that the RJ-45 connector fits in its hole correctly. After curing overnight, here's what you have:

The power pins in the case can be removed by heating them with a soldering iron until the surrounding plastic softens, then pulling them out:

The 3.3 volts for the electronics is provided by a mikroElektronica USB-Reg (MIKROE-658) regulator board. The input to this board is a mini-USB connector. It will be connected to a USB port on the top-side laptop.

I filed a hole in the case right by the reset button. This location will allow the USB power cable from the laptop to stream parallel to the network cable, keeping the cabling run neat.

Connect the power pigtail from the Homeplug electronics to the power supply, and then test it. Mount the power supply in the case with some more silicone:

Wire up the terminal block connections:

Close up the case (it takes a bit of jiggling), apply some labels, and you're done:

The great thing about using the original case is that the LED indicators are in their original positions:

Is that ridiculously awesome or what?



this is damn freakin awsome! Congrats!



Ridiculously Awesome.




Excellent work!

I opened my D-Link Powerline AV500 adapter, but it has everything on one PCB:

Has anyone else looked at alternative powerline products?

Can you recommend where to buy the Medialink MHP-EA200 Powerline Network Adapters?

(EDIT: found them at Amazon.com)