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I am currently working on a tethered UAV project (please refer this). I am thinking of tethering the power as well as data through the two power cables that will go up to the UAV. I plan to use 300V dc (rectified,filtered,regulated AC mains) for transmission along the tethering cable and thus, want to implement a powerline communication over this voltage.

However, I already have an AC powerline adapter (this) and was wondering if I could use this existing adapter on a 300V dc line.

If yes, what exactly would I have to do to achieve this? Also, I am unsure about the exact data rate desired but I want to stream an HD video to my ground station.

Please find the system description (block diagram) below.

schematic

simulate this circuit – Schematic created using CircuitLab

Any guidance is appreciated. Thanks in advance.


Update : 20th March,2020

I have ripped open my receiver; sharing the images below :

  1. This board has the AC stepdown and filtering alongwith Atheros controller ICs.

  1. This has the ethernet ports and (probably) a buck converter for powering the electronics.

They were connected with board-to-board connectors like this (I forgot to take a photo before I separated them) -

enter image description here

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Generally, yes, this should theoretically work.

Now, the PLC channel as seen by commercial off-the-shelf PLC modems is a strongly cyclo-stationary one, with long (in terms of communication technology) periods of bad signal conditions, which the modem has to work around, which is why they typically contain a lot of logic to estimate the grid-voltage-periodic behaviour of the cable. In your case, that 50 Hz (or 60 Hz, wherever you are) period doesn't exist, so these estimators might run amok. That might put the modem in a continuous "worst case" mode. I don't know. I don't think behaviour on a DC line is specified for any of these modems.

However, things probably work. You should try.

However:

PLC is pretty annoying, to be honest. Not a medium I ever enjoyed working with. Your data signal is competing with the noise of multiple motors, probably BLDC. That's the worst-case scenario for PLC.

Now, you, by definition of what a tether UAV is, pretty much always have something that is a line of sight, or nearly a line of sight, between ground station and vehicle.

Simply use radio comms. By now, they play at least in the same data rate regions, they tend to be cheaper and lower in power, and they (probably) add less weight to your UAV. From a reliability point of view, it's probably far more reliable than PLC with a lot of motors on the same line.

5GHz ISM-band Wifi would clearly be my prime choice here. The fact that you happen to have a cable running alongside your Fresnel zone will actually probably even help.

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  • \$\begingroup\$ Thank you for the reply Marcus. Also,how do I connect my PLC adapter on the DC powerline. Should I directly plug it in (it is rated 110-240V AC)? Or do I need to remove (desolder) some components? Please help. \$\endgroup\$ Mar 18, 2020 at 13:04
  • \$\begingroup\$ Nobody can tell you what exactly you need to do; that depends on what the internal coupler inside your modem looks like. A bit of reverse engineering on your side will be necessary. "Should I directly plug it in": no, you simply should not use PLC but wireless. There's really nothing in your application that says PLC is the appropriate technology. It's less efficient, reliable, lower rate, more expensive, heavier thing than radio comms. \$\endgroup\$ Mar 18, 2020 at 13:07
  • \$\begingroup\$ Thank you Marcus. I appreciate your feedback but still want to give it a try. I have taken apart my receiver and I will be updating my question shortly. \$\endgroup\$ Mar 20, 2020 at 11:46
  • \$\begingroup\$ be careful. 300V can kill. \$\endgroup\$ Mar 20, 2020 at 11:51
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If you are still looking for answers on implementing powerline communication on DC voltage, I found a great hack on : http://www.helicopting.de/

The project is discussed in great detail on Hack-A-Day forum : https://hackaday.com/2019/11/14/ethernet-over-dc-power/

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