Discussion on USRP-->Wall Socket for Power Line Comms

GNU Radio
1

Okay! So apparently there is some interest in power line communication
for
GSoC. But, what we would want to do is already have a safe way of
connecting the USRP in to the wall socket for the student(s), and for
the
future of GNU Radio and USRP power line communications development.

So, as a goal of this thread I’d like to get some feedback on how we can
make this possible. Ideally, something off-the-shelf would be great,
providing the highest amount of safety for those experimenting with it.

Please keep in mind my background is not EE, but I am more than happy to
try and lead this and test/try/sacrifice what needs to be done.

Jonathan mentioned that for a project he was working on before, generic
50-ohm wall socket power couplers were made. I don’t know how difficult
it
would be to replicate something like this.

Evan M. suggested picking up some power line telephone extenders
from Radio Shack and dissecting them.

Ideally, I think we could connect whatever it is to a basic TX/RX.

Any thoughts here?

  • George
2

On Tue, Feb 21, 2012 at 3:00 PM, George N. [email protected]
wrote:

and lead this and test/try/sacrifice what needs to be done.
Any thoughts here?
Not sure how much they are or where you can even buy them, but they’re
pretty much perfect for this:

http://www.onfilter.com/products.html?s=MSN01

Brian

3

On Tue, Feb 21, 2012 at 12:18, Brian P. [email protected]
wrote:

Not sure how much they are or where you can even buy them, but they’re
pretty much perfect for this:

http://www.onfilter.com/products.html?s=MSN01

They list two North American distributors, but I couldn’t find the
product on either distributor’s website. I’ll give them a call and
see what I can come up with.

Johnathan

4

On Tue, Feb 21, 2012 at 12:30, Johnathan C.
[email protected] wrote:

They list two North American distributors, but I couldn’t find the
product on either distributor’s website. I’ll give them a call and
see what I can come up with.

These guys sell it:

http://www.hiscoinc.com/

it is out of stock with a manufacturer lead time of 4-5 weeks. Qty.
1-10 pricing is $389 USD.

The datasheet only shows the frequency response up to 10MHz, but it
probably has a higher response with some attenuation. On the other
hand, it goes down to at least 10 KHz, and has a differential mode.
That could be interesting for channels that have metallic continuity.

Johnathan

5

On 2/21/2012 3:00 PM, George N. wrote:

Okay! So apparently there is some interest in power line communication
for GSoC. But, what we would want to do is already have a safe way of
connecting the USRP in to the wall socket for the student(s), and for
the future of GNU Radio and USRP power line communications development.

So, as a goal of this thread I’d like to get some feedback on how we can
make this possible. Ideally, something off-the-shelf would be great,
providing the highest amount of safety for those experimenting with it.

Here’s a very simple approach:

http://leapsecond.com/pages/ac-detect/

There was a bunch of discussion about this on the time-nuts mailing
list, and some folks suggested changes for increased safety (including
putting two resistors in series so that if one fails short – which is a
very unusual occurrence – there’s an extra layer of protection. But in
general, with large value resistors the current is limited to a very
safe level – and it’s current that kills, not voltage.

John

6

I think this is an active module with only receive capability. You may
want
to look into Homeplug.org or a phone or Ethernet adapter for
bidirectional
interface to the power line.

7

Well, I’d put it that large resistors result in high impedance. You
still have the full line voltage across the output of the two resistors,
but any load resistance will form a voltage divider and drop the voltage
very quickly.

A simple next step would be adding an appropriate load resistor and
using an op-amp as a follower to provide a low impedance output to drive
the BasicRX.

I’m not sure why you’d need to unground anything – the output is an AC
signal, and the resistors limit any current to a miniscule and safe
level. Folks have been plugging this design into all sorts of grounded
gear with no issues at all.

John

8

Two issues:

  1. Large resistors results in large attenuation. This circuit
    attenuates
    120VAC to ~5V for the microcontroller.
  2. You would need to un-ground all of the components (USRP + PC + you)
    and
    float everything to somewhere around 60V
9

Before anyone goes out there and barbecues themselves with a USRP, two
things:

  1. Use Ettus R. products for power-line or hazardous voltage
    applications at your own risk and after careful evaluation by competent
    engineer.
  2. VAC, Gredmann, Hitachi, Magnetica, and other companies make
    power-line-communications-specific transformers with IEC-approved
    isolation. Search for “PLC transformer”. Please don’t do anything with
    HV/line voltage without real isolation; using resistors for power line
    isolation is asking for trouble.

–n

10

On Tue, Feb 21, 2012 at 13:20, Nick F. [email protected] wrote:

Before anyone goes out there and barbecues themselves with a USRP, two
things:

  1. Use Ettus R. products for power-line or hazardous voltage
    applications at your own risk and after careful evaluation by competent
    engineer.

Yep. While of course individuals may choose to go whatever route for
their own experimentation, if we (GNU Radio project) do anything with
GSoC related to power line communications, the student would need to
use a commercially manufactured product that has been engineered for
the purpose and have UL and/or CE certification.

Johnathan

11

On Tue, Feb 21, 2012 at 5:03 PM, Johnathan C.
[email protected] wrote:

their own experimentation, if we (GNU Radio project) do anything with
GSoC related to power line communications, the student would need to
use a commercially manufactured product that has been engineered for
the purpose and have UL and/or CE certification.

Maybe something a little more accessible from MAXIM:

Mixed-signal and digital signal processing ICs | Analog Devices

They have an evaluation kit which might have some testpoints to
connect up to a USRP, or try to ship off samples through their 10/100
ethernet interface.

Brian

12

Thanks, Brian!

I will poke around the max series evaluation kits to see if there is
something there that could work out at a reasonable price.

13

Hi George,
The problem of connecting electronics cheaply to house wiring was
implemented maybe 20 years ago in the X10 system, in which simple
controllers would turn lights etc. on and off. There are inexpensive
computer interfaces as well. Here is just one example of the sort of
device that could probably easily be hacked apart to expose the line
connection alone:
http://www.aartech.ca/am466-pam02-x10-plug-in-appliance-module-3-pin.html

There are hundreds of these devices available, at prices from
$10-$200. But they all send or receive signals over AC wiring.

Cheers!

Hugh Pett

14

Oooh, yeah. I forgot about X10!

I once used an X10 control system
to turn a stirrer on and off under program control for an
electrochemical cell I was running for a month. Long story, unrelated to
Gnu Radio :slight_smile:

On Thu, 23 Feb 2012 08:59:06 -0800, Hugh and Irene Pett
wrote:

Hi George,
The problem of connecting electronics cheaply to
house wiring was implemented maybe 20 years ago in the X10 system, in
which simple controllers would turn lights etc. on and off. There are
inexpensive computer interfaces as well. Here is just one example of the
sort of device that could probably easily be hacked apart to expose the
line connection alone:

http://www.aartech.ca/am466-pam02-x10-plug-in-appliance-module-3-pin.html
[4]

There are hundreds of these devices available, at prices from
-0. But they all send or receive signals over AC wiring.

Cheers!

Hugh Pett

On 23/02/2012 6:46 AM, George N. wrote:

Maybe something a little more accessible from MAXIM:

Mixed-signal and digital signal processing ICs | Analog Devices [1]

They have an
evaluation kit which might have some testpoints to
connect up to a
USRP, or try to ship off samples through their 10/100
ethernet
interface.

Thanks, Brian!

I will poke around the max
series evaluation kits to see if there is something there that could
work out at a reasonable price.
_______________________________________________ Discuss-gnuradio mailing
list [email protected] [2]
Discuss-gnuradio Info Page [3]

Links:

[1] Mixed-signal and digital signal processing ICs | Analog Devices
[2]
mailto:[email protected]
[3]
Discuss-gnuradio Info Page
[4]
http://www.aartech.ca/am466-pam02-x10-plug-in-appliance-module-3-pin.html

15

The problem with many of these types of appliances is that they include
MODEM functions inside the module. For use with a USRP, you will need
to
dissect them to get to the physical interface to the powerline.

From: discuss-gnuradio-bounces+evan=removed_email_address@domain.invalid
[mailto:discuss-gnuradio-bounces+evan=removed_email_address@domain.invalid] On Behalf Of
[email protected]
Sent: Thursday, February 23, 2012 10:31 AM
To: [email protected]
Subject: Re: [Discuss-gnuradio] discussion on USRP–>Wall Socket for
Power
Line Comms

Oooh, yeah. I forgot about X10!

I once used an X10 control system to turn a stirrer on and off under
program
control for an electrochemical cell I was running for a month. Long
story,
unrelated to Gnu Radio :slight_smile:

On Thu, 23 Feb 2012 08:59:06 -0800, Hugh and Irene Pett wrote:

Hi George,
The problem of connecting electronics cheaply to house wiring was
implemented maybe 20 years ago in the X10 system, in which simple
controllers would turn lights etc. on and off. There are inexpensive
computer interfaces as well. Here is just one example of the sort of
device
that could probably easily be hacked apart to expose the line connection
alone:
http://www.aartech.ca/am466-pam02-x10-plug-in-appliance-module-3-pin.html

There are hundreds of these devices available, at prices from
$10-$200.
But they all send or receive signals over AC wiring.

Cheers!

Hugh Pett

On 23/02/2012 6:46 AM, George N. wrote:

Maybe something a little more accessible from MAXIM:

Mixed-signal and digital signal processing ICs | Analog Devices

They have an evaluation kit which might have some testpoints to
connect up to a USRP, or try to ship off samples through their 10/100
ethernet interface.

Thanks, Brian!

I will poke around the max series evaluation kits to see if there is
something there that could work out at a reasonable price.

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