Power Line communication

1. Jan 20, 2010

espanholito

Hello, I'm a newbie in electriacal circuits.

I want to implement a power line communication based on frequency modulation. At this point i'm able to "inject" bursts over the power line, but i'm having serious problems acquiring the burst.

I'm working with a 24AC line, and microcontrollers. I don't need high baudrates, just a reliable way to comunicate and a high immunity to noise.

From what i've learned the best way to archive a high noise immunity is to use frequency modulated signals to trabsmit bits (correct me if i'm wrong please).

I would appreciate if someone could answer to some questions:
-Is there any IC which can detect a signal between 100kHz and 150kHz and return a proporcional voltage?
-Or is any IC which can detect a 125kHz signal and retrieve a logic one?

Thanks

2. Jan 20, 2010

espanholito

You first need to determine how you will
a) differentially couple a high-frequency signal onto the 24V ac line, and
b) differentially pick a high-frequency signal off the 24V ac line.

If you plan to use a magnetic toroid (my choice), you need to choose one that will not saturate (meaning amp-turns) with the single turn of the peak 24 V ac current.

So:
a) What is the peak 24V ac current?
b) How do you plan to couple to/from the 24V ac line (be specific)?

Bob S
***************

Currently i'm using the schematics from AN236 from microchip (http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en012050) which uses a pwm output from the microcontroller and a transistor to insert a 120khz burst into the power line.

But I want to use different frequencies in order to implement a kind of PSK modulation. I've found some sites talking about the use of PLL's, but i only find PLL's for Mhz frequencies.

Last edited by a moderator: Apr 24, 2017
3. Jan 20, 2010

Bob S

The X-10 system has been on the market for over 35 years. I had one, and was able to turn lights on and off in my neighbor's house with my unit. Based on your schematics, it is voltage-coupled.

Bob S

4. Jan 20, 2010

Staff: Mentor

(Full disclosure -- the following links are from the company that I work for)

Welcome to the PF. Here is a web page with lots of info about powerline communication:

http://www.echelon.com/products/transceivers/powerline/ [Broken]

It's oriented mostly to the company's powerline transceiver products, but has lots of tutorial info about powerline comm in general in the app notes, FAQs, etc.

And the databook for the PLT-22 transceiver has lots of information about the powerline, about noise, about coupling circuits, etc:

http://www.echelon.com/support/documentation/manuals/transceivers/005-0193-01B_PL_Data_Book.pdf

I'm glad that you mention that you are using a dedicated 24Vrms powerline for the comm. If you were wanting to couple onto the AC Mains powerline, you need to meet the regulatory limits for an "intentional radiator" onto the powerlines (conducted emissions limits). These regulations vary from country-to-country. Even with your AC Mains-to-24Vrms isolation transformer, though, you will still have to meet those limits on the AC Mains side of the transformer.

Last edited by a moderator: May 4, 2017
5. Jan 21, 2010

espanholito

Thank you both for your replies. The link i've post is from a X-10 application note which i used to see how to put burst in the power line.

As I am a mechanical engineer i don't know much about electronic circuits. i want to established a communication based on frequency modulation in order to have i high noise immunity.

The best way to inject frequency on the line is using a magnetic toroid? where can i learn how to use it with a microcontroller.

How does the receiver retrieves the message?

Thanks

6. Jan 21, 2010

Mike_In_Plano

I did something like this playing around years ago. I used an LM567 PLL as my detector. You need a way to couple from the line, filter, and bring it into your chip. As I recall, I used a small value, high voltage capacitor to couple it from the AC line into a little hand-wound transformer and I tuned the transformer with a cap. Then I did the opposite on the transmit side. The little 567 chip was tenacious, and would lock onto the signal wherever I placed it in my apartment.

7. Jan 22, 2010

espanholito

Thank you for your reply, could you send me the schematics you used for that application? How mutch did the total components cost?

Thanks