Superimpose/combine signals

Discussion in 'The Projects Forum' started by packrat, Mar 4, 2009.

  1. packrat

    Thread Starter Member

    Feb 25, 2009
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    Hello again AAC-ers,

    I've got a 2:1 transformer through which I am transmitting a 20V p-p sine wave at 300kHz. On the output of the transformer, I'm full-wave rectifying this signal and using it to power some electronics. Currently it works rather well.
    However, I want to do more with this. Specifically, I want to insert higher-frequency bursts into the primary, and filter it out on the secondary as data.
    Additionally, I want to be able to send higher-frequency bursts (at a non-multiple with the others) into the secondary to be filtered out on the primary side as data simultaneously.

    Is this possible? If so, how would I go about combining the signals to do such a thing?

    I think that this is similar to how those Ethernet-over-powerline systems work. Is it? How do they piggyback their signals on top of that 60hz 120v signal?

    ANY insight in this regard would be greatly appreciated.
     
  2. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
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    You could insert the high frequency burst in COMMON MODE, by capacitive coupling to the lines AFTER the tranformer.

    However, you need to be careful about this. Not only could this be illegal, but it might not endure you to other users of the radio spectrum. Look at various references to BPL, which has been most accurately described as "...like transporting natural gas in an open trench."
     
  3. packrat

    Thread Starter Member

    Feb 25, 2009
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    Thanks.
    However, is your suggestion for the "transmit from primary to secondary" problem, or for the latter?

    Also, my application does not deal with actual power lines, but was invoked because I thought the implementation of ethernet-over-powerline might be similar, and any associated information would be very helpful. I am rather certain there will not be any interference problems, and all radios will go about their business blissfully unaware.
     
    Last edited: Mar 4, 2009
  4. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
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    This depends on the type of the transformer. Is it an air core, laminated, or ferrite? What frequency of signal are you looking at?

    eric
     
  5. packrat

    Thread Starter Member

    Feb 25, 2009
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    If you are inquiring about whether the transformer can handle the frequencies I am attempting to use, then I'll state that I have tested each of the frequencies independent of each other, and they have been demonstrated to be just fine at those frequencies.
    I don't mean to stonewall, but there are some things that I would prefer not to just lay out there in the open wilderness of the internet.
    I just need some ideas on how I might be able to feed a signal into the secondary of a transformer to be read on the primary, while a signal is being driven into the primary which powers some electronics on the secondary.
    One important point to make is that the electronics on the primary and secondary are physically and electrically isolated from each other. They do not share a common ground.
     
  6. KL7AJ

    AAC Fanatic!

    Nov 4, 2008
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    If you know the transformer will pass all the frequencies, you can just them into the transformer in parallel. Let the filter do the rest. (You might also want to put an additional lowpass filter on the 300kc signal, to prevent non-liniearities in the diodes from "backfeeding" into the other signals.

    eric
     
  7. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    X10 and similar protocols add data directly on the line with 120kHz modulation near the zero crossing points of the AC phase, no transformers involved. This extra "noise" is filtered out/overpowered at the pole transformer, although some people have had X10 devices in their house change states due to others in the neighborhood on the same channel.

    The name of the protocol was born from the frequency used (120khz).
     
  8. packrat

    Thread Starter Member

    Feb 25, 2009
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    I know that about X10. But the data rates are EXTREMELY slow. There is a reason that and similar protocols are pretty much only used for turning things on and off.

    I'm not inclined to believe that that is how BPL works.
     
  9. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
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    I was replying to the orignal post in the category of "Any information is helpful", and wasn't aware you already have worked with X10.

    For how the other technologies work, look at the patents, the second one is similar to your description as you've given it. There are hundreds more, most are referenced at the top of the 2nd one.

    5818821 - Power Line Ethernet
    7064654 - Data on Power Lines
    6404773 - Voce over Power Lines
    7072408 - Signaling/Telephony/Data over Power Lines
     
  10. packrat

    Thread Starter Member

    Feb 25, 2009
    12
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    Thanks for those links.
    I didn't mean to come across jumping down your throat or anything like that in my previous post.:cool:

    EDIT:
    I got all this stuff solved now. Thanks again!
     
    Last edited: Mar 5, 2009
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