Data over power

I need someone to please point me in the right direction. old thread, link to an article, or any helpful info at all. I have two propellers about ten feet apart both being powered by a 12v 77A DC power supply and I want to send data over the power line similar to a phone line, half duplex is fine if that's all that is possible.

Thanks in advance for any help.

Comments

  • 16 Comments sorted by Date Added Votes
  • This might be a good place to start.

    https://www.smarthome.com/sc-what-is-x10-home-automation

    You can also search the internet and this forum for X10, which is the the first popular communication protocol over power lines. Still in use today. There are also power line modems available.

    In science there is no authority. There is only experiment.
    Life is unpredictable. Eat dessert first.
  • Bnikkel,
    The power line you are referring to is 12VDC? Correct? If so you might be able to couple your data signals into the power with DC blocking Caps. How fast is your data going to run?
    Jim
  • yes the power line is 12vDC, it powers both propellers, right now I have them talking to each other over 2.4ghz transceivers but I would like them to communicate over the power line.
  • 9600baud right now,
  • bnikkel wrote: »
    yes the power line is 12vDC, it powers both propellers, right now I have them talking to each other over 2.4ghz transceivers but I would like them to communicate over the power line.

    Your first post mentions the current is 77A. Is that correct or is it a typo? Is it the supply rating or actual current draw?

    I ask because I designed a relatively simple power line comm for a long conveyor that may work for you.
    In science there is no authority. There is only experiment.
    Life is unpredictable. Eat dessert first.
  • its the supply rating.
  • actual is under 1A
  • jmgjmg Posts: 12,616
    edited November 19 Vote Up0Vote Down
    bnikkel wrote: »
    actual is under 1A

    That's quite a difference - 77A to 1A ?
    The main challenge with power+data is to raise the impedance enough at some frequency, to get enough voltage swing to measure...
    A series inductor for each end is common, but it needs to be rated at the supplied current.
    IrDA has examples of Serial to pulse and pulse to serial usage, there is bound to be some IrDA code for P1.


    The other issue, is what does the current draw by the system look like, frequency wise. You want to avoid lots of energy where you are trying to send data ....
  • im sorry if I said that incorrectly, the available current is 77A I am only drawing about 1A.
  • bnikkel wrote:
    im sorry if I said that incorrectly, the available current is 77A I am only drawing about 1A.
    But jmg's admonition still stands. If the supply is capable of delivering 77A, it has a very low impedance. So you will need to remedy that either with series inductors or, since your actual draw is so low, resistors -- assuming you don't need exactly 12V -- to increase the impedance to AC.

    -Phil
    “Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away. -Antoine de Saint-Exupery
  • Phil and jmg are right about both the impedance and possible noise frequency from the power supply. At 77A it is almost certainly a switcher so there will be some noise. A fairly large inductor between the PS and the two Propeller boards should take care of both the noise and impedance problems.
    In science there is no authority. There is only experiment.
    Life is unpredictable. Eat dessert first.
  • Attached the schematic and waveforms plus description of the circuit I used to communicate over a 24V power line with a master and five slave stations. Ran at 1200 baud and was tested to work at up to 4800.
    1214 x 639 - 61K
    In science there is no authority. There is only experiment.
    Life is unpredictable. Eat dessert first.
  • Only caveat is that the propeller boards had to have switching regulators to keep the line current and voltage drop down.
    In science there is no authority. There is only experiment.
    Life is unpredictable. Eat dessert first.
  • You might consider using my Bell 202 modem software for your communication needs:

    http://forums.parallax.com/discussion/110918/bell-202-modem-1200-baud-afsk-object/p1

    It's only 1200 baud, though.

    -Phil
    “Perfection is achieved not when there is nothing more to add, but when there is nothing left to take away. -Antoine de Saint-Exupery
  • Mark_TMark_T Posts: 1,714
    edited November 22 Vote Up0Vote Down
    A transformer is a standard approach, you both provide the HF isolation, adapt the impedance
    and inject the signal in one component. PoE does this with beefed up magnetics for instance.
    And you get isolation of course.

    Getting the right transformer is crucial, it has to handle the DC bias current without saturating.
    The AC signal needs to use a DC-free modulation technique.

    For low voltage other approaches using RFCs and capacitor injection may be cheaper - you still need to handle
    the DC current without saturating, you get less isolation, you need DC-free modulation. This
    may be easier to source.
  • Clock LoopClock Loop Posts: 1,569
    edited November 22 Vote Up0Vote Down
    DCC made for model railroads is a pretty refined data over power standard..
    Check it out, i have adapted the method to make my own data over power in the past, simple hbridge pushed by serial output , two wires, ...etc..
    My dcc equiptment can be set to 12v. I doubt op needs 77amps tho?

    https://www.nmra.org/beginners-guide-command-control-and-dcc

    https://www.nmra.org/sites/default/files/standards/sandrp/pdf/s-9.1_electrical_standards_2006.pdf



    serveimage?url=http:%2F%2Fusuaris.tinet.cat%2Ffmco%2Fimages%2FcompletoDCC.gif&sp=367fe294a725151b5138c51a81a891b4
    1. Silicon gel filled square. <---2.Sonics(ultra even). 3.Lazers. 4. ?
    https://hackaday.io/project/162734-a-trillion-year-clock
    54 propeller chips were connected to One, to rule them all....
    https://forums.parallax.com/discussion/127983/55-parallax-propeller-s-parallells-processing-of-permanent-perturbations/p1
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