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Power line modem with Serial Servo Controller? — Parallax Forums

Power line modem with Serial Servo Controller?

bigkahunabigkahuna Posts: 9
edited 2009-05-14 17:15 in General Discussion
I'm considering using one of these a power line communcations modem like this:

www.linksprite.com/product_info.php?cPath=217&products_id=3489&osCsid=c1fefd02eaa4a88c053db6c528933afc

with a Serial Servo Controller for a robotics project I'm working on. My robot is tethered to the base station with an power line umbilical cable, so being able to send RS232 data down the power line helps reduce the size/weight of the umbilical. Does anyone have any experience with these or can offer any advice on using them?

Next question: I have a pair of Parallax USB Servo Controllers that aren't being used for anything at the moment, how difficult / easy would it be to use the serial in on the USB PSC with the above modem? Or would I be better off buying a new Serial Servo Controller?

Comments

  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2009-05-14 14:59
    Hello,

    It looks like these modems support RS-232, but it doesn’t really say whether it supports logic-level signals directly. Assuming you’re stuck with RS-232 you could use the first circuit posted on the following link. It is for connecting an RS-232 serial port to the PSC (via its serial I/O, not USB). I hope this helps. Take care.

    http://forums.parallax.com/showthread.php?p=640507

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    Chris Savage
    Parallax Engineering
  • bigkahunabigkahuna Posts: 9
    edited 2009-05-14 15:25
    Perfect, thanks! One question regarding that circuit though, it requires 5 vdc which I wanted to supply with the built in BEC that are in the brushless ESC's that will connect to this. Is there some way I can tap that and supply power for both the PSC and this circuit? Thanks again!
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2009-05-14 16:26
    The RS-232 to PSC interface and the PSC itself both require a regulated 5V supply and they can share that supply. Not sure what you have available for options in that.

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    Chris Savage
    Parallax Engineering
  • bigkahunabigkahuna Posts: 9
    edited 2009-05-14 16:34
    I'll be using a Castle Creations Sidewinder ESC which, like many brushless ESC's, includes a builtin BEC that supplies 5 vdc. That 5 vdc is typically used to power an RC receiver, but in this case I'd like to use it to power both the PSC and the little circuit you were kind enough to direct me to. Can the PSC pick up the 5 vdc it needs directly from the servo connection (as RC radios do)? Or will I have to tap the circuit separately?

    Also, I will be using a total of 4 Sidewinder ESC's all controlled by the PSC. Do I need to disconnect any of the center (positive) leads on any of the ESC's servo connectors (as is the practice with RC radios)?

    Thanks!
  • Chris SavageChris Savage Parallax Engineering Posts: 14,406
    edited 2009-05-14 16:53
    The PSC logic circuits get power from the servo cable.

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    Chris Savage
    Parallax Engineering
  • bigkahunabigkahuna Posts: 9
    edited 2009-05-14 17:15
    Perfect! Then I'll just tap the + lead on one of the ESC servo lines to power the add-on circuit. Thanks very much!
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