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Help with an invisible fence circuit?

Discussion in 'Electronic Design' started by chapmjw, Nov 15, 2005.

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  1. chapmjw

    chapmjw Guest

    I'm looking to make a lawm mower robot this winter, and would like to
    use a perimeter wire for the boundry like a pets invisible fence. I
    have very limited knowledge of RF circuits and would appreciate any
    advise any one has to offer.
    thanks
    jim
     
  2. Fred Bloggs

    Fred Bloggs Guest


    Get off your lazy ass and use a push mower.
     
  3. Andrew

    Andrew Guest

    Put a peg in the middle of your yard and tie a rope from it to your power
    mower. Makes a nice spiral. This will likely mulch similar number of small
    mammals as the RF one you propose.
     
  4. Does not have to be RF, one or two kHz AC will work just fine. The real
    trick is in the sensor, you have to sense approximately which direction you
    "hit" the wire from in order to "bounce off" the field.

    I would go crude on this and use 3 open-core inductors mounted in a triangle
    pattern with experimentally-determined-spacing as sensors, amplify &
    threshold and then use a lookup table to perform an action based on what
    combination of sensors triggered first.
     
  5. Ken Smith

    Ken Smith Guest

    To extend:

    The amplifier should have a filter or two as part of it. You don't want
    anything below the signal frequency getting through. There is likely to
    be a fair amount of 60Hz and 180Hz (NA assumed).

    You also want to prevent the local radio stations from getting in. This
    should be a fairly simple low pass.

    You can series resonate the loop with a largish capacitor so that the
    power amplifier driving it see nearly a pure resistance.
     
  6. Rich Grise

    Rich Grise Guest

    An autonomous, engine-powered machine with whirling blades? Better put
    up a good wall, so that it doesn't eat the neighbor kids.

    Good Luck!
    Rich
     
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