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Help with an invisible fence circuit?

C

chapmjw

Jan 1, 1970
0
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
 
F

Fred Bloggs

Jan 1, 1970
0
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.


Get off your lazy ass and use a push mower.
 
A

Andrew

Jan 1, 1970
0
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.
 
F

Frithiof Andreas Jensen

Jan 1, 1970
0
chapmjw said:
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.

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.
 
K

Ken Smith

Jan 1, 1970
0
Frithiof Andreas Jensen said:
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.

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.
 
R

Rich Grise

Jan 1, 1970
0
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.

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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