metal dector for barbed wire fences

[Hul Tytus]

comp.arch.embedded,sci.electronics.components
metal dector for barbed wire fences

Anybody here have any suggestions for possible ways to detect fence wire,
mostly 1, 2 or 3 levels of barbed wire but also some 8 inch square matrix?
Typical mounting would be on a tractor or trailer, so the detector would need
a sense of direction, ie looking outward not inward. Minimum range would be
around one foot with 4 feet probably optimum.
Typical retail metal detectors have a short range and need a metal free
environment, leaving the methods they use somewhat doubtful. Evidently, there
are detectors with seperate heads/coils and 1-5 foot ranges but, once again,
require a metal free environment.
One possible area would utilize rf antenna's, one transmiting and the other
recieving a reflection from the wire(s). A parabolic or corner reflector type
antenna maybe if not for the high frequency - two 12 inch antenna's would be
about max size and that's in the gigaherts range, which might be a problem.
Any suggestions along this line will be appreciated.

Hul

[Tim Wescott]

What are you actually trying to do? Is this an operator aid, to keep
from driving into the fence, or for a robotic tractor, or what?

You may be able to make a metal detector directional simply by backing up
the detection coil with a metal plate, one or two feet back. Metal
detectors work with near-field radiation of a low frequency signal (in
the 100's of kHz, if I recall correctly), and look for changes in the
coil inductance caused by nearby metal. Placing the coil a foot or two
from the metal backing will leave the detector "detecting" the backing --
but it'll be constant; as long as there's enough change from the metal
you want to detect, things should work.

[Paul]

In article <jri79h$opj$1...@reader1.panix.com>, h...@panix.com says...

Alternatively use the barb wire fence as an antenna for LF low power
signal and get the strength detection of carrier to denote when too
close.



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[Jamie]

Ultra sonic projected on the fence wire should make it vibrated. A
ultrasonic mic just behind the transducer should detect this.

Fence wire is a hard surface and the only thing I can see that may
hamper this is rust..

If you transmit a low frequency magnetic wave in the vicinity,
surface rust on the metal may produce some nice G/T hz signals. Of
course, you need a detector for that. Maybe IR . who knows.. ;)

Jamie

[d...@kbrx.com]

Paul - that's definite possibility but, as you say, an alternative if
"plan a" doesn't prove feasible.

Hul

[Bruce Varley]

<d...@kbrx.com> wrote in message news:jrit4k$d6c$1...@reader1.panix.com...

Driving the fence with VLF, if you can do it, is likely to be the most
robust solution. I've done a similar thing for detecting underground wiring
where only one end is accessible, a simple loop coil detector easily
indicates proximities in the oo-1 metre range.

An unrelated thought, the barbed wire will make it easy to arrange a backup
override, in case whatever it is gets too close to the fence. A vertical
trip wire will catch on the barbs, and that can activate an energency stop.

[Morten Leikvoll]

"Hul Tytus" skrev i nyhetsmeldingen: jri79h$opj$1...@reader1.panix.com ...

> Anybody here have any suggestions for possible ways to detect fence
> wire,
>mostly 1, 2 or 3 levels of barbed wire but also some 8 inch square matrix?

This application makes my head shouts "radar!".. not metal detector..

[1 Lucky Texan]

On Saturday, June 16, 2012 10:04:18 AM UTC-5, Hul Tytus wrote:
> comp.arch.embedded,sci.electronics.components
> metal dector for barbed wire fences
>
> Anybody here have any suggestions for possible ways to detect fence wire,
> mostly 1, 2 or 3 levels of barbed wire but also some 8 inch square matrix?
> Typical mounting would be on a tractor or trailer, so the detector would need
> a sense of direction, ie looking outward not inward. Minimum range would be
> around one foot with 4 feet probably optimum.
> Typical retail metal detectors have a short range and need a metal free
> environment, leaving the methods they use somewhat doubtful. Evidently, there
> are detectors with seperate heads/coils and 1-5 foot ranges but, once again,
> require a metal free environment.

> One possible area would utilize rf antenna&#39;s, one transmiting and the other

> recieving a reflection from the wire(s). A parabolic or corner reflector type

> antenna maybe if not for the high frequency - two 12 inch antenna&#39;s would be
> about max size and that&#39;s in the gigaherts range, which might be a problem.

> Any suggestions along this line will be appreciated.
>
> Hul

Hmmm, wondering if a vision system could be made to do this. maybe something with a very limited depth of field on 3 cameras such that, a correction signal is generated by the outlying cameras if the image from the central camera blurs.

[mikelake]

>On Saturday, June 16, 2012 10:04:18 AM UTC-5, Hul Tytus wrote:
>> comp.arch.embedded,sci.electronics.components
>> metal dector for barbed wire fences
>>
>> Anybody here have any suggestions for possible ways to detect fence
wire,
>> mostly 1, 2 or 3 levels of barbed wire but also some 8 inch square
matrix?
>> Typical mounting would be on a tractor or trailer, so the detector would
need
>> a sense of direction, ie looking outward not inward. Minimum range would
be
>> around one foot with 4 feet probably optimum.
>> Typical retail metal detectors have a short range and need a metal
free
>> environment, leaving the methods they use somewhat doubtful. Evidently,
there
>> are detectors with seperate heads/coils and 1-5 foot ranges but, once
again,
>> require a metal free environment.

>> One possible area would utilize rf antenna's, one transmiting and the

other
>> recieving a reflection from the wire(s). A parabolic or corner reflector
type

>> antenna maybe if not for the high frequency - two 12 inch antenna's
would be
>> about max size and that's in the gigaherts range, which might be a

problem.
>> Any suggestions along this line will be appreciated.
>>
>> Hul
>
>
>
>Hmmm, wondering if a vision system could be made to do this. maybe
something with a very limited depth of field on 3 cameras such that, a
correction signal is generated by the outlying cameras if the image from
the central camera blurs.
>

I was also thinking about a vision based system - of course if the tractor
is going through fields with crops/grass/weeds blocking the camera's view
of the fence, then it isn't going to be reliable in all situations.

A camera with focus set for near objects would have a sharp view of a wire
fence. Edge detection techniques with some simple pattern matching would
probably work quite well for picking the horizontal wires of the fence. It
could be further developed to identify the actual 'barbed' pieces.

Maybe overkill for the intended application??





---------------------------------------
Posted through http://www.EmbeddedRelated.com

[Paul]

In article <2pmdnbTazcX715TN...@giganews.com>, 29427
@embeddedrelated says...

All vision systems used outside suffer from problem below

> I was also thinking about a vision based system - of course if the
tractor
> is going through fields with crops/grass/weeds blocking the camera's view
> of the fence, then it isn't going to be reliable in all situations.

Worst still heading towards the sun and see next to nothing.

> A camera with focus set for near objects would have a sharp view of a wire
> fence. Edge detection techniques with some simple pattern matching would
> probably work quite well for picking the horizontal wires of the fence. It
> could be further developed to identify the actual 'barbed' pieces.

Assumes all wire fences are nearly horizontal compared to camera
perspective. No breaks or other things attached to barbed wire like
signs syaing "keep out"..

> Maybe overkill for the intended application??

Very possibly

[David K. Bryant]

On 07/11/2012 07:18 AM, 1 Lucky Texan wrote:
> On Saturday, June 16, 2012 10:04:18 AM UTC-5, Hul Tytus wrote:
>> comp.arch.embedded,sci.electronics.components
>> metal dector for barbed wire fences
>>
>> Anybody here have any suggestions for possible ways to detect fence wire,

Search for "search coils pdf" will turn up
a lot of documents on the topic. The one
I keep around features many of the applicable
patents.

Anyway, you do have some interesting contstraints.
I'm thinking along the lines of how you could
excite the wire strands (exciter coil at one
end of the tractor) and a detector coil at
the other.

It wasn't clear whether you are trying to prevent
driving directly into a fence while crossing a
planted field or if you are trying to monitor
the fence location as in mowing close along the
fence.


--- Posted via news://freenews.netfront.net/ - Complaints to ne...@netfront.net ---

[1 Lucky Texan]

On Jul 25, 2:01 pm, "David K. Bryant" <dbryant_94...@earthlink.net>
wrote:

> On 07/11/2012 07:18 AM, 1 Lucky Texan wrote:
>

> > ...snip...

>
> It wasn't clear whether you are trying to prevent
> driving directly into a fence while crossing a
> planted field or if you are trying to monitor
> the fence location as in mowing close along the
> fence.
>

> --- Posted via news://freenews.netfront.net/ - Complaints to n...@netfront.net ---


Yes, I think there have been farming vehicles for some time now that
use GPS to mark the area in which they operate. I don't know how
accurate they are or if they require a large 'buffer' zone for error.
Perhaps switching from a GPS system to a more sensitive/accurate
system is what the OP is attempting?