Buried Wire Sensor
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Posts: 46,084
Has anyone had any luck with buried wire sensors? I have a underground
fence to confine pets within
a yard. I want to discard the electronic shock collar and build a circuit
that will sense the buried wire.
I found a couple of circuits on the web ( i.e. Robocut ) and another in a
library book. Their schematics
say to make a coil; however, I would prefer to use a component that is
already made ( inductor ? )
Does the coil have to be "modulated" to pick up on a signal? The Robocut
circuit
(http://www.lls.se/~mux/micro/pdf/rob_sch.pdf) shows the coil in parallel
with a capacitor comming
from ground and going to additional components ( oscillilator ? ) I would
like to connect the end going
to additional components to a LED, or Speaker instead. Nothing appears to
be happening when I
try moving the circuit towards/away from the buried fence wire. I do not
know about what kind of signal
is going through the buried fence wire.
Robocut Note about Coil ( http://www.lls.se/~mux/micro/robocut_us.html )
Many of you ara asking for formulas to calculate resonance frequency for the
detector coils. All coils has benefit of an parallel tuning capacitor. You
will get a giant swing at the right freq. and the capacitor will cut-off a
lot of noise and errors. Hard to type the formula on the web, this it what
it looks like in an excel spreadsheet.
Frekres. =1/((ROT(C1*L1))*2*3,14)
C1 = kapacitansen L1 = coil "indctance". ROT the same as "Square-root" see
what your excel calls it
Often hard to determine the valu of an home made coil. We have good
experiences from small PCB-coils with "iron-kernel". Then capacitors is only
available in specific "series" so it can be rather tricky to find a match
that ends up with 38.5 Khz. Of course you could adjust the frequency of the
buried cable instead, but since we are using the 38,5 oscillator for the
IR-beacon as well, we won't give up that easy.
fence to confine pets within
a yard. I want to discard the electronic shock collar and build a circuit
that will sense the buried wire.
I found a couple of circuits on the web ( i.e. Robocut ) and another in a
library book. Their schematics
say to make a coil; however, I would prefer to use a component that is
already made ( inductor ? )
Does the coil have to be "modulated" to pick up on a signal? The Robocut
circuit
(http://www.lls.se/~mux/micro/pdf/rob_sch.pdf) shows the coil in parallel
with a capacitor comming
from ground and going to additional components ( oscillilator ? ) I would
like to connect the end going
to additional components to a LED, or Speaker instead. Nothing appears to
be happening when I
try moving the circuit towards/away from the buried fence wire. I do not
know about what kind of signal
is going through the buried fence wire.
Robocut Note about Coil ( http://www.lls.se/~mux/micro/robocut_us.html )
Many of you ara asking for formulas to calculate resonance frequency for the
detector coils. All coils has benefit of an parallel tuning capacitor. You
will get a giant swing at the right freq. and the capacitor will cut-off a
lot of noise and errors. Hard to type the formula on the web, this it what
it looks like in an excel spreadsheet.
Frekres. =1/((ROT(C1*L1))*2*3,14)
C1 = kapacitansen L1 = coil "indctance". ROT the same as "Square-root" see
what your excel calls it
Often hard to determine the valu of an home made coil. We have good
experiences from small PCB-coils with "iron-kernel". Then capacitors is only
available in specific "series" so it can be rather tricky to find a match
that ends up with 38.5 Khz. Of course you could adjust the frequency of the
buried cable instead, but since we are using the 38,5 oscillator for the
IR-beacon as well, we won't give up that easy.
Comments
I am still struggling with a circuit that works.
Tim
Denver CO
In a message dated 10/29/2002 1:33:10 PM Mountain Standard Time,
bsmith@w... writes:
> Has anyone had any luck with buried wire sensors? I have a underground
> fence to confine pets within
> a yard. I want to discard the electronic shock collar and build a circuit
> that will sense the buried wire.
> I found a couple of circuits on the web ( i.e. Robocut ) and another in a
> library book. Their schematics
> say to make a coil; however, I would prefer to use a component that is
> already made ( inductor ? )
>
> Does the coil have to be "modulated" to pick up on a signal? The Robocut
> circuit
> (http://www.lls.se/~mux/micro/pdf/rob_sch.pdf) shows the coil in parallel
> with a capacitor comming
> from ground and going to additional components ( oscillilator ? ) I would
> like to connect the end going
> to additional components to a LED, or Speaker instead. Nothing appears to
> be happening when I
> try moving the circuit towards/away from the buried fence wire. I do not
> know about what kind of signal
> is going through the buried fence wire.
>
>
[noparse][[/noparse]Non-text portions of this message have been removed]
also posting the response to the group.
We did get it to work. It can now see a signal up to 4 feet away. My
friend's father was in the Air Force as an electronics technician. He
told us that the signal would have to be amplified 200,000 times for us
to see it. Up to this point we had been trying to use an Op-Amp with a
gain of 100. I found a Common-Emitter Amplifier design in "Practical
Electronics for Inventors", by Paul Scherz, Copyright 2000 by
McGraw-Hill on page 150. I did the calculations based on the following:
Gain= -100, f3Db = 100 Hz, Iq = 1mA, Hfe = 100, and Vcc = 9v. We then
tried the design in a electronics simulator called Tina. The design
seemed to work well, so we added three more similar circuits to the
first one. I have included a screen print of what Tina was showing us.
We had some problems when we actually tried building it. I originally
had electrolitic capacitors off the emitter to ground. My friend ended
up moving and playing around with the capacitors. The electrolitic are
now out of the base, and for the first amplifier, he used what we call
"Chickletts" ( they are green and look like a chicklette chewing gum I
don't know their real name ) for the emitter to ground; and ceramic for
the remaining three emitter to ground. We have a function generator
that the father had built many years ago. We are currently using it,
but hope to build a small one in the near future. The frequency that
worked best for our circuit was 65.5K I have found a function generator
design in "IC PROJECTS Fun for the Electronics Hobbyist and
Technician", by Carl Bergquist, ISBN 0-7906-1116-3 on page 128. It
uses a 8083 with a couple of resistors and capacitors. In the end, we
also had to use a Darlington to boost the signal from the function
generator. The Inductor we used is a TV 1363-B and is in parrallel with
a 104 "Chicklette". I found this idea from the work a Swedish guy has
been doing for his robot mower (
http://www.lls.se~mux/micro/robocut_us.html ). We connected our
receiver to the Stamp, and used the Frequency In command. The closer we
got to the wire, the higher the frequency, and the further away we got,
the frequency got smaller - we don't know why.
We have the buried wire detector set aside while we work out the design
for the wheels, motors, and navigation. My friend has a bid on e-bay
for an electric mower. I want to put castors in place of the front
wheels, but we don't know where we are going with it yet. My friend and
I both agree that we want it to mow in a straight line. I've looked at
Dinsimore, and Vector for compasses, but they have tilt constraints. I
found some sensors from Honeywell on Digikey ( HMC1052 ) and ( HMC1055 [noparse][[/noparse]
60 degreee tilt ] on another website ) that look promising.
Are you also working on a robot mower ?
Hope things work out for you. Let us know if you need additional
information.
Larry and Bryan
Original Message
From: Trkeenan@a... [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=eSV87UckQrNRYanthI8p4r7y5Zu5VY8uf6bPnnXhnwUa2fkEy1SXqTCZVN2TOqnoFDTH_AC-RQ]Trkeenan@a...[/url
Sent: Wednesday, July 30, 2003 9:13 PM
To: basicstamps@yahoogroups.com
Subject: Re: [noparse][[/noparse]basicstamps] Buried Wire Sensor
I was wondering if you have figured out how to make your buried wire
sensor.
I am still struggling with a circuit that works.
Tim
Denver CO
In a message dated 10/29/2002 1:33:10 PM Mountain Standard Time,
bsmith@w... writes:
> Has anyone had any luck with buried wire sensors? I have a
> underground fence to confine pets within a yard. I want to discard
> the electronic shock collar and build a circuit that will sense the
> buried wire. I found a couple of circuits on the web ( i.e. Robocut )
> and another in a library book. Their schematics
> say to make a coil; however, I would prefer to use a component that is
> already made ( inductor ? )
>
> Does the coil have to be "modulated" to pick up on a signal? The
> Robocut circuit
> (http://www.lls.se/~mux/micro/pdf/rob_sch.pdf) shows the coil in
> parallel with a capacitor comming from ground and going to additional
> components ( oscillilator ? ) I would like to connect the end going
> to additional components to a LED, or Speaker instead. Nothing
appears to
> be happening when I
> try moving the circuit towards/away from the buried fence wire. I do
not
> know about what kind of signal
> is going through the buried fence wire.
>
>
[noparse][[/noparse]Non-text portions of this message have been removed]
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